GB2191741A

GB2191741A - Adjustable trailer wheel suspensions

Info

Publication number: GB2191741A
Application number: GB08612421A
Authority: GB
Inventors: Brian William Clay
Original assignee: LODGE TRAILERS
Current assignee: LODGE TRAILERS
Priority date: 1986-05-22
Filing date: 1986-05-22
Publication date: 1987-12-23
Also published as: GB2191741B; GB8612421D0

Abstract

A trailer unit (12, Fig. 1) adapted for towing behind a tractor (10), has transverse axles 40,42 mounted on trailing arms 32,34 on a subframe 24 pivoted at one end on the trailer chassis 22. Inflatable air-springs 36,38 provide for trailer height adjustment and air-springs 44,46, mechanical jacks or hydraulic rams, between the subframe and chassis, provide for additional height adjustment or lifting of rear wheels (20, Fig. 1) from the ground if the subframe pivot 26 is at its rear rather than front end. A valve (52, Figs. 1 and 4) may control both sets of air-springs and operate the vehicle braking system when the springs are inflated. <IMAGE>

Description

SPECIFICATION Improvements in and relating to trailers and suspen sions therefor Fieldofinvention This invention concerns trailers of the type which are conventionally hitched to a towing tractor unit to form a so called articulated lorry and to suspension systems therefor. Such trailers will be referred to as trailers of the type described.

Background to the invention It is known to provide air-spring suspension units between trailers and their road wheel axles. One such unit is that marketed by Rubery Owen - Rockwell Ltd. Such units not only provide an air cushion between the axle and the trailer chassis to absorb vibration and bumps but can also be used in conjunction with a heightand/orlevel securing deviceto adjust the height of the trailer relative to the axles to compensate for differences which cou Id otherwise occur between the loaded and unloaded condition of the trailer.

However, where roll-on or roll-offloading and unloading is required at a variety of different levels it has been found that the range of height adjustment ofthestationarytrailerbypressurising ordep- ressurising a conventional air-spring is insufficient to overcome all but incidental differences in loading platform heights.

It is an object of the present invention to provide a suspension system for a trailer whereby the height of the rear ofthe trailer can be adjusted when the vehicle is stationary to accommodate a wide range of loading platform heights.

It is afurther objectofthe invention to provide an improved trailer incorporating such a suspension system.

Summary of the invention According to one aspect of the invention a suspension system for a trailer of the type described comprises: 1. a subframe adapted to be secured to the underside of the trailer by a pivotal connection at one end and via at least one expansible member at its opposite end, 2. at least one pair of trailing arm axle supports pivotally attached attheirfront ends to the subframe and at their rear ends via inflatable air-springs, each said pair of trailing arms being attached to a transverse road wheel carrying axle.

3. airline and control valve means for inflating and venting the airsprings to allowfor automatic trailer levelling and to provide in transit an air cushion suspension system between each axle and the subframe, and when stationaryafirst meansforaltering the height of the rear of the trailer relative to the axles (and therefore the ground), and 4. means for expanding and contracting the said at least one member to obtain additional lift by raising the trailer relative to the subframe.

The subframe may be attached to the trailer in the form of a trailing linkor if greater lift is required, may be adapted to be pivotally joined to the trailer at its rear end, so that the subframe extendsforwardly from its pivotal connection to the trailer and the expansible member(s) is/are located between the leading end of the subframe and the trailer.

The subframe is preferably attached by means of the pivotal connection and the said expansible memberto a chassis on which a load carrying deck or container is attached.

The expansible member may be a mechanical linkage and such as a scissors action jack, a nut and screw jack, a hydraulic ram or pneumatically inflatable member such as an airbag/air-spring. The latter is preferred where air springs are employed between the axle supports and the subframe since the air supplyforthe latter can also be used to inflate the expansible member(s) when the extra lift is required.

