Abstract:
A system and method for directly feeding unstacked paper sheets into a printing device having a moving image conducting element with a plurality of images placed thereon for transfer to the paper and having a wait station for controlling the timing of paper transfer to the image conducting element. A continuous stream of paper sheets is directed to a printing device wait station. The rate of the movement of the paper sheets into the wait station is controlled to present each paper sheet at a predetermined rate relative to the operating speed of the image conducting element. The spacing of the leading edge of each paper sheet, as it is presented to the wait station, is made relative to the linear spacing between consecutive images on the image conducting element.

Description:
1. Field of the Invention 
     This invention relates to a system and method for feeding a continuous stream of paper to a printing device without any need for stacking and deshingling individual sheets of paper. 
     2. Background of Invention 
     It is often desirable to input paper to a printing operation in roll form. The use of a roll, rather than single sheets, allows longer intervals between reloading of the paper source. Roll feed paper, cut just prior to feeding, allows sheets to be printed in various sizes without the need to change the size of the paper loaded in the stack. The use of a paper source roll also reduces packaging waste since stacked paper sheets must be stored in a large number of individual boxes. However, most printing devices are specifically designed to accept only stacked, pre-cut sheets of paper. The stack is fed by a deshingler that removes sheets from the stack and delivers them to the printing element. This deshingler operates slowly enough to accommodate the necessary timing of print operations. However, without the deshingler to regulate feeding, the printer cannot generally operate continuously unless some other method of regulating paper feed is provided. Previous devices have dealt with the problem of providing a continuous roll source of paper to a printer, designed only for use with stacked paper sheets, by continuously cutting and adding additional sheets from the roll to this input paper stack feed unit. This method has been particularly adapted for the Xerox™ 9700 Series Laser Printer. The problem with this method is that the printer must still deshingle and individually feed sheets of paper from the stack feed unit. The result is increased, rather than decreased overall complexity and a significantly greater chance of system failure due to the need to now accurately cut and stack paper sheets from the roll as well as to subsequently unstack the sheets of paper to feed them to the printer. 
     Other prior art devices also particularly directed toward the Xerox™ 9700 have eliminated the need for shingling and deshingling the paper, thus allowing direct feeding, by modifying the operating software of the printer so that its timing of operation will match that of the feeding device. The problem with such an approach is that the feeding device has lessened versatility with respect to other machines while installation time and expense are increased due to the need to modify software in the printer. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a system and method for continuously feeding a printing device from a continuous roll of paper material. 
     It is another object of this invention to provide a system and method for feeding a printing device that requires no alteration to the operating software of the device. 
     It is another object of this invention to provide a system and method for feeding a printing device that allows sheets of various sizes and shapes to be accurately fed and printed upon. 
     It is another object of this invention to provide a system and method for feeding a printing device that requires no shingling or deshingling of the paper between the source and the printer&#39;s image conducting belt or drum. 
     It is yet another object of this invention to provide a system and method for feeding a printing device that is specifically applicable to the Xerox™ 9700 Laser Printer, but may also be adaptable to a variety of other printers. 
     The present invention provides a system and method for directly feeding unstacked paper sheets into a printing device having moving image conducting element with a plurality of images for transfer to the paper placed thereon and also having a wait station for controlling the timing of paper transfer to the image conducting element. The system comprises a means for directing a continuous stream of paper sheets to a printing device wait station. There is a means for controlling the rate of movement of the paper sheets into the wait station to present each paper sheet at a predetermined time relative to the operating speed of an image conducting element of the printing device. Means are provided for regulating the spacing of a leading edge of each paper sheet as it is present to the wait station. This spacing is relative to the spacing between consecutive images on the image conducting element. 
