EP0377404B1 - Zig-zag sewing machine - Google Patents

Description

Many zig-zag sewing machines are known in which the throwing of the needle is obtained by a pendulum movement of the needle bar.

In some of these, this needle bar is slidably mounted in a cradle, articulated to the frame of the machine by an intermediate point of its length and whose upper end is subjected to the action of a control device itself. imposing back and forth movements of amplitude characteristic of that desired for the throwing movement of the needle. Swiss patent 458,899 and Japanese Kokai 51-103,547 and 51-103,548 precisely describe structures of this kind.

In other sewing machines, such as those disclosed by American patents 4,215,638 and 4,458,611, the needle bar is also associated with a cradle subjected to a pendulum movement, but this is made integral with the frame of the machine by two omni-directional joints, the first of which is near the upper end of the cradle and the second, located at the bottom of the sewing head, is generally mounted on a support lever, itself articulated on the machine frame.

In a third type of sewing machine, which is shown in particular by the patents FR 881 686, US 2 862 468, US 2 932 268, US 2 989 016 and 4 213 409, the sewing machine no longer comprises, strictly speaking, cradle, the needle bar being slidably mounted inside two bearings respectively associated with a first fixed support, for one, and with a second support, movable transversely to the longitudinal axis of the needle bar, for the 'Other, these bearings being made integral with the respective support by means of connecting members ensuring them, individually, mobility relative to their support in at least two orthogonal directions.

In the machine which is the subject of the French document above, the connecting members in question are constituted by sorts of cardan joints fixed between the bearing and a portion of the machine housing, for the upper bearing, and, for the lower bearing, between this bearing and the end of a control rod in translation, extending inside the upper arm of the machine up to a drive mechanism located in the vertical upright of the frame.

In the machines described in the last four American patents cited, the external face of the bearings has a spherical profile by which they are pivotally engaged in corresponding seats, of complementary shape, associated with a support lever articulated on the frame of the machine , for the upper bearing, and integral with the frame, for the lower bearing. The throwing movement of the needle bar is obtained by alternating tilting of the upper lever.

Whatever the structure of the pendulum-needle bar sewing machines mentioned above, it is heavy and complex: they are, in fact, mechanically controlled machines in which the throwing movement of the bar- needle is obtained by implementing linkage systems and mechanical transducers responsible for transforming the movement, originally rotary, of a drive device into axial displacements of amplitude adjustable according to the desired amplitude for the movement of pier of the needle bar.

Architectures of this type are no longer acceptable in modern sewing machines and, in particular in electronic machines which are known to constitute an optimum compromise between the overall dimensions of the housing and a reduced weight for a quality of high performance. On this last point, it will be noted that the natural inertia presented by the mechanical arrangements known from the state of the art mentioned above is such that it becomes practically impossible to control the movement at high speed from step motors. not to the market without having to oversize these and, therefore, also the frame which must incorporate them.

It should also be noted that these known arrangements are of a structural complexity which has become unacceptable these days, both in terms of the sole manufacture of the parts which they include. that, and above all, to that, on the one hand, of their assembly at the factory, and, on the other hand, of their repair, or even their possible replacement by the resellers.

The invention specifically proposes to eliminate all of the above drawbacks by implementing the invention, the essential characteristics of which are defined, in particular, by claims 1 to 18.

• sur la fig. 1, une élévation latérale d'une première forme d'exécution du mécanisme de commande de la jetée de la barre-aiguille de la machine selon l'invention,
• sur la fig. 2, une vue, partiellement coupée, selon II-II de la fig. 1 et,
• sur la fig. 2A, une vue schématique illustrant le fonctionnement de cette forme d'exécution.
• La fig. 3 est une vue selon III-III de la fig. 1.
• La fig. 4 montre, en coupe verticale, une unité "moteur, barre-aiguille, paliers" constituant le mécanisme de commande de la jetée d'une machine à coudre selon une deuxième forme d'exécution;
• La fig. 5 est une vue selon V-V de la fig. 4;
• La fig. 6 est une vue similaire à celle de la fig. 5, selon une variante.
• La fig. 7 montre, en coupe verticale, une unité "moteur, barre-aiguille, paliers, presse-étoffe" constituant notamment le mécanisme de commande de la jetée d'une machine à coudre selon une troisième forme d'exécution;
• La fig. 8 est une vue selon VIII-VIII de la fig. 7.
• La fig. 9 montre, en coupe verticale, une unité "moteur, barre-aiguille, paliers" constituant le mécanisme de commande de la jetée d'une machine à coudre selon une quatrième forme d'exécution;
• La fig. 10 est une vue selon X-X de la fig. 9.

