Print media supply apparatus with media parameter detection capability

Abstract: In hard copy machines, automatic detection of the size of print media (114) in a supply bin (102, 104, 106, 108) is provided by electrical devices (130/132, 601/603, 702/704, 901/903). Adjustable print media alignment fences (118, 122) are operatively connected to the electrical devices, such as potentiometers (130, 132), photovoltaic strips (901, 903), photoemitter-photodetector arrays (601), or the like. The output signals from the electrical devices are correlated to width and length dimensions of the print media (114) or the absence of print media availability. Embodiments are disclosed for standard and custom print media (114) size detection.

Description: The present invention relates generally to hard copy machines, more particularly to print media supply devices for printers, plotters, copiers, and the like, and, more specifically to a print media supply apparatus with print media parameter detection capability. In the state of the art, computer printers and plotters and photocopiers generally allow the use of different forms of hard copy print media such as cut sheets of paper in standard size (8.5 x 11 inches), legal size (8.5 x 14 inches), extended size (8.5 x 17 inches), A4 size (metric), or envelopes of varying dimensions, and the like. It is common for the manufacturers to equip for different sizes of print media by providing changeable media supply capability such as adjustable trays, multiple bins, or interchangeable media cassettes adapted for each different size of print medium. Thus, it is common for the manufacturer to provide several cassettes, trays or storage bins for different sized print media which the user must select from the control panel or manually change for each particular print job. Some machines provide limited automation in that datums, or other mechanical interface features of the cassette, provide indicators that the correct cassette has been inserted to match the user's request for a particularly sized hard copy. Some trays and cassettes are provided with sliding guides that are manually closed about a stack of print media in one or two directions in order to align the individual sheets of the stack. These guides may be used to adjust a cassette to more than one size of print media. For example, because of the very slight dimensional difference between standard U.S. paper (8.5 x 11 inches) and the metric A4 size (8.27 x 11.69 inches), a cassette may be adapted for use with both papers by providing adjustable width guides. Still, whenever a change in print media size is required, the user must take time to change a cassette or, using a manufacturer supplied control panel, select the appropriate tray or bin having the print media of the size matching the user's need. Standard cassette designs either do not allow automatic machine detection of the print media dimensions or can only utilize a small sub-set of print media sizes because the print media size detection is done using fixed position switches or detection devices. US-A-5,110,106 concerns a sheet size detector for a sheet container which stores sheets to be fed to a printing engine or the like. By means of a plurality of sheet guides, the sheets in the containers are biased towards a predetermined location, and detectors are provided for determining the positions of the sheet guides and for outputting position data corresponding to the size of the sheets disposed in the sheet container. The detectors are arranged to allow a wide range of sheet sizes to be detected based upon both length and width detection data wherein the detectors are not dedicated to accurately detect a single sheet size, but rather a size range increment including a range of individual sheet sizes. US-A-4,780,740 concerns a paper feeding cassette for a printing apparatus which stores and supplies paper to a smart printer or copier. A frame is provided for holding paper, and a moveable longitudinal paper guide and a pair of moveable horizontal paper guides are provided which are adjustable to the length of the paper and the width of the paper, respectively. The paper guides are arranged in such a manner that same protrude through a bottom of the paper cassette to enable the engagement with a series of sensing devices in the smart printer or copier. Starting from this prior art, it is the object of the present invention to provide an improved print media detection apparatus which is universal for many hard copy machines and is adapted for holding print media of various surface area linear dimensions (length x width) and automatic detection of those dimensions. This object is achieved by an apparatus according to claim 1. In its basic aspect, the present invention uses electrical feedback from a print media supply apparatus in conjunction with stored information on media size to inform a print engine of a hard copy machine of the dimensions of the print media. A print media holding mechanism is cooperatively engaged with an electrical signal generating device. Print media dimensions are correlated to the generated signals. The print engine controller or host computer of the hard copy machine is automatically adapted to the recognized print media dimensions. It is an advantage of the present invention that it provides the measurement of surface area linear dimensions of print media loaded into a media containment mechanism. It is an advantage of the present invention that it allows a hard copy machine print engine to detect the size of print media loaded in a media supply holder used in conjunction with the machine. It is another advantage of the present invention that it allows for a universal print media supply cassette, accepting different size media. It is another advantage of the present invention that it permits custom print media sizes to be used in a hard copy machine. It is yet another advantage of the present invention that it allows the same print media cassette to be used for various print engines. It