EP3969647B1

EP3969647B1 - Automatic sewing machine

Info

Publication number: EP3969647B1
Application number: EP20722992.3A
Authority: EP
Inventors: Dario MORANDIN
Original assignee: Sip Italy Benefit Srl Soc
Current assignee: Sip Italy Benefit Srl Soc
Priority date: 2019-05-13
Filing date: 2020-05-12
Publication date: 2023-06-07
Anticipated expiration: 2040-05-12
Also published as: EP3969647A1; PT3969647T; WO2020230020A1

Description

FIELD OF APPLICATION

The present invention relates to an automatic sewing machine equipped with a carousel loading system for loading the material to be sewn, with independent loading and processing stations.
This is a platform rotating on a vertical axis, or carousel, positioned in the centre between several independent processing stations, said carousel being able to continue to rotate normally in one direction.
In each processing station present in the main body of the carousel, the same movable structure is present. The same substantially quadrilateral jig for locking the material is used for each movable structure fixed to the carousel.
Unlike any previous solution, each processing station thus has the advantage of being able to run three actions/functions on the basis of the type of processing that has to be run for/in that specific position of the carousel.
The present invention is advantageously applied in the sector of industrial sewing plants, in particular in the sector of automatic processing for performing sewing operations, both for fixing between several fabric or of leather flaps , and for making embroidery or appliqués of various types on fabrics or leather.

PRIOR ART

It is known that in the sector of sewing textile or leather materials machines that are adapted to perform programmable sewing in sequence can be used, which sewing can be of various types for each of which some important problems have been detected, to obtain the correct quality or efficiency production that the invention proposes to solve.
As far as quality is concerned, in the case of processing in which the material to be sewn requires the upper and lower sewing yarn to be of a different colour or count, can be envisaged, thereby having to act on the type of sewing yarn.
As far as the efficiency aspect is concerned, it should be considered that if the machine involves various subsequent steps, the duration of the sewing cycle can also be very long so much that the operator, when he has already loaded the loader present in the automatic unit, may be forced to wait to perform the aforesaid operation again, with resulting downtime in loading the material onto the automatic unit.
In order to increase the efficiency of the operator in this case, the operator has to use two independent automatic units at the same moment, so as to work in tandem with two units, physically moving between the two units to load them alternatively first one and then the other.
In the construction technique of the automatic machines known to date, the operators of the sector turned to possible constructional choices that are influenced by the possible type of processing that can be performed with the dedicated automatic unit, with reference to the processing method, which implies that the material is loaded with its upper side of the cloth visible on the loader, and thus the seam performed with the upper sewing head, is the sewing that will remain visible in the trousers.
Two of these constructional choices are disclosed below.
In the first prior-art case, the automatic unit normally has a single sewing head positioned on the side of the unloader for the seam performed on the material, for example in the case of applying back pockets to trousers.
The loader is always positioned in front of the sewing head, and the machine has two or more mechanical grippers for locking in the material, so that the loader moves the material to be sewn from right to left or vice versa.
In this type of loading, the version with two sewing heads that are placed alongside one another is also known.
Using this first constructional embodiment also entails the material being loaded by the operator onto the loading plane, and being moved between the different processing stations by means of a mechanical gripper that clamps the material between two points of contact against the movable loading plane.
Using this first automatic unit entails the following consecutive operating steps:

In the first step, the operator starts to load the material to be sewn onto the loading plane, positions the flap of the panel inside the mechanical gripper, whilst the mechanical gripper is open. The loader is positioned in in its rest point;
In the second step the operator closes the loading gripper and actuates the movement cycle of the gripper assembly, the grippers open and close on the basis of the type of programmed operation. The loader is always positioned in its rest position.
In the third step, the loader moves the material, kept stationary by the mechanical gripper assembly in two points in the zone of the sewing head. The movement is performed only if the sewing head is in a condition to receive the load of the material. At the same time, if already sewn material is present, the gripper of the translator closes and moves the material to the next processing station or to the unloader on the basis of the type of automatic unit selected.
Fourth step: the sewing head locks the material that has just been loaded by means of its inner gripper and the loader opens the mechanical grippers.
Fifth step: the loader returns to its starting point. The sewing head locks the material and starts the programmed sewing cycle. In the last station, the step of unloading the material is performed.

