US3737051A

US3737051A - Apparatus for aligning edges of stacked sheets in the vertical direction

Info

Publication number: US3737051A
Application number: US00216063A
Authority: US
Inventors: S Horino
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1972-01-07
Filing date: 1972-01-07
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05

Abstract

In apparatus for aligning edges of stacked sheets in the vertical direction there are provided a supporting member for supporting a stack of sheets, a casing movable toward and away from the supporting member, a rectangular frame contained in the casing, the rectangular frame including four side plates adapted to face four side surfaces of the stack, means for adjusting inwardly and outwardly at least two adjoining side plates to vary the internal area of the rectangualr frame, and means for vibrating at least two adjoining side plates in directions perpendicular thereto for aligning the edges of the stack of sheets in the vertical direction.

Description

United, States Patent Horino June s, 1973 APPARATUS FOR ALIGNING EDGES OF STACKED SHEETS IN THE VERTICAL DIRECTION Inventor: Shigeo Horino, Tokyo, Japan Assignee: Tokyo Shibaura Electric Co., Ltd.,

Kawasaki-shi, Japan Filed: Jan. 7, 1972 Appl. N0.: 216,063

[52] U.S. Cl ..214/6 S, 259/DIG. 42, 271/89 [5]] Int. Cl ..B65g 57/00 [58] Field of Search .2l4/6 R, 6 S, 6 D, 214/6 G, 6 H, 6 S, 8 R; 271/89; 259/DlG. 42

[56]" References Cited UNITED STATES PATENTS 1,141,277 6/1915 Smith ..271/89 X 2,788,131 4/1957 Bergstrom et al. ..271/89 X Primary Examiner-Robert J. Spar AttorneyRobert D. Flynn, Stephen H. Frishauf.

Leonard Holtz et al.

[57] ABSTRACT In apparatus for aligning edges of stacked sheets in the vertical direction there are provided a supporting member for supporting a stack of sheets, a casing movable toward and away from the supporting member, a rectangular frame contained in the casing,

the rectangular frame including four side plates adapted to face four side surfaces of the stack, means for adjusting inwardly and outwardly at least two adjoining side plates to vary the internal area of the rectangualr frame, and means for vibrating at least two adjoining side plates in directions perpendicular thereto for aligning the edges of the stack of sheets in the vertical direction.

16 Claims, 14 Drawing Figures PATENTEDJUH 51975 3137051 SHEET 2 0F 6 FIG? 3 PATENTEUJUH 5 ms SHEET 0F 6 FIG. 7

: llll ll FIG. 8

PATENIEDJUH 5 197a SHEET 5 OF 37b 37m 37:32 37b3 FIG. 10

FIG. 11

. PATENTEUJUH 5|975 3.737.051

SHEET 8 OF 5 FIG. 12A 1({Dd FIG. 12B 10d L This invention relates to apparatus for aligning in the vertical direction of the edges of sheets of paper, more particularly thin and pliable sheets which are piled up I one upon the other.

It has been desired to provide apparatus capable of classifying at a high efficiency a plurality of post cards according to their addresses and then binding a predetermined number of piled up sheets into a bundle or for counting and checking the genuineness of a plurality of relatively pliable sheets and paper sheets that have been imparted with a tendency of folding back upon themselves during their use and then binding a predetermined number of such sheets into a bundle. Among the paper sheets that can be processed by the apparatus of this invention are included postcards, checks, paper moneies, certificates and the like. Hereinafter, these sheets of paper are merely called sheets or sheet. It is desirable to neatly pile up these sheets with their side and or end edges aligned in the vertical direction. Since post cards or the like are relatively stiff, it is possible to align their end edges in the horizontal direction while maintaining the surface of each sheet in the vertical plane. However, as the checks or the like are relatively pliable it is necessary to pile up them one upon the other while aligning their end or side edges in the vertical direction. Until today, however, no satisfactory apparatus has been proposed that can efficiently and neatly align the edges of such pliable sheets in the vertical direction.

Accordingly, it is an object of this invention to provide efficient apparatus that can neatly align the edges of relatively pliable sheets which are piled up one upon the other.

Another object of this invention is to provide apparatus for successively conveying a plurality of stacks of sheets onto a supporting member and for aligning the edges of the stack of sheets in the vertical direction while the stack is supported by the supporting member.

