US1926603A

US1926603A - Automatic feed for grinding machines

Info

Publication number: US1926603A
Application number: US496177A
Authority: US
Inventors: Byron F Stowell
Original assignee: VAN NORMAN MACHINE TOOL CO
Current assignee: VAN NORMAN MACHINE TOOL CO
Priority date: 1930-11-17
Filing date: 1930-11-17
Publication date: 1933-09-12
Anticipated expiration: 1950-09-12

Description

Sept. 12, 1933.

B. F. STOWELL AUTOMATIC FEED FOR GRINDING MACHINES Filed Nov. 17, 1930 '7 Sheets-Sheet l W INVENTOR. BY BYRfl/V FSTUWEU.

. Se t; 12,1933. B F STOWELL AUTOMATIC FEED FOR GRINDING MACHINES 7 sheets sheet Filed Nov. 17, 1950 INVENTOR. 5mm F smwm ATTORNEYS. v

Sept. 12, 1933, B. F. STOWELL 1,926 603 AUTOMATIC FEED FOR GRINDING MACHINES Filed Nov. 17, 1930 7 Sheets-Sheet 3 o o g IL? I/ 5 o o T 220 223 \wfi'il INVENTOR.

. #3 BYRflA/ F STOWELL #5 BY A TTORN S.

Sept. 12, 1933.

B. F. STOWELL AUTOMATIC FEED FOR GRINDING MACHINES Filed NOV. 1'7, 1930 7 Sheets-Sheet 4 97 I w w if M P 5 .1] mm 1/ W 4:7 I 6 96 94 fin. &5. 3

l I! 92 I i 75 d?! INVENTOR. BY/w/v Esmwm A TTORN S.

Sept. 12, 1933.

AUTOMATIC FEED FOR GRINDING MACHINES B. F. STOWELL 1,926,603.

Filed Nov. 17, 1930 '1 Sheets-Sheet 6 IN V EN TOR.

j BY

ATTORNEYS.

. 5mm ESZWWELL Sept. 12, 1933. STQWELL 1,926,603

AUTOMATIC FEED FOR GRINDING MACHINES Filed Nov. 17, 19,30 7 Sheets-Sheet 7 IN V EN TOR.

BY/MN ESUWELL ATTOR S.

Patented Sept. 12, 1933,

UNITED: STATES AUTOMATIC FEED FOB GRINDING MACHINES Byron F. Stowell, Springfield, Mass., ass'ignor to Van Norman Machine Tool Company, Springfield, Mass., a corporation of Massachusetts Application November 17, 1930 Serial No. 496,177

16 Claims.

This invention relates to automatic feed control mechanism for grinding machines and has particular utility in connection with oscillating grinders intended for use in the manufacture of the outer races for ball bearings. One object of the invention is to provide automatic devices comprising a detecting mechanism for gauging the exact size to which the work is ground which will operate with great accuracy in terminating the feed when the desired size has been reached. A further object is to provide amechanism of this character which will first reduce the rapidity of the feeding and will finally. after a predetermined amount of finishing feed, stop the feed movement altogether. A further object is to provide an electrically operated mechanism of this character in which the difiiculties hitherto experienced with arcing at the contact points will be eliminated. A further object is to provide a 20 mechanism of this character in which the amount of roughing cut, the amount of finishing cut, and the ultimate size of the article are all capable of independent adjustment. A further object is to provide a mechanism of this character capable 25 of operating upon ball bearings of the double race type. Other and further objects will appear from the following description and claims.

The preferred form of the mechanism will now be described in connection with the accompany- 30 .ing drawings, in which:

Fig. 1 is a side elevation of an oscillating grinder embodying my invention;

Fig. 2 is an enlarged detail corresponding to a portion of Fig. 1;

Fig. 3 is a section on line 3--3 of Fig. 2;

Fig. 4 is a section on line 4-4 of Fig. 3;

Fig. 5 is a rear elevation of the mechanism shown in Fig. 2;

Fig. 6 is a diagramof the electriccircuits;

Fig. 7 is a rear view of the sizing gauge and contact device with the cover plate removed;

Fig. 8 is a similar view showing one camand its corresponding contact piece also removed;

Fig. 9 is a section on line 9-9 of Fig. 5 taken on a larger scale;

