HYDRAULIC LIFTING DEVICE FOR A CHASSIS OF A MOBILE DEVICE, CHASSIS AND MOBILE DEVICE

Abstract

A hydraulic lifting device for a chassis of a mobile device has a valve block, a pump, a tank, a first cylinder device and a second cylinder device. The first cylinder device and the second cylinder device can be selectively pressurized by the pump or connected to tank via the valve block. The first cylinder device is connected to the pump via at least one primary non-return valve disposed in the valve block. The second cylinder device is connected to the pump via at least one secondary non-return valve disposed in the valve block. The valve block has at least one pressure accumulator downstream of the at least one secondary non-return valve in the flow direction from the pump to the second cylinder device. Furthermore, a chassis with such a lifting device and to a mobile device with a chassis is provided.

Claims

1. A hydraulic lifting device for a chassis of a mobile device, comprising: a valve block; a pump; a tank; a first cylinder device; and a second cylinder device; wherein: the first cylinder device and the second cylinder device can be selectively pressurized by the pump or connected to the tank via the valve block; the first cylinder device is connected to the pump via at least one primary non-return valve disposed in the valve block; the second cylinder device is connected to the pump via at least one secondary non-return valve disposed in the valve block; and the valve block has at least one pressure accumulator downstream of the at least one secondary non-return valve in the direction of flow from the pump to the second cylinder device.

2. The hydraulic lifting device according to claim 1, further comprising: a first pressure-reducing valve and a second pressure-reducing valve; wherein: the first cylinder device can be pressurized via the first pressure-reducing valve; and the second cylinder device can be pressurized via the second pressure-reducing valve; and an output pressure of the first pressure-reducing valve is different from an output pressure of the second pressure-reducing valve.

3. The hydraulic lifting device according to claim 2, wherein the output pressure of the first pressure-reducing valve is greater than the output pressure of the second pressure-reducing valve.

4. The hydraulic lifting device according to claim 1, wherein the at least one pressure accumulator has a volume of at most 1 cm.sup.3.

5. The hydraulic lifting device according to claim 4, wherein the at least one pressure accumulator has a volume of at most 0.5 cm.sup.3.

6. The hydraulic lifting device according to claim 1, wherein the second cylinder device comprises two secondary cylinders and the at least one secondary non-return valve of the valve block comprises two secondary non-return valves, each of the two secondary cylinders being connected to the pump via one of the secondary non-return valves.

7. The hydraulic lifting device according to claim 6, wherein the valve block comprises a second identical pressure accumulator, one of the pressure accumulator each being disposed upstream of the respective secondary non-return valve in the direction of flow from the pump to the respective secondary cylinder .

8. The hydraulic lifting device according to claim 1, wherein the at least one pressure accumulator is a spring accumulator.

9. The hydraulic lifting device according to claim 8, wherein the spring accumulator comprises a spring and a piston, the piston being disposed movably against a force of the spring in a receiving bore of the valve block.

10. The hydraulic lifting device according to claim 9, wherein the spring accumulator comprises a sealing cap fixed to the valve block and closing the receiving bore.

11. A chassis of a mobile device comprising a hydraulic lifting device according to claim 1.

12. A mobile device comprising a chassis according to claim 11.

13. The mobile device according to claim 12, wherein the mobile device is a mobile medical device

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention is explained in more detail below referring to an exemplary embodiment shown in the figures. The figures show schematically:

[0020] FIG. 1 is a hydraulic circuit diagram of a hydraulic lifting device according to the invention;

[0021] FIG. 2 is an exploded view of a valve block of a hydraulic lifting device according to the invention;

[0022] FIG. 3 is a side view of the valve block shown in FIG. 2 with a built-in pressure accumulator; and

[0023] FIG. 4 is a sectional view along section line A-A through the valve block shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0024] FIG. 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 has a valve block 2, a manually operated pump 3, a tank 4, a first cylinder device 5 and a second cylinder device 6. The valve block 2 comprises a first and a second pressure accumulator 9, 10. The first cylinder device 5 comprises two primary cylinders 5a, 5b and the second cylinder device 6 comprises two secondary cylinders 6a, 6b. In the embodiment shown, the primary cylinders 5a, 5b and the secondary cylinders 6a, 6b are configured as single-acting hydraulic cylinders with return springs.

[0025] The pump 3 is connected to the tank 4 and the valve block is connected to the pump 3 via a first connection 21. When the pump 3 is actuated, hydraulic fluid is pumped from the tank 4 via the first connection 21 to the valve block 2. In the valve block 2, a first line arrangement 22 supplies the first cylinder device 5 and a second line arrangement 23 supplies the second cylinder device 6 with pressure. Viewed in the direction of flow from the pump 3 to the first cylinder device 5, a first pressure-reducing valve 22, a primary non-return valve 7 and a drain line 24 with a manually operable drain valve 18 are disposed in the first line arrangement 22. A single primary non-return valve 7 is thus disposed in the first line arrangement 22, which secures the two primary cylinders 5a, 5b of the first cylinder device 5.

