Abstract:
A linear motor for controlling motions of thread being woven on a weaving machine is disclosed. The linear motor contains a stator (1) which produces a magnetic field, an armature (2) which is arranged in the magnetic field, and two flexible mounting parts (3) which are arranged parallel to one another in such a manner that the armature which is connected to the mounting parts is movable relative to the stator. The linear motor drives a member that can contact the thread and thereby influence its motion.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a linear motor for a textile machine, an apparatus for influencing a sequence of movement of a thread using a linear motor, and a weaving machine with an apparatus of this kind. 
     A linear motor for a weaving machine is described in U.S. Pat. No. 4,998,420 which has a stator with a ferromagnetic plate and a permanent magnet with different polarity as well as an armature with a winding. The stator is arranged at a fixed location and the armature is rotatably journalled on an axis of fixed location. 
     In this embodiment of the linear motor, the bearing friction which arises and also the bearing clearance prove to be disadvantageous. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to improve a linear motor. 
     The advantages which can be achieved with the invention are substantially to be seen in that the armature executes a movement in a plane; in that the movement is hysteresis-free and is absolutely free of clearance in the mountings; and in that the force which is exerted by the armature is directly proportional to the current strength. 
     The side walls of the coil body can be provided at the outer side with a copper layer or be manufactured of aluminum. This has the advantage that the permanent magnet, i.e. the magnet pair, produces eddy currents in the copper layer which damp the movement of the armature. 
     A weaving machine with an apparatus for influencing of the movement sequence of at least one thread or band using a linear motor is characterized in that the apparatus is arranged in the path of travel of the weft thread as a thread brake. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in the following with reference to the accompanying drawings. 
     FIGS. 1 and 2 show an embodiment of a linear motor in accordance with the invention in section; 
     FIG. 3 is a schematic illustration of a second embodiment of a linear motor; 
     FIG. 4 shows a first embodiment of an apparatus in accordance with the invention; 
     FIG. 5 schematically illustrates a second embodiment of the apparatus in accordance with the invention; 
     FIG. 6 schematically illustrates a third embodiment of the apparatus; 
     FIG. 7 schematically illustrates a fourth embodiment of the apparatus; 
     FIG. 8 is a section along the line VIII—VIII in FIG. 7; 
     FIG. 9 schematically illustrates a fifth embodiment of the apparatus; 
     FIG. 10 schematically illustrates a sixth embodiment of the apparatus; 
     FIG. 11 schematically illustrates a seventh embodiment of the apparatus; 
     FIG. 12 schematically illustrates an eighth embodiment of the apparatus; 
     FIG. 13 shows a third embodiment of a linear motor in accordance with the invention as a part of a thread brake in section; 
     FIG. 14 shows a fourth embodiment of a linear motor in accordance with the invention as a part of a thread brake in section; 
     FIG. 15 shows an embodiment of a spring in the linear motor in accordance with FIG. 14; 
     FIG. 16 schematically illustrates a tenth embodiment of the apparatus; 
     FIG. 17 schematically illustrates an eleventh embodiment of the apparatus; 
     FIG. 18 schematically illustrates a twelfth embodiment of the apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is made to FIGS. 1 and 2. The linear motor M has a stator  1 , an armature  2  and two leaf springs  3  which serve as mountings parts for the armature. The stator contains two plates  5  of ferromagnetic material, two spacers  6 ,  7  which connect the plates and hold them at a spacing, and two permanent magnet pairs  8  with different polarity which are mounted at the inner side of the plates. The armature  2  contains a coil body  9  with a core  10  and two side walls  11  of a non-ferromagnetic material, e.g. plastic, a coil  12  as well as a first connection member  13  and a second connection member  14 . The side walls  11  of the coil body are provided with a copper layer or are manufactured of aluminum. The leaf springs  3  are in each case mounted at the spacer  7  at one end and at the connection member  13 ,  14  at the other end. The leaf springs  3  have non-illustrated connections for the current supply and are connected to the connection wires of the coil. A reliable current supply to the coil is ensured with this arrangement. In the previously described embodiment the linear motor is arranged between the mountings  3 . It is however also possible to arrange the linear motor outside the bearing parts. 
     The method of functioning of a linear motor is known and will thus not be explained in further detail. When the coil is excited the armature  2  is deflected, with the armature  2  executing a movement in a plane as a result of the leaf springs  3 . Since the side walls of the coil body are provided with e.g. a copper layer at the outer surfaces which lie opposite to the permanent magnet pairs, eddy currents are induced in the copper layer during the operation which damp the movement of the armature  2 . 
     Through the parallel orientation of the bearing parts with respect to one another it is possible to provide an extremely small air gap between the armature and the stator. An absolutely clearance-free or play-free mounting results in that leaf springs are used which are firmly anchored at one side. 
