PHOTO-ELECTROSTATIC METHOD FOR GLAZE-DECORATING CERAMIC TILES, MACHINE THEREFOR, AND END PRODUCT OBTAINED THEREFROM

Abstract: The method disclosed is one of transferring the image from a transparency (13 or 111) - this either caused to reciprocate through a horizontal and longitudinal path, or revolve continu­ ously - onto a tile (2) travelling below, synchronised in its movement with that of the transparency; provision being made between transparency and tile for a conductive rotating cylin­ der (46) having a selenium outer surface (48), which, in con­ junction with a lamp (15 or 113) and optic fibres (42) transfer­ ring the image line by line onto its top-most surface area, holds the latter by virtue of a positive charge induced by 'corona' stress into the dark areas of said image, bringing it round to a first point of convergence (S) between cylinder (46) aforesaid and a feed-cylinder (62) where negative-charged dry glaze particles (59) are offered by the latter to said dark areas; there being a second point of convergence (S′) envisaged diametri­ cally opposite on said cylinder (46) to the optic fibres, where this dusting of dry glaze (59) is transferred onto the positively-­ charged top surface of the tile (2) to be decorated, this having been moistened beforehand, and given a base-coat of neutral glaze incorporating a bonding-agent which will fix the decora­ tive pattern thus 'copied' - the finished glaze being subse­ quently protected by application of a frit.

Description: Photo-electrostatic method for glaze-decorating ceramic tiles, machine therefor, and end-product obtained therefrom The invention relates to a photo-electrostatic method and machineryfor applying decorative glaze to ceramic tiles, and to the end-product turned out by adoption of such a method -that is, a new method, partly inspired by the Xerox photocopy principle, which will enable printing of a decorative glaze onto ceramictiles by utilising the appropriate machinery. Thus, the method itself, e machine, and the end-product obtained, constitute the collective subject which the application seeks to protect with letters patent. The prior art in this field consists of a variety of tile glaze-decorating methods and relative devices which provide for projection of the glaze-medium in liquid state through stencils onto the surface requiring decoration; said projection being brought about either centrifugally by disc, or by free-fall, or by spray-gunning, or with a system of revolving delivery-receptacles, or by silkscreen process this with either a flat screen, or a set of screens fitted to a revolving drumg Al such techniques are characterised by the use of glaze in liquid state1 Systems whereby glaze is applied to tiles by projection in the liquid state require -amongst other thins- a long production line per colour, which signifies capadous factory premises and a great deal of ancillary equipment to cover each single type of tile, not to mention all the necessary dust-vacuuming, cleaning and wash-down plant. In the case of silkscreen- ing, a screeassembly per single colour is necessary, as well as one operative for each such assembly, andtime in which to set up the screens themselves and keep a constant check on the glaze compound for correct consistency1 Whatever the individual system employed, the liquid glaze medium requires preparation, and cannot always by utilised to the last dropx Finally, production methods involving the application of glaze in liquid state give rise to a large reject percentage. The prior art thus outlined standes in need of improvement -considerable improvement- especially with regard to the undesirability of applying glaze in liquid state, and by the same token, of overlarge plant used therefor, of vacuum' and other cleaning installations, and wash-down facilities, and of uneconomical man-power requirements; such improvement bringing with it an end-product characterised by better finishing and enhanced definition1 From the foregoing, one may discern the need for a solution to the technical problem of discovering a glaze-decoration method capable of applying the medium in its dry state, and a machine for carrying said method into effect -a machine such as will rationalise the production of glazed ceramic tiles by reducing space-requirements, man-power, wasted material, operating-time and costs, and rejects The invention described herein solves said problem through the adoption of a decorating-method which is to some extent inspired by xeroprinting, the application of xerography to photocopy reproduction developed by the Xerox company The Xerox method makeS provision for buiId-up of a positive charge in a selenium-coated conductor to some 6000 volts (tis by inducing a 'coronas phenomenon) in order to render it light-sensitive1 Light reflicted by the white areas of tile image to be reproduced will then hit the selenium correspondingly, so as to allow selective earthing-out of the positive charge, leaving behind a positively-charged area which will correspond to the image's dark parts1 Being thus positively charged, the conductor-image is then capable of attracting a special black powder which is negatively charged and consists of a carrier-medium (graphite, usually) and a thermoplastic resin pigment, this being strewn onto the blank copy-paper and fixed by heat-teatment, so as to obtain a permanent reproduction1 The method to which the invention relates, wherein, in accordance with the Xerox principle, a cylindrical