US995393A - Machine for grinding variable curves. - Google Patents

Description

S. WITMER.

MACHINE FOR GRINDING VARIABLE CURVES.

WITNESSES:

Q. a (E, C/Q/ZKMMK APPLICATION FILED 11110.27, 1909.

Patented June 13. 1911.

3 SHEETSSHEET 1 INVENTOR S. WITMER.

MACHINE FOR GRINDING VARIABLE CURVES.

APPLICATION FILED B30127, 1909 Patented me 13, 1911.

3 SHEETS-SHEBT 2.

WITNESSES:

S. WITMER.

MACHINE FOR GRINDING VARIABLE CURVES.

APPLICATION FILED DEO.27,1909.

3 SHEETS-SHEET 3.

WITN ESES; INVENTO R 41 a. 2 221% WM 9%MW MYM,

Patented June 13, 1911.

broader aspect it is susceptible of embodi rirro SAMUEL WITMEB, 0F TOLEDG, OHIO.

MACHINE FOR GRINDING VARIABLE CURVES.

Specification of Letters Patent. Patented J 11119 13, 1911. Application filed December 27, 19%.

Serial N 0. 585,068.

To all whom it may concern:

Be it known that I, SAMUEL WrrMnn, a citizen of the United States, and a resident of Toledo, in the county of Lucas and State of Ohio, have invented a certain new and useful Machine for Grinding Variable Curves; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to makeand use the same, reference being had to the accompanying drawings, and to the figures of reference marked thereon, which form a part of this s ecification.

My invention relates to grin ing machines and particularly to machines for grinding variable curves on refractors and reflectors for the purpose of avoiding spherical aberrations, but is not restricted to such use as it may be employedifor any purpose or in any connection for which it may be adapted or appropriate.

The object of my invention is the provision of an apparatus of this class, which is efiicient and economical in its operation and construction, and which will produce in a simple and practical way substantially any of the curves required by the laws of refraction and reflection. Y

Theinvention is fully described in the following specification, and while in its ment in numerous forms, a preferred form and a few modifications of the same'are illustrated in the accompanying drawings, in which,

Figure l is a side elevation of the preferred form of my machine adapted for grinding substantially the parabolic curve with portions in section and broken awa Fig. 2 is a cross-section on the line ac m in Fig. 1. Fig. 2 is a side edge view of a slightly modified form of the grinding-tool. Fig. 3 is an enlarged elevation of a modified form of the grinding mechanism adapted for grinding curves of less variation than a parabolic in case of a concave, and of greater variation than a parabolic in case of a con vex. Fig. 4 is a front elevation of the grinding mechanism in Fig. 3. Fig. 5 is a diagram illustrating the changes which the work undergoes during different grinding operations. Fig. 6 is a plan of another form of my invention adapted for grinding curves of greater variation than a parabolic in case is shown as resting,

of a concave and curves of less variation than a parabolic in case of a convex. Fig. 7

is a side elevation of the same with ortions broken away, and Fig. 8 is an end e evation thereof,- with a part in section.

Referring particularly to F 1 and 2 of the drawings, 1 designates the table of the machine frame and 2 the supporting legs or standards therefor. Mounted in suitable bearings in the table 1 and a. subjacent frame part 3 are a plurality of vertical spindles, which are arranged in a common vertical plane, and, in the present instance, shown as being three in number, the two outer ones being designated 4, 4 and the inner or central one 5. These spindles are mounted for longitudinal adjustment in their bearings, which adjustment is effected by adjusting. screws 6, one of which is threaded through each bracket 7 carried by the frame part Sand has its inner end bear,- ing against the lower end of the associated spindle to form a pedestal bearing therefor. Each of the spindles 4, 4 carries a gear 8 in mesh with a gear 9 on the center spindle 5, the latter gear having its periphery preferably broadened to adapt the gears to remain in mesh during a relative adgustment of the shafts, as is apparent. One of the spindles 4 has a spiral or worm gear 10 feathered thereto and meshing with a drive worm 11, which is carried on a shaft 12. This shaft is journaled in suitable bearings at one end of the machine frame and is shown as carrying a belt-pulley 13, but power may be communicated thereto in any other suitable n1anner. The wormgear 10 is held against axial movement by the frame-part 3, on which it and by the casting or part 14, which extends over the worm-gear and has its ends attached to said frame part. Each of the spindles 4 carries a stock 15 at its upper end, which stock is shown as being removably fitted over the tapered end of the spindle to facilitate a tight fitting of the same on the spindle and at the same time an easy removal of the same therefrom. This stock has its top roadened or suitably shaped to support a templet or pattern 16,

which is preferably held in position thereon by a surrounding collar 17- in coiiperation with interposed rubber or other suitable form of gasket member 18 and a suitable cementitious substance. The collar 17 is preferably provided at its outer edge with an up wardly projecting flange to form a cup shape member around the pattern for the purpose hereinafter described.

