WO2025157798A1 - Shed forming device, circular loom for leno fabric equipped with same, and shed forming method - Google Patents

Abstract

The shed forming device (10) for a circular loom (1) has warp-strip lifting elements (20, 21) for guiding warp strips (5, 6) in two warp-strip groups (11, 12), to which mutually opposite alternating movements are imparted in order to form a shed (40). An adjusting element (24) acts on a group of the warp-strip lifting elements (20, 21) and imparts to the warp-strip lifting elements (20, 21) a lateral to-and-fro movement between a first end position, in which adjacent warp strips (5, 6) of the two warp-strip groups (11, 12) do not cross over one another, and a second end position, in which two adjacent warp strips (5, 6) of the two warp-strip groups (11, 12) at a time cross over one another longitudinally. The adjusting element (24) can be adjusted without contact by an actuator (35) and has an adjusting magnet (24b, 24c) which can be repelled or attracted without contact by the actuator (35) by virtue of magnetic interaction. Damping stop elements (33, 34) define the positions of the first and second end positions.

Description

Shed forming device, circular loom for leno fabrics equipped therewith and process for shedding

The invention relates to a shed forming device for a circular loom. The invention further relates to a circular loom and its use for producing leno fabric. The invention also relates to a method for shed forming.

Circular weaving machines for producing fabrics are generally known from the prior art. These machines have a circular reed arranged coaxially with a main shaft of the circular weaving machine. The main shaft forms a main axis of the circular weaving machine. Warp ribbon guide elements are arranged around the circular reed and are designed to feed a plurality of warp ribbons to the circular weaving machine. Shed forming devices group the fed warp ribbons into two sets of warp ribbons and impart opposing alternating movements to them, whereby a shed is opened and closed between the two sets of warp ribbons. A shuttle moves on an orbital path in the opened shed and carries a weft ribbon into the shed, thereby forming a fabric. In modern circular weaving machines, several shuttles usually rotate simultaneously in a respective shed in the circular reed. The fabric is drawn off through a weaving ring. Such a circular weaving machine is known, for example, from document CH 657163 A5.

Of the fabrics that can be produced on circular looms, so-called leno fabrics, also known as LENO fabrics, are particularly important because in these fabrics, two adjacent warp ribbons are not parallel to each other. Instead, one warp ribbon, the so-called leno ribbon or leno thread, crosses the other warp ribbon, the ground ribbon or ground thread, in such a way that the weft ribbons are securely bound between this pair of warp ribbons. Leno fabrics can therefore have spaced-apart weft ribbons so that air and water can flow through the leno fabric. This is important, for example, for the packaging of foodstuffs such as vegetables or fruit, and allows for the washing of empty or food-filled packaging, as well as the reuse of packaging. Leno fabrics can have a net-like structure. The fundamental problem in the production of leno fabrics on circular looms is to design and guide the counter-rotating warp ribbon guide elements, also called partial shafts, in such a way that after each shed-forming alternating movement, the two interacting warp ribbons can be arranged alternately to one another. This problem was solved by the circular loom described in EP 0267509 A2 in that, for the alternate arrangement of the leno ribbon longitudinally to the base ribbon of two adjacent warp ribbons, adjusting means act on at least one partial shaft of a partial shaft pair after each shed-forming stroke for the momentary lateral relative counter-displacement of the partial shafts, whereby the warp ribbons are guided by ribbon guide means on one partial shaft of a partial shaft pair for shed formation and on the other partial shaft for a lateral change. The partial shafts can carry comb-like guide means for the warp ribbons, the prongs of which each have a ribbon eyelet at the free end for the shed-forming guide of a warp ribbon and delimit ribbon guide slots between them for the warp ribbons guided freely for the side change, wherein it is necessary that the partial shafts of a partial shaft pair carry oppositely arranged comb-like guide means.

Based on this circular weaving machine described in EP 0267509 A2, various further developments have been made to circular weaving machines for the production of leno fabrics in recent years.

WO 2021/105847 A1 and CN 114787436 A disclose a circular weaving machine for producing leno fabrics, similar to that of EP 0267509 A2. WO 2021/105847 A1 proposes equipping the ribbon eyelets on the comb-like guide means of the warp ribbons with ceramic inserts to reduce friction between the warp ribbons and the ribbon eyelets. The above-mentioned CH 657163 A5 also proposes providing ribbon eyelets with eyelet inserts made of ceramic, sintered ceramic, steel, or the like. CN 202644 031 U also proposes ceramic eyelet inserts.

Document GB 2290088 A shows a device for producing Leno fabric with warp tapes, weft tapes, and a reed. The loop-forming mechanism shown in Fig. 1 comprises a plurality of spindles, two Leno deflectors, and a plurality of gate hooks. The Leno deflectors are driven by a drive via piston rods to a reciprocating movement. The Leno deflectors have a plurality of healds through which the warp tapes are guided. The reciprocating movement of the Leno deflectors form the leno fabric. The piston rods can be moved using a contactless drive via an electromagnet. When energized, the electromagnet pushes the piston rod in a first direction. When de-energized, the piston rod is pushed back in the opposite direction by a spring, causing the back-and-forth movement. The piston rods, which act as adjusting elements, are not equipped with magnets. It has been shown that the known circular looms for the production of leno fabrics have limitations that prevent an increase in process speed while maintaining maximum process reliability. These limitations include a sharp increase in wear and noise, as well as a decrease in the accuracy of the warp tape positioning as the process speed increases.

