US2103984A - Lapping machine - Google Patents

Description

Dec. 28, 1937. 9 H. 5. m: 2,103,984

LAPPING MACHINE Filed Sept. 11, 1935 3 Sheets-Sheet l I I3 54' .J

HERBERT 5'. INDG'E W/T-Ess Dec. 28, 1937. H. s. INDGE 2,103,984

LAPPING MACHINE Filed Sept. 11, 1935 5 Sheets-Sheet 5 [l2 :5 :m IIIIIIIIIIIIA WITNESS 3 6 w, mmazxm Patented Dec. 28, 1937 um'rso STATES- LAPPING MACHINE Herbert S. Indge, Westboro, Mass, assignor to Norton Company, Worcester, Mesa, is corporation of Massachusetts Application September 11, 1935, Serial No. 40,118

9 Claims.

This invention relates to lappingmachines, and more particularly to a hydraulically operated lapping machine. 1

One of the objects of this invention is to provide a simple, thoroughly practicable, hydraulically operated lapping machine. Another object is to provide a hydraulically operated lapping machine which is arranged so that hydraulic pressure may be equally distributed over the entire operative surface of the lapping elements.

Another object of this invention is to provide a hydraulically operated lapping machine in which the laps engage the work at a predeterminedpressure for a rough lapping operation and at a second predetermined pressure for a finish lapping operation.

Another object of this invention is to provide a hydraulically operated pressure mechanism for a lapping operation, in which either a high or a low pressure may be obtained.

Another object is to provide a pressure control device in which a high ora low pressure may be obtained or any desired pressure between the high and low. 1

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying'drawings, in which is shown one of the various possible embodiments of the mechanical features of this invention,

Fig. 1 is a side elevation of the improved lapping machine, having parts broken away and shown in section to more clearly show the construction;

Fig. 2 is a diagrammatic showing of the hy draulic system;

Fig. 3 is a horizontal section, on an enlarged scale, taken approximately on the line 33 of Fig. l;

Fig. 4 is a sectional view, partly in elevation, taken approximately on the line 4-4-of Fig. 3;

Fig. 5 is a fragmentary vertical section taken approximately on the line 5-5 of Fig. 4, showing the adjustable stop mechanism for the upper Fig. 6 is a fragmentary cross sectional view, taken approximately on the line 6-4: of Fig. 5, showing a top plan view of the movable stop member;-

- Fig. 7 is a vertical section, partly in elevation, on an enlarged scale, taken approximately on the line 'l'l of Fig. 5;

Fig. 8 is a fragmentary plan view, partlyin section, taken approximately on the line 8-8 of Fig. 7; I

Fig. 9 is a fragmentary cross sectional view, taken approximately on the line 9-9 of Fig. 4; and

Fig. 10 is a fragmentary vertical section, on an enlarged scale, showing the counterbalance mechanism for the upper lap, taken approximately on the line Ill-40 of Fig. 1.

Referring more particularly to the embodiment illustrated, the lapping machine may be I constructed in its general aspects similar to the lapping machines illustrated in the prior U. S. patent to Indge No. 1,870,328 dated August 9, 1932. This machine, as illustrated, may comprise a base I0 which rotatably supports a lower lapping wheel II. The base I0 is provided with an upwardly extending column 12 having an outwardly extending horizontal portion l3 which rotatably supports a vertical spindle M. The spindle l4 carries a rotatable lapping wheel l5 which is connected to the spindle H by means of a supporting plate l6.

