US1891777A - Grinding machine - Google Patents

Description

3 Sheets-Sheet 1 T W, F- M m Wm L G. my M Dec. 20, 1932. A. G. PLIMMER GRINDING MACHINE Filed April 4. 1952' a 1 null Dec. 20, 1932.

5 Sheets-Sheet 2 ALFRED GPUMMER (Minna/ Dec. 20, 1932 A. G. PLIMMER GRINDING MACHINE Filed April 4, 1932 3 Sheets-Sheet 5 Fig-10 r W 58 W5 \0 --|o9 8; IS? 5? \aa 057 :52. 63 I 64) 1: 9 el I n so it: ALFRED G. PUMMER Patented Dec. 20, 1932 UNITED STATES PATENT OFFICE ALFRED G. PLIMMER, OF CINCINNATI, OHIO, ASSIGNOR TO CINCINNATI GBINDEBS v INCORPORATED, OI CINCINNATI,

GRINDING Application filed April 4,

This invention relates to improvements in machine tools and especially to improvements in grinding machines and to a feed control mechanism for use therewith.

An object of the invention is the provision of an improved mechanism for modifying or stopping the feed between a tool and the Work when the work is reduced to a predetermined desired size.

Another object of the invention is the provision of an improved electrical sizing device having particular reference to grinding machines and which will interrupt the feed between the grinding wheel and the work when the said wheel and work have approached one another a predetermined distance.

A further object of the invention is the provision of a sizin device adapted to stop the feed of the grinding wheel upon engagement thereof with a mechanism positioned at a point representative of the final size of the work.

Other objects and advantages of the present invention should be readily apparent by reference '0 the following specification con- OHIO, A CORPORATION OF OHIO MACHINE 1932. Serial No. 602,990.

Figure 7 is a fra entary sectional View taken on line 7 7 Figure 4.

Figure 8 is a sectional view taken on line 88 of Figure 1.

Figure 9 is a sectional view taken on line 99 of Figure 1.

Figure 10 is a sectional view taken on line 1010 of Figure 9.

Figure 11 is a diagrammatic view of one of the circuits employed with the invention.

Figure 12 'is a diagrammatic view of another circuit which co-operates with the circuit shown in Figure 11.

Figure 13 is a diagrammatic view of an electrical circuit showing a modification of the invention employing part of the circuits of Figures 11 and 12.

Figure 14 is a semi-diagrammatical illustration showing the invention as used with a grinding machine of a different type from ,that shown in Figure 1.

Throughout the several views of the drawings similar reference characters are employed to denote the same or similar parts.

While this invention has application to vasidered in conjunction with the accompanyrious types of machine tools in which a relaing drawings, forming a part thereof, and it tive feed between the tool and the work is is to be understood that anymodifications may had in order to reduce the work to the desired be made in the exact structural details there size and the movement of one of which parts shown and described within the scope of the is stopped when the work is reduced to the appended claims without exceeding or deraid final or desired size, it has been shown in parting from the spirit of the invention. the drawings in connection with a grinding In the drawings: machine. The particular grinding machine Figure 1 is a front elevation of a grinding illustrated in the drawings is what is known machine embodying the improvements of commercially as a plung cut grinder or inthis invention. feed type of a grinding machine in which a Figure 2 is a fragmentary sectional view continuous feed is had of the grinding wheel showing the feed of the tool or grinding or work without relative traverse therebewheel and as seen particularly from line 22 tween during the grinding operation. It is on Figure 1. I to be understood, however, that with few Figure 3 is an enlargeddetail view of parts modifications the invention may be used with of the feed mechanism as seen substantially the traverse type of grinding machine.

from line 33 on Figure 2. Accordingly, the machine shown in the Figure 4.- is an enlarged elevational view drawings comprisesa bed 15 having formed of the improved sizing device of this invenon the upper surface thereof guideways 16 tion. for guiding the work supporting table 17 in Figure 5 is a top plan view of the parts its longitudinal movements along the bed.

shown in Figure 4. The table 17 has mounted thereon the ad]ust- Figure 6 is a sectional View as seen from able head stock 18 and opposed tail stock 19 line 66 on Figure 4. from WlllCh respectively extends the centers 20 and 21 for holding the work 22 therebetween. The head stock 18 is ada ted to be wer driven which throu h the g 23 efects the rotation of the wor while being supported by the centers and 21.

