Clamping device for drawing-in machine, drawing-in machine comprising such clamping device and corresponding drawing-in method

Abstract

The clamping device comprises a frame structure (10) which can move in the longitudinal direction relative to a drawing-in unit of the drawing-in machine, a first clamping rail (20A) and a second clamping rail which are used for clamping a first yarn layer (L1) and fixed to the frame structure (10) in the longitudinal direction. The third clamping rail (22A) and the fourth clamping rail are used for clamping the second yarn layer, are connected to the frame structure (10) through sliding connecting rods (88) and can move in the longitudinal direction (LD) relative to the frame structure (10). A switching element (100) longitudinally fixed to the third clamping rail (22A) is movable between a first position and a second position; in the first position, the switching element longitudinally fixes the third clamping rail to the first clamping rail (20A); in the second position, the switching element allows relative longitudinal movement of the third clamping guide rail relative to the first clamping rail and does not cooperate with the frame structure and does not cooperate with the first clamping rail and the second clamping rail.

Description

[0001] The present application relates to a clamping device for a warp drawing-in machine, a warp drawing-in machine comprising such a clamping device, and a method for drawing-in two layers of yarn on the warp drawing-in clamping device in the warp drawing-in machine. Background Art

[0002] The technical field of the present application is a drawing-in device and a method for preparing a weaving machine device.

[0003] In the art, it is known to automatically draw in the warp yarns into the bundle according to a drawing-in pattern, with the drawing-in yarns being alternately separated from the two individual yarn layers. The bundle usually comprises healds, sometimes also draw-ins and a reed. For example, the drawing-in pattern requires drawing in ten yarns into the first layer, then fifty yarns into the second layer, then twenty-five yarns into the first layer, and so on.

[0004] Depending on the drawing-in pattern, a single separating device can be used to alternately separate the yarns of the first yarn layer and the yarns of the second yarn layer. In this case, when one layer is selected, it must be correctly placed relative to the separating device and the other layer should be away from the separating device to achieve yarn separation. Yarn separation must occur when the selected layer faces the separating device in the longitudinal direction and its frontmost yarn is within the separation range accessible by the yarn separating device.

[0005] As a result of using a single separating device, the two layers must be moved relative to each other in the longitudinal direction at the appropriate time during the threading process. This movement is sometimes called layer compensation.

[0006] This drawing-in sequence can be realized with a drawing-in machine known from EP 4 033 020 A1, which works well. In this known drawing-in machine, the first yarn layer is clamped between a first upper clamping track and a lower clamping track fixed relative to the structure of the clamping device. The clamping device comprises a layer compensation device, which has an upper adjustment device and a lower adjustment device, respectively, for independently moving an upper second clamping track and a lower second clamping track configured to clamp the second yarn layer relative to the frame structure. The layer compensation device is manually driven and its operation requires a period of time, during which the working process should be stopped. In addition, the compensation of the top and bottom tracks may be different.

[0007] If the clamping device is moved in the preparation chamber during the drawing-in process, there is a risk that the movable second clamping rails are slightly displaced longitudinally relative to the frame structure and to each other, which involves more frequent layer compensations and some yarn separation errors.

[0008] Therefore, there is a need for a clamping device and a drawing-in machine that allow automatic and optimized ply compensation for both plies. Summary of the invention

[0009] The present application aims to solve the above mentioned problems by providing an optimized clamping device which allows to achieve a high drawing-in performance by automatically adjusting each of the two yarn layers relative to a separating device of a drawing-in unit in a drawing-in machine.

[0010] In this respect, the present application relates to a clamping device for a warp drawing machine, the clamping device being configured to clamp a first yarn layer and a second yarn layer and comprising

[0011] - a frame structure which is movable in the longitudinal direction relative to the drawing-in unit of the drawing-in machine;

[0012] - a first pair of clamping rails for clamping the first yarn layer, the first pair of clamping rails comprising a first clamping rail and a second clamping rail fixed to the frame structure in the longitudinal direction;

[0013] - a second pair of clamping rails for clamping the second yarn layer, said second pair of clamping rails comprising a third clamping rail and a fourth clamping rail connected to the frame structure by a sliding connection, such that the third clamping rail and the fourth clamping rail are movable in the longitudinal direction relative to the frame structure. According to the application, the clamping device comprises a switching element which is longitudinally fixed to the third clamping rail and is movable relative to the frame structure between the following positions:

[0014] a first position in which the switch element cooperates with the frame structure or the first clamping rail to longitudinally fix the third clamping rail to the first clamping rail; and

[0015] a second position in which the switching element allows a relative movement of the third clamping rail with respect to the first clamping rail in the longitudinal direction and in which the switching element does not cooperate with the frame structure or the first pair of clamping rails.

[0016] Due to the present application, the switching element allows the clamping device to work in different configurations. In a first configuration, corresponding to a first position of the switching element, the second clamping rail is longitudinally fixed to the first clamping rail, so that the two yarn layers clamped in these two clamping rails can be moved together in the longitudinal direction relative to the warp drawing-in unit. This allows the position of the two yarn layers to be adjusted simultaneously relative to the yarn selection device, in particular during a working phase of the warp drawing-in method using the clamping device. In a second configuration of the clamping device, corresponding to a second position of the switching element, one of the first clamping rail and the second clamping rail can be moved in the longitudinal direction without moving the other clamping rail, which allows the position of only one of the two yarn layers to be adjusted relative to the yarn selection device during the offset compensation phase and to adjust the position of the first yarn layer relative to the second yarn layer.

[0017] According to a further advantageous aspect of the present application, the clamping device can combine one or more of the following features in any technically compatible configuration:

[0018] The switching element is rotatable between its first position and its second position about a rotation axis relative to the frame structure and the third clamping rail, the rotation axis preferably being parallel to the longitudinal direction.

[0019] At least one guide bearing is fixed to the third clamping rail for guiding the switching element about the axis of rotation between its first position and its second position.

[0020] The clamping device is equipped with at least one elastic return member, in particular a spring, which pushes the switching element towards its first position.

[0021] The switching element comprises a clamping surface, preferably a toothed clamping surface, which is configured to cooperate with the threading unit when the switching element is in its second position and the clamping surface of the switching element extends over a longitudinal clamping length which is at least as long as the longitudinal clamping length of the third clamping rail.

[0022] - in the first position of the switching element, the clamping surface of the switching element cooperates with the frame structure, preferably by friction, to longitudinally fix the switching element relative to the frame structure, wherein the clamping surface extends over a longitudinal clamping length which is strictly smaller than a longitudinal clamping length of the third clamping rail, and wherein the clamping surface covers a longitudinal height of a midpoint of the longitudinal clamping length which is located in the longitudinal direction midway between the two longitudinal ends of the third clamping rail.

[0023] - the frame structure comprises a drive surface, in particular a toothed drive surface;

[0024] - the drive surface is configured to cooperate with a layer transfer device belonging to the threading unit for a relative longitudinal movement between the frame structure and the threading unit;

[0025] - at least one bracket longitudinally fixing the switching element to the third clamping rail;

[0026] Each bracket extends through the elongated hole of the frame structure so that the switch element is located on the side of the drive surface opposite the first and second yarn layers and extending in a transverse direction perpendicular to the yarn layers.

[0027] -The clamping device includes a transmission member, specifically a cable, whose ends are respectively fixed to the third clamping rail and the fourth clamping rail for synchronizing their movement relative to the frame structure in the longitudinal direction; and the transmission member can be deformed to adapt to the adjustment of the relative position of the third clamping rail and the fourth clamping rail in the direction perpendicular to the longitudinal direction.

[0028] The frame structure is pivotably mounted on a truck of the clamping device, said truck being equipped with wheels for moving the truck on the ground.

[0029] According to a second aspect, the present application relates to a warp drawing-in machine comprising

[0030] - A clamping device according to any one of the preceding claims;

[0031] - a drawing-in unit equipped with

[0032] Unit framework;

[0033] a layer selection device configured to select a yarn layer from among the first yarn layer and the second yarn layer clamped on the clamping device;

[0034] a yarn separating device configured to separate the yarns of the yarn layer selected by the layer selecting device;

[0035] - a layer transfer device configured to perform a relative longitudinal movement of the frame structure of the clamping device with respect to the unit frame;

[0036] - a layer compensation device comprising a part movable relative to the frame structure of the clamping device and configured to move the switching element at least from its first position to its second position;

[0037] - a controller, which controls at least the layer selection device, the yarn separation device, the layer conveying device and the layer compensation device;

[0038] In the second position of the switching element, the switching element is fixed to the unit frame of the threading unit in the longitudinal direction.