Power may be obtained from any suitable source, such as an overhead drive shaft or an electric motor mounted on the machine. For the sake of illustration, a belt drive has been shown, comprising a driving belt which serves to ro-' tate a pulley 2|. The inner portion of the pulley is formed as one part of a cone clutch. A slidable cone clutch member 22 serves to cooperate to permit the power to be readily connected or disconnected. The pulley 2| is rotatably supported on a horizontally extending shaft 23 which is supported in bearings 24, 25, 26 and 21 in the base HI. The clutch member 22 is slidably keyed to the shaft 23. When the clutch is in the full line position as indicated in Fig. 1, no power is transmitted to the shaft 23. When it is desired to rotate the shaft 23, the cone clutch member 22 is moved toward the right, as viewed in Fig. 1, into engagement with the cone clutch member within the pulley 2| so as to cause a rotation of the shaft 23. In order that the clutch may be readily actuated from the operating position adjacent the front of the machine, a pivotally mounted control lever 28 is supported on a stud 29 on the base Ill. The lower end of the lever 28 is connected by a pin 30 with a link 3| which is connected by means of a rod 32 supported in bearings 33 and 34 with a yoked memher 35 and engages a groove 36 in the hub 31 of the clutch member 22. By movement of the control lever 28 in a counterclockwise direction, the clutch member 22 may be thrown into engagement with the clutch member within the pulley 2i to cause a rotation of the shaft 23, or when moved into the position illustrated in full line in Fig. 1, may disconnect the clutch and stop the rotation ofthe shaft 23. A spring pressed roller 38 cooperating with an arrow point 39 on the yoked member 35 serves to hold the clutch either in or out of engagement.

In order that the shaft 23 may be stopped quickly when the clutch is disengaged, a brake is provided comprising a brake disk 40 which is operatively connected to the clutch member 22 and is arranged to engage a brake plate 4I mounted on the base of the machine.

The shaft 23 is provided with a worm which meshes with a Worm gear 46 on the lower end of a vertical shaft 41. The shaft 4'I is connected by a universal joint 48 with a shaft 49. The

' shaft 49 is preferably a telescopic shaft and is connected by a universal joint 50 with a vertical shaft 5i supported in bearings 52 and 53 in a bracket 54 mounted on the top of the column I2. The shaft 5I is provided with a pulley 55 which is connected by belts 56 with a pulley 51 which is mounted on a rotatable sleeve 58. The sleeve 58 is slidably keyed by keys 59 to an upwardly extending projection 60 of the spindle I4, so

that when the clutch 22 is engaged, the vertical spindle I4 supporting the upper lap I5 will be rotated.

The bracket 54 is adjustably mounted on the upper surface of the arm I2 and is provided with a screw adjustment comprising a screw 62 which is rotatably'supported in a bracket 63 fixed to the column I2 and is screw threaded into the bracket 54 so that the bracket 54 maybe adjusted transversely of the machine to obtain the desired driving tension on the belts 56.

The lower lap I1 is connected by a rotatable spider 65 and is rotated by means of a vertical sleeve (not shown). A work carrying cage 66 is supported above the lower lap II and is provided with a plurality of work receiving apertures for supporting a plurality of work pieces for simultaneous lapping thereon. The work carrying cage is carried by the driving pins or studs 61 and 68 and is carried through anirregular combined rotary and planetary movement by a power driven gear mechanism, the details of which have not been illustrated in the present drawings, since this mechanism ,is not considered part of the present invention. For details of disclosure as to the means for rotating the lower lap II and for rotating and gyrating the cage 66, reference may be had to the prior patents to Indge Nos. 1,610,527 dated December 14, 1926 and 1,870,328 dated August 9, 1932.

The shaft 23 is provided with a worm I0 which meshes with a worm gear II mounted on a rotatable, vertically extending sleeve which is connected with spider 65 to rotate the lower lap II. The gears I5 and I6 are connected in the manner illustrated in the prior Indge patents to produce a predetermined movement of the work carrying cage 66. For details of this mechanism, referencemay be had to the above-memtioned prior patents.

The spindle I4 which supports the upper lap 82 within the casing 83 which is formed on the front end of the arm I3.

