US3918400A

US3918400A - Blade mounting assemblies

Info

Publication number: US3918400A
Application number: US471625A
Authority: US
Inventors: Robert A Cheeseman
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-06-23
Filing date: 1974-05-20
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11
Also published as: JPS5037440A; AU7025074A; NL7408496A; SE7408168L; BE816534A; DE2427690C3; BR7405053D0; FR2234085B1; FR2234085A1; IT1015202B; DE2427690B2; CA1030339A; GB1419417A; DE2427690A1

Abstract

A blade mounting assembly and apparatus for urging a blade against a surface are described. The blade is held in a holder connected between a pair of arms independently pivotally mounted on a common axis and biased independently to urge the blade towards the surface, means being provided for limiting rotation of the blade holder with respect to the pivot arms. The couplings between the blade holder and the arms are sufficiently loose to permit small relative movements of the pivot arms sufficient to take up misalignment between the blade and the roll surface.

Description

United States Patent 11 1 Cheeseman Nov. 11, 1975 [5 BLADE MOUNTING ASSEMBLIES 3.186.377 6/1965 Schuessler 118/261 x 7 s 7 W51 Robert Cheeseman, Hiwhin, 3132111331 M33? 221E135-1111131111:11:11:11.T8756? England 3.802.339 4/1974 Andcrsson l5/356.5l [73] Assignee: vXerox Corporation, Stamford.

C Primary E.\'1r11ine1-Ronald Feldbaum Attorney, Agent, or Firm.lames J. Ralabate; Donald [22] F'led: May 1974 C. Kolasch; Ernest F. Chapman [21] Appl. No.1 471,625

[57] ABSTRACT [30] Foreign Application priority Data A blade mounting assembly and apparatus for urging a June 7} 1973 United Kingdom mug/7 blade against a surface are described. The blade 1s held in a holder connected between a pair of arms in- 52 us CL H 2 X dependently pivotally mounted on a common axis and l l Int 2 8/261 biased independently to urge the blade towards the [58] Field of 637 surface. means being provided for limiting rotation of 3565]? 101/157 169 the blade holder with respect to the pivot arms. The couplings between the blade holder and the arms are [561 285 ;?3183 321882222. 818:"232"21232522223 z L UNITED STATES PATENTS between the blade and the roll surface.

2.070.667 2/1937 Lougee 118/281 ux 2.213.980 9/1940 Ossing 118/107 12 Claims, 3 Drawlng Figures 2a 2 g g 2a fliff ,E 11111,

. I l 1 a ....1111| llllullllllh ...1ll||..| l" ll 8 A-- U.S. Patent Nov. 11, 1975 m, Q v m M 8 T 5:: 4. I i I. l|\|| UN BLADE MOUNTING ASSEMBLIES BACKGROUND OF THE INVENTION This invention relates generally to the mounting of blades and more particularly, it relates to an apparatus for mounting wiper or cleaning blades adapted to be urged against a moving surface for the purpose of metering or doctoring material on the surface or for at least substantially removing material from the surface.

In the prior art, doctor blades are mounted in a holder which is pivotally connected at opposite ends respectively to a pair of bearing members which are fixed solidly with respect to one another, the blade being urged against the surface by suitable biasing means. Such an arrangement is described, for example, in U.S. Pat. No. 3,195,500 in which the biasing means comprises two fluid pressure devices acting on opposite ends respectively of the blade holder. Due to the solid relationship of the mountings, where the surface is substantially inflexible, such an arrangement relies on the inherent flexibility of the blade to take up static and dynamic misalignments of the surface with respect to the blade mounting and is unsatisfactory for use where the blade-lacks the necessary flexibility and/or the angle of the blade to the surface is a critical factor.

Accordingly, it is an object of this invention to provide a blade mounting assembly capable of taking up such misalignments.

Another object of this invention is to provide an apparatus for urging a blade which lacks flexibility, against a substantially inflexible surface so that the blade will correct for static and dynamic misalignments.

SUMMARY OF THE INVENTION In accordance with the above objects there is provided an apparatus in which a blade is urged against a substantially inflexible surface,a blade mounting assembly including a pair of pivot arms independently mounted for pivotal movement about a common pivot axis, a blade holder loosely coupled at opposite ends to the respective pivot arms at locations remote from the pivot axis, means independently biasing the pivot arms to urge a blade in the blade holder towards a said substantially inflexible surface, and restraining means for limiting rotation of the blade holder with respect to the pivot arms, the couplings between the blade holder and the pivot arms being sufficiently loose to permit small relative movements of the arms sufficient to take up misalignment between the pivot axis and such substantially inflexible surface.

