U.S. patent number 3,717,802 [Application Number 05/246,686] was granted by the patent office on 1973-02-20 for solid state electronic bird repellent system.
This patent grant is currently assigned to Serex, Inc.. Invention is credited to Arthur L. Plevy, Vincent Wepprecht.
United States Patent |
3,717,802 |
Plevy , et al. |
February 20, 1973 |
SOLID STATE ELECTRONIC BIRD REPELLENT SYSTEM
Abstract
An electronic bird repellent system utilizes a "sandwich like"
transmission line assembly for conducting high voltage about an
area to be protected. The transmission line comprises a top and
bottom conductive foil separated by a suitable insulating member,
for providing support and separation. The system includes high
voltage protection circuitry to prevent prolonged shock hazard and
voltage monitoring circuitry to provide an indication determinative
of an open circuit in said transmission line.
Inventors: |
Plevy; Arthur L. (East
Brunswick, NJ), Wepprecht; Vincent (Greenbrook, NJ) |
Assignee: |
Serex, Inc. (Garwood,
NJ)
|
Family
ID: |
22931773 |
Appl.
No.: |
05/246,686 |
Filed: |
April 24, 1972 |
Current U.S.
Class: |
361/232; 256/10;
174/117FF; 361/235 |
Current CPC
Class: |
A01M
29/26 (20130101); H05C 1/02 (20130101) |
Current International
Class: |
A01M
29/00 (20060101); H05C 1/02 (20060101); H05C
1/00 (20060101); H05c 001/02 () |
Field of
Search: |
;174/706,72C,117F,117FF,117A ;339/28 ;317/262S,31 ;321/18,19,4
;256/10 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller; J. D.
Assistant Examiner: Moose, Jr.; Harry E.
Claims
We claim:
1. In a system for controlling bird nuisance of the type including
a source of high voltage for shocking a bird attempting to enter an
area to be protected, the combination therewith of apparatus for
providing a transmission path for said high voltage enabling
protection of said area comprising:
a. a central solid insulator member having a top and bottom surface
and side surfaces;
b. a conductive foil ground plane member secured to said bottom
surface of said insulator member;
c. a conductive high voltage member secured to said top surface of
said insulator member to thereby form a composite "sandwich like"
configuration;
d. connecting means coupled to at least one of said conductive
members adapted to coact with said source of high voltage.
2. The combination according to claim 1 wherein said conductive
high voltage member comprises a conductive mesh.
3. The combination according to claim 1 wherein said conductive
high voltage member comprises a conductive foil of a thin strip
configuration.
4. The combination according to claim 1 further comprising:
a. a plastic veneer covering at least one side surface of said
composite member to provide an overall aesthetic appearance to an
observer viewing said area to be protected.
5. The apparatus according to claim 1 wherein said connecting means
comprises a conductive tab including a female fastener for coacting
with a male counterpart.
6. A system for controlling bird nuisance of the type using a high
voltage shock in combination with said system apparatus for
preventing prolonged shocks, comprising:
a. an oscillator operative to provide a relatively stable frequency
signal at an output terminal thereof;
b. first means including a high voltage step-up transformer having
a primary and secondary winding, said primary winding coupled to
said output of said oscillator to develop a high voltage, high
frequency signal at said secondary winding;
c. rectifying means coupled to said secondary winding for providing
a predetermined high DC voltage therefrom;
d. protector circuit means coupled to said rectifying means for
monitoring said high voltage to provide at an output an indication
when said voltage falls below said predetermined value for a given
duration;
e. means coupling said protector means to said oscillator and
responsive to said indication to prevent said oscillator from
operating to thereby prevent the generation said high DC
voltage.
7. The apparatus according to claim 6 wherein said protector
circuit means comprises:
a. a first AND gate having first and second inputs, said first
input coupled to said rectifying means and said second input
coupled to said oscillator to provide at an output a first signal
indication when said high voltage falls below said predetermined
valve;
b. a monostable multivibrator having an input terminal coupled to
said output terminal of said AND gate and an output terminal and
operative to provide a predetermined length pulse when said AND
gate provides said first signal.