Only at this point the operator can start to load the next material to be sewn onto the loading plane inside the mechanical gripper.
In this case, the main problem arises from the translation/loading system that during the various processing stations does not properly keep the material locked on the entire surface, but only in the area where the mechanical grippers operate, with the result that the material cannot remain in a correct position during the various operations.
In this first type of automatic unit, there is no possibility of the material being moved between the different processing stations via a complete upper piece, with this piece touching and locking uniformly the upper side of the material to be sewn. In practice, the complete piece is only in the sewing station and is solidly constrained to the sewing head to which it is applied.
The material in the last station is unloaded automatically from the work surface.
The use of this automatic unit equipped with this type of loader has demonstrated that in order to increase efficiency, the operator has to work with an automatic unit with a single sewing head in tandem with another automatic unit with a single head. In this case, it is not possible to perform a double-colour seam on the same sewing piece, i.e. with upper two-colour/type sewing yarn combined with lower two-colour/type sewing yarn.
If the version of the double sewing head is loaded, the material between one sewing head and the other is not retained completely and so the quality of the second sewing cannot be constant because the formation of the stitch of the first seam "pulls" the material, especially in the case of light or elasticised materials and therefore in the case of parallel sewing, differences in width between the seams may be noticed.
The second choice of constructional type can be performable with a further dedicated automatic unit provides for this automatic unit being equipped with a carousel or turntable with 3 or 4 stations and two sewing heads.
The material to be sewn in this second case is placed inside a material locking-in device comprising two metal sheets that open like a book, pivoted on the upper side.
This material locking-in device enables the material to be kept locked-in internally, during the step of loading/rotation of the carousel and during each sewing step. The operator opens and closes manually the material locking-in device whenever it is necessary to perform an operation of loading and unloading of the material and this entails a significant waste of time, because the material locking-in device cannot be loaded with a new element until the preceding material has been unloaded.
The operator is then forced manually to position and push the material locking-in device against the positioning system fixed on the carousel, inasmuch as the fixing system in the carousel, does not have the possibility of coupling automatically the material locking-in device if the latter is placed in an incorrect position.
In this second case, fixing cylinders lock the fixing device on the carousel, and at this point the carousel performs a rotation to position the material where needed but in the case of very short seams, two operators have to be used to perform the two steps of loading and unloading the material to make the machine efficient.
The carousel loader is positioned in front of the two sewing heads and moves the material locking-in device between one processing station and the other.
As specified previously, the carousel, in this second prior-art case, has an automatic system with two pneumatic grippers to couple and uncouple the material locking-in device, but the aforesaid carousel system does not allow the material locking-in device to be lifted with the material inside in the different stations and thus all the system works at only one work level during rotation of the carousel. Further, this system is not equipped with any pneumatic actuator that would enable the material locking-in device to be pushed against the lower plane.
This second type of automatic unit has a central carousel with 3 or 4 stations and has two sewing heads.
The material is loaded manually by the operator inside a mechanical system formed by two hinged metal sheets that open like a book, forming said material locking-in device.
The sewing heads are at two angles of the loading plane, there are two opposite loading and unloading stations of the material locking-in device, and in this unit no automatic unloader of the material from the material locking-in device is in position.
Inside the material locking-in device between the two elements there is no mechanical system for aligning or positioning the material but a series of adhesive pieces of rubbers are used, which have to be moved whenever is necessary , on the basis of the size/parameter of the material to be sewn.
The carousel moves by a pitch and has the material locking-in device with the just sewn material positioned in the left station dedicated to unloading.
The processing steps for this second type of sewing unit are the following:

In the first step the operator actuates the cycle of unlocking the material locking-in device from the main body and removes from the carousel the material locking-in device with the material that has just been sewn;
In the second step the operator actuates rotation of the carousel, all the material locking-in devices present in the carousel move by one position anticlockwise. The rotation occurs only if seams have been performed in the two heads and if the material locking-in device in the loading station had already been previously loaded.
In the third step, the operator opens the material locking-in device and unloads the present content;
In the fourth step, the operator loads the new material to be sewn inside the material locking-in device, positions a flap of the panel against the foam stops or aligned with the reference marks.
In the fifth step the operator pushes the material locking-in device against the reference points present in the carousel in the loading station, which is currently free;
In the sixth step, the operator actuates the locking-in cycle of the material locking-in device.

