Machine for operating on workpieces

Abstract

 An automatic sewing machine, e.g. for shoe uppers, comprises workpiece supporting means operating instrumentalities (40,42) mounted at opposite sides of the supporting means to operate on a workpiece supported on the supporting means and drive means (124,160) for the supporting means arranged to move the supporting means and a workpiece supported by the supporting means (30) substantially in a plane relative to the operating instrumentalities (40,42). First motor means (19) rotate the instrumentalities (40,42) about axes (A,B) which are coaxial and extend generally transversely to the plane (30) to adjust the position of the instrumentalities (40,42) about the axes (A,B), assuming desired orientations relative to the direction of movement of work moved by the workpiece supporting means. Second motor means (6), mounted on the first carriage (16), and third motor means (28) mounted on the second carriage (27), are controlled by control means to operate in a synchronous relationship with one another.

Description

TECHNICAL FIELD

[0001] The invention relates to a machine for operating on workpieces, having workpiece supporting means, first and second rotatable carriages mounted at opposite sides of the workpiece supporting means, first operating instrumentalities mounted on the first carriage, second operating instrumentalities mounted on the second carriage, drive means for moving a workpiece relative to the first and second operating instrumentalities, and first motor means for rotating the first carriage about a first axis and for rotating the second carriage about a second axis, the axes extending substantially transversely to the direction of movement of the workpiece. The machines to which the invention relates are commonly used in operating on workpieces of flexible sheet material, such as, for instance, leather. The type of operations that may be carried out on flexible sheet materials are, for example, the stitching and folding operations involved in the manufacture of footwear.

BACKGROUND ART

[0002] Sewing machines are supplied by the applicant company, for example under the designation MPCS, in which a workpiece to be stitched either for decorative purposes or for structural reasons, for example to join together two or more components of the workpiece, can be mounted on workpiece supporting means for presentation to stitching instrumentalities. The workpiece supporting means is arranged to feed the workpiece to be operated upon past the stitching instrumentalities in feed directions controlled by suitable control means thereby to stitch the workpiece in a desired pattern. The workpiece in such a machine is moved rectilinearly along two coordinate axes and the workpiece supporting means may comprise a so-called X-Y table or other suitable workpiece support, for example as described in our copending Patent Application No. PCT/GB91/01449. Commonly the stitching instrumentalities are aligned with one or other of the two coordinate axes.

[0003] It has been found that in some circumstances, when the workpiece is moved in certain directions relative to the stitching instrumentalities, transversely to the alignment of the stitching instrumentalities, there is a tendency for stitch malformation to arise. This problem has been addressed in US-A-3808991 and US-A-4373458. However, neither of these proposals has been entirely successful. In the case of the proposal in US-A-3808991, the workpiece supporting means, including much of the operating mechanism, is moved. Such an operation is cumbersome and presents difficulties in movement of the workpiece supporting means and operating mechanism and such a machine further requires a considerable free space in order to accommodate the possibly extensive movements of the workpiece supporting means. The proposal of US-A-4373458 involves the use of complicated mechanical gearing and belting interconnections which are not only expensive, but cumbersome, mechanical interconnections are required between upper and lower stitching instrumentalities of the machine; and a differential mechanism is required in order to compensate for epicyclic effects.

[0004] Other techniques which have been adopted to mitigate the problems of directional sewing in automatic sewing machines have included the use of the so-called tri-point needle in the stitching instrumentalities. Such a needle has a point which is triangular in cross-section . However, whilst that reduces the tendency towards stitch malformation, it does not eliminate the problem entirely and furthermore, the quality of stitch formation in general tends to be less acceptable than when a preferred, wedge (or chisel) point needle is used.

