HYDRAULIC VALVE WITH PRESSURE LIMITING FUNCTION

Abstract

Valve arrangement for connecting to a pump (12, 112) which has a load sensing functionality, wherein the valve arrangement (S1, S2, C1) comprises the following: a distributor (20, 22; 120); a main valve (30, 130) located inside the distributor, the main valve having a variable opening (32, 132); a pressure compensator valve (50, 150) designed to maintain a constant pressure drop across the variable orifice of the main valve and to transfer fluid from the variable orifice to a working port (42, 142); and a pressure relief valve (60, 160) in conjunction with the main valve and the pressure compensator valve, wherein the pressure relief valve is biased by a threshold relief pressure and has a pilot surface (64, 164) which receives a local load sensing pressure from the working port, wherein the pressure relief valve discharges the fluid from the pressure compensator valve to a tank (46, 146) when the local load sensing pressure exceeds the threshold relief pressure of the pressure relief valve; wherein the pressure relief valve maintains the flow to the working port when the valve assembly is part of a hydraulic system (10, 100) with multiple valve assemblies, and when at least one other valve assembly of the multiple valve assemblies has a higher threshold relief pressure and operates under a higher load sensing pressure than the valve assembly.

Description

BACKGROUND

[0001] Hydraulic systems used in different applications often include different valve assemblies, each with different variable requirements, and each operating its own actuator under different operating conditions. A load sensing compensator can be used to adapt the operation of a hydraulic pump to the variable flow requirements of a particular hydraulic system based on the load sensing pressure. However, the inlet pump pressure received by each valve assembly is based only on the highest load sensing pressure sensed by the load sensing compensator. Thus, the inlet pump pressure supplied to each valve assembly is the same, even though the different valve assemblies may operate different actuators under different load pressures. Improvements in pump flow management in a hydraulic system with multiple valve assemblies are desired.

[0002] US 2017 / 0328380 A1 relates to a valve assembly comprising a valve body for fluid coupling to a source and an actuator, a spool movable within the valve body between the source and the actuator, and a pressure compensating valve disposed upstream of the spool for regulating the flow received from the source. The valve body defines a first passage disposed upstream of the spool for fluidly coupling the pressure compensating valve to the spool, and a second passage disposed downstream of the spool for fluidly coupling the spool to the actuator. The valve assembly further comprises a compensating valve disposed in the second passage downstream of the spool, wherein the compensating valve is opened to allow flow from the actuator to the spool in response to a pilot pressure derived from the first passage when the spool is displaced from a neutral position. SUMMARY

[0003] The disclosed technology generally relates to a valve assembly for connection to a pump having load sensing functionality. In certain examples, the pump is a variable displacement pump. In other examples, the pump is a fixed displacement pump having an inlet pressure compensator.

[0004] It is an object of the invention to provide improvements in pump flow management in a hydraulic system with multiple valve arrangements. This object is achieved by a valve arrangement according to claim 1 or 11 and a hydraulic system according to claim 7.

[0005] The invention, according to a first aspect, relates to a valve assembly according to claim 1. According to this aspect, the valve assembly comprises: a manifold; a main valve housed within the manifold, the main valve having a variable orifice; a pressure compensator valve configured to maintain a constant pressure drop across the variable orifice and to transfer fluid from the variable orifice to a work port; and a pressure relief valve in communication with the main valve and the pressure compensator valve. The pressure relief valve is biased by a threshold relief pressure and has a pilot area that receives a local load sensing pressure from the work port. The pressure relief valve diverts fluid from the pressure compensator valve to tank when the local load sensing pressure overcomes the threshold relief pressure of the pressure relief valve.The pressure relief valve maintains flow to the work port when the valve assembly is part of a hydraulic system having multiple valve assemblies, and at least one other valve assembly of the multiple valve assemblies has a higher threshold relief pressure and operates under a higher load sensing pressure than the valve assembly.

[0006] In some examples, the pressure relief valve includes a spool movable between a first position and a second position. The first position directs fluid from the variable orifice of the main valve to a pilot face of the pressure compensator valve, and the second position directs fluid from the pilot face of the pressure compensator valve to tank. The pilot face of the pressure relief valve is located on a first side of the spool, and a biasing member is disposed adjacent an opposite second side of the spool to bias the spool to the first position by the threshold relief pressure. The spool slides to the second position when the local load sensing pressure received by the pilot face of the pressure relief valve overcomes the threshold relief pressure.

[0007] In certain examples, the pressure relief valve is a two-way, two-position valve with a spool movable between a closed position and an open position, the spool having a pilot surface that receives the local load sensing pressure as the pilot pressure. The local load sensing pressure moves the spool of the pressure relief valve from the closed position to the open position. The closed position blocks the discharge of fluid into the tank, and the open position discharges the fluid into the tank.