The object of the present invention is to further develop the shed forming device for a circular loom for producing leno fabric and a circular loom equipped with such shed forming devices so that a higher process speed can be achieved in the production of leno fabric while simultaneously maintaining high process reliability. Furthermore, wear and tear on the shed forming device and the circular loom equipped with it, as well as noise generation, are to be reduced.

The present invention solves the stated problem by providing a shed forming device for a circular loom, with warp ribbon lifting elements arranged in a first group and in a second group for guiding warp ribbons in two warp ribbon sets, wherein the first group and the second group of warp ribbon lifting elements impart opposite alternating movements to the two warp ribbon sets to form a shed, wherein at least one actuating element acts on at least one of the groups of warp ribbon lifting elements, which actuates the warp ribbon lifting elements to perform a lateral back-and-forth movement between a first end position, in which adjacent warp ribbons of the two warp ribbon sets do not cross each other, and a second end position, in which two adjacent warp ribbons of the two warp ribbon sets cross each other longitudinally, wherein the actuating element is adjustable by an actuator in a contactless manner, wherein the The actuating element has at least one actuating magnet, wherein the at least one actuating magnet can be repelled or attracted by the actuator without contact through a magnetic interaction. The actuating magnet can be designed as a permanent magnet. This solution according to the invention offers the advantage that there is no wear of the components and noise is greatly reduced, but at the same time the operating speed can be increased by at least 30% compared to known circular looms.

Since at least one actuating magnet can be repelled or attracted by an actuator without contact through a magnetic interaction, the warp tape lifting elements remain in the end position for a certain period of time after lateral switching. This brief dwell of the warp tape lifting elements in the end position ensures the proper insertion of the warp tapes into the respective guides, e.g., into slots between prongs, as described in detail below. This is because the warp tapes can be positioned more precisely in their end position by the brief stopping of the warp tape lifting elements and reliably reach "their" guide. If mutual repulsion of the magnets is selected as the magnetic interaction, this enables a particularly simple design.

In a further development of this embodiment, the actuator has at least one actuator magnet designed as a permanent magnet, which can be brought into and out of magnetic operative relationship with the at least one actuating magnet. In principle, a ferromagnetic element could be provided instead of an actuator magnet or a actuating magnet, in which case the magnetic operative relationship would then be limited to attractive force. In reality, however, a combination of a permanent magnet and a ferromagnetic element has the disadvantage of an insufficiently high attractive force, as a result of which the desired high operating speed cannot be achieved. According to the invention, it can be provided that the actuator has a switching lever, preferably designed as a pivoting lever, on which the at least one actuator magnet is arranged such that it can be brought into and out of magnetic operative connection with the at least one actuating magnet by moving the switching lever.

In a robust design of the shed forming device comprising few individual parts and subject to little wear, the switching lever is mounted in a pivot bearing and pre-tensioned into a defined position by a leg spring.

In a further preferred embodiment of the shed forming device according to the invention, the actuating element has two spaced-apart actuating magnets which can be alternately brought into magnetic operative relationship with the actuator and thereby adjust the actuating element in such a way that it Warp tape lifting elements of the group assigned to it are moved back and forth between the first and second end positions.

In an alternative preferred embodiment of the shed forming device according to the invention, the actuator has at least one actuator magnet designed as an electromagnet, wherein the actuating magnet can be attracted or repelled by the actuator magnet by applying electric current to the actuator magnet, wherein preferably the actuator has a switching lever for applying electric current to the actuator magnet.

In a further alternative embodiment of the shed forming device according to the invention, the actuator has at least one actuator magnet designed as an electromagnet, wherein the actuating magnet can be attracted or repelled by the actuator magnet by applying electric current to the actuator magnet, wherein preferably the actuator has a switching lever for reversing the current direction of the electric current with which the actuator magnet is applied.

In a particularly expedient embodiment of the shed forming device according to the invention, the shed forming device comprises stop elements that define the positions of the first and second end positions. It is preferred if the stop elements are formed from a damping material or are provided with a damping material on their surface, wherein the damping material is, for example, a natural or synthetic elastomer.

These stop elements offer several advantages. First, they precisely define the end positions of the lateral reciprocating movement of the warp thread lifting elements, resulting in an improved leno fabric. Second, the dampening material absorbs the shock exerted by the warp tape lifting elements on the stop elements, thereby reducing both the dynamic stress on the circular loom's components and noise generation. Third, the stop elements, especially those with dampening material, reduce or even completely prevent the warp tape lifting elements from springing back from the stop elements after they have been struck. The warp tape lifting elements, and thus the warp tapes themselves, can thus be positioned in their end positions with less vibration or even without vibration. This enables improved movement sequences and higher operating speeds. When the warp tape lifting elements are in direct contact with the stop elements in the first and second end positions, there are no deviations in the positions of the warp tape lifting elements from the defined end positions, which would occur with a merely indirect mechanical relationship between the warp tape lifting elements and the stop elements. Instead, the final positioning of the warp tape lifting elements in the end positions is always guaranteed. This also simplifies the design of the shed forming device.

