US2434905A

US2434905A - Method of fabricating contacts for fluorescent starter switches

Info

Publication number: US2434905A
Application number: US544120A
Authority: US
Inventors: Harry M Burt; Guy H Burt
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-07-08
Filing date: 1944-07-08
Publication date: 1948-01-27
Anticipated expiration: 1965-01-27

Description

H. M. BURT ET AL 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT STARTER SWITCHES Jan. 27, .1948.

' Filed July 8, 1944 4 Sheets-Sheet l B RT w 8 4 1 2f A \P, if L; Lr LP .1 AM .n 5 0g 7 2 8N Q5 6: 5 @W m@ w a m h 2: m 02 147' OQNEY I Q3 i B Jan. 27, 1948. H. M. BURT ET AL 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT STARTER SWII'CHES Filed July 8, 1944 4 Sheets-Sheet 2 Q M mi) INVE RS HHRRY M- u 7 v G H. BU

ATTORNEY I Jan. 27, 1948. H. BURT ET AL METHOD OF FABRIGATING CONTACTS FOR FLUORESCENT STARTER SWITCHES 7 Filed July 8, 1944 4 Sheets-Sheet 3 V I I] v A ltlr'ljh N 1 \v a O VENTOR. v (\I Han-Ry M B vr }Q q 5' v GW #80" I I 4 v J I A TZOPNFY Jan. 27, 1948, H. M. BURT Em, I 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT S1'ARTER SWITCHES Filed July 8, 1944 4 Sheets-Sheet 4 0 L9 o g (D O q 3: 0 3* g 3 Q H W k 5 AAJTZOQNEY Patented Jan. 27, 1948 UNITED STATES ATENT OFFICE METHOD OF FABRICATING CONTACTS FOR FLUORESCENT STARTER SWITCHES Harry M. Burt, Narragansett, and Guy H. Burt, Edgewood, 1.

Claims.

This invention relates to a method of fabricating electrical contacts for fluorescent starter. More particularly, the invention is concerned with contacts of the character described which are fabricated from sheet metal stock, the term sheet metal being used herein to include flat, bent, curved, tubular and variously shaped lengths and pieces of thin self-form-maintaining material.

Heretofore, contacts for starter switches have been fabricated conventionally, by turning down solid metal stock, for example, by removing metal from a section of a rod in a screw machine, to impart the desired shape thereto. This practice has been assiduously followed due; principally, to the peculiar shape of most starter switch contacts. Such shape consists of (1) a cylindrical shank long enough to extend through the base of a starter switch socket, (2) a cylindrical extension on one end of the shank of smaller diameter than the shank and long enough to project through a starter switch base with its free end upset into engagement therewith, and (3) a pair of transverse spaced flanges at the other end of the shank to couple with a resilient blade in the socket and secure the starter switch against undesired displacement. The flange intermediate the ends of the contact has been the principal reason heretofore for making said contacts by machining. In some contacts, an axial bore is provided into which an electric lead from the interior of the switch may be inserted and secured by the introduction of fusible electrically conductive material, e. g., solder, from the outside of the switch. In solid contacts, the tubular extension is recessed to facilitate upsetting and making an electric connection to the starter switch.

The formation of these contacts by metal removing operations has been attended by substantial expense because much of the solid stock had to be removed when forming a contact. This entailed the purchase of metal which eventually had to be removed as scrap in expensive machining operations.

It is an object of the present. invention to provide a method for manufacturing an intermediately flanged contact such as described in which the majorportion of the scrap, if any, is removed, before the contact is formed, by a simple operation, such as shearing, to provide a work blank which can be fabricated into the desired shape with the subsequent removal of little or no scrap. Another object of the invention is to provide tact of the character described on an economical, rapid, mass-production basis.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements, arrangement of parts and performance of operations which will be exemplified in the constructions and methods hereinafter described, and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings, in which are shown various possible embodiments of this invention and wherein like numbers refer to like parts, I

Fig. 1 is a bottom plan view of a starter switch socket having disposed therein a starter switch with contacts made in accordance with our invention;

Fig. 2 is a sectional view taken substantially along the line 2-2 of Fig. 1;

