GB2247862A - Multicolour screen or stencil printing - Google Patents

Abstract

A multi-layered stencil printing is applied onto an article such as a print sheet in succession in respectively predetermined positions relative thereto by a plurality of stencil printing plates in such a manner that a second stencil printing plate is pressed onto the article bearing a print image provided by a first stencil printing plate regardless whether the former print image has dried or not. It is stated that colour offset from an earlier undried print on to a later stencil has no detrimental effect as it is only liable to be re-applied in exactly the same location on any later prints. Examples of printing using planar screens and rotary screens are given. In the latter case (see eg Fig 11) the printing couples are arranged so that the leading edge is printed by a subsequent colour before the trailing edge has left a previous colour. <IMAGE>

Description

MULTI-LAYERED STENCIL PRINTING Background of the Invention Field of the

Invention

The present invention relates to the art of stencil printing, and, more particularly, to a method of producing a multi-layered print such as a colour picture by the stencil printing, and a stencil printer for producing such a multi-layered print.

Description of the Prior Art

It is an old well know art to produce a multi-layered print such as a colour picture by overlapping a plurality of print images in different colour inks on an article. In this connection, it is also an old well known art to analyse a natural colour into a combination of a plurality of fundamental colours such as three fundamental colours and to produce a colour print by an overlap of three print images in those fundamental colours.

Conventionally, in such a multi-layered colour printing it has been considered to be a matter of course that a first print image in a first colour is dried before a second print image in a second colour is overlapped thereon, because otherwise a part of the wet ink forming the first print. image will transfer onto the printing surface of the printing plate for the second print image during the second printing process, thereby causing a blotting of the print image.

If the above-mentioned ink transfer occurs in the relief, the intaglio or the offset printing, the blotting ink on the second printing plate is further transferred onto an ink supply roller which is pressed against the second printing plate to supply ink thereto, so that a part of the ink supply roller is stained. Thereafter, the blotting ink on said part of the ink supply roller will be transferred back from the ink supply roller to another part of the second printing plate. As a result, after a repetition of such processes the second printing plate will be gradually more stained over the entire printing surface. Therefore, a posterior printing must be done after the ink by a prior printing has been dried so far that no such ink transfer occurs.

In the same manner as by the relief, the intaglio or the offset printing, it is possible to produce a multi-layered colour print by the stencil printing. It has also been considered to be a matter of course that also in the multi-layered stencil printing a posterior printing is to is be done after the ink of a prior printing has been dried. Particularly in the stencil printing, since the ink must flow through a small opening formed in the stencil sheet, it must have a relatively high fluidity which, however, is generally contradictory to fast dryability. Therefore, it has been considered that the stencil printing is substantially handicapped as compared with the relief, the intaglio or the offset printing with regard to the multi-layered printing.

As described above, when a natural colour is analysed into three fundamental colours and reproduced by an overlapping of print images in the respective fundamental colours, a more or less waiting time is required as a matter of principle between two successively performed printing processes to let the print ink dry in the meantime. Further, this waiting time has been considered to be inevitably longer in the stencil printing than in other types of printing because of the incompatibility between fluidity and fast dryability required for the ink in the stencil printing.

Summary of the Invention

The present invention has started from the recognition that in the relief, the intaglio or the offset printing the printing plate is supplied with ink on the same side as the side which contacts an article for printing, whereas in the stencil printing the printing plate is supplied with ink on the other side opposite to the side which contacts an article for printing, and contemplates, as a first object of the invention, to utilize this feature effectively for providing the multilayered stencil printing with the time required for waiting the ink to dry between successive applications of multi-layered images being obviated.

In the printing using ink, including the stencil printing, there is another problem which is concerned with the transfer of the printed article. Since the ink forming the printed image on the article is not yet dried and fixed immediately after the printing, the printed surface of the article should not be mechanically contacted by a transfer means because otherwise the printed image will be damaged and the transfer means will be stained. Therefore, it has been difficult to transfer the printed article by any mechanical means which can provide much higher positional precision in transfer than available by the transfer depending upon the inertia of the article itself or an air stream.

