U.S. patent application number 12/301298 was filed with the patent office on 2009-12-10 for method and device to discriminate two ends of an article from each other.
Invention is credited to Nerino Grassi, Antonio Magni.
Application Number | 20090301371 12/301298 |
Document ID | / |
Family ID | 38269050 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090301371 |
Kind Code |
A1 |
Grassi; Nerino ; et
al. |
December 10, 2009 |
METHOD AND DEVICE TO DISCRIMINATE TWO ENDS OF AN ARTICLE FROM EACH
OTHER
Abstract
The method comprises the steps of: generating a curve (PF) which
approximates the profile of one end (P) of an article; processing
said curve to determine whether it approximates the profile of said
first or said second end.
Inventors: |
Grassi; Nerino; (Mantova,
IT) ; Magni; Antonio; (Firenze, IT) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
P.O. BOX 9227, SCARBOROUGH STATION
SCARBOROUGH
NY
10510-9227
US
|
Family ID: |
38269050 |
Appl. No.: |
12/301298 |
Filed: |
May 3, 2007 |
PCT Filed: |
May 3, 2007 |
PCT NO: |
PCT/IT07/00328 |
371 Date: |
July 13, 2009 |
Current U.S.
Class: |
112/470.15 ;
112/475.12 |
Current CPC
Class: |
D05B 23/007
20130101 |
Class at
Publication: |
112/470.15 ;
112/475.12 |
International
Class: |
D05B 23/00 20060101
D05B023/00; D05B 39/00 20060101 D05B039/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2006 |
IT |
F12006A000118 |
Claims
1. A method for distinguishing from each other a first end and a
second end of an elongated article, said first end and said second
end having profiles differing from each other, the method
comprising the steps of: generating at least one curve which
approximates the profile of at least one of said ends; processing
said curve to determine whether said curve approximates the profile
of said first end or of said second end.
2. A method as claimed in claim 1, further comprising the steps of:
moving with respect to each other an article and an array of
photocells; gradually intercepting beams of the photocells with the
end of the article; determining a plurality of points which lie on
a profile that approximates the end of the article based on
relative positions taken by the article and the photocells and
electrical signals generated by gradual interception of the optical
beams of the photocells.
3. A method as claimed in claim 1, further comprising the steps of:
arranging a plurality of photocells according to a predetermined
arrangement; moving said arrangement of photocells and said article
with respect to each other along a direction of relative movement,
so that one end of said article intercepts the beams of said
photocells during the relative movement; determining the
coordinates of a plurality of points belonging to the profile of
said end of the article that intercepts said beams, on the basis
of: the relative positions taken by said article with respect to
said photocells during the reciprocal movement, and of the
arrangement of the photocells.
4. A method as claimed in claim 2, wherein each time a photocell is
intercepted by said article during said relative movement, the
relative position between article and photocells is detected, the
position of the intercepted photocell and the reciprocal position,
along said direction of relative movement, between photocells and
article defining the coordinates of a point belonging to said
profile.
5. A method as claimed in claim 1, further comprising the step of
generating said curve that approximates the profile of said end of
the article interpolating at least some of said points belonging to
the profile of said end.
6. A method as claimed in claim 5, wherein said points are
interpolated with linear segments.
7. A method as claimed in claim 5, wherein at least of the two end
points identified on said profile are discarded.
8. A method as claimed in claim 1, wherein said curve is processed
to determine the trend of the slope thereof, the first end and the
second end of said article being distinguished from each other as a
function of said trend of the slope.
9. A method as claimed in claim 1, wherein said curve is reproduced
in a system of coordinates with an axis on which the end points of
the curve lie.
10. A method as claimed in claim 1, wherein a difference between a
maximum value and a minimum value of a coordinate of said curve is
determined in a reference system, said difference forming a
parameter to distinguish said first end from said second end.
11. A method as claimed in claim 10, wherein said difference is
compared with a predetermined value; the end being recognized
according to whether said difference is greater or less than said
predetermined value.
12. A method as claimed in claim 10, further comprising the steps
of: determining the coordinates of two points spaced from each
other of said curve in a first reference system; identifying a
straight line joining said two points; taking said straight joining
line as one of the coordinates of a second reference system rotated
with respect to the first reference system; determining said
difference in said second reference system.
13. A method as claimed in claim 12, wherein said first and said
second reference systems are Cartesian reference systems, and
wherein said difference is represented by the difference between
the maximum value and the minimum value of the coordinate of the
points of said curve along a reference axis orthogonal to said
straight joining line.
14. A method as claimed in claim 1, wherein a derivative of said
curve is calculated.
15. A method as claimed in claim 14, wherein maximum and minimum
values of said derivative are determined.
16. A method as claimed in claim 15, wherein the difference between
said maximum and minimum values of the derivative are determined
and said first and second ends are discriminated on the basis of a
comparison between said difference and a threshold value.
17. A method as claimed in claim 1, wherein said article is moved
along a path and taken with one of the ends thereof to intercept
beams of photocells disposed in a fixed position.
18. A method as claimed in claim 1, wherein said article is made to
advance with respect to said photocells by a predetermined degree,
irrespective of the number of photocells intercepted.
19. A method as claimed in claim 1, further comprising the step of:
determining total number of photocells intercepted by the article
after the article has performed a predetermined movement subsequent
to interception of the first photocell; and comparing said total
number with a predetermined minimum number, wherein a first data is
obtained from said comparison to discriminate said first end from
said second end of the article.
