Sewing machine, sewing system with such a sewing machine and method for operating a sewing machine

Abstract

A sewing machine has a stitch plate (3a) and a fabric hold-down foot (13) for performing a lifting movement to hold the fabric on the stitch plate (3a) during a sewing operation. A driven stroke amplitude adjustment device (17) is used to set the stroke amplitude of the fabric hold-down foot's movement between a top dead center and a bottom dead center. A driven stroke level adjustment device is used to set the stroke level of the fabric hold-down foot's movement (13) relative to the stitch plate (3a). A control / regulating device (11) communicates with the stroke amplitude adjustment device (17) and the stroke level adjustment device. Furthermore, operating procedures possible with the sewing machine are described. The result is a sewing machine with which fabrics of varying thicknesses and / or different numbers of layers can be sewn precisely and flexibly.

Description

[0001] The content of the German patent application DE 10 2024 203 789 is incorporated herein by reference.

[0002] The invention relates to a sewing machine. Furthermore, the invention relates to a sewing system with such a sewing machine and to a method for operating such a sewing machine.

[0003] A sewing machine is known from EP 3 556 923 B1 and from EP 3 088 591 B1. A sewing system with a sewing machine is known from EP 3 088 587 B1.

[0004] It is an object of the present invention to further develop a sewing machine in such a way that it can be used to flexibly and precisely sew materials of different thicknesses and / or different numbers of layers.

[0005] This problem is solved according to the invention by a sewing machine with the features specified in claim 1.

[0006] According to the invention, it has been recognized that a design of a sewing machine with a driven stroke amplitude adjustment device and a driven stroke level adjustment device allows for the independent setting of, on the one hand, the stroke amplitude and, on the other hand, the stroke level of the fabric-holding foot. Accordingly, the sewing machine can be designed such that the stroke amplitude adjustment device and the stroke level adjustment device enable independent setting of the stroke amplitude and the stroke level of the fabric-holding foot. Such setting of the stroke amplitude and the stroke level can be performed independently of each other. This allows for the setting of a wide variety of stroke trajectories of the fabric-holding foot during sewing operations.Insofar as the fabric hold-down foot's movement is coupled to or synchronized with the movement of the sewing machine's stitch-forming tools, an intermittent or periodic lifting motion of the fabric hold-down foot is possible, fulfilling the respective set parameters "lift amplitude" and "lift level." The lift amplitude adjustment device can include a lift cam, which may be designed as a cam disc, and / or a tab drive, which may also be designed as a cam disc. The lift level adjustment device can include a fan cam. Holding the fabric down by the fabric hold-down foot can be achieved by pressing the fabric against the machine.Alternatively or additionally, the holding down by the fabric holding foot can also be designed in such a way that the fabric holding foot does not touch the fabric, but merely prevents the fabric from undesirably moving upwards, i.e. in the lifting dimension.

[0007] Drives for the stroke amplitude adjustment device and / or the stroke level adjustment device can be designed as stepper motors.

[0008] The lifting movement of the sewing material holding foot can be a continuous and / or periodic oscillation.

[0009] A sensor according to claim 2 enables controlled operation of a sewing machine's lifting drive comprising the stroke amplitude adjustment device and the stroke level adjustment device. The sensor can measure the distance, in particular, between a component of the fabric hold-down foot and the needle plate. Specifically, it can directly measure the actual stroke of the fabric hold-down foot above the needle plate. Alternatively, the sensor can measure the actual position of a gearbox or a component of this gearbox, which is used to adjust the stroke of the fabric hold-down foot. Alternatively or additionally, the sensor for detecting the actual stroke position of the fabric hold-down foot can be an encoder for a sewing drive and / or for a drive of the stroke amplitude adjustment device and / or the stroke level adjustment device, in particular a stepper motor encoder.

[0010] The sensor can be designed as an optical sensor and / or as a capacitive sensor.

[0011] The actual position of the fabric hold-down foot above the stitch plate can also be detected sensorially during the pressing of fabric by the fabric hold-down foot by detecting the motor current of an electric fabric hold-down foot drive.

[0012] A spring preload on the fabric hold-down foot according to claim 3 enables it to dip in a controlled manner when pressing down on the fabric, preventing a section of the fabric hold-down foot from lying undesirably too low relative to the stitch plate. This avoids an unwanted collision or obstruction of the fabric hold-down foot with the stitch plate.