Fig. 10 is a top plan view of a part of the gauging mechanism. taken substantially on the line 1010 of Fig. 2; I v v Fig. 11 is a partial similar view showing the 50 parts in another position of operation;

Fig. 12 is a section taken substantially on line 1212 of Fig. 14;

Fig. 13 is a view somewhat similar to Fig. '7 but showing the parts in a different position of operation;

Fig. 14 is a section on line 14-14 of Fig. 13;

Fig. 15 is a view similar to Fig. 8 but showing the inner cam and the corresponding contact member removed;

Fig. 16 is a back view of the indicator and con- 0 tact mechanism;

Fig. 17 is a side elevation of the mechanism for causing automatic feeding of the grinding wheel;

' Fig. 18 is a similar view showing the parts in 65 a different position of. operation;

Fig. 19 is a detail of a portion of the mechanism shown in Fig. 18;

Fig. 20 is a view similar to Fig. 18 but showing a still further position of operation;

Fig. 21 is a top plan view of the mechanism shown in Fig. 20; and

Fig. 22 is a rear view of a portion of the mechanism shown in Fig. 17.

The general construction of the machine will first be described in connection with Fig. 1, it being understood that this particular form of grinding machine has been chosen for purposes of illustration only and that the control mechanism is adapted to grinding machines of other types. The machine is mounted upon a frame upon which is journaled an oscillating head 31. As one form of oscillating mechanism for this head, I have shown a spindle 32 projecting downwardly from the frame through head 31 and carrying a crank pin 33. This pin is joined by a link 34 to a crank pin 35 mounted upon a shaft 36, which is suitably rotated continuously during the operation of the mechanism. Upon the oscillating head 31 are ways 37 in which a slide 38 is adjustably positioned by a screw 39. The work head 40 is suitably mounted upon this slide. In the work head is a spindle 41 bearing at its inner end a chuck 42 in which the work piece 43 may be gripped. Rotation is imparted 95 to the spindle by a pulley 44 around which passes a suitable belt coming from a motor or. other source of power.

A slide 45 is also mounted upon the frame 30 and base control handle-46 connected with any desired form of mechanism for causing the slide to be moved toward or away from the oscillating work head. A suitableform of mechanism for this purpose is shown in my application Serial No. 496,178, filed Nov. 17, 1930.- Ways 47 are formed in the slide 45 and carry a lower cross slide 48. A shaft 49 is axially fixed in the slide 45 and is threaded into a nut 50 carried by a bracket 51 secured to the cross slide 48. A ratchet wheel 52 is secured to the shaft and is actufeeding movement of the slide.

. pending application referred to above.

ated by suitable devices, to be described later, for causing a relatively slow mechanical cross In ways 53 formed on this cross slide is mounted a tool head 54 which may be given a rough positioning movement on these ways by mechanism controlled through the handle 46. A preferred form of this connection is described in my co- J ournalled in the tool head is a spindle 55 carrying a grinding wheel 56 and a pulley 57 by which the wheel may be rotated.

The mechanism for gauging the size of the work during the grinding operation and for controlling the feeding movement given to the ratchet 52 is carried by the head 40 and oscillates with it. A bracket 60 (Figs. 1 and 2) is secured to the work head 40 and supports a clamping mem-- ber 61 carrying a rod 62 upon the end of which is secured a trunnion cradle 63. Trunnions 64 mounted in this cradle support pivotally a carrier 65 having clamps 66 in which is gripped a tube 6'7. A rod 68 (Fig. 9) reciprocates vertically within this tube, forming the connection between the follower which rests on the work and the indicating and contact making device which is mounted at the top of the tube. The tube is provided with an internal enlargement 69 and the rod 68 is provided with an enlarged portion '70. Between the shoulders of these two enlargements is a spring 71 constantly urging the rod upwardly.

The lower end of the rod is threaded into a pair of semi-circular clamping members 72 held together by a screw 73 and having a tubular extension 74 slidable over a reduced lower end '75 of the tube 67. A shield 76, placed over the tube and the extension 74, provides a dust proof connection. The clamps '72 are formed with mating dove-tailing slots 7'7 which grip a diamond hold-' er '78 bearing a spherical diamond '79 (Fig. 5) at its outer end. A clamp 80 embraces the clamps "l2 and carries a diamond holder 81 arranged at right angles to the holder '78 and carrying a spherical diamond 82 at its outer end. These two holders are of different lengths and are adapted to engage alternatively with the work as the rod is rotated back and ,forth through an angle of 90. One of the diamonds is positioned to en-,

gage the outer race of a double ball bearing and v the second holder is adapted to engage the inner race. Only one of these diamonds is in opera-. tion at any one time.

