Abstract:
A media holding apparatus includes a tray having a support surface configured to receive media and a media stop carried by the tray. The media stop is movably supported for continuously adjustable positioning relative to the tray to conform dimensionally with media received in the tray. The apparatus also includes a position-detecting sensor associated with the tray and the media stop which is operative to generate a unique electrical pattern corresponding with a detected position of the media stop relative to the tray. The unique electrical pattern is indicative of the size of the media detected in the tray. A method is also provided.

Description:
FIELD OF THE INVENTION 
     This invention relates to media size detectors and media holding apparatus, and more particularly, to an automatic media size detector for detecting the size of media that is being delivered to a document-generating device, such as a printer, a copier or a facsimile machine. 
     BACKGROUND OF THE INVENTION 
     Document-generating is implemented by a number of hard copy output devices such as printers, copy machines, facsimile machines and multiple function peripheral (MFP) devices. In order to generate hard copy output, a supply of printable media needs to be made available to such devices. Typically, a stack of paper, or media, is supplied to a device from one or more removable paper trays. A host computer, or external device, submits a print, copy or facsimile job to the device which includes commands that tell the device on which size paper to print the job. 
     In order to determine the size of paper, or media, present within the paper tray of these devices, some technique is needed to detect the size of paper, or media, present in the supply tray. 
     Several techniques are known for conveying to a printing device information about the contents of a paper tray. According to one prior art technique, a uniquely sized tray is provided for each paper size that is accommodated by a printing device. For example, one tray is sized to receive letter-sized paper, while another tray is sized to receive legal-sized paper. Insertion of a specific size tray ensures only that size paper will be used. Accordingly, insertion of the specific size tray by a user notifies the user as to which sized paper is presently available. Optionally, a selection switch can be provided on the printing device that is set by a user to the paper size currently loaded in the device. Alternatively, mechanical identification features have been provided on a tray which are detected by the device once the tray is inserted, thereby identifying the specific paper size to the device. However, it is costly and inconvenient to utilize several different size trays. Additionally, storage space is needed to store the surplus trays. 
     According to another technique, a single paper tray can be reconfigured to receive various sizes of paper. Many home and small-business printers utilize such a single paper tray. However, re-configuration only accommodates a series of discrete paper sizes, such as letter-sized, legal-sized and A4-sized paper. Typically, a series of notches or holes is provided in the tray, and one or more media stops are positioned into a selected set of notches or holes to accommodate one of the available paper sizes. However, only a handful of predefined discrete paper sizes is available. 
     According to yet another technique, a single paper tray is reconfigured by a user after purchase to accommodate a single size of paper. According to such technique, the single paper tray is molded to accommodate a large selection of readily available paper sizes. The user indicates to a printer the size of paper that is present in the tray. One technique for indicating to the printer the size of paper involves “punching out” a marker or location in the paper tray corresponding to the specific paper size. A sensor detects the “punched out” marker which notifies the printer of the specific paper size. However, once punched out the tray is permanently configured for that particular paper size. The user must purchase a new tray in order to use a different paper size. 
     According to even another technique, U.S. Pat. No. 5,483,889 discloses an automatic media size detector for use with paper trays to detect the size of media present in a paper tray. A back stop and a side stop are each moved to unique associated receiving positions that are provided in the paper tray, with each position corresponding to a specific paper size. A plurality of conductive strips are provided in the tray, in proximity with each back stop. Each back stop, when received in an associated receiving position, makes electrical contact between a unique pair of the conductive strips so as to electrically connect the strips. The printer, using a look-up table, monitors all the strips to determine which two strips of the plurality are electrically connected together, which also indicates the received paper size. However, only a limited number of preselected paper sizes can be accommodated by such a paper tray. 
     Therefore, there exists a need for an improved automatic media size detector capable of detecting an infinite number of media sizes within a range of sizes. Furthermore, there is a need for an improved paper tray utilizing such a media size detector. 
