US2745895A - Vacuum tube shield and heat radiator - Google Patents

Description

May 15, 1956 E. J. LIDEEN VACUUM TUBE SHIELD AND HEAT RADIATOR Filed June 9, 1951 VACUUM TUBE SHIELD AND HEAT RADIATOR Ernest J. Lideen, Cicero, ill. Application June 9, 1951, Serial No. 23%,770 "7 (iiairns. (Cl. 174--35) This invention relates generally to vacuum tubes and more particularly to a combination radiation shield and heat radiator for use with such tubes.

In radio and television receivers and transmitters it is frequently advantageous to provide grounded shields to prevent interference between certain vacuum tubes and other components of the circuits. This is particularly true when glass walled tubes are employed in the radio frequency portions of the circuits.

Most vacuum tubes will operate more efficiently over long periods of time if they are cooled so that they cannot become overheated, as is likely to occur when the eat developed by the tube filaments is not dissipated to the atmosphere at a high enough rate.

When conventional tube shields are employed to protect against radiation and stray fields the shields tend to decrease the rate of heat transfer from the tube to the atmosphere, with a result that the tubes are even more likely to become overheated so that their effective life is shortened. I

Accordingly, one important object of this invention is to provide a tube shield which increases rather than decreases in the rate at which heat transferred from the tube yet which completely encloses the tube to prevent electrical interference.

Another object is to provide a cylindrical element which may he slipped over a metal walled vacutun tube, where shielding is of little importance, and which will increase the rate of heat transfer from the tube so that the tube will operate at a lower temperature.

A further object is to provide the tube shield which forms a finned radiator around the tube, having vertically disposed air ducts along the sides of the tube so that the tube may be cooled by conduction, radiation and convection.

hired States Patent 055cc A further object is a tube shield which also may be used as a shielding element or heat radiator or both for condensers, whether dry or electrolytic, and other circuit elements, the shield also being adapted to enclose either circular or non-circular elements.

Another object is to provide a cylindrical shield which may be easily fabricated from sheet material and whose diameter may be adjusted to suit various sized tubes.

Other objects and advantages of the combination tube shield and radiator of this invention will present themselves to those familiar with the art on reading the following specification in conjunction with the drawings and appended claims.

In the drawing:

Fig. l is a perspective view of a glass walled vacuum tube provided with the shield of this invention.

Fig. 2 is an elevation showing the manner in which the shield of this invention is used with a glass walled tube having straight sides, the shield being shown in section.

Fig. 3 is a view similar to Fig. 2, showing another form of the shield installed on metal tube as a heat radiator.

2,745,395 Patented May 15, 1956 Fig. 4 is a view similar to Fig. 2, showing shield of this invention installed on a peanut tube.

Fig. 5 is a view similar to Fig. 4, showing a modified form of the shield having a cover and mounted on a grounding ring.

Fig. 6 is a plan view of a portion of a strip of metal which has been severed longitudinally prior to corrugafrom.

Fig. 7 is a plan view of a portion of half the strip of Fig. 6 after corrugation, and

Fig. 8 is a perspective view showing a corrugated blank, bent to a cylindrical shape, for installation on a vacuum tube.

A fundamental concept of the vacuum tube cooler and shield of this invention is to provide a longitudinally corrugated piece of sheet metal, which is bent to a cylindrical shape about a longitudinal axis and slipped over a vacuum tube. The bottom edge of the corrugated cylinder is provided with an irregular contour so to to provide a plurality of inlet ports at the bottom of the shield so that cool air may enter near the base of the tube and flow upwardly through the space defined by the corrugations and over the surface of the tube to cool both the tube and the shield.

In the detailed description which follows and in the claims, the word shield is used to describe the cylindrical corrugated strip, regardless of whether its primary purpose is to prevent electrical interference or simply to facilitate the transfer of the dissipation of heat.

In Fig. l of the drawing a preferred embodiment of the shield 10 is shown installed on a glass-walled vacuum tube 11. The tube 11 is of the type having generally upwardly diverging side walls, and the upper portion of the tube is larger than the base. Accordingly the shield 10 is preferably supported on a grounding ring (shown in broken lines) which is fixed to the metal chassis 13.

The shield 10 is formed of a substantially rectangular piece of sheet metal, preferably thin aluminum, which is corrugated and bent to a cylindrical shape. The ends of the sheet indicated at 14 and 15 are slipped over one another so that the corrugations interlock as shown. If desired the ends may be riveted or otherwise fastened together, but this is not necessary or desirable in most cases. The bottom of the sheet which forms the shield 10, is cut to have a scalloped edge in order to provide a plurality of air inlet openings 16, thus each of the flutes 17 formed inside the shield 10 by the corrugations is open to the atmosphere outside of the grounding ring 12, near the base of the tube. This allows air to flow into the shield 10, up the flutes 17, over the tube 11 and out of the top end of the shield as indicated by the arrows 18, and both the tube and the shield are continually cooled by a rising column of air.

