US2998678A - Method and machine for grinding gears - Google Patents

Description

Sept. 5, 1961 H. D. BELOCK ET AL 2,998,678

METHOD AND MACHINE FOR GRINDING GEARS 3 Sheets-Sheet 1 Filed June '7, 1955 OWN Sept. 5, 1961 H. D. BELOCK ETAL 2,998,678

METHOD AND MACHINE FOR GRINDING GEARS Filed June 7, 1955 -35 Sheets-Sheet 2 INVENTORS flnmeyl/ aock BY Joy/v M 72am:

Sept. 5, 1961 H. D. BELOCK ET AL 2,998,578

METHOD AND MACHINE FOR GRINDING GEARS 5 Sheets-Sheet 3 Filed June 7, 1955 United States This invention relates to a method and apparatus for grinding gears. More particularly, the invention is specially applicable, although not so limited, to a gear grinder and a gear grinding method for precise finishing of plain or roughed out gear blanks that may have been heat treated for hardening and tempering.

conventionally, after gear teeth have been rough formed on a gear blank by hobbing, milling, shaping, forging or any other appropriate method, the blank is hardened and, optionally, tempered by known heat treating processes. Such processes distort the flanks of the teeth to an extent which limits the load carrying ability. The only commercially feasible method of correcting this defect and forming exact involute flanks on the teeth after hardening presently constitutes grinding the flanks of the teeth.

The usual gear grinding method now employed involves the use of a grinding wheel having its edge profile shaped in the form of a basic rack tooth which would accurately mesh with the finished gear teeth. The Wheel is rotated and, as it rotates, is rapidly reciprocated between two adjacent gear teeth on the rough blank. At the same time the blank is slowly revolved and its axis of revolution slowly bodily translated in a plane parallel to the axis of revolution of the grinding wheel in a fashion such that the pitch circle of the blank rolls, in effect, on the pitch line of the basic rack form of the grinding wheel. Thus the desired precise involute flanks of the gear teeth are ground by a generating action.

For accurate results it is usual to grind each entire flank of each tooth (a grinding of the flanks of two adjacent teeth of a gear blank is commonly referred to as a single pass and a single grinding of the flanks of all the teeth is referred to as complete pass) several, conventionally three or more, times in order to secure the desired precision and surface finish, the grinding wheel being reset to a greater depth after each complete pass. During a single pass the grinding wheel is reciprocated many times as it progressively works its way from the tip to the root of a tooth, or vice versa. After a single pass the gear axis is returned to its starting position and indexed to bring the next valley (intertooth space) into position for a single pass. Accordingly several complete passes are required, each consisting of a number of single passes equal to the number of teeth on the roughed blank.

The set up time and expensive equipment for an operation of this nature makes the price of precision gears extremely high and, indeed, the cost of single or small lots of gears is prohibitively high. Moreover due to the construction of present-day grinders great skills are called for and the use of special precision auxiliary tools such as master gears and racks, index plates, sine bars and gauge blocks many of which must be provided in sets of different sizes for different gear blanks.

It is the principal object of the present invention to provide a gear grinding apparatus and method which obviates the foregoing drawbacks.

It is a specific object of the present invention to provide a machine and process of the character described which enables a gear blank to be precisely ground to the desired dimensions and finish in but a single complete pass.

It is another specific object of the invention to provide a machine and process of the character described which atent will substantially reduce the set up time and costs, as well as operating time and costs, and thereby considerably lower the expense involved in precision gear grinding.

It is another specific object of the invention to provide a compact gear grinder of small size, nominal price, increased productivity and durable construction.

It is another specific object of the invention to provide a gear grinder whose operation is fully automatic so that lesser skills are required of an operator and one operator can handle several machines.

It is another specific object of the invention to provide a gear grinder which can be set up in a very short time without using gauge blocks and without changing master gears and racks, index plates or sine bars.

It is another specific object of the invention to provide a gear grinder the set up of which can be changed simply by shifting a few controls and replacing a few change gears, operations which obviously involve but little time.

It is another specific object of the invention to provide a gear grinder which can be utilized to produce gears for applications which formerly were considered uneconomical.

It is another specific object of the invention to provide a gear grinder having simple unique mechanisms for slowly rotating a gear blank during a single pass, for selectively varying the angular rate of rotation of the blank during a pass, for indexing the blank at the end of a single pass, and for selectively varying the indexing angle.

It is another specific object of the invention to provide a gear grinder having an electrical control circuit which renders operation of the gear grinder automatic and tool proof.

Other objects of the invention in part will be obvious and in part will be pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and series of steps which will be exemplified in the apparatus and process hereinafter described and shown in the drawings, and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings, in which is shown one of the various possible embodiments of the invention,

FIG. 1 is a perspective, partially schematic, view of a gear grinder constructed in accordance with the present invention, some of the supporting structure being removed to facilitate explanation;

FIG. 2 is an enlarged fragmentary sectional view taken sub tantially along the line 22 of FIG. 1, and being illustrative of a detail of the mechanism for selectively varying the angular rate of rotation of a gear blank during a single pass;

FIG. 3 is an enlarged fragmentary sectional view through the grinding wheel and gear blank, the same being taken in a plane including the axis of rotation of the grinding wheel and perpendicular to the axis of rotation of the gear blank;

FIG. 4 is an enlarged fragmentary sectional view taken in a vertical plane including the axis of rotation of the gear blank; and

FIG. 5 is a schematic view of the hydraulic actuating system and electrical control circuit for the gear grinder.

Referring now in detail to the drawings, the reference numeral 10 denotes a gear grinder embodying the present invention and adapted to precisely grind a roughed gear blank 12 with the aid of a grinding wheel 14 and suitable mechanisms to rapidly reciprocate the wheel transversely across the blank, to slowly roll the blank in phalsfi with the wheel, and to intermittently index the bla One important feature of the invention relates to the grinding of plural gear teeth at each single pass thereby Patented Sept. 5, 1961 to complete the grinding of the gear in one complete pass instead of several as heretofore. To this end the grinding wheel is formed to provide an edge profile constituting plural basic rack teeth spaced at intervals equal to the pitch of a basic rack of thesame diametral pitch as thegear to be. ground, the grinding. teeth having a common axis of rotation. After each single pass the gear blank is indexed, optionally through an are which subtends the number of teeth ground, but preferably through an arc subtending a lesser number ofteeth .so that there is an overlapping of the grinding operation and more accurate and better surface finishing of the. gear teeth. Precision is improved by indexing the gear only a single tooth at a time so that the final finishing. grind always will be performed by the same endmost grinding tooth. However great accuracy is comparatively diflicult to attain by this method alone for adjacent teeth on the. gear are subject to the errors of making the multiple. tooth forms on the grinding. wheel of identical shape and equal spacing to a very small tolerance.

