DESCRIPTION OF THE PRIOR ART There are known models of shoes, which have the sole, or bottom, simply glued to the upper, whereas other models have the sole stitched to the upper along the side (bowl- like sole) and yet others have the sole joined to the upper by stitching, which is substantially perpendicular to the sole and extends along the entire, or part of the, outer edge of the sole.

In the last mentioned type of footwear, the stitching often completes and strengthens the joining of sole and upper obtained by glue, thus the so obtained shoes are particularly strong, which is appreciated by the users.

The machines for stitching the sole to the upper in the way described above, are known as"Blake"to those skilled in the art, and have not been technically improved for many years.

Basically, these machines include a horn-like support oriented upwards, rotating on a vertical axis and featuring, connected to its upper part, a kind of disc driven into rotation with respect to the axis by gearing linkages associated to the support.

The disc has an axial hole and an eccentric hole, from which the stitching thread goes out.

When the stitching is to be preformed, the support is introduced into the upper.

A hook needle, coaxial with the support axis, cooperates with the support from outside of the sole and passes through the sole, thus perforating the sole, until it enters the axial hole of the disc, so as to hook the thread guided by the eccentric hole.

During its upward movement, the needle pulls a kind of thread loop, which is later hooked by a crochet, outside of the upper.

The operator guides the shoe manually below the needle to finish the stitching, substantially following the outer edge of the sole, being facilitated by the rotation of the arm, which is moved continuously to a position which is each time the most convenient.

The stitching pitch is determined by a transport foot which acts on the sole, when the needle is in the outer position and this can sometimes cause inconveniences, if the sole moves with respect to the upper.

The stitching obtained by the"Blake"machines features a non-negligible drawback resulting from the fact that the holes made by the hook needle are rather wide and leaves fractures in the sole, thus permitting entrance of water through these holes during use of the shoe.

Another structural disadvantage of the"Blake"machines results from the fact that their dimensions are suited to work also on heavy and thick soles, thus the entity of the masses moving alternately is big, in order to obtain

a thrust string enough for the needle to pass through the material of the above soles.

This causes vibrations and produces a loud noise, thus worsening the conditions in the working environment.

Currently, a lot of footwear models have thin and soft soles, and for their stitching the"Blake"machine is much too powerful, besides the above mentioned drawbacks.

There are also known sewing machines which feature a conventional pointed needle, and are equipped with an oscillating arm supporting the crochet group, which cooperates with the needle.

Due to the technical and structural problems, the arm of the above machine can oscillate through a limited angle (<180°) between two end positions.

This feature makes it impossible to make an endless stitch following a closed loop, as it is often required to stitch a sole to an upper, because it needs inevitably at least one interruption, when the arm, being in the end position, obstructs the stitching.

Thus, the stitching must be completed, after the positions of the article to be stitched and of the arm have been suitably changed, by a so-called"resume" operation.

It is obvious that this procedure is not only difficult, but is also inconvenient for the quality of the so obtained stitching, as far as the strength and aesthetic aspect are concerned.

SUMMARY OF THE INVENTION

Therefore, the main object of the present invention is to propose a stitching machine, designed especially for replacing the above mentioned"Blake"machines in all cases, in which the thickness and hardness-of-the sole- makes their use disadvantageous due to the above problems.

Another object of the present invention is to propose a machine which can stitch with two threads and obtain a knotted stitch, using a traditional needle, thus obtaining a stitching which is much more resistant to water infiltrations with respect to known solutions.

Another object of the present invention is to propose a machine, which is equipped with mechanisms for transporting material more precise and reliable than the "Blake"machines.

A further object of the present invention is to propose a machine, which uses different known, and consequently, widely tested, mechanisms, but presents an innovative combination of these mechanisms and a particular conformation, which increases its working versatility and allows to increase considerably the range of possible applications.

