LINEAR DRIVE AND LIFTING TABLE

Abstract

A lifting table contains a linear drive. The linear drive has a housing, a drive with an electric motor arranged outside the housing, and a linear unit arranged in the housing. In addition, a sensor device for determining a force acting on the linear drive is provided. The sensor device has a stress body, which is configured to axially support a drive-side end of the linear unit and on the inner or outer surface of which there is arranged a load sensor assembly for detecting a mechanical stress of the stress body.

Claims

1-18. (canceled)

19. A linear drive, comprising: a housing; a drive with an electric motor disposed outside said housing; a linear unit disposed in said housing and operatively connected to said drive, said linear unit having a drive-side end; a load sensor assembly; and a sensor for determining a force acting on the linear drive and having a hollow-cylindrical stress body, said hollow-cylindrical stress body configured to axially support said drive-side end of said linear unit, and on an inner surface or an outer surface of said hollow-cylindrical stress body there is disposed said load sensor assembly for detecting a mechanical stress of said hollow-cylindrical stress body.

20. The linear drive according to claim 19, wherein said hollow-cylindrical stress body is disposed axially in said housing between at least a part of said linear unit and at least a part of said drive.

21. The linear drive according to claim 19, wherein said drive has a gearing and said hollow-cylindrical stress body is disposed axially between at least a part of said linear unit and at least a part of said gearing.

22. The linear drive according to claim 19, further comprising a bearing assembly; wherein said linear unit has a threaded spindle and a nut; and wherein said housing is of modular construction and has a bearing housing part, a drive housing part and a linear unit housing part, said load sensor assembly is housed by said bearing housing part for said bearing assembly for rotatable mounting of said threaded spindle or said nut of said linear unit, said bearing housing part is disposed between said linear unit housing part for said linear unit and said drive housing part for at least a part of said drive.

23. The linear drive according to claim 22, wherein said hollow-cylindrical stress body has a radial flange which is clamped axially between said linear unit housing part and said bearing housing part.

24. The linear drive according to claim 22, wherein said bearing housing part has at least one axial through-bore formed therein; and further comprising a fastener passing through said at least one axial through-bore to fasten said bearing housing part to said linear unit housing part and on a drive side said fastener has a larger diameter than at an opposite end, so that a head of said fastener with an inner tool receptacle is recessed fully in said axial through-bore.

25. The linear drive according to claim 24, wherein said fastener has a circumferentially extending seal element on said head.

26. The linear drive according to claim 24, wherein said at least one axial through-bore is open at least in portions to an interior of said bearing housing part in a region of the larger diameter.

27. The linear drive according to claim 19, wherein: said sensor has signal processing electronics; and said housing has a top piece, below said top piece said signal processing electronics is disposed.

28. The linear drive according to claim 19, wherein: said housing has a bearing housing part and a drive housing part; and said sensor has signal processing electronics disposed in said bearing housing part or in said drive housing part.

29. The linear drive according to claim 19, further comprising a fastener; and wherein said hollow-cylindrical stress body, on an outer surface, has at least one recess formed therein for partly receiving said fastener, by means of said fastener said hollow-cylindrical stress body is fastened in said housing.

30. The linear drive according to claim 19, wherein said sensor is configured in such a way that safety level 2 according to international electrotechnical commission standard 61508 is satisfied.

31. The linear drive according to claim 19, wherein said load sensor assembly has at least two load sensors.

32. The linear drive according to claim 31, wherein every two said load sensors of said load sensor assembly are disposed in mutually opposite positions on an inner or outer surface of said hollow-cylindrical stress body.

33. The linear drive according to claim 31, wherein: said sensor has signal processing electronics; and said load sensor assembly includes a line clip, which engages circumferentially around an outer surface of said hollow-cylindrical stress body at least in part, and via said line clip at least one of said load sensors is connectable signal-conductingly to said signal processing electronics disposed outside said housing.

34. The linear drive according to claim 31, wherein said sensor has signal processing electronics with at least two separate channels for signal processing and each of said channels is able to be fed with signals from at least two said load sensors.

