Contact pieces are accommodated respectively in contact housings in a main body portion. Each of the contact pieces has an intermediate portion extending between a contact portion and a terminal portion and force-fitted and held as a first discharge electrode portion in first positioning grooves. An arcuate grounding conductor is disposed on the main body portion and has integral second discharge electrode portions and dust-prevention lug portions. The second discharge electrode portions are held in confronting and spaced relation to the first discharge electrode portions via discharge gap holes formed in a side wall portion of the main body and are force-fitted and held in second positioning grooves. The first and second discharge electrode portions define discharge gaps therebetween. The first and second discharge electrode portions, inner wall surfaces of the discharge gap holes, and the dust-prevention lug portions define discharge gap chambers with the discharge gaps contained therein, the discharge gap chambers being isolated from the exterior.

BACKGROUND OF THE INVENTION 
The present invention relates to a cathode-ray tube socket for use in 
connection between a cathode-ray tube and an electric circuit, and more 
particularly to a cathode-ray tube having a discharge gap for preventing 
an overvoltage from being applied by the cathode-ray tube to the electric 
circuit 
Prior cathode-ray tubes are disclosed in U.S. Pat. No. 3,251,016 (issued on 
May 10, 1966) and U.S. Pat. No. 3,636,412 (issued on Jan. 18, 1972), for 
example. In the disclosed cathode-ray tubes, a grounding conductor is 
curved arcuately in substantially concentric relation to the arrangement 
of contacts, and electrode members project from the grounding conductor 
with a discharge gap left between the electrode members and the contacts. 
The grounding conductor is positioned with respect to a body of the 
cathode-ray tube socket, but the electrode members are not positioned 
independently with respect to the respective contacts. Therefore, a 
discharge gap of a high dimensional accuracy cannot be produced in the 
assembled socket. If the discharge gap were to be disposed fully within 
the socket body to guard against entry of dust, the overall construction 
would be complicated, or the socket body would have to be constructed of a 
plurality of assembled members. Otherwise, dust would easily find its way 
into the discharge gap, causing varying discharging characteristics 
thereof which lower its reliability. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a cathode-ray tube 
socket which can easily be fabricated, has a discharge gap of a high 
dimensional accuracy, and prevents dust or other foreign matter from 
entering the discharge gap. 
According to the present invention, contact pieces are force-fitted into 
and held in first positioning grooves in a body of an insulating material, 
and the positioned contact pieces have portions serving as first discharge 
electrode portions. The body has second positioning grooves defined 
therein and spaced a distance from the first positioning grooves, and 
second discharge electrode portions are force-fitted and positioned in the 
second positioning grooves. These second electrode portions are integrally 
united with a grounding conductor which is angularly bent in an arcuate 
shape. The positioned second electrode portions and the positioned first 
electrode portions of the contact pieces jointly define discharge gaps 
therebetween. The first and second electrode portions and the body jointly 
constitute closed discharge gap chambers so that dust or other foreign 
matter will not enter the discharge gap chambers. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description when 
taken in conjunction with the accompanying drawings in which a preferred 
embodiment of the present invention is shown by way of illustrative 
example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As illustrated in FIGS. 1 through 4, a body 11 of an insulating material is 
composed of a main body portion 12 in which terminal pins of a companion 
cathode-ray tube (CRT) will be inserted, and a high-voltage discharge gap 
chamber 13 integral with a side of the main body portion 12. Although the 
main body portion 12 of the practical embodiment of the CRT socket has 
