Paper dispenser with proximity detector

• US 7,161,359 B2
• Filed: 09/09/2004
• Issued: 01/09/2007
• Est. Priority Date: 02/09/2001
• Status: Expired due to Term

• Current Assignee: GPCP IP Holdings LLC
• Original Assignee: Georgia-Pacific Corporation
• Inventors: Knittle, John J., Groezinger, Charles W., Myers, Gary Edwin, Denen, Dennis Joseph
• Primary Examiner(s): Deb; Anjan
• Assistant Examiner(s): Dole; Timothy J.
• Application Number:
  US10/938,927
• Publication Number:
  US 20050072874A1
• Time in Patent Office: 852 Days
• Field of Search: 324/686, 324/662
• US Class Current: 324/686
• CPC Class Codes: A47K 10/36 with mechanical dispensing, roll switching or cutting devices
• CPC Class Codes: A47K 10/3625 with electronic control means
• CPC Class Codes: A47K 10/3687 with one or more reserve rolls
• CPC Class Codes: A47K 2010/3668 Detection of the presence of a user
• CPC Class Codes: H05F 3/02 by means of earthing connections

Abstract

A paper dispenser having a proximity detector for dispensation of paper therefrom. The dispenser includes a housing having an inner chamber adapted to support a roll of paper. The housing also has a dispensing aperture. A motor is adapted to dispense paper from the roll through the dispensing aperture. The dispenser also includes a proximity detection circuit, which comprises an antenna, an oscillator circuit to charge the antenna, an operational amplifier operated as a unity gain follower which receives an antenna signal from the antenna, a detector circuit which detects changes in the antenna signal, and a comparator which actuates the motor in response to changes in the antenna signal.

Claims

1. A paper dispenser comprising:

a housing having an inner chamber adapted to support a roll of paper and having a dispensing aperture;

a motor adapted to dispense paper from the roll of paper through the dispensing aperture; and

a proximity detection circuit for detecting the presence of a moving hand in the vicinity of said dispensing aperture, said circuit comprising;

an antenna with which is associated a fixed time constant determined by a predetermined capacitance and a predetermined resistance, as well as a variable time constant that is longer than the fixed time constant by an amount determined by an external capacitive load, said variable time constant being on the order of twice said fixed time constant when the external capacitive load is a hand of a person in proximity to the antenna;

an oscillator circuit for charging the antenna with an oscillating signal with a periodicity greater than said fixed time constant;

an operational amplifier being operated as a unity gain follower and receiving an antenna signal from the antenna, the antenna signal being representative of an external capacitive load on the antenna and having a periodic exponential waveform that has a longer time constant and a lower amplitude when said external capacitive load is in proximity to said antenna, the waveform of the antenna signal being thus representative of changes in the external capacitive load on the antenna;

a detector circuit electrically coupled to the operational amplifier for detecting changes in a low frequency component of the antenna signal and for generating a detection signal in response thereto; and

a comparator responsive to the detection signal for generating an output signal to said motor when the detection signal is representative of a waving hand in proximity to the antenna.

2. The paper dispenser of claim 1, the proximity detection circuit further comprising at least one static protection circuit having at least one first diode adapted to conduct away from ground and at least one second diode adapted to conduct toward a supply voltage.

3. The paper dispenser of claim 1, the proximity detection circuit further comprising a voltage peak detector.

4. The paper dispenser of claim 1, the proximity detection circuit further comprising a low-pass filter electrically coupled between the detector circuit and the comparator for passing said low frequency signal component and rejecting a higher frequency noise component.

5. The paper dispenser of claim 4, the proximity detection circuit further comprising a gain and offset amplifier electrically coupled between the low-pass filter and the comparator, for amplifying said low frequency signal component.

6. The paper dispenser of claim 1, wherein the comparator is adapted to actuate the motor when the detection signal has a predetermined voltage level as compared to a reference voltage.

7. A paper dispenser comprising:

a housing having an inner chamber adapted to support a roll of paper and having a dispensing aperture;

a motor adapted to dispense paper from the roll of paper through the dispensing aperture; and

a proximity detection circuit for detecting the presence of a moving hand, said circuit comprising;

an antenna with which is associated a fixed time constant determined by a predetermined capacitance and a predetermined resistance, as well as a variable time constant that is longer than the fixed time constant by an amount determined by an external capacitive load, said variable time constant being on the order of twice said fixed time constant when the external capacitive load is a hand of a person in proximity to the antenna;

means for charging the antenna with an oscillating signal with a periodicity greater than said fixed time constant;

means for buffering an antenna signal from the antenna, the antenna signal being representative of an external capacitive load on the antenna and having a periodic exponential waveform that has a longer time constant and a lower amplitude when said external capacitive load is in proximity to said antenna, the waveform of the buffered antenna signal being thus representative of changes in the external capacitive load on the antenna;

means for detecting changes in a low frequency component of the buffered antenna signal and for generating a detection signal in response thereto; and

means for generating an output signal to said motor when the detection signal is representative of a waving hand in proximity to the antenna.

