GB2315311A - Articulated end fitting for a push-pull control cable - Google Patents

Abstract

An end fitting for a push-pull control cable comprises a hub member 32 and a resiliently deformable plastic sleeve member 31, both of which are tubular to accommodate respectively a core of a push-pull control cable and a rod member. One end of the hub member 32 is fixable to a casing of a push-pull control cable and the other end carries a ball member 35 which is a snap fit in a spherical cup member 34 formed on an end of the sleeve member 31 so as to form an articulatory ball joint between the hub and sleeve members 32,31 through which push-pull cable core can pass.

Description

An End Fitting for a Push-Pull Control Cable The present invention relates to an end fitting for a push-pull control cable.

Mechanical remote control mechanisms of the push-pull cable kind are well-known in the art. Such a push-pull control cable has a core which slidably reciprocates within a casing to transmit mechanical motion when subjected to either tensile or comprehensive forces. The casing is required to contain the buckling forces which are developed in the flexible core when in compression and thereby restrain the core from lateral movement. When assembled, one end of the core is attached to a means for applying the tensile or comprehensive force, for example a control handle, and the other end of the core is attached, through a push-pull rod member, to the object which is to be controlled. In order for the core to translate when subject to a control force, the casing must be restrained from longitudinal movement. This is normally achieved by fixing at least one end of the casing to a hub member, usually by a swaging or crimping operation, which can be clamped in position, for example by a bracket, therefore restraining the casing from moving, the hub member having an internal passage along which the core can reciprocate.

In addition to the push-pull cable having a casing to contain buckling forces, it is also necessary for the end of the core which protrudes from the hub member and for the rod member which is fixed to that end of the core to be housed within a rigid sleeve which contains the buckling forces developed in the end of the core and guides the sliding movement imparted to the rod by the core, and this sleeve must similarly be restrained from moving with the rod member which slides within it. This is usually achieved by joining the sleeve to the end of the hub member remote from the casing.

It is preferable for this joint to allow the sleeve to articulate with respect to the hub member in order to accommodate variations in the direction in which the rod member reciprocates relative to the longitudinal axis of the hub member. One known design for achieving such an articulating joint is to flare the end of the sleeve which is to be joined to the hub member and for the mating end of the hub member to have the diameter of its internal passage enlarged by a sufficient amount so that it can receive the flared end of the sleeve within it. Once the flared end is inserted into the enlarged section of the internal passage of the hub member, it is retained therein by deforming inwards the outer wall of the passage sufficiently so that the internal diameter of the internal passage of the hub at the deformation is smaller than the largest external diameter of the flared end of the sleeve.

However, this design has the disadvantage that an extra stage is required during assembly in which the hub member is deformed inwards, which increases assembly costs and also reduces process reliability.

Another known design for achieving an articulating joint between the sleeve and the hub is to form a ball shaped member on the end of the sleeve and to have a mating cup member on the mating end of the hub. The cup member has a spherical recess within it which complements the size and shape of the ball member so that the ball member can be received within it and form a snap fit therewith. However, this design has the disadvantage that, since the walls of the spherical recess must be manufactured from plastic or similar resiliently deformable material which allows the ball to be snapped into place, and the hub must be made from a material which will not deform or buckle when it is clamped in place, usually metal, the spherical recess must be manufactured as a separate component, for example from plastic, and this recessed component then inserted into the metal hub member. This, again, increases manufacturing costs.

In an embodiment of the invention at present preferred, there is provided an end fitting for a push-pull control cable comprising a hub member fixed at one end to a casing of a push-pull control cable and having a ball member formed on the other end, and a sleeve member having a spherical cup member formed on an end which is to connect to the hub member, the cup member being a resiliently deformable fit on the ball member to form an articulating ball joint through which a push-pull core cable can pass.

Such an articulating ball joint between a hub member and a sleeve member, which will be a snap fit joint, has the advantage that the ball member and mating spherical cup member can be formed relatively easily on the hub and sleeve respectively during manufacture ofthese two components, thereby reducing the number of manufacture and assembly stages and, hence, also production costs.

Also, since this design does not require any metal defonning operations at the assembly stage, process reliability is improved, and the core support is improved at the hub to sleeve interface.

