Hydraulic systems for raising and lowering loads

Abstract

A hydraulic system has a single-acting piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the piston-cylinder to cause the piston-cylinder to raise the load, and a pressure-compensated flow control valve (PCFC valve) which receives the hydraulic fluid from the single-acting piston-cylinder upon lowering of the load, wherein the PCFC valve causes the piston-cylinder to lower the load at a substantially constant speed regardless of the load amount. A PCFC valve may also or alternately be fluidly coupled to the hydraulic circuit and configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the PCFC valve is configured to cause the piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.

Description

HYDRAULIC SYSTEMS FOR RAISING AND LOWERING LOADSCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims benefit of priority to U.S. Provisional Application No. 63 / 567,976, filed March 21, 2024, which is hereby incorporated by reference in entirety.FIELD

[0001] The present disclosure relates to hydraulic systems having a single-acting pistoncylinder configured to raise and lower a load.BACKGROUND

[0002] U.S. Patent Nos. 2,676,573; 3,016,046; 4,088,151 and 4,111,283 provide background disclosure.SUMMARY

[0003] This Summary is provided to introduce a selection of concepts that are further described herein below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In independent embodiments, a hydraulic system is for raising and lowering a load. The hydraulic system comprises a hydraulic circuit for conveying a hydraulic fluid, a single-acting piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the single-acting piston-cylinder via the hydraulic circuit to cause the single-acting piston-cylinder to raise the load, and a pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the single-acting piston-cylinder upon lowering of the load, wherein the PCFC valve is configured to cause the single-acting piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.

[0005] In embodiments, the PCFC valve is removably coupled to the hydraulic system. In embodiments, the PCFC valve is removably coupled to the hydraulic circuit between the pump and the PCFC valve. In embodiments, the hydraulic system further comprises a check valve, thecheck valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and being configured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.

[0006] In embodiments, the hydraulic system further comprises a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the hydraulic system. In embodiments, the hydraulic system further comprises a check valve in the housing, the check valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and being configured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load. In embodiments, the housing comprises a cartridge that is configured to be removably coupled to the hydraulic system. In embodiments, the cartridge is configured to be removably coupled to the hydraulic circuit. In embodiments, the cartridge is configured to be removably coupled to the single-acting piston-cylinder.

[0007] In embodiments, the PCFC valve is disposed in the single-acting piston-cylinder. In embodiments, the hydraulic system further comprises a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the single-acting piston-cylinder. In embodiments, the hydraulic system further comprises a check valve that is configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and that is configured to close to cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.

[0008] In embodiments, the single-acting piston-cylinder is one of a plurality of singleacting piston-cylinders configured to raise and lower a plurality of loads, and each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is configured to raise and lower a respective load in the plurality of loads. In embodiments, the PCFC valve receives the hydraulic fluid from the plurality of single-acting piston-cylinders such that the PCFC valve causes the plurality of single-acting piston-cylinders to lower the plurality of loads at a speed that is substantially constant and is the same regardless of the load amount.

[0009] In embodiments, the single-acting piston-cylinder is one of a plurality of singleacting piston-cylinders configured to raise and lower a plurality of loads, and the PCFC valve is one of a plurality of PCFC valves that are fluidly coupled to the plurality of single-acting piston-cylinders in parallel so that each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is coupled to a different respective one of the plurality of PCFC valves.

[0010] In embodiments, the PCFC valve comprises a housing having an inlet that receives the hydraulic fluid from the single-acting piston-cylinder, an outlet that discharges the hydraulic fluid, and a pressure-compensation portion between the inlet and the outlet, wherein the pressurecompensation portion is configured to passively control a flow rate at which the hydraulic fluid flows from the single-acting piston-cylinder through the valve housing so that the flow rate and thus a lowering speed of the single-acting piston-cylinder remains substantially constant regardless of the load amount. In embodiments, the pressure-compensation portion is configured to automatically adjust a size of an orifice to restrict flow of the hydraulic fluid through the PCFC valve. In embodiments, the PCFC valve further comprises a flow control portion configured to set a target flow rate for the PCFC valve and wherein the pressure-compensation portion is configured to automatically adjust the size of the orifice according to the target flow rate. In embodiments, the flow control portion comprises a valve configured to adjust the size of the outlet of the housing.

[0011] In embodiments, the hydraulic system further comprises a controller configured to control the hydraulic system to raise and lower the load. In embodiments, the PCFC valve is a first PCFC valve and the hydraulic system further comprises a second PCFC valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the second PCFC valve is configured to cause the single-acting pistoncylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated. In embodiments, the hydraulic circuit is operable in a first load-raising state in which the pump pumps the hydraulic fluid to the single-acting pistoncylinder to raise the load without flowing through the first PCFC valve, a second load-raising state in which the pump pumps the hydraulic fluid to the single-acting piston-cylinder through the first PCFC valve and to the pump to raise the load, and a third hydraulic state in which the hydraulic fluid is exhausted from the single-acting piston-cylinder through the first PCFC valve to lower the load at the speed that is substantially constant and is the same regardless of the load amount. In embodiments, the hydraulic system further comprises a fluid control valve configured to cause the hydraulic system to operate in the first load-raising state, the second load-raising state, and the third hydraulic state. In embodiments, the hydraulic system further comprises a controller configured to control the fluid control valve based upon an input from a user.

[0012] In independent embodiments, a hydraulic system is for raising and lowering a load. The hydraulic system comprises a hydraulic circuit for conveying a hydraulic fluid, piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the piston-cylinder via the hydraulic circuit to cause the piston-cylinder to raise the load, and a pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the PCFC valve is configured to cause the piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.

[0013] In embodiments, the PCFC valve is a first PCFC valve and the hydraulic system further comprises a second PCFC valve configured to receive the hydraulic fluid from the pistoncylinder upon lowering of the load, wherein the second PCFC valve is configured to cause the piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount. In embodiments, the hydraulic system is operable in three operational states including a first load-raising state; a relatively slower and controlled, second load-raising state; and a load-lowering state.

[0014] In embodiments, the hydraulic system further comprises a flow control valve configured to switch the hydraulic system for operation in each of the three operational states. In embodiments, the hydraulic system further comprises a controller configured to control the flow control valve to switch the hydraulic system into each of the three operational states. In embodiments, in the first load-raising state, the pump is configured to pump the hydraulic fluid to the piston-cylinder via a substantially unrestricted fluid line, in the second load-raising state, the pump is configured to pump the hydraulic fluid to the piston-cylinder via the first PCFC valve, and in the load-lowering state, the hydraulic fluid is exhausted from the piston-cylinder to a tank via the second PCFC valve.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments are provided with reference to the following drawing figures. The same numbers reference like features and components.

[0016] FIG. 1 is a schematic view of a hydraulic system for raising and lowering a load according to a first embodiment of the present disclosure.

[0017] FIG. 2 is a diagram of a non-limiting embodiment of a prior art pressure compensating flow control valve in a first position.

[0018] FIG. 3 is a diagram of the pressure compensating flow control valve in a second position.

[0019] FIG. 4 is a schematic view of a hydraulic system for raising and lowering a load according to a second embodiment of the present disclosure.

[0020] FIG. 5 is a schematic view of an alternate configuration of the second embodiment.

[0021] FIG. 6 is a schematic view of a hydraulic system for raising and lowering a load according to a third embodiment of the present disclosure.

[0022] FIG. 7 is a schematic view of a hydraulic system for raising and lowering a load according to a fourth embodiment of the present disclosure.

[0023] FIG. 8A is a schematic view of a hydraulic system for raising and lowering a load according to a fifth embodiment of the present disclosure, showing the system in a first load-raising state.

[0024] FIG. 8B is a schematic view of the fifth embodiment, showing the system in a relative slower and controlled, second load-raising state.

[0025] FIG. 8C is a schematic view of the fifth embodiment, showing the system in a controlled load-lowering state.DETAILED DESCRIPTION OF THE DRAWINGS

[0026] During research and development of hydraulic systems, the present inventors determined that conventional hydraulic systems having a single-acting piston-cylinder for raising and lowering a load normally provide a lowering speed that is proportional to the weight of the load. Relatively higher loads (higher pressures) create a relatively high-pressure difference between the piston-cylinder and the tank (typically 0 psi), and thus the resultant return speed is relatively fast, and the piston-cylinder lowers relatively quickly. Relatively smaller loads (lower pressures) create a relatively low-pressure difference between the piston-cylinder and the tank, and thus the resultant return speed is relatively low, and the piston-cylinder lowers relatively slowly. While the present inventors realized it is possible to utilize one or more fixed restrictions to reducethe return speed under high-load conditions, unless the flow area on the return is large, such fixed restrictions disadvantagcously cause an unduly slow return under small- or no-load conditions.

