GB2345477A

GB2345477A - Restraining device

Info

Publication number: GB2345477A
Application number: GB9919610A
Authority: GB
Inventors: Ronald George Meager
Original assignee: ANDOVER TRAILERS Ltd
Current assignee: ANDOVER TRAILERS Ltd
Priority date: 1999-01-11
Filing date: 1999-08-19
Publication date: 2000-07-12
Anticipated expiration: 2019-08-19
Also published as: GB2345477B; GB9900446D0; GB9919610D0

Abstract

A restraining device for use in a vehicle suspension system (6) to prevent extension of an air-bag (16) forming part of the suspension system when the air-bag is deflated and the vehicle is lifted from an underlying surface; comprises a pair of latching members (24,26) which are arranged to cooperate to prevent said extension when the air-bag (16) is in a deflated state, but are arranged to be disconnected as the air-bag (16) is inflated so as to allow extension of the air-bag (16).

Description

RESTRAINING DEVICE This invention relates to a device for restraining the movement of an air-bag in a vehicle suspension system when the air-bag is in a deflated condition.

Suspension systems for road going vehicles and trailers frequently make use of air-bags as shock absorbers. A typical suspension system comprises a suspension arm pivotably attached to a mounting on the underside of the vehicle chassis, the suspension arm being fastened to the axles of the trailer or other vehicle by means of a fastening such as a U-bolt. An air-bag is disposed between the end of the suspension arm remote from the pivot point, and the underside of the chassis.

In an air-bag, as the name suggests, the pressure of gas within the bag provides a gas spring which acts to absorb shocks received from an underlying road surface. Air-bags typically are provided with a solid resilient region, usually connected to the underside of the chassis frame, known as a"bump stop". In the event that the air-bag is, for any reason, deflated, then the"bump stop"provides a small measure of shock absorbing capacity until such time as the air-bag can be repaired.

Standard practice with regard to the operation of vehicle trailers having compressed air systems is that when the vehicle and trailer reach a railhead, prior to loading onto a railway wagon, compressed air within the air brake and suspension system is"dumped"leading to deflation of the air-bags. This has the result of reducing the height of the trailer which is clearly desirable from the viewpoint of transporting the trailer on a railway wagon. Once the air has been released from the system, the vehicle trailer can then be lifted onto a suitable wagon or other carrier.

However, a problem with lifting the vehicle trailer when the air-bag is deflated is that the weight of the wheels and axles are then supported by the air-bag which therefore stretches into its extended position. Typically the air-bag can extend by as much as 300mm or more. Since there is no longer any air in the air-bag, but instead there is only a vacuum or partial vacuum, the air-bag cannot retain its shape and, as a consequence, when the trailer is lowered again onto a surface, for example a railway wagon, the air-bag can become buckled or twisted and therefore damage. In many cases the damage does not become apparent until after the vehicle has been unloaded from the wagon or other carrier and has been on the road for several kilometres. At this point, the air-bag may fail and the vehicle would be unable to continue with its journey in a safe manner. It has become apparent to the applicants that this is a very serious problem indeed and haulage companies are understood to spend large sums of money each year replacing air-bags which have been damaged in the manner described above. Despite the problem, there currently exists no solution, so far as the applicants are aware.

It is an object of the present invention to provide a device which prevents the stretching or extension of the air-bag when in a deflated condition yet is simple and easy to fit and maintain.

Accordingly, in a first aspect, the invention provides a restraining device for use in cooperation with an air-bag forming part of a vehicle suspension system; the restraining device being operable to prevent extension of the air-bag when the air-bag is in a deflated state and the vehicle and/or wheels thereof are lifted from an underlying surface, but being operable to allow extension of the air-bag as the air-bag is inflated.

In a preferred embodiment, the invention provides a restraining device for use in a vehicle suspension system to prevent extension of an air-bag forming part of the suspension system when the air-bag is deflated and the vehicle is lifted from an underlying surface; the device comprising a pair of latching members which are arranged to cooperate to prevent said extension when the air-bag is in a deflated state, but are arranged to be disconnected as the air-bag is inflated so as to allow extension of the air-bag.

