US2192370A - Apparatus for relieving cutters - Google Patents

Description

March 5, 1940. E. WILDHABER 2,192,370

APPARHTUS FOR RELIEVING CUTTERS Filed June 2, 1938 4 Sheets-Sheet 1 ATTORNEY 2 gre B A March 5, 1940. E. WILDHABER 2,192,370

APPARATUS FOR RELIEVING CUTTERS Filed June 2, 1938 4 Sheets-Sheet 2 INVENTOR est J 919mm March 5, 1940. I wlLDHABER 2,192,370

APPARATUS FOR RELIEVING CUTTERS Filed June 2, 1938 4 Sheets-Sheet 3 INVENTOR ATTORNEY Max-c115, 1940. E. WILDHABER ,192,370

APPARATUS FOR RELIEVING CUTTERS Filed June 2, 1938 4 Sheets-Sheet 4 ATTORNEY i Patented Mar. 5, 1940 UNITED STATES 2,192,370- APPARATUS FOR RELIEV'ING CUTTERS Ernest Wildhaber, Irondequoit, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application June 2, 1938, Serial No. 211,448

Claims.

The present invention relates to the relieving of all kinds of cutting tools thathave a 13111- relity of successive cutting edges, and more particularly it relates to the relieving of face-mill cutters, disc type gear cutters, and hobs.

Ordinarily the relieving of a multi-bladed cut- .181 effected by rotating the cutter on its axis at a uniform rate while providing a cam-controlled relieving motion between the relieving tool and the cutter at the rate of one relieving cycle for each blade of the cutter. In the relievin ofhobs, a lateral motion is added to correspond to the lead of successive teeth of the hob.

With the ordinary relieving process, the length of the portion of the blade which can be relieved is limited inasmuch as the relieving tool must be drawn back to starting position, afterrelieving blade of the cutter, in order to be in position to st t the relieving of the next blade of the cut. nd inasmuch as in this Withdrawal movement, the relieving tool must be kept clear of the blade on. which it is next to operate. To. obtain tl. maxim-um length of relieved surface in the ordinary relieving process, then, a very fast re- "n or withdrawal motion must be provided.

that only a small part of the track ieving cam can be devoted 0,0 the return motion. To avoid undue accelerations, in-

accuracies and shocks in the relieving machine,

however, such a cam must be run at relatively slow speed, thus slowing up the whole relieving operation.

The purpose of the present invention is to provide the effect of a very fast return movement in a relieving operation without having any of the drawbacks or disadvantages of a fast-return cam.

. The object of the invention is attained by imparting an algebraically added rotational movement to the cutter in addition to the rotary. movement ordinarily employed. This added movement is imparted in such way that the cutter becomes practically or even actually stationary the time of withdrawalof the relieving tool.

2 The result is that the relieving tool can be with- I drawn c ear of the cutter while the cutter is rotating irough a very short distance and yet can bdrawn at a speed which will avoid undue vibration. Theinvention may be embodied in various forms. if a worm and worm Wheel are used to L rotary motion to the cutter during the reliehsg operation, a relative reciprocatory rollmg movement may be imparted to the worm wheel the worm wheel rotates on its axis.

This rolling movement maybe controlled from the relieving cam. If the cutter is driven through helical. gears, the relieving cam may be employed to reciprocate one of the gears axially of the other as the gears rotate in mesh. Other means nay be employed, also, to obtain the desired" results, as will be obvious to those skilled in the With the method and apparatus of the present invention, the relieving action is smooth and accurate without any sacrifice in the speed of the.

cording to this invention for relieving a disc milling cutter where the relievingmotion is imparted to the milling cutter;

Figs. 2, 3 and 4 show that the invention is usable with the various known types of relieving tools, Fig. 3 being a sectional view of the cutter and grinding wheel shown in Fig. 4i 7 Fig. 5 is a more or less diagrammatic. view with parts hroken away, showing a modified form of apparatus forrelieving a disc milling cutter according to the invention, where the relieving motion is imparted to the relieving tool; I

Fig. 6 is a more or less diagrammatic view apparatus built according to one embodiment of the invention for relieving a face-mill type of gear cutter;

Fig.7 is a diagrammatic viewillustrating the variation in the relieving velocity ,at .various points in the relieving operation;

Fig. 8 is a diagrammatic view showing the path present inmodified path of movement of the tool during withdrawal where the process of the present invention is employed.