Pursuant to a most important refinement of. the foregoing. feature of my invention these. errors are materially diminished by the edge profiling of the grinding wheel which is best shownin FIG. 3. As there is plainly seen the grinding wheel 14 which is made from suitable abrasive material has its edge profiled to provide plural (as here illustrated three) basic rack tooth forms 16, 18, 20 spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear 12 and having a common axis of rotation. The tooth forms may constitute plural properly shaped grinding wheels placed adjacent one another or a single wheel with the plural basic rack teeth forms dressed on its periphery.

To diminish errors which would arise from nonidentity of the plural tooth forms, and the costs incident to obtaining and maintaining substantial identity, in accordance with the refinement hereinbefore referred to the multiple tooth forms 16, 18, 20 on the grinding wheel 14 are of stepped heights. The innermost tooth form 20 which last engages the gear blank is of minimum diameter, i.e. minimum effective height. The. intermediate tooth form 18 is of slightly greater effective height, a typical increase in effective height being in the order of 0.0005 inch. The outermost tooth form 16 is of still greater effective height, a typical progressive increase being in the orderof 0.0015 inch. Thus the tooth forms are progressively stepped. up in stages for. an overall increase in height of 0.002 inch. It is particularly to be noted that the increase in height is provided without altering the uniform pitch of the basic rack. These increases are grossly exaggerated in FIG. 3. As shown the tooth forms are of identical contour but their bases. are at progressively increased radial distances from the axis of rotation of the grinding wheel. However it is within the purview of the invention to employ tooth forms with their bases at.

the same distance from said axis but of progressively greater height as indicated and progressively slightly greater width.

The gear blank 12 has been preliminarily roughed, eg by shaping or hobbing, to oversize dimensions while still comparatively soft and thereafter heat treated to a greater hardness whereby to increase its strength and surface endurance limit. Such treatment, if the gear were finished to its ultimate shape and dimensions, would distort the involute surfaces and thus materially reduce load carrying ability and efliciency. The gear grinder brings the blank down to its desired accurate dimensions and shape.

The gear blank is securely clamped on a mandrel 22 which extends through the central opening in the gear. It will be observed that several gears can be mounted on the mandrel to be ground in the same operation; but for simplicity the grinder will be described as operating on but a single gear. A group of successive teeth 24, 26, 28, 30, 32 are shown on the gear blank 12 in FIG. 3, said teeth defining valleys 34, 36, 38, 40, 42.

Pursuant to the present invention the grinding wheel is spun about an axis parallel to the plane of FIG. 3, and at the same time is rapidly reciprocated in a direction perpendicular to said plane, such direction being parallel to the longitudinal axis of the mandrel in the set up shown. While the grinding wheel is thus turning and reciprocating, the gear blank is given a compound movement. This consists of a slow rotation of the blank about the longitudinal axis of the mandrel as indicated by the arrow 44 (counterclockwise as seen in FIG. 3), and a slow translation of the blank toward the eflectively shortest tooth form 20 as indicated by the arrow 46 (toward the right as seen in FIG. 3). The total effect of these two movements is to impart a rolling motion to the gear which is such that the pitch circle 48 of the blank rolls without slipping on the pitch line 50 of the basic rack form represented by the effectively longest tooth form 16.

It will be seen that each of the grinding tooth forms will generate by grinding involute surfaces on the flanks of teeth defining the valley through which that form passes. As shown in FIG. 3, the tooth form 16 will grind the flanks of the teeth 28, 30 on opposite sides of the valley 40 early in the single pass represented by said figure. The tooth form 18 will grind the flanks of the teeth 26, 28 on opposite sides of the valley 38 later in the pass. the two grinding operations being overlapped. The tooth form 20 will grind the flanks of the teeth 24, 26 on opposite sides of the valley 36 still later in the pass, the second and third grinding operations likewise being overlapped.

'I he effectively shortest tooth form 20 will perform a rough grinding operation. The eltectively medium height tooth form will perform a semi-finishing grinding operation and, as soon will be seen, it operates on flanks which previously have been rough ground. The effectively tallesttooth form will perform a finishing grinding operation and, as soon will be seen, it operates on flanks which previously have been semi-finished ground.

After a single pass the grinding wheel is shifted to an out-of-the way position where it remains while the gear blank experiences a reverse compound movement constituting a reverse translation indicated by the arrow 52 and a reverse rotation indicated by the arrow 54. In other words the blank rolls back, being thus moved to its original starting position which is clear of the path of the grinding wheel. Prior to the roll back the blank is indexed through an are which subtends one gear tooth, the direction of indexing being opposite to the direction of rotation during roll back, i.e. as indicated by the arrow 44, whereby to advance the blank one tooth.

The next single pass is now run whereupon the effectively shortest tooth form 20 will freshly rough grind the valley 34, the middle tooth form 18 will semi-finish grind the previously rough ground valley 36 and the effectively tallest tooth form 16 will finish grind the previously semi-finished ground valley 38. The previously finished ground valley 40 will have been indexed to the position formerly occupied, as shown in the first single pass of FIG. 3, by the valley 42 between the teeth 39, 32 where it is not touched by the grinding Wheel.

Single passes, followed by idle positioning of the grinding wheel, roll back of the blank, and indexing of the blank, are repeated until the gear blank has been completely ground (a complete pass). Desirably the complete pass may include one or a few, preferably two. more single passes than are absolutely necessary to ensure accurate shaping of the two teeth of the blank which initially were subjected to semi-finishing without rough grinding, and to finishing without rough grinding or semi-finishing.

In accordance with a further feature of the present invention the gear grinder 10 is so constructed as to impart the above-describedmotions to the grinding wheel and gear blank with comparatively simple mechanism which can be easily and quickly reset to provide different desired angular indexing movements for different numbers of teeth on a blank and to provide different desired generating ratios between the rate of blank rotation and the rate of blank translation for diiferent pitch diameters of a blank.

