US2704424A - Apparatus for abrading - Google Patents

Description

Mgrch 22, 1955 35 v D'AVAUCOURT 2,704,424

APPARATUS FOR ABRADING Filed July 28, 1952 7 Sheets-Sheet 2 f-lf ATTORNEY.-

March 1955 P. DE v. D'AVAUCOURT 2,704,424

APPARATUS FOR ABRADING INVENTUR Za'erre de Vzhg/ fizz Marl W Mk ATmRNEw March 1955 P. DE V..D'AVAUCOURT 2,704,424

APPARATUS FOR ABRADING Filed July 28, 1952 7 Sheets-Sheet 4 ,in V g ATTQRNEU March 1955 P. DE v. D'AVAUCOURT 2,704,424

APPARATUS FOR ABRADING 7 Sheets-Sheet 6 Filed July 28, 1952 I INVENTOR zerredelizyddmmvg MQW m ATTORNEYS March 1955 P. DE v. D'AVAUCOURT 2,704,424

APPARATUS FOR ABRADING 9 I INVESTOR o O Pier/2 defiiga'irawad ATTORNEYS U Ed States This invention relates to an apparatus for abrading, and more particularly to an apparatus for generating surfaces of lenses and other similar articles, including prisms and plane surfaces. It is particularly useful in the rough grinding of lens blanks.

The present application is a continuation-in-part of my application Serial Number 752,115, filed June 3, 1947, now Patent 2,616,226, dated November 4, 1952.

In the above-referred to application, a generating machine is disclosed which comprisesa rotating chuck .to receive the lens and a rotating lap which is brought into engagement with the lens by manually lowering the lap against the lens. At the completion of the grinding operation, a brake is brought into action manually to arrest the rotation of the chuck, and then a lens picker is manually operated to remove the lens from the chuck.

It is an object of the present invention to accomplish all of the foregoing results automatically upon initiating the operation of feeding the lap spindle toward the lens on the chuck.

In devices of the prior art, it has been common practice to adjust the position of the chuck vertically with reference to the grinding lap and such adjustments have universally been made from a position above the chuck, but in apparatus of the present kind, where the grinding lap is moved between two fixed limits, it is found that vertical adjustment of the chuck relative to the grinding position of the lap may be made from below the chuck so as to obtain the proper thickness of grind but without changing the grind plane.

In prior devices, and particularly those which employ a manual feed of the grinding lap into the lens blank, there is no means of regulating the pressure applied to the lens blank with the result that in many instances inaccurate grinding is effected or in many cases the lens blanks are broken.

A further object of the present invention is to eliminate this difficulty by adjustably regulating the pressure of the lap on the lens and to insure that such pressure will remain constant.

As in the machine of my prior application, the lens is applied to the chuck manually and must be removed from the chuck in the same manner. An object of the ,present application is to eliminate the tedious operation of removing the lens from the chuck by providing an automatically-operating lens pickerwhich is swung into engagement with the lens when the chuck has ceased rotating and lifts the lens off the chuck.

A further object of the invention is to provide a novel form of combined air cylinder and dashpot arrangement which enables the lens picker to operate rapidly both in l'lillovililg toward the lens and in moving the lens off the c uc Other objects and advantages will be evident as the description proceeds, and it is to be understood that changes Fig. 6 is a fragmentary plan view partially in section and showing the means for feeding the lap spindle;

Fig. 7 is a detailed view partially in section of the power unit;

Fig. 8 is a fragmentary, sectional view taken on the line of Fig. 3;

Fig. 9 is a detailed, sectional view taken along the line 99 of Fig. 7;

Fig. 10 is a detailed, sectional view taken on the line 10-10 of Fig. 9;

Fig. 11 is a diagram of ployed;

Fig. 12 is a wiring diagram showing the circuits employed in the feeding and control of the lap spindle;

Fig. 13 is a wiring diagram of the circuits employed in initiating movement of the chuck-driving motor;

