GB2371783A

GB2371783A - Air suspension for vehicles

Info

Publication number: GB2371783A
Application number: GB0129926A
Authority: GB
Inventors: Alan Geoffrey Dixon
Original assignee: Meritor Heavy Vehicle Systems Ltd
Current assignee: Meritor Heavy Vehicle Systems Ltd
Priority date: 2000-12-15
Filing date: 2001-12-14
Publication date: 2002-08-07
Also published as: GB0129926D0; GB0030593D0; WO2002047927A1; AU2002222209A1

Abstract

An air suspension unit for a road/rail trailer comprises a road wheel axle (10) which mounts to a chassis or frame of the trailer for movement by air-operated means (52;17,21) between lowered operative and raised stowed positions of the road wheel or wheels carried by the axle, and axle retention means (22) for retaining the axle in the stowed position for rail travel of the trailer. The retaining means comprises jaws (24) which are normally mechanically urged, e.g. by spring loading, to a closed position in which they engage around the axle (10) in its stowed position to retain the axle in that position, and are opened by an air operated piston (35) to release the axle. The piston connects to the air supply of the trailer to which the unit is applied for use. Therefore, when the trailer is supported on bogies for rail travel with the axle held in the stowed position by the jaws (24) and the trailer is separated from is tractor so that the air supply is disconnected, the piston (35) is automatically inoperative and cannot open the jaws to release the axle from the stowed position.

Description

It! AIR SUSPENSION FOR VEHICLES

This invention relates to air suspensions for vehicles wherein air springs are used and in which a long potential travel for the suspension is 5 required to facilitate lifting of the vehicle chassis or frame. An example of such a vehicle is a freight carrying road trailer adapted for rail travel, hereinafter referred to as a "road/rail trailer".

Road/rail trailers are usually supported on road wheels by air suspensions 10 for road travel. For rail travel they are transferred onto bogies on a rail track. When the trailers are supported on the bogies, the road wheels are raised to a stowed position well clear of the rail track. In order to load a trailer onto the bogies, the air suspension has to be jacked-up to raise the chassis or frame on the road wheels to a level for it to be received onto 15 the bogies. Then lift means, with which the air suspension is provided, is operated pneumatically to raise the wheels to the stowed position where a retaining arrangement is used to retain the wheels in the stowed position.

The trailer is then separated from its tractor, which can be driven away.

A number of bogey mounted trailers can be connected together into a 20 train for the rail travel.

When a trailer is supported on bogies for rail travel and separated from its tractor the air supply to the trailer is disconnected so that the air suspension and all other air operated parts of the trailer are made 25 inoperable.

It is an important requirement that the road wheels of a road/rail trailer are held securely in the stowed position for and during rail travel. Since air supply is not available mechanical means must be employed to secure 30 the road wheels in the stowed position. Various means have been proposed but they have tended to be expensive and complicated.

r The present invention is aimed at providing an air suspension for a road/rail trailer which meets the requirement for secure retention of road wheels of the trailer in the stowed position without undue expense and 5 complication.

According to a first aspect of the present invention there is provided an air suspension unit for a road/rail trailer, comprising a road wheel axle which mounts to a chassis or frame of the trailer for movement by 10 airoperated means between a lowered operative position of the road wheel or wheels carried by the axle and a raised stowed position of the road wheel or wheels, and axle retention means comprising jaws operatively connected to an air-operated piston which are normally mechanically urged to a closed position in which they engage around the 15 axle when the axle is in the stowed position, to retain the axle in that position, and which are opened by the piston to release the axle.

The piston will be connected to the air supply of the trailer to which the air suspension unit is applied for use. Therefore, when the trailer is 20 supported on bogies for rail travel, the axle being retained in the stowed position by the jaws, the piston will automatically be made inoperative so that the jaws cannot be opened by the piston to release the axle from the stowed position. Only when the air supply is restored to the trailer can the piston be operated to release the axle.

Preferably the piston is actuated under a small volume of air in its operating chamber, typically one quarter or less of the volume required for actuation of the air-operated means, so that there is rapid depressurisation and re-pressurisation of the chamber when the air 30 supply is respectively disconnected and restored. Re-pressurisation of the chamber to operate the piston for opening the jaws may be completed

before the air-operated means is at the required pressure to function for lowering the axle to the operative position.

