US2599411A - Filament support - Google Patents

Description

June 3, 1952 D. c. PULLIAM FLAMENT SUPPORT Filed May 16, 1950 2 SHEETS-SHEET 2 IIIllmlh.

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IN VEN TOR.' zal@ @MW Patented June 3,V 1952 UNITED STATES PATENT OFFICE FILAMENT SUPPORT Dudley C. Pulliam, Chicago, Ill.

Application May 16, 1950, Serial No. 162,187

4 Claims.

This invention is concerned, in the broad sense, with a simple filament-support structure adapted for rapid and inexpensive assembly. More particularly, the invention is adapted to the manufacture of electrical heating elements and other electrical apparatus wherein it is desirable that an electrical conductor be supported in zigzag arrangement on a framework.

Practically all electrical appliances wherein electricity is used as a source of heat employ heating elements formed from strips of resistance wire, such as Nichrome. Since the total heat generated for a given line current is proportional to the length of the resistance element, it is usually essential that the resistance wire or ribbon be mounted in zigzagarray on some sort of framework so as to permit a relatively greatA length of the ribbon to be carried within the limited dimensions of the toaster, iron, room heater, or other appliances.

The customary manner of making such devices in the prior art has been to wind the Nichrome ribbon by hand on a form made of mica, porcelain, or other suitable refractory material. Because of the large quantity of hand labor required, the cost of electrical heating elements has always been much higher than the cost of the raw materials themselves would justify.

I have provided a novel heating element wherein manual assembly is unnecessary. A heating element made according to my invention has only ve parts, including the resistance ribbon itself, and it can be assembled in its entirety by simple machine methods. While my invention is particularly useful in the manufacture of heating elements for electrical appliances, it can readily be employed in any application wherein a iilament, wire, or ribbon must be mounted inexpensively according t a zigzag pattern.

It may, therefore, be stated generally that the principal object of my invention is to provide a filament support, particularly adapted for use as a heating element, having a limited number of preformed parts readily susceptible of assembly by simple machine methods.

A further object of my invention is to provide a iilament support, such as an electrical heating element, the assembly of which involves no hand guiding, threading, or winding of the filament.

Another object of my invention is to provide an electrical heating element, embracing a rigid framework, a mounted resistance ribbon, and clamps for making external connections to an electrical circuit, comprising a total of only five parts, susceptible `of assembly by automatic means.

Other objects and advantages of my invention will appear as the specification proceeds.

I have illustrated two typical embodiments of my invention in the accompanying drawing, of which Figure 1 is a top view of a heating element made according to my invention; Fig. 2, a side view, partly in section, of the embodiment of Fig. 1; Fig. 3, an end elevation view of the Fig. 1 embodiment of my invention; Fig. 4, a sectional View of the Fig. 1 embodiment of my invention, taken along the line 4 4 of Fig. 2; Fig. 5, an enlarged fragmentary sectional view of a portion of the structure shown in Fig. 2, the enlargement being designed to bring out certain details of the spring clamp structure which anchors the various parts of the invention together; Fig. 6 is a perspective view of a spring clamp employed in my invention; Fig. 7 is a top view of an alternative embodiment of my invention; Fig. 8 is a side view in section of the Fig. 7 embodiment of my invention; Fig. 9 is an end elevation view of the Fig. 7 structure; and Fig. 10 is a sectional view taken along the line lll-'flo of Fig. 8.

In the drawing, referring now to Figs. 1-6 inclusive, I have shown my invention in the form of a heating element adapted for use with an electrical appliance such as a toaster. The frame structure is formed from two pieces of material porcelain, or any other suitable high-temperature-resistant material, molded into suitable form. The lower of the two frame pieces, as seen in Fig. 2, is denoted Il; for convenience, I shall refer to member Ilv as the base member. The upper frame member is denoted I2; I shall refer to member l2 as the cover member.

Base member Il and cover member l2 are structurally similar except with respect to certain modications along their side edges. Each of the two frame members Il and l2 is generally combshaped, having a body portion and a plurality of long, thin fingers extending outward at right angles from the body portion. Exemplary ngers on base member Il are denoted I3; exemplary fingers on cover member I2 are denoted I4.

The precise conformation of fingers I3 and I4 may be varied greatly as a matter of design; in general, however, it is desirable that the tip of each linger be suitably modied to make it vfunctional as a catch or guide member to receive the resistance ribbon which forms the heart of the heating element. In the particular embodiment shown, this catch or guide'nger tip is formed by providing on each side of each linger at its extremity a pair of narrow extensions, denoted I3a in the case of fingers I3 and Illa in the case of fingers I4. The body portion of each of the frame members |I and I2 is provided with a plurality of reduced-width zones indicated on the drawing as zones IIa and I2a respectively. Extensions I3a are separated sufliciently to clear snugly the reduced-width zones |2a and, correspondingly, the extensions Ida are proportioned to clear snugly the reduced-width portions I Ia on the base member II. As a result, the members II and |2a can be joined in mating, interlaced relation, as shown in Fig. 2. As may be seen from Figs. 2 and 4, the abutment of end portions I2b and IIb of frame members I2 and II respectively occurs before the tips of fingers I3 and I4 come into contact with the body portions of frame members I2 and II respectively, so that a continuous zone of open space between the frame members and I2 exists from one side thereof to the other, the two members abutting only at their end portions.

