GB2252090A - Rigid vehicle for bulk loads. - Google Patents

Abstract

The vehicle comprises a traction unit (1), front wheels (2) and a front chassis (3) which is connected by a step (4) to a rear chassis (5). A deck is supported on the rear chassis (5) which itself is supported by rear wheels (6), (7) which are smaller in diameter than the front wheels (2). The rear wheels (6), (7) are supported on axles (8), (9) which are attached to the rear chassis (5) by means of self-levelling suspension units. This arrangement provides a long, low load deck and increased load space. <IMAGE>

Description

Commercial Vehicle.

This invention reiates to an improved commercial vehicle for use in the transport of bulk loads.

i-he volume of goods being transported annually on roads by lorries and other commercial vehicles is increasing to a marked extent. Consequently there is a corresponding increase in pressure on designers of commercial vehicles to produce larger vehicles within the restrictions imposed by laws or official regulations relating to the design and operation of such vehicles.

Rigid vehicles ie. non-articulated vehicles with long decks in the order of 9-12 metres are now used widely. A deck is the flat platform on which a load is placed and it can be open or covered. However such vehicles suffer from the disadvantage in that the deck is situated at an undesirably high level due to the fact that wheels of large diameter ie of the order of 90 to 110 cms are required to carry the load and the deck is located above the wheels. References in this specification to a diameter of a wheel shall be taken to include the diameter of the wheel including its fitted tyre.

Consequently not only does this result in the vehicle having a relatively high centre of gravity which is undesirable but in addition the height of the deck creates difficulties in loading or unloading of the vehicle.

In order to avoid these difficulties a practice has developed of employing se called "low-loaders". These are articulated vehicles which incorporate a long low deck which is supported by a number of small wheels rotating about several axles. The deck is separate from the traction unit of the vehicle and the two have to be coupled together prior to use. Lowloaders are of especial value in the transport of very heavy or very voluminous loads. However they have the disadvantage in that they are expensive both to manufacture and to operate. Furthermore in a number of localities low-loaders attract higher licensing fees compared with those levied on non-articulated vehicles.

In order to overcome the limitations of these vehicles rigid vehicles have been developed with low slung decks. However they have not been satisfactory. In some of the vehicles smaller wheels are employed. However in such cases the length of the deck is too short to permit the carrying of large quantities of goods. In vehicles which have the desired length of deck the latter is not low slung continuously along its length. This is because hitherto wheels of large diameter have been required to carry the load and the part of the deck located towards its rear end is required to rise up and pass over these wheels. The low slung part of the deck then forms a well between the traction unit and the rear wheels. Consequently loading of the deck, particularly when it is covered, has to be carried out from the side of the vehicle.

The present invention is directed to a rigid vehicle having a long low slung deck, which avoids the disadvantages of the existing vehicles. In addition it provides a means whereby traction units originating from different manufacturers can be provided with a long low deck rearwardly of the drivers cab. The present invention is directed further to the production of a rigid vehicle in which the maximum height of a load falls within limits which comply with laws or other official regulations.

Accordingly this invention provides a rigid vehicle comprising a traction unit incorporating a front chassis carried by a plurality of front wheels and a rear chassis connected by a step to the front chassis the rear chassis carrying a deck extending in one plane from the traction unit to the rear of the vehicle, the deck extending over a plurality of rear wheels carried by a plurality of axles so as to form a small gap between the lower surface of the deck and the top of the rear wheels, the rear chassis being supported by a pneumatic self levelling suspension means which maintains the gap at a predetermined height, the diameter of the front wheels being greater than the diameter of the rear wheels.

This invention is illustrated but not restricted by the following drawings. Where appropriate all measurements relate to a vehicle which is both stationary and unladen.

Figure 1 is a side view of one preferred form of vehicle according to the invention Figure 2 is a plan view of the vehicle shown in Fig.l with deck removed.

Figure 3 is a side view of part of the self levelling suspension mechanism.

Figure 4 shows in greater detail the stepped connection shown as A in Fig.l With reference to the drawings the vehicle comprises a traction unit 1 consisting of a cabin, the engine and associated driving controls, front wheels 2 and front chassis 3 which is connected by a step 4 to rear chassis 5. The latter carries a long low deck which can provide an overall vehicle length of 12.5 metres. The deck extends in one plane from the step connection 4 to the rear of the vehicle and covers two axle assemblies each consisting of two pairs of two wheels 6 and 7 rotating about drive axle 8 and rear axle 9. Drive from the engine is transmitted by a multi sectional prop shaft 10 to drive axle 8.