In this connection, it is a second object of the present invention, in relation to the above-mentioned first object of the invention, to provide a method of and a device for multi-layered stencil printing in which a printed article bearing a wet ink image is transferred by a mechanical transfer means so that a high precision transfer is available, and therefore said first object of the invention is more ef f ectively accomplished.

According to the present invention, the above-mentioned first object is accomplished by a method of multi-layered stencil printing comprising the steps of pressing a plurality of stencil printing plates including first and second stencil printing plates onto an article in succession in respectively predetermined positions relative to said article in such a manner that said second stencil printing plate is pressed onto said article bearing a print image provided by said first is stencil printing plate regardless whether said print image has dried or not.

Further, the above-mentioned second object is accomplished by a method of multi-layered stencil printing providing a plurality of print images on a print sheet in succession in predetermined relative positions therebetween by employing a plurality of rotary stencil printing devices including first and second rotary stencil printing devices each comprising a printing drum and a back press roller cooperating to define a nip area therebetween for nipping said print sheet therein so as to f eed said print sheet therethrough while providing a print image thereon according to rotation of said printing drum and said back press roller, wherein said second rotary stencil printing device starts to f eed said print sheet before said print sheet is released f rom the feeding operation by said first rotary stencil printing device.

The above-mentioned second object is also accomplished by a stencil printing device for printing a plurality of print images on a print sheet in succession as overlapped one over another in predetermined relative positions therebetween, comprising a plurality of rotary stencil printing devices including first and second rotary stencil printing devices each comprising a printing drum and a back press roller cooperating to define a nip area therebetween for nipping said print sheet therein so as to feed said print sheet therethrough while providing a print image thereon according to rotation of said printing drum and said back press roller, said first rotary stencil printing device also serving as a means for feeding said print sheet from said nip area thereof directly to said nip area of said second rotary stencil printing device.

The above-mentioned method of multi-layered stencil printing according to the present invention may be practised in such a manner that each said stencil printing plate is removably mounted to a press plate in a predetermined position relative thereto, while said article is a print sheet placed on a base means in a predetermined position relative thereto, and said press plate is pivotably mounted to said base means so as to press each said stencil printing plate onto said print sheet placed on said base means in said respectively predetermined positions when pivoted relative to said base means.

The above-mentioned stencil printing device according to the present invention may be so constructed that said back press roller of said first rotary stencil printing device is common with said back press roller of said second rotary stencil printing device.

Since in the stencil printing the ink is supplied to the other side of the printing plate opposite to the side where it contacts an article for printing, even when the side of the printing plate contacting the article is stained by the wet ink of the print image formed by a prior printing, if the printing plate at each printing stage contacts the article correctly in a predetermined position relative to the article, the staining of the printing plate transfers to no other place. Therefore, even if the wet ink of a first print image transfers to the printing plate for printing a second print image as overlapped on said first print image, in spite of any time repetition of the first and second printings, the quality of the multi-layered print image is maintained as unchanged.

This fact provides a distinguished contrast of the stencil printing against the relief, the intaglio or the offset printing in which a staining at a portion of the printing plate spreads to other portions thereof via the ink supply roller.

Therefore, when it is particularly noted to satisfy the condition that the printing plate at each printing stage of a multi-layered printing always contacts an article for printing in a predetermined position relative thereto, the successive printings for the multi-layered stencil printing may be carried out without waiting the ink of a prior print image to get dried.

Further, when a print sheet is provided with print images by said first and second rotary printing devices in respectively predetermined positions relative thereto as being fed through said nip areas of said first and second rotary printing devices so that the print sheet is fed by said second rotary printing device before the print sheet is released from the feeding operation by said first rotary stencil printing device, the print sheet bearing a wet print image just provided by said first rotary stencil printing device is positively fed to said second rotary stencil printing device in a predetermined position relative thereto under the full holding on the opposite surfaces thereof by a mechanical transfer means available by the cooperating printing drum and ink supply roller of said first rotary stencil printing device with no problem of ink blotting.

