Methods and apparatus employing apparent resonant properties of thin conducting materials

• US 4,678,994 A
• Filed: 06/27/1984
• Issued: 07/07/1987
• Est. Priority Date: 06/27/1984
• Status: Expired due to Term

• Current Assignee: Digital Products Corp.
• Original Assignee: Digital Products Corp.
• Inventors: Davies, Ronald C.
• Primary Examiner(s): Eizensopf, Reinhard I.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US06/625,081
• Time in Patent Office: 1,105 Days
• Field of Search: 324/207, 324/208, 324/233, 324/234, 324/235, 324/236, 324/326, 324/327, 324/225-228, 194/100 A, 194/317-319, 331/64, 331/65, 331/67, 331/117 R, 336/84 C, 336/200, 336/232
• US Class Current: 324/236
• CPC Class Codes: G01V 3/102 by measuring amplitude
• CPC Class Codes: G07D 5/08 Testing the magnetic or electric properties

Abstract

Methods and apparatus for sensing, switching and modulating relying upon apparent resonant properties of thin conductive materials are provided in accordance with the teachings of the present invention. According to the present invention, an output of an oscillating circuit is selectively varied as a function of the relationship between a coil within the oscillating circuit, a thin conductive member and the apparent resonant condition of the thin conductive member to achieve appropriate sensing, switching and modulating conditions.

Claims

1. Apparatus for detecting electrically conductive material comprising:

a thin layer of conductive material capable of exhibiting spontaneous resonance wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit, said thin layer of conductive material defining a first surface and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency; and

oscillator means having a resonant tank circuit including capacitor means and coil means, said coil means having a plurality of turns defining a second surface substantially parallel to said first surface, said oscillator means having a frequency in relation to the thickness of said thin layer causing a marked reduction in the amplitude of oscillations of said oscillator means when said thin layer of conductive material is placed proximate to said coil in the absence of other conductive material.

2. The apparatus according to claim 1 wherein said plurality of turns of said coil means is formed as a single layer.

3. The apparatus according to claim 1 wherein said oscillator means takes the form of a Colpitts oscillator.

4. The apparatus according to claim 1 wherein said electrically conductive material detected is translated along a fixed path, said apparatus additionally comprising:

means for mounting said coil means having a plurality of turns and said thin layer of conductive material in a spatially aligned position adjacent to said fixed path in such manner that when conductive material to be detected is present at a particular location in said fixed path, said coil means, said thin layer of conductive material and said conductive material to be detected are spatially aligned; and

means for monitoring said oscillator means to determine if said conductive material to be detected is present.

5. The apparatus according to claim 4 wherein said oscillator means provides output oscillations of substantial magnitude only when conductive material to be detected is present.

6. The apparatus according to claim 5 wherein said means for monitoring includes counter means for counting each occurrence of output.

7. The apparatus according to claim 6 wherein said conductive material to be detected comprises coins and said fixed path comprises a coin chute.

8. The apparatus according to claim 5 wherein said conductive material to be detected comprises a conductive pad disposed for displacement to said particular location by key cap means connected thereto.

9. The apparatus according to claim 8 additionally comprising:

shaft means interconnecting said key cap means to said conductive pad; and

means for normally biasing said conductive pad away from said particular location.

10. The apparatus according to claim 4 wherein said coil means having a plurality of turns and said thin layer of conductive material are displaced from said fixed path by a distance such that when conductive material to be detected is at said particular location in said fixed path and has a predetermined normal thickness, said amplitude of oscillations of said oscillator means are of a predetermined magnitude.

11. The apparatus according to claim 10 wherein said monitoring means provides an indication of the magnitude of said amplitude of oscillations of said oscillator means.

12. The apparatus according to claim 1 wherein when conductive material to be detected is at said particular location in said fixed path and has a thickness less than said predetermined normal thickness, said amplitude of oscillations of said oscillator means will have a value less than said predetermined magnitude.

13. The apparatus according to claim 11 wherein when conductive material to be detected is at said particular location in said fixed path and has a thickness greater than said predetermined normal thickness, said amplitude of oscillations of said oscillator means will have a value greater than said predetermined magnitude.

14. The apparatus according to claim 12 wherein when conductive material to be detected is at said particular location in said fixed path and has a thickness greater than said predetermined normal thickness, said amplitude of oscillations of said oscillator means will have a value greater than said predetermined magnitude.

15. The apparatus according to claim 1 wherein said coil means takes the form of a printed circuit.

16. The apparatus according to claim 1 additionally comprising:

a member having at least a displaceable portion; and

means for mounting said thin layer of conductive material and said coil means to impart relative displacement therebetween in response to displacing of said displaceable portion.

