US3892092A

US3892092A - Automatic polishing apparatus

Info

Publication number: US3892092A
Application number: US471022A
Authority: US
Inventors: Jr Marvin W Keith
Original assignee: Buehler Ltd
Current assignee: Buehler Ltd
Priority date: 1974-05-17
Filing date: 1974-05-17
Publication date: 1975-07-01
Anticipated expiration: 1992-07-01
Also published as: JPS53156B2; FR2271561B1; FR2271561A1; JPS50160898A; GB1458476A

Abstract

An automatic polishing apparatus for polishing the surface of a specimen for purposes of microstructural analysis, the apparatus comprising first and second eccentric drive means driven at different speeds from a single drive motor and acting through one end of a drive arm which is movable both pivotally and axially and is connected at its other outer end with a specimen holder so as to move a specimen through a multidirectional path over a flat, horizontal polishing surface preferably comprising the base of a cup-shaped member containing abrasive slurry or the like. One of the eccentric drive means imparts a relatively high speed circular motion to an inner end of the drive arm, while the other drive means imparts a relatively low speed circular motion thereto, the composite of such motions being transmitted to the outer end of the drive arm which guides the specimen over the flat polishing surface. The invention also relates to an improved mechanism for automatically controlling the loading of the specimen against the polishing surface.

Description

United States Patent [191 Keith, Jr.

1451 July 1, 1975 AUTOMATIC POLISHING APPARATUS [75] Inventor: Marvin W. Keith, Jr., Evanston, Ill.

[73] Assignee: Buehler Ltd., Evanston, Ill.

[22] Filed: May 17, 1974 [21] Appl. No.: 471,022

Primary Examiner-Harold D. Whitehead Attorney, Agent, or Firm-Charles F. Pigott, Jr.

[57] ABSTRACT An automatic polishing apparatus for polishing the surface of a specimen for purposes of microstructural analysis, the apparatus comprising first and second eccentric drive means driven at different speeds from a single drive motor and acting through one end of a drive arm which is movable both pivotally and axially and is connected at its other outer end with a specimen holder so as to move a specimen through a multidirectional path over a flat, horizontal polishing surface preferably comprising the base of a cup-shaped member containing abrasive slurry or the like. One of the eccentric drive means imparts a relatively high speed circular motion to an inner end of the drive arm, while the other drive means imparts a relatively low speed circular motion thereto, the composite of such motions being transmitted to the outer end of the drive arm which guides the specimen over the flat polishing surface. The invention also relates to an improved mechanism for automatically controlling the loading of the specimen against the polishing surface.

15 Claims, 11 Drawing Figures i in JIIHLHM SHEET wmw III/I I III] II/ 1 AUTOMATIC POLISHING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to automatic polishing apparatus for the preparation of specimens for microstructural analysis such as used in the fields of metallurgy, petrography and mineralogy.

Polishing specimens for purposes of microstructural analysis is unlike polishing or grinding carried out in other unrelated fields, such as lens making. Unlike lens grinding where the lens is to be given a specific shape, polishing a specimen for microstructural analysis requires that the surface of the specimen be removed exposing the natural structure of the specimen but without imposing any distorting stresses on the surface. The polishing operation must remove material from the surface of the specimen in a random manner and from many directions so as not to cause any directional distortion of the natural structure.

An automatic polishing machine was developed recently for preparing specimens for microstructural analysis and it has proven capable of expediting the preparation of specimens by greatly reducing or eliminating the drudgery and the need for highly skilled labor. Such an automatic polishing machine is shown in the copending Kurt H. Roth, US. patent applications, Ser. No. 289,108, filed Sept. 14, I972, and Ser. No. 427,749, filed Dec. 26, 1973 and assigned to the assignee of the instant application.

The foregoing prior art polishing machine has a nonrotating drive arm with one end thereof adapted to move a specimen over a flat polishing surface which may comprise the base of a polishing cup. The drive arm is driven in the polishing motion by two drive means each having its own separate drive motor. One motor drives its associated drive means and one end of the drive arm in a low speed, large circumference, circular polishing motion. The second motor drives the other drive means and the end of the drive arm in a high speed, small circumference or localized circular polishing motion which is superimposed upon the larger circular polishing motion. In addition, such automatic polishing machine has a variable load mechanism operated by a third motor for decreasing the downward load on the drive arm, and consequently that of the specimen on the polishing surface, as polishing progresses.