The spindle 5, which is the work carrying spindle, has a stock 19 removably fitted over 7 its tapered upper end to revolve therewith,

such stock having its upper end approximately the diameter of the work 20 intended to be supported thereby, and fashioned to provide a suitable seat for the work, as indicated. Threaded to the upper portion of this stock is a-collar 21, which adjustably supportsa ring or collar 22 of Preferably the same material as the work or of like hardness. The ring or collar 22 is intended to fit closely around the rim of the work and has its top fashioned to form a continuation of the curved surface ofthe work, whereby the grinding tool or' medium, hereinafter referred to, is enabled to overreach the edges of the work in its abrading movements and to end its strokes on the ring 22 rather than on the worm itself, as the latter would cause an unevenness in thework surface at the end of the strokes. The work and ring being of the same material or hardness wear down together so that their top surfaces or lines are always coincident. The collar 21 and ring 22 are encircled by a collar 23 and interposed gasket member 24, the collar 23 having its outer edge formed with an upwardly projecting flange to form a receptacle or cup around the work to hold the abrasive material and the particles worn from the work in the grinding or abrading operations. The securing of the parts of the holder together in this manner enables the cup-rings 23 to be quickly removed to clean the same. I wish it understood, however, that both the pattern and work holders may be constructed in any other suitable manner.

Disposed above the pattern and work holders of the machine is a tool carrying frame 25 which is shown in the present instance as comprising the two transversely spaced parallel bars or side pieces 25 hav- -ing the connectingend pieces 26, 26, to

which the plates 27 forming shoes forriding on' the templets or patterns 16, 16, are secured, as by the cooperating action of the screws 28, and clamping plates 29. The plates or shoes 27 may be adjusted vertically between the clamping members as may be desired to compensate for wear, and stand in planes parallel with the spindle axes. 'The clamping faces of the pieces 26 and 29 should be fiat.

Rising from thebars or sides of the tool carrying frame adjacent an end thereof are the arms or uprights 30 which have the vertically spaced bars or links 31, 31; projecting therefrom toward the center of the frame.

These bars are pivotally attached at their 'outer ends to a vertically-disposed tool carrying head or member 32, to one side of which is clamped an abrading or grinding tool 33, by the cooperating action of the clamping plate 34 and screws It is thus apparent that the head 32 andabradingtool are permitted to freely rise and fall -1n a vertical plane due to its link connection with the arms 30, as indicated. The lowering movement of the tool head is limited, however, by a stop 36, which is adjustably carried by said'head and adapted to coact with a. subjacent part of the frame 25, as indicated.

The abrading tool 33 is intended't o rest freely upon the work 20 and to havehori- I zontal abrading movements with the frameits carrying head. This tool stands in a plane parallel to the spindle axes and is preferably of flat thin blade form of a sufficient width to preferably extend across about four-fifths of the work, but is notre stricted to this width as it may be more or less as working conditions'may require. The

working edge of the tool longitudinally co'n-' forms to the intended or desired shape of the work surface, whether such shape be of con= vex or concave form, and in thickness is preferably much lessthan one-eighth of the diameter of the work. It is apparent, how'- ever, that the tool in working over'an 1rregular surface may have its working surface changed slightly while reducing the irregularities, but the work and tool ultimately and naturally correct each other until the parabolic curve desired is substantially reached. While the tool is shown. as being of thin blade form, it may have its body thickened and its working edges reduced as indicated in Fig. 2 1

