US3658320A

US3658320A - Apparatus for feeding sheets

Info

Publication number: US3658320A
Application number: US29463A
Authority: US
Inventors: Frederick Reinhold Kuehn
Original assignee: Koppers Co Inc
Current assignee: United Container Machinery Group Inc
Priority date: 1970-04-17
Filing date: 1970-04-17
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25

Abstract

A sheet feeding apparatus includes an adjustable backstop assembly for supporting the trailing edges of a stack of sheets at varying heights above a feeding surface depending on the length of the sheets being fed. The backstop assembly is raised to a relatively high position above the feeding surface to permit the feeding of the bottom sheet of the stack by a conventional reciprocating spring feeder assembly when a stack of longer sheets is being processed, and adjusted to a relatively lower position to permit the feeding of the bottom sheet from a stack of shorter sheets by a new low-profile spring feeder assembly.

Description

United States Patent Kuehn 51 Apr. 25, 1972 [54] APPARATUS FOR FEEDING SHEETS 1 [72] Inventor: Frederick Reinhold Kuehn, Baltimore, t E'Yamlverjoseph wegbren M Asszstant Exammer-Bruce H. Sto ner, Jr. Attorney-Boyce C. Dent, Oscar B. Brumback and Olin E. [73] Assignee: Koppers Company, Inc. Williams 7 [22] Filed Apr 1 1970 ABSTRACT 21 l. N 29 463 1 App 0 A 'sheet feeding apparatus includes an adjustable backstop assembly for supporting the trailing edges of a stack of sheets at 1.8. CI- 1 R, varying heights above a feeding surface depending on the [51] Cl 3/24 length of the sheets being fed. The backstop assembly is raised [58] Field Of Search ..4....27 H44, 4

l

35, 32 to a relatively high position above the feeding surface to pen mit the feeding of the bottom sheet of the stack by a conven- [56] References cued tional reciprocating spring feeder assembly when a stack of UNITED STATES PATENTS longer sheets is being processed, and adjusted to a relatively I lower position to permit the feeding of the bottom sheet from Shields a ta k of horter heets a new ]ow profi]e pring feeder as. 1,637,833 8/1927 Mueller ...271/4l Semb|y 2,974,950 3/1961 Pasquinelli et al ...27l/44 3,409,289 1 H1968 Barnes ..271/44 7 Claims, 4 Drawing Figures DL ifl UPPER pas/mm 20 LflWER 1 05/ T/ON BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to sheet feeding and more particularly to separators of the reciprocating bottom feeder type.

2. Description of the Prior Art Conventionally, an apparatus used to feed sheets such as corrugated paperboard sheets from the bottom of a stack comprises a backstop assembly for supporting the trailing edges of the sheets in a position which permits a standard feeder bar to reciprocate beneath the stack. The backstop assembly usually includes individual backstops spaced laterally along a backstop support bar; the feeder bar usually includes resilient spring feeder plates spaced laterally along the bar and adapted to engage the trailing edge of the bottom sheet of the stack even though the trailing edge may be warped.

Palamenti U.S. Pat. No. 3,264,386 and Barnes U.S. Pat. No. 3,409,289 show the use of a backstop in cooperation with a spring feeder assembly for feeding sheets into adjacent machinery for operations on the sheets such as printing, slotting, scoring, and the like. The trailing edge of the bottom sheet of a stack of long sheets rests ona support-ledge provided on each backstop to maintain the trailing edge of the stack above the leading edge of the stack which rests on a feeding surface. The result is that the stack of sheets rests in a slightly inclined position. By long sheets is meant for example sheets longer than 22 inches. The standard feeder bar rapidly reciprocates beneath the stack and feeds the sheets, one by one, from the bottom of the stack into the adjacent processing machinery.

When short sheets are fed by the standard bar in the prior art apparatus a problem arises. By short sheets is meant for example sheets about 10.5 to 22 inches long, depending on the proportions of the machine. In the prior art apparatus the backstop is moved forward to support the trailing edge of the stack. .This movement causes the angle of incline of the stack to be increased. As a result, the standard feeder bar is operating closer to the vertex of the angle formed by the inclined stack with the feeding surface since the stroke of the feeder bar is fixed at, for example, about 10.5 inches. The standard feeder bar reciprocates to feed the bottom sheet in the same manner regardless of sheet length. However the resilient action of the spring feeder plates changes with sheet length. The spring feeders are subject to more weight with the larger sheets than with the smaller sheets. Consequently, the standard spring plates lift the stack of small sheets during the back stroke of the bar causing the stack to rapidly rock up and down as the bar reciprocates.

