Cylinder arrangement for a hydraulic lifting device with distance measurement, hydraulic lifting device, chassis and mobile device

Abstract

The invention relates to a cylinder arrangement 1 for a hydraulic lifting device, having a housing 2 and a piston rod 3 which is axially movable relative to the housing 2. A rotary element 4 is mounted on the housing 2 such that the rotary element 4 can be moved in rotation relative to the housing 2 and is prevented from being moved axially relative to the housing 2. The piston rod 3 has a movement transmission element 5, wherein the movement transmission element 5 converts an axial movement of the piston rod 3 into a rotational movement of the rotary element 4. A sensor unit 6 is fixed on the housing 2 for detecting the rotational movement of the rotary element 4. Furthermore, the invention also relates to a hydraulic lifting device having such a cylinder arrangement 1, to a chassis of a mobile device having a lifting device and to a mobile device having a chassis.

Description

TECHNICAL FIELD

[0001] The present application relates to a cylinder device for a hydraulic lifting device, a hydraulic lifting device having such a cylinder device, a chassis having a hydraulic lifting device, and a mobile device having a chassis. In particular, the mobile device can be a mobile medical instrument. BACKGROUND

[0002] Chassis of mobile devices are known from the prior art. In particular, special requirements are placed on the chassis in the use of mobile medical instruments, for example in the use of surgical robots or operating tables. During use, such mobile devices must be firmly secured, supported and leveled, regardless of the ground. Hydraulic lifting devices on the chassis, also referred to as "floor lock" systems, can be used for this purpose, as shown for example in DE 10 2012 001 555 A1.

[0003] In general, a cylinder device for a hydraulic lifting device is provided on or assigned to each caster wheel of the chassis. By pressing a pedal, usually manually, hydraulic fluid is pressed from a reservoir via a conduction system into the cylinder devices, which extend vertically downwards. The chassis is supported on the ground by a foot secured to the piston rod of the cylinder device. A central valve, which is operatively coupled to the pedal, prevents the pressure medium from flowing back into the reservoir, thus preventing a loss of pressure in the cylinder device. Systems are also known in which a power unit supplies the hydraulic fluid to the cylinder devices.

[0004] In such hydraulic systems, the pressure can gradually be lost over time, for example due to dirt on the check valves or load holding valves. As a result of this pressure loss, the chassis can slowly descend, in the worst case the casters can come into contact with the ground, thus causing the chassis to move.

[0005] DE 10 2012 001 555 A1 therefore also proposes a mechanically driven brake foot for braking and fixing the chassis in place, even in the event of a malfunction of the hydraulic system.

[0006] However, the use of a brake foot operated mechanically for additional fixation has the disadvantage that it can only intervene when the pressure loss of the system is already so great that the chassis has already descended or the cylinder devices have already partially retracted. The chassis is then at most fixed by the brake foot to prevent unwanted rolling. For example, depending on the medical requirements, it is no longer ensured that a firm support and leveling is provided.

[0007] In order to detect pressure fluctuations before the chassis can descend, the hydraulic pressure in the cylinder devices can be sensor-monitored. However, in addition to major malfunctions of the hydraulic system, small leaks associated with wear in the valves, temperature fluctuations or weight changes in the medical instrument can also cause certain pressure fluctuations.

[0008] The disadvantage of a hydraulic sensor monitoring of the cylinder device is that it cannot be distinguished which reason caused the pressure difference and thus whether there is a risk of device retraction. Therefore, as soon as a pressure fluctuation occurs, a reaction such as an alarm or stopping the application is triggered without ensuring that this is actually necessary because of the risk of device retraction. This often leads to false alarms or unnecessary stopping of the application. SUMMARY

[0009] Based on this, the object of the present application is to provide a cylinder device for a hydraulic lifting device of a chassis, with which a sudden drop of the chassis can be reliably detected at an early stage without the need for additional installation space.

[0010] The cylinder device according to the application comprises a housing and a piston rod. The piston rod is axially movable relative to the housing. In particular, the application differs from the prior art in that the cylinder device further comprises a rotary element, a motion transmission element and a sensor unit. The rotary element is arranged on the housing such that it can be moved in rotation relative to the housing and is prevented from being moved axially relative to the housing. The motion transmission element is arranged on the piston rod and converts the axial movement of the piston rod into a rotational movement of the rotary element. The sensor unit is fixed to the housing for detecting the rotational movement of the rotary element.

