CYLINDER DEVICE FOR A HYDRAULIC LIFTING DEVICE WITH DISTANCE MEASUREMENT, HYDRAULIC LIFTING DEVICE, CHASSIS AND MOBILE DEVICE

Abstract

A cylinder device for a hydraulic lifting device has a housing and a piston rod axially movable relative to the housing. A rotary element is mounted on the housing in such a way that a rotary movement of the rotary element relative to the housing is possible and an axial movement of the rotary element relative to the housing is prevented. The piston rod has a movement transmission element, wherein the movement transmission element translates an axial movement of the piston rod into a rotary movement of the rotary element. A sensor unit is attached to the housing, which detects the rotary movement of the rotary element. Furthermore, a hydraulic lifting device with such a cylinder device, a chassis of a mobile device with a lifting device and a mobile device with a chassis are provided.

Claims

1. A cylinder device for a hydraulic lifting device, comprising: a housing and a piston rod axially movable relative to the housing; a rotary element disposed in the housing in such a way that a rotary movement of the rotary element relative to the housing is possible and an axial movement of the rotary element relative to the housing is prevented; wherein the piston rod comprises a movement transmission element, the movement transmission element translating an axial movement of the piston rod into a rotary movement of the rotary element; and wherein a sensor unit is attached to the housing and the sensor unit detects the rotary movement of the rotary element.

2. The cylinder device according to claim 1, wherein the housing comprises a cylinder head and the sensor unit (6) is disposed in the cylinder head (7).

3. The cylinder device according to claim 1, wherein the movement transmission element is disposed inside the piston rod.

4. The cylinder device according to claim 1, wherein the rotary element projects into a cavity of the piston rod.

5. The cylinder device according to claim 1, wherein the rotary element and the movement transmission element have meshing threads.

6. The cylinder device according to claim 1, wherein the rotary element is a threaded spindle and/or the movement transmission element is a threaded nut.

7. The cylinder device according to claim 1, wherein the sensor unit is digital or analogue.

8. The cylinder device according to claim 1, wherein the rotary element is connected to the sensor unit via a bearing mandrel.

9. The cylinder device according to claim 8, wherein the rotary element and the bearing mandrel are supported via a ball bearing.

10. A hydraulic lifting device, comprising the cylinder device according to claim 1.

11. A chassis of a mobile device, comprising a lifting device according to claim 10.

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

[0022] The invention is explained in more detail below using an example of an embodiment shown in the figures:

[0023] FIG. 1 is a schematic cross sectional view taken along the longitudinal axis of a cylinder device according to the invention; and

[0024] FIG. 2 is an exploded view of a cylinder device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] As shown in FIG. 1 and FIG. 2, a cylinder device 1 comprises a support foot 13, a housing 2, a piston rod 3 and a cylinder head 7.

[0026] If such cylinder devices 1 are used in a lifting device for a chassis of a mobile device, usually several (namely regularly four) such cylinder devices 1 are used. The installation of the cylinder device 1 on the chassis of a mobile device is usually carried out in such a way that the end at the cylinder head of the cylinder device 1 points upwards. Consequently, the end of the cylinder device 1 on the support foot side points downwards, i.e. towards the ground. Often the cylinder devices 1 are mounted in the vicinity of castors (not shown) of the chassis or are directly integrated into the castors. Such a mobile device can in particular be a medical device, for example a surgical robot.

[0027] As can be seen in FIGS. 1 and 2, the upper end of the housing 2 is connected to the cylinder head 7. The cylinder head 7 can be attached to the housing 2 by screws, for example. The piston rod 3 is arranged inside the housing 2. The piston rod 3 is axially movable relative to the housing 2, i.e. it can be extended and retracted by applying pressure. The lower end of the piston rod 3 is hinged to the support foot 13. The support foot 13 projects out of the housing 2. The support foot 13 serves to support the cylinder device 1 on the ground when actuated. The piston rod 3 can also be pretensioned inside the housing 2 with a pretensioning element 15, in this case a spring, in the direction of the rest position.

[0028] A hydraulic connection 14 is also arranged on the housing 2. If the cylinder device 1 is to be actuated, hydraulic fluid is introduced into an working chamber 16 of the cylinder device 1 via the hydraulic connection 14, for example via a (not shown) power unit or via a pedal-operated pump. This creates a force on an annular surface 17 of the piston rod 3 which, after overcoming the counterforce of the spring 15, moves the piston rod 3 out of the housing 2. As soon as the piston rod 3 has extended so far that the support foot 13 is in contact with the ground, the chassis is lifted as the pressure in the working chamber 16 of the cylinder device 1 continues to increase.

[0029] By maintaining the hydraulic pressure in the working chamber 16 of the cylinder device 1, the chassis can be largely held in the desired raised state. In order to detect an imminent lowering of the chassis at an early stage, the cylinder device 1 according to the invention has a distance measuring device which detects a movement of the piston rod 3 relative to the housing 2.

