US2981497A

US2981497A - Thread tensioner

Info

Publication number: US2981497A
Application number: US683834A
Authority: US
Inventors: Schurich Herbert
Original assignee: STEINHOF APPARATEFAB KARL
Current assignee: KARL STEINHOF APPARATEFABRIK; STEINHOF APPARATEFAB KARL
Priority date: 1956-09-17
Filing date: 1957-09-13
Publication date: 1961-04-25
Anticipated expiration: 1978-04-25
Also published as: FR1187046A; GB851912A; DE1181855B; CH340305A

Description

April 25, 1961 H. scHURlcH THREAD TENsIoNER Filed Sept. 13, 1957 Fig.1

INVENTOR Fig 2 States; ,Patent THREAD TENSIONER Herbert Schurich,

Karl Steinhof Germany Berlin-Frohnau, Germany, assigner to Apparatefabrik, Berlin-Reinickendorf,

In hand-operated tlat knitting apparatus a thread guide is often used which, as in hand knitting machines, performs the function of feeding to the needles the thread coming from the ball or spool. In apparatus of this kind it is necessary to use a thread returner in the form of a sprung wire arm having at its outer end an eye through which the thread passes. The necessity for providing a thread returner of this kind arises from the reciprocating lock movement in hand-operated flat knitting apparatus since in each of the two end positions the lock has to be moved out beyond the last needles. Since the thread guide is mounted approximately in the middle of the lock, a free thread length, corresponding to about half the length of the lock, arises between the last needles and the thread guide. During the reversing movements of the lock this free thread length has to be brought back, since otherwise this thread length would collect as a loop at the lock, and not only would this cause trouble but also the thread would at first hang completely slack and would not be fed to the needles, so -that no stitches could be formed. These disadvantages are avoided by means of the thread returner.

It was also necessary to provide between the thread guide and the thread ball or spool a thread brake which gives the thread a certain tension for the purpose of swinging the returning bow towards the thread guide, stressing the spring of the thread returner, so that the returning bow is able, at the reversing points of the lock movement, to swing back and thereby return the thread surplus which arises.

ln practical operation it has been found that the thread brake, which usually consists of two sprung discs lying one upon the other, has to be continually regulated by means of an adjusting screw in order to obtain the cor rect thread tension. This regulation depends on the thickness and nature of the thread, and more particularly on the smoothness thereof. This adjustment in addition to being time-wasting and difficult also has the disadvantage that it -does not reliably ensure a uniform thread tension, and the detrimental effect of this appears more particularly when yarns are being used which are not uniform in nature throughout their whole length. Particularly serious trouble arises if there are knops or knots in the yarn.

According to the invention all these disadvantages are avoided by the fact that a thread tensioning device is used which continuously adjusts itself automatically in dependency on the yarn thickness and the nature of the yarn. This problem is solved by the fact that the thread brake is operatively connected with a rockably mounted sprung bow which is used not only for returning the thread but also at the same time for regulating the braking force of the brake, the bow swinging further out when the thread tension increases and weakening the braking action through suitable transmission means.

An embodiment of the invention chosen by way of example is particularly described hereunderwith reference to the accompanying drawings, in which:

Figure l is a longitudinal section through a thread tensioner with spring bow;

Figure 2 shows the thread tensioner in side elevation;

Figure 3 is a front view of the thread tensioner, seen in the direction of the arrow A; and

Figure 4 is a cross section through the thread ten sioner, on line IV-IV of Figure 1.

The thread tensioner comprises a box-shaped casing 1 of which the front wall 2 is made relatively thick and extends over` only part of the height of the box, as is shown in Figure 1. The top and bottom edges 3 of this wall are rounded and serve as support for a brake plate 4 which has curved lobes 5 and 6 engaging over these rounded parts and is thereby secured to the wall 2. The brake plate 4 is of upwardly tapering shape. This can be seen from the edges 7 which are inclined and converge upwards towards one another. At the point where the vertical surface of the brake plate 4 merges into the upper rounded part, guide wings 8 are provided on the two side edges 7, which wings extend vertically upwards; these wings are bent away at right angles out of the surface of the brake plate; their shape can be seen from Figure l. These guide wings areadapted to provide lateral guidance for the thread passing through.

The casing 1 has a rear wall 9 of which the bottom part is provided with a transverse slot 11 serving to accommodate the curved bottom end 12 of another brake plate 13. This second brake plate 13 is pressed against the iirst brake plate 12 by a twin helical spring 14. The two spring coils 15 are both mounted on one and the same pin 16 on the

side walls

17 and 18 of the casing. The wire ends at the two adjacent end faces ofthe spring coils are combined to form a U-shaped bow 1'9. The U-shaped bow bears against the surface of the brake plate 13. The outer wire ends Ztl of the spring coils bear against the rear wall 9 of the casing.

