US3516532A

US3516532A - Stacking system for paperboard blanks

Info

Publication number: US3516532A
Application number: US810869*A
Authority: US
Inventors: Mircea Calistrat
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1967-09-11
Filing date: 1968-11-27
Publication date: 1970-06-23
Anticipated expiration: 1987-06-23

Description

June 23, 1970 M. CALISTRAT STACKIHG SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll Sheets-Sheet 1.

- m- .i.|1|-l4..+i-lill- INVENTOR. M/ACEA CAL/SIPAT BY W a M5 filler/ta June 23, 1970 M. CALISTRAT STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll Sheets-Sheet INVENTOR. M/RC'EA 04L AS764 T BY @C; C

June 23, 1970 M. CALISTRAT STACKING SYSTEM FOR PAPERBOARD BLANKS ll Sheets-Sheet 5 Original Filed Sept. 11, 1967 INVENTOR.

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June 23, 1970 v M. CALISTRAT 3,516,532

STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll Sheets-Sheet 4 1 NVEN TOR. M/ACEA CAL IS 7Z4 7 BY A 4414/ June 23, 1970 M. CALISTRAT 3,516,532

STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 11 Sheets-Sheet 5 Q u R L 3,. E l

I a i G Q 1 Q Q g L Q, R w a s x & 3 1* INVENTOR.

M/PCEA CAL IS TEA T June 23, 1970 M. CALISTRAT 3,516,532

STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll Sheets-Sheet 6 (o M/RCEA CAL/S TEAT 6 BY LL fi/S June 23, 1970 M. CALIS TRAT 3,516,532

STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll SheetsSheet 7 4/2 FIG. 7

550 576 374 522 384 352 330- P380 3/0 308 388 J; v 384 m @386, {Q l INVENTOR.

FIG. I0 I M/RCEA CAL IS 73647" June 23, 1970 M. CALISTRAT STACKING SYSTEM FOR PAPERBOARD BLANKS ll Sheets-Sheet Original Filed Sept. 11, 1967 m m? NM w w w md J am mt M w w 7 Q a m Lw mm fl June 23, 1970 M. CALISTRAT STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11, 1967 ll Sheets-Sheet 11 3 w w A INVENTOR. M/RCEA CAL ISTP/JT 6 Ab/ United States Patent US. Cl. 198-33 2 Claims ABSTRACT OF THE DISCLOSURE An inverting conveyor for receiving consecutive individual stacks of blanks from a storage conveyor in a manner to stand the stacks on their leading edge; a first pivoting means for pivoting a first stack about its upstanding trailing edge to position the stack on a rising conveyor with its top face up and a second pivoting means for pivoting a second stack about its leading edge to position the stack on the rising conveyor with its top-face down; and, advancing means for thereafter advancing the automatically inverted stacks to a downstream portion of the conveyor which then advances the stacks at a faster rate to draw them away from the advancing means.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to material or article handling and more particularly to article piling or arranging apparatus. This is a division of application Ser. No. 666,605, filed Sept. 11, 1967 now US. Pat. No. 3,447,696.

Description of the prior art Corrugated paperboard blank-forming apparatus, commonly known as a corrugator, forms a continuous web of corrugated paperboard. Usually this web is longitudinally split into a plurality of parallel widths and each width is then cut laterally to form blanks of the material for making corrugated cartons such as boxes. The longitudinally advancing blanks are collected in stacks on a delivery conveyor which then discharges them transversely to the path of blank travel for manual stacking into piles on a skid or other conveyor.

Despite constant efforts to improve the quality of box blanks thus produced, the blanks still have a tendency to curl or warp, usually in a direction lateral to the web path. Warped blanks are difiicult to process by further processing machinery. To reduce the amount of warp in the blanks, it is customary to stack them in large piles of smaller stacks of which smaller stacks are alternately placed face up and face down. In this manner, the warped portions of one stack oppose the warped portions of an alternate stack so that the weight of the pile tends to flatten the blanks.

Another inconvenience exists in that the advancing parallel adjacent blanks tend to become misaligned on the discharge conveyor so that the individual blanks of adjacent stacks become interlaced. Thus, the attendants are required to manually separate these piles into discrete stacks before alternate ones can be inverted.

Letchworth Pat. No. 3,297,174 discloses apparatus for inverting alternate small stacks of blanks. The Letchworth apparatus receives the stacks of blanks from the corrugator on a plurality of conveyor delivery belts which are parallel but are at different levels so that one series of blanks can be placed on another to form a larger stack which is thereafter inverted.

