GB2358446A - Deactivating a trailer brake during reversing - Google Patents

Abstract

A brake of a brake assembly 106 of a trailer is activated by fluid entering an inlet 120 of a valve block 118 and exiting through an outlet 124. Upon reversing the brake of the assembly 106 is momentarily partially applied to cause a bracket 100 on which the brake assembly is mounted to move against the bias of a spring 110. This causes a valve 130 to block fluid communication from the inlet 120, deactivating the brake. Any excess pressure remaining on the brakes which would otherwise cause the brakes to remain applied is relieved by a piston 142 moving away from the inlet 120 to cause the bracket 100 to pivot in an anticlockwise direction against the action of the spring 110. Alternatively, excess pressure may be relieved by an accumulator (50, fig 1), while the bracket may have two relatively rotatable parts (32,34, fig 2).

Description

2358446 Brake control mechanism The present invention relates to a brake

control mechanism for incorporation into the overrun system of a towable 5 vehicle such as a trailer or the like.

Such braking systems are typically arranged such that braking of the towing vehicle causes, via the towing linkage, a lateral force, arising from the inertia of the towed vehicle, to be transmitted to the trailer, this force then being utilised by a known operating mechanism to activate the trailer braking system.

However, when it is required to reverse the vehicle and trailer combination it is clearly disadvantageous to have such an operating mechanism as the trailer braking system would then be activated inappropriately. Various attempts have been made at solving this problem, including collapsible drum brakes (for example GB 2 053 391), and, as set out in GB 2 319 314, a control device for use with cable operated brakes. The former requires a substantial "roll-off" force to initiate collapse, and the latter is not suitable for fluid-operated braking systems.

The present invention seeks to address problems associated with known towable vehicle braking systems, including those problems referred to above.

According to a first aspect of the present invention there is provided a control mechanism for incorporation into the overrun braking system of a towable vehicle, said braking system including at least one brake which may be activated to effect braking of the vehicle, the control mechanism 2 having, when incorporated into the braking system, a frst mode in which the brake may be activated to effect bralil,-ig and a second mode in which the brake is rende-red substantially ineffective, and means for switching the S control mechanism between the first mode and the second mode.

It will be appreciated that when the terms ineffective,sl.-id inoperative are used they are to include situations whece the brake is substantially or temporarily ineffective Dr inoperative and vice versa.

Preferably, the means for switching the control mechai-i!:-,m is responsive to the direction of travel of the towabLe is vehicle, such that the control mechanism will be switc,Ad from the first mode to the second mode during reversing)f the vehicle, f or instance as a. result of part J1 activation of a brake. The control mechanism may e arranged to be repeatedly switched to the second mode u:- Mn partial activation of a brake during reversing.

Preferably, the control mechanism is adapted to 1e connected to the fluid (hydraulic or pneumatic) brak.L.1g system of the towable vehicle, and has means, preferEtl)'y activated by reversing the tewable vehicle,:- r temporarily relieving fluid pressure in the braking syst. 1 m which would otherwise effect braking via said braL.E, thereby rendering the brake substantially inactive, (r example during reversing.

Conveniently this is achieved by the provision of a reverse accumulator which is, in use, may be connected to the braking system by means of the control mechanism:.rd 1 3 is brought into fluid communication with the braking system by reversing the towable vehicle. This acts as a fluid reservoir by means of which pressure applied from the braking system operating mechanism may be accommodated 5 during reversing.

Preferably, the reverse accumulator has resilient means whereby fluid in the accumulator is at least partially returned to the braking system when reversing is completed for instance when the towable vehicle is once again travelling in the forward direction.

Preferably, the control mechanism comprises a valve arrangement to be disposed between and for fluid connection to the braking system operating mechanism and said at least one brake via at least one f luid inlet and at least one fluid outlet means provided in the valve arrangement, and the valve arrangement is provided with switch means responsive to the direction of travel of the towable vehicle to determine whether or not fluid pressure applied to the valve arrangement inlet is transmitted, via the valve block outlet, to the brake.