[0008] In certain examples, the pressure relief valve is a three-way, two-position valve with a spool movable between a first position and a second position, the spool having a pilot surface that receives the local load sensing pressure as the pilot pressure. The local load sensing pressure moves the spool of the pressure relief valve from the first position to the second position. The first position transfers fluid to a pilot surface of the pressure compensator valve, and the second position diverts fluid to the tank. In some examples, the pilot surface of the pressure relief valve has a rounded or conical shape.

[0009] According to a second aspect, the invention relates to a hydraulic system according to claim 7. According to this further aspect, the invention relates to a hydraulic system comprising: a pump; a load sensing compensator mounted on the pump; a first valve assembly housed in a manifold and connected to the pump and a first actuator, the first valve assembly comprising: a main valve having a variable orifice; a pressure compensator valve configured to maintain a constant pressure drop across the variable orifice and to transfer fluid from the variable orifice to a work port; and a pressure relief valve in communication with the main valve and the pressure compensator valve. The pressure relief valve is biased by a first threshold relief pressure and includes a pilot area receiving a first load sensing pressure from the work port.The pressure relief valve diverts fluid from the pressure compensator valve to the tank when the first load sensing pressure exceeds the threshold relief pressure. The hydraulic system further includes a second valve assembly housed in a separate manifold and connected to the pump and a second actuator. The second valve assembly is configured to transmit a second load sensing pressure to the load sensing compensator. The second valve assembly includes: a main valve with a variable orifice; a pressure compensator valve configured to maintain a constant pressure drop across the variable orifice of the main valve; and a pressure relief valve biased by a second threshold relief pressure.In the hydraulic system, flow to the working port of the first valve assembly is maintained when the second threshold relief pressure is higher than the first threshold relief pressure and the second load sensing pressure is higher than the first load sensing pressure.

[0010] In some examples, the pressure relief valve is a two-way, two-position valve that receives the first load sensing pressure as a pilot pressure. The first load sensing pressure moves the position of the pressure relief valve from a closed position to an open position. The closed position blocks the discharge of fluid into the tank, and the open position discharges the fluid into the tank.

[0011] In certain examples, the pressure relief valve is a three-way, two-position valve that receives the first load sensing pressure as a pilot pressure. The first load sensing pressure is configured to move the position of the pressure relief valve from a closed position to an open position. The first position transfers fluid to a pilot surface of the pressure compensator valve, and the second position diverts fluid to the tank. In some examples, the pilot surface of the pressure relief valve in the first valve assembly has a rounded or conical shape.

[0012] According to a third aspect, the invention relates to a valve arrangement according to claim 11. According to this further aspect, the invention relates to a valve arrangement for connection to a pump with load sensing functionality, the valve arrangement comprising: a manifold; a main valve housed inside the manifold, the main valve including: a variable orifice having an opening proportional to a position of a spool inside the main valve;a pressure compensator valve configured to maintain a constant pressure drop across the variable orifice of the main valve, the pressure compensator valve including: a spool movable between at least one open position and a closed position, the closed position blocking fluid from the variable orifice of the main valve, the open position transferring fluid from the variable orifice to a work port, the work port configured to connect to an actuator, the spool having a pilot surface on a first side opposite a second side of the spool;and a biasing member disposed within a biasing chamber adjacent the second side of the spool for biasing the spool to the closed position, the biasing chamber being configured to receive a load sensing pressure from a second valve assembly via a load sensing line, the load sensing pressure applying an additional biasing force to move the pressure compensator valve to the closed position;and a pressure relief valve in fluid communication with the main valve and the pressure compensator valve, the pressure relief valve including: a spool movable between at least a first position and a second position, the first position transferring fluid from the variable orifice of the main valve to the pilot surface of the spool of the pressure compensator valve, the second position diverting fluid from the pilot surface of the spool of the pressure compensator valve to the tank, the spool of the pressure relief valve having a pilot surface on a first side of the spool opposite a second side of the spool, the pilot surface being configured to receive a local load sensing pressure from the work port;and a biasing member disposed adjacent the second side of the spool to bias the spool to the first position by a threshold relief pressure, the spool configured to move to the first position when the local load sensing pressure received from the pilot surface overcomes the threshold relief pressure. The pressure relief valve maintains flow to the work port when the valve assembly is part of a hydraulic system having multiple valve assemblies and when at least one other valve assembly of the multiple valve assemblies has a higher threshold relief pressure that is higher than the threshold relief pressure of the pressure relief valve, and the at least one other valve operates under a load sensing pressure that is higher than the load sensing pressure of the valve assembly.

[0013] In certain examples, the pressure relief valve is a two-way, two-position valve. In other examples, the pressure relief valve is a three-way, two-position valve. In some examples, the pilot surface of the pressure relief valve has a rounded or conical shape. In some examples, a hydraulic system includes multiple valve assemblies, at least one of which is the valve assembly described above.

