Reversing screw/high-low speed level wind screw

Abstract

Sharpening mechanism for moving at a variable speed along the length of the sharp edge of a reciprocating knife used in cloth cutting machines is disclosed. The apparatus includes a driven grinding apparatus (26) such as is known in the art for contacting an edge of a reciprocating knife (24). Driven grinding apparatus (26) is moved by a tubular carrier member (44) which moves the grinding mechanism (26) along the edge of reciprocating knife (24) in a manner also known in the art. A traverse mechanism for moving the carriage along the knife edge includes a guide mechanism (52) attached to tubular member (44) for following left and right hand peripheral threads (34) cut in the drive shaft (32). To achieve the variable speed, the peripheral left and right hand threads (34) cut in drive shaft (32) have a first pitch at an uppermost portion (56) and a pitch different from the first pitch in a lowermost portion (54) such that the traverse speed of the grinding mechanism (26 ) varies at selected portions of the reciprocating blade. In a preferred embodiment, the uppermost peripheral threads (34) have a higher pitch than the lowermost peripheral threads such that additional contact time is available for the grinding apparatus (26) at the lower tip of the reciprocating blade (24).

Dependencies are inferred from the claim text.