Abstract:
In order to achieve good lateral sealing in a simple construction of a chamber doctor, side parts are drawn toward the end sides of the work blade by magnets and/or the side parts are resiliently deformable and contact the work blade with pretensioning.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a chamber doctor which can be used, for example, in short inking mechanisms of rotary printing presses. 
     2. Description of the Prior Art 
     DE 37 04 433 C2 shows a chamber doctor arranged at a raster roller, which chamber doctor contains a working blade and a closing blade which are arranged at a doctor holder. The chamber doctor is enclosed laterally by sealing jaws which are resiliently adjustable against the raster roller and are guided, for this purpose, in guide slots of bearing blocks which are attached to the raster roller by screws. Further, the ends of the sealing jaws press against the doctor blades. For this reason, abutments which can be adjusted by means of displaceable guide pins are arranged in the region of the doctor blades. 
     However, such a device is costly to manufacture, since an abutment is required for each doctor blade. Moreover, the force by which the sealing jaws bear on the doctors cannot be adjusted in a defined manner with abutments for a stationary state. Also, excessive contacting force of the sealing jaws leads to increased wear of the doctor blade in the region of the lateral seals. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide lateral sealing in a simple construction in which wear on the doctor blades is kept low and permanently good sealing is achieved. 
     Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a chamber doctor in which the side parts are drawn by magnets against the work blade and possibly also against the closing blade and/or against the cylinder to be inked with a force which can be set by the dimensioning of the magnets and which is also permanently retained in stationary operation. The force can be adjusted so that the work blade and the closing blade can move freely between the side parts. Accordingly, there is no jamming of the doctor blade that would result in increased wear on the doctor blade. The side parts have good contact with the doctor blades and with the end side of the chamber doctor body particularly when constructed in a resilient manner. Good lateral sealing is achieved in this way. Also, a precise cutting down of the doctors is not required. Because of the good contact of the side parts at the work blade the chamber doctor does not tend to form ink rings in the region of the lateral seals. Moreover, the lateral seal is very narrow so that a wider printing area can be utilized 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawing: 
     FIG. 1 shows a portion of a chamber doctor pursuant to the present invention in a plan view; 
     FIG. 2 is a side view of the chamber doctor of FIG. 1; 
     FIG. 3 is a side part of the chamber doctor with a resilient body; 
     FIG. 4 is a side view of FIG. 3; 
     FIG. 5 is a side view of a second embodiment of the chamber doctor; 
     FIG. 6 is a view along arrow Z in FIG. 5; 
     FIG. 7 is a cross-section of a third embodiment of the chamber doctor along the line I--I in FIG. 8; and 
     FIG. 8 is a top view of the chamber doctor of FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The chamber doctor 1 shown in FIG. 1 contains a chamber doctor body 2 to which a work blade 3 and a closing blade 4 are fastened. A holder 6 is attached to the two end sides of the doctor body 2 (only the end on the right side is shown) by means of screws 5. The holder 6 is shaped so that it forms a gap 7 with the end side of the chamber doctor body 2. A side part 8 is inserted into this gap 7. The side part 8 is glued to a resilient body 9 which can be made of resilient plastic, e.g. polyurethane foam, or an oil-resistant foam rubber. The side part 8 is constructed so as to be resilient in a springing manner and is produced, for example, from spring steel with a thickness of 0.2 to 1 min. Together, the side part 8 and resilient body 9 are thicker than the width of the gap 7. Accordingly, the side part 8 resiliently contacts the work blade 3 and the closing blade 4 accompanied by pretensioning of the resilient body 9. The side part 8 can easily compensate for longitudinal tolerances of the doctor blades with an order of magnitude of up to 1 mm so that a precise cutting down or fitting of the doctor blade is unnecessary. Even with a less resilient construction of the side parts good contact at the doctor blades is provided. In this case, the lengths of the doctor blades should be adapted to one another more exactly. The thickness of the resilient bodies 9 and accordingly the contact pressure force on the doctor blades is dimensioned so that the doctor blades can easily bend between the side parts 8. Each resilient body 9 is so disposed on its respective side part 8 that a region 11 thereof projects out on the side of the side part remote of a raster roller 10 (FIGS. 3, 4). The side part 8 is supported by this region 11 in the base of the holder 6 and all appropriate overdimensioning of the region 11 causes the side part 8 to be pressed resiliently against the raster roller 10. Thus, the resilient body 9 advantageously takes over the springing contact pressure of the side portion 8 against the doctor blades 3, 4 and the raster roller 10. 
     Other springs can also be used to press the resilient side part against the doctor blades. According to another embodiment of the invention (FIGS. 5, 6), a side part 12 contacts the work blade 14 and closing blade 15 of a chamber-doctor 16 via a leaf spring 13. The side part 12 and the leaf spring 13 are inserted into a gap 17 formed by a holder 19 together with the chamber doctor body 18, the end of the holder 19 being screwed to the chamber doctor body 18. The resilient contact pressure of the side part 12 against the raster roller 20 is taken over by two pressure springs 21 guided in bore holes in the holder 19. 
     In the previous embodiments, the chamber doctor is enclosed by a closing blade. The invention also extends to equivalents such as closing strips which are arranged at a slight distance from the raster roller, e.g. 0.3 to 0.5 min. FIGS. 7 and 8 show a chamber doctor 22 of this type arranged at a raster roller 23. A work blade 25 and closing strip 26 are arranged at the chamber doctor body 24. The chamber doctor 22 is enclosed laterally by side parts 27, 28. Two magnets 29, 30 are embedded in the ends of the chamber doctor body 24. These magnets 29, 30 draw the side parts 27, 28 against the end sides of the work blade 25, the closing strip 26 and the chamber doctor body 24 so that an air gap 40 exists between the magnets and the side. The attractive force of thee magnets 29, 30 is dimensioned so that the side parts 27, 28 have good contact with the end sides, but the work blade 25 can easily bend outward. As in the preceding embodiment examples, the side parts can advantageously be constructed so as to be resilient, but the invention can also be used with a rigid construction of the side parts. The adjustment of the side parts 27, 28 toward the raster roller 23 is likewise effected by magnetic force. For this purpose, the side parts 27, 28 are magnetized in appropriate polarity and are attracted toward the raster roller 23 which is made of iron, for example. The number of magnets in the end sides of the chamber doctor body 24 can also vary. When suitably magnetized, the side parts may also be attracted toward the end sides of the work blade, the closing strip and the chamber doctor body without magnets 29, 30. In this case, the bearing force against the doctor roller can be exerted by a mechanical spring or by magnets which are fastened to the side parts in the vicinity of the raster roller. Within the scope of the invention, the side parts can also be pressed against the raster roller by magnetic force and against the end sides of the chamber doctor by means of mechanical springs. 
     Chamber doctors have been described in the above in connection with raster rollers, e.g. of short inking mechanisms or flexoprinting mechanisms. The invention can also be used for inking other cylinders, e.g. rotogravure form cylinders. 
     The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.