A counterbalance mechanism is provided to counterbalance the weight of the upper lap and its supporting mechanism. This mechanism comprises a rack bar 85 fixed to the sleeve 82. The rack bar 85 meshes with a gear 86 one. transversely extending shaft 81. The shaft 81 also supports a sprocket 88 which is connected by a link chain 89 with a sprocket 90 which is supported on a shaft M. I supported by an idler bracket 92 which is pivotally mounted on a shaft 93. The idler bracket 92 is formed as a bell crank, one arm of which serves to support the shaft SI and the other arm of which is provided with an adjusting screw 94 which permits adjusting the position of the bracket 92 so as to swing the sprocket 90 and tension the link chain 89 as desired. The shaft 9I is also provided with a sprocket 96. A link chain 9! wraps around the sprocket 96 and supports at one endthereof an adjustable weight 98 which is of a suflicient size to counterbalance the weight of the upper lap and its operating mechanism. By utilizing the reduction gear mechanism between the gear and link chain and sprocket mechanism-interposed between the rack 85 and the weight 98, a two-to-one reduction is obtained so that the weight 98 need be only half the weight of the parts which are counterbalanced, thus eliminating the necessity of a heavy counterbalance weight within the column I2. If desired, the shaft 87 may be manually rotated by means of a Wrench or crank (not shown) to turn gear 86 and move rack 85 to raise or lower the upper lap I5. v

In order to limit the downward movement of the upper lap I5, a suitable stop mechanism is provided to positively limit the downward movement of the lap so that it bears a definite and predetermined relation with the lower lap and the work. This stopcomprises an adjustable stop I00 which is adjustably mounted in a bracket I0l which is fixed to the frame 83 which supports the sleeve and spindle for the upper lap. The stop I00 is provided with a screw threaded portion I02 meshing with a correspond- The shaft BI is in turn ingly threaded aperture within the bracket IOI.

A transversely extended clamping member I03 is adjustably mounted within the bracket IM and is provided with a threaded portion arranged to engage the threadsof the screw I02. The member I03 may be forced into clamping relation with the screw I02 by means of a screw I04, so that the stop I00 may be adjusted into a predetermined position and then locked in fixed relation to the frame of the machine. A mov able stop screw I06 is supported in a bracket I01 which is adjustably fixed to the sleeve,82. The sleeve 82 is provided with a plurality of threaded holes I08 so that the bracket I01 may be clamped in various positions on the sleeve 82 by means of screws I09 and H0. The stop screw I86 passes through a threaded. aperture III in the bracket I01 and is provided at its'upper end with a graduated micrometer adjusting end II2 which enables a fine adjustment of the stop screw to vary the lower position of the upper lap I5 as desired. In order that the stop screw I06 may be locked in adjusted position, the bracket I0! is preferably provided with a slot II4 which extends from the end of the bracket to the threaded aperture III. A clamping screw II5 extends transverse 1y through the bracket III! at a point intermediate the slotted area and serves to bindthe 75 bracket when desired to lock the screw I06 in a predetermined adjusted position. By providing a plurality of threaded holes I in the sleeve 02, a quick adjustment of the bracket I01 may be obtained to adjust the stop in setting up the machine for lapping work pieces of varying thicknesses.

In order to obtain the desired lapping action between the opposed laps II and I5 as the work is. carried through an irregular path therebetween, it is essential to provide a pressure device to move the laps relatively toward each other and to maintain them in operative engagement with the plurality'of work pieces during the lapping operation. In certain lapping operations, it is desirable tostart the lapping operation with a considerable amount of pressure between the lapping elements to cause a rough lapping of the work piece and to then reduce the pressure for a finish lapping operation.

A fluid pressure system is provided to produce the desired operating pressure on the upper lapping member. It is desirable to provide a pressure device so that the pressure is uniformly applied to the upper lapping element so that the lapping surface thereof will remain parallel to the opposed lapping surface of the lower lap. In order to obtain this result, a pair of diametrically opposed fluid pressure cylinders I and I2I are mounted in brackets I22, I23, I24 and I25 which project from diametrice 'y opposite sides of the housing 83. The cylinders I20 and I2I are provided with pistons I26 and I21 re-' spectively. The pistons I26 and I21 are con nected by piston rods I28 and I29 with a flanged plate I30 which is mounted on the lower end of the sleeve 82 and is held in place thereon by means of a collar I3I. The piston rods I26 and I29 are fixedly connected to the flanged plate I30 by means of nuts I32, I33,. I34 and I35 so that when the pistons I26 and I21 are moved within the cylinders I20 and I2I, the piston rods will cause a corresponding movement to be transmitted to the vertically movabl, spindle I4 and the upper lap l5.

