US71360A - hoard - Google Patents

Description

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.GEORGE B. BRAYTON, OF PROVIDENCE, RHODE IsLANunssIeNOR `'ro HIMSELLSOLOMON W. YOUNG, JOHN W. HOARD, AND LYMAN A, 000K,

`Lettez-e Patent No. 71,360, dated November 26, 1867.

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v Beit known lthat I, GEORGE B, RAY'TN, of Providence, in the county of -Providence, and Stateof Rhode VIsland, have invented certain new and useful Improvbments in Cutting Screws and I hereby'declare thefol'-` lowing to be a full, clear, and exact description of the same, reference being hadto the accompanying drawings.` p

Myinventon'relates to mechanism for cutting screw-threads uponblanks,r and it hasmore particular reference to that speciesof such mechauism'n whichv the screwcutting surface orthre'ad `is formed upon the periphery of a die of circular form, ordinarily known as a. rotary die, the cutting surface being concave in shape, (including generally from one-thlrd to one-half of a 'circle,) and extending Vcontinuously around the die; While the employment of' such' dies is, as is well known, productive of important advantagesin certain respects, yet an objection arises to thcir'use from the fact that, as they are of circular form, there is no variation in the distance p ofthe cutting edge from the' centre or axis of motion of the die, and, therefore, thediein itself is incapable of following the tap'cr, or gradual decrease or increase in the size of the blank, so as to cut a thread of uniform size and proportions upon all parts of the blank. This result can only be attained `by the u'seof auxiliary mechanism, acting either in conjunction with the dies, or independently of them, such mechanism being,`in many y instances, both complicated and expensive. A p

The object of my invention is to produce a rotary die, which in itself', and without 'the aid of other mechan-` ism, shall be capable of cutting a thread from one` end of the screw-blank to the other, `no matter what may be the taper or varying dimensions of such blank; and', ytoV this end, it consists of a rotary die, in which the distance of each portion of the cutting surface from thecentre of motion or axis of the die varies, or is graduated to conform to the dimensions of the corresponding part of the blank upon whichl suchporton of the cutting surface is to operate. In other words, the die, instead of being circular, is cam-shaped, the gradual'increase-in the distance of the successive portions of the cutting surface from the centre of the diebeing `determined bythe formand taper of the screw-blank to, be cut. Thus, when the blank is passing between two or more of` such dies, (the feedtof the blank causing the gradual rotation of the dies,),the decreasein the size ofthe blank vwill be compensated by the expansion or swell of the cam-dies, and their cutting surfaces will continue to be held in' close contact with the blank until thethread is completedon the tapering pont,and` the screw is withdrawn` from between4 the dies. y V

Iu` order to adaptv the concave cutting surface to operate upon all parts ofthe blank, it `must be made tapering in the direction of its length, so as to conform to the shape 'which the blank-will ultimately have. Forl instance, suppose the blank gradually'decreases in size from the upper part of the shank to the point, the cutting surface of the die must, therefore, be of greatestdimensions at the point where it meets the upper n part of the blank, vand thence passing around the die, it decreases in width und depth, so ns toconform to thez'shapc of the blank, until, by the time it reaches that portion of the die from which it started, it yhasV tapered to such a degree as to be capable of cutting, with perfect facility, a finished thread upon the' extreme point of the blank.

It will be seen fromy this general description ofl my invention 4that it is susceptible of many modifications -Theshape of the cam-die'is of course determined by that of the blank, and its size, aswellas the number of cuttingl V threads or edges which it carries, must' be regulated by the length ofthe screw to be cut, `and the number of revolutions whichthe blank must make to cut any one portion of `the thread.

These, as well asoth'er features of my invention,- will be more fully understood by reference to the accomi panying drawings, in which I have illustrated one method of giving eect to myinvention.

