Smart flow sharing system

A smart flow sharing system, useful in hydraulic systems having more than one hydraulically demanding equipment function wherein more than one of the hydraulically demanding functions are sometimes activated at the same time, has modified hydraulic passages and at least two fixed displacement pumps. The system automatically prioritizes hydraulic fluid flow so that when only one of two hydraulically demanding functions is activated by an operator, it receives the hydraulic fluid flow from both fixed displacement pumps, but when both hydraulically demanding functions are activated, one of the functions receives hydraulic fluid flow from the first fixed displacement pump, and the other function separately receives hydraulic fluid flow from the second fixed displacement pump. The smart flow sharing system accomplishes the foregoing without resorting to complex hydraulics or expensive additional components. An equipment operator advantageously achieves superior controllability and quicker movement of equipment functions using the invention.

BACKGROUND OF THE INVENTION

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 system110illustrated inFIG. 1. The open center hydraulic valve system110inFIG. 1is illustrated in a hydraulic circuit diagram in schematic form as would be understood by a skilled practitioner. The open center hydraulic valve system110ofFIG. 1presently is in common use, for example, in off-road earth moving, construction, and forestry equipment, such as telehandlers.FIG. 1illustrates an example of an open center hydraulic valve system110for a telehandler.

While variations in the basic design of such a prior art open center hydraulic valve system110exist, the fundamental components and operation of such a system are briefly described below.

The prior art open center hydraulic valve system110ofFIG. 1typically includes one or more hydraulic fluid tanks112, one or more constant flow open center hydraulic valve banks (“valves”)114, and a fixed displacement pump116run by a motor150and driven by a motor shaft152. (While the hydraulic fluid tanks112are illustrated inFIGS. 1-4in multiple locations in the schematic illustrations for purposes of simplifying the illustration, skilled practitioners would recognize that the multiple illustrated locations of the hydraulic fluid tanks112in the schematics inFIGS. 1-4would preferably constitute a single hydraulic fluid tank112, or a system of hydraulically interconnected hydraulic fluid tanks112, in actual operation).FIG. 1illustrates a hydraulic system having one valve114. For ease of reference, the valve114is separated into blocks A-F.

The valve114, in turn, may include one or more spools118, with each spool118being activated by spool actuators120. The spool actuators120may 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 inFIG. 1, the spools118in blocks B and C of valve114are activated by using electro-hydraulic valves180, and the spools118in blocks D and E of valve114are activated by using a two-axis joystick182.

In order to more understandably illustrate the operation of a spool118to selectively interconnect hydraulic pathways within a valve114, a simplified drawing illustrating how a spool118of a simple prior art constant flow open center valve114is capable of redirecting the constant flow of hydraulic fluid is provided inFIG. 2. In the simplified drawing ofFIG. 2, the well-known means of activating the spools118are omitted from the schematic diagram. Also omitted inFIG. 2are ancillary hydraulic systems, such as the steering system184(including the steering/brake priority spool186) and the brake system188(including the brake accumulator charge190), which use relatively small amounts of hydraulic fluid flow/pressure compared to the remaining hydraulic functions, and the discussion of which is not pertinent to the invention herein.

In each of the blocks of the valve114illustrated inFIGS. 1 and 2, each spool118is capable of providing selective hydraulic communication with either one of a pair of associated hydraulic ports122and124, depending upon the position of spool118. The hydraulic ports122and124are hydraulically connected to a cylinder126on opposite sides of a piston128. Each spool118has a number of internal hydraulic pathways which permit the spool118, depending on its position, to direct hydraulic fluid flow to or from hydraulic ports122and124, or to remain in a neutral (non-actuated) position wherein hydraulic fluid is permitted to flow unrestricted through the spool118through open center core130.

Referring once again to the prior art open center hydraulic valve system110illustrated inFIGS. 1 and 2, each spool118is capable of selective hydraulic communication with a pair of associated hydraulic ports122and124. Each pair of hydraulic ports122and124, in turn, may be hydraulically connected to equipment applications in which the open center hydraulic valve system110is used to operate, typically utilizing a cylinder126and a piston128. The hydraulic ports122and124selectively provide pressurized hydraulic flow to or from the cylinder126on opposite sides of the piston128, thereby causing the piston128to move, and the application associated with the piston128to operate.

Referring again toFIGS. 1 and 2, each spool118of the valve114, and, hence, each pair of hydraulic ports122and124associated with each spool118, is associated with a function of the application on the equipment within which the open center hydraulic valve system110is utilized. In the example illustrated inFIG. 1, each one of the spools118(and the pair of hydraulic ports122and124associated with each spool118) is associated with a block (indicated by a letter) in the valve114, with each block, in turn, being associated with each of the following functions, which can be found, for example, in a telehandler: fork angle adjustment (block B), fork lock (block C), fork lift (block D), and fork extension (block E). Those functions are chosen for purposes of illustration, and, as would be recognized by skilled practitioners, those functions can vary, depending on the equipment and applications to which the open center hydraulic valve system110is assigned.

