Patent GB-1020373-A (GB)
Title: Improvements in thread severing mechanism for sewing machines
IPC: D05B65/00
Filed: 1963-11-27
Abstract: 1,020,373. Sewing machines. AMERICAN SAFETY TABLE CO. Inc. Nov. 27,1963 [Dec. 27, 1962], No. 46863/63. Heading D1G. A sewing machine is provided with electrically-heated elements adapted to sever the needle and bobbin threads, the elements being mounted on the presser foot and throat plate respectively. The presser foot comprises a sole plate 38 formed with spaced-apart toes 44, 45 and pivoted about a horizontal axis to a block 37 releasably secured to the presser bar. Toe 45 is formed in its upper surface with a groove in which is mounted a wire heating element 49. A leaf spring 52, secured to the upper surface of toe 45, overlies said element 49 and is formed adjacent the latter with a thread-grinding notch 55. A lever 42, pivoted to sole plate 38 about a vertical axis, carries at one end a blade 56 formed with a notch 58 which, when lever 42 is swung counter-clockwise, directs the needle thread under spring 52, first clamping the thread against the latter and then engaging the thread with the heated element 49. Blade 56 is also formed with a needle-passing notch 59. The other end of lever 42 is engaged in a slot 61 in one end of a lever 40 pivoted at 41 to block 37. A pin 62 at the other end of lever 40 engages a slot 75 in one end of a lever 63 pivoted at 69 to a frame 70. The other end of lever 63 is connected by a link 64 to a plate 65 rigid with the driving shaft 66 of a rotary solenoid 60 mounted by bushes 71 on frame 70. Energization of solenoid 60 serves to move lever 42 clockwise, and upon de-energization of solenoid 60 a spring 72, attached to lever 63, moves lever 42 counter-clockwise for clamping and severing the needle thread. A plate 80 pivoted on shaft 66 and adjustably fixed to plate 65, is formed with a cam slot 81 engaged by a pin 84 carried by an arm 85 rigid with a shaft 86 journalled in frame 70. Cam slot 81 is so shaped that when blade 56 moves in the thread clamping and severing direction, the hooked end of an arm 92, rigid with shaft 86, moves between the discs of a thread-tensioner to release the tension of the needle thread while the latter is being drawn into clamping position, arm 92 returning to its initial position for restoring the thread tension after clamping and severing is effected. Frame 70, which is detachably secured to the sewing machine head, comprises a plate 94 which rests on said head, and a vertical bar 100 carrying an adjustable pad 102 engaging the front surface of said head. The throat plate 34 is formed on its under surface with a groove in which is mounted a wire heating element 131 positioned adjacent the needle throat 132. A bar 134, slidably mounted in a groove in the under surface of the throat plate, is formed with a land 139 normally positioned adjacent the throat 132, and which, when bar 134 is moved to the right, carries the bobbin thread into engagement with the heated element 131. An insulating block 127, depending from the throat plate, carries a pair of pins 128 engaging sockets in an insulating block 122 carried by a plate 110 fixed to one side of a block 106. A bore 107 in the latter receives a pin depending from the sewing machine bed, said pin being clamped by a screw 108. A plate fixed to the other side of block 106 carries a rotary solenoid, the driving shaft of which is rigid with a lever 120 connected by a link 119 to one end of a lever 117 pivoted at 118 on plate 110. The other end of lever 117 engages an aperture 138 in bar 134, to move the latter for severing the bobbin thread upon energization of said solenoid. It is stated that energization of the solenoids and heating elements may be effected either simultaneously or in sequence, and the operation of the system may be effected either manually, as by the actuation of a switch, or automatically in combination with the operation of a mechanism for stopping the machine with the needle fully raised.