Sewing – Special machines – Buttonhole
Reexamination Certificate
2000-03-09
2001-03-27
Nerbun, Peter (Department: 3765)
Sewing
Special machines
Buttonhole
C112S248000, C112S302000
Reexamination Certificate
active
06205939
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 workpiece, comprising a needle mounted in an arm, which is reciprocatingly drivable in a Z direction for the production of stitches by means of a driving motor, and which 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 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.
2. Background Art
In a buttonhole sewing machine of the generic type known from U.S. Pat. No. 1,372,473, which is designed for the production of eye type buttonholes, stitch forming takes place in a zigzagging sequence of stitches in a conventional and known manner by alternating single thread chain stitches and double thread chain stitches. In the case of a single thread chain stitch, no under-thread or hook thread is fed, whereas an under-thread or hook thread is fed in the case of a double thread chain stitch. 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 an 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 which consist in that the thread feeding mechanism comprises a closed cam for guidance of the needle thread, which is drivable by a thread feeding drive to rotate about an axis of rotation, the cam comprising two different cam sections for tensioning and releasing the needle thread, which extend over angles at circumference
a
, b of 180°, and the cam performing a rotation during two stitches of the needle. The measures according to the invention ensure that a single rotating and closed cam enables the varying thread feedings to be possible which are needed for the alternating production of a single thread chain stitch and a double thread chain stitch. Fundamentally, the cam can be formed as cam sections which, over the circumference of the cam, are radially equidistant from the axis of rotation and parallel thereto; however, the design according to which the cam has a radially varying distance from the axis of rotation along its circumference is particularly simple, since in this case the cam is formed on a plane that is perpendicular to the axis of rotation, in particular on a comparatively flat cam disk when the cam is formed on the periphery of a cam disk. In this case, needle thread guidance takes place preferably approximately parallel to the axis of rotation of the cam and in needle thread guides on two sides of the cam.
Actuation of the cam may take place by way of its proper independent drive, which is for instance electrically coupled with the needle drive; however, the embodiment according to which the thread feeding drive is branched from an arm shaft by a reducing gear is especially simple and safe.
The thread tension device provided by the advantageous development, according to which a thread tension device is disposed upstream of the thread feeding mechanism, is usually triggered such that the needle thread, which is fed from a thread supply to the thread feeding mechanism, is clamped or braked, respectively, when it is pulled from the thread feeding mechanism, i.e. when it is tensioned. The thread tension device again releases the needle thread when it is loosened, i.e. released on the cam.
Details of the invention will become apparent from the description of the ensuing exemplary embodiment, taken in conjunction with the drawing.
REFERENCES:
patent: 1372473 (1921-03-01), Allen
patent: 1408185 (1922-02-01), Gatchell
patent: 4590879 (1986-05-01), Matsubara et al.
patent: 6044780 (2000-04-01), Kastrup et al.
patent: 6095066 (2000-08-01), Noltge et al.
U.S. application No. 09/256,853, Eyelet-Buttonhole Sewing machine Cross-Reference to Related Application.
Buchta Wolfgang
Bunte Jörg
Filges Karsten
Janocha Theodor
Meyer Klaus
Conte Robert F. I.
Durkopp Adler Aktiengesellschaft
Lee Mann Smith McWilliams Sweeney & Ohlson
Nerbun Peter
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