U.S. patent number RE37,007 [Application Number 08/292,408] was granted by the patent office on 2001-01-02 for device for aligning sheets with plural drive roller groups on a common shaft.
This patent grant is currently assigned to Mars Incorporated. Invention is credited to Andre Gerlier.
United States Patent |
RE37,007 |
Gerlier |
January 2, 2001 |
Device for aligning sheets with plural drive roller groups on a
common shaft
Abstract
In a sheet feeding device, the local feed of the sheet is
measured in the vicinity of respective drive rollers by means of
respective sensors for the purpose of aligning rectangular sheets
of a preselected set. On the basis of signals from the light
sensors, a control device determines an optimum pair of rollers for
aligning the sheet. The control device compares the signals of the
two associated sensors and adjusts the local feed of the sheet in
such a way that the two sensors establish the same local feed,
before the sheet leaves one of the selected rollers.
Inventors: |
Gerlier; Andre (Sciez,
FR) |
Assignee: |
Mars Incorporated (McLean,
VA)
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Family
ID: |
4275454 |
Appl.
No.: |
08/292,408 |
Filed: |
August 18, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
618483 |
Nov 27, 1990 |
05140166 |
Aug 18, 1992 |
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Foreign Application Priority Data
Current U.S.
Class: |
250/548;
271/227 |
Current CPC
Class: |
G07D
7/12 (20130101); G06K 13/063 (20130101); B65H
9/002 (20130101); G07D 7/17 (20170501); B65H
2511/242 (20130101); B65H 2701/1912 (20130101); B65H
2513/104 (20130101); B65H 2404/143 (20130101); B65H
2553/412 (20130101); B65H 2553/51 (20130101); B65H
2511/242 (20130101); B65H 2220/01 (20130101); B65H
2513/104 (20130101); B65H 2220/02 (20130101) |
Current International
Class: |
G07D
7/00 (20060101); G07D 7/16 (20060101); G07D
7/12 (20060101); G01N 021/86 () |
Field of
Search: |
;250/548,557,223R,559.37,559.3 ;271/227,228,272,273,274
;198/401,415,394,395 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3441977 |
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May 1985 |
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DE |
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0206675 |
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Dec 1986 |
|
EP |
|
4163157 |
|
Jul 1979 |
|
FR |
|
Primary Examiner: Lee; John R.
Attorney, Agent or Firm: Fish & Richardson P.C.
Claims
What is claimed is:
1. A device for aligning a single sheet fed in a plane of alignment
in a feed direction, comprising:
at least two drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
and a respective pressure roller which contacts the respective
drive roller generally in the plane of alignment so that the sheet
can be driven between the drive roller and the respective pressure
roller wherein the drive rollers of the drive groups are disposed
on a common shaft mounted transversely of the feed direction;
a position detector operable to detect an angle of twist of the
sheet; and
a control device responsive to the position detector to adjust a
local feed speed of each drive group in dependence upon the angle
of twist of the sheet.
2. A device according to claim 1, wherein the position detector
comprises a series of light barriers for detecting the position of
the sheet upstream of the drive rollers and sensors for detecting
the local feed speed of the sheet.
3. A device according to claim 1, wherein a single drive motor is
provided for jointly driving the drive rollers by means of the
common drive shaft, and each pressure roller having a respective
lifting device, the lifting devices being controllable
independently by means of the control device for lifting the
respective pressure rollers from the respective drive rollers.
.[.4. A device according to claim 1, wherein each drive roller has
a stepping motor which is controlled independently by the control
device..].
5. A device according to claim 2, wherein each of said sensors
comprises an angular encoder which senses rotary movement of a
respective measuring wheel which is freely rotatable on a common
shaft of .[.the respective.]. .Iadd.an associated drive
.Iaddend.roller and a contact wheel being associated with each
measuring wheel and rolling on .[.the.]. .Iadd.a .Iaddend.contact
surface of the respective measuring wheel.
6. A device according to claim 5, wherein each measuring wheel has
a controllable braking device.
7. A device according to claim 2, wherein each sensor is a light
sensor which has a light transmitter on one side of the plane of
alignment and a light receiver on the other side thereof, the
control device being operable to measure the local feed in the
region of each light sensor based on the degree of shading of the
respective light receiver by the sheet.
8. A device according to claim 1, 2, 3, .[.4,.]. 5, 6 or 7 wherein
there are at least three such drive groups, the distance between
each adjacent pair of the drive rollers of the respective drive
groups being less than the length, reduced by a predetermined
factor, of a smallest sheet of a preselected set of different sized
sheets, and the control device being operable to determine an
optimum pair of the drive groups from the signals of the position
detector for aligning the sheet..Iadd.
9. A device for aligning a single sheet fed in a plane of alignment
in a feed direction, comprising:
at least two drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
and a respective pressure roller which contacts the respective
drive roller generally in the plane of alignment so that the sheet
can be driven between the drive roller and the respective pressure
roller;
a detector operable to detect an initial angle of twist of the
sheet as the sheet becomes engaged by the drive groups and at least
one subsequent angle of twist as the sheet is driven by the drive
groups; and
a control device responsive to the detector to adjust a local feed
speed of each drive group in dependence upon the initial angle of
twist and the subsequent angle of twist of the
sheet..Iaddend..Iadd.
