Sealed load cell construction

• US 4,383,584 A
• Filed: 06/26/1981
• Issued: 05/17/1983
• Est. Priority Date: 02/15/1980
• Status: Expired due to Term

• Current Assignee: International Road Dynamics Incorporated (Quarterhill Inc. (f/k/a Wi-LAN Inc.))
• Original Assignee: International Road Dynamics Incorporated (Quarterhill Inc. (f/k/a Wi-LAN Inc.))
• Inventors: Dyck, George J.
• Primary Examiner(s): Miller, Jr., George H.
• Application Number:
  US06/277,704
• Time in Patent Office: 690 Days
• Field of Search: 177/208, 177/254
• US Class Current: 177/208
• CPC Class Codes: G01G 5/003 load-cell construction or mountings
• CPC Class Codes: G01G 5/04 with means for measuring the pressure imposed by the load on a liquid pressure gauges per se G01L

Abstract

A load measuring device is provided herein which operates with a small amount of vertical travel. The load measuring device includes a base with a thin sealed fixed volume reservoir having a non-compressible fluid (e.g. oil) or soft rubber therein forming the lower portion of the base. A flexible diaphragm is provided which seals such thin reservoir and is in direct contact with the non-compressible fluid or the soft rubber in the reservoir. A platform is provided for applying a load directly to the diaphragm. Finally, a transducer including an integral diaphragm is held in direct contact with the flexible diaphragm to provide a reading which is proportional to the absolute value of the load. The invention thus provides a sealed, shockproof, hydraulic load cell whose manufacture is greatly simplified and whose cost is reduced both in terms of time and material. Moreover, its installation in a weigh scale is much simplified since there is no hydraulic connection needed between the load cell and the transducer.

Claims

1. A load measuring device operating with a small amount of vertical travel comprising:

(a) a base;

(b) a thin sealed, fixed volume reservoir forming the lower portion of said base;

(c) a load-transmitting material in the form of a non-compressible fluid or a soft rubber in said thin reservoir;

(d) a flexible diaphragm sealing said thin reservoir and being in direct contact with said load-transmitting material in said reservoir;

(e) means for applying a load directly to said diaphragm; and

(f) a transducer including an integral diaphragm at the base thereof held with such integral diaphragm in direct contact with said flexible diaphragm to provide a reading proportional to the value of said load.

2. The load measuring device of claim 1 wherein said load-transmitting material is in the form of a non-compressible fluid which comprises a hydraulic fluid or a liquid silicone.

3. The load measuring device of claim 1 wherein said load-transmitting material comprises a soft rubber disc the flat surfaces of which are coated with graphite.

4. The load measuring device of claim 1 including means connected to said transducer to convert said value of said load to weight.

5. A load measuring device operating with a small amount of vertical travel comprising:

(a) a base including a cylindrical chamber near the bottom thereof;

(b) a thin sealed, fixed volume reservoir for a load transmitting material in the form of a non-compressible fluid forming the lower portion of said base;

(c) a flexible diaphragm sealing said thin reservoir and being in direct contact with said non-compressible fluid in said reservoir;

(d) means for applying a load directly to said diaphragm; and

(e) a transducer including an integral diaphragm at the base thereof held with such integral diaphragm in direct contact with said flexible diaphragm to provide a reading proportional to the value of said load.

6. The load measuring device of claim 5 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

7. The load measuring device of claim 5 including means connected to said transducer to convert said value of said load to weight.

8. The load measuring device of claim 5 wherein said base comprises:

(i) a base member including a thin central recess therein defining an oil chamber, and a sealed, fixed volume annular shelf therearound;

(ii) a flexible diaphragm secured to said annular shelf; and

(iii) a ring, secured to said annular shelf and defining said cylindrical chamber.

9. The load measuring device of claim 8 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

10. The load measuring device of claim 8 including means connected to said transducer to convert said value of said load to weight.

11. The load measuring device of claim 5 wherein said base comprises:

(i) a base member including a deep recess therein surrounded by an annular shelf, thereby defining said cylindrical chamber; and

(ii) a hollow disc-shaped sac formed of flexible material filled with a load-transmitting material in the form of a non-compressible fluid, disposed at the bottom of said cylindrical chamber, thereby defining in one unitary element said sealed, fixed volume thin reservoir and said flexible diaphragm.