The jaws may be spring-loaded to the closed position. They may be 5 weighted or supported to be urged by gravity to the closed position. The piston has to overcome the mechanical urging to open the jaws.

Spring-loading may act on the piston to cause the piston to urge the jaws to the normally closed position when the operating chamber of the piston is de-pressurised.

Preferably the jaws have an over-centre pivotal action such that extremities of the jaws pass through a medial plane containing the pivotal axis of the jaws in moving to their closed position. The jaws therefore each extend around more than half the circumference of the axle, 15 enhancing the security of the axle in the stowed position.

There may be spaced pairs of the jaws for engaging with the axle at spaced positions along its length. With the axle carrying road wheels at opposite ends, there may, for example, be a pair of jaws positioned 20 towards each end of the axle. The pairs of jaws may be linked for operation together. One piston may operate to open the pairs.

Alternatively, each pair of jaws may have its own operating piston for opening the jaws.

25 Preferably the jaws are arranged to be opened to receive the axle by engagement of the axle therewith as it is moved from the operative to the stowed position. The jaws may have cam profiles, for example, with which the axle engages as it moves towards the stowed position, the interaction between the axle and cam profiles forcing the jaws apart, 30 against the mechanical urging, to receive the axle. The mechanical urging automatically closes the jaws when the axle reaches the stowed

position. In another arrangement, the jaws may carry rollers or rotatable bearings positioned to be engaged by the axle for urging the jaws apart as it approaches the stowed position.

S The air-operated means of the air suspension unit may be of any suitable kind. In a preferred embodiment a double air spring system is provided in which two stacked air springs act on a member which is adapted to be movably mounted to the chassis or frame of the trailer and has the axle secured to it. One of the air springs, comprising for example an air bag, 10 may be pressurised for normal operation for road travel of the trailer to which the air suspension is applied for use, and the second air spring, comprising for example a convolute spring, may be pressurised in addition to the first air spring when the chassis or frame is required to be raised further than is possible by the first air spring. The second air 15 spring is pressurised to lift the chassis or frame sufficiently for it to be received onto, and separated from, bogies for rail travel of the trailer.

Although independently operable, both air springs may be connected to the same source of pressure air.

20 The air spring system may be in accordance with that disclosed in EP 042309 B1.

According to a second aspect of the present invention there is provided a road/rail trailer which includes an air suspension unit in accordance with 25 the foregoing first aspect of the present invention.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: 30 Figure l(a) - (f) shows stages in converting a road/rail trailer from road travel use to rail travel use;

Figures 2 and 3 are simplified side views of an air suspension unit in accordance with the present invention applied to the road/rail trailer, being shown respectively in a fully extended lifting position 5 and a closed position ( the jaws in Fig. 2 being shown in dash lines in Fig. 3); Figure 4 is a perspective view of axle retaining means of the air suspension unit, and Figure 5 is a side view of a modified form of the axle retaining means. Referring to Figure l(a) - (I) a multi-axle road/rail trailer 1 is shown 15 which for road travel is hitched to a tractor 2 and for rail travel is transferred to bogies 3 on a rail track. The trailer 1 has a chassis 4 supported by air suspension on the road wheel axles. For the trailer to be transferred to the bogies 3 the chassis 4 has to be raised, Figure l(b) and (c), to a level above that at which it is normally supported by the air 20 suspension. This is done by jacking-up the air suspension to increase the spacing of the chassis above the road wheels. When the trailer is supported on the bogies the air suspension is de-pressurised and lift means is operated pneumatically to raise the road wheels to a stowed position, Figure (d), where they are retained. In the stowed position the 25 wheels are tucked up closely under the chassis so that they are spaced well above the rail track. When the trailer is disconnected from the tractor, Figure 1 (e), the air supply is disconnected from the trailer so that the air suspension and other air-operated parts of the trailer are made inoperative.

Successive trailers can be supported on the bogies and connected to form a train on the rail track, as shown in Figure l(f).