THE INVENTION

[0005] The object of the invention is to provide a machine for operating on workpieces which overcomes, with the minimum of mechanical complexity, the difficulties which, when the machine is used for stitching operations, manifest themselves as the malformation of stitches. The object is achieved in that the invention comprises workpiece supporting means, first and second rotatable carriages mounted at opposite sides of the workpiece supporting means, first operating instrumentalities mounted on the first carriage, second operating instrumentalities mounted on the second carriage, drive means for moving the workpiece relative to the first and second operating instrumentalities, first motor means for rotating the first carriage about a first axis and for rotating the second carriage about a second axis, which axes extend substantially transversely to the direction of movement of the workpiece, and the invention is characterised by second motor means, mounted on the first carriage, for driving the first operating instrumentalities, third motor means, mounted on the second carriage, for driving the second operating instrumentalities, and control means for controlling the second and third motor means to operate in a synchronous relationship with one another. By having separate motor means for driving the first and second operating instrumentalities, there is no requirement for any form of mechanical interconnection between the instrumentalities. Rather than any mechanical interconnection, the control means provides an electrical connection between the second and third motor means, through which the control means ensures that the second and third motor means operate synchronously. Synchronous operation is crucial to the performance of the machine; stitch formation, for instance, requires a wholly synchronised sequence of steps.

[0006] Furthermore, mounting each of the instrumentality driving motor means to the associated carriage, and hence rotating the motor means together with the carriage and the associated instrumentalities, avoids the occurrence of any epicyclic effects and the need for any form of compensating differential mechanism.

[0007] In addition, independent driving motor means for each of the first and second instrumentalities permits independent control of the movements of the first and second instrumentalities, which can be especially useful in some situations.

[0008] The phrase "motor means", where used herein, is to be understood to encompass means including a motor, the operation of which is controlled by control pulses supplied thereto in accordance with digitised information appropriate to the desired operation of the motor. Examples of such motors are stepping motors and d.c. servo motors.

[0009] A machine according to the invention is especially suitable for use in operating upon workpieces of flexible sheet material, for example leather, and such machines include automatic sewing machines in which the operating instrumentalities are stitch forming instrumentalities, the first of such operating instrumentalities comprising a reciprocatable needle holder for holding a sewing needle and the second comprising a further mechanism, for example, a bobbin mechanism adapted to cooperate with a sewing needle carried by the needle holder to form a stitch. Suitably the control means is arranged to control the second and third motor means thereby to cause a bobbin mechanism to rotate through a whole number of revolutions for each needle stroke. Suitably the control means is arranged to be adjustable, for example, by an operator, thereby to adjust the number of revolutions through which the bobbin mechanism rotates for each needle stroke.

[0010] Other leather processing machinery which may comprise a machine according to the invention includes folding machines, for example as supplied by the applicant company under the designation UMF, in which the operating instrumentalities comprise a creaser foot, hammer and anvil, and punching machinery in which the operating instrumentalities include a plurality of punches and cooperating anvil means.

[0011] Preferably in a machine in accordance with the invention the first and second axes are coaxial.

[0012] The first and second carriages may each comprise a timing pulley around which an associated toothed timing belt extends, each belt passing around an associated toothed wheel secured to an output shaft of the first motor means. Alternatively, the first motor means may comprise two motors, each associated with one of the first and second carriages, in which case the first and second carriages each comprise a timing pulley around which an associated toothed timing belt extends, the belts passing around toothed wheels secured to an output shaft of the associated one of the first and second motors. Where the first motor means comprises first and second motors, the control means preferably controls the two motors to operate in a synchronous relationship with one another.

[0013] Preferably in a machine in accordance with the invention, the drive means moves work carried by the supporting means on two coordinate axes under the control of said control means in timed relation with the first motor means. One suitable machine comprises carrier means mounted for movement along the two coordinate axes. The drive means preferably comprises fourth and fifth motor means for moving the carrier means along the coordinate axes. Such a construction is commonly referred to as an X-Y table. In sewing machines, for example as supplied by the applicant company, a workpiece to be stitched, for example a leather shoe upper comprising one or more components, is mounted on such an X-Y table by workpiece supporting means comprising a pallet on which the workpiece is accurately located so that the position and orientation of the workpiece is established whereby the control means can cause a sewing operation to be effected on the workpiece supported by the workpiece supporting means in accordance with a desired stitch pattern. A preferred machine comprises a workpiece feeding system as described in our co-pending Patent Application No. PCT/GB91/01449 which does not utilise a pallet and recognises the work and its location and orientation by means of a suitable optical recognition system. The workpiece is supported on parallel rollers which are mounted for rotation about rotational axes thereby to move the workpiece along a first of the coordinate axes, and for movement in a direction parallel with their rotational axes to move the workpiece along a second of the coordinate axes at right angles to the first.

