Sewing – Stitch forming – Feeding work material
Patent
1991-01-02
1994-04-05
Crowder, Clifford D.
Sewing
Stitch forming
Feeding work material
D05B 2724
Patent
active
052995186
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains in general to a sewing machine with a lower feed dog movable in vertical and horizontal directions and in particular to a sewing machine where the lower feed dog can move either horizontally and vertically, or only horizontally.
2. Background Art
A sewing machine of this design has been known from West German Patent Specification No. DE-PS 21,08,309 and its parallel U.S. Pat. No. 3742880. It has a combined feed device, which consists of a lower feed dog and a needle feed device, in which an oscillating shaft controlling a needle bar oscillating frame is connected to an oscillating shaft moving a feed dog holder to and fro in a horizontal plane. The oscillating movements of the oscillating shaft are derived from a feed cam and the amplitude of these movements can be adjusted by means of a stitch length regulating device. Besides the horizontal reciprocating movements, vertical lifting movements are imparted to the lower feed dog by a driving cam via a cam rod and a crank mechanism, so that the lower feed dog performs a tetragonal movement. This combined feed device guarantees the displacement-free sewing together of a plurality of fabric layers.
A band strip bordering apparatus participates in the horizontal movements of the feed dog, and folds a bond strip in the shape of a U around the edges of the fabric. When fabric edges are bordered with a band strip, which is fed in and sewn on, the lower feed dog must not perform any vertical movements. In this machine, the lifting drive mechanism, the driving cam, and the cam rod must be removed. This takes very much time, when the sewing machine is to be used for bordering operations with the attached band strip bordering apparatus. For use in normal sewing operations, it is necessary to reinstall the lifting drive mechanism.
As an alternative, it is possible to use a second sewing machine in which only horizontal pushing movements, but no vertical lifting movements, are imparted to the lower feed dog. Such a sewing machine has been known from West German Offenlegungsschrift No. DE-OS 18,09,0979 and its parallel U.S. Pat. No. 3467039. However, this sewing machine is suitable only for certain sewing operations.
From FR-A-926 213 the insertion of a coupler in the hoist drive of the material slider of a sewing machine for the neutralization of the vertical motion of the material slider is known. However, the printed material does not indicate for which purpose this should be used.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to design a sewing machine with a lower feed dog having adjustable horizontal pushing motions imparted to it by a driving cam via a stitch length regulating mechanism. The lower feed dog can also have optional vertical lifting movements imparted to it by a driving cam via a lifting shaft. Thus the feed dog is able to optionally perform either tetragonal movements or only horizontal pushing movements.
This task is accomplished by a removable connection between the driving cam and the lifting shaft. When vertical movements of the feed dog are desired, an oscillating crank, oscillated by the driving cam, is rigidly fastened to the lifting shaft by a follower and a lifting crank. When vertical movements are not desired the follower is removed from the oscillating crank and movements of the oscillating crank then no longer effect the lifting shaft. The follower is then firmly attached to a housing of the sewing machine in order to keep the lifting shaft from moving.
Although the oscillating crank is mounted on the lifting shaft, it is rotatably mounted and therefore will have no effect on the lifting shaft when it is not connected to the lifting crank by the follower.
An adjustable holder for the follower makes it possible to adjust the height of the feed dog when the lifting movement is turned off, on one hand, and, on the other hand, it is also simple and easy to align the slots of the holder and of the crank on the lifting shaft
REFERENCES:
patent: 2496817 (1950-02-01), Schulthess
patent: 2526480 (1950-10-01), Hohmann
patent: 2713839 (1955-07-01), Engel
patent: 4391216 (1983-07-01), Hsiao
patent: 4559887 (1985-12-01), Sand
patent: 4756263 (1988-07-01), Sand
Dusch Albert
Walther Karl-Heinz
Crowder Clifford D.
Izaguirre Ismael
Pfaff Industriemaschinen GmbH
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