Patent Abstract:
Detection apparatus for sensing the operational state of an electric fence and thus an electric fence charger intended to maintain an electric charge on the fence, the invention and the several embodiments thereof find compatibility with known fence chargers whether pulse or continuous in appropriate supply voltage ranges. The detection apparatus of the invention includes a power supply such as a battery to drive a light source such as a light emitting diode which is caused to flash by circuitry carried by the apparatus, the apparatus being clipped to the fence at any location thereof to connect the circuitry to the electrical load on the fence. The light source operates in the event of a failure of the fence charger to perform properly including conditions ranging from complete failure to voltage drops of a predetermined degree or in the event of an open circuit such as can be caused by a separated fence conductor such as a fence wire. The circuitry of the invention includes in the several embodiments thereof control functions based on the operation of an integrated circuit or a transistor in combination with other circuit elements.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to apparatus for detection of the proper function of an electric fence and/or a fence charger intended to maintain charge on the fence. More particularly, the invention relates to a compact and durable sensing device which can be readily mounted to an electric fence for detecting proper operation of the fence and of a charging device intended to maintain a charge on the fence. 
     2. Description of the Prior Art 
     The imposition of an electrical charge on fencing intended to maintain livestock within a specified area has become well known as an alternative or addition to the fencing of livestock or the like by means of conventional fencing intended to retain such stock by virtue of the strength of the fencing rather than by an electrical charge which causes the stock to avoid the fencing. Electric fencing is charged to an appropriate voltage by means of fence charging apparatus which typically apply either continuous or pulsed current to at least one electrical conductor comprising the fencing. Examples of presently available electric fence chargers include the random pulse charging apparatus of Phillips et al which is disclosed in U.S. Pat. No. 4,316,232. McKissack, in U.S. Pat. No. 4,859,869, discloses the use of transformers for applying a continuous charge for energization of an electric fence. Standing, in U.S. Pat. Nos. 4,394,583 and 4,691,084, describe electrical fence chargers as does Shaw et al in U.S. Pat. No. 5,381,298. 
     While electric fence and fence charger combinations usually provide satisfactory operation, certain circumstances can occur whereby a fence can lose its electrical charge either by failure of the fence charger or by damage to the fence itself such as by cutting of the fence or other circumstance which causes an open circuit or “short” condition. While fence charging apparatus may employ visual or audible signals on the apparatus itself to indicate failure or incipient failure of the fence charger, it is not possible to determine these conditions unless personnel are deployed in the area of the fence chargers per se in order to detect such indications. Accordingly, a need has been felt in the art to provide a simple and inexpensive means by which an observer at essentially any location along an electric fence can be informed of the operational state of the electric fence so that a determination can be made in the event of an indicated failure as to whether a failure of the fence charger exists or whether conductive elements of the electric fence have been breached such as by cutting or other separation thus causing an open or short circuit. The art has previously provided monitoring an alarm system used in association with electric fences and fence chargers. Begg, in U.S. Pat. No. 4,523,187, provides one such alarm while Pope et al, in U.S. Pat. No. 4,220,949, provides a fence monitor as does Hamm in U.S. Pat. No. 5,550,530. McCutchan et al, in U.S. Pat. No. 4,297,633, provides remote devices on electric fence sections whereby the devices transmit signals to a central control location. Although the art has provided monitoring and alarm systems such as are represented by the United States patents cited herein, the art continues to feel the need for a compact and inexpensive device which can be placed on a conductive element of an electric fence and which provides a signal, particularly a visual signal in the form of a flashing light, in the event of the inability of a fence charger to maintain an electric charge on the fence or the lack of a charge on the fence such as can occur due to a separation of the electrical conductor of the fence such as by cutting or any separation causing an open or short circuit. The present invention provides in a compact, inexpensive and exceptionally durable apparatus circuitry for sensing the operational state of an electric fence and thus an electric fence charger intended to maintain an electric charge on the fence and in the several embodiments thereof finds compatibility with known fence chargers whether pulse or continuous and in supply voltage ranges of at least 3 to 15 volts DC while being operable within a wide range of temperatures at least from −40° C. to 85° C. 