conductor having a selenium covering is charged to 6000V by the corona phenomenon, replaces the special black powder aforesaid with a normal glaze compound in dry state and having a negative charge; the image to be transferred onto the tile being provided by a transparency caused to reciprocate horizontally through a longitudinal path above said cylindrical conductor, whilst projection of the image onto the cylinder top-side is brought about by lamp and optic fibres; movement of the transparency being synchronised with that of the tile which travels horizontally beneath the cylinder and opposed thereto, reproduction of the image onto the cylinder during the transparency's return travel being precluded by application of light from an auxiliary source; the cylinder being caused to rotate and transfer said image downwards towards a first convergence produced by a feed-cylinder from which the negatively-charged dry glaze medium is imparted to the image-transfer cylinder and caused to adhere to the positively-charged dark areas of the latter; there being a second restriction located in opposition to the optic fibres and at the bottom side of said image-transfer cylinder where the tile itself, positively-charged by conductors position beneath, passes beneath in order to receive the glaze therefrom; said glaze adhering to ie tile-surface by virtue both of the agency of a lamp which causes earthing-out of the positive charge, and of prior dampening of the tile-surface followed by application of a neutral base coat incorporating a bonding-agent. Multi-colour decoration involving three or four shades can be carried through by a set of machine-assemblies thus embodied, linked in series, with a final fixof the decoration being provided by a protective frit applied to the finished surface1 An improved embodiment of the machine set forth as per the invention described herein envisages positioning of the transparency within a revolving glass cylinder which is caused to turn synchronously both with the image-transfer cylinder, and with the ongoing movement of the tile beneath, whilst the tile's position with respect to the image-transfer cylinder is adjustable, such synchronous movement provided for by a drive- and transmission associating all the machine's rotating parts one with the other1 Advantages offered by the invention are these: a simplified glazing-procedure; elimination of glaze in the liquid state, and attendant problems; a more compact glaze-decoraticn plant; less maintenance; little or no waste/rejects; quick set-up for the single product scheduled; no large vacuum and cleaning installations; no glaze-encrusted equipment to clean and wash down; reduction in manpower and running-costs; a more faithful reproduction of the projected image; and finally, a cleaner and more clear-cut reproduction, perfectly centred on the decorated surface of the tile1 There are two possible embodiments of the invention illustrated -purely by way of example- in the ten sheets of drawings depicting the machine which accompany this specification, wherein: : Figure 1 is a side view of one possible embodiment, seen in cutaway; Figure 2 is a vertical cross-section of fig 1 taken through ll-ll, whose main purpose is that of illustrating the travel of both transparency and tile at that part of the machine; Figure 3 is a horizontal section taken along those parallel planes passing through the axes of the machine's rotary components; Figure 4 is a schematic view from one side of the machine which shows its transmission arrangement; Figure 5 is a large-scale section through fig 3, or fig 9, illustting the fed-cylinder; Figure 6 illustrates the elctrostatic contact-zone between tile and cylinder; Figure 7 is the same view as that in fig 1, though of a machine in which the transparency is fitted up inside a revolving glass cylinder; ; Figure 8 is a vertical cross-section through VIII-VIII in fig 7; Figure 9 is a horizontal section as per fig 3, taken through the second embodiment as described herein; Figure 10 is a side view of the machine in its second described embodiment, which illustrates the transmission arrangement; Figure 11 is the same drawing as in fig 6, though referred to the second said embodRenentX With reference to the drawings, 1 denotes a pair of belts carrying the single tiles 2 forward onto a cog-belt denoted 3 which propels them further forward onto guides 4 at the bottom side of the cylinders, these lying above said cog-belt 3, and between further lateral guides 5; 6 denoting fte teeth fixed to belt 3 which drag each single tile along through the machine, as well as carrying a synchroniser block 7 for timing purposes, 8 denotes a pair of guides made fast to the upper part 9 & the machine framework, this in turn associated with the base 10 by way of uprights 11, said guides 8 accommodating the slide of a carriage t2 which reciprocates the transparency 13 providing one of the colours to be printed on tile 2. 14 is the vertically-disposed reflector of a lamp 15 mounted to upper-framework 9 which projects a beam of light through transparency 13 by way of the slot 16 located in a baffle denoted 17; ventilation is±ford- ed by a tube 18. 19 denotes a transparent plate fitted to the frame 20 forming part of carriage 12, and providing the mount for said transparency 13, which is held in position by the weight of a further top transparent plate 21 hinged to said frame. 