Fabric guiding device and process of automatic sewing

A process and device are disclosed for automatic sewing of a piece of fabric along its edges. The process is of the type in which a rolling element (12) orientable by pivoting around a vertical axis YY' bears against the fabric in front of the presser-foot in order to guide and entrain the fabric in front of the sewing zone. The rolling element (12) is driven into rotational movement by a cylinder (16) bearing against that element in its upper zone traversed by the pivoting axis YY' in such a manner that the contact of the cylinder against the rolling element leaves this latter free to pivot, especially at high frequency, about the axis YY' independently of the value of the friction coefficient between the cylinder and the rolling element.

The invention relates to a device for guiding a piece of fabric parallel to 
a pre-determined reference line, consisting in particular of the edge of 
the fabric; it relates to a device adaptable to a sewing machine of the 
traditional type comprising more specifically a needle plate, and a 
mechanism with claws for advancing the fabric, associated with at least 
one needle; in the following the mechanism and its accessories will be 
designated by the term "presser foot". The invention also extends to a 
method of automatic sewing of a fabric, by means of a sewing machine 
equipped with such a guiding device. It extends further to the improved 
sewing machines equipped with one or more guiding devices in accordance 
with the present invention. 
In the garment trade, the operations of sewing pieces of fabric or material 
are usually directed to the sewing of two pieces of material along their 
edges or of making a hem at the edge of one piece of material or for 
fitting a ribbon, rubber band, a belt, etc. along an edge of one piece of 
material. These operations require the presence of an operator who guides 
the fabric in front of the needle in such a manner that the seam follows 
the desired line. In order to achieve economy in working personnel and 
improve the productivity, there has been proposed a guiding system which 
displaces the fabric in a transverse direction in front of the needle in 
order to constantly bring the region to be sewn next to the needle; these 
systems generally comprise rollers or chains on rollers arranged 
transversely in front of the needle; these rollers or chains can be 
rotated in one direction or the other so as to move the fabric 
transversely in the two directions and thus to carry out appropriate 
corrections of the positions. However, these systems are barely used 
because they lead to imperfect seams and to frequent defects; indeed, the 
material or fabric pushed by the presser-foot at the level of the needle, 
is braked by the guiding system before reaching the needle and has thus a 
tendency of rolling on itself, of folding or creasing in a manner which is 
incompatible with obtaining a regular seam of good quality; this defect is 
particularly grave in the case of extendible fabrics or fabrics with "soft 
eyes" which cannot be sewn with the known systems; in the case of two 
pieces of material to be assembled edge to edge, it leads to the 
displacement of one edge with respect to the other and to imperfection of 
the assembling which prejudices the quality of the product obtained. 
Moreover, most of the existing systems can be used only for fabrics of a 
definite thickness. 
French Patent 2,585,683 and European Patent 0,216,644 describe a guiding 
device for a fabric which comprises a spherical roller which bears against 
a fabric in front of the presser foot and rotates in a single rotation 
sense in order to guarantee advance and guiding of the fabric on top of 
the sewing zone; this spherical roller is pivotally mounted around a 
vertical axis in such a manner that it can be oriented in different 
directions of entrainment permitting to bring the fabric into the desired 
position. In the device in accordance with these patents, the spherical 
roller rotates by friction with another roller which bears against one of 
its sides in the horizontal plane containing the axis of said first 
roller. As explained in these patents (especially page 6, line 32 to page 
7, line 35 of French Patent 2,585,683), the entrainment roller turns at a 
constant speed and its arrangement with respect to the spherical one 
(sidewise contact in the horizontal plane containing the axis of rotation 
of the spherical roller), provides an automatic modulation of the rotation 
speed of said roller when this latter changes its orientation: in fact, 
the roller entrained at a constant rotation speed guarantees at the 
contact level a constant tangential speed of the spherical roller; when 
this latter takes an oblique orientation with respect to the other roller 
(axis of the roller and the spherical roller not parallel), the spherical 
roller entrained in circles of a smaller diameter, turns at a greater 
speed. This effect is favorable because the spherical roller entrains the 
fabric at a greater resultant speed whose component along the direction of 
entrainment of the presser-foot is constant no matter the orientation of 
the spherical roller; this component can thus be brought to coincide 
permanently with the entrainment speed of the presser-foot by adjusting 
once and forever the rotation speed of the second roller to a 
pre-determined appropriate value. 
