Sewing – Elements – Driving mechanisms
Patent
1999-04-01
2000-08-01
Nerbun, Peter
Sewing
Elements
Driving mechanisms
112304, 112322, D05B 6902, D05B 6916
Patent
active
060950706
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a drive means for feeding a material that may be sewn on a sewing machine, comprising a feed dog to be coupled to a continuous rotary drive by at least one intermediate drive.
DESCRIPTION OF THE PRIOR ART
Sewing machines almost exclusively include feed means for a stepwise feed of the workpiece, so that the material to be sewn stands still during the impingement of the needle, and the feed movement is effected only in that period in which the needle is outside the material to be sewn. These known feeding means mostly consist of a skipping conveyor, where the material to be sewn is seized by a toothed feed dog periodically emerging from the needle plate and is moved forward in the sewing direction. For this purpose, the movement of the feed dog is composed of a lifting movement and a pushing movement, which movements are performed by two special eccentric drives operating independently of each other as intermediate drives. Accordingly, these skipping conveyors require a complicated mechanical drive and transmission elements, requiring suitable maintenance and involving a high susceptibility to failure. In addition, in the case of higher feed rates the lifting movement of the feed dog involves the risk that the material to be sewn might be lifted off the feed dog due to the acceleration, so that the required accuracy of the feed of the material to be sewn is lost, and the feed rate and thus the sewing speed must remain restricted.
In accordance with DE 34 47 751 A there has also already been proposed a fabric feeding accessory which comprises a belt driven in feed direction via deflection rollers, where the belt driven continuously by means of a rotary drive drives a pressing device pressed onto the layer of fabric behind the needle in the feed direction, and is guided by a roller of the pressing device and a tension roller fixed on a spring-loaded lever in the tension line of the belt, and when the tensile stress of the belt, which is predetermined by the spring-loaded lever, is exceeded, the belt is loosened by the tension roller to such an extent that its feed can come to a standstill, so that an intermittent operation is possible. However, this feed means is exclusively used as an accessory for usual means for feeding material to be sewn and is designed to effect a transport of the material to be sewn without displacement. For this purpose, the belt of the accessory merely drives the pressing roller intermittently and synchronized with the stepwise feed of the material to be sewn. It can, however, not replace the feed of the material to be sewn, but can only support the same subsequently.
It is therefore the object of the invention to create a drive means as described above, which in a relatively simple and inexpensive way allows to perform an intermittent feed of the material to be sewn as a pure pushing movement without lifting component, and in addition derives this pushing movement from a continuous rotary movement.
SUMMARY OF THE INVENTION
This object is accomplished by the invention with an intermediate belt drive including a belt revolving around a drive wheel and a driven wheel, the belt having an excess length and its working position being guided over a control roller while its return portion is guided over a tension roller. The control roller and the tension roller are mounted so as to be reciprocated periodically tranversely to the direction in which the belt revolves to release or deflect the belt for decelerating, stopping and accelerating the rotation of the driven wheel. The drive wheel is in rotary connection with a feed dog designed as a circular conveyor, in particular as a conveyor belt. Due to the belt drive, which is preferably designed as a toothed belt drive, but might also be designed as V-belt, flat-belt, rope or chain drive or the like, the driven wheel is rotated in a certain transmission ratio by the drive wheel, while the control and tension rollers are standing still, and via corresponding drive connections can transmi
REFERENCES:
patent: 2678010 (1954-05-01), Pinkvoss
patent: 4413582 (1983-11-01), Landwehr et al.
patent: 4457243 (1984-07-01), Bowditch
patent: 4791877 (1988-12-01), Horie et al.
patent: 5579708 (1996-12-01), Kambara et al.
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