INTERFERENCE-SUPPRESSED LINEAR DRIVE

Abstract

To simplify assembly and to reduce the susceptibility to faults of a linear drive comprising a transmission housing, an interference-suppressed electric motor which is connected thereto and is accommodated in a motor housing and which by way of a rotor accommodated in the motor housing drives a shaft which is mounted on a rear shaft end in a rear shaft bearing and is mounted on a front shaft end, a commutator for the transmission of current to the rotor, electrical and/or electronic components for interference suppression of the electric motor, it is proposed that the rear shaft bearing is mounted in the motor housing, the front shaft bearing is mounted in the transmission housing and the electrical and/or electronic components required for interference suppression of the electric motor are arranged on an interference suppression circuit board arranged between the front shaft bearing and the commutator.

Claims

1-16. (canceled)

17. A linear drive comprising a transmission housing, an interference-suppressed electric motor which is connected to the transmission housing and is accommodated in a motor housing and by way of a rotor accommodated in the motor housing drives a shaft which is mounted on a rear shaft end in a rear shaft bearing and is mounted on a front shaft end, a commutator for current transmission to the rotor, electrical and/or electronic components for interference suppression of the electric motor, wherein the shaft by means of a worm drives a transmission arranged in the transmission housing for displacement of a lift tube guided longitudinally displaceably in a guide tube, wherein the rear shaft bearing is mounted in the motor housing, the front shaft bearing is arranged or mounted in the transmission housing and the electrical and/or electronic components required for interference suppression of the electric motor are arranged on an interference suppression circuit board arranged between the front shaft bearing and the commutator.

18. The linear drive as set forth in claim 17, wherein the interference suppression circuit board is arranged in the region between the transmission and the motor and outside the motor housing.

19. The linear drive as set forth in claim 17, wherein the interference suppression circuit board is arranged in the transmission housing.

20. The linear drive as set forth in claim 17, wherein the interference suppression circuit board includes carbon brushes for connection to the commutator.

21. The linear drive as set forth in claim 20, wherein the carbon brushes are arranged on a brush holder which is or can be connected to the interference suppression circuit board.

22. The linear drive as set forth in claim 17, wherein at least one limit switch is arranged on the interference suppression circuit board.

23. The linear drive as set forth in claim 17, wherein at least one relay and/or at least one Hall sensor is arranged on the interference suppression circuit board.

24. The linear drive as set forth in claim 17, wherein the motor housing is in the form of a deep-drawn steel casing.

25. The linear drive as set forth in claim 17, wherein the motor housing includes a bearing receiving means for the rear shaft bearing.

26. The linear drive as set forth in claim 25, wherein the bearing receiving means is in the form of a protruding projection of a reduced outside diameter for embracingly receiving or mounting the rear shaft bearing.

27. The linear drive as set forth in claim 17, wherein the motor housing extends into the transmission housing and is sealingly connected thereto.

28. The linear drive as set forth in claim 26, wherein the motor housing has a rear housing portion of a smaller outside diameter and that adjoining said rear housing portion with a step is a front housing portion which is enlarged in relation to the rear housing portion by 10 to 20 percent and which can be connected to the transmission housing.

27. The linear drive as set forth in claim 17, wherein the interference suppression circuit board is arranged in the edge region of the motor housing and contacting of interference suppression circuit board is made with the housing directly or by way of interpositioned contact means.

28. The linear drive as set forth in claim 17, wherein the outside diameter of the interference suppression circuit board corresponds to the outside diameter of the steel casing of the motor housing.

29. The linear drive as set forth in claim 17, wherein the interference suppression circuit board sits at the end in front of the motor casing, contacts the motor casing and together with the motor casing in the form of a steel casing forms a Faraday cage and the interference suppression circuit board thus forms a shield against the EMV disturbances in the interior of the motor.

30. The linear drive as set forth in claim 17, wherein the transmission housing includes a plurality of housing parts which are or can be releasably connected together.