The flanged plate I30 is connected to the'lower end of the sleeve 82 adjaxnt to the mounting I6 for the upper lap so that when pressure is applied to the diametrically opposite pistons, the pressure is uniformly distributed over the lapping surface and there is no tendency on the part of the lap toassume other than a parallel relation with the opposed lapping surfaces, thus minimizing any errors in the lapping operation due to any lost motionbetween the housing 83 and the sleeve 62.

Fluid for the pressure system is supplied from a reservoir :40 which is preferably mounted within the base of the machine. Fluid is conveyed from the reservoir I40 through a pipe' MI by means of a gear pump I42 which forces fluid through a. pipe I43 to a reversing or control valve I44. The valve I44 is of a balanced piston type comprising a valve stem I45 having valve pistons I46, I41 and I48 formed integrally therewith. The valve I44 is arranged to convey fluid in the position shown in Fig. 2 through a pipe I 49 and pipes I50 and I5I into cylinder chambers I52 and I53 to cause the pistons I26 and I21 to move into 'their extreme upward positions, as shown in Figs.

2 and 4, to separate the lap I5 from the lap II to permit loading and unloading of the work cage.

During the upward movement of the pistons I26 and I21, fluid is exhausted from cylinder chambers I54 and I55 through pipes I56 and I51 through a pipe I50, through a valve chamber I59 between the valve pistons I41 and I48 and out through an exhaust pipe I60 into the reservoir I40. When the reversing valve I44 is shifted into the reverse position, that is with the valve stem I45 moved downwardly (Fig. 2), the direction of fluid from the pump I42 is reversed so that it passes into a valve chamber I59 between valve pistons I41 and I40 and through pipe I58, and pipes I56 and I51 into cylinder chambers I54 and I55 respectively to simultaneously move the pistons I26 and. H1 downwardly to cause a downward movement of the sleeve 82 and spindle I4 to move the upper lap I5 into broken line position I5a. (Fig. 4) into lapping engagement with a plurality of work pieces I65.

In order that the valve I44 may be readily controlled from the operating position in front of the machine, a manually operable control lever I66 is pivotally mounted on a stud I61. The stud I61 is also provided with a lever I68 which is connected with the valve stem I45 by means of pins I69. By moving the lever I66 from the full line position (Fig. 1) into dotted line position I06a, the valve I44 is retersed and fluid is admitted to the upper cylinder chambers I54 and I55 to cause a downward movement of the upper lap I5. Similarly, when the lever I66 is moved from position I660, into full line position I66 (Fig. l), the valve is moved into the position illustrated in Fig. 2 to admit fluid under pressure to the lower cylinder chambers I52 and I53 so as to raise the upper lap I5 to permit removal of the work which has been lapped and permit insertion of new pieces of work. I

In order to attain the main object of this invention, it is desirable to provide a pressure controlling mechanism so that the fluid pressure apried to th. upper cylinder chambers I54 and I55 will cause the upper lap I5 to bear against the work pieces at a desired predetermined pressure for either a rough or a finish lapping operation. As illustrated in the drawings, this is accomplished by providing a variable pressure regulating valve I10. This valve is connected by a pipe I" with the pressure pipe I43. The valve I10 may be adjusted by means of an adjusting screw I12 so that if the pressure supplied by the pump I42 exceeds the desired pressure, a valve member I13 will be raised from its seat against the tension of a spring I14 and allow the excess fluid under pressure to exhaust through a pipe I15 into the reservoir.

