Document Feeding Device

Abstract

The present disclosure describes apparatus and techniques for creating a high-speed singulated flow of documents, such as mail pieces from a stack of said documents, in order that they may be subsequently identified and sorted to their proper destinations. The problem of double-feeding is virtually eliminated by the multiple restraint schemes provided by the present feeder. In particular, the device incorporates means whereby the documents to be processed are made to enter a channel formed between moving feed belts and a pivoting gate. The latter forms an extension of the registration wall along which documents to be fed are aligned, and incorporates within itself vacuum braking means. The pivoting gate member provides both a barrier restraint and a frictional restraint which act concurrently on the second or double document to stop it as it moves toward the conveyor transport system along with the document desired to be fed out of the stack.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The document processing system of which the present invention is a significant part also includes means for preparing the documents prior to feeding. To the extent that copending application Ser. No. 365,475, "Document Edging and Stack Advance System," by S. J. Lazzarotti, et al., describes such means, it is cross-referenced herein. The latter application and the present one are assigned to a common assignee. Certain prior art techniques in document singulation are also found in Canadian Pat. No. 567,020, "Paper-Handling Apparatus," by P. H. Wendt, et al., and this patent is referred to hereinafter.

BACKGROUND OF THE INVENTION

Many document feeders are in use which utilize vacuum forces to singulate or feed documents, such as mail pieces, one at a time from a stack. The strength of the vacuum forces employed in these feeders represents a compromise between the high vacuum force needed to feed heavy documents, with possible double feeds of lighter documents; and the lighter force needed for the latter documents which is insufficient to handle the heavier pieces. The search for an optimum feeder device to minimize both double feeds and skip feeds has continued for many years. For example in the reference Canadian patent a mechanism is provided on one side of the stack of documents which applies a suction or opposing vacuum pressure thereto in order to prevent more than one document from being drawn upward by the primary vacuum force associated with the feed drum. However, multiple feeds still occur with this type of feeder because the high strength of the primary force utilized results in a bleed-through force capable of attracting multiple relatively porous documents. Obviously documents having perforations therein, such as checks, are highly susceptible to multiple feeds. Moreover, the opposing vacuum force affecting the documents residing in the stack prior to feeding is often insufficient to separate those documents clinging to each other by adhesive and electrostatic forces.

The present invention virtually eliminates the problem of multiple feeds by utilizing combined barrier and vacuum braking restraints which halt the second or double document after it has left the stack and before it can contact the transport means toward which it is being driven by the feeder belts.

SUMMARY OF THE INVENTION

In accordance with the present invention, the problem of multiple-feeds inherent in high vacuum systems is solved by providing a channel between the moving feeder belts and a pivoting gate, which is an extension of the side registration wall along which the documents waiting to be fed are aligned. The width of the channel is chosen such that the gate acts as a barrier to a double document attempting to exit the feeder. The primary feeder vacuum drives the document to be fed along with the double to the gate where the latter pivots, if necessary, just enough to strip the double from the document being fed. This pivoting action also permits single documents of greater width than the aforementioned channel to exit the feeder. The barrier restraint is augmented by vacuum singulation provided by the pivoting gate itself. Thus, the gate forms a vacuum chamber supplied by the primary feeder vacuum which exerts a secondary vacuum force, considerably less than the primary force, upon the documents passing adjacent thereto. This secondary force while producing only a negligible effect upon a single document under control of the primary force, is nevertheless sufficient to brake to a stop and separate any double document from the document being fed.

Other features and advantages of the present invention will become apparent in the detailed description appearing hereinafter.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of the document feeder.

FIG. 2 depicts a vertical elevation of the feeder as viewed from the rear.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 depicts the basic elements which make up the feeder device of the present invention. A stack of documents 10 which may be mail pieces are depicted in position to be fed by the feeder. The arrow 12 indicates the direction of feed of the documents being processed. It may be assumed that the documents have arrived at the point shown in FIG. 1 by virtue of a stack advance system, such as that described in the reference copending application Ser. No. 365,475. In accordance with the techniques taught in the latter application, the stack advance has been halted through the operation of the stack sensing switch actuators 14 and 16. The documents 10 waiting to be fed are generally edged against registration wall 15 and are being restrained from contacting the feeder belts 18 by pusher fingers 20. Air flow created by a blower system (not shown) and routed to the feeder housing 22 which includes a vacuum chamber, exerts a vacuum pressure on the document waiting to be fed which pulls it against the pusher fingers 20.