[0014] A variety of additional aspects are set forth in the following description. These aspects may relate to individual features and to combinations of features. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not limiting of the broad concepts upon which the embodiments disclosed herein are based. DRAWINGS Fig. Figure 1 illustrates the fluid flow in two post-compensated valve assemblies included in a hydraulic system, each valve assembly having a local load sensing relief valve. Fig. 2 shows a hydraulic circuit according to a first example of the present disclosure, the hydraulic circuit comprising a plurality of valve assemblies each connected to an actuator and each comprising a two-way, two-position pressure relief valve. Fig. 3 shows a structural arrangement of the hydraulic circuit of Fig. 2. Fig. 4 shows the hydraulic circuit of Fig. 2, when a working load pressure in a first valve arrangement is less than a threshold relief pressure of the pressure relief valve. Fig. 5 shows the hydraulic circuit of Fig. 2, when a working load pressure in a first valve arrangement is greater than a threshold relief pressure of the pressure relief valve. Fig. 6 shows an alternative example of a hydraulic circuit according to another example of the present disclosure, wherein the hydraulic circuit includes a plurality of valve assemblies, wherein one valve assembly is connected to an actuator and includes a three-way, two-position pressure relief valve. Fig. Figure 7 shows a structural arrangement of the hydraulic circuit of Fig. 6. Fig. 8 shows the hydraulic circuit of Fig. 6, when a working load pressure in a first valve arrangement is less than a threshold relief pressure of the pressure relief valve. Fig. 9 shows the hydraulic circuit of Fig. 6, when a working load pressure in a first valve arrangement is greater than a threshold relief pressure of the pressure relief valve. Fig. 10 illustrates fluid flow in two valve assemblies in a hydraulic system according to the present disclosure. Fig. Figure 11 shows alternative arrangements for a pilot surface of a three-way two-position pressure relief valve used in the Fig. 7 to 9. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to the exemplary aspects of the present disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or similar structure.

[0016] A hydraulic system may include multiple valve assemblies, each connected to a pump and each operating its own actuator at a different load sensing pressure. Fig. 1, the flow rate A in a first valve arrangement is compared with the flow rate B in a second valve arrangement as the inlet pump pressure P from the pump increases. The inlet flow rate F is shown as relatively constant while the inlet pump pressure P of the pump increases. The load sensing pressure L Aof the first valve arrangement is shown to be relatively constant as the inlet pump pressure P increases. However, flow A in the first valve arrangement begins to decrease as the inlet pump pressure P begins to increase, eventually reaching zero before flow B in the second valve arrangement begins to decrease. This may be due to a local unloading valve in the first valve arrangement having a threshold unloading pressure that is less than the threshold pressure of a local unloading valve in the second valve arrangement. Because each local unloading valve opens and closes based on the same inlet pump pressure from the pump, flow A in the first valve arrangement will shut off before flow B in the second valve arrangement is shut off.This can occur even if the working port pressure in the first valve assembly has not exceeded the threshold relief pressure of the local relief valve in that assembly. Consequently, the operation of an actuator connected to the first valve assembly is affected, which can lead to energy loss in the hydraulic system comprising the first and second valve assemblies.

[0017] As in the Fig. 2 and Fig. 3, a hydraulic system 10 includes a plurality of valve assemblies, such as valve assemblies S1, S2, each housed in a separate manifold, such as manifolds 20, 22. Each valve assembly S1, S2 is connectable to a pump 12 for receiving a common inlet pump pressure, and each assembly is connectable to a separate actuator, such as actuators 16, 18. In certain examples, pump 12 is a variable displacement pump. In other examples, pump 12 is a fixed displacement pump with an inlet pressure compensator.

[0018] A load sensing compensator 14 is mounted on the pump 12 to control the inlet pump pressure of the pump 12 based on a load sensing pressure. The load sensing compensator 14 receives a load sensing pressure from a load sensing line 24 connected to a shuttle valve 26. The shuttle valve 26 is connected to one or more work ports 42 of the valve assemblies S1, S2. The shuttle valve 26 is configured to open toward the work port with the highest load sensing pressure. In some alternative examples, check valves may be used instead of the shuttle valve 26 to perform this function. Also, the figures illustrate the hydraulic system 10 as having two valve assemblies S1, S2, however, it should be understood that the hydraulic system 10 may include more than two valve assemblies or may include a single valve assembly.

[0019] Each valve assembly S1, S2 includes a main valve 30 connected to the pump 12 to receive hydraulic fluid. Each main valve 30 has a variable orifice 32, the opening of which is proportional to the movement of a spool 34 within the main valve 30. In some examples, the position of the spool 34 within the main valve 30 may be controlled by a solenoid 36. In other examples, other methods may be used to control the position of the spool 34.

[0020] Each valve assembly S1, S2 includes a pressure compensator valve 50 for maintaining a constant pressure drop across the variable orifice 32 so that output flow from the main valve 30 depends only on the metering orifice created by the movement of the spool 34 within the main valve 30. The pressure compensator valve 50 has a spool 52 movable between a closed position and an open position. In the closed position, fluid is blocked from the variable orifice 32 of the main valve 30. In the open position, fluid is transferred from the variable orifice 32 to a working port 42 connected to an actuator 16, 18.

