Flyback transformer with high voltage variable resistor built therein

A high voltage variable resistor section (8) for deriving the focusing voltage and screen is attached to an open portion formed on one surface of a first case (47) which receives primary and secondary windings (2, 3) included in a flyback transformer section (1). An insulating substrate (16) on which resistor elements (9-13) included in the high voltage variable resistor section are formed in housed in a second case (15). An opening is formed in one surface of the second insulating cases (15). With this opening communicating with the opening in the first insulating case, the two insulating cases are integrated. These insulating case define insulating case means, in which a high voltage capacitor (14) for compensating cathode ray tube capacity is housed. The high voltage capacitor is disposed between the secondary winding (3) and the resistor elements (9-13) in such a manner that the surfaces of the electrodes (38, 39) of the high voltage capacitor are opposed to the secondary winding (3) and the resistor elements (9-13). This arrangement prevents unnecessary radiation components due to ringing noise induced in the secondary winding from being transferred to the resistor elements and superposed on the focusing voltage.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a flyback transformer used for supplying high DC 
voltage to cathode ray tubes as in television sets, and more particularly 
to a flyback transformer with a high voltage variable resistor built 
therein for deriving focusing voltage, etc. 
2. Description of the Prior Art 
The cathode ray tube is supplied with a high DC voltage, as an anode 
voltage, which has been rectified after being elevated by a flyback 
transformer. Generally, this anode voltage is divided into medium-high 
voltages such as focusing voltage and screen voltage. As a voltage divider 
for obtaining these medium-high voltages, use has been made of a high 
voltage variable resistor. 
Generally, in CRT display devices and high quality television sets required 
to provide distortionless clear images, it is essential that dynamic 
regulation be low with respect to a high voltage producing circuit using a 
flyback transformer. Dynamic regulation means voltage regulation in the 
duration of one scanning of the screen; if this dynamic regulation is 
high, distortion will be produced on the screen in a region where contrast 
is high. For this reason, it has been usual practice to connect a 
capacitor between the anode electrode of the cathode ray tube and the 
ground in order to compensate the cathode ray tube capacity so as to 
provide clear images. 
Thus, a certain conventional type of high voltage producing circuit using a 
flyback transformer comprises the flyback transformer, a high voltage 
variable resistor, and a high voltage capacitor. An arrangement has 
already been proposed wherein a flyback transformer and a high voltage 
variable resistor are assembled as an integral component. In this case, 
the primary and secondary windings constituting the flyback transformer, 
and the resistor elements of the high voltage variable resistor are housed 
in a suitable insulating case, which is filled with insulating resin 
whereby the voltage-withstanding property of said parts housed in the 
insulating case is improved. 
In the flyback transformer with a high voltage variable resistor built 
therein as described above, the arrangement for dividing the anode voltage 
which is a high voltage and deriving the focusing voltage and screen 
voltage which are medium-high voltages by means of the high voltage 
variable resistor makes it necessary to increase the resistance values of 
the resistor elements of the high voltage variable resistor. As a result, 
the impedance between the ground and the focusing voltage deriving section 
positioned intermediate between the resistor elements of the high voltage 
variable resistor becomes high, so that when an unnecessary radiation 
component due to ringing noise induced in the secondary winding of the 
flyback transformer rides on the resistor of the focusing voltage deriving 
section, it will not escape to ground, with the result that it is 
superposed on the focusing voltage, adversely affecting the screen. There 
is another form in which the secondary winding of the flyback transformer 
is divided into parts with a high voltage diode interposed between 
adjacent parts. In this case, however, an unnecessary radiation component 
due to noise during the switching of the high voltage diodes is also 
superposed on the focusing voltage, thus exerting an adverse influence on 
the screen. 
The aforesaid arrangement wherein the primary and secondary windings of the 
flyback transformer and the resistor elements of the high voltage variable 
resistor are integrally built in the insulating case has advantages that 
desired electrical connection between the flyback transformer and the high 
voltage variable resistor can be made within the insulating case whereby 
simple wiring suffices in spite of high voltage. There is another 
advantage that as a whole the arrangement can be reduced in size as 
compared with an instance in which the flyback transformer and the high 
voltage variable resistor are constructed as separate parts. However, it 
is desired to eliminate the aforesaid drawbacks while enjoying these 
advantages. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a flyback power supply with a 
high voltage variable resistor built therein, wherein unnecessary 
radiation components rarely tend to be superposed on the focusing voltage 
deriving section of the high voltage variable resistor. 