[0039] This drawing-in machine provides the same advantages as the clamping device of the present application. In addition, since the drawing-in unit and the switching element are longitudinally fixed together when the switching element is in its second position, the longitudinal position of the switching element and the longitudinal position of any components longitudinally connected to the switching element are accurately controlled.

[0040] Advantageously,

[0041] - the threading unit comprises a layer compensation device;

[0042] - the movable part of the layer compensation device is movable relative to the unit frame of the threading unit only in a direction perpendicular to the longitudinal direction, between an inactive position and an active position;

[0043] - a movable part of the layer compensation device co-operates with the switching element in its active position and is longitudinally fixed to the switching element, said switching element being in its second position;

[0044] - The movable part of the layer compensation device does not cooperate with the clamping device in its inactive position.

[0045] According to the advantageous aspects of this application,

[0046] - the warp drawing machine comprises a yarn detection device, preferably a camera, configured to detect the leading yarn of the selected yarn layer;

[0047] - the yarn detection device is connected to the controller;

[0048] - the controller is configured to determine the longitudinal position of the leading yarn of the yarn layer relative to the unit frame based on the output signal of the yarn detection device; and

[0049] The drawing-in machine comprises a memory for storing information about the longitudinal position of the leading yarn relative to the yarn layer to which the leading yarn belongs.

[0050] According to another advantageous aspect of the application, the third clamping rail is closer to the yarn separating device than the fourth clamping rail.

[0051] According to a third aspect, the present application also relates to a warp drawing-in method for drawing-in a first yarn layer and a second yarn layer clamped on a clamping device of the warp drawing-in machine,

[0052] The clamping device comprises

[0053] - a frame structure which is movable in the longitudinal direction relative to the drawing-in unit of the drawing-in machine;

[0054] - a first pair of clamping rails for clamping the first yarn layer, the first pair of clamping rails comprising a first clamping rail and a second clamping rail fixed to the frame structure in the longitudinal direction;

[0055] a second pair of clamping rails for clamping the second yarn layer, the second pair of clamping rails comprising a third clamping rail and a fourth clamping rail connected to the frame structure such that the third clamping rail and the fourth clamping rail are movable in longitudinal direction relative to the frame structure;

[0056] The drawing-in unit includes

[0057] - unit frame;

[0058] - a layer selection device configured to select a yarn layer between a first yarn layer and a second yarn layer from which the yarn is separated;

[0059] - a yarn separating device configured to separate the yarns of the yarn layer selected by the layer selecting device;

[0060] The warp drawing machine comprises a controller for controlling at least the layer selection device and the yarn separation device;

[0061] The warp drawing method comprises at least alternation of a working phase and a deviation compensation phase;

[0062] In each working phase, the first clamping rail of the first pair of clamping rails and the third clamping rail of the second pair of clamping rails move together in the longitudinal direction relative to the unit frame;

[0063] in

[0064] -The working phase includes at least the following steps:

[0065] a) fixing the third clamping rail to the first clamping rail or the frame structure in the longitudinal direction so that a longitudinal relative movement between the first clamping rail and the third clamping rail is not possible;

[0066] b) using the layer selection device, selecting a yarn layer from which the yarn separating device is to separate the yarn, and deselecting another yarn layer;

[0067] - The offset compensation phase includes at least the following steps:

[0068] c) allowing longitudinal movement of the third clamping rail relative to the first clamping rail and the frame structure, and

[0069] Fixing the third clamping rail to the unit frame of the threading unit in the longitudinal direction; and

[0070] d) moving the first clamping rail in the longitudinal direction relative to the unit frame to adjust the longitudinal distance between the leading yarn of the first yarn layer and the leading yarn of the second yarn layer.

[0071] Thanks to the method of the present application, two pairs of clamping rails can be used to longitudinally move the first yarn layer and the second yarn layer together or one at a time to allow working phases and offset compensation phases to occur when necessary.

[0072] According to a further advantageous aspect of the present application, the method may combine one or more of the following features in any technically compatible configuration.

[0073] - the drawing-in unit comprises a yarn detection device configured to detect the longitudinal position of the leading yarn of the selected yarn layer relative to the unit frame;

[0074] - The working phase includes at least additional steps carried out before step b), including:

[0075] e) storing the last longitudinal position of the leading yarn of each yarn layer relative to the unit frame before the yarn layer is selected, the last position depending on the output signal of the yarn detection device;

[0076] f) calculating the offset between two yarn layers based on the last stored longitudinal position of the leading yarn of each yarn layer,

[0077] g) comparing the offset value calculated in step f) with a predetermined value; and

[0078] h) If the result of step g) is that the offset calculated in step f) is greater than a predetermined value, the working phase is stopped and an offset compensation phase is started. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The present application will be better understood through the following description given as non-limiting examples and with reference to the following drawings:

[0080] - Figure 1 is a perspective view of a drawing-in machine according to the present application, which includes, among other things, a clamping device and a drawing-in unit according to the present application;

[0081] - Figure 2 yes Figure 1 A front view of some parts of the clamping device and some parts of the threading unit;

[0082] - Figure 3 yes Figure 2 Enlarged view of detail III;

[0083] - Figure 4 yes Figure 2 A side view of the clamping device and some parts of the threading unit in the direction of arrow IV;

[0084] - Figure 5 is a rear view of the various parts of the clamping device;

[0085] - Figure 6 yes Figure 5 A magnified view of detail VI;

[0086] - Figure 7 It is a perspective rear view of the frame structure;

[0087] - Figure 8 yes Figure 7 A magnified view of detail 8;

[0088] - Fig. 9 When the switch element is in the first position, Figure 2 Detailed transverse section view at the height of midplane IX-IX;

[0089] -[ Fig.10 ] Fig.10 When the switch element is in the second position, similar to Fig. 9 Detailed cross-sectional view of the .

[0090] -[ Fig.11 ] Fig.11 is along Fig.10 Partial front view in the direction of arrow XI. DETAILED DESCRIPTION

[0091] Figure 1 The shown drawing-in machine 2 comprises a drawing-in unit 4, which is schematically represented by a housing in its axis, and a clamping device 6.

[0092] Figures 2 to 4 and Figures 9 to 11 Some parts of the drawing-in unit 4 are shown.

[0093] The main unit frame 42 of the threading unit 4 is fixed on the floor GS in the threading room where the threading is performed. Figure 2 and Figure 3 The threading unit 4 comprises only Figure 4 The single yarn separation device 5 shown in the drawing machine, the heald separation device not shown, the heald transmission device not shown, the reed transmission device not shown, and the threading device not shown. Optionally, the drawing machine also includes an introduction wire separation device not shown and an introduction wire transmission device not shown.

[0094] LD denotes the longitudinal direction of the clamping device 6. Hereinafter, "longitudinal" and "longitudinally" refer to movements parallel to the longitudinal direction LD. A longitudinal position is a position along the longitudinal direction LD.

[0095] The yarn separating device 5 may be a longitudinally movable vacuum gripper, as described in WO 02 / 088445 A2.

[0096] Alternatively, the yarn separating device is of another type.

[0097] The yarn separating device 5 is configured to separate the leading yarn from the selected yarn layer when the leading yarn is within a separation range defined relative to the unit frame 42 of the threading unit 4 .

[0098] During the drawing-in process carried out with the drawing-in machine 2, the drawing-in unit 4 and the thread layer selected on the clamping device 6 are moved relative to each other in the longitudinal direction LD.

[0099] In the embodiment of the figure, since the main frame of the threading unit 4 is fixed, the clamping device 6 moves along the longitudinal direction LD on the ground GS.

[0100] The clamping device 6 comprises a movable truck 8 and a frame structure 10 which is pivotably mounted on the truck 8 about an axis of rotation X6 parallel to the longitudinal direction LD of the clamping device 6 .

[0101] The truck 8 is equipped with wheels 12 which allow the clamping device 6 to be moved on the ground surface GS in the drawing room, in particular in the longitudinal direction LD.

[0102] The frame structure 10 is formed by two vertical columns 70 and 72 and two longitudinal cross beams 74 and 76 .

[0103] The frame structure 10 is provided with plates 14 which anchor the frame structure 10 on pins 16 of the truck 8 when the frame structure 10 is extended in a vertical plane for the threading process.

[0104] The clamping device 6, more specifically its frame structure 10, is configured to hold the first yarn layer L1 and the second yarn layer L2 for use by the yarn separating device 5. For simplicity, the yarn layers L1 and L2 are Figure 1 The middle part indicates that Figure 4 and Fig. 9 Indicated by dotted line.