12. The load measuring device of claim 11 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

13. The load measuring device of claim 11 including means connected to said transducer to convert said value of said load to weight.

14. A load measuring device operating with a small amount of vertical travel comprising:

(a) a base including a cylindrical chamber near the bottom thereof;

(b) a flexible diaphragm disposed in fixed position a small distance from the bottom of said cylindrical chamber to define, therebetween, a thin sealed, fixed volume reservoir for a load-transmitting material in the form of a non-compressible fluid;

(c) a piston slidable within said cylindrical chamber and resting in face-to-face contact with said flexible diaphragm to apply a load directly to said flexible diaphragm; and

(d) a transducer including an integral diaphragm at the base thereof held with such integral diaphragm in direct contact with said flexible diaphragm to provide a reading proportional to the value of said load.

15. The load measuring device of claim 14 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

16. The load measuring device of claim 14 including means connected to said transducer to convert said value of said load to weight.

17. The load measuring device of claim 14 wherein said piston is provided with a central recess and a concentric aperture and wherein said transducer includes a portion resting in said central recess and an integral diaphragm portion extending through said concentric aperture in direct face-to-face contact with said flexible diaphragm.

18. The load measuring device of claim 17 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

19. The load measuring device of claim 17 including means connected to said transducer to convert said value of said load to weight.

20. The load measuring device of claim 17 wherein said transducer includes an upper portion through which said load is transmitted to said flexible diaphragm via said piston.

21. The load measuring device of claim 20 wherein said thin reservoir contains a film of hydraulic fluid as thin as about 0.005 inches in depth.

22. The load measuring device of claim 20 including means connected to said transducer to convert said value of said load to weight.

23. A weigh scale comprising:

(a) a fixed peripheral frame base structure;

(b) a central load supporting platform;

(c) means for interconnecting said platform with said peripheral frame base structure to allow limited vertical motion of the platform, the interconnecting means comprising at least three torque transmitting tubular bars arranged around the perimeter of said load supporting platform, with one portion of each of said torque bars being supported with respect to said fixed peripheral frame base structure, and another portion of each said torque bars being supported with respect to said central load supporting platform; and

(d) a load measuring device centrally supporting said load supporting platform, said load measuring device comprising a base, a thin sealed, fixed volume reservoir for a load-transmitting material in the form of a non-compressible fluid or a soft rubber forming the lower portion of said base, a flexible diaphragm sealing said thin reservoir and being in direct contact with said load-transmitting material in said reservoir, means for applying a load directly to said flexible diaphragm, and a transducer including an integral diaphragm at the base thereof held with such integral diaphragm in direct contact with said flexible diaphragm to provide a reading proportional to the value of said load, and including means connected to said transducer to convert said value of said load to weight.

24. A weigh scale comprising:

(a) a fixed peripheral frame base structure;

(b) a central load supporting platform;

(c) means for interconnecting said platform with said peripheral frame base structure to allow limited vertical motion of the platform, the interconnecting means comprising at least three torque transmitting tubular bars arranged around the perimeter of said load supporting platform, with one portion of each of said torque bars being supported with respect to said fixed peripheral frame base structure, and another portion of each of said torque bars being supported with respect to said central load supporting platform; and

(d) a load measuring device centrally supporting said load supporting platform, said load measuring device comprising a base including a cylindrical chamber near the bottom thereof, a flexible diaphragm disposed in fixed position a small distance from the bottom of said cylindrical chamber to define, therebetween, a thin sealed, fixed volume reservoir for a load-transmitting material in the form of a non-compressible fluid or a soft rubber, a piston slidable within said cylindrical chamber and resting in face-to-face contact with said flexible diaphragm to apply a load directly to said flexible diaphragm, and a transducer including an integral diaphragm at the base thereof held with such integral diaphragm in direct contact with said flexible diaphragm to provide a reading proportional to the value of said load and including means connected to said transducer to convert said value of said load to weight.