GB1559081A - Method and apparatus for transporting material to a printing location - Google Patents

Description

(54) METHOD AND APPARATUS FOR TRANSPORTING MATERIAL AND APPARATUS TO A PRINTING LOCATION (71) We, COLORDRY LIMITED, formerly known as INDUSTRIAL HIGH DRY LIMITED, a British Company, of 16 Park Road, Kingston-on-Thames, Surrey, (formerly of 15, Penrhyn Road, Kingston on Thames, Surrey KT1 2DA) do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment This invention relates to improvements in methods and apparatus for transporting or feeding material to a printing location.

In order to print material at a printing location it is generally necessary for the material which is to be printed, whether it be in sheet, web or component form, to be accuratelv located at a printing position relative to the image carried on a printing surface from which the image is to be transferred, whether this surface be flat or cylindrical as in screen printing or in the form of a printing roller. This accuracy of location is particularly essential where more than one printing operation is required to be performed, e.g., for the superimposition of colours.

Known screen printing systems rely on the material to be printed being fed to an exact predetermined print position either manually or by mechanical and I or suction gripper means. The material is normally held positively in the print position on a supporting surface during the printing operation by an under surface suction provided bv a vacuum table although if the material is sufficiently rigid or heavy a vacuum is not always required. The sup porting surface, commonly referred to as the printing bed can have a flat, curved or cylindrical surface.

Most automatically sheet fed screen orinting machines rely on the material being fed directly into accurately located register stops on the printing bed by a suction andl or mechanical gripper system. This suction and/or mechanical gripper system picks up the material from a feed table or stack or pile and places it into the printing bed, usually approximately into register. The register stops then move inwards or outwards pushing or pulling the material into an accurate register pushing or pulling the material into an accurate register position, or the material is mechanically moved into an accurate register position against static register stops by pressure rollers acting on the surface of the material.

Once the material is in the register position on the printing bed and the printing bed is in a registered print position relative to the stencil image the actual printing operation is carried out. After printing the material is transported or extracted from the printing bed out of the printing machine.

Most automatically extracting screen printing machines extract the printed material by either pulling and/or lifting the material directly off the printing bed by a mechanical andjor suction gripper system which physically grips one edge of the printed material and then pulls andjor lifts it onto an extraction conveyor or delivery table. Some extraction systems do not employ a gripper system as the forward movement of the material during the printing operation is sufficient to propel the material directly onto an extraction conveyor or delivery table.

Conventionally the material after feeding, printing and extraction is further transported through a drying machine which is entirely separate from the actual printing machine. These dryers are often con veyorised and pass the printed material through a tunnel of heated fan blown air.

In another known screen printing system, the material to be printed in sheet form is registered on a vacuum table at a register location and is transported with the table to the print location for printing after which the material is extracted whilst the table returns to the register location for registration of the next sheet.

In addition to the complexity of the mechanical and/or suction gripper systems referred to above, the known vacuum system referred to above suffers from the disadvantage that the material is not registered until after the previous printing operation has been performed. Also, where a stationary vacuum table is employed, the vacuum is generally only applied to the material when it is in register in the print position and during the printing operation so that it operates on an intermitent basis in the sense that the material must be released for transportation away from the print position after printing.

It is an object of the present invention to provide an improved method and apparatus for feeding material to a print location whereby material can be registered for printing whilst a printing operation is taking place.

According to one aspect of the present invention there is provided a method of feeding material to a printing location and printing said material which comprises registering the material at a register location on a support surface forming part of an endless band, constraining the material on the support surface by an applied vacuum against displacement relative thereto, advancing the endless band to displace the support surface from the register location to the printing location, registering the support surface at the printing location printing the material supported on and in register with the support surface and advancing the endless band to displace the support surface away from the printing location whilst simultaneously advancing further material from the register location to the printing location.

The method of the invention is applicable both to the printing of long lengths of material in a continuous manner, e.g., using a printing roller at the print location or the printing of individual sheets or articles at the print location in an intermittent manner, e.g.. by using a roller or a flat bed, e.g., a printing screen. By " articles " is to be understood anything having a sufficiently flat surface to be printed.

Advantageously, the vacuum may be increased at the printing location to increase the constraint applied to the material during the printing opeIation.

The support surface may be advanced from the printing location to a drying location with the vacuum constraint applied during the advancement and during the interval the material is exposed to the drying location. This has the advantage that the material may be exposed to air blasts at the drying location of greater than normal intensity and further that it will be retained in register on the support surface for a subsequent further printing operation if such be required.

