WO1987004983A1

WO1987004983A1 - Emergency brakes for vehicles

Info

Publication number: WO1987004983A1
Application number: PCT/AU1987/000048
Authority: WO
Inventors: Joe Wigglesworth; Ian Desmond Erwin
Original assignee: Colin W. Skelton Industries Pty. Limited
Priority date: 1986-02-21
Filing date: 1987-02-20
Publication date: 1987-08-27

Abstract

An emergency brake apparatus for wheeled vehicles wherein a belt (20), one end affixed to the vehicle has its other end run over by one (10) of a pair of dual wheels (10, 10') or part of a wide wheel (10). One feature releases an extra length of belt (20) as the braking occurs, to accommodate wear under high load conditions. A further optional feature feeds the belt (20) under the wheel (10) from a point (21) well below the vehicle chassis (34). This ensures the belt (20) aligns correctly with the wheel and remains beneath the wheel (10) during emergency braking. Once the initial section of belt (20) has been at least partly consumed by the initial high load friction a further length of belt (20) is dispensed to complete the braking action.

Description

EMERGENCY BRAKES FOR VEHICLES

TECHNICAL FIELD

This invention relates to an emergency brake for wheeled vehicles and is particularly suitable for trucks and buses and other heavy veh i cl es having dual, or multiple, or relatively wide single rear wheel s rather than normal passenger vehicles and the like, which have a normal width single rear wheel only on either side.

BACKGROUND ART

There has previously been proposed a number of constructions of emergency brakes wherein a belt or other skid member is secured to the vehicle at one end and a release mechanism is provided whereby the other end of the belt may be dropped to contact the ground and inserted between the wheels of the vehicle and the ground from the forward direction to retard or prevent the further rotation of the wheels. In our U.S. Patent No 4386681 there is proposed an emergency braking system for use in connection with vehicles having dual wheels on either side. In this U.S. specification it is proposed that the belt be inserted between one only of the two wheels of each pair and the ground so that the other wheel remains in contact with the ground surface. This action maintains rotation of the dual wheel assembly, thereby creating an increased braking effect with a reduction in tendency for the vehicle to skid.

However, it can also apply to vehicles with single wheels in which case, the width of the reinforced belt will be approximately 50% of the width of the tyre, as is described in Australian patent No 524553.

It is important to ensure that, when the belt is dropped to the ground, it aligns correctly with the wheel under which it is desired to be led so that it is inserted and remains between that tyre only or portion of tyre, and the ground.

In order to obtain better control of the location at which the belt enters beneath the tyre, it is desirable for the belt to be adequately supported down to a level at least less than the overall height of the wheel and preferably to a level approaching the centre line or below the centre line of the wheel. Thus, the amount of lateral movement that the belt might undergo, as it is released prior to insertion beneath the wheel, is limited, reducing the risk of misalignment of the belt with the wheel.

In another construction discussed in the prior art, a support member for a drop brake is disclosed. However, this support member is pivotally mounted rearwardly of the wheels to be braked and the mechanism is cramped between the set of wheels involved and the tray of the vehicle. Under severe braking, particularly with heavily laden vehicles, it has been found that the rate of wear of the belt in contact with the road may be unacceptably high and it has been found des i rabl e to incorporate means to feed out a further length of belt to replace that which is wearing out. This may be particularly useful where a high wear rate belt is used.

It is not satisfactory to simply thicken the belt to provide greater "depth" of belt to wear out as the thickness of the belt must be such as to ensure the other tyre, or remainder of a wide tyre not riding on a belt, is not lifted from contact with the ground as this would defeat the advantages of the invention.

It is an object of the present invention to provide a drop belt type emergency brake for vehicles which will overcome or at least reduce the above discussed problems experienced in respect of previously proposed emergency brakes of this type.