More specifically the grinder includes a suitably supported flat horizontal bed 56 the ends of which areprovided with open-sided parallel ways 58, 60, one of which, 60, may be undercut. A table 62 is slidable on the bed, being guided by depending shoes 64 which are matched to and engage the ways. The table is reciprocated by any standard drive, for example a rod 65 driven by a piston (not shown) sliding in a stationary hydraulic cylinder 66. For convenience, the direction of movement of the table denoted by the arrow 68 hereinafter will be referred to as in and the opposite direction of movement denoted by the arrow 70 as ou A tailstock 72 fixed to the table carries an axially shiftable dead center 74 which is locked in any set position through the medium of a handle 76. Also secured to the table and in line with the dead center is a pedestal 78 in which a hollow shaft 80 is journalled by antifriction bearings such as a pair of ball bearings 82, 84. The shaft is aligned with the dead center. A drive spindle 86 coaxial with and within the hollow shaft is journalled therein by anti-friction bearings such as ball bearings 88, 90.

The tip 92 of the drive spindle facing the dead center protrudes from the hollow shaft to fixedly receive a lathe plate 94 having the usual radial slots 96. Said tip is seated in one countersunk end 98 of the mandrel 22, the other countersunk end 100 of the mandrel receiving the tip of the dead center 74. A conventional lathe dog 102 secured to the mandrel has its crank arm 104 snugly engaged in one of the slots 96 of the lathe plate whereby the blank and drive spindle are securely interengaged for joint rotation.

The hollow shaft 80 is provided with a coaxial drum 106 on which an elongated flexible member such as a steel ribbon 108 rides. Said ribbon is not permitted to experience angular movement relative to the drum, being suitably fastened to the drum, as by an anchor pin 110, at a portion of the ribbon which during the operation of the grinder as hereinafter described remains in contact with the drum. The ribbon is trained about reversing sheaves 112, 114 on the in and out sides of the pedestal at a level beneath the axis of the hollow shaft. In addition, idler sheaves 1-16, 118 engage the ribbon between the drum and reversing sheaves to increase the arc of contact between the ribbon and drum and to suitably tension the ribbon. The rotatable supports for all the sheaves are mounted on the table but have been omitted from the drawings for the sake of simplicity. The drive for the ribbon, and consequently for the drum, will be described later.

A shallow cylindrical housing 120 is carried by the drum in axial registery with the drive spindle. Said housing encloses the last gear 122 in an indexing train 124. Said gear is fast on the drive spindle '86 and is in mesh with a pinion 126. The pinion is secured on a jack shaft 128 which is journalled in the back cover plate 130 for the housing 120. It will facilitate understanding of the operation of the grinder to interrupt the detailed description of the indexing train at this point in order to observe that if the jack shaft is held against rotation in its bearing while the drum is turned said shaft will act as a crank operating through the thus locked together pinion 126 and gear 122 to rotate the drive spindle.

The indexing train further includes a gear 132 fast on the jack shaft and meshing with a pinion 134 secured to a counter shaft 136 which for convenience may be a igned wit the dri e pindle, The bearing (not shown) for the counter shaft must be so arranged as to permit free revolution of jack shaft about the axis of the drive spindle. To this end the counter shaft bearing may be carried by the housing 120, or, as just mentioned, may be aligned with the drive spindle and carried by the table 62.

Fast on the counter shaft 136 is a first change gear 138 meshing with a second change gear 140. The second change gear is secured to a back shaft 142 the bearing for which (not shown) is carried by the housing to allow the aforementioned revolution of the jack shaft. A third change gear 144 is fixed to the back shaft and meshes with a drive pinion 146 secured to the drive shaft 148 of a hydraulic indexing motor 150. The motor likewise must permit the free revolution of the jack shaft described above and for this purpose is carried by the housing 128 in the grinder shown.

The last change gear 144 carries a fixed abutment dog 152 arranged to be engaged by an anchoring latch 154. The latter (see FIG. 1) constitutes one end of a latching lever 156 which rocks on a spindle 158 that moves With the housing 120. The latch is biased by a spring 160 into engagement with the dog. The opposite end of the latching lever is connected by a pivot pin 162 to the movable core 164 of an indexing solenoid 166. The spring is anchored to and the solenoid is mounted on a structural element (not shown) carried by the housing 120.

It now will be appreciated that when the ribbon 108 is shifted to turn the drum, the ensuing angular movement of the housing 120 relative to the table 62 is followed by lthe jack shaft, the counter shaft and the back shaft (as well as the gear fixed thereto), the motor drive shaft, the latching lever, the biasing spring and the indexing solenoid, the elements of the indexing train being locked against relative movement by the dog 152 pressing against the latching lever.

The change gears are so selected that an integral number of revolutions of the drive pinion 146 will rotate the gear 122 through an are which subtends the pitch distance of a single tooth on the gear being ground. It may be mentioned here that although highly satisfactory operation is secured by picking the change gears to secure the desired rotation of the gear 122 with but a single rvolution of the drive pinion, more precise operation is obtained by what is designated herein as multiple indexing, pursuant to which the drive pinion turns through plural revolutions for each indexing operation and a high step down ratio is procured in the change gear train, thus reducing gear transmission error.

In accordance with the invention means is provided for shifting the ribbon 108 and thereby rotating the housing 120, said means being variably settable to readily and quickly secure any desired rate of rotation of the drive spindle relative to the rate of movement of the table 62 across the bed 58. Said means quite simply comprises a ratio slide bar 168 having three points thereon of which at least one is selectively variably positionable axially of the bar. One of said points is con nected to the ribbon, a second point is connected to the table and a third point is connected to ground, eg to the bed. The connections are such as to permit rocking of the bar as a lever about one point with the other two points moving in parallel paths and the ribbon point shifting in a proper direction to turn the housing 120 in the desired manner.

More specifically, and as shown in the drawings, the ribbon 108 is secured by an anchor pin 170 to a first slide block 172 that is axially self-shiftable along the ratio bar 168 adjacent an end thereof. The block is mounted for vertical rotation on a second slide block 174 that is captively reciprocable in a way 176 in the table parallel to the bed ways 58, 60.

At a point intermediate its ends said bar is secured on'a post 178 that is mounted for vertical rotation in a bearing 180 01.1 the table 62, Since the bearing is car- 7 ried by the table it is movable therewith parallel to the first slide block as the table shifts back and forth across the bed.

