US2829271A - Heat conductive insulating support - Google Patents

Description

April 1, 1958 c. E. BOUCHER 2,829,271

HEAT CONDUCTIVE INSULATING SUPPORT Filed Aug. 10, 1953 Y 2 Sheets-Shetet 1 INVENTOR.

I CORMACK E. BOUCHER BY ATTOR NEYS April I, 1958 c. E. BOUCHER I HEAT CONDUCTIVE INSULATING SUPPORT 2 Sheets-Sheet 2 Filed Aug. 10, 1953 INVENTOR.

CORMACK E. BOUCHER ATTORNEYfi HEAT CONDUCTIV E INSULATING SUPPORT Cormack E. Boucher, Seattle, Wash.

Application August 10, 1953, Serial No. 373,277

6 (Ilaims. (Cl. 250-89) The present invention relates to a heat conductive, electrically insulating supporting device, and more particularly to a device for supporting X-ray tubes or other electronic tubes and the like, and for conducting away the heat generated during the operation thereof.

During operation of an X-ray tube considerable heat is generated at the anode of the tube due to the impact thereon of the impinging electrons from the cathode. Unless some measures are taken to conduct away this heat, the temperature of the anode, which is generally formed of copper, may rise to an extent where occluded gases may be liberated or even rise above the melting point of copper, thus destroying the tube. It has been customary heretofore, and especially with tubes operating at relatively high potentials, to mount the X-ray tube within a housing filled with oil to which the heat will be transferred, the oil also serving as electrical insulation between the tube and the housing. Such arrangements, however, have been somewhat unsatisfactory since the insulating oils heretofore available have a relatively poor heat transfer efiiciency. Also, the dielectric strength of such oils is greatly impaired by heating thereof. Moreover, the use of such oils complicates the replacement of an X-ray tube when that is necessary.

Recently there have beeen available certain liquid fluorochemicals having excellent dielectric properties not impaired at elevated temperatures and which fluorochemicals have a very low viscosity whereby convection currents are easily established to transfer heat elfectively and efliciently. However, such fluorochemicals are relatively expensive and the cost of filling an entire housing as has been done heretofore is prohibitive in most instances.

It is an important object of the invention to provide new and improved means for supporting a pair of electrically insulated members in heat conductive relationship.

More particularly, it is an object of the invention to provide a new and improved device for supporting an X-ray tube within a housing and through which device heat from the anode may be efiiciently transferred to the housing.

A further object is to provide an electrically insulating, heat conductive X-ray tube support which facilitates replacement of tubes in X-ray apparatus.

Other objects and advantages of the invention will become more apparent hereinafter.

In accordance with an illustrated embodiment of the invention, a support device is provided comprising a sealed envelope of a dielectric having extending therefrom in spaced relation a pair of heat conducting elements. One of the elements is adapted to be connected to an electrical member such as the anode of an X-ray tube, and the other to a housihng or other supporting member to which heat is to be transferredand in relaionto which the electrical member is to be supported. The envelope is filled substantially with an electrically insulating liquid stable at high temperatures and having ventional glass-to-metal seal.

tive element.

conductivity characteristics.

high heat transfer efiiciency for transferring the heat Fig. 3 is a side elevation of a further embodiment of the invention;

Fig. 4 is a longitudinal sectional view of another embodiment of the invention;

Fig. 5 is a view partly in section showing a still further embodiment of the invention;

Fig. 6 is a sectional view taken substantially along line 66 of Fig. 5; and i Fig. 7 is a sectional view taken substantially along line 7-7 of Fig. 5.

7 Referring first to Figs. 1 and 2, a device made in accordance with the invention and indicated generally at 9 is illustrated in connection with an X-ray tube comprising an envelope 10, from one end of which projects the stem 11 of the anode (not shown), an electrical lead 12 being shown attached to the end of the anode stem for applying the potential difference between the anode and cathode (not shown). The device of the invention is shown in Figs. 1 and 2 as supporting the anode end of the tube below a housing 13 or other member to which heat may be transmitted from the anode. It is to be understood that the cathode end of the tube may be supported in any suitable manner. The device of the invention comprises an elongated, vertically arranged container, chamber or envelope 14 formed of glass or a corresponding mounting flange 18 brazed or otherwisesuitably connected to the heat connecting element 15 or 16 and sealed to the reentrant portion 17 by a con-- The portion of each of the heat conducting elements 15, 16 projecting into the envelope 14 comprises a heat radiating body and is provided with a plurality of fins 19, 20, respectively, to increase the effective heat radiating surface of the respec- Preferably the fins 19, 20 are axial radiating fins, as shown, rather than annular, to permit more effective circulation of the liquid convection currents. Preferably the heat conducting elements 15, 16 are formed of copper or other material having The portion of the lower heat conducting element 15 extending outwardly of the envelope 14 is formed with a split eye 23 adapted to receive the anode stem 11, the

