Patent Grant
10190451
1. Field of the Invention
The present invention relates to compression-release engine brake systems in general, and more particularly to a compression-release engine brake system and method comprising a lost motion type engine brake rocker arm assembly incorporating structure implementing a valve reset function.
2. Description of the Related Art
Compression release engine brake systems (or retarders) for diesel engines were designed and developed in North America starting in the early 1960's. There have been many changes that have been implemented that have increased retarding performance, reduced cost, reduced engine loading and reduced engine valve train loading.
Conventionally, the engine brake compression release retarders change a power producing diesel engine to a power absorbing air compressor. The air in the cylinder is compressed on the compression stroke and is released near top dead center (TDC) of the compression stroke just prior to the expansion stroke to reduce the cylinder pressure and prevent it from pushing the piston down on the expansion stroke. In the so-called exhaust brake systems, work on the air is done on the exhaust stroke when the piston is moving up and there may be a pressure increase in the exhaust manifold from turbocharger restriction or other exhaust restriction.
The opening of the exhaust valve(s) near TDC to vacate cylinder pressure can be accomplished by a number of different approaches. Some of the most common methods used are add-on housings that hydraulically transfer intake or exhaust cam motion from a neighboring cylinder, or fuel injector motion from the same cylinder to provide a method of timing the exhaust valve(s) to open near TDC of the compression stroke to optimize the release of compressed air in the cylinder.
Other engine brake systems have a rocker arm brake that utilizes an exhaust rocker arm (or lever) to open the exhaust valve(s) near TDC of the compression stroke. A term used to identify a type of rocker arm brake is a lost motion concept. This concept adds an additional small lift profile to the exhaust cam lobe that opens the exhaust valve(s) near TDC of the compression stroke when excess exhaust valve lash is removed from the valve train.
Rocker arm brake systems using the lost motion principle have been known for many years. One problem with the conventional rocker arm brake system is that valve overlap at exhaust/intake is extended and thus braking performance decreased. Moreover, a problem with opening a single valve is that exhaust/intake overlap is extended and valve opening by an exhaust bridge may be unbalanced during the initial normal exhaust lift and may result in engine overhead damage. Extended overlap allows exhaust gas to flow backwards into the engine from the exhaust manifold and through the inlet valve into the inlet manifold. In other words, the extended valve overlap causes an undesired exhaust manifold air mass flow into the engine intake system, thus reducing exhaust stroke work and decreasing braking performance.
Embodiments disclosed herein can operate to open an exhaust valve late in the expansion stroke, to open an exhaust valve at a faster rate, and to evacuate the cylinder quickly to provide a very high performance engine brake.
A first aspect of the invention provides a compression-release brake system for effectuating a compression-release engine braking operation in connection with an internal combustion engine including an engine cylinder that is associated with a four-stroke piston cycle including a compression stroke and an expansion stroke and is provided with at least one intake valve, at least one exhaust valve, and at least one exhaust valve return spring exerting a closing force on the exhaust valve to urge the exhaust valve into a seated state. The compression-release brake system includes a lost motion exhaust rocker assembly, an actuation piston, and a reset device. The lost motion rocker assembly includes a rocker arm. The actuation piston includes an actuation piston body that is slidably received by a first pocket of the rocker arm to define a piston cavity in the rocker arm and is movable between a piston retracted position and a piston extended position. The actuation piston is configured to be operatively associated with the exhaust valve to permit unseating of the exhaust valve from the seated state. The actuation piston body contains an actuation piston communication port and an actuation piston check valve configured to move between a first closed position and a first open position to provide a first hydraulic fluid flow pathway through the actuation piston communication port to the piston cavity. The reset device is received by a second pocket of the rocker arm, operatively associated with the actuation piston through at least one connecting conduit, and includes a reset check valve configured to move between a second closed position and a second open position to provide a second hydraulic fluid flow pathway through the at least one connecting conduit to the piston cavity, and a reset pressure control spring for applying a biasing force to the reset check valve to urge the reset check valve toward a second open position.
A second aspect of the invention provides a compression-release brake system for effectuating a compression-release engine braking operation in connection with an internal combustion engine including an engine cylinder that is associated with a four-stroke piston cycle including a compression stroke and an expansion stroke and is provided with at least one intake valve, at least one exhaust valve, and at least one exhaust valve return spring exerting a closing force on the exhaust valve to urge the exhaust valve into a seated state. The compression-release brake system includes a lost motion exhaust rocker assembly, an actuation piston, and a reset device. The lost motion rocker assembly includes a rocker arm. The actuation piston is slidably received by the rocker arm to define a piston cavity in the rocker arm and movable between a piston retracted position and a piston extended position. The actuation piston is configured to be operatively associated with the exhaust valve to permit unseating of the exhaust valve from the seated state. The actuation piston includes an actuation piston body containing a variable-volume accumulator cavity.
A third aspect of the invention provides a lost motion exhaust rocker assembly including a rocker arm and an actuation piston slidably received by the rocker arm to define a piston cavity in the rocker arm and movable between a piston retracted position and a piston extended position. The actuation piston is configured to be operatively associated with an exhaust valve of an engine cylinder of an internal combustion engine to permit unseating of the exhaust valve from the seated state. The actuation piston includes an actuation piston body containing a variable-volume accumulator cavity configured to feed hydraulic fluid to the piston cavity.
A fourth aspect of the invention provides an engine including the compression-release brake system of the first aspect of the invention.
A fifth aspect of the invention provides an engine including the compression-release brake system of the second aspect of the invention.
A sixth aspect of the invention provides an engine including the compression-release brake system of the third aspect of the invention.
A seventh aspect of the invention provides a method of effectuating a compression-release engine braking operation in connection with an internal combustion engine using the compression-release brake system of the first aspect of the invention.
A eighth aspect of the invention provides a method of effectuating a compression-release engine braking operation in connection with an internal combustion engine using the compression-release brake system of the second aspect of the invention.
A ninth aspect of the invention provides a method of effectuating a compression-release engine braking operation in connection with an internal combustion engine using the compression-release brake system of the third aspect of the invention.
Compression-release brake systems disclosed herein may be low cost and integrated into the overall engine design. Moreover, the compression-release brake systems may be lightweight, avoid mechanical and thermal overload of the engine system, exhibit quiet operation and high retarding power over the entire engine speed range where the engine brake is used.
Other aspects of the invention, including systems, assemblies, subassemblies, units, engines, processes, and the like which constitute part of the invention, will become more apparent upon reading the following detailed description of the exemplary embodiments.
The various aspects and embodiments of the invention described herein may be combined with one another. Such combinations would be within the purview of a skilled art having reference to this patent application.
The accompanying drawings are incorporated in and constitute a part of the specification. The drawings, together with the general description given above and the detailed description of the exemplary embodiments and methods given below, serve to explain the principles of the invention. In these drawings:
Reference will now be made in detail to exemplary embodiments and methods of the invention as illustrated in the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the drawings. It should be noted, however, that the invention in its broader aspects is not limited to the specific details, representative devices and methods, and illustrative examples shown and described in connection with the exemplary embodiments and methods.
This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “horizontal,” “vertical,” “front,” “rear,” “upper,” “lower,” “top,” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion and to the orientation relative to a vehicle body. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. Additionally, the words “a” and/or “an” as used in the claims mean “at least one”.
In summary, exemplary embodiments disclosed herein utilize a reset mechanism carried by or integrated into an engine rocker arm which actuates one of two exhaust valves. The disclosed exhaust valve reset device can eliminate the opening of an unbalanced exhaust valve bridge and additionally minimize exhaust/intake valve overlap near the start of the intake stroke. Actuating one of two exhaust valves results in reducing valve train loading and provides the ability to delay exhaust valve opening resulting in increased charge for better braking performance. The reduced valve overlap increases exhaust manifold back pressure by reducing the exhaust manifold air mass flowing back into the intake manifold. The increased exhaust stroke pressure creates additional engine work by the engine brake during the exhaust stroke.
During brake operation, a reset check valve in the reset device is hydraulically locked due to the increasing cylinder pressure during the compression stroke. As the cylinder pressure drops after top dead center of the compression stroke, the hydraulic pressure applied to the reset check valve begins to correspondingly fall. Eventually the hydraulic pressure drops sufficiently so that a biasing force applied to the reset check valve overcomes the hydraulic force and the reset check valve opens and allows engine oil to flow and thus resets the exhaust valve and allows both exhaust valves to move during the exhaust cycle.
It will be appreciated that each cylinder 11′ may be provided with one or more intake valve(s) and one or more exhaust valve(s), although two of each are shown in
The rocker arm compression-release engine brake system 12 according to the exemplary embodiment of the present invention is a lost motion engine brake system that, as best shown in
The rocker arm compression-release engine brake system 12 according to the first exemplary embodiment of the present invention includes a conventional intake rocker assembly (not shown) for operating two intake valves 1, and an exhaust rocker assembly 16 for operating first and second exhaust valves 31 and 32. The exhaust rocker assembly 16 according to the first exemplary embodiment of the present invention is of a lost motion type provided with automatic hydraulic adjusting and resetting functions. The exhaust rocker assembly 16 includes an exhaust rocker arm 22 pivotally mounted about a rocker shaft 20 and provided to open the first and second exhaust valves 31 and 32 through an exhaust valve bridge 24. The rocker shaft 20 is supported by rocker arm supports (or rocker arm pedestals) 25 and extends through a rocker arm bore 33 formed in the exhaust rocker arm 22 (as best shown in
The exhaust rocker arm 22, as best shown in
The driven end 22b of the exhaust rocker arm 22 includes an exhaust cam lobe follower 21, as best shown in
Moreover, the exhaust rocker arm 22 also includes a rocker arm adjusting screw assembly 68 (as best shown in
The adjustment screw 70 is provided with a hexagonal socket 71 accessible from above the exhaust rocker arm 22 for setting a predetermined valve lash (or clearance) 8 between the contacting foot 72 of the adjusting screw assembly 68 and the exhaust valve bridge 24 when the exhaust rocker roller follower 21 is in contact with a lower base circle 5 on the exhaust cam 2, i.e., when the exhaust cam 2 is not acting (pressing) on the exhaust rocker arm 22. The predetermined valve lash δ is set to provide a normal exhaust valve motion during positive power operation with clearance for valve train component growth at engine operating temperatures. In an engine brake operation all lash (except the predetermined valve lash δ) is removed from the valve train and the brake cam profile determines the opening timing, profile and lift of the exhaust valves.
