Apparatus for trimming stacks of paper sheets or the like

A machine for trimming the edges of stacked paper sheets at a trimming station has a conveyor which delivers successive stacks to the trimming station, several knives which are movable from raised positions to lower end positions to thereby trim the respective edges of a stack at the trimming station, anvil blocks which are penetrated into by the cutting edges of the knives when the knives complete their working strokes subsequent to trimming of a stack, and a control unit which prevents the knives from contacting the respective blocks if the knives perform working strokes in the absence of a stack at the trimming station. The control unit can shift the working strokes of the knives and/or lower the blocks to thus ensure that the cutting edges of the knives are arrested short of the respective blocks when a photocell detects the absence of a stack at the trimming station while the knives perform their working strokes.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in apparatus for trimming the 
edges of stacked paper sheets or analogous commodities. More particularly, 
the invention relates to improvements in trimming apparatus for brochures, 
pamphlets, magazines, signatures, books or the like. 
Commonly owned U.S. Pat. No. 4,202,232 (the disclosure of this patent is 
incorporated herein by reference) describes a trimming apparatus wherein 
several knives are movable between raised and lowered positions to trim 
three sides of a stack of sheets (e.g., a brochure) which is delivered to 
a trimming station. The arrangement is such that the operation of the 
conveyor which delivers successive stacks to the trimming station is 
synchronized with the working strokes of the knives so that the knives 
descend after the stack is properly positioned at the trimming station. 
Each knife descends toward and penetrates into the material of an anvil 
block which is provided therefor at the trimming station. Since the path 
of a knife during and after trimming of the stack at the trimming station 
is not identical with the path along which the knife advances in the 
absence of a commodity at the trimming station, the cutting edge of each 
knife enters a first portion of the respective block upon completion of a 
trimming operation and a different second portion of such block when the 
knife performs a working stroke without carrying out a trimming operation. 
This will be readily appreciated since the material of the stack offers a 
pronounced resistance to penetration of the cutting edge and invariably 
alters the path of the cutting edge by exerting upon the knife a lateral 
pressure which is the cause of penetration of the cutting edge into a 
portion of the block other than the portion which is penetrated into if 
the knife descends while the trimming station is unoccupied. The just 
discussed mode of operation entails the making of several grooves in the 
material of each anvil block with attendant pronounced shortening of the 
useful life of the blocks. 
Heretofore known proposals to prevent unnecessary penetration of the 
cutting edges of trimming knives into the associated blocks in the absence 
of stacks of paper sheets or the like at the trimming station include the 
provision of means for arresting the knives if the trimming station is 
unoccupied due to the failure of the conveyor to deliver a stack of sheets 
in good time before the knives begin their working strokes. However, 
frequent stoppages and repeated starting of the trimming apparatus entail 
pronounced wear on the parts of such apparatus and cause a pronounced 
reduction of the output. In other words, it is desirable to keep the 
knives and other mobile parts of the trimming apparatus in motion even at 
a time when the trimming station fails to receive successive commodities 
at anticipated intervals. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the invention is to provide a trimming apparatus for 
brochures, pamphlets or the like which is constructed and assembled in 
such a way that the wear upon its parts, as a result of intermittent 
failure of the conveyor system to deliver stacks of paper sheets at 
anticipated intervals, is but a fraction of the wear upon the parts of 
conventional apparatus. 
Another object of the invention is to provide a trimming apparatus wherein 
the useful life of the anvil blocks, which are penetrated into by the 
cutting edges of the knives when the knives complete their working 
strokes, is much longer than in heretofore known apparatus. 
A further object of the invention is to provide the above outlined 
apparatus with novel and improved means for regulating the working 
stroke(s) of its trimming knife or knives. 
Still another object of the invention is to provide the trimming apparatus 
with novel and improved means for controlling the positions of anvil 
blocks with reference to the associated trimming knives. 
An additional object of the invention is to provide a trimming apparatus 
wherein the operation of the drive means for the knife or knives need not 
be interrupted when the trimming station fails to receive stacks of paper 
sheets or the like at anticipated or prescribed intervals. 
Another object of the invention is to provide a novel and improved method 
of prolonging the useful life of selected parts in an apparatus for 
trimming brochures, books, pamphlets or the like. 
Another object of the invention is to provide a trimming apparatus whose 
operation need not be monitored by attendants for the express purpose of 
preventing the knife or knives from performing working strokes in the 
absence of commodities at the trimming station. 