The above mentioned objects are obtained, in accordance with the contents of the claims, by a two-thread sewing machine for stitching a sole to a shoe upper, said machine including: a base; a column, mounted on said base; a head joined to said column; first means situated inside the head for reciprocating a vertical needle; second means, working in step relation with the first means for operating a forward transport foot for moving forward the sole and upper stitched to each other;

an oscillating arm supported by said base and oscillating about an arm oscillating axis; a crochet group supported by the free end of said arm and situated under said needle for cooperating with said needle and obtaining two-thread stitching, said crochet group rotating about a rotation axis coincident with the arm oscillating axis; gear means constituting a mechanical links for maintaining unchanged the spatial arrangement of said crochet group with respect to said needle, independently from the position assumed by the oscillating arm; motion transmission means linked to said first means situated inside said head, and partially introduced into said arm, for operating said crochet group in step relation with the needle; said machine being characterized in that: said arm oscillation axis of said arm is inclined with respect to the vertical; said arm is capable of oscillating through of unlimited extension in one direction or in an opposite direction; motor driving means are provided for driving said arm into oscillation in both directions; toothed means are connected to said base and to said crochet group and are in mesh engagement with said mechanical link constituted by said gear means, said toothed means including circular tooth racks extending through 360° ; a basket and a crochet are included in said crochet group and cooperate with said needle in accordance with an incidence angle defined between the needle and the rotation axis of said crochet group.

BRIEF DESCRIPTION OF THE DRAWINGS The characteristic features of the present invention, which do not result from what above reported, will be

pointed out in the following description of a preferred, embodiment of the machine, in accordance with the contents of the claims and with reference to the enclosed drawings, in which: - Figure 1 is a schematic lateral view of the proposed machine; Figure 2 is a plan view taken along the line II-II of Figure 1 ; - Figures 3A and 3B re views of two operation moments of the machine of Figure 1 ; Figure 4 is vertical section view of the crochet basket; Figure 5 is top view of the same basket of Figure 4; Figure 6 is a perspective view of a sole and a relative upper of a shoe stitched by the proposed machine; Figure 7 is a section view taken along the line VII- VII of Figure 6, in which a stitch is emphasized out.

BEST MODES OF CARRYING OUT THE INVENTION With reference to the above mentioned figures, reference numeral 100 indicates the proposed stitching machine, which stitches a sole 90 to a shoe upper 80.

The machine 100 includes a head 2 of known type, with situated thereinside first means, not shown, for reciprocating a vertical needle 1, which is directed downwards, and second means, working in step relation with the first means, for operating a transport foot for moving forward the stitched material.

Also the second means and the transport foot have not been shown, since of known type: anyway, it is to be pointed out that the active step of the foot, during which the material is-transported, is performed with the needle 1 set in engagement with by the foot, thus the needle 1 is carried by a relevant bar, which oscillates in a plane parallel to the one on which the foot moves, crosswise to the head 2.

The use of this type of transport is advantageous with respect to the one used in"Blake"machines, mentioned in the introductory statement, since the forward movement is assured for both the sole 90 and the upper 80.

The head 2 is fastened to the top of a column 3, in turn fastened to a base 4, which extends horizontally in the same direction as the head 2.

The base 4 supports an oscillating arm 5, with its oscillating axis W being inclined with respect to the vertical, in accordance with a vertical plane parallel to the plane of longitudinal extension of the head 2; the inclination has been constructively determined as approximately 20°, which is considered the best, however it is obvious that this value is not mandatory.

The oscillating arm 5 is curved and supports, on its free end, a crochet group 50, whose rotation axis coincides with the oscillation axis W of the arm 5.

The crochet group 50 is suitably placed below the needle 1, and is operated by transmission means, not shown as they are known, so as to cooperate in step relation with needle, for obtaining a two-thread knotted stitch. The transmission means are connected to first means situated inside the head 2 and housed in the column 3, in the base 4 and in the arm 5.

The arm 5 and the crochet group 50 are like the ones described in the US Patent 5.048. 361, also owned by the Applicant, and include gear means 15 connected via a mechanical linkage, on one side to the stationary part, with respect to which the arm oscillates, and on the other side, to the basket 51 of the crochet group 50, so that an oscillation of the arm 5 in one direction corresponds to an oscillation of the same extension, but in the opposite direction, of the whole crochet group 50.

Consequently, the crochet group maintains unchanged its spatial orientation, i. e. it remains motionless, independently from the spatial position assumed by the arm 5.

The machine 100, proposed by the present application, includes the arm 5, which can oscillate, in one direction or the other, with an unlimited stroke, i. e. it can perform one or more complete rounds about its axis W.

For this purpose, a toothed crown 154 is fastened to the base 4 instead of a toothed section, and it constitutes the beginning of the mechanical linkage defined by the means 15; accordingly, the tooth rack 155, constituting the terminal part of the mechanical linkage, is extended to 360° on the basket 51.