To lower the rod 68 against the force of the spring 71 so that it may be introduced within a work piece and also to rotate it to bring one or the other of the diamonds selectively into action, a sliding ring 83 (Fig. 2) is fitted upon the tube 67 and is provided with a handle 84. A rod 85 joins this ring with the exposed upper end of the rod 68 so that as the handle is moved the rod is caused to follow it.

At the upperend of the tube 67 a bracket 86 (Figs. 9, 12 and 14) spaced at right angles to each other. A bar 88 is tightly fitted in a slot formed in the upper end of the rod 68 and is held in position by any suitable means, as for example an extension of the rod 85. Each of the abutments 8'1 carries spaced cap plates 89 secured in position by screws 90. These cap plates are formed as best shownin Fig. 14 to provide a space between them and the body of the abutment so that the bar 88 may slide vertically. The space between the two cap plates on each abutment is just sufficient so that the bar may passout between them. During the normal operation of the device this will not occur, but the arrangement permits the 90 rotation of the rod 68, which brings one or the other of the two diamond followers into action.

Besides the angular motion of the rod 68-which The work engag- 91 having a V groove 92 formed in one side. This groove engages over the wedge shaped end of a plunger 93 having a pin and slot connection 94 within a'recess formed in the trunnion cradle 63, and pressed outwardly by a spring 95. When the feeler mechanism is swung to the position of Fig. 11, the latch depresses the plunger tempor-v arily, the latter being immediately forced outwardly into contact with the sides of the V groove 92 by the spring 95. A stop screw 96 carried by the carrier 65 is positioned to strike against the abutment 97 on the cradle giving a positive limit to the permissible swinging movement of the carrier. It is desirable to locate the diamonds with accuracy in exactly the center of the race and the adjustment of the stop screw 96 permits of. this. The V groove 92 is preferably located somewhat off center with respect to the plunger 93, as best shown in Fig. 11, so that a sideways pressure is given, holding the stop screw firmly against its abutment.

' The mechanism for amplifying the motion of the diamond point so that the necessaryelectrical connections may be control1ed will now be described. It is preferable to combine with this. mechanism visual indicator, and in the embodiment shown he usual through shaft of a standard dial micrometer is iftilized to transmit motion from the rod 68 to the amplifying mechanism. A casing 100 (Fig. 14) is secured to the bracket .86 and carries a dial micrometer indicated generically at 101 with its dial face at 102. As the internal construction of this instrument forms no part in the working out of my invention, the instrument itself acting only as a convenient adjunct, it is neither illustrated nor described in detail. The only part of the micrometer which it is necessary to mention is a rod 103 which extends entirelythrough the case. Although the rod'has operating .connections with the micrometer indicating mechanism it may be considered for the purpose of the present description merely a vertically reciprocable member.

At its lower end the rod 103 is formed with a spherical-bearing head' 104 (Fig. 13) resting upon the enlarged portion 70 of the rod 68. At its upper end the rod has a similar bearing head 105 (Fig. 14) upon which rests the rounded lower end of a screw 106 adjustably held in a clamp bracket 107. The bracket 107 is fixed upon a vertically movable rod 108. A micrometer head 109 and a pointer 110 may serve for convenience in adjusting the screw 106. The rod 108 slides in bearings 111 and 112 (Fig. 15) formed in the casing 100, and at about its central portion is formedwith rack teeth 113. A pinion 114, mounted on a shaft 115, meshes with the rack teeth. A gear 116, larger than the pinion 114 but rotatable with it, meshes with a pinion 117 on a shaft 118. This train of gearing acts to multiply the motion given to it by the vertical movement of rod 68, so that the mechanism mounted on shaft 118 will have a sufficient amplitude of motion to operate the electrical contact members. The shafts supporting the several gears may be journaled in bearing plates 119, 120 (Fig. 13) suitably secured within the casing. A pin 121 (Fig. 15) secured to the rod 108'and running in a slot 122 in a block 123 prevents the rod from turning and keeps the rack teeth in mesh with the pinion.