rather a complex shape formed by many recesses and projections as seen 
from FIGS. 1, 1A and 1B, a simplified basic structure of the main body 12 
comprises a center cylindrical tube 12a, a first cylindrical side wall 12b 
disposed outside the center cylindrical tube 12a concentrically therewith, 
a front annular wall 12c connecting both front ends of the first 
cylindrical side wall 12b and the center cylindrical tube 12a, a second 
cylindrical side wall 12d disposed outside the center cylindrical tube 12a 
concentrically therewith and behind the first cylindrical side wall 12b, 
the outer diameter of the second cylindrical side wall 12d being larger 
than that of the first one 12 b, an intermediate annular step wall portion 
12e connecting a rear end of the first cylindrical side wall 12b and a 
front end of the second cylindrical side wall 12d to form a stepped 
portion of the socket, and a plurality of partition walls 12f disposed in 
parallel to the axis of the center cylindrical tube 12a at regular angular 
intervals to radially extend from the outer peripheral surface of the 
center cylindrical tube 12a to the inner peripheral surfaces of the first 
and second cylindrical side walls 12b, 12d, thereby forming a plurality of 
contact housings 17. Through holes 25 are made in the second cylindrical 
side wall 12d to communicate therethrough the respective contact housings 
17 with the outside, of the main body portion 12 defining discharge 
chamber holes 25. According to the present invention, positioning grooves 
23, 26 are provided both inside and outside of the second cylindrical side 
wall 12d near the respective through holes 25. Two discharge electrode 
faces 33, 42 are fixedly positioned in the respective inner and outer 
positioning grooves 23, 26 in opposing relation to each other via each 
through hole 25 to close the through hole from the respective inner and 
outer sides of the second cylindrical side wall 12d, thereby forming a 
substantially closed discharge chamber 25'. One of the two discharge 
electrode faces 33, 42 is a portion 33 of a contact piece 28 accommodated 
in the contact housing 17 and either one of the two discharge electrode 
faces 33, 42 has a semispherical projection 48 formed therein by a press 
to oppose the other discharge electrode face, thereby defining 
therebetween a discharge gap. 
Now, detailed explanations of a specific embodiment of the CRT socket 
according to the present invention will be given. The main body portion 12 
is substantially of a thick circular shape having a circular hole 15 of 
the center cylindrical tube 12a defined therethrough in coaxial relation 
to a central axis 14. The main body portion 12 has a plurality of terminal 
pin insertion holes 16 formed in the front annular wall 12c defining a 
front face at equal intervals along a circle concentric with the central 
axis 14 for the insertion of the terminal pins of the cathode-ray tube. 
The main body portion 12 also has the contact housings 17 (FIG. 4) 
communicating respectively with the terminal pin insertion holes 16 and 
extending in an axial direction to the rear (i.e. the bottom in FIGS. 1 
and 4) of the body 11. The contact pieces 28 (FIG. 7) are accommodated 
respectively in the contact housings 17 so that contact portions 18 of the 
contact pieces 28 are fitted in narrow portions of the housings 17 
adjacent to the terminal pin insertion holes 6. Each of the contact 
housings 17 has an expanded portion 19 outwardly expanding, at a position 
behind the contact portion 18, away from the central axis 14. The main 
body portion 12 also has an engagement recess 21 defined in an inner wall 
surface of the first cylindrical side wall 12b at the narrow portion of 
each contact housing 17, the engagement recess 21 being positioned 
adjacent the radially outer face of the contact portion 18 away from the 
central axis 14. The engagement recess 21 extends parallel to the central 
axis 14 rear to the expanded portion 19 of the contact housing 17 where 
the recess 21 ends to form an engagement step portion 22 as shown in FIG. 
1B. In the illustrated embodiment, no contact piece is accommodated in the 
contact housing 17 at an end of the circular arrangement of the contact 
housings 17 as seen from FIG. 3. 