[0027] The present inventors thus recognized a need in the ait for improving the abovedescribed conventional systems. The present disclosure is a result of their efforts. In non-limiting embodiments disclosed herein, hydraulic systems for raising and lowering a load may comprise in combination, (1) a single-acting piston-cylinder that is hydraulically operated by a pump and (2) a pressure-compensated flow control valve that is configured to cause the piston-cylinder to lower a load at a substantially constant speed that remains the same regardless of the load amount. In use, this advantageously provides systems wherein loads of various different amounts are all consistently and reliably lowered at a same rate. In other non-limiting embodiments disclosed herein, systems of the present disclosure may also or alternately be configured with a pressure- compensated flow control valve configured to configured to cause a piston-cylinder, which may be a single-acting piston-cylinder or a dual-acting piston cylinder, to raise the load at a speed that is substantially constant and controlled by the pressure compensated flow control valve.

[0028] The systems of the present disclosure advantageously may be configured so as to operate passively, i.e., in a way that does not require manual or other active control by the user or by a controller (e.g., conventional computer control) to achieve the above-noted same, substantially constant speed of lowering and / or raising. The systems of the present disclosure advantageously may be configured in a way that does not require a hydraulic accumulator or other similar known components for regulating pressure of the flow from a pump.

[0029] In non-limiting embodiments, the systems of the present disclosure advantageously may be configured so that a single pressure-compensated flow control valve is configured to cause a plurality of single-acting piston-cylinders to each lower a respective load at a same, substantially constant speed, regardless of the respective load amounts. The systems of the present disclosure advantageously may be configured so that a plurality of pressure-compensated flow control valves is arranged in parallel with a plurality of respective single-acting piston-cylinders, each of which being configured to lower a respective load at a substantially constant speed, regardless of the respective load amounts. In embodiments like this, each of the pairs of single-acting pistoncylinders and pressure-compensated flow control valves advantageously may be individually set to lower their respective load at a respective speed that is different from the other pairs in the pluralities.

[0030] As provided herein below, the systems advantageously may be configured to permit the user to set and thereafter passively control the flow rate of the hydraulic fluid out of a single- acting piston-cylinder, so that the flow rate and thus the lowering speed remains substantially constant regardless of load amount. As provided herein below, the systems advantageously may be configured to permit the user to set and thereafter allow the system to passively control the flow rate of the hydraulic fluid into a piston-cylinder, so that the flow rate and thus the raising speed remains substantially constant and at a predetermined speed, regardless of the speed of the pump and regardless of the load amount. Embodiments provided in the present disclosure may advantageously facilitate setting and thereafter passively maintaining a constant flow rate of hydraulic fluid exhausted from the single-acting piston-cylinder upon lowering of the load and / or provided to a piston-cylinder upon raising of the load.

[0031] In addition, the systems of the present disclosure may be configured so that the flow of the hydraulic fluid to the piston-cylinder for raising the load may be substantially unrestricted, at least in certain states, for example without routing of the hydraulic fluid through a switching device and / or without routing the hydraulic fluid through a pressure-compensated flow control valve. In other embodiments, as mentioned above, the systems of the present disclosure may be configured to that flow of the hydraulic fluid to the piston-cylinder for raising the load may be routed through a pressure compensation flow control valve so that the speed at which the load is raised remains substantially constant regardless of the speed of the pump and regardless of the load amount.

[0032] FIG. 1 shows a first, non-limiting embodiment of a hydraulic system 100 for raising and lowering a load that includes a pressure-compensated flow control (PCFC) valve 20 configured for use with a single-acting piston-cylinder 12. The single-acting piston-cylinder 12 includes a piston 24 having a piston rod 24a and a piston head 24b. The piston head 24b divides the piston-cylinder 12 into first and second chambers 26, 30. Extension or retraction of the piston 24 in the piston-cylinder 12 corresponds to lowering or lifting of a load (not shown) via the pistoncylinder 12. The piston head 24b is movable in the piston-cylinder 12 between a first end 32 and a second end 34 by the hydraulic fluid that is pumped into the first chamber 26 at the first end 32 and dispensed from the first end 32 under weight of the load. The piston 24 is considered to be fully retracted when the piston head 24b is positioned at the first end 32 and the piston 24 is considered to be fully extended when the piston head 24b is positioned at the second end 34. Thus,the single-acting piston cylinder 12 extends based on pressure from hydraulic fluid on one side and retracts based on an external force (i.e. , the bias of a return spring element and / or a load on the piston 24, as will be further described herein below) on the other side. This is the nature of a conventional single-acting piston-cylinder. The illustrated single-acting piston-cylinder should be contrasted to (i.e., is not the same as) a conventional double-acting cylinder which extends and retracts based on pressure from hydraulic fluid on both sides of its piston. In the illustrated embodiment, the single-acting piston cylinder 12 includes an optional return spring element 28 on the piston rod 24a. The optional return spring element 28 provides a spring bias that acts against a force exerted on the piston head 24b by the hydraulic fluid and thus assists return of the piston 24 to a lowered position in a situation where there is no load on the piston-cylinder 12 (i.e. a “no load condition”).

[0033] Referring to FIG. 1, the system 100 has a hydraulic circuit 10 that is fluidly connected to the piston-cylinder 12. The hydraulic circuit 10 has fluid lines 102, 103, 104, 106 that fluidly connect a tank 16 to the first chamber 26 of the piston-cylinder 12. A pump 14 is fluidly connected to the fluid line 103 and configured to generate (pump) flow of the hydraulic fluid in the hydraulic circuit 10. A pressure relief valve 18 is fluidly connected to the fluid line 104 and is configured to automatically open or close based upon the pressure of the hydraulic fluid, thereby automatically regulating pressure of the hydraulic fluid by dumping hydraulic fluid to the tank 16 in the event that the hydraulic fluid in the system 100 exceeds a predetermined limit, for example as the pump 14 is pumping the hydraulic fluid into the hydraulic circuit 10. The hydraulic circuit 10 also includes a fluid relief line 106 positioned between the fluid line 102 and the tank 16. The fluid relief line 106 is configured to convey the hydraulic fluid that is exhausted from the pistoncylinder 12 to the tank 16. A two-stage, solenoid-activated control valve 22 is fluidly connected to the fluid relief line 106 to selectively connect or disconnect the fluid relief line 106 to or from the tank 16. When the control valve 22 is moved into a closed position, as shown in FIG. 1, it prevents the hydraulic fluid from being exhausted from the piston-cylinder 12 to the tank 16 via the fluid relief line 106. When the control valve 22 is moved into an open position (i.e., moved to the right in FIG. 1), it allows the hydraulic fluid to be exhausted from the piston-cylinder 12 to the tank 16 via the fluid relief line 106.

[0034] The system 100 also includes the above-noted PCFC valve 20 which is fluidly connected to the hydraulic circuit 10 and in the non-limiting embodiment shown in FIG. 1 isparticularly connected to the fluid relief line 106. As will be evident from the embodiments described herein below, the PCFC valve 20 may be located elsewhere in the system 100. In the embodiment of FIG. 1, the PCFC valve 20 is positioned in the flow of hydraulic fluid between the fluid line 102 and the control valve 22. In a similar but alternate embodiment, the PCFC valve 20 may be positioned in the flow of hydraulic fluid between the control valve 22 and the tank 16. Again, there are other possible locations of the PCFC valve 20, as will be evident from the embodiments described herein below.

[0035] The system 100 may include a controller 97 that is configured to control aspects of the system 100, including but not limited to the pump 14 and the control valve 22. The controller 97 has a processor and a memory and is communicatively coupled to the system 100 via wired or wireless links, as is conventional in the art. The controller 97 is configured to control aspects of the system 100 such as the pump 14, for example being programmed to control the pump 14 to turn the pump 14 on and off, as well as the control valve 22, for example being programmed to cause the control valve 22 to move into its open or closed position. A user input device 99 may be included, which is communicatively coupled to the controller 97 and configured to allow a user to input commands to the controller 97 for controlling various operation of the system 100, such as the operations described above. The type of user input device 99 can vary widely and in some embodiments includes conventional means for manually inputting commands to the controller 97, such as a keyboard, a touch screen, and / or the like. Thus, via operation of the user input device 99, a user can control the system 100 to raise and lower a load by operating the pump 14 and the control valve 22. As further described herein below, in non-limiting embodiments, the controller 97 may also be configured to control the PCFC valve 20, as will be further described herein below, thus permitting the user to set a desired flow rate of the hydraulic fluid through the PCFC valve 20 via the user input device 99.

[0036] FIGS. 2-3 depict a conventional PCFC valve 20 that is suitable for use in each of the systems of the present disclosure. The final example described herein below includes a second PCFC valve 20’ and the embodiment shown in FIGS. 2-3 is also suitable for use as the second PCFC valve 20’ . It should be understood that the PCFC valve 20 shown in the drawings is merely exemplary and type and configuration of the PCFC valve can vary widely from what is shown and described.