[0013] An adjustment device according to claim 4 enables the application of a force with respect to the immersion process described above. The lifting level adjustment device can simultaneously perform the function of such an adjustment device.

[0014] The advantages of a sewing system according to claim 5 correspond to those already explained above with reference to the sewing machine. A sewing system with a sewing machine is known in principle from EP 3 088 587 B1. In addition to the sewing machine, the sewing system can also include a material holder that defines a sewing area within which the material is sewn by means of the sewing machine. Such a material holder can be designed as a clamp. Alternatively or additionally, such a material holder can be designed in the form of a material holding frame.

[0015] Another object of the invention is to specify operating methods that are possible with the sewing machine according to the invention.

[0016] An operating method according to claim 6 ensures that a stroke level precisely follows a setpoint specification, in particular independent of an absolute value of a predetermined stroke amplitude.

[0017] An operating method according to claim 7 ensures that a stroke amplitude precisely follows a setpoint specification, in particular independent of an absolute value of a predetermined stroke level.

[0018] An operating method according to claim 8 ensures an adjustment of a stroke level to requirements that change during a sewing path while maintaining a constant stroke amplitude.

[0019] An operating method according to claim 9 ensures an adjustment of the stroke amplitude to sewing requirements that change during a sewing path without changing the stroke position of the sewing material holding foot in the area of ​​the bottom dead center.

[0020] The operating method according to claim 10 enables the fabric holding foot to be lifted by means of the lifting level adjustment device. An additional fan drive is not required. The initial lifting amplitude specified in this operating method can also be set to 0.

[0021] When lifting the sewing material holding foot with this operating method, a maximum stroke amplitude can additionally be specified using the stroke amplitude adjusting device.

[0022] These operating procedures can also be combined. For example, if different stroke amplitudes and / or different stroke levels are specified, it can be ensured that the complementary parameters "stroke level" and "stroke amplitude" remain within the specified tolerance limit after a change in the target value for the first-mentioned parameter, and thus do not change undesirably.

[0023] An embodiment of the invention is explained in more detail below with reference to the drawing. This drawing shows: Fig. 1, perspective view of a sewing system with a sewing machine and an xy-type fabric holder for the driven displacement of the fabric held therein along two horizontal dimensions; Fig. 2, perspective view of an assembly of drive components of the sewing machine for driving a fabric-holding foot, comprising a driven stroke amplitude adjusting device for setting a stroke amplitude of a stroke movement of the fabric-holding foot and a driven stroke level adjusting device for setting a stroke level of the stroke movement of the fabric-holding foot; Fig. 3, the drive components according to Fig. 2 , from a perspective opposite to Fig. 2 ; Fig. 4 shows a section of the fabric-holding foot-side drive parts of the drive component assembly. Fig. 2 , again from perspective point IV in Fig. 2 ; Fig. 5 the drive parts according to Fig. 4 , again, from a perspective in the opposite direction to Fig. 4 obliquely from below; Fig. 6 a longitudinal section through the fabric hold-down foot and adjacent drive components of the drive component assembly along a section plane perpendicular to the drive and adjusting shafts of the drive component assembly; Fig. 7 along a section towards Fig. 6 parallel section plane, a section to illustrate a cam disk of the stroke amplitude adjusting device; Fig. 8 in a Fig. 7 A similar representation shows a section to illustrate a cam disc of the stroke level control device; Fig. 9 shows a schematic diagram to clarify setting parameters of the control devices of the drive component assembly; Fig. 10A / Bin is one to Fig. 2 / 3Similar representation: the drive component assembly with stroke "Y" set via the stroke amplitude adjusting device, in a momentary position "top dead center"; Fig. 11A / B the drive component assembly according to Fig. 10 , again in the stroke position "Y", this time in the instantaneous position "bottom dead center"; Fig. 12A / Again in a to Fig. 2 / 3 In a similar representation, the drive component assembly is shown in the stroke amplitude position "Y" and in comparison to the Fig. 10 and 11 larger stroke level position of the stroke level adjusting device, again at top dead center; Fig. 13A / B the drive component assembly according to Fig. 12 in the instantaneous position "bottom dead center"; Fig. 14 schematically in a to Fig. 9 A similar illustration shows an application of a lifting movement of the sewing material holding foot, controlled by the drive component assembly in a sequence of first the instantaneous positions according to the Fig. 10 and 11and then after the Fig. 12 and 13 ; Fig. 15A / I am one of Fig. 10 Similar representation of the drive component assembly with stroke amplitude position "X" in the instantaneous position "top dead center"; Fig. 16A / B the drive component assembly according to Fig. 15 in the instantaneous position "bottom dead center"; Fig. 17 in a to Fig. 14 A similar illustration shows another application of a lifting movement of the sewing material holding foot with the drive component assembly in a sequence of first the instantaneous positions according to the Fig. 10 and 11 and then after the Fig. 15 and 16 ; Fig. 18A / Again in a to Fig. 2 / 3 Similar representation of the drive component assembly with raised fabric hold-down foot; Fig. 19 in one of the Fig. 14 and 17A similar illustration shows an application of the lifting movement of the sewing material holding foot with the drive component assembly on the one hand in the positions according to the Fig. 10 and 11 and on the other hand in the ventilated position after Fig. 18 ; and Fig. 20A / B again in a to Fig. 2 / 3 In a similar representation, the drive component assembly is shown in a position of, on the one hand, the stroke amplitude adjusting device and, on the other hand, the stroke level adjusting device, in which the sewing material holding foot rests on a stitch plate and is pre-tensioned against the stitch plate via a bearing spring.