The parallel delivery belts of Letchworth require individual height adjustment for supporting the parallel advancing blanks whose width may vary from order to order. A disadvantage of this arrangement is that the parallel streams of blanks exiting from the cut-off portion of the corrugator are frequently interlaced. Therefore, it is ditficult for the blanks to drop to different levels as described by Letchworth. It is also observed that it would be difficult to maintain the height of the final pile since it is formed by adding stacks to the top of the pile. Finally, turning alternate stacks of very large blanks degrees in one continuous motion requires considerable energy because of the large air resistance encountered by the blanks during such movement.

SUMMARY The present invention is particularly useful with and as a part of apparatus for automatically forming a pile of alternatley inverted stacks of blanks which pile may be of unlimited height. The apparatus is adaptable for use in conjunction with existing delivery conveyors without the need for complex adjustments. The apparatus includes a transverse storage conveyor adapted to receive stacks of blanks from a corrugator delivery conveyor; an inverting apparatus for receiving consecutive individual stacks of blanks from the storage conveyor in a manner to stand the stacks on their leading edge, including an off-setting device for off-setting alternate ones of the stacks relative to the other ones of the stacks across their length, and a first pivoting means for pivoting a first stack about its upstanding trailing edge to position the stack on a rising conveyor with its top face up and a second pivoting means for pivoting a second stack about its leading edge to position the stack on the rising conveyor with its top face down; and a stacking means for receiving alternately inverted stacks from the rising conveyor and forming them in a pile one under the other by a lifting means for lifting each stack consecutively into engagement with a pile support means, the lifting means operable to discharge a pile of blanks of selected height onto subsequent processing apparatus.

The above and further objects and novel features of the invention will appear more fully from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are not intended as a definition of the invention but are for the purpose of illustration only.

DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts are marked alike:

FIG. 1 is a diagrammatic front elevation of a conventional delivery conveyor illustrating the usual discharge of interlaced blanks;

FIG 2 is a diagrammatic side elevation of an embodiment of the storage and loading conveyors and inverting mechanism illustrating stacks stored on the conveyor and a second stack being pivoted toward a top face-down position on the rising conveyor;

FIG. 3 is a diagrammatic side elevation of an embodiment of the rising conveyor and stacking mechanism illustrating a pile of alternately inverted stacks of blanks being formed;

FIG. 4 is a plan view of FIG. 1',

FIG. 5 is a plan view of FIG. 2;

FIG. 6 is a plan view of FIG. 3;

FIG. 7 is a partial view of the inverting mechanism of FIG. 2 illustrating a first stack being pivoted toward a top face-up position on the rising conveyor;

FIG. 8 is a section view taken along the line VIII VIII of FIG. 2 illustrating an ofi-set mechanism for laterally off-setting alternate stacks of blanks;

FIG. 9a is an elevational view of a portion of the rising conveyor illustrating the types of pivoting fingers and advancing fingers used to pivot a first stack of blanks and advance both first and second stacks of blanks;

FIG. 9b is a plan view in partial cross-section of one of the pivoting fingers of FIG. 9a illustrating its connection to the chains used on the rising conveyor;

FIG. 10 is a partial view of the stacking mechanism of FIG. 3 illustrating a squaring mechanism for aligning the stacks prior to lifting them to form the pile;

FIG. 11 is a schematic illustration of the sequence of pivoting the stacks in the inverting mechanism into alternate face-up and face-down positions; and

FIG. 12 is a schematic diagram of the controls used for controlling the functions of the invention.

THE PREFERRED EMBODIMENT In the manufacture of corrugated blanks, a web of corrugated paperboard is formed and then slit into a number of parallel streams of desired width. These streams are subsequently cut transversely to form parallel streams of blanks. The cutting operation, by its nature, inherently has a tendency to skew the blanks so that they are not exactly parallel to the flow of blanks. Accordingly, overlapping of the blanks between the parallel stream occurs. This overlapping is commonly known as interlacing. Stacks of interlaced blanks are illustrated in FIGS. 1 and 4.