[0105] Figure 4 and Fig. 9 Also shown are layer cords 24 inserted between the two yarn layers L1 and L2. The layer cords 24 extend parallel to the longitudinal direction LD and separate the yarns of the first yarn layer L1 from the yarns of the second yarn layer L2.

[0106] The clamping device 6 comprises a first pair 20 of two clamping rails, namely a first upper clamping rail 20A and a first lower clamping rail 20B for clamping the first yarn layer L1. The warp yarns of the yarn layer L1 extend in a vertical direction between the first upper clamping rail 20A and the first lower clamping rail 20B for drawing in. These yarns are adjacent to each other in the longitudinal direction LD. The frontmost yarn FY1 of the yarn layer L1 is a warp yarn located at the edge of the yarn layer L1 and on the yarn separating device side in the longitudinal direction LD.

[0107] The clamping device 6 further comprises a second pair 22 of two clamping rails, namely a second upper clamping rail 22A and a second lower clamping rail 22B for clamping the second yarn layer L2. The warp yarns of the yarn layer L2 extend in a vertical direction between the second upper clamping rail 22A and the second lower clamping rail 22B for drawing in the warp. These yarns are adjacent to each other in the longitudinal direction LD. The frontmost yarn FY2 of the yarn layer L2 is a warp yarn located at the edge of the yarn layer L2 and on the yarn separating device side in the longitudinal direction LD.

[0108] The clamping rails 20A, 20B, 22A and 22B are respectively a first clamping rail, a second clamping rail, a third clamping rail and a fourth clamping rail of the clamping device 6 .

[0109] exist Figures 1 to 3 In the embodiment, the yarn separating device side is located on the left side of each layer of yarn.

[0110] The second upper clamping rail 22A and the second lower clamping rail 22B are located between the first upper clamping rail 20A and the first lower clamping rail 20B in the vertical direction.

[0111] When clamped in a respective pair of clamping rails, each layer L1 , L2 extends in a vertical plane.

[0112] Each clamping track is provided with a longitudinal inner clamping volume to accommodate a clamping rod 30 for clamping the yarns of one yarn layer L1 or L2 in the corresponding clamping track. The clamping rod 30 is accommodated in 20A, 20B of the first pair of clamping tracks 20 and 22A, 22B of the second pair of clamping tracks 22, respectively.

[0113] To keep it simple, Fig.10 The clamping rod 30 is not shown.

[0114] The threading unit 4 comprises only Figure 4 The layer selection device 18 shown in the figure is configured to select one of the two yarn layers L1 and L2 by moving the layer cord 24 relative to the frame structure 10, and to deselect the other of the two yarn layers L1 and L2 by pushing the unselected yarn layer away from the yarn separating device 5.

[0115] The layer selection device may be as disclosed in CN211036281U.

[0116] Alternatively, the layer selection means may be of a different type.

[0117] The threading unit comprises a controller 44 mounted on a unit frame 42, a worm 46 pivotally mounted on the unit frame 42 and rotating about a rotation axis X4. A worm wheel 48 is mounted on the worm 46 and moves along the axis X4 according to the rotation of the worm 46. The only movement of the worm wheel 48 is a translation along the axis X4 on the worm 46. The worm 46 and the worm wheel 48 together belong to a worm gear mechanism, which also includes an actuator, not shown, such as a motor, for driving the worm 46 to rotate about the axis X4.

[0118] The head 50 is mounted on the worm gear 48 and is movable along a vertical axis Z4 perpendicular to the rotation axis X4. The movable head 50 is driven along the vertical axis Z4 by another actuator, not shown, such as an electric motor.

[0119] The movable head 50 is provided with teeth 52 oriented upwards along a vertical axis Z4 .

[0120] The parts 46 , 48 and 50 together form a layer transfer device 54 capable of moving the frame structure 10 along the longitudinal direction LD and selecting the yarn layer L1 or the yarn layers L1 and L2 , as will be apparent from the following description.

[0121] The threading unit 4 also comprises a layer compensation device 56 comprising a piston 58 which is movable relative to the unit frame 42 only along an axis Z′ 4 parallel to the vertical axis Z4 .

[0122] The axes Z4 and Z′4 are perpendicular to the longitudinal direction LD.

[0123] The threading unit 4 further comprises a yarn detection device 60, which in the example of the figure is a camera and is configured to detect at least the frontmost yarn FY1 of the first yarn layer L1 or at least the frontmost yarn FY2 of the second yarn layer L2, preferably the frontmost yarn of the selected yarn layer, by taking a photo of the frontmost yarn. For simplicity, the camera 60 is only Fig. 9 Shown in.

[0124] The camera 60 is used to detect the longitudinal position of the selected yarn layer relative to the reference position of the unit frame 42 of the warp drawing unit 4 based on the longitudinal position of its frontmost yarn. The camera 60 is also configured to detect whether the yarn separating device 5 has separated a single yarn from the selected yarn layer. Since the camera is fixedly mounted on the unit frame 42, it remains stationary with the warp drawing unit 4 and moves relative to the frame structure 10 during the warp drawing process.

[0125] Advantageously, the field of view 60A of the camera 60 is positioned relative to the frame structure 10 so that the unselected yarn layers pushed aside by the layer cords 24 by the action of the yarn selection device 18 are not within the field of view.

[0126] Figure 1 The components 42 to 60 of the warp drawing-in machine are not visible in the drawing-in machine because they are integrated in the housing of the stationary warp drawing-in unit 4 .

[0127] The first upper clamping rail 20A and the first lower clamping rail 20B are longitudinally fixed to the frame structure 10 .

[0128] Advantageously, the track 20A is screwed to the armature 84 of the frame structure 10. Alternatively, other techniques may be used to fix the track to the frame structure, such as riveting or welding. The fixation of the track 20B to the clamping device 6 is removable so that the yarn layer L2 can be mounted in the second pair of clamping tracks 22.

[0129] The frame structure 10 further comprises a drive surface 80 extending in the longitudinal direction LD. The drive surface 80 is provided with teeth 82 adjacent to each other in the longitudinal direction LD. It is a toothed drive surface. The drive surface 80 is made of the longitudinal edges of the folded portion 83 of the armature 84 of the frame structure 10.

[0130] L80 denotes the length of the toothed drive surface 80 measured in a direction parallel to the longitudinal direction LD. The length L80 is the longitudinal drive length of the toothed drive surface 80.

[0131] L20 denotes the longitudinal clamping length of the clamping rails 20A, 20B, 22A and 22B measured in a direction parallel to the longitudinal direction LD. In practice, these clamping rails are identical and have the same length L20, i.e. the longitudinal clamping length of these rails. The longitudinal clamping length L20 of the second upper clamping rail 22A is measured in the longitudinal direction LD between the two longitudinal ends of the second upper clamping rail 22A.

[0132] Advantageously, the longitudinal drive length L80 is at least as long as the longitudinal clamping length L20 of all clamping rails.

[0133] Preferably, the longitudinal drive length L80 is absolutely greater than the length L20.

[0134] Advantageously, the teeth 82 of the drive surface 80 are complementary to the teeth 52 of the movable head 50. Thus, the movable head 50 and the drive surface 80 may be in meshing engagement, such as Figure 3 shown.

[0135] In the meshing configuration of the layer conveying device 54 and the drive surface 80, i.e. when the teeth 52 of the layer conveying head 50 engage in the teeth 82 on the tooth drive surface 80, the layer conveying head 50 is longitudinally fixed to the drive surface 80, and the longitudinal movement of the worm wheel 48 of the worm gear mechanism of the layer conveying device 54 relative to the unit frame 42 of the threading unit 4 causes the same longitudinal movement of the armature 84. This longitudinal movement of the armature 84 is the same as the longitudinal movement of the frame structure 10 relative to the unit frame 42 of the threading unit, the yarn separating device 5 of the threading unit 4, the layer selection device 18 and the yarn detection device 60.

[0136] When the worm wheel 48 reaches the first longitudinal end of its path defined by the worm gear mechanism, the movable head 50 is retracted into a non-engaged configuration of its teeth 52 with the teeth 82 of the drive surface 80. The head 50 is then moved by the layer conveyor 54 toward the second longitudinal end of the path and away from the first longitudinal end. The movable head 50 then again enters a meshing configuration of its teeth 52 with the teeth 82 of the drive surface 80. The worm gear mechanism is then actuated and moves the worm wheel 48 along the worm 46, which allows the drive surface 80, and thus the armature 84, to move further longitudinally relative to the frame 42 of the threading unit 4.

[0137] With this engaging and non-engaging configuration, the drive surface 80 is configured to selectively engage the layer transport device 54 .