The third point constitutes a second slide block 182 that is axially selectively shiftable and self-shiftable along the ratio bar. Said block 182 is secured to a vertical pin 184 that is journalled for rotation about a vertical axis in a follower 186. The follower is formed with a female thread that meshes with a lead screw 188 extending perpendicular to the direction of reciprocation of the table 62. Suitable bearings, such as the bearing 190, mount the ends of the lead screw on the bed 56 for rotation about a horizontal axis. The follower 186 moves a dovetail shoe 192 slidable in a matching way 194 formed in the bed and extending parallel to the lead screw. Thus the position of the second slide block 182 along the bar with relation to the positions of the post 178 and the first slide block 172 can be varied by turning the lead screw 188.

In order to precisely position the second slide block and thereby establish any involute form desired, rotation of the lead screw is placed under the control of a dial group 196 mounted on an end of the lead screw projecting from the gear grinder. As is well known one turn of the handle 198 of the dial group rotates the lead screw through one full turn. Fractions of a single revolution are indicated on a drum 200 and the number of revolutions from an extreme position is indicated on a drum 202.

It now will be seen that reciprocation of the table and corresponding reciprocation of the ratio bar post 178 will rock the lever 168 about the slidable fulcrum provided by the second slide block 182 and cause a settable proportional reciprocation of the first slide block 172, the actual proportion being determined by the location of the follower 186. Obviously movement of the first slide block 172 shifts the ribbon 108 and turns the drum 106. Since during in movement of the table 62, as soon will be seen, the indexing train is locked and the jack shaft held against rotation, the drive spindle 86 will be slowly turned as it is reciprocated with the table 62, the speed of turning being determined by the location of follower 186. Inasmuch as the position of the follower 186 can be varied rapidly and precisely by turning the lead screw 188 it will be appreciated that the phase of setting up the grinder relating to the generating ratio requires no tools and little skill. and yet can be carried out exactly and speedily.

A single grinding pass during which the tooth flanks of three consecutive valleys of the gear blank are respectively finished ground, semi-finished ground and rough ground takes place on the in movement of the table. On the reverse, i.e. out movement of the table the gear blank is rolled back to its idle position clear of the grinding wheel. During out movement or at the end of in movement the solenoid 166 is energized to disengage the latch 154 from the dog 152. This permits the indexing motor 150, which constantly is energized as long as the grinder is in operation, to actuate the indexing train. The solenoid 166 is maintained energized by a conventional timing device until the change gear 144 has turned through the required number of revolutions (less a substantial fraction of a revolution) to advance the gear blank one tooth as described above. The solenoid is then deenergized, allowing the change gear 144 to stop when the dog 152 meets the latch 154.

To prevent back lash in the driving connection between the pinion 126 and the gear 122-during the transition from indexing to roll out and from roll out to roll in means is included to fix the gear 122 to the housing 120 against any movement relative thereto except such as is brought about by the indexing motor. Said means includes an annular friction shoe 204 loaded by axially directed coil (helical) springs 206 from the cover 130 and strongly pressed by said springs against a face of the gear 122. The ensuing friction slip coupling provides the connection between the housing and drive spindle during roll out and roll in, being automatically reset at each indexing operation when the friction shoe takes on a new angular orientation with respect to the gear 122.

The grinding wheel 14 is carried on a shaft 208 of an electric motor 210 secured to a head 211 which is suspended from a plate 212 by a dovetail tongue 214 on the frame slidable in a dovetail slot 216 in the underside of the plate 212. A hydraulic cylinder 220 carried by the plate 212 reciprocates the grinding head 211 parallel to the slot 204 by means of a piston rod 218.

The plate 212 is carried on a heavy vertical pin 222 journalled in a bracket 224 whereby to permit selection of any desired angular position of the grinding shaft 208 relative to the mandrel 22. A perpendicular relationship is employed for the grinding of spur gears and various angular relationships for helical gears.

The bracket 224 is guided by conventional means (not shown) for vertical movement relative to a standard 226 and is adjustable along the same by a lead screw 228 in mesh with a vertical tapped opening in the bracket, said screw being under the control of a hand wheel 230.

The foregoing description embraces the mechanical elements of the machine employed in obtaining the proper relative movements for gear grinding in accordance with the present invention. The machine as thus far described is fully capable under manual control of performing accurate and rapid grinding and simple and speedy set ups for different grinding operations. However, pursuant to an ancillary feature of the invention an electric circuit is provided which automatically will bring about the proper sequence of operations of the hydraulic cylinders 66, 220 for effecting a single grinding pass, and furthermore will bring about the proper operational sequence of said cylinders and of the indexing solenoid 166 for effecting successive single passes and proper indexing until a complete grinding pass has been performed.

The power for control and operation of the sundry drives is taken from a three phase four wire system consisting of three supply buses 232, 234, 236 and a neutral bus 238. The three supply buses furnish driving power and the supply bus 232 and neutral bus furnish control power.

To start the grinder a push button 240 of a normally open switch 242 is depressed whereby to energize a drive relay 244/4. For convenience, the reference numbers of all relays will be followed by a diagonal line and another number which indicates the number of contacts controlled by that relay; each contact will be denoted by the number of its controlling relay followed by a hyphen and the identifying number for that contact. Thus the relay 244/4 has four contacts 244-1, 2442, 2443 and 2444.

The circuit for the actuating coil of the drive relay runs from the supply bus 232 to the neutral bus through a normally closed contact 2461 of a control power relay 246/3, the normally open power starting switch 242, a normally closed power cut-ofi? switch 248 and the actuating coil of the drive relay. Actuation of the relay 244/4 closes its contacts, all of which are normally open. Three contacts 2442, 244-3, 2444 are power contacts in the energizing circuit for an electric motor 250 which drives a pump (not shown) that supplies liquid under pressure for operation of the hydraulic indexing motor and the hydraulic cylinders 66, 220. Thus when the button 240 is depressed the pump motor is started. The back contact 246-1 is included in the initial energizing circuit controlled by the pump start button to prevent the pump from being started except when all other elements are stationary, as they will be when no power is supplied to the control circuit. The purpose of the power cut out switch 248 is obvious.

Normally open contact 2441 is a stick contact for maintaining relay 244/4 actuated after its initial energization so that button 240 can be released. Said contact 9 shunts the series connected back contact 246-1 and switch 242.