8. The apparatus according to claim 7 wherein said means coupling
said protector circuit means to said oscillator comprises:
a. a bistable multivibrator having an input and output electrode,
said output electrode capable of being in one of two states defined
by first and second voltage levels, said input electrode coupled to
said output terminal of said monostable multivibrator and
responsive to the termination of said pulse to cause said output
terminal to revert to said other state;
b. means coupling said output terminal of said bistable
multivibrator to said oscillator for inhibiting the operation of
said oscillator when said bistable multivibrator is in said other
state, to thereby prevent the generation of said high DC
voltage.
9. In a system for controlling bird nuisance of the type including
a high voltage source coupled to a field producing transmission
line assembly for protecting a given area from said nuisance by
generating an electrical shock field, said high voltage source
operating at a first voltage when said source is connected to said
transmission line and at a second higher voltage when said source
is not connected to said transmission line, in combination
therewith apparatus for providing an indication when said source is
undesirably not connected to said line comprising:
a. first means coupled to said high voltage source for providing a
first signal at an output thereof when said high voltage source is
at said second voltage;
b. a source of low frequency signals;
c. coincidence means having first and second input terminals and an
output terminal, said first input terminal coupled to said output
of first means, and said second input terminal coupled to said
output of said oscillator, to provide at said output terminal of
said coincidence means said low frequency signal only during the
presence of said first signal; and
d. indicating means coupled to said output terminal of said
coincidence means to provide an indication at said low frequency
signal rate indicative of said second higher voltage state, to
thereby provide a warning that said high voltage source is not
connected to said transmission line.
10. The apparatus according to claim 9, wherein said first means
comprises:
a. a differential amplifier including first and second transistors
each having a collector, emitter and base electrode, said emitter
electrodes coupled together and said collector electrodes adapted
to be coupled to a source of operation potential;
b. first means coupling the base electrode of said first transistor
to said high voltage source;
c. second means for biasing the base electrode of said second
transistor at a predetermined reference potential, to cause the
collector potential of said second transistor to change when said
high voltage source is at said second state due to said
differential amplifier operation; and
d. means coupled to said collector electrode of said second
transistor and responsive to said change to provide said first
signal.
Description
BACKGROUND OF INVENTION
This invention relates to an electronic repellent system and more
particularly to a system adapted for keeping birds from roosting on
building structures.
The prior art is replete with a number of patents which relate in
general to electrified repellent systems; and which systems operate
to shock birds and other animals when they approach an area which
is to be protected. In regard to buildings it is well known that
birds will nest upon ledges and other structures, and due to their
droppings will eventually deface the building. Repellent systems
have been used to keep the exterior of these buildings clean and
disease free. Birds are a significant factor to pollution in
densely populated areas as they can pass on various viruses and
fungus diseases to man. Besides this, their droppings accumulate
and ruin the total overall appearance of the structure that they
have selected for nesting.
The present systems used, operate to provide a high voltage between
a pair of wires. This high voltage sets up a shock field within a
suitable distance from one of the wires. If a bird or other small
animal attempted to approach the wire they would receive a shock.
Due to the fact that the systems use a high voltage and a
relatively low current the shock is not sufficient to injure the
animal in any manner but serves to prevent the animal from gaining
access to the particular structure being protected.
The present systems utilized provide a series of wires which are
strung along the building or about the building and are separated
approximately by 2 or more inches by means of high voltage
insulator standoffs. Thus to protect such a building the workmen
have to drill into the concrete in order to mount the standoffs and
proceed to string the wire about the areas to be protected. This of
course is a cumbersome and time consuming task.
In any event, after wires have been properly routed, care has to be
taken by other people who maintain various other parts of the
building. Since it is desirable to maintain the aesthetic
properties of the building these wires are relatively thin and are
capable of being easily broken by window washers and other
maintenance people. Therefore, the systems require monitoring in
order to ascertain that they are still operational. In regard to
appearance the wires are often relatively unattractive and in many
instances do not blend into the architectural harmony of the
structure to be protected.
