EP0066525A2 - Method and apparatus for simultaneously cutting, at several spots, the welt thread of a mat or knitwork on a knitting machine - Google Patents

Abstract

1. Device for cutting the same weft thread (11) of a plaited or knitted article at several locations on a shot-type knitting machine incorporating, in particular, needles (4) with latches (15) having a to-and-fro movement between a low position and a high position, slots (6) for closing the latches (15) of the needles in the low position, bodkins (2) for arranging a warp thread (12) round each needle (4) with a latch (15) at the locations where stitches are made round the weft threads, and holding-down sinkers (8) having grooves (14) for receiving each weft thread which has been surrounded by stitches, the said device being characterised in that it comprises cutting elements (13) arranged fixedly on the needle (4)-carrying bar (3) and thus having the same to-and-fro movement as the needles (4), and making it possible to sever the said weft thread (11) at several locations simultaneously, just after it has passed into the grooves (14) of the holding-down sinkers (8) and after each stitch has been tightened round the said weft thread.

Description

The present invention relates to a method and a device for simultaneously cutting, in several places, the same weft thread of a mat or knitted fabric, on a knitting machine. The method and the device according to the present invention thus make it possible to obtain continuously and simultaneously, on the knitting machine, at least two distinct strips of knits or mats which can be collected each continuously, for example by winding around spools . More specifically, the present invention relates to a method and a device for simultaneously cutting and in several places the weft yarn of a mat or knitted fabric on a weft insertion knitting machine.

The cutting, in several places, of the same weft thread of a mat or knitted fabric is a delicate operation which must imperatively be carried out simultaneously at all the places chosen for cutting. Indeed the weft thread of the knitting or mat must be under tension at the time of cutting and if the latter does not take place at the same time in all the places chosen and desired for this cutting, from the moment when there has been cutting in one place it is practically impossible to have a correct cutting in the other chosen places because the weft thread is no longer taut.

An object of the present invention is therefore a method and a device making it possible to cut simultaneously, in several places, the same weft thread of a mat or knitted fabric on a knitting machine.

Another object of the present invention is a method and a device making it possible to cut the weft thread of a mat or knit in several places on a knitting machine, while being sure of obtaining equal lengths for each segment of thread sectioned frame.

Another object of the present invention is a method and a device specially well suited for cutting the weft thread of a mat or knitted fabric, when this weft thread is in the form of hollow fiber, for example in the form of hollow fiber usable in the field of artificial kidneys. Thus this hollow fiber can for example be made of cellulosic material.

Another object of the present invention is a process and a device specially well suited for cutting in several places the weft thread, in the form of hollow fiber, a mat or knitted fabric, while the threads used for making the stitches around the weft thread is in the form of non-hollow thread with a diameter less than the outside diameter of the hollow fibers, for example twisted multi-strand thread.

It has now been found, and this is what is the subject of the present invention, a device for simultaneously cutting, in several places, the weft thread of a mat or knitted fabric, on a knitting machine, said device being characterized by comprising at least three cutting elements which make it possible to cut said weft thread just after the stitch of each warp thread has been tightened around said weft thread and while a stitch is being formed on the thread next frame, where you want it.

An object of the present invention is also a method for cutting simultaneously and in several places the same weft yarn of a mat or knitted fabric on a knitting machine, characterized in that said weft yarn is cut into at least three places immediately after each stitch of each warp thread has been tightened around the weft thread and considering that a stitch is being formed, at the desired locations, on the next weft thread.

The description of the method and the device according to the present invention will be better understood with the aid of the attached figures which illustrate schematically and without a determined scale, an embodiment of the device according to the present invention.

• La figure 1 est une vue schématique représentant plus spécialement les éléments fondamentaux pour la formation d'un tricot ou natte sur une machine à tricoter telle que celle précédemment citée.
• La figure 2 est une vue schématique en perspective montrant plus particulièrement la position relative de certains éléments et plus particulièrement le positionnement des éléments coupants selon l'invention.
• Les figures 3 à 5 montrent de façon schématique comment agissent les éléments coupants selon l'invention lors de la formation des mailles autour des fils de trame.

