EP3935212A1

EP3935212A1 - Method and device for ensuring loop formation of the needle thread for a shuttle embroidery machine

Info

Publication number: EP3935212A1
Application number: EP19736674.3A
Authority: EP
Inventors: Jürgen TÜRTSCHER
Original assignee: Laesser AG
Current assignee: Laesser AG
Priority date: 2019-03-07
Filing date: 2019-07-03
Publication date: 2022-01-12
Also published as: CH715909A1; WO2020177882A1

Abstract

A holder (19) is used to press the stitching base (15) against the stitch plate (17) during the first forward stroke of the needle (3) before returning at the first reversal point and holds it in place during loop formation between the stitch plate (17) and the eye (3") of the needle (3) so that the stitching base (15) cannot be lifted by the retracting needle (3), thereby preventing the loop.

Description

Method and device for ensuring the

Loop formation of the needle thread for a shuttle embroidery machine The invention is a method for

Ensuring the loop formation of the needle thread on a shuttle large embroidery machine according to the preamble of claim 1 and a device for

Ensuring the loop formation of the needle thread for a shuttle embroidery machine according to the generic term of

Claim 5.

In the production of embroidery on an embroidery base with applied and sometimes very elastic fabrics or embroidery, in which large areas are drilled through holes, i.e. punched out or cut out

Areas of the embroidery base that are embroidered have the problem that, on the one hand, the appliqués cannot be kept taut enough so that they lie snugly on the embroidery base and, on the other hand, the embroidery base can have a larger area after drilling

Recesses cannot be re-tensioned at will, since the missing weft and warp threads in the area of the recesses around the recesses result in a loosening of the tensioned Stick bottom results. Due to the lack of tension in the

Applications or the embroidery base for large

There is a latent risk that the recesses

Application and possibly also the embroidery base in the axial direction of the needle when the needle is withdrawn

Loop formation stands out from the needle hole plate and consequently the formation of a loop large enough for the shuttle to pass through is not guaranteed. Skipped stitches are therefore common. These embroidery errors caused by dropped stitches lead to rejects. The main reason for these stitches being dropped is that the needle thread is not positioned sufficiently through the embroidery base when the needle is returned to form the loop, but rather it is positioned in the embroidery base

located thread lifts the embroidery base from the needle plate and is thus between the eye of the needle and the

Embroidery hole can only form too small a loop or no loop at all and consequently the needle thread cannot be knotted with the shuttle thread.

An object of the present invention is to provide a method and a device with which the lifting of the stick bottom with the retracting needle can be prevented between the presser paws and consequently the distance, ie the distance from the needle eye to the stick bottom, is reliably shortened and the construction of a thread loop can be ensured. These objects are achieved by a method according to the features of claim 1 and a device according to the features of claim 5.

With the method, when the needle is inserted into the application and the embroidery base, a spring-mounted hold-down device is brought up to the contact of the hold-down device with the embroidery base and / or the application on the embroidery base to the embroidery base and the needle hole plate. As the needle piercing process continues while the hold-down device comes to a standstill due to its contact with the application and the stick bottom, the pressure of the hold-down device is increased and remains at the first reversal point even after the needle stroke is reversed and during the partial retraction of the needle to form the loop Needle thread between the eye of the needle and the embroidery base. In this way, the stick bottom is held pressed against the needle hole plate by the hold-down device at least until the shuttle moves into the loop formed.

By locally pressing the application onto the

Embroidery base or the embroidery base in the case of large recesses directly next to the needle on the needle hole plate, after the needle has already pierced the application and the embroidery base, but before the stroke reversal of the needle begins, the hold-down device enables the Retraction of the needle, the embroidery base and / or the

Application does not lift off the needle plate and thus no shortening of the distance between the

The eye of the needle and the embroidery floor. By holding and pressing the embroidery base, the needle is pulled back between its eye and the

Embroidery base creates the loop formation necessary for the passage of the shuttle. The immediate passage of the shuttle after the loop formation through the loop formed and the subsequent release of the contact pressure of the

Hold-down on the application and the embroidery base enables the needle base to be moved smoothly across the needle plate over the needle hole plate for the next stitch formation immediately after the needle point has left the embroidery base.

By lifting the hold-down from the surface of the embroidery base or an application applied to it or an accumulation of satin stitches in particular, the embroidery base can be unimpeded relative to the needle and to that located above it at a distance from the embroidery base

Hold down to be moved. It can also be prevented that the hold-down device hooks into the recess or reaches under it when embroidering large drill holes (recesses).

A hold-down device designed as a spring does not require a separate drive. It is activated directly or indirectly by the needle pusher to which the hold-down device can be attached, compulsorily carried along and practices the necessary

Contact pressure on the surface of the embroidery base

forced by the after contacting the

Embroidery base through the further moving needle pusher. The lifting of the pressing force on the stick bottom ends only after the forcibly formed loop by withdrawing the needle without any necessary

Control means.

