Redundant Hubventil

Abstract

A lift valve, in particular a proportional lift valve, for hydraulic applications, comprising a main piston (11) and a pilot piston (12) arranged coaxially displaceably therein, or a valve needle attached to the actuator (6), wherein the main piston (11) is axially displaceably received in a valve bushing (16) and the pilot piston (12) can be actuated by means of an actuator (6), wherein the main piston (11) is axially biased in its return chamber (19) against a main sealing seat (21) by means of a return spring (20), so that in a closed position of the lift valve a fluid connection between a pump port (2) (pump side) and a load port (3) (load side) is blocked, characterized in that the lift valve has at least two check valves (35, 38) which are arranged to each other such that in a closed position either a pump port-side pressure can be directed into the return chamber (19) or a load port-side pressure can be directed into the return chamber (19). is manageable.

Description

[0001] The invention relates to a globe valve according to the preamble of claim 1.

[0002] Such lift valves, particularly proportional lift valves, are used for hydraulic applications. In known hydraulic lifting systems with which loads are lifted or lifted loads are held and / or moved, the combination of a proportional lift valve (2 / 2 directional seat valve) and an additional, external check valve is often used to connect a hydraulic pump to one or more lifting cylinders during lifting operation. The proportional lift valves used here are designed with a seat seal as so-called "cartridge" valves to prevent unwanted leakage in the area between the hydraulic pump and lifting cylinder. The proportional lift valve is preferably pilot-controlled according to the lift-follow principle and therefore has the property that the seat seal is only present in the direction from the hydraulic pump to the load in the form of the lifting cylinder or the like.The load holding in the event of non-operation of the lifting system must generally be ensured by a check valve within the inlet or outlet of the proportional lift valve.

[0003] One of the disadvantages of this is that if this load-holding check valve fails, no load is held. Redundant load holding is not possible when the hydraulic pump is switched off and can only be achieved with an additional load-holding check valve, which would require additional installation space and increase flow resistance.

[0004] An object of the invention is therefore to provide a compactly constructed lift valve, in particular for hydraulic lifting systems, with an integrated, redundant check function.

[0005] This object is achieved by the features of claim 1. Useful embodiments emerge from subclaims 2 to 6.

[0006] The new lift valve, in particular a proportional lift valve, for hydraulic applications eliminates the aforementioned disadvantages of the state of the art.

[0007] The inventive globe valve, in particular a proportional globe valve, for hydraulic applications has a main piston and a coaxially displaceably arranged pilot piston in the main piston. Alternatively, the globe valve has a valve needle attached to the actuator. The main piston is axially displaceably received in a valve bushing, and the pilot piston can be actuated by an actuator. The main piston is axially preloaded in its rear chamber against a main sealing seat by a return spring, so that when the globe valve is in a blocked position, a fluid connection between a pump connection (pump side) and a load connection (load side) is blocked. The globe valve has at least two check valves arranged relative to one another such that, in the blocked position, either a pressure from the pump connection side can be guided into the rear chamber or a pressure from the load connection side can be guided into the rear chamber.

[0008] Due to the two check valves integrated into the proportional lift valve, this proportional lift valve according to the invention takes on the function of an additional external check valve in the load branch, which would otherwise preferably be provided for safety reasons. The lift valve according to the invention provides redundancy of two load-side check valves, so that in the unlikely event of a failure of an external check valve required in the load branch, the load is then held via the one check valve integrated into the lift valve. The use of the lift valve according to the invention also results in space savings in a hydraulic system compared to a hydraulic system with a second external load-side check valve.

[0009] Preferably, at least one check valve is integrated into the main piston or the valve sleeve. This measure opens up another design option.

[0010] It is also advantageous if, to form the check valves, axial blind holes are made at the rear of the main piston, one of which is open on the bottom side to the pump connection and the other on the bottom side to the load connection, and which each have a valve seat on the mouth side for interacting with a closing body of the respective check valve.

[0011] The return spring can be supported by a spring plate that rests against the rear side of the main piston facing the return chamber. The spring plate forms an axial travel limit for the check valve's closing elements. This simplifies the design and assembly of the check valves.

[0012] Preferably, the at least two check valves each have a ball as their closing element. This results in a structurally simple and robust design of the check valves.