[0024] One in the Fig. 1 The sewing system 1 shown in the diagram has a sewing machine 2 for sewing two pieces of fabric together.

[0025] Sewing machine 2 sews the fabric in a stitch formation area 3 by forming at least one seam. Around the stitch formation area 3, sewing machine 2 has a stitch plate 3a for supporting the fabric.

[0026] A material holder 4 in the form of a material clamp with a lower, one-piece clamp section 5 and an upper, two-piece clamp section 6a, 6b serves to transport the material being sewn during seam formation relative to the stitch formation area 3. The material holder 4 is in the form of a material clamp with a lower, one-piece clamp section 5 and an upper, two-piece clamp section 6a, 6b. Fig. 1 The upper bracket section part 6a shown in the upper left is in the Fig. 1 lifted from the lower bracket section 5 and the other upper bracket section part 6b is in the Fig. 1 The lower clamp section 5 is shown lowered to clamp the fabric.

[0027] The clamping sections 5, 6 of the fabric holder 4 surround a rectangular sewing field 7. Within this sewing field 7, a seam can be formed in the fabric using the sewing device 1.

[0028] Depending on the design of the sewing system 1, instead of the sewing material clamp described above with clamp sections 5, 6, a different clamping system can also be used, in particular an interchangeable clamping system.

[0029] To facilitate understanding the spatial relationships, a Cartesian xyz coordinate system is used in the following description of the figures. The coordinates x and y define a fabric support plane. The y-coordinate runs parallel to an arm 8 of sewing machine 2. The z-coordinate runs perpendicular to the fabric support plane x and y.

[0030] Typical xy sewing field sizes can be (x-extension x y-extension) depending on the design of the sewing system 1: 150 mm x 100 mm, 220 mm x 100 mm, 250 mm x 160 mm, 300 mm x 200 mm.

[0031] To shift the sewing area 7 relative to the stitch formation area 3, the workpiece holder 7 has an x-drive with an x-guide 9 and a y-drive with a y-guide 10. The x-drive can be controlled independently of the y-drive. A control unit 11 of the sewing system 1 serves this purpose.

[0032] A clamp drive 12 with independent drive components 12a, 12b, of which in the Fig. 1 The drive component 12b, which is associated with the upper clamp section part 6b, is used to raise and lower the upper clamp section parts 6a and 6b. The clamp drive 12 is also in signal communication with the control unit 11.

[0033] The sewing machine 2 also has a fabric hold-down foot 13, the foot section of which is 14 (see below). Fig. 2 ) has a threaded sleeve for a sewing needle 15 of the sewing machine. Alternatively, depending on the design of the sewing machine 2, a presser foot can also be used instead of such a fabric-holding foot 13 designed as a jumping foot, which has a plate-shaped foot section instead of the threaded sleeve.

[0034] The fabric-holding foot 13 is designed to perform a lifting movement to hold the fabric down, in particular intermittently, on the stitch plate 3a during a sewing process.

[0035] Fig. 2 and 3 Details of a lifting drive 16 of the sewing material holding foot 13 are illustrated.