[0014] In a sewing machine in accordance with the invention the operating instrumentalities include stitch forming instrumentalities, the first of the operating instrumentalities comprising the reciprocatable needle holder for holding a sewing needle, the second motor means being adapted to cause reciprocation of the holder to take place. The second of the operating instrumentalities comprises a further mechanism, for example, a rotatable bobbin mechanism, driven by the third motor means and adapted to cooperate with a sewing needle carried by the needle holder to form a stitch. Suitably the bobbin mechanism may be a typical lockstitch sewing machine bobbin mechanism.

[0015] The first of the operating instrumentalities in a sewing machine in accordance with the invention preferably also comprises presser means adapted to engage the workpiece and press it firmly to the workpiece supporting means thereby to retain the workpiece in position as the sewing needle penetrates the workpiece and is consequently retracted therefrom. Conveniently the presser means is a reciprocating presser foot adapted to be reciprocated in timed relation with the needle holder. Alternatively, the presser means may comprise a roller which may be urged against the work.

THE DRAWINGS

[0016] 

Figure 1 is a perspective view of a sewing machine embodying the invention; and

Figure 2 is a plan view showing a workpiece feeding system of a sewing machine embodying the invention.

BEST MODE

[0017] The sewing machine shown in the drawings is suitable for use in stitching workpieces, for example in decorative stitching of shoe uppers. The illustrative sewing machine comprises a frame (1) which is generally C-shaped. The illustrative machine comprises a workpiece feeding system including workpiece supporting means (140,146) of a work handling system and first and second operating instrumentalities (40,42) mounted at opposite sides of the workpiece supporting means (140,146) and adapted to operate on the workpiece supported on the supporting means (140,146).

[0018] The first operating instrumentalities (40) include a needle holder (12) for holding a sewing needle (14) and presser means, namely a presser foot, whilst the second operating instrumentalities include a bobbin mechanism (29) adapted to cooperate with a sewing needle (14) mounted in the needle holder or needle bar (12).

[0019] The workpiece feeding system of the illustrative machine further comprises drive means comprising motor means (124,160) for the workpiece supporting means (140,146) adapted to move a workpiece carried by the supporting means substantially in a plane (30) relative to the operating instrumentalities (40,42) as the operating instrumentalities (40,42) operate on work supported by the supporting means (140,146), and control means (20) adapted to control the operation of various motor means (19,220,230,6,28,124,160). A first motor means (19) is adapted to rotate the first of the operating instrumentalities (40) about a first axis (A) coincident with the longitudinal centre line of a needle supported by the needle holder (12). The first axis (A) extends generally transversely to the plane in which the workpiece is supported by the workpiece supporting means (140,146). The first motor means (19) is also adapted to rotate the second of the operating instrumentalities (42) about a second axis (B) which extends, likewise, generally transversely to the plane and is coaxial with the axis (A). Alternatively, the first motor means (19) may have two motors (220,230), as illustrated in the machine embodiment shown in Figure 3 which is otherwise identical to the machine shown in Figure 1. Each of the two motors (220,230) is for rotating one of the first and second operating instrumentalities (40,42), and the control means (210), is adapted to cause the first and second motors (220,230) to operate synchronously. The first motor means (19), under the control of the control means (210), rotates the first and second operating instrumentalities (40,42) thereby to adjust the position of the operating instrumentalities (40,42) about the axes (A,B) to assume desired orientations relative to the direction of movement of a workpiece being moved by the workpiece supporting means (140,146).