In the past, to reduce the problem of rocking the stack of short sheets, a flat feeder bar i.e. one not having a resilient or flexible feeder plate, was supposed to allow the short sheets to be fed without causing the stack to rock. However this substitute required the replacing of the standard backstop with a backstop not having a ledge for supporting the trailing edge of the bottom sheet thereby letting the stack rest flatly with respect to the feeding surface except for the thickness of the flat feeder bar. A shortcoming of this arrangement, however, was the fact that the sheets were often warped and the flat feeder bar could not efficiently handle warped sheets since the flat feeder bar did not include resilient feeder plates independently operable to follow the contour of the trailing edge of the sheet. Since the sheets are frequently warped, the bar frequently failed to engage the trailing edge of the bottom sheet or, worse yet, partially engaged the trailing edge thereby skewing the sheet and this usually resulted in jam-ups.

The present invention takes advantage of the superior feeding characteristics of the standard spring feeder bar for feeding long sheets but also provides improved feeding apparatus easily adjustable for feeding either long or short sheets and adapted to take advantage of the superior characteristics of spring feeder plates in both instances.

SUMMARY or THE INVENTION The present invention contemplates the method of feeding a stack of blanks by supporting the trailing edge of the stack with an adjustable backstop assembly and reciprocating a spring feeder bar between the stack and feeding surface with the improved step of placing the backstop assembly at a first height above the feeding surface for feeding long sheets and thereafter adjusting the backstop to a lower position above the feeding surface for feeding shorter sheets.

The foregoing method may be performed by a sheet feeding apparatus which includes adjustable backstops slidably mounted on wcdges secured to a backstop support bar for providing upper and lower positions above a feeding surface for supporting the trailing edges of both long and short sheets, and a novel low-profile feeder bar having spring feeder plates of substantially increased resilience or flexibility placed laterally along the feeder bar.

The new backstop, when in the upper position, may be used to support long sheets in cooperation with a conventional spring feeder bar, or it may be adjusted to the lower position and moved forward to support a stack of short sheets. When the backstop is supporting short sheets, the novel low-profile spring feeder bar is preferably used to feed the short sheets from the bottom of the stack without rocking the stack as the conventional spring feeder tends to do. Adjusting the backstops to the lower position results in a greater distance between the warped sheet deflector and the backstop support bar which permits the feeder bar to reciprocate through its normal cycle without striking a warped sheet deflector, which is usually provided on the support surface for supporting the leading edge of the stack, on the forward stroke or without striking the backstop support bar on the backstroke.

The above and further objects and novel features 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.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation in partial cross-section illustrating the backstop and feeder bar assemblies of the present invention;

FIG. 2 is an enlarged side view in cross-section illustrating the adjustable mounting of a conventional spring feeder bar assembly in a feeder surface;

FIG. 3 is an enlarged side view of the low-profile spring feeder bar assembly showing its configuration and height in comparison to the conventional spring feeder bar assembly of FIG. 2; and

FIG. 4 is an isometric view of part of the backstop assembly and the feeder bar assembly of the present invention illustrating the lower position of the backstop in phantom outline.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the new sheet feeding apparatus is generally designated 10. Feeding surface 12 supports a backstop assembly generally designated 20 and feeder bar assembly 30. Trailing edge 42 of stack 40 is supported by backstops 22 above feeding surface 12, and leading edge 44 of stack 40 is restrained against forward movement by gate 50. Backstops 22 and gate 50 define a hopper for receiving the stack 40. The trailing edge 43 of bottom sheet 46 rests on ledge support 23 and leading edge 45 of bottom sheet 46 rests on warped sheet deflector bar 60. Feeder bar assembly 30 rapidly reciprocates along the top of feeding surface 12 and engages the trailing edge of each successive bottom sheet of stack 40 thus feeding sheets, one by one, from the underside of stack 40 through an opening 52 beneath gate 50 to adjacent processing machinery (not shown).

Feeding surface 12 is the supporting base for sheet feeding apparatus 10. Backstop assembly 20 is movably mounted on feeding surface 12 and may be moved toward or away from I gate 50 depending on the length of the sheets being fed.