[0036] The lifting drive 16 has a lifting amplitude adjusting device 17 for setting a lifting amplitude HA of the lifting movement of the sewing material holding foot 13 between a top dead center TDC (see also Fig. 9 ) and a bottom dead center UT. Furthermore, the lifting drive 16 has a lifting level adjusting device 18 for setting a lifting level HN of the lifting movement of the sewing material holding foot 13 relative to the stitch plate 3a.

[0037] Fig. 9 This illustrates these stroke movement parameters, namely the stroke amplitude HA and the stroke level HN. It is shown in the Fig. 9 a sinusoidally oscillating stroke H of the not shown sewing material holding foot 13 as a function of time t.

[0038] A solid line represents a stroke amplitude HA = X. A smaller stroke amplitude HA = Y is represented by a dashed line. Adjustment between these two exemplary stroke amplitudes X and Y is achieved using the stroke amplitude adjusting device 17. For this purpose, the stroke amplitude adjusting device 17 has a stroke mechanism 19 in the form of a linkage mechanism (see figure). Fig. 2 and 3The lifting mechanism 19 is driven via an eccentric 20, which is driven by an upper shaft 21 of the sewing machine running in the arm 8, which is located in the Fig. 2 This is illustrated schematically in sections. The upper shaft 21, in turn, is driven by a sewing machine drive. On the output side, the lifting gear 19 acts on a lifting shaft 22 of the lifting drive 16, which in turn acts via a lever 23 and a link chain 24 on a hold-down bar 25 of the fabric hold-down foot 13.

[0039] The lifting gear 19 is adjusted via an amplitude control shaft 26, which is controlled by an actuating lever 27 (see figure). Fig. 7 ) and a cam disk 28, driven by a stepper motor 29, is adjusted for the stroke amplitude setting of the stroke amplitude adjusting device 17. A preload spring, against which the cam disk 28 works, is located in the Figur 2 as shown in the other corresponding figures in a disengaged state, i.e. not in the pre-tension operating state.

[0040] The lifting level adjustment device 18 serves on the one hand to specify a respective lifting level HN and on the other hand to lift the sewing material holding foot 13, especially at the beginning and at the end of the sewing process.

[0041] The lifting level adjustment device 18 has a fan shaft 30 (see, among others, the following). Fig. 4 ), which interacts via a fan lever 31 on a system cam 32 with the hold-down foot bar 25 to lift the sewing material hold-down foot 13.

[0042] Waves 22, 26, 30 run parallel to the overtone 21 along the y-direction.

[0043] The lifting drive 16 of the sewing material holding foot 13 is guided via a linear guide 33.

[0044] The lifting drive 16 is secured against rotation by a sliding block 34 and a [missing element] in the Fig. 4 indicated z-guide 35, which is frame-fixed to the sewing machine 2. Fig. 4 further illustrates another z-guide 36 of the hold-down foot rod 25.

[0045] A pressure bracket 37, articulated to the fan lever 31, maintains a constant preload on a compression spring 38 between the pressure bracket 37 and the hold-down foot rod 25, as long as no force in the positive z-direction is exerted by the material being sewn on the foot section 14 of the material-holding foot 13. If such a force is exerted on the foot section 14 in the positive z-direction, the compression spring 38 is compressed accordingly, allowing the material-holding foot 13 to deflect in response to such a force in the positive z-direction and compress towards a spring bushing 39. The compression spring 38 is actually a combination of compression springs or a spring assembly, as shown, for example, in the sectional view according to [reference to relevant figure]. Fig. 6 as is evident.

[0046] The fan shaft 30 of the lift level adjusting device 18 is connected via an adjusting lever 40 at the end of the fan shaft 30 opposite the fan lever 31 to a lift level cam disc 41 (see, among others, [reference]). Fig. 8 ) in operative connection. A comparable cam disc is known from EP 3 556 923 B1.

[0047] The lift level cam 41 is driven by a lift level or fan actuator 42, which is also a stepper motor. Depending on its direction of rotation, the lift level cam 41 has several functions. Rotation in one direction results in a change in the lift level HN, which can be accompanied by a change in the preload of the compression spring 38. The lift level actuator 18 thus also serves as an adjustment device for setting a preload force of the at least one compression spring 38. Rotation of the lift level cam 41 in the opposite direction raises the fabric hold-down foot 13.