[0020] The first illustrative machine comprises a first carriage (16) on which the first operating instrumentalities (40) are supported and a second carriage (27) mounting the second operating instrumentalities (42) for rotation about the axes (A,B). The first carriage (16) comprises a plurality of journals (7,8) received respectively in upper and lower bearing rings (5,4) mounted on the frame (1). The first carriage (16) comprises a timing pulley (17) around which extends a toothed timing belt (18) which passes round a toothed drive wheel (not shown) secured to an output shaft (200) of the first motor means (19). A second motor means (6) is mounted on the first carriage (16) to drive the first operating instrumentalities (40). The first operating instrumentalities (40) comprise a combined crank and eccentric mechanism (9) mounted on an output shaft of the motor means (6). A presser foot (not shown) is guided for reciprocating movement parallel with the axis (A) by guide means (not shown) and is mounted at a lower end portion of a link (11) an upper end portion of which is journalled on an eccentric (9b) of the mechanism (9) so that as the output shaft of the second motor means (6) rotates, rotation of the eccentric (9b) causes reciprocating motion of the presser foot. The needle bar (12) is mounted in a slideway (12a) for sliding motion in a direction parallel with the axis (A). A first end portion of a link (10) is connected to the needle bar (12) and a second end portion of the link (10) is connected to a crank (9a) of the mechanism (9) so that as the output shaft of the second motor means (6) rotates, the crank (9a) is caused to rotate and the needle bar (12) is caused to reciprocate. The sewing needle (14) is secured in a lower end portion of the needle bar (12) and is coincident with and reciprocates along the axis (A). A support (3) for a bobbin is mounted on the frame (1), a bobbin on the support (3) providing thread for the needle carried by the needle holder (12) via a thread tensioning device (21) supported on the carriage (16) and a thread puller (20) pivotally mounted on a link (22) pivoted to the carriage (16) and to the crank (9a). If desired, the bobbin support providing thread for the sewing needle may be mounted on the carriage (16) itself.

[0021] The second carriage (27) is mounted on a disc-like support member (26) rotatably mounted by three equiangularly spaced bearings (25) arranged to run on a peripheral portion of the disc. A timing pulley (31) is secured to the disc (26) and a second toothed timing belt (32) extends around the pulley (31) and around a toothed drive wheel (34) secured to the output shaft of the first motor means (19), which in the case of the embodiment shown in Figure 3 is the output shaft of the second motor (23).

[0022] A third motor means (28) is mounted on the second carriage (27) and is arranged to rotate the bobbin mechanism (29) about an axis perpendicular to the axis (B). The bobbin mechanism (29) is a typical lockstitch bobbin mechanism of known type commonly used in lockstitch sewing machines.

[0023] The control means is adapted to control the second and third motor means (6,28) to operate in a synchronous relationship with one another so that the sewing needle carried by the needle bar (12) is reciprocated in a suitable phased relation with the rotation of the bobbin mechanism (29). The control means (210), shown schematically in Figure 1 in relation to the workings of the illustrated machine, is a portion of the electronic control circuitry of the whole machine, which circuitry portion is capable of analysing and distributing control signals for the motor means. The control means (210) monitors the operation of the second motor means (1), typically a d.c. servo motor with closed loop control, by sampling a position signal indicative of the second motor means (6) rotor position, thereby continually determining the state of the second motor means (6) and hence the position of the first operating instrumentalities (40). The third motor means (28), typically having a stepper motor with open loop control, is directed to operate, that is the operation of the third motors (28) control pulse generating circuitry is determined, by the control means (210) in accordance with the sensed behaviour of the second motor means (6). In other words, the control means (210) ensures that the output shaft of the second and third motor means (6,28) operate in a timed relationship with one another so that the desired synchronised relationship between the first and second operating instrumentalities (40,42) is achieved.

[0024] With reference to Figure 2, the workpiece feeding system which is generally similar, except as hereinafter described, to the system described in PCT/ GB91/01449, comprises a base (110) on which are supported, by means of four supports (112) arranged one at each corner of the base, two transverse carrier rods (114) on which is supported, for movement therealong, a carriage generally designated (116). The carriage (116) comprises two end blocks (118), each block having at each of its ends a lug in which is formed by a bore by which the block is supported on the carrier rods (114). The end blocks (118) are connected together by two racks (120) (one only shown in Figure 2) each meshing with a drive gear (122) secured on the output drive shaft of a stepping motor (124) mounted on the base (110). The two stepping motors (124) (constituting fourth motor means) are driven in synchronism with one another and thus seme to drive the carriage (116) transversely along the carrier rods (114).

[0025] At the rear of the base is formed an extension (130) on which is mounted the sewing machine shown in Figure 1, only the frame 1 and outline of which is shown in Figure 2. The arm of the machine projects forwardly over the path of the carriage (116), such that the path of the reciprocating needle (14) lies on a line which is parallel with the carrier rods (114) and centrally thereof. The axis (A,B) along which the needle (14) reciprocates is indicated in Figure 2 (which is hereinafter referred to as the needle penetration point). As previously stated, the movement of the carriage (116) under the control of the stepping motors (124) is effected in timed relation with the reciprocation of the sewing needle.

