US2571293A - Means for and method of forming grinding wheels - Google Patents

Description

Oct. 16, 1951 w. F. ROSS 2,571,293

MEANS FOR AND METHOD OF FORMING GRINDING WHEELS Filed Feb. 8, 1946 3 Sheets-Sheet l u r W 16' 2'7 25 P0 11 mmllll III! In Tm IIII/I mm "1m I N V EN TOR.

Oct. 16, 1951 V w, oss 2,571,293

' MEANS FOR AND METHOD OF FORMING GRINDING WHEELS Filed Feb. 8, 1946 s Sheets-Sheet 2 zwvi io.

Oct. 15, 1951 w, oss 2,571,293

' MEANS FOR AND METHOD OF FORMING GRINDING WHEELS Filed Feb. 8, 1946 s Sheeds-'neet 5 Q m Q 3 3 Q I V EN TOR.

Patented Oct. 16, 1951 UNlT MEANS FOR AND METHODOF FORMING GRINDING WHEELS Walter F; Boss, .Ncirthville," 19';- n

lfiesne assignments, to Niles Company, West Hartf of New Jersey .a sis ior by fiernent' Pond rd, Cohfi, a corporation Apmmanramia y' s, 1946, SerialNo. 555 253 a This" invention relates to means for and method of forming or dressing the periphery of' an abrasive wheel, such asni'ay be intended for the cutting oi gear teeth wherein the periphery of the said abrasivewheel is to be provided with a thread. form in whichithe threads and the'spacing between the threads are tobe of a'definitely predetermined contour in cross-section calculated to produce well-formed and properlyspaced teeth in the work eventually produced by the said abrasive wheel; U More partiem'ariy', the invention relates to the profiling of th e periphery of an abrasive wheel by the. crusher roller niethod in which a suitably hard abrasive resis'ting" rollr' having annular ribs thereon of a rackisfection, in counterpart of the crosssction' of: the" thread "to be formed on the wheel, is pressedlagainst and reciprocatecl laterally. across the'peribi ery of the wheel in tuned relation tgilj'therotatibn of the wheel so that it will lrtiiethread rdrm thrintof This method df crus hi ng a thread form into the periphery of a grinding wheeli s hot'broadly new, and the present,invention'relatesmore-particularly to the provision of a mcre ficiem forrn of crusher roll for'the rhor 'efiective purpose of producing a threaded 'formon' anabrasive wheel; As hitherto proposed, the" crusher roll has been of a cylindrical iorrh in which the diameter of the annular rackteeth' or ribs has been maintained equal throughout thfle ngth of th'ron and in which the profile of each of thesai'd ribs has been identical, so that, if sucha cylindrical cutter be disposed at an angle to the plaine oi the abrasive wheel, that is, with its axis at an angle to the axis of the said abrasive wheieljn order that the planes of the annular ribs will agree with the lead angle of the thread to be formed on the abrasive wheel, contact will be initially established between the crusher roller and a single point of rotation on the peripher'y'ofithe abrasive wheel, the outer ribs being out of contact therewith. H 7

Furthermore, such a cylindrical. crusher -roll has a characteristic crushing action which is exerted more especially on thetops of the grains comprising the grinding wheel, in a manner which leaves an undesirable surface of broken instead of dislodgedgrains on the formed thread and a surface structure of the thread which is undesirable in manyrespects for precision grinding of gear teeth'or for similar purposes. a a 4 Still further, the use of such a form of crusher roll fails to aifordsuch full and completesupport for the .threadl istructure, of the abrasive 2 Claims. (01. 125-11) wheelits iorniation as to effectively mini;

