Patent Application
20090158728
1. Field Of The Invention
The present invention relates to hydraulic valve systems used, for example, in off-road earth moving, construction, and forestry equipment, such as rough terrain forklifts (also known as telehandlers), earth movers, backhoes, articulated booms, and the like. Hydraulic valve systems are utilized, for example, to cause pistons to lower, lift, extend, retract, lock, unlock, or angle a fork in a telehandler. The present invention relates to an improved design for such hydraulic valve systems.
2. Brief Description Of The Related Art
Prior art hydraulic valve systems include the open center hydraulic valve system 110 illustrated in
While variations in the basic design of such a prior art open center hydraulic valve system 110 exist, the fundamental components and operation of such a system are briefly described below.
The prior art open center hydraulic valve system 110 of
The valve 114, in turn, may include one or more spools 118, with each spool 118 being activated by spool actuators 120. The spool actuators 120 may be activated by an equipment operator using a number of known means, such as mechanically (for example, using a lever), electrically (for example, using a solenoid receiving an electrical signal from a switch, a joystick, a computer, or other means), electro-hydraulically, hydraulically, pneumatically, or otherwise. In the example illustrated in
In order to more understandably illustrate the operation of a spool 118 to selectively interconnect hydraulic pathways within a valve 114, a simplified drawing illustrating how a spool 118 of a simple prior art constant flow open center valve 114 is capable of redirecting the constant flow of hydraulic fluid is provided in
In each of the blocks of the valve 114 illustrated in
Referring once again to the prior art open center hydraulic valve system 110 illustrated in
Referring again to
The valve 114 includes several hydraulic fluid pathways that may be selectively interconnected by activation of the spool 118, including an open center core 130, a power core 138, and a tank galley 132. The fixed displacement pump 116 pumps hydraulic fluid (at a constant flow rate for a given speed of the motor 150) from the hydraulic fluid tank 112 into the open center core 130. The tank galley 132 returns hydraulic fluid to the hydraulic fluid tank 112, where it is available to be re-pumped. The valve 114 also includes a hydraulic connection between the open center core 130 and the power core 138, namely, an open center/power core passage 140, upstream of the spools 118. (As commonly used, and as used herein, “upstream” shall mean in the direction towards a pump, “downstream” shall mean in the direction away from a pump). Typically, the valve 114 may also include smaller internal valves utilized to prevent, for example, overpressure or incorrect flow direction in the system, such as relief valves 142, or load drop check valves 144, which are not material to the explanation of the prior art or the invention.
The prior art open center hydraulic valve system 110 is typically housed in a standard manifold (not illustrated) attached to the equipment in which the open center hydraulic valve system 110 is being used. The fixed displacement pump 116 is typically driven by a motor 150, powered by a source such as by a power take-off (not illustrated), which, in turn, may be is directly mounted to a transmission (not illustrated), which, in turn, may be connected to the prime mover of the equipment in which the prior art open center hydraulic valve system 110 is being used.
The operation of the spools 118 in the valve 114 to direct hydraulic fluid flow to and to permit fluid flow from associated hydraulic ports 122 and 124 to cause, for example, a piston 128 to move within a cylinder 126 and thereby cause movement of a functional aspect of the equipment on which the open center hydraulic valve 110 is mounted is well-known to skilled practitioners, and can be ascertained by skilled practitioners by reference solely to the schematic diagrams found in
As can be seen in
Once again referencing
Thus, the net effect is that hydraulic fluid under pressure flows into the cylinder 126 associated with the activated spool 118 on the first side of the piston 128, and hydraulic fluid flows out of the cylinder 126 on the second side of the piston 128. This causes the piston 128 and any associated load to move toward the second side of the piston 128 associated with the activated spool 118 and the function to change (for example, in the case where the activated spool 118 is in block D associated with the fork lifting function, it would cause the fork to, e.g., rise). Any hydraulic fluid unused by the activated spool 118 flows through the restriction in that spool 118 via the open center core 130 to be either utilized by remaining downstream spools 118, or to then flow through the tank galley 132 to the hydraulic fluid tank 112.
