Laser scanning unit housing

The present invention relates generally to a laser scanning unit housing and, more particularly, to such a housing having a cover with at least one integrated lens seal structure.

Laser scanning units are known comprising a laser diode for generating a laser beam, a rotating polygonal mirror for reflecting the laser beam along a scan line on a photoconductive (PC) drum, and post-scan optics comprising at least one fΘ lens and at least one stationary mirror positioned between the rotating mirror and the PC drum. To prevent dust and like contamination from reaching the rotating polygonal mirror within a housing of a laser scanning unit, the housing is typically sealed to prevent air from passing into the housing. U.S. Pat. No. 5,953,042 discloses structure to seal a space between a housing cover and a lens. It is also known to use V-shaped polyester film strips to seal gaps between a lens and a cover of a laser scanning unit housing. The cover includes walls defining a lens-receiving opening. The film strips extend along longitudinal side portions of the lens and longitudinal walls of the cover defining a portion of the lens-receiving opening. The polyester film strips are die cut into rectangular blanks, formed into a V-shape and adhesively secured to the longitudinal cover walls. An edge of each strip opposite an edge adhesively secured to a cover wall engages a corresponding side portion of the lens. The strip edge is maintained in position against the lens side portion by a spring force, inherent within the V-shaped strip, acting on the strip edge contacting the lens.

In accordance with a first aspect of the present invention, a cover is adapted to form part of a housing of a laser scanning unit. The cover comprises a main body having walls for defining at least one opening adjacent a lens located in a base of a laser scanning unit housing. At least one of the walls comprises seal structure formed integral with an adjacent portion of the one wall. The seal structure is adapted to engage a side portion of the lens so as to seal a gap between the lens side portion and the one wall.

The adjacent structure of the one wall may comprise a support member and the seal structure may comprise a flexible arm extending from the support member. The flexible arm may extend from the support member at an angle of from about 95 degrees to about 175 degrees. The flexible arm may have a thickness of from about 0.1 mm to about 1 mm. The support member may have a thickness of from about 1 mm to about 3 mm.

The at least one main body wall may comprise at least one longitudinal wall and the seal structure may comprise longitudinal seal structure adapted to engage a longitudinal side portion of the lens.

The at least one main body wall may comprise first and second longitudinal main body walls. The first wall may define first seal structure adapted to engage a first longitudinal side portion of the lens and the second wall may define second seal structure adapted to engage a second longitudinal side portion of the lens.

The main body walls may define first and second openings. The first opening may be adapted to receive a first lens and may be defined in part by a first wall. The second opening may be adapted to receive a second lens and may be defined in part by a second wall. The first wall may comprise first seal structure formed integral with an adjacent portion of the first wall and may be adapted to engage a side portion of the first lens so as to seal a gap between the first lens side portion and the first wall. The second wall may comprise second seal structure formed integral with an adjacent portion of the second wall and may be adapted to engage a side portion of the second lens so as to seal a gap between the second lens side portion and the second wall.

The main body may be formed from a microcellular foam.

In accordance with a second aspect of the present invention, a housing is provided for a laser scanning unit. The housing comprises a base and a cover. The cover is adapted to be secured to the base. The cover may comprise a main body having walls for defining at least one opening adjacent to a lens located in the base. At least one of the walls may comprise seal structure formed integral with an adjacent portion of the one wall. The seal structure may be adapted to engage a side portion of the lens so as to seal a gap between the lens side portion and the one wall.

FIG. 1 is a schematic illustration of an electrophotographic image forming apparatus including a printhead constructed in accordance with the present invention;

FIG. 2 is a perspective view of the printhead illustrating a polygonal mirror, first and second pre-scan assemblies and a top section of the printhead housing;

FIG. 2A is a perspective view of the polygonal mirror, the first and second pre-scan assemblies and the post-scan optical assembly with the printhead housing removed;

FIG. 3 is a view of the printhead illustrating the bottom section of the printhead housing;

FIG. 4 is a perspective view of a cover of the printhead housing;

FIG. 5 is a cross-sectional view taken along view line 5 - 5 in FIG. 4 ;

FIG. 6 is a cross-sectional view taken along view line 6 - 6 in FIG. 4 ; and

FIG. 7 is an enlarged cross sectional view of a portion of a seal structure of the cover illustrated in FIG. 4 .

