Load cell and method of compensating the same

• US 4,630,491 A
• Filed: 04/09/1985
• Issued: 12/23/1986
• Est. Priority Date: 04/09/1984
• Status: Expired due to Term

• Current Assignee: Tokyo Electric Co., Ltd. (Toshiba Corporation)
• Original Assignee: Tokyo Electric Co., Ltd. (Toshiba Corporation)
• Inventors: Ushijima, Yasuhiro, Sakamoto, Koichiro, Kitagawa, Tohru
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/721,408
• Time in Patent Office: 623 Days
• Field of Search: 73/765, 73/766, 73/776, 73/862.63, 73/862.67, 219/121 LJ, 338/2-6, 338/9, 338/195, 338/308, 29/610 SG, 29/620
• US Class Current: 73/862.622
• CPC Class Codes: G01G 3/1412 the supports being parallelogram shaped
• CPC Class Codes: G01L 1/2243 the supports being parallelogram-shaped
• CPC Class Codes: G01L 1/2287 constructional details of the strain gauges adjustable resistors H01C10/00

Abstract

A load cell has strain gage resistors, lead portions for connecting them in a bridge and compensating portions for the compensation of the bridge balance, span or the like, which are laminated as metal thin films by means of the thin film technique. A protection film is formed over the metal thin films and trimmed by laser beams, and the protection film is made of a pigmented protection film made of synthetic resin for easy and accurate trimming.

Claims

1. A method of compensating a load cell which comprises the steps of:

laminating layers of thin metal films to form strain gage resistor portions, lead portions for bridge coupling of said resistor portions and compensating portions,

forming a pigmented protection film on said thin metal films, and

applying laser trimming to the thin metal films from above the protection film, whereby energy absorbtion is enhanced in said laser trimming step.

2. A laser trimmable load cell comprising:

a colorless and transparent insulation film formed on a beam having thin-walled strain causing portions,

at least four strain gage resistor portions, and

lead portions for bridge coupling of said resistor portions and compensating portions made of thin metal films laminated on said insulation film,

wherein said thin metal films are covered with a protection film made of a synthetic resin having a pigment incorporated therein, whereby laser energy absorbtion is enhanced.

3. The load cell as defined in claim 2, wherein said pigment is one of the group consisting of black, red, yellow and a mixture thereof.

4. The load cell as defined in claim 2, wherein said pigment is one from the group consisting of carbon and ferrite, and wherein said synthetic resin is polyimide.