The valve114includes several hydraulic fluid pathways that may be selectively interconnected by activation of the spool118, including an open center core130, a power core138, and a tank galley132. The fixed displacement pump116pumps hydraulic fluid (at a constant flow rate for a given speed of the motor150) from the hydraulic fluid tank112into the open center core130. The tank galley132returns hydraulic fluid to the hydraulic fluid tank112, where it is available to be re-pumped. The valve114also includes a hydraulic connection between the open center core130and the power core138, namely, an open center/power core passage140, upstream of the spools118. (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 valve114may also include smaller internal valves utilized to prevent, for example, overpressure or incorrect flow direction in the system, such as relief valves142, or load drop check valves144, which are not material to the explanation of the prior art or the invention.

The prior art open center hydraulic valve system110is typically housed in a standard manifold (not illustrated) attached to the equipment in which the open center hydraulic valve system110is being used. The fixed displacement pump116is typically driven by a motor150, 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 system110is being used.

The operation of the spools118in the valve114to direct hydraulic fluid flow to and to permit fluid flow from associated hydraulic ports122and124to cause, for example, a piston128to move within a cylinder126and thereby cause movement of a functional aspect of the equipment on which the open center hydraulic valve110is mounted is well-known to skilled practitioners, and can be ascertained by skilled practitioners by reference solely to the schematic diagrams found inFIGS. 1 and 2. For purposes of the following explanation, each of the hydraulic ports122and124will be assumed to be hydraulically connected to a cylinder126on opposite sides of a piston128, respectively, in a manner similar to that illustrated inFIGS. 1 and 2.

As can be seen inFIGS. 1 and 2, and as will be described further below, when a spool118is caused or permitted by spool actuator120to be in the neutral position (with the open center core130unrestricted by the spool118, and the fluid passageways between either the power core138or the tank galley132, on the one hand, and the pair of hydraulic ports122and124associated with the spool118, on the other hand, being obstructed by the spool118), no net hydraulic fluid flows to or from the hydraulic ports122and124to the cylinder126on either side of the piston128, and thus, the piston128associated with that spool118does not move. Instead, if all of the spools118in the valve114are in the neutral position, the hydraulic fluid delivered at a constant flow rate (for a given speed of motor150) by the fixed displacement pump116flows unrestricted through the open center core130and through the open center of the other spools118to the tank galley132and to the hydraulic fluid tank112where it is re-pumped. (The power used to pump the unused hydraulic fluid flow is, in that case, effectively a loss). Hence, the functions to which the pistons128and cylinders126are associated (e.g., the height of the fork, as illustrated in block D) do not change, because there is no net change in hydraulic fluid in the cylinders126on either side of the pistons128. The pistons128therefore do not move.

Once again referencingFIGS. 1 and 2, when a spool actuator120is activated by an operator (using electro-hydraulic valves180for spools118in blocks B or C for the fork angle adjustment or the fork lock, on the one hand, or using a joystick182for spools118in blocks D or E for the fork lift or the fork extension, on the other hand) to cause the associated spool118to move from the neutral position to a first non-neutral position, the activated spool118in the first non-neutral position restricts (partially or fully, depending on the design of the spool118) the flow of hydraulic fluid pumped by the fixed displacement pump116through the open center core130. The constant flow of hydraulic fluid delivered by the fixed displacement pump116is caused by the restriction by the spool118of the open center core130to increase in pressure. Referring toFIG. 1, the increase in fluid pressure upstream of the activated spool118in the open center core130is communicated hydraulically to the power core138through the open center/power core passage140. The activated spool118also directs pressurized hydraulic fluid to flow from the power core138to a pre-selected one of the two hydraulic ports122or124associated with the activated spool118into the cylinder126on a first side of the piston128. The activated spool118simultaneously allows fluid to flow out of the cylinder126through the other of the two second hydraulic ports122or124associated with the activated spool118which is connected on a second side of the piston128. That hydraulic fluid then flows through the tank galley132to the hydraulic fluid tank112(where it is available to be re-pumped).

Thus, the net effect is that hydraulic fluid under pressure flows into the cylinder126associated with the activated spool118on the first side of the piston128, and hydraulic fluid flows out of the cylinder126on the second side of the piston128. This causes the piston128and any associated load to move toward the second side of the piston128associated with the activated spool118and the function to change (for example, in the case where the activated spool118is 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 spool118flows through the restriction in that spool118via the open center core130to be either utilized by remaining downstream spools118, or to then flow through the tank galley132to the hydraulic fluid tank112.

