EP0413699B1 - Sewing machine with needle feed - Google Patents

Abstract

In known sewing machines in which the needle feed and sliding gear wheel are driven by stepping motors, the needle feed cannot be stopped. In the new design, the needle feed (n1, n2, n3, n4) is stopped by means of a switching arrangement so that the oscillation of the needle (13) in the direction of feed is stopped (point M), the distance (r2) by which the sliding gear wheel is advanced during the insertion phase (n1) of the needle is eliminated, and the distance (r3, r4, r1) by which the sliding gear wheel is advanced during the retracted phase (n3) of the needle is increased by the eliminated distance.

Description

The invention relates to a sewing machine according to the preamble of claim 1.

In the known sewing machines with fabric feed by needle and lower and / or upper slide wheel, the feed being driven by the main shaft of the sewing machine via mechanical gear arrangements, the needle drive cannot be switched off. The gear arrangement of the sewing machine type with the "moving needle" mode is compared to the sewing machine type with the "fixed needle" mode, i. H. Sewing machine without needle feed, so differently designed that a change is not possible. For this reason, only single-purpose sewing machines are available for both operating modes.Use of the two operating modes alternately with a single sewing machine, as would be desirable in some sewing processes, has thus far not been practicable.

From DE-PS 35 16 713 a sewing machine with needle transport is known, in which the feed units needle, pusher wheel and roller foot are driven by stepper motors working independently of one another.

Furthermore, a sewing machine with a fixed needle bar guide is known from DE-PS 35 16 715. With this sewing machine, the feed takes place exclusively via the sliding wheel and roller foot, whereby both feed units are each connected to their own stepper motor drive. The feed units are driven here - in contrast to the sewing machine with needle feed - only during the cut out phase of the needle.

As a result of the completely different feed conditions, a simple combination of the two types of sewing machine is therefore not easily possible.

The invention specified in claim 1 is therefore based on the object of making the feed drive by the needle switchable on and off in a sewing machine with a needle feed.

According to the invention this is solved by the features specified in the characterizing part of the patent claim.

With the solution according to the invention, there is now the possibility of temporarily switching off the needle feed in a sewing machine with the needle moving in the feed direction simply by switching over and executing the feed with the fixed needle bar guide exclusively through the lower and / or upper slide wheel. Switching can be done manually or by entering a program sequence.

In the drawing, an embodiment of the invention is shown in a sewing machine with needle feed.

• Fig. 1 eine Gesamtansicht einer mit Nadelvorschub ausgestatteten Nähmaschine, teilweise geschnitten,
• Fig. 2 eine vergrößerte Seitenansicht der Nähmaschine nach Fig. 1, teilweise geschnitten,
• Fig. 3 einen Schnitt nach der Linie III III der Fig. 2,
• Fig. 4 eine Rückansicht des Schrittmotorantriebes für das Ausschwingen der Nadelstange, teilweise geschnitten,
• Fig. 5 ein Blockschaltbild der elektronischen Schaltung für die Vorschubeinrichtung,
• Fig. 6 einen Schnitt durch die Stichplatte der Nähmaschine in vergrößerter Darstellung und
• Fig. 7 ein Diagramm der Vorschubbewegung.

It shows:

• 1 is an overall view of a sewing machine equipped with a needle feed, partly in section,
• 2 is an enlarged side view of the sewing machine of FIG. 1, partially in section,
• 3 shows a section along the line III III of FIG. 2,
• 4 is a rear view of the stepper motor drive for swinging out the needle bar, partly in section,
• 5 is a block diagram of the electronic circuit for the feed device,
• Fig. 6 shows a section through the needle plate of the sewing machine in an enlarged view and
• Fig. 7 is a diagram of the feed movement.

As shown in Fig. 1, the sewing machine consists of the base plate (1), the column (2), the stand (3), the arm (4) and the head (5). A main shaft (6) is mounted in the arm (4) in a conventional manner and is driven by a sewing motor (8) attached below the base plate (1) via a V-belt (7). The main shaft (6) is driven by a toothed belt (9), a gripper shaft (10) mounted in the base plate (1), which is in drive connection with a gripper (not shown).

The main shaft (6) drives a needle bar (14) equipped with the needle (13) via a crank (11) and a link (12). The handlebar (12) is articulated to the needle bar (14) via an articulated connection (15) (Fig. 2). This is mounted in a rocker (17) carried by an oscillating shaft (16) (FIG. 1). The oscillating shaft (16) is parallel to the main shaft (6) stored in the arm (4).