20. A method as claimed in claim 1, wherein said article is one of
a stocking and a sock.
21. A method as claimed in claim 20, wherein said first end is an
elastic band end and said second end is a toe of said sock.
22. A method according to claim 1, wherein both ends of an article
of manufacture are detected and two curves approximating the
profiles of both said ends are generated; and wherein both said
curves are processed to determine whether they approximate the
profile of said first or said second end.
23. A device for distinguishing from each other a first end and a
second end of an article, the device comprising; an arrangement of
sensors to identify a plurality of points belonging to a profile of
at least one end of said article; and a control and processing unit
which, as a function of the coordinates of said points, detects
whether said plurality of points belong to said first end or to
said second end.
24. A device as claimed in claim 23, wherein said control and
processing unit is programmed so as to generate a curve that
approximates the profile of said end as a function of said points
identified by said sensors.
25. A device as claimed in claim 23, wherein said sensors comprise
an arrangement of photocells, and wherein handling members are
provided to move with respect to each other, along a direction of
relative movement, said article and said arrangement of photocells,
a system being provided to detect the reciprocal position between
said article and said photocells.
26. A device as claimed in claim 25, wherein said control and
processing unit is programmed to determine said plurality of points
associating the positions of the photocells that are intercepted by
said article, during the relative movement between the article and
the photocells, with the position taken time by time by the article
with respect to the photocells along said direction of relative
movement.
27. A device as claimed in claim 25, wherein said arrangement of
photocells comprises a linear string of photocells.
28. A device as claimed in claim 27, wherein said string of
photocells is disposed according to an alignment orthogonal to said
direction of relative movement.
29. A device as claimed in claim 23, wherein said control and
processing unit is programmed so that each time a photocell is
intercepted by said article during said relative movement, the
relative position between article and photocells is detected, the
position of the photocell intercepted and the reciprocal position,
along said direction of relative movement, between article and
photocells defining the coordinates of a point belonging to said
profile.
30. A device as claimed in claim 23, wherein said control and
processing unit is programmed to approximate the profile of said
end of the article interpolating at least some of said points
belonging to said profile.
31. A device as claimed in claim 30, wherein said control and
processing unit is programmed to interpolate said points through
linear segments.
32. A device as claimed in claim 30, wherein said control and
processing unit is programmed to discard the first and the last of
said points.
33. A device as claimed in claim 23, wherein said control and
processing unit is programmed to determine the trend of the slope
of the curve generated through said points identified by said
sensors, the first end and the second end of said article being
distinguished from each other as a function of said trend.
34. A device as claimed in claim 23, wherein said control and
processing unit is programmed to identify a straight line passing
through two end points of said curve, and to reproduce the
coordinates of said points in a reference system, a coordinate of
which is parallel to said straight line.
35. A device as claimed in claim 23, wherein said control and
processing unit is programmed to determine a difference between a
maximum value and a minimum value of a coordinate of said curve in
a reference system, and to distinguish the first end from the
second end on the basis of said difference.
36. A device as claimed in claim 35, wherein said control and
processing unit is programmed to compare said difference with a
predetermined value; and to distinguish the end according to
whether said difference is greater or less than said predetermined
value.
37. A device as claimed in claim 35, wherein said control and
processing unit is programmed to perform the steps of: determining
the coordinates of two points spaced from each other of said curve
in a first reference system; identifying a straight line joining
said two points; taking said straight joining line as one of the
coordinates of a second reference system rotated with respect to
the first reference system; determining said difference in said
second reference system.
38. A device as claimed in claim 37, wherein said first and said
second reference systems are Cartesian reference systems, and
wherein said difference is represented by the difference between
the maximum value and the minimum value of the coordinate of the
points of said curve along an axis of reference orthogonal to said
straight joining line.
39. A device as claimed in claim 33, wherein said control and
processing unit is programmed to calculate the derivative of said
curve.
40. A device as claimed in claim 34, wherein said control and
processing unit is programmed for the minimum and maximum values of
said derivative.
41. A device as claimed in claim 40, wherein said control and
processing unit is programmed to determine the difference between
said maximum and minimum values of the derivative and to check the
difference with a threshold value.
42. A device as claimed in claim 23, wherein said control and
processing unit is programmed to perform a first discrimination
between the first end and the second end on the basis of the total
number of photocells intercepted by said article after said article
has performed, with respect to said photocells, a relative movement
of a predetermined degree starting from the interception position
of the first photocell.
43. A device as claimed in claim 23, wherein said sensors are
disposed in fixed position and handling members cause translation
of the articles along a direction of movement towards said
sensors.
44. A device as claimed in claim 23, including further comprising
handling members to move said article with respect to said sensors
such that both ends of said articles are passed in front of said
sensors.
45. A method as claimed in claim 2, comprising the steps of:
arranging a plurality of photocells according to a predetermined
arrangement; moving said arrangement of photocells and said article
with respect to each other along a direction of relative movement,
so that one end of said article intercepts the beams of said
photocells during the relative movement; determining the
coordinates of a plurality of points belonging to the profile of
said end of the article that intercepts said beams, on the basis
of: the relative positions taken by said article with respect to
said photocells during the reciprocal movement, and of the
arrangement of the photocells.
46. A method as claimed in claim 3, wherein each time a photocell
is intercepted by said article during said relative movement, the
relative position between article and photocells is detected, the
position of the intercepted photocell and the reciprocal position,
along said direction of relative movement, between photocells and
article defining the coordinates of a point belonging to said
profile.
