GB2327215A

GB2327215A - Supplementary axle unit for a commercial vehicle

Info

Publication number: GB2327215A
Application number: GB9810870A
Authority: GB
Inventors: John Hope Ancrum
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-05-20
Filing date: 1998-05-20
Publication date: 1999-01-20
Also published as: GB9810870D0; GB9710061D0

Abstract

A supplementary axle unit for a commercial vehicle comprises a chassis frame 12 to which a wheel-carrying axle 26 is secured. A king pin 44 is connected to the frame for connecting with the fifth wheel of a tractor unit. Additionally, there is provided a connection formation 30/32 for rigidly and releasably connecting the frame to a chassis of the tractor unit. The connection formation may include rails which can be slidably connected with rails on the tractor unit. The axle unit also includes a load carrier for carrying a load on the axle unit. The load carrier may be a fifth wheel 40, or may, alternatively, be suitable for carrying equipment or a cargo.

Description

SuPPlementarv axle unit for a commercial vehicle The present invention relates to supplementary axle unit for a commercial road vehicle.

Most particularly, this invention is intended for use with a tractor unit which can be used to tow a semitrailer. It is normal for such a tractor unit to carry a plate-like coupling member of standard design which can couple with a king pin carried on the trailer. People skilled in the art commonly refer to the plate-like coupling member as the fifth wheel of the tractor unit, and this usage will be adopted in the present application.

A tractor unit represents a major investment on the part of a transport company. It is therefore understandable that owners of tractor units which to use them in revenue-earning work as intensively as is reasonably possible. However, not all tractor units are alike, and some are better suited to particular purposes than others. One particular characteristic which differs between one tractor and another is the number of axles that the tractor has. Most commonly, road haulage tractor units have either two or three axles, although where exceptional loads are to be carried, a larger number of axles may be provided. When a light load is to be transported, a high-capacity tractor unit can be used.

However, the cost of running such a tractor unit will more likely be greater than would be the case for a smaller unit which has a loading capacity more closely equal to that of the load to be carried. Thus, a haulage operator must decide whether to invest a large amount of capital in several tractor units or tolerate the additional running cost of a unit which has greater capacity than a particular job requires.

A solution to this problem was set forth by the present applicant in UK Patent Application No. 8306799.

However, it was found that applicable legislation restricted the use of such a device in many countries, including the UK. In particular, the law did not allow its use in towing a semi-trailer.

The present invention has as its aim the provision of an axle unit which can be releasably connected to a tractor unit to provide additional load carrying capacity and which has better acceptance under existing legislation.

According to the invention there is provided a supplementary axle unit for a commercial vehicle comprising a frame, a wheel-carrying axle secured to the frame, a king pin connected to the frame for connecting with the fifth wheel of a tractor unit, a connection formation for rigidly and releasably connecting the frame to a chassis of the tractor unit, and a load carrier for carrying a load on the axle unit.

By ensuring that there is a rigid connection between the supplementary axle unit and the tractor unit, a tractor unit in combination with the present invention can legally tow a trailer.

In embodiments intended for towing a trailer, the load carrier may include a fifth wheel. Alternatively, or additionally, the load carrier might comprise a support for equipment, examples of such equipment including cement mixing equipment, electrical generating equipment, lifting equipment or vehicle recovery equipment. Alternatively or additionally, the load carrier may be suitable for carrying items, for example it may comprise a flat platform, a tipper body, a tank for fluids or a skip loader. Clearly, there are many further alternative carriers which might be used, and more than one type of carrier may be provided in combination.

In a preferred embodiment, the connection formation is configured so as to be slidable with respect to the tractor unit in order to effect connection with and release from the tractor unit. Most preferably, the connection formation is configured such that the sliding movement can be effected by driving the tractor unit under its own power. The connection formation preferably includes a projection which is received within a closelyfitting tubular formation on the tractor unit.

Conveniently, the connection formation of the axle unit may be configured to connect with mounting components for the fifth wheel of the tractor. In some tractor units, the fifth wheel of is mounted on parallel rails along which it can slide to a limited extent. In embodiments according to the last-preceding sentence such rails, or extensions of them, may constitute the mounting components with which the connection formation connects.

In most practical embodiments, the wheel-carrying axle is secured to the frame by a suspension system. The suspension typically includes a plurality of trailing arms, each of which is supported on a spring such as an air spring.

Embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of an axle unit being an embodiment of the invention; Figure 2 is a perspective view from below of the axle unit of Figure 1 with several components removed in the interest of clarity; Figures 3 and 4 are plan and side views of an axle unit, being an embodiment incorporating modifications as compared with that shown in Figure 1, in use on a tractor unit; Figures 5 and 6 are perspective and sectional views showing interconnection between side members of the axle unit of Figure 1 and rails on a tractor unit; and Figure 7 is a detailed view of an end portion of a rail on a tractor unit.

With reference to the drawings, an axle unit 10 embodying the invention is constructed around a chassis frame 12.

