GB2319314A

GB2319314A - A trailer braking system

Info

Publication number: GB2319314A
Application number: GB9622894A
Authority: GB
Inventors: Philip Andrew Hanson
Original assignee: Bradley Doublelock Ltd
Current assignee: Bradley Doublelock Ltd
Priority date: 1996-11-02
Filing date: 1996-11-02
Publication date: 1998-05-20
Anticipated expiration: 2016-11-02
Also published as: GB2319314B; GB9622894D0; DE19748230A1

Abstract

A trailer comprises wheels 2, brakes 4, Bowden cables 6 and a linkage 8 which extends between cables 6 and an overrun device 10. The linkage 8 includes a telescopic strut 14 which is movable in dependence upon conditions of wheel 4a, sensed by an electronic sensor 22. Linkage 30 extending to the handbrake on the tractor is connected between strut 14 and the brakes 4. The strut is initially in its collapsed state. When the trailer is decelerated on a downward incline, the overrun device actuates the brakes, and, when sensor 22 senses that the wheels are stationary a signal releases the brakes by extending the strut. In an alternative arrangement, the brakes are released when the sensor senses reverse movement of the trailer. In a further arrangement, which may be combined with the first or second arrangement, the brakes are released when the sensor senses "lock up" of the brakes.

Description

2319314 TOWABLE VEHICLE AND BRAKING SYSTEM THEREFOR This invention relates

to a towable vehicle and a braking system therefor and particularly, although not exclusively, relates to a braking system for a trailer.

Known braking systems for trailers include so-called "overrun brakes" on the trailer. Overrun brakes include an overrun linkage arranged to be operated automatically so as to reduce the speed of the trailer in a Controlled manner should the towing vehicle decelerate. one problem associated with overrun brakes is that the brakes also tend to operate automatically when the trailer is reversed. Solutions to this problem include the provision is of a means for rendering the overrun brakes ineffective during reversing of the trailer. For example, GB 2 053 391 and EP 0 253 463 provide collapsible reversing drum brakes having collapsing mechanisms between opposing ends of a pair of brake shoes, the mechanisms being arranged to reduce the distance between the brake shoes during reversing in order to reduce or eliminate their braking effect on the brake drum.

Known collapsible drum brakes tend not to be simple to manufacture. Also, the collapsing mechanisms of such brakes often require a substantial "roll-off" force by the towing vehicle in order to initiate collapse. Furthermore, after collapse with the trailer reversing, the force required to achieve the necessary brake torque to stop the trailer may be about twice the necessary brake torque to stop the trailer when it is moving in the forward direction, since the trailer's brake shoes are spaced further from-the brake drum when in the collapsed state. Additionally, with collapsing drum brakes, the handbrake travel required in a parking condition of the trailer may - 2 be about twice the travel of the overrun linkage during overrun braking of the trailer when travelling in the forward direction.

It is an object of the present invention to address problems associated with known braking systems.

According to a first aspect of the present invention, there is provided a towable vehicle comprising:

a wheel; brake means for braking the wheel; brake control means for controlling said brake means; linkage means between said brake means and said brake control means for transmitting a braking force therebetween; extender means for adjusting the length of said linkage means; wherein a sensor means is associated with said wheel and is arranged to sense a predetermined condition of the wheel, said extender means being controllable in dependence upon the condition sensed.

Said brake control means is preferably arranged to control the brake means, suitably automatically, when the trailer decelerates. Said brake control means is preferably an overrun device.

Said linkage means may include a cable, for example a Bowden cablef which extends between the brake control means and the brake.

Said extender means is preferably an integral part of said linkage means. For example, said extender means may be directly connected to a cable of the. linkage means.

Said extender means is preferably elongate. Said extender means preferably has f irst and second parts which are spaced apart. The distance between said first and second parts is preferably arranged to be adjusted. The. f irst and second parts are preferably arranged to be spaced apart a first distance or spaced apart a second distance, wherein said f irst distance is less than said second distance. When the first and second parts are spaced apart by said first distance, the effective length of said linkage means is suitably less than when the first and second parts are spaced apart by said second distance. Thus, when spaced apart by said first distance, the tension of said linkage means may be greater than the tension when the first and second parts are spaced apart by said second distance.

