DE29818691U1 - linear actuator - Google Patents

Description

OKIN Drive Technology GmbH & Co. KG 51645 Gummersbach

linear actuator

The invention relates to a linear drive for adjusting a movable element of a device with a drivable spindle on which an adjusting nut connected to a push tube is arranged, the push tube having a power take-off head at its end facing away from the adjusting nut, which is non-rotatably connected to the pivotable or parallel-guided elements and has a first and a second coupling part, which form a detachable connection against rotation of the two coupling parts relative to one another.

Such a linear drive is known from DE 296 19 988 Ul. The drive described in this document is intended for a patient lift, whereby it is arranged between a vertical column arranged on a chassis and a support arm, at the end of which a patient support can be hung. The push rod is connected to the support arm via the power take-off head in an articulated but rotationally fixed manner. Due to the rotationally fixed connection, when the spindle is rotated, the adjusting nut and the push rod connected to it are moved up or down, so that the support arm and the patient hanging on it are raised or lowered.

In the event of a power failure of the drive or failure of the adjusting nut, the support arm could be in a

remain in the upper position and cannot be lowered easily together with the patient. In this case, care must be taken to ensure that the rotationally fixed connection between the push rod via the power take-off head and the support arm is released and that the support arm can be lowered with the patient by manually turning the push rod.

Such an emergency lowering is achieved in the cited state of the art in that the power take-off head has a coupling sleeve or a coupling pin on its end facing the push tube, into which or onto which the push tube is inserted from below. The push tube and the coupling sleeve or the coupling pin have radial through-openings that can be aligned with one another, through which a driver pin is inserted to create a rotationally fixed connection. The connection can be released by pulling out the pin and the push tube can be manually turned downwards using the adjusting nut on the spindle. The support arm and the patient can thus be lowered in an emergency.

Since high torques act on the power take-off head both axially and radially when the push tube is moved, a slight deviation of the through holes from their aligned position can cause the driver pin to jam, making it more difficult to pull it out of the through holes in the event of an emergency lowering. If a non-rotatable connection between the power take-off head and the push tube is to be established again after an emergency lowering, it is usually difficult to achieve the aligned position of the through holes for inserting the driver pin by turning the push tube.

The present invention is therefore based on the object of developing a linear drive of the type mentioned at the beginning in such a way that an easy-to-use and reliable emergency lowering is ensured with simple production of a rotationally fixed coupling between the power take-off head and the push tube.

The object is achieved according to the invention in that, in a linear drive of the type mentioned at the beginning, one of the two coupling parts is arranged to be displaceable relative to the other against a preload in the longitudinal direction of the push tube by an actuating device, whereby in the non-displaced position the coupling parts form a rotationally secure connection to one another in any or almost any rotational position and in a displaced position the connection forces can be reduced at least to such an extent that the push tube can be manually rotated against the thrust direction.

The rotationally secure connection of the two coupling parts in the non-shifted position can be a positive or frictional coupling. With a slip clutch, the frictional forces causing the connection can be reduced to such an extent that the push tube can be manually rotated against the direction of thrust by a small amount of movement of the two coupling parts. The connecting forces do not have to be completely eliminated for this to happen. Of course, the connecting forces can also be completely eliminated in the shifted position with another type of coupling, e.g. a positive wedge coupling.

A mechanical actuating device is provided for easy handling of the movable coupling part.

In a preferred embodiment of the invention, the first coupling part is non-rotatably connected to the push tube and has first coupling elements at its end facing away from the push tube. In this case, the second coupling part is non-rotatably and axially mounted against the preload on a force-absorbing part that is pivotably connected to the movable element of the device and has second coupling elements at its end facing the first coupling part that interact with the first. By axially displacing the second coupling part on the force-absorbing part against the preload, the connecting forces that cause the rotationally fixed coupling are reduced or completely eliminated.

The first and second coupling elements expediently form a multi-spline toothing. Due to the large number of wedges arranged in a ring shape, the two interacting coupling parts can form a rotationally secure connection in almost any rotational position relative to one another.

In a preferred development of the invention, the second coupling part is guided as an annular element on the power take-off part.

The actuating device can have an eccentric device which runs radially to the longitudinal axis and is mounted in the second coupling part and which interacts with the power take-off part.

In another embodiment, the actuating device can have a cable pulling device that engages the second coupling part and is guided axially to the power take-off part.

