Feed system for feeding a secondary thread to a stitching station of a sewing machine and sewing machine comprising said feed system

Abstract

A feed system for a sewing machine has a feed wheel (13), which comprises a circumferential surface (14) provided with a groove (15) of variable depth for housing a secondary thread (29); and a mechanical transmission (16) for transmitting the motion from a drive shaft (11) of the sewing machine to the feed wheel (13); the circumferential surface (14) of the feed wheel (13) comprising a first portion (27), in which the groove (15) has a first depth (H1) such that the secondary thread (29) is compressed between the feed wheel (13) and a support platform (2) of the sewing machine, and a second portion (28), in which the groove (15) has a second depth (H2) such that the secondary thread (29) is at a distance from the support platform (2).

Description

[0001] Description

[0002] Title

[0003] Feed for feeding a thread to a stitching station of a machine and sewing machine said feed

[0004] The present invention relates to a feed system for feeding a secondary thread to a stitching station of a sewing machine.

[0005] The present invention also relates to a sewing machine comprising said feed system.

[0006] Prior art

[0007] Sewing machines of known types usually comprise a support platform that forms a substantially horizontal supporting bed for a fabric to be sewn; a stitching station formed in the supporting bed to create a plurality of stitches in the fabric to be sewn; and a feed device to feed the fabric to be sewn through the stitching station and along the supporting bed.

[0008] Known sewing machines also comprise a needle, which is mounted in the stitching station and is configured to be moved through the fabric to be sewn with an alternating motion comprising a forward movement to feed a main thread through the fabric to be sewn and a return movement to allow the main thread to form a loop under the fabric to be sewn, and a feed unit, commonly known as a hook, for inserting a secondary thread through the loop of the main thread and forming a stitch.

[0009] Additionally, known sewing machines comprise a drive motor provided with a drive shaft configured to rotate continuously around an axis of rotation, and a transmission unit for connecting the drive shaft mechanically to the needle and the feed device so as to synchronize the motion of the feed device and the needle with the rotation of the drive shaft.

[0010] Document EP0580260 relates to a sewing machine and discloses the forming of a modified stitch. In particular, the forming of said modified stitch requires the steps of inserting a stitch segment of the secondary thread into the loop formed by the main thread and then separating the stitch segment, by cutting, from the secondary thread, in such a way that, when the needle advances in the return movement, drawing the main thread with it and gripping the stitch segment between the fabric and the main thread, said stitch segment forms a modified stitch together with the main thread.

[0011] However, in order to form said modified stitch, the secondary thread must be fed intermittently, so as to position the stitch segment of the secondary thread within the loop of the main thread and keep the stitch segment in position for a specified time interval, until the stitch segment is separated from the secondary thread.

[0012] Object of the invention

[0013] An object of the present invention is to provide a feed system for intermittently feeding a secondary thread to a stitching station of a sewing machine which is capable of overcoming all the difficulties described above.

[0014] According to the present invention, a feed system is provided for intermittently feeding a secondary thread to a stitching station of a sewing machine, said machine comprising a support platform that forms a supporting bed for at least one fabric to be sewn, the feed system comprising:

[0015] - a feed wheel, which comprises a circumferential surface provided with a groove of variable depth for housing the secondary thread, and which is configured for rotating about a first axis of rotation and for being positioned relative to the support platform of the sewing machine so that at least a portion of the circumferential surface faces the support platform and is positioned near the support platform; and - a mechanical transmission for transmitting the motion from a drive shaft of the sewing machine to the feed wheel; the circumferential surface of the feed wheel comprising a first portion, in which the groove has a first depth such that the secondary thread is compressed between the feed wheel and the support platform when, in use, the first portion is positioned near the support platform, and a second portion, in which the groove has a second depth, greater than the first depth, such that the secondary thread is at a distance from the support platform when, in use, the second portion is positioned near the support platform.

[0016] Thanks to the present invention, the secondary thread can be fed intermittently to the stitching station of a sewing machine.

