Sheet stacking apparatus having adjustable length conveyor section

A sheet stacking system for transporting sheets and depositing them in a stack includes a layboy, a transport conveyor downstream of the layboy, and a main conveyor downstream of the transport conveyor, the main conveyor having a frame and being supported by a conveyor support, a discharge end of the main conveyor being movable between a lowered position and a raised position relative to the conveyor support. The main conveyor intake end is configured to move from a first position when the main conveyor discharge end is in the lowered position to a second position when the main conveyor discharge end is in the raised position, and also a variable length conveyor between the transport conveyor and the main conveyor, the variable length conveyor having a discharge end connected to and movable with the main conveyor intake end and movable relative to the transport conveyor discharge end.

FIELD OF THE INVENTION

The present invention is directed to a stacking apparatus having a tiltable main conveyor and a fixed transfer conveyor and an adjustable length conveyor between the main conveyor and the transfer conveyor, and, more specifically, to a stacking apparatus having a main conveyor with an intake end that moves laterally relative to a portion of a transfer conveyor when a discharge end of the main conveyor rises and an adjustable length conveyor between the main conveyor and the transfer conveyor that lengthens as the main conveyor moves away from the transfer conveyor.

BACKGROUND OF THE INVENTION

Devices for stacking generally planar articles of material, such as sheets of corrugated material, are well known. One example of a commercially available device is the AGS2000 Rotary Die Cut Stacker made by the assignee of the present invention, A.G. Machine, Inc., Weyers Cave, Va. Further examples of such devices are disclosed in U.S. Pat. No. 3,321,202 to Geo. M. Martin and U.S. Pat. No. 3,419,266 to Geo. M. Martin, each of which is expressly incorporated herein by reference in its entirety.

FIGS. 1-3illustrate a conventional apparatus for stacking sheets. The stacking apparatus100generally comprises a layboy section102which receives sheets, such as corrugated blanks produced by a rotary die cut machine103, and discharges the sheets onto a transfer conveyor104. The transfer conveyor104receives the sheets and transports them to a main conveyor106. The main conveyor106has an intake end108and a discharge end110, and the transfer conveyor has an intake end112and a discharge end114. At the main conveyor intake end108, the main conveyor106is mounted to a base116at a pivot point118so that the main conveyor106may be pivoted to raise its discharge end110. At the discharge end110of the main conveyor106, an accumulator section120receives discharged sheets.

In operation, the main conveyor106is pivoted about the pivot point118to lower the discharge end110of the main conveyor106to an initial or lowered position, illustrated inFIG. 2. Sheets are fed onto the main conveyor106at its intake end108, transported along the conveyor to its discharge end110, and discharged from the conveyor toward a backstop122in the accumulator section120. The sheets settle down, typically onto a discharge conveyor132, to form a stack of sheets.

As additional sheets drop onto the stack, the main conveyor106is pivoted to raise the discharge end110thereof vertically so that the sheets are discharged above the top of the growing stack. If the pivot point118were laterally fixed, the discharge end110of main conveyor106would follow an arc about pivot point118and move laterally away from the stack as the discharge end108of the main conveyor106was raised. This would likely interfere with the efficient formation of a stack of sheets. Therefore, the intake end108of the main conveyor106is supported by pivot arm126which pivots relative to base116and the main conveyor106. This allows the discharge end110of the main conveyor106to move generally vertically instead of following an arc and causes the intake end108of the main conveyor106to move laterally toward the stack as the discharge end110of main conveyor106rises.

While this movement of the intake end108of the main conveyor106helps ensure proper stack formation, it also pulls the transfer conveyor104away from the layboy section102and creates a gap between intake end112of the transfer conveyor104and the layboy section102. This problem has previously been addressed by providing slats128(illustrated inFIG. 3) extending from the discharge end of the layboy section102toward transfer conveyor104. As the intake end108of the main conveyor106moves away from the layboy section102, it moves the transfer conveyor104away from the layboy section102as well. However, the slats128span the gap between the layboy102and the transfer conveyor and prevent a gap from opening up as the transfer conveyor moves. This, in turn, helps ensure that product exiting the layboy section102will reach transfer conveyor104.

The slats128partially address the problem discussed above. However, they are relatively narrow, and small products and/or scrap material still occasionally catches on the slats.

Another method for addressing this problem is shown and described in U.S. Pat. No. 7,753,357 assigned to the assignee of the present application, which is incorporated herein by reference. The '357 patent describes a transfer conveyor that has a first end connected to the main conveyor and a second end connected to the layboy section. A belt tensioning system is provided that allows the length of the transfer conveyor to change so that a gap is not created between the layboy section and the transfer conveyor when the main conveyor deck is raised.

