US3037330A - Autoamtic grinding and polishing machine - Google Patents

Description

C- G. WElGAND AUTOMATIC GRINDING AND POLISHING MACHINE Filed April 15, 1959 June 5, 1962 7 Sheets-Sheet 1 m m m m 04/: mes G. WE/GAA/D June 5, 1962 c. G. VVEIGAND 3,037,330

AUTOMATIC GRINDING AND POLISHING MACHINE Filed April 15, 1959 '7 Sheets-Sheet 2 June 5, 1962 c. G. WEIGAND AUTOMATIC GRINDING AND POLISHING MACHINE 7 Sheets-Sheet 3 Filed April 15, 1959 June 1962 c. G- WEIGAND 3,037,330

AUTOMATIC GRINDING AND POLISHING MACHINE Filed April 15, 1959 '7 SheetsSheet 4 2/ 22 INVENTOR. Cf/AELES G. WE/GA/VD 22 v BY A T TUBA/E Y5.

June 5, 1962 QGWHGAND 3,037,330

AUTOMATIC GRINDING AND POLISHING MACHINE Filed April 15, 1959 '7 Sheets-Sheet 5 INVENTOR.

0/31/2455 6. WE/GAA/D Wm, Kolekmm new,

Kai/Milan a nc/ Wyn, ATT0zA/EYs.

June 5, 1962 c. G. WElGAND 3,037,330

AUTOMATIC GRINDING AND POLISHING MACHINE Filed April 15 1959 7 Sheets-Sheet 7 TRA V5255 RELA Y TEA VERSE SOLENOID /79 30L DELAY /64 iv SWITCH United States atent 3,037,330 I AUTOMATIC GRINDING AND POLISHING MACHINE I 7, Charles G. Weigand, Glencoe, Ill. assignor t Fijdelitone, Incorporated, Chicago, Ill; a corporation of Illinois Filed Apr. 15, E59, Sen. No. 806,729 17 Claims. (CI. 51-50) The present invention relates to automatic grinding and polishing machines, and more particularly to such machines adapted for grinding and polishing styli formed of precious stones for use in sound reproduction such as phonograph records and the like.

In transducer assemblies for reproducing sound from grooved records the tendency in recent years has been toward using styli for-med of precious stones such as sapphires and diamonds which possess the desired hardness characteristics. Preferably such diamond tipped styli are united with a shank element so that the diamond styli are oriented properly to assure the maximum hardness and the like of what will eventually become the tip portion engaging the record groove of a phonograph record. An improved process of uniting a precious stone such as a diamond to a shank element with proper orientation of the precious stone is disclosed in an application, Serial No. 760,5"13Curcio, filed September 11, 1958, and assigned to the same assignee as the present application. After the proper bonding of the diamond to the shank element or other suitable holding means, it is necessary to grind the bonded diamond to a predetermined configuration to provide a record engaging tip, and the present invention is concerned with improved apparatus for accomplishing this. It will be appreciated that such styli are very small and to perform a grinding operation it is necessary for the operator to view the grinding operation through a microscope or other means for providingan enlarged View of the grinding operation during the grinding process. Moreover, such apparatus must be completely free of vibration and, furthermore, should be automatic in opera tion so that the operator, with a rninirnum of effort, may be assured of obtaining a proper grinding operation and polishing operation.

Accordingly, it is an object of the present invention to provide a new and improved grinding and polishing apparatus.

It is another object of the present invention to provide a vibration free grinding apparatus for grinding precious stones such as those employed in phonograph styli.

It is another object of the present invention to provide a grinding machine with a movable carriage having automatic means for providing fast traverse at all times except during the actual grinding or polishing operation.

It is another object of the present invention to provide in an automatic grinding and polishing apparatus pneumatic counterbalancing means in the mechanism supporting the item to be ground, and/ or polished thereby, to eliminate any errors due to backlash in gears or the like forming a necessary part of the mechanism.

Still another object of the present invention resides in the provision in an automatic grinding and polishing machine of safety means whereby no interference between the chuck for holding the item to be ground and the grinding wheel can occur.

It is a further object of the present invention to provide an automatic grinding and polishing apparatus for precious stones in which the grinding wheels are automatically dressed between successive grinding operations.

It is a still further object of the present invention to provide an automatic grinding apparatus with tangential feed whereby grinding wheel size is immaterial and grinding at any angle may take place.

7 Still another object of the present invention resides in an automatic grinding and polishing machine of a combined hydraulic and pneumatic means for reciprocating the grinding wheel wherein the hydraulic means is rendered ineifective when fast motion in either direction of the grinding wheel is desired.

Further objects and advantages of the present invention will become apparent as the folowing description proceeds, and the features of novelty which characterize the invention will be pointed out with particularily in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of the automatic grinding and polishing machine of the present invention;

FIG. 2 is a front elevational view of the automatic grinding and polishing machine of the present invention;

FIG. 3 is a top plan view of FIG. 2 with certain portions cut away and effectively is a sectional view taken on line 36 of FIG. 2;

FIG. 4 is a sectional view taken on line 4 of FIG. 2;

FIG. 5 is a rear elevational view of the apparatus of FIG. 2 with certain portions thereof cut away;

FIG. 6 is a sectional view taken on line 6-6 of FIG. 2 but with the 'wheel dressing mechanism in actuated position;

FIG. 7 is a greatly enlarged sectional view taken along line 7 7 of FIG. 6;

FIG. 8 is a fragmentary view illustrating the work-piece held in the chuck and its relationship with the grinding wheel;

FIG. '9 is a schematic diagram of a control circuit for the automatic grinding and polishing apparatus of the present invention; and

FIG. 10 is a view illustrating a closed circuit television system associated with the grinding apparatus so the operator may watch the grinding operation without the use of a microscope.

Briefly, the present invention comprises a support for motor driven grinding and polishing wheels which may be moved to a position for either grinding or polishing a precious stone held in a chuck which is mounted for movement toward or away from such abrasive wheels. The chuck is mounted so that it will always be tangential with the abrasive wheels, so that regardless of the wheel size the grinding operation will be at the same predetermined angle. A vibrationless mechanism is provided for reciprocating the carriage supporting the abrasive wheels at high speed when moving toward or away from the chuck containing the tip but at slow reciprocating grinding or polishing speeds during either the actual polishing or actual grinding operations. The manual control means for supporting the chuck holding the item to be ground is supported on an air cushion so as to eliminate any error due to backlash or the like. Automatic controls are provided, so the operator in starting the machine must have his hands free. These controls provide for slow speed recip= rocating movement across either the grinding wheel or the polishing wheel and high speed movement at all other times.

Referring now to the drawings, the high speed grinding apparatus of the present invention is generally designated by reference numeral 20 and comprises a base or frame 21. For the purpose of preventing vibrations of the environment where the machine 28 is mounted from reaching the machine itself, the base 21 is preferably supported on a plurality of shock absorbers generally designated at 22. As illustrated, the frame or base 21 is provided with a plurality of integral projections 21a, three being shown in the drawings, for engaging the shock absorbers 22.