Feeder assembly 30 is provided to rapidly reciprocate between feeding surface 12 and stack 40. To accomplish this, feeder bar assembly 30 is slidably mounted on slides 38 provided in feeding surface 12 as best shown in FIG. 1.

Conventional feeder bar assembly 30a, FIG. 2, is efficient for feeding long sheets and comprises spring feeder plates 32a including a lip portion 34a for engaging the trailing edge of bottom sheet 46 of stack 40 at the completion of the backstroke. Thus, if long sheets are being fed, feeder assembly 30a could be used in the same manner in which feeder assembly 30 is used in FIG. 1. When feeder bar assembly 30 moves forward toward gate 50, bottom sheet 46 is moved forward. In order for lip portion 34, FIG. 3, to engage the trailing edge of bottom sheet 46 it is necessary that spring feeder plate 32 exert an upward force on the underside of stack 40. Thus, spring 32 should not reach its free position while it is beneath stack 40 if it is to effectively engage the trailing edges of each successive bottom sheet.

Conventional spring feeder plates 32a are stiff and therefore require a substantial force to cause them to flex or bend. The weight of a stack of long sheets is great enough to overcome the upwardly directed force exerted on the underside of the stack and the reciprocating feeder bar assembly 30a does not cause stack 40 to rock or bounce as a result of the upward force of spring 32a. However, when a stack of short sheets is fed by the conventional feeder bar assembly 30a the substantially lighter weight of the stack of short sheets is not sufficient to withstand the upward force exerted by spring feeder plates 3211, thus causing'the stack of short sheets to rock or bounce rapidly as feeder bar assembly 30a rapidly reciprocates beneath stack 40.

In the present invention, backstop assembly 20, as shown in FIG. 1, comprises backstop support 21 movably mounted in grooves provided within feeding surface 12 in the conventional manner. Generally there are two backstop supports 21 mounted in feeding surface 12. A channel or backstop support bar 24 is provided laterally above feeding surface 12 connecting both backstop supports 21 in a ganged assembly and providing a backstop support unit movably mounted on feeding surface 12. Fixedly mounted on backstop support bar 24 are wedge supports 25 arranged at laterally spaced intervals along backstop support bar 24. Backstops 22 are slidably mounted on wedge supports 25 by

bolts

26 and 26a and slot 28, as shown in FIG. 4, thus permitting backstops 22 to be moved from an upper position to a lower position as shown in the drawing. For example, to move backstop 22 from the upper position to the lower position, bolt 26 must be loosened and bolt 26a must be removed. Holes are provided in wedge 25 to accommodate

bolts

26 and 26a. The holes are spaced apart at a distance corresponding substantially to the length of slot 28. Therefore, backstop 22 may be moved toward gate 50 traversing the length of slot 28. Bolt 26a is then replaced and both bolts 26 and 2612, now at opposite ends of slot 28, are tightened to secure backstop 22 in the lower position as shown in FIG. 1.

Backstops 22 are moved to the upper position when feeding long sheets, as shown in FIG. 1, thus enabling the conventional spring feeder bar assembly 30a to be used. Backstop assembly 20 may be used successfully with continuous chain feeders or suction feeders but the feeder bar assembly 30a is believed to be the most efficient means of feeding long sheets. Furthermore, since trailing edge 43 of bottom sheet 46 rests on ledge support 23 when in the upper position and leading edge 45 rests on warped sheet deflector bar 60, there is adequate room between feeding surface 12 and the underside of stack 40 to permit feeder bar assembly 30a to reciprocate. In addition, the weight of the stack of long sheets is sufficient to substantially deflect spring feeder plate 32a. The result is the efficient feeding of long sheets from the underside of stack 40 without rocking or bouncing the stack.

When short sheets are fed, backstop assembly 20 is moved forward to accommodate the appropriate sheet length. As this is done, the angle of incline of stack 40, with respect to feeding surface 12 becomes greater as backstop assembly 20 is moved toward gate 50. Backstops 22 are moved to the lower position, see FIG. 1, to reduce the angle of incline thereby maintaining stack 40 substantially horizontal. With the bottom of stack 40 closer to feeding surface 12, and since the stack of short sheets weighs less than a stack of long sheets, the use of conventional feeder bar assembly 300 having stiff spring feeder plates 32a may exert a substantial upward force on the underside of stack 40, thus causing rocking of the stack as assembly 30a reciprocates in the now reduced area between stack 40 and feeding surface 12.