While the foregoing known automatic polishing machine operates in a satisfactory manner in the preparation of specimens for purposes of microstructural analysis, it does have the disadvantage of requiring three separate motors, and such machine is expensive to build. Further, the machine is somewhat bulky and awkward in appearance.

BRIEF SUMMARY OF THE INVENTION The automatic polishing apparatus of the present invention overcomes the disadvantages of the prior art polishing machine discussed above. The automatic polishing apparatus of the present invention comprises a housing on which is mounted a stationary polishing cup containing a slurry for polishing a specimen for micro structural analysis, a drive arm non-rotatably supported on the housing and having an outer end portion adapted to engage the specimen and move the same over a flat polishing surface comprising the base of the polishing cup, first drive means for moving the end portion of said drive arm and the specimen in a low speed polishing path in said polishing cup, second drive means for moving said drive arm and the specimen in said polishing cup in a high speed polishing path superimposed on the low speed path, motor means for driving one of the first and second drive means which in turn drives the other drive means, and variable load means for imposing a downward load on the drive arm and the specimen during polishing. The load means may be operated in a constant load mode or in a varying load mode, and comprises means driven by one of the first and second drive means for decreasing the load on the specimen as polishing progresses.

Thus, the automatic polishing apparatus of the present invention requires only a single motor, instead of three separate motors. The single motor of the automatic polishing apparatus of the present invention drives both the first and second drive means for imparting motion to the specimen, and may also drive the load means in its load varying mode. The automatic polishing apparatus of the present invention, therefore, is more economical to manufacture, is more compact, and is easily attractively packaged.

Other advantages of the automatic polishing apparatus of the present invention will become apparent from the following description and accompanying figures of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a preferred embodiment of an improved automatic polishing apparatus of the present invention for the preparation of specimens for microstructural analysis;

FIG. 2 is an enlarged top plan view showing the apparatus with the housing removed;

FIG. 3 is a fragmentary view, similar to FIG. 2, showing the apparatus in another position;

FIG. 4 is a cross-sectional view taken substantially along the line 4-4 of FIG. 2.

FIG. 5 is a cross-sectional view taken substantially along the line 5-5 of FIG. 4;

FIG. 6 is a cross-sectional view taken substantially along the line 6-6 of FIG. 4;

FIG. 7 is a fragmentary cross-sectional view taken substantially along the line 7-7 of FIG. 6;

FIG. 8 is a cross-sectional view similar to FIG. 4 showing the apparatus in another operating position;

FIG. 9 is a cross-sectional view taken substantially long the line 9-9 of FIG. 8;

FIG. 10 is a fragmentary cross-sectional view taken substantially along the line l0 10 of FIG. 8-, and

FIG. 11 is a fragmentary cross-sectional view taken substantially along the line 11-11 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a preferred embodiment of automatic polishing apparatus 12 of the present invention for the preparation of specimens for microstructural analysis such as used in the fields of metallurgy, mineralogy and petrography. The apparatus I2 includes a housing 13 having two L-shaped side walls 14, a front wall 16, a stepped top wall having a lower portion 18, a vertical portion 20 and an upper portion 22, a bottom wall 24 and a rear wall 26 (FIG. 2). Certain of the walls are secured together or integral with each other and form two separable housing halves, as is conventional.

A generally cup-shaped polishing cup 28 is mounted on the lower horizontal portion 18 of the housing top wall. The cup 28 has a cylindrical side wall and a flat, horizontal base. The lower portion 18 of the top wall and the base of the cup 28 have cooperating recessed and extended

portions

30 and 32, respectively, of noncircular shape, to hold the cup stationary on the hous- The interior of the cup 28 is adapted to receive a glass platen 34, on the upper surface of which an abrasive or polishing disc 36 may be secured, as by adhesive. The cup 28 has a small rib 37 (P16. 2) which projects into a notch 39 in the periphery of the platen 34 to prevent rotation of the latter in the cup. The interior of the cup 28 may be partially filled with an abrasive or polishing slurry, and for this reason it is preferable to have the bottom of the cup horizontal to prevent spilling of the slurry and to evenly distribute the same over the abrasive disc 36.