The flyback power supply with a high voltage variable resistor built 
therein according to this invention includes the following minimum 
configuration. It has a flyback transformer including a primary and 
secondary windings, a high voltage variable resistor having resistor 
elements connected between the high voltage delivery side of said flyback 
transformer and the ground, and a high voltage capacitor for compensating 
cathode ray tube capacity connected between the high voltage delivery side 
of the flyback transformer and the ground. The high voltage capacitor for 
compensating cathode ray tube capacity has electrodes located on opposite 
surfaces of a dielectric body such as a ceramic. Of these components, not 
only said primary and secondary windings and said resistor elements but 
also said high voltage capacitor are housed in the insulating case means, 
and with these components housed in the insulating case means, insulating 
resin means is injected into the insulating case means; this is a first 
feature. A second feature of the invention, resides in that the high 
voltage capacitor is disposed between the secondary winding and the 
resistor elements, the electrode surfaces of the capacitor intersect the 
region extending between the secondary winding and the resistor elements. 
One electrode surface faces toward the windings and the other electrode 
surface faces toward the resistor elements. According to this invention, 
the electrode of the high voltage capacitor associated with the ground 
serves as a shield against unnecessary radiation components which are 
produced owing to ringing noise induced in the secondary winding of the 
flyback transformer and, in the type in which high voltage diodes are 
placed in the secondary winding, unnecessary radiation components due to 
noise during the switching of the high voltage diodes, preventing them 
from being transmitted to the resistor elements of the high voltage 
variable resistor. Therefore, superposition of these unnecessary radiation 
components on the focusing voltage deriving section of the resistors can 
be prevented to a great extent. Further, in the instance where the 
electrode of the high voltage capacitor associated with the high potential 
side faces toward the secondary winding of the flyback transformer, it is 
possible to employ such an arrangement that the voltage-withstanding 
property of the secondary winding and the high voltage capacitor is 
improved. Further, an arrangement is also possible wherein the secondary 
winding and the high voltage capacitor are disposed closer to each other. 
Thus, it contributes advantageously to reducing the size of the flyback 
transformer. Further, in the instance where the electrode of the high 
voltage capacitor associated with the high potential side is arranged to 
face to the secondary winding, its electrode associated with the ground 
potential necessarily faces to the resistor elements, so that the distance 
between the electrode associated with the ground potential and the 
resistor elements is shortened, with the result that the shield effect of 
the electrode associated with the ground side is improved. 
In a preferred embodiment of this invention, the electrodes of the high 
voltage capacitor are positioned with respect to the resistor elements of 
the high voltage variable resistor so that said electrodes shield at least 
the focusing voltage deriving section positioned intermediate between the 
resistance value between the end of the resistor element connected to the 
high voltage delivery side of the flyback transformer and the end 
connected to the ground. This arrangement ensures that at the location 
where superposition of unnecessary radiation components due to noise from 
the secondary winding should be avoided, shielding against such 
unnecessary radiation components is effectively achieved. 
These objects and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a high voltage producing circuit using a flyback 
transformer for supplying a high voltage to the anode electrode 7 of a 
cathode ray tube 6 will now be described separately with reference to a 
flyback transformer section 1 and a high voltage variable resistor section 
8. 
The flyback transformer section 1 comprises a primary winding 2 and a 
secondary winding 3, and the secondary winding 3 on the higher voltage 
side is divided by a plurality of high voltage diodes 4a and 4b. One end 
of the secondary winding 3 is connected to the ground potential and the 
other end to the anode electrode 7 of the cathode ray tube 6 through a 
rectifying diode 5. 
The high voltage variable resistor section 8 is provided with five resistor 
elements 9-13 connected in series between the anode voltage delivery side 
of the secondary winding 3 and the ground, the second and fourth resistor 
elements 10 and 12 being variable resistor elements. A focusing voltage is 
derived from one variable resistor element 10, while a screen voltage is 
derived from the other variable resistor element 12. A high voltage 
capacitor 14 is connected between the anode electrode 7 and ground. 
