US2820972A - Method of stamping screw threaded fasteners from flat bar stock - Google Patents

Description

Jan. 28, 1958 w. F. PTAK 2,820,972

METHOD oF STAMPING SCREW mman FASTEN FROM AF BAR STOCK d May 1954 A INVENTOR. W/L .5l/F f Pfff/Y i BY 5M @mw /1 Tra/mfr United States Patent' O METHOD OF STAMPING SCREW THREADED FASTENERS FROM FLAT BAR STOCK Wilbur F. Ptak, Parma Heights, Ohio Application May 24, 1954, Serial No. 431,953

1 Claim. (Cl. 10-10) My invention relates to fastening devices and methods and apparatus for making them.

lIt is an object of my invention to provide simplified light, strong, eicient fasteners of reduced cost and weight which may be stored readily and compactly.

A further object of my invention is to provide a novel, relatively inexpensive method of making fasteners and threaded devices, which method is readily adapted to automatic operation and to using readily obtainable sheet or strip material.

A further object of my invention is to provide machine screws or like fastenings which may be driven by either atblade or Phillips screw drivers.

A further `object of my invention is to provide inexpensive spade lugs with threaded shanks.

Other and further objects, features and advantages of the invention will become apparent as the description proceeds. In carrying out my invention in accordance with a preferred embodiment thereof, I utilize a blank in the form of a metallic strip and provide a die head for a press with a plurality of stations for performing successive operations on the stock or blank strip. First the strip lis pierced to form an opening which will become the screw eye and also to provide for locating the stock in the forming apparatus during successive operations. After piercing, the slot is coined to provide tapered edges. Thereafter a portion of each side of the'strip is trimmed to form a shank; thereafter the edges of the shank are shaved to form a thread. Thereupon, the serrated shaved edges are laterally pressed in order to round the threads thereupon. The strip material is then severed in order to cut apart the individual fasteners or machine screws.

A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanying drawings, in which:

Fig. 1 is a fragmentary view, in vertical section, of apparatus which may be employed in carrying out the method of my invention, showing the blank strip in the condition operated upon in the successive steps of the forming process.

Fig. 2 is a plan view of the blank strip, showing the etect of successive Ioperations and illustrating the op erations performed thereon.

Fig. 3 is a plan view of a fastener in accordance with an embodiment of my invention.

Fig. 4 is a side view of the article of Fig. 3.

Fig. 5 is an end view of the articles illustrated in Figs. 3 and 4, showing the novel shape of the screw driver slot adapted for either dat blade or Phillips type screw drivers.

Fig. 6 is a perspective view of the articles illustrated in Figs. 3, 4, and 5, showing lthe manner in which a iiat bladed screw driver is used.

Fig. 7 is a perspective view of the head portion of the fastener of Figs. 3 to 6, illustrating the manner of using a Phillips type screw driver.

|Fig. 8 is a perspective view of a spade lug forming another embodiment of my invention, which may be formed in accordance with my invention.

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2 Fig. 9 is a fragmentary sectional view illustrating the coining operation for rounding the thread and fragmentarily illustrating the apparatus for this purpose.

Like reference characters are used throughout the drawings to designate like parts.

Threaded fasteners such as illustrated in Figs. 3 to 7 inclusive are made from strip stock 11, as illustrated in Fig. 2 in accordance with my invention. First an opening 12 is pierced. The opening 12 serves both for loeating strip stock 11 in successive operations thereon and for providing a lslot for receiving the screw driver blade. The next operation is coining the slot as illustrated at 13 in order to form tapered edges 14 thereon. The next operation is trimming away the sides of the shank portion 15, which is subsequently to be serrated to form threads.

=In forming the threads, the rst operation is shaving the shank sides 16 to form rough threads or serrations 17. Thereafter the serrated edges 17 are pressed laterally so as to round the thread and adapt is for mating a conventional nut or tapped hole in a piece to be assembled by means of the fastening illustrated. The coining operation for rounding the thread is illustrated at 18 in Fig. 2. The linal operation is severing the lengths of strip as shown at 19 for forming the individual fasteners 21.

The `operation may be carried out by means of a conventional power press using a six-station die-head as illustrated in Fig. 1. To the bed of the press is secured a bed plate 22 having -a slot or groove 23 of suitable width for receiving strip stock 11. To the reciprocating portion yor moving head of the press is secured a head 24, carrying a plurality of forming tools. These includes a piercing tool 25, having a shank 26, secured to the head 24, a coining tool 27 with a shank 28 secured to the head 24, a side trimming tool 29, having a shank 30, secured to the head 24, a side-serrating or thread shaving tool 32, having a shank 33, and a cut-off tool 34, having a shank 35, secured to the head 24. As illustrated in Fig. 9, laterally moving thread-rounding dies 36, which may if desired take the form of thread chasers, are provided, which are carried by horizontally sliding members 37, suitably connected by a driving means (not shown) synchronized with the driving means for the die head 24, so as to make the same number of strokes as the head 24.

Since the tools, 25, 27, 29 and 32 as well as 34, tend either to drive the work into position in the slot 23, or hold it therein, a separate hold-down mechanism is not required for these stations. However, for the station representing the operation at 18, a hold-down rod or bar 38 is preferably provided, which is carried in the head 24. The bar 38 is shown yieldably mounted in the head 24, with a suitable diagramatically indicated back-up spring 39 As illustrated in IFig. l, a plate member 41 is provided with suitably bushed openings 42 for receiving the shanks 26, 28, 30, 33, and 35. Preferably, non-friction sleeves 43 are pressed into the openings 42 for receiving the Shanks 26, 28, 30, 33 and 35.

For resisting the thrust of the hold-down rod 38 a foot post 44 is provided in the bed plate 22 at the coining station 18. The plate member 41 is recessed at 45 to receive mounting member 46, secured to the head 24 for carrying the spring-biased rod 38.