For each road wheel axle there is at each side of the chassis 4 an air 5 suspension unit 5 in accordance with the present invention. Each air suspension unit 5 is as shown in Figures 2 to 5 of the accompanying drawings. Each air suspension unit 5 comprises a hanger bracket 6 which is secured 10 to and depends from a chassis member 7 at one side of the chassis. A leaf spring 8 is pivotally connected at its front end to a lower end of the hanger bracket 6. The rear end of the leaf spring is connected to the forward end of an air spring support member 9. The respective axle, 10, has a spring seat 11 secured to it, as by welding. The spring seat 11, air 15 spring support member 9 and a bottom plate 12 are clamped to the leaf spring 8 by U-bolts 13 and nuts 14. A shock absorber 15 is connected at a lower end to the bottom plate 12 and at an upper end to the hanger bracket 6, at a position spaced above and rearwardly of the pivotal connection of the leaf spring 8 to the hanger bracket.

A piston 16 at a lower end of a main air spring 17 is bolted on top of the rear end of the air spring support member 9. An upper end of the main air spring 17 is connected to the underside of a rearward free end of a longer limb 18 of an L-shaped arm 19. A shorter, depending limb 20 of 25 the trailing arm 19 is pivoted to the hanger bracket 6 above the pivotal connection of the leaf spring. Seated on and connected to the rearward end of the longer limb 18 of the arm is a convolute air spring 21 the top of which is connected to the chassis 4.

30 The suspension unit 5 may be provided with a pneumatic lift system which may be any suitable known type and is shown at 50 in dash lines in

Figure 2 merely as an example. The lift system 50 comprises an ancillary or lift air spring 52 which acts on a thrust arm part 54 of a lever 56 pivoted at a fulcrum such as indicated at 58 on the hanger bracket 6, said lever having a lift arm part (not shown) extending from the fulcrum to act 5 on or below the axle 10 to apply lifting force to the axle when the thrust arm part is pushed down by the lift air spring. An upper end of the lift air spring 52 is secured to a sturdy bracing bar 60 secured to an under part of the chassis.

10 The air suspension unit 5 described is duplicated at the opposite side of the chassis and the axle extends between the leaf springs 8 of the two units. If the road wheels were to be independently suspended there would be one such air suspension unit for each independently suspended road wheel, the unit having a stub axle for the wheel.

For normal road travel the convolute air spring 21 of each air suspension unit 5 is deflated and the arm 19 occupies a position in which its longer limb 18 extends parallel to and is immediately below the chassis member 7, as shown in Figure 3. The main air spring 17 is pressurised 20 so that the leaf spring 8 and axle are urged away from the chassis.

Typically the main air spring allows approximately 1 OOmm vertical movement between the axle and the chassis.

For raising the chassis for supporting the trailer on the bogies, the 25 convolute spring 21 is pressurised and the main air spring is extended further by increased pressurization. Figure 2 shows the air suspension unit in this condition. Typically up to 400mm vertical movement of the chassis is provided. If desired, a limit of extension of the suspension may be provided by the shock absorber 15 with respect to that part of the 30 extension due to the main air spring 17, and by a restraining cable or

strap between the chassis member 7 and the limb 18 in respect of that part of the extension due to the convolute air spring 21.

When the trailer is supported on the bogies both the main air spring 17 5 and the convolute air spring 21 are fully deflated. The lift air spring 52 is pressurised pneumatically to push the thrust arm part 54 down, causing the lever 56 to pivot about the fulcrum 58 and raise the lift arm part of the lever which thus acts to raise the leaf spring and axle to a stowed position, as shown in Figure 3. The wheels carried by the axle are thus 10 lifted well clear of the rail track. In this stowed position the longer limb 18 of the arm 19 again extends parallel to and is immediately below the chassis member, and the leaf spring 8 is inclined upwardly towards the chassis from the hanger bracket 6. The air suspension unit is, therefore, tucked up closely under the chassis.

As indicated above, the axle 10 extends between two air suspension units 5. Between those two units axle retention means 22, as shown in Figures 2 and 3, is provided for holding the axle in the stowed position.