In Figures 1, 2, and 3, a dieconstructed according to my mvcnt'cn is shown in elevation,` horizontal sec tion, and vertical section, respectively. i V n `The die A, which is cored out, so as to be mounted on a'f-.pindle, as hereinafter described, is not circular, but-,cam-shaped, as shown clearly in figs. 2 and l3, the distance from thc axis `or centre of motion a of the die to 'the point on its periphery, being less than that from a to the point c, on the periphery,diametrically opposite The concave cutting surface dis formed in the die by means of a tap of suitable size and shape, as will be,`

readily understood without further explanation. Following the cutting surface around from'gthe point b, where it is nearest the centre of motion a-of the die, 'it willbe seen .that it gradually increase its distance from'the centre of motion, so that, when-it has completed the circuit of the die, arriving at the point e, adjoining b, it is at itsgreatest distance from the centre a.

In order to enable the cutting surface to operate with the best results vupon the blank, it has a tapering formation, as seen in the drawings, figs. 1 and 3, its dimensionsbeinggradually contracted as it approaches the point `e, so as to cause it to conform to the corresponding taper or decrease in size of the blank. Thus, as the eccentricity of the die is augmented, the cutting surface becomes smaller, until, at the part e, where the eccentricity of the die is the greatest, the cutting surface tapers or is brought to a point.

It willvbe understood that the form and taper of the cutting surface, aswell as the degree of eccen tricity possessed by the die, `are at all times governed bythe size and shape of the'screwto be cut, thedie being so formed as to follow or conform to the varying dimensions of the blank.V

The principle which regulates the construction of the die will best be understood by reference to figs. 2 and 4, Where the screw-blankf is represented as being out by two dies. It is manifest, however, that three or more dies may be employed, instead of two, as occasion may require.

lThe dies A A. are mounted opposite each other, so as to lie in the same plane, and upon spindles which should, of course, be geared or otherwise suitably connected together, so that the dies shall move in unison, and present corresponding or similar portions of their cutting surfaces to each other. By means of mechanism, such Vas ordinarily employed in screw-cutting machines, they maybe actuated to approach orrccede from one another'` according to the size of the-blank which is placed between them. v

When the blank is to be operated on, the points b of the dies, where the cutting surface is of -the greatest dimensions, and. where the eccentricity of the die is least, are brought opposite each other. The blankfis inserted between the dies until that portion ofthe shankis reached where the dies are to commence to-opcratc, the thread being cut from the upper part of the shank towards the point or taper end. The dies are then moved up, so as to grasp the blank, the portion b of each cutting surface being in contact with the blank.` The latter fis now caused tolrotate by any ordinary or suitable means, its feed, or movement lwhereby it is gradually drawn4 between the dies, being vregulated by'a leading-screw, or other suitable governing mechanism. The blank moves out from the dies in the direction indicated by the arrows, the rate at which 'it rotates upon its axis bearing such relation -to the feed movement as to c ause the thread to be formed and perfected upon each successive part of the blank drawn between the dies. For instance, the blank may be required to revolve eight or ten times, while'in its feed movement it only passes over thedistance w y, from one thread to another. This combined motion of the blank eiects the gradual rotation of thc dies. 'i

It is manifest that the feed of the blank, and rotary movement of fthe dies, oughtvtobear such relation to each otherthat, when the' taper cnd or point of the blank is about being withdrawn from between the dies, the

latter shall have rotated-suiiicicntly to bring. the points e of theirA cutting surfaces opposite each other, so as to grasp and out the taper end. Therefore, if the length of the cutting surface d is twice or thrice that of the blank `to be cut, the movement of the dies must bc proportionately in excess of the feed of the blank. This .result is elfectedby means of theblank, which,'in its revolutions, engages with the cutting threads or teeth of the dies, thus drawingthe latter. gradually around in the direction of the feed. The excess of the rotary movement of the'blank over its fecdnimparts the requisite increased movement to the dies, the blank being operated on by three, four,ror more successive teeth or cutting threads, according to thev number of revolutions it makes in passing over the distance x y, as will be readily understood by those skilled in the art to which my invention pertains. If the blank make `but few revolutions in traversing this distance, then, of course, the cutting threads or teeth will be proportionately few in number, andthe length ofthe cutting surface will be shortened. But if in cutting a screw of the same length, it be required to rotate the blank at a higher rate of speed, then, 'as the blank, while traversing the same distance xy, will be'brought in contact with a greater number of cutting threads or teeth, the length of the cutting surface must be increased to compensate for the increased rapidity of the movement ofthe dies, caused by the greater number of revolutions made by the blank.

