Stack changing apparatus

In a stack changing apparatus for sheet ejecting machines having a drop table vertically movable within a first frame structure, the drop table having a pallet to be placed thereon for receiving stacks; and a second vertical frame structure provided behind the first vertical frame structure having a carriage which is movable vertically and parallel to the drop table and, provided with pallet transport elements, is also horizontally movable between the second and the first frame structure, the improvement wherein one of two stacking platforms is alternatively used as the drop table, the platforms being selectively movable to one of the two sides of the first vertical frame structure and their stacking surfaces being below the level of the floor, the apparatus being further provided with an auxiliary skid for each stacking platform, the height of the auxiliary skid being such that when on a stacking platform the top of the skid is substantially level with the floor, each auxiliary skid having take-up elements for the pallet transport elements which can be lowered down to below the level of the floor.

The present invention relates to a stack changing apparatus for sheet 
ejecting machines with a drop table movable vertically within a first 
frame structure and a pallet mountable thereon for receiving the stacks, 
and a second vertical frame structure provided behind the first vertical 
frame structure, wherein a carriage is movable vertically and parallel to 
the drop table and, provided with pallet transport elements, is 
horizontally movable between the first and the second frame structure. 
An apparatus of this type is known for the process of automatically 
changing stacks of paper. The prior art apparatus is described in more 
detail with reference to FIGS. 1 and 2. In general, the known apparatus 
allows for the high speeds of modern cross cutters, so standstill times 
while changing the stacks are kept to a minimum. However, difficulties are 
always encountered when different sizes of pallets are to be placed onto 
the drop table. Firstly, there is the problem of placing the pallet on the 
drop table, when different formats and sizes are used, such that a fork 
lift is capable of transporting the pallet easily out of the first 
vertical frame structure, and accordingly, of supplying a new empty 
pallet. Secondly, the pallet must be located such that it can be received 
by the pallet transport elements of the carriage in the second vertical 
frame structure. However, since pallets come in different sizes and are 
accordingly used, it becomes necessary to align the pallet transport 
elements of the carriage with the take-up elements of the respective 
pallet. To this end, the pallet transport elements of the carriage, e.g. 
two or four forks, are slidably provided perpendicular to the direction of 
the paper feed. Additional work and time is spent on such alignments and 
in practice, it is often possible that pallets are used which do not have 
suitable take-up elements for the pallet transport elements. Thus, there 
are disadvantages in the use of the known stack changing apparatus with 
respect to transporting the pallets into and out of the first vertical 
frame structure, and also with respect to transferring the empty pallet to 
the take-up elements of the carriage. 
It is therefore an object of the present invention to provide an apparatus 
for changing stacks of paper automatically, ensuring a rapid stack 
exchange regardless of the size and format of the pallets used. 
The object of the present invention is realized in the stack changing 
apparatus according to the present invention by providing two stacking 
platforms which are alternatively used as a drop table and which are 
movable perpendicularly and selectively into one of the two sides of the 
first vertical frame structure, their stacking area being below floor 
level by the height of an auxiliary skid mountable thereon, and the 
auxiliary skids having take-up elements for the pallet transport elements 
which can be lowered down to below the floor level. Instead of a known 
drop table, this structure has two stacking platforms which are 
transversely movable on rails for example and receptive of auxiliary 
skids. The two stacking platforms are provided below the floor level such 
that they will become flush with the floor by the addition of the 
auxiliary skids which are placed on same. In comparison with the prior art 
system, the entire structure is thus below floor level by the height of an 
auxiliary skid, in the area of the two vertical frame structures. In 
combination therewith, two stacking platforms are provided which are 
movable on rails, for example, transversely to the first vertical frame 
structure. The auxiliary skids are advantageously of lightweight 
construction and have take-up elements for the transport elements of the 
carriage. If, for example, the carriage has two or four forks as transport 
elements, guides are advantageously provided in the auxiliary skids for 
receiving the forks. The auxiliary skids remain in the area of the movable 
stacking platforms or in the area of the pallet transport elements of the 
carriage. Thus, the pallet transport within the area of the two vertical 
structures is determined by the spatial shape of the auxiliary skid while 
the pallet transport outside of the vertical frame structure is effected 
by means of fork lifts, in a manner well known in the art. There are no 
difficulties in transporting to and away from the structure according to 
the invention since the stacking area of the auxiliary skids is even with 
the floor, thus making the auxiliary skids accessible from three sides 
from outside of the vertical frame structure. The structure according to 
the invention permits the optimum transport of the pallets to and fro when 
these pallets are of different format and size, since the auxiliary skid 
which is flush with the floor eliminates all of the problems which are 
encountered in known structures when the pallet is to be received by the 
transport elements of the carriage located in the second frame structure. 