However, this problem is overcome by the use of the novel low-profile feeder bar assembly 30 of this invention as shown in FIGS. 3 and 4. Feeder bar assembly 30 comprises lowprofile feeder bar 31 having tapered leading edge 35, tapered trailing edge 36 and flat spring feeder plates 32 spaced laterally along bar 31 and secured to leading edge 35 by screws 33. At the trailing edge of spring feeder plates 32 is lip portion 34 provided to engage the trailing edge of a sheet and feed the sheet through opening 52 to the adjacent processing machinery. Spring feeder plates 32 of the present invention are more highly resilient or flexible than prior art spring feeder plates 32a and therefore exert less upward force on the bottom of stack 40 and are also lower in height than the conventional plates as illustrated by comparison in FIGS. 2 and 3. Therefore, spring feeder plates 32 of the present invention reduce or eliminate the rocking up and down of stack 40 as feeder bar assembly 30 rapidly reciprocates back and forth beneath stack 40 but still retains the desirable feeding characteristics of a spring feeder assembly. Feeder bar assembly 30 reciprocates above feeding surface 12 in a similar manner to that used in the conventional feeding apparatus previously described.

The wedge mounted backstops 22, in addition to being movable from an upper position to a lower position, are movable toward or away from gate 50 with respect to support 21. This distance, with respect to support 21, is shown in FIG. 1 and designated DL. When short sheets are being fed, the distance between support 21 and deflector 60 may approach a length substantially equivalent to the length of the stroke of the feeder bar 31. In this case, the stroke of feeder bar 31 may require additional clearance to reciprocate unobstructed between deflector 60 and support 21. The additional clearance required is provided by the offset distance DL.

Spring feeder plates 32 are substantially flat. On the other hand, conventional spring feeder plates 32a FIG. 2 have a bend conforming the plate to fit over the substantially rectangular shape of conventional feeder bar 31a. Conventional spring feeder plates 32a require a second bend 29 to incline the feeder plate upwards toward the bottom of stack 40. Substantially flat feeder plates 32, when secured to the leading edge of feeder bar 31 incline upwards toward the underside of the stack, as best shown in FIG. 3. The low profile of feeder bar 31 and the more highly resilient, that is, more flexible spring feeder plates 32 operate efficiently within the reduced area between stack 40 and feeding surface 12 so as to feed short and straight or warped sheets to the adjacent processing machinery.

It has been found that the low-profile feeder bar assembly 30 operates efficiently for feeding sheets up to a length of about 20 to 25 inches long in conventional sheet feeding machines, it being understood that this range varies a little depending on the size of the machine and the type of board being used. However, in each operation the operator can determine at which point it is preferable to change feeder bars. At sheet lengths greater than this the conventional feeder bar assembly 30a was found to be more efficient.

In operation, a stack of long sheets 40 rests on ledge 23 and warped sheet deflector bar 60 between backstop 22 and gate 50. Backstop 22 is in the upper or first position above feeding surface 12 and at a distance from gate 50 corresponding appropriately to the sheet length.

Conventional feeder bar assembly 30a reciprocates between stack 40 and feeding surface 12 so that spring feeder plates 32a exert an upwardly directed force on the underside of stack 40. Lip portion 34a engages trailing edge 43 of bottom sheet 46 at the end of the backstroke. As feeder bar assembly 30a moves forward toward gate 50, bottom sheet 46 is advanced through opening 52. Before the forward stroke of feeder bar assembly 30a is completed, sheet 46 is engaged by adjacent processing machinery and withdrawn completely from the underside of stack 40. Feeder bar assembly 3011 continues to reciprocate and feed the subsequent bottom sheets from beneath stack 40.

When short sheets are to be fed, feeder bar assembly 30a is replaced by low-profile feeder bar assembly 30, and appropriate adjustments are made for feeding the short sheets from the bottom of stack 40. Backstop 22 is adjusted along wedge support to its lower or second position, and backstop assembly 20 is positioned with respect to gate 50, corresponding to the length of the short sheet. Low-profile feeder bar assembly reciprocates as before, sequentially feeding the bottom sheets of stack 40 in a smooth and efficient manner.

The foregoing has described a novel sheet feeding apparatus for feeding long and short sheets from the bottom of a stack without substantially rocking said stack and for effectively feeding warped sheets to the adjacent processing machinery.