22 denotes a spring anchored at one end to the end of frame 20, and at the other to framework 9 &num; 23 denotes the extremity of a cable fixed to the carriage 12 carrying transparency 13, and sliding within a flexible sheath 24 attached to the entry end of upper framework 9 and bent round and away so as to turn back in toward the machine and connect up with a longitudinal 25 disposed at centre and fixed to two cross-members 26. The pair of guides 4, together with lateral guides 5, their respective pairs of longitudinal supports 27 and 28 -both associated with flexibly-mounted exit cross-member 29- the entry-end crossmember 30 hinged to base 10, and the two cross-members 26 affording support b longitudinal 25, all combine in making up ie chassis denoted T which oscillates vertically and within the section of machineleing described, whilst bearing ceramic tile 2 and timing-block 7 along with it 31 denotes a horizontal slot in said longitudiral 25 extending the entire length of the latter and accommodating ie slide of two bottom cross-pieces 32, 32' associated with the cycle timing-block 7 33 is an adjustable sleeve fitted to the enry-end of said longitudinal and provided with a raked face 34 designed to draw the first cross-piece 32' offered by block 7 down into a recess 35 located below the level of slot 31 at that end thereof, such that the timing-block 7 itself dips forward and down so as to disengage its own trailing top-end 36 from the tooth 6 which would hitherto have been drawing it along together with tile 2. 37 denotes a transverse slot at the underside of said longitudinal 25 which underlies the first cr)ss-piece 32' when in its drawnback position, whilst 38 is a stop associating with said slot by virtue of its being fixed to the end of a flexible lath 39 fitted likewise to te underside of longitudinal 25. 40 represents an electromagnet which frees slot 37 whenever it is wished to avoid timing-block 7 being carried forward by tooth 6 -in short, when there is no tile 2 to be decorated 41 denotes the opposite end of the cable aforesaid made fast in like manner to end 23, in this case to the trailing end of the timing-block 71 42denotes a transversely-disposed screen of optic fibres located beneath the slot 16 in baffle 17 and arranged in two staggered sets, borne up thus at either side by the two side-walls 43 of a box structure 44 mounted on base 10. A pair of opaque side-members 45 fixed to the upper part of box 44 converge downward toward the optic fibres, and have the function of gathering in those outer rays emar*ing from lamp 15 whose beam is intended exclusively for the fibres 42 themselves, 46 denotes the basic structure of a cylindrical condudPr designed to transfer the docorative image, whose transversely-set shaft 47 lies in a vertical plane passing through the centre-line of lamp 15 and fibres 42 alike, said shaft journalled at either end to side-walls 43 and thus free to rotate; the outer cylindrical surface 48 of six conductor coated with selenium glass, and the entire component thus embodied -being a conductor- connected to earths 49 is a tungsten filament, taut and transversely disposed upward and away from cylinder 46-48, and boxed within an enclosure 50 fixed at either end to side-walls 43, this being the means by which a positive charge is imparted to cylindrical surface 48 by the corona effect aforementioned (see fig 6), which raises some 6000 volts between thefi lament itself and earth1 51 denotes a lamp having a reflector 52 with its throw-aperture 53 directed toward that bend of cylindrical surface 48 exposed to the beam emanating from optic fibres 42, provision being made for a shutter 54 attached to one end of a flexible strip 55 mounted to a support 56 suspended between side-walls 43 57 is a further elctromagnet designed to attract strip 55 aforesaid in order to open up aperture 53 during the return travel of transparency 13 -this in order that the beam from lamp 51 may cancel out the positive charge induced into surface 48 by filament 49 - said electromagnet being operated by the action of a cam during said return travel &num; 58 denotes a hopper -likewise a conductor- mounted between side-walls 43 and insulated therefrom, and containing the glaze compound in dry state (denoted 59, and of whatever colour happens to be selected for this machine stage) into which a negative electrostatic charge of a few hundred volts is induced1 The hopper incorpontes transversely-disposed rods 60 of prismatic shape, designed to agitate the dry glaze. 61 denotes a further agitator-rod, embodied cylindrically and located at the bottom end of the hopper alongside a further cylinder- the feed cylinder aforementioned - having an insulated body section 62 and a shaft 63 journalled to the sides 64 of the hopper 58 itself1 The surface-speed of cylinder 62 is greater than that of cylinder 46-48 by an amount sufficient to compensate for non-conductive interspaces1 65 denotes strips of conductive material (figs 3, 5) disposed about the cylindrical surface area of feeder 62, which makes contact with image-transfer cylinder 46-48 at the bottom entry-side thereof 66 and 67 inote sectors-to-a-circle of differing length, both conductive, annular in shape, and making-up one common circumference; said sectors fixed to the inside of one of said hopper-walls 64 and disposed thus coaxial with feed-cylinder 62, and furnished with radial conductors 68 directed toward the outer surface of said feed-cylinder1 Sector 66 is wired to a source of electrical energy supplying some few hundred volts positive charge -preferably of a lower potential than that of hopper 58- whilst sector 67 is wired to a negative source, and positioned nearest the image-transfer cylinder 46-48. 