US2757489A

US2757489A - Apparatus for grinding or polishing the two faces of a moving horizontal ribbon of glass simultaneously

Info

Publication number: US2757489A
Application number: US314826A
Authority: US
Inventors: Touvay Robert; Pillu Pierre
Original assignee: Pilkington Brothers Ltd
Current assignee: Pilkington Group Ltd
Priority date: 1951-10-16
Filing date: 1952-10-15
Publication date: 1956-08-07
Anticipated expiration: 1973-08-07

Description

W 1956 R muvmr ETAL -11 APPARATUS FOR GRINDING OR POLISHING THE TWO FACES OF A MOVING HORIZONTAL RIBBON OF GLASS SIMULTANEOUSLY Filed Oct. 15, 1952 5 Sheets-Sheet 1 wit.

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M I, 1956 R. TOUVAY ETAL 2, APPARATUS FOR GRINDING OR POLISHING THE TWO FACES OF A MOVING HORIZONTAL LTANEOUSLY RIBBON OF GLASS SIMU 5 Sheets-Sheet 2 Filed Oct. 15,

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APPARATUS FOR GRINDING OR POLISHING THE TWO FACES OF A MOVING HORIZONTAL RIBBON OF GLASS SIMULTANEOUSLY Filed 001;. 15, 1952 5 Sheets-Sheet '3 Y F/G.4. A 7

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9 APPARATUS FOR GRINDING OR POLISHING THE. TWO FACES OF A MOVING HORIZONTAL RIBBON OF GLASS SIMULTANEOUSLY Filed OGt 15, 1.952 5 Sheets-Sheet 4 ./9 s 4 Q N o o o Attorney;

A "R", W% W. TUUVAY mm. EWWNW APPARATUS FOR GRINDING OR POLISHING THE TWO FACES OF A MOVING HORIZONTAL RIBBON OF GLASS SIMULTANEOU-SLY Filed Oct. 15, 1952 5 sheets shee't 5 United States Patent APPARATUS FOR GRINDING OR POLISHING THE TWO FACES OF A MOVING HORIZONTAL RIB- BON 0F GLASS SIMULTANEOUSLY Robert Touvay and Pierre Pillu, Paris,'France, assignol's to Pilkington Brothers Limited, Liverpool, England, a British company Application October 15, 1952, Serial No. 314,826 Claims priority, application France October 16, 1951 Claims. (Cl. 51--112) This invention relates to grinding, lapping or polishing the two faces of a moving horizontal ribbon of glass simultaneously by means of pairs of rotating upper and lower surfacing tools.

In the polishing process, when the working surface of a polishing pad operating on the underface of the ribbon of glass is below the correct level of the working plane defined by the lower rollers for supporting and moving the ribbon between tools, for example owing to its felt wearing more rapidly than that of the other pads mounted on the same polishing tool, the ribbon is defiected when passing over this polishing pad under the pressure of the upper polishing pad and may break if the deflection exceeds a few tenths of a millimetre.

A main object of this invention is toreduce the risk of such breakage of the ribbon by preventing local saggingin a moving ribbon of glass being surfaced simultaneously on both faces, due to wear in. the tools.

Accordingly the invention is characterized by utilizing the deviation of the ribbon to initiate resetting of the respective tool in order to return the ribbon in the locality to the intended path of movement.

The invention also comprises the combination, in a glass surfacing apparatus, including pairs of upper and lower surfacing tools arranged to operate on the two faces of a moving horizontal ribbon of glass simultaneously and means to rotate the tools in horizontalplanes, of sensing means to determine the deviation of the ribbon from its intended path of movement in the locality of a pair of tools, resetting means to adjust the vertical level of the lower tool of a pair and control means to initiate operation of said resetting means to correct for any deviation thus determined.

In one embodiment of the invention, in which the path of the polishing pads of one tool overlaps the path of the pads of a contiguous tool, there is provided adjusting means to adjust the vertical level ofeach lower 'tool, sensing means located at a position adjacent the overlapping paths of the padsof contiguous tools, means to actuate the sensing means from time to time while a pad of a lower tool is passing said position, resetting means for each pad of a lower tool and control meansto initiate operation of the resettingmeans of the tool passing said position to correct for any deviation thus determined.

