Abstract:
An apparatus moves a warp thread in a controlled manner by a punctuate compulsory guidance between three positions, namely a middle, an upper and a lower position. It comprises a pendulum which is pivotal about an axis and into which an electrical coil is integrated and stationary permanent magnets. The named positions are given by equilibrium positions of the pendulum, with forces which act on the pendulum in these positions being in each case in an equilibrium. The equilibrium positions for the upper or the lower position respectively can be produced by forces between the permanent magnets and the currently carrying coil; the equilibrium position for the middle position is given by the pendulum with a current-less coil.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus for the controlled moving of a warp thread. It also refers to a weaving machine with an apparatus of this kind and to uses of the apparatus. 
     Leno apparatuses are used for the formation of selvedges: An eyed needle, which guides a warp thread in an eye, and a follower needle form a leno weave in interaction with a weft thread (see e.g. EP-A 0 737 764). The needles are moved by drive units which, in known weaving machines, comprise cable runs, control cams, rollers and levers. These mechanical components are expensive and prone to wear. When operating parameters (among others, heald stroke, shed geometry) are changed, time-consuming adjustments must be made by hand. 
     It is also known to use linear motors as drive units. An electronic processor, which is already used for the control of the weaving machine, can also be used for the control of the linear motors. In this it is however disadvantageous that control loops with special position sensors are required for the setting of warp thread layers using means which act point-wise—for example eyed needles (cf. WO 96/38608) 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a further apparatus by means of which warp threads—in particular for the formation of cloth edges—are controlledly movable by means of a punctuate compulsory guidance (i.e. with means acting point-wise) and in which the named disadvantages are absent. 
     This apparatus, controlled by means of a punctuate compulsory guidance, moves a warp thread between three positions, namely a middle position, an upper position and a lower position. It comprises a pendulum which is pivotal about an axis and into which an electrical coil is integrated as well as stationary permanent magnets. The named positions are given by equilibrium positions of the pendulum, with forces which act on the pendulum in these positions in each case being in equilibrium. The equilibrium positions for the upper and the lower positions respectively can be produced by means of forces between the permanent magnets and the current carrying coil; the equilibrium position for the middle position is given by the pendulum with a current-less coil. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an apparatus in accordance with the invention, 
     FIG. 2 shows a variant of this apparatus, 
     FIG. 3 shows a plurality of apparatuses which are arranged in parallel (for a Jacquard shed forming apparatus), 
     FIGS. 4-6 illustrate details of a further variant of the apparatus in accordance with the invention, 
     FIGS. 7,  8  illustrate two particular possibilities of connecting displaceable elements to a pendulum of the apparatus in accordance with the invention, 
     FIG. 9 shows a rotator apparatus; 
     FIG. 10 illustrates a half rotator apparatus in the rotator apparatus of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an apparatus  1  for the controlled moving of a warp thread  9  which comprises the following components: a pendulum  2  which is pivotal about an axis  20  into which a coil  3  which is arranged on a non-ferromagnetic sheet metal members  21  or between two such sheet metal member  21  respectively is integrated; permanent magnets  4  on a spatially fixed carrier plate  7 ; vertically displaceable elements  5  and  5 ′ which are in active contact with a bow  22  of the pendulum  2  via flexible bands  6  and  6 ′; and springs  65 . The bands  6  and  6 ′, which serve as draw means, can also be designed as cables. 
     A warp thread  9 , which is drawn in into an eye  50  of the element  5  and is compulsorily guided by the latter, can be punctuately moved between three positions, namely between a middle, an upper as well as a lower position. These positions are given by equilibrium positions of the pendulum  2  which set in as a result of the forces acting on the pendulum  2 . The middle position is given on the one hand by gravitational forces and on the other hand by draw forces of the springs  65 . The one coil  3 , which carries direct current, produces together with the permanent magnets  4  additional magnetic forces, through which the equilibrium position is displaced to the upper right or left respectively. Through a polarity reversal of the current in the coil  3  the pendulum  2  changes from the one to the other of these two equilibrium positions. The band  6 , which can partially lie in contact on the lower side  23  of the bow  22 , which is laterally secured with a screw  62  at the pendulum  2  and which is deflected via a roller  61  into the vertical direction, converts the pendulum movement into a linear movement of the element  5 . The equilibrium positions of the pendulum  2  are thus transferred to three stable positions of the eye  50 , through which the three named positions of the warp thread  9  are given. Sensors are not necessary for a regulation of these positions. 
     The strip-like or groove-like support surface  23  for the draw means  6  advantageously lies on a curve which is at least approximately a circle about the pendulum axis  20 . In particular the pendulum axis  20  can stand on the center of this circle. In this case the stroke of the eye  50 , i.e. the distance between its middle and upper (or lower) position, is proportional to the radius of the named circle. The stroke is in addition proportional to the pivotal angle of the pendulum  2 , which is determined by the location and shape of the magnets. 
     The current-less state of the coil  3  and thereby the middle position of the eye  50  is advantageously associated with the shed closure position of a shed which is formed by warp threads  9 . 
     Two elements  5  and  5 ′ for the moving of two warp threads  9  can be provided, with the movement taking place in a counter-similar manner or anti-symmetrical shape: when the coil  3  carries a current the one warp thread  9  is in the upper, the other in the lower position; when the coil  3  is current-less the two warp threads are in the middle position at the same time. When the polarity of the coil  3  is reversed the two warp threads move in opposite directions. 
     In contrast to linear motors, the weight of the movable part, namely the pendulum  2 , does not have to be taken up by electromagnetic forces in the apparatus in accordance with the invention. 
