Patent Application
20140023530
The invention relates to a multi-piston pump and more particularly to a multi-piston liquid propane injection pump for a vehicle.
In conventional diesel engines, it is known to inject liquid propane (LPG) into the fuel-air mixture in the fuel header or manifold of the engine. This is done to reduce emissions and increase performance of the vehicle. Typically, the vehicle would include an LPG tank and a pump which is in fluid communication with the LPG tank and pumps the LPG or other fluid into the engine manifold. In a known configuration, such a pump may be an in-tank, submersible turbine pump. However, such a configuration is known to have disadvantages associated therewith.
It therefore is an object of the invention to overcome disadvantages associated with the prior art.
The invention relates to a fuel supply system for a vehicle which uses an externally-mounted positive displacement pump to supply the LPG from the storage tank to the engine. More particularly, the invention relates to a multi-piston LPG injunction pump which is formed as a positive displacement pump for pumping the fluid from the storage tank to the engine intake manifold. In the preferred embodiment, the pump is provided in a dual piston configuration. The dual-piston pump is operated using the vehicle's pneumatic air system, wherein the pressurized air of this system alternatingly drives the two pistons of the dual-piston pump. The pump uses a common housing, with two piston bores in which the pistons are driven in a reciprocating manner. Each piston moves through a pumping stroke and a return stroke wherein the pistons move in opposite directions during their respective strokes. More specifically, as one piston moves through a pumping stroke, the opposite piston moves through a return stroke. The vehicle's air system is used to pressurize and drive the pistons through their pumping stroke, but is not used on the return stroke. Rather, to effect the return movement of the second piston, the pump of the invention provides barrier fluid chambers surrounding each of the pistons where each barrier fluid chamber is in fluid communication with the other. During a pumping stroke of one piston, a first barrier fluid chamber associated with the one piston decreases in volume as the piston displaces through its pumping stroke. This reduction in volume of the barrier chamber drives the barrier fluid out of the first barrier fluid chamber through a communication passage into the second barrier fluid chamber associated with the second piston. By driving the barrier fluid into this second chamber, this pressurizes the second chamber and effects the displacing movement of the second piston through its return stroke such that the barrier fluid chamber increases in volume through the movement of the second piston.
The multi-piston pump of the invention, therefore, does not require a mechanical linkage between the two pistons, and only uses a single air source that alternatingly and continuously pressurizes and drives one piston and then the other. Once the first piston is driven to the limit of its pumping stroke and the second piston has moved to the limit of its return stroke, the pressurized air that serves as the driving fluid is then turned off to the first piston and is turned on to supply driving fluid to the second piston. Thus, the single air supply will then drive the second piston through its pumping stroke wherein the function of the barrier fluid chambers causes the first piston to reverse and then move through its return stroke due to the transmission of the barrier fluid from the second barrier fluid chamber to the first barrier fluid chamber. The alternating operation of the pistons generates a continuous, uninterrupted flow of the LPG on the process fluid side of the pistons since one piston or the other is always moving through a pumping stroke.
In addition to serving as the motion-inducing force for one piston on its return stroke, the barrier fluid also serves additional functions. For example, the barrier fluid continuously lubricates the seals that are provided on the pistons which prevent leakage of the barrier fluid out of the barrier fluid chambers, as well as which seals prevent leakage of the higher pressure propane or drive air into the barrier chambers. This lubrication lengthens the life of the seals. Additionally, the barrier fluid impedes the leakage of propane past the seals and to the environment. Preferably, the invention includes leak detectors which detect the presence of the propane if it migrates into the barrier fluid or past the barrier fluid into an air discharge. Still further, this arrangement serves to dampen the tank pressure of the propane wherein the motion of the piston on its return stroke may pull a vacuum within the pumping chamber and wherein the pressure of the propane tank is offset by the barrier fluid and the restricted flow of the air being discharged on the near side of the piston moving through its return stroke.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.