Fig. 3 is a bottom plan view of the switch alone;

Fig. 4 is an enlarged sectional view of the novel switch contact, taken substantially along the line 4-4 of Fig. 3;

Fig. 5 is a side elevational View in partial section of an eyelet machine tooled up to make said contact; I

Fig. 6 is a plan View of the bed of the machine; Figs. 7 and, 8 are enlarged fragmentary sectional views of the blanking dies at successive stages of their operation;

Figs. 9 and 10 are similar views of the cup forming dies;

Figs. 11 and 12 are similar views of the deep drawing dies;

Figs. 13 and 14 are similar views of the twostep forming dies;

7 Figs. 15 and 16 are similar views of the threestep forming dies;

Figs. 17 and 18 are similar views of the intermediate flange forming dies;

Figs. 19 and 20 are similar views of the top flange forming dies;

Figs. 21 and 22 are similar views of the piercing dies; 4

Fig. 23 is a perspective view of a fully formed sheet metal contact made in accordance with our invention; and

Fig. 24 is a view similar to Fig. 4 of a modified form of sheet metal contact likewise made in accordance with. theinvention and in which the only flange is one intermediate the ends of the contact.

a method for manufacturing a sheet metal con- In g n al. we carry out the stated objects 01 the invention by first forming a sheet metal tube in any conventional manner, for example, by cupping and deep drawing, extrusion, or any well known tube forming method. A tubular element, or portion of the tube having a length corresponding to that of the tubular element, is then operated upon to impart thereto a shape consisting of a plurality of integrally connected coaxial tubular steps of different diameters, that is, in each tubular element at least two tubular steps of uniform diameter are provided, adjacent steps being of difierent diameters. If three steps are employed, the slenderest step may have a length and diameter corresponding to the tubular extension (2) which is used to secure the contact to a starter switch. breadth may have a diameter and length the same as that of the hollow tubular shank (I) in the finished contact. The tubular step of greatest diameter may have a length such that when further operated upon to provide the neces-- sary flange or flanges, the contact will be of the right overall length. The difierence in diameters between the second and third steps provides a shoulder intermediate thetwo steps which enables us to form the intermediate flange in a, novel manner.

After the tubular element or portion consisting of a plurality of tubular steps is formed, one of the steps, and preferably the larger of two adjacent steps, is axially compressed against an abutment member at the shoulder between said two steps. During this compression, the portion of the tubular element spaced from the shoulder is laterally, externally supported, leaving only a short portion, no greater than the diameter of the step, adjoining the shoulder laterally unsupported. The overall length of the laterally supported and unsupported portions of the compressed step is so proportioned relative to the diameter of said step, that this step will act as a pure compression member rather than as a column under axial compression and will tend to bulge outwardly rather than buckle, particularly when partially laterally supported as described. We prefer for this ratio of length to diameter of the compressed step not to exceed 3 and best results are obtained when said ratio does not exceed 1.5. According to the invention, the bulging movement of the laterally unsupported portion of said step is confined and directed to force said portion to assume the desired configuration of a double-walled intermediate flange.

While the intermediate flange is being formed, the free end of the compressed step may be curled over and subsequently, if desired, said step may again be compressed, this time without any external lateral support whatsoever, the dies employed in compression being so shaped as to force the curled portion outwardly to provide a doublewalled end flange spaced from, the aforesaid intermediate flange.

Finally, the bottom of the cup which is integral with the slenderest tubular step is pierced, so that a lead from the starter switch may be inserted therethrough; also, so that this opened end may be spun over or riveted onto a supporting member, e. g., a fibre disc or plastic can.

Referring now to the drawings, and more particularly to Figs. 1 through 4, we have there shown a sheet metal contact 30 made in accordance with the invention. Said contact is furnished as a part of a starter switch 32 which may be of .any conventional construction and is housed in a suitable container, such as a plastic can or the The step of intermediate light sheet metal can 34 whose ears 36 are inturned to secure the can to an insulating disc 38. The can houses a suitable switch, not shown, which may be adapted to close and open a starting circuit for a fluorescent electric discharge lamp. Said switch is connected in the starting circuit by a pair of lead wires 40.