These shock absorbers are preferably formed of steel mesh and three of them are employed, one beneath each projection 21a, so that the machine may readily be adjusted to a level condition as by adjusting screws 24 threadedly received one in each projection 2111. As best shown in FIGS. 3 and 4 of the drawings, two shock absorbers 22 are employed at the right end of the machine and one at the left end (FIG. 6). Lock nuts associated with screws 24 are preferably provided. As will become apparent from the description included herewith, the machine 20 is essentially a vibrationless' machine, but if mounted in a manufacturing plant there is bound to be some vibration of the floor where such a machine is supported, and the shock absorbers 22 are provided to eliminate the vibrations of any environment with which the machine is associated.

Supported for reciprocal movement with respect to the frame or base 21 is a slide assembly carriage 26 including a guide means 26a provided for accurate reciprocal movement by suitable ways 28 defined in the base 21 or means secured to the base. A grinding wheel motor 29 is supported on the slide assembly carriage 26, and the drive shaft of this motor extends through a suitable bearing housing 30 where the end remote from the motor may suitably support a pair of abrasive wheels which may comprise a grinding wheel 31 and a polishing wheel 32 arranged in parallel relationship and slightly spaced from one another. The housing 30 encloses suitable bearings to provide a substantially vibration-free arrangement so that the grinding wheels 31 and 32 are driven without vibration. In an embodiment built in accordance with the present invention, the motor 29 drove grinding wheel 31 and polishing wheel 32 in excess of 5000 surface feet per minute.

In order to reciprocate the entire slide assembly carriage 26 and, consequently, the grinding and polishing wheels 31 and 32, respectively, the carriage 26 is connected by a reciprocating rod 34 to a pneumatic-hydraulic mechanism generally designated at 35, which comprises effectively a pneumatic or air cylinder 36 and a hydraulic cylinder 37 arranged in axial or end-to-end relationship. As best shown in the somewhat schematic view of FIG. 1 of the drawings, the rod 34 suitably connected to the carriage 26 is really a piston rod and extends into both of the axially aligned cylinders 36 and 37, actually passing entirely through cylinder 37 into cylinder 36. A piston 38 is secured to rod 34 within cylinder 37, and a piston 39 is secured to rod 34 within cylinder 36.

As clearly shown in FIG. 1 of the drawings, the air cyllnder 36 of the combined hydraulic air mechanism is a conventional pneumatic means including piston 39 for reciprocating the carriage 26. A suitable source of air under pressure, not shown, is preferably supplied to a pressure regulator unit 40 also shown in FIG. 2 of the drawings. The unit 48 preferably includes lubricating means for introducing some lubricant into the air supply. This regulated air under pressure is supplied through a four-way valve 41 and a conduit 42 with one end of the air cylinder 36 or through this valve 41 and a conduit 43 with the other end of the air cylinder 36. The four-way valve 41 is also connected to atmosphere through a conduit 44. As illustrated schematically, the four-way valve 41 is a solenoid operated valve, and two solenoids and 46 having windings 45a and 46a are schematically indicated. From the above description it is apparent that solenoids 45 and 46 control the movement to the right or to the left, as viewed in FIG. 1, of the piston 39 and, consequently, of the carriage 26. Assuming that solenoid 45 is the right traverse solenoid and controls movement to the right of piston 39, it will be apparent that when solenoid 45 is energized the four-way valve 41 will permit air from hte regulated supply 40 to pass through conduit 42 into the left end of cylinder 39, as viewed in FIG. 1 of the drawings, and the four-way valve 41 under these conditions will connect the other end of cylinder 36 to atmosphere through conduit 44 so as to exhaust that end of the cylinder. Exactly the reverse occurs when solenoid 46, which might be termed the left traverse solenoid, is energized, since under these conditions air from regulated source 40 is permitted to enter the right end of cylinder 36 through conduit 43, while the other end of the cylinder is exhausted through exhaust 44. Thus, the selective energization of solenoids 45 and 46 will insure the reciprocating movement of carriage 26.

With the arrangement described thus far the carriage 26 would move at high speed to the right or to the left depending upon which solenoid 45 or 46 was energized. In accordance with the present invention, however, there is employed the hydraulic cylinder 37 containing therein the piston 38 connected to the same piston rod 34. In order to provide slow or fast speed operation of the piston 38 as desired, the hydraulic cylinder 37 is provided with a large solenoid controlled bypass generally designated at 48, which bypass interconnects the two ends of the cylinder 37 through a relatively large passageway. This passageway is controlled by solenoid operated valve 49 including the solenoid 50 having a winding 50a. When the winding 50a is energized, the large bypass 48 is opened, which means that hydraulic fluid contained in cylinder 37 can move freely from one side of the piston 38 to the other so as not to provide any drag on the piston 39. Additionally, the cylinder 37 includes a small controlled bypass 51 which, like bypass 48, interconnects the two ends of the cylinder 37. However, this bypass comprises a relatively small passageway with' in which is included a needle valve 52 whereby the size of this bypass may be adjusted. Bypass 51 is always open at some predetermined setting of the needle valve 52, and when bypass 48 is closed it provides the desired selective speed control of the piston 39. It will be apparent that when winding 50a is energized piston 39 will reciprocate the carriage 26 at high speed regardless of the direction in which it is moving, whereas when winding 50a is not energized and bypass 48 is closed the movement in either direction of piston 39 will be relatively slow and controlled by the needle valve 52 in bypass 51.

In order to make sure that diamond dust and the like removed during the grinding or polishing operation does not deleteriously affect the piston rod 34, the portion thereof which moves into and out of the combined pneumatic-hydraulic motor 35, as is clearly known in FIGS. 2, 3, 4 and 5 of the drawings, is enclosed within a protective rubber bellows or the like generally designated at 55, which bellows has one end thereof secured in sealed relationship to the wall surrounding the opening into the end of the cylinder 37 as indicated at 56, while the other end thereof is suitably clamped as indicated at 57 to the piston rod 34. Consequently, the portion of the shaft 34 which moves into and out of the cylinder 37 is completely protected from diamond dust and the like.

It will be understood that the grinding wheel 31 and the polishing wheel 32 are diamond impregnated abrasive wheels which may be made of metal or a vitreous mate rial. These abrasive wheels are essentially the same except that there is a difference in the diamond grit size and concentration thereof embedded in the metal or vitreous material so that, in elfect, grinding wheel 31 might be considered a coarse wheel whereas wheel 32 might be considered a fine wheel.

As illustrated in FIG. 2 of the drawings, the pressure regulator 40 is preferably provided with a pressure gauge 58 furnishing a continuous indication of the pressure of the air supplied to the various portions of the machine 20 including the air cylinder 36 described above. The air supply will be turned on before any grinding operation is to be initiated.

