Automatic cutter for blow molded plastic objects

An automatic cutter for separating a blow molded plastic object into two parts, said cutter and object comprising:

• a blow molded, hollow, plastic object having an irregular, cross-sectional shape, said hollow, plastic object having a first half and a second half, said first and second halves being attached to each other by a web at the base of an indented, peripheral groove, which groove lies in a single plane and which web is noncircular in the plane of the cutting line;
• a cutter machine frame;
• a first half grasping arm affixed to said cutter machine frame, said first half grasping arm holding said first half of the hollow, plastic object, said first half grasping arm including means for rotating said arm and said plastic object about an axis of rotation which is perpendicular to the plane of the peripheral groove of the hollow, plastic object, said first half grasping arm having a plurality of plates affixed to a base, said plates fitting closely the exterior of the hollow, plastic object;
• a second half grasping arm affixed to said cutter machine frame, said second half grasping arm holding said second half of the hollow, plastic object, said second half grasping arm including means for rotating said arm about an axis of rotation which is the same as the axis of rotation of the first half grasping arm, said second half grasping arm having a plurality of plates affixed to a base, said plates fitting closely the exterior of the hollow, plastic object;
• a knife assembly including a blade, said knife assembly being mounted on said frame, said knife assembly including means for actively driving said blade upwardly and downwardly into the plane of the peripheral groove to an extent that the blade of the knife assembly pierces the web at the base of the peripheral groove, said means for actively driving said blade upwardly and downwardly controlling the height of said blade from the rotational axis of the object so that the blade matains cutting contact with the web at the base of said peripheral groove as said hollow, plastic object makes one revolution about the axis of rotation of the grasping arms;
• and
• means for moving the first and second half grasping arms inwardly and outwardly along the axis of rotation of the grasping arms thereby moving the grasping arms into and out of contact with said blow molded plastic object.

A method for automatically making a planar cut in a hollow, plastic object having a noncircular shape at the line of cutting, said method comprising the steps of:

• moving a hollow, plastic object having a noncircular shape at the line of the desired cut into a cutting position;
• grasping
• grasping the hollow plastic object with two grasping arms, the arms being on the opposite sides of the line of the desired cut;
• moving a cutter downwardly into the hollow plastic object at the starting point of the cut line;
• rotating the hollow, plastic object 360 degrees in a direction so that the line of cutting stays in the same plane and the axis of rotation remains the same;
• and
• actively controlling the height of the cutter from the rotational axis of the object while the object is being rotated, said height being a function of the rotational position of the hollow plastic object so that the knife blade stays in a generally constant position with respect to the line of cutting.