In order that the invention may be more clearly understood, a preferred embodiment thereof will now be described by Way of example with reference to the accompanying diagrammatic drawings, in which:

Figure l is a diagrammatic View in plan of two polishing tools operating on a moving ribbon of glass and shows the position of the sensing means,

Figure 2 is a vertical section partly brokenaway showing the part of a tool supporting a polishing pad,

:Figure 3 is a horizontal section through the partof the tool illustrated in Figure 2,

Figure 4 is a vertical section throughthe sensing means on the lines IV-IV of Figure'S,

2,757,489 Patented Aug. 7, 1956 Figure 5 is a vertical section on the lines V-V of Figure 4,

Figure 6.is a vertical section through the driving shaft of a tool showing the sensing means and its connection with a polishing pad diagrammatically,

Figure 7. is a diagrammatic plan View of the gear train operating the sensing means,

Figure 8 is a side elevation of the gear train illustrated in Figure 7, and

Figures 9, 10, 11 and 12 illustrate diagrammatically the operation of the apparatus in various circumstances.

The glass polishing apparatus comprises two contiguous pairs of upper and lower tools 1, each carrying three polishing pads 2, arranged to operate simultaneously on the two fiat faces of a moving horizontal ribbon of glass 3. In known manner means .(not shown) are provided to rotate the tools of each pair and their pads in horizontal planes. The path of the polishing pads of one tool overlaps the path of the polishing pads of the contiguous tool. Resetting means to permit adjustment of .the vertical height of each lower polishing pad 2 is. provided comprising a not 4 (Figs. 2, 3 and 6) rotatably mounted in. a tool 1 co-axial with the polishing pad 2, and an externally threaded cylinder 5, engaged inthe nut 4 rotatably supporting the polishing pad 2 and vertieally slidable in the runner 1. At a position adjacent the overlapping paths of the polishing pads of the c0ntinuoustools, (Fig. l) sensing means to determine the deviation of the. ribbon 3 from its intended path of movement is provided comprisinga domed member 6 pivoted about a horizontal axis and having a sensing head 7 at one end thereof spaced from the vertical plane containingthe pivotal axis of the pivoted member 6 and capable of engagement with the underface of the ribbon 3 to determine the deviation of the ribbon. The deviation thus determined is utilised to initiate operation of the nut 4 of the lowerpolishing pad 2, during the passage of which past the position at which the sensing head .7

is applied, the deviation occurred. Operation of the nut 4 causes the cylinder 5 to rise, thus raising the level of the lower polishing pad 2 to return the ribbon 3 in the locality of the pad to its intented path of movement.

A spindle 8 (Figs. 4' and 5) is secured within the pivoted dome member 6 and is rotatably supported in bearings 9 near the top of a cover 10 extending upwardly from a recess in the frame 11 of the polishing apparatus. The top of the cover 10 is tightly closed by a lid 12, and an inspection door 13 is provided at one side. The cover 10 is rendered fluid and light tight by rubber washers 14 vulcanised on the spindle adjacent the bearings 9 whichpermit the member 6 to rock about its axis. A rigid downwardly depending arm 15, is secured to the spindle 8 and is connected at its lower end by a regulating screw 16, with differential 'pitch, to the lower end of a downwardly depending bifurcated support 17 rotatably mountedat the upper end upon the spindle 8.

The bifurcated support 17 is also connected atits lower end by means of aregulating screw 18 to a stifi' plate spring 19 secured to a downwardly depending Y-shaped cranked lever 20, pivotally supported at its upper end on .the spindle 8. The lower end of the lever 20 extends the main driven hollow shaft 29 of atool 1, (Figs. 6, 7

and 8). The gear 28 is secured on the shaft 29 and entime switch 43.

3 gages the gear wheel 27 which has the same number of teeth. The gear wheel 26 is fixed to the shaft of the gear wheel 27 and has a numberof teeth which is a multiple of 6, namely 6k. The gear wheel 25 which is fixed to the shaft 24, engages and is driven by the gear wheel 26 and has a number of teeth which is equal to (6n]l)k. Thus each time the shaft 29 rotates (n+%) times, the

notched wheel. 22 rotates once.

