US2997816A - Polishing apparatus - Google Patents

Description

Aug. 29, 1961 E. HOYET ET AL POLISHING APPARATUS Filed Aug. 25, 1959 IN V EN T 0R.

F'l G. 3

ATTOE/VEY 2,997,816 POLISHING APPARATUS Eugene Hoyet, Ford City, and Albert E. Junge, New Kensington, Pa., assignors to Pittsburgh Plate Glass Company, a corporation of Pennsylvania Filed Aug. 25, 1959, Ser. No. 835,969 12 Claims. (Cl. 51---112) This application relates to polishing apparatus and more particularly to improved polishing apparatus for use in the production of polished strip or ribbon material, such as ground and polished plate glass.

In the manufacture of plate glass, molten glass issues from a glass melting furnace and is formed, by means of a pair of cooperating rolls, into a ribbon of predetermined Width and thickness. This rough rolled plate glass, as it is called, is conveyed through an annealing lehr and is then ground and polished by rubbing the surface with abrasives to produce the finished product.

There are several known methods for grinding the rough rolled plate glass. The glass may be twin ground, in which case, the continuous annealed ribbon is conveyed between opposed grinding runners which simultaneously grind both major surfaces of the glass. In another method, the annealed ribbon is cut into sheets of predetermined length, the sheets are laid on tables which are propelled through a grinding apparatus, and the glass is ground on successive surfaces.

Twin grinding of the ribbon may be followed by twin polishing, wherein the continuous ribbon is conveyed between opposed polishing runners which simultaneously polish both major surfaces of the glass, after which the ribbon of ground and polished glass is cut into the desired sizes for ultimate use.

After a ribbon of glass is twin ground it may be cut into sheets of predetermined length, the sheets laid on tables which are propelled through a polishing apparatus and the glass is polished on successive surfaces.

Where sheets of predetermined length are ground on successive surfaces, polishing of a ground surface follows the grinding operation.

In twin polishing apparatus, the general practice is to rotate the opposing polishing runners in opposite directions, so as to balance the torque applied to the glass ribbon and thereby prevent its breakage. Also, it is necessary to support the glass ribbon from the bottom to prevent its deflection and possible breakage. Support means associated with the bottom polishing runners to support the ribbon against deflection have been suggested in the prior art. In one prior apparatus, a relatively narrow ring member positioned centrally of the bottom runner provides ribbon support. This prior device, however, performs no other useful function and may adversely affect the finish of the glass surface.

It is proposed according to the instant invention to provide a polishing runner construction for use as a bottom polishing runner with twin polishing apparatus which is so constructed to support the ribbon against deflection, and also to improve the finish of the glass surface.

Because the runner construction of this invention provides an improved surface finish, the runner may also be used as an upper runner in twin polishing apparatus or as a runner in polishing apparatus wherein only the upper surface of the glass is polished at any one time.

Conventional polishing runner assemblies are constructed of a power driven spider having a plurality of freely rotatable polishing runners circularly mounted thereon; the runners being freely rotatable about predetermined axes. Each runner therefore moves within certain circular paths.

Certain defects which impair the optical quality of ground and polished plate glass may be introduced duratent i it '1' f ing the polishing operation. One such defect is known as sweep. Sweep is characterized by a plurality of parallel, arcuate, shallow grooves of smoothly varying depth and possesses a comparatively regular pattern having a modified sinusoidal elevational configuration across a section of glass.

The optical effect of sweep may be materially reduced if the regular pattern is modified.

The polishing runner of the instant invention, by its construction modifies the regular pattern of any sweep which may be introduced on the polished glass surface.

In addition the runner of the instant invention is constructed to have a high felt area travel, i.e., considerable felt area is located in the high velocity zone of the runner, so as to increase the polishing action of the runner over the conventional runners operating at the same speed of rotation.

