Abstract:
An automatic document feeder is operable in a simplex, or one-sided, reproduction mode and a duplex, or two-sided, reproduction mode. In the duplex mode, the original document sheets are transported through the feed path only twice and output in the same relative page order in which the sheets were input. By this, 100% productivity can be achieved. The feeder assembly uses two separate feeders, one simplex top feeder and one duplex top feeder, to obtain two pass operation. Alternatively, a single feeder is used that can feed from both the top of the stack or from the bottom of the stack depending on the mode of reproduction. A controller allows selection between the simplex and duplex modes and controls the feeding assembly based on the selection.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to an image reproduction apparatus that can operate in a simplex, or one-sided, reproduction mode and a duplex, or two-sided, reproduction mode. More particularly, this invention relates to handling the feed path of the original document to control output of the original document. 
     2. Description of Related Art 
     To accomplish duplex copying, it is generally necessary to invert the original document to effect reproduction of both sides of the document. Inversion adds time to each copy job and generally requires a longer feed path with additional hardware elements to invert the document and control the elements in the assembly. 
     Duplex copying can reproduce both sides of an original document, either on a single sheet (two-sided reproduction) or on two different sheets (one-sided reproduction). With either type of reproduction, it is desirable to output the original document and the reproduced pages in the same order and orientation as the original input documents. When original documents are inverted during reproduction, it has been necesary to pass the original document sheets back through the feed path to output the sheets to face the same direction and be in the same page order as when input. 
     In Many conventional duplex reproduction devices, the original document is fed through an extended feed path in which one side of the original document is reproduced and then the original document is flipped over and returned to an original supply tray for reproduction of the other side. During the second pass the document is again inverted and output. One such example is shown in U.S. Pat. No. 4,125,325 to Batchelor et al. that uses a deflector to direct sheets bearing a reproduced image facing a first direction to a return transport that delivers the reproduced sheets facing a second, opposite direction to an auxiliary supply tray for duplex copying. However, such an extended feed path requires additional space within the device and time to transport the copied sheets to the auxiliary supply for refeeding. 
     Other reproduction devices use, what is commonly termed, an inverter. An inverter effectively reverses the sheet orientation in its direction of motion. In other words, the lead edge and the trail edge orientation of the sheet is reversed. Depending on the location and orientation of the inverter, such reversal may also cause the sheet to be inverted (turned over). Generally, an inverter is associated with a sheet by-pass path and gate so that a sheet may selectively enter or by-pass the inverter, thus providing a choice between inversion and non-inversion. Inverters are very useful in many different reproduction applications, but suffer from reliability problems. 
     An example of an inverter for use in a recirculating document handler is U.S. Pat. No. 4,553,828 to Burger et al. that uses an inverting roller to selectively invert or not invert a sheet as it is fed back to a bottom feed supply tray. For duplex copying when the sheets are finally stacked, they are each inverted from their original orientation. 
     Another example is U.S. Pat. No. 4,384,782 to Acquaviva in which documents are top fed in  1 -N order from a supply to a feed loop that selectively inverts the documents prior to reproduction and then restacks the originals from the bottom of the supply. 
     There are various known ways to control duplex reproduction. For example, in U.S. Pat. No. 4,278,344 to Sahay an inverter is actuated only during single document circulation and is inhibited during successions of contiguous plural document copying circulations. Thus opposite sides of the documents are copied in alternate successions. In U.S. Pat. No. 4,355,880 to Stemmle, copying documents in serial page order is accomplished by circulating the documents in a first and last circulation through a non-inverting reversing document path between the stack and the imaging station. Some devices, such as U.S. Pat. No. 4,468,114 to Pels et al., adjust the circulation based on the particular copy job for increased efficiency. 
