Sewing machine
A sewing machine includes an upper shaft rotatable so as to drive a needle bar, a lower shaft rotatable so as to drive a hook, an upper-shaft pulley attached to the upper shaft, a lower-shaft pulley attached to the lower shaft, a belt linking the upper-shaft pulley and the lower-shaft pulley, and synchronizing a rotation of the upper-shaft pulley and a rotation of the lower-shaft pulley with each other, a belt adjusting mechanism contacting the belt and changing a belt length at a tensioned side at which the belt is drawn, and a tensioner tensioning the belt in accordance with the change in the belt length of the belt at the tensioned side.
1. A sewing machine comprising:
an upper shaft rotatable so as to drive a needle bar;
a lower shaft rotatable so as to drive a hook;
an upper-shaft pulley attached to the upper shaft;
a lower-shaft pulley attached to the lower shaft;
a belt linking the upper-shaft pulley and the lower-shaft pulley, and synchronizing a rotation of the upper-shaft pulley and a rotation of the lower-shaft pulley with each other;
a belt adjusting mechanism contacting the belt and absorbing slack at a tensioned side at which the belt is drawn by moving in or away from a direction in which the belt adjusting mechanism pushes the tensioned side; and
a tensioner tensioning the belt in accordance with an absorbing level of the slack of the belt;
wherein the tensioner comprises;
a tension adjusting idler contacting the belt at the loosened side where the belt is drawn out; and
an elastic member connecting to the tension adjusting idler.
2. The sewing machine according to claim 1 , wherein the belt adjusting mechanism:
comprises at least one idler contacting the tensioned side; and
changes the absorbing level of the slack of the belt at the tensioned side by causing the idler to swing.
3. The sewing machine according to claim 1 , further comprising a restrictor restricting a movable range of the tensioner when a tensioned condition of the belt exceeds pushing force by the tensioner.
4. The sewing machine according to claim 3 , wherein:
the restrictor comprises a stopper arm and a stopper disposed with a predetermined distance from the stopper arm; and
the stopper arm contacts with the stopper to restrict the movable range of the tensioner when the tensioned condition of the belt exceeds the pushing force by the tensioner.