US2560967A - Apparatus for grinding gears and gear cutters - Google Patents

Description

y 17, 1951 F. LOHUTKO 2,560,967

APPARATUS FOR GRINDING GEARS AND GEAR CUTTERS Filed Dec. 14, 1948 4 Sheets-Sheet 1 INVENTQR FLOHYAN LOHUTKO BY ATTORNEYS APPARATUS FOR GRINDING GEARS AND GEAR CUTTERS Filed Dec. I4, 1948- 4 Sheets-Sheet 2 INVENTOR FLORYAN LOHUTKO By ATToHNEvs July 17, 1951 F. LOHUTKO v APPARATUS FOR GRINDING GEARS AND GEAR CUTTERS Filed Dec. 14, 1948 4 Shgets-Sheet 3 iNVENTfiR F'LQRYAN LQHUTHQ BY July 17, 1951 F. LOHUTKO 2,560,967

APPARATUS FOR GRINDING GEARS AND GEAR cuT'rERs Filed Dec 14, 1948 '4 Sheets-Sheet 4 WORK PIECE GRINDING WHE mvemoa FLORYAN BY ATTORNEYS Patented July 17, 1951 APPARATUS FOR GRINDING GEARS AND GEAR CUTTERS Floryan Lohutl-to, Detroit, Mich.,.a,ssignor to;-Th.e Thompson Grinder Company, Springfield, Ohio, a corporation of Ohio.

Application December 14, 1948; SeriallNo; 65,255

11 Claims.

This invention relates to grinding machines,

and particularly to grinding machines especially adapted-Tor grinding gears andgear cutters and the like.

The art of grinding'gears and gear cutters is highly complex andrrequires accurate fixtures and machinesand the like, and heretofore has been anaoperation requiring ahigh degree ofskill and consuming considerable-length of time.

This-is due-to-the fact that the tooth forms on the gears and gear cuters are finally finished by a grinding operation and therefore receive their ultimate accuracy therefrom.

Also in the case of gear cutters it is necessary to provide clearance angles along the sides of the:- utting teeth. in order to provide for the properv cutting action when it is utilized for forming agear blank into a gear.

Prior art arrangementsfor grinding gears and gear cutters generally took the form of a grinding wheel so shaped and arranged that itwould form only one sideof a-toothat a time. Thus, to grind completely around the periphery of a gear or gear cutter itwas. necessary to. grind one side of theteeth going around the workpiece in one direction and then. to reverse the workpiece and grind the other side of the teeth. It will be apparent. that this procedure, involving as it does two setups, was inherently inaccurate and troublesome.

Certain other arrangements have been proposed wherein the grinding Wheel, carried a helical thread form thereon so that as it rotated the reater gear cutter being ground also rotated.

'This arrangement was more satisfactory than the one described. above, but all machines heretofore which have utilized this principle have been exceedingly complex and expensive and difficult to operate.

The primary object of the present invention is to provide an improved arrangement for grinding' workpieces such as gears and gear cutters which is much simpler to operate than machines which have been constructed according to the prior art.

A still further object is the provision of a fixture in combination with a grinding machine in which Workpiecessuch as gears and; gear cutters can be mounted and ground to precise forms by simple grinding practices.

A still further object isthe provision of an improved method of grinding gears and gear cuttersrwhich results in a highly accurate product and which is muchmore easy to carry out than any of. the methods according to present day practices Theserand other objects; and advantages will .becomemcre apparent uponreference. tothe following description taken in connection with the accompanying drawings. inwhich-:

Figure lis a vertical. longitudinal. section through one form ofthe machine adapted: for practicing. this. invention;

Figure 2': is? a transverse section through. the machine and is indicated by the line '2-2 .on-Fig. ure 1;

Figure 3- istai vertical seetiomthroughthe head:- s-tock end of theworkpiece.supporting fixture and is-indicated'by the. line 3--3 on. Figure. 1.;

Figure; lr is a plansection through the. head:- stock and is indicated, by the:1ine-44.Qn.Fig, ure 3;

Figure 5. is,a. diagrammatic perspective view showing; the. electrical. interlock; between, the wheel driving motor. and the: headstock motor whereby synchronous operation of the-wheelland work-pieceanbor are. obtained;

Figure dis. a. view. similar. to Figure. 5- but. showing a, modifiedmanner of. interlocking the: wheel and workpiece arbor;

Figure? shows; still another view of. eiiecting synchronous. operation,- of, the, wheel.- and. work.- piecearbon;

Figures: 8- and. 9- are. view-s showing; atypical tooth. forming, operationon a small. gear. or; gear cutter; and

Figureslfl, 141, and lz showasimilar operation in connection with a largen gear.