0 In a preferred embodiment, two circular eccentric disks are provided as the eccentric device, which are mounted at radially opposite points in the wall of the second coupling part and which interact with the power take-off part and have 5 retaining grooves arranged parallel to one another on their outside for an actuating bracket.

The eccentric discs can have a driving pin arranged eccentrically and parallel to their axes, which engages in a groove formed in the power take-off part and running transversely to its longitudinal direction. The driving pin can also be designed as the radially bent end of the actuating bracket.

The eccentric device is expediently designed in such a way that a dead point relative to the preload can be overcome with the actuating device, so that the second coupling part can be fixed in a stable position in the position displaced relative to the first.

In a preferred embodiment, the second coupling part extends with a radial connecting web through a longitudinal groove in the power take-off part that is open at the free end and rests against the inner end of this longitudinal groove in the non-displaced position. The second coupling part is mounted on the first coupling part via the connecting web and the power take-off part against the preload of a compression spring inserted into the first coupling part from its end facing the thrust tube and a screw-nut connection that engages on the outside of the spring and the outside of the connecting web. The compression spring can have a support disk on its outside, on which the screw-nut connection engages at one end.

If the second coupling part is moved relative to the first using the actuating device in order to release the rotationally fixed coupling, the power take-off part is loaded onto the first coupling part due to the forces transmitted by the movable element of the device. In order to ensure smooth rotation when the push rod is manually rotated in the direction of the load, a bearing element, such as a bearing disk, is expediently provided between the power take-off part and the first coupling part. Since the power take-off part and the first coupling part (as well as the second coupling part) are preferably made of plastic, the bearing disk is made of metal.

Two preferred embodiments of the invention are described in more detail below with reference to the drawing.
30

In the drawing show:

Fig. 1 a side view of a patient lift,

Fig. 2 a longitudinal section through the upper end of a thrust tube with power take-off head,

Fig. 3 a section along the line marked III in

Figure 2,

Fig. 4 a section along the line marked IV in

Fig.2,
5

Fig. 5 a section along the line marked V in

Fig.1,

Fig. 6 is a longitudinal section rotated by 90° compared to Fig. 2 along the line V with the bracket drawn in in the un-

active state,

Fig. 7 is a longitudinal section according to Fig. 6 with marked

Bracket in the actuated state,
15

Fig. 8 is a longitudinal section rotated by 90° compared to Fig. 2

along line VIII,

Fig. 9 is a side view in the direction of arrow IX in Fig. 2,

Fig.10 a side view according to Fig. 9 in the actuated state of the bracket,

Fig.11 a longitudinal section through the upper end of a push tube and a power take-off head according to a second embodiment,

Fig.12 a longitudinal section rotated by 90° compared to Fig. 11 along the line XI and

Fig.13 is a side view of the embodiment shown in Fig.11 in the direction of arrow XIII.

Fig. 1 shows the use of a linear drive 1 in a patient lift. The use of the embodiments of linear drives described below is not limited to patient lifts, but extends in principle to

This applies to all devices in which a movable element is adjusted against a load by a drive.

As can be seen from Fig. 1, the linear drive 1 is arranged between a column 3 fastened to a chassis 2 and a support arm 4 hinged to the upper end of the column 3, on the free end of which a patient support can be hung. At its lower end, the drive is connected in an articulated manner to a web attached to the column by means of a fixing bolt with a fork head. At its upper end, the linear drive has a force take-off head that ends in a fork-shaped end, which is also hinged to a web attached to the support arm by means of a fixing bolt.

The linear drive 1 has a spindle (not shown in the drawing) driven by an electric motor, on which an adjusting nut connected to a push tube 5 is arranged. The adjusting nut and partially the push tube 5 are guided in a shaft tube 6. The electric motor, which drives the spindle, for example, via a worm gear, is arranged in a motor housing 7.

By turning the spindle in one direction or the other, the push tube 5 is moved up or down. This raises or lowers the support arm and the patient hanging on it.