Mounted on the shaft 118 and rotatable with the pinion 117 are cams 124 and 125 (Figs. 7 and 13). A contact lever 126, pivoted'at 127 to the casing, bears at one end against the cam 124. At its other end the lever bears a contact finger 128 adapted to bear against a point 129 suitably insulated from the casing and electrically connected as will be described below. In order to press the tail of the lever towards the cam 124 a spring 130 is attached to it and stretched to a pin 131 secured in the casing. A second contact lever 132 is pivoted upon an eccentric 133 which has pivot portions 134. A pointer 135 (Fig. 16) is secured to the eccentric and coacts with a scale 136 upon the outer casing wall. The adjustment of the rocking axis of lever 132 with respect to that of lever 126 is. used to vary the amount of slow feeding movement or depth of finishing cut in a manner which can best be described somewhat later. One end of lever 132 bears on the cam 125 and the other carries a contact finger 137 adapted to make contact with a point 138 insulated in a manner similar to point 129. A spring 139, stretched between the cam-engaging arm of lever 132 and a pin 140 in the casing, gives the lever atendency to bear constantly against the cam.

The

cams

124 and 125 have abrupt shoulders 141 (Fig. 8) and 142 (Fig. 7) which, as the cams are rotated simultaneously in the direction of the arrow in Fig. 7 by the raising of the rod 108, permit the contact levers to be snapped succes sively by their springs into positions where their contact fingers are pressed into electric contact with the

points

129 and 138. It will be noted that the action of the cams is to complete the electric circuits. This can be accomplished with no danger of injuring the points through arcing, as no arc occurs when a circuit is made but only when it is broken. When the cams are later reset by hand, the circuits have been broken elsewhere, as will be described, so that all possibility of injury to the delicate contact points from this cause has been eliminated. There are two ways in which the interval between the actuation-of the two contact levers by the cam shoulders could be controlled. One is by adjusting the two cams angularly relatively to each other, and the other is by changing the distance between the cam-engaging ends of the contact levers. The latter mode permits a simpler mechanical structure and has been used in the illustrated device. By rotating the eccentric 133 the end of lever 132 will be shifted upon the surface of its cam 125. Irrespectlve of the change in the rotating axis of the lever by a shift in the eccentric, the spring 139 will always keep the end of the lever resting on the cam, so that as the eccentric rotates its only effect will be to move the lever end in one direction or another around the cam surface. When the lever end is spaced further from the end of lever 126 there will be more vertical movement of the rod 108 between the making of the two electric contacts. As will be described later, the time between the making of these contacts represents the period between the start of the fine finishing feed and the stoppage of the grinding wheel feed altogether, and hence determines the amount of finishing out which is given to the work piece.

After the grinding on one work piece is completed, it is necessary to reset the contact mechanism, so that it may repeat its operation on a succeeding piece. In the present case, this resetting is done automatically when the diamond point is lowered so as to be inserted within a fresh work piece. It can be seen from Fig. 7 that after the contact levers have dropped past the shoulders of the cam they will blockbackward rotation of the cam unless they are positively drawn out of the way. To do this a rod 143 is fitted to slide within the casing and has an annular slot 144 (Fig. 15) near its upper end. Into this slot a pin 145 (Fig. 7) secured to the lever 132 projects. The rod 143 at its lower end has a disk 146 lying below and adapted to be engaged by a disk 147 (Fig. 14) secured to the rod 103. An arm 148 (Fig. 13) projects upwardly from the bar 88, and has a slot 149 loosely receiving the disk 147. As the rod 68 is lowered to place the diamond point within a work piece, the disk 147 strikes the upper surface of the disk 1.46 and lowers it, together with the rod 143. The pin 145, which is in constant engagement with the slot 144, is also lowered, swinging the lever 132 on its pivot and drawing its cam engaging end out beyond the shoulder 142. At the same time the opposite end of the lever v 132 strikes the lever 126, tilting this in the same direction and drawing its cam engaging end out beyond the shoulder 14. The cam is now free to rotate under the weight of the rod 108 and its attendant parts. It will be noted that there is no positive connection between the rod 103 and the screw 106 so that the former may be drawn down without exerting any pull on the screw and hence on the rod 108. As soon as the cams are released, however, the latter rod will descend of its own weight and will thus reset the parts for a subsequent gauging operation. Stop screws 150 and 151 (Fig. 2) may be used to limit the downward motion of

disks

146 and 147 respectively.