The figures below relate more specifically to a knitting machine of the type, known worldwide, LIBA COPCENTRA HS, with weft insertion, on which the method and the device according to the present invention are particularly effective.

• Figure 1 is a schematic view showing more specifically the fundamental elements for the formation of a knit or mat on a knitting machine such as that previously mentioned.
• Figure 2 is a schematic perspective view showing more particularly the relative position of certain elements and more particularly the positioning of the cutting elements according to the invention.
• FIGS. 3 to 5 schematically show how the cutting elements according to the invention act during the formation of the meshes around the weft threads.

• - la barre (1) à passettes sur laquelle sont fixées des passettes (2) oans lesquelles passent les fils (12) de chaîne servant à faire les mailles,
• - la barre (3) à aiguilles sur laquelle sont fixées les aiguilles (4),
• - la barre (5) à coulisses sur laquelle sont fixées les coulisses (6),
• - la barre (7) à platines de cueillage sur laquelle sont fixées les platines (8) de cueillage, et
• - la barre (9) à platines d'insertion sur laquelle sont fixées les platines (10) d'insertion du fil de trame.

Figure 1 shows the main elements involved in the formation of stitches around the weft threads in a knitting machine of the LIBA COPCENTRA HS type. We find in particular:

• - the bar (1) with passettes on which are fixed passettes (2) oans which pass the son (12) of warp used to make the meshes,
• - the needle bar (3) on which the needles (4) are fixed,
• - the slide bar (5) on which the slides (6) are fixed,
• - the bar (7) with picking plates on which the picking plates (8) are fixed, and
• - The bar (9) with insertion plates on which are fixed the plates (10) for inserting the weft thread.

The weft threads (11) advance towards the mesh formation zone by means of endless belts holding the threads by hooks, a belt being at each end of the weft threads. In FIG. 1 the weft threads (11) are for example hollow fibers, but we will still call them weft threads (11) for easier description. These son (11) advance in Figure 1, from right to left, driven by the belts not shown and they are substantially perpendicular to the plane of the drawing.

It has been found that a knitting machine such as that having the elements described above is particularly well suited for the manufacture of knitted fabric or mat for use in making bundles of hollow flora. Indeed with such a knitting machine, using as weft yarns (11) hollow fibers, for example in regenerated cellulose of CUPROPHAN brand (internal diameter 0.2 mm, wall thickness: 0.01 mm) and yarns ( 12) 70 denier chain (9,000 meters weigh 70 g) in polyester, it is convenient to obtain a knit or mat which can be used for the production of bundles of hollow fibers usable in artificial kidneys. It is for example possible, over the entire length of a weft thread (11) (which is about 3.2 meters) to make, with the warp threads (12), stitches every 2 to 3 centimeters . In this case the warp threads (12) pass through passers (2) spaced apart from 2 to 3 centimeters. On the other hand, at the places where it is desired to cut the weft thread (11) having a tight mesh around it, that is to say where it is desired to cut the knitted fabric or the mat obtained, it can be advantageous to provide a few closer stitches (for example 1 to 2 mm apart) so that the portions of knitted fabrics or mats obtained are better held at their sectioned ends, as will be better understood later. In this case, there are provided at the closer passettes (2).

It should be understood that, in the present application, the term mat or knit generally means any product comprising weft threads (11) (which may be in the form of hollow fibers) parallel to each other and warp threads (12) substantially perpendicular to the weft threads (11), said warp threads (12) forming meshes around the weft threads (11).

The different elements (1 to 10) participating in the formation of the stitches around the wefts (11) all have a particular known movement which will be specified below at the same time as the action of the cutting elements (13) included will be described. in the device according to the present invention. The weft thread inserting plates (10), the picking plates (8) and the needles (4) are all spaced from one another and during their respective movements do not come into contact with each other . Only the slides (6), also called tabs by specialists, are in contact with the needles. As for the cutting elements (13) they are also spaced from the other elements above.

