GB2116911A - Cleaning unit for an electrophotographic device - Google Patents

Abstract

A cleaning blade 10 which cleans the surface of a rotatable photosensitive drum D is mounted in blade inserting means 4 in a blade holding member 3. The blade inserting means 4 comprises two (or three, Figure 4) pairs of parallel walls 5, 6 disposed at an angle to each other and having bent points 8 therebetween. The cleaning blade 10, whose thickness is slightly less than the width of the means 4, is retained by frictional contact with the blade inserting means. It is stated that, apart from easier replacement, advantages include ability to accommodate fluctuations in blade thickness whilst maintaining a linear non-wavy cleaning edge. <IMAGE>

Description

SPECIFICATION Cleaning unit for an electrophotographic device This invention relates to a cleaning unit for an electrophotographic device, which is adapted to remove excess toner from a photosensitive drum.

In a conventional cleaning unit of this type (a so-called "wiper blade" cleaning system), a resilient cleaning blade is held by blade holding means such that an acute angle is formed between the cleaning blade and a contact plane with the image-bearing body (i.e. a plane including the contact line of the cleaning blade with the body) on the side of the body which has not yet been cleaned. The cleaning blade is clamped by first and second holding members which are tightened together with screws, or alternatively the cleaning blade is bonded to a single holding member so as to be held straight. These arrangements are however disadvantageous in the following respects: (1) The holding members are bent longitudinally by tightening of the screws.

(2) As the tightened portions are contracted, the blade edge is retracted.

(3) Fluctuations in the thickness of the blade canot be absorbed.

(4) As bonding is rather difficult, the cleaning edge is liable to be unsatisfactorily non-linear.

In other words, the cleaning blade is not uniformly abutted against the image-bearing member. As a result, toner may pass through non-linear portions of the cleaning blade giving rise to an unsatisfactory cleaning effect.

Furthermore, replacement of the cleaning blade is rather troublesome, because the holding members are secured with screws or the like directly to a body of the cleaning unit, and it is necessary to remove the cleaning unit body from the electrophotographic device before the cleaning blade can be replaced. Where the cleaning blade is bonded to the holding means, the latter must be removed from the electrophotographic device in order to replace the blade. This is not economical, rendering the maintenance of the cleaning unit considerably high in cost.

It is an object of the present invention to overcome the above-described disadvantages, and more particularly to provide a cleaning unit in which the cleaning blade can readily be replaced.

According to the present invention, a cleaning unit for an electrophotographic device comprises a resilient cleaning blade which is adapted to clean the surface of an image-bearing body, and a blade holding member including blade inserting means having at least one bent portion, the cleaning blade being inserted into the blade inserting means such that the blade is bent at said bent portion and is held in the blade holding member by means of friction between the blade and the blade inserting means.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figures 1 and 2 are diagrammatic views of a conventional cleaning unit for an electrophotographic device; Figure 3 is a side view of a first embodiment of a cleaning unit according to the present invention; Figure 4 is a side view of a blade holding member of a second embodiment of a cleaning unit according to the present invention; Figure 5 is an explanatory diagram of a cleaning unit which is arranged differently from that of the present invention; and Figure 6 is a similar view to Figure 3 but showing a cleaning blade of the unit reversed.

in Figures 1 and 2 there is shown a conventional cleaning unit for cleaning excess toner from the surface of a rotatable photosensitive member 1, the cleaning unit comprising a cleaning blade 10 held by a holder. In normal usage, the cleaning blade 10 is held with a first edge 16 thereof in contact with the member 1 (see Figure 1). When this edge has become worn through prolonged use, the blade 10 is reversed to present a second edge 17 thereof to the member 1. However, because the cleaning edge 10 is fatigued by its constant contact with the rotatable member 1, it becomes deformed in the manner depicted in Figure 2 so that when the blade is reversed the edge 17 does not make proper contact with the member 1. Hence, the cleaning action is unsatisfactory.

In addition to overcoming the disadvantages mentioned previously, the present invention seeks to obviate this problem also.

