AU614077B2 - Force transmission element - Google Patents

Description

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PCT

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 G01G 21/23, G01L 1/26 WO 88/ 07177 22 September 1988 (22.09.88) (21) International Application Number: PCT/AU88/00065 (22) International Filing Date: (31) Priority Application Number: 11 March 1988 (11.03.88) PI 0797 (32) Priority Date: (33) Priority Country: 11 March 1987 (11,03.87) Published With international search report.

A.O.j.p. 17 NOV 1988 (71)(72) Applicant and Inventor: KELLENBACH, Arthur [AU/AU]; 15 Awatea Avenue, St. Ives, NSW 2075

(AU).

(74) Agents: HALFORD, Graham, William et al.; Halford Maxwell, 49-51 York Street, Sydney, NSW 2000

(AU).

(81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (European patent), FR (European patent), GB (European patent), IT (European patent), LU (European patent), NL (European patent), SE (European patent), (54) Title: FORCE TRANSMISSION ELEMENT 2--I '/14

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/0 i I 1 14 (57) Abstract A load support device which transmits a load force to, for example, a load cell or other weighing device, while accommodating motion and spurious forces arising from distortion or thermal expansion or contraction. The device comprises a load receiving member (11) and a base (10) connected by a body of elastomeric material and a force transmitting element (13) extends between the base and the load receiving member.

I I. i 1" 7 -1- FORCE TRANSMISSION ELEMENT FIELD OF THE INVENTION This invention relates to load supports or force transmission devices, suitable for use in weighing apparatus of various kinds, and which may find application in other areas as well.

BACKGROUND ART It is known to support large objects or containers such as tanks, on means which include one or more load cells, to enable the weight of the tank and its contents to be measured. In order to avoid unacceptable inaccuracies in such weight measurement ee: 9 15 arising from spurious forces applied to the load cell due for example to structural distortion or temperature-related expansion or contraction, it is known to arrange for a point or small area contact with the load-receiving member of the load cell, and sooee 20 to mount the tank or other object in such a way as to allow a freedom of movement sufficient to provide for such distortions or dimensional changes. The arrangements necessary to restrict this freedom of 050555 S" movement are complex and expensive, and the 25 provisions of weight indication for large tanks and the like is therefore expensive and difficult.

In other areas of weighing technology, and in other oio applications requiring the support of objects in such 30 a way as to provide a limited freedom of movement, there exists the need for a simple support or force transmission device which is capable of transmitting large forces while maintaining the load line, and with minimum compression in the direction of the load line, and which is also capable of resisting tension S rU

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SUMMARY OF THE INVENTION Such a device is provided by the present invention, which broadly resides in a load support comprising a load support comprising a load receiving member attached to a support member by means of a body of elastomeric material, a rigid force transmitting element embedded in said material and extending directly between said members to transmit force therebetween said element not being fixed to at least one of said members.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings Fig. 1 shows in lateral cross-section, a load support embodying the present invention; Fig. 2 is a plan view of the load support of Fig. 1; Fig. 3 shows in lateral cross-section, a load support according to a second embodiment of the invention; Fig. 4 is an underneath plan view of the load support

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Fig. 8 of Fig. 3; Sis a lateral cross-section of a load support according to a further embodiment of the invention; 6 and 7 are lateral cross-sections of load supports according to still further embodiments of the invention; and is a lateral cross-section taken at right angles to that of Fig. 7.

LED DESCRIPTION 01 PREFERRED EMBODIMENTS I

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1 -3- Illustrated in Figs. 1 and 2 in a first embodiment of the invention, is a load support device for receiving a load and transferring the load force to a load cell or other weighing device.

The support illustrated in Figs. 1 and 2 comprises a base member 10 which may be of steel or other rigid material and a load-receiving plate 11 of similar material. Extending between the base 10 and the plate 11 and bonded to both, is a body of elastomeric material which may for example be natural rubber or a synthetic rubber such as polyurethane.

Located centrally of the support is a force transmitting element 13, in this case in the form of a boss extending upwardly from the base 10, and l. provided with a rounded, part-spherical end on which the plate 11 rests. The base 10 is provided with mounting holes 14, and the plate 11 is provided with 20 mounting holes 18.

i 0 0 The rigid element 13 will transmit to the base 10 the vertical force due to a load placed on the plate 11, which is however free to accommodate movement arising nll lr 25 from distortion of the apparatus or arising from 3000 thermal expansion or contraction, without effecting the force transmitted to the base. The elastomeric body 12 will provide an elastic response to forces applied between the plate 11 and base 10 in directions other than the vertical, the plate 11 in response to such forces being free to tilt in any direction, and the plate 11 may move to a limited extent horizontally over the element 13 in response to horizontal forces such as may arise, for example, from expansion of contraction of the associated /S-f apparatus.

P N 4~y ii;2 tV t I -4- Unlike devices incorporating resilient material employed in the prior art to accommodate such extraneous forces, however, in the illustrated support the elastomeric body 12 is not required to carry the applied load, as this is transferred to the base by the relatively rigid element 13. In this way damage to the body 12 arising from internal shear as the side walls of the body bulge outwardly under load, is prevented. As a consequence, the properties of the elastomer can be chosen with greater freedom to suit the requirements of a particular application, and generally the elastomer may be softer than would be required in the prior art.

Another advantage flowing from the use of the stiff load transfer element 13 is that it largely eliminates compression of the support in the direction of the load force. Supports capable of e significant compression in this direction may in some eOVO 20 situations lead to oscillation of the load and consequent damage or danger.

A further advantage of such a device is that by virtue of the bonding of the elastomer to the base °25 and the plate 11, the device will accommodate and accurately transfer forces tending to separate the plates.