DISCLOSURE OF THE INVENTION

There is provided according to one broad form of the present invention a drop brake for a vehicle or trailer having on either side thereof at least one relatively wide wheel, or one dual or multiple wheel arrangement wherein at least two coaxial wheels are rigidly interconnected to rotate together, said drop brake comprising: a reinforced belt of suitable material of sufficient length to extend from a suitable point of connection to the vehicle to at least the point of intersection between the ground and said wheel (s) said brake being adapted to be positioned on at least on side of said vehicle or trailer; a support means for securing one end of the belt, and releasable holding means adapted to hold the belt in an inoperative position and to selectively release the belt so that the other end of said belt drops to enter beneath part of the relatively wide wheel or one only of said wheels of each dual wheel arrangement, or, if more than two wheels are involved in such an arrangement, a proportion of said wheels (not being all the wheels); said support means comprising: a housing adapted to be suspended from the vehicle forward of the axle of the wheel or wheels under which the belt is to be inserted when in use; releasable holding means securing the belt at or adjacent one end thereof within the housing, whereby the belt may move from an upper inoperative position to a lower operative position wherein the lower end of the belt is inserted between a tyre and the road surface, said movement occuring in response to the release of the belt by the releasable holding means, guide means associated with said housing to limit lateral movement of the belt relative to the housing to maintain the centre line of the belt substanti al ly in the mid radial plane of the wheel or wheels beneath which the belt is to be inserted.

In accordance with another aspect of the present invention, the housing is pivotally connected at or adjacent its upper end to the vehi cl e and has a frangible member restraining the housing from movement about the pivotal connection. Accordingly, normally the housing will be restrained against pivotal movement. However, upon the belt being released for the purpose of operating the brake, the end of the belt will travel beneath the tyre to the extent of the limit of movement of its upper end within the housing and, at this point, a sudden and substantial force will be imparted to the lower end of the housing tending to pivot the housing about its pivotal connection to the vehicle so that the lower end will move towards the wheel or wheels. The frangible connection is designed so that it will fail when subjected to this sudden load transmitted via the belt beneath the tyre, and thus permit the housing to pivot about the pivotal connection to the vehicle.

The extent of pivotal movement of the housing is limited by the fact that the lower end of the housing will come into contact with the periphery of the tyre of the wheel. When such contact has been established, the housing will effectively be supported at both ends thereof thus removing the necessity for bracing the lower end of the housing against horizontal force components. In this position, and with the belt in its fully extended position there is substantially no bending stress applied to the housing as the stress applied by the belt being drawn under the wheel or wheels will be substantially a tension force along the length of the support member.

In a further preferred form, in order to feed out an additional length of belt during braking to compensate for the belt wearing below an effective level, it is proposed that upon release of the belt the upper end thereof contacts a load transfer means before it reaches its lowest final operative position; said load transfer means gradually or di scretel y allowing the upper end of the belt to complete its travel to its lowest final operative position in response to the tensile force applied to said belt by the braking action.

In a further preferred form the load transfer means comprises a hydraulically controlled mechanism to enable controlled extended release of said belt. In a further embodiment means are provided to feed additional belt under the wheel once the initial braking has occurred.

In a further embodiment the belt has a least one surface having a concave transverse cross-section.

In a further embodiment said means include means for applying a time delay before releasing said additional length of belt.

In a further embodiment the hydraulic mechanism is connected to a second frangible member which holds said mechanism in its rest position; said second frangible member being ruptured once the force on said load transfer means exceeds the strength of said frangible member.

In a further embodiment in order to feed out additional length of belt during braking to compensate for the belt wearing below an effecti ve level, it is proposed that upon release of the belt the upper end thereof contacts the lower end of said support means and a load transfer means, interposed between the vehicle and the said support in such manner that in respone to the tensile force applied by the braking to the belt the load transfer means lowers said support and thus feeds a further length of unused belt under said wheel.

In a further broad form of the invention there is provided a drop brake for a vehicle or trailer having on either side thereof at least one relatively wide wheel or a dual or multiple wheel arrangement wherein at least two coaxial wheels are rigidly interconnected to rotate together, said brake comprising: a reinforced belt of suitable material of sufficient length to extend from a support means mounted on the vehicle to at least the point of intersection between the ground and said wheel(s), said brake being adapted to be positioned on at least one side of said vehicle or trailer; said support means comprising: a housing adapted to be suspended from the vehicle forward of the axle of the wheel or wheels under which the belt is to be inserted when in use, releasable holding means securing the belt at or adjacent one end thereof within the housing, whereby the belt may move from an upper inoperative position to a lower operative position wherein the lower end of the belt is inserted between a tyre and the road surface, said movement occurring in response to the release of the belt by the releasable holding means, guide means associated with said housing to limit lateral movement of the belt relative to the housing to maintain the centre line of the belt substantially in the mid radial plane of the wheel or wheels beneath which the belt is to be inserted to release the belt so that the other end of said belt drops to enter beneath part of the relatively wide wheel or one only of said wheels of each dual wheel arrangement, or, if more than two wheels are involved in such an arrangement, a proportion of said wheels (not being all the wheels), and means to release additional length of said belt after the initial release of said belt has been completed, in such a manner as to provide a fresh wear surface to be inserted between said road and said wheel (s).