The invention is embodied in an apparatus for trimming the edges of stacks 
of paper sheets or analogous commodities at a trimming station. The 
apparatus comprises conveyor means (e.g., an endless belt or chain 
conveyor) for delivering successive commodities to the trimming station, 
at least one knife which performs recurrent working strokes by moving from 
a first (preferably raised) to a spaced-apart second (preferably lowered) 
position to thereby trim an edge of the commodity at the trimming station, 
drive means for moving the knife in the aforedescribed manner, an anvil 
block which is located in the path of movement of and is normally engaged 
by the knife when the latter completes a working stroke upon completed 
trimming of a commodity at the trimming station, and control means which 
is actuatable to prevent engagement between the knife and the block when 
the knife completes a working stroke in the absence of a commodity at the 
trimming station. 
The control means can comprise means for shifting the positions of the 
knife so that the latter cannot reach and cannot penetrate into the 
material of the anvil block. Alternatively, or in addition to such changes 
in the positions of the knife, the control means can comprise means for 
shifting the block with reference to the knife, again for the purpose of 
preventing penetration of the cutting edge of the knife into the material 
of the block when the knife completes its working stroke. 
The apparatus preferably further comprises means (e.g., a photocell having 
a signal generating means in the form of a photoelectronic transducer or 
the like) for monitoring the trimming station and for generating signals 
which actuate the control means in response to detected absence of a 
commodity at the trimming station while the knife performs a working 
stroke. The control means can comprise at least one fluid-operated (e.g., 
hydraulic) motor which serves to maintain the knife and the block out of 
contact with one another in response to a signal from the monitoring 
means. 
The apparatus can comprise at least one additional trimming knife which 
serves to trim another edge of the commodity at the trimming station, an 
additional anvil block for the additional knife, and additional drive 
means for causing the additional knife to perform working strokes. The 
control means is then arranged to prevent the additional knife from 
engaging the additional block in response to a signal from the monitoring 
means. The material of at least a portion of each anvil block is 
preferably sufficiently soft to allow the cutting edge of the respective 
knife to penetrate into the material of the block when the knife completes 
a working stroke in the presence of a commodity at the trimming station. 
The drive means for each knife can comprise a variable-length motion 
transmitting device which is connected with the respective knife, and the 
control means then comprises means for changing the length of the motion 
transmitting device in response to a signal from the monitoring means. In 
addition to changing the length of the just discussed motion transmitting 
device or devices, or in lieu of such mode of operation, the control means 
can also include means for shifting (in response to a signal from the 
monitoring means) the anvil block or blocks from a position nearer to a 
position more distant from the respective knife in the second position of 
the respective knife. 
The novel features which are considered as characteristic of the invention 
are set forth in particular in the appended claims. The improved apparatus 
itself, however, both as to its construction and its mode of operation, 
together with additional features and advantages thereof, will be best 
understood upon perusal of the following detailed description of certain 
specific embodiments with reference to the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, there is shown a trimming apparatus which 
comprises two spaced-apart parallel upright sidewalls or cheeks 1 (only 
one shown) forming part of a frame which supports an endless belt or chain 
conveyor 2 serving as a means for intermittently delivering successive 
stacks 5 of paper sheets to a trimming station TS in the space between the 
two sidewalls 1. The sidewalls 1 are connected to one another by rigid 
crossbeams (not specifically shown). The upper reach of the belt conveyor 
2 supports the stack 5 in the course of the trimming operation, and such 
upper reach is coplanar with the upper sides of two parallel anvil blocks 
4 which are inwardly adjacent to the sidewalls 1 and with the upper side 
of a third anvil block 3 which extends transversely between the two 
sidewalls. The conveyor 2 is driven by a suitable timing shaft (not shown) 
so that it supplies successive stacks 5 at selected (preferably regular) 
intervals and that it advances freshly trimmed stacks beyond the trimming 
station TS, e.g., into the range of a transfer device (not shown) which 
lifts successive trimmed stacks off the upper reach of the conveyor 2 and 
deposits them on a further conveyor, not shown, or onto a takeoff 
conveyor. Reference may be had to the commonly owned U.S. patent 
application Ser. No. 245,986 filed Mar. 20, 1981 by Hans Muller for 
"One-station block trimming machine", now abandoned. 