[0048] Holding the material down by the fabric-holding foot 13 can occur as an actual pressing of the material against the fabric. Alternatively or additionally, holding the material down by the fabric-holding foot 13 can also occur in such a way that the foot does not touch the material, but merely prevents it from unduly moving upwards, i.e., in the positive z-direction. The lifting movement of the fabric-holding foot can result in intermittent and, in particular, periodic pressing of the material against the fabric.

[0049] A positive z-distance between the fabric hold-down foot 13 at the bottom dead center of its stroke and the stitch plate 3a can be set via an adjustable stop. The adjustable stop can be fixed to the frame and adjustable relative to the frame between different stop positions.

[0050] The higher the z-position of the fabric-holding foot 13 is set at the bottom dead center of its stroke over the stop body, the more the compression spring 38 is compressed, assuming the pressure bar 37 remains in a constant z-position. The initial compressive force required by the compressed fabric against the fabric-holding foot 13 to move it in the positive z-direction against the force of the compression spring 38 is then increased due to the additional compression of the spring 38. This initial compressive force, which the fabric must overcome against the fabric-holding foot 13 at its bottom dead center of its stroke, can be adjusted by changing the z-position of the pressure bar 37. This adjustment can be made using the stroke level adjustment device 18, the fan shaft 30, and the fan lever 31, as explained above.

[0051] A z-distance between the fabric hold-down foot 13 and the stitch plate 3a can be specified in the range of 0 mm to 5 mm, for example in the range between 0 mm and 2 mm or between 0 mm and 1 mm via the stop body.

[0052] A sensor 43 of the sewing machine 2 serves to detect the current position of the fabric hold-down foot 13 above the stitch plate 3a. The sensor 43 can be designed as an inductive and / or optical sensor, in particular for measuring the distance of a component of the fabric hold-down foot 13 to the stitch plate 3a. Alternatively, the sensor 43 can be designed, for example, capacitively, to measure the current position of a component of the lifting drive 16 or of a gearbox for moving the fabric hold-down foot 13. Again, alternatively or additionally, the sensor 43 can be designed as an encoder for at least one drive component of the lifting drive 16, in particular as an encoder for the stepper motors 29 or 42.

[0053] The measurement accuracy of a distance measurement using sensor 43 can be at least 0.1 mm, can be better than 0.1 mm, can be better than 0.05 mm and can, for example, be 0.01 mm.

[0054] The actual position of drive components of the lifting drive 16 can also be determined by sensory means by detecting a motor current of a component of the lifting drive 16, in particular at least one of the stepper motors 29 or 42.

[0055] The Fig. 2 bis 8 The figures show the lifting drive 16 and its components in a home position. The lifting amplitude HA is 0 and the lifting level HN is also 0 or minimal. The fabric-holding foot 13 is therefore in a non-lifted position relative to the stitch plate 3a.

[0056] Fig. 10 shows the lifting drive 16 in one of the Fig. 2 A similar representation is shown in an instantaneous position with stroke amplitude HA = Y and stroke level HN equal to the stroke amplitude HA, where the sewing material holding foot 13 is in the position "top dead center TDC". This corresponds to the instantaneous positions "A" of the stroke diagram according to Fig. 14 , which is similar to the Fig. 9 This illustrates a lifting drive application of the sewing machine 1. In this case, the lifting level HN is set so that a first layer of single-layer sewing material NG1 can be arranged between the foot section 14 of the sewing material holding foot 13 and the stitch plate 3a.

[0057] In the instantaneous position of the lifting drive components according to Fig. 10 The two cam discs 28 of the stroke amplitude adjusting device 17 and 41 of the stroke level adjusting device 18 are adjusted accordingly, so that the described stroke parameters HA, HN (HN1) are present.

[0058] Fig. 11 shows the instantaneous position "B" of the lifting drive 16, which in turn is shown in the diagram. Fig. 14 This is illustrated. The stroke amplitude Y and the stroke level HN1 are again present. The fabric-holding foot 13 is at bottom dead center UT. The cam positions of the two cam discs 28 and 41 are as follows at the instantaneous setting. Fig. 11 compared to the current position after Fig. 10 unchanged.

[0059] Fig. 12A / 12B The figures show instantaneous positions of the lifting drive 16, again with the lifting amplitude Y, but now with an increased lifting level HN2, with the sewing material holding foot 13 at top dead center OT. This is therefore the instantaneous position "C" in the Fig. 14 . Due to the increased lifting height HN2, a further two-layer sewing material NG2, which is sewn together with the sewing material NG1 during the sewing process, can now be accommodated under the sewing material holding foot 13 next to the single-layer sewing material NG1.