In accordance with yet another aspect of the present invention, the housing is rigidly connected to the vehicle, preferably near the middle or lower end of the housing so as to reduce the torque on the housing, and is aligned in a substantially vertical position; the upper end of the belt being attached to a slidable tumbling block at a position above slide means which are part of the said tumbling block being adapted to slide within guides within said housing; said tumbling block being adapted to travel down the guides until it reaches a stop at which point the end of the belt is located under the wheel and after a predetermined time allow the tumbling block to rotate about said slide means to release an additional length of belt to pass under the wheel.

Preferably, the housing extends downwardly to a level corresponding substantially to the centre line of the wheel or wheels or preferably to a level below that centre line. The supporting and guiding of the belt as it moves from the inoperative to the operative position, and the locating of the- support means centrally with respect to the mid radial plane of the wheel or wheels, reduces the risk of the belt becoming misaligned with the wheel or wheels as it issues from the housing to enter beneath the wheel or wheels. Normally the belt is of a length such that the end of the belt when released will contact the road surface, whilst there is still a considerable portion of the length of the belt in cooperative relationship with the guide means. Having regard to the relative stiffness of the belt, there is little likelihood of the free portion of the belt extending beyond the lower end of the housing becoming laterally deflected before it enters beneath the tyre.

It is preferred that the first stage of attachment is by means of frangible rivets.

In a further embodiment the tumbling block is held in its upper, inoperative, position by clamping means comprising a ram controlled by a pressurized cylinder acting upon a flat spring, such that the tumbling block is released from the inoperative position by depressing action of the said cylinder, allowing the flat spring to move away from the tumbling block and allow it to drop downwardly along the guides.

In a further embodiment the slide means of the tumbling block comprise lower lugs extending outwardly from the lower end of the tumb l i ng block.

In a further embodiment there is provided a further set of lugs extending outwardly from the upper end of the tumbling block which lugs also slide in the guides; and a gateway on one side of each of the guides which will allow the upper lugs on the tumbling block to pass through thereby pivoting the block about the lower lugs so as to release the additional length of belt once said gateways are opened.

In a further embodiment the tumbling block is provided with a director element which will impart a small moment, about the lower lugs, to the tumbling block, so as to bias the block towards the gateways in the guide rails.

In a further embodiment there is provided as the gate for each gateway, a sliding element which is in a lowered position so as to cover the said opening at one side of the guides when it is not desired that the belt be lengthened which sliding element is raised at each gateway at a desired time to thereby allow the tumbling block to rotate about its lower lugs so as to lengthen the belt.

In a preferred embodiment the means by which each sliding element is raised is achieved when the said cylinder is repressurized and allowed to complete a full return stroke, due to the absence of the tumbling block in its path, and thereby acts on the spring, the upper end of this spring in turn acting on a crossbar connecting the pivoting plates; each sliding element being attached to a rod which is in turn attached to the adjacent side of a pivotting plate, so that when the plate is caused to pivot due to the action of the cylinder and spring, the rod and therefore the respective sliding element will experience a longitudinal upward movement, uncovering its opening.

In a further embodiment the cylinder is repressurized by means of a timer controlled valve.

In a further preferred form the belt of the drop brake is of a width less than the tread width of a tyre under which it is to be located when inserted between the road surface and a wheel. In such case it can be applied to a vehicle or trailer having only one wheel on either side thereof.

In a further embodiment, in order to reduce the shock loading on the housing when the tumbling block impacts against the bottom of the guides, the attachement of the belt to the tumbling block is by means of at least two stages, the first stage being designed to fail on impact and the second or final stage being sufficient to withstand the full braking force of the vehicle.

A drop brake according to the invention may be located either to the front or to the rear of each set of wheels, that is, forward of the wheel depending upon its direction of travel. This arrangement is parti cu l ar l y suitable for those vehicles which are adapted to progress with equal facility in e i ther direction, the seating arrangement being rotatable to assist the driver.

