US3804401A

US3804401A - Pneumatic stripping apparatus

Info

Publication number: US3804401A
Application number: US00302364A
Authority: US
Inventors: K Stange
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1972-10-30
Filing date: 1972-10-30
Publication date: 1974-04-16
Anticipated expiration: 1991-04-16
Also published as: JPS49102350A; CA998705A

Abstract

This invention relates to an apparatus for stripping copy sheets bearing developed electrostatic images from the surface of a photoreceptor drum member, in which the stripping member is supported on a cushion of air so as not to contact the drum surface during the stripping operation. A stripping member is formed with a wedge portion member positioned adjacent to the drum surface to affect stripping of the paper from the drum surface. A stripping member is formed with a plenum channel with the bottom thereof, and is in communication with a source of air that effects an air cushion formed between a stripping member and a drum surface. Air channels are formed at the leading edge of the stripping member to direct air in the vicinity of the leading edge of the copy sheet to facilitate lifting of the copy sheet off the drum surface. In another embodiment, air channels are formed in the face of the wedge portion to assist in separating the copy sheet from the drum surface after it has been initially stripped. The stripping member is loaded against the photoreceptor drum member by a gimbal spring which allows the stripping member to maintain a constant relationship to the photoreceptor under conditions of runout or eccentricity of the photoreceptor while operating under dynamic conditions.

Description

United States Patent [191 Stange PNEUMATIC STRIPPING APPARATUS Klaus K. Stange, Pittsford, NY.

[73] Assignee: XeroxCorporation, Stamford,

Conn.

[22] Filed: Oct. 30, 1972 [21] Appl. No.: 302,364

[75] Inventor:

[52] US. Cl 271/80, 271/195, 271/DIG. 2 [51] Int. Cl B65h 29/56 [58] Field of Search 271/80, DIG. 2, 74, 51,

[5 6] References Cited UNITED STATES PATENTS 8/1926 Y Minton.... 271/DIG. 2

3,578,859 5/1971 Stillings 271/D1G. 2 3,396,235 8/1968 Button et al.... 355/3 3,428,308 2/1969 Bernard 271/51 3,126,200 3/1964 Rehm 271/74 X Primary Examiner Evon C. Blunk Assistant Examiner-Bruce H. Stoner, Jr.-

57 ABSTRACT This invention relates to an apparatus for stripping [451 Apr. 16, 1974 copy sheets bearing developed electrostatic images from the surface of a photoreceptor drum member, in which the stripping member is supported on a cushion of air so as not to contact the drum surface during the stripping operation. A stripping member is formed with a wedge portion member positioned adjacent to the drum surface to affect stripping of the paper from the drum surface. A stripping member is formed with a plenum channel with the bottom thereof, and is in communication with a source of air that effects an air cushion formed between a stripping member and a drum surface. Air channels are formed at the leading edge of the stripping member to direct air in the vicinity of the leading edge of the copy sheet to facilitate lifting of the copy sheet off the drum surface. In another embodiment, air channels are formed in the face of the wedge portion to assist in separating the copy sheet from the drum surface after it has been initially stripped. The stripping member is loaded against the photoreceptor drum member by a gimbal spring which allows the stripping member to maintain a constant relationship to the photoreceptor under conditions of whom or eccentricity of the photoreceptor while operating under dynamic conditions.

6 Claims, 7 Drawing Figures PATENTEDAPR 161w 3.804.401

' saw 1 BF 2 Fla; la FIG. lb

PRIOR 4147' PR/OR HRT FIG. lc

1 7/01? EFT FIG. 2

PNEUMATIC STRIPPING APPARATUS Thisinvention relates generally to xerographic copying apparatus and in particular to an improved stripping apparatus for stripping copy sheets having an electrostatic toner image transferred thereon from a moving drum surface.

