Sewing machine

Abstract

A sewing machine includes a main body, a presser bar attached to the main body so as to move along a vertical direction of the sewing machine and detachably holding a presser foot, a needle thread tension adjustment mechanism selectively brought into inactive and active modes, the needle thread tension adjustment mechanism releasing a needle thread tension in the inactive mode and maintaining the needle thread tension in the active mode, and a presser bar lifting lever manually rotated along the vertical direction by a user of the sewing machine and adjusting a position of the presser bar in the vertical direction in accordance with the manual rotation, the presser bar lifting lever including a height adjustment cam portion adjusting the position of the presser bar in the vertical direction and a thread tension adjustment cam portion allowing the needle thread tension adjustment mechanism to adjust the needle thread tension.

1 . A sewing machine, comprising:
 a main body;   a presser bar attached to the main body so as to move along a vertical direction of the sewing machine and detachably holding a presser foot at a lower end;   a needle thread tension adjustment mechanism selectively brought into inactive and active modes, the needle thread tension adjustment mechanism releasing a needle thread tension in the inactive mode and maintaining the needle thread tension in the active mode; and   a presser bar lifting lever mounted to the main body for rotation about a rotary shaft along the vertical direction of the main body, the presser bar lifting lever including a height adjustment cam portion adjusting the position of the presser bar in the vertical direction and a thread tension adjustment cam portion allowing the needle thread tension adjustment mechanism to adjust the needle thread tension,   wherein the height adjustment cam portion of the presser bar lifting lever includes a cam profile arranging the presser bar in a lower position in which the sewing machine is operable in a normal sewing mode, the cam profile of the height adjustment cam portion allowing the presser bar to be maintained in a first higher holding position to which the presser bar is moved further upward from the lower position in the vertical direction, the cam profile of the height adjustment cam portion allowing the presser bar to be maintained in a second higher holding position to which the presser bar is moved further upward from the first holding position in the vertical direction, and   wherein the thread tension adjustment cam portion of the presser bar lifting lever includes a cam profile bringing the needle thread tension adjustment mechanism into the active mode when the presser bar is in the lower position, the cam profile of the thread tension adjustment cam portion bringing the needle thread tension adjustment mechanism into the inactive mode when the presser bar is in the first higher holding position, the cam profile of the thread tension adjustment cam portion bringing the needle thread tension adjustment mechanism into the active mode when the presser bar is in the second higher holding position.   
     
     
         2 . The sewing machine according to  claim 1 , wherein the presser bar includes a presser bar holding member supported by the presser bar, and
 wherein the cam profile of the height adjustment cam portion of the presser bar lifting lever comprises:   a first cam surface being in contact with the presser bar holding member at an upper side of the rotary shaft and positioned on a straight line when the presser bar is in the first holding position, the straight line passing through a central axis of the rotary shaft so as to be perpendicular to the central axis; and   a second cam surface being in contact with the presser bar holding member at the upper side of the rotary shaft and positioned on the straight line when the presser bar is in the second holding position.   
     
     
         3 . The sewing machine according to  claim 2 , wherein the first cam surface of the cam profile of the height adjustment cam portion extends along a horizontal direction of the sewing machine when the presser bar is in the first holding position, and the second cam surface of the cam profile of the height adjustment cam portion extends along the horizontal direction of the sewing machine. 
     
     
         4 . The sewing machine according to  claim 1 , further comprising a switch detecting the lower position, the first holding position, and the second holding position of the presser bar. 
     
     
         5 . The sewing machine according to  claim 4 , further comprising a switch lever rotating along with the rotation of the presser bar lifting lever, wherein the switch outputs a first ON signal when detecting that the switch lever is rotated in a first direction, the switch outputting an OFF signal when detecting that the switch lever is rotated to an intermediate position, the switch outputting a second ON signal when detecting that the switch lever is rotated in a second direction, and
 wherein the sewing machine is operable in the normal sewing mode when the lower position of the switch lever is determined on the basis of the first ON signal outputted from the switch, the sewing machine is not operable in the normal sewing mode when the first holding position of the switch lever is determined on the basis of the OFF signal outputted from the switch, and the sewing machine is operable in the normal sewing mode when the second holding position of the switch lever is determined on the basis of the second ON signal outputted from the switch.   
     
     
         6 . The sewing machine according to  claim 1 , further comprising an embroidery restriction member attached to the main body, the embroidery restriction member making contact with either one of the presser foot and a holder for attaching the presser foot to the presser bar, and restricting the presser bar from shifting to the second holding position in a state where the presser foot is attached to the presser bar. 
     
     
         7 . The sewing machine according to  claim 1 , further comprising:
 a thread tension releasing operation member selectively bringing the needle thread tension adjustment mechanism into the inactive and active modes;   a rod engaged with the thread tension releasing operation member;   a motor electrically operating the thread tension releasing operation member and the rod to bring the needle thread tension adjustment mechanism into the inactive mode; and   a thread tension releasing portion operating the thread tension releasing operation member in accordance with the manual rotation of the presser bar lifting lever by the user of the sewing machine to bring the needle thread tension adjustment mechanism into the inactive mode,   wherein the thread tension releasing operation member includes a protruding portion and the rod includes an elongated bore having a free space to which the protruding portion of the thread tension releasing operation member is fitted, the elongated bore being larger in size than the protruding portion, and   wherein when the motor is driven in a direction to move the rod in a thread tension releasing direction, the thread tension releasing operation member is moved via the protruding portion by the rod to bring the needle thread tension adjustment mechanism into the inactive mode.   
     
     
         8 . The sewing machine according to  claim 7 , wherein when the presser bar lifting lever is manually rotated by the user of the sewing machine and the thread tension releasing operation member is moved by the thread tension adjustment cam portion in the thread tension releasing direction to bring the needle thread tension adjustment mechanism into the inactive mode, the protruding portion moves in the elongated bore therealong and the free space of the elongated bore prevents the movement of the thread tension releasing operation member from being transmitted to the rod. 
     
     
         9 . A sewing machine, comprising:
 a main body;   a presser bar attached to the main body for movement along a vertical direction of the main body and having a lower end to which a presser foot is detachably connected;   a needle thread tension adjustment mechanism configured to, when being in its inactive and active modes, releasing and maintaining a needle thread tension, respectively; and   a presser bar lifting lever pivoted to the main body via a rotary shaft for manual rotational movement along the vertical direction of the main body,   the presser bar lifting lever including a height adjustment cam portion for adjusting a height of the presser bar upon the manual rotational movement of the presser bar lifting lever and a thread tension adjustment cam portion for adjusting the needle thread tension,   wherein the height adjustment cam portion of the presser bar lifting lever has a cam profile which allows the presser bar to locate at selective one of a lower position for a normal sewing mode, a first higher holding position having a higher elevation than the lower position, and a second higher holding position having a higher elevation than the first higher holding position, and   wherein the thread tension adjustment cam portion has a cam profile which causes the needle thread tension adjustment mechanism to operate in the active mode, the inactive mode, and the active mode, when the presser bar locates at the low position, the first holding position, and the second holding position, respectively.