GB2173566A

GB2173566A - Vehicle brake actuator

Info

Publication number: GB2173566A
Application number: GB08506857A
Authority: GB
Inventors: Herbert William Lock
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-03-16
Filing date: 1985-03-16
Publication date: 1986-10-15
Also published as: GB8506857D0

Abstract

A vehicle brake actuator, has a screwshaft 20 having a gearwheel 22 welded centrally, narrower, and in constant mesh with a layshaft gearwheel in a gearbox 18 whose side walls provide the journals. The gearbox is fixed in one of three ways to a rigid open ended box-frame 10 containing twin pivoting fork ended belcrank levers 42, 52 one end each astride a nut 32, 34 possessing close fitting lands for cursing inwards and outwards on screw threads formed on the screwshaft on both sides of the gearbox. The levers 42, 52 provide a linear output to lever 16 connected to a brake of the vehicle. <IMAGE>

Description

SPECIFICATION Motion transfer apparatus This invention relates to motion transfer apparatus and is particularly, but not exclusively, concerned with apparatus for controlling a parking brake of a vehicle such as a railway vehicle.

With regard to railway vehicle parking brakes, there are many inhererent disadvantages in the brakes which form the present state of the art. A lever type brake is in breach of safety for requiring the use of a stick to meet mandatory performances, while a screw type brake is ill-conceived and dangerously inadequate as well as being very inefficient. Modern bogie freight vehicles still require two separate parking brakes, each of which requiring at least eight turns on a handwheel to effect a highly suspect security of immobilisation.

Consequently the present arrangements lead to inordinate costs, breaches of statutory safety obligations, and incapacity to compete at any level.

According to the present invention there is provided motion transfer apparatus comprising means for transmitting applied input effort into rotation of rotary means, means for providing a substantially linear output effort to output means, pivotal means provided to each side of the output means for pivoting movement in a plane common to the plane of linear output movement, and means operatively interconnecting the rotary means with the pivotal means for pivoting of the latter in consequence of rotation of the rotary means, and thereby for linear movement of the output means, the operative interconnection between each of the pivotal means and the output means providing for equalisation of the forces applied to the latter.

Preferably the rotary means comprises a shaft on which means are provided at each of two locations for operative interconnection with respective ones of the pivotal means.

Preferably also the pivotal means comprises a pair of bellcrank levers whereby an input effort may be applied directly to either end of the shaft and simultaneously effect pivoting of both levers.

The pivotal means are preferably operatively connected with the shaft for further pivoting in consequence of abutment free axial movement of the shaft due to reaction forces on the latter effected by initial linear output movement. Means may be provided for indicating when an output effort has been applied, and means may be provided for biassing the indicating means to a non-operative condition. The axial movement of the shaft may be arranged to overcome the biassing force and means is provided for-transmitting the axial movement of the shaft into pivotal movement of the indicating means whereby the latter may be moved to an operative condition.The arrangement may be such that input effort applied to one end of the shaft may be transferred into the linear output effort, an additional shaft which is geared to the first mentioned shaft being provided, whereby input effort to an end of the additional shaft can be transferred into a linear output effort.

The invention is particularly applicable to use with a moveable vehicle wh.ereby input effort applied by wayof a handwheel from either side of the vehicle, or from a plafform provided thereon, may be transmitted into a linear output effort connected to a linkage with a brake of the vehicle.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which Fig. 1 is a side elevation of one embodiment of an apparatus according to the invention; Fig. 2 is a plan view, partly in section, of the apparatus of Fig.1; Fig. 3 is a schematic side elevation of a modified version of the apparatus of Figs. 1 and 2 on A-A of Fig.4; Fig. 4 is a part schematic plan view of the apparatus of Fig.3; Fig. 5 is a side elevation of an indicating arrangement for use with the apparatus of any of Figs. 1 and 4; Fig. 6 is a part end elevation of the apparatus of Fig. 5; and Fig. 7 is a plan view of another embodiment of an apparatus according to the invention.

