WO2000051926A2

WO2000051926A2 - Feeder apparatus for documents and the like

Info

Publication number: WO2000051926A2
Application number: PCT/US2000/005540
Authority: WO
Inventors: Tomasz K. Bednarek; Jose S. Pioquinto; Werner R. Lightner; Donald J. Stefanich; Jim T. Russo; Paul E. Brodzik; John V. Schiralli
Original assignee: Bell & Howell Company
Priority date: 1999-03-04
Filing date: 2000-03-02
Publication date: 2000-09-08
Also published as: WO2000051926A3

Abstract

The invention is a sheet feeder (10) including a skimmer (21), a bumper (68), a separator (19), and a guide plate (66, 81). The skimmer element (21) can be laterally reciprocated to assist in separation of the top sheet (44) from lower sheets in a stack (43). The bumper (68) extends across the feed path (14) and has a guide surface (84) positioned to confront the leading edges of the sheets (44) of the stack and direct the leading edge of an advancing engaged single sheet (44) away from the remainder of the stack (43). The separator (19) is designed for advancing the engaged sheet (44) while retarding any adjacent sheets. In one embodiment, a friction roller (34) and a stationary friction element (77) grip the engaged sheet between them. In another embodiment, the separator (19) has a driven advancing roller (34) nipped with a driven retarding roller (36) coupled to its drive (1605) by a friction clutch (1603). The clutch (1603) normally slips and permits the retarding roller (36) to be driven forward by the advancing roller(34). The clutch (1603) engages and drives the retarding roller (36) backward so long as a multifeed of two or more sheets is engaged between the advancing and retarding rollers (34, 36). The guide plate (66, 81) extends between the skimmer (21) and the separator (19), preventing the sheet from buckling.

Description

TITLE OF THE INVENTION FEEDER APPARATUS FOR DOCUMENTS AND THE LIKE

BACKGROUND OF THE INVENTION

The present invention relates to automated sheet feeder apparatus for scanning equipment and the like, and more particularly to a configuration that facilitates document separation and spacing for use with universal document feeder apparatus associated with high-speed image scanning equipment requiring high-volume document throughput.

Automated high-speed image scanning equipment utilizes an imaging device to scan the images from an input or source document. Such equipment must feed and transport documents to the imaging device quickly, smoothly, and automatically, and must be trouble-free. The feeding equipment must quickly and smoothly feed each original document or individual sheet from the backlog queue of input or source documents waiting to be scanned to the transport apparatus. The transport apparatus then brings each document or sheet to the imaging device. To achieve high- volume throughput, the high-volume feeder apparatus must be able to supply the individual documents or sheets in a spaced relationship to the input section of the transport apparatus in a manner that is completely reliable and trouble-free.

A problem associated with high-speed image scanning equipment found in the prior art is that the individual source or input documents commonly are not standardized. They vary in shape and size, and come in a variety of different thicknesses (e.g., sheets ranging from an onionskin thickness to thick card stock). This mandates that each non-uniform document be processed or handled in a uniform manner. Another related problem is that, in the majority of instances, the input or source document is an original document or a document that is not easily replaced. It becomes imperative that the document feed mechanism not damage any of the source documents under any circumstances.

A persistent problem found in the prior art is the more or less random feeding of multiple documents at one time by the document feed mechanism, rather than a single sheet. The problem is commonly referred to, by those skilled in the art, as the "multi-feeds" problem. The multi-feeds problem is made even more critical when a high-volume document throughput is required for high-speed image scanning equipment and the like. In such situations, the individual source documents waiting to be scanned are in a stack, and either the top or bottom document is fed sequentially to the image scanner by the document feed mechanism.

A number of variables are supposedly responsible for this negative result, including but not limited to the weight of the skimmer roller assembly (which rests on top of the first document in the stack of documents waiting to be scanned), the underlying dynamics of the friction that the bottom and top sheets experience as the document feed mechanism accelerates the next sheet from the stack forward, and the spacing required between individual documents as documents enter the document feed mechanism and are sequentially processed.

Yet another common problem with certain document feed mechanisms for high-speed image scanning equipment and the like found in the prior art is that, over time, this equipment will occasionally cause bottlenecks and/or jam-ups of downstream equipment, having an obvious negative effect on overall document throughput. Sometimes the problem can be corrected by timely maintenance of the document feed mechanism. High-speed image scanning equipment that provides for high-volume document throughput necessitates a reliable document feed mechanism that is easy to maintain and is capable of fulfilling document throughput requirements.

A particular prior device currently in use employs a relatively narrow skimmer roller at the entrance to the feeder together with an adjustable separate weight that causes the skimmer roller to grip the paper. The prior device also uses a pair of counter-rotating shafts with interleaved roller portions that are designed to advance the top page while retarding any adjacent or lower pages. Finally, in that device there is space between the skimmer roller and the interleaved forwarding and reversing rollers. Sheets being fed sometimes buckle or bunch up in that space. The counter- rotating shafts are set an adjustable distance apart. The inventors have found that this arrangement results in paper jams and multifeeds when stacks of documents with different thicknesses are introduced.

Another prior commercial device utilizes a driven advancing roller nipped with a retarding roller coupled by a brake assembly to a fixed shaft. The advancing roller urges one face of the sheet forward, while the retarding roller acts as a drag on the opposite face of the sheet. If multiple sheets pass between the advancing and the retarding rollers, the advancing roller will urge the first sheet forward and the retarding roller will drag on the other sheet. Since the friction between the retarding roller and the sheet is higher than the friction between two sheets, the retarding roller will prevent the passing of the lower sheet. While this is not a "reversing" roller per se, but rather a simple "drag" on the lower of two adjacent sheets, it tends to separate the two while the upper sheet passes through the gap under the drive of the advancing roller. The inventors have found that this invention, however, could not resolve the problem of multi-feed of three or more sheets at a time.

Also in the prior art are various arrangements for the retarding roller. The first of these is an earlier development in which a retarding roller is mounted on a fixed shaft and has a peripheral rubber surface that frictionally engages the peripheral outer surface of the advancing roller or the sheet between the rollers. A tubular coil spring is attached at one end to the retarding roller and wrapped around the fixed shaft. When the advancing roller moves in the forward direction, the friction between the outer surfaces of the retarding and advancing rollers urges the retarding roller forward, thus tending to turn the coil spring on the fixed shaft. This torsion motion tensions the coil spring and reduces its diameter. The coil spring constricts about the fixed shaft, acting as a brake. When more than one sheet is passed between the rollers, the advancing roller pushes the top sheet in the forward direction. The retarding roller is uncoupled from the advancing roller, as the two or more feed sheets between the advancing and retarding rollers slip relative to each other. Uncoupling the rollers allows the spring to unwind. The unwinding spring momentarily turns the retarding roll backward for about one revolution. An example of this mechanism can be found in Bell & Howell's Scanner Model Nos. 0101276 and 0101300. This arrangement can correct the mis-feeding of two sheets but not necessarily a stack of three or more mis- fed sheets. The reverse rotation or recoil of the retarding roller is limited, so the retarding effect is limited too. BRIEF SUMMARY OF THE INVENTION

The invention is a sheet feeder for engaging and removing a sheet of paper or other material from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path. The improvements of the present invention address the drawbacks and deficiencies of the prior art in a manner that facilitates high-speed image scanning of individual source documents irrespective of the size or thickness of the specific source document being scanned or processed.

Accordingly, in one aspect of the invention the sheet feeder includes a skimmer, a separator, and a first guide plate. The skimmer is designed for engaging and removing a sheet from one end of a stack of sheets of paper or other material and feeding the engaged sheet edgewise along a feed path. The separator is spaced downstream along the feed path from the skimmer. The separator is designed for advancing the engaged sheet while retarding any adjacent sheets. The first guide plate extends between the skimmer and the separator. The first guide plate is positioned substantially parallel to the feed path. The first guide plate guides the engaged single sheet substantially along the feed path.

One advantage of the first guide plate is that it prevents buckling of the engaged single sheet perpendicular to the feed path by confining the engaged sheet closely to its proper feed path. In another aspect of the invention, the sheet feeder has a separator interposed along the feed path for advancing an engaged single sheet of paper or other material while positively retarding adjacent (for example, simultaneously mis-fed) sheets. The separator includes first and second friction elements.

The first friction element has a generally cylindrical rotating peripheral surface. The peripheral surface is rotatable about an axis extending across, generally parallel to, and on one side of the feed path. The rotation of the peripheral surface engages a single sheet and propels it forward along the feed path.

The second friction element is positioned on the other side of the feed path. The second friction element includes a projection that is urged toward the first friction element for retarding the progress of a sheet along the feed path. The second friction element is stationary with respect to travel along the feed path. The first and second friction elements are axially offset from each other. The second friction element is interleaved radially with respect to the first peripheral surface. As a result, the engaged sheet is gripped between the interleaved first and second peripheral surfaces. This construction can advantageously be used by itself to separate two or more sheets, positively feeding the first sheet while retarding the motion of a second and further sheets until the first sheet is clear. Alternatively, this separator can be combined with other separators, such as a set of reversing rollers also interleaved with the first friction element, to further retard the advance of mis-fed additional sheets. In still another aspect of the invention, the sheet feeder has a sheet separator interposed along the feed path for advancing an engaged single sheet while positively retarding one or more adjacent sheets. The sheet separator includes an advancing and a retarding element.