On the other hand, if, as illustrated inFIGS. 1 and 2, the equipment operator manipulates the actuator120to cause the spool118to move from the neutral position to a second non-neutral position, that once again causes a restriction of the open center core130, and causes the fluid flowing through the open center core130to increase in pressure. That increase in hydraulic pressure is once again communicated from the open center core130to the power core138through open center/power core passage140. At the same time, hydraulic fluid is permitted by the activated spool118to flow out of the cylinder126on a first side of the piston128through a selected one of the two connected hydraulic ports122or124associated with activated spool118and through the tank galley132to the hydraulic fluid tank112. Also at the same time, the activated spool118directs pressurized hydraulic fluid (under pressure due to restriction of the opening in the open center core130by the activated spool118) to flow from the power core138through the other of the associated hydraulic ports122or124into the cylinder126on a second side of the piston128.

Thus, hydraulic fluid under pressure is introduced to the cylinder126on a second side of the piston128, and hydraulic fluid is drained from the cylinder126on a first side of the piston128. This causes the piston128to move toward the first side of the piston128and the equipment function to change (for example, in the case where the activated spool118is 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 spool118would flow through the restriction in the spool118via the open center core130to be either utilized by remaining downstream spools118, or to then flow through the tank galley132to the hydraulic fluid tank112.

A skilled artisan would recognize, of course, that this activation of spools118in the valve114can 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 system110illustrated inFIG. 1are described below. The explanation herein concerning the operation of a single spool118(and its associated pair of hydraulic ports122and124) within a single valve114associated with a particular single function is illustrative, and is not limited to that particular single spool118or valve114, and applies to other spools118within the open center hydraulic valve system110as well.

Because the pump for the prior art open center hydraulic valve system110is a fixed displacement pump116, the flow of the hydraulic fluid supplied by the fixed displacement pump116is constant for a given speed for the motor150on the equipment in which the prior art open center hydraulic valve system110is mounted.

When the activators such as the electro-hydraulic valves180and the joystick182associated with the spool actuators120for the valve114in the prior art open center hydraulic valve system110are in the neutral position, all of the associated spools118are likewise in the neutral position. As illustrated inFIG. 1, the centers of the valve spools118are open, the net flow paths to the associated hydraulic ports122and124(from the open center core130or the power core138), or from the hydraulic ports122and124(to the tank galley132), are blocked by the spools118, and all net hydraulic fluid flow pumped by the fixed displacement pump116from the hydraulic fluid tank112at a constant flow rate through the open center core130flows unrestricted through the open center core130through the spools118to the tank galley132and then back to the hydraulic fluid tank112, where it is again available to be re-pumped.

When one of the functions associated with the prior art open center hydraulic valve system110is desired to be activated, the spool actuator120associated with that function is activated by an equipment operator using an activator such as an electro-hydraulic valve180or a joystick182in order to move the associated spool118(upwards or downwards, or from side to side, as shown in the schematics inFIGS. 1 and 2) in order to restrict the opening through the open center core130to the tank galley132. This restriction of hydraulic fluid flow by the activated spool118in the open center core130increases the pressure of the hydraulic fluid in the open center core130being provided at a constant flow rate by the fixed displacement pump116upstream of the activated spool118. The resulting increased hydraulic fluid pressure in the open center core130upstream of the activated spool118is transmitted hydraulically through the open center/power core passage140to the power core138.

Assuming that the hydraulic port122associated with activated spool118is connected to the associated cylinder126on a first side of piston128, and associated hydraulic port124is connected to that cylinder126on the second side of piston128, and referring toFIGS. 1 and 2, if the chosen spool actuator120is activated with the intention of causing the associated piston128to move to a first non-neutral position (and to thereby, in the example described above of the spool118associated with block D, lift a fork and any associated load), then not only is the open center core130restricted to cause an increase in pressure to occur in the open center core130upstream of the activated spool118and be transmitted via the open center/power core passage140to the power core138, but the spool118at the same time opens a hydraulic passage in the valve114between associated hydraulic port122(hydraulically connected to a cylinder126at a first side of the piston128, in the manner illustrated inFIGS. 1 and 2) and the power core138. The hydraulic fluid, having increased hydraulic pressure in the power core138, is transmitted through associated hydraulic port122to the cylinder126on the first side of the piston128. Simultaneously, activated spool118opens a hydraulic passage in the valve114between associated hydraulic port124(hydraulically connected to a cylinder126at a second side of the piston128, in the manner illustrated inFIGS. 1 and 2) and the tank galley132. The result is that hydraulic fluid under pressure from the power core138flows through associated hydraulic port122and begins filling the cylinder126on the first side, e.g., below the piston128, and hydraulic fluid is permitted to leave the cylinder126on the second side, e.g., above the piston128by flowing through associated hydraulic port124into the tank galley132to return to the hydraulic fluid tank112, where it is available to be re-pumped. By adding sufficiently pressurized hydraulic fluid to the cylinder126below the piston128, and by reducing hydraulic fluid in the cylinder126above the piston128, the piston128(and, in the example described above, the attached fork and its associated load) is lifted.

