Coin discrimination apparatus

• US 5,180,046 A
• Filed: 02/26/1991
• Issued: 01/19/1993
• Est. Priority Date: 05/24/1990
• Status: Expired due to Fees

• Current Assignee: COIN Controls Limited New COIN Street Royton Oldham Lancashire OL2 6JZ England
• Original Assignee: COIN Controls Limited New COIN Street Royton Oldham Lancashire OL2 6JZ England
• Inventors: Hutton, Les, Kershaw, John
• Primary Examiner(s): Bartuska, F. J.
• Application Number:
  US07/661,487
• Time in Patent Office: 693 Days
• Field of Search: 194/317, 194/318, 194/319, 324/227, 324/236, 307/261, 307/268, 328/28, 328/29, 328/30
• US Class Current: 194/319
• CPC Class Codes: G07D 5/02 Testing the dimensions, e.g. thickness, diameter; Testing the deformation
• CPC Class Codes: G07D 5/08 Testing the magnetic or electric properties

Abstract

Coin discrimination apparatus comprises a path (1) for passage of coins under test; sensor coils (2, 3, 4) forming an inductive coupling with a coin under test during its passage along the path, each of the sensor coils being connected in a resonant circuit (10, 11, 12) which exhibits a resonant frequency that varies in dependence upon the inductive coupling between the coil and coin, control circuitry (14) which maintains the resonant circuit at the resonant frequency while a coin under test is inductively coupled to the coil, and amplitude responsive circuitry (MPU) responsive to the change in the amplitude of an oscillatory signal developed by the resonant circuit when the coin under test passes the sensor coil to discriminate between different coins, wherein the control circuitry includes a zero crossing detector (A1) responsive to the oscillatory signal crossing a zero threshold level for producing a rectangular waveform corresponding to the oscillatory signal, and drive circuitry (FF1, 2; OR1, 2) responsive to said rectangular waveform for driving the resonant circuit to maintain resonance.

Claims

1. Coin discrimination apparatus comprising:

means defining a path for passage of coins under test;

sensor coil means for forming an inductive coupling with coins under test during their passage along the path, said sensor coil means being connected in a resonant circuit which exhibits a resonant frequency that varies in dependence upon the inductive coupling between the coil and coin;

control means for maintaining the resonant circuit at the resonant frequency whilst a coin under test is inductively coupled to said coil means; and

amplitude responsive means responsive to the change in the amplitude of an oscillatory signal developed by the resonant circuit when the coin under test passes the sensor coil means, wherein the control means includes threshold detecting means responsive to the oscillatory signal crossing a given threshold level for producing a rectangular waveform corresponding to said oscillatory signal, and drive means responsive to said rectangular waveform for driving the resonant circuit to maintain resonance, said drive means including bistable circuit means having first and second stable states and being configured to be clocked between said states in response to said rectangular waveform, and means for feeding back the output of said bistable circuit means for modifying the rectangularity of said rectangular waveform.

2. Apparatus according to claim 1 wherein said bistable circuit means includes first and second flip-flops, the first flip-flop being configured to be clocked between its stable states in response to a falling edge of said rectangular waveform, and the second flip-flop is configured to be clocked between its stable states in response to a falling edge of an inverse of said rectangular waveform.

3. Apparatus according to claim 2 including an inverter responsive to the output of said threshold detecting means for producing said inverse of said rectangular waveform.

4. Apparatus according to claim 2 or 3 including means for logically combining the states of the flip-flop such as to produce a drive waveform for the resonant circuit to maintain resonance thereof.

5. Apparatus according to claim 4 wherein said combining means comprises an exclusive OR gate.

6. Apparatus according to claim 5 including means for applying the output of said exclusive OR gate to the output of the threshold detecting means, and means for applying the inverse of said gate output to the input of the second flip-flop.

7. Apparatus according to claim 1 wherein the threshold detecting means comprises a zero-crossing detector.

8. In a coin discrimination apparatus comprising:

means defining a path for passage of coins under test;

sensor coil means for forming an inductive coupling with coins under test during their passage along the path, said sensor coil means being connected in a resonant circuit which exhibits a resonant frequency that varies in dependence upon the inductive coupling between the coil and coin;

control means for maintaining the resonant circuit at the resonant frequency whilst a coin under test is inductively coupled to said coil means; and

amplitude responsive means responsive to the change in the amplitude of an oscillatory signal developed by the resonant circuit when the coin under test passes the sensor coil means, the improvement comprising that the control means includes threshold detecting means for detecting when the oscillatory signal crosses a given threshold level and for producing a rectangular waveform corresponding to said oscillatory signal, and drive means responsive to said detected crossings for driving the resonant circuit to maintain resonance, said drive means including bistable circuit means having first and second stables states and being configured to be clocked between said states in response to said rectangular waveform, and means for feeding back the output of said bistable circuit means for modifying the rectangularity of said rectangular waveform.