     SUMMARY OF THE INVENTION 
     An apparatus and method are provided for automatically sensing media size in a hard copy output device such as a printer, a copier and a facsimile machine. A media stop is coupled with a position-detecting sensor to determine the size of media received on a support surface. According to one implementation, the support surface is provided by a paper tray. Also according to one implementation, the position-detecting sensor is formed by a voltage divider circuit, including a linear potentiometer, a conductive strip and a conductive bridge. 
     According to one aspect, a media holding apparatus includes a tray having a support surface configured to receive media and a media stop carried by the tray. The media stop is movably supported for continuously adjustable positioning relative to the tray to conform dimensionally with media received in the tray. The apparatus also includes a position-detecting sensor associated with the tray and the media stop which is operative to generate a unique electrical pattern corresponding with a detected position of the media stop relative to the tray. The unique electrical pattern is indicative of the size of the media detected in the tray. 
     According to another aspect, a media size detector for detecting the size of media that is to be delivered to a document-generating device includes a support surface configured to receive media and a media stop carried by the support surface for movable repositioning to substantially conform dimensionally with the size of the media. A position-detecting sensor is electrically coupled with the media stop and is operative to generate an electrical pattern corresponding with a detected position of the media stop relative to the support surface and indicative of a dimension of the media on the support surface. 
     According to yet another aspect, a method for detecting the size of media placed within a tray of a document-generating device provides a movable media stop on a support surface and a voltage divider having a bridge connection carried by the movable media stop. The method also loads media onto the support surface, moves the media stop to contain the media and to conform with a dimension of the media, and detects the size of the contained media by monitoring the voltage drop across the voltage divider to determine the position of the media stop on the support surface. 
     One advantage is to provide an apparatus and method for detecting the size of media present on a support surface, such as a print tray, in a manner that is not limited to a few preselected sizes. Another advantage is to provide an automatic apparatus and method for sensing media size. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings depicting examples embodying the best mode for practicing the invention. 
     FIG. 1 is a perspective view of a preferred embodiment paper tray having a media size detector in accordance with one aspect of the present invention. 
     FIG. 2 is a partially exploded perspective view of the paper tray of FIG.  1 . 
     FIG. 3 is a top view of the paper tray of FIG. 1 showing the relationship of adjustable resistance components for the media size detector. 
     FIG. 4 is an enlarged perspective view taken from above and behind showing the construction of a media stop used on the paper tray of FIG.  1 . 
     FIG. 5 is an enlarged perspective view taken from above and in front showing the media stop of FIG.  4 . 
     FIG. 6 is an enlarged perspective view taken from behind and below showing the media stop and illustrating a frictionable rubber surface pad and shoe. 
     FIG. 7 is a simplified schematic diagram of the media size detector used on the paper tray of FIG.  1  and showing the voltage divider circuits. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts”. U.S. Constitution, Article 1, Section 8. 
     An apparatus and method for detecting media size when supplying media to a document-generating device is described. In the following description, numerous specific details are set forth for one specific implementation, as used on a print tray for a print device in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods and structural components are not described in detail in order to not obscure the present invention. It is understood that the present invention is comprised of paper tray components, some of which are readily manufacturable using well-known technology. 
     The present invention addresses an inherent problem of detecting media size when provided on a support surface, such as a paper tray, to a document-generating device, such as a printer. More particularly, media that does not fit standard sizes typically offered to a document-generating device are capable of being detected according to Applicant&#39;s invention. Historically, users have had to either use a multipurpose tray input, which causes throughput speed penalties because every piece of paper, or media, is assumed to have the longest possible length. Alternatively, users have historically been required to use a custom input tray, where the user manually enters the dimensions of the media that are being presented to the device. However, for general use such technique is cumbersome, at best. Accordingly, the automatic sensing technique of Applicant&#39;s invention enables size determination of any loaded media, which provides a better solution. With this terminology and historical perspective defined, the method and apparatus of the present invention for addressing the problem of detecting media size when loaded onto a support surface, or paper tray, are now discussed. 
