Patent GB-494603-A (GB)
Title: Double lock-stitch sewing machine
IPC: D05B15/04
Filed: 1937-07-01
Abstract: 494,603. Sewing-machines. BRETTELL, F. G. (Nollesche Werke Komm.-Ges. Weissenfels) July 1, 1937, No. 18279. [Class 112] In a double lock-stitch shoe-sewing machine with a rotary horn, the whirl is driven by a shaft which passes eccentrically through the horn carrier beyond the bearings of the horn and is driven by a pinion arranged below the horn carrier to rotate concentrically with the horn carrier axle under the action of outside driving means ; this arrangement reduces the amount of gearing required, allows of the horn being smaller, and facilitates heating of the thread. The shuttle drive is also modified to improve high-speed working, its motion being derived from a uniformly rotating crank instead of from cams or other reciprocating members. The needle drive is arranged to give a dwell in the top and bottom positions. The presser-foot is lifted through a constant distance irrespective of the thickness of the work. The thread-feeding mechanism is arranged to give a motion exactly corresponding to that of the needle. Lockstitching by barbed needles and shuttles ; rotary horns ; threads, waxing.-The horn 133, Fig. 7, is mounted on a carrier 132 rotatable in roller bearings in the frame, and contains the whirl, driven by a shaft 170, the threadfeed roller 129, carried on a sliding bar 127, and the thread clamp, comprising a member 143 spring-pressed against a roller 142 and released when required by a sliding bar 157 ; the thread-clamp unit is hinged at its upper end so that it can be swung clear when it is necessary to extract the bars 127, 157, which work in grooves on opposite sides of a rod 125 fixed in the horn-carrier 132. The thread passes through a brake, wax-pot and auxiliary thread-receiver and up through a central bore in the guide 125, which is heated by a member 140. The whirl-driving shaft 170 is jointed to a shaft 168 running through the horn-carrier parallel to its axis and having at its lower end a pinion 167 meshing with a pinion 166 which is rotatable about the axis of the horn-carrier and is driven through bevel gearing from a shaft 107. The slidebar 157 operating the thread clamp is actuated by a cam 148 on the shaft 107 through a crank engaging a ring guide 156 fixed to the bar 157 ; the angle between the crank arm is adjustable to vary the position of the upper end of the bar 157. The bar 127 actuating the feed roller 129 has at its lower end a ring guide 126 engaged by a swivelling block 124, Fig. 15, on a lever 121 which is pivoted at 122 and oscillated by a pin 118 on a member 110 pivoted to a crank-pin 109 on the shaft 107 and guided by a link 112 adjustably pivoted to the frame. In the simplest form of the mechanism the pivot 122 is fixed, but in the form shown in Fig. 15 it is carried on an arm 180 on a rocking shaft 181 which is oscillated by a cam 185 on the shaft 107, engaging an arm 182 on the shaft 181,. the arrangement being such that the movement of the thread-feed roller corresponds exactly to that of the needle, so that the auxiliary thread-receiver becomes unnecessary. The arm 182 is pressed against the cam 185 by a torsion spring on the shaft 181, so that the mechanism can yield if required by large variations in the thickness of the work the cam holds the arm 182 against a stop 191 during the downward stroke of the thread-feed slide-bar 127. The length of stroke of the bar 127 is varied by adjusting the pivot of the link 112. In a modified driving mechanism for the arm 121, giving a longer stoppage of the member 124 in its lowest position, the link 112 is replaced by a link 222, Fig. 18, having a fixed pivot and the pin-and-slot connection 118 by a link 229 and an arm 225 guided by a link 226 ; the pivot of the link 226 is adjustable to vary the stroke of the feed slide-bar, but this adjustment does not affect the upper extreme position of the bar, so that the thread is pulled uniformly deep into the work independently of the thickness of the latter. The shuttle 194 is mounted in a bracket 193, Fig. 3, slidable in guides on the machine frame so that it can be moved back from the needle to facilitate the placing of work on the horn ; the bracket 193 carries the shuttle picker shaft and the bevel gears 84 by which the latter is driven from a shaft 79, one of the gears being splined to the latter shaft to allow of the movement of the bracket. The rotation of the shuttle driving shaft 79 is derived from a crank 74, Figs. 3 and 5, on the uniformlyrotating main shaft 2 through a three-armed member 75 which is mounted on a link 77 pivoted to the frame and has a pin engaging a cam groove in a crank 80 on the shaft 79 ; the path of the pin, shown in Fig. 5, and the form of the groove are such that the motion of the crank 80 suffers a temporary reversal at one part of its revolution. The bracket 193 is shifted when necessary by a hand lever 196, Fig. 12, pivoted on the frame and provided with a slot engaging a pin 204 on the bracket 193, the bracket being held in both its extreme positions by a pivoted latch 200 on the lever 196 engaging an adjustable catch 201 ; a screw 205 adjustably mounted on the lever 196 engages a stop bolt 206 to determine the sewing position of the bracket. The spool is held in the shuttle 194 by a finger 208 pivoted on the bracket 193 and provided with a hand lever and holding latch; a spring-returned pin with push-button 214 is slidable in the bracket 193 for ejecting the spool from the shuttle, which has a hole in its rear surface for the passage of the pin. The needle-bar 15, Figs. 2 and 3, is driven from the main shaft 2 through a rocking arm 6 pivoted at 7, a link 9 and a lever 11 pivoted at 12 and having a sliding swivelling connection with the needle-bar at 13. The rocking arm 6 is connected to the shaft 2 by a crank-pin 4 on the latter engaging an arcuate slot 5 in the arm 6, the radius of this slot being equal to the crank-throw so that the arm 6 and the needle remain stationary in their uppermost position for some time while the thread loop is being pulled into the work ; the needle also pauses in its lowest position, to facilitate threading, owing to toggle action of the parts 6, 9. Presser-bars, lifting.-The presser-foot 91 is carried by a vertically-sliding bar 58 raised and lowered by a block swivelled on a pin 48 at the end of an arm 49 on a shaft 103 which is provided with a torsion spring 92, Fig. 3, to bias the presser-foot towards the work. The shaft 103 is oscillated to lift the presser-foot by means of a lever 102 on the shaft formed with an arcuate part 93 which is actuated by a lever 101 operated by a cam 100 on the main shaft 2 ; in order that the presser-foot may be always lifted the same distance, independent of the thickness of the work, the member 93 is not permanently connected to the arm 101, but is clamped thereto at the required time by a rocking member 94, which is mounted on the arm 101 and is actuated by a lever 96 operated by a face cam 98 on the shaft 2. The presser-bar may also be raised by engagement of a treadleoperated lever 105 with the end of the arm 49. Feed.-The feed-needle 61 is carried on a member 53 which is slidably attached to the presser-bar 58 by slots engaging pins 56, 57 and is reciprocated by a cam on the main shaft 2 acting through a crank 35, link 39, rocking arm 42, link 44, a lever 46 pivoted to the arm 49 at 48 and a link 51 ; the linkage is such that movement of the presser-bar does not affect the relation between it and the feed-needle. The feed is adjustable by moving the end of the link 39 along an arcuate slot in one arm of the crank 35 by means of a handscrew 71 acting through a crank 67 and link 65. The feed-needle holder is pivoted to the member 53, and is held against a stop on the latter by a spring attached to the lever 46.