The end of the oscillating shaft (16) projecting into the stand (3) carries a lever arm (18) which is connected to an eccentric rod (20) via a joint pin (19). This engages around an eccentric (21) (Fig. 4) which is fixedly connected to a drive shaft (22) of a stepper motor (23) fastened in the arm (4). The eccentric (21) is guided with a pin (24) in a housing bore (25) running coaxially to the drive shaft (22).

In the lower part of the column (2) (Fig. 2), a carrier (30) is mounted on an eccentric bolt (31) which has bearing pins (34 and 35) projecting into bores (32 and 33) in the column (2). The bearing journal (35) is provided with a slot (36). The eccentric (31) is clamped to the carrier (30) by a screw (37). A standing shaft (38) is mounted in the carrier (30) and is guided in the axial direction by an adjusting ring (39) and a coupling (40). The carrier (30) is equipped at the lower end with a flange plate (41) on which a stepper motor (42) is fastened, the drive shaft (43) of which is rigidly coupled to the standing shaft (38) by the coupling (40). At the upper end, the standing shaft (38) carries a pinion (44) of a spiroid gear (45), the ring gear (46) of which is firmly connected to a sliding wheel (47) which is ball-bearing-mounted in a known manner and an inner part with an axle stub (48) having. This is received by a bore in an arm (30a) of the carrier (30) and can be clamped by a screw (49) after adjustment in the axial direction.

By turning the eccentric bolt (31) using the Slot (36), the slide wheel (47) can be adjusted in height by means of the support (30) relative to a needle plate (50) which closes the column (2) upwards and through which it projects through a slot (50a). Parallel to the slot (50a), the stitch plate (59) is provided with a stitch slot (50b) (see also Fig. 6) for the passage of the needle (13).

The carrier (30) is firmly clamped to it by a screw (51) screwed into its upper part, which projects through a slot (52) in the column (2). The lateral position of the pusher wheel (47) can be aligned with the slot (50a) in the throat plate (50).

A vertical shaft (53) is loosely mounted in the head (5) of the sewing machine. A clamping piece (54) is screwed onto the shaft (53). This has a radial bore in which a pin (55) is pressed. A coupling piece (56) is also loosely mounted on the shaft 53. A web (57) projecting laterally from it protrudes through a slot in the head (5) and secures the coupling piece (56) against rotation. The coupling piece (56) is designed as a ring cutout in its lower region and thus encompasses the clamping piece (54). The ring cutout has a recess (59) into which the pin (55) projects and which at one end merges into a latching groove (60), while at the other end it ends with a wall (61). A compression spring (62), which is supported against an adjusting ring (63) attached to the shaft (53), presses the coupling piece (56) and thus the upper wall of its ring cutout slightly downwards against the pin (55).

On the web (57) (Fig. 3) is the free end of a leaf spring (64) which is fixed in the arm (4) and presses the coupling piece (56) down. A lever arm (65) of an angle lever (66) mounted in the head (5) protrudes below the web (57) and is connected via a link (67) to a lever linkage (not shown) which can be actuated by the operator. A cam (68) is fastened under the lever arm (65) on a shaft (69) mounted in the head (5). The shaft (69) (FIG. 2) carries a hand lever (70) on its outwardly projecting end.

At the lower end of the shaft (53) a block (71) is attached, which is equipped with a groove guide (72). An angular flap (73) with an elongated hole is screwed into this, which is firmly connected to a caster base (74). This has a pipe socket (75) (see also Fig. 3), which merges into a downwardly projecting end piece (76). A bore is provided in this for the attachment of an axle stub (78) of a roller bearing (80) with ball bearings. The roller foot (80) has a race (81) with which a ring gear (82) of a spiroid gear (83) is fixedly connected, the pinion (84) of which is off-center in engagement with the ring gear (82). A tubular support (85) is received in the pipe socket (75) and its position is clamped by screws (86) screwed into the pipe socket (75). The carrier (85) consists of a tube (87), a hollow cylinder (88) which adjoins at the top and an annular connecting flange (89). A shaft (90) is mounted in the tube (87), which carries the pinion (84) at its lower end and is fixedly connected to an annular shoulder (91) which bears against the lower end of the tube (87).

The shaft (90) is gripped in the area of its upper end by the inner ring of a ball bearing (93) pressed into the hollow cylinder (88). The upper end of the shaft (90) is rigidly coupled by a coupling (94) to a drive shaft (95) of a stepper motor (96), the housing of which is screwed onto the end flange (89).

