EP0014601B1 - Improved net-knottingmachine - Google Patents

Abstract

1. Machine for knotting nets in which a plurality of warp-beam threads and a plurality of threads (6) from shuttles (7) mounted on a movable cradle (12) are knotted two by to form a mesh by means of rows of movable needles comprising in particular hooked needles which are arranged to pass each warp-beam thread around the corresponding shuttle (7), the resulting net (8) being advanced, after each row of knots is made, between the facing surfaces of two smooth-faced bars (10, 11) arranged parallel to the rows of needles and positioned immediately below the level of the knotting zone (5), the rearward bar (10) more remote from the shuttles being fixed and the cradle (12) carrying the shuttles (7) being controlled to move in turn away from and towards the knotting zone, characterized in that said reciprocating movement of the cradle (12) takes place before the passing of the warpbeam threads around the shuttles (7), and that the forward bar (11) is movable and is mechanically controlled to move in a rhythmic manner firstly to engage against the rearward bar (10) before the commencement of said reciprocating movement of the cardle (12) and to grip the net (8) in order to immobilise it during the making of a row of knots, and thereafter to move away from the rearward bar (10) in order to permit the subsequent onward advance of the net (8).

Description

The invention relates to thread weaving machines in which a multiplicity of shuttle threads and a multiplicity of beam threads are knotted two by two to form stitches by means of rows of movable needles, notably comprising hook which pass each beam wire around the corresponding shuttle.

More specifically, such machines include a row of eyelet needles through which the beam yarns pass and which cause the latter to form at least one loop around first and second needles aligned in two other rows. In addition, said hook needles, also aligned in a row, attract the warp threads through the loops they form and pass them around the shuttles, so that these threads, after leaving the hook needles, pass around the shuttle wires, and exert a traction on them when tightening the knots (see French patent n ° 72/46 187).

This last phase of knot making is sometimes defective when the shells contained in the successive shuttles are unevenly full, because the resistance to rotation offered by the shells is different, which affects the tension of the threads. of shuttles, then warp yarn which also becomes different from one stitch to another, causing an irregular knotting.

To remedy this drawback, it is known to provide in the shuttles a weight attached to the wire which each of them delivers, and to move the cradle containing the shuttles alternately back and forward so that each advance following a decline, a certain length of shuttle wires is delivered, under constant tension defined by the precipitated weight. This arrangement has the disadvantage of requiring larger shuttles, since they must contain not only the wire shell, but the additional weight, which lengthens the path of the beam wires around the shuttles must be increased proportionally , with corresponding reduction in the speed of making the fillets. In addition, the greater length of beam yarn to be supplied then accentuates the effects of their elasticity, which makes adjustments more difficult and leads to irregular threads.

We know on the other hand, by the English patent n ° 660 370, a machine of the indicated type in which the finished net is evacuated, after each operation of making a row of knots, between the opposite faces of two flat bars parallel to the rows of needles and located immediately downstream of the knotting level, the rear flat bar being fixed, while the cradle carrying the shuttles is controlled to move away and alternately approach the knotting area. In this known machine, the tightening of the knots depends on the tension of the wire coming from the shuttles, which can vary from one shuttle to another, so that this machine also has the drawback mentioned above.

It is from a machine of the latter kind that the said drawback can be eliminated by virtue of the invention and that delivery by the shuttles of wires under constant tension can be obtained, without having to add additional weights to the shuttles. According to the invention, the aforementioned back-and-forth movement of the cradle of the shuttles is controlled before passage of the beam wires around the shuttles, and the front flat bar is movable and is controlled mechanically, in a clocked manner, for apply against the rear bar before the start of said back-and-forth movement of the shuttles and pinch the net in order to immobilize it during the operation of making a row of knots, then to move away from the bar posterior to allow subsequent evacuation of the net. Preferably, the cradle of the shuttles moves away from the knotting area by moving in the direction of evacuation of the net, and approaches it by moving in the opposite direction. This normally corresponds to a vertical back and forth movement.

Thus, in the machine according to the invention, the shuttles, moving away then approaching the knotting area, deliver a certain length of thread under zero tension, therefore always the same regardless of the filling of the shells, while the net, during this phase, is kept pinched between the anterior and posterior bars, thus being prevented from falling under its own weight while it is no longer supported by the shuttle wires.

The description which follows, with reference to the accompanying drawings by way of nonlimiting examples, will make it possible to understand clearly how the invention can be put into practice.

Figure 1 shows schematically, in side elevation with partial section, a part of a thread weaving machine incorporating the invention.