The structure according to the invention permits an operation wherein the 
transport function of the pallet within the vertical frame structures is 
clearly separated from the transport function of the pallet by means of 
fork lifts and on the outside of the claimed structure.

The known structure shown in FIGS. 1 and 2 has a cross cutter 1, a chamber 
2, a first vertical frame structure 3 and a second vertical frame 
structure 4 arranged in a line in the direction of the paper feed. The 
drop table 5 and the pallet 6 mountable thereon are provided within the 
first vertical frame structure 3. The drop table 5 with its pallet 6 is in 
the stacking position while the stacking height is nearly reached. Within 
the second vertical frame structure 4, there is an empty change pallet 7 
in waiting position, resting on the take-up elements 8 of carriage 9. The 
carriage 9 can be lowered downwardly within the second vertical frame 
structure to about floor level F such that take-up elements 8 can receive 
an empty change pallet from floor level F. The take-up elements 8 are 
movable within two horizontal guides of carriage 9 horizontally between 
the first vertical frame structure 3 and the second vertical frame 
structure 4. 
The method of operation of the known apparatus is as follows: 
As soon as the stacking height is reached in the first vertical frame 
structure 3, the drop table with the pallet 6 mounted thereon moves 
vertically downwardly and the change pallet 7 moves into the first 
vertical frame structure 3 by means of the take-up elements 8 from the 
second vertical frame structure 4. During this pallet exchange, a gap in 
the flow of sheets of paper is brought about by reducing the paper feed 
speed and, if necessary, by means of the channel. As soon as the change 
pallet 7 has reached the stacking position in the first vertical frame 
structure 3, the normal paper feed speed can be resumed. The function of 
the drop table is now temporarily assumed by the carriage 9, the take-up 
elements 8 and the change pallet 7. In the meantime, the lowered pallet 6 
is removed together with the finished stack from the first vertical frame 
structure 3 by means of fork lifts, such that the drop table 5 is 
subsequently movable vertically and upwardly under the change pallet 7. 
The drop table 5 resumes its function such that the take-up elements 8 and 
the carriage 9 are again available for transporting another change pallet. 
This empty new change pallet is received by the take-up elements 8 below 
the drop table 5 in position in the first vertical frame structure 3. 
Difficulties are here encountered when different sizes of pallets are 
supplied or when the pallets are not provided with suitable receiving 
elements which ensure the transport by means of fork lifts as well as the 
transport by means of the take-up elements 8 of the carriage 9. 
The structure according to the invention as shown in FIGS. 3-9 is 
essentially distinguished from the above described structure by the 
following features: 
Instead of a drop table, there are provided in the first vertical frame 
structure 3 two movable stacking platforms 10, 11 which are movable for 
example on rails transversely to the frame structure. The stacking 
platform 10 has a stacking surface A and the stacking platform 11 has a 
stacking surface B. In the lowest position of the stacking platform 10,11, 
the level of the respective stacking surface A and B is below the floor 
level F by the height of an auxiliary skid 12, 13 mountable thereon, such 
that the floor level F is reached when the auxiliary skids 12 and 13 
respectively are set in place. As shown in FIGS. 3-8, the recess below 
floor level extends beyond the second vertical frame structure 4 such that 
the carriage 9 with its take-up forks 8 is also vertically movable below 
the floor level F. The take-up forks 8 do not receive the pallet directly 
but the auxiliary skids 12 and 13 which are placed upon the stacking 
surfaces A and B respectively. Each auxiliary skid 12, 13 is of 
lightweight construction and has guides 14 (cf. FIG. 9) for receiving the 
take-up forks 8. The top views of FIGS. 4, 6 and 8 illustrate that each 
stacking platform 10, 11 adjacent to the first vertical frame structure 3 
is selectively movable to the respectively free space into a position X or 
a position Y respectively. When the auxiliary skids 12 and 13 are placed 
upon the stacking surface A and B respectively, the surface of the 
auxiliary skid 12 and 13 will form a flush surface with the floor level F. 