Having thus described the invention in its best embodiment and mode of operation, that which is desired to be claimed by Letters Patent is:

l. Feeding apparatus for selectively feeding long and short sheets from beneath a stack of sheets and along a path of travel through a metering means, comprising:

a feeding surface for supporting the leading edge of said stack adjacent said metering means;

backstop means on said feeding surface for supporting a trailing edge of said stack above said surface and being adjustable longitudinally from said metering means along said path for supporting sheets of varying length;

said backstop means selectively adjustable between a first elevated position above said feeding surface and a second elevated position lower than said first position for supporting the trailing edge of a stack of long sheets above said feeding surface at said first position and for supporting the trailing edge of a stack of short sheets above said feeding surface at said second position; and

mutually exclusive first and second feeding means selectively mountable to a slide means in said feeding surface for reciprocation thereby,

said first feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of long sheets through said metering means when said backstop means is in said first position, and

said second feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of short sheets through said metering means when said backstop means is in said second position.

2. The feeding apparatus of claim 1, wherein said first feeding means includes a laterally extending feeder bar having spring feeders spaced at intervals therealong, said feeders having a sheet engaging surface of sufficient height to engage the trailing edge of the bottom sheet of a stack of long sheets when said backstop means is in said first position.

3. The feeding apparatus of claim 2, wherein the height of said feeders is sufficient to engage the trailing edge of a sheet whose length is in excess of 25 inches when said backstop means is in said first position.

4. The feeding apparatus of claim 1, wherein said second feeding means includes a laterally extending feeder bar having spring feeders spaced at intervals therealong, said feeders having a sheet engaging surface of sufficient height to engage the trailing edge of the bottom sheet of a stack of short sheets when said backstop means is in said second position.

5. The feeding apparatus of claim 4, wherein the height of said feeders is sufiicient to engage the trailing edge of a sheet whose length is less than 25 inches when said backstop means is in said second position.

6. Feeding apparatus for selectively feeding long and short sheets from beneath a stack and along a path of travel through a metering means, comprising:

backstopmeans on said feeding surface for supporting the trailing edge of said stack above said feeding surface, said backstop means including:

a laterally extending backstop bar positionable along said feeding surface at a distance from said metering means corresponding to the length of sheets to be fed; wedge supports spaced at intervals along said backstop bar each including a top surface inclined toward said feeding surface in the direction of said metering means; and

backstops having inclined bottom surfaces corresponding to said top surfaces slidably secured to said wedge supports andhaving support ledges for supporting the trailing edge of said stack above said feeding surface at a distance corresponding to the position at which said backstops are secured along said inclined top surfaces; and

said first feeding means reciprocable along said path of travel for sequentially advancing successive bottom sheets from beneath a stack of long sheets when said backstops are secured at substantially their maximum height along said inclined top surfaces, said first feeding means including:

a laterally extending feeder bar including spring feeders secured at intervals therealong, said feeders including a sheet engaging surface spaced above said feeding surface a distance sufficient to engage the trailing edge of the bottom sheet of said stack of long sheets; and

said second feeding means reciprocable along said path of travel for sequentially advancing successive bottom sheets from beneath a stack of short sheets when said backstops are secured at substantially their minimum height along said inclined top surfaces, said second feeding means including:

a laterally extending feeder bar including spring feeders secured at intervals therealong, said feeders including a sheet engaging surface spaced above said feeding surface a distance sufficient to engage the trailing edge of the bottom sheet of said stack of short sheets.

7. Feeding apparatus for selectively feeding long and short sheets from beneath a stack of sheets and along a path of travel through a metering means, comprising:

said backstop means selectively adjustable between a first elevated position above said feeding surface and a second elevated position lower than said first position for supporting the trailing edge of a stack of long sheets above said feeding surface at said first position and for supporting the trailing edge of a stack of short sheets above said feeding surface at said second position;

mutually exclusive first and second feeding means selectively mountable to a slide means in said feeding surface for reciprocation thereby.

said first feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of long sheets through said metering means when said backstop means is in said first position, and said second feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of short sheets through said metering means when said backstop means is in said second position, said backstop means including:

a backstop support bar on said feeding surface extending along the width of said stack and adjustable longitudinally from said metering means a distance corresponding substantially to the length of sheets being advanced;

wedge supports spaced at intervals along said support bar and including top surfaces inclined toward said feeding surface in the direction of said metering means; and

backstops having inclined bottom surfaces corresponding to said inclined top surfaces and selectively secured thereto at said first or said second position,

said backstops further including ledge supports for supporting the trailing edge of said stack at a height substantially corresponding to either said first or second positions.