In mechanics, the term "stop" is defined as the intended end point of a body's trajectory. At this end point, the body "hit" another body—a physical obstacle itself referred to as a stop element.

It is furthermore expedient if the warp tape lifting elements of the first group are formed by the prongs of a first comb, in which warp tape-guiding eyelets are formed, and the warp tape lifting elements of the second group are formed by the prongs of a second comb, wherein the first or the second comb can be moved back and forth alternately between the first end position and the second end position by the adjusting elements. In this embodiment, it is preferred if the first comb is mounted on a comb carrier so that it can be moved back and forth, and the stop elements are arranged on the comb carrier on the side facing the first comb. Such an embodiment is robust, simple in construction, and ensures exact positioning of the comb at the end positions. Unintentional pivoting of the comb is impossible.

In a particularly preferred embodiment of the shed forming device according to the invention, the first comb is mounted on the comb carrier by means of an axis so as to be pivotable about the axis, wherein the stop elements and the axis span an isosceles triangle, wherein the distances between the axis and each of the stop elements form the legs and the distance between the stop elements forms the base of the isosceles triangle, wherein the length of the legs is greater than the length of the base. This embodiment offers the advantages of a robust, simple construction and exact positioning of the comb at the end positions and also has the advantage that the relatively large distance between the axis and the stop elements reduces the stop torque and thus reduces the mechanical load on the components.

The invention further solves the problem by a circular weaving machine comprising a circular reed, Warp ribbon guide elements arranged around the circular reed of the circular loom for feeding a plurality of warp ribbons to the circular loom, shuttles rotating in the circular reed for inserting weft ribbons into sheds formed by the warp ribbons and a main drive for driving the shuttles, and wherein the circular loom has shed forming devices according to the invention arranged around the circular reed and explained above.

In order to achieve particularly precise control of the circular loom in the production of leno fabric, but still to achieve a simple construction, the circular loom has a control cam carrier driven by the main drive, wherein a lifting control cam is formed on the control cam carrier, which controls the first group and the second group of warp tape lifting elements, wherein an actuator control cam is formed on the control cam carrier, which controls the actuator, wherein preferably the lifting control cam and the actuator control cam are designed in one piece on the control cam carrier.

It is further preferred that the circular reed has a plurality of reed dents and spacer dents, wherein a number of reed dents are arranged alternately with at least one spacer dent, wherein adjacent reed dents and adjacent reed dents and spacer dents are arranged at equal distances from one another in the circular reed and have the same width. This embodiment of the circular loom offers maximum freedom and flexibility when equipping the circular loom with warp tapes.

According to the method according to the invention for forming a shed on a circular loom, a plurality of warp ribbons are provided in two warp ribbon sets, the two warp ribbon sets are given mutually opposite alternating movements to form a shed, at least one of the two warp ribbon sets is given a lateral back and forth movement between a first end position in which adjacent warp ribbons of the two warp ribbon sets do not cross each other, and a second end position in which two adjacent warp ribbons of the two warp ribbon sets cross each other longitudinally, and the imparting of the lateral back and forth movement of at least one of the two warp ribbon sets is carried out contact-free by an actuating element which is controlled by an actuator is adjusted without contact, wherein the actuating element has at least one actuating magnet which is repelled or attracted by the actuator by a magnetic interaction.

Further advantageous embodiments of the invention will become apparent from the following description and the drawings.

Fig. 1 shows a circular weaving machine according to the invention in side view.

Fig. 2 shows the circular loom of Fig. 1 in plan view.

Figures 3a, 3b and 3c show the movement sequence of the warp tape lifting elements during the production of leno fabric.

Fig. 4a shows the shed forming device of the circular loom of Fig. 1 in side view.

Fig. 4b and Fig. 4c show two variants of the shed forming device of Fig. 4a in plan view.

Fig. 5a and Fig. 5b show perspective views of the shed forming device of Fig. 4a.

Fig. 6a and Fig. 6b show in plan view and perspective view an embodiment of a shed forming device according to the invention, in which the actuator has an actuator magnet designed as an electromagnet.

Fig. 7a and Fig. 7b show in plan view and perspective view an embodiment of a shed forming device according to the invention, in which the actuator has an actuator magnet designed as an electromagnet.

Fig. 8 shows a leno fabric that can be produced with the circular loom according to the invention.