In conventional xerography a photoconductive surface in the form of a drum is uniformly charged and then exposed to a light image of an original to be reproduced. Under the influence of the light image the charge of the surface is selectively dissipated to produce what is known as a latent electrostatic image. The charged latent image is developed, or made visible, by attracting oppositely charged toner particles, which are brought into close proximity to the drum surface. The developed image is then transferred to a paper support material, which must then be separated or stripped from the drum surface which concerns the present invention. The image is then affixed to the support material to form a permanent record of the original document.

To transfer the image, the copy sheet is placed over the image bearing the photoconductive surface and the back side of the sheet subjected to a spray of ionized air. As a result, a charge is built up on the sheet, having a magnitude and polarity sufficient to electrostatically attract the toner particles from the photoconductive surface onto the copy sheet. However, during transfer,

a charge opposite to the charge found on the nonimage areas on the drum surface is induced on the copy sheet support material causing the sheet to become electrostatically tacked to the drum surface The removal of the sheet with the toner image loosely adhering thereto has long been a problem of the xerographic copying art.

One of the best and most widely known stripping devices is a mechanically air puffing device and as described, for example, in U.S. Pat. No. 3,062,536. Normally, the copy sheet is stripped from the surface of the drum by introducing a jet of air between the copy sheet and the surface of the drum allowing the sheet to fall away from the photoconductive surface where it can be picked up by a transport belt or the like. While puffing devices are satisfactory they are not entirely reliable in operation as for example when puffing occurs too soon or too late.

Still, another type of stripping device is one or more mechanical stripping fingers which are actuated by an electrical signal brought into contact with the surface of the drum to contact the edge of the copy sheet and wedge the edge away from the photoconductive drum surface as described. for example in U.S. Pat. No. 3,578,859. While mechanical stripping fingers are satisfactory in one sense, they usually require frequent replacement and care must be exercised in the selection of the materials to prevent scratching or otherwise damaging the sensitive photoconductive drum surface.

The present invention is directed to a pneumatic stripping apparatus for removing copy sheets from a photoconductive surface and is accomplished generally speaking by a stripping member floating on a thin air cushion such that stripping is effected without contacting the drum surface. More than this the stripping apparatus may be used for stripping copy sheets from a moving fusing drum surface which is heated.

It is therefore a primary object of the invention to improve apparatus for removing electrostatically tacked image bearing support material from a moving photoconductive drum surface.

It is another object of the present invention to enable removing copy sheets from a moving photoconductive surface without scoring or otherwise damaging the photoconductive surface.

It is a further object of the present invention to achieve greater reliability for stripping copy sheets from photoconductive surfaces.

It is still a further object of the present invention to provide a simplified design and construction for a stripping assembly for stripping copy sheets from a drum surface.

It is still another object of the present invention to produce an inexpensive manufacture and assembly for stripping copy sheets from a drum surface.

It is still a further object of the invention to enable removing copy sheets from a moving heated fusing surface.

It is still a further object of the invention to enable a plurality of stripping members to be placed on a moving surface to facilitate simultaneous lifting of the entire leading edge of the copy sheet.

For a better understanding of the present invention as well as other objects and features thereof reference is had to the following detailed description of the invention to be read with the accompanying drawings in which:

FIGS. 1(a) (c) illustrates the prior art stripping de vices showing different sequencing of an air blast, respectively;

FIG. 2 illustrates schematically a partial view of xerographic reproducing apparatus employing a preferred embodiment of the pneumatic stripping apparatus according to the present invention;

FIG. 3 is a plan view of the stripping apparatus;

FIG. 4 is an end view of the stripping apparatus, and

FIG. 5 is a partial side sectional view of an alternative embodiment of the pneumatic stripping apparatus illustrating certain detail thereof.

