Multi-station printing machine for ceramic ware

[57] ABSTRACT

A machine for the multi-color printing of a ceramic article. The machine has a plurality of printing stations each arranged to carry out a printing operation in a different color on a piece of ceramic ware. The ceramic article is mounted and secured on a suction plate during the operation. The plate is situated on a rotating turntable which rotates to various transfer positions at the printing stations. Radially extending tracks support the plates for radial sliding movement on the turntable and structure is provided to move the ceramic ware supporting plates along these tracks. Corresponding tracks are located at each printing station to receive the supporting plate from the turntable and direct it to the printing station. After the article is printed, the moving structure slides the plate back to the turntable. After the ink is applied, powder is sprinkled over the article to prevent marring of the design at the next printing station.

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MULTI-STATION PRINTING MACHINE FOR CERAMIC WARE

BACKGROUND OF THE INVENTION

It is customary in the manufacture of an article of pottery ware to apply a coloured decoration thereto after the ware has been fired and either before or after it is glazed, the ware being subsequently fired again. One common procedure in which ceramic coldprinting colors, which usually comprise a pigment dispersed in a polymerisable oil media, are used is to apply to the ware from a designbearing plate an initial design in one color, and subsequently, after this colour has dried, to apply one or more further colors with a brush by hand to more or less fill in areas outlined in the initial design.

In carrying out a procedure as just referred to, the initial design can be applied to the ware by means of an off-set printing machine comprising a work support for the ware, an engraved plate, means for applying color to the design-bearing plate and for removing surplus color by means of a doctor blade, and a gelatine pad, shaped like an inverted dome, arranged in the operation of the machine to press, in the direction of its axis, first against the design-bearing plate to pick-up the color therefrom and thereafter against an article of ware on the work support to apply the color thereto, the pad spreading over the plate or ware as it is pressed thereagainst.

SUMMARY OF THE INVENTION

It is one of the various objects of the present invention to provide an improved printing machine suitable for use in automatically applying a succession of different colors to an article of ceramic ware.

It is another of the various objects of the present invention to provide a multi-colour printing machine for ceramic ware which exhibits improvements over the prior art apparatus in the location of pieces of ceramic ware at the printing stations, in the printing stations themselves, and in other respects so that a more efficient and cleaner to operate multi-color printing machine is obtained.

With the above and other objects in view, as will hereinafter appear, the present invention in one aspect thereof contemplates a multi-color printing machine for ceramic ware comprising a support for a piece of ceramic ware, centring arms providing means for bringing the piece of ware to a predetermined position on a rubber pad of the support, suction holding means for retaining the piece of ware in the predetermined position, conveying means in the form of a turntable on which the support is mounted for conveying the support around a closed circular path which includes a plurality of transfer positions, guiding means in the form of rails on which the support can slide associated with each transfer position for guiding the support from the transfer position to a printing station at which a printing operation is performed on the piece of ceramic ware and for guiding the support back to the transfer position when the printing operation has been completed, a gelatine printing pad at each printing station arranged to pick-up a design in colored ink from an intaglio plate and to print the design onto the piece of ceramic ware, doctoring means in the form of a doctor blade and means for sweeping the doctor blade across the surface of the intaglio plate for spreading ink over the intaglio plate prior to each printing operation of the station, a sieve containing talcum powder and a vibrator for vibrating the sieve which provide sprinkling means for sprinkling powder onto the newly printed piece of ware if a further printing operation is to be performed thereon so that the further printing operation does not mar the printed design on the piece of ware, and a nozzle contained in a hopper which by blowing air thereat provides means for removing excess powder sprinkled onto the piece of ware by the sprinkling means.

