GB2057100A - Manually-operable lever assemblies - Google Patents

Abstract

A hand operable lever assembly of the kind specified in GB 1118431 can only be adjusted with the aid of a tool. A hand lever 10, primarily intended for controlling a brake, is pivoted to a support 11 by means of aligned pins 12. A carrier 16 is mounted for adjustment lengthwise of the lever. The carrier is pivoted to one end of a link 18 of which the other end carries a guide pin 21 sliding in slots 22 in the support. In use a brake cable is connected to the guide pin. In operation the lever moves a little over centre to its operative position. To take up slack in the cable the position of the carrier can be adjusted by manual rotation of an adjusting knob 25 fixed to a screw threaded rod 24 engaging a tapped tube 23 on the carrier. To prevent inadvertent or unintentional manipulation of the knob there is in the knob a locking screw 31 which cooperates with a flat on an hexagonal boss 26 and can be unscrewed only with the aid of a tool. <IMAGE>

Description

SPECIFICATION Manually-operable lever assemblies This invention relates to manually-operable lever assemblies. Such assemblies are primarily intended for use in motorised vehicles such as diggers, fork-lift trucks, earth-moving equipment and the like. They may be used for controlling the brakes of such vehicles, but may also be used for actuating other mechanisms such as devices for retaining load-carrying parts of motorised vehicles in position after movement. For example, a motor vehicle having a scoop mounted on pivoting arms by means of which the scoop can be raised and lowered may incorporate a brake-like device device which when actuated holds the arms in any selected position within their range of movement.

The invention is particularly concerned with hand-operable lever assemblies of the kind (hereinafter referred to as the kind specified) comprising a manually-operable lever mounted on a support for pivotal movement about a pivot axis, a carrier on the lever, the position of which can be adjusted lengthwise of the lever, an adjuster on the lever, operation of the adjuster causing operation of a screw-threaded device so as in turn to cause adjustment of the position of the carrier lengthwise of the lever, and link means pivoted to the carrier and extending past the pivot axis, part of the link beyond the axis being constrained to move towards and away from the pivot axis on pivotal movement of the lever, and the arrangement being such that if a brake-actuating cable or the like actuating means is connected to the link the lever can be pivoted towards an end position so as to apply tension to the actuating means, but in the final stages of pivotal movement of the lever the link passes over centre relative to the pivot axis whereby the tension in the actuating means tends to retain the lever in that end position. It is known to provide a hand-operated lever assembly of the kind specified in which the adjuster is manually operable.

An assembly of the kind specified is the subject of Patent No. 1,118 431 granted to Sackville Limited.

When an assembly of the kind specified is used for the operation of a vehicle brake, for example, then in use it is usual for the vehicle to be halted and the brake to be applied by means of the lever assembly, the lever being pivoted to its end position. During much of the pivotal movement the brake is progressively applied, but during the final stages of movement the application of the brake is relaxed very slightly, though the brake remains fully effective.

If the brake contains shoes that become worn or compressed over an extended period of use it may become necessary to adjust the position of the carrier so that the position of the actuating cable, when the lever is moved to its end position, is such as to apply the desired force to the brake mechanism. Adjustment of the position of the carrier can of course be readily effected by operation of the adjuster.

Now we have found that in use of such an assembly (the adjuster being manually operable) some drivers or other operators tend to fiddle with the adjuster and, often without realising what they are doing, alter the position of the carrier to an extent such that the brake or other mechanism operated by the lever fails to operate, or fails to operate correctly (or to the optimum extent), when the lever is next moved to its end position. The aim of the present invention is to avoid or reduce this problem.

According to the present invention there is provided a hand-operable lever assembly of the kind specified in which manual adjustment of the adjuster can be effected only with the aid of a tool.

The adjuster may be so positioned as to be inaccessible for operation other than with the aid of a tool. Preferably, however, the adjuster is accessible for manual operation but there is releasable locking means for the adjuster which can be released only with the aid of a tool to permit manual operation of the adjuster. In a convenient arrangement the adjuster is rotatable about the longitudinal axis of the lever and the set screw is mounted radially in the adjuster and cooperates with a flat or recess on the lever so that when it is tightened to lock the adjuster against rotation its engagement with the flat or in the recess assists in resisting any attempt made to rotate the adjuster.