Referring. to. the drawings, more in. detail, the machine shown .in, Figures 1. through. 4 comprises abed. I ll andreciprocably mounted thereonis a table,- l2. Thertable l2 may be. supported inthe usual manner, onthe V and flat, ways, best-seen at. I 4. in Figure 2,. and, hasrconnected. therewith the. fluid. actuating plunger I .6. which. is. reciproe cahly mounted. in. the. hydraulic.- cylinder lfl in the bed l0. I

Adjacent toythe bed UL and. referably rigidly connected. therewith is, a. frame. part. 20- and the upper snrfacethereof.isformedwitna guide.-

' way. 22.. which, reciprocably supports. the.- upper frame, part 24. The frame,part.2..4..-is adjustable along theguideway 22. by. meansof the. screw. 2.6 andhand. wheel 2.8.. according. to usual practices. Thev upper .frame. part 2.4v has on, one. vertical face thereof a slide.30:which.recip1t0c.ab1y. supportsa wheel headstructure 32. As in the, case of theirame. part. 2.4. the, wheel head structure 32 is adjustable. vertically on, its, supporting slide by means. of the screw 34 and. hand. wheel 36,

It. will. be.- apparent'. that the. right, angle slide arrangement of the slides 22 and; 3%) permit. the

positioning of the wheel head 32 in any position of adjustment in its plane.

In combination with the adjustability of the table ii? on the bed I0, this combination provides for complete three dimensional relative positioning of the table l2 and the wheel head 32 in order to bring the workpiece on the table and the grinding wheel into proper operative engagement.

The wheel head has a wheel shaft 38 extending therethrough which may be supported in any suitable manner as by the bearings 40 in opposite ends of the wheel head. A motor 42 is connected to one end of the shaft for driving it and a wheel 44 is mounted on the other end in a suitable and well known manner. A wheel guard 46 is preferably provided which surrounds the said wheel. As will, be noted, especially in Figure 2, the wheel 44 has a helical groove therein as at 4B and the cross sectional configuration of this groove is exactly that of the thread form which it is desired to grind on the workpiece. This wheel may be formed by any dressing operation suitable for that purpose, but is preferably shaped by a dressing device and process, as shown and claimed in my co-pending application, Serial No. 65,258 and filed on the 14th day of December, 1948.

Returning to the table l2, this member pivotally mounts a sub-table or platform 50. The sub-table 50 is adapted for pivoting in a vertical plane on the table I2 by means of its arcuate lower surface which mounts in an arcuate recess in the upper part of the table l2. This construction is best seen in Figure 1.

For clamping the sub-table in any particular position of adjustment, there is preferably a T-slot 52 extending around the arcuate recess in the table [2 and into which the T-bolt 54 extends. The T-bolt may be drawn up to clamp the sub-table 50 into position by means of the tapered locking member 56, as will best be seen in Figure 2.

Mounted on top of the sub-table 50 is still another table or platen 5B which is pivotal in a horizontal plane about the pivot or dowel pin 60. Similarly, as with the table 50 the platen 58 is adapted to be clamped in any position of adjustment by means of the T-slot 62 in the table 50 and the clamping bolts 54 extending therein and through the platen 58.

The platen 58 has mounted at one end thereof a tailstock unit 65 and at the other end thereof a headstock unit 68. Between these units there is mounted a workpiece arbor l0 and which is drivingly connected with the output shaft 12 of the headstock unit by means of a dog member 14. The workpiece I6 is mounted on the arbor in any suitable manner so as to be rigid therewith during the grinding operation.

For driving the output shaft I2 of the headstock unit the arrangement shown in Figures 3 and 4 may be employed. In these figures it will be noted that there is a headstock drive motor 18 which drives through a worm and wheel arrangement at 80 into a shaft 82 which traverses the headstock unit from end to end. At the rear end, that is the left'end as viewed in Figure l, of the headstock unit there is a removable cover plate 84 and beneath which there are the change gears 86 which interconnect the shaft 82 with the drive shaft 88. The drive shaft 88 is splined, at its right end, to the rotatable member 90 which receives the headstock center or output shaft 12.