47. A device as claimed in claim 24, wherein said sensors comprise
an arrangement of photocells, and wherein handling members are
provided to move with respect to each other, along a direction of
relative movement, said article and said arrangement of photocells,
a system being provided to detect the reciprocal position between
said article and said photocells.
48. A device as claimed in claim 47, wherein said control and
processing unit is programmed to determine said plurality of points
associating the positions of the photocells that are intercepted by
said article, during the relative movement between the article and
the photocells, with the position taken time by time by the article
with respect to the photocells along said direction of relative
movement.
49. A device as claimed in claim 25, wherein said arrangement of
photocells comprises a linear string of photocells.
Description
TECHNICAL FIELD
[0001] The present invention relates to improvements to methods and
to devices for handling articles having a longitudinal extension
and two ends that differ from each other, for example and in
particular tubular knitted articles such as stockings or socks.
[0002] More specifically, the present invention relates to a new
method and a new device to detect, i.e. distinguish or discriminate
from each other two ends of the same article that differ in shape
from each other, such as, in particular although not exclusively, a
sock or stocking or other tubular knitted article.
STATE OF THE ART
[0003] In the manufacture of stockings and socks it is the trend to
increasingly use automation of production processes, starting from
knitting of the article up to sewing of the toe.
[0004] In this trend towards automation, one of the most critical
aspects is represented by the difficulty in automatically detecting
which of the two ends of a tubular article, such as a sock
delivered from a circular knitting machine with the toe open and
placed randomly in a container, is the band end and which is the
toe, to allow subsequent automated handling of the article in the
sewing machines.
[0005] Frequently, these operations are performed by hand: an
operator picks up the individual semi-finished articles from a
container, such as a basket, in which the semi-finished articles
coming from knitting machines are placed randomly with the toe end
still open, i.e. not yet sewn or linked. The operator then inserts
the semi-finished article onto a conveying tube oriented in the
correct direction, i.e. in the position required by the machinery
downstream, which will automatically perform sewing or linking of
the toe.
[0006] Attempts have been made to solve the problem of automating
detection, i.e. discrimination, of the elastic band end and toe of
semi-finished knitted articles. For example, U.S. Pat. No.
5,040,475 describes a complex machine that picks up individual
tubular articles from a container in which these are placed
randomly. By making the article follow a specific processing path,
detection means first detect the orientation of the tubular article
along the feed path, identifying whether the article is oriented
with the toe or with the elastic band end facing forward along said
path. After this has been detected, the tubular article is disposed
in an intermediate station, from which it is delivered in one
direction or in the opposite direction as a function of the
orientation with which it entered said station.
[0007] JP-A-7468502 and JP-A-1272801 describe other apparatus for
handling tubular articles such as stockings or socks in order to
orient them appropriately.
[0008] U.S. Pat. No. 6,719,577 describes a device that
longitudinally orients individual tubular articles coming from a
container, in which they are placed randomly.
[0009] EP-A-1221502 describes a device in which the individual
socks or other tubular articles are picked up from a container in
which they are placed randomly and are then oriented so that one of
the ends thereof is always the leading end by means of a particular
pneumatic path and using detection systems capable of
distinguishing the elastic band end from the toe of the article
through different stretch characteristics of the fabric.
[0010] U.S. Pat. No. 5,769,286 describes a spreading device for
longitudinally spreading socks or other tubular knitted
articles.
[0011] EP-A-178143 describes a further system to detect the
orientation of a tubular textile article by distinguishing the
elastic band end from the toe.
[0012] U.S. Pat. No. 5,511,501 describes a complex machine that
picks up individual tubular articles from a container, in which
they are placed randomly and separates them placing each individual
tubular article in a respective container of smaller dimensions.
Subsequently, each article is picked up from the respective
container of smaller dimensions and inserted in a specific
pneumatic path inside which the tubular article is oriented so that
it is delivered from the pneumatic path always with the same
orientation.
[0013] U.S. Pat. No. 5,884,822 describes a further device and a
method to pick up individual tubular articles from a container.
[0014] U.S. Pat. No. 5,992,712 describes yet another device to pick
up individual tubular knitted articles and orient them
appropriately.
[0015] Similar problems of orientation of tubular articles can be
found in the feed of stockings or socks to setting machines. For
example, In producing feminine stockings, there is the problem of
inserting each single stocking, with the toe already sewed, onto a
setting board and for this purpose the individual stockings must be
picked up from a container in which they are placed randomly to
insert them over the board.
[0016] The methods and devices currently known to automatically
distinguish from one another a first end and a second end of an
article, such as a tubular knitted article, are not particularly
reliable and are costly.
OBJECTS AND SUMMARY OF THE INVENTION
[0017] An object of an embodiment of the present invention is to
provide a method and a device that allow detection, i.e. automatic
distinguishing from each other of the two ends of an article, which
has ends that differ in shape from each other. According to a
particular aspect, the object of the invention is to provide a
method and a device which allow the toe or the elastic band end of
a sock or stocking to be distinguished and detected.
[0018] Although in the present description reference is frequently
made to the need to detect the toe of the sock still to be sewn, it
must be understood that the teachings of the present invention can
also be applied when the orientation of an already sewn article
shall be detected, for example to perform thereon further
operations required in the production and/or packaging cycle, such
as orienting the article correctly before it is placed on setting
boards, feeding the packaging machine or the like.
