US2027980A - Manufacture of screws and bolts - Google Patents

Description

i Patented 14, 193i)` UNITED STATES Parmi'` otr-'lcs 2,027,980 MANUFACTURE QF SCREWS AND BLTS win-iam M. norton, sewickley, ra., 'miglior to Pittsburgh Screw & Bolt Corporation, a corporation of Pennsylvania.

Application August 30, 1935, Serial No. 38,555

blank, after it has undergone the iirst shaping operation between dies; Figs. HI and IV are like views of the blank after the second and third operations, respectively. Figs. .V, VI, VII,

and VIII are views in end elevation of the blank in the successive stages of Figs. I, lI, III, and IV. Fig. IX is a view in axial section of the pair of dies by and between which the rst of the shaping operations is performed and between which the blank as seen in Figs. I andl V is shaped to the form illustrated in Figs. lI and VI; Fig. X is a view in axial section of the pair of dies by and between which the second of the shaping operations is performed and between Vwhich the blank of Figs. II and VI is shaped to the form shown in Figs. III and VII; and Fig. XI is a view in axial section of the `pair of dies by and between which the third of the shaping operations is performed, and between which the blank of Figs. III and VII is shaped to the form shown in Figs. IV and VIII. Fig. XI shows the Workv in position in the dies. 5

According to the teaching of Charles Kaufman (U. S. Letters Patent No. 1,933,737, November 7, 1933, and Re. 19,348, October 23, '1934), in the production oi screws andv bolts, an elongate blank of wire ofuniform cross-section is subjected'to two successive cold-working operations:

-the first is anoperaton of extrusion between to hexagonal or other desired particular shape.

Kaufman in the reissued patent named alludes to the possibility, not only of performing these successive operations in a succession of machines; but of performing them also between 1 claim. rc1. 11n- 27) a succession of pairs of dieswithin one and the same machine.

In the performance of the method of Kaufman insa machine organized in the manner last indicated, and particularly in the second operation of shaping between dies, a source of dilclty is found. That second operation is the operation of simultaneously spreading the posterior end of the blank to form a head and extruding the anterior end to reduced diameter and increased length. The portion of the die in which ythe extrusion is eiected is subject to heavy wear; the product soon loses perfection of shape; and the die has to be frequently replaced.

, I have perceived; (and herein lies my invention) that a change may advantageously be made in the succession of operations; I have perceived that the second operation of shaping between dies may be made to consist of spreading the blank at the posterior end to form a head and no more; and that the second extrusion of the blank at'its anterior end to smaller diameter, instead of being organized to be accomplished; simultaneously with the headspreading, may be made part of the third operation and accomplished between a pair of dies that in continuous operation accomplish also the trimming of the previously spread head. I have found that, by making this transposition and reorganization, the portion of the shaping die within which the second extrusion is effected may-be made of hard steel-of carballoy,-for example; and that, being made of such material, the'die becomes durable to produce an excellent article, even after long-continued service. The extruding die ofthe second operation as now carried out may-not be made of such hard steel, because the stress incident to the performance of thatvsecond operation. is so` great that an. extrusion die of-hard steel would be shattered under the stroke; the die is necessarily made of other materiaLand of material so susceptible to wear as to cause'in the production of these artil cles the embarrassment that has been indicated.

Referring to the drawing, ai sheared length of wire such as is` shown at l, Figs. I and V, is brought to the shape shown in Figs. l1 and VIIE.v In Fig. IX the pair of dies is` illustrated by means of which this rst shapingstep is accomplished. The die 2 is provided with a bore 3. This bore at one end (the left-hand end, as here viewed) is of a diameter corresponding to that of the blank I but to the right the bore is of diminished size., In operation a blank l is brought..-A

to position to the left of and in axial alignment with the bore in die 2 and the companion die 4 is advanced. The blank is driven powerfully from left to right into the bore and is extruded into the narrower portion of the bore with reduction of diameter and elongation, progressing from the anterior end of the blank rearwardly. A stop 5 arranged within the bore may check its progress, that as the dies come to position of complete closure the blank may be compressed within the die chamber. The stop 5 may be movable, to the end that, when the dies open, it may advance from right to left and eject the blank from die 2. In this first operation the blank at its anterior end is reduced in diameter and elongated, as shown at 6 in Fig. II.

Upon the blank of Figs. II and VI the machine operations go forward, with a departure in procedure and a regrouping of the shaping steps, in which regrouping and its attendant machine reorganization invention is found. The blank of Figs. II and VI is, between appropriate dies, brought to the shape shown in Figs. III and VII. In this second operation the only change in shape is the spreading of the blank at its larger and posterior end to larger diameter, with reduction in length, to form a head, as shown at 1. The previously extruded and attenuated anterior end 6 of the blank remains substantially unchanged in shape. The dies between which this second, head-forming operation is performed are shown in Fig. X. One of the dies of this pair, the die 8, is provided with a bore 9 of a diameter substantially vthe same as the diameter of the extruded anterior end 6 of the blank as seen in Figs. II and VI; and the two dies 8 and III form by and between themselves a recess within which, as the dies close, the metal of the posterior endof the blank is spread to form the head. Within the bore 9 of die 8 is a stop II, filling the space.

