Sheet conveying roller and production method therefor

Abstract

The present invention provides a sheet conveying roller, which effectively reduces the amount of paper dust accumulated on its outer peripheral surface to thereby suppress sheet transportation failure. The sheet conveying roller includes a nonporous tubular elastic member (1). The elastic member (1) has a plurality of recesses (6) or a plurality of through-holes (8) equidistantly arranged in a center axis (L1) direction thereof and equidistantly arranged in a circumferential direction thereof, and each having an opening having a round plan shape in an outer peripheral surface (2) thereof, wherein the recesses (6) each have a constant depth as measured thicknesswise of the elastic member (1), wherein the through-holes (8) each extend thicknesswise through the elastic member (1). A production method includes forming the elastic member by vulcanizing a rubber composition in a vulcanization mold having projections corresponding to the recesses or the through-holes.

Claims

1. A method of producing a sheet conveying roller including a nonporous tubular elastic member having a plurality of columnar through-holes extending through the elastic member, the method comprising the steps of: (1) providing a vulcanization mold which includes an outer mold and an inner mold, the outer mold being circumferentially dividable into at least two mold pieces, and having a shape-imparting tubular inner surface having an inner diameter equal to a sum of an outer diameter of the tubular elastic member and a predetermined grinding margin, the inner mold having a shape-imparting tubular outer surface to be located coaxially with the shape-imparting inner surface so as to be spaced a distance equal to a sum of a thickness of the elastic member and the grinding margin from the shape-imparting inner surface, and a plurality of projections projecting radially outward from the shape-imparting outer surface and each having a sectional shape corresponding to a plan shape of the columnar through-holes of the elastic member and a projection height that is not less than the thickness of the elastic member and less than the sum of the thickness of the elastic member and the grinding margin, and forming a nonporous tubular elastic body having a plurality of columnar recesses corresponding to the projections in an inner peripheral surface of the elastic body by preheating the vulcanization mold, locating the shape-imparting inner surface of the outer mold and the shape-imparting outer surface of the inner mold of the vulcanization mold coaxially with each other, filling a space defined between the shape-imparting inner surface and the shape-imparting outer surface with a rubber composition as a material for the elastic member, and vulcanizing the rubber composition; and (2) grinding an outer peripheral portion of the elastic body by the grinding margin to expose the columnar recesses in an outer peripheral surface of the resulting elastic body to form the plurality of through-holes in the elastic member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view showing the appearance of an elastic member which is a major portion of a sheet conveying roller according to one embodiment of the present invention.

(2) FIG. 2 is a sectional view illustrating a part of the elastic member of FIG. 1 taken perpendicularly to a center axis L1 of FIG. 1 on an enlarged scale.

(3) FIG. 3 is a sectional view illustrating a part of a modification of the elastic member taken perpendicularly to the center axis L1 of FIG. 1 on an enlarged scale.

(4) FIGS. 4A to 4H are plan views showing exemplary plan shapes of a through-hole or a recess having an opening in an outer peripheral surface of the elastic member as seen perpendicularly to the outer peripheral surface.

(5) FIG. 5 is a sectional view illustrating an exemplary vulcanization mold to be used for forming an elastic member having a plurality of recesses in an inventive production method.

(6) FIG. 6 is a sectional view illustrating an exemplary vulcanization mold to be used for forming an elastic member having a plurality of through-holes in another inventive production method.

EMBODIMENTS OF THE INVENTION

(7) FIG. 1 is a perspective view showing the appearance of an elastic member which is a major portion of a sheet conveying roller according to one embodiment of the present invention. FIG. 2 is a sectional view illustrating a part of the elastic member taken perpendicularly to a center axis L1 of FIG. 1 on an enlarged scale. FIG. 3 is a sectional view illustrating a part of a modification of the elastic member taken perpendicularly to the center axis L1 of FIG. 1 on an enlarged scale. FIG. 4A is a plan view showing an exemplary plan shape of a through-hole or a recess having an opening in an outer peripheral surface of the elastic member as seen perpendicularly to the outer peripheral surface.

