GB1597264A

GB1597264A - Tractor semi-trailer assemblies

Info

Publication number: GB1597264A
Application number: GB10849/78A
Authority: GB
Original assignee: Nicolas France SA J B
Current assignee: Nicolas France SA J B
Priority date: 1977-03-24
Filing date: 1978-03-20
Publication date: 1981-09-03
Also published as: FR2384665B1; FR2384665A1; BR7801772A; IT1103713B; DE2809628A1; DE2809628C2; IT7809386A0

Description

(54) IMPROVEMENTS TO TRACTOR SEMI-TRAILER ASSEMBLIES (71) We, J. B. NICOLAS FRANCE S.A., a French Société Anonyme, of 23, Bld. Davout, 89000 Auxerre, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to assemblies comprising a tractor and a semi-trailer and particularly to such assemblies for the transportation of heavy loads.

The transport capacity of a conventional tractor-semi-trailer assembly, whose semitrailer comprises a large number of axle lines from the rear, is generally limited by the load which must not be exceeded on the fifth wheel coupling plate of the tractor.

Different devices are already known for increasing this transport capacity.

A dolly may be located between the tractor and the semi-trailer; the dolly rests on the fifth wheel coupling plate of the tractor and carries a coupling plate which receives the swan-neck of the semi-trailer.

This solution has numerous disadvantages: the height and the length of the assembly are very much increased. The dead weight of the dolly is added to that of the tractor and the semi-trailer. Backing manoeuvres become almost impossible. Moreover. the load is generally placed in a zone remote from the base of the support triangle of the semi-trailer, which is unfavourable for stability.

U.S. Patent No. 3,203,711 discloses an assembly having an additional axle provided with pneumatic suspension under the front portion of the semi-trailer. The simultaneous presence of a support on the coupling plate of a support on the ground through the additional axle and of supports through the axles of the semi-trailer, introduces hyperstatism. Moreover. this solution has the disadvantages of the conventional dolly in respect of manoeuvrability and risk of skidding on bends.

It might be thought that these disadvantages would be removed by intercommunicating the pneumatic suspensions of all the axles (axles of the semi-trailer and axle of the floating shaft) in the same lateral line.

But the travel of the suspensions cannot be sufficient to avoid the bumping of these latter when going over humped back bridges or hollows.

It is an object of the invention to provide an improved vehicle assembly which can carry an increased load for a predetermined limit value of the acceptable load on the fifth wheel coupling plate.

In accordance with the invention there is provided a tractor semi-trailer vehicle assembly comprising: a semi-trailer having a swan neck for transfer of load from the semi-trailer to the tracter through a fifth wheel coupling plate carried by the tractor and fluid suspension means, at least a first axle train supporting the rear portion of the semi-trailer and at least one additional axle train supporting the front portion of the semi-trailer through second fluid suspension means said additional train comprising two additional axles, one on each side of the longitudinal midplane of the semi-trailer. and said first suspension means comprising two fluid pressure jacks located one on each side of the midplane of the tractor and each connectable to the fluid suspension means of the additional axle on the same side of the midplane by a pressure balancing conduit.

In this embodiment, the width of the support basis of the semi-trailer at the position where the centre of gravity of the transported load is generally found is increased as compared with an embodiment having a single jack.

Whatever the arrangement. movements of the articulated connection of the swan neck are added to the travel of the jacks which would alone be involved in the case of connection between the jacks alone. In other words, the semi-trailer will be favourably articulated when passing over humped back bridges and hollows.

The invention will be better understood from the following description of particular embodiments thereof. The description refers to the accompanying drawings.

Figure 1 shows the distribution of axle lines along a vehicle assembly not in accordance with the invention, Figure 2 shows a modified version of the vehicle assembly of Figure 1.

Figure 3 shows the support basis of the vehicle unit of Figs 1 & 2, Figure 4 is a simplified plan view of the embodiment of a vehicle assembly in accordance with the invention Figure 5 shows the support basis of the vehicle unit of Figure 4, Figure 6 is an elevational detail view of a further embodiment of a support means for a vehicle assembly.

Figure 7 is a schematic diagram showing a particular construction of semi-trailer; and Figure 8 is an elevational view showing a type of coupling between components of a composite semi-trailer.

The vehicle assembly shown schematically in Figure 1 comprises a tractor 10 and a semi-trailer 11. The tractor has a single steering axle 12 and two driving axles 13, but other constructions are possible. The semi-trailer 11 has a font swan-neck 14 supported by the tractor through support means 15. Semi-trailer 11 has a rear portion carried by several axle lines 16 (five in the embodiment illustrated). It will be assumed hereafter that each line comprises two axles or, in other words, that the semi-trailer is borne by two rows of axles placed one on each side of the vertical mid plane of the semi-trailer. These axles are provided with a steering linkage for locating them in the suitable angular position for negotiating bends. The linkage may be conventional and will not be described. It may be of the kind described in French patent No.