According to this invention, in apparatus for aligning edges of stacked sheets in the vertical direction there are provided a supporting member for supporting a stack of sheets, a casing movable toward and away from the supporting member, a rectangular frame contained in the casing, the frame including four side plates adapted to face the four side surfaces of the stack, means for adjusting inwardly and outwardly at least two adjoining side plates to vary the internal area of the rectangular frame, and means for vibrating at least two side plates in directions perpendicular thereto for aligning the edges of the stack of sheets in the vertical direction. Since the sheets are relatively loosely stacked one upon the other, when their side and end edges are subjected to the vibration applied by two adjoining side plates of the rectangular frame which are driven by the vibrating means, the displaced sheets are returned to the center of the stack thus neatly aligning the edges of the stacked sheets. As the side plates of the rectangular frame are moved inwardly while being vibrated or after vibrated, the displaced sheets can be well aligned. Each side plates may be supported by the casing to freely displace or vibrate perpendicular thereto. Opposite ends of each side plates may be shaped in the form of combs and the teeth of adjoining side plates are interfitted so as to permit the adjoining side plates to move inwardly or to vibrate in the direction normal thereto. Eccentric cams are positioned to be subtended by the extensions of the teeth so that as the eccentric cams are rotated the side plates are vibrated. The eccentric cams are moved along arcuated grooves to move inwardly the side plates of the rectangular frame for varying the internal area thereof.

Air may be admitted into the rectangular frame for separating adjacent sheets by thin layers of air thus facilitating the displacement thereof and hence more neatly aligning the edges of the stacked sheets.

The casing may be provided with means for separating the conveyor belt from the stack of the sheets supported by the supporting member when the casing is brought close to the supporting member, and for conveying again aligned stack of the sheets when the casing is brought away from the supporting member, thus permitting continuous running of the conveyor belt.

The state of the stack of sheets after aligning their edges may be checked by means of photoelectric means which operates once more the aligning mechanism when the edges of the stacked sheets are not well aligned.

Where the displacement of the stacked sheets is excessive, the sheets are aligned preliminary and then subjected to the automatic aligning operation.

The present invention can be more fully understood from the following detailed description when taken in conjunction with reference to the appended drawings, in which:

FIG. 1 is a perspective view of the essential elements of one embodiment of the invention,

FIG. 2 is a plan view of the movable aligning device showing the case wherein the rectangular frame mounted in a casing is expanded;

FIG. 3 shows a similar view as FIG. 2 but the rectangular frame has been contracted;

FIG. 4 shows a sectional view taken along a line 4-4 in FIG. 1 and showing the inside construction of the casing;

FIG. 5 is a cross-sectional view taken along a line 5--5 in FIG. 4;

FIG. 6 is a perspective view of the rectangular frame shown in FIG. 4 and ventilating device for supplying an air stream into the rectangular frame;

FIG. 7 is an elevational view of the elements shown in FIG. 1 as viewed in the direction perpendicular to the conveyor showing a pile of sheets conveyed onto a supporting member;

FIG. 8 is a front view showing the movable aligning device containing the pile of sheets and mounted on the supporting member;

' FIG. 9 shows an elevation of the vibrating device for the mounting member shown in FIG. 7;

FIG. 10 shows a block connection diagram of a primary detector for detecting the deviation of individual sheets conveyed to the position beneath the movable aligning device;

FIG. 11 shows a block connection diagram of a sec ondary detector for detecting the deviation of the individual sheets contained in the movable aligning device;

FIGS. 12A and 12B show the manner of piling up the sheets that have been conveyed to the movable aligning device; and

FIG. 12C is a perspective view of a stack of neatly piled up sheets.

FIG. 1 shows apparatus for aligning ends of sheets randomly piled up one upon the other and have been conveyed to the apparatus by means of a conveyor. A pile of sheets is conveyed in a direction indicated by arrow 22 by means of three parallel conveyor belts 11. When the pile is brought onto a supporting member 12 positioned below the conveyor belts 11, a movable aligning device 13 is descended for depressing downwardly belts 11 away from the lower side of the stack of sheets by means of six rollers 14 rotatably mounted on the bottom of the movable aligning device 13. In FIG. 1, only three rollers 14 on one side are shown but it is to be understood that another three rollers are mounted on the opposite side. Then, the belts 11 are caused to travel through grooves 15 of the supporting member 12, and the stack of the sheets is supported by the raised ridges 16 between the grooves 15 and surrounded by the casing of the aligning device 13. The edges of the sheets contained in the aligning device is then aligned in the vertical direction by the aligning mechanism contained in the aligning device in a manner to be described later. The movable aligning device 13 is provided with a projection 18 adapted to slide in a groove 17a of a stationary guide 17. The aligning device 13 is moved in the vertical direction by a driving belt 19 having one end connected to the movable alinging device on the side opposite the projection 18. The belt 19 passes around a guide roller 20a and is taken up by a take up roller 20b driven by a driving motor 20 which is controlled by a control signal from a control device, not shown. As shown by the sectional view shown in FIG. 4, the movable aligning device 13 comprises a rectangular casing 21 containing a rectangular frame 23 including four

