Load holding valve with separate hydraulic damping module

Abstract

Load holding valve (LH) with a valve body in which a consumer-side hydraulic connection (V), a pump-side hydraulic connection (P) and a control line (SL) with a control pressure connection (S) are arranged, wherein the load holding valve (LH) has a separate hydraulic damping module (1), wherein a control fluid inlet nozzle (D1) is arranged in the control line (SL) and a control fluid outlet nozzle (D2) and an outlet check valve (RV3) are arranged in a drain line (AL) branching off from the control line (SL), wherein the separate hydraulic damping module (1) has a housing (2), a first hydraulic port (3) and a second hydraulic port (4), wherein a first check valve (5) is arranged in a first hydraulic line (6) in the housing (2), a second check valve (7) is arranged in a second hydraulic line (8) and a throttle element (9) is arranged in a third hydraulic line (10), wherein the first hydraulic line (6), the second hydraulic line (8) and the third hydraulic line (10) each connect the first hydraulic port (3) to the second hydraulic port (4), wherein the first check valve (5) blocks the flow of hydraulic fluid in the direction of flow from the first hydraulic port (3) to the second hydraulic port (4) and the second check valve (7) blocks the flow of hydraulic fluid in the direction of flow from the second hydraulic port (4) to the first hydraulic port (3), and wherein the separate hydraulic damping module (1) is designed for detachable connection with the control pressure port (S) of a load holding valve (LH), wherein the second hydraulic port (4) is in hydraulic connection with the control pressure port (S) of the load holding valve (LH) when the separate hydraulic damping module (1) is detachably connected to the control pressure port (S) of the load holding valve (LH), where the drain check valve (RV3) is a spring-loaded drain check valve.

Description

[0001] The present invention relates to a load-holding valve with a separate hydraulic damping module.

[0002] Load-holding valves are a common feature in hydraulics and serve the purpose of preventing double-acting devices such as hydraulic cylinders or hydraulic motors with an attached pulling or pushing load from moving uncontrollably and at a higher speed than specified by the hydraulic fluid flow at the pump. This is particularly important in hydraulic lifting, swiveling, or turning devices. Thus, the load-holding valve not only enables the safe holding of a load, but also, for example, the safe and controlled lowering of that load without posing a risk to the environment or the hydraulic system.

[0003] These load-holding valves typically have a hydraulic connection on the pump side, a hydraulic connection on the consumer side, and a control pressure connection. Hydraulic fluid flows freely from the pump-side hydraulic connection to the consumer-side hydraulic connection via a check valve. However, the flow of hydraulic fluid in the opposite direction, from the consumer-side hydraulic connection to the pump-side hydraulic connection (which in this case is, for example, relieved towards the tank), is throttled. This is achieved by generating a dynamic throttling resistance that is always slightly higher than the current load pressure. This is accomplished in a generally known manner through a force equilibrium between pressure-actuated functional elements on the inlet and outlet sides on the one hand, and a preloading device, such as a spring, that loads these functional elements on the other.The opening of the load-holding valve for the flow of hydraulic fluid from the consumer-side hydraulic connection to the pump-side hydraulic connection is controlled via the control pressure connection of the load-holding valve.

[0004] For some applications where such load-holding valves are used, it has proven beneficial to integrate damping elements on the control pressure side of these valves due to application-specific pressure fluctuations. This effectively mitigates, or even completely suppresses, oscillations triggered by starting and stopping processes or rapid transitions from high speed to low speed. However, in other applications where load-holding valves are used, such pressure fluctuations during the flow of hydraulic fluid from the consumer-side hydraulic connection to the pump-side hydraulic connection of the load-holding valve do not pose a problem.

[0005] Against this background, the object of the present invention is to demonstrate a cost-effective, particularly flexible load-holding valve or load-holding valve system.

[0006] The problem is solved by a load-holding valve with a separate hydraulic damping module according to claim 1. The load-holding valve has a valve housing in which a consumer-side hydraulic connection, a pump-side hydraulic connection, and a control line with a control pressure connection are arranged. According to the invention, a control fluid inlet nozzle is arranged in the control line, and a control fluid outlet nozzle and an outlet check valve are arranged in a drain line branching off from the control line. The separate hydraulic damping module according to the invention has a housing, a first hydraulic connection, and a second hydraulic connection. A first check valve is arranged in a first hydraulic line within the housing, a second check valve is arranged in a second hydraulic line, and a throttling element is arranged in a third hydraulic line.The first, second, and third hydraulic lines each connect the first hydraulic port to the second hydraulic port. In other words, the first, second, and third hydraulic lines are connected in parallel between the first and second hydraulic ports. The first check valve blocks the flow of hydraulic fluid from the first to the second hydraulic port, and the second check valve blocks the flow of hydraulic fluid from the second to the first hydraulic port. The separate hydraulic damping module is designed for detachable connection to a control pressure port of a load-holding valve.

