Hydraulic lifting device for a chassis of a mobile device, chassis and mobile device

Abstract

Hydraulic lifting device (1) for a chassis of a mobile device comprising a valve block (2), a pump (3), a tank (4), a first cylinder assembly (5) and a second cylinder assembly (6), wherein the first cylinder assembly (5) and the second cylinder assembly (6) can be selectively pressurized by the pump (3) or connected to the tank (4) via the valve block (2), wherein the first cylinder assembly (5) is connected to the pump (3) via at least one primary check valve (7) arranged in the valve block (2), and wherein the second cylinder assembly (6) is connected to the pump (3) via at least one secondary check valve (8a, 8b) arranged in the valve block (2), characterized by the fact that the valve block (2) has at least one pressure accumulator (9, 10) in the flow direction from the pump (3) to the second cylinder assembly (6) downstream of the at least one secondary check valve (8a, 8b), so that a gradual pressure loss at the secondary check valve (8a, 8b) does not lead to an unintentional retraction of the second cylinder assembly (6).

Description

[0001] The present invention relates to a hydraulic lifting device for a chassis of a mobile device, a chassis with such a hydraulic lifting device, and a mobile device with a chassis according to the invention. The mobile device can, in particular, be a medical device.

[0002] Such hydraulic lifting devices or chassis are known from the prior art and are used particularly in the medical field for mobile medical devices, for example, mobile surgical robots or mobile operating tables. These hydraulic lifting devices, also known as "floor lock" systems, serve to securely fix, support, and level the mobile medical devices during their use, regardless of the surface.

[0003] To achieve this, such hydraulic lifting devices typically include a valve block, a pump, a tank, and multiple cylinder assemblies. The cylinder assemblies can be pressurized by the pump via the valve block, causing them to extend and brace against the ground, thus lifting or jacking up the chassis of the medical device. This causes the casters or wheels attached to the chassis to lose contact with the ground, preventing unintentional movement of the chassis. Furthermore, solutions are also known in which the cylinder assemblies brace themselves against the ground with a certain force without lifting the chassis. Nevertheless, this force is sufficient to prevent unintentional movement and simultaneously level the chassis.

[0004] The pump is usually designed for manual operation, for example, by hand or foot. Solutions where the pump is driven, such as by a power unit, are also possible. To lower the chassis, the valve block typically includes a manually operated drain valve that connects the hydraulic cylinders to the tank. When the drain valve is activated, the weight of the mobile medical device forces the hydraulic fluid from the cylinders into the tank until the chassis's wheels or rollers regain contact with the ground. Springs are usually incorporated into the cylinders to further assist in the return to the lowered position.

[0005] To hold the medical device in the raised position, the valve block has check valves in the flow direction from the pump to the respective cylinder assembly, as is known, for example, from EP 3 386 458 B1 or DE 10 2012 001 555 A1. EP 3 386 458 B1 discloses a chassis with a hydraulic lifting device, which has a first cylinder assembly with two primary cylinders and a second cylinder assembly with two secondary cylinders. The two primary cylinders are connected to the pump via a common first check valve, while the two secondary cylinders are each connected to the pump via a secondary check valve and thus protected.

[0006] These check valves are subject to particularly stringent requirements regarding their long-term tightness. It is essential to prevent the medical device from noticeably or even completely lowering during potentially lengthy treatments. This cannot be reliably guaranteed with only one check valve per cylinder assembly or cylinder due to manufacturing tolerances or contaminants in the hydraulic fluid. Small leakage flows through the check valve can then lead to an unintended lowering of the medical device over time. This is especially problematic when there is a relatively low (holding) pressure downstream of the check valve.

[0007] This problem could be largely solved by redundant safety measures. However, this significantly increases the required installation space of the valve block. This, in turn, affects the weight and cost of the hydraulic lifting device.

[0008] Based on this, the object of the present invention is to provide a hydraulic lifting device for a chassis of a mobile device in which unintentional lowering over time can be effectively prevented without a noticeable increase in the size of the valve block of the hydraulic lifting device.

[0009] The problem is solved with a hydraulic lifting device for a chassis of a mobile device according to claim 1. Advantageous further developments are described in the dependent claims.

[0010] The hydraulic lifting device according to the invention comprises a first cylinder assembly and a second cylinder assembly. The first cylinder assembly is connected to the pump via at least one primary check valve arranged in the valve block, and the second cylinder assembly is connected to the pump via at least one secondary check valve arranged in the valve block. The invention is distinguished from the prior art in that the valve block has at least one pressure accumulator in the flow direction from the pump to the second cylinder assembly downstream of the at least one secondary check valve.