The trimming apparatus of FIG. 1 further comprises two trimming knives 8 
(disposed one behind the other so that only one thereof can be seen in 
FIG. 1) which serve to trim the respective (head and foot) edges of a 
stack 5 at the trimming station TS and cooperate with the respective 
blocks 4, and a third trimming knife 19 which serves to trim a third 
(front) edge of the stack 5 at the station TS and cooperates with the 
transverse anvil block 3. The arrangement is such that the position of the 
stack 5 at the station TS is not changed between the instant of 
introduction by the upper reach of the conveyor 2 and the instant of 
removal of the finished (fully trimmed) stack into the range of a take-off 
conveyor. 
The knives 8 are suspended on a shaft 7 which moves sideways in suitably 
inclined guide slots 6 of the sidewalls 1 when the knives 8 are caused to 
perform their working and return strokes. The drive means for the knives 8 
comprises one or two elongated motion transmitting members in the form of 
push rods 9 whose upper portions 12 are connected to the shaft 7 at the 
outer sides of the respective sidewalls 1 and whose lower portions 12a are 
coupled to the eccentric pins 10 of discrete disc-shaped eccentrics 11 
mounted on a horizontal shaft 28 which is journalled in the sidewalls 1 at 
a level below the trimming station TS and is parallel to the shaft 7. When 
the eccentrics 11 are caused to rotate, the respective pins 10 orbit along 
endless paths and cause the knives 8 to perform working strokes 
alternating with return strokes. During its working stroke, each knife 8 
turns in its plane so that the cut begins at one end and terminates at the 
other end of the respective edge of the stack 5 at the trimming station 
TS. 
In accordance with a feature of the invention, the trimming apparatus 
comprises control means which includes means for varying the length of the 
motion transmitting members 9 and hence the positions of the knives upon 
completion of their working strokes. Such length-varying means comprises 
double-acting hydraulic cylinders 14 which are connected to the lower 
portions 12a of the respective motion transmitting members 9 and pistons 
13 which are reciprocable in the respective cylinders 14 and are 
preferably adjustably attached to the lower ends of the upper portions 12 
of the respective motion transmitting members 9. Each cylinder 14 is 
connected with two conduits 15, 16 which can admit a pressurized hydraulic 
fluid into or can permit escape of hydraulic fluid from the respective 
cylinder chambers. The cylinder chambers can receive pressurized fluid 
from a pump 34 or another suitable source by way of a solenoid-operated 
valve 33. The valve 33 discharges fluid from one cylinder chamber into the 
sump when the other cylinder chamber is ready to receive or is in the 
process of receiving pressurized fluid from the source 34, and vice versa. 
The sidewalls 1 are further formed with aligned vertical or nearly vertical 
guide slots 17 for a polygonal crosshead or rod 18 which is reciprocable 
in the slots 17 and supports the trimming knife 19. The drive means for 
the knife 19 comprises at least one elongated motion transmitting member 
20 having an upper portion 25 which is attached to the respective end of 
the rod 18 and a lower portion 25a which is attached to an eccentric pin 
21 of a disc-shaped eccentric 22. The latter is mounted on a horizontal 
shaft 29 which is journalled in the sidewalls 1 and is parallel to the 
shaft 28 for the eccentric 11. In the illustrated embodiment, the 
eccentrics 11 and 22 have annuli of mating teeth to ensure accurate 
synchronization of movements of the knives 8 with the movements of the 
knife 19. 
The aforementioned control means further comprises means for varying the 
length of the motion transmitting member 20, and such length varying means 
comprises a double-acting hydraulic cylinder 23 at the upper end of the 
lower portion 25a, a piston 24 which is adjustably secured to the lower 
end of the upper portion 25 and is reciprocably installed in the cylinder 
23, and two conduits 26, 27 which are connectable with or sealable from 
the source 34 of pressurized hydraulic fluid, e.g., oil, by the 
solenoid-operated valve 33. The shafts 28, 29 are driven by the 
aforementioned timing shaft for the conveyor 2 so that the delivery of 
successive stacks 5 to the trimming station TS is properly synchronized 
with the working and return strokes of the knives 8, 8 and 19. 