Still further considerations must be taken into account in regard
to the operation of such systems. Namely, one has to be sure that
people such as the above noted maintenance people are not injured
by the voltages produced by such systems and hence care has to be
taken in order to regulate the current and voltage to assure that
the system is safe to humans as well as to the animals.
Furthermore, such systems must be capable of easy maintenance in
case of a failure in the high voltage generating apparatus. Certain
other conditions dictate that the system should still be
operational during a power failure. The prior art systems receive
their energy from the AC lines and in case of a power failure,
which may be prolonged, these systems fail to operate. It would
therefore be desirable to utilize a battery standby technique with
such a system to keep the same operational during a lapse of
power.
It is therefore an object of the present invention to provide a new
and improved electronic bird repellent system which is easy to
install, simple to maintain and economical to manufacture. Coupled
with these advantages the present invention includes a plurality of
unique high voltage conductor or transmission assemblies which are
easy to assemble, while providing an overall attractive appearance
thus maintaining the aesthetic qualities of the structure to be
protected.
BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS
A bird repellent system of the type including a high voltage source
for shocking birds comprises a transmission assembly having a
central insulator member, having a top surface coated with a
conductive foil and a bottom surface coated with a conductive foil,
the source of high voltage being connected between said foils, said
configuration forming a sandwich like structure which can be easily
installed and maintained on a building or other structure.
Still other embodiments include protection circuitry responsive to
a predetermined decrease in the high voltage for a given period to
disable the system from operating.
A further embodiment includes high voltage monitoring equipment to
determine whether a break or open circuit in the transmission
assembly occurred and to provide an indication of the same.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram of an electronic bird repellent system
according to this invention.
FIG. 2 is a side view of a composite high voltage transmission
assembly according to this invention.
FIG. 3 is a perspective fragmentary view of a building structure
provided with the apparatus of this invention.
FIG. 4A to 4C are top views of alternate configurations of
transmission assemblies according to FIG. 2.
FIG. 5 is a side plan view of a laminated transmission
assembly.
FIG. 6A and 6B shown alternative are embodiments of transmission
assemblies.
FIG. 7 is a detailed circuit of a bird repellent system according
to this invention.
DETAILED DESCRIPTION OF DRAWINGS
Referring to FIG. 1 there is shown an AC line cord 15 which is
capable of being inserted into a conventional power outlet unit for
supplying 60 cycle, 117 volt power to the power supply unit
encompassed in module 16. The power supply unit 16 may be a
conventional full wave or half wave rectifier configuration. Shown
coupled to power supply 16 is a battery 17 which is utilized
strictly for standby purposes, and in case of a power failure the
battery 16 is switched in circuit to provide the functions of the
power supply 16. During normal operation the battery is being
charged from the power supply as will be explained in greater
detail subsequently. The high voltage generating circuitry
generally comprises an oscillator 18 which operates at a relatively
stable frequency for example 50 to 5,000 HZ.
The frequency of the oscillator as indicated may be from 50 to
5,000 HZ. This frequency is relatively low as one may drive the
transmission assembly directly with the AC signal. The high
frequencies can be used for relatively short runs where capacitance
is not a problem. For example, one may utilize a frequency of 5,000
HZ or greater for lengths from about 5 to 200 feet. However, if one
desired to operate this with greater lengths one would use a lower
frequency as for example 50 cycles to assure greater driving
ability and therefore to achieve greater distance. In this manner
the oscillator 18 may include a variable resistor to change its
frequency depending on the length of the transmission line to be
driven. The frequency output signal from oscillator 18 is applied
to a driver amplifier circuit 19 which may be a conventional high
power amplifier. The amplifier output is applied to a high voltage
transformer 20. The transformer has a large turns ratio between the
secondary and primary windings to enable the amplified oscillator
signal to be stepped up in voltage. The secondary winding of the
high voltage transformer 20 is coupled to a high voltage rectifier
circuit 21 to develop a large DC potential at a relatively low
current. For example, the magnitude of such a potential may be
between 15,000 to 20,000 volts at a current range of a few
microamperes. Alternatively, the high voltage stepped up AC signal
can be used directly if desired.