Since it could be dangerous to operate the trailer on a road with the trailer in an elevated mode, an interlock may be provided between the road wheel brakes and the power supplyforthe expansible member(s), which either inhibits the expansion of the latter if the brakes are not applied, or automatically applies the brakes if power is supplied to the expansible member(s) to lift the trailer relative to the subframe.

Preferably stop means is provided on the subframe orthe trailer (typically on the trailer chassis) to inhibit relative lateral movement of the subframe and trailer (typically the trailer chassis), at least when the expansible member(s) is/are in its/theircollapsed condition. Typically upstanding side cheeks are provided on the subframe, between which the main trai lerchassis slides and fitswhen the expansible member(s) is/are collapsed.

Where, as is conventional, air brakes are provided forthe road wheels, the supply of powerto the expansible memberto lift the trailer relative to the subframe, may be arranged to provide an air signal to the braking circuit equivalent to that which exists when the service brakes are applied as by depressing the brake pedal in the cab of the tractor unit.

Preferably control means for inflating the air spring suspension and for actuating the expansible member is provided on the subframe or is adapted to be fitted belowthe trailer typically on the main chassis ofthetrailer.

The invention also lies in a road trailer chassis and a roadtrailerwhen either is fitted with a suspension system having an expansible member as aforesaid.

In a preferred embodiment of the invention a road trailerfortowing behing a tractor unit having a cab fora driver comprises: 1. a chassis adapted at its front end for attachment to the tractor unit, 2. a subframe pivotally attached at one end to the trailer chassis towards (or at) the rear end of the chassis and at its other end via at least one expansible member comprising an inflatable air-spring located between the chassis and a mounting on the subframe, 3. at least one transverse axle and pair of air braked road wheels carried bythe subframe,the axle itself being attached to a pairoftrailing arm axle supports which are attached to the subframe attheirfront ends by means of pivotal connections and attheir rear ends by means of air-springs, in manner known perse, 4. an air supply on the tractor unit orthe trailer and pipeline and first valve means for conveying airto the air-springs, and 5. second valve means operableto supply air to (or vent airfrom) the air brakes (as required to apply the brakes) when thefirstvalve means is operated to supply airto the expansible memberto lift the trailer relative to the subframe.

The invention will now be described byway of example with reference to the accompanying drawings in which: Figure lisa side view of an articulated motorvehiclefitted with a lifting suspension embodying the invention.

Figure2 is a side view to an enlarged scale and partly cut away to show the air-springs and subframe ofthe lifting suspension system.

Figure 3 is a plan viewofthe rear end of the trailer chassis showing the relative positions of the subframe and air-springs, and Figure4 is a diagram of the pneumatic control cir- cuitandvalving.

Figure 1 illustrates an articulated vehicle comprising tractor unit 10 with driving can and a trailer 12 connected to the tractor unit byway of a conventional fifth wheel coupling (not shown in detail).

The tractor unit has two sets of road wheels 14, 16 and the trailer unit incl udestelescopic (or otherwise adjustable) legs (not shown) at its front end - for sup- porting itsfront end when detached from the tractor unit) and two sets of road wheels 18,20 on transverse axles which are carried by a subframe in accordance with the invention and which is itself sprung relative to the main chassis 22 of the trailer unit and is adjustable relative to the main chassis so that the latter can be raised and lowered relative to the road wheel axles.

The invention basically lies in the provision ofthe subframe and associated expansible memberforeffecting relative movement between it and the main chassis. In Figure 2 the subframe 24 is shown in a displaced condition (i.e. with trailer chassis slightly raised). The subframe is pivotally attached at its front end to hinge points such as 26 and has two downwardly depending mounting brackets 28,30 from the lower ends of which two rigid axle supporting arms 32 and 34 are hinged, respectively. The rear end of each arm 32,34 is attached to the lower end of an inflatable air-spring 36,38 respectively, the other ends of which are secured to the subframe.

The air-springs are of the type manufactured and sold by Rubery Owen - Rockwell Ltd.