2.210.969.

Semi-trailer 11 has two extra axle lines (the number two being in no wise limitative) placed under the front portion of the semitrailer so as to relieve the fifth wheel coupling plate of tractor 10. Each of these lines may comprise the same number of axles as the lines of the rear carriage. They may be fitted with steering linkages actuated in response to changes in angular orientation between the mid plane of tractor 10 and that of semi-trailer 11. These axles can also be provided with a degree of trail so that they steer themselves automatically when negotiating bends.

In what follows, it will be assumed that axle lines 17 and 18 are fitted with a steering linkage (not shown).

Each of the axles of lines 17 and 18 is fitted with a fluid pressure, e.g. hydraulic, suspension. Referring to Figure 2, each of the axles, 17 for example, comprises a fork 19 mounted on chassis 20 of the semi-trailer by a steering pin and a suspension arm hinged to the fork and connected thereto by a suspension cylinder 22. The same type of suspension may be used for the axle lines of the rear portion.

Swan neck 14 of the semi-trailer 11 does not have a fixed height support on the tractor. The load is transmitted to the tractor by a fluid pressure suspension cylinder or bag which communicates with the suspension cylinders or bags of the extra axles 17 and 18.

In the embodiment illustrated in Figure 2, the fluid pressure suspension of the swan neck comprises a jack 24 whose body is hinged to swan neck 14 and whose piston rod is fixed to the member 28 supported by the fifth wheel coupling plate 26 of the tractor. The longitudinal forces are taken up by a telescopic guiding system which comprises a ring 27 fast with the swan neck and a sleeve 28 fast with the steering pin.

Jack 24 is connected to the cylinders 22 of the extra axle lines 17 and 18 by a connecting conduit 29, fitted with a valve 30 for isolating jack 24 when required, and branch conduits each fitted with a shut off valve such as 31 and assigned to a cylinder 22.

The suspension fluid will typically be a hydraulic fluid due to the efforts to be transmitted. It may be noted that the presence of jack 24 does not represent an extra complication in most cases, for semitrailers for heavy loads are almost always fitted with a lifting jack above the pin.

The areas of the surfaces subjected to the hydraulic pressure in jack 24 and in cylinders 22 will be so selected as to ensure a suitable distribution of the stresses.

If the supports on the ground of the semi-trailer 11 shown in Figures 1 and 2 are analysed, it will be seen that an isostatic support is artificially achieved. Since jack 24 and the suspension means of axle lines 17 and 18 are in communication. this assembly forms a first support triangle 32 (figure 3).

Semi-trailer li then presents an equivalent support triangle 33 whose rear base is located along a line connecting the epicentres of the suspension means of the axles 16 of the rear portion and whose apex is formed by a virtual pivot located at the centroid of a triangle formed by the actual pivot located at 15 and the epicentres of the suspension means of the additional axles 17 and 18.

In certain cases. the semi-trailer has to carry loads whose centre of gravity G is situated considerably in front of the rear portion. In the embodiment of Figures 1 and 2, the centre of gravity may then be found in a zone where width I of the support triangle is much less than the spacing between the laterial lines of wheels, which reduces the stability (figure 3).

This phenomenom is not compensated for because all the wheels of the axle trains 17 and 18 are carried by suspensions which communicate and consequently the system is equivalent to a balance beam placed transversely to the mid plane of the vehicle unit.

Referring to Figure 4, there is schematically illustrated an embodiment, similar to that of figure 2, in which the problem is overcome. Two jacks 24a and 24b are provided side by side. Each of the jacks 24a and 24b is connected by a corresponding connecting conduit to the suspension means of the axles 17a-18a and 17b-18b of the corresponding row. A hydraulic accumulator 34a or 34b may be associated with each jack 24a or 24b. The support basis has then the shape shown in Figure 5.

A connecting valve 35 may be provided for connecting conduits 29a and 29b when it is not necessary to provide increased transverse stability: in the embodiment of Figures 4 and 5, the semi-trailer behaves like a conventional semi-trailer with three point support in so far as the load distributions are concerned (with however the difference that a very much greater load can be accepted at the forward point) but like a semi-trailer with four point support in so far as the resistance to lateral overturning is concerned.

In bends or in transverse banking there will be different pressures in the left-hand and right-hand suspension means. but this is not a problem; there will also be different pressures in jacks 24a and 24b of the lifting gear. which is without drawback for these jacks may be mechanically connected.

Valve 35 may be controlled manually by the driver, for example electrically, to increase the lateral stability when that is necessary. The valve may be as well control led automatically for separating conduit 29a from conduit 29b. for example when the difference between the pressures in the suspensions of the left-hand and right-hand lines of axles of the rear portion exceeds a predetermined value.

When it is not necessary to use the additional support formed by additional trains 17a-b and 18a-h. the latter may be lifted up so as not to bear on the ground.