By reason of this relation which .exists Abetween the feedmovement of the blank and rotary movement of the dies, it will be seen that, in proportion as the blank is withdrawn from the dies, that part of it which is presented to the cutters gradually taperingor becoming smaller in diameter, those portions of the cutting'surfaces d which are brought inl contact with the blank as gradually increase their distance from their respective centres of motion a, so as to compensate for the decrease in the size of the blank. At the same ltime the tapering formation of the cutting surfaces enables them to fit upon and cut with perfect facility the tapering shank. )3y-the time the point of the blank has arrived between, the dies, the latter will have completed their revolution, andthe end of the blank passes out from between the contracted ends e e of thccutting surfaces,which form the thread upon the extreme point'of the screw. The thread is thus cut at one operation, and is equally well finished on every part ofthe screw, the-end or gimlet-point being without any of the imperfections, or marks of thejamming and compressing action of the dies', so 'often seen in screws cut by ordinary means.

The die A may be made eccentric or-camshaped before the cutting surface is formed in it, or Ait may be of a circular form, the edge being bevelled at h h, as shownA in the drawings. In the latter case, the cam-like formation will be giveuthe die when the cutting surface d is tappedV out, a greater portion of the bevelled edge being cut away where the larger or deeper part Z) ofthe cutting surface is located, than at the points c e, where the surface is contracted and tapering. To form the cutting surfaces,la tap of suitable shape, to give the neces` sary taper to such surfaces, may be run through between the edges of two dies, placed opposite each other, as is done in the case of ordinary circular dies, or other suitablemcans may be employed.

In order to avoid the great increase in the diameter and size ofthe die, which would otherwise necessarily take-place, in case it should bc required to cut a screw of great length, the depth or thickness et' the dic-may 'be increased, and the cutting surface may be formed sprally upon the dic, boing carried two, three, or more times around the cam-surface of the die, according to the length of the screw to be cut. `By this means, without increasing the diameter of the die, I can obtain a cutting ,surface which will cut a screw ofi very great length,`

the thread being carried up as near the head of the blankV or screw `as .may be desired.

Between the beginning I and termination e of the cutting surface d, a cleaning-space, k, may beformed in` the edge of the die. This not only admits of the dies being more easily adjusted to the hlank,'before they r commence to operate, but also allows theublank, when it is first 4placed between the dies, to clear the projecting parts e of the cutting surfaces, with which itmght otherwise be brought in contact at the 'beginning of 'the' operation. notch or groove, l, is made in the cutting surfaced, extending throughout its whole length, and t dividing the threads, thus increasing the number of cutting edges or teeth.

The rotation of the dies may be'eifeeted by other means than herein described, and by a separate and indel pendent mechanism. In any event., however, their'movcment should always'bcar the relation te the feed move ment of the blank as hereinbefore set forth.

Having now described my invention, `and the manner in which thc same is o'i may be carried into effect,

what I claim, and desire to secure-by Letters Patent, i`s

1. rotary :diefor cutting screws, in which thc -cutting surface is at varying distances from the axis or` il centre of motion of the sai'ddie, so as to conform tothe taper and varying dimensions of 'the screw-blank to` be cut, substantially as herein shown and set forth.

2. A rotary-cam die, in` which the concave cutting surface is made tapering or of varying dimensions, so as' to fit both the shank andA taper end of the blank to benut, as herein specified; 1

3, The method herein described ofcutting the screw-thread upon, both thcshank and taper fend of a blank,

by the employment of two or morerotary-cam dies, constructed and arranged as specified, so that, while their centres of motion are fixed and unchanged, their-cutting surfaces shall approach or recede from each other, to 1 conform to' the varying dimensions of the blank passing between them.

4. In a rotary-cam die, as herein described, I claim the combination, with the tapering cutting surface, of 'the cleaning-space 7c, substantially in the manner' and for the purposes herein shown and specified;

I testimony whereof I have signed my name to this specification before two subscribing witnesses.

G EO. B. BRAYTON.

Witnesses:

M. BAILEY, 4 J. W. Horan.

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