GB2138579A

GB2138579A - Measuring weight

Info

Publication number: GB2138579A
Application number: GB08408967A
Authority: GB
Inventors: Geoffrey Cecil Malkin
Original assignee: CANTERBURY PRECISION ENGINEERS
Current assignee: CANTERBURY PRECISION ENGINEERS
Priority date: 1983-04-14
Filing date: 1984-04-06
Publication date: 1984-10-24
Also published as: GB8408967D0

Abstract

Apparatus for measuring the weight of a body, for example the load on one wheel of a vehicle, comprises a pad 1 of resiliently compressible material having interconnected ducts 2 extending therethrough and filled with a substantially incompressible fluid. The upper surface of the pad is provided with a member 10 of relatively rigid material on which a body to be weighed is placed and which transmits the weight to the pad, and the ducts 2 are connected to pressure sensing means 9 calibrated in weight and optionally to a variable volume fluid reservoir 5 for accommodating fluid expelled from the ducts in use. The pad 1 is generally rectangular and the ducts 2 extend in perpendicular directions to form closed loops connected to the pressure sensing means and optionally the reservoir. <IMAGE>

Description

SPECIFICATION Improvements in and relating to the measurement of weight The present invention relates to apparatus for use in measuring the weight of a body.

The apparatus is particularly but not exclusively fur use in determining the load on the axle of a vehicle by weighing a wheel of the vehicle.

There are prescribed maximum loads for commercial vehicles, which the vehicles are designed to carry safely. The conventional way of determining the load of a vehicle is by use of a weighbridge. However, particularly where there is a substantial distance between a loading site and a weighbridge, the user of such a vehicle may not bother to check the load on his vehicle and may then take it onto the public highway with an illegally high load.

According to the present invention, there is provided apparatus for use in measuring the weight of a body comprising a planar pad of resiliently compressible material having interconnected ducts extending therethrough and filled with a substantially incompressible fluid, a member on the upper surface of the pad of relatively rigid material on which a body to be weighed is placed and which transmits the weight to the pad, and means for sensing the pressure of the fluid in the ducts and for indicating the corresponding weight of the body supported on the member.

A variable volume fluid reservoir may be connected to the ducts for accommodating fluid expelled from the ducts in the pad when a load is applied to the member. It advantageously comprises a chamber of which one wall is moveable against a spring bias over the full range of weights to be measured by the apparatus.

The pad is advantageously rectangular in plan with ducts extending in perpendicular directions therethrough. The resilience of the pad is selected in dependence on the range of weights to be measured by the apparatus and such that it will be compressible over the full range of weights. For use in weighing vehicles, the pad may for example be made of neoprene or nitryl rubber.

Where the apparatus is to be portable, the pad is advantageously sandwiched between the member and a lower member, for example a metal plate, which supports the pad on a support surface.

The pressure sensing means may comprise a simple pressure gauge, for example a bourdon gauge, calibrated in weight, or may be an electromechanical transducer which senses the pressure and converts it into a suitable analogue or digital electric or electronic signal which is transmitted to any suitable readout device which may provide a visual or printed readout. The pressure sensing means may also include an alarm for providing an audible signal e.g. at a predetermined maximum weight.

Embodiments according to the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through an embodiment of apparatus according to the present invention, on the line I-I of Figure 3; Figure 2 is a section through the apparatus of Figure 1 on the Line Il-Il of Figure 1; Figure 3 is a section through the apparatus of Figure 1 on the line Ill-Ill of Figure 1; Figure 4 is a section similar to that of Figure 1 showing the pad of another embodiment of apparatus according to the present invention; and Figure 5 is a section on the line V-V of Figure 4.

The apparatus shown in Figures 1 to 3 is designed specifically for use in measuring the load on the wheel of a vehicle for determining the loading on the axle of the vehicle, and is portable so that one such apparatus can be used for all the vehicle wheels.

The apparatus comprises a generally rectangular resiliently compressible pad 1, e.g.

moulded of neoprene or nitryl rubber, through which inter-connected ducts 2 extend. The ducts 2 are filled with a substantially incompressible fluid, for example a water/glycol mixture, and are connected to two outlets 3, 4. Outlet 3 of the pad is connected to a pressure sensing device 9, as shown a bourdon gauge, which is directly calibrated in weight. Outlet 4 is connected to a variable volume fluid reservoir 5 for receiving fluid expelled from the ducts 2 in use, and which, as shown, comprises a chamber 6 of which one wall is provided by a diaphragm 7 which is biased by a spring 8 towards a position in which the chamber has a minimum volume. The difference in the minimum and maximum volumes of the chamber 6 is at least equal to the total volume of fluid expelled from the ducts 2 at the maximum load to be measured by the apparatus.The spring may be arranged so that, when the apparatus is unloaded, the spring is substantially uncompressed, so that the fluid in the ducts is at atmospheric pressure, or the spring may be slightly compressed so that the fluid in the ducts is above atmospheric pressure.

At the maximum load to be measured by the appratus, the spring is arranged to be within its range of compressibility. Advantageously, the spring is arranged to have a linear response so as not to complicate calibration of the apparatus.

The resilience of the pad is selected in dependence on the range of loads to be measured by the apparatus and such that it will be compressible over the full range of loads, and specifically that it will be within its range of compressibility at the maximum load. To transmit the load evenly to the pad 1, the pad is provided on its upper face with a member 1 0, as shown a plate, of relatively rigid material, for example steel, on which the load to be weighed is placed.