Positioning grooves 23a, 23b are formed in opposing relation to each other 
at corners where the opposing partition walls 12f meet the inner surface 
of the second cylindrical side wall 12d as shown in FIGS. 1B and 6, the 
positioning grooves 23a, 23b extending in a direction along the central 
axis 14 of the main body portion 12 to reach an inner wall surface of the 
intermediate annular step wall 12e. Between the positioning grooves 23a, 
23b, there is formed in the second cylindrical side walls 12d the 
discharge gap chamber hole 25 communicating therethrough the contact 
housing 17 with the outside of the body portion 12. The main body portion 
12 has a smaller outside diameter at a front side relative to the 
arrangement of the discharge gap chamber holes 25. A pair of positioning 
grooves 26a, 26b (FIGS. 1A and 5) are provided on the outer surface of the 
second cylindrical side wall 12d on both sides of each discharge gap 
chamber hole 25 in opposing relation to each other, the positioning 
grooves 26a, 26b extending in parallel to the central axis 14. Thus, the 
positioning grooves 23a, 23b are arranged along one circle concentric with 
the central axis 14, while the positioning grooves 26a, 26b are arranged 
along another circle concentric with the central axis 14 in radially 
outward relation to the positioning grooves 23a, 23b. 
As shown in FIGS. 4 and 7, each of the contact pieces 28 received in the 
contact housings 17, respectively, is produced by cutting and bending a 
single metal strip. The contact portion 18 is formed by bending a T-shaped 
end of the metal strip into a substantially tubular shape. The contact 
portion 18 has a flat face 18a remote from the central axis 14, in which 
is formed a small engagement finger 29 raised integrally therefrom as by 
slitting. The flat face 18a is held in plane-to-plane contact with the 
inner wall surface of the first cylindrical side wall 12b such that the 
small engagement finger 29 projects into the engagement recess 21 and the 
tip of the finger 29 engages the engagement step portion 22 for anchoring 
the contact piece 28 against removal (FIGS. 4 and 4A). The tubular contact 
portion 18 has an intermediate portion pressed and displaced inwardly, to 
form a resilient receptacle 31 for resiliently receiving the terminal pin 
inserted through the insertion hole 16. As illustrated in FIGS. 1B and 4A, 
a front end of the flat face 18a is fitted in between a projection 91 and 
the inner wall surface of the side wall 12b to keep the contact portion 18 
from radial movement relative to the axis 14 upon insertion and removal of 
the cathode-ray tube terminal pin. 
The contact piece 28 has a neck portion 32 extended from the contact 
portion 18 and bent outwardly along an inner wall surface of the 
intermediate annular step wall 12e. The engagement step portion 22 is 
sandwiched between the neck portion 32 and the finger 29 of the contact 
piece 28, so that the contact piece 28 is fixed in place in the direction 
parallel to the axis 14 so as to be positioned stably upon insertion and 
removal of the terminal pins. The neck portion 32 has an outer end from 
which a discharge electrode portion 33 extends rearwardly along an inner 
wall surface of the second cylindrical side wall 12d. The discharge 
electrode portion 33 has a rear end from which an outer extension 34 
extends radially outwardly away from the central axis 14 along a rear 
surface of the main body portion 12. A terminal 35 extends integrally 
rearwardly from a rear end of the outer extension 34. 
The discharge electrode portion 33 has on opposite sides thereof engagement 
flanges 36a, 36b projecting in a width direction thereof and being 
slightly bent toward the central axis 14 obliquely to the face of the 
discharge electrode portion 33. The engagement flanges 36a, 36b have the 
front edges inclined for facilitating insertion thereof into the 
positioning grooves 23a, 23b. For assembly, the engagement flanges 36a, 
36b are force-fitted respectively into the positioning grooves 23a, 23b 
from behind the main body portion 12 to cause the discharge electrode 
portion 33 to tightly close the discharge gap chamber hole 25 on the side 
of the inner surface of the second cylindrical side wall 12d owing to a 
biasing force of the bent engagement flanges 36a 36b against the chamber 
hole 25. As shown in FIGS. 3 and 4, the outer extension 34 of the contact 
piece 28 is substantially fitted in each of radially extending recesses 39 
defined in the rear end surface of the second cylindrical side wall 12d. 
