US2133386A

US2133386A - Gear grinding machine

Info

Publication number: US2133386A
Application number: US141588A
Authority: US
Inventors: Clarence T Galloway
Original assignee: Gleason Works
Current assignee: Gleason Works
Priority date: 1937-05-10
Filing date: 1937-05-10
Publication date: 1938-10-18
Anticipated expiration: 1955-10-18

Description

Oct 18, 1938.v c. T. GALLowAY GEAR GRINDING MACHINE 8 sheets-sheet 1 Filed May lo, 1937 Gttorneg Oct. 18, 1938. c. T. GALLowAY GEAR GRINDING MACHINE Filed May l0, 1957 8 Sheets-Sheet 2 Zaire/zc@ Z662 Oct. 18, 1938.`

C. T. GALLOWAY GEAR GRINDING MACHINE Filed May lO, 1957 8 Sheets-Sheet 4 c. T. GALLowAY GEAR GRINDING MACHINE Filed May '10, 19:57

8 Sheets-Sheet 5 QE ME" Oct. 18, 1938. c. T. GALLowAY .GEAR GHINDING MACHINE Filed May lO, 1957 '8 Sheets-Sheet 6 Wai-:25'12" Jmfentor Bg a ttorneg Oct. 18, 1938. c. T. GALLowAY GEAR GRINDING MACHINE Filed May l0, 1937' nventor @zz/"eme Z @5&7

attormg C. T. GALLOWAY GEAR'GRIN'DING MACHINE Filed May l0, 1957 8 Sheets-Sheet 8 ATTORNEY IPatented Oct. 18, 1938 UNITED STATES PATENT OFFICE Clarence T. Galloway, Rochester, N.

Rochester, N. Y., a

to Gleason Works, tion of New York Application May 10, 22 Claims.

The present invention relates to machines for grinding gears and particularly to machines for grinding longitudinally curved tooth gears, such as spiral bevel and hypoid gears.

In spiral bevel and hypoid gear grinding machines in general use, a cupped grinding wheel is used as the grinding tool and this wheel is rotated on its axis and simultaneously swung back and forth to grind the tooth surfaces of the gear. When it is required to dress the wheel, the operator stops the normal working operations of the machine, the wheel-is swung beyond its working path to dressing position, the wheel carrier is unclamped and advanced an amount determined by the wear of the wheel and the amount of stock to be dressed off, then the wheel carrier' is reclamped, and the wheel is dressed, and, when the dressing operation is completed, the wheel is returned to working position and the normal operations of the machine restarted. All of the steps embraced in effecting the dressing operation and return of the wheel to working position are effected manually or through manually operated controls. The operations connected with dressing, then, take a considerable time which, in large production shops, means money.

The primary purpose of the present invention is to provide a gear grinding machine which will be fully automatic in its operation, yet but slightly more expensive in construction than machines which are only semi-automatic.

Another object of the invention is to provide a compact, inexpensive control means which may readily be applied to existing semi-automatic gear grinders to make them fully automatic.

With the present invention, a control device is provided that is directly attachable to machines now in general use so that with but slight change, these machines may operate fully automatically. The stopping of the normal working operations of the machine, the movement of the grinding wheel to dressing position, the unclamping of the wheel carrier, the advance of this carrier to compensate for wear and for the stock which is to be dressed ofi of the wheel, the reclarnping of the carrier, the dressing of the wheel, the return of the wheel to operative position vthe restarting of the normal working operation of the machine may then all be effected automatically and in proper sequence.

The control device of the present invention comprises a series of cams, all mounted on the same shaft and properly shaped and positioned to effect in the desired order, the various operations described. In the preferred embodiment oi Y., assigner Corpora- 1937, Serial No. 141,588

the invention, the cams are driven by a motor forming part of the automatic attachment. When the desired, predetermined number of working operations of the machine are completed, as, for instance, the rough-grinding of all of the teeth of a gear, the automatic stop mechanism of the machine functions to stop the normal working operations and to allow a spring to shift a valve which controls the position of the grinding wheel. When this valve is shifted, the grinding wheel is moved to dressing position and when dressing position is reached, the motor, which drives the series of control cams is started and the cycle of unclamping, advance, and reclamping of the wheel carrier, dressing of the wheel, return of the wheel to working position, and restarting of the normal Working operations are all effected automatically. The control mechanism including the drive motor therefor and the series of control cams is compactly housed and can readily be attached to existing grinding machines and the necessary hydraulic and electrical connections can easily be made so that, as stated above, an existing semi-automatic grinding machine may with but little expense be converted into a fully automatic machine.

The automatic control mechanism illustrated in the accompanying drawings is intended specifically for application to spiral bevel and hypoid gear grinding machines of the type described in the copending application of Edward W. Bullock et al., Serial No. r"51,738, filed November 6, 1934, now Patent No. 2,099,674, dated November 23, 1937.

In the drawings:

Fig. 1 is a vertical sectional view taken longitudinally through the tool end of a machine of the type illustrated in the Bullock et al. application;

Fig. 2 is a sectional view through this same '40 part of the machine, taken at right angles to the view of Fig. 1, and showing the control mechanism of the present invention in position on the machine and various other parts required in order to effect automatic operation of the machine;

Fig. 3 is a plan-view of the tool end of the machine as modified for automatic operation, the view being on a somewhat reduced scale and parts 50 being broken away for purposes of illustration;

Fig. 4 is a sectional view on the line 4--4 of Fig. 3 but on an enlarged scale;

Fig. 5 is a view of the control box and motor, parts being shown in section and broken away; 55

Fig. 6 is a section through the control box this nipple and the thrust-bearing 49 is intertaken generally on the line 6-6 of Fig. 5; posed a coil-spring 52.

Fig. 7 is a section taken generally on the line Journaled in the quill 25 with its axis inclined 1-1 of Fig. 6; to the axis of the quill is the wheel spindle 55. Fig. 8 is a fragmentary sectional View taken The cupped grinding wheel W used on the maon the line 8 8 of Fig. '7; chine is secured in any suitable manner to this Fig. 9 is a diagrammatic view showing, in despindle. The grinding wheel spindle is driven VelODmeHt, the Shapes f the paths Of the Cams from a motor (not shown) that is mounted in the which Control the automatic dleSSiIlg function; base or frame of the machine. 'Ihe drive is from Fig. 10 is a fragmentary view showing the lever the motor through a belt 51 to a pulley 58 that which Controls the position of the valve which is keyed to a hollow shaft 59 which is journaled gOVeTHS the position 0f the grinding wheel and on anti-friction bearings 60 and 6| in an endshowing, also, the means for moving this lever; plate 62 which is secured by screws 63 to the Fig. 1l is a section on the line of Fig. 3, upright or column 20,

but on an enlarged scale; Journaled on anti-friction bearings 65 and 66 in Figl2 iS a Section 011 the lille |2-|2 O'f Fig. 11,' the sleeve V30 is a shaft 6B that has telescoping, Fig. 13 is a fragmentary elevational view looksplined connection with the hollow shaft 59.