However, the reduction to practice of such a system met with great 
difficulties. In order to permit a satisfactory entrainment of the 
spherical roller by the second roller, it is necessary that the surfaces 
of these two elements should roll without sliding against each other, and 
thus present a sufficient friction coefficient; when the spherical roller 
pivots around the vertical axis in order to adopt another orientation, the 
contact region of the second roller on this first roller describes a 
segment of a great circle and this movement is transverse with respect to 
the second roller (parallel to the axis of the second roller and 
perpendicualr to the tangential speed), in such manner that the friction 
between the two surfaces has a tendency to oppose the movement. Under 
these conditions, the pivoting movements of the spherical roller, in order 
to modify its orientation, require considerable forces and must, 
therefore, be slow with respect to the rotation speeds of the second 
roller and of the first one thus producing rapid wear of the surfaces, 
which requires frequent replacement of these elements. 
Thus, the problem of automatic sewing in the garment field is at present 
not solved in a satisfactory manner and the need for a full-time operator 
for each sewing machine, constitutes an impediment for equilibrating the 
job positions and increasing profit by increased productivity. 
The present invention proposes to provide a solution to the above mentioned 
problem. It is directed to a process for guiding the material and an 
improved device for achieving this, of the type containing a moving 
element which moves in a single sense, namely a sphere which is made to 
pivot around a vertical axis in order to orient it in relation with the 
directions of advance of different materials. The invention also relates 
to the mounting of one or more of these improved devices on a sewing 
machine of the known type (provided with a support plate and a 
presser-foot associated with at least one needle) in order to permit to 
sew automatically pieces of material parallel to a predetermined reference 
line, constituted in particular by the edge of such pieces. The invention 
is applicable to any object of the seam, namely: fitting of a ribbon, a 
belt, or a rubber band at the edge of a piece of fabric, sewing of a hem 
(the machine being provided with a conventional folding device), sewing 
together of two pieces of material (the machine being provided with two 
guiding devices). 
The object of the invention is to permit obtainment of a regular seam of 
good quality, independently of the type of fabric (namely, fine fabrics 
difficult to handle, extendible fabrics . . . ) by overcoming the 
performance of difficulties encountered by the devices of the same type 
described in the above mentioned patents. 
Another object of the present invention is to provide a guiding device of a 
simple structure which, mounted on a sewing machine of conventional type, 
permits automatic sewing of materials of any thickness. 
Certain terms used in the following are defined below in order to simplify 
the terminology and make the description clearer: 
"Piece of fabric": piece of fabric or of any similar material susceptible 
to sewing, 
"longitudinal" direction: direction of the line of sewing desired, 
"general longitudinal direction": the direction which may be angularly 
decalated with respect to said longitudinal direction at an angle of less 
than 30.degree. but whose general orientation is longitudinal, 
"transverse direction": direction perpendicular to the longitudinal 
direction, 
"vertical"direction: direction orthogonal to the sheet of material (or to 
the supporting plate of the sewing machine which supports the material), 
"horizontal" direction: direction parallel to the sheet of material (or to 
the supporting plate of the sewing machine), 
"presser-foot": assembly of the classic mechanism which guarantees the 
guiding and advance of the fabric or material at the level of the needle. 
The process in accordance with the present invention is of the type in 
which a rolling element, orientable by pivoting around a vertical axis, 
bears against a fabric in front of the presser-foot in such a manner as to 
guide and entrain the fabric in front of the sewing zone; the process in 
accordance with the present invention is characterized in that said 
rolling element is driven to a rotational movement by a cylinder bearing 
against that rolling element in its upper zone traversed by the vertical 
pivoting axis in such a manner that the contact of the cylinder against 
the rolling element leaves this latter free to pivot around the vertical 
axis, independently of the value of the friction coefficient between the 
cylinder and the rolling element. 
Moreover, in accordance with another characterising feature of the process, 
the cylinder is made to rotate at a variable speed which is a function of 
the orientation of the rolling element in such manner that said rolling 
element creates a speed of advancement of the fabric whose projection on 
the sewing line is substantially equal to the advance speed provided by 
the pressure-foot in the sewing zone. 
