Sheet Feeding Apparatus

Abstract

A tray for supporting a stack of sheet material to be fed sequentially therefrom. The tray includes side support plates to align the sheets in the direction of feed, a backup plate to retard rearward movement of the sheets in that direction and front snubber tabs engageable with the top, front edge of the topmost sheet in the stack. The sheets are fed therefrom by rollers which give an initial rearward movement to the topmost sheet. Rearward movement of the sheet is prohibited by the backup plates as the front edge of the sheet is withdrawn from beneath the snubber tabs as a reverse buckle is formed in the sheet. The feed rolls are then reversed to feed the sheet over the snubber tabs and out of the tray. The upper sheet supporting surface of the tray includes a contoured plate coactable with the rollers to maintain normal distribution of forces on each sheet of the stack, regardless of the height of the stack and thereby assure the feeding out of single sheets including the last sheet from the tray.

Description

This invention relates to sheet feeding apparatus and, in particular, to apparatus for retaining a stack of sheet material in the desired orientation whereby single sheets may be sequentially fed therefrom.

When feeding individual sheets from a stack of sheet material, it is extremely important that the stack be maintained in a proper orientation whereby the sheet forwarding elements may function properly while preventing misfeeds or double-sheet feeds. A wide variety of devices are known and used in the art for achieving this end. One such device is disclosed in pending application Ser. No. 838,907 filed July 3, 1969 now Pat. No. 3,601,394 issued Aug. 24, 1971 in the name of John M. Lang.

According to the disclosure of the aforementioned application, roller means are provided which contact the topmost sheet in a stack to rotate and direct the topmost sheet against the direction of sheet travel. The rearward movement of the sheet is prohibited by back stop plates. This action, however, forms a reverse buckle in the topmost sheet so that the leading edge thereof may be withdrawn from beneath front edge snubber tabs. The drive rolls are then reverse rotated to feed the topmost sheet in the desired direction of travel over the snubber tabs and out of the tray to supplemental sheet feeding means.

In such a system, the rollers are mounted for pivotal movement toward the surface of the fixed support tray so that the rollers contact each topmost sheet at a different location, with each subsequent sheet being contacted slightly more distant from the leading edge of the sheet. The sheets are all maintained in a flat orientation conforming to the plate supporting tray and, consequently, each sheet is acted upon by slightly different normal forces from the feeding rolls which results in a slightly less than desirable mode of operation. Beyond this, it is often difficult to feed out the bottommost sheet from the stack since it must overcome a different type of frictional force from the sheets thereabove inasmuch as it is the only sheet of the stack in contact with the support tray.

It is therefore an object of the instant invention to improve sheet material retaining apparatus for use in a sheet feeding device of the type wherein sheets are fed one at a time from the top of a stack.

A further object of this invention is to improve sheet feeding apparatus by holding the supported sheets in an orientation where they may more readily be fed therefrom in a dependable manner.

A further object of the instant invention is to support a stack of sheet material in a non-flat orientation whereby feedout rollers may be more effective in advancing the topmost sheet from the stack since normal distributional forces on each sheet are substantially the same.

Still a further object of the instant invention is to increase the ability of feedout rolls to feed the bottommost sheet from a stack of sheet material.

These and other objects of the present invention are attained by a tray for supporting a stack of sheet material to be fed sequentially therefrom. The tray includes side support plates to align the sheets in the direction of feed and front snubber tabs engageable with the top, front edge of the topmost sheet in the stack. The sheets are fed therefrom by driven rollers which are pivotally mounted above the stack. The upper sheet supporting surface of the tray includes a contoured plate coactable with the rollers to maintain constant the normal distribution of forces acting on the fed sheet to thereby assure the feeding out of only single sheets including the last sheet from the tray.

For a better understanding of these and other objects of the present invention reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 is an elevational view in partial section of a continuous and automatic xerographic machine employing the sheet handling apparatus constructed in accordance with the instant invention;

FIG. 2 is a top plan view of the sheet support tray associated mechanisms of FIG. 1 without sheet material and

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 with a nearly depleted stream of sheet material.

The apparatus of the present invention, as shown herein is partially described in the aforementioned U.S. Patent application. It is particularly well suited for use in an automatic xerographic reproducing machine capable of transferring toner images to sheet material supported on and fed from the sheet support tray of the instant invention.