According to another aspect of the present invention, there is provided apparatus for feeding material to a printing location comprising an endless band arranged to be advanced in one direction from a register location to the printing location, means for registering the material at the register location on a support surface forming part of the endless band vacuum means operable to constrain the material on the support surface against displacement relative thereto, means movable at the printing location to register the support surface with respect to the printing location, and means for printing at the printing location the material supported on and in register with the support surface.

Preferably. the constraining means comprises a vacuum table disposed below the endless band and extending at least from the register location to the printing location and the support surface is perforated to apply the vacuum to the supported material.

With advantage, the vacuum table may be composed of two or more vacuum chambers capable of being maintained at different sub-atmospheric pressures whereby the support surface at the register location can be exposed to a lesser vacuum than when located at the pruit position.

The support surface forming part of the endless band may be arranged to travel to a drying location whilst the vacuum is applied thereto to apply constraint to the material during the drying operation. When at the drying location, the constraint may be applied by a vacuum chamber which may be the same as or different to that at the printing location so that the material may be exposed to the same or a different subatmospheric pressure.

Where the printing operation is a substantially continuous operation, the means operable to locate the support surface at the printing location may comprise a pair of tracks and rollers or guides carried on or associated with the support surface or endless band and engaged with and guided by said tracks at least in the vicinity of the printing location.

Where the printing operation is intermittent the means operable to locate the support surface at the printing location preferably comprises locating members disposed at or in the vicinty of the printing location and operable positively to engage complementary formations on or associated with the support surface or the endless band.

The endless band may be a one piece or multi-section conveyor belt manufactured from any suitable material which will provide a sufficiently smooth flat, hard and inelastic printing surface but which is, at the same time, flexible enough to travel around drive and/or end rollers used to drive and guide the band. The endless band could be formed of very thin sheet steel, sometimes referred to as "shim" or it could be formed from a synthetic or natural material with or without reinforcement. The endless band can, as stated above be manufactured in one piece, with or without a single lateral flexible joining seam or can, for convenience be manufactured in sections. Where a sectional belt is used and the constraint is provided by a vacuum from vacuum tables over which the belt Is displaced, it is necessary for each section to be at least as large as the area of the material supporting surface. In order to minimise vacuum loss, each section of belt should overlap or underlap an adjacent section or if the opposed ends of adjacent sections are separated or butted up to one another, a suitable flexible joining material should be used to close the space between the ends.

In a preferred embodiment the conveyor belt is arranged to travel over the surface of a sectional vacuum table which is constructed with either vacuum holes and/or slots in its surface. These holes and/or slots are arranged so that as the belt moves forward or is stationary at least sufficient holes and/or slots align with the vacuum holes in the conveyor belt to sufficiently hold down the material whilst it is in the machine, and if required to have at least sufficient holes and/or slots to hold the belt in contact with the surface of the vacuum table as it moves forward and/or is stationary.

The surface of the sectional vacuum table is constructed in such a way as to minimise any friction between its surface and the undersurface of the conveyor belt.

Each section of the vacuum table is arranged so that the internal vacuum pressures can be controlled in order to provide variable degrees of suction hold down on the material being transported or processed on the upper surface of the conveyor belt, and to sufficiently hold down the conveyor belt whilst it is stationary and/or moving.

It is also necessary, in order that the conveyor belt remains in contact with the overall surface of the sectional vacuum table, for it to be manufactured in such a way that its upper surface is laterally as flat as possible throughout its length, with the exception of any unevenness caused by the vacuum holes and/or slots.

However, if a conventional cylinder printing head is to be used, the upper surface of the vacuum table can be curved outwardly towards the printing head either throughout its length or preferably only in the area where printing would normally take place. In this case any curvature which is provided in the printing area should be preceded and followed by sectional vacuum tables inclined tangentially to the curved portion to provide a transition between the flat portions and the curved portion and to ensure overall belt to vacuum table contact.

The conveyor belt is attached along each longitudinal edge to one or more chains or belts by suitable connectors affixed to its surface. Such connectors may be attached to the longitudinal edges of the conveyor belt or alternatively or additionally may be rigid members extending transversely across the conveyor belt at intervals along its length and secured thereto. These chains or belts are in turn run through cog wheels to provide alignment and motive power and are connected via a conventional stop-start mechanism to a drive motor. If the conveyor is to be used to carry material which is to be printed in web form by a continuously rotating rotary print head then the stop-start mechanism is not required but is essential in all other cases. Each chain or belt is aligned as accurately as possible and is arranged to impart both sufficient lateral and longitudinal force on the conveyor belt as is necessary to ensure that it is kept in sufficient tension and alignment through the machine. However, since a certain amount of tolerance is unavoidable both in the connections of the conveyor belt to the chains or belts, and in the chains or belts themselves, and in their connections to the cog wheels, additional alignment is required.

