Sewing machine with needle feed

Abstract

Sewing machine comprising a needle bar (5, 5') which is driven to oscillate parallel to its longitudinal axis for receiving a needle (5a) carrying an upper thread, the needle bar (5, 5') being provided with a first drive means for longitudinal transport of the needle bar (5, 5') in directions deviating from the longitudinal axis of the needle bar (5, 5'), the sewing machine further comprising at least one material transport means, wherein the material transport means being provided with at least a second drive means with which the material transport means can be set into a resulting feed movement for the material (14) intended for transfer to a material (14), wherein in a first movement phase of a stitch formation the needle bar (5,5') is movable during its longitudinal transport parallel and at least substantially in the same direction as the resulting feed movement of the sewing material transport means, and in a second movement phase of the stitch formation the longitudinal transport movement of the needle bar (5, 5') and the resulting feed movement for the sewing material transport means are directed at least substantially opposite to each other, characterized by the sewing material transport means which in the second movement phase generates a feed movement whose distance (s) differs from the distance traveled in the second movement phase of the needle bar (5, 5').

Description

[0001] The invention relates to a sewing machine with a stitch forming device, which has a needle bar that can be driven to oscillate parallel to its longitudinal axis for receiving a needle carrying an upper thread, the needle bar being provided with a first drive means for longitudinal transport of the needle bar in directions deviating from the longitudinal axis of the needle bar, the sewing machine further comprising at least one material transport means, wherein the material transport means being provided with at least a second drive means with which the material transport means can be set into a resulting feed movement for the material to be transferred to a fabric,In a first movement phase of stitch formation, the needle bar is movable during its longitudinal transport parallel and at least essentially in the same direction as the resulting feed movement of the sewing material transport device, and in a second movement phase of stitch formation, the longitudinal transport movement of the needle bar and the resulting feed movement for the sewing material are directed in opposite directions to each other.

[0002] In a certain type of sewing machine, unlike other sewing machine types, the needle bar, along with the sewing needle guided by the needle bar, is advanced parallel to the fabric feed direction during stitch formation. In addition to an oscillating up-and-down movement of the needle bar parallel to its longitudinal axis to form a loop of the upper thread, the needle bar also performs a forward movement parallel to the fabric feed direction and back again. When forming a stitch, which begins with the needle penetrating the fabric, the needle bar, as it moves parallel to the fabric feed direction, is driven and moved at the same speed as the fabric feed mechanism – and thus, in terms of direction and speed, synchronously with the fabric feed mechanism.The needle is moved from one end of a slot in the sewing machine's needle plate to the other end of the slot; this is called the first phase of movement. At the end of the first phase, the needle exits the fabric at the leading end of the slot (in the direction of the fabric feed). The second phase then begins. The needle bar reverses its direction of movement and, together with the needle, moves back to the rear of the slot in the opposite direction to the fabric feed, at the same speed as the feed mechanism moves the fabric. The needle bar moves at the same speed during this second phase as it did during the first.In the area of ​​the rear end of the elongated hole, relative to the direction of fabric transport, the needle then re-enters the fabric, thus forming the respective stitch with a specific stitch length. Such previously known solutions generally provide for the adjustment of different stitch lengths by changing the end positions of the needle bar during the first and second phases of movement. Different stitch lengths are achieved by shortening or lengthening the travel of the needle bar. Such a design is found, for example, in the applicant's type Kl. 481 sewing machine and the Adler type KI. 268-NF 82S sewing machine of Dürkopp Adler AG, Bielefeld.

[0003] A sewing machine with needle feed or needle transport is also known from DE 38 15 303 A1. Since such sewing machines, due to the elongated stitch slot in the stitch plate, pose a risk of insufficient clamping of the starting threads and thus of skipped stitches, DE 38 15 303 A1 proposes to shift a predetermined number of starting stitches to an end region of the stitch slot.

[0004] However, a disadvantage of this previously known solution is that the adjustability of the stitch lengths is not sufficiently variable.

[0005] The invention is therefore based on the objective of enabling a variation of the stitch length in so-called needle transport machines, in particular stitch lengths that are greater than before.

