Abstract:
The voltage detection stick comprises an elongate and hollow casing member that has a front and a back. A tip is rotatably and removably attached to the front of the casing member and a sensor is disposed within the casing member for sensing the presence of a voltage when the sensor is positioned adjacent an electrically conductive member. The casing member has an indicator and an integrated circuit entirely disposed within the casing member for receiving a signal from the sensor and transmitting the signal to the indicator. A power source is disposed within the casing member for powering the sensor, the integrated circuit and the indicator.

Description:
PRIOR APPLICATION 
     This is a continuation-in-part application of U.S. patent application Ser. No. 09/183,006, filed Oct. 29, 1998. 
    
    
     TECHNICAL FIELD 
     The invention relates to a voltage detection stick for non-contacting detection of voltage. 
     BACKGROUND INFORMATION AND SUMMARY OF THE INVENTION 
     Electrical voltage sticks of a contacting or non-contacting type are known in the art. The prior art voltage sticks sometimes include a metal casing that may be coated with an electrically insulative material. One drawback of the prior art voltage sticks is that a scratch in the nonconducting coating on the metal casing may cause a harmful shock if a naked wire is inadvertently contacted. 
     Another drawback of the prior art voltage sticks is that they sometimes have sensors and integrated circuits disposed within a probe tip that is bonded to the stick. This often makes the voltage stick unnecessarily fragile and relatively difficult to repair. 
     The voltage stick of the present invention comprises an elongate and hollow casing member that has a front and a back. A rotatable and removable front tip is attached to the front of the casing member and a sensor is disposed within the casing member for sensing the presence of a voltage when the sensor is positioned adjacent an electrically conductive member. The casing member has an indicator and an integrated circuit entirely disposed within the casing member for better protection. The integrated circuit is adapted to receive a signal from the sensor and transmitting the signal to the indicator. A power source is disposed within the casing member for powering the sensor, the integrated circuit and the indicator. Because the tip is rotatable and removable, an operator may access the inside of the casing member by carefully removing the removable tip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional side view of a casing of the volt detection stick of the present invention; 
     FIG. 2 is a cross-sectional side view of a probe tip of the volt detection stick of the present invention; 
     FIG. 3 is a cross-sectional side view of a battery cap of the volt detection stick of the present invention; and 
     FIG. 4 is a schematic view of the circuit board of the volt detection stick of the present invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 1-4, the voltage probe  10  of the present invention comprises a casing  12 , a battery cap  14  and a rotatable and removable probe tip  16  so that the battery cap  14  may be attached to a rear end  18  of the casing  12  and the probe tip  16  may be removably attached to an opposite front end  20  of the casing  12 . The battery cap  14  may be screwed onto the casing  12  and removed from the casing  12  by unscrewing the cap  14 . 
     The casing  12  is preferably an elongate hollow member having a channel  22  extending therethrough. The hollow member is preferably made of a polymeric material such as polypropylene. Polypropylene provides good electrical insulation and is durable. A rear section  24  of the channel  22  has a first inner diameter d 1  and a middle section  26  has a second inner diameter d 2  and a front section  28  has a third inner diameter d 3  wherein the first diameter d 1  is greater than the second diameter d 2  that in turn is greater than the third diameter d 3 . The middle section  26  has a length that is dimensioned to hold two AAA sized batteries and the second inner diameter d 2  is dimensioned to receive and hold such batteries. 
     A spring biased pocket clip  30  is, preferably, integrally formed with a side wall  32  of the casing  12  adjacent the rear end  18  thereof. The clip  30  has a pocket holder  34  and a cap holder  36 . The pocket holder  34  extends in a direction that is opposite to the cap holder  36 . The cap holder  36  has an enlarged outer portion  38  including a perpendicular flat clamp surface  40 . Similarly, the pocket holder  34  has an enlarged tip  42  that bears against the outer surface of the casing  12 . 
     The rear end  18  has a circumferential protrusion  44  that extends radially outwardly all around the rear end  18 . Similarly, the front end  20  has a circumferential protrusion  46  that extends radially outwardly all around the front end  20 . A helical groove  47  is defined in an inner wall  49  of the rear end  18 . The helical groove  47  extends at an obtuse angle relative to the longitudinal axis of the casing  12 . A metal sleeve  19  is disposed in the rear end  18 . A groove  21  defined inside the casing  12  extends from the rear end  18  along an inner wall of the middle section  26  to the front section  28 . A conductive member such as a metal member  23 , which could be made of copper, is disposed in the groove  21  so that there is an electrical contact between the metal sleeve  19  and a circuit board  25  disposed in the front section  28  of the casing  12 . The circuit board  25  is attached to the casing  12 . The metal sleeve  19  connects the printed circuit board, the insulated copper member and the batteries. 
     The tip  16  has a narrow tip portion  48  and conical shaped mid-section  50  and a cylindrical rear portion  52 . The tip  16  is rotatable about the casing  12  and may be removed by, for example, snapping it lose with a screw driver. The removable tip  16  is particularly useful if it is desirable to remove or repair a component disposed inside the casing  12 . For example, the operator may carefully remove the tip  16  by carefully using a tool such as a screw driver to snap off the tip from the casing  12 . The tip  16  is also rotatable. The tip  16  is substantially hollow and the tip portion  48  is closed while the rear portion  52  is open. A circumferential groove  54  is defined in an inner wall  56  of the tip adjacent the rear portion  50 . The inner wall  56  has an inner diameter that is adapted to snugly fit over the front end  20  so that the circumferential protrusion  46  may snap into the circumferential groove  54  when the front portion  20  is fully inserted into the tip  16 . The rear portion  52  has a circumferential protrusion  55  that extends radially outwardly. The protrusion  55  provides extra safety and prevent the hand of the operator from slipping forwardly into the area where the voltage is measured. It is to be noted that the tip  16  is not glued to the casing  12  but is only firmly snapped onto the front portion  20 . Preferably, the tip  16  is made of a polymeric material such as sicoamide-6 or any other suitable material. The tip  16  has the conical shape to permit easy probing into U.S. style sockets. 