[0017] In practice, during the rotation of the feed wheel, when the first portion of the circumferential surface is near the support platform, the secondary thread is driven towards the stitching station so as to be inserted into the loop formed by the main thread.

[0018] Conversely, when the rotation of the feed wheel brings the second portion of the circumferential surface near to the support platform, the secondary thread slides in the groove, because it is at a distance from the support platform. In this condition, the secondary thread remains stationary within the loop of the main thread for a specified time interval, so as to allow a cutting device to separate a stitch segment from the secondary thread. Thus, a modified stitch can be formed.

[0019] The feed device made according to the present invention is simple in construction, compact, and guides the secondary thread directly towards the stitching station without forcing the secondary thread to run along complex paths.

[0020] Furthermore, thanks to the present invention, existing sewing machines can be modified by incorporating into them the feed system proposed by the present invention. Another object of the present invention is to provide a sewing machine capable of overcoming the difficulties described above.

[0021] According to the present invention, a sewing machine comprising a support platform forming a supporting bed for at least one fabric to be sewn is provided, together with the feed system as described above.

[0022] Thanks to the sewing machine, the modified stitch can be formed in a simple and efficient manner, by feeding the secondary thread intermittently.

[0023] Brief description of the drawings

[0024] Further characteristics and advantages of the present invention will be made clear by the following description of non-limiting examples of embodiment of the invention, with reference to the figures of the attached drawings, of which:

[0025] - Figure 1 is a perspective view, with parts removed for clarity, of a sewing machine made according to the present invention;

[0026] - Figure 2 is a perspective view, with parts removed for clarity, of the sewing machine of Figure 1 ;

[0027] - Figure 3 is a sectional view, with parts removed for clarity, of the sewing machine of Figure 1 ;

[0028] - Figure 4 is a sectional view, with parts removed for clarity, of a detail of the sewing machine of Figure 3;

[0029] - Figures 5 and 6 are schematic sectional views, taken along respective section planes, of a detail of the sewing machine of Figure 1 in a first operating configuration;

[0030] - Figures 7 and 8 are schematic sectional views, taken along respective section planes, of a detail of the sewing machine of Figure 1 in a second operating configuration; and - Figure 9 is a further sectional view, with parts removed for clarity, of the sewing machine of Figure 1 .

[0031] Preferred embodiment of the invention

[0032] With reference to Figure 1 , the number 1 indicates the whole of a sewing machine comprising a support platform 2 forming a supporting bed P for a fabric to be sewn, and a feed system 3 for feeding a secondary thread intermittently.

[0033] In the following discussion, the term “fabric” denotes any medium made of any material that needs to be sewn.

[0034] The sewing machine 1 further comprises a frame 5, which holds up the support platform 2 and the feed system 3.

[0035] With reference to Figure 2, the sewing machine 1 comprises a stitching station 6, which is provided with a plurality of apertures 7 formed through the support platform 2 in a direction D1 (Figure 3) substantially perpendicular to the supporting bed P, and a feed device 8 configured for feeding the fabric along the supporting bed P in a transverse direction D2 relative to the direction D1 (Figure 3).

[0036] The feed device 8 is provided with a plurality of drive teeth 9, which engage the apertures 7, extend in the direction D2 and are moved by a drive device (not shown in the attached figures) along a closed-loop feed path in a containing plane substantially perpendicular to the supporting bed P.

[0037] The feed path (not shown) is configured for raising the drive teeth 9 above the supporting bed P so as to engage the fabric and feed it along the supporting bed P, and for lowering the drive teeth 9 below the supporting bed P so as to disengage the fabric.

[0038] With reference to Figure 3, the sewing machine 1 comprises a drive motor 10, preferably electric, which is provided with a drive shaft 11 , and a driving wheel 12, preferably of the endless screw type, which is connected to the drive shaft 11 and is coupled to the feed system 3 so as to transmit the motion to the feed system 3.