The contact 30 is made, from light, electrically conductive sheet metal, for example 22 gauge brass, and is generally tubular in shape so as to provide a continuous bore from end to end. The

shank of, the contact consists of a seamless tubular step 42; to which there is integrally connected another seamless tubular step 44 of smaller diameter. This latter step extends through an aperture 4B in the base of the insulating disc 38 or,

its, plastic. can isemployed, through an aperture in the bottom wall thereof. The step 44 is of suihcient length to permit the free end thereof to extend into the interior of the can 34, where it is, spun over, yeleted or riveted to. form a bead 48. which is clench d ti ht y aga st h i er surface of the disc 38.01. on ner. At t other end of the shank w provide a th'rdseamless tubu, lar step 50 of larger diameter than the

shank

4,2. The tubular step 50 includes two. flanges, one flange 52 immediately adjacent an end of the shank and the other flange 54 spaced from said first flange. Between the two flanges the third step 58 has a constricted portion 56 which is of greater diameter than that of the shank 42. The free end of the third step 50 has a portion 51. which is perpendicular to the longitudinal axis of the contact 30 and an inturned retroverted portion 58 which provides a smooth surface at the exposed end of the contact. After a contact, 30 is secured to a disc 38 or plastic can, one of the lead wires 431s inserted therein from the inner surface of the disc 38 or can, this lead wire only extending partly through the contact as indicated in Fig. 4 or the lead wire is extended completely therethrough and the protruding portion cut off. The disc or can is then inverted to place the flange 54 uppermost and a fused electrically conductive material of low mating point, e.,g., solder 60, is poured into firmly hold the lead wire in place.

A contact of the shape described is adapted to be used in any conventional present day socket for a fluorescent starter switch such, for example, as the socket 62 shown in Figs. 1 and 2. This socket may be of the type shown and described in Letters Patent No, 2,280,741 issued August 21, 1 942, and consists of side walls, 64 and an intermediate transv rs p n 66 w ch s rves est e s cket base. Said partition has a pair of arcuate concentric keyhole slots 88 formed therein in which the contacts 3!) are adapted to be received. On the under surface of the base 66, are a pair of lobster claw contacts 'lil whose spring fingers 12 are dap d to resiliently grasp t e c ntacts 38 when they are at the narrow end of the keyhole slots 68. It will be noted that the fingers 12 are so located that they will engage the contacts 39 between the two flan es 52, 54. This prevents the starter switch from shifting axially until the same has been rotated out of engagement with the fingers.

The steps for fabricating a sheet metal. contact such as iust described are shown in Figs. 5 and 7 through 22. First, a circular disc or work blank (Figs. 7 and 8) isblanked out of a sheet metal strip '82 which is fed from a reellnot shown) of such material. This disc is then formed into a large cup 84 (Fig. 9) of adiarneter greater than that of anyoi the tubular steps later to .beformed.

g. Next, the cup is stripped (Fig. from the cup forming dies. From this stage the large cup is transferred to a set of drawing dies (Fig. 11) which reduce the diameter and increase the length of the cup 84 to provide a cup 86 whose diameter is approximately equal to that of the third or largest tubular step and is, therefore, also approximately equal to the diameter of the constricted portion 56 between the two flanges 52, 54 ultimately to be formed.

The cup 86 is then stripped (Fig. 12) from the drawing dies and introduced to the two-step forming dies (Fig. 13) at which time the intermediate step 88 is impressed therein, the diameter of this step being approximately equal to thatof the shank 42. The cup-like element 98 with the two steps provided therein is stripped (Fig. 14) from the two-step forming dies and transferred to the three-step forming dies (Fig. 15) in which the last step 92 is drawn, the diameter of this step being equal to that of the tubular contact extension 44 and the length thereof being greater than the thickness of the disc 38 or base of the plastic container. The diameter of all the steps may be brought to their correct dimensions in the three-step forming dies.

It will be noticed that the step 88 in the element 90 is of such length that when the smallest step 92 is subsequently formed at the bottom thereof, the resulting intermediate step 94 and end step 92 are equal to the lengths of the tubular shank 42 and unspun tubular extension 44, respectively.

Next, the cup comprising three tubular steps is stripped (Fig. 16) from the three-step forming dies and shifted to the intermediate flange forming dies.