10. A device according to claim 9, wherein the detector comprises a
series of light barriers for detecting the initial angle of
twist..Iaddend..Iadd.
11. A device according to claim 9, wherein a single drive motor is
provided for jointly driving the drive rollers by means of the
common drive shaft, and each pressure roller has a respective
lifting device, the lifting devices being controllable
independently by means of the control device for lifting the
respective pressure rollers from the respective drive
rollers..Iaddend..Iadd.
12. A device according to claim 9, wherein each drive roller has a
stepping motor which is controlled independently by the control
device..Iaddend..Iadd.
13. A device according to claim 9, further comprising at least two
measuring wheels which are freely rotatable on a common shaft with
at least two of the drive rollers, and a contact wheel associated
with each measuring wheel and rolling on a contact surface of the
measuring wheel, wherein the detector comprises an angular encoder
which senses rotary movement of at least two of the measuring
wheels..Iaddend..Iadd.
14. A device according to claim 10, further comprising at least two
measuring wheels which are freely rotatable on a common shaft with
at least two of the drive rollers, and a contact wheel associated
with each measuring wheel and rolling on a contact surface of the
measuring wheel, wherein the detector further comprises an angular
encoder which senses rotary movement of at least two of the
measuring wheels to detect the subsequent angle of
twist..Iaddend..Iadd.
15. A device according to claim 13, wherein each measuring wheel
has a controllable braking device..Iaddend..Iadd.
16. A device according to claim 10, wherein the detector further
comprises a plurality of light sensors which have a light
transmitter on one side of the plane of alignment and a light
receiver on the other side thereof, the control device being
operable to measure the local feed in the region of each light
sensor based on the degree of shading of the respective light
receiver by the sheet to detect the subsequent angle of
twist..Iaddend..Iadd.
17. A device according to claim 9, wherein there are at least three
such drive groups, the distance between each adjacent pair of the
drive rollers of the respective drive groups being less than the
length, reduced by a predetermined factor, of a smallest sheet of a
preselected set of different sized sheets, and the control device
being operable to determine an optimum pair of the drive groups
from the signals of the position detector for alignment the
sheet..Iaddend..Iadd.
18. A device for aligning a single sheet fed in a plane of
alignment in a feed direction, comprising:
at least three drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
and a respective pressure roller which contacts the respective
drive roller generally in the plane of alignment so that the sheet
can be driven between the drive roller and the respective pressure
roller;
a detector including a series of light barriers operable to detect
an angle of twist of the sheet, wherein the light barriers detect
the initial angle of twist and the detector further comprises a
plurality of light sensors which have a light transmitter on one
side of the plane of alignment and a light receiver on the other
side thereof;
a control device responsive to the detector to adjust a local feed
speed of each drive group in dependence upon the angle of twist,
the control device being operable to measure the local feed in the
region of each light sensor based on the degree of shading of the
respective light receiver by the sheet to detect at least one
subsequent angle of twist and to adjust a local feed speed of each
drive group in dependence on the initial and subsequent angles of
twist; and
wherein the distance between each adjacent pair of the drive
rollers of the respective drive groups is less than the length,
reduced by a predetermined factor, of a smallest sheet of a
preselected set of different sized sheets, and the control device
is operable to determine an optimum pair of the drive groups from
the signals of the detector for aligning the
sheet..Iaddend..Iadd.
19. A device for aligning a single sheet fed in a plane of
alignment in a feed direction, comprising:
at least two drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
and a respective pressure roller which contacts the respective
drive roller generally in the plane of alignment so that the sheet
can be driven between the drive roller and the respective pressure
roller;
at least two measuring wheels which are freely rotatable on a
common shaft with at least two of the drive rollers, and a contact
wheel associated with each measuring wheel and rolling on a contact
surface of the measuring wheel;
a first detector comprising a series of light barriers for
detecting an initial angle of twist of the sheet;
a second detector comprising an angular encoder which senses rotary
movement of at least two of the measuring wheels to detect at least
one subsequent angle of twist of the sheet; and
a control device responsive to the detector to adjust a local feed
speed of each drive group in dependence upon the initial angle of
twist and subsequent of twist of the sheet..Iaddend..Iadd.
20. A method of aligning a single sheet fed in a plane of alignment
in a feed direction by at least two drive rollers comprising:
detecting an initial angle of twist of the sheet;
adjusting the feed speed of each drive roller dependent upon the
initial angle of the twist to deskew the sheet;
driving the sheet by the drive rollers;
detecting a subsequent angle of twist of the sheet while the sheet
is being driven by the drive rollers; and
adjusting the feed speed of each drive roller dependent upon the
subsequent angle of twist if necessary to further deskew the
sheet..Iaddend..Iadd.