Referring to Figs. 1 and 2 of the drawings, a parkihg brake adaptor for railway vehicles is of a ground operated and indicating type. The apparatus comprises a casing 10 open at its sides 10a, 10b and adapted to be mounted on a chassis of a railway vehicle (not shown) for example by means of a top face 12 on the underside of the chassis. At a central location within the casing 10, a guide bar 14 extends laterally thereof and slidably mounts a pull rod linkage 16 which extends out of the side 10a of the casing 10 and is adapted to be connected to a linkage (not shown) of a brake of the vehicle. A gearbox housing 18 is fitted on the side 10b of the casing 10 by any suitable mounting arrangement.

A screwshaft 20 extends through the gearbox housing 18to either end thereof, and non-movably mounts a gear 22 within the housing 18, the gear 22 being substantially centrally located on the screwshaft 20. A layshaft 24 also extends through the gearbox housing 18 to either end thereof and is parallel to, but spaced from, the screwshaft 20. In the arrangement shown in Figs. 1 and 2, the orientation of the gearbox housing 18 is such that the layshaft 24 is located vertically above the screwshaft 20. The layshaft 24 is hollow and rigidly mounts a gear 26 which is in mesh with gear 22. The gearbox is assembled by easing journal plates 28 over the screwshaft 20 and the layshaft 24 to accurately register on locating spigots for strict alignment, with bolts 30 completing the assembly.

The screwshaft 20 has two, double start, free fit square threaded sections, a right hand threaded section to one side of the gear 22 and a left hand threaded section to the other side. A right hand threaded trunnion nut 32 is located on the respective threaded section while a left hand threaded trunnion nut 34 is located on the respective threaded section, the trunnion nuts 32,34 being equispaced about an axis 36 of the apparatus which extends centrally through the gearbox housing 18 and the casing 10.

Pivot pins 38,40 extend vertically through the casing 10 in equispaced relation to respective sides of the axis 36. On the pivot pin 38 there is mounted a bellcranklever42which has a first forked end 44 for embracing a projecting part of the trunnion nut 32 and a second forked end 48 for embracing a projection 50 on the pull rod linkage 16. On the pivot pin 40 is mounted an assembly 51 which functions as a beilcrank and comprises a first arm 52 having a forked end 54for embracing a projecting part of the trunnion nut 34, and a second arm 56 extending at substantially right angles to the arm 52 and mounting a pivot 58 on its free end.An adjustable arm 60 is mounted on the pivot 58 and presents an extending abutment 62 for engagement with the projection 50 on the linkage 16. In a normal, nonoperative position as hereinafter described, the abutment 62 is spaced from the projection 50 by a distance A and this distance can be varied as required by varying the relative positions of the arms 56 and 60 by means of an adjustment mechanism comprising a set screw 64 with a lock nut 66. Also in the non-operative condition of the apparatus the screwshaft 20 is positioned with the axis of the gear 22 offset to one side of the central axis 36 by the distance A.

Referring to Figs. 3 and 4, the apparatus is shown with the gearbox housing 18 so orientated that the layshaft 24 lies in the same horizontal plane as the screwshaft 20. A support frame 68 is mounted on an end of the casing 10 and extends therefrom to the same side of the latter as the gearbox housing 18. A stay 70 extends between the frame 68 and the gearbox housing 18 for stabilising the latter.