ing at the tool end of the machine; and Keyed to the shaft 68 is a bevel gear 10 that Fig. 14 is an electrical wiring diagram of the meshes with another bevel gear 1|. The latter machine. gear is keyed to a shaft 12 which is journaled on Reference will now be had to the drawings for anti-friction bearings 13 and 14 in a sleeve 15 a more detailed description of the invention. that is xedly secured in the quill 25.

designates the upright or column of a semi-auto- Keyed to the shaft 12 at its forward end is a matic gear grinder such as described in the Bulpulley 11. This pulley drives a pulley 18, which is lock et al. application above mentioned. This upsecured to the wheel spindle 55, through the right or column supports the tool mechanism of belting 19,

the grinding machine. Through the gearing just described, a rotary Slidably mounted on the upper face of this upmotion is imparted to the grinding wheel W to right or column 20 is the tool head 2|. The tool effect grinding rotation.

head 2| is formed with depending bearing mem- In a machine of the type referred to, the grindbers 22 and 24 which provide a support for an ing of the lengthwise tooth surfaces of a spiral There iS a Sleeve Secured in an opening in any suitable source of power and as it rotates the rear end of the quill 25 by screws 3|. This will impart the desired oscillating movement to sleeve is mounted for rotating and sliding movethe quill and to the grinding wheel. ment in JChe bearing 24 and aCtS to support the In the grinding of a tooth surface of the gear,

quill at S rear end. the rotating and oscillating grinding wheel is There is a ball thrust-bearing 33 mounted in fed into full depth engagement with the gear bearing and formed at its rear end with a flange ment with the gear and the gear is indexed. to which a cam-follower 35 is secured by The alternate feed and withdrawal movements lower end with a semi-cylindrical bearing, as Ordinarily, it is desirable to shown in Fig. 2, in which the sleeve 38 is mounted. which is being ground screws 4|. The sleeve 38 is held against axial eration on the nal pass. movement in its bearing by the screw 42 and Two separate cams are employed to control the dowel-pin 43. feeding movements during rough-grinding and The sleeve 38 is slidable in the sleeve 34 but is finish-grinding, respectively. These are denoted held against rotation relative to the sleeve 34 by at 90 and 9|, respectively in Fig. 1. These cams the key 44. This key engages in an elongated are adapted to be engaged selectively with the key-slot formed internally in the sleeve 34 and is follower 35 to impart the desired feed movement secured by screws to the sleeve 38. to the quill 25.

There iS a plate 45 secured to the quill 25 by The two cams are integral with one another screws 46. This plate has a forwardly projecting and are secured to a shaft 9.3 which is journaled pin or stud 41 that is journaled on an anti-fricon anti-friction bearings 94 and 95 in a sleeve tion bearing 48 in the sleeve 38. The forward 96. The sleeve 96 is axially reciprocable in the end of the stud 41 is of reduced diameter and arm or bearing member 22 in order to shift one is mounted in a thrust-bearing 49 that is slidably cam out of engagement with the follower 35 and mounted in the sleeve 38. A nipple 58 is threaded bring the other Cam into engagement therewith.

in the forward end of the sleeve 38 and between The sleeve 96 is reciprocated by actuation of 75 Zli) , according to the present invention,

' This rack meshes with a spur Athe spur pinion 98 which meshes with a rack 99 that vis integral with the sleeve 95r and is cut into the periphery thereof. In a machine constructed is actuated automatically to effect shifting of the feed cam.

When it is desired to dress the grinding wheel, it is swung beyond its working path up to dressing position. This is accomplished the piston This piston slides in a cylinder and .is secured to a piston-rod ||2 which. an adjustable threaded connection with a block H4. The block screws to a slide H5 that slides in suitable ways .formed on the outside of the cylinder There is a rack ||6 secured to this slide by screws |11. gear segment ||8 shaft 83 through the differential. already referred to (not shown). When the piston H is moved upwardly. then. the quill 25 is swung beyond its normal working path to move the grinding wheel to dressing position.

The dressing mechanism. which is indicated as a whole at .D in Fig. l. may be of any suitable character but preferably is of the same type as described in the Bullock et al. application. It is secured to the column. 20 in. proper position by T- bolts |20 and |21. (Figs. 1 and ,1.3).

The wheel head 2|. is clamped to the column 20 during grinding. but is released and advanced axially of the quill 25, prior to dressing. in order to compensate for wear ofl tbe wheel and the amount of stock to be removed from the wheel in the dressing operation. The wheel head is clamped to the column 20 by four spaced. T- bolts |22 (Fig. l) which engage .in T-slots |23 formed in the upper face of the column 20.

The stem of each T-bolt is secured to a piston |24 which slides in a bore or recess formed in the wheel head. A. coil-sprintf |25 actuates the T- bolts to released position. The T-bolts are moved to clamping position by hydraulic pressure but are constantly urged to released position by coilsprings |25 one of which is interposed between the top of each piston |24 and a corresoondiner end-plate |25 which closes the bore in which the piston reciprocates. The end-plates are secured to the wheel-head 2| by screws |21 (Fig. 3).

The positions of the pistons |24 and T-bolts |22 are controlled by a valve |30 which is reciprccably mounted in a bore |3| formed in the wheel-head. The valve |30 is normally urged upwardly to cause the T-bolts to be moved to clamping position by a coil-spring |32 which is interposed between the end of the valve and an end-plate |33. The valve has a which projects through an opening in the upper end plate |35 of the cylinder |3|. There is a lever |31 pivoted between ears formed on this upper end plate. which can be manipulated to move the valve |30 downwardly against the resistance of the spring |32. The valve |30 is connected by four ducts |38 with the lower ends of the several pistons |24 so that the four pistons |24 are moved together in the same direction when the valve is operated. The valve is connected by an exhaust duct |39 with the sump of the math'at drives the the pinion 98 chine and by a duct 201 with the automatic control mechanism as will hereinafter be described.

To advance the wheel head for dressing the wheel, a screw |40 is provided (Fig. 3). This screw is formed integral with the shaft |4| that is suitably journaled in the wheel head and it threads into a nut |42 which is secured by screws |43 to the upright or column 20.

So far as has been described, the machine illustrated is identical with the semi-automatic machine shown in the Bullock et al. application.

For the purpose of full automatic operation of the machine, a control mechanism made accord- `ing to the present invention is mounted upon the machine. This control mechanism comprises a motor |50 (Figs. 2 and 5) and a control box or cam housing upon the upper face of which, the motor` is mounted.