(8) Referring to FIG. 1, the elastic member 1 according to the embodiment has a tubular shape having a constant thickness. The elastic member is a non-porous elastic member made of a natural rubber (NR), a urethane rubber (U), an ethylene propylene diene rubber (EPDM), a polynorbornene rubber, a silicone rubber or a chlorinated polyethylene rubber as in the prior art and containing substantially no air bubble therein.

(9) The elastic member 1 has an outer peripheral surface 2 to be brought into direct contact with a sheet, and an inner peripheral surface 3. The outer peripheral surface 2 and the inner peripheral surface 3 are disposed coaxially with each other about the common center axis L1. Thus, the thickness of the elastic member 1 is constant throughout the entire circumference of the elastic member 1.

(10) A sleeve not shown is fitted in the tubular elastic member 1 with an outer peripheral surface thereof fixed to the inner peripheral surface 3 of the elastic member 1 directly or with an adhesive agent to provide the sheet conveying roller.

(11) Opposite end faces 4, 5 of the elastic member 1 with respect to the center axis L1 are flat surfaces perpendicular to the center axis L1 and parallel to each other. Thus, the outer peripheral surface 2 of the elastic member 1 has a constant width throughout the entire circumference thereof.

(12) Referring to FIGS. 1 to 4(a), the elastic member 1 has a plurality of recesses 6 each having a predetermined depth D as measured along the thickness of the elastic member 1 or a plurality of through-holes 8 each extending from the outer peripheral surface 2 to the inner peripheral surface 3 of the elastic member 1. The recesses 6 or the through-holes 8 each have an opening having a round plan shape in the outer peripheral surface 2 of the elastic member 1 as seen perpendicularly to the outer peripheral surface.

(13) Referring to FIGS. 1, 2 and 4(a), the recesses 6 each have a bottom surface 7 having a round plan shape having the same diameter as the opening as seen perpendicularly to the outer peripheral surface 2. A portion of each of the recesses 6 between the opening and the bottom surface 7 has a round plan shape having the same diameter as the opening and the bottom surface 7 as seen perpendicularly to the outer peripheral surface 2. That is, the recesses each have a small cylindrical shape.

(14) The depth D of each of the recesses 6 measured along the thickness of the elastic member 1 may be set to any value less than the thickness T of the elastic member 1. The depth D is preferably not less than 50% of the thickness T.

(15) If the depth D is less than the aforementioned range, the recesses 6 each have a smaller volume, thereby failing to properly function as pockets for trapping paper dust and dirt for a long period of time.

(16) Where the depth D is within the aforementioned range, on the other hand, the recesses 6 can properly function as the pockets for trapping the paper dust and the dirt for a long period of time.

(17) The upper limit of the depth D may be defined to be less than the thickness T of the elastic member 1. This definition aims to practically discriminate the recesses 6 from the through-holes 8 which each have a depth D equal to the thickness T, and does not mean that the recesses 6 and the through-holes 8 have different functions.

(18) The openings of the recesses 6 in the outer peripheral surface 2 of the elastic member 1 may each have an opening diameter arbitrarily set, but the opening diameter is preferably not less than 0.5 mm and not greater than 5 mm.

(19) If the opening diameter is less than the aforementioned range, the recesses 6 each have a smaller volume, failing to properly function as the pockets for trapping the paper dust and the dirt for a long period of time. If the opening diameter is greater than the aforementioned range, on the other hand, the openings are too large, so that paper dust and dirt once trapped are liable to be released outside the recesses 6. Therefore, the recesses 6 are liable to fail to properly function as the pockets for trapping the paper dust and the dirt for a long period of time.

(20) In contrast, where the opening diameter is within the aforementioned range, the recesses 6 can properly function as the pockets for trapping the paper dust and the dirt for a long period of time.

