TECHNICAL FIELD

The invention relates to a platform scale, particularly of the personal weighing scale kind.

BACKGROUND ART

Platform scales particularly personal weighing scales such as bathroom scales often include a lever system and an internal calibrating support to provide accuracy in weighing with lightness and strength in construction. In order to provide for the accuracy of weighing, in particular, the lever system, or at least the individual levers thereof are often used in combination with knife-edge hangers. These hangers are expensive to manufacture .and complicated to install. _*

DISCLOSURE OF THE INVENTION

It is accordingly an object of the invention to seek to mitigate the disadvantage of the prior art.

According to the invention there is provided a platform scale comprising a base, for receiving a weight, supported over the base, and weight sensing means including a plurality of levers supported on the base and providing support for the platform, wherein there is adjacent an end of each lever adjacent the periphery of the base a support device between the platform and the respective lever pro'v ding a knife edge bearing for that lever and relative rotational movement between the platform and the lever.

Using the invention it is possible to provide a unitary support device which extends between the lever and the platform.

Preferably each support device may be captive between the platform and respective lever and is maintained in position by the lever.

Each support device may comprise a substantially planar member having a part for bearing on a bearing part of the platform, the knife edge being opposite the bearing part.

The bearing part of the platform may comprise a depression in the platform which extends below (in use) the plane thereof.

The depression may be elongate and and with a curved profile as considered in transverse cross-section.

The part of the device which may bear on the profile may be an edge of the device.

The support device may have projecting support limbs which engage the underside of the platform, in use.

The liirfas may project in opposite directions out of the plane of the device.

The knife edge may have an apex angle of 60° .

A part of a personal weighing platform scale embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded perspective view of the scale showing the mechanism thereof according to the invention;

Figure 2 is an enlarged schematic and elevational view of part of the inner surface of Figure 1; and

Figure 3 is an enlarged side elevational view of the part shown in Figure 2.

Referring to the drawings, first of all, a platform scale embodying the invention has a platform 1 and a base 2 which has an upstanding rim 3 _> the platform 1 having a dependent rim or skirt la which in use surrounds the rim 3 to provide a neat appearance. The base 2 includes weight sensing means including primary and secondary levers the primary levers 4 and 5 being secured to a corrmon plate 6 of a calibrating device to form a V-shaped single lever. The secondary levers 7 and 8 hang from respective primary levers 4 and 5 from hangers 9« A dial or mask (part shown) is mounted on a splined spindle 10 so that when that spindle 10 is rotated on deflection of the levers 4,5 and 7. 8 via a rack 11, the splined spindle 10, rack 11 and V-shaped single lever 4,6,5 forming part of a weight indicating mechanism, either a dial or numerical read-out of weight applied to the platform 1 can be read off through a viewing window of the platform 1. It will be appreciated that as the weight indicating mechanism 4 _? 6,5 and calibrating device are known, and form no part of the invention, they will not be referred to in greater detail.

Each lever 4 and 5j6 and 7 is, in the embodiment shown, stamped from a sheet metal plate and is supported upright adjacent one end on the rim 3 of the base 2 at a knife edge. Adjacent the periphery of the base 2 at a position inwards from the rim 3 each lever 4.5j or 7 supports the platform 1 via a support device 12 between the platform 1 and the respective lever 4 _. 5 _. 6 and 7.

Each support device 12 is made from a blank sheet of metal and comprises a substantially planar member 13 which is symmetrical about a centre line and has oppositely directed limbs 14 and 15 which in use bear on the underside of the platform 1, as considered in use and as shown in Figs 2 and 3- The planar member 13 has a notch or slot 16 terminating in a knife edge 17 of 60°

apex angle for bearing on the lever 8, and opposite the knife edge 17 a flat part of surface 18 which is an edge of the device and bears on a bearing part 19 of the platform 1. The bearing part 19 of the platform 1 comprises an elongate depression which is downwardly directed (in use) and has a substantially circular surface profile or configuration so that it has a rolling point contact with the bearing part 18 of the support device 12.

There are four depressions 19 at each corner area of the platform 1 and they are formed therein during fabrication in a relatively single forming step such as pressing or stamping. To assemble the scale each lever 4 _. 5*7.8 is positioned as required and each one has a bearing support device 12 supported on it before the scale platform 1 is placed in position, with the four depressions 19 bearing respectively on the four bearing parts 18 of the respective support devices 12. A simple cover or decorative panel on the upper (in use) surface of the platform 1 conceals the depressions 19, which do not in any way detract from the comfort of a user of the scale. The depressions 19 and their associated bearing devices 12 nevertheless accommodate any uneven loading of the platform by the depressions 19 or the planar bearing parts 18 "rolling" or rotating with respect to one another, so maintaining the knife edge 17 in the desired relationship to its respective lever, so that the calibration of the scale is not thrown out of true. The scale thus provides an accurate weight measurement even when the loading applied is asymmetric, in other words the scale can accommodate small or different inclinations or cants of the platform 1 with respect to the base 2 in use.