US2621450A - Abrading - Google Patents

Description

L. A. MARTIN Dgc. 16, 1952 ABRADING 3 Sheeqs-Sheet 1 Original Filed May 1, 1948 vmwrag law/fence ,q/l/arf/fl WW MXM I Dec. 16, 1952 L. A. MARTIN 2,621,450

ABRADING Original Filed May 1, 1948 3 Sheets-Stua-wv 2 Dec. 16, 1952 L. A. MARTIN 2,621,450

ABRAbING Original Filed May 1, 1 948 5 Sheets-Sheet 3 iii . WWMX Airman-'2':

l atented Dec. 16,, 1955 ABRADING Lawrence A. Martin, White Bear Township, Ramsey County, Minn., assignor to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware Original application May 1, 1948, Serial No.

1952, Serial No. 292,446

1 Claim.

This invention relates to machines for shape grinding, e. g., for grinding curved surfaces, particularly the edges of relatively thin objects such as sheets of metal, glass, plastic, wood, stone and other materials.

Heretofore such operations have been accomplished by abrasive belt abrading or grinding machines, applying the edge of the work piece along the length of the belt and using a backup or contact wheel having a periphery complementary in shape to the desired contour of the object being abraded. Such arrangements have certain disadvantages. One is the failure of the belt to bend or curve into exact conformity with the periphery of the contact wheel, due to the stiffness of the belt and/or the sharpness of the contours. Another is belt wastage; the margins of the belt are usually untouched insuch operations.

Abrasive wheel abrading or grinding machines have also been heretofore used, the wheel (like the above mentioned belt contact wheel) having a shaped periphery complementary to the desired contour of the object being abraded. A disadvantage of this is the necessity for a different wheel for each desired shape. Another is wheel wastage. The wheel wears and loses its desired shape so that it must be discarded if accurate grinding is desired; additionally, the wheel usually wears only along the center of its periphery, leaving the edges of the periphery or corners of the wheel unused.

Objectives of the present invention therefore include the provision or abrading or grinding machines capable of using heavy duty belts or wheels that will produce, grind, abrade and/or polish surfaces of a given contour on hard materials accurately and with a minimum of belt or wheel waste.

Briefly, the invention provides for bringing the work piece into contact with a rotating abrasive implement (e. g., a rotating abrasive belt contact wheel or a rotating abrasive wheel) and at the same time moving the implement with its axis of rotation always parallel with itself in a direction perpendicular to its axis in a path complementary to the desired contour.

The invention may be employed to give a square or angular shaped edge a curved shape, or to polish, abrade or otherwise further finish an edge that is already curved. It may also be employed to form or finish a square or straight edge.

As illustrative embodiments, an abrasive belt machine and an abrasive wheel machine for the Divided and this application June 9,

edge grinding of sheets of glass are described below and illustrated in the accompanying drawings in which:

Figure 1 is a side elevation of an abrasive belt machine with a portion of the frame broken away;

Figure 2 is a front elevation;

Figure 3 is a plan view of the forward portion;

Figure 3a is a greatly enlarged fragment of the sectional view of one of the two circular oscillator plates that appears in Figure 3, to show the shims;

Figure 4 is an enlarged side elevation of the oscillator;

Figure 5 is a diagram showing relative movements of certain parts;

Figure 6 is a side elevation of an abrasive wheel machine;

Figures 7, 8 and 9 are diagrams of alternative forms; and

Figures 10, ll, 12, 13 and 14 show various edge shapes that can be ground on the illustrated machines.

Three pulleys ll, l2 and I3 support an endless abrasive belt I4 (Figures 1 to 5). The belt is driven by the driving pulley II which in turn is driven or rotated by a motor 15 through a driving belt Hi.

The pulley l2, which is the contact roll or wheel, is rotatably mounted on a spindle or journal l9 that is fixed in a reciprocator or oscillator. The oscillator comprises two vertical parallel circular plates 20 and 29' connected by a spacer bar or girder 2|. A stationary cradle is formed of two upright frames 22 and 22' having circular openings with inside circular tracks that are shaped to make a sliding fit with the peripheries of the plates so as to support the oscillator in a manner to permit oscillating it about its horizontal axis 23. The said axis is indicated by the point 23 in Figure 4, and is sometimes referred to herein as the axis of oscillation.

For ease of assembly and future adjustment for wear, both of the plates 29-20 have V-shaped peripheries and are split radially into two halves l2ll-l2ll' and 228-220 along the groove of the V with a number of very thin sheets 8-8 or" metal inserted between the halves to serve as shims. Removal of a shim permits the two halves of a plate to be drawn closer together and thus take up peripheral wear.