The feeding in of the print sheet to the first stage rotary stencil printing device may be made by any conventional sheet transfer means, because the print sheet has yet no print image to be precisely positioned relative to the printing drum of the first stage rotary stencil printing device Brief Description of the Drawings

In the accompanying drawings, Figs. 1-6 are perspective views of a stencil printer in successive operational stage, showing an embodiment of practising the multi layered stencil printing method according to the present invention; Figs. 7-9 are schematic side views showing essential portions of a rotary stencil printer suitable for practising the present invention in three different operational states; Fig. 10 is a somewhat schematic front view of a printer including the construction shown in Figs. 7-9 as view from the right side in Figs. 7-9; Fig. 11 is a view showing the construction to combine three units of the rotary stencil printer shown in Figs. 7-10 into an integral rotary stencil printer for practising the multi-layered stencil printing method according to the present invention; and Fig. 12 is a view similar to Fig. 11 showing one more manner of practising the multi-layered stencil printing method according to the present invention. Description of the Preferred Embodiments

In the following the present invention will be described in detail with respect to some preferred embodiments with reference to the accompanying drawing.

Figs. 1-6 show in succession a manner of practising the present invention according to the progress of printing process in perspective views of a manually pressing type stencil printer for use on the table. In this embodiment, the portions designated by "a", 'V' and "c" at Fig. 6 are circular print images produced in three colours such as red, yellow and blue as overlapped one over the other to provide a multilayered colour print according to the present invention.

The construction of the printer herein used will be described with reference to Fig. 1. This Printer may be of the same type as the printer disclosed in Japanese Utility Model Publication 57-15814 assigned to the same assignee as the present application and widely used for these years under the trademark "PRINTGOCCW for printing new year cards or the like. However, the printer for use in the present application is Particularly provided with a means for determining the relative position between the print sheet and the printing plate, as described in detail hereinunder.

Referring to Fig. 1, 10 designates a printer base adapted to be placed on a flat surface like a table. A print sheet support base 12 is positioned on an upper surface of the printer base 10. Although not shown in the figure, it is more desirable that the print sheet support base 12 is constructed to be slidable on the upper surface of the printer base 10 and adjustable of its position on the printer base 10 in two dimensional directions along said upper surface by a position adjusting means, as in the press type stencil printer disclosed in Japanese Utility Model Application 2-24696 assigned to the same assignee as the present application.

A pair of stays 14 are fixed on the printer base 10, and a press plate 18 is mounted to the stays 14 by way of a rod 16 to be pivotable therearound. The press plate 18 is a plate member as shown in the figure, and has a pair of lugs 20 to pivotably engage with the rod 16.

The press plate 18 is formed with a pair of flexible bearing grooves 22, and a stencil printing plate support means 24 is mounted to the press plate by a pair of studs 26 provided at opposite ends thereof being received in the flexible bearing grooves 22 so that the stencil printing plate support means 24 is slightly tiltable relative to the press plate 18 about the axis of the studs 26.

The stencil printing plate support means 24 has a pair of holding means 30 adapted to hold a stencil printing plate 28 along opposite side edges thereof, and four projections 32 adapted to engage opposite end edges of the stencil printing plate 28 so as to restrict sliding movements of the stencil printing plate 28 along the side edges thereof, thereby fixing the position of the stencil printing plate 28 relative to the stencil printing plate support means 24. The stencil printing plate 28 may be of the type disclosed in Japanese Utility Model Laid-open Publication 51-132007 or Japanese Utility Model Application 1-117434 or 1- 117435, all assigned to the same assignee as the present application, having such a construction that a lamination 34 of a thermo-plastic film and a Japanese paper or a satin is supported by an annular f rame 36 made of cardboard as pasted to one side thereof while an ink impermeable sheet (not seen in the figure) is laid over on another side of the frame as pasted along one side of the annular frame 34 in a rectangular shape. Such a stencil printing plate may be perforated by the above-mentioned "PRINTGOCCO" according to an original or may be directly perforated by a thermal printing head incorporating a matrix of heat generating pin point elements, as disclosed in Japanese Patent Laid-open Publication 54-331117 assigned to the same assignee as the present application.

A pair of L shaped corner fittings 38 are provided on the print sheet support base 12 to help positioning a print sheet S placed thereon in a predetermined position relative thereto.

The embodiment shown in Fig. 1 is arranged to produce a print image having three circular images in red, yellow and blue, respectively, overlapped at one portion thereof. This print image is available by employing only one printer such as shown in the figure.