The hold-down includes one for the necessary

Contact pressure suitably designed spring which can be pressed onto the needle hole plate. No further moving mechanical parts are necessary. The hold-down device can be attached to the needle ram or driven indirectly by it. If not required, the hold-down device can easily be removed again. Alternatively, the

Downholder, of course, also independent of the needle drive provided specifically for this purpose

Drive member are operated. In a first embodiment of the invention, the hold-down includes a U-shaped bent spring profile, the first leg end of which is attached to the needle plunger and the end of the second leg has a bore or

Includes recess through which the needle can be passed. By bringing the free second leg of the spring up to the needle hole plate, the angle between the two spring legs and the pressure on the stick base and the application increased.

In a further embodiment the hold-down has a V-shape and comprises two together, e.g.

Spring steel sheet sections connected by rivets.

In the second embodiment of the hold-down device, this can also be diamond-shaped, i.e. be constructed from two symmetrically arranged V-shaped spring sections.

In a third advantageous embodiment of the V-shaped hold-down device, one of the two legs is configured as a parallelogram in order to optimize the guidance of the second leg.

In the fourth embodiment of the invention are on

Needle plunger two relative to this displaceable

Arranged guide rods, the ends of which are connected to one another on the needle side by a pressure plate. The

rear ends of the rods are axially displaceably mounted in at least one carrier. Between the pressure plate and the at least one guide plate on the

Needle pusher is attached, springs are on the

Arranged guide rods, which when the concern

The pressure plate on the embroidery base and the needle plate press the latter onto the needle plate in a spring-elastic manner. In the fifth embodiment of the hold-down device, this includes a single profiled open or

closed spring steel ring, which is connected to the needle plunger and opposite includes a recess for the needle.

Based on illustrated embodiments, the

Invention described in more detail. Show it:

Figure la is a partial view of the front

End of a needle pusher with an inserted needle, a drill and a hold-down device on an embroidery machine in the rest position,

Figure lb the arrangement according to Figure la with a needle in the

Embroidery base and in the needle hole plate

partially advanced shortly before the first reversal point of the needle,

Figure lc a partial view of a

Needle ram with inserted needle, a drill and a hold-down on one

Embroidery machine with completely in the

Embroidery floor retracted needle at the second reversal point,

2a shows the same arrangement as in FIG. La, but in a further diamond-shaped configuration of the hold-down device in the clamped state, Figure 2b is a perspective view of the

Hold-down in Figure 2a,

Figure 3a shows a detailed view of a hold-down device

a parallelogram arm and a simple spring arm,

Figure 3b is a perspective view of the

Hold-down device in Figure 3a,

FIG. 4a shows a further embodiment of the hold-down device with a pressure plate guided in parallel, FIG. 4b shows a perspective illustration of the

Hold-down device in Figure 4a,

FIG. 5a shows a further embodiment of the hold-down device comprising a spring profile bent as a ring,

Figure 5b is a perspective view of the

Hold-down device in Figure 5a,

FIG. 6 shows a path / time diagram of the needle movement and FIG. 7 shows a section through the needle hole plate, the

Stick bottom, the needle and a shuttle. In the figures, the arrangement of the individual corresponds

Elements of the device as is customary in large embroidery machines.

The presser foot arrangement 1 for an embroidery machine comprises a needle 3 which is attached to the end of a drivable needle pusher 5. In the figures, a drill 7 is clamped in a drill holder 9, which is intended for producing recesses, below the needle 3. Next is in the Figures a fabric paw 11 is shown. The paws 11 are each between two adjacent needles 3 and, if present, between the needles and drills 7

arranged. The cloth paws 11 or their front ends are offset with respect to the axes of the adjacent needles 3 which are arranged on a straight line. The fabric paws 11 are consequently both in the vertical and in the

in the horizontal direction at a distance from the axes of the needles 3.

With reference number 17, the needle hole plate is under an embroidery base 15 arranged thereon with an embroidery base

application (application not shown visibly). The needle 3 in Figure la is in the rear

Reversal point, that is, in the rearmost position and with the greatest distance of the tip 3 'of the needle 3 from the

Needle plate 17. At the front end of the needle pusher 5 is in the first

Embodiment a U-shaped hold-down 19 attached. This comprises a spring steel profile, e.g. a spring steel strip, one end of which is connected to the needle plunger 5 and the other end of which is perforated for the needle 3 to pass through. The attachment to the

The needle pusher 5 is backlash-free and can be done with the aid of a clamping screw or the like. The hold-down 19 according to the first exemplary embodiment (FIGS. 1 a to 1 c) thus comprises a curved leaf spring with a recess formed at its free end 21 through which the needle 3 is passed. The free end 21 encloses the needle 3 with play.

