CA1038690A - Inking device - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A device for applying ink to a printing surface is described. The device includes two resilient ink flow control blades. The blades are deflected by contact with said surface to allow ink to flow onto the latter. The blades close to cut off the flow of ink as the device is lifted off the surface.

Description

~038690 This invention relates to a device for use in applying ink and the like to a printing surface. For convenience of description reference is herein confined to the application of ink. However, it is to be under-stood that the device of the invention may be used for applying other liquids, for example, lacquers and water.
In many conventional printing techniques, ink is applied to a printing surface from a trough in which a cylinder (or roller) rotates. The printing surface may be the peripheral surface of the cylinder itself or the cylinder may transfer the ink to a remote printing sur-face. This method of applying ink from a trough has numerous disadvantages. For example, such cylinders are often necessarily of substantial length. Since support rollers cannot conveniently be provided where an ink trough is used, sagging of the cylinder tknown as "cylinder deflection") may be a problem. Also, where the cylinder is an impression cylinder, an impression can be taken only from the top of the cylinder, which has the disadvantage that gravity acts against transfer of ink to the paper being printed. Further, only one trough can be used with each cylinder with the result that only one impression can be taken per cylinder.
The present invention has been devised in con-nection with rotogravure printing (although the invention is not limited by this). Rotogravure is an intaglio printing technique in which the design to be printed is formed by recessed ink-carrying cells in the curved surface of a printing cylinder. The cells are arranged in the pattern of the design to be printed. Conventionally, the cylinder rotates in a trough of ink which floods the sur-face of the cylinder. A doctor blade positioned above the trough wipes excess ink off the cylinder so that the ceL~ re-main filled with ink for subsequent transfer to a web or sheet to be printed.
An object of the present invention is to provide an improved device for applying ink to a printing surface.
According to one aspect of the invention the device includes a body adapted to be positioned adjacent said surface in use, and two ink flow control blades coupled to the body in superposed positions. The blades define respective inner longitudinal portions which are spaced from one another and respective outer longitudinal portions which project from said body and which define parallel outer edges. The blades are arranged so that the outer longitudinal portions normally make at least line contact with one another whereby the blades and body together define an ink chamber. The blades are resiliently deflectable in use to allow ink to flow out of the chamber between the blades. Sealing means are located at respectively opposite ends of the blades to define ends of said chamber. Inlet means are provided in the body for delivery of ink to the ink chamber. In use, the blades can be deflected by contact with a printing surface to apply ink to the surface. Movement of the device to remove the blades from the printing surface will allow the blades to close and cut off the flow of ink from the ink cha~ber.
According to another aspect of the invention, the device includes a body adapted to be positioned adjacent a printing surface in use and two blades which are coupled to said body in superposed positions and which define an ink chamber with the body. The blades project 10386gO
from the body and define parallel outer edges for contact with the printing surface. Sealing means are located at respectively opposite ends of the blades to define ends of said ink chamber. Inlet means are provided in the body for delivery of ink to the chamber. In use, the blades are arranged with their outer edges in contact with the printing surface and spaced from one another so that ink flows from the ink chamber between the blades and onto the surface.
The invention will be better understood by refer-ence to the accompanying drawings which illustrate various embodiments of the invention by way of example. In the drawings:-Fig. 1 is a diagrammatic illustration of a device according to the invention in use for applying ink to a gravure printing cylinder;
Fi~. la shows the device of Fig. 1 retracted clear of the cylinder;