As shown in FIGS. 1, 2 and 8, a grounding conductor 41 is bent from a 
strip-shaped conductive member into an arcuate form extending along an 
outer peripheral surface of the main body portion 12 and having its width 
direction parallel to the central axis 14. From one marginal side of the 
grounding conductor 41 a plurality of discharge electrode portions 42 
extend in a width direction thereof. Each of the discharge electrode 
portions 42 has opposite engagement edges 43a, 43b extending from both 
sides thereof, the engagement edges 43a, 43b being bent slightly obliquely 
and radially outwardly away from the central axis 14. The engagement edges 
43a, 43b are tapered so that the distance therebetween is progressively 
reduced toward a distal end of the discharge electrode portion 42. The 
engagement edges 43a, 43b are force-fitted into the positioning grooves 
26a, 26b, respectively, from the front side of the main body portion 12 to 
position the discharge electrode portion 42. As thus assembled, the 
discharge electrode portion 42 tightly closes the discharge gap chamber 
hole 25 on the side of the outer peripheral surface of the second 
cylindrical side wall 12d owing to a biasing force of the bent engagement 
edges 43a, 43b against the chamber hole 25. The distal end of each 
discharge electrode portion 42 is fitted in a slot 45 formed integrally 
with the positioning grooves 26a, 26b adjacent a rear edge portion of each 
discharge gap chamber hole 25. 
The grounding conductor 41 has a plurality of dust-prevention lugs 46 each 
of which projects integrally from the other marginal side thereof and is 
bent toward the central axis 14 to close a guide recess 24 formed in the 
peripheral surface of the second cylindrical side wall at a boundary 
portion between the hole 25 and the outer surface of the intermediate 
annular step wall 12e to communicate therebetween. A plurality of shallow 
fitting recesses 47 are formed in the outer surface of the intermediate 
annular step wall 12e so as to surround marginal edges of the 
corresponding guide recesses 24. The dust-prevention lugs 46 are fitted 
respectively in the fitting recesses 47 to close the guide recesses 24. 
The guide recesses 24 are provided to allow passage therealong of 
semispherical projections 48 formed integrally with the respective 
electrode portions 42 at the centers thereof when the electrode portions 
42 are fitted into the positioning grooves 26a, 26b. The electrode portion 
33 of the contact piece 28, the electrode portion 42 of the grounding 
conductor 41, the dust-prevention lug 46, and the inner wall surface of 
the discharge gap chamber hole 25 jointly constitute a discharge gap 
chamber 25'. A discharge gap 49 is defined between each electrode portion 
33 and the semispherical projection 48 projecting from the corresponding 
electrode portion 42 toward the electrode portion 33. The grounding 
conductor 41 has substantially flat portions where the electrode portions 
42 and the dust-prevention lugs 46 project in opposite directions. 
Therefore, the grounding conductor 41 has a substantially polygonal shape. 
With the cathode-ray tube socket of the present invention, the discharge 
electrode portions 33 of the contact pieces 28 are force-fitted into the 
respective positioning grooves 23a, 23b, with the discharge gaps 49 being 
defined between the positioned electrode portions 33 and 42. The discharge 
electrode portions 42 are also fixedly positioned by force-fitting them 
into the positioning grooves 26a, 26b. The body 11 is molded of a 
synthetic resin material with a high dimensional accuracy. Therefore, the 
distance between the discharge electrode portions 33 and 42 can be of a 
high accuracy, and so is the length of the discharge gap 49. The electrode 
portions 42 of the grounding conductor 41 are simultaneously positioned 
simply by force-fitting the grounding conductor 41 from the front side of 
the body 11, and the contact pieces 28 are positioned by force-fitting 
thereof from the rear side of the body 11. Therefore, the parts can be 
assembled in a simple operation. The body 11 is a single construction, 
rather than an assembly of two front and rear halves, with the discharge 
gap chambers 25' being not defined by the body 11 itself. The discharge 
gap chambers 25' are closed by the electrode portions 33, 42 and the 
dust-prevention lugs 46 to guard against entry of dust through the guide 
recesses 24 and hence a reduction in operation reliability. The closed 
discharge gap chambers 25' are automatically constructed by force-fitting 
the contact pieces 28 and the electrode portions 42 in position. With the 
grounding conductor 41 being composed of a strip-shaped conductor 
angularly bent around the central axis 14, the material required of the 
grounding conductor 41 and the electrode portions 42 can be more 
effectively used than would be the case with a grounding conductor 
constructed as a ring-shaped strip with its transverse direction normal to 
the central axis 14. Accordingly, the socket can be of a reduced outside 
diameter. The contact pieces 28 may be of a so-called bifurcated type. 