[0060] In the current position "C" according to the Fig. 12A / 12BIs the cam disc 41 in comparison to the position after the Fig. 10 and 11 rotated counterclockwise. The position of the stroke amplitude cam disc 28 is, in comparison to the Fig. 10 and 11 unchanged.

[0061] Fig. 13A / 13B show the current position "D" in Fig. 14 , also stroke amplitude Y, stroke level HN2 and sewing material hold-down foot 13 at bottom dead center. Compared to the Fig. 12A / 12B The positions of cam discs 28 and 41 remain unchanged.

[0062] During the transition between instantaneous positions "B" and "C", the stroke level adjusting device is continuously switched from stroke level HN1 to the larger stroke level HN2 by actuating the stepper motor 42. This transition takes place during half a cycle of the stroke movement of the fabric-holding foot 13 between a bottom dead center (position "B") and a top dead center ("position C"), as shown in the Fig. 14 This is illustrated. To ensure that the stroke amplitude does not change when switching from stroke level HN1 to the larger stroke level HN2, but remains constant at the value Y, the stroke amplitude adjusting device 17 may need to be readjusted, as the stroke amplitude can depend on the respective position of the stroke level adjusting device 18. The same applies conversely to readjusting a stroke level after changing a stroke amplitude.

[0063] The Fig. 15 and 16 show in one of the Fig. 10 and 11 In a similar representation, the lifting drive 16 has a lifting amplitude HA = X, which is greater than the lifting amplitude Y of the instantaneous position, for example, after Fig. 10 . Fig. 15A / 15B show the sewing material hold-down foot at top dead center (TDC) and Fig. 16A / 16B the sewing material holding foot 13 at bottom dead center UT.

[0064] Fig. 15 shows a momentary position "E", illustrated in the Fig. 17 , and Fig. 16 shows a momentary position "F", again illustrated in the Fig. 17 .

[0065] In comparison, for example, to the instantaneous position of the lifting drive 16 after Fig. 10 , is in the current position after Fig. 15 The cam disk 28 of the stroke amplitude adjusting device 17 is displaced, namely rotated clockwise. A corresponding change in stroke amplitude from stroke Y to the larger stroke X is the result.

[0066] In the use case according to Fig. 17 Initially, a parameter combination of HA = Y and HN = HN1 is comparable to the initial situation in the application case according to Fig. 14 The process is set up. Instead of a single layer of fabric NG1, two thinner pieces of fabric NG1 and NG1' are sewn together. Following this, the last instantaneous position "B" in the application is adjusted. Fig. 17 and the first instantaneous position "E" changes both the stroke amplitude in value Y to the larger value X and the stroke level from value HN1 to the larger value HN2. In this subsequent application situation of the use case according to Fig. 17 Then, instead of sewing material NG1, another sewing material NG3, which is thicker than sewing material NG1, can be sewn to sewing material NG1'. During this sewing process, the foot section 14 of the sewing material holding foot 13 dips slightly into sewing material NG3 in the area of ​​the lower dead center (position "F"), which can be compensated for by a corresponding compression of the compression spring 38. A higher value for the stroke level and / or a higher value for the stroke amplitude can be used in particular to prevent fluffy or soft sewing material from being unintentionally pushed through the sewing material holding foot 13 during x- or y-transport over the sewing material clamp.

[0067] Fig. 18A / 18BThe figures show the lifting drive 16 in the instantaneous position "ventilation". The lifting level control device 18 is now switched to the position "ventilation", i.e., to the instantaneous position G, which is in the Fig. 19 This is illustrated. The stroke level is now L, which is the fan stroke level. An initial sewing situation in the application case according to Fig. 19 corresponds to that according to Fig. 17 with the stroke level HN1 and the stroke amplitude Y. To reach the instantaneous position G, the stroke amplitude is changed to the larger value.

[0068] Fig. 20A / 20B The figures show the instantaneous position of the lifting drive 16 and the fabric-holding foot 13 as the fabric-holding foot 13 is immersed in the spring bushing 39 or in a spring guide 44. The foot section 14 presses against the stitch plate 3a with a pressure or preload force determined by the compression spring 38. During the instantaneous adjustment according to the Fig. 20A / 20BThe stroke amplitude HA = 0 is set and the stroke level HN < 0.