     FIG. 3 shows another embodiment of a linear motor M. In this motor the armature  2  is mounted by means of links  15  at the stator  1 . A guide part  16  is arranged at each of the levers in order to guide the armature  2  without clearance at the parallel oriented plates of the stator during the movement. A spring  17  can be provided in order to return the armature  2  into the basic position in a switched off or pole-reversed motor respectively and an elastic part  18  can be provided in order to achieve a damping through a softer abutment. 
     FIG. 4 shows a thread brake  21  with a linear motor M. The thread brake contains a stationary braking part  22  and a movable braking body  23 . The stationary braking part  22  is formed as a braking band and is arranged yieldingly in holders  24 . The movable braking body  23  is connected to the armature  2 . The thread brake is connected to the linear motor and is mounted at a weaving machine by means of elastic elements  25  in order to damp the oscillations arising at the machine frame. 
     In the embodiment of the thread brake operated with linear motor M and shown in FIG. 5, an elastic body  27  is mounted at the stationary braking part in order to achieve a progressive spring suspension. 
     FIG. 6 shows an embodiment of a thread brake operated with linear motor M which has two braking bodies, so that a thread is braked at two locations. On the one hand an amplification of the braking action on the thread can be achieved thereby; on the other hand the specific braking stress can be distributed over the thread. 
     Reference is made to FIGS. 7 to  9 . FIGS. 7 and 8 show a thread brake for two threads extending in parallel with however only one linear motor M, with the braking body  23  being formed in the shape of a T and acting on the thread brakes which are arranged thereunder and are oriented in parallel. FIG. 9 shows a thread brake for a thread, with the braking body being formed in the shape of a hook in order to direct the braking force symmetrically onto the braking part. In order to facilitate the introduction of a thread into the thread brake, the linear motor M is arranged beneath the braking band in these embodiments. The braking body is connected to the armature of the linear motor by means of a bow  29 . 
     FIGS. 10 to  11  show embodiments of thread brakes with two linear motors M in each case which can be controlled independently of one another. With these embodiments there result further possibilities for, on the one hand, a braking force amplification and, on the other hand, a division of the specific braking stress over the thread. Furthermore, the reaction times for e.g. pair-wise braking of the thread travel can be shortened through alternate loading. 
     FIG. 12 shows a use of the linear motor M in connection with a known plate thread brake which is arranged at the thread draw-off side of a thread storage  60 . In this the movable brake plate  23  is mounted at an extended mounting part  61  of the linear motor. 
     Reference is made to FIGS. 13 to  15 . FIG. 13 shows a linear motor M which contains a stator  31 , an armature  32  and two mounting parts  33 . The stator contains a coil  34  which is provided in a housing  35 . The armature  32  is a permanent magnet which is mounted on the mounting parts  33 . The mounting parts are designed as leaf springs. This linear motor is illustrated as a part of a thread brake, which furthermore has a holder  36 , a stationary braking part  37  and a braking body  38 . The linear motor and the stationary braking part are arranged on the holder and the braking body is mounted on the armature. 
     FIG. 14 shows a fourth embodiment of a linear motor M which is designed substantially similarly to the linear motor in accordance with FIG.  13 . 
     The essential difference consists in the design of the housing  41  and of the mounting parts  42  (FIG.  15 ). In this embodiment the mounting parts are designed as ring springs and e.g. at the same time designed as current connection conductors for the coil. The thread to be braked can be conducted through between the braking members  37 ,  38  in the form illustrated in a solid line, or else radially up to the center of the latter in order to be guided through a non-illustrated central bore. 
     Reference is made to FIGS. 16 to  19 . FIG. 16 shows an apparatus for the controllable forwarding of a thread or band using a linear motor M. The apparatus contains a forwarding roller  51  which is set into rotation by a non-illustrated drive and a pressing roller  52  which is connected to the linear motor, whereby movement is produced by friction. In this apparatus a single deflection can be used instead of a double deflection. 
     FIG. 17 shows an apparatus for the acceleration of a thread using a linear motor. This apparatus contains a forwarding roller  53  which is driven by a motor (not shown) and a preferably likewise driven pressing roller  54  which is connected to the linear motor. This apparatus can e.g. be used for the acceleration of a weft thread for the purpose of avoiding the so-called stretch jolt during weft insertion in a projectile weaving machine as well as to assist the weft insertion in air-jet weaving machines. 
     FIG. 18 shows an apparatus for the deflection of a thread in order e.g. to achieve a controllable damping at the end of a weft insertion in e.g. airjet weaving machines. As is well known to and commonly practiced by those skilled in the art, a thread  61  can be contacted by a deflection member  62  which can engage and deflect the thread between two spaced-apart pins  63 . 
     The linear motor contains a stator  1  which produces a magnetic field, an armature  2  which is arranged in the magnetic field, and two flexible mounting parts  3  which are arranged parallel to one another in such a manner that the armature which is connected to the mounting parts is movable relative to the stator.