US3385008A

US3385008A - Lapping machine tool

Info

Publication number: US3385008A
Application number: US530105A
Authority: US
Inventors: Richard S Gentry; George A Sowden
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-02-25
Filing date: 1966-02-25
Publication date: 1968-05-28
Anticipated expiration: 1985-05-28
Also published as: GB1119899A; FR1512715A; BE694457A; NL6702170A; DE1652043A1

Description

May 28, 1968 R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL Filed Feb. 25, 1966 4 Sheets-Sheet 1 w z I .8

l l'lllll l l llll IW I06 I O 96 2 INVENTORS Richard S. Gentry Fig. 1 Ge me A. Sowden B WLM TO R NEYS May 28, 1968 R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL Filed Feb. 25, 1966 4 Sheets-Sheet 3 I 32 5 I 48 4e v 1 \20 {Mo 2 I V INVENTORS Rwhard S. Genfirg F1 4- TTORNEYS y 8, 1968 R. s. GENTRY ET AL 3,385,008

LAPPING MACHINE TOOL 4 Sheets-Sheet 4.

Filed Feb. 25, 1966 I 4 GM W M T C J M 2 CL M H H I 3 W slmfw Rnnw 0 5 T6 N S a Enao u A R N a o T T mm m owe O/ G United States Patent 3,385,008 LAPPING MACHINE TOOL Richard S. Gentry and George A. Sowden, Indianapolis, Ind., assignors, by mesne assignments, to Richard S. Gentry, Indianapolis, Ind.

Filed Feb. 25, 1966, Ser. No. 530,105 Claims. (Cl. 51--34) ABSTRACT OF THE DISCLOSURE An improved lapping machine tool. A lapping tool is biased forward by an air cylinder and is reciprocated by a cam which retracts the tool against the bias and controls the rate of its advance under the limited bias force. Work piece resistance arrests the tool at an intermediate point in its forward strokes, and as the lapping progresses to overcome such resistance, the tool advance beyond such arrest point actuates a switch to energize a feed motor which advances the stroke range. Such switch is adjustable to adjust the Operating stroke length. The tool reciprocating mechanism is mounted on a head above the work piece table. The feed motor is housed in the base and is an air cylinder which operates through adjustable strokes to actuate a feed screw to lower the head. An electrical motor operates the feed screw for rapid feed.

This invention relates to a machine tool for automatically performing lapping and like abrading and metal finishing operations.

It is a principal object of the invention to provide an improved machine tool embodying the general concept of that shown in United States Patent No. 3,151,992. In that patent, a lapping tool is biased forward by a limited resilient force, such as that of a spring or an air cylinder, and is reciprocated through a predetermined stroke range by a cam which acts to drive it in a retraction direction against such bias and to control the rate of its advance movement by the biasing force; so that the forward stroke of the tool is under a limited force sufiicient to produce the desired lapping but insufficient to produce galling. In operation, the tool is arrested at an intermediate point in its forward strokes by the workpiece resistance, and as the lapping progresses to overcome such resistance and the tool advances beyond such arrest point in a forward stroke, such movement actuates a switch to energize a feed motor which advances the stroke range.

It is a further object of the present invention to provide a machine for carrying out such lapping operations, which will be practical for a wide variety of lapping work and will provide a high degree of accuracy, and which will have improved controls and regulations.

In the preferred form of the present invention, the lapreciprocat-ing mechanism is mounted in a head assembly positioned above a work table and rigidly carried by slidable posts accurately guided for perpendicular movement through the plane of the table and connected at their lower ends to a vertically movable platen. The platen is raised and lowered by a main feed screw, which may be a non-rotating screw engaged in an internally threaded output gear of a reduction gear set, such as a worm and worm-wheel set. The gear set is connected for operation either by an electric motor, for rapid feed, or by an adjusta'ble-stroke incremental feed device, such as an airdriven rack and pinion.

The lap-reciprocating mechanism is driven by a variable-speed motor and the lap carrier is biased toward the work by an air cylinder, and both the rate and force of lapping strokes are accurately adjustable over a wide "ice range. The incremental feed device is actuated through a single stroke of adjustable length in response to movement of the lap carrier, in each lap stroke, beyond an intermediate point of the stroke range, and adjustment is provided both of the position of such intermediate point and of the length of the feed increment produced. Accordingly, accurate regulation and adjustment of all lapping conditions is provided.

