GB2184073A - Suspension units for trailers - Google Patents

Abstract

Trailers with close coupled axles and torsion bar springing are known in which each wheel is independently sprung. As there is no load equalisation between axles each has to be capable of reacting the full load. A "walking beam" type construction provides equalisation but is heavy due to the substantial beams and the shock absorber required for each wheel. A trailer suspension unit has a beam 5 with stub axle 6 at one end for a wheel 8. A joggled arm 22 has a wheel mounting portion 23 with stub axle 24 for a wheel 42. A torsion bar spring assembly is pivotally mounted in spherical bearings between brackets 2 depending from trailer chassis 1. The outer end of the torsion bar is connected to beam 5 intermediate its ends and the inner end is connected to mounting portion 26 of arm 22. Shock absorber 39 acts between beam 5 and arm 22. Movement limit stops are provided at 21, 46, 47. <IMAGE>

Description

SPECIFICATION Suspension units for trailers This invention relates to Suspension Units for a trailer vehicle of the type having close coupled axles with torsion bar springing, each axle comprising two aligned stud axles on which wheels are rotatably mounted.

Conventionally such trailers are fitted with two such torsion bar axles arranged so that their wheel mounting arms are either rearwardly directed for the front axle and forwardly directed for the rear axle or vice versa.

Such an arrangement does not provide equalisation of load between the axles. In consequence a situation can arise that one axle bears all the load and therefore the torsion bars have to be designed accordingly. This arrangement provides independent suspension for the wheels on each axle and accordingly requires four shock absorbers for damping their movement.

The problem of equalisation of load between the axles is avoided in another known construction wherein two torsion bar units are each mounted on a "walking beam". That is to say, on each side of the trailer a beam is pivotally carried intermediate its ends and oppositely directed torsion bar units are carried by the ends of the beams. Each torsion bar unit includes a wheel mounting arm and a stub axle on which a wheel may be rotatably mounted. Again, four shock absorbers are required. This construction is well suited to a high mobility role but it is heavy because of the two substantial walking beams. Both of these constructions require two torsion bars per axle, a total of four.

According to one aspect of the present invention a suspension unit for a trailer comprises a beam adapted at one end to carry a wheel rotatably thereon, an arm adapted at one end to carry a wheel rotatably thereon, a torsion bar spring assembly adapted for pivotal connection to a trailer and having one end of the torsion bar operatively connected to the beam intermediate its ends and the other end of the torsion bar operatively connected to the other end of the arm and shock absorber means operatively connected between the beam and the arm.

Preferably the beam and the arm are so ar ranged that respective wheels mounted thereon are in alignment longitudinally of the sus pension unit.

Preferably stop means are provided arranged to act between the beam and the arm adapted to limit relative movement of the beam and the arm when the suspension unit is under load in use.

According to another aspect of the present invention a trailer is provided at each side with a suspension unit as set out herein said units being in alignment transversely of the trailer whereby wheels fitted to the respective suspension units on each side of the trailer are in alignment.

Preferably further stop means are provided arranged to act between the trailer and the beam and between the trailer and the arm adapted to limit movement of the beam and the arm respectively towards the trailer when in use.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view from above of a suspension unit and showing a wheel carried by each of the beam and the arm, Figure 2 is a side elevation of the suspension unit of Fig. 1 on a larger scale and part of a trailer to which it is connected, the wheels and brake gear being omitted for clarity.

Figure 3 is a plan view of a torsion bar assembly, showing also a part of a beam and a part of an arm, viewed as in Fig. 1, and Figure 4 is an end view on the assembly of Fig. 3 in the direction of arrow A, the end cap being removed, and on a larger scale.

Referring to the drawings, Figs. 1, 2 and 3, a longitudinal chassis member 1 of a trailer has a depending bracket 2 which carries a spherical bearing assembly (not shown). A similar bracket 3, in transverse alignment with bracket 2, depends from another part (not shown) of the chassis of the trailer and also carries a spherical bearing assembly. A torsion bar assembly 4 (Fig. 3, to be described) is carried by the brackets 2, 3 in the spherical bearing assemblies.

