Title: Device for isolating and feeding the lowest sheet in each case from a stack
Abstract: In a device for isolating and feeding the lowest sheet (1) in each case from a stack (2), with pushing-out elements (9) which grip the rear edge (3a, 3b) of the sheet (1) and transport it through, under a front-edge stop (5), into a pair of drawing-off rollers (6), can be moved forwards and backwards, are mounted on a cross-member (7) and have faces (9a), which are optionally front-mounted, for supporting the rear region of the stack (2) and also have bearing elements (11, 12) supporting the stack (2), and lateral abutment strips (13), the front edge (4) of the said stack being constant with respect to the sheet length (H), provision is made, in order to achieve high isolating outputs and faultless feeding of the sheets (1) with a device of simple design, for the cross-member (7) which receives the pushing-out elements (9) to be guided so as to be capable of travel in a linear guide (14), and for there to be directly associated with the said cross-member (7), for the driving movement of the latter, a linear motor (15) whose path of travel (A) comprises both the isolating stroke (B) and also an adjusting path (C) which is intended for setting the sheet length (H).
Patent Number: 7,004,461 Issued on 02/28/2006 to Hansmann, et al.
| Inventors:
|
Hansmann; Rolf (Rahden, DE);
Lörken; Dieter (Düren, DE)
|
| Assignee:
|
Kolbus GmbH & Co. KG (Rahden, DE)
|
| Appl. No.:
|
442412 |
| Filed:
|
May 21, 2003 |
Foreign Application Priority Data
| May 25, 2002[DE] | 102 23 350 |
| Current U.S. Class: |
271/132; 271/137; 271/138; 271/139; 271/142; 271/144; 271/10.16 |
| Current Intern'l Class: |
B65H 3/64 (20060101) |
| Field of Search: |
271/1014,101.6,131,132,137,138,139,142,144,107
|
References Cited [Referenced By]
U.S. Patent Documents
| 2756113 | Jul., 1956 | Greenwood.
| |
| 2827290 | Mar., 1958 | Dixon et al.
| |
| 3754752 | Aug., 1973 | Thayer.
| |
| 3767186 | Oct., 1973 | Shields.
| |
| 3923297 | Dec., 1975 | Barny.
| |
| 4008889 | Feb., 1977 | Ayres.
| |
| 4131208 | Dec., 1978 | Vuilleumier.
| |
| 4181298 | Jan., 1980 | Capdeboscq.
| |
| 4202541 | May., 1980 | Leskiw et al.
| |
| 4227687 | Oct., 1980 | Schoonmade.
| |
| 4273321 | Jun., 1981 | Luther et al.
| |
| 4363478 | Dec., 1982 | Tsukasaki.
| |
| 4405124 | Sep., 1983 | Watanabe.
| |
| 4630812 | Dec., 1986 | Yano et al.
| |
| 4715596 | Dec., 1987 | Cantrell et al.
| |
| 4783064 | Nov., 1988 | Hayashi.
| |
| 4955854 | Sep., 1990 | Roth.
| |
| 5123887 | Jun., 1992 | Shimura.
| |
| 5145161 | Sep., 1992 | Bowser et al.
| |
| 5330171 | Jul., 1994 | Murad et al.
| |
| 5409205 | Apr., 1995 | Macke, Sr. et al.
| |
| 5423619 | Jun., 1995 | Kohno.
| |
| 5464203 | Nov., 1995 | Bowser et al.
| |
| 6098840 | Aug., 2000 | Ito et al.
| |
| 6193230 | Feb., 2001 | Tung-Ying.
| |
| Foreign Patent Documents |
| 196 53 343 | Dec., 1996 | DE.
| |
| 350749 | Jan., 1990 | EP.
| |
| 0 464 578 | Jun., 1991 | EP.
| |
| 2632430 | Dec., 1989 | FR.
| |
| 2145065 | Mar., 1985 | GB.
| |
| 2209517 | Mar., 1985 | GB.
| |
| 2274276 | Jul., 1994 | GB.
| |
| 75 18 810 | Sep., 1975 | GM.
| |
| 60036246 | Feb., 1985 | JP.
| |
| 63101241 | May., 1988 | JP.
| |
| 63047243 | Dec., 1988 | JP.
| |
Other References
Force Engineering's "Introduction to Linear Motors" at website http://www.force.co.uk/page2.html
□□ 1997 (site visited Apr. 28, 2005).
