U.S. patent application number 11/248238 was filed with the patent office on 2006-04-20 for sheet feed roll.
This patent application is currently assigned to HOKUSHIN CORPORATION. Invention is credited to Shuhei Noda.
Application Number | 20060082052 11/248238 |
Document ID | / |
Family ID | 36179924 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060082052 |
Kind Code |
A1 |
Noda; Shuhei |
April 20, 2006 |
Sheet feed roll
Abstract
A sheet feed roll having a concavity and a convexity formed on
an outer peripheral surface thereof, an irregular portion composed
of the concavity and the convexity being of a corrugated
cross-sectional shape, and the concavity extending along the axial
direction of the roll.
Inventors: |
Noda; Shuhei; (Yokohama-shi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
HOKUSHIN CORPORATION
|
Family ID: |
36179924 |
Appl. No.: |
11/248238 |
Filed: |
October 13, 2005 |
Current U.S.
Class: |
271/314 |
Current CPC
Class: |
B65H 2701/1912 20130101;
B65H 27/00 20130101; B65H 3/0638 20130101 |
Class at
Publication: |
271/314 |
International
Class: |
B65H 29/20 20060101
B65H029/20 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2004 |
JP |
2004-302549 |
Sep 26, 2005 |
JP |
2005-277834 |
Claims
1. A sheet feed roll having a concavity and a convexity formed on
an outer peripheral surface thereof, an irregular portion composed
of said concavity and said convexity being of a corrugated
cross-sectional shape, and said concavity extending along an axial
direction of said roll.
2. The sheet feed roll according to claim 1, wherein a width of
said concavity is 500 .mu.m or less.
3. The sheet feed roll according to claim 1, wherein a width of
said convexity is 500 .mu.m or less.
4. The sheet feed roll according to claim 1, wherein a width of
said concavity is 500 .mu.m or less, and a width of said convexity
is 500 .mu.m or less.
5. The sheet feed roll according to claim 1, wherein when the outer
peripheral surface of said roll is partitioned by a lattice of
cells 1 mm square each, one or more of said convexities and one or
more of said concavities are present in each of said cells.
6. The sheet feed roll according to claim 1, wherein a height of
said convexity is 50 to 150 .mu.m.
7. The sheet feed roll according to claim 1, comprising
polyurethane having a hardness of 25 to 50.degree. (JIS A), and
rebound resilience of 50 to 80%.
8. The sheet feed roll according to claim 1, having Rz of 40 to 120
.mu.m.
9. The sheet feed roll according to claim 1, wherein a length in
the axial direction of said concavity is two times or more a length
in a circumferential direction of said concavity.
10. The sheet feed roll according to claim 1, wherein a length in
the axial direction of said convexity is two times or more a length
in a circumferential direction of said convexity.
11. The sheet feed roll according to claim 1, wherein outer
peripheral corners in opposite end portions in a longitudinal
direction of said sheet feed roll have C-surfaces or
R-surfaces.
12. A sheet feed roll comprising polyurethane having a hardness of
25 to 50.degree. (JIS A), and rebound resilience of 50 to 80%, and
said sheet feed roll having a concavity and a convexity formed on
an outer peripheral surface thereof, an irregular portion composed
of said concavity and said convexity being of a corrugated
cross-sectional shape, and wherein said concavity extends along an
axial direction of said roll, a width of said concavity is 500
.mu.m or less, a width of said convexity is 500 .mu.m or less, a
height of said convexity is 50 to 150 .mu.m, and Rz of said sheet
feed roll is 40 to 120 .mu.m.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to various sheet feed rolls for use
in sheet feeding apparatuses of various types of office automation
equipment, including various printers, such as ink jet printers (to
be hereinafter referred to as IJP), copiers and facsimile machines
(FAX), and automated teller machines (ATM).
[0003] 2. Description of the Related Art
[0004] Rolls, which comprise a resin core or a metal shaft and EPDM
(ethylene-propylene-diene rubber), chlorinated polyethylene rubber,
silicone rubber, polyurethane rubber, etc., have so far been used
as sheet feed rolls of IJP, FAX and ATM. Some of these rolls have a
grain patter, a polished pattern or the like on their outer
peripheral surfaces (Japanese Patent Application Laid-Open (kokai)
Nos. 8-108591, 5-221059, and 10-071655).
