Adjusting device with a pneumatic cylinder in a printing press

An adjusting device has a pneumatically operating piston-cylinder unit pressurizable in an operating function thereof for actuating adjusting elements in a printing press. The piston-cylinder unit includes a cylinder housing formed with a cylinder chamber, a piston displaceable in the cylinder chamber, and an electromagnet for applying an activated holding force to the piston, the piston being subjectible pneumatically to a prepressurizing force in the cylinder chamber opposite to and less than the activated holding force.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an adjusting device with a pneumatic cylinder in a 
printing press and, more particularly, a pneumatically operating 
piston-cylinder unit for actuating final control or adjusting elements in 
a printing press, the piston-cylinder unit, hereinafter also referred to 
as a pneumatic cylinder, being pressurized in the operating function 
thereof by partial action thereon and being lockable in the pressurized 
setting. The invention relates, in particular, to such a device for use in 
an arrangement for preventing the entry or in-feed of a mis-fed sheet or 
multiple sheets into a printing press. 
The published German Patent Document DE 41 18 659 A 1 discloses an 
arrangement for actuating adjusting elements for starting and stopping 
printing in a sheet-fed printing press or for blocking the feeding of 
sheets, wherein latches which are able to be affected by electromagnets 
and by spring force are operatively associated with a lever which is 
pivotable about a fixed pivot point and connected to a drive member, and a 
piston-cylinder unit which is able to be acted upon hydraulically or 
possibly pneumatically, as well, for swivelling the lever after it has 
been unlocked, is provided, the piston-cylinder unit serving to swivel the 
lever, if mis-fed sheets are detected after the lever has been unlocked by 
the electromagnet, out of a relaxed or non-stressed zero or neutral 
position into a blocking position, wherein sheet grippers, for example, 
are blocked in the open position. For small-format pneumatic cylinders, 
the force is too low to re-open closed or partly-open grippers again, 
because they have to be quite small in order to travel the distance 
prescribed by the opening, within the shortest possible time. For 
electromagnets, the excitation time is very long, and the least force is 
available in the initial phase of the motion. The stroke of an 
electromagnet, under the prescribed conditions, is therefore limited. The 
physical conditions of a small pneumatic cylinder and of electromagnets 
have a particularly deleterious effect in high-speed printing presses. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the invention to provide an improved 
adjusting device with a pneumatic cylinder in a printing press having the 
foregoing general characteristics which exhibits extremely short switching 
times with adjusting forces having adequate strength and switching 
distances of adequate length. 
With the foregoing and other objects in view, there is provided, in 
accordance with the invention, an adjusting device with a pneumatically 
operating piston-cylinder unit pressurizable in an operating function 
thereof for actuating adjusting elements in a printing press, the 
piston-cylinder unit comprising a cylinder housing formed with a cylinder 
chamber, a piston displaceable in the cylinder chamber, and an 
electromagnet for applying an activated holding force to the piston, the 
piston being subjectible pneumatically to a prepressurizing force in the 
cylinder chamber opposite to and less than the activated holding force. 
In accordance with another feature of the invention, the cylinder chamber 
has an air inlet communicating with an air supply more highly pressurized 
in a volume greater than that within the cylinder chamber, the air inlet 
being openable for admitting air with a maximum pressure drop into the 
cylinder chamber without having to refill any of the air. 
In accordance with another aspect of the invention, there is provided an 
adjusting device for switching off or arresting travel of a mis-fed sheet 
in a feeder of a sheet-fed printing press having a pneumatically 
operational piston-cylinder unit secured to a press frame and being 
operatively engageable with a control lever for sheet grippers, the 
piston-cylinder unit comprising a cylinder housing fixed to the press 
frame and formed with a cylinder chamber, a piston displaceable in an 
axial direction thereof in the cylinder chamber, and an electromagnet for 
applying a holding force to the piston, the piston being subjectible 
pneumatically in the axial direction to a prepressurizing force in the 
cylinder chamber opposite to and less than the holding force. 
In accordance with a further feature of the invention, the adjusting device 
includes a piston rod connected to the piston and having an end extending 
out of the cylinder housing, an iron armature plate connected to the 
piston end outside the cylinder chamber, and an electromagnet secured to 
the cylinder housing opposite the armature plate, the electromagnet and 
the armature plate, respectively, being formed with mutually parallel 
contact surfaces. 
In accordance with an added feature of the invention, the iron armature 
plate is movably disposed in an interior chamber formed in the cylinder 
housing, the interior chamber having an end face located opposite the 
piston of the piston-cylinder unit which is formed by the electromagnet. 
In accordance with an additional feature of the invention, the adjusting 
device includes a piston rod connected to the piston and having a free end 
thereof extending out of the cylinder housing, an abutment fixed to the 
cylinder housing, an adjusting lever swivellable about an axis and 
spring-biased in a direction of movement thereof against the abutment, the 
abutment and the adjusting lever being formed with respective support 
surfaces converging wedgelike towards one another in a direction of 
operation of the piston, the free end of the piston extending out of the 
cylinder housing engaging between the support surfaces. 
In accordance with a concomitant feature of the invention, the adjusting 
lever is a bell crank having one arm whereon the support surface of the 
adjusting lever is formed, and including at least one roller supported 
with a roller bearing on the free end of the piston rod outside the 
cylinder housing, the roller having a peripheral surface with which the 
roller engages the support surface of the fixed abutment and the support 
surface on the one arm of the bell crank. 