An illuminated collimator 30, comprising a source of light 31, a lens 32 and a slotted mask 33, is carried by the support 17 with the ray of light from the mask directed downwardly. A slotted screening plate 34 is v mounted on the pivoted lever 20 under the collimator 30 in such a position that the rays of light from the collimator are cut off by the plate 34 when the spring '19 is unstressed. A safety screen 35 is secured to the frame 11 below the screening plate 34, and this screen prevents passage of rays of light from the slot in the screening plate when the lever 20 is positioned with the roller 21 at its lower end in engagement with an unnotched portion of the edge of the wheel 22. p A totally reflecting prism 36 is mounted below the safety screen 35 on the top of a rotatable shaft 37. A gear wheel 38 is secured to the shaft 37 and engages a gear wheel 39 secured to the shaft 24 of the notched wheel 22. The ratio of the

gears

38, 39 is inverse to the ratio of the

gears

26, 25 and is equal to 6/ (6n-l-1).

I Six photoelectric cells 40 are mounted equidistantly around the prism 36 on a ring 41. Each of the photoelectric cells 40 is connected to an amplifier 42 (Fig. 6) the output of which is connected to a make-and-break Each switch 43 is arranged in a circuit between a supply of electric current and a pair of brushes 44 within the frame 11 of the polishing apparatus.

Referring to Figures 2 and 3, each nut 4 associated with a lower polishing pad 2 is formed with a set of ratchet teeth on its periphery. A control arm 46 is pivoted within the portion of the tool carrying the lower polishing pad 2 and carries a pivoted pawl 47 at its end adjacent the ratchet teeth 45. The pawl 47 is normally urged out of engagement with the ratchet teeth by a tension spring 48, and has an armature head 49 at the tail of the pawl. An electro-magnet 50 is secured to the control arm 46 adjacent but spaced from the tail of the pawl. The electromagnet is connected to two electrically conducting rings 51 mounted on the main driven shaft 29 of the tool. Similar arrangements are provided for each of the pads of the tool, and one of the conducting rings 51 is common to all three electro-magnets. The brushes 44 bear upon their respective rings 51.

The other ends of each of the control arms 46 carry rollers 52 which engage an eccentric portion 53 of a stationary spindle 54 mounted in the frame 11 and supported at its upper end in ball bearings 55 in the shaft 29. The rollers 52 are held in engagement with the eccentric 53 by means of fiat springs 56.

A manually operable reversible worm 57 is rotatably mounted in the tool and engages a worm wheel 58 formed in the nut 4. This reversible worm and worm wheel arrangement is provided solely to give a manual means of adjustment and does not take any part in the automatic resetting.

In operation, the contiguous tools 1 revolve in opposite directions as the glass ribbon 3 passes between the polishing pads 2. Each lower tool is driven by its main shaft 29. This shaft carries with it the gear wheel 28 which drives the gear wheel 27 and thus the gear wheel 26 at the same speed as the shaft. The gear wheel 26 drives the gear wheel 25 at a speed equal to 6/(6n-I-1) times the speed of the shaft 29 as explained above. Thus the notched wheel 22 rotates once, each time the shaft 29 rotates (n|%) times. gages the notch in the wheel 22 and allows the spring 23 to rock the lever 20 about the spindle 8, once each The roller 21 thus en- 4 time the shaft 29 rotates (n+ times. Each time the shaft 29 rotates (n+%) times, a different polishing pad 2 is adjacent the position of the sensing head, first a polishing pad of one tool then a polishing pad of the other tool and so on in turn.

The rocking of' the lever 20 about the spindle 8 causes rocking of the support 17 and arm 15, by means of the spring 19, and thus tilts the dome member 6 and lifts the sensing head 7 until the latter engages the glass ribbon 3.

The lever 2 0 is tilted a predetermined amount dependent upon the depth of the notch in the wheel 22. The dome member, however, is limited in its movement by the engagement of the sensing head 7 with the glass ribbon 3. When the glass ribbon is engaged by the sensing head the arm 15 and support 17 are prevented from moving farther and the spring 19 ensures that the sensing head is resiliently urged against the ribbon 3. The relative movement between the support 17 and the lever 20 is a measure of the deviation of the level of the ribbon 3 from its intended path of movement. A deviation from this path is indicated by the collimator 30 which projects rays of light through the slotted mask 33 to strike the screening plate 34 on the lever 20. If the relative movement between the lever 20 and support 17 is suflicient, these rays of light pass through the slot in the screening plate 34 and strike the totally reflecting prism 36 below. The fixed screen 35 is provided to prevent untimely passage of the rays of light, for example after a sensing operation has been effected and the lever 20 and support 17 are returning to their inoperative positions.