Several practical arrangements of the emergency brake are depicted diagrammatically by way of example only in the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagrammatic view from one side of a belt support member, located forwardly of a set of dual wheels, the belt being shown in an upper inoperative position;

Fig. 1A is a cross-section along line A-A of the belt housing shown in Fig. 1 rotated through 90°;

Fig. 1B is a cross-section along line B-B of the belt shown in Fig. 6;

Fig. 1C is a cross-section of an alternative embodiment of the belt housing shown in Fig. 1A;

Fig. 2 is a diagrammatic view, from the same side as depicted in Fig. 1, of the be l t housing and set of dual wheels, the belt being shown in a lower operative position.

Fig. 3 is a diagrammatic view from the same side as Fig. 1 and 2 of the belt housing and belt in the stored condition, and with the addition of belt advance cylinders;

Fig. 4 is a diagrammatic view with the belt in the initial activated position with the load being applied to the belt advance cylinders;

Fig. 5 is a diagrammatic view from the same side as Fig. 4 with the belt being shown in the lower operative position, and the belt advance cylinders at the end of their stroke;

Fig. 6 is a diagrammatic view from the front of a set of dual wheels, and shows the belt housing with the belt in the stored condition, and with the belt advance cylinders as depicted in Fig. 3;

Fig. 7 is a plan view of a further form of the invention; and

Fig. 8 is an end elevation from direction D of Fig. 7. Fig. 9 is a diagrammatic view from one side of another belt support member, located forwardly of a set of dual wheels, the belt being shown in an upper inoperative position.

Fig. 10 is a diagrammatic view from the front of a set of dual wheels, and shows the belt housing of the embodiment of Fig. 9 with the belt in the stored condition.

Fig. 11 is a diagrammatic view of the belt support member of the embodiment of Fig. 9 and shows the belt in the upper inoperative position.

Fig. 12 is a diagrammatic view of the belt support member of the embodiment of Fig. 9, and shows the belt in a lowered first operative position.

Fig. 13 is a diagrammatic view of the belt support means of Fig. 9, and shows the belt in a lowered, second operative position.

Fig. 14 is a side elevation of the tumbling block of the embodiment of Fig. 9.

Fig. 15 is a plan view of the tumbling block of Fig. 14.

Fig. 16 is a forward elevation of the tumbling block of Fig. 14.

Fig. 17 is a diagrammatic view of the belt support means of the embodiment of Fig. 9 and shows the tumbling block in the upper position.

Fig. 18A is a part section view of the belt mounted normally on its holding rod;

Fig. 1 8B is a part sectioned view of a modified form of the belt prior to mounting on its rod;

Fig. 18C is a part section view of the belt of Fig. 18B mounted on its rod prior to activation of the brake; and

Fig. 18D is a view of the belt of Fig. 18C following activation of the brake.

MODES FOR CARRYING OUT THE INVENTION

In Figs. 1 to 6 wheel 10 is one of a set of dual wheels 10, 10' being preferably the inner wheel as can be seen from Figure 6 of the drawings. In Figs. 7 and 8 wheel 10 is a single "wide" wheel located on either side of a vehicle or trai ler.

A shaft 12 is mounted between bracket 8 attached to the vehicle frame 34 and part 9 of the vehicle frame 34, as best seen in Fig. 6. Outer and inner pivotal mounts 13 and 13' are shown at the respective ends of shaft 12.

Belt housing 11 is pivotally mounted on the shaft 12 and between inner pivotal mounts 13, 13'. The housing 11 may conveniently be fabricated from flat metal plate having a flat base 16 and side flanges 17 at the opposite longitudinal edges thereof. Along the inner face of each flange 17 is provided a track 19 defined by the flat base 16 of the housing 11 and a pair of longitudinal runner strips 15 (see Fig. 1A) extending along the length of the housing 11 and attached to the respective flanges thereof. Received within each of these tracks 19 are the respective end portions of a rod 18 to which the belt 20 is securely attached. The respective lower ends of the tracks 19 are partially closed by removable retaining rod 21 so that the rod 18 may move up and down along the tracks 19 within the housing 11, but may not move out of the lower end of the tracks 19. Removable rod 21 allows the belt to be easily replaced.

