Abstract:
The invention is directed to a touch-sensitive paper shredder control system. The touching feature is implemented through a series of electronic circuits, taking input from a conductive touch panel on the shredder feed throat, processing the signal, and through a motor driving circuit, stopping the mechanical parts of the shredder. The system has a touch detection circuit unit, which contains a bioelectricity controlled switching circuit to sense the conductive touch panel. The bioelectricity controlled switching circuit is configured to trigger a ground switching circuit in the touch detection circuit unit which outputs to a multifunction control circuit unit. The control circuit unit then takes care of the remaining protection issues. The touching device for paper shredders protects humans and other living beings including pets from injuries through automatic and real time monitoring. The complete control process is both safe and sensitive.

Description:
CROSS-REFERENCE TO RELATED PATENTS AND APPLICATIONS 
       [0001]    This U.S. Patent Application claims priority to, and is a Continuation of, U.S. application Ser. No. 11/827,798, entitled “Touch-Sensitive Paper Shredder Control System,” filed Jul. 12, 2007, which is a continuation-in-part of U.S. Pat. No. 7,471,017, which Patent being filed on Aug. 30, 2006 and issued on Dec. 30, 2008, with both Application and Patent being of the same inventor hereof, and both being assigned to the same Assignee hereof, and with both Application and Patent being respectively incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention is related to office equipment and the safe control of paper shredders, in particular touch-sensitive paper shredder control systems. 
       BACKGROUND OF THE INVENTION 
       [0003]    Automated office appliances have proliferated in modern life and workspaces, and one of the most common appliances are paper shredders. Currently, paper shredders have entered into homes, some of them with automatic sensors. The sensors may be configured to detect objects inserted therein and signal the paper shredder to begin to work by grabbing the object and shredding them. Unless the paper shredder is turned off, the shredder may always be in stand-by mode. However, because paper shredders are destructive devices, if human users are not careful when using them, an injury may occur. Many current paper shredders do not have protective devices to prevent objects or body parts from entering into the throat of the shredder—potentially bringing a safety hazard into the office or home. 
         [0004]    Among the present day paper shredders, there have been shredders using the technology of contact detection to stop the shredder&#39;s blades from injuring a person or pet. Referring to  FIG. 1 , the circuit shown therein is an example of this technology. SW 2  is a polarity conversion switch and it can exchange the hot lead and ground lead of the AC power. Resistors R 12  and R 13 , capacitors C 3  and C 2 , and diodes D 11 , D 12 , D 13 , D 14 , D 15  and D 6  comprise a 24V power supply for the relay. Diode D 6 , D 7 , and capacitor C 1  comprise a power supply for U 1 , the voltage detection integrated circuit. The positive terminal of the power supply is the hot line of the AC power. Relay switch RLY- 1 , diode D 2 , transistor Q 1 , resistors R 5 , R 27 , and R 6 , and optical coupler U 5  comprise a power supply for the equipment. Diodes D 1 , D 8  and D 21 , thermal control lamp (orange), transistor Q 4 , resistors R 4 , R 14 , and R 11 , and motor thermal control switch comprise a thermal control indication circuit. Fuse F 1 , switch RLY 1 , motor, function switch, and motor thermal control switch comprise a motor operation circuit. The rotation direction is determined by the function switch setting. Power supply, resistors R 7 , R 1 , R 9 , R 2 , R 8  and R 10 , diodes D 20 , D 16 , D 4 , D 5 , D 9  and D 10 , transistors Q 2  and Q 3 , and pin  5  of the voltage detection integrated circuit comprise a LED indication circuit. The metal part of the panel, resistors R 20 , R 19 , R 21  and R 22 , capacitor C 8 , and diodes D 19  and D 17  comprise a touch detection circuit. 