Fig. 14 is an expanded view of the cam shaft showing the angular displacement of the cams and dogs to bring about sequential operation; and

hFigure 15 is a fragmentary sectional view of the lens c uc Referring first to Fig. 1, the machine comprises a standard spindle rotating mechanism generally indicated by the numeral 2 which may be purchased from a manufacturer of machine tools. A standard drill press may be used for this purpose. The spindle is indicated at 3, and the motor 4 drives the spindle through the belt gearing 5. Mechanism is provided for raising and lowering the spindle 3 including the usual rack and pinion arrangement commonly used for this purpose. This is part of the standard drill press equipment. Encircling the spindle 3 and movable vertically therewith is a tripping arrangement indicated generally at 6 (Fig. 3) which includes a threaded member 7 attached to a bracket 8 movable with the spindle 3 in a vertical direction. An adjustable stop 9 in the form of a knurled nut is threaded on the member 7 and is secured in position by a lock nut 10. Adjustment of the knurled nut 9 controls the lens thickness as will be more fully described hereinafter.

Attached to the spindle 3 is a lap 11 which, in the embodiment shown, has an annular grinding surface 13 which may be formed of diamond particles embedded in a matrix. The lap 11 is secured to the spindle by any conventional means.

Mounted on an upright column 14 which constitutes the main connection of the machine to its base, is a bracket 15 which supports the lens holder and its associated mechanism including the mechanism for rotating the lens holder and the mechanism for adjusting the position of the lens holder with respect to the lap. Suitable means may be employed for raising and lowering the bracket 15 and for locking the same in place.

A plate 16 is attached to the bracket 15 and is fixed with respect thereto. The plate 16 is provided with ways 17 and 18 as shown in Fig. 1. A plate 19 is positioned for transverse movement along the ways 17 and 18 being the pneumatic circuits emguided by dovetail elements 20 and 21 which are secured to the plate 19 and interfit between the ways.

The plate 19 may be moved transversely with respect to the lap spindle 3 by means of the handle 22. By adjusting the plate 19 transversely with respect to the axis of rotation of the lap, it is possible to bring the lens blank and lap into proper transverse relationship. Attached to the plate 19 is a plate 23 as shown in Fig. 3, this plate being pivoted to the plate 19 so that the plate 23 which carries the lens blank chuck and its associated mechanism may be rotated about the pivot which joins the plates 19 and 23. This pivotal movement is produced by means of the adjusting screw 24 in order to adjust the angle of may be made in the details of the construction and other m curvature to be formed on the lens blank without changfeatures of the invention so long as they fall within the scope of the claims hereto appended.

Referring to the drawings, forming part hereof,

Fig. 1 is a side elevation of a machine embodying my invention;

Fig. 2 is a fragmentary side elevation looking from the other side of the machine;

Fig. 3 is a fragmentary front elevation;

Fig. 4 is afragmentary, vertical, sectional view taken along the line 44 of Fig. 3;

Fig. 5 is a plan view of the coolant pan and lens picker;

ing the transverse adjustment of the plate 19. Carried by the plate 23 and disposed at an angle normal to the plane thereof is another plate 25 to which is pivoted the plate 26 by means of the pivot 27, and the plate 26 has mounted thereon the bearings for'the chuck spindle.

The foregoing mechanism for adjusting the lens chuck with reference to the lap is clearly shown and described .in my application Serial Number 752,115 filed June 3, 1947, and reference may be made thereto for a full and complete understanding thereof.

The lens chuck is indicated at 28 and is carried on spindle 29 mounted on the bearing supports 30 and 31 secured to the plate 26. The motor 32 18 secured to the plate 23 and drives the chuck spindle 29 through the belt gearing 33, all as described in said PllOl' application. Secured to the chuck spindle 29 1s a brake wheel 34 for rotation therewith, and a friction brake engages the brake wheel 34 to arrest rotation of the spindle upon completion of the grinding operation, as will be described hereinafter.