     In the variant of the apparatus  1  in accordance with the invention shown in FIG. 2 the pendulum  2  is a segment plate of a non-ferromagnetic material in which the coil  3  (with connection wires  30 ) is embedded. The deflection rollers  61 ,  61 ′ have horizontally displaceable axes. A second roller pair  63  have axes with fixed positions. 
     A plurality of apparatuses in accordance with the invention, by means of which a plurality of warp threads can be moved at the same time, can be space-savingly arranged in parallel, as is schematically illustrated in FIG.  3 . 
     A side view of a pendulum  2 , as is contained in the apparatus  1  of FIG. 1, is shown in FIG. 4. A configuration of permanent magnets  4 ,  4   a  for this pendulum  2  which are arranged on the carrier plate  7  is illustrated in FIG. 5; and a horizontal cross-section through this pendulum  2  is shown in FIG. 6 with the permanent magnets  4 ,  4   a  which are arranged on both sides. 
     The electrical coil  3  is designed as a flat ring. The magnetic field which can be produced with the coil  3  is oriented at least approximately parallel to the pendulum axis  20  at the center of the ring. The permanent magnets  4 ,  4   a  are designed in disc shape and are arranged parallel to the coil  3 . The magnetizations of the permanent magnets  4 ,  4   a  are oriented the same as the named magnetic field of the coil or opposite to the latter respectively. The permanent magnets  4 ,  4   a  are advantageously arranged on both sides of the pendulum on ferromagnetic carrier plates  7  and form in each case a similar configuration. In FIG. 6 the magnetizations of the permanent magnets  4 ,  4   a  are given by arrows  41 ,  42 . Arrows  47  represent a magnetization of the ferromagnetic carrier plates  7 . The two adjacent permanent magnets  4  and  4   a  are arranged in the reversal region of the pendulum  2 ; they have magnetizations which are oriented oppositely to one another. The smaller partner  4   a  of this permanent magnet pair serves as a brake magnet for the pendulum  2 . With this a situation is achieved in which the pendulum  2  comes to rest rapidly in the upper equilibrium position as a result of a damping action. In addition, the permanent magnet pair  4  and  4   a  ensure a more precise reversal or end position of the pendulum  2 . 
     In order that the transition between the three equilibrium positions can take place without disturbing transient oscillations, the sheet metal laminae  21  are manufactured of a material which is a good electrical conductor but is not ferromagnetic. Aluminum can for example be chosen as a material. Eddy currents which are induced in these sheet metal laminae  21  during the movement of the permanent magnets  4 ,  4   a  in the magnetic field damp the movement of the pendulum  2 . A gap  24  is provided in the sheet metal laminae  21 —see FIG.  4 —in order that a ring current does not form through induction during the switching on or over of the coil current, which would represent an unnecessary dissipation of energy. 
     With the apparatus  1  illustrated in FIG. 7 a  heald  5  is controlled which contains the eye  50 , and at both ends of which the bands  6 ,  6 ′ grip on. The band  6 ′ is deflected via rollers by 180°. In the apparatus  1  of FIG. 8 the non-illustrated warp thread (or group of warp threads) is moved with an element  51 , the weight of which must be taken into account when setting the middle position. The springs  65  and  65 ′ can be chosen and set in such a manner that when the coil  3  carries no current the pendulum  2  is in an equilibrium position in which for example the center of gravity of the pendulum is located vertically beneath the axis  20 . 
     FIG. 9 shows the use of apparatuses  1 ,  1 ′ in accordance with the invention in half rotator apparatuses  8  and  8 ′: By means of a first apparatus  1  the warp thread  9 ′ is moved with an eyed needle  5 . A hooked needle  5   b  (with a double hook  51 ), which cooperates in a known manner with the eyed needle  5 , is actuated by a second apparatus  1 ′. With this second apparatus  1 ′ elements  5   a  and  5   a , which carry auxiliary edge heald frames  55 ,  55 ′, are simultaneously moved up and down in a counter-similar manner. The pendulum  2 ′ of the apparatus  1 ′ comprises two segment plates  2   a ,  2   b  with different radii. The hooked needle  5   b  is in connection with the segment plate  2   b  with the larger radius. Accordingly, a greater stroke results than for the auxiliary edge heald frames  55 ,  55 ′. Such different strokes are preferred for the production of a leno edge. A plate  80  which is fixed in space—see also the oblique view in FIG.  10 —is arranged between the half-cross leno elements  8  and  8 ′. Required deflections of the warp threads  9 ,  9   a  result through edges of this plate  80  in a known manner. 
     An apparatus for the formation of a leno selvedge is also known which comprises two lifter healds, which are to be moved counter-similarly, and a half heald (DE-A 40 00 035). This apparatus can be actuated with only one apparatus in accordance with the invention. 
     The equilibrium position with current-less coil can be influenced with additional permanent magnets. In this at least one magnet must be arranged on the pendulum: for example in the inner region of the ring-shaped coil (no figure). 
     In the examples described the warp threads are moved individually. They can also be moved combined together group-wise, such as for example is known for Jacquard shed formation apparatuses. The elements for the moving of warp threads are replaced in this by members by means of which in each case a group of warp threads can be moved at the same time. 
     Weaving machines can be equipped with a plurality of apparatuses in accordance with the invention. This is particularly advantageous when the weaving machine is operated by means of an electronic and programmable control system. A processor for a control system of this kind can also be used for the control of the apparatuses in accordance with the invention. The currents of the coils can thus be programmed so as to be automatically settable, and indeed in such a manner that they assume values which are correspondingly predetermined for the warp thread types.