     SUMMARY OF THE INVENTION 
     The invention provides a compact, inexpensive and exceptionally durable device which can be simply hung at a multiplicity of locations on a conductive portion of an electric fence with immediate electrical contact thus being provided between the fence and circuitry internal of the device, any desired number of the present devices being usable without drawing down voltage. The device of the invention in its several embodiments includes a self-contained power source such as batteries of appropriate size and voltage, a circuit board carrying circuitry elements, a source of illumination disposed within the device and a shock-resistant “plastic” lens which forms at least a part of a housing within which components of the device are disposed and interrelated for appropriate function. 
     Circuitry suitable to an appropriate operation of the invention can take a variety of forms according to the invention with that part of the circuitry causing communication with the electric fence and/or with the fence charger being a clip or mounting arrangement which simply and readily fits over an electrical conductor of the electric fence at any location of the fence, the clip being directly connected electrically to circuitry internal of the device, which circuitry causes operation of the device to provide an appropriate visual signal in the event of the failure of the fence to exhibit an appropriate charge or the failure of the fence charger to appropriately charge the fence. The circuitry can also sense voltage drops below a predetermined value and provides a signal indication of such a voltage drop. A particularly useful circuit defined according to the invention includes an integrated circuit as a part of the circuitry providing control, an output from the integrated circuit causing a transistor to oscillate, oscillation of the transistor controlling a light source carried by the device. It should be understood that the light source is preferably carried within the device in order to prevent damage to the light source. In this preferred circuit, the integrated circuit functions essentially as a timer and further provides means for adopting other functions to the circuitry as desired. For example, self-test functions or the like can be incorporated into the preferred circuitry due to the presence within the circuitry of the integrated circuit comprising the timer function. In a similar vein, auxiliary subsystems can be connected into the circuitry through the integrated circuit to provide other functions without any real modification of the original circuit. 
     The invention further contemplates provision of a control and/or timing function by means of the operation of discrete circuit elements including at least one resistor and at least one transistor which function to control the oscillation of a transistor and thus control of the light source. It is to be understood that the light source in the several embodiments of the invention can take several forms including low voltage DC lamps of the incandescent types as well as light emitting diodes of various description, it being desirable to utilize light emitting diodes having the capability of flashing operation. 
     In the several embodiments of the present circuitry, it is to be noted that the circuitry is not grounded to earth ground and that the electrical reference is at the battery negative terminal. Accordingly, it is thus seen that the impedance of air at the connection of the circuit to the fence conductor is used to prevent lowering of the voltage of the fence charger. 
     The invention in its several embodiments will be seen to be compatible with all types of fence chargers whether pulse or continuous and will accept wide ranges of supply voltages such as from 3 to 15 volts DC. The present devices function within a wide range of temperatures and within a wide range of weather conditions. The devices of the invention further will not drop the voltage of the fence charger, a clip connecting the device to the fence further connecting directly to circuitry within the device and providing input from the fence charger to such circuitry. The clip provides a means for hanging the devices of the invention on a high voltage fence wire without danger of shock. The illumination source of the several devices of the invention only flashes when a fence charger is not working properly or when the fence has an open or short circuit. 
     Accordingly, it is a primary object of the invention to provide a detection apparatus in several embodiments for sensing the operational state of an electric fence and thus an electric fence charger intended to maintain an electric charge on the fence, the detection apparatus being of compact, inexpensive and durable construction and housing circuitry and an illumination source driven by the circuitry, whereby the circuitry detects charge on the electric fence at any location thereof and provides an indication of malfunction when such charge does not exist due either to fence charger failure or the presence of an open circuit or short in the fence. 
