GB2201655A

GB2201655A - Motor-driven screw-and-nut actuator

Info

Publication number: GB2201655A
Application number: GB08805055A
Authority: GB
Inventors: Klaus Frohmuller
Original assignee: Licentia Patent Verwaltungs GmbH
Current assignee: Licentia Patent Verwaltungs GmbH
Priority date: 1987-03-07
Filing date: 1988-03-03
Publication date: 1988-09-07
Anticipated expiration: 2008-03-03
Also published as: DE8703448U1; GB2201655B; IT8819651A0; FR2612011A1; GB8805055D0; IT1215992B

Abstract

A screw-and-nut actuator comprises an electric motor (1, 2), a tubular drive shaft (21) connected to the rotor (2) of the motor, and a spindle (9) extending in the drive shaft and drivably coupled thereto by a reduction unit (6, 7, 17, 19). A spindle nut (18) is threadedly engaged on the spindle, and a tubular displacing shaft (11) extends in the drive shaft and around the spindle and is secured to the nut. These components are arranged in a tubular housing (28) closed by end caps (3, 4), from one of which projects the displacing shaft (11). The displacing shaft (11) is provided with a coupling eye (24) and another such eye (26) is provided at the opposite end of the housing (28) and fixed to the relevant end cap (4). <IMAGE>

Description

DRIVE DEVICE The present invention relates to a drive device, in particular for spatial resetting of a movably arranged article relative to a second, fixedly arranged article or base body. Drive devices of this kind serve for, for example, opening and closing of flaps of all kinds, opening and closing of garage doors, resetting of head and foot parts in beds, and the drive of lifting supports, car jacks and the like.

For such uses it is desirable to employ a device which provides a relatively large drive performance yet has a relatively small volume, with the individual components of the device being simply constructed and, if possible, capable of manufacture and assembly by manipulators.

The drive device should also be able to be mounted free of problems, even as subsequent equipment, and by unskilled persons.

According to the present invention there is provided a drive device comprising an electric motor, a tubular drive shaft connected to the rotor of the motor, a spindle extending in the drive shaft and drivably coupled thereto by reduction gear means, a spindle nut threadedly engaged on the spindle, and a tubular displacing shaft extending in the drive shaft and around the spindle and secured to the nut.

In a preferred embodiment the drive device serves for spatial resetting of a movably arranged article relative to a fixedly arranged article and comprises an electric motor which, through reduction gear means, drives a displacing shaft in axial direction, the rotor shaft of the motor being constructed as hollow shaft which by way of a pinion drives the gear wheels of which an output wheel is connected with the spindle. A shift nut runs on the spindle and is fastened to the tubularly constructed displacing shaft surrounding the spindle, the displacing shaft being arranged within the rotor shaft.

Preferably, all components of the device are arranged in the interior of a tubular housing, the interior width of which is preferably nearly equal to the outer diameter of the motor stator. The housing can be closed off at each end by a respective substantially pot-shaped end cap with a bearing. The bearing at an end of the housing where the gear means is arranged is preferably a thrust bearing or a conical roller bearing.

Expediently, a fastening eye is arranged at the cap at the gear means end and another fastening eye non-rotatably arranged at the displacing shaft. The device can also include limit switches actuable by the displacing shaft and/or components connected therewith.

Preferably, the gear means is a two-stage wheel gear, which with advantage can be arranged in a casing lying against the inside walls of the housing. The casing can be constructed to be substantially pot-shaped or, viewed in axial direction of the housing, of prismatic cross-section. Expediently, the empty spaces within the casing are filled with filler means.

For preference, the connecting locations between the housing and caps and also a feedthrough for the displacing shaft are sealed off by sealing means against ingress of liquids.

The motor can be, for example, an asynchronous motor or a commutator motor, which may be designed for low voltage operation by way of a motor vehicle battery.

A drive device embodying the present invention may have the advantages of being simple to manufacture and having a compact size yet providing a sufficiently high performance for a variety of uses, for which units of appreciably larger dimensions were previously required.

The external shape of the device may permit installation even where limited space is available. The tubular encapsulation entails the advantage of a smooth surface convenient to keep clean, which is of great importance particularly in regions which are subject to hygienic conditions. A further advantage results from the simplicity of the fastening of the device to the article to be reset, as this can take place merely by way of a fastening eye at the end of the housing. The encapsulation also permits use of the device in a wet environment and a water-tight construction for underwater operation is possible without difficulty.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of a drive device embodying the invention; and Fig. 2 is an elevation of the drive device of Fig. 1.

Referring now to the drawings, there is shown a drive device comprising an electric motor, which consists of a stator lamination packet 1 provided with a winding and a rotor 2 provided with a short-circuit winding, arranged within the tubular housing 28, which at its two ends is closed by pot-shaped end caps 3 and 4. The external measurements and shape of the stator 1 and the internal measurements and shape of the housing 28 are so matched that the stator can be pressed into the housing and has a firm seating therein. Arranged in the interior of the housing 28 is a gear casing 5, which can be made of sheet metal as a pot-shaped component manufactured in the deep-drawing process in the same manner as the end caps. The casing 5 receives a reduction gear, as described below.The rotor 2 is arranged on a rotor shaft 21, which is constructed as a hollow shaft and mounted at one end by means of a bearing 13 in the cap 3 and at the other end by means of a bearing 14 in the base of the casing 5. Disposed at the gear end of the rotor shaft 21 is a pinion 19 which projects into the casing 5 through a cut-out in its base. Also present in the base of the casing 5 is a stamped-out bush which serves as a one-ended mounting for an axle 8, on which a gear wheel 7, constructed integrally with a pinion 17, is mounted. The gear wheel 7 is driven by the pinion 19 and forms therewith the first stage of the reduction gear. The second stage is formed by the pinion 17 and a gear wheel 6, which is mounted axially in the housing 28 by means of a bearing 15 pushed onto the free end of the pinion 19.The gear wheel 6 possesses a hub-like projection, in which a bush 16 is fastened, the bush 16 being mounted in the cap 4 by means of a shoulder bearing 12 and receiving one end of a spindle 9. The other end of the spindle 9 is held by a setting nut 10. The spindle 9 carries, between its ends, a shift nut 18, which is firmly connected with one end of a tubular stroke rod 11. The opposite, free end of the stroke rod extends outwardly over and beyond the nut 10 by way of a central opening in the cap 3 and receives a fastening eye 24.

