Claims
- 1. A stitching system comprising:
- a stitching machine including a stitching head, the stitching head including a thread tensioning mechanism, the thread tensioning mechanism including a servo for setting thread tension in the stitching head;
- a control station including a computer, the computer including computer memory encoded with data for instructing the computer to command the servo to set the thread tension in the stitching head to desired thread tension values, whereby setting the thread tension is data-driven:
- wherein the thread tensioning mechanism further includes:
- a shaft;
- first and second thread tensioning discs mounted on the shaft;
- means, secured to a first end of the shaft, for applying a bias force that biases the first disc towards the second disc; and
- a cam having a cam surface, a second end of the shaft being movable along the cam surface to adjust the bias force;
- a pneumatic cylinder operative on the first and second discs for releasing thread tension; and,
- wherein the servo includes a stepper motor for rotating the cam to set the thread tension.
- 2. The stitching system of claim 1, wherein:
- the stitching machine further includes a motor group for positioning the stitching head:
- the data includes a first plurality of instructions for instructing the computer to make stitches and a second plurality of instructions for instructing the computer to set the thread tension values, the computer commanding the motor group to move the stitching head in response to an instruction of the first plurality of instructions, and the computer commanding the servo to set the thread tension in response to an instruction of the second plurality of instructions.
- 3. The stitching system of claim 2, wherein the computer fetches the instructions from the computer memory and responds to the instructions in the sequence fetched, whereby the computer automatically makes first and second stitches at different thread tensions when the computer sequentially fetches a first instruction for making a first stitch, a second instruction for indicating a new thickness value, and a third instruction for making a second stitch.
- 4. The stitching system of claim 1, wherein the data includes thickness values and instructions for instructing the computer to determine the thread tension values from the thickness values.
- 5. The stitching system of claim 4, wherein the data further includes a lookup table including a plurality of thread tension values and a plurality of corresponding thickness values, and wherein the computer determines the thread tension values by accessing the lookup table.
- 6. The stitching system of claim 5, wherein the servo includes a stepper motor, wherein the data further includes a second lookup table including a plurality of stepper motor counts and a plurality of corresponding thread tension values, and wherein the processor determines the stepper motor count by accessing the second lookup table, whereby the servo is operated in an open loop mode.
- 7. The stitching system of claim 5, further comprising means for taking thread tension measurements; wherein the computer is instructed to command the servo by generating an error signal from the thread tension values and the thread tension measurements, whereby the servo is operated in a closed loop mode.
- 8. The stitching system of claim 1, wherein the stitching head further includes a mechanism for adjusting thread path geometry, and wherein the computer memory is further encoded with data for instructing the computer to command the thread path geometry mechanism to desired values, whereby adjusting the thread path geometry is data-driven.
- 9. Apparatus for automatically adjusting thread tension in a stitching head, the apparatus comprising:
- a thread tensioning mechanism including a servo, the servo setting the thread tension in response to servo commands;
- a processor;
- computer memory encoded with data including instructions for instructing a computer to generate thread tension values based on thickness values;
- wherein the servo commands are generated from the thread tension values;
- wherein the servo commands are supplied to the servo; and,
- wherein the stitching head includes means for adjusting thread path geometry, the computer memory being further encoded with data including instructions for instructing the computer to generate thread path geometry commands based on the thickness values.
- 10. The apparatus of claim 9, wherein the data includes instructions indicating the thickness values, and instructions for instructing the processor to determine the thread tension values from the thickness values.
- 11. The apparatus of claim 10, wherein the data further includes a lookup table including a plurality of thread tension values and a plurality of corresponding thickness values, and wherein the processor determines the thread tension values by accessing the lookup table.
- 12. The apparatus of claim 9, wherein the servo includes a stepper motor, and wherein stepper motor counts are derived from the thread tension values.
- 13. The apparatus of claim 12, wherein the data further includes a second lookup table including a plurality of stepper motor counts and a plurality of corresponding thread tension values, and wherein the processor determines the stepper motor count by accessing the second lookup table.
- 14. A stitching head for stitching a preform made of multiple layers of a variable thickness textile composite, the stitching being performed with a thread made of a composite material, the stitching head comprising:
- a needle;
- reciprocating means for reciprocating the needle;
- a servo-driven thread gripper;
- a servo-driven thread cutter;
- a servo-driven thread path geometry controller for adjusting an amount of the thread used by the needle during stitching of the preform, adjustment of the amount of thread used during the stitching being based upon thickness of the preform; and,
- a servo-driven needle cooler, operation of the needle cooler being based upon the thickness of the preform.
- 15. The stitching head of claim 14, further comprising a servo-driven thread tensioning mechanism, operation of the thread tensioning mechanism being based upon the thickness of the preform.
- 16. The stitching head of claim 15, wherein the thread tensioning mechanism includes an electromechanical machine for adjusting the thread tension.
- 17. The stitching head as set forth in claim 14, wherein:
- the preform has a compound, contoured, three-dimensional surface; and,
- the servo-driven thread path geometry controller automatically moves the stitching head to successive stitching positions in accordance with a path geometry control program.
- 18. The stitching head as set forth in claim 14, further comprising a needle speed servo controller for controlling the speed at which the needle is reciprocated by the reciprocating means based upon the thickness of the preform.
- 19. The stitching head as set forth in claim 14, further comprising:
- a thread tension measurement means for taking measurements of the thread tension at each of a plurality of successive stitching positions; and,
- a thread tension servo controller that controllably varies the thread tension based upon the thread tension measurement taken at each of the successive stitching positions in order to achieve a desired thread tension value derived by a computer program based upon the thickness of the preform at each of the successive stitching positions.
- 20. The stitching head as set forth in claim 19, wherein:
- the thread tension servo controller includes a stepper motor and a cam rotated by the stepper motor to adjust the thread tension;
- the thread tension servo controller is responsive to a stepper motor count value derived by a computer program based upon the thickness of the preform at each of the successive stitching positions to control the stepper motor to rotate the cam by a prescribed amount that is related to the desired thread tension value at each of the successive stitching positions.
Government Interests
This invention was made under contract no. NAS1-18862 awarded by NASA. The Government has certain rights in this invention.
US Referenced Citations (42)