Preferably, the valve block has two outlets - a first outlet for connection to the brake, and a second outlet for connection to the reverse accumulator, and the switch means comprises a pair of valves adapted to automatically close the second outlet and open the first outlet during forward movement of the towable vehicle and to automatically open the second outlet and close the first outlet during reversing.

4 Conveniently, said valves are valve plungers which h:Rve protruding ends adapted to cooperate with the b:r:i.e assembly to effect said opening and closing. Pre f e ra). _y the valve plungers are urged by resilient means into thAr respective open and closed positio.lis when released L-Lm cooperative engagement with the brake assembly.

The control means may be arranged to switch from the to the second mode upon movement of a switch meii-L)tr effected by at least partial engagement of the brake n reversing. The brake may be movable with the swj-,. h member, for instance by being connected thereto. 11 1 e switch member may. be arranged to move pivotally,: c r instance about the axis of rotation of a wheel that tle is brake is associated with. The pivotal movement of t 1 e switch member may, be arranged to be translated ii:to translational movement to effect the switch from the fii,,:t to the second mode, Movement of the switch member on reversing may be arrancred to close a valve connecting fluid pressure from the brAe operating member to the brake.

The control mechanism may include means to at lezst partially relieve fluid pressure applied to a brake wl-.en in the second mode, for instance by causing movement 3f the switch member when in the second mode.

The switch member may be arranged to be biased towards t:i..-le position in which it is in the first mode by resilien: means, such as spr- ing means. The resilient means may A arranged to afford resistance to fluid pressure applied A the brake in the second mode.

The switch member may comprise a piston. The operative surface of the piston may be in fluid communication with fluid that is arranged to activate the brake in the first mode and also with fluid in communication with the brake in the second mode. The operating area of the piston may be greater than the operating area of a valve that the piston is arranged to cause to open and close when moving the mechanism between the first and second modes.

The control mechanism may be arranged to be mounted in the region of the hub area of a wheel including the brake.

The control mechanism may be arranged to switch at least is two brakes from the first mode to the second mode.

According to a second aspect of the present invention there is provided a control mechanism for incorporation into the overrun braking system of a towable vehicle, the braking system having brake actuation means coupled to at least one brake to effect the braking of the vehicle whilst the vehicle is being towed in the forward direction, the control mechanism including means for uncoupling the brake actuation means from said at least one brake in response to initial braking of the vehicle whilst it is being reversed.

By "uncoupling" is meant any means by which the actuating force deriving from the brake actuation means is temporarily diverted or otherwise rendered ineffective or largely ineffective in its effect on the brake, during reversing of the vehicle.

6 According to a th-rd aspect of the present invention t}-ere is provided a method of braking a towable veh.lcle comprising actuating at least one brake of the towzble vehicle to effect braking thereof whereby said actuation of said at least one brake discontinues braking of the vehicle during reversing thereof.

According to a fourth aspect of the present inventi:)n there is provided a method of operating the ove3:rjn braking system of a towable vehicle, the method inclu,-i-ig providing in said braking system a control mechari3m having a first mode in which at least one brake of Ale braking system may be activated to effect braking of Ale vehicle and a second mode in which the brake is rendE-rd ineffective, the method including the step of switchi-iq the control mechanism between first mode and the se,.,-D-id mode.

According to a fifth aspect of the present invention the e is provided an overrun braking system for fittina a towable vehicle incorporating i control mecharll m according to the first or second aspect of the pre::3-lt invention.

According to a s:lx,--h aspect of the present invention the-e is provided a towable vehicle fitted with an ove:t---ln braking system having a control mechanism according to _he first or second aspect of the present invention.

Any feature of any aspect of any invention or embodiTri7. t described herein may be combined with any feature of:i y aspect of any ol--',.ier invention or embodiment descr.L) d herein.