A first embodiment of a cleaning unit according to the invention is shown in Figure 3, where it is denoted by the reference numeral 2. The cleaning unit 2 includes a cleaning blade 10 made of a resilient material such as rubber, which blade is adpated to clean excess toner from the surface of a photosensitive member 1 in the form of a rotatable drum D, the blade 10 contacting the drum at an edge 15 thereof. The cleaning blade 10 is mounted in blade inserting means 4 formed in a blade holding member 3, the means 4 being composed of first and second straight sections 5 and 6 having bent points or corners 7 and 8 provided therebetween. Each of the sections 5,6 has two mutually parallel and opposed side walls.The two sections 5 and 6 are disposed at an angle a relative to one another, which in the illustrated construction is about 15". A positioning surface 9 is formed at the bottom of the blade inserting means 4.

The cleaning blade 10 has a thickness which is slightly smaller than the width or clearance of the blade inserting means 4, and is received in the means 4 by being bent along the sections 5 and 6 thereof. A rear end face 11 of the blade 10 is abutted against the positioning surface 9, while an upper edge 12 of this face 11 is abutted against an upper face 5a of the first section 5. A lower surface 1 0a of the blade 10 is engaged with the lower corner 8, while an upper surface lOb thereof abuts against an upper edge 13b of an opening 13 where the second section 6 opens onto an end of the holding member 3. A gap 14 is thus formed between a lower edge 13a ofthe opening 13 and the lower surface 10a ofthe blade 10.This positioning ofthe cleaning blade is reinforced by the action of the drum D rotating in the direction of the arrow. The cleaning blade thus engages the blade holding member 3 over three contact surfaces A, B and C.

As a suitable pressing force is imparted to the cleaning blade 10 by pressing means (not shown), the cleaning blade 10 is bent in a direction opposite to the direction of movement of the photosensitive drum 1, in this case. However, since the blade holding member 3 is formed as described above, the cleaning blade is frictionally engaged with the blade holding member 3 through three contact surfaces A, B and C.

Accordingly, rotation of the drum D will not cause the cleaning blade 3 to come out of the blade holding member 3.

In the above-described embodiment, the blade inserting means 4 has two straight sections 5 and 6 each defined by two parallel walls: however, it should be noted that the invention is not limited thereto or thereby.

That is, the blade inserting means may have more than two straight parallel sections, for example as shown in Figure 4, or may have a plurality of corners 8 instead of just one such corner. In the latter case, the same effect as described above can be obtained if the sum Sai of all of the bent angles formed at the corners 8 meets the following condition: O < E:aj S 45 The main features of the invention with respect to the blade holding member 3 have been described above. The features with respectto the cleaning blade 10 will now be explained.

As can be seen in Figure 3, the cleaning blade is arranged such that the angle of its bent portion 20 is formed forwardly with respect to the direction of rotation of the photosensitive drum D at all times. Consider now the case where rotation and stoppage of the drum Dare repeatedly carried out. When the drum D is in a stopped state (including when the cleaning blade 10 is set away from the drum D), the bent portion 20 of the cleaning blade 10 is maintained contracted. When the photosensitive drum D is turned in the direction of the arrow, the bent portion 20 is elongated.In other words, the following sequence is carried out with the contraction state as the reference: one cycle Contraction -- Elongation -- Contraction -- Elongation This is to be contrasted with the situation which would be the case if the bend angle were to be formed rearwardly with respect to the direction of rotation of the photosensitive drum D, as shown in Figure 5. Here, rotation of the drum D imparts a force to the cleaning blade 10 tending to make the latter come out of the holding member 3. In this case, the bent portion 20 of the cleaning blade 10 is elongated in the stopped state of the drum D. Under this condition, the following sequence of events occurs as the photosensitive drum D is turned: Elongation -- Elongation -- Contraction -- Elongation.