The next step is to depress a push button 252 which closes a normally open switch 254 and this supplies power to a grinder wheel relay 256/ through said switch 254, a normally closed power out 01f switch 258 and a normally closed back contact 260-1 of a brake relay 260/4. One normally open contact 256-1 is a stick contact which shunts the switch 254 to maintain the relay 256/5 energized after the push button 252 is released. Three normally open contacts 256-2, 256-3, 256-4 supply power to the grinder motor 210 when the relay 256/5 is energized. The fifth contact 256-5 is a normally closed, i.e. back, contact, and is in the circuit for the brake relay 260/4. Thus momentary depression of the grinder start button will set the grinder motor in operation providing that the braking circuit for said motor is not effective so that back contact 260-1 is closed.

Although braking of the grinding wheel motor is not the next normal operation, it most conveniently is described at this point. Depressing a push button 262 closes a normally open braking switch 264 that energizes the braking relay 260/4 through back contact 256-5 (preventing energization of the braking relay unless the grinding motor power cut ofi switch 258 previously has been depressed to deenergize relay 256/5 and open contacts 256-2, 256-3, 256-4). When the braking relay is actuated its normally open contacts 260-2, 260-3, 260-4 will be closed to feed power to drive the grinding wheel motor in reverse. Said power is fed through resistors 266 to cut the current thus supplied to the motor to approximately full load value and will bring the motor to a stop under visual control in about three to five seconds. It will be noted that no stick circuit is provided for the braking button so that the grinding wheel cannot inadvertently be operated in reverse.

The third step is to depress a push button 268 which closes a normally open control power switch 270 that energizes the relay 246/3 through a normally closed cut off switch 272. The switch 270 needs to be closed only momentarily since the relay 246/3 is locked in operation by the normally open stick contact 246-2 which shunts said switch 270. Actuation of the relay 246/3 completes the preparatory steps necessary to ready the gear grinder for production. When said relay is energized it closes normally open contact 246-3 which places power on a relay control bus 274 and a solenoid control bus 276. Energization of bus 274 lights indicator lamps 278, 280 through branch circuits soon to be described, thereby denoting to the operator that a counter 282/ 3 which totalizes the number of single passes for a predetermined complete pass and a counter 284/3 which totalizes the number of single passes between wheel dressing operations have been deenergized. Energization of bus 274 also activates a solenoid 286 which speeds up any motion undertaken by the grinding head 211. Energization of bus 276 shifts the grinder head to its extreme in position (sometimes hereinafter referred to as dwell). Dwell also denotes the extreme out position of the table.

The grinding head dwell position is to the right as seen in FIG. 1 and in this position the grinding wheel is clear of the gear blank. The extreme in position of the table 62 is at the end of the in travel denoted by the arrow 68. For convenience, movement of either the grinding head or table away from extreme in position will be denoted hereinafter as outward movement and the limit of outward movement as the out position.

To better understand the operation of the control circuit, it is best now to interrupt the description thereof in order to refer to five switches that are operated by the table, and grinding head, a single manually controlled 10 switch, the two counters and the valve controls for the hydraulic cylinders 66, 220.

There are three switches 288, 290, 292 operated by the table 62.

The switch 288 is a flipflop single pole double throw switch having an A and a B position, either of which it will maintain when so placed. Said switch is shown in FIG. 1 where it will be seen that it is mounted on the bed 56 and has an actuating element 294 adapted to be contacted by either of two adjustable cams 296, 298 on the table. The cam 296 throws the switch to B position to determine the limit of out travel of the table. The cam 298 throws said switch to A position to determine the limit of in travel of the table.

The switch 290 is a normally closed momentary switch mounted on the bed 56 and arranged to have its actuating element 300 operated by a carn302 adjustably mounted on the table. Said cam is positioned to hold the switch open in out position of the table and to release it to closed position after the table has moved a short distance, e.g. A inward.

The switch 292, like the switch 288, is a flip-flop single pole double throw switch having an A and a B position. Said switch is mounted on the bed 56 and has an actuating element 304 adapted to be contacted by either of two cams 306, 308 adjustably carried by the table. The cam 308 throws the switch 292 to A position a short time, eg one second, after the switch 288 is thrown to A position. The cam 306 throws the switch 292 to B position concurrently with the switch 288.

It will be seen now that the switches 288, 292 are in A position during outward (idle, i.e. roll bac movement of the table and in B position during inward (grinding) movement of the table, assuming A position as they reach the extreme inward limit of table travel.

There are two switches 310, 31-2 operated by the grinding head 2171. Both of these switches are of single pole double throw construction, being spring-loaded to one contact, herein called the C contact, and away from the other contact, herein called the D contact. Both said switches are snap and hence fast acting.

The switch 310 is mounted on the plate 212 and is shifted from C contact to D contact by engagement of its actuating element 318 with a cam 316 carried by the grinding head. This engagement determines the right hand (dwell) position of the grinding head during the reciprocating action. The other switch 312 also is mounted on the plate and is shifted from C contact to D contact by engagement of its actuating element 314 with a cam 317 to determine the outward position of the head. The actuating element of switch 312 also is engaged by cam 316 in dwell position of the head.

All the machine actuated switches 288, 290, 292, 310, 312 are shown in the circuit in the position they occupy when the table and head are in dwell position.

A flip-flop single pole double throw switch 320 is manually controlled by the operator and is positioned for automatic operation of the grinder against an E contact. The switch is thrown to close an F contact when selected movements of the machine are to be slowly run under manual control, an operation herein referred to as inching.

The two counters 282/3 and 284/3 are of like construction. Each includes an actuating coil which controls two normally open contacts 282-1, 282-2 and 284-1, 284-2 as well as a normally closed contact 282-3, 284-3. Each counter further includes a counting coil 282CL, 284CL. Each counter has a conventional settable counting mechanism (not shown) which when a preset count has been reached deenergizes the associated actuating coil. The counting mechanism further comprises a standard arrangement for maintaining the actuating coil deenergized; however said arrangement permits reenergization of the actuating coil when the counting mechanism has been manually turned back to zero,

Each hydraulic cylinder 66, 220 is similarly governed. Accordingly only the controls for one of them, the grinding head cylinder, is shown in FIG. 1 and will be described.

A conduit 322 connects one end of the head cylinder 220 to a two position valve 324. The valve is biased to one position. In said one position the conduit 322 is connected to a conduit 326 that runs to a valve 328 with a variably settable restricted opening. The valve 328 is connected to a drain 330. In its other position the valve 324 connects the conduit 322 to a high pressure line 332 supplied by the pump (not shown) that is run by the motor 250.

In like manner a conduit 334 connects the other end of the head cylinder to a valve 336 that selectively is connected either to the drain valve 328 or to the high pressure line 332. The valve 336 is biased to its drain position.

