Heat Dissipating Devices For The Collectors Of Electron-beam Tube

Abstract

A heat-dissipating device for the collectors of electron-beam tubes such as a traveling wave tube. The collector slides loosely into a bore within a cylindrical heat-absorbing and conducting member. The heat-absorbing member is connected to a finned heat-radiating structure to which heat is conducted for dissipation. A tight fitting between the collector and the heat-absorbing member is created by the presence of a restraining collar placed around the heat-absorbing member. The collar has a smaller coefficient of expansion than the heat-absorbing member, and the heat-absorbing member has longitudinal slots therein, the net effect of which is to cause the heat-absorbing member to constrict about the collector when the assembly heats to operating temperature. BACKGROUND OF THE INVENTION

Description

This invention relates to heat-dissipating devices for heat producing electronic elements and particularly for the collectors of electron-beam tubes such as the traveling-wave tube, backward-wave tube, and the like.

A heat-dissipating system for a traveling-wave tube has been widely used. According to this system, a tapered section of the collector fits into a conical bore of a heat-radiating member and the desired fit between the two concentric conical contacting surfaces is maintained by adjusting a clamping nut fitted on a threaded boltlike projection at the end of the collector.

The cooling efficiency of such a device for the collector has been found to be considerably higher when the two conical contacting surfaces of the collector and the heat radiating member are fitted tightly together. The need for manual control of the clamping nut, however, is inconvenient, in that it restricts the mounting position of the traveling-wave tube in the microwave communication equipment to positions where the clamping nut is accessible.

The ever-increasing demand for greater miniaturization of present-day electronic equipment has necessitated the efficient utilization of available space and a higher concentration per unit volume of component parts, including traveling-wave tubes in microwave communication equipment. In extreme cases, the heat-radiating member of a traveling-wave tube must be positioned in a remote location in the equipment in order to provide ease of tube replacement from the opposite side, which positioning prohibits manual adjustments of the aforementioned variety.

Therefore, there has been an increasing demand among equipment designers and users for the advent of a new heat-dissipating system for the collectors of electron-beam tubes which dispenses with the need for such clamping nut adjustment in tube insertion or removal.

It is consequently a general object of this invention to provide a new and improved heat-dissipating system for the collectors of electron-beam tubes which overcomes the aforementioned difficulties of the prior art. Stated more particularly, it is an object of this invention to provide a new and improved heat-dissipating device for the collectors of electron-beam tubes which dispenses with manual control of the clamping nut as in the prior art, automatically provides a tight fit between the contacting surfaces of the collector and the heat-conducting element after the tube has been operated for a predetermined time interval, and which further enables tube removal after the tube operation has been suspended for a predetermined time interval.

SUMMARY

A heat-dissipating device according to this invention comprises a heat transfer or conducting member, generally but not exclusively, of cylindrical or tapered cylindrical form provided with a cylindrical or conical axial bore for insertion of the collector of an electron-beam tube, one or more slots in the sides of the heat transfer member extend generally from one end inwardly in the axial direction thereof for a distance corresponding at least to a fraction of the overall length thereof, and in the transverse direction thereof by a width corresponding to the full wall thickness of the heat transfer member from the bore wall surface to the peripheral wall surface. A neck near the inner end of the heat transfer member generally facilitates the contraction of the slotted sides thereof about the collector. At least one annular retainer means made of a material having a smaller thermal expansion coefficient than the material of the heat-conducting element fitted around the peripheral surface of the heat transfer member so as to surround at least a fraction of the length of the slotted sides thereof. A heat radiating member of any suitable geometrical shape adapted for heat dissipation is disposed adjacent the heat conducting member to establish direct or indirect thermal contact therebetween. A single slot which extends throughout the full axial length of the heat-conducting member, or a plurality of slots the opposite ends of each terminate inside of the heat-conducting member are suitable alternatives to the above-described slots. An outstanding advantage of this assembly is that a tight fit between the tube collector and the heat transfer element is automatically obtained soon after the tube is put into operation.

The principles of this invention may best be understood by reference to the following description of two preferred embodiments of this invention illustrated in the accompanying drawings. Throughout the specification and drawings, all like parts or members are given like designation numbers to facilitate a better understanding of the invention.