eye being adapted to be clamped tightly to the stem 11 by means of a bolt and nut 24 cooperatively arranged volume of the liquid 26 is slightly less than the total volume of the envelope 14 so as to provide a space above the liquid for the expansion of any vapors therc- Patented Apr. 1, 1958 good heat from as the; temperature of the liquid and. its. vapors rises and to permit boiling of the liquid. Preferably, also, the volume of the liquid 26 is sufiicient so as substantially to, cover the radiating fins. 19', 2b in any position of the device The heat generated at the target of the anode will be conducted through the anode stem 11 and transmitted to the lower heat conducting element 15 through the fins 19 thereof, and thence to the liquid 26 within the envelope 14. Heating of the liquid will establish convection currents therein, causing the hot liquid to rise and transfer its heat to the fins 2b of the top heat conducting element 16 which will in turn lose its heat to the housing 13 from whence it can be dissipated in any suitable manner.

Referring now to Fig. 3-, a further embodiment Oil the invention is shown in connection with an. X-ray: tube comprising an envelope 31 from one end of which pro jects the stem 32 of the anode formed of copper or other suitable material. The electrical connection to theanode is indicated at 33. In this instance the anode stem 32 is provided with a plurality of heat radiating fins 34, at its outer end and which outer end is sealed within the envelope 35 of a heat transmitting and supportingdevice 40. The envelope 35 is preferably glass: and may. be formed with reentrant sleeve portions 36, 37 one one of which the anode stem 32 may be mounted as indicated at 38. Mounted in=the opposite end of theenvelope 35 is a heat conducting element 39 sealed to the reentrant: sleeve portion 37 in a suitable manner and having aplurality of heat absorbing fins 43 formed on the portionthereof:

withinthe envelope 35. Theouter end of theheat conducting element 39 may be adapted to beconnected' to any supporting member or cold body (not shown). to which heat may be transmitted for eventual. dissipation. The envelope 35 is filled with an electrical insulating heat conducting liquid 44 which preferably, as in the case=of the'previously described embodiment does not completely fill the envelope 35 but is suflicient in amount substantially to cover the fins 34, 43.

In the embodiment of the invention illustrated inFig. 4, the heat transfer device is formed integrally with an X-ray tube or generator comprising an envelope d and an anode 51. Only a fragmentary portion of theenvelope and anode are shown, it being understoodthat only the design of the illustrated portions is of concern to the present invention. The envelope is preferably ofglass or other dielectric. The anode S1 is supported on an end wall 52 sealed in a suitable manner to the envelope 55). If the envelope is-of glass, the end wall 52 isapreferably of a metal alloy having the same expansion coefficient as glass. Electrical connection may be made to the anode througha lead indicated at 53 secured to a suitable lug 54 formed on the end wall 52. The anode 51 includes a. stem portion S'extending through the end wall 52. and provided withv a plurality of heat radiating fins 56. The anode stem portion S5"- is soldered; brazed, or otherwise suitably sealed to the end wall 2'32.

Scaled at one end to the end wall 52. is an elongate tubular member 57 formed of suitable dielectric such as glass or plastic and positioned substantially concentrically of the. anode stem portion 55. Secured to the opposite end of the. tubular member 57 is an end wall. or closure, 58 which defines with the tubular member 57 and endwall 52a sealed envelope or chamber 59. A. heat receiving element 62 formed of copper or other metal of high heat conductivity extends through the end closure 55? and is sealed theretoin a suitable manner, the portion of the element 62 within the chamber 59 being spaced from the anode stem portion 55 and provided with a plurality of heat absorbing fins 6?. The portion of the heat receiving element 62. extending outwardly of the chamber-is adapted to be connecetd to aheat absorbing body'indicated at-64, such as, for example, We screw 65. Thechamber S9 is substantially filled by a liquid dielecl tric,.indic ated at,6,6,preferably one capable of transferring heat with high efiiciency. Preferably space for the vapors of the liquid should be provided as before explained.

