DE827894C - Device for creating overlock stitches on sewing machines - Google Patents

Description

The present invention relates to sewing machines and, more particularly, to chain stitch buttonhole sewing machines.

The main purpose of the present invention is to provide an improved practicing stitch forming device to create, which is able to stitches in fabrics of great diversity, such as z. B. wool fabrics, Leather, rubber, etc. with the least amount of necessary adjustment to the facility to form when switching from one of the substances to the other.

Another purpose of the invention is to provide an improved drive mechanism for the to create lower stitch forming devices of a chain stitch buttonhole sewing machine, in which the j Alechanism works calmly and efficiently, and is cheap to manufacture and assemble.

Another purpose of the invention is to provide a stitch forming mechanism which so is designed to guide and supervise the sewing threads so that the usual envelope is flat and arranged near the usual buttonhole slot. I.

When sewing the buttonhole, the needle guides its joints alternately in the line of the buttonhole slot and through the fabric at a distance from the line of the aforesaid slot the end. For the sake of simplicity, the needle threads are drawn through the line of the buttonhole slit as slot joints and the joints passing through the fabric at a distance from the slot as Designated engagement joints. The lower stitch-forming device of the machine has a thread-guiding Gripper or hole gripper, a threadless gripper and a right and a left loop spreader on. In the known buttonhole machines, it does during normal stitch formation of the type in question, the needle pushes its slot to make a loop of the needle thread to throw through the goods. When the needle begins its upward movement, it throws they select a needle thread loop into which the advancing thread-guiding looper enters, who carries his own thread with him, which is caught by the left loop spreader will. The left loop spreader holds the gripper

the thread loop spread out and in such a position that the next time the needle passes through which is its engagement joint, passes through the expanded looper thread loop. if the needle enters the retained looper thread loop, this loop is through the The left loop spreader is released around the shaft of the needle while the needle is moving towards the lower end of their way down. if

ίο the needle begins its next downward movement, it ejects a thread loop, which is grasped by the advancing threadless looper and carried sideways into a position to be grasped by the right loop spreader. The right Fadenausbreiter keeps control of the needle thread loop detected upright until the needle penetrates the work piece at their next slot shock and enters the retained X ^T needle thread loop. The right loop spreader releases the retained needle thread loop immediately after the needle enters it as it descends.

In carrying out the above-described stitch pattern cycle, it is essential that the \ ^T should needle discard a needle thread loop of sufficient size at its upward movement, to make sure that it is detected at the slot impact from the thread-guiding gripper and then of the stringless gripper in which engagement shock. Failure to capture these needle thread loops results in skipped stitches. Ordinarily, there has been no significant difficulty in forming appropriate needle thread loops when buttonhole is applied to conventional fabrics. However, when sewing fabrics such as rubber, leather, woolen fabrics, etc., which have a tendency to adhere to the shaft of the needle and follow it in its upward movement, which is called flutter in the jargon, proper needle thread loops will not, as a matter of fact, be always formed that the fabric does not pull the thread off the needle properly. Fabrics of an elastic nature have a tendency to give way up and down with the needle and therefore do not work with the needle to produce adequate needle thread loops. Considerable thought has been devoted to developing fabric clamps to prevent or reduce this flutter of the workpiece to a minimum in the vicinity of the up and down needle. Although these fabric clamps have proven to be more or less successful, it is necessary when a fabric, e.g. B. rubber, on another, z. B. leather, is passed to make settings of the stitching facilities. The present invention practically eliminates this hitherto required adjustment of the parts and also makes it possible to use a fabric clamp of a very simple design.

With the aim of achieving this end

According to the invention, an improved lower stitch forming device is provided in which the right and left loop spreader control over their respective thread loop sustained long until the needle has entered the retained loop of thread, its own Has thrown the thread loop and the needle thread loops at the slot joint from the thread-guiding Gripper and are detected in the engagement joint of the threadless gripper. The advantages, which are obtained by the fact that the loop spreaders hold back the thread loops for so long, until the grippers enter the thread loops in question, which are upwards from the moving needle are ejected, first, the work piece is against which the work piece bearing surface of the usual throat plate anchored downwards, so that it is during the puncture and withdrawing the needle cannot flutter; second, because the withheld The thread loop is not picked up or solidified until the one is moving forward When the hook enters the thread loop ejected from the needle, the ejected thread loop becomes not disturbed by a moving leg of the previously formed thread loop and thereby rotated out of the area of the advancing looper point, thirdly, the late one Releasing the thread loops through the spreader allows the needle to come out of these loops to move out or free before the loops of thread become solidified; thereby become prevented the thread loops from snapping off the tip of the needle and breaking the needle. This is of particular advantage when using heavy or thick threads or poorer thread types will.

