TECHNICAL FIELD

The present invention concerns sewing machine for articles made of leather or similar, in particular for production of footwear, bags and the like.

BACKGROUND ART

Known automatic machines for sewing leather articles usually feature a head, cantilevered on the front of the base structure and equipped with means for supporting the needle and related operating means. The needle is moved toward means, situated below and acting as a support on which the leather articles to be sewn rest. A rotary hook, provided with a thread spool, co-operates with the needle.

The above mentioned machines are equipped also with feeding means that move the two edges of leather articles to be sewn, positioned one over the other, after each stitch.

In this field, a need has been encountered to make stitches along two sewing Iines, situated side by side and forming also a kind of ornamental design.

Figure 11 shows, as an example, a shoe upper sewn along its edge to a bottom by a double sewing line of alternate stitch. Figure 12 shows a bag with its sides sewn by a double sewing line of cross-stitch.

In the second case, the stitch can be obtained by a machine with two needles acting together so as to produce stitches from two sewing threads.

The needles, one beside the other, are carried by a shaft oscillating angularly about its longitudinal axis, so as to invert the needles positions and produce a cross-stitch; in practice, for the above mentioned needles inversion, the shaft is axially rotated about 180°.

In the first case, the stitch is produced in similar way by only one needle, whose position is inverted after having produced each stitch, in such a way that alternate stitches are obtained from one sewing thread, along the double sewing line. Obviously, the production of such stitches requires suitable apparatuses.

In particular, traditional sewing machines with two needles include a hook that rotates or oscillates around an axis perpendicular to the surface containing the two needles. The needles are arranged side by side, i.e. they are aligned with respect to the moving direction of the hook bill. The above mentioned hook bill skims over the eyes of both needles.

The Italian Patent No. 1.233.657 describes an oscillating hook for sewing machines with two needles, arranged side by side, which is provided with a hook bill resting and working on a vertical median plane between the two needles.

This solution includes a driving element provided with a slot having opposite cam-like edges which bend the pair of needles introduced into the rotary hook for stitch formation thus getting them nearer to each other when the hook bill passes therebetween. In this way the hook bill enters both loops formed by the needles.

It is obvious that such a solution may be adapted only to the sewing machines in which articles to be sewn lie on horizontal surface and are moved by a dog and the needles are operated only vertically.

In this case, the hook position, below the working surface, does not affect the machine operation. Nevertheless, it limits the application of the above mentioned stitches to ones situated along a double sewing line. Consequently, these stitches can be formed only if the articles to be sewn can be worked on horizontal surface.

Another considerable drawback of the above mentioned solution is endurance of the needles subjected to strong stresses, and consequent wear and tear resulting from intermittent bending by the cams.

SUMMARY OF THE INVENTION

The object of the present invention is to propose a machine that can sew various articles of leather or the like, performing stitches along a double sewing line, with a rotary or oscillating hook working on a plane orthogonal to the surface on which these needles lie.

The above mentioned object is obtained by means of a machine for sewing various articles, in particular articles made of leather or the like, which comprises: at least one needle, provided with a thread and fixed to a shaft that oscillates around its axis so as to move alternatively the needle between two extreme positions corresponding to first and second parallel sewing Iines; means for moving said shaft and said needle vertically between a raised position and a lowered position in which said needle passes through the articles to be sewn; means for moving said shaft and said needle parallel to a translation plane perpendicular to a lying plane defined by said needle extreme positions, with a needle forward stroke, for feeding the articles to be sewn with predetermined steps while the needle is in said lowered position, and with a needle return stroke with the needle in said raised position; a support device provided with a hook rotating on an axis perpendicular to the said translation plane and provided with a crook lying in said translation plane for catching the loop formed by the thread when said needle is in one of said extreme positions; resting means on which the articles to be sewn are moved; pressing-holding means moved in direction orthogonal to said resting means for pressing and holding said articles to be sewn during respectively, penetration and extraction of said needle.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristic features of the invention are pointed out in the following description, with particular reference to the enclosed drawings, in which: • figs. 1 and 2 show prospective views of the sewing area of the subject machine, seen at different angles; • fig. 3 shows an exploded prospective view of the rotary hook of the machine;

• figs. 3a and 3b show lateral and plan views, respectively, of the machine rotary hook as in fig. 3; • figs. 4a and 4b show a frontal view of the subject machine sewing area, in different working steps;

• fig. 5 shows a sectional view of the two-needles configuration, taken along the plane V-V of fig. 4b;

• figs. 5a and 5b show a part of the same sectional view of the one-needle configuration, in different working steps;

• fig. 6 shows a sectional view taken along the plane VI-VI of fig. 5;

• fig. 7 shows a sectional view taken along the plane VII-VII of fig. 5;

• figs. 7a and 7b show the same sectional view taken along the plane VII-VII of figs. 5a and 5b, respectively; • figs. 8, 9 and 10 show respective prospective views of the sewing area, seen at different angles in different working steps;

• figs. 11 and 12 show prospective views of respective articles sewn by the subject machine.