Fig. 2 is a view similar to Fig. 1, diagrammatically illustrating an alternative form of inking device;
Fig. 3 is a vertical cross-sectional view through a conventional gravure doctor blade assembly converted to oper-ate as an inking device according to the invention;
Fig. 4 is a diagrammatic side view of an inking de-vice according to the invention in use in an offset printing installation;
Fig. 5 is a perspective view, partly broken away, of one end of the device used in the arrangement of Fig. 4;
Figs. 6 and 7 are side and end views respectively which diagrammatically illustrate a device according to the invention in use in a flat bed printing machine; and, Figs. 8 and 9 are diagrammatic sectional views of a further form of in~ing device.
Referring first to Figs. 1 and la, a conventional gravure printing cylinder is indicated at 20 in association with an inking device 22 according to the invention. A web of paper to be printed is indicated at 24 and is brought into contact with the surface of cylinder 20 in passing around an impression roller 26. The chain dotted outline at the peri-phery of the cylinder denotes a design to be transferred to the printed web. The design is in the ~orm o~ recessed cells in the surface of cylinder 20, which cells are filled with ink by the inking device 22 for subsequent transfer to the paper web 24.
Device 22 operates to simultaneously ink and doctor the surface of cylinder 20 as will be described. The device is mounted on the frame of the printing machine (not shown) so as to be movable between the "on" position of Fig. 1 and the "off'` position of Fig. la. Movement of the device may be effected manually or automatically from the controls of the machine by appropriate operating means (not shown in Fig.
1). In any event, the device is arranged in a plane at an angle of approximately 80 to a tangent to the surface of the cylinder 20 at the point of contact of the device with the cylinder. This angle is denoted 28 in Figs. 1 and la.
It is of course to be understood that the angle may be varied to suit particular printing conditions.
The device 22 includes a body 30 having an internal cavity 32 and an ink inlet 34 for the cavity. Cavity 32 opens into the forward end of the body at a slot 36 which extends generally parallel to the axis of cylinder 20. A
supply tube 37 coupled to an ink reservoir (not shown) is connected to the inlet 34 to cavity 32. A continuous supply of ink is available to cavity 32 from the reservoir. The ink may be fed by gravity or under controlled pressure. Slot 36 10386~0 receives two ink flow control blades 40, 42. The blades extend longitudinally of the slot 36 and are both made of relatively thin spring steel. In alternative embodiments, the blades may be plastic or combinations or laminations of plastic and steel. The blades are both of similar rectangular shape and include respective inner longitudinal portions 44, 46 located on respectively opposite sides of the slot 36.
The blades also include respective outer longitudinal portions 48, 50 which project from the body 30 and which define parallel outer edges. The blades are trapped inside the body 30 by an insert 52 formed with a plurality of longitudinal passageways, one of which is visible in the drawings. The blades define an ink chamber 38 which communicates with cavity 32.
Referring to the direction of rotation of the print-ing cylinder 20 as indicated by the arrow in Fig. 1, blade 40 is a leading blade and 42 is a trailing blade. The lead-ing blade 40 acts as a doctor blade when the device is in use as will be described. Fig. la shows the inking device in the "off" position; that is the position in which the devlce is not inking. It will be seen that the trailing - blade 42 lies in surface contact with the bottom wall of cavity 32 and adopts an almost flat condition at this time.
The leading blade 40 on the other hand is deflected inwardly at its outer longitudinal portion by an inwardly directed formation 54 along the portion of body 30 which defines the upper wall of the slot 36. As a result, continuous surface contact is established between the outer longitudinal portions 48, 50 of the blades 40, 42 along marginal bands of the inner surfaces of the blades. Accordingly,the blades are ~038690 normally "closed" when the inking device is out of contact with the cylinder as shown in Fig. la. At this time, ink is prevented from flowing from the ink chamber 3~ between the outer longitudinal portions of the two blades. The spaces at respectively opposite ends of the blade assembly are sealed by a flexible sealing compound (not shown in Figs. 1 and la) to be described later in connection with Fig. S.