To distinguish between the valves for the table and head, the table valves will be denoted by T and the head valves by H. If valve 324T is actuated the table will slowly move toward its extreme in position. If valve 336T is actuated the table will move toward its extreme out position. Similarly, actuation of the valve 324H moves the head in and actuation of the valve 336H moves the head out.

The hydraulic circuit only for the head cylinder includes a by-pass 338 shunting the restricted flow valve 328. A valve 340 movable between fully open and fully closed positions is inserted in the by-pass so that when the valve is closed the grinding head only can move slowly and when it is open the head will move rapidly. The valve 340 is biased to closed position.

Resuming the description of the control circuit, it will be recalled that the last action mentioned was depression of the push button 268 to apply power to the relay control bus 274 and the solenoid control bus 276.

When the relay bus 274 is live but the actuating coils of the counters 282/3, 284/3 still are deenergized the lamps 278, 280 will be energized through branch circuits including the normally closed counter back contacts 282-3, 2843, respectively, thus indicating that the counters are deenergized.

Applying power to the relay bus with the switch 320 in automatic position against the E contact energizes the solenoid 286 which actuates by-pass valve 340 so that any movement of the grinding head will be rapid.

Applying power to the solenoid control bus 276 energizes a solenoid 342 that controls head in valve 3241i and also energizesa solenoid 344 that controls table out valve 336T. It will be noted that the branch circuits for these valves include two normally closed control relay contacts hereinafter described. At this moment in starting up the machine no control relays have been energized so that the table will move to its out (dwell) position and the head will move to its in (dwell) position, the head moving at high speed.

The next steps are to put gear blanks on the mandrel 22, to place the proper grinding wheel on the shaft 208; to manually phase the rack forms of the grinding wheel with the rough-preformed gear blanks; to set the grinding wheel to proper depth; and to set the shaft 208 at the desired angle to the mandrel. The counters are turned back to zero thus readying their actuating coils for energization and desired total counts are set into them. The total count for the counter 282/3 is the number of single passes in a complete pass and the total count for the counter 284/3 is the number of single passes before the grinding wheel needs to be dressed.

Now a grind" push button 346 is depressed to start the automatic operation of the machine. Said push button closes an energizing circuit for a relay 348/3 from a motor terminal of the grinding motor 210 to the neutral bus. This live part of the circuit is chosen for the particular relay to ensure that translation of the 12 grinding head and table is not commenced with the grinding wheel stationary.

The contacts 348--1, 348--2 of grind relay 348/3 are in the branch circuits for the counter actuating coils 282/ 3, 284/3, respectively so that the counters thereupon are energized. Said contacts 3481, 3482 are shunted by normally open counter stick contacts 282-1, 284---1, respectively, whereby when button 346 is released and relay 348/2 deenergized the counter actuating coils are maintained energized. The counter branch circuits also include normally closed push button reset switches 350, 352.

Energizing the counters closes counter contacts 282- 2, 2842 to put power on automatic control sub-bus 354.

At this time the table is in its out (dwell) position and the head is in its dwell (right hand) position so that switches 288, 292 are in B position, switch 290 is held open, and switches 3 10, 312 are held in D position. An inspection-dwell relay 356/2 whose function and operation are described'hereinafter is idle so that its back contacts 3561, 3562 are closed.

The back contact 356-1 energizes a relay 358/3 through the B contact of table switch 292. This opens a normally closed contact 3582 in the energizing circuit for the table out (roll back) solenoid 344 and concurrently closes a normally open contact 3581 in the energizing circuit for the table in (grind) solenoid 360 which controls valve 324T and admits liquid under high pressure to the proper end of cylinder 66 to drive the table in, the other end of the cylinder now being connected to drain through restricted valve 328T. Thus the table starts to move in slowly and will continue to so move until it shifts flip-flop switch 292 to A position, opening relay 358/3 and reversing actuation of the sole noids 344, 360 whereby to start the table moving slowly back to out position. This in and out movement of the table is repeated as long as power is on bus 354 and relay 356/2 is idle.

The back contact 3562 brings power to table switch 288 which controls movement of the grinder head but since initially the switch 288 is in B position and the switch 290 is held in open position no action will occur. However after the table has moved (because of energization of relay 358/3) about one-quarter of an inch inward, switch 290 is permitted to close. This enables the table to get under way before rapid reciprocation of the grinder head starts. Now power flows through 28813, 290, 312D (which is actuated in the in position of the head) a relay 360/1 and 310D (which is actuated because the head at the moment is in in position). Actuation of relay 360/1 closes normally open contact 360-1 to energize a relay 3623 through 310D. A normally closed back contact 3623 in the energizing circuit for head in solenoid 342 thereupon opens and a normally open contact 362-2 closes in the energizing circuit for a solenoid 364 which controls head out valve 336H thereby causing the head to move away from dwell position. It will be recalled that this movement of the head 15 rapid since bypass valve 340 is open. As the head moves away from dwell, switches 310, 312 spring back to C position opening the initial energizing circuit for relays 360/1, 362/3; but a stick circuit for relay 362/3 is provided by the contact 3621 which shunts switch 310 and the contact 312C which shunts now open contact 360-1 so that the head continues to move out.

Eventually the head reaches the limit of outward travel and causes the switch 312 to be shifted to D position. This deenergizes 362/3 and opens the stick circuit through 362--1 for relay 362/3 so as to hold out relay 362/3 even when switch 312 returns to C position upon reversal of the head. When relay 362/3 opens, contact 362-2 will revert to its normally open position, deencrgizing head out solenoid 364, and contact 362-3 will revert to its normally closed position, energizing head in solenoid 13 344, thereby causing the grinder head to move in at high speed. Thus the head will rapidly shift in and out so long as switch 288 is in B position (the table is moving from extreme out to extreme in position) and switch 290 is closed (the table has moved a short distance away from extreme out position).

When the table nears its extreme in position (about a second before switch 292 is shifted from B to A position) switch 288 will be shifted from A to B position. This only affects movement of the grinder head. It opens the circuit for relays 360/1, 362/3, regardless of the position of the head whereby to energize head in solenoid 342 so that shortly before the table has reached its extreme in position and the gear blank is clear of the grinding wheel the grinding head will move to dwell and will stay there until the table has moved back to out position and then far enough in to release switch 290.