(21) Referring to FIGS. 1, 3 and 4(a), the through-holes 8 each extend from the outer peripheral surface 2 to the inner peripheral surface 3, and each have an opening having a round plan shape as seen perpendicularly to the outer peripheral surface 2. A portion of each of the through-holes 8 between the outer peripheral surface 2 and the inner peripheral surface 3 has a round plan shape having the same diameter as the openings of the through-holes 8 in the outer and inner peripheral surfaces 2, 3 as seen perpendicularly to the outer peripheral surface 2. That is, the through-holes 8 each have a small cylindrical shape.

(22) The openings of the through-holes 8 in the outer peripheral surface 2 of the elastic member 1 may each have an opening diameter arbitrarily set, but the opening diameter is preferably not less than 0.5 mm and not greater than 5 mm.

(23) If the opening diameter is less than the aforementioned range, the through-holes 8 each have a smaller volume, failing to properly function as the pockets for trapping the paper dust and the dirt for a long period of time. If the opening diameter is greater than the aforementioned range, on the other hand, the openings are too large, so that paper dust and dirt once trapped are liable to be released outside the through-holes 8. Therefore, the through-holes 8 are liable to fail to properly function as the pockets for trapping the paper dust and the dirt for a long period of time.

(24) In contrast, where the opening diameter is within the aforementioned range, the through-holes 8 can properly function as the pockets for trapping the paper dust and the dirt for a long period of time.

(25) In the illustrated examples, only the plurality of recesses 6 or only the plurality of through-holes 8 are provided in the elastic member 1, but the elastic member 1 may include recesses 6 and through-holes 8 in combination.

(26) The plan shape of the opening of each of the recesses 6 or the through-holes 8 is not limited to the round shape. FIGS. 4B to 4H are plan views showing other exemplary plan shapes of the opening of the recess 6 or the through-hole 8.

(27) That is, the openings of the recesses 6 or the through-holes 8 may each have a given shape inscribed inside a circle C indicated by a two-dot-and-dash line in FIGS. 4A to 4H, for example, a rectangular shape as shown in FIG. 4B, a rhombic shape as shown in FIG. 4C, a polygonal shape such as a hexagonal shape as shown in FIG. 4D, an oval shape as shown in FIG. 4E, a V-shape as shown in FIG. 4F, a W-shape as shown in FIG. 4G, or an X-shape as shown in FIG. 4H.

(28) The recesses 6 or the through-holes 8 may each have a plan shape and a size arbitrarily set. In order to facilitate the demolding of a vulcanized elastic member 1 from a vulcanization mold in a production method to be described later and to prevent fracture and cracking of the elastic member 1, the recesses 6 preferably each have the same plan shape in any portion between the opening in the outer peripheral surface 2 and the bottom surface 7. Similarly, the through-holes 8 preferably each have the same plan shape in any portion between the opening in the outer peripheral surface 2 and the opening in the inner peripheral surface 3.

(29) The recesses 6 each having the same plan shape in any portion between the opening in the outer peripheral surface 2 and the bottom surface 7 or the through-holes 8 each having the same plan shape in any portion between the opening in the outer peripheral surface 2 and the opening in the inner peripheral surface 3 may be each tapered in a demolding direction to facilitate the demolding.

(30) FIG. 5 is a sectional view illustrating an exemplary vulcanization mold to be used for forming the elastic member 1 having the plurality of recesses 6 having the openings in the outer peripheral surface 2 in an inventive production method.

(31) Referring to FIGS. 1 and 5, the vulcanization mold 9 includes a pair of outer molds 11 (upper and lower outer molds 11 in FIG. 5) circumferentially separable from each other and respectively having inner surfaces which cooperatively define a shape-imparting tubular inner surface 10 corresponding to the outer peripheral surface 2 of the elastic member 1, and an inner mold 13 having a shape-imparting tubular outer surface 12 to be located coaxially with the shape-imparting inner surface 10 of the outer molds 11 about a center axis L2 so as to be spaced a distance corresponding to the thickness T of the elastic member 1 from the shape-imparting inner surface 10.