The belt 20 and rod 18 are held in the "ready" position by a leaf spring 7. To release the rod 18 and belt 20 an air cylinder is retracted and the spring 7 moves from contact with the rod 18 allowing it to drop downwardly in the tracks 19. The air cylinder 6 is controlled by the driver from the cabin of the vehicle. It may also be interconnected to the brake system of the vehicle so that on failure of the brake system it may be automatically actuated to apply the safety drop brake.

Adjacent the upper end of the housing 11, an arm 22 extends forwardly from the housing 11 and is coupled by a shear pin 23 to the bracket 24 extending downwardly from the vehicle frame. When the shear pin 23 is in position extending through the arm 22 and bracket 24, the housing 11 is in a substantially vertical disposition as shown in Figure 1 and when the shear pin 23 is fractured, the lower end of the housing 11 will move into engagement 40 with the surface of the tyre of the wheel 10 as shown in Figure 2.

The shear pin 23 arrangement is one that could be varied depending on the specifications of the vehicle with which it is being used. It could be replaced by hydraulic means or other means to hold the housing 11 away from (usually forward of) the wheel 10 so that it does not interfere with the wheel 10 during normal operation.

It may also be important to vary the coefficient of friction of the housing 11 where it contacts area 40 of the tyre of the wheel 10 so'5 that excessive braking is not applied to the wheel 10, causing it to lock up.

In one construction shown in Figs. 3, 4, 5 and 6, a hydraulic cylinder 31 is mounted on each of the side flanges 17. The piston shaft 26 is connected by a frangible pin 27 to a bracket 28 attached to each of the side flanges 17. A housing 29 is attached to each of the cylinder shafts 26, and interconnected by load transfer bar 30. Cylinders 31 are connected to a reservoir 32 via a regulating one way valve 33 as shown in Fig. 6 and d iagrammati cal l y in Fig. 3. On release, the leading edge of the belt wi l l move down and under the tyre 10. As the belt 20 moves under the wheel 10 the rod 18 moves down the tracks 19 until it impacts against load transfer bar 30 whereupon the tensile force in the belt will cause the frangible connections 23 and 27 to fail. The housing 11 will pivot towards the wheel 1.0 until it contacts area 40 of the tyre of the wheel 10. The pistons 26 in each of the two cylinders 31 will then begin to move downwards under the belt tension, allowing a section of unworn belt 20' to move under the tyre 10 as shown in Fig. 5. The rate of movement of the pistons is controlled by regulating valve 33.

There can also be included a time delay mechanism, for example a bypass bleed line (not shown), so that once the piston has moved a certain small distance it will be able to move relatively quickly to feed out extra belt.

In the embodiment shown in Figs. 9-17, the belt support member 40 is rigidly mounted to the vehicle frame 41 by way of the mounting member 42 and the angled support bracket 43. The belt support member 40 is al i gned so as to be in a substantially vertical position. Figs. 9, 10 and 11 show the belt 44 in its upper inoperative position.

The mounting member 42 and the angled support bracket 43 may be seen more clearly in Fig. 10. Fig. 10 shows the front elevation view of the belt support member 40 with the centre line of the belt 44 corresponding to the centre line of the inner dual wheel 46. Also, shown in Fig. 10 is the tumbling block 45 which is shown in Figs. 14, 15 and 16 in more detail.

When the belt 44 is in the upper, inoperative position as seen in Fig. 11, the tumbling block 45 is held adjacent to the top of the support member 40. The tumbling block 45 is held within guide tracks 47 by lugs 49 and the ends 48' of the rod 48 which in effect provide a pair of upper lugs.

These lugs 49 and rod ends 48' allow the tumbling block 45 to travel along the longitudinal guide tracks 47. The top of the belt 44 is attached to the rod 48 and prevents the belt 44 from being lowered until it is desired. The rod 48 is detachable to allow for replacement of the belt 44.

When the belt is released from the inoperative position the tumbling block 45 is caused to travel down the longitudinal guide tracks 47 until the lugs 49 abut the stops 50 at the base of the guide tracks 47, as is seen in Fig. 12.

At this time, and position, a small anticlockwise moment, about the lugs 49, is imparted to the tumbling block 45 by way of the director element 51 attached to the tumbling block, seen in more detail in Fig. 14. However, at this stage the tumbling block 45 is restrained from turning about the pivot lugs 49 by the sliding element 52, these sliding elements

52 being in the lowered closed position and therefore covering the opening

53 which is provided in the side of the guide tracks 47. These elements 52 and openings 53 comprise a gateway.

