This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2013 010 751.2, filed Jun. 27, 2013; the prior application is herewith incorporated by reference in its entirety.
The present invention relates to a seal for doctor blade devices in printing presses. The invention also relates to a doctor blade device having a seal.
Printing presses include anilox inking units and varnishing units with screen rollers and co-operating doctor blade devices such as chambered doctor blades, which have two doctor blades (working blade and closing blade), and blade-type ink fountains with only one doctor blade (working blade). Such a doctor blade device has a rubbery-elastic seal on each of its ends which is engaged with the screen roller and the doctor blade or blades.
When the doctor blade moves relative to the seal, the area of contact between the seal and the doctor blade is prone to leakage. Such movement of the doctor blade occurs, for instance, when the doctor blade is bent while it is in engagement with the screen roller.
U.S. Patent Application Publication No. 200910193990A1 discloses a seal for a chambered doctor blade. The seal has a respective blade contacting section on each end. In the region of one blade contacting section, the seal is engaged with the working blade and in the region of the other blade contacting section, the seal is engaged with the closing blade. A roller contacting section in which the seal is engaged with the screen roller is situated between the two blade contacting sections.
In order to solve the leakage problem, the prior art indicated above proposes to equip the seal with a pair of protruding wings in each blade contacting section. The wings provide greater flexibility or elasticity and thus have an improved ability to follow the movements of the doctor blade. The wings are disposed on the front side, i.e. the side of the blade contacting section that is engaged with the doctor blade. However, the wings wear easily, causing renewed leakage and resulting in a shorter useful life.
It is accordingly an object of the invention to provide a seal for doctor blade devices and a doctor blade device having a seal, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which provide a low-wear seal that is less prone to leakage.
With the foregoing and other objects in view there is provided, in accordance with the invention, a seal for doctor blade devices in printing presses, comprising a blade contacting section with a front side engaged with the doctor blade and a rear side being softer, more elastic or more flexible than the front side.
The invention is based on the realization that it is not expedient to assign increased flexibility or elasticity of the blade contacting section to the front side thereof. Instead, the opposite is the case, i.e. it is expedient to assign an increased flexibility or elasticity of the blade contacting section to the rear side. The result is that the inherent dimensional stability of the front side is maintained, resulting in reduced wear. The rear side forms a resilient element that ensures that the engagement between the seal in the region of the blade contacting section and the doctor blade is maintained to prevent leakage. In the region of the blade contacting section the liquid provided in the doctor blade device, e.g. the printing ink or varnish, is prevented from leaking from the doctor blade device between the seal and the doctor blade.
The seal of the invention is not sensitive to changing loads such as the ones that occur when the doctor blade device is engaged with and disengaged from the screen roller. In practice, blade-type ink fountains are engaged and disengaged more frequently than chambered doctor blades since blade-type ink fountains are more suited for frequent engagements and disengagements due to their construction that does not require them to be emptied before being disengaged as is the case with chambered doctor blades. Against this background, the seal of the invention is particularly suited for use in blade-type ink fountains.
With the objects of the invention in view, there is concomitantly provided a doctor blade device, in particular a blade-type ink fountain that is equipped with two seals of the invention.
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 seal for doctor blade devices and a doctor blade device having a seal, 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.
Referring now to the figures of the drawings in detail and first, particularly, to
The rear wall 5 is pivotable towards the doctor blade 7 to increase the level of the fluid to a level above a blade edge that is engaged with the screen roller 2 by displacement of the fluid. In order to lower the level below the edge for maintenance and set-up work that requires the doctor blade device 3 to be disengaged from the screen roller 2 such as for an ink change, the rear wall 5 is pivotable away from the doctor blade 7 into the illustrated position.
As shown in
The two seals 9 are identical parts, a fact that is advantageous in manufacturing terms, and each one is compatible with the drive-side wall 6 and with the operator side wall 6.
Narrow depressions such as grooves are known to be difficult to clean, for instance because it is difficult for an operator to introduce a cleaning cloth into the depression. However, that disadvantage does not apply to the groove 12 because a thorough cleaning of the seal 9 is not necessary since the seal 9 is constructed to be disposable. If printing ink gets into the groove 12 and contaminates it, potentially contaminating the ink of a following print job, the seal 9 does not have to be cleaned in a time-consuming process. Instead, the seal 9 may simply be replaced by a new, clean seal.
A complementary protrusion or protrusions (connecting webs 13 seen in
The upper end and the lower end of the seal 9 have different contours: the upper end is obtuse and the lower end has a wedge-shaped tip 14. When the seal 9 is correctly fitted onto the side wall 6, the upper end forms an engagement surface 15 with which the seal 9 rests against a stop 16 (see
The blade contacting section 20 has a front side 17 and a rear side 18, which coincide in an edge 19 of the tip 14. The front side 17 is on the same side of the seal 9 as the lips 10 (see
The fact that the dimensions of the pockets 21, 22 are adapted to each other ensures that when pressure is exerted on the blade contacting section 20 or the front side 17 thereof by the doctor blade 7 engaged therewith, the rear side 18 with the first pocket 21 reacts in a softer, more resilient or elastic way than the front side 17 with the second pocket 22 because the front side 17 is more dimensionally stable than the rear side 18. Thus, it is substantially the rear side 18 and not the front side 17 that forms a spring system for the blade contacting section 20 and keeps the blade contacting section 20 in continuous contact with the doctor blade 7 even when the doctor blade 7 moves or is deformed, a contact that is firm or close enough to prevent fluid from leaking in the region of the blade contacting section 20.
As shown in
As shown in
In a non-illustrated modified embodiment, the row of connecting webs 13 may be replaced by a single connecting web that continuously extends across the entire length of the row.
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10 2013 010 751 | Jun 2013 | DE | national |
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