GB2352491A

GB2352491A - Drive mechanism for an actuating cable

Info

Publication number: GB2352491A
Application number: GB9917735A
Authority: GB
Inventors: Pierrot Nool Germaine Catry
Original assignee: Youngflex AG
Current assignee: L&P Swiss Holding GmbH
Priority date: 1999-07-28
Filing date: 1999-07-28
Publication date: 2001-01-31
Also published as: GB9917735D0

Abstract

A drive mechanism for use in tensioning the core of a Bowden cable comprises a casing (1) provided with recesses (20) for receiving the outer sheaths of Bowden cables, and a drum (9) upon which the Bowden cable is to be wound. The drum (9) is rotatable upon a portion (8) of a rotatable shaft that has an eccentric portion (10) upon which is mounted a gear wheel (11) having axially extending pegs (12) that engage loosely within apertures (13) in the gear wheel (9). In use the gear wheel (11) engages with an internal toothing (14) of the casing (1) and orbital motion transmitted thereto by the rotary shaft is accompanied by rotation of the gear wheel (11) at a rate determined by the relationship between the numbers of gear teeth on the internal toothing (14) and the gear wheel (11). Rotation of the gear wheel (11) is transmitted to the drum (9) via the pegs (12), and thus a substantial reduction is obtained between the rate of rotation of the rotary shaft and of the drum (9) mounted thereupon.

Description

2352491 DRIVE MECHANISM FOR AN ACTUATING CABLE This invention concerns a

drive mechanism for use in transmitting motion to an actuating cable such as a Bowden cable. Such a drive mechanism is particularly applicable to actuation of Bowden cable mechanisms of the kind that are incorporated in vehicle seats for the purpose of actuating adjusting mechanisms intended to provide adjustment of lumbar support provided by the upholstery of the seat. The mechanism of the invention is not limited to such an application, however, and may be of advantage in any application wherein it is desired to actuate a cable mechanism with high mechanical advantage wherein a drive member of the mechanism remains stably in a rest condition.

Various mechanisms are known for providing such adjustment, and generally comprise either lead screw and nut mechanisms, or mechanisms where the cable is wound onto a reel or cam member. In the latter case, it has proved difficult to provide a suitable manually or electrically actuatable drive mechanism for the cable reel which allows for stable actuation of the adjusting mechanism such that the latter is retained in a set position against unwanted displacement, without the need for supplementary latching Means, friction clutches or the like.

It is accordingly an object of the invention to provide an improved cable adjusting mechanism.

In accordance with the invention there is provided a cable adjusting mechanism comprising a rotary drum member for receiving a cable end and arranged, upon rotation to wind the cable thereon, a rotary drive transmitting element, and a reduction gear for transmitting drive from said rotary element to said cable drum, said reduction gear including a stationery element having an internally toothed annular gear ring and a gear wheel meshing with said toothed ring and arranged for orbital motion within the ring, said gear wheel being mechanically coupled to said cable drum in such a manner that the latter rotates with the gear wheel.

2 In a particularly compact and advantageous arrangement, the said drive element comprises a drive shaft mounted for rotation within a housing and having a first bearing surface coaxial with the rotary axis of the shaft and upon which the said cable drum is mounted for rotation relatively to the shaft, a second bearing surface arranged adjacent to the first and eccentric with the respect to the rotary axis of the shaft, the said gear wheel being mounted for rotation upon said second bearing surface and being coupled to the cable drum in such a manner that it is radially displaceable relatively thereto whilst being held against relative angular movement.

Advantageously the said annular gear ring is formed on an internal surface of an outer housing enclosing the gear wheel, the cable drum and the rotary shaft. The said outer housing may be provided with one or more passages for receiving one or more cables to be wound on said drum, whilst providing one or more anchorages for receiving the outer sheath of a cable attached to the drum.

In a further advantageous development of the invention, the rotary shaft comprises an axially extending surface provide with a helical thread form for engagement by means of an axially movable peg keyed within the outer housing, the said helical thread being provided with end stops for arresting the peg at end positions of the helical thread, thereby determining limits of available rotary movement of said drive shaft.