' of reciprocation of the As mentioned previously, it is necessary for the grinding wheel and for the workpiece being ground to rotate at synchronous speeds. This is due to the fact that the groove formed on the grinding wheel is helical, and therefore as it rotates the workpiece also rotates in order to maintain the teeth being formed thereon in exact register with the said groove.

One arrangement for maintaining the workpiece and the wheel in synchronous operation is shown in Figure 5. wherein the wheel head motor 42 and the workpiece driving motor 18 are synchronous motors and are interconnected by the wires 92 and 94 with the alternating current power lines LI and L2.

It will be apparent that closure of the switch 95 will result in synchronous operation of the grinding wheel and the workpiece arbor. It will be apparent that if the workpiece arbor were not driven by the motor 13 it would still rotate due to the threaded form of the grinding wheel. This is not desirable, however, because accurate thread forms cannot be generated in this manner. This is due to the fact that the grinding load shifts in magnitude and direction as the relative positions of the tooth being ground and the groove forming the said tooth change. If no compensation were to be made for this shifting load, then the workpiece being ground would have the greatest amount of material removed therefrom over the area where the greatest grinding load occurred, and this would produce an improper tooth form.

This is illustrated in Figures 8 and 9 wherein a relatively severe tooth grinding operation is being carried out. The gear or gear cutter being formed in Figures 8 and 9 is relatively small and due to this fact the pressure between the workpiece and the grinding wheel varies rapidly and from one side to the other.

As shown in Figure 8, wherein the tooth being formed is in the center position relative to the grinding wheel, it will be noted that the vectors Fl representing the force of the grinding wheel on the sides of the tooth are equal in size and are symmetrically arranged. In this particular position then the gear tooth will normally be properly ground. However, in Figure 9 the gear has rotated through a small angle while the wheel has turned through a relatively large angle and the tooth has shifted to one side of center. At this time, it will be noted that the line of force between the wheel and tooth, and represented by the vector F2, has shifted so that substantially the entire thrust of the wheel on the gear is toward one side. Under these conditions it would not be possible properly to grind the tooth form unless the position of the workpiece being ground were fixed by some instrumentality other than its grinding engagement with the wheel. It will be seen, therefore, that by driving the wheel and workpiece synchronously the shifting thrust between the wheel and workpiece is compensated for and an accurately formed tooth results.

In the grinding of gears the teeth thereof normally extend in a direction parallel with the axis of the gear. For grinding workpieces of this type the table 5t would thus normally be moved to a position where the axis of the mandrel 10 extended in a direction parallel with the direction table l2. In gear cutters, however, it is necessary for there to be a clearance angle extending backwardly from the cutting face of the cutter and to form a workpiece of this type assume:

.5 the workpiece 5D is tilted I as shown in: Figures 1 and? 2 It will be apparent that the workpiece will be ground with" the proper" clearance angle-extend ing' rearwardly fromthe cutting edge thereof-L Oncethe cutter has been-formed on' the grinding wheel the' face thereof; thatis the-left;hand face as viewed in Figure-1 may besuccessively'g-round back in order to I resharpen the-cutter during" use thereof.

Normally, for relatively thin cutters, a large wheel-may be-used and the'entire tooth form on the cutter ground without axially reciprocating the-table I2 However; ifthegear cutter err-gear to-beground has a substantialaxial'l'ength, such that" it cannot be completely formed except by axial reciprocation of thetable l2, this operation can be performed without" in any way" eflfectihg the formation of" the tooth; It will merely be necessary to go around the workpiecemore than onetime; either reciprocating" the table I 2 at the same'time or adjusting it to two ormoreposition's and grinding around the workpiece oneor" more times" for each of the'saidpositions;

In order-to indicate theseverity of the-grindingoperation shown-inFigures'il and 9and' also to indicate that similar conditions" obtain in" work= pieces of other sizes;,Figures 10,- 1'1 and 12 show a larger" type gear" being ground" and with the thrustsbetween the grinding 'wheel andgear tooth beingindicate'd. It'will. be apparent that while these thrusts do 'not'c'hange' as: rapidlyor'asmuch as'd'o the thrusts" in Figuresd and'9, there-is, neverthel'ess, sufiicientshifting thereof torequire: that the workpiece. be synchronously: driven in: order properly to formthe' gear'tooth thereon:

Figures 6 and 7' show modified arrangements for obtaining synchronous operation of the wheel and workpiece; In Figure: 6 the wheel. shaft is driven by a belt I which passes over a pulley I02 mounted on the wheel shaft; Also carried on. the. wheel lshaft. i'sa Selsyn type transmitter I04 connected with the power lines LI and L2. The Selsyn transmitteris=interlocked by the wires I05 in the. usual manner. withthe. Selsynreceiver I 06 which forms the headstock. driving motor. The Selsyn receiver is. also. connected with the power lines LI and" L2 and as well known in connectiorrwith this type of driving arrangementremains in absolute synchroni'sm with the Selsyn transmitterlM'atall-times.

