Patent ES-275525-A1 (ES)
Title: Automatic work guidance mechanisms
IPC: D05B73/12
Filed: 1962-03-08
Abstract: A machine for progressively operating on edge portions of a workpiece along a desired path comprises a reciprocating member adapted to penetrate the workpiece intermittently at an operating position, means for feeding the work intermittently when said member is disengaged therefrom, steering means arranged to engage the workpiece at a single locality spaced from the operating position, and means for detecting curvature of the edge portions of the workpiece and for causing the steering means to exert a torque, in accordance with said curvature, on the workpiece about said member when the latter is engaged in the workpiece. Work feeding, work holding and guiding, stands. A sewing machine 22, Figs. 1, 4, 6, having a throat plate 30 mounted on a pedestal 32, is supported by a table 24. The machine is adapted to stitch a binding strip S automatically around the edge of a shoe upper U. The throat plate has a needle hole 28 adjacent a slot for a feed dog 40. The latter co-operates with a presser wheel 44 journalled on an arm 46 carried by a bracket 48 fixed to a presser bar 52. A feed wheel 80, situated on the side of the feed dog remote from the needle hole, is driven via gearing by a motor 84. Wheel 80 co-operates with a presser wheel 82 journalled at one end of an arm 130 pivoted intermediately to bracket 48. A spring 134 acts on the other end of arm 130 to bias wheel 82 downwards. The tension in spring 134 is thereby released when the presser bar is raised by the feed dog during a feed stroke, thus causing slippage of wheel 80 on the work. When the feed dog is disengaged from the work and the latter is penetrated by the needle 26, rotation of wheel 80 causes the work to pivot about the needle. A photo-electric cell 108 is so set in the upper surface of the throat plate transverely to the direction of work feed and immediately in front of the needle hole, that, under normal operating conditions, about one half of the cell is covered by the workpiece. The cell is illuminated by a lamp 116 mounted on bracket 48, and is so connected by circuitry to the motor 84 that the latter remains inactive if the cell is normally covered, but rotates in one direction or the other to an extent determined by the degree to which the cell is more or less covered by the workpiece, which is thereby guided in accordance with the curvature of its edge so that the stitching will run parallel thereto. The strip 5 passes from a rotatable reel 66 to the stitching point through a guide 70 carried by bracket 48. The machine is normally started and stopped by respective depression and release of a foot switch 124. When a photo-cell 266, positioned in the throat plate ahead of photo-cell 108 and disposed in the line of feed, is energized, the machine continues to run after release of the foot switch while cell 266 remains covered by the workpiece, but stops when cell 266 is uncovered. Thereby, if the stitching is commenced at a sharp bend, the machine will stop automatically at the starting point if the foot switch is released immediately in advance of the bend. In a modification, Fig. 20, the presser wheel 82 is replaced by a U-shaped leaf spring 280, the upper ends of which are fixed to the machine frame. The work-engaging portion 284 of spring 280 is connected by a yoke 286 to one end of a tension spring 288, the other end of which is connected to an arm 290 pivoted at 292 to a block 294 rigid with the presser bar 52. A stud 296 carried by arm 290 thereby biases a pivoted arm 298 against a cam 300 turnable by a knob 302 for varying the tension of spring 288. A feed-advance shaft is oscillated via a connecting rod 216, Fig. 11, from a variable eccentric 202 driven by the main shaft 34 which passes loosely through eccentric 202. A cruciform flange 200, rigid with the latter, is pivoted at 204 to a flange 206 rigid with shaft 34. A rod 154, Fig. 1, axially slidable in shaft 34, has its tapered inner end 152 engaged with a pin 198, which is rigid with flange 200 and passes through a radial hole in shaft 34, under the influence of a spring-biased plunger 208 which is mounted in flange 200 and engages shaft 34. When rod 154 is in its innermost position, a stud 228 on flange 200 engages a stud 214 on flange 206 and eccentric 202 has its maximum eccentricity for normal stitching. When rod 154 is fully withdrawn, flange 200 rocks counterclockwise to engage a stud 210 thereon with stud 214, eccentric 202 then having its minimum eccentricity for shortening the stitch length when sewing around sharp bends. Rod 154 is pivoted at 192 to a bar 188 the upper end of which is pivoted to a fixed bracket 190 and the lower end of which is connected by a link 186 to one arm 182 of a lever pivoted at 178, a second arm 176 carrying a knee press 174, and a third arm 184 being biased by a spring 196 to urge rod 154 to its innermost position. Driving. The machine is driven by a D.C. motor 42, Fig. 1, the field winding of which is supplied from a rectifier connected to fired terminals of an auto-transformer. The armature is supplied from a second rectifier connected adjustably to the auto-transformer through a rotary switch for varying the motor speed. On release of the foot switch 124, the armature is supplied with current in the reverse direction at a reduced voltage from fixed terminals of the auto-transformer via a micro-switch 250. The motor then runs slowly in the reverse direction until switch 250 is opened by a moving part of the machine to stop the latter with the needle in the raised position. Motor 42 is connected by a belt 172 to a pulley 160 journalled on a reduced hub portion of a hand wheel 156 fast with the main shaft 34. A cam 158, Fig. 14, fast with pulley 160, is disposed within an aperture in a cam plate 162 slidably mounted between parallel cheeks 166 of a guide plate 164 rigid with hand wheel 156. In normal operation, cam 158 turns counterclockwise to engage a surface 254 on plate 162 for moving the latter inwardly and driving the machine. When foot switch 124 is released, cam 158 turns clockwise to engage a surface 256 on plate 162 for moving the latter outwards and driving the machine until a projection 240 on plate 162 engages a striker pin 242 carried by a lever 244. The latter then rocks about its pivot 245 against the bias of a spring 258, when a pin 248 depresses the plunger of microswitch 250 to stop the machine. Specifications 962,160 and 989,874 also are referred to.