The chassis frame 12 comprises a pair of spaced, parallel side members 14 interconnected by cross members 16 to form a ladder frame. When in use on a tractor unit, the side members 14 run substantially parallel to the normal direction of travel of the unit, and extend rearwardly from it. References to the front and the rear of the axle unit should, accordingly, be understood to refer to its orientation when in place on a tractor unit.

In Figures 1 and 2, the rear of the axle unit is shown towards the right, while in Figures 3 and 4 the rear of the axle unit is shown towards the left.

The side members 14 are formed of steel, and have a profile which will be described in detail below. The cross members 16 are steel rectangular box sections.

Towards the rear of the axle unit 10, a respective mounting legs 20 projects downwardly from each of the side members 14. A transverse bracing bar 28 extends between and is secured to the mounting legs 20, spaced from the side members, to enhance the rigidity of the mounting legs 20.

A respective trailing arm 22 is connected to each of the mounting legs 20, the trailing arms 22 extending rearwardly from the mounting legs 20. The trailing arms are mounted, for example, in flexible bushes, so as to permit amount of vertical pivoting movement with respect to the mounting leg 20. An air spring 24 is carried on each of the side members 14 close to their rear ends.

Each of the air springs 24 is connected to a respective trailing arm 22 at a position remote from the respective mounting leg 20. An axle 26 extends transversely between the trailing arms 22, and is secured to them approximately mid-way between the mounting legs 20 and the air springs 24. Road wheels 34 for the axle unit are carried on the axle 26. The trailing arms 22 are mounted below the side members 14 by a distance sufficient that the axle 26 can move freely within the range allowed by compression of the air springs 24. As will be understood, the suspension system employed in the axle unit is a substantially conventional trailing arm air suspension system.

A respective locating pin 30 projects forwardly from each of the mounting legs 20 in a direction parallel to the side members 14. The locating pins 30 are, in this embodiment, formed as rectangular steel box sections. An end portion of each locating pin 30 remote from the mounting leg 20 is tapered; the reason for this taper will become apparent in due course.

In the embodiment of Figure 1, a load carrier is constituted by a fifth wheel 40 is mounted on the chassis frame 12 generally above the mounting legs 20. The fifth wheel 40 can be of conventional construction. Indeed, it is preferable that the fifth wheel 40 can be used with trailers having a conventional king pin. The embodiment of Figures 3 and 4 is intended for use with an alternative type of load carrier, for example (amongst many possibilities) a tipper or a skip loader. As compared with the embodiment of Figure 1, the chassis of the axle unit extends rearwardly of the axle 26 by a greater distance to provide a larger supporting structure for a load carrier.

Retractable supporting legs 42 are provided forward of the axle 26. The supporting legs 42 can be extended, as shown in Figure 1, to support the front of the axle unit 10 when it is not connected to a tractor unit. When the axle unit 10 is connected to a tractor unit, the supporting legs are pivoted rearwardly and upwardly to be accommodated between the side members 14. It will be clear to those skilled in the art that the supporting legs 42 can be substantially the same as supporting legs which are already in widespread use on semi-trailers.

Forward of the supporting legs 42, a steel plate 46 is secured between the side members 14. A king pin 44 for connection to the fifth wheel of a tractor unit projects downwardly, centrally of the plate 46.

The side members 14 are so shaped and dimensioned to include connection formations of the axle unit 10. These will now be described with particular reference to Figure 5 to 7.

Each side member 14 includes, in this embodiment, an upper and a lower rectangular C-shaped steel channel section 50,52, the upper channel section 50 being somewhat larger than the lower channel section 52. The channel sections 50,52 are welded together along their length, and are oriented such that a base 54,56 of each of the channel sections 50,52 lies in a common, substantially vertical plane so as to form an outer surface of the side member 14, and such that walls 58,60 of each channel section 50,52 project normally from the respective bases 54,56 in a common substantially horizontal plane towards the other of the side members 14. The upper channel sections 50 serves to contribute most strength to the side members while the lower channel sections 52 serve as a connection formation for the axle unit.

End portions 60' of the lower wall 60 of the channel section may optionally be formed to slope downwardly away from the upper wall 58, as shown in Figures 2 and 4.

This measure is to aid interconnection with a tractor unit as will be explained below.

A tractor unit with which the axle unit 10 can be used includes a pair of spaced rails 66. The rails 66 extend longitudinally of the tractor unit, being spaced symmetrically about the fifth wheel of the tractor unit.

Each of the rails 66 has a free end which projects rearwardly of the tractor unit.

In this embodiment, each rail 66 includes a lower steel rectangular box section 68 and an upper steel bar 70 shaped as an inverted L. The steel bar 70 is welded along its length to an upper surface of the box section 68, such that it has an upright portion, and a substantially horizontal flange 74, parallel to and spaced from the upper surface of the box section 68. An elongate slot 76 is thus formed between the upper surface of the box section 68 and the substantially horizontal flange 74 of the steel bar 70. The rails 66 are disposed such that the slots open outwardly to each side of the tractor unit. The spacing between the walls 60 of the lower channel sections 52 of the side members 14 is selected to be larger than the thickness of the flange by a small amount.