When an assembly embodying the invention is in normal use the driver or other operator cannot inadvertently or unthinkingly manipulate the adjuster so as to vary the position of the carrier. To enable adjustment to be efffected deliberate use must be made of a tool. Although this means that adjustment can usually be effected less readily than before, this does not normally detract from the usefulness or effectiveness of the assembly as frequent adjustment is not generally necessary, and the need for adjustment is generally not a matter of urgency.

While it would be possible to provide an adjuster incapable of manual adjustment and capable of adjustment only with the aid of an appropriate tool, such as a screw-driver or Allen key, it is preferred to provide a manually-operable adjuster and additionally to provide releasable locking means for the adjuster, the locking means being such that it can be released only with the aid of a tool.

A lever assembly embodying the present invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a hand-operated lever assembly embodying the present invention, part of the lever being shown sectioned along the line 1-1 of Figure 2, Figure 2 is a plan view of the assembly shown in Figure 1, and Figure 3 is a section along the line 3-3 of Figure 1.

The assembly illustrated is intended for use in operating the brakes of a motorised vehicle, such as a digger. The assembly comprises a manuallyoperable lever 1 0 largely made from sheet steel and of generally tubular form.

One end of the lever is pivoted to a support 11 by means of a pivot 12 comprising a pair of axially aligned, transverse pivot pins. The support 11 comprises a pair of spaced parallel plates 1 3 one on each side of the end of the lever 1 0 and formed with holes 1 for mounting screws or bolts by means of which the plates can be firmly secured to the body of the vehicle. That part of the lever 1 0 adjacent to the pivot 12 has flat side walls 15 parallel with the plates 13 constituting the support. A carrier 1 6 is disposed between the side walls 1 5 of the lever and is slidable lengthwise of the lever. The carrier has spaced arms 1 7. One end of a link 18 lies between those arms 17.A connecting pin 19, parallel with the pivot 12, projects through aligned holes in the arms 1 7 and the link 1 8 to connect the carrier to the link in a manner permitting relative pivotal movement between them. The ends of the connecting pin 19 are located in parallel slots 20 formed in the side walls 1 5 of the lever and extending lengthwise of the lever. The carrier 1 6 is thus capable of sliding movement lengthwise of the lever but is restrained against other movement relative to the lever.

The other end of the link 1 8 lies between the plates 1 3 constituting the support. A guide pin 21 extends through the end of the lever, and the ends of the guide pin are located in parallel slots 22 in the support and aligned with the pivot 12.

An internally screw-threaded tube 23 is welded to the carrier 1 6 and projects axially inside the lever in a direction away from the link 18 and towards the free end of the lever. One end of a rod 24 formed with a complementary screw-thread projects into the tube, and the other end of the rod is anchored to the inside of a rotatable adjuster knob 25 at the free end of the lever. The rod 24 projects through a hole in an hexagonal boss 26 secured in a tube 27 fixed inside the free end part of the main body of the lever. The tube 27 projects slightly from the body of the lever, while part of the boss 26 projects from the tube. A collar 28 fixed to the rod 24 abuts the innerface of the boss 26 and thus prevents axial movement of the rod in a direction outwards of the lever.Likewise, the presence of the adjuster knob 25 prevents unrestricted axial movement of the rod in the other direction. A spring washer 29 is disposed on the rod 24 between the knob 25 and the boss 26 to urge the rod outwards and to urge the collar 28 into abutment with the boss.

The adjuster knob 25 includes a cylindrical skirt portion 30 which surrounds the boss 26 and the adjacent end portion of the tube 27. An Allen screw 31 is mounted in a radially extending tapped hole in the skirt portion 30, and can be turned so as to assume either a locking position in which it engages the boss 26 thereby preventing relative rotation between the knob and the lever, or an unlocked position (or range of unlocked positions) in which the knob can be manually rotated relative to the lever. The Allen screw can be tightened to its locking position and released to its unlocked position only with the aid of an Allen Kay or other similar tool.It will be appreciated that any other form of headless set screw can be used in place of the Allen screw 31, manipulation of the screw as between its locking and unlocking positions being capable of being effected only with the aid of an appropriate tool.

The boss 26, being of hexagonal shape, has six flats each one of which can be engaged by the screw 31. When the screw engages one of the flats, as shown in Figure 3, this engagement assists in resisting any attempt made to rotate the adjuster. In an alternative arrangement the boss is of cylindrical shape, but this is less satisfactory, for unless the screw is firmly tightened it may become possible for the knob to be manually rotated.

