US 3456985 A
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United States Patent O 3,456,985 TONGS Cyril Leslie Bullock, St. Helens, England, assignon to Pilkington Brothers Limited, Liverpool, Lancashlre, England, a corporation of Great Britain Filed June 15, 1967, Ser. No. 646,233 Claims priority, application Great Britain, June 28, 1966, 29,051/ 66 Int. Cl. B66c 1/48 US. Cl. 294-119 3 Claims ABSTRACT OF THE DISCLOSURE Tongs used for suspending glass in a vertical plane have tong arms pivoted together and extended beyond the pivot to form jaws which have clamping faces of granular refractory material.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to tongs for suspending glass in a vertical disposition.
Description of the prior art Such tongs are essentially used when heating sheets of glass, whether flat or curved, and conventional tongs comprise a pair of tong arms pivoted together near their lower ends by a hinge pin and extended beyond that hinge pin to form the jaws of the tongs.
The jaws of conventional tongs carry axially adjustable sharp pointed pins formed of heat-resisting steel.
The heat treatment of glass suspended by tongs in a vertical position may be followed by a rapid chilling treatment when it is desired to toughen the glass suspended by the tongs and after the chilling operation is completed the glass may be released from the tongs by lifting it with respect to the support for the tongs and thereby raising the jaws and opening the jaws to free the glass.
In the use of conventional tongs during heating operations on glass sheets, the edge of the glass held between the pins of the jaws is deformed by creating deep recesses near the upper edge of the glass.
When large sheets of glass are being treated, a considerable weight is carried by means of contact of the tong jaws over a comparatively smal area of the surfaces of the glass sheet. Consequently the tong points penetrate fairly deeply into the glass, and efforts to overcome this difiiculty by increasing the number of tongs which carry the glass sheet have not proved successful because of the difiiculty in insuring that each pair of tongs out of a considerable number is carrying its fair share of the weight of the large glass sheet. The use of a large number of tongs has tended to give unequal penetration of the tong jaws into the glass sheet, depending on how great a proportion of the weight of the glass sheet is borne by each set of tongs.
The main object of the present invention is to provide improved means of suspending the glass so as to minimise deformation of the marginal areas by which a sheet is held in vertical disposition.
SUMMARY According to the invention tongs intended for use in suspending glass in a vertical plane and comprising -,a pair of tong arms pivoted together by a hinge pin to form the jaws of the tongs, is characterised by the jaws having clamping faces of granular refractory material, each clamping face abutting the respective face of the 3,456,985 Patented July 22, 1969 glass when the glass is held in vertical disposition between them. a
In a preferred embodiment of the invention tongs intended for use in suspending glass in a vertical plane comprise a pair of tong arms pivoted together near their lower ends by a hinge pin (the lower hinge pin) and extended beyond the lower hinge pin to form the jaws of the tongs, the upper ends of the tong arms being linked by tong links to a second hinge pin (the upper hinge pin) above the level of the upper ends of the tong arms, characterised by jaws having clamping faces on blocks of bonded granular refractory material, each clamping face abutting the respective face of the glass when the glass is held in vertical disposition between them.
The tongs are usually suspended from the upper hinge pin whereby the tongs are suspended with the jaws in the clamping position.
Further according to the invention the blocks of bonded granular refractory material are axially adjustable in the tong jaws.
The blocks of refractory material may be solid cylindrical blocks, said blocks presenting flat end faces to the glass and being located in cups of heat-resisting steel mounted in said tong jaws for axial displacement of said cups in said tong jaws to compensate for wear resulting from use of the fiat surfaces of the cylindrical blocks in clamping part of the hot glass sheet.
By restrictively increasing the area of the glass held by the jaws a sufiicient area is gripped by the jaws to frictionally hold the suspended glass while at the same time there is a contact area of a size whereby significant heat losses are avoided and the deep penetration inherent in the use of sharp pins eliminated.
It is preferred that the clamping faces of the jaws be substantially flat circular surfaces of a diameter of the order of inch.
According to a further aspect of the present invention the jaws comprise flat faces of a refractory abrasive material deposited upon solid supports of heat-resisting steel axially adjustable in the jaws to compensate for wear resulting in use.
BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT The reference 1 indicates the suspending bar which at 1a is connected to a conveyor mechanism, not shown, by which mechanism a sheet of glass suspended by several tongs of the kind illustrated is carried through a furnace and, if so desired, through a quenching station where the heated glass is toughened. Alternatively, the
conveyor mechanism may transfer the glass to a bending station and the curved glass may be subsequently toughened by advancing the glass, through the agency of the conveyor mechanism, from the bending station to a quenching station.
To the lower end of the suspending bar 1 are pivoted a pair of identical tong links 2, 3 by an upper hinge pin 4, and the tong links in turn are pivoted, as shown at 5, 6, to the upper ends of a pair of identical tong arms 7, 8, which arms are bent towards each other at the lower ends (as in the manner of a pair of pincers) to be articulated on a lower hinge pin 9, and extended outwardly below the hinge pin 9 to form jaws 7a, 8a of the tongs.