This can be provided either by further attachments to the chains or belts in the form of guide wheels running against the smooth face or faces of guide bars, placed on either side of the conveyor running parallel to the conveyor, or by guide tracks arranged. on either side of the conveyor through which the chains or belts run, or by a combination of both. The guide wheels and/or guide bars and/or guide tracks are required to be adjustable to take up any variation caused by wear or movement over a period of time in the conveyor belt and/or its connections and/or in the chains or belts and their connections and/ or in the guide bars and/or guide tracks.

The conveyor is thus registered laterally and, in the case of continuously printing a web, the conveyor is continuously advanced at a speed corresponding to the peripheral speed of the rotating print head.

Where the printing operation is intermittent final alignment is required in order to achieve as accurate register as possible from each printing impression to the next and also from each printing impression to its preceding registering stage. This is achieved by providing final location devices of either points and/or holes, on or in or attached to the master printing and registering frames, which positively locate either directly into the chains or belts themselves or mto further attachments connected to the chains or belts and/or conveyor belt and/or into location holes in the conveyor belt and/or vacuum table.

Between the stop-start movements of the conveyor belt during intermittent printing, the final location devices have to be lifted and lowered. They can either be manufactured as rigid attachments to the master register and printing frames which would lift and lower with them, or can be designed to lift and lower independently from them.

In either case the lifting and lowering actions of the location devices are designed to positively lock in register the master register and printing frames as one integral unit to the respective feed and print areas on the conveyor, situated underneath them at that stage of the conveyor cycle, as another integral unit.

Because of the difficulty of fitting lifting and lowering registration stops or jigs through or into the flexible movable con veyor belt a system of overhead stops or jigs may be provided which are lifted and lowered onto and off the surface of the conveyor belt in the initial registration area. This is made possible by the fact that the conveyor belt is stationary when the preceding material is actually being printed and that the master printing frame has to be in close or actual contact with the material on the conveyor belt at the time of printing. The master registration frame is manufactured as an extension of the master printing frame and is therefore also in close contact with the conveyor belt in the initial registration area. The register stops or jigs which are mounted in the master register frame are designed to be adjustable vertically so that they can, if required, be lowered into actual contact with the stationary conveyor belt at the time of printing. Apart from acting as overhead register stops or jigs they are of conventional design and can be designed as either static fixtures or to either push or pull the material being printed into an exact preset register position on the conveyor belt. Their position is also adjustable within the master register frame. When, with the exception of continuous printing of material in web form, a rotary screen printing head is mounted over the conveyor, a similar register frame is used except that the lifting and lowering of the register stops or jigs in the feed area of the conveyor are activated by the movement of the rotary screen itself.

When the conveyor is used in conjunction with a rotary screen printing head to print continuous designs on material in web form, it is necessary to fit lateral web guiding mechanisms in place of the register stops laterally to register the web on the conveyor and to use conventional but separate feed and re-reel rollers at each end of the conveyor. It is also necessary to synchronise the rotating speed of the printing screen with the continuous forward speed of the cqnveyor belt.

SYNCHRONISATION OF MOVEMENTS AND LAYOUT The conveyor is designed so that at the time of printing there is always one full area of vacuum holes situated under the printing head on the upper surface of the conveyor belt. The vacuum holes in this area, which are not actually holding down the material are normally required to be masked out with suitable impervious flexible material as is conventional on other types of vacuum beds. This is of great importance if flexible lightweight material is being printed and is to be passed, after printing, under high velocity air drying heads, on an extended integrated drying conveyor.

At the same time as one full area of vacuum holes is situated under the printing head, the conveyor is arranged so that a predetermined proportion of the area of vacuum holes in the conveyor belt at the feed and extraction ends of the machine, are also situated on the upper surface of the conveyor.

The area at the feed end of the conveyor is sufficient in length to allow a sufficient area of material to be placed on it and, after registering, for it to be held down positively on the surface of the conveyor belt. After printing the conveyor belt moves forward bringing the whole of the vacuum area at the feed end onto the upper surface of the conveyor and in doing so is designed to pull the material, still held in register, off a feed table entirely onto its surface. In this way the whole area of the material becomes progressively subjected to under surface vacuum pressure and is con sequently held positively in register on the surface of the conveyor belt as it moves forwards under the printing head, the register stops or jigs having been lifted at the start of this forward movement.