To insure retraction of the tools 25, 27, 29, 32 and 34, from the work, suitable means such as a retraction post 47, mounted in the head 24 and a push-back spring 48 are provided. The spring 4S is shown as mounted in a socket 49 in the plate member 41. A corresponding unit at the other end of the plate 41 is omitted for simplicity in the drawing.

As illustrated in Fig. 6, the fastener 21, when comthe slot V51v in the fastener 21. The head portion 5.6 of` the fastener 21- is integral with the shank Vportion 1'5. Since the 'fasteners are flat, Ythey may be stored readily and takeup. little space in a warehouse. Being formed from Yatsheet stock, 'theyv are relatively inexpensive and lend themselves readily toy automatic production.

The lfasteners 21 may also be formed with greatV accuracy, since they are formed by a repetitive process.

For simiplicityyin Fig.k 1 a simple locating pin `61.v has been illustrated which may if desired be xed or may bel of a retractable type. If a simple, xedflocating pin 61 is employed,'the strip ll'is lifted up after each stroke of the -head 24V and advanced to another position with the just-formed'locating slot changed from the stationof the piercing tool y25 to that ofthe locating pin 61. Consequently, the length of each of the fasteners A,21 is precisely 'determinedgflikewise the location of the kthreads 17 in relation` to the head '56 isalso preciselydetermined.

Although the invention has been described 4as carried` out in connectionwith the Nformation, of threaded f asteners, having a universalhead yfor'ilat. blade. or IPhillips type screw drivers, the invention is not limited to this use and^may be employed in connection with the formation of other threaded devices and fasteners. u be used, for example, produeinguspadelugs 63 of the type illustrated in Fig.Y 8. A strip similar to the blank 11, is employed, and if desired, arfcircular mounting aperture 64 may b'e'piercedinstead of the square slot illustrated in Fig. -2`for locating thefbl'ank .strip andforsubsequent use in connection with the mounting .of the lug, for receiving a rivet or the like. As shown, the spade lug 63 illustrated in Fig. 8 hasa head portion 65 of the same Width as the strip blankll anda/shank portion with threads 66 formed onthe edges 16 thereof. rlhe process. of forming Vthe spade-lug 63 is the-same as'described ink the formation of the screw fastener V21 except that the step of coining the slotk at 13 is omitted. No screw driver slot is desired in thiscase, andy thesettingsof the cut-otf'tool'34 aswell as theztrimming and shaving tools 29 and 32 in relation to the locating'pin 61 are suitably adjusted so Vthat. the spade'lug V63is cut o at'the line 67 beyond the vopening 64 instead of at the edgethereof, as required in connection with the formation ofthe headed screw fasteners 21. Accordingly, the operation of formspade lug so mounted is adapted to receive knurled nuts or the like for making electrical connections/to such spade lugs. The pierced holes 64 are provided for receiving rivets or the like for making internal electrical connections in electronic and in other light electrical apparatus of the type employing insulating mounting panels.

I have discussed the use of the cut-otf tool 34 for separating the fasteners 2 1 or 63 completely, from the adjacent vfastener formed from the same strip; VIt will` be understood, however, that my invention is not limited thereto andY does not exclude the arrangement of the cut-olf tool 34 to elect only a partial severance, so that strips of fasteners may bestocked in which the -individual fasteners are joined onlyvby very .thin necks of metal to permit breaking them apart Vreadily when one is ready to use them. Such strips of fasteners may consist of a predetermined number of fasteners adapted to be stacked in a pneumatic or other automatic screw driving machine for assembling apparatus employingsuchstrips. For producingsuch strips an additional stage isprovided in the die-head following the stage in which the partial sever-y ance is effected. Theadditional stage consists of a cutoff tool like the tool 34 butindexedV to make a stroke only It may ing a spade lug 63, illustrated inFig. 8, consists4 ofthe steps of piercing the slot 64, trimming away the'sides 16 to leave-the head 65, thereafter shaving the side 16y to form roughthreads 17 asillustrated in Fig. 2V, thereafter laterally pressing theserrated sides 16-as at station 18 of Fig. 2 to round the edges and complete the formation of the threaded sides 6,6,- whereupon, the completed spade lugs are cut o along the .margin line 67. The shoulder 68, formed in the spade lug 63 serves forsecuring the head65, againsta slotted wallfwhen a suitable nut or the like is threaded Vuponthe shank portion A15 to secure the spade lug 63 in such a slotted wall. The

after the predetermined number of fasteners for a striphas been formed. f

l have herein shown and particularly described `cer-y tain mebodiments of myV invention and certain methods of operation embraced .therein for the purpose of explaining its principle of operation and showing .its application but it'will be obvious to those skilled in the art that many `modifications and 'variations' areA possible and I am, therefore, to cover all such modifications and variations as fall within the scope of my invention:

WhatI claim and desire toV secure by Letters Patent of the United States is:

The method of forming threadedfasteners comprising the stepsof piercing continuousstiip metal at spaced posi-v tions to form openings eachservingto locate the work in vsubsequent steps and beginning formation of a screw driver slot, forming tapered edges onthe side "surfaces ofthe slot by stamping, trimming kthe sides from portions oftheY Vstrip inthe region between successive piercedholes to formshank portions, shavingV the edges ofthe shank portions to commence the formation of screw threads, laterally pressing the metal at the edges of the Shanks to produce curvature in the` edges and complete .the formation of 'the'screw threads, and thereafter severing successive portions of the strip atlthe marginsfo'f the pierced holes to form Vcor'ripleted fasteners.

References Cited in' the "file .of this 'patent UNTED STATES. .PATENTS 138,413v Levavasseur r. .l A136129, 1873

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