WO2013068126A2

WO2013068126A2 - Sewing machine having a holding down clamp for material to be sewed

Info

Publication number: WO2013068126A2
Application number: PCT/EP2012/004686
Authority: WO
Inventors: Karl-Ludwig Manuel
Original assignee: Pfaff Industriesysteme Und Maschinen Ag
Priority date: 2011-11-10
Filing date: 2012-11-10
Publication date: 2013-05-16
Also published as: DE102011118083A1; WO2013068126A3

Abstract

The invention aims to further develop a sewing machine having a holding down device for holding down material to be sewed while a stitch is formed in said material by means of at least one thread-guiding stitch forming means, such as a needle (6) that can be attached to a needle bar (5), wherein the holding down device, in order to carry out an oscillating lift motion of a holding down clamp (12), is cooperatively connected to a drive means, in such a manner that, more reliably than in the past, adherence of the material to be sewed to the needle can be prevented, even if different materials are used. According to the invention, a holding down device is proposed, which is provided with a drive means that is separate from the at least one stitch forming means, for carrying out the movement of the holding down clamp (12) during the sewing process.

Description

Sewing machine with a hold-down for the sewing material

The invention relates to a sewing machine with a hold-down device for holding down sewing material during a stitch formation in the sewing material by at least one thread guiding stitch forming means, wherein the hold-down device for effecting an oscillating stroke movement of a hold-down device is operatively connected to a drive means. Sewing machines may be provided with a hold-down device comprising a hold-down, which is at least substantially oscillated up and down in response to movement of the needle as one of the stitching means of the sewing machine. The hold-down device, also referred to as a hump, hereby rests temporarily against the respective sewing material and has the task of preventing the needle from picking up the sewing material, in particular during the upward movement of the needle upwards, during which the needle moves out of the sewing material.

The hold-down device is in this case operatively connected to a drive, by which the hops can be placed in the oscillating up and down movement. Usually, the drive movement is tapped by the motor-driven main shaft of the sewing machine, with which also the oscillating movement of the needle is generated. Since both the needle and the hold-down are thus driven by the same drive shaft, the movements of the needle and the hold-down are synchronized with each other. By means of a transmission in this case a phase shift of the two oscillating movements of the needle and holddown can be specified, in particular to be able to hold down the material even if the needle has exceeded the bottom dead center in its movement and thus begins to move out of the sewing material. Since different material can behave differently with respect to a sticking to the needle, solutions have already become known in which the transmission is adjustable in order to be able to adjust a change in the phase shift between the movements of the needle and the hoppers. Likewise, a solution is known

BESTÄTSGI GS OPIE become in which by means of a separate motor, a presetting of the size of the hub can be made and then the thus preset stroke movement in turn is generated by means of the movement of the driven by another electric motor main shaft with which the stitching means are driven in the first place.

However, it has been shown that with these prior art solutions by far not be able to satisfactorily hold down the workpiece in all Nähsituationen the down material satisfying. Constellations occur again and again in which the needle takes along sewing material during its movement. Especially at high speeds have repeatedly problems of synchronization between the movement of the blank holder and the needle movement result, leading to unsatisfactory workflows. The invention is therefore the object of developing a hold-down device such that more reliable than before, even with different material sewing a same can be avoided on the needle.

This object is achieved with a sewing machine of the type mentioned in the present invention that the hold-down device with a, with respect to the at least one stitch forming means and its drive, separate, that is separate and preferably independent, drive means for carrying out the movement of the blank holder during the sewing process is provided. The object is also achieved by the subject matter of claim 12, which relates to the same inventive aspect as claim 1.

With the solution according to the invention it is now possible for the first time to determine and execute the movement sequence of the hold-down device independently of the movement of the at least one stitch-forming means, in particular a needle of the sewing machine. This opens up completely new possibilities for adjusting the time and duration of hold-down by the hold-down. According to the invention required for this drive movements by the separately provided by the drive means of the stitch forming means, so in addition, provided drive means of the hold-down device. Different movements and different phase shifts of the movements of the blank holder with respect to the stitch forming means can be achieved by varying the driving movement of the separate drive means, which can be unaffected and thus independent of the drive movement of the stitch forming means. For this purpose, the additionally provided for the retaining means drive means can be controlled accordingly by a control of the sewing machine. In a preferred embodiment according to the invention, the drive means provided in addition to the drive of the at least one stitch forming means may be a motor, in particular an electric motor, such as an electric stepping motor. With a stepper motor can be in a particularly simple manner, a precise variation of the drive movement of the blank holder and simultaneously produce a precise, mechanically uncoupled synchronization with stitch forming agent, even at high speeds.

