US2731707A - Method of assembling a filament and support - Google Patents

Description

Jan. 24, 1956 D Q PULLlAM 2,731,7@7

METHOD OF ASSEMBLING A FILAMENT AND SUPPORT Filed June 14, 1950 3 Sheets-Sheet l INVENTOR.'

ATTORNEYS.

Jan. 24, E956 D. c. PULLIAM 73H30? METHOD OF' ASSEMBLING A FILAMENT AND SUPPORT Filed June 14, 1950 5 Sheets-Sheet 2 INVENTOR:

TUHNEYS.

Jan. Z4, E956 D, C, PULLIAM 2,7311??? METHOD OF' ASSEMBLING A FILAMENT AND SUPPORT Filed June 14 1950 3 Sheets-Sheet 3 INVENTOR.' ,A l "f/ v ATTRNEYS.

United States Patentr METHOD F ASSEMBLING A FILAMENT AND SUPPORT Dudley C. Pulliam, Chicago, lil. Application June 14, 1950, Serial No. 168,115 4 Claims. (Cl. 2951555) This application relates broadly to filament supports and to a method for assembling them; in particular, it concerns a filament-supporting structure which is simple and inexpensive, involves only four parts, including the imum of manual elort.

Filament-supporting structures are encountered in many branches of technology, and my invention is applicable to a wide variety of specific types of devices. I am particularly concerned, however, with the use of my invention in the electrical appliance field as a heating element.

Heating elements for electrical appliances, in the prior porcelain, or other refractory material, on which a metallic ribbon or filament formed of Nichronie or other resistance wire, is wound. Electrical terminals to facilitate the ow of current through the resistance ribbon are customarily afixed to the frame with rivets or bolts. Such heating elements have, in the past, been assembled, and the resistance ribbon has been wound thereon, by hand. The resulting high labor cost has made electrical heating elements for appliances expensive out of proportion to the cost of the actual materials employed therein.

ln the present invention, I provide a filament-support structure, particularly adapted for use as an electrical heating element, wherein a high degree of mechanical ruggedno manual assembly cost.

It is accordingly an object of my invention to provide a method of assembly of my distinctive lament-support structure which greatly reduces over prior art methods the manual steps required in assembly.

Other and additional objects and advantages of my nvention will appear-as the specication proceeds.

In the accompanying drawing, I have shown a typical mounting on the frame structure the other elements of a completed filament-support structure according to my Fig. 2 is a sectional view, taken along the line 2-2 of Fig. l.

structure fully assembled, lying in position on the jig or bench after the assembly machine has been withdrafvns This figure also shows in plan view, partly in section, the

assembly operation. Fig. 6 is a greatly enlarged view,

pletion of its advance movement. Fig. 7 is a view showing the modified form o f fully assembled heating element material capable of withstanding the operating temperatures of electrical resistance ribbon. The general conformation of frame member 10 resembles that of a comb, in that it is provided with a pair of end members 10a and a plurality of tines 10b. As may be seen from Fig'. 2, end members 10a are, in the particular embodiment shown, similar in thickness to the transverse frame 10 proper and are slightly longer than tines 10b. This construction enables end members 10a to act as mechanical protective structures to shield tines 10b from damage, either when the heating element is lying on its side or when it is mounted in a vertical position.

Each of the tine elements 10b is provided with a modihook or projection member 13, shown in front elevation in Figs. l, 3, 4 and 5, and shown in side elevation in Fig. 2.

portion 14a in the portion of the slots 14 nearest the inner face of frame 10. Reduced-width portion 14a distinctive function in the operation of my assembly mechanism, as will be hereinafter explained in greater is supported on frame 10 zigzag between the spring clamp terminals 17, ribbon 12 being in turn carried on the end members 10c of tines 10b and on hook mem- Spring clamp members 17 `comprise ,once-.folded leaf springs having, in addition ,to the main fold, an additional bent portion slightly posterior of the main fold so as to prov-ide a latch ior-self-trapp'ing head portion which may-readily' be lforced through anarrow 4opening `'but which, once past Vthe narrow opening, will lock itself in posit-ion and require substantially greater `force to withdraw it. The legs vof the spring clamp vmembers 17 opposite the extra fold just mentioned are straight, while -the leg which Yconstitutes a continuation of the leaf spring 4on the side having the extra fold is somewhat longer than the other leg vand is 'bent slightly outward at its .lower end. I

