GB2516654A

GB2516654A - Axle clamping system for deflection sensing beam

Info

Publication number: GB2516654A
Application number: GB201313474A
Authority: GB
Inventors: Robert Clive Browning Davis
Original assignee: Ifor Williams Trailers Ltd
Current assignee: Ifor Williams Trailers Ltd
Priority date: 2013-07-29
Filing date: 2013-07-29
Publication date: 2015-02-04
Anticipated expiration: 2033-07-29
Also published as: GB201313474D0; GB2516654B

Abstract

A vehicle, such as a trailer with a fluid actuated braking system, is provided with a spring suspension arrangement providing axle load equalisation and with a spring deflection sensing beam to modulate braking force applied by those brakes. The beam is preferably in two parts 41, 42 and is mounted between midpoints of the front and rear axles 16, 18. The outer ends of the beam parts 41, 42 are mounted to the axle housings by means of clamping bracket assemblies 46, 48 which include pairs of resilient elements 47, preferably cylindrical in form, between which the beam end regions are engaged to allow for movement of the outer ends of the beam parts 41, 42 relative to the axle housings which will inevitably occur in a vehicle travelling over a variety of rough and uneven ground surfaces. A linkage 44 extends upwards from its first end 51 which is mounted at the midpoint of the beam, preferably between the two beam parts 41, 42, to its second end which is pivotally mounted to a lever 45 mounted upon the vehicle chassis. The lever 45 has one end 56 operatively connected to a 'load' sensing valve (not shown) which controls the fluid supplied to the brakes. In use, deflection of suspension springs 11, 12, 13, 14 mounting the axles 16, 18, which is equalised by means of rockers 30 and is dependent on the overall loading upon the vehicle axles causes substantially vertical displacement of the linkage, which moves an end of the lever 45 by a greater distance than the spring deflection so to control the sensing valve to appropriately modify supply of fluid to the brakes for required braking force at that vehicle weight.

Description

Axle clamping system for deflection sensing beam

TECHNICAL FIELD

[0001] This invention relates to a vehicle, particularly but not exclusively an agricultural trailer, having a spring suspension arrangement providing axle load equalisation and a load sensing mechanism.

BACKGROUND

[0002] The present invention has arisen in the context of expected legislative changes to increase the speed limit for agricultural tractors and trailers from 32 km/h (20 mph) to 40 or km/h. An increase in the weight limit is also proposed. This will require a commensurate improvement in the suspension and braking systems for such vehicles.

[0003] One aspect of better braking is likely to be a requirement to achieve the minimum 0.45g retardation currently specified for road-going articulated vehicles. Currently farm trailers are only required to achieve 0.25g retardation. The increase to the higher figure has major implications for farm trailers because if the retardation exceeds the available coefficient of friction between the tyres and the ground then the wheels will lock and the trailer then loses directional stability. By their very nature farm trailers will often be used in situations where the coefficient of friction is much lower than on normal highways so it is particularly important that all elements of a farm trailer braking system, if it is specified to achieve 0.45g minimum retardation, are configured so as to deliver the maximum possible adhesion utilization and thereby delay wheel locking as much as possible.

[0004] Suspension currently used on some farm trailers is rather primitive and may comprise a rigid pivoted beam with a stub axle at each end. Also known, and with good off-road performance is so-called "2-spring" suspension, where large springs, centrally pivoted, are mounted between the axles. These tend to result in poor braking performance, with load concentrated on the front axle and the back axle tending to lift. The best option is therefore "4-spring" suspension, as used for on-road heavy goods vehicles (HGV) where separate springs are provided each side of each axle.

[0005] One well known feature of 4-spring suspensions is that adjacent ends of front and rear springs are flexibly connected so as to deliver the joint objectives of axle load equalisation and also differential axle movement which is far greater than the spring deflection. Again, in the context of farm trailers and the terrain they are used on, the extent and frequency of high differential axle loads will be greater than on road going trailers.