The above and other aspects of the invention, including various novel details of construction and combinations of parts, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular machine embodying the invention is shown by way of illustration only and not by way of limitation of the invention. The principles and aspects of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a plan view of a machine embodying the invention with some parts broken away;

FIG. 2 is front elevational view of the first printing station of the machine shown in FIG. 1;

FIG. 3 is a view similar to FIG. 2 but showing the first printing station in a different condition;

FIG. 4 is an enlarged plan view with parts broken away of the first printing station shown in FIG. 2;

FIG. 5 is an enlarged view in side elevation with parts broken away of the machine;

FIG. 6 is a view of the machine, with parts broken away, taken in the direction of arrow VI in FIG. 1;

FIG. 7 is a view of the arrangement of microswitches which control part of the first printing station of the machine; and

FIG. 8 is a view with parts broken away of a latch of the machine which controls rotation of a turntable thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The machine shown in the drawings comprises a frame 2 (FIG. 2) which is rectangular in plan view and supports two tables 4 and 6 (FIG. 1) one at each end portion of the machine. Between the two tables 4 and 6, the frame 2 supports a mounting for a turntable 10 which is octangonal in plan view and is supported by four arms 11 (FIG. 6). The upper surface of the turntable 10 is at the same level as the upper surfaces of the tables 4 and 6 and the turntable 10 is mounted for rotation about a vertical axis so that it can be used to convey a series of supports for a piece of ceramic ware between a first printing station 12 on the table 4 and a second printing station 14 on the table 6. The turntable 10 is designed to convey four supports 16, 18, 20 and 22, which are each slidably mounted on a pair of rails 24 on the upper surface of the turntable 10. The center line of each pair of rails 24 extends normally to an edge of the turntable 10 and passes through said vertical axis; the rails themselves project beyond the edge of the turntable. The pairs of rails 24 are disposed at alternate edges of the turntable 10 so that the four supports 16,

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18, 20 and 22, are carried symmetrically disposed on the turntable 10.

The four supports 16,18, 20 and 22, of the machine are of identical construction and each comprises a square plate 25 on which is mounted an annular rubber pad 26 on which a piece of ceramic ware may be placed and held in position by suction applied through a flexible pipe 28 which leads from the center of the pad 26 at which there is an hexagonal pipe fitting 29 (FIG. 4). The pipe 28 leads from the pipe fitting 29 beneath the plate 25 to a pipe joint 30, which is situated on the axis of the turntable 10. The pipe joint 30 is rotatably connected to a vacuum pump (not shown) and the suction to each support 16, 18, 20 and 22, is individually switched on or off by means of a switch 32 on each support. Each support 16, 18, 20 and 22, also comprises four centring arms 34, mounted on the plate 25, each of which is pivoted about one of its end portions 36 and has a plastics presser member 38 mounted at its other end. The centring arms 34 of each support 16, 18, 20 and 22, are pivotably interconnected by rods 40 (see FIG. 4) so that, if one centring arm 34 is pivoted about its end portion 36 by an operator, the other three centring arms 34 of the same support also pivot in such a way that the four presser members 38 of each support are always all positioned on the circumference of a circle passing through the other presser members of that support. A return spring 42 is connected to one of the centring arms 34 of each support in order to provide a resistance to the pivoting of the arms 34 and to act to return the arms to their rest positions. The centring arms 34 provide means for bringing a piece of ware on the support to a predetermined position; once the piece of ware is in position suction is applied to retain it.

The plate 25 of each support 16, 18, 20 and 22, rests on four sliders 43 (FIG. 6) two of which rest on each of the rails 24. A latch 44 (FIG. 8) extends through a hole in the turntable 10 beside each pair of rails 24 and inter-engages a stop 46 on the side of each plate 25, a similar stop 47 (FIG. 6) being positioned on the opposite side of the plate 25. The latch 44 engages the stop 46 so as to prevent sliding movement of the support along the rails 24 until it is released by contact with a stationary cam member 49 which is mounted below the turntable 10. The latch 44 is pivotably mounted on a lug depending from the turntable 10 and a spring 45 is attached to its one end of the latch 44 to maintain it in engagement with the stop 46. The arrangement is such that, as the turntable 10 is rotated, the cam member 49 comes into contact with the latch 44 and causes it to release stop 46 but, once contact has been broken between the cam member 49 and the latch 44, the spring 45 causes the latch 44 to re-engage the stop 46.