After a predetermined period the sliding elements 52 are raised and the rod ends 48' pass through the opening 53 as the tumbling block pivots about lugs 49 by way of the anticlockwise moment imparted by the director piece 51. This action is seen in Fig. 13, and as the tumbling block 45 rotates about the pivotting lugs 49 the effective length of the belt 44 is increased so as to allow a new section of the belt 44 to enter between the tyre 46 and the road surface to replace the belt which was used for the initial braking and, depending on the speed and load of the vehicle, may be substantially worn.

In a preferred embodiment, as seen in Fig. 17, the means by which the tumbling block 45 is lowered and the sliding element 52 is raised is achieved by way of a pneumatic cylinder 53, a flat spring 54 and pivotting side plates 55.

The tumbling block 45 is, (in its upper inoperative position) held in place by the pressure exerted on it by the cylinder 53 acting on spring 54. Upon activating the drop brake mechanism (which can be done from the vehicle cabin or automatically if the normal braking system fails), pressurized air is released from the cylinder 53, and the pressure on the spring 54, and, therefore the tumbling block 45 is released. The tumbling block 45 then travels down the guide tracks 47 and abuts at the stops 50.

After a predetermined period of time the cylinder 53 is repressurized by means of a timer controlled valve (not shown). Due to the absence of the tumbling block 45 (which is now at the bottom of the guide 47) the cylinder 53 is allowed to move through a full stroke whilst still acting upon the flat spring 54. The upper end of the spring 54 contacts the cross bar 56, which is between the pivot plates 55, and causes these pivot plates 55 to pivot about the pivot points 57. The tops of the sliding elements 52 are attached to rods 58 which are in turn attached to the adjacent side of the pivot plates 55, and as the plates 55 pivot about the point 57 the sliding elements 52 and rods 58 are caused to move longitudinally upwards.

The sliding elements 52 are thereby removed from covering the openings 53 in the rails 47 and the tumbling block 45 is permitted to rotate about the lugs 49 to release the extra length of belt 44.

The director element 51 is used to locate the line of action of the belt 44 so that when the gateway is opened the tension on the belt 44 will cause the block 45 to rotate anticlockwise about the lower lugs 49.

In a preferred embodiment the upper portion of the belt 44 is separated or pre-split along its centre plane to form a closed loop (Fig. 18B) and the belt is fitted to the rod 48 as shown in Fig. 18C.

As the lower end of the belt enters between the tyre 46 and the road surface the lower lugs 49 of the tumbling block abut the stops 50 at the base of the guide tracks. The force applied through the belt causes the frangible fixing 55 to fail, allowing the belt to effectively lengthen by a small amount (Fig. 18D) thereby reducing the shock loading between the lugs 49 and the stops 50.

The frangible fixing 55 may comprise one or more stud type fasteners, or row(s) of stitching which will also fail during the initial shock loading.

The belt is of a suitable reinforced rubber construction having the necessary degree of reinforcement to take the tension load applied thereto, and also having the necessary wear resistance when braking from high speeds with variable road surfaces. The belt in general may be in accordance with the construction commonly used in heavy duty conveyor belts as used in the carrying of rocks or ore. A tread pattern may be provided on the lower side to assist the performance of the belt in wet conditions.

There are a number of materials available which may be included in the construction of belts for particular design conditions where higher or lower rates of abrasion may be experienced. Such materials include carboxylated nitrile rubber, metals, and synthetic fibres.

In one embodiment the lower portion of the belt has somewhat thicker edge portions than the remainder of the belt which is substantially of uniform thickness throughout its width (see Fig. 1B). The belt is arranged so that as it is inserted between the wheel and the road surface, the edge portions of increased thickness are downwardly directed, and the weight of the vehicle on the belt when it is entered beneath the tyre will deflect the central portion of the belt downwardly so that there will be a slight upturn in the opposite edge portions of the belt below the wheel.

Furthermore, housing 11 may be modified as shown in Fig. 1C, numeral 11' indicating a shallower embodiment, with lower side flanges 17' and longitudinal runner strips 15' formed by, for example, turning over respective portions of side flanges 17'.