An axial slot 17a is -cut into each of the spring clamps 17, the slot bisecting the clamp 'from 'its principal fold about 2/4 of thev distance Yto the 'lower end of the shorter leg.` The width of :slot 17a Iis `adjusted `to 'accommodate snugly, without crowding, -the resistance ribbon 12. As may be yseen from Fig. '5,- the resistance ribbon 12, -in

the assembled heating element, -is anchored `in the frameY by -passing .through slot 17a and pressing firmly against bosses and 16, spring clamp 17 being firmly anchored Iin slot 14.

The manner of assembly of my novel iilament-support structure, 4avoiding manual operations almost entirely, is brought out in Figs. 'l-5, inclusive. My as- Sembly .machine lis shown in -the figures only in plan view; it consists ot a very simple structure 'comprising a plurality of elements mounted in a vertical position on any type of suitable carriage adapted for 4periodic advancement and retraction. Since "I do not claim herein the .details of mounting and moving my assembly machine, those details are not shown in the drawing. ltgmay be understood, however, that any suitable means may be employed for that purpose. The critical operative Velements' of 'my assembly machine comprise a number of ribbon-carrying -lingers 21, equal in number to :the number of 4hooi: projections 13.- lThese fingers have a generally :V-shaped sectional conformation, and are oriented in transverse alignment with their open legs facing in the direction of advance of the assembly machine.

l. Mounted at each end of 4the row of fingers 21, and slightly behind such lingers, is a pair of clamp-carrying members 22. The members 22 perform two functions- {1) they serve as the means for advancing the clamp members `17 Ainto seated lposition 1in frame 10, and (2) they provide the means lfor cutting the ribbon 12 after the assembly ofv the heating element has been completed. This lastmentioned function is Aaccorrlplislled 'by means of a knife-blade 22a which 'is carried in a 'suitable recess in member 22 opposite the recess provided for support of spring member 17. 'The two slots 'just mentioned are oriented relative to one another suoli that when member 22 is vfully advanced into Yframe member 10, as shown in Fig. 4, `the knife-blade 22a andthe straight leg oi spring member 17 pass on opposite sides ofboss 16. This action is clearly -brought outin Fig. 6.

At the outset of the assembly process, the frame 10 is placed in a horizontal lposition on: a suitable jig so as to permit the carriage which supports elements 21 and 22 to pass beneath it, giving tingers 21 liberty to advance up to and'lap over'hookprojections13. The ribbon 12, normally coiled on a large reel, is drawn 'from the reel suiciently to pass between the singers 21 and the 'tips 10c of tines 10b at the level 4of notches 11. The end of ribbon 12 may, prior to the assembly operation, be anchored in any suitable manner, the reelbeing left free to -tnrn and thus release additional quantities of ribbon 12 as needed. Meanwhile, members'22 are suitably loaded `with spring members 17 supported 4in the position shown linlFigs. l, 3, and 4. n This loading operation may be accomplished by hand or, iif desired, by A`means of an automatic work feeder such as industrial .engineers frequently employ in mass-productionapparatus. The carriage carrying 4 I `members 21 .and .22 .is .thenadvanced wtoward ,frame member 10, spring members 17 intercepting ribbon 12 in slots 11 as they advance. The apparatus is shown in Fig. l shortly after the advance of the assembly machine has commenced.