When it is desired to initiate document feeding, the pusher fingers 20 are retracted behind the feeder belts 18 as indicated by the dashed outline 20a of the fingers. The pusher fingers 20 are shown in FIG. 2 attached to rotary solenoid 24 by shaft 26 and coupling 28. With continued reference to FIG. 1, the vacuum pressure exerted on the first document flexes a portion of the document about a pivot point located at the buffer plate 30. The buffer plate prevents contact of the document with the moving belts until substantially the entire angle has been traversed. This prevents any premature motion of the document in the direction of arrow 12. Once the flexure angle has been attained, the document contacts the moving feeder belts 18. These belts are perforated with a square hole pattern 32 (as seen in FIG. 2) which appears to provide an optimum driving force for the document being fed. The belts are contiguous with the face of the vacuum chamber and air entering the chamber passes through the belt perforations. The document forced against the feeder belts is accelerated in the direction of arrow 12. The belts are driven by pulleys 34 (as seen in FIG. 2), while idlers 36 and 38 (FIG. 1) provide the geometry for proper contact with the face of the vacuum chamber.

The moving document is now made to enter a channel 40 of minimum dimension "A" which is formed between the moving feeder belts 18 and a pivoting gate 42 which is a substantially coplanar extension of the inner surface of registration wall 18 and provides vacuum singulation. The vacuum pressure for the gate singulator 42 may be derived from the main feeder vacuum chamber in housing 22 through the use of a flexible tube 43 coupling ports 44 and 46. Also as indicated, the singulator has the capability of pivoting in order to increase the channel 40 dimension "A." The pivoting takes place in the direction of arrow 48 about point 50. Tension spring 52 permits the singulator 42 to return to the position shown, after a document is fed. The purpose of the singulator is to exert a small force via port 53 on a doubled document to prevent its entry in the acceleration rollers 54. The channel dimension is chosen to be such that the working face of the singulator will be in close proximity to a double document attempting to leave the feeder. For example, a dimension of approximately 0.150 inches has proved satisfactory in an actual operative embodiment for handling mail pieces. Single documents of thicknesses approaching the selected minimum channel dimension also contact the singulator 42, and in this special case the singulator acts to slightly retard the acceleration of the document. Although this would seem to be a detrimental effect, the overall effect is negligible because the gate singulator vacuum force is much smaller than the main driving force of the feeder vacuum chamber.

Since the minimum channel dimension "A" is chosen to be less than the maximum single document thickness expected to be processed, documents thicker than the minimum channel dimension must increase the channel width in order to exit the feeder. The force of the vacuum applied through feeder belts drives the document against the singulator gate 42, compressing spring 52 to a point which permits passage of the document. The pivoting action creates a stripping action which acts in a manner to separate double documents. In effect, the pivoting gate 42 creates a barrier restraint which in itself is a singulation method and enhances or augments the frictional restraint supplied by the vacuum singulator.

Once the feeder has advanced the document to the acceleration rollers 54, the pusher fingers 20 are required to be extended to inhibit the feeding of succeeding documents until the system is capable of processing them. This return motion is supplied by return spring 56 (FIG. 2) located in proximity to the rotary solenoid coupling 28. When the solenoid 24 is energized to retract the fingers, this spring is extended. De-energization of the solenoid permits the spring energy to return the fingers to their extended condition. With specific reference to FIG. 1, the de-energization of the solenoid 24 is effected by the documents leading edge as it breaks the light beam from lamp 58 directed toward photocell 60. The photocell 60 is positioned such that the light beam is interrupted only when the document has entered the acceleration rollers 54. The document must be under control of the rollers before it is stripped from the feeder belts by the extension of pusher fingers 20.

In the elimination of double feeds by the use of vacuum singulation in a pivoting gate member, certain geometric aspects of the feeder design are of interest. With reference to FIG. 1, the dimension "B," the distance from the point of common tangency of rollers 54 to the inner surface of registration wall 15 is significant. The larger dimension "B" is made, the more effective the vacuum singulator gate 42 becomes, since more time is available for the vacuum retarding forces to operate on the doubled document. Documents halted by the singulator, are permitted to enter the transport system on the next feed cycle. Since these documents are already partially singulated from the rest of the stack, the probability of doubling on this last mentioned cycle is very small.

The maximum length of dimension "B" is determined by the dimension "C" which as seen in FIG. 1 is the distance from the acceleration rollers 54 to the end of the vacuum chamber in housing 22. This last dimension must be greater than the minimum length document. If it is not, pickup of more than one document during a feed cycle is possible before effective inhibiting by fingers 20 can take place.

Another geometrical aspect of importance is dimension "D," FIG. 1. This is the distance from the closest edge of the vacuum chamber orifice to the registration wall 15. This dimension is significant in respect to initially mis-registered documents. The greater dimension "D" is, the less likely that two documents will overlap the vacuum chamber and be accelerated out together, creating a "double." In general, dimension "D" is designed to be a maximum within the constraints of dimension "C" (not to exceed the minimum document length) and dimension "E" (adequate to obtain the required acceleration forces for a specified feed rate).