side plates

23a, 23b, 23c and 23d. Each side plate is provided with a stub shaft 24 and is biased outwardly by a pair of springs 25. The outer ends of stub shafts are slidably received in respective sleeve bearings 26 secured to the

respective side walls

21a, 21b, 21c and 21d of the casing 21. The outer ends of the springs are also connected to the inner sides of the side walls of the casing.

Each end of the side plates of frame 23 is formed in the form of a comb, as shown in FIG. 6 and the teeth 27 of adjoining side plates are interleaved so that the adjoining side plates can be displaced or vibrated in the direction normal to the surfaces thereof.

Eccentric cams

29a, 29b, 29c and 29d, each having a driving shaft 28, are subtended by the teeth 27 of adjoining side plates. An air stream rectifying chamber 30 forming a part of a ventilating device is secured to the outer side of side plate 23a, and a flexible air pipe 31 extends through side wall 21a of the casing 21 for supplying air into chamber 30. As shown by dot and dash lines, the pile of the sheets 10 supported by the supporting mem' ber 12 is housed in rectangular frame 23.

Individual sheets

10a, 10b, 10c, 10d of the pile are randomly slacked, that is their edges are not well aligned in the vertical direction.

As shown in FIG. 5, the shaft 28 of each eccentric cam 29 extends upwardly through the upper wall 21c of casing 21 for mounting

pulleys

34a, 34b, 34c and 3411, respectively. A driving motor 35 is mounted upon the rear side wall 210 of casing 21 through bracket 35a for driving these pulleys through pulley 35b secured to the motor shaft and a expandable and contractable belt 36. A plurality of

electric lamps

37 and 38 forming a portion of a detector for detecting the state of aligning of the sheets (to be described later) are mounted on the inner side of the upper wall 21e of the casing 21.

As shown in FIG. 6, the side plate 23a connected to the air stream rectifying chamber 30 is provided with a plurality of perforations 39 for admitting air into the rectangular frame 23. Similar air discharge perforations 40 are formed through opposite side plate 23b.

As shown in FIGS. 2, 3 and 5, driving shafts 28 of

eccentric cams

29a, 29b and 290 are rotatably mounted on one ends of

arms

42a, 42b and 420, respectively, and are slidably received in respectivearcuate slots 41 formed through upper plate 21e of the casing 21. The inner ends of the

arms

42a, 42b and 42c are pivotally mounted on pins 33 secured to the upper plate 21e. In order to simultaneously rotate

arms

42a, 42b and 420 about pins 33, one ends of three cords 43 are connected to respective arms 42 and the other ends are connected to the periphery of a take-up roller 45 supported by a pin 44 secured to the upper plate 21e. By driving the take-up roller 45 by means of a driving motor (not shown), the rectangular frame 23 is contracted to have smaller area shown in FIG. 3 from the expanded state shown in FIG. 2. Under the contracted state, flexible belt 36 assures positive drive of eccentric cams 29a to 29:: through pulleys 34a to 34d.

As shown in FIG. 7, endless belts 11 pass around guide rollers 46 to convey the stack of the sheets 10 in a direction of arrow 22. A source of light 47a and a light receiver 47b of a sheet detector 47 are positioned on the opposite sides of the conveyor. The electric signal generated by detector 47 is applied to electric motor 20(FIG. 1) via a control device, not shown, to descend casing 21 toward supporting member 12 when the stack of sheets 10 is brought to a position just above the supporting member 12. The descending speed of casing 21 is made sufficiently larger than the speed of the conveyor belt 11 so that casing 21 can contain the stack of sheets 10. As will be described later, the edge aligning operation is performed while belts 11 are continuously running so that it is desirable to delay the signal generated by detector 47 such that the casing 21 is descended when the stack of the sheets is brought to the position just above the supporting member 12. As the casing 21 is brought close to the supporting member 12, six grooved rollers 14 depresses downwardly belts 11 into respective grooves 15 whereby the stack of the sheets 10 is directly mounted on the supporting member 12.