The end portions I2bof cover member I2 arc provided with symmetrically disposed recesses I5 molded therein. As may be seen best from Fig. 5, recess I5 has inner walls which are `generally parallel to the end surface of cover member I2 and the downwardly projecting fingers I6 which define the outer limits of recesses I5 are each provided with a smaller recess I6a roughly similar in shape to recess I5 but much smaller in size.

As may be noted from Fig. 3, the width of recesses I5 is somewhat less than the total thickness of cover member I2 so that the sides of recess I5 are wholly enclosed. Recesses I1, on the other hand, are closed off on only one side, leaving an open space IIc to permit the insertion of spring members 20 into recesses I1.

Base member contains in each of its end portions symmetrically disposed recesses I1 designed for co-operation with recesses I5 and IBcr in cover member I2. The recesses I1 are formed with an under-cut shoulder I8 which serves as a seat to hold securely in position spring clamp member l20 normally carried therein. In addition, the outer wall of each recess I1 is relieved at I9 to provide an external opening.

Spring clamps 2|] are normally received within the recesses just described. A perspective View of a typical spring clamp 20 is shown in Fig. 6, from which it may be seen that each clamp has an elongated shank portion 2|, a base portion 22 near its lower end and at right angles to shank 2|, a curved spring portion 23, and a J-shaped portion 24 which is folded back on shank 2 I. The outer terminal edge of portion 24 may be sharpened to provide a cutting edge 25. Notches 26 are provided in the body of J-shaped portion 24 for a purpose to be hereinafter described. As may be noted from Fig. 5, base portion 22 normally seats against under-cut shoulder I8 in recess I1.

In my assembled heating unit, a resistance wire or ribbon 21 extends continuously from the edge 25 of the spring clamp 20 at one end of the frame structure through the zone of clearance between the fingers I3 and I 4, zigzagging back and forth between the tips of the respective fingers, to the recess I5 at the other end of the frame structure, ribbon 21 finally terminating at the edge 25 of the clamp 20 mounted in the opposite end of the frame.

The wall of each of the recesses I5 is provided with a symmetrically arranged pair of projections 28 the function of which is to seat in notches 26 when spring clamp 20 is forced into recess I5, so as to lock spring clamp 20 therewithin and prevent its being withdrawn once it has been seated.

As may be seen from Fig. 2 or Fig. 5, resistance ribbon 21 passes from the space between the frame members into recess I5, over the contour of spring clamp 20, between notches 28, and into recess Ia, terminating at knife edge 25.

It may be noted from Fig. 2 or 5 that spring portion 23 of spring clamp 2D provides, in cooperation with aperture I9, a receptacle for receiving a prong 32 to which wire 3| is soldered or otherwise aiixed. Thus, by forcing prongs 32 into contact with springs 23, as shown in Fig. 5, electrical circuit connections to the respective terminals of resistance ribbon 21 may be made without the use of tools.

As may be seen from the drawing, my heating element has only five parts-frame members II and I2, a pair of spring clamps v2|), and ribbon 21. In the assembly of a heating element made according to my invention, hand threading or winding of the ribbon 21 is not necessary. Ribbon 21 may be supplied to the assembly point by a reel having mild spring tension.

Normally my invention should be assembled on a iiat surface, such as a horizontal table. The free end of ribbon 21 should be attached to a temporary anchor on the opposite side of the assembly table from the reel. A bas-e member I I is then supplied with spring clamps 25 suitably inserted into recesses I1, the shanks 2| project ing outward beyond recesses I1. Base member I I is then slid into position for assembly with ribbon 21 passing between the various projections |3a and resting on the tips of the respective fingers I3. A cover member I2 is then placed on the assembly table on the opposite side of ribbon 21 from base member and is then slid into mating, interlaced position with base member II. The projections Illa guide ribbon 21 into position for seating on the tips of fingers ILI, and, as the base and cover members are moved together, additional ribbon 21 is supplied from the reel. When the cover member I2 has reached the point of engagement with the outwardly projecting portions of spring clamps 20, ribbon 21 is guided around the portions 2| and 2G of spring clamps 20 and between projections 28. Member I?. is then forced into abutment with member I I, projections 28 lodged in notches 25, and the assembly of my invention is completed. The ends of ribbon 21 are then severed against knife edges 25, and the free end of ribbon 21 extending from the reel is moved over to the temporary anchor heretofore mentioned. The assembly table then ready for another assembly operation.