The turntable 10 is so constructed that it can be freely rotated for one quarter of a revolution so that the supports 16, 18, 20 and 22, are indexed between four rest positions 48, 50, 52 and 54, after which a latch 56 (FIG. 8) prevents further rotation until it is released. The latch 56, of which the machine has only one, is mounted on the frame * below the turntable 10 and comprises a lug 58 mounted at the end of a lever 57 which is pivotably mounted on the frame 2. The end of the lever 57 remote from the lug 58 is hook-shaped and is attached to a spring 59 which acts to pivot the lever 57 to move the lug 58 into contact with the turntable 10. Mounted in close proximity to the spring 59 is pneumatic cylinder 60, a piston rod of which can be utilised to pivot the lever 57 against the action of the spring 59 to move the lug 58 out of contact with turntable 10. The arrangement is such that as the turntable 10 is rotated the lug 58 contacts a slanting surface of a socket member 61, one of which is mounted below the turntable 10 beneath each of the supports 16, 18, 20 and 22. The contact with member 61 causes the lever 57 to pivot until the lug 58 falls into a socket of the socket member 61 making locking contact therewith and preventing further rotation of the turntable 10 until the cylinder 60 is used to withdraw the lug 58 from the socket. A microswitch 63 is mounted on the frame 2 beside the lever 57 so that it can detect when the lug 58 is engaged in the socket.

As mentioned above, the supports 16, 18, 20 and 22, have four rest positions 48,50, 52 and 54, which correspond to the positions at which the turntable 10 is stopped by the latch 56. The position 48 is a loading and unloading position of the supports at which pieces of ceramic ware can be placed on the supports. Position 50 is a transfer position opposite the first printing station 12 and it is below position 50 that the latch 56 is located. Position 52 is at a blowing station of the machine and position 54 is a transfer position opposite the second printing station 14. The four arms 11 of the turntable 10 are arranged so that each extends from a central portion of the turntable to below one of the supports 16, 18, 20 and 22. Each of the arms 11 carries, on its underside and almost beneath the edge of the turntable 10, a screw 64 which is arranged to operate a microswitch 65 which is mounted on the frame 2 below position 50. This microswitch 65, as will appear later, is arranged to prevent operation of parts of the machine when the turntable 10 is not correctly positioned.

When one of the supports 16,18, 20 and 22, is at position 50 opposite the first printing station 12, the rails 24 on which that support rests are in line with and in close proximity to rails 62 which extend across the table 4. The rails 62 are of hexagonal cross-section and are of the same gauge as the rails 24. The rails 24 and 62 are angled at their ends which approach one another, as shown at 66 (FIG. 1); this is to allow closer proximity between the rails 24 and 62 than would otherwise be possible because allowance must be made for the rotation of the turntable 10. The arrangement is such that, after release of the latch 44 from the stop 46, the support at position 50 can slide along the rails 24 onto the rails 62 away from the turntable 10, pipe 28 flexing to allow this. The rails 62 provided guiding means for guiding the support from the position 50 to the first printing station and back again. The rails 62 provide accurate guiding which is necessary in order that the design printed on the piece of ware is correctly positioned so that the parts of the design printed at the two printing stations will match one another.

The table 4 comprises a longitudinally extending pit 67 (FIG. 5) disposed between the rails 62. In the pit 67 is mounted on trunnions 68 an hydraulic cylinder 70 so that the cylinder 70 is disposed below the upper surfaces of the rails 62. A piston rod 72 (FIG. 2) of the cylinder 70 extends along the pit 67 in the direction of the turntable 10 and terminates in a catcher member 74 on which are mounted two rollers 76 with their axes extending vertically. The arrangement is such that, when the turntable 10 rotates to bring one of the supports 16, 18, 20 and 22 to position 50, a lug 78 (FIG. 4) which

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A carrier 80 for a rectangular design - bearing plate 84 (viz. an intaglio plate) is mounted on the rails 62 for sliding movement thereon. The carrier 80 is rigidly connected to the catcher member 74 so that movement of the piston rod 72 slides the carrier 80 along the rails 62 but the carrier 80 is always disposed further from the turntable 10 than the support 16, 18, 20 and 22, which is also being slid along the rails 62. The carrier 80 comprises a rectangular plate having on its upper surface four positioning screw holders 82 (FIG. 4) each providing mounting for two positioning screws 83. The holders 82 are located at the corners of a rectangle and the arrangement is such that a base plate 81 on which the design-bearing plate 84 is mounted may be accurately positioned on the holder 82 by adjustment of the screws 83. The plate 84 has a design engraved or etched onto a design-bearing area of its upper surface, which design is to be transferred to a piece of ceramic ware. A cloth 86 is attached to the side of the carrier 80 which is remote from the turntable 10, passes over a roller 88 mounted on brackets 89 (FIG. 2) at the end of the table 4 and is kept taut by a weight 90. The purpose of this cloth 86 is to catch ink drips and prevent them from falling into the pit 67.

