Leno Selvedge Device and Method of Forming a Leno Selvedge

This invention relates to mechanism for forming a leno selvage in a loom and the method for forming such a selvage.

One of the more successfull leno devices currently being used includes a rotating disc having a pair of spaced guide holes. A pair of leno threads extend through the guide holes from a pair of supply packages mounted on the disc to the selvage. For each rotation of the disc, the two leno threads occupy upper and lower shed positions alternately. Since the guide eyes are mounted on the disc, the movement of the leno threads between upper and lower shed positions is harmonic. Although vertical movement of the leno threads reaches the zero point at the extreme upper and lower positions, it is not a true dwell. Weft insertion in the loom occurs from a period of time before the leno threads reach their extreme vertical or "open" shed positions and a period of time after. The threads will cross after the weft has been inserted and as they move towards opposite vertical positions, a new weft is inserted. The timing of the various loom functions such as weft insertion has to be done within the bounds of the natural harmonic motion of the leno threads. In the past, this natural harmonic motion has been more than adequate. The leno shed is opened to a greater extent than necessary so that the leno threads will be spaced a sufficient amount for a longer period of time. With the advent of higher speed looms, less time is available for opening the leno shed so that there is a greater need to keep the leno shed opening to a minimum. It is also desired that the leno threads cross quickly so that the filling ends will be locked in place before beat-up. There are other leno devices which control the leno shed opening with cams so that the leno threads will dwell in the open position and then cross relatively quickly. This solution is not as good for the loom speeds which are contemplated. The cam has to be larger, there are more moving parts, the moving parts have greater mass and due to the mass of the moving parts, there are limitations in designing a cam contour. Accelerations have to be gradual when there is a change in direction of cam followers and associated parts.

It is a principal object of the invention to provide a mechanism and a method which combines the advantages of low inertia of the "rotating disc" type of leno device and timing versatility of a cam.

The object of the invention is accomplished by guides which are rotated around a horizontal axis. Each guide is mounted on one end of a pivoted lever and a cam follower is mounted on the other end of the lever. The cam follower engages a stationary cam surface which circumscribes said horizontal axis and is designed for causing the leno threads to dwell in the "open" position and to cross relatively quickly thereafter. The levers are relatively small and the amount of pivoting motion very short. The motion of the levers is a combination of pivoting and rotation around the track of the cam. This, together with the small mass of the levers, provides for greater versatility in the design of the cam track. The follower may move from a high point of the cam to a low point in very few degrees of rotation of the cam and consequently provide longer periods of dwell in the high and low positions.

FIG. 1 is a fragmentary elevational view of a portion of a loom with a device embodying the main features of the present invention shown in connection therewith;

FIG. 2 is an elevation of the leno device of the present invention, looking in the direction of arrow 2 in FIG. 1 and shown on an enlarged scale;

FIG. 3 is a vertical section taken along line 3--3 in FIG. 2 and looking in the direction of the arrows and shown on a reduced scale; and

FIG. 4 is a fragmentary plan view of the leno device shown in FIG. 2 showing the leno threads in the vertical crossing position.

Referring more particularly to FIG. 1 of the drawings, there is shown a portion of a loom including a warp beam 10 from which is fed warp yarns W which are formed into a shed 12 by shedding mechanism, not shown. Weft yarn is inserted into shed 12 and is then beaten in by a reed 14 to form a fabric F.

Located at each edge of the loom is a leno mechanism embodying the present invention and indicated generally at 16, only one of which is shown in FIG. 1. The mechanism at the other side of the loom is identical to the one shown in FIG. 1 but of opposite hand.

Leno mechanism 16 includes a hollow shaft 18 rotatably driven in timed relation with the loom and a support disc 20 fixed to the shaft. There are two thread supply packages, 22 and 24, mounted on one side of support disc 20 and two levers, 26 and 28, pivotally mounted at 29 and 30, respectively, on the opposite side of the disc 20. A stationary cam 32 is mounted adjacent levers 26 and 28 on a fixed shaft 34 which extends freely through hollow shaft 18. Cam followers 36 and 38 are mounted on levers 26 and 28, respectively for following engagement in a track 40 in cam 32, see FIG. 3. Tubular thread guides 42 and 44 are also mounted on levers 26 and 28, respectively, at points spaced from followers 36 and 38, respectively, and extend beyond the outer circumference of cam 32.

A leno thread 46 extends from package 22 through a guide 47 and an opening 48 in disc 20 and finally through guide 42 to the beat-up point at the fell of the fabric. A second leno thread 50 extends through a guide 51 and an opening 52 in disc 20 and finally through guide 44 to the fell. Spring tension members 54 engage threads 46 and 50 between guides 47 and 51, respectively, and openings 48 and 52, respectively, to take-up slack and maintain the threads under tension.

Shaft 18 is timed so that disc 20 makes one revolution for two beats of the loom or once for two shed crossings of the warp yarns W. During each revolution of the disc 20, followers 36 and 38 will make one complete trip along track 40. If we assume that a revolution begins from the position shown in the drawings, follower 36 will move from the upper position as shown in FIG. 3 to the lower position in half of a revolution of the disc 20 and follower 38 will move from the lower position as shown in FIG. 3 to the upper position. This will cause leno thread 46 to move from the upper position as shown in FIG. 1 to the lower position and leno thread 50 will move from the lower position to the upper position. During the next half of the revolution of disc 20, followers 36 and 38 will return to the positions shown in FIG. 3 and leno threads 46 and 50 will cross from the lower and upper positions, respectively, to the upper and lower positions, respectively.

The rotation of disc 20 also causes the leno threads to twist or to cross horizontally once for each vertical crossing. To make sure that the leno threads 46 and 50 are kept separated at the time they cross each other vertically, cam 32 is provided with an external cam surface 58 which urges the rearmost leno thread toward the center of the loom which is toward the right as shown in FIG. 4. As shown in that Figure, thread 50 is in the rearmost position and is shown deflected to the right by surface 58 to urge it away from thread 46 to avoid interference therewith. After one half of a revolution of the disc 20, the positions of guides 42 and 44 will be reversed so that thread 46 will be in the rearmost position and deflected to the right as viewed in FIG. 4. Cam surface 58 guarantees that leno threads 46 and 50 will not interfere with each other during vertical crossing thereof.

Cam track 40 is designed so that followers 36 and 38 dwell substantially in the upper and lower positions as shown in FIG. 3 and then move vertically relatively quickly thereafter. The vertical crossing of the leno threads coincides with the vertical crossing of the warp yarns. This crossing occurs before beat-up to insure that the weft yarn which has just been inserted is held sufficiently.