[0006] This problem is solved according to the invention in a sewing machine of the type mentioned above by the subject matter of claim 1. This claim provides for a fabric transport means in a sewing machine of this type with which a feed movement can be generated in the second movement phase, the distance s of which differs from the distance traveled by the needle bar in the second movement phase. In other words, in sewing machines according to the invention, the fabric transport means and the needle bar should be movable in the second movement phase, particularly by means of first and second drive means, depending on adjustable stitch lengths, such that the fabric transport means travels a distance whose length differs from the distance traveled by the needle bar during its longitudinal transport at the same time. The problem is also solved by a method according to claim 9.

[0007] The invention is based on the realization that, in needle feed machines, the stitch length is limited by the length of the slot in the needle plate. Previously, the stitch length was thus limited to a maximum of twice the length of the slot in the needle plate. The invention reveals that this limitation, previously considered insurmountable, can in fact be overcome. Furthermore, the invention is based on the understanding that, in contrast to known solutions, stitch formation can occur even when the needle bar, during its translational movement, and the fabric transport mechanism or the fabric itself, in the second phase of movement where they move in opposite directions, travel different distances. As has been demonstrated, not only can seams be formed in this way, but this can even be used in a surprising manner to overcome the previous limitation of the maximum achievable stitch length.In the second phase of movement, when the fabric feed mechanism and the needle bar move simultaneously in opposite directions, but preferably at different speeds, this allows for either a reduction or an increase in stitch length compared to previous solutions. The different speeds of the needle bar and the fabric feed mechanism, set at least temporarily during the second phase, ensure that the needle bar and the fabric cover different distances. This difference in distance is directly reflected in the resulting stitch length, which can thus be varied.

[0008] If, in the second phase of movement, either the speed of the material transport element (one of the stitch formation elements) is increased, or the speed of the needle bar (another stitch formation element) is decreased while the distance between the two end positions of the needle bar remains unchanged—each time relative to the speed of the other stitch formation element—a greater stitch length than the maximum stitch length previously possible due to the length of the slot can be achieved. The greater the difference between the distances traveled by the needle bar and the material transport element, the greater the resulting stitch length. In a preferred embodiment of the invention, the stitch length can therefore be adjusted in steps or continuously.In a particularly preferred embodiment, this can be achieved in particular - but not exclusively - by means of which a stepwise or stepless pre-adjustability of the speed of the sewing material transport means can be achieved.

[0009] On the other hand, reducing the speed of the fabric transport mechanism in the second phase of movement—particularly when the needle bar speed remains unchanged or is increased—can shorten the stitch length. It is therefore preferred that means are provided by which the speed of the fabric transport mechanism—relative to the speed of the needle bar—can be reduced in one or more steps or continuously.

[0010] In connection with the invention, the "speed" or "target speed" of the material transport device or the material being sewn, as well as the needle bar, can be understood as the average speed at which these elements move, or at which such movements are provided, in the first or second phase of movement. The present invention thus naturally also includes solutions in which the material being sewn, the material transport devices, or the needle bar are not moved, or are moved only partially, at a constant speed. The invention therefore also encompasses solutions in which the aforementioned elements move at a variable speed during the first and / or second phase of movement. In particular, the needle bar already performs an oscillating movement between its two insertion positions in the material being sewn, during which the needle bar is decelerated, its direction of movement reversed, and the needle bar accelerated again.

[0011] Further preferred embodiments of the invention are described in the claims, the description and the drawing.

[0012] The invention is explained in more detail with reference to exemplary embodiments shown in the figures, which are purely schematic and depict: Fig. 1 a sewing machine with needle feed in a front view; Fig. 2 a sketchy representation of the movements for forming stitch lengths that are greater than twice the distance between spaced-apart needle insertion positions; Fig. 3 a representation in the manner of Fig. 2 of stitch lengths as can be achieved with solutions from the prior art and, if applicable, also with sewing machines according to the invention; Fig. 4 a sketchy representation of the movements for forming stitch lengths that are less than twice the distance between spaced needle insertion positions.

