GB2160832A - Lowering suspension system - Google Patents

Abstract

A pull-type road trailer has a wheel suspension assembly actuated by hydraulic rams 10, 11 having a pneumatic accumulator 14 in parallel therewith and the arrangement being such that the trailer frame while supported at the front can be lowered to a position at which the rear end touches or is close to the ground. The trailer comprises two pairs of wheels and can be converted from a four wheel to a two wheel mode for unladen and light duty work. <IMAGE>

Description

SPECIFICATION Vehicle suspension assembly This invention relates to vehicle suspension assemblies. The invention is particularly but not exclusively applicable to suspension assemblies for use in trailers for use on roads and highways, but the invention may also be applicable to suspensions for other types of land vehicles.

In the case of a road trailer having more than one axle, the permissible gross trailer weight may be substantially greater than the unladen weight of the trailer. Hence, the suspension characteristics of the trailer suspension must be provided having more regard to the laden condition than to the unladen state of the trailer. Furthermore, in the case of small trailers especially those drawn by motor cars, it has been necessary to compromise, for reasons of cost, between the spring rates in bump, bounce, roll and pitch modes, and to neglect damping. Finally, it is difficult to load demountable bodies and wheeled vehicles on to this type of trailer.

A further factor in relation to trailer design concerns loading and unloading. In the case of trailers used for transporting horses and other livestock it is usual to provide a fold-down ramp and associated fold-down side rails. However, these arrangements are by no means entirely satisfactory, and some improvements are certainly called for not only with regard to loading and unloading livestock but also in relation to boat trolleys and other cargo which may be carried.

Thus, an object of the present invention is to provide an improved suspension assembly for a land vehicle, and/or a land vehicle incorporating same offering improvements in relation to one or more of the matters discussed above, or generally.

According to the invention there is provided a suspension assembly for a land vehicle, particularly but not exclusively a road trailer, comprising one or more of the following features. The suspension assembly may be converted from a four-wheeled configuration for load carrying purposes to a twowheeled configuration for unladen and light duty work. This conversion can have the effect of halving the wheel rate in bump and roll. The suspension assembly may comprise hydraulic cylinders or like actuators to effect change of configuration of the suspension assembly. The hydraulic cylinders may interconnect levers on adjacent trailing arms of the suspension assembly. A gas accumulator, or like means may be provided to offer resilience in the suspension assembly. The gas accumulator may be connected in parallel to the hydraulic cylinders.A manually operable hydraulic pump may be provided to actuate the hydraulic cylinders to effect changes in height of the vehicle suspension. Damping devices may be provided, for example incorporated into the hydraulic lines. A desired degree of resist ance to roll may be provided by torsion springs interconnecting oppositely-disposed suspension assemblies of a vehicle.

The invention provides as an important feature, a vehicle comprising one or more of the features as defined above in combination with an arrangement whereby the rear portion of the vehicle can be lowered towards the ground for loading and unloading purposes. This can be achieved by supporting the front end of the vehicle, where same is in the form of a trailer, either on the towing vehicle or by means of a jockey wheel, and then lowering the suspension so that the whole trailer is lowered and the rear end approaches the ground. Indeed, the rear end may touch the ground and thus itself form a sloping loading ramp. For this purpose it is arranged that the frame or chassis of the trailer is constructed so that, in the region of the ground wheels, the frame lies between the wheels and is thus able to be lowered sufficiently.In the case of certain previously proposed vehicles having adjustable suspension the frame of the vehicles overlies the ground wheels and renders the above-described function impossible.

The invention also provides a road vehicle, especially a trailer, incorporating suspension assemblies as defined above.

The invention also provides a vehicle, especially a road trailer, comprising a suspension assembly having one or more novel features or any novel combination of features disclosed herein.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a plan view of a trailer chassis incorporating a suspension assembly according to the invention; Figure 2 shows a side elevation view of the trailer of Figure 1; Figure 3 is a hydraulic circuit diagram of the trailer suspension assemblies of Figures 1 and 2; Figure 4 shows, in a view similar to that of Figure 2, the suspension assemblies of the trailer of Figures 1 and 2 in the configuration for unladen or lightlyladen use with only one pair of wheels carrying the trailer's weight; and Figure 5 shows the suspension assemblies of the trailer fully lowered for vehicle loading purposes.

