Needle selector for knitting machine

A needle selector for a knitting machine, comprising:

• a plurality of jacks fitted for movement respectively, in needle grooves formed in a needle bed, so as to control respective needles, each of said jacks having one end thereof serving as a fulcrum about which the jack is capable of rocking, the jack having a raising butt;
• a jack groove cam having a cam face for moving said jacks along their respective axes;
• a first control electromagnet arranged in facing relation to one of said jacks located at a welt position, which control electromagnet is disposed at a yarn feeding position, said first control electromagnet being excited in response to a needle-selecting signal to attract the jack to bring its raising butt into engagement with a tuck ascending cam face section of said cam face of said jack groove cam;
• a second control electromagnet arranged in facing relation to the jack at the same yarn feeding position, the jack being in a tuck position at a location which is spaced integer-times a pitch of said needles from said first control electromagnet in a direction of the forward movement of said jacks, said second control electromagnet being excited in response to a needle-selecting signal to attract the jack to bring its raising butt into engagement with a knit ascending cam face section of said cam face of said jack groove cam;
• a jack holding cam arranged in juxtaposed relation to the other rocking end of the jack at said yarn feeding position, said jack holding cam having a cam face which is so magnetized as to attract the jack towards said jack groove cam, said jack holding cam extending to a position beyond the knit ascending cam face section of said cam face of said jack groove cam;
• a pair of first and second non-magnetic regions provided on said cam face of said jack holding cam, said first second and second non-magnetic regions extending between a position just before a first needle-selecting area due to said first control electromagnet and a position just after said first needle-selecting area and between a position just before a second needle-selecting area due to said second control electromagnet and a position just after said needle-selecting area, respectively;
• a welt cam arranged at such a position as to clamp the other rocking end of the jack between said cam face of said jack holding cam and a cam face of said welt cam correspondingly just before said needle-selecting area and just before said second needle-selecting area, said cam face of said welt cam being so magnetized as to attract the jack.
• wherein said jacks passing between said holding cam and said welt cam having their respective cam faces magnetized can select the welt position, the tuck position and a knit position, in response to presence and absence of the needle-selecting signal to said first control electromagnet and the needle-selecting signal to said second control electromagnet, which is delayed integer-times the needle pitch.