Quick tightening system for change of printing plates

Abstract: The QUICK TIGHTENING SYSTEM FOR CHANGE OF PRINTING PLATES consists of two hydraulic clamps (4.5) that are to be located in the hollow (3) of the printing plate cylinder (1), that fixes the ends of the plate (6) between the teeth, actioned by a hydraulic circuit (8.9) that permits, in one second, the fixing of the printing plate's edges over their whole length, adjusting itself around the cylinder. The number of hydraulic pistons (10) that action the teeth depends upon the length of the clamp. This invention permits the quick fixing, warrant the uniform tightening of the edges over their whole length, obtain a equal wear, and obtain an immovable clinch of the printing plate, whose consequence is economy in the preparation of the offset presses used in the Graphical Industry.

Description: The following describes a QUICK TIGHTENING SYSTEM FOR CHANGE OF PRINTING PLATES in plate cylinders of offset presses. DE-U-8710030 discloses a system according to the preamble of claim 1. The present invention is referred to a fixing and adjusting system of the printing plate to the plate cylinder in an offset press. In the proceedings of impression with offset presses, generally used in the Industry of Graphic Arts, though exists other Industries susceptibles to use this impression system, it is necessary to count with quick, safe and economical proceedings at the moment of the preparation and final setting of the presses, due to its dynamics oppresses unnecessarely the final economical result. The printing plate fastening systems known in the offset presses, mounts the printing plate's edges into the plate cylinder using a mechanical tightening device with screws or eccentrics, tensioning later the printing plate by the movement of the clamps in the peripherical direction of the cylinder using strews or hydraulic systems. This system does not permit: a) Warrant the perfect uniform tightening of the printing plate over the whole lenght of the edges, due to the physical void occupied by the used screws or eccentrics. b) Realize the fixing of the printing plate over its whole lenght in a approximate time of one second, a time sensibly smaller then the one occupied of any expert person habituated in these proceedings, wich needs much more time in order to realize the fixing of the printing plate edges. c) Obtain a perfect uniform clinch over the whole edge lenght, hardly obtainable by mechanical medias, as these are made in determinated intervals. d) Warrant a much smaller clinch wear of the parts that the one obtained with mechanical tightening. e) Warrant a uniform clinch over the plate edges that avoid alterations of its position in the quick movement given to the plate cylinder. The present invention has the object to avoid these inconvenients, and brings a fixing and adjusting system of the printing plate to a plate cylinder of offset presses, though the use, for the fixing over the whole lenght of the printing plate ends, of the advantages offered by the hydraulic system used on the system of teeth, that locks over their whole lenght the edges of the printing plate, with a substantial reduction of the time of realization for the fixing plate operation, esential in the preparation and final setting of the offset presses at the beginning of their work operations. The plate cylinder has a parallel hollow to its geometrical shaft, enough to lodge two hydraulic clamps that fixes both ends of the printing plate, that will be adjusted all around the cylinder area. The printing plate is introduced between the teeth of the clamp, and the actioning of the hydraulic circuit permits, in the question of one second, the fixing, over its whole lenght, of the printing plate ends, adjusting itself later the plate all along the cyilinder by any of the known methods of plate adjusting. The advantages deduced by this invention consists essentially, as mentioned above, of the use of the hydraulic device in order to realize the tightening and longitudinal adjusting of a printing plate to its cylinder, securing the uniform tightening over the lenght of the printing plate edges, from the point of view of time reduction and uniform tightening over the whole lenght of the printing plate ends. As follows, we are realizing a short description of the drawings enclosed: The drawing 1 is a section of the cylinder hollow with the hydraulic clamps. The drawing 2 is a view of the pump assy for the actioning of the hydraulic circuit. The drawing is a plan over the part nr. 2 of the drawing 1. The following description referrs to a