GB2376218A

GB2376218A - Vehicle lift axles

Info

Publication number: GB2376218A
Application number: GB0208871A
Authority: GB
Inventors: Philip John Britton; Colin Partick Martin
Original assignee: Boler Co
Current assignee: Boler Co
Priority date: 2001-04-25
Filing date: 2002-04-18
Publication date: 2002-12-11
Anticipated expiration: 2022-04-18
Also published as: TR200201108A2; FR2824021A1; GB0110115D0; GB0208871D0; BR0201830C1; DE10218406A1; BR0201830B1; DE10218406B4; GB2376218B; FR2824021B1; BR0201830A

Abstract

A midlift axle intended for retrofitting to an existing vehicle comprises a spring seat 2 so located on a respective end of the midlift axle 1 that a spring 3, fitted to the spring seat has its free end in a position required for it to be attached to a hanger 8 on a vehicle, U-bolts 7 apply a pressure on the spring seat 2 to assist in its maintenance in its required position on the midlift axle and a means of securing the spring seat to the axle, and where on the assembly of the axle and its springs the U-bolts are left loose, and locking members on flanges 5 on the spring seat retracted, to allow the end of the spring to be slipped below a bridging plate 6, the axle is then presented to a jig to hold it against movement, and allow the free end of the spring to be put in the position necessary for its subsequent attachment to a hanger on the vehicle to cause the spring to assume a correct position on the seat, following which the locking members are driven inwards to contact the sides of the spring and the U-bolts tightened to lock the spring seat and hence the spring in position on the axle. The invention also embraces a front hanger 8 for a leaf spring 3 of a midlift axle 1.

Description

23762 1 8

VEHICLE SUSPENSION SYSTEMS

This invention relates to road vehicle suspension systems, and is particularly, but not necessarily exclusively, concerned with suspensions for tractor, trailer or fixed vehicles of the type where one axle at least can be lifted to bring its road wheels clear of the ground.

5 In the design of tractor, trailer and fixed vehicles careful regard must be made to local and current legislation defining the maximum permitted loads per axle, plus the reality that in certain countries, if loads per axle are mounted at lower set levels, there are tax advantages provided to the vehicle owner/user.

It must also be kept in mind, that whilst maximising the load on a commercial vehicle is 10 advantageous, there are a number of occasions where circumstances are such that a vehicle load is less than the permitted maximum, and can even be running with no load, e.g. on the return trip after delivering a load. Maintaining a greater number of road wheels in contact with the ground than is required by a load at less than the required maximum, or by an empty vehicle, generates increased running costs by increasing the fuel requirement per unit distance, 15 and unnecessary wear on tyres and ancillary equipment associated with road wheels such as brake pads and brake discs or drums.

It has therefore long been known to have at least one axle on a multiaxle tractor or trailer vehicle able to be lifted, to bring its road wheels clear of the ground at such times as the vehicle is running empty, or its load requires less than the total number of axles provided to take 20 a proportion of the vehicle load and keep axle loading at or below permitted levels.

Such liftable axles are generally referred to as midlift axles, and frequently they are fitted as accessories to existing tractor, trailer or fixed vehicles, subsequent to their manufacture.

Retrofitting of midlift axles poses numerous difficulties. Ordinarily, a spring seat is attached at top dead centre of an axle towards each of its outer ends, the spring seat having 25 been machined with a slot to accept the end of the spring. The seat is welded to the axle, and as a result, the longitudinal alignment of its spring slot cannot be assured. Equally, and

particularly with midlift axles for tractor or fixed vehicles, they are forged to provide a generally U-shaped centre section, to allow the axle to clear the vehicle prop shaft. Forging of the axle can cause an axial misalignment as between one end and the other, adding to the potential for the longitudinal misalignment of the spring slot in the spring seat. Additional to this, leaf 5 springs themselves can have a degree of lateral distortion between the end to fit the spring seat and an eye at the opposite end to fit a hanger arrangement strategically attached to the vehicle at a required distance from the midlift axles position.

The aggregate effect of those possibilities mentioned above is that in a relatively high proportion of instances, once the midlift axle has been presented to and secured to the vehicle, 10 the eye of the spring is spaced appreciably from the locating position of the front hanger, and considerable force is required to pull the spring end into register with the front hanger, and once secured in place, considerable strains are induced in the suspension system, that impair the efficiency of the suspension of the midlife axle, and can lead to premature failure.

It is the object of the present invention to provide a midlift axle for a tractor, trailer or 15 fixed vehicle, that avoids those disadvantages referred to above.

