GB2178861A - Weighing apparatus - Google Patents

Abstract

Weighing scales comprise a platen 4 carrying underneath a bellows 6 sandwiched between a piston 10 and the platen 4. Lever arms 14 are pivotally connected by pins 13 to the platen and to supporting legs 17 by pins 18. Inner ends 15 of the arms bear on the underside of the piston 10. Fluid displaced from the bellows is fed to a manometer tube to provide an indication of the weight on the platen. The leverage of the arms 14 may bead justable to give a reading on the manometer tube at a convenient height.

Description

SPECIFICATION Weighing apparatus The present invention relates to weighing apparatus.

It is known to measure weights by means of a fluid displacing load cell and a manometertube. The load whose weight is to be measured is placed on the load cell and its weight is measured in terms of displacement offluid in the manometer tube. Such weighing apparatus is described in UK Patent Specification No.

1509140.

However certain difficulties are encountered when such weighing apparatus is to be used in a domestic apparatus. In particular, for a weighing apparatus to weigh a human person, it is convenientto employ a manometertube of a length corresponding approxi matelyto human height. This restricts the pressure available to be generated in the apparatus. Whilst it is possible to use a larger cross-sectional area fluid displacer, there is a practical limit on the size of this in terms of load platen areaandstability.

These problems have been overcome in my invention by use of a leveragearrangementforapplying the force of the weight to be weighed to the fluid displacer of the apparatus.

According to the invention there is provided a manometer sight tube, a fluid displacer connected to the manometersighttube in a fluid tight manner, a chassis supporting one side of the fluid displacer, at least one lever arm pivotally connect to the chassis and bearing at its free end on a piston ofthefluid displacer and at least one load application member pivotally connected to the our a respective leverarm.

The arrangement is preferably such thattheforce applied tothefluid displacer is considerably reduced by the leverage ofthe lever arm from the load applied by the or all ofthe load application members. Nevertheless in an adaption of the apparatus for instance for kitchen use, the leverage may be close to oractual- ly one-to-one, or even such as to increase the force applied to the displacer with respect to the weight of the load.

Although a separate load platen ora base, ifthe apparatus is inverted, may be provided for transferring the weight of the load to the load application member(s), in the preferred embodiment, the apparatus is inverted and the chassis performs the function ofthe load platen with the load application member(s) supported on a load bearing structure, for instance a floor.

Thefluiddisplacermaytakevariousforms.The piston perferably moves in a cylinder in the chassis.

Whilstthe piston and cylinder may befluidtightly connected for displacement of fluid therefrom, a fluid tight enclosure may be provided between the piston and the cylinder. Where the enclosure is sufficiently rigid radially, for instance by being constructed in the form of an annular bellows, the chassis need not radially constrain the enclosure.

In an important feature of some embodiments of the apparatus, the leverage at which the lever arms are arranged may be adjusted. Preferably this is achieved by providing in the chassis a circulartrack in which a generally circular member is movable and which member has alternative knife edge parts four alternative knife notches on the or each lever arm.

Alternatively the point of action of the load application member(s) on the lever arm(s) may be adjusted.

To help understanding ofthe invention, two specific embodiments ofthe invention will now be de scribe by way of example and with reference to the accompanying drawings in which Figure lisa perspective view of an apparatus according to the invention; Figure2 is an underside view ofthe platen ofthe apparatus of Figure 1; Figure 3 is a diagonal cross-sectional side view on the linelll-lll in Figure 2; Figure 4 is an underside view of the platen of another apparatus of the invention; Figure 5 is a diagonal cross-sectional side view on the line V-V in Figure 4; and Figure 6 is a perspective view of a differently arranged apparatus ofthe invention.

The weighing apparatus or scales shown in Figures 1 to 3 has a manometer tu be 1 with a turned overtop for avoiding dirt falling into the liquid 3therein.The tube 1 is conveniently secured in a double channel member 2 attached to a wall. The scales have a load platen 4 conveniently of wood or moulded plastics material provided beneath with a cylindrical recess 5 for an annular elastomeric material bellows 6 whose top surface 7 bears against an under surface 8 ofthe platen 4 and whose bottom surfaceS bears on a top surface of a piston 10, itself a clearance fit in the recess 5. A pipe 11 leads offfrom the bellows, through to the back ofthe platen and is there connected to the manometertube.

The platen has on itsundersidefourpivot-pin- supporting slots 12for supporting pivot pins 13 pivot- ally connecting four arms 14to the platen. The arms are directed inwards and bear attheirfree ends on the underside ofthe piston 10 via loading dimples 15. The free ends are captive to the piston via a slotted top hat member 15a. The arms 14 extend in slots 16 in the underside ofthe platen. Closeto the pivoted ends of the arms they pivotally carry load applying legs l7via further pins 18, the arms passing through slots in the legs. The distance between the respective pins 13 and 18 and the pin 13 and loading dimple 15 in each arm is such as to substantially reduce the load applied to the piston from that applied by the legs 17.With the arms 14 extending radially from the piston towards the corners ofthe platen and the legs 17 being close to the corners stability ofthe platen is provided,forany normally positioned load applied to the platen.

In use a load, generally in the form of a human person, on the platen has its weight shared bythe legs 17. The force of the load reduced bythe leverage of arms is applied to the piston and generates pressure in the bellows.

Water - suitably coloured - is displaced from the bellows up the manometertube 1 to be read against a scale 19 graduated in terms ofthe weight to be measured.