fmizfbreakdown of the said structure or its dis- Then esent invention, therefore, has as a'n irhp'dt nt object the provision of a crusher roll whi'ch'lwill have a resultant component of crush-Q ing and tangential forces when in operation, and inyyhichj a rotary slipping action between the crusher-r011 an the w elipe iphe y w e rqe v'idedjfor toicreate the tangential force and to effecta' jdis'lodging oflg'rains from the struct'urejof the thread. as it is formed onthe grinding wheel; thereby minimizing 'the,,mere ,breaking of the 'grains'a'h'd' resulting inthe production f ah g 'l'y abrasive surfac'eyon the formed thread struck 'Stillfiirtherl objects or advantages, auxiliary or subsidiary tothe aforesaid objects, or. resulting from the construction or operation of the invena 1;. may e carried into effect, wiujbeccihe. app 7 "asth'e'said'invention is hereinafterfurtheridiscl'osed; lii' 'carfrying the saidinvention into efiecf may provide a crusher roller having a, substanf torti'on from' the precise, continuous profile tially hourglass form operated in theman'ner and the..mechanisrnghereinafter further. described, by wayofexarnple having reference" to the accompanying drawingrwhereintr Eigur lifs a somewhat schematic elevation of amechahism for the. profilingpf a abrasive gear grinding. wheelby means of. the improved crusher mu, thev precise. proportions of the elements. of the structure as shown .beingf departedfroin .or exaggerated for purposes of clear and simple illustration. a.

Figure 2 is'a schematic plan View of .soindfof the parts shown inFig. 1.

..F ure. 3 isa front elevation of the crusher w h eelftogether with the finishing wheel and'lth mountings therefore.v

Eigur 4- isla detailedvertical secticnal yieysfof the mountings:- ofthe crusher and finishing wheels-illustrating. their method of adjustment.

Figure 5 is a diagram illustrating in an e'xag gerated manner, the relationship; of the; crusher wheel to the abrasive wheel being operated on that by-as viewed along theaxis of the abrasive wheel and; 1- 4 Figure ,6 isz -asimilar-diagram;showing the abr siveuwheel: and-the crusher wheel as viewed perpendicularly tothe axesthereof. Y H

ar-charactersfof reierence indicate sirnj ar si zi e se er fi r he. w ngs.

' B eferring first to Figure lof the drawings; i0

indicates an abrasive wheel, such as may be intended for the grinding or forming of teeth on a spur wheel blank, the said abrasive wheel being characterized by its having formed on its periphery a thread II which is in cross-section conjugate to the rack form of the gear to be ground; and the present invention relates to the means of forming this thread on the periphery of the abrasive wheel.

For such purposes I utilize an annularly ribbed crushing roll 12 having a rib to rib spacing, which is equivalent to the circular pitch of the gear which the abrasive wheel is eventually intended to grind, and this roll is of a special slightly hourglass form as and for the purposes which will be further described.

I have also provided a further finishing roll l3, which is shown as being of a single channel dual-ribbed construction and is the substantial duplicate of the central portion of the crusher roll 12 embracing the two innermost ribs of the said crusher roll as will become still more apparent as the purposes and operation of these two rolls l2 and I3 are later dwelt upon.

The abrasive wheel l0 and the crusher roll I2 are. intended to have relatively reciprocal motion imparted thereto, and, in the present example, such reciprocation is confined to the abrasive wheel although as a matter of design it could be imparted to the crusher roll to produce the same result as will be well understood; and it is desired that throughout the present description and in interpreting the claims that the utilization of the terms reciprocating the abrasive wheel be considered in such broad sense as to embrace the obvious alternative of the reciprocation of the pressure roller relative to the abrasive wheel.

The abrasive wheel I0 is shown as being mounted for rotation on and by the shaft I4 which is splined, as at I5, for longitudinal sliding connection with a driving coupling IS, the latter being in turn driven by the bevel gear I! of a differential which includes pinions l8 and a further meshing bevel gear I 9.