The bed 15 is provided on its rear surface with a projection or support 24 having formed thereon guideways 25 for a grinding wheel carriage 26. The carriage 26 has journaled in bearings 27 a spindle 28 to one end of which is secured a grinding wheel 29. Any suitable or desirable means may be provided for effecting the rotation of the s indle 28 and grinding wheel 29 at the usual 'gh inding rate of speed. In order to reduce t e wor to the desired size, the carriage 26 and grinding wheel 29 are adapted to be fed relative ,to the ways 25 toward the work 22. For this purpose the carriage has secured to it interiorly thereof the nut 30 threadedly engaged with an adjusting or cross feed screw 31 ournaled in its outer end in a suitable bearing provided by the housing 32. This housing 32 encloses a gear 33 keyed or otherwise secured to the endof the adjusting screw 31 and meshing with an idler gear 34 supported by the housing 32. A gear 35 is further provided, which in turn meshes with the idler gear 34 for rotating said gear and is secured to the rear end of a transverse feed shaft 36 which terminates at its forward end interior- 1 of the bed 15. The forward end of the shaft 36 has secured to it a worm wheel 37 which is adapted to mesh with a worm 38 rotatably mounted in a bracket 39 pivoted at 40 to a fixed part 44 of the bed 15. The bracket 39 has depending from it a lug 41 in which is mounted a stud 42 carrying in its forward end a roller 43. J ournaled in the fixed part 44 of the bed 15 is a shaft 45 on which is secured a cam 46 in alignment with the roller 43 for engaging same. The shaft 45 is operatively connected with a manually operating lever 47 mounted on the forward face of the bed 15 for oscillating the said shaft and consequently the cam 46 secured thereto. Actuation of the lever 47 in the proper direction will oscillate the cam 46 in a counterclockwise direction as seen in Fi re 3, WhlCh through its interengagement with the roller 43 oscillates the bracket 39 in a corresponding counterclockwise direction to interengage the threads of the worm 38 with the teeth of the worm wheel 37. This oscillation of the bracket 39 is limited by an adjustable abutment screw 48 carried thereby and engaglng with the fixed portion 44 of the bed. The worm 38 is continuously rotated by a motor 49 illustrated diagrammatically in Figures 12 and 13 so that when the worm and worm wheel 38 and 37 are intermeshed the shaft 36 is being rotated to rotate the screw 31 and feed the grinding wheel toward the work. Simultaneously with the rotation of the shaft 36, there is rotated a drum 5O keyed or otherwise secured thereto, which has secured to it one end of a belt or band 51, the other end of which carries a weight 52. The weight 52 is enclosed within a suitable guide or the like 58. From this it will be seen that as the shaft 36 is rotated in a clockwise direction, for exam Ie, the band 51 is wound around the drum 5(? so that when the worm 38 and worm wheel 37 are disen aged, as seen in Figure 3, the weight 52 wi l reversely rotate the shaft 36 and retract the inding wheel carriage.

Referring now to Figure 12, it will be noted that there is shown a pair of main electrical leads 56 and 57 the former or positive lead havingethe master control switch 58 therein and ing connected through the handle 47a, which is the same as the handle 47, and branch lead 59 to one end of the motor 49. The remainin or negative lead 57 is connected to the ot er side of the motor 49 by a branch wire or lead 60. Extending from the branch lead 59 is a wire 61 terminating in one contact of a magnetic switch 62, the other contact of this switch being connected by a wire 63 with one end of a magnet coil. 64, the other end of this coil being in turn connected by a wire 65 with the branch negative or return lead 60. As shown in Figure 12, this magnetic switch 62 is closed, thereby completing an electrical circuit and energizing the electromagnet 64 which operates on the end of lever 47a to hold it in the position illustrated for maintaining engagement between the worm 38 and worm wheel 37. In actual practice, and as shown in Figure 3, the oscillating or pivot shaft 45 is provided with a finger 66 which engages with the magnet 64 for holding the parts in the position illustrated in Figure 12.

To discontinue the .feed the magnet 64 is de-energized thereby releasing the lever 47a or fin er 66 so that the worm wheel and worm may he disengaged to permit retraction of the grinding wheel, which will be described in detail later.

