De Corte, Antonius Wilhelmus Maria (Deltasingel 33, SL Deurne, NL-5751, NL)
Hiemstra, Hendrik (Wolfsklauw 14, NL Deurne, NL-5734, NL)
Puissant, Patrick (Bochtenstraat 35a, Laarne, B-9270, BE)
Cox, Gerardus (Peelhorst 3, GR Deurne, NL-5754, NL)
Gorris, Joannes Josephus Henricus Marie (St. Eligiuspad 3, EG Eindhoven, NL-5645, NL)
De Corte, Antonius Wilhelmus Maria (Deltasingel 33, SL Deurne, NL-5751, NL)
Hiemstra, Hendrik (Wolfsklauw 14, NL Deurne, NL-5734, NL)
Puissant, Patrick (Bochtenstraat 35a, Laarne, B-9270, BE)
Cox, Gerardus (Peelhorst 3, GR Deurne, NL-5754, NL)
DESCRIPTION The invention relates to a carrier according to the preamble of claim 1 for inserting a weft yarn into the shed of a weaving device via insertion means arranged on one side or on both sides of the shed. A carrier as referred to in the introduction above is described in Dutch Patent Application No. 73/09850, for example, and more in particular in US Patent No. 4,046,174. A weft yarn from a supply bobbin is connected to the known carrier, also called shuttle, after which the carrier is launched as a projectile by the insertion means disposed on either side of the shed, using a medium under pressure, for example pressurized air, and carried through the shed via guides arranged in the shed. A drawback of these known devices, and in particular the shuttle as disclosed in US-Al-4,046,174, is the fact that all the energy required for moving the voluminous and thus heavy carrier through the shed must be imparted to the carrier at the beginning of the movement, i.e. at the location of the insertion means. In order to be able to carry the projectile through a shed of reasonable width, a large amount of energy has be supplied to the carrier at the beginning of its movement, which means a very high initial velocity, resulting in high peak tensions in the weft yarn to be transported. Furthermore this means that the carrier needs to have a fairly large inert mass. These aspects of the known weaving device impose limitations on the functionality thereof as regards the speed, the complexity and the maximum width of the fabric to be manufactured. The above limitations are partially overcome by the carrier and the weaving device as described in Dutch Patent Application No. 1004173. In the weaving device that is described in said patent application, auxiliary blowers are disposed in the shed, which auxiliary blowers are provided with outflow openings for the medium under pressure, which impacts on an impact surface of the carrier to be guided during operation so as to assist in the movement of the projectile through the shed. Using these aspects, it is no longer necessary to impart all the energy required for carrying the projectile through the shed to the carrier at the beginning of the shed. Although in fact the width of the shed is no longer bound by limitations when auxiliary blowers are used, it is still necessary to use a carrier having a large inert mass, and this embodiment of a known weaving device is more complex as regards its construction and control. Dutch Patent Application No. 1023943 (not pre-published) furthermore proposes the use of a carrier that surrounds a weft yarn in the form of a clew, which clew extends the length of the shed upon insertion into the shed. The dimensions of said carrier correspond to the dimensions of the clew, and the weight of the carrier is of the same order as that of the clew to be inserted. The low weight and the limited dimensions of the carrier used in NL-1023943 obviate the need to use complex and robust means for inserting and decelerating the carrier, so that an insertion mechanism of simple construction will suffice. In addition to that, the movement of the known carriers through the shed is adversely affected by the air jet pulse being delivered to the carrier by the insertion means of the weaving device. The aerodynamic behaviour of the carrier is adversely affected by the air jet pulse, to such an extent that the movement of the carrier through the shed takes place in a rectilinear, not very stable manner. This leads to weaving faults caused by the fact that the movement through the shed and the insertion of the weft yarn do not take place (completely). To obviate in particular this latter drawback, it is the object of the invention to provide a carrier for inserting a weft yarn into the shed of a weaving device, which can be characterized by an improved aerodynamic behaviour and consequently a more stable movement through the shed during the "shot", resulting in a strongly improved weaving process. According to the invention, the air transmitting area of the pull-out opening is smaller than or equal to the air transmitting area of the means in the circumferential surface of the carrier that advance the transmission of air. Thus, a net transmission of air through the means in the circumferential surface that advance the transmission of air takes place at all times, so that the air jet pulse delivered by the insertion means, which is aimed at the pull-out opening, will exit the carrier via the circumferential surface at all times rather than via the pull-out opening. The latter situation would result in an uncontrolled