On either side of the design-bearing plate carrier 80 are mounted cam rails 91 and 92 (FIG. 4) which run parallel to the rails 62 and are arranged to operate microswitches, rail 91 operating microswitches 93 and 94 and rail 92 operating microswitch 95. Microswitches 93 and 94 are disposed on one side of the rails 62 and microswitch 95 on the other side. These microswitches 93, 94 and 95, are operated by the rails 91 and 92 as they are carried past by the carrier 80 and act to control the hydraulic cylinder 70 and other parts of the machine as is described later. Beside the rails 62 adjustable stops 96 (FIGS. 3 and 4) are provided to limit the sliding of the supports 16, 18, 20 and 22, and the carrier 80 by engaging the stops 46 and 47 of the supports 16, 18, 20 and 22, and stops 103 formed on the rails 91 and 92.

A framework comprising two struts 97 and two struts 98 supporting a bridge piece 99 (FIGS. 2 and 3) spans the rails 62. The bridge piece 99 supports an hydraulic cylinder 100, a piston rod 101 of which is connected to a pad support 102. The pad support 102 is mounted for sliding movement on the two struts 98. Bolted to the bottom of the support 102 and pivotably mounted on the support 102 close to one of the struts 98 is a horseshoe-shaped pad carrier 104. The pad carrier 104 fits underneath and is bolted to a base plate 106 of a gelatine pad 108. The pad 108 is shaped like an inverted dome and is designed to pick up a design in ink from the plate 84 and transfer it to a piece of ceramic ware on one of the supports 16, 18, 20 and 22. The arrangement is such that operation of the cylinder 100 moves the pad 108 downwards or upwards or away from the rails 62.

The pad 108 may be removed from the pad support 102 by unbolting the pad carrier 104 from the support 102, pivoting the carrier 104 about the strut 98 on which it is mounted until the pad 108 projects beyond the edge of the table 4, unbolting the base plate 106 of the pad from the carrier 104 and lifting the pad 108 and its base plate 106 away from the carrier 104. This arrangement provides a rapid and easy method of changing the pad 108.

Extending upwardly from the support 102 are two cam-carrying rods 110 and 112 (FIG. 3) which pass through holes in the bridge piece 99; rod 110 extends into a framework 114 which is mounted on bridge piece 99. The cam-carrying rod 110 has a sleeve cam 116 (FIGS. 3 and 7) adjustably mounted thereon which cam operates two microswitches 118 and 120 as the rod 110 moves with the pad 108 and carries the cam 116 past the microswitches. The microswitches 118 and 120 are used to control the lowermost position reached by the pad 108; the arrangement is such that microswitch 118 controls the position reached on one stroke of the cylinder 100 and microswitch 120 controls the position reached on the next stroke of the cylinder 100 and so on so that the pad 108 comes down a different distance on alternate strokes of the cylinder 100. The microswitches 118 and 120 are mounted on screw threaded rods 122 and 124 respectively, which are rotatably mounted in threaded holes in bridge piece 99 and the framework 114. The position of the microswitches 118 and 120 relative to the cam 116 can be individually adjusted by means of handles 126 and 128 connected to the rods 122 and 124 which are used to rotate the rods 122 and 124 and screw them up or down. The cam-carrying rod 112 has a sleeve cam 117 (FIG. 3) adjustably mounted thereon which is arranged to operate a microswitch 121 mounted below bridge piece 99 which is used to control the uppermost position reached by the pad 108.

Mounted on one of the struts 97 is an inking device 130 (FIGS. 2 and 4) of the machine which device comprises an ink reservoir 132 (FIG. 2) connected by a pipe 134 to a nozzle 136. The nozzle 136 is mounted on a bracket 138 on one of the struts 97 and its transverse position relative to the rails 62 may be adjusted by means of a screw 140. The opening and closing of the nozzle 136 is controlled by a pneumatic valve 142 operated by two air lines 144. An air line 146 supplies air to the reservoir 132 so as to apply pressure to ink contained therein which will assist the flow of ink from the reservoir 132 through the nozzle 136 when the valve 142 is open. A gauge 148 is provided on the line 146 so that the pressure on ink in the reservoir 132 is known to an operator of the machine.