[0039] With reference to Figures 1 and 3, the feed system 3 comprises a feed wheel 13, which comprises a circumferential surface 14 provided with a groove 15 of variable depth for housing the secondary thread, and which is configured for rotating about an axis of rotation A1 and for being positioned relative to the support platform 2 so that at least a portion of the circumferential surface 14 faces the support platform 2 and is positioned near the support platform 2. In particular, the feed wheel 13 is positioned under the support platform 2.

[0040] Additionally, the feed system 3 comprises a mechanical transmission 16 for transmitting the motion from the driving wheel 12 to the feed wheel 13. In particular, the mechanical transmission 16 is of the geared type and comprises a plurality of gear wheels 17, 18, 19, 20 configured for transmitting the motion from the drive shaft 11 to the feed wheel 13.

[0041] With reference to Figure 3, the stitching station 6 comprises a cutting device 21 configured for cutting the secondary thread into stitch segments. In particular, the cutting device 21 is configured for sliding along a cutting axis A2 substantially parallel to the direction D1 in an alternating manner and in synchronization with the rotation of the feed wheel 13.

[0042] In particular, the sewing machine 1 comprises a first transmission unit, not shown in the attached figures, which mechanically couples the drive shaft 11 to the cutting device 21 and is configured for converting the rotary motion of the drive shaft 11 to the alternating motion of the cutting device 21 , and for synchronizing the alternating motion of the cutting device 21 with the rotation of the feed wheel 13.

[0043] With reference to Figure 4, the stitching station 6 comprises a needle 22 configured for moving through the fabric to be sewn with an alternating motion, preferably, but not necessarily, an alternating rectilinear motion, comprising a forward movement to insert a main thread 23 through the fabric to be sewn and a return movement to allow the main thread 23 to form a loop 24 under the fabric to be sewn.

[0044] In particular, the sewing machine 1 comprises a second transmission unit, not shown in the attached figures, which mechanically couples the drive shaft 11 (Figure 3) to the needle 22 and is configured for converting the rotary motion of the drive shaft 11 to the alternating motion of the needle 22, and for synchronizing the alternating motion of the needle 22 with the rotation of the feed wheel 13 and with the alternating motion of the cutting device 21 .

[0045] In the case described and illustrated herein, which does not limit the present invention, the support platform 2 comprises a running seat 25, which faces the groove 15 of the feed wheel 13 and is shaped to house the secondary thread. In practice, the running seat 25 is formed in a lower portion of the support platform 2.

[0046] In particular, the running seat 25 extends in a rectilinear manner between the feed wheel 13 and the cutting device 21 so as to guide the secondary thread into the stitching station 6 through the loop 24 formed by the main thread 23.

[0047] In particular, the cutting device 21 is fork-shaped and is provided with two branches 26 positioned on opposite sides of the needle 22 so as to cut the stitch segment on either side of the loop 24 of the main thread 23 when said stitch segment is inserted into the loop 24.

[0048] With reference to Figures 5-8, the circumferential surface 14 of the feed wheel 13 comprises a portion 27, in which the groove 15 has a depth H1 such that the secondary thread 29 is compressed between the feed wheel 13 and the support platform 2 when, in use, the portion 27 is positioned near the support platform 2 (Figures 5 and 6); and a portion 28, in which the groove 15 has a depth H2, greater than the depth H1 , such that the secondary thread 29 is at a distance from the support platform 2 when, in use, the portion 28 is positioned near the support platform 2 (Figures 7 and 8). In practice, when, in the course of the rotation of the feed wheel 13 about the axis of rotation A1 , the portion 27 is near the support platform 2, the secondary thread 29 is propelled towards the stitching station 6. On the other hand, when the portion 28 is near the support platform 2, the secondary thread 29 slides in the groove 15 and remains substantially stationary relative to the support platform 2.