The chuck spindle 29 is mounted m the same manner as disclosed in the prior application, so-that the thrust is taken by the ball 36, but differs from said prior application in that the bearing supports 30 and 31 house bearings 37 and 38 to permit sliding movement thereof in the bearing supports 30 and 31 as the ad usting handie 39 is actuated. These bearings 37 and 38 comprise inner and outer ball races with the ball bearings 1nterposed therebetween, and the outer race be1ng sl1dably mounted in the bearing supports so that ad ustment thereof may be efiected from below the machine and thereby prevent any change in the plane of grind, as distinguished from machines of the prior art wherein adjustments have been made from above the chuck, and this is one of the important features of the present construction.

It will be seen from the foregoing that the mounting for the chuck spindle is in all respects substantially identical with that of my prior application, with the exception of the adjustable bearings and the fact that the brake 35 is power-operated through a cylinder and the piston arrangement carried by the plate26.

As seen in Fig. 3, the brake cylinder is indicated at 40 and the piston is indicated at 41. The piston rod has secured thereto a cross head 42 to which is attached a threaded rod 43 adjustably positioned in the cross head 42 by the lock nuts 44 and having its end secured to one end of the brake strap 35, the other end of the brake strap 35 being secured to the plate 26. It is obvious, therefore, that upon the application of fluid behind the piston 41, the brake will be applied to the brake wheel 34 and thereby stop rotation of the chuck spindle. The brake piston 41 is spring-loaded to released position, so that when fluid pressure is bled from the cylinder 40, the brake will be released.

In prior devices, it has been customary to remove the lens from the lens chuck manually, but in the present application means are provided for automatically removing the lens from the chuck.

Referring now to Figs. 3 and 4, the lens picker is supported on the base of the housing 45, which surrounds the chuck 28, by a standard 46 carrying a bracket 47 closely adjacent the chuck 28, and an operating rod 48 is rotatably mounted in the bracket 47 and extends through the side wall of the housing 45. At one end of the rotary rod 48 is mounted a lens picking arm 49 to which is attached a vacuum cup 50, it being understood that the lens chuck is the same as that described in said prior application including a rubber seat 28' for the lens and necessitating only the use of a film of water between the chuck and lens in order to hold the lens on the chuck against rotation. It is apparent, therefore, that as the operating rod 48 is rotated in counterclockwise direction as seen in Fig. 4, the suction cup 50 engages the lens, and upon reverse movement of the rod 48, the lens is picked from the chuck.

Secured to the plate 25 by means of bracket 51 is a fluid cylinder 52 having a piston therein, the piston rod of which is connected to a link 53 as seen in Fig. 2, this link connecting the piston rod and the outer end of the operating rod 48. Attached to the pivot 54 between the piston rod and the link 53 is a coiled spring 55 having its other end secured to the bracket 51 at 56, it being understood that the spring 55 normally biases the lens picker arm 49 into elevated position as shown in Fig. 4.

Fluid pressure is admitted to the lower end of the cylinder 52 below the piston, moving the piston rod upwardly and consequently swinging the lens picking arm 49 and the suction cup 50 into engagement with the lens, and as soon as this engagement has been established, the fluid is bled from the cylinder 52 through the vent screw 57, whereupon the-spring 55 returns the picker arm to its inoperative position. In the operations which will be subsequently described, a grinding operation is p the vacuum cup 50 into engagement with the lens, where performed, and in proper sequence, the brake 35 is automatically applied to stop rotation of the lens chuck 28, after which the lens picker is operated to remove the lens from the chuck, and air is exhausted from the brake cylinder 40 and the lens picking cylinder 52, which are thereby restored to inoperative position, whereupon the cycle of operations may be repeated.

It is, of course, essential that coolant be applied to the lens and lap during the grinding operation, and provision is made for automatically applying this coolant during the grinding operation only. This. mechanism consists of a coolant nozzle 58 projecting through the base of the housing 45 to a position adjacent the grinding chuck so that coolant may be applied to the lens and lap during the grinding operation. The coolant nozzle 58 is connected to a conduit 59 controlled by a trip valve generally indicated at 60, which valve is in turn connected to the coolant storage chamber 61 by means of a conduit 62. The trip valve 60 consists of a trigger finger 63 pressing on the valve stem 64, said valve beingnormally biased to closed position. The coolant storage receptacle is provided with a motor 65 driving a pump which feeds coolant to the trip valve 60 and is operated in proper sequence to supply the coolant to the lens only during the grinding operation, after which the trigger finger is released and the coolant-supply shut off.