69 denotes the bottom-most point of hopper 58, which is radiused parallel with the cylindrical surface of feeder 62, and has its farthest extremity located within that area where the two cylinders 62 and 46-48 turn away *om one another following contact 70 denotes a vertical baffle (likewise conductive) fitted to hopper 58 and disposed within a transverse plane dividing feed-cylinder 62, whose lower edge exhibits a bevel, and rides alongside the outer cylindrical surface of feeder 62 at distance such as will allow passage therebetween of a 'dusting' of glaze some few tenths-of-a-millimetre thick 71 denotes further conductors ranged in alignment below the lower generatrix offered by cylinder 46-48 -thatis, at the point of actual image- transfer onto the tile; said conductors fashioned from metal, directed toward the cylinder-generatrix, insulated *om composite-chassis T aforedescribed, and wired so as to receive a positive electrical charge, These conductors ride all-but-in-contact with the reverse face of the single tile 2. A further lamp 72 having a reflector 73 and positioned at the opposite side of the image-transfer cylinder to that of cylinder 62, has its rays directed at the imagetransfer line so as to cancel out the positive charge retained by that part of the cylindrical outer surface 48 already beyond the transfer-line and approaching the lamp itself1 74 represents a roller-brush turning around shaft 75 and suspended in rotation between side-walls 43 so as to lie parallel with cylinder 46,48 and act thereon at a point between filament 49 and lamp 72; the bristles of said brush performing a purely mechanical function:that of cleaning off residual glaze 59 from the surface of the image-transfer cylinder1 76 denotes a casing within which brush 74 is enclos ed, together with a filter 77 and a fan 78 which provide for the removal of residual glaze, In fig 1, 79 denotes the hinge-pin about which chassis T is caused to pivot, the remaining end of the chassis itself resting upon sprigs 80, these providing suspension for same1 In fig 4, 81 is a gearmotor which drives a shaft 82 journalled to base 10, whilst 83 and 84 are pulleys keyed onto said shaft 82 and further shaft 85, respectively, creating the loop for cogbelt 3 aforementioned1 A further pulley 86 likewise keyed to shaft 82 transmits drive by way of a belt 87 to shafts 47 and 75, which drive the image-transfer cylinder 46-48 and roller-brush 74, respectively1 A pulley 88 mounted onto return shaft 85 transmits to further shaft 89, this in turn driving a belt 90 whose function is that of turningfeed- cylinder shaft 63, cylindrical agitator rod 61 and prismatic rods 60. It will be observed that the gearmotor 81,being the only source of drive, guanntees synchronous movement of the machine's moving parts1 S denotes the coming-together of feed-cylinder 62 and image-transfer cylinder 46-48, whilst S' represents a similar narrowing between the latter and the tile 2 to be decorated, In fig 7, 91 denotes a pair of cogbelts, these carrying tiles forward into the machine; 92 denotes a Rir R uprights issuing from base I0 to which lateral guides 5 are made fast1 Bracket-type fixtures 93 associated with uprights 92 and facing inwards afford support, by way of springs 94, to a pair of guides 95 directing the top branches of said belts 91, these being driven by a pair of drive pulleys 96 and returned by further, idle pulleys 97, the drive pulleys being keyed to a shaft 98 journal led at either end to base 10. 99 represents a motorvariator imparting motion to shaft 98 by way of a drive-belt 100. 101 denotes a chain located centrally in the machine at a point between said pair of belts 91, and provided with a detent 102 designed to slow up and position the single tile 2, said chain 101 turning at a lesser speed than that of belts 91, 103 denotes the drive-sprocket for chain 101, and 104 the idle return-sprocket An electormagnetically operated stop 105 halts the passage of the tiles upon triggering of a microswitch not shown 106 denotes uprights issuing from the base 10 of the machine, whose function is tht of supporting the box structure 44 within which all the glazing-equipment carried by the machine is housed, 107 denotes a transversely-disposed, hollow glass cylinder having solid ends 108 supported in rotation by trunnions 109, these fitted to respective appendages 110 extending upwards from the side-walls 43 of box 44 A transparency 111 bearing the image for one of the glaze colours to be applied to tile 2 isiounted onto a sector of the inside surface of glasscylinder 107, whilst -likewise inside the cylinder- a vertically disposed reflector 112 and relative tube lamp 113 are associated with saidirunnions 109 at either end1 114 is the baffle defining a slot 115, beneath which one has the two staggered sets of optic fibres 42 aforementioned, suspended between the two side-walls 43 of box-iructure 44, as in the first embodiment described In fig 8, 116 denotes appendages from guides 95 which carry conductors 71 aforedescrib ed, A pulley 117 keyed onto drive-shaft 98 (see fig 10) turns a cog-belt 118 passing around the following rotary components: the shaft 75 of roller-brush 74, shaft 47 of the imagetransfer cylinder 46-48, pulley 119turning one end 108 of glass-cylinder 107, the uppermost of the two prismatic