Abstract:
A sheet inverter apparatus improves the handling capabilities of high speed printers and copiers. The sheet inverter apparatus includes a rotatable support having an axis of rotation and at least first and second arms radiating outwardly from the axis of rotation. First and second nip assemblies are is mounted to the first and second arms respectively. The support is rotatable to adjust positions of the first and second nips about the axis of rotation. Advantageously, with this arrangement, the support is adjustable so as to permit the first and second nips to receive sheets of paper at one location, be positionally adjusted with the sheets of paper moving therewith, and located at a second location so as to deliver the paper to an outlet feed path. This positional adjustment allows for inversion of the paper.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to document processing devices and methods for operating such devices. More particularly, the present invention relates to inverters for a document processing device. 
     BACKGROUND OF THE INVENTION 
     Inverters are known in the prior art for use with printmaking devices, particularly to invert a sheet of paper along a feed path. This allows for various operations, including front and back printing. Commonly, tri-roll inverters are used, such as that disclosed in U.S. Pat. No. 5,265,864 to Roux et al. With a tri-roll inverter, paper is introduced through a first nip of a tri-roll arrangement and fed into a reversing nip. The reversing nip accepts the sheet of paper moving in a first direction, causes the sheet of paper to stop and then drive the paper in a second direction, opposite that from the first direction. Upon being driven in the reverse direction, the sheet of paper is caused to pass through a second nip of the tri-roll arrangement. This allows for a sheet of paper to be flipped in orientation relative to the feed path. 
     With ever increasing volumes and velocities with printmaking devices, speed of handling paper at particular processes becomes a limiting factor. With a tri-roll arrangement, the need to accelerate the reversing nip in one direction, stopping and causing reverse movement provides a limiting factor as to the number of sheets per time intervals that can be handled through this arrangement. Although rapid servo motors and controls are available, the tri-roll inversion process can only be sped up to a certain level. 
     SUMMARY OF THE INVENTION 
     A sheet inverter apparatus is provided herein which includes a rotatable support having an axis of rotation and at least first and second arms radiating outwardly from the axis of rotation. An end of the first arm is attached to a first crank and an end of the second arm is attached to a second crank. The first arm and the second arm form a first coupling rod linking the first crank and the second crank in a drag link mechanism. A first nip assembly is mounted to the first crank. The first nip assembly includes a first nip drive roll and a first nip idler roll positioned so as to define a first nip therebetween. A second nip assembly is mounted to the second crank. The second nip assembly includes a second nip drive roll and a second nip idler roll positioned so as to define a second nip therebetween. The support is rotatable to adjust positions of the first and second nips about the axis of rotation. Advantageously, with this arrangement, the support is adjustable so as to permit the first and second nips to receive sheets of paper at one location, be positionally adjusted with the sheets of paper moving therewith, and located at a second location so as to deliver the paper to an outlet feed path. This positional adjustment allows for inversion of the paper. 
     In an embodiment, the sheet inverter apparatus includes a second coupling rod parallel to the first coupling rod, the second coupling rod being attached to the first crank and the second crank. 
     In an embodiment, the first and second cranks of the sheet inverter apparatus are vertically oriented in the document processing device, and the first coupling rod is attached to a top end of the first and second cranks, and the second coupling rod is attached to a bottom end of the first and second cranks. 
     In another embodiment, the present invention includes a document processing device. The document processing device includes a sheet inverter, which includes a rotatable support having an axis of rotation and at least first and second arms radiating outwardly from the axis of rotation, an end of the first arm being attached to a first crank and an end of the second arm being attached to a second crank. The first arm and the second arm form a first coupling rod linking the first crank and the second crank in a drag link mechanism. 