As further shown in FIG. 1, a conventional specimen mount 38 is positioned in the cup 28 and has a specimen to be polished mounted in the bottom face thereof adjacent the polishing disc 36. The specimen mount 38, including the specimen, is moved about the polishing cup 28 in a polishing motion by a drive arm 40 which extends through an opening 41 in the vertical housing portion 20. The upper surface of the specimen mount 38 has an opening for receiving a pointed arm 42 which depends from the outer end of the drive arm 40. As shown in dotted lines in FIG. 4, the drive arm 40 may be elevated to facilitate positioning of the specimen mount 38 in the cup 28, the arm then being lowered so the pointed arm 42 engages in the opening in the specimen mount.

Refering now to FIG. 2, the drive arm 40 extends rearwardly into the housing 13 and has a mediate portion on which is mounted a vertically extending cylindrical bushing 44. The bushing 44 has a horizontal opening 46 for receiving the arm 40 and is secured thereto by a set screw 48. The bushing 44 is disposed between a pair of vertical bearing walls 50 provided by a generally U-shaped guide member 52 which guides the drive arm for axial sliding and pivotal movement in the housing 13. The drive arm 40, bushing 44 and guide or saddle 52 permit the drive arm to pivot horizontally and also slide axially due to movement of the bushing between the guide walls 50 during a polishing operation, and the height of the saddle 52 permits upward pivoting movement of the arm 40 during insertion and removal of a specimen as previously described. The guide saddle 52 is mounted by nuts and bolts 53 which secure the lower end of the saddle to an intermediate frame member 54 of the housing 13. The frame member 54 extends between and is secured to the vertical portion of the front wall and the rear wall 26 of the housing and also extends laterally between the two side walls 14 of the housing.

An inner end 56 of the drive arm 40 is indirectly connected to and driven by first drive means 58 which thereby moves the outer end of the drive arm in a first, low speed, non-rotating, polishing motion which is preferably circular. FIG. 4, first drive means 58 comprises a first rotatable member or drive plate 60 driven by a motor 64. The motor 64 is mounted beneath the frame member 54 which has a large opening 65 therein through which extends a motor shaft 62. The drive plate 60 is secured to the motor shaft 62, as by the pin 66, so as to be rotated by the motor 64. The inner end 56 of the drive arm 40 is connected to the drive plate by means of a yoke 70, a bushing 80, and a second rotatable member or pulley 88 which is eccentrically mounted on the drive plate.

The inner end 56 of the drive arm 40 carries the yoke which a set screw 72 holds in place. The yoke 70 has a pair of arms 74 with downward opening notches 76 therein which receive a pair of pins 78 extending later ally from the bushing 80 so as to permit the drive arm 40 to pivot upwardly as previously described. The bushing 80 has an upper flange 82 to prevent inadvertent disengagement of the yoke 70 from the pins 78, and further has a pressed in needle bearing in its center which receives the upper end of a pin 84 carried on the pulley 88. A set screw 86 is provided in the bushing 80 for engaging the upper end of the pin 84 to provide a hard thrust surface and a wear adjustment should that be necessary.

The pin 84 is eccentrically mounted on the pulley 88 as shown in FIG. 2, and the pulley 88 is rotatably journalled on a shaft 90 by means of a needle bearing 92 and is held thereon by a snap ring 94. A thrust bearing 96 is located between the drive plate 60 and pulley 88. The shaft 90 is located off center of the first rotatable member 60, or eccentric of the shaft 62, as shown in FIG. 4.

As was mentioned above, the drive arm 40 is also driven by second drive means 100 in a second, high speed, polishing motion. This second polishing motion is also preferably circular.

Second drive means 100 is driven by the first drive means or drive plate 60 so that the same motor 64 also powers the second drive means 100, as will now be described. Second drive means 100 includes the pulley 88 previously mentioned, a third rotatable member or pulley 102, and a stationary member 104.

The second pulley 102 is rotatably mounted on an extended end 106 of the drive plate 60, the opposite end of the plate 60 also being extended to provide a counterbalance. The pulley 102 has a shaft 108 with an enlarged upper end secured, as by press fit, in a center opening of the pulley. The lower end of the shaft 108 extends downward through a pair of ball bearings 110 secured as by press fit in the drive plate 60 to rotatably mount the shaft. The shaft 108 is axially located in the inner races of the bearings 110 by a shoulder 112 on the upper portion of the shaft and a snap ring 114 secured to an intermediate portion of the shaft.