Referring now to FIGS. 1 and 4, piles of interlaced blanks A and B and shingled blanks C and D (a portion of one blank resting upon the next adjacent lower blank) are shown preparatory to lateral discharge from a conventional delivery conveyor, generally designated 10, of a corrugator (not shown). Delivery 10 may be of the type shown in Lopez Pat. No. 3,079,150 which includes belts 12 for advancing the blanks downstream in shingled fashion where they are temporarily halted by a gate '14. Beyond gate 14, delivery 10 includes a plurality of longitudinally mounted rollers at a lower elevation than belts 12. When gate 14 is removed from the leading edges of the shingled blanks C and D, they are advanced by belts 12 causing them to fall one on top of the other upon rollers 16 to form piles A and B. A back-stop 18 is provided to halt the forward progress of the blanks and is adjustable upstream and down to accommodate the length of blanks being handled. Hereinafter, the length of the blanks on stacks refers to their longitudinal dimension along the delivery 10 as viewed in FIG. 4.

When piles A and B reach a selected height, gate 14 is moved to intercept the flow of blanks C and D. Thereafter, rollers 16 are driven to discharge the piles A and B upon a storage conveyor assembly generally designated 20. When pile B is completely clear of delivery 10, the foregoing process is repeated.

Although only two parallel streams of blanks are shown, it is not uncommon to have the initially formed we'b slit into four and sometimes as many as seven streams. The slit web is usually divided into an equal number of narrower webs of which one-half are guided into an upper cut-off knife and the other half into a lower cut-off knife. The shingled blanks C and D are discharged from one of the knives. Another delivery 10 is provided to handle the discharge from the other knife. Either or both deliveries 10 may be provided with the present invention which is illustrated herein to handle four streams from each delivery at maximum corrugator speed and more at lesser corrugated speeds.

INVERTER AND OFF-SETTING ASSEMBLIES Inverter assembly 22 receives individual stacks of blanks and inverts alternate ones of the stacks to a facedown position upon a rising conveyor assembly 90. The remaining stacks are placed on conveyor in a face-up position.

Inverter 22 also offsets alternate stacks in a lateral direction as illustrated in FIG. 8. This off-set condition 4 contributes to ease of handling of the stacks in subsequent processing operations, providing a gripping surface which the attendants may use in moving the stacks.

As best illustrated in FIG. 2, a stack B is inverted to a face-down position by pivoting the stack B about its leading edge, as shown by the dotted lines. Pivoting is accomplished by an inverting lever 92 adjacent the bottom face of stack B. After stack B has been laterally offset, lever 92 is actuated to pivot the stack about its leading edge so that it falls face down upon conveyor 90. Thereafter, stack B is advanced along the conveyor by an advancing finger 94 and stack A (now on the conveyor 26) is discharged into inverter 22 by loading conveyor 26.

Stack A, FIG. 7, is pivoted about its trailing edge by a roller finger 96, as shown by the dotted lines so that it falls face-up on rising conveyor 90. Thereafter, stack A is advanced by a subsequent advancing finger 98.

FIG. 11 illustrates, in panels (D through the inverting sequence of four stacks A, B, C and D. The stacks are lettered and the heavy line adjacent the face of the stacks indicates the relative face positions of the stacks during operation of inverter 22 and rising conveyor 90. Certain of the roller and advancing fingers are disengaged when extra-width stacks are being handled. This feature will be subsequently described. Coincidentally, reading panels 6), and vertically shows the stacks A, B, C and D to be alternately inverted to face-up and face-down positions.

Inverter assembly 22, FIGS. 2 and 8, comprises side guides in the form of upright angles and 102 for receiving the stacks as they fall from loading conveyor 26. Each of the guides has a side leg 104 for engaging the ends of the stacks and a bottom leg 106 engaging the underside of the stacks to support them in an upright position. Slide block 108 secured to leg 106 of guide 100* and mounting block 110 secured to leg 106 of guide 102 support the guides on a pair of support rods 112.

INVERTER ASSEMBLY After each stack A or B has been offset, stack A is inverted to a face-up position and stack B is inverted to a face-down position. As previously mentioned, stack A is pivoted about its trailing edge by a roller finger 96 and then advanced along rising conveyor 90 by advancing finger 98. Stack B is pivoted about its leading edge by inverting lever 92 and then advanced along rising conveyor 90 by advancing finger 94.