The accompanying drawings illustrate, by way of non-limiting example,

• in fig. 1, a side elevation of a first embodiment of the mechanism for controlling the throwing of the needle bar of the machine according to the invention,
• in fig. 2, a view, partially cut away, along II-II of FIG. 1 and,
• in fig. 2A, a schematic view illustrating the operation of this embodiment.
• Fig. 3 is a view along III-III of FIG. 1.
• Fig. 4 shows, in vertical section, a "motor, needle bar, bearings" unit constituting the thrust control mechanism of a sewing machine according to a second embodiment;
• Fig. 5 is a view along VV of FIG. 4;
• Fig. 6 is a view similar to that of FIG. 5, according to a variant.
• Fig. 7 shows, in vertical section, a unit "motor, needle bar, bearings, press-stuffing" constituting in particular the mechanism for controlling the throwing of a sewing machine according to a third embodiment;
• Fig. 8 is a view along VIII-VIII of FIG. 7.
• Fig. 9 shows, in vertical section, a "motor, needle bar, bearings" unit constituting the thrust control mechanism of a sewing machine according to a fourth embodiment;
• Fig. 10 is a view along XX of FIG. 9.

The sewing machine according to the invention is similar to the machines of the state of the art of the first and second types described, as regards the pendulum oscillation mode chosen for the needle bar, and to those of the third type, from the point of view of the mechanical structures used, the simplicity of which is found, mutatis mutandis, in the embodiments which will be described below.

In a first embodiment of the sewing machine according to the invention (fig. 1 to 3), the needle bar 1 is driven in its alternating vertical movement from a shaft 2, itself controlled at its right end by a motor not shown and whose left end carries a discoidal plate 3 on which projects an eccentric pin 4.

On this axis is pivoted one end of a lever 5 (fig. 2) freely mounted in a rectangular notch 6 which has one end of a connecting rod 7. The lever 5 is made integral with this connecting rod by its second end which is mounted pivoting on an axis 8, integral with the connecting rod, and extending at right angles to the axis 4 already mentioned.

We find a similar arrangement at the other end of the connecting rod 7 which is provided with a second rectangular notch, not visible in the drawing, but in all points similar to the notch 6, enveloping a second lever also not visible but in shape and of dimensions identical to the lever 5, articulated on the connecting rod 7 by an axis 9, parallel to the axis 8, this second lever carrying an axis 10 extending at right angles to the axis 9.

This axis 10 is integral with a stud 11 fixed to the upper end of the needle bar 1.

Thanks to the arrangement which has just been described, it is possible to ensure the vertical movement of the needle bar regardless of the inclination thereof, within the limits of the usual jetty movements in the sewing machine. In fact, any inclination of the stud 11 due to a corresponding inclination of the bar 1 will be compensated by an inclination of the connecting rod 7 made possible by the presence of the articulated levers connecting it both to this stud and to the plate 3.

The needle bar 1 is slidably mounted in two bearings 12 and 13 having a spherical external profile and engaged in seats of complementary shape provided in a fixed support 14, for the first bearing, and, for the second bearing, in a lever 15 mounted tilting, by one end, around an axis 16 carried by a second fixed support 14 *, and the upper face of the other end of which has curved teeth 17 whose radius of curvature is centered on the axis 16.

The bearings 12 and 13 are preferably made of synthetic material with a low coefficient of friction but having good wear resistance: it may, for example, be Teflon, Delrin (registered trademarks) or even metals sintered. Thanks to the high elastic deformation capacities that such materials exhibit, it is indeed possible to introduce the bearings 12 and 13 into their respective seats by driving out.

The supports 14 and 14 * are both integral with the carcass of a stepping motor 18 controlling the tilting of the lever 15 by means of a pinion 19 meshing with the toothed sector 17 of this lever (fig. 3).