The lower end of the shaft 108 has a pinion 116 secured thereto which meshes with teeth formed around the circumference of the stationary gear member 104 to cause the pulley 102 to rotate. The stationary gear 104 has a large center opening 118 through which the shaft 62 and center hub of drive plate 60 extend, the stationary gear member being positioned below but concentric with the drive plate 60. The gear 104 is secured to the frame member 54 by a plurality of screw fasteners 120 which extend through the gear 104 and through a plurality of spacers or sleeves 122.

The diameter of the pinion 116 is much smaller than that of the stationary gear 104 so that the pinion makes about six to seven revolutions each time it is carried around the gear 104 by the drive plate 60. Thus, as the pinion 116 is moved about the stationary gear 104 by rotation of the drive plate 60, the pulley 102 also rotates six to seven times on its own center and it in turn rotates the eccentric pulley 88 by an endless belt 124. Preferably, the upper portions of the

pulleys

88 and 102 have semi-circular grooves, 126 and 128, respectively therein, and these grooves receive a circular cross-section elastic or rubber-type belt 124. Thus, rotation of the first drive means 58 also causes rotation of the second drive means 100, including the second and third rotatable members or pulleys 88 and 102 to drive the drive arm 40 and the specimen in a second, high speed, polishing motion.

The polishing motion of the specimen drive arm 40 driven by first drive means 58 and second drive means 100 is shown in FIGS. 2 and 3. As the motor 64 rotates drive plate 60, the inner end 56 of the drive arm 40 moves in a large circular path. The bushing 44 on the arm reciprocates in the guide saddle 52, and the outer end 42 of the drive arm 40 also moves in a similar circular-type path, this being the motion generated by first drive means 58. To this motion is added the motion of second drive means 100 generated by the rotation of the eccentric pulley 88 to which the drive arm 40 is attached. As the drive plate 60 rotates, it causes the pulley 102 and in turn the pulley 88 to rotate about six or seven times. Thus, the inner end 56 of the drive arm moves in a plurality of circles which are superimposed on the circular path of travel effected by first drive means 58. The outer end 42 of the specimen drive arm moves in a similar path, as depicted by the dotted arrow 129 in FIG. 3. Thus, the specimen is polished in a nondirectional manner so that the natural structure of the specimen is not distorted.

Load means 130 is provided to force or bias the specimen being polished in the mount 38 toward the abrasive disc 36 and slurry in the bottom of the cup 28. Load means 130 is operable either in a constant load mode, or in a varying or decreasing load mode wherein the load imposed on the specimen decreases as polishing progresses. Load means 130 comprises spring means 132, load adjusting means 134 for regulating the magnitude of the load imposed by spring 132, and actuating means 136 for decreasing the imposed load as polishing progresses.

Spring means 132 is in the form of a tension-type coil spring having its upper end hooked to a pin 138 on the bushing 44 and its lower end 140 secured to a load arm 142. The load arm 142 has one end pivotally mounted to the housing by a pin 143 mounted on brackets 145. The other end 144 of the arm 142 is adapted to engage and be held in a given pivotal position by load adjusting means 134. The placement of the upper and lower ends of the spring 132 is such that there is little or no change in the force exerted by the spring as the specimen drive arm 40 moves.

Load adjusting means 134 comprises cam means 146 selectively positionable in various rotational positions to impart various displacements to the arm 142 and consequently vary the loading of the spring 132. Cam means 146 is mounted on a rod 150 and secured thereto by a pin 152. The cam 146 (see FIG. 9) has a flat portion 153 and a varying radius portion having the largest radius 157 adjacent one end of the flat portion 153 and then decreasing to the smallest radius 159 adjacent the other end of the flat portion.

The rod 150 is rotatably and slidably mounted in the housing 13 so that cam 146 may be engaged or disengaged with the end 144 of the lever 142. At its outer end the rod 150 is rotatably and slidably mounted in a nylon bushing 154 provided in an opening in the front wall 16 of the housing, the outermost end of the rod having a selector knob 156 secured thereto. The inner end of the rod is rotatably and slidably mounted in a bushing 158 located in an opening provided in an upper portion 160 of a support 162 secured to the housing bottom wall 24.