At this point the operator starts again from the first step.
Each time the carousel brings a new material locking-in device in front of the sewing machine, these operations occur automatically in sequence before and after the sewing cycle:

BEFORE the sewing cycle:
- ▪ A) step of unlocking the material locking-in device from the main body of the carousel, whilst the sewing head remains stationary in its rest position
- ▪ B) step of locking the material locking-in device on the main support of the sewing head;
- ▪ C) start of the programmed sewing cycle.
AFTER the sewing cycle:
- ▪ A) step of unlocking the material locking-in device from the main support of the sewing head whilst the sewing head remains stationary in its rest position
- ▪ B) step of locking the material locking-in device on the main body of the carousel.

This second type of operating unit is basically unnecessarily complex and expensive and does not enable the desired results to be obtained from the point of view of operating time because the essential components for correct automation are lacking.
Document JP 2015 066384 A discloses a machine for automatic sewing that comprises a rotating table and several feeding mechanisms of jigs for locking in a material to be sewn.
Document CN 108 708 091 A discloses a rotary disc type automatic feeding, sewing and discharging tool. The rotary disc type automatic feeding, sewing anddischarging tool comprises a sewing station, a feeding conveying belt, a discharging conveying belt, a material circulation station and a cloth jig. A sewing machine base is provided with a sewing table which is located below a sewing machine and extend forwards, the material circulation station is arranged in front of the sewing table, the feeding conveying belt and the discharging conveying belt are respectively arranged on the left side and the right side of the material circulation station, and the conveying directions of the feeding conveying belt and the discharging conveying belt are identical.
Document WO 2016/155173 A1 discloses an automatic feeding mechanism capable of coordinating with a sewing machine. The automatic feeding mechanism comprises a rotary feeding rack, a feeding work platform being arranged on the rotary feeding rack, a template rotating mechanism being arranged in the feeding platform, the template rotating mechanism matching an automatic feeding fixture arranged thereon for feeding together, stitching templates being distributed on the feeding platform along a feeding route, and the sewing machine being assembled at the tail end position of the feeding route of the feeding platform.

DESCRIPTION OF THE INVENTION

The present invention aims to provide a carousel material loading system, with independent processing stations and with jigs for locking in material that operate with three specific functions, i.e. with performance capable of eliminating the aforesaid drawbacks.
The invention aims in particular to use a sewing unit of the carousel type, that is positioned in the centre between several independent processing stations, so that the carousel continues to rotate normally in one direction.
This is obtained by means of a carousel material-loading system with independent processing stations whose characteristics are described in the main claim.
The appended claims of the solution in question outline advantageous embodiments of the invention.
The system according to the invention provides for the same movable structure being present in each processing station that is present in the main body of the carousel and using the same jig for locking the material, which in this case can have a quadrilateral shape, fixed to the carousel for each movable structure.
Each processing station thus has the advantage of being able to perform several actions/functions, on average three, on the basis of the type of process, which needs to be performed for/in that specific position of the carousel.

ILLUSTRATION OF THE DRAWINGS

Further features and advantages of the invention will become apparent from reading the following description of an embodiment of the invention provided by way of nonlimiting example, with the aid of the figures illustrated in the appended tables of drawings, in which:

figure 1 shows the overall schematic plan view of an automatic sewing machine according to the invention equipped with a carousel loading system for loading the material to be sewn;
figure 2 illustrates a plan view of the machine according to the invention showing the position of the operator located at the loading position;
figure 3 shows section B-B of the machine of fig. 2;
figure 4 illustrates a schematic view according to the detail C of figure 3;
figures 5 to 9 illustrate front views of the sewing station during consecutive processing steps, using the machine according to the invention;
figures 10 to 12 show front views of the loading station during the first three processing steps, performed by using the machine according to the invention.

