|Publication number||US2799793 A|
|Publication date||Jul 16, 1957|
|Filing date||Oct 31, 1952|
|Priority date||Oct 31, 1952|
|Publication number||US 2799793 A, US 2799793A, US-A-2799793, US2799793 A, US2799793A|
|Inventors||Cain Donald J De|
|Original Assignee||Gen Precision Lab Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (33), Classifications (17)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Jul 16, 1957 D. J, DE CAIN ELECTRONIC TUBE SHIELD Filed Oct. 31. 1952 I N V EN TOR. DON/9L0 4/. 05 C/Q/N HTTOR/VEY.
United States Patent '0 ELECTRONIC TUBE SHIELD Donald J. De Cain, Mount Vernon, N. Y., assignor to General Precision Laboratory Incorporated, a corporation of New York Application October 31, 1952, Serial No. 317,888
9 Claims. (Cl. 313-312) This invention relates to shields for electronic tubes and especially to tube shields facilitating heat dissipation.
Electronic tubes require electrostaticshielding'in many applications. Frequently tubes also have to be shock mounted, and when the tube envelope is fastened to a base by means of a spring clip the conventional type of tube socket shock mounting cannot be used. .A problem is presented when clip fastening, shock mounting and electrostatic shielding are all required and the problem is complicated by the necessity for dissipating the heat generated inside the tube.
The problem is particularly acute with subminiature tubes when they are mounted by clipping the envelopes to a base card, as they frequently are. It is desirable to make the tube shield integral with and inseparable from the tube, to facilitate stocking and replacement, yet to incorporate in the shield the function of protecting the tube from mechanical shock.
The present invention solves this problem by covering the glass tube envelope with a form fitting metal sheet separated from the envelope by a layer of heat-conductive rubber-like material. This material is securely and permanently bonded both to the glass envelope and to the metal shield. The metal shield thus constitutes a solid external surface which can be gripped positively by the metal spring clip which mechanically secures the tube to the base card.
The principal purpose of this invention then is to provide a shield for electronic tubes which not only shields the tube electrostatically, but also protects the tube against mechanical shock while facilitating heat dissipation.
A further purpose of this invention is to provide a shield for subminiature tubes, the shield being integrally associated with the tube so as to facilitate stocking, mounting and replacement.
A complete understanding of this invention may be secured from the detailed description and drawings, in which:
Figure 1 is a plan view of a subminiature tube partly enclosed in a cover in accordance with the invention.
Figure 2 is an enlarged cross section of the tube and cover of Fig. 1 along the line 22. I
Referring now to Fig. 1, a subminiature tube 11 is provided with a cover 12 that is both shock absorbent and heat dissipative as well as constituting an electrostatic shield. The cover 12 is securely bonded and attached to the tube envelope, and is clipped by means of metal clips 13 and 13' to a card 14 of insulating material. Connections may be made between the tube terminal wires such as 16 and other components either directly or through terminals such as 17 by means of connecting wires or so-called printed conductive strips on the front or rear face of the card 14.
In the cross section of Fig. 2 the glass tube envelope is indicated at 18. Surrounding the envelope 18 there is a two-layer cover. The first layer 19 is made of a,
rubber-like material which is firmly and continuously bonded to the glass envelope at all points. This material consists of a silicone rubber loaded or impregnated with a quantity of metal particles to increase its heat conductivity. Any metal particles may be employed such as copper, aluminum, silver or zinc, and the particles may be of any convenient small size. The silicone rubber is resilient and the thickness of the layer is sufficient to provide mechanical shock protection for the tube. For example, in the case of a subminiature cylindrical tube envelope having a diameter of inch, a thickness of silicone rubber of A inch has been found to be satisfactory.
The silicone rubber layer is surrounded by a metallic shield 21, the two being firmly and permanently bonded together. The shield 21 serves as a mechanical protection for the silicone rubber layer and as a base for the mechanical support by clips of the entire tube and jacket assembly. In addition the shield 21 serves as an electrostatic tube shield and as an external heat radiating and conducting surface for dissipating the tube heat.