It may be mentioned at this point that the preceding operations are conventional per se; that is, it is well known to blank out work pieces which are subsequently formed into cups having tubular steps of different diameters, and it will, therefore, be realized that the tubular element having a plurality of tubular steps of different diameters may be formed in accordance with well known practices other than those disclosed. For example, more or less than the five steps illustrated may be used to make the three-step tubular element. Thus, the blank 80 may be out out and the cup 86 drawn in the same operation by a subpress die. Likewise, the three tubular steps all may be formed at once. Alternatively, the drawing and step forming operations may be extended over more than the four steps indicated in order to reduce the strain to which the sheet metal is subjected in any one operation. However, the actual form imparted by these operations, to wit, at least two tubular steps of diiferent diameters, is of particular importance in accomplishing the formation of the intermediate flange as will now be seen.

After its fabrication, the three-step cup is fed to intermediate flange forming dies in which the shoulder 96 between the largest tubular step 98- and intermediate tubular step 94 is seated on an abutment member (Fig. 17) which affords lateral support for the intermediate step but none for the largest step. Said largest step is now subjected to axial compression and at the same time the upper portion thereof is externally laterally supported, i. e., the external surfaces of its side walls are supported. Because of the relative dimensions of the length and diameter of the third step, in the ratio of approximately 1.25:1, said step aetsas a pure compression member rather than the shoulder 96. This will cause the bulged out of the undeformed portion of the large step 98 need not be pressed against the shoulder 96'but can be left spaced a slight distance thereabove.

In such case and with the aid of confining die portions of the proper shape, the intermediate flange may be given a truncated conical config-' uration such as shown in Fig. 19, the shoulder 62 being transverse to the longitudinal axis of the contact and projecting further than the shoulder 96 of the simple three-step cup. The side walls li l of said flange taper upwardly to provide the shape illustrated rather than extending perpendicular to the longitudinal axis of the contact as is the case in the bead I00. It will thus be appreciated that the specific contour of the intermediate flange can be varied at will and will depend in each instance upon the particular shape desired. It is even possible to have the shoulder i532 flare upwardly by providing a conical seat for the shoulder 98 of the requisite negative configuration.

- The essential elements of this stage of our invention are seating an end of one of two adjacent tubular steps of different diameters against an abutment member and axially compressing said one step while leaving a portion thereof laterally unconfined so as to cause a localized bulge to be formed at said unconfined portion where a flange is to be located. In addition, said bulge is preferably confined and forced into a desired and predetermined contour.

At thetime the intermediate flange is formed, we may also curl in the upper or free end of the large tubular step 93 to provide an inturned single-walled flange 36 (Fig. 17).

Next, the partially formed contact I08 is stripped (Fig. 18) from the intermediate flange forming dies and transferred to the top flange forming dies (Fig. 19) where the curled in portion are is retroverted and the large step 98 subjected to compression without lateral confinement. This causes the upper part of the said large step to bulge out, said bulged out portion being directed into the desired shape of the double-walled flange 54. This end flange forms at the required place, firstly, because the lower part of the third step 98 is reinforced against bulging by the previously formed bead I00, and,

secondly, since the dies are so shaped as to force the upper portion of said step outwardly. The effect of forming the end flange 54 is to provide the constricted portion 56 between the two' flanges. The upper flange normally assumes an inverted truncated conical shape, such as that indicated, with a flat top I89 and tapering side walls He. However, if it is desired to have thefiange 54 in the shape of a fiat double-wailedring such as the bead 100 shown in Fig. 1'7, a suitable abutment member may be inserted at the conresilienftlyfdriven through a spring KnOFShdw-n) has; the fihnsei t th ohei hm H4 o the-s p a d sarethe h) I qhhtact ready r sert n in an a e tu e. 4..

