EP0407433B1 - Process for executing a stitching operation with a sewing machine provided with needle feed - Google Patents

Abstract

Defective stitches frequently occur at the beginning of a stitching operation with a sewing machine provided with needle feed, because the starting threads are not tightly gripped in the needle plate as a result of the elongated stitching slot. In the new process, the needle (13) is positioned prior to the beginning of stitching in an end region (S1) of the stitching slot (50b) in order to execute a predetermined number of starting stitches.

Description

Process for performing a sewing process with a sewing machine with needle feed

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

Such a method is known from DE-C-3 516 713.

In a sewing machine with a needle swinging in the feed direction, the stitch hole in the needle plate is designed as a stitch slot running in the feed direction. The result of this is that the knotting of the initial stitches, in particular the first stitch, is loosened by the lack of friction of the threads at the edge of the stitch slot when tightened by the thread lever and a perfect stitch formation is prevented. This happens especially with short thread ends after a previous thread cutting process.

The invention is therefore based on the object of providing a method for a sewing machine with needle transport in order to ensure reliable stitch formation at the start of a new sewing process.

This is solved in a method according to the preamble of claim 1 by its characterizing features.

With the method according to the invention, there is now the possibility of considerably improving the stitch formation conditions right at the start of the seam formation by a sufficient clamping effect of the threads at the edge of the stitch slot and thereby achieving a reliable initial stitch formation.

Advantageous modifications of the method according to the invention are contained in the subclaims. The claim 2 contains a simple solution to the displacement of the axis of the needle.

By means of the measure according to claim 3, both the insertion and the removal of the needle into and out of the sewing material take place in the immediate end region of the stitch slot, which results in optimal clamping conditions of the free thread ends at the edge of the stitch slot.

The measure according to claim 4 brings about a reduction in thread consumption during the first stitch formation and thus a reduction in retraction of the sewing threads by the thread lever.

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 vergrößerten Darstellung und
• Fig. 7 einen vergrößerten Ausschnitt aus der Fig. 6.

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
• 7 shows an enlarged detail from FIG. 6.

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) fixed 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 mounted in the arm (4) parallel to the main shaft (6).

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 coaxial with a pin (24) to the drive shaft (22) running housing bore (25).

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) with the aid of 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 protrudes through a slot (50a). The stitch plate (50) with a stitch slot (50b) for the passage of the needle (13) is provided parallel to the slot (50a).

The carrier (30) is by a in its upper part screwed screw (51), which projects through a slot (52) in the column (2), firmly clamped to the latter. 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) fastened on the shaft (53), presses the coupling piece (56) and thus the upper wall of its ring section 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 for slow driving the stepper motors (42 and 96) are preferably provided in the forward or backward direction when the sewing machine is at a standstill in the needle raised 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 motor control (126) is connected to the control unit (105) via a collecting line (126a). The motor control (126) is specially provided for the control of the sewing motor (8) and connected to it via a line (8a). A speed setpoint generator (127) designed as a foot control element is connected to the engine control via a collecting line (127a) (126) connected. A counter (128) is connected to the control unit (105) via a bus line (128a) and a line (128b) and to the pulse generator (101) via a line (128c).

The facility works as follows:
The operator sets the desired feed amounts of the needle (13), the pusher wheel (47) and the roller presser (80) using the keypad (114), the corresponding digital values being taken from the data memory (116) via the control unit (105) and thus the Counters (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 is passed from the AND gates (107, 108 and 109) to the counters (111, 112 and 113) will.

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). At the same time, it uses the control lines (117a, 118a and 119a) connected to the power stages (117, 118 and 119) to determine 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 execute 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) rotates simultaneously over his Output shaft (22) the eccentric (21) gradually in one direction, its eccentricity transmitting deflection movements via the eccentric rod (20) and the lever arm (18) to the rocker (17), which then swings out by 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 (96) during one revolution of the main shaft (6), i.e. with each feed between two stitch formations, two sinusoidal partial step sequences 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 stepper 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) from the control unit (105) switched to L potential via the control line (107a, 108a or 109a), so that the further transmission of the clock pulses by the pulse generator (102) is prevented by the corresponding AND gate (107, 108 or 109).

To secure the stitch formation, the control unit (105) causes the axis of the needle (13) to be shifted into the end region of the stitch slot (50b) in the stitch plate (50) before each sewing operation. For this purpose, the control unit (105) tests the state of the sewing motor (8) and the speed setpoint generator (127) via the collecting line (126a). When the sewing motor (8) is at a standstill, the control unit (105) sends a signal to the motor control (126) via the bus line (126a), which first prevents the sewing motor (8) from starting.

The control unit (105) calculates from the stitch length (S) entered on the keyboard (114), the length (L) of the stitch slot (50b) in the stitch plate (50) and from a selectable value (K), which is the remaining distance of the needle (13) from the end of the stitch slot (50b) corresponds to a value (W = S / 2 + L / 2 - K) at which the first puncture of the needle (13) is to take place in the subsequent sewing process.

The control unit (105) reads out corresponding digital values for the needle (13), for the slide wheel (47) and for the roller presser (80) from the data memory (116), which correspond to the calculated value (W) and thus effects the Bus (110) a preset of the counters (111, 112 and 113). The control unit (105) then switches the changeover switch (106) to (E1), so that the pulses emitted by the oscillator (123) go to the inputs (E1) of the AND gates (107, 108 and 109).

As soon as the control unit (105) receives the information via the control unit (126) that the speed setpoint generator (127) is actuated, it switches the potential at the inputs (E2) of the AND- via the control line (107a, 108a and 109a). Gates (107, 108 and 109) to (H) so that the pulses from the oscillator (123) are switched in front of the AND gates (107) via the switching arrangement (106) connected to the input (E1) when the sewing motor (8) is at a standstill , 108 and 109) to the counters (111, 112 and 113).