Journaled on anti-friction bearings |53 and |54 in the cam housing is a shaft |55 to which is keyed seven cams, numbered |51, |58, |59, |60, |6|, |62 and |03, respectively.

There is a rod |65 (Figs. 5 and 7) mounted in the housing |5| parallel with the cam shaft |55. Pivotally mounted on this rod |55 are a series of levers denoted at |61 to |1| respectively, in Fig. 6, all of which are of the same shape as the lever shown in Fig. 7. These levers |51 to |1| inclusive are mounted opposite to and cooperate with the cams |51, |59, |60, |02 and |53. respectively. There is a nose or follower |12 on each lever which engages with the periphery of the cam with which the lever is adapted to cooperate.

Secured by screws |14 to one side of the housing |5| is a valve casing |15. This casing contains the sleeves |11, |18. |19, |80 and IBI in which slide valves |81, |88, |89, |90 and |9|, respectively. Into the inner end of each of these Valves is threaded a screw or adjustable stop |93 which is adapted to engage that lever, |61, |68, |09, |10 or |1|, which is associated with the valve in order to transmit the motion of the lever to the valve.

The valve |81 controls the movement of the piston |24 (Fig. l) during the automatic operation of the machine.

Pressure fluid is supplied to the valve |81 through the duct 204 and the ports 202 in the sleeve |11. It is exhausted from the valve chamber through the ports 20| and the duct 200. The valve is connected to the valve |30 (Fig. l) through the ports 20h` in the sleeve |11 and the duct 201.

During automatic operation of the machine the manually operable valve |30 is left in its upper position to which it is normally urged by the coil spring |32. Hence the lines |30, that lead to the several pistons |24, are constantly open to the line 201 that leads to the valve |81. Hence, when the line 201 is on supply, the bolts '|22 are held in clamping position and when the line 201 is on exhaust, the bolts are moved to released position. The valve |30 is simply employed. then.. when it is desired to manually adjust the wheel n In this case, the lever |31 can be used to push the valve |30 down to put the line |38 on exhaust through the line |39 to unclamp the wheel head and permit its adjustment.

|88 controls the automatic movewheel head. The pressure fluid is supplied to the valve |88 (Fig. 6) through the duct 2|4 and the ports 2|2 in the sleeve |18. The duct 2|4 communicates with the ports 202 in the sleeve |11. The motor fluid is exhausted from the chamber of the valve |88 through the ports 2|| of the sleeve |18 and the duct 2|0 which communicates with the ports 29| of the sleeve |11. This valve |88 is connected through the ports 2|6 of the sleeve |18 and duct 2|1 with a cylinder 258 (Fig. ll).

There is a piston 220 mounted to reciprocate in this cylinder and the duct 2|1 threads into an opening formed in the end-plate 22| of this cylinder. This end plate is secured by screws 222.

which is integral with the piston 220.

are rack teeth 226 formed in one side of which is journaled on a shaft 229. Keyed to this 230 and pivotally 226 to the shaft 229.

Keyed to the inner end of the shaft 229 (Fig. 3) is a bevel pinion 234 which meshes with a bevel gear 235 that is keyed to the screw shaft 4|. Thus, as the piston 220 moves to the right to the housing 240 by screws 24|. The housing 240 is secured to a bracket 242 by screws 243 (Fig. 12). This bracket 242 (Fig. 3) is secured in turn to the Wheel head 2| by a spring-pressed key The valve |89 controls the positions of the feed-cams 90 and 9| (Fig. 1). This valve is conis exhausted |89 either through the sleeve |18. from the chamber of this valve the ports 254 and duct 255 or through the ports 256 and duct 251. 255 leads into the duct 251 and the latter duct communicates with the ports 2H of the sleeve |18.

'I'he valve |89 the sleeve |19 and the duct 26| with a cylinder 252 (Fig. 4).

through an opening in the endplate 264 of the cylinder. This end-plate is secured to the cylinder by screws 265. The opposite side of the piston 263 is connected to the valve |89 by a duct 251 which communicates With the ports 268 in the sleeve |19.

The cylinder 262 is mounted upon a bracket 210 which is secured by screws 21|, (Figs. 3 and The piston-rod 212 piston 263 carries a back and forth in the sleeve |19 by operation of the cam |60, the shaft 93 (Fig. 1) is moved axially in one direction or the other to shift the roughing and nishing feed cams 90 and 9| alternately into and out of operative position. Y

The dressing mechanism shown generally at D in Fig. 1 of the present drawings. The valves 90 and |9| (Fig. 6) control the operation of the dressing mechanism.

I'he valve |90 is connected to the source of Iluid pply through the ports 280 in the sleeve and the duct 28| which communicates with the 1n turn communicates with communicate with a a duct 286, (Fig. 7). which controls the with a duct 290 that the duct 284.

of the grinding wheel.

The valve is connected and 296 and the ducts 291 and 298, respectively, with the dressing mechanism to actuate the same in opposite directions upon movement of the valve.

The valve |9| is connected to the source of fluid supply by the ports 300 in the sleeve |8| and by the duct 30| which communicates with the ports 280 in the sleeve |80. The motive fluid is exhausted from the chamber of the valve |9| either through the ports 302 or the ports 303. The duct 304 communicates with the por's'282 in the sleeve I8 The ports 303 connect with There is a needle valve 301 by the ports 295 Vduct 306 that leads The connections are Fig. 7.

in opposite directions.

The cam shaft |55 is driven from the motor |50 (Fig. 5) through the bevel gearing 355, SI5,

with the armature shaft of the motor |53 and is suitably connected to the same. The bevel gear 3|6 is keyed to the shaft 3|1 with which the worm to the cam shaft |55.

'erally at 326.

`the solenoid 335.

A solenoid brake mechanism is provided for the motor |50. This may be of any suitable type. As shown, it comprises a solenoid 325 (Figs. 2 and 5) and a brake mechanism designated gen- This solenoid brake is so connected with the controls for starting and stopping the motor |50 that the brake mechanism is released when the motor is started and is thrown on when the moor is stopped. Its purpose is to prevent coasting of the motor drive f shaft after the power to the motor is thrown ofi.

As previously described, the grinding wheel W is moved to and from dressing position by movement of the piston (Fig. 2). The movement of the piston ||0 is controlled by a valve 330 which is co-nnected by a pin 33| (Fig. l0) with an arm 332 which is keyed to a shaft 333. There is a lever 334 keyed to the outer end of this shaft. This lever is connected at one end with When this solenoid is energized, the lever is swung clockwise about the axis of its shaft 333 to move the valve 330 to the position shown in Fig; 2. A spring-pressed plunger 336 operates on the lever at the opposite side of the shaft 333 to constantly urge the lever in a counterclockwise direction about the axis of its shaft 333.