As can be seen from Fig. la, the trailing blade 42 protrudes slightly beyond the outer edge of blade 40 in the position of Fig. la. This ensures that the blades close and cut off delivery of ink before moving out of con-tact with the cylinder when the inking device is moved from the "on" position to the "off" position.
It will be appreciated that the inking device will be in the "off" position of Fig. la at the commencement or a printing run. To commence printing, the device 22 is progressively moved from the position of Fig. la towards the position of Fig. 1. The blades 40, 42 are deflected by contact with the surface of the printing cylinder 20 so that their respective outer longitudinal portions 48, 50 are - separated, allowing ink to flow onto the surface of the printing cylinder from the ink chamber 38. As the cylinder 20 rotates and ink is applied to its surface, the leading blade 40 of the inking device simultaneously acts as a doctor blade to wipe surplus ink from the surface of the cylinder.
Fig. 2 shows an inking device in use in a printing system which employs solid "thermal" or "chill set" inks in the form of granules. This system had the advantage that 103~
volatile solvents and heat drying o~ens are eliminated.
The inking device is generally indicated at ~6 and includes a body 58 and two blades 60, 62. In principle, the con-struction of the device is similar to that of Fig. l,o for this reason, details of the internal structure of the device are not shown. The device has an internal cavity 64 which communicates with the space between the blades 60, 62 and which is surrounded by precision thermostatically controlled heating elements 66. Cavity 64 has an inlet end fitted with a funnel 70. Ink in the form of solid resin granules 72 are placed in the funnel 70 and settle under gravity into cavity 64 where they are melted by the heating element 66. In an alternative embodiment, the ink may be delivered to device 56 through a heated tube from a heated reservoir. For the purpose of illustration only, it may be mentioned that typical melt temperatures for different coloured inks could be as follows:- yellow - 200F; red - 180F; blue - 160F;
black - 140F in order of laydown, so that the previous im-pressions are not affected.
In any event, the ink granules are melted by the heating element 66 and flow from the inking device under the control of the blades 60, 62 as described in connection with the Fig. 1 embodiment.
In Fig. 2, the printing cylinder is generally indi-cated at 74. The cylinder surface or plate is also heated.
Cylinder 74 includes a cylindrical base 76, the curved sur-face of which is covered by a layer of an electrically and heat insulating material 78. A metal intaglio printing plate 80 is fitted around the insulating layer 78. A conven-tional rotogravure cylinder may be used provided an insulating layer is incorporated before plating. Carbon brushes 82 run in contact with the plate 80 of cylinder 74 and are used to apply a low potential electrical current to the pla~e 80 whereby the plate is electrically heated.
In order to conserve heat, an apron 84 of a heat insulating material is fitted around the cylinder in close proximity to its outer surface. The apron is seen in cross-section only in Fig. 2. It is of generally cylindrical shape, and is gapped in the region of the inking device 56 and the impression roller 86 for the printing we~ 88. A chill roller 89 sets the ink before the next impression is made.
An apron such as apron 84 may be used in other embodiments when printing with highly volatile inks to con-serve solvent and prevent drying of ink residue in the cells of the printing cylinder.
Figs. 1, la and 2 are somewhat diagrammatic illu-strations of inking devices according to the invention.
Fig. 3 is a more detailed illustration of a conventional doctor blade assembly converted to form a device for sim-ultaneously inking and doctoring a gravure cylinder. The device as a whole is generally indicated at 90 and is shown in use in association with a gravure printing cylinder 92 fitted with a plastic plate 93. As is well known, the doctor blade assembly conventionally includes an apron which encloses the inking trough. In Fig. 3 a part of the apron is visible at 102. Part 102 is used to seal off the inking area 103.
This device is pivoted to the frame of the machine at 104 /o5 and includes a blade ~ which is co-extensive with inking device and which bears on the underside of the latter as shown in Fig. 3.