[0138] On the other hand, each of the second upper clamping rail 22A and the second lower clamping rail 22B is connected to the frame structure 10 by a sliding link 88. Each sliding link 88 includes a rib 88A, which is fixed to the corresponding clamping rail and engages in a rib profile 88B longitudinally fixed to the frame structure 10. Due to the sliding links 88, the upper and lower second clamping rails 22A and 22B can slide in the longitudinal direction LD relative to the frame structure 10 and the first upper and lower clamping rails 20A and 20B longitudinally fixed to the armature, when such relative movement is allowed, as will be apparent from the following description.

[0139] Advantageously, several brackets 86 are fixed to a longitudinal beam 90 fixed to the second upper clamping rail 22A. In the example of the figures, five brackets are provided over the longitudinal clamping length L20 of the second upper clamping rail 22A.

[0140] The number of brackets 86 is unlimited.

[0141] The clamping device further comprises a switching element 100 .

[0142] Advantageously, the switch element 100 is in the form of a rod and is made from a folded metal sheet.

[0143] L100 represents the length of the switching element 100 in the longitudinal direction.

[0144] This length is at least as long as the longitudinal clamping length L20 of the clamping rails, in particular the second pair of clamping rails 22 .

[0145] The switch element 100 is rotatable about a rotation axis X100 relative to the support 86 and the frame structure 10. The rotation axis X100 is preferably parallel to the longitudinal direction LD.

[0146] One or more warp beams, not shown, provide yarns for forming the yarn layers L1 and L2 clamped on the clamping rails 20A, 20B, 22A and 22B. They are located on the back of the frame structure 10 and provide the yarn layers L1, L2 from the bottom of the clamping device 6.

[0147] The switch element 100 is located on the back side of the frame structure 10 along the transverse direction LA perpendicular to the longitudinal direction LD and the vertical direction (i.e. perpendicular to the yarn layers L1, L2), i.e. on the side of the warp beam relative to the yarn layers L1 and L2 and relative to the toothed drive surface 80. Specifically, each bracket 86 is configured so that the switch element 100 is located on the side of the drive surface 80 opposite to the first yarn layer L1 and the second yarn layer L2 along the transverse direction LA.

[0148] The switch element 100 is located between the upper clamping rail and the lower clamping rail in a vertical direction parallel to the columns 70 and 72. Preferably, the second upper clamping rail 22A on which the switch element 100 is mounted is closer to the yarn separating device 5 than the second lower clamping rail 22B. This ensures high accuracy of the position of the second yarn layer L2 relative to the yarn separating device 5.

[0149] The brackets 86 extend from the longitudinal beam 90 in a direction parallel to the columns 70 and 72 into the intermediate volume V10 defined by the frame structure 10 between the two upper clamping rails and the two lower clamping rails and between these columns in the longitudinal direction LD. This is made possible by the upper vertical leg 86A of each bracket 86 passing through the elongated hole 84A of the armature 84.

[0150] The major dimension of each elongated hole 84A is parallel to the longitudinal direction LD. The major dimension of each elongated hole 84A allows relative longitudinal movement between the upper vertical leg 86A and the armature 84 when the second upper clamping rail 22A moves longitudinally relative to the armature 84.

[0151] The switching element 100 is pivotably mounted on each support 86 , can rotate about an axis of rotation X100 , and is guided in this rotation by a guide bearing 92 carried by each support 86 .

[0152] The switching element 100 is longitudinally fixed to the bracket 86. For this purpose, advantageously, at the level of each bracket 86, a rod 118 is screwed to the switching element 100 and extends in the longitudinal direction LD through the bracket 86 and the guide bearing 92 carried by this bracket 86. The rod 118 longitudinally maintains the two flanges of the bracket 86 clamped in the longitudinal grooves of the switching element 100. Since the bracket 86 is longitudinally fixed to the second upper clamping rail 22A via the longitudinal beam 90, the bracket 86 fixes the switching element 100 longitudinally to the second upper clamping rail 22A.

[0153] The switch element 100 can be moved around the axis X100. Figure 4 , 8 and the first position shown in 9 and Fig.10 and 11 The second position is shown.

[0154] The movement of the switching element 100 between its first position and its second position is controlled by the layer compensation device 56 .

[0155] Here, the "position" of the switching element refers to the angular position of the switching element 100 about the rotation axis X100. Therefore, the first position and the second position of the switching element are independent of the actual position of the switching element in the longitudinal direction.

[0156] In its first position, the switch element 100 cooperates with the frame structure 10 to longitudinally fix the second upper clamping rail 22A to the first upper clamping rail 20A. In the first position of the switch element, longitudinal relative movement between the first clamping rail 20A and the second clamping rail 22A is not possible.

[0157] like Figure 8 As shown, an extension plate 102 is fixed to the upper cross member 74. The extension plate forms a friction surface 104 that extends approximately mid-length of the upper longitudinal cross member 74.

[0158] On the other hand, the switch element 100 has a folded tongue 106 with a contact block 108. The contact block 108 forms a clamping surface 110 configured to cooperate with the friction surface 104 carried by the extension plate 102. The clamping surface 110 extends in the longitudinal direction LD, forming a longitudinal clamping length L110, which is absolutely smaller than the longitudinal clamping length L20 of the second upper clamping rail 22A, preferably at least 20 times smaller.

[0159] In the first position of the switch element 100 , the clamping surface 110 cooperates with the friction surface 104 and the switch element 100 longitudinally secures the second upper clamping rail 22A to the first upper clamping rail 20A.

[0160] Consider the central support 86, i.e. the support which is at least halfway between the two longitudinal ends of the second upper clamping track 22A in the longitudinal direction LD. Advantageously, the folded tongue 106 and the clamping surface 110 are located at the height of the central support 86 in the longitudinal direction LD. In other words, the clamping surface 110 covers the longitudinal height of the midpoint of the longitudinal clamping length L20, which is located halfway between the two longitudinal ends of the third clamping track 22A in the longitudinal direction LD. This ensures that the switching element 100 has a minimum torque when the piston 58 engages with the switching element 100 at one of its longitudinal ends.

[0161] Two springs 112 extend between the central support 86 and the folded tongue 106 and exert on the switching element 100 a torque about the axis of rotation X100 which by default pushes the switching element 100 towards its first position in which the clamping surface 110 abuts and contacts the friction surface 104 .

[0162] There is no limit to the number of springs 112. It can be equal to 1, or greater than or equal to 3.

[0163] In a variant of the present application, not shown, a torsion spring mounted around the axis of rotation X100 can be used to urge the switching element 100 towards its first position.

[0164] The contact exerted between the friction surface 104 and the clamping surface 110 results in the switch element 100 being fixed to the extension plate 102 and thus to the upper crossbeam 74 of the frame structure 10 in the longitudinal direction LD.

[0165] The switch element 100 also forms an elongated clamping surface 114 provided with teeth 116. Fig. 9 and Fig.10 As shown, the clamping surface 114 forms a longitudinal edge of a band 118 of the switch element opposite the contact block 108. The teeth 116 are adjacent to each other in the longitudinal direction LD.

[0166] L114 represents the length of the clamping surface 114 in the longitudinal direction LD.

[0167] In the example of the figure, the lengths L100 and L114 are the same.

[0168] The length L114 is at least as long as the longitudinal length L20 of the clamping rails, in particular of the second pair of clamping rails 22 .

[0169] L82 represents the length of the teeth 82 of the driving surface 80, that is, the gap between two adjacent teeth 82 in the longitudinal direction LD.

[0170] L116 represents the length of the teeth 116 of the clamping surface 114 , ie, the gap between two adjacent teeth 82 in the longitudinal direction LD.

[0171] Advantageously, the length L116 is definitely smaller than the length L82, preferably at least three times smaller.

[0172] d110 denotes the distance between this axis and the clamping surface 110 measured radially with respect to the axis of rotation X100 .

[0173] d114 denotes the distance between this axis and the clamping surface 114 measured radially with respect to the axis of rotation X100 .

[0174] Advantageously, the distance d110 is definitely smaller than the distance d114 . Thus, with respect to the axis of rotation X100 , the lever arm of the force exerted on the clamping surface 114 is greater than the lever arm of the force exerted on the clamping surface 110 .

[0175] In its first position, the switch element 100 cooperates with the extension plate 102 by friction between the surfaces 110 and 104. Thus, when the armature 84 and the first upper clamping rail 20A are moved by the layer conveying device 54 in the longitudinal direction LD relative to the structure of the threading unit 4, this longitudinal movement is transmitted to the extension plate 102, the switch element 100, the bracket 86 and the second upper clamping rail 22A.

