Sewing – Special machines – Buttonhole
Reexamination Certificate
2000-10-11
2001-05-29
Nerbun, Peter (Department: 3741)
Sewing
Special machines
Buttonhole
C112S470010, C112S254000
Reexamination Certificate
active
06237515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a buttonhole sewing machine for the production of buttonholes on a workpeice of fabric, comprising a needle mounted in an arm, which needle is reciprocatingly drivable in a Z direction by a driving motor, forming a series of stitches, which needle is drivable by a jogging drive for the production of a zigzag seam by a motion of the needle relative to the workpiece, and which needle is drivable to pivot about an axis by means of a pivot drive; a hook bearing, which is disposed in a base plate, and which is drivable by a pivot drive to pivot synchronously and equiangularly relative to the needle about a pivot axis which extends in the Z direction; and a thread feeding mechanism in the path of a needle thread which is fed in a direction of delivery.
2. Background Art
U.S. Pat. No. 1,372,473 teaches a buttonhole sewing machine of the generic type for the production of eye-type buttonholes, in which stitch forming takes place in customary and known manner in a zigzagging sequence of stitches with a single thread chain stitch and a double thread chain stitch alternating. Single thread chain stitching only requires a needle thread, whereas double thread chain stitching needs both the needle thread and a hook thread or under-thread. This known buttonhole sewing machine is provided with a device for the control of the needle thread, in which, on a shaft that rotates at half the speed of the arm shaft, a pair of disks, which co-rotate therewith, and a cam are disposed for the control of a thread clamp.
U.S. Pat. No. 4,590,879 teaches a thread feeding mechanism of a sewing machine, in which a cam disk is provided, which rotates at half the speed of the arm shaft and which, by two portions on its periphery that are remote from the axis of rotation and by two portions that are close to the axis of rotation, acts on the thread supplied to the needle in such a way that the thread is tensioned i.e., it is pulled or loosened i.e., released.
SUMMARY OF THE INVENTION
It is an object of the invention to embody a buttonhole sewing machine of the generic type such that by simple means varying thread feedings are attained for the alternating production of a single thread chain stitch and a double thread chain stitch.
According to the invention, this object is attained by the features wherein the thread feeding mechanism comprises a pivotal thread lever with an opening for the needle thread to be led through; and wherein the thread lever is drivable by a triggerable positioning motor to pivot between a zero position and several positions of thread delivery. The measures according to the invention help ensure that, by means of a thread lever to be triggered by a positioning motor, handling the needle thread i.e., feeding the thread or advancing the thread and tightening or withdrawing the thread, can be suited to given conditions of sewing, which helps obtain an optimum appearance of the array of stitches. Sewing conditions comprise for example the motion of the needle relative to the workpiece i.e., the factual consumption of thread. Further factors of influence are the type of workpiece, the thickness of the workpiece, the thickness of the needle thread, the conditions of friction between the workpiece and the needle thread, the work tolerances of the elements of stitch formation i.e., needle and hook. The solution according to the invention also enables the thread to be advanced for, and in combination with, thread cutting.
Details of the invention will become apparent from the ensuing description of an exemplary embodiment, taken in conjunction with the drawing.
REFERENCES:
patent: 6044780 (2000-04-01), Kastrup et al.
patent: 6095066 (2000-08-01), Noltge et al.
Conte Robert F. I.
Durkopp Adler Aktiengesellschaft
Lee Mann Smith McWilliams Sweeney & Ohlson
Nerbun Peter
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