The tray assembly 10 includes a horizontal support platform or plate 12 upon which sheet material 14 to be fed therefrom is placed. The support platform has an indexable inboard side margin guide 18 and an indexable outboard side margin guide 20. The inboard margin guide is slideably mounted on the support platform and has a vertically extending leg 22 thereon. The outboard guide similarly has a vertical leg 24 complementary to that of the inboard margin guide and is adapted to cooperate therewith to guide individual sheets forward from the tray along the predetermined path of travel into operative association with supplemental sheet forwarding mechanism which are in the form of supplemental roller members 26, 28, 30 and 32. These supplemental rollers are adapted to move the sheet at the same linear speed as the feedout rollers 34 and 36 and to continue the movement of the fed sheets after rotation of the feedout rollers has terminated.

The outboard side margin guide, in association with the inboard guide, is slideably carried upon the support platform and arranged to move laterally thereon making it possible to accommodate sheets of varying length upon the flat platform. To aid in the correct positioning of the stack of final support sheets within the tray, the tray is provided with an indexing scale 38 for laterally positioning the outboard side margin guide. As can be seen in the Figures the sheet support tray in oriented so as to present sn unobstructed path of movement for feeding sheets to the supplemental sheet feeding rollers.

To retain the front margins of the individual sheets of the stack in alignment during sheet separation and forwarding there is provided a pair of front margin sheet retaining members 40 and 42.

Each retaining member includes a main body portion or snubber tab 44 which is pivotally mounted by a hinge pin 46 for limited rotation. Each snubber tab is mounted upon a slide bar 48 and 50. A torsion spring is wound about each pin and normally biases the snubber against a stop affixed to the body of the slide bar to hold the snubber in a predetermined position against the top of the stack of sheets.

Each of the two retaining members 40 and 42 associated with the tray is carried within the free end of the slide bar 48 and 50 with the opposite end of the slide bar supported on the side guides for permitting proper movement of the snubbers tabs. Lifting means, not shown, are arranged by semi-automatic operations to move the slide bar and maintain the snubbers in the desired orientation. The snubber tabs thus have a horizontal portion 52 resting on the top of the stack of sheet material and an integral vertically extending portion 54 to prohibit immediate forward movement of the topmost sheet toward the supplemental feeding rollers. Front snubber tabs, as disclosed in the aforementioned application, rather than corner snubber tabs could also be utilized.

Motion of each sheet is provided through sheet feeding and separating rollers 34 and 36 supported in a self-aligning manner within floating bearings secured to a shaft 56. The shaft, in turn, is secured to bearings mounted in the front or free end of two support arms 58 and 60. The opposite ends of the support arms are similarly secured to a drive shaft 62 and the drive shaft is journaled for rotation in the machine frames 64 and 66 above and to the rear of the supply tray. This permits the feed rollers to rest freely in contact with the uppermost sheet in the stack. Suitable drive means including belt 68 as described, for example, in the aforementioned Lang application are employed. Curved rod member 70 in a slot 72 in arms 58 and 60 is employed to semi-automatically raise the rollers 34 and 36 so that paper may be readily loaded in the tray. This lifting action is preferably coupled to a lifting of the snubber tabs and bars 48 and 50 for further convenience.

The drive means provide for driving the rollers first in a reversed direction to remove the leading edge of the topmost sheet from beneath the snubber tabs. This forms a buckle in the sheet between the rollers and the backup plates which prohibit rearward movement of the sheet. The drive means then reverse drive the sheet from the stack in the predetermined direction of travel into supplemental feeding rolls for subsequent operations thereon. Automatic means for detecting the absence of sheets in the tray and for inactivating the apparatus in response thereto can also be employed.

In order to permit a more positive and reliable reverse feeding of only the topmost sheet in the stack and its proper advance over the snubber tabs, a supplemental sheet contouring plate 76 is secured to the upper face of the support plate contacting the lowermost fact of the bottommost sheet in the stack of sheet material to be forwarded.