[0037] In the embodiment shown, the PCFC valve 20 includes a valve housing 40 having a pressure-compensation portion 42 and a flow control portion 44. A series of fluid conduits 108, 110, 112 and a pressure communication line 114 extend through the valve housing 40 and provide fluid communication between an inlet 46 and an outlet 48. The pressure-compensation portion 42 includes an internal chamber 50. An elongated spool element 52 is axially displaced in the internal chamber 50. The internal chamber 50 has a first end 63 defining a left-most limit of the internal chamber 50 and a second end 65 defining a right-most limit of the internal chamber 50. The spool element 52 has a first annular stopper 54 and a second annular stopper 56 positioned at opposite ends of a center rod 58. The pressure communication line 114 extends from the first end 63 to a center portion of the internal chamber 50 to pilot fluid pressure building between the first annular stopper 54 and the first end 63. A compression spring 60 is housed in the internal chamber 50 and positioned in abutment with the second annular stopper 56 and the second end 65 of the internal chamber 50 and biasing the elongated spool element 52 to the left in the drawings. A pressure communication line 116 extends from the second end 65 to the fluid conduit 112 to pilot fluid pressure building between the second annular stopper 56 and the second end 65.

[0038] The first annular stopper 54 has a working surface 66 that is faced opposite a working surface 68 of the second annular stopper 56 and positioned interiorly of the first and second end 63, 65 of the internal chamber 50. The first annular stopper 54 has a primary working surface 67 that is faced outwardly toward the first end 63 of the internal chamber 50. The second annular stopper 56 includes a primary working surface 69 that is faced outwardly toward the second end 65 and engaged with the spring 60. The PCFC valve 20 is configured so that the hydraulic fluid that is conveyed through the internal chamber 50 exerts forces upon the working surfaces 66, 67, 68 and 69 in some cases against the bias of the spring 60 to axially displace the spool element 52 to the left or right in the drawings.

[0039] The internal chamber 50 provides fluid communication between the inlet 46 and the outlet 48 during certain configurations. The fluid conduit 108 extends from the inlet 46 to a first annular port 62 of the internal chamber 50. The fluid conduit 110 extends from a second annular port 64 of the internal chamber 50 to the How control portion 44. The first annular port 62 is positioned proximate to the first annular stopper 54 and in some positions the first annular stopper 54 overlaps the first annular port 62 and thus blocks or meters flow of hydraulic fluid therethrough, as shown in FIGS. 2 and 3. The second annular port 64 is positioned proximate tothe second annular stopper 56. The spool element 52 is movable in the internal chamber 50 so that the first annular stopper 54 is movable into partial or complete alignment with the first annular port 62 to provide varying degrees of restriction of the first annular port 62 to thereby meter flow of the hydraulic fluid into the pressure-compensation portion 42, as shown in FIGS. 2-3. The second annular' port 64 is positioned in the internal chamber 50 so that regardless of the position of the spool element 52 in the internal chamber 50, the second annular port 64 remains unrestricted by the first or the second annular' stopper 54, 56. When the first annular stopper 54 is positioned in complete alignment with the first annular port 62, fluid communication between the inlet 46 and the outlet 48 is cut off. The spring 60 is configured to bias the spool element 52 so that the first annular stopper 54 is normally prevented from complete alignment with the first annular port 62. In the event that the spring 60 fails against the fluid pressure, the spool element 52 is configured so that the first annular stopper 54 would move into complete alignment with the first annular port 62 and the flow of the hydraulic fluid would be completely restricted.

[0040] The flow control portion 44 is connected to the pressure-compensation portion 42 via the fluid conduit 110. The flow control portion 44 includes a variable orifice 70 and a flow adjustment valve 72. The variable orifice 70 is configured to fluidly couple the fluid conduit 110 to the fluid conduit 112. The variable orifice 70 has a flow area 71 that can be increased or decreased via the operation of the flow control portion 44. The flow area 71 of the variable orifice 70 thus defines a desired flow rate of the hydraulic fluid through the PCFC valve 20.

[0041] In the illustrated embodiment, the flow control portion 44 includes a flow adjustment valve 72 comprising a manually operable knob that is threadedly connected to the valve housing 40 so that rotation of the knob in a first direction moves a plunger 73 further into seating engagement with a valve seat 75 to close the variable orifice 70 and so that rotation of the knob in an opposite, second direction moves the plunger 73 further out of seating engagement with the valve seat 75 to open the variable orifice 70; however, in other embodiments the flow control portion 44 may be any another type of valve suitable for opening and closing the orifice, such as a solenoid-operated valve or other type of conventional valve that is manually operable and / or operable by the controller 97 to function in accordance with the above description, and optionally operable by the user input device 99 via the controller 97, as described herein above.

[0042] FIGS. 2 and 3 show the PCFC valve 20 in use. Initially, the hydraulic fluid is supplied via the inlet 46 into the internal chamber 50. The hydraulic fluid has a fluid pressurewhich is directly proportional to a flow rate of the hydraulic fluid into the inlet 46. As the hydraulic fluid is conveyed through the pressure-compensation portion 42, the flow rate of the hydraulic fluid is limited at the variable orifice 70 to the flow rate that is set by the flow adjustment valve 72, as explained herein above. Insofar as the flow rate into the inlet 46 is not the same as the flow rate that is set by the flow adjustment valve 72, when the flow area 71 of the variable orifice 70 restricts the flow of the hydraulic fluid, a resultant hydraulic pressure builds within the internal chamber 50 of the PCFC valve 20. The combined fluid pressure of the hydraulic fluid being conveyed through the inlet 46 and the resultant hydraulic pressure builds and produces a differential pressure that exerts working forces on the working surfaces 66, 67, and 68, which are within the pressure-compensation portion 42, and directly exposed to the hydraulic fluid within the internal chamber 50. Within the internal chamber 50, the working forces upon the working surfaces 66 and 68 are equal and opposite, and effectively cancel out. The working force upon the working surface 67 is not directly opposed by the hydraulic fluid, but rather, is opposed by the compression of the spring 60 via the working surface 69. As such, the differential pressure exerts working forces directly onto the working surfaces 66, 67, 68, and indirectly onto the working surface 69 to move the spool element 52 within the internal chamber 50. The axial (left-right) movement of the spool element 52 is a result of the difference between the working force on the working surface 67 and the working force exerted on the working surface 69 via the bias of the spring 60, and this difference moves the spool element 52 so that the first annular stopper 54 is brought into partial or complete alignment with the first annular port 62. The PCFC valve 20 is thus configured so that the differential pressure and resultant movement of the spool element 52 automatically adjusts the flow rate of hydraulic fluid into the internal chamber 50 until the flow rate into the internal chamber 50 via the first annular port 62 is the same as the flow rate through the variable orifice 70, which is set by the flow adjustment valve 72. In other words, the pressurecompensation portion 42 automatically calibrates the flow of hydraulic fluid through the PCFC valve 20 until the flow rate of hydraulic fluid into the PCFC valve 20 matches the flow rate of hydraulic fluid out of the PCFC valve 20.

[0043] Referring back to FIG. 1, the present inventors incorporated the PCFC valve 20 in the system 100 such that the system 100 automatically and passively compensates for varying fluid pressures that result from different loads being lifted and lowered by the piston-cylinder 12 and to output the hydraulic fluid to the tank 16 at a constant flow rate, which advantageously resulted ina controlled (constant or substantially constant) rate of lowering of the load, despite these variations. For example, as described herein below, the system 100 is advantageously configured to lower a first load (FIG. 2) and a different second load (FIG. 3) at the same rate, even when for example the loads are different, for example when the first load is smaller than the second load.

[0044] Referring to FIGS. 1 and 2, when the first load is lowered by the piston-cylinder 12, the hydraulic fluid is conveyed through the inlet 46 of the PCFC valve 20 at a first initial flow rate, and into the fluid conduits 108, 110 and the pressure communication line 114 before passing through the variable orifice 70. As the flow rate is restricted to a desired flow rate by the flow adjustment valve 72 and the variable orifice 70, the differential fluid pressure exerts working forces onto the working surfaces 66, 67, 68, and 69 which causes movement of the spool element 52 against the bias of the spring 60 and brings the first annular stopper 54 into a partial overlapping alignment with the first annular port 62, as shown in FIG. 2 and described herein above. As such, the PCFC valve 20 consistently outputs the hydraulic fluid at the flow rate set by the flow adjustment valve 72 of the flow control portion 44, which causes the load to be lowered at a constant speed.