Transverse axles 40,42 are secured to the arms 32, 34 (which have counterparts on the opposite side of the trailer) and the road wheels are mounted outboard thereof with air operated drum brakes (not shown).

Relative displacement of the subframe and chassis is effected by inflating or deflating air-springs shown at 44,46. If its load carrying capacity is sufficient, a single air spring may be located at 46. (As shown in Figure 4, there are foursuch air-springs of which only two are shown in Figure 2).

As shown in Figure 4,air is supplied tothetrailer from a compressor (not shown) on the tractor unit 10 via flexible hoses (not shown). A foot operated valve (not shown) controls the supply of air along a service braking pipeline 48. Air is also supplied along the emergency pipeline 50, in known manner, all the time the tractor unit is coupled to the trailer and air pressure is available.

Acontrol valve 52 is positioned at the rearofthe trailer chassis 22 (see Figure 1) and this has three positions.

In the normal ride position air from a suspension air reservoir 54 is prevented from passing through the valve and can only pass to the suspension air springs 36,38 (and 56,58 see Figure 4) via a levelling valve 60. This is ofthe type supplied by the air-spring manufacturers and operates in known matter to inflate orventthe airspring 36,38,56 and 58 to obtain a level trailer. This also effectively determines the ride height.

The lifting air-springs 44,46 (and 62,64 see Figure 4) are therefore incoperative in this mode.

If it is wished to lowerthe tail ofthe trailer, valve 52 is turned to its secured position in which line 66 is vented via the valve 52 whilst simultaneouslythe line 68 is shut off from the line 66 so that the air-springs 36,38,56 and 58 can deflate to the desired amount thereby lowering the rear of the trailer.

Raising from a iowered position to a normal ride position is achieved by simply rotating valve 52 back to its first described position when air can again flow from reservoir 54 via valve 60 to the air-springs 36, 38,56 and 58 to inflate them until the normal ride height is achieved.

Further elevation is possible if the valve is rotated to a third position in which air from 54 is supplied directly to the air-springs 36,38,56 and 58 via line 70, valve 52 and line 66 (i.e. reversing the previous role of line 66) and also via line 72 to the four lifting airsprings 44,46,62 and 64 mounted between the subframe 24 and the main chassis 22.

Pressure in the system is limited in a conventional manner by a pressure release valve (not shown) set to blowatthe desired maximum pressure.

In addition to supplying the four lifting air-springs, line 72 also supplies air under pressure via line 74to valve 76 in the service braking system,the re sponse to which is the same as if the service line had been pressurised as would arise if the service brakes had been applied from the driving position in the cab of the tractor unit.

It is to be noted in passing that the levelling of valve 60 also supplies a load feed-back signal to a proportioning valve 78 in the braking system to obtain load sensitive braking.

If the subframe 24 is reversed relative to its position shown in Figures 1 and 2 so that it is pivoted at its rear end to the rear of the trailer chassis, inflation ofthe air-springs 44 and 46 etc. will allowthe rearmostwheelsto be lifted clearoftheground and ion a lightly loaded condition, it is possible forthe trailerto be operated this with a shorterwheelbase (and therefore turning circle) and reduced tyre wear. To this end an overide control (not shown) must be pro vided if this facility is required, to inhibit the automatic braking when the line 72 is pressurised.

Claims

1. A suspension system for a trailer of the type which in use is hitched to a towing tractor unitto form a so-called articulated lorry, said suspension system comprising: (i) a subframe adapted to be secured to the underside of the trailer by a pivotal connection at one end and via at least one expansible member at its opposite end, (ii) at least one pair of trailing arm axle supports pivotally attached attheirfront ends to the subframe and at their rear ends via inflatable air-springs, each said pairoftrailing arms being attached to atransverse road wheel carrying axle, (iii) airline and control valve means for inflating and venting the airsprings to allowfor automatic trailer levelling and to provide in transit an air cushion suspension system between each axle and the subframe, and when stationary a first means for altering the height ofthe rear of the trailer relative to the axles (and therefore the ground), and (iv) means for expanding and contracting the said at least one member to obtain additional lift by raising the trailer relative to the subframe.