Summary of Germand Search Report for 102 23 350.0.
|
Primary Examiner: Walsh; Donald P.
Assistant Examiner: Kohner; Matthew J.
Attorney, Agent or Firm: Alix, Yale & Ristas, LLP
Claims
What is claimed is:
1. Device for isolating the lowest sheet in each case from a stack of sheets
situated in a stack holder and feeding said lowest sheet in a travel direction
into drawing off rollers, each sheet having a length in the travel direction between
a front edge and a rear edge and opposed lateral edges, comprising:
a front edge stop on the stack holder, which permits passage of only the bottom
sheet of the stack toward said drawing off rollers, the location of the front edge
of said stack being at said front edge stop for all sheets of any sheet length (H);
a cross member situated below the holder and extending transversely to the travel direction;
a pushing-out element supported by the cross member, which grips the rear edge
of the sheet in the stack and transports the sheet an isolating stroke distance
(B) in the travel direction under the front-edge stop, into the drawing-off rollers,
and having faces for vertically supporting the rear of the stack adjacent the rear edge;
means supporting the cross-member for moving the cross member and pushing out
element forwards and backwards along the travel direction;
bearing elements supporting the underside of the stack adjacent the lateral edges;
lateral abutment strips for maintaining registry of the lateral edges of sheets
of the stack;
a linear guide engaging the means supporting the cross member; and
a linear motor operatively connected to the means supporting the cross-member,
for linearly driving the movement of the cross member along a path of travel (A)
that comprises both the isolating stroke (B) and an adjusting path (C) which is
adjustable according to the sheet length (H); and
a position-controlling system associated with the linear motor and the drawing
off rollers for controlling the forward movement of the cross-member with the pushing-out
elements in dependence upon the conveying speed of the drawing off rollers.
2. Device according to claim 1, wherein said position-controlling system associated
with the linear motor and the drawing off rollers controls the forward movement
of the cross-member with the pushing-out elements in dependence upon the conveying
speed of the rollers in such a way that the lowest sheet is fed to said rollers
at nearly synchronous speed.
3. Device according to claim 2, wherein the sheet is fed to the pair of drawing-off
rollers at a higher speed than the conveying speed of drawing-off rollers.
4. Device according to claim 1, wherein said control system has control logic
for a fixedly configured movement profile (B) for the forward and backward movement
for clock-pulsed-synchronous feeding of the sheets to clock-pulse-controlled further-processing apparatuses.
5. Device according to claim 1, wherein that location of the isolating stroke
(B) on the path of travel (A) which depends upon the sheet length (H) is determined
by inputting the sheet length (H, Ha, Hb) in an operating unit associated with
a position-controlling system.
6. Device according to claim 1, wherein the location of the isolating stroke
(B) on the path of travel (A) is determined automatically by impingement, which
is controlled by a sensor, against the rear edge of the stack from an outer position.
7. Device according to claim 1, wherein the linear motor is provided with an
overload function.
8. Device according to claim 1, wherein the linear motor is force-controlled,
an admissible pushing-out force for the particular sheet material to be processed
is predetermined, and the speed of the pair of drawing-off rollers is controlled
commensurate with said pushing-out force.
9. Device according to claim 8, wherein when the device is moved up along an
approach ramp, adherence to the admissible pushing-out force is monitored, and
that, when said pushing-out force is reached, the device is operated at the processing
speed which has been reached up to that point.
