Bobbin winder device of a sewing machine and method for controlling or regulating the speed of the motor of a bobbin winder device

Abstract

A bobbin winder device of a sewing machine includes a motor ( 1 ), which is controlled by a motor controller ( 21 ), in order to drive a spindle ( 7 ), to which a thread bobbin ( 9 ) can be attached in order to wind on sewing thread. A brake device ( 3 ) with a brake pad ( 11 ), which brakes the bobbin arrangement when the winding radius of the wound sewing thread is greater than a predetermined reference value (C 0 ), is arranged next to the spindle ( 7 ). The motor controller ( 21 ) monitors at least one measured variable, which is dependent on the load on the motor ( 1 ), in the driving circuit of the motor ( 1 ). If this measured variable or the rate of change thereof changes such that it falls below or exceeds an associated stored comparison value, the motor controller ( 21 ) causes the motor ( 1 ) to be shut down.

1 . A bobbin winder device of a sewing machine, the bobbin winder device comprising:
 a motor;   a spindle mounted on a support and configured to rotate about a spindle axis and which is driveable by said motor, for releasable attachment of a thread bobbin to be filled with sewing thread;   a motor controller connected to the motor via electrical conductors and configured to control or regulate a rotational speed of the motor;   a brake pad with a friction surface held on the support so as to be movable, wherein a distance between the friction surface and the spindle axis is variable, such that the friction surface is positionable next to the spindle in a reference position with a predeterminable reference distance from the spindle axis corresponding to a maximum winding radius of the sewing thread to be wound and is displaceable radially outwards from the reference position counter to a force of a restoring element with respect to the spindle axis; and   the motor controller comprises a sensor configured to detect at least one measured variable, which is dependent on a load of the motor, in a driving circuit of the motor and at least one of a) a stored comparison value for said measured variable or b) a stored comparison value for a rate of change of the measured variable over time.   
     
     
         2 . The bobbin winder device as claimed in  claim 1 , wherein the brake pad comprises a pivot arm mounted on the support next to the motor to pivot about a pivot axis, and the friction surface is spaced apart from the pivot axis on a head protruding on a side of the pivot arm. 
     
     
         3 . The bobbin winder device as claimed in  claim 2 , further comprising a first stop ( 15   a ) arranged on the brake pad and a second stop arranged on the support, said first and second stops together limit a freedom of movement of the brake pad in a direction of the spindle axis to define the reference position of the brake pad and the reference distance between the friction surface and the spindle axis. 
     
     
         4 . The bobbin winder device as claimed in  claim 3 , wherein at least one of the first or second stops is moveable in order to adjust the reference position of the brake pad and the reference distance between the friction surface and the spindle axis. 
     
     
         5 . The bobbin winder device as claimed in  claim 1 , wherein the brake pad is convex in a region of the friction surface. 
     
     
         6 . The bobbin winder device as claimed in  claim 1 , wherein the motor controller comprises in at least one of the conductors an electronic switch for interrupting and closing the driving circuit. 
     
     
         7 . The bobbin winder device as claimed in  claim 1 , wherein the sensor of the motor controller comprises at least one voltage sensor for measuring a voltage between the conductors in the driving circuit of the motor. 
     
     
         8 . The bobbin winder device as claimed in  claim 7 , wherein the voltage sensor is arranged between the conductors such that the voltage sensor is connected to the motor even when the driving circuit is interrupted, and the motor controller comprises control specifications for periodically detecting a reverse voltage of the motor, and the motor controller is configured to periodically carry out the following steps:
 a) interrupting of the driving circuit,   b) measuring the reverse voltage using the voltage sensor after a delay time, and   c) closing of the driving circuit.   
     
     
         9 . The bobbin winder device as claimed in  claim 8 , wherein the motor controller comprises the control specifications stored in the motor controller for comparing the detected reverse voltage of the motor or a rate of change of the reverse voltage over time with an associated stored comparison value, and the control specifications stored in the motor controller for interrupting the driving circuit if the reverse voltage or the rate of change thereof over time falls below or exceeds the associated comparison value. 
     
     
         10 . The bobbin winder device as claimed in  claim 9 , wherein the motor controller comprises the control specifications for detecting the reverse voltage of the motor in case of a manual rotation of the spindle. 
     
     
         11 . A method for controlling or regulating the speed of the motor of the bobbin winder device as claimed in  claim 1 , the method comprising:
 winding the sewing thread onto the thread bobbin, which is attached to the spindle,   the motor controller monitoring a measured variable, which is dependent on the load on the motor and which is detected by the sensor in the driving circuit of the motor, and   causing the motor to shut down as soon as the value of the detected measured variable falls below the associated stored comparison value.