According to a first aspect of the present invention, a midlift axle for a tractor, trailer or fixed vehicle comprises a spring seat so located on a respective end of the midlift axle that a spring fitted to the spring seat has its free end in a position required for it to be attached to a hanger on a vehicle, a means of applying a pressure on the spring seat to assist in its 20 maintenance in its required position on the midlift axle and a means of securing the spring seat to the axle. Preferably, the means of applying pressure are two U-bolts lying to either side of the spring seat and extending round the axle from a bridging plate extending over the spring seat. The means of attaching the spring seat to the midlift axle may be an elastic resin bonding material interposed between the spring seat and the midlift axle. Alternatively, the 25 means of attaching the seat to the midlift axle is a weld by a compatible weld material between the seat edge and the midlift axle.

? The spring seat may have, on its upper surface, co-operating upstanding flanges to each side, to provide a space to receive the end of a leaf spring, and preferably the bridging plate overlies the end of the leaf spring. Advantageously, the distance across the spring seat between the upstanding flanges is greater than the width of the end of the spring, and 5 adjustable locking members extend through the flanges to bear against the side walls of the leaf spring. This avoids completely the need to provide machined spring slots in the spring seats.

When used the elastic resin may be a two part epoxy resin adequate to serve as a bond, and able to retain its elasticity for a number of years It will be understood that care must be exercised in the application of the resin to the axle, and the spring seat to the resin, with 10 adequate pretreatments of both to ensure that they are clean and free from grease before their contact by the resin. Employment of an elastic resin to bond the spring seat to the axle, plus the effect of the U-bolts provides a substantial guarantee that the spring seat is held against movement on the axle, under all conditions of loading, and the resilient nature of the resin is such as to ensure that all side impacts on the vehicle wheels are absorbed without the 15 shattering of the resin interface between the spring seat and the axle.

On the assembly of the axle and its springs the U-bolts are left loose, and the locking members on the spring seat retracted, to allow the end of the spring to be slipped below the locking plate, the axle is then presented to a jig to hold it against movement, and allow the free end of the spring to be put in the position necessary for its subsequent attachment to a hanger 20 on the vehicle. Consequently, and irrespective of any axle misalignment during its forging and any distortion of the spring, the spring assumes a correct position on the seat, following which the locking members are driven inwards to contact the sides of the spring and the U-bolts tightened to lock the spring seat and hence the spring in position on the axle. If resin is used it combines with the U- bolts to ensure that the spring seat maintains its position. Alternatively, 25 and after the tightening of the U-bolts, the front edge and possibly the rear edge of the seat may be welded to the midlift axle, but the degree of weld metal required is such that the welding

stage cannot introduce any distortion in the axle or the location of the seat thereon.

The axle and spring can then be presented to a vehicle with the certainty that the free end of the spring will be positioned correctly, and the disadvantages of prior art constructions

are substantially avoided.

5 Whilst the first aspect of the invention provides the certainty of accurate positioning of the spring seats and hence springs on the axle, it is such that the possibility exists for the front hanger to be so formed and so attached to the vehicle chassis that the location point for the front end of the spring is out of square, making it difficult to locate the eye on the hanger by way of a pivot pin, as is necessary for midlift axles.

10 According to a second aspect of the invention, a front hanger for a leaf spring of a midlift axle, comprises a means of connection to the vehicle chassis and a means of pivotal connection of the end of a leaf spring, the means of connection of the end of a leaf spring comprising a bracket-like component with side walls, said side walls being outwardly divergent towards the open end of the bracket, whereby to accept the spring and there being a means 15 of attachment of a pivot pin on the free end of the spring to the hanger bracket. In one form of construction there may be pivot holes in the side walls of a diameter greater than the diameter of a pivot pin intended to hold an eye of the spring within the bracket. Alternatively, the spring end may extend beyond the hanger, and bolts provided to pass through bolt holes in the pivot pin and engage threaded holes in the face of the hanger.

20 If as a consequence of the fabrication of the front hanger, its connection to the vehicle chassis has the effect of putting the bracket out of square in relation to the eye of a spring to be presented to it, the divergent or splayed disposition of the bracket walls allows the insertion of the spring, and either the oversize holes allowing the insertion of the pivot pin, followed by the walls of the bracket being clamped against the sides of the spring eye, or the pivot pin 25 bolted to the hanger to stop any lateral movement of spring, but allow a pivotal movement of the spring in relation to the bracket.

As has been mentioned above, conventional midlift axles are forged to ensure that the prop shaft of a tractor or fixed vehicle is not fouled.

The invention in its first and second aspects eliminate substantially those problems of fixing to vehicles that have historically been the case, but axle distortion can be such that not S only is spring misalignment a serious problem, but also can there be problems attached to the securing of the axle to the vehicle.