The restraining means comprises a locator bar extending between the pivot arms with its opposite ends loosely coupled to the respective pivot arms intermediate the pivot axis and the blade holder coupling, which bar is engaged by the blade holder, in which case the blade holder suitably is coupled to the pivot arms by lugs at opposite ends thereof engaging in oversize openended slots in the ends of the pivot arms remote from the pivot axis, and the blade holder is loosely, detachably, coupled to the locator bar. The coupling between the blade holder and locator bar may advantageously comprise a rotatable pin on the locator bar engaging in a keyhole slot in a projection on the blade holder.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of this invention as well as other advantages and features thereof, will become apparent from a further reading of the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a front elevation of a mounting assembly of this invention;

FIG. 2 shows a side elevation of the mounting assembly of FIG. 1 in which the blade is shown in engagement with the surface of an applicator roll; and

FIG. 3 is a schematic illustrating one form of liquid development system of an electrostatographic reproduction apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A blade mounting assembly of this invention is particularly suitable for mounting a blade used in a system for the liquid development of electrostatic latent images using the techniques generally described in U.S. Pat. No. 3,084,043 issued to Robert W. Gundlach on Apr. 2, 1963, for the purpose described below, U.S. Pat. No. 3,084,043 discloses apparatus and method for the liquid development of electrostatic latent images wherein liquid developer is presented to a photoreceptor having an electrostatic latent image on its surface, said presentation being by means of an applicator comprising lands and valleys such that liquid developer is contained in the valleys out of contact with the photoreceptor while the surfaces of the lands are in contact with the photoreceptor. In such an arrangement the liquid developer is attracted from the valleys to the electrostatic latent image in image configuration. A typical example of such an arrangement is an electrostatic copying apparatus wherein the applicator is a rigid (substantially inflexible) cylindrical member or roll having on its surface a pattern of ridges and grooves which comprise the lands and valleys respectively. The roll is positioned to come into contact with a photoreceptor bearing on its surface an electrostatic latent im age, the photoreceptor suitably being a cylindrical member comprising a conductive substrate and a photoconductive coating which supports the electrostatic latent image.

The electrostatic latent image is typically produced by first charging the entire surface of the photoreceptor in the dark and then exposing the charged surface to a light pattern of the image sought to be reproduced thereby to discharge the charge in the areas where light strikes the surface. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original image pattern.

The photoreceptor surface bearing the electrostatic latent image and the applicator roll are brought into moving contact during which the liquid developer is drawn to the photoreceptor from the valleys of the applicator roll by the charges which form the electrostatic latent image. Typically the image is then transferred to an image receiving member, such as paper, by pressure contact between the photoreceptor and the roll.

Using the development techniques above described, liquid developer is suitably applied to an applicator roll in excess of requirements, and the surface of the roll is engaged by a blade prior to arrival at the photoreceptor to meter or doctor the amount of liquid on the roll surface so as at least substantially to remove all liquid from the lands and to reduce the level of the liquid in the valleys to below the level of the lands. Typically, the

grooves of the applicator roll are about 60 microns deep with their centers across the lands about 100 microns apart.

For such application the blade is suitably made of a flexible plastics material or a rubber-like elastomer such as neoprene or polyurethane and has a rectangular sectioned operating or front edge, preferably maintained in pressure engagement with the roll surface during operation at a trailing angle with respect to the direction of movement of the applicator roll surface therepast. It has been found that for uniform doctoring or metering of the liquid developer on the applicator roll, a relatively inflexible blade material of a durometer shore hardness of between 60 and 90 should be used and the blade angle should desirably be maintained within close limits. Thus, in one embodiment in which the blade is 228 mm long and 3.15 mm thick, acting on. an applicator roll 25 mm in diameter, the blade is made of polyurethane of a durometer shore hardness of 75 plus or minus 5; the blade is maintained at an angle to the tangent to the roll surface at the line of engagement of the blade with said surface of 48 plus or minus 1, and is loaded against the roll surface at a pressure variable between 6 gm. per mm length and 18 gm. per mm length.

A blade as described above lacks the flexibility required to allow for expected static and dynamic misalignments, due to manufacturing tolerances, between the blade and the applicator roll by flexure of the blade itself during operation and the present invention provides a blade mounting assembly which permits such misalignments to be taken up.

Referring to the drawings, there is shown in FIGS. 1 and 2 a mounting assembly for a blade 1 adapted to engage the peripheral surface of an applicator roll 5.