The fabric guiding device in accordance with the present invention, in 
order to carry out the process described above, comprises: 
a rolling element for entrainment of the fabric, mounted in front of the 
presser-foot and free to rotate around a substantially horizontal axis in 
such a manner as to be able to get into contact with the fabric by 
entrainment generatrices situated in a vertical plane, 
a pivoting actuator on which said rolling element is mounted, adapted to 
make this latter pivot around a vertical axis, intersecting the rotation 
axis in such a manner as to be able to direct the entrainment generatrices 
in accordance with different advance directions, 
a cylinder situated along a transverse horizontal axis and bearing against 
the rolling element in order to make this latter turn around its axis of 
rotation, by friction, 
a drive-motor for causing rotational movement of the cylinder, 
a detector of the transverse position of the fabric, mounted in front of 
the presser-foot and associated with means for generating a position 
signal and with control means adapted to actuate the pivoting as a 
function of the position signal. 
In accordance with the present invention, the cylinder is situated on top 
of the rolling element in such a manner as to bear against the upper zone 
thereof, opposite the contact zone of said element with the fabric, the 
contact zone of said cylinder with said rolling element being 
substantially situated on the vertical axis around which the pivoting of 
said rolling element occurs. 
Thus, in the present invention the fabric is entrained longitudinally in a 
permanent manner in front of the guide zone and the corrections, of the 
position are effected by orienting, in appropriate manner, the direction 
of this longitudinal entrainment; the rolling element is rotated by the 
cylinder by friction at the level of a zone which is not subject to any 
displacement during the pivoting of this element, in such manner that the 
unavoidable friction between the two surfaces of said elements has no 
substantial influence on the pivoting movement which can be carried out 
without particular difficulties. 
Moreover, in accordance with other characterizing features, 
an orientation detector is associated with the pivoting actuator (or with 
the rolling element), said detector being connected with means for 
creating a signal adapted to deliver a signal representative of the 
direction of advance of generatrices of the rolling element, 
the motor causing the rotation of the cylinder being connected with control 
means receiving the signal emitted by the above mentioned orientation 
means, said actuating means being adapted for adjusting the rotation speed 
of the motor as a function of this signal. 
It is thus possible, by modulation of the speed of the cylinder, to ensure 
an advance movement of the fabric at the level of the rolling element, 
which corresponds to that in the fitting zone of the presser-foot and this 
no matter the direction of entrainment of the rolling element, in order to 
avoid any risk of bending, creasing, etc. of the fabric. 
In accordance with a preferred embodiment permitting to carry out automatic 
sewing of a piece of fabric along one of the edges (constituting the above 
mentioned reference line), the guiding device in accordance with the 
present invention is designed in the following manner: 
the position detector is a detector of the presence or absence of the 
fabric, associated with means generating a position signal in two 
representative stages, namely, absence or presence of the fabric, 
the pivoting actuator is an actuator with alternating pivoting adapted to 
bring the rolling element to pivot alternatively between two extreme 
positions at a frequency superior to five pivoting movements per second, 
the entrainment generatrices presenting in the two extreme positions, two 
directions substantially symmetrical with respect to the direction 
parallel to the advance direction of the fabric by the presser-foot, 
the means for actuating the pivoting actuator being adapted to move this 
latter alternatively from one position to the other at each change of 
state of the position signal, 
the orientation detector being a detector of extreme positions, associated 
with the actuator of the pivoting movement, the means for carrying out 
being adapted to deliver a signal of extreme positions when said actuator 
is positioned in one of these extreme positions, 
the electric drive motor of the cylinder being of the type having two 
rotation speeds, one slow and the other rapid, 
the means of actuating associated with the motor being adapted to actuate 
the rapid rotation of the motor in the presence of the signal of the 
extreme position and the slow rotation in the absence of said signal. 