35. The linear drive according to claim 19, wherein said electric motor has a motor shaft which runs radially at a distance from and parallel to said linear unit.

36. The linear drive according to claim 25, wherein said circumferentially extending seal element is an O-ring.

37. A lifting table, comprising: a scissor mechanism; and a linear drive according to claim 19 for actuating said scissor mechanism.

Description

[0040] The figures show, at least partly schematically:

[0041] FIG. 1 an example of a linear drive with a sensor device;

[0042] FIG. 2 an example of a sensor device arranged in a housing of a linear drive;

[0043] FIG. 3 a stress body in a three-dimensional illustration; and

[0044] FIG. 4 an example of a lifting table; and

[0045] FIG. 5 an example of a linear drive with a load sensor assembly which is arranged outside a housing of the linear drive.

[0046] FIG. 1 shows an example of a linear drive 1 with a sensor device 10 for determining a force acting on the linear drive 1. The linear drive 1 has a housing 2, an electric motor 3, and a gearing 4 for transferring a rotary movement generated by the electric motor 3 to a threaded spindle 21 of a linear unit 20, which is arranged in the housing 2. The electric motor 3 and the gearing 4 form a drive 14.

[0047] The sensor device 10, besides a load sensor assembly (see FIG. 4), can also have a signal processing electronics unit 25 for evaluating sensor signals of the load sensor assembly. The signal processing electronics unit 25 is arranged expediently for protection below a top piece 24, which is mounted on a housing outer side 2′.

[0048] A thrust tube 5 can be driven out from the housing at an end furthest away from the gearing 4. The thrust tube 5 is fastened to a nut 22, which is movable in translation by rotation of the threaded spindle 21 in the housing 2. The thrust tube carries a load-receiving means 6, here in the form of an eye, by means of which the thrust tube 5 can be fastened to a machine part or a gearing mechanism.

[0049] Alternatively, however, a so-called “screw-jack” design is also conceivable, in which the threaded spindle 21 is movable in translation by rotation of the nut 22.

[0050] In the shown example the linear drive 1 comprises a housing mounting 7 for support on a machine or a gearing part. The housing mounting 7 can have, for example, two pins 8 arranged on opposite sides of the housing 2, one of said pins being visible in FIG. 1. The pins 8 can form part of a bearing by means of which the linear drive 1 is mounted pivotably on the machine or the gearing part.

[0051] The housing 2 shown in FIG. 1 is of modular construction. The housing 2 comprises a linear unit housing part 2a for the linear unit, a bearing housing part 2b for a bearing assembly (see FIG. 2) for mounting the threaded spindle 21 in the housing 2, and a drive housing part 2c for a part of the drive 14, in particular the gearing 4. The sensor device 10 is preferably arranged on the bearing housing part 2b, particularly preferably at least in part in the bearing housing part 2b. This arrangement is advantageous since the force is thus measurable at a point where the force flow transitions via the bearing assembly to the housing 2.

[0052] Alternatively to the configuration shown in FIG. 1, it is also conceivable to arrange the sensor device 10 substantially completely outside the housing 2. In particular, the load sensor assembly can also be arranged on the housing outer side 2′, preferably in the region of the housing mounting 7. This is shown in conjunction with FIG. 5.

[0053] In a further variant, the load sensor assembly can also be arranged on an outer surface of the thrust tube 5. The load sensor assembly is expediently arranged here in a portion of the thrust tube 5 that also protrudes from the housing 2 when the thrust tube 5 is retracted to the maximum extent. A mechanical stress of the thrust tube 5 can be measured by a load sensor assembly arranged in this way.

[0054] By means of the external motor 3 and its spacing from the sensor device 10 on account of the gearing 4 arranged in between, the sensor device 10 can be protected against thermal and electromagnetic influences of the motor 3. It is therefore particularly advantageous if, as shown in FIG. 1, a motor shaft 3a of the motor 3 runs—through the gearing 4—radially at a distance from and parallel to the threaded spindle 21. Other arrangements, however, are likewise conceivable; see FIG. 5.