The angular positions of the eccentric pins 10 and 21 with reference to the 
corresponding shafts 28, 29 are selected in such a way that the knife 19 
performs its working stroke ahead of the knives 8, i.e., the front edge of 
a stack 5 at the trimming station TS is treated ahead of the head and foot 
edges. When the solenoid of the valve 33 is deenergized, the conduits 16 
and 27 receive pressurized fluid from the source 34 and the conduits 15, 
26 are connected to the sump. In other words, at such time, the length of 
each of the motion transmitting members 9, 20 is increased to a maximum 
value 
It is assumed that the conveyor 2 has completed the delivery of a fresh 
stack 5 to the trimming station TS and has come to a halt in a position 
corresponding to the optimum position of the stack with reference to the 
paths of movement of the knives 8, 8, and 19. The presence of the freshly 
delivered stack 5 at the station TS is detected by a monitoring device 30 
in the form of a photocell having a light source 30a at a level above and 
a photoelectronic transducer 30b at a level below the path of successive 
stacks 5. The transducer 30b transmits a signal to one input of a logic 
circuit here shown as an AND gate 31 the other input of which receives 
signals from a timer 32, e.g., a pulse generator which is operated by the 
shaft for the right-hand pulley 2a of the conveyor 2. In other words, the 
timer 32 transmits to the corresponding input of the AND gate 31 a pulse 
whenever a stack 5 is supposed to be located at the trimming station TS. 
The output of the AND gate 31 transmits a signal when its inputs 
simultaneously receive signals from the transducer 30b and timer 32, and 
such output signal is used to energize the solenoid of the valve 33 so 
that the latter connects the conduits 15 and 26 with the source 34 of 
pressurized fluid whereas the conduits 16 and 27 are free to communicate 
with the sump via valve 33. In other words, the appearance of a signal at 
the output of the AND gate 31 entails a shortening of the motion 
transmitting members 9 and 20. This causes the descending knife 19 to trim 
the front edge of the stack 5 at the trimming station TS and the cutting 
edge of this knife penetrates into the material of the associated anvil 
block 3 when the trimming of the front edge is completed. The descending 
knives 8 thereupon trim the head and foot edges of the partially treated 
stack 5 at the station TS and the cutting edges of the knives 8 ultimately 
penetrate into the material of the respective anvil blocks 4. 
FIG. 2 shows that, when the motion transmitting member or members 20 are 
shortened as a result of admission of pressurized hydraulic fluid via 
conduit or conduits 26 (while the conduit or conduits 27 are free to 
communicate with the sump), the cutting edge of the trimming knife 19 
penetrates into or at least contacts the upper side of the anvil block 3 
at a level below the freshly trimmed front edge 5a of the stack 5 at the 
trimming station TS. Penetration of the cutting edge of the knife 19 into 
the block 3 after the knife 19 completes its working stroke is possible 
because the length of the motion transmitting member 20 is reduced by the 
cylinder and piston unit 23, 24, i.e., the throw of the eccentric 22 is 
the same as if the solenoid of the valve 33 were deenergized but the upper 
end position of the polygonal rod 18 (which carries the knife 19) is moved 
to a lower level in response to a reduction of the distance between the 
axis of the rod 18 and the axis of the eccentric pin 21. 
The situation is analogous with the knives 8, i.e., the starting or upper 
end positions of these knives are moved to a lower level in response to 
admission of pressurized fluid into the upper chambers of the cylinders 14 
via conduits 15 and simultaneous connection of the conduits 16 with the 
sump. In other words, the distance between the axis of the shaft 7 on the 
one hand and the common axis of the two eccentric pins 10 on the other 
hand is reduced in response to energization of the solenoid of the valve 
33. 
If the source 34 contains or supplies a compressed gas, the conduits which 
are not connected with such source are free to communicate with the 
atmosphere. At least a portion of each of the conduits 15, 16, 26, 27 is 
flexible or comprises sections which are slidably telescoped into one 
another to allow for shortening or lengthening of the respective motion 
transmitting members 9 and 20. 
If the conveyor 2 fails to deliver a stack 5 to the trimming station TS at 
a time when the timer 32 transmits a signal to the corresponding input of 
the AND gate 31, the other input of the gate 31 does not receive a signal 
from the transducer 30b of the monitoring means 30 so that the solenoid of 
the valve 33 remains deenergized. Therefore, the conduits 16, 27 remain 
connected with the source 34 and the length of each of the motion 
transmitting members 9, 20 is increased to the maximum value. 