The coolant then drains by gravity from the housing 45 back to the storage tank through the conduit 66.

As mentioned heretofore, the lap spindle is moved to and from the work by means of a rack and pinion mechanism, and this is diagrammatically shown in Fig. 4, wherein the pinion 67 engages the rack 68 to feed the spindle 3 toward and from the work. This is shown more clearly in Fig. 6 on an enlarged scale. In my prior application, this feeding of the lap spindle was accomplished manually, but in the present application, the operation is automatic or power-operated by means of a power unit generally designated at 69 and which consists in part of a power-operated piston 70 housed within acylinder 71 and having connected thereto a rack bar 72 meshing with a pinion 73 on a cross shaft 74, the-cross shaft in turn carrying the pinion 67 meshing with the rack 68 on the spindle shaft.

As will be clearly described hereinafter, operation of the power piston 70 will feed the spindle toward and from the work on the chuck, and the rotating shaft 74 also brings into sequential operation the automatic application of the lens picker and brake, and at the same time initiates rotation of the lap spindle 3. This same shaft 74 also operates the coolant valve trigger finger to project the coolant at the proper moment.

In order that these operations may be more clearly understood, reference is made to Figs. 2 and 6. From these figures, it will be seen that the shaft 74 is provided with an extension 75 on which are mounted a cam 76 engageable with a switch member 77, a cam 78 engaging the trigger finger 63 of the coolant valve, and two one-way dog members, the dog member 79 engaging a trigger finger 81 on the valve 82 for admitting fluid to the brake cylinder 40, and the dog engaging a trigger finger 83 controlling a valve 84 for supplying fluid to the lens picker fluid cylinder 52.

Upon operation of the power piston included in the unit 69, the cam 76 is so arranged on the shaft 75 that as the lap advances toward the lens, the switch 77 is closed and the circuit through relay 85 is closed, the relay being connected to the chuck-operating motor 32 so as to initiate rotation of the chuck 28. At the same time, the pump for the coolant supplies fluid through the conduit 62 to the valve controlled by the trigger finger 63. The cam 78 is angularly displaced on the shaft 75 so that at the proper moment of rotation, the trigger finger 63 is tripped, the valve 60 opens, and the coolant flows to the lens and lap at the time thegrinding operation is taking place.

Immediately after the completion of the grinding operation, the dog 79 engages the trigger finger 81, opens the valve 82 in the fluid line to the brake cylinder 40, arresting movement of the chuck, and then releases the same by bleeding of the cylinder 40. As soon as the rotation of the chuck 28 has ceased, the dog 80 engages the trigger finger 83, opening the valve 84 and permitting fluid to flow to the bottom of the lens picker cylinder 52 to swing mosses upon fluid is bled from the cylinder 52, and the spring returns the picker arm 49 and the lens to its elevated position.

The fluid pressure for the power-operated cylinder in the unit 69 and also for the brake and lens picker is supplied through a manifold 86 connected to any suitable source of fluid pressure by the conduit 87. This manifold contains a lubricator 88, a pressure gauge 89, and a filter 90. A fluid, in this instance air, passes through the manifold 86 which is connected to the power cylinder in the unit 69 by means of a flexible conduit 91, and this manifold 86 is also connected to the brake-controlling valve 82 by means of flexible conduit 92 and to the valve 84 controlling the lens picker cylinder 52 by means of a conduit 93.

In view of the fact that the shaft 74 does not make a complete revolution during its operation and since the valve trigger fingers 81 and 83 are operated only momentarily, the one-way dogs 79 and are provided. These dogs consist of arms 94 and 95 secured to the shaft extension 75 and having pivoted thereon yielding fingers 96 and 97, it being clear from Figs. 2 and 14 that these fingers are yieldingly held against stops- 98 and 99 by means of springs 100 and 101, so that when the arms 94 and 95 are rotated in counterclockwise direction, the fingers 96 and 97 .are against the stops and therefore held in rigid position, but on the return stroke the springs 94 and 95 yield, allowing the dogs to pass over the trigger levers for the valves without depressing the same.