[0007] A detachable connection, as used here, refers to a fluid-tight hydraulic connection that can be established and then disconnected. This detachable connection can exist directly between the load-holding valve and the damping module, or it can be implemented via an intermediate element, such as a pipe section or an intermediate block. By providing a separate hydraulic damping module, uniformly designed, cost-optimized load-holding valves can be manufactured, which can be equipped with or without damping, depending on the application. The separate hydraulic damping module is detachably connected to the control pressure port of the load-holding valve as needed, thus being inserted into the control pressure line for controlling the load-holding valve. This optimizes design, production, and process costs and provides a simple, modular solution for providing damping for a load-holding valve.The opening ratio of the load-holding valve can be adjusted independently of the separate damping module via the diameter ratio of the control fluid inlet nozzle to the control fluid outlet nozzle.

[0008] By using the separate hydraulic damping module according to the invention in the load-holding valve according to the invention, it can be used in a particularly versatile way for applications with or without damping requirements, without having to provide differently designed load-holding valves for this purpose.

[0009] According to the invention, the second hydraulic port is hydraulically connected to the control pressure port of the load-holding valve when the separate hydraulic damping module is detachably connected to the control pressure port of the load-holding valve. The hydraulic connection between the second hydraulic port and the control pressure port can exist directly between the two elements or be implemented via an intermediate element, such as a pipe section or an intermediate block. This ensures damping of the control pressure acting on the load-holding valve.

[0010] The separate hydraulic damping module conveniently includes a thread for screwing into a mating thread on the load-holding valve, thus creating a detachable connection to the control pressure port of the load-holding valve. This allows for a secure connection between the separate hydraulic damping module and the load-holding valve, which can also be easily disconnected if necessary. Of course, any other type of hydraulic connection between the separate hydraulic damping module and the control pressure port of the load-holding valve is also conceivable.

[0011] It is advantageous if the first check valve is a pre-tensioned check valve. Specifically, the pre-tension is in the range of 15 to 30 bar. In particular, the first pre-tension is approximately 18 bar. In the flow direction from the second hydraulic port to the first hydraulic port, the hydraulic fluid must therefore flow through the throttling element for smaller pressure differences between the second and first hydraulic ports. This achieves a higher damping effect for small pressure differences. Only at higher pressure differences, specifically when the pressure at the second hydraulic port exceeds the pressure at the first hydraulic port at the level of the first pre-tension, does the first check valve open, so that the majority of the hydraulic fluid no longer flows through the throttling element, but through the first check valve.

[0012] Preferably, the second check valve is a check valve pre-tensioned with a second pre-tension, wherein the second pre-tension is lower than the first pre-tension. In particular, the second pre-tension is in the range of 0.2 to 5 bar. More specifically, the second pre-tension is approximately 0.5 bar. The second check valve thus serves to enable a sufficient flow rate from the first hydraulic port to the second hydraulic port. Otherwise, for high pressure differentials between the first and second hydraulic ports, the load-holding valve could not be actuated quickly enough due to the resistance of the throttling element.

[0013] Furthermore, it is advantageous to install a filter in the second hydraulic line, upstream of the second check valve, in the direction of flow from the first hydraulic port to the second hydraulic port. The filter serves to protect the separate hydraulic damping element from contamination.

[0014] Preferably, the throttling element comprises a threaded choke. The threaded choke is an effective throttling element that allows the throttling resistance to be adjusted even when installed. Furthermore, the threaded choke ensures strong attenuation of high frequencies and moderate attenuation of low frequencies. Of course, it is conceivable to use any other type of throttling element.

[0015] It is also advantageous if the throttling element includes a throttle that is arranged parallel to the threaded throttle in a fourth hydraulic line. The parallel arrangement of the throttle and threaded throttle allows for particularly precise adjustment of the throttling element's operating range.

[0016] The throttle is conveniently a screw-in nozzle that is screwed into an internal thread of the threaded throttle. The screw-in nozzle allows for strong attenuation of high frequencies and weak attenuation of low frequencies. The combination of threaded throttle and screw-in nozzle enables particularly precise adjustment of the throttle element's operating range. Specifically, the coarse adjustment is achieved via the screw-in nozzle's diameter, which is permeable to hydraulic fluid and can only be replaced when the threaded throttle is removed. Subsequent fine-tuning of the damping characteristics of the separate hydraulic damping module is then achieved, even when installed, by adjusting the screw-in depth of the threaded throttle.