[0026] A second pressure reducing valve 12 is disposed in the second line arrangement 23 in the direction of flow from the pump 3 to the second cylinder device 6. Downstream of the second pressure reducing valve 12, the second line arrangement 23 branches into a first branch 25 and a second branch 26. In each branch 25, 26 a secondary non-return valve 8a, 8b and a drain line 27, 28 with a manually operated drain valve 19, 20 are disposed downstream of the second pressure reducing valve 12. One of the pressure accumulators 9, 10 is disposed downstream of each of the secondary non-return valves 8a, 8b. In this exemplary embodiment, the pressure accumulators 9, 10 each have a volume of 0.5 cm.sup.3. In the second line arrangement 23, one of the secondary non-return valve 8a, 8b each secures one of the two secondary cylinders 6a, 6b of the second cylinder device 6.

[0027] The first pressure reducing valve 11 is set to a higher output pressure than the second pressure reducing valve 12. This allows hierarchical pressurization of the first cylinder device 5 and the second cylinder device 6. When the pump 3 is actuated, hydraulic fluid is pumped from the tank 4 into the valve block 2 and there via the first line arrangement 22 to the first cylinder device 5 and via the second line arrangement 23 to the second cylinder device 6. A uniform extension of the primary cylinders 5a, 5b and the secondary cylinders 6a, 6b takes place until the two primary cylinders 5a, 5b (or support feet or the like attached thereto) contact the ground. Due to the higher output pressure of the first pressure reducing valve 11, the primary cylinders 5a, 5b are then pressurized and the secondary cylinders 6a, 6b are readjusted or retraced due to the lower output pressure at the second pressure reducing valve 12. As soon as 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, corresponds at most to the output pressure of the second pressure reducing valve 12. Preferably, the output pressure of the second pressure reducing valve 12 is set to the weight of the mobile medical device.

[0028] When the secondary cylinders 6a, 6b are extended or when the first and second branches 25, 26 are pressurized respectively, the two pressure accumulators 9, 10 are charged. As soon as the maximum pressure downstream of the secondary non-return valves 8a, 8b is reached, the mobile medical device is fully jacked up or lifted. The holding pressure acting on the second cylinder device 6 is lower than the holding pressure acting on the first cylinder device 5, so that a possible creeping pressure loss at the secondary non-return valves 8a, 8b is compensated via the pressure accumulators 9, 10. The volume of 0.5 cm.sup.3 per pressure accumulator 9, 10 described above is sufficient for this. A possible creeping pressure loss at the primary non-return valve 7 is not critical due to the considerably higher holding pressure. However, it is conceivable that a pressure accumulator acting on the first line arrangement 22 downstream of the primary non-return valve 7 is also used. This could provide further protection for the first cylinder device 5. It is also conceivable that only one pressure accumulator 9, 10 is used for both secondary cylinders 6a, 6b.

[0029] Furthermore, a pressure relief valve 17 bridging the pump 3 is provided. When the primary cylinders 5a, 5b and the secondary cylinders 6a, 6b are fully extended and the pump 3 continues to be actuated, the pressure relief valve 17 opens and hydraulic fluid is pumped in circuit.

[0030] To lower the mobile medical device, the drain valves 18, 19, 20 are actuated so that the first line arrangement 22 and the second line arrangement 23 are connected to the tank 4 via the respective drain line 24, 27, 28 and a second connection 29. It is conceivable that the drain valves 18, 19, 20 are operated manually together and thus form a drainage device.

[0031] In the following, the construction of the pressure accumulators 9, 10 is described with reference to FIGS. 2 to 4. For reasons of clarity, only one of the two pressure accumulators 9, 10 is described.

[0032] The pressure accumulator 9, 10 is configured as a spring accumulator and has a spring 13, a piston 14 and a sealing cap 16 The spring 13 is supported on the one hand on a first receptacle 30 of the sealing cap and on the other hand on a second receptacle 31 of the piston 14. The sealing cap 16 is fixed to the valve block 2 by means of a clip 32 and two screws 33 in such a way that the piston 14 is movable in a receiving bore 15 of the valve block 2 against a force of the spring 13. As shown, the sealing cap 16 closes the receiving bore 15.

[0033] 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 16 to such an extent that a storage volume of 0.5 cm.sup.3 is provided in the maximum position of the piston 14. It has been shown that a storage volume of at most 1 cm.sup.3 is sufficient to compensate for a creeping pressure loss at the secondary non-return valves 8a, 8b. It has also been shown that such a storage volume still allows for the hierarchical pressurization described above, as an excessively large storage volume would necessitate a higher output pressure at the second pressure reducing valve 12.

LIST OF REFERENCE SIGNS

[0034] 1 hydraulic lifting device
2 valve block
3 pump
4 tank
5 first cylinder device
5a, 5b primary cylinder
6 second cylinder device
6a, 6b secondary cylinder
7 primary non-return valve
8a, 8b secondary non-return valve
9 pressure accumulator
10 pressure accumulator
11 first pressure reducing valve
12 second pressure reducing valve
13 spring
14 piston
15 receiving bore
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 line
25 first branch
26 second branch
27 drain line
28 drain line
29 Second connection
30 First receptacle
31 second receptacle
32 clip
33 screw