US 3156073 A
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Description (OCR text may contain errors)
Nov. 10, 1964 R. H. STRASBAUGH 3,156,073
IRREGULAR, NON-REPETITIVE, CLOSED-LOOP SURFACING MECHANISM Filed Jan. 15, 1963 3 Sheets-Sheet 1 IQ/4y H snaasewuew,
BY W X ATTY.
Nov. 10, 1964 R. H. STRASBAUGH 3,156,073
IRREGULAR, NON-REPETITIVE, CLOSED-LOOP SURFACING MECHANISM Filed Jan. 15, 1963 3 Sheets-Sheet 2 J94 .11, Srnnsanum; h INVENTOR. BY W05 44M R A T T Y.
Nov. 10, 1964 R. H. STRASBAUGH 3 Sheets-Sheet 5 ATTY.
United States Patent 3,156,073 IRREGULAR, NGN-REPETITIVE, CLQSED-LOO? SURFACING MECHANISM Ray H. Strashaugh, Downey, (Jalif. (10990 S. Santa Fe Ave., Lynwood, Calif.) Filed Jan. 15, 1963, Ser. No. 251,534 '10 Claims. (Cl. 51-57) This invention relates to a double-eccentric drive mechanism, particularly exemplified by an optical grinding or surfacing machine which is especially adapted for buffing or minutely smoothing various workpieces, whether of glass, metal or other material. It is usually employed in conjunction with an abrasive slurry or dressing composition. The mechanism moves a surfacing tool or polishing element over the workpiece in an endless path based on an oscillating or reciprocal movement. In addition, the workpiece may be simultaneously rotated, moreor-less axially to the polishing element. The workpiece and correspondingly shaped surfacing element may be either flat or curved, and when the curvature of the two do not normally conform, the surfacing element may be bendably resilient.
The illustrated type of construction embodies a (horizontally) oscillating, lever arm wherein the path followed by the laterally reciprocating (polishing) end is determined by eccentric connection of the arm to each of two (vertical, generally parallel) rotary shafts, having their rotation jointly determining the path followed by the polishing end of the arm; alternately each eccentric connection can be shifted to axial connection on its respective shaft. The two eccentric connections are spaced longitudinally along the oscillating arm from one end, so that the opposite (free) end thus magnifies the movement or pattern produced; essentially the arm is a Class 1 lever with a moving fulcrum (when both connections are eccentric).
Such an arrangement is shown, for example, in US. Patent 1,422,505. If either of the two pivot connections of the oscillating arm is axially located, the eccentric drive from the other rotary shaft produces a repetitive arcuate oscillation of the stylus. If both connections are shifted to eccentric positions on the shafts, the stylus follows a figure 8 pattern. However with either setting the resulting path followed by the stylus does not vary, and this may be undesirable.
An invariable pattern followed by the stylus or polishing head may result in spot polishing in that the result is unduly concentrated at one limited area. Or if a grain of abrasive becomes embedded on the surface of either the tool or workpiece, the repetitive movement of the head may cause the adhered particle to channel the opposing surface. To a certain extent the undesirable result may be minimized (or spread) by simultaneously moving the work iece, but still this does not completely eliminate the problem. 7
Now by the present invention, the pair of rotary shafts which are eccentrically connected to the oscillating arm,
' are rotated at different speeds (either independently or interconnected). This results in the stylus following an irregular and continually varying path, with each com plete oscillation still essentially describing a (nearly) closed loop which is a modification of the basic figure 8. Such result can be readily obtained, for example, by having one of the shafts drive the other by means of a spocket drive wherein one sprockel wheel has one more tooth than the other. The difference in number of teeth can of course be greater than one; but for the present purpose, it is essential that the two numbers be dissimilar.
However, by'shifting the connections of either rotary shaft to axial (from eccentric), the oscillating arm can 3,156,073 Patented Nov. 10, 1964 still be used to describe the prior, repetitive arcuate path, if desired, regardless of the different speeds of rotation (because it doesnt matter whether one axially pivoted shaft is rotated or not). But the conventional figure 8 pattern will be followed by the stylus, when the oscillating arm has a double eccentric drive, only when both drive shafts are rotated at the same speed. However, varying the amount of radial displacement of either eccentric connection will correspondingly modify the shape of the figure 8 without altering its repetitive and entirely closed pattern.
In addition, now the oscillating arm is segmented intermediate its respective connections to the pair of rotary shafts and the segments are adjustably connected end-t0- end for variable angular alignment between straight and bent positions in either direction. This changes the pattern produced by shifting its center relative to the rotational workpiece; and by suitable indexing means associated with the segmented arm, any such pattern can be returned to as desired. Likewise, shifting the workpiece relative to the rotational center of the workholder will alter the pattern.