In such a device, the pivoting actuator which may be a rotating 
displacement device, is alternatively actuated between two opposed angular 
positions depending on the state of the position signal. When the rolling 
element is situated in one or the other of these extreme positions, it 
carries out a correction on the fabric by introducing a transverse 
component into the advance speed at its level: moreover, the cylinder is 
driven in this case at a rapid speed by the driving motor (presence of 
extreme position signal) so that the transverse component of the speed is 
not created at the detriment to the longitudinal component. When, on the 
contrary, the fabric is in a substantially correct position, the position 
signal changes very rapidly its state and the displacement device, 
actuated at an elevated frequency, oscillates between the above two 
extreme positions. During these oscillations, the fabric is entrained by 
the entrainment generatrices in accordance with a very rapid succession of 
zig-zags of very small amplitude around a median direction; it thus moves 
along a resultant direction, which is parallel to the entrainment 
direction of the presser-foot; in this case, the detector of the extreme 
positions, does not supply any signal and the cylinder is driven at low 
speed by the driving motor; the rolling element moves more slowly, the low 
speed of the cylinder being controlled in such a manner that the rolling 
element gives rise to an advance movement of the fabric substantially 
equal to that caused by the presser-foot. On the contrary, the rapid speed 
of the rolling element is adjusted for producing a resultant speed of 
advance of the fabric of the order of 1% to 5% superior to the slow speed, 
so that the projection of this rapid speed on the longitudinal plane be 
substantially equal to said slow speed. By means of a very simple device 
an advance of the fabric in front of the fitting zone is thus obtained, 
which is at all times compatible with the advance created by the 
presser-foot. 
It should be noted that the above described mode of operation, involving 
alternative pivoting movements at high frequency, is caused by the manner 
of driving the rolling element in accordance with the present invention 
(contact of the driving cylinder on the vertical axis around which the 
pivoting movements are effected); this mode of operation is definitely 
incompatible with the manner of operation described in the two above 
mentioned previous patents. 
Moreover, in accordance with other characteristics of the present 
invention, the rolling element comprises a sphere of elastic material 
adjusted by a lateral calotte of its surface on a bearing shaft. This 
bearing shaft is mounted on the pivoting actuator in such a manner as to 
turn around the horizontal axis of rotation, which passes through the 
center of the sphere. The center of the sphere and the upper zone of 
contact between the cylinder and the sphere, are substantially aligned on 
the vertical axis around which the alternative pivoting movements of said 
sphere are carried out. These arrangements permit the rolling element to 
pass, without difficulties, the thicker portions of the fabric, without 
need to control the bearing pressure of this element (as is the case in 
the devices described in the above mentioned patents). 
Moreover, in accordance with another advantageous characteristic of the 
invention, the guiding device mentioned above is supported by a mobile 
lifting/lowering element of a jack whose body is attached to the bed of 
the sewing machine, in order to permit lowering of the guiding device in 
working position in front of the needle or lifting it into high position 
in such manner as to clear the portion in front of the needle. It is thus 
possible, to completely liberate the bearing plate of the sewing machine 
before and after the sewing operation in order to carry out the various 
operations of putting the fabric in fitting position or withdrawing it. 
The invention also comprises the guiding device defined above as such, as 
well as improved sewing machines equipped with at least one such guiding 
device.

The guiding device 1 represented in FIGS. 1 to 13 is mounted on a sewing 
machine 2 of the type having the head at the left side; in a conventional 
manner, this machine comprises a bed 3, a support plate for the work piece 
4 and a presser-foot 5 associated with the needle 6 with their 
conventional kinematics of engagement (claw type advance mechanism), means 
for distribution of the thread etc. The embodiment exemplified herein is 
intended for sewing an elastic ribbon of a belt E to the edge of a piece 
of fabric, and the machine is provided with conventional means for 
supplying and guiding the elastic ribbon towards the sewing zone (not 
represented). In the sewing machine with the head at the left which is 
used, the presser-foot 5 is arranged adjacent to an angle of the support 
plate 4; this angle is limited by a rounded edge Ra and by an edge Rb 
perpendicular to the previous one (parallel to the line of sewing). 
The guiding device in accordance with the present invention is intended to 
guide the piece of fabric which rests on the plate 4 in order to permit 
obtaining a stitching line parallel to the edge of the fabric without the 
help of an operator. 
