Machine tools abstract
A work-supporting deck for use in machine tools for processing
flat material comprises vacuum aspirators, which serve to support
and retain a workpiece and carry suction cups, which are adjustable
in height by actuators. To provide economical means for reliably
retaining the workpieces substantially independently of its shape
and size, a multiplicity of vacuum aspirators are provided, which
are arranged in rows and columns and are connected each to an individually
operable actuator for moving the suction cup between an inactive
lower position and an active upper position.
Machine tools claims
I claim:
1. A work-supporting deck for use in a machine tool, which comprises:
(a) a multiplicity of vacuum aspirators constituting a work-supporting
surface and operable to support and retain a workpiece on said surface,
the vacuum aspirators being arranged in a plurality of rows and
a plurality of columns wherein at least part of said aspirators
are regularly spaced apart, each of said aspirators comprising
(1) a lifting ram formed with an axial suction bore and
(2) a suction cup carried on top of the lifting ram and communicating
with the suction bore,
(b) a multiplicity of actuators operatively connected to respective
ones of said suction cups and individually operable to move the
associated vacuum cup between an inactive lower position and at
least one active upper position,
(c) means defining at least one vacuum chamber adapted to be connected
to a vacuum source,
(d) a plurality of vertical bushings mounted to extend in said
at least one vacuum chamber, each one of the bushings being formed
with a transverse through bore,
(1) each one of the lifting rams being vertically slidably fitted
in an associated one of the bushings and being formed with a transverse
port adapted to communicate with said transverse through bore whereby
each lifting ram and associated busing constitutes a sliding valve
controlling the communication of the axial suction bore in the lifting
ram with the vacuum chamber, and
(e) means for raising at least three suction cups to one of said
at least one active upper positions to support the workpiece and
subsequently raising additional suction cups into contact with the
workpiece.
2. The work-supporting deck of claim 1 wherein the aspirators
are arranged in at least two groups of rows, the spacing of the
aspirators in the rows of one of the groups differing from that
of the other group.
3. The work-supporting deck of claim 1 wherein the aspirators
are arranged in at least two groups constituting different sections
of the work-supporting surface, the aspirators of each one of the
groups being connected to an associated one of the vacuum chambers.
4. The work-supporting deck of claim 1 wherein said means for
raising includes raising the additional suction cups in at least
two groups, so that the additional suction cups are coupled with
the vacuum source in stages to maintain a predetermined vacuum level.
5. The work-supporting deck of claim 4 wherein one of said at
least one active upper positions that is farthest from said inactive
lower position is an uppermost position.
6. The work-supporting deck of claim 5 wherein said means for
raising comprises:
a controller coupled to said multiplicity of actuators for raising
said at least three suction cups to said uppermost position.
7. The work-supporting deck of claim 6 wherein said controller
raises said at least three suction cups with a first predetermined
force level.
8. The work-supporting deck of claim 7 further comprising means
for releasably locking said at least three suction cups in said
uppermost position.
9. The work-supporting deck of claim 8 wherein said controller
raises said additional suction cups with a second predetermined
force level that is less than said first predetermined force level.
10. The work-supporting deck of claim 9 wherein said controller
selects said at least three suction cups and said additional suction
cups as suction cups located within a perimeter of the workpiece.
11. The work-supporting deck of claim 10 wherein said second predetermined
force level raises said additional suction cups so that their respective
upper positions conform to a contour of the workpiece.
12. The work-supporting deck of claim 11 further comprising a
multiplicity of universal joints operatively coupled between respective
ones of said lifting rams and said suction cups so that said suction
cups are pivotable to securely attached to the workpiece.
13. The work-supporting deck set forth in claim 1 wherein each
of said bushings is formed on its inside surface with an annular
groove, which communicates with and is wider than said transverse
bore of said bushing and defines for said lifting ram a range of
elevations in which said port communicates with said transverse
through bore of said bushing.
14. The work-supporting deck set forth in claim 1 wherein
each of said lifting rams is rotatably mounted in the associated
bushing and
each of said suction cups is eccentrically mounted on the associated
lifting ram.
15. The work-supporting deck set forth in claim 14 wherein
each of said bushings is formed in its inside surface with an annular
cam groove defined by upper and lower cam faces and
each of said lifting rams carries a laterally protruding cam follower
pin, which is fixed to said lifting ram and extends into said groove
and is arranged to cooperate with said cam faces as said lifting
ram is raised and lowered.
