GB2216671A

GB2216671A - Weighing apparatus for rail vehicles

Info

Publication number: GB2216671A
Application number: GB8904011A
Authority: GB
Inventors: David Edward Smith
Original assignee: W&T Avery Ltd
Current assignee: Avery Weigh Tronix Ltd
Priority date: 1988-04-27
Filing date: 1989-02-22
Publication date: 1989-10-11
Anticipated expiration: 2009-02-22
Also published as: AU3115889A; IN174946B; GB8809949D0; GB2216671B; GB8904011D0; AU620081B2

Abstract

Moving rail vehicles are weighed by apparatus comprising a set (16, 17) of strain gauges mounted on the web of a rail (10') in such a manner as to measure shear stress in the web of the rail as a load to be weighed passes over the rail. Preferably four strain gauges may be mounted at each end of a rail adjacent at point where the rail is supported, the four strain gauges being connected in the form of a Wheatstone bridge. <IMAGE>

Description

WEIGHING APPARATUS.

The present invention concerns the weighing of moving vehicles and is particularly concerned with weighing the wagons of a train whilst the train is in motion.

Conventionally the weighing of moving trains is carried out by weighbridges which comprise a platform structure supported by load cells. This is a relatively expensive solution.

It has been proposed to avoid the need for weighbridges by using strain gauges. One weighing system utilising strain gauges measures bending of rails as loads pass over them.

The present invention has for an object to provide a particularly simple and inexpensive apparatus for weighing moving vehicles.

Accordingly the present invention consists in apparatus for weighing vehicles moving on a rail or rails, the apparatus comprising a set of strain gauges mounted on the web of a rail in such a manner as to measure shear stress in the web of the rail as a load to be weighed passes over the rail.

In accordance with a feature of the invention four strain gauges may be mounted at the end of a rail adjacent at point where the rail is supported, the four strain gauges being connected in the form of a Wheatstone bridge.

In a preferred embodiment, two groups each containing four strain gauges connected as a Wheatstone bridge may be mounted adjacent opposite ends of a rail.

In order that the present invention may be more readily understood, an embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a side view of a railway track fitted with weighing apparatus according to the present invention, Figure 2 is a side view of a rail, Figure 3 is a cross-section through the rail of Figure 2, and Figure 4 shows Wheatstone bridge circuits connected to strain gauges.

Referring now to Figure 1 of the accompanying drawings, this shows a railway track 10 mounted on standard support chairs 11. As can be seen some of the support chairs 11 are mounted on normal sleepers 12 in turn supported by ballast 13. The remainder of the support chairs are mounted on a semi-stiff fabricated steel support frame 14.

The central rail 10' of the track 10 acts as a weigh rail and is secured to the other rails by standard fish-plate joints 15 which for proper operation of the invention should be securely made and well maintained.

The central rail 10' above is shown in Figure 2, sets 16 and 17 of strain gauges are bonded to each end of rail 10', as can be seen in figure 2. The strain gauges of either set are mounted two on each side of the web of the rail as can be seen from the cross section of rail 10' shown in Figure 3. Further the four strain gauges of each set are connected to form a Wheatstone bridge as is diagrammatically shown in Figure 4 with each strain gauge forming one arm of the bridge. Thus the four strain gauges A, B, C and D of set 16 together form Wheatstone bridge 20 and the strain gauges A', B', C' and D' form the arms of Wheatstone bridge 21. The gauges are arranged to measure shear stress in the rail when a vehicle moves over the rail. Shear stress and the resulting strain is induced in a beam or body by the action of a shearing force, in this case the passage of the vehicle.

This shearing force is shown by the arrows in Figure 2. To measure the shears the sensing grids of the strain gauges are mounted so as to be at an angle of 45 to the applied force being measured.

The inputs and outputs of the Wheatstone bridge are connected together in such a manner as to minimise the change in electrical output with a change in load position. The electrical summation of the Wheatstone bridge outputs can be direct but in the embodiment shown in Figure 4 there are a number of span adjustment resistors Radj.

The strain gauges are mounted in such a way as to measure the shear strain in the web of the rail as a wagon moves over the rail.

The advantage of measuring shear stress in the rail as proposed by the present invention is that the electrical output obtained from the strain gauges for a given load on the rail, is less sensitive to wear on the top of the rail than on equivalent system measuring bending stress on the bottom of the rail.

Claims

1. Apparatus for weighing vehicles moving on a rail or rails, the apparatus comprising a set of strain gauges mounted on the web of a rail in such a manner as to measure shear stress in the web of the rail as a load to be weighed passes over the rail.

2. Apparatus as claimed in Claim 1 wherein four strain gauges may be mounted at the end of a rail adjacent at point where the rail is supported, the four strain gauges being connected in the form of a Wheatstone bridge.

3. Apparatus as claimed in Claim 2, wherein two groups each containing four strain gauges connected as a Wheatstone bridge may be mounted adjacent opposite ends of a rail.

4. Apparatus for weighing vehicles moving on a rail substantially as hereinbefore described with reference to the accompanying drawings.