Figures 2 and 3 illustrate two successive phases of the making of a knot.

We see in Figure 1 the knotting area 5 of a net weaving machine, where, for each column of stitches of the net to be made, a beam yarn (not shown) descending vertically is knotted by means of various needles (not shown) with a thread 6 from a shuttle 7. On the action of take-up rollers (not shown), the thread 8 produced descends step by step, after each operation of making a row of knots in the zone 5, along a fixed plate 9, passing between a rear flat bar 10, integral with the plate 9, and a front flat bar 11. The bars 10 and 11 extend horizontally over the entire width of the machine , as well as the rows of needles.

The shuttles 7, juxtaposed in a horizontal row, are carried by a common cradle 12 animated by a vertical back-and-forth movement thanks to a mechanism not shown.

The front bar 11 is carried by substantially vertical rods 18, which pivot about a horizontal axis 13 fixed under the action of cranks 14 - driven by an oscillating movement synchronized with the movement of the rows of needles and of the other members mobile of the machine - by means of connecting rods 15 articulated to the cranks 14 and connected by flexible seals 16 to the rods 18.

During each knotting operation, the front bar 11 is applied, by pivoting about the axis 13, against the front plate 10, so as to pinch the net 8 and immobilize it. The cradle 12 then lowers the shuttles 7, each then delivering a certain length of wire 6 by unwinding of the shell, then makes them rise, which gives slack to the strands of son 6 delivered. Each hook needle 19 (see FIG. 3) passes the corresponding beam wire 20 around the associated shuttle 7, so that the wire 20 comes around the relaxed strand of wire 6 and drives it effortlessly when tightening the node. All the nodes of the row being now made and tightened, the jaws formed by the bars 10 and 11 open by spacing the anterior bar 11 and the net 8 freely executes a downward evacuation step. Then the net 8 is again pinched for the next knotting operation, and so on.

The arrangement according to the invention has the advantage of ensuring the delivery of shuttle wires under constant tension, namely zero, therefore independent of the state of filling of the shells that they contain and of their faculty of rotation. It also has other advantages, illustrated by FIGS. 2 and 3.

Figure 2 shows the initial phase of knotting where the eyelet needle 21 lowers the beam yarn 20 to make it form a loop 20 '(see Figure 3) around' the first needle 22 and the needle second 23. According to the technique used until now, the anterior bar remains in a fixed position 11 a apart from the posterior bar 10, and the thread 20 takes the configuration 20a where it passes over the needle 23 in a region close to the end of it, so it may escape. On the contrary, according to the invention, the front bar is then in the pinching position 11b and the wire 20, guided by the upper edge of said bar, follows a path 20b more distant from the end of the needle 23, so that he cannot escape it.

FIG. 3 shows the knotting phase where the thread 20, passing through the loop 20 'which it forms around the needles 22 and 23, is pulled by the hook needle 19 in order to pass around the shuttle 7. This traction exerted by the needle 19 tends to cause said loop to escape from the needles 22, 23. This can easily occur when the front bar is in the fixed position 11a. But when this bar is in position 11b, the loop is perfectly maintained by the wire 20b which emerges therefrom and which is pinched between the bars 10, 11b.

Claims (2)

1. Machine for knotting nets in which a plurality of warp-beam threads and a plurality of threads (6) from shuttles (7) mounted on a movable cradle (12) are knotted two by two to form a mesh by means of rows of movable needles comprising in particular hooked needles which are arranged to pass each warp-beam thread around the corresponding shuttle (7), the resulting net (8) being advanced, after each row of knots is made, between the facing surfaces of two smooth-faced bars (10, 11) arranged parallel to the rows of needles and positioned immediately below the level of the knotting zone (5), the rearward bar (10) more remote from the shuttles being fixed and the cradle (12) carrying the shuttles (7) being controlled to move in turn away from and towards the knotting zone, characterised in that said reciprocating movement of the cradle (12) takes place before the passing of the warpbeam threads around the shuttles (7), and that the forward bar 111) is movable and is mechanically controlled to move in a rhythmic manner firstly to engage against the rearward bar (10) before the commencement of said reciprocating movement of the cradle (12) and to grip the net (8) in order to immobilise it during the making of a row of knots, and thereafter to move away from the rearward bar (10) in order to permit the subsequent onward advance of the net (8).

2. Machine in accordance with claim 1, characterised in that the cradle (12) for the shuttles (7) moves away from the knotting zone (5) by moving in the direction of advancement of the net (8), and moves towards the knotting zone by moving in the opposite direction.

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