Background Art During weaving, the warp threads in a loom are rais- ed in order to form sheds, through which a weft thread is guided, for example by means of a shuttle. The warp threads are raised in a combination defined for each filling, which is dependent on the pattern to be woven.

This means that certain specific warp threads are rais- ed while others are not. Nowadays, the warp threads are raised by means of shafts or, when more complicated patterns are to be woven, by means of a jacquard. The jacquard makes it possible to weave complicated patterns, for example in the form of pictures, but, especially when there is a large number of warp threads, has a very com- plicated construction as it contains a great many moving parts. The jacquard is therefore relatively slow and reduces the capacity of the loom. It is also expensive and requires a great deal of maintenance and space.

Summary of the Invention The object of the invention is therefore to provide a shed-forming device which has a considerably simpler construction than the known jacquard, has simple mecha- nics and relatively few moving parts, requires little maintenance and can be installed in a relatively small space, preferably below the warp threads in a loom.

According to the invention, this object is achieved by a device for shed-forming vertical displacement of horizontal warp threads in a loom, which device is char- acterised in that it has a horizontal upper primary plate, a horizontal lower primary plate positioned below

the upper one, a drive means which is arranged to cycli- cally displace these plates vertically relative to one another between a first position, in which the two plates are located at a predetermined minimum distance from one another, and a second position, in which they are located at a predetermined maximum distance from one another, and a number of vertically movable warp thread lifters which are arranged between the plates and, by means of a heddle cord which extends through the upper plate, are each con- nected to a respective warp thread so as to displace the warp threads during vertical movement and form a shed between them, that each warp thread lifter is arranged to interact with the plates in such a manner that, when the plates are located in said first position, it is by magnetic action attracted and attached to one or the other plate according to a predetermined order depending on the pat- tern to be woven, so as then, during a cycle, to be car- ried along in the displacement of this plate relative to the other plate, and that electromagnetic means are arranged to con- trol in their active state, by means of regulated current supply, the magnetic attraction according to said order.

In a preferred embodiment, the warp thread lifters consist of magnets, preferably permanent magnets, the plates are made of magnetic material and the electromag- netic means are arranged in at least one of the plates to influence, when activated, the magnetic attraction between the plates on the one hand and the respective warp thread lifters on the other hand.

The plates are preferably displaceable relative to one another symmetrically with regard to an intermediate horizontal plane.

Holding means are suitably arranged to hold, when the plates are located in said first position, the warp thread lifters mechanically in a starting position, in

which they are located between the plates without touch- ing either of them.

The holding means are preferably arranged to be moved away from the warp thread lifters when the elec- tromagnetic means are activated.

In a preferred embodiment, the holding means are arranged, after displacement of the plates from said second position into said first position, to release the warp thread lifter carried along with the respec- tive plate from the plate and move it to the starting position.

Each holding means preferably consists of a sleeve which is vertically displaceable in relation to the respective plate and through which the respective heddle cord extends.

In a preferred embodiment, the primary plates are each, on their side facing away from the warp thread lifters, coupled together with a respective horizontal secondary plate which is coupled to the drive means and is arranged in such a manner that, immediately before the vertical displacement of the primary plates from said first position into said second position, it is displaced a short distance in the direction away from the respec- tive primary plate so as then, by means of drivers which are fastened to the secondary plate, to carry the respec- tive primary plate along into said second position, the holding means being fixedly connected to the respective secondary plate and being vertically displaceably arrang- ed in the respective primary plate.

Brief Description of the Drawings The invention will now be described in greater detail with reference to the accompanying drawings.

Figs 1-7 are diagrammatic views and show a device according to the invention in different operating posi- tions.

Description of a Preferred Embodiment Figs 1-7 show two parallel warp threads 1 and 2 in a loom (not shown), which constitute two of a large number of parallel warp threads which, in their starting posi- tion, are located beside one another in a common horizon- tal plane (which is at right angles to the drawing plane in Figs 1-7).

The device shown in the drawings has a horizontal upper primary plate 3 and, positioned directly below the latter, a horizontal lower primary plate 4 which is iden- tical with the plate 3 but is inverted in relation there- to. In a first position (Figs 1-3 and 7), the two plates 3 and 4 bear against two distance blocks 5 which define a predetermined minimum distance between the plates.

The device also has a horizontal upper secondary plate 6 and a horizontal lower secondary plate 7 which is essentially identical with the plate 6 but is inverted in relation thereto. The upper secondary plate 6 is arranged directly above the upper primary plate 3, and the lower secondary plate 7 is arranged directly below the lower primary plate 4. The secondary plates 6 and 7 are coupled together with the respective primary plate 3 and 4 in a manner described in greater detail below. The secondary plates 6 and 7 are vertically displaceable by means of an electric motor 8, the output shaft 9 of which is connect- ed in a rotationally fixed manner to a vertical disc 10.