2. A suspension system according to Claim 1, wherein the subframe is attached to the trailer in the form of a trailing link.

3. A suspension system according to claim 1, wherein the subframe is adapted to be pivotally joined to the trailer at the rear end thereof, so thatthe subframe extends forwardly from its pivotal connection to the trailer and that least one expansible member is located between the leading end of the subframe and the trailer.

4. A suspension system according to claim 1, wherein the subframe is attached by means of a pivotal connection and the said expansible member to a chassis on which a load carrying deckorcontainer is mounted.

5. A suspension system according to any one of claims 1 to 4, wherein the expansible member is a mechanical linkage.

6. A suspension system according to any one of claims 1 to 4, wherein the expansible member is a pneumatically inflatable member.

7. A suspension system according to claim 6, wherein the inflatable member is an air bag/airspring.

8. A suspension system according to claim 7, having air-springs located between the axle supports and the subframe, whereby an air supplyfor said subframe can also be employed to inflate the at least one expansible member.

9. Asuspensionsystem according to any one of claims 1 to 8, including an interlock provided between the road wheel brakes and the power supply for the at least one expansible member, whereby the expansion of the at least one expansible member is inhibited if the brakes are not applied or the brakes are automatically applied if power is supplied to the at least one expansible member to Iiftthe trailer relative to the subframe.

10. A suspension system according to any of claims 1 to 9, wherein stop means is provided on the subframe or on the trailer chassis to inhibit relative lateral movement of the subframe and the trailer chassis, atleastwhen the at least one expansible member is in its collapsed condition.

11. A suspension system according to any of claims 1 to 9, wherein stop means is provided on the trailer chassis to inhibit relative lateral movement of the subframe and the trailer chassis, at leastwhen the at least one expansible member is in its collapsed condition.

12. A suspension system according to claim 10 or 11, wherein upstanding side cheeks are provided on the subframe, between which the main trailer chassis is slidable and is accommodated when the at least one expansible member is collapsed.

13. A suspension system according to any one of the preceding claims, having air brakes provided for the road wheels, wherein the supply of power to the at least one expansible member for lifting the trailer relative to the subframe is arranged to provide an air signal to the braking circuit equivalent to the at provided when the surface brakes are applied, ie the signal produced when depressing the brake pedal in the cab of the tractor unit.

14 Asuspensionsystem according to any one of the preceding claims, wherein control means is provided on the subframe or the trailer chassis for inflating the airspring suspension and for actuating the at least one expansible member.

15. A road trailer chassis equipped with a suspension system according to any one of the preceding claims.

16. Aroadtrailerfortowing behindatractorunit having a cabforthe driver, comprising: (i) a chassis adapted at its front end for attachmentto the tractor unit, (ii) a subframe pivotally attached to one end to the trailer chassis towards (or at) the rear end ofthe chasis and at its other end via at least one expansible member comprising an inflatable air-spring located between the chassis and a mounting on the subframe, (iii) at least one transverse axle and pair of air braked road wheels carried by the subframe, the axle itself being attached to a pair of trailing arm axle supports which are attached to the subframe attheirfront ends by means of pivotal connection and at their rear ends by means of air-springs, in manner known per se, (iv)an air supply on the tractor unit or the trailer and pipeline and irstvalve meansforconveying airtothe air-springs, and (v) second valve means operable to supply air to (or vent air from) the air brakes (as required to apply the brakes) when the first valve means is operated to supply air to the expansible member to lift the trailer relative to the subframe.

17. A suspension system substantially as here it before described with reference to the accompanying drawings.

18. A road trailer substantially as hereinbefore described with reference to the accompanying drawings.