Reference will now be had to the drawings for a more detailed description of the invention; In Figs. 1 to 4 inclusive, l5 denotes the cutter which is to be relieved, which is hereshown fragmentarily and comprises a disc milling cutter havrectly actuates the slide 26.

ing a plurality of cutting blades l6 arranged around its periphery.

For the relieving operation, any of the usual types of relieving tools may be employed. In Fig. 1, the relieving tool is a lathe tool 11.

The relieving motion itself may be imparted either to the relieving tool or to the cutter which is to be relieved. In Fig. 1, the relieving motion is shown imparted to the cutter. The cutter I5 is secured to the work spindle 25 that is journaled in a slide v26. This slide reciprocates the bed or base 21 of the machine.

There is a worm wheel, indicated partly in section at 3! and partly by its pitch line 28, which is secured to the work spindle 25. A worm .30

meshes with the worm wheel 28 to impart rotary motion to the spindle 25 so that successive blades of the cutter are presented to the relieving tool I1.

As each blade of the cutter moves past the relieving tool, the cutteris moved in the direction of the arrow 29 toward the relieving tool to effect the relieving operation and is then withdrawn away from the relieving tool again to return the cutter to initial position ready for the relieving of the next blade.

Therelieving and return movements of the cutter are controlled by the cam 32 which di- This cam may be of the same general shape as the relieving cams employed in the known relieving processes.

The relieving cam 32 is secured to a shaft 33 which is journaled in the base 2'! of the machine. The worm wheel 28 and the relieving cam 32 are driven in timed relation with one another through the bevel gears 34 and 35, and the spur change gears 36, 31, 38 and 39. The gear 39 is secured to the shaft 40 upon which the .worm 35.

is mounted. This shaft is journaled in anti-friction bearings 42 and 43. Power is applied to the shaft 33. Through the gearing described, the

relieving camr 32 and the worm are driven.

in timed relation at uniform velocities. These motions are the same as those employed in the known relieving'processes.

The novel step of the present invention resides in the relative movement of the worm 30 and the worm wheel 3! along the axis of the wormv which is parallel to the direction 29 of the relieving motion. This is effected by mounting the cutter.

' it which is of an algebraic nature, being first in one direction and then in the other.

-.On the relieving stroke, the rotational movement produced by the rolling movement of the worm wheel is added to the uniform rotational movement produced by rotation of the worm. On the return stroke, the direction of, the rolling movementfis reversed and the rotational movement produced by the rolling movement is subtractedfrom the constant rotationalmo'vement produced by the worm. On the return stroke of the slide 26, then, the resultant rotational ve-- locity of the cutter is slowed up and the relieving tool I! has ample time to clear one blade of the cutter before the next blade rotates into position As a result, the blades of the cutter may be relieved fora greater length from front,

to rear than by the'relieving methods hereto fore practiced and time enough can be taken for moving the cutter clear of the relieving tool to avoid objectionable shocks or accelerations.-

Often, the rotational movement due to rolling I of the worm wheel along the worm is sufficient to stip the rotation of the worm wheel entirely on the return stroke and even in some cases to reverse the direction of the worm wheel during Withdrawal. In such cases, the blades of: the

cutter can-be relieved for practically their-whole length by tool Ill. In Fig. 1, 28 and 28 denote,

respectively, two different positions of the worm wheel in its rolling movement.