[0026] In order to ensure that the carriage does not move so far along the carrier rods (114) that one of the end blocks (118) thereof is disposed below the needle, the left-hand supports (112) constitute end stops for the carriage, and in addition at a point intermediate the left-hand and right-hand supports (112) two further supports (not shown) may be provided which seme as end stops for limiting the movement to the right (viewing Figure 1) of the carriage (116); it will of course be appreciated that in each case the supports serving as end stops are engaged by the left-hand (viewing Figure 1) end block (118) of the carriage. The further supports of course also provide further support for the carrier rods (114) intermediate their length.

[0027] The carriage (116) supports workpiece supporting means and workpiece clamping and feeding means, which will now be described. In the workpiece feeding system the workpiece supporting means comprises two sets of work support rollers, each set comprising four rollers (140). End portions of each of the rollers (140) are supported in the end blocks (118) for rotation therein. The uppermost part of the workpiece support surface of each of the rollers lie in a common plane namely the plane (30) (hereinafter called the workpiece support plane). An aperture (142) is provided between the two sets of rollers, and extending parallel to the path of the carriage (116), and is aligned with, and accommodates, the needle penetration point. The workpiece supporting means further comprises two table portions (144), arranged one on the outside of each set of rollers, and the workpiece support surface of each table portion (144) lying also in the workpiece support plane (30).

[0028] The workpiece clamping and feeding means of the system also comprises two sets of workpiece clamping and feeding rollers (146), each set comprising four such rollers, one associated with each workpiece support roller (140), and the arrangement being such that the axes of associated rollers lie vertically one above the other. Thus the sets of rollers (146) are so arranged as also to provide the aperture (142) therebetween, said aperture thus extending parallel, or substantially so, to the rollers (146).

[0029] Each roller (146) has its end portions of reduced diameter, and the reduced end portions pass through vertical slots formed in each of the end blocks (118) and are supported in a lifting frame (148) for heightwise movement relative to the end blocks (118). The rollers (146) are thus able to be lifted bodily as a unit away from the workpiece support rollers (140). In addition, the reduced diameter end portion of each roller is supported in a bearing block (150) which is spring-urged downwardly under a light, but adjustable, pressure, whereby each roller is resiliently urged towards its associated workpiece support roller (140). A load of up to 30 Newtons applied to each roller has been found satisfactory for this purpose. For raising the lifting frame (148), furthermore, four piston-and-cylinder arrangements (152) are provided, mounted one at each corner of the carriage (116) and connected via a pivoting lever (154) with the lifting frame, the four arrangements (152) operating in synchronism with one another for this purpose.

[0030] Each of the workpiece clamping and feeding rollers (146) and also each of the workpiece support rollers (140) has a diameter in the order of 10 to 15mm and the workpiece-engaging surface of each roller has a relatively high frictional coefficient. In one embodiment of the invention the workpiece-engaging surface of each roller (140,146) may be constituted by a layer of abrasive material, e.g. emery paper or cloth.

[0031] Alternatively, the surface of each roller may be constituted by a layer of a tacky but non-adhesive material. One such material is a silicone rubber available from Dowty Woodville Polymers Ltd., of Swadlincote, England, under the trade name WPSP 3707.

[0032] The rollers (140,146) are driven in synchronism with one another, each set of rollers (i,e, set of rollers (146) together with its associated rollers (140)) having associated therewith a stepping motor (160) (constituting fifth motor means), said motors being arranged diagonally opposite one another on the carriage (116), more particularly one on each of the end blocks (118). Each stepping motor (160) is operatively connected to the rollers (140,146) of its set by timing belts (162) and double pulleys (164) mounted on the ends of the rollers. The stepping motors (160) are so mounted on the end blocks (118) so that heightwise movement of the lifting frame (148) does not affect the driving relationship between the motor and the first of the pulleys.

[0033] The workpiece feeding system further comprises a camera (170) (only an outline of which is shown in Figure 2) which is mounted on a frame (not shown) above the carriage (116) and to the right-hand side (viewing Figure 2) of the sewing machine, in alignment with the aperture (142). For cooperating with the camera (170) a lamp (172) is arranged beneath the carriage (116) so as to backlight (i.e. illuminate from behind) the aperture (142). The camera (170) comprises an array of cells by which, in a line scanning operation, the peripheral outline of a workpiece being fed across the aperture (142) can be progressively detected, i.e. line by line.