As fingers 21 and members 22 enter the spaces between elements 10a and 10b, the ribbon 12 is trapped in notches 11 and it begins to unwind from `the reel (not shown) with further advance of the : members 21 and 22. At this stage, also, the ribbon 12 passes over end members 10a of frame 10 and ribbon 12 Ythereupon seats in the bottom of slots 17a of .spring vmembers 17. This intermediate position of the assembly machine is shown in Fig. '3.

When the carriage .carryingmemberS'Zfland 22 reaches its most advanced position, the fingers 21 will have carried ribbon 12 into the zigzag position shown in Fig. 4, and the ribbon will be ready for seating in hooks 13. At the same lime, members 22 will .have zforced spring clamps 17 iinto seated position within slots '14 land, .as

lcn'iexedges22a come into pressure lcontact -with :bosses 16, ribbon 12 is severed. Art this time, :the carriage car. rying members 21 and 22 may be lowered asmall fraction of an inch, or, alternatively, means :may tbe provided for lowering members L21 and '22 'in their carriage mount. This causes .spring .clamp members 17 to. become .dislodged from clamp :carrying members 22, and, at the same vtima-.ribbon 12 is thus seated-within .the `notches 13.

The assembly .machine is .then .retracted ,to tits starting position .and restored to its original devel. The frame 10, at that'stage, is a :fully assembled 'heating element `as shown in Fig. 5, and lmay be removeditrom .the rjig :and replaced by another frame 10 ready for assembly. The

ribbon 12 may then be again Aplacedin A.position for anY assembly operation (this may .be :accomplished Vautomatically 'by means Vwell .known to industrial engineers, or it may be Vdone byihandj). Similarly, the clamp .carrying members :22 .are vagain loaded" wvith spring clampsV 17, Aand a newassembly operation :is commenced by once againzadvancing the carriage carrying : members 21 and 22.'

Numerous "modiiications yand variations in .the .machine which l-havc outlined suggest themselves :to )persons skilled in the art. 1 have foundit desirable, Vto insure .ac--

' curated seating of alie ribbon I2 in notcheslarto .maintain .the normal position of members121somewhatahead of imembers 422 while giving .them liberty, :either by Velasticity in the lingers themselves, or'by La suitable .spring mounting, vto .move backward into :alingnrnent with members .22 at the final .advanced-position shown in Pig. 4. This v.arrangement may -be .changed in many ways .according to the preference of particular engineers .or the reqnirements: of particular applications. Similarly, the .illustrated method .0f assembly produces .a stub lof ribbon 12 `from one'o .the clamp-,carrying members 22 tothe anchor :point :of .the free Vendzof .ribbon 12a loss of perhaps 7 `or 8 inches in .a typical `case. :In .the 4embodiment shown, Laccept `this .slight :loss .of ribbon in 'the interest of maintaining .simplicity of assembly structure, since :the ribbon vis inexpensive and represents a negligible part of the cost Iof the total assembly.

Spring members 17, -lit Ymay .be noted, provide an admirably effective and simple .means .of making electrical contact with the .terminalsof ribbon 12,=since1spadetype contactA prongs connected to anexternal circuit can readily be eslid into slots 14 and `placed I1in spring cngageber is the essential element of the assembly method. Vertical assembly, with the frame 10 held in a vertical plane, may of course be employed if desired.

I have shown in Fig. 7 a heating element assembled according to my invention but having a modified structure particularly adapted for use in toasters, room heaters, and other electrical appliances in which the heating element is normally supported in a vertical plane but in which uniform radiation of heat over a substantial area is desired.

Due to the tendency of heated air to rise, a conventional heating element of the type in Fig. will usually tend to be substantially hotter in its upper zone than in its lower zone, when mounted in a vertical position. In the form of heating element shown in Fig. 7, a substantially greater quantity of heat is radiated from the lower half of the frame structure than from the upper half, with the result that, after the effects of rising hot air are taken into account, the heat radiated over the frame area is substantially uniform.