     The battery cap  14  has an open end  58  and a closed bottom end  60 . The cap  14  has an inner wall  62  including a slanted protrusion  64  that extends at an obtuse angle from the bottom end  60 . An outer wall  66  includes a flange  68  at an outer end of the cap  14 . The open end  58  has an inner diameter that is adapted to snugly receive the rear end  18  so that the flange  68  may snap in behind the clamp surface  40  and the protrusion  44  bears against the inner wall  62 . In this way, the flange  68  is tightly held between the clamp surface  40  and a flat surface  41  of the side wall  32 . A special feature is that the slanted protrusion  64  may engage the helical cavity  47  when the cap  14  is twisted onto the rear end  18  until the cap  14  is fully fastened to the casing  12 . The cap  14  may be removed by turning the cap  14  in the opposite rotational direction so that the protrusion  64  is moved out of the helical cavity  47  and the cap  14  is disengaged from the casing  12 . A helical spring member  13  is disposed and attached within the cap  14 . The spring member  13  extends inwardly so that it comes into contact with a battery when the cap is screwed onto the casing  12 . 
     As mentioned above, the printed circuit board  25  is, preferably, entirely mounted to and disposed inside the front section  28  to protect the board  25  from external damage and to reduce the weight of the components disposed within the tip  16 . Preferably, the circuit board  25  is made of a polymeric material such as a glass-fiber reinforced epoxy resin. Other suitable materials may also be used. As best shown in FIG. 4, the circuit board  25  has an antenna  70  attached thereto that may be made of 22 swg tinned copper wire when the voltage to be detected is in the range of about 110 volts. When the voltage to be detected is about 220 volts then a CR25 carbon resistor (¼ watts) is preferably used. The antenna  70  is the only component that extends into the tip  16  for increased sensitivity. This makes the tip  16  very light in weight and easy to precisely position next to voltage sources. 
     An indicator or light source  72  such as a surface mounted light emitting diode (led) or a 3 millimeter 700 mcd red led is also attached to the circuit board  25  and may be used to indicate that a voltage has been detected. For example, the led may be made by Citizen or any other suitable manufacturer. Light emitting diodes are the preferred type of light source because they provide a high intensity at a relatively low current. The light source  72  provides sufficient illumination so that the light emitted from the light source  72  may be seen through the tip  16 . 
     An integrated circuit  76  is attached to the circuit board  25 . In the preferred embodiment, the integrated circuit  76  is a 74HC14 integrated circuit. It is to be understood that any suitable integrated circuit may be used. 
     A sensor  74  is disposed on the in ra circuit  76 . In the preferred embodiment, a C&#39;Mos I.C. Logic gate sensor is used. The sensor  74  may be adapted to detect a voltage between a live and a neutral two core cable. Preferably, it is designed to detect voltage ranging between about 90-130 V AC on 60 Hz alternating currents (AC). This means that the sensor may detect measurements below 90 V and measurements above 130 V but the volt stick may not be able to distinguish between the live and the neutral cord. The sensor  74  is extremely sensitive and does not require much current to activate the indicator  72 . To ensure that the sensor  74  has a more distinct sensitivity level, the sensor  74  may be connected to a resistor such as a resistor R 1  of about 300 Mohm for the U.S. version. The European version of the resistor R 1  is preferably about 155 Mohm. When the signal reaches about 1-1.5 volt, the integrated circuit may be switched over via a schmittrigger switch circuit. 
     The integrated circuit  76  may also include filters  77 ,  79  that may be used to remove static electricity so that the voltage probe is only detecting alternating voltage. For example, the filter  77  may be set to prevent undesirable activation of the volt stick when the frequency is below about 20 Hertz (Hz), more preferably below 10 Hz, or when only conventional direct current is flowing through the wires. By not removing the static electricity, the indicator  72  may turn on as soon as any static electricity is detected by the antenna  70  such as by moving the volt stick through static fields in the air. The filter  79  may be set to require at least three frequency cycles (50-60 Hz) to trigger an activation signal in the volt stick. More preferably, the filter  79  may be set to require at least five frequency cycles. This prevents any unnecessary blinking of the indicator  72  due to incoming transient signals. The filter  79  may also include a signal extending device  81  so that the indicator  72  is lit longer than the signal detected. The device  81  ensures that even very short signals that are detected are clearly indicated in the indicator  72 . 
     An audible sound source, such as a buzzer  83  may be in operative engagement with the circuit board  25  so that the user will hear a clear sound when the buzzer  83  is activated. The buzzer  83  may be attached to an underside of the circuit board  25 . Preferably, the buzzer  83  is activated as the same time as the indicator  72  is activated. 
     While the present invention has been described in accordance with preferred compositions and embodiments, it is to be understood that certain substitutions and alterations may be made thereto without departing from the spirit and scope of the following claims.