The inverting lever 92 is pivotably supported between a clevis bracket 124 by a pin 126 passing through lever 92 and bracket 124. Bracket 124 is secured to rising conveyor 90. Lever 92 includes an upstanding leg portion 128 which, in its retracted position, is on the same plane with the leg portions 102 of

guides

100 and 102. That is, leg 128 lies immediately behind the bottom face of a stack A or B in the inverter 22. Lever 92 includes a short leg 130 formed at a right angle with leg 128 and connected to a pneumatic ram 132 by a conventional pin connec tion 134. Ram 132 is pivotably secured to rising conveyor 90 by a similar pin connection 136. After a stack B in the inverter 22 has been offset, as previously described, ram 132 is actuated thereby pivoting lever 92 about pin 126 as shown by the dotted lines in FIG. 2. Upstanding leg 128 pushes against stack B thereby pivoting it about its leading edge so that it falls face down on conveyor 90. Thereafter, advancing finger 94 is moved forward to engage the trailing edge (previously the leading edge) of stack B and advance it along conveyor 90. Simultaneously, ram 132 is retracted to return lever 92 to its original posi tion.

To invert a stack A in inverter 22 to a face-up position on conveyor 90, a roller finger 96 is advanced against the lower portion of the back of stack A after the stack has been offset. A small roller 136 carried by finger 96 pushes against the stack thereby moving its leading edge forward and letting its trailing edge slide down the leg portions 106 of

guides

100 and 102. The end result is that stack A is generally pivoted about its trailing edge until it rests on conveyor 90. As the stack slides down onto conveyor 90, finger 96 continues to advance along the conveyor, with the small roller 136 rolling along the bottom of the stack, until finger 96 is forward of stack A. Thereafter, advancing finger 94 is moved forward to engage the trailing edge of the stack and advance it along conveyor 90.

RISING CONVEYOR Rising an advancing conveyor 90 advances the ofiF-set and inverted stacks to an entry conveyor 138 from which the stacks are discharged into a stacker portion 140. Conveyor 90 comprises a plurality of stack supports 142a, b, c, d and 2 extending substantially between a lower sprocket shaft 144 and an upper sprocket shaft 146. As best illustrated in FIGS. 2 and 3, supports 142 are mounted upon a pair of cross-members 148 which have their ends supported by longitudinally extending frame members 150a, 15% secured to

upstanding frame portions

70a, 70b and 1520, 15217.

Sprocket shaft 144 is rotatably mounted between

frame portions

70a, 70b and has an extended portion 154 extending beyond frame portion 70b upon which is mount-- ed a pulley wheel 156. A speed reducer 158 is mounted on frame portion 70b and carries a clutch 160 thereon, the clutch being substantially identical to clutch 72 previously described. Clutch 160 is driven by the rotation of speed reducer 158 which is in turn rotated by a pulley wheel 162 mounted thereon connected by a V-belt 164 to a pulley wheel 166 mounted on output shaft 78 of motor 76. An output pulley wheel 168 on clutch 160 drives pulley wheel 156 through a V-belt 170 and thereby rotates sprocket shaft 144.

Upper sprocket shaft 146 is rotatably mounted between

frame portions

172a, 172b of entry conveyor 138. Pairs of roller chains 174 located in spaces provided between stack supports 142

encircle sprockets

176 and 178 mounted respectively on the lower sprocket shaft 144 and upper sprocket shaft 146. The path traveled by the upper runs of chains 174 carries them over sprockets 180 secured to pulley shaft 182 of entry conveyor 138 for driving shaft 182.

As best illustrated in FIGS. 9a and 912, each pair of chains 174 carries roller fingers 96 and advancing fingers 94 therebetween so that the fingers travel with the chains. Four kinds of fingers, 94, 96, 184, and 186 are used. Each of the fingers includes a U-shaped body portion 183 as viewed in FIG. 9b, having a lug portion 188 on each leg thereof extending beside the adjacent chain 174. Chain 174 includes a link 190 extending upward so as to overlap lug portions 188. Pins 192 extend through holes provided in both the lugs 188 and links 190 to pivotably support the fingers to the chains. Pins 192 are retained by cotter pins 194.

Fingers

94 and 184 also include lug portions 196 similar to and spaced from lugs 188 to overlap a subsequent link 190 in chain 174. Pins 192 likewise connect lugs 196 to links 190 so that

fingers

94 and 184 will not pivot about pins 192 in lugs 188.

Fingers

96 and 186 include lug portions 198 extending beneath chains 174 between which a roller 200 is carried by a pin 202 passing through the roller 200 and lugs 198. Pin 202 is retained by cotter pins 194. Thus, it can be seen that

fingers

96 and 186 are free to pivot about pins 192 in lugs 188 as indicated in the right-hand portion of FIG. 9a. A counterweight 204 is secured between the legs of the U-shaped body portion of

fingers

96 and 186 by a bolt 206 and a nut 208 clamping the legs against the counterweight. The counterweight causes the stack engaging faces 210 of the fingers to lie substantially flat with respect to the chains 174 as viewed to the extreme right of FIG. 9a.