Referring to
As to the vehicle 11, this vehicle 11 is powered by a conventional diesel engine 12, which includes a diesel engine intake 14 that may be constructed in the form of a fuel header or manifold. This engine intake 14 is supplied through one or more fuel injectors 15 wherein a representative one of such injectors 15 is illustrated in
More particularly, a conventional vehicle may also include a supply tank 18 which is mounted to a vehicle body and is pressurized so as to store the LPG or other fuel additive therein. To deliver the injection fluid to the injectors 15 and to the engine intake 14, an inventive injection pump 19 is additionally provided which preferably is an air-driven LPG injection pump that is pneumatically driven by the air supply system 20 of the vehicle 11 as will be described in greater detail hereinafter. Since the air supply system 20 is the driving means, the pump 19 avoids the use of electric motors and other mechanical means to drive the pump 19. It will be understood that the pump 19 could also be driven by other pressurized fluid sources such as an “under the hood” air compressor on the vehicle 11, a hydraulic fluid supply system or by mechanical means such as one or more linear actuators. The particular construction of the inventive pump 19 provides a low flow, high pressure pumping of the LPG or propane. Further, the pump 19 readily accommodates changes in environmental temperature which can vary the pressure or psi of the propane depending upon whether environmental conditions are hot or cold.
Generally, as to the piping system connected between the supply tank 18, injection pump 19 and engine intake 14, these components are piped together in fluid communication with each other to define the supply lines for the delivery of LPG or any other process or injection fluid from the supply tank 18 to the engine intake 14. The piping system 21 also includes various system controls to control the delivery of the injection fluid. More particularly, the supply tank 18 is connected to the injection pump 19 by a first supply line 22 that is connected upstream of the injection pump 19 and receives the LPG or other injection fluid therethrough. Specifically, the supply line 22 includes an upstream segment 22A, a downstream segment 22B and a system shutoff valve 23 which is connected therebetween to control the flow of LPG through the supply line 22. The system shutoff valve 23 is configured for automatic control through a first control line 26 that is operatively controlled by a PLC 27 (Programmable Logic Controller) which serves as a system controller for controlling the operation of the various mechanical components and the various system controls provided therein. The system controller 27 may take other forms, such as different types of electrical or mechanical system controllers, although most preferably, a computer-based controller is provided to generate the necessary electronic signals to drive the various controls, as will be described further herein.
The system shut-off valve 23 preferably is operated by a solenoid 30 which is operatively connected to an electronic control line 26 which serves as the output from the PLC system controller 27 for effecting system shutoff. When the valve 23 is in an open operative condition, the injection fluid is able to flow through the supply line 22 from the upstream supply tank to the process fluid side of the downstream injection pump 19. The injection pump 19, during operation thereof, preferably draws the injection fluid through the supply line 22 and then pumps the fluid through another downstream supply line 32, which connects the injection pump 19 to the engine intake 14. The downstream supply line 32 exits the process fluid side of the injection pump 19 and extends to the injectors 15, which injectors 15 restrict the fluid flow there through to inject the LPG injection fluid into the engine intake 14 as diagrammatically indicated by reference arrow 32A. The injectors 15 serve to constrict the fluid flow therethrough so that the injector flow 32A essentially is pressurized and sprayed into the engine intake in an appropriate condition for use by the diesel engine 12.
Preferably, the injection pump 19 pressurizes the injection fluid to generate a specific constant pressure, which pressure is used to supply the engine intake 14 which may be in the form of a fuel header or manifold. To optimize operation of the diesel engine 12, the specific constant pressure should be maintained by operation of the system and excessive process fluid pressures are undesirable. In order to accommodate the possibility of excessive pressures within the supply line 32, the piping system 21 further includes a return line 33, which is fluidly connected to the supply line 32 upstream of the injectors 15. The return line 33 connects to a pressure bypass valve 34, which is normally closed, but opens if a pressure limit is reached and exceeded. The pressure bypass valve 34 therefore is connected to an upstream segment 33A of the return line 33, as well as a downstream segment 33B, which thereby defines the pressure bypass line 33. If the pressure bypass valve 34 encounters pressure in the upstream segment 33A which exceeds the pressure limit, the pressure bypass valve 34 then opens in response to the excessive pressure to allow the injection fluid to flow through the downstream segment 33B back to the supply tank 18. As the injection fluid flows through the bypass segment 33B, this reduces and stabilizes the line pressure to the desired specific constant pressure that is to be developed within the engine intake 14. If the excessive pressure condition continues, the pressure bypass valve 34 would maintain an open condition to allow excessive pressure to be relieved through the bypass line 33B. Should the pressure drop below the preset pressure limit of the valve 34, the valve 34 is then able to close to allow pressure to build back up within the supply line 32 and be maintained at the specific constant pressure desired for the engine intake 14. The pressure bypass valve 34 may be mechanically adjusted to set the pressure limit, although it is also possible to control the bypass valve 34 through electronic connections and settings controlled by the system controller 27.
