FORCE TRANSMISSION ELEMENT

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 (12), and a force transmitting element (13) extends between the base and the load receiving member.

Description: 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 applicati in other areas as well. BACKGROUND ART it is known to support large objects or containers such 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 i such weight measurement arising from spurious forces applied to the load cell due for example to structural distortion or temperature-related expansion or contracti it is known to arrange for a point or small area contact with the load-receiving member of the load cell, and to mount the tank or other object in such a way as to allow freedom of movement sufficient to provide for such distortions or dimensional changes. The arrangements necessary to restrict this freedom of movement are compl and expensive, and the provision of weight indication fo large tanks and the like is therefore expensive and difficult. In other areas of weighing tecHnology, and in other applications requiring the support of objects in such a as to provide a limited freedom of movement, there exist the need for a support or force transmission device whic is capable of transmitting large forces while maintainin the load line, and with minimum compression in the direction of the load line. SUMMARY OF THE INVENTION Such a device is provided by the present invention, which broadly resides in a load support comprising a load receiving member and a base member connected together by elastomeric material, characterised in that a force transmitting element is provided extending between said members and in free contact with at least one of said members. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, Fig. 1 shows in lateral cross-section, a load suppo 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 suppo according to a second embodiment of the invention; Fig. 4 is an underneath plan view of the load suppo of Fig. 3; Fig. 5 is a lateral cross-section of a load support according to a further embodiment of the invention; Figs. 6 and 7 are lateral cross-sections of load supports according to still further embodiments of the invention; Fig. 8 is a lateral cross-section taken at right angles to that of Fig. 7; Fig. 9 is a plan view of an " embodiment of the invention incoporating three force transmission elements; and Fig. 10 is a cross-sectional elevation taken on the line 10 - 10 of Fig. 9. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 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.l and 2 comprises a bas member 10 which may be of steel or other rigid material a load-receiving plate 11 of similar material. Extendi between the base 10 and the plate 11 and bonded to both a body of elastomeric material which may for example be natural rubber or a synthetic rubber such as polyuretha Located centrally of the support is a force transmittin element 13, in this case in the form of a boss extendin upwardly from the base 10, and provided with a rounded, part-spherical end on which the plate 11 rests. The ba 10 is provided with mounting holes 14, and the plate 11 provided with mounting holes 18. The rigid element 13 will transmit to the base 10 the vertical force due to a load placed on the plate 11, wh is however free to accommodate movement arising from distortion of the apparatus or arising from thermal expansion or contraction, without affecting the force transmitted to the base. The elastomeric body 12 will provide an elastic response to forces applied between t plate 11 and base 10 in directions other than the verti the plate 11 in response to such forces being free to t in any direction, and the plate 11 may move horizontall over the element 13 in response to horizontal forces su as may arise, for example, from expansion or contractio the associated apparatus. Unlike devices incorporating resilient material employe the prior art to accommodate such extraneous forces, however, in the illustrated support the elastomeric bod is not required to carry the applied load, as this is transferred to the base by the relatively rigid element In this way damage to the body 12 arising from internal shear as the side walls of the body bulge outwardly und 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 general 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 significant compression in this direction may in some situations lead to oscillation of the load and consequent damage or danger. In Figs. 3 and 4 a second embodiment of the invention is illustrated, in which the invention is incorporated into ' load cell. As in the case of the first embodiment, a bas 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 includes a thin central section 15 on which are mounted two pairs of strain gauges 16 and 17 The gauges 16 are mounted on the inner portion of the low 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 load to be measure in known manner. As in the case of the Fig. 1 and 2 embodiment, the load receiving plate 11 is in free contac with the force transmitting element 13, substantially isolating the strain gauges 16 and 17 froir the effects of extraneous forces or movements of the plate 11. A combined support and strain guage assembly of the kind illustrated in Figs. 3 and 4 may be provided at each leg a tank support stand, the combined outputs of the strain gauges providing a measure of the weight of the contents the tank. The 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 bod and its adhesion to the plate 11 and the base 10. Alth additional lateral restraint may be provided, this will not normally be required. In the embodiments thus described, the configuration of load receiving plate and the end of the force transmitt element on which it rests are such as to allow the plat tilt about any axis normal to the direction of the appl load. In other embodiments of the invention, the degre of freedom given to the plate are restricted. In the embodiments so far described, the force transmit element is fixed to the base. In other embodiments, th force transmitting element is in free contact with the base, and allows freedom of movement of the base 10 as as the plate 11. Examples of such configurations will be described. In Fig. 5 the element 13 consists of a steel ball in fr contact with both the plate 11 and the base 10, while i Fig. 6 the element 13 consists of a steel pin with tape ends, again in free contact with both the load receivin plate and the base. In each case, the load receiving pl is given the maximum possible degrees of freedom. In the embodiment illustrated in Figs. 7 and 8, the ele 13 consists of a rectangular steel plate with tapered up and lower edges, and therefore allows tilting rotation o the plate 11 or the base 10 about one axis only. In typical applications of the load supports of the invention, several supports will be employed, and the accommodation of tilting movementstybetween the base and t load receiving member will be possible only locally of t individual supports. Where such local tilting is to be restricted or eliminated, more than one force transmittin element 13 may be incorporated in the load support. Thus in Figs 9 and 10 there is illustrated a load support with three elements 13, which will allow only lateral sliding movement of the plate 11 and the base 10. Clearly where two such elements are employed, tilting about one axis wi be possible. The range of configurations possible for the manner of engagement between the force transmitting member and the load receiving member or the base will be apparent from t preceding description. In general, the manner of this engagement will be chosen to suit the application for the device, but will always provide at least one degree of freedom of movement of the plate or the base relative to the force transmitting element while maintaining force- transmitting contact. This may be a rotational movement, or a lateral movement, and such configurations are generically referred to herein by the requirement that th force transmitting element be in free contact with the member in question. The elastomeric material may be fixed to the load receivi member and to the base by any suitable means providing sufficient strength for the purpose at hand. Where polyurethane is used, the preferred method is thoroughly 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. In this specification, the expressions 'elastomer' and 'elastomeric' are used in a general sense to include bot natural and synthetic substances or mixtures of those, o devices, which exhibit elastic or resilient ϊbehaviour an are sufficiently flexible for the purpose. If desired, the opposed surfaces of the base and the lo receiving member may be provided with formations such a steps, grooves, peripheral flanges or other features to increase the lateral strength of the assembly. While the elastomeric material is preferably moulded ab 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 beiweent the load receiving plate and the base. In the preceding description of the invention a vertica orientaion has been assumed, but of course this is not essential, as the devices described will be capable of operation in any orientation. The use of expressions s as "base" is therefore a matter of convenience only, a'n should not be taken as limiting the invention to a verti 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 th application of the invention to a particular purpose. T 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 form other than those described, and is not to be regarded as being restricted in its scope by the specific embodiments included in this specification. ._>