10. Device according to claim 1, wherein the cross-member with the pushing-out
elements is constructed with a suction device that acts upon the lowest sheet.
11. Device for isolating the lowest sheet in each case from a stack of sheets
situated in a stack holder and feeding said lowest sheet in a travel direction
into drawing off rollers, each sheet having a length in the travel direction between
a front edge and a rear edge and opposed lateral edges, comprising:
a front edge stop on the stack holder, which permits passage of only the bottom
sheet of the stack toward said drawing off rollers, the location of the front edge
of said stack being at said front edge stop for all sheets of any sheet length (H);
a cross member situated below the holder and extending transversely to the travel direction;
a pushing-out element supported by the cross member, which grips the rear edge
of the sheet in the stack and transports the sheet an isolating stroke distance
(B) in the travel direction under the front-edge stop, into the drawing-off rollers,
and having faces for vertically supporting the rear of the stack adjacent the rear edge;
means supporting the cross-member for moving the cross member and pushing out
element forwards and backwards alone the travel direction;
bearing elements supporting the underside of the stack adjacent the lateral edges;
lateral abutment strips for maintaining registry of the lateral edges of sheets
of the stack;
a linear guide engaging the means supporting the cross member; and
a linear motor operatively connected to the means supporting the cross-member,
for linearly driving the movement of the cross member alone a path of travel (A)
that comprises both the isolating stroke (B) and an adjusting oath (C) which is
adjustable according to the sheet length (H);
wherein the stack holder is supported by a frame; and
wherein the linear motor has a secondary part which determines the path of travel
(A) and is disposed on a carrying plate which is integral with the frame and a
movable primary part fastened to the cross-member for driving the pushing out element
as the secondary part of the motor moves relative to the primary part of the motor.
12. Device according to claim 11, wherein the linear guide is formed from two
parallel guide rails which are disposed laterally along the path of travel (A)
and are fastened on the carrying plate in a torsion and deflection-resistant manner,
and from guide carriages which are fastened to the means for supporting the cross-member
and associated with the respective guide rails.
13. Device according to claim 12, wherein the secondary part of the motor and
the guide rails are attached to the underside of the carrying plate which is integral
with the frame, and the primary part of the motor and the guide carriages are fastened
to the means for supporting the cross-member.
14. Device according to claim 11, including a position-controlling system associated
with the linear motor and the drawing off rollers for controlling the forward movement
of the cross-member with the pushing-out elements in dependence upon the conveying
speed of the rollers in such a way that the sheet is fed to said rollers at nearly
synchronous speed.
15. Device according to claim 11, wherein control logic for a variably configurable
movement profile (B, Ba, Bb) for the forward and backward movement is stored in
a position-controlling system of the linear motor with respect to the sheet length
(H) of the particular sheet format to be processed, in such a way that gaps (D),
which are of predefinably equal size for different sheet lengths (H, Ha, Hb), are
produced between the sheets which are being fed.
16. Device according to claim 2 wherein the linear motor is force-controlled,
an admissible pushing-out force for the particular sheet material to be processed
is predetermined, and the speed of the pair of drawing-off rollers is controlled
commensurate with said pushing-out force.
17. Device according to claim 16, wherein when the device is moved up along an
approach ramp, adherence to the admissible pushing-out force is monitored, and
that, when said pushing-out force is reached, the device is operated at the processing
speed which has been reached up to that point.
18. Device according to claim 13, including a position-controlling system associated
with the linear motor and the drawing off rollers for controlling the forward movement
of the cross-member with the pushing-out elements in dependence upon the conveying
speed of the rollers in such a way that the sheet is fed to said rollers at nearly
synchronous speed.
19. Device according to claim 13, wherein control logic for a variably configurable
movement profile (B, Ba, Bb) for the forward and backward movement is stored in
a position-controlling system of the linear motor with respect to the sheet length
(H) of the particular sheet format to be processed, in such a way that gaps (D),
which are of predefinably equal size for different sheet lengths (H, Ha, Hb), are
produced between the sheets which are being fed.