In Figs. 3 and 4 a second embodiment of the invention is illustrated, in which the invention is incorporated into a load cell. As in the case of the first embodiment, a base 10 is attached to a load receiving plate 11 by a polyurethane body bonded to each, and a boss 13 again transfers the load force to the base 10, but in this embodiment the base 10 i: includes a thin central section 15 on which are t mounted two parts of strain gauges 16 and 17. The gauges 16 are mounted on the inner portion of the lower surface of the section 15, which portion is placed in tension by the downward deflection of the centre of the base, while the gauges 17 are placed on the outer portion of this surface, which is placed in compression by such deflection. The gauges 16 and 17 may therefore be used in a bridge circuit to enable the applied loads to be measured in known manner. As in the case of the Figs. 1 and 2 embodiment, the load receiving plate 11 is in free contact with the force transmitting element 13, substantially isolating the strain gauges 16 and 17 from the effects of extraneous forces or movements on the plate 11.

A combined support and strain gauge assembly of the kind illustrated in Figs. 3 and 4 may be provided at t.o each leg of a tank support stand, the combined outputs of the strain gauges providing a measure of the weight of the contents of the tank. The S. simplicity of this arrangement is most attractive, the weight of the tank being taken by the elements 13, while the lateral movement of the tank is restrained by the shear strength of the elastomeric body 12 and its adhesion to the plate 11 and the base *0 S: 10. Although additional lateral restraint may be provided, this will not normally be required.

In the embodiments thus described, the configuration Sof the load receiving plate and the end of the force transmitting element on which it rests are such as to allow the plate to tilt about any axis normal to the direction of the applied load. In other embodiments of the invention, the degrees of freedom given to the plate are restricted.

j 0 z ii 0 7i~ -6- In the embodiments so far described, the force transmitting element is fixed to the base. In other embodiments, the force transmitting element is in free contact with the base, and allows freedom of movement of the base 10 as well as the plate 11.

Examples of such configurations will now be described.

In Fig. 5 the element 13 consists of a steel ball in free contact with both the plate 11 and the base while in Fig. 6 the element 13 consists of a steel pin with tapered ends, again in free contact with both the load receiving plate and the base. In each case, the load receiving plate is given the maximum possible degrees of freedom.

In the embodiment illustrated in Figs. 7 and 8, the element 13 consists of a rectangular steel plate with tapered upper and lower edges, and therefore .allows tilting rotation of the plate 11 or the base 10 about one axis only.

The elastomeric material may be fixed to the load receiving member and to the base by any suitable means providing sufficient strength for the purpose at hand. Where polyurethane is used, the preferred a •method is thoroughly to clean the surfaces of the load receiving member and the base and to fill the space between them in a gravity or pressure mould, subsequently curing the polyurethane in situ and thereby achieving a strong bond with the load receiving member and the base.

.o*4 In this specification, the expressions 'elastomer' and 'elastomeric' are used in a general sense to i include both natural and synthetic substances or mixtures of those, or devices, which exhibit elastic Tr or resilient behaviour and are sufficiently flexible i z 2 oft I

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If desired, the opposed surfaces of the base and the load receiving member may be provided with formations such as steps, grooves, peripheral flanges or other features to increase the lateral strength of the assembly.

While the elastomeric material is preferably moulded about the force transmitting element and is in a single body there may be applications where alternatives are preferable, and the elastomer may, for example, be provided in several separate bodies between the load receiving plate and the base.

In the preceding description of the invention a vertical orientation has been assumed, but of course this is not essential, as the devices described will Sbe capable of operation in any orientation. The use of expressions such as "base" or "support" is ~therefore a matter of convenience only, and should not be taken as limiting the invention to a vertical orientation, or to gravitational loads.

The manner in which the load is applied to the load •receiving member of the device will be chosen to suit

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the application of the invention to a particular purpose. The plate 11 may, for example, be provided with a pin for engagement within an aperture in the load structure, or with apertures for bolts or other fasteners.

The invention is of course capable of embodiment in forms other than those described, and is not to be regarded as being restricted in its scope by the specific embodiments included in this specification.

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Claims (6)

1. A load support comprising a load receiving member attached to a support member by means of a body of elastomeric material, a rigid force transmitting element embedded in said material and extending directly between said members to transmit force therebetween said element not being fixed to at least one of said members.

2. Apparatus according to claim 1 wherein the force transmitting element is fixed to one of the support member and load receiving member and is not fixed to the other.

3. Apparatus according to claim 1 wherein the force transmitting element is not fixed to either the support member or the load receiving member.

4. Apparatus according to any one of the preceding S.o. claims wherein the contact between the element and .,:the member to which it is not fixed is such as to allow rotation of that member relative to the element about any axis normal to the direction of load force. Apparatus according to claim 4 wherein the end of the force transmitting element in such contact is substantially part-spherical.

6. Apparatus according to claim 3 wherein the force goj o transmitting element is substantially spherical.

455. 7. Apparatus according to claim 3 wherein the force transmitting element is in the form of a pin with at least one tapered end. R8. Apparatus according to any one of claims 1 to 3 0 of clim t wherein the contact between the element and the member to which is it not fixed is such as to allow rotation of the member in contact with the force transmitting element relative thereto about only one axis normal to the direction of the load force. 9. Apparatus according to claim 8 wherein the end of the force transmitting element in said contact comprises a knife edge. A load support substantially as herein described with reference to the accompanying drawings. DATED this 14th day of June 1991 ARTHUR KELLENBACH Patent Attorneys for the Applicant: HALFORD CO. 6 a o 9 V 4 t