EP3098338B1

EP3098338B1 - Reed for air weaving looms

Info

Publication number: EP3098338B1
Application number: EP16169465.8A
Authority: EP
Inventors: Fabio Rabolini; Giancarlo PREVITALI; Fabrizio MORANDI; Bruno BRIGNOLI
Original assignee: Itema SpA
Current assignee: Itema SpA
Priority date: 2015-05-26
Filing date: 2016-05-12
Publication date: 2018-04-18
Anticipated expiration: 2036-05-12
Also published as: HK1231528A1; CN106192170B; JP6839932B2; EP3098338A2; EP3098338A3; TR201810261T4; CN106192170A; JP2017020153A; ITUB20150706A1

Description

The present invention relates to a reed for air weaving looms and, in particular, a reed of this kind which allows to reduce the consumption of compressed air which is necessary for the transport of the weft threads through the shed.

FIELD OF THE INVENTION

As known, in air looms, the weft thread is inserted in the shed without the aid of mechanical elements, but simply conveying the weft thread along the shed by means of gas (normally compressed air) jets. The generation of air jets includes a system of main nozzles, normally placed on the left side of the machine, which provide initial acceleration to the weft thread, and a system of secondary nozzles, evenly distributed along the shed, necessary to maintain an appropriate speed of the weft through the shed length.
Equally well known is that, in order to provide a fast weft-thread transport air flow, i.e. a geometrically well-defined and sufficiently concentrated air flow, a launching channel is formed inside of the reed, by providing a recess of suitable shape in an enlarged central area of the single reed dents, delimited by upper and lower rounded portions or "noses" of the dent. Reed dents are in fact arranged at a short distance from each other on perfectly parallel planes, perpendicular to the direction of insertion of the weft thread; side-by-side recesses of the plurality of parallel dents which form a reed therefore define a launching channel, inside which the weft thread moves.

BACKGROUND OF THE PRIOR ART

The particular shape of the central recess of the individual dents - which is equal, as stated above, to the cross-section shape of the launching channel - strongly affects the mode of transport of the weft and the consumption of compressed air needed to transport the weft correctly.
The launching channel formed in the reed is in fact an outwardly "open" channel both in correspondence with the gaps between the individual dents and, above all, in the direction facing towards the fabric being woven, and it is therefore clear that a significant portion of the compressed air jets used to achieve the transport of the weft thread is dispersed through the reed or in front of it without contributing to the transport of the weft, thus decreasing the efficiency of use of compressed air.
EP 0 691 430 (Toyota) discloses several embodiments of a reed for air looms in which the recess formed in the dents has a U shape with rounded edges, the lower side of which is inclined towards the secondary nozzles to facilitate air going in and channelling into the launching channel. According to a main feature of this patent (Fig. 1), the connecting radius (r) of the upper inner angle of the U-shaped recess, - which inner angle is just the area in which the weft thread moves along the launching channel - has a smaller dimension than the connecting radius (R) of the lower angle of the U-shaped recess opposite thereto, and in absolute value it is a very small radius, smaller than 1 mm and preferably smaller than 0.5 mm.
A second important feature of this reed is that according to which the projecting portions of each dent which delimit the upper and lower U-shaped recess, simply defined in the textile jargon as "noses", do not have a symmetrical configuration; in particular, the width of the lower nose (in the direction of the warp threads) is smaller than that of the upper nose, so as to allow a closer approach of the secondary nozzles to the reed and to improve the efficiency of use of compressed air. In a first embodiment of this reed (Fig. 1), the width W3 of the lower nose is about 75% of the width W1 of the upper nose, both of said widths being measured with respect to the bottom wall 342 of the central U-shaped recess. In another embodiment (Fig. 2) the width W13 of the lower nose is even more reduced and is comprised in a range between about 25 and 55% of width W11 of the upper nose; also in this embodiment said widths are measured with respect to the bottom wall 842 of the central U-shaped recess.
A third feature disclosed by this patent is the one according to which the various walls delimiting the U-shaped recess have a moderate inclination of about 10° in the weft advancement direction, thus transversely to the plane of the dents, in order to divert the air jet towards the inside of the weft launching channel, at each single dent, and thus reduce the leakage of compressed air through the individual dents of the reed.
EP 2 455 520 (Toyota) afterwards discloses again the same second embodiment of the above cited Toyota patent, wherein some dimensional limits are however specified (Fig. 3) - which limits will be discussed below in greater detail - defining a preferred configuration of the lower wall of the U-shaped recess of the dents.

