GB2215801A

GB2215801A - Cable control mechanism

Info

Publication number: GB2215801A
Application number: GB8902651A
Authority: GB
Inventors: Andrew Charles Kenney; Philip William Thompson; John Louis Harris; Colin Eric Duncan; Michael Robinson
Original assignee: Bowden Controls Ltd
Current assignee: Bowden Controls Ltd
Priority date: 1988-02-08
Filing date: 1989-02-07
Publication date: 1989-09-27
Also published as: GB8902651D0; GB8802834D0

Abstract

A flexible remote control mechanism comprising a flexible force-transmitting inner member (1) which is axially displaceable relative to an outer guiding conduit (3) comprises an adjustment means (5) which engages a thread (3a) on the conduit so as to be displaceable therealong by screw action but wherein the elements (9) which co-operate with the thread are retained in operative position by a spring (10). When the adjustment means (5) is subjected to axial forces above a certain value the elements (9) becomes forced out of engagement with the thread to allow displacement of the adjustment means along the conduit. The adjustment means can therefore operate in either of two modes: a rotational mode for fine adjustment and a non-rotational mode for self-setting adjustment under excess load. <IMAGE>

Description

CABLE CONTROL MECHANISM This invention relates to flexible remote control mechanisms incorporating a flexible force-transmitting member (hereafter called "inner member") which is axially displaceable relative to an outer guiding sheath or conduit.

Such mechanisms can be used for transmitting motion along a curved path. Usually the inner member is connected to actuating and actuated parts for transmitting force from one to the other of such parts, the conduit being held by fixtures against longitudinal displacement with such inner member.

Mechanisms of the kind referred to include mechanisms wherein the inner member comprises a flexible strip which is supported within the conduit by bearings, usually ball bearings, and Bowden-type mechanisms wherein the inner member is a flexible wire or cable which is slidable within the outer member. The present invention is particularly but not exclusively concerned with the latter, Bowden-type, mechanisms.

It is common practice to provide the flexible remote control mechanisms with means whereby the effective length of the mechanisms, as installed, can be adjusted. Usually the adjustment means comprises a female threaded member which is in screw engagement with the control mechanism and which when the mechanism is in use abuts against or is connected to a fixture via which actuating force is transmitted to or from the control mechanism. For example in the case of a Bowden-type mechanism of which the conduit is attached at or near its ends to fixed abutments and the inner member is attached at one end to an actuating lever and at the other end to a member to be actuated, a female threaded adjustment member is often provided in the region of one end of.the conduit for transmitting axial reaction force from the conduit to one of said fixed abutments.By rotating such adjustment member in one direction or the other its axial position relative to the adjacent end of the conduit is varied and this alters the effective length and thus the operating characteristics of the control mechanism. The flexible conduit can be formed with an external male screw profile and the female adjustment member can be screwed directly onto the conduit. As an alternative the conduit can be provided with a screw-threaded end fitting, e.g. a machined metal end fitting, and the adjustment member can engage such end fitting.

The known screw-adjustment devices are satisfactory for making fine in-service adjustments to the installed remote control mechanisms.

However the setting up of the mechanisms for correct operation at the time of their installation cannot be as easily and rapidly effected as circumstances sometimes require. The installation of such mechanisms in road vehicles at a stage in their mass production assembly line is a case in point.

In order to facilitate correctly adjusted installation of flexible remote control mechanisms of the kind referred to, it has been proposed to provide an adjuster-cum-abutment which can be forced into a required position along the conduit by the exertion of a predetermined axial force exceeding that to which the adjuster is subjected during normal use of the mechanism . If for example a flexible remote control mechanism having such an adjuster is being installed as a vehicle throttle control, the mechanism is initially mounted with the adjuster in a position such that the effective length of the conduit is excessive and the accelerator pedal therefore cannot be displaced sufficiently to effect a full opening movement of throttle control lever unless the adjuster, which bears against a fixture, is displaced some distance along the conduit.In order correctly to adjust the mechanism it is then merely necessary for the accelerator pedal to be forced down as far as it will go. In this operation the reaction forces on the conduit force the adjuster to become axially displaced into its correct adjusted position along the conduit A control mechanism having adjustment means of that kind is disclosed for example in United States Patent 3,662,617. In that mechanism the conduit has transverse surface ribs forming ratchet teeth and the adjustment means, which is provided with co-operating teeth, is elastically deformable so that the conduit ratchets relative to the adjustment means if the axial reaction forces exceed a certain value.

