Insect electrocution apparatus and method of operation

An insect electrocution apparatus and method of operation utilizing a series connected, dual coil primary of a ballast/step-up transformer to provide increased impedance only during the starting of the insect attracting fluorescent tube. The fluorescent tube is connected between the two primary coils with the fluorescent tube starter and one of the primary coils connected in series with the fluorescent tube filaments. Upon starting, both coils are energized and provide the desired amount of impedance. Once the fluorescent tube ignites, the starter and the second primary coil are operationally removed from the circuit leaving only the first primary coil to provide ballast for the fluorescent tube.

BACKGROUND OF THE INVENTION 
The present invention relates to insect electrocution products and, more 
particularly, to an improved insect electrocution product utilizing a 
switchable, dual primary coil combination high voltage transformer and 
flourescent tube ballast. 
Conventional electric insect killers generally require the use of two 
devices working in concert: a flourescent tube with suitable phosphors to 
attract the insects, and a source of high voltage electricity to destroy 
them. The flourescent tube and high voltage power supply both employ a 
similar inductive component in their circuits. The flourescent tube or 
lamp requires a ballast to control the magnitude of the electric current 
flowing through the tube. The most common ballast is a simple inductor 
consisting of a laminated steel core surrounded by one or more windings of 
varnished copper wire. The required level of control is determined by 
three parameters: (a) the number of turns of wire, (b) the amount of iron 
or steel in the core, and (c) the dimension of a "gap" across the magnetic 
lines of flux. 
There are many different designs of ballast circuits, but they generally 
fall into one of three categories depending on the means used to "flash" 
or ignite the tube when first turned on. The simplest of these, called the 
"preheat" circuit, is commonly used for the smaller flourescent tubes 
found on desk lamps and bathroom cabinets. In this circuit, a 
manually-operated switch or automatic device called a starter is used to 
create a momentary current through the filaments at each end of the tube. 
This heats the filaments, producing a "space charge" of electrons which 
lights the lamp when this preheat current is interrupted. 
In order to achieve the proper control of the current during both the 
preheat phase and the operating phase, a ballast of a given physical size 
is required to meet the parameters outlined above. If this ballast is made 
smaller, (that is, if less steel in a smaller frame size is used), 
additional wire turns can be put on to compensate but--for any given 
number of turns--either the preheat current will be too high or the 
operating currents will be too low. Since tube wattages vary, e.g., 15 
watt, 25 watt and 40 watt, it would be desirable to use a single purpose 
ballast for a wide range of tube wattages. 
In recent years, the flourescent tube ballast and high voltage transformer 
have been combined into a single component. These devices use the same 
standard, cruciform-type lamination that has been used throughout the 
industry for the current-limited high voltage transformer; however, by 
creating an appropriate gap between the inner and outer laminations, the 
primary coil can also be used as the ballast for the tube. Unfortunately, 
this arrangement is not able to achieve the same degree of control over 
the several parameters of flourescent tube operation as a conventional, 
single-purpose ballast. Within the limit of 500 milliamperes, however, the 
span of control of such a device having the same lamination size and stack 
thickness as a conventional high voltage transformer is adequate for 
commercial purposes. 
Beyond this limit, the span between operating and preheat current levels is 
too great for reliable operation. Regaining such control would require a 
substantial increase in lamination size or stack thickness, thereby 
decreasing the cost advantages over using two discrete components. 
Since the operating level of commercially important 40 watt flourescent 
tubes is up to 800 milliamperes, it is desirable to reduce the span to 
that of a conventional ballast at these current levels. 
It is accordingly, a general object of the present invention to provide an 
improved combination high voltage transformer and flourescent tube ballast 
for insect electrocution products. 
It is a specific object of the invention to provide a switchable, dual 
primary coil ballast/step-up transformer that accomodates a wide range of 
flourescent tube wattages. 
It is a feature of the invention that one of the dual primary coil provides 
increased impedance only during the starting operation of the flourescent 
tube. 
BRIEF DESCRIPTION OF THE INVENTION 
An insect electrocution apparatus utilizes a dual coil primary as a part of 
a ballast/step-up transformer. An insect attracting flourescent tube is 
electrically connected between the two primary coils. The filaments of the 
flourescent tube are series connected through a conventional starter and 
one of the two primary coils of the ballast/step-up transformer. Both 
coils are in the starting circuit of the insect electrocution apparatus. 
After ignition of the flourescent tube, the second primary coil and 
starter are removed from the operating circuit.

DETAILED DESCRIPTION OF THE INVENTION 
Turning now to the drawings, FIG. 1 illustrates a prior art insect 
electrocution apparatus indicated generally by the reference numeral 10. 
The insect electrocution apparatus comprises an insect attracting 
flourescent tube 12 and a ballast/step-up transformer 14 that provides 
high voltage to an insect electrocution grid 16. The ballast/step-up 
transformer 14 has a single primary coil 18 and a secondary coil 20 that 
is shunted by capacitor 22. The flourescent tube 12 has conventional 
filaments 24 and 26 which are connected in series through a starter 28 
having a momentarily actuated switch 30. Alternating current of the 
required voltage is applied through input contacts 32 and 34 to the 
starting circuit comprising primary coil 18, filament 24, starter switch 
30 and filament 26. Upon ignition of the flourescent tube 12, the starter 
circuit is interrupted and the insect electrocution apparatus 10 opeates 
in a conventional manner. 
Referring now to FIGS. 2 and 3, the same reference numerals have been used 
to designate corresponding parts from the electrocution apparatus shown in 
FIG. 1. The improved electrocution apparatus of the present invention, 
indicated generally by the reference numeral 11 in FIGS. 2 and 3, has an 
additional primary coil 36 in the ballast/step-up transformer 14. The 
extra primary coil 36 is connected in series with the flourescent tube 
filament 24, starter switch 30 and flourescent tube filament 26. Upon 
application of alternating current to the input terminals 32 and 34, the 
additional primary coil 36 provides increased impedance for the starting 
circuit constituting input terminal 32, the first primary coil 18, 
filament 24, the second primary coil 36, starter switch 30, flourescent 
tube filament 26 and input terminal 34. After ignition of the flourescent 
tube 12, starter switch 30 opens as shown in FIG. 3, thus removing the 
second primary coil 36 from circuit operation. 
Having described in detail a preferred embodiment of my invention, it will 
now be apparent to those skilled in the art that numerous modifications 
can be made therein without departing from the scope of the invention as 
defined in the appended claims.