[0019] In substance, in an embodiment of the invention there is
provided a method for distinguishing from each other, i.e. for
discriminating one from the other a first end and a second end of
an elongated article, comprising the steps of: generating a curve
that approximates the profile of one of said ends; and processing
said curve to detect whether it approximates the profile of said
first or of said second end.
[0020] In substance, according to this aspect of the invention,
there is provided the generation by points of a curve that
approximates the real profile of one of the two ends of the
article, i.e. the one that is presented to the reading sensors. On
the basis of the conformation of this approximation curve the
device is able to detect whether this end is the first or the
second of two ends characterized by profiles which are
substantially different from each other, such as typically the toe
and the elastic band end of a sock.
[0021] According to an aspect of an embodiment of the invention,
the points of the approximation curve are each characterized by two
coordinates in a reference system, which can advantageously be a
Cartesian reference system, although it would also be possible to
use other reference systems, preferably two-dimensional, as the
article will normally have a flat conformation.
[0022] In practice, in a possible embodiment, the method provides
for moving with respect to each other an article and an array of
photocells, for example aligned along a straight line, to gradually
intercept the beams of the photocells with the end of the article.
On the basis of the relative positions taken by the article and the
photocells and of the electrical signals generated by gradual
interception of the optical beams of the photocells, a plurality of
points are determined lying on a profile that approximates the
profile of the end of the article. As the profiles of the two ends
differ from each other, the trends of the profiles reconstructed by
point approximation will also differ from each other. By processing
the curves that approximate these profiles the two ends can be
discriminated from each other.
[0023] According to a possible embodiment, the method provides the
steps of: arranging a plurality of photocells according to a
predetermined arrangement; moving said arrangement of photocells
and said article with respect to each other along a direction of
relative movement, so that one end of said article intercepts the
beams of said photocells during the relative movement; determining
the coordinates of a plurality of points belonging to the profile
of said end of the article that intercepts said beams, on the basis
of: the relative positions taken by said article with respect to
said photocells during the reciprocal movement, and of the
arrangement of the photocells.
[0024] Preferably, in an embodiment of the invention, each time a
photocell is intercepted by said article during said relative
movement, the relative position between article and said photocells
is detected, the position of the intercepted photocell and the
reciprocal position between photocells and article along said
direction of relative movement defining the coordinates of a point
belonging to said profile.
[0025] The curve that approximates the profile of the end of the
article that intercepts the photocells can be generated by
interpolating the points belonging to the profile of said end, for
example with a linear interpolation. More complex processing would
also be possible to obtain high degree interpolating polynomials
of, although this is not absolutely necessary. An approximation
through segments of straight line that join together the various
points identified on the profile of the end of the article is
usually sufficiently accurate. Therefore, in the present
description and in the appended claims, curve is intended in
general also as a broken line, obtained for example from the
sequence of the portions of straight lines that join the points
identified on the profile of the end of the article.
[0026] In a possible embodiment of the method according to the
invention, the curve that approximates the profile of the end of
the article read by the photocells is processed to determine the
trend of the slope thereof, the first end and the second end of
said article being detected and distinguished as a function of this
trend of the slope. This can, for example, be performed by
calculating the derivative of the curve obtained through the points
identified on the end profile. The derivative can also be
calculated by points, and therefore be constituted by a broken line
that approximates, even roughly, the trend of the derivative.
[0027] In a particularly simple embodiment, although sufficiently
accurate in many cases, the maximum and minimum values of the
derivative are determined and the difference is calculated. The two
ends of the article are detected, i.e. discriminated from each
other, on the basis of a comparison between the maximum and minimum
value of the derivative and a threshold value. This is possible
thanks to the fact that, for example in the case of socks, the toe
has a trend with a highly variable curvature, and therefore with a
derivative that takes values differing greatly from one another
along the extension of the profile representing the end, while the
greater part of the band end is instead normally more or less
rectilinear, and therefore its derivative has a flat trend.
[0028] According to another aspect, the invention relates to a
device to distinguish from each other, i.e. to discriminate from
one another a first end and a second end of an article, comprising
an arrangement of sensors to identify a plurality of points
belonging to the profile of an end of said article, and a control
and processing unit which, as a function of the coordinates of said
points, detects whether they belong to said first end or to said
second end.
[0029] In practice, the control and processing unit can be
programmed so as to generate a curve that approximates the profile
of said end as a function of said points identified by said
sensors.
[0030] According to a preferred embodiment of the invention, the
sensors comprise an arrangement of photocells, and there are also
provided handling members to move with respect to each other, along
a direction of relative movement, said article and said arrangement
of photocells, with a system to detect the reciprocal position
between said article and said photocells. The control and
processing unit can be programmed to determine the plurality of
points associating the positions of the photocells that are
intercepted by said article, during the relative movement between
the article and the photocells, with the position taken each time
by the article with respect to the photocells along said direction
of relative movement.
[0031] The arrangement of photocells can be of various types.
Preferably, they will be disposed according to a linear string of
photocells. This string of photocells is preferably disposed
according to an alignment orthogonal to said direction of relative
movement. In this way, a series of points in a system of Cartesian
coordinates is obtained simply by translating the article and the
array of photocells with respect to each other.
[0032] Advantageously, the control and processing unit can be
programmed so that each time a photocell is intercepted by said
article during said relative movement, the relative position
between article and photocells is detected, the position of the
intercepted photocell and the reciprocal position between article
and photocells along said direction of relative movement, forming
the coordinates of a point belonging to said profile.
