EP0512145B1 - Method for producing a seam which changes direction - Google Patents

Description

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

When sewing an angled seam parallel to the edge on a single-needle sewing machine, the corner of the angled seam is controlled in a known manner so that the last insertion of the needle is carried out at a predetermined position in the work piece and the needle is temporarily positioned in its lowered position in the inserted state. Now the work piece is rotated around the inserted needle in accordance with the angled seam course and then said seam is continued. In a two-needle sewing machine, the inner corner of the double seam to be produced is actuated in a known manner, and after the stitch formation has ended, the needle bar producing the inner seam is brought into its inactive position, that is to say switched off in a long-known manner, with the outer needle bar being sewn further into the outer corner, after which the needle guided by the outer needle bar is temporarily positioned in its low position. Now the work piece is made according to the angled seam course around the inserted needle is rotated and then the outer needle bar is sewn until it faces the inner corner point, after which the inner needle bar is brought into its active position, ie is switched on in a known manner. Now the double seam is continued.
From DE 32 16 993 C2 (contained in US Pat. No. 4,495,877), indications of such a procedure can be gathered, which is made possible by a sewing machine with a feed means that can be adjusted by an adjusting device. As a result, for precise corner sewing from the edge detection by the sensor, it is possible to control a predetermined end point in such a way that a change in the stitch length of the stitches contained in the remaining seam section is carried out for the sewing of the remaining seam section from the time the sensor responds to the said end point. In this way, by reducing or increasing the stitch length for the purpose of precise stitch formation at the predetermined end point, the required stitch length is evenly distributed over the stitches contained in the remaining seam section, as a result of which a very uniform-looking seam pattern is achieved in the vicinity of the corner. The disadvantage of the known sewing machine can be seen in the fact that changing the stitch length from the time the edge is detected by the sensor to the predetermined end point in the corner requires a considerable amount of construction work, namely a stepper motor and a worm gear. Another disadvantage is the fact that from the edge detection in a two-needle sewing machine it is not possible to perform the stitches of both seams in the arcuate course of the double seam with stitch lengths of different sizes.

The invention is therefore based on the object of demonstrating a method by which the sewing of corrected stitches which occur in the corner or arch-shaped transition region of a seam which changes direction in the course of the seam is made possible with little construction effort and in particular in the case of arched double seams.

This object is achieved in the generic method by the features listed in the characterizing part of claim 1.

With the method according to the invention it is advantageously achieved that the otherwise when sewing stitches with a large stitch length L - e.g. with decorative stitching - the required low feed rate for the stitches L ', L'1 etc. carried out after the sensor system has responded can be increased significantly. This is possible by increasing the machine speed based on the usual speed when sewing in the corner, because after the sensor system has responded, the stitches L ', L'₁ etc. contained in the seam near the edge are divided into n-sub-steps s, s' whose length is considerably smaller than the stitch length L. previously used

In addition, the method has the further advantage that a small mechanical construction effort is required for the sewing of corrected stitches which can be achieved thereby, because for the change in stitch length of the stitches L ', L'1 contained in the transition region between two angularly extending seam regions, additional actuators for pivoting the stitch regulator backdrop are not necessary, since these are already included in the sewing machine in question.

With regard to the division of a stitch into a number of sub-steps provided for by the invention, the needle insertion only being carried out during the last sub-step - that is to say shortly before the stitch formation ends - that the prior art (DE-OS 18 00 810 , contained in US Pat. No. 3,465,698) the following is already known per se: For the formation of stitching stitches with a relatively large stitch length, a missing stitch mechanism has been proposed which causes the reciprocating movement of the needle bar in its longitudinal axis at predetermined intervals depending on a programming device can be interrupted.

Useful and further advantageous developments of the method are listed in the subclaims (claims 2 to 9).
The further development according to claims 7 and 8 shows method steps for sewing corrected stitches in the transition region in the case of a double seam, which is produced in a known manner on a two-needle sewing machine with needle bars which can be switched off and are known per se. The development according to claim 9 shows method steps for sewing corrected stitches which occur in the arcuate transition region between two seam regions running at an angle to one another.