In FIG. 1b, the needle 3 is moved forward by an amount a and now penetrates an application, the embroidery base 15 and the needle hole plate 17. With the needle 3, the paws 11 have also been moved forward and the sole of the foot 23 is located at a distance d to

Surface of the needle hole plate. The front end 21 of the hold-down 19 touches the surface of the stick bottom 13 or an application lying on it, without the

Hold-down 19 is significantly deformed. The needle point 3 'and the needle eye 3 "are now completely behind the needle hole plate 17. The needle movement has not yet ended.

After the reversal of the needle movement at the beginning of the first stroke "F" directed to the left, the stick bottom 15 is kept pressed against the surface of the needle hole plate 17 by the hold-down device 19. As a result, the needle thread 35 guided through the embroidery base 15 is prevented from subsequently moving back to the right in synchronism with the needle 3. It forms between the eye 3 "of the needle 3 and the back of the needle plate 17 by shortening the distance between the eye 3" and a thread loop 37 (FIG. 7) on the embroidery base 15. Now the tip of a shuttle 39 with the

Insert the shuttle thread 41 into the loop 37 and traverse it. As soon as the tip of the shuttle 39 has penetrated the loop 37, the loop 37 of the needle thread 35 is opened further by the second lifting movement "H" of the needle 3 and thereby the passage of the

Shuttle 39 allows.

In Figure lc, the needle 3 is advanced by the amount a plus x and the hold-down 19 or its two ends have approached each other and, since the

Hold-down 19 consists of a spring steel, the free end 21 now presses the stick bottom 15 on the

Surface of the needle hole plate 17 and holds it firmly. The paw 11, which is driven independently of the needle 3, remains permanently at a distance d from the surface of the needle hole plate 17.

After the second reversal point, when the needle eye 3 ″ and the needle tip 3 ′ leave the embroidery base 15, the front end 21 of the hold-down 19 follows back in

Initial position. The hold-down 19 thus lifts off the embroidery base 15 so that it can be displaced essentially without friction on the needle hole plate 17 for displacement for the next stitch. The paw 11 is also lifted off in order to allow the movement of the

Stick bottom 15 not to hinder. By temporarily pressing the stick bottom 15 in

In the area around the needle 3, it can be ensured that a thread loop 37 is formed which is of a size that can be safely grasped or penetrated by the shuttle 39.

The attachment of the hold-down 19 directly to the

Needle pusher 5 ensures that the beginning of the

Pressing the stick bottom 15 against the needle plate 17 always takes place at exactly the right time and also their later lifting.

In the second embodiment of the hold-down device 19 according to FIGS. 2a and 2b, it comprises four leaf spring elements which form a rhombus and are connected to one another at their widest point by rivets 25 or other means. The leaf spring elements in front and those behind the

Connection points can each consist of interconnected legs. The respective V-shaped areas in the area of the rivets are mirror-symmetrical to the needle axis and ensure that the recess for the needle 3 in the area of the tip of the V-shaped parts in every position, i.e. tensioned and untensioned, always in the axis of the Stop needle 3. There is therefore no displacement parallel to the stick bottom 15 during the pressing and relaxing. In a third embodiment of the hold-down 19 according to FIGS. 3a and 3b, in which the hold-down 19 is arranged only on one side of the needle axis as in FIGS. La to lc, a vertical displacement of the front end 21 of the hold-down 19, that is parallel to the needle lock plate, occurs when pressed down by the fact that the rear legs 19 'as

Parallelograms are formed and comprise two rear legs 19 'connected at their ends, which are connected to one another at their ends with spacers 20.

In the fourth embodiment of the hold-down device 19 according to FIGS. 4a and 4b, it comprises two guide rods 33 running axially parallel to the needle 3, which are guided displaceably in a carrier 31 with the needle plunger 5, and on each of which a helical spring 27 is placed which has a pressure plate 29 Keep it guided parallel to the needle axis. The pressure plate 29 is as in the rest

Embodiments provided with a central recess which the needle 3 penetrates.

The two spaced apart parallel

Guide rods 33 are guided axially displaceably on the carrier 31. For this purpose, corresponding bores are provided in the carrier 31. In a preferred embodiment, the carrier 31 comprises two spaced apart plates, so that a relatively long guide path for the Guide rods 33 can be reached. The carrier 31 is preferably detachably connected to the needle pusher 5. On the guide rods 33, the two

Helical springs 27 held slightly tensioned between the pressure plate 29 and the carrier 31.

When embroidering, the pressure plate 29 comes into contact with the embroidery base and any application lying on it, as in the first-mentioned examples, and presses it against the surface of the needle hole plate 17. The pressure plate 29 is consequently precisely guided by the exact guidance in the carrier 31 and is pressed on held exactly parallel to the needle hole plate 17 on the stick bottom.