It has proved to be advantageous if the movement of the hold-down is infinitely adjustable, which can be particularly precisely tune the hold-down movement on the movement of stitch forming agent. If a stepper motor is used as the drive means, then "steplessly" an at least approximately stepless adjustability can be understood, which results from the fact that the step size of the electric motor is not considered to limit the adjustability.

It has been found to be particularly useful if, by varying the motor drive movement of the separately provided drive means, in particular an electric motor, the stroke of the hold-down can be varied. As a result, the size of the stroke and / or the position of at least one of the two directions of movement reversal of the oscillating movement of the blank holder can be varied and adjusted. Preferably, both the upper and the lower dead center of the oscillating movement should be changeable and adjustable. The different sewing conditions that occur in practice can be particularly flexible if the size of the stroke and the positions of the movement direction reversal points are separated and adjustable and adjustable independently of each other. The ease of operation of the sewing machine can be further increased if, in preferred embodiments, motion parameters of the blank holder on a control he sewing machine can be set and stored. The controller can then according to the settings made to drive the separate drive means such that the drive means generates drive movements of the blank holder according to the settings.

In previous solutions, the thread cutting after completing a seam formation could prove difficult, since the downholder was the cutting process in the way. In order to move the hold-down so that the thread is accessible to the fabric, it was also necessary to move the needle due to the recent coupling between the hold-down and the needle bar. This is actually undesirable, but was accepted. With the present invention, it is now possible to decouple the movement of the blank holder at least temporarily from the movement of the needle, since a rigid mechanical coupling is not required according to the invention. This can be used in particular for thread cutting. In a preferred embodiment it can therefore be provided that the hold-down device is movable independently of the needle bar, at least during a phase in which no puncturing occurs, in particular by a driven movement of the separate drive means. During the stitch formation phase, a likewise adjustable coupling of the movement of the hold-down can then take place by means of control. This coupling can be canceled again, since it takes place only by a coordinated control of the drive of the at least one stitch formation means and the separate drive means of the blank holder by the control of the sewing machine. Further preferred embodiments of the invention will become apparent from the claims, the description and the drawings. The invention will be explained in more detail with reference to embodiments shown purely schematically in the figures, in which:

Fig. 1 shows a partially disassembled sewing machine in a perspective

Presentation;

Fig. 2 shows a hold-down device of the sewing machine of FIG. 1 in a

Position of a top dead center, shown in three different views;

Fig. 3 is a hold-down device of the sewing machine of FIG. 1 in a

Position of bottom dead center, shown in three different views;

4 is an exploded perspective view of the hold-down device of the sewing machine of FIG. 1.

In Fig. 1, a partially disassembled sewing machine 1 is shown, the housing 2 has a lower housing-shaped so-called base plate 3. from which a stand 4 extends substantially vertically upwards. At an upper end of the stator 4, an arm 8 connects, which extends approximately parallel to the base plate 3.

The sewing machine has a arm 8 mounted in the arm, not shown, which drives an oscillating up and down movable needle bar 5, to which at least one needle 6 for receiving a top thread, not shown, can be attached. In other embodiments, two needles 6 may also be attached to the needle bar 5. The oscillating up and down movement of the needle bar 5 is in this case aligned at least substantially perpendicular to the base plate 3. Needle 6 and needle bar 5 are part of stitching means of the sewing machine. In the base plate 3, a needle plate 7 is disposed immediately below the needle bar. Under the throat plate 7 is a not shown for clarity, known per se, arranged gripper device, which also belongs to the stitch forming means. A rotary movement of the gripper device is synchronized with the oscillating movement of the needle bar 5. An unillustrated lower thread is located on a spool which is arranged in a bobbin case carrier of the gripper device. The gripper device leads in a conventional manner the upper thread around the bobbin case carrier so that it can form a seam together with the lower thread. Usually, the needle bar 5 and the gripper device are driven by a common drive, namely a non-illustrated servo electric motor whose rotational drive motion is translated to the needle bar 5 and the gripper device in a certain ratio. Alternatively, it can also be provided that the gripper device and the needle bar 5 are each provided with separate motors whose movements are coordinated.