21. A device for aligning a single sheet fed in a plane of
alignment in a feed direction, comprising:
at least three drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
and a respective pressure roller which contacts the respective
drive roller generally in the plane of alignment so that the sheet
can be driven between the drive roller and the respective pressure
roller;
a detector including a series of light barriers operable to detect
an angle of twist of the sheet;
a control device responsive to the detector to adjust a local feed
speed of each drive group in dependence upon the angle of twist;
and
at least two measuring wheels which are freely rotatable on a
common shaft with at least two of the drive rollers, and a contact
wheel associated with each measuring wheel and rolling on a contact
surface of the measuring wheel, wherein the detector comprises an
angular encoder which senses rotary movement of at least two of the
measuring wheels, the light barriers detect an initial angle of
twist of the sheet and the angular encoder detects a subsequent
angle of twist of the sheet, and the control device adjusts the
local feed speed of each drive group in dependence on the initial
and subsequent angles of twist;
wherein the distance between each adjacent pair of the drive
rollers of the respective drive groups is less than the length,
reduced by a predetermined factor of a smallest sheet of a
preselected set of different sized sheets, and the control device
is operable to determine an optimum pair of the drive groups from
the signals of the detector for aligning the sheet..Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to a device for aligning sheets, such as
bank notes in automatic service machines.
If rectangular sheets are guided between conveyor belts or between
rollers on long, winding transportation paths where there are a
number of points of transfer from the transportation means to a
stacking device or checking device, twisting of the individual
sheets in their plane from the ideal position can arise.
Particularly often, twisting arises to a great extent when the
sheet is put in by hand, e.g. when a bank note is put into the
automatic service machine. These automatic machines and devices
therefore need to have an aligning device.
DESCRIPTION OF THE PRIOR ART
With a known mechanical aligning device (DE-OS 34 41 977), a
longitudinal edge of a bank note is pushed against a displaceable
locking plate arranged perpendicularly to the transportation path
and perpendicularly to the plane of alignment, and the bank note is
aligned in this way on the locking plate. The locking plate is then
removed from the transportation path and the bank note which has
been retained for a short time is transported further.
SUMMARY OF THE INVENTION
The aim of the invention is to provide a device of the kind
mentioned in the introduction, which aligns rectangular sheets of a
predetermined set of different sized sheets quickly and reliably
with a predetermined side parallel to its feed direction.
In accordance with the invention, there is provided a device for
aligning a sheet fed in a plane of alignment in a feed direction,
comprising:
at least two drive groups which are controllable independently of
each other, each drive group comprising a respective drive roller,
the axes of the drive rollers extending transversely of the feed
direction, and a respective pressure roller which contacts the
respective drive roller generally in the plane of alignment so that
the sheet can be driven between the drive roller and the respective
pressure roller;
a position detector operable to detect an angle of twist of the
sheet; and
a control device responsive to the position detector to adjust a
local feed speed of each drive group in dependence upon the angle
of twist of the sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an aligning device,
FIG. 2 shows a cross-section through a drive group,
FIG. 3 shows a lifting device,
FIG. 4 shows a cross-section of a transportation device and the
alignment device,
FIG. 5 shows a direct drive, and
FIG. 6 shows the alignment device with light sensors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a drive shaft 1 is shown with drive rollers 2 to 5 of
equal size arranged on the drive shaft 1 at equal distances A
apart, and fixedly connected thereto. As an example, the drawing
shows an aligning device with four drive rollers 2 to 5. The drive
shaft 1 extends over the entire width W of a plane of alignment 6
and is arranged parallel to the plane of alignment 6 in such a way
that the plane of alignment 6 is tangential to contact surfaces of
the drive rollers 2, 3, 4 and 5. The drive shaft 1 is connected to
a drive motor 7 on the one side, and the drive motor is fixed on
the outside of a lateral boundary 8 of the plane of alignment 6,
and drives all drive rollers 2 to 5 jointly. The boundary 8 and a
boundary 8' parallel thereto define the width W of the plane of
alignment 6.
The side of the plane of alignment 6, a side which is oppositely
disposed to the drive rollers 2 to 5, is formed by a base plate 9.
The base plate 9 has a cut-out portion 10 in the region of the
drive rollers 2 to 5. In the drawings, the base plate 9 has a
greater cut-away portion in the region of the drive roller 2, so
that the drawing may show details disposed beneath the base plate
9.
Pressure rollers 11 roll on respective contact surfaces of the
drive rollers 2 to 5. The pressure rollers are arranged on the
second side of the plane of alignment 6 in such a way that the
plane of alignment 6 forms the common tangential plane between the
drive rollers 2 to 5 and the pressure roller 11. A pair of rollers
is formed by a respective one of the drive rollers 2 to 5 and a
respective one of the contact rollers 11.
In the immediate vicinity of each of the drive rollers 2 to 5, a
respective sensor is provided in the form of an angular encoder 16
which measures a local feed, effected by means of the respective
drive roller 2 to 5 in the plane of alignment 6, of a sheet 24
which has been gripped by the pairs of rollers.
Each drive roller 2 to 5 advantageously has a respective measuring
wheel 12, 13, 14 and 15 arranged on one side of that drive roller.
Each measuring wheel is of the same circumference as the drive
rollers 2 to 5, is constrained at its sides in the axial direction,
and is mounted so as to be freely rotatable about the common drive
shaft 1. Each cost-effective angular encoder 16 detects rotary
movement of the respective measuring wheel 12, 13, 14 and 15, which
is a direct measurement of the local feed of the sheet 24. A
respective contact wheel 17 rolls on the contact surface of each
measuring wheel 12 to 15. Each one of the measuring wheels 12 to 15
and its respective contact wheel 17 form a pair of wheels which
likewise has the plane of alignment 6 as the common tangential
plane. A drive group is formed by a pair of rollers and the
directly adjacent pair of wheels.