On the main shaft (6) (Fig. 1) of the sewing machine, a pulse disc (100) is attached, which has two pulse paths, each of which works with a pulse generator (101 or 102). One pulse path has a plurality of pulse markings (103) (FIG. 5) distributed uniformly over its circumference, while the other pulse path has only two pulse markings (104), one of which has the pulse generator (101) when the needle (13) emerges. out of the workpiece and the other happens when the needle (13) enters the workpiece.

The pulse generator (101) is connected to a control unit (105). A switchover arrangement (106), control lines (107a, 108a and 109a) AND gates (107, 108 and 109) and counters (111, 112 and 113) are connected to this via a control line (106a) . A keypad (114), a display unit (115) via a bus line (115a) and a data memory (116) via a bus line (116a) are connected to the control unit (105) via a bus line (114a).

The outputs of the counters (111, 112 and 113) are connected to inputs of power stages (117, 118 and 119) for the associated stepper motors (23, 42 and 96).

In addition, the outputs of the counters (111, 112 and 113) are connected to the control unit (105) via lines (111a, 112a and 113a). Lines (117a, 118a and 119a) lead from the control unit (105) to the power stages (117, 118 and 119). Three switches (120, 121 and 122) are also connected to the control unit (105), of which the switch (120) is used to actuate a reverse sewing process, while the two switches (121 and 122) are used to slowly drive the stepper motors (42 and 96 ) in the forward or backward direction when the sewing machine is at a standstill preferably in the needle up position. For this purpose, an oscillator (123) is connected to the two power stages (118 and 119) via a divider (124) and a switch (125). The switch (125) is connected to the control unit (105) via a control line (125a). The oscillator (123) is also connected to the input (E1) of the switching arrangement (106), the input (E2) of which is connected to the pulse generator (102). The output of the switching arrangement (106) leads to the inputs (E1) of the three AND gates (107, 108 and 109), the outputs of which are each connected to the associated counter (111, 112 and 113), which are designed as a down counter and which can be individually preset by the control unit (105) via the collecting line (110).

With the keypad (114) the number of steps of the stepper motors (23, 42 and 96) per sewing stitch and thus the feed length of the individual transport elements - needle (13), pusher wheel (47) and roller foot (80) - can be selected between the respective stitch formation, different feed amounts of the sliding wheel (47) relative to the roller foot (80) can also be set. The measure of the preselected stitch length is shown in the display unit (115).

A switch (126) is connected to the control unit (105) and is used to switch from the "moving needle" mode to the "fixed needle" mode and vice versa. Furthermore, a counter (127) can be provided, which is connected to the control unit (105) via a bus line (127a) and a line (127b) and a line (127c) both to the pulse generator (101) and to the control unit (105). connected is.

Fig. 6 shows schematically the distances traveled by the needle (13) during stitch formation as well as the movement of the sewing material caused by the pusher wheel (46) and the roller foot (80) for a predetermined stitch length (S). When the needle is fed, the needle (13) sticks into the sewing material at a puncture point (P1), moves with it over its center line (M) according to the distances (n1 and n2) to the puncturing point P2 from the sewing material. At the same time the pusher wheel (46) and roller foot (80) also move the sewing material by the same amount (distances r1 and r2). After the needle (13) has left the sewing material at point (P2), it moves outside the sewing material by the distances (n3 and n4) back to its insertion point (P1). During this time, the sliding wheel (46) and roller foot (80) move the sewing material by the two distances (r3 and r4).

The facility works as follows:
The operator uses the keypad (114) to set the desired feed amounts of the needle (13), the pusher wheel (47) and the roller presser (80), the corresponding digital values being taken from the data memory (116) via the control unit (105) and thus the counter (111, 112 and 113) can be preset. At the same time, values corresponding to the feed amounts are displayed in the display unit (115).

When the sewing machine is in operation, the sewing motor (8) drives the main shaft (6) via the V-belt (7), which moves the needle bar (14) up and down via the drive connection - crank (11) and handlebar (12). The main shaft (6) also drives the gripper (not shown) via the toothed belt (9) and the gripper drive shaft (10). The drive for feeding the workpiece is triggered via the pulse generator (101) whenever the needle (13) penetrates the workpiece and when it leaves it. The pulse generator (101) emits a pulse to the control unit (105). This now switches over the control lines (107a, 108a and 109a) to the potential at the inputs (E2) of the AND gates (107, 108 and 109) to (H), so that the pulses subsequently emitted by the pulse generator (102) the switching arrangement (106) connected to the input (E2) when the sewing machine is driven are passed through by the AND gates (107, 108 and 109) to the counters (111, 112 and 113).