movement through the shed and consequently a less controllable insertion of the weft yarn extending from the carrier. As a result of this net transmission of air, the carrier is much less sensitive to the air jet pulse that the insertion means deliver to the carrier with each "shot" for moving the carrier through the shed. This results in a much more stable "flight" of the carrier through the shed and an improved insertion of the weft yarn into the shed, and thus to a more easily controllable insertion of successive weft yarns. According to another method of inserting the weft yarn, it is also possible to dispose the carrier beside the shed and fix it in position, after which the insertion means pull the weft yarn from the carrier into the shed. The air transmitting means assist in the pulling of the weft yarn from the fixedly disposed carrier, in such a manner that the weft yarn is fully extended rather than being pulled out of the carrier as a whole clew of yarn. The presence of the air transmitting means furthermore assists in the filling of the carrier with a certain length of weft yarn, as well as in the launching of the carrier into the shed by means of an air pulse. The air pulse being delivered exerts a large (temporary) force/pressure on the carrier, which force needs to be quickly diverted in order to prevent damage to the carrier. The quick diversion of the forces and pressure differences across the carrier through the air transmitting means prevents possible deformation of the carrier, which would result in the carrier jamming or being blocked during the acceleration phase in the weaving device. According to a specific embodiment, the carrier is provided with openings. The openings may be in the form of perforations, cuts of slots. In another embodiment, the carrier is made of an air- permeable material, in particular a porous material, more in particular a gauze-like or filter cloth material. In all embodiments a carrier having air transmitting characteristics is obtained, as a result of which the air jet pulse delivered by the insertion means will have a much less adverse effect on the movement or "flight" of the carrier through the shed than is currently the case. The carrier according to the invention exhibits an aerodynamic behaviour that has a positive effect on the weaving process. The same line of reasoning applies to a fixedly disposed carrier from which the weft yarn is pulled. In that case, too, the weft yarn is not pulled from the carrier as a whole clew of yarn and does not get tangled, so that the weft yarn will fully extend into the shed. According to the invention, the carrier is made of a plastic material. This makes it possible to manufacture the carrier in large numbers as a light, inexpensive unit, which is furthermore reusable. According to a special embodiment, the carrier is cylindrical in shape so as to achieve a stable movement through the shed under the influence of the air jet pulse delivered by the insertion means on the one hand and an adequate retainment of the weft yarn and a smooth extension thereof from the carrier on the other hand. Also other sectional shapes are conceivable, however, in particular polygonal (triangular, square, etc) shapes. In a specific embodiment, the internal diameter of the carrier is so small, e.g. 6 mm or less, that the weft yarn's own bending resistance causes the windings to be supported against the inner wall of the carrier. As a result, the weft yarn is retained within the carrier in such a manner that the weft yarn will not get tangled upon being extended. This has a positive effect on the efficiency and the weaving result. In a functional embodiment, the carrier is narrowed at the location of the pull-out opening in order to prevent the weft yarn that is surrounded by the carrier from being pulled from the carrier as a whole in one go during movement through the shed. The packed weft yarn is thus retained within the carrier and the weft yarn is extended over its entire length during movement through the shed. Weaving faults and the like are prevented in this manner, too. The aerodynamic behaviour of the carrier during its movement through the shed is further positively improved in that according to the invention the carrier is provided with the supporting means that support the carrier upon insertion into the shed. Said supporting means may be configured as projecting edges formed on the carrier in the longitudinal direction thereof. The invention will now be explained in more detail with reference to a drawing, in which: Figures 1 and 2 show a weaving device according to the prior art; Figures 3a-3d show various embodiments of a carrier according to the invention; Figure 4 shows another embodiment of a carrier according to the invention. For a better understanding of the invention, like parts will be indicated by the same numerals in the description of the figures below. Figs. 1 and 2 show an embodiment of a known weaving device as described, for example, in Dutch Patent Application No. 73/09850 or Dutch Patent No. 1004173. The known weaving device comprises a lay 1 and is provided with means 2 for forming a shed 3 of warp yarns 4, which warp