The diameter of the drive rollers 2 to 5 and of the measuring
wheels 12 to 15 is approximately 40 mm, the width of the contact
surfaces thereof being 3 mm. The pair of rollers and the pair of
wheels of the same drive group are at a mutual spacing of
approximately 5 mm.
The pressure rollers 11 and the contact wheels 17 are preferably of
the same diameter, e.g. 10 mm with contact surfaces which are 3 mm
in width. They are guided individually by means of forks 18,
wherein each fork 18 is mounted for pivoting in a plane vertical to
the drive shaft 1. Under the effect of pressure force, the forks 18
resiliently push the pressure rollers 11 or the contact wheels 17
against the contact surface of the drive rollers 2 to 5 or of the
measuring wheels 12 to 15. The drive shaft 1 and the axles of the
pressure rollers 11 and of the contact wheels 17 lie in a common
axial plane which is vertical to the base plate 9, the axial plane
cutting the plane of alignment 6 along a line of intersection S.
The pressure rollers 11 or the contact wheels 17 touch the contact
surfaces of the drive rollers 2 to 5 or of the measuring wheels 12
to 15 along the line of intersection S.
The forks 18 which are associated with the pressure rollers 11 are
e.g. connected by mechanical means to respective lifting devices
19. Each lifting device enable the respective pressure roller 11 to
be lifted-off the contact surface of the respective drive roller 2,
3, 4 or 5 against the force or pressure, and independently of one
another.
The alignment device is complemented by a control device 20. This
is connected to the drive 7, the angular encoders 16 and the
lifting devices 19 by means of circuits 21 to 23. The control
device 20 contains a respective up/down counter for each angular
encoder 16, and the content Z.sub.1, Z.sub.2, Z.sub.3, or Z.sub.4
of each counter can be read and compared to those of the other
counters.
The sheet 24 is a rectangular sheet of a selected set of different
sized sheets. It is conveyed, for example, in the plane of
alignment 6 transversely to the longitudinal edge thereof in the
feed direction 25 indicated by means of an arrow. The sheet 24
generally reaches the plane of alignment 6 so that it is not
aligned parallel to the line of intersection S, the longitudinal
edge instead forming an angle of twist with the line of
intersection S.
The width W of the plane of alignment 6 is preferably by a
predetermined amount than a length B of the longitudinal edge of
the largest selected sheet 24, so that the aligning device can take
the largest sheet 24 with a predetermined maximum admissible angle
of twist .alpha.. The maximum value for this depends on the shape
of the sheet and may be, for example, 20.degree..
Advantageously, the distance A between the drive rollers 2 to 5 is
less than the length B, reduced by a predetermined factor, of the
smallest sheet 24 of the selected set of different sized sheets.
The factor corresponds to half the cosine for the maximum angle of
twist .alpha.. Therefore, the smallest sheet 24 from the selected
set is also able to be gripped by at least two of the drive rollers
2 to 5 at all admissible angles of twist .alpha. and independently
of its position on the plane of alignment 6. The distance between
the boundary 8 and one of the two outermost drive groups is
approximately half the distance A.
The sheet 24 is guided to the alignment device at the angle of
twist .alpha. from a first transportation device, not shown here,
in the feed direction 25 in the plane of alignment 6. Some of the
pairs of rollers grip the sheet 24 and align it parallel with the
line of intersection S, i.e. they reduce the angle of twist .alpha.
to zero, as described in more detail hereinafter. In this position,
it is taken by a second transportation device, not shown here, and
transported away.
By way of example, FIG. 2 shows a section through the common axial
plane for the first drive group. It consists of the drive roller 2
which is fixed firmly to the drive shaft 1, the pressure roller 11,
the rotatably mounted measuring wheel 12 and the contact wheel 17.
The pressure roller 11 or the contact wheel 17 is rotatably mounted
between the two tines of one of the two forks 18.
The pair of rollers 2, 11 and the pair of wheels 12, 17 clamp the
sheet 24. On the side of the sheet 24 facing the drive shaft 1, a
cover plate 26 covers the plane of alignment 6 and, together with
the base plate 9 and the boundaries 8, 8' (FIG. 1), forms a
passage. The cover plate 26 has a respective window 27 above each
cut-out portion 10 in the base plate 9, so that there is no
obstruction to the respective drive roller 2 and measuring wheel
12.
Each angular encoder 16 detects rotary movement made by the
respective measuring wheel 12, optically or mechanically, for
example. By way of a circuit 22, signal impulses reach the counters
in the control device 20 (FIG. 1). Rotary movement made by each
measuring wheel 12 and caused by local feed of the sheet 24 between
that wheel 12 and the respective contact wheel 17 is recorded in
both directions of rotation with the correct sign digit, so that
the content of the associated counter in the control device 20 is a
measurement of the local feed of the sheet 24 beneath the
respective measuring wheel 12.