In the device according to the present invention, the cutting elements (13) are fixed to the needle bar (3) (4), for example at places where needles (4) have been removed, the slides (6) having also been removed at these locations. Therefore the elements cutting edges (13), which are for example knives, pass between the picking plates (8) and the insertion plates (10). Figure 2 shows in perspective how the knives (13) pass between the plates (8) for picking, as well as the needles (4) with hooks (15).

Figures 3 to 5 show the mode of action of the cutting elements (13) of the device according to the present invention during the formation of meshes around a weft thread (11), it being understood that the needles (4) and the knives (13) are in different planes (see Figure 2).

Figure 3 corresponds to the position reached when a weft thread (11) having a formed mesh (at each desired location over its entire length) has just passed from the back (17) of the plates (8) for picking, in the groove (14) of these. Each picking plate (8) is in its extreme position towards the right and will start its movement towards the left, that is to say towards the front. Each insertion plate (10) has reached its highest and most advanced position, that is to say the leftmost of the figure. The weft thread (11) around which a new mesh will be formed (at the desired locations) is thus enclosed between the threads (12) passing through the passettes (2) and the insertion plates (10). The needles (4) have reached their lowest position and their hooks (15) or heads are closed by the slides (6). Each needle (5) comprises a loop of warp thread (12). The cutting elements (13) are in their lowest position, like the needles (4). The passettes (2) execute the piers-sous and will start their movement backwards, that is to say the right in the figure.

Figure 4 corresponds to a position when the needles (4) advance to their highest position. Each picking plate (8) has reached its most advanced position, towards the left, and the meshes previously felled in the groove (14) of each plate (8) are stretched to take their final shape.

The insertion plates (10) are in the advanced position and the weft thread (11) around which each mesh is being formed is well enclosed between each insertion plate (10) and the warp threads (12). The slides (6) are in the lower position and therefore the needles (4) have their hooks (15) open: the needles (4) are said open. Of course the cutting elements (13) fixed on the bar (3) to needles (4) had the same upward movement as the latter. The passettes (2) complete the piers-sous.

Figure 5 corresponds to the position when the needles (4) have reached their highest position, as well as the cutting elements (13). As shown in FIG. 5, each knife has cut, during its upward movement, the weft thread (11) which has just passed through the groove (14) of each picking plate (8). The length of each knife (13) is such that it cuts the weft thread (11) which has just passed through each groove (14) of each plate (8), thanks to its face (16) Lou side] cutting edge facing to this wire (11), but do not cut the weft wire (11) on the back (17) of each plate (8) and around the ₄ uel the meshes are in formation. The thickest part, or chest, of each needle (4) is in the loop of the corresponding warp thread (12), while each pass (2) is in its rearmost position and will begin its enveloping movement of the needle (4) and return to the front, as shown in dotted lines. Each insertion plate (10) is in its lowest position and is going backwards. The weft thread (11) around which meshes are formed is enclosed by the needles (4) and the warp threads (12).

The sequence of the respective movements of the different elements is not shown, because it is quite understandable without a figure. The insertion plates (10) continue their movement backwards, in the low position, to then get up and have their head (18) between the two weft threads (11) which follow the latter around which a mesh is in training. The insertion plates (10) are then in the rear extreme position. The needles (4) and the knives (13) descend to their low position and the slides (6) go up to close the hooks (15) of the needles (4) before the latter (15) pass through the chain mouth. Towards the end of the descending movement of the needles (4) and of the slides (6) the picking plate (8) begins its movement before and at the end of this the weft thread (11) around which meshes come from be dropped into the groove (14) of the inserts. We are then in the position of figure 3.

With the device described above, it is thus possible to obtain as many fractions of the knitted fabric or the mat before sectioning as there are cutting elements, minus one. If there are fourteen knives over the entire width of the machine (length of the weft thread) it is thus possible to obtain thirteen mats or knits which can all be wound simultaneously on take-up reels. Each fraction of the initial mat has its weft threads held together by warp threads forming meshes around them. It is clear from the description that the sectioning does not take place at the precise places where there are meshes.

Many variants of the device described above are within the reach of the technician. By way of example, the cutting elements (13) which have been described above in the form of knives having a cutting face (16) can be replaced by heated metal wires which then cut the weft wires under the effect of the heat. Like the knives previously described, these heated metal wires are fixedly placed on the needle bar (3) (4). These heated metal wires thus have the same reciprocating movement as that of the needles (4). These metal wires can be heated electrically.