FIG. 2 is a perspective view showing the external appearance of a flyback 
transformer with a high voltage variable resistor built therein for 
realizing the high voltage producing circuit using the flyback transformer 
of FIG. 1. In FIG. 2, the high voltage variable resistor section 8 is 
located in the upper position, while the flyback transformer section 1 is 
located in the lower position. They are assembled through separate steps 
and ultimately integrated together as shown in FIG. 2. First, referring to 
FIGS. 3 through 7, the high voltage variable resistor section 8 will be 
described. 
The high voltage variable resistor section 8 is housed in an insulating 
case made of resin. The insulating case 15 is open at one side, as shown 
in FIGS. 4 and 5. That is, in FIG. 4, the lower surface is open. An 
insulating substrate 16 is housed in the insulating case 15. 
The insulating substrate 16 is made of alumina or the like, the particulars 
being shown in FIG. 6. The insulating substrate 16 is quadrangular. One 
surface of the insulating substrate 16 is formed with film resistors 
forming the resistor elements 9-13 shown in FIG. 1. To facilitate 
comparison with the circuit diagram of FIG. 1, the reference numerals used 
in FIG. 1 are given to the corresponding parts. The film resistor 9 
forming the resistor element of the fixed resistor is sinuously formed, 
followed by the horseshoe-shaped film resistor 10 forming a resistor 
element of the variable resistor, by the sinuous film resistor 11 forming 
the resistor element of the fixed resistor, the horseshoe-shaped film 
resistor 12 forming a resistor element of the variable resistor, and 
finally by the film resistor 13 forming the resistor element of the fixed 
resistor. The centers of the regions surrounded by the horseshoe-shaped 
film resistors 10 and 12 are provided with central electrodes 17 and 18, 
respectively. The peripheral region of the insulating substrate 16 is 
provided with terminal electrodes 19, 20, 21, and 22 respectively 
connected to the film resistors 9 and 13 and central electrodes 17 and 18. 
Of these terminal electrodes, the terminal electrodes 20, 21, and 22 are 
formed with throughgoing holes 23, 24, and 25 extending substantially 
through the centers thereof, respectively, to facilitate electrical 
connection from the back of the insulating substrate 16. In addition, it 
is also possible to provide the terminal electrode 19 with a throughgoing 
hole extending through the insulating substrate 16. In this embodiment, 
the central electrode 17 and the terminal electrode 21 are connected by a 
film resistor and so are the central electrode 18 and the terminal 
electrode 22, whereby they can be made to function as protective 
resistors. The pattern of the film resistors deposited on the insulating 
substrate 16 is not limited to the one shown in FIG. 6 but may take any 
desired form. 
Of the reference numerals newly added in the description given above with 
reference to FIG. 6, those for which the corresponding parts are found in 
FIG. 1 are applied to these parts in FIG. 1. 
The insulating substrate 16 is positioned in the insulating case 15 so that 
its surface not formed with film resistors is opposed to the open side of 
the insulating case 15. The insulating substrate 16 is fixed by an 
adhesive agent on a rib 26 formed in the insulating case 15 to surround 
the film resistors 10 and 12, whereby a sealed space is defined between 
the insulating case 15 and the portion of the insulating substrate 16 
where the film resistors 10 and 12 forming the resistor elements of the 
variable resistor are formed. The means for fixing the insulating 
substrate 16 to the rib 26 is not limited to the aforesaid adhesive agent. 
For example, mechanical means may be used together with a rubber packing 
placed on the rib. Further, a pin 27 is set upright in the insulating case 
15. The pin 27, as shown in FIG. 6, extends through a hole 28 formed in 
the insulating substrate 16 to effect the positioning of the latter in the 
insulating case 15. 
With the insulating substrate 16 thus positioned, an epoxy type insulating 
resin 29 is applied to cover the surface of the insulating substrate 16 
not formed with said film resistors and is allowed to cure. The insulating 
resin 29 is formed up to the side where the film resistors on the 
insulating substrate are formed, but it is interrupted by a part of the 
rib 26 positioned at the central portion of the insulating case 15, so 
that it does not reach the region where the film resistors 10 and 12 for 
the variable resistor are formed. In addition, it is also possible to 
employ an arrangement wherein the insulating resin 29 does not at all come 
around to the side of the insulating substrate 16 where the film resistors 
are formed. The insulating resin 29 keeps the air-tightness of the 
clearance between the insulating case and the surface having the film 
resistors 10 and 12 formed thereon and improves the voltage-withstanding 
property of the film resistors 9-13 formed on the insulating substrate 16. 