It is desirable to provide some device for-limiting the freedom of motion of the parts so that they will not tend to chatter. Particularly during the first part of, the roughing cut the irregular 1125 surface of the work piece, which is revolving at high speed, causes the diamond point to vibrate badly and to transmit this vibration to the delicate parts of the gauging mechanism. This causeswear and also may even make a fluttering electric contact between the spring 137 and the point 138. To avoid this difficulty I preferably attach a dash pot so as to prevent sudden upward movement of the rod 68. Upon the bracket 86 is supported'a cylinder head 155 (Fig. 4) held in 1 5 place by a set screw 156. A dash pot cylinder 157 is threaded onto the cylinder head, and has a piston 158 running in it. To the piston is fastened a rod 159, passing through a stuffing box 160 and having a contact head 161 at itsupper end. A spring 162 surrounds the rod between the head and the stuffing box, to give a constant upward tendency to the piston. A lever 163 is pivoted in the bracket 86, hearing at one end on the contact head 161 and at the other against the upper end of the rod 68. Formed in the piston is a conical hole 164 which receives a ball 165, kept pressed into the hole by a spring 166. When the rod 68 is moved upwardly the motion is resisted by the viscosity of the fluid such as oil or glycerin with' which the cylinder is filled, movement being permitted only as the fluid leaks past the piston. Downward motion of the rod is unrestrained, the piston rising under the influence of its spring 162 and the ball 165 shifting from its socket to permit free passage of the viscous fluid. The restraint thus imposed on the: rod 68 is just enough to prevent it from following the minor variations in surface contour of the work piece, the diamond settling gradually into place and giving an accurate indication of the progress of the grinding.

Before describing the electrical connections which the contact springs 128 and 137 operate, the mechanical details of the cross feed will be considered. Upon the vertical shaft 36, previously mentioned (Fig. 1), is a cam 1'70 upon which bears a push rod 1'71. The upper end of this push rod strikes a plate 172 1 (Fig. 1'7) pivoted at 1'73 to the frame and having a contact surface 1'74. Adapted to ride directly on the surface 1'74, or

to be separated from it by a spacing-memberto be described, is a tappet 1'75 slidable vertically in a bracket 1'76 secured to the slide 45. The upper end of the tappet bears against the under side of an arm 177 secured to a shaft 1'78 jour naled in the bracket and also bearing a pawl arm 1'79. A pawl carrier 180 is pivoted to the pawl arm at 181 and is pressed towards the ratchet wheel 52 by a spring 182. At the end of the pawl carrier is mounted the pawl blade 183 which engages the teeth on the wheel. As the tappet 1'75 is elevated, the pawl is pressed upwardly, being held in contact with the ratchet wheel by the spring 182. As the tappet is lowered, the pawl clicks over the teeth of the ratchet while the arm 1'7'7 drops. The downward movement of this arm is limited by the surface 18 (Fig. 18)

of the bracket 1'76. The tappet 175, however,

drops below this surface an amount depending upon an adjustment now to be considered.

Pivoted at 185 to the bracket 1:76 is an arm 186 having a handle 18'7and a downward extension 188. A wedge-shaped plate 189 is pivoted at 190 to this extension, and is preferably curved. When the wedge plate is in the general position of Fig. 1'7 it comes between the plate 172 and the tappet 1'75 and thus raises the tappet an amount depending on how far the wedge is pushed under.