The pad 1 rests on a support member 11, for example as shown a metal plate, which is laterally extended to carry the reservoir 5 and gauge 9. The edges of the pad are protected by a tubular frame 1 2 surrounding the pad and fixed to the metal plates 10, 11, and the reservoir 5 and gauge 9 are protected by a metal housing 13, the face of the gauge being visible through the top wall of the housing, on which the gauge may be mounted.

In the embodiment shown in Figures 1 to 3, the ducts 2 in the pad comprise two longitudinal ducts 2a extending along each longitudinal edge of the pad and which are interconnected by a plurality of transverse ducts 2b and are connected at one end to outlets 3 and 4. Alternatively, as shown in the embodiment of Figures 4 and 5, in which like reference numerals have been used for like parts, the ducts 2 may comprise a plurality of, for example 3 or as shown 5, longitudinal ducts 2a which are connected at their ends by two transverse ducts 2b extending adjacent the transverse edges of the pad. The ends of two of the longitudinal ducts are connected to the outlets 3 and 4.

In the above described embodiments, the ducts 2a, 2b form a number of closed loops all connected to the outlets 3 and 4, and the ducts 2 together with the reservoir and pressure detector provide a sealed fluid filled system.

The pad 1 with the ducts 2 of the above described embodiments may be moulded in any suitable manner.

In a modification of either of the above described apparatus, where the volume of fluid in the ducts 2 is relatively slight or the range of loads to be applied to the apparatus is relatively small, the reservoir 5 may be simplified by replacing the spring biased diaphragm 7 by a resiliently flexible wall biased by its own resilience to a position giving the reservoir a minimum volume, or the reservoir 5 may be omitted. When omitted, outlet 4 is closed or omitted.

In the above described embodiments, the pressure sensing device may include an alarm system which is energised at a pre-set maximum weight. For example, the gauge may be provided with a second indicator which is settable at a preset weight. The second indicator, and the first indicator indicating the weight, may be provided with contacts which, when the pre-set weight is achieved, complete an electric circuit and energise an alarm. Alternatively, the pressure sensing means may comprise, in place of or in addition to a simple pressure gauge providing a visual indication of load, an electro-mechanical transducer which senses the pressure and converts it into a suitable analogue or digital electric or electronic signal which may then be transmitted to any suitable read-out device which may provide a visual or printed read-out.Such pressure sensing means may also include an alarm system providing a signal when a pre-set maximum load is achieved. There is thus provided a relative cheap, lightweight and portable weighing apparatus which is particularly suitable for use with vehicles. When so used, the apparatus is placed flat on the group and the vehicle is driven onto it so that one wheel rests on the member 10, with the housing 1 3 located beside the wheel. The load on that wheel is then read directly from the pressure gauge. To compensate for the slight tilt of the vehicle produced by driving one wheel onto the apparatus, a metal plate representing a dummy apparatus may be used onto which the other wheel of the axle is simultaneously driven.The operation is repeated for all the wheels of each axle and by addition of measurements, the axle load for each axle of the vehicle can be calculated.

Additionally, the individual measurements can be used to ensure that the load on the vehicle is evenly distributed.

It will be appreciated that the above described apparatus may be used and adapted for use for many other purposes and ranges of weights. For example the apparatus may be mounted permanently at a weighing site. Under such circumstances, the support member 11 may for example be provided by a concrete base. The upper member 10 may be adapted to receive a particular form of load, for example it may be suitably shaped to receive the load. Furthermore a plurality of such apparatus may be used together.

For example four may be provided, one at each corner of a platform, on which a load is to be placed, the weights sustained by each apparatus being summed to provide the total load weight.

Alternatively, the ducts of the pads may be connected in series or in parallel, or in series/parallel to a single weight indicating means and the system may include a single reservoir which is connected to a plurality of pads.

Claims

1. Apparatus for use in measuring the weight of a body comprising a planar pad of resiliently compressible material having inter-connected ducts extending therethrough and filled with a substantially incompressible fluid, a member on the upper surface of the pad of relatively rigid material on which a body to be weighed is placed and which transmits the weight to the pad, and means for sensing the pressure of the fluid in the ducts and for indicating the corresponding weight of a body supported on the member.

2. Apparatus as claimed in Claim 1, including a variable volume fluid reservoir connected to the ducts for accommodating fluid expelled from the ducts when a load is applied to the member.

3. Apparatus as claimed in Claim 2, wherein the reservoir comprises a chamber having a wall which is moveable to vary the volume of the chamber, the wall being biased towards a position minimising the volume of the chamber.

4. Apparatus as claimed in any one of the preceding claims, wherein the pad is rectangular in plan, the ducts extending in perpendicular directions therethrough.

5. Apparatus as claimed in Claim 4, wherein the ducts form closed loops connected to an outlet connected to the pressure sensing means.

6. Apparatus as claimed in any one of the preceding claims, comprising a lower support member for supporting the pad on a support surface, the pad being sandwiched between the lower member and the member on which a body to be weighed is placed.

7. Apparatus according to any one of the preceding claims, wherein the pressure sensing means comprises a pressure gauge calibrated in weight.

8. Apparatus as claimed in any one of claims 1 to 6, wherein the pressure sensing means comprises an electro-mechanical transducer for sensing the pressure and converting it into an electric or electronic signal for transmission to a read-out means.

9. Apparatus as claimed in any one of the preceding claims, wherein the pressure sensing means includes an alarm for indicating a predetermined maximum weight.

1 0. Apparatus for use in measuring the weight of a body substantially as herein described with reference to the accompanying drawings.