The insulating resin 29 selected is capable of retaining a suitable amount 
of flexibility even after curing, thereby absorbing the stress in the 
insulating substrate 16 to prevent damage to the latter. In addition, the 
height of said pin 27 serves as a measure of level in applying the 
insulating resin 29. 
The upper wall of the insulating case 15 shown in FIG. 4 is provided with 
two resistance adjusting rotary shafts 30 and 31 projecting therefrom. One 
rotary shaft 30 is used for adjusting the focusing voltage and the other 
rotary shaft 31 for adjusting the screen voltage. These rotary shafts 30 
and 31 are rotatably supported in bearings 32 and 33, respectively. The 
ends of the rotary shafts 30 and 31 located inside the insulating case 15 
hold sliders 34 and 35 thereon. The sliders elastically slide on the 
horseshoe-shaped film resistors 10 and 12 while contacting said central 
electrodes 17 and 18 in accordance with the rotation of the rotary shafts 
30 and 31. 
A passage 36 for leading out the high voltage lead wire for the focusing 
voltage projects from the left-hand side surface of the insulating case 15 
shown in FIGS. 3 through 5. 
The high voltage capacitor 14 is disposed within the insulating case 15 and 
on the side of the insulating substrate 16 where the film resistors are 
not formed. The high voltage capacitor 14, as shown in FIG. 7, comprises 
electrodes 38 and 39 formed on opposite surfaces of a dielectric 37 such 
as ceramics in the form of a rectangular parallelpiped, said electrodes 38 
and 39 having lead terminals 40 and 41 attached thereto. The outer 
peripheral surface of the high voltage capacitor 14 is covered with an 
insulating resin 42 such as of the epoxy type. The high voltage capacitor 
14 is installed in the insulating case 15 so that its surface with the 
electrodes 38 and 39 is opposed to the insulating substrate 16. One 
electrode 39 is connected to the high voltagedelivery side of the flyback 
transformer section 1 in the circuit diagram of FIG. 1 and is at a higher 
potential than the other electrode 38, said higher potential electrode 39 
being opposed to the open side of the insulating case 15. It is also 
possible to position the high voltage capacitor so that the other 
electrode 38 is opposed to the open side of the insulating case 15. 
The high voltage capacitor 14 is positioned with respect to, e.g., the 
insulating case 15. Thus, as shown in FIGS. 5 and 7, the outer surface of 
the insulating resin 42 is integrally provided with three projections 43 
arcuately projecting therefrom, while three recesses 44 are formed in the 
inner surface of the insulating case 15 at the correspondinq positions. 
These projections 43 fit in the recesses 44, whereby the high voltage 
capacitor 14 is positioned within the insulating case 15. The shape of the 
projections 43 can be easily obtained by imparting the corresponding shape 
to the mold when making the insulating resin 42 by molding. 
The insulating resin 42 may be formed with a step 45. This step 45 is 
formed by adhesively bonding an insulating chip, such as ceramics, to the 
surface of the electrode 38 on the dielectric 37 and serves to position 
the dielectric 37 inside the mold when molding the insulating resin 42. 
Further, as shown in FIG. 4, the step 45 can be used to define a clearance 
so that the lead terminal 40 led out of the same side as the step 45 is 
led out to the open side of the insulating case 15 through the space 
between the insulating resin 29 and the insulating resin 42. 
In this manner, the parts constituting the high voltage variable resistor 
section 8 shown in FIG. 1 are obtained. In addition, FIGS. 4 and 5 and 
FIG. 8 to be later described show lead wires for electrical connection, 
but these are shown only diagrammatically and it is desirable to refer to 
FIG. 1 for the correct wiring. 
The aforesaid high voltage variable resistor section 8, as shown in FIG. 2, 
is built in the flyback transformer section 1 and connected to the high 
voltage delivery side of the flyback transformer. 
