GB608983A - Improvements in and relating to a retaining device for a rotary loop-taker of a sewing machine - Google Patents

Abstract

608,983. Sewing - machines. MEFINA SOC. ANON. March 4,1946, No. 6617. Convention date, April 18, 1945. [Class 112] Lock-stitching by rotary hooks.-The bobbin-holder is prevented from rotation by two prongs thereon engaging two automatically actuated and alternately retreating stops, providing free passage of the needle thread. The stops are placed close to and on opposite sides of the needle axis, so as to allow the maximum time for their operation between engagement and release of the needle loop by the hook; they are shaped and arranged so that the force exerted on the bobbin-holder is constant and has a radial component counteracting to some extent the pull of the bobbin thread towards the needle, and also, in the case of a vertical-axis hook, so that the pressure of the bobbin-holder on the horizontal bearing surfaces of the hook is reduced. In the form shown in Fig. 1, the bobbin-holder 19 of a two-revolution vertical-axis rotary hook 11, driven by bevel gears from a shaft 16, is provided with two prongs 24, 25, and an arm 34, mounted on a spindle 28 and oscillated by a cam 29 on the shaft 16, has stop members 35, 36 to engage the prongs 24, 25 respectively to prevent clockwise movement of the bobbin-holder while permitting reverse movement to facilitate withdrawal of the work if the machine stops with the needleloop engaged with the bobbin-holder; the oscillation of the arm 34 carries the stop members alternately out of engagement with the respective prongs, one upwardly and the other downwardly, at least one being in engagement at any time. The member 36 is adjustable on the arm 34 so that both stops can be arranged to engage the bobbin-holder prongs together and the surfaces of the stops are made tangential to their arcs of oscillation; thus there is no vibration when one stop comes into action and the other moves away from its effective position. The engaging surfaces of the stops and prongs are also somewhat inclined to the corresponding radii of the hook, so that they act in opposition to the lateral pull of the lower thread on the bobbin, and the spindle 28 is arranged below the level of the hook so that the path of the stops is inclined and they afford a measure of vertical support to the bobbin-holder. Feed-bar mechanism; feed, reversing and regulating.-Fig. 5 shows a feed-bar mechanism actuated entirely from a cam 29 on the loop-taker shaft 16. The feedbar 42 is pivotally supported by a yoke 44 having a forked part 46 for oscillation by the cam 29 to produce the feed-lift movement and is connected by a link 47 to the end of a pitman 52 also actuated by the cam to produce the feeding movement, the connection between link and pin being guided by a link 50 which is pivoted to an adjustable arm 53 whereby the feed is regulated.