17. The apparatus according to claim 16 wherein said means for mounting establishes a spacing between said thin layer of conductive material and said coil means corresponding to a first position where said thin layer of conductive material has a minor effect upon the amplitude of oscillations of said oscillator means and extends to a second position where said thin layer of conductive material is proximate to said coil means and markedly reduces said amplitude of oscillations of said oscillator means.

18. The apparatus according to claim 16 wherein said amplitude of oscillations of said oscillator means varies as a function of said relative displacement between said thin layer of conductive material and said coil means.

19. The apparatus according to claim 18 wherein said member comprises a drum head.

20. The apparatus according to claim 19 wherein said thin conductive layer is mounted upon said drum head.

21. The apparatus according to claim 18 wherein said member comprises a diaphram.

22. The apparatus according to claim 21 wherein said thin conductive layer is mounted upon said diaphram.

23. The apparatus according to claim 18 wherein said member comprises a pivotable segment arranged to displace in accordance with the rotation of a shaft.

24. The apparatus according to claim 23 wherein said thin conductive layer is mounted upon said pivotable segment.

25. The apparatus according to claim 18 wherein said member includes piston means, said means for mounting includes cylinder means having walls and having a conductive liquid and said piston means disposed therein, and said thin layer of conductive material comprises a portion of said conductive liquid disposed between said piston and said cylinder walls.

26. The apparatus according to claim 19 wherein said coil means comprises a single layer helical coil disposed about said cylinder walls.

27. Apparatus for sensing electrically conductive material comprising:

a thin layer of conductive material capable of exhibiting spontaneous resonance and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit; and

oscillator means having inductor means therein, said inductor means being disposed to induce a field within said layer of conductive material, said oscillator means having a frequency in relation to the thickness of said thin layer of conductive material to cause spontaneous resonance to occur when said thin layer of conductive material is adjacent to said inductor means and no other conductive material is adjacent to said thin layer of conductive material and to cause the effect of spontaneous resonance to be negated when other conductive material is adjacent to said thin layer of conductive material.

28. The apparatus according to claim 27 wherein said inductor means takes the form of a planar printed circuit coil.

29. The apparatus according to claim 27 wherein said inductor means takes the form of a coil having a plurality of turns formed in a single layer.

30. The apparatus according to claim 27 wherein said oscillator means takes the form of a Colpitts oscillator.

31. The apparatus according to claim 27 wherein said electrically conductive material sensed is translated along a fixed path, said apparatus additionally comprising:

means for mounting said inductor means and said thin layer of conductive material in a spatially aligned position adjacent to said fixed path in such manner that when conductive material to be sensed is present at a particular location in said fixed path, said inductor means, said thin layer of conductive material and said conductive material to be sensed are spatially aligned; and

means for monitoring said oscillator means to determine if said conductive material to be sensed is present.

32. The apparatus according to claim 31 wherein said oscillator means provides output oscillations of substantial magnitude only when conductive material is present and said means for monitoring includes counter means for counting each occurrence of output oscillations of substantial magnitude.

33. The apparatus according to claim 31 wherein said conductive material to be detected comprises a conductive pad disposed for displacement to said particular location by key cap means connected thereto.

34. The apparatus according to claim 31 wherein said inductor means and said thin layer of conductive material are displaced from said fixed path by a distance such that when conductive material to be sensed is at said particular location in said fixed path and has a predetermined normal thickness, said amplitude of oscillations of said oscillator means is of a predetermined magnitude.

35. The apparatus according to claim 31 additionally comprising:

a member having at least a displaceable portion; and

means for mounting one of said thin layer of conductive material and said inductor means on said member and another of said thin layer of conductive material and said inductor means in a fixed position relative to said displaceable portion.

36. Apparatus for sensing electrically conductive material comprising:

a thin layer of conductive material capable of exhibiting spontaneous resonance and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit; and

oscillator means having coil means therein, said coil means being disposed to induce a charge pattern corresponding substantially to a mirror image of said coil means in said thin layer of conductive material, said oscillator means having a frequency in relation to the thickness of said thin layer of conductive material to cause said mirror image to be induced and to cause spontaneous resonance to occur when said thin layer of conductive material is adjacent to said coil means and no other conductive material is adjacent to said thin layer of conductive material and to cause spontaneous resonance to be inhibited when other conductive material is in proximity to said thin layer of conductive material.

37. The apparatus according to claim 36 wheren said coil means takes the form of a planar printed circuit coil.

38. The apparatus according to claim 36 wherein said coil means comprises a winding having a plurality of turns, said winding being formed as a single layer.