[0011] Axial movement in this context is to be understood as linear movement in axial direction along the longitudinal axis of the cylinder device.

[0012] The rotational movement of the rotary element can thus be converted into the distance traveled by the piston rod. For this purpose, the rotational movement of the rotary element is converted into a rotational increment, which is detected by the sensor unit via an encoder. By means of this distance measurement, it is possible to detect a drop of the chassis at an early stage without relying on the pressure. In this way, compliance with the tolerance for the drop distance of the chassis can be precisely monitored. Depending on the application, this tolerance can be less than 1 mm, for example, or can even amount to the extent that only a complete lowering is required, i.e. the casters come into contact with the ground. A further advantage of the application is that the additional elements for distance measurement can be completely integrated within the cylinder device. This means that no additional installation space is required.

[0013] Preferably, the housing comprises a cylinder head and the sensor unit is arranged in the cylinder head. This makes the sensor unit less susceptible to oil contamination and advantageously accommodates the sensor unit in terms of installation space. Furthermore, the signal transmission of the sensor unit signal can be carried out in a structurally advantageous manner.

[0014] Preferably, the motion transmission element is arranged within the piston rod. In particular, it is advantageous if the rotary element protrudes into the cavity of the piston rod. In this way, the other components of the cylinder device are less affected and no additional installation space is required.

[0015] Preferably, the rotating element and the motion transmission element have an engagement thread. In this regard, it is particularly preferred that the rotating element is a threaded spindle and / or the motion transmission element is a threaded nut. This makes it possible for the axial movement of the piston rod to be converted simply and reliably into a rotational movement of the rotating element. Furthermore, the travel distance of the piston rod can be easily calculated by the thread pitch. Moreover, this makes it possible for the design of the assembly to be simple and robust, which is able to withstand high pressures and mechanical loads.

[0016] Preferably, the sensor unit can be digital or analog. This makes it possible to record the measurement values reliably.

[0017] The rotating element is connected to the sensor unit by means of a bearing spindle. The bearing spindle also transmits the rotational movement of the rotating element to the sensor unit. This allows the cylinder device to be divided into a pressurized part and a non-pressurized part. These two parts can be sealed from one another, for example by means of suitable sealing means. As a result, the sensitive sensor unit can be protected from the pressure. Furthermore, the bearing spindle improves the stability of the rotating element during movement and prevents axial movement of the rotating element.

[0018] Preferably, the rotating element and the bearing spindle are supported via a ball bearing. This makes it possible for the rotating components to be provided with a low-friction, robust support. Furthermore, since only one bearing is required for all the rotating components, installation space and costs can be saved.

[0019] In particular, the mobile device can be a mobile medical instrument or a mobile medical device. BRIEF DESCRIPTION OF DRAWINGS

[0020] The application will be described in more detail below using the example of the embodiments shown in the drawings. The drawings show schematically:

[0021] Figure 1 A cross-section along the longitudinal axis of the cylinder device provided according to the application is shown;

[0022] Figure 2 An exploded view of the cylinder device provided according to the application is shown. DETAILED DESCRIPTION

[0023] As Figure 1 and Figure 2 shown, the cylinder device 1 comprises a foot 13, a housing 2, a piston rod 3 and a cylinder head 7.

[0024] If such a cylinder device 1 is used in a lifting device for a chassis of a mobile device, several, i.e. typically four, such cylinder devices 1 are typically used. The cylinder devices 1 are typically mounted on the chassis of the mobile device with their cylinder heads at the end pointing upwards. Thus, the end of the foot side cylinder device 1 is pointing downwards, i.e. towards the ground. Typically, the cylinder devices 1 are mounted near the casters (not shown) of the chassis, or are directly integrated into the casters. In particular, such a mobile device can be a medical device, e.g. a surgical robot.

[0025] As shown in Figure 1 and Figure 2 The upper end of the housing 2 is connected to the cylinder head 7. The cylinder head 7 can be fixed to the housing 2, e.g. by screws. The piston rod 3 is arranged within the housing 2. The piston rod 3 is axially movable relative to the housing 2, i.e. can be extended and retracted by applying pressure. The lower end of the piston rod 3 is articulated to the foot 13. The foot 13 protrudes out of the housing 2. The foot 13 serves to support the cylinder device 1 on the ground when actuated. Furthermore, the piston rod 3 can also be pretensioned within the housing 2 in the direction of the rest position by a pretensioning element 15, in this case a spring.

