Sheet-feed tractor with eccentric clamping device

In a sheet-feed tractor adapted to be slidably mounted on substantially parallel elongated support and drive shafts, the combination comprising:

• a. a tractor body having a support-shaft opening therethrough;
• b. a drive sprocket rotatably mounted in said tractor body and adapted to receive the drive shaft for sliding therealong and driving thereby upon rotation of the drive shaft about its longitudinal axis;
• c. an endless belt disposed about said tractor body in engagement with said drive sprocket for driving thereby upon driving of said sprocket by the drive shaft, said drive belt including sheet-engagement teeth adapted for engagement of perforated sheet material and advancement thereof upon driving of said drive belt by said sprocket;
• and
• d. clamp means mounted on said tractor body and having a support-shaft passage aligned with said support-shaft opening in said body, said clamp means including first and second clamp members each having an interior wall portion, said wall portions of said clamp members defining said support-shaft passage, said first clamp member extending outwardly from said body and being nonrotatably supported thereon, said second clamp member being pivotally mounted on said first clamp member for pivoting thereabout and about a pivotal axis, said passage-defining wall portions on said first and second clamp members having first and second opposed shaft-clamping wall portions respectively, along a common axial length of said support-shaft passage defined thereby for a portion of their axial length, said second clamp member including a ring portion having an inner aperture-defining surface providing said shaft-clamping wall portion of said second member along a portion thereof, said first clamp member including a projection portion extending into said aperture of said ring portion of said second clamp member, said projection portion having a first surface providing said shaft-clamping wall portion of said second clamp member and also having a second surface opposite said first surface, said second surface of said projection portion and said inner surface of said ring portion including slidably engaged arcuate mating surfaces having a common axis of curvature coincident with said pivotal axis, said sliding engagement permitting sliding of said arcuate mating surfaces along each other during pivoting of said second clamp member relative to said first clamp member, pivoting of said second clamp member on said first clamp member effecting relative movement of said shaft-clamping wall portions to reduce or increase the maximum transverse spacing therebetween diametrically of the passage defined thereby, pivoting of said second clamp member thereby clamping the support shaft between opposed portions of said clamping surfaces along said common axial length of said support-shaft passage or releasing it to permit sliding therealong if its width is within the range of transverse spacings provided by said shaft-clamping wall portions, clamping of a shaft between said shaft-clamping wall portions tending to press said arcuate mating surfaces together to increase friction therebetween to maintain said second member in clamping position.