The completed heating element thus assembled is mechanically strong, attractive in appearance, safe to use, and readily adapted for assembly into completed appliances such as toasters or room heaters.

In Figs. '7-10 inclusive, I have shown another embodiment of my invention, lemploying, however, the same basic principles. In this alternative embodiment, I use a pair of frame members denoted III and IIE, III being the base member and IIZ. the cover member. Each of the two frame members is roughly rectangular in shape and is made in the form of a frame open in the center. The principal body portion of base member III is equipped at each end with a ledge or recess IIB having a small up- 'half of the frame structure, is also generally rectangular in shape and also has an open central portion. In the lower extremities of its sides there are provided a pair of recesses IIS which correspond to recesses I5 in the Fig. 1 embodiment and having the same general shape as that recess. Each of the sides of cover member ||2 also contains a small recess II'I which corresponds to recess I6 in the Fig. 1 embodiment. The lower transverse side |I2a of frame member I I2 has molded in it a plurality of notched projections H9, spaced apart in the same manner as the notched projections |I5 on transverse bar II Ia and oriented with respect to projections I|5 so that each of the projections I I9 will pass midway between a pair of the projections ||5 when the two frame members are slid together into mating or interlaced position.

The spring clamp members are lingers similar to the clamp members 20 of the Fig. 1 embodiment, and the upper portions thereof are formed identically with those of clamps 20. To illustrate an alternative method of mounting the spring clamps, I have in this embodiment shown spring clamps bolted as aforesaid to the base member I I I and provided with spring extensions I2Ia to receive the electrical contact prongs |22.

In the assembled heating element of Figs. 7-10 a resistance ribbon |21 is mounted in zigzag array across the face of the frame, the ribbon being held in place by projections I5 and I I9 and being anchored at its ends by spring clamps |20.

The assembly of the Fig. 7 embodiment of my invention is similar to that of the embodiment previously described. This form of my invention involves somewhat less structural frame material than the first embodiment and, on the other hand, does not provide the resistance ribbon with as much protection from mechanical damage as does the iirst form. Otherwise, the two embodiments employ the same principles of operation and have identical advantages of simplicity and rapid assembly.

While I have in this specication described in detail two embodiments of my invention for purposes of illustration, it will be understood that persons skilled in the art can make many changes and variations therein without departing from the spirit of my invention. It is accordingly my desire that the scope of my invention be not limited to the specific embodiments herein shown and described but determined primarily by reference to the appended claims.

I claim:

1. In combination, a pair of frame members carrying a plurality of oppositely disposed catch members and a lament wound zigzag between said catch members and supported alternately on a catch carried by one frame member and a catch carried by the other frame member, said frame members being formed for interlaced mating to permit their being placed on opposite sides of the lament and slid into interlaced relation, and spring clamps on said frame members operative to secure the ends of the filament against movement and releasably to lock the frame members into interlaced position.

2. In combination, a pair of frame members carrying a plurality of oppositely disposed catch members and an electrically conducting lament wound zigzag between said catch members and supported alternately on a catch carried by one frame member and a catch carried by the other frame member, said frame members being formed for interlaced mating to permit their being placed on opposite sides of the filament and slid into interlaced relation, and spring clamps on said frame members operative to secure the ends of the filament against movement and releasably to lock the frame members into interlaced position.

3. In combination, a pair of co-op-erating frame members of substantially rectangular shape, each having a base strip, a leading strip and a pair of side strips joining the base and leading strips, said leading strips being each provided with a plurality of catch members staggered on the respective leading strips to permit interlaced passage of the catch members as the frame members are slid together, a filament having its ends secured to the frame members and being supported in zigzag array by the respective catch members, and a pair of spring clamps carried by said frame members, said clamps being operative to lock said frame members together in interlaced relation and providing also anchor means for the ends of said filament.

4.-. In combination, a pair of cooperating frame members, each of which is provided with a plurality of spaced catch members adapted to engage and hold a filament, said catch members on said respective frame members being staggered to permit interlaced passage as the frame members are slid together, a iilament having its ends secured to the frame members and being supported in zigzag array by the respective catch members, and

a pair of spring clamps carried by said frame members operative to lock the same together in interlaced relation and providing also anchor means for the ends of said lament.

DUDLEY C. PULLIAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 337,509 Laskey Mar. 9, 1886 936,123 Grimm et al Oct. 5, 1909 1,065,015 Youmans June 17, 1913 1,867,581 Marietta July 19, 1932 1,900,318 Van Valkenburg et al. Mar. 7, 1933 1,947,612 Moore Feb. 20, 1934 2,086,736 Palmer July 13, 1937 2,374,512 Van Dyke Apr. 24, 1945 FOREIGN PATENTS Number Country Date 446,813 Germany July 11, 1927 680,887 Germany Sept. 9, 1939

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