FIG. 1 is a longitudinal cross-sectional view of a heat-dissipating device according to a first preferred embodiment of this invention;

FIG. 2 is an end view of the device shown in FIG. 1;

FIG. 3 is a side view of a heat-conducting member used in the first embodiment of this in invention shown in FIG. 1;

FIG. 4 is an end view of the heat-conducting element shown in FIG. 3;

FIG. 5 is a longitudinal cross-sectional view of a heat-dissipating device according to a second preferred embodiment of this invention;

FIG. 6 is an end view of the device shown in FIG. 5.

Now referring in more detail to FIGS. 1 and 2, there is shown a heat-dissipating device 1 for dissipating heat produced by the collector 4 of a traveling-wave tube 3 (only the collector and its vicinity thereof are illustrated). The device is composed of a cylindricaL heat-radiating radiating member 9 provided with an axial bore 9a, and an axial counterbore 9b, and having a plurality of fins 8. A heat-conducting member 7 provided with a flangelike 7a at the inner end for maintaining a low-resistance thermal contact with the internal sidewall surface 10 of the heat-radiating member is attached to surface 10 by member 9 by means of solder or screws. Conducting member 7 has an axial bore 5 therethrough for the insertion of the collector 4, and a pair of symmetrical slots 6 extending inwardly from the outer end of conducting member 7 and disposed in a plane containing the axis of bore 5. An annular member 12 is fitted securely on the peripheral surface 7b of conducting member 7 to impose a restraint on the thermal expansion in the radial direction of the heat-conducting member 7 when the latter is heated.

The heat-conducting element 7 is made of a material possessing a high thermal conductivity and a high thermal expansion coefficient such as aluminum (thermal expansion coefficient is approximately 23.5.times.10 .sup.-.sup.6), whereas the annular member 12 is made of a material possessing a low thermal expansion coefficient such as a nickel-iron alloy containing 36 percent nickel (thermal expansion coefficient is approximately 1.5.times.10.sup.-.sup.6).

The figures illustrate the structure of the device 1 before being heated to operating temperature.

The diameter of the bore 5 is designed to be larger than the diameter of the collector 4 by tens of microns under this condition. When the tube 3 is placed in operation, a power loss of the collector 4 causes its temperature to rise. Since the collector 4 and the heat-conducting member 7 are initially in partial contact with each other in spite of the presence of a clearance therebetween, the temperatures of members 7 and 12 begin to rise gradually and simultaneously, and the heat-conducting member 7 begins to thermally expand.

Since the annular member 12 is made of a material possessing the smaller thermal expansion coefficient of the two, and is initially tightly fitted on the external peripheral surface 7b of the element 7, the outward radial thermal expansion of conducting member 7 is restrained, resulting in the inward expansion of the outer end of the element 7 as indicated by the arrows 16 and 17 (FIG. 2), which inward expansion is substantially perpendicular to the plane containing the slots. Therefore this portion of conducting member 7 is compressed firmly against the collector 4. The constricted neck portion 18 in conducting member 7 some distance removed from the edge of the annular member 12 to facilitates the inward expansion of the right-hand side of conducting member 7.

The compressive force of conducting member 7 against the collector 4 thus created is extremely large, resulting in a decrease in thermal resistance between the contacting peripheral surface 42 of the collector 4 and surface of bore 5 in the heat-conducting conducting member 7; and promotes efficient conduction of the heat generated by the collector 4 to the heat-radiating member 9 for subsequent dissipation into the air.

The region of the collector 4 compressed by the heat-conducting member 7 is restricted to that portion which is surrounded by the annular member 12. According to our experiment, however, excessive local temperature rises at that portion of the collector 4 not directly compressed are avoided and the temperature distribution along the axial length of the collector 4 made approximately uniform by selecting a collector made of material possessing a high thermal conductivity (such as copper), and having a wall sufficiently thick to carry heat to the region of contact between collector 4 and conducting element 7.