an in Ea ing s 8- hi fin shed whieqtii hownih F 3- t i l be. a e ed. hat, h o eg ing oper eti hsper p med p n bula sh et eta Sto areehhhmelr econom th a to time 3 1 hh iih a ount at m teria which ha t be s5 e that h contacts. an ma at m s e ter ee and le s. hpeh e than @9 1: setse? a s m lar-shap hereibieremeds in a ser w machin t; detail. one spe ific arm o epar te rwhieh ll-operat n ahi hl safii iiest and some its tm hhe v aid,a, par hi eemprises a multiple p e J20, qfth iy k o n n the t a as a eye e m q.,. i and n des a b 2 h i g eight plnngers (not shown), all carried above the bed was? rame has o the p nheers s ada ted tc-Qaus the e ormance o a s p t Opera i n up the wo pi e n p er y imessl Qn i The eri act in its hiiohs stag s. Qh m e from vinegar t P un ah fier slid 5 i Q IliI la in ist); fimllllv il g a P ir o Par l de ba l '2 A sh st tion o th m s he V1162? om opera en ior ex m le. b anking sli p n d awi stepping or flanging, is performed the bars I re fi ffil 'id fi w t a Pai of finger e h 1.2 3. 4 at e blan n stat on.- iT s are nir a y mou t d on, he h s and are e i e rg toward each o he y p n s 132- Ea hair o fin er t s-i sh ed s negat ve ohiorm o the xte nto of; the blank o a t y i med .q toqt at he station with hioli they are associated. Suitable mea Vine? hown s, provid d to re p o ate the side bars I26 a distance equal to the miforrn pec-2e b ween the adiaoentvlhhga inarertai timed relationship to the operation of the dies as gillsoonbe more fully explained.

As illustrated, the eyelet maoh-ine has seven sta ion denomi at 'A lH- In s? am th bla in stat on A, the cupp n s ation 3 the dra lng station .0, the twostepjorining station the hrees ming s t on h er-- mdi tefi ge rm s ation E, th to flan e form-m s a ion G hdih ie c ngsta h I {Ihe'blanking operation hereinlieforedescribed,

s ramm d at 'tat eh A. Thi s at on hee blan in dies comp is ng a a v l I 7 and 8 nd a p h 3 6 which is recip' b: atesi' i th r t l nge he z iace r the anvil has agroove L38 Iormed therein to rsssi a d guide the int m tten ly t s o l; stripfil whieh isslidably retaihfirl in position .by a o Plate lhel anhing p n h 6 co operates with re

iste ed ape

2, 4 11 the cover plate ar i d anvil, respectively, to ents air..- qua; work piece rom th o k trip 82 and dj, o t i upon ar rdeiie ste l blo 43 s nto the ed 22 of the ine hi eh D t Qh 1336 is pun h .361125 the c v pla e en the .h Plhh a h itd w h? he when 13,6 g, t pm 1 a n i c ntaot with until the p ir offingers I28, I30 at the thereof. The stock strip 82 is strippfid from the wash L fl sh s: t e .20? hi t tr k h tiiii sfer, slide will shift the flat blank 80 from iahehh. p statio B and oe te s d an t espesimf he u hihg d es at s atte s fIAtfstat on 36 555 5. 9 an 10) the b a k s urred, The-dies at h s stat on include a hard.- eped steel plogl I50 having an aperture I52 over wine the plank 80 is centered by the transfer s de fiaidbl -hh s iQlQd into the e r by a liardened steel c ipping pin I54 coaxially dis o ih e beci o i pe t e nd ha n a li ii r-szhal 'e than hat Of t ape e r n amount do b e the thic ss of th oc 8 be ing gr pped. The-pin I54 depends from a tapered 'plfig 156 which is driven from its" associated plunger through aspring I58. It will be apparent that, when't Plun r moves t u and n down, the blank 80 will be resiliently pressed into s a es; he cup 4- "H e relative timing of the transfer slide and sepond pl nger is such that the first pair of fingers I28, I30 associated with station A will hold the n n blank 80 atr fithtion B until said blank is Q 53!? y the d c ndin pin '54- mm d sglosegiient to this, the blank is released Joy the transfer slide which; however, does not retract o yeish ht me whims the fi s k iii the h hh hs 'si i eh, po t rs i sa fin ers n ermediate the o sta ions v rd to m t t e operations performed at said stations to be carried out beiore the article being' worked is grasped by thefihe rs- Ifheou'p' 8 4 is stripped from the block I55 by a knoels ont'pin' I which works in the aperture I5 andwhose operation is so timed that it will ior'ce tlregupM upwardly as the pin I54 retracts. L11; is'lals o necessary to employ a mechanism to rern'oye' theonp 84; from the pin I54, and to this ehdil e p i whi ping t mb '6 h v qfihtial .c'onical'apert'uie' I64 in which the tapered plng'ilfifi is'seated during the down-stroke of the m 5 Th a h' m leh s n ex e na annu grooye I56 inwliigh thebiinrcated arms I 52} of a stripping lever are disposed. Said lever is oper steed by filflqnventiona l cam firiotshownl which n he ih ih to mo e the f ll wih ashbn: the ih blel is s with the ta e ed us I55 hh the h 34 i e h stel ei h r d mn am ere t? by the k QQ TPQ Ri l I 5- Then the thimble stops, although the pin continues to rise, her a t ip h 911 9.1 film Pin- 4 ti 2331 i5 issthe ed t s graspe b a w d s t a esvefihse s se g to hold th su a te 1boeehih lysired- .N W the ihimbl i if ahsi trans e sli e advahe s ausi er tomo e thww .89 to st i n? w erev hissed with .re ehi t9 the ii es at hi i fhel nerative v m for the r in for}: 10. 5 1.91 Prevent epwh a sl WW 16mm? of sa d hhhhle so that it is epressed .11 the down: ir h s es 1.5-6-