Consequently, when the knife 19 performs a working (downward) stroke, its 
cutting edge fails to reach the associated anvil block 3 (see FIG. 3) so 
that the block 3 is not damaged (slotted, grooved, scored or similarly 
affected) when the knife 19 performs a working stroke in the absence of a 
stack 5 at the trimming station TS. The same applies for the knives 8, 
i.e., such knives fail to reach and penetrate into the material of the 
respective blocks 4 when the trimming station TS does not accommodate a 
stack 5 at the time when the element 32 transmits a signal to the 
corresponding input of the AND gate 31, namely, at the time when the 
station TS is supposed to accommodate a stack. The just described 
construction and mode of operation of the control means and of the 
monitoring means 30 ensures that the useful life of the blocks 3 and 4 is 
much longer than in heretofore known apparatus wherein the cutting edges 
of the knives continue to penetrate into the respective blocks whenever 
the knives perform their working strokes. Also, the output of the improved 
apparatus is higher than that of conventional apparatus wherein the 
detected absence of a stack triggers an immediate stoppage of the 
apparatus or, at the very least, a stoppage of means for driving the 
trimming knife or knives. Moreover, the wear upon the moving parts is much 
less pronounced if the apparatus is not arrested in response to the 
absence of a stack at the trimming station at a time when the stack should 
be there to undergo one or more trimming operations. 
As mentioned above, the cutting edges of the trimming knives travel along 
first paths if the knives are brought into engagement with a stack of 
sheets while they perform their working strokes, and along second paths 
when a working stroke is performed without contact with the sheets of a 
stack. This means that, in a conventional apparatus wherein the cutting 
edges of the knives are permitted to penetrate into the associated blocks 
irrespective of whether or not the knives have just completed a trimming 
operation, the wear upon the blocks is incomparably more pronounced than 
in the improved apparatus wherein the blocks are contacted by the 
respective knives only and alone if the knives have just completed their 
trimming operations. Since the operation of the drive means for the knives 
8 and 19 need not be interrupted when the absence of a signal at the 
output of the transducer 30b denotes the failure of the conveyor 2 to 
deliver a stack 5 at a time when such stack should be located at the 
trimming station TS, the wear upon the moving parts of the improved 
machine is much less pronounced than in conventional machines because the 
number of repeated stoppages and starts is a small fraction of those in a 
machine wherein the absence of a stack invariably entails a stoppage of 
the moving parts or, at the very least, a stoppage of the drive means for 
the knife or knives. 
The shortening and lengthening of motion transmitting members 9 and 20 in 
the above described manner entails a minimum of wear upon the parts of the 
control means so that the improved apparatus can stand long periods of 
uninterrupted use. 
FIG. 4 illustrates a portion of a second apparatus wherein all such parts 
which are identical with or clearly analogous to corresponding parts of 
the apparatus of FIG. 1 are denoted by similar reference characters. The 
length of the motion transmitting members 9' and 20' is constant. However, 
the positions of the anvil blocks 3 and 4 with reference to the associated 
trimming knives 19 and 8, 8 are changed in response to signals which the 
output of the AND gate 31 transmits to the solenoid of the valve 33. The 
cylinders 14', 23' and the associated pistons 13', 24' are designed to 
lower the conveyor 2 and the blocks 3, 4 at the trimming station TS 
whenever the transducer 30b fails to transmit a signal simultaneously with 
the transmission of a signal from the output of the timer 32. When the 
blocks 3 and 4 descend, the cutting edges of the respective knives 19 and 
8, 8 reach the lower ends of their strokes prior to penetration into the 
material of the respective blocks. 
In all other respects, the operation of the apparatus which is shown in 
FIG. 4 is or can be analogous to that of the first apparatus. A single 
cylinder and piston unit (e.g., the left-hand unit 23', 24' of FIG. 4) may 
suffice if the extent of axial displacement of the piston 24' is 
sufficient to ensure that the cutting edges of the knives 19 and 8, 8 
cannot reach the respective anvil blocks when the piston 24' assumes its 
lower end position, i.e., when the solenoid of the valve 33 is not 
energized at the time when the timer 32 transmits a signal to the 
corresponding input of the AND gate 31, namely, when the absence of a 
signal at the output of the transducer 30b denotes the absence of a stack 
5 at the trimming station TS at a time when the station TS should or is 
expected to accommodate a stack. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic and specific aspects of my contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the appended 
claims.