The valve 330 slides in a sleeve 340 and is connected through radia1 ports in this sleeve with ducts 34| and 342 which lead, respectively, to opposite sides of the piston ||0. The valve 330 is connected by radial ports in the sleeve 340 and a duct 343 with the source of fluid supply and it is connected by radial ports in the sleeve 340 and by the ducts 345 and 346, respectively, with the sump of the machine to permit exhaust of the motive fluid from the valve chamber.

The solenoid 335 is so connected electrically with the feed motor of the grinding machine that when the feed motor is operating, the solenoid is energized. Hence during the grinding operation upon a gear, the solenoid is energized and the valve 330 is held in the position shown in Fig. 2. When the grinding operation is completed, the automatic stop mechanism of the machine, which may be of any usual or suitable construction and is not shown, functions not only to stop the feed motor of the machine but also to break the circuit to the solenoid 335 and thereby deenergize the solenoid.

Mounted upon a plate 350 (Fig. 2) which is secured to the guard 35| of the upright or column 20 are a pair of

limit switches

352, 353 and mounted upon .the block ||4 is a plate 351 that carries spaced trip lugs 354 and 355. The limit switch 352 controls the starting of the motor |50 (Fig. 5). The limit switch 353 controls the starting of the feed motor of the machine. These two limit switches are normally open and they are closed only when the

lugs

354 or 355 engage the arms of the switches.

There are two limit switches 360 and 36| (Fig. 5) mounted in the cam housing |5|. The limit switch 360 is operated by the cam |6l, the roller 362 carried by the arm 363 of this switch riding upon the periphery of this cam. The limit switch 36| is operated by the cam |58, the roller 365 carried by the arm 366 of this switch riding upon the periphery of this cam.

The several cams |51, |58, |59, |60, |6|, |62 and |63 are suitably shaped to effect in proper order the various functions of the mechanism of the present invention. In the grinding of all gears, it is desirable to dress the grinding wheel between the rough and finish-grinding operations so as to get a smooth tooth surface for finishgrinding. Sometimes, it is desirable, also, to dress the grinding wheel prior to rough-grinding so that the wheel will be sharp and in good condition to rough-grind. Sometimes it is desirable to make a rough-grinding operation, a semifinish grinding operation and a final finishgrinding operation in the grinding of a gear and in this event, to dress the wheel between the rough-grinding and semi-finish grinding operations and between the semi-finish grinding and final-finishing operations. The wheel may be used, then, without further dressing to roughgrind the next gear put upon the machine.

It is because of these different possible methods of operation of the machine, and stillv other methods will suggest themselves to those skilled in the art, that the two cams |62 and |63 and the two valve mechanisms cooperating therewith are provided. One cam and its valve mechanism may be used to control the dressing of the grinding Wheel prior to nish-grinding and the other cam and its valve mechanism may be employed to control the dressing of the grinding wheel prior to rough-grinding, or prior to a semifinish grinding operation. Still further, as stated above, the wheel may be dressed only prior to finish-grinding and may be used without further dressing in the succeeding rough-grinding operations. In this latter case, the wheel is dressed only once for the grinding of each gear and one cam and its valve mechanism does not function at all. This last described modification of the invention is illustrated in the drawings. For this method of operation of the machine, one of the two dressing control members, as, for instance, the member |63 will be simply a circular disc and not a cam and hence it will not impart any motion to the valve |00. Where a disc is used, its diameter will be sufficient to hold the valve, that cooperates with it, in neutral position at all times. The valve |9| is shown in this position in Fig. 6.

The two needle-

valves

288 and 301 are provided to control the rates of movement of the diamonds or other dressing elements across the grinding wheel in the dressing operation. The slower a diamond or other dressing tool moves across a grinding wheel during dressing, the better the nish produced on the wheel and the better the finish produced upon the work being ground. For rough and finish-dressing, then, these two

needle valves

288 and 301 will be adjusted to permit different rates of iiow of the exhaust fluid back to Athe sump. The needle valve which controls the rate of dressing prior to a rough-grinding operation will be adjusted to provide the wider opening to exhaust so as to permit the freer movement of the dressing mechanism. The valve 301 is illustrated in this position in Fig. 8.

A typical layout of the tracks of the several control cams is illustrated diagrammatically in Fig. 9. In the layout illustrated, the cams are so formed that the cam shaft |55 makes half a revolution between rough-grinding and iinishgrinding and half a revolution after the finishgrinding operation is completed and the machine is stopped and the wheel is only dressed prior to finish-grinding. The wheel is not dressed prior to a rough-grinding operation. With this arrangement, the control member |63 will be a plain circular disc, and the control member or cam |62 will have but one lobe, which is denoted at 310 in Fig. 9. This lobe will produce a pass of -while the nose of the lever |69 70 y. there is a wedge-shaped member 38| the dresser across the grinding wheel in one direction, a dwell at the end of the passage, and return of the dresser across the grinding wheel.

Since it is only necessary to unclamp the wheel head 2| and advance the grinding wheel prior to a dressing operation, the cams |51 and |59 which control the clamping and the movement of the wheel head, respectively, may therefore have only one lobe or recess each. The cam |51 is recessed and its recess is denoted at 31| in Fig. 9. The lobe on the cam |59 is denoted at 312.

The three actuating portions, 310, 31| and 312 are so shaped and positioned angularly relative to one another that the wheel head is rst unclamped from the column 20, then advanced and then reclamped to the column and then the wheel is dressed. The dwell in the bottom of the recess 31| in the cam |51 is of suicient length to permit the wheel head to be advanced the desired amount before it is reclamped to the column. The advancing movement of the wheel head is effected, as above described, through the ratchet and pawl mechanism 232-230 (Figs. 11 and 12) which operate the screw shaft |4| (Fig. 3). 'Ihe resetting of the ratchet and pawl mechanism takes place on the fall of the lobe 312, but since this resetting movement does not affect the position of the screw shaft |4| it can take place before the wheel head is reclamped to the column.

While the wheel head is being advanced, the feed cam-shaft 93 may be shiftedk axially to shift the feed control cams 90 and 9| (Fig. 1). For the method of operation described, the shaft 93 is shifted downwardly after the rough-grinding operation to bring the finishing feed cam 9| into operative engagementwiththefollower35. It is shown in this position in Fig. 1. After the finish-grinding operation, when the grinding wheel shaft 93 upwardly again in order to bring the roughing feed cam 90 into operative position ready for the roughgrinding operation on the next gear which is put upon the machine.