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a front elevation of a machine embodying the invention, with parts broken away to show the operating mechanism;

FIG. 2 is a vertical section of the machine of FIG. 1, taken on the line 2-2 of FIG. 1;

FIG. 3 is a horizontal section, taken on the line 3-3 of FIG. 1, showing the head mechanism in plan;

FIG. 4 is a horizontal section, taken on the line 44 of FIG. 1, showing the feed mechanism in plan; and

FIG. 5 is an electrical diagram of the operating and control devices of the machine of FIG. 1.

The machine shown in the drawings comprises a base 10 formed of a rigid frame enclosed in a housing and supporting a work table 12 in a horizontal plane. Vertical guide bearings 14 at the four corners of the table 12 slidably receive guide posts 16 which are interconnected at their lower ends by a platen 18 and which rigidly support a head 20 above the table 12. The head 20 is adapted to be raised and lowered with respect to the table 12 by feed mechanism housed in the base 10, as described below.

The head 20 comprises a frame 22 which forms a central housing 24 for a bushing 26 in which a vertically reciprocable shaft or lap carrier 28 is mounted. Above the housing 24, the frame supports a pair of side plates 30 provided with bearings 32 in which a horizontal cam shaft 34 is mounted. The shaft 34 carries a central eccentric cam 36, and this is embraced by a yoke 38 having a cam-follower insert 40 bearing downwardly against the cam 36. The lower end of the yoke 38 is connected to the lap carrier 28, and the upper end of the yoke 38 is engaged for downward thrust by the piston rod 42 of an air cylinder 44. As is shown in FIG. 1, the yoke 38 has a lateral extension 46 which carries a guide bearing 48 received over a fixed guide pin 50, for the purpose of guiding the yoke for vertical movement and against lateral thrust from the cam 36.

The eccentric cam 36 may desirably have a throw or eccentricity of of an inch, so that it provides a reciprocating stroke range for the lap carrier 28 of of an inch. The shaft 34 carries a large pulley 52, by which it is belt driven from a smaller pulley 54 on the shaft of a variable-speed electric motor 56. Desirably, the reciprocation rate of the lap carrier 28' is variable from O to 600 strokes per minute. The air cylinder 44 is suppled with air pressure from any suitable source, controlled by a manually adjustable valve 58, and the pressure is desirably shown on an air gauge 60. The downward thrust exerted by the air cylinder 44 on the yoke 38 and hence on the lap carrier 28 is desirably variable to produce lapping pressures of from 0 to 400 pounds.

The lower end of the lap carrier 28 has an internally threaded bore in which is fitted a lap holder 62 by which a lap 64 is rigidly secured to the lap carrier 28.

The workpiece 66 to be lapped is mounted on blocks 68 on the table 12 and secured in place by suitable holddown clamps 70.

As shown in FIGS. 1 and 3, the lateral extension 46 on the yoke 38 carries a vertically adjustable screw 72 having a switch actuating head 74 at its lower end disposed to engage a feed switch S1 at an intermediate point in the downward reciprocating stroke of the yoke 38 and its lap carrier 28. This is the feed actuating switch, the function of which will be described below. The frame of the head 20 also carries a limit switch S-5 having an actuating arm positioned to be engaged by an adjustable rod 78 fixed to the table 12. This serves to terminate the lapping operation when downward feed movement of the head is sufficient to show that the lapping operation has been completed.

As is shown in FIGS. 1 and ,2, the platen 18 which carries the lower ends of the head supporting posts 16 is arranged to be raised and lowered by feed mechanism in the base 10. To this end, the platen 18- rests on a plate 80 carried by a feed screw 82 which extends downward through a reduction gear set 84 by containing a worm wheel (not shown) threaded onto and forming a runner on the feed screw 82 and driven by a worm on a cross shaft 86. The plate 80 is fixed to the feed screw 82 and is held against rotation by a pair of bolts 88 screwed into the platen 18 but sufliciently long to allow the plate 80 to retract away from the platen 18- with lost motion, in the event the head does not follow the lowering action of the feed screw 82.