It is understood that any angular displacement of the pinion 19, in one direction or the other, will result in a corresponding tilting of the needle bar. Referring to Figure 1, this tilting will take place to the right, if the pinion 19 is driven counterclockwise; it will take place in the opposite direction, for an angular displacement of the pinion 19 opposite to the previous one.

The needle bar can, in fact, be moved from its extreme right position 1 '(fig. 2A) to its extreme left position 1' 'and vice versa by corresponding displacement of the bearing 13 from its position 13' to its position 13 '' and vice versa.

As can be seen in the drawing, all the elements which have just been described are grouped in an autonomous and therefore removable unit including the motor 18,

In the embodiment which is the subject of FIGS. 4 to 6, the assembly "motor, needle bar, bearings" is in the form of a one-piece aggregate, of particularly reduced and removable volume. This aggregate can therefore be manufactured anywhere, independently of the other constituent elements of the sewing machine, and be assembled on the job with a minimum of adjustments.

In the drawing, the drive mechanism of the needle bar in vertical movement has not been shown, but it goes without saying that it can be of the kind described above without requiring any special adaptations.

In FIG. 4, we recognize, first of all, the stepping motor which comprises, mounted between two end flanges, an upper flange 20 and a lower flange 21, ball bearings 22 and 23 supporting a vertical shaft 24 to which is fixed, on the one hand, the armature 25 of the motor, and, on the other hand, a pinion 26. Surrounding the armature 25, we recognize the stack 27a of the sheets of the inductor and a excitation winding 27b.

The upper flange 20 extends to the right, in the drawing (fig. 4), and has an opening 20a of spherical profile forming one of the two seats between which is enclosed, by its external face, also spherical, a first bearing 28 held in position by a cover plate 29, fixed on the flange 20 and having an opening 29a, of spherical profile, located in line with the opening 20a of the flange, the wall delimiting the opening 29a constituting the seat of the bearing 28 in cooperation with the wall defining the opening 20a.

Below this first bearing and vertically thereof, the aggregate illustrated has a second identical one, 30, arranged coaxially with the previous one, and held in position by two shells 31a and 31b forming, by assembly, a lever 31 (Fig. 5) and which are clamped between the flange 21 of the motor and a complementary flange 32, bearing on a flange 21a of this flange visible only partially in FIG. 4 but also extending along the longitudinal edges thereof from this collar to its right end in the drawing.

The flange 32 is fixed to the flange 21a by screws, not shown, passing through the passage 32a; it has, in addition, an oblong window 32b, of arcuate profile located opposite a similar window, 21b, of the flange 21. These two windows are arranged one above the other and in line with the longitudinal axis of the opening of the bearings 28 and 30. These are in fact crossed by the needle bar 33 of the sewing machine whose stepping motor described must be able to control throwing movements.

To this end, the shells 31a and 31b forming the lever 31 are hollowed out, at the right end of their opposite faces, by a semi-spherical housing, 31c and 31d, located one to the right of the other and to the right corresponding housings 21c and 32c respectively, arranged on the facing faces of the flanges 21 and 32.

In the space formed between the housings 31d and 21c, as well as in that delimited by the housings 31c and 32c, the aggregate described has two balls 34 and 35 forming a pivoting member for the lever 31.

At the end situated opposite the balls 34 and 35 relative to the needle bar 33, the flanges 21 and 32 are further hollowed out, on their opposite faces, by a groove 21d, respectively 32d, of cross section having the profile of a circular segment centered on a point of each flange coinciding with the axis of symmetry of the housings 21c and 32c already described.

As for the shells 31a and 31b constituting the lever 31, the external face of each of them is hollowed out by two recesses 31e, respectively 31f, of spherical shape and opening in line with the grooves 21d and 32d of the flanges 21 and 32. These recesses, the radius of curvature of which corresponds to that of the profile of the section of the grooves 21d and 32b, form a seat for two pairs of balls 36 and 37 engaged, moreover, in the above grooves forming rolling and guide tracks for the lever 31, during its tilting around the pivot axis formed by the balls 34 and 35.

This lever 31 is in fact provided, at its left end (FIG. 5), with a toothed circular segment 38 with which the pinion 26 already cited engages.