In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.

FIG. 1 depicts a representative electrophotographic image forming apparatus, such as a color laser printer, which is indicated generally by the numeral 10 . An image to be printed is electronically transmitted to a controller 12 by an external device (not shown). The controller 12 includes system memory, one or more processors, and other logic necessary to control the functions of electrophotographic imaging.

In performing a printing operation, the controller 12 initiates an imaging operation where a top sheet 14 of a stack of media is picked up from a media tray 16 by a pick mechanism 18 and is delivered to a media transport belt 20 . The media transport belt 20 carries the sheet 14 past each of four image forming stations 22 , 24 , 26 , 28 , which apply toner to the sheet 14 . The image forming station 22 includes a photoconductive drum 22 K that delivers black toner to the sheet 14 in a pattern corresponding to a black image plane of the image being printed. The image forming station 24 includes a photoconductive drum 24 Y that delivers yellow toner to the sheet 14 in a pattern corresponding to a yellow image plane of the image being printed. The image forming station 26 includes a photoconductive drum 26 M that delivers magenta toner to the sheet 14 in a pattern corresponding to a magenta image plane of the image being printed. The image forming station 28 includes a photoconductive drum 28 C that delivers cyan toner to the sheet 14 in a pattern corresponding to a cyan image plane of the image being printed.

The media transport belt 20 then carries the sheet 14 with the unfixed toner image superposed thereon to a fuser assembly 30 , which applies heat and pressure to the sheet 14 so as to promote adhesion of the toner thereto. Upon exiting the fuser assembly 30 , the sheet 14 is either fed into a duplexing path 32 for performing a duplex printing operation on a second surface of the sheet 14 , or the sheet 14 is conveyed from the apparatus 10 to an output tray 34 .

To effect the imaging operation, the controller 12 manipulates and converts data defining each of the CYMK image planes into separate corresponding laser pulse video signals, and the video signals are then communicated to a printhead 36 (also referred to herein as a “laser scanning unit”). The printhead 36 comprises a printhead housing 100 , which comprises a base 110 and a cover 120 , see FIGS. 2-4 . The base 110 comprises a top section 112 A, illustrated in FIG. 2 , and a bottom section 112 B, illustrated in FIG. 3 . The cover 120 is received over and coupled to the base bottom section 112 B. The cover 120 comprises a main body 121 , see FIG. 4 . In order to properly locate the cover 120 relative to the base 110 , the cover main body 121 is formed with first and second tabs 121 A and 121 B, respectively. The first tabs 121 A are received in corresponding first recesses 114 A in the base 110 and the second tabs 121 B are received in corresponding second recesses 114 B in the base 110 . The cover main body 121 further includes integral clips 121 C having openings 121 D therein for receiving tabs 116 formed on the base 110 so as to releasably connect the cover 120 to the base 110 .

The printhead 36 further includes a single rotatable polygonal mirror 70 and a pre-scan optical assembly 40 comprising first and second pre-scan laser diode/lens assemblies 50 and 60 . The pre-scan assemblies 50 and 60 are spaced apart from one another by an angle of approximately 120 degrees, see FIG. 2 . The mirror 70 is supported for rotation about a rotational axis 70 A, driven by an appropriate motor and comprises a plurality of facets 72 , see FIGS. 1 and 2 .