D ehQlE lessesrat, 11-

A ter the blank fi fhas been seretes and ti h A hlbfiiihtQ when o t e tra s er; sl d o g s s i nection with station B. the only difference between them being in the shapes of the various forming pins and the matching apertures in the blocks which are set into the bed.

At station C the drawing pin "4 (Figs. 5, 11 and 12) has a smaller diameter than the cupping pin I54 at station B and the aperture I16 in the block I78 at station C is correspondingly smaller to provide clearance between the pin and said aperture equal to the thickness of the blank stock 82. The transfer fingers I80, I82 at station C have their tips contoured to receive the slender cup" formed at this station. The relative timing of the thimble I84, pin I14, and transfer fingers for said station is the same as that of the like elements at station B.

The two-step forming pin I84 (Figs. 5. 13 and 14) at station D has an upper portion I86 of the same diameter as that of the drawing pin I I4. However, this portion is shorter than said drawing pin and has depending from its lower end a thinner pin I88 which is adapted to form the intermediate tubular portion 88. The aperture I90 in the block I92 negatively conforms to the configuration of the pin I84, being slightly larger to accommodate the thickness of the stock. Due to the d fference in the diameters of the pin portions I86, I88, the shoulder 96 is formed in the tubular blank 90 intermediate the largest tubular step from which the flanges later will be fashioned and the intermediate tubular step 88, a portion of which will form the contact shank 42 and a portion of which will be drawn to provide the slenderest tubular step 44 at station E. Transffer fingers I94, I96 shift the two-step tubular blank from station D to the centered position shown in dotted lines (Fig. 16) at station E, where, as at previous stations, the tubular blank is held by the transfer fingers until initially engaged by the descending forming pin.

At station E (F gs. 5, 15 and 16) the forming pin I 98 is in three sections200, 202 and 204-f successively smaller diameters in order to fabricate the three-step blank heretofore described.

It may be mentioned at this time that the foregoing mechanisms for making the three-step tubular blank are described only by way of illustration and that other well known mechanisms as, for example, a rolling mill could be equally well employed.