20. Device according to claim 13, wherein the linear motor is force-controlled,
an admissible pushing-out force for the particular sheet material to be processed
is predetermined, and the speed of the pair of drawing-off rollers is controlled
commensurate with said pushing-out force.
21. Device for isolating the lowest sheet in each case from a stack of sheets
situated in a stack holder and feeding said lowest sheet in a travel direction
into drawing off rollers, each sheet having a length in the travel direction between
a front edge and a rear edge and opposed lateral edges, comprising:
a front edge stop on the stack holder, which permits passage of only the bottom
sheet of the stack toward said drawing off rollers, the location of the front edge
of said stack being at said front edge stop for all sheets of any sheet length (H);
a cross member situated below the holder and extending transversely to the travel direction;
a pushing-out element supported by the cross member, which grips the rear edge
of the sheet in the stack and transports the sheet an isolating stroke distance
(B) in the travel direction under the front-edge stop, into the drawing-off rollers,
and having faces for vertically supporting the rear of the stack adjacent the rear edge;
means supporting the cross-member for moving the cross member and pushing out
element forwards and backwards alone the travel direction;
bearing elements supporting the underside of the stack adjacent the lateral edges;
lateral abutment strips for maintaining registry of the lateral edges of sheets
of the stack;
a linear guide engaging the means supporting the cross member; and
a linear motor operatively connected to the means supporting the cross-member,
for linearly driving the movement of the cross member along a path of travel (A)
that comprises both the isolating stroke (B) and an adjusting path (C) which is
adjustable according to the sheet length (H);
wherein control logic for a variably configurable movement profile (B, Ba, Bb)
for the forward and backward movement is stored in a position-controlling system
of the linear motor with respect to the sheet length (H) of the particular sheet
format to be processed, in such a way that gaps (D), which are of predefinably
equal size for different sheet lengths (H, Ha, Hb), are produced between the sheets
which are being fed.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a device for isolating and feeding the lowest
sheet in each case from a stack of flat substantially planar items such as paper
sheets or the like.
A device of the type is known, for example, from EP 0 464 578 A1 and serves for
isolating boards which are fed to a subsequent unit for further processing. Possible
further-processing operations are printing, cutting-to-size or division into a
number of individual sheets, fluting or grooving and milling, the manufacture of
book covers, file covers, etc. This device has a transporter which can be moved
forwards and backwards and which is driven by a crank-slide mechanism with coupler-mechanism
expansion with a sinusoidal movement pattern. Fastened to the transporter are pushing-out
elements which are dimensioned in such a way, in terms of their height, that they
grip only the lowest sheet at the rear edge during the forward movement and push
it through an admission aperture formed by a base plate and a front-edge stop.
In the process, the sheet is pushed into a pair of drawing-off rollers which takes
over the transportation of the sheet from then on and feeds it to the subsequent
processing unit, while the transporter with the pushing-out elements returns to
its starting position for the purpose of pushing out the next sheet. From DE 75
15 810 U1, a device is known in which a suction device which acts upon the front
region of the lowest sheet is additionally provided for the purpose of isolating
and feeding curved materials.
The sheets rest against a stationary edge with their front edge. Accordingly,
as the sheet length becomes greater, the rear edge is displaced rearwards relative
to the front edge stop and to the pair of drawing-off rollers. For the purpose
of setting different sheet lengths, the transporter with its appertaining drive
is received in a carriage which can be brought, via adjusting spindles, into the
pushing-out position which corresponds to the sheet length. For the purpose of
driving the crank-slide mechanism, a rotating movement is tapped off, via a sliding
sleeve, from a spline shaft aligned along the direction of displacement, and is
reoriented via a bevel-gear mechanism. The prior art mentioned also indicates an
alternative form of embodiment for adjusting the pushing-out position. In that
embodiment, the mechanism for generating the forward and backward movement is disposed
in a stationary manner. It actuates a sliding carriage which has a transporter
which can be adjusted via adjusting spindles. The rotational movement for adjustment
purposes is transmitted in known manner via a sliding sleeve from a profiled shaft
to the moving system of the sliding carriage.