20 is a driving motor operating a driving pinion 2l which meshes with ring gear 22 of the said differential, this ring gear also meshing with the first of a train of change speed gears 23, 24, 25, 26 and 21. The said gear 2! drives a feed screw 28 which is threaded into the arm 29 of a bracket 30 secured to the said shaft 14. This bracket 30 is provided with suitably adjustable stops 3| and 32 positioned for the timed operation of a reversing switch 33 for effecting the reversing of the drive motor 20 as said switch isoperated by one or another of said stops.

34 is a shaft through which rotation of the gear [9 of the differential. may be effected from any suitable source, as by a belt 35, to control the speed of rotation of the shaft l4 relative to that of the driving motor to meet special circumstances; but this is not an essential part of the present invention and need not be discussed in any further detail herein.

It will be apparent that by means of the gearing described and the operation of the feed screw 23 thereby, the abrasive wheel I0 may be caused to reciprocate, say, to the extent indicated by the dotted lines in Figure 1, whilst it is at the same time being rotated, and that, as this reciprocation is reversed by the operation of the reversing switch 33 in the apparent manner, the direction of rotation of the abrasive wheel will at the same time be reversed; so that any stationary point presented to the surface of the" grinding wheel during such operation thereof will traverse a helical path thereon and retrace the same path in the opposite direction upon reversal of the motions described.

It has been heretofore suggested in the prior art that a thread could be so formed on such an abrasive wheel, utilizing the motion described, by pressing thereon a cylinder crushing roller capable of angular adjustment relative to the rotational axis of the grinding wheel to agree with the lead angle of the thread to be formed, said roller having identical annular ribs of crosssectional rack form; but it has also been recognized that such a roller has a non-uniform nor-' mal contact with the periphery of the abrasive wheel so that tangential oscillation or sliding movement of the cylindrical crusher roller across the face of the wheel has been resorted to for the purpose of insuring that the medial portion of the crusher roller (which is the only portion of such a roller having normal contact with the periphery of the abrasive wheel) may be caused to traverse the whole width of the wheel face to produce the required crushing of the thread form thereinto. Thus the medial portion of the said crushing roll has been charged with the greater part of the work of forming the thread on the said abrasive wheel. The use of such a cylindrical wheel has other rolling characteristics, in its relation to the surface of the abrasive wheel which detract from its efliciency and which will also be further referred to hereinafter.

A very important and advantageous feature of the present invention resides in the utilizing of a freely rotatable crusher roll which departs from the usual pylindrical form in that it is of greater diameter at the ends than in the medial portion thereof, the longitudinal contour of the said crusher roll being characterized by its being curved inwardly from the ends similar to an hour-glass.

An examination of Figures 5 and 6 of the drawings will readily show this hour-glass envelope form of the crushing wheel and its relationship to the abrasive wheel I0, the curved lines 36 indicating the envelope of the working surface of the said crusher roller the ends 31 of which are obviously of greater diameter than is the medial portion of the roller. a-b indicates the axis of the abrasive wheel and :ry the axis of the crushing roller set at an angle which is at right angles to the lead angle cd of the thread to be formed on the periphery of said abrasive wheel. It will be obvious that with this envelope of the correct curvature the outer edges of all the ribs provided on such a crushing roller will simultaneously contact the surface of the abrasive wheel l0 along the line :1;-- and it will be also apparent that those ribs so contacting the surface of the grinding wheel, and spaced outwardly from the medial portion of the roller as exemplified by the intersection of the lines ab and :ry, will be of progressively increasing diameter notwithstanding the fact that the diameter of the abrasive wheel 10 remains constant at such points of contact.

Consequently, the free rolling of the crusher roller on the surface of the abrasive wheel, as the said abrasive wheel is rotated, cannot be a true rolling action for all of the contacting ribs and at best can only be a compromise between the true rolling action of those ribs of smallest diameter and those of largest diameter; and this is a condition highly desirable and sought for in the. present. case. -It should :be understood that the depth andform of the grooves of .the crusher .roll are located from this :curved or hour- .glass surface andnot from theaxis of the roller, ,as has been the practice heretofore.

