EP0344546A2 - Control device for the opening of an ink fountain in a printing machine - Google Patents

Abstract

A control device for the opening of an ink fountain, the opening being defined by the gaps between the ink-fountain roller (105) and a series of lamellae (170) arranged side by side in one plane and movable orthogonal relative to the roller, associated with each lamella:… - a linear positioning actuator (200), the movement axle (150) of which is connected to the rear edge of the lamella by means of an intermediate piece (160) and of which the housing within a module (140) is fixed to the ink fountain by means of a frame (130),… - means (220) for detecting a reference position and each movement of the axle (150),… - control means (215) acting on the actuator (200). …<IMAGE>…

Description

The present invention relates to a device for controlling the opening of an inkwell in a printing machine making it possible to modulate the quantity of ink delivered to an inkwell roller and transmitted by distributor rollers to the printing plate.

The quality of the print run in offset printing machines depends on multiple parameters, the main ones being: the chemical characteristics and the structure of the paper surface, the quality of the pre-wetting of the plate mounted on the cylinder plate, printing speed and quality as well as quantity of printing inks delivered by an inking system. More precisely, the quantity of ink transferred to the printing plate must correspond to the minimum quantity necessary to ensure correct printing, and, as far as possible, this quantity must be compensated laterally and longitudinally according to the unevenness of consumption d ink that meets the requirements for a given image.

The inkwell of an offset printing machine is frequently in the form of a very wide bowl with an oblique bottom, the wall opposite the oblique bottom is formed by the rotary ink roller itself. The opening of the inkwell, through which the ink is delivered, is then formed by the gap located at the bottom of the bowl between the inkwell roller and a scraper blade covering the lower edge of the oblique bottom. In an old embodiment, this scraper blade is in one piece tangential to the ink roller. Its longitudinal edge outside is then more or less close to the inkwell roller thanks to a series of equidistant underlying adjustment screws. The major drawback of this device is the impossibility of fine adjustment at one point without affecting the adjacent points. In practice, this prevents an exact calibration of the quantity of ink to be delivered for the printing of a page having strong vertical contrasts.

To reduce this interference appearing between the adjacent adjustment means, it has been suggested to subdivide the scraper blade into a series of strips arranged side by side in a plane and to actuate these strips individually by mechanical or even electro-mechanical means . A first example is presented in US 4 328 748 in which each strip is normally pushed against the ink roller by a spring to be pulled back by an electromagnetic relay over a predetermined distance by two stops. Taking into account the only possible "open" or "closed" positions of these strips, the quantity of ink is then adjusted thanks to the time interval during which each strip remains in the withdrawn position. However, this device for delivering ink by "packet" only ensures a modest quality of inking.

According to a second embodiment, each strip constitutes the short branch of a lever mounted in rotation along an axis close to the ink roller and whose long vertical branch oriented downwards is moved laterally by an intermediate piece in which turns a horizontal worm screw actuated by an electric motor. A spring permanently holds the long branch against the intermediate piece. So a double effect reduction, on the one hand by the endless screw moving the intermediate piece, on the other hand by the dimensions of the respective branches of the lever, makes it possible to transform several turns of the electric motor into a small displacement of the front edge of the strip. However, the relatively slow speed of the electric motor and the reduction do not allow the setting to be changed quickly enough in cases where strong printing contrasts exist on the page in column and in rows simultaneously. In addition, a loss of mechanical precision cannot be prevented in the connection between the worm screw and the intermediate part.

According to another embodiment, developed by the applicant, an adjustment piece is moved in line over infinitesimal distances using a screw having two threads with different pitches: one screwed into the frame, the other in the intermediate piece . This screw is driven by a synchronous reciprocating motor through a gear reducer. Given the small movements at the outlet of the reduction gear, this device can only be controlled in position on a movement measurement taken on a second reduction gear output, measurement not taking into account any mechanical play inside this reduction gear in the output shaft / screw connection with differential thread and at the corresponding threads and tapped holes. In addition, it is not possible to modify the speed of the synchronous motor to accelerate, when necessary, the movement of the adjusting part. Last but not least, this device is complex and therefore costly to manufacture and maintain.

The object of this invention is to solve the aforementioned problems by means of a device for rapid and precise control of the opening of an inkwell in an offset printing machine allowing an exact supply of the quantity of ink delivered to the roller. '' rotary inkwell of the plate inking system. This device must involve a minimum of mechanical connection to reduce the uncertainties due to operating clearances as well as the cost of manufacturing and maintenance. In addition, the initial implementation of this device must be facilitated by a possibility of rapid control of the opening to a reference value and easy adjustment of this opening relative to the external members. This device must also allow other essential parameters to be taken into account for good inking such as the physico-chemical characteristics of the ink and of the paper.

