Sheet-separating Apparatus

Abstract

This invention is directed to improved sheet-separating apparatus for enabling feeding of single sheets from a superimposed stack to adjacent sheet transport means. Desirably, single sheets are fed from the top of the stack by engagement by friction driving means. Fortuitous multiple feeds from the stack are separated by providing an inclined separating member in the path of the sheets having an irregular separating surface which cooperates with the leading edges of the fed sheets to releasably entrap them. Entrapment of the engaged sheet is overcome by the driving force of the friction driving means and only that sheet is moved past the separating member. Each of the other sheets are similarly engaged and successively moved past the separating member. The irregular surface may comprise such materials as velour or pile, flock, abrasive material, or tricot fabrics.

Description

FIELD OF THE INVENTION

This invention relates in general to apparatus for feeding sheet material one sheet at a time from a superimposed stack to associated sheet transport means. In particular, this invention relates to improved sheet separating apparatus for reliably separating sheet material fed from a superimposed stack, thereby enabling feeding of only one sheet at a time to adjacent sheet transport means.

DESCRIPTION OF THE PRIOR ART

A vexatious problem in copying and duplicating apparatus of the type wherein the copying medium comprises precut sheet material stored in superimposed stacked relationship, is to reliably deliver only one sheet of copy paper per operational cycle of the apparatus from the sheet stack to adjacent sheet transport means of the apparatus. Multiple feeds, that is, delivering more than one sheet from the stack to the transport means per operational cycle is extremely undesirable in view of the consequent waste, inefficiency, poor copying results, increased drying time, possible damage to the copying apparatus, and in general, overall customer inconvenience and dissatisfaction.

While many factors contribute to the problem of feeding multiple sheets, the primary factors are believed to be surface friction between adjacent copy sheets and the manner in which the sheet material is cut, stacked, and stored for eventual use in the copying apparatus. Surface friction is difficult to overcome regardless of the direction in which the sheets are being fed from the stack, but it is especially difficult to overcome when the sheets are fed in a direction parallel to the plane of the sheet surface and when movement of the sheet is accomplished by frictionally engaging a surface thereof, as by motor-driven feed wheels. The feed wheels tend to increase the surface friction between adjacent sheets since the frictional engagement on the surface of the sheet being fed also exerts a force normal to and through the sheet which is transmitted to the opposing surfaces of that sheet and the next adjacent sheet, thereby frequently causing the next adjacent sheet and additional sheets to be dragged or moved along with the sheet upon which the frictional force is imposed.

The frequency of additional sheets being dragged along with the sheet being fed is particularly critical at the sheet-feeding station of an electrostatic copying machine of the type wherein one surface of the copy sheet is coated with zinc oxide in a resinous binder to provide a suitable charge retention and charge dissipation layer. The coefficient of friction characteristics of this coating or layer has been found to greatly multiply the problems encountered in reliably feeding one sheet at a time to adjacent sheet transport means of the copier.

In the manufacture and packaging of copy sheet material such as the zinc oxide paper referred to above, the individual sheets are typically cut from a long web or a large sheet and piled or stacked together. When cutting the sheets to proper size, slightly ragged edges are often produced which cause the edges or sides of the cut sheets to cling together. Thus, when one sheet is removed from the superimposed stack during a feeding cycle, one or more additional sheets may also be removed and fed to the sheet transport system.

The adverse effects of the above factors may be partially alleviated by instructing users of the copying or duplicating apparatus to "fan" the leading edges of the copy sheets prior to inserting a fresh stack thereof into the feed station. The copy sheets are fanned by grasping the stack at the trailing edge and flipping the leading edge between a thumb and forefinger to separate any clinging, ragged edges and also to allow air to enter between adjacent sheet surfaces to decrease the surface coefficient of friction therebetween.

Recent advances in the copying-duplicating art and in marketing of paper supplies therefor, have lead to the use of prepackaged copy paper wherein the paper is supplied in a sealed cartridge or housing which is opened by the user as needed and placed directly into the feeding station of the copying apparatus, without the user touching or adjusting the stacked paper in any manner. Obviously, when supplying such prepackaged paper, the user is not expected to fan the stacked sheets in the manner described above. Thus, the potential for multiple feeds is greatly increased.