Fig. 1

eine vereinfachte Vorderansicht einer Zweinadel-Nähmaschine mit ein- und ausschaltbaren Nadelstangen und mit hüpfendem Ober- und Untertransport, wobei der Vorschub- und der Haltefuß sowie der Stoffschieber nicht dargestellt wurden,

Fig. 2

eine Seitenansicht der Nähmaschine mit wenigstens einer ein- und ausschaltbaren Nadelstange, wobei die für das Nähen korrigierter Stiche erforderlichen Mittel zur Vorschublängen- Veränderung (Stichlängen-Veränderung) schematisch dargestellt wurden,

Fig. 3

eine vereinfachte Vorderansicht einer Einnadel-Nähmaschine mit einer ein- und ausschaltbaren Nadelstange und mit hüpfendem Ober- und Untertransport, wobei der Vorschub- und der Haltefuß sowie der Stoffschieber nicht dargestellt wurden,

Fig. 4

eine schematische Darstellung einer spitzwinklig abgewinkelten Doppelnaht, die auf einer Zweinadel-Nähmaschine hergestellt wurde,

Fig. 5

eine schematische Darstellung einer rechtwinklig abgewinkelten Doppelnaht,

Fig. 6

eine schematische Darstellung einer stumpfwinklig abgewinkelten Doppelnaht,

Fig. 7

eine schematische Darstellung einer spitzwinklig abgewinkelten Naht, die auf einer Einnadel-Nähmaschine hergestellt wurde,

Fig. 8

ein Flußdiagramm, aus dem der Funktionsablauf des erfindungsgemäßen Verfahrens in bezug auf korrigierte, im eckenförmigen Übergangsbereich auftretende Stiche ersichtlich ist,

Fig. 9

eine schematische Darstellung einer abgewinkelten Doppelnaht, die im Übergangsbereich bogenförmig verläuft.

The method is explained with reference to FIGS. 1 to 9. It shows:

Fig. 1

a simplified front view of a two-needle sewing machine with needle bars that can be switched on and off and with bouncing top and bottom feed, the feed and holding feet and the fabric pusher not being shown,

Fig. 2

2 shows a side view of the sewing machine with at least one needle bar that can be switched on and off, the means for changing the feed length (stitch length change) required for sewing corrected stitches being shown schematically,

Fig. 3

a simplified front view of a single-needle sewing machine with a needle bar that can be switched on and off and with bouncing top and bottom feed, the feed and holding feet and the fabric pusher not being shown,

Fig. 4

1 shows a schematic representation of a double seam angled at an acute angle, which was produced on a two-needle sewing machine,

Fig. 5

a schematic representation of a right-angled double seam,

Fig. 6

1 shows a schematic representation of a double seam angled at an obtuse angle,

Fig. 7

1 shows a schematic illustration of a seam angled at an acute angle, which was produced on a single-needle sewing machine,

Fig. 8

2 shows a flow chart from which the functional sequence of the method according to the invention can be seen with regard to corrected stitches occurring in the corner-shaped transition area,

Fig. 9

is a schematic representation of an angled double seam that runs in an arc in the transition area.

1 shows a two-needle sewing machine 1 designed in a conventional manner for carrying out the method according to the invention, which is equipped with needle bars 2, 3 which can be switched on and off. In this sewing machine 1, as a feed means for the transport of a work piece 4, a hopping material slide 5 and a feed foot 6 and a holding foot 7 interacting alternately with the latter in a known manner are provided. In Fig. 3, a single-needle sewing machine 1 'is shown, which is equipped with only one needle bar 3 which can be switched on and off. In this sewing machine 1 ', the fabric pusher 5 shown in FIG. 2, the feed foot 6 and the holding foot 7 are also used as feed means for the transport of the work piece 4. It is self-evident that the sewing machine 1 'shown in FIG. 3 can be equipped with a vertical hook shaft 9 instead of a hook 8 shown there with another hook which has a horizontal hook shaft.

