US2885830A - Gear lapping machine - Google Patents

Description

May 12, 1959 Filed Feb. 15, 1955 D. J. WATT GEAR LAPPING MACHINE 5 Sheets-Sheet 1 i5 1a 5 i 2 gg fi s 5 11:11:11 I i :3 LQZ-ZEII 'u. 1 I... =a 2Q 12 z A! J 15 4 /"I I I I W INVENTOR.

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GEAR LAPPING MACHINE 3 Sheets-Sheet 2 Filed Feb. 15, 1955 INVENTOR g g/nil Joseph Vail May 12, 1959 D. J. WATT GEAR LAPPING MACHINE Filed Feb. 15, 1955 3 Sheets-Sheet 3 2 m'roz/v am.

United States Patent GEAR LAPPING MACHINE David Joseph Watt, Clarence, N.Y., assignor to Farrel- Birmingham Company, Inc., Butfalo, N.Y., a corporation of Connecticut Application February 15, 1955, Serial No. 488,309

6 Claims. (11. 51-26) The present invention relates to a gear lapping machine and aims to provide certain improvements therein. The lapping of gears so that they will properly mesh with one another and thereby operate most efliciently f and quietly has been, up to the present, considered an art. In practicing this art, operators of lapping machines applied pressure between a pinion and a gear to be lapped v by the simple procedure of progressively advancing, by ffscrew means, the pinion and gear into intimate engagement with each other by closing the distance between the pinion shaft and the gear shaft. The [force developed by the application of screw pressure resulted in a deflection or spring in the lapping mechanism or lapping setup, hence, neither exact pressures nor exact cycling were ever known and the results were dependent upon the operators skill and attention devoted to the lapping operation. Moreover, lapping times could be extensive or relatively short, and the lost time, added expense incident to such .lost time, and the questionable accuracy obtained has caused many gear manufacturers to abandon lapping as a finishing procedure in gear manufacture.

The primary object of the present invention is to eliminate the uncertainties incident in the art of gear lapping. A further object of the invention is to transform gear lapping from an art to a science.

A still further object of the invention is to provide a machine for lapping gears under predetermined pressure between the mating gear and pinion and stopping such flapping action when the desired center distance between j the gear-set is reached.

A still further object of the invention is to rely upon L a controllable fluid pressure to apply the desired constant predetermined pressure between the pinion and the gear being lapped.

A still further object of the invention is to provide a "machine of the character set forth which will provide an inspection medium for checking any pitch line run-out detail.

Patented May 12, 1959 Figure 1 is a top plan view of a machine embodying the invention.

Fig. 2 is a side elevational view of the machine shown in Fig. 1.

Fig. 3 is a partial top plan view, on an enlarged scale, of the pinion mounting and pressure-applying means therefor.

Fig. 4 is a side elevational view of the parts illustrated in Fig. 3.

Figs. 5 and 6 show views corresponding respectively to Figs. 3 and 4, of another embodiment of the invention.

Referring first to Figs. 1 to 4 of the drawings, the reference numeral 10 indicates a machine bed having transverse ways 11, upon which are mounted a pair of spaced pedestal bearings or center heads 12 and 13 adapted to be adjustably positioned by pinion-operable means 15 and to be clamped to said bed by conventional means such as locking bolts 14 and 16. Also formed on said bed 10 is a pair of longitudinally-extending ways 17, 18, upon which is slidably movable a saddle 19 operable by a saddle screw 20 controlled by a hand wheel 21.

The pedestal heads 12 and 13 are herein shown fitted with centers 22 and 23, respectively, adapted to rotatably support a shaft 24 upon which is mounted a gear 25 to be lapped. It will be obvious, however, that the gear, on its journals, may be mounted in the pedestal heads.

The saddle 19 is formed with transverse ways 26 upon which are mounted a pair of pedestal bearings, or center heads 27 and 28 which are adjustable toward and away from each other by pinion-operable means 29 and adapted to be secured to said ways by locking bolts 30 and 31. Also formed on the saddle 19 is a transverse way 32 upon which a drive motor 33 is adjustably mounted. The pedestal heads 27 and 28 as herein shown are provided with centers 34 and 35, respectively, adapted to rotatably support a shaft 36 upon which a pinion 37 is mounted. As in the case of the gear 26, the pinion 37 may be mounted in the pedestal heads on its journals.

The pedestal heads 27 and 28 are substantially the same and only one of said heads will be described in Each pedestal head 27 and 28 consists of a lower part 38 adapted to be clamped to the saddle, and an upper pivoted or rockable head 39. The part 38 is formed with a pair of axially spaced bearings 38 and with an extended base or foot portion, which is hollowed spaced from and extending parallel to its axially spaced 'bearings, is formed with an overhanging or reentrant of ,a pinion and gear set and as an eccentricity check upon gearsets both before and after lapping.

