US2242664A - Machine for generating paraboloids of revolution - Google Patents

Description

May V29,- 1941. J. F. sToNE ETAL MACHINE FOR GENERATING PARABOLOIDS 0F REVOLUTION 4 Sheets-Sheet 1 Filed Jan. 5, 1940 QA d wr k2 Hl l. Il IME REE funn WT'WIIIIUl I O MWNN WN @MN MN. w w WN NN W r um o mv Nw? MW 1 Nl QN/mv/Jr QW MN ARN' m NN o m mm s N W g S, w @a .N NN

May 20, 1941. J. F. STONE ETA. 2,242,664`

MACHINE FOR GENERATING PARABOLOIDS OF REVOLUTION Filed Jan. 5, 1940 4 sneetssneet 2 g vwe/wtom/ Ju Per/yU/ey May 20 1941 J. F. STONE' Erm. 2,242,664

MACHINE FOR GENERATING PRBOLOIDSl OF REVOLUTION Filed Jan. 3, 1940 4 Sheets-Sheet 5 ya www@ .May 20, 1941. J. F. STNE 'HAL 2,242,664

MACHINE Foa GENERATING PARABoLoIDs oF REVOLUTION Filed Jan. 5, 1940 4 sheets-smul! F .4. I Jay/7% ll I /J L l f Patented May 20, 1941 UNITED STATES ATENT OFFICE MACHINE FOR GENERATING PARABOLOIDS OF IREVOLUTION This invention relates to a machine designed to generate and produce paraboloids of revolution. In its particular aspects, it may be used for grinding or polishing parabolic mirrors, or for machining or grinding dies, forms or molds for pressing, casting or forming parabolic shapes.

It is an object of the invention to provide a practical and efficient machine for the purposes set forth and one which may be adjusted quickly for parabolas of revolution of any diameter Within its capacity, and of any focal length desired, and which will generate forms either concave or convex.

For a further understanding of the invention, reference is to be had to the following description and the accompanying drawings, in which:

Fig. 1 is a side elevational view of a machine constructed in accordance with the present invention for producing paraboloids of revolution, the adjusting elements of the machine being shown in positions which they occupy at the commencement of an operation;

Fig. 2 is a similar View disclosing the' parts of the machine at the positions which they occupy at substantially the completion of a given operation;

Fig. 3 is a vertical transverse sectional View taken through the machine on the plane indicated by the line III-III of Fig. 1;

Fig. 4 is a similar view on the plane indicated by the line IV-IV of Fig. 1;

Fig. 5 is an enlarged vertical and longitudinal sectional view on the plane disclosed by the line V-V of Fig. 4, the movement regulating members shown in this ligure occupying the same relative positions as in Fig. 1;

Fig. 6 is a similar view showing the positions of the movement regulating members intermediately positioned between those disclosed in Figs. 1 and 2;

Fig. 7 is a diagrammatic view setting forth the development of a parabolic curve;

Fig. 8 is a similar view of another curve;

Fig. 9 is a detail side elevational view illustrating the movement regulating members of a machine in positions to produce convex curvatures; y

Fig. 10 is a detail perspective View of one of the slide members.

The principle upon which our improved machine operates is based on the well known method of developing a parabolic curve, as shown in Figs. 7 and 8, but for generating a paraboloid of revolution,it is necessary to consider only onehalf of the curve, i. e., that located on either side of the axis AB.

To facilitate a clear understanding of the invention, the line FD in Figs. 7 and 8 will be called the sine, the lines Aa', Ab', Ac', etc. are designated hypotenuses. Further, the points a', Zi', c', etc. formed by the intersection of the hypotenuse lines with the sine line are termed abscissae, and the distances Ba., Bbl, Bc, etc. are ordinates, Where the parallel lines defining these distances intersect the parabolas curve CAD.

It will be seen, by comparing Figs. 7 and 8, that the focal length of the parabola may be altered by changing the ratio of the abscissae spacing in relation to the heights of the ordinates. In Fig. 7, X indicates the focus, while in Fig. 8, the abscissae spacing being one-half that disclosed in Fig. 7, the focal length is doubled, the focus being located at X'.

Our improved machine is designed to reproduce automatically the processes followed in developing parabolic curves as indicated in Figs. 7 and 8, except that, in effect, the machine uses an infinite number of sines, hypotenuses, abscissae and ordinates.

Y Figs. 1 and 2 show the various elements of the machine and their positions and relations when grinding a parabolic mirror. Fig. 1 illustrates the grinding wheel at the center or axis of the mirror', and Fig. 2, the positions of the parts of the machine after the wheel has traversed the face of the mirror and arrived at the edge.