is still another advantage of the present invention that measurement of the size of the provided print media allows feedback of this information to a host computer system for validation or automatic selection of print media and media format settings, for example, print region margins. It is a further advantage of the present invention that it alleviates the necessity of user intervention to select print media size. Other objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the FIGURES. FIGURE 1 is a simplified, schematic detail, plan view (side) of a portion of a print media holding apparatus. FIGURE 2 is a schematic plan view (top) of a print media holding apparatus as shown in FIGURE 1. FIGURE 3 is a cutaway plan view (end) of a print media holding apparatus taken along line 3-3 as shown in FIGURE 2. FIGURE 4 is a simplified, schematic plan view (bottom) of a print media holding apparatus as shown in FIGURE 1. FIGURE 5, incorporating Table 1 and Table 2, is a schematic diagram of an electrical signal generating device as shown in FIGURE 1. FIGURE 6 is a simplified, schematic plan view (side) of a further print media holding apparatus. FIGURE 7 is a simplified, detail schematic of yet another print media holding apparatus. FIGURE 8, incorporating Table 3, is a schematic diagram of an electrical signal generating device in accordance with the apparatus shown in FIGURES 6 and 7. FIGURE 9 is a schematic plan view (top) of an embodiment in accordance with the present invention. FIGURE 10 is a schematic diagram of an electrical signal generating device in accordance with the embodiment of the present invention as shown in FIGURE 9. The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted. In FIGURE 1, a section of a print media tray 102, having a bottom floor 104 and a top edge 106, is substantially a standard tray, a removable cassette, or a print media bin of a hard copy machine for holding a supply of media, such as paper, envelopes, or the like, as would be known in the art. The tray 102 may also, for example, be an internal tray of the hard copy machine itself. The tray 102 includes a false floor 108. Referring briefly to FIGURES 2 and 4, two slot apertures 110, 112 are provided in the false floor 108. An exemplary stack of print media 114, such as cut sheet paper, is shown specifically in FIGURE 2 wherein one corner of the print media stack 114 is registered in a corner 116 of the tray 102. Fixed tray walls, reference datums, or edge separator devices (not shown) as are commonly known in the art to be used in print media supply devices are acceptable mechanisms for registering the print media stack 114 with respect to a print media pick and feed mechanism of a hard copy machine (not shown). Returning to FIGURE 1, a movable (manual or automated), print media alignment guide, or fence, 118 is provided for abutting at least a portion of the length of the print media stack 114. An arm portion 120 of the fence 118 extends through slot aperture 110. As shown in FIGURES 2 and 4 (in phantom lines), a similar movable fence 122 with an arm portion 124 through slot aperture 112 abuts at least a portion of the width of the print media stack 114. In other words, the print media stack 114 is held in registration to a predetermined orientation with the corner 116 of the tray (or other registration mechanism) by the movable fences 118, 122. The fences 118, 122 can be moved to a plurality of predetermined configurations along the slot apertures 110, 112 and thus can detect different predetermined print sheet alignments within the tray 102. Each arm portion 120, 122 is linked to a separate potentiometer 130, 132, respectively. As best seen in FIGURES 3 and 4, each linkage 126 comprises a tie rod 134 mounted on a fixed pivot post 136. The tie rod 134 is coupled to the arm portion of the fence at one extremity and to the respective potentiometer slide at the other extremity by any suitable mechanical connector. Each potentiometer 130, 132 is a slide potentiometer (linear); for example, the commercially available Bourns SSVA30B10300, 10K ohm potentiometer has been found to provide suitable resolution. Via the linkage 126, as a print media fence 118, 122 is moved into a position to accommodate a particular print media size, the slide potentiometer 130, 132 is adjusted accordingly. That is, the fence position can move from a minimum print media width (or length) position, "MIN," to a maximum print media width (or length) position, "MAX," and change the potentiometer electrical output setting accordingly. Referring now to FIGURE 5, an exemplary electrical schematic is provided. The potentiometers R1 and R2 are coupled via a suitable connector to a electrical power supply, designated +5V, and grounded appropriately. The power supply can be provided or, more economically, the tray 102 can be provided with an electrical connector (not shown) for connection to a suitable power supply of the hard copy machine. The respective output voltages of the potentiometers' taps are designated V 1 and V 2 . The output is similarly connected via an electrical connector to an appropriate print engine electronic controller (not shown) of the hard copy machine. The operation and position of the two print media fences 118, 122 are independent. As an exemplary embodiment, assume the width print media fence 118 has a motion range of nine to fourteen inches and the length print media fence 122 has a motion range of ten to 20 inches. Potentiometer 130, R1, will have an output based on position as shown in Table 1. Potentiometer 132, R2, will have an output based on position as shown in Table 2. The voltage output varies linearly with the position of the print media fence. Output voltages V 1 and V 2 can be measured and used accordingly by the print engine using a microprocessor and analog/digital ("A/D") converter, wherein, for example, a ROM (read only memory) table can be used to store a voltage to paper dimension correlation look-up table. The print media supply cassette can be universal for