US2420989A - Method and apparatus for polishing flat glass - Google Patents

Description

y 20, 1947- F. B. WALDRON 2,420,989

METHOD AND APPARATUS FOR POLISHING FLAT GLASS Filed March 50, 1945 12 /0 o T 26 A I: x-Q 55A J \\\\\\\\x\\\\\\ i ff 27 l3 7 FIG. 3. 36a

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:3 y .L 2a A m *2 I I i a nvenor Attorneys.

Patented May 20, 1947 METHOD AND APPARATUS FOR POLISHING FLAT GLASS Frederic Barnes Waldron, Prescot, England, assignor to Pilkington Brothers Limited, Liverpool, England, a British company Application March 30, 1945, Serial No. 585,684 In Great Britain March 28, 1944 3 Claims. 1 This invention relates to methods and apparatus for polishing flat glass.

In the usual apparatus for polishing fiat glass, pads are carried on supports which are mounted on frames, so that the pads are free to rotate on their axes, the frames rotating about axes normal to the surface polished. The frames are either positively rotated, or they are mounted, so as to be free to rotate as subsidiary frames, on a positively driven central frame.

Pads are so located on their frames, that during the rotation of the frames, each pad at intervals passes over the edge of the glass. Usually, the pads are located so that about half the area of the pad extends over the edge of the glass. The pads are sometimes mounted so that they are capable of small angular movement relatively to the plane oftheir faces, whereby they arelfree to bed themselves on the glass. Also they are sometimes mounted on axes in a fixed direction, and this direction is either vertical or slightly inclined in such a direction that, when a pad is extending over the edge of the glass, the edge of the pad beyond the glass is retracted from the plane of the surface of the glass. In the following description the pad will be said to be tilted inwards when its outer edge, when overhanging the glass, is so retracted.

In the process of polishing, the rouge forms a layer on the surface of the pad, and this layer, when it is fresh and moist, is effective for polishing. With continued operation, however, the layer thickens and becomes hard and dry, and it is then less effective.

Devices have been employed for cleaning the pads, that is to say for removing the layer which has become hard and dry, but they all entail an interruption in the polishing process. In the case of continuous polishing apparatus, in which the glass travels under or between a succession of polishing tools, the interruption of the operation of a tool is particularly harmful.

The main object of the present invention is to maintain the rouge on the pads of tools in a condition in which it is most effective for polishing, without interrupting the polishing process carried out by apparatus employing a succession of tools as hereinbefore mentioned.

The present invention consists in a method of removing a layer of rouge, or the outer surface of such a layer from polishing pads during the pol ishing of flat glass, wherein the pads are periodically tilted outwardly, from their normal predetermined operative position to a temporary op erative position in which they intersect the plane of the glass surface being polished by the pads as the latter pass over the edge thereof so that the edge of the glass is employed to scrape rouge from'the pads whilst they are so tilted, and, when 5 the said edge has scraped the hard and dry rouge from the pads, they are returned to their normal operative position.

Apparatus for polishing flat glass according to the present invention comprises a plurality of polishing pads each carried on a disc rigidly mounted on a pin disposed as a normal to the respective disc, each said pin being in turn connected by a support to a rotatable frame mounted to rotate over the glass and cause each polishing pad to travel on the glass in a circularpath,

, characterised in that each pin support is constituted as a socket to house a pin and is mounted on the frame about a chordwise axis disposed in a plane parallel to the plane of the pads to be tiltable relatively to the frame, setting means adapted to dispose each socket in a predetermined normal position for polishing, and means for actuating said setting means during the rotation of the frame to outwardly tilt the sockets from the said normal position to a predetermined tilted position, whereby the pads may be deflected from the normal position to a predetermined extent for the purpose specified and to return the sockets to normal position.

Preferably the said setting means includes an arm attached to each socket and extending inwardly of. the frame, and an axially displaceable member carried by the frame and engaging the inner ends of all the arms operatively connected to said actuating means.

The support may be hinged to the frame of the tool by employing a pivot pin, or since the tilting movement required is extremely small (less than one degree) the hinging of the support to the frame may be effected by connecting the support to a flexible plate, in turn secured tothe frame so that as the plate flexes the support is virtually hinged to the frame.

The invention is applicable to polishingappm ratus of the kind in which the glass is supp d on a table which carries the glass under a series of polishing tools, or to a polishing apparatus of the kind comprising upper end lower co-axial polishing tools, between which the glass to be 'polished passes as a ribbon and is supported by the lower tools and intermediate driving rollers, or to polishing apparatus of the kind in which the glass is carried on a rotating table.

