Method and apparatus for media height sensing

Information

  • Patent Grant
  • 6625561
  • Patent Number
    6,625,561
  • Date Filed
    Tuesday, October 10, 2000
    24 years ago
  • Date Issued
    Tuesday, September 23, 2003
    21 years ago
Abstract
The present invention employs an inexpensive method and apparatus for media height sensing. A sheet fed media-using-machine has a media holder. The media holder holds a stack of a variable quantity of sheets of a medium to be supplied to a media-using-machine. The media holder has a structure for supporting the sheets and has a stack pusher which may be a mechanical device that pushes the stack into a position such that said media-using-machine may withdraw the sheets from said stack. The stack pusher has a variable position within a range of motion wherein such position is dependent upon a quantity of sheets in the stack. A variable device is attached to the stack pusher such that an electrical property of said variable device varies in relation to said position thereby allowing calculation of an estimate of the quantity of sheets in said stack, where the calculation is performed using said electrical property. The variable device may be, for example, a capacitor or a resistor, and the electrical property being capacitance or resistance, respectively.
Description




FIELD OF THE INVENTION




The present invention relates to an inexpensive method and apparatus for sensing the height of a stack of media sheets, such as paper, used by media-using-machines such as desk top printers, fax machines, and the like, that are sheet fed from a media holder such as an input hopper or tray.




BACKGROUND ART




There are a variety of media-using-machines that are fed from a stack of sheets of media. For example, desktop printers, fax machines, and text scanning machines typically operate in this fashion with the media being paper, plastic for transparencies and so forth. The media stack is held in input hoppers or trays which may be removable or built-in.





FIG. 1

is a perspective view which shows a prior art sheet fed media-using-machine


20


. Machine


20


has a media holder


22


and is fed with media sheets


24


which are held in media holder


22


. In

FIG. 1

, media holder


22


is illustrated as a tray but other embodiments, such as a slot into which a stack of media sheets


24


are directly placed may also be employed. Media holder


22


is inserted into holder slot


26


and is thus housed within or attached to machine


20


. Media holder


22


is illustrated as a removable tray in which media sheets


24


form a media stack. Media sheets


24


move in the direction of arrow


22


A and are fed into media-using-machine


20


. Media sheets are withdrawn sheet-at-a-time (sheetwise) from what is referred to as the top of a stack. Media sheets


24


are processed within machine


20


, such as by printing upon the media or optically scanning the media, and are ejected from media eject opening


28


in the direction of arrow


28


A to be deposited into the pickup hopper location of sheet


24


A. Machine


20


has within it a control system


29


for controlling the operations of machine


20


that are described in this paragraph.




In prior art desktop printers, if the media holder


22


becomes empty such as resulting from normal use of all media sheets


24


that are held in media holder


22


, then control system


29


may cause an audible or visible signal (not shown) on machine


20


to activate. An operator using machine


20


may notice the alert signal, realize that no media sheets


24


remain in media holder


22


and then refill media holder


22


with additional media sheets


24


. Alternatively, or in addition to the foregoing signal, if in the process of printing a print job the printer is depleted of paper, then control system


29


may cause a message to appear on a display, such as a message to the effect “the printer is out of paper, do you wish to continue ( ) yes, or ( ) no?” This message is accompanied by a pause in machine operation since no media sheets


24


remain in media holder


22


. Once the operator has refilled media holder


22


and replaced it in holder slot


26


, the operator may click a computer mouse in the “yes” location and proceed with the print job. Alternatively, the operator may cancel the job. Alternatively, the machine


20


may automatically sense that the media holder


22


is no longer empty and begin to continue a print job.





FIG. 2

is a cut-away view which provides further details of the prior art media holder


22


. In this and in other figures described in this specification, like numerals are identified with like reference numbers. Media holder


22


provides a structure for supporting media sheets


24


, with the structure comprised of tray bottom


30


A which provides a common supporting structure for the sides of media holder


22


. These sides are front side


30


B, right side


30


C, back side


30


D, and left side


30


E (not shown). Media sheets


24


are stacked into media holder


22


with tray bottom


30


A providing vertical support to the sheets and with sides


30


B,


30


C,


30


D, and


30


E providing a structure to retain media sheets


24


stacked in a vertical column of sheets, one atop the another. The front side


30


B is “front” with reference to flow of media sheets


24


from media holder


22


, that is, as media sheets


24


are fed from media stack


24


into the media processing areas of machine


20


, such media sheets


24


flow past front side


30


B. Right side


30


C and left side


30


E are right and left, respectively, with reference to view in the direction of media feed direction, illustrated by arrow


22


A. The back side


30


D is the side that is opposite the front side.




Stack pusher


32


is disposed to provide a mechanical pushing force to push media sheets


24


(the media stack) into a position such that machine


20


may withdraw the sheets from the stack. Stack pusher


32


consists of pusher plate


32


A, pusher base


32


B, hinge


32


C, and spring


32


D. Pusher plate


32


A is pivotally connected by hinge


32


C to pusher base


32


B. Spring


32


D provides a compressive force to urge pusher plate


32


A away from pusher base


32


B. Pusher base


32


B may be attached to tray bottom


30


A, or tray bottom


30


may serve as pusher base


32


B. This urging force of spring


32


D causes pusher plate


32


A to push media sheets


24


into a position that machine


20


may withdraw the sheets from the stack. It should be noted that while the illustration shows spring


32


D pushing pusher plate


32


A, the prior art includes springs disposed to exert tensile force pull to pusher plate


32


A, and the prior art includes rotational forces to torque pusher plate


32


A, all to provide the same result of pushing media stack


24


.





FIG. 3

is a perspective view of the prior art media holder


22


of FIG.


