EP3556923A1 - Sewing machine - Google Patents

Abstract

A sewing machine has at least one presser foot for holding down sewing material during sewing. A pressure-adjusting device serves to specify a hold-down pressure, which the presser foot exerts on the sewing material when held down. To ventilate the presser foot is a fan device. The sewing machine has a common drive (12) for the pressure adjusting device and for the fan device. On a drive shaft of the common drive (12) a cam disc (13) is rotatably arranged, which cooperates with a cam lever (14) on the one hand for releasing the presser foot and on the other hand for driving the contact pressure adjusting device. The cam lever (14) cooperates with the cam disc (13) via a total Verschwenkweg. The cam lever (14) has two separate scanning body (22, 24), which cooperate with the cam (13) in each case in a portion of the total Verschwenkweges the cam disc (13). This results in increased reliability of the common drive for the pressure-adjusting device on the one hand and the fan device on the other.

Description

The present patent application takes the priority of the German patent application DE 10 2018 206 088.6 claim, the contents of which are incorporated herein by reference.

The invention relates to a sewing machine.

Such a sewing machine is known from the EP 2 975 169 B1 and the EP 2 105 526 B1 , The CN 202658372 U discloses a presser foot fan assembly comprising a stepper motor that interacts with other components of the fan assembly via a cam. The JP 07-231 991 A discloses a sewing machine with a presser foot drive. The EP 2 351 881 A1 discloses a multi-head embroidery machine having a gear for a presser foot of a presser unit. The US 2018/0016722 A1 discloses a sewing machine. From the DE-PS 292 059 a pusher foot lifting device for sewing machines is known.

Object of the present invention is to increase the reliability of a common drive for a pressure-adjusting device on the one hand and a fan device on the other.

This object is achieved by a sewing machine with the features specified in claim 1.

One from the EP 2 975 169 B1 basically known common drive for the pressure-adjusting device on the one hand and for the fan device on the other hand leads to a significant simplification of the sewing machine design. A drive can be saved. Also associated control components can be saved. The common drive can be designed so that this does not affect the fundamentally independent functions "foot ventilation" and "pressure adjustment" leads. By saving the drive, the overall construction is cheaper and more compact. By the execution of the cam lever with two separate arranged Abtastkörpern that cooperate with each in at least a portion of a total Verschwenkweges the cam can be ensured that a motion transmission between the cam and the cam lever is done safely. Unfavorable power transmission directions in the power transmission between the cam and the respective Abtastkörper the cam lever can be avoided. An undefined release of the cam lever of the cam can be prevented thereby. The sensing bodies may be separate components integral with the other cam lever. Alternatively, the sensing bodies may be portions of the cam lever itself. The cam can have exactly one curve, with which both Abtastkörper cooperate. In this case, the two Abtastkörper cooperate with different curve sections of the same curve of the cam.

A simultaneous interaction of the scanning of the cam lever with the cam according to claim 2 can ensure a particularly secure adhesion between the cam lever and the cam. In the section of the overall pivoting path of the cam in which the two scanning bodies interact simultaneously with the cam disk, "foot lifting" can take place in a drive region. There it can then be prevented that the cam lever undesirably loses its frictional connection with the cam, for example, when placing thick material, and thus an undefined state of the common drive can be avoided.

An embodiment of a cam of the cam according to claim 3 leads to a particularly secure frictional connection between the cam lever and the cam in a portion of a total Verschwenkweges the cam. The two scanning body can engage around a portion of the convex curve portion in such a configuration. In this way, a form-fitting contribution of a power transmission connection between the cam lever and the cam can be generated. The two Abtastkörper can cooperate with the convex curve portion in the manner of two intermeshing gear sections.

An embodiment of the Abtastkörper according to claim 4 is inexpensive and reliable.

An interaction of cam and cam lever according to claim 5 leads to an advantageous decoupling of mechanical transmission elements for foot ventilation on the one hand and for the Andruckeinstellung on the other.

A specification of a cam lever position "minimum hold-down pressure" according to claim 6 allows a defined specification of the minimum hold-down pressure.

A fan shaft according to claim 7 makes it possible to arrange the drive away from the sewing foot. Seen in a plane perpendicular to the fan shaft, the sample can be arranged between the fan shaft and the drive shaft of the common drive. Such an arrangement can simplify a curve design of the cam.