A shaft 72 is located through one end of the hollow layshaft 24 and is connected for rotation therewith by means of a drive pin 74, the latter being movable in a slot 76 of the layshaft 24 to provide for axial sliding movement of the shaft 72 in the layshaft 24. At its outer end, the shaft 72 mounts a handwheel 78 together with an indicating arrangement (see Figs. 5 and 6). An externally threaded and flanged sleeve 82 is pinned on the handwheel shaft 72, a coil spring 84 being retained by a threaded collar 80 within the layshaft 24 and acting to bias the handwheel shaft 72 to an axially outermost position in the layshaft 24, the collar 80 being adjustably positioned. Aflange on the sleeve 82 is engageable at diametrically opposed locations on its axially outermost face by lugs 86 provided on the ends of respective pivot arms 88.The latter are mounted on respective upper and lower part5 of a bracket 90 which is mounted on the frame 68. The other ends of the pivotal arms 88 mount an abutment plate 92 engageable by a set screw and lock nut arrangement 94 mounted on an adjacent outer end ofthe screwshaft 20. On the other end of the screwshaft 20 there is directly mounted a further handwheel shaft 96 for mounting another of the same handwheel and indicating arrangement, whereby only one of the handwheel and indicating arrangements need to be described and shown. It will be appreciated that the handwheel and indicating arrangements extend to respective sides of the vehicle.

In the non-operative condition of the apparatus as herein before described, the coil spring 84 biasses the handwheel shaft 72 to an axially outermost position in the layshaft 24, and this retains the indicating arrangement in a non-operative condition as hereinafter described. When the handwheel 78 is turned by an operator, rotation of the hanwheel shaft 72 effects rotation of the layshaft 24 and consequently rotation of the gear 26. The gear 22 is consequently rotated, effecting rotation ofthe screwshaft 20 and axial movement of the trunnion nuts 32,34. Movement of the nuts 32,34 effects pivoting of the bellcrank lever 42 and the assembly 51 and causes the guided pull rod linkage 16, possessing one degree of freedom, to be moved inwardly of the casing 10, by the lever 42, a distance related to the normal regulator setting.Following this, the reaction feedback force on the lever 42 and the nut 32 compels the screwshaft 20 to move axially, with the gear 22 moving in an abutment free manner within the gearbox housing 18 into the plane of the axis 36. This axial movement closes the present gap between the abutment 62 on the projection 50 and the linkage 16. There is therefore a direct relation between the further effort applied to the handwheel and the movement of the linkage 16 in an equalised system and the apparatus is mechanically highly efficient. The axial movement of the screwshaft 20 effects pivoting of the pivot arms 88 and consequently axially inward movement of the handwheel shaft 72 in the layshaft 24, overcoming the bias of the spring 84. The indicating arrangement can thus move to an operative position as hereinafter described.

Referring to Figs. and 6, the indicating arangementcomprises a grooved collar 98 on the handwheel shaft 72, the latter being supported by a frame 100 which presents a mounting bracket 102 on either side of the handwheel shaft 72. Each bracket 102 mounts a pivot pin 704 'iO4and, inwardly of each bracket 102, the respective pin 104 mounts a respective side member 106 of an indicator arm assembly 108. The latter mounts an indicating arm 110 between a pair of pivotal cover plates 112. The movement of the handwheel shaft 72 axially inwardly of the layshaft 24 effects the lateral movement of the collar 98.Studs 114, mounted on the upper ends of the side members 106, engage in the groove of the collar 98, such that movement of the latter effects pivoting of the side members 106 with the indicator arm 110 towards the handwheel 78. Consequential movement towards the handwheel 78 of the pivot mounting for the covers 112 moves the later into engagement with a forked abutment 116 at the lower end of the frame 100 whereby, although the indicator arm 110 can pivot in the abutment 116, the covers 112 abut the latter and thus pivot away from the indicator arm 110 on further movment of the pivot mounting. This arrangement thus assists the display of a "ON" motif 118 on the indicator arm 110.

Thus when an operatorturnsthe handwheel 78to render the vehicle brake effective, the indicating arrangement is visible from both sides of the vehicle to show the condition of the brake. On release of the brake, the biasssing spring 84 automatically moves the handwheel shaft 72 to its axially outermost position and this moves the indicator arm 110 back to its original position, with the covers 112 dropping to their original position under gravity so as to obliterate the "ON" motif 118.