     Additional circulation such as in the above devices to effect proper document orientation, however, adds time and increases energy consumption and thus adversely impacts efficiency and general wear on the reproduction machines. Reproduction devices must provide reliability and are generally required to have the ability to operate at high speed. It is also often desirable to provide compatible circulation of simplex and duplex documents in the same document handler. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is to decrease copy job time and energy requirements by employing only two passes for duplex reproduction. Such a design provides a simplified and shortened feed path. This also increases reliability of the machine by reducing the number of passes for all duplex print jobs and allows a device designed in accordance with the invention to effect 100% productivity. 
     An additional aspect of the invention is to allow for flexibility with respect to serial page order in the document supply. This invention allows feeding of original documents in an established order, including both  1 -N pages and N- 1  pages. 
     One embodiment of the invention provides a single input feeder with a dual feed head. Alternatively, separate feeders can be used without redesigning the feed head. The ability and latitude of an active retard feed head is also increased. 
     Another aspect of the invention is to provide an efficient control system. By this, document handling control can be provided directly from the automatic document feeder. Remote control is also possible. 
     An image reproduction device according to the invention can be operable in at least a simplex reproduction mode and a duplex reproduction mode. The device includes a feeder assembly that supports a stack of original document sheets in an established page order, such as  1 -N or N- 1 . An image reproduction station creates an image based on each sheet of the original document, and a sheet transport with a feed path transports each original document sheet through the feed path from the feeder assembly past the image reproduction station. An output receives the stack of original document sheets in the same relative page order from the sheet transport with each successive sheet stacking on top of a previously output sheet. A controller is connected to the sheet transport and operates in a simplex mode in which each original document sheet passes through the feed path only once and a duplex mode in which each original document sheet passes through the feed path only twice. 
     According to this invention, a stack of original document sheets are fed through an image reproduction apparatus by the method of placing a stack of original document sheets in a feeder in an established page order and selecting one of a simplex reproduction mode and a duplex reproduction mode. Each of the sheets is fed through a feed path including an image reproduction station, wherein the sheets are fed through the feed path once in the simplex mode and twice in the duplex mode. The stack of original document sheets is output in the same relative page order with each sheet stacked on the previously output sheet. 
     The invention is also embodied in a recording medium that stores a control program for use by a reproduction apparatus. The control program includes instructions for selecting one of a simplex reproduction mode and a duplex reproduction mode for reproducing a stack of original document sheets arranged in an established page order. The program controls feeding of each of the sheets through a feed path including an image reproduction station, wherein the sheets are fed through the feed path once in the simplex mode and twice in the duplex mode, such that the stack of original document sheets are output in the same relative page order with each output sheet stacked on a previously output sheet. 
     Other aspects, advantages and salient features of the invention will be become apparent from the following detailed description, which taken in conjunction with the drawings discloses preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of this disclosure: 
     FIG. 1 is a schematic side view of an image reproduction device according to an embodiment of the invention; 
     FIG. 2 is flow chart showing the operation of the invention according to an embodiment of the invention; and 
     FIG. 3 is a flow chart showing the operation of the invention according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     To facilitate description of the preferred embodiments of the invention and for ease of understanding, certain consistent terminology is used herein to establish a frame of reference. Face up means that the first page of the document is facing upwardly as to be seen by the operator. Face down means that the first page of the document is facing downwardly, or upside down, as seen by the operator. Serial order refers to the page order with respect to the top of the stack. For example, a stack of pages  1 ,  2  and  3  face down would be in N- 1  order. Documents in serial order described  1 -N, can similarly be used in reverse order as N- 1 . Page number order means consecutive numerical order. These descriptions are not intended to be limiting but are rather for descriptive purposes only. 
     FIG. 1 schematically shows the relevant portions of an image reproduction device  10 , also referred to herein for simplicity as a copier, in accordance with this invention. The invention can be implemented in any type of reproduction device, including, but not limited to, a xerographic copy device, an optical scanner, and a facsimile machine. The elements shown in FIG. 1 substantially show an automatic document feeder (ADF). 