[0005] With the above-mentioned rolls, however, the problems remain
unsolved that they have inadequate sheet feed performance, they are
susceptible to a load and a sheet feed speed, and their sheet feed
performance is unstable. Thus, further improvements are required of
them.
SUMMARY OF THE INVENTION
[0006] The present invention has been accomplished in the light of
the above-mentioned circumstances. It is an object of the present
invention to provide a sheet feed roll which has higher sheet feed
performance and can perform stable sheet feed.
[0007] A first aspect of the present invention for attaining the
above object is a sheet feed roll having a concavity and a
convexity formed on an outer peripheral surface thereof, an
irregular portion composed of the concavity and the convexity being
of a corrugated cross-sectional shape, and the concavity extending
along an axial direction of the roll.
[0008] A second aspect of the present invention is the sheet feed
roll according to the first aspect, characterized in that a width
of the concavity is 500 .mu.m or less.
[0009] A third aspect of the present invention is the sheet
feed-roll according to the first aspect, characterized in that a
width of the convexity is 500 .mu.m or less.
[0010] A fourth aspect of the present invention is the sheet feed
roll according to the first aspect, characterized in that a width
of the concavity is 500 .mu.m or less, and a width of the convexity
is 500 .mu.m or less.
[0011] A fifth aspect of the present invention is the sheet feed
roll according to any one of the first to fourth aspects,
characterized in that when the outer peripheral surface of the roll
is partitioned by a lattice of cells 1 mm square each, one or more
of the convexities and one or more of the concavities are present
in each of the cells.
[0012] A sixth aspect of the present invention is the sheet feed
roll according to any one of the first to fifth aspects,
characterized in that a height of the convexity is 50 to 150
.mu.m.
[0013] A seventh aspect of the present invention is the sheet feed
roll according to any one of the first to sixth aspects, comprising
polyurethane having a hardness of 25 to 50.degree. (JIS A), and
rebound resilience of 50 to 80%.
[0014] An eighth aspect of the present invention is the sheet feed
roll according to any one of the first to seventh aspects, having
Rz of 40 to 120 .mu.m.
[0015] A ninth aspect of the present invention is the sheet feed
roll according to any one of the first to eighth aspects,
characterized in that a length in the axial direction of the
concavity is two times or more a length in a circumferential
direction of the concavity.
[0016] A tenth aspect of the present invention is the sheet feed
roll according to any one of the first to ninth aspects,
characterized in that a length in the axial direction of the
convexity is two times or more a length in a circumferential
direction of the convexity.
[0017] An eleventh aspect of the present invention is the sheet
feed roll according to any one of the first to tenth aspects,
characterized in that outer peripheral corners in opposite end
portions in a longitudinal direction of the sheet feed roll have
C-surfaces or R-surfaces.
[0018] A twelfth aspect of the present invention is a sheet feed
roll comprising polyurethane having a hardness of 25 to 50.degree.
(JIS A), and rebound resilience of 50 to 80%, and the sheet feed
roll having a concavity and a convexity formed on an outer
peripheral surface thereof, an irregular portion composed of the
concavity and the convexity being of a corrugated cross-sectional
shape, and characterized in that the concavity extends along an
axial direction of the roll, a width of the concavity is 500 .mu.m
or less, a width of the convexity is 500 .mu.m or less, a height of
the convexity is 50 to 150 .mu.m, and Rz of the sheet feed roll is
40 to 120 .mu.m.
[0019] As described above, a sheet feed roll has a concavity and a
convexity formed on an outer peripheral surface thereof, an
irregular portion composed of the concavity and the convexity being
of a corrugated cross-sectional shape, and the concavity extending
along the axial direction of the roll. Since this sheet feed roll
has high sheet feed performance and can perform stable sheet feed,
it can be preferably used as a separating roll, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a more complete understanding of the present invention
and the advantages thereof, reference is now made to the following
descriptions in conjunction with the accompanying drawings.
[0021] FIG. 1 is a schematic perspective view representing an image
of the sheet feed roll of the present invention.
[0022] FIG. 2 is a schematic view showing a state in which a
plurality of concavities are provided on the outer peripheral
surface of the sheet feed roll of the present invention.
[0023] FIGS. 3A and 3B are enlarged views of a cross section of the
sheet feed roll of the present invention.
[0024] FIGS. 4A and 4B are side views of the sheet feed roll
according to an embodiment of the present invention.