[0069] In connection with the above, in particular with reference to the Fig. 14 , 17 and 19 In the described application cases, the following operating procedures can be used: In the first operating procedure of sewing machine 2 of sewing system 1, a stroke amplitude HA is specified via the stroke amplitude control device 17. Furthermore, a target stroke level HN Target is specified. Using sensor 43, an actual level HN Actual is determined, which results from the specified stroke amplitude HA. The stroke level control device 18 is then adjusted until the difference HN Actual - HN Target between the actual stroke level HN Actual and the target stroke level HN Target is within a specified tolerance limit. In particular, the following may apply: HN Ist − HN Soll 2 / HN Ist + HN Soll 2 ≤ 10 % .

[0070] The tolerance limit can also be smaller than 10% and can be, for example, 5%, 3%, 2%, or even 1%, or even smaller. Typically, the tolerance limit is greater than 0.01%. After adjustment, the sewing machine is operated with the stroke parameters set in this way.

[0071] In another operating procedure, a stroke level HN is first set via the stroke level control device 18. A target stroke amplitude HA Target is then set, and an actual amplitude HA Actual is determined using sensor 43, resulting from the set stroke level HN. The stroke amplitude control device 17 is then adjusted until the difference HA Actual - HA Target is within a predefined tolerance limit. The tolerance limit (HA Actual - HA Target) ≤ 2 / (HA Actual + HA Target) ≤ 2 can again be defined by the values ​​specified above in connection with the tolerance limit for the difference between the actual stroke level and the target stroke level. After adjustment, the sewing machine is operated with the stroke parameters set in this way.

[0072] In another operating procedure of sewing machine 2, a first stroke level HN1 is initially set via the stroke level adjusting device 18. Furthermore, a stroke amplitude HA is set via the stroke amplitude adjusting device 17. Sewing machine 2 of sewing system 1 is then operated with the first stroke level HN1 and the stroke amplitude along a first sewing path. A further stroke level HN2, which differs from the first stroke level HN1, is then set via the stroke level adjusting device 18. Subsequently, sewing machine 2 of sewing system 1 is operated with the further stroke level HN1 and the stroke amplitude HA along a further sewing path. This operating procedure was described above using the Fig. 14 already explained.

[0073] In another operating procedure of sewing machine 2 of sewing system 1, a first stroke level HN1 is initially set via the stroke level adjusting device 18. Furthermore, a first stroke amplitude HA = Y is set via the stroke amplitude adjusting device 17. Sewing machine 2 is then operated with the first stroke level HN1 and the first stroke amplitude Y along a first sewing path. A further stroke level HN2 is then set via the stroke level adjusting device 18, which differs from the first stroke level HN1. Additionally, a further stroke amplitude HA = X is set via the stroke amplitude adjusting device 17, which differs from the first stroke amplitude HA = Y. The setting of the further stroke level HN2 and / or the extended stroke amplitude X is such that a stroke position "B" and "F" of a lower dead center of the fabric hold-down foot 13 remains constant within specified tolerance limits, independent of the set stroke amplitudes y and x.For this tolerance limit, using the z-coordinates zB, zF of the bottom dead center at positions "B" and "F", the following applies: (zB - zF)2 / (zB + zF)2 ≤ 10%. The tolerance limit can also take other values, in particular smaller values ​​than 10%, as already explained above in connection with the tolerance limit for the stroke level difference and the stroke amplitude difference. Sewing machine 2 of sewing system 1 is then operated with the additional stroke level HN2 and the additional stroke amplitude X along a further sewing path. This further application was also described above in connection with the... Fig. 17 already explained.

[0074] In another operating procedure of sewing machine 2 of sewing system 1, at least one stroke level HN is first specified via the stroke level adjusting device 18. In addition, at least one stroke amplitude HA is specified via the stroke amplitude adjusting device 17. Sewing machine 2 is operated with the specified stroke level HN and the specified stroke amplitude HA along at least one sewing path. Subsequently, the fabric hold-down foot 13 is lifted by means of the stroke level adjusting device 18 after operation to remove the fabric.

[0075] Within the scope of the applications described above, the lifting level adjustment device 18 can also be used to set the preload force of the compression spring 38, so that, in particular, a predetermined immersion depth of the sewing material holding foot 13 into the sewing material is achieved in the area of ​​the bottom dead center. This was demonstrated above, especially in connection with position "F", using the Fig. 17 already explained.