As shown in the drawings, a road trailer has a chassis 1 and maybe towed by a motor vehicle or connected to such vehicle by a fifth wheel arrangement.

Suspension assemblies 2,3,4 and 5 are pivotally connected to chassis 1 by bearing assemblies (not shown) on axles which extend substantially laterally and horizontally. At the outer end of each suspension assembly 2,3,4 and 5 is a trailing arm at the extremity of which is an axle upon which is rotatably mounted a wheel and tyre assembly 6, 7, 8 and 9.

At the inner end of each suspension assembly 2, 3, 4 and 5 are levers. The levers are angularly disposed with respect to the trailing arms in such a way that upward movement of wheel and tyre assemblies 7 and 8 cause a component of movement in the forward direction of the lever ends and upward movement of wheel and tyre assemblies 6 and 9 causes a component of movement in the rearward direction of the lever ends.

Pivotally connected to the ends of the levers of adjacent pairs of suspension units are hydraulic cylinders or rams, cylinder 10 connecting suspen sion assemblies 2 and 3 and cylinder 11 connecting suspension assemblies 4 and 5. Interconnecting opposing suspension assemblies 3 and 4 and 2 and 5 are spring units 12 and 13, which may be positioned co-axially with the suspension units as shown, or otherwise.

The outlets of the rod or annular sides of hydraulic cylinders 10 and 11 are connected via restrictors 17 and 18 to each other and to gas accumulator 14, and viaavalve l9toahand pump 15 and reservoir 16.

During loading and unloading of the trailer, in particular with motor vehicles, and boat trolleys, and demountable bodies, hydraulic fluid may be introduced to or exhausted from hydraulic cylinders 10 and 11 using valve 19 and pump 15. When the load carrying platform is in the fully lowered position, as shown in Figure 5, further rotary movement of the front suspension units 3 and 4 can be prevented by means of latches (not shown). Subsequent pumping of hydraulic fluid into the cylinders 10 and 11 will raise the platform by means of rotary movement of the rear suspension assemblies 2 and 5 only.

In the above embodiment, attention is drawn particularly to the wheel mounting arrangements whereby the wheels themselves are mounted on lever arms 30,32,34 and 36 which are pivotally mounted on the frame 37 of the vehicle. These lever arms are connected by torque tubes 37A, 37B, 37C, 37D to corresponding short lever arms 38,40,42 and 44 between which the rams 10, 11 are pivotally interconnected.

It is also particularly noteworthy, as can be seen from Figure 1, that the frame 37 of the vehicle in the region of the ground wheels 6,7,8 and 9 is located entirely within ie inboard of, the ground wheels so that the frame can be lowered between the wheels to the sloping loading configuration. In this latter configuration, demountable bodies such as goods or livestock containers can be readily mounted and dismounted. For example, the trailer can be backed underneath a body supported on slightly outwardly cranked legs. At this stage, the trailer is in a somewhat lowered condition. Then, the trailer is raised to support the body and the latter is attached and the assembly can be driven away.

In an alternative configuration each hydraulic cylinder may be connected via a restrictor to its own gas accumulator. This eliminates the need for antiroll springs 12 and 13 but requires the addition of a device with which ride heights may be equalised.

Among the advantages provided by the embodiment of the invention disclosed above are the following: 1. The use of nitrogen gas as the springing medium together with the correct choice of suspension geometry provides a rising springing rate.

2. The interconnection of adjacent suspension units provides good ride characteristics.

3. The separation of the resistance to motion about lateral and longitudinal axes enables optimisation of the respective spring rates.

4. The connection of the hydraulic cylinders to the accumulator allows the installation of damping devices.

5. The variable length link between adjacent suspension units allows the raising and lowering o the platform either for the loading and unloading o vehicles orforthe mounting and demounting of detachable trailer bodies.

6. The above facility obviates the need for loading ramps for vehicles, boat trolleys and livestock.

7. The above facility also provides the means by which one pair of wheels may be locked into the raised position, converting the trailer into a twowheeled one for unladen use.

8. The conversion of a two-wheeled trailer provides a substantial reduction in spring rate with a corresponding improvement in ride and handling.

9. If the trailer is to be used for the transport of light but bulky articles, then it can be also used in this (two-wheel) mode.