The oscillation movement of the arm 5, in one direction or the other, is determined by the action of motor means 6, which are controlled by an operator and which include a motor reducer 60.

The motor reducer 60 is supported by the base 4 and its output pinion 61 is in mesh engagement with a toothed wheel 65, integral coaxially with the arm 5 (Figures 1 and 2).

The above mentioned inclination of the oscillation axis W of the arm 5, which as it has been already said, coincides with the rotation axis of the crochet group 50, makes the needle 1 enter-the group at an incidence angle Ax equal to the angle between the axis W and the vertical.

The crochet group 50 is designed according to this need: in particular, the basket 51 has a slot 510, through which the needle 1 passes.

The slot 510 is inclined with respect to the vertical by the same angle Ax, by which the rotation axis W of the crochet 52 is inclined with respect to the vertical: thus, the slot 510 is oriented vertically.

The crochet 52 features a smoothed portion Sm, extending for a suitable circumference arc, which is sufficient to prevent the needle 1 from interfering with the crochet 52.

The support surface 511 for the material to be stitched, formed by the basket 51 in the area surrounding the slot 510, is orthogonal to the latter, in a conventional configuration (Figures 4 and 5).

Each part of the crochet group 50 has been constructed in such a way, using all possible tricky features, as to reduce the total dimensions, in order to facilitate its introduction into the upper 80 and to allow it to reach the most difficult points during stitching the sole 90.

The machine 100 is especially indicated for stitching soles 90 equipped with a groove 91, aimed at containing the stitch.

The sole 90 is previously joined to the upper 80: the so pre-assembled shoe is fitted onto the arm 5, with the

crochet group 50 situated inside the upper 80, so as to position the initial stitching point under the needle 1.

The arm 5 is situated in a position, in which it forms as little obstacle as possible, by tne motor means 6, which are activated by the operator, e. g. by a pedal element (not shown).

The same operator, using another pedal element, not shown, actuates the machine and starts the stitching, holding the shoe with both hands and moving it suitably, so that the stitching being formed, is positioned correctly inside the groove 91 (Figure 7).

During the stitching, the operator rotates the arm 5 via a command element acting on the motor means 6, so as to move the arm to a position, in which it forms as little obstacle as possible, in accordance with the changing arrangement of the shoe.

Figure 3A shows, as example, the position of the arm 5 during the stitching of the shoe toe, while Figure 3B shows its position during the stitching of the shoe side.

It is to be pointed out that the machine 100 allows a stitching to be performed with any path, both open or close loop path, due to this characteristic feature of the arm 5, which can rotate freely, in one direction or the other, without any limit.

This allows any operation limit to be overcome in those machines mentioned in the preamble, which include a pointed needle and an arm, which can oscillate within a limited path between two end stop positions.

The inclined arrangement of the axis W of the arm 5 contributes advantageously to increase the operation. capacity of the machine 100.

Actually, as seen in Figure 1, the two diametrically opposite positions, assumed by the arm on the plane, along which the axis W is inclined, cause a different inclination of-the-extreme part of the arm 5-with respect to the crochet group 50, which remains motionless, thus obtaining different positions of the parts, which are to be introduced into the upper 80, so as to offer a wider range of arrangements, among which the least obstacle position of the arm 5 is to be found.

One of the advantages of the proposed machine results from the fact that, working with the pointed needle, it is possible to obtain circular holes of small diameter, which close elastically around the thread, when the stitching is finished, thus avoiding the water infiltrations occurring in the stitching obtained by the curved needle in the"Blake"machines, mentioned in the introductory statement.

Moreover, attention must be drawn to the operation low noise of the proposed machine with respect to the"Blake" machines, characterized by high noise, and to consequent advantages to the reduction of acoustic pollution of working environment.

The just described machine 100 is especially indicated for the footwear filed, but it is obvious that it can be used also in other fields, e. g. leatherwear and clothing, because the obtained stitching corresponds to the requirements of such types of production.

The advantages of the proposed machine appear evident from what has been said so far.

Although the machine uses widely known, and consequently tested, mechanisms, it presents an innovative combination of these mechanisms and a particular conformation, which

allows to fulfill all the objects mentioned in the preamble, and offers immediately these features of reliability and duration, which are indispensable in machines for industrial use.