Further preferred features and advantages of the invention will become apparent from the following description taken in conjunction with the drawings, wherein:

Figure 1 is an exploded perspective view of a drive mechanism in accordance with the invention, Figure 2 is an axial cross sectional view of the mechanism of the Fig. 1 shown in the assemble condition, Figure 3 is an end view of a cable drum shown in Fig. 1, and 3 Figure 4 is an radial view of the drum of Fig. 3 taken in the direction of the arrow X.

Referring to the drawings, a drive mechanism in accordance with the invention comprises a housing formed by a generally cylindrical outer shell 1 and an end cap 2 arranged to be secured against an open end of the end cap 1 by means of securing screws 3 engaging with threaded portions of the shell 1.

The end cap 2 is formed integrally with a cylindrical sleeve portion 2a incorporating a rectangular key-way 4.

The sleeve portion 2a serves as a bush receiving a cylindrical portion 5 of a drive shaft 6. The cylindrical portion 5 incorporates a helical screw thread that is engaged by a toothed peg 7 that is slidably engaged within the key-way 4. The ends of the helical screw thread in the cylindrical portion 5 are closed by end stops, so that the peg 7 is held captive within the screw thread and serves to limit the rotation of the drive shaft 6 when it reaches an end stop at either end of the screw thread.

The shaft 6 has a further cylindrical portion 8 that is coaxial with the cylindrical portion 5 and serves as a bearing support upon which is received a cable reel 9 that is freely rotatable on the cylindrical surface 'S.

Adjacent the cylindrical surface 8 is a further cylindrical surface 10 that is eccentric to the rotary axis of the shaft 6 and serves to support thereon a relatively rotatable gear wheel 11. The gear wheel 11 has projecting therefrom regularly angularly spaced pegs 12 that engage within axially extending bores 13 in the cable reel 9. The bores 13 are of larger diameter than the peg 12 in order to allow relative radial displacements of the gear wheel 11 and the cable drum 9 whilst preventing relative angular rotation thereof.

4 The outer shell 1 has an internally toothed annular gear ring 14 formed integrally therewith adjacent an end wall 15 which, as shown more clearly in Fig. 4, has a central aperture for receiving a further cylindrical portion 17 located at the end of the shaft 6 coaxial with the rotary axis thereof.

As shown more clearly in Figs. 2 and 3, the cable drum 9 incorporates a socket portion 18 for receiving the nipples conventionally provided at the ends of inner cores of Bowden cables, and further has a pair of radial groovesJ9 for guiding cables to be wound thereon. The outer shell 1 of the housing also comprises sockets 20 for receiving the fiftings at the ends of outer sheaths of the Bowden cables. Bowden cables can be attached to the drive mechanism in a particularly simple manner during assembly of the mechanism, by inserting cable ends through a radial slot 21 in the outer shell 1 and then inserting the cable drum 9 axially therein so that the socket 18 engages with the cables. In known manner the sockets 20 of the shell I also include radial slots through which can pass the inner cores of the cables during assembly.

In operation of the described device, rotation of the drive shaft 6 is effective to transmit orbital motion to the gear wheel 11 which is thus caused to rotate as a result of its meshing engagement with the annular ring 14. The gear wheel 11 is of slightly smaller diameter than the annular ring 14, and, in known manner, thus forms a reduction gear the transmission ratio of which with respect to the rotation of the shaft 6 is governed by the difference between the numbers of teeth on the gear wheel 11 and the ring 14 respectively.

Rotation of the gear wheel 11 is transmitted to the cable drum 9 via the pegs 12 and bores 13, the latter being of sufficiently large diameter to accommodate the relative radial motion of the gear wheel 11 during its rotation.