On the other hand, if, as illustrated in
Thus, hydraulic fluid under pressure is introduced to the cylinder 126 on a second side of the piston 128, and hydraulic fluid is drained from the cylinder 126 on a first side of the piston 128. This causes the piston 128 to move toward the first side of the piston 128 and the equipment function to change (for example, in the case where the activated spool 118 is in block D associated with the fork lifting function, it would cause the fork to, e.g., lower). Once again, any hydraulic fluid unused by the activated spool 118 would flow through the restriction in the spool 118 via the open center core 130 to be either utilized by remaining downstream spools 118, or to then flow through the tank galley 132 to the hydraulic fluid tank 112.
A skilled artisan would recognize, of course, that this activation of spools 118 in the valve 114 can be utilized to operate a number of different equipment functions having moving components, and would not be limited to fork lifting (or to telehandlers).
Further details of the operation of the prior art open center hydraulic valve system 110 illustrated in
Because the pump for the prior art open center hydraulic valve system 110 is a fixed displacement pump 116, the flow of the hydraulic fluid supplied by the fixed displacement pump 116 is constant for a given speed for the motor 150 on the equipment in which the prior art open center hydraulic valve system 110 is mounted.
When the activators such as the electro-hydraulic valves 180 and the joystick 182 associated with the spool actuators 120 for the valve 114 in the prior art open center hydraulic valve system 110 are in the neutral position, all of the associated spools 118 are likewise in the neutral position. As illustrated in
When one of the functions associated with the prior art open center hydraulic valve system 110 is desired to be activated, the spool actuator 120 associated with that function is activated by an equipment operator using an activator such as an electro-hydraulic valve 180 or a joystick 182 in order to move the associated spool 118 (upwards or downwards, or from side to side, as shown in the schematics in
Assuming that the hydraulic port 122 associated with activated spool 118 is connected to the associated cylinder 126 on a first side of piston 128, and associated hydraulic port 124 is connected to that cylinder 126 on the second side of piston 128, and referring to
Conversely, if the chosen spool actuator 120 is activated with the intention of causing the piston 128 to move to a second non-neutral position (and to thereby, in the example of the spool 118 associated with block D, cause a fork to lower), then not only does the activated spool 118 cause the open center core 130 to be restricted to cause an increase in fluid pressure in the open center core 130 upstream of activated spool 118 to be hydraulically transmitted to the power core 138 via open center/power core passage 140, but also the activated spool 118 opens a hydraulic passage in the valve 114 between the associated hydraulic port 124 (hydraulically connected to cylinder 126 at a second side of the piston 128) and the power core 138 (having pressurized hydraulic fluid). Simultaneously, the activated spool 118 opens a passage in valve 114 between associated hydraulic port 122 (hydraulically connected to cylinder 126 on a first side of the piston 128), and the tank galley 132, allowing hydraulic fluid to flow out of the cylinder 126 from the first side of the piston 128 to the tank galley 132 and the hydraulic fluid tank 112. The result is that hydraulic fluid under pressure from the power core 138 begins filling the cylinder 126 on the second side, e.g., above, and hydraulic fluid begins leaving the cylinder 126 on the first side, e.g., below, thereby causing the associated piston 128 (and, in the above example, the attached fork and its associated load) to lower.
When the open center hydraulic valve system 110 is used to operate a function on the equipment on which it is mounted, hydraulic pressure must be built up in the open center core 130 (which, as previously discussed, is then communicated via the open center/power core passage 140 to the power core 138, and then to one of the two hydraulic ports 122 or 124 associated with that function) sufficient to match the load for the function. In the example described above of an open center hydraulic valve system 110 used on a telehandler, with the raising or lowering of the fork lift function being associated with the spool 118 of block D of valve 114, for instance, the hydraulic pressure developed in the open center core 130, which is then delivered to the selected one of the two hydraulic ports 122 or 124 associated with block D must be sufficient to move associated piston 128, the fork attached to the piston 128, and the load on the fork, all under precise operator control. This is accomplished by the operator manipulating the activators (in the example discussed above for block D of valve 114 for raising or lowering the fork, the relevant activator would be movement of the two-axis joystick 182 in the horizontal direction as illustrated in
In the example previously discussed, where the operator was operating a joystick 182 to activate the raising of the fork function associated with block D of valve 114, the operator would cause the activated spool 118 to move to a first non-neutral position which would restrict the flow of hydraulic fluid to the point that sufficient hydraulic fluid pressure has been built up in the power core 138 and delivered to hydraulic port 122 (while at the same time allowing hydraulic fluid to drain from hydraulic port 124 to the tank galley 132 and then to the hydraulic fluid tank 112)—that is, sufficient hydraulic pressure would be generated to raise associated piston 128, the attached fork, and any associated load on that fork. Unless and until the operator had caused sufficient hydraulic pressure to be generated by the flow restriction caused by the activated spool 118, the fork and any associated load would not, of course, be raised. Stated another way, when any of the functions associated with valve 114 are operated, hydraulic pressure must be built up in the power core 138 to match the load associated with the chosen functions.