     According to the first embodiment, the image reproduction device  10  includes a first original document (also referred to as an original) supply  12  that has a sheet supporting surface. A second original document supply  14  is also provided. A stack of original documents are supported by first supply  12  or second supply  14  in an established page order such as  1 -N pages or N- 1  pages. First and second original document supply  12  and  14  can be configured as a tray or cassette or merely a supporting surface. Supplies  12  and  14  are also equipped with conventional sheet detecting mechanisms coupled to a controller  44 , discussed below, to signal the presence of an original document in the supply. 
     A transfer roll  16  is located adjacent each supply to which sheets of the original document are initially fed. Roll  16  can be a conventional constant velocity transfer (CVT) roll as shown or can be embodied as a movable platen, drum or endless belt. Roll  16  transports the original document through the feed path. 
     A separate output  18  is provided for the original documents with a stacking surface upon which the originals are restacked after being reproduced. Output  18  can also be a tray or cassette or merely a supporting surface. 
     In conjunction with first supply  12 , a supply feeder  20  is provided to selectively feed individual sheets of the original document to the transfer roll  16 . Supply feeder preferably includes at least one driven nip roll that frictionally engages a single sheet from the stock of originals and feeds it to roll  16 . FIG. 1 shows a nip roll  20  for top feeding of a sheet from the top of the stack and a bottom nip roll  22  for bottom feeding a sheet from the bottom of the stack. In practice, one nip roll could be provided for economy of both nip rolls (a dual feed head as discussed below) could be provided to increase flexibility of the machine by providing a choice of top feeding or bottom feeding. Any conventional feeding assembly such as a pair of nip rolls that work together for feeding or a feed belt could also be employed. 
     Similarly, a supply feeder is provided in conjunction with second supply  14  to selectively feed individual sheets of the original document to the transfer roll  16 . FIG. 1 shows a driven nip roll  24  positioned to top feed a sheet from the top of the stack of originals. As discussed with respect to first supply  12 , any conventional feeding assembly could be provided for feeding. Although top feeding is shown, the device could be configured to accommodate bottom feeding. 
     A take away roll (TAR)  26  is located adjacent transport roll  16  at the initial feed location to take the sheet from first supply  12  into the feed path. A roll  28  is provided upstream of an image reproduction station  30 , and roll  32  is provided downstream of image reproduction station  30 . Rolls  28  and  32  are commonly referred to as pre-rollers and post-rollers, respectively, and act to transport and support the document sheet as it passes image reproduction station  30 . Preferably, rolls  28  and  32  are constant velocity transfer (CVT) rolls, but any conventional feeder mechanism could be used to transport the original sheets through the feed path past image reproduction station  30 . Preferably, image reproduction station  30  includes a transparent support surface  34  through which an image on the original document can be reproduced using known methods. 
     A passive baffle  36  is provided downstream of image reproduction station  30 . Baffle  36  guides sheets in the feed path along guide surface  36   a  from image reproduction station  30  toward output  18  to a reversible drive mechanism, shown as a duplex roll  38  operatively coupled to a drive  40 . An idler roll  42  is provided opposed to duplex roll  38 . Any reversible drive mechanism, such as a roll or belt could be used. A sheet detector  46  is provided adjacent to duplex roll  38  to detect a sheet and signal controller  44  to operate drive  40 . A guide surface  36   b  is also provided on baffle  36  at an acute angle to guide surface  36   a  to guide an original sheet from duplex roll  38  back toward transfer roll  16  for a second pass over transfer roll  16  to image reproduction station  30 . 
     Passive baffle  36  and reversible duplex roll  38  act to invert the sheet in the feed path so that a first side (page  2 , for example) faces image reproduction device  30  in the first pass and a second opposed side of the original (page  1 , for example) faces image reproduction device  30  in the second pass. After the second pass, the original is ejected by forward driving duplex roll  38  to output  18 . It is also possible to use a pivoting diverter, in place of the passive baffle  36 , that selectively guides sheets to the chosen feed path. Additionally, the passive baffle can be in the form of sheet guides. 