[0006] The retardation requirement is that the minimum specified figure (assumed to be O.45g) shall be achieved at maximum load. However, if the trailer is empty or partially loaded this same braking effort is very likely to cause wheel locking. Thus the concept of load sensing", which is well known, will likely be another requirement imposed on farm S trailers allowed to travel at higher speeds. In the case of a 4-spring suspension it involves connecting a beam to midpoint of the front and rear axles such that vertical deflection due only to differential axle movement allowed by connection of adjacent ends of front and rear springs cancels out and all that is left is the deflection due to the weight imposed on the springs. This measure of spring deflection is then used as a control input by a "load sensing valve" to modify the brake pressure from the towing vehicle to a trailer brake actuation pressure appropriate to the load condition of the trailer. The actual spring deflection, in contrast to the maximum possible wheel movement is likely to be very small.

[0007] It is a characteristic of 4-spring suspensions that the axles do not move exactly in the vertical direction. There is invariably a small fore-and-aft movement associated with vertical deflection. Thus the distance between the axles, which the spring deflection sensing beam has to span, is not constant. Also in a 4-spring suspension braking torques applied by the wheel to the axle will be reacted partly by the springs such that, under the influence of these torques, both axles will rotate slightly, by approximately the same amount and in the same direction. It is therefore desirable that the suspension deflection sensing beam is mounted to the axles such that these rotations cancel out in the centre of the beam.

[0008] As any trailer crosses uneven terrain there will also be differential roll angles on the axles. Because of the nature of the terrain it will encounter this effect is particularly important on a farm trailer.

[0009] Overall, in the context of farm trailers, a load equalisation mechanism must be sufficiently robust to withstand travel over rough and uneven ground and significant shaking motion while maintaining function and resisting damage.

BRIEF SUMMARY OF THE DISCLOSURE

[0010] In accordance with the present invention there is provided, in a vehicle having brakes and a spring suspension arrangement providing axle load equalisation, preferably of four spring suspension style, namely a separate suspension spring for each end of adjacent front and rear wheel axles of the vehicle in which the front end of the spring of the rear axle is connected to the rear end of the spring of the front axle at each side of the vehicle by a respective rocker device which is pivotably connected to the vehicle chassis so as to equalise axle load on the springs between the front and rear axles at each side, a spring deflection sensing beam mounted between midpoints of the front and rear axles of the vehicle and a linkage extending upwards from a first end which is mounted at the midpoint of the beam to connect directly or indirectly to a load sensing valve to appropriately modify supply of fluid pressure to the brakes for required braking force at that S vehicle weight. The improvement of the present invention is that respective ends of the suspension spring deflection sensing beam are mounted to respective axles by respective clamping bracket assemblies which are secured around the housings of the respective axles so that the beam axis extends generally in the same horizontal plane as the axles of the vehicle and further that the ends of the beam are mounted to the bracket assemblies by engagement between pairs of resilient elements, preferably cylindrical elements with at least a resilient surface layer, provided on each bracket to allow for movement of the ends of the beam relative to the axle housings which will inevitably occur in a vehicle travelling over a variety of ground surfaces, often rough and uneven, where the axles may be violently bouncing, twisting and even moving together and apart slightly.

[0011] Thus the invention provides means of connecting a spring deflection sensing beam to axles, without any welding to the axle, such that it is tolerant of twisting resulting from differential axle roll angles, the angular movement resulting from differential vertical movement of the axles, small variation in the distance between the axles, and, at its centre, is unaffected by any axle rotation under braking, while still holding the beam securely over a long period of time in the harsh environment that exists underneath a farm trailer and still, at the centre of the beam, delivering an accurate replication of spring deflection.

[0012] In preferred embodiments fitments of resilient material, which may be termed "buffers", are provided at each end of the beam, or where the beam is formed in two coaxial parts, at the outer end of each beam part. These provide a resilient intermediate cushioning component in the event of any contact of the beam ends with the axle housings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Further features and advantages of the present invention will be apparent from the following description. The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary perspective view showing the underside of a trailer fitted with a 4-spring suspension arrangement and spring deflection sensing mechanism in accordance with a preferred practical embodiment of the present invention; Figure 2 is a similar view to figure 1, also from the underside, but omitting details of the trailer chassis and the tyres and showing relevant parts of the suspension arrangement and spring deflection sensing mechanism in isolation in relation to the wheel axles; Figure 3 is an enlarged scale detail of thatl portion of figures 1 and 2 showing the clamping of one end of the deflection sensing beam to one of the wheel axles; and Figure 4 is an enlarged scale detail showing one end of one beam part in the spring deflection sensing mechanism in the embodiment of the invention shown in the preceding figures.