[0049] In the case described and illustrated here, which does not limit the present invention, the depth H1 is less than a diameter of the secondary thread 29, and the depth H2 is greater than or equal to the diameter of the secondary thread 29.

[0050] In particular, the depth of the groove 15 increases continuously along the circumferential surface 14 of the feed wheel 13 from the depth H1 to the depth H2. In greater detail, the portion 27 is diametrically opposite the portion 28.

[0051] With reference to Figure 9, the mechanical transmission 16 comprises a shaft 30 configured for rotation about the axis of rotation A1 , on which is fixed the feed wheel 13; a gear wheel 17 fixed to the shaft 30; a gear wheel 18, which engages with the gear wheel 17 and is configured for rotation about an axis of rotation A3 substantially parallel to the axis of rotation A1 ; a shaft 31 configured for rotation about an axis of rotation A4 substantially parallel to the axes of rotation A1 and A3; a gear wheel 19, which is fixed to the shaft 31 and engages with the gear wheel 18; a gear wheel 20 (Figures 1 and 3), which is fixed to the shaft 31 and is configured for engaging with the drive wheel 12.

[0052] In particular, gear wheels 17, 18, 19 and 20 have substantially different diameters. In greater detail, the gear wheel 17 has a smaller diameter than the gear wheels 18, 19 and 20. The gear wheel 19 has a greater diameter than the gear wheels 17, 18 and 20.

[0053] In use, and with reference to Figure 3, the drive motor 10 causes the drive shaft 11 and the drive wheel 12 to rotate. The mechanical transmission 16 transmits the motion of the drive shaft 11 from the drive wheel 12 to the feed wheel 13, causing the feed wheel 13 to rotate about the axis of rotation A1 . The first and second transmission units, not shown in the attached figures, transmit the motion from the drive shaft 11 to the cutting device 21 and the needle 22, respectively, so as to synchronize the rotation of the feed wheel 13 with the alternating motion of the cutting device 21 and of the needle 22.

[0054] With reference to Figures 5-8, the rotation of the feed wheel 13 cyclically brings the portion 27 and the portion 28 of the circumferential surface 14 near to the support platform 2.

[0055] In particular, with reference to Figures 5 and 6, when the portion 27 is near the support platform 2, the secondary thread 29 is compressed between the feed wheel 13 and the support platform 2, and the secondary thread 29 is therefore propelled towards the stitching station 6.

[0056] With reference to Figures 7 and 8, when the rotation of the feed wheel 13 brings the portion 28 near to the support platform 2, the secondary thread 29 loses its contact with the support platform 2 and therefore slides in the groove 15. In this condition, the secondary thread 29 remains stationary in the stitching station 6 for a specified time interval. Thus, the feed system 3 feeds the secondary thread 29 intermittently to the stitching station 6.

[0057] With reference to Figure 4, the needle 22 is moved simultaneously, and in synchronization with the feed of the secondary thread 29 into the stitching station 6, through the fabric to be sewn, in an alternating motion. In particular, the needle 22 executes a forward movement to insert the main thread 23 through the fabric to be sewn and a return movement to allow the main thread 23 to form the loop 24 under the fabric to be sewn.

[0058] When the loop 24 has been formed, the feed wheel 13 feeds the secondary thread 29 into the running seat 25, which guides the secondary thread 29 towards the stitching station 6 so as to insert a stitch segment of the secondary thread 29 into the loop 24 of the main thread 23.

[0059] When said stitch segment is within the loop 24, the feed system 3 momentarily interrupts the feed of the secondary thread 29 for a specified time interval, during which the needle 22 executes the return movement, drawing the main thread 23 with it and gripping the stitch segment of the secondary thread 29 between the fabric to be sewn and the main thread 23.

[0060] Then, during said time interval, the cutting device 21 slides along the cutting axis A2 so as to separate the stitch segment from the secondary thread 29 on either side of the loop 24 of the main thread 23. Thus, the stitch segment of the secondary thread 29 forms a modified stitch together with the main thread 23.