The lost motion engine brake rocker arm assembly 16 is part of the rocker arm compression-release engine brake system 12 provided for the internal combustion (IC) engine. Pressurized hydraulic fluid, such as engine oil, is supplied to the exhaust rocker arm 22 under high pressure through a high pressure hydraulic circuit, as best illustrated in
The exhaust rocker arm 22 further includes a substantially cylindrical actuation piston bore 64 (best shown in
The actuation piston 62 defines an actuation (or reset) piston cavity 65 within the actuation piston bore 64 in the exhaust rocker arm 22 (best shown in
Moreover, the hemispherical bottom surface 63a of the actuation piston 62 of the exhaust rocker arm 22, which faces the exhaust valve bridge 24, is adapted to contact the top end surface 76a of the single-valve actuation pin 76. A bottom end surface 76b of the single-valve actuation pin 76, axially opposite to the first surface 76a thereof, engages a proximal end of the first exhaust valve 31. The exhaust single-valve actuation pin 76 allows the actuation piston 62 to apply sufficient pressing force against the first exhaust valve 31 to open the first exhaust valve 31 (only one of the two exhaust valves 3) during the compression-release engine braking operation (i.e., in the brake-on mode). In other words, the single-valve actuation pin 76 is reciprocatingly movable relative to the exhaust valve bridge 24 so as to make the first exhaust valve 31 movable relative to the second exhaust valve 32 and the exhaust valve bridge 24. Consequently, a bridge surface 76c of the single-valve actuation pin 76 (best shown in
The rocker arm compression-release brake system 12 further comprises an exhaust valve reset device 32 disposed in the exhaust rocker arm 22. The reset device 32 according to the first exemplary embodiment of the present invention (shown in detail
Each of the supply groove 36, the brake-on groove 38, and the piston groove 40 are on an outer peripheral cylindrical surface of the cartridge body 34 and axially spaced from each other. Moreover, the supply groove 36 is provided with at least one continuous supply port 37 through the cartridge body 34, the brake-on groove 38 is provided with at least one brake-on supply port 39 through the cartridge body 34, and the piston groove 40 is provided with at least one piston supply port 41 through the cartridge body 34. The cylindrical cartridge body 34 is non-movably disposed within a substantially cylindrical reset bore 23b in the exhaust rocker arm 22. Thus, the high-pressure conduit 28 fluidly connects the actuation piston bore 64 (the piston cavity 65) with the piston groove 40 of the cartridge body 34 of the reset device 32. An inner cavity 42 within the cylindrical cartridge body 34 is enclosed between an upper cartridge plug 35a and a lower cartridge plug 35b. In other words, the annular grooves 36, 38 and 40 are fluidly connected to the inner cavity 42 of the cartridge body 34 through one or more ports (or drillings) 37, 39 and 41. As best illustrated in
The reset device 32, as best shown in
The exhaust valve reset device 32 further comprises a reset trigger 50 axially slidable within the cartridge body 34. The reset trigger 50 has an elongated distal end 52 shown in retracted and extended positions as at least partially extending from the cartridge body 34 through a bore 35c in the lower cartridge plug 35b. In the retracted position, the distal end 52 may be stowed within the cartridge body 34. The reset trigger 50 is movable relative to the cartridge body 34 between an extended position shown in
When the reset trigger 50 is in the trigger retracted position (as best shown in
As further shown in
The trigger return spring 56 biases the reset trigger 50 upwardly to a counter-bore stop 35d in the cartridge body 34. The reset pressure spring 57, used only during the engine brake-on mode, has a higher spring force than the conical ball-check spring 46 enabling the upset pin 58 to keep the ball check 44 off the ball-check seat 45, thus allowing oil from the continuous supply conduit 26 to flow unrestricted into and out of the actuation piston cavity 65 to remove the actuation piston lash during the positive power engine operation to eliminate valve train clatter.
As best illustrated in
As further illustrated in
Specifically, the stop portion 5521 of the spring retainer 552 defines a mechanical stop activated by exceeding additional upward stroke of the reset trigger 50 than normal maximum stroke of the reset trigger 50. This additional stroke of the reset trigger 50 would occur should the pressure spring 57 fail and does not force the ball check 44 off its seat 45 and the single engine brake exhaust valve 31 does not reset prior to normal exhaust valve lift with a balanced bridge. The additional stroke of the elephant foot 722 pressing on a center of the exhaust valve bridge 242 results in a small unbalance of the exhaust valve bridge 242 until the addition of the trigger stroke resulting from the rocker rotation during the normal exhaust valve motion forces the stop portion 5521 of the spring retainer 552 to contact the internal stop portion 50a of the reset trigger 50. Then the reset trigger 50 through the upset pin 58 mechanically forces the ball check 44 off the seat 45 of the reset check valve 43 during the beginning of the exhaust valve stroke. This mechanical forcing of the ball check 44 off its seat 45 during the beginning of the normal exhaust lift profile continues until engine brake operation.
The rocker shaft 20 according the exemplary embodiment of the present invention, shown in
As further shown in
In operation, the pressurized hydraulic fluid is supplied to the accumulator cavity 94 through the supply passage 93 and the accumulator ball-check valve 92. Then, the pressurized hydraulic fluid flows from the accumulator cavity 94 to the continuous supply conduit 26 of the exhaust rocker arm 22 through the connecting port 96, the connecting passage 97 and the supply port 95. During engine braking reset operation, the pressurized hydraulic fluid is dumped back into the rocker shaft accumulator cavity 94. The accumulator ball-check valve 92 prevents hydraulic fluid flow back into the hydraulic fluid supply passage 93.
The rocker arm compression-release brake system 12 further comprises an on-off solenoid valve 98, shown in
The positive power operation of the engine is as follows. During positive power operation, i.e., when the engine brake is not activated, the hydraulic fluid continuous supply conduit 26 provides continuous flow of hydraulic fluid, such as motor oil, to the check-valve cavity 421 through the continuous supply groove 36 and the continuous supply port 37. Moreover, during positive power operation, the reset trigger 50 is in the retracted position due to the biasing force of the trigger return spring 56. In this position, the ball-valve member 44 is lifted off the ball-check seat 45 (to an open position of the reset check valve 43) by the reset trigger 50. Specifically, the reset trigger 50 lifts, through the resilient biasing action of the trigger return spring 56 and the upset pin 58, which contacts, lifts and holds the ball-valve member 44 off the ball-check seat 45 for all non-engine brake operation. As the reset check valve 43 is open, the pressurized hydraulic fluid flows past the check valve 43 from the check-valve cavity 421 through the piston supply port 41 and into the high-pressure conduit 28. Then, the pressurized hydraulic fluid flows through the high-pressure conduit 28 into the actuation piston bore 64. The pressurized hydraulic fluid completely fills the actuation piston cavity 65, thus eliminating valve train lash (except the predetermined valve lash δ), such as actuation piston lash, i.e., lash between the actuation piston 62 and the single-valve actuation pin 76. The increase in the volume of the hydraulic fluid in the actuation piston cavity 65 also allows the exhaust rocker roller follower 21 to maintain contact with the exhaust camshaft brake lift profile 7 and with the added displacement created by the actuation piston 62, eliminates the brake lift and provides a normal exhaust valve profile for the exhaust stroke marked in
In the engine brake-off mode, with the valve train lash eliminated (except the predetermined valve lash δ), the exhaust rocker arm 22 then proceeds from the lower base circle 5 on the exhaust cam 2 to the engine brake lift profile 7. When the engine brake lift profile 7 acts on the driven end 22b of the exhaust rocker arm 22 and pivotally rotates the exhaust rocker arm 22, and a distal end of the actuation piston 62 presses on the single-valve actuation pin 76, in turn pressing on an exhaust valve stem of the exhaust valve 31 only. Subsequently, the actuation piston 62 is forced to move upwardly so as to reduce the volume of the actuation piston cavity 65 without opening the exhaust valve 31. This results in increased pressure in the actuation piston cavity 65 created by a force of an exhaust valve spring 91 (shown in
During the exhaust stroke of the positive power operation, when the exhaust cam profile 6 acts on the driven end 22b of the exhaust rocker arm 22 and pivotally rotates the exhaust rocker arm 22, the single-valve actuation pin 76 presses on the actuation piston 62. Subsequently, the actuation piston 62 is forced to move upwardly so as to reduce the volume of the actuation piston cavity 65. This results in increased pressure in the actuation piston cavity 65 created by the force of the exhaust valve spring 91 (shown in
When the engine brake is not activated (brake-off mode) and the exhaust cam is on the lower base circle 5, the actuation piston 62 extends in the actuation piston bore 64 in the exhaust rocker arm 22 to remove all valve train lash (except the predetermined valve lash δ). The engine brake profile 7 of the exhaust cam 2 cannot open the exhaust valve 31 for compression release braking because the reset check valve 43 is held open by the upset pin 58. The hydraulic fluid flows out of the actuation piston cavity 65 and into the rocker shaft accumulator 77 located in the rocker shaft 20 (as shown in
During the brake-on mode, the solenoid valve 98 is energized, allowing the brake-on pressurized hydraulic fluid to be supplied to the brake-on supply conduit 30. The pressurized hydraulic fluid from the brake-on supply conduit 30 enters the reset cavity 422 in the cartridge body 34 of the exhaust valve reset device 32. The pressurized hydraulic fluid in the reset cavity 422 overcomes the biasing force of the trigger return spring 56 and moves the reset trigger 50 to the extended position. In this position, as best shown in
The engine braking operation is described hereafter.