plate cylinder destinated to sustain a printing plate in an offset press: It has been realized inside the hollow (3) of the plate cylinder (1) the hydraulic clamps with lower teeth (4) and upper teeth (5), for the tightening of the printing plate (6). As represented in the drawings 1 and 3 the canalization of the hydraulic fluid, that arrives from the hydraulic pump, drawing 2 (36), to the main canalization, drawings 1 and 2 (7), is realized through all the lenght of the hydraulic clamp, connects with the canalization (8) and (9) that are realized in spaced intervals over the whole body (2) lenght of the hydraulic clamp. The fluid moves a piston (10), wich brings an U-collar (11) and an O-ring (12), over the lower tooth (4), that moves the printing plate (6) upwards and with a uniform pressure over the whole lenght of the upper tooth (5), that does not move. To be able to realize a total air exit that may change the function of the hydraulic system in each one of the lodgings (9), we have a carriage (13) that is blocked by a steel ball (15) tightened with a set screw (14) wich loosening permits the air exit that the hydraulic circuit may have through the canalization (16), and so be able to realize a perfect purge of the hydraulic circuit. The actioning of each of the pistons that are intercalated all along the body (2) of the clamp, depending the number of pistons upon the lenght of the clamp, in order to the effort will be the necessary for a perfect distribution of the pressure all along the edge of the printing plate, in a way that a continuos use of this utensil does not mean a wear of the plate, taht prevent its posterior use, with its consequent increase of printing costs. The hermeticity of the main canalization (7) all along the body (2) of the clamp, is warranted by an O-ring (17), that is intercalated between the body (2) and the upper tooth (5), and these two parts of the hydraulic clamp are fixed by screws (19), wich have warranted their hermeticity by special copper washers (18), specially used in hydraulic circuits. The actioning of the hydraulic pump, as the regulating of the hydraulic pressure is detailed in the following manner, as the drawing 2; The bolt (26) is actioned by a hexagonal wrench turning it 90° over its shaft until a position determinated by a mechanical positioning top realized by the rod (27), that moves a shaft (28) guided over a holder (29); The shaft (28) is threaded to the shaft (30) wich moves the piston (31) over the pump body (32) passing the hydraulic fluid through the drilled hole (25) to the main canalization (7) of the hydraulic clamp body. The sealed system of the pump assy is warranted by two U-collars (33) and (34). In order to protect the body of the pump (32) from wear of the metalic parts from wich it is made it is provided with some guides (35) of plastic material, preferably Tephlon. The return of the piston (31) to its rest position is accomplished by two components: a) The pressure held by the hydraulic fluid, within its run; and b) The power held by the spring (36), that warrants the return of the piston to its initial position. The regulation of the pressure held by the hydraulic pump is realized by the regulator (37), that turns in one or another direction, increases or decreases the distance between the shaft (28) and the shaft (30), making that the piston (31), in its compression position, increases or decreases the compression chamber (38) originating with this movement a variation of the pressure all along the whole hydraulic circuit.

Claims: Quick change tightening system for changing printing plates in offset presses, said system comprising a plate-supporting cylinder having a hollow space which is parallel to the geometrical axis of said cylinder and in which two clamp means comprising upper and lower teeth and extending over the whole length of said hollow space are adapted to clamp each one an edge of a printing plate and wherein said lower teeth are hydraulically actuatable, characterised in that said system further comprises hydraulically actuatable piston means whereby said lower teeth of the clamp means are directly actuatable to clamp the plate between said upper and lower teeth."

Inventors: GARCIA-GIL RAFAEL SERRANO, MALO GUIJARRO FRANCISCO, MAZQUIARAN BRIS PEDRO, RUIZ MARIN FRANCISCO, UZQUIZA CONTRERAS ANGEL LUIS, GARCIA-GIL, RAFAEL SERRANO, MALO GUIJARRO, FRANCISCO, MAZQUIARAN BRIS, PEDRO, RUIZ MARIN, FRANCISCO, UZQUIZA CONTRERAS, ANGEL LUIS
Applicants: TGA INGENIERIA GRAFICA S L, TGA INGENIERIA GRAFICA, S.L.
Application year: 1995
Main classification: B41F27
IPC codes: B41F27