These aims are achieved by means of a device in a printing machine, the inkwell of which is in the form of a bowl with an oblique bottom oriented towards a rotary inkwell roller constituting the last face of the bowl, the opening at bottom of the bowl being defined by the interstices between the ink roller and a series of movable strips orthogonally to the roller, arranged, at the end of the oblique bottom close to the roller, side by side in a plane to form a blade of scraping parallel to this roller, thanks to a control device comprising for each strip:
- a linear positioning actuator whose axis of movement is aligned with the axis of movement of the strip at the rear edge of which it is connected by an intermediate piece and whose casing, possibly contained inside a module , is made integral with the inkwell thanks to a frame,
means for detecting a reference position and each movement of the axis of movement relative to the casing of the actuator,
- control means triggering, according to the electrical control signals which are applied to them, the actuator for imparting a specific movement of advancement or withdrawal of the lamella relative to the inkwell roller, then verifying, using the means of detection, that the movement of the axis has been carried out as required, and re-triggering the actuator if corrective action is necessary.

Advantageously, this device also includes computer means allowing an operator to define, from a keyboard and a screen and taking into account various parameters such as distribution of the condensed images on the page, characteristics of the ink and paper, the possible modification (s) of the position of one or more specific lamellae over time, translate these modifications in terms of direction and quantity of movement axis movement unit for each corresponding actuator under the form of electrical control signals which are transferred to electronic pre-amplification and interface means, which means organize the routing of the electrical control signals to each control means of the actuators concerned along an omnibus line connecting all these control means to the electronic pre-amplification and interface means.

Preferably, the plane defined by the series of strips arranged side by side constituting the scraper blade passes through a plane intersecting the ink roller. This intersecting plane could advantageously pass through the axis of rotation of the ink roller.

According to another preferred characteristic, the position, relative to the bowl of the inkwell, of the frame supporting the actuator can be adjusted by means of a screw having two threads of different pitch, one screwed into a tapped hole in the frame, the other screwed into a tapped hole in the bowl, and this before blocking this frame against the bowl by mechanical means.

• la figure 1 est un schéma de principe du dispositif de commande,
• la figure 2 est une vue en coupe tranversale d'un premier mode d'assemblage du dispositif dans l'encrier,
• la figure 3 est une vue en coupe partielle du dessus du mode de réalisation de la figure 2,
• la figure 4 est une vue en coupe transversale d'un second mode d'assemblage du dispositif, et
• la figure 5 est une vue en coupe partielle du dessus du dispositif selon la figure 4.

The invention is described below in more detail with the aid of working examples, without limitation, and illustrated by the accompanying drawings in which:

• FIG. 1 is a block diagram of the control device,
• FIG. 2 is a cross-sectional view of a first method of assembling the device in the inkwell,
• FIG. 3 is a partial sectional view from above of the embodiment of FIG. 2,
• FIG. 4 is a cross-sectional view of a second method of assembling the device, and
• FIG. 5 is a partial sectional view from above of the device according to FIG. 4.

Referring to Figure 1, a scraper blade 169 is constituted by a series of blades 170 arranged side by side in a plane. Each of these blades 170 is connected at its rear to the movement axis 150 of its corresponding actuator module 140. The latter can communicate to it, while maintaining it in the plane of the scraper blade, a movement of advance or withdrawal with respect to the ink roller not shown.

Each actuator module 140 includes in series inside a control card 215 receiving electrical control signals from the omnibus line 230 to which is connected a power amplifier 210 translating the control pulses processed by the card 215 into electrical power switching on. the actual actuator 200 which moves the axis of movement 150. A detector 220 reports through line 221 to the card 215 each movement carried out by this axis 150. This detector 220 also establishes the presence or not of this axis 150 in a reference position.

All the actuator modules 140 actuating a strip 170 belonging to the series constituting the same blade 169 are connected by an omnibus line 230 to a pre-amplification and interface card 240. This omnibus line 230 is in fact made up of a number reduces, for example five, cables in parallel, each control card 215 being connected in parallel to each of these cables. The card 240 is itself connected to computer means such as microcomputers or microprocessors 250 with which an operator can communicate thanks to a screen 270 and a keyboard 260. In the case of a full color printing machine not having from a single but from several plate cylinders and associated inkwells, the computer means 250 are then connected to as many pre-amplification and interface cards 240 as there are inkwells, each card 240 controlling a series of relative actuator modules to the series of blades making up the scraper blade 169 of one of the inkwells.