In the lapping of certain types of work,it is I desirable to provide a pressure controlling mechanism which enables the lapping operation to be started with the lapping elements pressing upon the work at a substantial predetermined pressure to initially lap the work pieces and to then change the pressure to produce a final or finish lapping operation. This is preferably accomplished by providing a second pressure regulating valve I which is connected by a pipe I8I with the pipe I43. This valve is identical with the pressure regulating valve I10 and comprises a movable member I82 which is held against its seat by means of a spring I83 the tension of which may be adjusted by an adjusting screw I84. In setting up the machine, the pressure regulating valve I10 is adjusted to give the predetermined maximum pressure desired upon the upper lap, and the pressure regulating valve I80 is adjusted for the predetermined minimum pressure. During the normal use of the mechanism may proceed to the desired extent. desired to reduce the pressure to a finish lapping above described, the fluid pressure system is so operated that any pressure in excess of the low pressure to which the valve I80 is set would cause the valve member I82 to rise from its seat and allow excess fluid under pressure to exhaust through a pipe- I85 into the reservoir.

In order that either a high or a low pressure may be applied to the upper lapping elements, a valve I90 is inserted within the pipe I8I. 'This valve is arranged so that in the position illustrated in Fig. 2, fluid under pressure is out 01f from the regulating valve I80, thus rendering the low pressure regulating valve I80 inoperative so that the upper lap will be maintained in lapping engagement with the work at the higher pressure to which the Valve I10 is set. In this position of the parts, the rough lapping operation When it is pressure, the valve I90 is turned through 90 to allow fluid under pressure to pass through pipe I8I into valve I80, thus rendering the low pressure regulating valve I80 operative so that if the pressure from the pump I42 exceeds the low pressure desired for the finish lapping operation, the valve member I82 opens and allows the excess fluid under pressure to exhaust through the pipe I85.

It will be readily apparent from this disclosure that by manipulation of the valve I90, that is opening the valve to a greater or lesser extent, practically any pressure between the high and the low pressure to which valves I10 and I80 have been set may be obtained.

In lapping certain types of work, such as thin objects which are readily distorted, it may be desirable to start the lapping operation with a comparatively light pressure of the laps on the work to remove any irregularities or high spots on the surfaces to be lapped and to then increase the pressure to lap the work to the approximate size and finish and then'to reduce the pressure to a light or final finishing pressure for the final lapping on the work piece. This may be accomplishedby opening the valve I90 and allowing the low pressure regulating valve I80 to be operative during the initial operation so that the laps will engage the work for an initial lapping operation and to then close the valve I90 and allow the valve I99 to cause the laps to engage the work at a higher pressure for lapping the surfaces of the work to the required'extent. Then a final or finish lapping is obtained by again opening the valve I90 to render the low pressure valve I80 operative so as to reduce the pressure of the laps on the work during the final or finish lapping operation.

In order to facilitate adjustment of the pressure regulating valves I10 and I80, a pressure indicating gauge I95 is connected in pipe line I43 by means of a pipe I96 so that in setting the high pressure valve I10 with valve I90 closed, an indicating control valve I91 may be opened to permitthe operator to observe a visible indication of the pressure within the systemwhile adjusting the screw I12 of valve I10. After valve I10 has been set to the desired pressure; the valve I90 may be opened to render the valve I operative and the adjusting screw I84 may be adjusted so that the release valve I80 will give the desired finish lapping pressure on the upper lap.

