GB2037942A - A Photocopier Fixing Roller Assembly - Google Patents

Abstract

A pressure fixing roller assembly in a photocopier comprises a frame 12, a first roller 28 rotatable in the frame, and a pair of arms 20 pivotably attached at 24 to the frame. A shaft 32 extending between the arms and pivotably attached thereto, is bendable toward the first roller 28 when the arms are pivoted at 24. A second roller 46 coaxially aligned with the shaft is mounted by means of bearings 48 on the shaft 32 for rotation and in pressure engagement with the first roller 28. The arms 20 may be pivoted about pins 24 by means of compression springs 36 adjustable by nuts 44 for bending the shaft 32, thereby changing the pressure exerted by the second roller on the first roller. <IMAGE>

Description

SPECIFICATION A Photocopier Roller Assembly This invention relates to a roller assembly in a copying machine.

Copiers of the type which utilize a copy sheet comprising a conductive substrate coated with a photoreceptive material such as zinc oxide; and which include conventional devices for depositing a uniform electrostatic charge on the coating of the copy sheet, illuminating the charged copy sheet with light reflected from a document being copied to dissipate sufficient charge from the copy sheet for forming thereon a charge pattern corresponding to the image of the document, applying a toner to the charge pattern for rendering the image visible, and pressure fixing the toner to the copy sheet are already known.In such copiers, it has been a long standing problem to provide cold pressure fixing apparatus including opposed rollers which are simply constructed and can apply pressure to copy sheets uniformly across the width of the copy sheets as they are respectively fed lengthwise between the rollers.

In the prior art, pressure fixing rollers have been suggested wherein the axis of a pair pf opposed longtitudinally extending rollers have been slightly skewed relative to each other and flexed toward each other longitudinally of their respective lengths in an effort to equalize the pressure exerted by the rollers across the width of a copy sheet fed between them; as a result of which the bearings for the rollers are subjected to stresses tending to reduce their useful life unless elaborate and prohibitively costly bearing mounts are provided. In addition, prior art fixing roller assemblies as shown for example in U.S. Patent No. 4 104 963 issued August 8, 1978 to H.

Fortmann, have included an arrangement of auxiliary pressure applying rollers constructed and arranged to exert pressure on one of the rollers, externally and lengthwise of the same at spaced intervals along its length; as a result of which a significant percentage of the energy transmitted to the rollers, for the purpose of applying pressure to a copy sheet being fed between the rollers, is absorbed by the mass of the roller to which the pressure is applied. Further, in prior art apparatus wherein pressure is applied externally to rollers, cleaning accumulated toner from the rollers is seldom completely satisfactory due to the need to additionally clean the pressure applying means to avoid continuously contaminating the cleaned rollers.

An attempt at a solution to these problems has been disclosed in West German Auslegeschrift publication 26 18 698, published for opposition May 24, 1978, wherein there is disclosed a composite roller including a flexed shaft which longitudinally extends substantially axially of, and is fixedly attached to, the interior of a sleeve by means of annular resilient pads. The pads permit the shaft and sleeve to rotate together while allowing for continuously changing the flexed attitude of the shaft so that it is always bent toward a fixed reference plane. However, with this arrangement, it is believed that a roller will have a short service life due to shaft fatigue.

According to the present invention, there is provided an electrophotocopying machine including a roller assembly comprising: a. a frame b. an elongated lower roller rotatably attached to the frame; c. a shaft; d. a pair of oppositely spaced and aligned bearings; e. an elongated upper roller coaxially aligned with and mounted by means of said bearings on said shaft for rotation of said upper roller about said shaft and in pressure engagement with said lower roller; and f. means movably attached to said frame and said shaft for bending said shaft toward said lower roller, whereby said upper roller is urged by means of said bearings toward said lower roller to change the pressure exerted by said upper roller on said lower roller.