In summary, it is apparent that the more restraint schemes that documents are exposed to in the feeding process, the lower the doubles rate and the more effective the process of singulation. The feeder described herein has registered an extremely low doubles rate in actual operating tests as a result of the multiple restraints incorporated therein.

First, the pivoting gate portion of the registration wall functions as a barrier restraint. Vacuum bleed through forces are not great enough on a double document to permit it to open the spring loaded pivoting wall. However, a thick single document when acted upon by the primary feeder vacuum forces is capable of pivoting the gate to enlarge the exit channel.

Second, the vacuum braking force within the pivoting gate, causes a frictional restraint to be imposed upon the double document. The braking force is of such strength that it is able to stop the document at a point past the registration wall but before it can enter the acceleration rollers of the transport system. By virtue of the vacuum force and the coefficient of friction, the brake prevents the second document from moving with the document desired to be fed.

Finally, a gravity restraint is present as a result of the backward tilt condition (the top edge of the document being displaced backward from the bottom edge) induced in the document stack by the initial biasing of the documents and the application of the sensing switches as taught in the reference copending application. When the first document is drawn against the feeder face by the primary vacuum force, a lesser force, perhaps due to a transient partial vacuum generated between the first and second document tends to cause the latter to move with the former. The gravity restraint on the second tilted-back document is greater than the aforementioned partial vacuum force, and the second document remains in place.

If the stack assumes a forward tilt geometry, the frictional resistance to movement of the lower edge of the document to the feeder face is overcome by the primary feeder vacuum force in the case of the first document, but such frictional restraint prevents movement of the second document along with the first.

In conclusion, the inventive concepts and implementations described herein have proved highly satisfactory in actual operative systems in which the doubles rate experienced in actual tests was approximately 0.2 percent. It should be understood that changes and modifications of the feeder may be needed to suit particular requirements. Such changes and modifications insofar as they are not departures from the true scope of the invention, are intended to be covered by the claims appended hereto.

Claims

What is claimed is:

1. A document feeding device comprising:

a feeder vacuum chamber operatively connected to generate an area of low atmospheric pressure adjacent a face portion thereof,

at least a single moving perforated feed belt operatively connected to contiguously traverse said face portion of said feeder vacuum chamber,

a registration wall situated in predetermined angular relationship to the face portion of said feeder vacuum chamber for enabling substantial alignment of the forward edges of the documents prior to their being fed,

a gate member pivotally mounted to provide a substantially coplanar extension of said registration wall, the face portion of said gate member being positioned in close proximity to said moving feed belt and forming therewith a channel through which said documents to be fed are driven by said belt, said gate member acting as a barrier restraint upon a double document to impede its exit from the feeder,

said gate member including additional vacuum chamber means operatively connected to generate an area of low atmospheric pressure adjacent its face portion, the gate member vacuum force acting as a frictional restraint upon said double document to impede its exit from the feeder, said barrier and frictional restraints being exerted concurrently on said double document by said gate member to effectively prevent the untimely feeding of said double document.

2. A document feeding device as defined in claim 1 further characterized in that the vacuum force present at the face portion of the gate vacuum chamber is less than that present at the face portion of said feeder vacuum chamber.

3. A document feeding device as defined in claim 2 wherein the minimum dimension of said channel is approximately the average width of the documents being fed.

4. A document feeding device as defined in claim 3 further including a tension spring coupled to said gate member and biased to pivot said member in a direction to maintain a predetermined minimum channel dimension.

5. A document feeding device as defined in claim 4 further including a pair of acceleration rollers located downstream from said gate member for receiving in turn the documents being driven thereto by said feed belt.

6. A document feeding device as defined in claim 5 wherein said vacuum chambers are coupled to each other by a flexible tube, whereby the vacuum pressure for said gate vacuum chamber is derived from that of said feeder vacuum chamber.

7. A document feeding device as defined in claim 6 further characterized in that said feed belt is perforated in a square hole pattern to optimize the vacuum driving force applied to said documents.

8. A document feeding device as defined in claim 7 wherein said documents are mail pieces and said minimum channel dimension is approximately 0.150 inches.

9. A document feeding device as defined in claim 8 further including a plurality of pusher fingers positioned adjacent said face portion of said feeder vacuum chamber and being intermeshed with said feed belt, said pusher fingers being capable of assuming either of two positions comprising respectively an extended position above and a retracted position below the surface of said feed belt, the former position inhibiting contact of the document with said feed belt, and the latter position permitting contact therewith.