The high voltage rectifier 21 further includes a voltage divider
22. A tap on the voltage divider 22 is coupled via a resistor 23 to
a protective circuit 24. The function of the protection circuit 24
is to monitor the high voltage supply 21 in order to ascertain that
the voltage is within predetermined desired limits.
If the voltage falls below a predetermined value for a specified
period the protection circuit 24 will disable the oscillator 18
thus preventing the generation of high voltage. The protection
circuit therefore serves to prevent a hazardous, long duration
shock which may result from a malfunction of equipment and if not
prevented could possibly cause injury to an animal or a person.
Also shown coupled to the divider 22 is a voltage monitor module
25. The function of module 25 as will be described in detail
subsequently is to monitor the high voltage supply and to provide
an indication if the high voltage exceeds a predetermined value.
This condition would occur if the high voltage distribution system
associated with the building develops an open circuit due to a
break in continuity of the transmission assembly. The output of the
voltage monitor 25 is coupled to an inverter amplifier 26 which has
its output coupled to an indicator lamp assembly 29. As will be
explained the indicator 29 will pulsate or blink on and off if the
high voltage condition is present. An AND gate 30 is shown having
its output coupled to one input of inverter 26. The function of the
AND gate 30 is to activate the indicator during normal operation by
monitoring the high voltage divider 22 and the high frequency
oscillator 18. The AND gate 30 functions to keep the indicator
illuminated if the oscillator is operating and if high voltage is
being provided at the output of divider 22. These conditions are
necessary to assure proper system operations as will be
explained.
Referring to FIG. 2 there is shown a high voltage distribution
system which is used to distribute the high voltage about the
desired areas of a building or similar structure. Basically, the
distribution system consists of a top conductive wire foil or strip
30 and a bottom conductive ground plane or sheet 31. The strip and
plane are held separate and apart and at a suitable distance by
means of an interposing insulator 32. The insulator 32 functions to
provide the adequate spacing between the high voltage conductor 30
and the ground plane 31, while further serving as a means for
providing the separation. The composite sandwich like structure has
two conductive tab-like connector assemblies at one or both ends,
designated respectively as 34 and 35. The connector 34 is
associated and coupled to the high voltage conductor 30 while
connector 35 is associated with the ground conductor 31. These
connectors are utilized to allow easy interconnection between
modules when installing the transmission units on the surface of
the building. Shown adjacent to the composite configuration is a
portion of another such assembly with interfacing conductors 36 and
37 which are respectively female or male snap connectors and are
adapted to be snapped into and to therefore coact with the
counterpart fasteners 34 and 35. This arrangement thus allowing one
to use of a plurality of such composite members to cover a desired
area of a building.
In the operation of such high voltage distribution systems there
are two factors which one has to take into consideration. First
there is capacitance. As one can readily see the transmission
assembly is basically a conductive foil, an insulator and a
conductive strip on top of the insulator. This configuration takes
the form of a capacitor. Care has to be taken to minimize the
capacity in order to adequately energize the effective length of
the transmission line. In this manner, the conductive strip 30 is
much thinner than the ground plane 31 and in essence can assume the
diameter of a typical wire. The conductive strip 30 in fact may
comprise a high voltage wire or a conductive foil. Since the strip
30 is relatively thin compared to the ground plane 31 there is
little capacity between them and hence one is capable of operating
the configuration at high voltage without fear of excess
capacitance and losses. The exact nature of the conductor 30 is
made clearer in reference to FIG. 4 where there is shown top views
of various embodiments of the high voltage assembly.
Referring to FIG. 3 there is shown a building 40 with a ledge 42.
On the ledge there is located a transmission assembly such as that
shown in FIG. 2. As indicated the output of the high voltage
generator is applied respectively to the top conductor and the
bottom conductor thereby creating a high voltage along the entire
length of the composite structure 43. Also shown in the figure is a
bird 44 which is about to nest or roost upon the ledge 42.