The sewing machine 1 essentially consists of a machine arm 10 which is mounted on a base plate 12 via a stand 11. In the front part of the machine arm 10, an arm head 13 is provided, in which the needle bars 2, 3 as well as a feed foot bar 14 and a holding foot bar 15 are mounted in a known manner. A switching device 16 for switching the needle bars 2, 3 on and off is provided on the top of the arm head 13. On the underside of the arm head 13, two buttons 17, 17 'are conveniently attached, as shown in FIG. 1, which enable the switching device 16 to be actuated remotely. Both buttons 17, 17 'are operatively connected to a computer 18 which, among other things, issues commands to the switching device 16 for switching the needle bars 2 and 3 on and off after actuation of one of the buttons 17, 17'. Structure and operation of the switching device 16 are known from German utility model 83 35 949, so that a further description can be dispensed with.
A seam 19 shown in FIGS. 4 to 6 and consisting of the partial seams 19 ', 19'', which in this case is designed as a double seam, is known to be formed from two needle threads 20 and two looper threads, not shown here. As is known, the needle threads 20 drawn off from an external thread supply pass through a thread tensioning device 21 which is attached to the arm head 13 according to FIG. 1.
An arm shaft 22 is mounted in the machine arm 10 and is driven by a positioning sewing drive 24 via a traction means, for example a V-belt 23. The arm shaft 22 causes, among other things, the up and down movement of the needle bars 2, 3 in a known and therefore not described here. If the needle bars 2, 3 are in their active position, they perform the above-mentioned up and down movement. After pressing one of the buttons 17, 17 ' the needle bar 2, 3 in question is brought into its inactive position, ie when the arm shaft 22 is rotated after the pushbutton is actuated, the needle bar 2, 3 in question reaches its high position, as a result of which it can now neither be moved up nor down. In other words: in this state, the relevant needle bar 2, 3 is in its inactive high position, ie it is switched off.

Outside the machine arm 10 there is a wheel 25 which is connected to the arm shaft 22 in a rotationally fixed manner and has slots 26 or other line markings arranged on its circumference at equal angular intervals. The slots 26 are detected by a sensor 28 attached to the machine arm 10, the wheel 25 and the sensor 28 forming a pulse generator 29. In the case of the seam courses shown in FIGS. 4 to 7, the pulse generator 29 defines the stitch completion degree, wherein after the edge 30 running transverse to the transport direction NV is detected by the sensors 33, 33 ', an increment count is carried out. The degree of stitch completion is expressed by the remaining stitch lengths L _X , L ' _X.
A position sensor 31 is fixedly connected to the arm shaft 22, which in a known manner effects the speed control and the positioning of the needle bars 2, 3 in predetermined positions and is operatively connected via a control line 32 to a control (not shown here) belonging to the sewing drive 24.
Provided on the arm head 13 of the two-needle sewing machine 1 are two sensors 33, 33 ′ arranged at a defined distance L _{S in} front of the plane of movement of the needle bar 2, 3 that can be moved up and down, which according to FIG. 2 each consist of a transmitter 34 and a receiver 35 . The latter is preferably arranged in a throat plate 36, in such a way that it does not hinder the movement of the fabric pusher 5.
The latter is attached to a carrier 37. In order to ensure the exact transport of a multi-layer work piece 4 in the two-needle sewing machine 1 mentioned at the outset, the fabric pusher 5 engages on the underside of the work piece 4 and the feed foot 6 on the upper side of the work piece 4. The operation of the feed foot 6 and the slider 5 has long been known from German patents 23 37 966 (contained in US patent 3 935 826) and 26 20 209 (contained in US patent 4 116 145), so that here on further description can be omitted.
At the right end of the carrier 37 shown in FIG. 2, a lever mechanism 38 engages to generate the lifting movement of the fabric slide 5. At the left end of the carrier 37, another lever gear 39 engages to generate the pushing movement of the fabric pusher 5. Both lever gears 38, 39 are pivotally mounted in the base plate 12 in a known manner.
In order to be able to change the size of the feed length (stitch length) of a feed step, the sewing machine 1, 1 'has a feed length adjustment device 40 which has been known for a long time and which consists of the lever gear 39 and a link guide 41 pivotably mounted in the base plate 12. To change the feed effect exerted by the fabric pusher 5 and also by the feed foot 6 on the work piece 4, the link guide 41 is also pivoted by the pivoting of a stitch regulator lever 42 via a pull rod 43. The stitch regulator lever 42 protrudes from the stand 11, on which it is pivotally mounted. The swivel range of the stitch regulator lever 42 is limited by two stops 44, 45 attached to the stand 11 and changing in position.