The movement of the stepper motors (23, 42 and 96) takes place in the manner described above until the number of steps specified in the data memory (116) for the sliding wheel, roller foot and needle drive have been carried out. Now the input (E2) of the respective AND gate (107, 108 or 109) is switched to L potential by the control unit (105) via the control line (107a, 108a or 109a), so that the corresponding AND gate ( 107, 108 or 109) the further passage of the clock pulses from the pulse generator (102) is prevented. At the same time, the sewing motor (8) is released through the manifold (126a). The axis of the needle (13) was pivoted into position (S1) (Fig. 7).

The counter (128) is loaded via the collecting line (128a) with a presettable value which corresponds to the number of initial stitches to be produced in the sewing phase, after which the needle bar (14) is to return to its normal sewing position.

The changeover switch (106) is operated by the control unit (105) switched to (E2) so that the pulses coming from the pulse generator (102) reach the inputs (E1) of the AND gates (107, 108 and 109). However, no data is read into the counters (111, 112 and 113) for the execution of the first stitch.

The motor controller (126) now drives the sewing motor (8) at the speed specified by the speed setpoint generator (127). The first stitch formation is carried out without feed because the counters (111, 112 and 113) contain no data which cause the stepper motors (23, 42 and 96) to be driven.

After the first stitch, the other stitches with the stitch length (S) entered on the keyboard (114) are carried out by calling up corresponding data values from the data memory (116) in the manner described above, the needle (13) moving in the manner shown in FIG. 7 with S '/ 2 area executes, so that a perfect stitch formation already takes place at the first stitch. For each stitch, the counter (128) is counted down by "1". As soon as the counter (128) is at "0", the stitch formation of the initial stitches is finished. The counter (128) sends a pulse to the control unit (105) via the line (128b), after which the next pulse from the pulse generator (101) triggers a movement when the needle (13) emerges from the sewing material, which moves the axis of the needle ( 13), the pusher wheel (47) and the roller foot (80) before the next stitch are moved back by the same amount by which they were moved in the feed direction before the sewing process. When the stitch is formed further, the needle (13) oscillates again in the central region of the stitch slot (50b) of the stitch plate (50) (labeled S / 2 in FIG. 7).

If the sewing process is started with a backward stitch sequence, e.g. B. by a bolt control, then the control device (105) shifts the axis of the needle (13) in the front, d. H. area of the stitch slot (50b) of the stitch plate (50) facing the operator. The production of the initial stitches then proceeds analogously to the embodiment described above with normal feed adjustment, after which the axis of the needle (13) is shifted into its central region.

According to a second embodiment of the invention, it is also possible to stop the needle (13) during the production of the initial stitches by setting the counter (111) to "0" during this time. The feed of the sewing material during the production of these initial stitches then takes place exclusively through the pusher wheel (47) and the roller foot (80).

When the needle (13) emerges from the material after the first sewing stitch has been carried out in the end region of the stitch slot (50b), the impulse that occurs from the pulse generator (101) triggers a stopping of the needle bar guide (17) via the control unit (105). At the same time, the control unit (105) controls the total feed amount of the pushing wheel (47) and the roller presser (80) for executing a stitch with the set stitch length (S) while the feed of pushing wheel (47 ) and roller foot (80) in the pierced phase of the needle (13).

This stitch is carried out until the counter (128) preset with the number of starting stitches (Fig. 5) has reset and emits a pulse to the control unit (105) via the line (128b).

As already described in the previous embodiment, this impulse triggers the backward movement of the needle (13), which is moved over its later puncture point in the sewing material. The further stitch formation then takes place again in the central region of the stitch slot (50b) of the stitch plate (50).

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). As soon as the sewing machine stops, clock pulses from the oscillator (123) to the inputs (E1) of the AND gates (107, 108 and 109) instead of the clock pulses from Given 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 (4)

1. Process for executing a sewing process by means of a sewing machine which is equipped with a control unit, which drives both the needle and a bottom and/or top advance means for carrying out an advance movement of the workpiece, and a puncture plate, which comprises a puncture slit and which extends in the advance direction for the passage of the needle, characterised by the following procedural steps:

   a) the axis of the needle (13) is displaced prior to the sewing process into an end region of the puncture slit (50̸b) of the puncture plate (50̸);

   b) in this position of the needle (13), a specified number of initial stitches is formed;

   c) the displacement of the axis of the needle (13) is then released;

   d) the advance movement of the workpiece, which is executed by the advance means (47, 80̸) during the release of the displacement of the needle (13) is corrected by the amount of the displacement.
2. Process according to claim 1, characterised in that, during the production of a specified number of initial stitches in the displaced position, the axis of the needle (13) executes an advance movement which corresponds with the advance movement of the workpiece by the advance means (47, 80̸).
3. Process according to claim 1, characterised in that, during the production of a specified number of initial stitches in the displaced position, the axis of the needle (13) is deactivated, whereby the entire advance movement of the workpiece is executed by the advance means (47, 80̸) exclusively during the punched-out phase of the needle (13), and that, after a return of the axis of the needle (13) into its normal swing range, the control unit (10̸5) controls the switch-on of its advance movement and the redirection of the advance means (47, 80̸) for carrying out an advance movement of the workpiece during both the punched-out and the punched-in phase of the needle (13).
4. Process according to one of claims 1 to 3, characterised in that the first stitch forming takes place whilst the advance movement of the advance means (47, 80̸) is switched off.

Images