Advantageously, each pair of wheels formed by one of the measuring
wheels 12 and the respective contact wheel 17 is fitted with a
braking device 28, the braking action of which is adapted for
pre-set adjustment. The braking action in turn prevents the wheels
12 and 17 of the pair of wheels from rotating further, as a result
of their angular momentum and their nearly frictionless bearings,
if the sheet 24 is no longer in contact with the pair of wheels,
and on the other hand it provides a predetermined frictional force
of the pair of wheels which is required for the aligning operation.
In one example, the effect of the braking device 28 is selectable
by the control device 20 preferably between a minimum and maximum
predetermined value, by way of a circuit, not shown here.
As an example, FIG. 2 shows a simple mechanical braking device 28
which lowers a brake lining 28' onto the contact surface of the
measuring wheel 12, in order to obtain the braking effect. The same
action can also be achieved, for example, by braking the contact
wheel 17, wherein the lining is protected on the contact surface of
the measuring wheel 12 and the measured result is not falsified as
a result of the diameter being reduced by wear. It is also possible
to use other braking systems, for example an electrodynamic
brake.
Preferably, the contact surfaces of the pairs of rollers and wheels
have linings having a large static friction coefficient, in order
to prevent undesired slippage between the pairs of rollers and
pairs of wheels and the sheet 24, since such slippage makes
accurate alignment impossible. The effect of the linings is
directly dependent on the pressure force of the pressure roller 11
or of the contact wheel 17.
FIG. 3 shows, by way of example, a pair of rollers 2, 11 and the
lifting device 19 therefor. For reasons of clarity, only one
segment of the drive roller 2 is shown, namely that immediately
above the sheet 24.
A parallel row of light barriers 29 is arranged in the form of
position sensors in the feed direction 25 at a predetermined
distance in front of the line of intersection S (FIG. 1). These
position sensors detect the presence and position of the sheet 24
prior to the aligning operation, when it is being fed in the
passage between the base plate 9 and the cover plate 26 in the
direction of feed 25 towards the pairs of rollers. The distance
between the adjacent light barriers 29 in the row is predetermined
by the set of sheets 24, for example 10 mm.
Each of the light barriers 29 comprises a light transmitter 30,
which is disposed, for example, above the cover plate 26, and a
light receiver 31 fixed beneath the base plate 9. The light
receiver 31 is connected to the control device 20 by way of a
control circuit 32. The base plate 9 and the cover plate 26 have
bores which are disposed directly over one another, so that the
beam of light produced by the light transmitter 30 reaches the
light receiver 31 through the bores in the plates 9, 26, if the
sheet 24 does not interrupt the beam of light.
Each fork 18 is rotatable about an axis of rotation 33 which is
perpendicular to the plane of FIG. 3. One arm of the fork 18
carries the respective pressure roller 11, and another arm is
urged, for example by a tension spring 34, in such a way that the
pressure roller 11 is pressed against the drive roller 2. Similar
forks 18 and tension springs 34 are provided for mounting the
contact wheels 17 and pressing them against the respective
measuring wheels 12.
In a simple embodiment, the lifting device 19 associated with each
pressure roller 11 comprises an electromagnet 35 with an armature
rod 36. The electromagnet 35 can be excited from the control device
20 by means of a control signal on the control circuit 23. The
armature rod 36, which is displaceable vertically with respect to
the base plate 9, is linked to the fork 18 by means of a connecting
link acting between the axis of rotation 33 and the axis of the
pressure roller 11. When the electromagnet 35 is excited, the
armature rod 36 is lowered, and the pressure roller 11 is lifted
from the contact surface of the drive roller 2. The frictional
connection between the drive roller 2 and the sheet 24 is thus
cancelled, and the drive roller 2 glides over the sheet 24.
In FIG. 4, a first transportation device is arranged in front of
the light barriers 29. It consists of at least one pair of
transportation belts 37 which run over fixedly arranged belt
pulleys 38 and over belt pulleys 39 which are displaceable
perpendicularly to the plane of alignment 6. The transportation
device is constructed symmetrically with respect to the plane of
alignment 6, wherein displaceable belt pulleys 39 are oriented
towards the pairs of rollers. The transportation belts 37 and the
displaceable belt pulleys 39 have two positions, wherein the first
position, marked by the solid lines, serves to transport the sheet
24, and the second position, shown by the broken lines, enables the
aligning process to take place.
The belt pulleys 38 and 39 guide the transportation belts 37 in the
first position in such a way that the transportation belts 37 make
contact over a predetermined extent through recesses 40 in the base
plate 9 and in the cover plate 26, and enclose the plane of
alignment 6. The belt pulleys 39 are connected, by mechanical
means, for example, to an adjustment mechanism 41, and are held
thereby in one of the two positions.
An adjustment signal circuit 42 connects the control device 20 to
the adjustment mechanism 41, which transmits an adjustment signal
to the adjustment mechanism 41 by means of the adjustment signal
circuit 42, so that the displaceable belt pulleys 39 are moved from
the first position symmetrically away from the plane of alignment 6
into the second position, marked by broken lines, and the
transportation belts 37 are separated. Except in the region of the
fixedly arranged belt pulleys 38, the transportation belts 37 are
moved from the plane of alignment 6 to the second position, and
they release the sheet 24, preferably without delay so that
unobstructed alignment takes place. A motor, not shown here, drives
the belt pulleys 38, 39 and the transportation belts 37, wherein
they feed the sheet 24 at the same speed as the drive groups.