[0025] FIG. 5 is a view showing the results of observation of the
outer peripheral surface of a separating roll in Test Example
2.
[0026] FIG. 6 is a view showing the method of Test Example 3.
[0027] FIG. 7 is a view showing the method of Test Example 4.
[0028] FIG. 8 is a view showing the results of observation of end
portions of a separating roll in Test Example 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention will now be described in detail based
on the embodiments offered below with reference to the accompanying
drawings.
[0030] FIG. 1 is a schematic perspective view representing an image
of a sheet feed roll according to the present invention. As shown
in FIG. 1, a sheet feed roll 1 has an elastic layer 3, comprising
polyurethane or the like, provided on a shaft 2. The sheet feed
roll of the present invention has an irregular portion, whose
section is in a corrugated form, formed on the outer peripheral
surface of the elastic layer 3. A concavity constituting the
irregular portion extends in the axial direction of the roll. That
is, the concavity is formed from a slot extending along the axial
direction of the roll. The term "axial direction" is taken to
include a direction at an angle of 45 degrees or less with respect
to the axis of the roll. A plurality of the concavities or the
single concavity may be provide in the circumferential direction or
the axial direction. An example of a case where a plurality of the
concavities are provided on the outer peripheral surface of the
roll is schematically expressed as an enlarged view of the outer
peripheral surface in FIG. 2. The shaded parts in FIG. 2 represent
the concavities. The sizes of the respective concavities and
convexities may be the same (FIG. 3A) or different (FIG. 3B), as
shown in FIGS. 3A, 3B which are enlarged sectional views taken in
the circumferential direction of the roll. The irregular portion of
the sheet feed roll according to the present invention is of a
corrugated cross-section which is smooth without corners. This
irregular portion does not have a grain pattern with steps as shown
in FIG. 1(a) of Japanese Patent Application Laid-Open (kokai) No.
8-108591.
[0031] The widths of the concavities are preferably 500 .mu.m or
less. If the widths of the concavities are larger than 500 .mu.m,
the distance over which the sheet is fed becomes short, resulting
in a tendency toward poor sheet feed performance. The width of the
concavity refers to the spacing between intermediate sites located
in a zone ranging from the tops of the adjacent convexities to the
bottom of the concavity formed between the convexities, as shown in
FIGS. 3A, 3B; namely, the width of the concavity refers to a width
based on a central plane which is defined by the average of the
heights of the irregularities shown in FIGS. 3A, 3B. The widths of
the concavities, and the widths and heights of the convexities (to
be described later) can be measured, for example, by an ordinary
surface roughness measuring machine (Surfcorder SE3500: Kosaka
Laboratory Ltd.).
[0032] The widths of the convexities are preferably 500 .mu.m or
less. In this case, the concavities constituting the irregular
portion are constituted by a plurality of slots arranged with
spacing. If the widths of the convexities are larger than 500
.mu.m, influences from load, the speed of sheet feed, and the type
of the sheet are easily exerted, or the distance of feed is short,
leading to a tendency toward poor sheet feed performance. The width
of the convexity refers to the spacing between intermediate sites
located in a zone ranging from the bottoms of the adjacent
concavities to the top of the convexity formed between the
concavities, as shown in FIGS. 3A, 3B; namely, the width of the
convexity refers to a width based on the central plane which is
defined by the average of the heights of the irregularities shown
in FIGS. 3A, 3B.
[0033] When the outer peripheral surface of the roll is partitioned
by a lattice of cells 1 mm square each, it is preferred that one or
more of the convexities and one or more of the concavities be
present in each of the cells throughout the outer peripheral
surface of the roll. However, the roll may be such that there are
none of the concavities and convexities in a part of the roll, for
example, at the end of the roll, or there are the concavities and
convexities partly on the roll.
[0034] The heights of the convexities are preferably 50 to 150
.mu.m. If paper dust or the like fills in the concavities, sheet
feed performance worsens. If the heights of the convexities are set
at 50 to 150 .mu.m, it becomes possible to trap paper dust or the
like in the relevant concavities. Upon repeated passage of sheets,
therefore, sheet feed performance is not deteriorated, and sheet
feed performance is stabilized. The height of the convexity refers
to the dimension from the bottom of the concavity to the top of the
convexity.