As shown in FIG. 1, the feed screw plate 80 carries a switch-actuating cam 90 which, in the event of such lost motion retraction, will actuate a limit switch S-4 to interrupt downward feed. A limit switch S2 is mounted on the base in position to be actuated by the platen 18 to interrupt upward feed at a suitable limit point.

In the feed mechanism, as shown in FIG. 2, the right end of the input shaft 86 of the gear set 84 is connected through an electromagnetic brake 92 to a pulley 94 which is belt driven from a reversible motor 96. This provides for manual raising and lowering of the platen 18 and head 20.

The opposite or left end of the input shaft 86 is connected through an electromagnetic clutch 102 to a pinion gear 104 engaged by a rack 106 connected to be reciprocated by an air cylinder 108 shown in FIGS. 1 and 4. The air cylinder 108 is connected to a suitable source of air under pressure through a solenoid valve 110 operated by a solenoid 112. In the normal position of the solenoid valve 110, as shown in FIG. 4, it supplies air to the cylinder 108 to bias its piston to the left to hold the rack in the leftward position shown in FIGS. 1 and 4. When the solenoid 112 is actuated, it supplies air to the cylinder 108 to drive the piston and the rack 106 to the right against an adjustable stop 114.

In the leftward position of the rack 106, a switch actuator arm 116 on the rack moves a switch S-6 to an actuated position with its main contacts S-6a open and with its timer contacts S-6b closed. When the rack 106 moves to the right against the stop 114, a switch-actuating arm 118 engages a reversing switch 5-3 which has the effect of deenergizing the solenoid to cause the rack 106 to be driven to the left by the air cylinder 108.

Controls for the machine may be mounted in the housing of the base as shown in FIG. 1, and include manual UP and DOWN switches 120 and 122, a reset button 124, a manual Run/Stop switch 126, a Hand/Auto switch 128 for setting the machine for either hand or automatic operation, and a timer 132 to interrupt operation if the lapping process does not proceed at a suitable rate. A stroke-rate control potentiometer 156 for varying the speed of the head motor 56 is also included in the control grouping.

The electrical supply and control system may be as shown in FIG. 5. The platen feed motor 96 is connected to a three-

wire

2,20 v. supply line 140 through a reversing contactor 142 having UP and DOWN actuating coils 143 and 144. A transformer 146 supplies 110 v. current to a two-wire circuit having a grounded wire 150 and a live wire 152.

A controller-rectifier unit 154 connected to the circuit 150-152 provides power to the head motor 56, and a potentiometer 156 controls the motor speed. A control circuit 158 for the unit 154 stops the motor 56 when closed. Such control circuit contains the manual Run/ Stop switch 126; and contains contacts 128a of the Hand/Auto switch 128 in series with the normally open contacts S-Sa of the limit switch S-5 and with a parallel timer switch 134.

A converter 160 connected across the circuit 150-152 provides DC. current for the windings of the brake 92 and clutch 102.

The Hand/Auto switch 128 comprises the contacts 128a which close to render the limit switch contacts S-Sa and timer switch 134 effective for automatic operation; contacts 128b which bridge the interlock relay R-3 during hand operation; selector contacts 128a for the brake circuit, selector contacts 128d for the clutch 102 circuit, selector contacts 128:; for energizing the manual controls for the platen motor 96; and selector contacts 128 for energizing the automatic controls.

The manual UP switch comprises normally-closed contacts 120a in the brake circuit and normally-open contacts 120b to energize the UP coil 143 of the contactor 142. The DOWN switch 122 comprises normallyclosed contacts 122a in the brake circuit and normallyopen contacts 12211 to energize the DOWN coil 144 of the contactor 142. For hand operation, the brake 92 is normally energized to braking position, and the brake is released when either UP or DOWN button is pushed.

The automatic control system comprises a feed advance relay R-l having a coil and three normally-open contacts, a feed retraction relay R-2 having a coil and one normally-closed and one normally-open contact; and an interlock relay R-3 with a coil and two normally-open contacts.