The advancing friction element has a rotary peripheral surface, which can revolve about an axis extending across, generally parallel to, and on one side of the feed path. The rotary peripheral surface engages a single sheet and propels it forward along the feed path.

The retarding friction element is positioned on the other side of the feed path. The retarding friction element has a rotary peripheral surface that can revolve about an axis extending across, generally parallel to, and on the other side of the feed path. The retarding friction element may be driven in reverse direction if more than one sheet is propelled forward along the feed path.

In still another aspect of the invention, the sheet feeder includes a skimmer and a bumper. The skimmer engages and removes a sheet from one end of a stack of sheets of paper or other sheet material. Each sheet in the stack has a leading edge.

The skimmer feeds the engaged sheet edgewise along a feed path.

The bumper extends across the feed path. The bumper has a guide surface positioned to confront the leading edges of the sheets of the stack. The guide surface also directs the leading edge of an advancing engaged single sheet away from the remainder of the stack.

Some advantages of this arrangement are that the bumper maintains the stack of sheets in precise positions and the bumper assists in separating the sheet intended to be fed from sheets beneath it, feeding the end sheet while preventing mis-feeding of additional sheets at the same time.

Yet another aspect of the invention is a sheet skimmer including at least one generally cylindrical endless rotating friction surface, a motor, and a positive drive, such as (1) a gear train, (2) a drive chain and sprockets, or (3) a timing belt and timing sheaves. The friction surface is positioned to engage the end sheet of a stack of sheets, for propelling the end sheet off the stack edgewise. The motor has a rotor. The positive drive engages the rotor and the rotating surface for turning the rotating surface in timed relation to the rotation of the rotor. Turning the rotating surface in timed relation to the rotation of the rotor does not concern the precise rate of feeding, and merely requires a uniform, essentially non-jerky feed of sheets of material.

This arrangement is desirable to prevent interruptions in the rotation of the rotating surface, as when a conventional belt drive is sporadically overloaded and temporarily slips. Uniform rotation of the rotating surface improves the reliability of feeding, tending to eliminate jerky feeding action and prevent mis-feeding of more than one sheet at a time.

Still another aspect of the invention is a skimmer for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path,. The skimmer includes a sheet path along which a sheet having a first and second surfaces is passed, a paper driving element (for one example, a roller), and a lateral reciprocator. The paper-driving element is positioned to drive forward one surface of a sheet in the sheet path. The lateral reciprocator imparts a lateral motion to the paper-driving element. The lateral motion can optionally be provided, for example, by providing a cam and cam follower, powered by the drive for the driving element. Optionally, the action of the lateral reciprocation can be unequal, with the drive element slowly moving in one direction, then quickly returning in the opposite direction. Providing a sawtooth cam surface that has a gradual ramp followed by a sudden drop can produce this action.

Laterally reciprocating the paper-driving element assists the driving element in separating the top sheets from lower sheets in a stack. The lateral travel of the skimmer breaks the top sheet loose without advancing or retarding it in the feed direction (and potentially interfering with the operation of other apparatus). Yet another aspect of the invention is a sheet separator. The separator can be used, for example, as part of a sheet feeder for engaging and removing sheets of paper or other material from one end of a stack of sheets and feeding the engaged sheets one by one edgewise along a feed path. The sheet separator includes a sheet path (along which a sheet or multifeed having first and second surfaces is passed), an advancing roller, a retarding roller, a drive, and a friction clutch.

The advancing roller is positioned to drive forward the first surface of a sheet in the sheet path. The retarding roller is positioned to drive back the second surface of a sheet in the sheet path. A drive is provided to rotate the retarding roller backward when the drive is engaged. A friction clutch is provided to engage the drive with the retarding roller.

The clutch normally slips and permits the retarding roller to be driven forward by the advancing roller when one or no sheets are engaged between the advancing and retarding rollers. The clutch slips when one or no sheets are engaged because the friction between either roller and the sheet, or directly between the rollers, is great enough to make the clutch slip. The clutch engages and drives the retarding roller backward when a multifeed of two or more sheets is engaged by the advancing and retarding rollers. The clutch engages when a multifeed enters because the sheet-to- sheet friction between two sheets interposed between the rollers is too low to cause the clutch to slip. The advancing roller thus engages and advances the top sheet and the retarding roller then engages and retards the bottom sheet of a multifeed of two or more sheets.

One particular advantage of the invention is that it can separate a multifeed of three or more sheets passed between the advancing and retarding rollers. The retarding roller drive can operate continuously (in one embodiment of the invention).

The friction clutch can remain engaged for as long as a multifeed of more than one sheet remains between the advancing and retarding rollers. The friction clutch remains engaged so long as a multifeed persists because sheet-to-sheet slippage between two or more sheets disengages the advancing roller from the retarding roller. The retarding roller will at least retard (and in one embodiment move back) the lowermost sheet of a multifeed the entire time the friction clutch is engaged. The retarding function will therefore continue to aπest or back up all the sheets but the top one (and particularly the lowermost sheet at any given moment, though intermediate sheets may also be driven back to some degree) until only the top sheet of the now- disassembled multifeed remains between the rollers. Only then does the advancing roller engage the retarding roller, thus disengaging the friction clutch, thus causing the retarding roller to rotate in a forward direction and pass the top sheet.

Even another embodiment of the invention is a sheet separator for breaking down multifeeds of two or more overlapping sheets into separate sheets. The separator includes a sheet path, an advancing drive, and a sheet retarding assembly.

The sheet path is the path normally followed by sheets going through the sheet separator. The sheet path is arranged to pass multifeeds of at least two sheets. A multifeed is defined as having first and second opposed outside surfaces. The multifeeds are separated as they travel along the sheet path. The advancing drive is positioned to engage and drive the first surface of the multifeed forward along the sheet path. The sheet retarding assembly includes a roller or other rotatable element, a drag, and a roller sleeve. The rotatable element is mounted for rotation with respect to a normally non-rotating element. The drag retards rotation of the rotatable element, providing friction-resisting rotation when the rotatable element is rotated.

The roller sleeve has an outer, generally cylindrical surface positioned to frictionally engage and be rotated by the second surface of the multifeed. The roller sleeve has an inner, generally cylindrical surface coupled to the rotatable element. Rotation of the rotatable element is retarded by the drag. The net result is that the sheet retarding assembly retards the forward progress of the second surface of the multifeed. The roller sleeve is axially slidable on the rotatable element for ready installation on and removal from the rotatable element.

Still another embodiment of the invention is a skimmer for engaging and removing a sheet having an exposed surface from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path. The skimmer includes at least one roller, optionally tandem rollers, and a freewheeling clutch or similar arrangement.

The first roller has a first rotation axis. The first roller is positioned to drive the outside sheet of a stack forward into the sheet path. The first roller is driven in the direction driving a sheet forward into said sheet path. The drive engages the first roller through a freewheeling clutch or similar arrangement.

The freewheeling clutch independently allows the corresponding roller free rotation in the forward direction when the sheet is moving forward faster than the peripheral speeds of the rollers. The sheet can be moved faster than the roller by later elements along the sheet path, such as a sheet separator or traction rollers. Thus, when the forward end of the sheet reaches a later element operated at a faster speed, the skimmer drive will not resist acceleration of the sheet by the later element.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Figure 1 is a perspective view of a document scanner with a document feeder attachment.

Figure 2 shows a top plan view of a prior art feeder tray (with the side covers and overlying structure cut away). Figure 3 is a left side elevation of the prior art assembly of Figure 2.

Figure 4 is a right side elevation, partially cut away, of the prior art assembly of Figure 2.

Figure 5 is a section taken along lines 5—5 of Figure 2, illustrating the prior art feed mechanism. Figure 6 is a diagrammatic perspective view of certain components of the modified feed assembly of the present invention.

Figure 7 is a more detailed, isolated perspective view of the improved advancing-retarding rollers, bumper and guide plate shown in Figure 6.

Figure 8 is an isolated side elevation of the major guide path components of the improved paper feed mechanism shown in Figures 6 and 7.

Figure 9 is a view similar to Figure 8 illustrating additional features and interactions.

Figure 10 is a side elevation of the feeder spring guide component shown in Figures 8 and 9. Figure 11 is a bottom plan view of the feeder spring guide of Figure 10.

Figure 12 is a rear elevation of the feeder spring guide of Figure 10. Figure 13 is a top view of the skimmer assembly.

Figure 14 is a section taken along lines 14 — 14 of Figure 13, illustrating the lateral reciprocator.

Figure 15 is a section taken along lines 15 - 15 of Figure 14, illustrating the cam.

Figure 16 is a block diagram of a retarding roller, a drive and a clutch.

Figure 17 is a diagrammatic view showing the operation of the advancing roller and retarding roller when a multifeed of more than two sheets is interposed between them. Figure 18 is a view similar to Figure 17 showing the operation of the advancing roller and retarding roller when a multifeed of two sheets is interposed between them.

Figure 19 is a view similar to Figure 17 showing the operation of the advancing roller and retarding roller when a single sheet is interposed between them. Figure 20 is a view similar to Figure 18 showing the operation of the advancing roller and retarding roller when a multifeed of two sheets is interposed between them.

Figure 21 is an isolated perspective view of an alternative embodiment of the retarding roller. Figure 22 is an exploded perspective view of the embodiment of Figure 21.

Figure 23 is a radial section taken along lines 23 — 23 of Figure 21.

