US 3440439 A
Description (OCR text may contain errors)
w. M.N'El.l.ls 3,440,439
TIME CONTROL FENCE CHARGER y April 2z, l1969 Filed Maron 16. 1966 United StatesI Patent O 3,440,439 TIME CONTROL FENCE CHARGER William M. Nellis, St. Paul, Minn., assigner to International Electric Fence Co., Inc., Albert Lea, Minn., a corporation of Washington Filed Mar. 16, 1966, Ser. No. 534,708 Int. Cl. H01h 51/34 U.S. Cl. 307--132 3 Claims ABSTRACT OF THE DISCLOSURE A time control fence charger circuit including a DC supply means and an SCR for delivering pulses through a transformer to a fence. The SCR has a control circuit which includes a four-layer diode coupled to the gate thereof. A capacitor is coupled across the input circuit and is charged and discharged according to the breakdown loads of the four-layer diode thereby delivering the pulse input which is coupled thereto.
This invention relates to a time control fence charger for applying a periodic energy impulse to an electrical `fence and in particular relates to a fence charger employing electronic switching devices for improving the eiciency and safety of an electrically charged fence.
In applying an electrical charge to a fence for conning animals within aselected areas, it has Ibeen found desirable to convert a standard AC electrical source into energy pulses which may then `be used as the charging signal. Energy pulses of short duration and large magnitude have the advantage of ybeing more effective in repelling animals after contacting the charged fence. Also, discrete pulses have the advantage of being safer in application both to livestock and to humans which may contact the fence. A person contacting such a fence, for instance, may receive an electrical shock for only several milliseconds, whereupon the individuals reflexes will cause the contact with the fence to be broken prior to the application of successive pulses. ln contrast, a continuous charge applied to such a fence may result in an individual or livestock contacting the fence for an eX- tended duration and receiving a continuous electrical shock thereby.
Various `devices have been developed for applying discrete energy pulses to a fence and thereby avoiding the disadvantages associated with the application of a continuous electrical signal. For instance, a motor-driven switch may be used for -alternately connecting and disconnecting an electrical power source to fence terminals in such a manner as to produce a pulse-like energization of the fence. Also, a tilting mercury switch or an oscillating steel ball may be used to perform a similar function. However, all these devices have the principal disadvantage of requiring mechanically moving parts which are subject to wear due to continued use and subject to deterioration due to adverse weather conditions.
To supplant the mechanically operated oscillation type devices, electronic fence chargers have been developed for applying a pulse energy signal from a standard AC source to the fence in such a manner as to avoid many of the disadvantages associated with the mechanical systems. .Mechanical systems, however, have had the advantage of -being capable of incorporating safety techniques for the purpose of assuring that a continuous energy signal is not applied to the fence. Heretofore, such safety techniques have not been available in electronic type fence chargers.
In addition, electronic fence charging devices currently available have generally used four-layer diodes for directly controlling the output energy applied to the associ- 43,440,439 Patented Apr. 22, 1969 ICC ated fence. Such devices have not been entirely satisfactory in that the current capable of being controlled by a four-layer diode is substantially less than would otherwise be `desirable for use directly at the fence circuit. Limiting resistors have had to be employed in such circuits to consume power which would otherwise be destructive of the diode. In addition to consuming power which could otherwise be available at the fence circuit, such resistors have tended to increase the time constant associated with the dicharge of the time control capacitor thereby lengthening the duration of the energy signal applied to the fence.
Accordingly, it is a principal object of this invention to provide a fence charger having an improved charging circuit for applying discrete electrical impulses to the associated fence.
It is another object of this invention to provide a fence charger having electronic means for applying electrical impulses to an associated fence and having a safety electronic switching circuit which prevents the application of a continuous electrical signal to the fence.
It is also an object of this invention to provide a fencecharger utilizing electronic switching devices having a low discharge time constant and a high output current.
It is a further object of this invention to provide a fence charging network using a four-layer diode which is responsive to a time charging capacitor for controlling the gate of a silicon controlled rectifier and for utilizing the output of the rectifier for energizing the associated fence.
It is an additional object of this invention to provide a fence charger having electronic switching devices for converting a continuous electrical signal into discrete energy pulses and having a control circuit which functions substantially independently of an output charging network.
These and other objects, features and advantages of the present invention will be understood from the following description and the associated drawing wherein reference numerals are utilized in designating an illustrative embodiment.
ON THE DRAWING The single ligure is a schematic diagram of an electronic network used in the fence charging device of this invention.
AS SHOWN ON THE DRAWING The advantages of this invention are particularly adaptable to an illustrative charging network 10. The network 10 is utilized to receive a standard AC signal such as a stan-dard l2() volt, 60 cycle signal and to convert that signal into discrete energy pulses and for applying those pulses to an electrical fence.