2


. In this view, right side


30


C, back side


30


D, and left side


30


E are attached to tray bottom


30


A. Window


30


F is provided on back side


30


D. Window


30


F is a vacancy or an aperture which is provided to allow a user of machine


20


to determine the presence or absence of media sheets


24


in media holder


22


, or to estimate the number of media sheets


24


in media holder


22


, without the need for withdrawing media holder


22


from holder slot


26


. Thus window


30


F provides a convenient way of ascertaining the amount of media sheets


24


in media holder


22


. A limitation of window


30


F is that it does not provide quantity information to control system


29


. Another limitation of window


30


F is that it requires the active attention of the operator of machine


20


, that is, the operator must pay attention to window


30


F. Yet another limitation is that machine


20


must be positioned or oriented on a desk or table such that the window is easily within view. In practice, when media sheets


24


are fully depleted, machine


20


stops operation. The view provided by window


30


F becomes simply a confirmation of what the operator already expects when machine


20


stops operation, that is, confirmation that media holder


22


is indeed empty with the convenience being that confirmation can be performed without withdrawing media holder


22


from machine


20


for inspection.





FIG. 4

is a perspective view of a prior art media holder


22


with some differences to that illustrated by FIG.


3


. In

FIG. 4

, pusher plate


32


A has tabs


36


A which project into slots


36


B. Slots


36


B are indentations, grooves, or the like, that are built into right side


30


C and left side


30


E. Tabs


36


A and slots


36


B allow pusher plate


32


A to change position in a constrained translational motion fashion in contrast to the rotational motion featured by prior art media holders


22


of

FIGS. 2 and 3

having a hinge


32


C allowing constrained rotational movement of pusher plate


32


A.





FIG. 4

also illustrates indicator mechanism


38


. Indicator mechanism


38


is a mechanism which is provided to allow a user of machine


20


to determine the presence or absence of media sheets


24


in media holder


22


, or to estimate the number of media sheets


24


in media holder


22


, without the need for withdrawing media holder


22


from holder slot


26


. While indicator window


30


F provided a direct viewing means, indicator mechanism


38


provides an indirect way of accomplishing the same result. Indicator mechanism


38


is comprised of indicator lever


38


A having indicator end


38


B which projects into window


30


F. Indicator lever


38


A has an opposite end, that is, a paper contact end


38


C. Indicator pivot


38


D is a pivot point that is supported by media holder


22


, such as by side


30


E or by holder bottom


30


A. Indicator lever


38


A is pivotally mounted on indicator pivot


38


D Double arrow


38


E indicates the two directions that paper contact end


38


C can travel. As additional sheets of media are properly placed into media holder


22


with sheets positioned under paper contact end


38


C, paper contact end


38


C is pushed upward and the pivot/lever action causes indicator end


38


B to move downward. The relatively downward positioned indicator end


38


B shows the machine user that media holder


22


is relatively full of media sheets


24


. Alternatively, indicator mechanism


38


can be located such that media sheets push paper contact end


38


C downward. In this case, the indicator end


38


B remains up until it falls downward as the last sheet is removed, i.e., only when the tray


22


becomes empty. In the examples of indicator mechanism just described, a spring exerting tensile or compressive force may be employed to bias indicator lever


38


A towards a selected position with a counter-force being exerted by the stack of media sheets.




Unfortunately, the indicator mechanism


38


of

FIG. 4

suffers from the same limitations as those of window


30


F that were described in connection with window


30


F of FIG.


3


.





FIG. 5

is a cut-away view which provides further details of the prior art media holder


22


of FIG.


4


. Note the tabs are identified with reference numeral


36


A. It should also be noted that while spring


32


D is illustrated as a compressed spring urging pusher plate


32


A away from bottom


30


A, an alternative spring is sometimes used in the prior art, and that alternative spring is a spring in tension, pulling pusher plate away from bottom


30


A to accomplish the same result.





FIG. 6

illustrates an aspect of prior art media holders


22


in that media feed rollers


39


are illustrated. Media feed rollers


39


are part of the media feed mechanism of media-using-machine


20


and which are used to withdraw sheets from a stack of media sheets


24


. Note that the stack pusher


32


is illustrated with pusher plate


32


A relatively close to pusher base


32


B. This corresponds to a media holder


22


that is relatively full of media sheets


24


.





FIG. 7

illustrates an aspect of prior art media holders


22


similar to that illustrated by FIG.


6


. In

FIG. 7

, stack pusher


32


is illustrated with pusher plate


32


A relatively away from pusher base


32


B. This corresponds to a media holder


22


that not relatively full of media sheets.





FIGS. 6 and 7

illustrate a media stack


24


in a rest position (

FIG. 6

) and in a lifted or pushed position (FIG.


7


). No spring is shown for media pusher


32


of

FIG. 7

, and in this media pusher


32


the media stack


24


pushing force is provided by the rotation of a bar (not shown) located on tray bottom


30


A and hinged about one of the edges of pusher plate


32


A. The lifting bar rotates the pusher plate


32


A upward until the media stack


24


is pressed against media feed rollers


39


of the media feed mechanism. The angle to which the bar rotates is therefore an indication of the quantity of sheets in media stack


24


.




From the limitations in the prior art that are described above, it can be seen that it is desirable to improve the ways in which the user of a sheet fed machine can determine the quantity of sheets in the media holder of such a machine. Also, since there is constant effort by manufacturers of such machines to make machines that are inexpensive, it can be understood that provision of low cost ways to determine the quantity of sheets is a highly desired goal.




SUMMARY OF THE INVENTION




The present invention employs an inexpensive method and apparatus for sensing the height of a stack of media. A sheet fed media-using-machine has a media holder. The media holder holds a stack of a variable quantity of sheets of a medium to be supplied to a media-using-machine. The media holder has a structure for supporting the sheets and has a stack pusher which may be a mechanical device that pushes the stack into a position such that said media-using-machine may withdraw the sheets from said stack. The stack pusher has a variable position of displacement within a range of motion wherein such position is dependent upon a quantity of sheets in the stack. A variable device is attached to the stack pusher such that an electrical property, or other property that can be sensed of said variable device, varies in relation to the position thereby allowing determination of an estimate of the quantity of sheets in said stack, where the determination is performed using the electrical or other property. The variable device may be, for example, a capacitor or a resistor, and the electrical property being capacitance or resistance, respectively.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view which shows a prior art sheet fed media-using-machine.





FIG. 2

is a cut-away view which provides further details of the a prior art media holder used with the media-using-machine of FIG.