As previously mentioned, the lap spindle 3 is fed toward and away from the chuck by a power unit 69, and upon reference to Fig. 7, the details of construction of this power unit will be clear.

At the rear end of the cylinder 71 is a valve 102 which may be actuated by means of an advancing solenoid 103 or a retracting solenoid 104 to permit air to be directed to either end of the cylinder for the purpose of causing reciprocation of the piston 70. A hydraulic check is provided so as to retard movement of the lap spindle during the grinding operation so that the spindle moves into the work at the proper speed, it being evident that-the speed of movement of the rack bar 72 will move the lap spindle rapidly toward the work, after which the speed of progress is slowed down in order that the lap may engage the work gently and thereby avoid breakage of the lens blanks.

Secured to the rack bar 72 is an upstanding bracket 105 provided with an aperture .106 therein through which passes a threaded plunger 107 carrying at its end a beveled nose 108. This plunger is connected to a cross head 109 to which is secured an operating rod 110 having a button 111 at its forward end.

The bracket 105 is also provided with a U-shaped groove 112 which straddles the screw threaded piston rod 113, this rod being connected to the piston 114 re-- ciprocably mounted in the cylinder 115.

The piston 114 is secured to the piston rod 113 by means of a sleeve 116 passing through the piston and being of a diameter slightly less than the diameter of the opening through the piston 114. At each end of the sleeve 116 are collars 117 and 118. A passageway 119 is provided around the collar 118, this passageway communicating with the opening through the piston 114, and the collars 117 and 118 are spaced apart such a distance as to permit relative movement between the piston rod 113 and the piston 114.

With this construction, it is evident that with the cylinder full of oil, movement of the piston 114 in one direction will force the collar 117 away from the piston 114, thereby permitting passage of fluid around the collar 117, through the bore of the piston and through the passageway 119 to the opposite side of the piston, thereby retarding movement of the rack bar 72.

Movement of the piston 114 in the opposite direction will, of course, pull the collar 117 against the piston, thereby preventing passage of fluid through the port in the cylinder.

The cylinder heads 120 and 121 are provided with passageways 122 and 123 connected by a by-pass tube 124 and the passageway 123 is controlled by a needle valve 125 which regulates the speed of flow of the'fluid through the by-pass tube 124 as the piston 114 reciprocates back and forth in the cylinder 115.

and 127 which are threaded onto the rod 113 and which may be ad usted to be engaged by the bracket 105 at any point along the piston rod. From the foregoing, it isclear that as the rack bar 72 moves to the left as in Fig. 7, the bracket 105 will strike the nut 126 thereby forcing the piston 1145 to the left and retarding the speed of travel of the rack bar 72 and consequentl the grinding lap. Upon the return stroke of the me bar 72, the bracket 105 engages the nut 127 and returns the piston 114 to a position for retarding action during the next cycle of operations.

Referring to Fig. 6, the power unit has attached t5 one side thereof an electrical conduit 128 including spaced switch boxes 129 and 130. The box 129 contains a master switch 131 and a push button microswitch 132, whereas the box contains a single push button microswitch 133 lying in the path of the beveled nose 108 carried by the plunger 107 so that upon actuation of the safety button 111, the plunger 107 is moved to actuate the microswitch 133 which is in circuit with the retracting solenoid 104 which actuates the valve 102 and thereby causes reverse movement of the power piston 70.

By the provision of this safety feature, it is evident that by operating the safety button 111, the power piston 70 can be reversed at any point in its movement, and the grinding lap returned to its inoperative position when desired.

The push button switch 132 is in circuit with the advancing solenoid 103, and this switch 132 is actuated by a switch arm 134 provided with a beveled toe 135 and extending through a slot 136 in the plunger 107, so as to contact the microswitch 132 upon operation of the hand lever 137 pivoted at 138 to a suitable portion of the frame of the power unit 69, as will be clearly seen from Figs. 9 and 10.