[0013] It is also advantageous if the pilot piston is guided in a recess in the main piston. This recess has at least one drain branch to relieve pressure in the rear chamber when the lift valve is open. This allows a sufficient amount of hydraulic fluid to flow through the main piston toward the first, load-side port if necessary.

[0014] In the following, a preferred embodiment of the lift valve according to the invention, in particular a proportional lift valve, for hydraulic applications is explained in more detail using simplified schematic representations. They show: Fig. 1 a side view of the lift valve in a first sectional view and Fig. 2 a side view of the lift valve in a second sectional view.

[0015] In the embodiment according to the Fig. 1 and Fig. 2, the new globe valve has a valve housing 1 with a pump-side connection 2 and a load-side connection 3 as well as an actuator housing 5 screwed into the valve housing 1 and sealed by means of a sealing element 4.

[0016] An armature 7 which can be moved between two end points above an actuator 6 is integrated into the actuator housing 5, wherein in this embodiment the actuator 6 is formed by an electromagnet 8 and a return element 9.

[0017] The armature 7 is positively and non-positively connected to a pilot piston 12 slidably inserted into a blind bore 10 of a main piston 11, said pilot piston 12 having an axial through-bore 13 for pressure equalization. In an end position of the pilot piston 12, this pilot piston 12 rests with its collar 14 on a pilot sealing seat 15 arranged between the pilot piston 12 and the main piston 11.

[0018] The main piston 11, in turn, is slidably arranged in a valve bushing 16. It is clamped in the valve bushing 16 between a main sealing seat 21 and a spring plate 18 via a return spring 20. The spring plate 18 rests on the main piston 11 and is guided by it during movement. The return spring 19 is located in the rear chamber 19 and is supported on a rear, stationary support ring 17 that surrounds the armature 7. The return spring 19 acts on the rear of the main piston 11, so that it is subjected to a mechanical restoring force that presses it against the main sealing seat 21 in the basic position of the main piston 11. The main sealing seat 21 is recessed into the valve bushing 16.

[0019] In addition, the main piston 11 has a plurality of pressure equalization grooves 22 which are open relative to the blind bore 10, as well as at least two outlet channels 23 which fluidically connect the blind bore 10 and the load-side connection 3, wherein the outlet channels 23 are fluidically closed in an end position of the pilot piston 12 by a conical section 24 of the pilot piston 12 in the blind bore 10.

[0020] The valve bushing 16 has a collar 25, via which it is pressed into the valve housing 1 by the actuator housing 5 screwed into the valve housing 1, wherein a plurality of sealing elements 26 are arranged between the valve bushing 16 and the valve housing 1.

[0021] In addition, the valve bushing 16 has at least two opposing transverse bores 27, 28, which are connected to each other via an annular channel 29. One transverse bore 27 opens into the pump-side connection 2, and the other transverse bore 28 opens into a recess 30 arranged between the valve bushing 16 and the valve housing 1.

[0022] The main piston 11 has a pressure surface 31 designed as an annular surface, which can be subjected to a hydraulic opening force directed toward the return chamber 19. The opening force results from a pump pressure applied to the pump-side connection 2 and is directed counter to the restoring force emanating from the return spring 20.

[0023] Starting from the load-side connection 3, the valve bushing 16 also has a radially tapered stepped bore 32 and an adjoining antechamber 33.

[0024] An axial channel 34 is arranged in the main piston 11, which is open to the load-side connection 3 and opens into a first check valve 35. The opening limit of the check valve 35 is formed by the upper side 36 of the spring plate 18, which faces away from the return spring 20.

[0025] In addition, a radial channel 37 is arranged in the main piston 11, which is open to the pump-side connection 2 and opens into a second check valve 38. The opening limit of the check valve 38 is also formed by the upper side 36 of the spring plate 18.

[0026] The operation of the lift valve according to the invention is explained below, starting from the closed representations according to the Fig. 1 and Fig. 2.

[0027] First, it is assumed that the pump-side connection 2 is fluidly connected to a pump not shown in the figures. It is also assumed that the load-side connection 3 is fluidly connected to a consumer not shown in the figures, e.g., a lifting cylinder of a forklift.