[0021] The pressure compensator valve 50 is biased in the closed position by a biasing element 54 housed in a biasing chamber 56 and located at one end of the spool 52 of the pressure compensator valve 50. A pilot surface 58, located at an opposite end of the biasing element 54, receives inlet pump pressure from the pump 12 to overcome the biasing force of the biasing element 54 and thereby move the pressure compensator valve 50 from the closed position to the open position.

[0022] Still referring to the Fig. 2 and Fig. 3, each valve assembly S1, S2 is illustrated as including a pressure relief valve 60 in fluid communication with the main valve 30 and the pressure compensator valve 50 within the manifolds 20, 22. The pressure relief valve 60 includes a spool 62 movable between an open position and a closed position. In the closed position, fluid is blocked from the variable orifice 32 of the main valve 30. In the open position, fluid is diverted from the pilot surface 58 of the spool 52 in the pressure compensator valve 50 to a tank 46. A biasing member 66 is disposed adjacent one end of the spool 62 to bias the spool 62 to the closed position by a threshold biasing force. In certain examples, the biasing member 66 is a spring. The spool 62 of the pressure relief valve 60 has a pilot surface 64 at an opposite end of the spool.The pilot surface 64 is configured to receive a working port pressure from the working port 42. The spool 62 is configured to move to the open position when the working port pressure received by the pilot surface 64 overcomes the threshold biasing force of the biasing element 66. In the embodiment shown in FIGS. Fig. 2 and Fig. In the example shown in Figure 3, each pressure relief valve 60 is a two-way, two-position valve.

[0023] The pressure relief valves 60 are each preloaded by a different threshold relief pressure. For example, the pressure relief valve 60 in valve assembly S2 is preloaded by a threshold relief pressure (e.g., 120 bar) that is greater than the threshold relief pressure (e.g., 60 bar) of the pressure relief valve 60 in valve assembly S1. The different threshold relief pressures are desirable depending on the characteristics of each valve assembly, including the requirements of the actuators (e.g., actuators 16, 18) connected to the valve assemblies.

[0024] Each valve arrangement S1, S2 can operate independently of the other valve arrangement, so that each valve arrangement can operate under a different load sensing pressure. For example, the actuator 18 connected to the second valve arrangement S2 can operate under a load sensing pressure (e.g., 100 bar) that is greater than the load sensing pressure (e.g., 50 bar) of the actuator 16 connected to the first valve arrangement S1. Fig. 2, the load sensing pressure in the second valve arrangement S2 is greater than the load sensing pressure in the first valve arrangement S1, so that the shuttle valve 26 is arranged to transmit the load sensing pressure from the second valve arrangement S2 to the load sensing line 24 and to block the load sensing pressure from the first valve arrangement S1 from entering the load sensing line 24. The load sensing line 24 transmits the load sensing pressure from the second valve arrangement S2 to the load sensing compensator 14. The load sensing line also transmits the load sensing pressure from the second valve arrangement S2 to the bias chambers 56 in each valve arrangement S1, S2. The inlet pump pressure from the pump 12 increases with increasing load sensing pressure in the second valve arrangement S2 to meet the increased pressure demand.

[0025] Referring now to the Fig. 2 and Fig. 4, the opening and closing of the pressure relief valve 60 in the first valve assembly S1 is independent of the inlet pump pressure from the pump 12. The pressure relief valve 60 in the first valve assembly S1 remains closed as long as the actuator 16 connected to the first valve assembly S1 has a load sensing pressure below the threshold relief pressure (e.g., 60 bar) in the first valve assembly S1. When the pressure relief valve 60 is in the closed position, the inlet pump pressure from the pump 12 is directed to the pilot surface 58 of the pressure compensator valve 50 to move the pressure compensator valve 50 to the open position by overcoming the combined force of the biasing element 54 and the load sensing pressure from the second valve assembly S2, which is transmitted to the biasing chamber 56 that houses the biasing element 54.When the pressure compensator valve 50 is in the open position, the fluid flow is transmitted to the actuator 16, which is connected to the first valve assembly S1.

[0026] The fluid flow to the actuator 16 connected to the first valve arrangement S1 is not interrupted even if the threshold relief pressure (e.g., 60 bar) in the first valve arrangement S1 is lower than the threshold relief pressure (e.g., 120 bar) in the second valve arrangement S2. Thus, the operation of the actuator 16 connected to the first valve arrangement S1 is not affected by the operation of the second valve arrangement S2, which allows the intake pump pressure to exceed the lower threshold relief pressure (e.g., 60 bar) of the first valve arrangement S1.