If one of the counters (111, 112 or 113) has reached the counting result "0", it issues a control pulse to the associated power stage (117, 118) or 119), whereby the corresponding stepper motor (23, 42 or 96) by one Step is advanced. At the same time, this counter (111, 112 or 113) sends a pulse to the control unit (105) via the associated control line (111a, 112a and 113a), which presets this counter (111, 112 or 113) to a new value. The control unit (105) retrieves the corresponding values from the data memory (116). they simultaneously determines via the control lines (117a, 118a and 119a) connected to the power stages (117, 118 and 119) whether the respective stepper motor (23, 42 and 96) is moved in the forward or reverse direction of rotation. The values that can be preset on the counters (111, 112 and 113) are selected so that the stepping motors (23, 42 and 96) can carry out their maximum number of steps both in the pierced phase of the needle (13) and in its pierced phase.

The step impulses acting on the stepper motors (23, 42 and 96) drive the rocker arm (17), the pusher wheel (47) and the roller foot (80) for the joint transport effect on the workpiece. The stepper motor (42) rotates the pusher wheel (47) via the standing shaft (38) which is firmly coupled to its output shaft (43) and the angular gear (45), while the stepper motor (80) simultaneously rotates via the shaft which is firmly coupled to its output shaft (95) Shaft (90) and the angular gear (83) drives the roller foot (80). The stepper motor (23) simultaneously rotates the eccentric (21) gradually in one direction via its output shaft (22), its eccentricity transmitting deflection movements via the eccentric rod (20) and the lever arm (18) to the rocker (17), which thereby swinging out corresponding angular amounts. This takes place when the needle (13) is inserted in the workpiece in synchronism with the feed of the pusher wheel (47) and the roller foot (80) and when the needle (13) is cut out by driving the eccentric (21) in the opposite direction.

As is known, the needle bar (14) performs a sinusoidal oscillating movement in the feed direction. During its pierced phase in the workpiece it swings in the feed direction and during the pierced phase it swings in the opposite direction. The control of the stepper motor (23) for swinging out the needle bar (14) is therefore designed so that it gives the stepper motor (23) during one revolution of the main shaft (6), i.e. with each feed during stitch formation, two sinusoidal partial step sequences, one of which one drives the stepper motor (23) in the feed direction and the other drives it in the opposite direction. The stepper motors (42 and 96) for the sliding wheel (47) and the caster (80) are advantageously also not driven as a constant step sequence, but in two sinusoidal partial step sequences.

After the individual step motors (23, 42 and 96) have completed the number of steps set on the keypad (114) and dependent on the correspondingly retrieved data values from the data memory (116), the input (E2) of the respective AND gate (107 , 108 or 109) are switched from the control unit (105) to L potential via the control line (107a, 108a or 109a), so that the corresponding AND gate (107, 108 or 109) allows the clock pulses from the pulse generator ( 102) is prevented.

The changeover from the "moving needle" operating mode to the "fixed needle" operating mode takes place by actuating the switch (126) in its closed state. The control unit (105) controls the switching process when the next pulse from the pulse generator (101) emerges when the needle (13) emerges (see also FIGS. 6 and 7) at the cut-out point (P2). This then runs in the cut phase the needle (13). The needle (13) is moved back into its central position M against the feed direction (V) (distance n3). Since the needle (13) normally only executes half the stitch length (S) during its pierced phase (distances n1 and n2), this movement is a quarter of the stitch length (S). Slider wheel (47) and roller foot (80) have to move the sewing material in the first part of their feed (distance r1) to the center line M and in the second part of their feed (distance r2) they only need 1/4 of the stitch length S of from the center line M have now carried out the remaining amount, namely three quarters of the stitch length (S) (distances r3, r4 and r1) in the cut-out phase of the needle (13) to complete the started stitch.

The corresponding data values for the movement of the needle (13), the pusher wheel (47) and the roller foot (80) are calculated from the entered stitch length (S) by the control unit (105) and when the stitch is carried out in the counter (111 , 112 and 113). In the subsequent stitches with the needle (13) stationary, no data values are entered into the counter (111). The counters (112 and 113) are likewise not given any data values during the pierced phase of the needle (13), while the total data values required for executing the set stitch length (S) are respectively entered during the pierced phase of the needle (13). These then each correspond to twice the amount of the data values entered on the respective counter (112 or 113) during needle feed during half a stitch execution.