[0061] Finally, the present invention evidently comprises further variants of the embodiments described, which embodiments are included in the protective scope of the attached claims.

Claims

Claims1 . Feed system for intermittently feeding a secondary thread to a stitching station of a sewing machine, said machine comprising a support platform (2) that forms a supporting bed (P) for at least one fabric to be sewn, the feed system (3) comprising:- a feed wheel (13), which comprises a circumferential surface (14) provided with a groove (15) of variable depth for housing the secondary thread (29), and which is configured for rotating about a first axis of rotation (A1) and for being positioned relative to the support platform (2) of the sewing machine (1) so that at least a portion of the circumferential surface (14) faces the support platform (2) and is positioned near the support platform (2); and- a mechanical transmission (16) for transmitting the motion from a drive shaft (11) of the sewing machine (1) to the feed wheel (13); the circumferential surface (14) of the feed wheel (13) comprising a first portion (27), in which the groove (15) has a first depth (H1) such that the secondary thread (29) is compressed between the feed wheel (13) and the support platform (2) when, in use, the first portion (27) is positioned near the support platform (2), and a second portion (28), in which the groove (15) has a second depth (H2), greater than the first depth (H1), such that the secondary thread (29) is at a distance from the support platform (2) when, in use, the second portion (28) is positioned near the support platform (2).

2. Feed system according to Claim 1 , wherein the first depth (H1) is less than a diameter of the secondary thread (29), and the second depth (H2) is greater than or equal to the diameter of the secondary thread (29).

3. Feed system according to Claim 1 or 2, wherein the depth of the groove (15) increases continuously along the circumferential surface (14) of the feed wheel (13) from the first depth (H1) to the second depth (H2).

4. Feed system according to any of the preceding claims, wherein the mechanical transmission (16) is of the geared type and preferably comprises a plurality of gear wheels (17, 18, 19, 20) configured for transmitting the motion from the drive shaft (11) of the sewing machine (1) to the feed wheel (13).

5. Feed system according to any of the preceding claims, wherein the mechanical transmission (16) comprises a first shaft (30) configured for rotation about the first axis of rotation (A1), on which is fixed the feed wheel (13); a first gear wheel (17) fixed to the first shaft (30); a second gear wheel (18), which engages with the first gear wheel (17) and is configured for rotation about a second axis of rotation (A3) substantially parallel to the first axis of rotation (A1); a second shaft (31) configured for rotation about a third axis of rotation (A4) substantially parallel to the first axis of rotation (A1) and the second axis of rotation (A3); a third gear wheel (19), which is fixed to the second shaft (31) and engages with the second gear wheel (18); and a fourth gear wheel (20), which is fixed to the second shaft (31) and is configured for engaging with a drive wheel (12) connected to the drive shaft (11) of the sewing machine (1).

6. Sewing machine, comprising:- a support platform (2) forming a supporting bed (P) for at least one fabric to be sewn; and- the feed system (3) according to any of the preceding claims.

7. Sewing machine according to Claim 6, comprising a drive motor (10), which is provided with a drive shaft (11) coupled to the feed system (3) so as to transmit the motion to the feed system (3).

8. Sewing machine according to Claim 6 or 7, wherein the support platform (2) comprises a running seat (25), which faces the groove (15) of the feed wheel (13) and is shaped to house the secondary thread (29).

9. Sewing machine according to any of Claims 6 to 8, comprising a stitching station (6) provided with a needle (22) configured for moving through thefabric to be sewn with an alternating motion comprising a forward movement to insert a main thread (23) through the fabric to be sewn and a return movement to allow the main thread (23) to form a loop (24) under the fabric to be sewn; the feed system (3) being configured for feeding a stitch segment of the secondary thread (29) through the loop (24) of the main thread (23).

10. Sewing machine according to Claim 9, wherein the stitching station (6) comprises a cutting device (21) configured for cutting the secondary thread (29) into stitch segments.

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