[0027] Referring now to the Fig. 2 and Fig. 5, when the load sensing pressure from actuator 16 exceeds the threshold relief pressure (e.g., 60 bar) of the first valve assembly S1, the pressure relief valve 60 in the first valve assembly S1 moves to the open position. For example, the load sensing pressure from actuator 16, detected at the working port 42, is transmitted to the pilot surface 64 of the spool 62 in the pressure relief valve 60 and overcomes the biasing force of the biasing element 66. When the load sensing pressure overcomes the threshold relief pressure of the biasing element 66, the pressure relief valve 60 moves to the open position, and the inlet pump pressure transmitted to the pilot surface 58 of the pressure compensator valve 50 is diverted to the tank 46.This causes the pressure compensator valve 50 to move to the closed position due to the combined force of the biasing element 54 and the load sensing pressure from the second valve assembly S2, which is transmitted to the bias chamber 56 via the shuttle valve 26. When in the closed position, the pressure compensator valve 50 prevents fluid from reaching the actuator 16. Thus, flow to the actuator 16 in the first valve assembly S1 is interrupted when the load sensing pressure in the first valve assembly S1 exceeds the threshold relief pressure.

[0028] Referring now to the Fig. 6 and Fig. 7, an alternative hydraulic system 100 according to the present disclosure may share components and features similar to those described above with respect to the hydraulic system 10 shown in FIGS. Fig. 2 to 5. The hydraulic system 100 may include multiple valve assemblies, such as valve assemblies C1, C2, each housed in a separate manifold 120, 122. Each valve assembly C1, C2 is connectable to a pump 112 for receiving a common inlet pump pressure, and each assembly is connectable to a separate actuator, such as actuators 116, 118. In certain examples, the pump 112 is a variable displacement pump. In other examples, the pump 112 is a fixed displacement pump with an inlet pressure compensator.

[0029] A load sensing compensator 114 is mounted to control the inlet pump pressure of pump 112 based on a load sensing pressure. The load sensing compensator 114 receives a load sensing pressure from a load sensing line 124, which is connected to a shuttle valve 126. The shuttle valve 126 is connected to one or more work ports 142 of the valve assemblies C1, C2. The shuttle valve 126 is configured to open toward the work port with the highest load sensing pressure. In some alternative examples, check valves may be used instead of the shuttle valve 126 to perform this function. Also, the figures illustrate the hydraulic system 100 as having two valve assemblies C1, C2, however, it is understood that the hydraulic system 100 may include more than two valve assemblies or may include a single valve assembly.

[0030] Each valve assembly C1, C2 includes a main valve 130 connected to the pump 112 to receive hydraulic fluid. Each main valve 130 has a variable orifice 132, the opening of which is proportional to the movement of a spool 134 within the main valve 130. In some examples, the position of the spool 134 may be controlled by a solenoid 136. In other examples, other methods may be used to control the position of the spool 134.

[0031] Each valve assembly C1, C2 includes a pressure compensator valve 150 for maintaining a constant pressure drop across the variable orifice 132 so that output flow from the main valve 130 depends only on the metering orifice created by the movement of the spool 134 within the main valve 130. The pressure compensator valve 150 has a spool 152 movable between a closed position and an open position. In the closed position, fluid is blocked from the variable orifice 132 of the main valve 130. In the open position, fluid is transferred from the variable orifice 132 to a working port 142 connected to an actuator 116, 118.

[0032] The pressure compensator valve 150 is biased to the closed position by a biasing element 154 housed in a biasing chamber 156 and located at one end of the spool 152 of the pressure compensator valve 150. A pilot surface 158, located at an opposite end of the biasing element 154, receives inlet pump pressure from the pump 112 to overcome the biasing force of the biasing element 154 and thereby move the pressure compensator valve 150 from the closed position to the open position.

[0033] Still referring to the Fig. 6 and Fig. 7, each valve assembly C1 includes a pressure relief valve 160 in fluid communication with the main valve 130 and the pressure compensator valve 150 within the manifold 120. The pressure relief valve 160 includes a spool 162 movable between a first position and a second position. In the first position, fluid flows from the variable orifice 132 of the main valve 130 through the pressure relief valve 160 and toward the pilot surface 158 of the pressure compensator valve 150. In the second position, fluid is vented from the pilot surface 158 of the pressure compensator valve 150 to a tank 146. A biasing member 166 is disposed adjacent one end of the spool 162 to bias the spool 162 to the first position by a threshold biasing force. In certain examples, the biasing member 166 is a spring. The coil 162 has a pilot surface 164 on an opposite side of the coil.The pilot surface 164 is configured to receive a working port pressure from the working port 142. The spool 162 is configured to move to the second position when the working port pressure received by the pilot surface 164 overcomes the threshold biasing force of the biasing element 166. In the embodiment shown in FIGS. Fig. 6 and Fig. In the example shown in Figure 7, the pressure relief valve 160 in the valve arrangement C1 is a three-way two-position valve.

[0034] In the Fig. 6, the valve assembly C2 includes a pressure relief valve 170 biased to a closed position by a biasing member 172. The pressure relief valve 170 includes a pilot surface 174 for receiving inlet pump pressure from the variable orifice 132 of the main valve 130. When the inlet pump pressure exceeds the force of the biasing member 172, the pressure relief valve 170 moves to an open position, and the inlet pump pressure is diverted to the tank 146. This causes the pressure compensator valve 150 in the valve assembly C2 to close due to the combined force of the biasing member 154 and the load sensing pressure that has entered the bias chamber 156 via the shuttle valve 126.It is contemplated that in alternative examples, the valve assembly C2 may include a pressure relief valve 160 similar to one included in the valve assembly C1, or a pressure relief valve 60 similar to that shown in FIG. Fig. 2.

