Patent GB-721329-A (GB)
Title: Improvements in or relating to threading devices for sewing machines
IPC: D05B87/02
Filed: 1952-08-22
Abstract: 721,329. Sewing. PFAFF AKT.-GES., G. M. Aug. 22, 1952 [Aug. 24, 1951; Nov. 10, 1951], No. 21092/52. Class 112. Needle threaders. A sewing machine needlethreader comprises a threading hook carried at the lower end of a slidable and rotatable bar arranged and guided so that on movement by an operating member it automatically performs a rotating movement at a predetermined height to carry the hook through the needle eye; the predetermined height may be constant, requiring the needle to be in a particular position, or it may be obtained by engagement between parts on the threader bar and needle-bar, enabling the needle to be threaded in any position. In the embodiment shown, the threading hook 5 is clamped to the lower end of a vertical rod 2 slidable and rotatable in the head 1 of the machine; a cross-pin 15 on the rod 2 engages an inclined slot 16 in a member 7 which is also slidable but is prevented from rotating by a lug 10 engaging a slot 11 in a fixed bar 14, and which carries an operating arm 20 projecting from the head 1. A return spring 18 is placed between a lower lug 9 of the member 7 and the bottom of the machine head, and another spring is placed between a lug 8 at the top of the member 7 and the pin 15, so that on downward movement of the member 7 the threader rod 2 is carried with it by the second spring until the movement of the rod is stopped, whereupon further movement of the member 7 causes rotation of the rod by the action of the inclined slot 16 on the pin 15, and on release of the arm 20 the rod is first held down by the second spring' while being rotated back by the rise of the member 7 and is then lifted with the latter member. The downward movement of the rod 2 is limited by engagement of the pin 15 with the block 17 connecting the needle-bar to its operating link, the distance between the pin and the threading hook being adjusted so that when the pin is in contact with the block the hook is opposite the needle eye; during the rotation of the rod to carry the hook into and out of the eye the pin rides on the top of the block. In a modification a surface for engagement by the pin 15 is provided on a member adjustably clamped on the needle-bar separately from the block 17; in this form the pin 15 in its rotation may move into a groove in, or under a cover-plate on, the engagement member, so that the rod 2 and needle-bar cannot be moved relatively while the hook 5 is in the needle eye. In a form applicable to a needle-bar mounted in a swinging gate for lateral vibration, the rod 2 and a member similar to the member 7 are mounted on the gate, and the operating arm 20 is replaced by a downward extension of the member, with a lateral fingerpiece accessible below the machine head; the second spring referred to above in this form placed the part carrying the hook 5 and the lower bearing of the rod 2 in the needle-bar gate. In another form, which requires that the needle shall be in a certain position, the member corresponding to the member 7 is attached to a cord passing round a pulley at the bottom of the machine head and upwards past other pulleys between which bights can be formed by a horizontally-sliding member pushed inwards from the front of the machine head, the upper end of the cord being anchored so that the formation of such bights causes the member to move downwards, against a return spring, until the bar 2 is stopped by a fixed stop and is then rotated as before. The threading hook may have a protecting wing at each side.