The axle retention means 22 is firmly mounted to the chassis, for example 20 to chassis members 7 in any suitable sturdy manner.

For example, the axle retention means 22 may be carried by brackets fixed to the chassis, an example of such brackets being indicated at 23 in Figures 2 and 3.

The axle retention means 22, as best seen in Figure 4, comprises two pairs of jaws 24 which are pivotally mounted at axially spaced positions on a pivot shaft 25 carried horizontally, parallel to the axle 10, by the chassis, for example by the brackets 23 as indicated in Figure 4 fixed to 30 the chassis. The jaws 24 of each pair are of a similar generally Sshape.

Each jaw 24 has a longer lower curved portion 26 which forms the jaw

proper and extends through more than 180 , and a shorter upper curved portion 27. The jaws are pivoted to the pivot shaft 25 at the transition of the S-shape between the lower and upper portions 26, 27. As the lower portions 26 extend through more than 180 , bottom ends 28 of those 5 portions extend over-centre the pivotal axis of the jaws at the pivot shaft.

Underside edges of the bottom ends are formed as concave cam profiles 29 tapering to the extremities of the bottom ends. When the jaws of each pair are closed together, as shown in Figure 4, their cam profiles 29 present in combination a concave recess 30 facing towards the 10 axle 10.

Upper ends 31 of the jaws of each pair are fixed respectively to two parallel connecting bars 32, 33 which extend between the upper portions 27 of the corresponding jaws of the two pairs. For rigidity and 15 weight saving each connecting bar 32, 33 is of channel section. Its ends are formed as parallel ears 34 which straddle and are fixed to the upper ends 31 of the respective jaws. Mounted centrally on a first connecting bar 32 is an air-operated piston 35 which has its air chamber housing 36 fixed to that connecting bar and its piston rod 37 extending transversely 20 between the two connecting bars. The piston is connected to the air supply to the main air springs 17 and convolute springs 21 of the air suspension units 5 carrying the axle. The piston rod 37 passes freely through a clearance hole 38 in the first connecting bar 32, and is fixed by nuts 39 at its externally screw-threaded outer end 40 to the second 25 connecting bar.

The piston rod 37 is spring-loaded to its fully retracted position which urges the connecting bars 32, 33 together and so closes the jaws 24 of each pair together, as in Figure 4. Air pressure applied to the piston 30 extends the piston rod 37, thereby pushing the connecting bars apart and opening the jaws. When there is no air pressure the spring-loading on the

piston rod automatically retracts it, closing the jaws. In Fig. 4 the piston 35 may be a diaphragm piston unit in which the spring-loading is applied by at least one spring within the housing 36.

5 The air chamber of the piston 35 is of small capacity, typically one quarter or less of the capacity of the air springs, so that it is rapidly filled with air to pressurise the piston, and emptied to depressurise it. The jaws need not be fully opened by the piston. Sufficient opening movement to separate their bottom ends 28 and have their extremities directed 10 downwardly, can be enough, which may be just a few centimetres, for example 8-lOcms.

Operation of the axle retention means 22 will now be described. The piston 35, as described, is connected to the air supply to the main air 15 springs 17 or convolute springs 21 of the air suspension units (5) carrying the axle. This holds the jaws 24 open so that the axle 10 may enter the gap between each co-operating pair of jaws during normal road running operation of the vehicle in the event of a full bump compressing the suspension. Upon initiation of deflation of the air springs 17,21 to raise 20 the axle 10 to the stowed position, the piston 35 is depressurised so that the jaws 24 are closed. At this point the or each lift system 50 is operated by pneumatically pressurising the lift air spring 52 which causes the lever 56 to lift the axle 10 up into the chassis. An interconnection of the air supply to the lift air spring 52 to the piston 35 causes the jaws 24 25 to open and be held open against the spring-loading. Thus the raised axle 10 can enter the gaps between the jaws of both pairs of jaws.

Deflation of the lift air spring 52 exhausts the piston 35 whereby the spring-loading closes the jaws which trap and retain the axle 10 in the stowed position.