         [0005]    When the function switch is set at the “off” position, the machine is not working. When the function switch is set at other positions and the wastepaper basket is separated from the machine, the machine is on but not capable of cutting paper. When the basket is detached from the machine body, the spring switch is open to cut power to the motor. The operation of the circuit for the breaking of the spring is as follows: pin  1  of U 1  detects the break of the spring, pin  5  of U 1  becomes “high”, Q 3  and Q 2  cutoff and the motor doesn&#39;t turn. The power indicator and touch/basket detach indicator are on because these two indicators, R 7 , R 8 , D 9 , and the motor thermal control switch form a current loop. 
         [0006]    When the function switch is moved away from “off”, and the wastepaper basket is in position, the machine is ready to work. The sequence of circuit operation is as follows: pin  1  of U 1  becomes “low” and Q 3  and Q 2  become conducting. At the same time, pin  6  of U 1  becomes “low”, Q 1  is on, and the relay RLY  1  is closed. Now if the function switch is set at “on”, the machine will cut the paper if there is paper in the throat, otherwise the shredder is on standby. Under these circumstances, if hands, metal, or living animals contact the metal part at the feed throat, AC power, circuit elements (R 21 , R 19 , R 20 ,) and the contact will form a circuit, and turn off the motor because pin  8  of U 1  now is “low” and pin  5  and  6  of U 1  are “high”. To be more specific, as pin  6  of U 1  is “high”, Q 1  is off and the motor power is turned off. As pin  5  of U 1  is “high” and Q 2  and Q 3  are cut off, the touch protection indicator is on. After the contact is removed from the feed throat, the shredder returns to normal operation. 
         [0007]    The touch protection is achieved through the installment of conductive touch panel at the paper intake. When touching the conductive panel, the conductivity of human body provides a faint signal to the control circuit to activate the touch protection. In this case, two 2.2M ohm resistors largely decrease the current that flows through the human body and thus the circuit may not harm a human. By using this technique, a sensitive voltage detection integrated circuit is needed to monitor the status of the touch panel in real time. Thus the demand for a highly stable and sensitive integrated circuit is apparent. Circuit aging caused by long-term usage will also diminish or even cut the circuit&#39;s detection capability. As for the two resistors with high values, they limit the current that may flow through the human body, but they may also lose their capability in a humid environment. Moreover, a human may come in direct contact with AC power, causing electric shock or even endangering life. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention solves the above-mentioned shortcomings by providing a touch-sensitive paper shredder control system making use of bioelectricity. The control process is safe and sensitive. The circuit is stable in performance, and can be applied in a wide degree of situations. To meet the above objectives, the touching device for paper shredders is constructed as below. 
         [0009]    The touch-sensitive paper shredder control system may include a function module, power supply module, conductive touch panel, and a shredder mechanical component. The function module may include a touch detection circuit unit, motor reversal detection circuit unit, paper intake detection circuit unit, overload protection circuit unit, control circuit unit, and function switch having on, off, and reverse positions. All units in the function module may be connected directly to the control circuit unit except for the function switch, which, together with the control circuit unit, controls the motor driving circuit unit, and thus the shredder&#39;s mechanical components. 
         [0010]    The power supply module may include an AC power interface switch, safety switch, fuse, control switch, power supply of control circuit unit, and motor driving circuit unit. The AC power interface switch, safety switch, fuse, and control switch may be connected in series and, through the control of the function switch, connect to the motor driving circuit unit. The control switch is a relay switch. The AC power, which flows through the fuse, is rectified, filtered and regulated to provide DC power to all circuit units. 
         [0011]    The conductive touch panel may be connected to the touch detection circuit unit. The touch detection circuit unit consists of a bioelectricity controlled switching circuit and a ground switch circuit. The bioelectricity controlled switching circuit may be a transistor circuit with a first transistor where the touch panel is connected to the base of the first transistor via a first resistor. The base of the first transistor is also connected to ground via a parallel combination of a second resistor and a first capacitor. The emitter of the first transistor is connected to ground via a parallel combination of a third resistor and a second capacitor, and is also connected to the input of the ground switch circuit. 