The stitch regulator lever 42 is pulled against the stop 44 by a tension spring 46. If the latter is in its uppermost position, the work piece 4 is transported during the forward sewing (in the direction of transport NV) by the interaction of the fabric pusher 5 with the feed foot 6 with the maximum feed length. If the stop 45 is in its lowest position, the work piece 4 is transported at the maximum feed length against the transport direction NV when sewing backwards - when the stitch regulator lever 42 is pressed against the action of the tension spring 46 against the stop 45. From the above it can be seen that the feed effect exerted by the fabric pusher 5 and the feed foot 6 on the work piece 4 can be changed by pivoting the link guide 41 with regard to the size of the feed step to be carried out.
On the base plate 12, two actuators 48, 49 - preferably two single-acting compressed air cylinders - are arranged in such a way that their plungers 50, 51 press against a cantilever 47 after exposure to compressed air and thus pivot the latter, as well as the link guide 41. The above-described arrangement of the actuators 48, 49 on the base plate 11 allows their adjustable position with respect to the arm 47, so that the plungers 50, 51 perform predetermined strokes. This ensures that the extended plunger 50 pivots the arm 47 and the link guide 41 such that the slider 5 and the feed foot 6 transport the work piece 4, for example during one revolution of the arm shaft 22, by a partial step s equal to 1 millimeter. Analogously, it is possible that the extended plunger 51, for example, permits a partial step s' equal to 0.5 millimeter. For the compressed air supply to the cylinder (actuator 48) is a 3/2-way solenoid valve 52 and for A further 3/2-way solenoid valve 53 is provided for the compressed air to the further cylinder (actuator 49). Both solenoid valves 52, 53 are operatively connected to the computer 18. The compressed air required to act on the two cylinders (actuators 48, 49) is supplied by an external, not shown here, pneumatic components, such as throttles and the like, not shown here Compressed air source removed. The start and duration of the respective application is specified by the computer 18.
It is self-evident that electromagnets known per se can also be used as actuators 48, 49, the activation of which is also controlled by the computer 18.
An input device 54 is provided at a convenient location either on the sewing machine 1, 1 'or on the frame (not shown here) which receives the sewing machine 1, 1'. On a front plate of the latter, input elements, not shown, such as multi-digit preselection switches, pushbuttons and display elements such as a display, light-emitting diodes and the like are provided. The parameters required for sewing corrected stitches in the corner or arc-shaped transition region of a seam changing the direction, such as:
Feed length (stitch length) of stitches L; Length of the sub-steps s or s'; Distance a of the seam 19 from an edge 55, distance b between the seams 19 ', 19''of a double seam 19; Angle α between the edges 55, 30 and the distance L _S between the sensor 33, 33 'and the plane of movement (see reference number 57 in FIGS. 4 to 7) of the needle bar 2, 3 that can be moved up and down are entered.

The method according to the invention can of course also be carried out on the single-needle sewing machine 1 'mentioned at the beginning. For the latter applies analogously and taking into account FIG. 3, what has already been said in the previous description.

The sequence of the method according to the invention is described below:

The sequence of the method according to the invention can be seen from the flow chart according to FIG. 8, the method steps which relate to the formation of the corrected stitches L _Y , L ', L'1 being designed in accordance with the seam course shown in FIG. 4. The method steps just mentioned are to be modified analogously if other seam courses - for example those shown in FIGS. 5 to 7 or others - occur. After the edge 30 has been recognized by the sensors 33, 33 ′, which are initially darkened by the work piece 4 running toward the sewing point 56, the computer 18 is activated. As a result, the degree of stitch completion is defined by the pulse generator 29 by increment counting in such a way that the remaining stitch lengths L _X , L ' _{X are} determined. The distance L _W (see FIGS. 4 and 6) and the remaining seam distances L _R , L ' _R are then calculated by the computer 18. Now the remaining seam section L _{R is divided} into an optimal number of stitches L ', L'₁ etc. according to the following example 1, whereby L', L'₁ etc. should only deviate slightly from the stitch length L originally set.

Example 1:

• Set stitch length L = 7 mm,
• residual seam distance L _R = 18.5 mm,
• α = 60 degrees.