The restraining device is most preferably actuated by the change of shape in the air-bag as air is introduced into or removed from the air-bag. Thus. for example, resilient means may be provided for biasing the pair of latching members together when the air-bag is in a deflated condition, and whereby inflation of the air-bag serves to urge the latching members apart so as to release the restraint.

In one embodiment, the restraining device comprises a first latching member connectable to the trailer chassis so as to extend downwardly therefrom; and a second latching member connectable to a suspension arm upon which the air-bag is mounted.

The first latching member can take the form of a latching arm, resilient means being provided for biasing the resilient arm towards the air-bag. The resilient means can take several forms. In one embodiment for example, the resilient means can take the form of a band of elastomeric material looped around the air-bag and arm. In another embodiment, the resilient means can take the form of a resilient, e. g. elastomeric, mounting securing the latching arm to the main chassis rail of the trailer. In a further embodiment, the latching arm can be formed from a resilient material such as a spring metal e. g. spring steel. In a still further embodiment, the latching arm can be held against the air-bag wall by suitable securing means such as, for example, a sleeve, channel, loop, slot or strap attached to or integral with the air-bag wall and through which the latching arm passes.

In a particularly preferred embodiment, the invention provides a restraining device for connection to a vehicle suspension system to prevent extension of an airbag forming part of the suspension system when the air-bag is deflated and the vehicle is lifted from an underlying surface; the device comprising a first latching member and a second latching member; the first latching member being securable to a vehicle trailer chassis adjacent an air-bag; means being provided for resiliently biasing the first latching member towards the air-bag; the second latching member being secured to a suspension arm to which the end of the air-bag remote from the trailer chassis is attached; the first and second latching members being arranged to co-operate to prevent extension of the air-bag when the air-bag is in a deflated state, but being caused to disengage by movement of the air-bag as the air-bag is inflated.

The restraining device of the invention can also be used with trailers which have more than one axle (for example three axles) where one or more of the axles and their wheels are arranged to be lifted away from the road when the trailer is in an unloaded state thereby to prevent unnecessary wear on the tyres. On such trailers, the restraining device can be used instead of the more complex pneumatic actuators currently used to retract the third axle. Thus, for example, in three-axle trailers fitted with restraining devices according to the invention, the air in the air suspension system can first be"dumped"so that the trailer chassis settles down onto the wheels.

Thereafter, the air bags associated with two of the axles can be reinflated causing the restraining device to disengage, but the air bag (s) on the third axle is/are left uninflated. The restraining device on the third axle therefore remains in engagement and consequently the third axle is held in a retracted position as the chassis is lifted away from the wheels. It will be appreciated from the foregoing that, if desired, more than one axle can be held in the elevated position by the restraining device of the invention, provided of course that there are sufficient axles/wheels left in contact with the ground to take the weight of the trailer.

Accordingly, in another aspect, the invention provides a method of raising a wheel bearing axle on a trailer having a plurality of wheel bearing axles mounted on a chassis or vehicle body, each of the axles having associated therewith an air-bag forming part of a suspension system for the trailer, and each of the air bags having associated therewith a restraining device as defined in any one of the preceding claims; which method comprises deflating the air bags to lower the chassis or trailer body, and then reinflaiing the air-bags associated with the axle or axles other than the axle to be raised; whereby the restraining device (s) associated with the reinflated airbag (s) disengage to allow the air-bag (s) to undergo extension and raise the chassis or trailer body, whereas the restraining device (s) associated with the non-reinflated airbag (s) remain engaged thereby holding the air-bag against extension and raising the associated axle with the chassis or trailer body.

In the aforementioned embodiments, the vehicle is advantageously be provided with means for differentially or selectively inflating and deflating the air-bags. Such means can take the form of, for example, an array of selectively actuable air valves, and control means for controlling actuation of the air valves.

In a further aspect, the invention provides a vehicle suspension system comprising one or more restraining devices as hereinbefore defined.