A stepping motor according to claim 8 allows in particular a gradation of the predetermined hold-down pressure. This can be used to adapt to the respective sewing environment. Even a fine gradation of a fan height is advantageous. When sewing thick fabrics, a high fan height can be preset. When sewing thinner fabrics, a lower fan height can be preset.

An arrangement of the drive may be such that a drive shaft of the drive, in particular of the stepper motor, either towards the sewing foot of the sewing machine or may alternatively be such that the drive shaft is oriented away from the sewing foot in the direction. Depending on the installation space requirements for the drive in the transverse or longitudinal direction, for example, a sewing machine arm, this can be realized in a critical dimension compact drive.

An adjustment range according to claim 9 enables a fine specification of the hold-down pressure without too great demands on a positioning accuracy or step division for the drive. Such a large adjustment range allows a low-torque drive with a simultaneous low slope of the curve of the cam.

It was also recognized that a cam lever with two separate arranged Abtastkörpern and a correspondingly shaped cam can also be used as a conversion assembly. In this way, an existing drive with a cam lever with exactly one sample can be replaced by a drive according to the invention with two Abtastkörpern, resulting in a correspondingly secure power transmission between the cam lever and the cam.

Fig. 1

perspektivisch eine Nähmaschine in einer Vorderansicht;

Fig. 2

ebenfalls perspektivisch eine Baugruppe der Nähmaschine nach Fig. 1 mit einer Andruck-Einstelleinrichtung zur Vorgabe eines Niederhaltedrucks, den ein Nähfuß beim Niederhalten auf Nähgut ausübt, mit einer Lüftereinrichtung zum Lüften des Nähfußes und mit einem gemeinsamen Antrieb für diese Einrichtungen;

Fig. 3

eine Aufsicht auf die Baugruppe nach Fig. 2, gesehen aus Blickrichtung III, in einer Stellung "Minimaler Niederhaltedruck";

Fig. 4

die Ansicht nach Fig. 3, wobei ein Abschnitt einer Grundplatte eines Kurvenhebels des Antriebs weggelassen ist;

Fig. 5

in einer zu Fig. 3 ähnlichen Darstellung die Baugruppe in einer Position "Maximale Fußlüftung";

Fig. 6

die Baugruppe nach Fig. 5, wiederum mit abschnittsweise weggelassener Grundplatte des Kurvenhebels;

Fig. 7

in einer zu Fig. 3 ähnlichen Darstellung die Baugruppe in einer Position "Mittlere Fußlüftungshöhe";

Fig. 8

die Baugruppe nach Fig. 7, wiederum mit abschnittsweise weggelassener Grundplatte des Kurvenhebels;

Fig. 9

in einer zu Fig. 3 ähnlichen Darstellung die Baugruppe in einer Position "Maximaler Niederhaltedruck";

Fig. 10

die Baugruppe nach Fig. 9, wiederum mit abschnittsweise weggelassener Grundplatte des Kurvenhebels;

Fig. 11

in einer zu Fig. 2 ähnlichen Darstellung eine weitere Ausführung einer Baugruppe mit einer Andruck-Einstelleinrichtung zur Vorgabe eines Niederhaltedrucks, den ein Nähfuß beim Niederhalten auf Nähgut ausübt, mit einer Lüftereinrichtung zum Lüften des Nähfußes und mit einem gemeinsamen Antrieb für diese Einrichtungen, wobei die Baugruppe nach Fig. 11 anstelle der Baugruppe nach Fig. 2 zum Einsatz kommen kann;

Fig. 12

eine Aufsicht auf die Baugruppe nach Fig. 11, gesehen aus Blickrichtung XII, in einer Stellung "Minimaler Niederhaltedruck", wobei ähnlich wie in der Fig. 4 ein Abschnitt einer Grundplatte eines Kurvenhebels des Antriebs weggelassen ist;

Fig. 13

in einer zu Fig. 12 ähnlichen Darstellung die Baugruppe in einer Position "Maximale Fußlüftung";

Fig. 14

in einer zu Fig. 12 ähnlichen Ansicht die Baugruppe in der Position "Mittlere Fußlüftungshöhe";

Fig. 15

in einer zu Fig. 12 ähnlichen Ansicht die Baugruppe in der Position "Maximaler Niederhaltedruck";

Fig. 16

perspektivisch eine Kurvenscheibe der Baugruppe nach Fig. 11; und

Fig. 17

perspektivisch den Kurvenhebel der Baugruppe nach Fig. 11.

