US2293497A - Air cooling for thermionic tubes - Google Patents

Description

s- 18, 1942. J. L. FINCH 2,293,497

AIR.COOI.;ING FOR THERMIONIC TUBES Original Filed June 16. 1936 INVENTQR JAMES LESLIE FINCH I BY mu ATTORNEY Patented Aug. 18, 1942 2,293,497 AIR COOLING FOR THERMIONIC TUBES James Leslie Finch, East Rockaway, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application 214,003. Divided June 16, 1938, Serial No. and this application September 13, 1940, Serial No. 356,606

Claims.

This invention relates to a novel and improved method for the cooling of metal anodes of thermionic tubes in an efiective and eflicient manner.

This is a division of my copending application Serial No. 214,003, filed June 16, 1938, and patented Jan. 21, 1941, Patent #2,229,446, which is a division of the parent application, Serial No. 126,124, filed Feb. 17, 1937, now United States Patent #2,176,657.

The claims in this application are directed to the circular casing arrangement.

An object of this invention is to simplify and improve the cooling of thermionic tubes generally by means of circulating air.

Another object of this invention is to provide an improved air cooling system for the cooling of thermionic tubes having electrical control contacts associated therewith.

Still another object of this invention is to improve the cooling of the vacuum tube by reducing the number of component parts required in a cooling system and thereby reducing the cost thereof.

In the prior art, a vacuum tube was generally cooled by a system employing a liquid medium, such a system requiring a second cooler for the liquid and numerous insulating connections for carrying the liquid from the point of the source to and around the anode of the tube. When direct air cooling has been used, it has been found inefiective and results in a reduction of the allowable output of the tubes.

Briefly, this invention comprises a system having a source of air supply, such as for example, a blower or fan, a chamber, and a supporting means for the tube, the supporting means being arranged with a plurality of curved radiating fins.

The outside contour of the supporting members is in two forms, one being rectangular and the other circular. The circular form provides a more economical unit for the same spacing, although it is not quite as efiicient as the rectangular surface which gives a slightly better cooling, due to the greater surface area of the cooling fins.

Electrical control contacts are located adjacent the cooling system and arranged to break the power supply circuit when undesired temperatures are reached.

This invention will best be understood by referring to the accompanying drawing, in which:

Fig. 1 is av sectional view of an improved air cooling system;

Fig. 2 is a. sectional view of another embodiment of this invention;

Fig. 3 is a sectional view of a further embodiment of this invention; and

Fig. 4 is a plan view of Fig. 1, showing a circular support and air chamber.

Referring now in detail to the drawing, l is a metal anode of a thermionic tube, 2 indicates its glass envelope, 3 is the grid lead and 4 and 5 the cathode and filament leads. Anode l is sealed into a suitable cavity formed in a metallic block 6 by means of some fusible metal, such as solder. Anode l is held in place by clamps l and 8 which serve to additionally hold member I in place, should the sealing material or solder melt at the rim portion thereof. The equivalent contour of block member 6 is in the form of a truncated cone and is fitted tightly within a conical aperture in metallic hub 9. Member 6 is firmly secured to hub member 9 by means of a stud l0, clamping spring II and nut l2. These clamping members can be removed with the tube when it is necessary to change the tube. Hub member 9 is provided with an extra large outer diameter. This provides a massive metal hub having a cross-section greater than block 6, which allows heat generated in anode l to travel through it to the ends of a large number of cooling fins IS with a minimum temperature drop. The fins l3 are soldered into slots in the periphery of hub 9 and leave the slots in approximately a radial direction, and are also curved so as to keep the space between adjacent fins approximately parallel or equal throughout their length, which arrangement gives an increased cooling area, and also maintains the air friction between the fins approximately the same throughout the whole sectional area of the cooling system. The outer ends of the fins are secured to an enclosing and supporting member I 4; as mentioned above, this may be rectangular or circular in form. A fan l5, driven by a motor I6, forces air upward and around the fins l3, thus carrying away the heat generated in anode I. Surrounding the fan is a duct or container H, which may be of metal or transparent insulating material, such as glass. The lower end of I! is preferably of circular section and fits closely around the blades of the fan l5, or, in the case of a blower, around the manifold. The upper end of duct I1 is of a section corresponding to that of the outside contour of supportin member M. The spacing between members l4 and I1 is enclosed by a duct l8, made preferably of insulating material, having the requisite insulating characteristics for withstanding the voltage normally placed upon the member l4 and also being of suitable size for confining the stream of air from the fan so that the most of it passes through the cooling fin area. Member I8 is removable, at least in part, to allow replacement of tubes, and it is preferable that member i8 be made of glass or other transparent insulating material, in order that the inside be visible. The filament leads 4 and 5 are preferably brought out through bushings in the walls of member [1, while the grid lead 3 is brought out through an aperture in member l8.