Because of the disposition of the adjusting system on the moving system,
the latter is burdened by additional masses for which allowance has to be made
in the guides of the carriage and also in the drive and which, moreover, restrict
the maximum isolating output. The driving connection of the adjusting system via
sliding sleeves is exposed to constant wear. Although the moving mass is reduced
to a minimum in the aforesaid form of embodiment, use is nevertheless made of a
very complicated driving system which has, in the sliding sleeve, a driving member
which is subject to play and wear.
The sinusoidal driving movement of the transporter which is generated via the
crank-slide mechanism or, in other embodiments, via a crank mechanism has ranges
of maximum, near-constant speed during both the forward and the backward movements.
The taking-over of the sheet during the forward movement through the pair of drawing-off
rollers ideally takes place within this speed range, and that at a speed which
is synchronous with the said pair of rollers. In order to achieve high isolating
outputs and/or in the case of large sheet lengths, however, the drawing-off speed
is set so as to be substantially higher. This leads to the sheets being pulled
in a skewed manner, which jeopardizes further processing of a good quality. Because
of the fixed period of the sinusoidal driving movement, the sheets are fed to the
pair of drawing-off rollers at a fixed clock-pulse interval. This is also necessary
for some further-processing apparatuses. During cutting-to-size or division into
a number of blanks, on the other hand, pushing-out of the sheets which is adapted
to the sheet length is appropriate in order to achieve maximum isolating outputs,
something which can be achieved only by means of major structural expense in the
designs of drive indicated.
SUMMARY OF THE INVENTION
The underlying object of the present invention is to provide a device for isolating
and feeding the lowest sheet in each case from a stack, which device permits high
isolating outputs and faultless feeding of the sheets, while being of simple design.
The inventive concept resides in using a linear motor for the driving movement
of the cross-member with the pushing-out elements, which cross-member is guided
so as to be capable of travel in a linear guide, the path of travel comprising
both the isolating stroke and also an adjusting path which is intended for setting
the sheet length. Driving and adjusting members which are subject to play and wear
are thereby eliminated, and the moving mass is markedly reduced. The driving movement
is changed over in a low-friction manner. The device is distinguished by a particularly
simple design—particularly when changing the setting over to different sheet lengths.
The mechanical decoupling of the drives of the drawing-off rollers and pushing-out
system result in advantageous possibilities for configuring the movement profile
of the forward and backward movements. A higher pushing-out speed with respect
to the drawing-off speed is chosen instead of the synchronous transfer speed. Suitably
stiff sheets are pushed, aligned more or less at the rear edge, into the drawing-off
rollers without the latter pulling the sheet away from the pushing-out elements
in a one-sided manner when gripping it for the first time. Two movement profiles
can be configured in principle. Clock-pulse-synchronous feeding operations are
thus possible with one and the same device, and so too are feeding operations with
gaps of equal size between the sheets that are being fed.
The driving of the linear motor in a force-controlled manner, combined with the
predetermining of an admissible pushing-out force, is advantageous if the speed
of the pair of drawing-off rollers, and thereby of the isolating output, is controlled
subject to adherence to the pushing-out force. This provides isolating and feeding
operations which treat the product particularly gently. Allowance is made for different
stack heights, to the effect that the pushing-out speed is reduced in the case
of large stack heights because a higher proportion of the pushing-out force is
needed for overcoming the surface friction and is no longer available for actually
accelerating the sheet. It is expedient to cause the processing speed when the
device is moved up along an approach ramp to be determined automatically through
the fact that the pushing-out force exerted is compared with the admissible pushing-out
force. In this context, "approach ramp" means that the device is running faster
and faster (by beginning with a low processing speed) while the admissible pushing-out
force is monitored. When the admissible pushing-out force is reached, the device
is operated at the processing speed which has been reached up to that point.