From the foregoing it will be observed that a machine minder, watching the process of polishing glass carried out in apparatus of the kind referred to, will, on seeing that the muse is becoming too dry, cause an outward tilting of the polishing pads to be effected in order to remove the hard dryrouge layer from the polishing pads, and that when a pad is slightly tilted outwards,

the edge of the glass acts to scrape rouge from the pad, during the passage of the pad over the edge. If then, during the polishing operation, the pads are tilted outwards is described, the scraping action of the edge of the glass gradually removes the hard and dry layer, or the hard and dry part of the layer. The pads are then untilted, or preferably, tilted slightly inwards, and they are then operating in conditions favourable for taking up fresh rouge to form a layer which is effective for polishing.

Thus, by operating the polishing apparatus with the pads alternately tilted outwards and in their normal operative position, the rouge on the pads is maintained in a condition which is effective for polishing, without any interruption of the polishing process.

In order that the invention maybe more clearly understood some preferred embodiments as incorporated in polishing apparatus including coaxial tools operating simultaneously on both faces of a ribbon of flat glass as it comes from the grinder, will now be described by way of exampie with refemnce to the accompanying diagrammatic drawings, in which Figure 1 is a fragmentary elevation, looking along the middle line of a ribbon of glass of a polishing tool, in which the hinge of the pad support comprises a pivot pin carried chordwise on the tool frame on the outside of the pad support;

Figure 2 is a view similar to Figure 1 showing a modification consistingin the manner of hinging the support, and

Figure 3 is also a view similar to Figure 1.

In the drawings like references designate the same or similar parts.

Referring to Figure 1, the ribbon of glass l is polished by pads 2 which, as is usual, are carried on discs 2a rotatably mounted on pins 2b carried in supports 3. The support 3 is in nature a socket for the pin 2b which is tiltable in a plane which is normal to the glass by being pivoted at 4 about a chordwise axis to a bracket 5 depending from a frame 6 rotated by the central shaft 1. A rod 9, having bearing collars I0, is adapted to slide vertically in a casing ll fixed centrally by a flange a to the lower surface of the frame 8. A bar l2 emanates from each support 3 and each bar has its end l3 engaged by the collars Ill, and each support takes its setting from the disposition of its bar so that, when the rod 9 is moved upwards, the pad 2 is tilted outwardly in the angular direction of the dotted line I, but only to an amount somewhat less than 1.

The upward motion of the rod 9 is given by the hydraulic thrust device I5, of known type,

which has a limited travel which is attached to the frame 6. When hydraulic pressure is applied to the thrust device l5, the end l6 of its piston rod turns the bar l1, pivoted at 18 on the casing H, in a counterclockwise direction. The end IQ of the bar I! inside the casing II is formed as a fork-straddling a flat on the rod 9, thus engaging a shoulder 20 on the rod. Counterclockwise rotation of the bar I! therefore moves the rod 9 upwards and outwardly tilts each pad 2 operatively connected thereto in the same manner.

The pads operate at such a radius that during rotation they overhang the edges of the ribbon of glass; the amount of overhang, as shown,

is commonly about half the diameter of a pad 2. When a pad thus tilted is overhanging the glass, its outer overhanging edge intersects the plane of the surface of the glass on which it is operating. The edge of the glass thus exercises a scraping action on the pad, as the pad, in its rotation, is brought fully on to the glass.

The amount of the tilt found suitable is too small to be shown in the drawing, being of the order of onesixth of a degree, that is to say a mere deflection of a polishing pad from the operative position. For a pad 20 inches in diameter, this is equivalent to a lift or depression of the edge relatively to the centre of 0.03 inch; the surface of the pad, being yielding, does not therefore come out of contact with the glass;

For the normal polishing operation the pad may rest on the glass with its pin 2b in a vertical position, but preferably the pad is slightly tilted in the opposite direction to that shown by the line M. It may also be slightly tilted in the same direction as for cleaning the pads, but to a much less extent.

The parts may be so arranged that, when the piston of the thrust device [5 is in its home position shown, the pad occupies the desired normal angular position. This, however, may be made adjustable by means of the nuts 2| on the screw 22 fixed to the frame 6, the nuts engaging a bracket 23 fixed to the bar 12 and thus limiting. the downward position of the bar l2 at this point. Thereby, after the cleaning operation has been effected, the pads are returned to the pristine angular position for normal operation.

In Figure 1, the tool is shown operating on the upper surface f a ribbon of glass of which the under surface is operated on simultaneously by a similar tool which also serves to support the strip. The pads of the lower tool are then similarly mounted so as to be capable of being tilted.

Figure 2 shows an alternative mounting of the pad 2. The support 3 is bolted at 24 to a strip of steel 25 which is flexible and is bolted to a lug 26 on the frame 6. The bar l2 may either emanate from the support 3 or, as shown, be connected to the strip 25. The thrust device, which may be the same .asin the construction of Figure 1 is not shown for sake of clarity in illustration. This form of pad mounting is not essentially different from that of Figure 1, since,

for the small turning movement, the pad is eflectively pivoted about a chordwise axis.