Depending upon the voltage of the generator if the bird attempts to
land on the ledge an arc will be drawn via the high voltage
conductor 30 which will shock the bird and thereby cause it to fly
off. The composite distribution structure can be glued by means of
a suitable outdoor epoxy or other means to the ledge in any desired
location. The installer merely has to snap these pieces together to
cover such a ledge or any other structure associated with the
building.
Referring to FIG. 4 there is shown top views of alternate
configurations of such composite structures. For example the unit
shown in FIG. 4B can be used to accommodate right angle turns on
ledges while the unit in FIG. 4C can be used to accommodate various
other angles or curvatures which may be associated with modern or
other building structures. The conductive strip 30 is shown herein
as a relatively thin member while the ground plane as indicated is
of a greater width.
FIG. 5 shows a side view of the composite structure with a front
surface thereof laminated with a thin sheet of plastic as mylar to
take on the appearance of a particular material which might be used
in the facade of a building. As one can readily ascertain from the
previous figures, the structures depicted for the high voltage
transmissions are virtually rectangular solids. Therefore it is a
relatively simple job to cover the surface of the composite
structure with a plastic lamination having the appearance of for
example brick, concrete and so on. Such materials for providing
such lamination are well known and are commercially available. This
particular feature afforded by the construction of the transmission
assembly therefore enables protection of the building from bird
nuisance, while virtually maintaining the same architectural
characteristics in that the unsightly wires of the prior art are
eliminated. FIG. 5 is merely one example of a particular
representation and shows a brick-like lamination 45 on this
surface. It is of course understood that any other type of facade
can be utilized as well.
Referring to FIG. 6 there is shown an alternate high voltage
transmission assembly arrangement which may be useful for
protecting large areas such as domes of buildings and so on. In the
case of a dome structure one can not really protect the entire
structure from bird nuisance because of the fact that such domes
are relatively large and a great plurality of wires or composite
structure strips would have to be utilized.
FIG. 6A shows a perspective view of an alternative embodiment of a
high voltage transmission assembly which can be utilized in
covering large, irregularly shaped surfaces. The high voltage
conductor is a conductive mesh 51 which is similar to a
conventional screen made of a conductive metal. The screen or
conductive mesh 51 is secured by an epoxy or other suitable means
to the top surface of the insulator member 52. The bottom surface
of the insulator member 52 is covered with a conductive ground
plane or wire mesh 53. The conductive ground plane may also be a
conductive metallic foil. Therefore it can be readily ascertained
that the composite structure depicted is pliable and flexible and
therefore can be placed or mounted upon an irregularly shaped
surface such as a dome.
FIG. 6B shows a top view of a member similar to that shown in 6A
with a thin mylar sheet or film 54 covering the mesh. The mylar
sheet may be colored and serves to again provide good aesthetic
qualities to keep the protected structure architecturally in
tact.
FIG. 7 shows a detailed schematic diagram of the electronic
repellent system as shown in block form in FIG. 1. Referring to
FIG. 6 there is shown a 60 HZ isolation transformer 61. This
transformer 61 is used to provide isolation to prevent shock
hazard. The secondary winding of transformer 61 is coupled to a
half wave rectifier circuit including diode 62 and filter
capacitors 63 and 64. The output of the half wave rectifier
provides a suitable DC potential which is used to supply operating
potential to the circuitry to be described. The output DC generated
by the power supply is available at output terminal 65. As
previously indicated the unit is capable of operating in a battery
standby condition in the case of power failure. A battery 66 is
shown having a positive output terminal coupled to a terminal of
filter capacitor 64 via a diode 67 in series with a resistor 68.
This output terminal is also coupled to the power supply output
terminal 65 via another diode 69 in series with a resistor 70. The
battery standby circuit operates as follows: As long as AC power is
supplied the battery 66 selected to be of a slightly lower
potential than the potential on filter capacitor 64 is being
charged via resistor 68 in series with diode 67. If a power failure
occurs there is no output DC available across the filter capacitor
64. This therefore reverse biases diode 67 and forward biases diode
69; to provide coupling of the positive terminal of the battery to
output terminal 65. Power is therefore supplied via the battery 66
to the circuitry.