In the drawing, an embodiment of the invention is shown.

Fig. Ι is a front side view, partially in section, of a sewing machine on which the invention is embodied;

Fig. 2 is a right side elevational view of the sewing machine on an enlarged scale showing one Part of the head, part of the fabric clamp and the lower stitch forming device with its looper saddle and the drive connection in section;

Figure 3 is a rear view of the gripper saddle assembly; it gives the star wheel drive and the gearbox for actuating the grapple and the spreader again;

Figure 4 is an enlarged vertical sectional view taken on line 4-4 of Figure 2; it provides the link between the crosshead that drives the loop spreader Rod and the carrying lever of the loop spreader again;

Fig. 5 is a vertical sectional view taken along line 5-5 of Fig. 1, detailing the Again driving the loop spreader according to the invention;

Fig. 6 is a horizontal sectional view taken along line 6-6 of Fig. 1 showing the parallel arrangement the two rotatable grippers for operating the gripper and the spreader again;

Figure 7 is a side view of the gripper saddle From the right, partly in section, it shows the parts of the stitch-forming device and the sewing thread in the Position at the beginning of a stitch formation cycle again; the needle begins its downward movement of the slit stitch, and the previous needle thread loop is made by the right loop spreader held;

Fig. 8 is a right side view of FIG

ίο Stitch forming devices with the throat plate in Cut, it shows the first stage in the stitch formation cycle, in which the needle moves downwards to begin the slit stitch and into the spread out loop of the needle thread has entered, which of the right! Loop spreader is restrained; j

Fig. 9 shows the stitch-forming means in the next stage of the stitch formation \ vill, in which the needle is located at the lower end of its path and the previous needle thread loop still \ ^- on the right Schleifenausbreiter is retained;

Fig. 10 shows the next stage of stitch formation again, when the thread-guiding looper has moved forward and into the next needle thread loop which is ejected by the rising needle, the previous one The needle thread loop is still held back by the right loop spreader, which means anchored the workpiece and prevented it from fluttering with the needle moving upward will;

Fig. 11 is the next position of the stitch formation again, in which the thread-carrying gripper moves towards the end of its needle thread loop-holding path, the right Schleifenausbreiter moves backward to the previous \ ^T adeIfadenschleife release, so that they correctly in .Arbeitsstück can be solidified;

Fig. 12 shows the next position of the stitch formation, in which the thread-guiding looper has moved to the end of its path that encompasses the needle thread loop and through this movement forward one leg of its own thread for the purpose of grasping through it has positioned moving left loop spreader;

Fig. 13 shows the position of the stitch forming devices essentially at the end of the slit stitch, in which position the looper thread loop is retained on the left spreader;

Fig. 14 shows the next position of the stitch formation, in which the needle pierced the workpiece to make the engagement stitch and has entered the looper thread loop to form the engaging stitch and into the looper thread loop has entered, which is kept spread out by the left loop spreader;

Fig. Ι s shows the needle moving upwards, after moving enough to eject a loop of needle thread into which the The nose of the threadless looper has entered, the looper thread loop from the left loop expander is still restrained in some way to anchor the work piece;

Fig. 16 shows the parts in the position after the threadless looper has opened the needle thread loop has detected which is ejected from the needle and that detected loop to engage is presented by the advancing right loop spreader;

FIG. 17 is a transverse vertical sectional view of that shown in FIG Parts with the gripper in view, it reproduces the right loop spreader as he did with the Work piece handle of the needle thread loop in engagement arrives, which is presented by the threadless gripper. ■

Referring to the drawings, the machine frame has a frame 20 and an overhanging head 2T. The usual movable workpiece holder is carried on the head 20 , comprising the lower fabric support plates 22 and the upper clamping members 23; This workpiece holder is given feed and lateral displacement movements in the longitudinal direction in order to arrange the stitches of a buttonhole at a distance from one another. The workpiece holder is moved relative to the stitch-forming device during the sewing process both before and after the sewing process by the usual connections.

