1 1 DEVICE FOR EFFECTIVELY LENO-WEAVING THE LATERAL EDGE, OF A FABRIC IN A
LOOM This invention relates to a new device for leno-weaving the lateral edge of a fabric in a loom which besides being constructionally simple, economical and of small overall size so that it can be installed between the sley and the first heddle frame without having to move the position of said first frame backwards and without having to use auxiliary members, also provides an effective, resisant and reliable three-yarn weave in that the cross-over of the crossing yarns above the straight yarn of the needle can now be obtained by a positive independent cam command, said crossover taking place at the centre of the shed where the point of said needle is carried, said weave consisting specifically of a straight yarn which is passed over the weft yarns plus two crossing yarns which cross over the straight yarn to pass under said weft yarns which fix their interlacement. The device also enables said weave to be obtained for each inserted weft yarn or alternatively every two or more successive inserted weft yarns by simply replacing said positive control cams, and also enables a leno weave to be effected with only two yarns. As is well known, to prevent Bo-called "edge floating", ie the X fraying of the lateral edges of the fabric due to the weft yarns not binding sufficiently to the warp yarns at said edges, a leno weaving of- the lateral edges of the fabric under formation is generally effected by suitable devices generally known as "splitz devices", and using a number of supplementary weaving yarns to be suitably interlaced with the inserted weft yarns. More specifically, in creating the leno weave it is essential that at least one supplementary lateral warp yarn, known as a crossing yarn, crosses over in terms of its position from the right to the left or vice versa of at least one other supplementary lateral warp yarn, known as the straight yarn, which generally passes through the eye of a vertical needle to extend parallel to the other warp yarns of the fabric, said cross-over then being fixed by interlacing with the weft yarns which are inserted between said supplementary lateral warp yarns. Said cross- over operations are generally effected by a plate provided with at least one slot$ at the ends of which the crossing yarn lies on opposite sides of the needle carrying the straight yarn. Various types of leno-weaving or splitz devices are known in the art, allowing various interlacing configurations between two or more supplementary weaving yarns. In one known type, said straight yarn needle and said slotted plate for the crossing yarns are driven with opposing vertical reciprocating motion by the first two heddle frames of the loom. This arrangement has however a series of drawbacks, the most serious of which is that in addition to reducing the number of operative frames available for forming the fabric, it affects the k textile efficiency of the loom in that the warp yarns must now be moved by frames which are necessarily more distant from the reed or rather from the vertex of formation of the fabric, resulting in a greater probability of clinging of the yarns, given their greater length, by the effect of their hairiness which tends to make them stick together, and because said frames have to undergo a longer vertical travel to attain the same shed opening, resulting in overloading of the dobbies because of the large acceleration required, with obvious constructional difficulties because of the high inertia in play, and a consequent undesirable tension increase and thus stressing of the warp yarns. Again said splitz devices controlled by the heddle frames are unable to form the specific three- yarn weave in which the straight yarn always passes over the weft yarns and the two crossing yarns cross over at the straight yarn to then pass under said weft yarns which fix their interlacement. Said drawbacks are overcome in another known type of splitz device in which the entire assembly is kept at rest except for the slotted plate, which is moved vertically by the travel of the sley to which said plate is connected by a cable, the return being provided by a spring. However this known arrangement also has a series of drawbacks, the most serious of which is due to the uncertainty of the positioning of the supplementary crossing yarns at the end of the slot plates, the positioning depending entirely on the particular shape of the slots, which have an upper hooked end. The crossing yarn is in fact very prone to accidentally leave the hooked end and shoot to the other end of the slot, so 4 - completely compromising the weave. A further drawback is that the needle is fixed with the result that the relative straight yarn remains in one and the same position, which necessarily corresponds to the upper or lower end of the shed opening. In this respect, as the cross-over of the crossing yarns must take place precisely in said position in which the point of the needle is exceeded, a considerable raising or lowering of the crossing yarns is required, and these drag the actual inserted weft yarn upwards or downwards, resulting in the triple negative consequence of causing the crossing yarns to slacken due to the tension of the dragged weft yarn with consequent production of a slack and poorly resistant weave, of causing a progressive slackening of the lateral warp yarns which consequent production of a poor quality fabric and weaving problems due to the need to halt the loom to take up the excessive slack of said yarns, and finally of resulting in a greater wastage of weft yarn following its upward or downward displacement as a result of being dragged by the crossing yarns. The object of the present invention is to overcome said drawbacks by providing a leno-weaving device for the lateral edge of a fabric in a loom, which is constructionally simple and of small overall size, in which the cross-over of the crossing yarns is controlled positively and reliably, and in which this cross-over takes place at the centre of the shed. This is substantially attained in that the two crossing yarns are passed through two holes axially opposing about the point of rotation of a rocker plate which, opposed by a spring, is reciprocatingly rotated into two symmetrical positions by a push bar pivoted to the fixed frame and provided with a spring for its return to the vertical, in which positions the two holes have crossed over about the straight yarn needle.