Claims: CLAIMS : 1. A load support comprising a load receiving member and a base member connected together by elastomeric material, characterised in that a force transmitting element is provided extending between said members and i free contact with at least one of said members. 2. Apparatus according to claim 1 wherein the force transmitting element is fixed to one of the base and the load receiving member and is in free contact with the other. 3. Apparatus according to claim 1 wherein the force transmitting element is in free contact with both the ba member and the load receiving member. 4. Apparatus according to any preceding claims wherei said free contact is such as to allow rotation of the member in contact with the force transmission element relative thereto about any axis normal to the direction the load force. 5. Apparatus according to claim 4 wherein the end of the force transmitting member in said free contact is substantially part-spherical. 6. Apparatus according to claim 5 wherein the force transmitting element is substantially spherical. 7. Apparatus according to claim 3 wherein the force transmitting member is in the form of a pin with at leas one tapered end. 8. Apparatus according to any one of claims 1 to 3 wherein said free contact is such as to allow rotation the member in contact with the force transmitting eleme relative^ thereto about only one axis normal to the direction of the load force. 9. Apparatus according to claim 8 wherein the end of force transmitting element in said free contact compri an edge having tapered sides. 10. A load support according to claim 1 wherein said elastomeric material comprises a body of elastomeric material substantially surrounding the force transmitti element and bonded to the base and the load receiving member. 11. Apparatus according to any preceding claim incorporating a plurality of force transmitting element 12. Load support apparatus .incorporating a plurality load supports according to any preceding claim.

Inventors: KELLENBACH ARTHUR, KELLENBACH, ARTHUR
Applicants: KELLENBACH ARTHUR, KELLENBACH, ARTHUR
Application year: 1988
Main classification: G01G21
IPC codes: G01G21, G01L1