         [0012]    The collector of the first transistor drives in parallel, a power indicator LED and a touch indicator LED and is then connected to the power supply. The ground switching circuit is also a transistorized switching circuit having a second transistor. The base of the second transistor is connected to the output of the bioelectricity controlled switching circuit, the emitter is grounded, and the collector is connected to the input of the control circuit unit via an optical coupler and to the power supply via a fourth resistor. 
         [0013]    The paper intake detection circuit unit is connected to the control circuit unit also. The paper intake detection circuit unit comprises a light emitting diode and a photosensitive diode. The emitting area of the former and the optics sensing part of the latter face each other and are installed on the walls of opposite sides of the feed throat. The overload protection circuit and the motor reversal detection circuit unit are connected to the control circuit unit. 
         [0014]    The touch-sensitive paper shredder control system has adopted cascaded circuits to ensure human safety when a human touches the conductive touch panel. The electricity from the human body enables the bioelectricity controlled switching circuit, and then all the connected circuits. The control circuit unit disables the mechanical part of the shredder and it ensures human safety. Even if the power switch is turned on, the mechanical part of the shredder still doesn&#39;t work. The shredder realizes real time monitoring. The complete control process is both safe and sensitive. The machine performance is stable and reliable and easy to operate without human oversight. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention is generally shown by way of reference to the accompanying drawings in which: 
           [0016]      FIG. 1  is a circuit diagram illustrating the electrical components of a shredder control system using prior art technology; 
           [0017]      FIG. 2  is a block diagram of the components and modules within a touch-sensitive paper shredder control system of the present invention; 
           [0018]      FIG. 3  is a circuit diagram of the electrical components of a touch-sensitive paper shredder control system of the present invention; 
           [0019]      FIG. 4  is the circuit diagram of the electrical components of another embodiment of a touch-sensitive paper shredder control system of the present invention; and 
           [0020]      FIG. 5  is a flow chart of the control process used in connection with a touch-sensitive paper shredder control system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Some embodiments are described in detail with reference to the related drawings. Additional embodiments, features and/or advantages will become apparent from the ensuing description or may be learned by practicing the invention. In the figures, which are not drawn to scale, like numerals refer to like features throughout the description. The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. 
         [0022]    In one embodiment, the touch-sensitive paper shredder control system may include the following components: a function module, a power supply module, and shredder mechanical parts. Referring to  FIG. 2 , the function module consists of a touch detection circuit unit  4 , motor reversal detection circuit unit  7 , paper intake detection circuit unit  5 , overload protection circuit  6 , control circuit unit  3 , and function switch  86 . All of these units are connected directly to control circuit unit except for the function switch, which together with the control circuit unit controls the motor driving circuit unit  2 , and then the shredder mechanical part  1 . A conductive touch panel is connected to the touch detection circuit unit, which consists of a bioelectricity controlled switching circuit and a ground switching circuit. 
         [0023]    The power supply module consists of an AC power interface unit  81 , security switch  82 , fuse  83 , control switch  84 , power supply of control circuit unit  85 , and the motor driving circuit unit  2 . The control switch is a relay switch, and the security switch is a door switch. The first four of the above-mentioned units are connected in series and, through the control of function switch  86 , connected to motor driving circuit unit. The power, through the fuse, is connected to the power supply of control circuit unit, and then to the control circuit unit. 
         [0024]    Turning to  FIG. 3 , in one embodiment, the bioelectricity controlled switching circuit is mainly a switching transistor circuit. The conductive touch panel is connected to the base of switching transistor Q 4  via resistor R 5 . Transistor Q 4  has its base connected to ground through paralleled capacitor C 7  and resistor R 6 , its collector connected directly to power VCC, and its emitter connected to ground through paralleled capacitor C 8  and resistor R 16 . The emitter of Q 4  is also connected directly to the ground switching circuit. 