[0045] Referring to FIGS. 1 and 3, when the second load, which is greater than the first load, is lowered by the piston-cylinder 12, the hydraulic fluid is conveyed into the inlet 46 at a second initial flow rate that is greater than the first initial flow rate. As the flow rate is restricted to the same desired flow rate by the flow adjustment valve 72 and the variable orifice 70, the differential fluid pressure exerts working forces onto the working surfaces 66, 67, 68, and 69 which causes movement of the spool element 52 against the bias of the spring 60 and brings the first annular stopper 54 into the depicted partial but lesser overlapping alignment with the first annular port 62, compared to FIG. 2. As such, the PCFC valve 20 consistently outputs the hydraulic fluid at the flow rate set by the flow adjustment valve 72 of the flow control portion 44, which causes the load to be lowered at the same, constant speed as when the first load is lowered.

[0046] Comparing FIG. 2 to FIG. 3, the spool element 52 is positioned so that the first annular port 62 is restricted to a greater degree when lowering the first load in comparison to the second load. As such, the degree of restriction of the first annular port 62 is dependent upon the load being lowered by the piston-cylinder 12 and the flow area 71 of the variable orifice 70. It will thus be understood by one having ordinary skill in the art that the PCFC valve 20 is configured tocause the single-acting piston-cylinder 12 to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.

[0047] Referring back to FIG. 1, to operate the system 100 to lift a load, the control valve 22 is caused by the controller 97 to move into the closed position, for example upon a request from the user via the user input device 99 to lift the load, which prevents the hydraulic fluid from being exhausted from the piston-cylinder 12 to the tank 16 via the fluid relief line 106. The pressure relief valve 18 remains in its closed position. The pump 14 is operated to pump the hydraulic fluid from the tank 16, through the fluid line 103 and the fluid line 102 and into the first chamber 26 of the piston-cylinder 12. As the hydraulic fluid is conveyed into the first chamber 26, the pressure of the hydraulic fluid causes the piston 24 to extend, which lifts the load on the piston-cylinder 12.

[0048] To operate the system 100 to lower the load, the control valve 22 is caused by the controller 97 to move into the open position and the pump 14 is turned off. This occurs for example upon a request from the user via the user input device 99. This allows the hydraulic fluid to be exhausted from the piston-cylinder 12 to the tank 16 via the fluid relief line 106. The pressure relief valve 18 remains in its closed position. The weight of the load and optionally also the force of the return spring element 28 causes the hydraulic fluid to be exhausted from the piston-cylinder 12 to the fluid line 102. The PCFC valve 20 is connected to the fluid relief line 106 and, as described above, is configured to receive and to automatically and passively restrict or meter the flow rate of the hydraulic fluid which is exhausted from the piston-cylinder 12 to the flow rate set by the flow control portion 44 of the PCFC valve 20. The hydraulic fluid exhausted from the PCFC valve is then conveyed to the tank 16.

[0049] More specifically, the hydraulic fluid is exhausted from the first chamber 26 via the fluid line 102 to the fluid relief line 106, wherein the hydraulic fluid passes through the PCFC valve 20, wherein the flow rate is restricted to the desired flow rate before being conveyed to the tank 16. As the hydraulic fluid is exhausted from the first chamber 26, the piston 24 is retracted into the piston-cylinder 12 according to the flow rate that is being controlled by the PCFC valve 20, which lowers the load on the piston-cylinder 12 at the noted substantially constant rate that remains the same regardless of the load amount.

[0050] FIG. 4 shows a second non-limiting embodiment of a hydraulic system 200 according to the present disclosure having a single-acting piston-cylinder 12 that is hydraulically operated by a pump 14 and a pressure-compensated flow control valve 20 that is configured tocause the piston-cylinder 12 to lower a load at a speed that is substantially constant and remains the same regardless of the load amount. The PCFC valve 20 may be configured according to the embodiment shown in FIGS. 2-3, or it may be another type of conventional pressure-compensation valve that functions in the manner described herein above regarding FIGS. 1-3.

[0051] Like the embodiment described herein above regarding FIG. 1, the piston-cylinder 12 shown in FIG. 4 is configured so that extension and retraction of the piston 24 corresponds to lifting and lowering of a load on the piston-cylinder 12. However, unlike the embodiment in FIG. 1, the PCFC valve 20 in FIG. 4 is advantageously configured for removable attachment to the system 200.

[0052] Like the embodiment described herein above regarding FIG.l, the system 200 has a hydraulic circuit 10 that is fluidly connected to the piston-cylinder 12 via a fluid line 102. The hydraulic circuit 10 includes the noted fluid lines 103, 104, the tank 16, the pump 14, and the pressure relief valve 18, as well as a fluid relief line 106 and associated control valve 22. These items are configured to function as is described herein above regarding FIG. 1. Unlike the embodiment described regarding FIG. 1, the system 200 shown in FIG. 4 has a PCFC valve 20 in combination with an associated check valve 21, which are contained together in a housing 80 that is configured for removable attachment to the system 200.

[0053] In FIG. 4, the housing 80 is shown connected to the fluid line 102 between the piston-cylinder 12 and the hydraulic circuit 10, and more particularly between the first chamber 26 and the intersection of the fluid lines 102, 104, and 106. The housing 80 has a fluid line 122 that is configured to provide the hydraulic fluid between the fluid line 102 and the PCFC valve 20. The housing 80 also has a fluid line 120 that is connected to the fluid line 122 on opposite sides of the PCFC valve 20 and generally runs parallel relative to the fluid line 120 extending therebetween. The check valve 21 is configured to control fluid flow through the fluid line 120. In its closed position, the check valve 21 prevents flow of the hydraulic fluid through the housing 80 past the PCFC valve 20. In other words, for the hydraulic fluid to flow through the housing 80 when the check valve 21 is in its closed position it must pass through the PCFC valve 20. In its open position, the check valve 21 permits flow of the hydraulic fluid through the housing 80 past the PCFC valve 20. In other words, in its open position, the hydraulic fluid is permitted to bypass the PCFC valve 20 as it flows through the housing 80. In the illustrated embodiment, the check valve 21 is a ballthat seats in a ball seat in the closed position; however, type of check valve 21 may vary from what is shown and may include any other type of passively or actively controllable valve.

[0054] The housing 80 may be a permanent fixture of the system 200. In other embodiments the housing 80 may be a cartridge- style or plug-in-style housing (e.g., drop-in style housing), and / or include any other removable, retrofittable connector or coupler device conventionally known in the art for coupling to the fluid line 102. This embodiment provides the opportunity for the manufacturer to provide a cartridge-style or plug-in style housing having a manifold with multiple inlet and outlet ports, for example being configured to couple to hydraulic lines of the hydraulic circuit 10, providing the ability to implement the PCFC valve 20 into various systems having a different number of piston-cylinder arrangements. The housing 80 may thus be configured so that the PCFC valve 20 and the associated check valve 21 can be easily added to an existing hydraulic system, thus effectively retrofitting that existing system into a new and improved system that is configured for providing controlled load lowering of differing loads at a substantially constant speed.

[0055] To operate the system 200 to lift a load, the control valve 22 is moved into its closed position, which prevents the hydraulic fluid from being exhausted from the piston-cylinder 12 to the tank 16 via the fluid relief line 106. The hydraulic fluid is pumped from the tank 16 to the piston-cylinder 12 via the hydraulic circuit 10. The pump 14 is operated to pump the hydraulic fluid from the tank 16, through the fluid line 103, and into the housing 80 via the fluid line 102. In the housing 80, the pressure of the hydraulic fluid causes the check valve 21 to open, which permits the hydraulic fluid to flow through the check valve 21 to the fluid line 102, bypassing the PCFC valve 20. The hydraulic fluid is then conveyed through the fluid line 102 and into the first chamber 26 of the piston-cylinder 12. As the hydraulic fluid is conveyed into the first chamber 26, the pressure of the hydraulic fluid causes the piston 24 to extend, which lifts the load on the pistoncylinder 12.

[0056] To operate the system 200 to lower a load, the controller 97 moves the control valve 22 into its open position and turns off the pump 14. As described herein above, this allows the hydraulic fluid to be exhausted to the tank 16 via the fluid relief line 106. The hydraulic fluid is conveyed from the piston-cylinder 12 to the tank 16 via the fluid line 102 and the hydraulic circuit 10. As described above, the PCFC valve 20 is contained in the housing 80 which is fluidly connected to the fluid line 102. As described herein above in reference to FIG. 2, the PCFC valve20 is advantageously configured to automatically and passively restrict the flow rate of the hydraulic fluid being exhausted from the piston-cylinder 12 to a set flow rate, thus lowering the load at a speed that is substantially constant and remains the same regardless of the load amount.

