BE1027384B1 - Shed-forming device - Google Patents

Abstract

This invention relates to a shed-forming device comprising a jacquard device (2) of which the heddles (16), (17) are connected to a retraction element (18), (19) for exerting a downwardly directed force on the heddle (16), (17) ), wherein per lever (16), (17) a yarn tension element (8) is provided to change the yarn tension in at least one associated warp thread (11), (12), and wherein a control or control unit is provided for per lever ( 16), (17), separately regulate or control the yarn tension in at least one associated warp thread (11), (12) to bring the total downward force on the lever (16), (17) to a certain value or vary according to a certain course.

Description

This invention relates to a shed-forming device comprising a jacquard device comprising a number of heddles for positioning at least one associated warp thread, each heddle being connected to a retraction element in order to exert a downwardly directed force on the heddle.

On a weaving machine, one or more weft threads are introduced into a shed formed between the warp threads during successive weft insertion cycles.

In order to weave according to a predetermined weaving pattern, the different warp threads in each shed must be correctly positioned with respect to the one or more levels at which weft threads are inserted.

A jacquard machine is used to position several warp threads differently in each shed.

Positioning is done by means of heddles which are connected via cords to respective hooks, each heddle having a lifting eye.

The hooks can be moved up and down by means of knives moving up and down and can be selected by means of selection means to be retained or not at one of a number of possible positions.

Each warp thread extends through a heddle eye of a heddle, so that a different position of the warp thread corresponds to each different position of the warp thread.

In order for the shed formation to proceed correctly and to facilitate downward movement of the hooks, each heddle is connected to a return spring which is provided to exert a downwardly directed force on the heddle.

In the lowest position of a lever, the extension of the spring is smallest so that the downward force exerted by this return spring on the lever is the smallest.

The return spring is selected in such a way that this smallest force is just enough to allow the hook connected to the lever to correctly engage on a selection edge of a knife.

In the lowest position of the lever, the warp threads extending through the lever eye also exert an upward force on the lever.

This is the result of the yarn tension in these warp threads.

In this lowest position, the return spring must therefore exert a downward force on the lever that is greater than this upward force and, moreover, the resultant downward force must be just sufficient to make the selection hook hook onto a selection edge of a knife. This minimum pull-down force cannot therefore be very small.

As the lever is moved to a higher position by the knife, the downwardly directed spring force increases proportionally with the upward movement of the lever to eventually reach a value much greater than necessary. As a result, the average tension on the warp threads is much higher than necessary. A higher tension causes more wear of machine parts, more and more frequent damage to the warp threads themselves, and more energy consumption of the machine.

The object of this invention is to overcome these drawbacks.

This object is achieved by providing a shed-forming device having the characteristics indicated in the first paragraph of this invention, wherein, according to this invention, the shed-forming device comprises, per heddle, a yarn tension element which is provided to change the yarn tension in at least one associated warp thread. , and that the shed-forming device comprises a control or regulating unit which is provided to individually regulate or control the yarn tension in at least one associated warp thread for each heddle, in cooperation with the respective yarn tension elements, such that the total downward force on the heddle is directed towards a certain value is brought or varies according to a certain course.

The tension development in the warp yarns can be controlled or controlled with a shed-forming device according to the present invention in such a way that the combined action of the yarn tension and the spring action together at any time produce a downward force on the heddles which is sufficiently great to obtain a good shed formation, but achieved less high values than with the existing shed-forming devices. This ensures less wear, less damage to yarns and lower energy consumption.

In addition, retraction elements can be selected that are less powerful. After all, in the lowest siphon position the yarn tension can be regulated or controlled to a lower value than with the existing shed-forming device. The retraction element must then provide less force to obtain the minimum required downward force.

The regulation or control may also be provided to cause the total downward force during the weaving process to assume a number of consecutive values that are predetermined.

Optionally, certain machine parameters, such as machine position or machine speed, or data related to weave or weave, may also be made available to the controller or controller to take into account in determining the target value for the total downward force.

Said gradient can for instance be selected from a collection of two or more reference gradients or from two or more reference series, such as for instance tables or files, with at least one reference value for the yarn tension. During weaving, for example, on the basis of machine parameters and / or machine parameters and / or weaving pattern data, an appropriate selection of a reference course or a reference sequence is made.