DETAILED DESCRIPTION

[0014] As shown in figures 1 and 2 of the drawings, the suspension arrangement in this preferred embodiment comprises four springs 11, 12, 13, 14 of conventional suspension leaf spring style. Springs 11, 12 are mounted at respective ends of a front axle 16 and springs 13, 14 are similarly mounted at respective ends of a rear axle 18, the mounting being in known manner so does not need to be described here. At one side of the vehicle, in this instance an agricultural trailer, of which various pads of the chassis 20, wheel hubs 22 and tyres 24 at one side only are shown in figure 1, the front-end of the spring 13 of the rear axle 18 is connected to the rear end of the spring 11 of the front axle 16 by means of a rocker assembly 30, which is pivotably mounted to the vehicle chassis 20 by means of brackets 32 and pivot pin 34. At the other side of the vehicle the springs 12, 14 are connected in corresponding manner, namely the front end of the spring 14 of the rear axle 18 is connected to the rear end of the spring 12 of the front axle 16 by means of a further rocker assembly 30.

[0015] The aforesaid arrangement serves to equalise load between the axles 16, 18 because the rockers 30 cause the front end of either one of the rear springs 13, 14 to be raised whenever the rear end of the corresponding front spring 11, 12 moves downwards and vice versa, depending on the position of the respective axles 16, 18 as the vehicle moves over uneven ground.

[0016] The rear end of the front axle spring 11, 12 and the front end of the rear axle spring 13, 14 at each side of the vehicle axles 16, 18 are mounted to the associated rocker assembly 30 by engagement between pairs of rollers or cylindrical members (not shown) which extend between respective rockable components 36, as shown in figures 1 and 3, but omitted from figure 2 for clarity of other features. This allows for fore and aft movement of the ends of the springs relative to the rockable components which needs to be allowed for in a vehicle travelling over a variety of ground surfaces, often rough and uneven, where the axles may be violently bouncing, twisting and even moving together and apart slightly.

The axles 16, 18 are located fore and aft by track rods 15 in parallel with each spring 11- 14, in this case underneath, although they could alternatively be above. These track rods 15 are attached at one end to a fixed chassis element by way of the brackets 32, which also mount the rocker assemblies 30, and at the other end to an axle element. This arrangement also avoids having to provide eyelets in the ends of the springs 11-14 for purposes of connection, which adds to manufacturing cost of springs and can weaken them.

[0017] Load equalisation is desirable to improve braking efficiency and minimise differential braking on different axles. It is also a necessary prerequisite to "load" sensing, more accurately spring deflection sensing, for purposes of brake pressure modulation because it is appropriate to sense the average weight of the loading of all the axles and all the wheels of the vehicle, more accurately the average spring deflection.

[0018] A suspension spring deflection sensing mechanism is provided which includes a two-part beam 41,42 mounted between midpoints of the front and rear axles 16, 18, thus on the longitudinal axis of the trailer chassis. More specifically the beam 41, 42 is mounted between cylindrical housings 16, 18 of the respective axles so that the beam axis extends generally in the same horizontal plane as the axles of the vehicle. The load sensing mechanism also includes a linkage 44 extending upwards from a midpoint of the beam, between the two beam parts 41, 42, to connect to a lever 45 mounted to the vehicle chassis 20, to which lever 45 a load sensing valve (not shown) controlling fluid supply to the brakes is connected. Outer ends of the respective parts 41, 42 of the beam are mounted to the respective axle housings 16, 18, by respective clamping bracket assemblies 46, 48, one of which is shown in more detail in figure 3. Each assembly 46,48 carries a pair of cylindrical elements 47 and the respective outer end of the beam engages between these elements 47 to allow for a certain amount of relative movement between the respective outer end of the beam 41,42 and the respective axle housing 16, 18. These elements 47 are either formed entirely of resilient material, such as rubber or synthetic rubber, or have a resilient outer surface layer, such as a surface layer of rubber or synthetic rubber. Again, this is to allow for a farm vehicle travelling in difficult environmental conditions over a variety of ground surfaces and the movement of the axles 16, 18 which will be occasioned by that.

[0019] At each outer end of the respective half beams 41, 42, a resilient fitment 43 is provided. As shown in figure 4 this may be in the form of a plug of suitable plastics material, such as nylon, which is pressed into the hollow end of the box section beam part 41, 42, with a projecting head, standing proud of the beam end and providing a buffer to cushion against any possible contact with the respective axle housing 16, 18.