For emergency lowering in the event of engine malfunctions or failure of the adjusting nut, the power take-off head 8, which non-rotatably connects the push rod 5 to the support arm 4, has, as shown in Fig. 2, a first and a second coupling part 9 and 10, respectively, which form a detachable connection against rotation of the two coupling parts 9 and 10 relative to one another. The second coupling part 10 is axially displaced relative to the first coupling part 9 against the preload of a compression spring 12 by an actuating device 11, as shown in particular in Figs. 6 and 7 and 9 and 10, whereby in the

In the non-displaced position shown in Fig. 2, the coupling parts 9 and 10 form a rotationally secure connection to one another in almost any rotational position, as will be explained in more detail below.
5

The first coupling part 9 is inserted into the upper end of the push tube 5 with a hollow pin 13 and is arranged so that it cannot rotate using a threaded connection 14. The first coupling part 9 rests on the upper end face of the push tube 5 with a disk-shaped widening 15. First coupling elements 16 in the form of a multi-spline toothing are formed on the radial outside of the widening 15.

The first coupling part 9 also has a hollow pin 17 on its upper side, the cross section of which is narrower than that of the hollow pin 13 arranged on the underside. A power take-off part 18 is mounted on the hollow pin 17 with a bearing disk 19 in between.

The second coupling part 10 is mounted as an annular element around the power take-off part 18 so that it can be moved axially. As can be seen in particular from Figures 6 and 7, the annular second coupling part 10 extends with a radial connecting web 20 through a longitudinal groove 21 in the power take-off part 18 that is open at the free end. In the non-displaced position, the second coupling part 10 with the connecting web 20 rests against a surface 22 that is adapted to the connecting web 20 at the inner end of the longitudinal groove 21.

The ring-shaped second coupling part 10 has at its lower end a collar 23 with second coupling elements 24 in the form of a radially inwardly facing spline toothing, which interact in a form-fitting manner with the first coupling elements 16 arranged on the first coupling part 9.

The compression spring 12 is inserted into an annular groove in the base of the inner cavity of the first coupling element 9, which extends with its outer end beyond the groove.

With the help of a screw-nut connection 25, which engages with one end on a support disk 26 resting against the compression spring 12 and with its other end on the outside of the connecting web 20 of the second coupling part 10, the second coupling part 10 and the power take-off part 18 are mounted on the first coupling part 9 against the preload of the compression spring 12.

For axial displacement of the second coupling part 10, circular eccentric disks 27 are provided, mounted at radially opposite points in its wall. As can be seen in particular from Figures 4 and 8, the eccentric disks 27 have a driver pin 28 arranged eccentrically and parallel to their axes, which engages in a groove 29 formed in the power take-off part 18 and running transversely to its longitudinal direction.

The eccentric discs 27 have retaining grooves 30 arranged parallel to one another on their outside for the actuating device 11 designed in the form of a bracket. The ends of the bracket, bent by 90°, sit in corresponding holes at the ends of the retaining grooves 30.

Figures 6 and 9 show the eccentric disk 27 and the bracket in the non-actuated state, in which the first and second coupling parts 9 and 10 form a rotationally fixed connection. By pulling up the bracket and the resulting rotation of the eccentric disks 27 mounted in the second coupling part, the second coupling part 10 is displaced relative to the first coupling part 9, so that the first and second coupling elements, which are designed as multi-spline teeth, no longer engage with one another. The eccentric disks 27 are oriented with their driver pins 28 relative to the groove 29 in such a way that when the bracket is pulled up, a dead center is overcome with respect to the spring preload, so that the raised position of the second coupling part 10 is fixed in a stable position. In this position, the push tube 5 can be manually turned down on the spindle, whereby the load-bearing part 10 can be moved.

■:"·'. jf-.ÜX

The movable element of the relevant device, e.g. the support arm of the patient lift, is lowered.

The second embodiment shown in Figures 11 to 13 differs from the first embodiment described above only in that it has a different actuating device 31 for the axial displacement of the second coupling part 10. This is again ring-shaped and is mounted on the power take-off part 18 so that it can be moved axially. At two radially opposite points, the second coupling part 10 has pockets 32 that open towards the push tube 5, in whose bottom sides facing the power take-off part 18 openings are formed for the passage of a traction cable 33. At the end of the traction cable 33 there is an abutment 34 mounted in a pocket 32. The eyelet 35 of a rigid cable guide 36 is inserted into the other pocket 32. The traction cable 33 is displaceable via the bolt (not shown in the drawing) for the articulated connection between the fork-shaped end of the power take-off part 18 and a frame, such as e.g.

0 the support arm of a patient lift.

