AU6547100A

AU6547100A - A weight measuring device

Info

Publication number: AU6547100A
Application number: AU65471/00A
Authority: AU
Inventors: Terrance Michael McLafferty
Original assignee: KELBA AUSTRALIA Pty Ltd
Current assignee: KELBA (AUSTRALIA) Pty Ltd
Priority date: 1999-10-15
Filing date: 2000-10-12
Publication date: 2001-04-26

Description

AUSTRALIA

Patents Act 1990 Kelba (Australia) Pty Ltd

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT r e* Invention Title: A weight measuring device The following statement is a full description of this invention including the best method of performing it known to us:- Field of the Invention This invention relates to the measurement of weight. More particularly, the invention relates to a weight measuring device.

Background to the Invention The applicant is aware of various ways of measuring weight of a material, in particular, a fluent material. Broadly, these can be categorised as invasive or non-invasive measuring devices.

The non-invasive measuring devices, while being more reliable and accurate, are expensive to install. The invasive types of device suffer from numerous disadvantages, the principle one of which is that they are not sufficiently accurate. Also, particularly when dealing with foodstuffs, there 0oois the additional problem of the measuring devices being in contact with the foodstuffs. This could give rise to hygiene problems.

Typically, the invasive types of devices are ultrasonic or capacitance devices. Due to the unreliability of these devices, frequent maintenance thereof is required.

**The non-invasive devices are generally in the form of load cells mounted externally of a vessel containing the fluent material. As indicated above, while these devices are very accurate, they are expensive and have to be installed with great accuracy. This increases the expense of the items.

Summary of the Invention According to a first aspect of the invention there is provided a weight measuring device which includes: a body member having a region of reduced thickness; a shear-inducing means defined in said region of reduced thickness of the body member; and a measuring means mounted on said region of reduced thickness, in proximity to the shear-inducing means, for measuring shear forces in said region of reduced thickness of the body member.

According to a second aspect of the invention, there is provided a mount for a weight measuring device, the mount including: a body member having a region of reduced thickness; and a shear-inducing means defined in said region of reduced thickness of the body member.

4 2 Preferably, the body member is in the form of an I-beam. It will be appreciated that such a beam has a pair of flanges interconnected by a web.

Thus, the web may define the region of reduced thickness of the body member.

The shear-inducing means may be in the form of a slot formed in the web.

The slot may extend along, or parallel to, a longitudinal axis of the Ibeam.

The slot may be a closed slot, ie. closed at both ends. This is known as a "double-ended" cell. Instead, the slot may be open at one end. This is known as a "single-ended" cell.

An end plate may be attached to the I-beam at its end, or ends, corresponding to the closed end, or ends, of the slot. The end plate(s) may be provided for load bearing purposes and for inhibiting twisting of the 15 I-beam, in use.

A height of the slot above an operatively lower flange of the I-beam may govern the load-bearing capacity of the measuring device. The lower the slot is located in the web, the higher the load-carrying capacity of the measuring device and vice versa.

The measuring means may be in the form of strain gauges. In the case of a single-ended cell, two strain gauges may be provided, one on each side of the web. The strain gauges may be arranged adjacent to the closed ends of the slot. It will be appreciated that where reference is made to a "strain gauge", it is actually a pair of strain gauges on a common backing, one for measuring tensile strain and one for measuring compressive strain. For ease of explanation, however, each strain gauge pair shall, hereafter, be referred to as a "strain gauge".

In the case of a double-ended cell, two strain gauges may be arranged on each side of the web, one adjacent to each closed end of the slot, ie. four strain gauges in total.

A mounting means may be mounted on the I-beam for facilitating location of a foot of a vessel on the I-beam. The mounting means may be in the form of a mounting plate. The mounting plate may be secured to a top surface of an operatively top flange of the I-beam. It will be appreciated that the mounting plate is mounted in position on the top flange such that it controls the area over which the force to be measured is applied.

The plate and the top flange may be drilled as an assembly to enable bolting of the foot of the vessel to the I-beam. Similarly, an operatively bottom flange of the I-beam may be drilled to facilitate its mounting to a base plate, structure, or other suitable substrate.

Brief Description of the Drawings The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 shows a schematic, side view of a weight measuring device, in accordance with a first embodiment of the invention; Figure 2 shows a sectional end view of the device of Figure 1 taken S•along line II-II in Figure 1; and oooFigure 3 shows a schematic, side view of a weight measuring device, in accordance with a second embodiment of the invention.

"Detailed Description of the Drawings In the drawings, reference numeral 10 generally designates a weight measuring device, in accordance with the invention. The device 10 includes $00.

0$ a body member in the form of an I-beam 12. The I-beam 12 is either a 20 standard commercially available I-beam section or is a fabricated I-beam o o section.

The I-beam 12 includes a central web 14 arranged between a pair of opposed, parallel flanges 16 and 18. The web 14 defines a region of reduced thickness for load measuring purposes.

In addition, to facilitate the measurement of load, and, more particularly, shear forces imparted to the device 10 when under load, a shear inducing means in the form of a slot 20 is formed in the web 14.

In the embodiment of the invention illustrated in Figure 2 of the drawings, the slot 20 is a closed slot having ends 20.1 defined in the web 14.

This type of device 10 is known as a "double-ended" cell.

In the embodiment of the invention illustrated in Figure 2 of the drawings, the slot 20 opens out at one end of the web 14 and has only one end 20.1 defined in the web 14. This type of device 10 is known as a "singleended" cell.

