Positive yarn feeder for textile machines and the like

Abstract

The yarn-feeder comprises a reel (R) having loops of yarn wound thereon and driven by a permanent-magnet, synchronous brushless motor to draw the yarn from a spool (RO) and to feed it to a textile machine arranged downstream (MF). The motor (M, M′) comprises a stator (STA, STA′) consisting of a substantially cylindrical, hollow housing having at least three elongated pole shoes (E 1 -E 3 , E 1 ′-E 3′ ) having respective excitation coils wound thereon (A, B, C, A′, B′, C′), and a rotor comprising a magnetic member having a circular profile with alternating poles, which is coaxially supported on the driving shaft (AM, AM′) near the coils.

1 . A yarn-feeder for textile machines, comprising a yarn winding reel (R) driven by a permanent-magnet, synchronous brushless motor to draw the yarn from a spool (RO) and to feed the yarn to a textile machine arranged downstream (MF), wherein said motor (M, M′) comprises a stator (STA, STA′) consisting of a substantially cylindrical, hollow housing having at least three elongated pole shoes (E 1 -E 3 , E 1 ′-E 3 ′) having respective excitation coils wound thereon (A, B, C, A′, B′, C′), and a rotor comprising a magnetic member having a circular profile with alternating poles, which is coaxially supported on the driving shaft (AM, AM′) near the coils.  
   
   
       2 . The yarn-feeder of  claim 1 , wherein said magnetic member consists of a thin cylinder (MC) made of a radially polarized, magnetic material with alternating poles, and said pole shoes (E 1 , E 2 , E 3 ) radially project inwards from the stator about the axis of rotation of the rotor.  
   
   
       3 . The yarn-feeder of  claim 1 , wherein said magnetic member consists of a thin disc (D) made of a magnetic material that is polarized longitudinally with alternating poles in the direction of its thickness, and said pole shoes (E 1 ′-E 3 ′, E 1 ′ b -E 4 ′ b ) project parallel to the axis of rotation of the rotor.  
   
   
       4 . The yarn-feeder of  claim 1 , wherein said stator comprises nine elongated pole shoes, three of which (E 1 -E 3 , E 1 ′-E 3 ′) are equally spaced at 120° from each other and support respective excitation coils (A, B, C, A′, B′, C′), and said magnetic member has four pairs of pole shoes.  
   
   
       5 . The yarn-feeder of  claim 4 , wherein said magnetic member has a number of pairs of pole shoes that is a multiple of four.  
   
   
       6 . The yarn-feeder of  claim 1 , wherein said stator comprises nine elongated pole shoes, three of which (E 1 -E 3 , E 1 ′-E 3 ′) are equally spaced at 120° from each other and support said excitation coils (A, B, C, A′, B′, C′), and said magnetic member has five pairs of pole shoes.  
   
   
       7 . The yarn-feeder of  claim 6 , wherein said magnetic member has a number of pairs of pole shoes that is a multiple of five.  
   
   
       8 . The yarn-feeder of  claim 3 , wherein said stator comprises eight pole shoes, four of which (E 1 ′ b , E 2 ′ b , E 3 ′ b , E 4 ′ b ) are equally spaced at right angles from each other and support respective excitation coils (A′b, B′b, C′b, D′b), and said thin disc (Db) has five pairs of pole shoes.  
   
   
       9 . The yarn-feeder of  claim 1 , wherein the motor (M, M′) is controlled by a control unit (UC) via an electronic power supply unit, and wherein a plurality of Hall sensors (H 1 -H 3 , H 1 ′, H 3 ′) are arranged in the angular gaps between the coils near the magnetic member and are connected to send position signals to said control unit.