Patent Application
20050269763
This invention relates generally to paper handling equipment, and more particularly to equipment which feeds cut paper sheets from stacks of such sheets.
In equipment that feeds cut paper sheets from stacks of sheets, it is not unusual for the cut sheets to be misted or for more than one sheet to be fed at one time (“multifeed”). In either case, such an occurrence may result in jamming or other faulty operation of the equipment.
The purpose for a paper feeder is to feed a single sheet of paper from a stack and to leave all other sheets remaining in the stack. To insure that at least one sheet is fed, the drive force on top of the sheet must exceed the retarding force elsewhere on the sheet. To prevent more than one sheet from feeding, the retarding forces on all sheets below the top sheet must be higher than the drag force exerted on the second sheet by the first sheet as it is being fed. For these reasons, the forces between sheets in a stack affect the performance of a feeder.
A number of factors may increase the likelihood of a misfeed or multifeed. One factor is the presence of so-called “edge welds” in the stack of cut paper sheets from which feeding is to be performed. Edge welds may occur during the paper manufacturing process during the step of cutting reams of paper prior to wrapping the reams. Large sheets of paper may be assembled into relatively large stacks of typically 500 sheets and then cut to a standard size such as letter size using a guillotine cutter. If the blade of the cutter is less than optimally sharp, individual sheets in the stack may be slightly bent downward at the edges as cutting takes place. The bending of the sheets at the edges may occur under very high local pressure, so that the edges of two or more sheets may be temporarily affixed to one another.
Another factor that may cause misfeeds or multifeeds is bonding between sheets other than at the edges. Such bonding may result during storage and transportation of wrapped reams of paper. For example, ten reams are commonly packed in a carton, and a considerable number of cartons may be stacked up during shipment and/or storage. The resulting load on the reams of the lower cartons in the stack of cartons may amount to hundreds of pounds. This loading may tend to press air out from between adjacent sheets in the reams and may lead individual paper fibers in neighboring sheets to interlock with each other. Both of these effects tend to form a bond between the surface of one sheet and the surface of a neighboring sheet. These bonds may cause the forces between adjacent sheets in a stack to be substantially higher than ordinary sheet-to-sheet friction and thereby cause misfeeds and/or multifeeds.
A third factor which may contribute to multifeeds arises from interfaces between reams in a stack of cut paper sheets. When a stack of paper in a paper tray is partially depleted, it is not unusual for an operator of the paper handling equipment to replenish the paper supply by adding additional paper to the top of the stack. This may occur when the stack is nearly completely depleted. The sheets within the original stack of sheets, as well as the sheets within the added stack, may have relatively high sheet-to-sheet coefficients of friction due to the edge welding and sheet-to-sheet bonding factors described in the previous two paragraphs. However, the coefficient of friction between the top sheet of the original stack and the bottom sheet of the added stack may be much lower than for the sheets above and below this interface. This is because the two sheets at the interface were not cut together or packed together so that there is little intermeshing of fibers. Also, when the operator adds new paper to the stack, a partial layer of air may be trapped between the new and old stacks at the interface.
Given such an interface, a problem may arise when the sheet feeder has fed most of the newly added sheets and then attempts to feed one of the few remaining sheets above the ream interface. In particular, the combination of high sheet-to-sheet friction for the few sheets above the interface and the relatively low sheet-to-sheet friction at the interface creates a relatively high probability that several sheets will be fed simultaneously. In other words, the singulation function of the feeder is more likely to fail at the ream interface by feeding more than one sheet just above the ream interface.
Still another factor that may lead to misfeeds and/or multifeeds may be present in stacks of pre-printed sheets, in which the ink printed on the sheets may tend to produce a mild adhesive effect between adjacent sheets.
It is a common practice for skilled operators of paper handling equipment to bend or fan a ream of paper before loading in order to break edge welds, break the bonds between interlocked fibers, and add a layer of air between adjacent sheets of a ream. Such conditioning of the ream may reduce sheet-to-sheet friction between the sheets in the ream, thereby reducing the chance of misfeeds and/or multifeeds. However, many operators are not aware of the desirability of bending or fanning a ream of paper before loading, and fail to do so. Also, some operators may have relatively small hands, and so may not be able to easily handle a ream in order to condition the ream before loading in a paper tray.
Accordingly, methods and apparatus are provided to reduce the likelihood of misfeeds and/or multifeeds when feeding cut paper sheets from a paper tray.
In one aspect, a method includes supporting a stack of cut paper sheets on a tray that includes a hinged portion. The method further includes pivoting the hinged portion of the tray to flex the stack of cut paper sheets without bringing the stack of cut paper sheets in contact with a feed member.
