The present invention relates to a yarn feeding apparatus for circular knitting machines and particularly to a yarn feeding apparatus for color-changing yarn feeding wheels of circular knitting machines.
Yarn feeding apparatus equipped with a yarn feeding wheel plays an intermediary role between a circular knitting machine and a yarn barrel. It mainly provides a smooth yarn supply path during knitting operation of the circular knitting machine and maintains a desired tensile strength of yarns. If the tensile strength of the yarns is too strong the yarns are easily broken. Too small tensile strength will result in unsmooth yarn supply. In order for single circular knitting machine to knit complex patterns, a great number of yarn feeding wheels are needed to supply yarns.
A conventional yarn feeding apparatus, such as R.O.C. patent No. I326725 basically includes a yarn feeding body, a yarn feeding board coupled with the yarn feeding body and a transmission shaft driven by the yarn feeding body. The transmission shaft is fixedly coupled with at least one yarn feeding wheel. The yarn feeding board has at least one yarn inlet and at least one yarn outlet, and also has at least one guiding unit. After the yarn passes through the yarn inlet, it threads through a yarn guiding eyelet at a distal end of the guiding unit, and then passes through the yarn outlet to be sent to the knitting machine for knitting. The guiding unit is drawn by the yarn to move reciprocally on a motion track between a yarn supply position and a yarn supply stopped position. As the yarn is constantly in contact with the yarn guiding surface of the yarn feeding wheel between the yarn supply position and the yarn supply stopped position, and the transmission shaft keeps rotating regularly, the yarn guiding surface constantly contacted by the yarn gradually wears off, hence the yarn feeding wheel has to be replaced frequently.
As mentioned above, if the transmission shaft continuously drives the yarn feeding wheel rotating even when the yarn is stopped supplying, the yarn guiding surface made of plastic material still receives constant friction of the yarn and results in unnecessary wear.
The primary object of the present invention is to solve the problem of the conventional technique with the yarn feeding wheel constantly driven by the transmission shaft to rotate even when the yarn is stopped supplying that results in excessive wear.
To achieve the foregoing object, the present invention provides a yarn feeding apparatus for circular knitting machines that includes a yarn feeding body and a transmission shaft driven by the yarn feeding body. The yarn feeding body includes at least one guiding unit which is drawn by a yarn to turn and move reciprocally on a motion track relative to the transmission shaft between a yarn supply position and a yarn supply stopped position. The invention is further characterized in that the transmission shaft is movably coupled with at least one yarn feeding wheel freely rotating against the transmission shaft, and also coupled with at least one transmission mechanism driven by the transmission shaft. The yarn feeding wheel has at least one wedge member corresponding to the transmission mechanism. The wedge member has a first position to separate from the transmission mechanism and a second position pushed by the guiding unit on the motion track to couple with the transmission mechanism to drive the yarn feeding wheel to rotate synchronously with the transmission shaft.
In one embodiment, the wedge member has a wedge portion to wedge in the transmission mechanism and an action strut pushed by the guiding unit. The guiding unit has a pressing section to push the action strut. The action strut has a drawing surface drawn by the pressing section to move the wedge member to the second position.
In one embodiment, the guiding unit has a pushing section to push the action strut and the action strut has a butting surface butted by the pushing section to move the wedge member to the first position.
In one embodiment, the transmission mechanism includes a plurality of ratchets and the wedge portion is a detent corresponding to the ratchets.
In one embodiment, the yarn feeding body further includes a friction plate in contact with the yarn feeding wheel regularly.
In one embodiment, the yarn feeding wheel has a mounting surface hinged by the wedge member, a cover plate to cover the mounting surface and a gap between the cover plate and mounting surface to receive entry of the guiding unit.
In one embodiment, the yarn feeding wheel has at least one yarn guiding surface, and the guiding unit has at least one yarn guiding ring corresponding to the yarn guiding surface to allow the yarn to thread through and guide the yarn to contact the yarn guiding surface.
In one embodiment, the yarn feeding wheel includes a first yarn guiding surface and a second yarn guiding surface, and the guiding unit has a first yarn guiding ring corresponding to the first yarn guiding surface to allow the yarn to thread through and guide the yarn to contact the first yarn guiding surface, and the yarn feeding body includes an ancillary guiding unit which has a second yarn guiding ring corresponding to the second yarn guiding surface to allow the yarn to thread through and guide the yarn to contact the second yarn guiding surface.
The invention, through the guiding unit moving on the motion track to drive the wedge member hinged on the yarn feeding wheel to move against the transmission mechanism, the transmission shaft and yarn feeding wheel can be fully coupled and separated. Thus the problem that the yarn feeding wheel is constantly contacted by the yarn to result in wear even when the yarn is stopped supplying can be eliminated.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
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In the aforesaid embodiment, the yarn feeding body 10 includes the guiding unit 30 and ancillary guiding unit 31; however, the invention also can achieve the same effect by providing merely single guiding unit. Please refer to
As a conclusion, the yarn feeding apparatus according to the invention includes a transmission mechanism driven by the transmission shaft, and the transmission shaft is movably coupled with at least one yarn feeding wheel, and the yarn feeding wheel has at least one wedge member to wedge in the transmission mechanism, hence the yarn feeding wheel can rotate idly against the transmission shaft corresponding to the guiding unit at the yarn supply stopped position, and rotate synchronously with the transmission shaft at the yarn supply position, thereby rotation of the yarn feeding wheel can be controlled independently. It provides significant improvements over the conventional techniques.
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.