In a preferred embodiment, each yarn tension element comprises a motor-driven roller which is provided to rotate, in contact with at least one warp thread, in one direction or the other to move said warp thread in a direction opposite to the feed direction. of the warp threads, respectively to move the warp thread or to facilitate the movement to move along with a displacement (i.e. a moving warp thread) in a direction equal to the feed direction of the warp threads, in order to maintain the yarn tension in said warp thread. increase or decrease respectively.

The retraction elements can be any elements provided to exert a force, such as elements where the force is provided at least in part by a pneumatically actuated element and / or by gravity. Preferably, they are elements in which the downward force is provided at least in part, preferably exclusively or mainly, by an elastically deformable element. In a most preferred embodiment, the retraction elements are springs.

The yarn tension device preferably comprises measuring means for measuring, in at least one warp thread or in several (at least two) warp threads forming a subgroup, the yarn tension, or a quantity that is a measure of the yarn tension. Preferably, a control unit is also provided with means for repeatedly or continuously comparing the measured yarn tension, or the quantity which is a measure of the yarn tension, with a reference value and, when determining a difference between the measured yarn tension or quantity and on the other hand, the reference value, to generate a control signal to drive a yarn tension element (eg by adjusting the current with which the motor is controlled or by adjusting the motor torque) in such a way that the difference between the measured value and the reference value is reduced.

A control unit preferably comprises a regulator which is provided to generate, when a specific target value for the yarn tension is set, a control signal in order to drive a yarn tension element (e.g. by adjusting the current with which the motor is controlled or by adjusting the motor torque) that the target value is approached or reached. The controller is preferably a controller of the "feedforward control" type.

In a particular embodiment of a control unit or of a control unit, machine parameters, such as the machine position or the machine speed or data related to the weaving pattern or the binding, can also be made available, and one or more of these parameters can be used for the control. or the scheme.

If one or more yarn tension influencing conditions are different for different warp threads subgroups, with this weaving machine a different reference yarn tension development can be determined for these warp threads or subgroups, and this reference yarn tension development during the weaving process in the different subgroups separately, and if necessary different. , adapt to conditions changed during the weaving process. The yarn tension can hereby be kept much lower on average, while the maximum values of the yarn tensions are also less high.

The yarn tension device comprises, for example, detection means for detecting one or more yarn tension influencing conditions during weaving and / or comprises storage means and / or data processing means for predetermining the point in time or the phase of the weaving process in which the yarn tension influencing conditions occur, e.g. on the basis of the weave pattern and / or on the basis of the intended path of the warp threads between the yarn stock and the fabric.

Preferably, in this weaving machine and according to the method according to the invention, a control is applied according to a "bidirectional forced feed forward function". This means that when there is a change in the movement of the yarn, the yarn tension unit intervenes to facilitate this change, resulting in a faster reaction. Further special features of this shed-forming device are stated in the claims.

The invention will now be further elucidated on the basis of the following more detailed description of a possible embodiment of a jacquard machine according to the present invention. It is emphasized here that the described device and method are only examples of the general principle of the invention and can therefore in no way be regarded as a limitation of the scope of the protection defined in the claims, nor of the scope of the invention.

In this detailed description reference is made by reference numbers to the accompanying figures, of which = figure 1 is a schematic side view of an arrangement of a weaving machine and a bobbin rack with an associated yarn tension device; Fig. 2 is a graph showing for a pile-forming pile warp thread, in a number of successive weft insertion cycles during weaving according to the prior art: - the course of the position of the heddle eye (in mm), - the course of the upward or downward component of the force (in N) exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread, - the course of the downward spring force exerted by the return spring on the heddle of that pile warp thread (in N); and - the course of the sum of the downward spring force (in N) on the heddle and the upward or downward component of the force (in N) exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread. Figure 3 is a graph showing for a pile-forming pile warp thread, in a number of successive weft insertion cycles during the weaving according to the invention, with a controlled or regulated yarn tension:

- the course of the position of the lever eye (in mm),

- the course of the upward or downward component of the force (in N) that is exerted on the lever as a result of the yarn tension in the pile-forming pile warp thread,

- the course of the downward spring force exerted by the return spring on the lever (in N);

- the course of the sum of the downward spring force (in N) on the heddle and the upward or downward component of the force (in N) that is exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread; and - the average of the said sum of forces.