It will also be appreciated that whilst only two methods of feeding out an extra length of belt to compensate for wear during excessive braking have been described, it is also possible to provide alternate means. For example, the housing 11 can have interposed between it and the vehicle a hydraulic load transfer device so that when the rod 18 reaches the end of the tracks 19 the load transfer device will lower the housing or change its angle by a predetermined amount depending upon the tensile load on the belt. Alternately, the belt may have a small length at its rod 18 end coiled around the rod 18 and capable of being uncoiled when the belt tension exceeds a predetermined value.

Claims

1. A drop brake for a vehicle or trailer having on either side thereof at least one relatively wide wheel, or one dual or multiple wheel arrangement wherein at least two coaxial wheels are rigidly interconnected to rotate together, said drop brake comprising: a reinforced belt of suitable materi al of sufficient length to extend from a suitable point of connection on the vehicle to at least the point of intersection between the ground and said wheel (s), said brake being adapted to be positioned on at least one side of said vehicle or trailer; a support means for securing one end of the belt, and releasable holding means adapted to hold the belt in an inoperative position and to selectively release the belt so that the other end of said belt drops to enter beneath part of the relatively wide wheel or one only of said wheels of each dual wheel arrangement, or, if more than two wheels are involved in such an arrangement, a proportion of said wheels (not being all the wheels); said support means comprising: a housing adapted to be suspended from the vehicle forward of the axle of the wheel or wheels under which the belt is to be inserted in use, means securing the belt at or adjacent one end thereof within the housing, whereby the belt may move from an upper inoperative position to a lower operative position, said movement occurring in response to the release of the belt by the releasable holding means, guide means associated with said housing to limit lateral movement of the belt relative to the housing to maintain the centre line of the belt substantially in the mid radial plane of the wheel or wheels beneath which the belt is to be inserted.

2. The drop brake of claim 1 wherein said housing is pivotally connected at or adjacent its upper end to the vehicle and has means to restrain the housing from movement about the pivotal connection, said means being extendible or rupturable to allow the housing to pivot into contact with said tyre upon application of load due to takeup of the belt under the tyre, following release thereof.

3. The drop brake of claim 1 wherei n said housing is pivotally connected at or adjacent its upper end to the vehicle and has a frangible member restraining the housing from movement about the pivotal connection.

4. The drop brake of claim 1 wherein means are provided to feed additional belt under the wheel once the initial braking has occurred.

5. The drop brake of claim 4 wherein said means include means for applying a time delay before releasing said additional length of belt.

6. The drop brake of claim 1 wherein upon release of the belt the upper end thereof contacts a load transfer means before it reaches its lowest final operative position; said load transfer means gradually or discretely allowing the upper end of the belt to complete its travel to its lowest final operative position in response to the tensile force applied to said belt by the braking action.

7. The drop brake of claim 4 wherein the load transfer means comprises a hydraulically controlled mechanism to enable controlled extended release of said belt.

8. The drop brake of claim 7 wherein the hydraul i c mechanism is connected to a second frangi bl e member which holds said mechanism in its rest position; said second frangible member being ruptured once the force on said load transfer means exceeds the strength of said frangible member.

9. The drop brake of claim 1 wherein upon release of the belt the upper end thereof contacts the lower end of said housing; and a l oad transfer means interposed between the vehicle and the said housing in such manner that in response to the tensile force applied by the braking to the belt the load transfer means lowers said housing and thus feeds a further length of unused belt under said wheel (s).

10. A drop brake for a vehicle or trailer having on either side thereof at least one relatively wide wheel or a dual or multiple wheel arrangement wherein at least two coaxial wheels are rigidly interconnected to rotate together, said brake comprising: a reinforced belt of suitable material of sufficient length to extend from a suitable point of connection on the vehicle to at least the point of intersection between the ground and said wheel(s), said brake being adapted to be positioned on at least one side of sai d vehi cl e or trai l er , a support means for secur i ng one end of the be l t , and releasable holding means adapted to hold the belt in an i noperati ve position and to selectively release the belt so that the other end of said belt drops to enter beneath part of relatively wide wheel or one only of said wheels of each dual wheel arrangement, or, if more than two wheels are involved in such an arrangement, a proportion of said wheels (not being all the wheels), and means to release additional length of said belt after the initial release of said belt has been completed, in such a manner as to provide a fresh wear surface to be inserted between said road and said wheel(s).

