Elastic roller for paper feeding

Abstract: An elastic roller (10) for paper feeding of an existing rubber compound has an outer circumferential surface divided into plural sections (11) to make a surface layer of the outer circumferential surface of the elastic roller (10) easily deformable, which increases frictional force on paper being conveyed, thereby obtaining a greater conveying force.

Description: The present invention relates to an elastic roller according to the preamble of claim 1 and the preamble of claim 2. for paper feeding in a paper feeder of copier, printer of information processing apparatus or the like. Such an elastic roller is known from EP-A-0 281 498. Generally, in the paper feeder for copier, printer of information processing apparatus or the like, an elastic roller is used for paper feeding. Such elastic roller is required to have a large conveying force in order to attain a reliable paper feeding. In particular, a greater conveying force is required when feeding film for overhead projector (OHP). Hitherto, attempts to provide the elastic roller with a great conveying force have been centered upon study for the rubber compound from which the elastic roller is made and which demonstrates a higher coefficient of friction by, for example, blending the materials for the elastic roller to be low in hardness or large in tackiness by impregnating much oil or the like. Incidentally, when considering the material blending for the elastic roller in order to obtain a large conveying force in the elastic roller, the optimum dosing must be calculated taking various blending agents or ingredients into account so as to satisfy many properties such as processability and storage stability, in addition to obtaining a high coefficient of friction. But such job requires much time, labor and material cost. Accordingly, in order to have a large conveying force with an existing rubber compound, an elastic roller with a ground surface (hereinafter called surface ground roller) has been in use. Although the surface ground roller obtains a large conveying force by increasing the frictional force against paper being conveyed by grinding and roughening the surface, the manufacturing cost is greatly raised for the addition of the process of surface grinding. Moreover, the surface ground pattern is worn as the paper feeding is repeated, and the conveying force is lowered as the wearing progresses, deteriorating paper feeding condition in a short period. Thus, the surface roughness of the surface ground roller is usually about 30 to 100µ, and accordingly the surface wearing of only 0.2 mm makes the surface smooth and slick, where paper cannot be fed satisfactorily. Besides, the surface ground roller is specified in the direction of frictional force since the surface ground roller has on its surface directional markings caused by abrasive in the process of surface grinding. In the case where two or more surface ground rollers are used mounted on one and the same shaft, attention should therefore be paid so that they are all in the same direction otherwise satisfactory paper feeding cannot be performed; e.g. paper can run obliquely to result in paper feeding failure. Fig. 10 shows the result of experiment conducted to prove the orientation of frictional force of the surface ground roller. In this experiment, by installing the surface ground roller in correct direction (normal grain use) and in wrong direction (reverse grain use), the coefficient of friction with respect to the surface roughness was measured The conditions of the experiment were 200g in load, 250 mm/s in roller peripheral speed, 23°C in temperature, and 55% in humidity. As a result, it is known that the coefficient of friction is greater in the normal grain use than in the reverse grain use. It is hence evident that the surface ground roller is specified in direction. EP-A-0281498 and US-A-4869410 each disclose an elastic roller for feeding paper by use of frictional force. An outer circumferential surface of the roller is divided into a plurality of sections. In this way a surface layer part of each of these sections may easily be deformed. The invention has been devised in the light of the foregoing, and it is a primary object thereof to provide an elastic roller for paper feeding capable of exhibiting a large conveying force, using an existing rubber compound. The present inventors, as a result of intensive studies to achieve the above object, have found the elastic roller for paper feeding capable of exhibiting a great conveying force using an existing rubber compound. The inventors prepared rubber rollers of the width of 40 mm, 30 mm, 20 mm and 10 mm each for the outside diameters of 38⊘, 34⊘, 31⊘, 27⊘, 24⊘, and measured the coefficient of friction µ in the conditions of load of 100 to 400g and roller peripheral speed of 100 to 500 mm/s. The results obtained are as shown in Table 1 as for the outside diameters of 38⊘, 31⊘, 24⊘ at the load of 100g and roller