High Capacity and High Resolution Scale

• US 20090090564A1
• Filed: 08/08/2008
• Published: 04/09/2009
• Est. Priority Date: 10/05/2007
• Status: Active Grant

• Current Assignee: Quadient Technologies France
• Original Assignee: Neopost Technologies S.A. (Quadient SA)
• Inventors: Kresina, Roman
• Granted Patent: US 7,989,714 B2
• Time in Patent Office: Days
• US Class Current: 177/25.13
• CPC Class Codes: G01G 1/243 having pans carried above the beam
• CPC Class Codes: G01G 19/002 for postal parcels and letters
• CPC Class Codes: G01G 19/021 having electrical weight-sensitive devices G01G19/04 - G01G19/07 take precedence
• CPC Class Codes: G01G 19/4146 for controlling caloric intake, e.g. diet control
• CPC Class Codes: G01G 23/005 Means for preventing overload
• CPC Class Codes: G01G 23/02 Relieving mechanisms; Arrestment mechanisms
• CPC Class Codes: G01G 3/1404 combined with means to connect the strain gauges on electrical bridges
• CPC Class Codes: G01G 7/04 with means for regulating the current to solenoids

Abstract

A scale can include a low capacity sensing mechanism operatively coupled to a load, wherein the low capacity sensing mechanism may detect movement of the load. A transfer mechanism can be operatively coupled to the low capacity sensing mechanism, wherein the low capacity sensing mechanism may enable the scale to weigh both relatively heavy loads and relatively light loads to a minor division resolution associated with the low capacity sensing mechanism.

Claims

1. A scale, comprising:

a support;

a sensor coupled to the support and productive of a sensor signal based upon an effect of a load upon the support, the sensor having a sensitivity range;

a force transmitter having a driving end and a counterforce end;

a force inducing mechanism coupled to the driving end of the force transmitter; and

a controller coupled to the sensor and the force inducing mechanism, wherein the controller produces a drive signal in response to the load having a weight outside the sensitivity range of the sensor;

wherein the force inducing mechanism is responsive to the drive signal to exert a force on the driving end of the force transmitter and reduce the effect of the load; and

wherein the controller computes the weight of the load based upon the drive signal and the sensor signal.

2. The scale of claim 1, wherein the effect of the load upon the sensor is reduced when the sensor is operating within the sensitivity range.

3. The scale of claim 1, wherein the drive signal is based upon the sensor signal.

4. The scale of claim 3, wherein the force inducing mechanism comprises:

a plunger coupled to the driving end of the force transmitter at a pivot; and

an electromagnetic actuator coupled to the plunger, wherein a voltage applied to the electromagnetic actuator is controlled by the controller.

5. The scale of claim 4, further comprising a power amplifier to amplify the drive signal from the controller to the electromagnetic actuator.

6. The scale of claim 1, wherein the controller comprises:

a pre-amplifier that amplifies the sensor signal;

an analog to digital converter that converts the amplified sensor signal into a digital feedback signal;

a processor that calculates and generates a digital drive signal based at least partly upon the digital feedback signal; and

a digital to analog converter that converts the digital drive signal into an analog drive signal.

7. The scale of claim 6, wherein the processor computes the weight of the load based upon the digital drive signal.

8. The scale of claim 1, wherein the sensor comprises a strain gauge load cell.

9. The scale of claim 1, wherein the sensor comprises a linear variable differential transformer.

10. The scale of claim 1, wherein the sensor comprises an optical sensor.

11. The scale of claim 1, further comprising a stop coupled to the support to limit displacement thereof.

12. The scale of claim 11, wherein the stop is positioned proximate the counterforce end of the force transmitter.

13. A scale, comprising:

a support;

a load cell coupled to the support, the load cell comprising a strain gauge mounted on a substrate that flexes in response to a change in a weight upon the support, the strain gauge producing a strain signal that changes in response to the change in weight within a load cell weight range;

a lever having a driving end and a counterforce end and fixed to a pivot therebetween;

an electromechanical force inducing mechanism coupled to the driving end of the lever;

a controller coupled to the sensor and the electromagnetic force inducing mechanism, wherein the controller drives current to the electromechanical force inducing mechanism such that the counterforce end of the lever exerts sufficient counterforce on the support to maintain flexion of the substrate such that the load cell operates within the load cell weight range in response to changes in the weight on the support; and

a processor that computes the weight of an object on the support based upon a signal from the controller, the signal from the controller based upon an amount of current driven to the electromechanical force inducing mechanism and the strain signal from the load cell.

14. A method for measuring a weight of an object, comprising:

receiving a signal from a load cell;

in response to the received signal indicating that the weight of the object upon the load cell exceeds a weight range of the load cell, driving current to an electromechanical force inducing mechanism;

in response to the driven current, generating a counterforce sufficient to cause the apparent weigh of the object as measured by the load cell to be within the weight range of the load cell; and

calculating the weight of the object based upon an amount of the driven current and the signal received from the load cell operating within the weight range.