[0017] Preferably, the drain check valve is a spring-loaded drain check valve. It is advantageous if the drain line branches off downstream of the control fluid inlet nozzle when viewed in the direction of flow from the control port. Furthermore, it is convenient if the control fluid outlet nozzle is located upstream of the drain check valve when viewed in the direction of flow from the control port.

[0018] The invention will now be explained in more detail with reference to exemplary embodiments shown in the figures. These schematically show: Fig. 1 a hydraulic circuit diagram of a load holding valve according to the invention with a separate hydraulic damping module according to a first embodiment; Fig. 2 a hydraulic circuit diagram of a separate hydraulic damping module according to a second embodiment; Fig. 3 a sectional view of the separate hydraulic damping module made of Fig. 1; Fig. 4 a sectional view of the separate hydraulic damping module made of Fig. 1 with a turned first screw-in cartridge; and Fig. 5 a partially cutaway view of the control pressure port of the load holding valve from Fig. 1 with a separate hydraulic damping module attached to it.

[0019] A first embodiment of a load-holding valve LH with a separate hydraulic damping module 1 is now described with reference to the Fig. 1 and 3 to 5 described.

[0020] The separate hydraulic damping module 1 according to the first embodiment has a housing 2, a first hydraulic port 3, and a second hydraulic port 4. A first check valve 5 is arranged in a first hydraulic line 6 within the housing 2, a second check valve 7 is arranged in a second hydraulic line 8, and a throttle element 9 is arranged in a third hydraulic line 10. The first hydraulic line 6, the second hydraulic line 8, and the third hydraulic line 10 each connect the first hydraulic port 3 to the second hydraulic port 4. The first check valve 5 blocks the flow of hydraulic fluid from the first hydraulic port 3 to the second hydraulic port 4, and the second check valve 7 blocks the flow of hydraulic fluid from the second hydraulic port 4 to the first hydraulic port 3.The separate hydraulic damping element 1 is detachably connected to a control pressure port S of the load holding valve LH.

[0021] As in Fig. As can be seen in Figure 1, the load holding valve LH also includes, in a generally known manner, a pump-side hydraulic connection P, a consumer-side hydraulic connection V, a bypass check valve RV1 in a bypass line BL, and a controlled, unlockable spring-loaded check valve or an unlockable pressure relief valve RV2 in a throttle line DL.

[0022] Furthermore, in the load-holding valve LH, on the side of the control pressure port S, a control fluid inlet nozzle D1 is arranged in a control line SL, and in a drain line AL branching off from the control line SL, a control fluid outlet nozzle D2 and a spring-loaded drain check valve RV3 are arranged. Viewed in the flow direction from the control port S, the drain line AL branches off downstream of the control fluid inlet nozzle D1, and the control fluid outlet nozzle D2 is arranged upstream of the drain check valve RV3 in the drain line AL. The opening ratio of the load-holding valve LH can be adjusted via the diameter ratio of the control fluid inlet nozzle D1 to the control fluid outlet nozzle D2.

[0023] The second hydraulic port 4 is hydraulically connected to the control pressure port S of the load-holding valve LH. The first hydraulic port 3, in turn, is hydraulically connected to a control pressure line of a higher-level hydraulic system (not shown) or can be connected to such a control pressure line.

[0024] As in the Fig. 3 and Fig. As shown in Figure 4, the separate hydraulic damping module 1 comprises a first screw-in cartridge 11 in which the first check valve 5 and the throttle element 9 are arranged. The first screw-in cartridge 11 has several bores that form hydraulic lines. Among other things, sections of the first hydraulic line 6, the second hydraulic line 8, and the third hydraulic line 10 run through said bores in the first screw-in cartridge 11. In the sectional views of the Fig. 3 and Fig. Figure 4 shows the first screw-in cartridge 11 rotated about its central axis A in two different positions to illustrate all fluid-carrying connections within the first screw-in cartridge 11. Specifically, the first screw-in cartridge 11 includes a connection channel 28 that opens into a hydraulic chamber 29 and connects this chamber to the second hydraulic connection 4. The second hydraulic line 8 opens into the connection channel 28 via a radial bore in the first screw-in cartridge 11. The first check valve 5 in the first hydraulic line 6 and the throttle element 9 in the third hydraulic line 10 are connected to the hydraulic chamber 29.

