WO1994011219A1

WO1994011219A1 - Load cell arrangement

Info

Publication number: WO1994011219A1
Application number: PCT/NZ1993/000111
Authority: WO
Inventors: Peter Graham Evans
Original assignee: Transweight Nz Limited
Priority date: 1992-11-13
Filing date: 1993-11-11
Publication date: 1994-05-26
Also published as: AU5578894A

Abstract

A method and apparatus for monitoring the load on a trailer unit by placing a load cell between the trailer's axle (7) and suspension springs (3). A load cell arrangement where a load cell outer part (21) is attached to the suspension springs (3), an inner part (20) attached to the axle (7) and the load cell itself located between the inner (20) and outer (21) parts, is also disclosed.

Description

LOAD CELL ARRANGEMENT

TECHNICAL FIELD

This invention relates to an apparatus and method for monitoring a load.

BACKGROUND ART

Reference throughout this specification will be made to the use of the present invention with respect to trailer units, however it should be appreciated that the principles behind the present invention can be used in relation to other situations.

To understand the present invention, it is necessary to have some background information on the general construction of trailers and how traditional load cell systems work.

Load cells are devices which can provide an electronic output proportional to the weight on the load cell. Load cells are used in trailer units to indicate the weight on the trailer unit. A maximum weight is allowed by regulations and road taxes are also required to be paid depending on the weight. Thus accurate, lightweight load cells are desired.

Traditionally, load cells are fitted under the trailer decks and on top of the chassis and have supporting gussets to hold the load cells in position. The gussets are required to be welded to the chassis and deck and not only does this take time, but also adds considerable weight to the trailer and installation/engineering costs. It should be appreciated that any extra weight added to the trailer lessens the amount of payload a truck driver can carry on the trailer.

Another position where load cells are traditionally placed is above the centre equaliser which forms part of the suspension system fitted under the trailer chassis. To fit a load cell in this position, it is necessary to remove the chassis. Again, this is a time consuming exercise, and furthermore, load cells fitted in this position are subject to torque caused by uneven stresses on the trailer unit (such as those caused by uneven ground). This often leads to inaccuracies in the recordal of the load weight occurring. It is apparent that conventional load cell systems for trailers all have their problems, whether it is excess weight, inaccuracy in data recordal or a lengthy time (and therefore considerable expense) in which to fit the load cells to the trailer units.

It is an object of the present invention to address the above problems or at least to provide the public with a useful choice.

Further objects and advantages of the present invention will become apparent from the following description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a method of installing a load cell arrangement with respect to a trailer unit including at least one axle and a suspension system containing a spring arrangement, characterised by the step of positioning the load cell arrangement between an axle of the trailer unit and the spring arrangement.

The term trailer unit used in this specification shall mean any transport device having an axle and a suspension system.

Traditional trailers have spring saddles which are units which fasten springs to the trailer axle assembly and are connected to the equalisers in front of the trailer axle. The top half of the spring saddle bracket has a torque rod eye which is connected by a torque rod to the equaliser on the other end and together holds the axle assembly in place. The equaliser is welded to the trailer chassis.

To hold the combination of axle, bracket and springs together, there is provided U-bolts which pass over the leaf springs and connect to an under-swing which is a bracket below the axle.

In one embodiment of the present invention, the spring saddle bracket which contains the torque rod eye is replaced by a load cell arrangement. Thus, the load cell can be positioned directly over the axle. It can be seen that the above embodiment has a number of advantages over the prior art.

The placement of the load cell arrangement directly over an axle means the readings received are directly representative of the load from the trailer on that axle. Greater accuracy can be obtained if there is provided more than one load cell per trailer unit, say a load cell associated with each spring saddle arrangement - usually two per axle.

One advantage of the present invention is that it is a relatively easy task to access the spring saddles in a trailer unit compared with the task of accessing the conventional positions in which load cells have previously been placed.

Another advantage is that less welding is required to secure the load cells.

It can be seen that the present invention provides advantages in terms of less time and hence less money spent in fitting the load cells as well as greater accuracy.

The present invention may come in a variety of forms.

In one embodiment of the invention there may be provided two parts. One part, hereinafter referred to as an outer, can be fixed to the spring arrangement in the suspension system. Another part, hereinafter referred to as an inner, can be fixed with respect to the axle. A load cell may be fitted between these two parts and the movement of the spring arrangement with respect to the axle can be transmitted directly to the load cell. This provides very accurate readings and has the capability of providing individual axle readings as well.

In some embodiments a load transfer part may be positioned between the outer and the load cell.

The present invention may be made from a number of materials. In one embodiment, the inner may be made from A4 steel. This is a mild steel which has a higher carbon and manganese content than A2 steel and can be readily welded to the axle. In other embodiments, inner may be cast. The outer may be made from A2 steel. This steel absorbs shock well which is particularly advantageous when the trailer is empty as it causes less damage to the suspension and load cell system. Again, the outer may be made from other materials and may also be cast.

To reduce the weight of the present invention, the design of the various parts making up same may be hollowed out as much as possible without compromising strength. There may be also incorporated lubrication or grease tracks within the inner and outer parts of the present invention which not only provides a lubrication means but also contributes to lessening the weight of the present invention.