7 An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a towable braking system having incorporated therein a brake control mechanism according to the present invention, Figure 2 is a detailed diagram of the brake control mechanism fitted to a disc on a wheel hub assembly, Figure 3 is a plan view of an overrun coupling adapted to cooperate with the brake control mechanism of the present invention; Figure 4 is a side view of the arrangement shown in figure 3; Figure 5 is a side view of an alternative form of brake control; Figure 6 is a view similar to Figure 5 with the direction of travel being in the reverse direction; Figure 7 is an exploded view of the control valve used in Figures 4 to 6; Figures 8 and 9 are side and end views respectively of the control valve shown in Figure 7 in an exploded position, and 8 Figure 10 is a schematic diagram showing the con,-rol circuit for the trailer brakes.

Referring to figure 1 of the drawi.-lgs, the brake con,Liol mechanism 10 of the present invention is incorporated:irto the braking system 20 of a towable vehicle. HydraLlic conduit 14 connects the brake callipers 12, 121 Aith control mechanism 10 via T-connector 11, and hydrai-lic conduit 16 connects to the control mechanism 10 with the master cylinder 22 (the braking system opera:ing mechanism) via overload protector 24.

One of the callipers 12 is illustrated in more detail in figure 2, which shows the calliper 12 mounted to a f:ixed is part of a wheel hub assembly which has mounted theret--:) a rotating disc 30 The calliper bracket 12 is free to pivot around poinb A on the brake support bracket 32.

Control mechanism 10 is mounted on support bracket 34 which is allowed to pivot at point A, but the bracket 34 is limited in its degree of movement by a "forward and reverse" stop bolt 36.

The calliper 12 and control mechanism 10 are, du:.,i g forward motion of the towable vehicle, held in the forsard direction by the action of "forward mode- spring 38. hen the towable vehicle is being towed in the forAard direction, the calliper 12 and all =-issociated brackets are butted up against forward and reverse stop bolt 36. In this position, hydraulic fluid from the master cylinde.-- 22 simply enters and leaves the control mechanism which in this "first" mode has no effect on the braking system and the brake is therefore engaged with disc 30, whereas hen 9 the towed vehicle is being reversed any pressure of the brake pad 15 on the disc 30 will cause the calliper 12 and the bracket 34 to pivot around point A in the opposite direction indicated by arrow "REW' until the bracket 34 engages switch means 43 of the control mechanism which relieves the hydraulic pressure applied to the calliper, thus allowing the disc 30 to rotate freely whilst reversing (,,the second model,). The calliper 12 and the bracket 34 are continuously biased in towards the IlFWDII position by the spring 38. Consequently once the hydraulic pressure is relieved by movement to the "REW' position, the spring 34 will move the mechanism in the opposite direction until the pressure is no longer relieved. The brakes then lightly engage the discs again to cause return movement to the REV position. This repeated light engagement of the brake pads with the discs is not noticeable by an operator and has no material braking effect on the trailer.

After reversing, once the vehicle is again being towed forward, the support bracket 34 and calliper 12 rotates forward under action of spring 38 in the direction indicated by arrow "FWW, pivoting around A until the bracket 34 engages with switch means 41 to thereby allow the pressure to be once again applied to the brake calliper 12.

Figure 3 in combination with figure 1 details how this selective disabling of the brake of the towable vehicle is achieved.

The control mechanism comprises a valve block 40 having inlet port 42, first outlet port 44 and second outlet port 45. Two valve plungers comprising a forward mode plurcer 41 and a reverse mode plunger 43 are disposed with= the valve block to selectively open an. d close outlets 44, 45 respectively. During forward motion, forward mode plu:-.cer 41 is urged by spring 38 against t_he action of sp:ting means 41a into the "open" position in which fluid ente.ting the valve block -,,-ia inlet 42 flows freely past the Lall 41b out of first outlet 44 to the trake callipers 12, 12' via hydraulic pipe 14 and T connector 11. At this t.Te, the reverse mode plunger 43 is urged by spring means 43a into the "closed" position, isolating reverse accumul-ilDr 50 from the braking system.