Then, the stack of the sheets 10 is contained in the rectangular frame 23 and the edges of the sheets are aligned in the vertical direction by the vibration imparted to side plates 23a to 23d and by the inward displacement of

side plates

23a and 23d in a manner to be described later.

As diagrammatically shown in FIGS. 12A and 12B,

respective sheets

10a, 10b, 10c, 10d of the stack are randomly piled up so that their side edges and end edges are not aligned in the vertical direction. In the case shown in FIG. 12A,

sheets

10b and 10c are so heavily displaced that they can not be aligned by the operation of movable aligning device. In this case, motor 20 is controlled such that it does not descend casing 21 toward the supporting member 12 by the first stack condition detector described later. In another cases, the casing 21 is descended to align the sheets in the vertical direction. However, where the sheets are not satisfactorily aligned by a single aligning operation as shown in FIG. 12B, this state is detected by the sec- 11 are released to convey the aligned stack of thesheets in the direction of arrow 22.

As shown in FIG. 10, the first stack state detector 37 comprises two

light sources

37a and 37b (also shown in FIGS. 5 and 7), light receivers 37a and 3712 cooperating with light sources 37a and 3711, respectively,

amplifiers

37a and 37b,,

inverters

37a and 37b;,, an AND circuit 37c with its inputs 37a and 3712 connected to the output terminals of

inverters

37a and 37b and an amplifier connected to the output of amplifier 37d. Theoutput from amplifier 37d is applied to motor 20 via the control device, not shown. The spacing between

light sources

37a and 37b amplifier 38fwould become 1. When the output 38g from amplifier is 1, motor 35 and take-up rollers 45 are driven. Alternatively, at first motor 35 is driven and then take-up roller 45. As the motor 35 is driven, four eccentric cams 29a through 29d are rotated so as to vibrate

side plates

23a and 23b in the lateral direction and

side plates

23c and 23d in the longitudinal direction as shown by arrows 48a to 48d in FIG. 6. The vibrations imparted to these side plates strike the side and end edges of the sheets so as to preliminary align them in the vertical direction. The state of stack of the measured in the direction of arrow 22 (FIG. 1) is determined by taking into consideration a desired longitudinal length of the stacked sheets. Where it is desired to detect whether the side edges of the stacked sheets are placed within a predetermined distance another circuit identical to that shown in FIG. 10 is added. If the length of the sheet stack were longer than the distance between

light sources

37a and 37b, the outputs from

light receivers

37a and 37b would become momentarily 0. Accordingly, the

outputs

37a and 37b,, would be I and the output of amplifier 37d would also be l As a result, motor 20 is controlled so as not descend casing 21. In this case, excessively displaced sheets such as 10b and 10c (FIG. 12A) may be aligned manually.

As shown in FIG. 11, the second stack state detector 38 comprises four

light sources

38a,

38b

38c and 38d (also shown in FIGS. 5 and 7),

light receivers 38a

38b,, 38c,, and 38d, cooperating with the light sources, amplifiers 3811,,

38b

38c and 38d, inverters 38a 38b 38c and 38:1 an OR circuit 382 connected to receive the

outputs

38, 38b, 38c and 38d, of respective inverters and an amplifier 38] connected to the output of the OR circuit. As before, the spacing between

light sources

38a and 38b is determined in accordance with a desired. longitudinal length of the sheet stack, whereas that between

light sources

38c and 38d is determined in accordance with a desired width of the sheet stack. However, these spacings are selected to be smaller than corresponding light source spacings of the first stack state detector 37. The output 38g from amplifier 38f is applied to a control device (not shown) for motor 35 and take-up roller 45 shown in FIG. 2.

In a case where one or more of the sheets 10 contained in the rectangular frame 23 are displaced in the direction of conveyance more than a predetermined value, the light from at least one of

light sources

38a and 38b is intercepted by the sheets so that the

inverted output

38a or 38b, from at least one of the inverters 38a, and 38kg will become I as well as the output 383 from amplifier 38f. In the same manner, in a case when one or more sheets are excessively desplaced in the lateral direction, the light from at least one of

light sources

380 and 38d will be intercepted by the sheets so that the

inverted output

38c, or 38d, from at least one of

inverters

380 and 38d, and the output 383 of preliminary aligned sheets is checked by the second stack state detector 38 so as to realign the sheets by the operation of the aligning device. As shown in FIG. 2, the shafts 28(FIG. 5 for rotating eccentric cams 29a to 29c are movable along slots 41 through upper plate 21a of the casing and since these shafts are mounted on rotatable arms 42a to 42c, when cords 43 are wound about take-up roller 45 it is possible to displace eccentric cams 29a to 290 along arcuate sl0ts 4l. By this movement of eccentric cams 29a to

29d side plates

23a and 23d are moved inwardly to decrease the internal area of the rectangular frame 23. Since springs 25 shown in FIG. 4 normally act to urge outwardly the side plates, thus assisting vibration of respective side plates caused by the rotation of eccentric cams 29a to 29d.