It is advantageous if the articulating joint between the hub member and the sleeve member has some means for preventing liquid, in particular water due to condensation, which could inhibit the free articulation of the joint, from entering the joint. This is achieved in the above described prior-art designs by surrounding the joint with a rubber seal, which, in the case of the first described prior art design, takes the form of a rubber shroud, and, in the case of the second described embodiment, takes the form of a rubber bellows, in both cases the shroud/bellows covering the joint as well as a short section of the hub member and the sleeve member on either side of the joint. With the end fitting of the present invention, no such addition external rubber seal in required since any moisture which might form on the sleeve and run down towards the joint when the sleeve member is oriented or inclined above the level of the joint will be naturally shed away from the articulating surfaces by the external surface of the cup member formed on the sleeve member.

In an advantageous development of the end fitting of the invention, the sealing of the joint can be easily, cheaply and reliably by the formation of an annular seal groove around the outer surface of the ball member formed on the hub, in which a sealing ring, such as a rubber "0" ring, could be placed.

Further features and advantages of the invention will appear from the following description of an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a sectional side view of a means for producing an articulating joint between a rod sleeve of a push-pull control cable and a hub member known in the art; Figure 2 is a sectional side view of another known design for producing an articulating joint between a rod sleeve of a push-pull control cable and a hub member; Figure 3 is a sectional side view of a snap on sleeve and hub member embodying the present invention; and Figure 4 is a side view of the hub member of Figure 3 which has been modified by forming an annular groove around the ball member.

Referring fist to Figure 1, there is shown a previously known design for connecting a sleeve 1 to a hub member 3. The sleeve 1 has a flared end 4 which faces towards the hub member 3, and the hub member 3, which is tubular to allow a core (not shown) of a push-pull control cable to reciprocate therethrough, has its internal passage 6, at the end 7 which mates with the sleeve 1, bored out for a short distance extending from the end 7, to a diameter which is sufficiently large to receive the flared end 4 of the sleeve 1 therein. To join the sleeve 1 to the hub 3, the flared end 4 of the sleeve 1 is inserted into the bored out section of the passage 6. The outer wall 8 of the bored out section between the flared end 4 of the sleeve 1 and the end 7 of the hub 3 is then deformed inwards to form a protruding lip 9 around the internal circumference of the bored out passage, which lip 9 prevents the flared end 4 from being extracted from the passage whilst still allowing a small amount of longitudinal movement between the sleeve 1 and hub 3 and, hence, also a certain degree of articulation between the sleeve 1 and the hub 3.

In another known system for producing an articulating joint between a sleeve and hub member, illustrated in Figure 2, the end 12 of a sleeve 11 which is to be joined to a hub member 14 is formed into a ball member 15. The hub member 14 has a cup member 16 formed on its end which is to connect to the ball member 15, the ball member 15 being received within the cup member 16 so that a core 20 of a push-pull control cable can pass between the internal passage 21 of the hub member 14 and the internal passage of the sleeve 1. Within the cup member 16 is disposed a mating member 23 for the ball member 15, the mating member 23 having a spherical recess within it which complements the size and shape of the ball member 15 so that when the ball member 15 is pressed into the mating member 23, the two snap together, restraining the sleeve 11 and hub 14 from longitudinal movement relative to each other whilst still allowing articulation therebetween.

In order for the ball member 15 to be able to be snapped into the spherical recess within the mating member 23, the material of the walls of the mating member 23 must be resiliently deformable. The hub member 14 will normally be produced from metal since the hub must not deform when firmly clamped in place, and it is therefore necessary for the mating member 23 to be manufactured separately from a suitable resiliently deformable material such as plastic, and subsequently inserted into the cup member 16 during assembly. This increases both manufacturing and assembly costs.

Figure 3 shows an improved design for producing an articulating joint between a resiliently deformable plastic sleeve 31 and a metal hub member 32. As in the prior art designs described above, both the sleeve 31 and the hub member 32 are tubular to accommodate respectively a rod member (not shown) and a core of a push-pull control cable (not shown) reciprocating therethrough, the sleeve 31 containing the buckling forces developed in the end of the core which protrudes from the hub member 32 and guiding the rod member attached to that end of the core. The two intemal passages 39, 40 are aligned to allow the cable core to pass easily between the sleeve 31 and hub member 32.

An articulating joint between the hub member 32 and sleeve 31 is produced by forming a snap together ball joint, the end of the hub member 32 being formed, for example by machining or die casting, into a spherical ball member 35 with the internal passage 40 of the hub member passing along its core, and the mating end of the sleeve 31 being formed, for example by moulding, into a spherical cup member 34 for receiving therein the ball member 35 as a snap fit.