[0035] In the exemplary hydraulic system 100 shown in the Fig. 6 and Fig. As shown in Figure 7, the pressure relief valve 160 and the pressure relief valve 170 are biased by different threshold relief pressures. For example, the pressure relief valve 170 in valve assembly C2 may be biased by a threshold relief pressure (e.g., 120 bar) that is greater than the threshold relief pressure (e.g., 60 bar) of the pressure relief valve 160 in valve assembly C1. The different threshold relief pressures may be desirable depending on the characteristics of each valve assembly, including the requirements of the various actuators that may be connected to the valve assemblies (e.g., actuators 116, 118).

[0036] Each valve assembly C1, C2 can operate independently of the other valve assembly, so that each valve assembly can operate under a different load sensing pressure. For example, the actuator 118 connected to the second valve assembly C2 can operate under a load sensing pressure (e.g., 100 bar) that is greater than the load sensing pressure (e.g., 50 bar) of the actuator 116 connected to the first valve assembly C1. Fig. 6, the load sensing pressure in the second valve assembly C2 is greater than the load sensing pressure in the first valve assembly C1, so the shuttle valve 126 is arranged to transmit the load sensing pressure from the second valve assembly C2 to the load sensing line 124 and to block the load sensing pressure from the first valve assembly C1 from entering the load sensing line 124. The load sensing line 124 transmits the load sensing pressure from the second valve assembly C2 to the load sensing compensator 114. The load sensing line 124 also transmits the load sensing pressure from the second valve assembly C2 to the bias chambers 156 in each valve assembly C1, C2. The inlet pump pressure from the pump 112 increases with increasing load sensing pressure in the second valve assembly C2 to meet the increased pressure demand.

[0037] With reference to the Fig. 6 and Fig. 8, the movement of the pressure relief valve 160 in the first valve assembly C1 is independent of the inlet pump pressure. The pressure relief valve 160 in the first valve assembly C1 remains in the first position while the actuator 116 connected to the first valve assembly C1 has a load sensing pressure below the threshold relief pressure (e.g., 60 bar). When in the first position, the inlet pump pressure from the pump 112 flows through the pressure relief valve 160 toward the pilot surface 158. This moves the pressure compensator valve 150 to the open position by overcoming the force of the biasing element 154 and the load sensing pressure from the second valve assembly C2 supplied to the bias chamber 156. When the pressure compensator valve 150 is in the open position, the flow is transmitted to the actuator 116, which is connected to the first valve assembly C1.

[0038] Flow to the actuator 116 connected to the first valve arrangement C1 is not interrupted even if the threshold relief pressure (e.g., 60 bar) in the first valve arrangement C1 is less than the threshold relief pressure (e.g., 120 bar) in the second valve arrangement C2. Thus, the operation of the actuator 116 connected to the first valve arrangement C1 is not affected by the operation of the second valve arrangement C2, which allows the intake pump pressure to exceed the lower threshold relief pressure (e.g., 60 bar) of the first valve arrangement C1.

[0039] Referring now to the Fig. 6 and Fig. 9, when the load sensing pressure from actuator 116 exceeds the threshold relief pressure (e.g., 60 bar) of the first valve assembly C1, the pressure relief valve 60 in the first valve assembly C1 moves to the second position. For example, the load sensing pressure from actuator 116, detected at work port 142, is transmitted to the pilot surface 164 of the spool 162 in the pressure relief valve 160, overcoming the biasing force of the biasing element 166. When the load sensing pressure overcomes the threshold relief pressure of the biasing element 166, the pressure relief valve 160 moves to the second position, and the inlet pump pressure transmitted to the pilot surface 158 of the pressure compensator valve 150 is diverted to the tank 146.This will cause the pressure compensator valve 150 to move to the closed position due to the combined force of the biasing element 154 and the load sensing pressure from the second valve assembly C2, which is transmitted via the load sensing line 124 to the bias chamber 156. When in the closed position, the pressure compensator valve 150 prevents flow from reaching the actuator 116. Thus, flow to the actuator 116 is interrupted when the load sensing pressure in the first valve assembly C1 exceeds the threshold relief pressure.

[0040] As in Fig. 10, the flow rate A in a first valve arrangement S1, C1 according to the present disclosure is compared with the flow rate B in a second valve arrangement S2, C2 when the inlet pump pressure P of a pump increases. The first and second valve arrangements may be included in a hydraulic system, such as those described in the Fig. 2 and Fig. 6, and the first valve arrangement S1, C1 may have a lower threshold relief pressure than the threshold relief pressure of the second valve arrangement S2, C2. Fig. Figure 10 illustrates that the inlet flow F remains relatively constant while the pump inlet pressure P increases.