the tappet. As the tappet 1'75 is raised by the wedge, assuming the plate 1'72 not at the moment raised byv the push rod 1'71, the top of the tappet is raised closer to the bottom of the arm 177 which is stopped in its descent by the surface 184. As the plate 1'72 is now raised, its motion will be transmitted to the arm' 1'7'7, and therefore to the pawl, with less lost motion due to the initial lack of contact between the tappet and. the arm. The wedge plate thus provides a device for adjusting the rotation of the ratchet wheel 52 which will be given at each rise 'of the push rod 1'71. This effect is utilized in the present machine in changing from a coarse roughing cut to a fine finishing out. For a roughing cut, the parts are in the position shown in Fig. 1'7, in which the wedge 189 takes out a predetermined amount of lost motion that otherwise exists in' the movement of the pawl by the push rod 1'71. Whenit is desired to change from a roughing cut to a finishing cut the arm 186 is swung to the position of Fig. 18, drawing the wedge completely out of contact with the tappet 1'75 and reintroducing all the lost momechanism here provided for this purpose acts to remove the pawl entirely from contact with the ratchet. A lever 191 is pivoted at 192 to the bracket 176 and is provided with a handle 193. At the end of the lever remote from the handle, a bent abutment 194 (Fig. 22) is secured by a screw 195 passing into the lever through a slot196 (Fig. 21). A pin 197 projects from the side of the pawl carrier 180 so that when the lever 191 is rocked the abutment will strike the pin and shift the pawl carrier out of ratchet-engaging position.

The lever 186 may be given a tendency towards the position of Fig. 18 by a spring if desired, but the overbalanced weight of the handle end of the lever is generally sufiicient to do this. The arm 191, however, is preferably pulled downwardly on its handle end by a spring 198 (Fig. 18) joined to it and to a lug 199 on the bracket 176. A stop screw 200, also mounted on the lug, limits the downward motion of the arm.

In order to hold the

arms

186 and 191 in their raised positions subject to release by the articlegauging devices already described, each lever is provided with a latch held by an electrically releasable device. In practice I have found the commercial electric door releases common in apartment houses to serve excellently in this connection. The two releases are similar, and the one relating to lever 191 has been shown diagrammatically in Fig. 19. A .latch member 201 is pivoted at 202 in a case 203 secured to the bracket 1'76. The latch is held against a fixed stop 204 by a spring 205. An electromagnet 206 is fixed in the casing, and coacting with it is an armature 20'7 pivoted at 208 and having a shoulder 110 209 overlying a portion of the latch. The armature is urged towards the position of Fig. 19 by a spring 210. When the electric circuit through the magnet is completed, the armature will be attracted, withdrawif1g the shoulder 209 from contact with the latch and permitting the latter to rotate freely -except as restrained by the spring 205. The latch is engageable with a hook 212 pivoted at 213 to the lever 191. When the latch is released as just described, the spring 198 will cause the lever and the hook to move from the position of Fig. 18 to that of Fig. 20, the latch 201 turning freely during this movement but immediately snapping back under the influence of its own spring 205.

. place. A similar arrangement is provided to hold the lower lever 186, a spring pressed hook 215 (Fig. 1'7) coacting with a latch within a case 216 and controlled by an electromagnet 217 (Fig. 6). The mechanism is preferably arranged so that the electric circuit through the magnets will be broken immediately upon the descent of the levers which they control. This is for the double purpose of preventing an undue expenditure of current and preventing the current being broken through the delicate contacts of the measuring device, as referred to above. The arm 191 is provided with a U-shaped clip 218 (Fig. 19) loosely embracingthe handle 219 of an ordinary toggle switch 220. Thearm 186 is similarly provided with a clip 221 (Fig. 18) loosely embracing the handle 222 of a toggle switch 223. Descent of each lever results in snapping its related switch in a direction to shut off the current. These switches may be made rugged enough, and with a quick enough break, so that the burning of the contact points due to arcing will be inconsequential. This is contact points 128 and 137 without interference with their operation is insured.

The manner of operation of the complete machine will now be considered. A work piece such as a'ball race 43 is placed in the chuck 42 and the spindle 41 started in rotation in the usual way. The handle 84 is depressed to lower the,

diamond point sufiiciently to permit it to enter the interior of the ball race. bracket 65, the diamond is positioned directly under the center of the upper curve of the roughed out raceway. Release of the handle now permits the spring 71 to bring the diamond into contact with the work, both contact springs 128 and, 137 being held away from their respective contact points as in Fig. 13. The grinding wheel 56 is now moved into position within the work piece, by any desired mechanism such as that described in my copending application Serial No. 496,178, filed Nov. 17, 1930, and is started in rotation and oscillation. Handle 187 is then raised to cause wedge 189 to pass under the tappet 175, and thus give to the latter its maximum stroke 'at each reciprocation of the push rod 171. Finally the handle 193 is raised, withdrawing the abutment 194 from contact with the pin 197 and permitting the pawl to contact with the ratchet. If desired, the parts may be arranged so that raising lever 186 will also raise lever 191, an abutment 230 on the lower lever striking an adjustable stop screw 231 on the upper.