31. The linear drive as set forth in claim 17, wherein the transmission includes a worm gear which meshes with the worm and which in turn can be non-rotatably connected to a spindle.

32. The linear drive as set forth in claim 31, wherein the spindle is non-rotatably received in a spindle holder which can be non-rotatably connected to the worm gear by way of a clutch.

33. The linear drive as set forth in claim 32, wherein running on the spindle is a spindle nut which is connected to the lift tube and which is held non-rotatably and axially displaceably in the guide tube and is displaceable along the longitudinal axis thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In the drawings:

[0062] FIG. 1 shows a perspective cross-section through the transmission housing of a linear transmission according to the invention,

[0063] FIG. 2 shows a plan view of the linear transmission shown in FIG. 1 with the rear housing part removed,

[0064] FIG. 3 shows a perspective cross-section of an alternative embodiment of the linear transmission according to the invention through the transmission and the motor housing,

[0065] FIG. 4 shows an enlarged perspective front view of the transmission housing and the intermediate wall of the transmission housing,

[0066] FIG. 5 shows an enlarged cross-section in detail to illustrate the limit switch,

[0067] FIG. 6 shows an enlarged perspective detail view of the cable connection on the transmission housing, and

[0068] FIG. 7 shows a perspective view of the linear drive with the motor housing removed.

DETAILED DESCRIPTION

[0069] Accordingly the linear drive according to the invention substantially comprises a transmission housing 2, a motor housing 4 which is fitted at the end into the transmission housing 2 and a hollow-cylindrical guide tube 6 in which a spindle nut 8 is longitudinally displaceable by way of the linear drive and which drives a lift tube 46.

[0070] The transmission housing 2 in turn includes two housing parts which can be fitted together at a join, namely a rear housing part 2.1 which is adapted to accommodate the motor housing 4 and a front housing part 2.2 which closes the transmission housing 2 and at the same time with the transmission housing 2 encloses the guide tube 6 in a shell-form configuration at both sides.

[0071] The rear housing part 2.1 has a substantially hollow-cylindrical internal space which is subdivided approximately at the center of the overall length of the rear housing portion 2.1 by a separating wall 2.3 extending transversely through that internal space, into a front housing portion towards the transmission and a rear housing portion towards the motor. A shaft 10 driven by an electric motor 25 projects into the front transmission region through a central through opening in that separating wall 2.3. The shaft 10 is supported in that separating wall 2.3 by means of a front shaft bearing 12 which in the present case is in the form of a rolling bearing. A radial shaft sealing ring 14 is fitted on the front side of the separating wall 2.3, that faces towards the transmission space, for sealing off the motor space. At the front free end of the shaft 12 it has a worm 16 meshing with the worm gear 18 extending transversely relative to the longitudinal axis of the shaft 10. That worm gear 18 is non-rotatably connected to a hollow-cylindrical spindle holder 20 into which the spindle 22 is in turn non-rotatably fitted. Finally, the spindle nut 8 runs on that spindle 22, which nut is thus displaceable by displacement in relation to the stationary guide tube 6 between an extension position determined by a front limit switch and a retraction position determined by a rear limit switch.

[0072] At the rear end the motor housing 4 has a substantially dome-shaped or nozzle-shaped bearing seat 4.3 which projects out of the rear wall and in which a rear shaft bearing 44 can be flush fitted, which supports the shaft 10 at the rear shaft end in the motor housing 4.

[0073] Arranged in the direction of the electric motor 24 in the motor portion of the transmission housing 2 is the interference suppression circuit board 26 according to the invention, more specifically being fixed by way of two spacer screws 28, 30 which are screwed into the separating wall 2.3.

[0074] Arranged in the direction of the electric motor 24 around or on the shaft 10 is a commutator 32 while provided on the rear side of the interference suppression circuit board 26, that faces towards the electric motor 24, are two diametrally opposed brushes in corresponding brush holders 26.1, 26.2 screwed on to the interference suppression circuit board 26. A relay 26.3 is also fitted on the rear side of the interference suppression circuit board, the relay switching the operating current of the electric motor 24 by means of the limit switches.