[0013] In Fig. Figure 1 is a highly schematic representation of a sewing machine designed as a needle-feed sewing machine, whose housing 1 has a lower, housing-shaped base plate 2, from which a stand 3 extends essentially vertically upwards. An arm 4 is attached to one upper end of the stand, running approximately parallel to the base plate 2.

[0014] The sewing machine has an arm shaft 7 mounted in arm 4, which, like the other fundamental components of the sewing machine mentioned below, is in Fig. 1 may be shown only partially or in a highly schematic form. The arm shaft 7 drives an oscillating needle bar 5, to which a needle can be attached to receive an upper thread (not shown in detail). The oscillating up-and-down movement of the needle bar, indicated by the double arrow 6, is parallel to the longitudinal axis of the needle bar 5 and perpendicular to the base plate 2. A stitch plate 9 is located in the base plate 2, below which a hook assembly 8 is arranged. A rotary movement of the hook assembly 8 is synchronized with the oscillating movement of the needle bar 5. A lower thread (not shown in detail) is located on a bobbin, which is arranged in a bobbin case holder 11 of the hook assembly 8. The hook assembly 8 guides the upper thread around the bobbin case holder in a manner known per se, so that it can form a seam together with the lower thread.Typically, the needle bar 5 and the gripper device 8 are driven by a common drive, namely a servo-electric motor (not shown in detail), whose rotary drive movement is translated to the needle bar 5 and the gripper device 8 in a specific ratio. Alternatively, it can also be provided that the gripper device and the needle bar are each equipped with separate motors whose movements are coordinated with each other.

[0015] In Fig. 2 is the area of ​​the stitch plate 9 of the sewing machine. Fig. Figure 1 is shown in a highly schematic form. The stitch plate 9 is shown in section, so that in the sectional view of Fig. 2. A slot 12 for the needle can be seen in the needle plate 9. The longitudinal axis of the slot 12 runs parallel to a feed or transport direction 13 of a material transport device, which is provided for the longitudinal feed of the respective material 14. The straight transport direction, which is parallel to the plane of the drawing of Fig. The path 2 is symbolized by arrow 13.

[0016] In the embodiment shown here, the material transport device has a driven roller foot 15 arranged above the material 14 and a sliding wheel 16 arranged below the material. Both are designed as friction wheels that rotate around parallel, perpendicular spokes perpendicular to the plane of the drawing. Fig. 2 and the rotary axes aligned with the transport direction 13 rotate, but are stationary with respect to the translational feed direction 13 of the material to be sewn 14. In other embodiments of the invention, the roller foot 15 may also not be driven; it then rotates passively due to the feed movement of the material to be sewn. Furthermore, as an alternative to the roller foot 15 and / or push wheel 16, including any drive, any other material transport means can be provided, either individually or in combination, with which a feed movement of the material to be sewn, coordinated with the movement of the needle transport, can be generated. For this purpose, for example, a presser foot, a belt transport, a chain transport, and the like are also suitable in principle.

[0017] The sliding wheel 16 and the roller foot 15 are located at the level of the elongated hole 12 with respect to the transport direction 13 and are oriented towards it in a direction perpendicular to the plane of the drawing. Fig. 2 - laterally offset. The sliding wheel 16, with its axis of rotation arranged below the needle plate, projects with part of its circumference 16a directly next to the elongated hole 12 from a recess in Fig. The roller foot 15 protrudes from the needle plate 9 through a recess that is not visible. It is positioned directly above the push wheel 16, forming a gap through which the fabric is guided and gripped by the roller foot and push wheel. Both the roller foot 15 and the push wheel 16 are in contact with the fabric 14 at their circumferences and move it in the feed direction 13 due to their synchronized rotary feed movements. The identical circumferential speeds of the roller foot 15 and the push wheel 16 correspond to the feed speed of the fabric 14 during the feed movements.

[0018] Both the sliding wheel 16 and the roller foot 15 are each operatively connected to a separate drive 17, 18, each assigned only to that specific element, in a manner not shown in detail but known per se. The two drives 17, 18 for the sliding wheel 16 and the roller foot 15 can each be designed as an electric stepper motor, enabling the precise travel of predetermined target distances. The two drives can also be synchronized with each other, or at least temporarily synchronized, so that the circumferences of the sliding wheel 16 and the roller foot 15 travel the same distance simultaneously.