The first pre-scan assembly 50 comprises first and second laser diodes 52 and 54 , each of which generates a corresponding laser beam 52 A and 54 A, see FIGS. 2 and 2A . The second pre-scan assembly 60 comprises third and fourth laser diodes 62 and 64 , each which generates a corresponding laser beam 62 A and 64 A. The first and second pre-scan assemblies 50 and 60 may be constructed in the same manner as the first and second pre-scan assemblies disclosed in U.S. patent application Ser. No. 10/808,131, filed on Mar. 24, 2004, and entitled “LASER SCANNING UNIT HAVING A SENSOR FOR DETECTING BOTH START-OF-SCAN AND END-OF-SCAN POSITIONS OF A CORRESPONDING LASER BEAM,” the disclosure of which is incorporated herein by reference.

Each of the laser beams 52 A, 54 A, 62 A, 64 A is modulated so as to write pixels or Pels according to an associated one of the video signals from the controller 12 as the beam scans along a corresponding scan path. In particular, the first laser beam 52 A is modulated according to a video signal corresponding to the cyan image plane. The second laser beam 54 A is modulated according to a video signal corresponding to the magenta image plane. The third laser beam 62 A is modulated according to a video signal corresponding to the black image plane. The fourth laser beam 64 A is modulated according to a video signal corresponding to the yellow image plane.

Each laser beam 52 A, 54 A, 62 A, 64 A is reflected off the rotating polygonal mirror 70 and is directed towards a corresponding one of the photoconductive drums 28 C, 26 M, 22 K, 24 Y by select mirrors and lenses in a post-scan optical assembly 101 , see FIGS. 2A and 3 . The first and second beams 52 A, 54 A, after being reflected off the rotating polygonal mirror 70 , are reflected by a reflection mirror 102 A and pass through a first F-1 lens 120 A, see FIG. 2A . After passing through the first F-1 lens 120 A, the first beam 52 A is reflected by first beam mirrors 104 A and 104 B prior to passing through a corresponding first F-2 lens 122 A, see FIGS. 2A and 3 . The second beam 54 A, after passing through the first F-1 lens 120 A, is reflected by second beam mirrors 106 A and 106 B prior to passing through a corresponding second F-2 lens 122 B. The rotation of the polygonal mirror 70 and positioning of the mirrors 102 A, 104 A, 104 B, 106 A, 106 B and lenses 120 A, 122 A, 122 B of the post-scan optical assembly 101 causes each laser beam 52 A, 54 A to repeatedly sweep, along a corresponding scan path in the scan direction, across its corresponding photoconductive drum 28 C, 26 M so as to write Pels to form a latent image on the drum.

After being reflected by the mirror 70 , the third and fourth beams 62 A and 64 A are reflected by a reflection mirror 102 B and pass through a second F-1 lens 120 B, see FIG. 2A . After passing through the second F-1 lens 120 B, the third beam 62 A is reflected by third beam mirrors 108 A and 108 B prior to passing through a corresponding third F-2 lens 122 C. The fourth beam 64 A, after passing through the second F-1 lens 120 B, is reflected by fourth beam mirrors 110 A and 110 B prior to passing through a corresponding fourth F-2 lens 122 D. The rotation of the polygonal mirror 70 and positioning of the mirrors 102 B, 108 A, 108 B, 110 A, 110 B and lenses 120 B, 122 C, 122 D of the post-scan optical assembly 101 causes each laser beam 62 A, 64 A to repeatedly sweep, along a corresponding scan path in the scan direction, across its corresponding photoconductive drum 22 K, 24 Y so as to write Pels to form a latent image thereon.

The post-scan optical assembly 101 may be constructed in the same manner as the post-scan optical assembly disclosed in U.S. patent application Ser. No. 10/808,131, filed on Mar. 24, 2004, and entitled “LASER SCANNING UNIT HAVING A SENSOR FOR DETECTING BOTH START-OF-SCAN AND END-OF-SCAN POSITIONS OF A CORRESPONDING LASER BEAM,” previously incorporated herein by reference.