[0057] When the control valve 22 is moved into the open position and the pump 14 is turned off, as described herein above, the hydraulic fluid is exhausted from the first chamber 26 and into the housing 80 via the fluid line 102. In the housing 80, the pressure of the hydraulic fluid forces the check valve 21 into its closed position and thus the hydraulic fluid is conveyed through the fluid line 122 and caused to flow through the PCFC valve 20, in which the flow rate of the hydraulic fluid is restricted to the desired flow rate set by the flow control portion 44, as described herein above. The hydraulic fluid is then conveyed through the fluid line 102, through the fluid relief line 106, and to the tank 16. As the hydraulic fluid is exhausted from the first chamber 26, the piston 24 is retracted into the piston-cylinder 12 at the above-noted same, substantially constant speed, regardless of the load amount, as set by the flow control portion 44 of the PCFC valve 20.

[0058] FIG. 5 shows an alternate configuration of the system 200 of FIG. 4, having a single-acting piston-cylinder 12 that is hydraulically operated by a pump 14 and a pressure- compensated flow control valve 20 that is configured to cause the piston-cylinder 12 to lower a load at a speed that is substantially constant and remains the same regardless of the load amount. In FIG. 5, the housing 80 containing the PCFC valve 20 and the check valve 21 is located in a housing 82 of the piston-cylinder 12. The housing 80 may permanently fixed inside the housing 82 or it may be removably attached to the housing 82, for example in the above-noted cartridgestyle or plug-in style arrangement. In other embodiments, the housing 80 may be omitted altogether and the PCFC valve 20 and check valve 21 mounted to an interior portion of the pistoncylinder 12. Otherwise, the system 200 shown in FIG. 5 operates substantially the same as is described herein above regarding FIG. 4.

[0059] FIG. 6 shows a third non-limiting embodiment of a hydraulic system 300 according to the present disclosure. Unlike the above-described embodiments, the PCFC valve 20 in FIG. 6 is provided in conjunction with more than one single-acting piston cylinder. FIG. 6 shows a first single-acting piston-cylinder 12 and a second single-acting piston-cylinder 12’; however, it should be understood that this embodiment may include three or more single-acting piston-cylinders. Like the embodiment described herein above regarding FIG. 1, the first piston-cylinder 12 has a piston 24 that extends in the piston-cylinder 12 so that extension and retraction of the piston 24corresponds to lifting and lowering of a first load. The second piston-cylinder 12’ has a piston 24' which extends in the second piston-cylinder 12’ so that extension and retraction of the piston 24’ corresponds to lifting and lowering of a second load. The first load and the second load may be the same as each other or different.

[0060] The system 300 also has a hydraulic circuit 10, which is fluidly connected to the first and the second piston-cylinder 12, 12’ via the fluid lines 102, 115, and 117. The fluid line 115 extends from the fluid line 102 to the first piston-cylinder 12 and the fluid line 117 extends from the fluid line 102 to the second piston-cylinder 12’. Like the embodiment described herein above regarding FIG.l, the hydraulic circuit 10 includes the noted fluid lines 103, 104, the tank 16, the pump 14, and the pressure relief valve 18, as well as the fluid relief line 106 and control valve 22. The system 300 also includes the PCFC valve 20 and a check valve 21 which are contained in a housing 80, as described above regarding FIG. 4. In the illustrated embodiment, the housing 80 is connected to the fluid line 102; however, this may vary, as described herein above.

[0061] To operate the system 300 to lift a load, the control valve 22 is moved into the closed position, as described herein above, which prevents the hydraulic fluid from being exhausted from the first and the second piston-cylinder 12, 12’ to the tank 16 via the fluid relief line 106. The pressure relief valve 18 remains in the closed position. The hydraulic fluid is pumped from the tank 16 to the first and the second piston-cylinder 12, 12’ via the hydraulic circuit 10. The hydraulic fluid is pumped from the tank 16, through the fluid lines 103, 104 and into the housing 80 via the fluid line 102. In the housing 80 the pressure of the hydraulic fluid opens the check valve 21 such that the hydraulic fluid bypasses the PCFC valve 20 and is conveyed through the fluid line 102 and into the first and the second piston-cylinder 12, 12’ via the fluid lines 115, 117, respectively. As the hydraulic fluid is conveyed into the first piston-cylinder 12, the piston 24 is extended, which lifts the first load on the first piston-cylinder 12. As the hydraulic fluid is conveyed into the second piston-cylinder 12, the piston 24’ is extended, which lifts the second load on the second piston-cylinder 12’.

[0062] To operate the system 300 to lower the first and second loads, the control valve 22 is moved into the open position and the pump 14 is turned off, which allows the hydraulic fluid to be exhausted from the first and the second piston-cylinders 12, 12’ to the tank 16 via the fluid relief line 106. The weight of the first and second loads forces the hydraulic fluid from the first and the second piston-cylinder 12, 12’ to the tank 16 via the hydraulic circuit 10. The PCFC valve20 is fluidly connected to the fluid line 102 and, as described in reference to FIG. 2, is configured to automatically and passively restrict the flow rate of the hydraulic fluid which is exhausted from the first and the second piston-cylinder 12, 12’ to the flow rate set by the flow adjustment valve 72 of the flow control portion 44.

[0063] More specifically, when the control valve 22 is moved into the open position, the hydraulic fluid is exhausted from the first and the second piston-cylinder 12, 12’ into the housing 80 via the fluid lines 102, 115, 117. In the housing 80, the pressure of the hydraulic fluid forces the check valve 21 into its closed position. As such, the hydraulic fluid is conveyed through the PCFC valve 20, in which the flow rate of the hydraulic fluid is restricted to the selected flow rate, as described herein above. The hydraulic fluid is then conveyed through the fluid line 102, through the fluid relief line 106, and to the tank 16. As the hydraulic fluid is exhausted from the first and the second piston-cylinders 12, 12’, the pistons 24, 24’ retract, which lowers the first load and the second load. Insofar as the PCFC valve 20 is positioned in the pathway of the hydraulic fluid between the fluid lines 115, 117 and the tank 16, the PCFC valve 20 restricts the hydraulic fluid so that the first and the second load are lowered at a same desired rate, as described herein above.

[0064] As stated above, the illustrated embodiment shows a system having two pistoncylinders; however, this is not limiting. In embodiments where the PCFC valve is positioned in series in the hydraulic circuit between a junction for a plurality of piston-cylinders and the fluid relief tank, the system may include any number or a plurality of piston-cylinders, which all may be restricted to lower at a speed that is substantially constant and remains the same regardless of the load amount.

[0065] FIG. 7 shows a fourth non-limiting embodiment of a hydraulic system 400 which is like the embodiment of FIG. 6, except it includes a second PCFC valve 20’ . The first PCFC valve 20 is configured to control lifting and lowering of the first load on the first piston-cylinder 12, whereas the second PCFC valve 20’ is configured to control lifting and lowering of the second load on the second piston-cylinder 12’. A first housing 80 contains the first PCFC valve 20, a first check valve 21, and fluid lines 120, 122. A second housing 80’ contains the second PCFC valve 20’, a second check valve 21’, and fluid lines 126, 128. The first housing 80 is connected to the fluid line 115 and the second housing 80’ is connected to the fluid line 117. In the system 400, the first piston-cylinder 12 and the first PCFC valve 20 are arranged in parallel to the second pistoncylinder 12’ and the second PCFC valve 20’, respectively, and as such, the first and the secondloads may be lowered at same or different rates according to the respective setting of the flow control portion 44 of each of the PCFC valves 20, 20’.

[0066] To operate the system 400 to lift a load, the control valve 22 is moved into the closed position, as described herein above, which prevents the hydraulic fluid from being exhausted from the first and the second piston-cylinder 12, 12’ to the tank 16 via the fluid relief line 106. The hydraulic fluid is pumped from the tank 16 to the first and second piston-cylinders 12, 12’. The hydraulic fluid is conveyed through the hydraulic circuit 10 and into the fluid lines 102, 115, 117. The hydraulic fluid is conveyed from the fluid line 102 into the first housing 80 via the fluid line 115 and into the second housing 80’ via the fluid line 117.

[0067] In the first housing 80, the pressure of the hydraulic fluid forces the check valve 21 into its open position such that the hydraulic fluid is permitted to bypass the PCFC valve 20 and flow through the fluid lines 120, 115 to the first piston-cylinder 12. As the hydraulic fluid is conveyed into the first piston-cylinder 12, the piston 24 is extended, which lifts the first load on the first piston-cylinder 12. In the second housing 80’, the pressure of the hydraulic fluid forces the check valve 21’ into its open position such that the hydraulic fluid is permitted to bypass the PCFC valve 20’ and flow through the fluid lines 126, 117 to the second piston-cylinder 12’. As the hydraulic fluid is conveyed into the second piston-cylinder 12’, the piston 24’ is extended, which lifts the second load on the second piston-cylinder 12’.