[0019] The needle bar 5 is in Fig. 2 is shown in its two end positions, namely a rear end position in the transport direction and a front end position in the transport direction. Both end positions also represent the entry and exit positions for the needle in the respective fabric for the respective stitch formation. The rear end position of the needle bar 5 is shown in Fig. The needle bar 5' is shown with solid lines in 2, while its forward end position is shown with dashed lines. The two end positions are a distance s1 from each other and are each located in the area of ​​one of the two ends of the elongated hole 12. By means of a further drive 19 of the sewing machine, also designed as a stepper motor, which may optionally include a gearbox interposed between the stepper motor and the needle bar 5, the needle bar 5 can be moved back and forth in a linear oscillating motion between the two end positions. The needle bar 5 moves from the rear to the front position 5' after the needle has entered the fabric in its rear position. This initiates the formation of a stitch.

[0020] The needle 5, located in the fabric, is subsequently moved in the transport direction together with the fabric 14. The drive 19 for the linear movement (needle transport) of the needle bar 5 moves the needle bar at the same speed as that generated by the drives 17, 18 of the push wheel 16 and the roller foot 15 at its circumference. In the exemplary embodiment, this movement takes place at a constant speed – apart from an initial acceleration ramp and a deceleration ramp at the end in the region of the front end position. The first phase of movement of the needle bar 5 and the feed means, push wheel 16 and roller foot 15, thus occurs through the movement between the rear and front end positions of the needle bar 5, 5'.

[0021] At the front end position 5', the needle 5a' emerges from the fabric and is then moved from the front to the rear end position 5. In this embodiment, this second phase of movement of the needle bar and needle 5a is also performed at a substantially constant speed; only at the beginning of the second phase does the needle bar accelerate and towards the end decelerate via its drive. Thus, during the second phase, the needle bar 5 moves at a specific average speed resulting from the individual speed states.

[0022] After the needle 5a' exits the fabric 14 in its forward end position 5', the feed rate for the fabric 14 is increased and this increased speed is maintained until the needle 5a reaches its rear end position and pierces the fabric 14 again. For this purpose, the needle bar drive 19 is decelerated to approximately zero and then accelerated again synchronously with the longitudinal movement of the needle bar 5 for the first movement phase of the subsequent stitch pattern cycle. During this transition from the second movement phase of the preceding stitch pattern cycle to the first movement phase of the subsequent stitch pattern cycle, the drives 17, 18 of the fabric transport mechanism are decelerated to a speed corresponding to that of the first movement phase.With the insertion of needle 5a into its rear end position and the formation of the loop between the upper and lower threads, the formation of this stitch 20 and the second movement phase are completed. With the advancement of the needle bar synchronously with the fabric feed mechanism, the first movement phase of the subsequent stitch 20 of the seam to be formed begins.

[0023] The described movements of the sewing material transport means 15, 16 and the needle bar 5 with respect to their paths during the first and second movement phases result in a greater stitch length s of the respective stitch 20 than is possible due to the previous limitation based on the length of the elongated hole 12 in the stitch plate 9 or the maximum possible distance between the two end positions 5, 5' of the needle in the elongated hole 12. This limitation was previously twice the distance between the two end positions 5, 5'. As shown in the illustration of Fig. As shown in Figure 3, in the first movement phase, the fabric being sewn traveled a distance of length s1, which corresponds to the distance s2 traveled in the second movement phase. Thus, in conventional solutions, the maximum stitch length is s = s1 + s2, where s1 = s2.

[0024] In the solution according to the invention, as exemplified in Fig. As shown in Figure 2, due to the higher relative speeds in the second movement phase between the fabric transport mechanism (here, the roller foot and the push wheel) or the fabric itself and the needle transport, distances s2 are achievable that are greater than the distance s1 covered in the first movement phase. As a result, stitch lengths s can be achieved that are given by s = s1 + s2, where s2 > s1. The drives for the fabric transport mechanisms, designed as electric stepper motors, thus allow for virtually stepless adjustment of larger stitch lengths s than previously possible, with the maximum stitch length in this embodiment being determined by the highest adjustable or achievable speed of the fabric transport mechanisms.