[0034] The camera and its associated detection system are generally similar to that described in GB-A 2067326 and form part of control means of the illustrative machine. Thus, this system is capable of operating in a "teaching" mode in which, by scanning the peripheral outline of a workpiece moved progressively across the aperture (142) and by processing the signals thus obtained from the camera, as described in the aforementioned U.K. specification, a unique set of parameters for each "taught" workpiece can be determined, which set of parameters is then stored in a computer memory forming part of the system. The system also operates in a "recognition" mode in which again, using the same principles, a set of parameters is determined for a workpiece presented thereto, but in this case the set of parameters is compared with the stored sets and an identification of the presented workpiece is thus established, again as described in the said U.K. specification.

[0035] In incorporating this system into the illustrative machine, there is associated with each stored set of parameters a stitch pattern data file which contains instructions for the motor means (160,124) of the drive means, which instructions thus define the appropriate movements to be imparted to the workpiece in first and second directions to move it relative to the sewing needle in accordance with the stitch pattern associated with the workpiece identification. Thus when a workpiece is recognised in the recognition mode of the camera/detection system and its set of parameters is determined, the relevant stitch pattern data file is automatically accessed for the appropriate stitch pattern to be sewing on the workpiece.

[0036] The camera/detection system, in its recognition mode, also identifies the location and orientation of the workpiece presented thereto and is capable of modifying the data stored in the appropriate stitch pattern data file, prior to commencement of the sewing operation, to take into account the location and orientation of the workpiece as determined by said system.

[0037] Thus, in the operation of the illustrative machine, the operator first places a workpiece to be operated upon on the forward table portion (144) and feeds the workpiece into the nip formed by the first rollers (140,146) whereupon the workpiece is fed by the operation of the driven rollers (146) beneath the camera (170) and across the aperture (142) in a first, workpiece recognition, step. As already mentioned, in this step not only is the workpiece shape detected and thus identified, but also the orientation of the workpiece is determined and its location within the rollers (140,146), and in accordance with such detection firstly the desired stitching pattern data file is accessed and data is then modified in accordance with the orientation and location of the workpiece. Under the programmed control of this modified data the carriage (116) is then driven and the rollers (146) are also driven to move the workpiece in the first and second directions so that the start position for the stitching is coincident with the needle penetration point, and thereupon a sewing cycle is initiated, the stepping motors (124,160) receiving drive signals according to the modified stitch pattern data whereby the carriage (116) and the rollers (146) are operated in order to cause the workpiece to follow the desired path.

[0038] The control means is adapted to cause work supported on the workpiece supporting means, to be moved along two coordinate axes in timed relation with the operation of the first, second, and third motor means; thus the workpiece is moved only when the needle is out of the workpiece.

[0039] It will be appreciated that an automatic stitching operation can be performed on a workpiece without the need for the workpiece to be held in a pallet in accordance with a programmed instruction, serving to supply the desired drive signals to the stepping motors (124,160), according to the particular stitch pattern appropriate to the workpiece. In the illustrative system, however, the computer means by which the drive signals are supplied to the motors (124,160) also provides the memory store in which the stitch pattern data files are stored and from which they can be accessed in accordance with the workpiece identification. The third and fourth motors (6,28) are caused to operate in timed relation with each other and with the fourth and fifth motors (124,160). The operation of the first motor means (19) is also coordinated by the control means with that of the motor means (6,28,124,160) so that the operating instrumentalities (40,42) assume a desired orientation relative to the direction of movement of the work as the workpiece supporting means moves the work. The desired orientation, in the case of the stitching instrumentalities, would be such that the stitching instrumentalities are aligned with the direction of feed of the workpiece, suitably with a lengthwise axis of the presser foot lying long or tangential to the direction of feed of the workpiece supporting means and with the wider dimension of a chisel point needle perpendicular to the direction of feed of the workpiece supporting means.

