Locking device for a bobbin case for a bottom thread bobbin

Abstract

A locking device having a connection element ( 11 ) that is securely connected to the hook base ( 1 ) but can rotate is provided. On the connection element ( 11 ), a coil spring ( 17 ) is supported that is compressed after setting the bobbin case ( 5 ) on or in the hook base ( 1 ). Through a slight tilting movement, the bobbin case ( 5 ) or the bobbin ( 7 ) could be pushed and guided over the connection element ( 11 ) and then held by the force of the spring ( 17 ) in the locking position.

1 . A locking device for a bobbin case ( 5 ) for a bottom thread bobbin ( 7 ) in a hook base ( 1 ) of a sewing machine, comprising a receptacle space in the hook base ( 1 ) for the bobbin ( 7 ) or the bobbin case ( 5 ) and a spindle ( 9 ), the locking device comprises a peripheral groove ( 21 ) constructed on the spindle ( 9 ) in the hook base ( 1 ) and a coil spring ( 17 ) located between an upper end of the spindle ( 9 ) and the bobbin case ( 5 ), and the spring is compressed by the bobbin case when the bobbin case ( 5 ) is set on top of the spindle. 
   
   
       2 . The locking device according to  claim 1 , wherein a connection element ( 11 ) is provided on the spindle connected to the hook base ( 1 ), and the peripheral groove ( 21 ) is located in the connection element. 
   
   
       3 . The locking device according to  claim 2 , wherein a flange ( 23 ) directed radially inward and only partially circular is constructed on the bobbin case ( 5 ) on a lower end thereof protruding into a central borehole ( 13 ) of the bobbin case. 
   
   
       4 . The locking device according to  claim 3 , wherein the flange ( 23 ) has a crescent-shaped construction. 
   
   
       5 . The locking device according to  claim 3 , wherein a cross section of the borehole ( 13 ) between the flange ( 23 ) and a lower region of the wall section of the borehole ( 13 ) is greater than a diameter of the connection element ( 11 ). 
   
   
       6 . The locking device according to  claim 5 , wherein the diameter of the connection element ( 11 ) corresponds on an upper end thereof approximately to a diameter of the borehole ( 13 ) in the bobbin case ( 5 ). 
   
   
       7 . The locking device according to  claim 5 , wherein the borehole ( 13 ) has a cylindrical construction in an upper region thereof and is cylindrical over about 180° in the lower region with the flange ( 23 ) and has a cylinder-barrel-shaped surface over a remainder of the lower region, and an axis of the cylinder-barrel-shaped surface lies at an acute angle relative to a rotational axis of the bobbin ( 7 ). 
   
   
       8 . The locking device according to  claim 1 , wherein a sleeve ( 31 ) is located in the bobbin ( 7 ) such that the bobbin can rotate about a central borehole ( 13 ) of the sleeve, the borehole ( 13 ) has a cylindrical construction in an upper region and is cylindrical over about 180° in a lower region having a flange ( 23 ) and has a cylinder-barrel-shaped surface over a remainder of the lower region, and the axis of the cylinder-barrel-shaped surface lies at an acute angle relative to a rotational axis of the bobbin ( 7 ). 
   
   
       9 . The locking device according to  claim 8 , wherein a cross section of the borehole ( 13 ) between the flange ( 23 ) and a tapered region of a lower wall section b of the borehole ( 13 ) is larger than a diameter of the locking element ( 11 ) above the peripheral groove ( 21 ).