In the case of both embodiments, the slot 20 extends along, or parallel to, a longitudinal axis of the I-beam 12. The position at which the slot 20 is located in the web 14 governs the load bearing capacity of the device 10. In use, the flange 16 is an upper flange of the device 10. The closer the slot is positioned to the upper flange 16, the lower its load bearing capacity and vice versa.

The device 10 includes a measuring means in the form of a plurality of strain gauges 22. In the case of the double-ended cell illustrated in Figures 1 and 2, two strain gauges 22 are provided on each side of the flange 14 in proximity to the ends 20.1 of the slot 20. The strain gauges 22 are connected in a Wheatstone bridge arrangement in such a manner that the two ends 20.1 are actually interconnected with each other. In other words, rather than the two sides of each end 20.1 being connected into separate Wheatstone bridges, the strain gauges 22 are interconnected not only at each end but from end to end. This improves the performance of the device 10 by reducing end to end errors.

In the case of the single-ended cell illustrated in Figure 3 of the drawings, a single strain gauge 22 is arranged on each side of the web 14, each strain gauge 22 being arranged in proximity to the end 20.1 of the slot End plates 24 are secured to both ends of the I-beam 12 in the embodiment illustrated in Figures 1 and 2 of the drawings. A single end plate 24 is secured to that end of the I-beam 12, opposite the end at which the slot 20 opens in the embodiment of Figure 3. The plates 24 are provided for load-bearing purposes and for inhibiting twisting of the I-beam, in use.

A mounting plate 26 is secured to an outer surface of the upper flange 16. The mounting plate 26 operates as a locating zone for a foot of a vessel (not shown) mounted on the device 10 in use to ensure that the area over which the force to be measured as applied by the foot of the vessel is controlled.

For this purpose, the mounting plate 26 and the upper flange 16 are drilled (not shown) for receiving bolts to bolt the foot of the vessel to the top of the device 10. Similarly, the lower flange 18 is drilled to facilitate its being bolted to a base plate, structure, floor, or other suitable substrate.

It will be appreciated that the provision of the slot 20 causes the I-beam 12 to mimic a shear beam in operation with the web 14 carrying the load while the flanges 16 and 18 carry bending forces. The unsupported web section 14 above the slot 20 is in shear and is allowed to deflect without restriction which would normally occur in a normal, unslotted web section.

This results in the additional benefit that the Poisson ratio is constant and does not increase with increasing load as in the case of a conventional compression load cell. This contributes to the linearity of the device It is a particular advantage of the invention that a device 10 is provided which functions as a weight transducer incorporating both measurement and mounting system in one integral assembly. Thus, the device 10 effectively becomes its own mount thereby automatically matching the device 10 to the load while significantly reducing the installation costs. In addition, the device 10 negates the need to machine pockets in the web area and this further assists in reducing manufacturing costs.

*ooIt will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

**e *ee oo*

Claims

1. A weight measuring device which includes: a body member having a region of reduced thickness; a shear-inducing means defined in said region of reduced thickness of the body member; and a measuring means mounted on said region of reduced thickness, in proximity to the shear-inducing means, for measuring shear forces in said region of reduced thickness of the body member.

2. The device of claim 1 in which the body member is in the form of an I- beam, having a pair of flanges interconnected by a web.

3. The device of claim 2 in which the web defines the region of reduced *thickness of the body member.

4. The device of claim 3 in which the shear-inducing means is in the form of a slot formed in the web.

5. The device of claim 4 in which the slot extends parallel to a longitudinal axis of the I-beam.

6. The device of claim 4 or claim 5 in which the slot is a closed slot. *o

7. The device of claim 4 or claim 5 in which the slot is open at one end.

8. The device of claim 6 or claim 7 in which an end plate is attached to the, or each, end of the I-beam corresponding to a closed end of the slot.

9. The device of any one of claims 4 to 8 inclusive in which a height of the slot above an operatively lower flange of the I-beam governs the load- bearing capacity of the I-beam.

10. The device of any one of the preceding claims in which the measuring means is in the form of strain gauges, with at least one strain gauge being arranged on each side of the region of reduced thickness.

11. The device as claimed in any one of the preceding claims in which a mounting means is mounted on the body member for facilitating location of a foot of a vessel on the body member and for controlling the area over which the force to be measured is applied.

12. A mount for a weight measuring device, the mount including: a body member having a region of reduced thickness; and a shear-inducing means defined in said region of reduced thickness of the body member.

13. The mount of claim 12 in which the body member is in the form of an I-beam, having a pair of flanges interconnected by a web. 7

14. The mount of claim 13 in which the web defines the region of reduced thickness of the body member.

The mount of claim 14 in which the shear-inducing means is in the form of a slot formed in the web.

16. The mount of claim 15 in which the slot extends parallel to a longitudinal axis of the I-beam.

17. The mount of claim 15 or claim 16 in which the slot is a closed slot.

18. The mount of claim 15 or claim 16 in which the slot is open at one end.

19. The device of claim 17 or claim 18 in which an end plate is attached to the, or each, end of the I-beam corresponding to a closed end of the slot. e

20. The mount of any one of claims 15 to 19 inclusive in which a height of :°ooothe slot above an operatively lower flange of the I-beam governs the load- bearing capacity of the I-beam. 15

21. The device as claimed in any one of the preceding claims in which a mounting means is mounted on the body member for facilitating location of a foot of a vessel on the body member and for controlling the area over which the force to be measured is applied. oo o

22. A weight measuring device substantially as described herein with 00.0%20 reference to the accompanying drawings.

23. A mount for a weight measuring device substantially as described herein with reference to the accompanying drawings. Dated this twelfth day of October 2000 *o Kelba (Australia) Pty Ltd Patent Attorneys for the Applicant: F B RICE CO