[0035] The concavity and the convexity each preferably have a
length in the axial direction which is two times or more the length
thereof in the circumferential direction. If the length in the
axial direction of the concavity is smaller than two times the
length in the circumferential direction of the concavity, the
effect of trapping paper dust declines. If the length in the axial
direction of the convexity is smaller than two times the length in
the circumferential direction of the convexity, the area of contact
between the sheet and the roll becomes too small, thus
deteriorating sheet feed characteristics.
[0036] The sheet feed roll of the present invention preferably has
a hardness of 25 to 50.degree. according to JIS A. Its rebound
resilience is preferably 50 to 80%. Deviations from these ranges
would render the sheet feed roll susceptible to a load, a sheet
feed speed, and the type of the sheet, or result in a short
distance fed, thus tending to deteriorate sheet feed
performance.
[0037] The ten-point mean roughness (surface roughness) Rz is
preferably 40 to 120 .mu.m, more preferably 50 to 80 .mu.m. If the
surface roughness is too low, the paper dust trapping effect is not
obtained. Too high surface roughness results in unstable sheet feed
characteristics. The ten-point mean roughness Rz is specified by
JIS B0601-1994. The ten-point mean roughness Rz is the sum of the
mean height of the five highest profile peaks and the mean depth of
the five deepest profile valleys measured from the mean line over a
sampling length of a roughness profile curve, the height and the
depth being measured along the direction perpendicular to the mean
line. Rz may be determined by means of a microscope for measurement
of surface profile or a similar instrument.
[0038] The material for the elastic layer 3 is not limited, and the
elastic layer 3 can be subjected to forming, for example, using
EPDM, silicone, chloroprene, NBR, or polyurethane. However, it is
preferred to use polyurethane, in particular. Since polyurethane is
particularly excellent in wear resistance, the wear of the
convexities in their height direction is suppressed, so that the
paper dust trapping effect can be maintained for a long period of
time.
[0039] The irregular surface of the sheet feed roll of the present
invention can be formed, for example, by forming using a mold. The
method of creating a grained surface, which constitutes the
irregular surface, is not limited. However, a predetermined
irregular surface can be formed conveniently and at a low cost by
machining, such as sand blasting or shot blasting, and other
chemical treatment methods, such as corrosion treatment.
[0040] An example of the method for forming the above-mentioned
irregular surface in the mold comprises cutting a steel stock
having a hardness of 38 (HRC) or higher to obtain a mold, masking
the mold into a desired pattern, and then blasting the mold with a
predetermined medium. In this case, a square-cornered medium (sand)
which has a particle size of 50 to 300 .mu.m and has variations of
.+-.10% from the reference particle size, is preferably used in
blasting. It is preferred to apply a hard chromium plating to the
surface blasted in this manner.
[0041] Using the mold with the irregular surface formed in the
above-described manner, the sheet feed roll of the present
invention can be produced by the same method as the method of
producing an ordinary roll.
[0042] Also preferably, outer peripheral corners in opposite end
portions in the longitudinal direction of the sheet feed roll of
the present invention have a C-surface or an R-surface; that is,
the outer peripheral end portions are thin-layered. By so forming
C-surfaces or R-surfaces in the outer peripheral end portions,
excellent wear resistance is imparted to the sheet feed roll, and
wear (chipping) at the end portions of the sheet feed roll can be
prevented upon long-term use. The C-surface or R-surface is
preferably formed such that a portion in a range of 1 to 2 mm from
a reference position of the end surface and outer peripheral
surface of the roll shape, namely, from the position of the roll
end in the absence of the C-surface or R-surface, has been removed.
That is, as shown in FIGS. 4A, 4B, a sheet feed roll 1A or 1B
according to the present invention preferably has such a C-surface
5 or an R-surface 6 that lengths L.sub.1 and L.sub.2 from a
standard position S are 1 to 2 mm. The C-surface represents a
chamfer surface defined by JIS Z8317 (dimensions in drawing), while
the R-surface represents an arcuate surface defined by JIS Z8317
(dimensions in drawing). However, the C-surface and R-surface
include similar chamfer surfaces and curved surfaces resembling an
arcuate surface.
[0043] The above-described C-surface or R-surface is preferably
formed simultaneously with the molding of the roll.