The interlock relay R-3 is closed by the reset button switch 124. Relay contact R-3a, when closed, energizes the wire leading to the automatic down-feed controls and holds the relay closed; and its contact R-3b is in series with the manual DOWN coil 144 of the platen motor contactor 142; hence this relay must be closed for down feed of the head.

In automatic operation, when automatic feed switch S-l is closed, this energizes the coil of relay R-l, which closes a relay hold contact R-1a, and closes contact R-lb in the clutch 102 circuit and contact R-lc in the solenoid 112 circuit. This causes the rack 106 to move rightward and to drive the feed gear 84. At the end of the rack stroke, the arm 118 actuates switch S-3, which opens contacts S-3a in the R-1 holding circuit, to open relay R-1 and the clutch 102 and solenoid 112 circuits. Switch S-3 also closes contacts S-3b to energize the coil of relay R-2. This opens contacts R-2a in series with the feed relay R-1 to prevent its closure, and closes hold contacts R-2b to hold relay R-2 closed while the rack 106 retracts.

During the time the rack is away from its extreme leftward position, switch S-6 will have its contacts S-6a closed, to energize relay R-2, and will have its contacts S-6b open, to reset the timer 132 to zero. When the rack 106 returns to its leftward position it will reverse switch 5-6, to deenergize the relay R-2 and reclose the timer circuit.

Accordingly, for each closure of the feed switch S-1, the rack 106 will make one stroke to the right and return, to feed the head down by an increment fixed by the setting of the stop at the end of the rack stroke.

Also, for each such closure of switch $4, the timer 132 is reset to zero. If the machine fails to feed within the time for which the timer is set, the timer will close switch 134 and thereby stop the operation of the head motor 56.

Limit switch S-2 is in series with the UP coil 143 of the platen motor contactor 142 and will stop up-travel when it is opened. Limit switch S-4 has contacts respectively in series with the DOWN coil 144 of the platen motor contactor and with the solenoid 112, so that if switch 54 opens it will stop down feed of the feed screw 82 under either manual or automatic operation. Limit switch S-S has contacts in the control circuit for the head motor 56 and in the energizing circuit for the interlock relay R-3, so that its actuation will stop the head motor and open relay R-3 to de-energize the automatic feed mechanism and to open the manual DOWN feed control circuit, and hence will stop down travel under any circumstances.

The operation of the mechanism described above is as follows. The workpiece 66 having a cavity to be lapped is formed to approximate size and configuration by other metal-working operations, and it is mounted on the table 12 on blocks 68 by suitable hold-down clamps 70. A lap 64 suitable for lapping the cavity of the workpiece 66 is secured in the lap holder 62, and the workpeiece 66 is adjusted into axial alignment with the lap 64. Lapping compound is supplied to the lap in accordance with conventional practice.

The pressure in the cylinder 44 is set to provide a downward force on the yoke 38 and lap carrier 28 suitable to the size and character of the lap, that is, sufficient to produce lap-cutting downward movement but not so great as to jam the lap into the cavity and cause galling.

The position of the screw 72 is set to actuate the feed switch 8-1 at a desired point in the lap stroke range, and hence to arrest the downward cutting stroke of the lap at a selected length of stroke movement, and by this means to control the operating stroke length. For example, with a short lap working on a short cavity, the presssure used will be lighter and the stroke shorter than with a long lap in a longer cavity.

The adjustable stop rod 78 is set at a suitable height to terminate the lapping operation when it is completed; and the head is raised or lowered by manual actuation of the feed motor 96 to place the lap 64 in a proper starting position.

The desired feed increment is selected by adjustment of the stop 114 for the air-driven rack 106.

The lap-reciprocating motor is energized and adjusted by the stroke-rate control 156 to a suitable level. With all such adjustments made, the machine is switched from manual to automatic operation by means of the switch 128.