The sizing mechanism here illustrated comprises an electromagnetic generator indicated structurally in Figures 1, 2, 4 and 6 by the reference character 67 and diagrammatically in Figures 11 and 13 by the reference character 68. The generator 67 or 68 is carried by an arm 69 pivoted at 70 to a block 71. The arm 69 has projecting from it on one side of the pivot 70 a lug 72 against whch abuts one end of a spring 73 contained within a socket 74 formed in the block 71. The spring 73 tends to oscillate the arm 69 in a counterclockwise direction about the pivot 70 to actuate the generator 67 toward the operative face of the grinding wheel 29. This movement of the arm 69 is adjustably limited b means of a stop screw 75 threaded throug a tongue 76 depending from the block 71.

The block 71 is provided with a dovetailed guideway 77 receiving a correspondingly shaped guide tongue 78 formed on a swivel plate 79. The swivel plate 79 is substantially L-shaped, as seen in Figure 6, to provide the depending arm 80 in which is journaled one end of an adjusting screw 81. The adjusting screw 81 is threadedly received in the tongue 76 of the plate 79 and is further provided on its outer end with an operating knob 82 whereby it may be rotated for effecting adjustment of the block 71 relative to the plate 79. i The swivel plate 79 has projecting from its upper surface a stud 83 rece'ved in an eye 84 formed in one end of an arm 85. The swivel plate 7 9 is secured to the arm 85 by means of a nut 86 received on the extreme threaded end of the stud 83 and it will be seen that the swivel plate 79 may be adjusted to any desired point about the axis of the stud 83 for aligning the generator 67 with the face of the grinding wheel 29.

The arm 85 is provided in its other end with a second eye 87 through which a T-bolt 88 extends having its T-shaped head 89 received in a slot 90 formed longitudinally of a beam 91. The beam 91 is formed integral with a slide 92 which is provided with a dove-ta'led guideway 93 receiving a correspondingly shaped guide tongue 94 formed on the fixed slide 95. The fixed slide 95 is secured in any desirable manner such as by cap screws 96 to the face of the head stock adjacent the grinding wheel. The fixed slide 95 is formed with an internally threaded lug or nut 97 receiving the threaded end of ad- 'usting screw 98. The screw 98 is sw'veled 1n a plate 99 secured to one end of the movable slide 92 and is further provided exteriorly of this plate with an actuating knob 100 whereby the said screw is rotated.

From the foregoing it will be noted that there has been provided a support for the siz'ng member or generator whereby the said generator may be actuated transversely of the grinding face by adjusting the arm 85 along the beam 91 and secured thereto by T-bolt 88, or the generator may be ad usted toward and from the operative face of the grinding wheel by means of the adjusting screw 98 such as when changing the wheel from a worn wheel to a new wheel or vice versa or it may be adjusted toward the operative face of the grinding wheel by the adjusting screw 81. This latter adjustment, of course, is employed for finer adjustments than the screw 98. Also the arm 69 may be extremely minutely adjusted relative to the o )erative face of the grinding wheel through t e adjustable stop 75 while being actuated about the pivot of its supporting arm by the spring 73. It will also be remembered that the swivel plate 79 may be adjusted in a horizontal plane about the axis of the swivel stud 83 projecting therefrom for thereby aligning the generator 67 with the plane of the operative face of the grinding wheel.

As is well known, the operative face of a grindin wheel while reasonably smooth to the tone while traveling at a high grinding rate of speed, is nevertheless composed of an infinite number of cutting edges or points with hollows or depressions between the adjacent cutting edges or points. Therefore a sensitive member riding on such a surface would tend to ride up and down the sides of the cutting edges causing an oscillatory vibration of the member. Such a member is the armature of the generator 67 indicated in the drawings by the reference character 101 and carrying at its extreme outer end a diamond or other hard substance 102. The armature is shown in Figure 11 as the pivoted arm 103 adapted to be oscillated about the pivot 104 for reciprocating the core 105 through the coil 106. These parts all constitice may be a magnetic pick up or an electromagnetic unit.