When the work is being ground to a pattern or patterns, as shown in Fig. 1, the patterns'16 have their working surfaces of the shape which it is desired to impart to .the work, and the shoes 27 of the frame, have their working edges of the same general contour as the abrading tool 33 or of a shape to fit the surface of the pattern on which it rides, and are substantially of the same thickness as said tool. It is thus apparent that on a reciprocation of the frame 25, ashereinafter described, such frame will rise and fall as the shoes pass forward and backward over the patterns 16 and the abrading toolv 33 will rise therewith due to the stop 36 resting on the frame and will lower by gravity or in any other suitable manner. A permissible vertical movement of the tool 33 relative to the frame 25 is= important, owever, as it enables the tool to rise and fall independent of the frame 25 when passing over irregularities in the work surface not present in the patterns. Such movement of the tool also permits it to grind surfaces without the guidance of the patterns, -as the stop 36 may be removed or the tool-head elevated free from the frame to permit the tool to follow the surface of the work and to gradually change the shape of the same to substantially a parabolic curve. Or in other words, the purpose of the patterns is merely to grind a plurality of articles to the same curvature. If, however, uniformity of curvature of different pieces of work is not important a multiplicity of articles may be ground in the same operation by placing separate work pieces on each spindle in lieu of the patterns 16 and employing the shoes 27 as grinding tools. It is apparent that the patterns and shoes may be made to correct their respective shapes or to grind each other to substantially parabolic curves by placing a suitable abrasive material in the cups formed by the collars 17 of the patternholders.

The reciprocatory movements are imparted to the frame 25 from the oscillations of a lever 37, which is carried by a shaft or stud at the end ofthe table 1 opposed to the drive-shaft 12, and has its upper end in connection with the frame 25 through the medium of one or more rods 39. The lower end of this lever is connected by a rod 40 to a crank-pin 41 carried by a disk 42 on the shaft 12. The crank-pin 41 is shown as being adjustable radially of the disk 42 to change the length of stroke of the frame 25 and the lower arm of the lever 37 is shown as comprising two relatively adjustable parts which permit of a change in the position of the frame 25 relative to the spindles 4 5, whereby the movements of the tool and shoes may be centered relative to the parts on which they respectively work.

The relative rotary movements of the spindle 5 and the reciprocatory movements of the frame 25 are preferably such that the frame will make approximately 54 strokes to one revolution of the spindle, as this is found in practice to be a proper ratio. It is not desired, however, to restrict the relative movements of these parts to any particular ratio as it may be changed as desired.

The operation of this form of my machine is as follows :-Preparatory to grinding the surface of a lens or other article, whether of concave or convex form, templets or patterns 16 are secured within the holders carried by the spindles 4, 4 and the lens or other work is secured within the holder carried by the spindle 5 with the collar or ring 22 surrounding itand forming a continuation of the surface to be ground. Should the patterns 16 and shoes 27 not have their coacting surfaces of like form the machine is operated for a time before placing the work therein so as to mutually correct the surfaces for the patterns and shoes, a suitable abrasive material being placed within the cups with the patterns to facilitate such action.

The patterns and work being in position in their respective holders and the former in proper condition, the frame25 is placed over the same with the shoes 27 thereof resting in proper position on the patterns and the abrading tool 33 resting in proper position on the work, as indicated. The spindles are also vertically adjusted to permit the tool to rest freely on the work with its stop 36 nearly in contact with the frame 25 when the shoes 27 are resting on the patterns. The drive-shaft 12 now being thrown into motion imparts slow rotary movements to the spindles 4, 5 through the medium of the worm 11, Worm-gear 10, and gears 8 and 9, to cause the'patterns and work to turn slowly under their respective contacting parts, and communicates the requisite reciprocatory movements to the frame 25 and attached parts through the medium of the crank-disk 4:2, rod 40, lever 37 and rods 39. The tool 33 in moving backward and forward over the work gradually reduces itto the shape of the patterns and when this is accomplished the stop 36 rests on the frame 25 and supports the tool-head to prevent further reduction of the work. The tool 33 finishes its strokes upon the collar or ring 22 to avoid any roughness at the edge of the work. Should it not be important to maintain an exact conformance between different pieces of work, a plurality of the same may be ground in one operation by placingseparate work pieces on each spindle, and employing the shoes 27 as grinding tools. \Vhen the work and tool conform to each other throughout the entire stroke of the tool, the required parabolic curve has been substantially formed and the grinding operation may then be stopped. The shoes and tools are shown as being reversible to adapt either end of the same to be used. During a grinding operation the grinding edge of the tool always stands at right angles to its stroke.

In the modification shown in Figs. 3 and 4., which is adapted for grinding surfaces to curves of less variation than a parabolic in case of a concave, and to curves of greater variation than a parabolic case of a convex, 45 designates the table or frame of the machine, 46 the workspindle, 47 the stock of the work-holder, 48 the collar threaded thereto. 49 the work embracing collar or ring, which is of like material or hardness to the work, 50 the cup-forming collar, 51 the gasket between the collar 50 and the collars 48 and 49. and 52 the work.

