Abstract:
A method for safeguarding against the entry of foreign bodies into a nip between two cylinders, which includes applying a deflection movement to one of the cylinders counter to a spring force applied thereto so as to overcome the spring force and, in accordance with a prescribed deflection distance, alternatively keeping the spring force to be overcome constant or reducing the spring force; and a device for performing the method.

Description:
This divisional application claims the benefit under 35 U.S.C. § 120 of U.S. application Ser. No. 09/084,556, filed May 26, 1998 now U.S. Pat. No. 6,009,801. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method and a device for safeguarding or protecting against penetration by foreign bodies into a roller nip, more particularly, between two cooperating cylinders, such as a contact-pressure roller cooperating with a plate cylinder in a printing press, in a manner that an automatically or semiautomatically supplied printing plate is mounted error-free on the plate cylinder and, in particular, a canted or bent trailing edge of the printing plate is introduced into a clamping and/or lock-up device for the printing plate. 
     A device of this general type has become known heretofore from the published German Patent Document DE 42 18 602 A1. In this known device, a contact-pressure roller corresponding in length to the length of the plate cylinder is provided, and is positionable against the plate cylinder by spring force. The spring force is applied by spiral compression springs, which have force action lines extending virtually radially to the plate cylinder. This known device has a protective function, in that a foreign member, such as a finger or hand, which may accidentally slip in between the contact-pressure roller and the plate, can displace the contact-pressure roller counter to the spring force of the spiral compression springs. A switch lever is connected to the contact-pressure roller via the shaft of the contact-pressure roller and, whenever the contact-pressure roller is deflected, actuates a switch that turns off the drive for the plate cylinder. 
     A disadvantage of the device disclosed in the aforementioned published German Patent Document DE 42 18 602 A1 is that the force causing the deflection of the contact-pressure roller increases as the distance traversed in the deflection increases, and can exceed an allowable distance; another disadvantage is that this force is exerted constantly on the foreign member, i.e., a finger or hand, for example. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a method and device for guarding against penetration by foreign bodies into a cylinder nip, wherein the force required for deflecting the contact-pressure roller is reduced to a permissible extent, and the continuous application of the force to the foreign body is also reduced or even eliminated. 
     With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for safeguarding against the entry of foreign bodies into a nip between two cylinders, which comprises applying a deflection movement to one of the cylinders counter to a spring force applied thereto so as to overcome the spring force; and keeping the spring force to be overcome constant in accordance with a prescribed deflection distance. 
     In accordance with another aspect of the invention, there is provided a method for safeguarding against the entry of foreign bodies into a nip between a plate cylinder and a contact-pressure roller disposed parallel thereto and cooperating therewith, which comprises applying a deflection movement to the contact-pressure roller counter to a spring force applied thereto so as to overcome the spring force; and keeping the spring force to be overcome constant in accordance is with a prescribed deflection distance. 
     In accordance with a further aspect of the invention, there is provided a method for safeguarding against the entry of foreign bodies into a nip between two cylinders, which comprises applying a deflection movement to one of the cylinders counter to a spring force applied thereto so as to overcome the spring force; and reducing the spring force in accordance with a prescribed deflection distance. 
     In accordance with an added aspect of the invention, there is provided a method for safeguarding against the entry of foreign bodies into a nip between a plate cylinder and a contact-pressure roller disposed parallel thereto and cooperating therewith, which comprises applying a deflection movement to the contact-pressure roller counter to a spring force applied thereto so as to overcome the spring force; and reducing the spring force in accordance with a prescribed deflection distance. 
     In accordance with an additional aspect of the invention, there is provided a device for safeguarding against the entry of foreign bodies into a nip between a plate cylinder and a contact-pressure roller disposed parallel thereto and cooperating therewith, comprising a movable actuating element formed with a control contour having an ascending incline and, adjoining the ascending incline, a contour segment selected from the group thereof consisting of a straight edge and a descending incline; the contact-pressure roller being formed with ends in cooperative engagement with the control contour. 
     In accordance with yet another feature of the invention, the device includes guides disposed at respective ends of the contact-pressure roller for displaceably supporting the contact-pressure rollers. 
     In accordance with yet a further feature of the invention, the device includes an adjusting element, the guides being disposed so as to be adjustable by the adjusting element. 
     In accordance with yet an added feature of the invention, the contact-pressure roller is formed of a contact-pressure roller body rotatably supported on a shaft. 
     In accordance with yet an additional feature of the invention, the actuating element is disposed so as to be deflectable counter to the force of a restoring spring and is bringable into operative engagement with a switch. 
     In accordance with still another feature of the invention, the actuating element is disposed so as to be displaceable in axial direction of the contact-pressure roller. 
     In accordance with still a further feature of the invention, the actuating element is disposed so as to be displaceable at an angle to the shaft of the contact-pressure roller. 
     In accordance with still an added feature of the invention, the angle is a right angle. 