The rocker shaft 20 that supplies the pressurized hydraulic fluid is designed with two passageways 97 and 99 to supply pressurized hydraulic fluid to the continuous supply conduit 26 and the brake-on supply conduit 30, respectively, of the engine brake rocker arm assembly 16. The brake-on supply conduit 30 is controlled by the solenoid valve 98 that supplies the pressurized hydraulic fluid to the brake-on supply conduit 30, which displaces the reset trigger 50 downwardly allowing the reset check valve 43 to seat (i.e., in the closed position) and functions as a check valve to lock the hydraulic fluid in the high-pressure conduit 28 and the actuation piston cavity 65. The hydraulic pressure within the actuation piston cavity 65 assures that all lash is removed (including the actuation piston lash) from the valve train assembly (except the predetermined valve lash δ) and the exhaust rocker roller follower 21 of the exhaust rocker arm 22 is kept in contact with the exhaust cam 2.
To start the engine brake-on mode, the solenoid valve 98 is energized to flow oil through the brake-on oil supply conduit 30 to the reset cavity 422 and bias the reset trigger 50 downward and provide a clearance between the ball-valve member 44 and the upset pin 58, allowing the ball-check spring 46 to bias the ball-valve member 44 against the ball-check seat 45. The pressurized engine oil is supplied to the rocker arm continuous supply port 37 through the reset check valve 43 and the high-pressure conduit 28 and into the actuation piston cavity 65, removing all valve train lash between the single-valve actuation pin 76 and the actuation piston 62, and the cam follower 21 and the lobe of the exhaust cam 2.
With all valve train lash eliminated (except the predetermined valve lash δ) and the hydraulic fluid locked in the actuation piston cavity 65, the roller follower 21 proceeds from the lower base circle 5 on the exhaust cam 2 to the engine brake lift profile 7 to open only the exhaust valve 31 through the single-valve actuation pin 76 just prior to a Top Dead Center (TDC) of the compression stroke to evacuate the highly compressed air in the cylinder resulting from the compression stroke. When the engine brake lift profile 7 acts on the driven end 22b of the exhaust rocker arm 22 and pivotally rotates the exhaust rocker arm 22, a distal end of the actuation piston 62 presses on the single-valve actuation pin 76, in turn pressing on an exhaust valve stem of the first exhaust valve 31 only. When the actuation piston 62 presses the single-valve actuation pin 76 towards the first exhaust valve 31 just prior to TDC of the compression stroke during the compression-release engine braking event, the fluid pressure in the actuating piston cavity 65 becomes higher than the fluid pressure in the check-valve cavity 421, thus forcing the ball-valve member 44 of the check valve 43 to be seated on the ball-check seat 45, and thus hydraulically locking the engine oil (hydraulic fluid) in the actuating piston cavity 65.
With all the valve train lash (except the predetermined valve lash δ) removed and hydraulically locked, the brake lift profile 7 of the exhaust cam member 2 opens only the first exhaust valve 31 just prior to TDC of the compression stroke during the compression-release engine braking event, as illustrated by a portion 881 of the exhaust valve lift profile 85 in
During the opening of the single exhaust valve 31 with the single-valve actuation pin 76, the cylinder pressure is increasing and rapidly reaches peak cylinder pressure just prior to TDC compression, and then cylinder pressure drops rapidly just after TDC compression. Because of the compression release near TDC and the engine piston in the cylinder moving downwardly in the engine cylinder, the cylinder pressure is decreasing rapidly and so does the pressure in the actuation piston cavity 65, resulting in lower pressure biasing the ball-valve member 44 against the ball-check seat 45.
During the compression-release engine braking event during the power stroke of the braking mode, i.e., the compression stroke, resetting the exhaust valve 31 is accomplished by the elongated distal end 52 of the reset trigger 50 coming in contact with a top surface 24a of the exhaust valve bridge 24, which acts as a preset stop member as the exhaust valve bridge 24 is not movable relative to the rocker shaft 20 during the compression-release braking operation due to the predetermined valve lash δ.
Upon the contact of the elongated distal end 52 of the reset trigger 50 with the exhaust valve bridge 24, as the driving end 22a of the exhaust rocker arm 22 rotates downwardly by the action of the brake lift profile 7 of the exhaust cam member 2, the reset trigger 50, which is biased downwardly by the fluid pressure of the brake-on supply conduit 30, is forced upward relative to the cartridge body 34 toward the reset check valve 43 (against the biasing force of the pressurized hydraulic fluid in the reset cavity 422) by the exhaust valve bridge 24. As a result, the reset pressure spring 57 is compressed and the upset pin 58 contacts the ball-valve member 44 in the seated position. The reset pressure spring 57 in the compressed state creates an upward force on the ball-valve member 44 and the hydraulic pressure in the actuation piston cavity 65 biases the ball-valve member 44 into the seated position. When the biasing force of the reset pressure spring 57 exceeds the force created by the decreasing pressure in the actuation piston cavity 65, the ball-valve member 44 is forced off its seat 45, thereby unseating the ball-valve member 44 of the check valve 43 (i.e., moving the ball-valve member 44 to the open position) against the biasing force of the ball-check spring 46 by the upset pin 58.
In other words, reset occurs when the reset trigger 50 is forced upwardly by rotation of the exhaust rocker arm 22 causing the reset pressure spring 57 to be compressed and apply a high force to the ball-valve member 44 of the check valve 43 that is initially not capable of moving the ball off its seat 45 until cylinder pressure and pressure in the actuation piston cavity 65 is reduced to the point that the reset pressure spring 57 will force the ball-valve member 44 off its seat 45. This occurs toward the end of the expansion stroke 89 when cylinder pressure is low.
Opening of the check valve 43 results in releasing a portion of the hydraulic fluid from the actuation piston cavity 65, i.e., allowing the pressurized hydraulic fluid in the actuation piston cavity 65 to return to the continuous supply conduit 26 in the exhaust rocker arm 22. This causes the actuation piston 62 and the single-valve actuation pin 76 to move upwardly, thus permitting the single exhaust valve 31 to reset and return the first exhaust valve 31 back to its valve seat.
During engine brake operation of an engine without the exhaust valve reset device 32, with all valve train lash removed (except the predetermined valve lash δ), a normal exhaust valve lift profile 14 will be increased in a lift 15 and duration, as shown in
During engine brake operation of the engine with the exhaust valve reset device 32 (shown at 88 in
As illustrated in
Make-up hydraulic fluid to refurbish the reset hydraulic fluid is supplied from the rocker shaft accumulator 77 that, according to the exemplary embodiment of the present invention, is located in the rocker arm shaft 20. Alternatively, the rocker shaft accumulator 77 can be located in the rocker arm shaft support. This accumulated hydraulic fluid is stored in the rocker shaft accumulator 77 in close proximity and at a higher pressure to assist in completely filling the actuating piston cavity 65 and the high-pressure conduit 28 for the next pre-charge lift profile 8 or the engine brake exhaust lift profile 7. The pre-charge lift profile 8 of the exhaust cam lobe 2 opens the first exhaust valve 31 near the end of the intake stroke. This adds a high pressure air charge and additional boost from the exhaust manifold to the cylinder at the start of the exhaust stroke to enable more work to be done on the air during the compression stroke and potentially on the exhaust stroke and, depending on high exhaust manifold backpressure, may produce a reduced engine brake exhaust sound level.
Therefore, the lost motion rocker arm compression-release engine brake system according to the first exemplary embodiment of the present invention opens only one of two exhaust valves during the engine compression release event and resets the one exhaust valve prior to the normal exhaust stroke valve motion. In the first exemplary embodiment of the present invention, the engine compression release single exhaust valve lift opening is approximately 0.100 inches and the lift starts just prior to TDC compression stroke.
Contemporary diesel engines are usually equipped with an exhaust valve bridge and two exhaust valves. A reset device according to the exemplary embodiments of the present invention is desirable to close the single braking exhaust valve prior to the opening of both exhaust valves during the normal exhaust stroke, so that the exhaust valve bridge is not in an unbalanced condition. An unbalanced condition is where the single-valve actuation pin has not returned the single braking exhaust valve to the seated position resulting in an unbalanced force on the bridge during normal exhaust valve opening.
The reset device 32, according to the first exemplary embodiment of the present invention, is located further away from the center of rotation of the exhaust rocker arm 22 (or the rocker arm shaft 20) than the center of the exhaust valve bridge 24 and the adjusting screw assembly 68 to provide the maximum trigger motion to allow the reset trigger 50 to move upwardly in the cartridge body 34, removing lash between the ball-valve member 44 and the upset pin 58, and to provide compression of the reset pressure spring 57. Compression release cylinder pressure results in biasing the reset check valve 43 closed by the high hydraulic circuit pressure. During the beginning of the expansion stroke, the cylinder pressure decreases rapidly to a value that the reset pressure spring 57 that is being compressed can lift the ball-valve member 44 off the seat 45 thereof.