     It is another object of the invention to provide compact and inexpensive detection devices capable of sensing the operational state of an electric fence including operation at a reduced voltage below a predetermined level at any location thereof as well as the appropriate function of an electric fence charger, the devices of the invention being usable at multiple locations and simply being clipped to or hung on electrically conductive fence elements of an electric fence at any location of the electric fence to provide an indication of the appropriate functioning of the fence and fence charger without drawing down the voltage imposed on the fence by the charger. 
     It is a further object of the invention to provide detection apparatus for sensing the operational state of an electric fence and thus an electric fence charger whereby an illumination source carried by the apparatus will be caused to flash in the event of a failure of the fence charger or the existence of an open circuit such as can be caused by a separated fence wire. 
     Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an idealized perspective view illustrating a detection device configured according to the invention and including a housing carrying a power source, an illumination source, controlling circuitry and a clip or similar mechanism for hanging the assembly to a portion of an electric fence in order to effectively communicate the condition of the fence and of a fence charger intended to charge the fence to circuitry contained within the apparatus of the invention; 
     FIG. 2 is a circuit diagram illustrating a preferred embodiment of the circuitry of the invention; and, 
     FIG. 3 is a block diagram illustrating an alternative circuit which can be used in the device of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and particularly to FIG. 1, a detector configured according to the invention is seen generally at  10  to comprise a housing  12  formed of a lens element  14  and a back plate  16 . A power source such as batteries  18  is mounted in any convenient fashion to an inner surface of the back plate  16 , the back plate  16  then being mounted either directly to the lens element  14  or to a rear housing element  17  in any convenient fashion. For example, the back plate  16  can be provided with screw threads (not shown) which mate with threads formed about an opening in the element  17  so that the back plate  16  can be conveniently and positively attached to the housing  12 . The lens element  14  and the rear housing element  17  can be permanently attached to each other or can be integrally formed, it only being necessary for the lens element  14  to be formed of a clear, “plastic” material having sufficient durability to withstand the rigors of the outdoor environment within which the detector  10  is intended to function. 
     Interiorly of the housing  12  and in a position to direct light through the lens element  14  is disposed a light source  22 , the operation of which is controlled by circuitry  26  mounted on a circuit board  20 , the circuit board  20  being mounted in any convenient fashion within the interior of the housing  12 . It is to be understood that reflector elements can be provided within the interior of the housing in order to efficiently reflect light through the lens element  14 . Further, the lens element  14  can preferably be formed of a material having a color tint which would cause illumination of the light source  22 , especially flashing illumination, to be more readily observed. In practice, an amber light emitting diode coupled with yellow reflective materials or yellow-tinted materials is preferred. 
     A connector  24  is mounted to the housing  12  and has conductive elements (not shown) which extend into electrical contact with the circuitry  26  mounted on the circuit board  20 . Electrical connection between this connector  24  and the circuitry  26  is illustrated in FIGS. 2 and 3. 
     The connector  24  not only provides a mechanism by which the detector  10  can be mounted to, that is, “hung” onto an electrically conductive fence element (not shown in FIG.  1 ), the connector  24  also couples the circuitry  26  of the detector  10  to an electrically conductive fence element and therefore a fence charger (shown in FIGS. 2 and 3) without providing a shock risk. In particular, the circuitry  26  of the detector  10  is not grounded to earth ground, the electrical reference of the detector  10  thus being at the negative terminal of the battery or batteries  18 . Accordingly, the impedance of the air in the vicinity of the hanging connection acts to prevent lowering of the voltage of the fence charger. This grounding of the detector  10  to the negative terminal of the battery  18  rather than to earth ground is of very substantial importance in that any number of the detectors  10  can be hung onto an electric fence without drawing down voltage on the fence, thereby allowing detection of the operational state of the fence charger  30  and of the fence at any desired number of locations by any desired number of the detectors  10  at any given time. Further, a voltage drop on the fence of a predetermined degree, such as 1000 volts, can be detected by the detector  10  with a resulting visual indication being provided by said detector. 
