Weight sensor

• US 20040112149A1
• Filed: 06/12/2003
• Published: 06/17/2004
• Est. Priority Date: 12/14/2000
• Status: Active Grant

• Current Assignee: Hi-Shear Technology Corporation (Chemring Group PLC)
• Original Assignee: Hi-Shear Technology Corporation (Chemring Group PLC)
• Inventors: Gebert, Rudiger Heinz
• Granted Patent: US 7,153,383 B2
• Time in Patent Office: Days
• US Class Current: 73/862.626
• CPC Class Codes: G01G 19/024 using electrical weight-sensitive devices
• CPC Class Codes: G01G 7/06 by electrostatic action
• CPC Class Codes: Y10T 156/1062 Prior to assembly
• CPC Class Codes: Y10T 156/1309 and securing separate part over hole or aperture
• CPC Class Codes: Y10T 156/1322 Severing before bonding or assembling of parts
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

The invention provides a weight sensor (10) which includes a first electrically conductive sheet (12) electrically isolated from a second electrically conductive sheet (14) by inserts of a closed cell foamed polymeric dielectric (16) and an elastic dielectric (18) in spaces (20) formed between the inserts (16) located between the sheets (12, 14). The sensor (10) also includes capacitive measuring means (24), electrically connected between the first sheet (12) and the second sheet (14), which measures a change of capacitance between the sheets (12, 14) when a vehicle passes over the sheets (12, 14). The sensor (10) further includes converting means (26) for converting the change of capacitance to a number related to a weight of the vehicle.

Claims

1. A method of manufacturing a weight sensor which includes the following steps:

electrically isolating a first electrically conductive sheet from a second electrically conductive sheet by inserting inserts of a foamed polymeric dielectric between the sheets;

placing an elastic dielectric into spaces formed between the inserts of the foamed polymeric dielectric to bond with the sheets; and

leaving the inserts of the foamed polymeric dielectric to remain between the sheets.

2. A method as claimed in claim 1, which includes repeating the prior steps of the method for sandwiching of inserts of a foamed polymeric dielectric and an elastic dielectric between the second sheet and a third electrically conductive sheet such that the second sheet is electrically isolated from the first and third sheets.

3. A method as claimed in either one of claims 1 or 2, wherein the elastic dielectric are chosen from those which elastically recover from compression very quickly and are capacitively insensitive to temperature changes in a range encountered on road surfaces.

4. A method as claimed in any one of claims 1 to 3, wherein the elastic dielectric is chosen from those which are water resistant and form a strong bond with the sheets.

5. A method as claimed in any one of claims 1 to 4, wherein placing of the elastic dielectric into spaces formed between the inserts includes injecting the elastic dielectric into the spaces.

6. A method as claimed in any one of claims 1 to 5, wherein the foamed polymeric dielectric is a dosed cell foamed polymeric dielectric.

7. A method as claimed in claim 6, wherein the dosed cell foamed polymeric dielectric is selected for good dielectric properties.

8. A method as claimed in any one of claims 1 to 7, wherein the inserts are of shapes that leave discrete areas to be occupied by the elastic dielectric.

9. A method as claimed in claim 8, wherein passages are left for the elastic dielectric to be injected into after the inserts are sandwiched between the sheets.

10. A method as claimed in any one of claims 1 to 9, wherein the surfaces of the sheets in the spaces between the inserts are primed for good bonding with the elastic dielectric.

11. A method as claimed in any one of claims 1 to 10, which includes electrically connecting capacitive measuring means between the first sheet and the second sheet, which capacitive measuring means is configured to measure a change of capacitance between the sheets when a vehicle passes over the sheets.

12. A method as claimed in any one of claims 2 to 11, which includes electrically connecting a capacitive measuring means between the second sheet and the third sheet, which capacitive measuring means is configured to measure a change of capacitance between the sheets when a vehicle passes over the sheets.

13. A method as claimed in either one of claims 11 or 12, which includes electrically connecting a converting means to the capacitive measuring means, which converting means, in use, converts a change of capacitance measured by the capacitive measuring means to a number related to a weight of the vehicle.

14. A method as claimed in any on of claims 1 to 13, which includes sealing the borders of the product of the method produced thus far to make it impervious of entry of water.

41. A product produced by a method as claimed in any one of claims 1 to 18.

15. A method of manufacturing a weight sensor which includes the following steps:

pre-cutting a first full layer of a foamed polymeric dielectric to a desired pattern to define inserts and removable spacers;

priming a first surface of a first electrically conductive sheet for bonding;

placing the first full layer over the first sheet immediately after the first sheet has been primed thereby protecting the first primed surface of the first sheet;

removing the spacers;

leaving the inserts of the first full layer in place;

priming a second electrically conductive sheet for bonding;

immediately sandwiching the inserts of the first full layer between the first and second sheets; and

adding an elastic dielectric into the spaces formed by the removal of the spacers so as to bond to the sheets.

16. A method as claimed in claim 15, which includes repeating the prior steps of the method for sandwiching of inserts of a foamed polymeric dielectric and an elastic dielectric between the second sheet and a third electrically conductive sheet such that the second sheet is electrically isolated from the first and third sheets.