Figure 24 is an axial section taken along lines 2 — 24 of Figure 21.

Figure 25 is an axial section taken along lines 25 — 25 of Figure 22.

Figure 26 is an exploded perspective view of the brake assembly of Figure 22. Figure 27 is a schematic perspective view of a tandem skimmer according to another embodiment of the invention.

Figure 28 is a schematic section taken along line 28 — 28 of Figure 27, showing the operation of the tandem skimmer.

DETAILED DESCRIPTION OF THE INVENTION While the invention will be described in connection with one or more embodiments, it will be understood that the invention is not limited to those embodiments. On the contrary, the invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims. In the following description and the drawings, like reference numerals represent like elements throughout. In accordance with the present invention, an improved document feed mechanism is described that facilitates reliable high-volume document throughput for associated image scanning equipment, and similar equipment and/or processes, irrespective of the varying thickness associated with input documents. It is designed to eliminate the feeding of multiple sheets (so-called "multifeeds" of several pages at one time) and to avoid damage to an individual input document or sheet (commonly referred to as "source document").

Figure 1 shows one suitable environment of the invention: a high speed, commercial document scanner 10. Scanners of this type typically process continuous streams of paper, like stacks of checks. The scanner 10 has a document imaging assembly 11 and a document feed mechanism 13. The document feed mechanism 13 would also be useful for feeding sheets of material other than paper from a stack into apparatus for performing any of a wide variety of operations on the sheets.

A typical scanner assembly 11 of this type uses photoelectric detectors and photo imaging devices for digitally capturing the image from a moving piece of paper. The scanner may be capable of single-sided or double-sided image capture. A scanner assembly contains a linear series of charge-coupled devices or the like, which traverse the path of the moving paper. The linear aπay is repetitively exposed to the light path and digitally "dumped" into memory to reformulate the image electronically in mass memory for display. The document feed mechanism or sheet feeder 13 of the disclosed embodiment is approximately 15 inches (37 cm) wide (from its left and right side control knobs), 12 inches (31 cm) long, and 5 inches (12 cm) high and is relatively lightweight.

A Prior Document Feeder Turning to Figures 2 through 5, the illustrated prior art sheet feeder 13 includes a skimmer 21 and a separator 19. The skimmer 21 engages and removes the outside or end sheet 44 from one end of a stack 43 of sheets and feeds the engaged sheet 44 edgewise along a feed path 14 which extends generally in the plane of the sheet 44 under the skimmer rollers 25, along the guide surface 15, and through the nip 58 of the separator 19. The separator 19 is spaced downstream along the feed path 14 from the skimmer

21 for advancing the engaged sheet 44 while retarding any adjacent sheets mis-fed along with the end sheet 44 intended to be fed.

The skimmer 21 is supported by and pivots in the vertical direction about a skimmer shaft 24 to facilitate the stacking of individual input documents into a single stack of input or source documents which are queued-up and positioned on the top surface of the document feed mechanism for image scanning or similar processing of each individual sheet or source document. Further, each individual input sheet or source document has an associated thickness, which may vary from one such sheet or source document to another. The paper-engaging portion of the skimmer roller assembly 21 is a first friction element 25 - here, a pair of driven skimmer rollers 25 having generally cylindrical endless rotating peripheral surfaces carried on a stub shaft 16.

The skimmer rollers 25 are brought into continuous contact (through gravity) with the topmost document or end sheet 44 of the input stack 43 (Fig. 4). The feeder could alternately be configured to feed from the bottom of the stack (as to allow additional sheets to be stacked while the sheet feeder is in operation.) In that event, the end sheet would be the bottom sheet of the stack. Since in the illustrated embodiment the roller assembly 21 desirably bears on the input stack 43 with more force than its own weight provides, an additional weight (not shown) is provided on the skimmer roller assembly to achieve more positive gripping of the top document from the input stack 43.

The construction of the skimmer rollers 25 maintains the correct pressure or force continuously on the top surface of the top sheet or source document 44 of the stack 43 of input documents by the skimmer rollers during operation of the document feed mechanism. In the prior device depicted in Figs. 1-5, approximately half of each skimmer roller is manufactured from a hard, smooth, relatively low friction coefficient, slippery material, such as steel, plastic or some other similar materials. The other half of each skimmer roller is manufactured from a much softer material having a relatively high friction coefficient, such as polyurethane rubber or a similar material.

During operation of the document feed mechanism, the skimmer rollers make contact with the top surface of the topmost sheet or source document in the stack waiting to be processed. The rubber portion of each skimmer roller will tend or act in a manner to intermittently urge the topmost sheet or source document in the stack of input documents waiting to be processed forward into the document feed mechanism. The plastic or steel (or other similar material) portion of each skimmer roller will tend to act in a manner to facilitate slight slipping on the top surface of the topmost document of the stack of input documents.

The separator 19 includes a series of axially spaced forwarding rollers 34 (four are shown in Figure 2) carried on a common shaft 26 and an interleaved series of axially spaced reversing rollers 36 (best seen in Figure 5) carried on a parallel common shaft 56. The concept of interleaving forwarding and reversing rollers 34 and 36, per se, is shown best in Figure 7 in connection with the present invention.

Returning to Figures 2 and 5, the shafts 26 and 56 rotate in the same direction - counterclockwise as shown in Figure 5. Therefore, where the bottoms of the rollers 34 interleave with the tops of the rollers 36, their facing surfaces are moving in opposite directions. The bottoms of the forwarding rollers 34 are moving from left to right (in the feeding direction) and the tops of the reversing rollers 36 are moving from right to left (contrary to the feeding direction), all with reference to Figure 5.

The opposing forwarding and reversing rollers, 34 and 36 respectively, are each made of different materials to enable the forwarding rollers 34 to have more friction on the input sheet than the reversing rollers 36. Thus, if only one sheet is presented, the net result is forward motion of the presented sheet through the forwarding and reversing rollers 34 and 36. However, if two or more sheets are presented, the forwarding rollers 34 engage the properly feed top sheet 44 only, and the mis-fed bottom sheet is engaged by the reversing rolls 36 only. This advances only the properly fed sheet and reverses the travel of any mis-fed sheets.

Adjustable paper guides 22 (left and right) are adjustable along a transverse slot 23 to the appropriate width of the input stack 43. The guides 22 maintain the documents in a stacked relationship below the skimmer rollers 25, which are in continuous contact with the top document of the input stack 43.

Cooperating shafts 24, 26 and 56 (see Figure 5) provide the necessary conventional drive mechanics to the skimmer rollers 25 and to the forwarding and reversing rollers 34, 36 (see Figure 5), respectively, that are associated with the document feed mechanism nip area 58 (see Figure 5). An electric motor 29 (see Figure 2) provides the necessary driving force for all the different parts driven by a drive belt 31 (see Figure 4), including the cooperating shafts 24, 26 and 56.

To avoid multi-feed problems, the forward and reverse roller mechanism 34 and 36 should have the rollers 25 spaced axially from each other, forming a gap that can be adjusted. This was resolved in the prior art by using a control knob 35 that adjusts the position of the lower or reversing rollers relative to the upper or forwarding rollers.

Turning to Figure 3, there is shown a left side panel 30 and the control knob 35. The left side panel 30 provides left side stability and lateral rigidity to the document feed mechanism 13, and facilitates attachment of the left-side exterior side cover 20 (see Figure 2) to the document feed mechanism 13. The control knob 35 is used to adjust spacing between the forwarding and reversing rollers 34 and 36 (see Figure 5). A variable to the successful operation of the document feed mechanism 13 is the gap or space existing between the forwarding and reversing rollers 34 and 36.

The forwarding and reversing rollers 34, 36 are adjustable with respect to the interleaving of the rollers during operation of the document feed mechanism 13. Turning the control knob 35, a spacing arm 69 moves a support bracket that supports the drive shaft 56 of the reversing rollers 36 (see Figures 4 and 5). This pivoting adjusts the spacing between the forwarding and reversing rollers 34 and 36.

Turning now to Figure 4, the conventional feeder includes a right side panel 42 that provides right side stability and lateral rigidity to the document feed mechanism 13 and facilitates attachment of the right-side exterior side cover 28 to the document feed mechanism 13. To provide the coπect positioning and alignment of numerous piece parts of the document feed mechanism 13, the right side panel 42 contains numerous holes, cutouts and/or otherwise keyed areas associated therewith. Figure 5 is a cross sectional view of the prior art feeder taken along the lines 5- 5 of Fig. 2, and best shows the operation of the feeder. Shown there is a flat feeder tray 52 having a feeder tray lip 54 at one end. Adjustable paper guides 22 are internally supported by a side guide support 51 (one support for each side). During operation of the document feed mechanism, the skimmer rollers 25, 26 are in continuous contact with the top surface of the topmost sheet in the stack of input documents. Whenever required, a side guide cover 23 can be removed to facilitate interior access to the adjustable paper guide 22 and its associated apparatus.

In operation, the skimmer rollers 25, 26 take the top sheet from the input stack 43 and drive this sheet into the stationary guide chute 50 located in front of the document feed mechanism nip area 58 associated with the document feed mechanism 13. Upon making initial contact with the stationary guide chute 50, the paper is driven downward until the input sheet enters the document feed mechanism nip area 58 of the document feed mechanism 13. The moving paper then comes into contact with two opposing rollers, namely the forwarding rollers 34 and the reversing rollers

36. The forwarding rollers 34 and the reversing rollers 36 are radially interleaved or overlapped and axially displaced so at least some of the forwarding rollers pass between the reversing rollers and vice versa. The forwarding rollers 34 and reversing rollers 36 rotate in the same direction (counterclockwise in Figure 5), and thus work in opposition respecting paper or other sheets fed between them. The forwarding rollers 34 advance the top sheet and the reversing rollers 36 arrest the progress of any additional sheets.