As previously described, the lap spindle carries a tripping arrangement comprising the threaded member 7 movable with the lap spindle and having the adjustable stop 9 thereon. Attached to the frame of the machine adjacent the threaded member 7 is a micro-' switch 139 having a push button operator 140. Ply-- oted to the frame at 141 is a trip lever 142 having a nose 143 lying in the path of travel of the adjustable stop 9, and having at its other .end a threaded finger 144 which engages the push button operator to actuate the switch 139. This switch is in parallel with the switch 132 and is connected to the retracting solenoid 104.

By adjusting the knurled nut 9 along the threaded member 7, it will be apparent that it is possible to control the thickness of the lens to be ground, because during the descent of the grinding lap, the nut 9 engages the nose 143 of the lever 142 and actuates the push button operator 140 for the purpose of reversing the movement of the power piston 70 and thereby elevating the grinding lap from the lens.

The lever 142 normally rests on a stop 145, and by adjusting the threaded finger 144, the time of operation of the switch 139 can be controlled.

In prior devices, it has been difficult if not impossible accurately to control the pressure of the grinding lap on the work, but this is of extreme importance in order that accurate grinding may be produced and breakage or chipping of the lenses eliminated.

The present invention embodies means for controlling the pressure so that it will remain constant under all conditions.

The power unit 69 carries a yoke 146 which surrounds the cross shaft 74, and this cross shaft is the sole means of support for the entire power unit 69. It is evident from an inspection of Fig. 1 that the center of gravi of the power unit 69 is to one side of the cross shaft 7 and that this power unit is free to turn about the shaft 74 as a fulcrum point.

In normal operation, the power unit 69 is maintained in horizontal position by a counter-Wei t, but in Fig. 1 it is shown at the opposite extreme of its rocking movement. When pressure is applied to the power piston 70, the lap is fed into engagement with the work. If the lens being ground is unusually thick, it is evident that the downward pressure of the lap on the lens will be excessive. Under these conditions, there is an upwanl thrust on the lap spindle 3 which tends to rotate the The piston rod. 113 is provided with spaced nuts 126 05 gear 73 and force the rack bar 72 to the right as shown in Fig. 7. However, since at that time there ispressure behind the piston 70, the rack bar 72 can not move to the right, and consequently the upward thrust on the lap spindle 3 causes rotation of the power umt 69 bodily about the cross shaft 74.

In order to regulate the pressure of the la p on the lens, there is provided a counter-weight consisting of a con necting rod 147' pivoted to the power unit at 148 and to a counter-weight arm 149 at 150. The counter-weight arm 149 is pivoted on a stud 151 carried by bracket 152 which is secured to the frame of the machine. The counter-weight arm 149 terminates in a rod 153' on which is mounted a slidable counter-weight 154, which may be held in adjusted position by a lock screw 155. Suitable stops 156 and 157 are provided on the bracket 152 to limit the swinging movement of the counter-weight arm 149.

From the foregoin it will be seen that by ad usting the counter-weight 154 along the rod 153, the pressure of the lap on the work is controlled and that when this pressure exceeds the force of the counter-weight, the rear end of the power unit 69 will move downwardly against the counter-weight and due to the thrust of the rack bar 72 on the teeth of the pinion 73, this rockmg movement of the power unit 69 will cause the lap to be elevated to the proper degree, thereby relieving the pressure on the lens. By this means, constant pressure can be maintained accurately, and all danger of injury to either the.lap or the lens eliminated.

The operation of the machine is as follows: With the motor 4 for rotating the lap spindle 3 in operation and with the coolant pump 65 functioning, the operator actuates the hand lever 137 to close the advancing switch 132, thereby actuating the advancing solenoid 103 and causing air to pass into the cylinder 71 of the power unit 69 and thereby move the power piston 70 to the left, as seen in Fig. 7, and thus advance the grinding lap toward the work rapidly.