However, in order to expedite the production of such printed articles, in the embodiment shown in Figs. 1-6 three similar printers are employed to carry out the printing processes indicated by Figs. 1 and 2, Figs. 3 and 4, and Figs. 5 and 6 separately in the three different printers, so that the printing of circles in red, yellow and blue are carried out in the first, second and third printers, respectively.

Referring to Fig. 1, the stencil printing plate 28 is mounted to the printer as perforated at a circular portion 40 and supplied with red ink at the perforated portion, while a print sheet S is placed on the print sheet support base 12 as positioned at a predetermined position relative thereto by the corner fittings 38.

Starting from this state, when the press plate 18 is pressed against the printer base 10, a print image in red is formed on the print sheet as shown by "a". In Fig. 2, the printer is shown in the state that the press plate 18 was returned to its open position after the print image "a" in red was printed.

Then, the print sheet S is transferred to the similar printer shown in Figs. 3 and 4 so as to be placed on the print sheet support base 12 at a position determined by the corner fittings 38 as shown in Fig. 3. A stencil printing plate 28' of the same type as that mounted in the printer in Figs. 1 and 2 is mounted in the printer shown in Figs.

3 and 4 as perforated at a circular portion 41 and supplied with yellow ink at the perforated portion.

Then, further starting from the state shown in Fig. 3, the press plate 18 is pressed against the printer base 10 so that a circular print image "b" in yellow is additionally formed on the print sheet S as shown in Fig. 4. In Fig. 4, the printer is shown in the state where the yellow circle has been printed and the press plate 18 has been returned to its open position. In this case, if the printing in the yellow ink is carried out immediately after the printing in red ink in the condition that the red ink at the print image "a" is not yet dried, the stencil Printing plate 28' will be stained at a portion "a"' by the red ink transferred from the image "a" due to the contact therewith.

However, even when the press plate 18 is pressed against the print base 10 for the next printing in yellow ink on the next print sheet, the portion "a"' stained by red ink is only laid just over the print image "a" in red ink, and therefore no problem arises.

The print sheet provided with the print images "a" and "b" in red and yellow, respectively, as shown in Fig. 4 is then transferred to the similar printer shown in Figs. 5 and 6 so that it is placed on the print sheet support base 12 at a positioned determined by the corner fittings 38. A stencil printing plate 28" of the same type as the stencil printing plates 28 and 28' is mounted to the printer in Figs. 5 and 6 as perforated at 42 and supplied with blue ink at the perforated portion.

Then, further starting from the state shown in Fig. 5, when the press plate 18 is pressed against the printer base 10, the print sheet S is further provided with a circular print image "c" in blue ink as partly overlapped with parts of the circular print images "a" and "b" in red and yellow, respectively.

In this case, if the printing in the blue ink is carried out before the red and yellow inks forming the print images "a" and "b" are not yet dried and fixed, the stencil printing plate 2W is stained at portions "a"' and "b"' with the red and yellow inks transferred from the print images "a" and "b", respectively, as shown in Fig. 6. Therefore, for the second and subsequent print sheets transferred to the third printer for printing the circular print image "c" the stencil printing plate 2W is not in the condition shown in Fig. 5 but in the condition shown in Fig. 6. However, even when the printing for the image "c" is carried on in this condition of the stencil printing plate 28% since the stained portions "a"' and "b"' in red and yellow inks are laid just over the image portions "a" and "b", in red and yellow, respectively, there arises no problem either.

Thus, if the condition that the stencil printing plate is always contacted with the article for printing in a predetermined relative position is satisfied, a multi-layered stencil printing is available in providing print images by a plurality of stencil printing plates on one article with no need of taking a time for drying the ink of a first print before applying a second print thereon.

The multi-layered stencil printing according to the above-described principle can be practised in the rotary type stencil printer. Figs. 7-10 show the construction of a rotary stencil printer disclosed in Japanese Patent Application 1-341020 assigned to the same assignee as the present application. The construction of this rotary stencil printer is herein described only with respect to those portions necessary for the description of the present invention. Further details of the construction and the operations/ ef f ects thereof, if required, will be available from the specification and/or the drawing of said application.