An identical second transportation device, not shown here, the
elements of which will hereinafter be denoted by the same reference
numerals, is arranged with its pairs of rollers in mirror
symmetrical relationship with respect to the first transportation
device. The aligned sheet 24 is pushed in the feed direction 25 by
the pairs of rollers between the separated transportation belts 37
of the second transportation device towards the belt pulleys 38,
and after the adjustment signal has been removed, the
transportation belts 37 are brought into contact with the sheet 24
and take hold of it for further transportation.
The advantage with these transportation devices is that the sheet
24 is driven through the alignment device for the whole period of
its travel, whilst the alignment operation is unhindered and
movement of the sheet 24 is controlled at all times. After the
aligning operation, the sheet 24 is held firmly and is prevented
from twisting again.
In its first position, the first transportation device conveys the
sheet 24 in the feed direction to the pairs of rollers. One of the
light barriers 29 detects the presence of the sheet, and sends a
signal to the control device 20 by means of its control circuit 32.
The control device 20 switches on the drive motor 7 (FIG. 1) and
rotates the drive shaft 1 e.g. anti-clockwise, as shown by an arrow
on the drive roller 2.
The control device 20 arrests the lifting devices 19 (FIG. 3) and
the action of the braking device 28 (FIG. 2) so that the pressure
rollers 11 can be placed on the contact surfaces of the drive
rollers 2 to 5 (FIG. 1) and the pairs of wheels can rotate
freely.
The transportation device conveys the sheet 24 further towards the
pairs of rollers or drive groups, which are shown in FIG. 3 by way
of example as drive roller 2 and pressure roller 11. One after the
other, the front longitudinal edge of the sheet 24 covers
adjacently disposed light barriers 29. From the sequence of signals
of the light barriers 29, the control device 20 detects the
position of the front edge of the sheet 24 and the angle of twist
(FIG. 1) and the two optimum drive groups for aligning the sheet
24. This precautionary measure ensures that none of the selected
drive groups rolls over one of the lateral edges of the sheet
24.
As soon as the front longitudinal edge of the sheet 24 is gripped
by one of the pairs of rollers, the corresponding one of the
measuring wheels 12 to 15 (FIG. 1) begins to rotate and the
associated angular encoder 16 (FIG. 1) sends signal impulses to the
control device 20, which adds them up in the respective associated
counter in the direction of rotation of the measuring wheel 12, 13,
14 and 15. If one of the two selected counter contents Z.sub.1 to
Z.sub.4 (FIG. 1) is different from zero, the control device 20
sends the adjustment signal by way of the adjustment signal
circuits 42 to the adjustment mechanism 41 of the two
transportation devices. The sheet 24 which has been released by the
transportation belts 37 is now conveyed by at least one of the
driver rollers 2 to 5.
Advantageously, the control device 20 contains an electronic,
programmable control means 43 with a value memory 44, wherein the
electronic control means 43 takes on all the functions of the
control device 20, for example, and the value memory 44 contains
measured values and predetermined adjustment parameters, e.g.
dimensions of the sheets 24 of a selected set, which considerably
simplify determination of the angle of twist .alpha..
The alignment procedure will now be described with the aid of the
example shown in FIG. 1. The first transportation device (FIG. 4)
feeds the sheet 24 to the pairs of rollers in the plane of
alignment 6. The sheet 24 is aligned so that it is inclined to the
line of intersection S with an accidental value of the angle of
twist .alpha.. In this example, it is gripped in turn by the
fourth, third and second drive groups. The control device 20 has
detected the position of the front longitudinal edge of the sheet
24 by using the light barriers 29 and defines as optimal the two
drive groups with the pairs of rollers 5, 11 and 3, 11 and the
associated counter contents Z.sub.2 and Z.sub.4.
At first, the sheet 24 is seized by the fourth pair of rollers 5,
11. The fourth counter in the control device 20 begins to increment
the counter content Z.sub.4 with the signal impulses from the
angular encoder 16 of the measuring wheel 15; this has the effect
of emitting an adjustment signal for the transportation
devices.
Since the control device 20 considers only the two selected counter
contents Z.sub.2 and Z.sub.4, it makes no other decisions as long
as only the one counter content Z.sub.4 is different from zero.
As soon as the front longitudinal edge of the sheet 24 is also
seized by the second selected pair of rollers 3, 11, the counter
content Z.sub.2 of the second counter begins to increase. Since the
two counter contents Z.sub.2 and Z.sub.4 are now different from
zero, the control device 20 determines the appropriate state from
the three possible ones: Z.sub.2 >Z.sub.4, Z.sub.2 =Z.sub.4 and
Z.sub.2 <Z.sub.4.