The insulating case 15 of the high voltage variable resistor section 8 is 
formed with a flange 46, while the insulating case 47 of the flyback 
transformer section 1 is formed with a U-shaped groove 48 to slidably 
receive said flange 46. One end of the groove 48 is closed as shown at 
left in FIGS. 4 and 8, while the other end of the groove 48 is open as 
shown at left in FIG. 2. Thus, by inserting the flange 46 into the groove 
48 from the left-hand side in FIG. 2 (i.e., the right-hand side in FIGS. 4 
and 8), the insulating case 15 and the insulating case 47 are mechanically 
fixed. In addition, in order to facilitate the insertion of the flange 46 
into the groove 48 and to make reliable the fixing of the insulating cases 
15 and 47, the flange 46 is tapered as shown in a dash-dot line in FIG. 4 
and, as can be analogized from FIG. 2, the groove 48 is also tapered. 
Referring to FIGS. 2 and 8, the arrangement of the flyback transformer 
section 1 will be described. A low voltage bobbin 51 integral with a 
terminal block 50 having a plurality of pin terminals 49 attached thereto 
has the primary winding 2 shown in FIG. 1 wound thereon. A high voltage 
bobbin 52 is disposed to surround the low voltage bobbin 51. The high 
voltage bobbin 52 has the secondary winding 3 shown in FIG. 1 wound 
thereon. Of the high voltage diodes 4a and 4b dividing the secondary 
winding into three parts, the high voltage diode 4a is shown in FIG. 1 as 
placed on the high voltage bobbin 52. Though not shown, the low voltage 
bobbin 51 may have a tertiary winding together with the primary winding 
wound thereon, as occasion demands. 
After predetermined electrical connection has been made between the flyback 
transformer section 1 and the aforesaid high voltage variable resistor 
section 8, an insulating resin 53 such as of the epoxy type is charged 
into the space between the insulating cases 15 and 47 and allowed to cure. 
Further, a pair of U-shaped cores 54 and 55 are disposed end to end. 
In the aforesaid arrangement, as best shown in FIG. 8, the high voltage 
capacitor 14 for compensating the capacity of the cathode ray tube 
connected between the anode electrode of the cathode ray tube and the 
ground is interposed between the secondary winding 3 and the film 
resistors 9-13 (FIG. 6) formed on the insulating substrate 16. 
Particularly, the higher potential electrode 39 (FIG. 7) of the high 
voltage capacitor 14 is opposed to the secondary winding, while the lower 
potential electrode 38 (FIG. 7) is opposed to the film resistors 9-13. The 
electrodes 38 and 39 of the high voltage capacitor 14 are positioned so 
that they shield at least the film resistor 10 constituting a resistor 
element of the variable resistor which is a part having a high impedance 
between the terminal electrode 19 on the input side of the series of film 
resistors 9-13 and the terminal electrode 20 providing the ground 
potential. In this way, the tendency that unnecessary radiation components 
due to noise at the time of switching of the high voltage diodes 4a and 4b 
and due to ringing noise induced in the secondary winding 3 are superposed 
on the focusing voltage delivery side can be effectively reduced. 
FIG. 9 shows a modification of a projection 43 formed on the insulating 
resin 42 covering the high voltage capacitor 14. As shown in this figure, 
the projection 43 may be trapezoidal. Further, though not shown, it may 
take any other shape. 
FIGS. 10 and 11 show modifications of recesses 44 formed in the insulating 
case 15. As shown in these figures, the recesses 44 are formed with a rib 
or ribs 56 projecting at an acute angel (preferably 30 degrees or less). 
In FIG. 10, a single rib 56 is formed, and in FIG. 11 two ribs 56 are 
formed. When the projections 43 fit in the recesses 44, the ribs 56 are 
suitably deformed to make firmer the engagement between the projections 43 
and the recesses 44. 
FIG. 12 shows another example of the positioning of the insulating case 15 
and the insulating resin 42 covering the high voltage capacitor 14. In the 
example shown in FIG. 12, four sets of combinations of projections 43 and 
recesses 44 are provided. That is, what is intended to mean in this 
example is that the number of combinations of projections 43 and recesses 
44 is optional and that the position where these projections 43 and 
recesses 44 are to be formed is optional. 
FIG. 13 shows another example of the positioning of the high voltage 
capacitor 14 with respect to the insulating case 15. In this example, the 
amount of the insulating resin 29 to cover the insulating substrate 16 is 
increased so as to embed at least part of the high voltage capacitor 14, 
and the high voltage capacitor 14 is positioned by this insulating resin 
29. In this case, the insulating resin 42 for covering the high voltage 
capacitor 14 is shown in FIG. 13, but this insulating resin 42 may be 
removed and instead the insulating resin 29 may be used to cover the high 
voltage capacitor 14 at the same time. 