A first embodiment of the scraper blade and its associated equipment is illustrated seen in cross section in FIG. 2 and in top view in FIG. 3. In these figures, identical references are used to describe the same parts. As seen on the Figure 2, the inkwell 100 is formed on the right by the oblique bottom 110, in front and behind by two walls not shown that closes on the left the inkwell roller 105. A series of strips 170 constituting a scraper blade 169 parallel to the ink roller 105 limits the opening left between the lower edge of the oblique bottom 110 and the ink roller 105, opening through which the ink driven by the roller 105 is rotated in a clockwise direction. watch.

To reduce the drawbacks of the static and dynamic forces appearing between the ink, the walls of the bowl and the ink roller, the strips 170 are oriented so that the plane which they define passes through the axis of rotation of the inkwell roller.

The frame 120 and the oblique bottom 110 constitute a single piece arranged so that it has a series of equidistant cylindrical housings 125 whose central axes parallel to each other intersect orthogonally the axis of rotation of the ink roller 105. The frame 120 is drilled at the level of each housing 125, along the central axis of three orifices: a first orifice 128 close to the edge, and two tapped orifices 131 and 132. All the housings 125 open on the side of the ink roller on two parallel flat lips: a lower 126 and an upper 127 machined along the edge of the frame 120 and the bottom 110 respectively. The spacing between these lips corresponds to the thickness of the strip 170. These lips lead the strips 170 in their advance or withdrawal movements relative to the roller.

In each of these housings 125 is inserted the cylindrical front part of a frame 130 whose rear parallelepiped part is offset upwards. This rear part has, in the axis of the front cylindrical part, a circular chamber with an internal diameter greater than the internal diameter of the front part. This rear part also has in its upper section a tapped orifice 183. A second tapped orifice 185 is drilled in the oblique bottom 110 above each of the housings 125. This orifice 185 is simultaneously parallel to the axis of the housing 125 and in the extension of the first port 183. A position screw 180 having two reverse threads of different pitch, one corresponding to that of the port 183, the other smaller corresponding to the thread of the port 185, is engaged simultaneously in these two holes. Because of these threads of different pitches, each turn of the screw 180 makes it possible to move the frame over a very small distance relative to the frame 120 and to the oblique bottom 110, thus facilitating an exact adjustment of its position relative to these latter parts. A locking screw 175 engaged in the orifice 131 makes it possible to block the position of the frame once it has been determined.

The actuator module, mentioned with reference to FIG. 1, is in the form of a cylindrical block screwed against the rear face of the frame 130 so that the axis of movement 150 of its internal actuator 200 is coincident with the axis of the housing 125 and therefore that of the front part of the frame 130. A cylindrical intermediate piece 160 engaged inside the frame 130 is secured to the axis of movement 150 by means of a screw 172 for tightening its rear crown. This screw can be tightened by means of an access hole 133 drilled in the lower frame 120 at the level of each housing 125 slightly behind and offset with respect to the axis of the housing. This intermediate piece 160 carries at its front end the strip 170 proper tightened by the fixing screw 171 accessible through the hole 128 mentioned above.

As can be seen, the connection between the strip 170 and the axis of movement 150 is direct and this strip 170 is advanced or withdrawn with the same precision as the movement of the axis 150.

Figures 4 and 5 show a variant of the mounting of the actuator module 140 and the slats 170. In these two figures, identical references are used to describe parts similar to those encountered previously. We recognize in particular an inkwell 100 formed by the oblique bottom 110, the side walls not shown and which is closed by an ink roller 105. A series of bolts 179 supplemented with a wedge 178 keeps the oblique bottom 110 at a predetermined distance from the chassis. lower 120, distance slightly greater than the thickness of the strips 170 arranged at this level side by side to form a scraper blade 169.

In other words, the lower part of the bottom 110 and the upper part of the frame 120 form two lips 126 and 127 for guiding the slats 170 in their movement orthogonal to the roller 105. Each of these slats 170 is actuated from the rear, through an intermediate piece 160, by an actuator 200 internal to the actuator module 140 mounted on a frame 130. The strip 170 is fixed to the intermediate piece 160 by means of a bolt 171. This piece 160 is made integral with the axis 150 of movement of the module 140 by means of the internal clamping piece 111 and the corresponding nut 172. As previously, the position of this frame 130 relative to the lower frame 120 is adjusted by means of a double-threaded screw 180 acting in a threaded hole 183 of the frame and a second hole 185 drilled opposite each strip in the frame 120. A bar 177 tightened on either side by two bolts 175 makes it possible to block this chassis 120 in position after adjustment.