According to a third aspect of the present invention, a midlift axle comprises a straight beam, upstanding support members to each end of the beam, each support member having an outwardly extending stub axle.

10 Desirably, the straight beam is of a hollow tube-like beam, to provide high strength and reduced weight, and the upstanding support members are fabricated constructions that enable the accurate orienting of the respective stub axle, at the ends of the beam, to assist in the accuracy of the location of the spring seats and springs.

In the discussion above, reference is made to the positioning of a spring on the spring 15 seat. It will however be fully understood, that the invention applies equally to the positioning of a support arm between the midlift axle and front hanger, for an airbag of an airbag suspension system. Not discussed above is the manner of attachment of the midlift axle to the vehicle, and the means whereby the wheels of the midlift axle can be lifted and lowered out of contact and 20 into contact with the ground when required. Conventional securing means and lifting and lowering means can be employed, as will be fully understood by the artisan.

Five embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a spring seat and spring in accordance with the first 25 aspect of the invention; Figure 2 is a perspective view of a front hanger in accordance with the second aspect

J of the invention; Figure 3 corresponds to Figure 1 but shows a third embodiment of the invention; Figure 4 corresponds to Figure 2 but shows a fourth embodiment of the invention; and Figure 5 is an elevation of a straight beam in accordance with the third aspect of the S invention, to which are fitted spring seats and springs as in Figure 1.

Figures 1 to 4, employ like reference numerals for like parts.

In Figure 1, a midlift axle 1 for a vehicle, intended to be retrofitted to the vehicle has a spring seat 2 so located thereon that a spring 3 fitted to it has its eye 4 positioned correctly in relation to the axle, such that when the axle is fitted to a vehicle, the eye is at a required 10 position to be attached to a hanger secured to the vehicle frame. The spring seat has upstanding flanges 5 to provide a space into which the spring fits and a bridging plate 6 overlies the spring, and U-bolts 7 engage around the axle and are attached to the bridging plate to apply pressure to the spring and seat, to assist its firm location on the axle.

In the embodiment of Figure 1, a two part epoxy resin of a nature to secure adequately Is as a bond and able to retain its elasticity over a number of years is interposed between the spring seat and the axle.

To position the spring seat 2 and spring 3, a jig (not shown) can be provided, having a recess to accept the axle, and recesses to accept the bases of the U-bolts. The jig also has a fastener for the eye 4 of the spring. Thus, with the U-bolts positioned in the groove and the 20 axle laid in the recess, the spring seat can be positioned on the axle at a required distance from one end, the spring 3 fitted in the space between the flanges 5, the bridging plate 6 fitted and the U-bolts 7 tightened to finger tight.

As illustrated in Figure 1, the flanges 5 have location studs in threaded engagement with threaded holes in the flanges, left loose at the outset, and tightened into contact with the spring 25 once fitted in the space between the flanges The spring eye 4 is then attached to the fastener on the jig, to set the alignment of the

spring, and locate the seat 2 on the axle 1 in its required position. With epoxy resin applied between the seat and the axle, and with the Ubolts tightened to apply pressure through the bridging plate 6 to the spring and the spring seat, a most secure attachment of the spring to the axle is provided with the spring and spring eye in the position required to lend considerable 5 assistance to the attaching of the spring eye to a hanger on the vehicle frame when the midlift axle is retrofitted to a vehicle.

Even with the attachment of a spring and spring seat to an axle as above described, a degree of misalignment of the spring and hence position of its eye might be encountered, possibly caused by a slight inaccuracy in the fitting of a hanger to a vehicle. Therefore, an as JO illustrated in Figure 2, a hanger 8 has flanges 9 for attachment to a vehicle frame, the arm 10 carrying the flanges having a bracket 11 with outwardly divergent side walls 12 in a downward direction, the walls 12 having through holes 13 for a pivot pin. Thus, with the axle 1 and the hanger 8 attached to a vehicle, the spring eye 4 can be presented to bracket 11, the divergent walls 12 of which make relatively easy the locating of the spring eye such that a pivot pin can 15 be inserted through the holes 13 and through the spring eye.

In Figures 3 to 4 an essentially similar spring assembly and hanger are respectively shown. In Figure 3, the assembly of spring seat 2, spring 3, bridging plate 6 and U-bolts 7 are fitted to an axle in an essentially similar manner to that described in relation to Figure 1. Here, and to further assist in the correct positioning of the spring and seat, the spring is attached to 20 the seat by a rearward pivot bolt 14.

In Figure 3, and in place of an epoxy resin between the spring seat 2 and the axle, the seat, after tightening of the U-bolts 7 to clamp the assembly to the axle, is welded at its front edge 15 to the axle, and if desired, additionally welded at its rear edge. The degree of welding required to supplement the clamping of the assembly and ensure that the spring seat does not 25 move in use, is not sufficient to cause any distortion of the axle or the spring seat.