[0041] The load sensing pressure L Aof the first valve arrangement S1, C1 remains relatively constant as the inlet pump pressure P increases. According to the present disclosure, the flow rate A in the first valve arrangement S1, C1 remains relatively constant as the inlet pump pressure P increases, even if the flow rate B in the second valve arrangement S2, C2 decreases. This is because the flow rate A in the first valve arrangement S1, C1 is independent of the inlet pump pressure and the flow rate B in the second valve arrangement S2, C2. Thus, an actuator connected to the first valve arrangement S1, C1 is not affected by an increase in the inlet pump pressure P or the decrease in the flow rate B to an actuator connected to the second valve arrangement.

[0042] With reference now to Fig. 11, the pilot surface 164 of the coil 162 of the three-way two-position pressure relief valve, which is in the Fig. 7 to 9. In certain examples, the shape of the pilot surface 164 may be conical or rounded, as shown in Fig. 11. In other examples, the shape of the spool 162 may be cylindrical, so that the pilot surface 164 is a flat surface. In such examples, a seat 168 may be formed in the body of the pressure relief valve 160, as shown in Fig. 11. In further examples, the seat 168 in the body of the pressure relief valve 160 may be reduced or eliminated by adding dynamic seals 169 to the spool 162. The shape of the spool 62, as well as the body of the pressure relief valve, allows the pressure relief valve 160 to fit within specific constraints as needed or desired.

[0043] Various modifications and alterations of this disclosure will be apparent to those skilled in the art without departing from the scope and spirit of the invention, and it is to be understood that the scope of this disclosure is not intended to be unduly limited to the embodiments set forth herein.