In a particular arrangement, a weaving machine (1) is arranged in cooperation with a jacquard device (2) next to a bobbin rack (3), and in the interspace between the weaving machine (1) and the bobbin rack (3) a boom stand (4) is arranged with four rolls (40) - (43) containing a respective yarn supply.

In the space between the bobbin rack (3) and the weaving machine (1) a yarn tensioning device (6) is arranged, consisting of a yarn tension module (20) extending horizontally parallel to the vertical plane in which the front sides (30a) of the plurality of rack units (30) placed together.

The yarn tension module (20) consists of two panel-shaped carriers (21), (22) with a flat outer surface, which converge symmetrically with respect to a horizontal plane in the direction of the weaving machine (1), meeting angularly and against connect each other.

The yarn tension module (20) has a V-shaped profile when viewed in a vertical cross-section.

Each carrier (21), (22) carries a plurality of rows of closely spaced yarn tension elements (8). For the sake of clarity, only three yarn tension elements (8) have been proposed per carrier (21), (22).

For each warp thread that is guided from a respective bobbin in the bobbin rack (3) to the weaving machine (1), a guide tube (10) is provided to guide the warp thread stress-free to a respective yarn tension element (8).

The warp threads are further moved from the yarn tension elements (8) to a grid (100) with the same width as the yarn tension module (20) but with a smaller height. From that grid (100) the warp threads (11), (12) run to the weaving machine (1), where they pass through the heddle eye of a respective heddle (16), (17) - symbolically represented by a vertical line with a circular widening that represents the siphon eye. A downward force is applied to each siphon (16), (17) by a respective return spring (18), (19). According to the prior art, the warp threads are supplied in the stretched state from the bobbin rack (3) to a first grid (X). In Figure 1, that state of the art situation was represented by the straight line (S1) that would run from the top row of bobbins in the bobbin rack (3) first through the grid (X) of an existing arrangement and then continues to the grid (100), and the straight line (S2) that would run from the bottom row of bobbins in the bobbin rack (3) through the grid (X) of an existing setup and then continues to the grid (100) . For the avoidance of doubt, the grid (X) is not part of the arrangement according to this invention, and has been added to the figure only to illustrate an effect of the invention by comparison with the prior art.

The lines (S1), (S2) show at which large angles (relative to a horizontal plane) the warp yarns are brought to the grid (X) and then to the grid (100) according to the prior art, and consequently which then take up the supplied warp threads at a great height.

During weaving, the heddles (16), (17) are moved up and down to perform the correct positioning of the warp threads (11), (12) according to the predetermined weaving pattern. The return springs (18), (19) in their lowest position provide the necessary downward force for the shed formation to proceed correctly, but also have to overcome the upward force resulting from the yarn tension.

When the shed-forming lever moves to a higher position, the downwardly directed spring force increases proportionally with the upward movement of the lever to eventually reach a value that is much greater than necessary.

In figure 2 we see, each time for a number of consecutive weft insertion cycles (the position of the main axis of the weaving machine is shown in degrees on the horizontal axis), on graph line G1 the development of the downward force exerted by the springs (18), (19) on the lever

(16), (17) exert (on the left vertical axis, in N) of a pile-forming pile warp thread, and on graph line G2 the course of the alternating upward and downward component of the force (in N) that as a result of the yarn tension in said pile-forming pile warp thread is applied to the heddle (16), (17). This latter force is hereinafter referred to as "the yarn tension force" for short. For the sake of clarity, when in Figures 2 and 3 a force (spring force or yarn tension force) is negative, it means that this force pulls the lever upwards. This is evident, for example, in that the yarn tension force is negative in the graph areas where the heddle is in its lowest position. It goes without saying that the force exerted on the heddle by the yarn tension then has an upwardly directed component that pulls the heddle upward.