11. The drop brake of claim 1 wherein the belt has at least one surface having a concave transverse cross-section.

12. A drop brake for a vehicle or trailer having on either side thereof at least one relatively wide wheel or a dual or multiple wheel arrangement wherein at least two coaxial wheels are rigidly interconnected to rotate together, said brake comprising: a reinforced belt of suitable material of sufficient length to extend from a support means mounted on the vehicle to at least the point of intersection between the ground and said wheel(s), said brake being adapted to be positioned on at least one side of said vehicle or trailer; said support means comprising: a housing adapted to be suspended from the vehicle forward of the axle of the wheel or wheels under which the belt is to be inserted when in use, releasable holding means securing the belt at or adjacent one end thereof within the housing, whereby the belt may move from an upper inoperative position to a lower operative position wherein the lower end of the belt is inserted between a tyre and the road surface, said movement occurring in response to the release of the belt by the releasable holding means, guide means associated with said housing to limit lateral movement of the belt relative to the housing to maintain the centre line of the belt substantially in the mid radial plane of the wheel or wheels beneath which the belt is to be inserted to release the belt so that the other end of said belt drops to enter beneath part of the relatively wide wheel or one only of said wheels of each dual wheel arrangement, or, if more than two wheels are involved in such an arrangement, a proportion of said wheels (not being all the wheels), and means to release additional length of said belt after the initial release of said belt has been completed, in such a manner as to provide a fresh wear surface to be inserted between said road and said wheel(s).

13. The brake of claim 12 wherein the housing is aligned in a substantially vertical position; the upper end of the belt being attached to a slidable tumbling block at a position above slide means which are part of the said tumbling block being adapted to slide within guides within said housing; said tumbling block being adapted to travel down the guides until it reaches a stop at which point the end of the belt is located under the wheel and after a predetermined time allow the tumbling block to rotate about said slide means to release an additional length of belt to pass under the wheel .

14. The brake of claim 13 wherein the housing extends downwardly to a level corresponding substantially to the centre line of the wheel or wheels.

15. The brake of claim 12 wherein the tumbling block is held in its upper, inoperative, position by clamping means comprising a ram controlled by a pressurized cylinder acting upon a flat spring, such that the tumbling block is released from the inoperative position by depressing action of the said cylinder, allowing the flat spring to move away from the tumbling block and allow it to drop downwardly along the guides.

16. The brake of claim 15 wherein the slide means of the tumbling block comprise lower lugs extending outwardly from the lower end of the tumbling block.

17. The brake of claim 16 wherein a further set of lugs extending outwardly from the upper end of the tumbling block which lugs also slide in the guides; and a gateway on one side of each of the guides which will allow the upper lugs on the tumbling block to pass through thereby pivoting the block about the lower lugs so as to release the additional length of belt once said gateways are opened.

18. The brake of claim 17 wherein the tumbling block is provided with a director element which will impart a small moment, about the lower lugs, to the tumbling block, so as to bias the block towards the gateways in the guide raiIs.

19. The brake of claim 18 wherein there is provided as the gate for each gateway, a sliding element which is in a lowered position so as to cover the said opening at one side of the guides when it is not desired that the belt be lengthened, which sliding element is raised at each gateway at a desired time to thereby allow the tumbling block to rotate about its lower lugs so as to lengthen the belt.

20. The brake of claim 19 wherein the means by which each sliding element is raised is achieved when the said cylinder is repressurized and allowed to complete a full return stroke, due to the absence of the tumbling block in its path, and thereby acts on the spring, the upper end of this spring in turn acting on a crossbar connecting the pivoting plates; each sliding element being attached to a rod which is in turn attached to the adjacent side of a pivoting plate, so that when the plate is caused to pivot due to the action of the cylinder and spring, the rod and therefore the respective sliding element will experience a longitudinal upward movement, uncovering its opening.

21. The brake of claim 20 wherein the cylinder is repressurized by means of a timer controlled valve.

22. The brake of claim 12 wherein the belt of the drop brake is of a width less than the tread width of a tyre under which it is to be located when inserted between the road surface and a wheel.

23. The brake of claim 13 wherein the attachement of the belt to the tumbling block is by means of at least two stages, the first stage being designed to fail on impact and the second or final stage being sufficient to withstand the full braking force of the vehicle.

24. The brake of claim 13 wherein the first stage of attachment is by means of frangible rivets.