During the operation of the chosen functions, the operator often requires quick movements and fine control. In addition, the operator often executes more than one function associated with the valve 114 simultaneously. Furthermore, different functions and different movements associated with a function require different hydraulic pressures. In the example discussed above for the valve 114 associated with a telehandler, for instance, the fork lifting and fork extension functions (blocks D and E) require considerably more hydraulic pressure than the fork angle and fork lock functions (blocks B and C). Additionally, different movements of functions require more hydraulic pressure than others. For instance, raising the fork with a load requires more hydraulic pressure than lowering the fork with a load. Moreover, even similar movements of the same function may require different hydraulic pressures depending upon different conditions. For example, raising the fork may require more or less hydraulic pressure depending upon the fork position or weight of the load being raised.
As discussed above, operation of the fork angle and fork lock (blocks B and C,
In practice, during the operation of equipment commonly utilizing valve 114, such as the telehandler example discussed above, the operator of the equipment will activate several functions simultaneously. In the example of the telehandler, the fork lifting and fork extension functions (blocks D and E of
In order to overcome the issues discussed above with respect to the open center hydraulic valve system 110, and to establish better equipment controllability, load sensing anti-saturation systems have been used. Such a system, however, is much more complicated and much more costly, because it requires the introduction of a variable displacement pump and flow/pressure compensators. Consequently, this potential alternative has been largely deemed unacceptable as being more difficult to maintain and somewhat cost prohibitive.
The present invention, known as a smart flow sharing system, overcomes the problems associated with both the prior art open center hydraulic valve system 110 and the potential alternatives that have been considered and largely rejected in many applications (for example, the load sensing anti-saturation system). The smart flow sharing system provides a relatively uncomplicated and cost-effective alternative hydraulic system that achieves superior controllability for the operator of the equipment on which it is installed.
In view of the foregoing, it is an object of the embodiments of the invention herein to provide a hydraulic valve system, called a smart flow sharing system, that overcomes the shortcomings of prior art open center hydraulic valve systems.
It is another object of the embodiments of the smart flow sharing system invention described herein to provide a hydraulic system capable of hydraulically operating the functions of heavy off-road equipment, such as earth moving, construction, and forestry equipment, including telehandlers, in a manner wherein hydraulic fluid flow is prioritized for the more hydraulically demanding functions of the equipment.
It is yet another object of the embodiments of the smart flow sharing system invention described herein to achieve precise control and fast equipment speed in activated hydraulic functions, regardless of whether the activated functions are among the more hydraulically demanding functions or among the less hydraulically demanding functions, and regardless of whether more than one of the more hydraulically demanding functions are activated at the same time.
Still another object of the embodiments of the smart flow sharing system invention described herein is to achieve the above objects without the addition of complex and difficult to maintain components, without the addition of expensive additional components or systems, and in a manner that is not cost-prohibitive, but rather in a manner that is cost-efficient.
The disclosed embodiments of the present smart flow sharing system invention achieve the aforementioned objects and others because they include features and combinations not found in prior art open center hydraulic valve systems or their known alternatives.