As an example, it will be noted that the injection pump 19 typically governs or dictates the outlet pressure in line 32 by the construction of the piston area and ratios thereof. As such, in the preferred design illustrated herein, the inlet air pressure supplied by the air system 20 would be preferably set at a desired constant pressure which would then govern the desired constant outlet pressure in line 32. However, in one potential scenario, the system may be turned off which might result in an increase in temperature within the line 32. This condition may cause expansion of the process fluid in line 32 which in turn causes the undesirable increase in line pressure, which pressure increase is preferably relieved by the bypass valve 34. It will also be understood that in some situations it may be desirable to eliminate the pressure bypass line 33 and the associated bypass valve 34.
Generally as to the injection pump 19, the pump operates to supply the injection fluid through the piping system 21. In order to operate the injection pump 19, the pump 19 is connected to and is operatively driven by the air supply system 20 of the vehicle 11. The air supply system 11 preferably is already provided on the vehicle 11 such that installation of the injection pump 19 does not require substantial changes to the vehicle systems.
The air supply system 20 illustrated in
Still further, the valve 43 connects to a discharge line 50 which passes through an air discharge restriction 51 to a discharge port 52 for discharging air to the environment. The air discharge system 51 serves to control the discharge of air from the pump 19 which also assists in controlling the rate of the return stroke of the pistons 68 and 69 as will be described further herein. When the control valve 43 is in the first operative condition, as diagrammatically shown in
Accordingly, the PLC 27 is able to control switching of the valve 43 between the first and second operative positions and thereby control operation of the injection pump 19 as will be described further hereinafter.
As will be understood in additional detail in the following discussion of
Turning next to
The pump 19 comprises an outer housing 60 that is preferably formed as an assembly which includes the housing body 61, a top or cover plate 62 and a bottom plate or valve body 63. Preferably, the outer housing is formed of cast iron or other structurally rigid material and has a mount 63A with fastener bores 63B for mounting the pump 19 to the vehicle frame. Internally of the housing body 61, the housing body 61 defines at least two piston bores 66 and 67 which each receive a respective, dual-area piston 68 and 69 therein. Generally, each of the pistons 68 and 69 move through a linear pumping stroke and return stroke wherein the pistons 68 and 69 move in opposite directions during their respective strokes. More particularly, as one piston 68, for example, moves through a downward pumping stroke, the opposite piston 69 moves upwardly through its respective return stroke. As will be described herein, the vehicle's air system 20 is used to pressurize and drive the pistons 68 and 69 through their respective pumping stoke, but is not used on the return stroke. Rather, as one such piston 68 or 69 is moving through its pumping stroke, the other, or second piston, is returned upwardly by a barrier fluid configuration which operatively drives the second piston through its return stroke. The configuration of the barrier fluid and air system also assists in dampening the return stroke of each piston 68 and 69 and counters the pressure of the propane tending to push the pistons 68 and 69, such that the barrier fluid and air discharge serve to control the rate of the return stroke. The barrier fluid configuration will be described in further detail hereinafter.
Referring to
As to the upper housing section 72, this housing section 72 also includes a pair of parallel piston bore sections 80 which open vertically from a top housing face 81 of the housing section 72. The bore sections 80 terminate at their bottom ends at the annular step-like housing shoulder 74. As such, the bore sections 80 have a greater diameter than the bore sections 73 to thereby define the annual shoulder 74 best shown in
Additionally, the housing body 61 is provided with an intermediate, balancing passage 93 that is formed so as to extend completely through an intermediate divider wall 94 that is defined between the piston bore sections 80 and 73. This balancing passage 93 extends horizontally or laterally through the divider wall 94 and has one end in open connection with the first piston bore 66 and the opposite open end in fluid communication with the piston bore 67 on the opposite side of the divider wall 94.
