Radiant energy – Photocells; circuits and apparatus – Housings
Reexamination Certificate
2000-08-30
2002-05-28
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Housings
C250S216000
Reexamination Certificate
active
06396055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display screen, which includes a front pane portion and a circumferential flange portion, whose outer surface includes a circumferential ring-shaped region, designated in the following as a KC surface, which extends substantially parallel to a central longitudinal axis that is perpendicular to a surface passing through a center point of the front pane portion. A circumferential solder edge is located on an opposite side of the flange portion from the front pane portion. The invention also relates to an apparatus including a press tool for making the display screen according to the invention.
2. Prior Art
A display screen of the above-described type comprising a front pane portion and a circumferential flange portion with an outer surface having the KC surface and a solder edge is known from DE 34 43 498 A1.
An apparatus for making the known display screen is described in DE 198 23 710 A1. This apparatus includes a press tool comprising an upper die, a lower molding part and a neck ring that rests on the lower molding part.
Display screens are required for making cathode ray tubes, which are used for example in televisions or monitors. The principal parts of the image-forming tube are the display screen, a funnel, a slot mask in the case of color forming tubes, an electron gun for forming an electron beam, a deflection device for the electron beam and an implosion-protecting frame.
In the course of the manufacturing process of an image-forming tube solder glass is applied to the solder surface that contacts the opposing surface of the funnel. To connect the funnel with the display screen, which both are made of glass, the funnel is inserted with its neck pointing down in a frame and the display screen is placed with its solder surface formed on the peripheral frame on it. After that both parts are transported through a tunnel oven in which the glass solder is melted. By its own weight the display screen distributes the melted solder glass uniformly between the bearing surfaces. After cooling the screen and funnel are rigidly connected with each other. Subsequently the electron beam system is bonded onto the funnel neck.
Cathode ray tubes must be operate with a high vacuum. In order to produce this high vacuum, the image-forming tubes are heated in another tunnel oven to 350° C. and pumped out through their still open neck to empty them of the air inside them. After the end of this process step, which lasts about 2 ½ hours, the funnel neck is melted to close it. Because of this evacuation of the funnel tube the display screen is strongly stressed or loaded by the surrounding air pressure. The display screen is slightly deformed about a few tenths of a millimeter by this pressure. In order to stabilize the screen and thus to protect the image-forming tube effectively from implosion, a steel frame is provided around the outside on the screen frame. Furthermore this steel frame is heated inductively to 450° C. and the image-forming tube is pushed in this frame. Finally the deflection device is put on the funnel neck.
The display screens are pressed from glass material. The pressing process is illustrated in
FIG. 6
, which shows a conventional pressing tool
10
. The pressing tool
10
comprises an upper die
11
, a lower mold part
13
and a neck ring
12
. A glass portion
16
is dropped into the mold formed by the neck ring
12
and the lower mold part
13
and is brought to the desired shape with the upper die
11
. The circumferential surface (also designated the KC surface), on which the implosion-protecting frame is mounted in the finished display screen, is formed by the inner surface
14
of the neck ring
12
.
At the positions, on which the lower mold part
13
and the neck ring
12
bear on each other, both parts do not ideally fit snugly on each other. A mold seam at this location is a manifestation of this situation in the pressed display screen. This mold seam can be formed as an offset, wherein either the upper part or the lower part protrudes, or as a pressed out region, i.e. a circumferential bulge.
A conventional display screen is shown in FIG.
5
. The display screen I has a convex front pane portion
2
and a circumferential flange portion
3
, on which a KC surface
5
is formed, which extends parallel to a central axis
8
of the front pane
2
. The circumferential flange portion
3
has a mold seam
4
on its lower edge. Display screens which are designated as flat have a radius of curvature of less than 10 m. Display screens which have a radius of curvature greater than that are designated as convex display screens.
Flat front pane portions
2
, i.e. flat display screens, are of increasing importance, because the trend is to ever flatter televisions and monitors. One problem with the flat front display screen is that its reduced curvature makes it less resistant to elevated pressures and increases the implosion danger in comparison to curved front pane portions. The implosion danger is usually reduced in the art by increasing the height of the circumferential flange portion so that the flange portion can take the additional stresses. The disadvantage of this method is that the degree of flatness that one has obtained by making the front pane portion flatter in the finished television or monitor is lost again because of the larger display screen flange portion.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved display screen which can be used to build a flatter television or monitor than currently known in the art, without increasing the implosion danger.
It is an additional object of the present invention to provide an apparatus for making the improved display screen, from which the flatter television or monitor is constructed.
These objects, and others which will be made more apparent hereinafter, are attained in a display screen for an imaging-forming tube of a television or monitor comprising a front pane portion and a circumferential flange portion, the flange portion having an outer surface and a circumferential solder edge on an end of the circumferential flange portion opposite from the front pane portion.
According to the invention the outer surface of the flange portion has a circumferential ring-shaped region, designated a KC surface, the circumferential ring-shaped region of the outer surface extends substantially parallel to a central axis, which is perpendicular to a surface of the front pane portion passing through a center point on the front pane portion; and a part of the circumferential flange portion between the solder edge and the circumferential ring-shaped region has a wall thickness that is greater than a wall thickness of the circumferential flange portion in the circumferential ring-shaped region.
The above objects are also attained in an apparatus for making the display screen comprising a pressing tool for pressing a glass portion to form the display screen, the pressing tool including a lower mold part having an interior space for the glass portion, a neck ring resting on the upper edge of the lower mold part and an upper die that is insertable into the interior space of the lower mold part through the neck ring in order to shape the glass portion.
According to one embodiment of the invention neck ring has an interior radially widened cavity that is wider than the interior space of the lower mold part, which forms or molds the part of the circumferential flange portion between the solder edge and the circumferential ring-shaped region having the wall thickness that is greater than the wall thickness of the circumferential flange portion in the circumferential ring-shaped region.
According to another embodiment of the invention a radially widened portion of the interior space of the lower mold part that is wider than a remaining portion of interior space is provided at the upper edge of the lower mold part. This radially widened portion of the lower mold part together with the lower part of the neck
Le Que T.
Schott Glas
Striker Michael J.
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