US2254838A - Resistor - Google Patents

Description

Sept. 2,1941. J'. w. coNKLlN x-:rAL

RES ISTOR Filed Sept. 8, 1938 mwN James W Con HZ red MeneeLy mtorneg Patented Sept. 2, 1941 nrsrsron James W. Conklin and Alfred Meneely, Audubon,

N. J., assigfnors to Radio Corporation otAmerica, a. corporation of Delaware Application September 8, 1938, Serial No. 228,916

4 Claims.

This invention relates to high frequency apparatus and has special reference to the provision of an improved resistor capable of effectively .dissipating large amounts of'energy derived from relatively intense high frequency currents. The

resistors of the invention iind useful application in radio and television systems where they may be employed as coupling resistors (e. g. in video modulating circuits), as loading resistors (e. g. in antenna loading circuits) or they may be employed in test circuits (e. g. as a dummy antenna). The apparatus of the invention finds maximum utility where space is at a premium and rapid and effective dissipation of large quantitie` of electrical energy is required.

An object of the present invention is to provide a non-inductive resistor capable of effectively dissipating larger quantities of energy than similar resistors of comparable size.

Another object of the invention is to provide a non-inductive fluid-cooled resistor which shall exhibit a high capacitive reactance.

Still another object of the invention is to provide a durable, inexpensive, trouble-free, watercooled resistorl and one characterized by the simplicity and economy of its parts.

Other objects and advantages, together with certain details of construction, will be apparent and the invention itself will be b'est understood by a reference to the following specification and to the accompanying drawing, wherein Figure 1 is a longitudinal sectional view of a fluid-cooled non-inductive resistor constructed in accordance with the principle of the invention; Figure 2 is a cross-sectional view taken on the line 2-2 of Fig. 1; and

Figure 3 is a fragmentary longitudinal sectional view of an alternate form of water-cooled resistor embodying the invention.

Like reference characters designate the samek or corresponding parts in all figures.

Referring rst to Figs. 1 and 2, I indicates generally a fluid-tight vessel comprising an elongated hollow cylinder 3 constituted of. glass, Pyrex or other preferably transparent heat resistant material, closed vat its opposite ends by cup-shape metallic caps 5 and 'I, respectively. Each of the caps 5 and 'I is provided with a tapped orifice which accommodates a nipple or gland coupling 9, II, respectively, through which water or other cooling uid may be circulated.

A non-inductive resistor which may comprise a non-soluble resistive material applied in the form of a coating I3 to a tubular or rod-like porcelain or similar base I5, is mounted within the vessel in spaced relation with respect to its inner walls as by means of threaded metal studs Il and I9 which extend axially through the caps 5 and l, and through retaining nuts 2| and 23, respectively, to engage the terminal ends of the resistor base I5. In the illustrated embodiments of the invention the resistor base I5 is of hollow cylindrical construction tted somewhat loosely (to avoid the effects of expansion) upon an inner core or rod I5a which may be constituted of Bakelite or other suitable insulating material. As previously indicated, however, base I5 may comprise a unitary or solid rod-like structure. Metal washers 25 and 2l serve to maintain the base I5 carrying the resistive coating I3 against longitudinal displacement. The washers 25 and 21 or one of them may be perforated, as shown at 25a, 21a and at 21a, Fig. 3, to permit the cooling fluid to circulate in the space between the resistor base I5 and its supporting core I5a.

. Gaskets 29 and 3| are seated in suitable recesses in the rims of the cup-shape caps 5 and 1, respectively. When the studs I1 and I9 are tightened a clamping force is applied to the gaskets through the caps 5 and 'I so that a iluidtight metal to glass seal is achieved.

An annular recess or groove in each of caps 5 and 1 accommodates a coiled wire spring 33, 35, respectively. These springs serve to establish electrical connections from the studs i'I and I9 to the resistor I3 through the metal cap 5 and 1, respectively. The open work construction of the springs 33 and 35 permits the cooling fluid to ilow therepast without being retarded. Cap nuts 31, 39 on the free ends of the studs I'l and I9 may be employed in making electrical connections to the device.

Itl will be observed upon inspection of the drawing that the space between the resistor I3 and the inner surface of the tubular body portion 3 of the enclosing vessel is quite narrow. This spacing is quite important where the device is to be employed in ultra-high frequency circuits (say, above 20 megacycles) as it has been found that the cooling uid comprises the dielectric of a "phantoml capacitor whose armatures comprise the metal caps 5 and 'I. l

If the cross sectional area of the dielectric medium (in this case water) is doubled, the

capacitance is doubled. This is evidencedby the formula:

where:

S is the surface area of one side of one plate, t is the thickness of the dielectric, and K is the dielectric constant.

Since the dielectric constant (K) of water is substantially 80 it will be appreciated that disturbing values of capacitance are much more readily developed than in the case o! ordinary capacitors employing the usual dielectric materials. Accordingly, wherever, as in high frequency work, a high capacitive reactance rating is required, it is desirable to employ the minimum instantaneous quantity of cooling fluid consistent with efdcient operation. In one device designed to handle 5 kilowatts and having an overall length of 12 inches and circumference of 31/2 inches, the spacing between the resistor and inner walls of the vessel was substantially no greater than 1,66 of an inch. Y Spacings less than I/g of an inch may give rise to air bubbles which impede the flow of the cooling uid.

Referring vto Fig. 3, in some installations it is desirable to have the Water inlet and outlet terminate at the same end of the device. In this event-a hollow nipple or coupling 41 is employed in place of the solid axially arranged stud I1 of the device of Fig. 1. A second hollow coupling 49 shown mounted parallel to' the central coulpling 41 preferably comprises the inlet for the cooling fluid. The path of the cooling fluid is indicated by the arrows. other difference between this and the rst described embodiment of the invention is in the provision of a lateral oriiice I5b in the supporting core I5a, which orifice is in registerl with a' similarly oriented orifice 41b in the hollow stud 41.

Other modiiications of the invention will suggest themselves to those skilled in the art. It is to be understood'therefore that the foregoing is to be interpreted as illustrative and not in a limiting sense except as required by the prior art and the spirit of the appended claims.

What is claimed is:

1. A device for dissipating electrical energy comprising a fluid tight vessel containing a hollow insulating member coated with a resistive material and mounted in spaced relation with respect to the inner surface of said vessel, and means forcirculating a cooling uid in contact with the inner surface of said vessel, the coated y surface of said coated hollow member, and the interior surface of said coated hollow member.

2. The invention as set forth in claim 1 wherein said vessel comprises an elongated tubular structure provided with metal terminals through which electrical connections may be established to said resistive coating, and wherein said fluid is admitted into said vessel through one and discharged through the other of said metal terminals.

3. 'I'he invention as set forth in claim 1 wherein said vessel comprises an elongated tubular structure provided with metal terminals through which electrical connections may be'established to said resistive coating and wherein said fluid is admitted into said vessel and discharged therefrom through a common of said metal terminals.

Substantially the only 4. A device for dissipating electrical energy comprising a hollow cylinder provided with cupshape metal terminal members closing the otherwise open ends thereof, a non-inductive resistor mounted between said cup-shape terminal members within said hollow cylinder, means for circulating a cooling uid through said device and an electrical connection between a cup-shape member and said resistor, said connection comprising a coiled spring seated within the cup in contact with said resistor and between the turns of which said cooling iluid passes.

JAMES W. CONKLIN. ALFRED MENEELY.

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