Sewing – Special machines – Darning
Patent
1990-11-19
1992-03-17
Nerbun, Peter
Sewing
Special machines
Darning
11212114, 112221, 112443, D05B 2100, D05B 302
Patent
active
050958348
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a sewing machine with a stitch formation unit including a head and shuttle holder which may be guided along a predeterminable seam line. The head is provided with a needle bar holder mounted transversely movably for receiving the needle bar driven to perform oscillating movement in the direction of its longitudinal axis. The needle bar holder may be driven via a gear drive with an oscillation frequency corresponding to the oscillating frequency of the needle bar.
BACKGROUND OF THE INVENTION
Such a sewing machine has been known from West German Patent Specification No. DE-PS 3,336,683. A fabric clamped in a fabric holder is moved by a feed mechanism relative to the needle under the head of the sewing machine.
The needle bar is received by a needle bar rocker mounted in the head, which is driven for needle transport. The pivotable mounting of the head makes it possible to perform the needle transport movement for any stitch formation in the direction of the feed motion of the fabric in any direction of feed of the fabric relative to the stitch formation site. The pivotable design of the shuttle holder guarantees that the shuttle is always in the correct position relative to the needle. Even though the pivotable arrangement of the head and shuttle holder permits stitch formation without pivoting the fabric, the function of the sewing machine is limited to straight stitch seams prepared with needle feed. These seams can be prepared with tacking or locking stitches.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to design a sewing machine with a fabric holder for moving the fabric without pivoting such that different types of seams can be prepared while maintaining stitches formed at the stitch formation site at a predeterminable angle to the direction of feed of the fabric.
According to the invention, a sewing machine is provided with a stitch formation unit. The stitch formation unit includes a head and a shuttle holder which may be guided along a predeterminable seam line. The head is provided with a needle bar holder, mounted transversely movably for receiving the needle bar driven to perform oscillating movement in the direction of its longitudinal axis. The needle bar holder may be driven via a gear drive with an oscillation frequency corresponding to the oscillating frequency of the needle bar, the gear drive is designed to change this frequency ratio in a plurality of steps and has a shifting device for shifting from one gear ratio to another.
As a consequence of the use of the multistep gear drive in a sewing machine with pivotable head and pivotable shuttle holder, it is additionally possible, while maintaining all the usual advantages of this class of machine, to form seams with different stitch types, such as straight stitch or zigzag stitch. This may be done by changing the oscillation frequency of the needle bar holder relative to the oscillation frequency of the needle bar, so that it is not necessary to transfer the fabric to another sewing machine in order to prepare another seam.
Due to the pivotable arrangement of the head and shuttle holder, the needle and the shuttle can always be moved into the position that is optimal for stitch formation, so that no loop stitches are formed, regardless of the type of stitch to be prepared.
Even though sewing machines designed for performing different types of stitching have been known from the state of the art, these are sewing machines which belong to a different class compared with the sewing machine according to the invention and therefore fail to offer its special advantages.
For example, a sewing machine with stationary head and shuttle holder, whose needle bar is mounted in a needle bar rocker, has been known from West German Patent Specification No. DE-PS 3,000,831. To deflect the needle bar rocker, a crank mechanism connected to a two-step gear drive acts on it.
The gear drive is provided to transform the movement received from the arm shaft and to tran
REFERENCES:
patent: 3450076 (1969-06-01), Bender
patent: 4674421 (1987-06-01), Iwase
patent: 4787324 (1988-11-01), Fischer et al.
patent: 4867084 (1989-09-01), Braun
Nerbun Peter
Pfaff Industriemaschinen GmbH
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