Just prior to engagement between the lap and the lens, the hydraulic check comes into action and slows down the advancing movement of the lap so that it engages the lens gently and then moves slowly into the lens 9to a distance determined by the setting of the stop nut During the downward movement of the lap spindle, the stop nut 9 engages the trip lever 142 and actuates the switch 139 to cause reverse movement of the power piston 70, since the switch 139 energizes the retracting solenoid and permits air to flow to the opposite side of the power piston 70. It will be seen from the foregoing that the thickness of grind can be nicely and automaticallydcontrolled, and that extreme accuracy may be obtaine The advance motion of the grinding spindle 3 is caused by rotation of the cross shaft 74, and during the rotae tion of this shaft, the cam 76 engages the switch 77 just prior to the eniegement of the lap with the lens, and the closing of t 's switch energizes the relay 85 to energize the chuck-driving motor 32. At the same time, the cam 78 engages the trigger finger 63 of the coolant valve, thereby permitting the ,coolant to be supplied to the lap and lens during the actual grinding operation.

When the in has advanced into the lens the required distance, and e trip lever has been actuated to reverse the power piston, the lap will be elevated and the grinding operation completed. Immediately after the lap has been returned to its retracted position, the dog 79 engages the trigger finger 81 and air is supplied to the brake cylinder 40 to apply the brake 35, and thereby stop rotation of the chuck spindle. With the chuck spindle stationary, the dog 80 engages the trigger finger 83 on the lens picker valve, and air is supplied to the lens picker cylinder 52, thereby rotating the rod 48 and causing engagement of the suction cup with the lens. It will be apparent that this engagement between the dog 80 and the trip finger 83 is only momentary and that upon release of the valve 83, the spring returns the lens picker piston to its lowered position and elevates the suction cup together with the lens away from the chuck.

It should be noted in connection with the lens picker cylinder that provision is made for rapidly bleeding air from behind the piston during its return stroke. As previously described, this bleeding is controlled by the vent screw 57 passing into an aperture at the lower end of the cylinder 52. The aperture is open at all times, but

the screw 57 controls the area of the aperture and is so adjusted that in the advance movement of the p1ston which swings the suction cup into engagement with the lens, the volume of air flowing into the cylinder 18 so great that an insufficient amount will escape through the vent to prevent proper operation of the piston. When the piston has reached the end of its advancing stroke, the flow of air is immediately cut off by release of the trigger finger 83 and the spring 55 returns the iston, thereby forcing the air rapidly through the opening 57 and permitting the lens picker to return to inoperative position.

From the foregoing it will be seen that an efficient, accurate, and rapid lens grinding apparatus has been disclosed requiring only the placing of the lens on the chuck and the operation of the hand lever 137 to initiate a complete cycle of operation in which the lens is ground to the proper thickness, coolant is supplied during the grinding, the chuck spindle quickly braked, and the lens removed from the chuck.

I claim:

1. In an abrading machine, a rotatable work-carrying chuck and a rotating abrading element, means for feeding the abrading element to and retracting the same from the work including a reciprocable spindle, adjustable trip means carried by said spindle and engaging a switch-actuating arm on the machine to cause retracting movement of the spindle, and thereby regulate the grinding thickness, a switch operable upon feeding movement of the spindle toward the work to initiate rotation of the chuck, a coolant conduit for directing coolant onto the work and having a valve therein, a cam operable by the feeding means to actuate said valve and permit flow of coolant to the work, a fluid-actuated brake for arresting rotation of the chuck, a conduit for directing fluid to said brake and having a valve therein, a dog carried by said feeding means engageable with the valve in the brake conduit to open the same, and a fluid-operated lens picker, said lens picker including a fluid conduit having a valve therein, and another dog on the feeding means engageable with the lens picker valve to open the same and actuate the picker to remove the work from the chuck. 1

2. The combination with a rotatable lens chuck having a rubber lens seat therein and a film of water on said seat between said seat and a lens mounted in the chuck to hold the lens against relative rotation in said chuck, of a lens picker comprising a swinging arm, a suction cup on one end of said arm, and means at the other end thereof for swingin said arm, said suction cup being positioned to engage the lens when swung in one direction and to lift the lens from the chuck when swung in the opposite direction. 3. The combination with a rotatable lens chuck havmg a rubber lens seat therein and a film of water on said seat between said seat and a lens mounted in the chuck to hold the lens against relative rotation in said chuck, of a lens picker comprising a swinging arm, a suction cup on one end of said arm, and means at the other end thereof for swinging said arm, said means including a rotary rod secured to said swinging arm at one end, a link secured to the opposite end of the rod, and a piston rod secured to said link, means for supplying fluid pressure behind the piston to swing the suction cup into engagement with the lens, and spring means for moving the piston in the opposite direction to swing the suction cup and lens away from the chuck.