[0011] This ensures that a gradual pressure loss at the secondary check valve does not lead to an unintended lowering of the system due to the retraction of the second cylinder assembly. Furthermore, such a pressure accumulator can be easily integrated into the valve block, so that the overall installation space of the valve block is not significantly increased. This, in turn, has a positive effect on the cost and weight of the valve block. In addition, the pressure accumulator can also compensate for pressure losses that do not necessarily occur at the secondary check valve. It is also conceivable that a micro-leak in the drain mechanism could lead to a gradual pressure loss.

[0012] It is advantageous if the first cylinder assembly can be pressurized via a first pressure-reducing valve and the second cylinder assembly can be pressurized via a second pressure-reducing valve, wherein the outlet pressure of the first pressure-reducing valve differs from the outlet pressure of the second pressure-reducing valve. In particular, it is advantageous if the outlet pressure at the first pressure-reducing valve is greater than the outlet pressure at the second pressure-reducing valve. In this context, it is especially advantageous if the pressure accumulator has a volume of no more than 1 cm³. 3 , in particular of no more than 0.5 cm 3 exhibits.

[0013] The pressure reducing valves allow for hierarchical actuation of the first and second cylinder assemblies. First, the cylinder(s) of the first cylinder assembly are extended by the pump when pressurized, for example, up to a predefined stop. The second cylinder assembly is only extended to the extent that the output pressure acting on it is lower than that acting on the first cylinder assembly. Once the first cylinder assembly is fully extended, a holding pressure can be built up at the second cylinder assembly by further actuation of the pump. However, this holding pressure is limited by the output pressure set at the second pressure reducing valve.Therefore, the holding pressure at the first cylinder assembly is greater than the holding pressure at the second cylinder assembly, making a gradual pressure loss at the secondary check valve particularly critical. This potential pressure loss is compensated for by the pressure accumulator. To avoid compromising the functionality described above with the hierarchical actuation of the two cylinder assemblies, it has proven advantageous to forgo a large-volume pressure accumulator and use one with a volume of no more than 1 cm³. 3 to be used, which completely compensates for the potential leakage volume. Furthermore, such a pressure accumulator is also small and can be integrated directly into the valve block, so that no disadvantages in terms of installation space arise.

[0014] It is advantageous for the second cylinder assembly to have two secondary cylinders and the valve block to have two secondary check valves, each of the two secondary cylinders being connected to the pump via a secondary check valve. In this context, it is beneficial for the valve block to have a second identical pressure accumulator, with each accumulator positioned upstream of the respective secondary check valve in the flow direction from the pump to the respective secondary cylinder. This prevents pressure loss at the respective secondary check valve from affecting either secondary cylinder.

[0015] Preferably, the at least one pressure accumulator is a spring accumulator, or the pressure accumulators are spring accumulators. It is advantageous if the at least one pressure accumulator comprises a spring and a piston, wherein the piston is movably arranged against a force exerted by the spring in a receiving bore of the valve block. This allows for a particularly compact design that can be directly integrated into the valve block.

[0016] It is advantageous if the pressure accumulator has a sealing cap that is fixed to the valve block and closes the receiving bore. This allows the installation space of the valve block to be further reduced.

[0017] Furthermore, the problem is solved with a chassis according to claim 9, which has a hydraulic lifting device according to the invention as described above. The solution is also achieved with a mobile device according to claim 10, which has such a chassis. The mobile device can, in particular, be a mobile medical device.

[0018] The invention will now be explained in more detail with reference to an embodiment shown in the figures. The figures schematically illustrate: Fig. 1 a hydraulic circuit diagram of a hydraulic lifting device according to the invention; Fig. 2 an exploded view of a valve block of a hydraulic lifting device according to the invention; Fig. 3 a side view of the in Fig. 2 valve blocks shown with integrated pressure accumulator; and Fig. 4. Make a cut along the intersection line AA through the in Fig. 3 shown valve block.

[0019] Fig. Figure 1 shows a hydraulic circuit diagram of a hydraulic lifting device 1 according to the invention for a mobile medical device, for example, a surgical robot. The hydraulic lifting device 1 comprises a valve block 2, a manually operated pump 3, a tank 4, a first cylinder assembly 5, and a second cylinder assembly 6. The valve block 2 has a first and a second pressure accumulator 9, 10. The first cylinder assembly 5 has two primary cylinders 5a, 5b, and the second cylinder assembly 6 has two secondary cylinders 6a, 6b. In this embodiment, the primary cylinders 5a, 5b and the secondary cylinders 6a, 6b are designed as single-acting hydraulic cylinders with return springs.