The coil 106 has extending from its opposite ends, leads or wires 107 and 108, the former being biased as by the battery 109 and terminating in a ground connection. The line 108 terminates in the rid 110 of a vacuum or radio amplifying tu e 111. As usual, this tube 111 includes the plate 112 upon which is impressed the electrical energy of the grid 110 and which plate is connected by wire'or lead 113 to the primary coil 114 of a transformer115. The tube 111 is an amplifier tube for amplifying the current generated in the generator 68. The transformer 115 has the secondary coil 116 receiving the current from the primary 114 and passing same on to the grid 117 of a biased detector tube 118. The bias on the detector tube grid 117 is obtained in the usual manner by a battery 119. The current in the grid 117 is in turn impressed on the plate 120 of the tube 118, which plate is connected by a lead or wire 121 to one terminal of a current meter 122, from the other side of which meter extends lead or wire 123. The lead or wire 123 is connected to one terminal of the B battery 124. This B battery has its other end connected with the opposite phase terminal of a second B battery 125 which is in turn connected through the transformer primary coil 114 with the plate 112 of the amplifier tube 111.

In order to effect the transferof current from the grids 110 and 117 to the plates 112 and 120, each of the tubes 111 and 118 is respectively provided with a filament or heating element 126 and 127 having one end thereof connected in series by a wire or lead 128 which terminates at one terminal of the A battery 129. The other terminal of the filaments 126 and 127 are likewise connected in series by means of a lead or wire 130 termitute the generator 68, which in actual pracnating at the other terminal of the battery 129.

From the above it will be noted that when the grinding wheel engages with the diamond or other hard substance 102 it effects a. relative movement between the core and coil of the generator for generating a relatively weak-current. This current is, however, immediately amplified to a oint for operating a current flow meter which would indicate that the grinding wheel has approached a definite distance as respects the axis of the work and that the work has now been reduced to the ultimate desired size. The amplifier tube 111, detector 118, transformer and parts associated therewith are mounted on a base 195 and enclosed in a suitable housing or cover 196, as shown in Figure 8. This unit may then be mounted on the front face of the bed 15.

As shown in Figures 9 and 10, the meter comprises a housing 131 in which is mounted a dial 132 normally carrying the graduations or indications to determine the amount of flow of current in the line. Also mounted within the housing 131 is a needle arm 133 carried by a shaft or axle 134 and adapted to be oscillated relative to the plate 132 to indicate the amount of current flow. This needle or arm 133 is deflected in the usual mannenand may be connected by suitable wires or leads extending from the leads 121 and 123.

As shown in Figures 9 and 10, the dial plate 132 is provided with an aperture or opening 135 which is normally closed to prevent light passing therethrough by an obstruction or mask 136 carried by the needle 133 and adapted to uncover the said aperture when the needle is deflected.

The meter and its housing 131 are adapted to be enclosed within a suitable casing 137 which includes the base 138 and mounted as a unit on the forward face of the grinding machine bed as indicated in Figure 1. Within the casing 137 there is also provided a lamp or other source of light 139 adapted to direct its rays as indicated at 140. in Figure 10, on to the mask 136, which if deflected will pass through the aperture 135 to the other end of the casing 137. Mounted in the other end of the casing 137 is a control mechanism operated by a light sensitive cell indicated by the reference character 141 in Figure 10. This light sensitive cell energizes or completes an electrical circuit for disconnecting the feed, as will later appear.

The photoelectric cell 141 is shown diagrammatically in Figure 12, which diagrammatically illustrates the electrical circuit controlled and operated thereby. This circuit includes a suitable transformer 142 coupled with a source of current or main power lines 143 and 144 for feeding current of the desired voltage to the several electrical instrumentalities here coupled. The coil 145 has feed lines 146 and 147 extending therefrom and terminates in a potentiometer 148 which, through the line 149 extending from the potentiometer places a negative potential on the grid 150 of the radio or vacuum tube 151. The vacuum tube 151 includes a plate 152 and filament 153, the latter receiving our rent from the coil 154 through the lines 155, 147 and 156 to one side of the filament and through lines 157, 158 and 159 to the other side thereof. The late 152 receives current from the coil 160 tlirough the line 161, solenoid 162 and line 163, the current tending to return throu h the filament and line 159 to the upper sife of the coil, but being blocked by the negative electrical potential on the grid 150. The intermediate portion of the coil 160 isconnected by a line 164 to one element 165 of the light sensitive or photoelectric cell 141 while the second element 166 thereof is connected by a line 167 to the potentiometer grid line 149. The solenoid 162 has extending therethrough a core 168 secured to a bell crank 169 pivoted at 170 for o erating a switch blade 171. This switch b ade 171 is employed for completing an electrical circuit including the conductor 172 from the main line 143 through a conductor 173.to the second main line 144. This conductor 173 has included therein the solenoid 174. A core 175 associated with the solenoid 174 is employed for operating a switch blade 176 about its pivot 177 to complete a second shu'nt circuit extending from the line 173 through a conductor 178 and a second conductor 179 extending from an electrical contact associated with switch blade 176. i