The disc 10 has an annular eccentric groove 11, in which two pins 12 and 13 engage, which are diametrically oppo- site with regard to the disc 10. One pin 12 is connected to the upper secondary plate 6, and the other pin 13 is connected to the lower secondary plate 7. When the elec- tric motor 8 is operating, it rotates the disc 10 and in doing so cyclically displaces the secondary plates 6 and 7 vertically relative to one another between a closer- together position (Fig. 1), in which the secondary plates 6 and 7 bear against the respective primary plates 3 and 4 which are in turn located in their first position, that

is to say they bear against the distance blocks 5, and a further-apart position (Fig. 5), in which the secondary plates 6 and 7 are located at a predetermined maximum distance from one another, at the same time as the pri- mary plates 3 and 4 are located in a second position, in which they are also located at a predetermined maximum distance from one another.

Compression springs 14 are fitted in vertically between the upper plates 3 and 6 in recesses 15 and, respectively, 16 formed therein, and compression springs 17 are fitted in vertically between the lower plates 4 and 7 in recesses 18 and, respectively, 19 formed there- in.

Vertical driving rods 20, which are fastened in the upper secondary plate 6, extend in a freely displaceable manner through holes 21 in the upper primary plate 3 and, at their end projecting from the lower side thereof, have a driving head 22, the diameter of which is greater than the diameter of the holes 21. Vertical driving rods 23, which are fastened in the lower secondary plate 7, extend in a freely displaceable manner through holes 24 in the lower primary plate 4 and, at their end projecting from the upper side thereof, have a driving head 25, the dia- meter of which is greater than the diameter of the holes 24.

Holding means 26 in the form of vertical sleeves are fastened in the upper secondary plate 6. The sleeves 26 project from the lower side of the upper secondary plate 6 by a distance which is slightly greater than the thick- ness of the upper primary plate 3, and are freely dis- placeable in through-holes 27 in the upper primary plate 3. Holding means 28 in the form of vertical sleeves are fastened in the lower secondary plate 7. The sleeves 28 project from the upper side of the lower secondary plate 7 by a distance which is slightly greater than the thick- ness of the lower primary plate 4, and are freely dis- placeable in through-holes 29 in the lower primary plate

4. The upper holding means 26 and the lower holding means 28 are located in pairs vertically in front of one another, one pair of holding means 26 and 28 being pro- vided for each warp thread in the loom. In the drawings, only two such pairs are shown, that is to say one pair for each warp thread 1 and 2.

The primary plates 3 and 4, which are made of mag- netic material, preferably iron, have on their mutually facing sides an annular recess 30 and, respectively, 31 around each hole 27 and, respectively, 29. The recesses 30 and 31 are therefore located in pairs vertically in front of one another. The recesses 30 and 31 each accom- modate an electromagnetic coil 32 and, respectively, 33.

The coils 32 and 33 located vertically in front of one another are optionally coupled together in pairs elec- trically. Optionally, one of the coils in each such pair can be omitted.

A warp thread lifter belongs to each warp thread in the loom. In the drawings, only two such warp thread lifters 34 are shown, that is to say one for each warp thread 1,2. The warp thread lifters 34 consist of strong permanent magnets, for example the supermagnets sold under the trademark Neodym, and are therefore attracted with great force to a surface of a body made of magnetic material, such as the lower side of the upper primary plate 3 or the upper side of the lower primary plate 4.

The warp thread lifters 34 are in the form of circular cylinders with a vertical axis.

The warp thread lifters 34 are each connected to a respective warp thread 1,2 by means of a vertical heddle cord 35 which, at its upper end, has an eye 36 through which the warp thread extends. The heddle cords 35 con- sist of relatively rigid steel wires. Each heddle cord 35 extends freely displaceably through both the upper secondary plate 6 and the upper primary plate 3, to be precise through the sleeve forming the respective holding means 26, through the respective warp thread lifter 34,

to which it is fixedly connected, and freely displaceably through the lower primary plate 4 and into and, in cer- tain operating positions of the device, through the lower secondary plate 7, to be precise in the sleeve forming the respective holding means 28.

The operation of the device will now be described in greater detail from the starting position shown in Fig. 1, to which the device returns cyclically during the continuous rotation of the disc 10. In the starting position of the device, the two primary plates 3 and 4 are located in their first position, that is to say they bear against the distance blocks 5, and the two secondary plates 6 and 7 are located in their closer-together posi- tion, that is to say they bear against the respective primary plate 3 and 4. In the starting position, the warp thread lifters 34 are located in a position midway between the two primary plates 3 and 4 and are retained in this position by the holding means 26 and 28 which, when the secondary plates 6 and 7 are located in their closer-together position, project a distance into the gap between the primary plates 3 and 4. The warp thread lifters 34 are centred in relation to a horizontal plane 37, in relation to which the plates 3,6 on the one hand and the plates 4,7 on the other hand are symmetrically displaceable relative to one another. The warp thread lifters 34 are here located in a balanced position as far as the magnetic attraction to the primary plates 3 and 4 is concerned, for which reason the only real task of the holding means 26 and 28 is to define this balanced posi- tion and prevent the warp thread lifters 34 being guided in an uncontrolled manner into contact with one of the primary plates on account of the balance being disturbed, for example owing to impacts against the device. In their balanced position, the warp thread lifters 34 hold the respective warp thread 1,2 in an unaffected, horizontal position. In the starting position, the heads 22 and 25 of the driving rods 20 and, respectively, 23 are located

at a distance from the lower side of the upper primary plate 3 and, respectively, the upper side of the lower primary plate 4. In this position, the electromagnetic coils 32 and 33 are currentless.