16. The work-supporting deck set forth in claim 15 wherein
said inside surface of said bore is constituted by two sleeves,
which have confronting end faces constituting said upper and lower
cam faces and defining said cam groove.
17. The work-supporting deck set forth in claim 1 wherein
each of said lifting rams is rotatably mounted in the associated
bushing,
each of said bushings is formed in its inside surface with an annular
cam groove defined by upper and lower cam faces and
each of said lifting rams carries a laterally protruding cam follower
pin, which is fixed to said lifting ram and extends into said groove
and is arranged to cooperate with said cam faces as said lifting
ram is raised and lowered.
18. The improvement set forth in claim 12 wherein
said inside surface of said bore is constituted by two sleeves,
which have confronting end faces constituting said upper and lower
cam faces and defining said cam groove.
19. The work-supporting deck as set forth in claim 1 wherein
said deck comprises a frame, and
said vacuum aspirators are laterally adjustably mounted in said
frame.
20. The work-supporting deck set forth in claim 1 wherein
said deck is provided with means for connecting each of said suction
cups to a vacuum source when, and only when, it is in the active
upper position.
Machine tools description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a work-supporting deck for use in machine
tools, particularly in cutting machines for cutting flat stock,
which deck comprises vacuum aspirators, which serve to support and
retain a workpiece and carry suction cups, which are adjustable
in height by actuators.
2. Description of the Prior Art
Work-supporting decks having a work-supporting surface, at which
a vacuum can be applied, have proved satisfactory for use in the
processing of flat stock, such as the trimming or contour milling
of metal plates and parts of wood, and particularly of monolayer
plastic blanks or multilayer plastic blanks (composites), because
the two-dimensional workpieces can reliably be retained on the work-supporting
surface by the applied vacuum substantially independently of their
geometric configuration. But in order to avoid damage to such so-called
vacuum decks, they must be provided with cover plates which support
the workpieces and consist of an air-permeable material or of contour
templates provided with suitable gaskets. But contour templates
involve a substantial expenditure and must conform to specific workpieces
so that their use is restricted. The porous cover plates of foamed
plastic also cannot be satisfactory because furrows will be cut
into the cover plate as it is penetrated by the tool during its
processing operation and such furrows will adversely effect the
application and action of the vacuum which is required for this
reason it is necessary to use a tool which laterally protrudes over
the workpiece only to the smallest possible extent and to cover
the workpiece at its edges with plastic films so that the utilization
of the tool is decreased and the films must be handled in a complicated
manner.
In EP-A-0069 230 it has already been suggested to provide a work-supporting
deck with several vacuum aspirators and to support the workpieces
only by the suction cups of said aspirators rather than on a continuous
work-supporting surface. But the workpiece cannot be retained as
desired by the known vacuum aspirators unless they engage the workpiece
at predetermined points so that each aspirator must individually
be laterally adjusted and the work-supporting decks provided with
said aspirators can be used only to support workpieces having a
predetermined shape. Besides, the workpiece is supported only at
a few points so that the processing of the workpiece gives rise
to vibration, which often preclude the use of mechanical means for
additionally fixing the workpiece.
SUMMARY OF THE INVENTION
For this reason it is an object of the invention to eliminate these
disadvantages and to provide a work-supporting deck which is of
the kind described first hereinbefore and which ensures an effective
retaining of work-pieces regardless of their shape and also establishes
optimum conditions for a processing with a desired quality and for
a full utilization of the tools.
That object is accomplished in accordance with the invention in
that a multiplicity of vacuum aspirators are provided, which are
arranged in rows and columns and are connected each to an individually
operable actuator for moving the suction cup between an inactive
lower position and an active upper position. Because the work-supporting
surface is constituted by a multiplicity of aspirators, which are
arranged in rows and columns, the workpiece will effectively be
supported by said aspirators throughout its surface rather than
only at discrete points so that the workpiece will reliably be retained
as desired. Because each suction cup can independently be raised,
the elevations of the points at which the workpiece is supported
can be adapted to workpieces of any shape because it will be sufficient
to raise and activate in accordance with a suitable control program
only those of the existing suction cups which are disposed within
the contour of a given workpiece so that any given workpiece regardless
of its geometric configuration will snugly rest on the suction cups
and will be retained by the raised suction cups whereas a marginal
portion of the workpiece will be left free for being processed.
Any suction cup which partly underlies and partly protrudes laterally
from the workpiece will not be raised and activated so that the
processing tools can operate satisfactorily and can be optimally
utilized. The application of the vacuum to the workpiece will not
be adversely affected by the operation of the tool. The provision
of a multiplicity of aspirators precludes an exciting of a vibration
of the workpiece by the processing and ensures that the workpiece
will satisfactorily be retained without a need for additional means,
such as intermediate plates and covering films.