The electronic network 10 consists essentially of four circuits which are cooperable for performing the indicated objects of this invention. In particular, a feed circuit 11 is employed to receive a standard AC signal and to convert that signal into a unidirectional or half-wave rectified waveform. A [control circuit 12 cooperates with the feed circuit 11 for utilizing the unidirectional energy signal to develop discrete pulses through an electronic switching device. An input circuit 13 cooperates with the control circuit 12 and with the feed circuit 11 for developing a discrete pulse signal which is separated from but which is in response to the discrete pulse signals produced by the control circuit 12. Finally, the output circuit 14 utilizes the discrete pulse energy developed by the input circuit 13 for energizing an associated electrical fence.
The feed circuit 11 has input terminals 15 and 16 for receiving a standard AC voltage signal and for applying the signal to the remainder of the network to ultimately energize the electrical fence at the output cincuit 14. Feed resistors 17 and 18 are connected in series with the respective terminals 15 and 16 and Lmay represent` either limiting resistors for fixing the current and voltage levels to be made available to the network or fuses for interrupting the current applied to the charging network in a well understood manner.
' A diode 19 is connected in series with the resistor 17 and is used to provide half-wave rectification for the standard AC signal as applied at the terminals and 16.
A capacitance means or capacitor completes the feed network 11 and provides a conduction path between the resistor 18 and the collector 21 of the diode 19. Hence, the rectified AC signal available at the collector 21 will tend to charge the capacitor 20 indefinitely through the completed feed circuit consisting of the resistor 17, the diode 19, the capacitor 20` and the resistor 18.
The capacitor 20, however, will not in fact charge indefinitely due to a discharging circuit which is made available in the form of the control circuit 12. The capacitor 20 forms a common branch between the feed circuit 11 and the control circuit 12 and has a first terminal 22 connected to an electronic switching means or a four-layer diode 23. As is well understood, the four-layer diode 23 may be either a PNPN or an NPNP diode having the characteristic of being placed in a conducting state due to a given voltage level applied across its terminals and of being placed in a nonconducting state due to a reduction of current through the diode to a iminimurn threshold level.
The dio'de 23 has an input terminal which is identical with the terminal 22 of the capacitor 20 and an output terminal 24 which is connected to a resistor 25. The resistor 25 is used to control the voltage level applied to the input circuit 13. The resistor 25 is connected to a resistor 26 which is used to limit the current level within the control circuit 12. The resistor 26 has a terminal 27 which is connected directly to the terminal 27a of the capacitor 20 for completing the control circuit 12.
In order for the four-layer diode 23 to function properly, current within the control circuit 12 must be limited to a value determined by the ratings of the diode. This limitationv on the circuit current is accomplished through the combination of the resistors 25 and 26, and the need for such resistors is one of the factors which makes the use of the diode 23 not entirely desirable for `directly controlling the current within the output circuit 14. However, as shown in the charging network l10, the control circuit 12 is so separated from the output circuit 14 such that current within the circuit 14 is not dependent upon the magnitude of current within the control circuit 12.
The input circuit 13 may be referred to as ia controlled circuit having a current which is controlled, not in magnitude, but in time, by current within the control circuit 12. The input circuit 13 includes a unidirectional electronic switching means or a silicon controlled rectifier 28 which has a first terminal 29 connected to the terminal 22 of the capacitor 20 and a second terminal 30 connected to a primary winding 31 of an energizing means or coupling transformer 32. The winding 31 is in series with the silicon controlled rectifier 28 and has a terminal 33 which is connected directly to the terminal 27a of the capacitor 20.
The silicon controlled rectifier 28 has its gating means or gate terminal 34 connected to a junction point 35a which is intermediate the resistors 25 and 26 of the control circuit 12. As is well understood, when the gate 34 of the silicon controlled rectifier 28 attains a threshold voltage level, the rectifier 28 will be retained in a conducting state for all voltages at the gate 34, provide'd such voltages do not fall -below the threshold value. Also, since the input circuit 13 does not require limiting resistors to limit the magnitude of current therein, the current within the input circuit may be allowed to approach a sizeable magnitude in comparison to the current used within. the control circuit 12. In this way, more energy is made avail- 4 able at the transformer 32 for energizing the output circuit 14.
The output circuit 14 includes a secondary winding 35 of the transformer 32 which is connected at a terminal 36 to a fence 37. The other terminal 38 of the winding 35 is connected to ground as at the point 39. Also, a permeable core 40 of the transformer 32 is grounded as at the point 39. The coupling transformer 32 may have a secondary-to-primary winding ratio of approximately 60:1, indicating a step-up in voltage from the primary winding 31 to the secondary Winding 35 by a factor of `60. The voltage received at the secondary winding 35 may be in the order of 3,000 volts or higher.
The secondary or output circuit 14 is completed when an animal engages the electrical fence 37 while standing on ground, such animal being represented by a resistance 41 which may have a value ranging from 10,000 to 100,- 000 ohms.
A signal device such as a discharge glow tube 42 may be connected in series combination with a high resistance 43 and the combination then placed in parallel with the secondary winding 35. The glow tube 42 may be of the neon type, for instance, thereby consuming a minimum of power and giving a satisfactory signal whenever the secondary winding 35 is energized.