The inside of the shield 10 contacts the glass wall of the tube 11 near the top of the tube and, accordingly, heat is transferred by conduction from the tube to the shield. Similarly heat is transferred directly by radiation from the various parts of the tube to the shield. The shield 10, of course, is also cooled on the outside by convection and radiation in addition to the cooling effect to the air flowing upwardly through the flutes it. In some cases it has proved desirable to employ a cylindrical sleeve around the outer surface of the shield 30, in order to provide exterior ducts to promote air circulation over the outside of the shield 10. In most instances, however, the construction shown is adequate.

The natural resiliency of the corrugated shield 16 causes it to engage the sidewall of the tube 11 and the locking ring securely and also makes some variation in size possible, since the shield may be stretched to slip over tubes or rings which are somewhat larger than the normal diameter of the shield. Similarly the engaging edges 14 and 15 maybe disengaged and made to overlap one or more additional corrugations to increase or decrease diameter of the shield 10, thus a given shield may be used with tubes of many difierent sizes, making it unnecessary tomanufacture and stock large'numbers of shields. The resiliency of the sidewall also makes it possible to use the shield, 10 on non-circular cylindrical. or prismatic objects since the shield tends to. follow the, shortest periphery when stretched over an object. This makes it possible to use the shield 10, on most types of circuit components including condensers.

In Fig. 2, a shield 10 is shown installed on a-tube 111: having cylindrical sidewalls. In this. installation no grounding ring is used, thefluted. ends of the, shield merely resting on the chassis 13 to groundthe shield. In this installation the fluted sides of the shield 11) engage substantial portions of the tube wall to eflfect heat transfer by conduction from the tube to the shield. The lower end of the shield N is scalloped to provide air inlet ports 1% and engages the tube socket 20.

The manner in which the shield of this inventionmay be used as a cooler for a metal tube 11b is shown in Fig. 3. in this case the function of the shield 18 is primarily to cool the tube 11b, and, accordingly, the shield is slipped directly over the metal shell of the tube and, is not separately grounded. The shield 1% contacts the walls of the tube 111; along its entire length to eflect very good conductive heat transfer from the metal of the tube to the shield. The internal flutes 17b form a plurality of chimneys or ducts about the side of the. tube through which cool air flows by convection, the chimney eifect substantially increasing the rate of heat transfer over that which would occur if the tube were merely exposed to static air. The shield 10b differs from the preferred embodiment in that both its upper and lower ends are scalloped. Otherwise it is identical, the scalloping of the upper end serving no function when the top of the tube is not covered. The scalloped upper end results when a number of narrow strips are cut from a wide strip to form the blanks from which the shields are formed. This will be clarified in the description of Figs. 68 which follows:

In Fig. 4 a smaller sized shield 10c is shown installed on peanut or baseless type tube 110. This embodiment, except for size, is substantially identical with that shown in Figs. 1 and 2.

In Fig. 5 a peanut tube 1111 is provided with a grounding ring 12!; surrounding, the socket Ztld and a two-piece shield i012 which completely encloses the tube. The side portion of the shield, 10b is identical with the shield ltlc, the shield; being stretched somewhat to fit over the grounding ring 1%. Toenclose the top of the' tube 11d a cup shaped cap 21 is provided. Thiscap has preferably the same diameter, as the ring 121;, and it is slipped inside the shield 1% so as to leave the upper ends of the flutes 17b open to the atmosphere, thus the circulation of air through the flutes and over the tube is not impeded by the cap 21., To prevent the accumulation of heated air about the tube, an opening 22 is .provided in the center of cap 21. This opening also permits the tube to be readily inspected to see whether the filament is glowing.

Although a number of adaptations of, the shield of this invention have been shown, the examples are not exhaustive and other modifications or combinations of the diflerent adaptations may be made in order to meet particular situations. For example, the. shield of Fig. 1 may be provided with a cap similar to the cap 21 should it prove desirable to shield the top of the tube 11. If the tube to be shielded is of the type which has a connection terminal on the top, a larger opening 22 or other conventional arrangement would have to be provided in the cap 21 so that the lead wire to the top terminal would not touch the cap 21.

In some instances it, has. proved desirable. to use. a.

modified form of corrugation wherein the wave form is square or rectangular instead of sinusoidal. This produces somewhat better conductive heat transfer because of the larger area of contact.

A preferred method of making the corrugated shields of this invention is shown in Fig. 6-8. The first step in this method is to sever an elongated strip of sheet metal into two halves along a sinusoidal line as indicated at 24. This cut' 24 serves to form the scalloped edge which forms the inlet ports 16 after the strips have been corrugated. The next step of the process is to take either half of the. longitudinally severed strip and pass it through corrugating rolls to give it the shape shown in Fig. 7. It is preferred that the scallops formed by the cut 24 be in register with the corrugations so that when the shield is formed each of the internal flutes 17 is provided with a port 18 at its lower end. However, registration between the scallops and the flutes is not necessary, and, if the period of the sinusoidal variation of the scalloped edge is different from the period of the sinusoidal corrugation, random spacing will result with the further result that the bottoms of the flutes 17 will be sufiiciently open to. permit free air flow.