In this manner the crossing yarns are positively and reliably guided into the required position about the needle and hence about the straight yarn, there being no longer any risk in the crossover. Again, not only is said rocker plate moved with vertical reciprocating motion, but the straight yarn needle is also moved with vertical reciprocating motion but in the opposite direction to the former, these movements being obtained by two oppositely shaped cams fixed onto the saze shaft, which is itself driven by the loom drive shaft via a suitable reduction linkage, said cams acting on the underside of follower rollers carried by said elementsy with contact being ensured by springs. In this manner the cross-over of the crossing yarns now takes place at the centre of the shed with the result that the aforesaid yarn problems no longer occur. In addition the independent can drive means that besides making it now simple to establish any law of movement and in particular to therefore provide for a specific three-yarn weave in which the straight yarn always passes above the weft yarns and the other two crossing yarns cross over about the straight yarn to always pass below said weft yarns, it also allows weaving not only at each inserted weft yarn (l/1 weave) but also at every two (2/2 weave) or more inserted weft yarns, ie it enables the weave frequency to be varied by simply replacing the - 6 drive cams by other appropriately profiled cams. Finally the compactness and self-sufficiency of the device as constructed mean that the device can be quickly and easily adjusted in terms of axial position, this being essential when varying the weaving 5 height of the loom. Thus, the device for leno-weaving the lateral edge of a fabric in loom, comprising a needle through the eye of which there passes supplementary lateral warp yarn known as the straight yarn and extending parallel to the other warp yarns of the fabric under formation, and a plate for guiding two supplementary lateral crossing yarns and connected to a structure driven with vertical reciprocating motion, is characterised according to the present invention in that said plate is rocker-pivoted on said vertically reciprocating structure and comprises on its vertical axis two holes axially opposing each other about its pivot pin, said two supplementary crossing yarns being passed through said holes, said rocker plate being opposed by a spring and being reciprocatingly rotated into two symmetrical positions by a push bar pivoted to a fixed frame and provided with a spring for its return to the vertical, in which positions the two holes have crossed over about said straight yarn needle. According to a preferred embodiment of the present invention, said rocker plate is reciprocatingly rotated into the two said symmetrical positions by the fact of said push bar cooperating with two lateral recesses provided in said rocker plate and arranged symmetrically about said vertical axis. The invention will be wore apparent from the description given
1 hereinafter with reference to the accompanying drawings which show a preferred embodiment by way of non-limiting example in that technical or constructional modifications can be made thereto but without leaving the scope of the present invention. For example, instead of using cams, the vertical reciprocating movement of the rocker plate and needle can be obtained by using vertical racks rigid with said elements and cooperating with toothed sectors fixed onto said single shaft. In addition, instead of three-yarn weaves, weaves can be obtained comprising two supplementary yarns by simply eliminating one of the two crossing yarns, and finally instead of weaves at every inserted weft yarn (l/1 weave), weaves at every two inserted weft yarns (2/2 weave) can be obtained, this weave frequency variation requiring mere replacement of the operating cams.
In said drawings: Figure 1 is a perspective view of the device for lenoweaving the lateral edge of a fabric, constructed in accordance with the invention; Figures 2 and 3 show successive stages in the three-yarn weave cycle of the device of Figure 1; Figures 4 to 7 illustrate to an enlarged scale the weaves obtainable with the device of Figure 1, and of which: Figure 4 shows the specific three-yarn 1/1 weave; Figure 5 shows the corresponding three-yarn 212 weave; Figure 6 shows a two-yarn 111 weave; Figure 7 shows the corresponding two- yarn 2/2 weave. In the figures, the reference numeral 1 indicates the fixed frame of the weave device of the invention, acting as a vertical guide for a needle 2, through the eye 3 of which there passes a supplementary warp yarn 4, which is known as the straight yarn because it originates from a feeder not shown in the figure and extends in a straight line parallel to the other warp yarns 5 of the fabric 6 under formation. Said needle 2 is also guided vertically by a Z- shaped structure 7, comprising a hole 8 through which said needle passes, said structure being itself guided vertically by said fixed frame 1 and supporting, rocker-pivoted thereon by the pin 9, a plate 10 for guiding the two supplementary lateral crossing yarns 11 and 12 which pass respectively through the two holes 13 and 14 axially opposing each other about said pin 9 in said plate 10, and through two corresponding arcuate slots 15 and 16 in said structure 7, and are to cross over below the weft yarns 17, 17'q 17" by passing to opposite sides of said straight yarn 4, whereas said straight yarn 4 must always pass above said weft yarns.
Said plate 10 is pivoted at its upper end to the end of a rod 18 slidable telescopically within a block 19 which is pivoted to said structure 7 by the pin 20. A compression spring 21, coaxial with said rod 18 and acting between said block 19 and the fork 22 by means of which said rod 18 is pivoted to said plate 10, tends to extend the rod 18 into its paximum extension position, which is adjustable by the shoulder nut 23 positionable along the thread on the free end of the rod 18, and hence to rotate said plate 10 into one of two end positions which are symmetrical about the vertical, and in which said two holes 13 and 14 in the plate 10 have crossed 1 over their positions about said needle 2, these positions corresponding to the lateral ends A and B of said arcuate slots 15 and 16 respectively. In this respect, said assembly constitutes a bistable system which, energized by the spring 21, finds stable equilibrium only in either of the two positions of maximum rotation of the plate 10 which are symmetrical about the vertical, in these positions the crossing yarns 11 and 12 being made to pass through the ends A or B of the slots 15 and 16.