1


.





FIG. 3

is a perspective view of the media holder of FIG.


2


.





FIGS. 4

is perspective view of another prior art media holder.





FIG. 5

is cut-away view which provides further details of the prior art media holder of FIG.


4


.





FIG. 6

illustrates an aspect of a prior art media holder.





FIG. 7

illustrates an aspect of a prior art media holder





FIG. 8

illustrates an aspect of the present invention, the aspect being a variable capacitor inexpensively used to sense rotational displacement corresponding to the quantity of sheets that are stacked in a media holder of a stack fed media-using-machine of the present invention.





FIG. 9

illustrates an aspect of the present invention, the aspect being a variable capacitor inexpensively used to sense translational displacement corresponding to the quantity of sheets that are stacked in a media holder of a stack fed media-using-machine of the present invention.





FIG. 10

illustrates a different translational displacement embodiment of a stack fed media-using-machine of the present invention.





FIG. 11

illustrates a variable capacitor that is indirectly linked to a media pusher of a stack fed media-using-machine of the present invention.





FIG. 12

illustrates a form of rotational linkage between a stack pusher of the present invention and a variable device of the present invention.





FIG. 13

illustrates a perspective view of a media-using-machine of the present invention.





FIG. 14

provides a functional diagram of the electrical function elements of an embodiment of the present invention.





FIGS. 15 and 16

illustrate methods provided by the present invention.











DETAILED DESCRIPTION




In the following detailed description and in the several figures of the drawings, like elements are identified with like reference numerals.




The desktop printing industry can benefit greatly from a low-cost device and method, and from low cost media-using-machines that can measure the quantity of media in an input media holder such as an input hopper or input tray. It will be beneficial to measure the quantity of media in such media holders provided that such measurement can be done without significant manufacturing cost to the printer or other machine. Information about media quantity available in a desktop printer may enable automatic notification to the user of the printer to load more media into the printer and may allow the control system of a sheet fed media-using-machine to control functions of the machine based upon the quantity of media available.




The present inventions described below are preferred embodiments and provide various sensory means and methods within a desktop or other machine to sense the amount of media present in the media holder. A key benefit of the present inventions is that they add little cost to the overall cost of a printer or other media-using-machine. The objects of the present inventions are provided by integrating low cost displacement sensors into media holders, and a preferred embodiment is to integrate the sensor into the previously known media-stack pushing mechanism that functions to push the media stack to a position where the media-using-machine may conveniently withdraw sheets from the media holder.





FIG. 8

illustrates an aspect of the present invention; this aspect is variable capacitor


40


which is used to sense the quantity of sheets that are stacked in a media holder


22


. This aspect of the present invention may be inexpensively used with media holders


22


of the prior art. In particular, this aspect of the present invention may be conveniently attached to a stack pusher


32


such as those of the prior art that are used to provide a mechanical force to push a stack of media sheets into a position such that the media-using-machine


20


may withdraw the sheets from the media holder


22


. Alternatively, a stack pusher


32


may be provided using a similar construction but which serves no other function other than pushing a stack of media sheets such that the quantity of sheets may be measured using the media stack displacement method.of the present invention. In any event, a stack pusher


32


provides a mechanical force upon the media stack such that a difference in the quantity of sheets of a stack causes a difference in the amount of displacement of the stack pusher.




In

FIG. 8

, variable capacitor


40


is one type of variable device that may be employed by the present invention. In

FIG. 8

, the variable capacitor will be illustrated in connection with a stack pusher


32


wherein the stack pusher is of the type illustrated in

FIGS. 2

,


3


,


6


, and


7


which type employs a hinge


32


C to govern the motion of pusher plate


32


A relative to pusher base


32


B. Such variable devices have properties which may be employed by the present invention. In the case of a variable capacitor, the electrical property is capacitance. Variable capacitor


40


has linked plate


40


A which is linked or attached to pusher plate


32


A. Linked plate


40


A is a conductive element that is structurally mounted on pusher plat


32


A. Variable capacitor


40


also has non-linked plate


40


B which is not linked or attached to pusher plate


32


A. Thus, non-linked plate


40


B is a conductive element that is structurally mounted on a structural member of media holder


22


or to a structural member attached to media holder


22


. For example, non-linked plate


40


B may be attached to tray bottom


30


A of a prior art media holder


22


of a prior art media-using-machine


20


, or may be mounted, as shown in

FIG. 8

to pusher base


32


B.




It should be understood that in the embodiment illustrated in

FIG. 8

, and in other embodiments, linked plate


40


A and non-linked plate


40


B may be substantially two dimensional as needed to provide plate surface area in order to achieve the desired capacitance (range) of variable capacitor


40


. In other words, the plates


40


A and


40


B may extend in a direction into the illustration page such that the plates have both length and breadth.




Linked plate wire


42


A provides an electrical communication path from linked plate


40


A to a capacitance measuring circuit (the circuit is shown in a subsequent figure,

FIG. 13

) while non-linked plate wire


42


B provides an electrical communication path from non-linked plate


40


B to the capacitance measuring circuit.




In

FIG. 8

, pusher plate


32


A is disposed at an angle α with respect to pusher base


32


B and with respect to tray bottom


30


A, the vertex of the angle being defined by hinge


32


C. Linked plate


40


A and non-linked plate


40


B extend from one radius R


1


to another radius R


2


, where R


2


is greater than R


1


and each of the radii are measured from hinge


32


C.




It is well known in the prior art how to use capacitance to measure changes in relative separation of two electrodes. The present inventions employ this principle to sense the relative amount to which the media pusher


32


displaces media stack


24


. The capacitance of the electrode pair (


40


A and


40


B) can be calibrated at the non-displaced position corresponding to a full media stack


24


(as illustrated in FIG.


6


), calibrated at a fully displaced position corresponding to a media holder


22


holding no media sheets, and can be calibrated at intermediate displaced positions corresponding to a media stack


24


that is less than full but more then empty (illustrated in FIG.


7


). It should be noted that in this embodiment, angle α varies from its minimum angle when media holder


22


is full to its maximum angle when media holder


22


is empty of media stack


24


.