The branch circuit conduit 172 is connected by a wire or lead 180 with one end of a coil 181 of magnetic switch 182. The other end of this coil 181 is connected to the lead 179. The magnetic switch 182 includes the core 183 which passes through the coil 181 and carries the switch blade 184. This blade 184 is normally elevated by means of a spring 185 acting on the end of the core 183 for normally holding the switch 182 in an open condition. Extending from one contact of the switch 182 is a wire or lead 186 that connects with one end of solenoid switch coil 187 of the solenoid switch 62. The other end of this coil is connected by a wire or lead 188 to the electric line 59. The other contact of the switch 182 is connected by the wire or lead 189 with the line 60 of the main motor circuit.

The operation of the mechanism is as follows. When the grinding wheel has reduced the work to the final desired size, it operates the generator 68 for generating a current which is amplified as above described for actuating the needle arm 133 of the meter 122. The light source or lamp being constantl burning is directing its rays on the mask 136. Upon deflection of the needle 133 the 152 and from there to the filament 153 of the vacuum tube 151 to the line 159 and complete an electrical circuit. Due, however, to the negative electrical otential on the grid 150 this current flow 1s prohibited. However, upon completion of the electrical circuit through the light sensitive cell 141, the current will flow through the conduit 164 and 167 to the grid 150 thereby nullifyin the electrical negative potential thereon an permitting the flow of the current from the plate 152 to the filament 153. This flow of the current energizes the solenoid 162 causing the core therein to be actuated relative thereto and through the bell crank lever 169 actuates the switch blade 171 and completing an electrical circuit through the branch conduits which includes the line 173, coil 174 and line 172. This in turn operates the switch blade 176 thereby completing the control circuit which includes the solenoid switch coil 181. This circuit, of course, takes in the lead 178 extending from the branch lead 173, switch blade 176, lead 179. coil 181, lead 180 to the lead 172. 1

The energization of the coil 181 closes the switch 182 against the yielding resistance of the spring 185 thereby completing the electrical circuit which includes the lead 188, coil 187, of magnetic switch 62, lead 186, switch 182 and lead 189. The energization of the coil 187 opens the switch 62 for deenergizing the circuit including the electromagnet 64. As above described'the magnet 64 normally holds the worm 38 and Worm wheel 37 in operative engagement with one another so that upon removal of the holding force the worm drops from the worm wheel disconnecting or discontinuing the relative feed and through the weight 52 retracting the grinding wheel from the work.

The modification shown in Figure 13 includes the generator 68 and the electrical circuit operated thereby, but instead of having the plate line 121 connected with one terminal of. the meter 122, it is connected directly to one end of the magnetic switch coil 181. The other end of this coil 181 is connected to one terminal of the battery 124. From this it will be seen that the electrical circuit may be connected directlywith the control mechanism without passing through the electrical circuit operated and controlled by1 the light sensitive or photoelectric cell 14 The modification illustrated in Figure 14 shows the sizing control mechanism as used with an internal grinder in which the work piece 190 is held in a chuck 191 on the end grinding wheel 193 secured to the spindle,

or shaft 194. In this construction the generator 67 is positioned to engage the surface of the wheel when it reaches the desired size of the hole.

What is claimed is:

1. In a device of the class described the combination of a tool, a support for the tool, a work support adjacent the tool, means for actuating the tool and work support toward and from one another, means for engaging the tool after it has approached the work a predetermined amount, said means generating a current upon contact of the work therewith, and means amplifying said current for discontinuing the relative-feed between the work and tool.

2. In a machine tool of the class described the combination of a bed, a grinding wheel mounted thereon for movement relative thereto, a work support carried by the bed for supporting a work piece in the line of movement of the grinding wheel, means for effecting the said movement of the grinding wheel, and current generating, means carried by the bed in the line of movement of the grinding wheel adapted to be engaged thereby for generating a current when the grinding wheel has been actuated toward the work a predetermined amount.