Said extender means is preferably elongate. Said first and second parts are preferably linearly movable relative to one another. Said extender means is preferably a telescopic member.

Parking brake means, suitably user operable by means of a handbrake, is preferably provided. said parking brake means is preferably connected to said linkage means. Said parking brake means is preferably connected to said linkage means at a position downstream of said extender means. Thus, preferably, adjustment of the length of the linkage means does not affect operation of said parking brake means.

Said sensor means is preferably arranged to sense movement of the wheel. Said sensor means may be arranged to initiate said extender means to adjust the length of the linkage means in dependence upon whether or not the wheel is rotating and/or in dependence upon the-direction of rotation of the wheel.

According to a second aspect of the present invention, there is provided a braking system for a towable vehicle, the braking system comprising:

a brake means for braking a wheel of a towable vehicle; a brake control means for controlling operation of said brake means; linkage means for transmitting a braking force between the brake means and the brake control means; extender means for adjusting the length of the linkage means; and sensor means for sensing a predetermined condition of a wheel of the towable vehicle and for controlling said extender means in dependence upon the condition sensed.

According to a third aspect of the present invention, there is provided a method of controlling braking in a braking system of a towable vehicle, the method comprising:

arranging a brake means to be operable on a wheel of the towable vehicle; providing a brake control means for controlling operation of said brake means; providing linkage means for transmitting a braking force between the brake means and the brake control means; providing an extender means for adjusting the length of the linkage means; providing a sensor means for sensing a predetermined condition of a wheel of the towable vehicle and for controlling said extender means in dependence upon the condition sensed.

Specific embodiments of the invention will now be described, by way of example, with reference to the Figure which is a schematic representation of a braking system.

Referring to the Figure, there is shown two wheels 2 of a trailer provided with a braking system according to the present invention. A respecti ve brake 4a, 4b is provided for each wheel 2. The brakes 4 are connected to respective Bowden cables 6 which are, in turn, connected to a linkage 8 which extends between the Bowden cables 6 and an overrun device 10 of known type.

The linkage 8 includes a first linkage part 12, directly connected at one end to the overrun device 10 and at its opposite end to one end of an extendible strut 14 of the linkage. The other end of the extendible strut 14 is directly connected to one end of a second linkage part 16. The other end of the second linkage part is connected, by means of a joining member 20, to the Bowden cables 6.

The extendible strut 14 is suitably a telescopic strut which may be selectively arranged in a collapsed (minimum length) state or an extended (maximum length) state, as described further below.

An electronic sensor 22 is positioned adjacent wheel 4a and is arranged to sense certain predetermined conditions of the wheel 4a, for example, whether the wheel is rotating or not; and whether, if the wheel is rotating, it is rotating in a forward or reverse direction. The sensor 22 is linked by a wire 26 to the extendible strut 14 and is arranged to initiate adjustment of the. length of the strut 14 in dependence upon the condition it senses.

One end of a handbrake linkage 30 is connected to the second linkage part 16. At its other end, the handbrake linkage 30 is connected to a handbrake (not shown).

The braking system of the, trailer may function as described below. In each of the embodiments described, the extendible strut 14 is initially in a collapsed (minimum length state), for example when the trailer is travelling in the forward direction.

In a first embodiment, the trailer may be decelerated and subsequently stopped on a downward incline. During forward travel and deceleration of the trailer the extendible strut 14 is in a collapsed (minimum length) state. During the deceleration process, the overrun device 10 causes the brakes 4 to be activated via linkage 8 and Bowden cables 6. once the trailer has stopped, the sensor 22 senses that the wheels (and, therefore, the trailer) is are static and will initiate a signal to release the brakes by causing extendible strut 14 to extend to its extended (maximum length state), thereby increasing the overall length of the linkage 8 and releasing any tension between the overrun device 10 and the brakes 4. The trailer can then easily be, for example, reversed up the incline, if desired. In contrast, reversing up a downward incline may be relatively dif f icult in the case of a trailer fitted with known collapsible drum brakes.

