Boring device

A punching unit comprising:

• a plurality of punches and dies for punching holes in a sheet member to be punched, said punches being movable in a moving direction;
• a reciprocating member capable of reciprocating in a reciprocating direction orthogonal to the moving direction of said punches;
• a plurality of cams and cam followers that are operably interposed between said reciprocating member and said plurality of punches so that reciprocating movement of said reciprocating member converts to movement of said punches in the moving direction between punching and non-punching positions;
• wherein said plurality of punches are grouped into a first group of punches that is composed of a predetermined number of punches and a second group of punches that includes one of said punches of said first group and that has a smaller number of punches than said predetermined number of punches of said first group;
• wherein said plurality of cams and cam followers include cams and cam followers corresponding to said first group of punches that are arranged to produce a predetermined number of holes in a punching state by moving said punches of said first group in the moving direction in response to reciprocation of said reciprocating member within a first movable range;
• wherein said plurality of cams and cam followers include cams and cam followers corresponding to said second group of punches that are arranged to produce a punching state for a smaller number of punches than the predetermined number of punches by moving said punches of said second group in the moving direction in response to reciprocation of said reciprocating member within a second movable range;
• wherein said plurality of cams are each formed in said reciprocating member extending in the reciprocating direction, have at least one V-shaped portion for moving one of said punches from said non-punching position to said punching position and back to said non-punching position, and have straight sections connecting with said at least one V-shaped portion that hold the one of said punches at said non-punching position;
• wherein at least one of said cams is exclusively used with said first group or said second group, and said at least one of said cams that is exclusively used engages said cam follower with said V-shaped portion thereof when producing said punching state of said first movable range or said second movable range, and engages said cam follower continuously with said straight portion across its entire range when not producing said punching state of said first movable range or second movable range;
• wherein said cam that corresponds to said punches of said one of said first group that is also included in said second group has a first said V-shaped portion that engages with said cam follower in said first movable range and a second said V-shaped portion that engages with said cam follower in said second movable range;
• and
• wherein said first movable range is a range in which said reciprocating member has moved when it has advanced by one step in one direction of reciprocation from a home position with respect to a main frame that supports said reciprocating member and said second movable range is a range in which said reciprocating member has moved when it has advanced by another step in said one direction of reciprocation.