As the internal area of the rectangular frame 23 is decreased, the inner surfaces .of respective side plates thereof continue to strike the side and end edges of the sheets, thus more neatly align the sheets as shown in FIG. 120. FIG. 3 shows the reduced internal area of the rectangular frame 23. In FIG. 3, the sheets are not shown for the sake of brevity.

While the edges of the stacked sheets are subjected to the vibrating action, it is desirable that the sheets are loosely piled up one upon the other. To this end, it is advantageous to supply parallel air streams between adjacent sheets from air conduit 32 through air rectifying chamber 30 mounted on the outer side of side plate 23a. More particularly, air under a relatively low pressure is admitted into the rectangular frame 23 through a plurality of perforations 39 of side plate 23a. Then the air is passed through the gaps between adjacent sheets and is discharged through perforations 40 of side plate 23b. Thus, adjacent sheets are separated by a thin air layer, thereby reducing the friction between sheets and efficiently aligning the same in the vertical direction.

The aligning action of the stack of sheets may be enhanced by vibrating the supporting member 12 in the vertical direction. FIG. 9 shows one example of the vibrating device comprising eccentric rollers 50 which are maintained in contact with the lower surface of supporting member 12. The shaft 52 for supporting the eccentric rollers 50 is rotated by a pulley 53 and a belt 54.

In the arrangement shown in FIG. 6 it is also possible to vibrate only two adjoining

side plates

23a and 23d, for example, and to make remaining two

side plates

23b and 23c to reciprocate. Alternatively, it is also possible to vibrate and reciprocate two adjoining side plates and to hold stationary remaining two side plates.

Although the invention has been shown and described in terms of a preferred embodiment thereof, it will be clear that many changes and modifications are obvious to those skilled in the art without departing.

from the true spirit and scope of the invention as defined in the appended claims.

gular frame contained in said casing, said frame includ-' ing four side plates adapted to face four side surfaces of said stack; means for adjusting inwardly and outwardly at least two adjoining side plates to vary the internal area of said rectangular frame; and means for vibrating at least two adjoining side plates in directions perpendicular thereto for aligning the edges of said stack of sheets in the vertical direction.

2. Apparatus as claimed in claim 1 wherein each of said side plate of said rectangular frame is provided with an outwardly projecting shaft which is journalled by a bearing secured to the inside of said casing.

3. Apparatus as claimed in claim 1 wherein means is provided for supporting at least two adjoining side plates of said rectangular frame in said casing to be movable inwardly and outwardly and to be vibratable.

4. Apparatus as claimed in claim 1 wherein each end of said side plates of said rectangular frame is shaped in the form ofa comb, and the teeth ofa pair of adjoining side plates are interleaved for permitting the same to move relatively to vary the internal area of said rectangular frame or to vibrate in the direction normal to the surface thereof.

5. Apparatus as claimed in claim 1 wherein each end of said side plates of said rectangular frame is shaped in the form of a comb and the teeth of a pair of adjoining side plate are interleaved for permitting the same to move relatively to vary the internal area of said rectangular frame, and wherein said vibrating means includes eccentric cams and their driving means, said eccentric cams being respectively positioned in a space subtended by the protruding portions of said interleaved teeth of said adjoining side plates and being rotated in contact with said protruded portions of said teeth.

6. Apparatus as claimed in claim 5 wherein said driving means of said eccentric cams comprises pulleys mounted upon the shafts of said cams, a driving belt passing around respective pulleys, and means for driving said belt.

7. Apparatus as claimed in claim 5 wherein said driving'means of said eccentric means further comprises a plurality of swinging arms, one end of each swinging arm being pivotally mounted on said casing and the other end rotatably supporting said eccentric cam, a plurality of cords, end of each cord being connected to one swinging arm, and a take-up roller connected to the other ends of said cords for wrapping the cords thereabout thereby to displace said eccentric cams with respect to said side plates for varying the internal area of said rectangular frame.

