US1240919A - Process for making gears. - Google Patents

Description

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H. N. ANDERSON.

GEAR RoLLlNG MACHINE.

APPLlCATiON FILED OCT. I5. 1915.

lutvnt'od Nept. 25, 1912.

6 SHEETS-SHEET 6.

Ff/a? AH. N. ANDERSON. PROCESS FOR MAKING GEARS.' APPLICTION FILED DEC. 23. 1916. l QQQ, 91 9v Patented Sept. 25, 191?.

` 2 SHEETS-SHEET 2.

iinrr- HAROLD-N. ANDERSON, 0F GLEVELANL-OHO.

PRGCESS FOR MAKING- GEARS.

astenia.

Specication of Letters Patent. Patented. Sept. 25, 191 F31' Application led December 23, 1916. Serial No. 136,554.

ments in Processes for Making Gears, of

which the following is a full, clear, and eX- act description.

This invention relates to forming teeth on gears and the like by rolling a blank and toothed die together, and the present application is a continuation of my pending application, Serial No. 857,282, filed Aug. 1.8, 1914. In my Patent No. 1,001,799, and in my pending applications Serial Nos. 643,010 and 875,251 I have described machines 1n which teeth are rolled on spur gears, while in my pending application Serial No. 41,857 I have described a machine for rolling teeth on bevel gears. In each of said applications and in several other pending applications provision is `made for maintaining Xed speed ratio between-the blank and die, thereby maintaining synchronous relations between the4 die teeth and the teeth which are being formed on the blank. In the patent referred to substantially Xed speed ratio.

and hence substantially synchronous relations are maintained between the die teeth and the developing teeth on the blank. In manufacturing gears on machines of the kind referred to I prefer to use blanks whose diameters are about equal to the pitch-diameters of the gearswhen finished. The dieteeth are gradually sunk into the blank,'the displaced metal being forced outward to form the addenda of the teeth. The die effects a mechanical refinement of the metal of the teethand of portions of the blank adjacent to the teeth, ar-ranging the brous and crys-l talline elements of the metal in approximate parallelism to the tooth surfaces and compacting or condensing the metal, which renders the teleth very strong and wear resisting. The characteristics of rolled gears are described at length in my Patent No. 1,199,332, wherein the reasons for the superiority of such gears are fully, explained. Maintaining synchronism between the die teeth and the teeth which are being formed on the blank causes the die teeth, as they gradually sink into the blank to progress along radial lines, which produces a symmetrical ibrous and crystalline structure having a form approximately like that of the teeth.

While the desirable results described are primarily the result of rolling the teeth, I havefound that superior results, and results not otherwise possible are obtained by operating the die against the blank at a high lineal velocity. Teeth with sharp contours are thus formed, and the metal is rendered more dense than when the rolling is done atv l lower velocities. In rolling at high velocity the number' of revolutions employed in the processmay 'be increased while the total time required for the operation is reduced. By increasing the number of revolutions the displacement of metal per revolution is less, which reduces the torque on the blank and diminishes the tendency for the blank to slip in the holder. At the reduced rolling time there is less opportunity for the blank to cool and4 the output is increased. The .flic is benefited by the increased velocity and reduced rollingtime; its periods of contact with the heated blank being shortened it absorbs less heat from the blank. For this reason the die is not injured by the heat, and if desired a different grade of materialmay be used in the die than would otherwise be required. The reduced torque above referred to beingA due to diminished die pressure it 'follows that wear and tear on. the die is reduced.

. I will now describe my invention with reference to the accompanying drawings, in which,

Figure 1 is a plan of a machine adapted to roll spur gears at a high velocity of rotation; p

Figs. 2 and 3 are diagrams illustrating the effect of maintaining synchronous relations between the die-roll and blank.

Referring to Fig. l, the shafts 1 and 2 are rotatably mounted in bearings carried by a bed plate 3, each shaft having rigidly secured thereto a gear 4, which are connected together by an intermediate gear 5. Shaft l carries a toothed breaking-down die roll 6. and shaft 2 carries a toothed finished dieroll 7. A. plate 8 lies upon the bed plate 3 and is pivotally secured thereto at 9. A shaft is journaled-inV a bearing carriedvby plate 8, and on one end thereof -a blank holder 10 is mounted. A gear 11 is rigidly secured to the other end of the shaft 2. The axis of the pivot 9 is in line with the point where the pitch circles of gears 11 and 12 touch, and also .in line with one edge ef a: 11. .Obviously, the plate can be the pi vot'9 without varying' the distance between the axis of gear ll and the axis'of the pivot 9; therefore, the depth of enmeshment of gears lil and l2 at the side lying upon the axis of dthe pivot does not vary when the plate 8 moves, .from which it follows that the speed ratio between the blank and the finishing roller is Xed whether the blank is enmeshed with it, with the breaking-down' roller or is anywhere between these extremes. Furthermore, since the shafts l and 2 are geared together, the speed ratio between the blank and the breakingdown roller is also fixed. As will be readily understood, the plate 8 is moved to and fro between the shafts either by the hand wheel 13 or pulley 14, which operates the screw l5. Adjustable stops 16 and 17 limit the movement of the plate 8.

lVhen in operationthe machine is driven by means which is not shown, acting upon shaft 2. A blank is placed'in the machine, and by means of the' hand wheel itis pressed against the breaking-down roller 6; having received suiicient of that treatment it is brought over into engagement with the finishing roller 7. From what has already been said, it is obvious that the lineal velocity of the pitch line of the blank is the same as that of the die-rolls during the entire tooth forming operation. The use of the breaking-down die-roll is not essential; operation on the blank may be by the dieroll 7 alone.