17. A method of manufacturing a weight sensor which includes the following steps:

coating a first and a second side of a first full layer of a foamed polymeric dielectric with a contact adhesive or the like;

placing a first and a second protective non-stick foil against the contact adhesive coating the first and the second side respectively;

pre-cutting the first full layer and the foils to a desired pattern to define inserts and removable spacers;

removing the foil from the first side of the first full layer, only in the zones which cover the inserts;

priming a first surface of a first electrically conductive sheet and a first surface of a second electrically conductive sheet for bonding;

immediately placing the first full layer having foils attached thereto onto the first surface of the first sheet such that the first side of the first full layer is in contact with the first surface of the first sheet and such that the inserts stick to the first surface, but the spacers do not stick due to the presence there of the foil;

immediately removing the foil from a second side of the first full layer;

immediately removing the spacers, which include foil adhered to the first side thereof, from the first full layer;

immediately sandwiching the inserts between the sheets; and

adding an elastic dielectric into spaces formed by the removal of the spacers so as to bond to the sheets.

18. A method as claimed in claim 17, which includes repeating the prior steps of the method for sandwiching of inserts of a second full layer of a closed cell foamed polymeric dielectric and an elastic dielectric between the second sheet and a third electrically conductive sheet such that the second sheet is electrically isolated from the first and third sheets.

19. A weight sensor which includes a first electrically conductive sheet electrically isolated from a second electrically conductive sheet by inserts of a foamed polymeric dielectric and an elastic dielectric in spaces formed between the inserts located between the sheets.

20. A weight sensor as claimed in claim 19, which includes a third electrically conductive sheet electrically isolated from the second sheet by inserts of a closed cell foamed polymeric dielectric and an elastic dielectric in spaces formed between the inserts located between the second and third sheets.

21. A weight sensor as claimed in either one of claims 19 or 20, wherein the elastic dielectric is chosen from those which elastically recover from compression very quickly and are capacitively insensitive to temperature changes in a range encountered on road surfaces.

22. A weight sensor as claimed in any one of claims 19 to 21, wherein the elastic dielectric is chosen from those which are water resistant and form a strong bond with the sheets.

23. A weight sensor as claimed in any one of claims 19 to 22, wherein the foamed polymeric dielectric is a dosed cell foamed polymeric dielectric.

24. A weight sensor as claimed in claim 23, wherein the dosed cell foamed polymeric dielectric is selected for good dielectric properties.

25. A weight sensor as claimed in any one of claims 19 to 24, wherein the inserts are linear strips.

26. A weight sensor as claimed in any one of claims 19 to 24, wherein the inserts are of shapes that leave discrete areas to be occupied by the elastic dielectric.

27. A weight sensor as claimed in claim 26, wherein passages are left for the elastic dielectric to be injected into after the inserts are sandwiched between the sheets.

28. A weight sensor as claimed in any one of claims 19 to 27, wherein the electrically conductive sheets are metallic sheets of good conductivity and sufficient strength to ensure a long operational life of the weight sensor.

29. A weight sensor as claimed in any one of claims 19 to 27, wherein each sheet includes an electrically conductive film covering a plate mad from a material which ensures a long operational life of the weight sensor.

30. A weight sensor as claimed in any one of claims 19 to 29, wherein the inserts between each sheet are Integrally connected to each other to form a full layer of the foamed polymeric dielectric between each sheet.

31. A weight sensor as claimed in any one of claims 19 to 30, which includes capacitive measuring means, electrically connected between the first sheet and the second sheet, which capacitive measuring means is configured to measure a change of capacitance between the sheets when a vehicle passes over the sheets.

32. A weight sensor as claimed in any one of claims 20 to 31, which includes capacitive measuring means, electrically connected between the second sheet and the third sheet which capacitive measuring means is configured to measure a change of capacitance between the sheets when a vehicle passes over the sheets.

33. A weight sensor as claimed in either one of claims 31 or 32, which includes converting means for converting the change of capacitance to a number related to a weight of the vehicle.

34. A weight sensor as claimed in any one of claims 19 to 33, wherein borders of the sensor are sealed to make it impervious of entry of water.

35. A weight sensor which includes

a top electrically conductive sheet electrically isolated from a lower electrically conductive sheet by an elastic dielectric, the elastic dielectric being configured between the sheets to allow lateral expansion of the elastic dielectric when a downward force is applied to the weight sensor causing the sheets to compress;

and

a border part of the sensor, which border part extends from a border region of a part of the sensor located on the ground, in use, to a border region of the top sheet, wherein the border part is connected to an upper surface of the top sheet so that the top sheet does not rest on the border part.

36. A weight sensor as claimed in claim 35, wherein the border part is shaped and dimensioned to form a ramp for vehicles to drive on and off the sensor, in use.

37. A weight sensor as claimed in either one of claims 35 or 36, which includes a still lower electrically conductive sheet electrically isolated from the lower sheet by an elastic dielectric, the elastic dielectric being configured between the sheets to allow lateral expansion of the elastic dielectric when a downward force is applied to the weight sensor causing the sheets to compress, wherein the part of the sensor located on the ground, in use, is a border region of the still lower sheet.

38. A weight sensor as claimed in any one of claims 35 to 37, wherein the elastic dielectric is configured between the sheets to allow lateral expansion of the elastic dielectric by way of the elastic dielectric being in the form of a plurality of linear strips separated by air gaps.

39. A weight sensor as claimed in any one of claims 35 to 38, wherein the elastic dielectric is configured between the sheets to allow lateral expansion of the elastic dielectric by way of the elastic dielectric being placed in spaces formed between inserts of a foamed polymeric dielectric located between the sheets.

40. A weight sensor as claimed in any on of claims 35 to 39, which includes two like border parts connected to apposing border regions of the top sheet.

42. A method, a weight sensor, or a product according to the invention, as hereinbefore generally described.

43. A method, a weight sensor, or a product as specifically described with reference to or as illustrated in the accompanying drawings.