Patent GB-851215-A (GB)
Title: Improvements in or relating to feeding mechanisms for sewing machines
IPC: D05B27/14
Filed: 1957-04-16
Abstract: 851,215. Sewing machines. PFAFF A. G., G. M. April 16, 1957 [April 17, 1956], No. 12333/57. Class 112 [Also in Group XXIV] Speed change mechanism for a work-feeding wheel in a sewing machine comprises two variable speed transmissions, each including co-operating gear means, arranged on two common rotational axes, the gear means being mounted on hollow shafts and being selectively engaged by draw keys or the like carried by shift bars guided in the bores of the hollow shafts and operating from a common stitch setting device provided above the base plate of the machine. As shown, a feeding wheel 57 is driven by variable speed gearing contained in a housing 30 situated under the baseplate 1, the gearing being controlled by a pair of levers 151, 168 mounted concentrically on the standard 2 of the machine. A vertical shaft 29, driven by the arm shaft 8, has at its lower end a worm meshing with a worm wheel 59 on a hollow shaft 60 journalled in the housing 30. Four gear wheels 64-67, fixed to shaft 60, mesh respectively with four gear wheels 72-75 rotatably mounted on a hollow shaft 77 also journalled in housing 30. A shift bar 83, slidable longitudinally in shaft 77, has pivoted thereto a pawl 81 biased outwardly by a spring 86, whereby, on movement of bar 83, pawl 81 may engage slots 80 formed in the hubs of the gears 72-75 to couple selectively any one of the latter to shaft 77. Four gears 91-94, fixed to shaft 77, mesh respectively with four gears 99-102 rotatably mounted on a hollow shaft 104 aligned with shaft 60. A shift bar 108, slidable in shafts 60 and 104, carries a pivoted pawl 106 biased by a spring 111 for selective engagement in slots 105 formed in the hubs of the gears 99-102 to couple any one of the latter to shaft 104. The front end of shaft 104 carries a gear 120 which meshes with a gear 123 on a shaft 55 carrying the feed wheel 57. Shaft 55 is journalled in a frame 117 which is pivoted on shaft 104. A screw 124 engaging frame 117 and screwing into the baseplate 1 against the bias of a spring 127, serves to adjust the angular position of frame 117 and thereby the height of the feed wheel 57. A lever 138, pivoted on a pin 140 carried by the standard 2, has its lower end pivotally engaged with bar 108 and its upper end pivotally engaged with a pin 146 on a disc 147 fixed to a hollow shaft 148 journalled in a boss 150 on standard 2. The lever 151 on the outer end of shaft 148 enables the latter to be turned for moving bar 108. A lever 162, also pivoted on pin 140, has its lower end pivotally engaged with bar 83 and its upper end pivotally engaged with a pin 165 on an arm 162 fixed to a shaft 166 journalled in shaft 148. The lever 168 carried by shaft 166 enables the latter to be turned for moving bar 83. A cover 171, surrounding boss 150, is formed with a lower aperture through which lever 151 passes, and with a frontal centrally -apertured flange 174. The opposed faces of the latter are formed with dimples engagable by spring-biased pins 176, 179 mounted in the levers 168, 151 respectively, to retain the latter at positions corresponding to the engagement of the pawls 81, 106 with a respective gear. A curved plate 153, carried by lever 151, is marked with Roman numerals I to IV spaced angularly and axially, one of said numerals appearing under an aperture 184 in cover 171 on engagement of pawl 106 with a gear. Lever 168 is marked with an arrow 186 which may be aligned with any one of four marks, on the bevelled edge of flange 174, corresponding to the engagement of pawl 81 with a gear. Each said mark has aligned therewith on the cover 171 four axially spaced Arabic numbers 185 denoting the stitch lengths to provide a choice of 16 stitch lengths. Any one of the latter may be selected by moving arrow 186 opposite the line of numbers 185 containing said stitch length, and then turning lever 151 to disclose in the aperture 184 the corresponding Roman numeral angularly aligned with said stitch length. The needle bar 12 is mounted in a guide 14 pivoted on a pin 13 to swing in the direction of work feed, guide 14 being connected by a crank 17 to a rock shaft 18 provided with a crank 19 co-operating with a cam 20 on the arm 8. A pin 22, slidably mounted in the arm 3 and biased upwardly by a spring, may be depressed to engage a recess 23 in the periphery of a member 24. of the cam, when variation of the eccentricity of the cam can be effected by turning shaft 8 manually.