Thus, any angular displacement of this pinion, due to its drive by the stepping motor, results in a corresponding tilting of the lever 31 around its pivot axis (balls 34 and 35) and, consequently, of the bar needle 33 (throwing movement) inside the slots 21b and 32b.

As in the case of the executions already described, it will suffice to control the stepping motor with an appropriate impulse voltage to obtain from the needle bar that it performs a throwing movement of well-defined amplitude which can, moreover, be even different on both sides from the vertical position, from rest, from the needle bar.

In the variant of FIG. 6, the lever 31 has been replaced by a slide 39 capable of being moved in opposite directions, F1 and F2, by rolling on balls 40, associated with this slide, at the bottom of rectilinear grooves 41 formed in the flanges 21 and 32, all in the image of what has been described with reference to the execution of Figures 4 and 5. An oblong slot 32d, formed in the flange 32, allows the needle bar d '' make its jetty movement. This variant is more particularly intended for a sewing machine whose loop sensor rotates around a horizontal axis.

In its third embodiment, the sewing machine according to the invention comprises an aggregate forming a body with a hollow rod 42 forming a support for a presser foot 43 (fig. 7).

This rod 42 is slidably mounted inside a tubular shaft 44, constituting the shaft of a stepping motor of which 45 is the armature, 46 the inductor, 47 and 48 of the end plates in a housing from which two ball bearings, 49 and 50 are driven, engaged, by their internal cage, with the shaft 44.

A spring device, not shown, makes it possible to move the rod 42 vertically in order to drive it either in the illustrated position, in which the foot 43 is applied elastically against the working surface 51 of the lower arm 52 of the machine, or in a high position in which the foot 43 is distant.

As in the case of the third embodiment (fig. 4), the upper flange, 47, of the motor extends to the right, in the drawing, beyond the inductor 46, and forms a seat, in cooperation with an attached plate 53, for a bearing 54 with a spherical external profile.

This bearing is intended to ensure, in cooperation with a second bearing of the same type, 55, the maintenance and the axial guidance of a needle bar 56 which is driven in an alternating vertical movement by a mechanism not shown in the figure but of the genre illustrated in Figures 1 and 2, for example.

The bearing 55 is mounted between two shells 57a and 57b constituting a lever 57, integral, by its left part, (fig. 7) with the shaft 44 of the stepping motor of the aggregate and whose right part has , for each shell, on the one hand, a passage 57c, respectively 57d, the edges of which have a spherical profile complementary to the external profile of the bearing 55, and thus forming the seat of this bearing, and, on the other hand, a housing semi-spherical 57e and 57f, respectively.

The composite lever 57 is disposed between the flange 48 and a complementary flange 58, bearing on a flange 48a of the flange 48, a flange which is only partially visible in FIG. 7 but which also extends along the edges longitudinal of the flange 48, to the right end thereof, in the drawing.

The flange 58 is fixed to the flange 48a by screws (not shown) passing through passages 58a; it has, moreover, a window 58b, of arcuate profile, centered on the axis of the shaft 44 of the motor, window located opposite a similar window 48b of the flange 48. These two windows are superimposed and their length corresponds at the maximum amplitude of the desired throwing movement for the needle bar 56 which passes through them.

The flanges 48 and 58 finally comprise, on their opposite faces and at a distance from the axis of the shaft 44 corresponding to that separating this axis from the semi-spherical housings 57e and 57f of the shells 57a and 57b of the lever 57, a oblong groove of semi-circular section, 48c, respectively 58c, and of arcuate profile, centered on the axis of the shaft 44.

Balls 59 and 60 are arranged in the spaces delimited between the housings 57e and 57f and the respective grooves 48c and 58c.

The aggregate which has just been described is more particularly intended for a sewing machine whose loop sensor is mounted on a vertical axis disposed at the rear of the needle bar, or to the left of the latter in the drawing.

Thus, any angular displacement of the armature 45 of the stepping motor will result in a displacement of the same direction and amplitude of the composite lever 57 and, consequently, of the bearing 55 so that the needle bar 56 will tilt, relative to its pivot point constituted by the bearing 54, by an angle characteristic of the angular displacement of the armature.