In the operation of this machine, the work pieces I65 are inserted in the work receiving apertures within the cage 66, the control lever 28 is then moved in a counterclockwise direction (Fig. 1) to engage the clutch 22 and rotate the shaft 23 which through connecting mechanism causes the lower lap II and the upper lap I5 as well as the cage 66 to beset in motion. The operator then moves the lever I66 from the full line position into the broken line position I56a. (Figs. 1 and 4) which serves to move the stem I45 of the valve I44 downwardly from the full line position illustrated in Fig. 2 to the dotted line position so as to admit fluid under pressure through pipe I58 simultaneously into the upper cylinder chambers I54 and I55 to cause the upper lap I5 to move into lapping engagement with the work pieces. Assuming the pressure regulating valves I10 and I80 to have been previously set to the desired pressures, the lap I5 in the position of the parts illustrated in Fig. 2 is moved into lapping engagement with the work at a pressure governed by the high pressure valve I10 to cause a rough fast lapping of the work piece. After the preliminary or initial lapping has been carried on to a predetermined extent, the valve I is shifted to admit fluid under pressure through pipe IIlI so as to render the pressure regulating valve I80 operative, thereafter allowing the valve I80 to control the pressure applied to the upper lap to permit a' final or finish lapping operation for a predetermined period. After the lapping operation has been completed to the desired extent, the control lever I66 is raised from the position I650. into the full line position, causing the valve stem I45 to move into the full line position, as illustrated in Fig. 2, so as to admit fluid under pressure through the pipe I49 simultaneously into cylinder chambers I52 and I53 to cause the upper lap to move out of engagement with the work and into an inoperative position.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with may thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A lapping machine comprising a base, a rotatable lap supported on said base, an opposed rotatable lap, a rotatable spindle to support said second lap, means to rotate said spindle, means including a sleeve to support said spindle, means including a pair of fluid pressure pistons and cylinders arranged on diametrically opposite sides of said spindle, a pair of piston rods connected with each of said pistons, a mounting for said second lap on the lower end of said spindle which is adjacent to the end of the sleeve, and rigid connections between the lower end of said sleeve and the piston rods which are arranged so that when fluid under pressure is admitted to said cylinder, the pressure will be distributed substantially equally over the entire surface of the lap.

2. A lapping machine of the type having a base, a pair of opposed, relatively rotatable lapping elements. and a work carrying cage arranged therebetween for supporting a plurality of work pieces for a simultaneous lapping operation between said laps, a rotatable spindle to support one of said laps, bearings for said spindle,

a sleeve to support said bearings, a counterbalance weight to counterbalance the weight of said movable parts, an adjustable micrometer stop screw to positively limit the movement of said movable lap toward and from the other, a pair of fluid pressure cylinders which are fixed to the base and arranged on diametrically opposite sides of said spindle and sleeve, pistons within said cylinders, a control valve to control the admission and exhaust of fluid from said cylinders, piston rods connected to said pistons respectively and extending beyond said cylinders, and con nections between said piston rods and the lower end of said sleeve which are located adjacent to the movable lap mounting which serve to distribute a substantially equal pressure over the entire lapping surface.

3. A lapping machine of the type having a pair of opposed relatively rotatable lapping elements one of which is movable relatively toward and from the other and a work cage therebetween for simultaneously supporting a plurality of work pieces for a simultaneous lapping action between the operative faces of-said lapping elements, a rotatable spindle rigidly to support said movable lapping element, a movable sleeve rotatably to support said spindle, and means to cause a relative approaching and receding movement between said lapping elements comprising a plurality of spaced fluid pressure cylinders arranged symmetrically with respect to the axis of said movable lapping element, pistons within said cylinders, connections between the pistons and movable sleeve which are located adjacent to said movable lapping element, and means including a control valve which is operatively connected to admit fluid under pressure simultaneously to either end of said cylinders to cause a relative approaching or receding movement between said lapping elements and to maintain said elements in lapping engagement with the work at a predetermined positive pressure.

from the other and'a work cage therebetween forsimultaneously supporting a plurality of work pieces for a simultaneous lapping action between the opposed faces of said lappingelements, a rotatable spindle rigidly to support said movable lapping element, a movable sleeve rotatably to support said spindle, and means to cause a relative approaching and receding movement between said laps comprising a pair of spaced fluid pressure cylinders fixed on diametrically opposed sides of the axis of said movable lapping element, pistons within said cylinders, connections between the pistons and movable sleeve which are adjacent to said lapping element, and means including a control valve which is operatively connected to admit fluid under pressure simulta neously to either end of said cylinders to cause a relative approaching or receding movement between said lapping elements to maintain said elements in engagement with the work at a predetermined positive pressure.

5. A lapping machine of the type having a pair of opposed rotatable lapping elements which are movable relatively toward and from each other and a work carrying cage therebetween arranged to carry a plurality of work pieces through an irregular path between the operative faces of said laps, a fluid pressure system including a piston and cylinder which are arranged to cause a relative approaching or receding movement between said lapping elements, a control valve to convey fluid under pressure to eitherend of said cylinder, means including a fluid pump and. a pipe to tain the laps in engagement with the work at a second predetermined positive pressure for a fin ish lapping operation, and means including a valve between the pipe and said second pressure regulating valve to render said second pressure regulating valve inoperative during the rough lapping operation.