With the switch 288 in A position a make-ready indexing relay 366/1 is energized through contact 312D, relay 360/1 and contact 310D since the head is in dwell position. It may be noted that relay 366/1 is a high resistance relay so that it does not permit a suflicient flow of current to energize relay 360/1. Subsequently when the table reaches its extreme in position and starts the return out (roll back) movement switch 292 is shifted to A position and power flows through the previously closed normally open contact 3661, through a normally closed back contact 368 -1 of a time delay relay 368/1 and through an indexing relay 370/1 to energize the latter. A normally open contact 3701 thereupon closes to actuate indexing solenoid 166 and thus release abut ment dog 152 so that the indexing motor starts turning the last change gear 144.

At the same instant that the relay 370/1 is energized power starts to flow through a conventional adjustable time delay device 372 and the time delay relay 368/1. The device 372 is adjusted to permit sufficient power flow to take place after a predetermined time to energize the relay 368/ 1. This time is computed as sufficient to allow the gear 144 to make the requisite number of turns, less a fraction of a turn. When relay 368/1 energizes it opens its back contact 3681 in the energizing circuit for the indexing relay 370/1 which upon deenergization cuts out the indexing solenoid and causes the anchoring latch 154 to arrest the dog 152 at the end of a full revolution of the gear 144. Thus the drive spindle 86 and gear blank are indexed while the grinder head is in dwell position and during out movement of the table (roll back of the gear blank).

When table actuated switch 292 is shifted to A position as the table reaches its extreme in position the branch circuits for counting coils 282CL, 284CL are actuated to advance the counters by one'each toward their total counts.

It will be seen that the counting coils are not protected by the made-ready contact 366-1 since no damage will be done if the counting takes place before the grinder head is returned to dwell, although obviously the same does not hold true should the grinding head be shifting during indexing.

After a total count is reached on either counter, the associated actuating coil will be deenergized. This will open one of the contacts 2822 or 2842 to remove power from the automatic control sub bus 354 so that relays 362/3, 358/3 are deenergized causing solenoids 342, 344 to become actuated whereby the head and table will be moved to their dwell (table ou and head in) positions awaiting the operator. The operator by looking at the lamps 278, 280 can tell which total count has been reached and take appropriate action.

If the operator desires to inspect the work on the grinding wheel at any time except when the relay 348/3 is energized, he presses inspect-dwell push button 373 closing a circuit through a relay 374/2. The relay is kept energized upon release of the button by a by-pass circuit through a normally open stick contact 374-1. Energization of the relay 374/2 also closes a normally open contact 3742 to complete an energizing circuit for the inspection dwell relay 356/2. Actuation of the latter relay causes its normally closed contacts 3561, 3562 to open the circuits of switches 292, 288, respectively, whereby the solenoids 342, 344 are energized to shift the table and head to dwell positions. The back contact 3483 opens the inspection-dwell circuit when the grind button 346 is pressed. An indicator lamp 376 tells the operator when the machine is in inspectiondwell condition.

Upon occasion it is desirable to inch the table or head in or out. The grinder is readied for inching by throwing flip-flop switch 320 from its E (automatic) position to its F (inching) position. This deenergizes solenoid 286 and closes by-pass valve 340 so that further motion of the head will be slow. In its F position switch 320 energizes relay 378/8. Said relay has four normally closed contacts 378-1, 378-2, 378-3, 378-4 in the energizing circuits for the head and table in and out solenoids 342, 364, 344, 360, which circuits are under the control of the automatic reversing relays 358/3, 362/ 3. Hence the machine is taken out of automatic control when the switch 320 is moved to inching position. The relay 378/8 also has four normally open contacts 378-5, 378-6, 3787, 3788 providing alternate energizing circuits for the said solenoids 342, 364, 344, 360, respectively. These circuits further include inching push buttons 382, 384, 386, 388, respectively. Thus when an inching push button is depressed it will energize the associated valve control solenoid 342, 344, 360, or 364 to cause the table or the head slowly to move in or out as the case may be as long as the button is held depressed.

It thus will be seen that there has been provided a gear grinder which achieves the several objects of this invention and is well adapted to meet the conditions of practical use.

Since various possible embodiments might be made of the above invention, and since various possible changes might be made in the embodiment above set forth, it is to be understood that the foregoing description of the details of the grinder and the accompanying drawing have been presented only by way of illustration and are not to be construed as limitative.

Having thus described the invention there is claimed as new and desired to be secured by Letters Patent:

1. In a method of grinding a gear blank having teeth with valleys therebetween, that improvement comprising the steps of rotating a grinding wheel having an axial edge profile constituting plural basic rack tooth forms of successively different effective heights spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear blank being ground, reciprocating the grinding Wheel perpendicularly to its axis of rotation, and rolling the gear blank toward and past the effectively highest tooth form in a manner such that the pitch circle of the gear blank rolls without slipping on the pitch line of the effectively highest basic rack tooth form whereby a plurality of consecutive valleys of successively different depths are progressively generatively ground in a single repetitively transversely shifting grinding pass.

2. In a method as set forth in claim 1 that further improvement including the steps of moving the grinding wheel to a position clear of the gear blank, while the wheel is there step indexing the gear blank one valley and rolling the gear blank back to a starting position and then repeating the steps set forth in claim 1.

3. An apparatus for grinding a gear blank, said apparatus including means rolling a gear blank without slipping on a line tangent to its pitch circle, a grinding wheel having an axial edge profile constituting plural basic rack tooth forms spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear blank, the tooth forms being of successively different effective heights and having their tips successively closer to the axis of the wheel, means rapidly spinning the wheel about its axis, and means rapidly reciprocating the wheel in a direction transverse to the direction the gear blank is rolled and with the pitch line of an endmost tooth form tangent to the pitch circle of the gear blank.

4. An apparatus for grinding a gear blank, said apparatus including means rolling a gear blank without slipping on a line tangent to its pitch circle, a grinding wheel having an axial edge profile constituting plural basic rack tooth forms spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear blank, the tooth forms being of successively different elfective heights and having their tips successively closer to the axis of the wheel, means rapidly spinning the wheel about its axis, means rapidly reciprocating the wheel in a direction transverse to the direction the gear blank is rolled and with the pitch line of an endmost tooth form tangent to the pitch circle of the gear blank so as to generatively grind the blank and means for step indexing the gear blank after each grinding movement thereof a number of teeth less than the number of tooth forms on the grinding wheel.

5. An apparatus as set forth in claim 4 wherein the indexing means step indexes the gear blank only a single tooth after each rolling movement.