.The hour-glas crusher .roller described, in contra-distinction to .the cylindrical pressure rollerheretofore known, has a resultant component of a crushing force and tangential force in action. While the peripheral speed .of .the crusher roller along its actual rollingdiameter is uniform, a slippage occurs at diameters .other than the rolling .circle, due to the hour-glass shape-of the roll, creating tangential force which,

1 the finally threaded abrasive wheel. .On the contrary, the old type cylindrical roller has asingle high compressive force in one direction toward the axis of the abrasive wheel which crushes and breaks the tops of the grains in such a manberas t a e an ndes rab e workin ac of broken grains.

In the crusher roller as illustrated it will be understood that, with the symmetrical form of crusher roller shown, the point of intersection between the lines ab and ;ry 'falls midway between the ends of the roller for which reason this portion of the roller of smallest diameter is herein referred'to as the medial portion for the sake of identification; but it is not intended that "such definition shall be so narrowly interpreted as to exclude the positioning of this portion of smallest diameteqat other than precisely midway between the ends of the roller as it will be perfectly obvious that the said roller will still operate in the mannerdescribed should one or other of the end portions of the roller be cut ofi so that the waist of the roller would no longer be midway of the ends thereof.

It will also be understood that in addition to the free rolling action of the crusher roller, the said abrasive wheel (in the particular example illustrated) is moved backwards and forwards along its axis a-b as by the mechanism already described, the direction of rotation of the said abrasive wheel being reversed with each movement, as stated, so that the rolling direction of the crusher roll is also reversed at such times.

Means are provided for supporting the crusher roller in operative position relative to the abrasive wheel with provision for its angular setting and fitting into the surface of the abrasive'wheel as the operation of forming the thread is carried out and Figures 3 and 4 show a suitable fixture for this purpose.

In its preferred form, the curved hour-glass shape of the crusher roller conforms precisely with the curvature resulting from the intersection of the plane of the setting angle of the crusher roller with the peripheral surface of the abrasive wheel (which is the angle at which the roller is to be set in order that its ribs will truly follow the lead angle of the thread to be formed on the abrasive wheel), so that an even crushing pressure on all contacting ribs on the crusher roller with the said peripheral surface of the abrasive wheel may be maintained throughout all relative reciprocal and rotary motions of the roller and the wheel; but it is within the purview of this invention that the true hourglass curvature referred to may be departed from within reasonable limits without material loss" of v the component of crushing force sand tangential :force .;resu1tingfr.om differences .in diameterof the several annular ribs, as hereinsome detailin Figures 3 and 4; 38 .beingairame structure. bolted .to the bed} 9i'of.the..machine and carryinga slide fiadjustable by micrometer'feed M towardand from ,anaxis of abrasive wheel). The front end of the said slide carries a bracket 42 in which the spindle l3v of the crusher roller roller [3.

similarly positioned so that its axis is projected I2 is suitably mounted, this bracket. being, pivoted at M for swinging about an axis passing transversely through the axes .of the crusher roller [2 and the abrasive wheel In. It is preferred that this pin be located opposite the medial portion or the waist of the hour-glass crusher roller 'with its axis directed between adjacent annular ribs vof the said crusher roller-as clearly seen/froman examination of the said Figures 3 and 4.

.4 5 are locking screws for securing the said bracket 42 in position of angular adjustment about the axis of the said pin 44. The purpose of .this angular adjustment is to secure the required setting angle of the crusher roller 12 relatiye'to the axis of the abrasive wheel H] as dictated by the lead angle of the thread to be crushed into the peripheral surface of thesaid abrasive wheel.

Also mounted on the top of the said slide 40, and adjustable thereon by the micrometer feed 36, is a supplementary slide ll carrying-thebracket 43, which in turn is pivoted at $9. This bracket 38 is inverted in relation to the previously described crusher roller bracket '42 and similarly carries the spindle 56 of the finishing or straddle The pivot 49 of this bracket 48;.is

through the axes of the said straddle roller l3 and of the abrasive wheel [8 and bearsthe same disposition to the-ribs of the roller as doesv the ivot M-to the adjacent ribs of the crusher-roller l2.