THE PRESENT INVENTION

Figures 6-28 illustrate the improvements that have been made in connection with the present invention. In general, only selected components that have been modified are shown. For the remaining components of the system reference is made to Figures 1-5 and to Bell & Howell's prior document feeding apparatus and published descriptions of such apparatus.

Figure 6 shows a skimmer roller assembly 21 of the present invention with relatively wide elastomeric rollers 64, as opposed to the relatively naπow skimmer rollers 25 used in the prior art. The generally cylindrical endless rotating surface 70 of each roller 64 can have an axial length longer than its circumference, in a preferred embodiment. This allows for a more positive gripping of the feed sheet. Also, the rubber used in the present invention can have a higher friction coefficient than the rubber used in the prior art. This eliminates the need for excessive weight to provide for a more positive gripping.

Figure 9 illustrates the improved skimmer roller mechanism 21 of the present invention. A toothed belt 91 is driven by a shaft 92, from the rotor schematically represented as 18 of the feeder drive motor schematicaly represented as 17. The prior belt drives for this purpose use belts that are smooth and prone to slipping which, in turn, produces uneven torque, and increases the multifeed problem. The toothed belt

91 engaging the timing sheaves 93 and 94 defines a positive drive engaging the rotor 18 (optionally through a further linkage) and engaging the rotating surface 70 (again, optionally through a further linkage) for turning the rotating surface 64 in timed relation to the rotation of the rotor 18. The timing sheave 93 is constrained to rotate in timed relation to the rotor 18. The timing sheave 94 is constrained to rotate in timed relation to the generally cylindrical endless rotating surface 70. The timing belt 91 is driven by the timing sheave 93 and drives the timing sheave 94. A gear drive, chain drive, crank drive, or other mechanical arrangement also would be suitable as timing drives. "Timing drive" is used here synonymously to a "positive drive" to indicate a drive that resists slipping, and thus feeds at an even rate under ordinary circumstances. There is no need for a timing mechanism having the capacity to or aπanged to synchronize different functions to achieve the purposes of the present invention.

The remaining driveshaft mechanics are similar to the prior apparatus. A suitable drive aπangement can readily be designed by a person having ordinary skill in this art.

Each of the wide elastomeric rollers 64 of the skimmer 21 defines a first friction element having a generally cylindrical endless rotating peripheral friction surface 70 rotatable about an axis 71 extending across and generally parallel to the feed path 14 on one side of the feed path 14. While in this embodiment the friction surfaces 70 are defined by rollers, other endless rotating peripheral friction surfaces, such as traction belts, are also contemplated for use as skimmers. The peripheral surface 70 of each roller 64 is positioned for engaging and advancing a single sheet 44 along the feed path 14. The rollers 64 take the top sheet or source document from the input stack 43 and drive the input sheet 44 into a guide mechanism located in front of the feeder nip area. This action of the skimmer rollers 64 on the top surface of the topmost document 44 of the input stack 43 imparts to each top document 44 a gentle intermittent urging forward. This intermittent urging forward, in conjunction with the confining of the paper by the bumper 68 and the guide plates 66 and 81 (see Figure 8), the downstream action of the forwarding rollers 34, and the action of the reversing rollers 36 prevents the feeding of multiple documents of the input stack 43 by the document feed mechanism 13. Buckling of the paper or damage to a source document because of a multifeed situation is reduced, minimized, or avoided altogether.

As the paper is pushed forward by the skimmer roller assembly, it is confined by the bumper 68 and the guide plate 66 on the one side, and the feeder spring guide plate 81 on the other. In the illustrated embodiment, the feeder spring guide 81 is a guide plate supported at least in part by and pivotable with respect to the support 16 for the skimmer rollers 25. The support 16 is a rotating shaft and the feeder spring guide 81 is mounted to be pivotable independent of the rotation of the rotating shaft 16. Turning to Figures 7 and 8, there are shown a bumper 68, a guide plate 66 and a supporting bolt 72 around which there is a spring that provides upward pressure to the bumper 68. Figure 8 shows a guide plate 81, and both Figures show an improved separator 19 including forwarding rollers 34 and reversing rollers 36.

The bumper 68 extends across the feed path 14. The bumper 68 is a rectangular bar, box or tube supported by two springs that suπound each of the bolts

72 underneath the bumper. The guide plate 66 is also supported by the same bolts 72 and extends to the document feed mechanism nip area 58. The bumper 68 has a guide surface 84 positioned to confront the leading edges such as 85 and 86 of the sheets of the stack 43 and to direct the leading edge 85 of an advancing engaged single sheet 44 away from the remainder of the stack. The guide surface 84 accomplishes this directing function because it is angled upwardly in the direction of the feed path 14 (to the left in Figure 8). The top surface 83 of the bumper plate and the guide plate 66 are fixed relative to each other in this embodiment, and are substantially parallel, defining an extended guide plate extending from the downstream or upper edge of the surface 84 into the nip 58.

The guide plates 66 and 81 are positioned on opposite sides of the feed path 14. As will be seen, each guide plate 66 and 81 acts to prevent buckling or other damage to the sheet 44 being fed as it is forwarded through the space between the skimmer 21 and the separator 19, and between the two guide plates. Either one or both of the guide plates 66 and 81 can be used.

Turning now to Figure 8, the wide elastomeric skimmer rollers 64 urge the paper into an intermediate area where it is confined by the guide plates 66 and 81 (see

Figure 8) closely adjacent the feed path 14. The guide plates 66 and 81 extend at least part way between the skimmer 21 and the separator 19 substantially parallel to the feed path 14 to guide the engaged single sheet 44 substantially along the feed path 14, preventing buckling of the engaged single sheet 44 perpendicular to the feed path 14. The feeder spring guide 81 is attached to the skimmer roller assembly 21, is hinged about the axis of the skimmer roller assembly, and extends to the document feed mechanism nip area 58. The guide plates 66 and 81 converge as they extend to the left (in Fig. 8) in the direction of the feed path 14. The guide plate 81 is slightly bent to allow for a wide gap between the guide plate 81 and the bumper 68 at the entrance of the intermediate area and a naπow gap between the feeder spring guide 81 and a guide plate 66 near the downstream document feed mechanism nip area 58. The feeder spring guide 81 defines a guide plate on the opposite side of the feed path 14 with respect to the first guide plate 66.

The guide plate 66 has a "teeth-like" end with portions 67 that extend between the reversing rollers 36. Besides this "teeth-like" end, the guide plate contains intermediate fingers 73 supporting ribs 77. These fingers 73 fit the recessed channels 75 in the reversing rollers 36. The ribs 77 extend from the guide plate 66 radially into recessed circumferential channels 75, at least at some times while the feeder is in operation. The channels 75 divide the first peripheral surface of each forwarding roller 34 into two friction elements 80 and 82. A projecting friction surface or rib 77 is positioned to normally project into each recess 75, in this embodiment, though a one to one coπespondence between ribs and forwarding rollers 34 is not required. Each rib 77 is a projecting friction surface adjacent to and positioned on the opposite side of the guide path from the first peripheral surface of the rollers 34 for biasing an engaged single sheet 44 against the peripheral surfaces of the rollers 34 for advancement while separating any additional sheet positioned between the friction surface of the rolls 34 and the engaged single sheet 44. The ribs 77 thus function as another mechanism, independent of any reversing rollers such as 36, for cooperating with the forwarding rollers 34 to prevent the advance of mis-fed additional sheets along the feed path 14.

The guide plate 66 is biased toward the first peripheral surfaces defined by the rollers 34 by a spring 76 carried on a bolt 72 which is fixed by other structure (not shown). The spring 76 bears between the guide plate 66 and a fixed structure represented by the head 78 of the bolt 72.

The separator 19 illustrated here thus defines an axially alternating series of at least two axially spaced first friction elements, such as 80 and 82, and at least one second friction element 73 interposed between the friction elements 80 and 82. The second friction element 73 can be stationary with respect to travel along the feed path 14, and retards the progress of a sheet fed along the feed path 14.

After a fed sheet enters the document feed mechanism nip area 58, the ribs 73, which can be metallic, push the paper in the channels 75 of the improved forwarding rollers 34, which then force the paper into the gap between the improved forwarding rollers 34 and reversing rollers 36. The first and second friction elements 80/82 and 73 are axially offset from each other and the second friction element 73 is interleaved radially with respect to the first peripheral surfaces such as 80 and 82, thereby gripping the engaged sheet 44 between the first and second peripheral surfaces 34 and 73.