4. A lens picker comprising a fluid cylinder and a piston therein, a swinging arm operable by said piston and having a suction cup on the end thereof to engage a lens, means for supplying fluid pressure to said piston to move the same in one direction, and a spring for moving the piston in the opposite direction, and means for bleeding air from said cylinder upon said last-mentioned movement comprising a constantly open vent aperture and an adjustable screw for regulating the flow of fluid therethrough, the area of said aperture being at all times insutficient to permit escape of fluid as fast as it is supplied to the cylinder, but of an area rapidly to vent the cylinder when the supply ceases.

5. In an abrading machine, a rotatable lens-carrying chuck and a rotating abrading lap carried by a reciprocable spindle, a rotary cross shaft having a gear thereon meshing with a rack on said spindle to feed the lap to and away from the work, a second gear on said cross permit the unit'to rock about said shaft against the action of the counter-weight when pressure on the abrading lap overcomes the counter-weight thereby to relieve the pressure of the lap on the lens.

6. An abrading machine as claimed in claim 9 in which the counter-weight comprises a connecting rod secured to the power unit rearwardly of the cross shaft, a counter-weight arm pivoted intermediate its ends to a bracket on the machine and having one end pivoted to said connecting rod, said counter-weight arm terminating at its other end in a rod, and a counter-weight slidable along said rod to adjust the pressure on the grinding 7. An abrading machine comprising a lens-carrying chuck and a rotating grinding lap spindle, a power-operated shaft lying behind said spindle and connected to said lap spindle for feeding the same to and, from the lens, and including a gear, a power unit mounted on said shaft and rockable thereabout, said. power unit including a rack bar engageable with said gear, and an adjustable counter-weight for maintaining the desired pressure of the lap on the lens secured to said power unit on the opposite side of said shaft from said lap spindle, whereby upward thrust on the lap spindle causes rocking of the power unit about said shaft against the action of the counter-weight to maintain desired pressure of the lap on the spindle.

8. An abrading machine comprising a rotatable lenscarrying chuck and a rotating grinding lap, a fluid cylinder having a piston therein operatively connected to the lap to feed the lap to and from the work, a manifold through which fluid is supplied to said cylinder to operate the piston, a fluid brake for arresting movement of the rotatable lens chuck and a fluid-operated lens picker for removing a lens from said chuck, said brake and lens picker being supplied through conduits communicating with said manifold, and valve means in said conduits automatically operable to pass fluid therethrough during operation of the feeding means.

9. An abrading machine comprising a lens-holding chuck, a lens picker for removing the lens from the chuck, said picker comprising a swinging arm, a suction cup secured to one end of the arm and movable into engagement with the lens when the arm is swung in one direction and to lift the lens from the chuck when rotated in the-opposite direction, and means for swinging said arm.

10. An abrading machine comprising a lens-holding chuck, a lens picker for removing the lens fromthe chuck, said picker comprising a swinging arm, a suction cup secured to one end of the arm and movable into engagement with the lens when the arm is swung in one direction and to lift the lens from the chuck when rotated in the opposite direction, and fluid means for swinging said arm.

11. In combination, a rotatable lens-carrying chuck and a rotating abrading element, fluid means for feeding the abrading element to and retracting the same from the lens, and a fluid-operated lens picker comprising a swinging am having a suction cup mounted on one end thereof and engaging the lens when the arm is swung in one direction,'a rotary rod connected to the other,

end of said arm, a fluid cylinder having a piston therein secured to said rod to rotate the same, and means controlled by the spindle-feeding means for actuating the piston to swing the arm in the opposite direction to remove the lens from the chuck.

References Cited in the file of this patent Silven Oct. 23, 1951

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