Referring to
During assembly, the pistons 68 and 69 are slidably fitted through the open upper end of the housing section 72 and then are captured within the housing 61 by the installation of the top plate 62 and bottom plate 63 as will be described further herein. It will be noted that the pump construction of
Referring to the piston 68, the piston 68 has a cylindrical shape, defined by a major piston face 95 and a minor piston face 96 wherein these faces 95 and 96 are differentiated by their respective diameters and respectively define the driven or air side of the piston 68 and the pumping or process side of the piston 68. The major piston face 95 has a larger diameter than the minor piston face 96 wherein the respective diameters are defined by a major cylinder surface 97 and the minor cylinder surface 98. The major cylinder surface 97 extends partially along the axial length of the piston 68 and abrupt steps or extends radially inwardly to the minor cylinder surface 98 to thereby define an annular step or shoulder 99. The differences in diameters results in an increase or amplification of pressure between the drive side of the pistons 68 and 69 and the pumping side of the pistons 68 and 69. For example, the pressurized air that drives the pistons 68 and 69 may be about 100 psi while the output pressure from the pump 19 through the discharge line 32 may be up to 178 psi, which is the feed pressure desired for feeding the injectors 15. In this manner, the outlet pressure from the pump 19 which defines the feed pressure can be governed or controlled by selectively defining the air input pressure. Additionally, the output pressure may also be designed through selectively constructing the pistons 68 and 69 and the ratio of the major piston face 95 to the minor piston face 96 of each piston 68 or 69. By selectively choosing the diameter ratio, or dimensional ratio between these piston faces 95 and 96, the ratio of the input pressure to the output pressure can be selectively designed into the pump 19. Secondarily, the outlet pressure of the pump 19 can be further adjusted by selectively choosing the input pressure of air that is used to drive the piston 68 and 69.
Next as to the barrier fluid configuration referenced above, the radial dimension of the piston shoulder 99 is proximate to the radial width of the housing shoulder 74 wherein the surfaces of the respective shoulders 74 and 99 are disposed in axially facing relation. The pistons 68 and 69 move axially relative to each other so that the piston shoulder 99 both moves toward the housing shoulder 74 and then moves away from such shoulder 74 during pump operation. As a result, the surfaces of the shoulders 74 and 99 define the axial boundaries of an annular barrier fluid chamber 101. More specifically, the barrier fluid chamber 101 extends annularly about the minor cylindrical surface 98 of each piston 68 and 69, and is thereby defined radially between the piston surface 98 and the opposing housing surface 102, and is defined axially between the housing shoulder 74 and the opposing piston shoulder 99. Due to the relative movement of these shoulders 74 and 99 toward and away from each other, the total volume of the barrier fluid chambers 101 varies, i.e. increases and decreases as the piston 68 and 69 reciprocate through their pumping and return strokes.
Each of these barrier fluid chambers 101 is in fluid communication with each other through the intermediate balancing passage 93 described previously and each of said chambers 101 includes a barrier fluid therein which fills the total volume of the two barrier fluid chambers 101 and the passage 93. The barrier fluid may be a suitable oil or other liquid or in some conditions might be supplied as a gas. Preferably, the barrier fluid is a liquid that is both non-compressible and has lubricating properties. The barrier fluid therefore lubricates the pistons and their piston bores 66 and 67, and serves as the hydraulic means for returning the pistons 68 or 69 to their retracted position at the end of the return stroke. The barrier fluid is supplied to these chambers 101 through the fill ports 90 and their associated plugs 91.
The barrier fluid is sealed within such chambers 101 by the provision of annular piston rings or seals 105 and 106 which prevent the barrier fluid from migrating along the major and minor cylindrical surfaces 97 and 98 of the pistons 68 and 69 and thereby leaking past the major and minor piston end faces 95 and 96. Preferably, the seals 105 and 106 are formed of any suitable material which will maintain contact with the interior surfaces of the piston bores 66 and 67. In the preferred embodiment, the seals 105 and 106 have a generally U-shaped cross-section which defines an annular grove or channel within the seals 105 and 106 which channels open axially towards the high pressure sides of the piston 68/69. More specifically, the channel of the seal 105 preferably would open actually upward (
Further, one advantage of the barrier fluid between the seals 105 and 106 is that the barrier fluid also acts to lubricate the seals 105 and 106 and increase the operating life thereof before the seals 105 and 16 undergo wear and any leakage occurs.
