As is known, knitting machines draw the yarn either directly from a spool or through a yarn-feeding device which draws the yarn from the spool and feeds it to the machine under a regulated tension.
For certain particular machinings, such as the knitting of the heel in the sock-manufacturing processes, the yarn fed to the machine must be periodically recovered, and then returned more or less progressively. Since neither the traditional feeders nor the spools are capable of recovering the yarn previously fed, this function is performed by a dedicated yarn-recovering device located upstream of the machine.
To this purpose, devices are known which are provided with a pneumatically operated rocking arm having an eyelet mounted to its free end, through which the yarn passes. At rest, the arm is arranged with its eyelet aligned to the running direction of the yarn, between two stationary eyelets which are also passed through by the yarn. By rotating the arm, the yarn is deviated from its rectilinear path and a length of yarn is consequently recovered.
The above known devices provided with a rocking arm have the main drawback that their yarn-recovering capacity, i.e., the maximum length of yarn recoverable at each operation, is rather limited since strictly correlated to the length of the arm, which of course, for size reasons, cannot exceed predetermined values, typically in the range 300 to 400 mm.
Moreover, the operation of the arm can subject the yarn upstream of the device to considerable peaks of tension, which circumstance, as well known to the person skilled in the art, is undesirable because it may cause the yarn to brake and may affect the accuracy and the exactness of the feeding process.