The strip of glass I is shown on a table 21 of the form used in continuous grinding ap aratus.

Figure 3 shows the invention ap lied to the form of polishing tool in which the pads are mounted on subsidiary frames free to rotate on a central frame. The supports 3 are pivoted about chordwise axes as in Figure 1 to lugs 5 on the subsidiary frame 28, which is free to turn in the central frame 6. The pads are tilted as in the constructions described with reference to Figures 1 and 2 by bars l2 engaged by collars I on a rod 9 capable of upward movement centrally in the subsidiary frame 28; The rod 9 extends above the frame 6 and has pivoted to it at 29 a bar 30 pivoted at 3| to a bracket 32 on the frame 6. The other end of the bar 30 is engaged by collars 34 on a rod 35 adapted to slide downwards inthe centre of the frame 6.

The rod 35 is moved upwards, to outwardly tilt the pads. by an electric motor 36 fixed to the frame 6 and provided with a reduction gear 36a adapted to rotate the screw 31. A nut 39 on the screw 31 has pivoted to it at 39 a bar 49 which is pivoted at 4| to a bracket 42 on the frame 6. The inner end of the bar 40 is forked and pivoted at 43 to a collar 44 on the rod 35, engaged between a securing collar 45 and the lower collar 34.

If the motor 33 be turned to move the nut 38 upwards, the rod 35, and the right hand end of the bar 30, are moved downwards and consequently the rod 9 is lifted to tilt the pads in the desired outwardly direction.

Both the hydraulic thrust device and the electric motor 36 are operable by well known methods during the rotation of the polishing tool,

. and therefore the tilting of the pads can be effected without interruption of the polishing operation.

The construction shown in Figures 1 and 2 permits the use of any desired number of pads to be carried on the frame 6, each pad being tiltable by reciprocation of the central rod 9. Similarly the construction shown in Figure 3 permits the use of any desired number of subsidiary frames, each carrying any desired number of pads. It is to be understood that the complete polishing apparatus comprises a plurality of tools operating in succession on the traveling glass.

In operation, the machine minder, on seeing that the rouge on the pads of any tool has become unduly hard and dry, will operate the tilting device to tilt outwards all the pads of the tool. When the resulting scraping action by the edge of the glass has sufficiently cleaned the pads, he will operate the device toreturn the pads to their normal position. And these operations will be effectedwithout interruption of the polishing process.

By the present invention standard forms of apparatus. at present employed for polishing sheet or plate glass may be modified to assure that the rouge on each individual polishing pad is maintained in good condition for polishing, without interrupting the process of polishing carried out by such forms of apparatus.

I claim:

1. In the polishing of flat glass by polishing pads each of which passes over the edge of the glass at intervals during the polishing operation and to which pads rouge is supplied, the method of removing hard and dry rouge from the polishing pads during the polishing operation, wherein the pads are periodically tilted outwardly from 0 her carried by the their normal predetermined operative position to a temporary operative position in which they intersect the plane of the glass surface being polished by the pads as the latter pass over the edge thereof so that the edge of the glass is employed to scrape rouge from the pads whilst they are so tilted, and, when the said edge has scraped the hard and dry rouge from the pads, they are returned to their normal operative position.

2. Apparatus for polishing flat glass comprising a plurality of polishing pads each carried on a disc rigidly mounted on a pin disposed as a normal to the respective disc, each said pin being in turn connected by a support to a rotatable frame mounted to rotate over the glass and cause each polishing pad to travel on the glass in a circular path, characterized in that each pin support is constituted as a socket to house a pin and is mounted on the frame about a chordwise axis disposed in a plane parallel to the plane of the pads to be tiltable relatively to the frame, setting means adapted to dispose each socket in a predetermined normal position for polishing, and mean for actuating said setting means during the rotation of the frame to outwardly tilt the sockets from the said normal position to a predetermined tilted position, whereby the pads may be deflected from the normal position to a predetermined extent for the purpose specified and to return the sockets to normal position.

3. Apparatus according to claim 2, characterized by the said setting means including an arm attached to each socket and extending inwardly of the frame, and an axially displaceable memframe and engaging the inner ends of all the arms operatively connected to aid actuating means.

FREDERIC BARNES WALDRON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,548,105 Soderberg Aug. 4, 1925 1,872,694 Drake Aug. 23, 1932 1,934,797 Galey Nov. 14, 1933 1,836,542 Miller Dec. 15, 1931 1,687,959 Waldron Oct. 16, 1928 1,854,507 Drake Apr. 19, 1932 1,922,912 Fox Aug. 15, 1933 1,928,196 Betrancourt Sept. 26, 1933 2,372,824 Gould Apr. 3, 1945

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