In Figure 7- a similar arrangementis shown wherein the wheel shaft is selectively connected with the headstock by means-of the gearing I08 and shafting- Ht. As is well' known this provides for-a positive mechanicalinterconnectioni of. the headstock and wheelshaft and thereby positively insures synchronization thereon In order to permit the wheel head and the table supporting the workpiece tobe adjusted relativelyto each other" the shafting' H0" preferably includes the splined connections at 1 l2 and the differential units at H4. By this arrangement the full flexibility of adjustment of the wheel and workpiece is maintained without in any way interfering with the synchronous driving thereof.

If it is desired to grind helical gears or gear cutters, the platen 58 is set to the proper angle about its pin 60 and then clamped in position. Thereafter the grinding of the helical work member can proceed as outlined above.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications witln'nrthisrimzentionnas. may falliwitlnmthescnpe ofitheappended claims.

I claim:

1. In combination in agrinding. machine for grinding gears andgear'cutterm; a grinding-wheel havinga spiral groovei-on. the periphery-"thereof; a bed, a table movable on said bed, a fixturemountted. on said: table comprising a sub-table directly supported by'said' bed andia platen supported" on said table; headstock and tailstock means on said platen defining a -work axis", and 'mean for' pivotally adjusting said sub-table on said table and said platen on said sub-table thereby to vary the angularity between the axis of-said wheel and said Work axis, and means for. driving-said wheel and a workpiece" mounted on said axisat synchronous speed.

2. In a grinding machine; a bed; a table reciprocable on said bed, a sub-table mounted on said bed for pivotal movement on ahorizontal axis; a platen mounted on said sub-table for pivotal movements on an axis perpendicular to the said horizontal axis; a headstock and a tailstock on said platen defini'nga work axis, a columnadjacent said bed, a wheel head carried on said-column and movable vertically and horizontally thereon, a grinding wheel rotatably mounted on said-wheel head andhaving a spiral groove on the outer peri'phery thereof, and drive means operable for driving said wheel head and said headstock in synchronism.

3: In a grinding machine; a bed, atable reciprocable' on said bed, a, sub-table mounted on said bed for pivotal movement ona. horizontal axis, a platen mounted on said sub-table-for pi'v otal movements on an axis perpendicular to the said horizontal axis, a headstock and a tailstock on said platen defining a workaxis, acolumnadjacent said bed, a wheel head carried on said column and movable vertically and horizontally-thereon, a grinding wheel.rotatablymounted'on said'wheel head andlhaving a spiral groove on-the outer.periphery" thereof, and drive" means operable for driving. saidwheclhead andsaidheadstockinsynchronismsaid headstock including change gears for changing the ratio of itsspeedt'o that of said wheel;

4. In a grinding machine; a bed, a table. re"- ciprocable on said bed, a sub-table mounted on said bed for pivotal movement on a horizontal axis, a platen-mounted on said sub-table-for piv otal. movements on an, axis perpendicular to the saidhori'zontal axis, a. headstock and a tail'stock on said platendefinin'g a work'axis, a column ad'- jacent said bed, a wheel head carried on said column and movable, vertically and horizontally thereon, a grinding wheel rotatably mounted on said wheel head and having a spiral groove on the outer periphery-thereof, and drive means operabl'e-for driving said' wheel head and said head stock in synchronism, the said drive means com prising individual synchronous motors drivingly connected with each of said headstock and said wheel.

5. In a grinding machine; a bed, a table reciprocable on said bed, a sub-table mounted on said bed for pivotal movement on a horizontal axis, a platen mounted on said sub-table for pivotal movements on an axis perpendicular to the said horizontal axis, a headstock and a tailstock on said platen defining a work axis, a column adjacent said bed, a wheel head carried on said column and movable vertically and horizontally thereon, a grinding wheel rotatably mounted on said wheel head and having a spiral groove on'theouter periphery thereof, and-drive means operable for driving said wheel head and said headstock in synchronism, said drive means comprising means for driving said wheel and means connecting said headstock with said wheel whereby said wheel and headstock are driven in synchronism.