[0025] The first screw-in cartridge 11 is received in a recess 12 of the housing 2 and inserted through the housing 2. On one side with respect to the central axis A (upper side in Fig. 3 and Fig. 4) The first screw-in cartridge 11 has a tool engagement head 13 which has a larger diameter than the recess 12 of the housing 2. On its side facing the housing 2, a sealing ring 14 is located between the tool engagement head 13 and the housing 2 in a sealing ring receptacle of the tool engagement head 13, which seals the fluid-carrying connections within the recess 12 to the outside when the separate hydraulic damping module 1 is mounted on the load-holding valve LH. On the other side with respect to the central axis A (lower side in the Fig. 3 and Fig. 4) The first screw-in cartridge 11 has a thread 15 which is screwed into a mating thread LHG of the load holding valve LH (see Fig. 5) to create the detachable connection of the separate hydraulic damping module 1 with the control port S of the load-holding valve LH. The first screw-in cartridge 11 is inserted through the housing 2 and screwed into the mating thread LHG of the load-holding valve LH, thus securing the housing 2 to the load-holding valve LH, see figure. Fig. 5. The connecting channel 28 is therefore hydraulically connected to the control port S of the load holding valve LH.

[0026] The first check valve 5 is pre-tensioned by a spring with a first pre-tension of approximately 18 bar, and the second check valve 7 is pre-tensioned by a spring with a second pre-tension of approximately 0.5 bar. The second pre-tension is therefore lower than the first. The second check valve 7 ensures a sufficiently large flow rate in the direction of flow from the first hydraulic port 3 to the second hydraulic port 4. The first check valve 5 only opens at a pressure differential greater than 18 bar, so that at smaller pressure differentials in the direction of flow from the second hydraulic port 4 to the first hydraulic port 3, the hydraulic fluid must flow through the throttling element 9, thus maintaining the control pressure towards the load-holding valve LH.

[0027] Furthermore, the separate hydraulic damping module 1 includes a filter 16, which is arranged in the second hydraulic line 8 upstream of the second check valve 7, in the direction of flow from the first hydraulic port 3 to the second hydraulic port 4. The filter 16 prevents contaminants from entering the separate hydraulic damping element 1 via the second hydraulic line 8 from the first hydraulic port 3.

[0028] The first screw-in cartridge 11 is, as in the Fig. 3 and Fig. As shown in Figure 4, a second screw-in cartridge 17 is screwed into the internally hollow tool engagement head 13. This second cartridge has a hollow tool engagement head 30, which is designed analogously to the tool engagement head 13 of the first screw-in cartridge 11. A sealing element 18 is arranged between the tool engagement head 30 of the second screw-in cartridge 17 and the tool engagement head 13 of the first screw-in cartridge 11 to ensure the tightness of the separate hydraulic damping module 1 to the outside.

[0029] In the first embodiment, the throttle element 9 comprises, as shown in the Fig. 3 and Fig. Figure 4 shows a threaded throttle 19. The threaded throttle 19 is screwed into the second screw-in cartridge 17 through its internally hollow tool engagement head 30. The screw-in depth of the threaded throttle 19 can be adjusted via a lock nut 20. The engaging section of an external thread 21 of the threaded throttle 19 with an internal thread 22 of the second screw-in cartridge 17 forms the throttling travel of the throttle element 9. Depending on the screw-in depth of the threaded throttle 19, this throttling travel is longer or shorter, and the throttling can be adjusted accordingly.

[0030] The threaded throttle 19 also has an internal thread 23, into which a sealing screw 24 is screwed in the first embodiment. This sealing screw 24 blocks a fourth hydraulic line 25, which would bridge the throttling travel of the throttle element 9 via a radial bore 26 in the threaded throttle 19, and thus be connected in parallel with this section of the third hydraulic line 10.

[0031] In a second embodiment, whose hydraulic circuit diagram is in Fig. As shown in Figure 2, the sealing screw 24 is replaced by a screw-in nozzle 27. In the second embodiment, the screw-in nozzle 27 is screwed into the internal thread 23 of the threaded throttle 19, and the fourth hydraulic line 25 is thus connected in parallel to the third hydraulic line 10 via the screw-in nozzle 27. In the second embodiment, the throttle element 9 therefore comprises the threaded throttle 19 and the screw-in nozzle 27.