     The present invention is not limited to a specific embodiment illustrated herein. A media size detector according to Applicant&#39;s invention is described below with reference to FIG.  1  and identified by reference numeral  10 . Media size detector  10  is shown in one embodiment implemented on a paper tray  12  which forms a media-holding apparatus. Paper tray  12  is configured to receive media having a generally square or rectangular planar configuration, as is typically used when forming sheets of paper or documents. Media size detector  10  includes a longitudinal size detector, or sensor,  14  and a lateral size detector, or sensor,  16 . A stack of media, or paper, is received on support surface  18  where it is placed by a user in abutment with back stop  20  and side stop  22 . 
     As shown in FIG. 1, longitudinal size detector  14  is formed by back stop  20  which is slidably supported, or supported for sliding motion, on tray  12  for adjustable positioning at an infinite number of locations along slots  24  and  26 . Similarly, side stop  22  is slidably supported on tray  12  by slots  28  and  30  for adjustable positioning along an infinite number of locations extending along slots  28  and  30 . 
     Tray  12  comprises a media holding apparatus that may be removably received by a document-generating device, such as a printing device or printer, a copier, or a facsimile machine. Optionally, tray  12  can be secured to the document-generating device so as form a drawer, shelf or other receptacle. Additionally, such tray  12  can be utilized with a multi-function peripheral device (MFP). In operation, tray  12  is removed by a user from such device, and a fresh stack of paper is loaded onto support surface  18  by sliding the stack of paper into biased engagement with guide surfaces  46  and  48 . Subsequently, back stop  20  is slid into contact with the stack of paper by upwardly biasing a locking shoe  50  on back stop  20  which enables slidable movement of back stop  20  along slots  24  and  26  until back stop  20  engages with such stack of paper. Similarly, side stop  22  is moved by upwardly biasing locking shoe  50  and sliding side stop  22  until guide surface  40  of side stop  22  engages a lateral edge of such stack of paper. Accordingly, the distance between back stop  20  and guide surface  46  matches the length of the stack of paper, and the distance between side stop  22  and guide surface  48  matches the width of the stack of paper. Once stops  20  and  22  are engaged with the stack of paper, respective shoes  50  are released which spring biases shoes  50  into frictionally engaging contact with the topmost surface of the paper tray  12 , causing stops  20  and  22  to be securely fixed thereto. 
     After completing the above loading procedure, tray  12  is reloaded into the document-generating device where an electrical connection is made with the circuitry depicted in FIG. 7. A media size determination is made via longitudinal size detector  14  and lateral size detector  16  by detecting the position of back stop  20  and side stop  22 . Accordingly, a determination can be made as to the size of paper that has been loaded into tray  12 . 
     As shown in FIGS. 1 and 2, back stop  20  and side stop  22  are constructed the same. FIGS. 4-6 illustrate the construction of stops  20 ,  22  in even greater detail as discussed below. Each of stops  20  and  22  contains a pair of guide arms  32  and  34  which are received in associated slots  24 ,  26  and  28 ,  30 , respectively. Arms  32  and  34  enable slidable support of stops  20  and  22  within slots  24 ,  26  and  28 ,  30 , respectively. 
     As will be discussed below in greater detail, locking shoe  50  is downwardly biased when released in a resting state which causes shoe  50  to be engaged with support surface  18 . The resulting frictional engagement prevents movement of stops  20  and  22 , respectively. Upward biased movement of locking shoe  50  eliminates frictionable engagement between stops  20 ,  22  and support surface  18 , respectively, which enables slidable movement of stops  20  and  22  along support surface  1   8  when readjusting and sizing a new stack of paper. 