The blade mounting assembly comprises a pair of L- shaped pivot arms 3 which are independently pivotally mounted on stub shafts 8 for pivotal movement about a common axis A. The pivot arms are constructed in mirror image configuration to one another. A blade holder 2 is loosely coupled at opposite ends to the pivot arms 3 respectively at their ends remote from the pivot axis and is restrained against rotation relative to the pivot arms in the manner described below. The blade holder 2 carries a blade 1 which has a rectangular sectioned operating or front edge and is securely held along its rear end by the holder. In operation the blade is urged into pressure engagement with the surface of the applicator roll by a pair of pressure springs 6 acting independently on the pivot arms respectively. The loose coupling between the blade holder 2 and the pivot arms 3 is provided in the illustrated embodiment by lugs Zn on the blade holder engaging in oversize open-ended slots 9 in the ends of the pivot arms remote from the pivot axis A, the couplings being sufficiently loose to permit static and dynamic misalignments between the applicator roll and the pivot axis A of the blade mounting, for example cone shaping of the applicator roll and misalignment between the applicator roll axis and the pivot axis, to be taken up during operation. The lugs are suitably circular and in the case of a doctor blade 9 inches long, it has been found suitable for the lugs to be /a inch in diameter and to engage in slots which are 0.008 inch over a running fit.

In the embodiment illustrated the blade holder 2 is restrained against rotation relative to the pivot axis A by engaging against a locator bar 4 connected between the pivot arms intermediate the pivot axis and the blade holder couplings; specifically, as shown, the locator bar is connected between the pivot arms at the elbows thereof with the end portions of the locator bar engaging in oversize holes in the pivot arms. Again for a doctor blade 9 inches long engaging an applicator roll 1 inch in diameter it has been found suitable for the end portions of the locator bar to be Vs inch in diameter engaging in holes which are 0.008 inch over a running fit.

As described above the lugs Zn on the blade holder engage in open-ended slots in the ends of the pivot arms, this construction being provided to permit easy removal of the blade holder for blade replacement, and in order to prevent the blade holder becoming disengaged from the pivot arms it is coupled to the locator bar. This coupling is provided by a tang 15 on the rear end of the blade holder engaging a pin 16 on the locator bar as illustrated in FIG. 1. To satisfy the requirement for removal of the blade holder, the tang is provided with a keyhole slot 17, and the lug is rotatable and provided with a flat area so that in one rotational position it will be received in the entrance of the slot and upon rotation will prevent disengagement of the tang therefrom. Again, in order to permit the necessary relative movement between the pivot arms, the coupling between the blade holder 2 and the locator bar 4 is a loose one.

In this embodiment, the pivot axis of the assembly is suitably arranged along the tangent to the applicator roll 5 where the blade 1 engages the roll surface. However, other arrangements of the pivot axis are possible and for example, the pivot axis could be arranged in the plane of the doctor blade in which case the pivot arms would not be cranked or angular.

Suitable means which act on the pivot arms 3 in opposition to the springs 6 are provided for holding the blade out of engagement with the roll surface when the latter is inoperative by pivoting the assembly about the axis A.

For a better understanding of a typical liquid development system in which the applicator roll 5 may be embodied, reference will now be made to FIG. 3. Liquid developer is supplied to the applicator roll 5 by a supply roll 10 running in a liquid developer tray 11, a small gap, e.g. 0.25 mm being provided between the two rolls such that an excess of developer is applied to the applicator roll in order to give a thorough covering of developer along its entire length. The applicator roll itself is, during operation, arranged in pressure engagement with the surface of a photoreceptor drum l2 and the blade 1 is arranged to engage the applicator roll to doctor or meter the liquid developer applied thereto by the supply roll, prior to engagement with the photoreceptor drum surface.

While a particular embodiment has been described above, it will be appreciated that various modifications may be made to the specific details referred to herein without departing from the scope of the invention as defined in the appended claims. For example, while a construction of assembly which permits easy removal of the blade holder has been described above, the lugs on the blade holder may engage in enclosed openings and be non-circular in cross section so as to restrain the blade holder against rotation during operation in which case the locator bar could be eliminated, but in such a case provision would desirably be provided for removing the blade from the blade holder or the blade holder could be in two separable parts for removal of the blade.

Furthermore, although a particular application of assembly of this invention has been described above it should be appreciated that the assembly finds general use in other applications. For example, in the field of electrostatography, it may be used for mounting a blade for cleaning the surface of a photoreceptor following development of an electrostatic latent image thereon and the transfer of such image to an image receiving surface, such as paper.

. What is claimed is:

1. An apparatus for urging a blade against a substantially inflexible surface comprising a blade mounting assembly having a pair of pivot arms independently mounted for pivotal movement about a common pivot axis and a blade holder movably coupled at opposite ends to the respective pivot arms at locations remote from the pivot axis, the blade holder being capable of movement independent of the pivotal movement of the pivot arms;

means independently biasing the pivot arms to urge a blade in the blade holder towards a said substantially inflexible surface; and

restraining means for limiting movement of the blade holder with respect to the pivot arms, the couplings between the blade holder and the pivot arms being sufficiently movable to permit small relative movements of the arms sufficient to take up misalignment between the pivot axis and such substantially inflexible surface.

