A SWIVELLING BLADEHOLDER FOR THE WIPER DEVICE OF THE PRINT CYLINDER IN A ROTARY PRINTING MACHINE

Abstract: The invention falls within the art field of rotary printing machines using an intaglio print cylinder, and relates to a doctor (5) in which the wiper blade (21) is inserted in a cylindrical bar (20) held by a gripping mechanism which can be released and clamped manually so as to permit of swivelling the bar about its own longitudinal axis and varying the angle of the blade in relation to the external surface of the print cylinder.

Description: The invention relates to a swivelling bladeholder for the wiper device of a print cylinder as utilized in rotary printing machinery. In conventional rotary printing machines, the print cylinder is inked over its entire surface by partial immersion of the cylinder itself in a tank located beneath the cylinder and containing ink. Use is made of a wiper device, known in the trade as a "doctor", to remove superfluous ink from the non-printing area of the cylinder; thus, the ink remains in the cells of the printing surface only. The doctor consists substantially in an adjustable support, and a blade, of length matching that of the cylinder, permanently attached to the support. The support is able to rotate about an axis parallel to that of the print cylinder, and is also traversed back and forth along the same axis by a conventional mechanical drive. In urging the blade against the print cylinder, pressure is applied by adjustable pneumatic means of conventional type; more exactly, the angle assumed by the blade, in relation to the radius of the cylinder that passes through the point of contact between blade and cylinder, depends on a number of factors, including surface speed of the print cylinder, viscosity of the printing inks, the type of print, and other contingencies that are not easily controlled. Selection of the blade angle is thus left to the judgement of the machine operator, who must find the combination which gives the best results ultimately in print. In certain conventional machines, the doctor is set at an angle to suit the diameter of the cylinder by displacing the entire blade and holder vertically, using a heavy, complex bearing structure; besides being raised and lowered in this fashion, such a structure must also be reciprocated horizontally, and in consequence, will be massive in embodiment so as to avoid the hazard of vibration. US-A-2 324 298 discloses a printing press comprising a swivelling blade holder having a cylindrical bar into which a blade is inserted and held. Said document does not overcome the drawbacks of the prior art because the cylindrical bar is clamped at a given angular position in relation to the print cylinder and it can not be rotated about its own axis. The prior art embraces machines designed by the same applicant, in which the doctor incorporates a blade holder, fitted to a shaft, that can be reciprocated along the axis of this same shaft, and rotated so as to adapt the position of the blade to the diameter of the print cylinder. However, none of the doctor devices embraced by the prior art affords a generous angular adjustment -that is, of the position of the blade in relation to the surface of the cylinder. Moreover, the holders in such devices are markedly complicated and heavy, and their bearing structures must offer high levels of precision in operation; also, replacement of the blade is a rather involved procedure that demands considerable down time. Again, conventional types of doctor do not admit of operation with the blade positioned at a negative angle -i.e. reversed in relation to the cylinder. Accordingly, the object of the invention is to allow for adjustment of the position of the wiper blade of a doctor mechanism, effected independently of the angular position of the doctor itself, in such a way as to obtain a much wider range of adjustment of the wiper device as a whole, in comparison with prior art embodiments. An additional object of the invention is to enable swift replacement of the blade, thereby reducing down time, and a further object is that of enabling operation with the blade set at a negative angle. The stated objects are achieved by adoption of a swivelling bladeholder as described in the following specification and as characterized in the appended claims, which is designed for incorporation into the doctor mechanism of a rotary printing machine. The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: fig 1 is a side elevation showing the wiper device, or doctor, seen in its entirety, offered to a print cylinder of given diameter; fig 2 is a further side elevation of the device, viewed on larger scale than in fig 1, which shows the swivelling blade offered to a print cylinder of different diameter. With reference to fig 1 of the drawings, 1 denotes a print cylinder; 2 denotes a pressure roller directly above the cylinder, by which a strip 3 of material to be printed is urged against the inked surface as it runs through between the two rotary components in the direction of the arrow 4. The drive means are conventional, and therefore not illustrated. 5 denotes a "doctor" wiper device in its entirety, comprising a support 6 which appears in section as a class-A lever, mounted rotatably to a pivot 7 and capable of traversing back and forth along the axis of this same pivot. The pivoted support 6 exhibits a projecting arm 8, and two further arms 10 and 12 extending in the opposite direction to the arm 8 first mentioned. 11 denotes a bar of square section made fast to the first arm 8, which carries a swivelling bladeholder, denoted 9. The arm denoted 10 is rotated about the pivot 7 by operating a handwheel 13; thus, a lead screw 14 is made to turn in a nut 15 permanently attached to the block 16 carrying the pivot 7, in such a way that the entire doctor assembly can be rotated about the axis of the pivot 7 toward or away from the print cylinder 1. The remaining arm 12 of the support 6 provides an anchor point to which a pneumatic cylinder 13 is hinged, the rod 14 of the cylinder connecting via an additional arm (not illustrated) with the square section bar 11. The swivelling bladeholder 9 substantially comprises a bar 17, functioning as a fixed jaw, to which a plurality of removable jaws 19 are clamped by means of screws 18. The two jaws 17 and 19 thus constitute gripping means for retention of a cylindrical bar 20 in which a blade 21, the wiping member proper of the doctor device, is inserted. In the embodiment shown in the drawings, the cylindrical bar 20 consists in two half-round sections 23 and 23, between which the blade 21 is held. The single removable jaws 19 are seated in respective annular grooves 24 formed in the periphery of the cylindrical bar 20, though such grooves might equally well be dispensed with, and a clamping action effected simply by applying adequate pressure to the cylindrical surface of the bar 20. 27 denotes a conventional device serving to adjust parallelism between the blade and the axis of the print cylinder, whilst 25 denotes the system whereby the bladeholder 9 is held in place. It will be seen from fig 2 that the cylindrical bar which carries the blade 21 can be made to assume any given angular position internally of the gripping means, relative to the print cylinder 1 (see phantom line), and the angle is easily readjusted simply by loosening off the clamp screws 18 and swivelling the cylindrical bar 20 in its jaws. Thus, the gripping means and the bar, which effectively constitute the swivelling bladeholder assembly, provide increased possibilities for adjustment of the angle of the blade relative to the surface of the print cylinder. The facility of rotating the bladeholder according to the invention also provides the option of running the machine with the doctor blade set at a negative angle in relation to the print cylinder.

Claims: A swivelling bladeholder (9) for the wiper device (5), or doctor, of a print cylinder (1) in a rotary printing machine, comprising an element, embodied as a cylindrical bar (20), into which a blade (21) is inserted and made fast, characterized in that it comprises means (17, 19) for gripping the cylindrical bar (20), whereby the cylindrical bar can be rotated about its own axis between said gripping means in order to adjust the angular position of blade (21) in respect of the surface of the print cylinder (1), independently from the angular position of the doctor wiper device (5). A swivelling bladeholder as in claim 1, wherein the cyindrical bar (20) is split into two half-round sections (22, 23), between which the blade (21) is inserted. A swivelling bladeholder as in claim 1, wherein the gripping means comprise a fixed jaw (17) associated rigidly with the wiper device (5) and a plurality of removable jaws (19) that impinge on the cylindrical bar and are made fast to the fixed jaw by means of clamp screws (18).

Inventors: MAGGI, LUIGI
Applicants: SCHIAVI CESARE COSTRUZIONI MECCANICHE S.P.A.
Application year: 1988
Main classification: B41F9
IPC codes: B41F9