The general model of a parallel plate capacitor is given by the well known formula where capacitance in the ideal case is given by Eq. (1)








C=A∈,∈




0




/d


  (1)






where A is the area in square meters of one of the plates, d is the distance in meters between the plates, ∈


0


is the permittivity of empty space with the numerical value of 8.85×10


−12


farad/m, and ∈


r


is the relative permittivity of the dielectric material between the plates. In this embodiment, the dielectric material is air and for air, ∈


r


is nearly unity. It should be understood that electrodes


40


A and


40


B may be covered with a protective paper, plastic, or other layer and such a layer would affect result in a composite dielectric material consisting of both air and the protective layer, resulting in a different ∈


r


. In fact, electrodes


40


A and


40


B may be disposed such that one of the electrodes is located on one side of media stack


24


while the other electrode is located on the other side of media stack


24


. An example of this type of location would be to place non-linked plate


40


B in the media-using-machine at the location which would comprise a roof of media tray


22


when media tray


22


is inserted into the media-using-machine. Another example would be when a slot rather than a tray is used. The non-linked electrode


40


B may be disposed on one side of the thickness dimension of the slot while the linked electrode may be disposed on the other side of the thickness dimension. By “thickness dimension” the inventor means that dimension that becomes increasingly occupied as the slot becomes increasingly filled with paper. It should be noted that in a slot type arrangement, it would be feasible to have both electrodes be “linked” electrodes, that is, one electrode may be on one side of the media stack


24


while the other electrode being on the other side of the media stack


24


. The media would serve as the dielectric and the varying thickness of the media stack


24


would result in varying capacitance.




In the embodiment of

FIG. 8

, it may be observed that electrodes


40


A and


40


B are not parallel but are instead disposed at the varying angle α. This will result in capacitive behavior in variable capacitance that is different from that modeled in Eq. 1 and better expressed in Eq. 2 for an ideal case:







C=∈




r





0




l


/αln


R




2




/R




1


  (2)




where l is the dimension of electrodes


40


A and


40


B perpendicular to the page of FIG.


8


.




We may expect that the opposite charges on the respective opposite electrodes will not be equally distributed on the electrodes but instead will migrate to the vicinity of the plates that are closest to each other until an equilibrium is reached. In other words, the charge will migrate to areas that are closer to hinge


32


C since opposite charge attracts. As angle α becomes greater, such migration will become more pronounced. As angle α becomes closest to zero such migration will become less pronounced and there will be a more uniform distribution of charge on the plates since electrodes


40


A and


40


B become very close to parallel. The non-ideal behavior of the variable capacitor


40


of the present embodiment, and of other embodiments described herein simply means that the capacitive behavior of the variable capacitor should be empirically determined and an appropriate conversion circuit, lookup table, or conversion expression employed for conversion of measured capacitance values to media quantities.





FIG. 9

illustrates an aspect of the present invention; this aspect is variable capacitor


45


, which is used to sense the quantity of sheets that are stacked in a media holder. This aspect of the present invention may also be inexpensively used with media holders


22


of the prior art. In particular, this aspect of the present invention may also be conveniently attached to a stack pusher


32


such as those of the prior art.




In

FIG. 9

, variable capacitor


45


is a one type of variable device that may be employed by the present invention. In

FIG. 9

, the variable capacitor will be illustrated in connection with a stack pusher


32


wherein the stack pusher is of the type illustrated in

FIGS. 4 and 5

which type employs tabs


36


A with slots


36


B or which employ some other means to provide translational (as opposed to rotational) movement of pusher plate


32


A relative to pusher base


32


B. Variable capacitor


45


has linked plate


40


A which is linked or attached to pusher plate


32


A. Variable capacitor


45


also has non-linked plate


40


B which is not linked or attached to pusher plate


32


A. For example, non-linked plate


40


B may be attached to tray bottom


30


A of a prior art media holder


22


of a prior art media-using-machine


20


. Linked plate wire


42


A and non-linked plate wire


42


B serve the same function as described for these elements in connection with FIG.


8


. Shim


46


may be provided to make linked plate


40


A and non-linked plate


40


B parallel or more close to parallel. Shim


46


may be attached to and sandwiched between pusher plate


32


A and linked plate


40


A. Since displacement of media pusher


32


A of

FIG. 9

is translational rather than rotational, the parallelism provided by shim


46


is maintained at different displacements.





FIGS. 8 and 9

illustrate variable capacitors


40


and


45


of the present invention that rely upon the principle that capacitance changes with a change in the distance between two plates of a capacitor. That is, as the linked plate


40


A is displaced by either rotational or translational displacement further away from the non-linked plate


40


B, capacitance of variable capacitor


40


or


45


decreases in accordance with an increasing d in Eq. 1, above, or increasing θ in Eq. 2, above, while the converse is true in the case in which linked plate


40


A is displaced closer to non-linked plate


40


B.





FIG. 10

illustrates a different aspect of the present invention. This aspect relies upon the principle that capacitance changes with a change in the amount of overlapping surface area of a capacitor. This corresponds to an increase in A of Eq. 1 resulting in an increase of C.

FIG. 10A

illustrates variable capacitor


50


which is used to sense the quantity of sheets that are stacked in a media holder. This aspect of the present invention may also be inexpensively used with media holders


22


of the prior art. In particular, this aspect of the present invention may also be conveniently attached to a stack pusher


32


such as those of the prior art. This aspect of the intention can be used with stack pushers


32


that rely on either translational displacement or rotational displacement.




In

FIG. 10

, variable capacitor


50


is illustrated in connection with a stack pusher


32


wherein the stack pusher is of the type illustrated in

FIGS. 4 and 5

which type employs tabs


36


A with slots


36


B or which employ some other means to provide translational displacement although, as mentioned above, this embodiment may be used with stack pushers


32


that employ rotational type displacement. Variable capacitor


50


has linked plate


50


A which is linked or attached to pusher plate


32


A. Linked plate


50


A is disposed such that it is parallel to tray sides


30


C and


30


E.