At first, until the lap begins its work, the lap strokes will be full strokes and on each stroke the feed control switch 8-1 will be closed by the stroke movement of the screw 72 carried with the yoke, and upon each such closing the incremental feed air cylinder 108 will be actuated one stroke, to feed the head downward by one increment, in the manner described above. When the lap begins work, the work resistance will prevent the lap from completing its downward strokes until the lapping has progressed, and when the lap is arrested above the intermediate point for which feed actuation is set by the screw 72, the lap reciprocation will continue without feed until the lap has cut its way deeper into the cavity so that it will again advance to the intermediate point at which the feed switch is actuated. An equilibrium condition is thus established during the lap working operation, in which feeding will occur in accordance with and in response to progress of the lapping operation into the workpiece cavity.

In this equilibrium state which obtains during the lapping operation, all significant conditions will be regulated in accordance with the settings of the several adjustments, and the working conditions of the lap will be under precise and selectively variable control, and any desired combination of conditions may be obtained within a wide range.

We claim as our invention:

1. An automatic lapping machine, comprising a base supporting a work table for mounting a workpiece,

a head above said table carried by post members guided for perpendicular sliding movement through the plane of the table,

a lap carrier mounted for reciprocation in said head perpendicular to said table, lap drive means for reciprocating the carrier through forward and return strokes of predetermined length,

means to limit the forward-stroke force on the carrier to less than sufficient to overcome a predetermined workpiece resistance whereby such resistance will arrest forward-stroke movement at an intermediate point,

feed mechanism below said table connected to said post members for raising and lowering said head with respect to said table,

feed drive means which in each actuation thereof drives said feed mechanism to lower said head a predetermined amount,

feed actuating means effecting an actuation of said feed drive means in response to each forward-stroke movement of said lap carrier beyond said intermediate point,

and means to adjust the intermediate point in the maximum stroke length at which said feed mechanism is actuated to advance the head, and thereby to vary the operating stroke length under load conditions. 2. An automatic lapping machine according to claim 1 in which said lap carrier is biased forward by yieldable biasing means exerting a limited forward thrust thereon, and

said lap-drive means comprises an eccentric rotor operative to drive the lap carrier through a return stroke against the thrust of said biasing means but inoperative to drive the carrier forward, the carrier being thrust forward by the biasing means, the eccentricity of the rotor determining the maximum stroke length of carrier reciprocation.

3. An automatic lapping machine according to claim 2, with the addition of means to regulate the force exerted by the biasing means on the carrier.

4. An automatic lapping machine according to claim 3 with the addition of means to vary the speed of the eccentric rotor thereby to vary the velocity and stroke-rate of the lap carrier.

5. An automatic lapping machine according to claim 3 with the addition of means to vary the predetermined amount by which each actuation of the feed drive means lowers the head.

6. An automatic lapping machine according to claim 1, in which said feed mechanism comprises a feed screw element and runner element, one of which is arranged as a lift element to lift said post members and the other of which is a driven element driven by said feed drive means.

7. An automatic lapping machine according to claim 6 in which said lift element lifts said post members through a lost-motion one-way drive connection, and means responsive to lost-motion movement of said connection for interrupting said feed drive means.

8. An automatic lapping machine according to claim 6, in which said feed drive means comprises a reciprocable member driven through drive strokes to drive said feed mechamsm,

and means to adjust the increment by which the feed mechanism is driven during each such drive stroke.

9. An automatic lapping machine according to claim 1, in which said feed drive means comprises a reciprocable member and an air pressure device for driving the same through a drive stroke for driving said feed mechanism,

means to actuate said air pressure device in response to movement of said lap carrier past said intermediate point,

and adjustable stop means to vary the length of the drive strokes of said reciprocable member and thereby to regulate the increment by which the feed mechanism is driven during each drive stroke.

10. An automatic lapping machine according to claim 9, which includes an air valve actuated in response to carrier movement past said intermediate point, to supply air to drive said air pressure device through a drive stroke,

and reversing means actuated by said reciprocal member to reverse said air valve for a return stroke of said air pressure device.

References Cited UNITED STATES PATENTS LESTER M. SWINGLE, Primary Examiner.

G. WEIDENFELD, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,385 ,008 May 28, 1968 Richard S. Gentry et a1.

It is certified-that error appears in the above identified patent and that 'seid Letters Patent are hereby corrected as' shown below:

Column 1, line 34, "3,151,992" should read 3,161,992

Signed and sealed this 18th day of November 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer