Sewing machine workpiece edge alignment apparatus

An installation for linear treatment, such as the edging of textile pieces. It comprises a sewing machine, equipped with a feed dog/presser foot system, a work table which supports the piece during edging, a detection device and two recentering means controlled together or independently of each other by the instructions given by the detection device. The two recentering means consist, on the one hand, of an active guide placed immediately in front of the presser foot and ensuring displacement of that part of the piece located near the presser foot, substantially transversely with respect to the line of stitching, and, on the other hand, of a mobile support placed upstream of the active guide presenting a mobile flat surface, on the same plane as the work table.

BACKGROUND OF THE INVENTION 
The present invention relates to apparatus for stitching along the line 
parallel to an edge of a supple workpiece and comprising: 
a machine such as a sewing machine; 
a drive device for moving the workpiece, including the feed dog and 
pressure foot of the sewing machine; 
a worktable for supporting the workpiece; 
and a correction device for detecting the workpiece and including 
recentering means controlled by the detection device for moving the 
workpiece in the desired manner. 
French Pat. No. 2,525,008 discloses recentering means which is comprised of 
a turntable having a plurality of shoes applied to the workpiece during 
treatment. The installation described therein is complicated and required 
that the workpiece be held flat to prevent creasing. 
French Pat. No. 2,457,920 discloses recentering means rotated by drive 
means under the control of an action device to follow a curved edge but is 
not cable of following a changing profile such as one having a successive 
convex/concave curvature nor is the apparatus usable to treat workpieces 
of reduced dimensions. 
The present invention overcomes the disadvantages of the prior art by 
providing recentering means comprising an active guide and drive means 
cooperating to move the workpiece. 
The workpiece is initially delivered to the worktable whereupon the 
detection device controls the recentering of the workpiece by displacement 
of the active guide and the movable support either alone or in 
combination. The aforesaid installation compared with conventional 
installations provide more precise recentering. 
The detection device comprises first and second detectors arranged between 
the drive device of the sewing machine and the active guide. A third 
detector is located upstream relative to the active guide and remote from 
a reference line parallel to the treatment line and tangential to the edge 
of the workpiece at the point of treatment. 
In those cases where the workpiece has a convex edge, four detectors are 
employed, the fourth detector being located upstream relative to the 
active guide and to the left of the aforesaid reference line. 
In a preferred embodiment, the first two detectors are arranged to be 
symmetrical with respect to the reference line. Similarly the third and 
fourth detectors are placed so that they are symmetrical with respect to 
the reference line for cases in which four detectors are employed. 
The active guide includes a rotating member comprised of a plurality of 
disc-shaped elements arranged for movement about the periphery of a 
rotating member and engaging the workpiece to impart movement thereto. 
The rotatable support rotates about a perpendicular axis, as is described 
in French Pat. No. 2,457,920 and may alternatively consist of an endless 
belt whose upper run lies in the plane of the worktable and forms a 
continuation thereof. 
There exist certain situations in which the workpiece recentering means 
operates in an unsatisfactory manner. As one example, when the edge of the 
workpiece lies to close to a portion of the sew line, the recentering 
means automatically follows the edge of the workpiece without stopping the 
sewing operation at the spot desired for the end of the sewing operation. 
As another example, in cases where supple workpieces formed of knitted 
fabrics undergo considerable rotation, the knitted fabric becomes 
deformed. These problems are incapable of being overcome by the 
conventional apparatus described herein. 
The present invention overcomes the above-mentioned problems by providing a 
counting device for counting the stitches along the selvage which may be 
generated by the reciprocating action of the sewing machine needle arm. 
The counting device controls the action of the recentering means by holding 
the turntable drive means and lifting the active guide when the counting 
devices reaches the predetermined count which is a function of the length 
of the sew line. 
The digital count may correspond to the number of stitches necessary for 
providing a seam along a distance slightly less the total length of the 
edge to be sewn. The detection system may be of the reflector type which 
is mounted on the active guide in such a way as to be positioned opposite 
a photoelectric sensor. 
When the count reaches a given number, the counting device stops the 
turntable drive means and lifts the active guide to permit linear 
stitching. 
For safety purposes, a retractable guide stop may be added to the counting 
device to permit the end of the sewing operation while the edge of the 
workpiece is guided by the guide surface of the guide stop. 
In a second embodiment, the drive device for displacing the workpiece may 
be comprised of means for varying the advance of the workpiece arranged at 
a location upstream relative to the point of treatment. 