The distance between the register stops or jigs and operator, if the machine is being fed manually, need only be the length of the material itself, therefore only a rela tively short feed table is required. This advantage also applies if the machine is to be fed automatically because the distance between the register stops and the feed end of the conveyor can be kept as short as is sufficient to initially hold down the material.

Thereby the forward movement of the material out of the automatic feeder into register can also be relatively short.

Once the material on the conveyor belt has been moved forward from the initial feed area into the print area the conveyor belt is again designed to stop at a predetermined point on the conveyor. This point is fixed so that each vacuum area stopping under the print head is positioned in exactly the same relative position. It is positively locked in this position by the location devices previously described.

Immediately after printing these location devices are lifted and the conveyor belt again moves forwards carrying the material still held down by vacuum either directly out of the machine or onto an integrated extension of the conveyor which acts as a drying conveyor.

In the case of the material being passed directly out of the machine after printing, the extraction area of the conveyor can also be designed to be as short as possible.

The length of the area of vacuum holes on the upper surface being determined by the amount of vacuum area required to prevent the trailing edge of the material lifting as it is automatically released from vacuum pressure at the end of the conveyor by the conveyor belt passing over and under the end roller.

If the machine is designed with an extended integrated drying conveyor, then as the conveyor belt progressively moves forwards, with the material on its surface, drying heads can be mounted over it. The material is then finally eiected in the same manner as a machine without an extended integrated drying conveyor.

Since material remains positively held down still in register, with all unused vacuum holes in the conveyor belt being masked out, several advantages are gained over conventional printing and drying systems. Firstly a far greater velocity of cool or warm air can be blown onto the surface of the printed material before there is any fear of it lifting and marring the undried printed sheet.

Secondly it is possible with expanded conveyors carrying the material still in register, to fit further printing heads over the conveyor to print second and subsequent colours with further drying stages in between each printing head.

As stated above most tvpes of conventional screen printing heads can be mounted over the print area of the machine.

These would normally consist of (1) A printing screen with either a flat or cylindrical surface.

(2) A master carrier frame assembly for flat screens or a master rotary screen carrier for cylindrical screens (3) A mechanised printing squeegee with standard attachments.

(4) A conventional system (if required) in corporate in the master carrier frame to provide assisted "snap-off" follow ing the squeegee printing action on flat screens.

(5) An adjustable lift and lower mechanism to raise the printing head for screen in spection, cleaning and to vary the distance between the under-surface of the screen and conveyor printing bed.

A conventional screen printing cylinder machine head with attachments can also be fitted over a curved conveyor belt and would include a conventional reciprocating mechanism to move the flat screen over the moving print area of the conveyor.

One embodiment of the invention will now be described by way of example, reference being made to the accompanying drawings in which : Fig. 1 is a perspective view of part of the apparatus according to the invention for use in a silk screen printing operation, Fig. 2 is a part-sectional part-elevational view taken on the line II-II of Fig. 1, Fig. 3 is a plan view of the apparatus of which part is shown in Fig. 1, Fi. 4 is a section taken on the line IV-IV of Fig. 3, Fig. 5 is a fragmentary plan view illustrating a part of the apparatus of Fig. 1, and Fig. 6 is a fragmentary view similar to Fig. 4 illustrating an extension of the apDaratus.

Fig. 7 is a fragmentary plan view illustrating a modification.

The apparatus of this embodiment is intended for screen printing of individual sheets and comprises an endless band in the form of a conveyor belt 1 provided along each longitudinal edge with outwardly extending locating elements 2 secured to the belt 1 as by rivets 3 and secured to the links 4 of a longitudinally extending belt drive chain 5 having spaced outwardly extending arms 6 each carrying a guide wheel 7 running in a track 8. The drive chain 5 runs in a shallow guide slot 9.

The upper flight of the belt 1 follows a Dath which extends from a register position 10 (E7igs. 3 and 4) to a printing position 11 and beyond. The belt 1 is guided and advanced bv two spaced toothed rollers 12 and 13 (Fig. 4) which engage the chain 5 and one of which, e.g., the roller 12, is driven as by a belt 14.

Between the toothed rollers 12 and 13 the upper flight of the belt 1 is supported on the respective surfaces 15, 16 and 17 of three adjacent vacuum tables or chambers 18, 19 and 20.