6. In a grinding machine; a bed, a table reciprocable on said bed, a sub-table mounted on said bed for pivotal movement on a horizontal axis, a, platen mounted on said sub-table for pivotal movements on an axis perpendicular to the said horizontal axis, a headstock and a tailstock on said platen defining a work axis, a column adjacent said bed, a wheel head carried on said column and movable vertically and horizontally thereon, a grinding wheel rotatably mounted on said wheel head and having a spiral groove on the outer periphery thereof, and drive means operable for driving said wheel head and said headstock in synchronism, said drive means comprising a Selsyn transmitter driven synchronously with said wheel and a Selsyn receiver connected with said transmitter and driving said headstock.

7. In a grinding machine; a bed, a table reciprocable on said bed, a sub-table mounted on said bed for pivotal movement on a horizontal axis, a platen mounted on said sub-table for pivotal movements on an axis perpendicular to the said horizontal axis, a headstock and a tailstock on said platen defining a work axis, a column adjacent said bed, a wheel head carried on said column and movable vertically and horizontally thereon, a grinding wheel rotatably mounted on said wheel head and having a spiral groove on the outer periphery thereof, and drive means operable for driving said wheel head and said headstock in synchronism, said drive means comprising gears and shafting connecting said wheel with said headstock.

8. In a grinding machine; a bed, a fixture on said bed having a headstock and tailstock defining a work axis, means for pivoting said headstock and tailstock as a unit to move said work axis about a horizontal axis extending transversely therethrough or about another axis at right angles to said horizontal axis, a frame on said bed adjacent said fixture and adjustable toward and from said work axis in the direction of said horizontal axis, a wheel head carried on said frame and adjustable vertically thereon, a shaft in said wheel head extending in the same direction as said horizontal axis, a grinding wheel on one end of said shaft overhanging said work axis and having a spiral groove therearound, a drive means at the other end of said shaft for driving said wheel through said shaft, and means interlocking said shaft and said headstock whereby a workpiece on said work axis is driven in synchronism with said wheel.

* 9. A fixture for supporting gears and gear cutters to be ground comprising a reciprocable table member having an arcuate slot therein, a subtable mounted on said table and having a portion thereof engaging said arcuate slot for pivoting movement about a first axis, a platen mounted on said sub-table for pivoting movement about an axis thereon perpendicular to said first axis, and headstock and tailstock means on said platen defining a Work axis.

10. A fixture for supporting gears and gear cutters to be ground and comprising a reciprocable table, a sub-table having an arcuate slot therein mounted on said table and having a portion thereof engaging said arcuate slot for pivoting movements about a first axis, a platen mounted on said sub-table for movement about an axis perpendicular to said first axis, means for clamping said platen to said sub-table and said sub-table to said table in any of their positions of adjustment, and headstock and tailstock means on said platen defining a work axis on which the workpiece to be ground is supported.

11. In a grinding machine; a bed, a table reciprocable on said bed, a sub-table mounted on said bed for pivotal movement on a horizontal axis, a platen mounted on said sub-table for pivotal movements on an axis perpendicular to the said horizontal axis, a headstock and a tailstock on said platen defining a work axis, a column adjacent said bed, a wheel head carried on said column and movable vertically and horizontally thereon, a grinding wheel rotatably mounted on said wheel head and having a spiral groove on the outer periphery thereof, and drive means operable for driving said wheel head and said headstock whereby the rotation of the workpiece by said headstock is synchronized to the rotation of said spiral threaded wheel for center positioning of the tooth being formed relative to the spiral groove of the grinding wheel.

FLO-RYAN LOHUTKO.

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

UNITED STATES PATENTS Number Name Date 686,599 Fellows Nov. 12, 1901 1,642,554 Olson Sept. 13, 1927 1,917,504 Curtis July 11, 1933 1,989,651 Drummond Jan. 29, 1935 2,249,251 Mentley July 15, 1941 2,385,650 Rickenmann Sept. 25, 1945 2,449,354 Wickman Sept. 14, 1948 2,482,800 Ross Sept. 27, 1949 FOREIGN PATENTS Number Country Date 508,744 Great Britain July 5, 1939

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