It will 'be appreciated that in any grinding apparatus means must be provided for holding the object to be ground and polished during the actual grinding or polishing operation, which means must also be movable .5 toward and away from the abrasive wheels. To this end there is provided a work spindle assembly generally designated at 60 which, as best shown in FIG. 4 of the drawings, comprises a carriage 61 which is movable along a predetermined axis specifically designated in FIG. 4 by the reference numeral 62. Movement along the axis 62 results in movement of the carriage 61 towards and away from the grinding and polishing wheels 31 and 32, respectively. The spindle carriage 61 is reciprocably movable along the axis 62' relative to a carriage support 63 which is suitably supported from the base 21. The position of the spindle carriage 61 relative to the support 63 is controlled by a lead screw 65 (FIG. 4) to which is secured the conventional manually adjustable handle 66. A micrometer gauge 67 permits the operator to determine the relative movement of the carriage 61 along the axis 62. In accordance with the present invention, the lead screw 65 has associated with the lower end thereof a pneumatic cylinder 69 which is connected to the source of air pressure and specifically the regulator 40 at all times when the machine is in use. To this end a regulator 4011 (FIG. 2) is provided for the cylinder 69 by means of which the air pressure to cylinder 69 is independently controlled. A piston 68 associated with cylinder 69 biases carriage 61 in a predetermined manner thereby to counterbalance the weight of the spindle assembly 69 including the carriage 61 to take up any slack in the lead screw 65. In other words, this pneumatic cylinder 69 including piston 68 causes the spindle assembly 60 and carriage 61 to be biased upwardly by the air pressure so that when manipulating the handle 66 there is positive feed against air pressure so that no change of position by virtue of slack in the threads in the lead screw 65 can occur.

The spindle assembly 60 is supported from the carriage 61 by the pivotal means designated as 70 (FIG. 4), so that the spindle assembly 66 may be adjusted at various angles with respect to the carriage 61. To this end a bracket 71, which may be cast integrally with other portions of the spindle assembly, is provided from which certain portions of the spindle assembly, to be described hereinafter, are supported. This bracket 71 is pivotally mounted to the spindle carriage 61 about the pivotal means 70. In order to secure bracket 71 to carriage 61 in any selected predetermined position, the former is provided with a pair of diametrically opposed elongated arcuate slots 72 through which extend clamping screws 73. By means of suitable nuts 74 the bracket 71 may be supported at a predetermined angular relationship with respect to the carriage 61.

So that this angular relationship can readily be determined, spindle carriage 61 of the automatic grinding and polishing machine 2%) of the present invention is preferably provided with suitable indicia indicated at 75, as clearly indicated in FIG. 2 of the drawings. A suitable index mark 76 on the bracket 71 cooperating with this indicia 75 permits the operator readily to see what the particular setting is. This setting will determine the grinding or polishing angle of the object being ground. The specific setting of the device indicated in the drawings is to produce a sixty degree angle, but this may be adjusted to either a greater or smaller angle as desired.

In order to insure initial alignment of the parts of machine 20 a suitable opening 77 is provided in bracket 71 which is adapted to receive a gauge, not shown, suitably secured on carriage 26 in place of the shaft of motor 29.

Supported from the bracket 71 is a spindle motor 78 suitably connected by a belt drive, not shown, housed within a belt guard 79 to a spindle 80. In an embodiment built in accordance with the present invention the spindle 80 was driven at 7200 r.p.m. The spindle 80' is rotatable in suitable bearings housed within a housing 81 forming a part of this spindle assembly 60*. Supported from the end of the spindle 80 remote from the housing 6 or belt guard 79 is a suitable chuck 82 for holding a stylus element designated as 83 (FIG. 8). In accordance with the present invention the spindle assembly 60 is so designed that the stylus element 83 is substantially at the axis of the pivotal means '70, which means that the grinding operation will in all cases be tangential to the grinding or polishing wheels 31 and 32, respectively, and consequently is unaffected by the abrasive wheel size. Thus with the arrangement described above any size may be employed for the grinding or polishing wheel without in any way affecting the angle at which the device is ground, the grinding always occurring tangentially to the wheel. Furthermore, in a very simple manner the angle of cut may be adjusted in a relatively simple manner. The bear ings for the grinding spindle are such as to insure vibrationless operation. Preferably the spindle 80 is provided with an indexing disk or scale, not shown, whereby the operator may during a grinding operation hold the spindle at some indexed position or positions such as for grinding pyramid faces on a stylus or the like. This indexing disk or scale may be identical with those shown in Hille Patent 1,981,174.

It will be appreciated that a stylus is a very small element and in order for the operator to know what is happening it is necessary to magnify the view of the grinding operation which the operator sees. To this end there is mounted on the spindle assembly 60 or bracket 71 a suitable optic support 85 for supporting a microscope 86 which in an embodiment built in accordance with the present invention was a thirty power microscope. Since this microscope is mounted on the spindle assembly 60 or the bracket 71, it is stationary relative to the location of the spindle 80 at any time, and once properly focused as by adjusting screw 88 it will remain in focus during the grinding or polishing operation. Suitable lamps 90 are provided which are supported as by lamp brackets 91 from the bracket 71, so that when once properly positioned to direct their respective light beams on the object which is being ground and polished they will remain so regardless of the position of the carriage 61 relative to the support 63.

From the above description it will be understood that the grinding wheels 31 and 32 are reciprocably movable from a position such as shown in FIGS. 1, 2, 3 and 5 of the drawings, where the grinding and polishing wheels are to one side of the chuck 82 and the object 83 held thereby, to a position where grinding and polishing may take place. Obviously, if the chuck 82 were moved downwardly along the axis 62 as viewed in FIG. 4 to a sufiicient extent, it would be struck by the grinding and polishing wheels during their reciprocable movement. For the purpose of insuiing that this cannot happen, there is mounted on the support 63 a feed safety switch 93 which is connected in an electrical control circuit to be described hereinafter. This feed safety switch 93 is adapted to be actuated by an adjustable rod 94 supported on the spindle carriage 61. Thus, when the spindle carriage 61 is moved along the axis 62 toward the abrasive wheels a sufiicient distance which would cause it to interfere with the abrasive wheel 32, should this Wheel be moved by reciprocating motor 35, rod 94 would actuate the feed safety switch 93 to prevent motor 35 from operating. The rod 94 is adjustable by being threadedly mounted in an extension 61:: of the carriage 61. This safety arrangement is useful in the setting up operation when the object 83 is chucked in the chuck 82 of the spindle assembly 60, since under these conditions the operator cannot actuate the machine and cause the grinding and polishing wheels to move into grinding or polishing positions unless the spindle assembly 60' is so positioned that no damage or interference could occur by this relative movement between the abrasive wheels and the spindle assembly.