[0068] To operate the system 400 to lower the first and the second load, the control valve 22 is moved into the open position, as described herein above, which allows the hydraulic fluid to be exhausted from the first and the second piston-cylinder 12, 12’ to the tank 16 via the fluid relief line 106. The weight of the first and second loads forces the hydraulic fluid from the first and the second piston-cylinder 12, 12’ to the tank 16 via the hydraulic circuit 10. As will be understood from the embodiments described herein above, the first PCFC valve 20 is configured to automatically and passively restrict the flow rate of the hydraulic fluid that is exhausted from the first piston-cylinder 12 according to the setting of the flow control portion 44 of the first PCFC valve 20. The second PCFC valve 20’ is configured to automatically and passively restrict the flow rate of the hydraulic fluid that is exhausted from the second piston-cylinder 12’ according to the setting of the flow control portion 44 of the second PCFC valve 20’.

[0069] When the control valve 22 is moved into the open position, the hydraulic fluid is exhausted from the first piston-cylinder 12 and into the first housing 80 via the fluid line 115.Simultaneously, the hydraulic fluid is exhausted from the second piston-cylinder 12’ and into the second housing 80’ via the fluid line 117. In the first housing 80, the hydraulic fluid is conveyed through the fluid line 122 and through the first PCFC valve 20, in which the flow rate of the hydraulic fluid is restricted to the flow rate set via the flow control portion 44 of the first PCFC valve 20. The hydraulic fluid is then conveyed through the fluid line 102, through the fluid relief line 106, and to the tank 16. In the second housing 80’, the hydraulic fluid is conveyed through the fluid line 124 and through the second PCFC valve 20’, in which the flow rate of the hydraulic fluid is restricted to the flow rate set via the flow control portion 44 of the second PCFC valve 20’. The hydraulic fluid is then conveyed through the fluid line 102, through the fluid relief line 106, and to the tank 16.

[0070] As the hydraulic fluid is exhausted from the first piston-cylinder 12, the piston 24 is retracted, which lowers the first load. As the hydraulic fluid is exhausted from the second pistoncylinder 12’, the piston 24’ is retracted, which lowers the second load. Both of these loads, respectively, are lowered at a substantially constant speed regardless of the load amount.

[0071] The illustrated embodiment shows a system having two piston-cylinders, although this is not limiting. The system may include any number or a plurality of piston-cylinders, which all may be restricted to lower at same or a different respective substantially constant speed regardless of individual or combined load amounts. In embodiments where a system has a plurality of piston cylinders, a corresponding PCFC valve may be positioned in the flow of the hydraulic fluid between each of the plurality of piston-cylinders and a junction which joins the hydraulic fluid exhausted from the plurality of piston cylinders. In other embodiment systems, some of the plurality of piston-cylinders may be restricted via a common PCFC valve, as described regarding FIG. 6, while some of the plurality of piston-cylinders may be restricted via individual PCFC valves, as described regarding FIG. 7.

[0072] Through additional research and development, the present inventors determined that it would be advantageous to incorporate the above-described pressure compensation flow control valve technology into the lifting side of the hydraulic circuit 10, in particular so that the hydraulic fluid pumped by the pump 14 flows through the pressure compensation flow control valve. This advantageously produces a controlled force from the hydraulic fluid to the pistoncylinder 12, thus achieving a controlled load raising at a constant rate that remains the sameregardless of the load amount and regardless of other factors such as the operating speed of pump. FIGS. 8A-8C depict a non-limiting embodiment of such a system.

[0073] FIGS. 8A-8C are schematic views of a hydraulic system 500 for raising and lowering a load according to a fifth embodiment of the present disclosure. As will be further described herein below, the system 500 is advantageously operable in the three operational states shown in FIGS. 8A-8C, respectively, including a first load-raising state (FIG. 8A); a relatively slower and relatively controlled, second load- raising state (FIG. 8B); and a controlled loadlowering state (FIG. 8C).

[0074] In general, the system 500 includes the above-described hydraulic circuit 10, the single-acting piston-cylinder 12 that is fluidly coupled to the hydraulic circuit 10 and configured so that extension and retraction of the piston 24 corresponds to lifting and lowering of a load on the piston-cylinder 12, the pump 14 that is operable to pump the hydraulic fluid from a tank 16 to the piston-cylinder 12 via the hydraulic circuit 10, and the control valve 22 that is moved into a closed position to prevent the hydraulic fluid from being exhausted from the piston-cylinder 12 to the tank 16 and into an open position to allow the hydraulic fluid to be exhausted from the pistoncylinder 12 to the tank 16. The system 500 also includes the PCFC valve 20 configured to cause the piston-cylinder 12 to lower the load at a speed that is substantially constant and remains the same regardless of the load amount, as described herein above. In the system 500, the PCFC valve 20 is located in the hydraulic circuit 10 between the control valve 22 and the tank 16; however, as explained herein above, the location of the PCFC valve 20 may vary from what is shown and described.

[0075] In addition, the system 500 includes a second PCFC valve 20’, which, like the above-mentioned PCFC valve 20 (the “first PCFC valve 20”), may be configured according to the embodiment shown in FIGS. 2-3, or may have another configuration that is known in the art. A three-way fluid control valve 90 is also provided in the hydraulic circuit 10 for controlled switching amongst the above-noted operational states of the system 500. In non-limiting embodiments, the three-way fluid control valve 90 is a solenoid valve that is selectively (electrically) actuated by the controller 97 into the three positions shown in FIGS. 8A-8C, respectively. A pressure relief valve 18 is also provided and is configured to automatically open or close depending upon the pressure of the hydraulic fluid, thereby automatically regulating pressure of the hydraulic fluid in the event that the hydraulic fluid in the system 500 between the pump 14 and the fluid control valve 90exceeds a predetermined limit, for example if and when the pump 14 is pumping the hydraulic fluid into the hydraulic circuit 10 with the fluid control valve 90 in the closed position shown in FIG. 8C, as will be described herein below.

[0076] Referring to FIG. 8A, the system 500 is operable in the first load raising state based upon an input from controller 97 to the control valve 22, which can for example be prompted based on programming of the controller and / or based upon an input by the user to the user input device 99. The controller 97 causes the control valve 22 to move into its closed position, as shown. The controller 97 also moves the fluid control valve 90 into the position shown, particularly wherein hydraulic fluid pumped by the pump 14 is prevented from flowing from the fluid line 102 into the fluid line 122 to the second PCFC valve 20’, and is permitted to flow from the fluid line 102 through the fluid line 120 to the first chamber 26 of the piston-cylinder 12, which as described above causes the piston-cylinder 12 to raise the load. In some embodiments, the controller 97 may also turn on the pump 14 to pump the hydraulic fluid from the tank 16 to the piston-cylinder 12 via the fluid lines 102, 120; however, in the particular non-limiting embodiment shown in FIG. 8A, the pump 14 is configured to continuously operate in all of the operating modes. The pressure relief valve 18 remains in its closed position and thus the hydraulic fluid from the pump 14 is supplied to the piston-cylinder 12 unless for some reason the pressure of the hydraulic fluid in the hydraulic circuit 10 exceeds an expected pressure, at which point the pressure relief valve 18 opens to dump hydraulic fluid back to the tank 16.

[0077] Thus, when the fluid control valve 90 is in the position shown, the pump 14 is directly connected to the piston-cylinder 12 via the fluid line 120, apart from the second PCFC valve 20’. The pump 14 is configured to convey hydraulic fluid from the tank 16, through the fluid lines 102, 120, and into the first chamber 26 of the piston-cylinder 12. As the hydraulic fluid is conveyed into the first chamber 26, the piston 24 is extended, which lifts the load on the pistoncylinder 12. As such, it will be understood that in the non-limiting illustrated embodiment the first load raising state provides full flow of hydraulic fluid from the pump 14 to the piston-cylinder 12 without an intervening flow restriction or pressure compensated control (e.g., without flowing through the second PCFC valve 20’), and thus raises the piston-cylinder 12 at a relatively high speed compared to the second mode described herein below, in which the hydraulic fluid does flow through the second PCFC valve 20’ .

[0078] Referring to FIG. 8B, the system is operable in the relatively slower and controlled, second load-raising state based upon an input from controller 97, which can for example be prompted based on programming of the controller and / or based upon an input by the user to the user input device 99. The controller 97 causes the control valve 22 to move into its closed position, as shown. The controller 97 also moves the fluid control valve 90 into the position shown, particularly wherein hydraulic fluid pumped by the pump 14 is prevented from flowing from the fluid line 102 into the fluid line 120 and is caused to flow from the fluid line 102 through the fluid line 122 to the second PCFC valve 20’ . As described herein above regarding FIGS. 2-3, the second PCFC valve 20’ is configured to consistently output the hydraulic fluid it receives at the flow rate set by the flow control portion 44 and thus is configured to provide a flow of hydraulic fluid to the piston-cylinder 12 via the line 122 that causes the piston-cylinder 12 to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump 14 is operated and regardless of the amount of the load on the piston-cylinder 12.