Referring now to FIGS. 1(a) to) there is shown a prior art stripping system, which directs high pressure air through an array of jets 2 at a distance spaced from the photographic conductive drum toward copy sheet 4 carried on drum 6. As best shown in FIG. 1(a), when the air blast 6 occurs too soon, the energy is exhausted before the leading edge of sheet 4 arrives. By the same token, if the air blast is too late, as shown in FIG. 1(b), the blast of air will actually push the copy sheet down toward the drum surface. Even when the air blast is timed perfectly as in FIG. He), the jets are not capable of pushing all the air below the leading edge of the sheet as some of the air will always push the sheet down onto the drum surface. As a result, more air than is needed is employed, which may cause turbulence in a machine and may cause toner on the copy sheet to shift.

Referring now to FIG. 2, there is shown in schematic form a reproduction machine which incorporates the stripping apparatus of the invention generally designated 10. As in all electrostatic copying systems, image rays or an original to be copied are projected by means of an optical system exposing the photosensitive surface of a xerographic plate in the form of a drum generally designated by the reference numeral 16. As the drum surface continues, its movement of the electrostatic image passes through a development station at which development of the image takes place as by cascading developer material thereacross.

As shown in FIG. 2, the developed electrostatic images passes a transfer station where a sheet of copy paper 22 is advanced at a speed in synchronism with the drum in order to accomplish transfer to the developed image. At the transfer station is a sheet transfer corotron 25 which effects electrostatic transfer of the developed image from the surface of the drum to the copy sheet. A detack corotron 27 which is opposite in polarity to the transfer corotron 25 serves to neutralize the charge generated by transfer corotron 25 on the copy sheet. The sheet is stripped from the drum by a pneumatic stripping apparatus 10 according to the present invention as will be described hereinafter. The sheet is advanced to a conveyor such as a vacuum transport 30 which conveys the sheet to a fuser (not shown) where the developed image is permanently fixed to the sheet. It should be understood that the stripping apparatus can be used for stripping sheets from a fuser roll surface as well. The foregoing brief description is deemed sufficient for an understanding of the copying steps of the machine and reference is made to foregoing patents for a more detailed description thereof.

As shown in FIGS. 2, 3, and 4, the pneumatic stripping apparatus 20 according to the present invention which includes a stripping head member 33 which is formed with wedge portion 34 and contoured on the under side to conform to that of the drum surface and to define a plenum chamber as will become apparent. Supporting the stripping head member is gimbal spring member 35 provides a normal force against the drum surface and enables the stripping head member to conform to the drum surface in the pitch and yaw directions under conditions of runout or eccentricity of the drum surface while operating under dynamic conditions. Positioned at the sides of the stripping head member are a pair of lift rail members which serve to guide and continue lifting the leading edge of the copying sheet after it is stripped from the drum surface by the stripping head member as will become more apparent.

Stripping head member 33 which may be made of any suitable material, such as, Bakelite aluminum with anodized hardcoating or ceramic, or mixture thereof, is maintained at a predetermined distance from the drum surface on a thin cushion of air. Connected to the stripping head member is an air conduit member 46 which is connected to a flexible conduit member 47 which in turn is connected to an air manifold 48 which is formed in the suspension arm 37. It will be noted that the manifold 48 is connected to a suitable source-of air (not shown) which enables low pressurized air to be communicated to the stripping head member to effect an air cushion on the bottom thereof creating a floating stripping head member against the action of spring member 35. Formed near the leading edge of the stripping head apparatus are one or more air escape grooves 49 which serve to direct escaping air directly below the leading edge of the copy sheet to insure lifting with the wedge portion 34. It will be appreciated that the distance of the stripping head member 33 above the drum surface is less than the thickness of the sheet being stripped. In this manner, the wedge portion 34 serves to strip the leading edge of the copy sheet which further acted on by air from grooves 49 to lift the sheet toward guide rails 45. Now it will be appreciated, that the copy is stripped from the drum surface reliably without contact of the stripping head member on the drum surface to prevent damage and/or wear.

FIG. 5 shows a second embodiment in which air escape conduits 51 are formed in wedge portion 34 to further enhance lift of the sheet from the drum surface.