     A controller  44  is connected to transfer roll  16  and duplex roll  38  to selectively drive the rolls to transport the original sheet through the feed path in two passes. Controller  44  is also operatively connected to control the feeders associated with first supply  12  and second supply  14  and CVT rolls  28  and  32 . 
     Preferably, controller  44  operates by one or more control programs. Such a control program is preferably implemented on a programmed general purpose computer. However, the control program can also be implemented on a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, in an ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or logic circuit such as a discrete element circuit, a programmable logic device such as a PLD, PLA, FPGA or PAL, or the like. In general, any device, capable of implementing a finite state machine that is in turn capable of implementing the flowcharts shown in FIGS. 2 and 3, which are described below, can be used to implement the control program. The control program is preferably recorded on a storage medium, which can be embodied in any medium capable of storing a control program, including but not limited to a hard drive, a conventional floppy disk, compact disk or chip. 
     In the following description the various steps are represented by the reference symbol S. In operation, as shown in FIG. 2, the mode of reproduction is selected at S 1 . Selection may effected by manually actuating an input, such as by an operator via a control panel, sending a signal from a remote controller, such as a mainframe computer, or by merely placing a stack of original document sheets in the appropriate supply  12  or  14 . The first possible mode is simplex  1 - 1  reproduction (S 2 ) in which a one-sided original is reproduced on one side of a copy sheet. The second possible mode is Simplex  1 - 2  reproduction (S 3 ) in which a one-sided original is reproduced on one side of a copy sheet and the next one-sided original is reproduced on the reverse side of the copy sheet. Both of these modes handle the original document sheets in the same manner. The third possible mode is duplex  2 - 2  reproduction (S 4 ) in which a two-sided original is reproduced on both sides of a copy sheet. Of course, a two-sided original could be reproduced such that each side of the original is reproduced on a single copy sheet ( 2 - 1  reproduction), but such reproduction would be treated as simplex  1 - 1  reproduction in this system, and the original document sheets would require special handling as conventionally known. 
     For either simplex mode, the stack of original document sheets would be placed in the supply  12  face up for a top feeding assembly in  1 -N page order in S 5 . The individual sheets in  1 -N page order are then fed at S 6  by supply feeder  20  from the top of the stack to transfer roll  16 . At S 7 , each sheet travels through the feed path past roll  28  through image reproduction station  30  and past roll  32  to baffle  36 . Because the original is supplied to supply  12  in a face-up orientation, as the sheet travels around transfer roll  16 , the image is facing outwardly and therefore faces toward transparent surface  34  when it passes through image reproduction station  30 . The sheet travels adjacent to guide surface  36   a  to duplex roll  38  at S 8 , which drives the sheet to output  18 . Each sheet is discharged at S 9  onto output  18  face down in N- 1  order. Thus, in a single pass through the feed path, each original is reproduced and output in a collated stack in the same page order as when stacked in supply  12 . 
     In duplex mode S 4 , as shown in FIG. 2, the stack of original document sheets are placed in supply  14  face down in N- 1  order in S 10 . The top sheet is then fed by supply feeder  24  to transfer roll  16  at S 11 . Each sheet passes through image reproduction station  30  via rolls  28  and  32  at S 12  with the image facing down toward transparent surface  34  in a first pass. The sheet then travels through the feed path to baffle  36  adjacent guide surface  36   a  to duplex roll  38 . When a sheet is detected by sheet detector  46 , controller  44  operates drive  40  to reverse duplex roll  38  at S 13  and drive the sheet back toward baffle  36  to guide surface  36   b  toward transfer roll  16 . The side of the sheet that was facing outwardly on the first pass now faces toward transfer roll  16 . 
     The sheet travels through the feed path around transfer roll  16  via rolls  26 ,  28 , and  32  for a second pass by image reproduction station  30  at S 14 . On the second pass, the opposite side of the original sheet faces transparent surface  34 . The sheet is then driven toward baffle  36  and is guided past guide surface  36   a  to duplex roll  38 , which now drives the sheet forward to output  18  at S 15 . The original sheet is then discharged to output  18  at S 16  collated face up in  1 -N order. Thus, a third pass to flip the original sheet is not required. Since every pass through the feed path past the image reproduction station is used to reproduce the image from the original document sheet, 100% productivity can be realized. 