Variable capacitor


50


also has non-linked plate


50


B which is not linked or attached to pusher plate


32


A. For example, non-linked plate


50


B may be attached to tray bottom


30


A of a prior art media holder


22


of a prior art media-using-machine


20


. Non-linked plate


50


B is disposed such that it is parallel to tray sides


30


C and


30


E and parallel to linked plate


50


A.




The principle of operation of variable capacitor


50


is that when pusher plate


32


A is displaced to be closer to pusher base


32


B there is a greater area of overlap for linked plate


50


A and non-linked plate


50


B. This greater area of overlap causes the capacitance of variable capacitor


50


to increase with increasing A, somewhat as in Eq. 1.




In these and the following embodiments of the present invention, linked plate wire


42


A and non-linked plate wire


42


B are not necessarily shown but instead are omitted for clarity. It should be understood that such wires are used with other embodiments of the invention to connect the capacitor plates to a capacitance measuring circuit (shown in a subsequent figure, FIG.


13


).





FIGS. 10B

,


10


C, and


10


D illustrate linked plate


50


A and non-linked plate


50


B in positions of no overlap, partial overlap, and full overlap, respectively. These correspond to pusher plate


32


A being not displaced, partially displaced, and fully displaced towards pusher base


32


B which in turn correspond to an empty, partially full, and a completely full media tray


22


, respectively.




Linked plate wire


42


A and non-linked plate wire


42


B serve the same function as described for these elements with in connection with FIG.


8


. Shim


46


of

FIG. 9

may be provided to make linked plate


50


A and non-linked plate


50


B parallel or more close to parallel. Shim


46


may be attached to and sandwiched between pusher plate


32


A and linked plate


50


A.




In the embodiments of the present invention illustrated by

FIGS. 8

,


9


, and


10


, a direct linking means was used to link the linked plate of the variable capacitor to the media pushing surface.





FIG. 11

illustrates an indirect linkage between pusher plate


32


A and a linked plate


52


A of variable capacitor


52


. Variable capacitor


52


is generally similar to the variable capacitor of

FIG. 10

, that is, they both rely upon the overlapping surface area principle. Linkage


54


is constructed of four rigid link arms


54


A,


54


B,


54


C, and


54


D as well as four link pivots


54


E,


54


F,


54


G, and


54


H. Link arms


54


A and


54


B are pivotally attached to pusher base


32


B with link pivot


54


E. Link arms


54


C and


54


D are pivotally attached to pusher plate


32


A with link pivot


54


F. Link arms


54


A and


54


C are pivotally attached to each other with link pivot


54


G. Link arms


54


B and


54


D are pivotally attached to each other with link pivot


54


H. Double arrow


56


illustrates the displacement that is transmitted by linkage


54


from pusher plate


32


A to linked plate


52


A of variable capacitor


52


. As linked plate


52


A is displaced downward, there is a greater area of common overlap with non-linked plate


52


B and a corresponding increase in capacitance.




It should be understood that an indirect linkage of the present invention could be constructed by using a media pusher of the type of indicator lever


38


A as described in connection with FIG.


4


. This would be an instance of a stack pusher (indicator lever


38


A) serving no other function other than pushing a stack of media sheets such that the quantity of sheets may be measured using the present invention, which was alluded to in connection with FIG.


8


.





FIG. 12

illustrates yet another form of linkage between stack pusher


32


A and a variable device


60


of the present invention. Rod


62


, which may be a part of a hinge mechanism, provides an axis about which stack pusher


32


A may rotate. Rod


62


is attached to a movable part of variable device


60


. Variable device


60


is attached to a part of the structure of media holder


22


, such as attached to pusher base


32


B. Variable device


60


may be a variable capacitor of the well known type having a set of parallel plates connected to comprise a capacitor electrode, with a similar set of parallel plates connected to constitute a second electrode, wherein the sets of plates are interleaved and wherein relative rotation of the sets causes a change in overlapping surface area and thus a change in capacitance. Alternatively, variable device


60


may be a resistance potentiometer, or any other device used to measure rotational positions or displacements.




The description of the present invention has described sensors embodied as capacitive plates that vary in capacitance with angle of rotation, capacitive plates that vary with area of overlap, translational displacement and rotational displacement sensors, as well as direct and indirect linkages. It should be understood that other mechanical displacement embodiments and other sensing elements (such as magnetic proximity sensors, optical-transmissive sensors, optical-reflective sensors, etc.) may be devised that are within the scope of the invention. It is desired that the embodiment depend upon displacement of media stack


24


and a monotonic relationship between the amount of displacement and the value produced by the sensor.





FIG. 13

is a perspective view of a media-using-machine


63


of the present invention. The media-using-machine


63


of the present invention has media holder


64


which incorporates the present invention as described in

FIGS. 8

to


12


. Media holder


64


includes stack pusher


32


, a variable device which will be discussed in terms of variable capacitor


40


.




Linked plate wire


42


A and non-linked plate wire


42


B have terminals located at front side


30


B and there is a corresponding set of terminals (not shown) in holder slot


26


that mate with


42


A and


42


B when media holder


64


is inserted into holder slot


26


. The terminals in holder slot


26


are not shown but will be referred to as the “on-machine terminals” in contrast to those for


42


A and


42


B which are referred to as the “on-holder terminals.”




Measuring device


65


is a capacitance measuring circuit, located on media holder


22


, that measures changes in the capacitance of variable capacitor


40


. Measuring device


65


may be supplemented with value translator


66


, also located on media holder


22


. Value translator


66


is a processor, or a part of a processor, and uses the capacitance value that is measured by measuring device


65


and translates the capacitance value into a quantity of pages value. In one embodiment, value translator


66


makes a determination of a quantity of pages value, or makes a determination of an estimate of quantity of sheets, by using digital methods as by calculation. In another embodiment, value translator


66


uses analog methods for to make this determination.