At the time when the ball-valve member 44 is forced off its seat 45, the hydraulic fluid in the actuation piston cavity 65 will be released, thereby resetting the single engine brake exhaust valve 31. The resetting function occurs prior to the normal exhaust stroke, resulting in both exhaust valves 31 and 32 being seated and the exhaust valve bridge 24 can now be opened by the exhaust rocker arm 22 with the exhaust bridge 24 in a balanced condition.
Present lost motion rocker brakes are commercially available without resetting and are accomplished by incorporating increased strength bridge guide pins to solve the unbalanced bridge loading problem. The prior art approach is more costly and provides less retarding performance because of the extended intake/exhaust valve overlap condition. Extended intake/exhaust valve overlap results in the loss of exhaust manifold air mass and pressure back into the cylinder and inlet manifold. The loss of exhaust manifold pressure decreases engine brake retarding performance.
The single valve rocker arm lost motion compression-release engine brake system with reset, according to exemplary embodiments of the present invention, reduces cost of a conventional engine brake system or even a dedicated cam brake. The rocker arm compression-release engine brake system of exemplary embodiments the present invention provides better performance than an exhaust cam driven brake or even an injector driven one. The performance of the single valve rocker arm compression-release engine brake system of exemplary embodiments of the present invention compared to a dedicated cam engine brake in most circumstances will be close. Compared to other engine brake configurations, the single valve rocker arm lost motion compression-release engine brake system with reset of exemplary embodiments of the invention is better in weight, cost of development, requirements to make fundamental changes to existing engines, engine height and manufacturing cost per engine.
The valve train assembly 110 includes a rocker arm compression-release engine brake system 112 according to the second exemplary embodiment of the present invention, provided for an internal combustion (IC) engine. Preferably, the IC engine is a four-stroke diesel engine.
As illustrated in
The exhaust rocker assembly 116 according to the second exemplary embodiment of the present invention is a lost motion type provided with automatic hydraulic adjusting and resetting functions as disclosed herein. The exhaust rocker assembly 116 includes an exhaust rocker arm 122 pivotally mounted about a rocker shaft 20 and provided to open first and second exhaust valves 31 and 32, respectively, through an exhaust valve bridge 24. The rocker shaft 20 is supported by rocker arm supports (or rocker arm pedestals) 25 and extends through a rocker arm bore 133 formed in the exhaust rocker arm 122 (shown in
The rocker arm compression-release brake system 112 further comprises an exhaust valve reset device 132 disposed in the exhaust rocker arm 122. The exhaust valve reset device 132 according to the second exemplary embodiment of the present invention is substantially structurally and functionally identical to the exhaust valve reset device 32 of the first exemplary embodiment of the present invention (shown in detail
As best illustrated in
Alternatively, an outer peripheral cylindrical surface 149 of cartridge body 134′ of an alternative embodiment of an exhaust valve reset device, generally depicted with the reference numeral 132′, is wholly or at least partially threaded as best illustrated in
An upper cartridge plug 135a is non-movably secured (i.e., fixed) to the cartridge body 134′ and is provided with a hexagonal socket 171 accessible from above the exhaust rocker arm 122 for setting the predetermined valve lash δ. A lock nut 151 is provided on the adjusting threaded cylindrical cartridge body 134′. The predetermined valve lash δ is set to provide normal exhaust valve motion during positive power operation with clearance for valve train component growth at engine operating temperatures. During engine brake operation all lash (except the predetermined valve lash δ) is removed from the valve train and the brake cam profile determines the opening timing, profile and lift of the exhaust valve. In other words, the reset device 132 combines the functions of a rocker arm adjusting screw assembly and a check valve and reset device. Such an arrangement of the exhaust valve reset device is especially beneficial for an IC engine with an overhead camshaft.
The valve train assembly 310 includes a rocker arm compression-release engine brake system 312. Preferably, the IC engine is a four-stroke diesel engine, comprising a cylinder block including a plurality of cylinders. The rocker arm compression-release engine brake system 312 includes a conventional intake rocker assembly (not shown) for operating two intake valves 1, and a lost motion exhaust rocker assembly 316 for operating first and second exhaust valves 31 and 32. The exhaust rocker assembly 316 according to the third exemplary embodiment of the present invention is of lost motion type provided with automatic hydraulic adjusting and resetting functions. The exhaust rocker assembly 316 includes an exhaust rocker arm 322 pivotally mounted about a rocker shaft 20 and provided to open the first and second exhaust valves 31 and 32, respectively, through exhaust valve bridge 24. The rocker shaft 20 is supported by rocker arm supports (or rocker arm pedestals) and extends through a rocker arm bore 333 formed in the exhaust rocker arm 322 (shown in
The rocker arm compression-release brake system 312 further comprises an exhaust valve reset device 332 disposed in the exhaust rocker arm 322 in a direction substantially parallel to the exhaust valves 31 and 32. The exhaust valve reset device (or spool cartridge) 332 according to the third exemplary embodiment of the present invention, as best illustrated in
The reset device 332 further comprises a substantially cylindrical reset spool 340 axially slidingly disposed within the cylindrical cartridge body 334. The reset spool 340 is movable within and relative to the cartridge body 334 between a retracted position shown in
As further illustrated in
The reset spool 340 is further formed with a second annular spool recess 354 between the inner peripheral surface 335 of the cartridge body 334 and the outer peripheral surface 347 of the reset spool 340. The second annular recess 354 defines an upper spool cavity and is in fluid communication with the check-valve cavity 3421 through at least one second communication port 355 in the reset spool 340. As best illustrated in
The reset device 332 further comprises a ball-valve member 344, and a ball-check spring 346 disposed between the ball-valve member 344 and the upper cartridge plug 335. The ball-valve member 344 is held on a ball-check seat 345 by a biasing spring force of the ball-check spring 346 so as to close a communication port 348 in the reset spool 340, which fluidly connects the continuous pressure supply port 337 of the cartridge body 334 and the check-valve cavity 3421 of the reset spool 340. The ball-valve member 344, the ball-check seat 345 and the ball-check spring 346 define a reset check valve 343. The check valve 343 provides selective fluid communication between the continuous supply conduit 26 and the high-pressure conduit 28 (i.e., between the continuous supply conduit 26 and the actuation piston cavity 65) through the second communication ports 355. It will be appreciated that any appropriate type of the check valve is within the scope of the present invention.
The continuous pressure supply port 337 and the piston supply port 341 are formed on an outer peripheral cylindrical surface of the cartridge body 334 and axially spaced from each other. The threaded cylindrical cartridge body 334 is adjustably disposed within the substantially cylindrical reset bore in the exhaust rocker arm 322.
The exhaust valve reset device 332 further comprises a reset trigger 350 axially slidable within the reset cavity 3422 of the reset spool 340. The reset trigger 350 has a hemispherical distal end 352 at least partially extending from the cartridge body 334. The reset trigger 350 is movable relative to the cartridge body 334 between a retracted position shown in
The valve train assembly 310 according to the third exemplary embodiment of the present invention further comprises a compression release actuator 376 provided to selectively move the reset spool 340 between the retracted position shown in
The compression-release brake system 312 operates in a compression brake mode, or brake-on mode (during the engine compression brake operation) and a compression brake deactivation mode, or brake-off mode (during the positive power operation).
In operation of the IC engine with the rocker arm compression-release engine brake system 312 with the reset device 332 according to the third exemplary embodiment of the present invention, during the brake-off mode the compression release actuator 376 is deactivated and the brake-on piston 380 is in the retracted position so that the brake-on piston 380 is axially spaced from the reset spool 340 of the reset device 332, as illustrated in
Accordingly, during brake-off mode, the pressurized fluid is continuously supplied from the continuous supply conduit 26 to the actuation piston cavity 65 through the lower spool cavity 351 and the piston supply port 341 of the reset device 332, and the high-pressure passageway 28, as shown in
The engine braking operation during the brake-on mode is as follows.
To activate the engine brake, the compression release actuator 376 is activated and the brake-on piston 380 moves into the extended position, as best shown in
During the engine compression stroke the biasing forces of the brake-on piston 380 of the compression release actuator 376 and hydraulic pressure in the upper spool cavity 354 bias the reset spool 340 into the extended position. On the other hand, the reset pressure spring 357 and the trigger return spring 356 bias the reset spool 340 into the retracted position. As the cylinder pressure continues to increase, the hydraulic pressure in the upper spool cavity 354 also increases, creating a larger biasing force to maintain the reset spool 340 in the downward, extended position and continuing to lock the hydraulic fluid in the actuation piston cavity 65 above the single valve actuation piston 62.
When the engine stroke changes from the compression stroke to the expansion stroke, the cylinder pressure decreases rapidly to approximately atmospheric pressure. When the pressure in the piston supply port 341 and the upper spool cavity 354 decrease to approximately 250 psi pressure, any significant hydraulic biasing force on the reset spool 340 is eliminated, resulting in the upward biasing force of the reset pressure spring 357 exceeding the downward biasing force of the compression release actuator 376. As a result, the reset spool 340 transitions upwardly to open the piston supply port 341 to the lower spool cavity 351, thus unlocking the actuation piston 62, i.e., allowing the hydraulic fluid from the actuation piston cavity 65 to flow back into the continuous oil supply conduit 126 through the continuous pressure supply port 337. This oil flow through the continuous pressure supply port 337 allows the single exhaust valve 31 to be reseated and completes a single valve reset function. The reset pressure spring 357 has a spring rate sufficient to generate an adequate force to overcome the force of approximately 100 pounds from the valve spring 91 of the braking exhaust valve 31 that creates the pressure differential across the reset ball-valve member 444 of the reset check valve 443 at the end of the expansion stroke to reset the single exhaust valve 31.
