Patent GB-511493-A (GB)
Title: Improvements in or relating to buttonhole sewing machines
IPC: D05B3/06
Filed: 1937-11-17
Abstract: 511,493. Button-hole sewing-machines. JACKSON, L. MELLERSH-. (International Button Hole Sewing Machine Co.). Nov. 17, 1937, No. 31640. [Class 112] In a buttonhole sewing-machine, the rotation of the stitch-forming devices in the formation of the end of the buttonhole is performed during relative longitudinal movement of the stitch-forming devices and the work between two points in that movement which are fixed in relation to one another but are adjustable within a certain range longitudinally of the buttonhole. The relation between these points is determined by the formation of cams producing the rotation and longitudinal movement, and the cams are preferably formed so that the points are coincident, in order to produce a symmetrical buttonhole. Independent adjustments are provided for varying the length and width of a button-hole eye, the length of the part of the eye round which the stitches are placed radially, the length and width of the fly-bar, and the overall length of the buttonhole. The machine shown comprises a fixed bed 40, having work clamps 41, and a,stitching head 42, slidable longitudinally of the bed 40, having fixed to it a casing 61 and bracket 82 supporting the feeding and guiding mechanism; the head 42 is also capable of slight rotation about a vertical axis, to move the stitch forming devices laterally of the work, being guided by an arm 56, adjustably fixed to the cam casing 61, pivoted to a block 59 sliding in a longitudinal guide in the bed 40. The stitchforming mechanism comprises a laterally-jogging needle in a turret 53 and co-operating loopers in a similar turret beneath the bed 40, the turrets being rotated through half a revolution at each end of the longitudinal travel of the head 40 by toothed sectors 194 on a shaft 190 engaging teeth 195 on the turrets or their shafts; stitching is started and stopped by mechanism 44 operated by engagement with a cam 50 adjustable along the bed 40. The longitudinal movement of the head 42 is invariable being produced by engagement of a pin 48 fixed to the bed 40 with a groove in the upper face of the main cam 45 in the casing 61. The shaft 190, which rotates the turrets of the stitching devices is oscillated by means of a singletooth geneva gear 189, 188, Fig. 24 (underneath view), actuated by a crank 182 having a pin engaging a groove 180 in the lower face of the cam 45. The connection between the crank 182 and member 188 is constituted by a pin 186 adjustably fixed in a slot in the crank 182 and engaging a slot 187 in the member 188; according to the position of the oin 186, the movement of the member 188 may, as shown, only be sufficient to move the member 189 through its full range, or may be greater, giving lost motion before and after moving the member 189, so that the movement of the member 189, and therefore the rotation of the stitching devices, takes place while the crank 182 is performing all or a variable part of its oscillation and therefore during a variable part of the movement of the cam 45 and the head 42. Similar mechanism, comprising elements 80, 78, 65, actuated by a groove 62 in the lower face of the cam 45, is connected to a rack 85 engaging a shaft 91 by which the head 42 is oscillated first to one side and then the other in forming the eye of the button-hole, this oscillation thus taking place during a variable portion of the travel of the head 42 to produce an eye of variable length; the oscillation is produced by a stud 96 eccentrically carried by the shaft 91 engaging a guiding device 109 which is longitudinally adjustable on the bed 40. The stud 96, Fig. 18, is fixed to a part 95 slidable in a transverse groove in a member 93 on the upper end of the shaft 91, and is adjustable from a position concentric with the shaft 91 (in which no eye is produced) to a position of eccentricity corresponding to the width of the eye of the button-hole by means of a cap 98 rotatably adjustable on the member 93, having an eccentric arcuate slot 101 engaging a pin on the part 95. The stud 96 has flat sides 162, 163 on its upper part, with bevelled edges, and a notch 164 in one side. The guiding device 109 (Fig. 14) for the stud 96 comprises an assemblage of plate members, shown separated in Fig. 17, secured to a base 113 slidably adjustable in a guide channel 116 in the bed 40 and secured by a screw 117 which passes through a hole in a plate 51; the plate 51 has a pointer co-operating with a scale on the bed 40 to indicate the length of the button-hole, and has adjustably fixed to it the cam 50 by which stitching is started and stopped. The plate members of the guiding device 109 for most of their length form a plain slot 114 of width equal to the diameter of the stud 96, but are cut away as at 173 to allow adjustable guide members 132 ... 135, sliding in grooves inclined to the slot 114, to be engaged by the bevelled flat portions of the stud 96; the members 133, 134 are opposite one another, 135 next above, and 132 at the top, the member 132 co-operating with 134 and 135 with 133. These four guide members have teeth engaging pinions 138, 139 which are inter-connected to rotate in opposite directions by a rack 150 sliding in a groove in the part next to the base 113; the four guide members are thus adjusted simultaneously, the co-operating members of each pair being maintained at the same distance apart, equal to the width of the flat-sided part of the stud 96, and the two pairs being always equally offset to opposite sides of the slot 114. The adjustment is effected by means of a rack 153, engaging the pinion 138, having a vertical groove engaged by an eccentric rotated by a finger-knob 156. The upper part of the slot 114 is formed with a constriction 175 to engage the flats of the stud 96 to guide the stud after it leaves the adjustable members 132 . . . 135 and before its lower part is properly guided by the slot 114. The shaft 91 carrying the stud 96 has its lower end screw-threaded and engaging an adjustablyfixed nut 105 so that when the shaft is rotated in sewing round the eye of the button-hole it is also moved downwards; the stud 96, which cooperates with the guide members 132, 134 during sewing of the first side of the hole (the member 135 being ineffective owing to the notch 164 in the stud), is thus shifted to co-operate with the members 135, 133 during sewing of the other side of the hole. Operation. The first part of the movement of the head 42, carrying the stud 96 along the left-hand part of the slot 114, is idle; the stud is then shifted laterally by engagement with the guide members 132, 134 to bring the machine into position for making the initial barring stitches, offset from the stitches along the side of the button-hole. At a point in the longitudinal motion of the parts in the offset position, determined by the adjustment of the cam 50 relatively to the guiding device 109 in accordance with the length of fly-bar required, stitching is commenced. At the end of the flybar the stud is brought back along an inclined path to the centre of the slot 114 for sewing along the side of the button-hole; later, the shaft 91 is brought into operation for one revolution for the formation of an eye of length and width determined by the adjustments previously described, the longitudinal feed of the head 42 being reversed during the eyeforming operation. In its return along the slot 114, the stud 96 is moved aside by the guide members 135, 133 for the formation of final barring stitches corresponding with the initial ones and overlapping the latter partially or completely according to the offset given by the guide members 132...135 in relation to the length of stitch; stitching is automatically stopped at the same point as that at which it started, and during the remaining idle movement to the left the stitching devices and the shaft 91 are brought back to their initial positions. The fly-bar may be abolished either by delaying stitching until the stud 96 has entered the slot 114 to the right of the guide members 132, 134 or by setting the latter to give no offset. The length of the complete button-hole is varied by adjustment of the guiding device 109 along the bed 40 to vary the amount of idle travel before the guide members 132, 136 come into action.