• 1.1 Wahl der Anzahl der in L_R enthaltenen Stiche:
  Stichzhal = $$\frac{{\text{L}}_{\text{R}}}{\text{L}}$$
  
  = $$\frac{\text{18,5 mm}}{\text{7 mm}}$$
  
  = 2,64 , aufgerundet X = 3 Stiche
• 1.2. Erforderliche Länge der korrigierten Stiche:
  erforderliche Stichlänge = $$\frac{{\text{<figure-callout id="3" label="L R" filenames="imgf0001.png,imgf0002.png" state="{{state}}">L</figure-callout>}}_{\text{R}}}{\text{3}}$$
  
  = $$\frac{\text{18,5 <figure-callout id="3" label="mm" filenames="imgf0001.png,imgf0002.png" state="{{state}}">mm</figure-callout>}}{\text{3}}$$
  
  = 6,17 mm , abgerundet 6 mm
• 1.3. Optimierte Aufteilung der in L_R enthaltenen drei Stiche:

  Dritter (letzter) Stich L'₁

  = 6 mm ,
  verbleibt Rest = 12,5 mm

  zweiter Stich L'₁

  = 6 mm ,
  verbleibt Rest = 6,5 mm

  erster Stich L'

  = 6,5 mm ,
  Rest = Null

  
  Anschließend ermittelt der Rechner 18 die in der Teilnaht 19' enthaltene Reststichlänge L_Y (vergleiche Fig. 4) zu:

This example relates to the seam course shown in FIG. 4.

• 1.1 Choosing the number of stitches contained in L _R :
  Stichzhal = $$\frac{{\text{L}}_{\text{R}}}{\text{L}}$$
  
  = $$\frac{\text{18.5 mm}}{\text{7 mm}}$$
  
  = 2.64, rounded up X = 3 stitches
• 1.2. Required length of corrected stitches:
  required stitch length = $$\frac{{\text{L}}_{\text{R}}}{\text{3rd}}$$
  
  = $$\frac{\text{18.5 mm}}{\text{3rd}}$$
  
  = 6.17 mm, rounded 6 mm
• 1.3. Optimized division of the three stitches contained in L _R :

  Third (last) stitch L'₁

  = 6 mm,
  remains = 12.5 mm

  second stitch L'₁

  = 6 mm,
  remains = 6.5 mm

  first stitch L '

  = 6.5 mm,
  Remainder = zero

  
  The computer 18 then determines the remaining stitch length L _Y contained in the partial seam 19 '(see FIG. 4):

Example 2:

$${\text{L}}_{\text{Y}}{\text{= L '}}_{\text{R}}\text{- L = 8 - 7 = 1 mm}$$

Now the needle bar 3 is switched off (brought into its inactive position) and the feed length adjusting device 40 is pivoted via the solenoid valve 52, the actuator 48, the plunger 50 and the extension arm 47, whereby the material slide 5 and the feed foot 6 the work piece 4 by one Transport step s = 1 millimeter in the direction of sewing point 56. Simultaneously with the pivoting of the feed length adjusting device 40 just described, the positioning drive 24 is switched to a constant machine speed, which cannot be influenced by the operator and is also higher than usual machine speed when sewing in the corner. The execution of the three stitches L ', L'₁ L'₁ contained in the residual seam section L _R (see FIG. 4) is carried out according to the method steps described in the flowchart in FIG. 8. It is essential to the invention that the needle bar 3 is moved up and down only during the last sub-step s or s 'of each stitch L' or L'₁. After the work piece 4, which is known per se, is rotated about the needle 61 which is inserted into the end point 59 and is positioned in the lower position, the machine speed is switched back to a variable value which can be influenced by the operator. Sewing is then carried out with the needle bar 3 switched on and with the stitch length L = 7 millimeters switched on again via the feed length adjusting device 40, the needle bar 2 being switched on again by the computer 18 after x-1 stitches. The partial seams 19 ', 19''are now carried out in this way. Through the process steps just described and can be seen in FIG. 8, a corner occurring in the course of the double seam 19 was created under the Provided that the end points 59, 59 'are at a predetermined location in the work piece 4 and that the last stitches L', L'₁ etc., which are before the end point 59, have been corrected so that they are only slightly different from the originally set stitch length L.

In the case of a single-needle sewing machine 1 ', the seam 19 thus produced is monitored by the sensor 33 according to FIG. 7. The signals supplied to the computer 18 by the sensor 33 after the detection of the edge 30 initiate the course of the method, for which the same applies as has been previously described with regard to the formation of the seam 19 ″.