The jaws 7a and 8a are each provided with means 10 and 11, now to be described, for clamping between them the upper marginal area of a sheet 12 of glass suspended by the tongs in vertical disposition.
The said clamping means present clamping faces 13, 14 (see FIGURE 2) which faces are caused to firmly engage and hold the two parallel faces of the glass by means of the axial forces exerted through the faces and derived from the suspended tong arms 7, 8.
The clamping faces 13 and 14 are formed on contact blocks 15, 16 of bonded granular refractory material and apply to the glass flat faces having a width dimension of the order of inch.
The contact blocks 15 and 16 are of cylindrical form of a radius of inch, and are held in cups 17 and 18 of heat-resisting steel integrally formed with threaded elements 19 and 20 which are axially adjustable in the jaws 7a and 8a of the tongs, and lockable in the operative position in the respective jaws by nuts 21 and 22 which nuts are screwed up to the outer faces 23, 24 respectively of the jaws 7a and 8a to hold the contact blocks 15 and 16 in any selected position, thereby permitting adjustment of the tong jaws to clamp and suspend glass of varying thickness within the compass of the fully open position of the jaws, and to make minor adjustment as wear takes place on the clamping faces 13 and 14 of the contact blocks 15 and 16.
The contact blocks are formed, in the construction being described, of a bonded granular refractory material consisting predominantly of a refractory abrasive material e.g. silicon carbide.
By the use of the invention as herein described with reference to the drawings, it is found that the depth of penetration of the clamping faces 13, 14 into the adjacent surfaces of a glass sheet gripped therebetween is decreased by a factor of at least 3 as compared with the depth of penetration of the sharp pointed pins of heat-resisting steel used in the jaws of conventional tongs.
In particular cases, it was found that, where the depth of penetration of conventional pointed pins of heat-resisting steel was 0.025", the depth of penetration of gripping surfaces of silicon carbide as described was only 0.003". In another case where the same glass sheet was treated at a similar temperature, carried firstly between sharp pins of heat-resisting steel and then between the clamping faces of blocks of silicon carbide as described, the depths of penetration were found to be 0.030" and 0.010" respectively.
The bonded granular refractory material used for the contact blocks is a material which is resistant to heat, corrosion and spalling at elevated temperatures near to the softening point of glass, is mechanically strong, and has a high coefiicient of friction relative to the surface of polished glass.
Alternatives to bonded granular silicon carbide, which is mentioned above by way of example, are aluminium oxide, zirconium oxide, chromic oxide or diamond. A combination of two or more of these refractory abrasive materials may be used.
The granular refractory abrasive material forming the contact blocks may be in the form of particles which are sintered together or combined with a heat resistant bonding medium which binds the particles into a solid matrix.
In another embodiment of the invention the jaws of the tongs comprise clamping faces of a granular refractory material deposited to form a spiculate surface by a flame spraying process upon solid supports of heat-resisting steel which are axially adjustable in the jaws to compensate for wear in use. Alternatively the granular refractory material is in layer form prepared by plating on to the solid supports to the full depth of the grain using a high melting point metal.
By the use of the present invention, the glass product which is obtained after a toughening process is much stronger and less liable to spontaneous bursting, which tends to arise from the points of weakness in a toughened glass sheet where the toughened glass sheet has been held by the sharp pins of conventional tongs in the toughening process.
Also a toughened glass sheet which is held during a toughening process by tongs in accordance with the prescut-invention has substantially less optical distortion than a similar glass sheet which has been held by conventional tongs in a toughening process.
1. Tongs intended for use in suspending glass in a vertical plane and comprising a pair of tong arms pivoted together by a hinge pin and extended beyond that hinge pin to form the opposed jaws of the tongs, characterized by clamping elements for the opposed jaws presenting each a plane clamping face of bonded granular refractory material throughout such face and possessing a high coefiicient of friction with respect to polished glass surfaces, said clamping elements being adjustable with reference to their respective tong jaws in a direction perpendicular to the plane of their respective clamping faces to compensate for wear resulting from use whereby to effect the engagement of said clamping elements over their entire clamping faces with the opposed surfaces of the glass sheet suspended between them, said clamping elements comprising blocks having ends on which said clamping faces of bonded granular refractory material are presented, and said blocks being located in cups of heat-resisting steel mounted in said tong jaws.
2. Tongs according to claim 1, wherein each block is cylindrical in shape, presents a circular clamping face, and is formed throughout of bonded granular refractory material.
3. Tongs according to claim 2, wherein each clamping face has a diameter of the order of A inch.
References Cited UNITED STATES PATENTS 3,010,753 11/1961 G. A. Russ et a1. 294118 3,184 259 5/1965 E. R. Almdale 2941l8 X 3,273,933 9/1966 F. Jochim 294-418 EVON C. BLUNK, Primary Examiner