     In accordance with still an additional feature of the invention, the guides form part of the actuating element, and the control contours are disposed in the guides so that they are in mirror symmetry with one another. 
     In accordance with a concomitant feature of the invention, the guides, respectively, form an acute angle with a horizontal, and the ascending incline forms with the horizontal an angle which is greater than the acute angle. 
     The invention offers the particular advantage that severe injuries to human operators can be prevented by the safeguarding device according to the invention. This is achieved by providing that upon the deflection of the contact-pressure roller after a high point has been exceeded, the spring force no longer increases but instead is maintained at an allowable level. In a second exemplary embodiment, this allowed spring force is reduced even further. 
     In the first exemplary embodiment, the maintenance of the spring force at a predetermined level is advantageously attained by a runup incline of a control contour, which merges into a straightedge support region for one end of the shaft of the contact-pressure roller; the rectilinearly extending support region is disposed perpendicularly to the line of action of the spring force. 
     In a second exemplary embodiment, an advantageous feature of the invention is provided in that the runup incline merges into an oppositely oriented runout decline. 
     In a space-saving arrangement, a tripping mechanism is disposed in the side wall of the printing press. In this regard, the control contour having the runup incline segment is formed as a piston, which is supported displaceably in a bore of the side wall. At the same time, the piston is disposed in combination with an emergency shutoff switch. 
     To assure that a deflection of the contact-pressure roller over the length of the plate cylinder or the contact-pressure roller or the roller or cylinder nip defined thereby will lead to the shutoff of the printing press and, in particular, of the drive mechanism of the plate cylinder, the control contour of the axially displaceable piston is disposed in mirror symmetry with the control contour fixedly disposed on the other side wall. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a method and device for guarding against the penetration of foreign bodies into a roller nip, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic top plan view, partly in section and partly broken away, of a first exemplary embodiment of the safeguarding device of the invention; 
     FIG. 2 a  is a diagrammatic and schematic side elevational view of a second exemplary embodiment of the safeguarding device in an operating phase thereof wherein a contact-pressure roller is disposed in engagement with a plate cylinder; 
     FIG. 2 b  is a view like that of FIG. 2 a  of the second embodiment of the device in another operating phase wherein the contact-pressure roller is disposed at a spaced distance away from the plate cylinder; and 
     FIG. 2 c  is another view like those of FIGS. 2 a  and  2   b  showing the device in a further operating phase wherein the contact-pressure roller is forcibly pressed away from the plate cylinder. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and, first, particularly to FIG. 1 thereof, there is shown therein a plate cylinder  1  of a printing press rotatably supported in side frames  2  and  3 . A contact-pressure roller  4  is disposed parallel to the axis of the plate cylinder  1 . The contact-pressure roller  4  is supported by the ends thereof in a respective slot  6 ,  7  formed in a respective holder  8 ,  9 . The contact-pressure roller  4  has a contact-pressure roller body carried by a roller shaft  5  and provided with rings  15 , the roller body being formed as a rotatably supported sleeve  10 . The holders  8  and  9  are displaceably supported on the respective side frames or walls  2  and  3 . Respective pneumatic cylinders  11  and  12  execute a sliding motion having a displacement direction along an imaginary line between the axis of the plate cylinder  1  and the axis of the shaft  5  of the contact-pressure roller  4 , i.e., from one to the other axis. The shaft  5  of the contact-pressure roller  4  protrudes on both sides through the respective slots  6  and  7  and, with respective spherically formed ends  13  and  14  thereof, engages a respective control contour  16 ,  17  of a guide  18  and an actuating element  19 , respectively. The control contours  16  and  17  are formed as a mirror symmetric image of one another. The actuating element  19  is embodied as a piston having a piston rod  21  which protrudes through a bore  22  formed in the side wall  3 . A control inclination or slope  22  provided at the end of the piston rod  21  is operatively engageable by a trigger or trip member  23  of a switch  24 . The switch  24  is connected to the control system of the printing press and, when actuated, turns off the drive of the printing press. 
     A restoring spring  26  coaxially surrounds the piston rod  21  and is braced, at one end thereof, against the piston  19  and, at the other, against a bottom surface of a cylinder chamber  27  wherein the piston  19  is received, the cylinder chamber  27 , in this exemplary embodiment, being formed by a bore in the side wall  3 . 
     Adjusting cylinders  28  and  29 , respectively, are disposed on the inner sides of the respective side walls  2  and  3 , each of the adjusting cylinders  28  an  29  having a respective piston rod  31 ,  32 , which is constructed so as to be extensible in order to position the contact-pressure roller  4  against the plate cylinder  1 . The direction of operation is likewise an extension of the imaginary line from one of the respective axes of the plate cylinder and the contact-pressure roller to the other. 
     To mount a printing plate on the plate cylinder  1 , the piston rods  31  and  32  are extended and engage the shaft  5  of the contact-pressure roller  4 . The shaft  5  is thereby displaced to such an extent counter to the force of the pneumatic cylinders  11  and  12  in a direction towards the plate cylinder  1 , that the rings  15  rest on the printing plate mounted on the plate cylinder  1 . 