On rotation of the rotor 2, the hollow shaft 21 and the pinion 19 are rotationally entrained and - by way of the double step-down through the gear wheels and pinions 19, 7, 17 and 6 - the spindle 9 is driven. The spindle thread causes the nut 18 inclusive of the stroke rod 11 fastened thereto to be moved in the axial direction of the motor.

The setting of the stroke length can take place by means of the setting nut 10. The nut 18 can, in each of its two end positions, actuate a respective limit switch for switching off the motor. The securing of the stroke rod 11 and thereby also the nut 18 against rotation takes place by fastening of the eye 24, which is secure against rotation relative to the stroke rod 11, to an article to be displaced.

The gear casing 5 can - viewed transversely to the axis of the housing - have a semicircular, triangular or differently shaped crosssection. It is thereby ensured that, due to the smaller empty space, less lubricant is needed and lubrication of the gear wheels is improved at the same time. The same result can be achieved by filling the interior of the casing with moulded bodies, for example of a synthetic material.

The thrust bearing 12 fulfils the task of absorbing the counterpressure during resetting of the stroke rod 11 under load. For this reason, the use of a conical roller bearing can be of advantage.

The displacing of the stroke rod 11 by means of the nut 18 moved by the spindle 9 entails the advantage of self-locking, i.e. the rod 11 cannot be pressed back into its initial position by the weight or pressure of the moved load.

The drive motor can, if desired, be a commutator motor. Also advantageous is a direct current motor operating at low voltage, such as that supplied by a car battery. A device driven in such a manner is universally usable in motor vehicles, for example as a jack, boats, caravans, for example as a locating support drive or for lifting rooves, and so forth, i.e. wherever mains current is not available.

In Fig. 2, the drive is illustrated as a component ready for installation and constructed as an encapsulated unit. Fastening to a fixed support takes place by way of the eye 26 and to a movable article by way of the eye 24. A connecting lead 25 permits operation of the device from a socket and a switch 23, for selection of direction of rotation, is included. The smooth external shape of the device is also illustrated by Fig. 2.

A drive device of the described kind can, for example, be constructed with an asynchronous motor having a power rating of about 100 watts and a rotational speed of about 2600 revolutions per minute. The stepdown ratios of the gear wheel and pinion can be 7:1 and the spindle 9 can have a thread pitch of 1 millimetre. A stroke force greater than 200 newtons may be achieved with a device constructed in that manner.

Claims

1. A drive device comprising an electric motor, a tubular drive shaft connected to the rotor of the motor, a spindle extending in the drive shaft and drivably coupled thereto by reduction gear means, a spindle nut threadedly engaged on the spindle, and a tubular displacing shaft extending in the drive shaft and around the spindle and secured to the nut.

2. A device as claimed in claim 1, comprising a tubular housing receives ing the motor, shafts, spindle and nut.

3. A device as claimed in claim 2, wherein the outer diameter of the stator of the motor is substantially equal to the inner diameter of the casing.

4. A device as claimed in either claim 2 or claim 3, wherein the housing is closed at each end thereof by a respective end cap with a bearing receiving a rotatable component of the device.

5. A device as claimed in claim 4, the gear means being disposed in the region of one of the caps and the respective bearing being a thrust bearing.

6. A device as claimed in claim 4, the gear means being disposed in the region of one of the caps and the respective bearing being a conical roller bearing.

7. A device as claimed in claim 4, the gear means being disposed in the region of one of the caps and that cap being provided with a respective fastening eye.

8. A device as claimed in any one of the preceding claims, wherein the displacing shaft is provided with a respective fastening eye secured against rotation relative to that shaft.

9. A device as claimed in any one of the preceding claims, comprising limit switch means arranged to be actuable by at least one of the displacing shaft and a component carried by that shaft.

10. A device as claimed in any one of the preceding claims, the gear means comprising a pinion connected to the drive shaft and a plurality of gear wheels drivable by the pinion, an output one of the gear wheels being connected to the spindle.

11. A device as claimed in any one of the preceding claims, the gear means providing a two stage speed reduction.

12. A device as claimed in any one of claims 2 to 6, the gear means being arranged in casing lying against the interior wall surface of the housing.

13. A device as claimed in claim 12, wherein the casing is substantially pot-shaped.

14. A device as claimed in claim 12, wherein the casing is of prismatic cross-section viewed in the axial direction of the housing.

15. A device as claimed in any one of claims 12 to 14, wherein the interior space of the casing between the wall thereof and the gear means is occupied by filler means.

16. A device as claimed in claim 4, comprising sealing means liquidtightly sealing connections of the caps to the housing and an outlet in one of the caps for the displacing shaft.

17. A device as claimed in any one of the preceding claims, wherein the motor is an asynchronous motor.

18. A device as claimed in any one of claims 1 to 16, wherein the motor is a commutator motor.

19. A device as claimed in claim 18, wherein the motor is a low voltage motor operable by a motor vehicle battery.

20. A drive device substantially as hereinbefore described with reference to the accompanying drawings.