[0075] On the front side the interference suppression circuit board 26 has two threaded bushes 26.4, 26.5 for receiving the spacer screws 28, 30. In addition disposed on the front side of the interference suppression circuit board 26 is a limit switch 26.6 in which there engages a push rod 34 which projects through a corresponding opening in the separating wall 2.3 into the transmission portion of the transmission housing 2 and is media-tightly covered by way of a rubber cap 36. That push-rod 34 thus actuates the rear limit switch for limiting the retraction movement of the spindle nut 8 in the guide tube 6.

[0076] FIGS. 3 and 4 show a linear transmission according to the invention of an alternative configuration. Therein the motor housing 38 has, in the front housing region which is fitted into the transmission housing 40, a front motor housing portion 40.1 which is radially outwardly enlarged in relation to a longer rear motor housing portion 40.2 for increasing stiffness with the formation of a step. That front motor housing portion 40.1 in the installed position sits in an internal inner step 40.1 of the transmission housing 40, at which the interference suppression circuit board 46 is also arranged.

[0077] Furthermore disposed on the interference suppression circuit board 26 is a cable plug 26.7 which projects radially laterally from the interference suppression circuit board 26 and which in the installed position can be non-rotatably fitted in a cylindrical cable connection 42 having an external fixing thread, as shown on an enlarged scale in FIG. 6. That design therefore provides for a sealed rotation-preventing fit of the cable plug 26.7 in the transmission housing 30.

[0078] As in the first embodiment the motor housing 28 at the rear end has a bearing insert 38.3 which projects substantially in a dome-shaped or nozzle-shaped configuration out of the rear wall of the motor housing 28 and into which a rear shaft bearing 44 can be fitted in flush relationship and which thus supports the shaft 10 at the rear end in the motor housing 28.

[0079] FIG. 7 shows a perspective plan view of the linear drive with the motor housing 4 removed, looking on to the interference suppression circuit board 26, the brush holders 26.1, 26.2 arranged thereon and the relay 26.3. Accordingly the linear drive at the rear end includes a rear fork head 50 which is fitted into the transmission housing 40 and which is arranged at the left in FIG. 7, while at the front end it has a front fork head 50 which is connected to a lift tube 46 and by way of which the linear drive can be fitted or arranged between two components to be displaced. That can be for example a sick bed which is connected with the rear end to a transverse strut of the bed frame and with the front fork head to a foot or head part of the bed or the frame, that is to be pivoted with respect to the frame.

LIST OF REFERENCES

[0080] 2 transmission housing [0081] 2.1 rear housing part [0082] 2.2 front housing part [0083] 2.3 separating wall [0084] 4 motor housing [0085] 4.3 bearing insert [0086] 6 guide tube [0087] 8 spindle nut [0088] 10 shaft [0089] 12 front shaft bearing [0090] 14 radial shaft sealing ring [0091] 16 worm [0092] 18 worm gear [0093] 20 spindle holder [0094] 22 spindle [0095] 34 electric motor [0096] 26 interference suppression circuit board [0097] 26.1, 26.2 brush holder/brush carrier [0098] 26.3 relay [0099] 26.4, 26.5 threaded bush [0100] 26.6 limit switch [0101] 26.7 cable plug [0102] 26.8 Hall sensor [0103] 28, 30 spacer screws [0104] 32 commutator [0105] 34 push rod [0106] 36 rubber cap [0107] 38 motor housing [0108] 38.1 front motor housing portion [0109] 38.2 rear motor housing portion [0110] 38.3 bearing insert [0111] 40 transmission housing [0112] 40.1 internal step [0113] 42 cable connection [0114] 44 rear shaft bearing [0115] 46 lift tube [0116] 48 rear fork head [0117] 50 front fork head