In particular, in the case of a seam, the sewing machine comprises a 
differential feed dog whose adjustment is controlled during sewing by the 
counting device. This embodiment is particularly well adapted to control 
the deformation of a knitted fabric during sewing. For a given type of 
workpiece, of which the location of the wales of stitches with respect to 
the edge to be sewn is known, the adjustment of the differential feed dog 
is predetermined as a function of the expected deformation of the knitted 
fabric during sewing; and adjustment during sewing is controlled by the 
counting device as a function of the number of stitches counted from the 
beginning of sewing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, the installation is adapted to edge textile 
workpieces 1 being made up, for example, to elasticate or similarly treat 
underpants along a leg opening. This installation comprises a sewing 
machine 2, especially equipped to effect the edging operation, with its 
drive device comprising a feed dog 33 and a presser foot 3, and the needle 
4 which effects stitching along the stitching line AA' constituting the 
line of treatment in this embodiment. The stitching must be made at a 
certain distance e from the edge 5 to be sewn. At the point of stitching, 
the edge of workpiece 1 is located dotted line BB', parallel to the 
stitching line AA' and spaced therefrom by the distance e towards the 
right in the direction of advance of the workpiece 1 in the course of 
edging. 
Around the sewing machine 2, the work table 6 supports the workpiece 1 
during and after the edging operation. A part 7 of the table 6 is mobile 
and is rotatable about axis 6 which is perpendicular thereto: this mobile 
part, hereinafter referred to as turntable, has an annular form, 
surrounding the sewing machine 2 and a fixed part 8 of the work table 6. 
The turntable is driven in one direction or in the other by drive means 
whose structure is disclosed in U.S. Pat. No. 4,312,281 which discloses 
bi-directional drive means. Control means for such turntable drive means 
are also known from U.S. Pat. No. 3,742,878, which patents are 
incorporated herein by reference thereto. 
The active guide 9 is positioned upstream of the presser foot 3, below 
reference line BB' and level with the fixed part 8 of the work table. This 
guide 9, as illustrated in FIG. 5, is constituted by a rotatable member 10 
rotating about an axis 11 and bearing on its periphery ten discs 12, free 
to rotate in recesses 13 made radially in the member 10. Guide 9 is placed 
above the table 6 so that it abuts on the workpiece 1 during edging and so 
that the plane perpendicular to the table 6 passing through its axis of 
rotation 11 is parallel to the stitching line AA'. The action of 
transverse displacement of discs 12 during rotation of the member 10 is 
effected along line CC' perpendicular to the axis of treatment AA' in a 
zone 17 located at a distance D3 from the reference line BB'. Distance D3 
is a function of the behaviour of the material constituting the workpiece 
1 and also of the minimum radius of curvature of the workpiece; in any 
case, D3 must be sufficient for the active guide 9 always to be in contact 
with workpiece 1 during the edging operation, as long as said workpiece 
has not gone beyond line CC'. 
Two photoelectric detectors 14 and 15 are placed on either side of the 
reference line BB' in a plane perpendicular to said line located between 
the presser foot 3; one, 14, to the right, the other, 15, to the left of 
line BB', they are placed symmetrically with respect to said line and 
their spaced apart relationship defines the width of the correct guiding 
zone and is a function of the distance e admitted for the edging 
operation. Another photoelectric detector 16 is placed above line BB' and 
upstream of the active guide 9: it is spaced apart from line BB' by a 
distance D1 which is much greater than that existing between the detector 
14 and the line BB' and which is a function of the minimum radius of 
curvature of the workpiece 1 to be edged: the greater the curvature of the 
edge to be treated, the greater the distance D1 will be. Each of the three 
detectors 14, 15, 16 is designed to emit a signal when the workpiece 1 is 
present thereabove. The information emitted by the three detectors, 
concerning presence or absence of the workpiece 1 at each of their 
positions, makes it possible to know the exact position of the workpiece 1 
in front of the sewing head, and to control the turntable 7 and/or the 
active guide 9 to orient the workpiece 1 during the whole of its edging, 
in a predetermined program. 
According to a first embodiment of the counting device, the installation 
comprises a sensor 30 placed in the upper part of the needle arm or bar 4' 
and capable of counting the number of "rise" and "fall" movements of said 
arm 4' during the stitching operation and therefore the number of 
stitches. Counting devices are generally known from U.S. Pat. No. 
4,359,953. A double-acting air cylinder or jack 18, fast with the sewing 
machine 2, is connected to the support 19 of the active guide 9. 
Conventional reciprocating jacks are already known and have been utilized 
in similar environments as described as for example in U.S. Pat. Nos. 