'I'he blank of Fig. II, oriented as shown and aligned with the bore 9 in die 8, is, by the thrust of die I0, driven from left to right. The tore 9 being, as has been said, of substantially equal diameter with the attenuated anterior end 6 of the blank, the blank advances freely until itv comes-to engagement upon the stop Il. The blank is arrest-ed. The further traverse of die I Il then effects the spreading of the posterior end of the blank in the recesses of the meeting faces of the dies, to form the head 1.- The stop II that serves to arrest the left-to-right advance of the blank may be movable axially within the bore, and by virtue of such movability may serve as an ejector, after the die I has advanced and receded again.

In the third operation the blank at its righthand end (Fig. III) is further attenuated and elongated (cf. Fig. IV) and the head-'I is trimmed to the desired angular (or, it might be round) outline-here (Figs. IV and VIII) shown, typically, at 10, to be square. The dies I2 and I3 between which the second extrusion and the trimming are done are shown in Fig. XI. The die I2 is provided with a bore I4, into which the blank is introduced, anterior end first, and into which the introduced blank is caused to advance. The bore in die I2 at the left-hand end (to which the numeral I4 is immediately applied) is of substantially equal diameter with the previously attenuated anterior end 6 of the blank (Figjm) but the bore in its left-to-right extent is of diminished diameter. And within the diminished right-hand portion I of the bore the blank is at its anterior end extruded, further reduced in diameter, and elongated, as indicated at I6, Fig. IV.

The blank of Fig. III, oriented as there shown,

is brought to axial alignment with the bore in die I2, and the dies I2 and I3 are then closed upon it; and in the closing of the dies two things are successively and in continuous course accomplished,-the blank at its anterior end is further attenuated, as at I6, Fig. IV; and the head upon the posterior end is at its margin sheared, and trimmed to the desired size and shape, as indicated at 10, Figs. IV and VIII. In this respect it will be perceived that the die.I3 is specifically a shearing die, and that with respect to it the die I2 carrying the blank, as seen in Fig. XI, becomes a punching die. As the dies close a stop I'I limits the left-to-rghtdisplacement of the metal, and as the closing of the dies continues this stop is effective to consolidate the body of the blank. At substantially the same time the head 1 comes to abutment upon the left-hand face of die I2; and further closing of the dies effects the shearing. As in the case of the dies of Figs. IX and X already described, the stop I1 may be made to serve as an ejector also.

In-Fig. XII it will be perceived that the lefthand end I4 of the bore within die I2 is of unform and, relatively large diameter; that the right-hand end I5 is of uniform and relatively small diameter; and that the transition from the larger to the smaller diameter is by a step I8 in the wall of the bore. The face of this step I8 is oblique to the axis of the bore. As the blank is driven powerfully from left to right, its edge impinges on this oblique step, and over this step the metal ows and. the blank is extruded to the desired smaller diameter.

Turning again to Fig. X, it will be perceived that the thrust of `die I0 must be powerful enough to crush the end of the blank (Fig. II) and form the head 'I; and in Fig. XII it will be perceived that the thrust of die I3 must be powerful enough to extrude the blank over the step I8 and into the narrower portion/I5 of the bore within die I2. In the present practice, in which the forming of the head 'I and the extrusion of the end I6 are accomplished by the single operation of a pair of dies, it is manifest that the thrust of the movable die must be lpowerful enough to accomplish both of these two shaping steps; and it has been found that, as a matter of fact, the thrust must be so powerful that the die with contracted and stepped bore must sustain tremendous punishment. It may not be made of hard steel, because, under the impact of the powerfully driven companion die, delivered through the body of the work itself upon the face of the step, this stepped die would be shattered. It must be made of softer steel; and, being made of softer steel, it wears rapidly, produces imperfect articles, and must frequently be I replaced.

The power necessary to trim the head 1 (Fig. III) is, when compared with the power necessary to form the head, relatively small; and, by combining the second step of attenuation, not with the head-forming step of the second operation (as now is done), but (as I have perceived to be permissible) with the head-trimming step of the third operation, the stroke of the die, in this third operation, need not be so powerful as the stroke of the die must be inthe second operation as it now is performed. The thrust requisite in the third operation in the procedure as I have reorganized it is sufciently less to permit of the prohibitive liability to breakage.

extrusion die being made of hard stee1, without Accordingly, the durability of the machine as a whole is improved, less time is lost in stoppage to replace worn parts, and the product is more perfect.

Referringto Fig. Xi, it will be found advantageous to form the die I2 as a compound structure. The main body, to which the numeral I2 is immediately applied, andl Within which the bore in its left-hand portion I4 is formed, is advantageously formed of relatively soft and inexpensive steel, and, properly secured in a recess in body 'I2 formed to receive it, is a block I9 of hard steel (which is a relatively expensive material) through which the bore is prolonged and Within which the step I8 and the narrower continuation of the bore are formed.

'Ihe blank as seen in Figs. IV and VIII is I reaihr, it will be perceived, for the further steps of pointing and thread-tapping.

I have shown and described the invention applied in the production, specifically, of a blank for a, cap-screw; manifestly it is applicable generally in the production of such articles, where in successive steps an elongate article is extruded between dies and headed.

I claim as my invention:

The method herein described of producing a headed blank for screw and bolt manufacture from a. length of wire which consists in, rst, extruding the wire from the anterior end thereof toward the posterior to reduced diameter and increased length, second, restricting the next op-A time from the anterior en d toward the posterior.

and simultaneously trimming the head previously formed.

WILLIAM M. HORTON. j 20

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