This guiding device is mounted on a pneumatic jack 7 whose body 7a is 
attached by means of an element 8 to the bed 3 of the machine and whose 
mobile rod 7b is fixedly attached at its end to a support bracket 9 of the 
guiding device. The jack 7 is slightly inclined to the vertical position 
so as to enable displacement of the guiding device between a working 
position (FIG. 1) where this latter is situated just in front of the 
presser-foot 5 and needle 6 of the machine and a lifted position (FIG. 2) 
where the front parts of these elements are completely disengaged. The 
movement of the jack is guided by rods 23 permitting the guiding device to 
perform a translational movement without any angular movement. In the low 
position, the guiding device is located in front of the presser-foot 5 in 
the vicinity of the above mentioned angle of the support plate 4. 
In the exemplified embodiment, the presser-foot 5 is attached to a cable 10 
(which is better seen in FIG. 7) which passes through an eye provided in 
the support bracket 9 and has at its upper free end a contact plate which 
automatically lifts the presser-foot when the guiding device reaches its 
lifted position. 
Moreover, the machine is provided with an optical detector 11 of the 
presence of the fabric, capable of capturing the light reflected by a 
small plate 11a situated near the presser-foot 5 (towards the inside of 
the fabric, i.e. near the edge Rb); when the fabric appears at its level, 
this detector actuates the jack 7 and causes the downwards movement of the 
guiding device towards the working position; when the fabric disappears, 
it actuates the lifting movement of the jack 7. In addition, a proximity 
pin (not seen) is provided on the jack 7 in order to detect the moment 
when the rod reaches its low deployed position corresponding to the 
working position of the guiding device. The pin actuates the start of the 
sewing machine when the guiding device reaches its working position; it 
also actuates the start of the means for entrainment and rotation of the 
rolling element of this device and that of the actuator of the alternating 
pivoting movement. 
As illustrated in the figures, the guiding device comprises essentially the 
following five functional assemblies: 
a rolling element 12 comprising a sphere of elastic material supported by a 
mobile bracket 13 and which, in the working position, is situated in front 
of the presser-foot 5 in such a manner as to contact the fabric by 
entrainment generatrices (creating a rolling band BR represented by dashed 
lines in the figures), this contact being effected at the level of the 
rounded edge Ra of the support plate of the sewing machine in the 
immediate vicinity of the other edge Rb, 
an actuator 14 for alternating pivoting movement comprising a rotating 
displacement device whose body 14a is attached to the support 9 and whose 
rod 14b bears a mobile bracket 13 enabling it to cause the sphere 12 to 
pivot between two extreme positions, in which the entrainment generatrices 
BR define two different directions (whose traces have been represented in 
D.sub.1 and D.sub.2 on the working plate), 
means for rotating the sphere 12 comprising an electrical drive motor 15 
and cylinder 16 bearing against the surface of the sphere 12, 
an optical detector 17 (FIG. 3) mounted in front of the presser-foot 5 
transversely displaced with respect thereto towards the interior of the 
support plate, in order to detect the presence or absence of the fabric at 
this level, this detector being associated with a circuit 18 for actuation 
and amplification creating an electric position signal in two states 
S.sub.p ; which is connected with an electropneumatic distributor 19 
actuating the rotating displacement device 14, 
a detector of the extreme positions 24 associated with the rotating 
displacement device 14 and constituted by two proximity projecting pins 
24a and 24b situated with respect to the end-of-course stops 14c and 14d 
of the rotating displacement device, in order to deliver a signal when the 
stops are situated in front of the pins (this position corresponding to 
the two extreme angular positions of the rod of the rotating displacement 
device and thus of the sphere 12 attached to the latter). 
The specific structural and functional characteristics of these different 
assemblies are described in detail below. 
The sphere 12 which may be a hollow rubber ball is transversely displaced 
with respect to the presser-foot 5 in such a manner as to contact the 
fabric in a zone nearer to the edge Rb than the presser-foot. This sphere 
is attached by a lateral calotte of its surface on a substantially 
horizontal support shaft 21 which rotates in an opening of the mobile 
bracket 13 in such manner that said sphere is free to turn around an axis 
XX' passing through its centre O. 
The mobile bracket 13 is fixedly attached to the rod 14b of the 
displacement device 14 in such manner that the extension of the vertical 
axis YY' of said rod passes through the centre O of the sphere. Thus, the 
pivoting movement imposed by the displacement device modifies the 
orientation of the axis XX' around which the sphere turns without changing 
its spatial position. 