As the machine continues to operate, the ratchet will be intermittently advanced an amount depending on the distance to which wedge 189 is inserted between the plate 172 and the tappet 175. The arm 186 has a fixed upper position where its hook 215 is held by the latch and the wedge position is accordingly preferably controlled by set screws 225 carried upon arm 188 and furnishing the connection between this arm and a projection 226 on arm 186. This.

comparatively rapid operation ofthe ratchet continues until the cam 1250f the detecting mechanism has been rotated by the continued ascent of the diamond to apoint where contact lever 132 drops off the end of the shoulder 142. As

contact is thus established between the points 4 137 and 138 (Figs. 6 and 7) current will flow through the latch release magnet, the switch 223 having previously been closed by the raising of lever 186. Activation of the magnet 217 releases the arm 186 and permits its'handle end to drop as shown in Fig. 18, also opening the switch 223 so as to isolate the contact points 137, 138 completely. The ratchet is now fed at each reciprocation of push rod 171 an amount less than the roughing cut by the lost motion introduced by the withdrawal of wedge 189. When the finish grinding has proceeded to the final diameter of the ball race, the contact lever 126 slips 011 the shoulder of cam 124 -(Fig. 8) making contact between the spring 128 and the point 129. Current is thus allowed to flow through magnet 206, releasing arm 191, disengaging the pawl from the ratchet, and isolating the contact points 128 and 129. The machine may be permitted to stop Upon swinging the ceased between the grinding wheel and the work piece. During this period of drift, as it is called, minor inequalities will be taken out of the Work piece and a polish given to its ground surface. The final ground diameter can be automatically determined to within a tolerance of two tenthousandths of an inch, and it will be observed that this accuracy in grinding is reached irrespective of the wear on the grinding wheel,-

the wheel each time being advanced until the desired ultimate diameter is reached.

What I claim is: r

1. A cross feed mechanism for grinding machines comprising a grinding head, a ratchet wheel, screw and nut connections between the ratchet wheel and the grinding head whereby rotation of the ratchet wheel will cause linear movement of the grinding head, a pawl mounted for engagement with the ratchet, a periodically reciprocated plate, a tappet interposed between the plate and the pawl with a lost motion rela tion, and a wedge movable between the plate and the tappet to reduce the extent of the lost motion.

2. A cross feed mechanism for grinding machines comprising a ratchet, a pawl engageable with the ratchet, members forming a lost motion connection to impart periodic movement to the ratchet, and a wedge movable between the members to reduce the extent of the lost motion.

3. A cross feed mechanism for grinding machines comprising a grinding Head, a ratchet wheel, screw and nut connections between the ratchet wheel and the grinding head, whereby rotation of the ratchet wheel will cause linear movement of the grinding head, a rocking lever mounted adjacent the ratchet, a pawl carrier mounted upon said lever, a pawl carried upon the pawl carrier so as to engage the teeth of the ratchet, a periodically reciprocated plate, a tappet interposed between the plate and the rocking lever with a lost motion relation, a member pivoted adjacent the tappet, and a wedge freely pivoted to the member and resting upon the rocking plate to partake of its movement and 0 according to the position of said pivoted member being either inserted between the plate and the tappet so as to" reduce the extent of the lost vmotion or withdrawn from contact with the tappet.

4. A cross feed mechanism as claimed in claim 3, having a second pivoted member, and abut-. ments on said member and the pawl carrier engageable with each other when the member is rocked to remove the pawl from engagement with the ratchet. 5. An automatic control for a grinding machine having a contact member pressed against the work, multiplying mechanism actuated by the movement of the contact member, a shaft rotatable by said multiplying mechanism, a pair of cams having abrupt shoulders mounted on the shaft, a pair of contact levers each engageable with one of the cams, springs pressing the contact levers against the cams so that the levers will snap 011 the shoulders when the cams are rotated a predetermined amount, and electric contacts closable by such movement of the levers.

6. An automatic control for grinding ma chines as claimed in claim 5 in which one of the contact levers is mounted upon an adjustable eccentric pivot to vary its point of contact with its mating cam.