Spanning the rails 62, on the side of the framework comprising struts 97 and 98 remote from the turntable 10, is a framework 150 (FIG. 2). This framework 150 comprises two struts 152 which together with the struts 97 support a pair of supporting bars 154 which run parallel to the rails 62. Between the supporting bars 154 extend two parallel hexagonally shaped guide rods 156 (FIGS. 4 and 5) and slidably mounted on the guide rods 156 is a doctor blade carrier 158. Mounted on trunnions 160 on top of the doctor blade carrier 158 is an hydraulic cylinder 162 which extends in a direction parallel to the guide rods 156. The end of a piston rod 164 of the cylinder 162 remote from the cylinder is pivotably attached to one of the supporting bars 154 so that operation of the cylinder 162 causes the doctor blade carrier 158 to slide on the guide rods 156 carrying cylinder 162 with it. A cam-carrying rod 161 (FIG. 4) extends between the tops of the two supporting bars 154 and has two adjustable sleeve cams 163 mounted thereon. A microswitch 165 (FIG. 2) is mounted on top

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Ί of the doctor blade carrier 158 and is designed to be carried past the cams 163.

Rotatably mounted on the underside of the doctor blade carrier 158 is an axle 170 on which is mounted a doctor blade holder 166 which holds three doctor blades 168 made of strip steel and radially disposed at 120° to one another. The doctor blade holder 166 is mounted on the axle 170 in such a way that it can be rigidly held in three orientations at 120° to one another. The arrangement is such that a lug (not shown) on the axle 170 will fit in to any of three slots of the holder 166 and the lug is kept in the slot by the action of a spring (not shown). It is however possible to press the holder 166 against the spring, rotate it through 120° and allow the lug to enter a different slot thus changing the orientation of the doctor blades 168. The doctor blades 168 extend in a direction parallel to the rails 62 and transverse to the guide rods 156. The axle 170 has adjustment screws 171 at its bearings which can be rotated to alter the orientation of the axle 170 to bring the doctor blades 168 parallel to the design-bearing plate 84.

Mounted on one end of the doctor blade carrier 158 is a pneumatic cylinder 174 to a piston rod 172 of which the axle 170 is pivotally connected by a lever 169. The arrangement is such that the cylinder 174 can be used to rotate the axle 170 and thus the doctor blade holder 166 through a small part of a revolution and back again, the amount of the rotation which the cylinder 174 causes of the doctor blade holder 166 being limited by an adjustable stop 175. A lever 173 is also connected to the piston rod 172 of the cylinder 174 and a screw 177 carried by the lever 173 operates a microswitch 178 mounted on the doctor blade carrier 158. This microswitch 178 is designed to operate to ensure that cylinder 162 is not operated to move the doctor blades 168 transversely across the machine when the doctor blades 168 have not been rotated to the correct orientation by cylinder 174.

Suspended above position 50 of the supports 16, 18, 20, and 22, from a bracket 179 is a sieve 180 (FIG. 1) alongside which is an electrically powered vibrator 181 which is arranged to vibrate the sieve 180 to cause powder desposited in the sieve to fall through it. The sieve 180 and vibrator 181 provides sprinkling means of the machine for sprinkling powder onto a newly printed piece of ware. However alternative sprinkling means such as a brush moving across a gauze could be used.

Suspended above position 52 of the supports 16, 18, 20 and 22, is a conically shaped hopper 182 (FIG. 6) which is arranged to be moved up and down along a vertical path by means of a pneumatic cylinder 184 mounted on the frame 2 of the machine. A piston rod 186 of the cylinder 184 is connected to the hopper 182 by means of an L-shaped bracket 188 which slides between guide rollers 190 mounted on the frame 2 as the hopper 182 is moved up and down. In its uppermost position the hopper 182 is clear of the support 16, 18, 20 and 22, at position 52 so that the turntable 10 is free to rotate but in its lowermost position the hopper 182 encloses the pad 26 and extends between the centring arms 34 and the pad 26 almost to the upper surface of the plate 25 of the support. At the top thereof a pipe 192 enters the hopper 182 and through this pipe air may be sucked from the hopper 182 by a vacuum pump (not shown). An inlet pipe 194 enters the hopper 182 through which air may be blown into a rotatably mounted nozzle 196 which is contained in the hopper 182 and which comprises a series of air outlets 198.