The stitch forming device has the usual upper, axially movable back and forth and swinging out needle 24, which works together with the lower stitch forming devices, carried by the rotatable jaw saddle 25; these lower facilities include the usual thread-guiding and threadless grippers 26 and 27 and the reehten and the left Loop spreaders 28 and 29. The gripper saddle 25 carries the usual throat plate 30, which with a Tap hole 31 is provided. The stitch forming device is driven by means which a Machine main shaft 32 includes which in the machine frame 20 is stored. The machine main shaft 32 is connected by means not shown the needle 24 moving back and forth in the axial direction and swinging out laterally. A rotation of the machine main shaft causes the upper and lower stitch forming devices to work in a way to make two-thread chain stitches. It is also common to to provide the lower stitch-forming device with two threadless grippers instead of one thread-guiding one Looper and a sutureless looper, in this case the resulting seam becomes one Be single thread chain stitch chaining. It is also common to use two thread-guiding grippers, in which case the resulting seam is a three thread arrangement. The advantages which through the use of the present invention are obtained, regardless of whether the Machine is equipped for sewing with one thread, two threads or three threads.

The one carrying the lower stitch formation devices Gripper saddle 25 is provided with a tubular shaft 33 (Fig. 2), which in a vertical bearing bush 34 is mounted, which is pressed into a frame block 35, which is removable is attached to the machine housing 20. From the gripper saddle 25 extends upward a post 36, in the upper end of which a horizontal stud 37 is screwed on which a gripper carrier 38 (Fig. 3) is mounted, the one with oppositely extending arms is provided, on which the grippers 26 and 27 are rigidly attached.

The drive connections for the grippers 26 and 27 comprise a link 39 (Figs. 3 and 4), at its upper end on an arm of the gripper carrier 38 and at its lower end the remote head 40 is attached, which is mounted on the upper end of a tubular rod 41

ao is formed, which is slidably fitted into the tubular shaft 33 of the gripper saddle 25. on the lower end of the tubular rod are the spaced apart collars 42 (Fig. 1) placed with thread, between which the end provided with an opening an arm 43 is arranged, which is clamped on a guide rod 44, which for the purpose of lowering ^ right shift is mounted in bearing lugs which are provided on the frame block 35. Of the Arm 43 is therefore able to raise and lower the tubular rod 41, and thereby the gripper carrier 38 to 'pivot its pivot pin 37. The means of raising and lowering of the arm 43 preferably has a handlebar 45 (Fig. 1 and 6), which at its lower End is connected to a crank 46 which is carried at the front end of a short shaft 47 which is stored in the frame block 35. The shaft 47 bears at its inner end Pinion 48 meshing with a three-fold sized gear 49 which is supported by a pin 50 (AbI). 2) supported by the frame block 35. On the rear surface of the Gear 49 is attached to a star wheel 51 which, by means of a pair of drive pins 52, is stepwise Rotary movements are granted; the bolts are diametrically opposite each other on one Drive pulley 53 is arranged, which is fastened on the main machine shaft 32. The teeth of the star wheel 51 are shaped in such a way that there are periods of noticeable standstill between generate the periods of movement of the star wheel. During these periods of downtime, the Crank 46 in one or the other of its middle positions between its extreme upper and lower positions held immovable and in this way arrests the movement of the grippers, in order to avoid a disruptive intervention in the loop spreaders now to be described.

The loop spreader 28 works together with the thread-guiding gripper 26, which in the following Description is referred to as the right loop spreader. As in Figs. 2 and 7 is shown, the right loop spreader 28 is arranged on a support lever 54 which is swingable is mounted around a horizontal bolt 55, which at its opposite ends by im Spaced vertical post 56 is supported which extend from the gripper saddle 25 upwardly. The right loop expander 28 is at its free end with a curved and pointed, a loop sensing horn 57 which will be described later is working to enter a needle thread loop and maintain its control which is presented to the loop spreader by the threadless gripper 27. The right loop spreader 28 adjacent is a second or left loop expander 29 (Fig. 2), which on a support lever 58 is arranged, which is also mounted on the horizontal bolt 55. Like the first loop spreader 28, the second loop spreader 29 is also at its free end a curved and pointed horn 59 (Fig. 12). The two loop spreaders 28 and 29 are pivoted on their common bearing pin 55 by means, which two handlebars 60 and 61 (Fig. 2), which at their upper ends with the support levers 54 and 58 and connected at their lower ends to the opposite ends of a cross head 62 are. The cross head 62 is preferably formed in one piece with the upper end of a control rod 63, which is provided with a bore in the longitudinal direction to provide a passage 64 for the To create looper thread. The rod 63 is for the purpose of back and forth displacement in the axial direction in the tubular rod 41 fitted.