DESCRIPTION OF THE INVENTION

With reference to the accompanying figures, and initially in particular with reference to figure 1, the reference number 10 generally indicates an automatic sewing machine equipped with a carousel loading system for loading the material to be sewn, with independent loading and processing stations.
Substantially, referring also to figure 1, this machine of the carousel type comprises a system of the type with a platform 11 rotating on a vertical axis, known as a carousel, positioned in the centre between several independent processing stations, indicated by 12, 13, 14 and 15, said carousel being able to continue to rotate normally in one direction, which, in the case represented, is anticlockwise.
In each processing station present in the main body of the carousel a locking-in jig 16 is present, having a quadrilateral, in this case substantially rectangular, shape, which is a material locking-in system and which is used for each movable structure fixed to the carousel.
Each processing station is further equipped with a lifting system with independent actuators in this case consisting of pneumatic cylinders indicated with 17, 18, 19, 20, which act on the respective locking-in jig 16 to bring the locking-in jig 16 from a first lowered position to a second raised position.
Again with reference to figure 1, the carousel machine according to the invention comprises two sewing heads 21 and 22, positioned at two contiguous processing stations and at 90° from one another with respect to the dial of the carousel and suitable for performing seams, for example by using sewing yarns of different colours, or for different sewing operations.
The two stations 21 and 22 are arranged at 90° from one another with respect to the quadrant of the carousel and are located at the stations 13 and 14, that is in positions respectively opposite the loading station 12 affected by the action of the actuator 17 and opposite the unloading station 15 affected by the action of the actuator 20.
Thus in sequence, according to the embodiment shown in a plan view in figure 1, the loading station 12 is followed, at a distance of 90°, by a first processing station 13 in which a seam is performed by the machine 21, then a second processing station 14 follows, at a distance of 90° from the preceding station, in which a second seam is performed by the machine 22 and lastly an unloading station 15 follows, spaced 90° apart from the preceding station, in which the processed material is unloaded.
More precisely, with reference to figure 3 and to the detail of figure 4 that shows the detail C of figure 3, in each single independent processing station of the carousel, and in this case reference is made to the processing station 13, there is a movable structure 23 that is moved vertically with respect to the loading plane, by the pneumatic cylinder or actuator 18, and two linear guides 24.
The function of this movable structure is to be raised/lowered above the locking-in jig 16 for locking in the material, and also to maintain the material locking-in jig against the loading plane, at an adjustable operating pressure, during the rotation of the carousel.
The frame of the locking-in jig 16 for locking in the material comprises four metal elements 25 and 26, one for each corner of the jig, two of which, indicated with the reference number 25, are placed at the side of the movable structure of the carousel, whereas other two elements 26 are arranged on the side of the main structure of the sewing head. Said elements have a substantially frustoconical conformation with a vertical axis.
With reference also to figure 3 and to the detail of figure 4, on a support assembly 31 associated with a main structure 32 of the sewing head 21, two centring elements 27 are fixed having a substantially cylindrical or prismatic conformation inside which a cavity is obtained with a frustoconical section that is open on the side of the larger base placed below. A respective frustoconical element 26 is housed inside said cavity.
These centring elements 27 have the function of centring the material locking-in jig with respect to a support assembly 31 associated with the main structure 32 of the sewing head 21 when the latter is lowered, getting inserted 26, causing a self-centring with respect thereto. An identical conformation is present at the sewing head 22.
Two further centring elements 28 are fixed on the movable structure on the carousel side, a metal plate 29 being fixed to the upper part of the movable structure and a permanent magnet 30 being fixed to the metal plate 29 and being positioned inside each centring element.
According to the embodiment shown in figure 4, these centring elements 28 placed on the movable structure 23 on the carousel side has the function of centring the locking-in jig 16 for locking in the material with respect to the position of the movable structure 23 of the carousel when the latter is lowered.
The function of the permanent magnet 30 is to maintain the coupling between the frustoconical element 25, fixed on the locking in jig 16 for locking in the material, the centring element 28, fixed to the movable structure 23, when the movable structure 23 of the carousel is lifted in the loading station 12 of the material, with the intervention of the respective actuator 17, as shown in figure 1.
As said, four jigs for locking in material are fixed in the carousel and each jig for locking in material passes through the loading station at least once during each full rotation of the carousel.
The frustoconical elements 25 and 26 present in the locking in jigs for locking in material work in synergy with the entire movable structure of the main body of the carousel and of the machine. The movement of each actuator 17, 18, 19 and 20 is independent in each processing station so as to perform the following operations:

a) pushing the locking-in jig 16 against the loading plane, to be able to move the material without positioning problems during the rotation of the carousel
b) keeping the locking-in jig 16 for locking in material raised so as to enable the material to be inserted on the loading plane when the carousel is in the loading station 12
c) lowering or raising the movable structure of the carousel synchronously with the support assembly 31 associated with the main structure 32 of the sewing heads 21 and 22, whenever each locking-in jig 16 is positioned in front of a sewing head 21 or 22. In this case, whenever a new locking-in jig 16 is positioned in front of a respective sewing head 21 or 22 the following operations occur automatically before sewing and at the end of sewing.