many hard copy machines, accepting any size print media in a continuous range which will fit within a particular cassette. The size of the print media is then determined by the print engine which accepts the print media supply cassette by measuring the media through the appropriate setting of the print media dimension sensor fences. This scheme also allows custom sized print media to be used in the cassette to be handled by the hard copy machine in the same manner as standard sized media without requiring special procedures. As will be recognized by those skilled in the art, this allows a "soft" solution to print media size support by the print engine; that is, the same print media cassette can be used for various print engines and the set of media sizes supported by the engine is determined by programmable software media size tables. Moreover, the ability to measure the print media size present in a computer printer or plotter allows feedback of this information to a host computer system for validation and automatic selection of print media and media settings, such as print region margins, tab settings, and the like. As depicted in FIGURE 6, no electrical connection to the print media tray 102 is required. An array of photoemitters and photodetectors is used to determined the positions of the print media fences. Commercially available parts such as the Digikey LT102B-ND infrared LED emitter and Digikey LT1030-ND photodetector can be used. The array 601 is suitably mounted in the print engine at positions for standard cut sheet print media. A mirror 603 is mounted appropriately on an extension member 605 of the print media fence 118 parallel to the floor 108 of the tray 102. As the fence 118 is moved in adjustment to a changed dimension, as indicated by arrow B -- B, a corresponding emitter-detector pair of the array 601 is activated and an appropriate signal generated to designate the relative dimension of the print media in the tray 102. In other words, the mirror 603 on the print media alignment fence extension member 605 is positioned such that a particular emitter-detector pair is activated by light reflected from the mirror 603 when the movable print media fence 118 is in a designated position corresponding to a known standard print media size. In FIGURE 7, emitters 702 and detectors 704 of an array are aligned such that the print media fence position may include more variety than standard print media sizes in order that custom print media may be used. The fence 118 is again slidable with the emitters 702 and detectors 704 oriented to project and receive a beam as indicated by arrow C -- C. As shown in FIGURE 8, the position of the print media fence 118 can be determined by examining (e.g., with microprocessor) the state of a D-type flip-flop 706 latch (such as a 74LS175 by Texas Instruments) to determine its state. Table 3 provides an exemplary fence position to print media size correlation table. A preferred embodiment of the present invention is depicted in FIGURES 9 and 10. Print media size and, in this embodiment, presence is measured by determining the voltages V 1 and V 2 which vary proportionally to the amount of illuminated photovoltaic strips 901, 903, respectively, occluded by print media 114 in the tray 102. These photovoltaic strips are commercially available, such as model no. G39808 by Edmund Scientific. As shown in FIGURE 10, light (arrows D) from a provided source 905 falls on the strips 901, 903 and thus causes the strips to provide voltage output signals that can be transformed to a print media dimensional length and width through a conversion algorithm or table. The advantage of this scheme is that it allows a nearly infinite range of print media sizes (i.e., within photovoltaic strip resolution capability) which can be determined to be present in the print media supply cassette 102. Additionally, this scheme is also valid for detecting the absence of print media in the containment holder (i.e., full scale voltage sensed) and the absence of a replaceable media supply cassette (i.e., zero voltage sensed), provided merely that the specific design allow for some portion of the strips to be not occluded for the largest acceptable print media sheet size. Thus, it has been demonstrated that various schemes within the scope of the present invention are possible wherein adjustment of print media alignment devices in hard copy print media bins, trays, cassettes, and the like, can be used to provide a signal representative of presence of print media and the media size being held therein.

Claims: An apparatus for detecting the area dimensions of a cut sheet of print media (114) for a hard copy producing machine, having a means for holding a supply of cut sheet print media (114), characterized by: a light source; a first photovoltaic strip (901) mounted within said holding means (102, 104, 106, 108) to be illuminated by said light source, said photovoltaic strip having a length dimension greater than a maximum width of said cut sheet print media (114) and being oriented in a plane parallel to the width dimension of said supply of print media (114); a second photovoltaic strip (903) mounted within said holding means (102, 104, 106, 108) to be illuminated by said light source, said photovoltaic strip having a length greater than a maximum length of said cut sheet print media (114) and being oriented in a plane parallel to the length dimension of said supply of print media (114), such that said cut sheet print media (114) in said holding means (102, 104, 106, 108) covers said first and second photovoltaic strips to the extent of its width and length dimensions, whereby output signals of said first and second photovoltaic strips are indicative of the width and length dimensions of said cut sheet print media (114) in said holding means (102, 104, 106, 108).

Inventors: KAZAKOFF JAMES A, KAZAKOFF, JAMES A.
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1995
Main classification: G03G15
IPC codes: B65H1, B41J11, H04N1, G03G15, G03G21, B41J13