ABSTRACT DESCRIPTION OF THE INVENTION

In this framework of the prior art, and taking into account that the costs for compressed air consumption have now become the main operating costs of an air loom weaving factory, the Applicant tackled the problem of further optimizing the shape of the central U-shaped recess of a reed for an air loom, in order to obtain a further possible reduction in the consumption of compressed air, without detriment to the effectiveness of the weft thread transport.
This problem is solved and the above objects are achieved by means of a reed for an air loom in which the shape of the U-shaped central recess of the dents thereof has the features defined in claim 1. Other preferred features of the reed according to the present invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the reed for air weaving looms according to the present invention will anyhow become more evident from the following detailed description of a preferred embodiment of the same, given by mere way of non-limiting example and illustrated in the accompanying drawings, wherein:

Fig. 1 is an elevational side view of the central portion of a reed dent of a known type, according to a first embodiment of patent EP 0 691 430 (Toyota);
Fig. 2 is an elevational side view of the central portion of a reed dent of a known type, according to a second embodiment of patent EP 0 691 430 (Toyota);
Fig. 3 is an elevational side view of the central portion of a reed dent of a known type, which is a specific embodiment of the dent shown in Fig. 2, disclosed in EP 2 455 520 (Toyota);
Fig. 4 is an enlarged scale view of the central portion of a reed dent according to the present invention;
Fig. 5 is a further enlarged scale view showing in greater detail the reed dent of Fig. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to achieve the above-mention object, the inventors started from the current state of the art, according to which - as already discussed in the introductory part of the present description - the consumption of compressed air to transport the weft inside the reed channel decreases with the decrease of the distance of the secondary nozzles from the weft. In particular, and as shown in Fig. 3, which illustrates the prior art closest to the present invention, the distance to be considered is that between the blow point 18 of the secondary nozzles 17 and the bottom wall 22 of the U-shaped central recess of the dent. As a matter of fact, the weft moves along the launching channel in proximity of said bottom wall 22, and more precisely of the upper end of the same.
At the same time, said blow point 18 must be maintained external to the U-shaped central recess and at a certain minimum distance from the reed, so that secondary nozzles 17 do not give rise to defects in the weft or warp threads.
To obtain the desired reduction of the distance between the blow point 18 of the secondary nozzles and the bottom wall 22 of the U-shaped central recess, according to the preferred known solution the transverse dimension of the lower nose 20 of the reed dents is significantly reduced. In other words, the length B of lower nose 20 protrusion, in relation to the bottom wall 22 of the U-shaped central recess, is significantly lower than the corresponding length A of the upper nose 19 protrusion of the dent.
According to the known art disclosed in patent EP 2 455 520 , illustrated in Fig. 3, the shape of the wall 23 of the dent, i.e. the lower wall of the U-shaped central recess, must be such that the sum of radiuses CR and DR of the arcuate connecting surfaces 25 and 29 which delimit it is less than the distance B, preferably by more than 1.5 mm. Therefore, with this limitation, a flat portion α is formed on the lower wall 23 of the dent, comprised between the arcuate connecting surfaces 25 and 29, the presence of which, as reported in the above cited patent, prevents effectively air flow coming from secondary nozzles from being diffused outside the launching channel and then stabilizes the weft along the desired path position, considerably reducing the number of incorrect wefts.
However, later studies made by the Applicant on reeds for air looms, starting from this state of the art, have shown that the above-described solution, although capable of providing a satisfactory performance, is not open to further improvements. In fact, trying to further decrease the distance B in order to further reduce the air flow sent to the secondary nozzles 17, it could be noted that the effect of weft stabilisation induced by the flat portion α of the lower surface 23 of the launching channel quickly becomes insufficient. It was therefore assumed that, in this situation, the diffusion effect caused by the curved surface 29 having radius DR becomes probably predominant. The length of the flat surface α remaining unchanged, such radius, in fact, necessarily becomes smaller and consequently shows a higher curvature, the smaller the distance B becomes.
Having the objective to overcome this limitation, the Applicant has then assumed to provide a completely different shape of the lower wall of the central recess of the dents, abandoning the traditional shape according to which arcuate connecting surfaces tangent to the straight portions of the walls delimiting the central recess have always been provided, and suggesting instead for the outer arcuate connecting surface of the lower nose of the dents (namely the one indicated with reference 29 in the prior art illustrated in Fig. 3) a curved profile tangent to the flat portion α, at one end, and forming a corner with the outer wall of the dent, at the other end.