[0032] With the throttle element 9 removed, the screw-in nozzle 27 can be replaced, allowing for a rough adjustment of the damping behavior of the separate hydraulic damping module 1 by using different nozzle diameters. Fine adjustment is then achieved by screwing the threaded throttle 19 into the second screw-in cartridge 17 and setting the throttle travel using the lock nut 20. Reference sign 1 damping module 2 cases 3 first hydraulic connection 4 second hydraulic connection 5 first check valve 6 first hydraulic line 7 second check valve 8 second hydraulic line 9 Throttle element 10 third hydraulic line 11 first screw-in cartridge 12 Exclusion 13 Tool engagement head of the first screw-in cartridge 14 Sealing ring 15 threads 16 filters 17 second screw-in cartridge 18 Sealing element 19 Threaded throttle 20 locknuts 21 External threads of the threaded throttle 22 internal threads of the second screw-in cartridge 23 Internal threads of the threaded throttle 24 sealing screw 25 fourth hydraulic line 26 radial bore 27 Screw-in nozzle 28 connection channels 29 Hydraulic chamber 30 Tool engagement head of the second screw-in cartridge A Central axis of the first screw-in cartridge AL drain pipe D1 Control fluid inlet nozzle D2 Control fluid drain nozzle DL throttle line LH load holding valve LHG counter thread of the load-holding valve P pump-side hydraulic connection RV1 Bypass Check Valve RV2 controlled unlockable spring-loaded check valve / unlockable pressure relief valve RV3 spring-loaded drain check valve S control pressure connection SL control line V consumer-side hydraulic connection

Claims

[1] Load holding valve (LH) with a valve body in which a consumer-side hydraulic connection (V), a pump-side hydraulic connection (P) and a control line (SL) with a control pressure connection (S) are arranged, wherein the load holding valve (LH) has a separate hydraulic damping module (1), wherein a control fluid inlet nozzle (D1) is arranged in the control line (SL) and a control fluid outlet nozzle (D2) and an outlet check valve (RV3) are arranged in a drain line (AL) branching off from the control line (SL), wherein the separate hydraulic damping module (1) has a housing (2), a first hydraulic port (3) and a second hydraulic port (4), wherein a first check valve (5) is arranged in a first hydraulic line (6) in the housing (2), a second check valve (7) is arranged in a second hydraulic line (8) and a throttle element (9) is arranged in a third hydraulic line (10), wherein the first hydraulic line (6), the second hydraulic line (8) and the third hydraulic line (10) each connect the first hydraulic port (3) to the second hydraulic port (4), wherein the first check valve (5) blocks the flow of hydraulic fluid in the direction of flow from the first hydraulic port (3) to the second hydraulic port (4) and the second check valve (7) blocks the flow of hydraulic fluid in the direction of flow from the second hydraulic port (4) to the first hydraulic port (3), and wherein the separate hydraulic damping module (1) is designed for detachable connection with the control pressure port (S) of a load holding valve (LH), wherein the second hydraulic port (4) is in hydraulic connection with the control pressure port (S) of the load holding valve (LH) when the separate hydraulic damping module (1) is detachably connected to the control pressure port (S) of the load holding valve (LH), where the drain check valve (RV3) is a spring-loaded drain check valve. [2] Load holding valve (LH) according to claim 1, characterized by , that the separate hydraulic damping module (1) includes a thread (15) for screwing into a mating thread (LHG) of the load holding valve (LH) to realize the detachable connection with the control pressure port (S) of the load holding valve (LH). [3] Load holding valve (LH) according to any one of the preceding claims, characterized by, that the first check valve (5) is a check valve pre-tensioned with a first pre-tension. [4] Load holding valve (LH) according to claim 3, characterized by , that the second check valve (7) is a check valve pre-tensioned with a second pre-tension, wherein the second pre-tension is smaller than the first pre-tension. [5] Load holding valve (LH) according to any one of the preceding claims, characterized by , that in the direction of flow from the first hydraulic port (3) to the second hydraulic port (4) in the second hydraulic line (8) before the second check valve (7) a filter (16) is arranged. [6] Load holding valve (LH) according to any one of the preceding claims, characterized by , that the throttle element (9) comprises a threaded throttle (19). [7] Load holding valve (LH) according to claim 6, characterized by, that the throttle element (9) further comprises a throttle which is arranged parallel to the threaded throttle (19) in a fourth hydraulic line (25). [8] Load holding valve (LH) according to claim 7, characterized by , that the throttle is a screw-in nozzle (27) which is screwed into an internal thread (23) of the threaded throttle (19). [9] Load holding valve (LH) according to any of the preceding claims, characterized by , that the outflow line (AL) branches off behind the control fluid inflow nozzle (D1) in the direction of flow from the control connection (S). [10] Load holding valve (LH) according to any of the preceding claims, characterized by , that the control fluid drain nozzle (D2) is located upstream of the drain check valve (RV3) in the direction of flow from the control port (S).

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