The valve train assembly 410 includes a rocker arm compression-release engine brake system 412. Preferably, the IC engine is a four-stroke diesel engine, comprising a cylinder block including a plurality of cylinders. The rocker arm compression-release engine brake system 412 comprises a conventional intake rocker assembly (not shown) for operating two intake valves 1, and a lost motion exhaust rocker assembly 416 for operating first (or braking) and second exhaust valves 31 and 32, respectively. The exhaust rocker assembly 416 according to the fourth exemplary embodiment of the present invention is a lost motion type provided with automatic hydraulic adjusting and resetting functions as disclosed herein. The exhaust rocker assembly 416 includes an exhaust rocker arm 422 pivotally mounted about a rocker shaft 20 and provided to open the first and second exhaust valves 31 and 32, respectively, through an exhaust valve bridge 24. The rocker shaft 20 is supported by rocker arm supports (or rocker arm pedestals) and extends through a rocker arm bore 433 formed in the exhaust rocker arm 422 (shown in
The IC engine incorporating the compression-release brake system 412 in accordance with the fourth exemplary embodiment of the present invention includes a pushrod (shown in
The rocker arm brake system 412 also comprises a substantially cylindrical actuation piston bore 464 formed in the exhaust rocker arm 422 for slidably receiving an actuation piston 462 (best shown in
The rocker arm brake system 412 further comprises an exhaust valve reset device 432 disposed in the exhaust rocker arm 422. The exhaust valve reset device 432 includes a reset check valve disposed in the actuation piston 462, as shown in
The ball-valve member 444 is biased open, i.e., held off the ball-check seat 445 by the biasing spring force of the reset spring 446, so as to open a communication port 448 in the actuation piston 462, which fluidly connects the reset piston cavity 465 with a communication conduit 453 formed through the actuation piston 462. In turn, the communication conduit 453 in the actuation piston 462 is fluidly connected directly to the continuous supply conduit 426. In other words, when the reset check valve 443 is open, the continuous supply conduit 426 is fluidly connected to the reset piston cavity 465.
The exhaust valve reset device 432 of the rocker arm brake system 412 further includes a rocker check valve 450 also disposed in the exhaust rocker arm 422. In the exemplary embodiment of the present invention, the rocker check valve 450 is in the form of a ball-check valve, which is normally biased closed. It will be appreciated that any appropriate type of the check valve, other than the ball-check valve, is also within the scope of the present invention. The rocker check valve 450 is disposed in check-valve bore 434 formed in the exhaust rocker arm 422 substantially perpendicular to the rocker arm bore 433 receiving the rocker shaft 20. The bore 434 is closed by a plug 435. The rocker check valve 450 comprises a ball-valve member 440 disposed in the check-valve bore 434, and a ball-check spring 442 biasing the all-valve member 440 to its closing position. In other words, the ball-valve member 440 is held on a ball-check seat by the biasing spring force of the ball check spring 442 so as to close a communication opening 452 through the rocker check valve 450, which fluidly connects the continuous supply conduit 426 and the reset piston cavity 465 through a reset conduit 428.
The rocker arm brake system 412 according to the fourth exemplary embodiment of the present invention further comprises a compression release actuator 476 provided to selectively control the exhaust valve reset device 432. The compression release actuator 476, shown in
The rocker arm brake system 412 according to the fourth exemplary embodiment of the present invention further comprises a reset pin 458 extending between the brake-on piston 480 and the reset ball-valve member 444 of the reset check valve 443.
Moreover, the exhaust rocker arm 422 includes a rocker arm adjusting screw assembly 468 (as best shown in
As best illustrated in
The screw assembly 468 comprises an adjustment screw 470 having a ball-like end 471 for being received in a socket (not shown) coupled to a top end of the pushrod. The adjustment screw 470 is adjustably, such as threadedly, mounted in the driven end 422b of the exhaust rocker arm 422 and fastened in place by a locknut 473.
The compression-release brake system 412 operates in a compression brake mode, or brake-on mode (during the engine compression brake operation) and a compression brake deactivation mode, or brake-off mode (during the positive power operation).
The engine braking operation during the brake-on mode is as follows.
To activate the engine brake, the compression release actuator 476 is activated and pressurized fluid enters the brake-on piston cavity 481 through the brake-on fluid supply port 482. Pneumatic or hydraulic fluid, such as engine oil, supplied to the brake-on piston cavity 481, forces the brake-on piston 480 downwardly. Subsequently, the brake-on piston 480 moves into the extended position to engage and move downwardly the piston stroke limiting pin 484, as shown in
The operation of the compression-release engine brake system 412 according to the fourth exemplary embodiment requires opening only one of the two exhaust valves 31 and 32 so as to not exceed the valve train maximum valve train loading specifications. The opening of the braking exhaust valve 31 incorporates a single valve brake lift of approximately 0.100 inches. The compression-release engine brake system 412 requires the brake-on piston 480 to provide substantial downward biasing force to the ball-valve member 444 of the reset check valve 443 via the reset pin 458 to seal (i.e., close) the reset check valve 443 for approximately 50% of the typical 0.100 inch lift of the braking exhaust valve 31 for the initial valve opening. In other words, the ball-valve member 444 is biased closed mechanically during the first 0.050 inches of the single valve brake lift.
When the lift of the braking exhaust valve 31 is at approximately 50% (or 0.050 inches) of its entire engine brake braking lift, the brake-on piston 480 engages the adjustable piston stroke limiting pin (or positive stop) 484. From that moment on, downward linear movement of the brake-on piston 480 is prevented. Subsequently, as the exhaust rocker arm 422 continues to move the exhaust bridge 24 downwardly, the brake-on piston 480 stops pushing the reset pin 458 downward.
Cylinder pressure and, therefore, the valve force against the actuation piston 462 continue to rise during the second half of the motion of the braking exhaust valve 31. The increasing hydraulic pressure now holds the reset ball-valve member 444 firmly on its seat 445, such that contact with the reset pin 458 is no longer needed for the last (or second) 50% of motion. In other words, the downward biasing force of the reset pin 458 on the ball-valve member 444 is eliminated at approximately 50% of the opening of the braking exhaust valve 31 resulting from the contact of the brake-on piston 480 with the adjustable positive stop 484, as the exhaust rocker arm 422 continues to open the braking exhaust valve 31. Cylinder pressure continues increasing during the compression stroke, thus biasing the braking exhaust valve 31 upward and increasing the pressure of the oil in the reset piston cavity 465. As a result, a downward biasing force acting to the reset ball-valve member 444 is provided. The high pressure in the reset piston cavity 465 produces a high pressure differential across the reset ball-valve member 444 to continue to bias the reset ball-valve member 444 seated, i.e., into the closed position of the reset check valve 443. In other words, the pressure in the actuation piston cavity 465 hydraulically biases the reset check valve 443 closed for the second and final half (i.e., 0.050 inch lift) of the single valve brake lift.
As described above, internal to the actuation piston 462 is the reset spring 446 that biases the reset ball-valve member 444 upward to an open position of the reset check valve 443 with an approximate initial force of the reset spring 446 of 13 pounds of force. During the expansion stroke 89 the cylinder pressure 89P will decrease rapidly due to air being released from the cylinder during the engine brake's compression relief event near TDC compression stroke.
The cylinder air mass, which is released through the opening of the braking exhaust valve 31 into the engine's exhaust manifold, results in a very low cylinder pressure near the end of the expansion stroke. Because the braking exhaust valve 31 remains open at approximately 0.100 inches lift, the valve spring 91 of the braking exhaust valve 31 creates an upward biasing force of approximately 100 pound-force (lbf) on the actuation piston 462.
Towards the end of the expansion stroke 89, when the cylinder pressure is close to atmospheric and an added small biasing force from the valve spring 91 of the braking exhaust valve 31, the higher biasing force from the reset spring 446 lifts the reset ball-valve member 444 off the seat 445, resulting in hydraulic fluid returning from the reset piston cavity 465 to the continuous supply conduit 426 and the hydraulic fluid supply passage 93, such as an engine oil supply. The returning hydraulic fluid flow allows the valve spring 91 of the braking exhaust valve 31 to force the actuation piston 462 upwardly to initiate contact between the reset pin 458 and the brake-on piston 480.
The resilient biasing force of the valve spring 91 of the braking exhaust valve 31 is approximately 100 pound-force (lbf), creating approximately 220 psi pressure in the reset piston cavity 465 to force the hydraulic fluid back into the hydraulic fluid supply passage 93 and allowing the actuation piston 462 to travel upwardly. When the braking exhaust valve 31 approaches 0.050 inches from the seated position, the reset pin 458 contacts the brake-on piston 480 and reset ball-valve member 444 will be seated, i.e., the reset check valve 443 is closed.
The biasing force of the valve spring 91 of the braking exhaust valve 31, which is approximately 100 lbf, exceeds the approximately 12 pound downward biasing force of the brake-on piston 480, forcing the brake-on piston 480 upwardly and positioned to approximately 0.050 inches above the adjustable positive stop 484. This causes the actuation piston 462 and the single-valve actuation pin 76 to move upwardly, thus permitting the single exhaust valve 31 to be reset and return the first exhaust valve 31 back to its valve seat. In other words, resetting the single exhaust braking valve 31 is achieved by sensing the decreasing cylinder pressure and corresponding hydraulic pressure in the actuation piston cavity 465 during the expansion stroke to unseat the ball-check 444 and release hydraulic fluid from the actuation piston cavity 465 to close or reset the single exhaust valve 31 to eliminate unbalanced exhaust bridge prior to the normal exhaust valve lift.