The contact wheel I2 is rotatably mounted on the outer or right hand surface of the oscillating plate 20 with its axis parallel with the axis of oscillation. The spindle i9 is adjustably fixed in the plate so that it may be moved toward or away from the axis 23, as desired. The periphery of the contact wheel [2 is normally positioned slightly below the axis of oscillation.

The plates Eli-29' are cut away about their centers and a sector is removed from their upper portions to permit passage through the oscillator of a work piece 2d along a guide groove that is cut in a guide bar or rack 26. The plates are thus, in effect, crescent shaped, with their outer peripheries sliding in the circular tracks in the upright cradle frames 22-22.

The oscillator assembly is oscillated about its axis 23 by an arm 21 which is fixed to the spacer 21 of the assembly and is moved up and down by a pitman 28. The pitman is operated by a crank wheel 29 which is rotated through a worm gear assembly 36 by a motor 3!. Such an arrangement produces an advantageous variable speed oscillation. When the contact wheel 12 is at the center of its oscillation, the pitman is midway of its downward (or upward) travel (Figure 1) and is moving at its fastest rate of speed. As the pitman nears the end of its stroke, its speed gradually slackens until it reaches zero at the turning point. The result is that when contacting the center of the glass where only a little abrasion is needed, the oscillating movement of the contact wheel 32 is rapid and it passes quickly over the area; but when contacting the corners where the grinding is heavy, the movement is slow and the contact wheel thus dwells longest where it is most needed.

When the oscillator 20-20 is oscillated about its axis 23 in the cradle '2222, the rapidly spinning contact wheel 12 is reciprocated with its axis always parallel with itself (i. e., with its axis always parallel with its immediately previous position) in a direction perpendicular to its axis, in a path complementary to the surface being formed or ground. The contact point or contact line of the wheel [2 will reciprocate or oscillate in a circular path about the axis of oscillation 23, and the lower edge of the work piece 25 will be ground to a shape complementary to the said path, i. e., the piece will be given a cylindrical edge, i. e., a convex rounded edge that is circular in cross section such as is shown in Figure 10 or 11 (sometimes called a pencil edge). The axis of oscillation 23 lies wholly within the guide groove 25. The bottom of the groove is below the axis so that the bottom edge of the work piece 24 will contact the abrasive belt I4 on the contact wheel I2 when the work piece is advanced through the machine along the path defined by the groove. The path of the object lies within a plane that is determined by the axis of oscillation and that at the same time is always parallel with the axis of the contact wheel H.

To compensate for the movement of the abrasive belt l4 that is caused by the oscillation of the contact wheel I2, and to keep the belt taut, the idler pulley I3 is rotatably mounted on an upright arm which is pivoted at 35. A horizontal arm 31 extending from the arm 35 is impelled downwardly by a spring 38, whereby the upright arm 35 and with it the pulley i3 is impelled forwardly to maintain a desired tension on the abrasive belt M. The spring yields when the pulley i3 is impelled rearwardly by the belt when the contact wheel l2 moves from its center position toward either extremity of its oscillation.

Positional adjustment of the idler pulley l3 4 may be made by moving the bed plate 49 which supports the arm 35, rearwardly or forwardly by the screw assembly 4!.

Where it is desired to use an abrasive wheel as the abrading implement rather than an abrasive belt, the contact wheel 12 of the described belt machine may be replaced by an abrasive wheel H2 and a driven pulley ill, both fixed to each other and journaled on the spindle 19 (Figure 6). The illustrated abrasive belt I4 would then be replaced by a power or driving belt I 14 which would drive the pulley H7 and thereby rotate the abrasive wheel H2. The operation and construction would otherwise be as herein described in connection with the use of an abrasive belt, with the wheel H2 swinging or oscillating about the axis 23 in the same manner as the abrasive belt contact wheel 12 so as to abrade the lower edge of the work piece 24. A single machine could thus be equipped with interchangeable parts so as to employ either an abrasive belt or an abrasive wheel, as desired.

It will thus be seen that the invention involves certain prescribed movements of what may accurately be termed rotating abrasive implements.

The illustrative examples of a rotating abrasive implement that are specifically described and illustrated herein are (1) an abrasive belt that is supported by the periphery of a contact wheel (which may also be described as a contact wheel carrying on its periphery an abrasive belt) and (2) an abrasive wheel. These two examples, in turn, may accurately be termed abrasive surfaced wheels.

Other implements that abrade by being rotated about their own axes with their peripheries in contact with the work, are also contemplated by the invention.

The abrasive wheel l l2 may be a solid abrasive wheel or it may comprise a non-abrasive core coated on its periphery with a layer or thickness of abrasive substance. The term abrasive wheel as used herein, is intended to embrace both.

Numerous other alternatives and equivalents may be employed that embody the principles of the invention.

