US2772336A - Infra-red generator - Google Patents

Description

Nov. 27, 1956 H. A. MERRICK INFRA-RED GENERATOR Filed July 10, 1953 mmvroza. Hermon A. Merrick BY Fig.7

United States Patent 2,772,336 INFRA-RED GENERATOR Herman A. Merrick, Seattle, Wasln, assignor, by mesne assi nments, to United Service 8; Utilities Co., Seattle, Wash, a corporation of Washington Application July 10, 1953, Serial No. 367,227

1 Claim. (Cl. 201-63) This invention relates to infra-red generators of the type disclosed in United States Patent No. 2,535,268, issued December 26, 1950, and namely, a generator comprising an electrically energized coil of filament wire encased in a glass tube. The coil is peculiarized in that the convolutions of the coil are coated with a jacketing cement permitting the coil, while operating under a condition of high heat transmittal, to safely contact the glass wall of the container without any liability of either the coil failing or the glass disintegrating due to the heat of the coil. In this generator heat waves of two frequencies are created, high-frequency waves emanating from the coated coil and low-frequency waves from the tube. These waves are held to a predetermined constant throughout the length of the generator and will operate to distribute the radiated heat such as to give substantially uniform penetration throughout the entire area to which the heat is directed.

In the aforesaid patent the ends of the glass tube are annealed and closed with stainless steel caps which are internally coated with a sealing cement. The ends of these caps have central openings so that the caps can be fed over the projecting terminals of the coil and onto the annealed ends of the tube. These terminals are then secured to the caps by solder which also serves to seal the openings in the latter. This arrangement requires that the caps be socketed in electrically conductive clips, such as copper fuse clips, thus making a far more expensive installation than would be found if the ends of the coil could have a wire interconnection with the power leads to the heating unit in which the tube is mounted.

Accordingly, it is a principal object of the present invention to provide an inexpensive arrangement whereby the ends of the glass tubes are sealed without requiring a modification of such ends and which permits the terminals of the energized coil to be easily connected to wire extensions. In carrying out this object, the invention further aims to electrically insulate the coil at the ends of the tube and to provide means whereby the generator can be supported at its ends without directly contacting the glass of the tube.

Other more particular objects and advantages will appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

In the accompanying drawings:

Figure 1 is a fragmentary plan view of an uncoated coil with the wire leads attached.

Fig. 2 illustrates the step of dipping the coil into a bath of a cement coating material.

Fig. 3 shows the manner in which the coating on the coil is dried.

Fig. 4 is a side view of one of my novel end plugs.

Fig. 5 is a front end view of the plug.

Fig. 6 is a side view of a completely assembled generator unit.

Fig. 7 is a fragmentary view of an end portion of 2,772,336 Patented Nov. 27, 1956 the generator assembly and with the respective end plug being shown in vertical section taken longitudinally through the center of the plug.

In forming the energizing coil 10 for the generator, the ends thereof are formed with terminal hooks 11. Over these hooks are looped the respective ends of nickel wire extensions 12, 13, silver solder 14 being used to make permanent connections. These wire leads have asbestos insulating jacets 15. As disclosed in the aforesaid patent, the wire of the coil 10 is desirably Nichrome and is insulated with a jacket of cement such, for example, as Sauereisen cement mixed with magnesium oxide in the approximate proportion of 2 to 1. To apply this cement jacket the assembly of Fig. 1 is manually grasped by the asbestos jackets 15 and dipped into a bath 16 of the coating as illustrated in Fig. 2. The free ends of the wire extensions 12, 13 are then bridged across live terminals 17, 18 (Fig. 3) to pass current through the coil and thereby heat the same until the coating is dry.

Continuing to the other figures in the drawing, it is seen that I employ round plugs 20 to close the ends of the Pyrex glass tube 21 of uniform diameter in which the filament coil is to be housed. These plugs are stepped to provide a capping section 22, having a diameter corresponding to the outside diameter of the tube 21, and a shorter plugging section 23 having a diameter slightly less than the inside diameter of the tube. Each plug has a central through-bore 24 and its outer face is radially grooved from this bore as at 25 to a depth exceeding the outer diameter of the asbestos jacket-s 15. The material for the end plugs is desirably ceramic or glass so as to be electrical insulators and not susceptible to breakage due to high temperatures.

In assemblying my improved infra-red generator the coated filament coil 10 with the attached asbestos-jacketed wire extensions 12, 13 is placed in the tube 21 with the said sections extending therebeyond. Cement 26 which is not subject to deterioration from high temperature conditions, such as, for example, Sauereisen Insalute Adhesive Cement #1 Paste, is applied to the plugs 20 along the underside of each capping section 22 and the circumferential side face of each plugging section 23. The plugs are then slipped over the wire extensions 12, 13 to seat the plugging sections in the ends of the tube where they are permanently held by the cement 26 as best shown in Fig. 7.

After the plugs are thus seated, the wire extensions 12, 13, which are at this time extending lengthwise out through the plug bores 24, are bent at right angles to the longitudinal axis of the tube so that they can be seated in the radial grooves by an application of cement 27 which may be the same type as the cement 26 used to bond the plugs to the tube. The cement 27 also covers the mouth of the bores 24 so that the tube is sealed.

The resulting final assembly is shown in Fig. 6 and it will be seen that it can be readily installed in dryers, food warmers, heaters, etc. by socketing the exposed capping sections of the plugs 20 in simple clips, desirably thermally insulated, and connecting the free ends of the wire extensions 12, 13 to power leads. Since the plugs 20 are electrically non-conductive, and the asbestos insulating jackets 15 for the extensions 12, 13 are thermal resistant, the clips holding the genertor'do not have to be electrically insulated. The Nichrome Wire is applicable to the normal operating temperatures below 2,000 F. Wire of other material as, say, tungsten, is necessarily used in those instances where higher operating temperatures are required.

The invention admits to minor changes in the details of construction and it is my invention that the hereto annexed claim be given a scope commensurate with the 3 broadest interpretation which the employed language fairly'perrn'itsi What I claim is:

An infra-red generator comprising a glass tube, cerarn'ic terminal plugs extending by. necked-down portions into "said tube and having enlarged heads without the tube; said plugs each having a longitudinal bore and a groove in the outer end face of its enlarged head' extending laterally from'the said bore to the'si'de extremity of the head, a wire coil assembly in the tube and'having extensions passing endwise through the said bores and seated in the said grooves, said extensions having asbestO S j 'dkf; fiid" (:eiii'ei'if 'lioifdliig"theplugs" to the tube, holding the jacketed extensions in the grooves, and sealing the said bores in the plugs.

References Cited in the file of this patent UNITED STATES PATENTS 1,525,331 Steineret'a'lf Feb. 10, 1925 10 v2,42%,021 Henklerretialr June 24, 1947 2,535,268" Coats 1360.26, 1950

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