     The safeguarding or protective device according to the invention, in this position of the contact-pressure roller  4 , namely when it is operatively engaged with the plate cylinder  1  or with the printing plate mounted on the plate cylinder  1 , is set or placed out of operation. 
     The safeguarding or protective device is not activated until the piston rods  31  and  32  are retracted to the starting position thereof. The contact-pressure roller  4  is thereby displaced into a standby position by the holders  8  and  9  and, in this position, it is spaced a slight distance a =5 mm, for example, from the surface of the plate cylinder  1 . In this position, the spherically formed ends of the contact-pressure roller shaft  5  rest on a runup or approach incline  33 ,  34  of the respective control contours  16  and  17 . In this position, a deflection of the contact-pressure roller  4  caused, for example, by the entry of foreign bodies, such as fingers or hands, into the nip formed between the contact-pressure roller  4  and the plate cylinder  1 , lead to a sliding of the spherical end  13 ,  14  in the region of the runup inclines  33  and  34 , respectively, and a resultant axial movement of the contact-pressure roller  4  together with the actuating element  19  and the piston rod  21  which actuates an emergency shutoff switch. 
     The axial movement takes place in the region of the runup incline  33 ,  34  counter to the force of the restoring spring  26 . After this relatively short switching distance has been bridged or spanned, the respective spherical end  13 ,  14  reaches a rectilinearly extending region  20  of the respective control contour  16 ,  17 . The effect of this provision is that the contact-pressure roller  4  is extraordinarily easily displaceable in the region  20 , and a spaced distance thereof from the plate cylinder  1  can thereby be readily increased, so that the foreign bodies that have entered the nip can be withdrawn out of the nip by exerting only a relatively slight force. 
     Because of the mirror-symmetrical arrangement of a second exemplary embodiment of the invention shown in FIGS. 2 a ,  2   b  and  2   c , a description thereof is presented hereinafter with respect to only one side thereof. As illustrated in FIGS. 2 a ,  2   b  and  2   c , the shaft  5  of the contact-pressure roller  4  is supported displaceably by ends  36 , respectively, of the shaft  5  or of the roller  4  in a guide  41  formed with a slot. The guide  41  is mounted on a holder  45 , which is displaceably supported substantially horizontally by a pneumatic cylinder  47  disposed rigidly on a side frame  46 , so that the contact-pressure roller  4  can be positioned against or into engagement with the plate cylinder  1  and moved away therefrom. The guide  41  is inclined to the horizontal, so that an acute angle a is formed. The end  36  protrudes through the slot  41  and, in the condition wherein the contact-pressure roller  4  is positioned against or engages the plate cylinder  1 , this end  36  rests on an incline  48  of an actuating element  49 . The incline  48  forms an angle β with the horizontal that is larger than the angle a formed between the guide  41  and the horizontal. The actuating element  49  is displaceably supported on the side frame  46  of the printing press, counter to the force of a restoring spring  51 , and presses the contact-pressure roller  4  with the force of the spring  51  against the plate cylinder  1 . The incline  48  terminates at an apex point  52  into an incline  53  having negative pitch or, in other words, a decline. 
     For applying a printing plate, the contact-pressure roller  4  is positioned against or brought into engagement with the plate cylinder  1  by the pneumatic cylinder  47 . In this regard, the end  36  of the contact-pressure roller  4  or the shaft  5  thereof slides downwardly, as viewed in FIGS. 2 a  to  2   c , in the guide  41  until the circumference of the contact-pressure roller  4  comes into operative engagement or connection with the printing plate disposed on the circumference of the plate cylinder  1 . At the same time, the incline  48  presses against the end  36  and thus presses the contact-pressure roller  4  against the plate cylinder  1  and against the printing plate to be applied to the plate cylinder  1 , respectively. If a foreign body should enter the nip between the contact-pressure roller  4  and the plate cylinder  1  during the application of the printing plate, a deflection movement of the contact-pressure roller  4  and consequently a movement of the contact-pressure roller  4  away from the plate cylinder  1  takes place. In this regard, the end  36  slides in the guide  41  and presses against the incline  48  protruding into the guide  41 , so that the actuating element  49  is displaced counter to the force of the restoring spring  51 . A non-illustrated sensor or switch disposed on the actuating element  51  detects the motion of the actuating element  51  and transmits an emergency shutoff signal to the printing-press control the instant the end  36 , during the deflection movement of the contact-pressure roller  4 , exceeds or passes beyond the apex  52  and reaches the region of the inclines  53 . According to the invention, in this region, the restoring spring  51  reinforces the motion of the contact-pressure roller  4  away from the plate cylinder  1 . During normal operation, that is, upon the positioning of the contact-pressure roller  4  against and away from the plate cylinder  1 , or in other words, when the contact-pressure roller  4  is brought into engagement with or disengaged from the plate cylinder  1 , the end  36  always remains in the region of the inclines  48 .