[0040] The illustrative machine ensures that the direction of feed of the workpiece supporting means always adopts an optimum direction relative to the stitching instrumentalities and this militates. against the stitch malformation problems which have arisen in other cases. The signals for controlling operation of the first and second motors (19,33) are readily derived from the conventional stitching coordinate data stored in the stitch pattern data file (commonly on an EPROM) utilised in known automatic sewing machines, for example the MPCS machine supplied by the applicant company. It is important that the phase of the motor means of the illustrative machine and the various displacements are accurately controlled. It is, of course, essential that the needle bar (12) and bobbin mechanism (29) are correctly positioned initially. Thereafter the first motor means (19) rotates the carriages (16,27) through equal angles, so as to maintain them in correct alignment with one another.

[0041] In a machine otherwise similar to the illustrative machine, work to be stitched is first mounted in the plane (30) on a so-called X-Y table of known construction, suitably positioned in a pallet in a manner well known in automatic stitching of shoe uppers. In this case control means is likewise programmed with the details of the stitching pattern to be applied to the shoe upper and the operating instrumentalities (40,42) are caused to operate to stitch the desired pattern on the shoe upper, the control means controlling the operation of the fourth and fifth motor means (not shown) to appropriately move the X-Y table rectilinearly along two coordinate axes perpendicularly to one another, thus moving the workpiece supporting means, namely the pallet, and the work carried thereby passed the sewing instrumentalities (40,42)

Claims

1. A machine for operating on workpieces, comprising workpiece supporting means (140,146), first and second rotatable carriages (16,27) mounted at opposite sides of the workpiece supporting means (140,146), first operating instrumentalities (40) mounted on the first carriage (16), second operating instrumentalities (42) mounted on the second carriage (27), drive means (124,160) for moving a workpiece relative to the first and second operating instrumentalities (40,42), first motor means (19) for rotating the first carriage (16) about a first axis (A) and for rotating the second carriage (27) about a second axis (B), which axes (A,B) extend substantially transversely to the direction of movement of the workpiece, characterised by second motor means (6), mounted on the first carriage (16), for driving the first operating instrumentalities (40), third motor means (28), mounted on the second carriage (27), for driving the second operating instrumentalities (42), and control means (210) for controlling the second and third motor means (6,28) to operate in a synchronous relationship with one another.

2. A machine according to Claim 1 wherein the first and second axes (A,B) are coaxial.

3. A machine according to Claim 1 or Claim 2 wherein the first and second carriages (16,27) each comprise a timing pulley (17,31) around which an associated toothed timing belt (18,32) extends, each belt (18,32) passing around an associated toothed wheel secured to an output shaft (200) of the first motor means (19).

4. A machine according to Claim 1 or Claim 2 wherein the first motor means (19) comprises two motors (220,230) each associated with one of the first and second carriages (19,27).

5. A machine according to Claim 4 wherein the first and second carriages (16,27) each comprise a timing pulley (17,31) around which an associated toothed timing belt (18,32) extends, the belts (18,32) passing around toothed wheels secured to an output shaft of the associated one of the two motors (220,230).

6. A machine according to Claim 4 or Claim 5 wherein the control means (210) controls the two motors (220,230) of the first motor means (19) to operate in a synchronous relationship with one another.

7. A machine according to any proceeding Claim wherein the control means (210) controls the first motor means (19) to operate in a synchronous relationship with the second and third motor means (6,28).

8. A machine according to any of the preceding Claims wherein the drive means (124,160) moves a workpiece on two coordinate axes under the control of the control means (210) in synchronous relationship with the first motor means (19).

9. A machine according to Claim 8 wherein the workpiece supporting means comprises parallel rollers (140,146) by which a workpiece can be supported and which are mounted for rotation about rotational axes thereby to move the workpiece along a first of the coordinate axes and for movement in a direction parallel with the rotational axes to move a workpiece along a second of the coordinate axes, perpendicular to the first axis.

10. A machine according to Claim 9 wherein the drive means comprises fourth motor means (124) for moving a workpiece on the second of the coordinate axes and fifth drive means (160) for rotating the rollers (146).

11. A machine according to Claim 8 further comprising carrier means for carrying the workpiece supporting means (140,146), the carrier means being mounted for movement along the two coordinate axes, and wherein the drive means comprises fourth motor means (124) and fifth motor means (160) for moving the carrier means along the coordinate axes.

12. A machine according to any preceding Claim which is for sewing.

Drawing