For the purposes of controlling the gap or space existing between the improved forwarding rollers 34 and the reversing rollers 36, the improved reversing rollers 36 are adjustable with respect to the meshing of the forwarding rollers 34 during operation of the document feed mechanism 13. The control knob 35 of Figure 6 is pivotable about its axis and defines a cam having a lobe 37. Rotation of the knob 35 causes the lobe 37 to bear against a cam following surface 38 of a lever or spacing arm 69 which is rotatable about a pivot 61. Brackets 65 are secured to a square- section bar 63, which in turn is secured to the spacing arm 69. The brackets 65 support the shaft 56 (cut away in Figure 6, shown in Figure 7) supporting the reversing rollers 36. Bearing of the lobe 37 against the cam surface 38 thus rotates the spacing arm 69 and the shaft 63 counetclockwise about the pivot 61, rotating the shaft 56 back and down and thus reducing the degree of meshing between the forwarding and reversing rollers 34 and 36. Reverse rotation of the knob 35 has the opposite result. Springs or other structure can be provided to normally bias the cam follower surface 38 against the cam lobe 37.

For thinner sheets of source documents there can be provided a smaller gap between the forwarding and reversing rollers and, conversely, for thicker sheets of source documents a larger gap can be provided between the forwarding and reversing rollers. Accordingly, as required or whenever necessary, the control knob 35 is used to incrementally adjust the gap present between the forwarding and reversing rollers.

The recessed regions or channels 75 of the forwarding rollers 34 are formed deep enough to allow the fingers 73 to urge the paper into the channels 75 far enough to insure a substantial friction "grip" of the paper

Turning to Figure 8, upon entering the feeder nip area, the moving input sheet comes into contact with two opposing sets of rollers, namely, the improved forwarding rollers 34 and the reversing rollers 36, which function together in essentially the same way as described before. As before, the forwarding rollers 34 assist in moving any and all input documents of the input stack 43 in a forwarding direction. In the preferred embodiment, the improved forwarding rollers 34 are split into two axial portions to accommodate the intermediate finger assembly 73 that biases the paper into a more positive gripping by the improved forwarding rollers 34. The forwarding rollers are made of rubber or another elastomer material, and molded securely to an interior aluminum hub. This "channel" 75 fits each of the fingers of the intermediate finger assembly 73 that extend from the guide plate 66 to ensure more positive friction force. In the preferred embodiment, the size of the channel is 0.06 inches (1.5 mm) in width and a similar depth. The reversing rollers 36 rotate more slowly, but in the same direction as the forwarding rollers 34. The reversing rollers 36 are harder and engage paper or other sheets with less friction than the forwarding rollers 34 impart, which helps them retard any sheets other than the topmost sheet 44 gripped by the forwarding roller. The reversing rollers 36 and improved forwarding rollers 34 are axially spaced and interleaved, as before. More reversing rollers 36 than before are provided.

Figures 10-12 illustrates in greater detail the feeder spring guide 81 that extends from the skimmer roller assembly 21 to the document feed mechanism nip area 58. As it was earlier pointed out, the purpose of the feeder spring guide is confining of the source document, and preventing the same from buckling or being damaged.

Figures 13-15 show a schematic elevation view of an alternative skimmer assembly. A radial arm 1301 of the skimmer 21 is rotatably and slidably carried on the shaft 24 so the shaft 24 can rotate relative to the radial arm 1301. The radial arm

1301 has an annular cam surface 1302 protruding axially. The illustrated cam surface

1302 is a single saw-tooth extending 360 degrees about the shaft 24. The surface 1302 thus defines a gradual ramp extending around nearly the entire circumference, terminating at an apex 1401 representing its greatest axial projection, followed by a precipitous drop to a low point 1402 representing its least projection. More than one saw-tooth can be provided, if desired. For example, three 120-degree saw teeth or several saw teeth of different angular extents can be used. Other cam surface configurations and reciprocation patterns are also contemplated. For example, the cam surface could be arranged to reciprocate the cam follower in each direction at an equal rate, or dwell times could be incoφorated between strokes of the reciprocating apparatus.

A cam follower 1303 is fixed to and rotates with the shaft 24 and is adjacent to the cam surface 1302. On the other side of the radial arm 1301, a compression spring 1304 is carried on the shaft 24 and is confined between a stop 1305 fixed to the shaft

24 and the radial arm 1301.

The cam follower 1303 rotates with the shaft 24, sliding along against the cam surface 1302, and causes the radial arm 1301 to move laterally in both directions. The radial arm 1301 moves laterally slowly to the left most of the time (as shown in Figure 13). Once per revolution of the cam follower 1303, the radial arm 1301 jerks back suddenly to the right as the cam follower 1303 passes from the apex 1401 of the cam surface (where the cam follower 1303 is shown in full lines in Fig. 15) to the lowest point 1402 of the cam surface (where the cam follower 1303 is shown in phantom lines in Fig. 15).

Figure 14 is a side view taken along lines 14 - 14 of Figure 13. The lateral reciprocator 1407 comprises the cam follower 1303 and the cam surface 1302. The cam follower 1303 rotates with the shaft 24 and slides along the cam surface 1302.

Figure 15 is a sectional view of the cam surface 1302 taken along lines 15 - 15 of

Figure 14.

Other reciprocation apparatus, such as a fluid drive, a crank, a servo drive, a linkage, or other like or unlike apparatus capable of causing reciprocation is also contemplated herein.

The periodic lateral jerk to the right (as shown in Figure 13) of the skimmer 1301 allows for more reliable separation of the top sheet in the stack, as the lateral travel of the skimmer breaks the top sheet loose without advancing or retarding it in the feed direction (and potentially interfering with the operation of other apparatus). Another alternative feature of the present sheet feeder is shown in Figures 16-

20. Figure 16 shows a block diagram of the relation between retarding rollers such as 1601, a driven shaft 1602, a friction clutch 1603, a drive shaft 1604, and a drive motor 1605. An advancing roller 1606 and its drive 1607 are also shown.

Referring to Figures 16 and 17, the advancing roller 1606 is positioned to drive forward (by rotating in the direction of the aπow 1607) the first surface 1608 of a sheet 1610 in the sheet path defined between the rollers 1601 and 1606. The sheet 1610 is driven to the left, or forward, as a result. The retarding roller 1601 is positioned to drive back the second surface 1612 of a sheet 1614 in the sheet path (i.e. drive the sheet 1614 to the right in Figure 17 by turning in the direction of aπow 1616). A drive 1605 is provided, tending to rotate the retarding roller 1601 backward.

A friction clutch 1603 is provided to engage the drive 1605, via the shaft 1604, with the retarding roller 1601, via the shaft 1602.

In operation, the clutch 1603 normally slips and permits the retarding roller 1601 to be driven forward by the advancing roller 1606 when one or no sheets such as 1610 are engaged between the advancing and retarding rollers 1606 and 1601 (as shown in Figure 19, in which the reversing roller 1601 is driven forward, or in the direction of the aπow 1618 in Figure 19). The clutch 1603 slips because the friction between either roller (1601, 1606) and the sheet 1610, or directly between the rollers 1601 and 1606, is great enough to make the clutch 1603 slip as the advancing roller 1606 drives the sheet 1610, which in turn drives the roller 1601 forward in the direction of the aπow 1618. This action drives the shaft 1602 of the retarding roller 1601 contrary to the drive direction of the shaft 1604 by the motor 1605. Since the shafts 1602 and 1604 are each driven with sufficient force in contrary directions, the clutch 1603 slips and uncouples them.

The clutch 1603 engages and drives the retarding roller 1601 backward when a multifeed of two or more sheets is engaged by the advancing and retarding rollers 1606 and 1601. This situation is shown in Figures 17 (multifeed of three sheets), 18

(multifeed of two sheets), and 20 (multifeed of two sheets). The clutch 1603 engages when a multifeed enters because the sheet-to-sheet friction between two sheets interposed between the rollers 1601 and 1606, such as the sheets 1610 and 1614 in Figure 18, is too low to cause the clutch 1603 to slip. More specifically, a pair of sheets 1610 and 1614 passed between the rollers 1601 and 1606 greatly reduces the driving force of the driving advancing roller 1606 on the formerly-driven retarding roller 1601. The shaft 1602 is not driven with much, if any, force by the retarding roller 1601. The shaft 1604 is driven in the retarding direction. Under these conditions the friction clutch 1603 does not slip, and the drive imparted by the input shaft 1604 drives the output shaft 1602, and thus the retarding roller 1601. The advancing roller thus engages and advances the top sheet such as 1610 and the retarding roller engages and retards the bottom sheet such as 1614 of a multifeed of two or more sheets.

Any sheets between the top sheet such as 1610 and bottom sheet such as 1614 of a multifeed, for example the sheet 1620 in Figure 17, slips with respect both to sheets above and below. Depending on the exact circumstances, the middle sheets such as 1620 may be driven with little force in either direction, or may even remain stationary.

One particular advantage of this aπangement is that it can separate a multifeed of three or more sheets passed between the advancing and retarding rollers. The retarding roller drive can operate continuously (in one embodiment of the invention). The friction clutch can remain engaged for as long as a multifeed of more than one sheet remains between the advancing and retarding rollers. The friction clutch remains engaged so long as a multifeed persists because sheet-to-sheet slippage between two or more sheets disengages the advancing roller from the retarding roller. The retarding roller 1601 will retard the lowermost sheet of a multifeed the entire time the friction clutch is engaged. The retarding function will therefore continue to aπest or back up all the sheets but the top one (and particularly the lowermost sheet at any given moment, though intermediate sheets may also be driven back to some degree) until only the top sheet of the now-disassembled multifeed remains between the rollers. Only then does the advancing roller engage the retarding roller, thus disengaging the friction clutch, thus causing the retarding roller to rotate in a forward direction and pass the top sheet.