(32) The pair of outer molds 11 each have a plurality of projections 14 projecting radially inward from the shape-imparting inner surface 10, and each having a sectional shape corresponding to the plan shape of the recess 6 and a projection height corresponding to the depth D of the recess 6 as measured along the thickness of the elastic member 1.

(33) The projections 14 are arranged on the shape-imparting inner surface 10 according to the arrangement of the recesses 6 to be formed in the elastic member 1.

(34) The outer molds 11 are vertically separable from each other with respect to a separation plane 15 extending through the center axis L2 of the shape-imparting tubular inner surface 10.

(35) In the inventive production method, a rubber composition is first prepared as a material for the elastic member 1. More specifically, at least one of the rubbers previously described, vulcanization-related agents such as a vulcanizing agent, a vulcanization accelerating agent and a vulcanization acceleration assisting agent for vulcanizing the rubber, and additives are blended in a predetermined ratio, and the resulting mixture is kneaded to prepare the rubber composition.

(36) Then, the vulcanization mold 9 is preheated to a predetermined vulcanization temperature, and a space defined between the shape-imparting inner surface 10 of the outer molds 11 and the shape-imparting outer surface 12 of the inner mold 13 of the vulcanization mold 9 disposed coaxially with each other about the center axis L2 is filled with a predetermined amount of the rubber composition.

(37) More specifically, the upper and lower outer molds 11 are opened to be each spaced a greater distance from the inner mold 13 as shown in an upper portion of FIG. 5 and, in this state, the predetermined amount of the rubber composition is supplied into the space. At this time, the rubber composition may be preheated to a predetermined temperature below the vulcanization temperature.

(38) Then, the upper and lower outer molds 11 are closed to be kept in press contact with each other with a predetermined contact pressure as shown in a lower portion of FIG. 5, so that the outer molds 11 abut against each other on the separation plane 15 with the shape-imparting inner surface 10 thereof disposed coaxially with the shape-imparting outer surface 12 of the inner mold 13 about the center axis L2.

(39) In turn, this state is maintained for a predetermined period of time to vulcanize the supplied rubber composition, and then the resulting elastic member 1 is removed by opening the molds. As required, the outer peripheral surface 2 of the elastic member 1 is ground, and the elastic member 1 is finished to have a predetermined width by cutting axially opposite end portions of the elastic member 1.

(40) Then, a sleeve not shown is fitted in the elastic member 1 with an outer peripheral surface thereof fixed to the inner peripheral surface 3 of the elastic member 1 directly or with an adhesive agent. Thus, the sheet conveying roller is produced.

(41) According to this production method, the sheet conveying roller including the elastic member 1 having the plurality of recesses 6 can be efficiently produced at higher productivity.

(42) FIG. 6 is a sectional view illustrating an exemplary vulcanization mold to be used for forming the elastic member 1 having the plurality of through-holes 8 having the openings in the outer peripheral surface 2 in another inventive production method.

(43) Referring to FIGS. 1 and 6, the vulcanization mold 16 includes a pair of outer molds 18 (upper and lower outer molds 18) circumferentially separable from each other and having inner surfaces cooperatively defining a shape-imparting tubular inner surface 17 having an inner diameter equal to a sum of the outer diameter of the elastic member and a predetermined grinding margin, and an inner mold 20 having a shape-imparting tubular outer surface 19 to be located coaxially with the shape-imparting inner surface 17 about a center axis L3 so as to be spaced a distance equal to a sum of the thickness of the elastic member and the grinding margin from the shape-imparting inner surface 17.

(44) The inner mold 20 includes a plurality of projections projecting radially outward from the shape-imparting outer surface 19 and each having a sectional shape corresponding to the plan shape of the through-hole 8 and a projection height P (TPG) that is not less than the thickness T of the elastic member 1 and less than the sum G of the thickness of the elastic member 1 and the grinding margin.

