US3449865A - Deck support for abrading tool - Google Patents

Description

June 17, 1969 J. M. suoDARTH DECK SUPPORT FOR ABRADING TOOL Filed .July 22, 196s ora Sheet /8 L /a2 RRloR ART PRIOR` ART F/ G' 3 Rm mp. M NM R o f WU m 5 M. Y M

June 17,' l969 J. M; suDoARTH 3,449,865

DECK SUPPORT FOR ABRADING TOOL Filed July 22, 1966 sheet 2 of 2 /N vE/vron JACK M. SUDDARTH BY ATT RNEYS United States Patent O 3,449,865 DECK SUPPORT FOR ABRADING TOOL Jack M. Suddarth, Muskogee, Okla., assignor to Coburn Manufacturing Company, Inc., Muskogee, Okla., a corporation of Oklahoma v Filed July 22, 1966, Ser. No. 567,132

Int. Cl. B24b 7/00, 9/00 U.S. Cl. 51-55 1 Claim ABSTRACT OF THE DISCLOSURE A supporting assembly for the abrading cup of a lens generator of a type having a pivotal rst deck wherein an additional deck is provided which is pivotal about the same axis as said first deck and pivotal with respect thereto whereby the cup can be positioned to grind both convex and concave curves without disturbing the built-in orientation between the axis about which the decks pivot and the abrading edge of the cup.

This invention relates to an improved lens generator of the type designed to grind both the concave and convex curves on an ophthalmic lens blank. In particu-lar, the generator of this invention provides an operating assembly whereby the grinding edge of an abrading tool does not require re-orientation upon a changeover from convex to concave grindings.

The improvement of this invention is in that type generator utilizing a rotating grinding cup as the grinding element. In this type of machine, the grinding edge of the abrading tool must be located accurately with respect to the lens blank so that as the grinding tool traverses the lens blank, the proper prescription surfaces are formed on the lens blank. In the prior art devices, when switching from positive to negative surfacees the quill or the abrading tool supporting structure is normally moved from side to side on its supporting deck whereby as the grinding sweep is made, a different edge of the grinding tool is presented to the lens blank. In the instant invention, structure is provided to eliminate this sliding by including a separate pivoting deck for the quill or supporting tool assembly. Therefore, another objective of this invention is to provide a means whereby a lens generator is easily adapted for grinding both convex and concave curves without major adjustments being made to the sweep mechanism.

A still further objective of this invention is to provide a lens generator wherein the direction of sweep is opposite for plus and minus cuttings.

These and other objects of the invention will become more apparent upon a reading of the following speciications taken together with the attached drawings in which:

FIGURES 1 and 2 are diagrammatic, horizontal plan views of the abrading sweep supporting structure of the prior art;

FIGURE 3 is a diagrammatic elevational view of the structure shown in FIGURES 1 and 2;

FIGURE 4 is a diagrammatic horizontal plan of the invention of this disclosure showing the disposition of parts as a minus curve is generated;

FIGURE 5 is a diagrammatic horizontal plan of the embodiment disclosed wherein a. plus curve is generated;

FIGURE 6 is a diagrammatic elevation of the improvement shown in FIGURES 4 and 5; and

FIGURE 7 is a horizontal cross section through the abrading tool.

The advancement of this invention can best be understood when it is analyzed together with the operation of a prior art device. One such prior art device is shown ICC in FIGURES 1, 2 and 3. Such a lens generator is conveniently divided into two major assemblies; namely an abrading tool support assembly 12 and the work or lens blank holder assembly 14. The assembly 14 is only disclosed in FIGURE 1 since it is conventional in operation and design and is eliminated from the other drawing for purposes of clarity. A lent blank L is supported by assembly 14 in the path of the grinding sweep of the abrading tool T. The assembly includes means well known to the art for moving the blank L toward and away from the assembly 12 along the longitudinal length of a supporting base 18 such as by tracks 19. (Again the tracks are only shown in FIGURE 1.)

The sweep assembly 12 of this prior art device consists of four principal elements: a base slide 22, a generally lower deck member 24, an upper pie-shaped deck 25 and a workholder or quill 26 which is slidably received on the member 25 via the slide tracks 28 and 29 between the adjustable abutments 30 and 32.

As best seen in FIGURE 3, the grinding assembly 12 is pivotally supported about a trunnion 34 of base 18 about a fixed axis 36. The position of axis 36 remains constant throughout all grinding sweeps. The upper surface of base slide 22 is equipped with tracks 40 which slidably receive the lower deck member 24. The deck member 24 is provided at its end toward the work piece with an upstanding pin 42. The horizontal relationship, distance D, between pin 42 and axis 36 can therefor be varied by moving lower deck 24 along base slide 22.

Pivotally disposed about pin 42 is the upper desk 25. The upper deck is movable about pin 42 in order to vary the angle of the abrading tool during the generating sweep in order to determine cross curve. Note (FIGURE 7) that the edge of the abrading tool is located precisely over the central axis 41 of pin 42. As is conventional, the base curve of the prescription is set by locating the pin 42 with respect to axis 36 and the cross-curve is determined by selecting the angle between the quill and the slide 22. See the U.S. patent to Suddarth et al. 2,556,604 issued .Tune 12, 1951.