A relatively stable frequency oscillator circuit includes a
unijunction transistor 72 which may operate at a relatively high
frequency between the range for example of 50 to 5,000 HZ. The
unijunction transistor 72 is arranged in a typical sawtooth
oscillator configuration and has one electrode thereof connected to
the power supply terminal 65 and the other base electrode connected
via a resistor 73 to a point of reference terminal. The emitter
electrode of the unijunction 72 is coupled to the source of
operating potential via a timing resistor 74 and is returned to
ground via a timing capacitor 75. The combination of the resistor
74 and the capacitor 75 serve to determine the operating frequency
of the oscillator configuration. The resistor 74 may be variable in
order to change the frequency of the oscillator if desired. The
sawtooth output signal of the oscillator is coupled via a low pass
filter, including resistor 76 and capacitor 77, to the base
electrode of a driver transistor 80. The collector electrode of
transistor 80 is coupled through the primary winding of a high
voltage transformer 81 to terminal 65. A diode is coupled across
the primary winding for transient protection of transistor 80. The
transformer 81 is a typical high voltage transformer and has a
large turns ratio between the primary and secondary windings to
produce a large voltage signal at the secondary winding. This large
voltage signal may be in excess of 25,000 volts peak to peak. The
secondary winding is coupled via a capacitor 82 to a high voltage
rectifier assembly shown enclosed within the dash line 84 used to
provide a large voltage DC component across the output capacitor
85. It is of course also understood that the assembly shown
enclosed within the dashed line 84 may be eliminated and the high
voltage AC signal may be used directly for activation of the
composite transmission line structure 90 (similar to the format as
described in conjunction with FIGS. 2, 3, 4, 5 and 6). In any event
the DC rectifier is still included to provide protection and
monitoring functions.
There is shown a differential amplifier configuration comprising
transistors 91 and 92 with the conventional constant current source
transistor 93. It is of course understood that the differential
amplifier can be easily implemented by means of a conventional
integrated circuit module. The differential amplifier configuration
provides the function of the voltage monitor assembly 25 shown in
FIG. 1.
The operation of the circuit is as follows: The base electrode of
transistor 91 is coupled to the high voltage DC output of the
rectifier assembly 84 via the voltage divider including resistors
94 and 95. The base electrode of transistor 92 is coupled to power
supply output terminal 65 which provides a reference potential for
the base electrode of transistor 92 and for the constant current
source transistor 93. During normal operation transistor 91 is
conducting as is transistor 92. However, due to the current flow in
the respective base to emitter and paths of the transistors, the
collector voltage of transistor 92 is at a lower positive potential
than is the collector voltage of transistor 91. A diode 97 is
coupled between the collector electrodes of transistors 91 and 92.
Now assume that the output load on the high voltage rectifier (the
output load being transmission line 90) is somehow open circuited.
This condition unloads the high voltage supply and causes the
voltage on filter capacitor 85 to rise. This rise in voltage which
may be 25 percent or greater causes transistor 91 to conduct harder
therefore causing its collector potential to fall. Due to the
operation of the differential amplifier the collector potential of
transistor 92 increases thus forward biasing diode 97 causing it to
conduct. The cathode electrode of diode 97 is coupled to an input
of an AND gate 98. The AND gate 98 is shown in typical logical form
as it is well known how to implement the same. Another input of AND
gate 98 is coupled to the base electrode of a low frequency
unijunction oscillator configuration 100. Basically, the
unijunction oscillator circuit 100 provides a sawtooth wave form at
a relatively low frequency which may, for example, be 20 HZ or
lower. Therefore, during a high voltage condition the AND gate 98
is enabled providing at its output the low frequency sawtooth wave
form. This is applied to one input of an inverter 101 having an
output coupled to an indicator lamp assembly 102. Therefore, during
a high voltage condition the lamp assembly 102 will blink on and
off according to the repetition rate of the sawtooth to thereby
provide a visual indication to an operator that a high voltage
condition has occurred. This might be due to a break in the
conductor assembly used on the building facade or for some other
reason.
