Manually assemblable and disassemblable sheet-feed tractor employing improved clamp assembly

Claim 1

A sheet-feed tractor adapted to be slidably mounted on spaced apart and substantially parallel extending elongated support and drive shafts comprising: a. a first frame member having a support-shaft opening therein; b. a second member assembled on said first frame member to form a tractor frame therewith; c. a drive sprocket mounted on said tractor frame for rotation about the axis of said drive sprocket and having an aperture therethrough adapted to receive the drive shaft for sliding therealong and for driving thereby upon rotation of the drive shaft about its longitudinal axis; d. an endless belt disposed about said tractor frame in engagement with said drive sprocket to be driven thereby upon driving movement of said sprocket by the drive shaft, said drive belt including sheet engagement teeth adapted to engage in the perforations of sheet material perforated against the side margins thereof for advancement thereof upon driving of said belt by said sprocket; e. clamp means, having an aperture therethrough adapted to receive the support shaft therein, for clamping the support shaft received therein, said clamp means including a first clamp part on said second frame member and extending through said support-shaft opening in said first frame member to the side of said first frame member opposite that on which said second frame member is disposed, said first clamp part having a generally cylindrical outer surface, said clamp means also including a second clamp part disengageably mounted on said first clamp part and moveable relative thereto to clamp a support shaft received in said aperture in said clamp means, said second clamp part including a ring portion receiving the generally cylindrical exterior surface of said first clamp part therewithin, one of the interior surface of said ring portion and said generally cylindrical exterior surface of said first clamp part providing a radially extending tab and the other providing an engagement surface and an axial slot, said engagement surface engaging said tab throughout a first range of rotational positions of said second clamp part to cause said ring portion to bear against said side of said first frame member opposite that on which said second frame member is disposed to retain said first and second frame members in assembly and prevent axial removal of said second clamp part from said first clamp part, said slot being aligned with said tab in at least one second rotational position of said second clamp part to permit axial removal of said second clamp part from said first clamp part, said second clamp part also including an extension portion extending from said ring portion to provide a second engagement surface spaced from said first-mentioned engagement surface in a direction generally perpendicular to the axis of said support-shaft opening; and f. a post on said second frame member, said first frame member having a post aperture spaced from said support-shaft opening, said post extending from said second frame member through said post aperture in said first frame member to provide a second tab on the side of said first frame member opposite that on which said second frame member is disposed, said second tab engaging said second engagement surface throughout said first range of rotational positions of said second clamp part to cause said extension portion to bear against said side of said first frame member opposite that on which said second frame member is disposed to retain said first and second frame members in assembly and prevent axial removal of said second clamp part from said first clamp part, said second engagement surface clearing said second tab in said second rotational position of said second clamp part to permit axial removal of said second clamp part from said first clamp part, said frame members being held in assembly by said clamp parts, removal of said second clamp part from said first clamp part permitting ready disassembly of said frame members from each other.