In a still further aspect, the invention provides a vehicle fitted with a suspension system incorporating a restraining device (s) as hereinbefore defined.

The invention will now be illustrated, but not limited, by reference to the specific embodiments shown in the accompanying drawings of which: Figure 1 is a schematic illustration illustrating the attachment of a restraining device according to one embodiment of the invention to a vehicle suspension system ; Figures 2a and 2b are schematic views illustrating the mode of action of the restraining device according to a second embodiment of the invention; Figure 3 is a schematic view illustrating a vehicle suspension system after the vehicle has been lifted from the underlying surface; Figure 4 is a side elevation of a restraining device according to a third embodiment of the invention with the air-bag inflated; Figure 5 is a view from direction D of the embodiment of Figure 4 with the air-bag deflated; and Figure 6 is side elevation of the latching arm of the embodiment of Figures 4 and 5.

Referring now to the drawings, Figure 1 illustrates a schematic view of a typical vehicle suspension incorporating an air-bag shock absorber. Thus the trailer chassis 2 has welded thereto a mounting point 4 to which suspension arm 6 is pivotably attached at a pivot point 8. Suspension arm 6 is attached to axle 10 bearing wheel 12 by means of U-bolt 14.

At the end of the suspension arm 6 remote from the pivot point 8, is mounted an air-bag 16. As can be seen from Figures 1 and 2, air-bag 16 comprises a pedestal portion 18 and a"bump stop"portion 20. Pedestal portion 18 is bolted to the end of the suspension arm 6, whereas"bump stop"20 is bolted through concave metal plate 22 to the underside of the chassis 2.

As shown in the Figures, a restraining device is fitted to the suspension system. The restraining device shown in Figure 1 comprises a first latching member or latching arm 24 and a latching plate 26. Latching arm 24 is set into a rubber shoe or block 28 bolted (bolts not shown) to the trailer chassis. Latching plate 26 is interposed between the air-bag 16 and the end of the suspension arm 6 and is held in place by means of a bolt (not shown) secured by nut 30. Latching arm 24 has a hooked end 32 which can engage over an enlarged edge portion 34 on the latching plate 26.

A slightly different embodiment of the restraining device is shown in Figures 2a and 2b. In this embodiment, the latching arm 124 is formed from a spring steel material. Latching arm 124 has a similarly hooked end 132 which engages the enlarged rim 134 of latching plate 126.

The operation of the restraining device is shown in Figures 2a and 2b. Thus, when a vehicle arrives at a destination such as a railhead, the vehicle's air suspension system is deflated and hence the chassis sinks onto the wheels. As a result of the resilient biasing of the latching arm 24/124, the latching arm moves with the wall of the deflating air-bag until the hooked end 30/130 engages over and forms a latch with the enlarged rim 341134 of the latching plate 26/126, as shown in Figure 2b. When the vehicle is subsequently lifted, for example onto a railway wagon, the latch prevents the air-bag from undergoing longitudinal extension and stretching.

Consequently, when the vehicle is lowered again, the air-bag does not fold or buckle in the manner that it would have done if the restraining device were not present.

When the vehicle is unloaded, and the air suspension system is re-inflated, inflation of the air-bag 40 causes the wall 40a of the air-bag to move outwardly urging the latching arm 24/124 away from latching plate 26/126 thereby releasing the restraint upon further expansion of the air-bag.

It will thus be appreciated that an advantage of the restraining system of the present invention is that it allows a vehicle to be lifted from the ground, after its air suspension system has been deflated, without the air-bag being stretched and extended by the weight of the wheels and axles. This in turn means that when the vehicle with deflated suspension system is lowered onto the surface of, for example, a railway wagon or other carrier, or is unloaded from the wagon onto a surface at a depot or port, kinking or buckling of the air-bag as a consequence of being over-extended when lifting, is avoided.

The restraining system of the invention can be fitted to the trailer during manufacture of the trailer, or it can be"retro-fitted"at a subsequent date. An arrangement particularly suited for retro-fitting is shown in Figures 4 to 6.