A beam 5 has at one end a stub axle 6 on which a drum brake assembly 7 is mounted and carries a rotatable wheel and tyre assembly 8 (shown in a broken line on Fig. 2).

Intermediate its ends the beam 5 incorporates a sleeve 9 and a flange 11. A generally cylindrical inner housing 12 of the torsion bar assembly 4 has a flange 13 secured to it as by welding. The housing 12 is stepped down successively in diameter away from the end to which flange 13 is secured. Flanges 11 and 13 are provided with a ring of registering holes (see Fig. 4). The holes in flange 11 are drilled and tapped whilst those in flange 13 are counterbored to receive the heads of bolts to secure flanges 11, 13 together.

The housing 12 has a cylindrical mounting 14 inserted therein, located against a shoulder 15, and secured in the housing as by welding.

The mounting 14 has a central hole 16 of generally square shape, as seen in Fig. 4, in which one end of a torsion bar 17 of corresponding shape and size is slidably received.

The torsion bar 17 is located in mounting 14 by a radially directed bolt inserted through the housing 12 and mounting 14, for example in the plane of line 18.

The housing 12 has an end cap 19 secured thereto as by-welding. End cap 19 has an outer cylindrical surface which is received in the spherical bearing assembly associated with the bracket 2. A screw threaded bore in the end cap 19 permits use of a bolt to push the torsion bar 17 out of mounting 14, for example for replacement of the torsion bar.

The beam 5 is assembled to housing 12 by inserting the sleeve 9 over the housing at its small diameter end, abutting the flanges 11, 13 with their holes in register and bolting them together. A rubber stop 21 (Fig. 2) is secured, as by bolting, to the underside of beam 5 adjacent the end remote from stub axle 6.

An arm 22 comprises a wheel mounting portion 25 which carries a stub axle 24 towards one end, a tubular portion 25 which extends transversely of the trailer and a mounting portion 26 which includes a sleeve 27 and a flange 28.

A generally cylindrical outer housing 29 has a flange 31 secured to it as by welding. The flanges 28, 31 are provided with a ring of registering holes as has been described with reference to the flanges 11, 13 whereby they can be bolted together.

The housing 29 has a cylindrical mounting 32 inserted therein, located against a shoulder 33, and secured in the housing as by welding.

The mounting 32 is similar to mounting 14 with a central hole of generally square shape in which the other end of torsion bar 17 of corresponding shape and size is slidably received. The torsion bar 17 is located in the housing 29 by a radially directed bolt inserted through the housing 29 and mounting 32, for example in the plane of line 34. Housing 29 has an end cap 35, similar to the end cap 19, secured thereto as by welding, and has an outer cylindrical surface which is received in the spherical bearing assembly associated with the bracket 3.

The arm 22 is assembled to the outer housing 29 by sliding sleeve 27 over the housing until flange 28 abuts flange 31, aligning the holes in the flanges and inserting bolts to secure them together.

Bearing bushes 36, 37 are provided between the housings 12, 29 and these are protected by an oil seal (not shown) in a recess at 38.

Referring again to Figs. 1 and 2 a telescopic shock absorber 39 is pivotally mounted between the beam 5 and wheel mounting portion 23 of arm 22. A drum brake assembly 41 is mounted on stub axle 24 and carries a rotatable wheel and tyre assembly 42, shown in broken line on Fig. 2, and in alignment with the wheel and tyre assembly 8.

The upper surface of wheel mounting portion 23 has a plate 43 secured to it for engagement with the rubber stop 21. Similar plates 44, 45 on upper surfaces of portion 23 and beam 5 respectively are provided to engage rubber stops, shown in broken lines at 46, 47, mounted on the trailer.

