GB2027542A - Calibrating a weighing device - Google Patents

Abstract

Apparatus for checking and/or calibrating a weighing device for a container 10 includes means 26 for pushing or pulling the container against the restraint exerted thereon by the weighing device at 16 and incorporating in said means at least one force measuring transducer 24 having energising means and output signal means, said output signal means being utilised to indicate the load applied to the container by the pushing or pulling means. A hydraulic compression cam 32 supplied by pump 34 is connected between members 28 and 30 so that the cam causes contraction of means 26. Means for connecting to the container comprises turnbuckle 22 in series with adjustable length chains. Means 48 are provided for reversing the signal from transducer 24, so that it can be incorporated in connecting means between frame work 12 and the top of container 10 to measure compression. <IMAGE>

Description

SPECIFICATION Weight measuring method and apparatus The present invention concerns a weight measuring method and apparatus for carrying out said method, and relates particularly but not exclusively to a method and apparatus for checking and calibrating weighing devices on hoppers, silos and other such vessels, for example those for containing cement and aggregate in a concrete batching plant.

Such hoppers, in some instances, have mechanical scales coupled therewith such that the scales record the weight of the contents of the hoppers. As a result of the arduous conditions in which said scales operate it is advisable that they are frequently checked and re-calibrated. However, this has proved difficult in the past as the normal method of checking has involved loading the hopper with standard certified weights and calibrating the scales as the weights are progressively added and removed from the hopper.

This method is clearly disadvantageous, the most obvious and considerable disadvantage being the time and labour involved in placing and removing the weights.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to the present invention there is provided a method of checking and/or calibrating a weighing device for a container comprising applying a force to the container by pushing or pulling it against the restraint thereon provided by said weighing device, incorporating at least one force measuring transducer in the means for applying the force and measuring the applied force by reading the signals emitted by said force measuring transducer.

The force may be applied hydraulically by pulling on the base of the container and it is preferable that two means for applying force are provided, said means being spaced equally on either side of the load centre line of the container.

Preferably the force measuring transducer outputs are added together and connected to a measuring device comprising amplification means, digital readout means and scale zeroing means. This device includes also means for reversing the output signal of the force measuring transducer such that they can be used in a compressive mode when the method is carried out by pushing down on the container.

Further according to the present invention there is provided apparatus for checking and/or calibrating weighing means for a container comprising means for applying a force to the container to push it or pull it against the restraint thereon provided by the weighing means, said force applying means including at least one force measuring transducer for measuring the applied force.

Preferably the force applying means comprises connection means for attachment between the base of the container and a rigid point on the ground, the connection means incorporating the force measuring transducer, and, in series therewith, a hydraulic ram for applying the force. Turn-buckles may be incorporated in the connection means together with adjustable length chains.

Preferably the hydraulic ram is of the type which applies a compressive force and is located in a yoke means comprising a first member against which the lower end of the jack abuts and which is connected to the base of the container and a second member surrounding said first member against which the upper end of the jack abuts and which is connected to said rigid point such that when the ram applies a compressive force the connection means are placed in tension.

Preferably two connection means are arranged in parallel, equally spaced on either side of the load centre line of the container.

The output from the force measuring transducers of the connection means are added together and connected to a measuring device which incorporates a digital read-out and a zeroing arrangement, whereby the force exerted by each connection means can be determined independently and the total applied force can be measured.

Preferably the measuring device includes two separate channels each having a different range.

The measuring device may include also means for reversing the output signal from the force measuring transducer whereby they can be used in a compressive rather than a tension mode.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawing which shows diagrammatically a container and an arrangement for checking and calibrating the weighing means thereof.

A hopper 10 is mounted on a rigid framework 12 in a rigid ground support 14. In this particular example the hopper 10 is mounted to the framework 12 by spring means generally indicated at 16 and a mechanical weighing device (not shown) is incorporated in the connection whereby the weight of material in the container is indicated by the device.

To check and calibrate the weighing device two connecting means 20 are temporarily connected between the base of the hopper 10 and the ground 14. As each connecting device is identical only one will be described in detail. While not illustrated in the drawing, the connecting device includes chains, which are adjustable in length so that the connecting means can be used on hoppers on sites where the ground-to-hopper dimension differs. To provide fine adjustment the connecting means includes a turnbuckle 22 connected in series with the chains and a 10,000 Ib capacity force measuring transducer or load cell 24 is included also. Means for applying tension to the connecting means comprises a first member 28 having an open box configuration mounted in a second member 30 for longitudinal movement relative thereto.A hydraulic compression ram 32 is incorporated between the top of the second member and the bottom of the first member such that expansion of the ram causes corresponding contraction of the connecting means. A portable hydraulic pump 34 supplies pressure fluid to the ram 32. Thus it will be seen that by applying pressure fluid to the ram 32 a force will be applied to the containerto pull it downwards.

Leads 36 from each load cell 24 are taken by way of a junction box 38 and a connection 40 to a measuring devce 42. The leads 36 are connected in parallel.