(45) The projections 21 are arranged on the shape-imparting outer surface 19 according to the arrangement of the through-holes 8 to be formed in the elastic member 1.

(46) The outer molds 11 are vertically separable from each other with respect to a separation plane 22 extending through the center axis L3 of the shape-imparting tubular inner surface 17.

(47) In the inventive production method, the vulcanization mold 16 is preheated to a predetermined vulcanization temperature, and a space defined between the shape-imparting inner surface 17 of the outer molds 18 and the shape-imparting outer surface 19 of the inner mold 20 of the vulcanization mold 16 disposed coaxially with each other about the center axis L3 is filled with a predetermined amount of the rubber composition.

(48) More specifically, the upper and lower outer molds 18 are opened to be each spaced a greater distance from the inner mold 13 as shown in an upper portion of FIG. 6 and, in this state, the predetermined amount of the rubber composition is supplied into the space. At this time, the rubber composition may be preheated to a predetermined temperature below the vulcanization temperature.

(49) Then, the upper and lower outer molds 18 are closed to be kept in press contact with each other with a predetermined contact pressure as shown in a lower portion of FIG. 6, so that the outer molds 18 abut against each other on the separation plane 22 with the shape-imparting inner surface 17 thereof disposed coaxially with the shape-imparting outer surface 19 of the inner mold 20 about the center axis L3.

(50) In turn, this state is maintained for a predetermined period of time to vulcanize the supplied rubber composition, and then the resulting elastic body is removed by opening the molds.

(51) In this state, a rubber layer having a thickness corresponding to the grinding margin is present in an outer peripheral portion of the elastic body, so that the recesses formed as corresponding to the projections 21 are not open in the outer peripheral surface 2. Therefore, the outer peripheral portion is ground by the grinding margin, whereby the recesses are open in the outer peripheral surface 2 to form the through-holes 8.

(52) Then, the resulting elastic member 1 is finished to have a predetermined width by cutting axially opposite end portions of the elastic member 1. Then, a sleeve not shown is fitted in the elastic member 1 with an outer peripheral surface thereof fixed to the inner peripheral surface 3 of the elastic member 1 directly or with an adhesive agent. Thus, the sheet conveying roller is produced.

(53) According to this production method, the sheet conveying roller including the elastic member 1 having the plurality of through-holes 8 can be efficiently produced at higher productivity.

(54) The present invention is not limited to the embodiments described above with reference to the drawings.

(55) For example, the recesses 6 or the through-holes 8 are merely required to be equidistantly arranged in the center axis L1 direction of the elastic member 1 and equidistantly arranged in the circumferential direction of the elastic member 1, but the arrangement of the recesses 6 or the through-holes 8 is not limited to that shown in FIG. 1.

(56) Further, all the openings of the recesses 6 or the through-holes 8 are not required to have the same round shape as shown in FIG. 1, but openings of the recesses 6 or the through-holes 8 having two or more different plan shapes may be present in combination in the outer peripheral surface 2. In this case, the openings of the recesses 6 or the through-holes 8 having different plan shapes preferably have the same opening area in order to ensure that the recesses 6 or the through-holes 8 can efficiently and evenly function as the pockets for trapping the paper dust and the dirt on the entire outer peripheral surface 2.

(57) It should be understood that various modifications may be made without departing from the scope of the present invention.

Examples

(58) An elastic member 1 having a three-dimensional shape as shown in FIG. 1, an outer diameter of 24.6 mm and a width of 28.5 mm as measured in a center axis L1 direction thereof and including a plurality of through-holes 8 each having a round plan shape as seen perpendicularly to the outer peripheral surface 2 and arranged in an arrangement as shown in FIG. 1 was produced by the vulcanization utilizing the mold 16 shown in FIG. 6, the grinding of the grinding margin for the exposure of the through-holes 8, and the cutting of the opposite end portions thereof. A mold temperature of 160 C. to 170 C. and a vulcanization period of 20 minutes were employed for vulcanization conditions.