Conversely, if the chosen spool actuator120is activated with the intention of causing the piston128to move to a second non-neutral position (and to thereby, in the example of the spool118associated with block D, cause a fork to lower), then not only does the activated spool118cause the open center core130to be restricted to cause an increase in fluid pressure in the open center core130upstream of activated spool118to be hydraulically transmitted to the power core138via open center/power core passage140, but also the activated spool118opens a hydraulic passage in the valve114between the associated hydraulic port124(hydraulically connected to cylinder126at a second side of the piston128) and the power core138(having pressurized hydraulic fluid). Simultaneously, the activated spool118opens a passage in valve114between associated hydraulic port122(hydraulically connected to cylinder126on a first side of the piston128), and the tank galley132, allowing hydraulic fluid to flow out of the cylinder126from the first side of the piston128to the tank galley132and the hydraulic fluid tank112. The result is that hydraulic fluid under pressure from the power core138begins filling the cylinder126on the second side, e.g., above, and hydraulic fluid begins leaving the cylinder126on the first side, e.g., below, thereby causing the associated piston128(and, in the above example, the attached fork and its associated load) to lower.

When the open center hydraulic valve system110is used to operate a function on the equipment on which it is mounted, hydraulic pressure must be built up in the open center core130(which, as previously discussed, is then communicated via the open center/power core passage140to the power core138, and then to one of the two hydraulic ports122or124associated with that function) sufficient to match the load for the function. In the example described above of an open center hydraulic valve system110used on a telehandler, with the raising or lowering of the fork lift function being associated with the spool118of block D of valve114, for instance, the hydraulic pressure developed in the open center core130, which is then delivered to the selected one of the two hydraulic ports122or124associated with block D must be sufficient to move associated piston128, the fork attached to the piston128, 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 valve114for raising or lowering the fork, the relevant activator would be movement of the two-axis joystick182in the horizontal direction as illustrated inFIG. 1) to activate the associated spool actuator120for the spool118in block D so as to cause the spool118in block D to restrict the flow of hydraulic fluid provided by the fixed displacement pump116(at a constant rate for a given motor speed) through the open center core130. This restriction by the associated spool118of the hydraulic fluid flow through the open center core130causes the hydraulic pressure to increase upstream of the activated spool118. That increase in hydraulic pressure is transmitted to the open center/power core passage140, then to the power core138, and then through the activated spool118to the selected one of the two hydraulic ports122or124associated with the activated spool118, as determined by the operator.

In the example previously discussed, where the operator was operating a joystick182to activate the raising of the fork function associated with block D of valve114, the operator would cause the activated spool118to 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 core138and delivered to hydraulic port122(while at the same time allowing hydraulic fluid to drain from hydraulic port124to the tank galley132and then to the hydraulic fluid tank112)—that is, sufficient hydraulic pressure would be generated to raise associated piston128, 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 spool118, the fork and any associated load would not, of course, be raised. Stated another way, when any of the functions associated with valve114are operated, hydraulic pressure must be built up in the power core138to 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 valve114simultaneously. Furthermore, different functions and different movements associated with a function require different hydraulic pressures. In the example discussed above for the valve114associated 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,FIGS. 1 and 2) require considerably less amounts of hydraulic pressure than the fork lifting and fork extension functions (blocks D and E,FIGS. 1 and 2), and therefore are not discussed further. Similarly, operation of the brake system188and the steering system184(FIG. 1) require relatively small amounts of hydraulic pressure, and can be effectively disregarded for purposes of further discussion of the valve114. They have been removed fromFIG. 2for purposes of clarity.

In practice, during the operation of equipment commonly utilizing valve114, 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 ofFIGS. 1 and 2) are often operated simultaneously, frequently using a two-axis joystick182(seeFIG. 1). For instance, the operator may simultaneously lift and extend the fork arm so that the load on the fork follows a substantially vertical trajectory. In the open center hydraulic valve system110illustrated inFIGS. 1 and 2, if the operator simultaneously activates several functions, especially including the fork lifting and fork extension (blocks D and E), the equipment will not respond as the operator commanded. Generally, the fork extension function (block E) requires a lower hydraulic pressure in the hydraulic fluid than does the fork lifting function (block D). On the other hand, in hydraulic systems, absent some compensation in the system design, the flow of hydraulic fluid follows the path of least resistance (i.e., the path in which the pressure is lowest). Consequently, in order for an operator to control both functions (fork lifting and fork extension), the operator is required to utilize the activator (e.g., joystick182) in a manner to meticulously meter the flow of hydraulic fluid through the extension function (block E of valve114) creating a power loss. Furthermore, the controllability that can be attained using that technique is not very high and depends considerably on the ability and skills of the operator, because the two hydraulic pressures to be delivered to the functions are dependent on the load and fork position (extension, height, and angle), which change.