In this example, the counter content Z.sub.4 is greater than the
counter content Z.sub.2. The control device 20 sends a control
signal by way of the control circuit 23 to the lifting device 19 of
the fourth pair of rollers 5, 11, in order to lift the pressure
roller 11 and to reduce the local feed thereat. If present, the
braking device 28 (FIG. 2) of the fourth pair of wheels 15, 17 is
also switched on. Since the sheet 24 is now only driven by the
second drive roller 3 and as a result of friction is braked in the
region of the fourth pair of wheels 15, 17, the sheet 24 twists in
the plane of alignment 6 about a pivot point beneath the fourth
measuring wheel 15. Accordingly, the second counter continues to
count its local feed correspondingly, but the fourth counter
receives no, or only a few, additional signal impulses. When the
difference between the two counter contents Z.sub.2 and Z.sub.4
reduces to zero, the sheet 24 is aligned with its front edge
parallel to the line of intersection S. The control device 20 then
switches off the control signal to the lifting device 19 of the
fourth pair of rollers 5, 11. Therefore, the respective pressure
roller 11 again presses the sheet against the fourth drive roller 5
and again produces the frictional connection of the fourth drive
roller 5 with the sheet 24, so that the sheet 24 leaves the
aligning device in an aligned condition. The adjustment signal is
simultaneously released on the adjustment signal circuit 42 and the
adjustment mechanism 41 returns both transportation devices to the
first position, so that the second transportation device takes on
the operation of further transporting the aligned sheet 24. If
present, the action of the braking device 28 of the fourth pair of
wheels 15, 17 is cancelled.
If the front longitudinal edge of the sheet 24 by chance reaches
the two selected pairs of rollers 3, 11 and 5, 11 at the same time,
the control device 20 must not engage, because the counter contents
Z.sub.2 and Z.sub.4 would always be equal during transportation.
The sheet 24 is, in this case, simply transported further on.
An analogous procedure takes place if the front edge of the sheet
24 first reaches the second pair of rollers 3, 11, or if, during
the alignment procedure, the sheet 24 is aligned, for example, by
the first and third or by the first and fourth drive groups or by
two adjacent drive groups.
The alignment device is advantageous in that it delays on the
leading side only for aligning the sheet 24, and, without stopping
the sheet 24, it aligns it at high speed. The accuracy of alignment
is determined by the resolution of the sensor (angular encoder 16).
The afore-described aligning device has, for example, four drive
groups and four counters integrated into the control device 20 and
associated with the respective drive groups. In other embodiments,
the alignment device has at least two pairs of rollers with the
sensors therefor and with the associated counters therefor in the
control device 20, and the number of these pairs of rollers is
determined by the width W and by the dimensions of the selected set
of sheets 24.
Instead of the independent adjustment device 41 (FIG. 4) associated
with each transportation device, it is also possible for a single
adjustment device 41 to be arranged so that it acts jointly on both
transportation devices.
In an alternative embodiment, the drive group which is of a design
such as that shown in FIG. 5 advantageously has pairs of rollers
with a direct, independent drive by means of a respective stepping
motor 45, for one roller of each pair. In this case there is no
braking device 28 (FIG. 2). In FIG. 5 the pair of rollers 2, 11 is
shown as an example of one of the pairs of rollers of the aligning
device.
The drive roller 2 is mounted on the drive shaft 1 of the stepping
motor 45. Each stepping motor 45 is connected to the control device
20 by way of its independent circuit 21, and is rotationally
stepped by means of a sequence of drive impulses. The drive shafts
1 of all pairs of rollers are arranged in juxtaposed relationship
and transverse with respect to the feed direction 25 (FIG. 1),
wherein the pairs of rollers are at the predetermined distance A
apart (FIG. 1) and the drive shafts 1 are aligned so that they are
coaxial to one another.
Instead of the angular encoder 16, an advantageous and
cost-effective sensor is an optic sensor without movable mechanical
parts. The elements 12 to 17 (FIG. 2) are abandoned with this
design, so that the drive groups are reduced to the pairs of
rollers.
The optic sensor shown in FIG. 6 is advantageously provided in the
feed direction 25 at a predetermined distance from the line of
intersection S (FIG. 1), and is connected, by means of a sensor
circuit 47, to the control device 20, to act as a light sensor
46.
A beam of light 48 from the light sensor 46 is arranged vertically
to the plane of alignment 6. A light transmitter 30 sends the beam
of light 48 through openings in the cover plate 26 and in the base
plate 9 to a light receiver 31. The analog sensor signals which are
produced by the light receiver 31 are conveyed to the control
device 20 by means of the sensor circuit 47, and are converted by
electronic control means 43 into digital values of intensity with a
resolution of e.g. 8 bits. As soon as the beam of light 48 is
impaired by the sheet 24, the light receiver 31 becomes partially
shaded, and the sensor intensity signal decreases.
The light sensors 46 form a row which is parallel to the line of
intersection S and which is transverse across the plane of
alignment 6. Seen in the feed direction 25 there is, for example,
at least one light sensor 46 behind each drive roller 2 to 5 (FIG.
1), possibly displaced laterally by a predetermined number of
millimeters, at a distance of some 20 mm from the line of
intersection S.
At a given moment, for example when the light of the first light
barrier 29 (FIG. 4) is interrupted by the sheet 24 coming into the
plane of alignment 6, the electronic control means 43 establishes
the value of intensity of each sensor signal, which value is stored
for each light sensor 46 in the value memory 44 as a starting
value.