Associated with the cooling unit, is an air flow trip l9 which closes a circuit between member [9 and contact 20, when the force of air reaches above that of a predetermined value, and allows the circuit to open when the flow is below a predetermined value. A thermostat 2! is also associated with member I4 and is located in such a position that with or without the fan running normally, any excess in temperature will cause the circuit between members 2| and 22 to open, while normal temperatures will allow this circuit to remain closed. These two circuit devices are so connected in the electrical circuit that the power will be removed from the device in the case of failure of the cooling air, or in the case of an excess temperature due to any cause.

The modification shown in Fig. 2 is generally similar to that of Fig. 1, except that the air duct l8 can be dispensed with for the reason that the area of the fin section is tapered outwardly toward the top, the upper area being greater where the air leaves than where it enters. A blast of air from the fan directed against the intake of the fins has stored in it kinetic energy, and as this air passes through the expanding fin area, its velocity decreases and therefore emerges at a reduced velocity. This decrease in velocity represents a transfer of energy and this transfer is arranged so as to be substantially sufficient to supply the energy required to overcome the friction of air passing between the fins l3; thus, no difference in pressure is required to force the air through the fins and therefore, essentially all of the air directed to the fins will pass through them, whereas without this taper, the pressure would have to be greater at the intake than at the exhaust. Since the exhaust pressure will be atmospheric, the intake will have to be above atmospheric. This would result in only a part of the air from the fan I 5 passing through the fins, if the ducts l1 and M3 were omitted.

A still further modification is shown in Fig. 3. In this modification, member I8 is also dispensed with, and the area through the fins proper does not expand, and although this modification is not as efiicient as that of Fig. 2, it is slightly more economical to construct than that shown in Fig. 2. To compensate for the omission of taper 14, a duct 23 is placed at the intake side. The

area of the intake of duct 23 is less than that of the fins. The stream of air from the fan is directed at this opening. After entering, it slows down, due to the increased area and the kinetic energy thus expended is converted into potential energy in the form of pressure. Thus, while the pressure at the entrance of 23 is atmospheric, at the entrance of the fins it is somewhat above atmospheric. This pressure overcomes the friction through the fins.

An improving cooling or radiating member is shown by Fig. 4. The vanes l3 are provided to give substantially equal spacing by the use of a curve member radially spaced. It will be noted that from a desired distance from the anodes, the

vanes run substantially parallel, at which point the most effective cooling is obtained. By the use of the curved vane, a greater cooling of the tube can be obtained for the same amount of space and air pressure than if the cooling fins or vanes were only straight and arranged radially.

While only a few modifications of this invention have been disclosed, it is to be distinctly understood that it is capable of taking other forms within the spirit and scope thereof.

What is claimed is:

1. A cooling system comprising an electron discharge device having at least an anode and cathode, a metallic sleeve surrounding said anode, a metallic hub member surrounding said sleeve, a circular metallic band concentrically surrounding said anode and said hub member, a plurality of slots in said hub member, a plurality of radiating fins extending outward and located to be substantially equally and parallelly spaced from each other, said metallic band supported to and connecting the outside ends of said fins, and means for supplying cooling air to said tube by a device located adjacent said metallic member.

