Capacitive, operator-sensing circuit for disabling engine of mobile power equipment

• US 6,501,281 B1
• Filed: 07/19/2000
• Issued: 12/31/2002
• Est. Priority Date: 07/19/2000
• Status: Active Grant

• Current Assignee: Delta Systems Inc.
• Original Assignee: Delta Systems Inc.
• Inventors: Rundo, James A.
• Primary Examiner(s): Sherry, Michael
• Assistant Examiner(s): NGUYEN, TRUNG Q
• Application Number:
  US09/618,868
• Time in Patent Office: 895 Days
• Field of Search: 324/76.66, 324/382, 324/427, 324/519, 324/584, 324/658, 324/686, 318/751, 318/794, 318/796, 340/545.1, 340/562, 361/15, 361/181, 361/251, 702/47, 702/52
• US Class Current: 324/658
• CPC Class Codes: A01D 34/828 Safety devices
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

A capacitive, operator-sensing circuit for mobile power equipment includes a charge-transfer touch sensor that is electrically coupled to at least one sensing electrode mounted on a gripping surface of the mobile power equipment. The charge-transfer touch sensor is preferably a digital integrated circuit that operates to change an output voltage between two levels or states (logic high and logic low) depending upon a quantity of charge sensed on the at least one sensing electrode, the sensed charge on the at least one sensing electrode changing with the presence or absence of an operator'"'"'s hand on the at least one sensing electrode. The charge-transfer touch sensor outputs a DC voltage signal, maintaining a given output voltage level until the sensor senses a predetermined change in sensed charge on the sensing electrode. The capacitive operator-sensing circuit additionally includes coupling circuitry coupled between the charge-transfer touch sensor and a component of the equipment. A change in sensor output voltage from a first level to a second level causes a cessation of operation of the component. For example, the component may be an internal combustion engine of the equipment and a change in sensor output voltage from the first level to the second level causes the coupling circuitry to electrically couple a magneto of the engine to be coupled to ground thereby shutting off the engine.

Claims

1. A capacitive, operator-sensing circuit for sensing the presence of a hand of an operator on a gripping surface of a unit of power equipment having an internal combustion engine and shutting off the engine if the operator'"'"'s hand is removed from the gripping surface, the operator-sensing circuit comprising:

a) a sensing electrode affixed to the gripping surface, a quantity of charge present on the sensing electrode having a first value if the operator'"'"'s hand overlies a portion of the sensing electrode and having a second value if the operator'"'"'s hand does not overlie the sensing electrode;

b) a charge-transfer sensor electrically coupled to the sensing electrode periodically transferring charge to the sensing electrode and sensing the quantity of charge on the sensing electrode, an output of the charge-transfer sensor generating a first output signal when the first value of the sensed charge on the sensing electrode is sensed and a second output signal, different from the first output signal, when the second value of the sensed charge on the sensing electrode is sensed; and

c) coupling circuity electrically coupling a magneto of the engine and the charge-transfer sensor for grounding the engine magneto and thereby shutting off the engine when the second output signal is generated by the charge-transfer sensor.

2. The operator-sensing circuit of claim 1 wherein the sensing electrode is affixed to the gripping surface.

3. The operator-sensing circuit of claim 2 wherein the sensing electrode comprises a conductive wire coiled around a length of the gripping surface and adhesively attached to the gripping surface.

4. The operator-sensing circuit of claim 1 wherein the sensing electrode is integral with the gripping surface.

5. The operator-sensing circuit of claim 1 wherein the sensing electrode comprises a section of conductive wire mesh fabricated into the gripping surface.

6. The operator-sensing circuit of claim 1 wherein the gripping surface comprises first and second spaced apart grips and the sensing electrode comprises a first sensing electrode affixed to the first grip and a second sensing electrode affixed to the second grip.

7. The operator-sensing circuit of claim 1 wherein the charge-transfer sensor comprises a digital integrated circuit.

8. The operator-sensing circuit of claim 1 wherein the first output signal of the sensor output is a logic low voltage output state and the second output signal of the sensor output is a logic high voltage output state.