In the drawings, like reference numerals designate like or corresponding parts throughout the several figures: Fig. 1 is a perspective view of one example of a pressure fixing roller assembly for a copying machine according to the invention; Fig. 2 is a partial cross'sectional view, in elevation, of the fixing roller assembly of Fig. 1 taken substantially along the line 2-2 of Fig. 1, showing the details of the apparatus for changing the pressure engagement of the upper roller against the lower roller; and Fig. 3 is a partial view, in elevation, of the fixing roller assembly of Fig. 2, showing an exaggeration for the sake of clarity of the manner in which the shaft, extending through the upper roller, is bent to urge the upper roller into pressure engagement with the lower roller.

Figure 1 illustrates a pressure fixing roller assembly 10 for a copier (not shown) including an elongated frame 1 2 having parallel-spaced vertically extending walls 14 which respectively include a pair of opposed and aligned end supports 1 6 vertically extending therefrom. The walls 1 4 are rigidly joined to each other by means of a horizontally extending cross-piece 1 8; and, as thus joined, the end supports 1 6 of each of the walls 14 are aligned in parallel with a corresponding, adjacently disposed, end support 16 of the other wall 14.

The roller assembly 1 0 (Fig. 1) also includes a pair of opposed and aligned arms 20, each of which comprises an upright channel member having a rear wall 21 and opposed side walls 22.

The upper ends of the respective arms 20 are disposed between the frame side walls 14. In addition, each of the arms 20 is pivotably attached to the adjacently disposed frame end supports 1 6 by means of two pivot pins 24, each of which extends through an associated frame end support 1 6 and arm side wall 22.

The roller assembly 10 (Fig. 2) further includes a pair of axially aligned bearings 26, which are spaced apart from each other and suitably mounted in the frame 12 between the side walls 14; and an elongated lower roller 28, the opposite ends of which are mounted in the bearings 26 to permit rotational movement of the lower roller 28 with respect to the frame 12. Preferably, one end of the lower roller 28 is adapted, as by means of a sprocket gear 30 fixedly attached thereto, for rotation of the roller 28 from a suitable source of supply of motive power including a sprocket chain (not shown).

The roller assembly 10 additionally includes an elongated shaft 32 which longitudinally extends between the rear walls 21 of the respective arms 20. The opposite ends of the shaft 32 are suitably pivotably secured to the adjacent side walls 22 of the arms 20, as by means of pivot pins 34, so as to permit the arms 20 (Fig. 2) to urge and bend the shaft 32 (Fig. 3) toward the lower roller 28 (Fig. 2). To that end, the shaft 32 includes a pair of elongated apertures 35 formed therein to loosely receive the pivot pins 34, and the pivot pins 24 (Fig. 1) are spaced from each other a greater distance than the pivot pins 34.

To pivotably move the arms 2Q (Fig. 2), the assembly 10 includes a pair of elongated compression spring 36; an elongated threaded stud 38, which is centrally fixedly attached to the frame 12 by means of a block 40 secured thereto; and opposed bosses 42, extending toward each other from the opposite rear walls 22 of the respective arms 20. The springs 36 respectively horizontally extend between one of the arms 20 and the block 40, with one of the spring ends mounted over the boss 42 of the associated arm 20 and seated against the arm's rear wall 21. The other end of each of the springs 36 is mounted over one of the ends of the threaded stud 38. As thus arranged, the springs 36 are substantially axially aligned with each other.In addition, the roller assembly 10 includes a pair of nuts 44, each of which is threadably mounted on each of the ends of the stud 38 and is seated against the associated end of a spring 36, so as to permit adjustably fixing the compression of the respective springs 36 against the respective arms 20, by tightening and loosening the nuts 44. As thus arranged the arms 20 may be pivoted away from each other to a greater or lesser extent, for adjustably and fixedly changing the extent to which the shaft 32 is bent toward the lower roller 28.

The roller assembly 10 (Fig. 2) further includes an elongated, cylindrically-shaped, upper roller 46, which longitudinally extends parallel to the lower roller 28; and a pair of oppositely spaced, axially-aligned, bearings 48. The upper roller 46 is coaxially mounted on the shaft 32 by means of the bearings 48, for rotation of the upper roller 46 in pressure engagement with lower roller 28. The respective rollers, 28 and 46, and the shaft 32 axially extend parallel to each other when the shaft 32 is not bent toward the lower roller 28.