For proper grinding operation it is desirable to supply a suitable coolant to the object being ground so the bond between the diamond and supporting shank is not broken. This coolant preferably is supplied in mist form and comprises a water solution of some sort which is atomized by air. Accordingly, a tank 97 is supported from the base 21 as by brackets 95. This coolant tank is disposed in an elevated position so that the liquid contained therein flows by gravity through a suitable tubular passageway 98 which might be a flexible hose of some sort or the like. This coolant is supplied to a mixing area, not shown in the drawings but which may be identical with the mixing area shown in Skriba Patent 1,715,574, where it is mixed with air and atomized, from whence it is supplied to a suitable flexible conduit 100 to a nozzle 101 which directs the atomized cooling liquid in the vicinity of the object being ground, as clearly indicated in FIGS. 1, 2 and 3 of the drawings. The supply of coolant is controlled by a suitable solenoid actuated valve, not shown but which may be identical with solenoid actuated valve 49, but the winding 102 of which solenoid (FIG. 9) is energized selectively during the operation of the machine as will be described hereinafter in connection with the circuit diagram of FIG. 9 of the drawings.

For the purpose of confining the coolant mist in the vicinity of the abrasive wheels and also to prevent the diamond dust from being dispersed throughout the surrounding atmosphere, the abrasive wheels are continuously housed within a suitable hood 103 (best shown in FIG. 6) suitably supported on the carriage 26. This hood is provided at the rear with a suction opening connected to a suitable suction nozzle 104 so that diamond dust and the like is sucked away. Furthermore this suction prevents the coolant mist from interfering with the vision of the operator during a grinding operation. The hood 103 is provided with a window 105 through which the operator may view the grinding operation and also to permit the chuck to enter in response to reciprocating motion of the abrasive wheels. The hood 103 is furthermore provided with an upper L-shaped shield 106 secured thereto as by fastening means 107 so as to substantially prevent coolant from being thrown around by the wheel into the operators face. A similar shield 108 is provided for the lower end of the opening 105 which is also secured to the hood 103 as by fastening means 109.

In accordance with the present invention there are provided adjacent the operators position two sets of control switches associated with switch boxes 110 and 111, respectively. The box 110 includes a start button 113 and a stop button 114, whereas the control box 111 includes a grind button 116 and a polish button 117. These control boxes 110 and 111 are mounted one on either side of the grinding station and in order to start the machine the operator must press the start button 113 with one hand and either the grind button 116 or the polish button 117 with the other hand. This means that both hands of the operator are required to be free of the machine so that no danger to the operator is involved. The control boxes 110 and 111 are suitably connected to the elements of the control circuit described in connection with FIG. 9, and to this end suitable electrical conduits 118 and 119 are connected to the boxes 110 and 111, respectively.

In any kind of grinding operation it becomes necessary to dress the grinding or polishing wheel, as the case may be, and this is especially important in an accurate type of grinding operation such as the grinding of precious stones for use as phonograph styli. In accordance with the present invention there is provided an abrasive wheel dressing mechanism 120 which is automatically rendered efiective at the end of each grinding and polishing operation. This wheel dressing mechanism is best shown in FIGS. 1, 2, 6 and 7 of the drawings. As there illustrated, a wheel dressing stick generally designated at 121 is mounted for guided reciprocal movement in an elongated support 122 mounted on hood 103 as by a bracket 123. The lower end of support 122 extends into an opening 124 defined in the top of hood 103. Since two abrasive wheels 31 and 32, slightly spaced from each other, are disclosed in the drawings, the dressing stick 121 is illustrated as comprising two separate sticks 121a and 121]; (FIG. 7) which are secured together to move as a unit but spaced in the identical manner as the abrasive wheels 31 and 32. These dressing sticks may be made of pumice or similar material.

In order to reciprocate the dressing sticks 121a and 121b as a unit, any suitable pneumatic or other means may be employed. As best illustrated in the schematic showing of FIG. 1, the stick generally designated at 121 is reciprocated by a suitable pneumatic motor comprising a cylinder 126 and a piston 127. The cylinder 126 is suitably mounted on support 122 (FIG. 7). The piston 127 is secured to a piston rod 128, which in turn is fastened to the dressing sticks 121a and 121.: as indicated at 129. The air motor comprising cylinder 126 and piston 127 may be employed to actuate the dressing sticks in both directions. As schematically illustrated in FIG. 1, however, the dressing sticks may be actuated in one direction by suitable spring means designated at 130. AS there illustrated, spring 130' mounted within the cylinder 126 normally biases the piston 127 and hence the dressing sticks 121a and 1221b to the nondressing position. When it is desired to cause a wheel dressing operation, the pneumatic motor comprising the air cylinder 126 and piston 127 is actuated. As schematically illustrated in FIG. 1 of the drawings, air from the pressure regulated source 40 is preferably supplied to the cylinder 126 through a suitable solenoid actuated valve 132 including the solenoid 133 having a winding 133a (FIGS. 1 and 9). Whenever the solenoid winding 133a is energized, a wheel dressing operation will occur by virtue of the fact that the pneumatic motor comprising the cylinder 126 and the piston 127 move the dressing stick 121 into engagement with the abrasive wheels 31 and 32 as indicated in FIGS. 6 and 7 of the drawings.

A suitable cooling liquid is preferably supplied during the wheel dressing operation of the abrasive wheels 31 and 32, and to this end tank 97 containing a cooling liquid is connected through a suitable flexible hose 134 and a solenoid controlled valve 135 to a conduit 136 which terminates at 137 in support 122 in the space between dressing sticks 121a and 121b. The solenoid controlled valve 135 is indicated schematically in FIG. 1 of the drawings, including the solenoid 140 having a winding 140a (FIGS. 1 and 9).

In accordance with the present invention the wheel dressing operation occurs each time the carriage 26 moves to the position shown in FIG. 1 of the drawings, which should be at the end of a grinding and polishing operation. Moreover, this dressing operation should be timed for a short interval of time of the order of several seconds, which is all that is necessary. To this end there is provided a suitable time delay relay of the thermal type generally designated at 142 (FIG. 9 of the drawings) which is connected in circuit with the windings 133a and 140a of the solenoids 133 and 140 controlling the movement of the dressing stick 121 and the supply of liquid to the abrasive wheels 31 and 32, respectively. This circuit is preferably energized each time the carriage 26 reaches the position indicated in FIG. 1 of the drawings, and the time delay relay 142, having a bimetallic element 1425, will then open the circuit after a time delay of several seconds, whereupon the wheel dressing operation is terminated.

In connection with the operation of the grinding and polishing machine of the present invention, it is desired that under certain conditions the carriage 26 cause short reciprocating strokes of the grinding wheel 31 so that the object being ground moves back and forth across the width of the wheel. This reciprocating motion should. therefore, be of the order of the width of the wheel 32 plus about 0.005 of an inch at each end of the stroke.