This approach works well in certain environments. However, it is sometimes necessary or desirable to use a transfer conveyor (transfer deck or diverting conveyor) that must be fixed in the length (sheet transport) direction. In such cases, when the discharge end of the main conveyor rises, the intake end of the main conveyor pulls away from the stationary diverter/transfer deck and leaves a gap into which sheets of material may fall.

SUMMARY

This problem and others are addressed by embodiments of the present disclosure, a first aspect of which comprises a sheet stacking system for transporting sheets in a downstream direction and depositing the sheets in a stack, the system comprising a conveyor support, a layboy comprising opposed upper and lower conveyors configured to receive the sheets from a rotary die cut machine at a layboy intake end and output the sheets from a layboy discharge end, a transport conveyor downstream of the layboy and configured to receive the sheets from the layboy at a transfer conveyor intake end and output the sheets from a transfer conveyor discharge end, and a main conveyor downstream of the transport conveyor. The main conveyor comprises a frame and is supported by the conveyor support and has a main conveyor intake end and a main conveyor discharge end, and the main conveyor discharge end is movable between a lowered position and a raised position relative to the conveyor support. The main conveyor intake end is configured to move from a first position relative to the conveyor support when the main conveyor discharge end is in the lowered position to second position relative to the conveyor support when the main conveyor discharge end is in the raised position. The system also includes a variable length conveyor between the transport conveyor discharge end and the main conveyor intake end, the variable length conveyor having a variable length conveyor intake end and a variable length conveyor discharge end connected to and movable with the main conveyor intake end and movable relative to the transport conveyor discharge end.

Another aspect of the disclosure comprises a sheet stacking system for transporting sheets in a downstream direction and depositing the sheets in a stack, the system comprising a conveyor support, a transport conveyor having a transport conveyor intake end and a transport conveyor discharge end, the transport conveyor discharge end being fixed relative to the conveyor support, and a main conveyor downstream of the transport conveyor. The main conveyor comprises a frame and is supported by the conveyor support and has a main conveyor intake end and a main conveyor discharge end. The main conveyor discharge end is movable between a lowered position and a raised position, and the main conveyor intake end is configured to move from a first position relative to the conveyor support when the main conveyor discharge end is in the lowered position to second position relative to the conveyor support when the main conveyor discharge end is in the raised position. The system also includes a variable length conveyor between the transport conveyor discharge end and the main conveyor intake end, the variable length conveyor having a variable length conveyor intake end and a variable length conveyor discharge end connected to and movable with the main conveyor intake end and movable relative to the transport conveyor discharge end. The variable length conveyor includes a first wheel supported by the frame of the main conveyor, a second wheel fixed relative to the discharge end of the transport conveyor, a third wheel mounted at the end of an arm pivotably connected to the frame and at least one belt mounted on the first, second and third wheels.

A further aspect of the disclosure comprises a sheet stacking system for transporting sheets in a downstream direction and depositing the sheets in a stack, the system comprising a conveyor support, a layboy comprising opposed upper and lower conveyors configured to receive the sheets from a rotary die cut machine at a layboy intake end and output the sheets from a layboy discharge end, a transport conveyor downstream of the layboy and configured to receive the sheets from the layboy at a transfer conveyor intake end and output the sheets from a transfer conveyor discharge end, and a main conveyor downstream of the transport conveyor. The main conveyor comprises a frame and is supported by the conveyor support and has a main conveyor intake end and a main conveyor discharge end. The main conveyor discharge end is movable between a lowered position and a raised position, and the main conveyor intake end is configured to move from a first position relative to the conveyor support when the main conveyor discharge end is in the lowered position to second position relative to the conveyor support when the main conveyor discharge end is in the raised position. The system also includes variable gap spanning means between the transport conveyor discharge end and the main conveyor intake end for carrying sheets from the transport conveyor to the main conveyor as a distance between the discharge end of the transport conveyor and the intake end of the main conveyor changes.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for purposes of illustrating embodiments of the disclosure only and not for the purpose of limiting same,FIGS. 4 and 6together show a stacking system150mounted next to the output of a rotary die cut machine103. The stacking system includes a layboy152, a transfer conveyor154downstream of the rotary die cut machine103, and a main conveyor156downstream of the transfer conveyor154. A variable length conveyor158is located between the transfer conveyor154and the main conveyor156. At least the main conveyor156is attached to a conveyor support160that is in turn configured to rest on or be mounted on a floor or other surface. In the present embodiment, the transfer conveyor154and the layboy152are also be mounted on the conveyor support160(formed by joining individual support elements together) but each individual conveyor sections could alternately be mounted on separate supports that are located immediately adjacent to one another.