The sphere 12 is arranged vertically with respect to the rounded edge Ra of 
the work support plate 4, in such manner that its center (O) slightly 
exceeds the edge of said plate as illustrated in FIGS. 7 to 10; the sphere 
and the rounded edge define in their contact zone a common tangent Tc 
inclined with respect to the horizontal. Thus the fabric is entrained by 
the sphere at the level of the bend which it forms at the rounded edge Ra; 
at the level of this bend the fabric has greater rigidity which 
contributes to reduce the risks of creasing, even in the case of very 
light fabrics. 
Blowing means 27 are provided underneath the rounded edge Ra of the support 
plate in order to disengage the fabric from the vertical edge of said 
plate and thus put it in a better position for being entrained by the 
sphere 12. Moreover, the support plate 4 comprises preferably a small 
rounded flank 28 situated underneath the edge Rb in the vicinity of the 
sphere 12. Such guidance of the fabric improves the conditions of 
entrainment of this latter by the sphere 12. 
The rotating displacement device 14 is a pneumatic displacement device of 
known type, with adjustable angular amplitude; owing to its low inertia it 
is capable of changing position at an elevated frequency higher than 5 
pivoting movements per second and may even reach 10 to 15 pivoting 
movements per second. This device comprises end-of-course stops 14c and 
14d which permit the control of its pivoting amplitudes to a value 
2.alpha. of the order of 20.degree. to 30.degree. especially to a value of 
about 24.degree.. As already indicated, these stops serve to detect the 
moments when the rotating device reaches one or the other of the extreme 
angular positions (owing to the proximity pins 24a, 24b). In one angular 
position, the rotation axis XX' of the sphere is displaced by an angle 
.alpha.=12.degree. with respect to the transverse direction (FIGS. 3, 4 
and 11), while in the other angular position, this axis of rotation XX' is 
symmetrically displaced with respect to the said transverse direction at 
an equal angle (FIGS. 5 and 12). Thus in the first position, the 
entrainment generatrices BR of the sphere define a direction D.sub.1 
angularly displaced towards the interior of the fabric by the angle 
.alpha. with respect to the longitudinal direction, in such manner that 
the rotation of the sphere guarantees a longitudinal entrainment of the 
fabric with a smaller transversal component directed towards the inside of 
the fabric (FIG. 11); in the second position, the entrainment generatrices 
BR define a direction D.sub.2 angularly displaced towards the edge B of 
the fabric by the angle .alpha. and the rotation of the sphere ensures a 
longitudinal entrainment with a smaller transverse component directed 
towards the edge (FIG. 12). 
The entrainment cylinder 16 causing rotation of the sphere is situated 
above the sphere 12 along a transverse horizontal axis ZZ' in such a 
manner as to bear against the upper zone of said sphere (upper pole Su of 
the sphere) opposite the lower contact zone of the sphere with the fabric. 
This upper zone Su of contact between the cylinder 16 and the sphere 12 is 
situated on the vertical axis YY' passing through the centre O, around 
which the sphere is made to pivot in alternative manner by the actuating 
device 14. Zone Su does not move during this pivoting movement so that 
whatever the entrainment friction between the cylinder and the sphere, the 
contact of the latter does not interfere with the performance of the 
pivoting movement. 
The cylinder 16 is supported by the moving shaft 22 of the electric motor 
15, this shaft being situated above the shaft bearing the sphere 12. For 
this purpose, the motor 15 is attached at the rear of the support 9 and 
its moving shaft 22 passes through a hollow space provided in the mobile 
bracket 13. 
The detector 17 is an optical detector of conventional type, which captures 
the light reflected by a platelet 17a supported by the work support plate 
4. Preferably, the optical detector 17 is associated with control means 
for controlling the transverse position in order to permit the adjustment 
of the position of the stitching line with respect to the edge of the 
fabric. In the longitudinal sense, detector 17 is arranged between the 
presser-foot 5 and the rolling sphere 12 which corresponds to an optimal 
efficiency of guiding. 