peripheral speed of 100 mm/s, and as shown in Table 2 as for the outside diameters of 38⊘, 31⊘, 24⊘ at the load of 400g and roller peripheral speed of 500 mm/s. Outside diameter 38 38 38 38 31 31 31 31 24 24 24 24 Width 40 30 20 10 40 30 20 10 40 30 20 10 Coefficient of friction µ 2.9 2.9 3.0 2.9 2.9 2.8 2.9 2.7 2.7 2.9 2.9 2.7 Outside diameter 38 38 38 38 31 31 31 31 24 24 24 24 Width 40 30 20 10 40 30 20 10 40 30 20 10 Coefficient of friction µ 2.4 2.4 2.2 2.1 2.5 2.4 2.0 2.4 2.0 2.2 2.9 2.8 It is known from these results that, provided the load and the roller peripheral speed be constant, the friction of coefficient µ is nearly unchanged, almost regardless of the width and outside diameter. However, summing up in terms of the load per width, as shown in Table 3 (which shows the result of measurement at the load of 100 mg per 10 mm of width, and roller peripheral speed of 500 m/s), it is known that the coefficient of friction µ is higher in a narrower rubber roller. Width (mm) 40 30 20 10 Load (g) 400 300 200 100 Load per width (g/mm) 10 10 10 10 Coefficient of friction µ of outside diameter 38⊘ 2.4 2.6 2.8 3.2 Coefficient of friction µ of outside diameter 34⊘ 2.5 2.7 2.8 3.3 Coefficient of friction µ of outside diameter 31⊘ 2.4 2.5 2.7 3.1 Coefficient of friction µ of outside diameter 27⊘ 2.4 2.6 2.8 3.0 Coefficient of friction µ of outside diameter 24⊘ 2.3 2.4 2.7 3.0 Therefore, as the elastic roller for paper feeding in which a large conveying force is required, it is preferable to have a plurality of narrow rubber rollers instead of one broad roller. The reason for the increase in frictional force is considered to be such that the surface layer portion of the rubber roller is easily, elastically deformable when the rubber roller width is narrower than when broader, so that the frictional resistance to paper increases. According to one aspect of the present invention, there is provided an elastic roller for paper feeding making use of frictional force, wherein an outer circumferential surface of said roller is divided into plural sections, so that a surface layer part of each of said sections may be easily deformed, characterised in that multiple microveins with a pitch not greater than 1 mm and front end width not greater than 0.5 mm are formed on an outer circumferential surface of said roller, orthogonally to the direction in which paper is conveyed. In this elastic roller, the surface roughness of the outer circumferential surface thereof becomes coarser due to the microveins, and the frictional resistance to paper increases, so that a greater conveying force may be obtained. According to another aspect of the present invention, there is provided an elastic roller for paper feeding by making use of frictional force, wherein an outer circumferential surface of said roller is divided into plural sections, so that a surface layer part of each of said sections may be easily deformed, characterised in that annular cuts are formed at a predetermined pitch in an outer circumferential surface of said roller. In this elastic roller, the surface layer portion of each narrow elastic roller is easily deformable owing to the annular cuts, which, in combination with the deformability of edge portions of each narrow elastic roller, further increase the frictional resistance to paper to obtain a greater conveying force. Thus, according to the invention, an elastic roller for paper feeding capable of exhibiting a great conveying force is provided, using an existing rubber compound, and as compared with the conventional method of considering the material blending, the time, labor and material cost may be greatly saved. Besides, unlike the surface ground roller, the frictional force is not specified in direction, and there is no difference in the conveying force depending on the rotating direction. Consequently, a plurality of elastic rollers, if mounted at random with regard to rotational direction, may be utilized concurrently without attendance of any troubles such as those encountered by the surface ground roller. Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings of which:- Fig. 1 is a front view of an elastic roller for paper feeding in a first embodiment of the invention; Fig. 2 is an explanatory drawing showing an example of an elastic roller used in an experiment for explaining that the elastic roller of the first embodiment can exhibit a great conveying force; Fig. 3 and Fig. 4 are respectively, a front view and a side view of elastic roller for paper feeding in a second embodiment of the invention; Fig. 5 is a diagram showing the result of an experiment for explaining that the illustrated elastic roller in the second embodiment can exhibit a great conveying force; Fig. 6 is an explanatory drawing showing an example of vein shape and dimension of the elastic roller used in the same experiment; and Fig. 7 is a diagram showing the result of an experiment for explaining that the frictional force of the surface ground