The foregoing and other objects of the invention not specifically enumerated are accomplished by mounting a pinion on an axis which is parallel to and movable toward and away from the axis of a gear; applying a constant predetermined pressure, preferably through fluid pressure operated means, to press the pinion and gear into engagement; providing means for adjusting the desired center distance between the pinion and the gear; and providing stop means which will prevent further movement of the pinion toward the gear when the desired center distance between the pinion and gear is reached. The invention also embodies the use of instruments which will enable the pitch line run-out to be checked during and after the lapping operation.

The invention, which embodies a novel machine including the various combinations and sub-combination of parts, will be fully understood from the detailed descripition which follows, when considered in connection with I the accompanying drawings, wherein:

flange 42, the under face of which provides a stop shoulder 43 for a purpose presently to be described. The pivoted or rockable head 39 is formed with a lower central bearing portion 39 mounted on an intermediate portion of a shaft 40, the ends of which shaft are mounted in the axially spaced bearings 38 in the part 38 and with upper bearing portion 39" for supporting the center 34 and with an extended base or foot portion 44 of a width to fit within the hollowed portion 41 of part 38. The foot portion 44 is of a length to engage beneath the stop shoulder 43 on the flange 42. The base or foot portion 44 is of a thickness to have limited movement within the hollowed part 41 as the head 39 pivots or rocks about the shaft 40. Mounted in the overhanging flange 42 is an indicator 45, the contact member of which is adapted to engage the top surface of an upstanding enlargement 46 on the foot portion 44 and to register when the enlargement 46 and stop shoulder 43 are out of engagement, the amount of such disengagement. At times it may be desirable to lock the rockable head 39 against movement relative to the part 38 and, for. accomplishing this, a pair of locking screws 47-eachhaving an operating handle 48, may "be turned to engage threaded sockets 49 in the enlargement 46. The part 38 is formed with a pair of cylindrical sockets 50 extending inwardly from the bottom of the hollowed outportion 41, .and mounted in each of said sockets is a piston 51 adapted to press against the under side of the foot portion 44 tourge the top surface of the enlargement 46 into abutting relation with the stop shoulder 43 when said piston is actedupon by' fluid pressure admitted to the socket 50 from a'flu'id pressure system. As'herein shown, the fluid pressuresystem is of thehydraulic type and comprises an accumulator 52 adapted to be charged by a hand pump 53" having a .pressure gauge 54, there being a conduit 55 leading-from the-accumulator to a distributor-head 56 from which conduits 57, 58, 57 and 58 lead to the cylindrical sockets 50.

Y The pressure to be employed in'thefluid pressure system will be governed by experience and depends uponthe .size of gear tobe lapped. For each diametral pitch of gear-set that is to be lapped, a predetermined unit pressure (or desired pressure per: inch of face) will be determined For example, if it beassumed that a' 3 DP gear having a face width. of 12" is to be lapped and it has been determinedthat the most desirable unit pressure is -40 pounds, vunder these conditions the: hand pump 53 will be operated to apply pressure tliroughthe accumulator 52 to the four pistons 51 until .the pressure {gauge 54 reads 480 lbs. force, or40 12. i It will readily be seen that the pressure can .be adjusted to any predetermined unit pressure for agiven diametral pitch ofgear, times. the face width of the gear.

For. indicating the center-distance .betweenthe subject gear and the lapping gear, a scale 59'is mounted on the :bed for cooperationwith a vernier 60 mounted Hon-the saddle and with a cooperating. indicator 61. mounted on the saddle.

Operation The gear-set to be lapped, consisting or a'gear '25 and pinion 37, will be mounted on the centers, or bearings for the gear and pinion journals supported in the pedestals 1 2, '13, and."27,28, respectively, and a predetermined fluid pressure will beapplied to the pistons "'51 in thecylindrical sockets 50to force the top surface of the enlargements 46. against the stop -shoulders"43. The gear and its. mating pinion will thenbe checked [I for parallelism of journals aridface.