In an embodiment of the present invention having measuring device


65


and value translator


66


located on media holder


22


, it should be understood that the on-machine terminals


42


A and


42


B are used to transmit the translated quantity of sheets from media holder


22


to stack the fed media-using-machine


63


. It should be further understood that measuring device


65


and value translator


66


may conveniently be provided and located not on media holder


22


but instead on media-using-machine


63


as is indicated by reference numerals


65


A and


66


A. In such an instance, on-holder terminals


42


A and


42


B simply transmit electrical signals from variable capacitor


40


, which is on media holder


22


, to the measuring device


65


A and translator


66


which are located within the media-using-machine


63


and not on the media holder


22


.




It should be mentioned that value translator


66


will not necessarily create an output that is an integer number as the quantity of sheets in media holder


22


. For example, since the ability of value translator


66


to resolve a measured value into a number of sheets may be limited, value translator


66


may produce an output that is along the lines of quintiles of fullness, such as 100%, 80%, 40%, 20%, 0% full. Depending upon resolution, deciles could be used, and so forth. An integer number could be output with the user understanding that the integer number may only be an approximation, depending upon the resolution provided by value translator


66


.




Media control system


70


is a processor which is located within media-using-machine


63


. Media control system


70


serves several functions. Media control system


70


provides a quantity display function. In providing the quantity display function, media control system


70


uses the quantity of sheets value (the output) provided by value translator


66


and displays the quantity of sheets on display


72


A or display


72


B which may be built into the outside structural case housing of the media-using-machine


63


. Media control system


70


may also display the quantity of sheets as display


72


C on monitor


73


where monitor


73


is either directly attached or networked to media-using-machine


63


. Monitor


73


may be a personal computer type monitor that is part of a monitor-keyboard combination of a desk top computer, or may be a similar such monitor.




Media control system


70


is a processor and value translator


66


is a part of the processor. Media control system


70


may update the quantity of sheets value by polling or interrogating measuring device


65


on a basis having a defined period. If a printer has a print rate of six pages per minute, for example, then it would be unnecessary to poll more frequently than once each ten seconds or so since the quantity of sheets could change by only one sheet in such a time interval. Other polling arrangements could be provided, such as polling immediately after media holder


22


is inserted into holder slot


26


and then polling only when sheets are being withdrawn from media holder


22


, such as during printing.




In another embodiment, media control system


70


makes an initial determination of an estimate of a quantity of sheets in media stack


24


when media holder


22


is inserted into holder slot


26


and a sheet counter is used to subtract sheets that are printed or otherwise used. Thus media control system


70


may make a determination that media holder


22


is “full” and then a sheet counter (not shown) which is interfaced with media control system


70


, counts off sheets as sheets are used. This counting-off-sheets process maintains a current determination of number of sheets in media holder


22


and may be a substitute for polling. Naturally, after a pre-determined number of sheets has been counted-off, media control system


70


may use polling of measuring device


65


in order to use the displacement method of the present invention to prepare an updated determination of the quantity of sheets in media holder


22


. In another embodiment, a sheet thickness sensor (not shown) is included within media-using-machine


63


and data from the sheet thickness sensor is provided to media control system


70


. Sheet thickness information from a sheet thickness sensor may be used, along with displacement information provided by measuring device


65


, to determine a number of sheets in media hopper


22


. This determination would use a total stack thickness value measured by measuring device


65


divided by a sheet thickness value to determine a total number of sheets.




Display


72


A,


72


B and


72


C are representative of the various types of displays that may be used by the present invention. The displays that may be used are limited only by the imagination. For example, a thermometer image could provide an analog to the quantity of sheets in media holder


22


. A series of ten side-by-side bars could represent quantity of sheets if resolved into deciles. A numerical value may be displayed. Graphical, including pictorial images such as a stack of paper of varying height may be displayed, and so forth.




Media control system


70


also provides a function of low-media quantity intervention. In this aspect, media control system


70


determines if a media using job has been requested of media-using-machine


63


. An example of such as job would be to print a document consisting of fifty-two pages. If such a job has been requested, then, before commencing the job, media control system


70


updates the quantity of sheets value, for example, determining that approximately thirty sheets remain in media holder


22


. Then media control system


70


, compares the number of sheets needed for the job (fifty-two) with the number of sheets remaining in media holder


22


(approximately thirty) and determines that insufficient sheets remain. Media control system


70


then causes a message to be activated. This message activation may be the display of a message, for example message


72


C on monitor


73


. The message would be to the effect: “You have asked to print a job having fifty-two pages, however, only approximately thirty pages remain in the paper tray. Do you wish to proceed with printing now or do you wish to add paper before proceeding with printing? Please use your computer mouse to click on the appropriate button.” Alternatively, an indicator light on media-using machine


63


may be activated, and this light may be supplemented by an audible signal. Adjacent to the activated light may be a legend permanently printed on media-using-machine


63


; such a legend being to the effect: “Insufficient Media for Next Job” or “Insufficient Media for Queued Jobs.”




One value of the present invention is apparent. Since desk top printers and other devices tend to print at slow speeds, for example at six pages per minute, a job of fifty pages would take more than five minutes. An operator of a media-using-machine


63


may wish to start processing the job and then proceed to undertake other work away from the vicinity of media-using-machine


63


, in other word, the operator may wish to leave the machine unattended as it prints the job. In such an event, the operator would be subject to reduced efficiency if the operator were to return several minutes later only to find that a few sheets printed before exhausting the few sheets remaining in media holder


22


. The present invention avoids such inefficiencies since the system advises the operator of insufficient sheets before the print job commences. It can also alert an operator at such times that queued print jobs are queued and evaluated against the current media supply in media hopper


22


.





FIG. 14

provides a functional diagram of the electrical functional elements of the present invention. Variable device


40


is illustrated as a variable capacitor connected to capacitance measuring circuit


65


by terminals


42


A and


42


B. Capacitance measuring circuit


65


provides its output through communication lines to value translator


66


. Value translator


66


may refer to lookup table


74


, in which case lookup table


74


is either connected to value translator


66


by communication lines or lookup table


74


is integrated into value translator


66


. Value translator


66


may be an amplifier, to amplify voltages in order to display capacitance quantities as analogs of page quantity, may be an analog to digital converter to convert capacitance quantities as estimates of page quantities, and so forth. Media control system


70


receives information from job request module


75


, such as the number of sheets required by the next job to process, and so forth. Media control system also receives page quantities from value translator


66


. Media control system


70


compares such page quantities with the number of sheets required for the next job, as mentioned above. Media control system


70


causes messages, such as the message mentioned in the foregoing paragraph, to be displayed on displays built into media-using-machine


63


(shown in

FIG. 13

) or on video monitor


72


C.