The process of the'invention is the same when the relieving motion is imparted to the relieving tool. In Fig. 5, there is illustrated apparatus for effecting the relieving of a cutter by imparting the relieving motion to the relieving tool. Here The relieving tool is shown at 55. Itis secured to a block 56 that is in turn secured to a The slide 51 is mounted to reciprocate slide 57. upon the baseor frame 53 of the machine. The

slide is actuated by the relieving cam fill'which may be of the usual construction.

The worm wheel 52 is rotated by the worm'fit i This form is integral with a shaft 62 that is mounted toreciprocate with the slide 51.

antifriction bearings'63 and the nuts 64 and 65'. The worm shaft 62 has a one end with the hub of aspur gear 61 and slides in the'hub of this gear. This gear is journaled The V shaft 52 is connected to the slide 5'! through the splined connection at by'means of its hub in the frame 58. The worm shaft 62 slides at its opposite ends in a plain bearing' formed in the frame 58. I

The shaft 62 and the cam 66 are connected to rotatein'timed relation through the spur gears 61, '68, -69and 10, the shaft H, the bevel gears 12 and 13 and the shaft 14. The cam 60 issecured to the shaft I l and power may be applied to this shaft. I

As the relieving tool 55 moves inwardly in the direction of the arrow 15, on the relieving stroke,

through operation of the cam 60, the shaft'62 and worm 6| are carried inwardly with it, causing the worm iii to roll axially over the teeth of the wormrwheel 52. Thus, a uniform rotational movement is imparted to the worm wheel which is added tothe uniform rotational movement produced by the rotation of the worm 6|.

i Onthe return stroke of the tool 55, however, the

rotational movement due to roll is subtracted from the constant rotational movement due to the rotation of the worm and hence the resultant rotation of the cutter is slowed up. It may I be stopped entirely or may even be reversed.= Thus, in this embodiment of the invention, as

in the previously described modification of the invention, it is possible to relieve the blade of acutter for a greater part of its lengththan in previous practice without danger of the relieving tool striking a succeeding blade of the cutter on the return stroke of the'tool. In the apparatus of both Figs. 1' and 5, springs or other suitable means will in practice be em? v grinding wheel is inclined to the axis X of the cutter.

The relieving motions which may be employed with the grinding wheels I8 and I9 are the same as may be employed with the lathe tools" I1 and 55. In fact, the grinding wheels can be substi tuted' for the lathe tools and mounted directly on the tool block of the apparatus shown in Fig. l or Fig. 5'.

In Fig. 6, I have shown an application of the invention to the relieving of face-mill gear cutters. The cutter to be relieved is denoted at C. It comprises a rotary head 80 and a plurality of cutting blades 8 I which project beyond one side face of the head in the general direction of the axis of the head. The relieving tool is here shown as a cylindrical grinding wheel W' which is mounted to rotate about the axis of a shaft 82.

To relieve the blades of the cutter C, the cu ter head is secured by bolts 83 to the spindle 84 of the relieving machine. This spindle 84 is mounted to rotate and reciprocate axially in the work head 85 of the machine.

The reciprocating movement of the spindle 84 is produced by the relieving cam 81 which may be usual or suitable construction. This cam engages a hardened nose or follower 88 that'is secured by screws 89 to an end face of the spindle. The rotary motion of the spindle 84 is produced by rotation of the helical gear 80 which is here shown as formed integral with the spindle.

This helical gear 90' is driven by a long-faced helical pinion 92 which is secured to a shaft 83 that is journaled in the head 85 parallel to the spindle 84.

The relieving cam 8'! is driven in timed relation withthe pinion 92 by the bevel gears 98 and 94, the shaft 95, the spur gears 88, 91, 98 and 89 and the shaft I00. The cam 81 is secured to the shaft I00. Power may be applied to the shaft 93.