The cam |60 is formed, therefore, with a recess in its periphery which has a dwell at its bottom of sulcient length that the valve |89 is only moved in one direction during a cycle of operation of the control mechanism. The downward shifting of the shaft 93 takes place while the nose |12 (Fig. 7) of the lever |69 (Fig. 6) is rolling down the slope 313 of this recess and the shift of the cam shaft 93 upwardly takes place is travelling up the incline 314 of this recess. The recess is of suiicient peripheral extent so that the cam shaft is shifted downwardly on one operation of the control mechanism and remains in downward position during the ensuing finish-grinding operation of the gear and is only shifted upwardly after the wheel has again been swung to dressing position on the completion of' the finish-grinding operation. Y

To hold the parts as rigidly as possible during the finish-grinding operation, there is a tapered recess 380 provided in the sleeve 96 (Fig. 1) and adjustably secured to the bearing 22 by screws 382. This Wedge-shaped member ts into the recess 380 so that when the sleeve 96 is moved downwardly, it will hold the sleeve very rigidly.

Since for diiferent settings of the

needle Valves

288 and 301,di1erent periods of time will be required for dressing, it is necessary to stop the motor |50 during Vdressing and restart it again after the dressing of the wheel is completed. For this purpose, a limit switch 395 (Fig. 13) is mounted on the machine in position to be operated by the dressing ment. This limit switch is incorporated in the electrical circuit to the motor |50 so that when the limit switch is closed, the motor may operate and when the limit switch is opened, the motor is stopped.

In the dressing mechanism illustrated, one side of the grinding wheel is dressed by a diamond that is carried by a swinging arm 396 which is moved in opposite directions on the shifting in opposite directions of the valve |90 or the valve 9|.

Adjustably secured to this arm are a pair of cam plates 391 and 398 which are fastened to a plate 400 by screws 399 which pass through arcuate slots 40| in the cam-plates. The plate 400 is secured to the arm 396 by screws 402.

The cam plates 391 and 398 have beveled

corners

405 and 406, respectively, at their adjacent ends and can be spaced apart any de' sired distance within the range of adjustment permitted by the length of the slots 40|. In effeet, then, a recess of any desired length may be provided between the two cam plates and the roller 401 carried by the switch is adapted to ride olf of the cam plates into this recess during oscillation of the arm 396.

During the grinding operation, the arm 396 is at one limit of its swinging movement as shown in Fig. 13 and the limit switch is held closed to maintain a circuit to the motor |50. When the drive the control cams |51, |59, |60, |62 and |63. When the dressing mechanism is actuated by movement of the valve |90 or the valve |9|, the arm 396 begins to swing counterclockwise. The roller 401 rides down off the beveled part 405 of the cam-plate 391 and the motor |50 is stopped. The needle valve 288 or the (Fig. 8) controls the rate of 396, that is, the rate of dress- The motor then drives the cam shaft |55 on to complete the cycle of operations of the control mechanism.

By providing the limit switch motor neness without upsetting the time-cycle of the whole control mechanism.

After the dressing operation is finished, the grinding wheel is returned to operating position. This is done by energizing the solenoid 335 (Figs. 2 and 10) which causes the valve 330, the piston ||0 and the quill 25 to be moved to the positions shown respectively in Fig. 2. The cam |58 is provided with a lobe 385 to effect operation of mechanism in its movehe limit-switch 36| to cause the solenoid 335 to be energized at the proper time. When the piston has returned to the position shown in Fig. 2, the lug 355 strikes the arm of the limit- `switch 353 and closes this switch to start the feed motor of the machine. The solenoid 335 is so connected with this feed motor, as already described, that it remains energized as long as the feed motor is in operation and hence holds the valve 330 in the position shown in Fig. 2 during grinding. Therefore, when the roller 365 (Fig. 5) of the arm 366 of the limit-switch 36| rides down off of the lobe 285 of the cam |58, the solenoid 335 is not deenergized and the piston ||0 does not move upwardly.

When the quill 25 and the grinding wheel have again returned to operative position, the controller motor (Fig. 5) is stopped. This is done by operating the limit-switch 360. There are two lobes 386 and 381 provided on the cam |6I to operate this limit switch. One trips the switch at the end of the finish-dressing cycle after the grinding wheel has been returned to grinding position ready for the finish-grinding operation and the other trips the switch at the end of the second operation of the controlling mechanism after the grinding wheel has returned to grinding position ready for rough-grinding a new gear.

The dotted line 390 has been drawn across the path of the several cams in Fig. 9. As has already been stated, in the embodiment illustrated in Fig. 9, the cam shaft makes only half a revolution during an operation of the control mechanism. The parts of the cam path to the -left of the line 390 are in operation during the rst cycle of operation of the control mechanism, that is, between the rough and finish-grinding operations and the parts of the cam path to the right of this line are in operation during the second cycle of operation of the control mechanism between the finish-grinding and roughgrinding operations of the machine.

One way in which the machine may be wired electrically to accomplish the desired functions is illustrated diagrammatically in Fig. 14. 4|0 denotes the feed motor, while the motor which operates the automatic control mechanism is again designated at |50. The automatic stop mechanism of the machine is denoted at 4|2.

A start button 4| is provided at some convenient point on the machine. When this start button 4|| is pressed in, a circuit is made from the main line L1 through the line 4|4, the automatic stop 4|2, which is at this time closed, the

lines

433 and 469, the start button 4| the line 4|5 and the coil 4|6 of a standard control 4I8 to the main line L2. This energizes the coil 4|5 and pulls in the switch arms 420, 42|, 422 and 423, thereby closing the circuit from the main lines L1, L2 and L3 to the feed motor 4|0 and starting this motor.

When the switch arm 420 is closed, the solenoid 335 is energized, the circuit to this solenoid being made from the main line L1 through the switch arm 420, the line 425, the solenoid coil 335, the line 426, the line 421 of a standard relay 428, and the line 429 to the main line L2. The solenoid, when energized, operates to hold the lever 334 in the position shown in Figs. 14 and 2 to hold the Valve 330 in the position shown in Fig. 2.

The start button 4|| is, as usual, a normally open button and when it is released by the operator, it ies open. The circuit to the solenoid 335 and the controller coil 4|6 is maintained,

however, through the normally closed stop button 430. This circuit is from the main line Lz through the coil 4|6, the switch arm 423, the line 432, the stop button 430, the line 433, the automatic stop 4|2, and the line 4|4 to the main line When the automatic stop mechanism 4|2 is tripped, at the end of a series of grinding operations on a gear, as above described, the coil 4|6 and solenoid 335 are deenergized. Thus, the feed motor 4|0 is stopped and the spring pressed plunger 336 is able to shift the valve 336 (Fig. 2). This causes the piston ||0 (Fig. 2) to be shifted upwardly to swing the grinding wheel to dressing position. At the end of the up-stroke of the piston I0, when the grinding wheel is in dressing position, the lug 354 (Fig. 2) will close the nor- Inally open limit switch 352. This will close a circuit to the coil 435 of the relay 428, energizing this coil. The circuit is from the main line L1 through the line 436, the limit switch 352, the line 431, the coil 435 and the line 429 to the main line L2. When the coil 435 is energized, the switch arms 440 and 44| of the relay 428 will be closed. This will close the circuit to the coil 443 of the standard controller 445, the circuit being made from the main line La through the line 446, the coil 443, the line 441, the switch arms 44| and 440 of relay 428, the line 448, the limit switch 395, which is at this time closed, the line 449, the line 450, the line 45| and the line 436 to the main line L1.