     A consideration of the structure of the detector  10  as seen in FIG. 1 reveals alternatives as to the construction thereof. For example, a light emitting diode can be utilized as the light source  22  and particularly a light emitting diode capable of flashing operation. While a DC-driven light source such as an incandescent bulb can be utilized, power drain on the batteries  18  will be substantially reduced through use of a light emitting diode as the light source  22 . The light source  22  is connected into the circuitry  26  in a manner as is disclosed in the discussion of FIGS. 2 and 3 as provided hereinafter. It is further to be understood that the batteries  18  could take the form of disc-type batteries which could be mounted within circular depressions formed in the back plate  16 , for example. Such batteries are usually slotted to allow removal from circular depressions which are threaded to mate with threads formed on the batteries themselves. 
     Referring now to FIG. 2, a preferred circuit is seen as comprising the circuit  26 . The circuit  26  of FIG. 2 includes a light emitting diode  48  having flashing capability as the light source  22 . The batteries  18  of FIG. 1 are seen to also be a part of the circuit  26  and are described as battery  55  in the circuitry of FIG.  2 . 
     FIG. 2 illustrates an electrically conductive fence element  28  in schematic fashion, such a fence element  28  being typically formed of wire and being that portion of an electric fence on which the connector  24  is hung in order to mount the detector  10  to the electric fence. The fence element  28  is shown in a schematic fashion to be connected to a fence charger  30  which may essentially comprise a charger of any known type whether continuous or pulse and within the usual voltage ranges of such chargers, that is, having a supply voltage of between 3 and 15 volts DC. When the fence charger  30  is operable to charge the fence element  28  on which the detector  10  is mounted through the connector  24 , resistors  32  and  34  sense the voltage provided by the fence charger  30 . The fence charger  30  causes a small current to be fed from junction  33  of the resistors  32  and  34 , this current flowing to the base of transistor  36  and thereby turning the transistor  36  on. Activation of the transistor  36  charges capacitor  38  with a resultant activation of the transistor  40 . When the transistor  40  is thus activated or caused to be in an “on” condition, capacitor  42  is discharged through the transistor  40 , thus causing output of timer  44  to go “high”. When the output of the timer  44  goes high, transistor  46  turns off and the light source in the form of the light emitting diode  48  is also “off”. Accordingly, in the condition whereby the fence charger  30  is properly operating and causing a charge to be imposed upon the fence element  28 , the detector  10  senses the charge imposed upon the fence element  28  and thus senses that the fence charger  30  is performing properly and that a charge exists as is expected on the fence element  28 . In this condition, the light source, that is, the light emitting diode  48 , is inoperative. 
     In the condition whereby the fence charger is in the “off” condition for any reason such as by actual failure, the charge in the capacitor  38  slowly drops to zero volts, thus preventing the capacitor  42  from being discharged. It is thus seen that the capacitor  42  charges through resistor  50  and resistor  52 , a network  54  being essentially formed by the resistors  50 ,  52  and the capacitor  42 . Once the capacitor  42  has charged up to approximately one-third of the supply voltage, the output of the timer  44  will go “low” and the capacitor  42  will slowly discharge through resistor  52 . When the capacitor  42  is discharged below approximately one-third of the supply voltage, the output of the timer  44  will go “high” and the capacitor  42  will be recharged again. This charge/recharge cycle of the capacitor  42  causes the timer  44  to oscillate the transistor  46  since the gate of the transistor  46  is controlled by the output of the timer  44 . The rate of oscillation is determined by the product of the resistor  50 , the resistor  52  and the capacitor  42  which form the network  54  as indicated previously. The light source, that is, the light emitting diode  48 , is controlled by the oscillation of the transistor  46 . Accordingly, failure of the fence charger to maintain the appropriate charge on the fence element  28  causes the light emitting diode  48  to flash and thus provide a visual failure indication. The detector  10  thus only provides a visual failure indication when the fence charger  30  is not working properly or when the electric fence has an open or short circuit such as can be caused by cutting of the fence or by a separation occurring due to the other causes. 