Device 90 includes a body made up of an upper part 106 and a lower part 108 coupled together by a series of screws spaced along the length of the device.
One of the screws is visible at 110. Part 106 is in 1038~90 fact a con~entional doctor blade holder and is coupled to the frame of the machine (not shown)in normal fashion.
Con~entional gravure cylinders are often of substantial length; the body of the inking device 90 will be of generally corresponding length. As in the case of the previous embodiments device 90 includes an ink chamber 112 which communicates with a cavity 114 in the body o~
the device. Cavity 114 has an ink inlet 116. However, the device of Fig. 3 differs from the previous devices in that the ink is circulated through the device and excess ink not used for printing is returned to a reservoir (not shown). For this reason, cavity 114 has an ink outlet 118. The inlet 116 and outlet 118 are positioned at respectively opposite ends of the inking device; inlet 116 is at the far end in Fig. 3. Also, the outlet 118 is disposed nearer the upper end of the device than the inlet 116. Inlet 116 and outlet 118 are coupled to a reservoir and associated pump arrangement (not shown) by which ink is delivered to inlet 116 under controlled pressure, travels along the device and is returned to the reser~oir through outlet 118. When the device is being used for printing, some of the ink leaves the device between the ink flow control blades (denoted 120 and 122 in Fig. 3).
If friction between the blades and the cylinder causes a problem, the ink may be conditioned in the circu-lation system as to temperature and viscosity to avoid melting the plastic plate of the printing cylinder.
As in the case of the previous embodiments, the blades, together with the body of the device, define the ink chamber 112. Blade 120 is the leading blade and blade 122 is the trailing blade. The blades have respective inner longitudinal portions which are located inside the body on respectively opposite sides of the cavity 114. These portions of the blades are trapped between the respective parts 106, 108 of the body of the device, and an insert 124 located inside the cavity 114. Insert 124 is formed with two longitudinally ex-tending passageways 126, 128 which communicate at respect-ively opposite ends with the respective inlet 116 and outlet 118. A plurality of transverse passageways, one of which is visible at 130 extend parallel to one another and communicate at their inner ends into passageways 126, 128. The arrows in Fig. 3 indicate the flow path of the ink inside the inking device.
The blades 120, 122 are positioned as in the prev-ious embodiments so that they are closed when the inking device is out of contact with the cylinder 92 but are opened upon contact with the cylinder to apply ink thereto.
Blade 120 simultaneously performs a doctoring function as described above.
Fig. 4 illustrates an arrangement in which an inking device according to the invention is applied to an offset printing machine. Only the principal cylinders of the machine are shown in Fig. 4. These are: a plate cylinder 132, a blanket cylinder 134 and an impression cylinder 136.
A continuous web of paper is indicated at 138 passing through the nip between the blanket cyllnder 134 and the impression cylinder 136. Of course, the machine could equally well be sheet fed. Plate cylinder 132 is a conven-tional offset cylinder fitted with a wrap-around intaglio printing plate 140 secured in an axial r~cess 142 in the cylinder by clamps 144. The blanket cylinder 134 and the impression cylinder 136 are also basically conventional.
As is well known, ink is applied to the plate 140 of plate cylinder 132. The image on plate 140 is then transferred to the blanXet cylinder 134 ana from there to the web 138.
An inking device 146 is secured to a shaft 148 turnably mounted in the frame of the machine (not shown).
The fact that the shaft 148 is turnable allows the inking device to move between the full line position 146' in 1~ which the device is in contact with the surface of the printing plate 140 (the "on" position) and the chain line position 146" in which the inking device is clear of plate 140 (the "off" position). The inking device is of the form shownin Fig. 5, which figure will be described later. For present purposes, it is sufficient to note that the device includes two ink flow control blades which operate as de-scribed in connection with the preceeding figures.
Due to the presence of a gap in the printing sur-face of plate 140 at the position of the recess 142, it is necessary to move the inking device 146 to the "off"