The known cable control mechanisms constructed to utilise this self-setting adjuster principle do not allow of easy movement of the adjuster along the conduit. Such movement may be required for example preparatory to installation of the flexible control mechanisms and to facilitate fine in-service adjustments. The present invention provides control mechanisms which give additional advantage in this respect.

According to the present invention, there is provided a flexible remote control mechanism comprising a flexible force-transmitting member ("inner member") which is axially displaceable relative to an outer guiding conduit, and comprising an adjustment means by which, when the mechanism is in use, axial reaction forces on the conduit can be transmitted to a fixture, the conduit having ribbing thereon and said adjustment means having at least one element which co-operates with such ribbing to resist axial movement of the adjustment means along the conduit under axial reaction force up to a certain value but which yields to allow such axial movement to take place under forces above that value, characterised in that said ribbing forms a screw thread so that the position of the adjustment means along the conduit can also be changed simply by rotating such adjustment means.

In a mechanism according to the invention the advantage of an adjustment means which is self-setting under excess load as hereinbefore described is combined with the advantage of a screw-type adjuster and these advantages are afforded by one and the same adjustment device.

The pitch of the screw thread can be chosen to provide for as fine an adjustment as is required when the adjustment means is operated in its screw mode.

As in the case of some well known flexible control mechanisms with a screw-type adjuster, the adjustment screw thread on the conduit of a control mechanism according to the invention can be formed by a helically wound wire or by helically interwound wires forming a flexible tube which constitutes the wall or an integral part of the wall of the flexible conduit. However it is not essential for the said adjustment screw thread on the conduit to be directly formed by a flexible tube. The said screw thread can be formed on a rigid or semi-rigid fitting, e.g. an end fitting, secured to the flexible conduit.

The form and depth of the adjustment screw thread are obviously factors which should be chosen to suit any given control mechanism having regard to the forces which it is intended to transmit in normal use. In general, for an adjustment means of a given yield resistance the deeper the thread and the steeper its flanks, the greater will be the resistance which it can afford to displacement of the adjustment means under axial load. An Acme-type thread is very suitable.

The adjustment means can be of various forms. In certain embodiments of the invention, the adjustment means can comprise a tubular body wherein one or more elements for co-operating with the conduit screw thread is or are mounted for radial retraction against a biasing force.

The or each such element can for example comprise a spring-loaded pin, the shape of the pin and/or the angle of the abutting flank of the screw-thread being such that the pin becomes radially displaced in a direction away from the conduit by a kind of cam action when it is pressed against the screw thread with sufficient force.

In a preferred embodiment of the invention the adjustment means comprises one or more spring-biased balls or rollers. It is advisable to use a plurality of such balls or rollers, angularly spaced around the conduit.

As another example, the adjustment means can comprise a tubular elastically deformable component having one or more integral internal protuberances which is or are located at one or more regions around the axis of the component and which intrude between the convolutions of the adjustment screw thread. In this case, the outward radial displacement of the protuberance(s)under reaction forces exceeding a certain value is permitted by the elastic deformability of the tubular component. Such a one-piece adjustment means is easy to handle for assembly to the conduit and can be made quite cheaply. The component may for example be made of metal or synthetic polymeric material, e.g. an acetal resin or a nylon, e.g., glass-filled nylon. The choice of material can be made taking into account the temperature range to which the mechanism is liable to be exposed in use.This is important if it is necessary to ensure that the yield point of the adjustment means, i.e. the axial load value at which it becomes displaced relative to the conduit, remains constant or within a constant predetermined range, under all environmental conditions of use. The one-piece component can be in the form of an unsplit sleeve provided that under axial loads above a given value it can undergo the deformation that is necessary to allow the internal protuberance(s) to ride over the adjustment screw thread. If the sleeve is of metal, this deformability can be ensured by forming the sleeve with slits or slots abreast of the protuberance(s).

Certain embodiments of the invention are shown by way of example in the accompanying drawings in which: Fig. 1 is a side view, partly in longitudinal cross-section of part of one mechanism according to the invention; and Figs. 2 and 3 are an elevation and a cross-sectional elevation respectively of part of another such mechanism.

In Fig.l, 1 is the inner cable of the Bowden type cable control mechanism; 2 is a plastics self-lubricating sheath or liner; and 3 represents the outer conduit whose surface is provided by helically interwound wires, one of which forms a male screw thread 3a.

Only part of the Bowden type cable control mechanism is shown, and what is shown is that part of its length where the mechanism is attached to a fixed abutment 4 by an adjustment means which permits adjustment of the length of the conduit 3 extending between the abutment 4 and another fixed abutment (not shown). When the device is in its intended mode of operation, the cable 1 is loaded in tension by operating force applied at its left-hand end in the aspect of the drawing. The reaction force on the conduit loads it in compression, thereby urging the adjustment means towards the abutment 4.