Claims

1. Sewing machine (2) - with a stitch plate (3a), - with a fabric hold-down foot (13) designed to perform a lifting movement to hold fabric (NG) down on the stitch plate (3a) during a sewing operation, - with a driven stroke amplitude adjusting device (17) for setting a stroke amplitude (HA = X, HA = Y) of the lifting movement of the fabric hold-down foot (13) between an upper dead center (A, C, E) and a lower dead center (B, D, F), - with a driven stroke level adjusting device (18) for setting a stroke level (HN) of the lifting movement of the fabric hold-down foot (13) relative to the stitch plate (3a), - with a control / regulating device (11) which is in signal communication with the stroke amplitude adjusting device (17) and with the stroke level adjusting device (18).

2. Sewing machine according to claim 1, characterized by a sensor (43) for detecting the actual stroke position of the sewing material hold-down foot (13) above the stitch plate (3a).

3. Sewing machine according to claim 1 or 2, characterized by a bearing for the sewing material holding foot (13), wherein the sewing material holding foot (13) is pre-tensioned in a bearing position via a spring (38) of the bearing.

4. Sewing machine according to claim 3, characterized by an adjustment device for specifying a spring preload force (38).

5. Sewing system (1) with a sewing machine (2) according to one of claims 1 to 4.

6. Method for operating a sewing machine according to one of claims 1 to 4 comprising the following steps: - specifying a stroke amplitude (HA) via the stroke amplitude adjusting device (17), - specifying a target stroke level (HN) Soll ), - Determining an actual lift level (HN Ist ), which results at the specified stroke amplitude (HA), - Adjusting the stroke level control device (18) until there is a difference between the actual stroke level (HN) Ist ) and the target stroke level (HN Soll ) within a specified tolerance limit.

7. Method for operating a sewing machine according to one of claims 1 to 4 comprising the following steps: - specifying a stroke level (HN) via the stroke level adjusting device (18), - specifying a target stroke amplitude (HA) Soll ), - Determining an actual stroke amplitude (HA Ist ), which results at the specified stroke level (HN), - Adjusting the stroke amplitude control device (17) until there is a difference between the actual stroke amplitude (HA) Ist ) and the target stroke amplitude (HA Soll ) within a specified tolerance limit.

8. Method for operating a sewing machine according to any one of claims 1 to 4 comprising the following steps: - specifying a first stroke level (HN1) via the stroke level adjusting device (18), - specifying a stroke amplitude (HA) via the stroke amplitude adjusting device (17), - operating the sewing machine (2) with the first stroke level (HN1) and the stroke amplitude (HA) along a first sewing path, - specifying a further stroke level (HN2) via the stroke level adjusting device (18), which differs from the first stroke level (HN1), - operating the sewing machine (2) with the further stroke level (HN2) and the stroke amplitude (HA) along a further sewing path.

9. Method for operating a sewing machine (2) according to any one of claims 1 to 4 comprising the following steps: - specifying a first stroke level (HN1) via the stroke level adjusting device (18), - specifying a first stroke amplitude (HA = Y) via the stroke amplitude adjusting device (17), - operating the sewing machine (2) with the first stroke level (HN1) and the first stroke amplitude (Y) along a first sewing path, - specifying a further stroke level (HN2) via the stroke level adjusting device (18), which differs from the first stroke level (HN1), - specifying a further stroke amplitude (HA = X) via the stroke amplitude adjusting device (17), which differs from the first stroke amplitude (Y), wherein the specification of the further stroke level (HN2) and / or the further stroke amplitude (X) is such that a stroke position of a lower dead center (B, F) of the fabric hold-down foot (13) is independent of the specified stroke amplitude (Y, X) remains constant within specified tolerance limits,- Operating the sewing machine (2) with the additional stroke level (HN2) and the additional stroke amplitude (X) along an additional sewing path.

10. Method for operating a sewing machine (2) according to one of claims 1 to 4 comprising the following steps: - specifying at least one stroke level (HN) via the stroke level adjusting device (18), - specifying at least one stroke amplitude (HA) via the stroke amplitude adjusting device (17), - operating the sewing machine (2) with the at least one stroke level (HN) and the at least one stroke amplitude (HA) along at least one sewing path, - lifting the fabric holding foot (13) by means of the stroke level adjusting device (18) after operation to remove fabric.

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