Foot Controller for Sewing Machine and Sewing Machine

Abstract

A foot controller for a sewing machine includes a drive start switch ( 18 ) provided in a drive circuit ( 17 ) of a sewing machine motor ( 10 ) and a speed adjusting circuit ( 25 ) having a variable resistor ( 26 ) for adjusting a speed of the sewing machine motor ( 10 ) and a switching element ( 28 ) cooperating with the variable resistor ( 26 ), characterized by an interruption circuit ( 19 ) interrupting the drive circuit ( 17 ) of the sewing machine motor ( 10 ) when the switching element ( 28 ) is short-circuited while the drive start switch ( 18 ) is in an off-state.

1 . A foot controller for a sewing machine, which comprises a start switch ( 18 ) provided in a drive circuit ( 17 ) of a sewing machine motor ( 10 ) and a speed adjusting circuit ( 25 ) provided with a variable resistor ( 26 ) for adjusting a speed of the sewing machine motor ( 10 ) and a switching element ( 28 ) cooperating with the variable resistor ( 26 ), characterized by an interruption circuit ( 19 ) interrupting the drive circuit ( 17 ) of the sewing machine motor ( 10 ) when the switching element ( 28 ) is short-circuited while the drive start switch ( 18 ) is in an off-state.  
   
   
       2 . The foot controller according to  claim 1 , wherein the interruption circuit ( 19 ) has a thermal fuse ( 20 ) connected in series to the drive circuit ( 17 ) of the sewing machine motor ( 10 ) and an electrical resistance ( 21 ) provided to be capable of applying heat to the thermal fuse ( 20 ) and connected in parallel with the drive start switch ( 18 ).  
   
   
       3 . The foot controller according to  claim 2 , wherein the interruption circuit ( 19 ) comprises a cement resistor ( 19 ) with the built-in thermal fuse ( 20 ).  
   
   
       4 . The foot controller according to  claim 1 , wherein the switching element ( 28 ) comprises a triac ( 28 ) switched by a diac ( 30 ) connected to the variable resistor ( 26 ).  
   
   
       5 . A sewing machine which comprises a needlebar driving mechanism vertically moving a needlebar ( 5 ) having a lower end to which a sewing needle ( 6 ) is attached, a feed-dog vertically moving mechanism, a feed-dog horizontally moving mechanism, a thread loop taker accommodating a lower thread bobbin and cooperating with the sewing needle ( 6 ), a drive start switch ( 18 ) provided in a drive circuit of a sewing machine motor ( 10 ), and a foot controller ( 15 ) having a speed adjusting circuit ( 25 ) provided with a speed adjusting variable resistor ( 26 ) of the sewing machine motor ( 10 ) and a switching element ( 28 ) cooperating with the variable resistor ( 26 ), characterized in that the foot controller ( 15 ) includes an interruption circuit ( 19 ) interrupting the drive circuit ( 17 ) of the sewing machine motor ( 10 ) when the switching element ( 28 ) is short-circuited while the drive start switch ( 18 ) is in an off-state.  
   
   
       6 . The foot controller according to  claim 2 , wherein the switching element ( 28 ) comprises a triac ( 28 ) switched by a diac ( 30 ) connected to the variable resistor ( 26 ).  
   
   
       7 . The foot controller according to  claim 3 , wherein the switching element ( 28 ) comprises a triac ( 28 ) switched by a diac ( 30 ) connected to the variable resistor ( 26 ).