     A first nip assembly is mounted to the first crank, the first nip assembly includes a first nip drive roll and a first nip idler roll positioned so as to define a first nip therebetween. A second nip assembly is mounted to the second crank, the second nip assembly includes a second nip drive roll and a second nip idler roll positioned so as to define a second nip therebetween. The support is rotatable to adjust positions of the first and second nips about the axis of rotation. One of the nips is generally aligned with the paper feed path, and a sheet of paper is caused to enter the aligned nip and be engaged thereby such that the sheet of paper moves with the aligned nip, the sheet of paper moving with the aligned nip as the aligned nip rotates about the axis of rotation, the sheet of paper being caused to enter said paper outlet path with said aligned nip coming into general alignment with the paper outlet path. 
     The document processing device further includes a second nip assembly mounted to the second arm, the second nip assembly including a second nip drive roll and a second nip idler roll positioned so as to define a second nip therebetween. A paper feed path is positioned to direct paper therefrom, and a paper outlet path, spaced from the paper feed path, is positioned to receive paper from the inverter. The first and second nips can be rotated about the axis of rotation so as to be sequentially aligned with the paper feed path and the paper outlet path, and, wherein, with one of the nips being generally aligned with the paper feed path, a sheet of paper is caused to enter the aligned nip and be engaged thereby such that the sheet of paper moves with the aligned nip, the sheet of paper moving with the aligned nip as the aligned nip rotates about the axis of rotation, the sheet of paper being caused to enter the paper outlet path with the aligned nip coming into general alignment with the paper outlet path. 
     In another embodiment, the first arm of the sheet inverter apparatus radiates outwardly from the rotatable support diametrically opposed to the second arm so that the first and second arms are about 180° apart on a circumference formed by the arms. In another embodiment, the rotatable support of the sheet inverter apparatus is mounted on a movable frame. 
     In an embodiment, the sheet inverter apparatus further includes a third arm and a fourth arm, each radiating outwardly from the axis of rotation, an end of the third arm being attached to a third crank, and an end of the fourth arm being attached to a fourth crank. The third arm and the fourth arm form a third coupling rod linking the third crank and the fourth crank in a drag link mechanism. A third nip assembly is mounted to the third crank, the third nip assembly including a third nip drive roll and a third nip idler roll positioned so as to define a third nip therebetween. A fourth nip assembly is mounted to the fourth crank, the fourth nip assembly including a fourth nip drive roll and a fourth nip idler roll positioned so as to define a fourth nip therebetween. 
     The sheet inverter apparatus may further include a fourth coupling rod oriented parallel to the third coupling rod, the fourth coupling rod being attached to the third crank and the fourth crank. In another embodiment, the third and fourth cranks are vertically oriented in the document processing device, and the third coupling rod is attached to a top end of the third and fourth cranks, and the fourth coupling rod is attached to a bottom end of the third and fourth cranks. 
     In an embodiment, the third arm radiates outwardly from the rotatable support diametrically opposed to the fourth arm so that the third and fourth arms are about 180° apart on a circumference formed by the arms, wherein the first arm, third arm, second arm, and fourth arm are spaced at about 90° intervals respectively in a circumference formed by the arms. 
     In yet another embodiment, the sheet inverter apparatus of the present invention further includes a paper feed path leading into the sheet inverter, the paper feed path being defined by a nip drive roll and a nip idler roll. Further included is a paper outlet path defined by a nip drive roll and a nip idler roll, each of the paper feed path and paper outlet path being positioned adjacent one of the first, second, third, or fourth arms to define a pathway through with paper is fed and exited from the sheet inverter apparatus. Preferably, the first nip assembly is receptively positioned to receive paper from the paper feed path. 
     In an embodiment, the first nip assembly rotates away from the paper feed inlet after receiving a paper between the first nip drive roll and the first nip idler roll. The first nip assembly then rotates about 90° to a space previously occupied by the second nip assembly, wherein the first nip drive roll pauses in its rolling action in order to stably hold the paper between the first nip drive roll and the first nip idler roll during rotation of the nip assembly. Preferably, the first nip drive roll is controlled by a first drive motor, and the second nip drive roll is controlled by a second drive motor. In yet another embodiment, the rotatable support is controlled by an indexing motor for indexing said rotatable support, wherein the first drive motor and the second drive motor are independent of said indexing motor. 