In order to overcome the issues discussed above with respect to the open center hydraulic valve system110, 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 system110and 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.

BRIEF SUMMARY OF THE INVENTION

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.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the smart flow sharing system210of the present invention is illustrated schematically inFIGS. 3 and 4in a manner using schematic symbols that would be understood by persons skilled in the art. Once again, for ease of reference, the schematic of the smart flow sharing valve214is separated into blocks A-H.

Referring toFIG. 3, the smart flow sharing system210includes hydraulic fluid tanks212, one or more open center hydraulic valve banks designed in the manner described and illustrated herein (“smart flow sharing valves”)214, a first fixed displacement pump216, a second fixed displacement pump217, and a single motor250preferably running both the first and second fixed displacement pumps216and217, with the motor250preferably driving first and second fixed displacement pumps216and217using a common single motor shaft252. Each smart flow sharing valve214may include one or more spools218, with each spool218activated by a pair of associated spool actuators220. The spool actuators220may be activated by an operator using a variety of activating means, such as electro-hydraulic valves280(for the spools218in blocks C and D in the embodiment illustrated inFIG. 3) and a two-axis joystick282(for the spools218in blocks B, F, and G in theFIG. 3embodiment), although as previously discussed, the spool actuators220may be activated by an operator using a variety of known means, including mechanically, electrically, hydraulically, pneumatically, or otherwise.

The smart flow sharing system210of 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 system210is being used. The first and second fixed displacement pumps216and217may be driven by a motor250, 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 spool218of the smart flow sharing system210inFIG. 3operates in the same manner as described above for spools118in the prior art open center hydraulic valve system110to provide selective hydraulic communication with a pair of hydraulic ports222and224associated with each spool218. In a typical application of the invention, each pair of hydraulic ports222and224associated with each spool218communicate hydraulically with a cylinder226on opposite sides of a piston228to cause piston movement, in a manner similar to that described above for hydraulic ports122and124, cylinders126, and pistons128for the open center hydraulic valve system110.

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 toFIGS. 3 and 4, the operation of the hydraulic ports222and224hydraulically connected to a cylinder226on either end of a load-supporting piston228in the smart flow sharing system210is the same as explained and illustrated for hydraulic ports122and124hydraulically connected to the cylinder126on either side of piston128in the prior art open center hydraulic valve system110previously described and illustrated (see, e.g.,FIGS. 1 and 2).

Referring once again toFIG. 3, each spool218and associated pair of hydraulic ports222and224of the smart flow sharing valve214is associated with a function to be performed by the equipment on which the smart flow sharing system210is mounted. Once again, inFIG. 3, the exemplary associated functions that are illustrated are those commonly associated with a telehandler: fork angle adjustment (block C), fork lock (block D), fork lift (block F), and fork extension (blocks B and G), although skilled practitioners would recognize that the above functions and equipment associated with the smart flow sharing system210are provided for illustration purposes, and can vary considerably in actual applications.

Referring toFIGS. 3 and 4, an open center core230flows through each of the spools218of the smart flow sharing valve214. The smart flow sharing valve214also includes a first power core238for hydraulic communication of pressurized hydraulic fluid, and a tank galley232for return of hydraulic fluid to one or more hydraulic fluid tanks212, where it becomes available to be re-pumped. (While hydraulic fluid tanks212are illustrated inFIGS. 3 and 4in multiple locations for purposes of simplifying the schematics, skilled practitioners would recognize that the multiple illustrated locations of hydraulic fluid tanks212would preferably constitute a single hydraulic fluid tank212, or a system of hydraulically interconnected hydraulic fluid tanks212, in actual operation).

Importantly, the first power core238of the smart flow sharing system210(seeFIGS. 3 and 4) differs significantly from the power core138of the open center hydraulic valve system110(seeFIG. 1). First power core238does not extend through all of the blocks of the smart flow sharing valve214, unlike the power core138in prior art valve114. Instead, first power core238hydraulically connects with a predetermined selected number of spools218before terminating (“deadheading”). First power core238preferably connects to those spools218that are associated with hydraulic functions that are less demanding, and to only one of the functions that is more demanding. In the embodiment illustrated inFIGS. 3 and 4, first power core238is hydraulically connected to the spools218associated with the fork angle and fork lock functions (blocks C and D of smart flow sharing valve214) which, as previously discussed, are less demanding hydraulic applications than the fork lift and fork extension functions (blocks F and G). In addition, one of the spools218(preferably the most upstream spool218) hydraulically connected to first power core238(see block B) is also one of two spools218hydraulically connected to one of the more hydraulically demanding functions. In the illustrated embodiment, the hydraulic output (hydraulic ports222and224) of both the spool218in block B (hydraulically connected to the first power core238) and the spool218in block G are hydraulically connected to cylinder226associated with the hydraulically demanding fork extension function (block G) on opposite sides of piston228. The actuators220of the aforesaid pair of spools218(in blocks B and G) for the fork extension function are preferably connected to and simultaneously activated by the same activation device, in this embodiment, the same activating output from joystick282(vertical movement of the joystick282, as illustrated inFIG. 3).