In some embodiments of the present invention, the torque rod eye may be connected to the part of the present invention which is attached to the suspension system. The torque rod eye may be welded onto the outer or be cast with respect thereto. If this system is used it can be seen that the only modification applied to a trailer is in the spring saddle region and that the positioning of torque rods and so forth remains the same. This is less difficult than removing the chassis or welding gussets as with traditional systems.

BRIEF DESCRIPTION OF DRAWINGS

Aspects of the present invention will now be. described by way of example only with reference to the accompanying figures in which:

Figure 1: is a diagrammatic side view of a traditional suspension system for a trailer unit, and

Figure 2: illustrates a load cell fitted in accordance with one embodiment of the present invention, and

Figure 3: is a view of the parts of a load cell arrangement in accordance with one embodiment of the present invention. BEST MODES FOR CARRYING OUT THE INVENTION

With respect to Figure 1, there is illustrated a typical suspension system for a trailer unit generally indicated by arrow 1.

The suspension system 1 comprises an centre equaliser 2 which is connected by three leaf springs 3 to an end equaliser 4. U-bolts 5 fit over the leaf springs 3 and hold an under-swing 6 in position under the trailer axle 7.

A bracket 9 fits between the axle 7 and the bottom of the leaf springs 3. At one end of the bracket 9 is a torque rod eye 10. Connected to the torque rod eye 10 is a torque rod 11 which also connects to the end equaliser 4.

Figure 2 illustrates a typical suspension system for a trailer as described above, but which incorporates a load cell arrangement in accordance with the present invention.

The bracket 9 illustrated in Figure 2 has been replaced by a two part system comprising an inner 20 and an outer 21. These are illustrated again in greater detail in Figure 3.

The inner 20 is comprised of two halves 20a and 20b which are welded to the axle 7.

Referring to Figure 3, it can be seen that there are two key ways 22 and 23 which extend out from the walls of the inner 20. The key ways 22 and 23 have bores (not shown) drilled in which can receive bolts.

Sitting on top of the inner 20a, is a load cell 29 having electrical connections 30. A load transfer part in the form of disc 31 may sit on top of the load cell.

The outer 21 has grooves 24 and 25 which are complementary to the key ways 22 and 23, allowing the inner 20 to be readily aligned therewith. Aligned with the sides 26 of the outer 21 are bolt holes 27 which assist in securing the outer 21 with respect to the spring saddle arrangement.

The outer 21 has insets 32 and 33 which are complementary to the load cell 29 and disc 31 respectively. Extending from the outer 21 is also a torque rod eye 28. The torque rod eye 28 performs the same function of the torque, rod eye 10 illustrated in Figure 1.

Operation of the present invention may occur as follows. The outer 21 is fixed with respect to the leaf springs 3. The inner 20 is fixed with respect to the axle 7. The load cell 29 is fixed to the inner 20 and the disc 31 placed on top of the load cell 29. When there is a load on the trailer, the leaf springs 3 bend downwards pushing the outer 21 onto the disc 31. This pressure is transmitted directly to the load cell 29 which provides an output indicative of the weight on the trailer via the electrical connection 30.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE:

1 . A method of installing a load cell arrangement with respect to a trailer unit including at least one axle and suspension system containing a spring arrangement, characterised by the separate positioning the load cell arrangement between an axle of a trailer unit and the spring arrangement.

2. A method as claimed in claim 1 wherein the trailer unit includes a spring saddle bracket, the method being characterised by the further step of removing the top half of the spring saddle bracket and inserting a load cell arrangement.

3. A method of installing a load cell arrangement with respect to a trailer unit wherein the load cell arrangement has an outer part, and an inner part, characterised by the steps of:-

fitting the outer part to the spring arrangement in the suspension system, and fitting the inner part with respect to the axle of the trailer unit, fitting a load cell between the inner part and the outer part so that movement of the spring arrangement with respect to the axle can be transmitted directly to the load cell.

4. A method of installing a load cell arrangement with respect to a trailer unit as claimed in claim 3, characterised by the further step of placing a load transfer part between the outer and the load cell.

5. A method of installing a load cell arrangement with respect to a trailer unit as claimed in any one of claims 1 to 4 characterised by the further step of connecting a torque rod eye to the load cell arrangement.

6. A method of installing a load cell arrangement with respect to a trailer unit substantially as herein described with reference to and is illustrated by the accompanying drawings.

7. A load cell arrangement for installment in a trailer unit comprising an outer part, an inner part and a load cell fitted between the outer part and the inner part.

8. A load cell arrangement as claimed in claim 7 wherein there is included a load transfer part positioned between the outer part and the load cell.

9. A load cell arrangement as claimed in either claim 7 or claim 8 wherein the outer part and the inner part are substantially hollow.

10. A load cell arrangement as claimed in either claim 6 or claim 7 where either the inner and/or outer part incorporates lubrication tracks.

1 1. A load cell arrangement as claimed in either claim 6 or claim 7 wherein there is provided a torque rod eye connected to the outer part of the load cell arrangement.

12. A load cell arrangement substantially as herein described with reference to and is illustrated by the accompanying drawings.

13. A trailer unit incorporating a load cell arrangement as claimed in any one of claims 6 to 12.

14. A trailer unit substantially as herein described with reference to and is illustrated by the accompanying drawings.