     In a preferred embodiment, the printing device is a laser printer and the image conducting element is one of either a constant speed belt or drum, upon which, images are placed for transfer. This system may be particularly adapted to a Xerox™ 9700 series laser printer. There may be provided a means for controlling the rate of paper sheet feeding that includes a predetermined rate equal to approximately 20 inches per second and a means for regulating the spacing of fed paper sheets that includes a spacing equal to approximately 10 inches. The system may also comprise a means for cutting the paper sheets to predetermined sizes from the input of a continuous paper web. This continuous paper web may be input from a roll. There may be included in this system a means for driving the roll in synchronization with the means for directing the paper sheets so that each cut paper sheet proceeds without delay to the wait station. The means for regulating paper spacing may include a means for detecting the leading edge of each paper sheet. 
     A method for directly feeding unstacked paper sheets according to this invention may comprise the step of directing a continuous stream of paper sheets to a printing device wait station. The rate of movement of the paper sheets is then controlled so that each paper sheet is presented to the wait station at a predetermined rate relative to the operating speed of the image conducting element of the printing device. The spacing of each of these sheets of paper is also regulated so that each sheet is presented to the wait station with a spacing relative to the linear spacing between consecutive images on the image conducting element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing objects and advantages of the present invention will be more clearly understood in connection with the accompanying drawings in which: 
     FIG. 1 is a schematic illustration of a prior art method of feeding paper requiring deshingling of stacked sheets; 
     FIG. 2 is a schematic illustration of a direct feeding system according to this invention; 
     FIG. 3 is a schematic illustration of the direct feeding system of FIG. 2 including a paper feeding roll and sheet cutting device for increased production volume; and 
     FIG. 4 schematically illustrates an edge detector used with the feed mechanism in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A photoreprographic printing system of the prior art is generally depicted in FIG. 1. This type of printing system is used, for example, in the Xerox™ 9700 Series Laser Printer. It generally consists of an image conductor element 22 comprising either a belt or drum upon which printing toner is placed in the form of the desired print images. The image conductor belt 22 shown herein contains several images 28 that are laid down at 24 upon a piece of paper 26 as it passes under the contacting surface of the belt. Each piece of paper is fed to the image element by means of a &#34;wait station&#34;. This wait station includes a pair of rollers that forcibly drive a sheet of paper into the image element at a given time corresponding to the motion of the image conductor belt. The wait station 30 is synchronized to drive the leading edge 31 of a sheet of paper 32 into the image conductor belt each time an image on the image conductor belt 22 is aligned to properly print upon the sheet of paper when it reaches the image conductor belt. The feeding of the wait station, as shown in FIG. 1, is accomplished in most printer systems by deshinqling a stack of paper 46, one sheet at a time, and feeding each sheet 44 at a predetermined rate to the wait station 30, using a feed driving belt and pinching roller 40 and 42, respectively. As each sheet is fed to the wait station it is held for a small interval until the image element is again ready to receive a new piece. If the wait station does not receive a new piece of paper by the time the next image is ready to be printed, the system will shut down displaying a jam or paper refill signal. 
     Any feeding system that correctly interfaces with this type of printer must be able to directly feed the wait station of the printing element so that it receives a sheet of paper within the correct period of time to prevent the wait station from indicating an error. Also, it must not feed too quickly since this would cause a feeding backlog at the wait station. 
     Reference is now made to a direct feeding system as depicted in FIG. 2 and as in accordance with the present invention. In this schematic drawing, paper sheets 70 are fed to a conveying or feeding 60 that moves paper at a specific rate R 68 to the wait station 30. Each sheet is delivered to the station 30 at a specific point of time in order to insure that it be fed to the image conducting belt 22 in synchronization with the print images laid down on the belt. In order to insure that this precise synchronization be obtained, the parameters of image conducting belt speed S 50 and the distance between the leading edge of each new image d 52 on the image conducting belt is determined. These parameters are directly relative to the feeding speed. In the example of a Xerox™ 9700 Laser Printer, the image belt speed is 20 inches per second and the distance between each image leading edge D is 10 inches. As such, the system 60 is designed to separate each leading edge of input paper sheets by a distance D 62 that equals the image conducting belt image distance d 52. In this case, the distance is 10 inches. 