The hydraulic fluid supply passage 93 adds the final required make-up oil to the reset piston cavity 465 through the rocker check valve 450.
The rocker check valve 450 is fluidly connected to the continuous supply conduit 426 for supplying hydraulic fluid to the reset piston cavity 465. The rocker check valve 450 allows the reset piston cavity 465 to be completely filled prior the start of the compression braking stroke. The operation of the brake-on piston 480 biases the reset check valve 443, seated for approximately 0.050 inches of the lift of the braking exhaust valve 31, both during opening 911 and closing 912 exhaust lift profiles.
During refilling of the actuation piston cavity 465, the passageway 453 adds supply oil only until the brake-on piston 480 and the reset pin 458 bias the reset ball-valve member 444 of the reset check valve 443 prior to the last 0.050″ of the single valve brake lift (or lost motion) to be taken up. Because the reset ball-valve member 444 seals the reset check valve 443 for the first 0.050″ of the single braking lift, it cannot add make-up reset supply oil during the last the last 0.050″ of the single braking lift. For this reason, the rocker check valve 450 is provided.
The reset check valve 443 is biased closed by the brake-on piston 480 (through the reset pin 458) for the initial 0.050 inch of an opening portion 88, of an exhaust cam profile lift 88 during the compression-release engine braking event, thereby preventing the continuous supply conduit 426 to add any make-up oil at normal oil supply pressure. The conical biasing spring 442 of the rocker check valve 450 has a low biasing force providing the make-up oil from the continuous supply conduit 426 to completely fill the reset piston cavity 465 and remove all exhaust valve train clearance prior to the next compression-release engine braking event 88 (shown in
During the expansion stroke 89, the hydraulic fluid from the reset piston cavity 465 flows back into the continuous supply conduit 426, permitting the seating (displacement) of the braking exhaust valve 31 into its closed position. With the braking exhaust valve 31 seated (or closed), the normal exhaust cycle commences operation with both exhaust valves 31 and 32 closed, which eliminates unbalanced exhaust valve bridge 24 opening consisting of the closed outer exhaust valve 32 and the partially opened braking exhaust valve 31.
During the engine compression operation, a peak cylinder pressure in the engine cylinder can be as high as 1000 psi, resulting in a pressure of approximately 4000 psi in the reset piston cavity 465. The reset pin 458 comprises an enlarged, such as cylindrical, portion (or stop portion) 458a formed integrally (i.e. non-moveably or fixedly) between distal ends of the reset pin 458 and disposed in the reset piston cavity 465. The stop portion 458a of the reset pin 458 is configured to control an upper stop of the reset pin 458 in the reset piston cavity 465 and to control the upper biasing force resulting from hydraulic pressure in the reset piston cavity 465. A cross-sectional area (or diameter) of the stop portion 458a is larger than a cross-sectional area (or diameter) of the reset pin 458 outside of the cylindrical portion 458a. The differential area of the reset pin 458 minimizes the internal surface area of the reset pin 458 inside the reset piston cavity 465 to reduce or eliminate undesired biasing of the reset ball-valve member 444 during seating and unseating functions. Moreover, an upper pin stop surface 458b of the stop portion 458a faces and is configured to selectively engage a reset stop surface 459 of the exhaust rocker arm 422 to limit an upward movement of the reset pin 458.
The engine operation during the brake-off mode is as follows.
In operation of the engine with the rocker arm compression-release engine brake system 412 and the exhaust valve reset device 432 according to the fourth exemplary embodiment of the present invention, during the brake-off mode, the compression release actuator 476 is deactivated and the brake-on piston 480 is in the retracted position. Consequently, the reset check valve 443 is biased open by the reset spring 446.
In this position, the reset pin 458 does not bias the reset check valve 443 closed. In the brake-off mode, the pressurized hydraulic fluid, such as engine oil, is continuously supplied to the reset piston cavity 465 from the continuous supply conduit 426 through the communication conduit 453, the communication port 448 and the open reset check valve 443. Moreover, the open reset check valve 443 allows the pressurized hydraulic fluid to flow into and out of the reset piston cavity 465 through the communication conduit 453 and the communication port 448 to the continuous supply conduit 426. This continuing oil flow removes the mechanical clearance in a valve train (except the predetermined valve lash δ, best shown in
When the brake-on fluid supply to the brake-on piston cavity 481 through the brake-on fluid supply port 482 is off, the reset pin 458 is biased upwardly to the reset stop surface 459 of the exhaust rocker arm 422 by the reset spring 446 and the hydraulic fluid pressure acting on lower pin stop surface 458c of the stop portion 458a, thereby biasing the reset ball-valve member 444 upward to the open position for allowing unrestricted fluid flow in the reset piston cavity 465 to flow engine oil from the continuous supply conduit 426 freely into and out of the reset piston cavity 465 and to remove all exhaust valve train lash to reduce valve train impact and mechanical noise during positive power engine operation.
During the compression stroke 86, all valve train lash is removed by the addition of the pressurized hydraulic fluid to the reset piston cavity 465 through the continuous supply conduit 426, so that the reset piston 462 engages the braking exhaust valve 31. Near the end of the compression stroke 86, the engine brake lift profile 7 of the exhaust cam 2 causes rotation of the exhaust rocker arm 422. As the exhaust rocker arm 422 moves pivotally toward the braking exhaust valve 31, the reset piston 462 is unable to overcome the resilient biasing force of the valve spring 91 of the braking exhaust valve 31 and is displaced into the reset piston bore 464, so that the pressurized hydraulic fluid flows from the reset piston cavity 465 through the open reset check valve 443, which is biased off its seat 445 by the reset spring 446, into the continuous supply conduit 426.
After completion of the exhaust lift profile 88 (as shown in
Subsequently, the exhaust rocker arm 422 is on the exhaust cam profile (or upper base circle) 6 of the exhaust cam 2 ready to continue the normal exhaust cam lift profile 85. With the reset spring 446 continuously holding the reset ball-valve member 444 off its seat 445, thereby allowing unrestrictive flow of the engine oil in the reset piston cavity 465, the valve train lash is eliminated during the positive power operation of the engine.
Therefore, incorporating a hydraulic lash adjuster and an exhaust valve reset device on a lost motion rocker arm brake as disclosed herein has the advantages of not having to adjust brake valve lash at initial installation and at service intervals and having an automatic valve train adjustment to accommodate valve train wear and to reduce valve train mechanical sound levels. Moreover, the rocker arm compression-release engine brake system according to exemplary embodiments of the present invention is lighter than conventional compression-release engine brake systems, and provides lower valve cover height and reduced cost.
The compression-release brake system 512 is particularly useful for an IC engine, such as a four-stroke diesel engine, as generally shown in
Like the systems discussed above, the compression-release brake system 512 of the fifth exemplary embodiment is selectively operable in the positive power operation (brake-off mode) and the engine brake operation (brake-on mode). For example, a switch may be provided in the operator's cab to activate and deactivate the compression-release brake system 512.
Referring principally to
The exhaust rocker assembly 516 further includes a stop member in the form of an exhaust valve bridge 524 having an opening 525. The rocker shaft 520 may be supported by rocker arm supports (such as designated by reference numeral 25 in
The exhaust rocker arm 522 features a dual-supply hydraulic circuit that includes a continuous supply conduit (or passageway) 526 and connecting conduits (or passageways) 528 and 529. Pressurized hydraulic fluid, such as engine oil, is supplied through the hydraulic circuit to remove valve train lash (except the predetermined valve lash δ). The exhaust rocker arm 522 further includes a separate brake-on supply conduit (or passageway) 530, shown for example in
The exhaust rocker arm 522 includes a substantially cylindrical actuation piston pocket or bore 564 at the driving end of the exhaust rocker arm 522 for slidably receiving an actuation piston 562. The actuation piston 562 is reciprocatingly movable in the piston pocket 564 between a piston retracted position and a piston extended position. The actuation piston 562 is shown in the piston extended position in
A single-valve actuation pin 576 is positioned between the actuation piston 562 and the first exhaust valve 31. The single-valve actuation pin 576 is slidable relative to the exhaust valve bridge 524 through the opening 525. A hemispherical bottom 562b of the actuation piston 562 engages the top 576t of the single-valve actuation pin 576. The bottom of the single-valve actuation pin 576 operatively engages the first exhaust valve 31. The actuation piston 562 is operatively associated with the exhaust valve 31 through the actuation pin 576 to permit unseating (opening) of the first exhaust valve 31 from the seated state during compression-release engine braking operation near or at TDC) without unseating the second exhaust valve 32.
Although the exemplary embodiments described herein, including the fifth exemplary embodiment, make use of an actuation pin such as the pin 576 for actuation of the first exhaust valve 31 while maintaining the second exhaust valve 32 unactuated, it should be understood that actuation of only the first exhaust valve 31 may be accomplished by other operations. For example, the bridge 524 may be pivotally movable by the actuation piston 562 to actuate the first exhaust valve 31 but not the second exhaust valve 32.