Fig. 1 and Fig. 2 show an embodiment of a circular loom 1 according to the invention. The circular loom 1 comprises a frame 2, e.g. of polygonal construction, which is preferably formed by a plurality of shaped tubes welded or screwed together and which serves as a reed for the components of the circular loom 1. In the center of the frame 2, on a frame 32, a circular reed 4 is arranged. The circular reed 4 comprises an upper ring 4c and a lower ring 4d, between which a plurality of reed dents 4a and spacer bars 4b are evenly distributed. The spacer bars 4b hold the upper ring 4c and the lower ring 4d spaced parallel to one another. The upper and lower rings 4c, 4d hold the reed dents 4a together with the spacer bars 4b in position. The upper ring 4c and the lower ring 4d represent guides for the circulation of shuttles 9 in the round reed 4. Concentric to the round reed 4, a weaving ring 14 is arranged centrally within the round reed 4, through which the finished tubular fabric 3 is drawn off. Outside the round reed 4 Feeds 7 for the warp ribbons 5, 6 are arranged distributed all around the circular reed 4. Furthermore, warp ribbon guide elements 8, e.g. in the form of length compensation compensators, are arranged around the circular reed 4. A large number of warp ribbons 5, 6 are fed to the circular weaving machine 1 via these warp ribbon guide elements 8 or through them. From the warp ribbon guide elements 8, the warp ribbons 5, 6 run to shed forming devices 10, which are described in more detail below. Several shed forming devices 10, each of which represents a shed forming segment, are arranged around the circular reed 4. From the shed forming devices 10, the warp tapes 5, 6 run through slots between reed dents 4a and/or spacer bars 4b of the circular reed 4 in the direction of the weaving ring 14. In the production of leno fabric 60 (see Fig. 8), two warp tapes 5, 6 always run through the slot between two reed dents 4a or between a reed dent 4a and a spacer bar 4b. In order to have the greatest possible freedom and flexibility when equipping the circular loom 1 with warp tapes 5, 6, it is advantageous if the reed dents 4a and the spacer bars 4b have the same width and the same distance from one another, so that all slots formed between the reed dents 4a or between a reed dent 4a and a spacer bar 4b have the same width. The spacer rods 4b are usually slightly longer than the reed dents 4a in order to engage and be fixed in grooves in the upper ring 4c and the lower ring 4d. The purpose of the difference in length is to ensure that after the round reed 4 has been assembled - the ends of the spacer rods 4b are first screwed to the reed rings 4c, 4d - the reed rings 4c, 4d rest snugly on the spacer rods 4b and the reed construction is stable. The reed dents 4a are inserted (glued) into the space between the spacer rods 4b - with the aid of an assembly comb (= spacer comb) for setting the same spacing between the reed dents 4a - so that their lower and upper ends have a slight difference in length compared to the spacer rods. The reed dents 4a can, for example, be installed in a "pack of three", i.e. three reed dents 4a connected to one another, e.g. welded together. This is more cost-effective than, for example, producing several reed dents 4a from one piece.

Alternatively, the spacer bars 4b can be of the same length as the reed bars 4a.

The warp ribbons 5, 6 are divided into two warp ribbon groups 11, 12 at the shed forming devices 10, which are given opposing alternating movements (here up and down movements) by the opposing movement of warp ribbon lifting elements 20, 21, whereby the shed 40 (also travelling shed called) is opened and closed (also called shed change). See also Fig. 3a to 3c. In the shed 40, a shuttle 9 moves in an orbit along (the inside) of the circular reed 4, pulling the weft ribbon 61 from the weft ribbon spool 62 carried by it and inserting it into the shed 40, see Fig. 2. As a result of the shed change, i.e. the reversal of the movement imparted to the counter-rotating warp ribbon sets 11, 12, the last inserted weft ribbon 61 is clamped between the warp ribbon sets 11, 12, and is thus tied in and fixed in the fabric 3 in a slip-resistant manner. Usually, several shuttles 9 run at equal distances from one another in the circular reed 4, each shuttle 9 moving in its own shed 40. The produced tubular fabric 3 is guided by the weaving ring 14 to take-off rollers 13 and deflected by these away from the circular loom, see Fig. 1. An annular cable duct 15 serves to control all electrical and electronic parts of the circular loom 1. The circular loom 1 is controlled by a control panel 16, which also contains the operating devices for an operator, see Fig. 2. A control cam carrier 17 serves to control the shed forming devices 10 and is driven by a main drive 18 of the circular loom 1, so that the control cam carrier 17 rotates about a central axis 19 of the circular loom 1. In the illustrated embodiment of the circular loom 1, the control cam carrier 17 is formed by a ring 17a, which is connected via spokes 17b to a hub 17c, which is located on the central axis 19. On the underside of the ring 17a, webs are formed that form the control cams. Alternatively, the control cam carrier 17 can be a centrally arranged disc with webs that form the control cams.

Referring to Figures 3a, 3b, 3c in conjunction with Fig. 4a, a shed forming device 10 of the circular loom 1 of Fig. 1 is shown schematically in side view. The shed forming device 10 has warp ribbon lifting elements 20 arranged in a first group for guiding warp ribbons 5 in a first warp ribbon group 11 and warp ribbon lifting elements 21 arranged in a second group for guiding warp ribbons 6 in a second warp ribbon group 12. The warp ribbon lifting elements 20 of the first group represent inner warp ribbon lifting elements 20 with respect to the central axis 9 of the circular loom 1, whereas the warp ribbon lifting elements 21 of the second group represent outer warp ribbon lifting elements 21 with respect to the central axis 9 of the circular loom 1. The first group and the second group of warp ribbon lifting elements 20, 21 impart opposing alternating movements to the two warp ribbon sets 11, 12 to form a shed 40. The shed forming device 10 is designed to produce a leno fabric 60, with intersecting warp ribbons 5 as leno thread, warp ribbons 6 as ground thread and weft ribbons 61 bound in between in a slip-resistant manner (see Fig. 8). Actuating elements 24 act on at least one of the groups of warp tape lifting elements 20, 21 - in this embodiment on the warp tape lifting elements 20 arranged in the first group - which impart to the warp tape lifting elements 20 a lateral back and forth movement between a first end position in which adjacent warp tapes 5, 6 of the two warp tape groups 11, 12 do not cross each other, and a second end position in which two adjacent warp tapes 5, 6 of the two warp tape groups 11, 12 cross each other longitudinally.