The cross-member with the pushing-out elements is advantageously constructed
with a suction device which acts upon the front region of the lowest sheet. By
this means, thin or curved sheets can be reliably transported through under the
front-edge stop. Under these circumstances, it is possible, in some cases, to dispense
with the pushing-out elements.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in greater detail with the aid of an exemplified
embodiment which is represented in the drawings, wherein:
FIG. 1 shows the device according to the invention, in a side view;
FIG. 2 shows the device in a sectional view along the sectional line II—II
shown in FIG. 1; and
FIG. 3 shows a movement diagram of the device, wherein the movement profiles
for a small format and a large format are represented.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A stack
2 which is to be isolated and which contains sheets
1 is
located in a magazine or holder comprising rear limiting elements
20, front
lateral abutment strips
13 and front-edge stops
5, and also bearing
strips
11 and metal bearing plates
12 which form the lower limit
and are fastened to front and rear bearers
18a,b. In the exemplified
embodiment, the magazine is filled with sheets
1 which are arriving continuously
via a conveyer belt
19. Filling with partial stacks by hand is equally possible.
For isolating the lowest sheet
1 in each case, a cross-member
7
(extending transversely to the conveying direction F) is provided which can be
moved forwards and backwards and on which two pushing-out elements
9 with
front-mounted bearing faces
9a are disposed in an adjustable and
exchangeable manner via gripping-type fastening systems
10. During the forward
movement, the lowest sheet
1 in each case is gripped at the rear edge
3a,
3b with the aid of that edge of the pushing-out elements
9
which is adapted to the sheet thickness and protrudes in relation to the bearing
face
9a, and the said sheet is transported through, with its front
edge
4 under the front-edge stops
5, into a pair of drawing-off rollers
6. From then on, the pair of drawing-off rollers
6 takes over the
transporting operation in the direction of conveyance F and feeds the sheet to
a subsequent further-processing unit. The shape of the face of the pushing out
element
9 preferably includes a shoulder or notch whereby bearing surface
9a supports the bottom sheet from below while the shoulder pushes
the bottom sheet. On the return stroke, the flat top surface to the right of the
notch slides along the underside of the bottom of the next sheet. FIG. 1 shows,
by way of example, a cutting device which is formed by knife shafts
32 and
a pair of feeding-out rollers
33.
The cross-member
7 is guided so as to be capable of travel in a linear
guide
14 which is formed from guide rails
14b disposed so
as to be integral with the frame that supports the holder, and from guide carriages
14a fastened to the cross-member. Its driving movement is generated
by a linear motor
15 which is directly associated with it. The primary part
15a of the motor is fastened to the cross-member
7 via a bracket
8, while the secondary part
15b is associated with a carrying
plate
16 disposed, in a manner integral with the frame, between a front
wall and a rear wall
17a, b of the frame. The length of the secondary
part
15b, minus the length of the primary part
15a, produces
approximately the maximum possible path of travel A of the linear motor
15.
The entire linear motor
15 does not travel along the carrying plate
16.
The primary part
15a moves actuated by electromagnetic forces relatively
to the secondary part
15b, which includes permanent magnets and which
is mounted fixed to the carrying plate. The guiding is realized by the linear guide
14 and defines the moving direction and the exact arrangement/relating of
the primary and the secondary part to one another.
The forward and backward movement for isolating and pushing-out purposes is marked
as the isolating stroke B in the drawings. The available adjusting path C, with
the aid of which the location of the isolating stroke B can be set in dependence
upon the sheet length H, is defined by the difference between the path of travel
A and the isolating stroke B.