The diameter of the rear wheels 6 and 7 are preferably as small as practicable taking into consideration the anticipated weight of the load to be carried and the type of drive axle utilised. The diameter of the wheels can be in the range of 76 to 77 cms whereas the diameter of the front wheels carrying the traction unit can generally be within the range of 100 to 105cms. Wheels of the latter size are generally used for conventional rigid vehicles in this category and are therefore considerably larger than those in the present vehicle for carrying the deck. Consequently the use of wheels of relatively small diameter assists materially in enabling a low deck to be employed.In the present vehicle the height of the chassis above the road surface can be as low as 780cms as compared with conventional height of 1054cms.

Another factor affecting the height of the deck is' the size of gap between the top of the wheel and the underside of the deck. During movement of the vehicle this gap is liable to vary especially when the vehicle moves over irregularities on the surface of a road. In addition the gap is liable to be reduced to varying extents according to the weight of the load which is being carried. Gaps of the order of 25-30 cms are generally provided in conventional vehicles. However in accordance with the present invention a substantially smaller gap can be employed which is maintained at a predetermined height of for example 10 cms or even less by means of a pneumatic automatic self levelling supension a part of which is illustrated in Fig 3. In this figure axle drive 8 is secured to a spring arm 31, one end of which is connected to a mounting bracket 32.The latter is fixed to the side of a rail forming part of chassis 5. The other end of the arm is connected to a an air bag 33 which has flexible walls and is fitted with an inlet pipe (not shown) leading to a source of air pressure in the traction unit. The bag is also fitted with a release valve (not shown). The rear axle 9 is mounted on the vehicle in a similar way by means of spring arm 34, mounting bracket 35 and it is also positioned near an air bag 36 which is fitted with an inlet for air pressure and an outlet valve. When air is forced into a bag from a pump located in the traction section of the vehicle the bag expands causing the spring arm and the axle to which it is attached to be fcrced away from the deck thereby increasing the gap between the top of the wheel and the underside of the deck.Conversely when air is released from the bag the latter contracts causing the axle to move towards the deck thus narrowing the gap. Each pair of bags on each axle assembly can be inflated or deflated independently of the other and the suspension system can be controlled from within the traction unit to maintain a gap of a predetermined height. A sensor cooperates with a valve which detects when the deck moves away from its required position and air is ihjected into or allowed to escape from the appropriate pair of bags to redress the situation.

The deck and rear chassis are connected to the traction unit in the manner illustrated in Fig.4. Chassis 3 which supports the traction unit is located above chassis 5 which carries the deck. The two are joined together by a reinforcement plate 41 is fitted to the two chassis by puddle welds 42 and stitch welds 43. Welded mitre joints 44 are also formed into the rails forming the chassis. By this means a long low deck can be connected to traction units originating from different manufacturers. Since such units are liable to vary the method of fixing the unit to the deck may require modification.

Whilst the long decks can be connected to traction units as described above, they can also be connected to other donor units which can comprise complete vehicles. In such instances some parts may need to be removed prior to the addition of a low deck.

Claims (9)

1A rigid vehicle comprising a traction unit incorporating a front chassis carried by a plurality of front wheels and a rear chassis connected by a step to the front chassis, the rear chassis carrying a deck extending in one plane from the traction unit to the rear of the vehicle, the deck extending over a plurality of rear wheels carried by a plurality of axles, a small gap being formed between the lower surface of the deck and the top of the rear wheels, the rear chassis being supported by a pneumatic self levelling suspension means to maintain the gap at a pre-determinded height, the diameter of the front wheels being greater than the diameter of the rear wheels.

2 A rigid vehicle as claimed in claim 1 in which the suspension means comprise a spring arm secured at adjacent the ends of each rear axle, one end of each spring arm being pivotally attached to the rear chassis, and the other end being attached to an air bag.

3 A rigid vehicle as claimed in claimed 2 in which each air bag is provided with pressurising means, and a pressure relief valve.

4 A rigid vehicle as claimed in claim 3 including a position sensor to detect the gap between the deck and the rear wheels, the sensor being operatively connected to the pressurising means to inflate or deflate the or each airbag to increase or decrease the gap.

5 A rigid vehicle as claimed in claim 4 in which the pair of air bags on each on each axle can be inflated or deflated independantly of each other.

6 A rigid vehicle as claimed in any one of the preceding claims in which teh gap can be controlled from within the traction unit.

7 A rigid vehcicle as claimed in any one of the preceding claims in which the front and rear chassis are connected together at their sides by reinforcement plates welded to the side rails of the front and rear chassis.

8 A rigid vehicle as claimed in claim 7 which the side rai3s of the front and rear chassis have mitred joints welded to the reinforcement plates.

9 A rigid vehicle constructed and arranged for use and operation substantially as herein described, and with reference to the accompanying drawings.