7. An automatic control for grinding machines of the type having feeding mechanism for causing relative approach of the tool and work at a definite rate, comprising mechanical means for holding the feeding mechanism in a definite feeding condition, electrically operated means operable by a momentary flow of current therethrough to release saidmechanical means and thereby to control the operation of the feeding mechanism, a feeler'responsive to the progress of the grinding operation, electrical contact members controlled by the feeler for closing the circuit through said mechanically operated means, and a switch automatically actuated upon the release of the mechanical means to reopen the circuit through said electrical means.

8. An automatic control for grinding machines comprising a grinding wheel feeding mechanism, a work measuring device, a pair of electric contact members closable successively by said device as the size of the work varies, electric circuits including said contact devices, a feed control device actuable by the flow of current in one of said circuits to decrease the rapidity of the feeding movement of said mechanism, a feed control device actuable by the fiow of current in the other circuit to cause the feeding movement of said mechanism to cease, and a switch in each of said circuits opened by the actuation of the feed control device actuated thereby to terminate the flow of current in said circuit.

9. An automatic control for grinding machines comprising a feeler riding on the work surface being ground, control mechanism actuated by the feeler, a dash pot coacting with the feeler to retard its motion, and means preventing the dash pot from exerting a substantial restraining force on the feeler in a direction opposite to the progress of the grinding.

10. An automatic control for a grinding machine having a contact member pressed against chines 'as claimed in claim 10 in which one of the contact levers is adiustably mounted to vary the time of snap oil from its mating cam shoulder, said mounting including a manually movable indicating pointer through which the desired interval is determined.

12. An; automatic ,control for grinding ma chines comprising a rotary grinding wheel and feeding mechanism therefor, means for holding and rotating a work piece, a feeler having a single work contacting point, a slide upon which the feeler is mounted, guiding means for the slide constraining it for movement in such a path that the feeler moves in a straight line in a radial direction with respect to the work piece, motion multiplying mechanism actuated by the feeler as the feeler moves in accordance with the progress of the grinding operation but unconnected to the feeler for movement in the opposite direction whereby the feeler may be moved freely out of contact. with the work piece when the latter is to be removed, means actuated by said mechanism when thefeeler point reams pres chines of the type having feeding mechanism for causing relative approach of the tool and work,

, a feeler responsive to the progress of the grinding operation, a rotatable member having a shouldered cam-like surface, a detent engaging the surface and movable suddenly when it registers with the shoulder, means controlled by the feeler for causing progressive rotation of the member, electrical contact members connected with the detent to be actuated when the detent passes over the shoulder, and electromagnetic control means operable upon actuation of the contacts to vary the action of the feeding mechanism.

14. An automatic control for grinding machines of the type having feeding mechanism for causing relative approach of the tool and work, a single feeler responsive to the progress of the grinding operation, a rotatable member having two shouldered cam-like surfaces, detents engageable respectively with said surfaces and movable suddenly and successively when they register with the shoulders, means controlled by the feeler for causing progressive rotation of the member, electrical contact members connected with each of the detents to be actuated successively as the detents pass over the shoulders,

change in the rate of feeding of the feed mechanism, and electromagnetic control means operable upon the actuation of the other set of contacts to cause stoppage of the feeding operation.

15. In an automatic control for grinding machines of the type having feeding mechanism for causing relative approach of the tool and work, a

feelerhaving a single work contacting point, a slide on which the feeler is carried mounted for movement in a direction normal to the surface of the work, means for pressing t e feeler point towards the work so that it will b responsive to the progress of the grinding operation, motionmultiplying mechanism actuated by the feeler as the feeler moves in accordance with the progress of the grinding operation but unconnected to the feeler for movement of the latter, in the opposite direction whereby the feeler may be moved freely out of contact with the work piece, and mechanism controlled by said feeler for controlling the progress of the grinding operation.

16. An automatic control for grinding machines of the type having feeding mechanism forcau sing relative approach of the tool and work, a single feeler for gauging-the progress of the grinding operation, a plurality of mechanisms operable toproduce upon their individual actuation distinct changes in the operation of the feeding mechanism, electromagnetic control means operable upon a momentary flow of current to actuate said mechanisms, a plurality of electrical contacts progressively closed. by the feelerin its motion resulting from the continuance of the grinding operation, and mechanism for reopening each control circuit immediately upon the actuation of the electromagnetic device includedinit. BYRON F. STOWELL.