Envelope printing

Abstract: Envelopes (9) are fed flap first and flap closed, long dimension first, into the nip of fixing rollers (3,4). The fixing rollers are less wide than the envelopes, and the printing system does not print on the edge of the envelope which is not fixed. Since this adds very little to the apparatus and software, wrinkle-free envelope printing is achieved at very low initial and overall cost.

Description: This invention relates to printers the operation of which includes a pressure and heat application to fix an image by fusing and capable of printing on letter size paper and envelopes. More specifically, this invention relates to printing envelopes with such a printer without wrinkling the envelopes. Wrinkling of envelopes being printed upon has been a continuing problem when the printing involves fixing with heat in a nip between pressure rollers. Conventionally, envelopes have been fed short dimension first since printers have been designed to accommodate correspondence paper sizes, not the envelopes. Typical previous attempts to print envelopes without wrinkles have involved relieving the pressure on the envelopes at various places in the fixing operation. U.S. Patent No. 5,268,726 to Oleksa et al is representative. A prior alternative is known in which the fixing rollers are separated for the last 76 mm (three inches) of the envelope, requiring that the envelope be oriented such that there was no text in this area since it would not be fused. A conventional printer capable of printing on letter size paper comprises an imaging system for applying images to said paper as loose toner, nip rollers having a heated roller for fixing said images, and means to feed letter size paper from said imaging system into the nip of said nip rollers with the long dimension of said paper parallel to the direction of said feeding into said nip. In such a conventional printer the said nip rollers are shorter in length than the long dimension of envelopes for said paper and therefore, as mentioned above, such envelopes have conventionally been fed short dimension first, with a consequent problem with wrinkling. US-A-4903047 discloses a printer of the above type which prints envelopes when fed long dimension first, with the flap leading and closed, but there is no suggestion in this disclosure that the said nip rollers are other than of a length commensurate with the long dimension of the envelopes, i.e. are longer than those of a conventional printer as described above. The problem is solved by a printer having the features as set out in claim 1. The present invention is characterised in that the portion of the printer adjoining one end of said nip rollers is clear of obstructions whereby the printer is capable of printing on said envelopes when fed into the nip of said nip rollers with the short dimension of said envelopes parallel to the direction of said feeding into said nip and with the flap of said envelopes leading and closed. Since the fixing rollers need not be actually lengthened, this modification adds very little to the printer apparatus cost. With respect to software this invention is a simplification, since the lines printed correspond to lines which would be input from a conventional address list. Accordingly, wrinkle-free envelope printing is achieved at very low initial and overall cost. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a diagrammatic perspective view of a printer; Fig. 2 shows details of the fixing of an envelope entering the fixing rollers. The fuser design used in the laser printer 1 of this embodiment is one in which one side of the medium being printed is against a reference edge in the printer. Unlike previous printers, however, envelopes are fed with the short side parallel to the feed direction. The fixing station comprises a hot roller 3 and a backup roller 4, which form a nip receiving the media to be fixed. Control is by a microprocessor 5, which is standard in electronic printers. Imaging apparatus 7 may be any system resulting in a toned image, for example that of a typical electrophotographic laser printer. More specifically, the printer 1 may preferably be, except as modified by this invention, the Optra (trademark) laser printer sold commercially by the present applicant. The existing Optra printer feeds envelopes short side first and uses a smaller envelope tray when feeding envelopes. In accordance with this embodiment envelopes 9 are stacked in tray 11 for printing. Where letter correspondence is being printed tray 11 would have letter size paper which is less wide than the envelopes 9. Rollers 3 and 4 are not as wide as the envelopes 9 and the portion of printer 1 to the side of rollers 3 and 4 is unobstructed, for the free passage of envelopes 9. In operation a conventional pick roller mechanism 13 pushes a single envelope 9 from the top of tray 11 toward pinch rollers 15 and 17. Guide 19 directs the envelope 9 to pinch rollers 15 and 17 which are then continuously turning. Rollers 15 and 17 move the envelope 9 to imaging mechanism 7 which creates an image of loose toner on envelope 9. For the printing of envelopes, microprocessor 5 restricts printing from occurring in the 12.5 millimeters from the leftward edge in Fig. 1, which is that portion which will not be fixed by rollers 3 and 4. After such printing on envelope 9 the envelope 9 enters the nip of fixing rollers 3 and 4 as shown in Fig. 1, which rotate and apply pressure to envelope 9 to fuse the toned image into a cohesive, permanent image on envelope 9. Immediately subsequent to fixing, the envelope 9 is conveyed out of the printer 1 for access by an operator of the printer as a finished document, as is conventional. Fig. 2 illustrates the fixing step in more detail. Top roller 3 is the hot roller, typically heated by an internal quartz lamp (not shown). The paper feed direction is left to right in Fig. 2, and roller 3 therefore rotates counterclockwise as shown by the arrow. The bottom roller 4 is not a heated roller and is electrically grounded to reduce stray effects of the toner. The pressure between the rollers 3 and 4 on an envelope 9 may be up to at least 0.145 N/mm 2 (21 pounds per square inch). As shown in Fig. 2, the envelope 9 is wider than rollers 3 and 4 and enters the rollers with its top side 9a (conventionally used for a return address) between the rollers 3 and 4, and with the opposite side 9b having the last 12.5 mm to its edge not between rollers 3 and 4. The flap 9c of the envelop must be closed and lead into the nip of roller 3 and 4. Many existing fusers can be made to accommodate envelopes in accordance with this invention with only minor changes to the fuser frame. The length of the fixing rollers need not be changed. The region adjoining one end of the fixing rollers need only be cleared of obstructions to permit passage of 12.5 mm of the envelopes. Use of this invention typically would be to print on envelopes of size up of the largest standard letter envelopes. Such envelopes have a long-side width of 250 millimeters (mm) in Europe and 241 mm in the United States. The largest standard correspondence paper in Europe is A4, which is 210 mm by 297 mm (8¼ in. by 11¾ in). The paper would be fed with the 8¼ in. dimension first, which is 210 mm. The largest standard correspondence paper in the United States is 216 mm by 279 mm (8½ in. by 11 in). The paper would be fed with 8½ in dimension first, which is 216 mm. In accordance with this invention the fuser rollers 3 and 4 have an effective width of 216 mm, with typically about 4 mm additional on each side for structural purposes.

Claims: A printer (1) capable of printing on letter size paper and envelopes, comprising an imaging system (7) for applying images to said paper or envelopes as loose toner, nip rollers (3,4) having a heated roller (3) for fixing said images, said nip rollers being shorter in length than the long dimension of envelopes (9) for said paper, and means to feed letter size paper from said imaging system into the nip of said nip rollers with the long dimension of said paper parallel to the direction of said feeding into said nip; characterised in that the portion of the printer adjoining one end of said nip rollers is clear of obstructions whereby the printer is capable of printing on said envelopes (9) when fed into the nip of said nip rollers with the short dimension of said envelopes parallel to the direction of said feeding into said nip and with the flap (9c) of said envelopes leading and closed.

Inventors: WILLIAMS GEORGE THOMAS, WILLIAMS, GEORGE THOMAS
Applicants: LEXMARK INT INC, LEXMARK INTERNATIONAL, INC.
Application year: 1996
Main classification: G03G15
IPC codes: B41L47, G03G15