The pivoting may include pivoting the hinged portion of the tray downwardly so that a first portion of the stack of cut paper sheets is moved to an elevation that is below an elevation of the first portion of the stack of cut paper sheets prior to the pivoting. The pivoting may include contacting a top sheet of the stack with a first engagement member and moving the first engagement member downwardly to apply a downward force to the hinged portion of the tray via the stack of cut paper sheets to move the hinged portion of the tray downwardly from an initial position of the hinged portion of the tray. The downward pivoting of the hinged portion of the tray may be performed against an upward force applied by a spring to the hinged portion of the tray.
The method may further include contacting the top sheet of the stack of cut paper sheets with a second engagement member at an opposite portion of the stack from the first engagement member while the hinged portion of the tray is downwardly inclined relative to the initial position of the hinged portion of the tray. The method may further include allowing the hinged portion of the tray to return to the initial position while the second engagement member is in contact with the top sheet of the stack. The method may further include moving the second engagement member upwardly away from the stack of cut paper sheets after the hinged portion of the tray has returned to the initial position.
The tray may include a first hinged portion and a second hinged portion, with a first portion of the stack of cut paper sheets supported on the first hinged portion of the tray and a second portion of the stack supported on the second hinged portion of the tray. In such a case, the pivoting may include upwardly pivoting the first and second hinged portions of the tray to raise the first and second portions of the stack above their elevations in respective home positions in which the first and second hinged portions are in alignment with each other and/or downwardly pivoting the first and second hinged portions to lower the first and second portions of the stack below their elevations in respective home positions in which the first and second hinged portions are in alignment with each other.
In another aspect, a method includes supporting a stack of cut paper sheets on a tray, where the tray includes a hinged portion. The method also includes pivoting the hinged portion downwardly to flex the stack of cut paper sheets.
The pivoting may move a first portion of the stack of cut paper sheets to a second elevation below a first elevation of the first portion of the stack of cut paper sheets. The pivoting may include contacting a top sheet of the stack of cut paper sheets with an engagement member and moving the engagement member downwardly to apply a downward force to the hinged portion of the tray via the stack of cut paper sheets.
In still another aspect, a method includes supporting a stack of cut paper sheets on a tray, where the tray includes a first hinged portion and a second hinged portion, with a first portion of the stack of cut paper sheets supported on the first hinged portion of the tray and a second portion of the stack supported on the second hinged portion of the tray. The method also includes pivoting both hinged portions of the tray to flex the stack of cut paper sheets.
In yet another aspect, an apparatus includes a tray for supporting a stack of cut paper sheets. The tray includes a hinged portion. The apparatus also includes a feed mechanism disposed above the tray for selectively feeding sheets seriatim from the stack of cut paper sheets. The apparatus further includes a stack flexing mechanism for pivoting the hinged portion of the tray to flex the stack of cut paper sheets without bringing the stack of cut paper sheets in contact with the feed mechanism.
The stack flexing mechanism may include a mechanism for downwardly pivoting the hinged portion of the tray. The stack flexing mechanism may include a mechanism for inclining the hinged portion of the tray downwardly from a hinge point of the tray.
The stack flexing mechanism may include a first engagement member disposed above a first end of the tray for selectively contacting a top sheet of the stack of cut paper sheets to apply a downward force to the hinged portion of the tray via the stack of cut paper sheets. The apparatus may include a bias mechanism for upwardly biasing the hinged portion of the tray. The apparatus may also include a second engagement member disposed above a second portion of the tray, where the second portion is opposite the first portion of the tray. The second engagement member may be for selectively contacting the top sheet of the stack of cut paper sheets.
The apparatus may further include a control device operatively coupled to the first and second engagement members to:
The tray may include a first hinged portion for supporting a first portion of the stack of cut paper sheets and a second hinged portion for supporting a second portion of the stack of cut paper sheets. The apparatus may also include a mechanism for upwardly pivoting the first and second hinged portions of the tray to respective elevations that are higher than their elevations in respective home positions in which the first and second hinged portions are in alignment with each other and/or a mechanism for downwardly pivoting the first and second hinged portions of the tray to respective elevations that are lower than their elevations in respective home positions in which the first and second hinged portions are in alignment with each other.
In still a further aspect, an apparatus includes a tray for supporting a stack of cut paper sheets. The tray includes a hinged portion that is pivotable about a hinge point. The apparatus also includes a stack flexing mechanism for downwardly pivoting the hinged portion of the tray so that an end of the hinged portion is at an elevation lower than its elevation in a home position in which the hinged portion is in alignment with another portion of the tray.
The stack flexing mechanism may include an engagement member disposed above the hinged portion of the tray, and a mechanism for downwardly moving the engagement member to contact a top sheet of the stack of cut paper sheets to apply a downward force to the hinged portion of the tray via the stack of cut paper sheets. The apparatus may further include a bias mechanism for upwardly biasing the hinged portion of the tray toward a horizontal position.
In yet a further aspect, an apparatus includes a tray that includes a first hinged portion to support a first portion of a stack of cut paper sheets and a second hinged portion to support a second portion of the stack of cut paper sheets. The apparatus also includes a stack flexing mechanism for selectively pivoting the first and second hinged portions of the tray.