position 146" once during each revolution of the plate - cylinder 132 at the position of the gap so that the inking device in effect "jumps" the gap. This is achieved by means of an edge cam 15D mounted to rotate with the blanket cylinder 134. An arm 152 is coupled to the shaft 148 which supports the inking device and has at its outer end a cam follower 154 which runs on cam 150. A tension spring 156 urges arm 152 inwards at lower end. The spring is attached between the arm 152 and a part 158 of the frame of the machine. As can be seen, the cam 150 is profiled to define a "flat" 160. The cam follower 154 begins to '10~8690 move along the flat 160 as the gap in the printing plate 140 approaches the inking device 146. As the follower 154 runs along the flat, ~he inking device 146 is lifted clear of the cylinder and the supply of ink to the printing plate is cut off. When the follower 154 reaches the end of the flat 160, the inking device is returned to the surface of the printing plate and inking recommences.
Referring now to Fig. 5, the inking device 146 will now be more specifically described. Fig. 5 shows only a part of the inking device and since the length of the de-vice will depend on the length of the plate cylinder with which it is used. In some cases, the device may be several feet along.
The structure of the device is in principle similar to the devices described above. It includes a body 162 and two ink flow-control blades 164, 166. The body 162 is of three part construction comprising three specially shaped plates 168, 170 and 172. Blade 164 (the leading blade) is trapped between the top plate 168 and the centre plate 170 and blade 166 (the trailing blade) is trapped between plate 170 and bottom plate 172. Fig. 5 shows the inXing device in its normal, inoperative position. It will be noted that blade 166 projects straight from the body 168 at this time and adopts an almost flat configuration.
Blade 164 on the other hand is deflected downwardly by a de-pending formation 174 on the top plate 168. The blades are arranged so that the outer edges are in parallel super-posed positions. As can be seen, the trailing blade 166 projects slightly beyond the outer edge of blade 164.
Blades 164 and 166 together define an ink chamber 103B69~
176 which is closed when the blades are in contact as shown. The ends of chamber 176 are sealed by plugs of a resilient sealant. One of these plugs is visible at 178 in Fig. 5. The sealant is applied when the blades are in their deflected "on" position so that the sealant is not stressed or is stressed to a minimal extent when the device is in use.
Both blades are adjustable by means of a series of screw assemblies spaced along the length of the inking device. One of these assemblies associated with blade 164 is generally indicated at 180 in Fig. 5; it will of course be appreciated that each blade of the device will be provided with at least two such assemblies spaced longi-tudinally of the device. Assembly 180 includes a screw 182 which is accessible from the rear of the device and which is received in a screw-threaded aperture formed between the top plate 168 and the centre plate 170 of the inking device. At its inner end, screw 182 bears against a pin 182 which in turn acts on the inner edge of the leading blade 164. It will be appreciated that the extent to which the blades protrude from the body 162 can be controlled by turning the screws of the adjusting assemblies.
It is primarily intended that such adjustment shall be carried out during initial assembly of the device since only minimal adjustment of the blades will be possible once th~
sealing plugs 178 have been applied. Of course, if necessary, the plugs could be removed to permit sharpening and adjust-ment of the blades, and subsequently replaced with fresh plugs.
Ink is delivered to the chamber 176 through a series of tubes which extend transversely of the device through ~ 14 10~
the centre plate 170 of body 162. One of these tubes is visible at 186 in Fig. 5. Other similar tubes are provided ~t spaced intervals along the length of the device. The tubes are all connected to a gravity or pressure fed reservoir system as described above. In an alternative arrangement, ink may be arranged to circu-late through the device as in the embodiment of Fig. 3.
Figs. 6 and 7 illustrate the application of an inking device according to the invention to a flat bed printing machine. The inking device is generally denoted 188 and is of similar form to the device shown in Fig.
5. The bed of the machine is indicated at 190 and recipro-cates in the directions indicated by arrow 192. An intaglio printing plate 194 is mounted on the bed 190 and a cylinder of the machine is indicated at 196.
The inking device 188 is mounted on a shaft 198 turnably located in parts 200 (see Fig. 7) of the frame of the machine. Two arms 202 are coupled to respectively opposite ends of the shaft 198. Each arm 202 is pro-vided at its outer end with a cam follower 204 which runson a cam or bearer 206. The cams 206 are designed so that, as the bed 190 of the machine reciprocates the arms 202 are lifted at appropriate times to maintain the inking device 188 in contact with the printing plate 194.
When they reach the ends of the cams 206, the arms 202 move downwardly at their outer ends, lifting the inking device. The cams are arranged so that the device is lifted adjacent respectively opposite ends of the printing plate 194. In other words, the inking device 188 occupies its operative "on" position only when the printing 103B69~
plate 194 is positioned below the device. A spring 208 (Fig. 7) maintains the followers 204 in contact with the cams 206.
Figs. 8 and 9 are diagrammatic sectional views through a device according to a further embodiment of the invention and show the device respectively in the "on" and "off" positions. The device includes two blades 210, 212 spaced by an insert 214 and located between two body parts 216, 218. Blade 212 is the leading blade and blade 210 is the trailing blade. The blades define an ink chamber 220.