The high voltage capacitor 14 may be positioned by being supported from the 
high voltage bobbin 52 included in the flyback transformer section 1. Some 
examples of such positioning method are given below. 
Referring to FIG. 14, the high voltage bobbin 52 is provided with a 
plurality of flanges 57 for guiding and controlling the winding operation 
of the secondary winding 3 (not shown in FIG. 14). However, in the regions 
where the aforesaid high voltage diodes 4a and 4b are disposed, the 
distance between adjacent flanges 57 is increased to accommodate the high 
voltage diodes 4a and 4b. These relatively increased spaces between 
adjacent flanges 57 are utilized to form socket-like portions 58 on the 
high voltage bobbin 52. On the other hand, the insulating resin 42 for 
covering the high voltage capacitor 14 is formed with plug-like portions 
59 to be received in the socket-like portions 58. Each socket-like portion 
58 has its front end bifurcated to receive the plug-like portion 59 in the 
bifurcation so as to elastically hold the plug-like portion 59. In this 
manner, the high voltage capacitor 14 is positioned with respect to the 
high voltage bobbin 52. 
In an example shown in FIGS. 16 and 17, positioning members 60 are 
provided, extending from the opposite end surfaces of the high voltage 
bobbin 52, each positioning member 60 having a pair of holder elements 61 
formed on the front end thereof. On the other hand, opposite surfaces of 
the insulating resin 42 for covering the high voltage capacitor 14 are 
formed with grooves 62 for receiving the aforesaid holder elements 61. In 
addition, in this example, the grooves 62 formed in opposite surfaces are 
interconnected by a connecting groove 63 formed in the insulating resin 
42, and a portion of the positioning member 60 fits in said connecting 
groove 63. However, such connecting grooves 63 are not always necessary. 
The elasticity of the material of which the positioning members 60 are 
made acts to cause the holder elements 61 to elastically hold the 
insulating resin 42, whereby the high voltage capacitor 14 is positioned 
with respect to the high voltage bobbin 52. 
In an example shown in FIG. 18, positioning members 64 similar in shape to 
the positioning members 60 of FIG. 16 are provided, extending from the end 
surfaces of the high voltage bobbin 52. The positioning members 64 are 
each formed with a pair of holder elements 65. Each holder element 65 is 
formed with a hole 66. On the other hand, the insulating resin 42 for 
covering the high voltage capacitor 14 is formed with projections 67 to be 
received in the holes 66. Thus, the high voltage capacitor 14 is 
positioned with respect to the high voltage bobbin 52 in that the 
projections 67 are received in the holes 66. In addition, in the example 
shown in FIG. 18, grooves corresponding to the grooves 62 shown in the 
example illustrated in FIGS. 16 and 17 may be formed in the insulating 
resin 42. 
The method of positioning the high voltage capacitor 14 has been described 
so far by giving various examples, but other modifications are possible. 
For example, as shown in FIG. 5, in order to position the high voltage 
capacitor 14 with respect to the insulating case 15, projections 43 are 
formed on the high voltage capacitor 14 and recesses 44 are formed in the 
insulating case 15, but this may be reversed; that is, projections may be 
formed on the insulating case and recesses may be formed in the high 
voltage capacitor. 
The positioning of the high voltage capacitor 14 is in any sense temporary, 
being effective until the insulating resin 53 (FIG. 8) is charged into the 
insulating cases 15 and 47. Therefore, the positioning is not required to 
be so accurate and may be only to the extent of preventing deviation of 
the high voltage capacitor 14. That is, the high voltage capacitor 14 will 
be completely fixed in position by the insulating resin 53 to be 
subsequently charged. 
Further, the insulating case means to be provided for the flyback 
transformer need not be divided into the first and second case portions 
(insulating case 15 and insulating case 47) to be joined together, and 
instead it may be an integral insulating case. 
Although the present invention has been described and illustrated in 
detail, it is clearly understood that the same is by way of illustration 
and example only and is not to be taken by way of limitation, the spirit 
and scope of the present invention being limited only by the terms of the 
appended claims.