Figures 17-20 illustrate how a multifeed of three sheets is progressively broken down into individual sheets by the present separator. In Figure 17, a multifeed including sheets 1610, 1620, and 1614 has been inserted between the advancing roller 1606 and the retarding roller 1601. The advancing roller 1606 drives the top sheet

1610 forward, as the friction between the top sheet 1610 and the roller 1606 is greater than the friction between the top sheet 1610 and middle sheet 1620 of the multifeed. The retarding roller 1601 drives the bottom sheet 1614 backward, as the friction between the bottom sheet 1614 and the roller 1601 is greater than the friction between the bottom sheet 1614 and the middle sheet 1620. Ideally, the middle sheet 1620 will remain essentially stationary, as the top sheet 1610 and the bottom sheet 1614 are sliding in opposite directions with about equal friction. This ideal condition will not be met, however, if the middle sheet 1620 is adhering or attracted more to one of the sheets 1610 and 1614 than to the other. Since the top sheet 1610 is advancing, the bottom sheet 1614 is retreating, and the middle sheet 1620 moves very little, the multifeed is broken up first into three shingled sheets, as shown in Figure 18. As illustrated, the top sheet 1610 and the middle sheet 1620 define a two-sheet multifeed at this point. The two-sheet multifeed is readily separated by the counter-rotating advancing roller 1606 and retarding roller 1601, leading to the situation shown in Figure 19. Here, the sheet 1610 is completely downstream of the separator made up of the rollers 1606 and 1601. The sheet 1620 that was next in the original stack is now the top sheet engaged between the rollers 1601 and 1606. The bottom sheet 1614 has been driven completely back out of the separator. Thus, the first sheet 1610 has been fully separated and advanced and the multifeed has been temporarily broken down to leave a single sheet 1620 between the rollers 1601 and 1606. Once the multifeed has been reduced to a single sheet between the rollers 1601 and 1606, the single sheet 1620 is engaged with approximately equal friction by the rollers 1601 and 1606. The advancing roller 1606 is thus again able to drive the retarding roller 1601 forward, in the direction of the aπow 1618, causing the friction clutch 1603 to slip and thus eliminate the retarding action of the retarding roller 1601. The sheet 1620 advances at the rate dictated by the rotation of the advancing roller

1606.

If the sheets 1620 and 1614 again form a multifeed between the rollers 1601 and 1606, as shown in Figure 20, the drive coupling between the rollers 1601 and 1606 is again broken by the interposition of two sheets, 1620 and 1614. The friction clutch 1603 again engages and the retarding roller 1601 is again driven backward, driving back the bottom sheet 1614.

The separator aπangement illustrated in Figures 16-20 can break down a multifeed of any number of sheets into individual sheets fed in the original sequence. This occurs because the uppermost sheets are driven forward in sequence (the top sheet of the multifeed first, then the second sheet of the multifeed when it becomes the top sheet, and so forth) and the lowermost sheets are driven backward in sequence (the bottom sheet of the multifeed first, then the second to bottom sheet once the bottom sheet is removed, and so forth). This action first shingles the sheets of the multifeed, then completely separates them into individual sheets. Figures 21-26 show an embodiment of a reversing roller assembly 1701 providing an alternative to the reversing rollers 36 of Figure 9 for a sheet separator otherwise having the same parts as shown in previous embodiments. One difference is that the reversing roller 1701 is axially wider than each individual reversing roller 36. As will be seen, this has the potential benefit of equalizing the drag force applied by two independent, coaxial, axially separated reversing roller assemblies, though it is not an essential feature. Another difference is the internal construction and operation of the assemblies 1701. Yet another difference is that the reversing roller of Figure 21 is accurately cylindrical, so it is not suited for interleaving with an opposed series of drive rollers. This is not an essential distinction, however, as interleaving rollers having the construction shown in Figures 21-26 could be devised by a skilled person. Referring now particularly to Figures 21-22, the sheet retarding or reversing roller assembly is shown as 1701. The roller assembly 1701 includes a brake assembly generally indicated as 1703. Here, the brake assembly 1703 includes two independently rotatable elements 1705 and 1707. More or fewer rotatable elements 1705 can be provided, within the scope of the present invention. The roller assembly 1701 is normally disposed within a housing, as shown in Figure 1. Referring back to Figures 21-22, the assembly 1701 includes at least one drag

1709 defined by internal elements of the brake assembly 1703 operating between its stationary shaft 1711 and its rotatable element 1705. These internal elements are further described below in connection with Figures 25-26. As shown in the Figures, in this embodiment the assembly 1701 also includes a second, independent drag 1713, also defined by internal elements of the brake assembly 1703 operating between its stationary shaft 1711 and its rotatable element 1707.

Still referring to Figure 22, the rotatable elements 1705 and 1707 are mounted for independent rotation with respect to a normally non-rotating element, here, the shaft 1711. The drags 1709 and 1713 respectively retard rotation of the rotatable elements 1705 and 1707, providing friction and thus resisting rotation when the rotatable elements 1705 and 1707 are rotated.

The brake assembly 1703 itself can function as a complete retarding roller assembly, with each rotatable element 1705 and 1707 acting like the reversing roller 1601 of Figures 17-20. To adapt the assembly 1703 to this purpose, the rotatable elements 1705 and 1707 are configured as rollers surfaced with high- friction, resilient, sheet-engaging material. Similar construction has been used commercially for this purpose. In the illustrated embodiment of Figures 21-26, however, the rotatable elements 1705 and 1707 are roller hubs made of machined steel, plastic, or other suitable material. The reversing roller assembly 1701 of Figures 21-26 further includes a roller sleeve 1715. The roller sleeve 1715 has an outer, generally cylindrical surface 1717 made of a high-friction, resilient material that will frictionally engage the material of the fed sheets, acting like the reversing rollers 1601 of Figures 17-20. The roller sleeve 1715 has an inner, generally cylindrical surface 1719 coupled to the hubs 1705 and 1707.

In this embodiment the coupling between the inner, generally cylindrical surface 1719 and the hubs 1705 and 1707 is provided by a tongue and groove joint.

An machined-in integral tongue 1721 extends axially along the inner surface 1719 of the sleeve 1715. The hubs 1705 and 1707 respectively have mating grooves 1723 and 1725. The roller sleeve 1715 is axially slidable onto or off of the rotatable elements 1705 and 1707 for ready installation on and removal from the rotatable elements.

The spacers 1723 and 1725 center the sleeve 1715 during use between the end plates of a bracket (not shown). TEFLON® polytetrafluoroethylene O-rings 1727 and 1729 are disposed in the seats 1731 and 1733, and bear between the shaft 1711 and the seats 1731 and 1733 to center the spacers 1723 and 1725, providing a low-friction bearing. (TEFLON® is a trademark of E.I. du Pont de Nemours & Co., Wilmington,

Delaware for polytetrafluoroethylene material.)

One advantage of the tongue-and- groove coupling of the roller sleeve 1715 and the hubs 1705 and 1707 is that, when the outer surface 1717 of the sleeve 1715 becomes worn or soiled, the assembly 1701 can be lifted out of its bracket, the spacer 1723 and O-ring 1727 can be removed, the roller sleeve 1715 will slide off, a new roller sleeve 1715 will slide on, and the assembly 1701 can be reassembled and put in its bracket, all easily and without the need for any tools. If the assembly 1701 normally is disposed within a housing, servicing can be further facilitated by providing an access door in the housing suπounding the reversing roller 1701, opposite one axial end of the assembly 1701. Servicing the reversing roller assembly

1701 can thus be made simple.

Refeπing now to Figures 25-26, more internal details of the brake assembly 1703 are illustrated. The parts of the assembly 1703 shown in Figure 26 are the shaft 1711, two retaining rings 1735 and 1737, two washers 1739 and 1741, two hubs 1705 and 1707, two bushings 1743 and 1745, two clutch springs 1747 and 1749, two reverse spring bodies 1751 and 1753, two reversing springs 1755 and 1757, a hub pin 1759 and two felt oilers 1761 and 1763. In the subsequent description, one side of this two-sided structure will be described; the same description applies to the other side as well, however.

In the assembly 1703, the reverse spring body 1751 is retained on the shaft

1711, and is free to rotate on the shaft 1711. The reverse spring body 1751 has an integral sector stop 1765 (and the spring body 1753 has a sector stop 1767) including a lower abutment 1769 and an upper abutment 1771. (These "lower" and "upper" designations are arbitrary, based on the respective positions of the abutments 1769 and 1771 in Figure 26). Either of the lower and upper abutments 1769 and 1771 can engage the hub pin 1759, depending on the rotational orientation of the spring body 1753 on the shaft 1711. Thus, the reverse spring body 1751 can rotate on the shaft

1711 within the limits permitted by the abutments 1769 and 1771 and the hub pin

1759.

The reverse spring 1755 is a coil spring retained on the spring body 1751. The spring 1755 has tangs on its respective ends (not shown). The respective tangs engage the hub pin 1759 and a hole in the sector stop 1765. The spring 1755 biases the lower abutment 1769 of the reverse spring body 1751 toward and against the hub pin 1759.

The reverse spring body 1751 can be rotated against this bias to the limit at which the upper abutment 1771 engages the hub pin 1759 by exerting a turning force on the spring body 1753. The clutch spring 1747 is another coil spring that bridges between the reverse spring body 1751 and the bushing 1743. The bushing 1743 is fixed to the hub 1705.