i t i i i

Claims

1. Feeding apparatus for selectively feeding long and short sheets from beneath a stack of sheets and along a path of travel through a metering means, comprising: a feeding surface for supporting the leading edge of said stack adjacent said metering means; backstop means on said feeding surface for supporting a Trailing edge of said stack above said surface and being adjustable longitudinally from said metering means along said path for supporting sheets of varying length; said backstop means selectively adjustable between a first elevated position above said feeding surface and a second elevated position lower than said first position for supporting the trailing edge of a stack of long sheets above said feeding surface at said first position and for supporting the trailing edge of a stack of short sheets above said feeding surface at said second position; and mutually exclusive first and second feeding means selectively mountable to a slide means in said feeding surface for reciprocation thereby, said first feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of long sheets through said metering means when said backstop means is in said first position, and said second feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of short sheets through said metering means when said backstop means is in said second position.

5. The feeding apparatus of claim 4, wherein the height of said feeders is sufficient to engage the trailing edge of a sheet whose length is less than 25 inches when said backstop means is in said second position.

6. Feeding apparatus for selectively feeding long and short sheets from beneath a stack and along a path of travel through a metering means, comprising: a feeding surface for supporting the leading edge of said stack adjacent said metering means; backstop means on said feeding surface for supporting the trailing edge of said stack above said feeding surface, said backstop means including: a laterally extending backstop bar positionable along said feeding surface at a distance from said metering means corresponding to the length of sheets to be fed; wedge supports spaced at intervals along said backstop bar each including a top surface inclined toward said feeding surface in the direction of said metering means; and backstops having inclined bottom surfaces corresponding to said top surfaces slidably secured to said wedge supports and having support ledges for supporting the trailing edge of said stack above said feeding surface at a distance corresponding to the position at which said backstops are secured along said inclined top surfaces; and mutually exclusive first and second feeding means selectively mountable to a slide means in said feeding surface for reciprocation thereby, said first feeding means reciprocable along said path of travel for sequentially advancing successive bottom sheets from beneath a stack of long sheets when said backstops are secured at substantially their maximum height along said inclined top surfaces, said first feeding means including: a laterally extending feeder bar including spring feeders secured at intervals therealong, said feeders including a sheet engaging surface spaced above said feeding surface a Distance sufficient to engage the trailing edge of the bottom sheet of said stack of long sheets; and said second feeding means reciprocable along said path of travel for sequentially advancing successive bottom sheets from beneath a stack of short sheets when said backstops are secured at substantially their minimum height along said inclined top surfaces, said second feeding means including: a laterally extending feeder bar including spring feeders secured at intervals therealong, said feeders including a sheet engaging surface spaced above said feeding surface a distance sufficient to engage the trailing edge of the bottom sheet of said stack of short sheets.

7. Feeding apparatus for selectively feeding long and short sheets from beneath a stack of sheets and along a path of travel through a metering means, comprising: a feeding surface for supporting the leading edge of said stack adjacent said metering means; backstop means on said feeding surface for supporting a trailing edge of said stack above said surface and being adjustable longitudinally from said metering means along said path for supporting sheets of varying length; said backstop means selectively adjustable between a first elevated position above said feeding surface and a second elevated position lower than said first position for supporting the trailing edge of a stack of long sheets above said feeding surface at said first position and for supporting the trailing edge of a stack of short sheets above said feeding surface at said second position; mutually exclusive first and second feeding means selectively mountable to a slide means in said feeding surface for reciprocation thereby, said first feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of long sheets through said metering means when said backstop means is in said first position, and said second feeding means reciprocable along said path for sequentially advancing successive bottom sheets from beneath a stack of short sheets through said metering means when said backstop means is in said second position, said backstop means including: a backstop support bar on said feeding surface extending along the width of said stack and adjustable longitudinally from said metering means a distance corresponding substantially to the length of sheets being advanced; wedge supports spaced at intervals along said support bar and including top surfaces inclined toward said feeding surface in the direction of said metering means; and backstops having inclined bottom surfaces corresponding to said inclined top surfaces and selectively secured thereto at said first or said second position, said backstops further including ledge supports for supporting the trailing edge of said stack at a height substantially corresponding to either said first or second positions.