The measuring device 42 comprises excitation means for the load cell an amplifierfor return signals from the load cell and a digital read-out device. A sensitive zeroing arrangement provided for the read-out 44 is operable by a knob 46. Means are provided for reversing the output signal from the load cell such that it can be used in a compressive mode, for instance it can be incorporated in a connecting means between the framework 12 and the top of the container such that the container can be pushed down rather than pulled as described above. This excitation reversal means is controlled by a switch 48.

Advantageously the measuring device includes a second separate channel having its own amplifier digital read-out means and zeroing means, the second channel having a different range, and reading out in weight increments different from that of the first channel. This facility enables one measuring device to be utilised simultaneously for two checking and calibrating operations, for example, on the cement and on the aggregate hoppers of a concrete batching plant.

In operation, afterthe connecting means have been connected between the ground 14 and the base of the hopper 10 and the turn-buckles adjusted, the read-out 44 is zeroed. Force is applied to the connecting means by operating the hydraulic pump 34. By altering the connection of the leads 36 from the load cells 24 the force applied by each connecting means can be ascertained from the read-out, as can the total applied force. In this way the operator can ensure that the hopper 10 is loaded evenly on either side of the load centre line by each connecting means.

At intervais the measured applied force can be checked against the force indicated by the weighing device for the hopper and the device can be calibrated if required. Force is applied until the maximum reading of the weighing device is obtained; thereafter the force can be removed gradually and the calibration checked on a decreasing force.

It will be realised that the apparatus described above with reference to the drawing is relatively light-weight and consequently portable and thus can be assembled and utilised with assured accuracy in a relatively small time at any number of locations.

Furthermore it can be utilised simultaneously on a number of hoppers.

Use of the apparatus is not confined to checking and calibrating the weighing means for hoppers but it can be used equally easily on weigh bridges, etc.

Various modifications can be made without departing from the scope of the invention, for example the force can be applied by mechanical means and the connection means may be altered. Furthermore it will be realised that only one connection means need be utilised in certain applications while in others more than two may be provided.

Claims (17)

1. A method of checking and/or calibrating a weighing device for a container comprising applying a force to the container by pushing or pulling it against the restraint thereon provided by said weighing device, incorporating at least one force measuring transducer in the means for applying the force and measuring the applied force by reading the signals emitted by said force measuring transducer.

2. A method as claimed in claim 1, in which the force is applied hydraulically by pulling on the base of the container.

3. A method as claimed in claim 1 or claim 2, in which two means for applying force are provided, said means being spaced equally on either side of the load centre line of the container.

4. A method as claimed in any one of claims 1 to 3, in which the force measuring transducer outputs are added together and connected to a measuring device comprising amplification means, digital readout means and scale zeroing means.

5. A method as claimed in claim 4, in which said device includes also means for reversing the output signal of the force measuring transducer such that it can be used in a compressive mode when the method is carried out by pushing down on the container.

6. Apparatus for checking and/or calibrating weighing means for a container comprising means for applying a force to the container to push it or pull itagainstthe restraint thereon provided bythe weighing means, said force applying means including at last one force measuring transducer for measuring the applied force.

7. Apparatus as claimed in claim 6, in which the force applying means comprises connection means for attachment between the base of the container and a rigid point on the ground, the connection means incorporating the force measuring transducer, and, in series therewith, a hydraulic ram for applying the force.

8. Apparatus as claimed in claim 6 or 7, in which turn-buckles are incorporated In the connection means.

9. Apparatus as claimed in any one of claims 6 to 8, in which adjustable length chains are incorporated in the connection means.

10. Apparatus as claimed in any one of claims 7 to 9, in which the hydraulic ram is of the type which applies a compressive force and is located in a yokes means comprising a first member against which the lower end of the ram abuts and which is connected to the base of the container and a second member surrounding said first member against which the upper end of the ram abuts and which is connected to said rigid point such that when the ram applies a compressive force the connection means are placed in tension.

11. Apparatus as claimed in any one of claims 6 to 10, in which two connection means are arranged in parallel, equally spaced on either side of the load centre line of the container.

12. Apparatus as claimed in any one of claims 7 to 11, in which the output from the force measuring transducers of the connection means are added together and connected to a measuring device which incorporates a digital read-out and a zeroing arrangement, whereby the force exerted by each connection means can be determined independently and the total applied force can be measured.

13. Apparatus as claimed in claim 12, in which the measuring device includes two separate channels each having a different range.

14. Apparatus as claimed in claim 12 or claim 13, in which the measuring device includes also means for reversing the output signal from the force measuring transducer whereby it can be used in a compressive rather than a tension mode.

15. A method of checking and or calibrating a weighing device for a container, substantially as hereinbefore described with reference to the accompanying drawing.

16. Apparatus for checking and or calibrating a weighing device for a container substantially as hereinbefore described with reference to the accompanying drawing.

17. Any novel subject matter or combination including novel subject matter herein disclosed.

whether or not within the scope of or relating to the same invention as any of the preceding claims.