Thus, in the first embodiment, the sensor 22 need only be arranged to sense whether the wheels 4 are rotating or not and initiate the extension of the strut 14 when the wheels are not rotating.

In a second embodiment, the trailer may be stopped on a downward incline as in the first embodiment. In this case, however, means is provided for facilitating a small amount of movement of the wheels 2, in thd reverse direction. Accordingly, as the towing vehicle starts to reverse, the sensor 22 is arranged to sense this movement and initiate a signal to release the brakes 4 by causing extendible strut 14 to extend (to its maximum length state), as in the first embodiment.

Thus, in the second embodiment,, the trailer can easily be reversed once the sensor 22 has caused extension of the strut 14.

In a third embodiment, the sensor 22 is arranged to sense whether the brakes "lock up" during towing which is a problem that often occurs on trailers with trailing arm suspensions. should the sensor 22 sense locking-up of the brakes, it will initiate a signal to release the brakes 4 by causing the extendible strut 14 to extend (to its maximum length state) as described above.

The arrangement of the third embodiment may be combined with the arrangement of the first and second embodiments, if desired.

It should be noted that, as a consequence of the position of connection of the handbrake linkage 30 to the linkage 8 (i.e. downstream of the extendible strut 14), the operation of handbrake linkage 30 is unaffected irrespective of whether the strut is in an extended (maximum length state) or collapsed state (minimum length state). Thus, the travel of the handbrake linkage 30 to apply brakes 4 is the same whether the trailer is on an incline or on level ground.

It should now be appreciated that the braking system described herein may replace previously proposed collapsible reversing drum brakes.

The reader's attention is.directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such. features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one.. or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

9

Claims

CLAIMS 1. A towable vehicle comprising: a wheel; 5 a brake means for

braking the wheel; a brake control means for controlling said brake means; linkage means between said brake means and said brake control means for transmitting a braking force therebetween; extender means for adjusting the length of said linkage means; wherein a sensor means is associated with said wheel and is arranged to sense a predetermined condition of the wheel, said extender means being controllable in dependence upon the condition sensed.
2. A vehicle according to Claim 1, wherein said brake control means is an overrun device.
3. A vehicle according to Claim 1 or Claim 2, wherein said linkage means includes a cable which extends between the brake control means and the brake.
4. A vehicle according to any preceding claim, wherein said extender means is an integral part of said linkage means and includes first and second spaced apart parts, wherein the distance between said first and second parts is arranged to be adjusted.
5. A vehicle according to Claim 4, wherein the spacing between said first and second parts is adjustable to adjust the effective length of the linkage means.
6. A vehicle according to any preceding claim, wherein said extender means is a telescopic member.
7. A vehicle according to any preceding claim, wherein said parking brake means is connected to said linkage means at a position downstream of said extender means.
8. A vehicle according to any preceding claim, wherein said sensor means is arranged to sense movement of the wheel and is arranged to initiate said extender means to adjust the length of the linkage means in dependence upon whether or not the wheel is rotating and/or in dependence upon the direction of rotation of the wheel.
9. A braking system for a towable vehicle, the braking system comprising:

a brake means for braking a wheel of a towable vehicle; a brake control means for controlling operation of said brake means; linkage means for transmitting a braking force between the brake means and the brake control means; extender means for adjusting the length of the linkage means; and sensor means for sensing a predetermined condition of a wheel of the towable vehicle and for controlling said extender means in dependence upon the condition sensed.
10. A method of controlling braking in a braking system of a towable vehicle, the method comprising:

arranging a brake means to be operable on a wheel of the towable vehicle; providing a brake control means for controlling operation of said brake means; providing linkage means for transmitting a braking force between the brake means and the brake control means; providing an extender means for adjusting the length of the linkage means; providing a sensor means for sensing a predetermined condition of a wheel of the towable vehicle and for controlling said extender means in dependence upon the condition sensed.
11. A vehicle substantially as hereinbefore described with reference to the figure.
12. A braking system substantially as hereinbefore described with reference to the figure.
13. A method substantially as hereinbef ore described with reference to the figure.