When the secondary plates 6 and 7 are, in their continued cyclical movement, displaced from their closer- together position in the direction of their further-apart position, the driving rods 20 and 23 and the holding means 26 and 28 are carried along, while the primary plates 3 and 4 are initially retained in their first position (see Fig. 2) by means of the springs 14 and 17.

Current is supplied to the coils 32 and 33 in a regulated manner depending on the pattern to be woven, which in the example shown in the drawings means that the current sup- ply takes place in such a direction that the coils shown on the left generate a magnetic field which increases the attractive force on the associated warp thread lifter 34 in the upward direction, while the coils shown on the right generate a magnetic field which increases the attractive force on the associated warp thread lifter 34 in the downward direction. With a relatively small current, such disturbance of the balanced position of the warp thread lifters 34 is thus brought about that the left warp thread lifter 34 is attracted with very great attractive force and attached to the upper primary plate 3, while the right warp thread lifter 34 is in the same way attracted with very great attractive force and attached to the lower primary plate 4, as shown in Fig. 2. In the operating position shown in Fig. 2, the secondary plates 6 and 7 have just reached such a verti- cal position that the lower and, respectively, upper end of the holding means 26 and 28 carried along are located level with the lower side of the upper primary plate 3 and, respectively, the upper side of the lower primary plate 4. In this position, the current supply to the coils 32 and 33 is cut off. By virtue of the displacement of the warp thread lifters 34 from the balanced position

into a position in contact with the respective primary plate 3,4, the warp threads 1 and 2 have, via the heddle cords 35 connected to the warp thread lifters, been moved apart somewhat as the warp thread 1 has been moved a dis- tance upwards and the warp thread 2 has been moved a dis- tance downwards, the formation of a shed 38 between these warp threads having started.

When the secondary plates 6 and 7 have reached the operating position shown in Fig. 3, in which the heads 22 and 25 of the driving rods 20 and, respectively, 23 have come into contact with the lower side of the upper pri- mary plate 3 and, respectively, the upper side of the lower primary plate 4, the rods 20 and 23 carry the pri- mary plates 3 and 4 and thus the warp thread lifters 34 along during the continued displacement of the secondary plates 6 and 7 towards the further-apart position, the primary plates 3 and 4 with the warp thread lifters 34 attached thereto, as shown in Fig. 4, then leaving the distance blocks 5, which in turn results in the size of the shed 38 increasing.

When the secondary plates 6 and 7 have reached their further-apart position, and the primary plates 3 and 4 have thus reached their second position (Fig. 5), in which the size of the shed 38 is at its maximum, the secondary plates turn back and are returned to their closer-together position. During this displacement, the primary plates 3 and 4 are carried along thanks to the springs 14 and 17 which keep the distance between secondary plate and primary plate constant (see Fig. 6) until the primary plates 3 and 4 come into contact with the distance blocks 5 again (Fig. 7), that is to say reach their first position and stop moving. During their continued displacement towards the closer-together posi- tion, the secondary plates 6 and 7 are displaced, against the action of the springs 14 and 17, in the direction of the primary plates 3 and 4, so that the driving rods 20 and 23 and the holding means 26 and 28 are pushed a dis-

tance out of the respective primary plate 3 and 4. During this pushing-out, the holding means 26 and 28 release the warp thread lifters 34 from the respective primary plate 3,4 and move them to their starting position shown in Fig. 1.

Before the next cycle, current is again supplied to the coils 32 and 33 in a regulated manner, the current supply taking place in such a direction that the coils generate magnetic fields which increase the attractive force on the respective warp thread lifters 34 in one or the other direction depending on the pattern to be woven.

The embodiment described above can be modified in many different ways within the scope of the invention.

Therefore, for example, the warp thread lifters 34 can be made of a magnetic material, such as iron, while the primary plates 3 and 4 instead consist of powerful mag- nets, for example permanent magnets, or are provided with powerful magnets in the areas located in front of the warp thread lifters.

Lastly, it should be noted that"upper","lower", "horizontal"and"vertical"and corresponding terms in the description above and the appended claims relate only to the most usual position of use of the device and are used in order to describe the mutual position of the various components in a simple manner. It should be understood that the device can be arranged in other posi- tions of use than that described above.