Before sewing, the following further four steps occur completely automatically:

F1) The carousel couples the frustoconical elements 25 of the locking-in jig 16 with the centring elements 28 by means of the vertical thrust downwards of the actuator 18 and starts the rotation step to position the locking-in jig 16 for locking in material opposite the sewing head 21 while the movable structure is lowered, with the locking-in jig 16 for locking in material under pressure against the loading plane to lock in the material (figure 5);
F2) subsequently, locking of the material locking-in jig 16 by the main structure of the sewing head 21 is commanded, with the frustoconical elements 26 being coupled with the centring elements 27 while the carousel keeps the movable structure lowered and stationary in this position. In this step, the locking-in jig 16 for locking in material has all four frustoconical elements 25 and 26 which are working coupled with the respective centring elements 27 and 28, (figure 6);
F3) the actuator 18 raises the centring element 28 and thus unlocks the locking-in jig 16, overcoming the force of the permanent magnets 29 (figure 7).
F4) At this point, the sewing head 21 starts the sewing cycle on the material (figure 7).

After sewing, the following further four steps occur completely automatically:

F5) the centring elements 28 on the carousel are lowered on the frustoconical elements 25 by the actuator 18 to lock the locking-in jig 16 for locking in material by the carousel, whilst the main structure 31 of the sewing head keeps the material locking-in jig lowered and stationary in this position. Also, in this step, the locking-in jig 16 for locking in material has all four frustoconical elements working (figure 8);
F6) unlocking the locking-in jig 16 for locking in material by the support assembly 31 associated with the main structure 32 of the sewing head 21 with the centring elements 27 that are released from the frustoconical elements 26, whilst the carousel has the movable structure lowered with the actuator 18 that maintains the locking-in jig 16 for locking in material against the loading plane (figure 9).
F7) The carousel carries out a rotation to position the locking-in jig for locking in material in the next processing station (figures 9 and 10) with the movable structure lowered, with the locking-in jig 16 for locking in material under pressure to lock in the material against the loading plane.

In figures 10, 11 and 12, further operating diagrams are illustrated that refer to views from the loading station, where in figure 10 a step is shown in which the carousel brings an empty locking-in jig 16 onto the loading position, in figure 11 the actuator 18 raises the locking-in jig by the metal plate 29 equipped with a permanent magnet placed in the centring element 28, leaving the passage free for loading the new fabric and in figure 12, after loading the material, the locking-in jig is lowered by the actuator 18 to lock in the fabric ready to be brought to the sewing area as per step F1 of figure 5.
As it is possible to notice from what has been disclosed and illustrated, the machine according to the invention offers the main advantage that derives from the use of an automatic loading system that enables the material to be sewn to be loaded initially manually or automatically, and after loading in the first processing station, the material moves between the various carousel stations autonomously and without positioning problems due to the presence of the self-centring system consisting of frustoconical elements 25 and 26 and centring elements 27 and 28.
This advantage is made possible thanks to the locking-in jig 16 for locking in the material that is always present in the upper part of the material and to the carousel which via the actuator automatically always maintains the locking-in jig for locking in material under pressure, during the movement of the material between the various processing stations.
The advantage of maintaining the material constantly locked-in during the various movements, is to avoid that even if the first seam "pulls" the material around the seam itself, performing a new sewing cycle, the new sewing will always be positioned correctly with respect to the first seam.
Thanks to the loader according to the invention, production efficiency is increased significantly, both in the case of the same type of upper and lower sewing yarn and in the case of seams with a different upper and lower sewing yarn, because the sewing cycle can always be divided among several combined sewing heads and that are present in the processing stations and therefore the operator has only half a sewing cycle to load the carousel with the new material to be sewn, compared to a loading system.
The material is automatically unloaded and does cause a waste of time and moreover also in the case of very short processing steps in each processing station, and to maintain the efficiency level high, it does not need to increase the workers engaged in loading and unloading operations compared to a loading system.
Each processing station has thus the advantage of being able to perform three actions/functions on the basis of the type of processing that needs to be performed for/in that specific position of the carousel.