• 2c·····

11

LIPPERT, STACHOW, SCHMIDT & PARTNER

Patent Attorneys ■ European Patent Attorneys European Trademark Attorneys P.O.Box 30 0208, D-51412 Bergisch Gladbach Telephone +49(0)22 04.92 33-0 Fax +49(0)22 04.6 26 S/sr October 20, 1998

OKIN Drive Technology GmbH & Co. KG 51645 Glimmersbach

linear actuator

List of reference symbols

1 linear drive

2 Chassis

3 pillar

4 Support arm

2 0 5 thrust tube

6 Shaft tube

7 Engine housing

8 Power take-off head

9 Coupling part 25 10 Coupling part

11 Actuating device

12 compression spring

13 hollow pins

14 Threaded connection 30 15 Widening

16 first coupling elements

17 hollow pins

18 Power take-off part

19 Bearing disc

35 20 Connecting bridge

21 Longitudinal groove

22 Surface 2 3 Collar

24 second coupling elements

2 5 screw-nut connection

26 Support disc

27 Eccentric disc 28 Driving pin

2 9 Groove

30 Holding element

31 Actuating device

32 Bag
33 Pull rope

34 Abutments

35 sleeve

36 Rope guide

Claims (10)

linear actuator Expectations Linear drive (1) for adjusting a movable element (support arm 4) of a device (patient lifter) with a drivable spindle on which an adjusting nut connected to a push tube (5) is arranged, wherein the push tube (5) has a force take-off head (8) at its end facing away from the adjusting nut, which is non-rotatably connected to the movable element (support arm 4) and has a first and second coupling part (9) or (10) which form a detachable connection against rotation of the two coupling parts (9 and 10) relative to one another, thereby
characterized in that one of the two coupling parts (10) is arranged to be displaceable relative to the other coupling part (9) against a prestress in the longitudinal direction of the push tube (5) by an actuating device (11; 31), wherein in the non-displaced position the coupling parts (9 and 10) form a rotationally secure connection in any or almost any rotational position relative to one another and in a displaced position the connection forces can be reduced at least to such an extent that the push tube (5) can be manually rotated against the thrust direction. 2. Linear drive (1) according to claim 1, characterized in that the coupling parts (9 and 10) can be displaced relative to one another by a mechanical actuating device (11; 31). 3. Linear drive (1) according to claim 1 or 2, characterized
characterized in that the first coupling part (9) is non-rotatably connected to the thrust tube (5) and has first coupling elements (16) at its end facing away from the thrust tube (5) and the second coupling part (10) is mounted non-rotatably and axially against the preload on a power take-off part (18) and has second coupling elements (24) at its end facing the first coupling part (9), which interact with the first coupling elements (16). 4. Linear drive (1) according to claim 3, characterized in that the first and second coupling elements (16) and (24) respectively form a splined toothing. 5. Linear drive (1) according to claim 3 or 4, characterized
characterized in that the second coupling part (10) is designed as an annular element on the power take-off part (18) is carried out. 6. Linear drive (1) according to one of claims 3 to 5, characterized in that the actuating device (11) has an eccentric device which runs around an eccentric device radially to the longitudinal axis of the push tube (5) and is mounted in the second coupling part (10) and which cooperates with the power take-off part (18). 7. Linear drive (1) according to one of claims 3 to 5, characterized in that the actuating device (31) has a cable pulling device (31) engaging the second coupling part (10) and guided axially to the power take-off part (18). 8. Linear drive (1) according to one of claims 3 to 6, characterized in that the second coupling part (10) has circular eccentric disks (27) mounted at radially opposite points in its wall, which interact with the power take-off part (18) and have retaining grooves (30) arranged parallel to one another on their outside for an actuating bracket. 9. Linear drive (1) according to claim 8, characterized in that the eccentric discs (27) have a driver pin (28) arranged eccentrically and parallel to their axes, which engages in a groove (29) formed in the power take-off part (18) and running transversely to its longitudinal direction. 10. Linear drive (1) according to one of claims 3 to 9, characterized in that the second coupling part (10) is connected to a radial connecting web (20) extends through a longitudinal groove (21) in the power take-off part (18) which is open at the free end and rests against the inner end of the longitudinal groove (21) in an undisplaced position, the second coupling part (10) being connected via the connecting web (20) and the power take-off part (18) on the first coupling part (9) against the prestress of a compression spring (12) inserted into the first coupling part (9) from its end facing the thrust tube (5) and a screw-nut connection engaging the outside of the compression spring (12) and the outside of the connecting web (20). (25) is stored.