Other objects and advantages will become apparent as the description proceeds, having reference to the presently preferred embodiment illustrated in the accompanying drawings wherein FEGURE 1 is a perspective view of a portion of a cabinet which supports several of my polishing units;
FIGURE 2 is a top plan view of a single unit as mounted on the cabinet;
FIGURE 3 is a schematic representation showing successive positions of the stylus, pair of eccentric drives, and the bend point of the segmented arm during one cycle;
FIGURE 4 is a vertical sectional view through a mounted unit with portions shown in elevation;
FIGURE 5 is a transverse section through the pair of rotary shafts as seen along the line 5-5 of FIGURE 4, with the sprocket wheels seen in top plan; and
FIGURES 6 through 10 are actual patterns produced by the unit upon placing a pen in the position of the stylus. They thus represent the path followed by the center of the polishing element as it is oscillated over a workpiece by the double-eccentric, dissimilar-speed dual drive. The longitudinal alignment of the segmented oscillating arm remained the same, but one, or both eccentric positions were changed from one pattern to. another. In FIGURE 10 the workpiece was simultaneously rotated at a constant speed; the other patterns were produced on a stationary workpiece.
One or more of the present polishing units may be mounted in a floor-supported frame or housing cabinet C which provides for each unit an annular pan P and centered workholder H at workbench level B. The laterallyoscillating arm A is supported atop a higher ledge or shelf L of the cabinet, with its forwardly overhanging extremity vertically holding an axially adjustable stylus Q. The lower end of the quill or stylus Q is received (like a ball and socket) in an upward-opening socket 12 (FIG. 4) of an abrasive or polishing element E which thus gravitationally (and with added weight if desired) bears upon the upper face of a workpiece W. The workpiece may be temporarily anchored to the holder H as by wax, (either centered or elf-center as the case may be), and the holder may be rotated from beneath by the dependent shaft 14, by manual or mechanical means (not shown). Y
The purpose of the pan P is to accumulate scrapings and dressing fluid spun off from the face of the Workpiece W by the moving element E. It will be understood thatif the (final) surface configuration of the workpiece is dished upward or curved downward (e.g.'
a cylindrical lens), either a resiliently flexible or else a correspondingly shaped polishing element E is employed. For a flat or level workpiece W, a flat polishing element E is used. The present irregular, non-repetitive, closedloop pattern here produced is most useful in precisiongrinding or polishing fiat surfaces or workpieces, that is, with a flat polishing element E, or alternately for surfacing spherical workpieces with a spherical polishing element.
Vertically traversing the horizontal shelf L, are a spindle S and a rotary drive shaft D, generally parallel to each other. A continuous power source, such as an electric motor M, by a transmission belt B, operates a gear reduction unit R, which in turn rotates the drive shaft D. Keyed to the lower end of the drive shaft D is a sprocket wheel SR which by a general y horizontal chain drive X, rotates the aligned sprocket wheel SP of the spindle S. As here illustrated, the drive sprocket SR has one less tooth than the driven sprocket SP; hence the two continuously rotate at different speeds.
The main length of the spindle S is retained in a tubular housing 16 journalled by upper 18 and lower 20 ball bearing raceways. The housing tube 16 is inserted through an annular aperture 21 of the cabinet C until an upper flange 22 of the housing, frictionally overlies the forward margin of the ledge L, being secured thereto by upright bolts 24, 25 which also traverse the ledge L and the dependent bracket hangers 26, 27. Above the ledge L, the spindle disposes a peripherally flared, annular cap 23 which is formed with an upward-opening, inverted-T- shaped radial slot extending outward from the center. An upright stem 32, having a bottom flange 33 is slidable along the slot 30 and is surrounded proximately by a bottom-flanged sleeve 34 and outwardly by a pair of ball bearing raceways 35, 36 vertically separated by an annular spacer 37. The raceways are received within the apertured end of a generally flat or horizontally disposed segment 38 of the oscillating arm A. A washer 4i frictionally overlies the inner ring of the bearing assembly and is tightened thereagainst by the nut 42 which is threadedly mounted on the stem 32 so as to anchor the latter at the selected eccentric or axial positions relative to the spindle S. The lower portion of the stem is transversely tapped to receive a headed screw 31, the inner end of which bears against the terminal wall of slot 30.