Any variation in the amplitude and direction thereof will correspond to a proportional change in the angle of the needle bar. Such a variation can be obtained, in a well known manner, by supplying the stepping motor with periodic signals of various polarity and number, depending on the direction and amplitude desired for the pendulum movement of the needle bar.

In its embodiment illustrated in Figures 9 and 10, the aggregate that comprises the sewing machine according to the invention has a simplified and particularly functional general architecture.

We find the stepping motor comprising a shaft 61 mounted on two ball bearings 62 and 63, between two flanges 64 and 65, and carrying the armature 66 of the motor as well as, at its lower end, a pinion 67. The inductor 68 is represented, on the left of the shaft 66, by its stack of stator sheets and, on the right, by one of its windings.

The flange 64 extends to the right, beyond the inductor 68 to form a tab 64a having an opening 64b of frustoconical profile, going by tightening towards the top of the figure and which forms a seat for the external face, spherical, of a bearing 69 held in this opening by a vertical spring 70 engaged, by the upper end, on a neck 69a projecting from the lower part of the bearing 69 and, by its lower end, on a neck 71a which has the upper part of a second bearing 71, identical to the bearing 69 and resting on a seat formed by an opening 72a, of frustoconical profile, formed in a horizontal lever 72. This profile becomes narrower towards the bottom of the figure.

The lever 72 is in the general form of a sector of a circle, toothed at 72b, in engagement with the pinion 67 and resting, on the upper face of a complementary flange 74, on the one hand, by two semi-protrusions 72c and 72d, and, on the other hand, by a ball 73, engaged both in a semi-spherical housing 72e of the lever and in a semi-spherical housing 74a of the flange 74. A slot 72f, extending near the toothing 72b guarantees an elastic contact without play and damping, between the pinion 67 and the toothing itself.

The flange 74 is fixed to a flange 65e of the flange 65, of which only a portion is visible in the drawing but which also extends along the longitudinal edges of the latter, up to its straight end. This fixing is carried out by means of screws, not shown, passing through passages 74b and engaging in corresponding threaded holes made in the flange.

A window 74c, of arcuate shape, allows the vertical passage and the lateral movement of a needle bar 75 slidably mounted in the bearings 69, 71.

Indeed, the ball 73 constitutes a pivot axis for the lever 72 which can therefore be tilted clockwise and counterclockwise by corresponding angular displacement of the armature 66 of the stepping motor, each time in one direction contrary to that of tilting of the lever 72. As a result, it will therefore be possible to drive the needle bar in a pendulum movement around the upper pivot point that constitutes the bearing 69 and thus obtain the throwing of the needle 76 carried by the needle bar 75. Of course, the pendulum movement in question will be of amplitude programmed by sending to the stepping motor voltage pulses in number and polarity depending on the type of stitches to be sewn.

In addition, thanks to the force exerted by the spring 70 on the bearing 71 and transmitted by the latter on the lever 72, this lever is ensured to be permanently maintained in the correct position on the flange 74, by support of the projections. 72c on this flange, on the one hand, and by engagement of the ball 73 both in the housing 74a of the flange and in the housing 72e of the lever 72, on the other hand, without involving other holding members.

Thus, and as can be seen in the drawing, the aggregate described consists of a reduced number of parts, easy to assemble: it will suffice, in fact, to start by mounting the additional flange 74 on the flange 65e of the flange 65 of the stepper motor, then place the lever 72 on the flange 74 by engaging it, by its teeth 72b, with the pinion 67 secured to the motor shaft while inserting the ball 73 in the delimited space by the housing 72e of the lever and the housing 74a of the flange 74.

Next, two bearings are mounted separately, such as those indicated by the references 69 and 71, at the two ends of a spring, such as the spring 70, by engaging the neck 69a, respectively 71a, of the bearings in the first end opening. of the spring, respectively in the second end opening.

The whole is compressed axially until the length of the assembly becomes slightly less than the distance separating the underside of the extension 64a from the flange 64 of the motor and the upper face of the lever 72, so as to be able to pass this assembly between these elements (flange 64 and lever 72), and leads the bearings 69 and 71 to the seats 64b and 72a formed respectively in this flange and this lever.

The spring 70 is allowed to relax so that the bearings will engage in the above seats.

Finally, the needle bar 75 is introduced into the opening of the first bearing (69 or 71), then through the spring 70 and, finally, into the opening of the second bearing, by axial sliding of the bar in the bearings.