[0176] This transmission of longitudinal movement is more effective because the friction surface 104 is provided with adjacent openings or recesses and the clamping surface 110 is made of rubber in order to increase the friction between the surfaces 104 and 110. Advantageously, when the switch element 100 is in its first position, the clamping surface 110 cooperates with at least two adjacent openings of the friction surface 104. These adjacent openings are optional.

[0177] The fact that the second pair of two clamping rails 22 are mounted on the frame structure 10 and can move longitudinally relative to the frame structure when the switch element 100 is in its second position allows layer compensation. This is why each second clamping rail 22A, 22B is supported by a sliding link 88 on the frame structure.

[0178] L102 denotes the length of the extension plate 102 measured parallel to the longitudinal direction LD. This length is relatively small compared to the lengths L20 and L80, so only limited layer-compensating longitudinal movement can occur between the clamping surface 110 and the friction surface 104. The extension plate 102 is located midway between the posts 70 and 72 along the longitudinal direction LD.

[0179] The frame structure 10 further comprises a brush 120. The brush 120 is used to stretch the yarn before it is clamped by the clamping rod 30 in the first pair 20 and the second pair of clamping rails 22. When the brush 120 is not used to stretch the yarn, it can be retracted relative to the frame structure 10 to reduce the overall size of the frame structure. A sensor (not shown) of the drawing-in machine 2 can detect the position of the brush 120 relative to the frame structure 10 in order to detect whether the brush is retracted.

[0180] The cable 124 connects the second upper clamping rail 22A and the second lower clamping rail 22B and enables the two rails to move together in the longitudinal direction LD relative to the frame structure 10. In other words, the cable 124 is a transmission member between the second pair of clamping rails 22 and synchronizes the longitudinal movement of the second upper clamping rail 22A relative to the frame structure 10 with the longitudinal movement of the second lower clamping rail 22B relative to the frame structure 10 in any sense of movement along the longitudinal direction LD. The cable 124 allows the second upper clamping rail 22A to pull the second lower clamping rail 22B along the longitudinal direction LD. The cable 124 or the sheath surrounding the cable is also sufficiently rigid to allow the second upper clamping rail 22A to push the second lower clamping rail 22B along the longitudinal direction LD. Due to its flexibility and deformability, the cable 124 allows and accommodates vertical relative movement between the second upper clamping rail 22A and the second lower clamping rail 22B, i.e., movement in the transverse direction relative to the longitudinal direction LD, which is used to tension the second yarn layer L2 when necessary.

[0181] like Figure 1 , 2, 5 and 7, the cable 124 is placed on the back of the frame structure 10 along the transverse direction LA relative to the clamping rails 20A, 20B, 22A and 22B, and the first end of the cable 124 is connected to one of the brackets 86 of the second upper clamping rail 22A, such as the bracket 86 closest to the vertical column 72. The other end of the cable 124 is connected to a connector plate 126, which is fixed to the second lower clamping rail 22B on the side of the vertical column 70, for example, screwed to the rail, and extends from the second lower clamping rail.

[0182] Alternatively, another type of transmission member, such as a semi-flexible rod, may be used in place of the cable 124 .

[0183] The first upper clamping rail 20A and the second upper clamping rail 20B are mounted on the frame structure 10 and cannot be moved in the vertical direction. In order to allow each of the two yarn layers L1 and L2 to be tensioned individually, the first lower clamping rail 20B and the second lower clamping rail 22B are each mounted on the frame structure 10 and can be moved vertically individually parallel to the columns 70 and 72, as shown in FIG. Figure 5 As shown by the double arrows A20 and A22.

[0184] The first lower clamping rail 20B includes at least two support bases 130. A nut 140 is fixed to each support base 130 in rotation and vertical direction. The second lower clamping rail 22B is mounted on at least two support bases 132 by means of a sliding link 88 for possible longitudinal movement of the second lower clamping rail 22B relative to the support base 132. The nut 142 is fixed to each support base 132 in rotation and vertical direction. For example, the nut is welded to the support base. Each nut 140 cooperates with a threaded rod 150, and each nut 142 cooperates with a threaded rod 152. The threaded rod 150 is used to move up and down on the first lower clamping rail 20B and is driven to rotate by a set of chains 160 and gears 170 controlled by a common respective wrench 180. Similarly, the threaded rod 152 is used to move up and down on the second lower clamping rail 22B and is driven to rotate by a set of chains 162 and gears 172 controlled by a respective universal wrench 182. The chains 160, 162 and the gears 170, 172 are supported by the frame structure 10, in particular by the lower crossbeam 76. Near the two vertical columns 70 and 72, the vertical movement of each lower clamping rail is guided by guide vertical columns 190 and 192 of the frame structure 10 that cooperate with corresponding grooves of the support bases 130 and 132. The support bases 130, 132 cannot move longitudinally relative to the frame structure 10. Therefore, the second lower clamping rail 22B is connected to the frame structure 10 by a sliding link 88 for possible relative longitudinal movement, and by the cooperation of the guide vertical column 192 and the support base 132 for possible relative vertical movement. The wrenches 180 and 182 are located on one longitudinal side of the frame structure 10, in this example close to the vertical column 72. They are manually and individually actuated by the operator when the clamped yarn layer L1 or L2 requires more tension or less tension.

[0185] The cable 124 is compatible with vertical movement of the lower clamping rails 20B and 22B relative to the frame structure 10 initiated by the wrenches 180 and / or 182 .

[0186] The piston 58 is the movable part of the layer compensation device 56 and has an upwardly turned end face 58A which is provided with teeth 59 whose shape allows them to mesh with the teeth 116 of the clamping surface 114 of the switching element 100 .

[0187] The piston 58 can be in an inactive or lowered position (eg, Fig. 9 As shown, it does not interact with the clamping device 6) and the active or higher position (such as Fig.10 and 11When the piston 58 moves from its inactive position to its active position, its toothed end face 58A cooperates with the clamping surface 114 of the switch element 100 and pushes the clamping surface upward, which causes the switch element 100 to overcome the force applied by the spring 112 and move along the Fig.10 100. As a result, the clamping surface 110 of the switching element 100 is disengaged from the friction surface 104 of the extension plate 102. In other words, when the piston 58 of the layer compensation device 56 is in its active position, it brings the switching element 100 into its second position, in which it does not hold the second upper clamping rail 22A, which is translationally fixed to the armature 84 or the first upper clamping rail 20A along the longitudinal direction LD.

[0188] The cooperation between the clamping surface 114 and the piston 58 is achieved by means of the teeth 59 and 116, which enables the switching element 100 to be longitudinally fixed to the layer compensation device 56 in the active position of the piston 58 and thus to the unit frame 42 of the pass-through unit when the switching element is in its second position. Since the switching element 100 is fastened in the longitudinal direction LD to the second upper clamping rail 22A in its second position, the fact that the switching element is longitudinally fixed relative to the unit frame 42 results in the second clamping rail 22A also being longitudinally fixed to the unit frame 42. Due to the action of the cable 124, the second lower clamping rail 22B is also longitudinally fixed to the unit frame 42.

[0189] When the piston 58 returns to the inactive position, the switch element 100 rotates in the direction opposite to the arrow A100 under the elastic urging of the spring 112. The switch element 100 follows the downwardly directed movement of the piston 58 until the engagement between the piston 58 and the switch element 100 ends and the clamping surface 110 of the switch element 100 again engages with the friction surface 104 of the extension plate 102. The switch element 100 returns to its first position.

[0190] The clamping surface 114 and the drive surface 80 are oriented in the same direction, in particular downwards in the illustrated example. The clamping surface 114 is displaced relative to the drive surface 80 along the transverse direction LA toward the rear of the frame structure 10 by a non-zero distance d1. The clamping surface 114 is also displaced relative to the drive surface 80 downwards by a non-zero height difference h1 in the vertical direction.

[0191] The clamping surface 114 serves as an actuation surface which is configured to work together with the layer compensation device 56 to move the switching element 100 from its first position to its second position.

[0192] When the switching element 100 is in its second position, the first upper clamping rail 20A and the first lower clamping rail 20B follow the longitudinal movement set by the layer conveying device 54 to the frame structure 10 relative to the unit frame 42, while the second upper clamping rail 22A and the second lower clamping rail 20B do not move longitudinally relative to the frame 42 of the passing unit 4 because they are locked in the appropriate position relative to the unit frame 42 by the cooperation of the teeth 59 and 116.

[0193] Thus, the first and second yarn layers L1 and L2 have a relative longitudinal movement, which makes it possible to adjust the longitudinal offset distance between the frontmost yarn FY1 of the first yarn layer L1 and the frontmost yarn FY2 of the second yarn layer L2. During this relative longitudinal movement, the second clamping rails 22A, 22B move longitudinally relative to the first clamping rails 20A, 20B and vice versa. This is called the offset compensation phase.