[0020] Referring to figures 1 and 2, the lower end of the linkage 44 is pivotably attached to the midpoint of the beam 41, 42 and the upper end of the linkage 44 is pivotably attached to the levei 45. Each end of the linkage 44 is formed as a substantially cylindrical enlaigement 51, 53. The lowei end enlargement 51 is held in position between the parts 41, 42 of the beam by respective straps 49 which are bolted to the inner end regions of the beam parts 41, 42 with a pivot pin for the lower end enlargement 51 extending between midpoints of those straps 49. This allows for a certain degree of relative pivoting of the beamparts4l,42.

[0021] The upper end enlargement 53 of the linkage 44 is pivotally mounted between the cential locations on side-by-side aims of the lever 45. One end of the lever 45 is fixed to a crossbar 28 of the chassis 20 while a sensing valve (not shown) is mounted to the other end 56 of the lever 45. The sensing valve controls fluid supply to the vehicle brakes, and it does not mattel whether these are supplied with liquid, as in the case of hydraulic brakes, or aft as in the case of pneumatic brakes. The purpose of the arrangement of the lever 45 is to magnify any deflection in the position of the suspension springs 11, 12, 13, 14 as caused by a change in the vehicle loading. In this respect, the spring deflection is not very great when the loading is equalised over the foui spnng aiiangement.

[0022] Veitical displacement of the linkage 44 is dependent upon and effectively a measure of the deflection of the suspension springs 11, 12, 13! 14 mounting the axles, which deflection is equalised because of the provision of rockers 30, as explained above.

The deflection of the suspension springs is dependent on the loading upon the vehicle axles, moie specifically upon the weight of the matenal oi livestock being carried by the vehicle. Accordingly, in use, as the vehicle load changes, the change in position of the suspension springs, equalised between the axles 16, 18, moves the linkage 44 and thus pivots the fiee end 56 of the lever theieby causing adjustment of the sensing valve to appropriately modify supply of fluid pressure to the brakes for appropriate braking for that vehicle weight. This ieduces the risk of the brakes locking when actuated.

[0023] The invention is not restricted to the details of the foregoing embodiment and variations are possible in other embodiments within the scope of the claims.

[0024] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean including but not limited to", and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Claims

BCLAIMS1. A vehicle having brakes, a spring suspension arrangement providing axle load equalisation and a spring deflection sensing mechanism to modulate braking force applied by those brakes, the sensing mechanism comprising a beam mounted between midpoints of the front and rear axles of the vehicle and a linkage extending upwards from a first end mounted at the midpoint of the beam to connect directly or indirectly to a load sensing valve to appropriately modulate the brakes for required braking force at that vehicle weight, characterised in that respective ends of the beam of the sensing mechanism are mounted to respective axle housings by respective clamping bracket assemblies so that the beam axis extends generally in the same horizontal plane as the axles of the vehicle, and in that said ends are mounted to the bracket assemblies by engagement between pairs of resilient elements on each assembly to allow for movement of the ends of the beam relative to the axle housings.
2. A vehicle having a suspension arrangement and spring deflection sensing mechanism according to claim 1 wherein the beam is a two-part beam having outer ends of the respective parts mounted to the bracket assemblies on the axle housings and the first end of the linkage is mounted at the midpoint of the beam between the two beam parts.
3. A vehicle having a suspension arrangement and spring deflection sensing mechanism according to claim 1 or 2 wherein the pairs of resilient elements are in the form of cylindrical elements made of resilient material.
4. A vehicle having a suspension arrangement and spring deflection sensing mechanism according to claim 1 or 2 wherein the pairs of resilient elements are in the form of cylindrical elements each having an outer surface layer of resilient material.
5. A vehicle having a suspension arrangement and spring deflection sensing mechanism according to claim 1 wherein fitments of resilient material are provided at each end of the beam of the load sensing mechanism.
6. A vehicle having a suspension arrangement and spring deflection sensing mechanism according to claim 2 wherein fitments of resilient material are provided at each outer end of the respective parts of the two-part beam of the load sensing mechanism.
7. A vehicle having a spring suspension arrangement providing axle load equalisation and a suspension spring deflection sensing mechanism to modulate braking force applied by those brakes substantially as hereinbefore described by reference to and as illustrated in the accompanying drawings.