As is conventional in machines of this type, there are means to lock lower deck 24 with respect to the base slide 22 and to lock the upper deck 25 with resect to the lower deck 24 when the proper settings have been made. As is well known to the art, the grinding sweep occurs as the assembly 12 is rotated about axis 36.

For minus cuttings, the grinding sweep occurs to the right of axis 36 (as viewed from the top as seen in FIG- URE 1). As the assembly 12 is rotated about the axis 36 in the direction indicated 'by the arrow 50, as can be seen in FIGURE l, the grinding edge 52 of the abrading cup T forms the surface on the lens blank L. As previously mentioned, the base curve of the lens depends on the distance D set into the machine between the pivot axis 36 and the axis of pin 42. As will also be well understood to those skilled in the art, the cross-curve or vertical component of the prescriptive lens surface is determined by the angle 54 made between the axis of the abrading tool and the longitudinal axis of the base slide. This setting is made by swinging the deck 25 with respect to the deck 24 and locking them into position. The lower deck 24 is equipped with an arcuate slide portion 27 to receive the upper deck 25.

In the event it is desired to form a convex or plus curve, the abrading sweep must occur to the left of axis 36 (FIGURE 2). As seen in FIGURE 2, both the work piece L and the deck 24 are moved an appropriate amount to the right of axis A for a sweep of this type. See the dotted line position in FIGURE 3. In order to obtain the proper relationship between parts, the quill 26 is moved exactly one abrading tool width between the stops 30` and 32 so that the edge 53 of the abrading tool will sweep over the lens blank L as the assembly 12 is moved in the direction of arrow 50. Again, the distance between the grinding edge 53 and the main pivot 36 will determine the base curve and the angle between the longitudinal axis of the abrading tool and the longitudinal axis of the base determine the cross curve.

From the above, it can be seen that the quill moved exactly one abrading tool width in converting from a minus curve to a plus curve sweep. Since, in kgenerators of this type, the grinding edge of the abrading tool must be closely controlled with respect to the pin 42, it is essential that the edge 53 assumes the same relationship with the axis 42 as the edge 52 has with this axis. Therefore, the movement of the quill 26 between the stops 30 and 32 is critical.

The essence of the present invention is providing a structure whereby the abrading edge 52. maintains its relationship With pin 42 whether plus or minus curves are generated. The above is accomplished by rotatably mounting a second upper deck 60 about the pin 42 and mounting the quill 26 to this upper deck 60. All other elements of the combination remain the same except that slides 28-29 and stops 30 are eliminated. In their place, a pair of stops 62 and 64, against which the upper deck 60 abuts are provided. In the device, FIGURES 4-6, the edge 52 always remains disposed over the pin 42. Referring now to FIGURE 4 where the assembly is disposed for minus cutting, the edge 52 will traverse the lens blank along its sweep as the assembly 12 is moved in the grinding direction indicated by the arrow 70. Again the base curve is determined by the distance between the axis 36 and the axis of pin 42 and the cross-curve is determined by the relationship of the axis of the abrading tool and the axis of the lens blank. As seen in FIGURE 5, the angular disposition of the abrading tool T is changed with respect to the lens blank while rotating the upper deck 60 with respect to the lower ldeck 24. With this arrangement, note that a minus curve is ground when the assembly 12 is rotated clockwise as indicated by the arrow 20 and that the plus Curves are ground when the assembly 12 is rotated in the counter-clockwise direction as indicated by the arrow J72. As a result of this, the operator is fully aware of whether he is cutting a convex or a concave surface by the direction of sweep.

Although the adjustment stops 62 and 64 are necessitated in the device for grinding accurate lenses, their function is not so critical as the precise placement of the abrading edge 52 over the axis of the pin 42. Therefor, accurate lenses can be ground in a lens generator of the type described even though the lens generator is adapted for quick and easy convertibility between minus and plus curves.

What has been set forth above is intended primarily as exemplary to enable those skilled inthe art in the practice of the invention and it should therefore be understood that, within the scope of the appended claim, the invention may be practiced in other ways than as specifically described.

What is new and therefore desired to be protected by Letters Patent of the United States is:

1. A lens generator comprising an elongated base having a generally horizontal upper surface, a work holder slidably and adjustably supported on said base for movement along the longitudinal axis of said base, a cup shaped abrading tool having an annular grinding edge disposed in a vertical plane and said edge having a uniform semi-circular cross-section throughout its annular length, a vertical pivot pin disposed below said tool having a center axis intersecting one portion of said edge at the center of a cross-section dened by a horizontal plane which also intersects the axis of rotation of said abrading tool, a sweep assembly for supporting said tool, said assembly including a base slide rotatably supported on said base about first vertical axis which intersects said longitudinal axis of said base, a lower deck carrying said pivot pin, rst means mounting said lower deck for slidable movement with respect to said base slide whereby the distance between said pivot pin and said iirst vertical axis is adjustable, a first upper deck pivotally mounted on said lower deck about said pin, a second upper deck carrying said abrading tool and pivotally mounted on said first upper deck about said pin.

References Cited UNITED STATES PATENTS 1,325,789 12/1919 Johnson 51-33.1 3,117,396 1/1964 Dalton 51-33 2,806,327 9/1957 Coburn 5l-55 X 2,556,604 6/1951 Suddarth et al. 51-55 JAMES L. I ONES, JR., Primary Examiner.

U.S. C1. X.R. 51-124

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