[0026] Furthermore, a hydraulic connection 14 is provided on the housing 2. If the cylinder device 1 is to be actuated, hydraulic fluid is introduced into the working chamber 16 of the cylinder device 1 via the hydraulic connection 14, e.g. via a power unit (not shown) or via a pedal operated pump. This results in a force on the annular surface 17 of the piston rod 3 which, against the counterforce of the spring 15, moves the piston rod 3 out of the housing 2. As soon as the piston rod 3 is extended to the extent that the foot 13 comes into contact with the ground, the chassis is lifted as the pressure in the working chamber 16 of the cylinder device 1 continues to increase.

[0027] By maintaining the hydraulic pressure in the working chamber 16 of the cylinder device 1, the chassis can be largely maintained in the desired lifted state. In order to detect at an early stage that the chassis is about to descend, the cylinder device 1 provided according to the application has a distance measuring device which detects the movement of the piston rod 3 relative to the housing 2.

[0028] To this end, the cylinder device 1 provided according to the application comprises a rotary element 4, a motion transmission element 5 and a sensor unit 6 arranged in the cylinder head 7. The rotary element 4 and the motion transmission element 5 have a thread 9, 10 which engages with one another and by which they are operatively coupled. In this embodiment, the rotary element 4 has an external thread and the motion transmission element 5 has an internal thread. In particular, in this embodiment, the rotary element 4 is configured as a threaded spindle. In this embodiment, the motion transmission element 5 is configured as a threaded nut. However, other configurations are also conceivable, e.g. in the form of a slot-hole chain guide.

[0029] The threaded spindle 4 is rotatably mounted in the upper end of the cylinder head 7 by means of a ball bearing together with a bearing core shaft 11. The threaded spindle 4 and the bearing core shaft 11 are for example firmly connected to each other by means of a press fit. One end of the bearing core shaft 11 projects into a recess in the threaded spindle 4, which stabilizes the rotational movement of the threaded spindle 4 about the longitudinal axis. An annular washer on the bearing core shaft 11 prevents axial movement of the threaded spindle 4. A sealing device is also provided on the bearing core shaft 11. The cylinder device 1 is divided by means of the sealing device into a pressurized part and a non-pressurized part. In the non-pressurized part, the bearing core shaft 11 is connected to the sensor unit 6. The bearing core shaft 11 thus connects the threaded spindle 4 to the sensor unit 6.

[0030] The lower end of the threaded spindle 4 projects into the cavity 8 of the piston rod 3. The threaded nut 5 is accommodated in a recess which is provided in the cavity 8 of the piston rod 3 for this purpose. This is firmly connected to the piston rod 3 so that no relative movement between the threaded nut 5 and the piston rod 3 is possible. This connection can for example be achieved by means of a clamping ring and / or by means of a press fit. However, other configurations are also possible. For example, the threaded spindle 4 and the threaded nut 5 can for example be fixed to the outside of the piston rod 3 in the intermediate space between the piston rod 3 and the housing 2.

[0031] If the piston rod 3 is moved axially as a result of the application of pressure, the threaded nut 5, which is firmly connected to the piston rod 3, moves with the piston rod 3. By means of the engagement of the threads 9, 10 of the threaded nut 5 with the threaded spindle 4, the axial movement of the threaded nut 5 and the piston rod 3 is converted into a rotational 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, the threaded spindle 4 not being able to move axially as a result of the support via the bearing core shaft 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 depends on the direction of rotation of the threads 9, 10, in relation to the extension or retraction movement of the piston rod 3.

[0032] The rotational movement of the threaded spindle 4 is transmitted to the bearing core shaft 11, which in turn transmits the rotational movement to the rotatable part 18 of the sensor unit 6. The sensor unit 6 can be an analog or digital sensor unit. The fixed part 19 of the sensor unit 6 detects the rotational movement of the rotatable part. For this purpose, the rotational movement is converted into a rotational increment, which is detected via an encoder. This signal is transmitted via a signal line. The distance travelled by the piston rod 3 can be calculated from the rotational increment using the known pitch and direction.