3,889,614 and 4,312,281. The latter comprises a horizontal axis of 
rotation 21 for lifting and lowering part 10 of guide 9 under the action 
of jack 18. Connection between the rod of jack 18 and support 19 of active 
guide 9 is ensured by a flexible cable 20; in this way, when discs 12 of 
guide 9 are applied on workpiece 1, the cable 20 is relaxed and the discs 
12 may follow the differences in thickness that the workpiece 1 may 
present when moving over table 6. Moreover, on table 6 there is positioned 
a guide stop 34 actuated by a jack 35, fixed on table 6. Guide stop 34 
prevents a guide surface 36, against which abuts the edge of the workpiece 
1 to be treated, when jack 35 is extended. In that case, guide surface 36 
of guide stop 34 is at a distance from the axis of stitching AA' which 
corresponds substantially to the width e necessary between the axis of 
stitching AA' and the edge of the workpiece represented by dotted line 
BB'. Guide surface 36 may, as illustrated in FIG. 2, present a bent form 
36' adapted to prevent the edge of the workpiece to be guided from rising 
and therefore maintaining it against table 6. Jacks 18 and 35 are 
controlled by the counting device 30. 
The installation operates as follows: The workpiece 1 to be edged is placed 
on the turntable 7, then the corner by which the stitching must begin is 
introduced beneath the active guide 9 and the pressor foot 3. The sewing 
machine 2 is switched on and the feed dog 33/presser foot 3 system takes 
the workpiece 1 along in the direction of stitching line AA'. The 
preceding three operations, namely placing the workpiece 1 on the 
turntable 7, introduction beneath the active guide 9 and beneath the 
presser foot 3, switching on of the sewing machine 2, are carried out 
either by an operator or automatically. During the edging operation, the 
recentering means constituted by the active guide 9 and the turntable 7 is 
selectively operated to guide the workpiece 1 so that the stitching is 
effected along the edge 5, substantially parallel thereto and at a 
distance e. It should be understood that guide 9 and turntable 7 may be 
actuated to move in the same direction (FIG. 6 first example) or in 
opposite directions (FIG. 6, last example) and in certain instances only 
one of the guide 9 and turntable 7 will be operated independently of one 
another (FIG. 6, third example). The action of the recentering means is 
controlled by the information received from detectors 14, 15, 16 in 
accordance with a defined program of which an example is given in Table 1 
of Enclosure I. The columns headed 14, 15, 16 define the state of each 
detector depending on whether the workpiece is present (X) above said 
detector or absent (-). The column headed "active guide" defines either 
the inaction of the rotatable member 10 (O) or its rotation in the 
direction driving the workpiece 1 towards the right (D) or its rotation in 
the direction driving the workpiece 1 towards the left (G). The column 
headed "turntable" repeats the same parameters as the preceding column for 
the turntable 7. The right-hand part of the Table illustrates the position 
of the workpiece with respect to the detectors and the action of the 
recentering means: arrow f for active guide 9 and arrow F for turntable 7. 
If workpiece 1 presents an edge EF to be treated and if this edge, as 
illustrated in FIG. 3a, has near the point F corresponding to the end of 
the stitching treatment, an inwardly curved profile, without sudden change 
in direction, the installation according to the first embodiment of the 
counting devices operates as follows: The stitch counting device 30 is 
programmed on the one hand to count the stitches to be counted from the 
beginning of stitching of each workpiece 1 to be treated, on the other 
hand for controlling, when the number of stitches counted by the counting 
device 30 attains a given value which is a function of the size of each 
workpiece, both the stoppage of the recentering means, namely the stoppage 
of the drive means of the turntable 7 and the action of jack 18 which 
raises the active guide 9 and also the action of jack 35 which advances 
the guide stop 34 in position of operation. By way of example, a pair of 
underpants, as shown in FIG. 3a, has a length EF to be edged equal to 50 
cm. It is desired to interrupt the action of the recentering means when 
the stitching is effected along curve EE', stitch F' being distant by 2 cm 
from stitch F which marks the end of the edge to be treated. The density 
of stitches obtained by the sewing machine 2 is 5 stitches per centimeter. 
The given digital value is equal to the number of stitches for covering 
the distance EF', viz. 240 stitches. In this way, guiding of workpiece 1 
along edge EF' is obtained thanks to recentering means, turntable 7 and 
active guide 9, then when the device 30 has counted 240 stitches and 
therefore stitch F' is reached, device 30 controls on the one hand the 
withdrawal of jack 18 which causes the active guide 9 to be lifted and the 
drive means of the turntable 7 to be stopped and, on the other hand, the 
extension of jack 35 which presents the surface 36 of the guide stop in 
guiding position along the edge F'F to be treated. Consequently, the 
stitching continues along the curve F'F and in continuation thereof (in 
broken lines in FIG. 3(a) and not along edge FG. 