Figs. 7, 8 and 9 are schematic side views showing certain essential portions of the rotary stencil printer disclosed in the above- is mentioned Japanese Application 1-341020 in three different operating states, and Fig. 10 is a somewhat schematic front view of the rotary stencil printer shown in Figs. 7-9 as viewed from the right side in these figures.

In these figures, 101 designates a printing drum, and 102 is a back press roller. The printing drum 101 comprises two annular members 103a and 103b forming opposite end portions thereof, and a net material 104 made of woven, non woven- or knitted string materials, such as, for example, a net made of warps and wefts of stainless wires in a shape of rectangular sheet, said rectangular net sheet being formed into a cylindrical shape to engage the outer peripheral surfaces of the annular members 103a and 103b at opposite side edge portions thereof to b ' e slidable thereon. A transverse bar 105 is mounted to bridge between the two annular members 103a and 103b along a generatrix of the cylindrical configuration of the printing drum 101. The transverse bar 105 bears a stencil sheet leading edge mounting means 105a for selectively mounting the leading edge of a stencil sheet mounted around the printing drum 101. Although the transverse bar 105 serves as a member for connecting the annular members 103a and 103b with one another, since these annular members are individually driven in synchronization with one another as described hereinunder, the transverse bar need not be a very strong member.

The printing drum 101 is supported to be rotatable about the central axis of the annular members 103a and 103b by tubular portions 106a and 106b extended axially outwardly from the annular members 103a and 103b being rotatably supported from a frame 108 at bearing portions 107a and 107b, respectively. The back press roller 102 is supported to be rotatable about its own central axis by shaft portions 109a and 109b extended axially outwardly from opposite ends thereof being supported from the frame 108 at bearing portions 110a and 110b, respectively.

The printing drum 101 and the back press roller 102 are adapted to rotate in synchronization with one another at a same speed in opposite directions as shown by arrows in Figs. 7-9 by ring gears 111a and 111b provided at opposite ends thereof meshing with one another, when the shaft portion 109b of the back press roller 109 is driven by a drive unit 113 including a motor not shown in the figure. Since the back press roller 102 may have a firm construction, the synchronous operation of the annular members 103a and 103b with no twisting therebetween is available even when the transverse bar 105 is not a very strong member. The back press roller 102 is formed with a groove 114 adapted to receive the transverse bar 105 when they meet together.

In Figs. 7-10, the distance between the peripheral surfaces of the printing drum 101 and the back press roller 102, or the distance between the central axes of the printing drum 101 and the back press roller 102 relative to the diameters thereof, is exaggerated for the purpose of illustration. In fact, said distance between the peripheral surfaces, or the difference of said distance between the central axes relative to said diameters, may be very small to be of the order of 2 to 5 mm when the diameter of the printing drum is ten and a few centimetres. The space to provide said clearance is a nip area 115 to nip the print sheet S when it is subject to printing. Feed rollers 116 and 117 are provided for feeding the print sheet S toward the nip area 115.

An inner press roller 118 is provided at the inside of the printing drum 101 so as to bulge a portion of the cylinder body substantially made of the net material 104 along a generatrix thereof radially outwardly toward the back press roller 102. The inner press roller 118 is supported to be rotatable about the central axis thereof by a shaft 119 extending along the same central axis, said shaft 119 being supported at opposite ends thereof from a shaft 120 via arms 121a and 121b. The shaft 120 extends through the tubular portions 106a and 106b at the opposite ends of the printing drum 101 and is supported at opposite ends thereof by the frame 108 via bearings 122a and 122b to be rotatable about its own axis. One end of the shaft 120 is connected with the drive unit 113 via a lever 123 and a link 124. When the printing drum 101 carries a stencil sheet mounted thereto in a regular position, and when it is detected by a sensor not shown in the figure that a print sheet is supplied to the nip area 115 in a regular manner, the drive unit is actuated in response to a control signal to drive the inner press roller 118 to bulge a portion of the cylindrical net body along a generatrix thereof radially outwardly toward the back press roller 102, as shown in Figs. 8 and 9, wherein, in Fig. 8, the transverse bar 105 is just at a position received in the groove 114 of the back press roller 102, and a stencil sheet T mounted around the printing drum 101 with its leading edge being fastened to the transverse bar 105 is going to contact a print sheet S.