Broadly, this invention includes a runner assembly constructed of a power driven runner support rotatable about a fixed axis, a plurality of freely rotatable polishing runners circularly mounted on the runner support, each runner being freely rotatable about predetermined axes, and a plurality of runner blocks, hereinafter referred to as blocks, fixedly connected to the runner support, at least one of which is positioned between each pair of rotatable runners. The blocks fixedly connected to the runner support are preferably substantially pie or wedge shaped in plan.

The combination of motion of the freely rotatable runners and the fixed block, both connected to the rotatable runner support, modifies any regular pattern of sweep introduced on the surface of the ribbon. The fixed blocks also, when such an assembly is used as a bottom runner in twin polishing apparatus function to support the glass ribbon against deflection as well as improve the finish imparted to the glass. The fixed blocks, being located adjacent the periphery of the runner support, are in a high velocity zone thereof and increase the felt area travel giving rise to good glass polishing action. The addition of these fixed blocks results in a material decrease of runner support velocity to obtain the same polishing action as compared with runners wherein they are not employed.

In the accompanying drawing forming a part of this disclosure and showing a preferred embodiment of the invention:

FIG. 1 is a plan view of a runner assembly constructed according to the teachings of this invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1; and

FIG. 3 is an elevational view of a twin polishing apparatus employing the runner assembly of this invention.

In the drawing, there is shown a runner support 10, which may be a circular metal plate or of web construction to reduce mass, connected to a shaft 12. The shaft 12 is drivingly connected to a suitable driving means, such as a motor (not shown). The shaft 12 is journaled for rotation in bearings 14, preferably of the ball or roller variety. The runner support 10 is provided with joined cavities 16 and 18 located substantially equidistant from its rotational axis and spaced substantially equally about its periphery to receive bearings 20 and 22 preferably of the roller or ball variety. Circular runners 24, having conneoted shafts 26 are provided, the shafts 26 being journaled for free rotation in the bearings 20 and 22. Blocks 28 are fixed to the runner support 10 adjacent its periphery and each is preferably positioned between a pair of adjacent runners 24.

Attached to each runner 24 and blocks 28, as by a suitable cement, is a resilient pad 30, and such as sponge rubber or other elastomer, and attached to each pad 3.0,

also as by a suitable cement, is a surfacing material 32, such as a felt pad.

In the illustrated polishing assembly, there are three runners 24, equidistant from each other and three blocks 28, each spaced from a pair of adjacent runners 24. The perimeter of the runner support defines the perimeter of the assembly, so that the blocks 28 are substantially pie or wedge shaped in plan and are defined by arcs having a diameter equal to that of the runner support and two edges complementary to the perimeters of the runners 24. These defining edges are joined by straight lines in such a manner that no sharp portions or projections exist which could dig into the surface of the glass and cause polishing ditficulty.

In FIG. 3, there is illustrated a twin polishing apparatus employing the runner assembly of this invention as both top and bottom runner assemblies. The glass G is conveyed by means of spaced pinch rolls 34 through the top and bottom runner assemblies. Means (not shown) are provided to rotate the runner assemblies in opposite directions, as indicated by appropriate arrows. As will be obvious from an inspection of this drawing, the runner assembly of this invention provides ribbon support throughout its entire area of contact, so as to prevent deflection of the ribbon of glass G between the spaced pinch rolls 34. i

It will be noted that as the runner support 10 rotates, each of the fixed blocks 23 also rotate in the same circular path while each of the freely rotatable runners 24 rotate not only in the same circular path but also in circular paths about their own axes; thus, the combined motion is effective to modify any regular sweep formation or pattern.

As a specific example, a runner assembly constructed according to this invention has successfully twin polished glass. In this assembly, the runner support 10 had a diameter of 32 inches, and there were three runners 24 and three blocks 28, each freely rotatable runner 24 had a 14 inch diameter and the fixed blocks 28 were spaced one inch from the runners 24. In this example the ratio of the area of the freely rotatable felts to the fixed felts was 2.4: 1.

It is to be understood that the number of freely rotatable runners and fixed blocks may differ from that described without departing from the spirit of this invention. Also, while it is preferred to have the area of the freely rotatable felts to the area of the fixed felts bearing a ratio of 2.4:1, it is to be understood that other ratios may be employed without departing from the spirit of the invention.