As best shown in
The actuation piston body 563 also defines an actuation piston check-valve cavity 585 containing the ball-valve member 581 and the ball-valve check spring 583, an actuation piston communication port 586 surrounded by the actuation piston check-valve seat 582, actuation piston feed conduits 587 feeding into a vertical passage below the communication port 586, and actuation piston outlet conduits 588 above the communication port 586. The illustrated embodiment includes four feed conduits 587 spaced ninety degrees apart from one another, and four outlet conduits 588 circumferentially spaced ninety degrees apart from one another. It should be understood that the actuation piston 562 may contain a different number of conduits 587 and 588, and thus different angular spacing.
The actuation piston check valve 580 is movable between open and closed positions. In the open position shown in
It should be understood that the actuation piston check valve 580 illustrated in the exemplary embodiment may be replaced by other suitable check valves, and that such modifications are within the scope of the invention.
As best shown in
As best shown in
The cartridge body 534 has a reset device cavity 535 containing a reset trigger 550, a reset piston 554, a reset trigger return spring 556, and a reset pressure control spring 557. The reset trigger 550 is axially slidable within and relative to the cartridge body 534 between a trigger retracted position and a trigger extended position. A distal end 552 of the reset trigger 550 extends through bottom opening (unnumbered) of the cartridge body 534. When the reset trigger 550 is in the trigger extended position, the distal end 552 protrudes through the bottom opening 572o of the foot 572 and, depending on the pivotal position of the rocker arm 522, contacts the exhaust valve bridge 524, as discussed further below.
The reset trigger 550 is biased upwardly towards the trigger retracted position by the reset trigger return spring 556 disposed in the reset device cavity 535 between a shoulder portion 534s of the cartridge body 534 and a flange portion 550f of the reset trigger 550. As best shown in
The reset device cavity 535 also includes the reset pressure control spring 557, which is positioned between the reset trigger flange portion 550f (opposite to the reset trigger return spring 556) and the flanged portion 554f of the reset piston 554. The reset pressure control spring 557 biases the reset piston 554 (and the upset pin 558 seated on the reset piston 554) upward.
An activation cavity 539 is positioned above a top surface 554t of the reset piston 554 to surround the lower end of the upset pin 558. The activation cavity 539 communicates with the brake-on supply conduit 530, as shown for example in
As mentioned above, the reset device 532 includes a lower subassembly (described above) and an upper subassembly (described below). The upset pin 558 extends through a hole or bore in the exhaust rocker arm 522 to connect the two subassemblies. An appropriate sleeve or other component may be provided around the upset pin 558 to provide a seal and thereby prevent the hydraulic or other fluid from escaping from the activation cavity 539 or a reset check-valve cavity 542 discussed below.
Referring to
The hydraulic circuit will now be discussed in greater detail. The various conduits of the hydraulic circuit may be positioned in locations other than those shown in the drawings.
The hydraulic fluid is fed from an accumulator such as described above in connection with
The hydraulic fluid received by the annular groove 527 is fed into the actuation piston feed conduits 587, which are best shown in
The annular groove 527 is also connected to the connecting conduit 529, which is sometimes referred to herein as the first connecting conduit. As best shown in
The connecting conduit 528, which is sometimes referred to herein as the second connecting conduit, connects the reset check-valve cavity 542 to the piston cavity 565. When the reset check valve 543 is in the closed position as shown in
The positive power operation (brake-off mode) of the IC engine is now described with reference to
The compression-release brake system 512 in brake-on mode will now be described with reference to
The pressurized hydraulic fluid accumulates in the activation cavity 539 and exerts a downward force on the top surface 554t of the reset piston 554. This downward force overcomes the biasing force exerted by the reset trigger return spring 556 to compress the trigger return spring 556 and drive the reset trigger 550 downward from the trigger retracted position, which is discussed above in connection with the brake-off mode to the trigger extended position shown in
The reset trigger return spring 556 may be provided with a lower spring constant than the reset pressure control spring 557, so that the downward movement of the reset piston 554 at this activation stage primarily compresses the reset trigger return spring 556 and not the reset pressure control spring 557. Because of the higher spring constant of the reset pressure control spring 557, the height of the reset pressure control spring 557 remains fixed at the piston stroke limiting pin 555, i.e., the piston stroke limiting pin 555 does not slide downward along the slot 550s of the reset trigger 550 at this time. In the trigger extended position shown in
In addition to moving the reset trigger 550 into the trigger extended position, the downward movement of the reset piston 554 translates downward the upset pin 558 connected to the top surface 554t of the reset piston 554. The upper end of the upset pin 558 is thereby lowered below the reset communication port 548. The biasing force exerted by the reset ball-valve check spring 546 on the reset ball-valve member 544 urges the reset ball-valve member 544 onto the reset check-valve seat 545, closing the reset check valve 543.
The reset check valve 543 closes after the hydraulic fluid has flowed into the piston cavity 565 to extend the actuation piston 562 into the piston extended position to retain contact with the actuation pin 576 and drive the exhaust rocker arm 522 away from the exhaust valve bridge 524, as shown in
Next, the cam follower 21 of the driven end 22b (
As the exhaust rocker arm 522 moves from lower base circle 5 towards upper base circle 7, the downward motion of the driving end of the exhaust rocker arm 522 drives the actuation piston 562 against the single-valve actuation pin 576. Initially, the downward moving actuation pin 576 lacks sufficient force to open the exhaust valve 31. With the actuation piston 562 in the piston extended position and the piston cavity 565 and the second connecting conduit 528 filled with the hydraulic fluid, the hydraulic fluid in the piston cavity 565 and the connecting conduit 528 acts on the reset ball-valve member 544 to hydraulically lock the reset check valve 543 in the closed position with the reset ball-valve member 544 retained on the reset check-valve seat 545 to prevent backflow.
The continued downward rotational movement of the distal end of the exhaust rocker arm 522 as the exhaust rocker arm 522 moves toward the upper base circle 7 causes the actuation piston 562 in its piston extended position to drive the single-valve actuation pin 576 downward and open the first exhaust valve 31 just prior to or at TDC of the compression stroke during the compression-release engine braking event. Due to the predetermined valve lash δ (
When the biasing force applied by the compressed reset pressure control spring 557 exceeds the force exerted by the decreasing hydraulic pressure above the reset ball-valve member 544 (the force exerted by the reset ball-valve check spring 546 is negligible), the upward force exerted by the potential energy in the compressed reset pressure control spring 557 drives the reset piston 554 and the upset pin 558 upward and thereby unseats the reset ball-valve member 544 from the reset check-valve seat 545, opening the reset check valve 543 at the beginning of the expansion stroke.
Referring back to
Maintaining the piston cavity 565 filled with the hydraulic fluid helps keep the single-valve actuation pin 576 in continuous/uninterrupted contact with both the actuation piston 562 and the exhaust valve 31, as well as continuous/uninterrupted contact between the exhaust cam lobe follower 21 and the exhaust cam 2. As a consequence, opening and closing of the exhaust valve 31 is not unintentionally delayed by unwanted lash, and engine brake performance is enhanced.
The description of
The compression-release engine brake system 512 of the fifth exemplary embodiment may provide various advantages, including reduced cost and enhanced performance compared to conventional lost motion rocker brakes.
The reset device 532 and/or the actuation piston 562 may be substituted into the embodiments described above. For example, the actuation piston 562 may replace the actuation piston 62 of the first exemplary embodiment.
The actuation piston 662 includes an accumulator 690 received in a lower pocket or bore 691 of the actuation piston body 663 below the one-way actuation piston check valve 680. The internal feed conduits 687 extend radially and perpendicularly to a longitudinal axis of the actuation piston body 663, rather than at the inclined angle of the feed conduits 587 of the fifth embodiment illustrated in
The accumulator 690 includes a spring-loaded accumulator piston 692, an accumulator charge pressure control spring 693, an accumulator plug 694, a variable volume accumulator cavity 695, an accumulator port 696, and protrusion(s) 697. The accumulator port 696 provides a fluid passageway between the internal feed conduits 687 and the accumulator cavity 695. The accumulator cavity 695 has a bottom defined by the upper surface of the accumulator piston 692. The accumulator piston 692 is received within and reciprocatingly slidable relative to the lower pocket 691 of the actuation piston 662 to vary the volume of the accumulator cavity 695. The radial outer edge of the accumulator piston 692 may provide a seal with an internal wall of actuation piston body 663 defining the lower pocket 691. The accumulator plug 694 is fixed to the bottom of the actuation piston body 663. The accumulator charge pressure control spring 693 sits on the accumulator plug 694 and has an upper end engaging the accumulator piston 692 from below to bias the accumulator piston 692 upward toward the accumulator port 696 and the actuation piston check valve 680. The top surface of the accumulator piston 692 may include one or more protrusions or a protruding ring 697 similar to rear extension 63b described above in connection with the first exemplary embodiment.
The actuation piston 662 of the sixth exemplary embodiment illustrated in
In operation, when hydraulic fluid is needed in the piston cavity 565, such as due to delayed filling of the piston cavity 565 through the connecting conduits 528 and 529, a pressure differential across the actuation piston ball-valve member 681 causes the hydraulic fluid to travel from the accumulator cavity 695 up through the accumulator port 696 and the actuation piston communication port 686 by opening the ball-valve member 681, as shown in
Advantageously, the closer proximity of the accumulator 690 to the piston cavity 565 allows hydraulic fluid to be charged to and returned from the piston cavity 565 more quickly than when the accumulator is located in the rocker shaft 20, thereby improving operation of the overall system.
The compression-release brake system 712 of the seventh exemplary embodiment includes an exhaust valve reset device 732 that is similar in construction and operation to the exhaust valve reset device 532 of the fifth embodiment.