A leading edge portion of the stencil sheet and a trailing edge portion thereof which is positioned relatively close to the leading edge portion when the stencil sheet is mounted around the printing drum are normally not perforated. Therefore, even if the cylindrical net body is bulged by the inner press roller when these leading and trailing edge portions are at a position to oppose the inner press roller, the back press roller is not stained by ink. Further, the area of the cylindrical net body extending between the leading edge portion and the trailing edge portion is mostly occupied by the transverse bar 105, and the back press roller is spaced from the printing drum at the portion to meet with the transverse bar by the groove 114. Therefore, even when the inner press roller is maintained at its advanced position throughout the state shown in Fig. 8 in which a preceding print sheet (not shown) has passed through the nip area and the next print sheet S has not yet reached the nip area, the back press roller will not be stained by ink.

Although not shown in the figure, ink is supplied to the inside of the printing drum in the same manner as in the well known conventional art so that the ink is then supplied onto the surface of the inner press roller 118 to form an ink layer thereon, and is then transferred to the inner peripheral surface of the cylindrical net body of the printing drum and then to the inside surface of the stencil sheet. Therefore, the inner press roller 118 operates as the means to bulge a portion of the cylindrical net body of the printing drum radially outwardly and also as an inking roller. Therefore, the inner press roller 118 is comparable in its function with the manual press roller in the old manual stencilprinter in which the manual press roller was rolled with ink over a stencil sheet mounted to a net supported by a rectangular f rame.

Fig. 11 shows, in the same schematic illustration as Figs. 7-9, a rotary stencil printer constructed to combine three units of the rotary stencil printer shown in Figs. 7-10 for practising the multi-layered stencil printing method according to the present invention. As shown in the figure, the three units are arranged to be close to one another is along the direction of feeding of the print sheet S, wherein, as compared with the unit U1 positioned at the upstream end as viewed in the flow direction of the print sheet, the next unit U2 is shifted, in its operational phase, for about 120 degrees, and the next to the next unit U3 is shifted, in its operational phase, further for about 120 degrees.

Of 'course these three units are operated in synchronization with one another to maintain a predetermined phase difference therebetween.

In this rotary stencil printer, a first print image in a first colour is printed on a print sheet in the unit U1, then a second print image in a second colour is printed on the print sheet as overlapped on said first print image in the unit U2, and then a third print image in a third colour is printed on the print sheet as overlapped on said first and second print images in the unit U3 while the units Ul, U2 and U3 are operated to maintain a predetermined phase difference therebetween with the print sheet being transferred through these units in a predetermined sequential relation. Therefore, in this rotary stencil printer, in the same manner as described with reference to Figs. 1-6, the second printing is carried out without waiting the ink of the first print image to dry, and the third printing is carried out without waiting the inks of the. first and second print images to dry, with no problem of ink blotting in the prints thus produced.

In Fig. 11, 125 and 126 designate guide means to support and guide the print sheet at the lower surface thereof. Such guide means may contact the whole area of the print sheet. Further, 127 and 128 are also guide means to guide the print sheet by contacting only side edge portions of the print sheet so as not to damage the wet print images.

The print sheet S is fed to the first unit U1 by rollers 116 and 117 operated in synchronization with the unit U1 to be in a predetermined position relative to the rotational phase of the unit UL Thereafter, the position of the print sheet S relative to the unit U2 is determined by the feeding function of the unit Ul, and the position of the print sheet S relative to the unit U3 is determined by the feeding function of the unit U2.

In more detail, when the printing on the print sheet S proceeds from the state shown in the figure, the print sheet S is transferred rightward in the figure as nipped between the printing drum 101 and the back press roller 102 of the unit Ul, and before the print sheet is released f rom the nipping in the unit Ul with the printing on the print sheet by the unit U1 having been finished or with further lapse of a small time thereafter, the leading end of the print sheet S is caught in the nipping by the printing drum and the back press roller of the unit U2. In the same manner the feeding of the print sheet is continuously transferred from the unit U2 to unit U3.