The warp tape lifting elements 20 of the first group are formed by the prongs 22a of a first comb 22, in which prongs 22a are formed eyelets 22b for guiding warp tapes 5. Between the prongs 22a, tape guide slots are formed for the warp tapes 6, which are freely guided for the side change. The warp tape lifting elements 21 of the second group are formed by the prongs 23a of a second comb 23, in which prongs 23a are formed eyelets 23b for guiding warp tapes 6. Between the prongs 23a, tape guide slots are formed for the warp tapes 5, which are freely guided for the side change. The first and second combs 22, 23 are oriented in opposite directions, i.e. the free end of the tines 22a of the first comb 22 points downwards and the free end of the tines 23a of the second comb 23 points upwards. The first comb 22 can be moved back and forth alternately between the first end position and the second end position by an adjusting element 24. This is achieved in the illustrated embodiment in that the first comb 22 is mounted on a comb carrier 22c by means of an axle 22d and can be pivoted between the first end position and the second end position by an eccentric bolt 24a of the adjusting element 24, see Fig. 3a, 4b. In an alternative embodiment not shown in the drawing, the first comb 22 can be mounted in guide rails on the comb carrier 22c and moved by means of an eccentric, slider or gear. The warp ribbons 6 guided by the warp ribbon lifting elements 21 of the second group or the second comb 23, which are imparted only an up-and-down movement, are referred to as "ground threads" or "ground ribbons." The warp ribbons 5 guided by the warp ribbon lifting elements 20 of the first group or the first comb 22, which are imparted both an up-and-down movement and a reciprocating movement, are referred to as "leno threads" or "leno ribbons."

The shed forming device 10 has an upper deflection roller 25 and a lower

Deflection pulley 26, see e.g. Fig. 4a, around which belts 27 are guided, on which the first group of warp tape lifting elements 20, in this example the comb carrier 22c, and the second group of warp tape lifting elements 21, in this example the second comb 23, are mounted. The first comb 22 and the second comb 23 are connected opposite one another to the belts 27 in an endless configuration. The control cam carrier 17 has a lifting control cam 17d (see Fig. 5a), which is designed as an eccentric web, on which control rollers 28 of a lifting control lever 29 pivotally mounted on a bearing block 30 engage and deflect the lifting control lever 29 following the lifting control cam 17d. The lifting control lever 29 is connected to one of the belts 27 (alternatively to the comb carrier 22c), whereby its deflection raises or lowers the belt 27 and thereby generates the lifting movement. The bearing block 30 sits on a base plate 31.

Fig. 3a shows the warp ribbon lifting elements 20 in an open position of the shed 40 so that the shuttle can move in the shed 40 and the weft ribbon can be inserted into the fabric 3. The warp ribbons 5 of the warp ribbon group 11 delimit the space of the shed 40 upwards. The warp ribbons 6 of the warp ribbon group 12 delimit the space of the shed 40 downwards. The warp ribbons 5 and 6 are aligned parallel to one another, with the warp ribbon 5 being guided to the left of the warp ribbon 6 in the illustration in Fig. 3a. The first comb 22 is pivoted into its first end position (the left end position in the drawing). After the weft ribbon insertion has been completed, the pivoting of the first comb 22 can take place. Fig. 3b shows a position of the first and second warp ribbon lifting elements 20, 21 in which the warp ribbons 5 are located below the warp ribbons 6. In this position, the crossing of the adjacent warp ribbons 5, 6 can take place. The first comb 22 has already pivoted into its second end position (the right-hand end position in the drawing). Fig. 3c shows the open shed 40 after a completed changeover stroke, similar to Fig. 3a, with the difference that the adjacent warp ribbons 5, 6 are crossed over in the longitudinal direction. This can be seen from the fact that in the illustration the warp ribbon 5 is guided to the right of the warp ribbon 6. The first comb 22 is in the second end position. During the next stroke, the first comb 22 can then be pivoted back into its first end position, which again leads to the change of sides of the warp ribbons 5, 6, and so on.

Figures 3a to 3c also show a stop element 33 that defines the first end position of the first comb 22, and a stop element 34 that defines the second end position of the first comb 22, whereby the position of the warp strips 5 in relation to the warp strips 6 is precisely defined. The stop elements 33, 34 lie directly against the comb in the respective end position of the first comb 22, so that no tolerances in the Positioning of the first comb 22 in the end positions can occur, which leads to an improved leno fabric 60. Since the first comb 22 is mounted on a comb carrier 22c so as to be movable back and forth and the stop elements 33, 34 are arranged on the comb carrier 22c on the side facing the first comb 22, a particularly simple, yet precise construction results because tolerances are not important due to the direct contact between the first comb 22 and the stop elements 33, 34. As can be seen from Figures 3a to 3c, the first comb 22 is mounted on the comb carrier 22c by means of an axis 22d so as to be pivotable about the axis 22d. The stop elements 33, 34 and the axis 22d form an isosceles triangle. The distance between the axis 22d and the stop element 33 as well as the distance between the axis 22d and the stop element 34 each form a leg a of the isosceles triangle. The distance between the stop elements 33, 34 forms the base b of the isosceles triangle. As can be seen in Figures 3a to 3c, the length of the legs a is greater than the length of the base b of the isosceles triangle. This large distance between the axis 22d and the stop elements 33, 34 greatly reduces the stop moment of the first comb 22 on the stop elements 33, 34. The stop elements 33, 34 have a damping material 33a, 34a, e.g. a natural or synthetic elastomer. This dampens the striking of the first comb 22 on the stop elements 33, 34, thereby reducing the dynamic stress on the parts of the circular loom 1 and the noise generation. The damping is based on the absorption of impact forces by the damping material 33a, 34a, or a shock absorber effect. The damping material also prevents unwanted bouncing of the first comb 22 when it strikes the stop elements 33, 34.

