Positive Drive Knife Folder

This invention relates generally to a knife folder for use with an electrophotographic printing machine, and more particularly concerns an improved knife folder apparatus.

As cut and folded web sections emerge from other press folder operations, they often are given a final fold by means of a blade which descends in a chopping motion when a sheet is in position under it. The blade pushes the sheet down between two nip rollers, creating a fold at that point. A knife folder requires deskewed and centered copy over the folding nip rollers or the sheet may be folded off center or crooked. Also, caution in the blade positioning relative to the nip rollers is essential or the sheet may be damaged or acquired too slowly. Accordingly, it is highly desirable to simplify the folding of sheets without damage while at the same time improving the reliability of the folder. The following disclosures appear relevant:

U.S. Pat. No. 1,124,375, Patentee: Wood, Issued: Jan. 12, 1915.

U.S. Pat. No. 4,508,527, Patentee: Uno et al., Issued: Apr. 2, 1985.

The pertinent portions of the foregoing disclosures may be briefly summerized as follows:

Wood discloses a folding and stapling device in which a folder blade drives and creases collected sheets into a receiving head and clips of an arm member.

Uno et al. discloses a method and apparatus for quantitatively dividing zig-zag folded sheets. A sheet of paper having a plurality of linear perforations is continuously transferred vertically through a roller and is folded in zig-zag form by operation of a crank mechanism.

In accordance with the present invention, there is provided an improved knife folder in which a blade collapses a sheet into position to be gently buckled by nip rollers into a nip formed by a pair of folding cylinders that apply a final fold to the sheet and thereby insuring positive acquisition of the sheet, elimination of a critical set up and the potential for knife related copy damage while reducing potential for disturbing the centering of the sheet over the folding cylinders.

While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims.

For a general understanding of the features of the present invention, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate identical elements.

FIG. 1 is a schematic showing an electrophotographic machine feeding sheets to be folded by the improved folder of the present invention. However, it will become apparent from the following discussion that the present folder could be used to fold sheets from any machine, and is not limited to the embodiment shown herein.

FIG. 2 is a fragmentary elevational end view of FIG. 3 along line A--A.

FIG. 3 is a partial side view of the apparatus of the present invention.

FIG. 4 is a partial isometric view of the knife folder of the present invention showing the relationship between the knife, nip rollers and folding cylinders.

Turning now to FIG. 1, printing machine 10 includes conventional controller 58 and a recirculating document handling system 12 for advancing successive original documents onto the platen of the processing module 14. Inasmuch as the art of electrophotographic printing is well known, the operation of the various processing stations employed in processing module 14 will be described briefly.

Processing module 14 employs a belt 16 having a photoconductive surface deposed on a conductive substrate. Preferably the photoconductive surface is made from a selenium alloy with the conductive substrate being preferably made from an aluminum alloy which is electrically grounded. Belt 16 advances successive portions of the photoconductive surface sequentially through the various processing stations disposed about the path of movement thereof. Belt 16 is entrained about stripping roller 18, tensioning roller 20 and drive roller 22. Drive roller 22 is coupled to a suitable motor so as to rotate and advance belt 16.

Initially, a portion of belt 16 passes through charging station A. At charging station A, a corona generating device 24 charges the photoconductive surface of belt 16 to a relatively high, substantially uniform potential.

After the photoconductive surface of belt 16 is charged, the charged portion thereof is advanced through exposure station B. At exposure station B, an original document is advanced by the recirculating document handling system 12 to a transparent platen 26. Lamps 28 flash light rays onto the original document. The light rays reflected from the original document are transmitted through lens 30 forming a light image thereof. Lens 30 focuses the light image onto the charged portion of the photoconductive surface to selectively dissipate the charge thereon. This records an electrostatic image on the photoconductive surface of belt 16 which corresponds to the informational areas contained within the original document.

Thereafter, belt 16 advances the electrostatic latent image recorded on the photoconductive surface to development station C. At development station C a magnetic brush development system, indicated generally by the reference numeral 32, advances developer material into contact with the latent image. Preferably, magnetic brush development system 32 includes two magnetic brush developer rollers 34 and 36. Each roller advances developer material into contact with the latent image. These rollers form a brush of carrier granules and toner particles extending outwardly therefrom. The latent image attracts the toner particles from the carrier granules forming a toner powder image on the photoconductive surface of belt 16.

After the electrostatic latent image is developed, belt 16 advances the toner powder image to transfer station D. A sheet of support material is advanced to transfer station D from a copy sheet stack supporting apparatus 38 or 40. Transfer station D includes a corona generating device 42 which sprays ions onto the backside of the copy sheet. This attracts the toner powder image from the photoconductive surface to the copy sheet. After transfer, the copy sheet moves onto conveyor 44 which advances the sheet to fusing station E.