The lower end of said plate 10 is shaped as a lead-in to facilitate the sliding of a push bar 24 within the one or other of two lateral recesses 25 and 26 provided in the sides of said plate 10, to rotate said plate from one to the other of said syametrical end positions. Said push bar 24 is pivoted to the fixed frame 1 by the pin 27, the flat return spring 28 tending to always maintain it in a perfectly vertical position by acting on an appendix 29 of said push bar 24, verticality being ensured by the shoulder block 30 fixed to the frame 1, which cooperates with the flat portions of said return spring 28. Said verticality ensures that the push bar 24 always acts alternately on the one and other of said two recesses 25 and 26. Again, said cooperation between the plate 10 and push bar 24 is made possible by the fact that the structure 7 and consequently the plate 10 are moved with reciprocating notion by a cam 31 fixed onto an auxiliary shaft 32 rotatably supported by said fixed frame 1 and driven by the loom drive shaft, not shown in the figures, via a suitable reduction linkage of which only the gear wheel 33 rigid with the shaft 32 is visible in the figures. Said cam 31 acts on a follower roller 34 provided on said structure 7, with contact being ensured by a spring 35 acting between said structure 7 and the fixed frame 1.
Finally, the needle 2 is driven with vertical reciprocating motion, but in opposition to the motion of said structure 7, by a cam 36 also fixed on said auxiliary shaft 32 but having an opposite profile to the cam 31, and acting on a follower roller 37 provided on said needle 2, contact being ensured by a spring 38 acting between said needle 2 and the fixed frame 1. The method of operating the device is as follows. Starting from the stage in which a new weft yarn 17' is inserted into the open shed, the corresponding situation is that the needle 2 is at the top dead centre of its travel (see specifically Figure 1) with its straight yarn 4 thus passing above said weft yarn 1V, whereas the structure 7 is at the bottom dead centre of its travel, with consequent interaction between the push bar 24 and recess 26 having generated an anticlockwise rotation of the plate 10 with consequent cross- over of the crossing yarns 11 and 12 which pass respectively through the end A of the slot 15 and through the end B of the slot 16. This cross-over of the crossing yarns 11 and 12 cannot however propagate as far as the forming edge of the fabric 6 because of the presence of the needle 2. In this respect, those portions of the yarns 11 and 12 lying between the fabric 6 and the slots 15 and 16 are not influenced by the cross-over action resulting from the snap-over movement of the bistable system but instead by remaining in their previous positions relative to the straight yarn 4 they rotate about the needle 2. During the next stage the needle 2 and structure 7, controlled by the respective cams 36 and 31, begin to descend in the case of the former and to rise in the case of the latter until they reach the other dead centre of their respective travel. In descending, the needle 2 causes the straight yarn 4 to rotate about and above the inserted weft yarn 17' (see specifically Figure 2), the free end of the push bar 24 disengaging from the plate 10 and the push bar returning to the vertical position under the thrust of the return spring 28, so that the two crossing yarns 11 and 12, no longer hindered by the needle 2, can finally cross over by passing under the inserted weft yarn 17' and over the straight yarn 4 (see Figure 2, but taking account of the fact that the two crossing yarns 11 and 12 have in effect crossed over, even though this way not be apparent in the particular perspective view). At this pointg again under the control of the respective cam 36, the needle 2 returns to its top dead centre ahd with its straight yarn 4 it drags the cross-over point 39 of the crossing yarns 11 and 12 against the edge of the fabric 6 under formation (see Figure 3). The structure 7 descends to its bottom dead centre and the interaction between the push bar 24 and recess 25 generates a clockwise rotation of the plate 10 with a consequent further snapover of the bistable system into its other equilibrium position, with the crossing yarns 11 and 12 crossing over in terms of their positions at the ends A and B of the respective slots 15 and 16 (see Figure 3). Again however, the cross-over cannot take place 4 R - 12 because of the presence of the needle 2, and thus the cycle has again reached the initially described starting state, but with the difference that the crossing yarns 11 and 12 are now at the other ends of their slots because of the opposite position assumed by the bistable system. The described cycle is repeated after the insertion of another weft yarn 17". In this manner, by rotating the auxiliary shaft 32 at one half the speed of the loom drive shaft a three-yarn leno weave of 1/1 type is obtained as illustrated in Figure 4, whereas by eliminating one crossing yarn, for example the yarn 12, a 1/1 weave is again obtained but comprising only two yarns as illustrated in Figure 6. Finally, by merely replacing the cams 31 and 36 with others of appropriate profile a 2/2 weave can be obtained, ie a weave at every two successive inserted weft yarns, either with three yarns as illustrated in Figure 5 or with two yarns as illustrated in Figure 7.