SUMMARY OF THE INVENTION

This invention obviates many of the above-mentioned problems and difficulties encountered in reliably feeding single sheets of copy paper from a superimposed stack to adjacent copy sheet transport means by providing a sheet-separating member in the path of the leading edges of the sheet material, but substantially forward of the front edge of the stack. The sheet separating member cooperates with each additional sheet which may have been prematurely fed from the stack by releasably entrapping the leading edges thereof, holding the sheets in a fixed position, and releasing the sheets one at a time for sequential movement to the adjacent sheet transport apparatus. The invention is particularly advantageous when using prepackaged, zinc oxide coated copy paper.

In accordance with the invention, the sheet-separating member is fabricated of a material having a rough, irregular surface which is disposed forwardly of the front edge of the stacked sheet material, but in the path of the leading edges thereof. In the event that more than one sheet is removed from the stack, the leading edges thereof, including the leading edge of the particular sheet which it is desired to feed, abut the separating member which entraps each of the fed sheets. However, the separating member is fabricated of a material having particular characteristics which allow the leading edge of the sheet being fed to escape its entrapment and to slide along the material in response to the frictional force exerted on it by the sheet-driving means. On the other hand, the entrapment of the next adjacent sheets is sufficiently firm to withstand the frictional dragging force exerted between the sheet being fed and the adjacent sheets to thereby prevent sliding movement of the leading edges of the latter sheets along the separating member. Thus, although a number of sheets may be displaced from the stack, only one sheet at a time will overcome the entrapment of the sheet-separating member and will be delivered to the sheet transport means.

As noted above, the separator member is fabricated of a material displaying an irregular, rough surface and may include pile materials such as silk and nylon velour; abrasive materials such as crocus cloth, sandpaper, emery paper and textured paint finishes; and oriented textile weaves such as tricot acetate.

Accordingly, the primary object of this invention is to provide means for feeding sheet material, one sheet at a time, from a superimposed stack to adjacent sheet transport means.

Another object of this invention is to provide means for reliably feeding single sheets of paper from a superimposed stack of prepackaged copy sheet material to adjacent sheet transport means, without previously fanning the leading edges of the sheet stack.

An additional object of this invention is to provide means for separating sheets of copy paper fed from a superimposed stack to adjacent sheet transport means by releasably entrapping the leading edge of each additional copy sheet fortuitously transported along with a given copy sheet, and to thereafter move only said given sheet while retarding movement of the additional sheets.

It is also an object of this invention to provide sheet-separating means for separating a number of sheets fortuitously removed from a superimposed stack along with a given sheet including a separator member for entrapping the leading edges of said sheets, wherein said separator member is fabricated of a material exhibiting a rough, irregular surface.

Additional objects of this invention will become apparent to those versed in the art upon an understanding of the following detailed description of the sheet-separating apparatus of the invention taken in conjunction with the accompanying drawings in which preferred embodiments of the invention are shown, and wherein:

FIG. 1 is an isometric view of an electrostatic copying machine incorporating the sheet-separating apparatus of the invention;

FIG. 2 is an enlarged top plan view of the feed shelf and sheet-separating apparatus of the invention with a superimposed stack of sheet material placed on the shelf;

FIG. 3 is an enlarged cross-sectional elevational view of the sheet-separating apparatus of the invention taken along section line 3--3 of FIG. 2;

FIG. 4 is a greatly enlarged cross-sectional elevational view of a portion of the sheet-separating apparatus shown in FIG. 3 illustrating a separator member 80 having a pile surface; and

FIG. 5 is a view similar to that of FIG. 4 but illustrating a different separator member 102 having an abrasive surface.

Referring now to FIG. 1 of the drawings, an electrostatic copying machine 10 is seen to include a centrally disposed copy-paper-feeding station 12 having a cartridge 14 containing a stack of prepackaged copy paper 16 and a lid 18 hinged to the machine at 20. The lid is shown in its open position for replacement of the copy paper but would be swung to its closed position for concealing the feeding station during normal operation of the machine. Single sheets of copy paper are desirably fed from the top of stack 16 into a nip formed by a pair of driven rollers 22-24 which comprise a portion of the sheet transport system, in accordance with the feed cycle program of the machine or responsive to insertion of an original document into the machine through a document entrance opening 26.