[0033] Further advantageous features and embodiments of the method
and of the device according to the invention are indicated In the
appended claims and will be described in greater detail hereunder
with reference to non-limiting possible embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The invention will be better understood by following the
description and accompanying drawing, which shows practical
non-limiting embodiments of the invention. In the drawing:
[0035] FIG. 1 shows a diagram of the device in a front view;
[0036] FIG. 2 shows a section according to II-II in FIG. 1;
[0037] FIGS. 3A-3D schematically show a sequence of movement of an
article like a stocking or sock, which is positioned with the toe
facing the optical reading system;
[0038] FIG. 4 shows a diagram of the profile of the toe of the
article and the derivative thereof;
[0039] FIGS. 5A-5B schematically show a sequence of movement of an
article which is positioned with the band end facing the optical
reading system;
[0040] FIG. 6 shows a diagram of the profile of the band end and
the derivative thereof;
[0041] FIG. 7 schematically shows a different method of processing
to discriminate the first and the second end of an article from
each other, on the basis of the trend of a curve that approximates
the profile of the end of the article viewed by the sensors of the
device;
[0042] FIGS. 8 and 9 show a further embodiment of the method
according to the present invention; and
[0043] FIGS. 10A and 10B show a modified embodiment of the
invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0044] FIGS. 1 and 2 very schematically show the device according
to the invention. The numeral 1 indicates a supporting surface of
an article M, which in the example illustrated is a sock with a toe
P to be sewn and an elastic band end B.
[0045] Above the supporting surface 1, which can be constituted by
a conveyor or the like, there is disposed a movable element 3, such
as a presser provided with a lifting and lowering movement fv and a
translational movement according to the double arrow fo. The
presser 3 is moved according to the double arrow fv by a
piston-cylinder actuator 5, in turn carried by a slide 7 sliding in
a guide (not shown). The movement according to fo of the slide 7
along the guide is controlled by a belt 9 driven around two pulleys
11, 13 the second of which is motorized by means of a motor 15. The
numeral 17 indicates an encoder or other angular transducer that
allows detection of the movement of the motor 15 and consequently
of the slide 7 according to the double arrow fo. Instead of an
encoder associated with the motor 15, any other means could be used
to detect the movements of the slide 7 or even of the presser 3
directly. This detection means (the encoder 17 in the example) is
connected to a programmable control unit, indicated with 19,
interfaced, for example, with a monitor 20 or other user interface.
The control unit 19 can be provided with a keypad and other
peripherals and units typical of a programmable control device
usable to control the device.
[0046] The numeral 21 indicates a system of photocells comprising a
linear array of photoemitters and a linear array of photoreceivers,
the two arrays being parallel to and opposite each other. In the
drawing the numeral 23 indicates a first of said arrays, for
example the array of photoemitters, while the numeral 25 indicates
the opposite array, for example the array of photoreceivers. As
will be apparent from the description below of two operating
cycles, the arrangement is such that the article M is made to
translate with one or other of the ends thereof facing towards the
detecting or reading device 21, to intercept with said end the
beams of the photocells to detect whether the end that intercepts
the photocells is the band end B or the toe P.
[0047] As in general the two ends P, B of the article M have
profiles which differ from each other, by feeding the article M
gradually with the end thereof under the linear array of photocells
of the reading system 21 it is possible to read and detect the form
of the profile of said end, using the following data: the position
in space of the photocells; the signal of each photocell; the
position of the presser 3 along the direction of movement fo and
consequently the position of the article along the direction of
feed according to the arrow F.
[0048] FIGS. 3A-3D and 4 show detection of a toe P of the article
M. These figures show four relative positions of the toe P with
respect to the array of photocells 21, indicated in these diagrams
with X1-X8. In the examples eight emitter-receiver pairs are shown,
but it must be understood that a different number of photocells can
also be used. The number is dictated by requirements of cost and
sufficient detection accuracy. In the position in FIG. 3A none of
the photocells is intercepted by the toe P of the article. In FIG.
3B the photocell X4 is intercepted, while in the position in FIG.
3C the position photocells X3-X6 are intercepted. In FIG. 3D the
position photocells X2-X7 are intercepted.
[0049] The positions of the photocells X1-X8 represent a
corresponding number of values on the axis of the abscissas of a
Cartesian diagram reproduced in FIG. 4, while the positions of the
article M, determined by the encoder 17 associated with the motor
15, represent the ordinates. By reproducing on a diagram X,Y (FIG.
4) in the abscissas the coordinates corresponding to the photocells
that for each discrete value of Y (position of the article) are
intercepted, a set of points P1-P6 is obtained which, interpolated,
approximately provide the profile PF of the end of the article.
More specifically, the point P4 is defined by the coordinate on the
axis of the abscissas (x) defined by the position of the photocell
X4 (the first which is intercepted) (FIG. 3B) and by the coordinate
Y0. It is not necessary to know the absolute value of the
coordinate Y0 on the axis of the ordinates, as what matters is the
position of the coordinates on said axis of the subsequent points
of the profile. As the article M advances, the position photocells
X3, X5 are intercepted at the value of the ordinate Y1, followed by
the photocell X6 (FIG. 3C) at the ordinate Y2 and finally the
photocell X7 at the ordinate Y3 (FIG. 3D). In this way the points
of the profile PF are obtained. The value of the ordinate Y0 can be
taken as the zero value and the subsequent ordinates are determined
on the basis of the relative movement performed by the presser 3
and therefore by the article M.