As used herein, the term “downstream” refers to the direction from the rotary die cut machine103to the main conveyor156, the direction that sheets of material will travel along the stacking system150when it operates.

The layboy152is conventional and has an intake end162and a discharge end164. It will not be described in detail herein.

The transfer conveyor154has an intake end166and a discharge end168, and the discharge end168of the transfer conveyor154is fixed relative to the conveyor support160. The transfer conveyor includes a plurality of belts170, which form a support surface for carrying the sheets from the layboy152toward the main conveyor156.

The main conveyor156has a frame172, an intake end174and a discharge end176from which sheets of material (not illustrated) fall to form a stack (not illustrated). The main conveyor156also includes a driveshaft178(FIGS. 9 and 10) near the intake end174and a drive180configured to rotate the driveshaft178to cause the top surfaces of a plurality of belts182of the main conveyor156to move in the downstream direction. The belts182are mounted on support wheels184mounted on the driveshaft178.

The intake end174of the main conveyor156is connected to the conveyor support160by a plurality of struts186, each of which has an upper end pivotably connected to the main conveyor frame172and a lower end pivotably connected to the conveyor support160. The pivotable connection between the main conveyor frame172and the struts186and between the struts186and the conveyor support160enables the intake end174of the main conveyor156to move between a first position, illustrated inFIG. 4, when the discharge end176of the main conveyor156is in a lowered position, and a second position, illustrated inFIG. 5, when the main conveyor156is somewhat raised, and a third position (not illustrated) when the main conveyor156is in a fully raised position. In other words, the intake end174of the main conveyor156moves from the right to the left inFIG. 4as the main conveyor discharge end176rises.

Because the discharge end168of the transfer conveyor154is fixed, it cannot move with the main conveyor intake end174as would the conventional transfer conveyor104illustrated inFIGS. 2 and 3. Therefore, if the variable length conveyor158, described in more detail below, were not present, the distance between the discharge end168of the transfer conveyor154and the intake end174of the main conveyor156would grow when the discharge end176of the main conveyor156rises. This would adversely affect the movement of sheets from the transfer conveyor154to the main conveyor156and could lead to jams.

Beneficially, the variable length conveyor158spans the gap between the transfer conveyor154and the main conveyor156to provide a support surface for sheets of material moving downstream which support surface is present regardless of the position of the discharge end176of the main conveyor156.

The variable length conveyor158comprises a plurality of drive wheels190mounted on the drive shaft178of the main conveyor156between the support wheels184which drive wheels190support a plurality of belts192. (Alternately, the drive wheels190could be mounted on a separate shaft parallel to the drive shaft178which shaft is mechanically connected to the drive shaft178and/or to the drive180). The drive wheels190are fixed against rotation relative to the drive shaft178so that the drive wheels190rotate with the driveshaft178to drive the plurality of belts192. The plurality of belts192of the variable length conveyor154are caused to rotate by the drive180and the rotating drive shaft178so that the tops of the belts192mounted on the drive wheels190carry sheets toward the main conveyor156.

The variable length conveyor158also includes an idler shaft194at the discharge end168of the transfer conveyor154which supports a plurality of idler wheels196. The idler shaft194may be directly supported by a portion of a frame of the transfer conveyor154, or, as illustrated, mounted to the conveyor support160or mounted in some other manner that holds the idler shaft194at a fixed location relative to the transfer conveyor discharge end168. The idler shaft194may be fixedly mounted to side supports with the idler wheels196mounted for rotation relative to the idler shaft194, or, alternately, the idler wheels196may be fixed to the idler shaft194, and the idler shaft194itself may be journaled to side supports so that the idler shaft194and the idler wheels196rotate as a unit. The plurality of belts192extend from the drive wheels190of the driveshaft178to the idler wheels196.

A transverse portion of the conveyor support160runs perpendicular to the downstream direction and beneath the gap between the transfer conveyor discharge end168and the main conveyor intake end174, and a plurality of guide plates198are mounted thereto. Each of the guide plates198projects vertically and lies in a plane parallel to the downstream direction. Each of the guide plates198includes a curved slot200having a first curved guide wall202(first cam surface) and a second curved guide wall203(second cam surface) that extend upwardly and in the downstream direction.