     In order to enhance the frictionable engagement between each of stops  20  and  22 , and with support surface  18 , individual frictionable adhesive strips  52  and  54  are adhesively bonded to support surface  18  for engagement with respective locking shoes  50 . One such suitable frictionable adhesive strip comprises a strip of non-skid material such as  3 M marine protective tape sold by the Marine Trades Department of 3M Company, St. Paul, Minn., and comprising non-skid, adhesive-backed, anti-slip products. Such products comprise a grit-based or abrasive material, similar to sandpaper, that is contained within a protective coating and formed into a tape-like material having an adhesive backing for application to a surface. Alternatively, support surface  18  can be imparted with a roughened surface, such as a machined surface, sand-blasted surface, or etched surface, which imparts frictionable engagement with locking shoe  50  so as to prevent movement of stops  20  and  22  when received in a resting state there against. Optionally, surface  18  can be molded in place. 
     Stops  20  and  22  also include a pair of fingers  36  and  38  which limit the amount of paper that is loaded into paper tray  12  and which contain and support such paper therebelow. 
     As shown in FIG. 1, guide surfaces  46  and  48  are formed directly from integrally molded components comprising tray  12 . Guide surface  46  provides a front stationary guide, or stop,  42  for receiving a stack of paper, and guide surface  48  provides a similar, perpendicular side stationary guide, or stop,  44  for receiving such stack of paper. Upon loading such stack of paper and moving stops  20  and  22  into engagement therewith, the longitudinal edges of such paper are engaged between guide  42  and back stop  20 , and the lateral sides of such paper are engaged between guide  44  and side stop  22 . 
     According to the construction depicted in FIG. 1, longitudinal size detector  14  and lateral size detector  16  each comprise a voltage divider circuit that includes an adjustable resistance component  56  and  58 , respectively. As shown in FIGS. 2 and 3, adjustable resistance components  68 ,  72  and conductive strips  70 ,  74  electrically communicate via back stop  20  and side stop  22 , respectively. 
     As shown in FIG. 2, adjustable resistance component  56  is formed by linear potentiometer  68  and conductive strip  70 , which are electrically joined together by a conductive bridge strip  78  (see FIG. 4) provided on stop  20 . Similarly, adjustable resistance component  58  is formed by linear potentiometer  72  and conductive strip  74 , which are joined together by such conductive bridge strip on side stop  22 . 
     In order to facilitate the presentment of a smooth and flat support surface  18 , surface  18  comprises a top surface within tray  12 , with a bottom surface being provided therebelow such that support surface  18  comprises an elevated false bottom in tray  12  in which potentiometer  68 ,  72  and conductor strip  70 ,  74  reside therein. 
     As shown in FIG. 2, slots  60 ,  62  and  64 ,  66  are provided in upper support surface  18 , and potentiometer  72 , strip  74  and potentiometer  68 , strip  70  are supported beneath the slots, respectively. It is understood that potentiometers  68 ,  72  and strips  70 ,  74  are provided within slots  60 - 66  in a slightly recessed manner such that back stop  20  and side stop  22  can be slidably supported for movement by support surface  18 . As will be described below in greater detail, a conductive bridge strip, or electrically conductive connection,  78  (see FIG. 4) is provided on the underside of back stop  20  and side stop  22  in order to make electrical connection between associated potentiometers  68 ,  72  and conductive strips  70 ,  74 , respectively. The formation of such electrical contact forms a voltage divider that enables detection of the positioning for stops  20  and  22  by a print generation device in which tray  12  has been received. Additionally shown in FIG. 2, a pair of pins  76  is provided for supporting a spring loaded bottom feed tray (not shown) on top of which a stack of media is supported. The construction of such feed tray is well known in the art, and is omitted here since it does not directly pertain to implementation of Applicant&#39;s invention. 