[0194] Regardless of whether the switching element 100 is in its first position, second position or somewhere in between, the switching element 100 does not directly cooperate with the toothed drive surface 80 of the layer conveying device 54 or the frame structure 10 .

[0195] During the operation of the warp drawing machine 2, when the camera 60 detects that the front yarn of the selected yarn layer is not within the separation range, that is, within the operating range of the yarn separation device 5 along the longitudinal direction LD, a common longitudinal movement of the first yarn layer and the second yarn layer L1 and L2 relative to the warp drawing unit 4 is necessary.

[0196] If the longitudinal offset distance between the leading yarns FY1, FY2 of the two yarn layers L1 and L2 exceeds a predetermined value, a phase of offset compensation is required before selecting the layer of yarn to be separated by the yarn separating device 5. For example, the predetermined value is 50 mm.

[0197] Advantageously, the controller 44 is configured to process the output signals of the yarn detection device or the camera 60. Optionally, the controller 44 is also configured to process the drawing-in mode and the output signals of various other sensors installed on the drawing-in machine 2. The processor 44 comprises a memory 45 and controls the layer selection device 5, the yarn separation device 18, the layer transfer device 54, the layer compensation device 56 and the yarn detection device 60. Optionally, the processor 44 controls the heald detection device, the introduction wire separation device, the heald transfer device, the introduction wire transfer device, the reed transfer device and the threading device.

[0198] Since the frame structure of the two-layer clamping device is more cumbersome than that of the single-layer clamping device, the drawing-in machine includes a sensor, not shown, connected to the controller 44, which is configured to detect whether the frame structure is for a single layer or for two layers. In the case of a single-layer frame structure, the layer compensation device 56 is disabled by the controller 44 during the drawing-in process. In the case of a two-layer frame structure, the layer compensation device 56 is controlled by the controller to correctly and effectively draw the two layers, as described above.

[0199] For the two-layer drawing-in process, the drawing-in machine operates as follows:

[0200] At the beginning of the two-layer drawing-in process, the switch element 100 is in its first position. The clamping surface 110 is longitudinally centered on the extension plate 102 and engages with the friction surface 104. The longitudinal position of the leading yarn of each yarn layer L1 and L2 relative to the reference position of the unit frame 42 of the drawing-in unit 4 is detected by the yarn detection device 60 and determined by the controller 44 based on the output of the yarn detection device 60. Information about the longitudinal position of the leading yarn FY1 or FY2 of each yarn layer L1 and L2 relative to the reference position of the frame 42 of the drawing-in unit 4 is stored in the memory 45 associated with the corresponding yarn layer L1, L2. This information can be the output of the yarn detection device 60, such as a picture, or a decision of the controller 44.

[0201] The threading method can be automatically implemented by the controller 44 and includes alternating working phases and offset compensation phases; in the working phase, the yarns are separated and threaded into the bundle; in the offset compensation phase, the longitudinal positions of the yarn layers L1 and L2 relative to each other are longitudinally adjusted so that the subsequent working phase can proceed smoothly.

[0202] In the working phase, the switching element 100 is in its first position, the layer compensation device 56 is in the inactive position, the piston 58 does not cooperate with the clamping device 6, and the yarns from the first yarn layer L1 and the second yarn layer L2 are separated and drawn in continuously according to the drawing-in mode. To this end, the frontmost yarn of the selected layer is brought into the separation range by the longitudinal displacement of the frame structure 10 relative to the drawing-in unit 4. The layer transfer device 54 causes the first pair of clamping rails 20 and the second pair of clamping rails 22 to move longitudinally together, i.e. exactly the same as the longitudinal displacement when the switching element 100 is in the first position, which longitudinal displacement is based on the output signal of the yarn detection device 60. The frontmost yarn of the selected yarn layer L1 or L2 is separated by the yarn separating device 5 and transferred to the threading device for insertion into the separated healds or possibly into the separated draw-in wires and / or reeds. According to the number of yarns to be separated in the selected layer, according to the drawing-in mode, this operation is repeated for the next frontmost yarn of the selected layer.

[0203] Just before selecting another layer, i.e. when the previously selected yarn layer is about to be deselected, i.e. just before the layer cord 24 is moved in a direction perpendicular to the yarn, in order to be able to separate the yarn of the other layer according to the threading pattern, the controller 44 determines the new longitudinal position of the front yarn of the previously selected layer relative to the reference position of the threading unit based on the output signal of the yarn detection device 60, and this information is stored in the memory 45 in relation to the layer to which the front yarn belongs, where it overwrites the information on the longitudinal position previously detected for the same yarn layer. The offset, i.e. the longitudinal distance between the front yarns FY1, FY2 of the two yarn layers L1, L2, is calculated based on the last stored longitudinal position of the front yarn of each layer and the joint longitudinal movement of the two layers that occurred between these storages during the working phase. If this offset exceeds a predetermined value, the working phase is stopped and the offset compensation phase is started by the following steps:

[0204] - If the next layer to be selected is the first layer L1:

[0205] The second pair of clamping rails 22 is released from the first pair of clamping rails 20 in the longitudinal direction LD by allowing a relative longitudinal movement between the first pair of clamping rails 20 and the second pair of clamping rails 22 and preventing any relative longitudinal movement between the second pair of clamping rails 22 and the unit frame 42. This is achieved by longitudinally fixing the second upper clamping rail 22A to the unit frame 42 via the switching element 100, which is brought into its second position. The layer compensation device 56 is brought into its active position and the movable head 50 of the layer conveying device 54 is in a meshing configuration with the drive surface 80.

[0206] The first yarn layer L1 is longitudinally retracted from the separating device 5 in a backward longitudinal movement. For this backward longitudinal movement, the movable head 50 of the layer conveying device 54 is in meshing configuration with the drive surface 80 and the worm gear mechanism is activated. The layer compensation device 56 is in the active position and the switching element 100 is in its second position. The longitudinal retraction movement stroke of the first layer L1 corresponds to the previously calculated offset. By this backward longitudinal movement, the longitudinal distance between the frontmost yarn FY1 and the frontmost yarn FY2 is reduced.

[0207] - If the next layer to be selected is the second layer L2:

[0208] In the backward longitudinal movement, the two yarn layers L1 and L2 are longitudinally retracted from the yarn separating device 5. For this backward longitudinal movement, the movable head 50 of the layer conveying device 54 is in a meshing configuration with the drive surface 80 and the worm gear mechanism is activated. The layer compensation device 56 remains in the inactive configuration, the switching element 100 is in its first position. Here, the layer compensation longitudinal movement has a stroke corresponding to the previously calculated offset.

[0209] The second pair of clamping rails 22 are released from the first pair of clamping rails 20 in the longitudinal direction LD by allowing a relative longitudinal movement between the first pair of clamping rails 20 and the second pair of clamping rails 22 and preventing any relative longitudinal movement between the second pair of clamping rails 22 and the unit frame 42. Here, the second upper clamping rail 22A is longitudinally fixed to the unit frame 42 by the switching element 100 in its second position. The layer compensation device 56 is placed in the active configuration and the movable head 50 of the layer conveying device 54 is in the meshing configuration with the drive surface 80.

[0210] The first layer L1 is brought towards the yarn separating device 5 in a forward longitudinal movement into its original longitudinal position before the deviation compensation phase. This forward longitudinal movement has a stroke corresponding to the previously calculated deviation. For this forward longitudinal movement, the movable head 50 of the layer conveying device 54 is in meshing configuration with the drive surface 80 and the worm gear and worm mechanism is activated. By this forward longitudinal movement, the longitudinal distance between the frontmost yarn FY1 and the frontmost yarn FY2 is reduced.

[0211] Then, after the offset compensation phase, the working phase can start again. Regardless of whether the next layer to be selected is the first layer or the second layer, the working phase starts with the step of longitudinally fixing the first pair of clamping rails 20 and the second pair of clamping rails 22 by bringing the switching element 100 into its first position under the action of the spring 112 and moving the piston 58 into its inactive position. When the layer compensation device 56 is moved into its inactive configuration, the movable head 50 of the layer conveying device 54 is in a meshing configuration with the drive surface 80.

[0212] After the deflection compensation phase, when the switch element 100 returns to its first position, the clamping surface 110 may again engage with the friction surface 104 of the extension plate 102 at a position different from the position before the deflection compensation phase.

[0213] For two offset compensation phases that follow one another, with a working phase in between, the piston 58 of the layer compensation device 56 will cooperate with the switching element 100 at different positions along the clamping surface 114, i.e. along the length of the frame structure 10. The relatively small size of the teeth 116 and the corresponding teeth 59 allows the parts 58 and 114 to cooperate at any position along the length of the switching element 100.