The reset device 732 includes a substantially cylindrical, hollow cartridge body 734 with an attached swivelable foot (or “elephant foot”) 772. A reset trigger 750 and a reset piston 754 are received in and reciprocatingly slidable relative to cartridge body 734. The reset trigger 750 has a distal end 752 protruding through a bottom opening in the cartridge body 734. A reset trigger return spring 756 inside the cartridge body 734 biases the reset trigger 750 towards a trigger retracted position. A piston stroke limiting pin 755 connects the reset trigger 750 to the reset piston 754 while permitting relative movement there between. An upset pin 758 integrally formed with the reset piston 754 extends upward through an activation cavity 739 sitting above an annular flange portion 754f of the reset piston 754. A reset pressure control spring 757 inside the cartridge body 734 biases the reset piston 754 (and the upset pin 758) upward. The activation cavity 739 communicates with the connecting conduit 729 to receive hydraulic fluid to activate the reset device 732.
Above the upset pin 758, the reset device 732 also includes a reset check valve 743 embodied as including a reset ball-valve member 744 contained in a reset check-valve cavity 742 having a reset check-valve seat 745 defined by inner walls of the exhaust rocker arm 722. The reset ball-valve member 744 is movable relative to the reset check-valve seat 745 between an open position (shown in
The reset trigger 750 is axially slidable within and relative to the cartridge body 734 between a trigger retracted position and a trigger extended position. In the trigger retracted position shown in
It should be understood that the reset check valve 743 illustrated in this exemplary embodiment may be replaced with other suitable check valves, and that such modifications are within the scope of the invention.
The hydraulic circuit will now be discussed in greater detail. The various conduits of the hydraulic circuit may be positioned in locations other than those shown in the drawings.
The hydraulic circuit includes a supply conduit 726 (
The accumulator feed conduit 799 connects the supply conduit 726 with an annular groove 727 in an actuation piston body 763 of an actuation piston 762, which is identical in structure to the actuation piston 662 of the sixth exemplary embodiment illustrated in
The positive power operation (brake-off mode) of the IC engine of the seventh exemplary embodiment is similar to the brake-off mode operation described above in connection with the fifth exemplary embodiment and
During positive power operation, the reset trigger 750 is maintained in the trigger retracted position shown in
Operation of the seventh exemplary embodiment in the brake-on mode is similar to the operation shown in
The downward movement of the reset piston 754 lowers the upset pin 758 below the reset communication port 748 so that the reset ball-valve member 744, which is urged downward by the reset ball-valve check spring 746, can sit on the reset ball-check seat 745 to permit closure of the reset check valve 743. The reset check valve 743 closes after the hydraulic fluid has pressurized the piston cavity 765 to extend the actuation piston 762 into the piston extended position to retain contact with the actuation pin 776. The hydraulic fluid fed through the reset communication port 748 fills the connecting conduit 728 and the piston cavity 765 with the actuation piston 762 in the piston extended position. All valve train lash between the single-valve actuation pin 776 and the actuation piston 762, and the cam follower 21 and the lobe of the exhaust cam 2, is eliminated. In this closed position, the reset check valve 743 prevents the reverse flow of the hydraulic fluid from the piston cavity 765 through the reset communication port 748 back into the first connecting conduit 729 and the supply conduit 726.
At the same time, the hydraulic fluid travels from the accumulator cavity 795 up through the accumulator port 796 and the actuation piston communication port 786, overcoming the biasing force of the actuation piston biasing member 783 of the one-way actuation piston check valve 780, to the piston cavity 765, thereby supplementing the feed of hydraulic fluid to the piston cavity 765 and ensuring that the hydraulic circuit is filled with the hydraulic fluid prior to an engine braking event. The filling of the piston cavity 765 moves the actuation piston 762 into the piston extended position.
Next, the cam follower 21 of the driven end 22b (
As the exhaust rocker arm 722 continues toward the upper base circle 7 to move the exhaust rocker arm 522 farther downward towards the exhaust valve bridge 724, the reset trigger 750 continues its upward movement relative to the cartridge body 734 until the reset trigger 750 is in the trigger retracted position.
Upward movement of the reset piston 754 is prevented by the upset pin 758 contacting the bottom of the reset ball-valve member 744, which is hydraulically locked in the closed position by the high pressure in the second connecting conduit 728 and the piston cavity 765. As the reset trigger 750 moves upwardly relative to the reset piston 754, the slot 750s of the reset trigger 750 is guided by the piston stroke limiting pin 755 of the reset piston 754. The reset pressure control spring 757 compresses between the flange portion 750f of the reset trigger 750 and the flange portion of the reset piston 754, building potential energy in the reset pressure control spring 757.
The continued downward rotational movement of the distal end of the exhaust rocker arm 722 as the exhaust rocker arm 722 moves towards the upper base circle 7 causes the actuation piston 762 in its piston extended position to drive the single-valve actuation pin 776 downward and open the first exhaust valve 31 just prior to or at TDC of the compression stroke during the compression-release engine braking event. Due to the predetermined valve lash δ, the foot 772 does not press the exhaust valve bridge 724 downward, and consequently the bridge 724 remains stationary and the second exhaust valve 32 remains closed. The opening of the first exhaust valve 31 at or near TDC compression causes the engine cylinder pressure to rapidly drop, thereby relieving the upward force acting on the actuation piston 762 through the actuation pin 774, and decreasing the pressure in the piston cavity 765 and the second connecting conduit 728 connected to the piston cavity 765.
When the biasing force applied by the compressed reset pressure control spring 757 exceeds the force exerted by the decreasing hydraulic pressure above the reset ball-valve member 744 (the negligible force of the reset ball-valve check spring 746 may be ignored), the compressed reset pressure control spring 757 drives the reset piston 754 and the upset pin 758 upward and thereby unseats the reset ball-valve member 744 from the reset check-valve seat 745, opening the reset check valve 743 at or near the beginning of the expansion stroke.
A portion of the hydraulic fluid in the piston cavity 765 and the second connecting conduit 728 is released through the reset communication port 748 and the conduits 729 and 799 to the accumulator cavity 795, where the hydraulic fluid is stored for the next braking event. The release of the hydraulic fluid from the piston cavity 765 allows the actuation piston 762 to move into the piston retracted position as the closing force of the exhaust valve return spring 91 resets the exhaust valve 31 into the seated state by the end of the expansion stroke, that is, prior to the exhaust stroke. Because both exhaust valves 31 and 32 are seated before the exhaust stroke, the exhaust rocker arm 722 can act on the exhaust valve bridge 724 to simultaneously open the exhaust valves 31 and 32 in a balanced condition during the exhaust stroke.
The hydraulic fluid flow pathway through the actuation piston 762 assists in maintaining the hydraulic circuit, in particular the piston cavity 765 and the second connecting conduit 728, filled with hydraulic fluid at all times during brake-on mode (as well as during brake-off mode). When the piston cavity 765 or the second connecting conduit 728 is not completely filled via the hydraulic fluid flow pathway associated with the reset device 743, the hydraulic fluid may enter into the piston cavity 765 through the hydraulic fluid flow pathway associated with the actuation piston 762. The hydraulic fluid in the feed conduits 787 and below the ball-valve member 781 exerts an upward force that exceeds the combined downward force exerted by the actuation piston ball-valve check spring 783 and the hydraulic fluid in the piston cavity 765, which fluid acts on the ball-valve member 781 through the stopper passage 789, causing the ball-valve member 781 to unseat from the check-valve seat 782 and thereby open the communication port 786. The hydraulic fluid flows from the feed conduits 787, through the open communication port 786, the outlet conduits 788, and the stopper passage 789 into the piston cavity 765 to supplement the filling of the piston cavity 765. Filling the piston cavity 765 through the reset valve 780 can occur, for example, whenever hydraulic fluid is needed in the piston cavity 765, but is particularly likely to occur when the exhaust cam lobe follower 21 of the exhaust rocker arm 722 moves from upper base circle 7 down to lower base circle 5 of the exhaust cam 2.
The description of
The compression-release engine brake system 712 of the seventh exemplary embodiment may provide various advantages, including reduced cost and enhanced performance compared to conventional lost motion rocker brakes.
The embodiment of
The various components and features of the above-described embodiments may be substituted into one another in any combination. It is within the scope of the invention to make the modifications necessary or desirable to incorporate one or more components and features of any one embodiment into any other embodiment.
The foregoing description of the exemplary embodiments of the present invention has been presented for the purpose of illustration in accordance with the provisions of the Patent Statutes. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. The embodiments disclosed hereinabove were chosen in order to best illustrate the principles of the present invention and its practical application to thereby enable those of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated, as long as the principles described herein are followed. Thus, changes can be made in the above-described invention without departing from the intent and scope thereof. It is also intended that the scope of the present invention be defined by the claims appended thereto.
This application is a continuation of U.S. application Ser. No. 15/695,627, filed Sep. 5, 2017, now U.S. Pat. No. 9,885,263, which is a continuation of U.S. application Ser. No. 15/241,609, filed Aug. 19, 2016, now U.S. Pat. No. 9,752,471, which is a continuation-in-part of U.S. application Ser. No. 14/553,177, filed Nov. 25, 2014, now U.S. Pat. No. 9,429,051, which claims the benefit of U.S. Provisional Application No. 61/908,272 filed on Nov. 25, 2013 by V. Meneely and K. Price, and of U.S. Provisional Application No. 62/001,392 filed on May 21, 2014 by V. Meneely and R. Price, each of which are hereby incorporated herein by reference in their entireties and to which priority is claimed.
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| Child | 15241609 | US |