The high-voltage chamber 13 of the body 11 will now be described. As shown 
in FIGS. 1, 9 and 10, the high-voltage chamber 13 is composed of a square 
box member 51 integrally projecting from a side of the main body member 
12, and a cover member 52 closing a front opening in the box member 51. 
High-voltage discharge electrodes 53, 54 are disposed in the box member 51 
in confronting relation to each other. These high-voltage discharge 
electrodes 53, 54 comprise square metal plates having central 
semispherical protuberances projecting toward each other with a 
high-voltage discharge gap defined therebetween. In the illustrated 
embodiment, the electrode 53 extends substantially centrally in the box 
member 51 in a direction parallel to the central axis 14, while the 
electrode 54 is held against a side wall 51a of the box member 51 which 
faces the electrode 53. The electrode 54 has opposite edges guided and 
held in support grooves 55a, 55b defined in the side wall 51a and 
extending in the direction parallel to the central axis 14. 
One of the contact pieces 28 closest to the high-voltage chamber 13 serves 
as a high-voltage contact 28h, which, as shown in FIGS. 4 and 11, is 
formed integrally with the high-voltage discharge electrode 53. The 
high-voltage contact 28h includes a contact portion 18a having a rear end 
extending rearwardly and from which a connecting portion 57 is bent 
substantially at a right angle toward the high-voltage chamber 13. The 
connecting portion 57 passes through a passage 59 defined in a partition 
58 between the main body portion 12 and the box member 51 into the 
high-voltage chamber 13, as shown in FIG. 10. The connecting portion 57 
extends along an inner surface of a rear plate 51c of the box member 51. 
The connecting portion 57 is positioned on one side of the electrode 53 
opposite from the electrode 54, and includes a neck portion 57a (FIG. 11) 
extending obliquely in a forward direction (i.e. in an upper direction in 
FIGS. 10, 11) toward the electrode 53 and integrally joined to a rear edge 
of the electrode 53. The electrode 53 is connected to a high-voltage front 
terminal 35h extending in the forward direction remotely from the 
high-voltage contact 28h and the electrode 54. 
The electrode 53 is coupled to the high-voltage front terminal 35h by a 
bent portion 61 which is substantially surrounded by a rectangular tubular 
wall 62 integrally projecting from the rear plate 51c. The opposite edges 
of the electrode 53 are held in a support slot 63a defined in the 
partition 58 and a slot 63b formed in the rectangular tubular wall 62. 
Ribs 64 are disposed on inner surfaces of the box member 51 between 
marginal edges of the electrodes 53 and 54 for increasing the creeping 
distance. The electrode 54 has a terminal 65 projecting rearwardly from 
the rear plate 51c of the box member 51 as shown in FIG. 4. 
