Sheet Turnover Mechanism

This invention relates in general to sheet transport apparatus, and more particularly to a mechanism for use with a sheet transport apparatus for turning over a sheet transported along a travel path.

In transporting sheets along a travel path, it is sometimes required that the sheet be turned over so that the leading edge becomes the trailing edge and its surface orientation is reversed. One typical mechanism for accomplishing such sheet turnover includes a three-roller cluster located in association with the sheet travel path; see for example U.S. Pat. No. 3,856,295 (issued Dec. 24, 1974 in the name of Looney). In such mechanism, the transported sheet is directed into the nip between a first roller and the middle roller of a three-roller cluster and is fed therethrough into a curved chamber until the trailing edge clears such nip. The leading edge of the sheet is directed against a resilient stop which causes the sheet to reverse its direction of travel. Due to the curvature of the chamber and the beam strength of the sheet, the sheet traveling in the reverse direction is directed into the nip between the middle roller and the third roller of the cluster. The sheet is thereby transported back into the travel path with the trailing edge becoming the leading edge and its surface orientation being reversed.

While the use of a resilient stop is generally effective in cooperation with a three-roller cluster for turning over a sheet, it is subject to certain limitations. The resilient stop must have its spring characteristics tailored to the characteristics of the sheet being turned over. That is to say, the stop must have sufficient resilience to assure that the sheet will receive enough impetus to return to the appropriate nip of the three-roller cluster, but must not damage the edge of the sheet as it imparts such impetus. If a variety of weights of sheets must be handled, a resilient stop selected to ensure reversal of movement of a heavy weight sheet may damage the engaged edge of a lighter weight sheet; and a resilient stop selected to prevent damage to a light weight sheet may not provide sufficient impetus to a heavier weight sheet. Further, the resilient stop must be located a distance from the three-roller cluster to ensure that the trail edge of the sheet clears the cluster, that the inertia of the sheet imparted by the cluster will be sufficient to enable this sheet to reach the stop, and that the return impetus is sufficient for the sheet to be returned into the appropriate nip of the cluster. Therefore, the resilient stop must be adjustably located so as to accommodate a variety of sheet sizes (measured in the direction of the travel path) or, if not adjustably located, must be utilized with only a narrow range of sheet sizes.

This invention is directed to a mechanism for use with a sheet transport apparatus for turning over a sheet transported along a travel path, such mechanism reliably functioning irrespective of sheet weight or size. With the mechanism, a sheet is selectively moved in one direction from a travel path or in an opposite direction into such travel path. The surface of the moving sheet is engaged so that energy derived by the sheet being transported in the direction from the travel path is stored. When the sheet is no longer being transported in such direction, the stored energy is utilized to move the sheet in the opposite direction to a point where it can be transported in such one direction, the stored energy is utilized to move the sheet in the opposite direction to a point where it can be transported in such opposite direction back into the travel path with its trail edge becoming the lead edge and its surface orientation reversed.

With the mechanism according to this invention, sheets of various weights and sizes may be turned over with any adjustments to the mechanism being required. Engagement of the sheet surface during turnover, as opposed to edge engagement as found in the prior art, avoids potential damage to a sheet edge. Further, such surface engagement eliminates the requirement to adjust the location of the turnover mechanism to effect turnover of different size sheets.

The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.

In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawings, in which:

FIG. 1 is a view, in perspective, of the mechanism for turning over a sheet moving along a travel path according to this invention, with portions removed to facilitate viewing;

FIG. 2 is a side elevational view of the mechanism of FIG. 1, with portions broken away or removed to facilitate viewing; and

FIG. 3 through 6 are schematic side elevational views of the mechanism of FIG. 1 respectively taken at various times during the operation of such mechanism.

Referring now to the accompanying drawings, FIGS. 1 and 2 show a mechanism, designated generally by the numeral 10, for turning over a sheet according to this invention. The mechanism 10 is associated with an apparatus 12 for transporting sheets seriatim along a travel path P. The transport apparatus 12 includes, for example, spaced pairs of nip drive rollers 14, 16 for urging a sheet along the travel path described by wire-form guides 18.

The mechanism 10 comprises a pair of diverters 20a, 20b located in juxtaposition with the sheet travel path P. The diverters are pivotally mounted for movement between a first position (solid line position of FIG. 2) out of the path and a second position (phantom line position of FIG. 2) intercepting the path P. In their respective intercepting positions, the diverter 20a directs a sheet out of the travel path into a three-roller cluster 22 and diverter 20b directs a sheet out of the three-roller cluster into the travel path.