[0025] The solution according to the invention also allows for the realization of small stitch lengths, as is the case in Fig. 4 is shown. For this purpose, the distance between the front and rear end positions 5, 5' can be reduced from a maximum distance such that a connecting line 21 is visible in the representation of Fig. The line 4 between the two axes of rotation of roller foot 15 and sliding wheel 16 runs through the midpoint of the distance between the two end positions of the needle 5. When the distance between the two end positions 5, 5' is reduced or increased, the distance of the two end positions to the connecting line 21, and thus also to the center of the elongated hole, is always reduced or increased in the same way. The two adjustable end positions 5, 5' therefore always have the same distance to the connecting line 21.

[0026] For stitch lengths that are less than twice the maximum distance between the two end positions, the fabric transport means and the needle bar 5 are moved at the same speed during both the first and second movement phases of this embodiment. In the first movement phase, the needle bar 5 and the fabric transport means move synchronously in the same direction at identical speeds, and in the second movement phase, they move at the same speeds but in opposite directions. Thus, for stitch lengths less than twice the maximum distance between the two end positions, this embodiment according to the invention achieves a reduction in stitch length by decreasing the distance between the two end positions 5 and 5' of the needle bar in the elongated hole 12.Both the needle bar 5 and the fabric transport means, and thus the fabric itself, travel correspondingly shorter distances s1 and s2 for smaller stitch lengths, where in this case s1 and s2 are identical. The adjustable distances s1 and s2 each correspond to half the stitch length s to be produced.

[0027] In further embodiments of the invention, it is also possible to achieve stitch lengths s that are less than or equal to the maximum achievable distance between the two end positions of the needle bar in an elongated hole of the needle plate, by varying the speeds of the needle transport and the material transport means, in contrast to the previously described embodiment. One possibility is to adjust the speeds such that the needle bar 5 travels a shorter distance than the material being sewn and thus also than the material transport means during the second movement sequence.

[0028] In principle, embodiments are also conceivable in which the distances traveled in the second movement phase result in different distances s1 and s2 for the needle bar 5 and the fabric transport mechanism, respectively, in a manner other than previously described. For example, it is conceivable to temporarily stop or decelerate the fabric transport mechanism or the drive for the needle bar during the second movement phase and then accelerate it again. It is also possible for at least one of the drives to execute specific movement profiles with frequently or even constantly changing speeds during the second movement phase. The speeds should be selected such that the fabric transport mechanism or the needle bar covers its respective predetermined distance.

[0029] All movements of the stitch formation and feed mechanisms of the sewing machine are shown in the exemplary embodiment of the Fig. 1, Fig. 2 and Fig. 4. The sewing machine's operation is coordinated and controlled by an electronic control system. The desired stitch lengths can be entered or set at an input interface on the sewing machine (not shown). The control system then translates the set stitch length into the fabric for the subsequent sewing process by sending signals to the drives corresponding to the stitch lengths. This causes the drives to execute a number of revolutions and angular velocities corresponding to the stitch lengths for the first and second phases of movement. Furthermore, the control system also coordinates the movement of the needle bar with the respective hook of the sewing machine, ensuring that, after the upper needle inserts into the fabric for each intended stitch formation, the hook tip is positioned at the point of entry and engages the thread loop formed by the needle.