In the described embodiments of the present invention, an improved hydraulic valve system, called a smart flow sharing system, is provided, wherein hydraulic fluid flow under pressure is provided on an automatically prioritized basis to the more demanding hydraulic functions. This prioritization is accomplished without the addition of complex components or expensive extra equipment. Instead, the smart flow sharing system provides a uniquely designed hydraulic system using more than one (preferably two) fixed displacement pumps rather than one, combined with an additional spool, which directs hydraulic fluid flow/pressure in a manner such that if more than one of the more demanding hydraulic functions are simultaneously activated, then one of those more demanding hydraulic functions receives, separately, the hydraulic fluid flow output from the first fixed displacement pump, and the other demanding hydraulic function receives the separate hydraulic fluid flow output from the second fixed displacement pump. On the other hand, if only one of the two more demanding hydraulic functions is activated, then that hydraulic function receives the hydraulic fluid flow output from both the first and second fixed displacement pumps.
As a result, the shortcomings of the prior art are overcome. The provision of hydraulic fluid flow from two fixed displacement pumps to a single demanding hydraulic function results in more precise controllability and quicker equipment speed, permitting even less experienced equipment operators to achieve superior performance. On the other hand, when the two most demanding hydraulic functions are activated at the same time, the automatic prioritization of hydraulic fluid flow so that each of the two demanding hydraulic functions automatically receives hydraulic fluid output from its own separate dedicated fixed displacement pump eliminates complicated and meticulous metering of hydraulic fluid flow, once again enabling even inexperienced operators to achieve fast equipment movement and precise control of the equipment. Furthermore, the smart flow sharing system accomplishes this result without resorting to complex, difficult to maintain hydraulic systems or expensive additional components. The result is a cost-effective and maintenance friendly hydraulic system that is superior to prior art options.
These and other features, objects, and advantages will be understood or apparent to skilled practitioners from the following detailed description and the various drawing figures herein.
An embodiment of the smart flow sharing system 210 of the present invention is illustrated schematically in
Referring to
The smart flow sharing system 210 of the present invention may be housed in a standard manifold (not illustrated) attached to the equipment (e.g., such as a telehandler or other off-road construction, earth moving, or forestry equipment--not illustrated) in which the smart flow sharing system 210 is being used. The first and second fixed displacement pumps 216 and 217 may be driven by a motor 250, powered by a power take-off (not illustrated), which, in turn, is mounted to a transmission (not illustrated) connected to the prime mover of the equipment.
Each spool 218 of the smart flow sharing system 210 in
In order to prevent undue repetition, to serve the function of brevity, and to avoid belaboring what is known to skilled practitioners in the art, referring to
Referring once again to
Referring to
Importantly, the first power core 238 of the smart flow sharing system 210 (see
As illustrated in
A first open center/power core passage 240 hydraulically connects the open center core 230 with the first power core 238 upstream of the first upstream spool 218 (e.g., see block B) associated with the first power core 238. If one or more of the spools 218 associated with the first power core 238 (e.g., blocks B, C, and D in
At the same time, and in the same manner discussed previously for activated spools 118, the activated spools 218 open one of the two associated hydraulic ports 222 or 224 to receive the pressurized hydraulic fluid from the first power core 238, and open the other of the two associated hydraulic ports 222 or 224 to hydraulically connect via the tank galley 232 to the hydraulic fluid tank 212. Because the hydraulic ports 222 and 224 are connected to an associated cylinder 226 on either side of the associated piston 228, pressurized hydraulic fluid enters the associated cylinder 226 on one side of the piston 228, and drains out of the cylinder 226 on the other side of the piston 228, causing the piston 228 to move toward the side of the cylinder 226 where hydraulic fluid is draining, and the associated hydraulic function to occur.
Downstream of the spools 218 associated with the first power core 238 are one or more spools 218 associated with a second power core 237. Second power core 237 is separated from first power core 238. A second open center/power core passage 241 is separated from both open center core 230 and second power core passage 237, upstream of any spools 218 associated with the second power core 237, and downstream of any spools 218 associated with first power core 238.
Second fixed displacement pump 217 pumps hydraulic fluid from hydraulic fluid tank 212 through second pump passage 231, which is hydraulically connected to the open center core 230 downstream of the spools 218 associated with the first power core 238, and upstream of any spools 218 associated with the second power core 237. Preferably and advantageously, second pump passage 231 may be hydraulically connected to open center core 230 by hydraulically connecting second pump passage 231 to second open center/power core passage 241.