As can be seen in Figures 4a and 4b, the actuating element 24 is pivotably mounted on the comb carrier 22c and has the eccentric pin 24a, by means of which the first comb 22 is pivoted. The eccentric pin 24a enables or actuates the actual pivoting of the first comb 22 through its movement about its axis. The path covered by the first comb 22 during its movement is therefore predetermined by the eccentricity of the pin 24a. The actuating element 24 has at least one actuating magnet 24b, 24c, optionally designed as a permanent magnet, wherein the at least one actuating magnet 24b, 24c can be repelled or attracted by an actuator 35 without contact through a magnetic interaction, thereby pivoting the actuating element 24. For this purpose, the actuator 35 in the embodiment shown in Fig. 4a has at least one actuator magnet 35a, 35b designed as a permanent magnet, which can be brought into and out of magnetic operative relationship with the at least one actuating magnet 24b, 24c. It is essential that the pivoting of the actuating element takes place without contact. This means that during operation, the Actuator magnets 35a, 35b are always spaced apart from the actuating elements 24. This minimizes mechanical stress and noise. The actuator 35 has a switching lever 36, preferably designed as a pivoting lever, which is pivotally mounted in a pivot bearing 37 and preloaded into a defined position by a leg spring 38. A control roller 39 engages the switching lever 36 and, under the preload of the leg spring 38, bears against an actuator control cam 17e formed on the circumference of the control cam carrier 17, follows the actuator control cam 17e, and thereby adjusts the switching lever 36 of the actuator 35. The actuator control cam 17e and the stroke control cam 17d are formed integrally on the control cam carrier 17. As a result, no offset can occur between the two control cams 17d, 17e, which increases the precision of the control, see also Fig. 5a and 5b.

Fig. 4b shows the shed forming device 10 of Fig. 4a in plan view. The switching lever 36 of the actuator 35 is designed as a pivoting lever and has two spaced-apart actuator magnets 35b, 35c. Depending on the position of the switching lever 36, the actuator magnets 35b, 35c come into magnetic operative relationship with one of the actuating magnets 24b, 24c of the actuating element 24. In the embodiment shown in Fig. 4b, the actuator magnet 35a is currently in operative relationship with the actuating magnet 24b. The specific shapes of the switching lever 36 and the actuating element 24 can be arbitrarily designed according to practical requirements, e.g., moon-shaped, semicircular, circular, rectangular, and the like. It is essential that they fulfill the functions according to the invention and offer a certain degree of freedom so that the interaction of the movements of the switching lever 36 and the actuating element 24 is guaranteed under all operating conditions. For example, the actuating element can be designed in a simple rod-shaped manner, as shown in the variant in Fig. 5a. Depending on the polarity of the actuating magnets 24b, 24c and the actuator magnets 35a, 35b, the actuating magnets 24b, 24c and the actuator magnets 35a, 35b, which are in magnetic interaction, repel each other or attract each other and thereby adjust the actuating element 24, which in turn deflects the first comb 22 from the first end position to the second end position or vice versa via the eccentric bolt 24a. In a simple embodiment, the magnets 24b, 35a and 24c, 35b, which are in magnetic interaction, are designed to repel each other. Alternatively, if the magnets 24b, 35a and 24c, 35b, which are in magnetic interaction, are polarized to attract one another, the above-described stop elements 33, 34 should be provided to limit the respective end positions of the first comb 22 and its deflection, as mentioned, as well as to dampen its stops. This is particularly important because the magnetic attraction forces become stronger the closer the attractively polarized magnets 24b, 35a and 24c, 35b approach one another, whereby the movement of the first comb 22 accelerates the more it approaches one of its end positions. In this embodiment, the stop elements 33, 34 can implement and ensure the contactless adjustability of the actuating element 24 by the actuator 35 in a particularly effective, yet structurally simple manner due to the attractive magnetic interaction. In the plan view of Fig. 4b, the actuating magnets 24b, 24c are not visible, as they are arranged on the underside of the actuating element 24. They are therefore symbolically marked with arrows in the drawing. The switching lever 36 is preloaded against the actuator control cam 17 in the pivot bearing 37 by the leg spring 38 resting on a stop 38a; see also Fig. 4c.