[0030] In further embodiments of the invention, the different stitch lengths, in particular those longer than twice the maximum distance between the end positions of the needle bar, can also be achieved by an adjustable mechanism. In this context, adjustable gears are particularly suitable as components of the drive means for the fabric transport mechanism and / or the needle bar, with which different speeds and different travel lengths s1 and s2 can be achieved despite any constantly operating motors or other drives, due to different gear ratios. Reference symbol list 1 case 2 Base plate 3 stands 4 Arm 5 needle bar 5' Needle bar 5a Needle 7 Arm shaft 8 Gripper device 9 Stitch plate 11 coil capsule carriers 12 elongated holes 13 Feed and transport direction 14 sewing supplies 15 casters 16 sliding wheel 16a Scope 17 Drive 18 Drive 19 Drive 20 stitches 21 connecting line

Claims

[1] Sewing machine, which has a needle bar (5, 5') which can be driven in an oscillating manner parallel to its longitudinal axis and is intended to receive a needle (5a) which guides an upper thread, the needle bar (5, 5') being provided with a first drive means for the longitudinal transport of the needle bar (5, 5') in directions deviating from the course of the longitudinal axis of the needle bar (5, 5'), the sewing machine furthermore has at least one material transport means, wherein the material transport means is provided with at least one second drive means with which the material transport means can be set in a resulting feed movement for the material (14) which is intended for transfer to a material (14), in this case in a first movement phase of a stitch formation the needle bar (5,5') is movable during its longitudinal transport parallel and at least substantially in the same direction to the resulting feed movement of the material transport means and in a second movement phase of the stitch formation the longitudinal transport movement of the needle bar (5, 5') and the resulting feed movement for the material transport means are at least substantially opposite to each other, characterized by the material transport means which, in the second movement phase, generates a feed movement whose distance (s) deviates from the distance covered in the second movement phase of the needle bar (5, 5'). [2] Sewing machine according to claim 1, characterized by that the material transport means in the second movement phase covers a greater distance (s) than the needle bar (5, 5') between its two insertion points of the second movement phase. [3] Sewing machine according to claim 1 or 2, characterized bythat the material transport means in the second movement phase covers a smaller distance (s) than the needle bar (5) between its two insertion points in the second movement phase. [4] Sewing machine according to at least one of the preceding claims, characterized by that the material transport means can be moved in the second movement phase at a speed which differs from the speed of the needle bar (5, 5'). [5] Sewing machine according to at least one of the preceding claims, characterized by that the first and second drive means (17, 18) can be controlled by means of a control system in such a way that the feed movement of the material transport means in the second movement phase takes place over a distance (s) which deviates from the distance covered at the same time by the needle bar (5, 5') during its longitudinal transport. [6] Sewing machine according to at least one of the preceding claims, characterized bythat the feed movement in the second movement phase occurs at a higher speed than in the first movement phase. [7] Sewing machine according to at least one of the preceding claims, characterized by that the sewing material transport means is designed in several parts, wherein a first part of the sewing material transport means is arranged above the sewing material (14) and a second part is arranged below the sewing material (14), at least one of the two parts of the sewing material transport means is operatively connected to the second drive (17, 18) which generates the feed movement for the sewing material (14). [8] Sewing machine according to claim 1, characterized by a needle plate (9) with an elongated hole (12) for arranging the needle (5a) in different piercing positions, and by an achievable stitch length (s) which is greater than twice the greatest distance between two piercing positions of the needle (5a) resulting from the length of the elongated hole (12). [9] A method for producing seams with predetermined stitch lengths by means of a sewing machine having a needle bar (5, 5') which can be driven in an oscillating manner parallel to its longitudinal axis for receiving a needle (5a) guiding a top thread, the needle bar (5, 5') being moved in a direction deviating from the course of the longitudinal axis of the needle bar, the sewing machine further comprising at least one material transport means which is set in a resulting feed movement for the material (14) intended for transfer to a material (14), in which case, in a first movement phase, the needle bar is moved during its longitudinal transport parallel to and at least substantially in the same direction as the resulting drive movement of the material transport means, and in a second movement phase, the longitudinal transport movement of the needle bar (5, 5') and the resulting drive movement for a feed of the material (14) are oriented opposite to one another, characterized bythat in the second movement phase of the material transport means a feed movement is generated whose distance (s) deviates from the distance covered in the second movement phase of the needle bar (5, 5'). [10] Method according to claim 9 characterized by that the needle bar is driven during a stitch formation cycle with at least two different target speeds, wherein a first target speed corresponds to a target speed of the material transport means to be set simultaneously and a second target speed provided in particular for the second movement phase deviates from the target speed of the material transport means to be set simultaneously.

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