[0214] To improve the safety of the drawing-in operation, the controller 44 may be configured to provide:

[0215] - when the movable head 50 of the layer transfer device 54 is in the disengaged configuration relative to the drive surface 80 , the switching element 100 is always in its first position, so that a relative longitudinal movement of the first pair of clamping rails 20 and the second pair of clamping rails 22 is not possible;

[0216] When the layer selection device 18 is actuated, in particular when the layer cord 24 is moved, the switch element 100 is always in its first position, which ensures that the relative position of the two yarn layers L1 and L2 in the longitudinal direction LD is maintained.

[0217] The present application provides numerous advantages, in particular an optimized offset compensation between the yarn layers L1 and L2.

[0218] Some other advantages of the clamping device, drawing-in machine and method of the present application may include:

[0219] - During the operation and deflection compensation phase, due to the selective mechanical coupling of the second pair of clamping rails 22 to the frame structure 10 or the threading unit 4, there is no risk of combined movements of the clamping rails, i.e., simultaneous deflection compensation movements and longitudinal movements of the frame structure 10 relative to the unit frame 42, as can occur with the threading unit of EP 4 033 020 A1. Furthermore, there is no risk of floating / parasitic relative longitudinal movements between the first pair of clamping rails 20 and the second pair of clamping rails 22.

[0220] - Through the present application, the current position of each yarn layer can be accurately known, and no specific braking mechanism is required to fix the position of the yarn layer.

[0221] - Due to the selective mechanical coupling of the second pair of clamping rails 22 to the first pair of clamping rails 20, the offset between the yarn layers can be calculated without detecting the current position of the unselected layers, which would require selecting another layer and taking a picture before calculating the offset and would be time-consuming.

[0222] - The deviation compensation phase and the actuation of the layer selection device are activated only when needed, which gives more time to the working phase and improves the overall drawing-in performance.

[0223] - This allows the non-selected plies to adopt a more advanced position relative to the selected plies, since they do not have to be selected to calculate the offset and start the offset compensation phase. This therefore makes it possible to reduce the number of offset compensation phases to be started during the drawing-in process, depending on the drawing-in mode. This again gives more time for the working phase and improves the drawing-in performance of the drawing-in machine.

[0224] -The present application also provides a simplified design. With respect to a conventional clamping device for one layer, the only additional actuator is a two-position upper and lower actuator forming a layer compensation device 56. In addition, the actuator does not require highly precise control. No motor or actuator is mounted on the clamping device 6. In fact, all power devices are mounted on the threading unit 4, which is particularly advantageous when the threading unit is static and the clamping device moves longitudinally in the space where the threading is performed, as shown in the figure. This allows the threading unit to remain compact and there are no elongated clamping surfaces on the threading unit. In addition, the transmission cable 124 allows only one actuator to synchronously move the upper and lower second clamping rails longitudinally. This lightweight design is also compatible with vertical adjustment between the clamping rails used for layer tensioning.

[0225] - Furthermore, since the switching element 100 has an elongated clamping surface 114, it can be actuated in any longitudinal position of the threading unit or relative to the clamping device 6. The threading unit 4 can be compact and the switching element 100 does not increase the longitudinal dimensions of the clamping device 6. By default, the springs 112 ensure the correct engagement between the clamping surface 110 and the frame structure 10, since their action does not depend on the longitudinal position of the contact between the layer compensation device 56 and the clamping surface 114 along the length of the frame structure 10. The fact that the switching element 100 is rotatable between its two positions ensures the correct disengagement between the clamping surface 110 and the frame structure 10, since the rotational movement is more tolerant to the contact position between the layer compensation device 56 and the clamping surface 114 along the length of the frame structure 10 than a translationally movable switching element. The corresponding lever arms caused by the distances d110 and d114 are useful here.

[0226] The present application is not limited to the examples of the figures.

[0227] In a variant of the present application that is not shown, the switching element 100 may cooperate directly with the clamping rails of the first pair of clamping rails 20 instead of cooperating with the frame structure 10 .

[0228] In a variant of the present application, not shown, the yarn detection device 60 is formed by a photoelectric barrier or a capacitive sensor instead of a camera.

[0229] In a variant not shown in the present application, the calculation of the offset compensation can also be based on the yarn density and the drawing-in pattern of each layer, rather than just based on the new storage position. In this case, the new position of the frontmost yarn can be equal to the last stored position plus the yarn gap multiplied by the number of separated yarns.

[0230] In a variant of the present application which is not shown, the shape of the switching element 100 differs from the shape shown in the figures and / or the switching element 100 is not made of a folded metal sheet.

[0231] The cooperation between the switch element 100 and the frame structure 10 at the height of the surfaces 104 and 110 can be achieved by a shape fit, with teeth or other protrusions on the two surfaces, rather than by friction;

[0232] In a variant of the present application which is not shown, the layer compensation device 56 is supported by the clamping device 6. In particular, it can be fixed longitudinally to the second upper clamping rail 22A without relative movement between the second clamping rail and the layer compensation device 56 along the longitudinal direction LD. The layer compensation device 56 can be installed at the height of the central support 86. In this case, the clamping surface that cooperates with the layer compensation device to move the switching element 100 from its first position to its second position is different from the clamping surface of the switching element cooperating with the threading unit in the second position. The layer compensation device 56 can be moved horizontally between its active and inactive configurations. The clamping surface of the switching element can cooperate with the static surface of the threading unit in its second configuration. The layer compensation device 56 can move the switching element 100 positively from its second position to its first position. In other words, the spring is not relied upon to bring the switching element back to its first position.

[0233] Instead of using a spring, other elastic return means may be used to default the switch element 100 to its first position.

[0234] In a variant of the present application which is not shown, the clamping device 6 is fixed in the chamber, while the threading unit 4 can be moved in the chamber in the longitudinal direction on the ground surface GS during the threading process.

[0235] In a variant of the present application that is not shown, the switching element 100 is mounted longitudinally fixedly and pivotably on the second lower clamping rail 22B.

[0236] In a not shown variant of the present application, the second pair of clamping rails 22 is fixed to the frame structure 10 in the longitudinal direction LD, while the first pair of clamping rails 20 is movable in the longitudinal direction LD relative to the frame structure 10. In this case, the switching element 100 is longitudinally fixed and pivotably mounted on the first upper clamping rail 20A or the first lower clamping rail 20B.

[0237] Some additional sensors may be provided on the frame structure 10 and connected to the controller 44 to detect:

[0238] - an initial position of the clamping surface 110 relative to the extension plate 102 relative to the central position of the extension plate 102;

[0239] - Directly on the clamping rails, longitudinal position differences of the clamping rails, irrespective of the yarn clamped in these clamping rails. If a predetermined maximum longitudinal position difference is exceeded, the controller 44 stops the drawing-in method;

[0240] - Any parasitic longitudinal relative movement between the two clamping rails of a pair of clamping rails 20 or 22. If such a parasitic movement occurs, the controller 44 stops the threading method.

[0241] The above-described embodiments and modifications can be combined to create new embodiments of the application within the scope of the appended claims.

Claims

1. A clamping device (6) for a warp drawing machine (2), the clamping device being configured to clamp a first yarn layer (L1) and a second yarn layer (L2), and comprising: - a frame structure (10) movable in the longitudinal direction (LD) relative to the drawing-in unit (4) of the drawing-in machine; - a first pair of clamping rails (20) for clamping the first yarn layer (L1), the first pair of clamping rails comprising a first clamping rail (20A) and a second clamping rail (20B) fixed to the frame structure (10) in the longitudinal direction; - a second pair of clamping rails (22) for clamping the second yarn layer (L2), said second pair of clamping rails comprising a third clamping rail (22A) and a fourth clamping rail (22B) connected to the frame structure (10) by a sliding link (88), such that said third clamping rail and said fourth clamping rail (22A, 22B) are movable relative to said frame structure (10) in the longitudinal direction (LD); The clamping device comprises a switch element (100) which is longitudinally fixed to the third clamping rail (22A) and is movable (A100) relative to the frame structure (10) between the following positions: a first position in which the switch element (100) cooperates with the frame structure (10) or the first clamping rail (20A) to longitudinally fix the third clamping rail (22A) to the first clamping rail (20A); and - a second position, in which the switch element (100) allows the third clamping rail (22A) to move relative to the first clamping rail (20A) in the longitudinal direction (LD); and in which the switch element (100) cooperates neither with the frame structure (10) nor with the first pair of clamping rails (20).