In FIG. 6, the alignment process is shown using, by way of example,
the direct drive of FIG. 5. The control device 20 determines, on
the basis of the signals of the light barriers 29 (FIG. 4), as
described hereinabove, the two optimum drive groups or pairs of
rollers, and selects the two light sensors 46 which are disposed in
the feed direction 25 directly behind the selected pairs of
rollers. For each of the two selected light sensors 46, the
electronic control means 43 periodically measures the instantaneous
intensity value of the sensor signal, and determines its difference
from the stored starting value, the difference being compared to a
predetermined differential value for each light sensor 46. The
differential values are placed in the value memory 44, for
example.
The control device 20 simultaneously, and independently for each
stepping motor 45, generates uniform drive impulses, wherein the
pair of rollers convey the sheet 24 at the same speed as the
transportation devices, not shown here. The stepping motors 45 of
the pairs of rollers not selected have a high impedance on their
circuits, so that the respective pairs of rollers and the
non-selected stepping motors can rotate substantially freely. In
addition, the pressure roller 11 of these pairs of rollers can be
lifted.
As soon as the front longitudinal edge of the sheet 24 has been fed
as far as the light sensors 46, the beam of light 48 of at least
one of the two selected light sensors 46 is impaired. The
instantaneous value of intensity of the sensor signal of this light
sensor 46 decreases depending on the degree to which the light
receiver 31 is shaded. When the difference between the
instantaneous value of intensity and the starting value has reached
the predetermined differential value, the electronic control means
43 generates a displacement signal, in response to which the two
transportation devices release the sheet 24 for alignment. At the
same time, the control device 20 reduces the speed of the stepping
motor 45 associated with this light sensor 46, or it stops it and
brakes it by means of a permanent signal on the circuit 21.
If, for example, the drive roller 2 is braked, the sheet 24 twists
in the plane of alignment 6 about a pivotal point disposed beneath
the drive roller 2, until the light receiver 31 of the second light
sensor 46, selected by the control device, is shaded by the sheet
24 in such a way that the intensity values of the two sensor
signals are equal to the respective starting values less the
predetermined differential value.
The sheet 24 is thus aligned so that it is parallel to the line of
intersection S. The accuracy of alignment can be altered by the
selection of the differential value or by displacing a diaphragm
49, which is arranged in the path of light in front of the light
receiver 31 of each light sensor 46. Both selected stepping motors
45 in turn receive uniform drive impulses. The displacement signal
is switched off and the aligned sheet 24 is gripped by the second
transportation device to be conveyed further. Then, once none of
the light sensors 46 is covered, the electronic control means 43
once again determines the new starting values of the sensor
signals.
If, accidentally, the sheet 24 is drawn out of the beam of light 48
of the first selected light sensor 46 by its twisting movement, or
if the difference between the instantaneous intensity value of this
light sensor 46 and the starting value changes, the pressure roller
11 is lowered onto the drive roller 2 and/or the stepping motor 45
which has been stopped is driven forwards or backwards, until the
predetermined differential value is obtained again.
In a cost-effective embodiment of the sensors, optic sensors are
advantageously provided in the form of a predetermined number of
light barriers 29 (FIG. 4), and they are used to advantage to
control the aligning operation, enabling the light sensors 46 and
the sensor circuits 47 to be omitted. These selected light barriers
29 are hereinafter termed light sensors 50. As viewed in the feed
direction 25, the light sensors 50 are arranged directly in front
of each pair of rollers. A sensor beam 51 produces a signal in the
light receiver 31' of the light sensor 50, and this signal is
transmitted to the control device 20 by means of the control
circuit 32. The intensity values of these signals are used not only
qualitatively, together with those of the other light barriers 29,
for detecting the position of the sheet 24, but since they are
sensor signals they are also processed quantitatively to detect the
local feed in the control device 20.
For the light sensors 50, the control means 43 periodically
determines the above-described intensity values of the sensor
signals, until the light of one of the light barriers 29 is
interrupted for the first time, and the electronic control means
compares these intensity values with the starting values which have
been stored from the previous period.
As soon as the front longitudinal edge of the sheet 24 enters one
of the light barriers 29, the electronic control means 43 stores
the intensity values of the sensor signals from the previous period
in the value memory 44 in the form of starting values. The control
device 20 drives the stepping motors, and lowers the pressure
rollers 11 onto the drive rollers 2 to 5 (FIG. 1). For the purpose
of aligning the sheet 24, the control device 20, as described
hereinabove, uses the signals from the light barriers 29 as a basis
for determining the two optimum drive groups and the two associated
light sensors 50.
The sheet 24 is transported beneath the drive rollers 2 to 5, and
the intensity of the sensor beams 51 decreases to a minimum value
because of the complete obstruction by the sheet 24. The electronic
control means 43 compares the difference between the instantaneous
intensity values of the sensor signals of the two selected light
sensors 50, with the starting values.
As soon as the rear longitudinal edge of the sheet 24 partially
releases the sensor beam 51 in one of the light sensors 50, the
intensity of the respective sensor signal begins to increase again.
The control device 20 triggers the aligning process by delaying or
blocking the stepping motor 45 of that one of the pair of rollers,
whose difference between the instantaneous intensity value of the
sensor signal of its associated light sensor 50 and the respective
starting value has reached the predetermined differential value,
and the process ends when the predetermined differential value has
been reached for both selected light sensors 50.
* * * * *