| CPC D05B 29/12 (2013.01) [D05B 29/08 (2013.01)] | 8 Claims |
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1. A sewing machine comprising:
a sewing machine motor;
a needle bar extending in an up-down direction and having a lower end portion on which a needle is mountable, the needle bar being configured to be driven by the sewing machine motor to move in the up-down direction;
a throat plate formed with a needle hole and an opening, the needle being configured to pass through the needle hole in accordance with movement of the needle bar in the up-down direction;
a feed dog configured to emerge from and be retracted beneath the opening, the feed dog being configured to feed a workpiece placed on the throat plate;
a feed mechanism configured to be driven by the sewing machine motor to drive the feed dog;
a presser bar extending in the up-down direction and having a lower end portion on which a presser foot is mountable, the presser bar being configured to move in the up-down direction in synchronization with movement of the feed dog;
a presser bar spring having an upper end and a lower end in the up-down direction, the presser bar spring being configured to urge the presser bar downward with an urging force;
an adjustment spring having an upper end and a lower end in the up-down direction, the adjustment spring being configured to urge the presser bar downward with an urging force smaller than the urging force of the presser bar spring;
a presser bar clamp fixed to the presser bar, the presser bar clamp being configured to define a position of the lower end of the adjustment spring in the up-down direction; and
an adjusting mechanism comprising:
an adjustment part supported to be movable in the up-down direction, the adjustment part being configured to define a position of the lower end of the presser bar spring in the up-down direction and a position of the upper end of the adjustment spring in the up-down direction; and
a restricting part configured to restrict a moving range of the adjustment part in the up-down direction when the restricting part contacts the adjustment part,
wherein during a first prescribed period of time in which a top of the feed dog is above a top surface of the throat plate, the adjustment part is spaced apart from the restricting part in the up-down direction to cause the urging force of the presser bar spring to be transmitted to the presser foot, and
wherein during a second prescribed period of time in which the top of the feed dog is beneath the top surface of the throat plate, the adjustment part is in contact with the restricting part in the up-down direction to prevent the urging force of the presser bar spring from being transmitted to the presser foot.
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