Referring now to FIGS. 2 and 3, sheet-feeding station 12 includes a horizontal shelf 27 supporting the cartridge 14 and its stack of prepackaged copy paper 16, and also includes cooperating sheet-feeding means 28 for desirably feeding the single sheets of copy paper from the top of the stack into the nip of rollers 22-24. Sheets fed from the stack are guided into the nip by a horizontally oriented, transversely extending upper guide wall 30 and a second, similarly extending lower guide wall 32. Wall 30 forms an acute angle with the plane of the paper stack while wall 32 forms an obtuse angle therewith. Thus, the walls are seen to converge in the direction of sheet travel and together define a throat 34 at the converging edges remote from the stack for facilitating accurate entrance of the copy sheet into the nip. Each of the copy sheets is subsequently transported through various processing stations of the electrostatic copier whereat the zinc oxide layer on the sheet surface is sequentially electrostatically charged, exposed to an image of the original document previously inserted into the document entrance 26, developed to produce a resultant image and finally dried if necessary and delivered to the operator.

The stack of sheet material 16 is positioned on shelf 27 in any suitable manner such as by providing lateral or side guides 36 rearwardly adjacent a forward edge 37 of the stack which are adjustable to accommodate different widths of copy paper. Adjustment of the side guides may be provided by thumbscrews 38 which cooperate with longitudinal slots 42 provided in a transverse member 44 of the frame. It should be noted that side guides 36 are not functional in separating the copy sheets but are merely loosely positioned adjacent the side edges of the stack for facilitating movement of the copy sheet in a straight forward direction without side skewing thereof.

Cartridge 16 per se is immovably secured on the shelf by a pair of upstanding posts 46 disposed on opposite lateral sides of the cartridge adjacent the rear thereof. Each post 46 carries an enlarged, knurled, circular head 48 forming a thumbscrew which partially overlies the cartridge top wall and which may be manually tightened into a threaded nut, not shown, beneath the shelf to firmly hold the cartridge in a fixed position. A number of different cartridges having various widths and lengths may be accommodated between posts 46 by manipulating them along V-shaped slots 50 formed in the shelf, and subsequently tightening thumbscrews 48.

Sheet feeding means 28 include a horizontal, laterally extending drive shaft 52 journaled in suitable bearings 54 carried by the machine sidewalls. Drive shaft 52 is disposed substantially above the paper stack and is intermittently driven at a uniform rate during one or more phases of each copying cycle by suitable motor means and a chain drive, not shown, housed interiorly of the copying machine.

Drive shaft 52 pivotally supports a pair of arms 56 and 58 journaled at their ends on the drive shaft by bearings 60 fabricated of nylon or other suitable material. Bearings 60 provide slippage between the drive shaft and the arms to prevent rotational movement of the shaft from being positively communicated to the arms. The bearings also allow the free ends of arms 56 and 58 to be lifted from the top surface of the copy sheet stack during replacement of the cartridge upon depletion of the copy paper, and further enable the arms to "ride" the stack as the copy sheet level is reduced. The free ends of arms 56 and 58 carry a short, horizontally disposed driven shaft 62 journaled in suitable bearings 64. Shafts 52 and 62 are drivingly coupled by a flexible timing belt 65 trained over a ribbed driving pulley 66 staked to shaft 52 and a driven ribbed pulley 68 staked to shaft 62.

A pair of copy paper feed wheels 69 fabricated of a material exhibiting a high coefficient of friction, such as soft neoprene, are captivated on the ends of shaft 62 outwardly of arms 56 and 58 by E-clips 70 placed on the shaft on each side of each wheel. The feed wheels are positioned rearwardly of leading edge 37 for frictional engagement with the uppermost shelf of the stack and are disposed generally equidistant from the lateral edges. Feed wheels 69 include hubs having integral, one-way roller bearing clutches, not shown, which enable shaft 62 to rotatably drive the wheels in a clockwise direction as viewed in FIG. 3, and also allow the wheels to rotate freely on shaft 62 in the clockwise direction when the copy sheet is under the control of driven rollers 22 and 24.