In place of an eye at the end of the spring, Figure 3 illustrates a pivot bar 16 with bolt

holes 17. In Figure 4, there is illustrated an alternative embodiment of hanger 8 with a plate 8A for attachment to the side of a vehicle frame. Here, the bottom face of the hanger has an integral bracket formed by divergent walls 18, the walls depending from bosses 19 having bolt holes 20. Here again, the employment of divergent walls makes easy the location of the spring 5 in the bracket, but with the end of the spring projecting beyond the bracket to allow its attachment by bolts passing through the bolt holes in the pin and into the bolt holes in the bosses. To avoid all those problems mentioned above with forged axles, Figure 5 shows a form of construction where the axle is formed by a straight beam 21, the beam towards each of its to ends being provided with spring assemblies as are described above in relation to Figure 1 or to Figure 3. At the outer ends of the beam, upstanding support members 22 are provided on which stub axles 23 for road wheels are to be secured, whereby to offset the horizontal axes of the stub axles and the beam, to allow the beam to clear such as a prop shaft running below the vehicle without having to forge or otherwise distort the beam itself.

Claims

1. A midlift axle for a tractor, trailer or fixed vehicle characterised by a spring seat (2) so located on a respective end of the midlift axle (1) that a spring (3) fitted to the spring seat has its free end in a position required for it to be attached to a hanger (8) on a vehicle, a means 5 (7) of applying a pressure on the spring seat to assist in its maintenance in its required position on the midlift axle and a means of securing the spring seat to the axle.

2. A midlift axle as in Claim 1, characterised in that the means of applying pressure

are two U-bolts (7) lying to either side of the spring seat and extending round the axle (1) from a bridging plate (6) extending over the spring seat (2).

to

3. A midlift axle as in Claim 1 or Claim 2 characterised in that the means of attaching the spring seat (2) to the midlift axle (1) is an elastic resin bonding material interposed between the spring seat (2) and the midlift axle (1).

4. A midlift axle as in Claim 1 or Claim 2 characterised in that the means of attaching the seat to the midlift axle is a weld by a compatible weld material between the seat edge (15) 15 and the midlift axle (1).

5. A midlift axle as in any of Claims 1 to 4 characterised in that the spring seat (2) has on its upper surface, co-operating upstanding flanges (5) to each side, to provide a space to receive the end of a leaf spring (3).

6. A midlift axle as in any of Claims 1 to 5 characterised in that the bridging plate (6) 20 overlies the end of the leaf spring.

7. A midlift axle as in Claim 5 or Claim 6 characterised in that the distance across the spring seat (2) between the upstanding flanges (5) is greater than the width of the end of the spring, and adjustable locking members extend through the flanges to bear against the side walls of the leaf spring.

25

8. A front hanger for a leaf spring of a midlift axle, characterised by a means of connection (8A) to the vehicle chassis and a means of pivotal connection of the end of a leaf

spring (3), the means of connection of the end of a leaf spring comprising a bracket-like component with side walls (12,18), said side walls being outwardly divergent towards the open end of the bracket (8), whereby to accept the spring and there being a means of attachment of a pivot pin (16) on the free end of the spring (3) to the hanger bracket (8) .

5

9. A front hanger as in Claim 8, characterized in that there are pivot holes (13) in the side walls (12) of a diameter greater than the diameter of a pivot pin intended to hold an eye (4) of the spring within the bracket.

10. A front hanger as in Claim 8 characterized in that the spring end extends beyond the hanger, there being bolts to pass through bolt holes (17) in a pivot pin (16) and engage to threaded holes (20) in the face of the hanger.

11. A midlift axle characterized by a straight beam (21), upstanding support members (22) to each end of the beam, each support member having an outwardly extending stub axle (23).

12. A midlift axle as in Claim 11 characterized by the presence of spring seats (2) and 15 springs (3) as hereinbefore defined in any one of Claims 1 to 7.

13. A method of constructing a midlift axle as in any of Claims 1 to 7, characterized in that on the assembly of the axle (1, 21) and its springs (3) the U-bolts (7) are left loose, and the locking members on the spring seat retracted, to allow the end of the spring to be slipped below the locking plate (6), the axle is then presented to a jig to hold it against movement, and allow 20 the free end of the spring to be put in the position necessary for its subsequent attachment to a hanger (8) on the vehicle to cause the spring to assume a correct position on the seat, following which the locking members are driven inwards to contact the sides of the spring and the U-bolts tightened to lock the spring seat and hence the spring in position on the axle.