         [0025]    The ground switching circuit is also a switching transistor circuit. The output from the bioelectricity controlled switching circuit is connected to the input of the ground switching circuit, i.e. the emitter of transistor Q 2 . Transistor Q 2  has its emitter connected directly to ground, its collector connected to VCC through resistor R 7 , and its collector connected to the input of control circuit unit through an optical coupler U 1 . 
         [0026]    Referring to  FIG. 4 , in another embodiment a bioelectricity controlled switching circuit is based on transistor Q 3 . The touch panel is connected to the input of the bioelectricity controlled switching circuit, i.e. the base of the switching transistor Q 3  through a serial combination of resistors R 6  and R 7 . Transistor Q 3  has its base connected to ground via a parallel combination of capacitor C 3 , diode D 4 , and resistor R 8 , the collector is connected to power supply VCC through a parallel combination of power indicator and touch indicator LED 3 , and the emitter is connected directly to the input of the ground switching circuit. 
         [0027]    The ground switching circuit is also a transistor circuit. The output from the bioelectricity controlled switching circuit, i.e. the emitter of transistor Q 3 , is connected directly to the base of the switching transistor Q 2 . The emitter of transistor Q 2  is connected directly to ground, and the collector is connected to the input of the control circuit unit  3 . 
         [0028]    Referring to  FIG. 2  the paper intake detection circuit unit is connected to the control circuit unit  3 . Now turning to  FIG. 3 , the paper intake detection circuit unit consists of a light emitting diode IT 1 , and a photosensitive diode IR 1  which face each other on opposite positions on the wall of the feed throat of the shredder. Both the overload protection circuit unit  6  and the motor reverse detection circuit unit  7  are connected to the control circuit unit  3  of the touch-sensitive paper shredder. 
         [0029]    Referring back to  FIG. 2 , both the motor reversal detection unit  7  and the paper intake detection unit  5  are connected to control circuit unit  3 , then the motor driving circuit unit  2 , and then to the shredder mechanical part  1 . The motor reversal detection unit  7  detects the reversal signal, sends the electric signal to the control circuit unit  3 , then electrically controls the shredder mechanical part  1  to reverse the motor direction through motor driving circuit unit  2 . The paper intake detection circuit unit  5  detects the paper insertion at the feed throat, sends the signal to the control circuit unit, and then drives the shredder mechanical part to cut the paper through motor driving circuit unit. 
         [0030]    Referring now to  FIG. 5 , during the paper shredding process, if a human body touches the touch panel of the feed throat, the shredder will slop immediately. The touch signal is sent to touch detection circuit unit  4 , then goes to control circuit unit  3 , and stops the shredder by cutting the power to motor driving circuit unit  2 . If a human body doesn&#39;t touch the conductive touch panel, the control circuit unit will release the control to motor driving circuit unit  2  to allow the mechanical part to work independently. 
         [0031]    Referring back to  FIG. 3 , the shredder has the following features: overload protection; optics controlled shredding; shredding, shutdown, and reversed rotation functions; and automatic touch-stop. 
         [0032]    The power supply of the control circuit unit is described below. AC input power is divided, rectified, regulated, and filtered by the circuit consists of resistors R 1  and R 2 , capacitors C 1  and C 2 , diodes D 5  and D 6 , and Zener diode ZD 1 . The regulated 24 volts DC power is the power source for the control circuit unit. It&#39;s far below the safety voltage to pass through human body and will do no harm to human or animals. 
         [0033]    The power supply for the touch detection circuit unit is described below. The AC input power, going through a bridge rectifier, is regulated and filtered to provide 12 volts DC voltage. The circuits consists of diodes D 1 -D 4 , Zener diode ZD 2 , resistor R 12  and capacitor C 3 . 
         [0034]    When a human touches the metal panel, the bioelectricity from the human body goes to the base of the transistor Q 4  via a 1 MW resistor. The bioelectricity triggers transistors Q 4  and Q 2  on, cuts off transistor Q 3 , and thus cuts the motor power so that the shredder automatically stops when people touch the feed throat. 