In a variant of this first embodiment of the counting device, the active 
guide 9 comprises a system for detecting the oscillations to which the 
discs 12 are subjected when the thickness of the workpiece 1 varies. This 
system of detection comprises a reflector 31, fast with the support 19 of 
the active guide 9, and a photoelectric sensor 32. This particular 
arrangement is especially suitable when the workpiece to be treated is 
constituted by elements assembled together by stitching and consequently 
presenting a thickness greater than desired. FIG. 3b shows a pair of 
underpants, to be edged along EF, which is constituted by three pieces 24, 
27 and 28 assembled together by sewing. Due to the imprecision of the cut 
for each of the pieces to be assembled and also by reason of the assembly 
zones 25 and 26, there are considerable differences in length from one 
workpiece to the other for the same edge EF to be treated; such 
differences are detrimental to the precision in following the profile F'F, 
the recentering means being stopped either too early, or too late. In 
order to reduce this discrepancy, the counting device 30 is programmed to 
count the number of stitches, no longer from the beginning E of stitching, 
but from stitch H. The imprecision is therefore limited to the difference 
over length HF alone (and no longer EF). Beginning-of-count stitch H is 
located thanks to a system detecting the vertical movements of the active 
guide 9. The crotch 24 of the underpants is constituted by two pieces of 
knitted fabric and therefore has a thickness double that of the back 28; 
the passage of the discs 12 of the active guide from the crotch 24 to the 
back 28 thus creates a descending movement of the active guide 9, which 
movement is detected by the displacement of the reflector 31 in front of 
the photoelectric sensor 32: the signal obtained allows the beginning of 
the counting of stitches by device 30. 
According to a second embodiment of the counting device, the installation 
comprises, in addition to the counter 30 placed in the upper part of the 
needle arm 4', a differential feed dog 48. As is known, this feed dog is 
placed upstream of the needle 4 and is animated by a movement allowing the 
workpiece 1 to advance at a speed greater, equal or less than that of feed 
dog 33. Such differential feed dogs are known from U.S. Pat. No. 
4,067,274. Automatic feed control means are known from U.S. Pat. Nos. 
3,980,032; 3,808,995 and 4,412,498. The differential feed dog 48 is 
controlled by counting device 30. This particular arrangement is 
especially useful when the workpiece 1 to be treated is a knitted fabric 
which will tend to be deformed during treament. Such deformation is 
compensated by the operator when the stitching is done manually; in 
automatic mode, it will be compensated thanks to the variations of 
adjustment of the differential feed dog preprogrammed as a function of the 
number of stitches counted by counter 30. If the underpants shown in FIG. 
3b are considered, the selvage EF to be edged may be divided approximately 
into three parts as a function of the direction of the rows and wales of 
stitches: part EI of which the direction is substantially parallel to the 
rows of stitches; part IH whose direction is substantially perpendicular 
to the rows of stitches (and therefore parallel to the wales of stitches); 
and part HF whose direction is oblique with respect to the wales of 
stitches. During stitching along edge EF, the passage of the knit (herein 
the term "knit" is used as an abbreviation for a knitted workpiece) in the 
drive members (feed dogs 33,48) of the sewing machine provokes extensions 
which vary depending on whether the line of stitching AA' is parallel, 
perpendicular or oblique with respect to the wales of stitches: for 
example, along part EI, the knit will tend to undergo a considerable 
extension during its passage beneath the drive members of the sewing 
machine; along part IH, no extension, and along part HF a weaker 
extension. If distance EF is 60 cm in all, with EI equal to 10 cm, IH to 
27 cm and HF to 23 cm, and if the stitch density is 5 stitches per 
centimeter, the counter 30 is preprogrammed to begin to count the number 
of stitches from point E, beginning of stitching of each workpiece 1, and 
to successively control a linear speed of the differential feed dog 48 
clearly greater than that of feed dog 33 from 0 to 50 stitches; equal to 
that of feed dog 33 from 51 to 185 stitches, and slightly greater than 
that of feed dog 33 from 186 to 300 stitches. The variation of the linear 
speed of the differential feed dog 48 is obtained by changing the 
amplitude of the horizontal movement of said feed dog. 
In certain cases, difficulties in guiding may arise with underpants made of 
slippery knits such as, for example, fine lace or non-run fabrics for 
ladies' briefs. 