[0055] FIG. 2 shows an example of a sensor device 10 arranged in a housing 2 of a linear drive 1 shown only in part. The housing 2 expediently comprises a linear unit housing part 2a and a bearing housing part 2b. A linear unit 20 (only partly visible) with a threaded spindle 21 and a nut 22, which is designed for translation in the linear unit housing part 2a when the threaded spindle 21 is rotated, is arranged in the linear unit housing part 2a. The threaded spindle 21 is mounted rotatably in the bearing housing part 2b by a bearing assembly 9. Here, the threaded spindle 21 is expediently fixed axially to the bearing assembly 9 with the aid of a spindle securing means 23.

[0056] The spindle securing means 23 preferably fixes the threaded spindle 21 axially to the bearing assembly 9 in such a way that a proximal end 21a of the bearing spindle 21 protrudes axially from the bearing housing part 2b. At the proximal end 21a, the threaded spindle 21 is expediently coupled to a drive (not shown), in particular a gearing. The term “proximal” refers here to the position relative to the drive (see FIG. 1).

[0057] The sensor device 10 has a stress body 11, which is hollow-cylindrical. The stress body 10 is designed to axially support the drive-side end 15 of the linear unit 20. A sensor assembly (see FIG. 4) is arranged on an outer surface 11a of the stress body 11. Alternatively, however, the sensor assembly can also be arranged on the inner side of the stress body 11. The sensor assembly expediently has at least one load sensor (see FIG. 3), which is preferably electrically contacted with the aid of a line clip 12 engaging at least partially around the outer surface 11a. A connection part 12a of the line clip 12 is expediently guided out from the housing 2, in particular the bearing housing part 2b, through a housing opening 2″. The connection part 12a is preferably connected to a signal processing electronics unit (not shown) arranged on the housing outer side 2′. A top piece (see FIG. 1) can house this signal processing electronics unit and at the same time the housing opening 2″.

[0058] The stress body 11 expediently has a radial flange 11b at a distal stress body end. The flange 11b is preferably fixed axially between the linear unit housing part 2a and the bearing housing part 2b.

[0059] At the opposite proximal or drive-side stress body end, the stress body 11 preferably has an inner shoulder 11c. The shoulder 11c expediently supports the bearing assembly 9 axially against a thrust force pushing the proximal end 21a of the threaded spindle 21 out from the bearing housing part 2b.

[0060] On a side opposite the shoulder 11c, a bearing securing means 13, for example in the form of a securing nut, expediently supports the bearing assembly 9 axially against a tensile force drawing the proximal end 21a into the bearing housing part 2b. The bearing securing means 13 is preferably fixed axially in the stress body 11, for example is screwed into the stress body 11.

[0061] A force flow from the threaded spindle 21 can thus be transferred via the bearing assembly 9 to the stress body 11 and from there further via the flange 11b to the housing 2. The load sensor assembly is expediently arranged therefore in the region of the distal stress body end, in particular axially between the bearing securing means 13 and the flange 11b. Independently of the direction of the force flow, this leads specifically to a compression or stretching of the stress body in the region of the distal stress body end, i.e. axially between the bearing securing means 13 and the flange 11b. The mechanical stresses occurring here in the stress body 11 can be determined reliably with the aid of the load sensor assembly, in particular the at least one load sensor.

[0062] Alternatively, an assembly is also conceivable in which the nut 22 is mounted rotatably by the bearing assembly 9 and optionally fixed axially to the bearing assembly 9 by a corresponding securing means. In this case, the threaded spindle 21 is axially movable by rotation of the nut 22. The above explanations apply similarly.

[0063] FIG. 3 shows an example of a stress body 11 of a sensor device 10 in a three-dimensional view. Here, the viewer faces a distal stress body end at which there is provided a radial flange 11b for fastening the stress body 11 to a housing of a linear drive (see FIG. 2).