The plate or follower 88 is held against the cam 8'Iby operation of coil springs I02 of which a plurality are provided although one only is shown in the sectional view of Fig. 6. These coil springs are spaced around the spindle 84 and each seats at one end in a recess I03 formed in the head 85 and at its opposite end in a recess I04 formed in a collar I05. The collar I05 seats against a flange or shoulder I 06 formed on the spindle 84 and it is held against rotation by one or more lugs or keys I01. The key or keys I! is or are secured by screws I08 to the head 85 and engage in a slot or slots I08 formed in the ment is imparted to the cutter spindle 84 during the axial movement of the spindle 84 under actuation of the cam' 81. This movement is sepa' rate from the rotational movement imparted to the spindle by rotation of the helical'pinion 92 itself andit is added to this last named rotational movement during therelieving stroke of the spindle 84 while it is subtracted from this last named rotational movement on the return.

stroke of the spindle 84. Thus with the mechanism of the present invention, it is possible again to slow up, stop entirely, or even reverse the direction of rotation of the cutter head during the return stroke of the relieving tool. As a result it is possible to grind the blades of a face-mill gear cutter for a greater length from front to rear with the present invention than has been possible with the processes previously used.

Let-us now'further analyze the relativ path of the relieving tool particularly with reference to the illustrated embodiments of the invention. Let n: denote the angular velocity of the relieving cam and N the number of teeth or blades in the complete circumference of the cutter which is to be relieved. Let 1' denote the mean radius of the cutter and Rthe pitch radius of the worm wheel 3! or 52 (Figs. 1 and Then the turning velocity of rotation 01 of the cutter at radius 1", due to the worm rotation I alone, is for a singlethreaded worm:

, R and the velocity D2 of the cutter at the radius r is therefore:

7 'U 7.C'.w

The resultantrotational velocity v of the cutter is equal to 01-1-02, or

1 c I)7'.w

It is ,well known that the tangent of the top relief angle p of a cutter blade, when the relievirig tool moves in a radial path, is

tan

or v

tan p=- 1 Through transformation: I

tan p(% and 1 tan tan v c r R N and t c= +(l tan p) (1A) Formulas 1 and 1A give the top relief angle 1 obtainable with a given cam characterized by a rate 01 throw c'andthe cam characteristic c tora given top relief p, respectively.

Let us now consider the return stroke. Fig. '7 is a diagram using the angle of rotation of the. cam as an abscissa and the velocity ofthe re'-' lieving motion or as the ordinate. Instead of Ur,

the quantity might be plotted if desired. Distance 00 denotes the complete circumference of the relieving cam, that is 360.

During the relieving stroke from A to B, the

relieving velocity U1 is constant. At the end of the relieving stroke, the velocity drops to zero and reverses rapidly. At C, the maximum return velocity has been reached. The straight-lines BC and CD indicate constant accelerations: When the cam is constructed in this way; the

acceleration may be kept at a minimum with the result of a minimum of shock or vibration in the operation of the relieving machine. The way of designing cams to obtain constant acceleration is known and needs no explanation. A cam with constant acceleration curves on the return' stroke is preferred,.but this construction is not essential to the invention. Other curves may b usedif desired. a

In determining the return stroke and the constant accelerations desired, it must be kept in mind that obviously the return stroke must cover the same distance as the relieving stroke. The

distance covered is the product of the velocity and the time and the latteris proportional to the rotation of the cam. The distance travelled in the relieving stroke 062 is therefore pro'portional to the area of the'rectangle OQBA. The

relieving distance per revolution of the cam is proportional to the area OO'DA.

The total forward motion, as expressed by the areas OQBA+QSB+S'O D must be equal to the total return motion expressed by'therarea SCS. Add area SSDB to both items and we The acceleration is such as to give a change in velocity of 2 BB during the time corresponding to rotation of the cam through the angleBD.

The return velocity '0: at any point P is given by its ordinate. From Fig. 6, then, we have:

B is a point midway between B and D.