It should be understood that depending upon the amount of system integration, capacitance measuring circuit


65


, value translator


66


, and media control system


70


may be integrated into fewer discrete devices or one such device. It should be further understood that these circuits may require software in their implementation.




Media control system


70


may be interfaced with a communications network


80


to a remote print-job server


82


. Such a remote print-job server would then be a part of an embodiment of the present invention and the server would provide information such as the number of pages of queued jobs, and so forth. The media quantity determination features of the present invention would be provided to remote print-job server


82


by way of communications network


80


. The message display features of the present invention may be proved by way of a video display


72


C, or a machine mounted display


72


A or


72


B that is a part of print-job server


82


.





FIG. 15

illustrates a process chart of methods provided by the present invention. One aspect of a method of the present invention is to provide each of the elements of the invention that are described above and use these elements with a machine fed from a stack of sheets. To summarize this process of provision of elements would include the following steps:




Step


102


, provide a structure for supporting media sheets. This structure is adapted to be used as a media holder by a sheet fed media-using-machine.




Step


104


, provide a stack pusher which is supported by the structure supplied in step


102


. The stack pusher will have a variable displacement position within a range of motion wherein such displacement position is dependent upon a quantity of sheets in the stack.




Step


106


, provide a variable device attached to the stack pusher such that a measurable property, such as an electrical property of the variable device, varies in relation to the position.




Step


108


, provide a processor in communication with the variable device, where the processor calculates an estimate of the quantity of sheets in the stack, and where the calculation is performed using the electrical property of the variable device.




Step


110


, provide a display in communication with the processor, such that the display displays the estimate of the quantity of sheets in the stack.




Step


112


, use the equipment provided in the foregoing steps to display an estimate of the quantity of sheets in the stack, and to use the estimate of the quantity of sheets as a part of the media using process, such as part of a printing process. The display could be a numerical display, a graphical display such as a bar chart or a pictorial element, or so forth. The display may be a multi-function display such as a video screen.





FIG. 16

illustrates a process chart of another method of the invention which may further comprise the following steps:




Step


120


, determining if a media using job has been requested of the machine. This determination is done on a periodic basis or may be done as a part of a selected process.




If a media using job has been requested of the machine, then performing step


122


which is preparing a sheet requirement estimate, which is an estimate of the number of sheets that will be used by the job. Then step


124


is performed which is the determination of an estimate of sheets that are in the stack of the media holder, ready to be used by the media-using-machine.




Next, in step


126


, comparing the sheet requirement estimate with the estimate of the quantity of sheets in the stack. If the quantity of sheets in the stack is sufficient for the job, then proceed to step


128


in which the job is printed.




If in step


126


, the quantity of sheets is not sufficient for the job, then perform step


129


which is display a message to the effect that there is an insufficient quantity of sheets in the media holder to compete the job. Then the operator of the machine can perform step


130


which is to decide whether or not to add paper. If the decision is affirmative, then the operator proceeds to perform step


132


which is to add paper, that is, to add paper. After having added paper, the process continues to step


128


in which the job is fully printed. If the operator makes a negative decision in add paper at decision step


130


, then the operator decides in step


134


whether or not to partially print the job. If the answer to this latest decision is “yes” then the process proceeds to step


128


where pages are printed until they are exhausted. If, on the other hand, the operator decides in step


134


not to partially print the job, and the operator has already decided in step


130


not to add paper, then the print job is canceled as step


136


.




It should be understood that the foregoing is a summary of the methods of the invention and other aspects of the methods would be to include further elements of the invention that are mentioned above and to use these elements in the manner described above.




Although several embodiments of the present invention have been disclosed and illustrated, the invention is not limited to the specific forms or arrangements of parts so described and illustrated. The invention is only limited by the claims.