     As shown in FIG. 3, the layout of slots  24 - 30  and adjustable resistance components  56  and  58  can be seen within support surface  18  of tray  12 . More particularly, the layout of linear potentiometers  68 ,  72  and conductor strips  70 ,  74  enables the automatic sensing of paper size via placement of the back stop and side stop along adjustable resistance components  56  and  58 , respectively. Hence, accurate sensing of media size can be provided in a paper feeding direction and in a transverse direction perpendicular to the feed direction. The ability to accurately sense the length of paper provided in tray  12  allows a printer to make paper feed adjustments that maintain a maximum throughput of paper when drawing a supply of paper from tray  12 . 
     If, for instance, the media size of a sheet of paper is sensed as being longer than it actually is, the inter-page spacing between adjacent pages will be too large, which will reduce paper throughput and print time. Conversely, if the media is sensed too short, the inter-page spacing between sheets of paper may not be enough to avoid inadvertently feeding multiple pages sequentially for a single page being printed. 
     The same problem occurs with accurately detecting the width of media in the transverse direction. For the case of a laser printer having multiple heater bulbs within a fusing unit, the ability to achieve consistent roller temperature is very important. The consistency of roller temperature is quite sensitive to where media actually travels through the hot roller, due to the control algorithms that are used to govern how heat is applied to the roller and media. In the case of other types of devices, the objective may be to limit any tendency to print off the edge of the media and onto a roller. In either case, it is desirable to realize accurate sensing of media size in order to enhance device performance. 
     FIGS. 4-6 illustrate in greater detail the construction of back stop  20  and side stop  22 . It is understood that back stop  20  and side stop  22  are constructed in essentially the same manner. For purposes of describing the invention, the construction of back stop  20  and side stop  22  is illustrated in FIGS. 4-6 as being identical. 
     As shown in FIG. 4, stops  20 ,  22  are each formed from a piece of molded plastic material from which fingers  36  and  38  are integrally molded. Locking shoe  50  is carried in stops  20 ,  22  within a recess. Locking shoe  50  includes a pair of vertically extending and exposed tongues  84  that are received within complementary grooves  86  of stops  20 ,  22 . A coil compression spring  88  is carried on a topmost portion of shoe  50  such that shoe  50  is downwardly biased via coaction of spring  88  when left in a resting state. A user need only upwardly bias locking shoe  50  with a finger, compressing spring  88 , when movably positioning stops  20 ,  22  within a tray. Preferably, the top surface on shoe  50  and a corresponding surface on stops  20 ,  22  each form a nipple over which each end of spring  88  is received so that spring  88  is entrapped and held between shoe  50  and stops  20 ,  22 . Preferably, grooves  86  terminate at a bottom-most location so as to prevent ejection of shoe  50  from stop  20 ,  22 . One manner of terminating groove  86  comprises adhesively gluing an end plug at the bottom of grooves  86 , following assembly of locking shoe  50  therein. 
     Also according to FIG. 4, a metal conductive bridge strip  78  is affixed to a rear face on stops  20  and  22 . According to one implementation, conductive bridge strip  78  is adhesively bonded to stops  20  and  22 . Alternatively, strip  78  is secured with fasteners to the back surface of stops  20  and  22 , or snap-fit into place with complementary surface features that interfit. Strip  78  includes a pair of flexible, spring-like terminating fingers  80  and  82  which, in assembly, maintain slidable, electrical contact with adjustable resistance components  56  and  58  (of FIG.  2 ). More particularly, fingers  80  and  82 , as shown in FIG. 6, maintain contact with one of potentiometers  68 ,  70  and conductive strips  70 ,  74  as shown in FIGS. 1 and 2. 
     FIG. 5 illustrates stops  20 ,  22  from a front side that shows guide surface  40 . Locking shoe  50  can be seen in a lowered, resting state which maintains frictionable contact with one of strips  50 ,  52  as shown in FIG.  1 . Additionally, the construction of guide arms  32  and  34  is clearly shown in FIG.  5 . Arms  32  and  34  comprise a vertical finger  90 ,  94  and a horizontal finger  92 ,  96 , respectively. Vertical fingers  90  and  94  are configured to pass through slots  24 ,  28  and  26 ,  30 , respectively. Likewise, horizontal fingers  92 ,  96  are configured to extend laterally of slots  24 ,  28  and  26 ,  30 , respectively, so as to retain stops  20  and  22  within such slots. 