Let 0 denote the angle of rotation of the cam between B and P and 0 the angle of rotation of the cam during travel of the distance BD. Then:

' ent analysis.

.In Fig. 8, the'relative path of the point tr a relievingtool during the relieving of the tipisur faces offsuccessiveblades of a cutter is illustrated. ;A cutter of large diameter has been as- I sumed so that the cutter periphery maybe considered as straight for the purposes of the. presin devlo'pment.

The uniform relieving motion during the 1 0. tation of a blade under the relieving tooli gi-ves' a relief line-l Iii-4 l2 for the top of. the blade.

A smaller cutter would be shown This line is inclined at the top relief angle p to the cutter periphery. The uniform inward'relieving motion ceasesat the point H2. .At this.

point deceleration begins. Then the return stroke of the relieving tool commences and the tool I begins to be accelerated outwardly. At

point H3, the relieving tool is halfway withe.

drawn and at point H5, theuniform relieving motion starts again for the relieving of the next blade of the cutter. 1

" The-relative path H2-H3"H 5 is shown on a larger scale in Fig. 9. It is to be noted that the relieving tool moves almost straight out relative to the cutter. Thisis so even though in the instance illustrated the return stroke H2'H,5.

occupies a full quarter of the track of therelievingcam and of the time of a complete relieving, cycle.

Anypointsuch as H6 in the return stroke of the relieving tool may be obtained by plotting distance :y' from-any assumed point -i i6, which i'sjtthesameas point P in Fig.57, and first obtainirrgapoint H6. Point H6 is on a peripheral line H6.l I6" at, a distance proportional to. 5

: and; to the ratio.

In other words, distance l161l6=y a Tr Inathe example P shown in Figs. 9 and 10,

hasbeen assumed as equal to two-thirds and p; as.equal to.12,. line ||2| |3| l5 (Fig. 9)

corresponds to a turning angle 0=90. InFigf 10,. the. relative path |lI-H8l. |9 has been plotted. forthe return movement of a relieving tool where the turningangle 0=60.

At point p :20 (Fig. 9), where the tangent I22:

to .the path of the relieving toolis parallel to Y-Y., the rotation of the cutter comes to a stop and. v infthe instances illustrated performs a slightreverse rotation'at mean point H3 or H8. The advance 'A .of point H5 from line Y-Y is seen be quite smalland if desired may even be made axn'egative quantity by suitably assumin the turning angle 0", and the ratio The point H5 or H9 will then be to the left of the line Y-,-Y. Forv the sakeof comparison, I have shown in Fig. 9 the relative path I l2--l23 I25 of the return stroke: of the relieving tool in the conventional relieving process for the same time and same cam angle 0'=90 as the path Il2--ll3ll5. The path lI2-l2|-,|29 is such as would be produced in' the conventional relieving process if a cam having a faster return movement were employed. The path |l2--l21 I29 corresponds toa cam having a return angle, 0=45. As will be clear from Fig. 9, even with such a cam, there is a considerable lost time as compared with the relieving process of the present invention. Moreover, for a return angle of 0=45, if the cam is operated at the same rotational speed, accelerations and inertia forces will be four times as large as where the return path is ll2l23|25. The advantage of the relieving method of the present invention is plainly evident from the. diagrams of Figs. 8 to 10 inclusive which show that the relieving tool receded nearly radially with very little overlap while nevertheless it has ample time to recede. Excessive stresses, vibrations and inaccuracies are thereby avoided while a maximum efiiciency in the relieving process is attained.

While the invention has been illustrated and described in connection with several different embodiments thereof, it will be understood that it is capable of further modification. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including suchdepartures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. Apparatus for relieving the blades of a rotary multi-bladed cutter comprising a rotary Work support, a relieving tool, a slide on which one of said members is mounted, means for rotating the work support, means for reciprocating said slide in time with the rotation of the work support once for each blade of the cutter to be relieved, and means whereby the movements of the slide vary the rate of rotation of the work support.