We claim:

1. Apparatus for polishing sheet material, such as glass, comprising a runner support adapted to be rotated about a fixed axis, a plurality of runners connected to said runner support for rotation therewith and for free rotation about predetermined axes, and a plurality of blocks fixed to said runner support, each of said runners and blocks having a surfacing means attached thereto for rubbing contact with said material, at least one of said blocks being positioned between an adjacent pair of runners.

2. Apparatus as recited in claim 1 wherein there are an equal number of runners and blocks and each block is positioned between an adjacent pair of runners.

3. Apparatus as recited in claim 2 wherein said runners are equally spaced about the periphery of said runner support and an equal distance from said fixed axis, and said blocks are also equally spaced about the periphery of said runner support and an equal distance from said fixed axis.

4. Apparatus as recited in claim 3 wherein the perimeter of the runners and said block is defined by the perimeter of the runner support.

5. Apparatus as recited in claim 4- wherein there are three runners and three blocks and the ratio of surfacing 4 area of said runners to the surfacing area of said blocks is 2.4 to 1.

6. In a polishing apparatus for simultaneously surfacing the top and bottom surfaces of a ribbon of sheet material, such as plate glass, conveyed between opposed polishing means and including a runner assembly for polishing the top of said material, the improvement comprising, a polishing runner assembly for polishing the bottom of said material, said assembly comprising a runner support adapted to be rotated about a fixed axis, means for rotating said runner support about said fixed axis, a plurality of polishing runners connected to said runner support for rotation therewith and for free rotation about predetermined axes, and a plurality of polishing blocks fixed to said runner support, at least one of said blocks being positioned between a pair of adjacent freely rotatable runners, said fixed blocks serving to support said ribbon of material against deflection from a predetermined plane while performing a polishing operation on said material.

7. Polishing apparatus as recited in claim 6 wherein there are an equal number of runners and blocks and each block is positioned between an adjacent pair of runners.

8. Polishing apparatus as recited in claim 7 wherein said runners are equally spaced about the periphery of said runner support and an equal distance from said fixed axis, and said blocks are also equally spaced about the periphery of said runner support and an equal distance from said fixed axis.

9. Polishing apparatus as recited in claim 8 wherein the perimeter of the runners and said block is defined by the perimeter of the runner support.

10. Polishing apparatus as recited in claim 9 wherein there are three runners and three blocks and the ratio of surfacing area of said runners to the surfacing area of said blocks is 2.4 to 1.

11. In a polishing apparatus for simultaneously polishing the top and bottom surfaces of a ribbon of sheet material, such as plate glass, conveyed between opposed polishing means, the improvement comprising opposing polishing runner assemblies for simultaneously polishing the top and bottom of said material, each said assembly comprising a runner support adapted to be rotated about a fixed axis, and in opposite directions, means for rotating each runner support about said fixed axis, a plurality of polishing runners connected to each runner support for rotation therewith and for free rotation about predetermined axes, and a plurality of polishing blocks fixed to each runner support, at least one of said runner means being positioned between a pair of adjacent freely rotatable blocks, said fixed runners of said bottom runner assemblies serving to support said ribbon of material against deflection from a predetermined plane while performing a polishing operation on said material.

12. Apparatus for polishing sheet material, such as glass, comprising a support adapted to be rotated about a fixed axis, a plurality of polishing means connected to said support for rubbing contact with said glass, at least one of said polishing means being connected to said support for rotation with said support and for free rotation about a predetermined axis other than said fixed axis and at least another polishing means fixedly connected to said support for rotation only with said support, said polishing means presenting a substantially greater surface area in a zone adjacent the periphery of said support and in a high velocity zone of said support than in a zone adjacent the fixed axis of said support and in a low velocity Zone of said support.

References Cited in the file of this patent UNITED STATES PATENTS 2,511,831 Adamson June 20, 1950 2,567,163 Wallace M Sept. 4, 1951 2,757,489 Touvay Aug. 7, 1956

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