The plate is symmetrically positioned on the tray and is preferably of a width at least as wide as the distance between the extreme most points of the feedout rollers 34 and 36. It is constructed to have a contour including three major portions. The central or intermediate portion 78 includes a sharp incline located so as to be contacted by the feedout rolls if no sheet material were resting thereon. Forwardly of this section is a leading section 80 with a slightly angled smaller face which tapers toward the lowermost end of the sharply inclined intermediate portion. The third portion 82 or rearward section extends from the uppermost portion of the intermediate section and slowly tapers down toward the rearmost portion of the plate. This slight angling, like the slight angling of the leading section assists in accentuating the sharper incline of the intermediate section. If a single sheet of paper or other support material were placed thereon, it would substantially conform to this cross-sectional shape. If an entire ream of sheet material, such as paper, were placed thereon, the paper would approximate this contour at the topmost sheet of the stack to only a slight degree.

With the feedout toll resting on the topmost sheet in the stack, regardless of the thickness of the stack, the normal distributional forces of the rollers 34 and 36 on the top sheet are substantially equal. The rollers are constructed to swing in an arc whereby, when a full ream of paper, normally two inches in height, is on the tray, the axis of the rollers is above the forward section 80 of the plate. But since the contours are virtually ineffective to deform the upper sheet, the roller is substantially normally acting on the sheet to be fed. When, however, the stack is approaching depletion, the axis of the rollers is over the intermediate section 78, acting perpendicularly to its face to present normal forces to these final sheets to be fed. Thus, throughout the feeding of the entire stack the forces of the rollers on the sheet being fed are substantially the same, i.e., normal and optimum. As sheets are depleted from the stack by being forwarded therefrom, the axis of the rollers drops by gravity, moving vertically and horizontally toward the contoured intermediate portion of the plate. This movement is also true of that portion of the roller which is contacting the topmost sheet. Note the arc line of FIG. 3.

In the preferred mode, the entire plate is made of a plastic with pads 84, 86, 88 and 90 of neoprene sponge being placed on the faces of the leading and rearward sections of the plate in contact with the bottom face of the lowermost sheet in the stack. This sponge material has a high friction or holding characteristics with sheet material contacting it. Movement of sheets, placed on the trays will thus be minimized. The intermediate inclined section is preferably covered with cork pads 92 and 94 so that the feeding out of the bottommost sheet will be better facilitated due to less frictional interference than created by the neoprene sponge.

As can be understood from the foregoing, the utilization of the contoured plate as described herein increases utility of sheet supporting apparatus wherefrom individual sheets are sequentially fed therefrom. The contour is such as to insure the separation of the topmost sheet from the sheet immediately therebeneath to reduce double sheet feeds while also minimizing the possibility of misfeeds due to well balanced characteristics of the forces of the rolls which are preferably visco elastic materials such as rubber. And while the particular materials as described herein have been found highly desirable to increase the overall efficiency by equalizing forces acting in the system, certain obvious functional substitutions to these materials are available without departing from the inventive concept described herein. In like fashion, the contoured plate, as described herein is equally effective for feeding sheets directly from the tray rather than in the reverse buckle mode.

While the instant application as to its objects and advantages, has been described as being carried out in a particular embodiment thereof, it is not intended to be so limited but it is intended to be protected broadly within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. Apparatus for feeding the topmost sheet from a stack of sheet material including

support means adapted to hold a stack of cut sheet material, said support sheet including

a contoured sheet supporting plate having at least one inclined surface for deforming said sheet material supported thereon,

rotating means arranged to contact the topmost sheet in the stack within a plane substantially perpendicular to said inclined surface,

means to drive said rotating means to advance the sheet in contact therewith, and

pivot means operatively associated with said rotating means to continually position said rotating means in contact with the topmost sheet in said plane normal to the inclined surface as the stack becomes depleted whereby a substantially uniform force is exerted on each sheet fed from said stack.

2. The apparatus as set forth in claim 1 wherein the means is positioned above said support means.

3. The apparatus as set forth in claim 1 wherein said rotating means is a roller means.

4. The apparatus as set forth in claim 3 further including pad means of cork mounted on said inclined surface and being arranged to coact with said roller to facilitate the feeding out of the last sheet.

5. The apparatus of claim 4 wherein rotation of said rotating means causes the contacted sheet to move in an uphill direction.