39. The apparatus according to claim 36 wherein said electrically conductive material sensed is translated along a fixed path, said apparatus additionally comprising:

means for mounting said coil means and said thin layer of conductive material in an aligned position adjacent to said fixed path in a manner such that when conductive material to be sensed is present at a particular location in said fixed path, said coil means, said thin layer of conductive material and said conductive material to be sensed are aligned; and

means for monitoring said oscillator means to determine if conductive material to be sensed is present.

40. The apparatus according to claim 39 wherein said oscillator means provides output oscillations of substantial magnitude only when coductive material is present and said means for monitoring includes counter means for counting each occurrence of output oscillations of substantial magnitude.

41. The apparatus according to claim 39 wherein said conductive material to be detected comprises a conductive pad disposed for displacement to said particular location by key cap means connected thereto.

42. The apparatus according to claim 39 wherein coil means and said thin layer of conductive material are displaced from said fixed path by a distance such that when conductive material to be detected is at said particular location in said fixed path and has a predetermined normal thickness, said amplitude of oscillations of said oscillator means is of a predetermined magnitude.

43. The apparatus according to claim 39 additionally comprising:

a member having at least a displaceable portion; and

means for mounting one of said thin layer of conductive material and said inductor means on said member and another of said thin layer of conductive material and said inductor means in a fixed position relative to said displaceable portion.

44. Apparatus for sensing electrically conductive material comprising:

a thin layer of conductive material capable of exhibiting spontaneous resonance and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit; and

oscillator means having a resonant circuit including inductor means, said inductor means taking the form of a coil formed as a single layer defining a surface, said oscillator means having a resonant frequency selected in relation to the thickness of said thin layer for causing spontaneous resonance to occur when said thin layer is disposed proximate to said coil.

45. The apparatus according to claim 44 wherein said oscillator means takes the form of a Colpitts oscillator.

46. The apparatus according to claim 44 wherein said coil takes the form of a planar printed circuit.

47. The apparatus according to claim 44 wherein said electrically conductive material sensed is translated along a fixed path, said apparatus additionally comprising:

means for mounting said coil means and said thin layer of conductive material in an aligned position adjacent to said fixed path in a manner such that when conductive material to be sensed is present at a particular position in said fixed path, said coil means, said thin layer of conductive material and said conductive material to be sensed are aligned; and

means for monitoring said oscillator means to determine if conductive material to be sensed is present.

48. The apparatus according to claim 47 wherein said oscillator means provides output oscillations of substantial magnitude only when conductive material is present and said means for monitoring includes counter means for counting each occurrence of output oscillations of substantial magnitude.

49. The apparatus according to claim 47 wherein said conductive material to be detected comprises a conductive pad disposed for displacement to said particular location by key cap means connected thereto.

50. The apparatus according to claim 47 wherein coil means and said thin layer of conductive material are displaced from said fixed path by a distance such that when conductive material to be detected is at said particular location in said fixed path and has a predetermined normal thickness, said amplitude of oscillations of said oscillator means is of a predetermined magnitude.

51. The apparatus according to claim 47 additionally comprising:

a member having at least a displaceable portion; and

means for mounting one of said thin layer of conductive material and said inductor means on said member and another of said thin layer of conductive material and said inductor means in a fixed position relative to said displaceable portion.

52. Apparatus for detecting electrically conductive material comprising:

a thin layer of conductive material capable of exhibiting spontaneous resonance and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit; and

oscillator means having a resonant circuit including coil means, said coil means defining a surface, said surface defined by said coil means being disposed proximate to and substantially parallel with said thin layer of conductive material, said oscillator means having a resonant frequency selected in relation to the thickness of said thin layer to cause the magnitude of oscillations produced by said oscillator means to be markedly reduced in the absence of other conductive material adjacent to said thin layer of conductive material and to be of substantially full magnitude when other conductive material is adjacent to said thin layer of conductive material.

53. The apparatus according to claim 52 wherein said coil means is formed as a single layer.

54. A method of sensing electrically conductive material comprising the steps of:

disposing a thin layer of electrically conductive material having a thickness which is less than the skin effect depth of said layer at a predetermined frequency in the field of an inductive coil of an oscillator;

operating said oscillator at a frequency in relation to the thickness of said thin layer of electrically conductive material to cause said inductive coil to establish an induced tuned circuit in said thin layer of electrically conductive material and to establish therewith an associated induced lectromagnetic field; and

monitoring the presence of said induced tune circuit in said thin layer of electrically conductive material to determine the presence of electrically conductive material in said area.