Before an empty return journey. it will be sufficient to bring the axles into the position shown schematically in dash lines in Figure 2, possibly by using the hydraulic suspension and to lock them in this position. It is not necessary to described appropriate locking means which may be formed by simple hooks carried by the chassis of the semitrailer.

Instead of using a vertical jack as shown in Figures 4, other equivalent arrangements may be used. In the modified embodiment shown in Figure 6, a jack 24c is placed between the front of the floor of the semi-trailer lic and a bell crank lever 36 hinged to the floor and carrying the pin and the coupling member 38.

Due to the different loading possibilities which it offers, the invention finds an important application in the case of semitrailers formed by elements able to be assembled in several arrangements. By way of example, there is shown in Figure 7 a semi-trailer lid comprising a front portion 39 having axle trains 17d and 18d and a swan neck 14d and a rear portion 40 having axle lines 16d. The front portion and the rear portion may be rigidly connected directly.

They may also be coupled by means of variable length connecting members such as 41 and 42 according to the loads to be transported.

In all cases, the junction may be conventionally made by a transverse pin, fitted into respective forks of the parts to be joined.

It is however preferable, for increased rigidity and easier assembly, to use the connecting system shown schematically in Figure 8.

Referring to Figure 8 there is shown schematically the rear end lid of the front portion and the front end of an intermediate platform 41. The longitudinal side beams of the two parts have the same shape and are intended to bear against each other through a top stop 42 and a lower transverse member 43. The members 43 are welded on the side beams and extend laterally therebeyond so as to form bosses. An insert piece 44 may be provided for centring stops 42 in relation to each other. The parting of the coupling is avoided by clamps 45 which straddle the sideward projecting parts of pins 43. It is much easier to place such a clamp 45 than to fit a cylindrical pin. Once in place, the clamps may be held, for example by pressure screws 46 screwed into half-stirrup pieces fast with the pins.

The invention is not limited to the particular embodiments which have been described and numerous modifications are possible. In particular. the or each extra axle may be provided with a steering mechanism. Among the possible constructions thereof there can be mentioned: - a mechanical linkage controlled by jacks placed on a rear steering cross-piece and which also control the swivelling of the axles of the rear portion: - a linkage controlled by one or two jacks situated on the semi-trailer in proximity to the additional axle or supplied with fluid by a metering system coupled with those of the rear portion, for example by a flow divider, this solution avoiding the use of linkages of great length.

WHAT WE CLAIM IS: 1. A tractor semi-trailer vehicle assembly comprising: a semi-trailer having a swan neck for transfer of load from the semi-trailer to the tractor through a fifth wheel coupling plate carried by the tractor and fluid suspension means, at least a first axle train supporting the rear portion of the semi trailer and at least one additional axle train supporting the front portion of the semi-trailer through second fluid suspension means, said additional train comprising two additional axles, one on each side of the longitudinal midplane of the semi-trailer, and said first suspension means comprising two fluid pressure jacks located one on each side of the midplane of the tractor and each connectable to the fluid suspension means of the additional axle on the same side of the midplane by a pressure balancing conduit.

2. A vehicle assembly according to claim 1, further comprising a communicating conduit connecting said two jacks and provided with an optionally actuatable shutoff valve.

3. A vehicle assembly according to claim 1 or 2, wherein the fluid pressure jacks are located between the fifth wheel coupling plate and the swan neck.

4. A vehicle assembly according to claim 1, 2 or 3, wherein the fluid suspension for each axle is provided with means for raising the axle.

5. A vehicle assembly according to claim 4. further comprising mechanical locking means for holding the axle in raised position.

6. A vehicle assembly according to claim 1, wherein the additional axle train or trains are free swivelling and present a trail angle for self-steering.

7. A vehicle assembly according to claim 1, wherein the semi-trailer has a front part provided with said additional axle train and the swan neck. a rear part provided with said first axle train having suspension means independent of the suspension means of the additional train and an intermediate plat form connected rigidly and removably to the front part and to the rear part and therebe tween.

8. A vehicle assembly constructed and arranged substantially as hereinbefore de scribed with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. - a linkage controlled by one or two jacks situated on the semi-trailer in proximity to the additional axle or supplied with fluid by a metering system coupled with those of the rear portion, for example by a flow divider, this solution avoiding the use of linkages of great length. WHAT WE CLAIM IS:

1. A tractor semi-trailer vehicle assembly comprising: a semi-trailer having a swan neck for transfer of load from the semi-trailer to the tractor through a fifth wheel coupling plate carried by the tractor and fluid suspension means, at least a first axle train supporting the rear portion of the semi trailer and at least one additional axle train supporting the front portion of the semi-trailer through second fluid suspension means, said additional train comprising two additional axles, one on each side of the longitudinal midplane of the semi-trailer, and said first suspension means comprising two fluid pressure jacks located one on each side of the midplane of the tractor and each connectable to the fluid suspension means of the additional axle on the same side of the midplane by a pressure balancing conduit.