As may be seen by referring to Fig. 7, this is accomplished by providing a modified zigzag mounting arrangement in which alternate hooks are carried on a transverse cross member rather than on the transverse body of the frame proper, as in the Fig. 5 embodiment. convenience, the reference numerals in Fig. 7 are like those of corresponding elements in the other figures except that they have been increased by 100. As may be seen, the frame 110 is provided with end pieces l10n and tines llb. Similarly, each of the tines 110b has an end portion 110e formed identically with terminals 10c in the Fig. 5 embodiment. Hooks 113 serve the same function as in the other embodiment of my invention, but, it may be noted, only alternate hooks are molded as part of the transverse frame portion 110. The other hooks 113 are molded onto cross members 130 which bridge adjacent tines 110b at about half the distance from their base portions to their tips.

The assembly of the structure of Fig. 7 may be accomplished in the same manner as described with the Fig. 5 embodiment, the only difference being that alternate lingers 21 would, in the assembly of the Fig. 7 embodiment, be staggered with alternate fingers held in a substantially more advanced position than the others.

While I have in this specification, for purposes of illustration, described in considerable detail two specific embodiments of my invention, it will be understood that many variations and changes can be made therein by persons skilled in the art Without departing from the spirit of my invention. It is, accordingly, my desire that the scope of my invention be determined primarily with reference to the appended claims and that the particular embodiments described in the specification be regarded as exemplary only.

I claim:

1. The method of assembling a heater filament and support structure therefor having a frame equipped with spaced-apart filament-carrying tines and hooks carried at the base of the tines and interposed therebetween and a slot adjacent each end thereof for receiving clamp members, comprising the steps of extending a filament strip the length of said frame in planar alignment with said tines and securing a free end thereof, advancing the filament into engagement with said tines, pressing the filament downwardly between said tines and advancing clamp members into engagement with said filament and toward said slots, seating the filament upon said hooks and advancing said clamps into said slots to clamp said filament to said frame, and severing said filament at points adjacent said slots.

2. In a method ot' assembling a heater filament and a comb-shaped support structure providing a row of spaced-apart tines and hooks disposed between the tines and adjacent the bases thereof, the steps of extending a heater filament across said tines adjacent the outer ends thereof and in planar alignment therewidi, advancing said filament into engagement with the outer end of said tines, further advancing said filament between said tines, securing said filament to said hooks, and severing said filament and clamping the ends thereof adjacent the ends of said support structure.

3. in a method of assembling a heater filament and a comb-shaped support structure providing a row of spaced-apart tines and hooks disposed between the tines and adjacent the bases thereof, said support structure having clamp-receiving slots anking the row of tines, the steps of supporting a heater filament for free Withdrawal and filament, ing said filament into engagement with the outer ends of said tines and inwardly and into the spaces therebetween, securing said iilament to said hooks, providing clamp members adapted to receive said filament therein and advancing the clamp members into said slots to secure said filament, and severing said lament adjacent said slots and clamp members.

4. The method of claim 3 in which said clamps are seated in said slots and said filament is severed simultaneously.

References Cited in the file of this patent UNITED STATES PATENTS 936,123 Grimm Oct. 5, 1909 1,056,225 Snedeker Mar. 18, 1913 1,591,183 Reynolds July 6, 1926 1,825,481 Shindledecker Sept. 29, 1931 1,867,581 Marietta July 19, 1932 1,881,981 Trussell Oct. 11, 1932 1,900,318 Van Valkenburg et al. Mar. 7, 1933 1,958,870 Stuart May 15, 1934 2,086,736 Palmer July 13, 1937 2,163,716 Turner .Tune 27, 1939 2,374,512 Van Dyke Apr. 24, 1945 2,432,267 Adamson Dec. 9, 1947 2,449,712 Mulvany Sept. 21, 1948 2,450,974 Mallina Oct. 12, 1948 2,485,282 Green Oct. 18, 1949 2,599,411 Pulliam June 3, 1952 FOREIGN PATENTS 319,555 Germany Apr. 29, 1919

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