In their truly vertical positions of adjustment, the axes of the spindles 43 and are in alignment, but it will be seen that when the crusher roller is adjusted to an angular setting, as shown in Figure 3, the finishing or straddle roller I3 may be adjusted to a like angle of setting and locked in such position of setting by the locking screws 5|.

Regardless of the setting angle determined upon and effected by the adjustable means described, it will be observed that those portions of the two rollers intersected by the axes of the pivots 44 and 49 remain stationary, one above the other so that by so arranging the limits of axial feed of the abrasive wheel l0 it may be caused to move from its engagement by the crusher roller I2 to engagement by the finishing of straddle roller l3 which will then have the same relationship to the thread formed on the abrasive wheel by the crusher roller as had the crusher roller itself.

for any correction for hour-glass shape as such would be infinitesimal and impractical, and its purpose is to provide a finishing or final forming pressure for the thread in a manner applied to both sides thereof such as to avoid any tendency, during such finishing, to break away the thread b simple unsupported side pressure, especially as such thread approaches the extremities of the abrasive wheel, the crusher having by that time accomplished the greater portion of the thread forming work.

What I claim is:

1. In a machine for crusher rolling a helical thread on the peripheral surface of a cylindrical abrasive wheel composed of abrasive particles bonded in a crushable bond, in combination, driving means operatively connected to said abrasive wheel for rotating said wheel, an annularly ribbed, freely rotatable crusher roller of substantially hourglass shape and having a surface characterized by a plurality of annular, V-shaped grooves, said crusher roller being of non-abrasive material and being of suificient hardness to crush-form the peripheral surface of said abrasive wheel, means operatively connected to said crusher roller for supporting said roller for free rotation and for holding and pressing said roller against and into the periphery of said abrasive Wheel during rotation thereof, whereby said crusher roller and abrasive wheel rotate at substantially the same peripheral velocity, means operatively connected to said support and holding means for pivotally adjusting said support and holding means about a transverse axis radial to said wheel to adjust the axis of said roller at right angles to the thread to be formed on said wheel, and means operativel connected to said crusher wheel for effecting traversing motion between said wheel and said roller during rotation of said wheel, whereby the ribs of said roller will traverse the thread to be formed on said Wheel.

2. A method of crusher rolling a helical thread on the peripheral surface of a cylindrical abrasive wheel composed of abrasive particles bonded in a crushable bond which comprises mounting said wheel adjacent an annularly ribbed, freely rotatable crusher roller having a surface of substantially hourglass shape with the axis of the wheel positioned in a plane parallel to the axis of the roller and at an acute angle thereto, said crusher roller being of non-abrasive material and being of sufiicient hardness to crush-form the peripheral surface of said abrasive wheel, rotatin said wheel while holding and pressing the said roller against and into the periphery of said wheel and simultaneously traversing said wheel across said roller, whereby said crusher roller and abrasive wheel rotate at substantially the same peripheral velocity and the ribs of said roller traverse the helical threads being crush rolled on said wheel.

WALTER F. ROSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,759,333 Wildhaber May 20, 1930 2,112,679 Rickenmann et a1. Mar. 29, 1938 2,135,202 Scrivener Nov. 1, 1938 2,145,202 Rickenmann Jan. 24, 1939 2,350,897 Jellis June 6, 1944 2,377,241 Kavle May 29, 1945 2,385,644 Polk Sept. 25, 1945 FOREIGN PATENTS Number Country Date 329,595 Great Britain May 22, 1930 638,686 Germany Nov. 20, 1936 515,397 Great Britain Feb. 25, 1938 Great Britain Apr. 26, 1940

Images