2. The clamping device according to claim 1, wherein: The switching element (100) is rotated (A100) relative to the frame structure (10) and the third clamping rail (22A) between its first position and its second position about a rotation axis (X100), preferably parallel to the longitudinal direction (LD).

3. The clamping device according to claim 2, wherein: At least one guide bearing (92) is fixed to the third clamping rail (22A) to guide the switching element (100) in rotation about the rotation axis (X100) between its first position and its second position.

4. The clamping device according to claim 1, wherein: The clamping device (6) is equipped with at least one elastic return member (112), in particular a spring, which pushes the switch element (100) toward its first position.

5. The clamping device according to any one of claims 1 to 4, wherein the switching element (100) comprises a clamping surface (114), preferably a toothed clamping surface, configured to cooperate with the threading unit (4) when the switching element is in its second position; and The clamping surface (114) of the switching element extends over a longitudinal clamping length (L114) which is at least as long as a longitudinal clamping length (L20) of the third clamping rail (22A).

6. The clamping device according to claim 5, wherein: In the first position of the switch element (100), the clamping surface (110) of the switch element (100) preferably cooperates with the frame structure (10) by friction to longitudinally fix the switch element (100) relative to the frame structure, wherein the clamping surface (100) extends over a longitudinal clamping length (L110), the longitudinal clamping length (L110) being absolutely smaller than the longitudinal clamping length (L20) of the third clamping rail (22A), and wherein the clamping surface (110) covers the longitudinal height of the midpoint of the longitudinal clamping length, the midpoint being located in the middle between the two longitudinal ends of the third clamping rail (22A) along the longitudinal direction (LD).

7. The clamping device according to any one of claims 1 to 4, wherein - the frame structure (10) comprises a drive surface (80), in particular a toothed drive surface; - the drive surface (80) is configured to cooperate with a layer transfer device (54) belonging to the threading unit (4) for relative longitudinal movement between the frame structure (10) and the threading unit (4); - at least one bracket (86) longitudinally fixing the switching element (100) to the third clamping rail (22A); - Each bracket (86) extends through the elongated hole (84A) of the frame structure (10) so that the switching element (100) is located on the side of the driving surface (80) opposite to the first yarn layer (L1) and the second yarn layer (L2) along a transverse direction (LA) extending perpendicular to the yarn layers (L1, L2).

8. The clamping device according to any one of claims 1 to 4, wherein - the clamping device (6) comprises a transmission member (124), in particular a cable, the ends of which are respectively fixed to the third clamping rail (22A) and the fourth clamping rail (22B) for synchronizing their movement in the longitudinal direction (LD) relative to the frame structure (10); and The transmission member (124) is deformable to accommodate adjustment of the relative position of the third clamping rail (22A) and the fourth clamping rail (22B) in a direction (A22) perpendicular to the longitudinal direction (LD).

9. The clamping device according to any one of claims 1 to 4, wherein: The frame structure (10) is pivotably mounted on a truck (8) of the clamping device (6), the truck being equipped with wheels (12) for moving the truck on the ground (GS).

10. Warp drawing machine (2), comprising: - A clamping device (6) according to any one of the preceding claims; - a drawing-in unit (4) equipped with · Unit frame (42); a layer selection device (18) configured to select a yarn layer from among a first yarn layer (L1) and a second yarn layer (L2) clamped on the clamping device (6); a yarn separating device (5) configured to separate the yarns of the yarn layer selected by the layer selecting device; - a layer transfer device (54) configured to perform a relative longitudinal movement of the frame structure (10) of the clamping device (6) relative to the unit frame (42); - a layer compensation device (56) comprising a portion (58) movable relative to the frame structure (10) of the clamping device (6) and configured to move the switching element (100) at least from its first position to its second position; - a controller (44) which controls at least the layer selection device (18), the yarn separation device (5), the layer conveying device (54) and the layer compensation device (56); Wherein, in the second position of the switch element (100), the switch element (100) is fixed to the unit frame (42) of the threading unit (4) along the longitudinal direction (LD).

11. The drawing-in machine according to claim 10, wherein - the threading unit (4) comprises the layer compensation device (56); - the movable part (58) of the layer compensation device (56) is movable relative to the unit frame (42) of the threading unit (4) between an inactive position and an active position only in a direction (Z'4) perpendicular to the longitudinal direction (LD); - the movable part (58) of the layer compensation device (56) cooperates with the switching element (100) in its active position and is fixed to the switching element (100) in the longitudinal direction (LD), the switching element (110) being in its second position; - the movable part (58) of the layer compensation device does not cooperate with the clamping device (6) in its inactive position.

12. The drawing-in machine according to claim 10, wherein - the drawing-in machine (2) comprises a yarn detection device (60), preferably a camera, which is configured to detect the frontmost yarn (FY1, FY2) of the selected yarn layer; - the yarn detection device (60) is connected to the controller (44); - the controller (44) is configured to determine the longitudinal position of the leading yarn (FY1, FY2) of the selected yarn layer relative to the unit frame (42) based on the output signal of the yarn detection device; and The drawing-in machine comprises a memory (45) for storing information about the longitudinal position of the leading yarn (FY1, FY2) relative to the yarn layer (L1, L2) to which the leading yarn (FY1, FY2) belongs.

13. The drawing-in machine according to claim 10, wherein: The third clamping rail (22A) is closer to the yarn separating device (5) than the fourth clamping rail (22B).

14. A warp drawing-in method for drawing-in a first yarn layer (L1) and a second yarn layer (L2) clamped on a clamping device of the warp drawing-in machine (2), The clamping device comprises: - a frame structure (10) movable in the longitudinal direction (LD) relative to the drawing-in unit (4) of the drawing-in machine; - a first pair of clamping rails (20) for clamping the first yarn layer (L1), the first pair of clamping rails comprising a first clamping rail (20A) and a second clamping rail (20B) fixed to the frame structure (10) in the longitudinal direction (LD); - a second pair of clamping rails (22) for clamping the second yarn layer (L2), the second pair of clamping rails comprising a third clamping rail (22A) and a fourth clamping rail (22B) connected to the frame structure (10) so that the third and fourth clamping rails (22A, 22B) are movable relative to the frame structure (10) along the longitudinal direction (LD); The drawing-in unit includes - a unit frame (42); - a layer selection device (18) configured to select a yarn layer between a first yarn layer and a second yarn layer (L1, L2) from which the yarn is separated; - a yarn separating device (5) configured to separate the yarns of the yarn layer selected by the layer selecting device; The warp drawing machine comprises a controller (44) for controlling at least the layer selection device (18) and the yarn separation device (5); The threading method at least includes alternation of a working phase and a deviation compensation phase; In each working stage, the first clamping rail (20A) of the first pair of clamping rails (20) and the third clamping rail (22A) of the second pair of clamping rails (22) move together along the longitudinal direction (LD) relative to the unit frame (42); in -The working phase includes at least the following steps: a) fixing the third clamping rail (22A) to the first clamping rail (20A) or the frame structure (10) in the longitudinal direction (LD) such that a longitudinal relative movement between the first clamping rail (20A) and the third clamping rail (22A) is not possible; b) using the layer selection device (18), selecting a yarn layer (L1, L2) from which the yarn separating device (5) is to separate the yarn, and deselecting another yarn layer (L1, L2); - The offset compensation phase includes at least the following steps: c) allowing the third clamping rail (22A) to move longitudinally relative to the first clamping rail (20A) and the frame structure (10), and Fixing the third clamping rail (22A) to the unit frame (42) of the threading unit (4) in the longitudinal direction (LD); and d) moving the first clamping rail (20A) relative to the unit frame (42) in the longitudinal direction (LD) to adjust the longitudinal distance between the frontmost yarn (FY1) of the first yarn layer (L1) and the frontmost yarn (FY2) of the second yarn layer (L2).

15. The drawing-in method according to claim 14, wherein - the warp drawing unit (4) comprises a yarn detection device (60) configured to detect the longitudinal position of the leading yarn (FY1, FY2) of the selected yarn layer relative to the unit frame (42); - said working phase comprises at least additional steps carried out before step b), including: e) storing the last longitudinal position of the frontmost yarn (FY1, FY2) of each yarn layer relative to the unit frame (42) before the yarn layer is selected, the last position depending on the output signal of the yarn detection device (60); f) calculating the offset between two yarn layers based on the last stored longitudinal position of the leading yarn (FY1, FY2) of each yarn layer (L1, L2), g) comparing the offset value calculated in step f) with a predetermined value; and h) If the result of step g) is that the offset calculated in step f) is greater than a predetermined value, the working phase is stopped and an offset compensation phase is started.

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