If one or more spools 218 associated with second power core 237 (preferably, one such spool 218, as illustrated, in block F of
Once again, the activated spool 218 (in the embodiment illustrated in
Further downstream of the spools 218 associated with the first and second power cores 238 and 237 are one or more spools 218 (preferably one spool 218) associated with a third power core 239. Third power core 239 is separate from either the first or second power cores 238 or 237. A third open center/power core passage 243 hydraulically connects the third power core 239 and the open center core 230 upstream of any spools 218 associated with third power core 239, and downstream of any spools 218 associated with first power core 238 or second power core 237.
If one or more spools 218 associated with third power core 239 is activated (in the embodiment depicted in
As previously discussed, an operator's activation of the joystick 282 in order to activate the spool 218 in block G simultaneously activates the spool 218 in block B, because the actuators 220 for both spools 218 (blocks B and G) have a common activator (the vertical movement of the two-axis joystick 282 in the illustrated embodiment in
Upon activation of spools 218 in blocks B and G, the spool 218 in block G restricts the open core passage 230 passing through that activated spool 218. Because the hydraulic fluid flow is pumped at a constant rate (for a given speed of motor 250) by the first fixed displacement pump 216 and the second displacement pump 217 through open center core 230 upstream of spool 218 in block G, the restriction caused by spool 218 in block G (of any unused hydraulic fluid from the first and second fixed displacement pumps 216 and 217) causes hydraulic pressure upstream of that activated spool 218 (in block G) to rise. The increased hydraulic pressure is hydraulically communicated through third open center/power core 243 to third power core 239. The activated spool 218 (in block G) at the same time opens one of the two associated hydraulic ports 222 or 224 to receive pressurized hydraulic fluid from the third power core 239, while the other of two associated hydraulic ports 222 or 224 is connected by the spool 218 to the tank galley 232.
Because the spool 218 in block B is simultaneously activated when the spool 218 in block G is activated, that spool 218 also restricts the open center core 230 (which at that location is receiving hydraulic fluid flow from the first fixed displacement pump 216 only), and, as discussed previously, activated spool 218 (in block B) provides pressurized hydraulic fluid to the same selected one of hydraulic ports 222 or 224 in block G as does spool 218 in block G.
Consequently, spool 218 in block B causes pressurized hydraulic fluid provided by the first fixed displacement pump 216, and spool 218 in block G causes pressurized hydraulic fluid provided by the second fixed displacement pump 217, both to be transmitted to the selected one of the two hydraulic ports 222 or 224 in block G. Thus, the fork extension function has the benefit of using hydraulic flow from both the first and second fixed displacement pumps 216 and 217 when the fork lift function (block F) is not simultaneously in operation (in which case the spool 218 associated with the fork lift function in block F would be activated, thereby restricting the hydraulic fluid flow of the second fixed displacement pump 217 through open center core 230 to block G).
The smart flow sharing system 210 described above, has distinct advantages versus prior art systems, such as the open center hydraulic valve system 110 described previously. As discussed above, the open center hydraulic valve system 110 suffers from performance issues, in particular, controllability problems, when more than one of the more hydraulically demanding functions (such as the fork lift and fork extension functions in the example of a telehandler) are operated at the same time, as frequently happens. The smart flow sharing system 210 described herein overcomes such problems without adding significantly costly components, and without greatly adding to the complexity and maintainability of the hydraulic system.
The smart flow sharing system 210 invention adds, among other features, a second fixed displacement pump 217, and a spool 218 (in block B), relatively inexpensive components, in order aid in overcoming the problems associated with the standard prior art open center hydraulic valve system 110. In addition, the invention described herein provides an improved system of routing and automatically prioritizing hydraulic fluid flow that facilitates the operation of more than one demanding hydraulic functions simultaneously.
The additional second fixed displacement pump 217, together with the improved system of routing hydraulic fluid flow, combine to prioritize fluid flow simultaneously to the more demanding hydraulic functions so that none of the more demanding hydraulic functions uses an amount of hydraulic fluid flow to the detriment of the remaining demanding hydraulic functions.