Fig. 12 is a view similar to Fig. 11, showing another embodiment of practising the multi-layered stencil printing method according to the present invention. In this embodiment, a single common back press roller 102 is used for the three printing drums 101 to apply three times printings on a print sheet. In this case, the print sheet S moves as supported on the single back press roller all through between the first, second and third printing drums and the back press roller. In order to hold the print sheet as attached onto the back press roller while it is being curved along the cylindrical surface of the back press roller, the back press roller is formed with a vacuum nozzle 130 arranged along a generatrix as a continuous slit or openings distributed therealong, and a vacuum is supplied thereto from a vacuum pump not shown in the figure, so that the leading edge portion of the print sheet is held to the. cylindrical surface of the back press roller. The holding of the leading edge portion of the print sheet by the vacuum nozzle 130 need only be enough to keep the leading edge portion of the print sheet as laid on the back press roller. In this embodiment, also, the positioning of the print sheet for the second printing drum is positively effected by the feeding function of the first printing drum, and the positioning of the print sheet for the third printing drum is positively effected by the feeding function of the second printing drum.

Since the vacuum nozzle 130 needs to operate only for holding the leading edge portion of the print sheet S, it may be replaced by an appropriate clamp means.

Although the invention has been described with respect to some preferred embodiments thereof, it will be clear to those skilled in the art that various modifications are possible with respect to the shown embodiments without departing from the scope of the present invention defined by the appended claims.

Claims (8)

Claims

1. A method of multi-layered stencil printing comprising the steps of pressing a plurality of stencil printing plates including first and second stencil printing plates onto an article in succession in respectively predetermined positions relative to said article in such a manner that said second stencil printing plate is pressed onto said article bearing a print image provided by said first stencil printing plate regardless whether said print image has dried or not.

2. A method of multi-layered stencil printing according to claim 1, wherein each said stencil printing plate is removably mounted to a press plate in a predetermined position relative thereto, while said article is a print sheet placed on a base means in a predetermined position relative thereto, said press plate being pivotably mounted to said base means so as to press each said stencil Printing plate onto said print sheet placed on said base means in said respectively predetermined positions when pivoted relative to said base means.

3. A method of multi-layered stencil printing providing a plurality of print images on a print sheet in succession in predetermined relative positions therebetween by employing a plurality of rotary stencil printing devices including first and second rotary stencil printing devices each comprising a printing drum and a back press roller cooperating to define a nip area therebetween for nipping said print sheet therein so as to feed said print sheet therethrough while providing a print image thereon according to rotation of said printing drum and said back press roller, wherein said second rotary stencil printing device starts to feed said print sheet before said print sheet is released from the feeding operation by said first rotary stencil printing device.

4. A stencil printing device for printing a plurality of print images on k a print sheet in succession as overlapped one over another in predetermined relative positions therebetween, comprising a plurality of rotary stencil printing devices including first and second rotary stencil printing devices each comprising a printing drum and a back press roller cooperating to define a nip area therebetween for nipping said print sheet therein so as to feed said print sheet therethrough while providing a print image thereon according to rotation of said printing drum and said back press roller, said first rotary stencil printing device also serving as a means for feeding said print sheet from said nip area thereof directly to said nip area of said second rotary stencil printing device.

5. A stencil printing device according to claim 4, wherein said back press roller of said first rotary stencil printing device is common with said back press roller of said second rotary stencil printing device.

6. A stencil printing device according to claim 4, wherein said back press rollers in said plurality of rotary stencil printing devices ' are provided by a single common roller.

7. A method of multilayered stencil printing substantially a 5 hereinbefore described with reference to, and asillUstrated in, Figs. 1 to 9; or Figs. 1 to 9 modified according to Fig. 10; or Figs. 7 to 10 a 0 modified according to Fig. 11; to Figs 7 to 10 modified according to Fig. 12 of the accompanying drawing.

8. A stencil printer substantially as hereinbefore described with reference to, and as illustrated in, figs. 1 to 9, Figs. 1 to 9 modified according to Fig. 10-, or Figs.7 to 10 modified according to Fig. 11; or Figs. 7 to 10 modified according to Fig. 12 of the accompanying drawings.

Published 1992 at The Patent Office, Concept House. Cardiff Road, Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point, Cwmfelinfach. Cross Keys. Newport. NP I 7HZ. Printed ky Multiplex techniques lid, St Marv Cray. Kent.