As is evident, heat generated at the target of the anode 51 during operation of the tube will be conducted to the stem 55 and transferred throughthe fins 56 to the liquid 66. The convection currents established in the liquid will effect aflow of the heated liquid past the fins 63 of the heat receiving element 6?. to which the heat will be lost and then conductedto the heat absorbing body 64.

Obviously the embodiments of Figs. 1 to 4 are particularly adapted for supporting a tube which is maintained in fixed position relative to the housing or supporting member whereby the liquid convection currents will efi'1- ciently effect the transfer of the heat from the hot radiating surfaces to the relatively cold heat absorbing surfaces. It is'not to be expected, for example, that a single heat conducting. device 9 such as that shown in Fig. 1 would be particularly eflicient if the relative position of the X-ray tube and the supporting member 13 were reversed whereby the. relatively hot radiating surfaces were at the top rather than at the bottom of the envelope 14. If this occurred, then, of course, the natural convection currents would not establish. On the other hand, if the X-ray equipment and housing is subjected to a relatively great amount of agitation during the operation of the X-ray'tube, the consequent movement of the liquid within the envelope 14 may be sufiicient to effect the transfer of the heat from the hot to the cold radiating surfaces.

Referring now to Figs. 5, 6 and 7, a preferred arrangement is'shown for supporting an X-ray tube 70 within a tubular housing 71 of apparatus wherein the tube and housing rotate relatively about the horizontally disposed, longitudinal axis of the tube. An example of such apparatusis shown in my prior Patent 2,547,996, entitled Portable X-Ray Unit. The tube 70 comprises an en- Velope 72 from one end of which projects the anode stem 73, the endmost portion 74 of which is of reduced diameter to provide a shoulder 75 therein. The supporting device, inthis instance, comprises a relatively small, metal ring or spool 76 of copper or like heat conductive material having a central aperture in which is received the reduced stern portion 74, the spool being clamped against the shoulder 75 by a washer and screw 77. The screw 77 may also serve as a fastening means for a conductor 78 supplying potential to the anode. The outer periphery of the spool 76 is'preferably provided with a plurality of outwardly projecting fins 79 to increase the effective heat radiating surface thereof. Mounted on the inner periphery of the housing 71 in annular relationship to the spool 76' is a ring 8?. preferably formed of copper or other heat conductingimetal. The ring 82 is shown secured in position by screws $3, though it may be secured to the housing'in any suitable manner such as by welding or brazing the same thereto. The inner periphery of the ring 82 is provided with a plurality of inwardly projecting. annular ribs or fins $4- to increase the heat absorbing surface thereof. Secured in liquid-tight relation to corresponding sides of the spool 76 and ring 82 are a pair of annular discs or plates 85, d6 formed of glass or other suitable dielectric. The rings 76, 82 and plates 85, 86 do? fine-an annular sealed chamber which is filled with an electrically insulating liquid 87 having a high heat transfer 'efiiciency and high dielectric strength, a space for the expansion of the vapors of the liquid being provided as in the previously described embodiments. It will be observed that, whatever the relative rotational position of the housing 71 and X-ray tube 79 about the axis thereof, natural convection currents may readily establish to transfer heatfrom the-spool 76 to the ring 82.

While-many liquids are suitable for use in the device of the, invention, certain liquid fluorochemicalshave beenfound-to be particularly usefulbecause of their chemical and thermal stability and high dielectric strength. Be-

cause of their low viscosity and ability rapidly to establish convection currents, fiuorochemicals such as, for example, heptacosafiuorotributylamine, (C 1 N, and a completely fluorinated cyclic ether having an empirical formula C F O have been found to be particularly suitable. The first of these fiuorochemicals is sold by Minnesota Mining & Manufacturing Company under the trade designation Fluorochemical N-43 and the latter under the designation Fl-uorochemical -75.