A standard 53 rises from thctable45 at one side of the work-holder and has an arm 54 projecting therefrom over the work. This arm is mounted for vertical adjustment relati've'to the standard, due to the bolt 55 carrying the arm working through a longi tudinal slot 56 in the standard. A block or guide member 57 is pivoted to the outer end of the arm 54 by a bolt 58, or in any other, suitable manner, for vertical oscillatory movements, and reciprocally working through a guide opening in such block or member is the vertically-disposed arm 59 ofa tool-carrying head 60. Olamped to one side of this head by a plate 61 and cooperating screws 62. is an abrading tool 63 of the form of machine described for grinding substantially arabolic' cur'ves. This tool when in vertlcal position stands substan-- tially over a diametrical line of the work,

and when oscillated by Ca 'reciprocatory movement of the attached rod 64 is adapted to move first in one direction and then the other over the work surface with the axis of the block 57 as its pivot.

In grinding a convex surface the pivot 58 may be vertically adjusted by an adjustment of the arin 54 on the standard 53 to secure a greater or less departure from ya parabolic curve, as the nearer the pivot to the work surface the greater the departure from the parabolic curve. When the pivot of the grinding tool is placed without the center of curvature of the work, when working'on a concave surface it grinds a curve which substantially coincides with the short or end curve of an elliptic circle, and when placed within the center of curvature of the work it produces a curve which substantially coincides with the long or side curve of an elliptic circle. I

I will now describe the form of my invention disclosed in Figs. 6, 7, and 8, which is the meshing gears on the spindles; 70 the form,

drive-shaft; 71 the worm for driving a worm-gear (not shown) on one of the spindles; 72 the tool carrying frame, which superimposes the work-holders; and 73 the lever which is connected at one end to the tool-frame by the link member. 74 and at its other end to the crank 75 on the drive-shaft by the rod 76. The frame 72 is shown in the present instance asbeing of rectangular and as carrying a tool-carrying head 7 7 above each work-holder. Blades or tools 78 of the form previously described are clamped tothese heads ina suitable manner. The end heads 77 are pivotally hung within the frame 72 by pivot studs or screws 79, while the center or intermediate head or heads, if more than three beemployed, is

shown as being pivotally hun from the ends of arms 80, which are pivote at. their oppo- 'site ends to the frame 72 as at-81-.' --Tl1e purpose of this is to permit the end heads and tools to have vertical movements relative to the center head and tool, as two supports for the frame would always rest on the work while a thirdwould tend to'raise vone of the tools from the work if the'diiferent pieces'of the same are not uniform. In order to cause the tools "when movedbackward and forward with the frame to assume the angle with reference to the work surface which the curves to be produced may require, I provide each tool-head with an arm 82, which projects outwardly. from an end thereof in a plane with the grinding tool and at one side of its pivot in the frame 72, and has its free end angled to form the vertically disposed part 83. This part has its free end portion working loosely through a guide opening in a swivel-block 84, which is pivoted'to a carrying-block or part 85. The blocks 85 are shown as being vertically adjustable on a graduated slide ,86 to produce greater or less variations in the surface curvatures of the work. Either convex or concave surfacesmay be ground with this form of machine by simply changin the shape of the tool. The operation 0 this form of my invention is apparent.

In Fig. 5 the line a a represents the spherical curve of a convex piece of work before being ground; the'line b 6 represents the spherical curve of a concave piece of work before being ground, and the heavy line 0 0 represents theform of the curve of the finished work. The spaces between the light lines and the'heavy line represent the portions which are ground away in obtaining the desired form of curve.

It is apparent that I have provided a machine and attachments therefor, which render the production of variable curves simple and easy and avoids much of the difliculty encountered in other methods, principal among such objections being the presence of circles on the surfaces of ground articles. It is also apparent with this construction that the tools and workmutually act to correct each other, and when the tools and work conform in curvature throughout the entire stroke of the former the desired curve is produced.

While I have shown the employment of three spindles for carrying the'work or the work and patterns, it is obvious that any number of such spindles may be used, alnd that all may be used for carrying workor a portion utilized for carrying patterns when the work is being ground to patterns.

I also wish it understood that I do not limit tool having a broad thin grinding edge. I further wish it understood that my invention is not limited to any specific construction or arrangement of the parts except in so far as such limitations are specified in the claims. 5

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

1. In a machine of the class described, the combination of a rotatable work-support, an abrading tool adapted for reciprocatory movements across the work transverse to its turning axis, said tool completing its strokes without the zone of the Work, and mechanism for actuating the movements of the tool and work-support.

2. In a machine of the class described, the combination of a rotatable Work-support, an abrading tool adapted to rest for free vertical movements upon the work and to have reciprocatory movements across the surface of the same, said tool having a long thin working edge conforming longitudinally to the desired cross-sectional curvatures of the work surface, and mechanism for rotating the work-support and reciprocating the tool across the same.