The second printing station 14 is identical to the first printing station 12 and like parts are numbered identically except that position 54 has no sieve similar to sieve 180 suspended above it and the turntable 10 has no latch at position 54 similar to latch 56. The machine also comprises three control boxes 200, 201, and 202, mounted on the frame 2, which contain the various setting and operating controls of the machine.

The operation of the machine described above will now be described starting from the state in which support 16 is at position 48, support 18 is at position 50, support 20 is at position 52 and support 22 is at position 54. But before the machine commences operation two design-bearing plates 84 are first positioned on the plate carriers 80 by means of the positioning screws 83. The two design-bearing plates 84 bear two complementary designs which together make up a total design of two colours to be applied to a piece of ceramic ware, each design-bearing plate bearing the portion of the total design which is of one colour. The ink reservoirs 132 are each filled with an ink of appropriate color, depending on which plate 84 is at the same decorating station as the reservoir. Talcum powder is placed in the sieve 180 and suitably shaped pads 108 are mounted on the pad carriers 104, the shape of the pads 108 being selected with a view to the profile shape of the pieces of ceramic ware to be decorated. The machine is then ready for operation once the various pneumatic, hydraulic and electric circuits have been switched on.

The operator of the machine stands in front of position 48 and places a glazed or unglazed piece of ceramic ware 204 on the pad 26 of the support 16. Next the operator takes hold of one of the presser members 38 of the centring arms 34 and moves it towards the piece of ware 204 thus pivoting the arms 34. The presser members 38 contact the piece of ware 204 and move it until all four presser members 38 contact the piece of ware 204 so that it is moved to a central position on the pad 26. The operator then presses switch 32 which causes air to be sucked through pipe 28 so that the piece of ware 204 is held in its central position on pad 26 by suction. The operator now releases the presser member 38 which he has moved and allows the centring arms 34 to pivot back to their rest positions under the influence of the spring 42.

The operator now presses a button on the control box 202 and this operates a pneumatic circuit to activate cylinder 60 which operates to release the lug 58 from the socket in the socket member 61. The removal of lug 58 from the socket frees the turntable 10 for rotation and the operator rotates the turntable 10 by hand so that the support 16 moves to position 50, or in other words through one quarter of a revolution. While this rotation of the turntable 10 is taking place, at both the first and second printing stations 12 and 14, the pad 108 descends under the influence of cylinder 100 and picks up ink from the design-bearing plate 84 which is at that time positioned below the pad 108 and has ink contained in the design engraved thereon. The pad 108 now carries the design in ink which is on the designbearing plate 84 and is ready to impart the design to the piece of ware 204. The distance which the pad 108 descends onto the design-bearing plate 84 is controlled by microswitch 118. The pad 108 then moves upwards again and reaches a height determined by microswitch

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121. The pad 108 deforms as it presses onto the designbearing plate 84 (as is best seen in FIG. 3). Meanwhile the doctor blade carrier 158 moves transversely across the machine to return the doctor blade 168 to its starting position. The doctor blade 168 thus moves across the machine to its starting position when the designbearing plate 84 is not below it. The operation of the doctor blade 168 will be more fully described hereinafter. The movement of the pad 108 and the doctor blade carrier 158 while the turntable 10 is being rotated is initiated by the button which the operator has pressed.

When the support 16 reaches position 50, the lug 58 enters the socket of socket member 61 below support 16 to lock the turntable 10 against further rotation and lever 57 operates microswitch 63, the lug 78 enters between the rollers 76 of the catcher member 74, the cam member 49 acts on the latch 44 which releases stop 46 freeing the support 16 for sliding movement on the rails 24, and screw 64 operates microswitch 65. It is necessary that the turntable 10 is correctly positioned and locked against further rotation before the next part of the operation of the machine takes place; this is to avoid the possibility of the supports 16, 18, 20 and 22, falling off from either the rails 24 or the rails 62.