Pallets 6 and 7 can thus, without difficulties, be set onto the surface of 
the auxiliary skids 12 and 13 respectively by means of fork lifts. The 
auxiliary skids 12 and 13 respectively, on the same level with the floor 
F, is then accessible from three sides in position X or Y by means of a 
fork lift such that there are no problems with respect to the transport of 
pallets 6,7. 
In the following, the operation of the apparatus according to the invention 
is described at different time intervals: 
In the operation shown in FIGS. 3 and 4, the stacking platform 10 with the 
auxiliary skid 12 placed onto the surface A and the pallets 6 resting on 
the auxiliary skid 12 is in a stacking position while more than half the 
stacking height is already reached. Coming from position X, there is a 
second stacking platform 11 arranged in the first vertical frame 
structure, the auxiliary skid 13 being placed upon its stacking surface B. 
There are two empty change pallets 7 on the auxiliary skid 13 which were 
deposited by a forklift in position X onto the auxiliary skid 13. The 
surface of the auxiliary skid 13 is level with the level of the floor F. 
To prepare the exchange of pallets, the carriage 9 in the second vertical 
frame structure 4 moves with its take-up forks 8 down to below the floor 
level F such that the take-up forks 8 take up the auxiliary skid 13 by 
moving horizontally into the first vertical frame structure. The change 
pallets 7 are thus transported indirectly through the taking of the 
auxiliary skid 13 into the second vertical frame structure 4 and from 
there vertically upwardly. Simultaneously, the stacking platform 11 from 
the first vertical frame structure 3 is moved transversely into position Y 
such that the necessary conditions for a rapid stack change are created 
for the stacking platform 10 located in stacking position. The situation 
shortly before the stack exchange is shown in FIGS. 5 and 6. The stacking 
platform 11 and the auxiliary skid 13 with the change pallets 7 resting on 
the forks 8 are in waiting position. As soon as the pre-selected stacking 
height is reached on pallets 6 of the stacking platform 10, a gap is 
introduced in the paper sheet flow by reducing the speed. The necessary 
steps, such as the reduction of the speed at the cross cutter and the 
opening of a channel are known in the art. As soon as the sheet gap 
reaches the stacker, the stacking platform 10 moves downwardly with the 
finished stack, and by means of the forks 8, the auxiliary skid 13 with 
change pallets 7 is moved into the stacking position. While the cross 
cutter accelerates again to the originally set speed, the new sheets are 
now received by the pallets 7 on the auxiliary skid 13, held by forks 8. 
The stacking platform 10 with the finished stack can be lowered down to 
the rails and then be moved transversely from the first vertical frame 
structure 3 into the empty position X. From position Y, the stacking 
platform 11 with the stacking surface B is movable into the first vertical 
frame structure 3 (FIGS. 7 and 8). Now the stacking platform 11 and its 
surface B is moved under the auxiliary skid 13 such that the forks can be 
moved back into the starting position in the second vertical frame 
structure 4. Simultaneously, in position X, the finished stack can be 
removed from the stacking platform 10. For this purpose, a fork lift moves 
toward the auxiliary skid 12 being flush with the floor level and receives 
pallets 6 with the finished stack. Subsequently, new empty pallets are 
placed in stacking position onto the auxiliary skid 12. 
Even with the most different pallet shapes, the described arrangement poses 
no problems since the auxiliary skids 12 and 13 which are flush with floor 
level F are accessible from three sides by fork lifts in their positions X 
and Y respectively, and on the other hand, the shape of the pallets does 
not impair the pallet exchange within the two vertical frame structures 
since this is dependent only upon the auxiliary skids 12 and 13 
respectively which are flush with the floor level F. 
This becomes very clear in the vertical sectional view along lines IX--IX 
of FIG. 8. FIG. 9 shows that the auxiliary skid 12 is flush with the floor 
level F where the skid 12 is placed onto the surface A of the stacking 
platform 10. Below the floor level F, the auxiliary skid 12 which is of 
lightweight construction has four guides 14 for taking up the four forks 8 
of the carriage. As shown in FIG. 9, the pallets 6 provided with the 
stacks can be removed from the right without any problems by means of a 
fork lift movable at floor level. Should it not be possible to approach 
the pallet from the right on the outside, there are the two lateral sides 
of position X since the pallets 6 on the auxiliary skid are accessible 
from three sides. 
It will be appreciated that the instant specification is set forth by way 
of illustration and not limitation, and that various modifications and 
changes may be made without departing from the spirit and scope of the 
present invention.