The cover member 52 is substantially fitted over a front outer peripheral 
surface of the box member 51. As illustrated in FIGS. 9 and 10, locking 
members 66a, 66b of a V-shaped cross section extend integrally rearwardly 
from rear ends of side plates 52a, 52b of the cover member 52 which are 
held respectively against confronting side walls 51a, 51b of the box 
member 51. Tapered ridges 68a, 68b are integrally formed on outer surfaces 
of the side walls 51a, 51b, the tapered ridges 68a, 68b progressively 
projecting laterally toward the rear ends thereof. The cover member 52 is 
fixed to the box member 51 when the locking members 66a, 66b, are locked 
by the tapered ridges 68a, 68b. As shown in FIG. 1, the main body portion 
12 has a high-voltage protective groove 71 defined in a front surface 
thereof in surrounding relation to the high-voltage contact 28h, the 
protective groove 71 communicating with the central hole 15. A protective 
member 72 (FIG. 10) is inserted in the protective groove 71 and held 
against the partition 58. The protective member 72 is integral with the 
cover 52 and closes the passages 59 while pressing the connecting portion 
57 against the rear plate 51c (FIG. 4). As shown in FIG. 9, a plurality of 
ribs 73 are integrally formed with the cover member 52 between the 
electrodes 53 and 54 to increase the creeping distance along an inner 
surface of the cover member 52 between the electrodes 53 and 54. A presser 
projection 74 is integrally formed on an inner surface of the cover member 
52 for pressing the bent portion 61 rearwardly against a projection 75 
integrally projecting from the rear plate 51c. 
The high-voltage terminal 35h projects out of the cover member 52 through a 
small hole 76 defined in the cover member 52. In the illustrated 
embodiment, the high-voltage terminal 35h is shielded by a protective 
cover 77 molded of synthetic resin integrally with an edge of the cover 
member 52 remotely from the main body portion 12 so that the protective 
cover 77 will be angularly movable about the joined edge. When the 
protective cover 77 is turned into confronting relation to the front 
surface of the cover member 52, U-shaped locking members 78a, 78b formed 
integrally with the protective cover 77 are locked on locking ridges 81a, 
81b (FIG. 2) on the side plates 52a, 52b of the cover member 52. The 
protective cover 77 has a recesss 83 through which a lead wire connected 
to the high-voltage terminal 35h can be led out of the protective cover 
77. 
When the electrode portions 33 and 42 of the contact pieces 28 and the 
grounding conductor 41 are respectively force-fitted into the main body 
portion 12, they are automatically positioned in confronting relation with 
distance gaps of a prescribed length defined therebetween. Since the 
discharged gap chambers 25' can be closed off the exterior by the 
electroce portions 33, 42, and the inner surfaces of the discharge gap 
chamber holes 25, the dust-prevention lugs 46 may be dispensed with. 
As mentioned before, the guide recesses 24 are required for allowing the 
passage of the semispherical projections 48 as long as the discharge 
electrode portions 42 are inserted into the positioning grooves 26a, 26b 
in the direction of the axis 14, and these guide recesses 24 must be 
covered with the lugs 46 for dust-prevention. However, in the case where 
the electrode portions 42 are forcibly mounted on the main body member 12 
to close one of the openings of the holes 25 in the direction in which the 
semispherical projections 48 project, the guide recesses 24 are not needed 
and the dust-prevention luge 46 may be dispensed with. 
Semispherical projections may be formed on the electrode portions 33 of the 
contact pieces 28, as indicated by the broken lines in FIG. 7. With such 
an alternative, the semispherical projections 48 on the electrode portions 
42 may be replaced by flat electrodes and those guide recesses 24 are not 
required anymore. Therefore, the dust-prevention lugs 46 as well as the 
fitting recesses 47 may also be dispensed with. However, it will be 
necessary to form guide recesses in the inner surface of the second 
cylindrical side wall 12d along and between the positioning grooves 23a 
and 23b at the respective contact housing 17, thereby allowing the 
semispherical projections on the electrodes 33 to pass therethrough when 
the latter are to be force-fitted into the positioning grooves 23a, 23b. 
Such guide recesses may be closed by the outer extensions 34 of the 
contact pieces 28 shown in FIG. 7, which double as duct-prevention lugs. 
Although a certain preferred embodiment has been shown and described, it 
should be understood that many changes and modifications may be made 
therein without departing from the scope of the appended claims.