[0020] Pump 3 is connected to tank 4, and the valve block is connected to pump 3 via a first connection 21. When pump 3 is actuated, hydraulic fluid is pumped from tank 4 to valve block 2 via the first connection 21. In valve block 2, a first line assembly 22 supplies pressure to the first cylinder assembly 5, and a second line assembly 23 supplies pressure to the second cylinder assembly 6. Looking in the direction of flow from pump 3 to the first cylinder assembly 5, the first line assembly 22 contains a first pressure reducing valve 22, a primary check valve 7, and a drain line 24 with a manually operated drain valve 18. Thus, the first line assembly 22 contains a single primary check valve 7, which protects the two primary cylinders 5a and 5b of the first cylinder assembly 5.

[0021] In the second line assembly 23, a second pressure reducing valve 12 is arranged in the flow direction from the pump 3 to the second cylinder assembly 6. Downstream of the second pressure reducing valve 12, the second line assembly 23 branches into a first branch 25 and a second branch 26. In each branch 25, 26, downstream of the second pressure reducing valve 12, a secondary check valve 8a, 8b and a drain line 27, 28 with a manually operated drain valve 19, 20 are arranged. Downstream of each secondary check valve 8a, 8b, one of the pressure accumulators 9, 10 is arranged. In this embodiment, the pressure accumulators 9, 10 have a volume of 0.5 cm³. 3 In the second line arrangement 23, a secondary check valve 8a, 8b protects each of the two secondary cylinders 6a, 6b of the second cylinder assembly 6.

[0022] The first pressure reducing valve 11 is set to a higher outlet pressure than the second pressure reducing valve 12. This allows for hierarchical actuation of the first cylinder assembly 5 and the second cylinder assembly 6. When the pump 3 is activated, hydraulic fluid is pumped from the tank 4 into the valve block 2 and from there via the first line assembly 22 to the first cylinder assembly 5 and via the second line assembly 23 to the second cylinder assembly 6. The primary cylinders 5a, 5b and the secondary cylinders 6a, 6b extend uniformly until the two primary cylinders 5a, 5b (or their attached support legs or the like) make contact with the ground. Due to the higher outlet pressure of the first pressure reducing valve 11, the primary cylinders 5a, 5b are then pressurized, and the secondary cylinders 6a, 6b are advanced due to the lower outlet pressure at the second pressure reducing valve 12.Once the primary cylinders 5a, 5b are extended to their mechanically limited maximum position, further actuation of the pump 3 generates a certain holding pressure in the secondary cylinders 6a, 6b, which, however, does not exceed the outlet pressure of the second pressure reducing valve 12. Preferably, the outlet pressure of the second pressure reducing valve 12 is set to the weight of the mobile medical device.

[0023] When the secondary cylinders 6a, 6b are extended, or when the first and second branches 25, 26 are pressurized, the two pressure accumulators 9, 10 are charged. As soon as the maximum pressure downstream of the secondary check valves 8a, 8b is reached, the mobile medical device is fully raised. The holding pressure acting on the second cylinder assembly 6 is lower compared to the holding pressure acting on the first cylinder assembly 6, so that any possible gradual pressure loss at the secondary check valves 8a, 8b is compensated for via the pressure accumulators 9, 10. The volume of 0.5 cm³ described above is used for this purpose. 3One pressure accumulator 9, 10 is sufficient. A possible gradual pressure loss at the primary check valve 7 is not critical due to the significantly higher holding pressure. However, it is conceivable that a pressure accumulator acting on the first line assembly 22 downstream of the primary check valve 7 could also be used. This would provide additional protection for the first cylinder assembly 5. It is also conceivable that only one pressure accumulator 9, 10 could be used for both secondary cylinders 6a, 6b.

[0024] Furthermore, a pressure relief valve 17 is provided to bypass pump 3. When the primary cylinders 5a, 5b and the secondary cylinders 6a, 6b are fully extended and pump 3 continues to be operated, the pressure relief valve 17 opens and hydraulic fluid is circulated.

[0025] To lower the mobile medical device, the drain valves 18, 19, 20 are actuated, so that the first line assembly 22 and the second line assembly 23 are connected to the tank 4 via the respective drain lines 24, 27, 28 and a second connection 22. It is conceivable that the drain valves 18, 19, 20 are actuated manually together and thus form a draining device.

[0026] The following will now refer to the Fig. Sections 2 to 4 describe the structural design of pressure accumulators 9 and 10. For the sake of clarity, only one of the two pressure accumulators, 9 and 10, is described here.