Referring specifically to FIGS. 3 and 4, in accordance with the invention a sheet-separating member 80 is provided in covering relation to a portion of wall 32. More specifically, separating member 80 is fabricated in two sections which are positioned on the surface of wall 32 facing the stack, in spaced apart relation on each side of the center thereof. The separating member is fabricated of a material which presents an irregular, rough surface 81 to the leading edges of the copy sheets. Separating member 80 may be fabricated integral with the surface of wall 32, or in as the illustrated embodiment, may comprise separate elements which are either secured to the wall surface by an adhesive or by other suitable means such as double sided adhesive tape.

In the embodiment illustrated in FIGS. 3 and 4, sheet-separating member 80 comprises a velour material, such as silk or nylon velvet, which is characterized by a pile surface 81 formed of many closely spaced upstanding bristles or fibers having inherent flexing capabilities. Other pilelike surfaces fabricated of fibers, such as flocked surfaces comprising short or pulverized fibers may also be employed.

During the feed portion of the copying cycle, feed wheels 69 are driven and an uppermost sheet 82 of stack 15 is displaced from the stack and moved forwardly towards transport rollers 22 and 24. However, due to the surface friction between the top sheet and the lower adjacent sheets, and due to the clinging ragged edges of the sheets, additional sheets such as sheets 84, 86 and 88 may be fed from the stack along with top sheet 82. When the copy sheets are fed from the stack, whether it be only the top sheet or the top sheet plus additional adjacent sheets, the leading edges of each sheet strikes the separating member 80 and becomes entrapped or captivated by the bristles or fibers forming the pile surface 81. Although the sheets are momentarily entrapped, the frictional engagement of feed wheels 69 on the top surface of sheet 82 is sufficient to continue driving its leading edge forward by bending or flexing the fibers, thus overcoming its entrapment. Additional movement of the leading edge allows it to ride along the separating member until it reaches the end thereof and is guided through throat 34 and into the nip of transport rollers 22 and 24.

On the other hand, the coefficient of friction between the lower surface of sheet 82 and the upper surface of the next adjacent sheet 84 is insufficient to enable the leading edge of sheet 84 to break loose from its entrapment by the fibers thus, sheet 84 as well as sheets 86 and 88 remain stationary while sheet 82 is moved to the transport roller. Prior to the next copying cycle, feed wheels 69 frictionally engage the upper surface of sheet 84 and the frictional engagement therebetween is sufficient to cause the leading edge of that sheet to flex the fibers and overcome its entrapment thereby moving to rollers 22 and 24. The action is repeated for each of the additional sheets 86 and 88 which were fed along with top sheet 82.

As best illustrated in FIG. 4, as a number of sheets strike the separating members, the surface fibers are forced between the leading edges of adjacent sheets to provide a space therebetween which reduces the coefficient of friction and facilitates removal of only the next top sheet.

It should be noted that in accordance with the invention specific means are not provided for limiting the removal of only one sheet from the top of the stack per operational cycle, but the consequence of feeding more than one sheet is immediately remedied by the above described cooperation of the leading edges of the removed sheets with the fiber surface of the separating member.

A pair of forwardly extending fingers 90 and 92 having downwardly curved ends 91 and 93 respectively are also pivotally mounted on shaft 52 by means of bearing collars 94 and 96 respectively. The bearing collars are retained in position on shafts 52 by E-clips 98 inserted in circular grooves provided in the shaft. Curved ends 91 and 93 extend over edge 37 of the stack and are supported thereon. The weight of the fingers on the sheets fed from the stack biases them downwardly to insure that the leading edges thereof strike the sheet-separating member. This function is particularly important when a full stack of paper has been placed in the feeding station, since the top of the stack may be above the level of the separating member.

While the above operation has been described with respect to a pile surface having fibers or bristles for entrapping the leading edges of a number of simultaneously fed sheets, other materials have also been found to function satisfactorily as a sheet-separating member.

Referring to FIG. 5, separating member 80 is replaced by a sheet-separating member 102 having a rough abrasive surface 103 fabricated of abrasive material such as crocus or sand particles having a grit size designation of approximately 100 mesh. When these abrasive materials are employed, the leading edges of the fed sheets are held by the small abrasive particles and the spacing between the leading edges at surface 103 is a function of the slope of wall 32 and the particle size.