In the alternative shown in Figures 4 and 5 in place ofthe pins 13, a generally circular knife edge member 20 is provided in a circulartrack 21. It has radially inner knife edge portions 22 and radially outer knife edge portions 23, both of which are circularly curved.

These portions alternate and are connected by interconnecting portions 24. A handle 25 extending out through the front of the platen is provided. The knife edge portions 22,23 have downwardly directed knife edges which cooperate with alternative upwardly directed notches 26,27 in the lever arms. The arms and the knife-edge member 20 are of hardened steel.

With the knife-edge member 20 in one position the high leverage ones ofthe knife-edge portions 22 and notches 26 engage and with the member in its other angular position, shown via the dotted handle 25, the low leverage portions 23 and notches 27 engage.

With no load on the platen, the track member can be adjusted with it riding out of the engaged notch. It will be noted that sliding wear occurs only on the interconnecting portions and the top surface ofthe arms between the notches 26,27. Due to the close, but not friction inducing, fitting ofthe legs in the platen,the radial movement of the arms is restrained during adjustment.

According to the leverage selected, the displace mentofthefluid in the tube will be altered for unit load on the platen since, with the varying leverages, the unit load will generate altered pressures in the fluid displacer. Corresponding alternate graduations are provided on the scale.

The invention is not intended to be restricted to the details above described embodiments. For instace, where the manometertube is to be positioned at a height such that the liquid would not normally extend so high orso lowonaccountofthe pressuregenerated inthefluid displacer,thefluid in the displacer may be gaswhilstthe manometer is provided inthe form of a U-tube on one surface of which the pressurized gas acts. Such an arrangement is shown in Figure 6. Furtherthe liquid in the manometertube may be oil or alcohol for instance as opposed to water.

Claims (17)

1. Weighing apparatus comprising a manometer sighttube, a fluid displacer connected to the mano metersighttube in afluidtightmanner, a chassis supporting one side of the fluid displacer, at least one lever arm pivotally connected to the chassis and bearing at its free end on a piston ofthefluid displacer and at least one load application member pivotally connected to the or a respective lever arm.

2. Weighing apparatus as claimed in claim 1, wherein the arrangement is such thatthe force applied to the fluid displacer is considerably reduced by the leverage ofthe lever arm from the load applied by the or all of the load application members.

3. Weighing apparatus as claimed in any one of claims 1 or claim 2, wherein the chassis incorporates an upwards directed load platform and the or each load application member is downwardly directed.

4. Weighing apparatus as claimed in claim 3, wherein the or each lever arm is/are pivotally connected to the chassis outwardly of its load application member and bears at its opposite end on the under side ofthe piston for displacement thereof upwardly towards the chassis.

5. Weighing apparatus as claimed in any preceding claim, wherein the fluid displacer comprises a cylinder incorporated with the chassis in which the piston fluid tightly engages for displacement offluid.

6. Weighing apparatus as claimed in any one of claims 1 to 4, wherein the fluid displacer comprises a cylinder incorporated with the chassis and a flexible fluid-tight enclosure accommodated in the cylinder and acted on by the piston for displacement offluid.

7. Weighing apparatus as claimed in any one of claims 1 to 4, wherein thefluid displacer comprises a radially rigid fluid-tight enclosure supported at one axial end by the chassis and acted on at the other axial end by the piston.

8. Weighing apparatus as claimed in any preceding claim, wherein the leverage at which the or each lever arm is arranged is adjustable.

9. Weighing apparatus as claimed in claim 8, wherein the leverage of the or each lever arm is adjustable by adjustment of the point of action of its load application memberonthe leverarm longitudinally thereof.

10. Weighing apparatus as claimed in claim 8, wherein the leverage ofthe or each lever arm is adjustable by adjustment of the point of action of the chassis on the lever arm longitudinally thereof.

11. Weighing apparatus as claimed in claim 10, wherein the chassis adjustably carries a track member having alternative knife edge parts and the or each lever arm has alternative knife notches, the arrangement being such that in one position of the track member a respective one of its knife edge parts engages one ofthe knife notches to provide one lev erageforthe or each lever arm and in anotherposi- tion ofthetrack member a respective other knife edge part engages another notch for another leverage.

12. Weighing apparatus as claimed in any preceding claim, wherein a plurality of lever arms are provided arranged radially from the piston, pivotally con- nected to the chassis at outer points thereon and pivotally connected to the load application members at intermediate points.

13. Weighing apparatus as claimed in claim 12 as appendantto claim 11, wherein the track member is arranged circularly about the piston, with ones of its knife edge parts being disposed radially outwardly of others, the one and other knife edge parts being circumferentially alternated.

14. Weighing apparatus as claimed in any preceding claim, wherein the or each lever arm extends in a respective slot in the chassis extending from the piston and crossed at its outer end by a slot ortrack accommodating means for pivotal connection ofthe arm to the chassis.

15. Weighing apparatus as claimed in any preceding claim, wherein fluid provided in the displacer is a liquid and the manometertube extends upwardly from the level ofthefluid displacer.

16. Weighing apparatus as claimed in anyone of claims 1 to 14, wherein fluid provided in the fluid displacer is a gas and the manometertube incorporates a liquid containing U tube.

17. Weighing apparatus substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 4 and 5 (either possibly modified according to Figure 6) of the accompanying drawings.