However, when the towable vehicle is reversed the rev,:.c-3e mode plunger 43 is caused to be pushed in the direc-L)n shown by the "REV" arrow thereby opening outlet 45 Aid forward mode plunger 41 is released and therefore, ur3 d by the action of spring means 41a, the ball 41b seals i d is held in that position by the pressure in the line L. 20 In this configuration any fluid pressure in the brakes iLd line 14 is relieved by the fluid flowing into --Le reservoir of the accumulator SC thereby prevent::-iig engagement of the brake with the disc. once reversing s completed and the vehicle is again being towed forward.,, 25 the spring means 51 pushes the piston in the reservo: r back to cause the f luid to f low back into the brak: 1 9 system, the valve 43 plunger closes, the valve plunger zi opens and the brakes are once again enabled. 30 As can be seen in Eigures 2 and 3, support bracket 34 lis arms 34a, and 34b which selectively engage with tle reverse plunger 43 and forward plunger 41 upon pivoting cf the calliper 12 and bracket 34 in the appropriate direction.

Figures 3 and 4 illustrate an overrun coupling 52 which 5 contains a sliding member controlled by an internal damper. During forward motion, when the coupling device 52 receives an input force from the towing vehicle the brake actuation screw 54 strikes a brake link 56 which in turn puts stroke into the master cylinder 22 thereby transmitting fluid to the valve block 40, the system being protected by means of overload limiter 24. An optional test gauge 25 may be associated with the overload protector.

is The embodiment referred to in Figures 5 to 10 will now be described.

A bracket 100 is pivotally mounted about the axis 102 of the brake by engaging with the outside of the axle housing 104. Mounted on the bracket 100 is the brake assembly 106 containing the brake pads that are able to engage with the rotatable disc 108 to effect braking of the trailer.

The bracket 100 is biased in the anticlockwise direction by a compression spring 110. The spring acts to urge an arm 112 that is constrained to move with the bracket 100 away from a rotatably fixed mounting 104.

In the forwards direction of movement, the wheel rotates in a clockwise direction, as shown by arrow 116 and the bracket 100 is in the position shown in Figure 5. In that position hydraulic brake fluid is supplied to a rotationally fixed control block 118 through an inlet 120.

12 That fluid press-,-ire is able to be transmitted thr(.ugh respective outlets 122 and 124 in the block 118 to Llie nearside and o.Ef.,.--:.Lde brake callipers 126 and 128 show..-i in Figure 10.

A valve 130, shown in details in F--gures 7 to 9, is 1,eld open to allow the fluid communication from the inlet 120 to the outlets - 22 and 124. The valve 130 is bicised downwardly by a spring 132 to urge a. sealing portion L34 into sealing engagement with an axially facing suri-:5.,-e defined at the end of a reduced diameter bore 136 in inlet 120. The valve 130 includes a projection 138 at its innermost position, projects beyond the inlet L20 into an enlarged diameter cylinder 140.

is A piston 142 is reciprocally mounted in the cylinder -1 2 In the forwards direction of movement, the piston is u:,-,d upwardly in the cylinder such that the top of the cylinier abuts the projection 138 to hold the valve 130 ol.:)ili, against the bias of the spring 132. Thus the inlet 12C _s opened to the ouLlets 122 and 12,1 and the brakes i-e rendered operative.

The bracket 100 Is connected to the piston 142 by a Ad 144 and a pusher 146. The rod 144 is secured to Ae bracket 100 by a nut 148. The pusher comprises a 3 iib shaft having upper and lower semi spherical ends. Tli,:., e ends rest in corresponding recesses 147 and 148 in.lie facing parts of the pusher 144 and piston 30 respectively. Consequently, rotational movement of..1Le bracket 100 is translated into linear movement of 1 Ae piston by the 3tLil,.) shaft rocking a]:)(--)ut the recesses '7 and 148.