The prism 36 is rotated at the same speed as the shaft 29 through the

gears

38 and 39 which have a ratio inverse to that of the

gears

26, 25 as explained above. The prism is arranged to face one of the photo-electric cells 40 when the roller 21 is in the notch in the wheel 22. Thus, each time a sensing is efiected when a particular polishing pad is passing the position of the sensing head, the prism 36 faces a particular photo-electric cell corresponding to that polishing pad.

Figure 9 shows diagrammatically the position of the collimator between sensing operations. The sensing head 7 is out of contact with the ribbon 3 and there is no relative movement between the support 17 and lever 20 so that the rays of light from the collimator strike the screening plate 34 and are reflected back, so that no light reaches the photo-electric cells through the prism.

Figure 10 shows diagrammatically the position when a sensing operation occurs without any ribbon of glass passing between the polishing tools. The sensing head 7 rises freely and there is no relative movement between the lever 20 and support 17. No light reaches the photo-electric cells through the prism.

Figure 11 shows diagrammatically the position when a sensing operation occurs with the ribbon 3 in its intended path of movement. The sensing head 7 rises to the level of the underface of the ribbon and the lever 20 continues its movement. The relative movement between the lever 20 and the support 17 is not, however, sufficient to cause the rays of light to pass through the slot in the screening plate 34 on the lever 20.

Figure 12 shows diagrammatically the position when the sensing operation occurs with the ribbon of glass sagging below its intended path of movement. The sensing head engages the ribbon and prevents further movement of the support 17. The lever 20 continues moving and brings the slot in the screening plate 34 into alignment with the rays of light from the collimator. The rays of light pass through the slot in the screening plate, past the edge of the screen 35, and enter the top face of the prism 36. Here they are totally reflected out of the side face of theprism and strike the operative face of the photo-electric cell corresponding to the polishing pad passing the position of the sensing head. The resultant signal from the photo-electric cell is amplified in the respective amplifier 42 and the amplified signal applied to the make-and-break time switch 43. The signal causes the switch to complete .the circuit from the supply of electric current to the respective brushes 44 for a predetermined period of time.

The completion of this circuit energises the electromagnet 50 corresponding to the respective polishinggpad 2, and the armature 49 is attracted thereby andthe'pawl 47 engaged in the ratchet teeth 45 ofthe nut 4. During energisation of the electro-magnet, which may last for approximately one revolution of the shaft;29, the roller 52 at the end of the control arm 46 passes over the eccentric portion 53 of the shaft 54 and oscillates the control arm, thus causing rotation of the nut 4 through a distance equal to one of the ratchet teeth. Rotation of the nut 4 raises the screwed cylinder 5 supporting the polishing pad 2. Thus the deviation of the ribbon is utilised to initiate resetting of the polishng pad in order to return the ribbon in the locality to its intended path of movement.

If no signal from the respective photo-electric cell is received, that is in any of the positions corresponding to those in Figures 9, and 11, the electro-magnet 50 remains de-energised and the pawl 47 is held clear of the ratchet teeth by the spring 48, so that oscillation of the control arm 46 does not alter the level of the polishing pad.

The spring -38, by holding the pawl 47 out of engagement with the ratchet teeth, allows the manual raising and lowering of the polishing pad by rotation of the worm 57.

While the apparatus above described effects a sensing of the level of the underface of a ribbon from time to time in a discontinuous manner, it will be understood that sensing may be effected in a continuous manner, the levels of the polishing pads being reset continuously.

The operation of the adjusting means in response to deviation of the ribbon may be effected pneumatically, or hydraulically instead of electrically. Thus the deviation may be used to cause relative movement between a valve and its seat controlling fluid pressure in a container, alteration in the pressure in the container causing operation of the raising means for the respective polishing pad.

The deflection of the ribbon may also be detected by means of a stream of air projecting on to the ribbon from a tube, the back-pressure in the tube being a function of the distance of the tube mouth from the ribbon.

The raising of each polishing pad may be effected in any suitable manner, for example, by means of an electric motor through reduction gear.

It will be understood that while reference has been made in the foregoing description to the application of the invention to a glass polishing apparatus comprising pairs of tools, each tool having at least two polishing pads the invention may equally be applied to glass grinding apparatus. In this case the polishing tools will be replaced by grinding runners. In the following claims the operations of grinding and polishing are referred to as surfacing.

