GB2160986A

GB2160986A - Electronic steelyard

Info

Publication number: GB2160986A
Application number: GB08513402A
Authority: GB
Inventors: Donald Frank Taylor
Original assignee: Hong Kong Productivity Council
Current assignee: Hong Kong Productivity Council
Priority date: 1984-06-25
Filing date: 1985-05-28
Publication date: 1986-01-02
Also published as: GB8513402D0; GB8416167D0; HK67790A; GB2160986B

Abstract

The invention relates to steelyard weighing devices, particularly to those for use in retail outlets. A steelyard according to the invention uses a beam 2 at either end of which the item to be weighed 12 and a balance weight 20 are respectively attached. A strain gauge 16 is mounted on the beam to monitor the weight of the item. The strain gauge is coupled to an electronic device having a calculator and a display system for presenting the measured weight in chosen units and the price. <IMAGE>

Description

SPECIFICATION Improvements in weighing This invention relates to weighing and in particular to an improved steelyard for weighing objects.

A steelyard is a balanced beam weighing device which comprises a beam with a fulcrum placed between the load being weighed and the balancing weights which are adjusted both in amount and displacement from the fulcrum in order to determine weight. Hand held steelyards are very popular in the Asian environment and in Chinese societies are called Ching.

While part of the popularity of the steelyard is derived from its cheapness it is undoubtedly also very popular with the user in the open market place environment because of its portability, its ease of storage, and the fact that it does not need a fixed location for operation.

However use of the steelyard is not easy for the consumer to audit and the consumer may easily be cheated by the vendor both in terms of price calculation and weight estimation. It is therefore an object of this invention to provide a weighing device analogous to a steelyard where these problems can be largely avoided.

In a steelyard according to the invention items are weighed by measuring the deflection of the substantially balanced beam, as against the balance weight itself. To this end a strain gauge is mounted on the beam, and is coupled to an electronic device which measures the bending moment in the beam. From this measurement, the device calculates an indication of the weight carried by the weighing pan, and displays the indication. It will be appreciated that by suitable programming of the device, the steelyard can be adapted to indicate weight in any chosen unit, and by varying the balance weight, in various ranges of weights. Compared to the beam in known steelyards, that used in the present convention may be relatively flexible, and plastics materials can be used in their construction.

Thus, whilst the electronic steelyard is similar in appearance to a balanced beam steelyard, it operates according to a different principle and does not require the user to make any calculations which could be wrong or misleading. Also to the customer the operation appears to be rather conventional since the user has to set the balance weight to give an approximate balance, although this does not always have to be an exact balance as with a traditional steelyard.

An example of an electronic steelyard is shown in the accompanying diagram.

The steelyard illustrated comprises a beam 2 supported on a fulcrum 4 at a central fixed location on the beam which is itself suspended by a chain 6 from an housing 8 containing an electronic device described below. A carrying handle 10 is attached to the housing 8. The beam carries at the left hand end as shown a weighing pan 1 2 suspended from a knife edge 14, normally in a groove in the beam, to permit pivotal movement thereof. A strain gauge 1 6 is mounted on the beam between the knife edge 1 4 and the fulcrum 4 for monitoring flexure of the beam 2.The strain gauge is connected to the electronic device by a wire 1 8. It will though, be appreciated that the precise location of the strain gauge 1 6 may be varied, with the electronic device requiring programming for a particular location. To the right of the fulcrum 4 as shown, the beam 2 carries a balance weight 20 also suspended from a knife edge 22. The knife edge 22 is movable along an uniform upper surface of the beam 2 to balance the beam when an item is being weighed.

The electronic device in the housing 8 comprises a calculator coupled to a display device 24 and to an input keyboard 26. The wire 1 8 is connected to the calculator and a suitable power supply, such as a mains connection or battery, is provided. The keyboard enables the calculator to be adjusted to a zero setting, and the desired unit of weight to be selected. The calculator can of course be programmed for one of a variety of units of weights and if needed, to one of a number of ranges of weights to be accommodated. Thus, the balance weight 20 may be changed as can the beam itself if desired, with the consequence only that some reprogramming of the calculator is needed. A replacement beam 2 will normally have its own strain gauge 1 6 already attached, which will require connection to the calculator in place of its predecessor.

The strain gauge, beam and calculator are all capable of standardised production, while scale pans and weights can be fitted according to the physical bulk and weight of typical items being weighed. A vendor can therefore easily attach a variety of weights and scale pans to a standard beam and calculate dependent on choice of items to be weighed.

The use of strain gauges together with flexible beams as part of a weighing device is well known in electronic scales and the like used in shops. Therefore the construction of suitable beams, the incorporation of strain gauges and the convertion of the electrical output from the strain gauge electronically to a displayed weight are all well known and not believed to need further explanation. Also the display of the output by means of a light emitting diode display or liquid crystal display is also a well known technique not believed to need further explanation.

When an electronic steelyard according to the invention is used the weight is first zeroed by setting the beam horizontally with an empty scale pan and setting a zero input on the attached calculator. The object to be weighed is then placed in the scale pan, the weight is moved along the beam away from the fulcrum until an approximate horizontal balance is obtained. The unit of weight be it pound, catty or kilogram can then be entered in the calculator and the price per unit is also entered, dollars per catty etc. The calculation based on the elastic bending moment measurement and the entered data then calculates and displays the weight and the price.

Amongst the advantages of the invention are the following: (1) It allows weighing operations to be carried out without physical modification in a variety of weight units. Thus the unit of weight, pound, catty, kilogram can be chosen by the customer. This feature is very important in a society undertaking a process of voluntary metrication.

(2) It allows indisputable weight and price information to be displayed to the customer.

(3) It allows electronic averaging of the bending moment over finite periods of time to be undertaken to allow a degree of accuracy to be introduced into weighing which is not normally obtainable in hand held steelyards.

(4) It requires less skill in use than the hand held steelyard.

(5) Its electronic image is appealing to progressive societies in Asia that still enjoy traditional shopping practices, although equally the traditional appearance and usage of the item can give confidence to customers.

Claims

1. A steelyard comprising a beam supported on a fulcrum between the bearing points for a weighing pan and for balance weight wherein a strain gauge is mounted on the beam for monitoring deflections of the beam, the strain gauge being coupled to an electronic device for measuring the bending moment in the beam and for calculating therefrom an indication of the weight carried by the weighing pan, the device including means for displaying such indication.

2. A steelyard according to Claim 1 wherein the strain gauge is mounted on the beam between the fulcrum and the bearing point for the weighing pan.

3. A steelyard according to Claim 1 or Claim 2 wherein the electronic device is mounted in an housing to which a carrying handle is attached.

4. A steelyard according to any preceding Claim wherein the bearing point for the weighing pan is fixed, and the bearing point for the balance weight is movable.

5. A steelyard according to any preceding Claim wherein the electronic device can be selectively programmed to display weight in one of a range of measurement units.

6. A steelyard according to any preceding Claim wherein the electronic device can be selectively programmed for use with different balance weights.

7. A steelyard according to any preceding Claim wherein the electronic device can be selectively programmed for use with different beam and weight combinations.

8. A steelyard substantially as described herein with reference to the accompanying drawing.