As illustrated inFIGS. 3 and 4, smart flow sharing valve214has an open center core230extending substantially the length of the smart flow sharing valve214through all of the spools218associated with each of the hydraulic functions. Open center core230receives the hydraulic fluid pumped by first fixed displacement pump216. As will be discussed further below, open center core230also receives, further downstream, hydraulic fluid pumped by second fixed displacement pump217. The hydraulic fluid provided by first displacement pump216and second displacement pump217flows substantially unimpeded through the open center core230to the connected tank galley232and then to the hydraulic fluid tank212if all of the spools218are in the non-activated neutral position. Indeed, tank galley232receives all hydraulic fluid conducted through open center core230that is unused by the hydraulic functions associated with spools218.

A first open center/power core passage240hydraulically connects the open center core230with the first power core238upstream of the first upstream spool218(e.g., see block B) associated with the first power core238. If one or more of the spools218associated with the first power core238(e.g., blocks B, C, and D inFIG. 3) are activated, the activated spool218restricts the passage of hydraulic fluid through the open center core230upstream of the activated spool218, causing an increase in hydraulic fluid pressure. The increase in hydraulic fluid pressure is hydraulically communicated through the first open center/power core passage240to the first power core238.

At the same time, and in the same manner discussed previously for activated spools118, the activated spools218open one of the two associated hydraulic ports222or224to receive the pressurized hydraulic fluid from the first power core238, and open the other of the two associated hydraulic ports222or224to hydraulically connect via the tank galley232to the hydraulic fluid tank212. Because the hydraulic ports222and224are connected to an associated cylinder226on either side of the associated piston228, pressurized hydraulic fluid enters the associated cylinder226on one side of the piston228, and drains out of the cylinder226on the other side of the piston228, causing the piston228to move toward the side of the cylinder226where hydraulic fluid is draining, and the associated hydraulic function to occur.

Downstream of the spools218associated with the first power core238are one or more spools218associated with a second power core237. Second power core237is separated from first power core238. A second open center/power core passage241is separated from both open center core230and second power core passage237, upstream of any spools218associated with the second power core237, and downstream of any spools218associated with first power core238.

Second fixed displacement pump217pumps hydraulic fluid from hydraulic fluid tank212through second pump passage231, which is hydraulically connected to the open center core230downstream of the spools218associated with the first power core238, and upstream of any spools218associated with the second power core237. Preferably and advantageously, second pump passage231may be hydraulically connected to open center core230by hydraulically connecting second pump passage231to second open center/power core passage241.

If one or more spools218associated with second power core237(preferably, one such spool218, as illustrated, in block F ofFIGS. 3 and 4) is activated by an operator using an activator (inFIG. 3, by moving the joystick282in a horizontal direction, as illustrated inFIG. 3) acting upon one of the spool actuators220associated with the to-be-activated spool218, then the spool218that is activated thereby restricts flow of hydraulic fluid received from the first fixed displacement pump216(if any, because the activation of upstream spools218associated with the first power core238could restrict hydraulic fluid flow from first fixed displacement pump216through open center core230) and the second fixed displacement pump217through the open center core230. Because the first and second fixed displacement pumps216and217are providing hydraulic fluid at a constant rate of flow (for a given speed of motor250), the restriction by the activated spool218associated with second power core237(see spool218in block F) of the open core passage230results in an increase in hydraulic fluid pressure in the open center core230upstream of the activated spool218, which is then hydraulically communicated through the second open center/power core passage241to the second power core237.

Once again, the activated spool218(in the embodiment illustrated inFIGS. 3 and 4, located in block F) at the same time opens the selected one of the two associated ports222or224to receive pressurized hydraulic fluid from the second power core237, while the other of the two associated hydraulic ports222or224is connected to the tank galley232and thereby caused to drain hydraulic fluid to the hydraulic fluid tank212. This, once again, causes the associated cylinder226to be filled with pressurized hydraulic fluid on one side of the piston228, and causes hydraulic fluid to drain out of the associated cylinder226on the other side of the piston228, which, in turn causes the piston228to move toward the draining side of the cylinder226. Piston movement causes the hydraulic function to operate. In the case of the embodiment of the invention discussed above, and in particular block F of the smart flow sharing valve214, this would cause the fork lift to operate.

Further downstream of the spools218associated with the first and second power cores238and237are one or more spools218(preferably one spool218) associated with a third power core239. Third power core239is separate from either the first or second power cores238or237. A third open center/power core passage243hydraulically connects the third power core239and the open center core230upstream of any spools218associated with third power core239, and downstream of any spools218associated with first power core238or second power core237.