[0028] If the pump, not shown in the figures, is switched on, then a pressure fluid, e.g. a hydraulic oil, is present at the pump-side connection 2, through which an opening force acts on the main piston 11 in the direction of the rear chamber 19 via the pressure surface 31.

[0029] In addition, as the effective line 40 shows, the pressure fluid passes via the transverse bore 27, the annular channel 29 and the transverse bore 28 into the radial channel 37 arranged in the main piston 11.

[0030] From there, the pressurized fluid presses on the check valve 38, causing it to open and the pressurized fluid to enter the return chamber 19. The upper side 36 of the spring plate 18 serves as the opening limit of this check valve 38.

[0031] In the return chamber 19, the hydraulic fluid presses on the check valve 35, closing it. Furthermore, the pilot piston 12 is in its one end position, so that the discharge channels 23 to the load-side connection are closed. The main piston 11 is thus subjected to a mechanical restoring force and a hydraulic closing force that is greater than the opening force acting on the pressure surface 31. Consequently, despite the opening force acting on it, the main piston 11 continues to be pressed by the return spring 20 against the main sealing seat 21 recessed in the valve sleeve 16.

[0032] If an electric current is now supplied to the electromagnet 8 via a power supply not shown in the figures, the armature 7 including the pilot piston 12 is attracted by the electromagnet 8, whereby the pilot piston 12 is partially pulled out of the blind bore 10. In this case, pressure equalization between the bottom of the blind bore 10 and the rear chamber 19 occurs through the axial through-bore 13 of the pilot piston 12, so that the pilot piston 12 can be slightly lifted and does not "suck" itself into the blind bore 10.

[0033] The pilot piston 12 has left its one end position and its conical section 24 no longer rests on the pilot sealing seat 15 arranged between the pilot piston 12 and the main piston 11. The pilot piston 12 has thus opened the discharge channels 23 fluidly connected to the load-side connection 3, whereby, according to the line of action 41, the hydraulic fluid located in the rear chamber 19 flows out via the load-side connection 3 and no longer presses on the main piston 11.

[0034] The opening force acting on the pressure surface 31 now overcomes the restoring force of the return spring 20, with the result that the main piston 11 is lifted toward the return chamber 19 against the return spring 20. Consequently, the main piston 11 is no longer supported on the main sealing seat 21 recessed into the valve sleeve 16, so that a fluidic connection is created between the pump-side connection 2 and the load-side connection 3.

[0035] Thus, the hydraulic fluid delivered by the pump (not shown in the figures) flows via the pump-side connection 2 and then via the transverse bore 27 and, in a flow-parallel manner, via the annular channel 29 and transverse bore 28 into the antechamber 33 and then via the stepped bore 32 to the load-side connection 3. In a flow-parallel manner, a small portion of the hydraulic fluid available at the pump-side connection 2 flows via the radial channel 37, the return chamber 19 and the discharge channels 23 to the load-side connection 3.

[0036] From the load-side connection 3, the hydraulic fluid reaches the consumer not shown in the figures, with which the consumer performs, for example, a lifting work.

[0037] If the electrical current applied to the electromagnet 8 is now switched off, the return element 9 pushes the armature 7, including the pilot piston 12, away from the electromagnet 8 and into the blind bore 10, whereby the outlet channels 23 are fluidically closed by the conical section 24 of the pilot piston 12. The pressure fluid in the return chamber 19 can no longer flow out via the outlet channels 23. Instead, the pump-side pressure fluid flows (again) according to the line of action 40 via the transverse bore 27, the annular channel 29, the transverse bore 28 and via the radial channel 37 arranged in the main piston 11 and the check valve 38 into the return chamber 19. The check valve 35 is closed, so that the main piston 11 is subjected to the hydraulic closing force acting in addition to the return force, which is greater than the opening force applied to the pressure surface 31.The main piston 11 is pressed again against the main sealing seat 21 recessed in the valve sleeve 16, whereby the fluidic connection between the pump-side connection 2 and the load-side connection 3 is separated.

[0038] If the fluidic connection between the pump (not shown in the figures) and the pump-side connection 2 is defective or if the pressure of the hydraulic fluid in the pump-side connection 2 becomes lower than the pressure of the hydraulic fluid in the load-side connection 3, then the check valve 35 opens, whereby, as the line of action 39 shows, the hydraulic fluid available via the load-side connection 3 passes through the axial channel 34 into the return chamber 19 and the check valve 38 closes.