Graph line G4 shows the position of the lever eye (in mm on the vertical axis to the right). Graph line G3 shows the development of the sum of the spring force and the yarn tension force. Here we see two high peaks (P1), (P2) of this total force. The graph line G3 shows which forces the different machine parts undergo. It should be noted that the graphs of Figures 2 and 3 show the forces resulting from the movements of a single pile warp thread, while on a typical two-piece weaving machine there may be, for example, 32,000 pile warp threads or more.

Figure 3 then shows how the spring force and the yarn tension force on the heddle of a pile-forming pile warp thread develop when the yarn tension is controlled or regulated to obtain lower peak values and a lower average of the sum of the spring force and the yarn tension force.

This regulation or control also made it possible to use a spring with a lower spring constant, as well as a lower pre-tension force (0.15 N lower) of the spring - this is the downwardly directed spring force when the lever is in its lowest position -. The pretension force could be lower because by controlling or controlling the yarn tension, less upward yarn tension force is exerted by the pile warp thread.

In figure 3 the same designations (G1) (G2), (G3), (G4) as in figure 2 are used for the graph lines that indicate the same thing, namely the development of the downward spring force (G1), the development of the yarn tension force (G2), the course of the sum of the spring force and the yarn tension force (G3) and the position of the lever (G4). The left vertical axis indicates the force values (in N), and the right vertical axis indicates the lever position values (in mm). The horizontal axis indicates the position of the main axis of the weaving machine in degrees. Graph line (G5) - the dashed line - gives the value of the mean of the said sum of the spring force and the yarn tension force.

The graph line (G3) clearly shows that the high peaks have disappeared for the total force on the siphon (compare with figure 2, the peaks P1 and P2). In addition, the mean value of this total force has also been reduced. In the version without control or control (figure 2), the calculated average of this total force is 2.91 N, while this total force is on average 2.72 N in the version with control (graph line G5 in figure 3).

These effects result in a lower load on the machine, whereby it should again be borne in mind that the values from the graphs represent the forces resulting from the movements of a single pile warp thread, while on a typical two-piece weaving machine, for example, 32,000 pile warp threads or more may be present.

The advantageous aspects of this invention are not limited to pile warp threads, but also apply to warp threads of another type that are positioned by the Jacquard direction or for single piece weaving machines.

Claims (5)

CONCLUSIONS Shed-forming device comprising a jacquard device (2) comprising a number of heddles (16), (17) for positioning at least one associated warp thread (11), (12), each heddle being connected to a withdrawal element (18), (19) ) to exert a downward force on the heddle (16), (17), characterized in that the shed-forming device comprises, per heddle (16), (17), a yarn tension element (8) which is provided to adjust the yarn tension change at least one associated warp thread (11), (12), and that the shed-forming device comprises a control or regulating unit which is provided for each lever (16), (17), in cooperation with the respective yarn tension elements (8), Yarn tension in at least one associated warp thread (11), (12) can be individually regulated or controlled in such a way that the total downward directed force on the lever (16), (17) is brought to a certain value or varies according to a certain course. Shed-forming device according to claim 1, characterized in that each yarn tension element (8) comprises a motor-driven roller, which is provided to rotate, in contact with at least one warp thread, in one or the other direction of rotation, about said warp thread ( 11), (12) to move in a direction opposite to the direction of feed of the warp threads, respectively to move or move the warp thread (11), (12) with its movement or facilitate its movement, in a direction which is the same as the feeding direction of the warp threads, for increasing or decreasing the yarn tension in said warp thread, respectively. Shed-forming device according to claim 1 or 2, characterized in that parameters of the Jacquard device (2) or of a weaving machine (1) cooperating with the Jacquard device or data or parameters relating to the weaving pattern are made available to the control or control unit. to consider when determining the target value for the total downward force. Shed-forming device according to one of the preceding claims, characterized in that it comprises a storage unit in which two or more reference yarn tension courses and / or two or more reference series with at least one reference value for the yarn tension are stored, and in that the control or regulation unit is provided to select a reference course or a reference sequence from this set to use as target value (s) or sequence of target values for control or control. Shed-forming device according to one of the preceding claims, characterized in that the retraction elements are springs (18), (19).