An embodiment of the invention will be explained in more detail with reference to the drawing. In this show:

Fig. 1

in perspective, a sewing machine in a front view;

Fig. 2

also in perspective an assembly of the sewing machine Fig. 1 with a pressure-adjusting device for specifying a hold-down pressure, which exerts a presser foot when holding down on sewing material, with a fan device for releasing the presser foot and with a common drive for these devices;

Fig. 3

a view of the assembly after Fig. 2 , seen from viewing direction III, in a position "minimal hold-down pressure";

Fig. 4

the view after Fig. 3 wherein a portion of a base plate of a cam lever of the drive is omitted;

Fig. 5

in one too Fig. 3 similar representation of the assembly in a position "maximum foot lift";

Fig. 6

the module after Fig. 5 again with partially omitted base plate of the cam lever;

Fig. 7

in one too Fig. 3 similar representation of the assembly in a position "average Fußlüftungshöhe";

Fig. 8

the module after Fig. 7 again with partially omitted base plate of the cam lever;

Fig. 9

in one too Fig. 3 similar representation of the assembly in a position "maximum hold pressure";

Fig. 10

the module after Fig. 9 again with partially omitted base plate of the cam lever;

Fig. 11

in one too Fig. 2 Similarly, another embodiment of an assembly with a pressure-adjusting device for specifying a hold-down pressure exerted by a presser foot while holding down on sewing material, with a fan device for releasing the presser foot and with a common drive for these devices, the assembly according to Fig. 11 instead of the module Fig. 2 can be used;

Fig. 12

a view of the assembly after Fig. 11 , seen from view XII, in a position "minimal hold-down pressure", being similar to the Fig. 4 a portion of a base plate of a cam lever of the drive is omitted;

Fig. 13

in one too Fig. 12 similar representation of the assembly in a position "maximum foot lift";

Fig. 14

in one too Fig. 12 similar view, the assembly in the position "average Fußlüftungshöhe";

Fig. 15

in one too Fig. 12 similar view of the assembly in the position "maximum hold pressure";

Fig. 16

perspective a cam of the assembly after Fig. 11 ; and

Fig. 17

perspective view of the cam lever of the module Fig. 11 ,

A sewing machine 1 has a stand 2, an arm 3 and a head 4, so that together with a housing base plate 5, a total C-shaped structure of the sewing machine 1 results. A driven via a main drive not shown arm shaft drives a needle bar 6 with a sewing needle 7 fixed thereto up and down. The needle 7 passes through a stitch hole in a throat plate, which forms part of a support plate 8, which in turn represents the top of the housing base plate 5 of the sewing machine 1.

The sewing machine 1 has a presser foot 9 for holding down sewing material during sewing, which is also referred to as a presser foot. The presser foot 9 is mounted on a presser foot rod 10.

To specify a hold-down pressure exerted by the presser foot 9 while holding down on the sewing material and for releasing the presser foot is an assembly that in the Fig. 2 generally designated by the reference numeral 11.

The assembly 11 comprises a pressure-adjusting device for setting the hold-down pressure, a fan device for releasing the presser foot and a common drive for these two devices. The pressure adjustment device and the fan device will be explained in detail below. The common drive is designed as a stepper motor 12. A drive shaft 12a (see e.g. Fig. 3 ) of the stepping motor 12 is oriented away from the presser foot rod 10, so that a free end of the drive shaft 12a, ie in the opposite direction to the viewing direction III of the view of Fig. 3 pointing to the viewer.

The drive shaft of the stepping motor 12 is rotatably connected to a cam 13. The cam 13 cooperates with a cam lever 14 on the one hand for releasing the presser foot 9 and on the other hand for driving the pressure-adjusting device. The cam lever 14 cooperates with the cam 13 via a total Verschwenkweg the cam 13. The cam lever 14 is in turn rotatably connected to a fan shaft 15 which extends parallel to the arm shaft in the arm 3 of the sewing machine 1 and is rotatably mounted on a frame of the sewing machine 1. Rotatably connected to the fan shaft 15 is a fan lever 16 which cooperates with a presser foot driver 17 which is fixedly connected to the presser foot rod 10. The fan shaft 15 serves to transmit a shifting force from the cam lever 14 to the presser foot 9.

At the opposite end of the cam lever 14, the fan shaft 15 is eccentrically connected to a fan shaft longitudinal axis hinged to a pull rod 18 which is used for pressing in the Fig. 2 not shown presser foot 9 presses from above via a sleeve 19 against the compression spring 21.