The construction of the oscillator may vary. For example, it could comprise a single plate, such as the plate 28, and such plate (or both plates if there are two) may be of a shape or design other than that illustrated as long as it will clear the work that is being passed through the machine and oscillate the contact wheel about an axis parallel with the axis of the wheel.

The path of reciprocation or oscillation of the contact wheel 12 here shown as circular, may follow the contour of other desired shapes, e. g., of an oval, an ellipse, a compound curve, a reverse curve, etc. Also the path may be straight, if desired. The non-circular curved shapes are usually used in connection with work pieces that are relatively thick.

Apparatus suitable for producing reciprocations or oscillations of the contact wheel in paths other than circular is shown in diagram in Figure 7. The abrasive belt contact roll l2 rotates on a journal i9 which is slidably held in a slot 45 that is cut in a stationary bearing plate 45. The journal [9' and with it the contact wheel i2 is reciprocated in the slot by a crank 29 and pitman 28. The slot 45, here shown as of a non circular curved shape, may be of any desired shape. Its shape will be reproduced on the surface or edge of the work piece 2 3 being ground.

For example, if the slot is a portion of an ellipse. the piece will be given a cylindroid edge, i. e., a convex rounded edge that is elliptical in cross section. If the slot is straight, as shown in Figure 8, the piece will be given a straight edge, such as the square edge shown in Figure 14. If the slot has a downward curve such as shown in Figure 9, the piece will be given a. concave edge such as shown in Figure 13.

When the path of reciprocation is circular, as in the machine shown in Figures 1 to 5, the edges of work pieces will variously appear as shown in Figures 10, 11 and 12, depending on the distance between the contact wheel and axis of oscillation 23. In forming the edge shown in Figure the point or line of abrasive contact was below the axis a distance equal to half the thickness of the work piece, and the resultant edge is semi-circular in cross section; in Figure 11 the point of abrasive contact was below the axis more than half the said thickness; and in Figure 12 the point of abrasive contact and the axis of oscillation coincided. Holding the contact wheel at one point without reciprocation will produce a concave edge such as that shown in Figure 13.

The path of movement of the work piece here shown as being along the axis of oscillation in a straight line to accommodate the straight edge of the illustrated work piece, may be curved in respect to horizontal to accommodate a work piece having a curved edge, such as automobile window glass, and yet still be straight in respect to vertical. It would lie within a plane that is determined by the axis of oscillation. Such a path is still regarded as being along the axis of oscillation within the meaning of that phrase as used herein.

It will be understood that the terms vertical, horizontal, front, back, top, upper, upright, etc. are relative and not limiting, because the illustrated machines that here show the work piece in a vertical position with the edge that is being ground in a horizontal position, may be constructed and/or positioned so that the work piece would be, for example, horisaonltal or the edge being ground would be verica Machines may of course be constructed of any size. The illustrative machine shown in Figures 1 to 5 has an abrasive belt contact wheel I2 measuring 5" x 5" and it has successfully'produced and finished edges on sheets of glass ranging in thickness from A" to A".

The use of the full width of the abrasive belt of life. Belts used according to the present invention for the edge grindling of sheets of glass have been found to possess at least ten times the life of the same belts when used in machines and methods heretofore known. Consequently, the abrasive belt machine and method provided by this invention is far superior to any means for the edge finishing of glass heretofore known.

The abrading of objects of all kinds, made of a variety of materials as previously mentioned,

is contemplated. Such objects include glass doors, automobile window glass, marble slabs, laminated wood, plastic sheets, etc.

The examples herein show the abrading of the narrow surfaces of relatively thin objects, such narrow surfaces commonly being called the "edges." The abrading of other types of surfaces, however. is also contemplated. For example, the edges of an article such as a sheet of glass, may be beveled by tipping the sheet at an angle and abrading the corners of the edge; 1. e., where the broad surfaces of the glass and the narrow edge surface meet.

This application is a division of the copending application'of Lawrence A. Martin, Theodore J. Miller and Lluellynn A. Wright Serial No. 24,486 filed May 1, 1948.

Iclaim:

In an abrasive belt machine for abrading an edge of a sheet of glass; a plurality of pulleys for supporting an endless abrasive belt, one of the pulleys serving as a contact wheel; means for rotatably mounting the pulleys; means for reciprocating the contact wheel mounting in a direction perpendicular to the wheels axi with the said axis always parallel with itself; and guide means for maintaining a sheet of glass in a plane that is parallel with the wheel's axis and for conducting the sheet across the width of the belt where the belt is trained around the contact wheel in a path lying along an edge of the sheet with the edge in position to contact the belt.

LAWRENCE A. MARTIN.

No references cited.

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