     In an embodiment, the sheet inverter apparatus can invert at least about 225 pages per minute. In another embodiment, the sheet inverter apparatus can invert at least about 250 pages per minute. 
     These and other features of the invention will be better understood through a study of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic side view of a prior art tri-roll inverter. 
         FIG. 2  is a schematic diagram of the multiple nip inverter of the present invention. 
         FIG. 3  is a schematic diagram showing a first rotational position of the multiple nip inverter of the present invention during its operation. 
         FIG. 4  is a schematic diagram showing a second rotational position of the multiple nip inverter of the present invention during its operation. 
         FIG. 5  is a schematic diagram showing a third rotational position of the multiple nip inverter of the present invention during its operation. 
     
    
    
     DETAILED DESCRIPTION 
     The following terms shall have, for the purposes of this application, the respective meanings set forth below. 
     A “document processing device” refers to a device that performs an operation in the course of producing, replicating, or transforming a document from one format to another format, such as from an electronic format to a physical format or vice versa. Document processing devices may include, without limitation, printers (using any printing technology, such as xerography, ink-jet, or offset); document scanners or specialized readers such as check readers; mail handling machines; fabric or wallpaper printers; or any device in which an image of any kind is created on and/or read from a moving substrate. 
     A “substrate of media” refers to, for example, paper, transparencies, parchment, film, fabric, plastic, or other substrates on which information can be reproduced, for example, in the form of a sheet or web. 
     A “nip” refers to a location in a document processing device at which a sheet is propelled in a process direction. A nip may be formed between an idler wheel and a drive wheel. 
     A “nip assembly” refers to components, for example and without limitation, a nip drive roll and an nip idler roll which form a nip. 
     A “drive roll” refers to a nip assembly component that is designed to propel a sheet in contact with the nip. A drive roll may include a wheel, roller or other rotatable member. The drive roll may have an outer surface including a compliant material, such as rubber, neoprene or the like. The drive roll may be directly driven via a stepper motor, a DC motor or the like. Alternately, a drive roll may be driven using a gear train, belt transmission or the like. 
     An “idler roll” refers to a nip assembly component that is designed to provide a normal force against a sheet in order to enable the sheet to be propelled by the drive roll. An idler roll may include a wheel, roller or other rotatable member. The idler roll may have an outer surface including a non-compliant material, such as plastic. 
     A “drag link mechanism” refers to a four bar mechanism also known as a double crank mechanism useful for conveying motion between cranks which are linked together via a coupling rod. 
     Provided herein is an improved multiple nip inverter used to invert a substrate of media in a document processing device. Preferably, a sheet inverter is provided including a first nip assembly attached to a second nip assembly in rotatable fashion via a drag link coupling. The drag link preferably stays oriented vertical to the ground, and coupled with the rotation of the coupling rod it provides a natural motion for sheet inversion. 
     In a preferred embodiment, four nip assemblies are located at 90 degree intervals on a circumference, each supported by an arm rotating outwardly from a rotatable center of the sheet inverter apparatus. Advantageously, the inverter provides increased throughput for a document processing device without an increase in sheet velocity or acceleration. The inverter can work at the corresponding speed of the sheet through the rest of the document processing device, e.g., a linear speed of 1060 mm/sec and suitable account for typical accelerations within the document processing device; e.g., 2 g acceleration. 
     Because the nip assemblies are mounted on a movable assembly via a drag link mechanism, it provides for increased efficiency since the movement of the assembly can be used to correspond to the relative motion of the sheet in the machine space. Each nip assembly serves as a reversing roll inverter, but having multiple nip inverters enables parallel processing which improves throughput speed. 
     Additionally, the present invention is less expensive to produce than the prior art (e.g., reversing roll, or tri nip inverter) because of cost savings in the framework and baffles required to produce the design. The multiple nip inverter of the present disclosure further provides for a document processing device with a smaller machine footprint. Still further, the design of such document processing devices utilizing the multiple nip inverter allows for modularization of the design more so than the prior art. 