I 8. Apparatus as claimed in claim 5 wherein each side plate of said rectangular frame is biased outwardly by means of spring means interposed between said side plate and said casing, said spring means cooperating with said eccentric cam for vibrating said side plate.

9. Apparatus as claimed in claim 7 wherein said driving means of said eccentric cams includes a flexible belt passed around the pulleys for driving said eccentric cams, said belt being expandable and contractable in r the longitudinal direction.

10. Apparatus as claimed in claim 1 which further includes ventilating means for passing air streams between adjacent sheets of said stack, and wherein one of said side plates of said rectangular frame is provided with a plurality of perforations for admitting said air streams into said rectangular frame.

11. Apparatus as claimed in claim 10 wherein another side plate opposed to said one side plate is provided with a plurality of perforations for discharging the air from said rectangular frame.

12. Apparatus as claimed in claim 1 wherein said supporting member includes a plate member and means for vibrating said plate member in a direction perpendicular to the surface of said plate member.

13. Apparatus as claimed in claim 1 which further includes a conveyor for conveying said stack of sheets onto said supporting member, means for driving said casing toward and away from said supporting member, a detector associated with said conveyor for depositing said stack of sheets on said supporting member and means responsive to an electric signal generated by said detector for controlling said aligning device so as to align said sheets in the vertical direction.

14. Apparatus as claimed in claim 13 wherein said conveyor includes a plurality of spaced apart parallel belts for conveying said stack of sheets, said casing includes means for separating said belts away from said stack of sheets when said stack is mounted on said supporting means and wherein said supporting member includes a plurality of parallel. grooves adapted to receive said belts when they are separated from said stack of sheets and raised ribs extending above said grooves for supporting said stack-of sheets.

15. Apparatus as claimed in claim 13 which further includes a first stack state detector for detecting the displacement of said stacked sheets, said stack state detector generating an electrical signal which is supplied to said casing driving means for preventing said casing from approaching to said supporting member when said displacement of said sheets exceeds a first predetermined value.

16. Apparatus as claimed in claim 15 which further includes a second stack state detector for detecting the displacement of said sheets after the edges of said sheets have been aligned in the vertical direction by an aligning mechanism contained in said casing, said second stack state detector generating a second electric signal when the displacement of said sheets exceeds a second predetermined value, said second electrical signal being applied to said vibrating means for realigning the edges of said sheets in the vertical direction.

* i i i

Claims

1. Apparatus for aligning edges of stacked sheets in the vertical direction comprising a supporting member for supporting a stack of sheets; a casing movable toward and away from said supporting member; a rectangular frame contained in said casing, said frame including four side plates adapted to face four side surfaces of said stack; means for adjusting inwardly and outwardly at least two adjoining side plates to vary the internal area of said rectangular frame; and means for vibrating at least two adjoining side plates in directions perpendicular thereto for aligning the edges of said stack of sheets in the vertical direction.

4. Apparatus as claimed in claim 1 wherein each end of said side plates of said rectangular frame is shaped in the form of a comb, and the teeth of a pair of adjoining side plates are interleaved for permitting the same to move relatively to vary the internal area of said rectangular frame or to vibrate in the direction normal to the surface thereof.

7. Apparatus as claimed in claim 5 wherein said driving means of said eccentric means further comprises a plurality of swinging arms, one end of each swinging arm being pivotally mounted on said casing and the other end rotatably supporting said eccentric cam, a plurality of cords, end of each cord being connected to one swinging arm, and a take-up roller connected to the other ends of said cords for wrapping the cords thereabout thereby to displace said eccentric cams with respect to said side plates for varying the internal area of said rectangular frame.

8. Apparatus as claimed in claim 5 wherein each side plate of said rectangular frame is biased outwardly by means of spring means interposed between said side plate and said casing, said spring means cooperating with said eccentric cam for vibrating said side plate.

9. Apparatus as claimed in claim 7 wherein said driving means of said eccentric cams includes a flexible belt passed around the pulleys for driving said eccentric cams, said belt being expandable and contractable in the longitudinal direction.

14. Apparatus as claimed in claim 13 wherein said conveyor includes a plurality of spaced apart parallel belts for conveying said stack of sheets, said casing includes means for separating said belts away from said stack of sheets when said stack is mounted on said supporting means and wherein said supporting member includes a plurality of parallel gRooves adapted to receive said belts when they are separated from said stack of sheets and raised ribs extending above said grooves for supporting said stack of sheets.