10. The conversion to a two-wheeled trailer also reduces tyre wear and noise and makes the vehicle more manoeuvrable by hand.

11. If the trailer is required for off the road use, th ride height can be increased further and the suspen sion stiffened considerably by raising the pressure the system.

12. As a tipping trailer, the facility provided by th suspension assemblies enables a benefit in terms c increasing the tipping height and furthermore, the hand pump together with a divertervalve may be used to effect the tipping.

13. The trailer has a built in jacking device which allows simple wheel changes.

14. Summarising the advantages provided by the above embodiment, attention is drawn to the use o a manual or powered hydraulic pump and valve allowing simple raising and lowering to ground lev of the rear of the trailer. This enables vehicles, boat trolleys and livestock to be loaded with the minimu of difficulty without using ramps. Additionally, the suspension system, by using hydraulic rams and parallel gas accumulators, in conjunction with valv within the interconnecting pipes, provides greatly improved ride and handling characteristics. Mores er, the suspension system allows the trailer simply to be converted from a four wheeled configuration a two wheeled condition for unladen use. In this way, the bouncing associated with empty trailers is reduced and manoeuvring, especially by hand, is rendered much easier and tyre wear reduced. The interlinking of adjacent suspension arms further enhances the smoothness of the ride which is of particular benefit for use over rough terrain.

Many modification can be made in the abovedescribed embodiment without departing from the scope of the invention, including use of the suspen sion assemblies in other vehicles, despite the fact that road trailers represent a field of longfelt want f the invention.

Among the modifications mentioned above whic fall within the scope of the invention, are the following: a) For the purpose of counteracting any hydraulic leakage which may occur over a period of time and/or during use of the suspension system, there may be provided pump means to maintain pressur in the system. For example, such pump means ma) comprise a small diameter piston pump (piston diameter for example 6.4 millimetres) arranged to be mechanically actuated by relative movement of structural components of the suspension system.

b) As an alternative to the manually operated pump, there may be provided a suitable power pump. For example, an electrical pump could be provided on the trailer and provided with an electric supply cable from the towing vehicle. Alternatively, a belt-driven or otherwise mechanically driven pump could be provided on the towing vehicle with a suitable hydraulic supply to the trailer. In either case, suitable fluid control means may be provided. For example, a control valve may be arranged to sense when the vehicle suspension has reached the desired height. At that point, further fluid supply may be dumped to a tank or else (in the case of the electrically operated pump) the pump can be shut down.

Claims (11)

1. A road vehicle comprising a suspension assembly for at least one pair of wheels, the suspension assembly being actuatable to permit the rear portion of the vehicle to be raised and lowered between a raised travel position and a lowered loading/unloading position.

2. A vehicle according to claim 1 in the form of a pull-type trailer having a drawbarfor attachment to a towing vehicle.

3. A vehicle according to claim 1 or claim 2 wherein the frame or chassis of the vehicle lies between the wheels thereof, at least in the region of said wheels.

4. A vehicle according to any one of the preceding claims wherein said suspension assembly comprises a hydraulic actuator to permit said raising and lowering.

5. A vehicle according to claim 4 comprising a pneumatic reservoir connected to the said hydraulic actuator to provide a degree of resilience in the suspension operating characteristics.

6. A vehicle according to any one of the preceding claims comprising two pairs of ground wheels arranged to be actuated to permit said raising and lowering of the rear of the vehicle, the arrangement being such that the suspension assembly may be converted from a four-wheeled configuration for load carrying purposes to a two-wheeled configuration for unladen and light duty work.

7. A vehicle according to claim 6 wherein an actuator for the suspension assembly is connected between the suspension mechanisms of each of said pairs of ground wheels.

8. A vehicle according to claim 7 wherein said actuator is connected between lever arms which are pivotally mounted on the vehicle frame and arranged to be turned by raising and lowering movement of the vehicle wheels.

9. A vehicle according to any one of the preceding claims comprising a demountable load-carrying structure adapted to be mounted on the vehicle frame.

10. A road vehicle in the form of a pull-type trailer substantially as described herein with reference to the accompanying drawings.

11. A method of loading a trailer comprising the step of supporting the front end of the trailer at a given height from the ground, and actuating the trailer suspension so that the rear portion of the trailer is lowered towards the ground.