In the embodiment described herein, for instance, ignoring for purposes of this discussion the hydraulic fluid flow used by less demanding hydraulic functions (such as the brake system 288, the steering system 284, the fork angle adjustment (block C), and the fork lock (block D) functions, which even when in use utilize relatively little hydraulic fluid flow compared to the fork lift (block F) and fork extension (block G) functions), the smart flow sharing system 210 automatically prioritizes the hydraulic fluid flow output of the first and second fixed displacement pumps 216 and 217 as described below.
(1) Fork Lift Activated, But Fork Extension Not Activated. When the fork lift function (block F in the embodiment in
Depending on how many, if any, of the less demanding upstream hydraulic functions (blocks C and D) are activated, first fixed displacement pump 216 provides most or substantially all of its hydraulic fluid flow through open center core 230 to spool 218 in block F. The second fixed displacement pump 217 provides substantially all of its hydraulic fluid flow through second pump passage 231 (through second open center/power core passage 241 and then through open center core 230) to spool 218 in block F. Because spool 218 in block F is activated, it restricts the open center core 230. This causes the hydraulic fluid flow supplied by both the first and second fixed displacement pumps 216 and 217 to increase in pressure upstream of the activated spool 218 in block F. That increase in hydraulic fluid pressure caused by the restriction of the flow of both the first and second fixed displacement pumps 216 and 217 is communicated through the second open center/power core passage 241 to the second power core 237, where it is thereafter transmitted through the activated spool 218 in block F to the selected one of the two associated hydraulic ports 222 or 224, and then the cylinder 226 and piston 228 in block F to perform the selected hydraulic function, in this case, lifting or lowering of the fork. Thus, the hydraulic fluid output of both the first and second fixed displacement pumps 216 and 217 is available for the fork lift function.
(2) Fork Extension Activated, But Fork Lift Not Activated. When the fork extension function (blocks B and G in the embodiment in
That is, activation of spool 218 in block B restricts hydraulic fluid flow from first fixed displacement pump 216 through the open center core 230, causing an increase in hydraulic fluid pressure upstream of that activated spool 218. That increased hydraulic fluid pressure is communicated through first open center/power core passage 240 to first power core 238, where it is directed by the activated spool 218 to the selected one of the two hydraulic fluid ports 222 or 224 and then to the cylinder 226 and piston 228 associated with the fork extension function (block G).
At the same time, substantially the entire hydraulic fluid flow from second fixed displacement pump 217 flows through second pump passage 231 through second open center/power core passage 241 into open center core 230. Because spool 218 associated with the fork lift function (block F) is not activated, the hydraulic fluid flow output of second fixed displacement pump 217 flows through open center core 230 to the activated spool 218 associated with the fork extension function (block G). That activated spool 218 restricts the hydraulic fluid flow through open center core 230, causing an increase in hydraulic pressure upstream of the activated spool 218 in block G. That increased hydraulic fluid pressure is then communicated to third power core 239, where it is directed by the activated spool 218 to the selected one of the two hydraulic fluid ports 222 or 224 (the same hydraulic port to which pressurized hydraulic fluid was directed by spool 218 in block B) and then to the cylinder 226 and piston 228 associated with the fork extension function (block G). Consequently, the hydraulic fluid output of both the first and second fixed displacement pumps 216 and 217 is available for the fork extension function.
(3) Fork Lift Activated And Fork Extension Also Activated. When both of the most demanding hydraulic functions in the described embodiment, namely, both the fork lift function (block F in the embodiment in
When both of the more demanding hydraulic functions are activated at the same time, the following occurs.
With respect to the fork extension function (block G), activation of spool 218 in block B restricts hydraulic fluid flow from first fixed displacement pump 216 through the open center core 230, causing an increase in hydraulic fluid pressure upstream of that activated spool 218 in block B. The increased hydraulic fluid pressure is communicated through first open center/power core passage 240 to first power core 238, where it is directed by the activated spool 218 to the selected one of the two hydraulic fluid ports 222 or 224 and then to the cylinder 226 and piston 228 associated with the fork extension function (block G). The simultaneous activation of the spool 218 in block G does not provide hydraulic fluid flow/pressure to third power core 239 and to the fork extension function because, as will be described below, substantially all of the hydraulic fluid flow from second fixed displacement pump 217 through open center core 230 is restricted, and thereby diverted by activated spool 218 in block F (due to simultaneous activation of the fork lift function) before the hydraulic fluid flow reaches the spool 218 in block G. Thus, the fork extension function operates based upon hydraulic fluid flow provided by first displacement pump 216, but not second displacement pump 217.