The barrier fluid chambers 101 generally are provided to cause automatic return of a non-driven piston 68 or 69 in response to driving movement of the other of the pistons 68 or 69. As will be described in further detail hereinafter, driving movement of one piston, such as piston 68 through its pumping stroke in the downward direction reduces the volume of the first barrier fluid chamber 101 and drives the barrier fluid out of this first chamber 101 through the passage 93 and into the other of the barrier fluid chambers 101. This other or second piston 69 is in a condition where it is no longer driven by the vehicle air system 20 and as such is able to freely move in the opposite direction through its return stroke. Hence, by reducing the volume of the first barrier fluid chamber 101 associated with the driven piston 68, the chamber volume decreases and drives the barrier fluid into the second chamber 101 of the other piston 69 which increases the pressure and thereby drives the second piston 69 upwardly through the return stroke. Hence, only one of the two pistons 68 and 69 needs to be driven by the air system 20, while the other piston is passively driven through its return stroke by the provision of the interconnected barrier fluid chambers 101 and balancing passage 93.
The volume of barrier fluid in the chambers 101 preferably has a fixed non-variable volume. The pressure of the barrier fluid is monitored in the control system of
In addition to the lubricating benefit provided by the barrier fluid, the barrier fluid also serves as an intermediate barrier to prevent leakage of the propane out of the system to the ambient environment. In this regard, if the propane were to leak past the seals 105 and 106, the propane could then escape through the discharge port 52. As an additional or redundant leak-detection mechanism, a propane sensor or detector may be included within the system to detect the presence of propane or other contaminants within the barrier fluid. For example, the fluid pressure line 58 may be provided with a sensor 108 (see
To effect driving of the pistons 68 and 69, the top plate 62 is provided with the air supply connections 46 and 48 which connect to the air supply lines 45 and 47 discussed above. These air supply connections 46 and 48 define air passages through the top plate 62 which permit the application of the pressurized air from the air system 20 selectively to either the piston bore 66 or alternatively, to the piston bore 67. The above-described control valve 43 controls the application of the pressurized air first to the piston bore 66, and then to the piston bore 67. When air is being supplied to one of such piston bores 66 or 67, the other piston bore 66 or 67 is open to environment to allow the air to vent or escape through the discharge line 50.
If desired, the respective piston 68 and 69 also may be provided with blind bores 115 to assist in movement of the pistons 68 and 69, as will be described further herein.
To control the time at which the valve 43 switches between the first and second operative conditions, the bottom housing plate 63 is provided with two proximity sensors 116-1 and 116-2 that have respective electrical sensor lines 117-1 and 117-2 (
While the proximity sensors are illustrated as a preferred embodiment for reversing the movement of the pistons 68/69, other sensing or control means may be used to reciprocate these pistons 68/69. One example, the PLC may simply control the solenoid 44 using a timing signal or circuit wherein the valve 43 may be switched between its operative conditions after preselected time periods which are calculated based upon the time that each piston 68/69 moves through their respective pumping and return strokes. Preferably, the time period as selected serves to limit or prevent bottoming out of the pistons 68/69 against the housing 60. Other methods may be used to determine the time or location at which the piston stroke should be reversed. For example, it also may be desirable to monitor the discharge pressure in line 32 which would indicate when the pump bottoms out wherein detection of a pressure drop in such line 32 would indicate that one-piston had reached the end of its pumping stroke.
As seen in
In this manner, the pistons 68 and 69 are hydraulically connected to each other and able to reciprocate simultaneously with each other without the need for any mechanical linkages therebetween. Further, the system only requires that one piston or the other piston be actively driven with the non-driven piston being automatically returned through its return stroke.
To further describe the pumping of the LPG or other fuel additive by the injection pump 19, the following discussion describes the pumping of this injection fluid during the reciprocating movement of the piston 68 and 69 described above.
Referring to
More particularly, these piston bores 66 and 67 respectively define at the bottom ends thereof piston chambers 124 and 125 that have variable volumes and are defined axially between the minor piston face 96 and the plate surface 127 of the bottom plate 63. Hence, as one of the pistons 68 and 69 is moving through a pumping stoke, such as piston 68, its respective check valve in inlet port 123-1 is closed. While the other piston 69 moves through its return stroke, this creates suction within the pumping chamber 125 to draw the fuel additive through the inlet passage 121 and through the open check valve in port 123-2. Hence, these check valves in ports 123-1 and 123-2 are normally closed under pressure, but open when a vacuum is formed in either of the pumping chambers 124 or 125. When encountering such vacuum, the upward movement of one piston or the other essentially refills the pumping chamber 124 and 125 with LPG process fluid until the pistons 68 and 69 switch or reverse their directions of movement.