The cluster 22 includes a plurality of sets of outboard rollers 24 and 26 in nip relation with a plurality of cooperating rollers 28 respectively. The rollers 24 are mounted on a common shaft 24a, rollers 26 are mounted on a common shaft 26a, and rollers 28 are mounted on a common shaft 28a. The shafts 26a and 28a are respectively supported for free rotation in bearings 26b and 28b, while the shaft 24a is supported at one end in a bearing 24b and coupled at the other end to a motor 24c to be rotatably driven by such motor. Accordingly, when the motor 24c rotates the shaft 24a in a counter-clockwise direction, the rollers of the cluster 22 rotate in the respective directions indicated by their associated arrows. By such rotations, a sheet directed by diverter 20a from the path P into the nip between rollers 26 and 28 is transported away from the path P; and a sheet in the nip between rollers 26 and 24 is transported in a direction which, in cooperation with diverter 20b, returns the sheet to the path P. A sheet transported away from the path P is confined within a path P' described by wire-form guides 30 (see FIG. 2) for example.

The mechanism 10 further comprises a plurality of sets of passive nip rollers 32, 34 located in association with the path P' adjacent to the cluster 22 on the opposite side thereof from the path P. The rollers 32 are mounted on a common shaft 32a, and the rollers 34 are mounted on a common shaft 34a. The shafts 32a and 34a are respectively supported for free rotation in bearings 32b and 34b, and shaft 32a is urged toward shaft 34a by springs 36. The springs 36 are selected to have a spring constant sufficient to provide effective frictional engagement between the rollers 32, 34 and a sheet located therebetween, while enabling the rollers to move apart to accommodate a wide variety of sheet weights (thicknesses). The shaft 34a has an extension 34a' upon which a flywheel 38 is mounted. Additionally, a clock spring 40 is connected at one end 40c to the shaft extension 34a' and at the opposite end 40b to a fixed reference plane 42.

While the cluster 22 and passive nip rollers 32, 34 have been respectively shown and described as including a plurality of roller sets, they could each comprise a single roller set located on their respective shafts in a substantially vertical plane passing through the center line of the sheet travel path in the mechanism 10.

With the above described construction, the mechanism 10 of this invention operates to turn a sheet over in the manner described hereinbelow with particular reference to FIGS. 3-6. A sheet S traveling in the path P in the direction of its associated arrow has a lead edge S.sub.L, a trail edge S.sub.T and opposing surfaces S.sub.a and S.sub.b. The lead edge S.sub.L is directed (by diverter 20a) into the nip between rollers 26 and 28 of the three-roller cluster 22 which transports the sheet along path P' toward the passive nip rollers 32, 34 as shown in FIG. 3. The spacing between the cluster 22 and the passive nip rollers 32, 34 is selected so that, irrespective of the length of a transported sheet (i.e., the distance measured between lead edge S.sub.L and trail edge S.sub.T ), the sheet will enter the passive nip rollers while being transported by the cluster. When the sheet S under the influence of the cluster 22, enters the passive nip rollers 32, 34, the engagement of the moving sheet surfaces with the nip rollers cause the nip rollers to rotate in the direction of the associated arrows as shown in FIG. 4. Rotation of the passive nip rollers causes the shaft 34a (and extension 34a') to rotate which, in turn, rotates the flywheel 38 and winds up the clock spring 40. The clock spring 40 thus serves to store energy resulting from the positive drive of the sheet through the passive nip rollers by the three-roller cluster.

When the trail edge S.sub.T of the sheet S leaves the nip between the rollers 26, 28 of the cluster 22, the sheet is of course no longer being positively driven thereby. However, the inertia of the fly wheel 38 causes the shaft extention 34a' (and thus shaft 34a) to continue rotating the passive nip rollers 32, 34 for a sufficient time to ensure that the trail edge has fully cleared the cluster 22. The inertia of the flywheel continues to rotate the shaft extension 34a' until it is overcome by the force of the clock spring 40 on the shaft extension. At the time the inertia of the flywheel 38 is overcome by the clock spring, the energy stored by the clock spring is effective to reverse rotation of the shaft extension 34a' (and thus shaft 34a). The rotation of the shaft 34a', due to the energy stored in the clock spring, causes the passive nip rollers 32, 34 to rotate in the direction of their associated arrows as shown in FIG. 5. Such rotation of the passive nip rollers is effective on the surfaces of the sheet S to transport the sheet along path P' in the direction of its associated arrow into the nip between rollers 24 and 26 of the cluster 22 with the lead edge S.sub.L becoming the trail edge. The cluster 22 then transports the sheet S back into the path P for movement in the direction of its associated arrow as shown in FIG. 6. The sheet S is thus turned over with its lead edge S.sub.L becoming its trail edge, its trail edge S.sub.T becoming its lead ledge, and with the orientation of its surfaces S.sub.a and S.sub.b being reversed when compared to their orientation prior to entering the mechanism 10. The sheet S is thereafter transported along path P by the apparatus 12 in this desired turned over orientation.

The invention has been described in detail with particular reference to the preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.