As shown in Figures 4 to 6, the restraining device comprises an air-bag 216 secured at its upper end to the underside of a vehicle chassis 202 and at its lower end to a latching plate 226 which in turn is mounted on a suspension arm 206. As with the embodiment of Figures 1 to 3, a latching arm 224 is pivotably mounted on the underside of the trailer chassis.

However, in this embodiment, the means for resiliently biassing the latching arm towards the air-bag is provided by an elastic band 250 which encircles the air-bag and latching arm. The elastic band may conveniently be bonded to the air-baa at one or more locations around the bag circumference in order to prevent dislodsement of the band. In order to prevent or reduce wear and damage to the bag as a result of the latching arm chafing against the bag during use, a contact patch 260 is bonded to the bag. The outer surface of the contact patch is preferably formed from a low friction material such as PTFE.

Figure 4 illustrates the air-bag when inflated. In this state, the latching arm 224 is urged outwardly by the wall of the inflated bag such that it is disengaged from the latching plate 226. When the air-bag is deflated, the restoring force of the elastic band 250 draws the latching arm 224 back into latching engagement with the latching plate 226. Thus, as with the embodiment of Figures 1 to 3, the latching arm holds the air-bag against extension when the trailer chassis is subsequently lifted away from the wheels and suspension.

The restraining device shown in the illustrated embodiments is particularly advantageous since it is of very simple construction and requires no valves, air systems or other moving parts. Once fitted, it is essentially maintenance free. In the illustrated embodiments, it is the movement of the wall of the air-bag as it is reinflated that causes the disengagement of the restraining device, whilst deflation of the air-bag causes the restraining device to engage.

It will readily be appreciated that numerus modifications and alterations can be made to the restraining device shown in the accompanying drawings without departing from the principles underlying the invention. Thus, by way of example, whilst the restraining devices illustrated are actuated directly by inflation and deflation of the air-bags, it is possible to provide alternative and/or independent means for engaging and disengaging the latching members. Such means can be pneumatic, mechanical or electrical, or any combination thereof. For example, means for actuating the latching members can be linked to an electronic control unit or switch located on the vehicle or on a tractor unit connected to the vehicle (where the vehicle is a trailer), the switch or control unit being linked to an engaging/disengaging mechanism located in operative engagement with the latching members. Such an engaging/disengaging mechanism can be pneumatic or mechanical in nature, for example. One example of such a mechanism is a servo motor linked electronically to the control unit or switch, the servo motor being linked to one or other of the latching members. In a further alternative, an engaging/disengaging mechanism can be linked directly to the vehicle's air system, for example such that as the air is released from the air-bags, the restraining device is actuated to bring the latching members into latching engagement. In one such arrangement, the latching members can be held apart by the pressure of air in a pneumatically operated mechanism, release of the air from the suspension system allowing the latching members to move together into latching engagement. In another such arrangement, when the air suspension system is vented to deflate the air-bags, a portion of the escaping air can be diverted into a pneumatically operated mechanism forcing the latching members together. As a further alternative, the latching members can be brought into latching engagement by means of a manually operated mechanism which may be, for example, a mechanical system.

As an alternative to the use of pair of latching members, a restraining member such as a chain, wire, rod or a telescopic or sliding member can be mounted so as to extend between the vehicle's suspension system and chassis in close proximity to the air-bag. The length of restraining member extending between the suspension system and chassis can then be shortened or lengthened as required in order to control the degree of extension of the air-bag.

In a further application of the restraining devices shown in the accompanying drawings, they may be used as a means of raising one of the axles relative to the other axles so as to reduce tyre scuffing and wear when the vehicle is driven in an unloaded condition. It is commonplace with three-axle trailers to raise one of the axles when the vehicle is driven in an unloaded state and, at present, a separate pneumatic actuating system is used for this purpose. However, when the restraining devices of the invention are fitted to each of the air-bags forming part of the suspension system, the need for a separate and often complex pneumatic system is obviated. Thus, after the air has been initially dumped from the suspension system to lower the trailer chassis, the air-bags other than those attached to the axle to be raised are selectively reinflated. The restraining devices attached to the reinflated air bags are disengaged during reinflation whilst those attached to the non-reinflated airbags remain engaged. The result is that as the air suspension system is partially reinflated and the trailer chassis rises, so the axle on which the non-inflated air-bag is mounted rises with the chassis.