9. The operator-sensing circuit of claim 1 wherein the coupling circuit includes a triac electrically coupled between the engine magneto and ground and additionally includes circuitry to electrically couple a signal representative of the sensor output to a gate terminal of the triac, the triac being turned on when the sensor generates the second output signal and being turned off when the sensor generates the first output signal.

10. The operator-sensing circuit of claim 1 wherein the sensor is adjustable with respect to a magnitude of decrease in sensed charge on the sensing electrode that will result in the sensor output switching from the first output signal to the second output signal and a magnitude of increase in sensed charge on the sensing electrode that will result in the sensor output switching from the second output signal to the first output signal.

11. A capacitive operator-sensing circuit in combination with a mobile power equipment unit, the combination comprising:

a) the mobile power equipment including an internal combustion engine, an engine magneto, and a gripping surface for an operator to grip and control movement of the mobile power equipment unit; and

b) the capacitive operator-sensing circuit adapted to sense the presence of a hand of an operator on the gripping surface to shut off the engine if the operator'"'"'s hand is removed from the gripping surface, the capacitive operator-sensing circuit including;

1) a sensing electrode affixed to the gripping surface, a quantity of charge present on the sensing electrode having a first value if the operator'"'"'s hand overlies a portion of the sensing electrode and having a second value if the operator'"'"'s hand does not overlie the sensing electrode;

2) a charge-transfer sensor electrically coupled to the sensing electrode periodically transferring charge to the sensing electrode and sensing the quantity of charge on the sensing electrode, an output of the sensor generating a first output signal when the first value of sensed charge on the sensing electrode is sensed and a second output signal, different from the first output signal, when the second value of the sensed charge on the sensing electrode is sensed; and

3) coupling circuity electrically coupled between the engine magneto and the charge-transfer sensor for grounding the engine magneto and thereby shutting off the engine when the second output signal is received from the charge-transfer sensor.

12. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the operator-sensing circuit sensing electrode is affixed to the gripping surface.

13. The combination operator-sensing circuit and mobile power equipment of claim 12 wherein the operator-sensing circuit sensing electrode comprises a conductive wire coiled around a length of the gripping surface and adhesively attached to the gripping surface.

14. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the operator-sensing circuit sensing electrode is integral with the gripping surface.

15. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the operator-sensing circuit sensing electrode comprises a section of conductive wire mesh fabricated into the gripping surface.

16. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the mobile power equipment gripping surface comprises first and second spaced apart grips and the operator-sensing circuit sensing electrode comprises a first sensing electrode affixed to the first grip and a second sensing electrode affixed to the second grip.

17. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the operator-sensing circuit charge-transfer sensor comprises a digital integrated circuit.

18. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the first output signal of the operator-sensing circuit sensor output is a logic low voltage output state and the second output signal of the sensor output is a logic high voltage output state.

19. The combination operator-sensing circuit and mobile power equipment of claim 11 wherein the operator-sensing circuit coupling circuit includes a triac electrically coupled between the mobile power equipment engine magneto and ground and additionally includes circuitry to electrically couple a signal representative of the sensor output to a gate terminal of the triac, the triac being turned on when the sensor generates the second output signal and being turned off when the sensor generates the first output signal.

20. A method of sensing the presence of a hand of an operator on a gripping surface of a mobile power equipment unit and causing cessation of operation of a component system of the equipment if the operator'"'"'s hand is removed from the gripping surface, the steps of the method comprising:

a) providing a sensing electrode affixed to the mobile power equipment gripping surface wherein a quantity of charge on the sensing electrode has a first value if the operator'"'"'s hand overlies a portion of the sensing electrode and has a second value if the operator'"'"'s hand does not overlie the sensing electrode;

b) providing a charge-transfer sensor electrically coupled to the sensing electrode and periodically transferring charge to the sensing electrode, sensing the quantity of charge on the sensing electrode and generating a first output signal when the first value of sensed charge on the sensing electrode is sensed and a second output signal, different from the first output signal, when the second value of sensed charge of the sensing electrode is sensed; and

c) providing coupling circuitry electrically coupled between the charge-transfer sensor and the component, the coupling circuitry causing cessation of operation of the component system when the second output signal is generated by the charge-transfer sensor.

