Abstract: A tractor for a web feeding assembly has a chassis providing a pair of apertures extending therethrough and a belt extending thereabout. A drive pulley mounted in one of the chassis apertures is engaged with the driven surface of the belt and has an aperture therethrough receiving the drive shaft. Convexly arcuate belt support means cooperates with the drive pulley to define the web drive path for the belt therebetween, and a cover on the chassis overlies the belt and web drive path. An integrally formed belt tensioning means is movably supported on the chassis below the drive path for resiliently biasing the belt against the guide means. The belt tensioning means includes a support plate portion and at least one resiliently deflectable leg portion depending therefrom and slidably seated in a recess in the tractor chassis.

Abstract: A tractor for a web feeding assembly having spaced support and drive shafts has a chassis providing a pair of apertures extending therethrough and a belt extending thereabout. A drive pulley mounted in one of the chassis apertures is engaged with the driven surface of the belt and has an aperture therethrough receiving the drive shaft. A convexly arcuate belt support surface cooperates with the drive pulley to define the web drive path for the belt therebetween. A resilient spring clamp is mounted adjacent the other aperture in the chassis and releasably clamps the tractor on the support shaft. The mounting desirably permits the clamp to rotate about the axis of the aperture receiving the support shaft.

Abstract: A tractor for a web feeding assembly has a chassis providing a pair of apertures extending therethrough and a belt extending thereabout. A drive pulley mounted in one of the chassis apertures is engaged with the driven surface of the belt and has an aperture therethrough receiving the drive shaft. Convexly arcuate belt support means cooperates with the drive pulley to define the web drive path for the belt therebetween, and a cover on the chassis overlies the belt and web drive path. Belt tensioning means is movably supported on the chassis below the drive path for resiliently biasing the belt against the guide means. As a result, pressures on the belt during operation of the tractor tending to produce deflection away from the cover are resisted by the belt tensioning means to maintain a rectilinear drive path for the web tightly against the cover.

Abstract: A sheet-feed tractor for printers employs two principal frame members, one of which is integrally molded with a part of the tractor clamp. A second clamp part is assembled onto the first clamp part, and the two clamp parts together hold the frame members in assembly. A snap-fit cover prevents rotation of the second clamp part to a position in which it can be removed from the first clamp part, so the tractor is held in assembly so long as the cover is in place. Disassembly is easily achieved by removing the cover, pivoting the second clamp part to a position in which it can be removed from the first clamp part, and then easily removing the remaining parts of the tractor.

Abstract: A sheet-feed tractor in which the frame members are held together by the clamp parts employs a movable clamp part with a ring portion from which extend a lever and an extension portion. The stationary clamp portion provides a tab on its outer surface, and the frame member from which the stationary clamp part extends also has a post extending from it with a tab on the post. The interior surface of the ring portion provides an engagement surface that engages the tab on the stationary clamp part, while the extension provides an engagement surface that engages the tab on the post. The two sets of tabs and posts cause the movable clamp part to bear against one of the frame members at least at two positions and thereby hold the frame members reliably in position.

Abstract: A sheet-feed tractor includes clamp means made of two members through which a passage is provided defined partly by both members. One member is pivotably mounted on the other in such a manner that the size of the passage is reduced by pivoting of the pivotable member. Reduction of the size of the passage can clamp a support shaft received in the passage, and the clamping force tends to enhance the static friction between the members so as to keep the clamping means in clamping position.

Abstract: A drive tractor of the type usually mounted in pairs at opposite edges of a web of edge-perforated sheet material such as printout paper has an endless drive belt mounted on a chassis. The chassis is movably mounted on a base member locked to a support bar. A positioning screw permits fine lateral shifting of th chassis relative to the base member to adjust transverse tension in the web. The drive belt preferably has pins projecting from it to engage edge perforations in the web and is trained over sprocket wheels having teeth which engage a tread on the inner surface of the belt. The sprocket wheel is engaged by a drive shaft. The sprocket teeth and belt tread are respectively configured to mesh only in a selected position of the pins relative to the rotational position of the sprocket wheel. This automatically transversely aligns the pins of paired tractors mounted on a common drive shaft.

Abstract: A drive tractor of the type usually mounted in pairs at opposite edges of a web of edge-perforated sheet material such as printout paper has an endless drive belt mounted on a chassis. The drive belt has pin members projecting from it to engage edge perforations in the web and is engaged with a drive wheel having sprocket teeth which engage a drive formation on the inner surface of the belt. The sprocket wheel is engaged by a drive shaft to be driven thereby. The sprocket teeth and belt tread are respectively configured to mesh only in a predetermined relative position of the pin members relative to the rotational position of the drive wheel. The drive wheel is configured to seat on the drive shaft in a predetermined rotational orientation. Therefore, when a pair of such tractors is mounted on a common drive shaft their respective drive wheels are in the same rotational orientation which automatically transversely aligns the respective pin members of the paired tractors.