2. Apparatus for relieving the blades of a multi-bladed cutter comprising a rotary work support, a relieving tool, a slide on which one of said members is mounted, a pair of gears for rotating the work support which are rotatable and reciprocab-le relative to one another, one of said gears being mounted to move with said slide, means for rotating said gears to efiect rotation of the work support, and meansfor reciprocating said slide in time with the rotation of said gears once for each blade of the cutter to be relieved, one of said gears beingso connected to said slide that the reciprocatory movement of the slide simultaneously imparts an added rotational movement to the driven member of said pair of gears which is in opposite directions, respectively, for-opposite directions of movement of the slide,

3. Apparatusfor relieving the blades of a multi-bladed rotary cutter comprising a rotary work support, a relieving tool, a slide upon which one of reciprocating the slide once for each blade of the cutter to be relieved, means for rotating the worm and worm wheel continuously in one direction in time with the slide reciprocation, and meansfor effecting relative movement between the worm and worm wheel axially of the worm on reciproca-. tion of the slide.

4.,Apparatus for relieving the blades of a ro tary multi-bladed cutter comprising a rotary work support, a relieving tool, a slide upon which one of said members is mounted, a worm and worm wheel for rotating the work support, one of which parts is mounted to rotate on a relatively fixed axis and the other of which is mounted to move with the slide in the direction of the worm axis, means for rotatingthe worm and worm wheel, and means for reciprocating the slide in time with said rotating means. i

5. Apparatus for relieving the blades of a ro-" tary multi-bladed cutter comprising a rotary work support, a relieving tool, a slide upon which one of said members is mounted, a worm and worm wheel for rotating the work'support, one of which is mounted to rotate on a relatively fixed axis and the other of which is mounted to move with the slide in the direction of the worm axis, a rotary cam for reciprocating the slide, means for rotating the worm. and worm wheel, and means for rotating the cam in timed relation therewith once for each blade of the cutter to be relieved. 6. Apparatus for relieving the blades of a rotary multi-bladed cutter comprising a rotary work support, a relieving tool, means for recip-.

rocating the work support relative to the relieving tool, a pair of gears for rotating the work support, one of which is rotatable and reciprocable relative to the other and is connected to said reciprocating means to reciprocate on actuation of said reciprocating means, and means. for rotating the gears in time with the reciprocating means.

'7. Apparatus for relieving the blades of a rotary face-mill gear cutter comprising a rotary work support, a relieving tool, means for reciprocatingthe work support relative to the relieving tool axially of the work support, a pair of helical gears for rotating the work support, one of which is rotatable and reciprocable relative to the other axially of the work support, means connecting said gear to said reciprocating means to reciprocate on actuation of said reciprocating means, and means for rotating the gears in time with the reciprocating means.

8. Apparatus for relieving cutter blades comprising a tool support, a work sllpport, means for rotating the work support continuously at a uniform velocity, means for producing a relative reciprocating movement between the tool and work supports in time with said rotary movement once.

for each blade of the cutter to be relieved, and means whereby said reciprocating movement itself produces an additional rotary movement ofonce for each blade of the cutter to be relieved,

and means whereby the reciprocating movement imparts an added rotary movement to the'work support which is in opposite directions for opposite directions of the reciprocating movement.

10. In a machine for relieving cutter blades, a frame, a slide reciprocable on the frame, a work spindle journaled in the slide with its axis perpendicular to the direction of reciprocation of the slide, means for rotating the work spindle comprising'a Worm wheel secured to the spindle and a worm which meshes therewithand' which is journaled in the frame, said worm being mounted so that its axis extends in the direction of movement of the s1ide,.means for rotating the worm, and means driven in time with the lastnamed means for reciprocating the slide once for each blade to be relieved. i

' I ERNEST WILDHABER.

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