Stop means is provided for holding the cam 146 and the rod 150 in the selected position. The stop means comprises a disc member 164 secured to the rod 150 and cooperating with

projections

166, 168 and 169 provided on the base of the support 162. The disc 164, as best shown in FIG. 5, has a roughened peripheral portion 170, and is secured to rotate with the shaft 150, as by a pin 172. A notch or opening 171 is provided in the circumference of the disc 164 so that, when desired, the disc may move axially

past projections

168 and 169. In addition, the disc 164 has a radially extending dog 173 which can engage stop

surfaces

175 and 177 provided on the support 162 for preventing the cam 146 and knob 156 from making a complete revolution. The disc 164 is biased into engagement with the

projections

166, 168 or 169 by a compression spring 174 located on the rod 150 between the disc I64 and the upper portion 160 of the support 162.

Load means 130 and cam means 134 are shown in an off" or disengaged position in FIGS. 4 and 5. In this position, the rod and knob 156 extend as far outward or to the right as shown in FIG. 4 as possible so that the projection 168 is in the notch 171 of the disc 164 to hold the cam 146, rod 150, and knob 156 in a fixed rotative position in which the cam 146 does not engage the end 144 of the lever 142 and thus no load is imposed on the specimen drive arm 40 by the spring 132. The lever is thus free to pivot upwardly (dotted lines in FIG. 4) to permit a specimen mount 38 to be installed on or removed from the drive arm 40.

Load means 130 may be operated in a constant load mode, as is shown in FIGS. 6 and 7. In this mode, the knob 156 is pushed inward against the spring 174, to the left in FIG. 6 to an intermediate position where the disc 164 clears the projection 168. In this intermediate position, the flat portion 153 of the cam 146 is directly above but does not touch the end 144 of the lever 142. Then, the knob 156 may be rotated clockwise to engage the desired portion of the cam 146 with the end 144 of the lever 142 to place the desired load on the drive arm 40. Upon release of the knob 156, the spring 174 forces the roughened surface 170 of the disc 164 into position against the rear edge of the projection 168 to hold the cam 146 in the desired position until changed by manually resetting the knob 156.

Load means 130 may be also operated in a varying or decreasing load mode, as shown in FIGS. 9 through 11. Load means 130 includes actuating means 136 for decreasing the load on the specimen as polishing progresses. Actuating means 136 comprises a one-way clutch 182 which drives the rod 150 and cam 146 in a clockwise direction when viewed as shown in FIG. 9. The outer portion of the clutch 182 has an integral arm 184 extending upwardly therefrom with its upper end disposed between a pair of

vertical stop plates

186 and 188 secured to the housing 13. The one-way clutch 182 and arm 184 is biased toward the stop 186 by a wire spring 190 secured to the clutch 182 by a screw and clamp 191.

An actuating lever 183 is pivotally mounted on a vertical stud 192 secured to the frame member 54. The lever 183 has one end 194 for engaging the upper end of the arm 184, and the other end 196 of the lever 183 is engageable by an eccentric pin 198 which depends from the hub portion of the drive plate 60. Thus, each time the drive plate 60 rotates, the pin 198 moves or kicks the lever 183 clockwise as shown in dotted lines in FIG. 6. The end 194 of the lever thereby kicks or moves the arm 184 clockwise as shown in FIG. 10 to rotate the cam 146 to a decreasing load position.

Load means 130 may be placed in the decreasing load mode by pushing the knob 156 inward as far as possible so that the notch 17] in the disc 164 passes over the projection 169. The knob 156 is then rotated clockwise, as viewed from the front, to the desired initial load position. When the knob 156 is released, the spring 174 forces the disc 164 against the rear vertical edge of the projection 169 to hold the cam 146 in position until the drive plate 60 completes a revolution. With each revolution of the drive plate 60, the lever 183 kicks the one-way clutch 182 in the load reducing direction and the clutch in turn rotates the cam 146 in that direction. Thus, the load is gradually reduced for each revolution of drive plate 60 as polishing progresses. After a period of time, the notch 171 moves into alignment with projection 169, and the spring 174 returns the disc 164 forward to the off" position so that the end 194 of the lever 183 can no longer contact the end of the arm 184 and the cam 146 can no longer contact the lever 142. Thus, the load means can be operated in a decreasing load mode and in that mode is driven by one of the driven means for the specimen drive arm 40 instead of a separate motor.