As the drive shaft 6 rotates, the peg 7 is driven axially by means of the helical screw thread in the portion 5 of the drive shaft, the peg 7 being held against rotation within the key-way 4. The worm and peg arrangement has the advantage both of providing a simple means of limiting the rotary movement of the drive shaft 6 to correspond with the required degree of movement of the cable mechanism, whilst at the same time providing a degree of friction in the mechanism that is not sufficient to restrict the mechanical adjustment of the drive shaft 6, but is nevertheless sufficient to restrain the latter in an adjusted rest condition against rotary force exerted on the cable drum 9 by means of tension in the cable, as a result of the very high transmission ratio provided by the reduction gear in the direction from the cable towards the drive shaft 6.

It will be appreciated that the device described above provides a relatively simple and compact drive mechanism for use in the mechanical or electrical adjustment of a Bowden cable mechanism. Moreover the form of the device is such that all components thereof can be manufactured economically, for example by injection moulding from suitable synthetic plastic material.

6

Claims

1. A cable adjusting mechanism comprising a rotary drum member for receiving a cable end and arranged, upon rotatio, to wind the cable thereon, a rotary drive transmitting element, and a reduction gear for transmitting drive from said rotary element to said cable drum, said reduction gear including a stationary element having an internally toothed annular gear ring and a gear wheel meshing with said toothed ring and arranged for orbital motion within the ring, said gear wheel being mechanically coupled to said cable drum in such a manner that the latter rotates with the gear wheel.

2. A cable adjusting mechanism according to Claim I wherein the said drive element comprises a drive shaft mounted for rotation within a housing and having a first bearing surface coaxial with the rotary axis of the shaft and upon which the said. cable drum is mounted for rotation relatively to the shaft, a second bearing surface arranged adjacent to the first and eccentric with the respect to the rotary axis of the shaft, the said gear wheel being mounted for rotation upon said second bearing surface and being coupled to the cable drum in such a manner that it is radially displaceable relatively thereto whilst being held against relative angular movement.

3. A cable adjusting mechanism as claimed in Claim 2 wherein the said annular gear ring is formed on an internal surface of an outer housing enclosing the gear wheel, the cable drum and the rotary shaft.

4. A cable adjusting mechanism as claimed in Claim 3 wherein the said outer housing is provided with one or more passages for receiving one or more cables to be wound on said drum and is further provided with one or more anchorages for receiving the outer sheath of a cable attached to the drum.

5. A cable adjusting mechanism as claimed in any one of Claims 2 to 5, wherein the rotary shaft comprises an axially extending surface provide with a helical thread form for engagement by means of an axially movable peg keyed within the outer 7 housing, the said helical thread being provided with end stops for arresting the peg at end positions of the helical thread, thereby determining limits of available rotary movement of said drive shaft.

6. A cable adjusting., mechanism substantially as described herein with reference to the accompanying drawings.

6. A cable adjusting mechanism substantially as described herein with reference to the accompanying drawings.

Amendments to the claims have been riled as follows 1. A cable adjusting mechanism comprising a rotary drum member for receiving a cable end and arranged, upon rotation, to wind the cable thereon, a rotary drive transmitting element, and a reduction gear for transmitting drive from said rotary element to said cable drum, said reduction gear including a stationary element having an internally toothed annular gear ring and a gear wheel meshing with said toothed ring and arranged for orbital motion within the ring, said gear wheel being mechanically coupled to said cable drum in such a manner that the latter rotates with the gear wheel.

2. A cable adjusting mechanism according to Claim 1 wherein the said drive element comprises a drive shaft mounted for rotation within a housing and having a first bearing surface coaxial with the rotary axis of the shaft and upon which the said cable drum is mounted for rotation relatively to the shaft, a second bearing surface arranged adjacent to the first and eccentric with the respect to the rotary axis of the shaft, the said gear wheel being mounted for rotation upon said second bearing surface and being coupled to the cable drum in such a manner that it is radially displaceable relatively thereto whilst being held against relative angular movement.

5. A cable adjusting mechanism as claimed in any one of Claims 2 to 5, wherein the rotary shaft comprises an axially extending surface provide with a helical thread form for engagement by means of an axially movable peg keyed within the outer housing, the said helical thread being provided with end stops for arresting the peg at end positions of the helical thread, thereby determining limits of available rotary movement of said drive shaft.