As soon as microswitches 65 and 63 have been operated, which indicates that the turntable 10 is correctly positioned and that it is locked against further rotation, and microswitch 121 has been operated by the return of the pad 108 to its uppermost position indicating that the pad 108 has completed picking up ink, the hydraulic cylinder 70 operates to slide the support 16 onto the rails 62 away from the turntable 10. The support 16 is slid along the rails 62, the pipe 28 flexing to allow for the greater distance between pad 26 and the pipe joint 30, and comes to rest beneath the pad 108 with its stops 46 and 47 engaging stops 96 (the stops 96 therefore act to determine the position the support takes up beneath the pad 108); at the same time the design-bearing plate 84 is carried to a position beneath the doctor blade 168. As the design-bearing plate carrier 80 moves to carry the design-bearing plate 84 beneath the doctor blade 168, the rail 92 operates microswitch 95 which operates cylinder 142 to open nozzle 136 to allow a ribbon of ink to fall onto the moving design-bearing plate 84 beside the design engraved thereupon until the rail 92 has passed microswitch 95 whereupon cylinder 142 operates to close nozzle 136. The condition of the machine when the support 16 has arrived below pad 108 and the design-bearing plate 84 below the doctor blade 168 is shown in FIG. 1. While this has been happening at the first printing station 12, the same sequence is happening at the second printing station 14 to bring support 20 below the pad at that station.

The arrival of the support 16 and the design-bearing plate 84 is their correct positions is signalled by microswitch 94 which is operated by the second rail 91 of the plate carrier 80 and this initiates the next part of the cycle of operation of the machine. The pad 108 descends onto the piece of ware 204 and deposits the ink which it picked up previously onto the piece of ware. On this descent of the pad 108, the microswitch 120 controls the lowermost position reached by the pad 108. The two different lowermost positions of the pad 108 are necessary because the design-bearing plate 84 and the piece of ceramic ware 204 are at different heights. The pad 108 dwells at its lowermost position for a short time (e.g., 0.3 seconds) and then returns to its uppermost position. While the pad 108 is descending onto the piece of ware 204 and subsequently returning to its uppermost position, the doctoring blade 168 is carrying out a doctoring operation.

The doctoring operation is initiated by microswitch 94 which causes the cylinder 162 to move the doctor blade carrier 158 transversely across the machine (from right to left in FIG. 4). As the carrier 158 moves, the microswitch 165 strikes the first of the sleeve cams 163 and this causes the cylinder 174 to operate. Cylinder 174 causes the doctor blade holder 166 to rotate through part of a revolution to bring one of the doctor blades 168 down to the surface of the plate 84 (the other two doctor blades 168 held by the holder 166 are spare blades which can be brought into use by rotation of the holder 166 independently of the axle 170 in the manner described above). The doctor blade 168 sweeps transversely across the surface of the designbearing plate 84, as the doctor blade carrier 158 is moved. The ribbon of ink previously laid on the designbearing plate 84 is swept into the engraved design on the plate 84 by the blade 168. Surplus ink not left in the engraved design is swept into a drip tray 206 (FIG. 1) positioned beside the rails 62. When the microswitch 165 strikes the second of the sleeve cams 163, the cylinder 174 reverses its previous operation and rotates the doctor blade holder 166 to move the doctor blade 168 clear of the surface of the plate 84. The action of the cylinder 174 also operates microswitch 178 which is a safety switch which ensures that the cylinder 162 cannot reverse its operation to sweep the doctor blade 168 back to its starting position unless the blade 168 is clear of the surface of the plate 84; this precaution is to prevent damage to the design-bearing plate 84. The cylinder 162 completes its stroke after the second operation of microswitch 165 until the doctor blade carrier 158 abuts the support bar 154 on that side of the machine. The doctor blade 168 is now in the position which it occupied when the operator initiated operation of the machine.

When the pad 108 has returned to its uppermost position operating microswitch 121 and the doctor blade 168 has completed its sweep across the surface of the plate 84, the hydraulic cylinder 70 operates in the reverse direction to its previous operation and returns the support 16 to the turntable 10 and the plate 84 to beneath the pad 108. This motion is limited by the stops 103 engaging the stops 96. The stops 96 therefore act to determine the position which the plate 84 comes to beneath the pad 108. The microswitch 93 detects when this operation has been completed and causes the next part of the operation of the machine to begin.

