GB938505A - Improvements in or relating to sewing machines - Google Patents

Abstract

938,505. Sewing-machines. G. M. PFAFF A.G. Aug. 18, 1960 [Nov. 24, 1959], No. 28591/60. Class 112. A buttonhole sewing machine 1 has a frame 14 on which work is clamped, the frame being both pivotable about a bar 32 to accommodate the movement of the work due to the action of the feeding foot 6 and movable along the axis of the bar 32 to index the work between buttonholes. The buttonhole sewing machine has a starting lever 10 operated by an electromagnet 9, while raising of the feeder foot lever 7 is effected by an electromagnet 8. Feed by clamps.-The frame 14 comprises end bars 33, 34 connected by the bars 32, 38 and 52. Work-holding clamps 40 mounted on the bar 38 are openable in unison by a slide 41 moved by a cable 43 on depression of a pedal bar 44, or may be opened manually. Guide rollers 93, attached to a member 90 connected to the lever 7, embrace a bar 94 secured to the bar 38 to swing the frame about the bar 32 as the lever 7 and feed foot move. The bar 32 is carried for rotation and axial movement in rollers 49 (see Fig. 3), the upper pair of which are adjustably mounted on eccentric bolts 48. A chain 50 stretched between the end bars passes over a sprocket 22 driven to move the frame parallel to the axis of bar 32, through a slipping clutch from the shaft 18 of a feed motor. A ratchet wheel 21 secured to the shaft is engaged by pawls 56, 57 when the feed of the frame is to be stopped while a buttonhole is being sewn. The motor sprocket and clutch are mounted on the fixed plate 16, which also carries linkage 65, 69, 76, 80 co-operating with an electromagnet 60 and with cams 53 adjustably mounted on the rod 52 to provide automatic indexing of the frame between buttonholes. Operation.-After the completion of the first buttonhole the lever 10 actuates a switch 12 on the machine to energize electromagnet 8 and, momentarily, electromagnet 60 to respectively raise the feeding foot and rock the lever 65 about its pivot 64. The switchbar 69 is thus raised, its pin 86 raising the lug 84 on the cut-off finger 80 clear of the cam 53. As the bar 69 rises its upper end engages the pawls 56, 57 and lifts them clear of the ratchet wheel so that the feed motor may rotate the sprocket 22 and drive the frame until the material is correctly disposed for the next buttonhole. The spring 81 draws the locking slide 76 to the right to position its projection 75 below the end 73 of the raised switchbar 69, where it prevents the bar from falling to its previous position when the electromagnet 60 is de-energized, finger 80 being in its position of rest. The next cam 53 then engages the lug 84 to move the locking slide. 76 to the left to allow the bar 69 to fall and engage the pawls with the ratchet wheel. Reversing cams 55 engage with reversing switches 87, 88 to reverse the motion of the frame at the end of the series of buttonholes.