[0027] The pressure accumulator 9, 10 is designed as a spring accumulator and comprises a spring 13, a piston 14, and a sealing cap 15. The spring 13 is supported on one side by a first receptacle 30 of the sealing cap and on the other side by a second receptacle 31 of the piston 14. The sealing cap 14 is fixed to the valve block 2 by means of a clamp 32 and two screws 33 such that the piston 14 is movable against a force exerted by the spring 13 in a receiving bore 15 of the valve block 2. As shown, the sealing cap 16 closes the receiving bore 15.

[0028] When the second line arrangement 23 is pressurized, the piston 14 is moved against the force of the spring 13 in the direction of the sealing cap 14 so that in the maximum position of the piston 14 a storage volume of 0.5 cm³ 3 is provided. It has been shown that a storage volume of at most 1 cm³ is sufficient. 3This is sufficient to compensate for a gradual pressure loss at the secondary check valves 8a, 8b. It has also been shown that such a storage volume still allows the hierarchical application described above, because an excessively large storage volume would necessitate a higher outlet pressure at the second pressure reducing valve 12. Reference symbol list 1 Hydraulic lifting device 2 Valve block 3 Pump 4 Tank 5 first cylinder assembly 5a, 5b primary cylinder 6 second cylinder device 6a, 6b secondary cylinder 7 primary check valve 8a, 8b secondary check valve 9 pressure accumulators 10 pressure accumulators 11 first pressure reducing valve 12 second pressure reducing valve 13 spring 14 pistons 15 Mounting hole 16 Cap 17 Pressure relief valve 18 Drain valve 19 Drain valve 20 Drain valve 21 first connection 22 first line arrangement 23 second line arrangement 24 Drain pipe 25 first branch 26 second branch 27 Drain pipe 28 Drain pipe 29 second connection 30 first recording 31 second recording 32 bells 33 screw

Claims

[1] Hydraulic lifting device (1) for a chassis of a mobile device comprising a valve block (2), a pump (3), a tank (4), a first cylinder assembly (5) and a second cylinder assembly (6), wherein the first cylinder assembly (5) and the second cylinder assembly (6) can be selectively pressurized by the pump (3) or connected to the tank (4) via the valve block (2), wherein the first cylinder assembly (5) is connected to the pump (3) via at least one primary check valve (7) arranged in the valve block (2), and wherein the second cylinder assembly (6) is connected to the pump (3) via at least one secondary check valve (8a, 8b) arranged in the valve block (2), characterized by , that the valve block (2) has at least one pressure accumulator (9, 10) in the flow direction from the pump (3) to the second cylinder assembly (6) downstream of the at least one secondary check valve (8a, 8b), so that a gradual pressure loss at the secondary check valve (8a, 8b) does not lead to an unintentional retraction of the second cylinder assembly (6). [2] Hydraulic lifting device (1) according to claim 1, characterized by , that the first cylinder assembly (5) can be pressurized via a first pressure reducing valve (11), and the second cylinder assembly (6) can be pressurized via a second pressure reducing valve (12), wherein an output pressure of the first pressure reducing valve (11) is different from an output pressure of the second pressure reducing valve (12), in particular greater. [3] Hydraulic lifting device (1) according to one of the preceding claims, characterized by , that the pressure reservoir (9, 10) has a volume of at most 1 cm3 , in particular of no more than 0.5 cm 3 exhibits. [4] Hydraulic lifting device (1) according to one of the preceding claims, characterized by , that the second cylinder assembly (6) has two secondary cylinders (6a, 6b) and the valve block (2) has two secondary check valves (8a, 8b), each of the two secondary cylinders (6a, 6b) being connected to the pump (3) via a secondary check valve (8a, 8b). [5] Hydraulic lifting device (1) according to claim 4, characterized by , that the valve block (2) has a second identical pressure accumulator (9, 10), wherein each pressure accumulator (9, 10) is arranged in the flow direction from the pump (3) to the respective secondary cylinder (6a, 6b) upstream of the respective secondary check valve (8a, 8b). [6] Hydraulic lifting device (1) according to one of the preceding claims, characterized by , that at least one pressure accumulator (9, 10) is a spring accumulator. [7] Hydraulic lifting device (1) according to claim 6, characterized by , that the pressure accumulator (9, 10) has a spring (13) and a piston (14), wherein the piston (14) is arranged to be movable against a force of the spring (13) in a receiving bore (15) of the valve block (2). [8] Hydraulic lifting device (1) according to claim 7, characterized by , that the pressure accumulator (9, 10) has a sealing cap (16) fixed to the valve block (2) and closing the receiving bore (15). [9] Chassis of a mobile device with a hydraulic lifting device (1) according to one of the preceding claims. [10] Mobile device, in particular mobile medical device, with a chassis according to claim 9.

Images