     In order to facilitate assembly, preferably guide arms  32  and  34  are each formed from a somewhat rigid, but slightly flexible, plastic material which enables assembly by mechanically urging horizontal fingers  92  and  96  towards one another to facilitate insertion within slots  24 ,  28  and  26 ,  30  during assembly. 
     FIG. 6 illustrates a lower, rearmost view of stops  20  and  22  in a manner that shows the sprung positioning of fingers  80 ,  82  and the resting position of locking shoe  50  shown in a lowermost position. Locking shoe  50  includes a rubber surface pad  98 . Pad  98  is configured to frictionably and securely engage with one of adhesive strips  52  and  54  (of FIG. 1) so as to ensure rigid securement of stops  20  and  22  within a paper tray. Upward biasing of shoe  50  disengages rubber surface pad  98  from such frictionable adhesive strips which facilitates slidable movement of back stop  20  and side stop  22  within a tray during alignment and abutment of such stops in engagement with a stack of media being sized within a tray. 
     FIG. 7 depicts a simplified schematic diagram of media size detector  10  used on paper tray  12  of FIGS. 1-6. FIG. 7 comprises a simplified view taken from beneath a paper tray, showing the layout of longitudinal size detector  14  and lateral size detector  16  within the bottom of paper tray  12 . The minimum and maximum displacement values for back stop  20  and side stop  22  are indicated by MIN X, MIN Y and MAX X, MAX Y, respectively. Linear potentiometers  68  and  72  and conductive strips  70  and  74  are shown in simplified form, with the conductive bridge strip on back stop  20  and side stop  22  forming an electrical bridge connection therebetween. A  4 -pin electrical connection, or connector,  100  is provided for connecting media size detector  10  with a document-generating device, or printer. 
     The longitudinal size detector  14  and lateral size detector  16  of media size detector  10  each form a voltage divider circuit  102  and  104 , respectively. Such voltage divider circuits  102  and  104  provide automatic sensing of media size. One end of travel for each voltage divider circuit  102  and  104  corresponds with the lower bound of supported media size for the corresponding direction being detected. The other end of travel senses the upper bound of supported media size. Voltage divider circuit  102  detects media size in the paper feed direction, and voltage divider circuit  104  detects media size in a transverse direction. 
     It is not necessary that linear potentiometers  68  and  72  (of FIG. 1) be highly accurate, so long as the resistance is consistent throughout the length of travel of stops  20  and  22 , respectively, there along. Alternatively, a multipleturn rotary potentiometer can be used with gears, cables, or other means used to couple the potentiometer to the traveling member or stop. Further alternatively, a custom adjustable potentiometer can be used that is capable of being adjusted in resistance such that the smallest and largest supported media sizes correspond with the extreme ends of the complete range of the voltage applied to each voltage divider. 
     Connection  100  includes two inputs and two outputs; namely +V,−V and S x , S y , respectively. A power supply and a voltage sensing circuit (not shown) are provided within the printing device, or printer, with the voltage sensing circuit connecting with connection  100  when the paper tray is loaded into the printer. The voltage sensing circuit compares the voltage applied by a power supply with the divided voltage, then calculates the media size. One type of power supply comprises a printing device power supply. Another type of power supply comprises a battery. Preferably, a four-contact connector is used to connect connection  100  with the printer. Once media tray  12  is assembled, all that is needed is a two-point calibration in order to ensure proper sensing. 
     Optionally, stationary guides  42  and  44  can be constructed in the same manner as back stop  20  and side stop  22 , with each stop including a respective size detector having a linear potentiometer. Accordingly, the relative positioning of each stop and guide can be compared to determine the size of media placed therebetween. 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.