Claims

An automatic sewing machine (10) comprising a work surface and a carousel loading system for loading the material to be sewn, said machine comprising a carousel in the form of a rotating platform (11) having a centre placed on an axis that is vertical with respect to the work surface and on which several independent processing stations (12, 13, 14 and 15) are present, in which each processing station (12, 13, 14 and 15) of the carousel comprises a movable structure (23) comprising a locking-in jig (16) for locking in the material to be sewn, said machine further comprising two sewing heads (21, 22), positioned at respective adjacent processing stations (13, 14)
characterized in that it further comprises, in every processing station (12, 13, 14 and 15), a lifting system having an independent actuator (17, 18, 19, 20) that acts by means of linear guides on the locking-in jig (16) to bring the locking-in jig (16) from a lowered position to a raised position with respect to the work surface.
The automatic sewing machine (10) according to claim 1, characterized in that each of said locking-in jigs (16) for locking in the material comprises four frustoconical elements (25, 26), one for each corner of the jig, at least two of which (25) are placed at the side of the movable structure (23) of the carousel and the other two frustoconical elements(26) are arranged on one side of a support assembly (31) associated with a main structure(32) of said sewing heads (21, 22).
The automatic sewing machine (10) according to claim 2, characterized in that said support assembly (31) associated with the main structure (32) of the sewing heads (21, 22) comprises two centring elements (27), each of which has a cavity of frustoconical shape for centring the locking-in jig (16) for locking in material when the support assembly (31) is lowered and the frustoconical elements (26) are inserted into said cavity, and self-centered with respect thereto.
The automatic sewing machine (10) according to claim 3, characterized in that two further centring elements(28) are fixed on the movable structure (23) on the carousel side, each further centring element having a cavity of frustoconical shape for centring the locking-in jig (16) for locking in material when the movable structure (23) is lowered and the frustoconical elements (25) are inserted into said cavity, and self-centered with respect thereto, whereby a metal plate (29) is fixed in the upper part of each further centring element (28), a permanent magnet(30) that is positioned inside a corresponding cavity of frustoconical shape being fixed to said metal plate (29) .
The automatic sewing machine (10) according to claim 4, characterized in that said further centring elements (28) comprising a magnet (30) that are placed on the carousel side of the movable structure (23) cause the raising of the locking-in jig (16)and the manual or automatic loading of the material under the locking-in jig (16).
The automatic sewing machine (10) according to claim 4, characterised in that said further centring elements (28) placed on the carousel side of the movable structure (23) cause the centring of the locking-in jig (16) for locking in material with respect to the position of the movable structure (23) of the carousel when the latter is lowered by means of said actuator (18).
A method carried out by an automatic sewing machine (10) according to any one of claims 2 to 6, characterized in that the following processing steps are performed in sequence.
F1) in a first processing station (12) partial locking-in of a material to be sewn by the locking-in jig (16);

F2) rotating by 90° the platform to arrange the locking-in jig (16) at a second processing station (13) at which a first sewing head (21) operates;

F3) total locking-in of the locking-in jig (16) and performing a first seam by the first sewing head (21) ;

F4) partial unlocking of the sewing jig (16) and rotation by 90° of the platform to arrange the locking-in jig (16) at a third processing station (14) at which a second sewing head (22) operates;

F5) total locking of the locking-in jig (16) and performing a second seam by the second sewing head (21);

F6) partial unlocking of the sewing jig (16) and rotation by 90° of the platform to arrange the locking-in jig (16) at a fourth processing station (14);

F7) total unlocking of the locking-in jig (16), lifting of the locking-in jig (16) and unloading of the sewn material.
A method according to claim 7, wherein said automatic sewing machine (10) comprises the frustoconical elements (25, 26) and the centring elements (27, 28) according to claims 2 to 6, characterized in that during step F1 the movable structure (23) couples the frustoconical elements (25) of the locking-in jig (16) with the centring elements (27) by a vertical downward thrust of a actuator (18) and starts the rotation step to position the locking-in jig (16) for locking in material in front of the sewing head (21) whilst the movable structure is lowered, with the locking-in jig (16) for locking in material maintained under pressure against the loading plane to lock the material.
The method according to claim 8, wherein during step F3 the locking of the material locking-in jig (16) is made by the main structure of the sewing head (21), with the frustoconical elements (26) that are coupled with the centring elements (27) whilst the movable structure (23) maintains the locking-in jig (16) lowered and stationary in this position, in this step the locking-in jig (16) for locking in material having the four frustoconical elements (25, 26) coupled with the respective centring elements (27, 28).