Operationally, when a number of sheets have advanced so such that their leading edges engage surface 103, further rotational movement of feed wheels 69 advances the leading edge of top sheet 106, shown in phantom, with sufficient force to overcome the holding resistance of the abrasive material and advances the leading edge through throat 34 and into the nip of feed rollers 22-24. In the same manner as described above, the penultimate and lower adjacent sheets are prevented from moving due to their engagement with surface 103 and the lower coefficient of friction between the adjacent sheet surfaces. The remainder of the displaced sheets are fed in a similar manner.

In addition to the above-described materials, ribbed fabrics such as tricot acetate have been successfully employed as separating members. When using ribbed materials the ribs which in tricot are formed by the warp of the fabric, should be disposed on wall 32 so as to extend parallel the leading edge of the copy sheets.

It is important to note that proper operation of the separating member is not a function of the coefficient of friction of the material from which the member is fabricated since materials exhibiting a high coefficient of friction such as polyurethane, rubber foam, and urethane foam have been tried without significant success.

While the invention has been described in terms of copy sheet material supplied in prepackaged or cartridge form, it is obvious that the improved separating apparatus may also be employed when using unpackaged copy sheet materials.

It is obvious that upon study by those skilled in the art the disclosed invention may be altered or modified both in physical appearance and construction without departing from its inventive concept. Therefore, the scope of protection to be given this invention should not be limited by the embodiments described above, but should be determined by the essential descriptions thereof which appear in the appended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for separating sheet material fed from a superimposed stack comprising: shelf means supporting said stacked sheet material; driven means engaging the uppermost sheet of said stacked material for imparting movement thereto and fortuitously imparting movement to a plurality of additional sheets in a direction generally parallel to the plane of said stack thereby displacing said sheets from the stack, and sheet-separating means disposed in the path of movement of the leading edges of said displaced sheets forwardly of said stack and inwardly of the sheet lateral edges for cooperating only with said leading edges of said displaced sheets comprising a pile surface having short fibers for entrapping said uppermost sheet and each of said additionally fed sheets and wherein said fibers enter beneath the lowermost corner of the leading edges of said uppermost sheet and said additional sheets thereby forming a space therebetween for releasably entrapping said sheets.

2. The sheet-separating apparatus as set forth in claim 1 including additionally: a wall inclined away from said stack in the direction of sheet movement and presenting a surface disposed in the path of movement of said displaced sheets, and wherein said pile surface comprises a velour pile covering over at least a portion of the wall surface having closely spaced upstanding, flexible fibers capable of individually entrapping and separating the leading edges of said displaced sheets, said fibers flexing responsive to the force exerted by said driven means on the engaged sheet thereby causing said engaged sheet to overcome its entrapment.

3. The sheet-separating apparatus of claim 2, wherein said wall surface forms an obtuse angle with the plane of said stack.

4. Apparatus for delivering sheet material, one sheet at a time from a superimposed stack thereof to associated sheet transport means comprising: shelf means supporting said stacked sheet material with its leading edge spaced from said sheet transport means; driven means engaging the uppermost sheet of said stacked material for imparting movement to said uppermost sheet in the direction of said sheet transport means thereby displacing said uppermost sheet from the stack; a pair of horizontally extending walls having vertically inclined wall surfaces converging in the direction of sheet movement and forming a throat for guiding the sheets to said sheet transport means; the lower one of said horizontal walls being disposed in the path of movement of the leading edge of said uppermost sheet, at least a portion of the surface of said lower wall being covered with a pile material having short flexible fibers for entrapping said uppermost sheet and any additional sheets of said stack fortuitously displaced from said stack with said uppermost sheet and captivating said displaced sheets by said flexible fibers entering beneath the lowermost corner of the leading edges thereof in a manner whereby engagement of said uppermost sheet by said driven means affects movement of only that sheet over said surface and towards the transport means.

5. The sheet-separating apparatus as set forth in claim 4 wherein said pile surface comprises a velour pile covering at least a portion of said lower wall inwardly of the lateral edges of said sheet.

6. The sheet-separating apparatus of claim 5, wherein said lower wall forms an obtuse angle with the plane of said stack of sheets.