Alternatively, in the event that the supply of air to the piston 35 is blocked or prematurely interrupted, so that the jaws 24 do not open or close prematurely, then as the axle is raised to the stowed position it enters the concave recesses 30 at the jaws 24 and the interaction of the 5 axle with the cam profiles 29 forces the jaws to open, against the spring-loading on the piston, to allow the axle to be received into the jaws. The spring-loading urges the jaws to close round the axle as soon as it passes the bottom ends 28 of the jaws. When fully received into the jaws the bottom ends overlap in the over-centre position so that the 10 weight of the axle on the bottom ends actually acts to hold the jaws together. Hence the axle is held very securely in the stowed position by the jaws. While the air supply to the trailer is disconnected the piston cannot be operated to open the jaws.

15 When the air supply is re-connected, upon initiation of pressurization of the air springs 17, 21 the air chamber of the piston 35 is quickly pressurised and the piston rod 37 is extended to open the jaws. Once the jaws have opened sufficiently to separate their bottom ends the axle is able to push the jaws apart as it is lowered from the stowed position, so 20 as to be released from the jaws.

The piston holds the piston rod extended while the air supply is connected to the air springs 17,21.

25 In a modification, as shown in Figure 5, the bottom ends of the jaws 24 are provided with rollers 41 instead of the cam profiles 29 to facilitate separation of the jaws by the axle, as the axle is moved to the stowed position, for the axle to be received into the jaws.

30 Also in Figure 5, the piston 35 of Figure 4 is substituted by a piston and cylinder unit 35A, and spring-loading is applied by at least one tension

spring 62 external of the unit 35A and acting between ends 31 of at least one pair of jaws 24 or between the connecting bars 32, 33 (see Fig. 4) to close the jaws when the piston and cylinder unit is not pressurised.

5 It will be understood from the foregoing description that a simple yet

effective arrangement is provided for holding the axles of the road/rail trailer in the stowed positions. The axle retention means for each axle is relatively cheap to manufacture and install. It may be fitted as original equipment to a trailer, or it may be readily applied to an existing trailer.

Claims

1. An air suspension unit for a road/rail trailer, comprising a road wheel axle which mounts to a chassis or frame of the trailer for 5 movement by air-operated means between a lowered operative position of the road wheel or wheels carried by the axle and a raised stowed position of the road wheel or wheels, and axle retention means comprising jaws operatively connected to an air-operated piston which are normally mechanically urged to a closed position in which they engage around the 10 axle when the axle is in the stowed position, to retain the axle in that position, and which are opened by the piston to release the axle.

2. An air suspension unit according to claim 1 wherein the piston is actuated under a small volume of air in its operating chamber so that 15 there is rapid de-pressurisation and re-pressurisation of the chamber when the air supply is respectively disconnected and restored.

3. An air suspension unit according to claim 2 wherein re-pressurisation of the chamber to operate the piston for opening the 20 jaws is caused to be completed before the air-operated means is at the required pressure to function for lowering the axle to the operative position. 4. An air suspension unit according to any preceding claim wherein 25 the jaws are spring-loaded to the closed position.

5. An air suspension unit according to claim 4 wherein the spring-loading acts on the piston to cause the piston to urge the jaws to the normally closed position when the operating chamber of the piston is 30 depressurised.

i 6. An air suspension unit according to any preceding claim wherein the jaws are weighted or supported to be urged by gravity to the closed position. 5 7. An air suspension unit according to any preceding claim wherein the jaws have an over-centre pivotal action such that extremities of the jaws pass through a medial plane containing the pivotal axis of the jaws in moving to the closed position, and the jaws extend around more than half the circumference of the axle.

8. An air suspension unit according to claim 7 wherein the jaws are each of a generally S-shape comprising two oppositely curved portions a first one of which extends through more than 180 and forms the jaw proper and the second is operatively connected to the piston, a pair of the 15 jaws being relatively pivoted about a pivotal axis at a transition of their Sshapes between said curved portions for movement between the closed and opened positions.

9. An air suspension unit according to claim 8 wherein the second 20 portions of the jaws of the pair are connected to two parallel bars, a housing of the operating chamber of the piston being attached to one of the bars and a piston rod of the piston extending between the two bars and being attached to the other bar.