In operation, an AC, 60 cycle signal applied at the terminals 15 and 16, is rectified by the diode .19 and used to charge the timing capacitor 20. The charge on the capacitor 20 will continuously increase due to the lack of a discharge path. Discharge cannot be accomplished through the silicon controlled rectifier 28' or through the four-layer diode 23, as both these devices are in a nonconducting state initially. However, as the charge on the capacitor 20 increases, a threshold voltage level will be reached at which the four-layer diode 23 becomes conductive.
When the diode 23 conducts, a voltage appears across the resistors 25 and 26 and at the junction point '35, and hence, the gate 34 is placed at an adequate voltage level for placing the silicon controlled rectifier 28 in a conducting state. With the rectifier 28 in a conducting state, the capacitor 20 then is provided with an immediate discharge path through the rectifier 28 and the primary winding 31 back to the terminal 27a of the capacitor. Therefore, through the use of the control circuit 12, a high current signal can be applied to the primary winding 31 which has an extremely short time constant. This is because the winding 31 and the silicon controlled rectifier offer only small resistance to the input circuit y13, and hence the capacitor discharge will be substantially instantaneous.
In addition to the improved magnitude and short duration of the energy signal -delivered to the primary winding 31 and hence to the electrical fence 37, the use of the control circuit 12 introduces a safety device for preventing the application of a continuous energy signal to the fence 37. In particular, should the four-layer diode 23 fail such that a short-circuit path is effectively provided between the terminal 22 of the capacitor 20 and the Iresistor 25, the input circuit 13 Will be maintained in a nonconducting state and a continuous energy signal will not be applied to the output circuit 14. With the diode 23 short-circuited, the capacitor 20 will not develop a sufficient voltage level for energizing the gate 31 of the silicon controlled rectifier 28. Accordingly, the fence charger of this invention incorporates safety features not currently available in fence charger networks.
It will be understood that the fence charging network 10 is constructed entirely of available solid state components such that the entire network may be encapsulated in an epoxy resin or the like for making the entire network more durable from both shock and adverse weather conditions. Such encapsulation of the network has been made possible due to the `development of the safety features of this invention without the use of mechanical or moving components.
It will also -be understood that various modifications and combinations of the features disclosed herein may be accomplished by those versed in the art, but I desire to claim all such modifications and combinations as properly come within the spirit and scope of my invention.
I claim as my invention:
1. A time control fence charger comprising:
a circuit including an electronic switching means having three terminals, said switching means being connected by two of said terminals to control the flow of unidirectional current in said circuit, said switching means including gating means for regulating the flow of current between said first and second terminals, and connected to the third of said terminals, energizing means for energizing a fence, said energizing means being responsive to current in said circuit,
capacitance means for developing a time-increasing voltage thereon, said capacitance means being connected to sai-d circuit at such point as to enable the discharge thereof to flow through said switching means, and n -a four-layer diode coupled to said third terminal for applying a predetermined gating voltage present on said capacitance means thereto.
2. A time control fence charger comprising:
an input circuit, said input circuit including:
(1) a primary winding of said transformer, (2) an elcetronic unidirectional switching means, said switching means having a gating means and first and second terminals, said gating means connected for regulating the ow of current through said primary winding of said transformer,
an output circuit coupled by said transformer to said input circuit, said output circuit including a secondary winding of said transformer and fence terminals connected thereto for being energized by said secondary winding, and
a control circuit, connected to said gating means, for
applying a periodic control signal thereto, said control signal rendering said unidirectional switching means conductive, and said control circuit connected for applying said periodic control signal to one of said first and second terminals of the switching means,
said control circuit having a capacitance means and means for charging the same, a four-layer diode connected in parallel with said capacitance means and being rendere-d conductive by a predetermined voltage developed at said capacitance means, said fourlayer diode being connected to the gating means for applying the predetermined voltage on said capacitance means thereto.
3. A time control fence charging network comprising:
a feed circuit, said feed circuit including means for developing a unidirectional current from a standard AC source,
an input circuit, said input circuit having a unidirectional electronic switching means and a primary winding of a coupling transformer connected at a point to enable the current within said primary Winding to be controlled by said switching means,
a control circuit, said control circuit having capacitance means for being charged unidirectionally by said feed circuit and having a four-layer diode means for substantially simultaneously applying a control signal to said unidirectional switching means and for discharging said capacitance means in response to a predetermined voltage present on said capacitance means, and
an output circuit, said output circuit having a secondary winding coupled to the primary Winding of said input circuit and having means for energizing a fence in response to current in said secondary winding.
References Cited UNITED STATES PATENTS 3,218,511 11/1965 Rosenbaum 323-364 XR 3,275,855 9/1966 Wright 323-22 X 3,324,381 6/1967 Bock et al 323-22 X 3,103,618 9/1963 Slater. 3,192,462 6/1965 James.
3,296,419 1/1967 Sels 307-252 X 3,302,128 1/1967 Schoemehl et al. 331-111 X 3,320,435 5/ 1967 Watters 307-252 3,325,717 6/1967 Nellis 307-132 X ROBERT K. SCHAEFER, Primary Examiner.
T. B. JOIKE, Assistant Examiner.
U.S. Cl. X.R.