A spring 150 acts between the rod 144 and the piston 142 to urge the parts away from each other. The spring 150 and the pusher 146 are largely located with a hollowed portion of the cylinder and the spring and pusher together with the exposed portion of the piston are protected by a rubber boot 152. An annular seal 154 of square crosssection seals the piston in the cylinder.

When a trailer is being reversed, the brake pads will lightly engage the disc to cause the bracket 100 to move, against the action of the spring 110, in an anticlockwise direction, to the position shown in Figure 6. This allows the piston to move away from the inlet 120 under the is hydraulic pressure therein to cause the valve sealing portion 134 to seal the inlet 120 from the outlets 122 and 124.

Any pressure in the braking system that may tend to hold the brakes against the pads is able to be relieved by that pressure urging the piston 144 yet further away from the inlet. That movement of the piston causes further anticlockwise movement of the bracket against the action of the springs 110 and 150. Thus smooth pressure relief is able to be obtained. In practice, the bracket 100 is able to rotate through a maximum of 50 from the "valve close& position but is designed to move through 3 or 40 to accommodate the fluid expansion to relieve the brake pressure.

The spring 110 is constantly urging the bracket back in the clockwise direction to open the valve. As the bracket returns, the valve 130 may be momentarily opened such that 14 the brakes are applied albeit momentarily and lightly s-it the reverse movement of the bracket caused by t-- il L t engagement immediately releases the brakes as descrj-5JE!d above.

The spring 150 helps smooth the movement of the pusher L 6 and assists in the., quick return of Ihe piston to open Ae valve.

When reversing and braking, upon release of the brakinc-f)f the towing vehicle, the pressure in the system reduces id the piston is urged upwardly in the cylinder to open Ae valve and ensure that the brakes will be acted upon on Ae next application of the brakes, by the vehicle advan(:.-:ig is or reversing.

The control circuit for the embodiment described Figures 5 to 9 is illustrated, schematically, in Fic A-e 10, with the control block 118 being shown separated f Arn the callipers 1.26 and 128. The circuit upstream of Ae control block 1.18 is conventional and comprises a mas fr cylinder 152 that exerts pressure on the fluid to ca.t,e braking, an optional test gauge 154 and an overl.,)id protector 156.

The reader's attention is directed to all papers titd documents which are filed concurrently with or previous lo this specification in connection with this application Ad which are open to public inspection with t": t: S P specification, and the contents of all such papers iad documents are incorporated herein by reference. 1 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 extend 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.

16

Claims (30)

1. A control meclianism for incorporation into the ove,-r-in braking system of a towable vehicle, the system including at least one brake which may be activated to ef 1:,e:t braking of the vehicle, the control mechanism having, ien incorporated into the braking system, a first mode, in which the brake r,.iay be activated to effect braking, aril a second mode in which the brake is rendered substantialLy ineffective, and means for switchincl the control mecharii3m between the first mode and the second mode.

2. A mechanism aS claimed in Claim 1 in which the m,ca.-is for switching the control mechanism is responsive to Aie is direction of travel of the towable vehicle, such that Aie control mechanism is arranged to be switched from Aie first mode to the second mode during reversing of ---ie vehicle.

3. A mechanism as claimed in Claim 2 in which the con..'cDl mechanism is arranged to be switched from the first m:)1e to the second mode during reversing of the vehicle Et: a result of partial. activation of a brake.

4. A mechanism as claimed in Claim 3 in which the conti- 1 mechanism is arranged to be switched from the first mAe to the second mode during reversing of the vehicle a result of repeated partial activation of the brake.

5. A mechanism as claimed in any preceding claim _n which the control. mechanism is adapted to be connectecl to the fluid braking system of a towable vehicle.