Transfer fingers

206, 208 shift the three-step blank to station F (Figs. 5, 17 and 18) and hold same there in centered position until the smallest step 92 is engaged by a pressure finger 2I0. The dies at station F are designed to form the lower flange or head I00 intermediate the two ends of the contact. Said dies comprise a hardened steel block 2I2 set into the bed of the machine and having an aperture 2 I4 consisting of a lowerportion 2I5 which is adapted to snugly receive the lower tubular step 92 and an upper portion 2I6 which is adapted to snugly receive the intermediate tubular portion 94, the shoulder 96 between these portions being seated at the base of the upper portion 2I6. This construction permits the upper and broadest tubular section 98 to wholly protrude from the block 2I2 when the three-piece blank is fully seated in the aperture 2I4 by the pressure finger 2I0. The reciprocating compression die 2I8 at station Fhas a hollow lower end 220 which is adapted to fit around the sides of the upper tubular portion 98. The top of the hollow portion is rounded at 222 adjacent the side walls thereof to curl in the top of the tubular portion 98 during the down-stroke of said die until the edges of the aperture at the top of the partially formed contact abut against the pressure finger 2I0, as best shown in Fig. 17. As the curled in portions I06 reach the foregoing position, the full compressive eifort Of the die is applied to the side walls of the upper tubular portion 98. Due to the fact that said tubular portion is only about 1.25 times as long as it is wide, it acts as a pure compression member-and tends to bulge outwardly. However, the major portion of the side walls of said portion are externally laterally supported by the side walls 224 of the compression die 2I8 which define the hollow lower portion thereof. This leaves laterally unsupported a short part of the tubular portion adjacent the shoulder 96; said unsupported part buckles outwardly near the end of the downstroke of the die 2I8 to form the double-walled bead'lflfl. I

In Fig. 17 the stroke of the die 2I8 has been illustrated as of such nature as to force the upper and lower walls of the bead together so as to form a flat ring-like double-walled projecting flange. This stroke, however, may be slightly shorter and the tip of the die 2 I8 providedwith a beveledseat, if desired, to impart to the bead I00 the truncated conical shape illustrated inFigs. 19.throug'h 23.

It will be noted that the pressure finger 2 I 0 is backed by a spring 226 weaker than the spring 228 operating the, die 2I8,' so that the pressure finger holds its position as the bead is being formed. The pressure finger spring is set into a cavity 230 in the upper part of the die 2I8, The die 2I8 has a cylindrical outer contour and slides freely in a central bore 232 of a thimble 234 at station F, said thimble being driven positively into engagement with the block 2I2 by a cam which moves the forked stripper arm carrying the bifurcated fingers 236. The lower end of said thimble has an enlarged recess 238 to accommodate the periphery of the flange I00 and'aid in imparting the desired contour thereto by forming the outer portion of the confined space into which the bulge is directed.

After the partially formed contact pin I08 has had the intermediate flange I00 formed thereon, it is ejected from the aperture 2I4 by knock-out pin' 240 and grasped by

transfer fingers

242, 244

before being stripped from the pressure finger 2 I 0 and die 2I8 by the thimble 234. Said transfer fingers thereupon shift the contact element 238 to station G.

At station G (Figs. 5, 19 and 20) the element I08 is centered over an aperture 246 in a hardened steel block 248 set into the bed I 22. Said aperture has an enlarged upper portion to receive the contact shank 42 and a smaller lower portion to receive the smallest tubular step 44, the bead I00 resting upon the upper surface of the block 248. The element I08 is seated in the aperture 246 by a pressure finger 250' which is slidably mounted in a compression die 252 and urged to outthrust position by a spring 254. The lower end of said die has a, coaxial annular nib 256 which is adapted to inturn the central curled-in portion I06 and thus provide a smooth external surface on the exposed and of the contact pin. Said nib is connected by an annular fillet 258 to the fiat base 260 of the die which. subsequent to the inturning action just mentioned, engages the curled-in portion and compresses the upper tubular step 98 in which the intermediate bead I00 has already been formed. The presence of this bead restricts to the upper portion of the large tubular step 98 the bulging efiect caused'by the 13 bular sheet metal contact for a fluorescent starter switch, said method including the steps of forming two integrally connected tubular sheet metal steps of different diameters, axially compressing, against the shoulder interconnecting the steps, the larger step while externally supporting the side walls of said compressed step except at a circumferential zone immediately adjacent and including said shoulder, whereby said walls will locally bulge out at said zone to form a double-walled flange in said compressed step, one of whose walls includes said shoulder, curling in the end of said step remote from said shoulder, and subsequently axially compressing said larger step without laterally confining the same and while turning the curled in portion and internally supporting said turned in portion whereby said end will expand to form a second flange spaced from the first named flange by an annular groove.

HARRY M. BURT.

GUY H. BURT.

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

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France Sept. 13, 1909