8. The paper dispenser of claim 7, the proximity detection circuit further comprising at least one static protection circuit having at least one first diode adapted to conduct away from ground and at least one second diode adapted to conduct toward a supply voltage.

9. The paper dispenser of claim 7, the proximity detection circuit further comprising means for filtering alternating current interference frequencies from the detection signal.

10. The paper dispenser of claim 7, the proximity detection circuit further comprising means for amplifying the detection signal.

11. The paper dispenser of claim 7, the proximity detection circuit further comprising means for detecting a voltage peak in the buffered antenna signal.

12. The paper dispenser of claim 7, wherein the output signal actuates the motor when the detection signal has a predetermined voltage level as compared to a reference voltage.

13. A paper dispenser comprising:

means for supporting a roll of paper within a housing;

means for dispensing paper from the roll of paper;

a proximity detector circuit comprising;

an antenna with which is associated a fixed time constant determined by a predetermined capacitance and a predetermined resistance, as well as a variable time constant that is longer than the fixed time constant by an amount determined by an external capacitive load, said variable time constant being on the order of twice said fixed time constant when the external capacitive load is a hand of a person in proximity to the antenna;

an oscillator circuit for charging the antenna with an oscillating signal with a periodicity greater than said fixed time constant;

an operational amplifier being operated as a unity gain follower and receiving an antenna signal from the antenna;

a detector circuit electrically coupled to the operational amplifier for detecting changes in a low frequency component of the antenna signal, the antenna signal being representative of an external capacitive load on the antenna and having a periodic exponential waveform that has a longer time constant and a lower amplitude when said external capacitive load is in proximity to said antenna, and for generating a detection signal in response thereto; and

a comparator responsive to the detection signal for generating an output signal to said dispensing means when the detection signal is representative of a waving hand in proximity to the antenna.

14. The paper dispenser of claim 13, the proximity detection circuit further comprising at least one static protection circuit having at least one first diode adapted to conduct away from ground and at least one second diode adapted to conduct toward a supply voltage.

15. The paper dispenser of claim 13, wherein the output signal actuates the motor when the detection signal has a predetermined voltage level as compared to a reference voltage.

16. A paper dispenser comprising:

a housing having an inner chamber adapted to support a roll of paper and having a dispensing aperture;

a motor disposed within the housing and adapted to dispense paper from the roll of paper through the dispensing aperture; and

a proximity detection circuit disposed within the housing, the proximity detection circuit comprising;

an antenna;

an asymmetric oscillator circuit electrically coupled to the antenna, the asymmetric oscillator circuit having an on-period and an off-period, wherein the asymmetric oscillator circuit is adapted to send an approximately uniform charge to the antenna during the on-period;

an antenna impedance buffer electrically coupled to the antenna, the antenna impedance buffer including an operational amplifier adapted to operate as a unity gain follower;

a voltage peak detector electrically coupled to an output of the antenna impedance buffer, the voltage peak detector comprising a diode, a current-limiting resistor, a peak storage capacitor, and a bleed off resistor, the diode and the peak storage capacitor being adapted to capture positive peaks of exponential waveforms from the antenna impedance buffer, the current limiting resistor being adapted to limit current flow from the antenna impedance buffer, and the bleed-off resistor being adapted to provide a discharge pathway for the peak storage capacitor,

a gain and voltage offset amplifier electrically coupled to an output of the voltage peak detector,

an output comparator adapted to receive an input signal from the gain and voltage offset amplifier and a reference voltage, the output comparator being further adapted to actuate the motor when the input signal has a predetermined voltage level as compared to the reference voltage, and

an auto-compensation capacitor electrically coupled between the gain and voltage offset amplifier and the output comparator, the auto-compensation capacitor being adapted to filter out changes in DC voltage levels in the signal while allowing passage of transient portions of the signal representative of a waving hand in proximity to the antenna.