As illustrated, for example inFIGS. 10 and 11, the variable length conveyor158further comprises a plurality of guide arms204each having a first end206pivotably mounted at or to the one of the struts186and a second end208near the curved slot200of one of the guide plates198. The second end208of each guide arm204supports a cam roller210. A shaft211(seeFIG. 10) connecting the second ends208of the guide arms204supports a plurality of idler wheels212. The cam roller210is mounted in the curved slot200between the first curved guide wall202and the second curved guide wall203. The idler wheels212support the plurality of belts192of the variable length conveyor158. The plurality of belts192thus extend around the triangles formed by each set of one drive wheel190, one idler wheel196at the discharge end168of the transfer conveyor158and one idler wheel212at the second end of one of the guide arms204.

The shape of the curved slots200is selected to ensure that the cam rollers210maintain a desired tension on the plurality of belts192. There is very little clearance between the cam rollers210and the first and second curved guide walls202,203of the curved slots200. The relationship between the cam rollers210and the drive wheels190is therefore substantially fixed for any given spacing between the drive wheels190and the idler wheels196. The interaction between the cam wheels210and the curved slots200thus maintains the desired tension on the plurality of belts192for all locations of the cam wheels210along the curved slots200.

In operation, the rotary die cut machine103outputs cut sheets of material that are received into the intake end162of the layboy152. The sheets exit the discharge end164of the layboy152and are received onto the intake end166of the transfer conveyor154and travel along the belts170of the transfer conveyor154to the transfer conveyor discharge end168. After leaving the transfer conveyor154, the sheets move onto the belts192of the variable length conveyor158and travel across the variable length conveyor158to the intake end of the main conveyor174. The sheets than travel along the main conveyor156in a conventional manner and drop off the discharge end176of the main conveyor to form a stack.

This operation continues, and the main conveyor156remains in the generally horizontal position illustrated inFIG. 4until the stack grows to a predetermined height. At that time, under the control of a conventional stacking apparatus controller (not illustrated), the discharge end176of the main conveyor156is raised gradually and reaches an intermediate position illustrated inFIG. 5.

FIG. 7is a detail view of the variable length conveyor158when the main conveyor156is in the position shown inFIG. 5. As will be appreciated from this figure, the generally vertical upward movement of the main conveyor discharge end176pulls the main conveyor intake end174toward the left in the figure, which movement is accommodated by the pivotal connections between the main conveyor frame172and the struts186and between the struts186and the conveyor support160. This movement of the main conveyor intake end174pulls the drive shaft178, which is attached to the frame172of the main conveyor156, away from the idler shaft194and causes the top surface of the variable length conveyor158to lengthen. The tilting of the struts186also pulls the first end of the guide arm204away from the curved slot200, which in turn causes the cam roller210roll along the first curved guide wall202of the curved slot200. Because the top surface of the variable length conveyor158lengthens as the main conveyor discharge end176moves upwardly, sheets traversing the stacking apparatus150from the transfer conveyor154to the main conveyor156continue to travel smoothly without encountering gaps which could adversely affect sheet flow.

FIG. 8shows the variable length conveyor158when the discharge end176of the main conveyor156is fully raised. In this Figure, the struts186have tipped further to the left, pulling the first ends206of the guide arms204to the left and causing the cam rollers210to roll along the curved guide walls202to a location at or near the top of the curved slots200, thus bringing the idler rollers212on the second ends208of the guide arms204closer to the idler wheels196on the idler shaft194and to the discharge end168of the transfer conveyor154.

When the stacking system150finishes forming a given stack, the main conveyor discharge end176is returned to the position shown inFIG. 4. The cam rollers210travel back between the first curved guide walls202and the second curved guide walls203toward the bottom of the curved slots200. Because the second curved guide walls203also control the positions of the cam rollers210as the intake end174of the main conveyor156moves closer to the discharge end168of the transfer conveyor154, they force the bottom portions of the plurality of belts192downward and maintain tension on the plurality of belts192during the downward movement of the main conveyor156.

The presence of the variable length conveyor158thus allows a gap between a transfer conveyor154and a main conveyor156to be filled when a transfer conveyor154having a fixed position discharge end168(fixed against movement in the sheet travel direction) is used.

The present invention has been described herein in terms of a preferred embodiment. However, modifications and additions to this disclosure will become apparent to persons of ordinary skill in the art upon a reading of the foregoing description. It is intended that all modifications and additions form a part of the present invention to the extent they fall within the scope of the several claims appended hereto.