At other times during a polishing operation the reciprocating motion should be across the surface of the polishing wheel and of a magnitude of the order of the width of the polishing wheel plus about 0.005 of an inch at either end. In order to automatically control the carriage 26 in this manner, a plurality of limit switches, specifically designated as 151, 152, 153, 154 and 155, are provided, which are suitably supported from the base 21 at the rear of the machine 20 as best shown in FIG. of the drawings. These switches are schematically indicated in the schematic diagram of FIG. 9 and are designated by the same reference numerals. Actually the switch 151 is an end limit switch which is normally closed and is opened when the carriage 26 is in the position shown in FIGS. 1 and 5 of the drawings. It is used to terminate certain operations at this time. This limit switch includes a contact 151a, which is closed when the carriage 26 is in the FIG. 1 position, and this contact is connected across the power circuit in series with the time delay relay 142 and windings 133a and 140a described above.

The limit switches 152 and 153 are limit switches for controlling the reciprocating movement of the carriage 26 during a polishing operation, while the switches 154 and 155 are limit switches for controlling the reciprocating movement of the carriage 26 during a grinding operation. For the purpose of actuating these switches in accordance with predetermined positions of the carriage 26, there are provided a plurality of cams specifically designated as 161, 162, 163, 164 and 165 which actuate the switches 151, 152, 153, 154 and 155, respectively. These cams are supported on a suitable rod 157, which in turn is supported from the carriage 26. The cams may be adjustably positioned along the rod 157 and secured thereto to give any desired operation.

In order to understand fully the operation of the automatic grinding and polishing machine of the present invention, the electrical control circuit schematically indicated in FIG. 9 of the drawings will first be described. The corresponding parts of FIG. 9 are designated by the same reference numerals as in the preceding figures of the drawings. schematically shown in FIG. 9 are such elements as the grinding motor 29, the spindle motor 78, the switch box 110 including the start button 113 and the stop button 114, the switch box 111 including the grind button 116 and the polish button 117, the cam actuated switches 151, 152, 153, 154 and 155, and the associated cams 161, 162, 163, 164 and 165, the feed safety switch 93, the sources of illumination such as the lamps 90, the winding 45a of right traverse solenoid, the winding 46a of left traverse solenoid, the winding 50a of fast traverse bypass solenoid, spray solenoid 102, and the like.

As illustrated in FIG. 9 of the drawings, there is provided a conventional three-phase source of power generally designated by the reference numeral 170 which is connected through a suitable main switch 171 which controls all the electrical power to the apparatus. Whenever switch 171 is closed, the grinding motor 2% is energized. The spindle motor 78 is not energized when the main switch 171 is closed, since obviously the operator must be able to chuck and unchuck the object to be ground. Consequently, the spindle motor 78 is periodically and automatically energized during the grinding operation, and to this end there is provided a solenoid actuated switch 172, including the solenoid winding 172a which when energized closes the switch supplying power from source 170 to the spindle motor 78.

In order that the spindle motor may be stopped rapidly upon deenergization of the solenoid winding 172a, it is preferably provided with a suitable brake 173 schematically indicated in FIG. 9 as comprising a brake drum 173a rotatable with the spindle motor 7 8 and a cooperating brake shoe 17%. The brake shoe 173b is actuated into braking engagement with the drum 173 by a solenoid 175 including the solenoid winding 175a. The winding 10 a is preferably energized immediately upon deenergization of winding 172a or, in other words, upon opening of the switch 172 to the spindle motor 78, whereby the chuck 82 driven by spindle motor 78 is immediately stopped.

For the purpose of controlling the right and left traverse solenoids having windings 45a and 46a, respectively, there is provided a suitable traverse relay generally designated at 178, which relay is illustrated as comprising a normally open contact 178a controlled by a switching member 17%, a normally open contact 17812 controlled by a switching member 1791), and a normally closed contact 1780 controlled by the same switching member 179]). The contact 178:: controls the right traverse solenoid 46, while the contact 17% controls the left traverse solenoid 45.

in order selectively to control the polish or grinding operation, as the case may be, there is provided a polishgrind relay generally designated at 180, which relay includes a normally open seal-in contact-a controlled by a switch member 181a. It also includes a switch member 1811) cooperating with a normally open contact 18011 and a normally closed contact 180b, a switch member 18 10 cooperating with a normally open contact 180d and a normally closed contact 180e, and a switch member 181d cooperating with a normally open contact 180 and a normally closed contact 180g. The polish-grind relay 180 is indicated as normally biased tothe polish direction so that when the winding of the relay 180 is not energized the relay will be in the position for controlling the polishing operation. When the winding 180* is energized then the contacts will be actuated so as to control a grinding operation. This polish-grind control is indicated by suitable arrows immediately adjacent the relay 180.

The control circuit of FIG. 9 also includes a start relay generally designated at 18 3 including a set of normally open contacts 184. This relay essentially is a seal-in relay for the start button 113 and either the polish button 116 or the grind button 117, so that immediately upon actuating the necessary controls it will seal them in so that even though the start button is released the machine 20 will function automatically in its desired m anner.

One additional relay is included in FIG. 9 generally designated by the reference numeral 135, and it performs two functions. It controls the start and stop of the coolant spray or mist during a grinding and polishing operation by controlling the energization of the spray solenoid 102 and it also controls the high speed or fast traverse movement of the carriage 26 by controlling the bypass valve 49 through winding 50a of bypass solenoid 50. It is generally designated as the spray and fast traverse relay 185. As illustrated in the drawings, it comprises a normally open contact a controlled by a switching member 186a, a normally open spray solenoid contact 185b controlled by a switching member 186b, and a normally closed fast traverse bypass solenoid contact 1850 controlled by the switching member 18611.

The contact details of the limit switches 151 to 155, inclusive, are illustrated in FIG. 9 of the drawings. As there shown, the end limit switch 151 has a single switch element controlling a normally closed power cutolf contact 1511b and a normally open dressing stick control contact 151a already described. The limit switches 152 and 153 determine the limits of reciprocating movement of carriage 2 6 during a polishing operation, while the limit switches 154 and 155 similarly determine the limits of reciprocating movement of carriage 216 during a grinding operation. As illustrated the switches 152 and 154 are identical and each comprises a single switching member. This switching member in the case of polish limit switch 152 controls a normally closed contact 152a and a nor mally open contact 15215, While in the case of grind limit switch 154 the switching member controls a normally closed contact 154a and a normally open contact 154D.

1 1 The polish limit switch 153 and the grind limit switch 155 are identical and each comprises a single switching member controllng a normally closed contact, 153a in the case of swtch 153 and 155a in the case of switch 155.

As illustrated in FIG. 9, the start and stop buttons 113 and 114, respectively, are mounted in a common housing 110. The start button 113 comprises two normally open contacts 113a and 1131) controlled by switching members 1136 and 1130!, respectively. The stop button 114 includes a normally closed contact 114a and a normally open contact 11417 controlled by switching members 114C and 114d, respectively. The contact 114a is the main power control contact, and when opened causes immediate termination of the operation of the grinding or polishing operation. The contact 11% is the spindle motor brake control contact to insure immediate stopping of spindle motor 78.