Fig. 4c shows a plan view of a variant of the shed forming device 10 from Fig. 4a. This variant differs from the embodiment of Fig. 4b in that the switching lever 36 has only one actuator magnet 35a, which, depending on the position of the switching lever 36, alternately comes into a repulsive or attractive magnetic relationship with one of the actuating magnets 24b, 24c. In this embodiment, the switching lever 36 has a longer pivoting path during operation compared to the embodiment according to Fig. 4b in order to alternately bring the actuator magnet 35a into magnetic operative connection with one of the two actuating magnets 24b, 24c. The magnetic operative connection is established when the actuator magnet 35a is substantially opposite one of the two actuating magnets 24b, 24c. All other functions and elements of this variant of the shed forming device 10 correspond to the embodiment of Fig. 4b, which is why reference is made to the above description.

Fig. 5a shows a perspective view of the shed forming device 10 of Fig. 4a and Fig. 4b, viewed from the inside out. Fig. 5b shows a perspective view of the shed forming device 10 of Fig. 4a and Fig. 4b, viewed from the outside in. These two views clearly illustrate the functionality and interaction of the components described with reference to Fig. 4a and Fig. 4b.

Figures 6a and 6b show an alternative embodiment of a shed forming device 10, in which the actuator 35 has an actuator magnet 50 designed as an electromagnet with an electromagnet coil 51 and a C-shaped iron core 52. The electromagnet coil 51 is supplied with electrical current from a power source 56 through a switch 55. The switch 55 can be an on/off switch or a changeover switch that reverses the current direction and is actuated by the switching lever 36 of the actuator 35, for example, when the switching lever 36 is deflected, it switches a rocker switch of the switch 55, as symbolically represented by an arrow. In the air gap between the free ends of the C-shaped iron core 52, a Adjusting tab 53 is arranged as an adjusting element 24, on which adjusting tab 53 are mounted adjusting magnets 24b, 24c designed as permanent magnets, opposite one another. Depending on the polarity of the adjusting magnets 24b, 24c and the direction of the electric current through the electromagnetic coil 51, the adjusting tab 53 is repelled or attracted to one or the other free end of the C-shaped iron core. If the switch 55 is designed as an on/off switch, the adjusting tab 53 is preloaded into a basic position by a spring (not shown) and is deflected from this basic position by the magnetic operative connection when the electromagnetic coil 51 is supplied with electric current. The adjusting tab 53 is fixedly connected to the first comb 22, which is arranged displaceably in the comb carrier 22c, and moves the first comb 22 back and forth between two end positions. It should be emphasized that the adjusting tab 53 or the adjusting magnets 24b, 24c arranged on it never come into contact with the iron core 52. Even when the adjusting tab 53 has reached an end position, a gap 54 always remains between the adjusting magnets 24b, 24c and the iron core 52. In other words, the magnetic adjustment of the adjusting tab 53 by the actuator magnet is contactless. The contactless magnetic adjustment of the adjusting tab 53 under all operating conditions can be further ensured if the above-mentioned stop elements limit the movement of the first comb 22. This is particularly important when the adjusting magnets 24b, 24c and the actuator magnet are operated in an "attractive pole setting." The air gap between the free ends of the C-shaped iron core 52 is dimensioned such that the adjusting tab 53 acting as the adjusting element 24 can always be moved smoothly and without contact in the air gap, even taking into account the up and down movement that takes place in addition to the back and forth movement during shed formation.

Figures 7a and 7b show a further embodiment of a shed forming device 10 which, in contrast to the embodiment of Figs. 6a, 6b, has a rocker arm with an actuating magnet 24b as the actuating element 24, which, upon repulsion or attraction by the actuator magnet 50, pivots the first comb 22, which is pivotally mounted in the comb carrier 22c, between two end positions. The actuation of the comb 22 is achieved - similar to the variants of Figs. 3 to 5 - by means of an eccentric bolt which passes through a through-bore in the comb carrier 22c and is seated in a correspondingly provided bore in the comb 22. The eccentricity of the eccentric bolt determines the path that the comb 22 travels in its pivoting movement, whereby this path is shorter than in alternative embodiments, such as those shown in Figs. 6a and 6b. In connection with the actuating magnet 24b, it should be mentioned that it is also conceivable to provide the rocker arm with two actuating magnets. In this embodiment, too, the actuating element 24 is preloaded into a basic position by a spring (not shown) and, when the electromagnetic coil 51 is subjected to electric current, is deflected from this basic position by the magnetic operative connection. In this embodiment, too, the magnetic adjustment of the first comb 22 is contactless.