While use of an hexagonal boss is preferred, it will be appreciated that a boss with a single flat or a different number of flats may be used. The flat or any one or more of the flats may be repiaced by a recess which can be entered by the screw to assist in resisting any attempt made to rotate the knob.

In use the support plates 1 3 are fixed to the body of the vehicle, and the brake cable is anchored to the guide pin 21. The lever 10 is so arranged as to be movable between an off position in which the brakes are not applied and an on position or end position in which the brakes are applied. When the lever is in the off position the guide pin 21 is at its furthest possible position from the pivot pin. As the lever is moved towards its on position the guide pin 21 moves closer to the pivot 1 2 and tension is applied to the brake cable. During the final stages of movement, however, the link 1 8 passes over centre relative to the pivot axis; in other words the plane containing the axes of the guide pin 21 and the connecting pin 1 9 crosses the axis of the pivot 12.The accompanying drawings show the lever in the dead centre position in which those three axes lie on a common plane. On continued movement of the lever to its end position the guide pin 21 moves very slightly further away again from the pivot 12 but not enough to affect significantly the operation of the brake. The tension in the brake cable, however, tends to retain the lever in its end position. In the end position of the brake the link 18 abuts a sleeve 32 on a support pin 33 which extends between the plates 1 3. The support pin also passes through a pair of retaining plates 34 which serve to locate the inner ends of the pivot pins constituting the pivot 12, each of the plates 1 3 of the lever 10 being sandwiched between an adjacent one of the support plates 1 3 and an adjacent one of the retaining plates 34.

Should it be necessary to adjust the assembly so as to cause the guide pin 21, when in the end position, to lie closer to the pivot 1 2 than before, the adjustment can be effected by manual rotation of the adjuster knob 25. On rotation of the knob the screw-threaded rod 24 rotates and causes axial movement of the internally screw-threaded tube 23 inside the lever. This in turn causes axial displacement of the carrier 1 6 and the connecting pin 19. Consequently the link 18 and guide pin 21 are also displaced. Adjustment is normally effected when the lever is in its off position. When the appropriate adjustment has been made the Allen screw 31 is tightened so as to prevent further manual rotation of the knob relative to the lever. Likewise, an Allen Key or other appropriate tool must be used to release the screw 31 before any subsequent adjustment can be made.

It will be seen that as the end portion of the lever 10 is constituted by the projecting end of the tube 27, it is possible for the outer diameter of the knob 25 and its skirt portion 30 to be made of the same outer diameter as the adjacent part of the main body part of the lever.

The adjuster knob may be knurled or otherwise formed to enable it to be the more readily turned manually on release of the Allen screw.

In a modified construction of assembly (not illustrated) there is no rotatable adjuster knob, but the lever has an axial opening, at its free end, which is too small to enable a finger to be inserted through it. The adjacent end of the screwthreaded rod is situated inside the lever, spaced a short distance from the hole. The end face of the rod is formed with a screw-driver slot. In use, adjustment is effected by inserting the head and part of the shank of a screw-driver axially through the hole, so that the head engages the slot, and rotating the screw-driver by means of the handle thereof, which remains outside the lever.

Claims (7)

1. A hand-operable lever assembly of the kind specified in which manual adjustment of the adjuster can be effected only with the aid of a tool.

2. An assembly according to claim 1 in which the adjuster is so positioned as to be inaccessible for operation other than with the aid of a tool.

3. An assembly according to claim 1 in which the adjuster is accessible for-manual operation but in which there is releasable locking means for the adjuster which can be released only with the aid of a tool to permit manual operation of the adjuster.

4. An assembly according to claim 3 in which the releasable locking means comprises a headless set screw in the adjuster.

5. An assembly according to claim 3 in which the adjuster is rotatable about the longitudinal axis of the lever and the set screw is mounted radially in the adjuster and co-operates with a flat or recess on the lever so that when it is tightened to lock the adjuster against rotation its engagement with the flat or in the recess assists in resisting any attempt made to rotate the adjuster.

6. A hand-operable lever assembly of the kind specified and substantially as herein described.

7. A hand-operable lever assembly of the kind specified and substantially as herein described with reference to the accompanying drawings.