The new dent configuration according to the present invention is illustrated in Fig. 4 and includes respectively lower and upper internal arcuate connecting surfaces R2 and R3, having a known shape, i.e. being tangent at each end thereof to the adjacent flat walls of the central recess C of the dent that they connect. Specifically, the lower arcuate connecting surface R2 is tangent to the lower wall L2 and to the bottom wall L3, while the upper arcuate connecting surface R3 is tangent to the lower wall L3 and to the upper wall L4. Preferably, the arcuate connecting surfaces R2 and R3 are in the shape of circular arcs, respectively of radius r2 and r3 having a small value, for example greater than or equal to 1 mm; preferably, the radius r3 of the upper arcuate connecting surface R3, which delimits the area of most likely weft path, has a slightly higher value than radius r2 of the lower arcuate connection surface R2.
As already anticipated above, the arcuate connecting surface R1 which connects the lower wall L2 of the central recess C of the dent to the lower outer wall L1 of the same dent also has a circular arc profile having, however, a radius r1 clearly greater than radiuses r2 and r3 defined above. In fact, the radius r1 of the arcuate connecting surface R1 has a value so high that the following relationship is always satisfied: $r 1 + r 2 > B .$
In addition, the r1 radius of such arcuate connecting surface is tangent only to the inner wall L2 of the central recess (C) of the dent, but not to the outer wall L1 of the dent, forming an angle different from 0° and thus an edge with respect to the latter. Due to limitations imposed by the construction technology of the dents, this edge may have a radius which, however, for obtaining the best performances, should be kept at the minimum possible value.
Finally, as it clearly appears from the drawings (Fig. 5), the lower wall L2 of the central recess C of the dent is diverging with respect to the opposed upper wall L4, according to the geometry already taught in the prior art, with the aim of facilitating the entry of the air flow coming from the secondary nozzles for improving the weft transport within the launching channel. However, in the illustrated embodiment, best results were obtained in terms of air consumption efficiency for the transport of the weft, forming said two divergent walls L2 and L4 according to a slightly wider angle than the known one and specifically an angle between 12° and 14°.
The above described shape of the lower wall L2 of the central recess C of the dent and relative arcuate connecting surface R1, according to the present invention, allows to obtain some important advantages. Firstly, by using a relatively large radius value r1 for the arcuate connecting surface R1, the degree of curvature of such a surface is very low, and then the first portion thereof, tangent to the straight lower wall L2, substantially causes the same effect of an extended straight lower wall L2, in terms of weft stabilization inside the launching channel, which weft stabilisation is therefore greatly improved. The critical value of the length of the straight lower wall L2 pointed out by the prior art does not exist anymore and the length of said lower wall L2 can also drop below said critical value, without experiencing any adverse effect on weft stabilisation, as long as the radius r1 has sufficiently high values.
By selecting a particularly high radius r1 of the arcuate connecting surface R1, the straight lower wall L2 can also be completely eliminated, then going to directly connect the arcuate connecting surface R1 with the arcuate connecting surface R2. The tangent to these curved surfaces, at their joining point, which is in this case a flex point, will of course preferably meet the conditions of inclination with respect to the upper wall L4, already previously defined in relation to the straight lower wall L2.
A second desired advantage of this shape consist in the resuiting reduction of the width B of the protrusion of the bottom portion of the dent with respect to the bottom wall L3 of the central recess C. As can be clearly seen in Fig. 5, at an enlarged scale, the value of this width B of the dent according to the present invention is in fact significantly smaller than the width B' of a dent in which the arcuate connecting surface R1 is extended over a wider circular arc until it can join the lower outer wall L1' of the dent, by being tangent thereto. The dent shape according to the present invention achieves the desired object of decreasing the width B, and therefore also the objects of making the secondary nozzles closer to the weft traveling area and of reducing accordingly the air flow needed to keep flying the weft itself.
Finally, a third advantage of the dent shape according to the present invention is to decrease the width of the opening mouth of the central recess C of the dent, from width K' to width K (Fig. 5), width K' being just the opening mout width of a dent in which the arcuate connecting surface R1 covers a wider circular arc, until it joins the lower external wall L1' (shown in dashed lines) of the dent, by being tangent thereto.
It should be appreciated that the reduction from K' to K of the width of the opening mouth of the central recess C of the dent is also obtained by excluding the terminal portion of arcuate connecting surface R1, namely the one that would show a nearly vertical slope. The width reduction of the opening mouth of the central recess C of the dent - which coincides with the opening mouth of the launching channel - does not therefore causes, on the one hand, a significant reduction of input air flow in said launching channel while, on the other hand, it reduces the interference of the lower nose of the tooth with the warp threads during opening and closing steps of the shed, thus entailing a reduction of possible defects in the woven fabric.
It is understood, however, that the invention is not to be considered as limited by the particular arrangement illustrated above, which represents only an exemplary embodiment of the same, but different versions are possible, all within the reach of a person skilled in the art, without departing from the scope of the invention, as exclusively defined by the following claims.