In the drawings, the numeral I represents a mirror to be ground to a parabolic contour, the element 2 being a face plate upon which the mirror is mounted, and clamps are indicated at 3 for centering and securing the mirror in its position on the face plate. The face plate 2 is carried on a vertical shaft II, running in'a bearing in the bracket Ii, forming a part of the base plate 1. A pulley 5 is keyed to the shaft 4 and is suitably actuated so that the mirror I may be rotated. An abrasive wheel 8 is mounted to rotate on a spindle 9 by means of a pulley Il). The spindle 9 is attached to a vertical slide II, the latter having means by which vertical adjustment of the wheel 8 may be made as, for instance, by a screw operated by the ball crank I2. The slide II may be dovetailed to the end of a reciprocating frame I 3, which frame serves to traverse the grinding Wheel across the face of the mirror from the center of the latter to its edge.

The frame I3 is provided with eight pivots., two of which are indicated at I4, and on. which are mounted bearing shoes I5, these being free to rock on pivots I4.

The bearing shoes carry the weight of frame I3, and they lslide upon pivoted planes which, for convenience and description, will be called hypotenuse bars and are indicated at I1. These bars are pivoted as at I8 in connection with the upper ends of brackets I9. When the position of the grinding wheel 8 is directly over the axis of the mirror being ground, it is essential that the pivots I4 and I8 be axial with each other. The free end of each hypotenuse bar is supported on its bottom surface by a bearing shoe 20, pivoted at 2I in the upper ends of bars 22 which slide in guides 23. These bars may be called sine bars, since they are in effect equivalent to the line FD in Figs. 7 and 8. These bars must be parallel to the axis of the mirror supporting shaft 4.

Mounted on pivots IS at the lower ends of the bars 22 are shoes 24 which bear upon the planes 25 and which may be turned upon pivots 2B car ried in brackets which are a part of the bar shown at 28, the latter being mounted to reciprocate on the base plate 1. rIhe angle of the planes 25, which may be called abscissae planes, may be adjusted by means of the calibrated screws 21. The frame i3 and bar 28 are caused to move like distances and in opposite directions through the medium of the lever 29, pivoted in its center as at 30 to an arm 3I.

The top and lower ends of the lever 29 are pivotally connected with sliding blocks 32, worklng in guides 3d formed in one end of the bar 28 and the frame i3. The frame I3 may be reciprocated in any suitable way. In this instance, the base plate 1 is extended to effect the support of a bracket 63 in which is journaled a shaft E4. The shaft carries a pulley 65 driven by a belt or other suitable means. Fixed to rotate with the shaft 64 is a disk @E having a radially adjustable crank pin 61. Connected with this crank pin is one end of a link 88, the opposite end of said link being pivotally connected as at 69 with one end of the frame I3. This construction, among others which may be used, provides for the lcontrolled reciprocation of the frame I3 and variations in the length of its stroke. The bracket 83 is also mounted for slidable adjustment on the base plate 1 toward and away from theiframe by means of the screw shaft 18 to center the grinding Wheel relative to the axis of the mirror I.

Having described the essential elements of the machine, its operation may be briey explained.

If the abscissae bars or planes 25 are so adjusted that they are parallel to the hypotenuse bars I1, the abrasive wheel 8, when in operation, will traverse a straight line and grind a plane surface on the mirror I.

When, however, the planes 25 are set at any angle to the horizontal, whether mostminute or great, a parabolic curve will be described by the center of the grinding wheel during its traverse from the center of the mirror to the edge, and the 4characteristics of the curve will depend solely upon the angle at which the planes 25 are set. A change in the angle of these planes acts to alter the ratios of the abscissae of the curve to its ordinates or, in other words, the angle of the planes 25 determines the focal length of the mirror to be ground, and is equivalent to changing the length of the line FD shown in Figs. '1 and 8.

By the use of the graduations on the screws 21,

the machine can at once be set to grind a paraboloid of any predetermined focal length.

By reversing the angle of these planes, as shown in Fig. 9, the abrasive wheel will grind a convex paraboloid of revolution, this feature being convement in punch and die work. It will be seen that the machine automatically performs the operations followed when drafting the curves of Figs. 7 and 8.

In operation, the sine bars 22 may be considered to act as an ininite number o-f points 1ocated along the sine FD of Figs. 7 and 8. The hypotenuse bars I1 may likewise be taken as an infinite number of hypotenuses swinging between F and D, the travel of the grinding wheel between the center and edge of the work develops an infinite number of ordinates.

The bars 25 serve as a means to manually change the value of the abscissae from Zero to the maximum value permitted by the particular machine being used, and also tol change from concave to convex contours.

Obviously a cutter may be used toremove material instead of a .grinding wheel, nor need the periph-ery of the wheel have the shape shown in Figs. l and 2. It must, however, have a line contact on the piece being worked when the final contour is being generated.

It will be noted in Fig. 3 the arrangement of the shoes I5, riding on the guides I1, prevents any lateral movements between these parts so that the frame I3 can have only linear motion in the horizontal plane. Further, in Fig. 3, it will be noted that the center line, indicated at L-L,

` of the axes of the pivot-s is in line with the three planes of the system, this line corresponding to the numerals I1 as shown in Figs. l and 2.