The means for reciprocating the rod 63 controlling the loop spreader is in the essentially the same as that used to control the grippers 26 and 27. From the Fig. I, 5 and 6 it can be seen that on the control rod 63 at a distance from one another collar 65 with Thread are placed between which the lower end of an arm 66 is arranged, the upper end is clamped on a guide rod 67 for vertical displacement are mounted in bushings 68 and 69 (Fig. 5) which are provided in the frame block 35. The means used to raise and lower the arm 66 preferably comprises a handlebar 70, which is connected at its lower end to a crank 71, which is on the front end a second shaft 72 is carried in the frame block 35 substantially parallel to the shaft 47 is stored. The shaft 72 carries a pinion 73 at its inner end, which is connected to the gear 49 combs; the gear ratio between the gear and the pinion is 1: 3. It is obvious that the intermittent rotation of the gear 49 of the loop spreader actuating Rod 63 given an intermittent movement, and that derived from the star wheel 51 Movement is modified by the crank 71, which is attached to the opposite

linden their stroke passes through a dead center position. The resulting control the two loop spreaders 28 and 29, when operated with the controls of the grippers 26 and 27 is brought into the correct relationship in terms of time, a mutual cooperation between the Grippers and the loop spreaders, which results in an improved stitch formation.

Figures 7 to 16 inclusive form explanations of the various stages in stitch formation, and for the purpose of understanding the through the Use of the invention achieved advantages reference is made to them. It should be noted that in the present In the case of a complete stitch formation cycle, two complete back and forth movements of the needle with the circuit in the raised position of the needle and ready to move down begins to form the slit stitch. Since in the complete stitch formation cycle two

Even complete reciprocating movements of the needle are included, the machine arm shaft rotates by 720 ^° . With this in mind, now assume that the machine has made several stitches and that the parts are in the position shown in Figure 7 with a loop 74 of needle thread N ^T retained and on horn 57 of the right Loop spreader 28 is kept spread out, and in which the thread-guiding looper 26 is in a rest position and awaits the downward movement of the needle 24 in order to start with the slit stitch. It will be understood that the needle thread loop 74 extends into the work piece from the previous stitch and that it is sufficiently taut to pull the work piece downward and anchor it to the throat plate 30. Continuing the cycle, the needle (Fig. 8) now moves downward through the workpiece and enters the needle thread loop 74 which has been retained by the horn 57 of the right loop spreader 28. In known machines, the right loop spreader was operated so that immediately after the needle had entered the retained thread loop, the loop spreader was withdrawn and the needle thread loop was left around the needle. When the needle continued its downward movement to the lowest position and began its upward movement to eject the next thread loop, the released thread loop was picked up around the needle to initiate the stitch bonding process, and this picking up or movement of the thread in the needle thread loop often interfered with the next one Needle ejected needle thread loop and rotated it around the needle and into a position outside of the advancing hook point. This resulted in a skipped stitch. In the invention, as can be seen from FIGS. 9 and 10, the right loop spreader 28 is controlled in such a way that it remains in a state of rest and control of the thread loop 74 is maintained until the needle 24 j is in its lowest position Moves down the path and begins to move up again to eject the next loop of thread 75. Indeed, as shown in FIG. 11, the needle thread loop 74 is not ejected from the horn 57 of the spreader 28 until the looper 26 has grasped the next thread loop 75 that has been ejected from the needle 24. One of the major advantages of the delayed release of the retained thread loop 74 is that the work piece is anchored downwardly on the throat plate 30 and, as a result, cannot flutter when the needle moves upward. This is important for the anchored work piece to better strip the thread from the upwardly moving needle, thereby causing a larger loop of needle thread to be ejected through the needle and thus avoiding skipped stitches. Another advantage of the delayed release of the retained thread loop 74 is that the release takes place after the subsequent thread loop 75 has been gripped by the advancing gripper 26. Apparently, the thread loop released around the needle cannot affect the correct position of the subsequent needle loop 75, because it has already been gripped by the gripper 26.

After the looper 26 has grasped the thread loop 75 ejected from the needle 24, the looper moves to the end of its thread-grasping path and in doing so it arranges its own thread V for grasping by the left loop spreader 29. Fig. 12 shows the left loop spreader which has moved forward to the position in which its horn 59 has engaged the looper thread L ^T which leads from the tip of the looper 26 to the last stitch in the workpiece. After the left loop spreader has grasped the looper thread L ^T , the looper is withdrawn to release the needle thread loop 75, leaving a loop 76 of the looper thread on the horn of the left loop spreader 29, as shown for example in Fig. 13. It can be seen that when the needle thread loop 75 is pulled upward and solidified against the work piece, the looper thread loop 76 is relatively taut and actually anchors the work piece against the throat plate 30. With the workpiece in this anchored position, the needle 24 moves through the workpiece and looper thread loop 76 as it engages, as shown in FIG. After the needle has reached the lowest position of its way, it begins its upward movement and throws out another needle thread loop 77 (Fig. 15), into which the advancing tip of the threadless looper 27 enters. Shortly after the looper 27 has entered the needle thread loop yy , the left loop spreader 29 releases the looper thread loop 76, which then moves upwards