Operation of the automatic polishing apparatus 12 of the present invention is as follows. The specimen is mounted in the mount 38, and the cup 28 is fitted with an appropriate abrasive disc 36 and filled with slurry. The specimen drive arm 40 is raised, and the specimen mount 38 is positioned in the cup 28 with the depending end 42 of the arm 40 engaged therein. .The knob 156 is positioned for a constant load or decreasing load mode and rotated to get the proper load. The motor speed is selected or set on the dial 200, the speed of the motor 64 being controlled by speed control devices operated by the dial 200. The polishing time is selected or set on a dial 202, the operation of the motor 64 being controlled by conventional timer devices operated by the dial 202. If not on," the power switch 204 is placed in the on position, and the start button 206 is pressed to start the polishing. The specimen mount 38 is moved in the low speed first polishing motion with the second high speed motion superimposed on the first motion. After the selected time has elapsed and the ap paratus stops, the specimen mount 38 may be removed from under the arm 40. Further, if desired, the cup 28 can also be removed from the apparatus so that a different cup having a proper abrasive disc and slurry for preparation of a different specimen may be substituted.

It will be understood from the foregoing that the apparatus of the present invention acts through the specimen drive arm 40 to impart to a specimen a motion which is a composite of a motion which is circular with respect to a center (the axis of pulley 88) which center is a moving point on a second circle having a fixed center (the axis of drive plate 60). The velocity of the'motion of the moving point (the axis of pulley 88) on the circle having a fixed center is relatively slow, while the velocity of the motion about the center or axis of the pulley 88 is relatively high. In other words, the pulley 88 rotates several times about its own axis during each revolution of that axis about the axis of rotation of the drive plate 60.

In the apparatus described herein there are two eccentric drive means. The axis of the pulley 88 which is carried on the drive plate 60 is eccentric with respect to the axis of rotation of the drive plate 60, and the axis of the drive pin 84 carried by the pulley 88 is eccentric with respect to the axis of the pulley 88. In the particular embodiment illustrated, the two eccentricities are approximately although not precisely equal in magnitude. However, these values may be varied as desired in order to vary the composite motion or path of travel imparted to the specimen.

It will further be noted that in the embodiment described herein the vertically oriented cylindrial bearing or bushing 44 on the specimen drive arm 40 is located mid-way between the ends of the drive arm with the result that the movement imparted to the specimen by the depending pointed end 42 of the drive arm is a mirror image of and equal in magnitude to the motion imparted to the inner end of the drive arm bythe drive pin 84. The bearing 44 may be located other than at the midpoint of the drive arm 40, in which case the composite motion imparted to the specimen will be the mirror image of the motion of the drive pin 84 but the amplitude or magnitude of the motion of the specimen will not be equal in magnitude to the motion of the drive pin 84 with respect to the component of motion which is transmitted through pivotal movement of the drive arm 40, i.e., motion perpendicular to the guide plates 50.

Relative to the above subject of transmitting motion from one end of the drive arm 40 to the other end thereof, and particularly motion perpendicular to the guide plates which cause pivoting of the drive arm 40, it will further be noted that in accordance with the preferred embodiment of the present invention the vertical pivot axis of the drive arm 40 does not shift along the length of the drive arm during operation of the machine for the reason that the cylindrical bearing 44 does not move relative to the drive arm but rather moves with the drive arm. Consequently, a motion component of the drive pin 84 perpendicular to the guide plates 50 will be transmitted to the specimen without a change in its magnitude regardless of the position of the drive arm.

lf the bearing 44 is located other than at the midpoint of the specimen drive arm 40, there will be a change in the foregoing magnitude, but whatever the degree of change in such magnitude of movement of the two ends of the drive arm 40, the relationship will nevertheless remain constant in all positions of the drive arm. On the other hand, if the drive arm is slidable between a pair of bearings or the like and does not have its own bearing fixed thereon, the pivot axis of the drive arm will continually move along the length thereof and thus continually change the relationship between the magnitude of movement of the drive pin 84 and the magnitude of movement of the specimen.