It is obvious that the machine need not of necessity follow the specific design here shown and described, as this arrangement was selected merely to provide a simple presentation of the fundamental mechanical principles involved in the present invention.

What is claimed is:

1. A machine to produce paraboloids of revolution, comprising a rotary work-carrying member, a reciprocating frame, a material removing element carried by said frame, means for reciprocating said frame transversely of the work, a guide swingable about a xed pivot, means on said frame slidably engaging said guide and cam means for causing said guide -to swing about its pivot as said frame reciprocates to guide said frame in a feeding movement` at substantially right angles to the axis of said element whereby said element is caused to vdescribe a parabolic curve.

2. A machine to produce paraboloids of revolution comprising a rotary work-carrying member, a reciprocable tool frame, a material removing tool carried by said frame, a guide-way swingable about a iixed pivot in the plane of movement of said tool frame, means slidably supporting said tool frame in said guide-Way, means for longitudinally reciprocating said tool frame, and cam means for simultaneously swinging said guide-way about its pivot to guide said frame in a feeding movement at substantially right angles to the axis of said tool whereby the latter is caused to describe a parabolic curve.

3. A machine to produce paraboloids of revolution, comprising a rotary work-carrying member, a longitudinally reciprocable tool frame, a material removing tool carried by said frame, a guide-way swingable about a fixed pivot in the plane of movement of said frame, means slidably supporting said frame in said guide-way, a longitudinally movable, inclined bar, means slidably engaging said bar for swinging said guide-Way on its pivot, means for longitudinally reciprocating said frame and means for simultaneously and oppositely reciprocating said inclined bar to cause a feeding movement of said frame in a direction at right angles to the axis of said tool whereby the latter is caused to describe a parabolic curve.

4. A machine to produce paraboloids of revolution comprising a rotary work-carrying member, a longitudinally reciprocable 4tool frame, a material removing tool carried by said frame, a pair of longitudinally spaced guide-ways swingable about fixed pivots, means slidably supporting said frame in said guide-ways, means for reciprocating said frame, cam means for swinging said guide-ways on their pivots, and means for so timing the swinging of said guide-ways with the reciprocation of said frame, as to cause said frame and tool to simultaneously partake of a distributing movement transversely of said work and a feeding movement in a direction at right angles to the axis of said tool. Y

5. A machine to produce paraboloids of revolution comprising a rotarywork-carrying member, a reciprocable tool frame, a material removing tool carried by said frame, a pair of longitudinally spaced guide-ways swingable about iiXed pivots, means slidably supporting said frame in said guide-ways, an inclined plane adjacent each guide-way and a vertically reciprocable bar interposed between each guide-way and its respective inclined plane, means slidably supporting said bars on respective planes, means for reciprocating said frame in a distributing movement from the periphery to the center of the work, and means for simultaneously reciprocating said inclined planes to cause said guideways to swing about their pivots whereby said frame partakes of said movement toward and away from said material.

6. A machine to produce paraboloids of revolution comprising ya rotary work-carrying member, a reciprocable tool frame, a material removing tool carried by said frame, a pair of longitudinally spaced guide-ways swingable about fixed pivots, means slidably supporting said frame in said guideways, an inclined plane adjacent each guide-way and a vertically reciprocable bar interposed between each guide-way and its respective inclined plane, means slidably supporting said bars on respective planes, means for reciprocating said frame in a distributing movement from the periphery to the center of the work, means for simultaneously reciprocating said inclined planes to cause said guide-Ways to swing about their pivots whereby said frame partakes of said movement toward and away from said material, and means for varying the angle of inclination of said planes to regulate the parabolic curve described by said tool.

7. A machine to produce paraboloids of revolution comprising a rotary work-carrying member, a horizontally reciprocating frame, a material removing tool carried by said frame, a guideway swingab-le about a ixed transverse pivot, means on said frame slidably engaging said guide-way, a vertically reciprocating bar operatively engaging said guide-way, means for longitudinally reciprocating said frame, and means for simultaneously reciprocating said vertical bar to swing said guide-way on its pivot, the reciprocations of said frame and bar being so timed as to cause the frame and tool to describe a parabolic curve.

8. A machine to produce parabcloids of revolution comprising a rotary work-carrying member, a reciprocable frame, a material removing tool carried by said frame, means for longitudinally reciprocating said frame, a guide-Way swingable about a fixed transverse pivot, means on said frame slidably engaging said guide-way, a supporting bar operatively engaging said guideway and reciprocable in a plane at right angles -to the movement of said frame, a longitudinally reciprocable supporting member, an inclined plane carried by said supporting member, means on said Vertical bar slidably engaging said plane, and means for reciprocating said supporting member simultaneously with, but in a direction opposite to that of said frame whereby said tool undergoes a distributing movement across the Work while advancing in a feeding movement toward said work.

JULIUS F. STONE. PERRY OKEY.

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