     Still further, because inversion of the sheet is being accomplished at lower velocity and accelerations as compared to the stationary reversing roll inverters, the substrates, or printing sheets suffer from less image abrasion on solid ink copies. 
     With reference now to the drawings, the known tri-roll inverter  10  of the prior art is shown. Such a tri-roll inverter is used, for example, in the Xerox iGen®, and includes an input nip formed by rollers  12  and  14  and an output nip formed between rollers  14  and  16 , collectively a tri-nip roll. Input and output baffles  18  and  20  guide copy sheets into and out of the inverter. A corrugation system, or reversing system  22  includes a nip formed between rollers  24  and  26  which corrugates copy sheets entering the nip as they are driven by the input nip in the direction of arrow  28  and as the copy sheets are driven out of the inverter in the direction of arrow  30 . Upon entry of the lead edge of a copy sheet  34 , the copy sheet is propelled into the corrugator driver  26  of corrugation system. The copy sheet follows the baffle into the corrugator, where there is force applied throughout the remaining length of the copy sheet. This decreases the speed of the copy sheet. When the trail edge of the copy sheet clears the tri-roll input nip, the corrugator roller  26  slows the sheet to a stop, reverses the motor direction, accelerates the sheet back to the tri roll velocity, then delivers the sheet to the tri roll output path. It then slows down and stops after the tail end of the outgoing sheet has cleared the corrugating roll, reverses direction and accelerates up to the tri roll velocity to accept the next sheet. In order to achieve 250 papers per minute (ppm), the cycle time for this to happen is only 240 milliseconds. Each of these events happens serially and therefore the sheet velocities and accelerations required for this style of inverter are very high and would cause concern for sheet damage and jams. Solid ink images are particularly susceptible to corruption in this process. 
     The acceleration rates required by the reversing (or corrugating) roll can be estimated as a function of the tri roll velocity. At a tri roll velocity equal to the transfix roll velocity (1060 mm/sec), the reversing roll must accelerate/decelerate at a rate of 5.96 g&#39;s to maintain a 250 page per minute rate. If the tri roll velocity increases, this creates more of an inter document gap between the sheets and hence more time to accelerate and decelerate. Diminishing returns exist. Furthermore, going faster than approximately 1600 mm/second with an acceleration/deceleration rate of 3.1 g&#39;s is difficult to accomplish. 
     With reference now to  FIGS. 2-4  of the drawings, a multiple nip inverter  36  of the present invention is shown. The multiple nip inverter is housed in document processing device  110 . The inverter is used to invert a substrate of media in document processing device  10 , typically a sheet of paper. The sheet inverter apparatus  36  includes a rotatable support  38 . The rotatable support has an axis of rotation and at least first arm  40  and second arm  42  radiating outwardly therefrom. A third arm  44  and a fourth arm  46  also may radiate outwardly from the rotatable support  38 . The support may rotate, for example in the counterclockwise direction  48  as shown in  FIG. 2 . Each of the first, second, third, and fourth arms support nip assemblies. A first nip assembly  50  is mounted to a first crank  82 , which is in turn connected to first arm  40 , the first nip assembly includes a first nip drive roll  52  and a first nip idler roll  54  positioned so as to define a first nip  56  therebetween. A second nip assembly  58  is mounted to a second crank  84 , which in turn is mounted to second arm  42 , the second nip assembly including a second nip drive roll  60  and a second nip idler roll  62  positioned so as to define a second nip  64  therebetween. 
     A third nip assembly  66  is mounted to a third crank  86 , which in turn is mounted to third arm  44 , the third nip assembly includes a third nip drive roll  68  and a third nip idler roll  70  positioned so as to define a third nip  72  therebetween. A fourth nip assembly  74  is mounted to a fourth crank  88 , which in turn is mounted to fourth arm  46 , the fourth nip assembly including a fourth nip drive roll  76  and a fourth nip idler roll  78  positioned so as to define a fourth nip  80  therebetween. 
