Machine tool, particularly cutting machine

A machine tool for processing flat stock comprises a work table having a processing surface, which can preferably be subjected to a vacuum, and a tool carriage, which is movable along the processing surface. A feeder is associated with the work table at one end thereof. In order to provide such a machine tool which involves a relatively small structural expenditure and distinguishes by an economical mode of operation, the work table is supplemented toward the feeder by a receiving table having a receiving surface of the work table, and the machine table composed of the work table and the receiving table supports two pallets, which are reciprocable between positions on the work table and the receiving table and in alternation constitute the processing surface of the work table and the receiving surface of the receiving table.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a machine tool, particularly to a cutting machine 
for processing flat stock, comprising a work table having a processing 
surface, which can preferably be subjected to a vacuum, and a tool 
carriage, which is movable along the processing surface, wherein a feeder 
is associated with the work table at one end thereof. 
2. Description of the Prior Art 
Such machine tools serve mainly to cut blanks out of strip material, such 
as prepregs, or to surface-finish flat workpieces etc. in an operation in 
which the flat stock to be processed is delivered by the feeder to the 
processing surface of the work table and by suitable holding-down members 
or preferably by the application of a vacuum is held down on the 
processing surface during the processing. After the processing the blanks 
or other workpieces must be removed to clear the processing surface for 
receiving additional flat stock. That operation will be rather 
time-consuming if the usual simple work tables are used, on which the 
processing surface corresponds to the cavity length or to the workpiece 
portion to be processed because additional flat stock cannot be applied 
before the processed workpieces and the waste have been removed from the 
processing surface. Other work tables, called conveyor tables, have been 
proposed, which comprise conveyor belts, which constitute the processing 
surface so that the flat stock can be deposited on the conveyor belt in a 
receiving region, which precedes the processing surface, and the conveyor 
belt is intermittently operated to move the stock to a processing region 
and subsequently to a delivery region so that the time is desirably 
utilized. But a machine tool for such an operation, in which stock can be 
deposited, processed and removed at the same time, requires a large space 
and a high structural expenditure because the machine table must have 
three times the size of the processing surface area. 
U.S. Pat. No. 4,514,246 discloses cutting plants comprising two juxtaposed 
work tables so that the stock can be processed on one of the tables and 
stock can be removed from and deposited on the other table at the same 
time. Such plants are subject to the same remarks as the conveyor tables 
because the sequence of operations can be performed within a shorter time 
but the expenditure is increased by the provision of two fully equipped 
work tables and of feeders and tool means which reciprocate between the 
two tables. 
SUMMARY OF THE INVENTION 
It is an object of the invention to eliminate said disadvantages and to 
provide a machine tool which is of the kind described first hereinbefore 
and involves a relatively small structural expenditure and distinguishes 
by an economical mode of operation. 
That object is accomplished in accordance with the invention in that the 
work table is supplemented toward the feeder by a receiving table having a 
receiving surface which has substantially the same size as the processing 
surface of the work table, and the machine table composed of the work 
table and the receiving table supports two pallets, which are reciprocable 
between positions on the work table and the receiving table and in 
alternation constitute the processing surface of the work table and the 
receiving surface of the receiving table. Because each pallet is used in 
alternation to provide a processing surface and a receiving surface, stock 
can be processed, on the one hand, and removed and deposited, on the other 
hand, at the same time so that the desired economical sequence of 
operations will be ensured. Experiments have shown that the processing 
time is about as long as the total of the removing and depositing times so 
that each step can be initiated before the preceding step has been 
completed and the positions of the pallets can be shifted virtually 
without a delay in that a pallet which carries new flat stock is moved to 
the work table and a pallet which carries processed workpieces is moved to 
the receiving table at the same time and it is possible to remove the 
processed workpieces and the waste and to deposit new stock during the 
time in which all processing steps are performed. In spite of the fact 
that stock is deposited and processed at the same time it is sufficient to 
provide a single work table equipped with suction boxes or other 
holding-down means and with a tool carriage and the like and it is 
sufficient to supplement that work table by a simple receiving table, 
which is merely required to support a pallet during the removal of 
workpieces and waste and the deposition of additional stock. A further 
advantage will be afforded by the fact that the receiving table can be 
designed for specific adaptation to a suitable stock feeder and suitable 
feeders for depositing stock in one layer or in a plurality of layers can 
be provided without difficulty. Besides, the pallets may be changed as 
required for adaptation to specific processing operations or to specific 
stock to be processed. 