While the invention, for convenience, has been described with particular reference to X-ray apparatus, it is to be understood that its usefulness is not limited thereto.

Having illustrated and described preferred embodiments of the invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

I claim:

1. An electrically insulating device for conducting heat between a pair of members electrically insulated from each other comprising a sealed envelope formed of a dielectric, a pair of spaced-apart elements of a heat conductive material extending into said envelope, the portion of each of said elements within said envelope having a plurality of fins thereon, the portions of said elements protruding from said envelope being adapted to be connected one to each of said members in heat conductive relation therewith, and a nonionizing liquid within said envelope, the volume of said liquid being sufficient substantially to cover said fins in any position of said device, but less than the volume of said envelope to provide expansion space for the vapors of said liquid.

2. An electrical apparatus comprising an X-ray generator including an envelope having a disclike end wall of electrically conductive material, an anode in said generator having a stem portion projecting outwardly through said end wall and sealed thereto in electrically conductive, liquid-tight relation, said stem portion having a plurality of heat radiating fins thereon, a tubular member of a dielectric sealed at one end thereof to the aforementioned end wall in substantially concentric relation with said anode stern portion, a second end wall sealed to the opposite end of said tubular member to define with said tubular member and said aforementioned end wall a sealed chamber, a heat receiving element of heat conductive material extending through said second end wall, the portion of said element within said chamber having a plurality of heat radiating fins thereon, the portion of said element projecting outwardly of said chamber being adapted to be connected to a heat abosrbing body, and a liquid dielectric of relatively low viscosity within said chamber and substantially covering said fins.

3. A heat conductive, electrical insulating device for supporting an electrical unit normally operating at an elevated temperature and conducting heat from said unit to a cold body, said device comprising a first metal ring adapted to be secured to a relatively cold body in heat conductive relationship, a second metal ring coaxial with said first ring and adapted to be secured to said unit in heat conductive relationship, a pair of annular discs of electrical insulating material secured to opposite sides of said first and second rings to define therewith a chamber, and a fluid of high heat transfer efiiciency and high dielectric strength substantially filling said chamber.

4. In electrical apparatus, having a first member operating at an elevated temperature and at a given potential, and a second member operating at a lower temperature and a different potential and capable of accepting heat generated at said first member, the combination therewith of means to transfer heat from said first memher to said second member while maintaining the same in electrically insulated relation, said means comprising means defining a sealed container enclosing a portion of each of said members, said container having a dielectric wall portion electrically insulating said member portions from each other, and a nonionizing liquid of low viscosity and high heat transfer efiiciency in said container in contact with both of said member portions whereby said liquid will convey heat from said first member portion to said second member portion.

5. An electrically insulating heat transfer device for use in electrical apparatus having a first element operating at an elevated temperature and at a given potential, and a second element operating at a lower temperature and a diiferent potential and capable of accepting heat generated at said first element, said device comprising a sealed envelope of electrical insulating material, a pair of spaced apart heat conductive members each having a portion within and a portion without said envelope, a nonionizing liquid of low viscosity and high heat trans fer efficiency in said envelope in contact with both of said member portions within said envelope whereby said liquid will convey heat between such portions, and means on the said portions of each of said members without said envelope for connecting the same one to each of said elements in heat conductive relationship whereby heat may be transferred through said device from said first element to said second element.

6. An X-ray apparatus comprising a housing and an X-ray generator having an anode mounted within said housing and operating at a different potential than said housing, the combination therewith of means to transfer heat from said anode to said housing while maintaining the same in electrically insulated relation, said means comprising means defining a sealed envelope, a first heat conductive element mounted on said envelope and having a portion within and a portion without said envelope, the latter portion being connected in heat conductive relation to said anode, a second heat conductive element mounted on said envelope and having a portion Within said envelope spaced from the corresponding portion of said first element and a further portion without said envelope, means connecting the latter of said portions to said housing in heat conductive relation, and a nonionizing liquid of low viscosity and high heat transfer efiiciency in said envelope in contact with both of said element portions therein whereby heat from said anode will be conveyed through said device to said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,804 Zodtner Aug. 23, 1932 1,874,478 Fayer Aug. 30, 1932 2,253,264 Burleson Aug. 19, 1941 FOREIGN PATENTS 471,910 Canada Mar. 6, 1951

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