The optical signal delivered by the detector 17 is converted by a cell into 
an electric signal which is processed by the circuit 18 in order to send a 
position signal Sp towards an electropneumatic distributor 19 associated 
with the rotating device 14. In the presence of the fabric, the signal Sp 
assumes a state, designated as State 1, corresponding to that position of 
the sphere 12 for which its entrainment generatrices define a direction 
D.sub.1 : the fabric is longitudinally entrained with a tendency to slide 
transversally in a direction opposite to its edge (FIG. 11); the platelet 
detector 17a which was covered by the fabric is now exposed. The detector 
17 thereupon detects the absence of the fabric and the signal S.sub.p 
passes to its second state, designated State 2, corresponding to the 
position of the sphere 12 in which the entrainment generatrices define the 
direction D.sub.2 : the fabric is still entrained longitudinally but with 
a tendency to slide transversally in the direction towards its edge (FIG. 
12). Thus, by pivoting the axis of rotation XX' of the sphere at each 
change of state of the position signal S.sub. p, the fabric is guided in 
such a manner that its edge passes substantially above the platelet 17a, 
i.e. it remains at a substantially constant transverse distance from the 
presser-foot 5. 
When the signal S.sub.p changes its state very rapidly (the edge of the 
fabric vertically displaced with respect to the platelet 17a), the 
rotating device 14 actuated from one side and from the other side at a 
high frequency, oscillates between the above mentioned two extreme 
positions: FIGS. 6 and 13 illustrate these alternative pivotings which may 
reach an elevated frequency (higher than 5 hertz). During this 
oscillation, the entrainment generatrices BR of the sphere 12 entrain the 
fabric along a resultant direction Dc parallel to the line of sewing. In 
this case, the detector of the extreme positions 24 does not deliver any 
signal. 
The pins 24a, 24b of the detector of the extreme positions 24, are 
connected by signal generating means 25 which upon receipt of a signal, 
create a signal Pe in two states (for example State 1 in the case of 
detection of the extreme stable position and state 0 in the contrary case 
corresponding to an oscillation between the extreme positions). This 
signal is delivered to the actuating means 26 which actuate the driving 
motor 15 of the cylinder 16. This motor is an electric motor with 2 
speeds, one slow capable, for example, of making the sphere turn at 100 
rotations per minute, the other rapid capable of making the sphere turn at 
103 rotations per minute. The actuating means 26 cause rapid rotation when 
the signal Pe represents an extreme position and low speed in the contrary 
case. 
The guiding device in accordance with the present invention thus entrains 
the fabric in front of the sewing zone in a generally longitudinal 
direction and guides it permanently by creating a transverse component 
when necessary in order to obtain a seam parallel to its edge; this 
entrainment co-operates with that of the presser-foot in order to avoid 
the risk of pleating, creasing, etc. In FIGS. 11 and 12, the edge of the 
fabric is represented by B, C represents the desired line of sewing and, 
as already indicated, D.sub.1 and D.sub.2 are the entrainment directions 
of the fabric by the sphere 12 when this latter is in the two extreme 
opposed positions; these entrainment directions D.sub.1 and D.sub.2 are 
symmetrical with respect to the longitudinal direction Dc (this latter 
being parallel to the entrainment direction of the presser-foot). In FIG. 
13, the sphere is schematically represented when about to oscillate 
between the two extreme positions (the average entrainment direction being 
the direction Dc). 
When the entrainment directions D.sub.1 and D.sub.2 are angularly inclined 
with respect to the longitudinal direction (FIGS. 11 and 12), the 
entrainment speed Vr of the fabric is greater (rapid speed of the motor) 
so that the component Vl along the longitudinal direction remains equal to 
the speed V' corresponding to the slow speed (FIG. 13), at which the 
fabric is entrained when the average entrainment direction coincides with 
the longitudinal direction. 
Moreover, when the piece of material to be sewn arrives at the end of the 
sewing and its outer edge is beyond the sphere 12 (in which case it is not 
entrained by the latter), the fabric is guided by an elastic tongue 29 
situated in the transverse direction between the sphere 12 and the 
presser-foot 5 as shown in the figures, this tongue bearing elastically on 
the fabric, avoids transverse sliding of the latter at the end of sewing. 
This tongue 29 may be mobile vertically and designed in such a manner as 
not to descend against the fabric until the end of the sewing when the end 
of the fabric arrives near the sphere 12. 
The device described above may be used in any application where a seam has 
to be made along the edge of a fabric in order to make this operation 
automatic. If several sheets of fabric have to be sewn, a guiding device 
is provided for each such sheet.