A second embodiment of this invention is illustrated in FIGS. 5 and 6. This embodiment differs from the first in the following respects: (a) element 7 is tapered toward the outer end, and annular member 12 is correspondingly shaped so that together they form two concentric conical surfaces 13 that can fit together; (b) the end outer portion of element 7 is threaded as shown at 14 and annular member 12 is internally threaded to thread thereon. The clearance between the collector 4 and the heat-conducting member 7 is initially set by tightening annular member 12 on element 7, and no further adjustment is needed. This adjustment is accomplished before installation of the device in communication equipment.

The second embodiment functions upon the same principles and in substantially the same manner as the embodiment of FIG. 1; therefore a detailed description is omitted. An advantage of the second embodiment over the first is that dimensional tolerances of the mating surfaces of members 7 and 12 less rigorous and machining becomes easier, because the tightness of fit between elements 7 and 12 and the clearance between element 7 and collector 4 can be suitably controlled by tightening threaded member 12.

The relationship between the dimensions of various components and materials to be used therefor which have been taken into consideration in designing the heat-dissipating devices above described are as follows.

SYMBOL DEFINITIONS

T.sub.0 = room temperature

d.sub.1 = diameter of the collector 4 of a traveling-wave tube when the tube is at room temperature

d.sub.2 = diameter of bore 5 of heat-conducting member when member 7 is at room temperature 7

d.sub.3 = inside diameter of annular member 12 (maximum inside diameter of the tapered section in case of the second embodiment) when at room temperature

T.sub. 1 = temperature of collector 4 under steady operating condition of the traveling-wave tube

T.sub. 2 = temperature of heat-conducting member 7 and annular member 12 fitted thereon under steady operating conditions of the traveling-wave tube

.alpha..sub.1 = thermal expansion coefficient of the collector 4

.alpha..sub.2 = thermal expansion coefficient of the heat-conducting member 7

.alpha..sub.3 = thermal expansion coefficient of the annular member 12

d .sub.1 ' = diameter of collector 4 under steady state operating conditions of the traveling-wave tube

d.sub.2 ' = diameter of bore 5 at that part of collector which is compressed by members 7 and 9 in a direction perpendicular to the plane containing two slots 6 under steady state operating condition of the traveling-wave tube.

Then d.sub. 1' and d.sub. 2 ' can be expressed as

d.sub.1 '=d.sub.1 [1+.alpha..sub.1 (T.sub.1 -T.sub.0)] (1)

d.sub.2 '=d.sub.2 +(T.sub.2 -T.sub.0)[ .alpha..sub.2 d.sub.2 -(.alpha..sub.2 -.alpha..sub.3) d.sub.3 ] (2)

In order for collector 4 to be compressed by the heat-conducting member 7 will be

d.sub.1 '>d.sub.2 ' (3)

Numerical data for an experimental model which was designed and fabricated according to the second embodiment on the basis of the foregoing equations is as follows: ##SPC1##

Diameters at various parts of the heat-conducting member 7 and the annular member 12 are as indicated in Table 1. ##SPC2##

Using the numerical data indicated in Table 1 and the temperature rises assumed above, the diameter d.sub.1 ' of the collector 4 and the diameter d.sub.2 ' at the compressing part of the heat-conducting member 7 under operating condition of the tube were derived by computation as 8.972 mm. and 8.957 mm., respectively. Therefore the condition for compression (3) is well established.

In the above experiment, the clearance between the collector 4 and the heat-conducting member 7 was made to be 0.05 mm. with the assembly at T.sub.0, so that the tube could easily be inserted into and withdrawn from the bore therefrom. It was observed that the compression occurred in about 7 minutes after the tube was put into operation. It was further confirmed that the temperatures of collector 4, heat-conducting member 7, and heat-radiating member 9 under steady state of tube operation were 105.degree. C., 93.degree. C., and 80.degree. C., respectively. In view of the allowable maximum temperature of 180.degree. C. for the collector, it was confirmed that cooling of the collector was satisfactory. No excessive temperature rise of the collector 4 was detected during the 7-minute warmup interval, and the tube could be easily withdrawn after the operation of the tube had been suspended for about 45 seconds.

Among the outstanding merits of this invention as reduced into practice will be recapitulated.

No manual control on the collector side of the device such as turning the clamping nut is required in tube replacement; the replacement tube can thus be inserted or removed from the end opposite that of the collector, as the collector slides freely within the heat-dissipating device of the invention. Thus the device may be located at an inaccessible or innermost part in the equipment.