The air discharge restriction 51, as described above, serves to throttle the exhausted air being discharged to the environment through the discharge port which throttling or restriction thereby provides control to the return stroke of the pistons 68 and 69. This reduces the pressure drop on the inlet side of the pump to insure that the liquid propane remains in the liquid state.
Referring to
Referring to
Another advantage of the above design relates to an improved ability to refurbish the pump 19. In this regard, the top plate 62 can be readily removed to allow for replacement of the seals 105 and 106 or the various gaskets 75 and 82. Also, the bottom plate 63 is similarly removable which allows for ready replacement of the sensors 116-1/116-2 and the valves in the inlet ports 123-1/123-2 and outlet ports 129-1/129-2.
Referring to
Most significantly, the system of
More particularly, the pump 19A has feed line connection 46A which allows for the flow of air into and out of the piston bore. This connection 46A connects to feed line 45A that connects to a valve 43A. The feed line 45A is operatively connected to the discharge line 50 when the valve 43A is in the first operative position shown, and connects to the air supply line 42 when the valve 43A is in the second operative position after switching by the PLC-controlled solenoid 44. When the feed line 45A is connected to the air supply line 42, the pump 19A has its piston move through the pumping stroke as described above, and when connected to the discharge line 50, the pump 19A discharges air to the discharge port 52.
The supply tank 18 connects to the pump 19A at the inlet port 123-1A and the propane is pumped out of the pump 19A through the outlet port 129-1A. The inlet port 123-1A and outlet port 129-1A are controlled by the check valves previously described above, and where desired a proximity sensor or other similar sensor may also be provided to control switching of the valve 43A
The pump 19A further has a barrier fluid chamber constructed the same as that described above, which chamber connects to the barrier fluid pressure line 58 through the outlet port 57A. Since the pump 19A has the barrier fluid chamber sealed by the gaskets 105A and 106A in the same manner as described above, the barrier fluid serves the same functions of lubricating the seals 105A and 106A of the pump 19A, and the air discharge restrictor 51 throttles or controls the discharge of air through connector 46A and thereby controls the return stroke of the piston 66A.
The barrier fluid also serves the same function of resisting leakage of propane since it defines a fluid barrier intermediate or between the propane side and the air side of the piston 66A, which air side discharges to atmosphere. The system of
The most significant difference results from the elimination of the second piston which would be used to effect the return stroke of the first piston. In the single-piston design, the return of the piston 66A is effected by the pressure of the barrier fluid and/or the propane or other fluid being pumped. In this regard, the propane would have a fluid pressure that would tend to drive the piston 66A through the return stroke when the drive pressure was deactivated such as by depressurization. Additionally, the system of
Since the pump 19A would cycle through the pumping stroke which would discharge pressurized propane through the outlet port 129 and then through its return stroke which would not effect pumping of propane, the system of
In this embodiment, a single piston pump is provided which still possesses many of the advantages of the buffer fluid that are found in the multi-piston design.
Referring to
The injection pump 19B is formed as a dual-piston pump that functions as a positive displacement pump and is described herein separate from the remaining system components of
In this pump 19B, the barrier fluid configuration is provided similar to that described above. In this regard, the housing body 61B is provided with an annular step 74B, and includes at least one intermediate, balancing passage 93B that is formed so as to extend axially along the housing wall 94B between the piston bores 66B and 67B. The illustrated embodiment uses two balancing passages 93B located on diametrically opposite sides of the housing 60B. Each balancing passage 93B has one end in open connection with the first piston bore 66B and the opposite open end in fluid communication with the piston bore 67B.
Referring to the pistons 68B and 69B, the pistons 68B and 69B have a cylindrical shape, each defined by a major piston face 95B and a minor piston face 96B wherein these faces 95B and 96B are differentiated by their respective diameters and respectively define the mechanically driven side of the pistons 68B and 69B and the pumping or process side of the pistons 68B and 69B. The pistons 68B and 69B have a step along the length to thereby define an annular step or shoulder 99B which is disposed in axially opposing relation with the respective housing shoulder 74B.