55. Apparatus for detecting electrically conductive material comprising:

a thin layer of conductive material having a thickness which is less than the skin effect depth of said layer at a predetermined frequency; and

oscillator means having a resonant circuit including coil means, said coil means defining a surface, said surface defined by said coil means being disposed proximate to said thin layer of conductive material, said oscillator means having a resonant frequency selected in relation to the thickness of said thin layer to cause the magnitude of oscillations produced by said oscillator means to be markedly reduced in the absence of other conductive material adjacent to said thin layer of conductive material and to be of substantially full magnitude when other conductive material is adjacent to said thin layer of conductive material.

56. The apparatus according to claim 55 wherein said surface defined by said coil means is additionally disposed substantially in parallel with said thin layer of conductive material.

57. The apparatus according to claim 55 wherein said coil means takes the form of a planar printed circuit.

58. A method of sensing electrically conductive material comprising the steps of:

selecting a thin layer of conductive material capable of exhibiting spontaneous resonance and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit;

employing a coil having a plurality of turns forming a surface in a resonant tank circuit of an oscillator; and

operating said oscillator at a frequency in relation to the thickness of said thin layer to cause spontaneous resonance to occur when said thin layer of conductive material is proximate to and substantially parallel with said surface formed by said plurality of turns and no other conductive material is adjacent to said thin layer of conductive material.

59. A method of sensing electrically conductive material comprising the steps of:

disposing a thin layer of conductive material adjacent to a path of translation of electrically conductive material to be sensed, said thin layer of conductive material forming a first surface substantially parallel to said path of translation and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency;

placing a coil having a plurality of turns forming a second surface proximate to said thin layer of conductive material in such manner that said first and second surfaces are substantially parallel and each of said plurality of turns in said coil is equidistant from said first surface; and

connecting said coil in the tank circuit of an oscillator having a frequency which in relation to the thickness of said thin layer of conductive material will cause a marked reduction in the magnitude of oscillations produced by said oscillator in the absence of other conductive material adjacent to said thin layer of conductive material and to be of substantially full magnitude when other conductive material is adjacent to said thin layer of conductive material.

60. A method of sensing electrically conductive material comprising the steps of:

selecting a thin layer of conductive material capable of forming a charge pattern corresponding substantially to a mirror image of a coil therein, said thin layer having a thickness which is less than the skin effect depth of said layer at a predetermined frequency;

connecting a coil having a plurality of turns formed as a surface in the tank circuit of an oscillator having a frequency which in relation to the thickness of said thin layer of conductive material will inhibit electron flow between charge pattern images formed in said thin layer of conductive material;

placing said thin layer of conductive material proximate to and in parallel with said surface formed by said coil; and

monitoring the operation of said oscillator to determine the presence of electrically conductive material.

61. A method of detecting electrically conductive material comprising the steps of:

disposing a thin layer of conductive material capable of exhibiting spontaneous resonance adjacent to a path of translation of electrically conductive material to be sensed wherein spontaneous resonance is defined as a characteristic enabling said thin layer to emulate a passive resonant circuit and absorb energy from an appropriately tuned oscillating circuit, said thin layer of conductive material forming a first surface substantially parallel to said path of translation and having a thickness which is less than the skin effect depth of said layer at a predetermined frequency;

placing a coil having a plurality of turns forming a second surface proximate to said thin layer of conductive material in such manner that said first and second surfaces are substantially parallel and each of said plurality of turns in said coil is equidistant from said first surface; and

connecting said coil in the tank circuit of an oscillator having a frequency which in relation to the thickness of said thin layer of conductive material will cause spontaneous resonance to occur in said thin layer of conductive material in the absence of electrically conductive material to be sensed.

62. Apparatus for sensing electrically conductive material comprising:

a plurality of thin layers of electrically conductive material disposed about a path to be translated by electrically conductive material to be sensed, each of said plurality of thin layers having a thickness which is less than the skin effect depth of said layers at a predetermined frequency;

a plurality of coil means, each coil means defining a surface and being associated with and disposed substantially in parallel to a particular one of said plurality of thin layers of electrically conductive material such that each of said plurality of thin layers of electrically conductive material has one of said plurality of coil means associated therewith;

a plurality of oscillator means, each of said plurality of oscillator means having a resonant circuit including one of said plurality of coil means, each of said plurality of oscillator means having a resonant frequency selected in relation to the thickness of a thin layer of conductive material associated with said one of said plurality of coil means in the resonant circuit thereof; and

means for monitoring said plurality of oscillator means for sensing electrically conductive material.