yarns 4 come from warp yarn supply bobbins 5. A large number of dents 6, together forming the so-called "reed", are arranged on the lay 1, which dents can move between the warp yarns 4. A number of guides 7 are furthermore arranged on the lay 1 for guiding a projectile 8 from one side of the shed 3 to the other side thereof. As is shown in the figure, the projectile 8 is present in an insertion station 9 disposed on the left-hand side of the shed 3, whilst a braking station 10 is disposed at the other side of the shed 3. A weft yarn 11 from a supply bobbin 12 can be connected to the projectile 8 in a known manner. A considerable amount of impulse energy is imparted to the projectile 8 by means of a medium under pressure, for example compressed air or water. As a result, the projectile 8 undergoes an acceleration and is moved or "shot" through the shed 3 at a high velocity, carrying along the weft yarn 11. The projectile 8 is also called the shuttle, therefore. The projectile 8 that moves through the shed 3 at a high velocity must be decelerated on the other side of the shed 3 (on the right in figure 1). To that end, a braking station 10 is disposed directly beside the shed 3, which station 10 intercepts and decelerates the projectile as it leaves the shed 3. Likewise, the projectile 8 can be moved ("shot") from the right-hand side to the left-hand side of the shed 3 at a high velocity by an insertion station 9' (not sjiown) arranged analogously to the insertion station 9, which is disposed on the right- hand side of the shed 3. A braking station 10' (not shown) is furthermore disposed at the location of the insertion station 9 for intercepting and decelerating a projectile 8 moving from the right-hand side to the left- hand side of the shed 3. The large inert mass of the projectile 8 and the frequently considerable width L of the shed 3 require that the projectile 8 be moved through the shed 3 at a relatively high velocity. The forces set up in the weft yarn 11 as a result of the acceleration and the velocity of the carrier lead to undesirable peak tensions, which may cause the yarn to break. In addition to that, the projectile 8 moving through the shed at a high velocity must be intercepted at the end of the shed and be decelerated by a separate braking station 10 (101). Said deceleration, too, may lead to undesirable peak tensions in the weft yarn, especially in situations in which the weft yarn is used for decelerating the projectile. In order to prevent in particular the undesirable peak tensions in the weft yarn 11, a lower initial speed of the projectile 8 being "shot" through the shed 3 is required, which also limits the maximum width of the shed 3, however. In the prior art it has already been proposed to embody the guides 7 that primarily function to guide the movement of the projectile 8 through the shed 3 as medium blowers. Said medium blowers 7 are mounted on the lay 1 and are connected to a medium supply line 17. Each guides 7 may be connected to a main medium supply line 19 via an electromagnetic valve 18. This configuration of a known weaving device in any case leads to lower peak tensions in the weft yarn 11 during the movement thereof through the shed. The braking station 10 for decelerating the weft yarn 11 and the projectile 8 exiting the shed are still indispensable, costly components of the weaving device, however, so that the known carrier and the known weaving devices are still complex to a certain extent. Also the deceleration of the weft yarn by the braking station 10 results in peak tensions in the weft yarn and an increased risk of yarn breakage. Figures 3a-3d disclose embodiments of a carrier according to the invention. The carrier- 20 is made up of an elongated, preferably cylindrical element having a circumferential surface 21 with a substantially closed front end 20a (seen in the direction of movement through the shed) and an open rear end 20b (likewise seen in the direction of movement through the shed). The weft yarn 22 is present in the hollow cylindrical carrier 20 in the form of a packed clew, so that the carrier 20 at least partially surrounds the packed clew of weft yarn 22. An end portion 23 of the weft yarn 22 projects from the carrier 20 via the open rear end 20b thereof. The yarn end 23 is held by the insertion means (see figure 1), whilst the carrier 20 is "shot" into the shed, for example by means of a medium under pressure such as air or water. The weft yarn 22 is pulled from the open carrier end 20b during the movement of the carrier through the shed, causing it to extend over the entire width of the shed. The weaving device can thus be constructed with lighter components that allow a higher speed of operation, i.e. high-speed weaving. More in particular, when using a carrier according to the invention, the forces are exerted on the carrier and on the packed clew of yarn 22 rather than on the yarn itself. Now that a clew of yarn rather than separate yarns is inserted into the shed, peak tensions in the yarn are prevented, since it is the clew of yarn (instead of a separate yarn) that is subjected to the acceleration forces that are exerted by the insertion means upon insertion of