25 10. An air suspension unit according to claim 8 or claim 9 wherein there are spaced pairs of the jaws which engage with the axle at spaced positions along its length.

11. An air suspension unit according to claim 10 wherein the pairs of 30 jaws are linked for operation together.

12. An air suspension unit according to claim 11 wherein the piston operates to open the linked pairs of jaws.

13. An air suspension unit according to claim 12 as dependent from 5 claim 9 wherein the two parallel bars extend between and are connected to the spaced pairs of jaws.

14. An air suspension unit according to claim 10 wherein the pairs of jaws each have their own operating piston for opening the jaws.

15. An air suspension unit according to any preceding claim wherein the, or each, piston is connected to the air supply to the air-operated means. 15 16. An air suspension unit according to any preceding claim wherein the jaws have cam profiles with which the axle engages as it moves towards the stowed position, the interaction between the axle and cam profiles forcing the jaws apart, against the mechanical urging, to receive the axle.

17. An air suspension unit according to any of claims 1 to 15 wherein the jaws carry rollers or rotatable bearings positioned to be engaged by the axle for urging the jaws apart as the axle approaches the stowed position. 18. A road/rail trailer which includes an air suspension unit according to any preceding claim and comprises a chassis or frame and air-operated means, the road wheel axle of the air suspension unit carrying a road wheel or wheels, being mounted to the chassis or frame and movable by 30 the air-operated means between a lowered operative position of the road wheel or wheels and a raised stowed position of the wheel or wheels, and

the axle retention means being carried by the chassis or frame with the jaws supported for pivotal movement about an axis parallel to the axle.

19. A road/rail trailer according to claim 18 wherein the air suspension 5 unit includes a hanger bracket which is secured to and depends from the chassis or frame, a leaf spring pivotally connected at one end to the hanger bracket for pivotal movement about an axis parallel to the road wheel axle, an air spring support member fixed to an opposite end of the leaf spring and an air spring of the air-operated means mounted on the air 10 spring support member, the road wheel axle being attached to the leaf spring intermediate the hanger bracket and the air spring support member, the air spring being pressurised to urge the leaf spring and road wheel axle away from the chassis or frame to the lowered operative position of the wheel or wheels for normal road travel of the trailer and deflated for 15 the road wheel axle to be raised to the stowed position, and the axle retention means being retained to the chassis or frame over the road wheel axle for the jaws to engage with and retain the axle when the axle is raised to the stowed position.

20 20. A road/rail trailer according to claim 19 wherein a shock absorber is connected to, to act between, the hanger bracket and the attachment of the road wheel axle to the leaf spring.

21. A road/rail trailer according to claim 19 or claim 20 wherein the 25 air spring has a piston at a lower end fixed on the air spring support member and an upper end of the air spring is connected to an arm, extending lengthwise of the leaf spring, which is pivoted to the hanger bracket about an axis parallel to the axis of the pivotal connection of the leaf spring to the hanger bracket, and which arm is connected to a further 30 air spring of the air-operated means mounted to act between the arm and

l the chassis or frame for raising the chassis or frame for the trailer to be supported on bogies for rail travel.

22. A road/rail trailer according to any of claims 18 to 21 wherein the 5 air-operated means further comprises a lift air spring which acts on a lever pivoted at a fulcrum on the hanger bracket and is anchored to the chassis or frame, the lever being pivotally moved by the lift air spring to apply lifting force to the road wheel axle for moving the axle to its stowed position.

23. A road/rail trailer according to any of claims 18 to 22 wherein the air suspension unit is provided at one side of the chassis or frame and is duplicated at the opposite side of the chassis or frame.

15 24. A road/rail trailer according to any of claims 18 to 22 wherein the air suspension unit is provided at one side of the chassis or frame and is duplicated at the opposite side of the chassis or frame, the road wheel axle being common to the two units and pairs of the jaws being spaced axially of the road wheel axle for engaging with, and retaining, the axle 20 in its stowed position.

25. An air suspension unit substantially as described herein with reference to the accompanying drawings.

25 26. A road/rail trailer substantially as described herein with reference to the accompanying drawings.