The vacuum table 18 extends from the register position 10 towards the printing position 11, the vacuum table 19 is located at the printing position 11 and the vacuum table 20 extends from the printing position 11 to the roller 12. The surfaces 15, 16 and 17 are formed with rows or columns of small apertures 21 which communicate with the interior of the respective vacuum tables and which communicate with each other in rows or columns as by shallow grooves 22. This is illustrated in Fig. 5 where it can also be seen that the belt 1 is similarly formed with rows or columns of apertures 23 which register with the grooves 22 so that material supported on the belt 1 is exposed to a vacuum generated in the vacuum tables 18, 19 and 20.

At the printing position 11 is located a printing frame 24 carrying a screen mesh 25 carrying the image to be printed. The printing frame 24 is carried on a master frame 26 mounted on pillars 27 at the four corners. The master frame 26 also carries two spaced longitudinally extending runner bars 28 supporting a squeegee printing blade 29 and an ink return blade 30 associated therewith. The master frame 26 is lifted and lowered by the pillars 27 in known manner and carries on each side normal to the direction of travel of the belt 1 or more frusto-conically shaped location locks 31 which are located and dimensioned to engage in conical aperture 32 in the locating elements 2. There is preferably one location lock 31 at each corner of the master frame 26.

At the register position 10 is located a register frame 33 carrying register stops 40 which are adjustable to the size of the material to be printed and which locate sheet material 34 both transversely of the belt 1 and by its leading edge. The register frame 33 is associated with the master frame 26 so that both lift and drop together.

In this example, the first vacuum table 18 considered in the direction of advance of the bolt 1 extends only part way into the register position 10 as does the upper fliht of the belt 1 but it will be understood that it could extend completely below the register position 10 if desired. There is therefore provided at the register position 10 a support 35 for the rearward part of the registered material 34 to be printed. This limits the vacuum applied to the material 34 to the forward part thereof and facilitates registration and also materially reduces the overall length of the machine.

In the operation of the apparatus thus far described (with both the master frame 26 and the register frame 33 and register stops 40 lowered, and the belt 1 stationary, a sheet of material 34 is fed to and is registered at the register position 10 against the register stops 40. At this time and to facilitate registration the vacuum chamber 18 is preferably at atmospheric pressure and, once the sheet 34 is registered, a vacuum is applied in the chamber 18. The master frame 26 and the register frame 33 and register stops 40 are then raised a short distance and the belt is driven to advance that part of the surface supporting the registered sheet material 34 in close approximation to the printing position 11. Whilst at the register position 10, the sheet material 34 is constrained against displacement by the vacuum applied thereto from the vacuum table 18 through the surface 15 and the apertures 21, grooves 22 and apertures 23. As the sheet material leaves the register position 10 it becomes increasingly exposed to the vacuum table 18 until it is whollv supported on the belt 1 and wholly exposed.

Continued movement of the belt 1 brings it over the supporting surface 16 of the vacuum table 19 until it reaches the printing position 11 when the belt is stopped.

At this position, the sheet material 34 is wholly exposed to the vacuum in the table 19 and it is preferred, but not essential, that this vacuum should be greater than that of the table 18 so that in the printing position, the sheet material 34 is exposed to a greater constraint against displacement than at the register position. The master frame 26 and printing frame 24 are then lowered by the pillars 27 and the register frame 33 and register stops 40 are similarly lowered. The location locks 31 are lowered with the master frame 26 and engage i mesh 25 squeezing ink therethrough and printing the image on to the sheet material 34. At the same time, the next sheet is being placed and held in register at the register position 10.

When the printing blade 29 has completed its traverse the frames 24 and 26 are raised together with the register frame 33 and register stops 40 and the belt 1 is advanced to bring the next sheet to the printing position 11. As this is happening, the printing blade is returned to its initial position and the ink return blade 30 operates to return to the starting position the ink swept before the printing blade 29 during its traverse. As the belt 1 is bringing the next sheet material 34 to the printing position, the printed sheet is advanced out of the printing position and leaves the constraint imposed by the vacuum table 19 and becomes exposed to that of the vacuum table 20. The latter may have the same vacuum as the table 19 but is preferably less and advantageously the same as that of table 18 when the material has been registered.

Once the printed sheet has been advanced beyond the printing position it may be advanced to a drying location 36 in any suitable and conventional manner, e.g., as by being fed from the belt 1 to a further conveyor belt la over a support plate lb.