We claim:

1. In a glass surfacing apparatus, including pairs of upper and lower surfacing tools arranged to operate on the two faces of a moving horizontal ribbon of glass simultaneously, the path of the polishing pads of one tool overlapping the path of the pads of a contiguous tool, and means to rotate the tools in horizontal planes, the combination of sensing means located at a position immediately adjacent the overlapping paths of the pads of contiguous tools, to determine the deviation of the ribbon from its intended path of movement at said position, means to actuate the sensing means at predetermined time intervals while a pad of a lower tool is passing said position, resetting means foreach pad of a lower tool to adjust the vertical level of the IOWClltOOl of a pair, and control means to efiect operation of the resetting means of the .tool passing said position to correct for any deviation thus determined.

2. The combination according to claim 1 wherein the sensing means comprises a pivoted member carrying a sensing head for engagement with the underface of the ribbon at a position adjacent the overlapping paths of the pads of contiguous tools, means being provided to swing the pivoted member to engage the sensing head with said underface from time to time while a polishing pad of a lower tool is passing said position.

3. The combination according to claim 2 wherein the means to swing the pivoted member comprises a lever pivoted on the same axis as the pivoted member, a re silient connection between the pivoted lever and the pivoted member, spring means connected to the pivoted lever in a direction to urge the sensing head into engagement with said underface, and cam means operated from time to time by the rotation of the tools to permit rocking of the pivoted lever under the action of the spring means to engage the sensing head with said underface while each lower polishing pad in turn is passing said position.

4. The combination according to claim 2, wherein the means to swing the pivoted member comprises a lever pivoted on the same axis as the pivoted member, a resilient connection between the pivoted lever and the pivoted member, spring means connected to the pivoted lever in a direction to urge the sensing head into en gagement with said underface, and cam means operated from time to time by the rotation of the tools to permit rocking of the pivoted lever under the action of the spring means to engage the sensing head with said underface while each lower polishing pad in turn is pass ing said position, and wherein said combination comprises a downwardly directed illuminated collimator fixed to the pivoted member to give an indication of the level of the sensing head, a slotted screening plate secured to the pivoted lever in the path of the rays from said collimator, a totally reflecting prism mounted below said collimator, means to rotate said prism in accordance with the rotation of the tools and a plurality of photoelectric cells, one for each lower polishing pad arranged equally around said prism to receive rays reflected in the prism from the collimator and each operatively connected to the control means for the lower polishing pad.

5. The combination according to claim 2, wherein the means to swing the pivoted member comprises a lever pivoted on the same axis as the pivoted member, a resilient connection between the pivoted lever and the pivoted member, spring means connected to the pivoted lever in a direction to urge the sensing head into engagement with said underface, and cam means operated from time to time by the rotation of the tools to permit rocking of the pivoted lever under the action of the spring means to engage the sensing head with said underface while each lower polishing pad in turn is passing said position, and wherein said combination comprises a downwardly directed illuminated collimator fixed to the pivoted member to give an indication of the level of the sensing head, a slotted screening plate secured to the pivoted lever in the path of the rays from said collimator, a totally reflecting prism mounted below said collimator, means to rotate said prism in accordance with the rotation of the tools and a plurality of photo-electric cells, one for each lower polishing pad arranged equally around said prism to receive rays reflected in the prism from the collimator and each operatively connected to the control means for the lower polishing pad, and wherein the resetting means comprises rotatable adjusting nuts, one mounted coaxially with each lower polishing pad on a tool, externally threaded vertically slidable cylinders each engaged in a respective nut and rotatably supporting a pad to permit adjustment of the level of the pad and Vratchet teeth on said nuts, means being provided to amplify signals received from the photo-electric cells, and wherein the control means for each lower polishing pad comprises a control arm pivoted in the tool, a pivoted pawl at one end 'of the control arm adjacent the ratchet teeth, second spring means to urge the pawl out of engagement with the teeth, an electro-magnet adjacent the tail of the pawl, means to energize the electro-magnet in response to amplified signals from its respective photo-electric cell to rock the pawl into engagement with the ratchet teeth against the action of the second spring means, and a stationary ec centric engaging the free end of said pivoted control arm I to rock the arm during rotation of the tool and cause rotation of the adjusting nut when the electro-magnet is energized.

References Cited in the file of this patent UNITED STATES PATENTS 1,729,498 Waldron Sept. 24, 1929 2,007,507 Steiner July 9, 1935 2,033,922 Cole W Mar. 17, 1936 2,148,744 Hall Feb. 28, 1939 2,590,717 Lowe Mar. 25, 1952, 2,647,347 Blanchette Aug. 4, 1953