Automatic control for sewing machines

Claim 2

Sewing apparatus comprising a sewing machine having a main drive shaft, stitch forming mechanism including a needle and a cooperating loop forming mechanism, a work feeding mechanism comprising a four motion feed dog and connections from said drive shaft for imparting movement to said feed dog along an elliptical path, a throat plate along the surface of which work pieces are advanced step by step by said feed dog, means for changing the position of said throat plate in relation to the path of movement of the feed dog to vary the length of movement of the work by the feed dog in a cycle of operation of the machine, power means and connections therefrom to said means for changing the position of said throat plate, and means responsive to the movement of a work piece to and through the stitch forming region of said machine for controlling the operation of said power means to change the position of said throat plate.

Claim 3

In sewing apparatus as set froth in claim 1, said means responsive to the movement of a work piece comprising at least one photo-electric cell.

Claim 4

In sewing apparatus as set forth in claim 1, said means responsive to the movement of a work piece comprising two photo-electric cells in spaced relation to each other.

Claim 5

In sewing apparatus as set forth in claim 3, said photo-electric cells being arranged in two different electric circuits, said circuits having in common a solenoid which controls the operation of said power means.

Claim 6

In sewing apparatus as set forth in claim 4, said power means comprising a fluid operated member, said solenoid being arranged to control the delivery of fluid to said power means and the discharge of fluid therefrom.

Claim 7

In sewing apparatus as set forth in claim 4, said photo-electric cells and said circuits being arranged to close a circuit through said solenoid at the beginning and again neAr the end of the formation of a line of stitching in a work piece.

Claim 8

In sewing apparatus as set forth in claim 6, at least one of said circuits including a capacitor adapted to receive and store electric energy, and means in said circuits for controlling the delivery of said stored energy to said solenoid to insure activation of the latter for a period enabling the production of a predetermined number of stitches.

Claim 9

In sewing apparatus as set forth in claim 6, each of said circuits having a trigger therein for rendering it operative under predetermined conditions.

Claim 10

In sewing apparatus as set forth in claim 7, each of said circuits having a Schmitt trigger therein for rendering it operative under predetermined conditions.

Claim 11

Sewing apparatus comprising a sewing machine having means for performing work on workpieces advanced step-by-step and successively through a stitch forming region of said machine, said work performing means being adapted for variable performance of said work on said pieces, and means for creating a change in the performance of said work at different times during the continuous operation of the machine, said last mentioned means comprising power means for producing said change, means for directing light toward successive pieces as they are being advanced, light responsive means arranged in spaced relation to each other and adapted to receive light from said light directing means except when interrupted by movement of a workpiece across the path of said light, and electrical circuitry incorporating the light responsive means for controlling the operation of said power means and which is arranged to be energized to effect said change in the performance of the work upon the movement of a workpiece into a position in which the delivery of light is interrupted for both of said light sensitive means; said circuitry including means for restoring the work performing means to its original condition after a predetermined number of operations of the machine; said means for producing said change in the performance of the work being operable again in response to the exposure of one of the light responsive means by movement of the workpiece beyond the region in which it interrupts the delivery of light to said light responsive means and said circuitry includes a capacitor which receives and stores electrical energy periodically.

Claim 12

Sewing apparatus comprising a sewing machine having means for performing work on workpieces advanced step-by-step and successively through a stitch forming region of said machine, said work performing means being adapted for variable performance of said work on said pieces, and means for creating a change in the performance of said work at different times during the continuous operation of the machine, said last mentioned means comprising power means for producing said change, means for directing light toward successive pieces as they are being advanced, light responsive means arranged in spaced relation to each other and adapted to receive light from said light directing means except when interrupted by movement of a workpiece across the path of said light, and electrical circuitry incorporating the light responsive means for controlling the operation of said power means and which is arranged to be energized to effect said change in the performance of the work upon the movement of a workpiece into a position in which the delivery of light is interrupted for both of said light sensitive means; said circuitry including means for restoring the work performing means to its original condition after a predetermined number of operations of the machine; said means for producing said change in the performance of the work being operable again in response to the exposure of one of the light responsive means by movement of the workpiece beyond the region in which it interrupts the delivery of light to said light responsive means and said circuitry includes a capacitor which receives and stores electrical energy periodically.

Claim 13

Sewing apparatus as set forth in claim 10 in which resistors are provided in said circuitry for controlling the rate of discharge of electrical energy from said capacitor.

Claim 14

A sewing machine having a stitch forming mechanism for operating on a workpiece including a needle, cooperating loop forming and work feeding mechanisms, a power drive for positioning a component of the stitch forming mechanism and a control for operating the power drive, said control comprising means for operating the power drive to move said component of the sewing machine to a first predetermined position in response to passage of a first predetermined portion of the workpiece, past a predetermined point in the sewing machine, a timing device in the control for operating the power drive to move the component to a second predetermined position a predetermined length of time thereafter, and means for operating the power drive to return the component to its first predetermined position in response to passage of a second predetermined portion of the workpiece past a second predetermined point in the sewing machine.

Claim 15

A sewing machine having a stitch forming mechanism for operating on a workpiece including a needle, cooperating loop forming and work feeding mechanisms, a power drive for positioning a component of the stitch forming mechanism and a control for operating the power drive, said control comprising means for operating the power drive to move said component of the sewing machine to a first predetermined position in response to passage of a first predetermined portion of the workpiece, past a predetermined point in the sewing machine, a timing device in the control for operating the power drive to move the component to a second predetermined position a predetermined length of time thereafter, and means for operating the power drive to return the component to its first predetermined position in response to passage of a second predetermined portion of the workpiece past a second predetermined point in the sewing machine.

Claim 16

A sewing machine according to claim 12 wherein the means for operating the power drive to move the component to the first predetermined position comprises a first device for sensing the passage of the first predetermined portion of the workpiece past the first predetermined point, the means for operating the power drive to return the component to its first predetermined position includes a second device for sensing the passage of the second predetermined workpiece portion past the second predetermined point, and said first sensing device oPerates in the path of travel of the workpiece at a point downstream of the point at which the second sensing device operates.

Claim 17

A sewing machine according to claim 12 wherein said control includes a second timing device for operating the power drive to return the component to its second predetermined position a predetermined length of time after being returned to its first predetermined position.

Claim 18

A sewing machine according to claim 12 wherein said component comprises a throat plate along the surface of which the workpiece is advanced through the stitch forming mechanism.

Claim 19

A sewing machine according to claim 15 wherein the means for operating the power drive to move the plate to the first predetermined position comprises a light sensitive device operating adjacent the needle for energizing the drive to move the plate to said position in response to interruption of the receipt of light due to passage of the leading edge of the workpiece past the first predetermined point, and the means for returning the plate to said first predetermined position comprises a second light sensitive device which energizes the drive in response to receipt of light due to passage of the trailing edge of the workpiece past the second predetermined point.

Claim 20

A sewing machine according to claim 16 wherein the first predetermined position of the plate is a raised position and the second predetermined position of the plate is a normal position lower than the raised position.

Claim 21

A sewing machine according to claim 13 wherein the stitches are formed in the workpiece at a predetermined point and both the first and second sensing devices lie in positions in advance of this point.

Claim 22

A sewing machine according to claim 12 wherein the power drive includes a piston member within a cylinder and the power drive control includes light responsive means for controlling the delivery of fluid under pressure to said cylinder for operating the piston member.

Claim 23

Apparatus according to claim 19 in which the light responsive means also controls the release of said fluid from said cylinder.