agitator-rods 60, and further pulley 120 keyed to the sprocket 103 driving chain 101. Pulley20 and drive-sprocket 103 are of size such that the speed of said chain 101 will be less than that of the pair of cog-belts 91 -this in order to enable positioning of the single tiles 2 beneath cylinder 46-48 by means of the detent 102. Pulleys 117 and 119 are of relative diameter such that the surface speed of said glass-cylinder 107 will be equal to the travel-speed of belts 91. Provision is made for a screw-adjusted stretcher 122 acting on belt 118 at a point between pulleys 119 and 120, whilst a further stretcher 123 tensioned by means of a spring is located between pulleys 120 and 117: by working stretcher 122 back or forth at the turn of its screw, pulley 120 can be made to advance or retard with respect to pulley 119 so as to synchronise movement of the transparency 113 with that of the detent 102 offered by chain 101, this bringing about the correct timing between tile 2 and transparency 113. 124 denotes a pulley keyed to the shaft of the uppermost agitator-rod of the two denoted 60 (prismatic) so as to transmit drive to the lower agitator rod 60, the cylindrical agitator-rod 61, and the shaft 63 of feed-cylinder 62 -this by way of a belt 125 looped around semes Funtion of the machine, in the case of the embodiment as illustrated in figs 1 - 6, is as follows: having started the gearmotor 81 and supplied electrical power to those parts of the machine requiring same in all stages of the line -e1g. three such units as described hereiin the case of a glaze-decoration involv-ing three distinct colours- and mounted the three transparencies intoiheir respective sliding carriages 12, tiles may be fed onto the belt 3 çpropria- tely spaced apart, already moistended and given their neutral glaze base-coat1 The leader-tile now triggers electromagnet 40, which engages the trailing top-end 36 of the timing-block 7 with the tooth 6 offered by belt 3 already propelling tile 2 toward idD the machine; ; ifus tooth 6 carries block 7 forward, and occasions movement of the carri age 12 and transparency 13 in the opposite direction by way of cable 41-23. As the transparency passes little-by-little beneath the beam emitted by lamp 15, the obtic fibres 42 below project the image line by line onto the top side of transfer-cylinder 46, whose outer surface 48 is already invested with a uniform positive electric charge produced by the 'coronet phenomenon generated by filament 49. The clear areas of the transparency allow passage to the light which, as a result, cancel out the corresponding positively-charged areas on 48 of the cylinder passing beneath. Thus,the positively-charged area, or pattern remaining on surface 48 will correspond to the tansparency's dark parts, whilst the boundary of the transparency either matches, or is proportioned to, that of the tile 2 itself Crosspiece 32' forming part of the timing-block 7 now comes up against the recess 35 offered by longitudinal 25 and, thanks to the incline 34 iicorporated thereinto, top-end 36 is freed from tooth 6 of the carrier belt 3, and the carriage 12 and timing-block 7 make their respective returns -to-originai-position, at the same time triggering electromagnet 57 whose excitation permits light-emission from lamp 51 so as to render the transparency 13 without influence during its return1 With the formed image now round at the meeting-point of the two cylinders 62 and 46-48 -clearance at point S narrowing to some few tents-of-a-millimetre- a dusting of negative:y- charged glaze is carried into the narrowed area by the feedcylinder 62 itself -this by virtue of the fact that strips 65 aforementioned are positively- charged by sectorial conductor denoted 66, and thus attract the negatively-charged dry glaze particles. Passing from thence into the negatively-charged sector denoted 67, strips 65 reverse polarity so as to throw the powdered glaze toward area S and onto the facing surface offered by image-transfer cylinder 46-48, still retaining the pattern received from the t°nsparency 13. The dry glaze adheres to the 'dark' parts of surface 48, being positively-charged, though not to those areas already discharged, A remnant will return toward the hopper held by the positively-charged areas of feed-cylinder 62, whilst the particles 59 held by positive charge on surface 48 continue toward ts second narrowed area, S', where a tile will be moving forward, in receipt of a positive charge from the conductors 71 beneath1 At this point, glaze 59 adhering to the dark areas of cylinder-surface 48 are attracted by the positively-charged tile, to whose surface they immediately 'take', according to the image imparted, since the light emitted by lamp 72 earths-out the positive charge carried by surface 48, and in addition, the base-coat already applied to the tile itself incorporates a bonding agent, as mentioned at the outset, Once the final colour has been thus copied onto the tile, a fix provided by frits or a transparent glaze-compound will wovide the protective final coat1 Referring now to figs 7-11, funcion comes about thus: - havig started up the motorvariator 99 and supplied electrical power to all parts of the machines making up the line -e1g1 three such units as described herein, in the case of a glaze-decoration involving three distinct colours and mounted the transparencies 111 into their three respective glass-cylinders 107, the tiles 2, already moistened and given their neutral glaze base-coat, can be