Thus, it will be understood that, when the bent portion 20 is elongated in he reference (stopped) state, the motion of the cleaning blade 10 tends to cause the blade to come out of the holding member 3. This phenomenon will never occur with the cleaning unit of the invention, since the operation of restoring the contraction of the bent portion to its original state is repeatedly carried out, and the characteristics of the resilient material of the blade are fully utilized in the blade holding construction.

in general, the cleaning blade 10 is made of a material such as polyurethane. If it is held for a long time, or after it has been used for a long time, it becomes fatigued, i.e. the rigidity of the cleaning blade 10 decreases, as a result of which its cleaning characteristic is lowered. However, in manufacturing the cleaning blade, two edges 15 and 21 thereof may be finished to the extent that they are practically useable for cleaning purposes.

Thus, when the blade becomes fatigued as aforesaid, it may be reversed to present the other of said edges to the drum D, as indicated in Figure 6. In contrast to the conventional arrangement described above with reference to Figures 1 and 2, when the cleaning blade is reversed the deformation of the blade is such that it is substantially upright with respect to the surface of the photosensitive drum D when set free. Accordingly, even after the first cleaning edge 15 has been used for a long time, use of the second cleaning edge 21 is scarcely affected by the fatigue of the cleaning blade.

As described in detail above, in the cleaning unit of the invention, a blade inserting means 4with at least one bent point 8 is formed in the blade holding member 3, and the resilient cleaning blade 10 is inserted into the blade holding means 4 so that it is held by the friction with the blade inserting means 4 caused by its elastic deformation. Accordingly, the drawbacks of the conventional cleaning unit, namely the unsatisfactory non-linearity of the cleaning edge, the tendency of the blade holding member to become wavy, and the inability to accommodate fluctuations in the thickness of the cleaning blade, are eliminated according to the invention. Furthermore, the cleaning blade 10 can readily be replaced by removing same together with the blade holding member 3, and then removing the cleaning blade 10 from the blade holding member 3 for replacement. Thus, the cleaning blade can be replaced in a short period of time without extraneous and dirty work.

Claims (11)

1. Acleaning unitforan electrophotographic device, comprising a resilient cleaning blade which is adapted to clean the surface of an image-bearing body, and a blade holding member including blade inserting means having at least one bent portion, the cleaning blade being inserted into the blade inserting means such that the blade is bent at said bent portion and is held in the blade holding member by means of friction between the blade and the blade inserting means.

2. A cleaning unit as claimed in Claim 1, wherein the blade inserting means has at least two pairs of parallel walls intersecting at an angle to form said bent portion.

3. A cleaning unit as claimed in Claim 2, wherein said angle is about 15 degrees.

4. A cleaning unit as claimed in Claim 1,2 or 3, wherein the holding member includes a positioning surface which is abutted by one end face of the blade.

5. A cleaning unit as claimed in Claim 4 when appended to Claim 2, wherein a first pair of said parallel walls are disposed adjacent to the positioning surface, and a second pair of said parallel walls are continuous with said first pair of walls.

6. A cleaning unit as claimed in Claim 5, wherein said second pair of parallel walls are angled with respect to said first pair of walls such that said second pair of walls extend more generally into the direction of rotation of said image-bearing body than do said first pair of walls.

7. A cleaning unit as claimed in Claim 5 or 6, further including a third pair of parallel walls extending from said second pair of walls and forming an angle therewith, said third pair of walls being angled from said second pair of walls in the same direction as said second pair of walls is angled from said first pair of walls.

8. A cleaning unit as claimed in any preceding claim, wherein the thickness of the blade is slightly less than the width of the blade inserting means.

9. A cleaning unit as claimed in any preceding claim, wherein the blade contacts the blade holding member over at least three contact surfaces.

10. A cleaning unit as claimed in any preceding claim, wherein the blade includes a pair of cleaning edges, and is reversible in the blade holding member and in the blade inserting means such that said cleaning edges may be interchangeably employed.

11. A cleaning unit for an electrophotographic device, substantially as hereinbefore described with reference to Figure 3 or Figure 4 of the accompanying drawings.