When the coil 443 is energized, the

switch arms

455, 456 and 451 will be closed. thus closing the circuit to the control motor |50 from the main lines L1, L2 and L3 and starting this motor. The motor |50 drives the control cams, as already described. The control cams, as already described, govern the clamping and unclamping, and the shifting of the wheel head, and the operation ci the wheel-dressing mechanism.

As the dressing mechanism swings across the grinding wheel, the limit switch 395, (Figs. 13 and 14) will be allowed to open when the roller 401 drops 01T of the plate 391 or the plate 398, as above described. When the limit switch 395 opens, it breaks the circuit to the feed motor |55 and the feed motor is stopped. When the roller again rides up on one of theV plates 391 or 368, this circuit is again made, however, and the control drive motor |50 is again started.

When, in the course of operation of the control mechanism, the control cam |6| closes the normally open limit switch 36| (Figs. 5 and 14), a circuit is again made to the solenoid 335 and this solenoid is energized to shift the valve 330 back to the position shown in Fig. 2 and return the grinding wheel to operative position. The circuit is from the main line L1 through the line 436, the line 45|, the limit switch 36|, the line 460, the solenoid coil 335, and the

lines

426, 421 and 429 to the main line L2.

When the piston ||0 moves downwardly in its cylinder (Fig. 2), the lug 354 moves away from the arm of the limit switch 352 and this limit switch flies open, deenergizing the coil 435 of the relay 426. The control motor |50 continues to run, however, until the cam |58 (Fig. 5) closes the normally open limit switch 360 (Figs. 5 and 14). Then a coil 465 of the relay 428 is energized and this pulls the switch arms 440 and 44| open, breaking the circuit to the coil 443 of the controller 445 and allowing the

switch arms

455, 456 and 451 to drop open. The circuit to the coil 465 is from the main line L1 through the line (Figs. 6 and 9).

436, line 45|, the line 450, the line 466, the coil 465, the lines 421 and 429 to the main line Lz.

The diamond dresser stops at one end of its When the piston ||0 is returning to the position shown in Fig. 2, the normally open limit switch 353 is closed by the lug 355. The automatic stop 4|2 is of the construction that closes inmediately after it is opened so that it is closed at the moment. A circuit is therefore made from the main line L2 through the coil 4|6, line 4| 5, limit switch 353, line 468, line 469, line 433, automatic stop 4|2 and line 4|4 to the main line L1, energizing the coil 4|6 of the controller 4|8. This therefore causes the feed motor 4|0 to be restarted as above described and the machine again goes through a grinding cycle. Then the feed motor is stopped and the grinding wheel is swung to dressing position. When the wheel reaches dressing position, the control motor |50 is again started as before.

The cam |58 (Figs. 5 and 9) is so shaped, as above described, that it will close the limit switch 36| only on the first half revolution of the cam. On the second half revolution of the cam, the limit switch remains open, the solenoid 335 is not energized to return the grinding wheel to operating position and the machine is stopped with the grinding wheel in dressing position. To resume grinding, then, it is necessary for the operator to again press in the start button 4| The principles of the present invention will be understood from the preceding description but may be summed up .briey here.

We shall assume that the parts are in the positions shown in Fig. l. The operator starts the machine by pressing the start button 4I that starts the feed motor 4|0. The rotating grind ing wheel then commences to swing about the axis of the quill 25 and to feed into full depth engagement with the gear under actuation of that feed cam which is in engagement with the follower (Fig. l), in the first instance, the roughing feed-cam 90. When a tooth surface 0r tooth surfaces of the gear have been ground, the wheel is withdrawn and the gear is indexed. Then the rotating and swinging wheel is fed back into engagement with the gear and. another tooth surface or pair of tooth surfaces of the gear are ground. The alternate grinding and indexing proceeds until all of the teeth of the gear have been rough-ground, when the automatic stop mechanism 4| 2 of the machine functions. This stops the feed motor 4| 9 of the machine, but not the wheel drive motor. The stopping of the feed motor causes the shaft 93 to be stopped and stops the crank 80 which oscillates the quill 25. The stoppage of the feed motor also causes the solenoid 335 to be deenergized. The spring-pressed plunger 336 then operates to shift the lever 334 (Figs. 2 and 10) in a counter-clockwise direction about the axis of the shaft 333 and the valve 330 is moved downwardly and the piston ||0 upwardly. This causes the` quill 25 to swing upwardly and move the grinding wheel out of its working path to dressing position. When the lug 354 (Fig. 2) on the block |4 strikes the arm of the limit-switch 352, the control drive motor |50 is started.

This imparts rotation to the cam shaft |55 As this shaft rotates, the nose |12 (Fig. '1) on the arm |61 (Fig. 5) rides down into the recess 31| (Fig. 9) of the cam |51, allowing the valve |81 to move to the position shown in Fig. 6 under actuation of its spring 95. This puts the line 201 (Fig. 1) on exhaust and allows the coil springs |25 to move the T-bolts |22 to released position. Then the lobe 312 of the cam |59 operates to shift the valve |88 downwardly from the position shown in Fig. 6 to cause the piston 220 to be moved to the right to the position shown in Fig. 1l, causing the screw-shaft |4| to be rotated to advance the wheel head 2|. Simultaneously the nose of the lever |69 rides down the side 313 (Fig. 9) of the recess 315 in the cam |60, allowing the valve |89 to move upwardly under actuation of the spring |95. This puts the line 26| on supply (Fig. 4) .and through the gearing 214, 215, 98, 99 (Fig. l) moves the sleeve 96 and shaft 93 downwardly to bring the nishing feed cam 9| into the position shown in Fig. 1. Then the cam |51 causes movement of the valve 81 downwardly from the position shown in Fig. 6 and the line 201 (Fig. l) is put on supply to reclamp the wheel head 2| to the column 20. At approximately the same time, the cam |59 permits the valve |88 to return to the position shown in Fig. 6 and the line 2|1 (Fig. 11) is put on exhaust, permitting resetting of the pawl and ratchet mechanism 232-230. Then the cam |62 shifts the valve |90 downwardly from the position shown in Fig. 6 to cause the dressing mechanism to be actuated. As the dressing mechanism starts its movement, the roller 401 (Fig. 13) of the limit switch 395 drops Volf the camplate 391 and the motor |50 is stopped. The dressing mechanism continues on to the end of its movement, however. 'I'he rate of dressing is cam |62 on to permit the valve 90 to be shifted back to the position shown in Fig. 7 under actuation of the spring |95. This reverses the direction of movement of the dressing mechanism and the parts return to original position. During this return movement, the motor |50 is again stopped by operation of the limit switch 395 and at the end of this return movement is again started. The cam |58 then trips the limit-switch 36| to energize the solenoid 335. This causes the valve S36, piston ||0 and quill 25 position shown in Fig. 2` strikes the arm of the limit-switch 353, the feed motor restarts and the grinding wheel begins again to swing about the axis of the quill 25 and to feed into the gear to eifect the finish-grinding operation upon the tooth surfaces of the same. Just prior to the restarting of the feed motor, the controller motor |50 is stopped by operation of the cam |6|, the lug 386 on this cam operating the limit-switch 360.