The cross-member with the pushing-out elements is advantageously constructed
with a suction device
9b, which acts upon the front region of the
lowest sheet. The suction device is located in the bearing face
9a of
the pushing-out elements
9 and acts (as shown with dashed arrows) upon the
underside of the lowest sheet
1 for drawing the sheet against the bearing
face to secure the taking with by the pushing-out element
9.
For providing protection against falling dust and the like, the secondary part
15b of the linear motor
15 is mounted on the carrying plate
16 from below. The two guide rails
14b of the linear guide
14 are likewise fastened to the carrying plate in a torsion and deflection-resistant
manner below, that is to say, to the left and right of, the secondary part
15b.
The above mentioned bracket
8 on the cross-member
7, which cross-member
is moved forwards and backwards, encloses the arrangement, which is integral with
the frame, constituted by the carrying plate
16, the guide rails
14b
and the secondary part
15b. The bracket also carries a scanning
head
29 with the aid of which a material measure
30 attached laterally
to the carrying plate
16 is scanned for the purpose of detecting the position
of the cross-member
7 in an absolute manner.
The power cable
24, which is connected to the moving primary part
15a,
and other signal lines
23 are laid in a trailing chain
21 which
serves as a cable duct and is fastened by one end to the bracket
8 on the
cross-member
7, and by the other end to a holder
22 on the front
wall
17a of the frame. The other driving and controlling elements
of the device are represented symbolically in FIG. 1. Associated with the linear
motor
15 is a control system
26 which, in turn, receives its parameters
which are necessary for operating purposes from a superordinated position-controlling
system
25, or exchanges them. Also connected to the position-controlling
system
25 are an operating unit
31 for indicating and inputting the
parameters, as well as a motor-controlling system
28 which controls the
motor
27 which drives the drawing-off roller system
6, the knife
shafts
32 and the pair of feeding-out rollers
33. Via the operating
unit
31 there is inputted, inter alia, the sheet length H according to which
the linear motor
15 conveys the cross-member
7 into a suitable location
or position on the path of travel A, from where the isolating stroke B is carried
out as a cyclical forward and backward movement. Alternatively the location of
the isolating stroke B on the path of travel A is determined automatically by driving
the cross-member
7 with the pushing-out elements
9 against the rear
edge
3a, 3b of the stack
2 from an outer position,
which is controlled by a sensor
34.
The movement profiles with the aid of which the lowest sheet
1 in each
case is advanced and transported onwards, are represented in the movement diagram
in FIG. 3 for a small format and a large format in each case. The time T is plotted
on the X-axis of the diagram, and the path S on the Y-axis. The gradient of the
curves recorded in the diagram reproduces the level of the speed at which the elements
represented move or are moved. For orientation purposes, the position of the pair
of drawing-off rollers
6 is reproduced on the left, near the Y-axis. Located
at a distance E behind the said position is the front-edge stop
5—to
be identified by the fact that the front edges
4 of the sheets
1a,
1b, which are represented in hatched form, are disposed at that
point. The sheet
1a represents the large format and has a sheet length
Ha. Correspondingly, the sheet
1b is the small format, with a sheet
length Hb.
The movement profile Ba of the cross-member
7 with the pushing-out elements
9 for the sheet
1a is represented in the lower region of the
diagram. During the forward movement, the sheet
1a is pushed forwards
at the rear edge
3a until the front edge
4 passes, after the
length of path E, into the pair of drawing-off rollers
6, and the said sheet
1a is, from then on, transported onwards at the constant conveying
speed of the said pair of rollers. At the point in time of take-over by the pair
of drawing-off rollers
6, the movement profile Ba exhibits a pronounced
zone of constant speed of advance, which speed of advance is synchronous with the
drawing-off conveying speed. For a given setting of the unit
31, the stroke
of the pushing out element
9 will be forward and back along a length B,
which is sufficient for the rollers to grab and advance the sheet the remaining
distance of greater than H-B to fully advance the sheet past the front end stop
5. During this advance by the rollers, the sheets are supported from below
only by bearing strips
11 and bearing plates
12, but not at the back
edge. On the return stroke of the pushing out element
9, the underside of
the next bottom sheet lies on the advanced sheet until it falls down onto the bearing
elements
11,
12. The back edge of the next sheet lies on the flat
surface to the right of the notch on pushing out element
9 until the pushing
out element
9 moves with its shoulder or notch behind the rear edge of the
next sheet (
3a or
3b). On the return stroke of the
pushing out element
9 the rear edge of the advanced sheet is no longer supported.