In Fig. 8, a corrugated strip is shown after having been cut to length and bent to form a cylinder. The step of cutting the strips to length may be performed before the corrugation step, if desired, and when this is done the corrugated rollers can be so arranged to bend the strip into a cylinder during corrugation.

From the foregoing, it will be apparent that a superior shield has been provided, which not only encloses the circuit element to be shielded but also promotes the cooling thereof and is useful as a cooling element even when shielding is not required, moreover, the device of this invention is universal in size so as to accommodate tubes or elements of different diameters and shapes and is inexpensively and easily fabricated.

Various other changes or modifications in addition to those set forth herein and such as will present themselves to those familiar to the art may be made without departing from the spirit of this invention the scope of which is commensurate with the following claims.

What is claimed is:

1. In combination a vacuum tube mounted in a tube socket, a grounding ring surrounding said socket, and a tube shield supported upon said'grornding ring in slid able, telescoping relationship therewith and enclosing the sides of said tube, said shield comprising a corrugated piece of sheet metal affording vertical air flow channels and bent to a cylindrical form having an internal diameter substantially the same as said tube, the bottom of said shield having an irregular edge to provide air inlet openings sidewardly into the air flow channels formed by the corrugations adjacent to said grounding ring.

2. A combination wave shield and heat dissipating accessory slidably received on thermionic valves which comprises a cylindrical jacket constructed of circumferentially undulating springable sheet metal coextensive longitudinally with the envelope of a valve and forming alternate inner and outer longitudinally disposed flutes, the inner flutes having tangential contact with the periphery of the valve envelope and the spaces intervening the flutes forming vertical chimney flues stimulated by the radiant and convected heat emanating tom the valve, and means for increasing the accessibility for replacement air to said flues comprising a lowermost skirting portion of said jacket scalloped at coincidence with said undulations.

3. In combination a vacuum tube mounted in a tube socket,, a grounding ring surrounding said socket, and a tube shield supported upon said grounding ring in slidabletelescoping relationship therewith and enclosing the sides of said tube, said shield comprising a corrugated. piece ofsheet metal bent toform a cylinder having an internal diameter substantially the same as the maximum diameter of said tube, the bottom of said shield having an irregular edge to provide air inlet openings sidewardly into the internal flutes formed by the corrugations adjacent to said grounding ring, and a cup shaped cap shield having a flange of approximately the same diameter as the ring received in readily removable sliding relationship within the upper end of the shield to leave the upper ends of the flutes open to the atmosphere, said internal flutes providing air flow chimneys Whose upper inner walls are defined by said cap.

4. The combination called for in claim 3 in which the cup shaped cap telescopes in sliding relationship to a depth in the shield limited only by the tube itself to leave the top of said flutes open and unobstructed in a vertical direction.

5. A readily installed and removable radiation shield slidably received upon an electron discharge tube comprising a corrugated sheet metal member of. high heat conductivity bent to a cylindrical form with edges overlapping difierent distances to afford difierent inside diameters, said corrugations extending longitudinally of said member to encompass and contact the tube along the inner folds of the corrugations to provide intermediate vertically disposed air passageways defined by protuberant flutes, said sheet metal corrugations being of springable stock permitting expansion of the shield to accommodate a range of variations in tube dimensions, the heat of said tube inducing convective flow of air through said passageways in direct contact with the tube, and means for increasing the intake capacity through said passageways comprising inclined cutaway portions at the lower ends of said corrugations affording lateral intake of air to said passageways.

6. A radiation shield slidably received upon an electron discharge tube which comprises an encircling jacket of corrugated sheet metal formed to present alternate and opposite flute formations of sinusoidal cross-section, the sheet metal of said shield jacket being of thin flexible stock whereby to afford garter-like stretching to accommodate for variations of tube envelope circumferences while permitting a chimney forming engagement of the internal flute formations in heat exchange contact against the tube periphery along the entire tube length, and a top closure for said shield comprising a plug formed cylinder cap with sides proportioned to have telescoping engagement with said flute formations at one end of said shield bottom of said shield having an irregular edge to provide air inlet openings sidewardly into the internal flute formations formed by the corrugations.

7. In combination a vacuum tube mounted in a tube socket, a grounding ring surrounding said socket, and a tube shield supported upon said grounding ring in slidable telescoping relationship therewith and enclosing the sides of said tube, said shield comprising a corrugated piece of sheet metal bent to form a cylinder having an internal diameter substantially the same as the maximum diameter of said tube, the bottom of said shield having an irregular edge to provide air inlet openings into the internal flutes formed by the corrugations adjacent to said grounding ring, and a cup shaped cap shield having a flange of approximately the same diameter as the ring received in readily removable sliding relationship within the upper end of the shield to leave the upper ends of the flutes open to the atmosphere, said shield having overlapping interlocking nesting edges capable of engagement in a plurality of diflFerent relationships to provide a shield of different diameter.

References Cited in the file of this patent UNITED STATES PATENTS 1,206,260 Schaanning et al Nov. 28, 1906 1,568,727 Frank Jan. 5, 1926 2,080,913 Hafecost et a1 May 18, 1937 2,250,647 Miller July 29, 1941 2,432,513 Depew Dec. 16, 1947

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