The grind and polish buttons 116 and 117, respectively, are shown in FIG. 9 as mounted in a common housing 111. The grind button 116 includes two normally open contacts 116a and 11612 and a normally closed contact 1166 controlled by switching members 116d, 116a and 116 respectively. Similarly, the polish button 117 includes two normally closed contacts 117a and 117i) and a normally open contact 1170 controlled by switching members 117d, 117s and 117 respectively.

Assuming now that the automatic grinding and polishing machine 20 is in the position indicated in FIG. 1 of the drawings and it is desired to start a grinding or polishing operation, the main power switch 171 is closed and the supply of air for actuating the various pneumatic motors and producing the atomized spray is turned on. The closure of the main switch 171 causes the grinding and polishing motor 29 to be energized so that the grinding wheels 31 and 32 are rotated at high speed. Closure of the switch 171 also supplies single phase power at conductors 170a and 17% which is fed to the control circuit through fuse 190 and where it energizes lights 90 through a transformer 191. The operator then secures an object to be ground such as 83 into the chuck 82 and is now ready to start a grinding operation. If the spindle chuck is properly positioned so that it will not interfere with the abrasive wheels in their reciprocating movement, the safety feed switch 93 will have its contacts closed as indicated in the schematic view of FIG. 9 of the drawings.

In order to start a grinding operation of the automatic grinding and polishing machine 20 of the present invention, the operator must simultaneously actuate not only the start button 113 but also the grind button 116. In view of the positions of these buttons on the machine 20, it is quite obvious that the operator must use both hands to actuate them, thus providing an additional safety feature in that the operators hands must of necessity be free of the machine. With all of the controls in the positions indicated in FIG. 9 of the drawings except that switch 171 is closed and the contacts of time delay switch 142 have been opened by the bimetal 142a, when the operator simultaneously actuates the start button 113 and the grind button 116 a plurality of elements of the automatic machine 20 are actuated, as follows:

(1) The start relay 183 is energized to close its contacts 184 thereby sealing in the power even though the start and grind buttons are immediately released.

(2) The fast traverse bypass solenoid 59- has its winding 50a energized so as to open the bypass 48 around the hydraulic piston 38 thereby insuring high speed movement of the carriage 26 as soon as it starts to move.

(3) The traverse relay 178 is also immediately energized.

(4) The polish-grind relay 180 is energized so as to move the switching elements 181 thereof in the direction of the grind arrow shown in FIG. 9 of the drawings.

The energization of the traverse relay 178 causes immediate energization of the right traverse solenoid winding 45a through closing of contact 178b, and since the fast traverse solenoid 50 has been energized the carriage 26 moves at high speed to the right, as viewed in FIG. 1 of the drawings.

(6) Such movement of carriage 26 causes end limit switch 151 to close its contact 151b and to open its contact 151a.

The various operations which occur can readily be determined from the schematic diagram of FIG. 9 of the drawings. Power to energize the start relay can readily be traced from one side 170a of the power source through the normally closed contact 114a of the stop button 114, the contacts of the speed safety switch 93, conductor 193 to the contact 116b ofgrind switch 116, conductor 194, contact 113a of start switch 113 and the winding of relay 183 to the other side 17Gb of the source of power. The energization of start relay 183 and closure of its contacts 134 then bypasses the speed safety switch 93 and seals in start relay 183 across the source 170a, 1701: through its own contacts 184.

The circuit for energizing the fast traverse bypass solenoid valve having winding 56a can readily be traced from one side 17Gb of the source through the normally open contact 11312 of start button 113, conductor 195, fast traverse bypass solenoid winding 50a, normally closed contact 1350 of spray and fast traverse relay 185 and conductor 1% back to side 170a of the source. The energization circuit for the traverse relay 178 may be traced from conductor 1701) of the source, through conductor 197, through the Winding of the traverse relay 178, conductor 198, the normally closed contact 180g of the polish-grind relay 1%, normally closed contact 152a of limit switch 152, conductor 199, contact 154a of limit switch 154, conductor 200 and through contacts 184 of start relay 183 to side 170a of the source of control power. As soon as traverse relay 178 is energized it seals itself in from conductor 197 connected to one side 17% of the power source through its winding and its normally open contact 178a, conductor 201, normally closed contact 180e of polish-grind relay 180 and limit switch 153 to conductor 2% which is connected to the other side 170a of the source. It should be appreciated that polish-grind relay 180, as will be described immediately hereafter, is also energized, but this does not affect the energization circuit of the traverse relay 178 since switching members 1810 and 181d when actuated to the grind position close contacts 180d and 180], respectively, each of which will complete an electrical circuit through limit switches and 154, respectively, directly to the conductor 200.

The energization circuit for the polish-grind relay 180 can readily be traced from the conductor 197 connected to one side of the power source through the winding of the polish-grind relay 180, through the normally open contact 116a of the grind button 116 and back to the conductor 20% which goes to the other side of the power source. Energization of the polish-grind relay 180 to the grind position thereof causes switching member 181a to close seal-in contact 180a thereby completing a seal-in circuit for the winding of relay 180 from conductor 197 connected to one side 17811 of the source through the winding of relay 180, seal-in contact 18011, normally closed contact 117a of polish button 117 and back to conductor 20% which is connected to the other side a of the power source.

As the carriage moves to the right as viewed in FIG. 1 at high speed, the cam support 157 as viewed in FIG. 9 moves to the left (FIG. 9 showing a view of the cam support 157 and associated limit switches similar to the rear view shown in FIG. 5 of the drawings). Just before the leading edge of the grinding wheel 31 comes into position so as to perform a grinding operation on the object to be ground, cam 164 engages limit switch 154. As a matter of fact, by this time cam members 162 and 163 have engaged their respective limit switches to actuate them. but this has no effect on the circuit when the relay 1% is energized. The actuation of limit switch 154 opens normally closed contact 1540 and closes normally open contact 15412, which results in immediate energization of the spray and fast traverse relay 185. This energiza tion circuit leads from conductor 200 connected to the side 1701: of the power source through contact 1541) of limit switch 154, contact 18017 of grind relay 180, the winding of spray and fast traverse relay 185, through conductor 204 to the conductor 197 which goes to the side 17 b of the power source.

Energization of the spray and fast traverse relay 185 does two things. First of all, it opens contacts 185e, resulting in immediate deenergization of the fast traverse bypass solenoid winding 5011, resulting in the immediate slowing down of the carriage 26. Secondly, it closes contact 135b with the immediate energization of the spindle motor relay 172, which causes the spindle motor 78 to be energized. The circuit for the energization of the spindle motor relay 172a can be traced from side 170a of the power source through conductor 196, normally open contact 1851) of relay 185, conductor 2%, the winding of spindle motor relay 172a and conductor 205 to conductor 197 which goes to the other side 1701) of the power source. Simultaneously with the energization of the spindle motor relay winding 172a the spray solenoid 102 is energized. The circuit for the spray solenoid can be traced from side 170a of the power source through conductor 196, normally open contact 18Sb of the spray and fast traverse relay 185, conductor 204, to the spray solenoid winding 1G2, and thence to the other side 170 b of the power source.