     In FIG. 2 the leading edges 64 and 66 of each paper sheet 61 are separated by the distance D. This spacing may be accomplished by detecting at 72 the leading edge of a sheet each time a sheet is presented to a feeding mechanism or conveyor 60. Each sheet is motioned down the feeding mechanism 60 when the appropriate distance from the preceding leading edge has been attained. Furthermore, each sheet of paper driven at this distance D travels down the feeding mechanism at a fixed rate R 68. In this example, the rate R will equal 20  inches per second, or the rate of the image conducting belt. The advantage of such a leading edge detect system is that various sizes of paper may be aligned to print accurately since each sheet is fed accurately with timing of feed based solely upon its own leading edge. As shown in FIG. 2, the second sheet 61 and third sheet 63 are of different sizes while each sheet&#39;s leading edge is aligned at precisely the same distance from the preceding one. The system only allows the next sheet to begin motion when the preceding leading edge has travelled exactly a distance D from the next sheet&#39;s leading edge. Since printing may occur without regard to size, the printing of unfolded envelopes, among other applications, is possible in large unstacked volume. 
     A significant feature of the direct feeding concept is the ability to input a continuous web of paper to the printing system. A roll 90 of paper web 92 is shown in FIG. 3. This paper web 92 is fed in a continuous manner into a cutting unit 96 The cutting unit 96 cuts sheets to a predetermined size sheet 82 that are then driven down the feeding device 80 with the required spacing D 62. The sheets are then delivered by the feeding mechanism or conveyor 80 to the wait station 30 and printed upon in the manner described herein above. The feed rate of the roll 94 to the cutting device 96 is synchronized to the general feed rate of the feeding mechanism 80. If so, each time a sheet is cut it may proceed on to the feeding device without delay. 
     In accordance with the invention, the station 30 may operate continuously assuming that the spacing D is proper as introduced to the station 30. Alternatively, the station 30 may operate somewhat intermittently with a slight wait possible for proper synchronization. Sheets can be provided early to the station 30 but cannot be provided late as this would cause a malfunction and shut-down. 
     As indicated previously, in accordance with the present invention, each sheet of paper, such as illustrated in FIG. 2, is carried by the feeding mechanism or conveyor 60 once the appropriate distance from the preceding leading edge has been attained. Assuming that the feeding mechanism 60 is set up for operation at a predetermined speed to match that of the image conducting belt 22, then one can employ a leading edge detector to determine the presence of a leading edge of a sheet being fed to the feeding device 60. Once this leading edge is detected, the input feed to the feeding mechanism 60 can be interrupted until the proper spacing occurs, namely the spacing D in FIG. 2 at which time the input feed proceeds so that all leading edges are spaced the proper predetermined distance, namely distance D in FIG. 2. 
     By way of further example, there can be separate feeding mechanisms, including an origination feeding mechanism and a feeding mechanism such as the conveyor like feeding mechanism 60 shown in FIG. 2. The leading edge detector would, in essence, be between these two feeding mechanisms and would in essence take input sheets fed in a serial course that might be unsynchronized positionally and essentially convert the sheets into a synchronized positional arrangement on the feeding mechanism 60. Again, this occurs by detecting leading edges on the input feed mechanism and then permitting the sheets to be fed to the feeding mechanism 60 but only once the proper spacing D has been achieved. 
     Now, with regard to the synchronization of sheets onto the feeding mechanism or conveyor 60, refer to FIG. 4 which is a schematic diagram illustrating the conveyor 60 as well as an input feed 74, and edge detector 72, and a typical sheet 73. The sheet 73 is fed on the input feed. The edge detector 72 detects an edge of this sheet and essentially holds the sheet in readiness for the conveyor 60 moving to particular position at which time the sheet 73 continues to be fed onto the conveyor 60 with the proper spacing between sheets as illustrated in FIG. 2 by the spacing D. 
     It should be understood that the preceding is merely a detailed description of a preferred embodiment. It will be obvious to those skilled in the art that various modifications can be made without departing from the spirit or scope of the invention. The preceding description is meant to describe only a preferred embodiment and not to limit the scope of the invention.