Patent GB-481564-A (GB)
Title: Improvements in or relating to sewing machines or mechanisms suitable for use therein
IPC: D05B15/00
Filed: 1936-09-11
Abstract: 481,564. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd., and KEALL, F. B. Sept. 11, 1936, No. 24757. [Class 112] Sewing-machines for uniting uppers of shoes to soles, having a, hooked needle operated by crank and toggle mechanism, and means for varying the needle stroke in accordance with the thickness of the work, of the type described in Specification 21786/02, [Class 112], are provided with means for automatically rendering the connection between the needle and presser foot to effect movement of the needle-adjusting member by the lifting of the presser-foot to allow the work to be fed during each stitch-forming cycle. The needle-bar] is actuated by the belL- crank 9, 11 the movement of which is governed by the arm 21 and link 15, which constrain the pin 7 on the needle-bar to reciprocate vertically. The arm 21 and link 15 are actuated from the cam-shaft 5 by link 35, curved arm 27, pin 33, and link 25 pivoted to 21. As the cam-shaft 5 rotates, the .curved arm 27 is swung, by its connection to the crank-pin 3, about the pivot 29 on the needle-adjusting arm 31. The relative lengths and angular dispositions of the parts are adjusted so that when the needle-bar is at the top of its movement, the axes of the shaft 5, the pin 3 and the pivot 33 lie on a line at about thirty degrees from the -horizontal. As the pin 3 approaches and leaves this line, it imparts little or no movement to the needle-bar 1, since little or no endwise movement is imparted to the link 35. Also, when the needle-bar 1 is at the top of its up-stroke, the axis of the shaft 29 and the axes of the pivots 26 and 24 lie on a line at about sixty degrees to the horizontal, and as the needle-bar I approaches and leaves its uppermost position, the axis of the pivot 26 moves across this line. These two toggle devices (crank 3 and link 35 on one hand and curved arm 27 and link 25 on the other hand) straighten and break as the needlebar approaches and leaves its uppermost position, giving the bar a dwell at this point. A similar action causes the needle-bar to dwell longer at the bottom of its stroke, to provide time for the thread to be laid in the needle hook by a whirl of the usual type in the horn 36. The height of the needle-bar relative to the horn 36 is determined, as described in Specification 21786/02, by the position of the presserbar 37. By swinging the needle adjusting arm 31 about the pivot 17, the needle-bar 1 can be moved upwards or downwards, except when the needle-bar is in its lowermost position, when the axes of the pivots 33, 17 and 29 are in line. The arm 31 is swung by a cam-arm 39 having a curved face 41 engaged by a roll 43 in an arm 45 of a presser-box lever 47 which has another arm 51 connected to the presser-bar 37 ; adjustment of the presser-bar 37 by the screws 59 for various thicknesses of work correspondingly varies the position of theneedle-bar through the member 31. The presser-bar lever 47 and member 31 are connected by a stirrup member 61 and screw 67. The presser-lifting mechanism for permitting the feed is as described in Specification 21786/02. The shaft 17 of the needle-adjusting member 31 has secured to it an arm 99 connected by a link 103 to a ratchet bar 105, which when engaged by a pawl cannot move downwards and, consequently, prevents rotation of the shaft 17 in a clockwise direction to permit lifting of the needle-bar. The pawl is operated by a link and lever connection to the shaft 5 as described in Specification 21786/02. Feed. The feed point carrier 145 lies behind the presser-bar 37 and is guided by the block 141 and pin 147 extending from the presser-bar and engaging a slot at the end of the carrier 145. The feed-point arm 153 carrying the feed-point 155, is freely pivoted at the end of the carrier. The arm 153 is drawn towards the presser foot 69 by a spring 157. When the presser bar 37 is raised to allow the feed-point to progress the work, the pawl engages 'the ratchet bar 105 to prevent upward movement of the feed-point carrier from its dug-in position in the work. The feed-point carrier 145 is operated by a link 171, bell-crank 173, bell-crank 177, 179, arm 181, and cam 185 on the shaft 5. The cast-off mechanism is as described in Specification 228,489, [Class 112].