If one or more spools218associated with third power core239is activated (in the embodiment depicted inFIGS. 3 and 4, and discussed above, there is one such spool218in block G) by an operator using an activator (movement of the joystick282in the vertical direction as illustrated in the embodiment inFIG. 3) acting upon a spool actuator220associated with the spool218that is being activated, then the smart flow sharing valve214is designed to have several things occur at the same time.

As previously discussed, an operator's activation of the joystick282in order to activate the spool218in block G simultaneously activates the spool218in block B, because the actuators220for both spools218(blocks B and G) have a common activator (the vertical movement of the two-axis joystick282in the illustrated embodiment inFIG. 3). (The spool218associated with block F is also activated by the two-axis joystick282illustrated inFIG. 3, however, the spools218in blocks B and G are simultaneously activated by movement of the joystick282in the vertical direction illustrated inFIG. 3, while movement in horizontal direction of the joystick282as illustrated inFIG. 3activates the spool218in block F).

Upon activation of spools218in blocks B and G, the spool218in block G restricts the open core passage230passing through that activated spool218. Because the hydraulic fluid flow is pumped at a constant rate (for a given speed of motor250) by the first fixed displacement pump216and the second displacement pump217through open center core230upstream of spool218in block G, the restriction caused by spool218in block G (of any unused hydraulic fluid from the first and second fixed displacement pumps216and217) causes hydraulic pressure upstream of that activated spool218(in block G) to rise. The increased hydraulic pressure is hydraulically communicated through third open center/power core243to third power core239. The activated spool218(in block G) at the same time opens one of the two associated hydraulic ports222or224to receive pressurized hydraulic fluid from the third power core239, while the other of two associated hydraulic ports222or224is connected by the spool218to the tank galley232.

Because the spool218in block B is simultaneously activated when the spool218in block G is activated, that spool218also restricts the open center core230(which at that location is receiving hydraulic fluid flow from the first fixed displacement pump216only), and, as discussed previously, activated spool218(in block B) provides pressurized hydraulic fluid to the same selected one of hydraulic ports222or224in block G as does spool218in block G.

Consequently, spool218in block B causes pressurized hydraulic fluid provided by the first fixed displacement pump216, and spool218in block G causes pressurized hydraulic fluid provided by the second fixed displacement pump217, both to be transmitted to the selected one of the two hydraulic ports222or224in block G. Thus, the fork extension function has the benefit of using hydraulic flow from both the first and second fixed displacement pumps216and217when the fork lift function (block F) is not simultaneously in operation (in which case the spool218associated with the fork lift function in block F would be activated, thereby restricting the hydraulic fluid flow of the second fixed displacement pump217through open center core230to block G).

The smart flow sharing system210described above, has distinct advantages versus prior art systems, such as the open center hydraulic valve system110described previously. As discussed above, the open center hydraulic valve system110suffers 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 system210described 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 system210invention adds, among other features, a second fixed displacement pump217, and a spool218(in block B), relatively inexpensive components, in order aid in overcoming the problems associated with the standard prior art open center hydraulic valve system110. 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 pump217, 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 system288, the steering system284, 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 system210automatically prioritizes the hydraulic fluid flow output of the first and second fixed displacement pumps216and217as described below.

(1) Fork Lift Activated, But Fork Extension Not Activated. When the fork lift function (block F in the embodiment inFIG. 3) is activated, but the fork extension function (block G) is not activated, any unused hydraulic fluid output of the first fixed displacement pump216(i.e., unused by the hydraulically less demanding upstream functions and unused by the fork extension function) and substantially the entire hydraulic fluid output of the second fixed displacement pump217is available to be directed to the second power core237, and is thereby directed by the activated spool218in block F to the selected one of the two associated hydraulic fluid ports222or224, and thereby to the cylinder226and piston228associated with the fork lift function.

Depending on how many, if any, of the less demanding upstream hydraulic functions (blocks C and D) are activated, first fixed displacement pump216provides most or substantially all of its hydraulic fluid flow through open center core230to spool218in block F. The second fixed displacement pump217provides substantially all of its hydraulic fluid flow through second pump passage231(through second open center/power core passage241and then through open center core230) to spool218in block F. Because spool218in block F is activated, it restricts the open center core230. This causes the hydraulic fluid flow supplied by both the first and second fixed displacement pumps216and217to increase in pressure upstream of the activated spool218in block F. That increase in hydraulic fluid pressure caused by the restriction of the flow of both the first and second fixed displacement pumps216and217is communicated through the second open center/power core passage241to the second power core237, where it is thereafter transmitted through the activated spool218in block F to the selected one of the two associated hydraulic ports222or224, and then the cylinder226and piston228in 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 pumps216and217is 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 inFIG. 3) is activated, but the fork lift function (block F) is not activated, hydraulic fluid output of the first fixed displacement pump216and substantially the entire hydraulic fluid output of the second fixed displacement pump217is directed by the simultaneous activation of the two spools218, namely, spool218associated with block B and spool218associated with G, to the selected one of the two associated hydraulic fluid ports222or224in block G, and thereby to the cylinder226and piston228in block G associated with the fork extension function, in the manner previously described herein.