6. An apparatus for grinding a gear blank, said apparatus including means rolling a gear blank back and forth between two extreme positions without slipping on a line tangent to its pitch circle, a grinding wheel having an axial edge profile constituting plural basic rack tooth forms spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear blank, the tooth forms being of successively different effective heights and having their tips successively closer to the axis of the wheel, means rapidly spinning the wheel about its axis, means rapidly reciprocating the wheel between two extreme positions in a direction transverse to the direction the gear blank is rolled and with the pitch line of an endmost tooth form tangent to the pitch circle of the gear blank whereby a plurality of consecutive valleys between the teeth of the gear blank are consecutively generatively ground in a single grinding pass of the gear blank, means step indexing the gear blank after each single grinding pass, means counting the number of single grinding passes, and means responsive to a predetermined number of single grinding passes to stop the rolling means adjacent an extreme position thereof.

7. An apparatus for grinding a gear blank, said apparatus including means rolling a gear blank back and forth between two extreme positions without slipping on a line tangent to its pitch circle, a grinding wheel having an axial edge profile constituting plural basic rack tooth forms spaced at intervals equal to the pitch of a basic rack of the same diametral pitch as the gear blank, the tooth forms being of successively different effective heights and having their tips successively closer to the axis of the wheel, means rapidly spinning the wheel about its axis, means rapidly reciprocating the wheel between two extreme positions in a direction transverse to the direction the gear blank is rolled and with the pitch line of an endmost tooth form tangent to the pitch circle of the gear blank whereby a plurality of the consecutive valleys between the teeth of the gear blank are consecutively generatively ground in a single grinding pass of the gear blank, means step indexing the gear blank after each single grinding pass, means counting the number of single grinding passes, and means responsive to a predetermined number of single grinding passes to stop the rolling means and the reciprocating means adjacent an extreme position of each.

8. In a machine, a bed, a table, means mounting the table for slidable movement across the bed, a shaft, means mounting the shaft for rotation relative to the table about an axis perpendicular to the direction of movement of the table, means including an indexing change gear train to index said shaft, means to lock said train, and means responsive to slidable movement of the table for rocking the locked train.

9. In a machine, a bed, a table, means mounting the table for slidable movement across the bed, a shaft, means mounting the shaft for rotation relative to the table about an axis perpendicular to the direction of movement of the table, a drum coaxial with said shaft and rotatable with respect thereto, an indexing change gear train for indexing said shaft, said train being mounted to turn with said drum, means to lock said train, and means responsive to slidable movement of the table for rocking said drum with the train locked whereby to rock said shaft through said train independently of indexing.

10. A gear grinder comprising a frame, a member reciprocally slidable on the frame between two extreme positions, means on said member mounting a gear blank for rotation about its axis with said axis extending transversely to the direction of sliding movement of said member, a grinding head including a rotatable grinding wheel having an axis of rotation transverse to the axis of rotation of the gear blank, means mounting the grinding head on the frame for reciprocal sliding movement in a direction perpendicular to the axis of rotation of the wheel from an extreme position to an opposite extreme position, generative means responsive to sliding movement of the member in one direction for rotating the blank to impart a rolling generative motion thereto, means for reciprocating said member, means for repeatedly reciprocating said grinding head as said blank is undergoing said rolling generative motion while said member is moving in said one direction, means for maintaining said grinding head adjacent one of said extreme positions thereof as said member is moving in a direction opposite said one direction, and means for step indexing said blank, said indexing means comprising a motor, means drivingly connecting said motor to the gear blank, locking means normally preventing rotation of the motor and releasable to permit said motor to rotate, and means for slidably releasing said locking means.

11. A gear grinder as set forth in claim 10 wherein the releasing means comprises a solenoid device connected to the locking means for releasing the latter when said device is energized, a limit switch actuable in response to the member reaching one of its extreme positions, and means for energizing said solenoid device in response to actuation of said limit switch.

12. A gear grinder as set forth in claim 11 wherein the locking means comprises a movable latch element, the means drivingly connecting the indexing motor to the gear blank comprises a rotatable element drivingly connected to said gear blank and said motor, a lug mounted on said rotatable element, and spring means normally biasing said latch element into a position in engagement with said lug to prevent rotation of said rotatable element and thereby prevent rotation of said blank by said motor, said solenoid device being connected to said latch element for moving the latter out of engagement with said lug when the solenoid device is energized.

13. A gear grinder as set forth in claim 12 comprising means for automatically de-energizing the solenoid device after a predetermined time interval to allow the spring means to urge the latch element back to lug-engaging position before the rotatable element is rotated by the motor through a complete revolution.

14. A gear grinder comprising a frame, a member reciprocally slidable on the frame between two extreme positions, means on said member mounting a gear blank for rotation about its axis with said axis extending transversely tothe direction of sliding movement of said member, a grinding head including a rotatable grinding wheel having an axis of rotation transverse to the axis of rotation of the gear blank, means mounting the grinding head on the frame for reciprocal sliding movement in a direction perpendicular to the axis of rotation of the wheel from an extreme position to an opposite extreme position,

generative means responsive to sliding movement of the member in one direction for rotating the blank to impart a rolling generative motion thereto, means for reciproeating said member, means for repeatedly reciprocating said grinding head as said blank is undergoing said rolling generative motion While said member is moving in said one direction, means for maintaining said grinding head adjacent one of said extreme positions thereof as said member is moving in a direction opposite said one direction, and means for step indexing said blank, said blank mounting means comprising a rotatable spindle, means drivingly connecting the blank to said spindle, a sleeve element rotatably mounted on said spindle coaxially therewith, a gear fixed to said spindle, a shaft rotatably mounted on said sleeve element on an axis eccentric and parallel to the axis of the sleeve and spindle, a gear fixed to said shaft, said gears constituting the indexing means, the generative means comprising means for locking said gears and for rotating said sleeve element in response to movement of the member.

UNITED STATES PATENTS Drummond et a1. Apr. 13, Sears July 7, Olson Jan. 4, Hanson Aug. 30, Trbojevich May 15, Schurr Feb. 5, Colman May 7, Burgess Jan. 26, Aeppli Aug. 9, Sinderson Apr. 25 Uhlich June 26, Bullows Sept. 11, Wolf Dec. 25, Tanner Nov. 26, Anderson May 10, Flanders et a1. May 2, Emrick Dec. 26, Osplack Aug. 19, Brady Mar. 23,

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