Referring now to FIGS. 2 and 3, conveyor 90 also in cludes a roller support 212 beneath the upper run of each 6 pair of chains 174 for engaging rollers 200 of

fingers

96 and 186 to maintain the fingers in an upright position as viewed in FIG. 9a. However, roller supports 212 may be lowered to the position shown by dotted lines in FIGS. 2, 3, 9a, and 11. When in the lowered position,

fingers

96 and 186 will lie fiat as previously explained.

lowering of roller supports 212 is accomplished by pivotably supporting them on frame members 150a, 150-b. Pivot rods 214 are provided between

frame members

150a, 150b. Pivot rods 214 are provided between frame members 150a, 1501? with pivot arms 216 secured thereto in a position beneath roller supports 212. Pivot arms 216 are connected to the supports 212 by a conventional pin connection 218 which allows the supports to swivel with respect to the pivot arms. Thus, when the pivot arms 216 are rotated clockwise, as viewed in FIGS. 2 and 3, the roller supports 212 will be lowered to the position indicated by the dotted lines. An operating lever 220' is provided on one end of one of pivot rods 214 for rotating the rod. A suitable clamp (not shown) is provided to lock the pivot rod in the desired position when the supports 212 are in either the raised or lowered position.

Thus, it can be seen that when the supports 212 are in the lower position,

fingers

96 and 186 will traverse the upper run of chains 174 in a flat position, as viewed in FIG. 9a, since rollers 200 do not contact the supports 212. However, when supports 212 are in the raised position, rollers 200 will flip the fingers 96' and 186 into an upright position as they approach the supports 212. A lead-in portion 222 on supports 212 aids in pivoting the fingers to an upright position.

Fingers

96 and 186 merely hang free from pins 192 during the traverse of chains 174 along the lower run between the

sprockets

176 and 178.

The length of rising conveyor is made to accommodate the widest stack to be handled. As viewed in FIGS. 2 and 3, which may conveniently be joined to give a complete picture of conveyor 90, stack A is being discharged onto entry conveyor 138 as stack B is being inverted to fall face down on conveyor 90. Thus, sufficient space must be allowed between finger 98 and the finger 94 approaching inverter 22. For example, if the maximum width stack to be handled is five feet, a space of about six feet is required between the fingers. However, if the stack width is less than half the maximum width, that is, two and onehalf feet or less, obviously two stacks can be accommodated between

fingers

98 and 94. This explains the reason for providing some of the fingers with rollers 200 supported by roller supports 212.

FIG. 11 illustrates stacks of two and one-half feet or less being processed. For stacks A and C two fingers are required; roller finger 96 to invert the stack to a face-up position and advancing finger 94 to advance the stack along the conveyor. On the other hand, stacks B and D require only an advancing finger 186 to advance it along the conveyor. Thus, three fingers are required for each set of stacks A-B and 0-D. Since a set of narrow stacks can be accommodated simultaneously on conveyor 90, obviously another set of three fingers can be carried on the lower run of chains 174. Accordingly, a total of six fingers are provided at the proper sequential spacing on chains 174. However, appropriate ones of the fingers may be lowered to an inoperative position by lowering roller supports 212 so that only three fingers remain upright for handling stacks wider than two and one-half feet.

Obviously, lowering three adjacent fingers will leave three fingers upright at a short spacing. Therefore, selected ones of the fingers are lowered to leave three fingers upright at the required spacing for wide stacks. FIG. 11 illustrates in dotted lines those fingers to be lowered when wide stacks are handled.

As previously mentioned, finger 96 is provided with a roller 136 to permit the finger to pass beneath stack A after the stack has :been inverted thereby. Finger 184 is likewise provided with a roller 136. Roller 136 is carried between upstanding lug portions 224 of

fingers

96 and 184 7 by a pin 226 passing through both the roller 136 and lugs 224. Cotter pins 194 retain pin 226, as illustrated in FIG. 9b.

Although the foregoing arrangement of conveyor 90 has been described for wide stacks of from two and one-half to five feet and narrow stacks of two and one-half feet and less, obviously, the proportions may be designed to handle other size stacks which may be manufactured.

Conveyor 90 normally runs continuously. However, in the event that a stack is not present in loading conveyor 26, a signal is provided to disengage clutch 160 so that conveyor 90 is not driven. The signal also energizes a brake 228 (similar to *brake 86) carried by an extension 230' on sprocket shaft 144 extending beyond frame portion 70a. The signal will be discussed further in the control portion of the specification. Brake 228 is used to stop the chains 174 immediately after the signal is received so that the fingers will remain in timed relation to loading conveyor 26. Otherwise, a stack could be loaded in inverter 22 with the fingers in the wrong position to maintain the inverting sequence.