Between a further frame-fixed sleeve 20, which is penetrated by the presser foot rod 10, and the presser foot driver 17 is a Compression spring 21 is arranged, which surrounds the presser foot 10 in sections helically.

The Fig. 2 to 4 show the assembly 11 in the drive position "minimum hold-down pressure". In comparison to Fig. 3 is in the Fig. 4 omitted a portion of a base plate of the cam lever 14 to further illustrate its interaction with the cam lever 14.

A first sensing pin 22 of the cam lever 14, which is a first sensing body of the cam lever 14, is engaged in a Kurvenausnehmung 23 of the cam 13, which defines the cam lever position "minimum hold-down pressure". In the associated pivot position of the fan shaft 15, the pull rod 18 exerts a minimum compressive force on the sleeve 19. The compression spring 21 is minimally biased. The force of the compression spring 21 is transmitted via the presser foot driver 17 to the presser foot rod 10, so that a corresponding, minimum hold-down pressure of the presser foot 9 during operation of the sewing machine 1 results. In this drive position "minimum hold-down pressure" of the fan lever 16 is disengaged from the presser foot driver 17th

The FIGS. 5 and 6 show the drive position "Maximum foot lift". To reach this position, move from the position "Minimum Hold Down" to Fig. 2 to 4 the stepper motor 12 is operated so that its drive shaft by about 80 ° counterclockwise from the perspective of Fig. 3 to 6 is twisted. A second sensing pin 24 of the cam lever 14, which is a second scanning body of the cam lever 14, has thereby run clockwise on the cam 13 to a curve portion 25 in which the cam 13 in turn acts as a lever on the second sensing pin 24. In this position, the fan lever 16 presses the Presser-foot driver 17 against the pressure force of the compression spring 21 in the direction of the frame-fixed sleeve 20 upwards and takes the presser foot 10 for releasing the presser foot 9 with.

The two sensing pins 22, 24 of the cam lever 14 are arranged separately from each other. The two sensing pins 22, 24 are fixedly connected to the cam lever 14.

The two sensing pins 22, 24 are arranged so that they cooperate with the cam 13 in each case at least in a portion of the total Verschwenkweges the cam 13. In the swing path range of the cam lever position "minimum hold-down pressure" (see the 3 and 4 ), the first sensing pin 22 cooperates with the cam 13 in the region of the cam recess 23. In the further cam lever position "maximum foot lift" (see the FIGS. 5 and 6 ), the second sensing pin 24 cooperates with the curve portion 25.

The cam recess 23 on the one hand and the cam portion 25 on the other hand represent two concave cam portions of the cam disc 13. Between these two concave cam portions 23, 25, the cam disc 13 has a convex curve portion 26 which is formed in the shape of a nose of the curved line of the cam disc 13.

The FIGS. 7 and 8 show the drive position "average lift height" between the two drive positions described above "minimum hold pressure" and "maximum lift". In this drive position "average foot ventilation height", the convex curve section 26 engages between the two sensing pins 22, 24 and thus secures the engagement of the cam lever 14 on the cam disk via a positive engagement contribution 13. Regardless of a force that is transmitted to the cam lever 14, for example via the sewing material, the presser foot 9 and the presser foot 10, its contact position on the cam 13 is secured.

In a portion of the range between the drive position "minimum hold-down pressure" (see, for example, FIGS 3 and 4 ) and the drive position "maximum foot lift" (cf. FIGS. 5 and 6 ), the two sensing pins 22, 24 together with the cam 13 at the same time, so are at the cam 13 at the same time.

FIGS. 9 and 10 show the drive position "maximum hold-down pressure". In comparison to Fig. 3 In this case, the stepper motor 12 is switched so that its drive shaft, the cam 13 in comparison to the position after Fig. 3 has pivoted about 320 ° clockwise. The first sensing pin 22 of the cam lever 14 runs on the cam 13 up to a curve area 27 "maximum hold-down pressure". The second sensing pin 24 is in this position "maximum hold-down pressure" out of engagement with the cam 13th

In this position, the pull rod 18 is displaced downwardly due to its eccentric connection with the fan shaft 15 and accordingly exerts a tensile force on the sleeve 19, which is accordingly pressed to a maximum of the pull rod 18 down. As a result, the compression spring 21 is biased to a maximum. The result is the maximum hold-down pressure that the presser foot rod 10 and thus the presser foot 9 exerts on the sewing material during operation of the sewing machine 1. In the position "maximum hold-down pressure" the fan lever 16 is again out of engagement with the presser foot cam 17. The cam lever 14 is thereby compared to the drive position "Minimum hold-down pressure" after Fig. 3 in the drive position "maximum hold-down pressure" after the FIGS. 9 and 10 pivoted about 60 ° counterclockwise.

