Flat electronic scales

Details Flat electronic scales Flat electronic scales

1998-11-13

2001-04-03

Gibson, Randy W. (Department: 2859)

Weighing scales

Means holding load-driven element against motion

C177S211000, C177S229000, C073S862634

Reexamination Certificate

active

06211472

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to electronic scales. More specifically, this invention relates to portable, battery-operated scales which have a flat construction without significantly reducing the stability of the scale.
BACKGROUND OF THE INVENTION
Weighing instruments measure the mass of an object by measuring its weight. In a strain-gauge balance, the electrical properties of materials change when the material is stressed by either compression or extension as a result of a change in length, cross-section, and specific resistance. Strain-gauges are usually positioned at four different points in a double bending beam. Because a double bending beam incorporates parallel guides, it counters the effects of torque resulting from off-center loading. A value for a weight and therefore a mass is derived from the voltage generated when the four strain-gauges form part of a Wheatstone bridge.
The idea of strain-gauges, that is, measuring the stress, caused by the weight of an object on the structure supporting the object, is also used in several scale designs capable of handling varying weights. Larger loads, for example, may be measured by testing the deformation and stress on a solid cylindrical “spring body.” This type of scale can handle loads in excess of a ton.
Weighing scales, weighing instruments or balances of this kind are known from, for example, German Patent Application DE 44 27 088 A1 (U.S. Pat. No. 5,719,357) or, with the exception of the integral construction for the load receptor, guides and system carrier, also from German Patent DE 20 09 858 C1 (U.S. Pat. No. 3,667,560).
It is a disadvantage of the known constructions that the weighing system or scale requires relatively large space.
OBJECTS OF THE INVENTION
It is therefore one object of the invention to develop a balance that is portable and battery-operated. In particular, the flattest possible mode of construction is desired without significantly reducing the stability of the balance.
SUMMARY OF THE INVENTION
The invention relates to a top-loading balance with a housing, a weighing pan, and a load receptor. According to one formulation of the invention, the load receptor is connected with a system carrier by a parallel guidance consisting of an upper guide and a lower guide. The system carrier is fixed relative to the housing. One of the guides is divided into two part-guides which, seen in plan view, are disposed preferably on either side of the undivided guide so that the guides do not overlap. In addition, the load receptor, the guides and the system carrier preferably form an integral component. The top-loading balance also includes strain gauges on at least one of the guides to generate a load-dependent electrical signal.
According to one aspect of the invention, the integral component has two cavities for batteries and the system carrier extends between the two battery cavities. Furthermore, the load receptor is constructed to be approximately U-shaped and the two limbs of the U are disposed laterally near the battery cavities. In addition, the strain gauges are arranged only on the inner side of the undivided guide.
A space-saving arrangement results from this design of the integral component. The system carrier is disposed substantially between the batteries, and parts of the load receptor are arranged around the batteries. Due to the arrangement of the strain gauges on the inner side of the one guide, the physical height of the entire balance hardly needs to be higher than the vertical spacing of the upper and lower guide. Since there is no need to provide the strain gauges, including their wires, on the outer side of the one guide, strain gauges on the outer side are superfluous.


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