It is possible to provide two pallet tracks, which are spaced one over the 
other and extend along the machine table, and each of said tracks may be 
provided adjacent to the work table and the receiving table with means for 
lifting and lowering a pallet from one pallet track to the other. In that 
case the pallets can be shifted on different levels and suitable means may 
be provided for placing each pallet on each of the tables and for 
reciprocating the pallets between the two pallet tracks. As a result, the 
two pallets can be shifted at the same time and virtually directly so that 
the shifting times and the distance over which the pallets are shifted 
will be short whereas the structure may be simple. 
To provide a simple and robust structure the pallets are supported on the 
pallet tracks by rollers, the lifting means comprise hydraulic cylinders, 
which are provided with rollers for engaging and supporting the pallets 
when they are in their end positions on the work table and the receiving 
table, and the upper pallet track is formed with recesses, which 
constitute passages for the laterally protruding rollers of the pallets 
when they are in said end positions. In such an arrangement each pallet 
track is associated with shifting means and the recesses in the raillike 
tracks permit the pallets to be lifted and lowered along a straight line. 
If the lower pallet track is disposed on the level of the table top, each 
pallet disposed on the lower track will be on the proper level for the 
processing operation so that a single lifting movement between the two 
tracks will be sufficient. If the lower pallet track is disposed above the 
level of the table top for reasons of design, the lower pallet track will 
also have to be formed with corresponding recesses so that the pallets can 
be lowered from the lower pallet track to the level of the table top. But 
on principle this will not be significant and one pallet track will guide 
each pallet as it is shifted in one direction and the other pallet track 
will guide each pallet as it is shifted in the opposite direction. 
To permit an automation of the change of pallets, suitable actuating means 
for displacing the pallets are required and may inherently consist of any 
suitable drive comprising power screws, racks, chain drives. But it will 
be desirable to provide the tool carriage, on the one hand, and each 
pallet, on the other hand, with mutually associated coupling means so that 
the tool carriage can be coupled to each pallet and be used to reciprocate 
each pallet and the structural expenditure will further be reduced. 
According to a particularly desirable further feature of the invention a 
laying carriage is mounted on the machine table to be movable along the 
receiving surface of the receiving table, the laying carriage and each 
pallet are provided with coupling means, which are associated with each 
other, and each pallet is provided on the side which faces to the feeder 
with the coupling means for cooperation with the laying carriage and on 
the side that is remote from the feeder with the coupling means for 
cooperating with the tool carriage. Such a laying carriage can be used to 
efficiently deposit flat stock onto each pallet when it is disposed on the 
receiving table, in a manner known per se, and laying carriages of various 
kinds can be used for that purpose, but the laying carriage can be used 
jointly with the tool carriage to shift the pallets. For such a change the 
two pallets are displaced by the two carriages in opposite directions over 
equal distances approximately to the middle of the shifting path and the 
pallets are subsequently uncoupled from one carriage and coupled to the 
other whereafter each carriage carries the respective other pallet along 
to the proper end position. In that case the carriages will have to travel 
only over shorter distances and that fact as well as the use of two 
carriages will substantially permit the pallets to be shifted in a much 
shorter time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An illustrative embodiment of the invention will now be described with 
reference to the strictly schematic drawing. 
A machine tool 1 for processing flat stock comprises a machine table 2, 
which is composed of a work table 3 and a receiving table 4 disposed at a 
receiving end of the work table 3. As clearly shown in FIGS. 3a-3e, work 
table 3 and receiving table 4 adjoin each other. The work table 3 is 
provided with a processing surface 6, which is adapted to be subjected to 
a vacuum by means of suction boxes 5 and on which the flat stock is 
retained while it is processed by means of a tool unit 8, such as an 
ultrasonic cutter, which is mounted on a tool carriage 7, which is movable 
along the processing surface of work table 3. The receiving table 4 is 
provided with a receiving surface 9, which has substantially the same size 
as the processing surface 6. The stock to be processed is deposited on the 
receiving surface and the processed stock is removed from the receiving 
surface. A feeder 10 is associated with the receiving table 4 and 
comprises a laying carriage 11, which is movable along the receiving 
surface 9, and a replaceable coil magazine 12, which contains coils 13 of 
flat stock that is to be processed. The laying carriage 11 comprises a 
gripper 14, which is only schematically indicated and is adapted to grip 
the flat stock at its free end so that the flat stock can be extended over 
the receiving surface by a suitable movement of the laying carriage 11. 
Marking means 15, by which the workpieces to be processed can be 
identified as the flat stock is deposited, as well as other means, such as 
means for cutting the flat stock to length, may be mounted on the laying 
carriage 11. 