All such modifications and alterations are intended to be embraced by this Application.

Claims

CLAIMS 1. A restraining device for use in cooperation with an air-bag forming part of a vehicle suspension system; the restraining device being operable to prevent extension of the air-bag when the air-bag is in a deflated state and the vehicle and/or the wheels thereof are lifted from an underlying surface, but being operable to allow extension of the air-bag as the air-bag is inflated.
2. A restraining device for use in a vehicle suspension system to prevent extension of an air-bag forming part of the suspension system when the air bag is deflated and the vehicle is lifted from an underlying surface; the device comprising a pair of latching members which are arranged to cooperate to prevent said extension when the air-bag is in a deflated state, but are arranged to be disconnected as the air-bag is inflated so as to allow extension of the air bag.
3. A restraining device according to claim 1 or claim 2 which is actuated by the change of shape in the air-bag as air is introduced into or removed from the air-bag.
4. A restraining device according to claim 2 which is actuated by the change of shape in the air-bag as air is introduced into or removed from the air-bag, resilient means being provided for biasing the pair of latching members together when the air-bag is in a deflated condition, and whereby inflation of the air-bag serves to urge the latching members apart so as to release the restraint.
5. A restraining device according to any one of the preceding claims which comprises a first latching member connectable to a trailer chassis so as to extend downwardly therefrom; and a second latching member connectable to a suspension arm upon which the air-bag is mounted.
6. A restraining device according to claim 5 wherein the first latching member takes the form of a latching arm, resilient means being provided for biasing the resilient arm towards the air-bag.
7. A restraining device according to claim 6, wherein the resilient means takes the form of a band of elastomeric material looped around the air-bag and arm.
8. A restraining device according to claim 6 wherein the resilient means takes the form of a resilient, e. g. elastomeric, mounting securing the latching arm to the main chassis rail of the trailer.
9. A restraining device according to claim 6 wherein the latching arm is formed from a resilient material such as a spring metal e. g. spring steel.
10. A restraining device for connection to a vehicle suspension system to prevent extension of an air-bag forming part of the suspension system when the air bag is deflated and the vehicle is lifted from an underlying surface; the device comprising a first latching member and a second latching member; the first latching member being securable to a vehicle trailer chassis adjacent an air bag; means being provided for resiliently biasing the first latching member towards the air-bag ; the second latching member being secured to a suspension arm to which the end of the air-bag remote from the trailer chassis is attached; the first and second latching members being arranged to co-operate to prevent extension of the air-bag when the air-bag is in a deflated state, but being caused to disengage by movement of the air-bag as the air-bag is inflated.
11. A restraining device substantially as described herein with reference to the accompanying drawings.
12. A vehicle suspension system comprising one or more restraining devices as defined in any one of the preceding claims.
13. A vehicle fitted with a suspension system incorporating a restraining device as defined in any one of claims 1 to 11.
14. A method of preventing the extension of an air-bag forming part of in a vehicle suspension system the air-bag is deflated and the vehicle is lifted from an underlying surface; the method comprising the use of a restraining device as described in any one of claims 1 to 11.
15. A method of raising a wheel bearing axle on a trailer having a plurality of wheel bearing axles mounted on a chassis or vehicle body, each of the axles having associated therewith an air-bag forming part of a suspension system for the trailer, and each of the air bags having associated therewith a restraining device as defined in any one of the preceding claims; which method comprises deflating the air bags to lower the chassis or trailer body, and then reinflating the air-bags associated with the axle or axles other than the axle to be raised; whereby the restraining device (s) associated with the reinflated air-bag (s) disengage to allow the air-bag (s) to undergo extension and raise the chassis or trailer body, whereas the restraining device (s) associated with the non reinflated air-bag (s) remain engaged thereby holding the air-bag against extension and raising the associated axle with the chassis or trailer body.