If the aspirators are arranged in groups which differ in pitch,
it will be possible to provide different work-supporting regions
for supporting different work-pieces. For instance, relatively small
workpieces may be supported in regions in which the aspirators are
more closely spaced apart, and aspirators may be arranged in specially
designed arrays for retaining certain workpieces.
The work-supporting surface of the work-supporting deck is desirably
divided into at least two sections and the aspirators in each of
said sections may be connected to a common vacuum source. Such sections
can then be used for per supporting the workpieces for a performance
of different operations. For instance, a workpiece may be processed
while it is supported in one section and a different workpiece may
be applied to or removed from the other section at the same time.
Because the suction cups of each section are connected to a common
vacuum source it will be sufficient to apply a vacuum only to the
suction cups of that section on which a workpiece is to be retained
at a time so that the economy of the operation will be improved.
It will be understood that aspirators of the two sections may be
connected in alternation to one and the same vacuum source if it
is sufficient to apply a vacuum only to one of said sections at
a time.
According to a further feature of the invention, each suction cup
is vertically movable to different active positions within a predetermined
elevation range and the actuators for raising and lowering the suction
cups are preferably operable in two power stages. Even uneven work-pieces
can satisfactorily be supported by the suction cups in that elevation
range because the elevations of the suction cups can be adapted
to the shape of the bottom surface of the workpiece. When it is
desired to retain a workpiece, only those aspirators which are to
engage the workpiece close to its edges are initially raised by
a normal power so that said aspirators can perform their normal
supporting function and the aspirators for engaging the workpiece
in an inner region are then raised with a lower power into engagement
with the workpiece to retain the latter. To ensure that the retaining
of the workpiece will not adversely be effected by the subsequent
engagement of the inner aspirators, said inner aspirators are raised
by a force which is smaller than the supporting force exerted by
the marginal aspirators so that the desired support will be ensured
even if the workpiece has a curved surface.
In a desirable design, each aspirator comprises a lifting ram,
which is formed with an axial suction bore and which at its top
carries the suction cup, and said lifting ram is operatively connected
to an actuator and is vertically slidably fitted in a bushing, which
is contained in a vacuum chamber. The lifting ram is formed with
a transverse port bore, which is adapted to communicate with a transverse
bore of the bushing as in a sliding valve. Such a lifting ram can
be adjusted in a simple manner by the associated actuator, which
preferably consists of a piston-cylinder unit, and by its displacement
does not only impart to the suction cup the desired adjustment in
height but also connects the suction cup to the vacuum chamber,
to which a vacuum is constantly applied. As soon as the lifting
ram has been raised to a position in which the port bore communicates
with the transverse bore of the bushing, the suction bore with the
vacuum chamber and the vacuum maintained in the vacuum chamber is
applied by the suction cup to the workpiece.
If the transverse bore merges on the inside surface of the bushing
into a wider annular groove, that groove will define an elevation
range within which the active position of the suction cup can be
selected because the port bore of the lifting ram will communicate
with the vacuum chamber when the suction cup is in any position
within that elevation range. In that case the elevation of the suction
cup can automatically be adjusted in adaptation to a curved underside
surface of the workpiece as the suction cup is raised.
According to a particularly preferred feature of the invention
the suction cup is eccentrically disposed on the lifting ram, which
is rotatably mounted in the bushing, so that the pitch of the suction
cups can intentionally be altered by a rotation of the lifting ram
and the positions of the suction cups can be adjusted in adaptation
to the contour of a given workpiece.
The bushing may comprise two cam sleeves having confronting end
faces, which define a cam groove and constitute cam faces for cooperating
with a cam follower pin, which extends into said cam groove and
is connected to the lifting ram. In that case the cooperation of
the cam follower pin and the cam faces will have the result that
a vertical movement of the lifting ram will effect a rotation of
the lifting ram and of the suction cup so that the actuators can
be controlled to determine the rotational positions of the suction
cups and the desired pitch will automatically be obtained. The cam
faces may have various shapes and, for instance, may have the configuration
of sawtooth lines which are offset from each other so that the lifting
ram will be rotated in steps as it is raised and lowered. Alternatively,
said cam faces may be stepped in height to define certain elevations
of the lifting rams so that the elevations of the suction cups can
be adjusted in adaptation to the shape of the bottom surface of
a given workpiece.