As described above, this device operates as follows: during an initial implementation of the device or regular maintenance, the operator commands the device by action on the keyboard 260 to establish all the slats 170 in the reference position of the actuator 200. Translated as electrical signals, this command is transferred through the interface 240 to the control card 215 of each actuator module 140. The actuator 200 then actuates the movement axis 150 until the detector 220 locates this reference position. The operator can then modify the position of each module 140 and its frame 130 relative to the chassis 120 or bottom 110 by action on the position adjustment screws 180 so that all the slats 170 are aligned, therefore have the same interstice vis-à-vis the ink roller 105. Once the position of these modules 140 established, they are blocked by the bolt 174. This alignment of the slats 170 can be done visually or by iterative tests leading to the delivery of an absolutely homogeneous film all along the scraper blade 169.

Once this preliminary adjustment has been made, the operator can undertake the calibration of the scraper blade 169 as a function of the lateral and longitudinal contrasts of the page to be printed.

According to a first operating mode, in particular for pages having only contrasts in columns, the operator can directly decide the position of each of the respective slats, which positions are translated in the form of a series of electrical commands transferred to the card interface 240 which organizes the transmission of the latter to each control card 215 in the form of a pulse designating the direction of movement and of several pulses describing the quantity of elementary movements necessary that the actuator 200 must apply to the axis of movement 150. In each of the control boards 215, this direction and this number of displacement units are translated into electrical impulses directly activating the actuator 200. During these movements, the detector 220 verifies that each of these is indeed carried out and if this is not the case, informs the control card 215 thereof for corrective action.

According to a second more complex operating mode, the computer means 250 contain a calculation program residing in a part of random access memory or permanent memory making it possible, after description of the page to be printed, to determine the sequence, according to the angular position of the roller d inkwell as read by a sensor disposed at the end of the shaft, the spacings of each of the strips relative to the ink roller. This program can also include, in the calculations, parameters initially entered on the keyboard, such as viscosity of the ink, absorbency of the paper, materials used on the rollers making up the inking system.

This device can be the subject of numerous improvements within the framework of this invention.

Claims (5)

1. Device for controlling the opening of an inkwell (100) which is, in a printing machine, in the form of a bowl with an oblique bottom (110) oriented towards a rotary ink roller (105) constituting the last face of the bowl, the opening at the bottom of the inkwell being defined by the interstices between the inkwell roller (105) and a series of strips (170) which are movable orthogonally to the roller and which are arranged side by side in a plane at the end of the oblique bottom (110) close to the roller to form a scraper blade (169) parallel to this roller (105), characterized in that it associates with each strip:
- A linear positioning actuator (200) whose axis of movement (150) is aligned with the axis of movement of the strip at the rear edge of which it is connected by an intermediate piece (160) and whose housing possibly contained inside a module (140), is made integral with the inkwell thanks to a frame (130),
means of detection (220) of a reference position and of each movement of the axis (150) of movement relative to the casing of the actuator,
- control means (215) acting, according to the electrical control signals applied to them, on the actuator (200) to impart a specific movement of advance or withdrawal to the lamella (170) relative to the roller d inkwell (105), verifying, thanks to the detection means (220), that the movement of the axis has been carried out as required and acting again on the actuator if corrective action is necessary. 2. Device according to claim 1 or 2, characterized in that it comprises computer means (250) allowing an operator to define, from a keyboard (260) and a screen (270), the or any changes in the position of each lamella (170), and translate these changes in terms of direction and amount of movement unit of the movement axis (150) for each corresponding actuator in the form of electrical signals from control which are transferred to electronic pre-amplification and interface means (240), which means (240) organize the routing of the electrical control signals to the control means of the actuators concerned along an omnibus line ( 230) connecting all the control means (215) to the electronic means (240). 3. Device according to claim 1, characterized in that the plane defined by the series of blades (170) arranged side by side constituting a scraper blade passes through a secant plane of the ink roller. 4. Device according to claim 1, characterized in that the position, relative to the inkwell (100), of the frame (130) supporting the actuator (200) or the module actuator (140) can be adjusted using a screw (180) having two threads with different pitches (182,184), one screwed into a threaded hole (183) in the frame, the other screwed into a threaded hole (185 ) of the bowl, and this before blocking this frame by mechanical means (175). 5. Device according to claim 4, characterized in that the strips are guided by an upper lip (127) and lower (126) of the inkwell during their movement under the action of the linear actuator (200).

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