[0079] In some embodiments, the controller 97 may also turn on the pump 14 to pump the hydraulic fluid from the tank 16 to the piston-cylinder 12 via the fluid lines 102, 120; however, in the particular non-limiting embodiment shown in FIG. 8A, the pump 14 is configured to continuously operate. The pressure relief valve 18 remains in its closed position and thus the hydraulic fluid from the pump 14 is supplied to the second PCFC valve 20’ via the fluid control valve 90, unless for some reason the pressure of the hydraulic fluid in the hydraulic circuit 10 exceeds an expected pressure.

[0080] Thus, when the fluid control valve 90 is in the position shown, the pump 14 is connected to the piston-cylinder 12 via the fluid line 122. The pump 14 is configured to convey the hydraulic fluid from the tank 16, through the fluid lines 102, 122, and through the second PCFC valve 20’. As described above, and as shown in FIG. 2, the second PCFC valve 20’ is configured to automatically and passively restrict the flow rate of the hydraulic fluid which is conveyed from the pump 14 into the piston-cylinder 12 to a desired flow rate. The hydraulic fluid is output from the second PCFC valve 20’ at the desired flow rate and conveyed through the fluid line 122 and into the first chamber 26 of the piston-cylinder 12. As the hydraulic fluid is conveyed into the first chamber 26, the piston 24 is extended, which lifts the load on the piston-cylinder 12.

[0081] Thus, it will be understood that in the non-limiting illustrated embodiments, the second load-raising state provides a relatively slower and controlled load raising rate compared to the first load- raising state, as governed by the second PCFC valve 20’.

[0082] Referring to FIG. 8C, the system 500 is operable in the load-lowering state based upon an input from controller 97, which can for example be prompted based on programming of the controller 97 and / or based upon an input by the user to the user input device 99. The controller 97 causes the control valve 22 to move into its open position, as shown. The controller 97 also moves the fluid control valve 90 into the closed position shown, particularly wherein hydraulic fluid pumped by the pump 14 is prevented from flowing from the fluid line 102 into either the fluid line 120 or the fluid line 122 to the second PCFC valve 20’. Instead, the pumpl4 is either shut off by the controller 97, or continued operation of the pump 14 increases the pressure of the hydraulic fluid in the fluid line 102 until the pressure relief valve 18 is forced open, which discharges the hydraulic fluid back to the tank 16.

[0083] The weight of the load and optionally the bias of the return spring element 28 causes the piston 24 to lower in the piston-cylinder 12 and forces the hydraulic fluid through the open control valve 22 and to the tank 16 via the first PCFC valve 20. As described herein above regarding FIGS. 2-3, the first PCFC valve 20 is configured to consistently output the hydraulic fluid at the flow rate set by the flow control portion 44 and thus is configured to provide a return flow of hydraulic fluid to the tank 16, which in turn causes the piston-cylinder 12 to lower the load at a speed that is substantially constant and remains the same regardless of the load amount, all as described herein above regarding the previous embodiments.

[0084] Although FIGS. 8A-8C depict a single-acting piston-cylinder 12, it should be recognized that in other embodiments the system 500 may include a double-acting piston-cylinder 12 in combination with the second PCFC valve 20’, wherein the second PCFC valve 20’ is configured to provide the above-noted controlled raising of the piston 24b in the double-acting piston-cylinder.

[0085] Advantageously, non-limiting embodiments disclosed herein do not necessarily require a user input to set a valve to dial in the speed or load. Non-limiting embodiments disclosed herein may be used in various known devices for lifting heavy objects, including but not limited to lifting devices in the fields of rail car care, off highway, and / or any application where a doubleacting piston-cylinder with a counter-balance valve is currently used to control the lowering rate.Non-limiting embodiments disclosed herein facilitate use of a smaller, lighter and less expensive assembly than the prior ail. Non-limiting embodiments disclosed herein advantageously may not require a user to manually set the device, which limits a risk of improper setting or lowering a low too quickly or too slowly. However advantageously the pressure-compensated flow control valve may be user adjustable, which may permit the user to change the setting for different loads on the piston-cylinder.

[0086] This written description uses embodiments to disclose the invention and enables any person skilled in the ail to make and use the invention. Certain terms have been used for brevity, clarity and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed.

[0087] The present disclosure comprises the subject matter described in the following clauses which may form the basis for claim amendments and / or future divisional applications:Clause 1. A hydraulic system for raising and lowering a load, the hydraulic system comprising: a hydraulic circuit for conveying a hydraulic fluid, a single-acting piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the single-acting piston-cylinder via the hydraulic circuit to cause the single-acting piston-cylinder to raise the load, and a pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the single-acting piston-cylinder upon lowering of the load, wherein the PCFC valve is configured to cause the single-acting piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.Clause 2. The hydraulic system according to clause 1, wherein the PCFC valve is removably coupled to the hydraulic system.Clause 3. The hydraulic system according to clause 1, wherein the PCFC valve is removably coupled to the hydraulic circuit between the pump and the PCFC valve.Clause 4. The hydraulic system according to clause 1, further comprising a check valve, the check valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and being configured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.Clause 5. The hydraulic system according to clause 1, further comprising a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the hydraulic system.Clause 6. The hydraulic system according to clause 5, further comprising a check valve in the housing, the check valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and being configured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.Clause 7. The hydraulic system according to clauses 5 or 6, wherein the housing comprises a cartridge that is configured to be removably coupled to the hydraulic system.Clause 8. The hydraulic system according to clause 7, wherein the cartridge is configured to be removably coupled to the hydraulic circuit.Clause 9. The hydraulic system according to clause 7, wherein the cartridge is configured to be removably coupled to the single-acting piston-cylinder.Clause 10. The hydraulic system according to clause 1, wherein the PCFC valve disposed in the single-acting piston-cylinder.Clause 11. The hydraulic system according to clause 10, further comprising a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the single- acting piston-cylinder.Clause 12. The hydraulic system according to clauses 10 or 11, further comprising a check valve that is configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and that is configured to close to cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.Clause 13. The hydraulic system according to clause 1, wherein the single-acting pistoncylinder is one of a plurality of single-acting piston-cylinders configured to raise and lower a plurality of loads, and wherein each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is configured to raise and lower a respective load in the plurality of loads.Clause 14. The hydraulic system according to clause 13, wherein the PCFC valve receives the hydraulic fluid from the plurality of single-acting piston-cylinders such that the PCFC valve causes the plurality of single-acting piston-cylinders to lower the plurality of loads at a speed that is substantially constant and is the same regardless of the load amount.Clause 15. The hydraulic system according to clause 1, wherein the single-acting pistoncylinder is one of a plurality of single-acting piston-cylinders configured to raise and lower a plurality of loads, and wherein the PCFC valve is one of a plurality of PCFC valves that are fluidly coupled to the plurality of single-acting piston-cylinders in parallel so that each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is coupled to a different respective one of the plurality of PCFC valves.Clause 16. The hydraulic system according to clause 1, wherein the PCFC valve comprises a housing having an inlet that receives the hydraulic fluid from the single-acting piston-cylinder, an outlet that discharges the hydraulic fluid, and a pressure-compensation portion between the inlet and the outlet, wherein the pressure-compensation portion is configured to passively control a flow rate at which the hydraulic fluid flows from the single-acting piston-cylinder through the valvehousing so that the flow rate and thus a lowering speed of the single-acting piston-cylinder remains substantially constant regardless of the load amount.Clause 17. The hydraulic system according to clause 16, wherein the pressure-compensation portion is configured to automatically adjust a size of an orifice to restrict flow of the hydraulic fluid through the PCFC valve.Clause 18. The hydraulic system according to clause 17, wherein the PCFC valve further comprises a flow control portion configured to set a target flow rate for the PCFC valve and wherein the pressure-compensation portion is configured to automatically adjust the size of the orifice according to the target flow rate.Clause 19. The hydraulic system according to clause 18, the flow control portion comprises a valve configured to adjust the size of the outlet of the housing.Clause 20. The hydraulic system according to clause 1, further comprising a controller configured to control the hydraulic system to raise and lower the load.Clause 21. The hydraulic system according to clause 1 , wherein the PCFC valve is a first PCFC valve and further comprising a second PCFC valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the second PCFC valve is configured to cause the single-acting piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.Clause 22. The hydraulic system according to clause 21, wherein the hydraulic circuit is operable in a first load-raising state in which the pump pumps the hydraulic fluid to the singleacting piston-cylinder to raise the load without flowing through the first PCFC valve, a second load-raising state in which the pump pumps the hydraulic fluid to the single-acting piston-cylinder through the first PCFC valve and to the pump to raise the load, and a third hydraulic state in which the hydraulic fluid is exhausted from the single-acting piston-cylinder through the first PCFC valveto lower the load at the speed that is substantially constant and is the same regardless of the load amount.Clause 23. The hydraulic system according to clause 22, further comprising a fluid control valve configured to cause the hydraulic system to operate in the first load-raising state, the second load-raising state, and the third hydraulic state.Clause 24. The hydraulic system according to clause 23, further comprising a controller configured to control the fluid control valve based upon an input from a user.Clause 25. A hydraulic system for raising and lowering a load, the hydraulic system comprising: a hydraulic circuit for conveying a hydraulic fluid, a piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the piston-cylinder via the hydraulic circuit to cause the piston-cylinder to raise the load, and a pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the PCFC valve is configured to cause the piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.Clause 26. The hydraulic system according to clause 25, wherein the PCFC valve is a first PCFC valve and further comprising a second PCFC valve configured to receive the hydraulic fluid from the piston-cylinder upon lowering of the load, wherein the second PCFC valve is configured to cause the piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.Clause 27. The hydraulic system according to clause 26, wherein the hydraulic system is operable in three operational states including a first load-raising state; a relatively slower and controlled, second load-raising state; and a load-lowering state.Clause 28. The hydraulic system according to clause 27, further comprising a flow control valve configured to switch the hydraulic system for operation in each of the three operational states.Clause 29 The hydraulic system according to clause 28, further comprising a controller configured to control the flow control valve to switch the hydraulic system into each of the three operational states.Clause 30. The hydraulic system according to clause 27, wherein in the first load-raising state the pump is configured to pump the hydraulic fluid to the piston-cylinder via a substantially unrestricted fluid line, in the second load-raising state the pump is configured to pump the hydraulic fluid to the piston-cylinder via the first PCFC valve, and in the load-lowering state the hydraulic fluid is exhausted from the piston-cylinder to a tank via the second PCFC valve.