At least one of the hinged portions of the tray is pivotable about a hinge point, and the stack flexing mechanism may include a mechanism for selectively upwardly pivoting the hinged portions to respective elevations that are higher than their elevations when in a home position in which the first and second hinged portions are in alignment with each other and/or a mechanism for selectively downwardly pivoting the hinged portions to respective elevations that are lower than their elevations when in a home position in which the first and second hinged portions are in alignment with each other.
Therefore, it should now be apparent that the invention substantially achieves all the above aspects and advantages. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Various features and embodiments are further described in the following figures, description, and claims.
The accompanying drawings illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the principles of the invention. As shown throughout the drawings, like reference numerals designate like or corresponding parts.
The present invention includes a mechanism that bends or flexes a paper stack while it is in a paper tray. The flexing of the paper stack “conditions” it by, e.g., breaking edge welds between sheets of the stack, adding a layer of air between sheets of the stack, and/or separating paper fiber and/or adhesive ink bonds between sheets. Thus the conditioning of the paper stack may generally reduce sheet-to-sheet drag forces between sheets in the paper stack or make the drag forces more uniform to reduce misfeeding or multifeeding of sheets from the paper tray.
Referring now to the drawings, and particularly to
The stack flexing mechanism includes a first (downstream) engagement member 50 which is disposed above the hinged portion 32 of the tray 22a. A first actuator 52 is operatively coupled to the first engagement member 50 to selectively move the first engagement member up and down, in a manner to be described below, to selectively bring the first engagement member 50 in contact with the top sheet of the stack 42. The first actuator, which is schematically represented at 52, for example, may be constituted by a suitable motor and cam arrangement or by a solenoid. It may be preferable to use a cam and motor as such an arrangement may be more reliable than a solenoid, particularly in view of the presence of paper dust in the apparatus which may adversely affect a solenoid over time.
The stack flexing mechanism also includes a second (upstream) engagement member 54 disposed above the upstream end 56 of the tray 22a. (The upstream end 56 of the tray 22a is opposite to the hinged portion 32 which constitutes the downstream end of the tray 22a.) A second actuator schematically represented at 58 is operatively coupled to the second engagement member 54 to selectively move the second engagement member up and down, in a manner to be described below, to selectively bring the second engagement member in contact with the top sheet of the stack 42. The second actuator 58 may also be constituted for example by a suitable motor and cam arrangement or by a solenoid. Again a motor and cam may be preferable from the point of view of reliability.
A control device 60 (e.g., an electronic controller, microcontroller and/or microprocessor, which may perform other control functions for the apparatus besides those described herein) is also included in the stack flexing mechanism 30. The control device is operatively coupled, via first and second control signal paths 62, 64, respectively, to the actuators 52, 58 to control operation of the actuators 52, 58. Thus the control device 60 is also operatively coupled to the engagement members 50, 54 to control movement thereof (The control signal paths may include suitable buffers, driver circuitry, etc., which are not separately shown.)
A sensor 66 is associated with the tray 22a (though not necessarily positioned as indicated in the drawing) to detect occasions on which paper is loaded into the tray 22a. The sensor may be, for example, an optical or pressure-sensitive sensor. In addition or alternatively, the sensor may be able to detect closing of the tray 22a (or of a door—not shown—giving access thereto) after the tray or door has been opened to give an operator access to the tray. In any case, the sensor 66 is operatively coupled to the control device 60 via a sensor signal path 68 so that the sensor 66 can indicate to the control device 60 occurrence of an event in which paper has, or may have, been loaded into the tray.
Referring once more to
Referring once more to
Next, as indicated at step 94 in
The embodiment illustrated in connection with
The stack flexing mechanism 30a shown in
A control device 60a (again, e.g., an electronic controller, microcontroller or microprocessor) is also included in the stack flexing mechanism 30a. The control device 60a is operatively coupled, via first and second control signal paths 62a, 64a, respectively, to the actuators 96, 98 to control operation of the actuators 96, 98. Thus the control device 60a is also operatively coupled to the hinged portions 32a, 32b of tray 22b to control movement of the hinged portions 32a, 32b. (The control signal paths may include suitable buffers, driver circuitry, etc., which are not separately shown.)
A sensor 66, which may be like that described in connection with the embodiment of
Referring once more to
Referring once more to
It will be noted that in both the upward and downward pivoting of the hinged portions, the two hinged portions are pivoted in opposite angular directions to each other.
The operation of the stack flexing mechanism 30a may be modified in a number of respects from that described with respect to
While the drawings and descriptions herein show paper trays arranged in a horizontal orientation, it will be appreciated that the trays may alternatively be mounted at an angle from the horizontal.
According to other possible modifications of the embodiment illustrated in
The words “comprise,” “comprises,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, elements, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, elements, integers, components, steps, or groups thereof
A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Other variations relating to implementation of the functions described herein can also be implemented. Accordingly, other embodiments are within the scope of the following claims.