When the sleeve 31 is pressed on to the ball member 35 of the hub member 32, the mouth 38 of the cup member 34, which has a smaller internal diameter than the maximum external diameter ofthe ball member 35, is resiliently forced open by the ball member 35 and then closes around the ball member 35 as the ball member passes into the internal cavity of the cup member 34. Once in place, the mouth of the cup member 35 restrains the ball member 35 from axial movement relative to the cup member 35, but allows the sleeve 31 to articulate freely on the ball member 35.

Preferably, the internal diameters of both the internal passage 40 of the hub member 32 and the internal passage 39 of the sleeve 31 increase towards the mating end of each component 31,32 so that the clearance between the side walls of each passage 39,40 and the core which passes therethrough increases at the transition between the two passages 39,40. In this way, it is ensured that even when the sleeve 31 is moved to its maximum angle of articulation relative to the hub member, the core still has ample clearance from the lip of each passage 39, 40 to allow it to slide freely therethrough, i.e. the cable core cannot be gripped between diametrically opposite lips of the two passages 39,40.

Additionally, the internal diameter of the passage 40 of the hub member 32 is also preferably enlarged towards its end remote from the sleeve 31 so that the end of the casing of the push-pull control cable can be inserted therein for fixing to the hub member 32, for example by a swaging or crimping operation.

As shown in Figure 4, the ball member 35 may be modified to include an annular groove 36 formed into the surface of the ball member 35, preferably about the longitudinal axis 37 of the hub 32, into which a seal member, for example a rubber "0" ring can be placed to improve the sealing of the joint.

The cup member 34 and ball member 35 are preferably formed as integral parts of the sleeve 31 and hub 32 respectively, but may also be manufactured separately and then fixed, for example using adhesive, to the sleeve 31 and hub 32, respectively.

Whilst the hub member is described above as being produced from metal, other rigid materials may also to be used instead, such as a high grade nylon or other rigid plastic material which falls within the upper tensile range, the only requirement being that the hub member should not collapse when clamped in a mounting bracket.

Claims (14)

1. An end fitting for a push-pull control cable comprising a hub member and a sleeve member, the hub member being fixed at one end to a casing of a push-pull control cable and having a ball member on the other end, and the sleeve member having a spherical cup member on an end which is to connect to the hub member, the cup member being a resiliently deformable fit on the ball member to form an articulating ball joint through which a push-pull cable core can pass.

2. An end fitting as claimed in claim 1, wherein the external surface of the spherical cup member will shed away from the interior of the ball joint any moisture which might form on the sleeve member and run towards the joint when the sleeve member is oriented or inclined above the level of the joint.

3. An end fitting as claimed in claim 1 or claim 2, including a sealing ring positioned in an annular seal groove formed around the outer surface of the ball member and sealing against the complementary interior surface of the cup member.

4. An end fitting as claimed in claim 3, wherein the sealing ring is a rubber '0' ring.

5. An end fitting as claimed in any of the preceding claims, wherein both the sleeve member and the hub member are tubular.

6. An end fitting as claimed in claim 5, wherein the internal passages ofthe sleeve member and the hub member are aligned when the cup member and the ball member are connected together to allow the cable core to pass easily the sleeve member and the hub member.

7 An end fitting as claimed in claim 5 or claim 6, wherein at least one of the internal passage of the hub member and the internal passage of the sleeve member, at its end which mates with the sleeve member or hub member, respectively, is flared so as to facilitate free passage of the cable core between the sleeve and the hub member when the ball joint is at its maximum angle of articulation.

8. An end fitting as claimed in any of the preceding claims, wherein the internal diameter of the passage of the hub member is enlarged towards the end remote from the ball member so that the end of the casing of the push-pull control cable can be inserted therein.

9. An end fitting as claimed in claim 8, wherein the end of the casing is retained in the enlarged portion of the internal passage of the hub member by a swaging or crimping operation.

10. An end fitting as claimed in any of the preceding claims, wherein the ball member and the cup member are each formed as an integral part of the hub member and the sleeve member respectively.

11. An end fitting as claimed in any of the preceding claims, wherein the hub member is of a rigid material.

12. An end fitting as claimed in any of the preceding claims, wherein the rigid material is metal or a high grade plastics material.

13. An end fitting as claimed in any ofthe preceding claims, wherein the sleeve member is of a resiliently deformable plastics material.

14. An end fitting substantially as herein described with reference to the accompanying drawings.