The, pinion "37 will then be moved toward the gear byactuatingthe saddlescrew 20 through the hand whe'el"21 until-the l indicator'45 moves slightly fromits zero reading. 'This will indicate that the gear-set is meshed with'zero back- 1 lash. The operator will 'thenread the Vernier- scale 59, 60, and determine the .amount that itis: necessary to advance the pinion toward the, gear'to obtain the "final'desired lapped gear centers. "For descriptive purpose, let it be assumed that the'gear centers of the meshed jgear'set is @010 wider than the'finally'. desired lapped centers. Knowing the amountthat the centers are in excess of desired specifications by'a certain amount, the indicator 61 can be set to this amount. The operator -will then set .the indicator 61 to read .010" plus, and

will then advance the saddle l9 through the. hand wheel "'21 and saddle screw'20 until'the indicator 61- reads zero, .at which time the scale 59,60, will read the'desir'ed lapped gear center distance. This indicator'61 is mere- 'ly a device used to allow' the operator to control his -action as he manipulates-the hand wheel 21 to advance the pinion saddle 19 and heads 27 and'28 to the desired center distances. 'In .other words, by again turning hand wheel 21.he can make the indicator'61 return" to zero by moving the pinion saddle and head assemblytoward ;the gear or away from indicator 61. "If desirablep he "can again check thevernier scale"59, '60, by walking around the 'side of the mechanism to see that theffinished Icenter distance corresponds tothe designedspecification.

enlargement 46 on the swivel head39 will abut against pressure against'the gear-set teeth, at which-time the lapping cycle is commenced, the pinion journal or-'shaft 36 being rotated bythe drive-motor 33- and-belt 63. A suitable lapping compound will, of course, be applied to the gears during'the' lapping' operation. It Will be readily seen that as material is removed from the gear and pinion by the lapping action, continuous predetermined. pressure will be applied to the geariteeth until suchwtimeasthe desired center distance is reached. Whenthe desired lapped center distance is reachedfthe the stop shoulder v43, preventing any further advancement of. the pinion toward the. gear, thus removingthe predetermined. lapping pressure. 'When this occurs, the

lapping machine may be shut down.

'The indicator 45may also serve to check any pitch line run-out in the gear and the pinion and will serve asan eccentricity checkof gear-sets, both before and after. lap.-

. ping, without the necessity of a separate set-up in acheck- -ing machine for. this purpose.

Pitch line run-out will be -shown:-on. indicator 45, which, if there ispitch line runout, should-fluctuate to about twice the amount ofithe pitch: line run-outat-the start-and can beobserve'd atfthe .'discretion.of the operator.

It is obvious that the. lapping will .undoubtedly follow and perpetuatev the pitch line run-out until the end of the lapping cycle, when the proper center distance is being approached, at which time the enfluid pressure force to be transmitted to the pinion andgear largement 46 on the head 39 will contact the stop shoulder 43 which will absorb the force exerted by thefluidpressure mechanism. If there is pitch line run-out, thestop will be contacted during the time that the pitchline is low, removing the force between the lapping gear and subject gear. When the pitch line run-out becomes high, the-pressure between the subject gear and the lappingv gear will separate the enlargement 46 from the stop, causing'the in mesh. This forces the gear to lap and removev metal at the high pointnon the pitch' line run-out-whilethe tendency to remove metal at the low point will be reduced to near zero. During this time there will be a continued period where the fluctuations in indicator 45,approa'ch' a condition of longerand longer periods of no fluctuation.

.Assoon as the needle on the indicator 45 ceases to fluctuate, the lapping cycle has been completed, the, gears may be cleaned of lapping compound, the fluid pressure can be reduced andthe-saddle advanced an additional few'thousandths, so that the gears may run together and a pitch line line run-out check made of the finished lappedgears. At this point it would be necessary for the operator to continuously observe the indicator 45.

In-the embodiment of the invention shown in Figs. 5 and 6 the pivot shafts 40a for the right and left side of the pinion have been lowered and incorporated in a H single pedestal bearing, or center head'27A in whicli the 58 of'Figs. l to 4. part pedestal 27Ais formed with transverse ways 64 on top surface of the enlargement 46a which controls'the maximum rotation about the pivot shaft 40a has been -moved to act against a shoulder stop 43a formed on the saddle 19. "The lock 47a and locking handle-48a and theindicator 45a have been moved correspondingly. In this embodiment the-saddle 19 is formed with cylindrical sockets 50a for the operating pistons, and conduits 55a, 57a and 58a correspond in function to the conduits 55 to The lower member 38a of thetwowhich the upper members 39a, which support the pinion,

are adjustably mounted. The difierence between this embodiment of the invention and that shown in Figs. 1 to 4 is that a strong structural member 38a which extends completely under the pinion, ties both pinion supports 39a together, requiring unitary pivoting of both said supports. This provides a means of pre-assembly of the mating gear and pinion shafts and insures maintaining parallelism between said shafts throughout the lapping cycle. The operation of this embodiment is precisely the same as that of the mechanism shown in Figs. 1 to 4, although the performance may be slightly diiferent.

In cases where the straightness of the teeth across the face has not been manufactured correctly, whereby to provide a concentration of force on one side of the contact with no contact on the other side, the procedure outlined above would, of course, apply considerably nore pressure in the contact for the same fiuid pressure as used previously for the mechanism shown in Figs. 1 to 4. This would, in efiect, produce more rapid lapping where the load is concentrated in the pinion to give additional correction more rapidly at the start of a lapping cycle, with the finish lapping similar to that accomplished by the embodiment shown in Figs. 1 to 4.