It is preferred, however, to advance the printed sheet material to the drying location 36 (Fig. 6) by the belt 1 which is correspondingly extended and to constrain it against displacement during such advance by a further vacuum table 37 having a perforated supporting surface 38. The constraint exerted by the vacuum table 37 may be the same as or different from that exerted by the tables 18 and 20 or the table 19 but advantageously is sufficient to hold the printed sheet against displacement even against the effect of hot air blasts in the drver unit 39 so that greater than usual airblasts may be employed without displacing the sheet material resulting in a shorter drying time. This means that the drying units 39 can be made shorter than is usual and require less space. In order to extend the belt 1 to beyond the drving unit, the drive wheel 12 shown in Fig. 4 can be correspondingly displaced as shown in Fig.

6 or an additional drive mechanism provided.

By constraining the printed sheet material 34 against displacement from the time it is registered at the register position 10 to beyond the drver unit 39, it will be appre ciated that the sheet material 34 is in register for any further printing operation which may be required, e.g., where two colour printing is required. In such cases, the belt 1 is advantageously further extended from the drying location 36 to beyond a further printing location (not shown) and even beyond to a further drying location (not shown) the constraint being maintained by further vacuum tables with supporting surfaces.

It will be appreciated from the above description that the belt 1 and the sheet material 34 is always advanced in one direction away from the register location 10 and that the registered sheet material is constrained against displacement. Also, when a printing operation is being performed on one sheet of material 34 the next sheet is being registered.

It will also be appreciated that the invention is applicable to the continuous printing of web material fed from a roll and printed by means of a roller at the printing location 11. In such a case, the web is laterally registered on the belt 1 at the register location 10 and is constrained against displacement by the vacuum applied thereto, the belt 1 being guided by the guide wheels 7 and tracks 8 to bring the web into the correct printing position and being continuously advanced at a speed corresponding to the peripheral speed of the printing roller.

In Figs. 4 and 6, the spacing between various surfaces, e.g., between the surfaces of the vacuum tables and the belt 1 and between the belt 1 and the sheet material 34 has been markedly accentuated for clarity.

As has been previously mentioned, the conveyor belt 1 may be attached to the chains 5 by rigid members which extend across the belt 1 at spaced intervals. Such rigid members may be alternative or additional to the locating elements 2. Where the rigid members are provided, they would be spaced longitudinally of the belt to define intervening areas sufficiently large to accommodate sheet material 34 to be printed such as, for example, the areas of the belt 1 indicated in Fig. 4 by dotted lines to denote perforated areas of the belt 1 for supporting the sheet material. Such rigid members could be formed with apertures corresponding to the apertures 32 in the locating elements 2 for cooperation with complementary and appropriately located locating locks on the master frame 26. It will be noted that where such rigid members are provided together with the locating elements 2 thev would effectively form a frame surrounding the supporting surface carrying the sheet material which frame could be located on all four sides bv locating locks corresponding to the locks 31 and complementary apertures corres pondin to the apertures 32.

Fig. 7 illustrates such a belt in which the rigid members indicated at 200 are alter native to the locating elements 2. These rigid members 200 are attached in a manner (not shown) to the drive chain 5 and the arms 6, guide wheel 7 and track 8 are omitted. The belt is formed of sections 201 and is advanced intermittently in the direction of the arrow A. The leading edge 202 of each section 201 is positively attached to a rigid member 200 so as not to be displaceable relative thereto. This can be achieved by rivets or adhesive. The trailing end 203 of each section 201 is attached to the next rearward rigid member 200 with a limited degree of freedom to move relative thereto in the direction of length of the belt. This can be achieved by rivets in the section 200 engaged in slots in the rigid member 200. The arrangement and dimensions are such that the rigid members 200 are advanced by the chain 5 and pull the rearwardly extending section 201 along so that each section is positively located by its loading end 202 and its trailing end 203 abuts the leading end 202 of the next section 201 with the rigid member thereover. This minimises loss of vacuum where the sections 201 abut and gives the sections at their trailing end 203 a degree of freedom to facilitate their travel over the non-planar part of the path, as when the chain 5 passes over rollers 12 and 13.

The rigid members 200 are formed with locating conical apertures 32.

The sections 201 are conveniently from fibre glass coated with Telflon (Registered Trade Mark) which exhibits the required low friction characteristic and is resistant to the heat generated at the drying stations.