The unit described herein also includes a protection circuit shown
in block form as 24, FIG. 1. The function of the protection circuit
is to prevent an animal or a human receiving a prolonged shock
which might serve to injure under proper conditions. Basically, the
protection circuit operates as follows: An AND gate 110 is shown
having one input coupled to the collector electrode of transistor
92. During normal operating conditions the voltage at the output of
the system is relatively constant as indicated above. However, if a
bird or person receives a shock the voltage at the output of the
rectifier will decrease. This decrease in voltage causes the
following ot occur: Transistor 91 becomes less conductive due to
the decrease in the voltage, therefore causing the voltage at the
collector electrode of transistor 92 to decrease towards ground
potential. This enables an input of AND gate 110. The other input
of the AND gate 110 is coupled to resistor 73 in the base electrode
of the unijunction transistor 72. Due to the operation of the
unijunction circuit, sharp current spikes are provided across
resistor 73. Due to the fact that AND gate 110 is enabled the
pulses are permitted to pass through the AND gate and serve to
trigger the monostable multivibrator or one shot 112. This circuit
112 provides a pulse of a predetermined width at the output. This
pulse is applied to an input of another AND gate 115. Another input
of AND gate 114 is coupled to the collector electrode of transistor
92. Thus if the high voltage decrease lasts for a duration longer
than the pulse width provided by the one shot 112, the AND gate 114
will pass the trailing edge transition of the pulse and trigger the
flip-flop or bistable multivibrator 115. This is due to the fact
that the voltage decrease lasted and hence the reset lead via diode
150 and inverter 151 is no longer enabled. Thus the trigger caused
by the end of the one shot cycle permits the flip-flop 115 to
change state. The flip-flop will stay in this other state until the
high voltage goes back up. This will occur automatically as the
inverter 151 will force the flip-flop 115 back into the reset mode
for a positive voltage at the collector of transistor 92.
Triggering the flip-flop 115 causes the output to go from a
positive level towards ground. This condition forward biases the
PNP transistor 120 causing it to saturate. The transistor 120 is
coupled across the timing capacitor 72 of the high frequency
unijunction oscillator system. The shorting out of this capacitor
72 disables the unijunction oscillator thereby turning off the high
voltage. When this condition occurs the unit is disabled until the
flip-flop 115 is reset either automatically or manually by means of
the switch 125. This action prevents a prolonged shock from
occurring. Alternatively if the drop in voltage is less than the
time duration of the one shot 112 the collector voltage of
transistor 92 will immediately rise again and therefore the
transition of the one shot will not pass through the AND gate 114
and will not trigger flip-flop 115. This thereby permits the system
to continue to operate normally.
As was mentioned above an indicator lamp 102 is used during the
high voltage mode to apprise a maintenance man or operator of this
condition. Also shown coupled to the indicator-driver circuit 101
is an AND gate 100. The AND gate 130 has one input coupled to the
voltage divider monitoring the output of the high voltage amplifier
assembly 84. This coupling is afforded via diode 131 in series with
resistor 132. As long as high voltage is being generated within
acceptable limitations the input of the AND gate is enabled.
Another input to AND gate 130 is derived from the unijunction
oscillator circuit 72 by means of a half wave rectifier module
generally designated as 135. As long as the oscillator 72 is
operating a DC voltage is provided at the output of filter
capacitor 136. This output voltage is sufficient to enable the
respective input of AND gate 130. Therefore during normal operation
AND gate 130 is enabled and serves to directly operate the
indicator lamp 102 to therefore illunimate the same. If for example
the unijunction oscillator 72 fails to operate and no high voltage
is provided AND gate 130 is disabled thereby turning off the
indicator. During this condition AND gate 98 is inhibited and
therefore the lamp 102 will go off. The lamp 102 will also be
extinguished if the high voltage fails because of the
malfunctioning of transistor 80 or the high voltage rectifier
assembly 84. This also causes the lamp to be extinguished thereby
informing the operator that the trouble is either in the oscillator
circuit, the power supply or the various other mentioned
components.
* * * * *