         [0035]    Referring now to  FIG. 4 , the shredder in this embodiment has the following features: on-off LED indicator; touch protection LED indicator; overload LED indicator; AC Power indicator; optics controlled shredding; and shredding, shutdown, and reversed rotation function. 
         [0036]    The overload protection and door open LED indicating functions are implemented by the circuit consists of R 18 , R 14 , R 13 , R 11 , and R 12 , light emitting diodes LED 1  and LED 2 , diodes D 10 , D 9 , and D 6 , Zener diode ZD 2 , capacitor C 5  and silicon controlled rectifier SCR. 
         [0037]    The power supply for the control circuit unit includes a circuit consisting of resistors R 1  and R 2 , capacitors C 1  and C 2 , diodes D 1  and D 2 , Zener diode ZD 1 , and capacitor C 2 . The same regulated 24 volts DC power is used as the power source for the control circuit unit. It&#39;s far below the safety voltage to pass through a human body and will do no harm to human or animals. 
         [0038]    The touching function is described below. When human touches the metal panel, the bioelectricity from a human body goes to the base of the transistor Q 3  via resistors R 6  and R 7 . The signal triggers Q 3  and Q 2  on, turns Q 1  off, and cuts the power to the motor. The motor stops turning and people are protected. The touch detection circuit unit will be more stable if it uses an independent bridge power supply and is isolated from the motor by an optical coupler. 
         [0039]    When a human touches the panel, the touch of human on the metal part of the panel provides a triggering signal which via base bias circuit, turns Q 3  on. The base bias circuit consists of resistors R 7 , R 6  and R 8 , diode D 4 , and capacitor C 3 . With enough forward voltage from a human Q 3  and Q 2  are both turned on. When Q 2  is on, its collector voltage drops and thus it turns on touch indicator via R 5 , turns off Q 5  via D 16 , and turns off Q 1  via D 15 . If the machine were turning reversely at this moment, Q 5  would be on. But because of the touch voltage, Q 5  is turned off and so is the motor. The other situation is when the machine is in a shredding state. In this case Q 1  would be on to turn the motor in the forward direction. But because of human touch Q 1  is turned off and motor is turned off, too. In either case, the machine is shut off to ensure the safety of human. 
         [0040]    When a human no longer touches the machine&#39;s metal plate, transistor Q 3  turns off because there is no trigger voltage and the machine returns to a normal working state. The working principle of the power on indicating circuit is as below. When the machine is in the shredding or reversal state as selected from the function switch, the power on indicator in on and when the machine is in a stopped state, the indicator is off. The indicator circuit includes an indicator lamp, resistors R 17  and R 16 , and transistor Q 4 . When the machine is in the stop state, the indicator is off because transistor Q 4  is not conducting. As for the reversal state, the emitter junction of transistor Q 4 , diode D 12 , and function switch complete a circuit and the power on indicator is on. While the machine is in the shredding state, the emitter of Q 4 , diode D 13 , and the function switch complete a circuit and the power indicator is on. 
         [0041]    As detailed above, the touch-sensitive paper shredder control system has adopted cascaded circuits. On the machine feed throat there is a conductive touch panel, which is connected to bioelectricity controlled switching circuit, ground switching circuit, control circuit unit, and then shredder mechanical part. All these circuits ensure human safety when human touches the conductive touch panel. The electricity from a human body enables the bioelectricity controlled switching circuit, and then all the connected circuits. The control circuit unit disables the shredder mechanical part and it ensures human safety. Even if the power switch is turned on, the mechanical part of the shredder still won&#39;t work if a human is touching the touch panel. The shredder realizes real time monitoring and the complete control process is both safe and sensitive. The machine performance is stable and reliable. It is easy to operate without human intrusion, can be applied in wide situations, and brings safety assurance. 
         [0042]    Although the present invention has been described by way of example with references to the circuit drawings, it is to be noted herein that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.