Claims (3)

is pulled and solidified. It is evident that the timing of the left loop spreader is such that the looper thread loop 76 is not released by the left loop spreader until the threadless looper 26 has entered the needle thread loop 77 (Fig. 15) which is ejected by the ascending needle 24 is. In this way, the workpiece is anchored against the needle plate 30 during the upstroke of the needle 24 and in this way the workpiece is prevented from fluttering during that particular part of the stitch-forming cycle. The threadless gripper 27 carries the needle thread loop 77 (Fig. 16) in a position in which the horn 57 of the right loop spreader 28 can enter the loop. ₍ Then the threadless looper moves back, leaving the needle thread loop 77 on the loop spreader 28, where the needle can enter the loop of the needle thread with its next slot thrust the known machines, the solidification of the looper thread is delayed. This is advantageous for the reason that, when the right Schleifenausbreiter 28 (Fig. 16 and 17) moves forward to enter the needle thread loop 77 which of the stringless gripper 27 presented the looper thread loop 76 is not firmly solidified against the work piece but is loose, as shown in Fig. 17. Since the looper thread loop 76 is loose, the needle thread loop 77 lies at a greater inclination from the underside of the work piece to the threadless looper 27, and in doing so it offers the largest possible loop of thread 77 for the Entry through the needle 24 during its next movement through the workpiece. After the needle point has definitely entered the needle thread loop 77 , the thread-guiding looper 26 will cause the looper thread L ^{T as it} moves forward (Fig. 17) to come into contact with the upper edge 28 'of the right spreader. The edge 28 'acts as an abutment which works to pull the looper thread loop 76 over close to the buttonhole slot (to the right in Fig. 17) as the looper thread loop is solidified by the advancing looper 26. From the foregoing it can be seen that the right and left loop spreaders be operated in such a way that they maintain a control of their respective thread loops until the needle has ejected its loop and the corresponding looper in the ejected loop has occurred. By maintaining possession of these loops of thread until they are thrown out Needle thread loops are detected, the workpiece is inevitably down or up held anchored in the throat plate so that it does not flutter with the needle moving back and forth can. If the work piece does not flutter but is held firmly against the throat plate, the needle thread is better stripped off the upwardly moving needle, and this is ensured the formation of larger needle thread loops for gripping by the grippers. The anchoring of the work piece against the throat plate 30 is advantageous if to be provided with buttonholes Workpieces of such a kind are used that a secure clamping is not possible is. In addition, the delay in the release of the needle thread by its loop expander until the thread loop ejected by the needle is detected, the ejected needle thread loop not twisted or by the moving leg of the thread loop around the needle brought out of the area of the approaching tip of the gripper, which is the case with known machines the case is when the thread loop on the shaft of the needle is released, immediately after the needle point enters the thread loop on the spreader. Godfather ι a ns ρ is Γ ι · _cn: ι. Device for forming overlock stitches on sewing machines with an upper up and down movable and laterally swinging thread-guiding needle, a pair of grippers arranged below the work piece, which can alternately enter needle thread loops, and a pair of loop spreaders for grasping the thread loops from the loops, after which the loop spreaders present the thread loops of the needle, characterized in that each loop spreader (2 ^, 29) has a curved and pointed loop-engaging horn (57, 59) and is driven by a rod (63) which performs an intermittent reciprocating movement, whereby the loop spreaders remain stationary until one of the grippers (26, 27) enters the needle thread loop ejected by the needle. 2. Apparatus according to claim 1, characterized in that the drive means provided for working the grippers (26, 27) comprise a first shaft (47), to which a second shaft (72) for actuating the loop spreaders (28, 29) is parallel. Serving drive means is arranged and these shafts are given variable rotary movements. 3. Apparatus according to claim 1 and 2, characterized in that the drive connections for actuating the gripper (26, 27) and the loop spreader (28, 29) in addition to the rotatable shafts (47, 72) a gear (49) and meshing with this , have pinions (48, 73) seated on the shafts, For this purpose 2 sheets of drawings 2718 1.