I claim:

1. In an automatic polishing apparatus of the type for polishing specimens for purposes of microstructural analysis including a housing and a generally cup-shaped member mounted on the housing and having a flat base or polishing surface on which abrasive slurry or the like is dispersed and over which a specimen is moved during a polishing operation, the improvement comprising, in combination, a specimen drive arm supported on said housing for composite axial and pivotal movement and having an outer end engageable with a specimen for moving the same over said polishing surface, first drive means mounted in said housing for rotation about a fixed axis, a drive motor connected to said first drive means for rotating the same, second drive means rotatably mounted eccentrically on said first drive means, means interconnecting said first and second drive means causing said first drive means to rotate said second drive means relative to said first drive means, means connecting an inner end of said specimen drive arm to an eccentric portion of said second drive means, and guide means associated with said drive arm intermediate the ends thereof whereby a composite motion is imparted to said inner end of said drive arm and a related composite motion is imparted to said outer end of said drive arm and a specimen engaged therewith.

2. Apparatus as defined in claim 1 where said first drive means is rotated by said drive motor at a relatively low speed and said second drive means is rotated by said first drive means at a relatively high speed.

3. Apparatus as defined in claim 1 where the eccentricity of said inner end of said drive arm relative to the axis of said second drive means is approximately equal to the eccentricity of said axis of said second drive means relative to the axis of said first drive means.

4. Apparatus as defined in claim 1 where said means interconnecting said first and second drive means includes third drive means rotatably mounted on said first drive means and connected with said second drive means for rotating the latter.

5. Apparatus as defined in claim 4 including discshaped stationary drive means which imparts rotation to said third rotatable member upon rotation of said first drive means by said drive motor.

6. Apparatus as defined in claim 5 including pinion means mounted on a common shaft with said third rotatable member and engageable with the circular periphery of said stationary drive member, said pinion being circumferentially movable around said stationary drive member in engagement therewith during rotation of said first drive means.

7. Apparatus as defined in claim 4 where said second and third drive means comprise pulleys interconnected by an endless belt.

8. Apparatus as defined in claim 1 where said specimen drive arm comprises an elongated rod having a depending portion at its outer end which extends into said cup-shaped member and is engageable with a specimen disposed on said polishing surface.

9. Apparatus as defined in claim 8 where said guide means comprises a vertically oriented cylindrical bearing fixedly mounted on said drive arm, and a pair of parallel spaced apart elongated guide walls, said bearing being slidable between said guide walls and being rotatable to accommodate sliding and pivotal movement of said drive arm.

10. Apparatus as defined in claim 1 where said means connecting an inner end of said drive arm to an eccentric portion of said second drive means comprises yoke means which permits said outer end of said drive arm to be raised and lowered during insertion of a specimen in said cup-shaped member and removal of a specimen therefrom.

11. Apparatus as defined in claim 1 including load means which applies a downward load on said specimen urging the same against said polishing surface.

12. Apparatus as defined in claim 11 including loadreducing means for substantially continuously reducing the downward load applied by said load means during a polishing operation, said load-reducing means being actuated by one of said drive means.

13. Apparatus as defined in claim 12 where said load means includes tension spring means one end of which is connected with said drive arm and the other end of which is movable by said load-reducing means to vary the load imposed on said drive arm by said spring means.

14. Apparatus as defined in claim 13 including means carried by said first drive means for actuating said loadreducing means.

15. Apparatus as defined in claim 14 where said loadreducing means comprises rotatable cam means controlling the position of the lower end of said spring means thereby controlling the amount of load imposed on said drive arm and specimen, lever means connected with said cam means through one-way clutch means to rotate said cam means in a load-reducing direction, and means carried eccentrically on said first drive means for actuating said lever means at least once during each rotation of said drive means.

* k i i

Claims

5. Apparatus as defined in claim 4 including disc-shaped stationary drive means which imparts rotation to said third rotatable member upon rotation of said first drive means by said drive motor.

12. Apparatus as defined in claim 11 including load-reducing means for substantially continuously reducing the downward load applied by said load means during a polishing operation, said load-reducing means being actuated by one of said drive means.

14. Apparatus as defined in claim 13 including means carried by said first drive means for actuating said load-reducing means.

15. Apparatus as defined in claim 14 where said load-reducing means comprises rotatable cam means controlling the position of the lower end of said spring means thereby controlling the amount of load imposed on said drive arm and specimen, lever means connected with said cam means through one-way clutch means to rotate said cam means in a load-reducing direction, and means carried eccentrically on said first drive means for actuating said lever means at least once during each rotation of said drive means.