As is also apparent from Fig. 1, the needle 6 is in a sleeve-like portion 1 1 of a hold-down 12, which is also referred to as Hüpferfuß. The sleeve-like portion 1 1 has substantially the shape of a cylindrical sleeve with a constant inner diameter, whose longitudinal axis is aligned parallel to the longitudinal axis of the needle 6 and the needle bar 5. A passage opening of the sleeve-like portion 11 of the blank holder 12 is in this case dimensioned such that the needle can move freely within the passage opening and escape collision-free from a lower opening of the section 1 1. The sleeve-like section is used for later explained in more detail contact and hold down for sewing material. The hold-down 12 is connected to an obliquely upward attachment arm 13 of the blank holder 12. At its free end of the mounting arm 13 of the hold-down is a clamping sleeve 14, with which the hold-down 12 is attached to a rod 15. The rod 15 is arranged parallel and spaced therefrom. With its upper end, the rod 15 protrudes into the arm 8 of the housing 2. As can be seen in FIGS. 2-4, sits on the rod 15 in the region of its upper end a clamping sleeve 16 which can be mounted on the rod 15 in different positions with respect to the longitudinal axis of the rod 15. Disposed against the clamping sleeve 16 is a support element 17, which can likewise be fastened in different positions with respect to the longitudinal axis of the rod and has a contact surface for a helical spring 20. The coil spring 20 is located between the support member 17 and a bridge 21 which is loosely slid onto the upper end of the rod 15. The coil spring 20 can be compressed and relieved by a movement of the bridge 21 on the rod 15. The bridge 20 extends from the rod 15 in a direction which extends at least substantially transversely to the longitudinal axis of the rod 15, laterally away from the rod 15 and is secured at its other end to the lower end of a rack 22.

In the field of attachment of the rack 22 to the bridge 21, this is tooth-free. Above this section, the rack 22 is provided with a toothing, in which a toothing of a pinion 23 engages. The rotatably mounted on a motor shaft 24 of a stepper motor designed as an electric motor 25 arranged pinion 23 protrudes into a recess of a multi-part carrier 27, in which the rack 22 is mounted and arranged to be longitudinally displaceable. The carrier 27 in turn is attached to the housing 2 of the sewing machine 1. The stepping motor is intended to generate rotational movements in alternately different directions of rotation, in which the respective rotation angles can be predetermined in each direction of rotation. The stepper motor is separated from other components of the sewing machine to be driven and is exclusively intended to drive the hold-down 12 of the hold-down device. The drive movement of the stepping motor is not used in particular to drive stitch forming means.

As a separate motor for the hold-down device, a commercially available stepper motor can be used. The selection of the particular motor used should in particular be based on the size of the mass to be moved, the available time windows (speed of the sewing machine) and the maximum for the hold 12 to be generated hub. As a drive for the hold-down is in principle any engine or other drive means suitable that can perform reproducible positions in appropriate time and force. These include in a non-exhaustive list especially servomotors with conversion of the rotating in linear movements z. As gear / rack combinations, spindle or crank, linear drives, in particular linear motors or pneumatic drives. Suitable stepper motors are offered, inter alia, by the company Sanyo Denki Germany GmbH, Eschborn (Germany).

The hold-down device can also be provided with a detection means with which the instantaneous position of the hold-down 12 can be determined directly or indirectly. An indirect determination is made when positions of other parts of the hold-down device are determined as the hold 12 itself and is closed due to this position determination on the position of the blank holder 12. For this purpose, may be attached to one of the moving parts of the hold-down device, for example on the rack 22, a non-illustrated position sensor whose position is determined by a sensor 26. The signals of the sensor 26 can be fed to the control of the sewing machine 1. The pinion thus transmits the rotary drive movement of the stepping motor on the rack 22 and this on the bridge 21 on the spring 20. About the support member 17 and the clamping sleeve 6, the movement of the rack 22 then passes to the rod 15, which thereby depending on the respective The direction of rotation and the angle of rotation of the motor shaft 24 that has been traveled in the respective direction of rotation moves either downwards or downwards along a specific rectilinear path. The spring 20 should in this case preferably be designed so that the possible travel parallel to the longitudinal axis of the rod 15 corresponds to at least the maximum adjustable stroke of the blank holder. In this way it can be ensured that the movement of the blank holder 12 and its impact on non-compressible material does not lead to damage to the retaining device and possibly also the needle 6. On the other hand, if the hold-down 12 hits on compressible material during its downward movement, then the movement of the hold-down 12, the size or length of its stroke, but above all the speed of the arm or needle driving the needle, is adjusted by setting the bottom or top dead center. Main shaft (motor driven by the main motor of the sewing machine), set the duration during which the hold-down 12 presses from above on the respective fabric. By changing these values, it is thus also possible to set or change the duration of the contact of the hold-down 12 with the sewing material. The hold-down 12 should, in particular, during at least a portion of the duration during which the needle 6 is moved from its bottom dead center up and still in contact with the fabric in contact with the respective fabric in order to prevent the needle 6 pulls the fabric up by this movement. The hold-down 12 may preferably always press in the same rotational angle range of the arm shaft on the fabric. According to the invention, however, it is only possible by inputting corresponding values, in particular to the control of the sewing machine, to produce phase shifts for the duration and time of entry and exit of the contact of the hold-down 12 with the sewing material, based on the angle of rotation of the arm shaft. The adjustment of the stroke length, the position of the bottom dead center and / or the top dead center of the blank holder 12 can be done on an input device of the sewing machine not shown in detail, on which also other parameters of the sewing process are adjustable. The input of the intended values can be effected, for example, via keys or via a touch-sensitive screen. The set values are fed to the control of the sewing machine 1, which controls the needle bar 5 and the gripper in addition to the hold-down device. The controller thus controls the stepper motor of the hold-down device separated from other drives of the sewing machine such that, due to the set values for the stroke length and the positions of the movement reversal points, the stepper motor generates corresponding drive movements. The position values of the hold-down 12 determined by means of the detection means are also taken into account by the control for controlling the stepping motor of the hold-down device in order to tune the movement of the hold-down 12 to the movement of the needle 6. It can be provided that hold-down device 12 and needle move synchronously up and down or have a phase shift to each other. The size of the phase shift can also be adjustable, in particular steplessly between a smallest and a largest phase shift. The controller also agrees to a feed movement of a not shown in the throat plate 7 arranged per se known transport device on the movement of the blank holder 12, so that the transport of the material is not complicated by contact of the blank holder with the fabric or the fabric or the holddown thereby to be damaged.