[0064] An outer surface 11a of the stress body 11 is engaged around over at least part of its circumference by a line clip 12. The line clip 12 is expediently designed as a flexible printed circuit board (PCB). With the aid of the line clip 12, a plurality of load sensors 18 (in the example, four) of a load sensor assembly 17 are electrically contacted, so that electrical signals generated by the load sensors 18 can be picked up. Only two of the load sensors 18 are visible on account of the illustration selected in FIG. 3. The use of multiple load sensors 18 allows a particularly precise measurement of the mechanical stresses in the stress body 11.

[0065] The sensor device 10 formed in such a way preferably satisfies safety level 2 according to IEC standard 61508. To this end, the load sensors 18 can work redundantly, for example in pairs, for example by every two of the load sensors 18 being arranged at two opposite positions of the outer surface 11a and being connected correspondingly to the signal processing electronics unit. The signal processing electronics unit expediently has at least two separate channels here for signal processing. For example, the signal processing electronics unit can then process the signals from two load sensors 18 working in a pair per channel.

[0066] FIG. 4 shows an example of a lifting table 100 with a linear drive 1 and a gearing mechanism in the form of a scissor mechanism 19, which can be actuated with the aid of the linear drive 1. By actuation of the scissor mechanism 19, a platform can be raised or lowered relative to a base 102. Here, a sensor device 10 makes it possible to monitor the load state of the linear drive 1. For example, overloads can be determined in good time, before a person located on the platform 101 is injured.

[0067] FIG. 5 shows an example of a linear drive 1 with a load sensor assembly 17 which is arranged outside a housing 2 of the linear drive 1. The load sensor assembly 17 is in particular arranged in such a way that a mechanical stress 16 of the housing 2 is detectable in the region of a housing mounting 7.

[0068] The housing 2 has a linear unit housing part 2a for a linear unit 20, a bearing housing part 2b for a bearing assembly for rotatably mounting a threaded spindle or nut of the linear unit 20, and a drive housing part 2c for at least a part of a drive 14, in particular a gearing 4 and/or an electric motor 3. The electric motor 3, gearing 4 and linear unit 20 are arranged here “in-line”. Here, a motor shaft 3a and the linear unit 20, in particular threaded spindle or nut, expediently run coaxially. By means of the bearing assembly in the bearing housing part 2b, a force F acting on the linear unit 20 can be transferred to the housing 2, which, on account of the mounting 7, leads to a deformation of the housing 2 and consequently to a mechanical stress 16 in the housing 2. The load sensor assembly 17 is preferably arranged in such a way that this stress 16 of the housing 2 is detectable tangentially to an axis defined by the housing mounting 7. In other words, the load sensor assembly 17 is arranged at the point on the housing outer side 2′ where the distance d between the axis and the load sensor assembly 17 is minimal, so that the stress 16 runs at right angles to a connecting line between the axis and the load sensor assembly 17. In the shown example, the axis is formed by pins 8.

LIST OF REFERENCE SIGNS

[0069] 1 linear drive [0070] 2 housing [0071] 2′ housing outer side [0072] 2″ housing opening [0073] 2a linear unit housing part [0074] 2b bearing housing part [0075] 2c gearing housing part [0076] 3 motor [0077] 3a motor shaft [0078] 4 gearing [0079] 5 thrust tube [0080] 6 load-receiving means [0081] 7 housing mounting [0082] 8 pin [0083] 9 bearing assembly [0084] 10 sensor device [0085] 11 stress body [0086] 11a outer surface [0087] 11b flange [0088] 11c shoulder [0089] 11d recess [0090] 12 line clip [0091] 12a connection part [0092] 13 bearing securing means [0093] 14 drive [0094] 15 drive-side end [0095] 16 mechanical stress [0096] 17 load sensor assembly [0097] 18 load sensor [0098] 19 scissor mechanism [0099] 20 linear unit [0100] 21 threaded spindle [0101] 21a proximal end [0102] 22 nut [0103] 23 spindle securing means [0104] 24 top piece [0105] 25 signal processing electronics unit [0106] 100 lifting table [0107] 101 platform [0108] 102 base [0109] F force [0110] d distance