In cases where previous processing of gears has pro duced tooth straightness or helix trueness, so that true distribution is obtained from one side of the face to the opposite, then the mechanism shown in Figs. 1 to 4 would be preferable, since small advances of each pedestal will be allowed to suit the lapping requirements of the mating gear and pinion and maintain constant tooth pressure throughout the lapping cycle. This procedure is also preferable for extremely rapid lapping, wherein it is desirable to apply pressure approaching, but not exceeding, the crushing pitting strength of the gear teeth being lapped. The crushing pitting strength refers to a fatigue characteristic which results in small, inverted cones of material extracted from the gear tooth at the pitch line. This phenomenon occurs when the Hertz stress for allowable sub-surface shear is exceeded.

The embodiment shown in Figs. 5 and 6 would allow more rapid correction utilizing lower overall pressures wherein tooth straightness or helix trueness required improvement. It will thus be seen that each of the embodiments of the invention has advantages in the control of the lapping procedures in converting such procedures from an art to a science.

Although there has been shown and described two embodiments of the invention applied to the lapping of spur gears, it is to be understood the invention is applicable to helical and herringbone gears and that these specific constructions disclosed may be modified within the range of engineering skill without departing from the spirit of the invention as hereinafter defined.

What I claim is:

1. A gear lapping machine comprising a bed having supports for rotatably mounting a gear, a saddle slidable on said bed having bearing supports for rotatably mounting a pinion on an axis parallel to and movable toward and away from the axis of said gear supports, cooperating means on said saddle and said bed for indicating the center distance between a gear-set consisting of a gear and a pinion when mounted in the respective supports, cooperating means on said bed and said saddle for presetting the desired lapped center distance of a gear-set to be lapped, said pinion supports consisting of a lower part fixable on the saddle and an upper part consisting of a pair of coaxially spaced heads for supporting a pinion rockably mounted on the lower part to permit movement of the pinion supporting axis through said heads toward and away from the gear supporting axis of the gear supports, means for applying an equal predetermined constant force to each of the rockably mounted upper parts to urge the supporting axis of the pinion toward the gear supporting axis and cooperating means on the lower and upper parts of the pinion supports for limiting such rockable movement of said upper part toward the gear to the pre-setting of the desired center distance of the gearset to be lapped.

2. A gear lapping machine according to claim 1 wherein the means for applying an equal predetermined constant force against each of the rockably mounted upper parts are fluid pressure operable means.

3. A gear lapping machine according to claim 1 wherein the cooperating means on the lower and upper parts for limiting the rockable movement of the pinion comprises a base or wing portion on the upper part engageable with an overhanging flange on the lower part.

4. A gear lapping machine according to claim 1 wherein the upper heads are independently adjustable.

5. A gear lapping machine according to claim 1 wherein the lower part is formed integral with the saddle.

6. A gear lapping machine comprising a bed, bearing supports on said bed for rotatably mounting a gear, a saddle movable on said bed toward and away from said bearing supports, pedestal heads carried by said saddle and having bearing supports for rotatably mounting a pinion on an axis parallel to the axis of the bearing supports for the gear, said pedestal heads being rockable to move the bearing supports thereof toward and away from the axis of said gear bearing supports, means for maintaining a constant equal pressure on the pedestal head bearing supports transversely to the axis thereof to urge said axis toward the axis of the gear supports, means for limiting the rockable movement of said pedestal heads toward the axis of the gear supports so that said limiting position of the axis of said pinion supports is that of the pinion at the end of a lapping operation of a gear and pinion set mounted in the respective supports, cooperating indicating means on said bed and on said saddle for indicating the distance between the axes of the respective gear and pinion supports when the pinion supports are at the limit of their rockable movement toward the axis of the gear supports, and means for moving the saddle toward the gear supports a distance such that when the desired center distance of a gear-set to be lapped mounted in the supports in meshing engagement is indicated by said indicating means, the pinion supports of the pedestal heads will have been rocked back from the limiting mean an amount equal to the excess of the desired center distance of the gear-set before lapping.

References Cited in the file of this patent UNITED STATES PATENTS 1,078,570 Aichele Nov. 11, 1913 1,154,830 Alquist Sept. 28, 1915 1,697,823 Schurr Jan. 1, 1929 1,960,841 Fellows May 29, 1934 1,966,172 Jackowski July 10, 1934 2,060,803 Falk Nov. 17, 1936 2,257,989 Sykes Oct. 7, 1941 2,326,368 Kullman et 'al Aug. 10, 1943 2,385,129 Davis Sept. 18, 1945

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