It will be appreciated that not only will the object 83 to be ground be rotated by the spindle motor 78-, but a coolant will be supplied in spray or atomized form to cool such object, and this occurs just as the object to be ground approaches the leading edge of the grinding wheel 31. Moreover, the carriage 26 is now moving at low speed. The operator will manipulate the spindle carriage control 66 while observing the object to be ground through the microscope 86 but not only until contact with the grinding wheel is made, but throughout the entire grinding operation. The grinding wheel 31 moves so that effectively the object to be ground is moved across the surface of this grinding wheel. As soon as the trailing edge of the grinding wheel has moved past the object to be ground, cam 165 actuates cam switch 155 opening contact 155a, which interrupts the circuit through the winding of the traverse relay 173 with the resultant de-energization of right traverse solenoid winding 45a, thus stopping movement to the right of the carriage 26. The traverse relay 178 is deenergized upon opening of contact 155a, since the energization circuit through contact 1813:! and conductor 231 is interrupted. Moreover, the energization circuit for. traverse relay 1'78 through conductor 198 has already been interrupted by a previous operation of the cam switch 154.

Thus, traverse relay 17$ closes its normally closed contact 178e, which results in the immediate energization of the left traverse solenoid winding 46a through the closed contact 15112 of end limit switch 151 with the result that the carriage 2d reverses itself permitting limit switch 155 to reclose. When the reversal has occurred to an extent that the object being ground just moves off the right or leading edge of the grinding wheel 31 as viewed in FIG. 1 of the drawings, limit switch 154 is released by cam 164 so as to return to the position shown in KG. 9 of the drawings. This immediately reenergizes the traverse relay 178 through conductor 1% with the result that the left traverse solenoid winding 46a is deenergized and the right traverse solenoid winding 45a is again energized. It will thus be apparent that the carriage 26 will reciprocate back and forth at slow grinding speed so that the object being ground just moves back and forth across the face of the grinding Wheel 31 and perhaps five thousandths of an inch beyond at each 1d edge of the wheel. During all this time the coolant in atomized form will be supplied within the hood 103 through nozzle 101.

When the grinding operation is completed, the operator may decide to press either the stop button or the polish button. If the polish button 117 is actuated that causes immediate deenergization of the polish-grind relay by interrupting the energization circuit therefor through normally closed contact 117a and the seal-in contact 180a of the polish-grind relay 180. This causes the polish-grind relay to move to the position shown in FIG. 9 with the result that the control of carriage 26 is taken over by the limit switches 152 and 153 instead of the limit switches 154 and 155 which control the grinding operation. As is obvious from the arrangement disclosed in FIG. 9 of the drawings, the carriage 26 will move toward the left as viewed in FIG. 1 untilthe polish wheel is effective, and then it will reciprocate back and forth so that the object being ground just moves slightly off each edge of the polish wheel.

When the polishing operation is completed or when the grinding operation is completed in the event it is decided not to polish following the grinding operation, the operator merely actuates the stop button 114, which does the following things:

(1) It deenergizes the start relay 183.

(2) It deenergizes the spray and fast traverse relay 185.

(3') The deenergization of the relay immediately deenergizes the spray solenoid 1412 which cuts oif the coolant for the grinding and polishing operation.

(4) The deenergization of the relay 185 interrupts the energization circuit for the solenoid actuated switch 172 which deenergizes the spindle motor 78.

(5) The deenergization of the spray and fast traverse relay 185 causes reclosing of contact 185C with the result that the fast traverse bypass solenoid winding 50:: is energized and movement toward the position shown in FIG. 1 of the drawings of the carriage 26 occurs at high speed.

(6) The stop button 114 also momentarily closes its contact 114b, which causes immediate energization of the brake solenoid winding 1750 resulting in immediate stopping of the spindle motor 78 so that the operator can unchuck the object 83 being held by the chuck 82 without injury.

(7) When the carriage 25 reaches the left end position shown in FIG. 1 of the drawings, the cam 161 actuates end limit switch 151, which opens contact 151b and interrupts the circuit to the left traverse solenoid winding 46:: as well as the circuit to the fast traverse bypass solenoid winding 50a, thus stopping carriage movement.

(8) When normally open contact 151a of end limit switch 151 is closed, the dressing stick mechanism including the dressing stick solenoid winding 133a and the dressing stick liquid control winding 140a are energized so that the dressing stick performs a dressing operation on the grinding and polishing wheel.

(9) The thermal time delay switch 142 is energized so that the bimetallic element 142a thereof operates to interrupt the circuit through the windings 138a and 140a and terminate the dressing operation after a few seconds.

The operation of the automatic grinding and polishing machine 20 of the present invention will readily be understood in view of the detailed description included above and no further discussion thereof is included herewith. It will be appreciated that there has been provided a fully automatic machine which operates at high speed at all times except during the actual grinding and polishing operation. Moreover, this operation is completely safe as far as the operator is concerned.

It will oe-appreciated that instead of utilizing the microscope as the means by which the operator can view the grinding operation, a closed circuit television system may be employed, and in FIG. of the drawings such an arrangement is schematically illustrated. As there shown, there is provided a unit generally designated at 220 which includes a pickup tube, video amplifier, wave form generator and a power supply. This unit would be placed so as to scan the object being ground. This unit 220 would be connected by suitable coaxial cable 221 to a reproducing unit generally designated at 222 which would include the picture tube, scanning generator, power supply and the like, and which would give a large view as designated at 223 whereby the operator could continuously watch the grinding operation. With such an arrangement it would be possible to provide reproducing units for a whole battery of machines in a supervisors office or in a quality control division so that he would be able to watch the grinding operations of all the operators in a factory.

While there have been illustrated and described several embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A grinder for accurately grinding small work pieces, comprising an abrasive wheel, motive means for rotating said wheel at high speed, a reciprocating carriage for moving said wheel, means for reciprocating said carriage including a combined hydraulic and pneumatic unit, said combined hydraulic and pneumatic unit including a hydraulic portion and a pneumatic portion, and means for effectively rendering the hydraulic portion of said unit ineffective when high speed movement in either direction of said carriage is desired.

2. The grinder of claim 1 wherein said combined hydraulic and pneumatic unit comprises a pair of aligned cylinders having a common connecting rod with a piston in each cylinder secured to said connecting rod, the piston of the pneumatic cylinder being operated from a source of air under pressure, a hydraulic fiuid in said other cylinder, and bypass means for selectively permitting said hydraulic fluid to move freely from one end of said other cylinder to the other end.