     Of course, the original stacks could be supplied in either  1 -N or N- 1  order and by adjusting the top or bottom feeding would be output in collated order as described above. 
     Alternatively, first supply  12  can function as both a simplex and duplex feeder. As such, a dual feed head is employed as noted above to top feed originals in a simplex mode or bottom feed originals in a duplex mode. In this case, second supply  14  is not needed and therefore need not be provided. The dual function supply could be located on either side of transfer roll  16  positioned as shown in FIG. 1 as supply  12  or as supply  14 . 
     Operation of the dual function supply is shown in FIG.  3 . In the dual function supply, two supplies are not required as one supply can accept original documents for both simplex and duplex reproduction because the supply can top feed for simplex reproduction and bottom feed for duplex reproduction. For the sake of explanation, use of supply  12  as shown in FIG. 1 is described below. Alternatively, supply  14  could be provided for simplex feeding positioned as shown in FIG. 1 with the supply stack reoriented. For example, rather than providing the stack in supply  12  face up with top feed as described below, the stack could be supplied to supply  14  face down for bottom feeding. 
     First, the mode is selected in S 20 . As described above with respect to the process shown in FIG. 2, simplex  1 - 1  (S 21 ), simplex  1 - 2  (S 22 ), or duplex  2 - 2  (S 23 ) can be selected. In either simplex mode S 22  or S 21 , the stack of original document sheets is placed in supply  12  face up in  1 -N order at S 24  (or face down in supply  14  for bottom feeding.) Then, each sheet is fed by supply feeder  20  from the top of the stack in S 25  to transfer roll  16 . The sheet is transported through the feed path via rolls  26 ,  28  and  32 . The sheet with the image facing outwardly away from transfer roll  16  passes through image reproduction station  30  at S 26 . As the sheet passes baffle  36 , it is guided by guide surface  36   a  toward duplex roll  38 . Controller  44  operates drive  40  to drive duplex roll  38  forward at S 27 . The sheet is discharged to output  18  at S 28  collated face down in N- 1  order. Alternatively, if the stack was supplied face down in N- 1  order for bottom feeding from supply  14 , the output stack would also be discharged face down in N- 1  order. 
     For duplex reproduction (S 23 ), a stack of original document sheets is placed in supply  12  face up in  1 -N order or in supply  14  face down in N- 1  order at S 29 . Each sheet is fed from the bottom of the stack from feeder  12  or from the top of the stack from feeder  14  in S 30 . Each sheet passes through image reproduction station  30  via rolls  28  and  32  at S 31  with the image facing down toward transparent surface  34  in a first pass. The sheet then travels through the feed path to baffle  36  adjacent guide surface  36   a  to duplex roll  38 . When a sheet is detected by sheet detector  46 , controller  44  operates drive  40  to reverse duplex roll  38  at S 32  and drive the sheet back toward baffle  36  to guide surface  36   b  toward transfer roll  16 . The side of the sheet that was facing outwardly on the first pass now faces toward transfer roll  16 . 
     The sheet travels through the feed path around transfer roll  16  via rolls  26 ,  28 , and  32  for a second pass by image reproduction station  30  at S 33 . On the second pass, the opposite side of the original sheet faces transparent surface  34 . The sheet is then driven toward baffle  36  and is guided past guide surface  36   a  to duplex roll  38 , which how drives the sheet forward to output  18  at S 34 . The original sheet is then discharged to output  18  at S 35  collated face up in  1 -N order. Thus, a third pass to flip the original sheet is not required. Since every pass through the feed path past the image reproduction station is used to reproduce the image on the original document sheet, 100% productivity can be realized. 
     While advantageous embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be lade therein without departing from the scope of the invention as set forth in the appended claims.