Claims

Claims: 1. Weaving shed forming device (10) for a circular loom (1), with warp ribbon lifting elements (20, 21) arranged in a first group and in a second group for guiding warp ribbons (5, 6) in two warp ribbon sets (11, 12), wherein the first group and the second group of warp ribbon lifting elements (20, 21) impart mutually opposite alternating movements to the two warp ribbon sets (11, 12) to form a weaving shed (40), wherein at least one actuating element (24) acts on at least one of the groups of warp ribbon lifting elements (20, 21), which actuates the warp ribbon lifting elements (20, 21) a lateral back and forth movement between a first end position, in which adjacent warp ribbons (5, 6) of the two warp ribbon sets (11, 12) do not cross each other, and a second end position in which two adjacent warp ribbons (5, 6) of the two sets of warp ribbons (11, 12) cross each other longitudinally, characterized in that the adjusting element (24) can be adjusted in a contactless manner by an actuator (35), wherein the adjusting element (24) has at least one adjusting magnet (24b, 24c), wherein the at least one adjusting magnet (24b, 24c) can be repelled or attracted by the actuator (35) in a contactless manner by means of a magnetic operative relationship. 2. Shed forming device according to claim 1, characterized in that the actuating magnet (24b, 24c) is designed as a permanent magnet. 3. Shed forming device according to claim 1 or 2, characterized in that the actuator (35) has at least one actuator magnet (35a, 35b) designed as a permanent magnet, which can be brought into and out of magnetic operative relationship with the at least one actuating magnet (24b, 24c). 4. Shed forming device according to claim 3, characterized in that the actuator (35) has a switching lever (36), preferably designed as a pivoting lever, on which the at least one actuator magnet (35a, 35b) is arranged such that it can be brought into and out of magnetic operative connection with the at least one actuating magnet (24b, 24c) by moving the switching lever (36). 5. Shed forming device according to claim 4, characterized in that the switching lever (36) is mounted in a pivot bearing (37) and is pretensioned into a defined position by a leg spring (38). 6. Shed forming device according to one of claims 2 to 5, characterized in that the adjusting element (24) has two spaced-apart adjusting magnets (24b, 24c) which can be alternately brought into magnetic operative relationship with the actuator (35) and thereby adjust the adjusting element (24) such that it moves the warp tape lifting elements (20, 21) of the group assigned to it back and forth between the first and the second end position. 7. Shed forming device according to claim 1 or 2, characterized in that the actuator (35) has at least one actuator magnet (50) designed as an electromagnet, wherein the actuating magnet (24b, 24c) can be attracted to or repelled by the actuator magnet (50) by applying electric current to the actuator magnet (50), wherein preferably the actuator (35) has a switching lever (36) for applying electric current to the actuator magnet (50). 8. Shed forming device according to claim 1 or 2, characterized in that the actuator (35) has at least one actuator magnet (50) designed as an electromagnet, wherein the actuating magnet (24b, 24c) can be attracted to or repelled by the actuator magnet (50) by applying electric current to the actuator magnet (50), wherein preferably the actuator (35) has a switching lever (36) for reversing the current direction of the electric current with which the actuator magnet (50) is applied. 9. Shed forming device according to one of the preceding claims, characterized in that the warp ribbon lifting elements (20) of the first group are formed by the tines (22a) of a first comb (22), in which warp ribbon-guiding eyelets (22b) are formed, and in that the warp ribbon lifting elements (21) of the second group are formed by the tines (23a) of a second comb (23), wherein the first or the second comb (22, 23) can be moved back and forth alternately between the first end position and the second end position by the adjusting element (24). 10. Shed forming device according to one of the preceding claims, characterized in that the shed forming device has stop elements (33, 34) which define the positions of the first and the second end position, wherein the stop elements (33, 34) are formed from a damping material or are provided on their surface with a damping material (33a, 34a), wherein the damping material (33a, 34a) is preferably a natural or artificial elastomer. 11. Circular loom (1), comprising a circular reed (4), Warp ribbon guide elements (8) arranged around the circular reed (4) for feeding a plurality of warp ribbons (5, 6) to the circular loom (1), shuttles (9) rotating in the circular reed (4) for inserting weft ribbons (61) into sheds (40) formed by the warp ribbons (5, 6), and a main drive (18) for driving the shuttles (9), wherein the circular loom (1) has shed forming devices (10) according to one of claims 1 to 10 arranged around the circular reed (4). 12. Circular loom according to claim 11, characterized by a control cam carrier (17) driven by the main drive (18), wherein a stroke control cam (17d) is formed on the control cam carrier (17), which controls the first group and the second group of warp tape stroke elements (20, 21), wherein an actuator control cam (17e) is formed on the control cam carrier (17), which controls the actuator (35), and wherein preferably the stroke control cam (17d) and the actuator control cam (17e) are formed in one piece on the control cam carrier (17). 13. Circular loom according to claim 11 or 12, characterized in that the circular reed (4) has a plurality of reed dents (4a) and spacer bars (4b), wherein a number of reed dents (4a) are arranged alternately with at least one spacer bar (4b), wherein adjacent reed dents (4a) and adjacent reed dents (4a) and spacer bars (4b) are arranged at equal distances from one another in the circular reed (4) and have the same width. 14. Use of a circular weaving machine (1) according to one of claims 11 to 13 for producing a leno fabric (60). 15. Method for forming a shed (40) in a circular loom (1), wherein: a plurality of warp ribbons (5, 6) are provided in two warp ribbon sets (11, 12), the two warp ribbon sets (11, 12) are given mutually opposite alternating movements to form the shed (40), at least one of the two warp ribbon sets (11, 12) is subjected to a lateral back-and-forth movement between a first end position in which adjacent warp ribbons (5, 6) of the two warp ribbon sets (11, 12) do not cross each other, and a second End position in which two adjacent warp ribbons (5, 6) of the two warp ribbon groups (11, 12) cross each other longitudinally, is given, characterized in that the lateral back and forth movement of at least one of the two warp ribbon groups (11, 12) is given without contact by an actuating element (24) which is adjusted without contact by an actuator (35), wherein the actuating element (24) has at least one actuating magnet (24b, 24c) which is repelled or attracted by the actuator (35) by a magnetic operative relationship.