In a relatively simple arrangement, a common vacuum chamber is
associated with a plurality of aspirators. In that case the number
of vacuum lines required for the connection to a vacuum source will
be reduced and the application of a uniform vacuum will be ensured
in a simple manner.
The adaptation of the aspirators to different workpieces can also
be improved in that the aspirators are mounted in the frame of the
deck so as to be laterally adjustable. For that purpose each aspirator
may be individually adjustable or a row of aspirators may be adjustable
in unison by a displacement of a commonly associated, slidably mounted
vacuum chamber structure. By such an adjustment the work-supporting
deck can be adjusted in adaptation to various processing programs,
workpieces shapes and workpiece sizes.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic top plan view showing a work-supporting table
in accordance with the invention.
FIG. 2 is an enlarged vertical sectional view showing a vacuum
aspirator of that work-supporting deck.
FIG. 3 is a vertical sectional view showing another illustrative
embodiment of a vacuum aspirator.
FIG. 4 is a schematic showing a controller connected to the individual
vacuum pod valves; and
FIG. 5 is a flow chart representing the basic sequence of operations
undergone by the work-supporting deck.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Embodiments of the invention will now be described by way of example
with reference to the drawing.
Flat stock to be processed, e.g., to be machined at its edges by
contour milling, should reliably be retained in position regardless
of its shape and size. For that purpose a work-supporting deck 1
is provided, which has a work-supporting surface 2 that is constituted
by a multiplicity of vacuum aspirators 3 which are arranged in
rows and columns. Each of said vacuum aspirators 3 comprises a vacuum
cup 4 which is adapted to be raised and lowered by means of an
individually operable actuator consisting of a piston-cylinder unit
5 between a lower inactive position, in which no vacuum is applied,
and an active upper position, in which a vacuum is applied. For
that purpose each vacuum aspirator 3 comprises a lifting ram 6
which at its top carries the suction cup 4 and is connected to the
actuator 5 and is vertically slidably fitted in a bushing 8 which
extends in a vacuum chamber 7. The lifting ram 6 is formed with
an axial suction bore 9 and with a transverse port bore 10 which
opens into the axial bore 9. The bushing 8 is formed with a transverse
bore 11 which is adapted to register with the port bore 10 so that
the suction bore 9 will communicate with the vacuum chamber 7 via
the port bore 10 and the transverse bore 11 or will be shut off
from the vacuum chamber 7 in dependence on the elevation of the
lifting ram 6. The position of the port bore 10 in the lifting ram
6 and the position of the transverse bore 11 in the bushing 8 will
be so selected that the lifting ram 6 can be raised to an active
position, in which a vacuum is applied to the suction cup 4 from
the vacuum chamber 7 whereas the vacuum cup will be exposed to
atmospheric pressure when the lifting ram 6 has been lowered to
an inactive lower position, in which the port bore 10 is disposed
outside of the vacuum chamber 7.
As is indicated by dash lines in FIG. 2 the transverse bore 11
of the bushing 8 may open into an annular groove 12 formed in the
inside surface of the bushing 8. That annular groove 12 defines
an elevation range, within which the active position of the associated
suction cup 4 can be selected while an application of the vacuum
is ensured. In that case the elevations of the suction cups can
be adjusted in adaptation to a curved bottom surface of a workpiece.
An excessive loss of the vacuum at a suction cup which does not
engage the workpiece can be prevented if the cross-sections of the
bores and lines are rather small or said bores and lines are formed
with constrictions so that the application of a sufficient vacuum
and a satisfactory operation will be ensured, provided that a sufficiently
powerful vacuum pump is used.
As a separate vacuum chamber or a separate vacuum line is not required
for each vacuum aspirator 3 a common vacuum chamber 7 is provided
for the aspirators of each row thereof. Said vacuum chambers are
defined by chamber structures, which are mounted in the frame of
the deck and also serve as carriers. The vacuum chamber structures
are joined at their ends to longitudinal side bars 13 of the frame
of the deck and said side bars 13 contain vacuum lines, by which
the vacuum source, not shown is connected to the vacuum chambers
7.
The supporting surface 2 of the work-supporting deck 1 is suitably
divided into, e.g., two sections 2a, 2b and the aspirators 3 of
each of said sections 2a and 2b are adapted to be connected to a
common vacuum source. In that case a vacuum can be applied to the
aspirators of one section independently of the aspirators of the
other section so that one section can be used to retain workpieces
as they are processed whereas workpieces can be placed on or removed
from the other idle section at the same time.