The cooling efficiency of the devices compares favorably with those of conventional devices for the following. The outward radial thermal expansion of the heat-conducting member is restricted by the provision of at least one annular retaining member possessing a smaller thermal expansion coefficient. This causes inward radial thermal expansion of the heat-conducting member 7, which is further aided by the presence of the slot or slots. As a result, the collector is strongly compressed by the thermally expanded heat-conducting member along at least a fraction of the full length thereof, which reduces the thermal resistance between the contacting surfaces. Even if the temperature rise is not so large, the compression achieved is at least equal to that which could be obtained by tightening the nut according to the conventional design.

Utilization of the invention frees the designer of microwave communication equipment and the like incorporating electron-beam tubes from past restriction arising from the need for access to the heat-dissipating device therefore.

While the principles of the invention have been described in connection with the above specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

Claims

What we claim is:

1. A heat-dissipating device for the collector of an electron-beam tube comprising a heat-radiating member, a heat-conducting member disposed adjacent said heat-radiating member in thermal contact therewith, said heat-conducting member having an axial bore having a normal diameter for relatively loosely receiving therein the collector of an electron-beam tube prior to the operation of the tube, said bore extending from one end of said heat-conducting member inwardly a distance corresponding to at least a fraction of the full length thereof, at least one slot extending in the axial direction of said bore a distance corresponding to at least a fraction of the full length of said heat-conducting member and in the transverse direction thereof the full width of said heat-conducting member, and at least one annular member fitted on the peripheral surface of said heat-conducting member coaxially therewith and surrounding at least a fraction of the full length thereof containing said at least one slot, said at least one annular member being made of a material possessing a smaller thermal expansion coefficient than that of the material of which said heat-conducting member is made, said annular member defining means when the tube is in operation and thus heated for acting upon said conducting member to thereby restrain the outward radial expansion of said heat-conducting member, modify the diameter of said bore, and cause the collector to establish a relatively close fit between the collector and said heat-conducting member.

2. A heat-dissipating device for heat-generating electronic elements or the like comprising: a heat-dissipating structure having a recess therein, heat-conducting means positioned within the recess of and in heat-transferring relationship with said heat-dissipating structure so that heat will flow from said heat-conducting member to said heat-dissipating structure, said heat-conducting means having an aperture therein adapted to slidingly receive a heat-generating element, and at least one substantially longitudinal slot through the body thereof communicating around and against a portion of said heat-conducting means and within a plane substantially normal to the longitudinal axis there to retard outward radial expansion of said heat-conducting means, said band being constructed of a material having a coefficient of expansion substantially smaller than the coefficient of expansion of the material of which said heat-conducting means is constructed, so that when heated by the heat-generating element placed therein, said retaining band means acts on said heat-conducting means to cause the latter to expand radially inwardly and thereby modify the diameter of said aperture to thereby establish a relatively close fit between the heat-generating element and said heat-conducting means.

3. The device of claim 2 wherein said retaining band is disposed around the area of said heat-conducting means containing said slot, and wherein said heat-conducting means has a neck therein, said neck being between the portion of said heat-conducting means having the slot therein and the remainder thereof.

4. The device of claim 3 wherein said heat-dissipating structure and said heat-conducting means have a common bore therethrough sized to slidingly receive a collector of an electron-beam tube, and wherein the aperture in said heat-conducting means comprises a portion of the bore.

5. The device of claim 4 wherein said heat-conducting device is substantially cylindrical and has opposing slots therein along a plane containing the longitudinal axis of said heat-conducting device, and extending from the end opposite the neck thereof through said neck.

6. The device of claim 5 wherein said retaining band comprises a ring frictionally fitted around a substantial portion of said cylindrical heat-conducting means containing the opposing slots.

7. The device of claim 6 wherein one end of said heat-conducting means abuts said heat-dissipating structure, and wherein a substantial portion of said heat-conducting means opposite said abutting end tapers outwardly, and wherein said retaining ring tapers correspondingly, and wherein said heat-dissipating device is further comprised of means to thread said retaining ring into said heat-conducting means.