By this operation, one obtains an absolutely correct self-centering of the bearings 69 and 71 in their respective seats and therefore a perfect positioning of the needle bar relative to the other parts of the aggregate which is thus ready to be mounted in the body. of the sewing machine.

The invention is not limited to what has been described or shown: in particular, the spring 70 of the embodiment of Figure 9 could very well be replaced by an elastic member of another nature. He could, in particular, be a prestressed elastic blade, having for example the shape of a V, in support, by the end of its brassur, the weights 69 and 71 respectively.

Claims (15)

1. A zig-zag sewing machine, with a sewing head comprising:

   - a needle bar (1; 33; 56; 75);

   - a first bearing (12; 28; 54; 69) and a second bearing (13; 30; 55; 71) formed respectively by a first and a second body, each being traversed by a rectilinear passage, the needle bar being axially slidable in the passage of each body, each body having a contact surface on its external surface of a profile corresponding to that of the lateral surface of an annular segment of a sphere centred on a point of the longitudinal axis of the passage;

   - a first support (14; 29; 53; 64a) and a second support (15; 31; 57; 72) for the needle bar, each comprising at least one annular seat with a profile corresponding at least partly to that of the contact surface of the first body, for the first support, and a profile corresponding at least partly to the contact surface of the second body, for the second support;

   - means (2 to 11) for controlling the axial and bidirectional drive of the needle bar,

   - guiding means for the second support along a path transverse to the sliding displacement of the needle bar in the passages of the first and second bearings respectively;

   - means for controlling the drive of the second support on its transverse path in accordance with an alternating reciprocating movement, to which a periodic lateral displacement of the needle bar corresponds;

   - means to ensure the support of the body of each bearing via its contact surface on the respective support seat, irrespective of the position of the needle bar and/or that of the second support on their respective paths;