In this embodiment, both body parts 216, 218 have inwardly directed formations 222, 224 respectively arranged so that both blades are always slightly curved in the same direction. As a result of the illustrated arrangement, the volume of the ink chamber 220 remains substantially constant in both the "on" position and the "off" position of the device. This avoids or at least minimizes any increase in pressure in chamber 220 as the device moves from the "on" position to the "off" position, which could cause leakage of ink between the blades.
- It should of course be noted that the preceding description applies to specific embodiments of the invention and that many mod~ifications are possible within the broad scope of the invention.
For example, although specific forms of inking devices have been described in use in connection with particular types of printing machines it is to be under-stood that there is no limitation in this. Thus, the device of Fig. S could for example be applied to a printing machine of the type described in connection with Figs.
1 to 3. Such a device could also be used for rotary letterpress type machines converted to gravure printing and to replace the ink troughs on Flexographic machines.
Inking devices as described above may also be applied to screen stencil printing.
In the accompanying drawings, the inking devices are all shown with approximately the same position in relation to the cylinder to which ink is being applied.
It is to be understood that there is no limitation in this and that the inking device may be located at any position around the cylinder. Moreover, more than one inking device may be used in association with a single cylinder. For example, two or more devices each supplying a different coloured ink could be used. The devices could be po~itioned at different angular locations around the cylinder or they could be arranged at different axial positions along the length of the cylinder.
A multiple inking device arrangement may also be used to simultaneously take several impressions from one cylinder. For example, two or more webs may be run in contact with a single cylinder with an inking device arranged in advance of the point of contact of each web with the cylinder, thereby doubling or more the product-ivity of the press without increasing the speed.
The above examples are not necessarily exhaustively described since it is believed that the wide range of possible applications of the device will be readily appre-ciated by a person skilled in the art.
As is customary in conventional gravure doctor blade ~L0~
installations, provision may be made to continuously oscillate the inking device in the axial direction of the cylinder in association with which it is used. Such oscillation may be derived from a suitable low speed high tor~ue motor coupled with the device through an appropriate mechanical arrangement designed to additionally allow movement of the device towards and away from the associated cylinder as described above.
Further, in some instances, it may be desirable to additionally provide a reverse doctor blade in association with the printing cylinder in advance of the inking device in order to remove from the cylinder "hickeys" (paper particles) and other foreign material which may be picked up from the web to avoid contaminating the ink applied by the inking device.
With reference to the range of application of the invention, the description with reference to the drawings relates to gravure printing, and to rotary offset and flat bed printing. It is to be understood that these are merely examples of possible applications of the invention.
In fact, it is believed that the device of the invention - may be used in any situation in which ink is to be applied either to a flat surface or to an intaglio type of surface in which the ink carrying part of the surface is recessed.
Where the surface is flat, it may be necessary to balance inX pressure with the blade pressure to cause ink to be applied to the printing surface. Of course, the inking device need not apply the ink directly to a surface from which an impression is taken. The ink could be applied to an inking roller from which the ink would be transferred -iO3~1;90 to the impression surface. Accordingly, the term "printing surface" as used in this specification and in the claims is to be interpreted as including any surface to which ink is applied.
In any arrangement in which the printing surface has a gap (e.g. as in Fig. 4), appropriate means will normally be provided to cause the inking device to "jump"
the gap. These means may take a variety of forms. One example of a cam operated mechanism is shown in Fig. 4.
In other cases, pneumatic, hydraulic, electrical or other devices may be used.
Where an inking device according to the invention is used in a situation in which the device is always in contact with the printing surface, the self-closing blade feature is not necessary. In this event, the device would not have to be moved out of contact with the printing surface to terminate delivery of ink to the surface. It would merely be necessary to cut off the supply of ink to the device and allow the device to run dry.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for applying ink to a printing surface, the device comprising:
a body adapted to be positioned adjacent said surface in use;
two ink flow control blades coupled to said body in superposed positions, said blades defining respective inner longitudinal portions which are spaced from one another, and respective outer longitudinal portions which project from said body and which define parallel outer edges, the blades being arranged so that said outer longitudinal portions normally make at least line contact with one another, so that the blades define an ink chamber with said body, the blades being resiliently deflectable in use to allow ink to flow out of said chamber between the blades;
sealing means located at respectively opposite ends of said blades to define ends of said chamber;
and, inlet means in said body for delivery of ink to said chamber;
whereby the blades can be deflected by contact with a printing surface in use to apply ink to said surface, movement of the device to remove the blades from the printing surface allowing the blades to close and cut off the flow of ink from said chamber.

