A cam-support carriage for a knitting machine comprises movable cams for controlling knitting needles. The cams are adapted to be put out of operation by an electro-magnetic positioning device. The electro-magnetic device comprises a permanent magnet having a low coercive field associated with a magnetization/demagnetization coil and a moving part of ferromagnetic metal, integral with the cam to be positioned. The coil is connected to an excitation and control circuit ensuring magnetization and demagnetization of the permanent magnet by a current pulse in the coil, in order respectively to attract and release said moving part and its integral cam in order to being the cam out of or into operation.

This invention relates to an electronically controlled electromagnetic needle selection device which is used in the in a circular knitting machine. The device operates in the direction of the needle cylinder rotation and can include reciprocating motion. It is used particularly for making ladies' stockings and includes a cylinder with needles and elastic pusher jacks which are housed in corresponding longitudinal grooves. Each pusher jack is provided with three butts: an upper butt which cooperates with a first ring cam for lowering into the selection position, an intermediate butt which cooperates with a presser cam in the centripetal direction, and a lower butt provided with a cam for raising the pusher jack to activate the corresponding needle. The device also has a rim structure fixed to the needle cylinder and provided, in line with each pusher jack, with a radial horizontal groove for housing an elastic selector. This has its foot fitted onto the outer circumference of the rim structure and its head underlying the foot of the pusher jack when the jack is in its rest position. The device further has a selection electromagnet interposed between two permanent retaining magnets and fixed under each horizontal elastic selector. The electromagnet cooperates with the selector when it is urged against the electromagnet by the foot of the pusher jack to preferentially select the corresponding lower butt of the pusher jack after its intermediate butt has passed along the presser cam.

A circular knitting machine for hosiery includes an electromagnetic needle selection system. This selection system includes pivotal selector devices which act on resilient pushers and which are pushed indiscriminately or selectively against the resilient action of the pushers by radially acting cams. The system also includes groups of electromagnets which are placed annularly around the cylinder to exert a retaining effect on the selected cams when they are pushed against these by radially acting cams. In addition, electromagnets are placed between adjacent retaining electromagnets and they are of a size not exceeding the gap between the needles and the adjacent jacks. The jacks are excited selectively by means of a program control in order to exert the same retaining action as the retaining electromagnets and to effect abandonment or relinquishing of a selector which is moving.

In order to carry out the three-position selection of needles, that is, for floated stitch, retained stitch and discharged stitch, in either direction of rotation of the needles cylinder of a circular knitting machine with alternate motion for the production of socks with inlay patterns a cylinder is provided with needles and underneedles, and with pusher jacks provided with a heel (7,8) at both ends and engaged to a rear, centrifugal action spring. Two oscillating selectors vertically superimposed and symmetrically disposed with respect to the horizontal separation line are provided. Two electromagnets are provided vertically superimposed for the selection of said oscillating selectors. Such selection apparatus it is possible to reduce the diameter of the needles cylinder to less than 4" with a fineness above 120 needles and to work at a speed higher than the one presently allowed.