After the taking-over operation, the cross-member
7 returns to its starting
position. The next movement cycle for pushing out the sheet
1a.2
starts when the preceding sheet
1a.1 has passed the front-edge
stops
5. This interrelation gives rise, for the movement profile Ba, to
a clock-pulse time Ta and, derived therefrom, an isolating output of 1/Ta. The
two sheets
1a.1 and
1a.2 are conveyed
through the further-processing unit with a gap D.
The pushing-out of a small sheet
1b is conducted in a manner analogous
with the above observations. Because of the shorter sheet length Hb, the movement
profile Bb here exhibits a substantially lower clock-pulse time Tb, from which
a high isolating output 1/Tb is derived. The gap D between the successive sheets
1b.1,
1b.2,
1b.3,
etc. is identical to that when isolating and feeding the large sheet
1a.
The logic for movement profiles Ba, Bb are derived, for the particular sheet
length H, from a variably configured movement profile which has been stored in
the position-controlling system
25. It will be perceived that the forward
movement is almost identical, while the backward movement is carried out in a manner
corresponding to the remaining time available.
In a given machine (e.g., device of EP 0464578, the disclosure of which is incorporated
by reference) there is a substantially constant relationship between distance E
and distance B. B is slightly greater than E to guarantee receiving the isolated
sheet by the drawing-off rollers
6. In a given machine the distance C symbolizes
the adjusting path.
Ha is the sheet length of a large sheet, and Hb the length of a short sheet. H
shows also the distance between the front-edge stop
5 and the limiting element
20. The path of travel A arises approximately from the difference of Ha
(length of large sheet) and Hb (length of short sheet) plus the isolating stroke
B. The distance H-A is equal to Hb-B. In the illustrated embodiment the isolating
stroke B is a constant unaffected by the sheet length H. According to the invention
the isolating stroke B need not be constant for all length H of sheets. B could
be programmed by one of ordinary skill in the art, to different stroke lengths.
The device is preferably part of a board-cutting installation, in which long
sheets are cut from large-format sheets in a first step, and are then transferred
into the device represented here and divided up into the desired final formats.
The output of the entire plant is determined, in particular, by this second station.
The device according to the invention results in new output potentials, since the
sheets
1 are now isolated in dependence upon their sheet length H, and medium
and smaller formats in particular, which make up by far the largest spectrum of
board-cutting installations of this kind, are produced in a substantially higher
production output. At the same time, the quality of the sheet blanks produced goes
up, since the take-over takes place with an almost synchronous speed of the pair
of drawing-off rollers
6 and the pushing-out elements
9.
The device according to the invention for isolating purposes is also suitable
for feeding sheets to clock-pulse-controlled further-processing apparatuses. Use
is then made of a fixedly configured movement profile with a fixed clock-pulse
time or period. Because of the direct association of the linear motor
15
on the cross-member
7 which is moved forwards and backwards, and also because
of the very low-friction linear guide
14, the pushing-out force applied
can be employed for force-controlling the device. In addition to a general overload
function, it is possible to push out the sheets
1 in a manner which treats
the products gently, while observing an admissible pushing-out force which can
be predetermined in the operating unit
31. To that end, the drawing-off
speed of the pair of drawing-off rollers
6 is varied accordingly.
*