6. A lapping machine of the type having a pair of .opposed rotatable lapping elements one of which is movable relatively toward and from the other, a work carrying cage therebetween for simultaneously supporting a plurality of work pieces for a simultaneous lapping action between the opposed faces of said laps, a rotatable spindle rigidly to support one of said laps, an axially movable sleeve rotatably to support said spindle, andmeans comprising a pair of spaced fluid pressure cylinders arranged on diametrically opposite sides of the axis of the movable lap, pistons within said cylinders which are operatively connected to the end of said sleeve adjacent to said lap to cause a relative approaching and receding movement between the laps, a control valve arranged simultaneously to admit fluid under pressure to either end of said cylinders, means including a fluid pump and pipe which are operatively connected to convey fluid under pressure to said control valve and cylinders, a pressure regulating valve in said pipe which is arranged to regulate the pressure of the fluid so as to cause the laps to be maintained in engagement with the work at a predetermined positive pressure for an initial lapping operation, a second pressure regulating valve in said pipe line which is connected in series with said first pressure regulating valve to maintain the laps in lapping engagement with the work at a second predetermined positive pressure for a finish lapping operation which is inoperative during the initial lapping operation, and means including, a stop valve to render said second pressure regulating valve operative after a predetermined initial lapping operation.

7. A lapping machine of the type having a pair of opposed relatively rotatable lapping elements one of which is movable relatively toward and from the other and a work carrying cage therebetween arranged to carry a work piece through an irregular path between the operative faces of said laps, a fluid pressure system including a piston and cylinder which are arranged to cause a relative approaching or receding movement between said lapping elements, a control valve to convey fluid under pressure to'either end of saideration, and means including a valve located between the pipe and said second pressure regulating valve by which any positive pressure between the maximum and minimum of the two pressure regulating valves may be obtained.

8. A lapping machine of the type having a pair of opposed rotatable lapping elements which are movable relatively toward and from each other and a work carrying cage therebetween arranged to carry a plurality of work pieces through an irregular path between the operative faces of said laps, a fluid pressure system including a piston and cylinder which are arranged to cause a relative approach and receding movement between said lapping elements, a control valve to convey fluid under pressure to either end of said cylinder, means including a fluid pump and pipe to convey fluid to said valve and cylinder, a pressure regulating valve in said pipe line which is arranged to be set for a maximum pressure between said lapping eiements and the work, a second pressure regulating valve in said pipe which is connected in series with the first pressure regulating valve and arranged to be adjusted for a minimum pressure between said lapping elements and work, and means including a manually operable valve operatively connected with said second pressure regulating valve and pipe whereby any positive pressure may be obtained between the said minimum and maxlmum pressures.

9. A lapping machine of the type having a pair of opposed relatively rotatable lapping elements one of which is movable relatively toward and from the other and a work carrying cage therebetween arranged to carry'a plurality of work pieces through an irregular path between the operative faces of said laps, a rotatable spindle rigidly to support one of said laps, a movable sleeverotatably supporting said spindle, a fluid pressure system including a piston and cylinder which are operatively connected to move said sleeve and cause a relative approaching and receding movement between said lapping elements, a control valve to convey fluid under pressure to either end of said cylinder, means including a fluid pressure pump and pipe to convey fluid to said valve and cylinder, a pressure regulating valve in said pipe which is arranged to maintain said laps in engagement with the work at a maximum positive pressure, a second pressure regulating valve in said pipe which is connected in series with the first pressure regulating valve to maintain said laps in engagement with the work at a minimum predetermined positive pressure, and means including a valve between said pipe and said second pressure: regulating valve whereby the pressure between said lapping elements may be adjusted to produce any pressure between the minimum and maximum pressures of said pressure regulating valves.

HERBERT S. INDGE.

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