When the stitch is formed in the "fixed needle" mode, the pusher wheel (47) and the roller foot (80) are at hand inserted needle (13) silently, while with the needle (13) removed the entire feed amount to be carried out for one stitch length.

To switch from the "fixed needle" mode to the "moving needle" mode, the changeover switch (126) is switched back to its open position. The next time the pulse from the pulse generator (101) occurs when the needle (13) emerges from the material to be sewn in the central position (M), the control unit (105) controls the needle (13) from its central position M by a quarter of the stitch length (S) Sewing direction back to the puncture point (P1). At the same time, the feed wheel (47) and the roller presser (80) transport the sewing material by three quarters of the stitch length (S) in the sewing direction, namely by the distances (r2, r3 and r4), so that the needle (13) is exactly at the next stitch at the next stitch Stitch length (S) from the previous stitch at the puncture point (P1). The control unit (105) subsequently controls the control sequence of the movement of the needle (13), pusher wheel (47) and roller foot (described above in the "moving needle" operating mode when the impulse of the pulse generator (101) occurs when entering the material to be sewn). 80).

Instead of the manual changeover using the changeover switch (126), the changeover of the operating modes can also be controlled by the presettable counter (127), for example at the start of a sewing process. The counter (127) can be preset via the keyboard (114) to a certain amount, which corresponds to the number of stitches during which the needle bar guide (17) is to be stopped and during which the pusher wheel (47) and the roller presser ( 80) should take over the feeding of the sewing material alone. This The amount can then be transferred to the counter (127) by the control unit (105) via the collecting line (127a) before each sewing operation.

Before the stitch formation begins, there is an automatic switchover from the "moving needle" mode to the "fixed needle" mode. After each stitch is executed, the counter (127) is then counted down by "1" when the needle (13) emerges from the sewing material via the pulse emitted by the pulse generator (101). As soon as the counter (127) is at "O", the system switches to the "moving needle" operating mode, which then proceeds in the manner described above.

For reverse sewing, e.g. for locking at the seam end, the switch (120) is actuated, whereby the control unit (105) at the start of a new pulse from the pulse generator (101) via the control lines (117a, 118a and 119a) at the power stages (117, 118 and 119) reverses the direction of movement of the stepper motors (23, 42 and 96) so that they drive the pusher wheel (47), the roller presser (80) and the needle bar (14) in the opposite direction as long as the actuation of the switch ( 120) continues. The sequence of steps of the stepper motors (23, 42 and 96) is carried out by calling up the corresponding values set in the keypad (114) from the data memory (116) in the manner described above.

When the sewing machine stops, which usually ends at the top dead center of the needle (13), the control unit (105) switches the switching arrangement (106) to the input (E1), so that the pulses emitted by the oscillator (123) reach the inputs (E1 ) of the AND gates (107, 108 and 109). Once the sewing machine stops, clock pulses are thus given by the oscillator (123) to the inputs (E1) of the AND gates (107, 108 and 109) instead of the clock pulses by the pulse generator (102). In this way, the preselected advance of the needle (13), the pusher wheel (47) and the roller presser (80) is completed even after the last needle (13) has been cut out of the material, so that the needle (13) is already moving over the next needle insertion point. As soon as the end position of the preselected feed amount is reached, the control unit (105) switches the AND elements (107, 108 and 109) off via the control lines (107a, 108a and 109a).

Claims (1)

1. Sewing machine with a needle bar, which is mounted in a swing which is connected to a step motor for swinging the needle out in the advance direction, with a lower and/or upper advance wheel, which is driven synchronously with the advance movement of the needle by a respective additional step motor, with a store containing selectable information for directing the respective step motor, with a control unit between the store and the step motors for selecting and converting information into step pulses for the step motors, and with a pulse generator operating synchronously with the main shaft of the sewing machine for triggering and transmitting step pulses to the step motors, characterised in that the control unit (10̸5) comprises a control, which is connected to the change-over switch (126) and

   a) arrests the step motor (23) for the swing movement in the advance direction of the needle bar (14) in its centre position:

   b: suppresses the amount of advance of the lower and/or rupper advance wheel (47, 80̸) which coincides with the inserted phase of the needle (13); and

   c: increases by the suppressed amount the advance amount, which coincides with the phase of the retracted needle (13) and drives the lower and/or upper advance wheel (47, 80̸) of the driving step motor (42, 96).

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