fed onto the pair of carrier cog-blets 91. The tiles will in fact be appropriately spaced apart by stop 105 via triggering of a microswitch timed with the detent 102 offered by chain 101, such that the detent -travelling at a lesser speed than that of the belts 91 themselves- is enabled to position the single tiles correctly with respect to said glass-cylinder 107; ; transparency 111 mounted within the latter being synchronised with said stop 105 so as to pass over the slot 115 in baffle 114, the result 6 which is that the beam emitted from lamp 113 passes through the optic fibres 42 so as to project the image line by line onto surface 48 of the transfer-cylinder 46, this retaining a formed image which will correspond to the transparency's dark area1 Once the border of the transparency passes over slot 115, any further image therefrom will be cancelled out automatically from cylinder 46-48 by light emitted from lamp 51 which projects through the aperture 53 at that point opened up by excitation of electromagnet 57, this operated by a cam timed by glass-cylinder 107 itself1 The actual image-transfer stages are similar in all respects to that described in the case of the embodiment in figs 1-6. Synchronous movement of cylinders 107 and 46-48 with tile 2 is obtained by the transmission system which associates chain 101, glasscylinder 107 and image-transfer cylinder 46-48 by way of a single drive-belt 118 looped around the self-same motor- variator output shaft 99 turning belts 91. Pulley-diameters are such that the speed travelled by belts 91 matches the surface-speeds of both cylinders 107 and 46-48; also, the speed travelled by chain 101. -hence of detent 102- is less than that of belts 91, thus permitting correct alignment ae the single tile 2 with respect to the image revolving on cyli nder 48. Fine adjustment of the tile-position thus obtained, giving perfect alignment both with the image on surface 48 and with the transparency 111 itself, is then had by working the screw-operated stretcher 122, so as to advance or retard pulley 120 (that driving chain 101) with respect to the two cylinders which bring about image-transfer: glass-cylinder 107, and transfer-cylinder 46-48. When carrying the invention into effect, materials, dimensions, constructional and design details such as the shape of hopper 58, the method of bringing about traverse of carriage 12 and timing-block 7 (substituting pulley-drive for sheath 24, for instance), may all differ from those disclosed, whilst remaining equivalent in terms of the art, and by no means straying from within the bounds of protection afforded to the invention by claims as appended, With this in mind, the microswitch which operates stop 105 might well be cam-controlled from the end 108 of glass-cylinder 107, or from the shaft 47 of image-transfer cylinder 46-48, or from the chain's 101 drive-sprocket 103, or even from the detent 102 offered by said chain, or, indeed, from any other moving part of the machine whose operation is sychronised with said cylinders 107 and 46-48.

Claims: CLAIMS 11 &num; A photo-electrostatic method for applying glaze-deco- ration to ceramic tiles, characterised in that glaze in the dry state, invested with some few hundred volts negative charge, is transferred onto the dark areas of an image projected optical liy be means of a lamp and a transparency (13 or 111) caused either to reciprocate or to rotate, onto a revolving conductive image-transfer cylinder (46) having an outer surface of selenium glass (48) to which a positive charge of some 6000V is imparted; it being envisaged that siiid cylinder transfer said glaze according to the pattern of said image, onto single tiles (2) passing ine- ath said cylinder; said tile having been previously moistened and given a base-coat of neutral glaze-and-bonding-agent on its top side, and in receipt of a positive charge of some few hundred volts imparted by conductors, whilst residual positive charge carried by said image-transfer cylinder is earthed out optically at the point of transfer; provision being made for movement of the tile to come about synchronously with and in the opposite direction to that of said transparency during said image-transfer, and for further transfer of said image to said cylinder during return travel of the transparency to be inhibited by optic means; multi-colour decoration being brought about by utilising one machine per colour envisaged, with relative amouits of coloured glazes calculated on the basis of the degree of darkeness between one transparency and the next1 2. Machine as in claim 1, characterised in that a carriage (12) and relative frame (20) carrying said transparency (13) between two transparent plates (19 & 21) -the topmct of which hinged to said frame- is caused to slide back and forth through a longitudinal path along horizontal guides (8) made fast to the upper part (9) of the machine framework and directly above said image-transfer cylinder (46-48); such alternating movement being regulated by the action of a spring (22) and synchronised with the movement of a timing-block ( 7) drawn together with said tile (2) by teeth offered by a cog-belt (3) carrying said tiles through a longitudinal aid horizontal path and looped therefor around pulleys (83 & 84), with drive imparted by a gearmotor (81); the top branch of said belt travelling marginally below said image-transfer cylinder (46,48) and disposed at a level slightly below a pair of lower guides (4) along which the tile slides forward whilst bounded at either side by further, lateral guides (5). 