To enable the thread to be easily inserted between the brake plates, one of the side walls, that is to say the side wall 18, is made relatively narrow over almost the whole of its length and is offset towards the yrear wall 9, as shown in Figure 2. In its upper part only, the side wall 18 is ywidened to form a circular disc 21. A stud 22 extends from the top part of the other side wall 17 and bears against the circular part 21 of the side wall 18. The side wall 18 is connected to the stud 22 by means of a screw 23. Beforehand, a helical spring part 24 of a spring bow 2S is slid on to the stud 22 from the side. The helical spring part 24 has a downwardly extending end 26 with a hook 27 engaging in the end of the U-shaped bow'19 of the twin helical spring 14. At the end of the spring bow 25 is an eye 28 through which the thread 29 passes. A forwardly open slot 31 through which the thread 29 can pass, is provided in the bottom 30 of the thread tensioner casing.

In order to guide the thread satisfactorily in the region of the tensioning discs, in addition to the presence of the Wings l3 on one tensioning plate the other tensioning plate 13 is also made slightly curved, so as to form a channel, over the whole of its vertical portion, as is shown in Figure 4. The camber of this curved part amounts to about one to two tenths or a millimetre. The side edges 32 and the top edge 33 of the brake plate 13 are made curved, in order to enable the thread to be inserted easily and also to prevent sharp edges from arising, which might damage the thread or increase the braking action undesirably.

The manner of operation of the thread tensioner is as follows:

lf for instance the tension in the thread 29 increases as a result of a knot reaching the point of entry between the two tensioning plates, the bow 25 is moved downwards at its free end whereby the helical spring end 26 is stressed and urged towards the right so that the stress due to the U-shaped bow 19 of the twin spring 14 is weakened slightly in such a manner as to loosen the brake. This causes the braking action between the two brake plates to decrease, so that theV knot canV slip through the widening gap between the brake plates. When the knot has passed the brake plates in this way, and the thread tension decreases again, the free end of the bow 25 then swings upwards again accordingly so that the helical spring end 26 relaxes again, to the left in Figure 1. The relaxing or unstressing action onl the twin spring 14- thereby decreases, so that this spring again presses the* brake plate 13 somewhat more strongly against the other brake plate 4. In this way uniform thread tension is automatically ensured even when the thread has great irregularities such as knops and knot formations. In the same way, regulation takes place when threads of difterentsurface friction and different tliicknessare used. The required tension for knitting is always produced quite automatically.

-I' claim:

1. A thread tensioner particularly for hand operated at knitting machines, comprising aY casing, a relatively fixed brake component in the casing, a movable brake component within the casing and cooperable with the fixed brake component to coact with the thread passing therebetween, spring means within the casing and in cluding a looped portion bearing against and normally urging the movable brake component against the fixed brake component, an elongated resilient bow-shaped element having a thread guide adjacent one end of said resilient element exteriorly of the casing, a shaft within the casing above the brake components, the resilient element having a helical coil portion mounted on and turnableabout said shaft, said resilient element having a portion extending downwardly from said helical coil portion, connecting means on said downwardly extending portion connecting said downwardly extending portion ofwthe resilient element with the looped portion of the spring means so that as thread tension increases, the thread guide is displaced in a direction' toward the brake components, thereby movingvsaid downwardly extending portion of the resilient element and looped portion of the spring means in a direction away from the movable brake component, thus widening the space between the fixed and movable brake components, and when the tension is relieved, the thread guide moves in a direction away from the brake components so that the downwardly extending portion and looped portion ofthe spring means again bears against the movable brake component.

2. A thread tensioner as claimed in claim l in which said spring means includes a pair of spaced helical coils mounted on a second shaft xed in the casing with thc free ends of the coils bearing against the casing and said looped'portion being provided between the pair of helical coils, and said connecting means being defined by a hook engageable with the looped portion of the spring means.

3. A thread tensioner' as claimed in claim l in which said movable brake component comprises an elongated sheet metal member having outwardly curved side edges and upper and lower curved ends with the curvature extending in a direction away from the xed brake component and the lower curved end being disposed in a transverse slotformed in the rear wall of the casing.

4. A thread tensioner as claimed in claim 3 wherein said sheet metal member is concavely curved throughout the length thereof to provide a channel between thc brake components for guiding the thread.

5.'A thread tensioner as claimed in claim 1 wherein said shaft is secured in the casingy between a circular disk on one side wall and the opposite side wall of the casing.

References Cited in the file of this patent UNITED STATES PATENTS Lindsay July 28, 1953