In a device constructed in this manner, in accordance with the invention, 
the piston of the piston-cylinder unit can be prestressed or pressurized 
in advance by being acted upon with compressed air and can be held in this 
prestressed position by the electromagnet. If mis-fed sheets are detected, 
the electromagnet becomes voltageless. Due to the air prepressurized or 
prestressed in the cylinder chamber and and due to the air flowing-in 
thereafter, the adjusting motion is executed immediately, and entry of the 
mis-fed sheet into the printing press is thus prevented. Compared with 
conventional devices, economies in switching times, control time for the 
air control valve, and the filling time of the cylinder are realized with 
the device according to the invention. 
To attain the strongest possible adjusting forces and short adjusting 
paths, as noted hereinbefore, in a further concept of the invention, the 
piston rod which extends out of the cylinder housing has a free end which 
is received between two surfaces, respectively, of an abutment fixed to 
the cylinder housing and of an adjusting lever swivellable or pivotable 
about an axis and urged by a spring in the direction of the motion thereof 
against the abutment fixed to the housing, and the support faces extend 
convergingly towards one another in a wedgelike manner in the direction of 
operation of the piston of the piston-cylinder unit. The free end of the 
piston rod thus presses into the wedge-shaped gap, creating a transverse 
force which becomes many times stronger than the piston force. The 
transverse force advantageously acts upon one arm of the gripper lever. It 
is sufficiently strong to rotate this arm counter to the springs of the 
gripper lever and to reopen the grippers. Preferably on the free end of 
the piston rod outside the cylinder housing, at least one roller is 
supported with a roller bearing and engages by the peripheral or 
circumferential surface thereof with the support surface of the fixed 
abutment and the support surface of one arm of a bell crank constituting 
the adjusting lever. Frictional forces are thereby avoided to the greatest 
possible extent, and low-noise operation is achieved. 
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 an adjusting device with a pneumatic 
cylinder in a printing press, 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, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the figures of the drawing, there is shown, therein, at a 
reduced scale, on the right-hand side of FIG. 1, a sheet gripper 1, which 
is able to be affected or influenced by the adjusting device of the 
invention, together with a gripper pad 2 of a gripper system of a 
pregripper for sheet feeding in a sheet-fed printing press. A plurality of 
sheet grippers 1 with a gripper pad 2, disposed side-by-side crosswise to 
the sheet feeding direction, form the gripper system of the pregripper 
which, with the gripper system thereof, grasps a respective sheet by a 
leading edge thereof and feeds the sheet to the printing press by 
swivelling the pregripper about a swivel axis of a pregripper lever. The 
pregripper per se is not shown in the drawing, in the interest of clarity 
and simplicity. The sheet gripper 1 is suitably mounted so as to swivel 
about an axis 4 on the pregripper lever. 
A cam disk 5 controls the opening and closing motion of the sheet gripper 1 
about the axis 4 by means of a cam roller 6, which rests on the cam disk 5 
and is supported on an arm 7 of an angle lever or bell crank 9, which is 
connected to a shaft 23 by an indexing segment 3 and is biased by spring 
force of a spring 8, so that the cam roller 6 is pressed by the spring 
force against the circumference of the cam disk 5 and, via the indexing 
segment 3, presses the roller 22 downwardly, as viewed in FIG. 1. 
The other arm 10 of the bell crank 9 is formed with a support surface 12, 
which extends wedgelike to a support surface 11 formed on a fixed abutment 
The adjusting device includes a piston-cylinder unit 14 which can be acted 
upon pneumatically, and has a cylinder housing 15 which is secured to the 
press frame yet is anchored so as to be rotatable about a bolt 24 (note 
FIG. 2). A piston 16 is movable in the cylinder chamber and connected by a 
piston rod 17 to an iron armature plate 18 which cooperates with an 
electromagnet 19 having a current supply which is switchable on and off. 
The armature plate 18 is movable in an interior chamber 20 formed in the 
cylinder housing 15, wherein an electromagnet 19 is also received, so that 
both the armature plate 18 and the electromagnet 19 are suitably 
protected. 
An opposite free end of the piston rod 17 extends out of the cylinder 
housing 15, and at least one roller 21 is freely rotatably supported with 
a roller bearing thereon; the circumference of this roller 21 presses, on 
the one hand, against the support surface 11 on the fixed abutment 13 and, 
on the other hand, against the support surface 12 on the free end of the 
arm 10 of the bell crank 9. In operating position, the electromagnet 19 
has a voltage applied thereto, so that it attracts the armature plate 18 
and locks it with a predeterminable holding force. As a result, the piston 
16 in the cylinder chamber 25 can be prestressed or preloaded by an 
application of compressed air to approximately the holding force of the 
magnet 19. A higher pressure of the air prevails in the connecting line, 
however. In this setting, the adjusting device does not hinder or impair 
the opening and closing motions of the sheet gripper 1 by the cam disk 5 
via the cam roller 6. The instant the sensors detect a mis-fed sheet 
situation, the electromagnet 19 is switched to a no-voltage condition, and 
the air in the cylinder chamber 25 is replenished via an open valve so as 
to act upon the piston 16. The roller 21, or a plurality of rollers 21 
supported side-by-side, are thereby pressed between the support surfaces 
11 and 12 of the fixed abutment 13 and of the arm 10 on the bell crank 9, 
respectively, so that the sheet gripper 1 is opened again counter to the 
action of the spring 8. The higher prestressing or prepressurizing of the 
air upstream of the inlet into the cylinder chamber 25 is advantageous in 
such a process, because the filling of the cylinder chamber takes place 
after the opening of the inflow valve and with a maximum pressure drop, 
without air replenishment or refilling. 
By activating the electromagnet 19 and filling the cylinder chamber 26 with 
air, the adjusting device returns to the starting position thereof. The 
function of the device according to the invention is independent of the 
thickness of the sheets and, thus, the device is fully functional in the 
case of multiple sheets, as well, such as double sheets, triple sheets, or 
the like.