Crotch 24 of the underpants (FIG. 3a) is constituted by two layers of knit 
of which the edges 45 to be stitched are matched when this crotch 24 is 
assembled with the front 27 and the back 28 of the garment. When this part 
24 is subjected to the action of the active guide 9, the latter comes into 
contact with the upper layer and drives it transversely to the direction 
of stitching in accordance with the process described hereinabove. 
However, as the upper layer slides more easily on the lower layer than the 
lower layer slides on the fixed part 8 of the work table, this lower layer 
does not follow the movement imposed by the active guide 9. This results 
in a shifting of the two edges to be stitched, which is inadmissible. 
In order to overcome this drawback, a second, lower, active guide 42 may 
complete the action of the upper guide 9 (FIG. 4). This second guide 42 is 
identical to guide 9. It is placed beneath the fixed part 8 of the work 
table and emerges by some millimeters through the recess 43. Rotation 
thereof is obtained by drive means 46 similar to those of guide 9 and by a 
pulley/belt/pulley assembly 44/40/47. A flexible blade 41 fast with the 
frame exerts above the knit a pressure in the direction of table 6 in 
order to urge the lower layer of knit against the active guide 42. 
Rotation of active guides 9 and 42 is controlled by the same information 
received from detectors 15 and 16. The two guides therefore act 
simultaneously, upper guide 9 rotating anti-clockwise and lower guide 42 
in the opposite direction, or vice versa. Each guide acts on a thickness 
of knit and moves it by the same amount. Consequently, edge-to-edge 
matching is maintained. 
According to a particular embodiment of the invention, the drive means of 
the turntable 7 allow said turntable to be driven at two different speeds, 
this making it possible to accelerate in certain cases the modifications 
of orientation of workpiece 1 with respect to the line of stitching. 
Multispeed drive means for turntables are already known from U.S. Pat. No. 
4,312,281. Moreover, the sewing machine 2 also has a normal speed and a 
slow speed, the latter being advantageously used in the event of a 
curvature to be corrected which is particularly marked i.e., extreme. 
Multispeed drive and control means for sewing machines are already known 
from U.S. Pat. No. 4,359,953. FIGS. 6 and 7 give an example of program for 
control of the two recentering means and of the sewing machine 2 as a 
function of the information emitted by the three detectors 14, 15, 16. In 
the column headed "turntable", the speed of the drive means has been 
differentiated by using a capital letter for high speed and a small letter 
for the low speed. 
In a specific embodiment, the arrangement of the different means with 
respect to one another is as follows: Taking as origin the stitch 4 and as 
reference axis the line of stitching AA', the three detectors 14, 15 and 
16 are located respectively at 40, 32 and 70 mm from the needle and 5, 2 
and 30 mm from the line of stitching AA'. The active guide 9 has an outer 
diameter of 24 mm, each of the ten discs has a diameter of 8 mm. The axis 
of rotation 11 of the active guide 9 makes an angle of a 35.degree. with 
the work table 6. The point of contact of the active guide 9 with the work 
table 6 is on the line of stitching AA', at 45 mm from the needle 4. The 
fixed part 8, inside the turntable 7, has a diameter of 480 mm, its center 
being located on the perpendicular to the axis of stitching AA' passing 
through the needle 4 at a distance of 200 mm therefrom. The speed of the 
sewing machine 2 in normal operation is 4170 r.p.m., in slow operation, 
2000 r.p.m. 
The above example has been given by way of illustration and does not limit 
the invention. Other types of active guide may for example be used, such 
as the one described in French Pat. No. 2 518 134, i.e. a guide wheel 
whose axis of rotation is parallel to the line of stitching AA' and 
applied on the workpiece with a modulatable pressure. Other types of 
mobile support may be used, such as an endless belt of which the surface 
of the upper edge, on which is placed the workpiece 1, is in the plane of 
the work table and in continuation thereof. The belt is associated with 
drive means allowing it to be displaced in both directions; it is directed 
either transversely with respect to the line of stitching AA', or 
obliquely with respect to said line, in which case it ensures recentering 
of the workpiece and it also facilitates the advance of the workpiece 1 
towards the stitching head 4. This latter arrangement is particularly 
advantageous in the case of a heavier workpiece. 
More than three detectors may also be employed, for example, by adding a 
fourth detector 49 symmetrically to the third detector 16 with respect to 
the reference line BB'. This complementary arrangement makes it possible 
to recenter very precisely the edges presenting convex curvatures, such as 
the one illustrated in FIG. 3b. In that case, the turntable 7 will 
advantageously be animated by two speeds towards the right.