As can be seen most clearly in Figure 5, the side members 14 of the axle unit can be connected to the rails 66 by sliding the lowermost channel wall 60 of each side member into the slot 76 of the corresponding rail 66, such that the flange 74 is retained between the walls 60 of the lower channel section 52. The spacing between the side members 14 is selected such that both of the side members 14 are properly connected in this way, with a minimum of transverse movement being thereafter permitted between the tractor unit and the axle unit 10. An end region 78 of each of the flanges 74 is preferably chamfered to help to guide the side members 14 into proper location between the rails 66.

In general, only minor modifications must be carried out to a tractor unit to enable it to be used with an axle unit embodying the invention. Some tractor units are equipped with rails on which the fifth wheel is mounted, and in such cases, it may be that no modification is necessary, or that it is necessary only to extend the rails. In other cases, it may be necessary to secure suitable rails to the tractor unit. This is a task that can be readily undertaken by a competent engineer.

The locating pins 30 are positioned on the axle unit 10 such that each enters a rear end portion of the box section 68 of the corresponding rail 33. The locating pins 30 are shaped and dimentioned to be a close fit within the box sections 68. The tapered end portions 32 of the locating pins 30 help to ensure that the locating pins 30 and the box sections 68 are properly aligned with one another.

During sliding interconnection of the side members 14 and the rails 33, the king pin 44 approaches the fifth wheel 90 of the tractor unit. The axle unit 10 is dimentioned such that the king pin 44 is locked in engagement within the fifth wheel 90 when the locating pins 30 are fully inserted within the box sections 68. When locked together in this way, the axle unit 10 is connected rigidly to the tractor unit with no appreciable movement between them being possible. In the present example, the fifth wheel 90 of the tractor unit can slide longitudinally on the tractor unit. As shown in Figure 3, the fifth wheel is at the forward extent of its travel; its rearmost extent of travel is shown in dashed lines at 90'.

As an optional enhancement, the embodiment of Figures 3 and 4 incorporates a towing hitch 92 for towing a trailer. The towing hitch 92 is carried on a support member 94 which extends downwardly from the rearmost of the cross members 16. Angled members 98 extend between the support member 94 and the side members 18 to locate the towing hitch 92 securely against forward or rearward movement.

Claims

1. A supplementary axle unit for a commercial vehicle comprising a chassis frame, a wheel-carrying axle secured to the chassis frame, a king pin connected to the chassis frame for connecting with the fifth wheel of a tractor unit, a connection formation for rigidly and releasably connecting the chassis frame to a chassis of the tractor unit, and a load carrier for carrying a load on the axle unit.

2. A supplementary axle unit according to claim 1 in which the load carrier includes a fifth wheel.

3. A supplementary axle unit according to claim 1 or claim 2 in which the load carrier includes a support for equipment.

4. A supplementary axle unit according to claim 3 in which the equipment includes any one of cement mixing equipment, electrical generation equipment, lifting equipment, or vehicle recovery equipment.

5. A supplementary axle unit according to any preceding claim in which the load carrier is suitable for carrying items

6. A supplementary axle unit according to claim 5 in which the load carrier is flat platform, a tipper body, a tank for fluids or a skip loader.

7. A supplementary axle unit according to any preceding claim in which the connection formation is configured so as to be slidable with respect to the tractor unit in order to effect connection with and release from the tractor unit.

8. A supplementary axle unit according to claim 7 in which the connection formation is configured such that the sliding movement can be effected by driving the tractor unit under its own power.

9. A supplementary axle unit according to any preceding claim in which the connection formation includes a projection which is received within a closely-fitting tubular formation on the tractor unit.

10. A supplementary axle unit according to any preceding claim in which the connection formation of the axle unit is configured to connect with mounting components for the fifth wheel of the tractor.

11. A supplementary axle unit according to claim 10 in which the mounting components include spaced parallel rails secured to a chassis of the tractor unit.

12. A supplementary axle unit according to claim 11 in which the rails are rails on which the fifth wheel of the tractor is slidably mounted, or extensions thereof.

13. A supplementary axle unit according to any preceding claim in which the wheel-carrying axle is secured to the chassis frame by a suspension system.

14. A supplementary axle unit according to claim The suspension typically includes a plurality of trailing arms, each of which is supported on a spring such as an air spring.

15. A supplementary axle unit for a commercial vehicle substantially as herein described with reference to the accompanying drawings.

16. A commercial vehicle comprising a tractor unit and an axle unit according to any preceding claim secured to the tractor unit.

17. A commercial vehicle comprising a tractor unit, an axle unit according to claim 2 secured to the tractor unit, and a semi-trailer connected to the fifth wheel of the axle unit.