3. In a machine tool of the class described the combination of a bed, a grinding wheel mounted thereon for movement relative thereto, a work support carried by the bed for supporting a work piece in the line of movement of the grinding wheel, means for effecting the said movement of the grinding wheel, current generating means carried by the bed in the line of movement of the grinding Wheel adapted to be engaged thereby for generating a current when the grinding wheel has been actuated toward the work a predetermined amount, and means operated by said generated current for effecting a cessation in the feed of the grinding wheel.

4. In a machine tool of the class described the combination of a bed, a grinding wheel mounted thereon for movement relative thereto, a work support carried by the bed for supporting a work piece in the line of movement of the grinding wheel, means for effecting the said movement of the grinding wheel current generating means carried by the bed in the line of movement of the grindlng wheel adapted to be engaged thereby for generating a current when the grinding wheel has been actuated toward the work a predetermined amount, means operated by said generated current for effecting a cessation in the feed of the grinding wheel, a pivotally mounted arm for supporting the current generator,

means supporting the arm on the bed for adjustment toward the rinding wheel and transversely thereof, and means for locking the arm in its several adjusted positions.

5. In a grinding machine of the class described the combination of a work support and a grinding wheel support, means for effecting a relative feed between the grinding wheel and work, and means for limiting said relative feed comprising a current generator adapted to be engaged by the rinding wheel, an amplifier for amplifying t e current, and means for effecting the disconnection of the feeding means operated by the amplified current.

6. In a grinding machine of the class described the combination of a bed, a grinding wheel mounted thereon for movement relative thereto, a work support mounted on the bed, means for effecting a relative axial approach of the grindin wheel and work to effect a stock removal rom the work, means for interrupting said relative approach of the work and grinding wheel comprising a current generator for generating a current upon contact of the wheel therewith, a current amplifier for amplifying the current to a point for operating a current flow meter, a control circuit for discontinuing the relative approach of the work and wheel, and means controlled by the current flow meter for de-energizing the feed control circuit.

7. In a grinding machine of the class described the combination of a bed, a work support mounted on the bed, a grinding wheel mounted on the bed, means including a pair of disengageable members for efl'ecting a relative feed between the worlo support and grinding wheel, electromagnetic means for holding the members in operative engagement with one another, means for stopping the relative approach between the work and grinding Wheel comprising a current generator adapted to engage the grinding wheel, and a current amplifier for amplifying the enerated current to a point for de-energizmg the electro magnetic means.

8. In a grinding machine of the class described the combination of a bed, a work support and a tool support carried by the bed, the former supporting a work piece and the latter supporting a grinding wheel, an

interruptable transmission mechanism for effecting a relative approach of the work support and tool support, means for interrupting the transmission mechanism includ ing an electrical circuit, a current generator disposed in the path of movement of the work and tool when actuated toward one another for engagement with one of said members for enerating a current when the said members have reached a definite relative position, and means operated by said generated current for operating the control circuit.

9. In a grinding machine of the class described'the combination of a bed, a grinding wheel carried thereb a work sup rt on the bed, means for e ectin a relative feed between the grinding whee and work support to effect a stock removal from a work piece on the work support, electrically controlled means for stopping the relative feed when the work has been reduced to the'desired size, a current generator adapted to engage the grinding wheel when the work is reduced to the desired size for generating a current, an amplifier for amplifying the current, and an o erative connection between the amplifier an electrically controlled means for actuating said means by the amplified current.

10. In a grinding machine of the class described the combination of a bed, a grinding wheel and work support mounted thereon for movement relative to one another, a feeding mechanism for effecting said relative movement, a current generator adapted to engage the grinding wheel when the work is reduced to the desired size for generating an electrical current, a current flow meter, an amplifier for amplifying the generated current to a' point for operating the current flow meter, the current flow meter having an aperture therethrough, a mask normally sealing said aperture but deflected upon operation of the current flow meter, and means operated by the deflection of the mask for discontinuin the relative feed of the grinding wheel and work,

11. In a grinding machine of the class described the combination of a bed, a grinding wheel and work support mounted thereon for movement relative to one another, a feeding mechanism for effecting said relative movement, a current generator adapted to engage the grinding wheel when the work is reduced to the desired size for generating an electrical current, a current flow meter, an amplifier for amplifying the generated current to a point for operating the current flow meter, the current flow meter havin an aperture therethrough, a mask norma ly sealing said aperture but deflected upon operation of the current flow meter, and means operated by the deflection of the mask for discontinuing the relative feed of the grinding wheel and work, said means comprising a li ht sensitive cell, a source of light in line wit and adapted to direct its rays on the light sensitive cell and I normally interrupted by the mask, and an electrical circuit controlled by the light sensitive cell.

