Crankpin lathe and tool head and work head therefor

A crankpin lathe wherein a work head is mounted on a bed for supporting a work spindle driven by a work spindle drive device;

• said work spindle is provided for clamping a journal of a crankshaft thereon with a crankpin being positioned on the rotational axis of said work spindle;
• and a tool head for attaching at least one cutting tool is mounted on said bed to be moved by a tool head feed device relative to said work head for turning said crankpin;
• said crankpin lathe further comprising:
• an index member supported on said work spindle for rotation about an axis which is parallel with, and offset by an eccentricity of said crankpin, from the axis of said work spindle;
• a clutch mechanism interposed between said index member and said work spindle for restraining the relative rotation between said index member and said work spindle when brought into engagement, but for permitting the relative rotation when released from engagement;
• a clamp device provided on said work spindle for removably clamping said journal;
• a pin pusher mounted on said bed and movable by a pin pusher feed device toward the axis of said work spindle for causing said pin pusher to push said crankpin;
• and a control device for positioning the machined crankpin to a position spaced by a predetermined distance from the axis of said work spindle by pushing with said pin pusher said machined crankpin with said clutch device being made disengagement and for rotating said work spindle by half an angle through which said crankshaft is to be indexed rotationally relative to said work spindle so as to position a crankpin to be machined next onto the axis of said work spindle before bringing said clutch device into engagement.

A tool head for a crankpin lathe wherein a crankshaft is clamped on at least one work spindle rotatably carried on a work head, with a crankpin to be machined next being in axial alignment with the axis of the work spindle so that said crankpin is machined with a cutting tool moved radially thereof while being rotated about the axis of said work spindle;

• said tool head comprising a tool head body mounted to be movable in a first direction parallel with the axis of said work spindle and a second direction transverse to the axis of said work spindle;
• first and second feed devices drivingly connected with said tool head body for moving the same respectively in said first and second directions, a plate-like index body carried on said tool head body and rotationally indexable about an axis parallel with the axis of said work spindle, said index body having a thickness larger than the distance between a pair of shoulder surfaces formed on axial opposite ends of said crankpin to be machined;
• an index drive device provided on the tool head body for rotationally indexing said index body;
• and a plurality of tool attaching portions arranged on the circumferential portion of said index body for respectively attaching cutting tools thereon and formed as locally thin portions whose width is narrower than said distance between said pair of shoulders, so that each of said locally thin portions is able to advance between said pair of said shoulder surfaces without interfering with the same.

A work head for a crankpin lathe wherein a work spindle clamping thereon a crankshaft is rotated with a crankpin to be machined being in axial alignment with the axis of said work spindle;

• said work head comprising said work spindle rotatably supported in a housing thereof;
• a chuck body connected with one end of said work spindle;
• an index member mounted in said chuck body with the axis thereof being offset by an eccentricity of said crankpin from the axis of said work spindle and rotatably indexable about the axis thereof;
• a collect chuck co-axially received in said index member and rotatable bodily with said index member;
• an operating mechanism received in said work spindle and connected with said collet chuck for operating the same so as to clamp a journal of said crankshaft on said work spindle;
• a clutch mechanism interposed between said chuck body and said index member for selectively making the same freely rotatable or restrained from free rotation;
• and a servomotor for rotating said work spindle with said clutch mechanism being disengaged whereby relative rotation between said work spindle and said crankshaft is brought about thereby to rotationally index a crankpin onto the axis of said work spindle.