While the invention has been described with reference to the structure disclosed, it is not confined to the details set forth, but is intended to cover such modifications, or changes as may come within the scope of the following claims.

What is claimed is:

1. Apparatus for stripping copy sheets bearing developed electrostatic images from a xerographic surface in the shape of a drum comprising;

a frame,

a stripping member supported from said frame on resilient mounting means in close proximity to a xerographic drum at a distance from said xerographic drum less than the thickness of copy sheets bearing developed images to be stripped,

said stripping member having a wedge portion positioned adjacent to the drum path and being formed with a plenum chamber on the bottom thereof,

air supply means to provide low pressurized air in communication with said plenum chamber to effect formation of an air cushion between said stripping member and the drum surface acting against said resilient mounting means to maintain a predetermined uniform spacing therebetween while the wedge portion strips the leading edge of each copy sheet from the drum surface without destroying the developed images on the copy sheets.

2. Apparatus according to claim 1 wherein said plenum chamber is formed with plurality of channels at the leading end thereof.

3. Apparatus according to claim 1 wherein guide members are positioned on said stripping member to assist in sheet separation.

4. Apparatus according to claim 1' wherein said wedge portion is formed with a plurality of conduits in communication with the air supply to exert an air force against the leading edge of each copy sheet as it is moved along the surface of the wedge portion.

5. Apparatus according to claim 1 wherein said frame is pivotally mounted for loading and unloading of said stripping member into stripping position.

6. Apparatus for stripping copy sheets bearing developed electrostatic images from a xerographic surface in the shape of a drum comprising;

a frame,

a stripping member supported by said frame in close proximity to a xerographic drum at a distance from said Xerographic drum less than the thickness of copy sheets bearing developed images to be stripped,

air supply means in communication with said plenum chamber to effect formation on an-air cushion between said stripping member and the drum surface 6 to maintain a predetermined spacing thereabove, and unloading of said stripping member into stripwhile the wedge portion strips the leading edge of ping position, each copy sheet from the drum surface without dewherein said frame includes a gimbal spring to mainstroying the developed images on the copy sheets, tain constant relationship of stripping member and 5 drum surface for stripping subsequent copy sheet. wherein said frame is pivotally mounted for loading i

Claims

1. Apparatus for stripping copy sheets bearing developed electrostatic images from a xerographic surface in the shape of a drum comprising; a frame, a stripping member supported from said frame on resilient mounting means in close proximity to a xerographic drum at a distance from said xerographic drum less than the thickness of copy sheets bearing developed images to be stripped, said stripping member having a wedge portion positioned adjacent to the drum path and being formed with a plenum chamber on the bottom thereof, air supply means to provide low pressurized air in communication with said plenum chamber to effect formation of an air cushion between said stripping member and the drum surface acting against said resilient mounting means to maintain a predetermined uniform spacing therebetween while the wedge portion strips the leading edge of each copy sheet from the drum surface without destroying the developed images on the copy sheets.

4. Apparatus according to claim 1 wherein said wedge portion is formed with a plurality of conduits in communication with the air supply to exert an air force against the leading edge of each copy sheet as it is moved along the surface of the wedge portion.

6. Apparatus for stripping copy sheets bearing developed electrostatic images from a xerographic surface in the shape of a drum comprising; a frame, a stripping member supported by said frame in close proximity to a xerographic drum at a distance from said xerographic drum less than the thickness of copy sheets bearing developed images to be stripped, said stripping member having a wedge portion positioned adjacent to the drum path and being formed with a plenum chamber on the bottom thereof, air supply means in communication with said plenum chamber to effect formation on an air cushion between said stripping member and the drum surface to maintain a predetermined spacing thereabove, while the wedge portion strips the leading edge of each copy sheet from the drum surface without destroying the developed images on the copy sheets, wherein said frame is pivotally mounted for loading and unloading of said stripping member into stripping position, wherein said frame includes a gimbal spring to maintain constant relationship of stripping member and drum surface for stripping subsequent copy sheet.