In a fifth embodiment of the presser foot arrangement (FIGS. 5a and 5b), the presser foot (19) comprises an annular leaf spring profile which, like the embodiment in FIG. 2, is connected to the needle pusher 5 and comprises a recess for the needle 3. In the rearmost position of the needle pusher, the presser button 19 appears to be circular or already slightly oval, in the foremost position of the needle the oval is compressed to such an extent that a pressing force is generated on the embroidery base 15, which lies on the needle plate 17. In a symbolic representation (stroke / time diagram) it can be seen that in order to form a thread loop 37 at the point in time (E), the holding-down device 19 touches the embroidery base 15 reached and then the contact pressure is increased up to the stroke reversal (F) and when the needle retracts in the area of the crossed hatching up to (G) a safe

Looping can take place. The pressing of the embroidery base 15 is maintained until the needle has left the embroidery base after the second stroke after (J).

FIG. 7 illustrates how the shuttle 39 or its tip grasps the thread loop 37.

As an alternative to attaching the hold-down device 19 to the

The hold-down 19 can also use a separate ram or drive to attach the needle ram 5 to the embroidery base

be pressed on (not shown).

Claims

1. Method to use a shuttle embroidery machine to ensure the formation of loops when embroidering elastic embroidery bases (15), embroidery bases (15) with appliqués or embroidery bases (15) with recesses to be embroidered in the embroidery base (15) created by drills,

characterized by the following steps:

- Insertion of the needle (3) into the embroidery base (15) and bring up a spring-mounted one

Hold-down device (19) until the hold-down device (19) makes contact with the embroidery base (15) or the application on the embroidery base (15),

- Continuation of the piercing process of the needle (3) with simultaneous standstill of the hold-down device (19) on the application and the embroidery base (15) and increasing the contact pressure on the embroidery base (15) through built-up spring tension,

- Reversal of the stroke of the needle (3) in a front one

Reversal point and partial retraction of the needle (3) to form a loop of the needle thread between the needle eye (3 ") and the embroidery base (15), which is held by the spring-loaded hold-down device (19) on the

The needle plate (17) is pressed,

Moving the shuttle into the thread loop, - Further withdrawal of the needle (3) from the

Stick base (15) and lifting of the hold-down device (19) from the surface of the stick base (15).

2. The method according to claim 1, characterized in that the hold-down device (19) is brought directly or indirectly from the needle ram (5) or by a feed element driven independently of the needle ram to the stick base (15) and is temporarily pressed against the stick base (15) .

3. The method according to claim 2, characterized in that the pressing of the hold-down device (19) is canceled after the thread loop (37) has been captured by the shuttle from the needle pusher (5) or a feed element from the stick bottom (15).

4. The method according to claim 3, characterized in that the cancellation of the pressing force of the hold-down device (19) takes place by pulling back and lifting the hold-down device.

5. Device for a shuttle embroidery machine for

Ensuring the formation of loops when embroidering elastic embroidery bases (15), embroidery bases (15) with

Applications or embroidery bases (15) with large areas to be embroidered and produced by drills Recesses in the stick bottom (15), the

Embroidery machine a needle plate (17) on the needle side, a drivable one in the needle pusher (5) of the

Embroidery machine-held needle (3) and next to the needle (3) arranged paws (11) and a shuttle track,

characterized in that

A resiliently designed, displaceable hold-down device (19) is arranged as a device between the paws (11) and surrounding the needle (3).

6. The device according to claim 5, characterized in that the hold-down device (19) is carried by the needle plunger (5) and is carried along with the needle (3).

7. Device according to one of claims 5 or 6,

characterized in that the hold-down device (19) is a U- or V-shaped spring plate

comprises, the first end of which can be fastened to the needle plunger (5) and the second end of which is a

Has recess through which the needle (3) can be moved relative thereto.

8. Apparatus according to claim 7, characterized in that the legs (19 ') of the spring steel sheets are riveted together.

9. The device according to claim 8, characterized in that one leg of the spring steel sheet comprises two parallel rear legs (19 ') made of spring steel sheet, which are kept spaced apart by spacers (20).

10. Device according to one of claims 5 or 6,

characterized in that the hold-down device (19) comprises two guide rods (33) which are displaceably guided in a carrier (31) that can be fastened to the needle pusher (5) of the embroidery machine and that the ends of the guide rods (27) are

Pressure plate (29) are connected and that the

The pressure plate (29) and guide rods (33) can be displaced against spring force relative to the carrier (31).

11. The device according to claim 10, characterized in that the spring force by a between the

Pressure plate (29) and the support (31) inserted spring (27) can be generated.

12. The device according to claim 11, characterized in that a spring (27) is arranged on at least one of the guide rods (33).

13. The device according to claim 5, characterized in that the hold-down device (19) from one of the drive of the Needle plunger (5) independent drive is actuated.