A disk 44 is formed with a top-opening, inverted-T- shaped, radial groove 45 and with a centrally dependent, tubular boss 46 (FIG. 4) having a rectangular, bottomopening socket 47 in which the upper, square-end of drive shaft D is inserted and secured as by a screw 48. A longitudinal rod 50, having a horizontally disposed eyelet or ring 52, 54 at each end, forms the other segmented portion of arm A, being pivotally connected to the adjacent segment 38 by a pintle 56. For assembly, the rod 50 has its central cylindrical shaft threaded partway inward from each end (right and left threads respectively), and these extremities are screwed into each ring portion; thus the elfective length of the arm can be adjustably lengthened or shortened simply by rotating the central shaft in one direction or the other.
An niverted-T-shaped stem 58 has its bottom annular, flat head 59 slidingly received in the slot 45 with its central shaft projecting upward through eyelet 54 and threadedly engaged terminally by a cap 60. A spacing washer 61 between the disk 44 and the segment 5i] serves to keep the latter horizontal or at least spaced above the top of the disk 44. The other eyelet 52 is loosely traversed by a pintle 56 which is inserted then through the end of segment arm 38 and terminally secured by an internally threaded knob 64. The two eyelets 52, 54 thus have limited (reciprocal) rotation about the vertical axles ss, 58 as the latter is revolved by the rotating disk 44. Since the disk 44 is rotated at a different speed (as determined by the two sprocket wheels SP, SR) than the spindle S, the two eccentric stems 32, 58 will rotate at diiferent rates even when located the same distance otfcenter from their drive shafts. Hence the path of each successive closedloop described by the stylus will be diiferent and nonrepetitive. Also each orbit will diifer suificiently from a true ellipse as to be termed irregular.
The arm segment 38 (FIG. 2) is a casting with generally flat top and bottom, and formed with an arcuate slot 56 through which the pintle 56 is inserted, the pintle being movable laterally therealong and fastened by tightening the knob 64 against the arm 38. An index scale 63 along one edge of the slot 66 allows quick resetting of the unit to any previous position for repetition as desired. From a medially constricted waist 70, the casting 38 widens forwardly to present a transversely aligned pair of trunnions 71, 72 between which is journalled a generally triangular, overhanging head 74. The head 74 can thus swing in a generally vertical plane toward and away from the workpiece W approximately a quarter turn between a horizontal, overhanging, operative position wherein a set screw 76 (FIG. 4) adjustably traversing a dependent lug '78 abuts the vertical wall 39, and an upswung position wherein the set screw 30 in the upper lug 82 rests upon the upper face of t e casting 38.
The forward converging end of the head 74 is formed with a horizontally dependent, tubular housing 84 through which is inserted a cylindrical extension rod 86 anchored at any desired adjustment length by a tightening screw 88. Forwardly, a terminal mounting collar 90, with a tightening screw 92, disposes the inserted stylus Q in the desired upright or slanted position as determined by the rotational position of the rod 86 in the housing 84. For example, it may be desired to change the disposition of the stylus Q between upright and (varied) angular positions from time to time without moving the workpiece W or adjusting other variables.
Thus it will be apparent that an infinite variety of stylus patterns are possible (1) by changing the amount of offcenter displacement of the oscillating arm A from its axial connection to either the spindle S or the shaft D, (2) altering the diiference in dissimilarity of rotational speed of the two shafts S and D, and (3) simultaneously rotating the workholder H at different positions of displacement of the center of the workpiece W from the center of the stylus pattern. This last alteration (3) can be effected either by bending the segmented arm 38, 50, or by locating the workpiece oifcenter relative to its rotational axis 14 (or both).
It should be appreciated also that the exemplified arrangement whereby one shaft S is driven by the other D by means of connected sprocket drive, is only one way of obtaining dissimilar rotational speeds, and that (among other alternatives) each shaft could be independently rotated, even manually if desired.
It will be clear to those skilled in the art that various changes of construction and operation may be made within the scope of the present inventive concept, having in mind the substitution of functional equivalents and the like. Therefore this disclosure is not to be limited by the precise details shown in the drawings and particularly described by way of example, but it is the intention to hereafter claim the invention broadly aside from the limitations of the prior art.
1. In combination with a laterally oscillating lever arm carrying a generally transverse stylus disposed by terminal engagement therewith to slide a polishing or coursing element over a workpiece, which workpiece is disposed spacedly underlying and generally parallel to the length of said laterally oscillating arm, the improvement comprising: continuous drive means connected to said arm at two points remote from said stylus and spaced longitudinally therealong, each connection adapted to latera ly oscillate said arm at a different speed whereby the phase relation between the two oscillations is continually changing, md such composite pattern of oscillations, amplified by the effective length of the lever arm, directs said stylus in describing a pattern of successive, irregular, non-repetitive, nearly closed loops.