3. A precision grinder for small work pieces, comprising an abrasive wheel, motive means for rotating said wheel, a reciprocating carriage for moving said wheel, means for reciprocating said carriage including a combined hydraulic and pneumatic unit, said combined hydraulic and pneumatic unit including a hydraulic portion and a pneumatic portion, means for effectively rendering the hydraulic portion of said unit ineffective when high speed movement in either direction of said carriage is desired, a second carriage for supporting a work holder, and a manually actuatable lead screw for moving said second carriage toward and away from the path of reciprocating movement of said wheel.

4. A precision grinder comprising an abrasive wheel, motive means for rotating said wheel at high speed, a reciprocating carriage for moving said wheel, means for reciprocating said carriage including a combined hydraulic and pneumatic unit, said combined hydraulic and pneumatic unit including a hydraulic portion and a pneumatic portion, means for effectively rendering the hy' draulic portion of said unit ineffective when high speed movement in either direction of said carriage is desired, a second carriage for supporting a work holder, 21 manually aetuatable lead screw for moving said second carriage toward and away from the path of reciprocating movement of said wheel, and pneumatic means for continuously biasing said second carriage in a predetermined direction along the axis of said lead screw.

5. The grinder of claim 4 wherein said pneumatic means comprises a piston biasing said second carriage in a direction away from said wheel.

6. A grinder for accurately grinding small work pieces, comprising a pair of abrasive wheels arranged on a common shaft in closely spaced relationship, motive means for rotating said wheels at high speed, a base, a reciprocating carriage on said base supporting said motive means and wheels, vibrationless means for supporting said wheels and motive means from said carriage, means for reciprocating said carriage including a combined hydraulic and pneumatic unit, a source of air under pressure connected to said pneumatic unit to move said carriage at high speed in either direction, said hydraulic unit including a controlled bypass for producing a predetermined drag on said carriage to reduce the speed of movement thereof, a large bypass for said hydraulic unit, means for selectively controlling said large bypass effectively to remove said predetermined drag, a second carriage for supporting a work holder, a manually actuatable lead screw for moving said second carriage toward and away from the path of reciprocating movement of said wheels, and pneumatic means for continuously biasing said second carriage in a predetermined direction along the axis of said lead screw.

7. In a precision grinder, the combination of a first movable carriage, an abrasive wheel rotatably mounted on said carriage, a prime mover for rotating said wheel, a second carriage movable at an angle transverse to the axis of rotation of said wheel, a work holder supported by said second carriage for supporting a work piece, means for producing relative movement between said wheel and work holder effectively to cause movement of said wheel into grinding engagement with the work piece supported by said work holder, and pivot means for supporting said work holder from said second carriage at selected predetermined angles for disposition of the work piece tangentially with respect to said wheel, the grinding surface of said abrasive Wheel being disposed on the pivotal axis of said pivot means whereby Wheel size is immaterial.

8. In a device for performing a grinding operation, the combination of a first movable carriage, an abrasive wheel rotatably mounted on said carriage, a prime mover for rotating said wheel, a second carriage movable at an angle transverse to the axis of rotation of said Wheel, a work holder supported by said second carriage, means for moving said wheel into grinding engagement with the work supported by said work holder, means for pivotally supporting said work holder for disposition of the work held thereby at selected predetermined angles tangentially with respect to said wheel, and means for rendering said means for moving said wheel ineffective to move said wheel if said carriage is in a position which would cause interference between said wheel and said work holder.

9. A precision grinder for small work pieces, comprising an abrasive wheel, motive means for rotating said wheel, a reciprocating carriage for moving said wheel, means for reciprocating said carriage including electric control means, a second carriage, a rotatable work hold cr supported on said second carriage, and a manually actuatable lead screw for moving said second carriage toward and away from the path of reciprocating movement of said wheel, said control means to initiate actuation of said reciprocating carriage requiring both hands of an operator thus insuring safety to said operator.

10. The precision grinder of claim 9 wherein means are provided to rotate said work holder and a microscope for viewing the work piece supported in said work holder, said microscope being supported on said second carriage.

ll. A precision grinder for small work pieces, comprising an abrasive wheel, motive means for rotating said wheel, a reciprocating carriage for moving said wheel to and from a grinding station and during a grinding operation, means for reciprocating said carriage including a combined hydraulic and pneumatic unit, electric control means including a pair of manual actuating means for controlling said unit, a second carriage for supporting a work holder, and means for moving said second carriage toward and away from the axis of rotation of said wheel, said pair of manual actuating means requiring simultaneous actuation thereof to initiate operation of said means for reciprocating said carriage, said manual actuating means being spaced apart a sufficient distance so that simultaneous actuation thereof requires both hands of the operator.

12. The precision grinder of claim 11 wherein said abrasive wheel compirses a grinding wheel and a polishing wheel and said manual actuating means includes means for selectively initiating a grinding or a polishing operation.

13. A precision grinder comprising a first movable carriage, a rotatable abrasive wheel mounted on said carriage, a prime mover for rotating said wheel, motive means for moving said car-riage, a second carriage movable at an angle transverse to the axis of rotation of said wheel, a rotatable Work holder supported by said second carriage, means for moving said Wheel into grinding engagement with the work supported by said work holder, means for rotating said work holder, means for pivotally supporting said work holder to support the work held thereby at selected predetermined angles tangentially with respect to said wheel whereby wheel size is immaterial, and control means for said motive means to cause said first carriage to move at high speed in either direction except when said work holder is directly adjacent the surface of said wheel, said control means causing said wheel to move back and forth automatically at slow speed whereby work held by said work holder efliectively moves back and forth across the surface of said wheel.

14. The precision grinder of claim 13 wherein stop means are provided to terminate said grinding operation, and means included in said control means for automatically stopping the rotation of said Work holder upon actuation of said stop means.

15. The device of claim 14 wherein wheel dressing means are supported adjacent said wheel and means for rendering said Wheel dressing means momentarily effective following each actuation of said stop means.

16. The device of claim 15 wherein a coolant is supplied to said wheel during the momentary operation of said wheel dressing means.

17. In a device for performing a grinding operation on precious stones, the combination of a first movable carriage, an abrasive wheel rotatably mounted on said carriage, a prime mover for rotating said wheel, a second carriage movable at an angle transverse to the axis of rotation of said wheel, a rotatable work holder supported by said second carriage, means for reciprocating said first carriage and said wheel to a position adjacent said work hoider for grinding engagement with the work supported by said work holder, and a microscope supported on said second carriage and movable therewith so as to remain in focus on said work during a grinding operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,467,023 Willson Sept. 4, 1923 1,715,574 Skriba June 4, 1929 1,723,852 Haas Aug. 6, 1929 1,981,174 Hille Nov. 20, 1934 2,024,268 Bausch et al. Dec. 17, 1935 2,144,095 Z'wick Jan. 17, 1939 2,187,231 Frei Jan. 16, 1940 2,288,508 Arms et al June 30, 1942 2,354,509 Dreher July 25, 1944 2,560,944 Garrison July 17, 1951 2,663,976 Jacoby Dec. 29, 1953

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