12. In a grinding machine the combination of a bed, a grinding wheel and a work support mounted thereon for movement relative to one another, a feed mechanism for effecting the relative movement between the grinding wheel and work support to reduce a work piece carried by the support to the desired size, means adapted to engage the grinding wheel when the work is reduced to the desired size for generating a current of a given intensity, a current flow meter, means for amplifying the generated current to a point for 0 erating the current flow meter, said amp ifying means including a radio vacuum tube, a needle associated with the current flow mete-r and adapted to be deflected upon flow of current therethrough, and a light controlled mechanism normally inoperative but rendered operative upon deflection of the needle for discontinuing the relativefeed between the grinding wheel and work.

13. In a grinding machine the combination of a bed, a grinding wheel and a work support mounted thereon for movement relative to one another, a feed mechanism for effecting the relative movement between the grinding wheel and work support to reduce a work piece carried by the support to the desired size, means adapted to engage the grind ing wheel when the work is reduced to the desired size for generating a current of a given intensity, a current flow meter, means for amplifying the generated current to a point for operating the current flow meter, said amplifying means including a radio vacuum tube, a needle associated with the current flow meter and adapted to be deflected upon flow of current therethrough, a light controlled mechanism normally inoperative but rendered operative upon deflection of the needle for discontinuing the relative feed between the grinding wheel and work, and means retracting the wheel and work upon discontinuance of the feed.

14. In a grinding machine the combination of a bed, a grinding wheel and a work support mounted thereon for movement relative to one another, a feed mechanism for effecting the relative movement between the grinding wheel and work support to reduce a work piece carried'by the support to the'desired size, means adapted to engage the grinding wheel when the work is reduced to the desired s'ze for generating a current of a iven intensity, a current flow meter, means or amplifying the generated current to a point for o erating the current flow meter, said ampli ying means including a radio vacuum tube, a needle associated with the current flow meter and adapted to be deflected upon flow of cnrrent therethrough, a light controlled mechanism normally inoperative but rendered o erative upon deflection of the needle for discontinuing the relative feed between the grinding wheel and work, means retracting the wheel and work upon discontinuance of the feed, and means for supporting the current generator for universal adjustment relative to the operative face of the grinding wheel.

15. In a sizing control mechanism for use with grinding machines to cut off the relative feed between a grinding wheel and work piece when the work piece is reduced to the final desired size, the combination of a current generator positioned at a point in the path of travel of the wheel representative of the final size of the work and adapted to contact with the face of the wheel, and means operated by the generated current for interruptin the feeding mechanism.

16. n a sizing control mechanism for use with rinding machines to cut off the relative feed tween a grinding wheel and work piece when the work piece is reduced to the final desired size, the combination of a current generator positioned at a point in the path of travel of the wheel representative of the final size of the work and adapted to contact with the face of the wheel, means operated by the generated current for interrupting the feeding mechanism, a pivotally mounted arm supporting the generator, means supporting the arm for adjustment toward and away from the grinding wheel, means supporting the arm for ad ustment transversely of the operative face of the wheel, and means for supporting the arm for oscillatory adjustment to vary the an ular relationship between the generator an operative face of the wheel. t

17. In a sizing control mechanism for use with grinding machines to cut off the relative feed between a grinding wheel and work piece when the work piece is reduced to the final desired size, the combination of a current generator positioned at a point'in the path of travel of the wheel representative of the final size of the work and adapted to. contact with the face of the wheel, means op-. erated by the generated current for interrupting the feeding mechanism, a pivotally mounted arm sup orting the enerator, means supporting t e arm for a justment toward and away. from the grinding wheel,

-means supporting the arm for ad ustment transversely of the operative face of the wheel, means for supporting the arm for oscillatory adjustment to vary the angular relationship between the generator and operative face of the wheel, and meansfor retracting the grinding whwl from the work upon cessation of the feed.

In'testimony whereof, I afiix my signature.

ALFRED G. PLIMMER.

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