# US 4,565,140 A · Method and apparatus for automatically adjusting the sensitivity of edge sensors in a semi-automatic sewing machine

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- Number: US 4,565,140 A
- Document ID: US4565140A
- Status: Granted
- Kind: A
- Application number: 06/577,579
- Filed: 1984-02-06
- Granted: 1986-01-21
- Earliest claimed: 1984-02-06
- Assignees: Microdynamics, Inc.
- Inventors: Charles R. Martell; Donald D. Isett; Stephen S. Treadwell
- Web page: https://patentgrep.com/patent/US4565140A

## CPC

- D05B 69/20: Control devices responsive to the number of stitches made
- D05B 35/102: {Edge guide control systems with edge sensors}
- D05B: SEWING (appliances for the tailoring trade A41H; sewing tables A47B29/00; sewing in bookbinding B42B2/00; sewing machines modified for knitting D04B39/08)

## Abstract

An adaptive semi-automatic sewing system (10) comprises a sewing machine (12), a drive unit (42) including a variable speed motor and encoder for counting stitches sewn and for sensing the rotation of the motor, at least one material edge sensor (40a) mounted ahead of the needle (22) of the sewing machine, and a microprocessor controller (51) coupled to the sewing machine controls. Accurate control of seam lengths and end points is achieved by initiating countdown of a variable number of final stitches responsive to detection of the material edge by the sensors (40a). The system includes controls (98) coupled to microprocessor controller (51) for dynamically adjusting the sensitivity of the sensors (40a) for variances in the materials being sewn.

## Claims

### Claim 1

In a sewing machine having a reciprocable needle for stitching seams in material advanced in a feed direction, seam length control apparatus comprising:
means having variable sensitivity for detecting a material discontinuity in advance of a seam;
means for controlling an operation of the sewing machine in response to detection of said material discontinuity by said detecting means; and
means for automatically adjusting the sensitivity of said detecting means to compensate for variances in the material being sewn.

### Claim 2 (depends on 1)

The sewing machine of claim 1 wherein said adjusting means adjusts the sensitivity of said detecting means to further compensate for the number of plies of the material being sewn.

### Claim 3 (depends on 1)

The sewing machine of claim 1 wherein said detecting means comprises at least one on/off sensor mounted ahead of said needle in a direction opposite the material feed direction.

### Claim 4 (depends on 3)

The sewing machine of claim 3 wherein said sensor comprises an infrared emitter and an infrared sensor mounted in vertically spaced relationship.

### Claim 5 (depends on 4)

The sewing machine of claim 4 wherein said adjusting means adjusts the sensitivity of said sensor by varying the light level required to switch said infrared sensor.

### Claim 6 (depends on 4)

The sewing machine of claim 4 wherein said adjusting means adjusts the sensitivity of said sensor by varying the output of said infrared emitter.

### Claim 7 (depends on 1)

The sewing machine of claim 1 wherein the operation of the sewing machine comprises sewing a predetermined number of stitches after detection of said material discontinuity.

### Claim 8

In a sewing machine having a reciprocable needle for stitching seams in material advanced in a feed direction, seam length control apparatus comprising:
at least one variable sensitivity on/off sensor mounted ahead of said needle in a direction opposite the material feed direction for detecting a material discontinuity in advance of a seam;
a microprocessor controller responsive to said sensor to operate said reciprocable needle to sew a number of stitches after said sensor detects said material discontinuity;
said microprocessor controller being further operative to automatically adjust the sensitivity of said sensor to compensate for the number of plies of material being sewn.

### Claim 9 (depends on 8)

The sewing machine of claim 8 wherein said microprocessor controller adjusts the sensitivity of said sensor to further compensate for the physical characteristics of the material being sewn.