The piece of ceramic ware 204 on the support 16 now has a design formed on it in wet ink which has been deposited by the pad 108 and at position 54 is support 20 carrying a piece of ceramic ware with a twocolour design formed on it. Microswitch 93 is operated by rail 91 and causes the vibrator 181 to operate to shake the sieve 180 to cause talcum powder to fall onto the piece of ware 204. The vibrator 181 operates for a predetermined time to cause talcum powder to be lightly sprinkled over the piece of ware 204, whereupon the machine is free to repeat the above-described operation on a piece of ceramic ware carried by the support 22.

The talcum powder is sprinkled onto the piece of ware 204 to cover the wet ink thereon so that the de3,868,902 sign formed by the ink will not be marred by subsequent application of another coloured ink at the second printing station 14. It is however necessary to remove surplus powder from the piece of ware 204 so as to free its surface for the second ink to adhere.

While the illustrative machine has been carrying out the above-described operations automatically, the operator has removed an already-decorated piece of ceramic ware from the support 22 which is now at position 48. In order to do this he first presses switch 32 to remove the suction which holds the piece of ware on the pad 26 of support 22. He has then placed, positioned, and secured by suction, another piece of ceramic ware on the pad 26 of the support 22. He now presses the button on control box 202 again and then turns the turntable 10 through another quarter revolution in the same direction as before which brings the support 22 to position 50 and the support 16 to position 52. The first printing station 12 now operates as before on the piece of ceramic ware on the support 22 while the second printing station 14 operates on a piece of ceramic ware on the support 18. Meanwhile the hopper 182 descends over the support 16 under the influence of cylinder 184, the operation of which is also initiated by the three microswitches 63, 65 and 121. The hopper 182 descends until it encloses the piece of ware 204 whereupon air is blown into the hopper 182 through inlet pipe 194. The air passes into the nozzle 196 and escapes through outlets 198 and causes the nozzle 196 to rotate above the piece of ware 204. The air issuing through the outlets 198 blows the surplus talcum powder off the piece of ware 204, whereupon it is sucked out of the hopper 182 through the pipe 192. The hopper 182 is then once again raised clear of the support 16 by operation of cylinder 184 in the reverse direction to its previous operation.

The operator continues to operate the machine as described above and upon the next quarter revolution of the turntable 10, the support 16 arrives at position 54 and the second printing station 14 operates to complete the total design on the piece of ware 204 by the addition of the complementary design in the second color. Meanwhile the support 22 is at position 52 having surplus talcum powder removed and the support 20 having had a piece of ceramic ware placed thereon is being operated on by the first printing station 12.

A further quarter revolution of the turntable 10 brings the support 16 to position 48 once again where the operator releases the suction by pressing switch 32 and removes the piece of ware 204 from the pad 26. The piece of ware 204 now has the total two-color design formed upon it. The design in the second color is still wet and the piece of ware 204 is placed in a drier until the second color is dry as it is not necessary to sprinkle talcum powder onto the piece of ware 204 a second time since, as no further colors are to be added, there is no further danger of smudging.

It is found that, in using the machine described above, designs in two different colors can be applied to pieces of ceramic ware with satisfactory registration between the two different colors and without smudging. A further advantage of the machine is that unlike some previous off-set printing machines it is possible to vary the time taken to doctor the design-bearing plate with ink by varying the speed of operation of cylinder 162; this can be done within limits without altering the speed of operation of the rest of the machine since in general a greater period is required for the pad 108 to apply the ink to the piece of ware 204 and return to its uppermost position than is required for the doctoring operation.

While the machine described above can only be used for applying designs in two different colors, a machine in accordance with the invention could be used for applying more than two colors to an article of ceramic ware. Such a machine has a printing station for each color, sprinkling means to apply powder after the ware has passed each printing station except the last one, and means for removing surplus powder following each sprinkling means. A piece of ceramic ware being printing by such a machine is moved to a first transfer position, then to a first powder removing position, then to further transfer positions and powder removing positions, then to a final transfer position and finally to an unloading position.