To permit an adaptation of the work-supporting surface 2 to different
workpieces, it will be desirable to provide at least in one region
2c of the supporting surface 2 a group of aspirators 3 having a
different pitch, preferably a smaller pitch, so that particularly
smaller workpieces can reliably be supported in that region.
To permit an adjustment of the aspirators 3 in adaptation to workpieces
having different shapes and sizes, the aspirators or their suction
cups may be laterally adjustable, e.g., by a lateral adjustment
of the vacuum chamber structures defining the vacuum chambers 7
if they are slidably mounted on the side bars 13 by carriages 14.
In a particularly desirable arrangement, which may be used for
that purpose and is shown in FIG. 3 each vacuum aspirator 3 comprises
an eccentrically mounted suction cup 4 which is rotationally adjustable.
The suction cup 4 is mounted in an eccentric head 15 of the lifting
ram 6 which cooperates with two cam sleeves 16a, 16b, which are
generally designated 16 and are fixed in the bushing 8 and having
confronting end faces, which constitute cam faces 17 defining a
cam slot. The lifting ram 6 is provided with a laterally protruding
cam follower pin 18 which extends into said cam slot and cooperates
with the cam faces 17 so that the lifting ram 6 will be rotated
as it is moved up and down. As a result, the lifting ram 6 can be
raised and lowered several times by the actuator 5 so that the lifting
ram 6 and the suction cup 4 will be rotated about the axis of the
lifting ram 6 to move the suction cup 4 to a desired position on
its orbit. Whereas the cam faces 17 may be designed to define different
elevations of the lifting ram, such an adjustment in elevation will
usually not be desirable unless the suction cup 4 is centered on
the lifting ram 6 so that the rotational position and elevation
can be selected independently of each other.
Because the actuators 5 for the vacuum aspirators 3 can be individually
operated, the work-supporting deck 1 can be adjusted in adaptation
to any desired workpiece by a simple program control, which in dependence
on the shape and size of the workpiece causes only those aspirators
3 to be activated which are disposed entirely within the contour
of the workpiece. As said aspirators 3 are raised, the workpiece
is snugly supported on a large area, with the exception of a small
margin, which is left free for being processed. That practice will
permit a processing with a high quality and a favorable utilization
of the tools. Because the raising of the aspirators will automatically
move the suction cups to their active positions, in which a vacuum
is applied, the workpiece will automatically be supported and retained
as the aspirators are raised so that an economical operation will
be ensured. As the aspirators are lowered, the workpiece will be
relieved from the vacuum and can then easily be removed or replaced.
Because simple design features will permit different active positions
to be assumed by the vacuum cups within a certain elevation range,
it will be possible to automatically support even curved or stepped
or other shaped workpieces because aspirators disposed near the
edges of the workpiece and the inner aspirators can subsequently
be raised until they engage the bottom surface of the workpiece
and can thus be adapted to the shape of the workpiece.
In order to support the non-flat workpiece, the work-supporting
deck includes means for raising at least three suction cups to one
of the active upper positions, the uppermost position, for example,
to support the workpiece and subsequently raising additional suction
cups into contact with the workpiece. The additional suction cups
are raised in at least two groups, so that the additional suction
cups are coupled with the vacuum source in stages to maintain a
predetermined vacuum level. By raising the suction cups in stages,
the danger of a sudden collapse of the vacuum is avoided. The suction
cups are raised by a controller 20 that is coupled to the actuators,
as can be seen in FIG. 4. The controller raises the at least three
suction cups with a first predetermined force level and then releasably
locks them in the uppermost position. The workpiece is then supported
by the at least three suction cups with the additional suction cups
being raised with a second predetermined force level that is less
than the first predetermined force level. The additional suction
cups are raised until they automatically contact the workpiece surface.
Vacuum cups 4 are made from an elastic material and/or are connected
to lifting ram 6 with a universal joint 22 so that vacuum cup 4
can conform to the workpiece surface regardless of the shape of
the workpiece. The controller selects the at least three suction
cups and the additional suction cups as those being wholly within
the perimeter of the workpiece. A method for supporting a workpiece
with vertically-movable suction cups for machining includes the
steps of raising three suction cups to their uppermost position
and locking them in place. The workpiece is then places on the three
raised suction cups and additional suction cups that are below the
workpiece are raised until they contact the workpiece. The workpiece
is machined, the additional suction cups are lowered, and the workpiece
is removed. FIG. 5 is a flow chart showing these basic steps 30-39.
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