There is thus provided unhindered equalisation of the bellcrank lever 42 and the assembly 51 in order to confine the reaction force within the screwshaft 20. This is achieved by accommodating the intended movement plus generous manufacturing tolerances at the direct handwheel shaft by making the movement of the components abutment free.

Within the gearbox this is achieved by a suitable reduction of the thickness of the gear 22 on the screwshaft 20 relative to the gear 26 on the layshaft 24. There is also provided close clearance fittings between the trunnion nuts and the bellcrank components, so as to prevent excessive rotation of one nut relative to the other. An access hole 120 is provided in one of the gearbox journal plates 28 so as to enable probing of the position of the gear 22 within the housing 18, and a monitor stop 122 is provided in the casing 10 to guard against override to the pull rod linkage 16 resulting, for example, from a discontinuity in the rigging or regulator malfunction.

In the embodiment of Fig. 7 the brake adaptor is provided to be a non-indicating type. The apparatus is similar to that described and shown with reference to the first embodiment, although there is no guide bar for a pull rod linkage and no linkage monitor. A second bellcrank lever 124 takes the place of the assembly 51 of the first embodiment.

The screwshaft preferably has its gear on the centre.

Replacement of the gearbox by conventional journal bearings can transform the indicating and the non-indicating adaptor units decribed above into a platform operated version. An indicator of simplified design, where called for, may be provided with the single direct handwheel and shaft then used.

Various modifications may be made without departing from the invention. It is to be appreciated that the invention is not restricted to use with railway vehicles but can be used in other applications for example as a parking brake adapator for mobile cranes. The construction of the apparatus may vary from that described and shown.

The gearbox can preferably be mounted in a selected one of three alternative dispositions on the frame, two of which positions have been described and shown.

Whilst endeavouring in the foregoing Specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentabie feature or combination of features hereinbefore referred to whether or not any particular emphasis has been placed thereon.

Claims

1. Motion transfer apparatus comprising means for transmitting applied input effort into rotation of rotary means, means for providing a substantially linear output effort to output means, pivotal means provided to each side bf the output means for pivoting movement in a plane common to the plane of linear output movement, and means operatively interconnecting the rotary means with the pivotal means for pivoting of the latter in consequence of rotation of the rotary means, and thereby for linear movement of the output means, the operative interconnection between each of the pivotal means and the output means providing for equalisation of the forces applied to the latter.

2. Apparatus according to claim 1, wherein the rotary means comprises a shaft on which means are provided at each of two locations for operative interconnection with respective ones of the pivotal means.

3. Apparatus according to claim 2, wherein the pivotal means comprise a pair of bellcrank levers whereby an input effort may be applied directly to either end of the shaft and simultaneously effect pivoting of both levers.

4. Apparatus according to claim 3, wherein the pivotal means are operatively connected with the shaft for further pivoting in consequence of abutment free axial movement of the shaft due to reaction forces on the latter effected by initial linear output movement.

5. Apparatus according to any of claims 2 to 4, wherein means is provided for indicating when an output effort has been applied.

6. Apparatus according to claim 5, wherein means is provided for biassing the indicating means to a non-operative condition.

7. Apparatus according to claim 6, wherein the axial movement of the shaft is arranged to overcome the biassing force and means is provided for transmitting the axial movement of the shaft into pivotal movement of the indicating means whereby the latter may be moved to an operative condition.

8. Apparatus according to any of claims 2 to 7, wherein the arrangement is such that input effort applied to one end of the shaft may be transferred into the linear output effort, an additional shaft which is geared to the first mentioned shaft being provided, whereby input effort to an end of the additional shaft can be transferred into a linear output effort.

9. A vehicle having motion transfer apparatus according to any of the preceding claims, wherein input effort applied by way of a handwheel from either side of the vehicle, or from a platform provided thereon, is transmitted into a linear output effort connected to a linkage with a brake of the vehicle.

10. Motion transfer apparatus substantially as hereinbefore described with reference to the accompanying drawings.

11. A vehicle substantially as hereinbefore described with reference to the accompanying drawings.

12. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.