ENTRY CONVEYOR Entry conveyor 138 removes stacks of blanks from conveyor 90 at a slightly faster speed than they are traveling so that they move away from the advancing finger to allow the finger to clear the stack as it passes over sprocket 180 and thereafter around sprocket 178. The stacks are also made level for entry into stacker 140.

Conveyor 138 comprises a pulley shaft 182 mounted for rotation between frame portions 152a, 152b and a pulley shaft 232 mounted for rotation between frame portions 234a and 234b, the latter frame portions being common to stacker 140. Pulley wheels 236 are mounted on shaft 182 adjacent each of the sprockets 180 as shown in FIG. 6. Corresponding pulley wheels 238 are mounted on shaft 232. Endless belts 240 encircle corresponding pairs of

pulley wheels

236 and 238. Pulley wheels 236 are driven by the rotation of shaft 182 which is in turn driven by sprockets 180 being rotated by chains 174. Sprockets 180 are somewhat smaller than the pulleys 236 so that the surface speed of belts 240 is greater than the velocity of the advancing fingers. An increase in speed of about 5% is usually sufficient to allow the fingers to clear the stacks being advanced by the entry conveyor 138.

Stack A is received by inverter 22 and guided into an upright position. The

guides

100 and 102 are operated to laterally offset the stack. Stack A is pivoted about its trailing edge by a pivoting finger carried on the rising conveyor 90 so that it falls face up on the conveyor. Thereafter, an advancing finger carried by the conveyor engages the trailing edge and advances stack A along the conveyor. Meanwhile stack B on the storage conveyor 24 has been advanced upon conveyor 26 to the position previously occupied by stack A. At the proper interval of rotation of chains 174 on conveyor 90, conveyor 26 will be rotated to load stack B into inverter 22. Stack B is offset and then pivoted about its leading edge by the inverting lever 92, so that it falls face down upon conveyor 90. Thereafter an advancing finger on chains 174 engages its trailing edge and advances it along conveyor 90. Meanwhile stack A, which has preceded stack B, is received upon entry conveyor 138 which rotates faster than chains 174 so that the trailing edge of stack A ad vances faster than the advancing finger so that the finger will clear the stack as it begins its return along the lower 8 run of chains 174. Entry conveyor 138 loads stack A into stacker 140.

I claim:

1. An advancing conveyor having an upstream portion and a downstream portion for alternately inverting and advancing stacks of blanks, placed sequentially on said upstream portion in a substantially upright position, toward said downstream portion from said upstream portion, comprising:

support means for supporting said stacks on said conveyor; first inverting means operatively associated with said conveyor for inverting a first one of said stacks to a face-up position on said support;

second inverting means operatively associated with said conveyor for inverting a second one of said stacks to a facedown position on said support;

first advancing means operatively associated with said conveyor for advancing said first stack along said conveyor from said upstream portion toward said downstream portion; and second advancing means operatively associated with said conveyor for advancing said second stack along said conveyor sequentially behind said first stack;

said first and second advancing means having upstanding portions for engaging the trailing edges of said stacks for advancing the same along said upstream portion of said conveyor and onto said downstream portion at a first rate of speed,

said downstream portion operative to advance said stacks at a second rate of speed faster than said first rate of speed,

whereby said stacks are drawn sequentially away from said first and second advancing means so that said first and second advancing means can be returned to a position for engaging subsequent sequential first and second stacks of blanks placed on said upstream portion.

2. The advancing conveyor of claim 1 wherein said first and second advancing means comprise first and second fingers secured between a pair of laterally spaced endless chains at selected positions therealong,

said chains encircling both a first sprocket wheel adjacent the upstream end of said upstream portion of said conveyor and a second sprocket wheel adjacent the downstream end of said upstream portion of said conveyor,

said second sprocket wheel positioned beyond the upstream end of said downstream portion of said conveyor,

whereby said advancing fingers advance said stacks onto said downstream portion at said first rate of speed.

References Cited UNITED STATES PATENTS 814,442 3/1906 Graham 198-76 X 2,780,342 2/1957 Good 198--34 X FOREIGN PATENTS 392,367 9/1965 Switzerland.

EDWARD A. SROKA, Primary Examiner U.S. Cl. X.R. 19876