     Referring again to FIG. 2, it is seen that the timer  44  takes the form of an integrated circuit, the output of which at 3 controlling the gate of the transistor  46  to thereby oscillate the transistor  46 . The integrated circuit comprising the timer  44  provides flexibility to the circuit  26  when considered relative to discrete element circuitry since options can be connected to the circuit  26  through the integrated circuit comprising the timer  44  with minimum or no modification to the circuit  26 . Such modifications can include circuit subsystems providing other alarm indicators, self-test functions, etc. The integrated circuit of the circuit  26 , that is, the timer  44 , can be provided with GND at 1, a TRIGGER function at 2, an OUTPUT function at 3, a RESET function at 4, a THRESHOLD function at 6, a DISCHARGE function at 7 and a VCC function at 8. A control function could be provided at a position such as the 5 position (not shown). The circuit  26  can otherwise be provided with conventional discrete circuit elements. However, it is to be understood that the resistors can preferably be carbon film of ⅛ watt or better while capacitors are all 15 V. The light emitting diode  48  must have high MCD. Further, all transistors must have a gain of a minimum of 200 while the integrated circuit taking the form of the timer  44  is preferably of the CMOS type. The resistor  50  can be 1 M or 2 M and potted for flash rate setting. All electrical components can be surface mounted or through-hole mounted on the circuit board  20 . The detector  10  functions maximally with all types of fence chargers and especially where pulses are less than 0.5 Hz or once every two seconds. The flash rate of the detector  10  is approximately once every three seconds. It is further to be noted that the transistors  36  and  40  are NPN type transistors while the transistor  46  is a PNP transistor. The capacitors are typically 1 microfarad, 15 V electrolytic devices. The integrated circuit, that is, the timer  44 , is chosen to be a TC 555 CMOS timer. 
     Referring now to FIG. 3, an alternative circuit is seen at  57  and comprises a number of discrete circuitry elements which are present in the circuit  26  of FIG. 2, these elements functioning in essentially the same manner. However, the timer  44  has a transistor  56  and a resistor  58  substituted therefor. In operation, the resistors  32  and  34  sense voltage when the fence charger  30  is operating appropriately, the fence charger  30  feeding a small current from the junction  33  of the resistors  32 ,  34 , this current flowing to the base of the transistor  36  with the result that the transistor  36  is turned on. The capacitor  38  is charged through the transistor  36  and turns on the transistor  40 . When the transistor  40  is in the “on” condition, the capacitor  42  is discharged through the transistor  40  causing the transistor  56  to turn off, the transistor  46  also being caused to turn off so that the light emitting diode  48  is also off. When the fence charger  30  is not functioning, the charge in the capacitor  38  slowly drops to zero volts thus preventing the capacitor  42  from being discharged. As with the circuit  26  of FIG. 2, the capacitor  42  charges through the resistors  50  and  52 . When the capacitor  42  has charged up to a value of approximately 0.7 V, which is the saturation point of most transistors, and thus causing the transistor  56  to turn on, the transistor  56  simultaneously turns the transistor  46  on, thus causing the light emitting diode  48  to flash. The flash rate of the light emitting diode  48  is determined by the inherent rate of the LED itself. 
     As is the case with the circuit  26  of FIG. 2, the circuit  57  is not grounded to earth ground, the electrical reference being at the negative terminal of the battery  55 . Accordingly, the impedance of the air functions to prevent lowering of the voltage of the fence charger  30 . The transistor  46  of the circuit  57  of FIG. 3, is an NPN transistor rather than the PNP transistor of the circuit  26  of FIG.  2 . 
     While the detector  10  including the circuits  26  and  57  have been described as explicit embodiments of the inventive concept disclosed herein, it is to be understood that the conformation of the detector  10  and particular circuit elements can be configured other than as explicitly shown and described herein without departing from the scope of the invention as defined by the appended claims.

Technology Classification (CPC): 6