The cam 13 and the cam lever 14 thus act together so that in a rotational direction of a rotation of the cam airing of the presser foot 9 takes place and in an opposite direction of rotation, a drive of the pressure-adjusting device.

An adjustment range of the drive shaft of the stepping motor 12 between the cam lever position "minimum hold-down pressure" (see. Fig. 3 ) and the cam lever position "maximum hold-down pressure" (cf. Fig. 9 ) is more than 180 °.

The stepper motor 12 can be actuated, for example, via a pedal of the sewing machine 1 by an operator for foot lifting.

To specify the hold-down pressure, a default can be done via a control device 26, which in the Fig. 1 is shown schematically. The controller 26 is in signal communication with the stepper motor 12 in a manner not shown.

Based on Fig. 11 to 15 a further embodiment of an assembly 28 for specifying a hold-down pressure and for releasing a presser foot is explained below, which can be used instead of the above-described assembly 11 in the sewing machine 1. Components and functions that correspond to those already discussed above with reference to the assembly 11 bear the same reference numerals and will not be discussed again in detail.

In the assembly 28, the stepper motor 12 is arranged so that its drive shaft in the direction of the presser foot rod 10, so in turn in the opposite direction of the viewing direction XII to the viewer of Fig. 12 too, is oriented. The orientation of the drive shaft of the stepping motor 12 with respect to the pusher rod 10 is thus opposite to the assembly 11 in the assembly 28.

The Fig. 11 and 12 show the drive position "minimum hold-down pressure". Here again, the first sensing pin 22 of the cam lever 14 comes into contact with the cam 13 in the Kurvenausnehmung 23rd

The Fig. 13 shows the drive position "Maximum foot lift". The stepper motor 12 of the assembly 28 is operated so that the fixedly connected to the drive shaft cam 13 by approximately 180 ° counterclockwise from the perspective of FIGS. 12 and 13 , starting from the drive position "minimum hold-down pressure" Fig. 12 , is twisted. In this drive position "maximum foot lift", the second sensing pin 24 dips into a further concave curve region 25 of the cam disc 13, which corresponds to the curve region 25 of the assembly 11. By this pivoting of the cam plate 13, the cam lever 14, starting from the drive position "minimum foot pressure" is pivoted by approximately 45 ° counterclockwise. In this position, in turn, the fan lever 16 presses the presser foot driver 17 against the pressure force of the compression spring 21 in the direction of the frame-fixed sleeve 20 upwards, as above in connection with the FIGS. 5 and 6 already explained for the assembly 11.

The Fig. 14 shows the drive position "middle foot lift", so an intermediate drive position between the positions "minimum foot pressure" after Fig. 12 and "Maximum Foot Ventilation" after Fig. 13 , In this drive position "average foot lifting height", the two drive pins 22, 24 simultaneously with the convex curve portion 26 of the cam 13 cooperate.

Between the two concave curve portions 23 and 25 of the cam 13 of the assembly 28 in turn is a convex curve portion 26 which is formed voluminous in the cam 13 of the assembly 28 as in the cam 13 of the assembly 11th

Fig. 15 again shows the drive position "maximum hold-down pressure". Compared to the drive position after Fig. 12 the cam plate 13 of the assembly 28 is pivoted about 210 ° clockwise, which in turn takes place via the stepper motor 12. The first sensing pin 22 in this case runs on the cam 13 of the assembly 28 to the curve portion 27 "maximum hold-down pressure". The cam lever 14 is in this drive position "maximum hold-down pressure" compared to the drive position "minimum foot pressure" in the view of the Fig. 12 and 15 pivoted about 90 ° clockwise.

In this position, the pull rod 18 is displaced downwardly due to its eccentric connection with the fan shaft 15 and accordingly exerts a tensile force on the sleeve 19, which is accordingly pressed to a maximum of the pull rod 18 down. As a result, the compression spring 21 is biased to a maximum. The result is the maximum hold-down pressure that the presser foot rod 10 and thus the presser foot 9 exerts on the sewing material during operation of the sewing machine 1. In the position "maximum hold pressure" is the fan lever 16 in turn disengaged from the presser foot cam 17. The second sensing pin 24 is in this position "maximum hold-down pressure" out of engagement with the cam 13th

In the "maximum hold-down pressure" position, the curve region 27 also serves as a stop for referencing the stepping motor 12. For this purpose, the stepper motor 12 moves into the "maximum hold-down pressure" drive position until the first sensing pin 22 abuts the stop formed by the curve region 27. The curve region 27 designed as a stop does not require the use of further referencing sensors, which may otherwise be formed by a light barrier or an inductive switch.

