Abstract: Apparatus for feeding perforated webs which has a form factor and cost which may be much less than conventional perforated paper feed mechanisms such as pinwheels and tractors, and in a preferred form is an elliptical path pin feed using an endless belt having pins which engage the perforations in the paper and a frame guides the belt over an elliptical path having major curved surfaces and minor curved surfaces along opposite sides and at the ends of the path, respectively. A sprocket journaled in the frame drives the belt. Guide members upstream and downstream of the web feed path and spaced from the opposite ends of one of the major surfaces guide the web so that it remains in contact with the belt along the major surface and enters and leaves the major surface along tangents thereto which are common to the major and minor end surfaces of the elliptical belt path.

Abstract: High performance tractor apparatus having one or more of the following features: selectable tractor feed or friction feed of the web where the tractor and friction feed modes are carried out in non-interfering relationship and with precision line registration in either mode; a latch-down lid which is movable between closed position over the tractor belt and open position for threading of the web with one hand without sacrificing the hold-down force exerted by the latch when the lid is in closed position; hinging of the lid from the frame without any parts other than the frame and lid themselves which can be latched together to provide a unitary assembly; and tensioning of the belt with a shoe which is spring-biased but fixed in position upon assembly of the tractor to apply predetermined tensioning to the belt which may be reestablished from time to time by releasing and then reapplying the clamping force which holds the frame together and fixes the position of the shoe in the frame.

Abstract: A web feed tractor having an endless belt with drive pins which engage the perforations in a web such as computer forms which are to be driven has a frame which define concave and convex reaches of the belt. An outwardly open convex slot and a partially closed concave slot along opposite edges of the frame support and guide the belt reaches. The tips of the pins extending from the belt along the concave reach of the belt are in sliding contact with the outer wall of the partially closed slot. The tractor is compact and the concave reach of the belt which is not in driving relationship with the web is retained inside the tractor structure so that it does not interfere with other parts of the equipment in which the tractor is installed. The tractor is concavo-convex and oblong in shape or somewhat banana shaped.

Abstract: A bi-directional feed mechanism for webs, especially for plotting and generating special characters, forms and shapes on the webs, uses twin pairs of tractors which feed a web around a loop which may contain a platen roller. Each pair of tractors is mounted on and driven by its own drive shaft. The drive shaft of one of the tractor pairs is driven from the drive shaft of the other tractor pair through a manually releasable clutch which may be mounted on, and movable along the axis of, the driven shaft. The tension in the loop may be adjusted by releasing the clutch so that one of the tractor pairs may be driven while the other is stationary. Webs and other documents which may vary in length and require tension adjustments may readily be fed by means of the mechanism. The arrangement of the tractors also enables the webs to be easily loaded from the top.

Abstract: In order to removably yet reliably assemble the frame parts, endless belt and sprocket of a document tractor, holes are provided in the hub of one of the frame parts which provide a guide platform for the endless belt which has pins engageable with perforations on the document to be metered. Flexible rods in registry with these holes extend from the other frame part. Latches on the outer ends of these rods engage the outsides of the holes when the rods move into latching engagement as the frame parts are brought together. The tractor may be disassembled by manually deflecting the rods to release the latches.

Abstract: In order to clamp a document metering tractor to a support shaft which together with a drive shaft provide a mounting for the tractor and without causing interference, such as binding, with the drive imparted by the drive shaft, a device is provided for clamping the tractor to the support shaft. This device consists of two parts one of which contains a split ring through which the support shaft extends and the other is a member for closing the ring and retaining it in closed condition. The split ring part may be a collet located internally of the tractor or a sleeve extending externally of the tractor and having the split ring as a portion thereof. In either case, a floating connection is provided between the split ring part and the tractor such as may be afforded by an enlarged opening in the tractor which contains the split ring part.