[0039] Because the lift valve is closed, there is no fluidic connection between the pump-side port 2 and the load-side port 3, so that there is no pressure drop in the hydraulic fluid at the consumer, which is fluidically connected via the load-side port 3 and not shown in the figures. Consequently, the consumer can remain in its lift position and hold its load, like the lifting cylinder of a forklift.

[0040] Disclosed is a lift valve, in particular a proportional lift valve, for hydraulic applications, with a main piston 11 and a pilot piston 12 arranged coaxially displaceably therein, or a valve needle fastened to the actuator 6, wherein the main piston 11 is received axially displaceably in a valve bushing 16 and the pilot piston 12 can be actuated by means of an actuator 6, wherein the main piston 11 is axially preloaded in its rear chamber 19 against a main sealing seat 21 by means of a return spring 20, so that in a blocking position of the lift valve, a fluid connection between a pump connection 2 (pump side) and a load connection 3 (load side) is blocked, characterized in that the lift valve has at least two check valves 35, 38 which are arranged relative to one another in such a way that in the blocking position either a pressure from the pump connection side can be guided into the rear chamber 19 or a pressure from the load connection side can be guided into the rear chamber 19. List of reference symbols 1 valve housing 2 pump-side connection 3 load-side connection 4 Sealing element 5 actuator housing 6 Actuator 7 anchors 8 Electromagnet 9 Reset element 10 blind bore 11 main pistons 12 pilot pistons 13 Through hole 14 collars 15 Pilot sealing seat 16 Valve bushing 17 Support ring 18 spring plates 19 backcourt 20 return spring 21 Main sealing seat 22 Pressure equalization groove 23 Drain channel 24 Cone section 25 collars 26 Sealing element 27 Cross hole 28 cross hole 29 Ring Canal 30 recess 31 printing area 32 stepped bore 33 Anteroom 34 axial channel 35 Check valve 36 Top 37 Radial canal 38 Check valve 39 Effective line via the load-side connection 3 40 Effective line via pump-side connection 2 41 Effective line from rear space 19 to load-side connection 3

Claims

[1] Lift valve, in particular a proportional lift valve, for hydraulic applications, with a main piston (11) and a pilot piston (12) arranged coaxially displaceably therein, or a valve needle fastened to the actuator (6), wherein the main piston (11) is received axially displaceably in a valve bushing (16) and the pilot piston (12) is actuated by means of an actuator (6), wherein the main piston (11) is axially prestressed in its rear chamber (19) against a main sealing seat (21) by means of a return spring (20), so that in a blocking position of the lift valve, a fluid connection between a pump connection (2) (pump side) and a load connection (3) (load side) is blocked, characterized by that the lift valve has at least two check valves (35, 38) which are arranged relative to one another in such a way that in the blocking position either a pump connection-side pressure can be guided into the rear chamber (19) or a load connection-side pressure can be guided into the rear chamber (19). [2] Lift valve according to claim 1, wherein at least one check valve (35, 38) is integrated in the main piston (11) or in the valve sleeve. [3] Lift valve according to claim 1 or 2, wherein to form the check valves (35, 38) axial blind holes (34, 37) are introduced into the rear of the main piston (11), one of which is open on the bottom side to the pump connection (2) and the other on the bottom side to the load connection (3), and which each have a valve seat on the mouth side for interacting with a closing body of the respective check valve (35, 38). [4] Lift valve according to claim 1, 2 or 3, wherein the return spring (20) is supported on a spring plate (18) which bears against a rear side of the main piston (11) facing the rear chamber (19), wherein the spring plate (19) forms an axial travel limit for the closing bodies of the check valves (35, 38). [5] Lift valve according to one of the preceding claims, wherein the at least two check valves (35, 38) have a ball as a closing body. [6] Lift valve according to one of the preceding claims, wherein the pilot piston (12) is guided in a recess (10) of the main piston (11), which has at least one outlet branch (23) for relieving pressure in the rear chamber (19) in the open position of the lift valve (see Fig. 2).

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