In the assembly 11, for example, in the drive position "minimum hold-down pressure" (see Fig. 3 to 4 ), the two sensing pins 22 and 24 in the supervision of the 3 and 4 Seen between the fan shaft 15 and the drive shaft 12 a of the stepping motor 12 is arranged. In the assembly 28, for example, in the drive position "maximum foot lift" (see. Fig. 13 ) the two sensing pins 22, 24, viewed in the plan to Fig. 13 , approximately at the height of the drive shaft 12 a of the stepping motor 12.

The FIGS. 16 and 17 show in perspective the cam 13 ( Fig. 16 ) and the cam lever ( Fig. 17 ) of the assembly 28.

The cam 13 and the cam lever 14 of the assembly 28 can be used as a conversion assembly for retooling an existing drive assembly, the fan lever of this existing drive assembly originally has exactly one sensing pin.

Claims (10)

Sewing machine (1) with at least one presser foot (9) for holding down sewing material during sewing, with a pressure-adjusting device for specifying a hold-down pressure, which the presser foot 9 exerts on the sewing material when held down, - with a ventilation device for lifting the presser foot, - With a common drive (12) for the pressure-adjusting device and for the fan device, - Wherein on a drive shaft of the common drive (12) a cam (13) is rotatably arranged, which cooperates with a cam lever (14) on the one hand for releasing the presser foot (9) and on the other hand to drive the Andruck-adjusting device, wherein the cam lever (14 ) is designed such that it cooperates with the cam disc (13) over a total Verschwenkweg of the cam disc (13), - Wherein the cam lever (14) has two separately arranged Abtastkörper (22, 24) which are arranged so that they cooperate with the cam (13) in each case at least in a portion of the total Verschwenkweges the cam disc (13). Sewing machine according to claim 1, characterized in that the two scanning bodies (22, 24) are arranged so that they cooperate with the cam disc (13) at least in a portion of the total Verschwenkweges of the cam disc (13). Sewing machine according to claim 2, characterized in that a cam curve (13) has a convex curve section (26) adjoined by two concave curve sections (23, 25) on either side of the convex curve section (26), the convex curve section (26). 26) is the one via which a simultaneous interaction of the two Abtastkörper (22, 24) with the cam (13). Sewing machine according to one of Claims 1 to 3, characterized in that the two scanning bodies (22, 24) are designed as sensing pins fixedly connected to the cam lever (14). Sewing machine according to one of claims 1 to 4, characterized in that the cam disc (13) and the cam lever (14) cooperate so that in a rotational direction of a rotation of the cam disc (13) airing of the presser foot (9) takes place and in an opposite Direction of rotation of the cam (13) a drive of the pressure-adjusting. Sewing machine according to one of claims 1 to 5, characterized in that the cam disc (13) has a Kurvenausnehmung (23) for specifying a cam lever position "minimum hold-down pressure". Sewing machine according to one of claims 1 to 6, characterized by a fan shaft (15) for transmitting a Umstellkraft from the cam lever (14) on the presser foot (9). Sewing machine according to one of claims 1 to 7, characterized in that the drive (12) is formed by a stepper motor. Sewing machine according to one of claims 1 to 8, characterized by an adjustment range of the drive shaft of the common drive (12) between a cam lever position "minimum hold-down pressure" and a cam lever position "maximum hold-down pressure" of more than 180 °. Conversion assembly (13, 14) for use in a sewing machine according to one of claims 1 to 9, - With a cam (13), arranged on the drive shaft (12 a) of the common drive (12), - With a cam lever (14) which cooperates with the cam disc (13) on the one hand for releasing the presser foot (9) and on the other hand for driving the pressure-adjusting device, - Wherein the cam lever (14) is designed such that it cooperates with the cam disc (13) over a total Verschwenkweg of the cam disc (13), - Wherein the cam lever (14) has two separately arranged Abtastkörper (22, 24) which are arranged so that they cooperate with the cam (13) in each case at least in a portion of the total Verschwenkweges the cam disc (13).

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