Fusing station E includes a fuser assembly, indicated generally by the reference numeral 46, which permanently affixes the transferred powder image to the copy sheet. Preferably, fuser assembly 46 comprises a heated fuser roller 48 and a back-up roller 50. The copy sheet passes between the fuser roller and back-up roller with the toner powder image contacting the fuser roller. In this manner, the toner powder image is permanently affixed to the copy sheet. After fusing, the copy sheet is either advanced to output tray 52, returned to duplex tray 54 for subsequent recycling so as to enable a toner powder image to be transferred to the other side thereof, or if folding is required, directed into folder 60 that is partially supported by castor mounted support 90. The detailed structure of knife folder 60 will be described hereinafter with reference to FIGS. 2-4.

Referring now to FIG. 2, there is shown a fragmentary elevational view illustrating positive drive knife folder 60 in greater detail. As depicted thereat, knife folder 60 includes a blade 70 that is fixedly secured by bolts 64 and 65 to rods 72 (not shown) and 73. Also mounted on the rods are nip rollers 61, 62, 63 and a fourth nip roller not shown with both the nip rollers and the blade being moveable up and down by conventional means a predetermined distance D as shown in FIG. 2. The function of blade 70 is to buckle the sheet, and begin to direct it into the folding nip between cylinders 66 and 67. The improvement of this particular blade control of sheets is that the sheets are positioned over the folding cylinders in the precise time required by the machine feeding the sheets without damage to the sheets. The key feature of the present invention is that a buckling blade 70 is used only to facilitate downward collapse of a sheet the predetemined distance D. The continued movement of the blade downward brings nip rollers 61 and 62 into engagement with folding rollers 66 and 67 without the point of blade 70 coming in contact with either roller 66 or 67 or the nip formed between the two rollers. The contact between nip rollers 61 and 62 and folding rollers 66 and 67 and having a sheet 31 therebetween causes the sheet to continue to gently buckle down into the folding nip between rollers 66 and 67. As a result, positive acquisition of the sheet in the folding nip is obtained without damage to the sheet by the blade while at the same time reducing the potential of sheet movement over the center of the folding nip.

The knife folder apparatus 60 is adjusted at 78 for handling a wide variety of sheet sizes. To make an adjustment, all one need do is move adjustable guide 78 toward fixed support 79. The sheets are supported on member 77 for transport into the folder and registered against members 76 and after folding has occurred the folded sheets exit folding cylinders 66 and 67 and are guided by appropriate baffles into catch tray 37. The folding cylinders 66 and 67 are driven by conventional means on shafts 68 and 69. If one desired, rollers 61 and 62 could be the drive rollers and rollers 66 and 67 idler rollers. Registration members 76 are slidable backwards and forwards to adjust for various incoming sheet sizes.

In reference to FIGS. 3 and 4, it can be seen that the improved folder 60 is quite different from a knife folder where the knife driving the sheet into the folding nip creates the fold. In contrast, the knife folder of the present invention employs a blade 70 which bends a sheet 31 to establish a buckle in the sheet and gently but positively directs the sheet into pinch rollers 61 and 63 as shown in FIG. 3 for folding. The pinch rollers may be stationary until the buckle of the sheet by knife 70 is established, then actuated to crease the sheet in conjunction with rollers 66 and 67. This reduces the potential for disturbance of a copy being centered over pinch rollers 66 and 67 as well as other damage to the copy that could be caused by knife action. As can be seen from FIG. 4, the knife or buckling blade 70 contacts the copy sheet 31 before nip or pinch rollers 61 and 62 but does not jam the sheet into folding cylinders 66 and 67. Once actuated by controller 58, knife 70 insures downward collapse of the copy sheet into the cylinders 66 and 67. The positive drive of the nip rollers will reliably introduce the copy sheet into the folding cylinder nip between rollers 66 and 67. The blade will then insure the downward direction of collapse of the copy sheet. By protruding the blade just below the nip rollers, the disturbance of the copy sheet is minimal and there is no likelyhood of damaging the copy sheet by jamming the blade into the folding cylinder nip.

It should now be apparent that an improved knife folder has been disclosed that insures the folding of a sheet along a predictable centerline without risk of damage to the sheet. The folder employs a blade and nip rollers to buckle a sheet into a folding cylinder pair with the folding cylinder pair taking the initially buckled sheet and applying a permanent fold in the sheet and then passing the sheet into an output tray. The nip rollers work in conjunction with the folding cylinder pair to gently turn an initial buckle in the sheet into a complete fold.