The clutch spring 1747 has an unstressed inner diameter smaller than the outer diameters of the reverse spring body 1751 and the bushing 1743. When the clutch spring 1747 is in place, it is strained sufficiently to fit over the reverse spring body 1751 and the bushing 1743 within its respective ends. This strain creates friction between the clutch spring 1747 and the spring body 1751, and also between the clutch spring 1747 and the bushing 1745. This friction creates a drag force resisting rotation of the hub 1705 relative to the spring body 1751.

The brake assembly 1703 is so aπanged that the drag force provided by the clutch spring 1747 is greater than the bias provided by the reverse spring 1755, within the limits of rotation of the reverse spring body 1751 relative to the hub pin 1759.

The clutch spring 1747 and the reverse spring 1755 and the associated structure define the first drag 1709 briefly mentioned above.

In operation, the assembly 1703 as shown in Figure 25 has a two-stage action. When the hub 1705 is rotated to a limited degree, the rotation force is transmitted via the hub bushing 1743, the clutch spring 1747, and the spring body 1751, to the reverse spring 1755. During this limited rotation, the hub bushing 1743, the clutch spring

1747, and the spring body 1751 turn as a unit, since the clutch spring 1747 engages too tightly to permit slipping. The rotation of the hub 1705 thus strains the reverse spring 1755, and rotates the spring body 1751 against its spring bias. The limit of this rotation occurs when the upper abutment 1771 abuts and thus is stopped by the hub pin 1759.

The hub 1705 can be further rotated beyond the limit at which the upper abutment 1771 abuts the hub pin 1759. If this occurs, the reverse spring body 1751 is stopped against the hub pin 1759, and will not rotate further. The hub 1705 and the bushing 1743 thus are rotating, while the reverse spring body 1751 is stopped. The clutch spring 1747 creates a drag between the hub 1705 and the reverse spring body

1751 during this further rotation. This drag force will continue as long as the further rotation continues with sufficient force to keep the upper abutment 1771 stopped against the hub pin 1759. Should the turning force diminish below this threshold force at any time, the bias of the reverse spring will cause the spring body to recoil, rotating back to its starting position at which the lower abutment 1769 is in contact with the hub pin 1759.

When the roller sleeve 1715 is in contact with a single sheet that is being driven by a drive roll forming a nip, the friction between the single sheet and the sleeve 1715 is sufficient to transmit the driving force via the sleeve 1715, the hub 1705, and so forth to the reverse spring body 1751. The reverse spring body is wound to the point where the upper abutment 1771 is against the hub pin 1759, and further rotation forward is allowed, with a drag force, by the clutch spring 1747. As long as the sleeve 1715 is either in contact with the single sheet or with the drive roller (as between two sheets fed successively), the separator is devised so rotation of the sleeve, with the present drag, continues.

If, however, a multifeed of two or more sheets is introduced into the nip, the low friction between the sheets interrupts the transmission of driving force from the driving roll to the sleeve 1715. When this force is removed, the reverse spring 1755 recoils, quickly rotating the sleeve 1715 on its hub 1705 a fraction of a turn and backing up the nearest sheet of the multifeed. So long as the multifeed remains in the nip, the reverse spring 1755 is strong enough to keep the roller sleeve from rotating, and the friction of the roller sleeve 1715 against the nearest sheet of the multifeed prevents that sheet from moving forward while the sheet driven by the drive roll keeps going forward. This action separates the multifeed, and continues to do so as long as more than one sheet is disposed in the nip.

Returning to Figures 21-23, the assembly of the two hubs 1705 and 1707 and the sleeve 1715 turns as a unit on the shaft 1711, and this rotation is resisted by the combined dragging force of the first and second drags 1709 and 1713. Thus, as illustrated schematically in Figures 17-20 (for the roller 1601) and described above, the roller sleeve 1715 is rotated by a multifeed driven along the sheet path and engaging the outer surface of the roller sleeve 1715. The rotating roller sleeve 1715 in turn rotates the rotatable elements 1705 and 1707. Rotation of the rotatable elements

1705 and 1707 is retarded by the drags. The net result is that the sheet retarding assembly retards the forward progress of the second surface of any multifeed, separating the multifeed.

It will be appreciated that the double drag mechanism shown in Figures 22 and 25-26 is not essential, as a single drag mechanism could be provided.

One embodiment of a skimmer roll was shown, for example, as the roll 64 in Figure 8. Turning now to Figures 27 and 28, a modification of the skimmer described previously is shown. This embodiment is a tandem skimmer 1780 for engaging and removing a sheet having an exposed surface from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path. It should be understood that the freewheeling clutch feature described here also has application to a single skimmer roll.

The skimmer 1780 includes first and second tandem rollers 1782 and 1784 and a drive mechanism for them. The rollers 1782 and 1784 are carried for rotation about tandem axes defined by their shafts 1786 and 1788. The drive mechanism for the tandem rollers 1782 and 1784 includes gears 1790 and 1792 respectively fixed to the shafts 1786 and 1788. A drive gear 1794, which is driven by a further mechanism (not shown), meshes with the gears 1790 and 1792, driving them, and thus the rollers 1782 and 1784, in the same direction at the same peripheral speed. The gears could be aπanged to drive the downstream roll 1784 at a slightly faster peripheral speed than the upstream roll 1782, if desired, to flatten the sheet slightly as it is conveyed. The first roller 1782 and the second roller 1784 are positioned in tandem. The first and second rollers are driven together in the direction driving a sheet forward into said sheet path.

In one embodiment, the drive gear 194 engages each roller 182 and 184 through a separate freewheeling clutch or similar aπangement. Alternatively, the freewheeling clutch could be used on just one of the rollers, for example the downstream roller 1784. Instead of a mechanical freewheeling clutch, an electronically controlled clutch that senses and responds to forward acceleration of the sheet, a ratchet and pawl or other one-way escapement, or other aπangements can be provided. The freewheeling clutch independently allows the coπesponding roller free rotation in the forward direction when the sheet is moving forward faster than the peripheral speed of the rollers. The sheet can be moved faster than the roller by later elements along the sheet path, such as a sheet separator or traction rollers. Thus, when the sheet forward end reaches a later element operated at a faster speed, the skimmer drive will not resist acceleration of the sheet by the later element. The details of one suitable freewheeling clutch are shown in Figure 28, which illustrates a ball clutch. The rollers 1782 and 1784 are shells defining or fixed to outer races 1796 and 1798. The outer races 1796 and 1798 are rotatable with respect to the inner races 1800 and 1802. The gears 1790 and 1792 are fixed with respect to the inner races 1800 and 1802, so driving the gears 1790 and 1792 drives the inner races 1800 and 1802. A series of rods or balls (refeπed to below simply as balls for convenience) such as 1804 for the roller 1782 (marked as 1806 for the roller 1784) are captured between the inner races such as 1800 and outer races such as 1796. The inner races such as 1800 include wedge-shaped recesses such as 1808 (1810 for the roller 1784) in which the rods or balls such as 1804 are captured. This is a conventional freewheeling clutch, and operates as described below in relation to the sheets 1812 and 1814 being driven. Figure 28 shows the freewheeling clutch for the roller 1782 in the engaged or driving position. In this position, the drive rotates the inner race 1800 counterclockwise. Since there is no pulling force on the paper sheet 1812, and it is merely being passively driven and presents some resistance, the inner race 1800 tends to rotate counterclockwise with respect to the outer race 1796. This relative movement of the races forces the balls such as 1804 into the naπower left sides of the recesses such as 1808. The movement of the balls into the naπower portions of the wedge-shaped spaces jams the outer race and the inner race together, so the drive force on the inner race 1800 is transmitted to the outer race 1796. To keep the outer races 1796 centered, each clutch has several wedge-shaped recesses and captured balls such as 1804 around its circumference.

Figure 28 shows the freewheeling clutch for the roller 1784 in the disengaged or freewheeling position. In this position, the drive may continue to rotate the inner race 1802 counterclockwise, but the outer race 1798 is travelling counterclockwise faster than the inner race 1800. This may occur if there is a forward pulling force on the paper sheet 1814. This pulling force may be provided, for example, by a later nip with a faster peripheral speed than the normal driven speed of the outer race 1798. This relative movement of the races releases the balls such as 1804 into the wider left sides of the recesses such as 1810. The wider sides of the recesses are further from the outer races such as 1798 than the diameter of the balls such as 1806. The balls

1806 are the only mechanism provided to transmit the driving force from the inner race to the outer race, and they are not in a position to drive the outer race, so the outer race 1798 turns without any substantial resistance and allows the sheet 1814 to be pulled forward. As soon as the pulling force on the sheet 1814 ceases, the inner race 1802 again overtakes the outer race 1798, the balls such as 1806 jam in the recesses such as 1810, and the inner race 1800 again drives the outer race 1796 as shown for the left roller 1782 of the skimmer 1780.

The foregoing detailed description of the present invention has been described by reference to specific embodiments, and the best mode contemplated for carrying out the present invention has been shown and described. It should be understood, however, that modifications or variations in the structure and aπangement of other than those specifically set forth herein may be achieved by those skilled in the art. Any and all such modifications are to be considered as being within the overall scope of the present invention. Therefore, it is contemplated to cover the present invention and any and all modifications, variations, or equivalents that fall within the true spirit and scope of the underlying principles disclosed and claimed herein. Consequently, the scope of the present invention is limited only by the limitations of a particular claim that is under study.