The action ofthe teeth of the cnemembcr upon the metal of the blank will now be eX- plained in detail, with reference 'to Figs. 2 and 3. The position of a tooth 'of the die member relative to the blank at the commencement of the tooth forming operation is illustrated in full lines in Fig. 2, and the arrow 34 is a line which if extended upwardly would pass through the center of the die member (assuming that it is in this case circular). Once during each revolution of the die members this arrow points directly at the center 36 of the blank. lf, as the tooth is caused to sink deeper and deeper into the metal of the blank, a succession of dots 37 were made on the blank, each dot being made at the point where the line 34 crosses the end of the tooth and at the moment when the arrow points at the center 36, a line drawn through these dots would be straight and radial to the center of the blank. The foregoing would be equally true were'the die member .a rack; in which case the line 34 would be perpendicular to its pitch-line. That the tooth of the die meniber does enter the blank along this radial path is due to the synchronous relations maintained between the die members and the blank; t'. e., to the fact that the pitch line velocities of the'die member and blank are equal. As the tooth. enters the metal of the made in accordance with the invention, tlie fine irregular lines illustrating the manner in which the grain of the metal follows the contour of the teeth, and the stippled portion of theitsurface indicating the increased density of the metal due to the process of forming the teeth. lmportance is attached to the teeth of the die member entering the.

blank in a radial or substantially vradial path, because if the teeth enter the metal of the blank in a curvilinear path they will distort the metal of the blank so that the teeth of the finished gear will not be a homogenous mass with the body and therefore will not Apresent the characteristics of strength and durability which are present in gears formed according to my improved process. The blanks may beordinary drop-forgings and used in the condition in which they come from the forging die. As before stated they are about the diameter of the pitch-w circle of the finished gears and there is therefore substantially no waste of material,

only a slight surplus being required to .in-f

sure that the teeth of the blank shall be quite filled out. In rolling gears at low or moderate velocities the displacement of metal is slow'and the metal remains inert. As the metal is displaced by the die-roll teethits momentum tends to overcome this inertia, or

what I prefer to call inertness, and when v the displacement is suiciently rapid, due to high velocity of rolling, the inertness is entirely overcome and the metal endowed with kinetic energy. That is, the metal, under the influence of its momentum, moves itself. There is then a double effect; the metal is compressed bythe impact and pressutr` of the die, and it is thrown by its momentum into the interstices of the die, which not only increases the compacting and 'condensing of the metal but imparts a sharper contour to the teeth than is otherwise obtained. Just what velocity is needed to endow the metal with this kinetic energy depends upon the character of the metal and its temperature. With a given metal at a given temperature there is a velocity at which momentum just overcomes inertia. 'z Then any increase in this velocity will impart a surplus of momentum and thus endow the metal with the kinetic energy referred Yto. At a rolling velocity which is equivalent to a pitch-line velocity of 20() feet per minute the benefit of velocity is obtained; z'. e., at that and higher speeds velocity becomes an active factor in the product. fy rapid rolling I have formed teeth required Velocity is the appearance of the teeth formed. When the corners Yof the teeth come out sharp it is evident that the rolling velocity has been suiiicient to endow the metal with kinetic energy; that the effect produced by the impact of the die has been supplemented by the momentum of the displaced metal. The frequently recurring impact of the blank and die breaks up this scale, which at high rolling velocities is thrown 0E by centrifugal force. Moreover, at high rolling velocity the recurrence of the impacts is so rapid that scarcely any time is allowed for formation ofthe oxid. This promotes smoothness of the tooth surfacess., Y l

Althbugh but one type of machine is here shown it is to be understood that the carry- -ing out of my method is not limited to the machine shown. Nor is it limited in its application to spur gears. Bevel and other types of gears may also be rolled at high velocity.

What I claim is as follows:

l. The method of rolling gear teeth in ma.,f l

chines 'ofthe kind referred to, said -method comprising rolling the die and blank in contact at a pitch-line Velocity of 200 or more feet per minute.

2. The method of rolling gear wheels as herein described, comprising rotating the blank and die at a pitch-line velocity of 200 or more feet per minute, while pressing the die into the blank.

. 3. A-method of rolling teeth on gears, comprising rolling a 'blank and a toothed die in contact at a velocity suiiciently great to endow the displaced metal with kinetic energy.

4L..A method of rolling teeth on. gears, Y

comprising rolling a blank and a toothed die in contact at a Velocity suiiciently great to cause the momentum of the displaced metal to supplement the impact of the die.

fA method of rolling gears, comprising rolling a heated blank and a toothed diev in contact at such aV velocity as Vwill prevent the die remaining in contact with the blank long enough to raise the temperature of the die to an injurious point.

In testimony whereof I affix my signature in the presence of two subscribing witnesses.

HAROLD N. ANDERSN.

Witnesses:

A. G. DRAHEIM, DAVID T. FLETCHER.

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