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AssigneePfaff Industriemaschinen GmbH
InventorsFritz Jehle, Erich Willenbacher, Oskar Braun, Dietmar Becker
Estimating the term…
Method and apparatus for determining and regulating the amount of advance of a plurality of workpiece plies at a sewing machine which is affected by scanning the individual plies while recording the stitches being formed between two separate feed points and actuating top and bottom feed devices to achieve a desirable feed of each ply. Signs present or to be applied at any desired point of the workpiece plies are scanned at two successive points, and pulses generated by a pulse generator connected with the main shaft of the machine are summed during this period of time. The pulse sum is compared with a number of pulses which depends on the mutual spacing of the scanning points and on the adjusted stitch length. For two work plies the pulse sums formed between the recognition of the signs are compared directly. As signs to be scanned are used either imprinted marks, the jags of a pinked workpiece edge, or the bright, dark structure of a surface section of the workpiece.
A method for determining the amount of advance of at least one work ply fed by a sewing machine which is driven by a main drive shaft using a sensor device which scans the ply at two points succeeding each other in a feed direction and a signal processing system connected to the sensor device, comprising connecting a pulse generator to the main shaft so as to generate a pulse in proportion to the speed of operation of said main shaft, delivering the pulse signals to the sensor device for evaluating the pulses generated between recognition of the sign of the two scanning points, and wherein for scanning there is used a sign situated at any desired point of the work ply, and comparing the pulse sum formed between the successive recognition of the sign with a desired pulse number corresponding to the stitch length and the distance between the scanning points.
A method of operating a sewing machine which has a thread needle reciprocating on one first side of a support surface onto which multiple plies of material are fed and which is adapted to cooperate with a bobbin on the opposite second side to form stitches of the material comprising feeding each ply by engaging the plies from respective first and second sides, scanning the material as it is being fed from at least one side, generating pulses in response to the speed of the needle and the feed, while the material is being scanned, comparing the sum of the pulses formed between successive scanning points with a desired pulse number corresponding to the stitch length and the distance between the scanning points.
In a sewing machine having a thread needle reciprocating and swinging on one first side of a support surface under which multiple plies of materials are fed and which is adapted to cooperate with a bobbin on the opposite second side to form stitches in the materials, the improvement comprising, a first feed mechanism engageable with the materials on said first side to advance them in a feed direction, a second feed mechanism engageable with the materials on said second side to advance them in the feed direction, feed drive means connected to said thread needle and to said first feed mechanism and said second feed mechanism and including a stitch setting means for setting the swing of the needle and its reciprocation, and drive regulating means for regulating the drive of said first feed mechanism and said second feed mechanism sensor device including a scanner arranged at spaced locations along the feed of the materials, at least two spaced apart scanning locations, pulse generating means associated with said feed drive driven by said feed drive to generate a pulse signal in response to and in to the speed of said drive means and connected to said sensor device and being actuated by said sensor device at said scanning locations to evaluate the pulses generated between said scanning locations, said sensor device providing a comparison between desired pulse number corresponding to the stitch length and the distance between said scanning locations.
Dependencies are inferred from the claim text.