The tube and cover assembly is firmly gripped and held by the spring clips 13 and 13, these clips being riveted at 22 and 22 to the base 14. A ground wire 23 is desirable because of the electrostatic shielding function of the shield 21. As a specific example of one tube cover assembly, a subminiature tube type 5902 having an outer envelope diameter of 0.375 inch is provided with a shield made to a similar shape but inch larger at all points and therefore having an inner diameter of 0.5 inch. The shield is made of & inch copper sheet formed into a round bottomed cup by punching and die forming. The silicone rubber layer is compounded starting with uncured silicone rubber having the consistency of soft putty. Into this is thoroughly mixed 5% to 50% of electrolytic copper dust. A primer coating of silicone resin varnish is applied to the interior of the copper cup, the mixture placed into the copper cup, and then the subminiature tube is pressed into the cup and positioned centrally thereof. The waste extruded compound is removed and the assembly is baked at C. for one hour to cure the silicone rubber. No primer coating is necessary for the glass tube envelope. In curing, the silicone rubber expands slightly to fill all voids, sets and becomes resilient, and bonds firmly to both the glass tube envelope and the interior of the copper cup. After trimming any excess silicone rubber from the edge of the cup the assembly is ready for clipping to the card 14 and for making terminal connec tions.
This method of securing and shielding the tube thus provides good heat dissipation while protecting the tube from injury by mechanical shock and permitting the use of conventional clip mounting. The silicone rubber with stands the highest temperatures to which it can here be subjected. The assembly takes but little space, and stocking and replacement of the covered tube as a unit are no more diflicult than stocking and replacing the bare tube.
What is claimed is:
1. An electronic tube cover assembly comprising, an electronic tube having an envelope, a layer of resilient, heat-conductive silicone material bonded to the outer surface of said envelope, and an exterior metallic layer bonded to the outer surface of said resilient heat-conductive material.
2. A shield for an electronic tube comprising, a thickness of rubber-like material containing silicone bonded to the outside envelope of said electronic tube, and metallic electrostatic shielding means bonded to the outer surface of said rubber-like material thickness.
3. A shield for an electronic tube having a glass enhaving relatively high heat conductivity bonded to the outer surface of said envelope, and a metallic shell securely bonded to the outer surface of said layer of silicone rubber.
5. A shock-resistant, heat-transmitting shield for the envelope of an electronic tube comprising, a sheath of resilient silicone rubber containing an admixture of finely divided metallic particles and having relatively high heat conductivity, said sheath being bonded to the outer sur face of the envelope of said electronic tube, and a metallic cup bonded to the outer surface of said sheath to form a surrounding shell.
6. A shock-resistant, heat-transmitting shield for the envelope of an electronic tube in accordance with claim 5 in which said finely divided metallic particles consist of electrolytic copper dust.
7. A shock-resistant, heat-transmitting shield for the envelope of an electronic tube in accordance with claim 6 in which the electrolytic copper dust in said admixture is of from 5% to 50% of the quantity of said silicone rubber.
8. An electronic tube cover and clip assembly comprising, an electronic tube having an envelope, a layer of resilient heat-conductive silicone material bonded to the outer surface of said envelope, an exterior metallic layer bonded to the outer surface of said resilient heat-conductive material, and spring clip means partly surrounding said metallic layer for securing it to a base.
9. An electronic tube cover and clip assembly comprising, a layer of resilient silicone rubber containing metallic particles and having relatively high heat conductivity bonded to the outer surface of said electronic tube, a metallic shell securely bonded to the outer surface of said layer of silicone rubber, and spring clip means partly surrounding said metallic layer for securing it to a base.
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|U.S. Classification||174/395, 165/69, 439/485, 62/304, 439/607.1, 313/312, 165/905, 165/185, 165/180, 200/33.00A, 165/80.3, 313/17|
|International Classification||H01J19/66, H01J5/12|
|Cooperative Classification||Y10S165/905, H01J5/12|