17

6. A mechanism as claimed in Claim 5 including means for temporarily relieving fluid pressure in the braking system from the brake that would otherwise effect braking of the brake in the second mode.

7. A mechanism as claimed in any preceding claim including a switch member arranged to effect the switch from the first to the second mode upon at least partial engagement of the brake on reversing.

8. A mechanism as claimed in Claim 7 in which the brake is movable with the switch member.

9. A mechanism as claimed in Claim 7 or 8 in which the 15 switch member is pivotally movable.

10. A mechanism as claimed in Claim 9 in which the pivotal movement is arranged to be about the axis of rotation of a wheel that the brake is associated with.

11. A mechanism as claimed in Claim 9 or 10 in which pivotal movement of the switch member is arranged to be translated into translational movement to effect the switch from the first to the second mode.

12. An arrangement as claimed in any of Claims 7 to 12 in which movement of the switch member on reversing is arranged to close the valve connecting fluid pressure from the brake operating member to the brake.

13. A mechanism as claimed in any of Claims 7 to 12 including means to at least partially relieve fluid pressure applied to the brake when in the second mode.

18

14. A mechanism as, claimed in Claim 13 when dependent i-F-on any of Claims 7 to 11 in which the switch member is arranged to move, in the second mode, to at least partially remove fluid pressure applied to the brake.

15. A mechanism as claimed in any of Claims 7 to 1,1 in which the switch member is biased r-owards the first iicde by resilient means.

16. A mechanism -as claimed in Claim 15 in which the resilient means comprises spring mea.ns.

17. A mechanism as claimed in Claim 15 or 16,.en dependent upon Claim 14 in which the resilient means are arranged to afford resistance to fluid pressure actin..- on the brake in the second mode.

18. A mechanism as claimed in any of Claims 7 to 1-7 in which the switch member comprises a piston.

19. A mechanism as claimed in Claim 18 in which the operative surface of the piston is connected to fluid.,.at is arranged to activate the brake in the first mode an(- to fluid in communication with the brake in the second mo,.!,-.

20. A mechanism as claimed in Claim.18 or 19 in which the operating area of the piston is greater than the opera.,ing area of a valve that the piston is arranged to cause to open and close wlen moving between the first and se(--cnd modes.

19

21. A mechanism as claimed in any preceding claim in which the control mechanism is arranged to be mounted in the hub area of a wheel containing the brake.

22. A mechanism as claimed in any preceding claim in which one control mechanism is arranged to switch two brakes between the first and second mode.

23. A control mechanism substantially as herein described, with reference to, and as shown in any of Figures 1 to 4 or any of Figures 5 to 10.

24. A method of controlling the operation of a brake of a towable vehicle comprising switching the brake from a first mode, in which the brake is operative when the vehicle is travelling forwardly and a second mode in which the brake is rendered substantially inoperative in the second mode.

25. A method as claimed in Claim 24 in which the operation of the brake from the first mode to the second mode is caused by a switch being activated when the brake is at least partially applied when reversing.

26. A method as claimed in Claim 25 comprising repeatedly at least partially applying the brake when reversing to maintain or repeatedly return the brake to the second mode.

27. A method as claimed in any of Claims 24 to 26 comprising at least partially relieving the fluid on the brake when in the second mode.

28. A method as claimed in Claim 27 comprising at 1EzA;t partially relieving the pressure on the brake in -ie second mode witli the same means that are arranged. --o switch the operation of the brake from the first mode --o 5 the second mode.

29. A method as claimed in any of Claims 24 to 28 comprising switching to the first mode when braking c, - a towing vehicle in reverse is halted.

30. A method of controlling the operation of a brake c-)E a towable vehicle substantially as herein described jjl--h ref erence to and Ei.s shown in any of 17iqures 1 to 4 or 3. -iy of Figures 6 to 10.