BEST MODE OF CARRYING OUT THE INVENTION

With reference to the above described figures, reference numeral 1 indicates the head of the sewing machine, that supports devices for driving sewing means. The head 1 is integral with the machine stationary frame 2; in particular, the head 1 is cantilevered on the front of the horizontal base structure 3 of the

stationary frame 2.

The head 1 supports a vertical shaft 4 carrying the needles and moved axially by known means, not shown. At its lower end, the shaft 4 supports, in eccentric position, a needle 5 with a thread 37. The assembly formed by the shaft 4 and the needle 5 reciprocates axially, in known way, between a raised position and a lowered position. In the lowered position the needle passes through the articles to be sewn. Otherwise, a pair of needles 5a, 5b, arranged side by side, are used, as will be described later.

The needle 5 passes freely through a hole 36 of a foot 6 (Fig. 8) which is provided with ribs in its lower part and presses the articles to be sewn during their penetration by the same needle 5. The foot 6 is carried by an arm 7 which is moved vertically by a lever link system 8 (figs. 4a and 4b).

The shaft 4, the needle 5 and the foot 6, which can translate independently from one another along their respective axes, are carried by an assembly 105 which is fastened to the head 1 by a pivot 9 and oscillates parallel to a vertical translation plane Y. This oscillation is performed according to strokes, whose amplitude defines a movement pitch of the articles to be sewn. The variation of the stroke amplitude causes the variation of the pitch.

A leather pressing element 10, situated behind the needle 5 and moved vertically, holds the articles to be sewn, during the needle 5 withdrawal. The leather pressing element 10 is carried by a bar 11 , slidingly supported by the head 1 and operated vertically by known pneumatic means.

Under the needle 5 there is a support device 12 equipped with a rotary hook 14 and a suitable sewing thread spool, which co-operate with the needle 5 in forming the stitch. As can be more precisely seen in fig. 3, the device 12 includes a ring-like body 13 that acts as a case for the rotary hook 14, commonly called "crochet".

This ring-like body 13 defines a circular chamber, inside which the rotary hook 14 and hook driving member, not shown for clearness' sake, are housed. The hook 14 rotates around the axis of the same ring-like body 13.

The sewing thread spool 15, housed inside a relative case 16, is joined in

known way with the rotary hook 14. The rotary hook 14 features a crook 17 that moves along the translation plane Y, perpendicular to the hook rotation axis.

The rotary hook 14 has also two thread guiding shoulders 14a and 14b, situated respectively on two sides of the plane Y. In its upper part, the ring-like body 13 of the device 12 supports an apertured plate 18 provided with a U-like slot 19, through whose branches, indicated with 19a and 19b, the needle passes. The plate 18 acts as rest surface for the articles to be sewn, preventing the material from diving, when the needle goes down, Moreover, the same plate prevents the needle 5 from bending during the descent, thus keeping the best mutual position of the (lowered) needle and the hook.

As will be more evident from the following description, the U-shape of the slot 19 allows the needle to pass from one sewing line to the other, as a consequence of the needle carrying shaft 4 oscillation.

The ring-like body 13 is rotatably supported by the free end of a support arm 20 which can oscillate with respect to an axis A, coincident with the oscillation and/or rotation axis of the body 13. Teeth 22, made on the outer part of the ring-like body 13, engage means that keep it motionless independently from the position taken by the arm 20; see e.g. the US Patent 5.048.361 of the same Applicant.

The needles carrying shaft 4 is driven into oscillation by a pneumatic, mechanical or electric actuator 27, fastened to the front of the machine head 1.

The actuator 27 rotates a toothed pulley 28 which engages a toothed belt 29 turning around another toothed pulley 30 keyed to the needles carrying shaft 4

(figs. 5 and 6).

The pin 9 is fastened to a vertical wall 33 of the head 1 by a threaded tang 31 tightened by a nut 32. The pin 9 is also joined with a bushing 34 made integral with a cylindrical body 35 crossed by the needles carrying shaft 4, this latter being left free to rotate axially. It is to be noted that the pin 9 lies on the intersection line between the horizontal medium plane P1 and vertical medium

plane P2 of the driving belt 29 (figs. 5 and 6) so that the pin 9 axis results parallel to the runs of the same belt 29.