3. In a machine of the class described, the combination of a work-support having a part adapted to closely surround the Work, said part being of equal hardness with the work, and an abrading tool reciprocally movable across'the work and completing its movements upon such part.

4. In a machine of the class described, the combination of a rotatable work-support, mechanism having an abrading' part movable across work carried by said support in a plane transverse to the turning axis of the support, and means cooperating with said mechanism to limit the abrading action of said part on the Work.

5. In a machine of the class described, the combination'of a rotatable work-support, mechanism having an abrading part reciprocally movable across work held by the support, rotatable patterns conforming in shape to the desired shape of the work cooperating with said mechanism for controlling the abrading action of such part on the work, and means for rotating the Work-support and patterns.

' 6. In a machine of the class described, the combination of a rotatable work-support mechanism having an abrading part reciprocally movable across work held by the support and provided with a long thin working edge, rotatable patterns cooperating with said mechanism to control the abrading action of said part, and means for rotating the work-support and patterns.

7. In a machine of the class described, a vertically adjustable rotatable work-support, mechanism having an abrading part reciprocally movable over work held by the sup-, port vertically adjustable patterns cooper-at ing with said mechanism to control the abrading action of said part, and means for rotating the work-support.

8. In a machine of theclass. described, the combination of a vertically adjustable r0- tatable work-support, mechanism having an abrading part adapted to freely rest on the work held by the support and reciprocally movable over the same, vertically adjustable rotatable patterns cooperating with the mechanism to control the abrading action of said part, and means for rotating the work'support and patterns in unison.

9. In a machine of the class described, a plurality of spindles, Work-holding means carried by same and patterns carried by others of said spindles at their upper ends, means for rotating said spindles, a frame disposed over said work-holding means and patterns, shoes carried by said frame and riding on said patterns, an abrading tool carried by the frame and adapted to rest freely on work held by said holding means, and means for moving the frame to'impart reciprocal movements to the shoes and tool across the parts on which they ride.

10. In a machine of the class described, a plurality of rotatable members, templets carried by a part of such members and Workcarried by another part of such members, a frame having parts working on said templets to uide the movements of'the frame,

, an abra ing element carried by said frame and Working over the work, and mechanism for rotating said members and imparting reciprocatory movements to said frame.

11. In a machine of the class described, the combination of a plurality of rotatable parts, /templets carried by a part of said members and work carried by the others of said members, a frame" capable of reciprocatory movements over said members and having parts riding on said templets, an abrad- 11G ing member carried by said frame for free vertical reciprocatory movements relative thereto and capable of riding on the Work, and mechanism operative to reciprocate said frame and impart rotary movements to said members.

12. In a machine of the class described, the combination of a plurality of rotary members, templets carried by a part of said members and work carried by the other part of said members, a frame reciprocally movable oversaid members and having bladelike. parts resting upon said templets for reciprocatory movements thereover and hav ing their working edges conforming to the contour of the templets, a part earned by said frame for limited vertical reciprocatory movements relative thereto and adapted to normally rest upon the frame, an abradmg .tool carried by said part for acting on the work, said tool having a lon thin working edge conforming to the esired crosssectional contour of the work surface, and mechanism .for rotating Saidmembers and imparting reciprocatory movements to said frame.

13. In a machine of the class described, rotatable work-holding means comprising a spindle, a stock carried by such spindle, such stock having its upper end approximately the diameter of the work to be operated on and fashioned to provide a seat therefor, a collar threaded to the stock, a ring supported by said collar and surrounding the edge of the work with its top fashioned to form a continuation of the upper work surface, said ring being of a material of substantially equal hardness with the work, and a second collar adjustably mounted upon said first collar and cooperating therewith to hold said ring in position.

14. In a machine of the class described, the combination with a rotatable work support, of mechanism having an abrading-part reciprocally movable across work held by the. support and having a long thin working edge, said part making a plurality of strokes across the work at each complete rotation of the support.

15. In a machine of the class described, the combination of a rotatable work support, an abrading tool mounted for reciprocatory movements across the work and having a long thin working edge with its length transverse to its stroke and mechanism for rotating the work support and moving-the abrading tool, the tool having a plurality of strokes to each complete rotation of its support.

In testimony whereof I have hereunto signed my name to this specification in the presence of two subscribing witnesses.

SAMUEL WITMER.

Witnesses:

C. W. OWEN, E. E. THOMAS.

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