After all of the teeth of the gear have been nish-ground, the automatic stop mechanism 4| 2 again functions grinding wheel to dressing grinding wheel has reached trip-lug 354 again trips the Fig. 9, however, the only operation which takes place is shifting of the valve |89 back to the position shown in Fig. 6 by operation of the cam |60, causing the piston 263 (Fig. 4) to be moved back to the position shown in Fig. 4 and the sleeve 96 and shaft 93 to be moved upwardly from the position shown in Fig. 1, to bring the roughing feed cam 90 into operative engagement with the follower 35.

This time, there is no unclamping of the wheel head, no advance of the wheel head, and no dressing of thegrinding wheel because with the described method of operation of the machine, the wheel is not dressed prior to a rough-grinding operation. Moreover, this time the cam |58 does not close the limit switch 36|. Hence, this time, the solenoid 335 is not energized and the grinding wheel is not returned to operating position.

Just prior to the time that the cam shaft |55 completes a revolution, the cam |6| operates through its lobe 381 to trip the limit-switch 360 again and stop the controller motor |50. Since the feed motor of the machine is already stopped, only the grinding wheel continues running. It simply rotates idly in dressing position until the operator has removed the gear which has been ground and chucks a new gear. Then he restarts the feed motor, causing the grinding wheel to be swung back to operating position and begin the grinding operation upon the new Work piece.

While the invention has been described in connection with a machine for grinding longitudinally curved tooth gears with a particular type of grinding wheel and particular motions thereof, it will be understood that the mechanism of the invention may be employed, with suitable modification, to operate automatically any machine for grinding gears regardless of type and regardless of the 'form or motion of the grinding wheel. In general it may be said that while the invention has been described in connection with a particular embodiment thereof, it will be understood that it is capable of further modification .and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

l. In a machine for grinding gears, a ginding wheel, means for actuating the wheel to effect the grinding operation, means for moving the grin-ding wheel from working position to dressing position and back, dressing mechanism, a motor, means operatively connecting said motor to said dressing mechanism to operate the same on actuation of the motor, means operative when the grinding wheel reaches dressing position t o start said motor, and means operative when the grinding wheel has been returned' to operative position, to stop said motor.

2. In a machine for grinding gears, a grinding wheel, means for actuating the grinding wheelto effect the grinding operation, a fluid-pressure operated piston for moving the grinding wheel from operative to dressing position and back, dressing mechanism, means for actuating the dressing mechanism, limit-switches adapted to be operated at opposite ends of the travel of the piston to start the means for actuating the dressing mechanism and to start the means for actuating the grinding wheel, respectively,

- said support means for causing said piston to move the grinding wheel to dressing position when a grinding operation has been performed on all of the teeth of a gear, and means for causing said piston to v return the wheel to operative position after the wheel has been dressed.

3. In a machine for grinding gears, dressing mechanism, fluid-pressure operated means for actuating said dressing mechanism, a pair of reverse valves, either of which is adapted to control the direction of movement of said dressing mechanism, a valve associated with each of said valves to predetermine the rate of dressing during operation of the corresponding reverse valve, and separate means for controlling the operation of each reverse valve.

4. In a machine for grinding gears, a grinding wheel, means for actuating the grinding wheel to effect the grinding operation, means for moving the grinding wheel from operative to dressing position and return, dressing mechanism, fluid-pressure operated means for actuating said dressing mechanism, a pair of reverse valves either of which is adapted to control the direction of movement of the dressing mechanism, a valve associated with each of said reverse valves to predetermine the rate of dressing, said last named valves being separately adjustable so that the dressing of the wheel may take place at one rate when one of the reverse valves is in operation and at a different rate when the other reverse Valve is in operation, a control member for controlling the movement of each reverse valve, said control members being mounted on the same shaft, and means for rotating said shaft through a part of a revolution each time the grinding wheel is moved to dressing position.

5. In a machine for grinding gears, a grinding wheel, means for actuating the grinding wheel to effect the grinding operation, means for moving the grinding wheel from operative to dressing position, dressing mechanism, a cam for controlling the operation of the dressing mechanism, and means for imparting a stepby-step movement to the cam each time the grinding wheel is moved to dressing position.

6. In a machine for grinding gears, a frame, a support slidable on the frame, a grinding wheel journaled in the support, means for clamping the support to the frame during the grinding operation, dressing mechanism, means for moving the grinding wheel from operating to dressing position, means for actuating said clamping means to move the same to or from operative position, means operable to advance said support with reference to said dressing mechanism, when the support is unclamped, to compensate for wear of the wheel, means operable to actuate said dressing mechanism, control mechanism for clamping, advancing and dressing mechanisms, and means for imparting step-by-step movement to the control mechanism each time the grinding wheel is moved to dressing position.

'7. In a machine for grinding gears, a frame, a support slidable on the frame, a grinding wheel journaled in the support, means for clamping the support to the frame during the grinding operation, dressing mechanism, means for moving the grinding wheel from operating to dressing position, means operable to advance with reference to the dressing mechanism when it is unclamped, to compensate for wear of the grinding wheel, a series of cams for controlling the dressing, advance and clamping mechanisms, a shaft to which all of said cams are secured, and means for rotating said shaft through a part of a revolution each time the grinding wheel is moved to dressing position.-

8. In a machine for grinding gears, a grinding wheel, means for imparting grinding movement to the grinding wheel, separate cams selectively operable to control the relative rate of feed movement of the grinding Wheel into the gear for rough and nish-grinding, respectively, dressing mechanism, means for moving the grinding Wheel from operating to dressing position and means operable on successive movements of the grinding Wheel to dressing position to move the two feed cams alternately into operative position.