Claims

[1] Valve arrangement for connection to a pump (12, 112) having a load sensing functionality, the valve arrangement (S1, S2, C1) comprising: a distributor (20, 22; 120); a main valve (30, 130) housed inside the manifold, the main valve having a variable opening (32, 132); a pressure compensator valve (50, 150) configured to maintain a constant pressure drop across the variable orifice of the main valve and to transfer fluid from the variable orifice to a working port (42, 142); and a pressure relief valve (60, 160) in communication with the main valve and the pressure compensator valve, the pressure relief valve being biased by a threshold relief pressure and having a pilot area (64, 164) receiving a local load sensing pressure from the work port, the pressure relief valve diverting the fluid from the pressure compensator valve to a tank (46, 146) when the local load sensing pressure overcomes the threshold relief pressure of the pressure relief valve; wherein the pressure relief valve maintains flow to the work port when the valve assembly is part of a hydraulic system (10, 100) having multiple valve assemblies, and when at least one other valve assembly of the multiple valve assemblies has a higher threshold relief pressure and operates under a higher load sensing pressure than the valve assembly. [2] The valve assembly of claim 1, wherein the pressure relief valve (60, 160) includes a spool (62, 162) movable between a first position and a second position; wherein the first position directs the fluid from the variable orifice (32, 132) of the main valve (30, 130) to a pilot surface (58, 158) of the pressure compensator valve (50, 150), and the second position diverts the fluid from the pilot surface of the pressure compensator valve to the tank (46, 146); wherein the pilot surface of the pressure relief valve is located on a first side of the spool and a biasing member (66, 166) is disposed adjacent an opposite second side of the spool to bias the spool to the first position by the threshold relief pressure; and wherein the spool slides to the second position when the local load sensing pressure received by the pilot surface (64, 164) of the pressure relief valve overcomes the threshold relief pressure. [3] The valve assembly of claim 1, wherein the pressure relief valve (60, 160) is a two-way, two-position valve having a spool (62, 162) movable between a closed position and an open position, the spool having a pilot surface (64, 164) receiving the local load sensing pressure as a pilot pressure; wherein the local load sensing pressure moves the spool of the pressure relief valve from the closed position to the open position; wherein the closed position blocks the discharge of fluid into the tank (46, 146) and the open position discharges the fluid into the tank. [4] The valve assembly of claim 1, wherein the pressure relief valve (60, 160) is a three-way, two-position valve having a spool (62, 162) movable between a first position and a second position, the spool having a pilot surface (64, 164) receiving the local load sensing pressure as a pilot pressure; wherein the local load sensing pressure moves the spool of the pressure relief valve from the first position to the second position; wherein the first position transfers the fluid to a pilot surface (58, 158) of the pressure compensator valve (50, 150) and the second position discharges the fluid to the tank (46, 146). [5] Valve arrangement according to claim 4, wherein the pilot surface (64, 164) of the pressure relief valve (60, 160) has a rounded or conical shape. [6] A hydraulic system comprising a plurality of valve assemblies (S1, S2, C1, C2), wherein at least one valve assembly is the valve assembly according to claim 1. [7] Hydraulic system comprising: a pump (112); a load sensing compensator (114) mounted on the pump; a first valve assembly (C1) housed in a manifold (120) and connected to the pump and a first actuator (116), the first valve assembly being configured to transmit a first load sensing pressure to the load sensing compensator, the first valve assembly comprising: a main valve (130) with a variable opening (132); a pressure compensator valve (150) configured to maintain a constant pressure drop across the variable orifice of the main valve and to transfer fluid from the variable orifice to a working port (142); and a pressure relief valve (160) in communication with the main valve and the pressure compensator valve, the pressure relief valve being biased by a first threshold relief pressure and including a pilot area (164) receiving the first load sensing pressure from the work port, the pressure relief valve diverting the fluid from the pressure compensator valve to a tank (146) when the local load sensing pressure overcomes the threshold relief pressure; a second valve assembly (C2) housed in a separate manifold (122) and connected to the pump and a second actuator (118), the second valve assembly being configured to transmit a second load sensing pressure to the load sensing compensator, the second valve assembly comprising: a main valve (130) with a variable opening (132); a pressure compensator valve (150) configured to maintain a constant pressure drop across the variable opening of the main valve; and a pressure relief valve (170) biased by a second threshold relief pressure; wherein flow to the working port of the first valve assembly is maintained when the second threshold relief pressure is higher than the first threshold relief pressure and the second load sensing pressure is higher than the first load sensing pressure. [8] The hydraulic system of claim 7, wherein the pressure relief valve (160) is a two-way, two-position valve receiving the first load sensing pressure as a pilot pressure; wherein the first load sensing pressure moves the position of the pressure relief valve from a closed position to an open position; wherein the closed position blocks the discharge of fluid into the tank (146) and the open position discharges the fluid into the tank. [9] The hydraulic system of claim 7, wherein the pressure relief valve (160) is a three-way, two-position valve receiving the first load sensing pressure as a pilot pressure; wherein the first load sensing pressure is configured to move the position of the pressure limiting valve from a first position to a second position; wherein the first position transfers the fluid to a pilot surface (158) of the pressure compensator valve (150) and the second position discharges the fluid to the tank (146). [10] Hydraulic system according to claim 9, wherein the pilot surface (164) of the pressure relief valve (160) in the first valve arrangement (C1) has a rounded or conical shape. [11] A valve arrangement for connection to a pump (12, 112) having load sensing functionality, the valve arrangement (S1, S2, C1) comprising: a distributor (20, 22, 120); a main valve (30, 130) housed inside the distributor, the main valve including: a variable orifice (32, 132) having an orifice proportional to a position of a spool (34, 134) within the main valve; a pressure compensator valve (50, 150) configured to maintain a constant pressure drop across the variable opening of the main valve, the pressure compensator valve comprising: a spool (52, 152) movable between at least one open position and a closed position, the closed position blocking fluid from the variable opening of the main valve, the open position transmitting fluid from the variable opening to a working port (42, 142), the working port being adapted to be connected to an actuator (16, 18, 116), the spool having a pilot surface (58, 158) on a first side opposite a second side of the spool; and a biasing element (54, 154) disposed within a biasing chamber (56, 156) adjacent the second side of the spool for biasing the spool to the closed position, the biasing chamber being adapted to receive a load sensing pressure from a second valve assembly (S2, S1, C2) via a load sensing line (24, 124), the load sensing pressure applying an additional biasing force to move the pressure compensator valve to the closed position; and a pressure relief valve (60, 160) in fluid communication with the main valve and the pressure compensator valve, the pressure relief valve including: a coil (62, 162) movable between at least a first position and a second position, the first position transferring fluid from the variable opening of the main valve to the pilot surface of the spool of the pressure compensator valve, the second position diverting fluid from the pilot surface of the spool of the pressure compensator valve to a tank (46, 146), the spool of the pressure relief valve having a pilot surface (64, 164) on a first side of the spool opposite a second side of the spool, the pilot surface being adapted to receive a local load sensing pressure from the working port; and a biasing member (66, 166) disposed adjacent the second side of the spool for biasing the spool to the first position by a threshold relief pressure, the spool being configured to move to the first position when the local load sensing pressure received from the pilot surface overcomes the threshold relief pressure; wherein the pressure relief valve maintains flow to the working port when the valve assembly is part of a hydraulic system (10, 100) having a plurality of valve assemblies (S1, S2, C1, C2), and when at least one other valve assembly of the plurality of valve assemblies has a threshold relief pressure higher than the threshold relief pressure of the pressure relief valve, and the at least one other valve operates under a load sensing pressure higher than the load sensing pressure of the valve assembly. [12] Valve arrangement according to claim 11, wherein the pressure relief valve (60, 160) is a two-way, two-position valve. [13] Valve arrangement according to claim 11, wherein the pressure relief valve (60, 160) is a three-way two-position valve. [14] Valve arrangement according to claim 13, wherein the pilot surface (64, 164) of the pressure relief valve (60, 160) has a rounded or conical shape. [15] A hydraulic system comprising a plurality of valve assemblies, wherein at least one valve assembly is the valve assembly (S1, S2, C1) according to claim 11.

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