[0033] The pitch of the two threads 9, 10 is chosen such that the friction between the thread flanks is 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 movement transmission ratio must be chosen such that the rotational movement of the threaded spindle 4 is large enough to be accurately detected.

[0034] 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, during the so-called fixed state and / or during the return movement of the piston rod 3. The data can be acquired continuously throughout the operation of the cylinder device 1 or only at certain times.

[0035] The cylinder device 1 according to the application can monitor the travel distance of the piston rod 3 and thus the position of the piston rod 3. When pressure is applied, the extension distance of the piston rod 3 can be recorded. This data can be compared with the current position of the piston rod 3 during the fixed state. If the piston rod 3 retracts due to pressure loss, for example due to gravity, this is recorded. The return stroke of the piston rod 3 can be compared with a predetermined tolerance. If the return stroke of the piston rod 3 exceeds the permissible range, the system can react accordingly, for example with an alarm or a stoppage of the application.

[0036] List of reference signs

[0037] 1 cylinder device

[0038] 2 housing

[0039] 3 piston rod

[0040] 4 rotational element / threaded spindle

[0041] 5 movement transmission element / threaded nut

[0042] 6 sensor unit

[0043] 7 cylinder head

[0044] 8 cavity

[0045] 9 thread

[0046] 10 thread

[0047] 11 bearing core

[0048] 12 ball bearing

[0049] 13 foot

[0050] 14 hydraulic connection

[0051] 15 pretensioning element / spring

[0052] 16 working chamber

[0053] 17 annular surface

[0054] 18 rotatable part (of the sensor unit)

[0055] 19 stationary part (of the sensor unit)

Claims

1. A mobile medical device having a chassis and a hydraulic lifting device, wherein the hydraulic lifting device is used to lift the chassis off the ground, the hydraulic lifting device comprising a cylinder device (1), the cylinder device (1) comprising, a housing (2) and a piston rod (3) movable axially relative to the housing (2), It is characterized in that The rotating element (4) is arranged on the housing (2) so that the rotating element (4) can rotate relative to the housing (2) and is prevented from axially moving relative to the housing (2), wherein The piston rod (3) has a motion transmission element (5), wherein the motion transmission element (5) converts the axial motion of the piston rod (3) into the rotational motion of the rotation element (4), wherein A sensor unit (6) is fixed to the housing (2), and the sensor unit (6) detects the rotational movement of the rotating element (4); wherein, The rotating element (4) is connected to the sensor unit (6) via a bearing core shaft (11), and a sealing device is provided on the bearing core shaft (11), and the cylinder device (1) is divided into a pressurized part and a non-pressurized part by the sealing device; wherein, The sensor unit (6) comprises a rotatable part (18) and a fixed part (19), wherein the rotatable part (18) and the fixed part (19) are arranged in a non-pressurized part of the cylinder device (1); The fixed state of the piston rod (3) is a state in which the piston rod (3) is maintained in an extended position in which the chassis is lifted from the ground, wherein The sensor unit (6) detects the retraction of the piston rod (3) during the fixed state; and, the retraction of the piston rod (3) during the fixed state is compared with a predefined tolerance to detect an unexpected lowering of the chassis.

2. The mobile medical device according to claim 1, It is characterized in that The housing (2) includes a cylinder head (7), and the sensor unit (6) is arranged in the cylinder head (7).

3. The mobile medical device according to any one of the preceding claims, It is characterized in that The motion transmission element (5) is arranged in the piston rod (3).

4. The mobile medical device according to any one of the preceding claims, It is characterized in that The rotating element (4) extends into the cavity of the piston rod (3).

5. The mobile medical device according to any one of the preceding claims, It is characterized in that The rotating element (4) and the motion transmission element (5) have meshing threads (9, 10).

6. The mobile medical device according to any one of the preceding claims, It is characterized in that The rotating element (4) is a threaded spindle and / or the motion transmission element (5) is a threaded nut.

7. The mobile medical device according to any one of the preceding claims, It is characterized in that The sensor unit (6) is digital or analog.

8. The mobile medical device according to claim 7, It is characterized in that The rotating element (4) and the bearing spindle (11) are supported via ball bearings (12).

9. The mobile medical device according to any one of the preceding claims, It is characterized in that When it is detected that the chassis is unexpectedly lowered, an alarm is sounded or the application of the mobile medical device is closed.

Images