21. The method of sensing the presence of a hand of an operator of claim 20 wherein the component system is an internal combustion engine of the equipment and the coupling circuitry electrically couples a magneto of the engine to ground to shut off the engine when the second output signal is generated by the charge-transfer sensor.

22. The method of sensing the presence of a hand of an operator of claim 20 wherein the component system is a power take-off drive of the equipment and the coupling circuitry includes a relay and a controller to disengage a drive shaft of the power take-off drive from an engine of the equipment when the second output signal is generated by the charge-transfer sensor.

23. The method of sensing the presence of a hand of an operator of claim 20 wherein the component system is an electric motor of the equipment and the coupling circuitry interrupts a supply of power to the electric motor to shut off the electric motor when the second output signal is generated by the charge-transfer sensor.

24. A capacitive, operator-sensing circuit for sensing the presence of a hand of an operator on a gripping surface of a unit of power equipment and causing cessation of operation of a component of the equipment if the operator'"'"'s hand is removed from the gripping surface, the operator-sensing circuit comprising:

a) a sensing electrode affixed to the gripping surface, a quantity of charge present on the sensing electrode having a first value if the operator'"'"'s hand overlies a portion of the sensing electrode and having a second value if the operator'"'"'s hand does not overlie the sensing electrode;

b) a charge-transfer sensor electrically coupled to the sensing electrode periodically transferring charge to the sensing electrode and sensing the quantity of charge on the sensing electrode, an output of the charge-transfer sensor generating a first output signal when the first value of the sensed charge on the sensing electrode is sensed and a second output signal, different from the first output signal, when the second value of the sensed charge on the sensing electrode is sensed; and

c) coupling circuity electrically coupled between the charge-transfer sensor and the component, the coupling circuitry causing cessation of operation of the component system when the second output signal is generated by the charge-transfer sensor.

25. The operator-sensing circuit of claim 24 wherein the component is an internal combustion engine of the equipment and the coupling circuitry electrically couples a magneto of the engine to ground to shut off the engine when the second output signal is generated by the charge-transfer sensor.

26. The operator-sensing circuit of claim 24 wherein the component is a power take-off drive of the equipment and the coupling circuitry includes a relay and a controller to disengage a drive shaft of the power take-off drive from an engine of the equipment when the second output signal is generated by the charge-transfer sensor.

27. The operator-sensing circuit of claim 24 wherein the component is an electric motor of the equipment and the coupling circuitry interrupts a supply of power to the electric motor to shut off the electric motor when the second output signal is generated by the charge-transfer sensor.

28. The operator-sensing circuit of claim 24 wherein the sensing electrode is affixed to the gripping surface.

29. The operator-sensing circuit of claim 24 wherein the sensing electrode comprises a conductive wire coiled around a length of the gripping surface and adhesively attached to the gripping surface.

30. The operator-sensing circuit of claim 24 wherein the sensing electrode is integral with the gripping surface.

31. The operator-sensing circuit of claim 24 wherein the sensing electrode comprises a section of conductive wire mesh fabricated into the gripping surface.

32. The operator-sensing circuit of claim 24 wherein the gripping surface comprises first and second spaced apart grips and the sensing electrode comprises a first sensing electrode affixed to the first grip and a second sensing electrode affixed to the second grip.

33. The operator-sensing circuit of claim 24 wherein the charge-transfer sensor comprises a digital integrated circuit.

34. The operator-sensing circuit of claim 24 wherein the first output signal of the sensor output is a logic low voltage output state and the second output signal of the sensor output is a logic high voltage output state.

35. The operator-sensing circuit of claim 24 wherein the coupling circuit includes a triac electrically coupled between the engine magneto and ground and additionally includes circuitry to electrically couple a signal representative of the sensor output to a gate terminal of the triac, the triac being turned on when the sensor generates the second output signal and being turned off when the sensor generates the first output signal.

36. The operator-sensing circuit of claim 24 wherein the sensor is adjustable with respect to a magnitude of decrease in sensed charge on the sensing electrode that will result in the sensor output switching from the first output signal to the second output signal and a magnitude of increase in sensed charge on the sensing electrode that will result in the sensor output switching from the second output signal to the first output signal.