2. The combination of the preceding claim 1 which additionally includes a workholder disposed to support a workpiece frictionally underlying said polishing or coursing element, and locating means for selectively changing the center of said workpiece relative to the center of the pattern followed by the stylus.
3. The combination of the preceding claim 2 wherein said locating means include a portion of said lever arm being formed of longitudinal segments adjustably joined together end-to-end for variable angular positioning between straight and bent alignment.
4. The combination of the preceding claim -2 wherein said workholder has means for continuously rotating said workpiece off-center relative to the center of the pattern followed by the stylus.
5. The combination comprising: a pair of rotary shafts and operative means for simultaneously rotating both shafts at dissimilar speeds; coupling means eccentrically located at adjacent ends of each of said shafts; and oscillating arm pivotally secured adjacent one end to the coupling means of one shaft, being medially connected to the coupling means of the other shaft and with the opposite end of the arm thus disposed for transverse oscillating movement adjacent a workpiece upon joint rotation of said shafts, the portion of the arm which is disposed between said eccentric attachments being segmented and adjustably connected end-to-end for variable angular positioning between straight and bent alignment, whereby said opposite end of the arm may follow various irregular, non-repetitive, nearly closed loop patterns relative to such workpiece.
6. The combination of the preceding claim 5 wherein at least one of said eccentric coupling means are adapted for selective shift to axial location on its respective shaft.
7. The combination comprising: a pair of rotary shafts, one a drive shaft and the other a driven shaft, and operative connecting means for the drive shaft to rotate the driven shaft at a different speed than that of the drive shaft; coupling means carried by adjacent ends of each of said shafts and individually adjustable between axial and eccentric locations thereon; an oscillating arm pivotally secured adjacent one end to the coupling means of one shaft, being medially connected to the coupling means of the other shaft and with the opposite end of the arm thus disposed for transverse oscillating movement adjacent a workpiece upon joint rotation of said shafts, whereby said opposite end of the arm may follow various irregular, non-repetitive, nearly closed loop patterns relative to such workpiece.
8. The combination of the preceding claim 7 wherein said connecting means include a drive sprocket and a driven sprocket associated with the respective shafts, one of which sprockets has at least one more tooth than the other.
9. A polishing device of the character described, comprising in combination: operative means including a rotary drive shaft and a rotary driven shaft, and connecting sprocket and chain means for the drive shaft to rotate the driven shaft at a different speed than that of the drive shaft; adjustable coupling means located on adjacent ends of each of said shafts and individually shiftable between eccentric and axial locations relative thereto; an oscillating arm pivotally secured adjacent one end to one shaft coupling, being medially connected to the other shaft coupling, with the opposite end of the arm thus disposed for transverse oscillating movement upon joint rotation of said shafts, the portion of the arm which is disposed between said shafts being segmented and adjustably connected end-to-end for variable angular positioning between straight and bent alignment, by means of which several adjustments the path followed by said opposite end of the oscillating arm may be progressively varied from an arcuate, repetitive oscillation when either rotary shaft coupling is axially located, to diverse patterns of irregular, non-repetitive, nearly closed loops when both coupling means are eccentrically located; the oscillating arm having a head on said opposite end disposed longitudinally extensible along the arm, which arm is provided with hinge means adapting it selectively to gravitationally overlie a workpiece and to be withdrawn therefrom, which overlying head carries a transversely, dependently disposed, axially adjustable stylus distally adapted to be received in the socket of la polishing element which may thus be pressed against a workpiece jointly by the stylus and oscillating arm and slidingly moved over the surface of such workpiece by oscillation of said arm in a pattern jointly determined by location of the coupling means of the two shafts and by the angular positioning of the arm segments.
10. The polishing device of the preceding claim 9 which additionally includes a rotatable workholder disposed to support a workpiece frictionally underlying said oscillating head, whereby upon changing the angular positioning of the segmented portions of the oscillating arm, the pattern followed by the stylus relative to a rotating workpiece may be selectively varied by reason of the thus changed spacing between the rotational axis of the workholder and the center of said pattern.
References Cited in the file of this patent UNITED STATES PATENTS 1,238,612 Wilson Aug. 28, 1917 2,192,486 Lockhart Mar. 5, 1940 2,371,303 Liebowitz Mar. 13, 1945 2,821,813 Degler Feb. 4, 1958 FOREIGN PATENTS 755,354 France Sept. 4, 1933 655,306 Great Britain July 18, 1951