Claims

CLAIMS:

1. A sheet feeder comprising:

(a) a skimmer for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path; (b) a separator spaced downstream along the feed path from the skimmer or advancing the engaged sheet while retarding any adjacent sheets; and

(c) a first guide plate extending between said skimmer and said separator substantially parallel to said feed path to guide the engaged single sheet substantially along the feed path, preventing buckling of the engaged single sheet perpendicular to the feed path.

2. The sheet feeder of claim 1, wherein said skimmer comprises a first friction element including a generally cylindrical endless rotating peripheral surface carried on a support.

3. The sheet feeder of claim 2, wherein said first guide plate is supported at least in part by and pivotable with respect to said support.

4. The sheet feeder of claim 3, wherein said support is a rotating shaft and said guide plate is mounted to be pivotable independent of the rotation of said rotating shaft.

5. The sheet feeder of claim 1, wherein said separator comprises a first friction element having a generally cylindrical endless rotating peripheral friction surface rotatable about an axis extending across and generally parallel to said feed path on one side of said feed path, said peripheral surface being positioned for engaging and advancing a single sheet along said feed path.

6. The sheet feeder of claim 5, wherein said guide plate has a downstream edge including a notch and at least a portion of said first peripheral surface passes within said notch.

7. The sheet feeder of claim 1, further comprising a second guide plate on the opposite side of the feed path with respect to said first guide plate, said second guide plate extending substantially parallel to said feed path to guide the engaged single sheet substantially along the feed path, preventing buckling of the engaged single sheet perpendicular to the feed path.

8. The sheet feeder of claim 7, wherein said separator comprises a first friction element having a generally cylindrical endless rotating peripheral surface rotatable about an axis extending across and generally parallel to said feed path on one side of said feed path, said first endless rotating surface being positioned for engaging and advancing a single sheet along said feed path.

9. The sheet feeder of claim 8, wherein said second guide plate comprises a projecting friction surface adjacent to and positioned on the opposite side of the guide path from said first peripheral surface for biasing an engaged single sheet against said first peripheral surface for advancement while separating any additional sheet positioned between said friction surface and the engaged single sheet.

10. The sheet feeder of claim 9, wherein said first peripheral surface is a pair of peripheral surfaces separated by a circumferential recess and said projecting friction surface is positioned to normally project into said recess.

11. The sheet feeder of claim 10, wherein said second guide plate is biased toward said first peripheral surface.

12. The sheet feeder of claim 11, further comprising a spring positioned for biasing said second guide plate toward said first peripheral surface.

13. The sheet feeder of claim 7, wherein said first and second guide plates converge in the direction of said feed path.

14. A sheet feeder for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path, said sheet feeder having a separator interposed along the feed path for advancing an engaged single sheet while positively retarding adjacent sheets, the separator comprising: (a) a first friction element comprising a generally cylindrical rotating peripheral surface rotatable about an axis extending across, generally parallel to, and on one side of said feed path for advancing an engaged single sheet along said feed path; and

(b) a second friction element on the other side of said feed path defined by a projection biased toward said first friction element for retarding the progress of a sheet along said feed path, wherein said second friction element is stationary with respect to travel along said feed path; wherein said first and second friction elements are axially offset from each other and said second friction element is interleaved radially with respect to said first peripheral surface, thereby gripping the engaged sheet between said first and second peripheral surfaces.

15. The sheet feeder of claim 14, wherein said first peripheral surface is a pair of peripheral surfaces separated by a circumferential recess and said second friction element is sized, shaped, and positioned to normally project into said recess.

16. The sheet feeder of claim 14, wherein said second friction element is a rib extending generally along said feed path.

17. The sheet feeder of claim 16, wherein at least a portion of said rib normally projects into said groove while said feeder is in operation.

18. The sheet feeder of claim 14, comprising an axially alternating series of at least two axially spaced first friction elements and at least one second friction element interposed between said two first friction elements.

19. A sheet feeder comprising: (a) a skimmer for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path, each sheet in said stack having a leading edge; and

(b) a bumper extending across said feed path, said bumper having a guide surface positioned to confront the leading edges of the sheets of the stack and to direct the leading edge of an advancing engaged single sheet away from the remainder of the stack.

20. The sheet feeder of claim 19, further comprising a guide plate extending substantially parallel to said feed path and downstream from said bumper.

21. A sheet skimmer for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path, said skimmer comprising: (a) at least one generally cylindrical endless rotating friction surface positioned to engage the end sheet of a stack of sheets;

(b) a motor having a rotor; and

(c) a positive drive engaging said rotor and said rotating surface for turning said rotating surface in timed relation to the rotation of said rotor.

22. The sheet feeder of claim 21, wherein said at least one generally cylindrical endless rotating surface has an axial length longer than its circumference.

23. The sheet feeder of claim 21, wherein said positive drive comprises a first timing sheave constrained to rotate in timed relation to said rotor, a second timing sheave constrained to rotate in timed relation to said generally cylindrical endless rotating surface, and a timing belt driven by said first timing sheave and driving said second timing sheave.

24. A skimmer for engaging and removing a sheet from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path, said skimmer comprising: (a) a sheet path along which a sheet having a first and second surfaces is passed;

(b) a paper driving element positioned to drive forward one surface of a sheet in said sheet path; and (c) a lateral reciprocator which imparts a lateral motion to said paper driving element.

25. A skimmer according to claim 24, wherein said lateral reciprocator comprises a cam follower and a cam surface biased against each other and associated with said paper driver element to cause said skimmer to laterally reciprocate.

26. The skimmer according to claim 25, wherein said cam surface has a sawtooth pattern that slowly moves the paper driving element laterally in a first direction and then quickly returns the paper driving element laterally in a second direction.

27. A skimmer for removing a sheet having an exposed surface from one end of a multifeed of sheets and feeding the engaged sheet edgewise along a feed path, said skimmer engaging the exposed surface of the sheet, said skimmer comprising:

(a) at least a first roller having a first rotation axis and positioned to drive one surface of a sheet forward into said sheet path; and

(c) at least a first freewheeling clutch for driving said first roller in the direction driving a sheet forward into said sheet path, while allowing said first roller free rotation in the forward direction when the sheet is moving forward faster than the peripheral speeds of said first roller, said first freewheeling clutch allowing said sheet to be easily drawn forward by later elements along said sheet path.

28. The skimmer of claim 27, further comprising: (d) at least a second roller having a second rotation axis mounted parallel to said first axis and positioned in tandem with said first roller to drive the same surface of the sheet forward into said sheet path; and

(e) a second freewheeling clutch for driving said second roller together in the direction driving a sheet forward into said sheet path, while allowing said second roller free rotation in the forward direction when the sheet is moving forward faster than the peripheral speeds of said second roller, said second freewheeling clutch allowing said sheet to be easily drawn forward by later elements along said sheet path.

29. The skimmer of claim 28, where said first and second freewheeling clutches are commonly driven.

30. A sheet separator, comprising: (a) a sheet path along which a sheet having a first and second surfaces is passed;

(b) an advancing roller positioned to drive forward the first surface of a sheet in said sheet path;

(c) a retarding roller positioned to drive the second surface of a sheet in said sheet path;

(d) a drive for driving said retarding roller backward; and

(e) a friction clutch connecting said drive with said retarding roller, said clutch permitting said retarding roller to be driven forward when fewer than two sheets are engaged between said advancing and retarding rollers, and said clutch permitting said retarding roller to be driven backward when two or more sheets are engaged by said advancing and retarding rollers.

31. The sheet separator according to claim 30, wherein said retarding roller is mounted on a shaft and is allowed to move toward and away from said advancing roller.

32. The sheet separator according to claim 31 , wherein said retarding roller is biased against said advancing roller.

33. The sheet separator according to claim 32, wherein said retarding roller is biased against said advancing roller by a spring.

34. A sheet separator for breaking down multifeeds of two or more overlapping sheets into separate sheets, the separator comprising:

(a) a sheet path along which a multifeed of at least two sheets can be passed, the multifeed having first and second opposed outside surfaces; (b) an advancing drive positioned to engage and drive the first surface of the multifeed forward along said sheet path;

(c) at least a first rotatable element mounted for rotation with respect to a normally non-rotating element;

(d) a drag operatively associating said first rotatable element and said normally non-rotating element to provide friction when said first rotatable element is rotated; and

(e) a roller sleeve having an outer, generally cylindrical surface positioned to frictionally engage the second surface of the multifeed and an inner, generally cylindrical surface coupled to said first rotatable element for retarding the forward progress of the second surface of the multifeed; wherein said roller sleeve is axially slidable on said first rotatable element for ready installation on and removal from said rotatable element.

35. The sheet separator of claim 34, wherein said drag is a spring clutch.

36. The sheet separator of claim 34, further comprising at least a second rotatable element coaxial with and axially displaced from said first.rotatable element, and rotatable with respect to said normally non-rotating element.

37. The sheet separator of claim 36, wherein said second rotatable element is coupled to said roller sleeve, constraining the first and second rotatable elements and said roller sleeve to rotate together when said roller sleeve is coupled with said first and second rotatable elements.

38. The sheet separator of claim 36, wherein said roller sleeve is axially slidable on said second rotatable element for ready installation on and removal from said second rotatable element.

39. The sheet separator of claim 36, further comprising a second drag providing friction between said second rotatable element and said normally non- rotatable support.