2. In an air cooled thermionic tube, means for transferring heat from said tube to the surrounding air, comprising a plurality of circular casing members, a plurality of fins arranged to maintain substantially uniform spacing throughout their length, the outer ends of said fins terminating and secured to at least one of said casing members, all of said casing members arranged one above the other for confining the air surrounding said tube.

3. In an air cooled thermionic tube, means for transferring heat from said tube to the surrounding air, comprising a plurality of circular casing members, a plurality of fins arranged to maintain substantially uniform spacing throughout their entire length, at least one of said casing members being in the form of a circular metallic band concentrically arranged with respect to said tube, the outer ends of said fins terminating and secured to said metallic band, all of said casing members arranged one above the other for confining the air surrounding said tube.

4. In combination, a thermionic tube having at least an anode and cathode, a metallic sleeve in intimate thermal conact with said anode, a metallic hub member surounding said sleeve, a circular metallic band surrounding said hub memher, a plurality of metallic fins radially extending outwardly from said metallic hub member and joined to said band, an insulating duct disposed below said metallic band, and an impeller for forcing a stream of air to flow between said fins and said duct member so as to confine the air discharge to the area between the fins.

5. An electron discharge device cooling system for use in a radio transmitter, said electron discharge device having at least anode and cathode, a plurality of circular casing members, a metallic sleeve surrounding said anode, a metallic hub member'surrounding said sleeve, a plurality of.

metallic sleeve surrounding said anode, a metallic hub member surrounding said sleeve, a plurality of radiating fins extending outwardly from said metallic hub member and secured to one of said casing members, means for supplying cooling air to said discharge device, said means comprising an impeller located adjacent said metallic hub member, and a plurality of electrical contacts located adjacent said metallic hub member, said contacts being secured to one of said casings and arranged in an electrical circuit, a device responsive to temperature connected in said electrical circuit, said temperature-responsive device being connected and so located with respect to said anode that it responds to the temperature of the fins whether the impeller is in operation or not, to control the heat being liberated in the tube anode.

7. In an air cooled thermionic tube, comprising means for transferring heat from said tube to the surrounding air, a metallic hub member surrounding said tube, a plurality of curved fins arranged to radially extend out from said hub member to maintain the spacing of said fins, said fins being curved to be of a greater length than the shortest radial distance between the hub and said metallic band and located to be spaced apart from an adjacent fin, a shell of circular crosssection for supporting and for confining the cooled air.

8. A cooling system comprising an electron discharge device having at least an anode and cathode, a metallic sleeve surrounding said anode, a metallic hub member surrounding said sleeve, a circular metallic band surrounding said hub member, a plurality of radiating fins extending outwardly from said metallic hub member to join said metallic band, each of said fins being curved to be of a greater length than the shortest radial distance between the hub and said metallic band, and means for supplying cooling air to said discharge device by a member located adjacent said metallic hub member, the area of said fins being substantially greater where the cooling air leaves than at the point where it enters.

9. A cooling system comprising an electron dis charge device having at least an anode and cathode, a metallic sleeve surrounding said anode, a metallic hub member surrounding said sleeve, a circular metallic band surrounding said hub member, a plurality of radiating fins extending outwardly from said metallic hub member to join said metallic band, each of said fins being curved to be of a greater length than the shortest radial distance between the hub and said metallic band and located to be spaced apart from an adjacent fin, and means comprising an impeller for supplying cooling air to said discharge device by a member located adjacent said metallic hub memher, the area of said fins being substantially greater where the cooling air leaves than at the point where it enters, said fins being arrangedto receive the air from said impeller.

10. A cooling system comprising an electron discharge device having at least an anode and cathode, a metallic sleeve surrounding said anode, a circular metallic hub member surrounding said sleeve, a circular metallic band surrounding said hub member, a plurality of radiating fins extending outwardly from said metallic hub member to join said metallic band, each of said fins being curved to be of a greater length than the shortest radial distance between the hub and said metallic band and located to be spaced apart from an adjacent fin, and means comprising an impeller for supplying cooling air to said discharge device by a member located adjacent said metallic hub member, a circular duct member having sloping side walls located below said metallic band so that said radiating fins receive the air from said impeller.

JAMES LESLIE FINCH.

Images