2. An inking device as claimed in claim 1, wherein said body is formed with an internal cavity communicating with said inlet means, said cavity also communicating with the ink receiving chamber by way of a slot in said body, and wherein said inner longitudinal portions of the blades are located against respectively opposite walls of said slot.

3. An inking device as claimed in claim 2, further comprising an insert located in said cavity between the inner longitudinal portions of the blades, said insert defining a passageway for ink between said inlet means and said ink chamber.

4. An inking device as claimed in claim 3, further comprising ink outlet means communicating with said ink chamber, said inlet means and outlet means being located adjacent respectively opposite ends of the body, whereby ink may be circulated through the ink chamber between said inlet means and said outlet means in use, separation of the outer longitudinal portions of the blades allowing some of said circulating ink to flow-out of the ink chamber between the blades.

5. An inking device as claimed in claim 1, wherein one of said blades is arranged in a normally flat configuration, and wherein the body includes an inwardly directed formation which extends longitudinally of the body and which is positioned to normally deflect the outer longitudinal portion of the other of said blades towards and into contact with the corresponding longit-udinal portion of the first mentioned blade.

6. An inking device as claimed in claim 1, wherein the body comprises a plurality of superposed parts between which the blades are located, and wherein the device further comprises at least two adjusting assemblies for each of said blades, each assembly including an adjusting screw acting on the inner longitudinal portion of the blade and movable to vary the extent to which the blade protrudes from said body and hence the alignment between the outer edge of the blade and the corresponding edge of the other blade.

7. An inking device as claimed in claim 2 for use with ink in the form of solid granules, wherein said inlet means communicates with supply means for said granules, and wherein the device further comprises thermostatically controlled heater means associated with said body and adapted to melt the ink granules in said cavity.

8. In a printing machine, the combination of an inking device as claimed in claim 7; a printing cylinder including an electrically conductive printing plate;
means for heating said plate during rotation of the cylinder in use; and an apron surrounding said cylinder at a spacing from its peripheral surface.

9. In a printing machine including a printing cylinder fitted with a wrap-around printing plate which defines a printing surface having a transverse gap, the combination of an inking device as claimed in claim 1;
support means positioning the device adjacent said cylinder so that the device is movable between an "off"

position clear of the cylinder and an "on" position in which said blades are deflected by contact with the cylinder to apply ink to the latter; and means for moving the inking device between said positions so that the device is moved to said "off" position once during each revolution of the cylinder at the position of the gap in said printing surface said means including: a cam rotating at the speed of said printing cylinder; a cam follower co-operating with said cam;
and means coupling the cam follower to said inking device to cause the device to move between said two positions in accordance with the profile of the cam.

10. In a flat bed printing machine including a bed supporting a printing plate and adapted to be longitudinally reciprocated in use, the combination of: an inking device as claimed in claim 1; means supporting said inking device adjacent to the bed for movement between an "off" position clear of said printing plate and an "on" position in which the blades of the device are deflected by contact with said printing plate so that ink is applied to the plate by the device;
means for moving the inking device between two positions so that the device occupies said "on" position only during movement of the printing plate past the device;
said means including at least one cam associated with said bed for reciprocation therewith; a cam follower co-operating with said cam; and means coupling the cam follower to said inking device so that the inking device moves in accordance with the profile of the cam.