It may also be advantageous, towards the ends of the weft thread (11) to be cut by the two cutting elements (13) located at the ends of the knitting machine, to provide means for ensuring that said thread is substantially straight in its places, that is to say in the extension of said wire located in the grooves (14) of the plates (8) for picking. Indeed, towards its ends, the wire is still maintained and driven, at the time of cutting, in particular by the hooks of the endless bands. To make the thread substantially straight over the entire length where it is cut by the cutting elements (13) it is therefore advantageous, on each side of the knitting machine, between each extreme cutting element (13) and the most endless strip close, to provide a device which makes the weft wire to be sectioned substantially straight, that is to say in the extension of the same weft wire included in the grooves (14) of the plates (8) for picking. To do this, we can have these two places on a fixed part of the machine, a device such as a wire or metal rod, rigid and smooth, the positioning of which can be fixed both in a horizontal plane and in a vertical plane with respect to the ground. The positioning of each end device of the frame wire is obviously done by trial and error until the cutting of the frame wire (11) is satisfactory over its entire length.

Other embodiments of the method and device described above are within the reach of the technician. It can be said that the present invention is not departed from whenever a weft thread, around which stitches have just been formed and tightened, is cut in several places of its length, while a stitch is in training on the next weft thread. It can also be considered that it is not departing from the present invention insofar as the cutting elements (13), cutting the weft thread in several places, are fixed on the needle bar (3) (4) and cut said thread during the upward movement of said needles.

Claims (10)

1. - Device for simultaneously cutting and in several places the same weft thread (11) of a weft of a mat or knitting, on a knitting machine, said device being characterized by the fact of comprising at least three cutting elements (13) which allow to cut said weft thread just after the mesh of each warp thread has been tightened around said weft thread and while a mesh is being formed on the next weft thread, at the desired locations. 2. - Device for cutting, simultaneously and in several places, the same weft thread (11) of a weft or knit on a knitting machine with weft insertion comprising in particular needles (4) with hooks (15) having a back and forth movement between a low position and a high position, slides (6) to close the hooks (15) of the needles in the low position, passettes (2) to arrange a thread (12) of warp around each hook needle (4) (15) at the places where stitches are made around the weft threads, picking plates (8) having grooves (14) for receiving each weft thread having been surrounded by stitches, and weft thread insertion plates (10), said device being characterized by comprising cutting elements (13) which make it possible to cut said weft thread (11) immediately after it has passed through the grooves (14) plates (8) for picking and after each stitch has been tightened around said weft thread . 3. - Device according to claim 2, characterized in that the cutting elements (13) are fixedly disposed on the bar (3) with needles (4) and thus have the same reciprocating movement as the latter (4 ). 4. - Device according to any one of claims 2 and 3, characterized in that the cutting elements (13) are arranged on the bar (3) with needles (4), in locations where the needles (4) have been removed. 5. - Device according to any one of claims 2 to 4, characterized in that the cutting elements (13) cut the thread (11) weft having stitches during the upward movement of the needles (4) after the tightening of each mesh. 6. - Device according to claim 5, characterized in that the cutting elements (13) have a length such that they cut during their upward movement the thread (11) of weft having just passed through the grooves (14) of the plates ( 8) for picking, but that they do not cut the next weft thread which has not yet passed through the groove (14) of the picking plates (8). 7. - Device according to any one of the preceding claims, characterized in that each cutting element (13) consists of a knife. 8. - Device according to claim 7, characterized in that each knife (13) cuts by its side (16) cutting edge facing the weft thread. 9. - Device according to any one of claims 1 to 6, characterized in that each cutting element (13) consists of a heated metal wire. 10. - Method for simultaneously cutting and in several places the same weft thread of a mat or knitting on a knitting machine, characterized in that said weft thread is cut in at least three places immediately after each stitch of each warp thread has been tightened around the weft thread and while a stitch is being formed, at the desired locations, on the next weft thread.

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