Referring to FIGS. 4 and 6 , the cover main body 121 comprises first and second longitudinal walls 130 A and 130 B and first and second end walls 130 C and 130 D defining a first opening 130 ; third and fourth longitudinal walls 132 A and 132 B and third and fourth end walls 132 C and 132 D defining a second opening 132 ; fifth and sixth longitudinal walls 134 A and 134 B and fifth and sixth end walls 134 C and 134 D defining a third opening 134 ; and seventh and eighth longitudinal walls 136 A and 136 B and seventh and eighth end walls 136 C and 136 D defining a fourth opening 136 . When the cover 120 is coupled to the base 110 , each of the openings 130 , 132 , 134 and 136 is in general alignment with a corresponding one of the F-2 lenses 122 A, 122 B, 122 D and 122 C so as to allow the first, second, fourth and third beams 52 A, 54 A, 64 A and 62 A to exit the housing 100 after passing through the F-2 lenses 122 A, 122 B, 122 D and 122 C, see FIG. 4 .

It is desirable to minimize the amount of dust and like contamination from entering the housing 100 so as to prevent dust and the like from reaching and, possibly, adhering to the rotatable polygonal mirror 70 . Dust and like contamination on the mirror 70 may cause print defects. In this regard, each of the cover longitudinal side walls 130 A, 130 B, 132 A, 132 B, 134 A, 134 B, 136 A, 136 B comprises a longitudinal seal structure 200 to engage an adjacent longitudinal side portion or wall of a corresponding F-2 lens. The seal structure 200 forms a seal between the lens longitudinal side portion and the cover longitudinal side wall 130 A, 130 B, 132 A, 132 B, 134 A, 134 B, 136 A, 136 B to prevent air and dust from passing through a gap between the lens side portion and the cover longitudinal side wall. In FIG. 5 , the seal structures 200 for longitudinal side walls 132 A and 132 B are shown engaged with longitudinal side portions 222 A and 222 B of the second F-2 lens 122 B.

The longitudinal seal structure 200 for each longitudinal side wall 130 A, 130 B, 132 A, 132 B, 134 A, 134 B, 136 A, 136 B comprises a flexible arm 204 . Each flexible arm 204 is integral with an adjacent portion or support member 206 of its corresponding longitudinal side wall 130 A, 130 B, 132 A, 132 B, 134 A, 134 B, 136 A, 136 B, see FIGS. 5 and 6 . In the illustrated embodiment, the support member 206 has a length L SM of from about 5 mm to about 20 mm and a thickness T SM of from about 1 mm to about 3 mm, see FIGS. 5 and 7 . The flexible arm 204 has a length L FA of from about 3 mm to about 20 mm and a thickness T FA of from about 0.1 mm to about 1 mm. The flexible arm 204 may extend relative to the support member 206 at an angle theta of from about 95 degrees to about 175 degrees and preferably about 135 degrees, see FIG. 7 .

When the cover 120 is assembled to the base 110 , the flexible arms 204 flex to allow a corresponding F-2 lens 122 A, 122 B, 122 D and 122 C to be received between a pair of the longitudinal side walls 130 A, 130 B, 132 A, 132 B, 134 A, 134 B, 136 A, 136 B. The thickness T FA , length L FA and angle theta of each flexible arm 204 are chosen so as to allow the flexible arms 204 to flex and receive a corresponding F-2 lens without requiring an operator to apply excessive force when assembling the cover 120 to the base 110 yet still allow each seal structure 200 to create an adequate seal to prevent dust and the like from passing between the gap between a cover longitudinal side wall and a lens side portion.

So as to allow the flexible arms 204 to be formed with a narrow thickness T FA , the cover main body 121 may be formed from a microcellular foam using a process developed by Trexel Inc. and commercialized under the Trademark MuCell®. Materials from which the cover main body 121 may be formed include an engineering resin such as a blend of polycarbonate alloy plus acrylonitrile butadiene styrene.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.