Sewing – Method of sewing – Workpiece manipulation other than straight line feeding
Reexamination Certificate
2000-03-20
2001-01-30
Nerbun, Peter (Department: 3765)
Sewing
Method of sewing
Workpiece manipulation other than straight line feeding
C112S313000, C112S470040
Reexamination Certificate
active
06178904
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process and a unit for working in extra width in a fabric layer with a sewing machine having a main feeder and at least one differential feeder, a main stitch-adjusting means and a differential stitch-adjusting means, an adjusting element for adjusting the differential stitch-adjusting means and a computer for controlling the sewing machine.
BACKGROUND OF THE INVENTION
A plurality of versions of a sewing unit called an integrated sewing station for working in extra width in a fabric layer have been known from the PFAFF information brochure “PFAFF 3811,” printed in April 1989. During this sewing operation, which is also called pre-gathering, the fabric layer is crimped or gathered by the combined feeding of a main feeder operated with a basic stitch length and at least one differential feeder performing larger feed steps than the main feeder, and this state is fixed by a seam. A stabilizing ribbon is optionally sewn on as well.
The degree of pre-gathering or the degree of gathering can be set by a differential stitch regulator. Depending on the equipment of the machine, the differential stitch regulator is actuated either manually or by an adjusting element, which can be driven electrically and which is associated with twenty sensor buttons, which each represent a defined gathering value. In a second version, two preselected gathering values can be alternately selected during the sewing process by actuating a manual button. In a third version, programs with a larger number of different gathering values can be stored, and these can likewise be selected during the sewing process one after another by actuating a manual button.
However, a human operator must select in all cases a gathering value that appears suitable to obtain the desired length of the fabric layer or a range of extra width. Even though an experienced operator can sometimes do this first straightaway, she must also sew a sample seam in order to determine on the basis of the finished result whether the selected gathering value was correct or incorrect. However, an inexperienced operator will usually find the correct gathering value only after some trial and error, as a result of which time is lost and reject materials are produced.
SUMMARY AND OBJECTS OF THE INVENTION
The basic object of the present invention is to provide a process and a sewing unit by which the determination of the gathering values necessary for properly working in extra width and optionally the determination of the position of an extra width section are simplified. The object is accomplished by providing a main and differential feeder in a sewing machine. An initial and desired length of the fabric layer is determined. A maximally setable gathering value of the of the differential feeder is also determined for the fabric layer. Then a current gathering value is calculated from the initial length, the desired length, and the maximally setable gathering value. The differential feeder is set to the current gathering value. A real stitch length value is determined for the current gathering value which takes into account for the gathering value dependent slip of the feeders. Using the real stitch length value and the desired length, a current number of stitches is calculated. An end point of the extra width section is determined from the current number of stitches.
In another embodiment, a preliminary gathering value R
v
is determined from the initial length, the desired length, and the maximally setable gathering value. A slip correction value for the preliminary gathering value R
v
is determined to take into account for gathering value dependent slip of the feeders. A corrected stitch length is calculated using the slip correction value, and the main feeder is adjusted to the corrected stitch length. A corrected gathering value R
k
is then calculated using the slip correction value. The differential feeder is set to the corrected gathering value. The current number of stitches is calculated from the desired length and the basic stitch length. The end point of the extra width section is determined in the same way as in the first embodiment, i.e. by the current number of stitches.
The present invention is based essentially on the idea of having the computer associated with the sewing machine calculate the gathering value necessary for working in the extra width from the starting position and the desired length of the fabric layer to be pre-gathered. This current gathering value is either used immediately to set the differential stitch-adjusting means by means of the adjusting element, or it is first entered into a memory, from which it can be selected during the sewing either by pressing buttons or after the end of a set number of stitches and is then likewise used to set the differential stitch-adjusting means.
If the length of an extra width range is not set manually or by counting the stitches during a teach-in mode, but is determined during the preparation of a program to be formed by data entry, the number of stitches are calculated. The program determines how much extra width section has been produced by counting the number of stitches produced and knowing the stitch length. When the length of the extra stitch length produced equals the length desired, the computer knows that the end point of the extra width section has been reached. It has been discovered that actual or real stitch length varies depending on the amount of extra width gathered. The gathering of the extra width causes slippage of the feeders, and this amount of slippage increases as more width is gathered. The present invention determines how the actual or real stitch length changes for each amount of extra width gathered, preferably by recording actual measurements of stitch length for different amounts of width gathered. The actual stitch length can be determined by a formula or in a lookup table stored in a memory of the sewing unit. When determining how much extra width section has been presently produced, the present invention counts the number of stitches and multiplies this by the actual or real stitch length. A more accurate determination of the end point is then obtained.
By taking into account the slip of the feeder, i.e., the difference between the set feed value and the actual feed value, where the size of the slip increases with the current calculated gathering value, the number of stitches that will occur during the sewing of an extra width range can be accurately calculated in advance and be used to determine the end point.
In another variant of the solution, the correction value by which the gathering value-dependent slip of the feeders is taken into account is used to increase the feed of the feeders to the extent that the slip will be compensated. This causes that the real number of stitches will be directly obtained from the desired length of the fabric layer and the value of the basic stitch length.
When the amount of slippage is known, instead of operating the sewing unit with the same amount of feeding and producing smaller stitches, the second embodiment adjusts the main feeder so that the feeding is increased and the stitch length remains substantially constant. The determination of the end point is then calculated using the original or basic stitch length.
EP 124 211 B2 discloses a process and a sewing unit for automatic feed control, in which process and sewing unit, extra width is worked in during the sewing in of a sleeve into an arm hole at predetermined seam distances in the sleeve by an upper feeder performing larger feed steps than a lower feeder. The sewing unit operates with a “teachable” control for this purpose, i.e., after the values of the extra width that are necessary in the particular case have been programmed, the control stores the length of the particular extra width sections during sewing by counting the stitches. Consequently, even though extra width is worked in section by section in a fabric layer in the case of the sewing unit known from EP-B2 as well, the two machines
Bastian Eduard
Maue Bernd
G.M. Pfaff Aktiengesellschaft
McGlew and Tuttle , P.C.
Nerbun Peter
LandOfFree
Process and sewing unit for working in extra width in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and sewing unit for working in extra width in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and sewing unit for working in extra width in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2447509