[0030] For this purpose, the cylinder device 1 according to the invention comprises a rotary element 4, a movement transmission element 5 and a sensor unit 6 arranged in the cylinder head 7. The rotary element 4 and the movement transmission element 5 have threads 9, 10 engaging in each other and are thereby operatively coupled. In this embodiment, the rotary element 4 has an external thread and the movement transmission element 5 has an internal thread. In particular, the rotary element 4 in this embodiment is configured as a threaded spindle. In this embodiment, the movement transmission element 5 is configured as a threaded nut. However, other configurations are also conceivable, for example in the form of a slotted link guide.

[0031] The threaded spindle 4 is rotatably mounted on the cylinder head 7 at its upper end together with a bearing mandrel 11 via a ball bearing. The threaded spindle 4 and the bearing mandrel 11 are firmly connected to each other, for example by press fitting. One end of the bearing mandrel 11 projects into a recess in the threaded spindle 4, which stabilizes the rotary movement of the threaded spindle 4 about the longitudinal axis. An annular washer on the bearing mandrel 11 prevents axial movement of the threaded spindle 4. A sealing arrangement is also provided on the bearing mandrel 11. The cylinder device 1 is divided by the sealing arrangement into a pressurized portion and an unpressurised portion. In the unpressurised portion, the bearing mandrel 11 is connected to the sensor unit 6. The bearing mandrel 11 thus connects the threaded spindle 4 with the sensor unit 6.

[0032] The lower end of the threaded spindle 4 projects into a cavity 8 of the piston rod 3. The threaded nut 5 is accommodated in a recess provided for this purpose in the cavity 8 of the piston rod 3. This is firmly connected to the piston rod 3 so that no relative movement is possible between the threaded nut 5 and the piston rod 3. This connection can be made, for example, by fitting a clamping ring and/or by press-fitting. However, other configurations are also possible. For example, the threaded spindle 4 and the threaded nut 5 can be attached to the outside of the piston rod 3, for example in an intermediate space between the piston rod 3 and the housing 2.

[0033] If the piston rod 3 is moved axially as a result of pressure being applied, the threaded nut 5, which is firmly connected to it, moves with it. Through the meshing of the threads 9, 10 of the threaded nut 5 and the threaded spindle 4, the axial movement of the threaded nut 5 and the piston rod 3 is translated into a rotary movement of the threaded spindle 4. In other words, when the piston rod 3 is extended and retracted, the threaded nut 5 moves along the longitudinal axis of the threaded spindle 4, which is axially immovable due to the support via the bearing mandrel 11. The threaded spindle 4 is rotated by the axial movement of the threaded nut 5. The amount of rotation of the threaded spindle 4 is proportional to the distance of the axial movement of the piston rod 3. The direction of rotation of the threaded spindle 4 corresponds to either the extension or the retraction movement of the piston rod 3, depending on the direction of rotation of the threads 9, 10.

[0034] The rotary movement of the threaded spindle 4 is transmitted to the bearing mandrel 11, which in turn transmits the rotary movement to a rotatable portion 18 of the sensor unit 6. The sensor unit 6 may be an analogue or digital sensor unit. A fixed portion 19 of the sensor unit 6 detects the rotary movement of the rotatable portion. For this purpose, the rotary movement is translated into a rotary increment which is detected via an encoder. The signal is transmitted via a signal line. The distance that the piston rod 3 has travelled can be calculated from the rotary increment using the known thread pitch and direction.

[0035] The thread pitch of the two threads 9, 10 is selected in such a way that the frictional forces between the flanks of the threads are low enough to allow the transmission of movement between the threaded nut 5 and the threaded spindle 4 without significantly impairing the outward stroke of the piston rod 3. At the same time, the ratio of the movement transmission must be selected so that the rotary movement of the threaded spindle 4 is large enough to be detected accurately.

[0036] The data acquisition can take place during the outward movement of the piston rod 3, during the desired holding of the extended position of the piston rod 3, the so-called immobilization state, and/or during the return movement of the piston rod 3. The data can be acquired continuously during the entire operation of the cylinder device 1 or only at specific times.

[0037] The cylinder device 1 according to the invention can monitor the travelled distance of the piston rod 3 and thus the position of the piston rod 3. It can be recorded how far the piston rod 3 has been extended when pressure is applied. This data can be compared with the current position of the piston rod 3 during the immobilization state. If, for example, the piston rod 3 is retracted due to gravity as a result of a pressure loss, this is recorded. The return travel of the piston rod 3 can be compared with predefined tolerances. If the return of the piston rod 3 exceeds the tolerated range, the system can react accordingly, for example with an alarm or a shutdown of the application.

LIST OF REFERENCE SIGNS

[0038] 1 cylinder device

[0039] 2 housing

[0040] 3 piston rod

[0041] 4 Rotary element/threaded spindle

[0042] 5 movement transmission element/threaded nut

[0043] 6 sensor unit

[0044] 7 cylinder head

[0045] 8 cavity

[0046] 9 thread

[0047] 10 thread

[0048] 11 bearing mandrel

[0049] 12 ball bearing

[0050] 13 support foot

[0051] 14 hydraulic connection

[0052] 15 pretension element/spring

[0053] 16 working chamber

[0054] 17 annular surface

[0055] 18 rotatable portion (of the sensor unit)

[0056] 19 fixed portion (of the sensor unit)