Next as to the barrier fluid configuration, the pistons 68B and 69B move axially relative to each other so that the piston shoulder 99B both moves toward the housing shoulder 74B in the pumping stroke and then moves away from such shoulder 74B in the return stroke. As a result, the surfaces of the shoulders 74B and 99B define the axial boundaries of an annular barrier fluid chamber 101B. More specifically, the barrier fluid chamber 101B is defined radially between the pistons 68B and 69B and the opposing housing wall 94B, and is defined axially between the housing shoulder 74B and the opposing piston shoulder 99B. Due to the relative movement of these shoulders 74B and 99B toward and away from each other, the total volume of the barrier fluid chambers 101B varies, i.e. increases and decreases as the pistons 68B and 69B reciprocate through their pumping and return strokes.
Each of these barrier fluid chambers 101B is in fluid communication with each other through the intermediate balancing passage 93B described previously and each of said chambers 101B includes a barrier fluid therein which fills the total volume of the two barrier fluid chambers 101B and the passage 93B. As described previously, the barrier fluid may be a suitable oil or other liquid or in some conditions might be supplied as a gas. Preferably, the barrier fluid is a liquid that is both non-compressible and has lubricating properties. The barrier fluid therefore lubricates the pistons 68B and 69B and their piston bores 66B and 67B, and serves as a barrier to the leakage of propane process fluid.
The barrier fluid is sealed within such chambers 101B by the provision of annular piston rings or seals 105B and 106B which prevent the barrier fluid from migrating along the pistons 68B and 69B and thereby leaking past the major and minor piston end faces 95B and 96B. One advantage of the barrier fluid between the seals 105B and 106B is that the barrier fluid also acts to lubricate the seals 105B and 106B and increase the operating life thereof before any leakage occurs.
During operation, the driving movement of one piston, such as piston 68B through its pumping stroke in the leftward direction reduces the volume of the first barrier fluid chamber 101B and drives the barrier fluid out of this first chamber 101B through the passage 93B and into the other of the barrier fluid chambers 101B surrounding piston 69B. In this embodiment, the pistons 68B and 69B are mechanically interconnected by the shaft 153 and are driven in unison by the motor drive 152.
Like the prior embodiments, the volume of barrier fluid in the chambers 101B preferably has a fixed non-variable volume, and the pressure of the barrier fluid can be monitored in the control system of
To effect driving of the pistons 68B and 69B, the actuator 151 is controlled by the PLC 27 to reciprocate the drive screw 153 in opposite axial direction. To control the time at which the actuator 151 switches the direction of shaft movement, the end housing plate 63B is provided with two proximity sensors 116-1B and 116-2B that have respective electrical sensor lines which connect to the PLC 27 previously shown in
Pumping of the process fluid is accomplished through the reciprocating movement of the pistons 68B and 69B. In this regard, the housing wall 94B further is provided with an elongated inlet passage 121B which connects to the supply line 22 (
More particularly, these piston bores 66B and 67B respectively define at the bottom ends thereof piston chambers 124B and 125B that have variable volumes and are defined axially between the minor piston face 96B and the end plate 63B. Hence, as one of the pistons 68B and 69B is moving through a pumping stoke, such as piston 68B, its respective check valve in inlet port 158 is closed. While the other piston 69B moves through its return stroke, this creates suction within the pumping chamber 125B to draw the fuel additive through the inlet passage 121B and through the open check valve 158. Hence, these check valves 158 are normally closed under pressure, but open when a vacuum is formed in either of the pumping chambers 124B or 125B. When encountering such vacuum, the upward movement of one piston or the other essentially refills the pumping chamber 124B and 125B with LPG process fluid until the pistons 68B and 69B switch or reverse their directions of movement.
The housing wall 94B also includes the outlet passage 122B that communicates with the pumping chambers 124B and 125B through respective outlet ports 159 which ports are controlled by check valves. The check valves of these outlet ports 159 operate opposite to the above described check valves in that the check valves in ports 159 are normally closed when a vacuum is applied thereto to prevent in-flow, but open in response to pressure within the pumping chambers 124B and 125B to permit out-flow. In this configuration, the reciprocating movement of the piston 68B and 69B effect simultaneous refilling and pumping through the respective inlet passage 121B and outlet passage 122B. This therefore provides a continuous pressure of propane fuel additive being supplied through the supply line 32 to the engine intake 14.
In view of the foregoing, the embodiment of
Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.
This application asserts priority from provisional application 61/583,430, filed on Jan. 5, 2012 which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61583430 | Jan 2012 | US |