3 Machine as in claims 1 and 2 characterised in that said pairs of guides (4 lower & 5 lateral) are made fast to a rear cross-member (3C) associated with the machine base (10) by way of a hinge (79), and to an exit cross-member (29) floating on a pair of suspension springs (80), thus constituting an oscillating chassis (T) operating in conjunction with belt (3) aforementioned which carries the tiles (2) forward over a longitudinal member (2N) fixed to further crossmembers (26) of the chassis itself; ;said longitudinal (25) provided with a transverse and horizontal slot (31) in which timing-block (7) aforesaid is caused to slide1 4. Machine as in claims 2 and 3 characterised in that said timing-block (7) is furnished with a trailing top-end (36) and a pair of bottom cross-pieces (32 & 32') designed to slide in said slot (31), the leading one of which comes up at the end of its forward travel against the raked surface (34) of an adjustable end-sleeve (33) associated with said longitudinal (25) so as to engage in a recess (35) incorporeted into the latter at one end of, and slightly below, said slot (31); said longitudinal further comprising a second, transverse slot (37) underlying cross-piece (32) of the timing-block in its fully-drawn-back position, said slot (37) closed by a stop (38) fixed to one end of a flexible lath (39) associated with the underside of said longitudinal; provision being made for an electromagnet (40) located beneath said stop and connected to the underside of said longitudinal (25) 5. Machine as in claims 2, 3 and 4 characterised in that one end of the carriage (a) carrying saidirasparency (t3) is connected by way of a cable with forward-upper and rearlower ends (23 and 41 respectively) to the trailing end of said timing-6lock (7), said cable bent through an arc and passing within a sheath (24)between carriage and timingblock, one end of said sheath made fast to the upper part (9) of the machine framework at its entry end, and the remaining end made fast at bottom to the rear end of said longitudinal (25) in the centre of the machine 6. Machine as in claims 1, 2, 3 and 4 characterised in that it comprises a longitudinally-disposed box structure (44) mounted to base (10) between the carriage (12) carrying said transparency (13) and the cog-belt (3) carrying single tiles (2) and operating in conjunction with the oscillating chassis (T) carrying timing-block (7), said box structure accommodating said image-transfer cylinder (46) with its outer selenium surface (48) and shaft (47), the latter disposed transversely and journalled to said box structure; it being envisaged that the vertical plane concurrent with said shaft (47) further coincide with:a lamp(15) and surrounding reflector (14) provided with a baffle (17) at bottom having a slot (16) through which a beam may pass, gathered in by converging members (45), to optic fibres (42) beneath, the lower end of the latter lying marginally above the topmost generatrix of said cylinder (46-48) -these components located above the latter; whilst in the same plane, and below said cylinder: metallic conductors (jar1 ) impating a positive charge to, and riding all but on the reverse side of said tiles (2) during their passage along the guides (4) offered by chassis (T); at which point the bottom-most generatrix of cylinder (46-48) and the tile itself meetS thus defining a second narrow (S'), or convergence, 7. Machine as in claims 1 and 6 characterised in that said box-structure (44) which houses the image transfer cylinder (46-48) also accommodates, at the machine-en-try side of said cylinder and following rotation of same: a lamp (51) whose reflector (52) is directed toward the top of said cylinder through an aperture (53) during return travel aforementioned of the transparency (13),said aperture closed by a shutter (54) attached to a flexible Frip (55) and operated by electromagnet (57) when triggered by a cam, said strip anchored to a support (56) suspended between side-wails (43) of the box structure itself; also, a conductive hopper (58) made fast to and insulated from said side-walls, containing dry state glaze particles (58) negatively-charged with some few hundred volts, and furnished with agitatorrods, two of which prismatic (60) and one cylindrical (61); also, a feed-cylinder (62), likewise insulated and having a shaft (63) journalled to the sides (64) of said hopper, which revolves in the opposite direction to that of siid image-transfer cylinder (46-48) and combining with the latter at its bottom adjacent quadrant to form a first narrow (S), or convergence allowing a clearance of some few tenths-of-a-millimetre; ; said feed-cylinder located at the bottom end of said hopper at the outlet thereof, and positioned beneath a veitical baffle (70) such that a few tenths-of-a-millimetre's ceannce remains between the two, the cylinder in turn located some few tenths-of-a-millime- tre above the similarly radiused and parallel curved hopper bottom-section, and below and to one side of said cylinders cal agitator rod-thislocated at the opposite side of feedcylinder (62) to that entering area (S) aforesaid, 8. Machine as in claim 7 characterised in that said feedcylinder (62) is furnished with peripheral longitudinal strips (65) ranged one next to the other, and has one of its ends located within an appendage of one of the hopper (58) sides (64) where two annular conductive sectors (66 & 67) are accommodated, these insulated one from the other and lying concurrent to a common cylindrical surface placed outwarly of and coaxial with said feed-cylinder, said sectors furnished with radially-disposed conductors (68) directed inward towards the latter; said sector (67) nearest the image-transfer cylinder being negatively charged, and of lesser angular length than its counterpart (66) in order to induce an electrostatic charge only into those strips (68) on the feed-cylinder moving through said area of convergence (S), the first said narrow1 91 Machine as in claims 1. and 6, characterised in that sid box structure (44) which houses the image-transfer cylinder (46 - 48) also accommodates, at the machine-exit side of said cylinder and following rotation of same: - a lamp (72) whose reflector (73) projects light toward the imagetransfer area immediately following the transfer-cylinder's bottom generatrix as the latter revolves upward thence; also, a roller-brush (74) suspended in rotation between side-walls (43) of the box-structure itself (44), within a casing (76) also housing a filter (77) and extractor-fan ), whose function is that of cleaning-off said imagetransfer cylinder (46 - 48); and a filament (49) disposed transversely within an enclosure (50) fixed to said sidewalls (43) and charged with some 6000V, whose location is alongside said cylinder, and between the roller-brush and the topmost cylinder-generatrix1 10. End-product of the method disclosed in claim 1, characterised in that the glaze-finish obtained - single-shaded or otherwise, colour-pattern or no - is produced by elettrostatic transfer of a glaze compound in dry state onto the tile, the latter having been previously treated with a basecoat incorporating a suitable bondig-agent therefor" 11. Machine as in claims 1, 6 and 7, characterised in that it comprises a transversely-disposed revolving glass cylinder (107) located directly above said image-transfer cylinder, supported in rotation via trunnions (109) at its two ends (108) in a pair of respective appendages (iso) extending upwards from the side-wails (43) of said box-structure (44); it being envisaged that a transpareny (111) be mounted to the internal surface of said cylinder, and that a tubular lamp (113) and relative reflector (112) be suspended between said trunnions (109) within the cylinder itself (107); the bottom-most generatrix of said cylinder disposed directly over a transverse slot (its) let into the top face of said box structure (44) above optic fibres (42) aforesaid. 12. Machine as in claim 11, characterised in that it comprises a pair of longitudinally-disposed ccgbelts (91) carrying the tiles (2) forward, the top branches of which travel marginally below said image-transfer cylinder (46-48), and a chain (101) provided with a detent (102) designed to slow up the single tile (2) and position it with respect to said cylinder (46 - 48); said chain being located immediately prior to said cylinder along the line of travel of the tiles, and caused to move at a slower speed than that of said belts (91);the top branches of said belts (91) sitting upon a pair of guides (95) positioned via springs (94) so as to rest on bracket fixtures (93) extending from respective uprights (92) issuing from the machine base (io). 13. Machine as in claims 11 and 12, characterised in that said cog-belts (91) are driven from a motor-variator (99) which transmits drive by way of a cog-belt (118) to glasscylinder (107), image-transfer cylinder (46-48) and chain (101); pulley-diameters and associated drive-components being such that surface-speed of the glass-cylinder (107) and of the image-transfer cylinder (46-48) will match drivespeed of said pair of belts (91), and that the speed travelled by said chain (ion) will be less than that of said belts (91) 14. Machine as in claims 11, 12 and 13, characterised in that it comprises a screw-operated belt-stretcher (122) located between the pulley (119) turning said glass-cylinder (107) and the pulley (121) driving said chain (101), whose adjustment back or forth produces advance or retard of said pulley (121) with respect to said pulley (119) in order4 sychronise movement of detent (102) aforementioned offered by said chain (101) with that of transparency (111) mounted within said glass-cylinder (107); provision being made for a springtensioned stretcher (123) which operates in conjunction with said screw-operated stretcher (122). 15. Machine as in claims 11, 12, 13 and 14, characterised in that the agitator-rods (60 & 61) and glaze feed-cylinder (62) aforesaid are turned by a drive-belt (125) from a pulley (124) keyed to the upper of the two prismatic agitator-rods (60), this in receipt of initial rotation from said cogbelt (118). 16. Machine as in claims 11 to 15, characterized in that its entry-point is provided with a stop (105) bringing tiles (2) to a halt on arrival-in from off the infeed belts (1); said stop (105) actuated by electromagnet and triggered by @@croswitch c@m-operated from one of the ends (108) of s@id lass cylinder (107), or from the shaft (47) of said image-transfer cylinder (46-48), or from the shaft (121) turning the sprocket (t03) driving chain (101) aforesaid; it being envisaged that such a microswitch might equally well be operated by the detent (102) offered by said chain (101).

Inventors: MORANDI, EUGENIO
Applicants: OFFICINA MECCANICA MORANDI LEO
Application year: 1983
Main classification: G03G15
IPC codes: B28B11, G03G15