GB792328A - Improvements in or relating to sewing machines - Google Patents

Abstract

792,328. Sewing machines. PFAFF AKT.-GES. G..M. Nov. 9, 1955 [Nov. 9, 1954], No. 32057/55. Class 112 A zig-zag sewing machine adapted to produce embroidery patterns automatically comprises a control cam, means for advancing said cam in steps, means for adjusting continuously a variation in the magnitude of said steps, and means for selectively establishing connections between mechanism for transferring motion controlled by said cam and levers for adjusting the stitch position and width. A stack of rotary control cams 8 is adapted to be driven in steps by a ratchet-andpawl device 9 connected by a link 10 to one end of a two-armed lever 11 pivoted at 19 to a plate 21 slidably mounted on a plate 4 fixed in the arm 1 of the machine , the other arm of lever 11 carrying a roller 16 which is biased by a spring 14 against a conical cam 13 fixed to the drive shaft 12. A control knob mounted on the top of arm 1 is adapted to impart lateral movement to a pin which extends through a notch 31 in plate 21. The latter may thereby be moved to vary the position of roller 16 on cam 13 for altering the stroke of link 10, or for disengaging roller 16 from cam 13 to disconnect the drive to the control cams. A cranked lever 44, pivoted at one end to plate 4, carries at its apex a stud 46 provided with a series of finger 47 each of which is adapted to engage a respective. control cam when stud 46 is turned by means of an adjusting knob fixed thereon. The other end of lever 44 is connected by adjustable links 49, 51 to one end of a lever 55 pivoted at its other end, at 54, to plate 4. A spring 56, connected to lever 55, normally biases a finger 47 into contact with its respective control cam. Rotatably mounted on lever 55 are three pins 65, 66, 67 each having a slotted end bridged by a pin, the latter being engagable in respective notches 80, 81, 82 in the front end of coupling bars 77, 78, 79 which are biased downwardly by respective springs 130, 131, 132. Bar 77 is pivoted at its other end, at 86, to an extension 87 of a lever 90 pivoted on a shaft 141. The other ends of bars 78, and 79 are respectively pivoted at 93 and 94 to a lever 95 pivoted on shaft 141. Lever 90 is formed at its other end with a bearing 91 in which is journalled a shaft 92 carrying a crank 100 connected by a link 98 to lever 95. The inner end of shaft 92 carries a slotted guide-member 147 slidably engaging a block 149 fixed to a link 148, one end of which is pivoted to the swinging gate carrying the needle bar and the other end of which is forked at 150 to embrace a rotary cam carried by shaft 12. Rotation of shaft 92 is thereby adapted to adjust the swinging of the needle bar gate from zero to a maximum amplitude. Pivoting of lever 90 moves shaft 92 transversely for shifting the neutral position of the needle. The outer end of shaft 92 carries a knob 143 which serves for manually setting the width of the stitch, and which cooperates with a dial 144 for indicating said width. A pointer 145 on dial 144 co-operates with markings 146 on arm 1 to indicate the mean position of the needle. A knob 110 is geared to a shaft 105 which carries three cams adapted respectively, in appropriate settings of knob 110, to lift bars 77, 78, 79 to disengage the latter from pins 65, 66, 67. Shaft 105 also carries a cam 117 adapted to abut a lug 118 on lever 55 for moving the latter against the bias of spring 56 for disengaging the fingers 47 from the control cams. A further cam 119 on shaft 105 is adapted to abut one arm of a lever 120 pivoted at 124, so as to move the lever against the bias of a spring 126 and thereby to engage one of three notches 122 formed in the other end of said arm with an edge 128 formed on a handle 129 resiliently fixed to bearing 91. Edge 128 may thus be engaged manually with any one of said notches, the middle notch providing a central seam and the other notches moving the seam to the extreme left and right hand positions respectively. To use the machine non-automatically, roller 16 is moved off cam 13 to disconnect the drive to the pattern cams 8, and knob 110 is moved to the zero position in which cam 117 abuts lug 118 to move lever 55 for disconnecting fingers 47 from the pattern cams, and cam 119 abuts lever 120 for engaging a notch 122 with handle 129. The seam width is then adjustable by means of knob 143, and the seam position by means of handle 129. For automatic sewing, roller 16 is engaged with cam 13, the length of the pattern being determined by the position of said roller, the required cam 8 is engaged with its -finger 47, and knob 110 is turned to the required one of its positions 1 to 5, in all of which positions cam 117 is free from lug 118. In position 1, cam 119 abuts lever 120, bars 77 and 79 are uncoupled from lever 55 and bar 78 is coupled to lever 55. The stitch width is thereby controlled automatically, the position of bar 78 and pivot 93 being so arranged that the maximum width of the seam produced is limited to half the full width, while the seam position is manually adjustable by means of handle 129. In position 2, cam 119 is free from lever 120 whereby the latter is uncoupled from handle 129, while bar 79 is uncoupled from lever 55 and bars 77 and 78 are coupled thereto. The seam width, up to half of full width, and the seam position are thereby automatically controlled. In position 3, bar 77 remains coupled and handle 129 remains uncoupled, while bars 78 and 79 are uncoupled. The seam position is thereby controlled automatically, while the seam width is manually controllable by knob 143. In position 4, bar 77 is uncoupled and handle 129 is coupled, while bar 79 is coupled and bar 78 is uncoupled. The seam width, up to the full width, is thereby automatically controlled while the seam position is manually controllable. In position 5, bar 77 is coupled and handle 129 is uncoupled, while bar 79 remains coupled, the seam width, up to the full width, and the seam position being thereby automatically controlled. Specification 753,820 is referred to.