Claims

Reed for air weaving looms comprising a plurality of side-by-side dents, each dent being provided with a wide central recess (C), which separates an upper portion from a lower portion of the dent, for forming the reed launching channel, said central recess (C) being limited at least by a lower wall (L2), a bottom wall (L3), an upper wall (L4), two inner curved arcuate connecting surfaces (R2, R3) which connect said walls to each other and an outer arcuate connecting surface (R1) which connects said lower wall (L2) to the outer wall (L1) of said lower portion of the dent, characterised in that one end of said outer arcuate connecting surface (R1) is tangent to said lower wall (L2) and its other end forms an angle other than 0° with said lower outer wall (L1) of the lower portion of the dent.
Reed for air weaving looms as in claim 1, wherein said outer and inner arcuate connecting surfaces (R1, R2) which limit the lower wall (L2) of the central recess (C) are circular arcs with radius r1 and r2, respectively, and said radiuses meet the following relationship: $r 1 + r 2 > B$
where B is the width of the lower portion of the dent projecting crosswise with respect to the bottom wall (L3) of said central recess (C), in correspondence of the wider part of said lower portion of the dent.
Reed for air weaving looms as in claim 2, wherein the lower wall (L2) and the upper wall (L4) of the central recess (C) of the dent are mutually divergent, toward the opening mouth of the central recess (C), by an angle ranging between 12° and 14°.
Reed for air weaving looms as in claim 2, wherein said inner arcuate connecting surfaces (R2, R3) which limit the bottom wall (L3) of the central recess (C) are circular arcs with radiuses r2 and r3, respectively, and said radiuses meet the following relationship: $r 2 \leq r 3.$
Reed for air weaving looms as in claim 4, wherein said radiuses r2 and r3 have a value equal or greater than 1 mm.