To permit depositing and removing operations, on the one hand, and 
processing operations, on the other hand, to be performed at the same 
time, the machine table 2 carries two pallets 16, 17, which are slidably 
mounted on the machine table 2 and are reciprocable between first and 
second end positions on the receiving table 4 and the work table 3, 
respectively. Said pallets 16 and 17 constitute in alternation the 
processing surface 6 of the work table 3 and the receiving surface 9 of 
the receiving table 4. The pallets are guided by two vertically spaced 
apart lower and upper pallet tracks 18, 19, which extend along the machine 
table 2 and on which respective pallets are supported by laterally 
protruding rollers 20. In each of the regions which contain the pallets 
when they are in their end positions over the work table 3 and the 
receiving table 4, respectively, (FIGS. 1 and 3a) a lifter 21 is provided 
for reciprocating the associated pallet 16 or 17 between the two pallet 
tracks 18 and 19. For that purpose the upper pallet track 19 is formed 
with inwardly open recesses 22, which constitute passages for the 
laterally protruding rollers 20 of the pallets, and the lifters 21 
comprise hydraulic cylinders 23, which are provided with supporting 
rollers 24 for engaging the pallets as they are lifted and lowered. 
To eliminate the need for separate drives for shifting the pallets, the 
tool carriage 7 and the laying carriage 11 are used as means for shifting 
the pallets 16, 17. For that purpose said carriages, on the one hand, and 
the pallets, on the other hand, are provided with coupling means 25, 26 
and 27, 28, which are associated with each other. The coupling means 27, 
28 of the pallets 16 and 17 are retaining members provided at opposite 
side edges thereof for engagement by coupling hooks 25 of tool carriage 7 
and coupling hooks 26 of laying carriage 11. The coupling hooks are 
pivotal 180.degree. about horizontal axes for engagement with, and 
disengagement from, retaining members 27, 28. 
The sequence of operations performed by that machine tool is schematically 
illustrated in FIGS. 3a to 3e. In FIG. 3a the pallets 16 and 17 are shown 
in an initial position on the receiving table 4 and the work table 3, 
respectively. As the sequence of operation begins pallets 16, 17 are 
guided on lower pallet track 18 and the flat material to be processed can 
be deposited in one or more layers on the pallet 16 by means of the laying 
table 11 and it is possible to deposit layers of different materials one 
over the other. The laden pallet 16 is then lifted by the lifter 21 from 
the lower pallet track 18, which is on the level of the table top, into 
the upper pallet track 19 and the shifting of the pallets can now be 
initiated (FIG. 3b). For that purpose the laying carriage 11 and the tool 
carriage 7 are coupled each to the associated pallet 16 or 17 by the 
coupling means 25, 26 and 27, 28, respectively, and are moved in mutually 
opposite directions over equal distances toward each other until both 
pallets 16 and 17 are disposed approximately in the middle of the path 
along which they can be shifted (FIG. 3c). In that position the coupling 
hooks 3 of tool carriage 7 are pivoted to be disengaged from retaining 
members 27 of lower pallet 17 and to engage retaining members 28 of upper 
pallet 16 while coupling hooks 26 of laying carriage 11 are disengaged 
from upper pallet 16 and engaged with lower pallet 17. The laying carriage 
11 is now coupled to the lower pallet 17 and the tool carriage 7 is 
coupled to the upper pallet 16 and the carriages coupled to the respective 
pallets thereafter return to their initial position (FIG. 3d) along lower 
and upper pallet tracks 18, 19. It will then be sufficient to lower by 
means of the lifter 21 the pallet 16, which carries the flat stock to be 
machined, onto the work table 3 (FIG. 3e) so that the laden pallet 16 now 
lies on the work table and the empty pallet 17 lies on the receiving 
table. The stock on the pallet 16 can then be properly processed by the 
tool unit 8 and new stock, which has not yet been processed, is placed on 
the empty pallet 17 at the same time. When the processing has completed, 
the pallets are shifted once more in the manner which has been described. 
Thereafter the pallet laden with new stock lies on the work table and the 
other pallet lies on the receiving table, which now serves also as the 
table from which the processed material is removed. As soon as the 
processed material has been removed, fresh stock can be placed on the 
pallet and the next shifting of pallets is effected. As the processing 
time is about as long as the sum of the removing and laying times, the 
cycle of operations comprising processing and pallet shifting is performed 
virtually without a delay. 
It is apparent that an efficient operation can be performed by a machine 
which involves a comparatively small structural expenditure in a sequence 
in which the processing, on the one hand, and the depositing and removing 
of the flat stock and optionally also a proper marking of the workpieces, 
on the other hand, are performed at the same time and said steps to be 
matched to each other will not adversely affect each other.