A seam course shown in FIG. 9 can also be produced using the sewing method according to the invention. Until a sensor system responds, which is embodied, for example, by the operator's eye or by a video camera, the partial seams 19 ′, 19 ″ belonging to the double seam 19 are sewn with the stitch length L. When the sensor system responds - for example by the operator actuating a button (not shown here) - a signal is sent to the computer 18. As a result, a program stored in the computer 18 is called up. With the parameters contained therein, appropriately corrected stitches L ', L'₁ can be produced in an arcuate seam region 62, which are characterized in that each of them is formed from at least two substeps s, s', and that the needle bar 2, 3 is only moved up and down during the last sub-step s, s'. In order to be able to execute the arcuate seam region 62, the work piece is handled by the operator or guided by a known pivoting device, not shown here.

Claims (9)

1. A method of making a seam (19) which changes direction and extends parallel to edges (30, 55) of a workpiece (4) which meet at an angle, and which is formed by a sewing machine (1, 1') comprising at least one engageable and disengageable needle bar (2, 3), in which

   - a needle (60, 61) is moved up and down by the needle bar (2, 3),

   - the advance of the workpiece (4) made by a feed means is monitored by sensor means, and

   - after response of the sensor means, a number of stitches are made and have a length L', L'₁ etc deviating from a previously-made stitch length L,

   characterised in that

   - the stitches L made until the sensor means responds are formed by a single advance step made by the feed means,

   - the corrected stitches L', L'₁ etc made after response of the sensor means are formed by at least two component steps s, s' made by the feed means,

   - during each component step s, s', an arm shaft (22) of the sewing machine (1, 1') is rotated through an angle of 360°,

   - the needle bar (2, 3) is moved up and down only during the last component step s, s' of each stitch L', L'₁ etc, and

   - after a further response of the sensor means, stitches L are made which as before are formed by a single advance step made by the feed means.
2. A method according to claim 1,
   characterised in that
   each stitch L', L'₁ etc is made up of component steps s of equal length.
3. A method according to claim 1,
   characterised in that
   each stitch L', L'₁ etc is made up of component steps s, s', the last component step s' being smaller than the preceding component step s.
4. A method according to claim 1,
   characterised in that
   each stitch L', L'₁ etc as nearly as possible is made smaller or larger than the preceding stitches L.
5. A method according to claim 1,
   characterised in that

   - before the beginning of each stitch L', L'₁ etc the needle bar (2, 3) is moved into its inactive (disengaged) position,

   - during production of each stitch L', L'₁ etc, beginning from the last rotary motion (rotation) of the arm shaft (22), the needle bar (2, 3) is brought into its active (engaged) position, and

   - at the end of each stitch L', L'₁ etc the needle bar (2, 3) is returned to its inactive position.
6. A method according to claim 1,
   characterised in that
   during production of a bent seam (19) made on a single-needle sewing machine (1'), the edge (30) is detected by the sensor (33) after which the remaining seam length L_R is determined and divided into an optimum number of stitches L', L'₁ etc.
7. A method according to claim 1,
   characterised in that
   during production of a seam (19) made on a two- needle sewing machine (1) and bent through an angle α less than or greater than 90°, the edge (30) is recognised, after which:

   - triggered by the sensor (33') the remaining seam length L'_R and the length of the last stitch L_Y therein, comprising the component steps s, s', are determined, and

   - triggered by the sensor (33), the remaining seam length L_R is determined and divided into an optimum number of stitches L', L'₁ etc.
8. A method according to claim 1,
   characterised in that
   during production of a seam (19) made on a two- needle sewing machine (1) and bent through an angle α greater than 90°, the edge (30) is recognised, after which:

   - triggered by the sensor (33), the remaining seam length L_R is determined and divided into an optimum number of stitches L', L'₁ etc, and

   - triggered by the sensor (33'), the remaining seam length L'_R and the length of the last stitch L_Y therein, comprising the component steps s, s', are determined.
9. A method according to claim 1,
   characterised in that
   during production of a seam (19) having an arcuate region (62) between two regions meeting at an angle, stitches L', L'₁ etc are formed between the first and a further response of the sensor means, and the parameters for forming them are called up from the computer (18).

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