[0050] The same occurs in the case in which the end that is read by
the array of photocells is the band end. This case is represented
schematically in FIGS. 5A and 5B, and FIG. 6 shows the curve PF
which is obtained by appropriately interpolating the points
identified by the coordinates X,Y thus determined. The points on
the diagram are again indicated with P1-P6.
[0051] It can be seen that the diagrams PF in FIGS. 4 and 6 have a
highly different shape in the two cases. In particular, it can be
seen that the interpolating curve in FIG. 4 has a much more
variable slope with respect to the curve in. FIG. 6. Having
generated the interpolating curve, with any suitable criterion, the
derivative can be calculated. The trend of the derivative (again
reproduced for the two cases in the diagrams in FIGS. 4 and 6 and
indicated with D) represents the variation of the slope of the
curve and is therefore indicative of the greater or lesser
curvature of the profile PF detected by the photocells.
[0052] The derivative can be used, for example through a simple
criterion of comparison with a threshold value, to detect i.e. to
distinguish the toe from the band end. In fact, it is for example
possible simply to determine the maximum and minimum values of the
derivative and calculate the difference. The difference in value
can be compared with an experimentally determined threshold. If the
difference in value exceeds the threshold value, this is indicative
of a curved profile and consequently identifies a toe, while if the
difference in value does not exceed the threshold, this is
indicative of a flat profile and consequently identifies a band
end.
[0053] Experimentally, it is easy to identify a threshold value
according to which the difference between maximum and minimum value
of the derivative is significantly below and above this threshold
for band end B and toe P profiles of the article, respectively.
[0054] FIG. 7 schematically shows a different embodiment of the
invention. In substance, in this case the device remains
substantially as described with reference to FIGS. 1 and 2. The
methods with which the points P1-Pn belonging to the profile of the
end of the article that is read by the sensors, for example
constituted by the photocells 23, 25, also remain substantially the
same. Conversely, the methods with which the data representing the
points belonging to the approximation curve are processed
change.
[0055] FIG. 7A represents a Cartesian reference system, the
abscissas and ordinates of which are represented respectively with
X and Y. P1-P5 indicate points belonging to the profile of the end
of the article M. In this example five points are shown, but it
must be understood that the number of points can vary (in this as
in the previous embodiment) on the basis of the conformation of the
system and of the shape of the article.
[0056] In this embodiment, the curve on which the points P1-P5 lie
is sloping with respect to the coordinates X-Y. This means that the
article has reached the photocells 23, 25 in an inclined and not in
a straight position. This embodiment includes a preliminary step to
process the data detected to correct this error. In substance, the
curve on which the points P1-P5 lie is reproduced in a system of
reference X'-Y' rotated by an angle .alpha., the straight line X'
of the abscissas of which is more or less orthogonal to the axis of
the article, consequently passing through the end points P1, P5 of
the curve. Indicating with (a) and (b) the differences between the
abscissa and the ordinate of the point P5 and the abscissa and the
ordinate of the point P1, therefore
.alpha.=arctan(b/a)
the equations that transform the coordinates of the points P1-P5
from the system X-Y to the system X'-Y' are:
X'=X cos(-.alpha.)-Y sin(-.alpha.)
Y'=X sin(-.alpha.)+Y cos(-.alpha.)
[0057] FIG. 7B represents the curve obtained by interpolation of
the points P1-P5 in the reference system X'-Y', where the
coordinates have been placed in horizontal and vertical position
respectively. It is understood that this preliminary operation to
correct the slope of the approximation curve of the profile of the
end of the article (and consequently the interpolation curve of the
points belonging to the profile) can be performed as a preliminary
step also in the embodiment described with reference to FIGS. 3 to
6.
[0058] Once the curve has been reproduced in the reference system
X'-Y', the difference between the maximum value and the minimum
value of the ordinates of the points P1-P5, indicated in FIG. 7B
with .DELTA.Y', can be determined. As the two ends of the article M
(toe P and band end B) are characterized by profiles that differ by
degree of curvature, the value .DELTA.Y' of the difference of
ordinates will differ significantly for the two ends. FIG. 7B
reproduces with a broken line the curve approximating the band end
B of the article and AC indicates a comparison value determined
experimentally on the basis of analysis of the shape of the ends of
an adequate number of articles. The device can be programmed so
that all the ends of articles in which .DELTA.Y'>.DELTA.C are
classified as "toes" and all the ends of articles in which
.DELTA.Y'.ltoreq..DELTA.C are classified as "band ends".
[0059] FIGS. 8A and 8B describe an improved procedure or method to
discriminate between toe and band end, which prevents
discrimination errors due, for example, to interception of the
photocells by the side of the article rather than by the end
profile (band end or toe) if the article is positioned with a
particularly high inclination with respect to the direction of
movement.
[0060] In FIGS. 8A and 8B, B indicates the band end of the article
M, F0, F1 . . . FN indicate the photocells in number equal to N+1
and X, Y or X', Y' indicate the Cartesian reference axes with
respect to which the coordinates of the points belonging to the
profile of the end (toe or band end) of the article M that
intercepts the photocells are identified (the system X,Y is
constituted by axes parallel respectively to the alignment of the
photocells and to the relative movement between photocells and
article, while the system X'Y' is the one rotated by an angle
corresponding to the angle of inclination, with respect to the axis
X, of the line joining the first and the last point of the profile
considered for discrimination, according to the criterion of
rotation described with reference to the previous embodiment).