Claims

CLAIMSWhat is claimed is:

1. A hydraulic system for raising and lowering a load, the hydraulic system comprising: a hydraulic circuit for conveying a hydraulic fluid, a single-acting piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the single-acting piston-cylinder via the hydraulic circuit to cause the single-acting piston-cylinder to raise the load, and a pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the single-acting piston-cylinder upon lowering of the load, wherein the PCFC valve is configured to cause the single-acting piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.

2. The hydraulic system according to claim 1, wherein the PCFC valve is removably coupled to the hydraulic system.

3. The hydraulic system according to claim 1, wherein the PCFC valve is removably coupled to the hydraulic circuit between the pump and the PCFC valve.

4. The hydraulic system according to claim 1, further comprising a check valve, the check valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and being configured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.

5. The hydraulic system according to claim 1, further comprising a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the hydraulic system.

6. The hydraulic system according to claim 5, further comprising a check valve in the housing, the check valve being configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and beingconfigured to close and thereby cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.

7. The hydraulic system according to claims 5 or 6, wherein the housing comprises a cartridge that is configured to be removably coupled to the hydraulic system.

8. The hydraulic system according to claim 7, wherein the cartridge is configured to be removably coupled to the hydraulic circuit.

9. The hydraulic system according to claim 7, wherein the cartridge is configured to be removably coupled to the single-acting piston-cylinder.

10. The hydraulic system according to claim 1, wherein the PCFC valve disposed in the singleacting piston-cylinder.

11. The hydraulic system according to claim 10, further comprising a housing that contains the PCFC valve, wherein the housing is configured to be removably coupled to the single-acting piston-cylinder.

12. The hydraulic system according to claims 10 or 11, further comprising a check valve that is configured to open to permit the hydraulic fluid to bypass the PCFC valve when the pump is pumping the hydraulic fluid to the single-acting piston-cylinder and that is configured to close to cause the hydraulic fluid to flow through the PCFC valve upon lowering of the load.

13. The hydraulic system according to claim 1, wherein the single-acting piston-cylinder is one of a plurality of single-acting piston-cylinders configured to raise and lower a plurality of loads, and wherein each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is configured to raise and lower a respective load in the plurality of loads.

14. The hydraulic system according to claim 13, wherein the PCFC valve receives the hydraulic fluid from the plurality of single-acting piston-cylinders such that the PCFC valve causesthe plurality of single-acting piston-cylinders to lower the plurality of loads at a speed that is substantially constant and is the same regardless of the load amount.

15. The hydraulic system according to claim 1, wherein the single-acting piston-cylinder is one of a plurality of single-acting piston-cylinders configured to raise and lower a plurality of loads, and wherein the PCFC valve is one of a plurality of PCFC valves that are fluidly coupled to the plurality of single-acting piston-cylinders in parallel so that each single-acting piston-cylinder in the plurality of single-acting piston-cylinders is coupled to a different respective one of the plurality of PCFC valves.

16. The hydraulic system according to claim 1, wherein the PCFC valve comprises a housing having an inlet that receives the hydraulic fluid from the single-acting piston-cylinder, an outlet that discharges the hydraulic fluid, and a pressure-compensation portion between the inlet and the outlet, wherein the pressure-compensation portion is configured to passively control a flow rate at which the hydraulic fluid flows from the single-acting piston-cylinder through the valve housing so that the flow rate and thus a lowering speed of the single-acting piston-cylinder remains substantially constant regardless of the load amount.

17. The hydraulic system according to claim 16, wherein the pressure-compensation portion is configured to automatically adjust a size of an orifice to restrict flow of the hydraulic fluid through the PCFC valve.

18. The hydraulic system according to claim 17, wherein the PCFC valve further comprises a flow control portion configured to set a target flow rate for the PCFC valve and wherein the pressure-compensation portion is configured to automatically adjust the size of the orifice according to the target flow rate.

19. The hydraulic system according to claim 18, the flow control portion comprises a valve configured to adjust the size of the outlet of the housing.

20. The hydraulic system according to claim 1 , further comprising a controller configured to control the hydraulic system to raise and lower the load.

21. The hydraulic system according to claim 1, wherein the PCFC valve is a first PCFC valve and further comprising a second PCFC valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the second PCFC valve is configured to cause the single-acting piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.

22. The hydraulic system according to claim 21, wherein the hydraulic circuit is operable in a first load-raising state in which the pump pumps the hydraulic fluid to the single-acting pistoncylinder to raise the load without flowing through the first PCFC valve, a second load-raising state in which the pump pumps the hydraulic fluid to the single-acting piston-cylinder through the first PCFC valve and to the pump to raise the load, and a third hydraulic state in which the hydraulic fluid is exhausted from the single-acting piston-cylinder through the first PCFC valve to lower the load at the speed that is substantially constant and is the same regardless of the load amount.

23. The hydraulic system according to claim 22, further comprising a fluid control valve configured to cause the hydraulic system to operate in the first load-raising state, the second loadraising state, and the third hydraulic state.

24. The hydraulic system according to claim 23, further comprising a controller configured to control the fluid control valve based upon an input from a user.

25. A hydraulic system for raising and lowering a load, the hydraulic system comprising: a hydraulic circuit for conveying a hydraulic fluid, a piston-cylinder configured to raise and lower a load having a load amount, a pump configured to pump the hydraulic fluid to the piston-cylinder via the hydraulic circuit to cause the piston-cylinder to raise the load, anda pressure-compensated flow control (PCFC) valve fluidly coupled to the hydraulic circuit and being configured to receive the hydraulic fluid from the pump upon raising of the load, wherein the PCFC valve is configured to cause the piston-cylinder to raise the load at a speed that is substantially constant and remains the same regardless of a speed at which the pump is operated.

26. The hydraulic system according to claim 25, wherein the piston-cylinder is a single-acting piston cylinder.

27. The hydraulic system according to claim 25, wherein the PCFC valve is a first PCFC valve and further comprising a second PCFC valve configured to receive the hydraulic fluid from the piston-cylinder upon lowering of the load, wherein the second PCFC valve is configured to cause the piston-cylinder to lower the load at a speed that is substantially constant and remains the same regardless of the load amount.

28. The hydraulic system according to claim 26, wherein the hydraulic system is operable in three operational states including a first load-raising state; a relatively slower and controlled, second load-raising state; and a load-lowering state, and further comprising a flow control valve configured to switch the hydraulic system for operation in each of the three operational states.29 The hydraulic system according to claim 28, further comprising a controller configured to control the flow control valve to switch the hydraulic system into each of the three operational states.

30. The hydraulic system according to claim 27, wherein in the first load-raising state the pump is configured to pump the hydraulic fluid to the piston-cylinder via a substantially unrestricted fluid line, in the second load-raising state the pump is configured to pump the hydraulic fluid to the piston-cylinder via the first PCFC valve, and in the load-lowering state the hydraulic fluid is exhausted from the piston-cylinder to a tank via the second PCFC valve.

Images