   characterised in that the said driving means of the second support comprise a control motor with a shaft movably rigid with the second support, and members connect the first and second supports and the motor in such a manner that the supports and the shaft occupy a predetermined relative position, the said head thus forming a self-contained unit.
2. A machine according to claim 1, characterised in that the second support comprises a lever (15) pivotable on a reinforcement (14) integral with the motor (18), and one end of the lever has a toothing (17) with a profile in the shape of an arc of a circle centred on the fulcrum (16) of the lever, one end of the shape of the motor having a pinion (19) engaged in the toothing of the support.
3. A machine according to claim 1, characterised in that the first support is formed by assembly of a first (29; 53) and a second (20; 47) shell, each with a first and second surface, the wall of each shell being traversed by an aperture (20a, 29a) the straight portion of which increases in extent from one surface to the other of the respective shell, the said apertures communicating with each other via their portions of maximum extent, and defining a housing for the first body (28; 54) of the first bearing between themselves, a ring-shaped portion of the lateral surface of this housing forming the said seat, and means retaining the first and second shells in their assembled position.
4. A machine according to claim 1, characterised in that the second support is formed by assembly of a first (31a; 57a) and a second (31b; 57b) shell, each with a first and second surface, the wall of each shell being traversed by an aperture (57c, 57d) the straight portion of which increases in extent from one surface to the other of the respective shell, the said apertures communicating with each other via their portions of maximum extent, and defining a housing for the second body (30; 55) of the second bearing between themselves, a ring-shaped portion of the lateral surface of this housing forming the said seat of the second body, and means retaining the first and second shells in their assembled position.
5. A machine according to claim 4, characterised in that the second support is situated between a first (20; 48) and a second (21; 58) wall of a cage integral with the control motor, these first and second walls being mutually parallel and having an elongate opening (21b, 32b, 32d; 48b, 58b) each elongate opening being opposite the aperture of each shell, the said elongate openings being at a distance from one another and being traversed by the needle bar and respectively comprising an oblong slot of a width greater than the diameter of the needle bar and of a length and profile corresponding substantially to the length and profile of the path followed by the needle bar during its periodic lateral displacement, and the said shells are retained in their assembled position between the first and second walls of the cage by means of at least one ball (59, 60; 34, 35, 36, 37) interposed between the shells and the walls respectively, each ball engaging in a groove (31c, 31d, 31e, 31f; 57e, 57f) hollowed into each shell, and in a groove (21c, 21d; 32c, 32d; 48c, 58c) hollowed into each wall of the cage, the said shell grooves being opposite, in pairs, to the respective grooves on the walls, and having a profile corresponding to that of the path of the needle bar.
6. A machine according to claim 5, characterised in that one end of the shaft (24) of the control motor has a toothed pinion (26) engaging in a corresponding toothing (38) formed on one end of the second support, the said grooves being arranged between the elongate openings of the walls (21, 32) of the cage on one side, and the toothing on the other, the second support being pivotable on the walls of the cage by means of one part (21c, 32c) of the support situated opposite the grooves with respect to the first and second elongate openings, and the said toothing, grooves and elongate openings each have a profile in the shape of an arc of a circle centred on the same point of the said part of the second support.
7. A machine according to claim 5, characterised in that the said shells are held in their assembled position between the first and second walls (21, 32) of the cage by at least one pair of balls (40) interposed between the shells and the walls respectively, each pair of balls engaging in a groove (41) hollowed into each of the shells and in a groove hollowed into each wall of the cage, the said shell grooves being at a distance from each other and each one being parallel to its corresponding wall groove, the pairs of grooves being mutually opposite each other and the grooves having a profile corresponding to that of the path of the needle bar, and one end of the shaft (24) of the motor has a toothed pinion (26) engaged in a corresponding toothing formed on a first end of the second support, the said grooves, elongate openings and toothing being rectilinear and mutually parallel.
8. A machine according to claim 5, characterised in that the said second support is mounted on a first end of the shaft (44) of the motor, the grooves (57e, 57f, 48c, 58c) and the elongate openings (48b, 58b) each having a profile in the shape of an arc of a circle centred on the longitudinal axis of symmetry of the shaft.
9. A machine according to claim 8, comprising a bar (42) bearing a presser foot (43), characterised in that the shaft (44) has an axial passage extending along its entire length, the bar (42) being slidably mounted in the said axial passage.
10. A machine according to claim 1, characterised in that each support (64, 72) has, on its surface facing the other support, a seat (64b, 72a) for one of the bodies (69, 71), the seat communicating with an elongate opening which opens on to a surface of the support opposite that of the seat and which allows passage of the needle bar (75), and the bodies of the bearings are retained in position by their respective contact surfaces on the respective support seat by means of at least one resilient member (70) exerting a thrust on each bearing towards its own seat.
11. A machine according to claim 10, characterised in that one of the ends of the shaft (61 ) of the motor bears a pinion (67) engaging in a corresponding toothing (72b) associated with a movable support (72) which comprises a lever pivoted on a point (73) opposite the said toothing with respect to the seat (72a), and the toothing has a curved profile with a centre of curvature coinciding with the pivotal point (73) of the lever, and the said lever rests on a plate (74) integral with the motor and located opposite the fixed support (64) with respect to the movable support (72), and to the right of the said fulcrum the lever (72) and the plate (74) each have a recess (72a, 74a) of a spherical cap shape, the openings of the recesses facing each other, and a ball (73 ) of a diameter substantially corresponding with that of the caps is located simultaneously in both the recesses, and forms the pivotal member for the lever on the plate, and also, finally, the lever is supported on the plate by means of at least two projections (72c, 72d) arranged on the lever between the toothing (72b) and the seat, the position of the recesses (72e, 74a) in relation to the lever seat being selected in such a manner that the seat is in alignment with that of the fixed support (64) at least in one of the angled positions of the needle bar.
12. A machine according to claim 10, characterised in that the resilient member is a spring (70) prestressed between the bearings (69 and 71).
13. A machine according to claim 12, characterised in that the spring is a helical spring enclosing the needle bar (75) over its portion contained between the bearings.
14. A machine according to claim 13, characterised in that the body of each bearing has a collar (69a, 71a) with an external diameter substantially equivalent to that of the aperture of the spring and comprising a portion of the passage of the respective bearing, and each end of the spring covers the collar of one of the bearings and is supported on the corresponding body.
15. A machine according to claim 12, characterised in that the spring is formed by a spring rod arranged between the bearings in a prestressed position, supported by each end on one or other of the bearings respectively.

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