9. In a machine for grinding gears, a grinding wheel, dressing mechanism, a frame, a tool support on which the wheel is mounted and which is movable on the frame to advance the wheel into the dressing mechanism to compensate for wear of the wheel, means for clamping the tool support to the frame, means for moving the wheel from grinding to dressing position, and separate motor driven means mounted on the machine and operable, when the Wheel is in dressing position, to release said support, advance the same, reclamp the support to the frame, and then actuate the dressing mechanism.

10. In a machine for grinding gears, the combination with a grinding wheel, means for r0- tating the wheel, means for producing a relative feed movement between the wheel and the Work to effect grinding of the tooth surfaces of a gear to the desired depth, and means for stopping the feed mechanism when a predetermined number of grinding operations have been performed on the work, of means operable to move the Wheel to dressing position when the feed mechanism is stopped, separate motor driven means operable, when the Wheel is in dressing position, to effect dressing of the wheel and means operable, when dressing is completed, to return the wheel to operative position, restart the feed mechanism and stop the separate motor.

11. An attachment for a gear grinding machine having uid-pressure operated dressing mechanism comprising'a motor, a reverse valve for controlling the direction of movement of the dressing mechanism, a separate valve for controlling the rate of dressing, means adapted to be driven by the motor for actuating said reverse valve, and means for operatively connecting the reverse valve to said dressing mechanism.

l2. An attachment for a gear grinding machine having separate means for controlling the feed of the grinding Wheel during rough and finishgrinding operations, respectively, huid-pressure operated means for bringing the two control means alternately into operative position, and duid-pressure operated dressing mechanism, comprising a motor, reverse valves for controlling the direction of movement of the dressing mechanism the shifting of the feed control` means, respectively, and means adapted to be driven by said motor for actuating said reverse valves, and means operatively connecting the reverse valves, respectively, with the dressing mechanism and the means for shifting the feed control means.

13. An attachment for a gear grinding machine which has a frame, a grinding wheel, a dressing mechanism therefor, a wheel support on which the Wheel is mounted that is movable on the frame to advance the wheel into the dressing mechanism to compensate for wear of the wheel, fluid pressure operated means for moving said tool support, fluid pressure operated means for clamping the support in grinding position, and huid-pressure operated means for moving the grinding wheel from grinding to dressing position and back, comprising a motor adapted to be mounted upon the machine, valves controlling, respectively, the operation of the dressing mechanism, the movement ofthe wheel support and the clamping of the same, means driven by said motor for actuating said valves in timed relation, and means operatively connecting the valves with the parts controlled thereby.

14. An attachment for a gear grinding machine Which has means for dressing the grinding wheel and means for advancing the Wheel reiative to the dressing mechanism to compensate for Wear, said attachment comprising a plurality of cams that are adapted to be connected operatively to the two named means to operate them in timed relation, and means for actuating said cams.

l5. An attachment for a gear grinding machine which has means for dressing the grinding wheel, means for advancing the wheel relative to the dressing mechanism to compensate for wear, and means for securing the Wheel in any position to which it is advanced, said means being releasable to permit advance of the wheel, said attachment comprising a plurality of cams that are adapted to be connected operatively to the three named means to operate them in timed relation, and means for actuating said cams.

16. An attachment for a gear grinding machine which has means for dressing the grinding Wheel, means for advancing the wheel relative to the dressing mechanism to compensate for wear, means for securing the wheel in any position to which it is advanced, a pair of feed cams for governing the feed of the grinding Wheel into the work during rough and finish grinding, respectively, and means for shifting the feed cams to move them alternately into operative position, said attachment comprising a plurality of cams that are adapted to be connected operatively to the four named means to operate said means in timed relation, and means for actuating said cams.

17. An attachment for a gear grinding machine which is provided with means for moving the grinding wheel from grinding to dressing position, means for dressing the grinding wheel, and means for advancing the wheel relative to the dressing mechanism to compensate for wear, said attachment comprising a plurality of cams that are adapted to be connected operatively to the two last named means to operate them in timed relation, and means adapted to be actuated, When said grinding wheel is moved to dressing position, to actuate said cams. v

18. An attachment for a gear grinding machine Which has a grinding wheel, means for moving the wheel automaticaliy from grinding to dressing position when a predetermined number of operations on the gear have been completed, means for dressing the grinding wheel, and means for advancing the wheel relative to the dressing mechanism to compensate for Wear, said attachment comprising a plurality of control members that are adapted to be connected operatively to the two last named means, respectively, to operate them in timed relation, and means adapted to be actuated when said grinding wheel is moved to dressing position to actuate said control members.

19. An attachment for a gear grinding machine which has a grinding wheel, means for moving the grinding wheel automatically from grinding to dressing position when a predetermined number of operations on the gear have been completed, means for dressing the grinding Wheel, means for advancing the Wheel relative to the dressing mechanism to compensate for wear, and means for securing the Wheel in any position to which it is advanced, said means being releasable to permit advance of the Wheel, said attachment comprising a plurality of control members that are adapted to be connected operatively to the dressing, advancing and clamping means, respectively, to operate them in timed relation, and means adapted to be actuated When said grinding Wheel is moved to dressing position to actuate said control members.

20. An attachment for a gear grinding machine Which is provided With a grinding wheel, with means for moving the grinding Wheel from grinding to dressing position, means for dressing the grinding Wheel, and means for advancing the Wheel relative to the dressing mechanism to compensate for Wear, said attachment comprising a motor, means operatively connecting the motor with the two last-named means to operate them in timed relation on actuation of the motor, and means adapted to be actuated, When said grinding Wheel is moved to dressing position, to start said motor.

21. In a machine for grinding gears, a grinding Wheel, means for moving the grinding Wheel from operative to dressing position and back, means for actuating said rst named means to cause the Wheel to be moved to dressing position after a predetermined number of operations have been completed on a gear, dressing mechanism, fluid pressure operated means for actuating said dressing mechanism, a reverse valve controlling the direction of movement of the dressing mechanism, two control members, means operatively connecting one of said members to the reverse valve to shift said valve alternately in opposite drections, means operatively connecting the other member to the first-named means to cause the grinding wheel to be returned to grinding position, adjustable valves for controlling the rate of movement of the dressing mechanism during dressing, means for actuating the control members, and means for stopping the last named means during dressing and for restarting it again.

22. In a machine for grinding gears, a grinding Wheel, means for moving the grinding wheel from operative to dressing position, actuating means, dressing mechanism, means for operating the dressing mechanism, means actuatable by said actuating means for controlling the direction of movement of the dressing mechanism, means actuatable in timed relation with said control means for causing return of the grinding Wheel to operative position, means for starting the actuating means when the grinding Wheel reaches dressing position and means for stopping the actuating means When the grinding Wheel returns to operative position, adjustable means for controlling the rate of movement of the dressing mechanism during dressing, and means controlled by movement of the dressing mechanism in either direction to stop and restart said actuating means.

CLARENCE T. GALLOWAY.