Claims
  • 1. A medium holder for holding a stack of a variable quantity of sheets of a medium to be supplied to a media-using-machine, the media holder comprising:a structure for supporting the sheets; a stack pusher, supported by said structure, said stack pusher having a variable displacement position within a range of motion wherein such variable displacement position is dependent upon a quantity of sheets in said stack; a variable device having a pair of spaced conductive elements and attached to said stack pusher, such that an electrical property of said variable device varies in relation to said variable displacement position of said stack pusher depending upon the quantity of sheets in said stack and as one conductive element moves relative to the other conductive element, thereby allowing determination of an estimate of the quantity of sheets in said stack from the electrical property.
  • 2. The media holder of claim 1 wherein said stack pusher is disposed to push the stack into a position such that said media-using-machine may withdraw the sheets from the stack.
  • 3. The media holder of claim 2 wherein said variable device comprises a variable capacitor and said electrical property comprises a capacitance of said capacitor.
  • 4. The media holder of claim 3 wherein said variable capacitor comprises said first conductive element including a first conductive plate and said second conductive element including a second conductive plate, said first conductive plate is mechanically linked with said stack pusher such that a change in position of said stack pusher causes said first conductive plate to be displaced in relation to said second conductive plate thereby causing the capacitance of the variable capacitor to vary.
  • 5. The media holder of claim 1 wherein said variable device is indirectly coupled to said stack pusher.
  • 6. The media holder of claim 1 wherein said variable device comprises a variable resistor and said electrical property comprises a resistance of said resistor.
  • 7. A media-using-machine fed from a stack of a variable quantity of sheets of a medium, the machine comprising:a structure for supporting the sheets; a stack pusher, supported by said structure, said stack pusher having a variable displacement position within a range of motion wherein such variable displacement position is dependent upon a quantity of sheets in said stack; a variable device having a pair of spaced conductive elements and attached to said stack pusher such that an electrical property of said variable device varies in relation to said variable displacement position of said stack pusher depending upon the quantity of sheets in said stack and as one conductive element moves relative to the other conductive element; and a processor in communication with said variable device, said processor making a determination of an estimate of the quantity of sheets in said stack from the electrical property of said variable device.
  • 8. The machine of claim 7 wherein said stack pusher is disposed to push the stack into a position such that said media-using-machine may withdraw the sheets from the stack.
  • 9. The machine of claim 8 wherein said variable device comprises a variable capacitor and said electrical property comprises a capacitance of said capacitor.
  • 10. The machine of claim 9 wherein said variable capacitor comprises said first conductive element including a first conductive plate and said second conductive element including a second conductive plate, said first conductive plate is mechanically linked with said stack pusher such that a change in position of said stack pusher causes said first conductive plate to be displaced in relation to said second conductive plate thereby causing the capacitance of the variable capacitor to vary.
  • 11. The machine of claim 7 wherein said variable device is indirectly coupled to said stack pusher.
  • 12. The machine of claim 7 wherein said variable device comprises a variable resistor and said electrical property comprises a resistance of said resistor.
  • 13. A method of using a media-using-machine fed from a stack of a variable quantity of sheets of a medium, the method comprising:providing a structure for supporting the sheets; providing a stack pusher, supported by said structure, said stack pusher having a variable displacement position within a range of motion wherein such variable displacement position is dependent upon a quantity of sheets in said stack; providing a variable device having a pair of spaced conductive elements and attached to said stack pusher such that an electrical property of said variable device varies in relation to said variable displacement position of said stack pusher depending upon the quantity of sheets in said stack and as one conductive element moves relative to the other conductive element; and providing a processor in communication with said variable device, said processor making a determination of an estimate of the quantity of sheets in said stack from the electrical property of said variable device.
  • 14. The method of claim 13 further comprising the step of providing a display in communication with said processor, such that the display displays said estimate of the quantity of sheets in said stack.
  • 15. The method of claim 14 wherein said display displays a numerical representation of said estimate.
  • 16. The method of claim 14 wherein said display displays a graphical representation of said estimate.
  • 17. The method of claim 14 wherein said display is a multi-function display and display of said estimate is one such function.
  • 18. The method of claim 17 wherein said display is a video screen.
  • 19. The method of claim 13 further comprising the steps of:determining if a media using job has been requested of said machine; if a media using job has been requested of said machine, then preparing a sheet requirement estimate, which is an estimate of the number of sheets that will be used by the job, comparing said sheet requirement estimate with said estimate of the quantity of sheets in said stack, if said estimate of the quantity of sheets in said stack is insufficient to meet said sheet requirement estimate, then causing an insufficient media message to be activated.
  • 20. The method of claim 19 wherein if said estimate of the quantity of sheets in said stack is insufficient to meet said sheet requirement estimate, then further comprising the step of causing said media using job to pause to permit an operator to add additional sheets of media to said machine.
  • 21. A media holder for determining an estimate of a quantity of medium sheets in a stack, comprising:a base member; a sheet-pushing member pivotally coupled to the base member and having a variable displacement position from the base member which is dependent on the quantity of sheets in a stack of medium sheets engaged by the sheet-pushing member; a first conductive element supported by the base member; and a second conductive element supported by the sheet-pushing member such that an electrical property associated with said first and second conductive element varies in relation to said variable displacement position of said sheet-pushing member depending upon the quantity of sheets in said stack and as the second conductive element moves relative to the first conductive element, thereby allowing determination of an estimate of the quantity of sheets in said stack from the electrical property.
  • 22. The media holder of claim 21 additionally comprising a variable capacitor having said first conductive element including a first conductive plate and said second conductive element including a second conductive plate, and wherein a change in position of said sheet-pushing member with respect to said base member causes said first conductive plate to be displaced in relation to said second conductive plate thereby causing the capacitance of the variable capacitor to vary.
  • 23. The media holder of claim 22 wherein said variable capacitor comprises a dielectric disposed between said first conductive plate and said second conductive plate.
  • 24. The media holder of claim 23 wherein said dielectric comprises air.
  • 25. The media holder of claim 21 additionally comprising a shim member connected to said sheet-pushing member and to said second conductive element for paralleling the second conductive element relative to the first conductive element.
  • 26. The media holder of claim 24 additionally comprising a shim member connected to said sheet-pushing member and to said second conductive element for paralleling the second conductive element relative to the first conductive element.
  • 27. The media holder of claim 21 additionally comprising a hinge mechanism for pivotally coupling the base member to the sheet-pushing member.
  • 28. The media holder of claim 26 additionally comprising a hinge mechanism for pivotally coupling the base member to the sheet-pushing member.
  • 29. A method for determining an estimate of a quantity of medium sheets in a stack, comprising:engaging a stack of medium sheets with a sheet-pushing member supporting a first conductive element and pivotally coupled to a base member supporting a second conductive element; moving the sheet-pushing member relative to the base member to cause an electrical property associated with said first and second conductive element to vary in relation to a variable displacement position of the sheet-pushing member from the base member depending upon the quantity of sheets in said stack and as the second conductive element moves relative to the first conductive element; and determining an estimate of the quantity of sheets in said stack from the electrical property.
  • 30. The method of claim 29 wherein said first conductive element includes a first conductive plate and said second conductive element includes a second conductive plate.
  • 31. The method of claim 29 additionally comprising overlapping the first conductive element and the second conductive element.
  • 32. The method of claim 30 additionally comprising overlapping the first conductive plate and the second conductive plate.
  • 33. The method of claim 30 additionally comprising forming a variable capacitor with said first conductive plate and said second conductive plate, and overlapping said first conductive plate with said second conductive plate such that the electrical property of the variable capacitor is a capacitance which changes with a change in the amount of overlapping surface area of the first conductive plate with the second conductive plate.
US Referenced Citations (5)
Number Name Date Kind
4508332 Nishio Apr 1985 A
4734747 Okuda Mar 1988 A
5486903 Kanno et al. Jan 1996 A
5721627 Kamiya Feb 1998 A
6100993 Eom Aug 2000 A