The conduit 3 passes through an aperture in the abutment 4. The adjustment means 5 comprises a tubular component 6 having at one end a recess in which is fitted a resilient grommet 7. The grommet 7 elastically grips the conduit 3 and has a spigot portion 8 which is forced through the aperture in the abutment 4.

Steel balls 9 are located in holes in the component 6 and are surrounded by a C-spring or clip 10.

The spring 10 exerts inward radial pressure on the balls 9. If the axial reaction force on the conduit exceeds a certain magnitude, the outward pressure of the balls 9 resulting from their being thrust against the screw thread 3a overcomes the resistance of the spring 5 and the conduit becomes displaced to the right relative to abutment 4. During this displacement the balls 4 ride over the thread 3a. As soon as the axial reaction force on the conduit 3 drops below the predetermined level, the conduit becomes again firmly held against displacement by the retention of the balls in the thread groove under the action of the spring.

The resistance of the spring 10 to radial expansion is such that the axial force which has to be exerted on the conduit to cause its displacement relative to the adjuster exceeds the maximum load which will be exerted on the conduit during normal operation of the mechanism so that when installing the mechanism the adjustment means can be set in correct position by over-loading the cable control as hereinbefore referred to. In one particular control mechanism according to the invention, having an adjustment means as represented in Fig. 1 and intended for use as a vehicle throttle control cable having a normal maximum operating load of 15 pounds the adjustment means was made resistant to axial displacement along the conduit under axial loads up to about 60 pounds. The depth of the thread 3a was 0.6 mm and the balls 9 were ball-bearings having a diameter of 4 mm.

Fine adjustments to the mechanism, e.g. periodic in-service adjustments, can be made simply by rotating the adjustment means so that it screws along the conduit. Thus the adjustment means affords two modes of adjustment: a slow mode achieved by screw action, and a faster mode where the screw threaded engagement is over-ridden.

Reference is now made to Figs 2 and 3. The conduit 11 of the mechanism represented in these figures is formed in the same way as the conduit of the mechanism shown in Fig. 1. However the adjustment means is of a substantially different form. It comprises a one-piece tubular component 12 in the wall of which there are two pairs of longitudinal slots 13. One pair of slots is clearly apparent in Fig. 2. The other pair is disposed opposite that pair, in the other half of the tube.

Between each pair of slots there are two protuberances 14 of generally oval form in plan outline, these protuberances engage in neighbouring convolutions of the helical groove in the surface of the conduit and they are transversely inclined to suit the inclination of that groove. These protuberances are rounded so that when pressed with sufficient axial force against the screw thread on the conduit they will be forced radially outwards. This displacement is allowed by the deformability of the narrow portions of the tubular component which are between the slots. The tubular component can be made of metal or synthetic polymeric material. A vibration damper 15 is force-fitted into a socket at one end of the component 12 and this damper has an enlarged free end portion 16 and is elastically deformable to permit that end portion to be forced through a locating hole in a fixture 17.

Claims

1. A flexible remote control mechanism comprising a flexible force-transmitting member ("inner member") which is axially displaceable relative to an outer guiding conduit, and comprising an adjustment means by which, when the mechanism is in use, axial reaction forces on the conduit can be transmitted to a fixture, the conduit having ribbing thereon and said adjustment means having at least one element which co-operates with such ribbing to resist axial movement of the adjustment means along the conduit under axial reaction force up to a certain value but which yields to allow such axial movement to take place under forces above that value, characterised in that said ribbing forms a screw thread so that the position of the adjustment means along the conduit can also be changed simply by rotating such adjustment means.

2. A mechanism according to claim 1, wherein the adjustment means has at least one said element in the form of a ball which is spring-biased towards the conduit.

3. A mechanism according to claim 2, wherein there are two or more said balls which are angularly spaced around the axis of the conduit and are surrounded by a spring clip.

4. A mechanism according to claim 1, wherein there is at least one said element which is an integral portion of a one-piece component which is elastically deformable to permit said yield of such element.

5. A mechanism according to claim 4, wherein said one-piece component is a metal sleeve having slits or slots abreast of the or each said element.

6. A mechanism according to any preceding claim, wherein the screw thread is formed by a helically wound wire which forms or forms part of a flexible tube.

7. A mechanism according to any of claims 1 to 5, wherein the said screw thread is formed on a rigid or semi-rigid fitting, e.g. an end fitting, secured to the flexible conduit.