(59) Such elastic members 1 were produced with the outer diameter, the number and the interval of the projections 21 for the through-holes 8 changed to change the opening diameter and the number of the through-holes 8 aligned in each line extending in the center axis L1 direction (in a line containing through-holes greater in number by one) as shown below in Table 1. The number of the through-holes 8 aligned in each line was set so that the product (N) of the opening diameter and the number N was substantially constant as shown below in Table 1.

(60) A sleeve not shown was fitted in each of the elastic members 1 with an outer peripheral surface thereof fixed to the inner peripheral surface 3 of the elastic member 1 with an adhesive agent. Thus, sheet conveying rollers were produced, which were compatible with a laser printer HP LaserJet (registered trade name) P4515n available from Japan Hewlett Packard Company.

(61) For comparison, an elastic member having the same dimensions as the elastic members 1 but having no through-holes was formed, and a sheet conveying roller was produced by using the elastic member thus formed.

(62) The sheet conveying rollers thus produced were each brought into press contact with a paper sheet (Xerox Business 4200 available from Xerox Corporation and having a width of 60 mm and a length of 210 mm) placed on a TEFLON (registered trade name) plate with a vertical load of 340 gf and, in this state, a transportation force F acting on the paper sheet was measured by means of a load cell while the sheet conveying roller was rotated at a circumferential speed of 105 mm/sec. Then, a friction coefficient was determined from the following expression (4):
=F/340(4)

(63) Measurement was performed immediately after the production of each of the sheet conveying rollers (initial measurement) and after 10000 paper sheets (available under the trade name of SILVER STAR from Silver Star Paper Corporation in China) were passed over each of the sheet conveying rollers incorporated as a sheet feed roller in the laser printer (post-endurance measurement).

(64) The results are shown in Table 1.

(65) TABLE-US-00001 TABLE 1 Through-holes 8 Opening Number N of Friction coefficient diameter through-holes Initial Post-endurance (mm) in each line N measurement measurement 0.4 42 16.8 2.05 1.0 0.5 34 17 2.0 1.7 1 17 17 1.9 1.6 5 3 15 1.9 1.7 6 2 12 1.7 0.9 7 2 14 1.7 1.0 No through-holes 2.05 0.9

(66) Table 1 indicates that the opening diameter of the through-holes 8 as measured on the outer peripheral surface 2 of the elastic member 1 is preferably not less than 0.5 mm and not greater than 5 mm in order to permit the through-holes 8 to properly function as pockets for trapping paper dust and dirt.

(67) Further, it was found that, where the through-holes 8 are provided equidistantly in the center axis L1 direction of the outer peripheral surface 2, the through-holes 8 occupy an area of 50% to 60% of the outer peripheral surface 2 as measured in the center axis L1 direction.

(68) This application corresponds to Japanese Patent Application No. 2012-031793 filed in the Japan Patent Office on Feb. 16, 2012, the disclosure of which is incorporated herein by reference in its entirety.

DESCRIPTION OF REFERENCE CHARACTERS

(69) 1 ELASTIC MEMBER 2 OUTER PERIPHERAL SURFACE 3 INNER PERIPHERAL SURFACE 4,5 END FACES 6 RECESSES 7 BOTTOM SURFACES 8 THROUGH-HOLES 9 VULCANIZATION MOLD 10 SHAPE-IMPARTING INNER SURFACE 11 OUTER MOLDS 12 SHAPE-IMPARTING OUTER SURFACE 13 INNER MOLD 14 PROJECTIONS 15 SEPARATION PLANE 16 VULCANIZATION MOLD 17 SHAPE-IMPARTING INNER SURFACE 18 OUTER MOLDS 19 SHAPE-IMPARTING OUTER SURFACE 20 INNER MOLD 21 PROJECTIONS 22 SEPARATION PLANE