Reference numeral list Sewing machine 21 Bridge Housing 22 Rack base plate 23 Pinion stand 24 Motor shaft Needle bar 25 Electric motor Needle 26 Sensor needle plate 27 Carrier Arm

sleeve-like section

Stripper plate

Mounting Arm

collet

pole

collet

supporting

coil spring

Claims

claims

1. A sewing machine with a hold-down device for holding down material during a stitch formation in the fabric by at least one thread guiding stitch forming means, such as a needle bar (5) attachable needle (6), wherein the hold-down means for performing an oscillating

Lifting movement of a hold-down (12) is operatively connected to a drive means;

characterized in that

the hold-down device with a, with respect to the at least one

Engraving means, separate drive means for carrying out the movement of the blank holder (12) is provided during the sewing operation.

2. Sewing machine according to claim 1, characterized in that the separate drive means for the hold-down device comprises an electric motor (25), in particular a stepping motor.

3. Sewing machine according to at least one of the two preceding claims, characterized in that the hold-down movement is adjustable by driving the separate drive means.

4. Sewing machine according to claim 3, characterized in that the movement of the hold-down (12) is at least approximately continuously adjustable.

5. Sewing machine according to at least one of the preceding claims, characterized in that a size of a stroke of the movement of the blank holder (12) is adjustable.

6. Sewing machine according to at least one of the preceding claims, characterized in that a position of a bottom dead center and / or the Position of a top dead center of the movement of the blank holder (12) is adjustable, in particular at least approximately continuously adjustable.

7. Sewing machine according to at least one of the preceding claims, characterized in that a size of a stroke of the movement of the blank holder on the one hand and a position of a bottom dead center and / or the position of a top dead center of the blank holder on the other hand, are adjustable separately.

8. Sewing machine according to at least one of the preceding claims, characterized in that for synchronization of the movement of the stitch forming means and the movement of the blank holder (12) a position of the blank holder by means of a detection means is detectable and a control of

Sewing machine, taking into account the detection result of the position of the hold-down controls the separate drive means of the hold-down device.

9. Sewing machine according to at least one of the preceding claims, characterized in that the hold-down, at least during a phase in which no stitch formation takes place, independently of the needle bar (5) is movable, in particular by a driven movement of the separate

Drive means.

10. Sewing machine according to at least one of the preceding claims,

characterized by a pinion (23), with which a drive movement of the separate drive means on a rack (22) is transferable.

11. Sewing machine according to claim 10, characterized in that by means of a spring element, the drive movement to the hold-down (12) is transferable.

12. A sewing machine with a hold-down device for holding down sewing material during a stitch formation in the sewing material by at least one thread-guiding stitch forming means, such as a needle bar (6) attachable to a needle bar (5), wherein the hold-down means for performing an oscillating

Stroke movement of a hold-down (12) is operatively connected to a drive means, characterized by means for a movement of the hold-down (12) for the stitch formation process, regardless of the movement of the at least one stitch forming means, in particular a needle of

Sewing machine, set and execute.

Sewing machine according to claim 12, characterized in that the means are not mechanically coupled to the at least one stitch forming means.

14. Sewing machine according to claim 12 or 13, characterized by features of one or more of claims 2 to 11.