US 4,245,711 AGranted

Weighing apparatus including a tapped electromagnetic load compensation coil

AssigneeMettler Instrument AG

InventorPeter Kunz

Life of this patent

Estimating the term…

Loading patent…

Abstract

Weighing apparatus of the electromagnetic load compensation type is disclosed, including a load support connected for movement relative to a frame, a mechanical-transmission ratio-establishing lever connecting the load support with a compensation coil arranged for displacement relative to a permanent magnet arrangement connected with the frame, a position-responsive circuit for supplying compensation current to the coil for creating an electromagnetic force that reacts with the permanent magnet field to maintain the load support in its initial no-load condition, and indicating means for displaying the magnitude of the applied load as a function of the compensation current. To permit the use of the lever in different lever-ratio-establishing environments without the use of attendant balancing weights, the compensation coil is tapped to define a pair of coil portions (28a, 28b) that are alternately energized by a switching device (42) to apply different forces upon the load support.

Claims9

Dependent claims

In a weighing apparatus of the electromagnetic load compensation type including a frame (14);

load support means (10, 12) connected for movement relative to the frame;
lever means (18) pivotally connected with said frame, a first portion of said lever means being connected with said load support means;
load compensation means including a compensation coil (28) connected with another portion of said lever means, and permanent magnet means connected with the frame adjacent said compensation coil;
position-responsive means operable upon the application of load to the load support for supplying compensation current to the compensation coil to maintain the load support means in its initial no-load position;
and indicating means for displaying the magnitude of the applied load as a function of the compensation current supplied to the compensation coil;
the improvement wherein
(a) said coil includes intermediate its ends a tap for defining first and second coil portions (28a, 28b);
(b) and further wherein said compensation current supply means includes switch means (42) for supplying the compensating current alternately to said coil portions.

5 more elements

Dependencies are inferred from the claim text.