     Each of the idler rolls may have an outer surface including a noncompliant material, such as hard plastic. Each of the drive rolls may include an outer surface having a compliant material such as rubber, neoprene or the like. The compliant material helps to grip the sheet and permit the drive roll to move the sheet through the nip. Each of the drive rolls rotates about a drive shaft and may be directly driven by a drive motor (not shown), such as a stepper motor, a DC motor or the like. A transmission device (also not shown) may extend between the drive motor and the drive roll for imparting motion to the drive roll. The transmission device may include a timing belt, gear trains or other transmission means known to those of ordinary skill in the art. 
     First arm  40  and second arm  42  radiate outwardly from a center point of the rotatable axis such that they are diametrically opposed and 180° apart on a circumference formed by the arms. First and second arms may be formed contiguously, and may be a first coupling rod, linking first crank  82  and second crank  84  in a drag link mechanism. The first coupling rod comprised of first arm  40  and second arm  42  is attached to first crank  82  and second crank  84  at the top of the vertically oriented cranks. A second coupling rod is substantially parallelly oriented to the first coupling rod. Second coupling rod is comprised of arms  140  and  142 , and is attached to the bottom of vertically oriented first crank  82  and second crank  84 . Drag link mechanisms are well known in the art, and provide further relative motion of the sheet inverter apparatus which enables it to better receive a sheet of paper. The cranks remain in a vertical orientation as can be seen in  FIGS. 2-4 . 
     Third arm  44  and fourth arm  46  radiate outwardly from a center point of the rotatable axis such that they are diametrically opposed and 180° apart on a circumference formed by the arms. Third and fourth arms may be formed contiguously, and may be a third coupling rod, linking third crank  86  and fourth crank  88  in a drag link mechanism. The third coupling rod comprised of third arm  44  and fourth arm  46  is attached to third crank  86  and fourth crank  88 , respectively, at the top of the vertically oriented cranks. A fourth coupling rod is substantially parallelly oriented to the third coupling rod. Fourth coupling rod is comprised of arms  144  and  146 , and is attached to the bottom of vertically oriented third crank  86  and fourth crank  88 . The four arms together form a drag link of a cross mechanism. 
     A paper feed path  90  leads into said sheet inverter apparatus, the paper feed path including a nip drive roll  92  and a nip idler roll  94 . A paper feed outlet path  96  is also provided, the paper feed outlet path including a nip drive roll  98  and nip idler roll  100 . 
     With reference now to  FIGS. 3-5 , a sheet of paper  102  enters sheet inverter apparatus  36  via paper feed path  90 . The sheet is driven by nip drive roll  92 . First arm  40  including first nip assembly  50  is positioned at the 9 o&#39;clock position in order to receive sheet  102  in first nip  56 . The sheet is motored through the paper feed path into first nip. As the trail end of sheet  102  passes an entrance sensor (not shown), first nip assembly slows down then stops sheet  102  relative to the nip drive. Rotatable support  38  then rotates 90° counter-clockwise in direction  48  so that first nip assembly  50  is then in the 6 o&#39;clock position as shown in  FIG. 4 . Because the drive motor associated with first nip drive roll  52  has stopped, sheet  102  is held by nip  56  during the rotation. 
     Once the rotatable support has rotated 90°, fourth arm  46  is then positioned at 9 o&#39;clock, the receiving position for a second sheet of paper  104 . Fourth arm  46  including fourth nip assembly  74  is positioned at the 9 o&#39;clock position in order to receive second sheet  104  in fourth nip  80 . As the trail end of second sheet  104  passes the entrance sensor (not shown), fourth nip assembly then slows down then stops second sheet  104  relative to the nip drive. Rotatable support  38  then rotates again 90° counter-clockwise in direction  48  so that fourth nip assembly  74  is then in the 6 o&#39;clock position, and first nip assembly  50  is positioned in the 3 o&#39;clock position, as shown in  FIG. 5 . 
     After the second rotation, first nip drive roll  52  then powers up and drives first sheet  102  out of the inverter apparatus into paper outlet path  96 . The process repeats continuously every 240 millisecond to invert multiple sheets on simultaneous tracks. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.