And, when the shaft 32 is so bent, the respective upper and lower rollers 28 and 46, still extend parallel to each other, with the shaft 32 slightly bent within the upper roller 46 to urge the bearings 48, downwardly; thereby urging the upper roller 46 into pressure engagement with lower roller 28. Preferably, each of the bearings 48 is equidistantly spaced from the other bearing 48 and the next adjacent end of the upper roller 46, and is equidistantly spaced from a plane which extends through the center of the upper roller 46 and perpendicular to its longitudinally extending axis. Preferably, the bearings 48 are also equidistantly spaced from a plane extending through the center of the shaft 32 and perpendicular to the length thereof.As thus arranged, the resultant force exerted by the shaft 32 on the bearings 48, when the shaft 32 is bent toward the lower roller 28, is divided between the bearings 48 and transmitted therethrough to the upper roller 46. The upper roller 46, in turn, substantially equally distributes the forces, imposed thereon by the bearings 48, lengthwise of the upper roller 46 along the line of engagement between the upper and lower rollers, 46 and 28.

It will be seen that there has been particularly described a pressure fixing roller apparatus for a copier, including a pair of parallel extending rollers and a bendable shaft for changing the pressure engagement between the rollers.

Inasmuch as certain changes may be made in the above described details without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted in an illustrative rather than a limiting sense.

Claims (10)

Claims

1. An electrophotocopying machine including a roller assembly comprising; a. a frame; b. an elongated lower roller rotatably attached to the frame; c. a shaft; d. a pair of oppositely spaced and aligned bearings; e. an elongated upper roller coaxially aligned with and mounted by means of said bearings on said shaft for rotation of said upper roller about said shaft and in pressure engagement with said lower roller; and f. means movably attached to said frame and said shaft for bending said shaft toward said lower roller, whereby said upper roller is urged by means of said bearings toward said lower roller to change the pressure exerted by said upper roller on said lower roller.

2. An electrophotocopying machine including a roller assembly comprising: ~ a. a frame; b. an elongated first roller rotatably attached to the frame; c. a pair of arms pivotably attached one to each end of the frame; d. a shaft extending between said arms and pivotably attached thereto so as to permit said arms to bend said shaft toward said first roller when said arms are pivoted; e. a pair of oppositely spaced and aligned bearings; f. an elongated second roller coaxially aligned with and mounted by means of said bearings on said shaft for rotation of said second roller about said shaft and in pressure engagement with said first roller; and g. means for pivoting said arms, whereby said second roller is urged by means of said bearings toward said first roller to change the pressure exerted by said second roller on said first roller.

3. A machine according to claim 1 or 2, wherein said bearings are equidistantly spaced from a plane extending through the center of, said shaft and perpendicular to the longitudinal axis thereof.

4. A machine according to Claim 1, 2 or 3, wherein said pivoting means includes means for adjustably fixing the pressure exerted by said second roller on said first roller.

5. A machine according to Claim 1 or 2, wherein each of said bearing is equidistantly spaced from the other bearing and the next adjacent end of said second roller.

6. A machine according to Claim 1 or 2, wherein said rollers extend substantially parallel to each other for rotation in engagement along a line extending parallel to the axis of the respective rollers.

7. A machine according to any of Claims 2 to 5, wherein said frame includes a pair of oppositely spaced and aligned supports, said arms being pivotably attached to said supports on a one for one basis, and said pivoting means including spring means for pivoting said arms about said supports.

8. A machine according to Claim 4, wherein said adjustable means includes a pair of compression springs associated with said arms on a one for one basis for urging said arms away from each other, and said adjustable means includes means for adjusting the compression of said springs against said arms for pivoting said arms.

9. A machine according to Claim 1, in which the bending means include arm means pivotably attached to said frame, and also include spring means for pivoting said arm means.

10. An electrophotocopying machine including a roller assembly substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.