2. Apparatus of claim 1, wherein the restraining means comprises a locator bar extending between the pivot arms with its opposite ends loosely coupled to the respective pivot arms intermediate the pivot axis and the blade holder couplings, the locator bar being engaged by the blade holder.

3. Apparatus of claim 2, wherein the blade holder is coupled to the pivot arms by lugs at opposite ends thereof engaging in oversize open-ended slots in the ends of the pivot arms remote from the pivot axis, and the blade holder is movably detachably, coupled to the locator bar.

4. Apparatus of claim 3, wherein the coupling between the blade holder and locator bar comprises a non-circular rotatable pin on the locator bar engaging in a keyhole slot in a projection on the blade holder.

5. Apparatus of claim 1, wherein they substantially inflexible surface is arcuate and the pivot arms are cranked, the pivot axis being arranged in the plane of the tangent to the substantially inflexible surface where the blade engages said surface.

6. Apparatus of claim 1, wherein the substantially inflexible surface is defined by the periphery of a roll.

7. Apparatus of claim 6, wherein the roll has a pcripheral surface comprising a pattern of lands and valleys.

8. Apparatus of claim 7, for the liquid development of electrostatic latent images wherein liquid developer is presented to a photoreceptor surface having an electrostatic latent image on its surface by means of the peripheral surface comprising a pattern of lands and valleys which is contacted with the photoreceptor surface, the peripheral surface being engaged by the blade in the blade holder prior to contact with the photoreceptor surface, such that upon the peripheral surface contacting the photoreceptor surface, the liquid developer is contained substantially in the valleys out of contact with the photoreceptor surface.

9. A blade mounting assembly to permit small relative movements between a blade and the surface which the blade contacts comprising:

a pair of pivot arms independently mounted for pivotal movement about a common pivot axis and a blade holder movably coupled at opposite ends to the respective pivot arms at locations remote from the pivot axis, the blade holder being capable of movement independent of the pivotal movement of the pivot arms;

means independently biasing the pivot arms to urge a blade in the blade holder against a surface; and

restraining means for limiting movement of the blade holder with respect to the pivot arms, the couplings between the blade holder and the pivot arms being sufficiently movable to permit small relative movements of the arms sufficient to take up misalignment between the pivot axis and the surface which the blade contacts.

10. Apparatus of claim 9, wherein the restraining means comprises a locator bar extending between the pivot arms with its opposite ends loosely coupled to the respective pivot arms intermediate the pivot axis and the blade holder couplings, the locator bar being engaged by the blade holder.

11. Apparatus of claim 10, wherein the blade holder is coupled to the pivot arms by lugs at opposite ends thereof engaging in oversize open-ended slots in the ends of the pivot arms remote from the pivot axis, and the blade holder is movably detachably, coupled to the locator bar.

12. Apparatus of claim 11, wherein the coupling between the blade holder and locator bar comprises a non-circular rotatable pin on the locator bar engaging in a keyhole slot in a projection on the blade holder.

Claims

1. An apparatus for urging a blade against a substantially inflexible surface comprising a blade mounting assembly having a pair of pivot arms independently mounted for pivotal movement about a common pivot axis and a blade holder movably coupled at opposite ends to the respective pivot arms at locations remote from the pivot axis, the blade holder being capable of movement independent of the pivotal movement of the pivot arms; means independently biasing the pivot arms To urge a blade in the blade holder towards a said substantially inflexible surface; and restraining means for limiting movement of the blade holder with respect to the pivot arms, the couplings between the blade holder and the pivot arms being sufficiently movable to permit small relative movements of the arms sufficient to take up misalignment between the pivot axis and such substantially inflexible surface.

5. Apparatus of claim 1, wherein the substantially inflexible surface is arcuate and the pivot arms are cranked, the pivot axis being arranged in the plane of the tangent to the substantially inflexible surface where the blade engages said surface.

7. Apparatus of claim 6, wherein the roll has a peripheral surface comprising a pattern of lands and valleys.

9. A blade mounting assembly to permit small relative movements between a blade and the surface which the blade contacts comprising: a pair of pivot arms independently mounted for pivotal movement about a common pivot axis and a blade holder movably coupled at opposite ends to the respective pivot arms at locations remote from the pivot axis, the blade holder being capable of movement independent of the pivotal movement of the pivot arms; means independently biasing the pivot arms to urge a blade in the blade holder against a surface; and restraining means for limiting movement of the blade holder with respect to the pivot arms, the couplings between the blade holder and the pivot arms being sufficiently movable to permit small relative movements of the arms sufficient to take up misalignment between the pivot axis and the surface which the blade contacts.