The sections are perforated as at 23 and slide on a diffuser sheet 204 which is conveniently of expanded sheet steel and which rests on a steel sheet 205 formed with slots 206. The steel sheet 205 forms the top of a vacuum table and the diffuser sheet 204 serves to diffuse the vacuum to the underside of the sections 201 and prevent localised loss of vacuum.

It is to be understood that the term "drying" as used herein refers not only to the drying of the ink or the location at which the ink is dried, but also includes curing of the ink or the location at which the ink is cured whenever applicable.

WHAT WE CLAIM IS:- 1. A method of feeding material to a printing location and printing said material which comprises registering the material at a register location on a support surface forming part of an endless band, constraining the material on the support surface by an applied vacuum against displacement relative thereto, advancing the endless band to displace the support surface from the register location to the printing location, registering the support surface at the printing location, printing the material supported on and in register with the support surface and advancing the endless band to displace the support surface away from the printing location whilst simultaneously advancing further material from the register location to the printing location 2. A method according to Claim 1 in which the vacuum is increased at the printing location to increase the constraint applied to the material during the printing operation.

3. A method according to Claim 1 or 2 in which the support surface is advanced from the printing location to a drying location with the vacuum constraint applied during the advancement and during the interval the material is exposed to the drying location.

4. A method according to Claim 1, 2 or 3 in which the printing operation is performed intermittently at the printing location by a printing head and the support surface is located at the printing location by engaging locating members on the printing head with complementary forma tions on or associated with the support surface.

5. A method of feeding sheet material to a printing location and printing said material which comprises the steps of a) registering the material at a register location on a support surface forming part of an endless band, b) advancing the endless band in the direction to displace the support surface from the register location to the printing location, c) registering the support surface at the printing location, d) printing at the printing location, the material supported on and in register with the support surface, e) advancing the endless band in said direction to displace the support surface away from the printing location whilst simultaneously advancing further material from the register location to the printing location, and f) constraining the registered material on the support surface against displacement relative thereto by exposing the material to a vacuum applied through the support surface at least during steps b), c) and d).

6. A method according to Claim 5 in which the registered material is constrained against displacement relative to the support surface by exposure to an applied vacuum before step b).

7. A method according to Claim 5 or 6 in which the registered material is constrained against displacement relative to the support surface by exposure to an applied vacuum during step e).

8. A method according to Claim 5, 6 or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

**WARNING** start of CLMS field may overlap end of DESC **. native to the locating elements 2. These rigid members 200 are attached in a manner (not shown) to the drive chain 5 and the arms 6, guide wheel 7 and track 8 are omitted. The belt is formed of sections 201 and is advanced intermittently in the direction of the arrow A. The leading edge 202 of each section 201 is positively attached to a rigid member 200 so as not to be displaceable relative thereto. This can be achieved by rivets or adhesive. The trailing end 203 of each section 201 is attached to the next rearward rigid member 200 with a limited degree of freedom to move relative thereto in the direction of length of the belt. This can be achieved by rivets in the section 200 engaged in slots in the rigid member 200. The arrangement and dimensions are such that the rigid members 200 are advanced by the chain 5 and pull the rearwardly extending section 201 along so that each section is positively located by its loading end 202 and its trailing end 203 abuts the leading end 202 of the next section 201 with the rigid member thereover. This minimises loss of vacuum where the sections 201 abut and gives the sections at their trailing end 203 a degree of freedom to facilitate their travel over the non-planar part of the path, as when the chain 5 passes over rollers 12 and 13. The rigid members 200 are formed with locating conical apertures 32. The sections 201 are conveniently from fibre glass coated with Telflon (Registered Trade Mark) which exhibits the required low friction characteristic and is resistant to the heat generated at the drying stations. The sections are perforated as at 23 and slide on a diffuser sheet 204 which is conveniently of expanded sheet steel and which rests on a steel sheet 205 formed with slots 206. The steel sheet 205 forms the top of a vacuum table and the diffuser sheet 204 serves to diffuse the vacuum to the underside of the sections 201 and prevent localised loss of vacuum. It is to be understood that the term "drying" as used herein refers not only to the drying of the ink or the location at which the ink is dried, but also includes curing of the ink or the location at which the ink is cured whenever applicable. WHAT WE CLAIM IS:-

1. A method of feeding material to a printing location and printing said material which comprises registering the material at a register location on a support surface forming part of an endless band, constraining the material on the support surface by an applied vacuum against displacement relative thereto, advancing the endless band to displace the support surface from the register location to the printing location, registering the support surface at the printing location, printing the material supported on and in register with the support surface and advancing the endless band to displace the support surface away from the printing location whilst simultaneously advancing further material from the register location to the printing location

2. A method according to Claim 1 in which the vacuum is increased at the printing location to increase the constraint applied to the material during the printing operation.