[0061] FIGS. 8A and 8B represent an article M (such as a sock) from
the side of the band end while it passes in front of the photocells
slightly inclined with respect to the direction of relative motion,
represented by the arrow F. The amount of movement (H), i.e. the
relative movement of the article with respect to the photocells, is
established in advance and the article moves forward by said amount
irrespective of the number of photocells effectively intercepted at
the end of this movement. The amount H is preferably just
sufficient to allow the profile of the band end B of an inclined
article (angle .beta. in the figure) to pass, to prevent a high
number of photocells from intercepting the side of the article in
the event of an inclined article. The amount (H) is determined
experimentally on the basis of the type of article.
[0062] As can be easily understood by observing FIG. 8A, in order
not to distort the analysis, not all the points of the profile that
have been intercepted by the photocells must be considered, but it
is advisable to discard the two end points, as the point that
intercepts the photocell marked with F8 would cause a distorted
signal.
[0063] To discard both the first and the last point of the profile
an algorithm described below can be used. To understand the
following, it must be mentioned that before starting a detection
operation the variables involved in the calculations are put equal
to zero and ordered from 0 to N (with N+1 equal to the number of
photocells) in the sense that the first photocell is assigned the
input 0 of a PLC or other programmable control unit and the
corresponding captured ordinate is Y0; the second photocell is
assigned the input 1 and the ordinate Y1 and so forth up to the
last with input N and ordinate YN. Moreover, the second point of
the profile intercepted by the photocells is indicated with n1 and
the second last point with n2 respectively.
[0064] This being stated, the detection algorithm is developed in
the following steps:
Assignment of the Variables
[0065] 1) at the start of the procedure all the variables Yj and
all the pointers j and z are reset, where j is the pointer or
counter relative to the photocells (from 0 to N) and z is a flag
required for correct execution of the algorithm, and which can take
two alternative values: 0 or 1; [0066] 2) after resetting the
values of the variables the relative motion between photocells and
article M is started. It is necessary to take into account that the
distance between the article and the photocells is not known in
advance and therefore the movement continues until the profile of
the article intercepts the first photocell; [0067] 3) at the first
signal (interception of the first photocell by the article) the
position Yj is captured (as according to the aforesaid j=0). This
value is considered as the "zero" value of the relative movement,
in the sense that the final value of the movement is set at this
point. As H is the maximum travel between the instant in which
interception starts and stopping of the relative movement between
article and photocell, consequently [0068] 4) the position at which
the motor that feeds the article stops is determined equal to the
sum Yj+H [0069] 5) during the movement from Y0 to Y0+H the
interception positions of the profile (ordinates Yi) are captured
and memorized. I.e.: during the relative movement equal to the
travel H the values of the relative movement corresponding to each
single interception signal of a photocell are collected; [0070] 6)
the motion is stopped at the position Y+H. Definition of the
Polygonal that Approximates the Profile: The polygonal is
determined considering the coordinate points Yj excluding the first
and the last point intercepted. With reference to FIG. 8A, the end
points of the polygonal which must be considered are the points n1
and n2 (second and second last). The procedure to discard the point
preceding n1 and the point subsequent to n2 is as follows: [0071]
7) reading of the ordinate Yj indicated by the pointer j [0072] if
Yj=0 and z=0, skip to step 8 [0073] if yj>0 and z=0, skip to
step 9 [0074] if Y=0 and z=1, skip to step 9 [0075] if Yj>0 and
z=1, skip to step 8 [0076] 8) j=j+1 and return to step 7 [0077] 9)
if z=0, n1=j+1, z=z+1, skip to step 8 [0078] if z=1, n2=j-1, skip
to step 10 At the end of this iteration the points n1 and n2 have
been identified and consequently the polygonal that approximates
the profile intercepted by the photocells is given by the totality
of the points n1, n2 and intermediate points. In the subsequent
step analysis of the polygonal is performed. The coordinates in the
system X, Y of the points n1 and n2 respectively are indicated with
Xn1, Yn1, and with Xn2, Yn2. [0079] 10) A=arctan
((Yn2-Yn1)/((Xn2-Xn1)) [0080] 11) rotation of the coordinates (the
equations already described with reference to the preceding example
are applied) [0081] 12) search for the minimum and maximum values
of the ordinates Y [0082] 13) comparison with the value set to
assign the type of profile: if the difference between maximum and
minimum value of the ordinates Y' is greater than the predetermined
value, the profile intercepted belongs to a toe, otherwise it
belongs to a band end.
[0083] It is understood from the algorithm described and from FIG.
8 that by discarding the first and the last point identified by
passage of the profile of the article in front of the photocells,
the end identified is prevented, for example in the case in FIG. 8,
from being interpreted as a toe, while it is actually a band end.
Due to the inclination between axis of the article and direction of
motion, this error could derive from interception of the point n3
belonging to the side of the article by the photocell F8.
[0084] In the embodiment previously described it was assumed that
the article M will be positioned with a toe P always substantially
flattened frontally, i.e. with an arched profile as shown in the
figures. However, this is not always the case and in particular
according to how the article is handled and flattened, it can be
positioned lying on one side, so that the toe P does not have the
arched profile, shown for example in FIG. 2, but a stepped profile,
as shown in FIG. 9, with an approximately rectilinear area.