the carrier. Since the unwinding of the clew of yarn into a weft yarn upon insertion into the shed takes place gradually, a substantially constant lower tension is present in the weft yarn without the peak tension that usually occurs upon full deceleration of the weft yarn in one go in the currently known weft weaving machines. It is also possible to dispose the carrier at a fixed position beside the shed and have the insertion means pull the weft yarn from the carrier, so that the weft yarn is gradually pulled into the shed at a substantially constant low tension. In the case of air weaving, an air pulse is delivered to the carrier so as to cause it to accelerate and move through the shed. The open rear end 20b of the carrier allows the carrier to function more or less as an air interceptor, so that an acceleration of the carrier takes place to assist in the movement thereof through the shed. On the other hand, said movement becomes unpredictable due to the occurrence of air swirls, so that said movement will take place in a less stable and less gradual manner. Figures 3b-3d present a number of proposals to eliminate this drawback. According to the invention, the carrier as shown in figures 3b-3d are provided with means that advance the transmission of air from the air pulse being delivered by the insertion means. In one embodiment (figure 3b) the means that advance the transmission of air consist of a large number of openings or perforations 24 formed in the circumferential surface 21 of the carrier 20. The air pulse delivered by the insertion means with every weft stroke, which is intercepted by the carrier 20, can thus readily escape via said openings or perforations 24, resulting in a less erratic but more stable and more gradual "flight" during the movement through the shed. As a result, the aerodynamic behaviour of the carrier 20 according to the invention is strongly improved. In another embodiment as shown in figure 3c, the openings that advance the transmission of air by the carrier 20 consist of several cuts or slots 25 formed in the circumferential surface 21. Said cuts may be V-shaped. The openings may be configured to open at a specific pressure difference across the carrier wall so as to equalise said present difference and pull the weft yarn from the carrier in a trouble- free manner. In another functional embodiment, as shown in figures 3d, the carrier is made of an air-permeable or porous material 26. A filter cloth or gauze-like material is a very suitable material, through which the air flow that enters via the rear end 20b can easily escape. More in particular, the openings that advance the transmission of air by the carrier 20 are uniformly distributed over the circumferential surface 21 of the carrier 20. Because the clew of yarn is usually present in the front end 20a of the carrier 20, however, it is also possible for the means that advance the transmission of air to be distributed less uniformly over the circumferential surface 21 of the carrier, in such a manner that the greater part of the openings 24, the slots 25 or the meshes of the gauze-like material 26 are mainly located near the pull-out opening 20b of the carrier 20. Figure 4 shows another embodiment of the carrier according' to the invention, in which the carrier is provided with a narrowed portion or constriction 26 near the pull-out opening 20b. Said narrowed portion or constriction 26 functions to ensure that the clew of yarn 22 is fully extended into a weft yarn 22 via the loose end 23 during the movement of the carrier 20 through the shed instead of being pulled out of the carrier in the form of a clew. This construction prevents the occurrence of further weaving faults. In general the aerodynamic behaviour of the carrier, both during the filling of the carrier with the weft yarn to form a clew of yarn and during the movement of the carrier through the shed and the simultaneous extension of the clew of yarn into a weft yarn, is significantly improved if, according to the invention, the air transmitting area X of the pull-out opening 20b (which may or may not be constricted) is smaller than or equal to the air transmitting area Y of the means 24-25-26 in the circumferential surface 21 of the carrier 20 that function to advance the transmission of air. Thus, the amount of medium that may flow into the carrier will at all times be smaller than the amount of medium that can escape via the means 24-25-26 in the circumferential surface 21 that advance the transmission of air, so that medium under pressure cannot accumulate in the carrier 20. In this way undesirable (erratic) movement of the carrier through the shed is prevented, therefore. Yet another embodiment is shown in figure 5. In order to further improve the aerodynamic behaviour of the carrier 20 during movement thereof through the shed, the carrier is according to the invention provided with one or more projecting edges 27 formed on the carrier 20 in the longitudinal direction thereof. Said projecting edges 27 function as supporting fins or flaps that support the carrier during its movement through the shed, thus enabling a more rectilinear and more stable movement through the shed.