Due to this configuration, the oscillation of the cylindrical body 35 on the pin 9, or the rotation of the other pulley 30 with respect to the pulley 28, is absorbed by elastic deformation of the belt 29.

It is evident, that very limited oscillation amplitude in region of the pin results in equally limited deformation of the belt 29 runs. This deformation affects the length of the runs, but is very limited. Therefore any undesired rotation of the needles supporting shaft 4, that could change the predetermined positions of the needle 5, is avoided.

Now, operation of the machine will be described, beginning from the step in which the needle 5 is introduced into the ring-like body 13, for stitch formation (see figs. 4a and 8). In this condition the needle 5 is in the extreme position A1 (fig. 7a). The assembly foot 6 - needle 5 is then lowered. The foot 6 finishes its stroke when it gets in contact with the articles 40 to be sewn, in order to press them against the plate 18, while the needle 5, guided by the slot 36 of the foot 6, passes through these articles and, consequently, enters the ring-like body 13 through the end of the first branch 19a of the slot 19. After the needle 5 has passed through the articles 40, it performs an oscillation thus making the articles move one step forward (arrow F: fig. 9). As has been already said, this oscillation is caused by oscillation of the whole assembly 150.

When the above mentioned translation stroke has been completed, the leather pressing element 10 is actuated and, while going down, it clamps the articles 40 in a position adjacent to the stitch just made (fig. 4b). This holds the stitched area of the articles down, when the needle 5 arises, so that the thread

37 hooked by the rotary hook 14 forms, in known way, the loop K (see fig. 5a).

When the needle 5 has arisen, the actuator 27 provokes oscillation of the needles supporting shaft 4 through 180°, so that the needle 5 reaches the second extreme position Z2 (fig. 7b). This rotation brings the needle 5 near the second branch 19b of the slot 19 of the apertured plate 18.

Subsequently, oscillation of the assembly 150 causes the needle 5 run the return stroke. At the end of this stroke, as has already been said, the needle goes down.

Articles forward movement occurs in the same way, but with the needle 5 guided by the second branch 19b of the slot 19. In this way, it is possible to perform alternate stitches, with only one sewing thread, along a double sewing line 50a, 50b, as illustrated e.g. at 11. The two extreme positions 21 , Z2 of the needle 5 define a needles lying plane X, which in the shown example is perpendicular to the hook translation plane Y. In this way, it is possible to obtain, on the sewing Iines 50a,50b, stitches which are staggered according to different transversal planes, and consequently, different inclination of the stitches.

Otherwise, it is possible to perform cross-stitch, as shown for instance in fig. 12, using two needles 5a, 5b arranged side by side and mounted symmetrically and eccentrically to the shaft 4: these needles define the lying plane X. Also in this case, the crook 17 moves along the translation plane Y, which crosses the needles lying plane X (fig. 7).

However, since this lying plane X is not perpendicular to the translation plane Y, the needle 5a is not aligned with the needle 5b, i.e. they do not lie on a unique plane perpendicular to the crook 17 translation plane: this allows regular forming of loops K1.K2 (indicated with broken Iines) which do not hinder each other.

The needles 5a,5b engage simultaneously the device 12, while passing through the branches 19a,19b of the slot 19 made in the apertured plate 18. The crook 17 of the rotary hook 14 passes between the needles 5a,5b, hooking rapidly one after another, the loops K1.K2.

Obviously, after the needles 5a,5b have been extracted from the articles 40, rotation of the shaft 4 by 180° inverts the positions of the needles 5a, 5b. Sewing process goes on in this way moving the needles alternatively from one to the other of the above mentioned sewing iines 50a, 50b.

It is to be pointed out, that the shape of the rotary hook is of the utmost

importance for the best performance of the assembly including the needle and rotary hook, when they form the stitch. Therefore, this shape has been accurately examined in every detail, as shown in the figs. 3a, 3b, in every position of the needle. In particular the crook 17 and the thread guiding shoulders 14a, 14b have been examined, since they allow formation of regular loops on both sides.

Consequently, the described machine can sew articles of leather or the like, performing stitches along a double sewing line, with a hook rotating or oscillating on a plane orthogonal to the plane in which the needles lie. The described solution is very versatile, as it can be used for performing the stitches on a big number of articles. In particular, these stitches are not limited to articles to be sewn only on a horizontal working surface.

Moreover, the proposed solution can be used for both rotary and oscillating hook. It is to be pointed out, that the above mentioned invention is designed particularly for the sewing machines equipped with the above mentioned device aimed at maintaining unchanged the position of the ring-like body 13 during the stitch formation.

It is understood that what above has been described as a pure example, non limitative, therefore all possible constructive variations remain under protection of the present technical solution, as described above and claimed hereinafter.