As concerns the fork lift function, substantially the entire hydraulic fluid output of the second fixed displacement pump 217 is directed to the second power core 237 and is thereby directed by the selected one of the two associated hydraulic fluid ports 222 or 224 to the cylinder 226 and piston 228 associated with the fork lift function. The hydraulic fluid flow output of the first fixed displacement pump 216, however, is substantially diverted by activated spool 218 in block B from the open center core 230 before reaching activated spool 218 in block F, for the reasons discussed in the preceding paragraph. Thus, substantially all of the hydraulic fluid flow output of first fixed displacement pump 216 is unavailable for the fork lifting function (block F), because it is being made available to the fork extension function (block G).
The second fixed displacement pump 217 provides all of its hydraulic fluid flow through second pump passage 231 (through second open center/power core passage 241) to spool 218 in block F. Activation of spool 218 in block F restricts the open center core 230. This causes the hydraulic fluid flow supplied by the second fixed displacement pump 217 to increase in pressure upstream of the activated spool 218 in block F. That increase in hydraulic fluid pressure caused by the restriction of the flow of the second fixed displacement pump 217 is communicated through the second open center/power core passage 241 to the second power core 237, where it is thereafter transmitted through the activated spool 218 in block F to the selected one of the two associated hydraulic ports 222 or 224, and then to the cylinder 226 and piston 228 in block F to lift or lower the fork. Consequently, the fork lift function operates based upon hydraulic fluid flow provided by the second fixed displacement pump 217, but not the first fixed displacement pump 216.
The smart flow sharing system 210 invention described above enables an equipment operator to exercise fine control of the equipment's main functions, including the most hydraulically demanding functions operated simultaneously, without introducing expensive components into the hydraulic system. By automatically prioritizing the supply of pressurized hydraulic fluid to the most demanding hydraulic functions (the fork lift and fork extension functions in blocks F and G of the embodiment described and illustrated herein), the smart flow sharing system 210 invention provides an equipment operator with precise control and faster equipment speed than prior art systems, without adding cost-prohibitive extra components.
In situations where only one of the two most demanding hydraulic functions are activated by the operator, both first and second fixed displacement pumps 216 and 217 supply the activated function, resulting in the operator achieving faster speed of the equipment function. When, on the other hand, the two most hydraulically demanding functions are activated at the same time, the smart flow sharing system 210 separately causes the first fixed displacement pump 216 to supply hydraulic fluid flow/pressure to one of the demanding hydraulic functions (in the described embodiment, to the fork extension, block G), and the second fixed displacement pump 217 to supply hydraulic fluid flow/pressure to the other demanding hydraulic function (in the embodiment, to the fork lift, block F). The separate supply to each demanding function allows precise controllability, and eliminates the need for meticulous metering of the hydraulic flow to operate both functions. Consequently, the invention enables precise control by less experienced or skilled operators.
By adding a small number of relatively inexpensive components and changing the hydraulic passages to prioritize the flow of hydraulic fluid, the invention of the smart flow sharing system 210 significantly improves hydraulic performance while maintaining cost effectiveness.
While the above-described embodiment of the smart flow sharing system 210 invention has been found and is believed to be useful and preferable, particularly in certain application using the invention in connection with telehandlers or other off-road earth moving, construction, and forestry equipment, skilled practitioners will recognize that other combinations of elements, dimensions, or materials can be utilized, and other equipment applications can be realized, without departing from the invention claimed herein. Moreover, although certain embodiments of the invention have been described by way of example, it will be understood by skilled practitioners that modifications may be made to the disclosed embodiments without departing from the scope of the invention, which is defined by the claims.
Having thus described exemplary embodiments of the invention, that which is desired to be secured by Letters Patent is claimed below.
This application claims priority from and is related to the following prior application: Smart Flow Sharing System, U.S. Provisional Application No. 61/015,463, filed Dec. 20, 2007. The prior application, including the entire written description and drawings figures, is hereby incorporated by reference into the present application.
| Number | Date | Country | |
|---|---|---|---|
| 61015463 | Dec 2007 | US |