That is, activation of spool218in block B restricts hydraulic fluid flow from first fixed displacement pump216through the open center core230, causing an increase in hydraulic fluid pressure upstream of that activated spool218. That increased hydraulic fluid pressure is communicated through first open center/power core passage240to first power core238, where it is directed by the activated spool218to the selected one of the two hydraulic fluid ports222or224and then to the cylinder226and piston228associated with the fork extension function (block G).

At the same time, substantially the entire hydraulic fluid flow from second fixed displacement pump217flows through second pump passage231through second open center/power core passage241into open center core230. Because spool218associated with the fork lift function (block F) is not activated, the hydraulic fluid flow output of second fixed displacement pump217flows through open center core230to the activated spool218associated with the fork extension function (block G). That activated spool218restricts the hydraulic fluid flow through open center core230, causing an increase in hydraulic pressure upstream of the activated spool218in block G. That increased hydraulic fluid pressure is then communicated to third power core239, where it is directed by the activated spool218to the selected one of the two hydraulic fluid ports222or224(the same hydraulic port to which pressurized hydraulic fluid was directed by spool218in block B) and then to the cylinder226and piston228associated with the fork extension function (block G). Consequently, the hydraulic fluid output of both the first and second fixed displacement pumps216and217is 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 inFIG. 3) and the fork extension function (block G) are activated, the smart flow sharing system210of the present invention provides substantially the entire hydraulic fluid output of the first fixed displacement pump216to the selected one of the two associated hydraulic fluid ports222or224in block G, and thereby to the cylinder226and piston228in block G associated with the fork extension function, while at the same time substantially the entire hydraulic fluid output of the second fixed displacement pump217is directed to the second power core237, and is thereby directed by the activated spool218in block F to the selected one of the two associated hydraulic fluid ports222or224in block F to the associated cylinder226and piston228for the fork lift function. The hydraulic fluid flow output of the first and second fixed displacement pumps216and217is effectively shared by the two most demanding hydraulic functions when they are operated simultaneously. This is in stark contrast to the tendency, as occurs for instance with the prior art open center hydraulic valve system110, of the hydraulic fluid to flow through the path of least resistance (thereby requiring extensive oversight and metering skill by the operator in order to attempt to simultaneously operate the two most demanding functions, and sacrificing quick movements and fine control of equipment functions).

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 spool218in block B restricts hydraulic fluid flow from first fixed displacement pump216through the open center core230, causing an increase in hydraulic fluid pressure upstream of that activated spool218in block B. The increased hydraulic fluid pressure is communicated through first open center/power core passage240to first power core238, where it is directed by the activated spool218to the selected one of the two hydraulic fluid ports222or224and then to the cylinder226and piston228associated with the fork extension function (block G). The simultaneous activation of the spool218in block G does not provide hydraulic fluid flow/pressure to third power core239and to the fork extension function because, as will be described below, substantially all of the hydraulic fluid flow from second fixed displacement pump217through open center core230is restricted, and thereby diverted by activated spool218in block F (due to simultaneous activation of the fork lift function) before the hydraulic fluid flow reaches the spool218in block G. Thus, the fork extension function operates based upon hydraulic fluid flow provided by first displacement pump216, but not second displacement pump217.

As concerns the fork lift function, substantially the entire hydraulic fluid output of the second fixed displacement pump217is directed to the second power core237and is thereby directed by the selected one of the two associated hydraulic fluid ports222or224to the cylinder226and piston228associated with the fork lift function. The hydraulic fluid flow output of the first fixed displacement pump216, however, is substantially diverted by activated spool218in block B from the open center core230before reaching activated spool218in block F, for the reasons discussed in the preceding paragraph. Thus, substantially all of the hydraulic fluid flow output of first fixed displacement pump216is 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 pump217provides all of its hydraulic fluid flow through second pump passage231(through second open center/power core passage241) to spool218in block F. Activation of spool218in block F restricts the open center core230. This causes the hydraulic fluid flow supplied by the second fixed displacement pump217to increase in pressure upstream of the activated spool218in block F. That increase in hydraulic fluid pressure caused by the restriction of the flow of the second fixed displacement pump217is communicated through the second open center/power core passage241to the second power core237, where it is thereafter transmitted through the activated spool218in block F to the selected one of the two associated hydraulic ports222or224, and then to the cylinder226and piston228in 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 pump217, but not the first fixed displacement pump216.

The smart flow sharing system210invention 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 system210invention 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 pumps216and217supply 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 system210separately causes the first fixed displacement pump216to 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 pump217to 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 system210significantly improves hydraulic performance while maintaining cost effectiveness.

While the above-described embodiment of the smart flow sharing system210invention 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.