roller is specific in direction. The elastic rollers for paper feeding in the first embodiment of the invention will now be explained with reference to Fig. 1. The elastic roller 20 shown in Fig. 1 has a plurality of, for example, seven annular cuts 22 formed at a predetermined pitch in the outer circumference of a broad roller 21. In the elastic roller 20 of the first embodiment, the surface of the roller 21 is easily deformable owing to the presence of the cuts 23 and the contact area with the paper increases, so that a larger conveying force is obtained. Table 4 shows the measurement result of the experiment conducted for proving that the elastic roller of the first embodiment can exhibit a great conveying force. That is, in the experiment, rubber rollers of 38⊘ outside diamter, 20⊘ inside diameter and 40 mm width were processed as shown in Fig. 2 A to E to obtain the elastic rollers No. 1 to No. 5 for the first embodiment, while the elastic roller No. 6 was not processed, and the coefficient of friction µ for plain paper and OHP film was measured. The experimental conditions were as follows: load of 400g, roller peripheral speed of 100 mm/s, temperature of 23°C and humidity of 55%. Numerals appearing in Fig. 2 indicate the dimensions in the unit of mm. Coefficient of friction (µ) Roller effective width (mm) Plain paper OHP film Elastic roller No. 1 1.98 2.15 40 Elastic roller No. 2 2.05 2.18 40 Elastic roller No. 3 1.93 2.18 40 Elastic roller No. 4 2.03 2.23 40 Elastic roller No. 5 2.03 2.23 40 Elastic roller No. 6 1.85 2.05 40 It is known from the result of experiment that the elastic rollers No. 1 to No. 5 of the first embodiment of the invention are higher in the coefficient of friction µ as compared with the unprocessed elastic roller No. 6. It is hence evident that the elastic roller 20 of the first embodiment of the invention bring about a great conveying force. An elastic roller for paper feeding of the second embodiment of the invention will now be explained with reference to Figs. 3 and 4. In this elastic roller 40, ridges or veins 41a having a triangular cross-section are formed on the outer circumference of the broad roller 41, the pitch between the adjoining veins 41a being 1 mm or less. In the elastic roller of the second embodiment, since the veins 41a are formed on the outer circumference at a pitch of 1 mm or less, the surface roughness on the outer circumference of the roller 41 is coarse same as on the surface ground roller, and the frictional resistance with the paper increases, so that a great conveying force is brought about. The veins 41a are shown as having a triangular cross-section, but this is not limitative in the invention, and the cross-sectional shape may be other than triangular as far as the pitch of the veins 41a is not greater than 1 mm and the top end width is not greater than 0.5 mm. Fig. 5 shows the result of experiment for three elastic rollers having the shape, dimension (unit: mm), pitch, top end width and height of veins as shown in Fig. 6A to C, and for the surface ground roller as a comparative one, in the conditions of load of 100g and roller peripheral speed of 500 mm/s. However, it should be appreciated that the veins of the triangular cross-section shown in Fig. 6A is pointed at the top, and has not top end width as such. It is known from the experiment that the conveying force becomes smaller when the vein pitch exceeds 1 mm, and that the conveying force after long-term use is lowered when the top end width exceeds 0.5 mm. Therefore, the veins may preferably have a pitch not greater than 1 mm and a top end edge not greater than 0.5 mm, and when these conditions are satisfied, the surface does not become slick, with less lowering of conveying force if the wear is promoted, unlike the surface ground roller.

Claims: An elastic roller (40) for paper feeding making use of frictional force, wherein an outer circumferential surface (41) of said roller (40) is divided into plural sections, so that a surface layer part of each of said sections may be easily deformed, characterised in that multiple microveins (41a) with a pitch not greater than 1 mm and front end width not greater than 0.5 mm are formed on an outer circumferential surface (41) of said roller (40), orthogonally to the direction in which paper is conveyed. An elastic roller (40) for paper feeding by making use of frictional force, wherein an outer circumferential surface (41) of said roller (40) is divided into plural sections, so that a surface layer part of each of said sections may be easily deformed, characterised in that annular cuts (22) are formed at a predetermined pitch in an outer circumferential surface of said roller (40).

Inventors: ITANI HITOSHI, ITO YASUTOKI, TANAKA HIROAKI, UENO MASAHIKO, ITANI, HITOSHI, ITO, YASUTOKI, TANAKA, HIROAKI, UENO, MASAHIKO
Applicants: SUMITOMO RUBBER IND, SUMITOMO GOMU KOGYO KABUSHIKI KAISHA
Application year: 1991
Main classification: B65H20
IPC codes: B65H20, B65H27