3. A method according to Claim 1 or 2 in which the support surface is advanced from the printing location to a drying location with the vacuum constraint applied during the advancement and during the interval the material is exposed to the drying location.

4. A method according to Claim 1, 2 or 3 in which the printing operation is performed intermittently at the printing location by a printing head and the support surface is located at the printing location by engaging locating members on the printing head with complementary forma tions on or associated with the support surface.

5. A method of feeding sheet material to a printing location and printing said material which comprises the steps of a) registering the material at a register location on a support surface forming part of an endless band, b) advancing the endless band in the direction to displace the support surface from the register location to the printing location, c) registering the support surface at the printing location, d) printing at the printing location, the material supported on and in register with the support surface, e) advancing the endless band in said direction to displace the support surface away from the printing location whilst simultaneously advancing further material from the register location to the printing location, and f) constraining the registered material on the support surface against displacement relative thereto by exposing the material to a vacuum applied through the support surface at least during steps b), c) and d).

6. A method according to Claim 5 in which the registered material is constrained against displacement relative to the support surface by exposure to an applied vacuum before step b).

7. A method according to Claim 5 or 6 in which the registered material is constrained against displacement relative to the support surface by exposure to an applied vacuum during step e).

8. A method according to Claim 5, 6 or

7 in which the support surface is advanced from the printing location to at least one further operational station and registered material is constrained against displacement relative to the support surface by exposure to a vacuum applied through the support surface at least until the operation at such further operational station is complete.

9. A method according to Claim 5, 6 or 7 in which the endless band is advanced in said direction to displace the support surface from the printing location successively to a drying station and a further printing location and the registered material is constrained against displace ment relative to the support surface by exposure to a vacuum applied through the support surface at least until the material has been printed at said further printing location.

10. A method of feeding material to a printing location and printing said material substantially as herein described.

11. Apparatus for feeding material to a printing location and printing said material comprising an endless band arranged to be advanced in one direction from a register location to the printing location, means for registering the material at the register loca tion on a support surface forming part of the endless band, vacuum means operable to constrain the material on the support surface against displacement relative thereto, means movable at the printing location to register the support surface with respect to the printing location, and means for printing at the printing location the material supported on and in register with the support surface.

12. Apparatus according to Claim 11 in which the constraining means comprises a vacuum table disposed below the endless band and extending at least from the register location to the printing location and the support surface is perforated to apply the vacuum to the supported material.

13. Apparatus according to Claim 12 in which the vacuum table is composed of two or more vacuum chambers capable of being maintained at different sub-atmospheric pressures whereby the support surface at the register location can be exposed to a lesser vacuum than when located at the printing location.

14. Apparatus according to Claim 11, 12 or 13 in which the support surface forming part of the endless band is arranged to travel tc a driving location whilst the vacuum is applied thereto to apply constraint to the material during the drying operation.

15. Apparatus according to any one of the Claims 11 to 13 in which the means operable to locate the support surface at the printing location comprises a pair of tracks, and rollers or guides carried on or associated with the support surface or endless band and engaged with and guided by said tracks at least in the vicinity of the printing location.

16. Apparatus according to any one of Claims 11 to 13 in which the means operable to locate the support surface at the printing location comprises locating members disposed at or in the vicinity of the printing location and operable positively to engage complementary formations on or associated with the support surface or the endless band.

17. Apparatus according to Claim 16 for intermittent printing at the printing location by a printing head in which the locating members are carried on the printing head which is displaceable to a printing position in which the locating members engage the complementary formations.

18. Apparatus according to Claim 17 in which the endless band is manufactured from a plurality of sections each of which carries a rigid member formed with at least one of said complementary formations.

19. Apparatus according to Claim 18 in which the sections are attached to a rigid member at their leading end considered in the direction of advance of the band and to a separate similar rigid member at their trailing end.

20. Apparatus according to Claim 19 in which the rigid members extend across the width of the band and each section is positively attached to the rigid member at its leading end to be drawn thereby in the direction of advance and loosely attached to the rigid member at its trailing end to have a limited movement relative thereto to facilitate advance of the band over the non-planar part of its path.

21. Apparatus according to any one of Claims 11 to 20 including a plurality of printing locations with a drying location between each and means for locating the support surface at each printing location.

22. Apparatus for feeding material to a printing location and printing said material constructed, arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.