17. The paper dispenser of claim 16, the proximity detection circuit further comprising at least one static protection circuit having at least one second diode adapted to conduct away from ground and at least one third diode adapted to conduct toward a supply voltage.

18. The paper dispenser of claim 16, wherein the current limiting resistor is adapted to prevent oscillation at the antenna impedance buffer.

19. The paper dispenser of claim 16, the proximity detection circuit further comprising a low-pass filter electrically coupled between the voltage peak detector and the output comparator, the low-pass filter being adapted to filter out about 50 or about 60 Hz alternating current interference frequencies.

20. A method of dispensing paper comprising:

supporting a roll of paper within a housing, the housing including a dispensing aperture and having a motor affixed thereto;

affixing an antenna to the housing;

charging the antenna with an oscillating signal to thereby produce a periodic antenna signal, the antenna having an associated fixed time constant determined by a predetermined capacitance and a predetermined resistance, as well as a variable time constant that is longer than the fixed time constant by an amount determined by an external capacitive load, said variable time constant being on the order of twice said fixed time constant when the external capacitive load is a hand of a person in proximity to the antenna, said oscillating signal having a periodicity greater than said fixed time constant,

detecting low frequency changes in the antenna signal representative of changes in said external capacitive load on the antenna caused by a moving hand in proximity to the antenna;

generating a low frequency detection signal component in response to said low frequency changes in the antenna signal;

selectively amplifying said low frequency detection signal component and rejecting a higher frequency noise component to thereby produce an amplified and filtered detection signal component;

compensating for slow environmental changes in the amplified and filtered detection signal component to thereby provide a compensated detection signal with increased sensitivity to transient signals representative of a waving hand in proximity to the antenna; and

actuating the motor in response to the compensated detection signal, wherein the motor is adapted to dispense paper from the roll of paper through the dispensing aperture upon actuation.

21. The method of claim 20, wherein actuating the motor includes comparing the detection signal to a reference voltage.

22. The method of claim 20, wherein charging the antenna with the oscillating signal includes charging the antenna with an oscillating asymmetric signal.

23. The method of claim 20, wherein detecting changes in the antenna signal includes detecting a peak voltage.

24. The method of claim 20 further comprising providing protection from static utilizing at least one static protection circuit having at least one first diode adapted to conduct away from ground and at least one second diode adapted to conduct toward a supply voltages.

25. The method of claim 20 further comprising providing a current limiting resistor to prevent oscillation in the low frequency detection signal.

26. The method of claim 20 further comprising filtering out alternating current interference frequencies from the antenna signal.

27. The method of claim 20 further comprising wherein compensating for slow environmental changes includes filtering out changes in DC voltage levels from the detection signal component while passing transient portions thereof.

28. A method of dispensing paper comprising:

supporting a roll of paper within a housing, the housing including a dispensing aperture and having a motor affixed/d thereto;

producing an oscillating asymmetric signal having an on period and an off period;

charging an antenna with the oscillating asymmetric signal, the antenna being affixed to the housing, wherein the oscillating asymmetric signal is adapted to provide an approximately uniform amount of charge to the antenna during the on period;

discharging the antenna to a fixed voltage for every oscillation period;

buffering any impedance mismatch between the antenna and a peak detector utilizing an operational amplifier adapted to operate as a unity gain follower;

detecting a peak voltage in the antenna discharge with the peak detector;

offsetting and amplifying the detected peak voltage from the peak detector;

filtering out changes in DC voltage levels of the offset and amplified peak voltage while allowing passage of transient portions thereof; and

actuating the motor upon detection in said transient portions of a signal which is within predetermined duration, amplitude, and rate of change criteria, wherein the motor is adapted to dispense paper from the roll of paper through the dispensing aperture upon actuation.

29. The method of claim 28, wherein detecting the peak voltage includes providing the peak detector with a diode and a peak storage capacitor, the diode and peak storage capacitor being adapted to capture peaks of exponential waveforms output from the operational amplifier.

30. The method of claim 28 further comprising providing protection from static utilizing at least one static protection circuit having at least one first diode adapted to conduct away from ground and at least one second diode adapted to conduct toward the supply voltage.

31. The method of claim 28 further comprising preventing oscillation by including a current limiting resistor at the output terminal of the operational amplifier.

32. The method of claim 28, wherein after detecting the peak voltage the method further comprises filtering out about 50 Hz and about 60 Hz alternating current interference frequencies through a low-pass filter.

33. The method of claim 28, wherein actuating the motor includes comparing the signal to a reference voltage to determine if the signal has a predetermined voltage level as compared to the reference voltage.