It will be appreciated that in building the torsion bar spring assembly 4 the orientation of housings 12, 29 relative to one another is controlled by the torsion bar 17 within the mountings 14, 32. Accordingly, the orientation of the beam 5 relative to the arm 22 will be controlled by the positions of the bolt holes in the flanges 13, 11 and 31, 28. Consequently these flanges have to be secured to their respective housings, beam and arm so that the bolt holes are arranged in the correct positions to give the desired orientation of beam 5 and arm 22 in the unloaded condition of the torsion bar spring.

An assembly of beam, arm, torsion bar spring assembly, brakes and wheels is fitted on each side of the trailer in alignment. In operation, vertical movement of the wheel; 8, 42 is resiliently resisted by the torsion bar 17 and the movement is damped by the shock absorber 39. The limit of movement is defined by the rubber stop 21. The assembly of beam 5 and arm 22 is free to pivot in the spherical bearings between limits defined by the rubber stops 46, 47. The shock absorber is constructed and arranged so as to act as a rebound stop in its extended position.

The suspension unit of this invention provides for equalisation of the load between the axles and only one shock absorber and one torsion bar spring is required for each suspension unit. The beam pivoting movement in conjunction with the spring movement of beam and arm make this suspension unit particularly suited to use in a high mobility role.

Claims (13)

1. A suspension unit for a trailer comprising a beam adapted at one end to carry a wheel rotatably thereon, an arm adapted at one end to carry a wheel rotably thereon, a torsion bar spring assembly adapted for pivotal connection to a trailer and having one end of the torsion bar operatively connected to the beam intermediate its ends and the other end of the torsion bar operatively connected to the other end of the arm and shock absorber means operatively connected between the beam and the arm.

2. A suspension unit as claimed in claim 1 wherein the beam and the arm are so arranged that respective wheels mountable thereon are in alignment longitudinally of the suspension unit.

3. A suspension unit as claimed in claim 2 wherein the arm comprises a wheel mounting portion extending longitudinally of the unit and having a stub axle thereon for mounting of a wheel, a mounting portion extending longitudinally of the unit and connected to one end of the torsion bar spring and a transversely extending portion connecting the wheel mounting portion and the mounting portion whereby the stub axle is in alignment with a corresponding stub axle on the beam.

4. A suspension unit as claimed in claim 3 wherein a telescopic shock absorber is pivotally connected between the beam and the wheel mounting portion of the arm.

5. A suspension unit as claimed in any preceding claim wherein the beam and the arm is each mounted on a generally cylindrical housing which housings extend longitudinally of the torsion bar spring and are supported one on the other by bearings for relative pivotal movement.

6. A suspension unit as claimed in claim 5 wherein each end of the torsion bar is operatively connected to a respective first flange, the beam and the arm are each connected to a respective second flange and bolt or like connections are made between corresponding first and second flanges whereby the desired relative positions of the beam and the arm are set on assembly of the suspension unit.

7. A suspension unit as claimed in any preceding claim wherein stop means are provided arranged to act between the beam and the arm so as to limit relative movement of the beam and the arm when the suspension unit is under load in use.

8. A suspension unit as claimed in any preceding claim wherein the shock absorber means is constructed and arranged to act as a rebound stop for the suspension unit.

9. A trailer provided at each side with a suspension unit as claimed in any preceding claim, said suspension units being in alignment transversely of the trailer whereby wheels fitted to the respective suspension unit on each side of the trailer are in alignment transversely of the trailer.

10. A trailer as claimed in claim 8 wherein each suspension unit is carried in spherical bearings between inner and outer brackets depending from the trailer.

11. A trailer as claimed in claim 8 or claim 9 wherein further stop means are provided arranged to act between the trailer and the beam and between the trailer and the arm so as to limit movement of the beam and the arm respectively towards the trailer in use.

12. A suspension unit substantialiy as described herein with reference to the accompanying drawings.

13. A trailer fitted with suspension units substantially as described herein with reference to the accompanying drawings.