[0085] This could cause difficulty in interpretation, i.e. a risk
of incorrect detection, as both the toe and the band end would in
this case have rectilinear profile portions, although of different
lengths, if the amount H of reciprocal movement between article M
and photocells is below the length L. On the other hand, in the
case of inclined articles (angle .beta. FIG. 8), to prevent an
excessive number of photocells from being intercepted by the sides
of the article rather than by the end profile, the amount H must be
limited.
[0086] To avoid an error in discriminating between toe and band end
in the case in which the toe is positioned as shown in FIG. 9,
rather than using the criterion of discrimination described above,
based on the difference between maximum and minimum height with
respect to the system of reference X', Y', of the points of the
profile, a toe is discriminated from a band end by counting the
number of photocells that have intercepted the profile, as in the
toe these are undoubtedly fewer than those involved in a band end.
According to an improved embodiment of the method of the present
invention, therefore, after performing the movement of a degree H
between article and photocells, in the first place the total number
of photocells intercepted by the profile of the article is
determined. If this is below a given minimum number, then the end
that has passed before the photocells is a toe. If the number of
photocells intercepted is higher than said given minimum, then the
discrimination procedure described is performed on the basis of the
difference of coordinates.
[0087] In conclusion, the more efficient system comprises both the
criterion of rotation of the coordinates of the profile and
therefore of comparison between Ymax and the set value, and the one
that takes account of the number of photocells that intercept the
profile.
[0088] In the above described embodiments, only one end of the
article is caused to interact with the photocells or other sensors,
in order to recognize whether said end is the first end or the
second end of the article. Once said end is recognized as being the
first end (for example the toe), the other end is assumed to be the
second end (for example the band end). This way of performing the
method is not however the only possible alternative. Indeed, e.g.
in order to achieve a higher degree of accuracy and reproducibility
of the method, or else in order to reduce the risk of
misinterpretation of the detected data, in an improved embodiment
of the method according to the invention both ends of one and the
same article are subject to detection by means of the same or of
two different sensor arrangements.
[0089] In one possible embodiment, described here below with
reference to FIGS. 10A and 10B, the device includes a single linear
array of photocells 21. In an embodiment, said photocells include
photoemitters 23 and photoreceivers 25 arranged on two sides of an
intermediate position where the article of manufacture M is caused
to pass, as described above. However, in a different embodiment
(which can be applied in the above disclosed embodiments as well)
the photocells can include photoemitters arranged on the same side
of e.g. a reflective surface or conveyor on which the article M is
placed.
[0090] Two handling members 5A and 5B are arranged, one on each
side of the photocells arrangement 21. In an embodiment the members
5A, 5B are movable in a vertical direction according to double
arrow fv and are suspended from a supporting structure
schematically shown at 8. In an embodiment the two handling members
5A, 5B include respective endless belts 6A, 6B, entrained around
rollers (three for each handling member in the example shown). At
least one of each three-roller cluster is motorized while the
others can be idle. The motorized roller causes the respective belt
6A, 6B to move according to double arrow fo.
[0091] An article of manufacture M having a first end (e.g. a toe
end P) and a second end (e.g. a band end B) is moved under the
handling members 5A, 5B. As in the previous examples the
orientation of the article M is random, i.e. it is not known
beforehand which is the toe end and which is the band end. In the
example shown the band end B is on the left-hand side of the figure
and the toe P is on the right-hand side.
[0092] Once the article M is placed underneath one or the other of
the two members 5A, 5B, the members are lowered (arrow fv), such
that at least one of said handling members touch the article M and
presses it against the supporting surface 1, for example a conveyor
moving orthogonally to the figure. One or both belts 6A, 6B are put
in motion in the same direction, for example such as to push the
article towards the left-hand side. During this motion one of the
ends of the article pass between the surface 1 and the emitters 23,
i.e. intercepts the emitter-receiver pairs 23, 25. In the example
shown, in the position shown in FIG. 10A the band end B has just
intercepted the photocells. Once this happened, the device is able
to determine, on the basis of one of the above disclosed modes,
whether the end which just passed between the photoemitters 23 and
photoreceivers 25 is the first or second end. The motion of the
belts 6A, 6B can be reversed or continued (depending on the
starting position of the article) such that also the second end
passes through the photocells 21. The device determines whether the
second end is a band end or a toe end, adopting one of the above
disclosed methods.
[0093] If the two readings are consistent (i.e. if the first
reading determines that the end first detected is e.g. the band
end, as in the example shown, and the second is the toe end) then
the orientation of the article M is properly determined. If,
however, the readings are inconsistent (e.g. if both ends are read
as being toe ends or both as being band ends), then the control
unit considers the reading as aborted and discards the article. The
article can in such case e.g. be resent to the basket or other
container from which it is picked up again for a subsequent
detection process.
[0094] Errors (double-toe detection or double-band end detection)
can be caused e.g. if the article is not properly spread on the
surface 1.
[0095] If both ends are read the system reduces the chance of
errors to a really negligible value, even if a somewhat less
reliable algorithm is used to discriminate between toe and band end
portions respectively. Thus a reliable system can be implemented
using a substantially simple algorithm.
[0096] It is understood that the drawing only shows an example
provided purely as a practical embodiment of the invention, which
can vary in forms and arrangements without however departing from
the scope of the concept underlying the invention. Any reference
numerals in the appended claims are provided to facilitate reading
of the claims with reference to the description and to the drawing,
and do not limit the scope of protection represented by the
claims.
* * * * *