EXAMPLES
Example 1
[0044] A polyol (100 parts by weight) produced by dehydration
condensation of 1,9-nonanediol, 2-methyloctanediol, and adipic acid
was mixed with 30 parts by weight of 4,4'-diphenylmethane
diisocyanate (MDI), 6 parts by weight of diethylene glycol (DEG) as
a chain extender, and 22 parts by weight of P3403 (DAICEL CHEMICAL
INDUSTRIES, LTD.) being an ether-ester-based triol having a
molecular weight of 4,000 as a crosslinking agent. The mixture was
charged into a mold preheated at 150.degree. C. and having an
entire surface grained. The configuration of the grained surface of
the mold is described in Table 1. A curing product of the charge
was aged with heating for 12 hour sat 100.degree. C., was subjected
to a cutting-off operation, and force-fitted with a shaft having an
external diameter of 15 mm to obtain a separating roll comprising
polyurethane and having an outer diameter of 25 mm, an inner
diameter of 15 mm, and a width of 25 mm.
Example 2
[0045] A separating roll was obtained in the same manner as in
Example 1, except that the grained surface was as shown in Table
1.
Example 3
[0046] A separating roll was obtained in the same manner as in
Example 1, except that the grained surface was as shown in Table 1,
the amount of DEG was 2 parts by weight, and the amount of P3403
was 125 parts by weight.
Example 4
[0047] The separating roll of Example 1 was chamfered at the
opposite end portions such that the lengths L.sub.1 and L.sub.2
from the reference position S were 1 mm (to be hereinafter referred
to as "C=1") The so chamfered separating roll was used as the
separating roll of Example 4.
Comparative Examples 1 to 3
[0048] Separating rolls were obtained in the same manner as in
Example 1, except that the grained surfaces were as shown in Table
1.
Comparative Examples 4 and 5
[0049] Separating rolls were obtained in the same manner as in
Example 1, except that the grained surfaces were as shown in Table
1, and EPDM was used instead of the polyurethane.
Comparative Example 6
[0050] A separating roll was obtained in the same manner as in
Example 1, except that the crosslinking agent was 1 part by weight
of trimethylolpropane (TMP).
Comparative Example 7
[0051] A separating roll was obtained in the same manner as in
Example 1, except that the roll was prepared using a mold without a
grained surface, and was polished with a grinding wheel to render
the surface shape of the roll polishing marks.
Test Example 1
[0052] The separating rolls of the Examples and the Comparative
Examples were measured for the hardness (JIS A), rebound resilience
at 25.degree. C. (JIS K6251), Rz (JIS B0601:1994), the width of the
concavities, the width of the convexities, and the height of the
convexities. The results are described in Table 1, along with the
direction of the concavities and the shape of the opposite end
portions. The rolls which were not chamfered are indicated by C=0
in Table 1. The results show that the irregular surface having the
same width of the concavities, the same width of the convexities,
and the same height of the convexities as those of the mold was
formed in each separating roll. TABLE-US-00001 TABLE 1 Rebound
Height of Ratio of width in Shape of resil- Width of Width of con-
circumferential direction opposite Hardness ience concavities
convexities vexities Direction of to width in axial direction end
Rz Material JIS A.degree. % .mu.m .mu.m .mu.m concavities
Convexities Concavities portions .mu.m Ex. 1 Polyurethane 45 70 400
or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 2 Polyurethane 45
70 400 or less 400 or less 130 Axial 1/5 1/5 C = 0 105 Ex. 3
Polyurethane 33 60 400 or less 400 or less 80 Axial 1/7 1/5 C = 0
65 Ex. 4 Polyurethane 45 70 400 or less 400 or less 80 Axial 1/3
1/3 C = 1 65 Comp. Polyurethane 45 70 700-1000 400 or less 80 Axial
1/3 1/3 C = 0 65 Ex. 1 Comp. Polyurethane 45 70 400 or less
800-1200 80 Axial 1/2 1/2 C = 0 65 Ex. 2 Comp. Polyurethane 45 70
400 or less 400 or less 80 Random* 1/1 1/1 C = 0 65 Ex. 3 Comp.
EPDM 35 80 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 4
Comp. EPDM 43 70 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65
Ex. 5 Comp. Polyurethane 68 70 400 or less 400 or less 80 Axial 1/3
1/3 C = 0 65 Ex. 6 Comp. Polyurethane 45 70 -- -- 35 Polishing --
-- C = 0 18 Ex. 7 marks *"Random" means to include the concavities
extending along the direction perpendicular to the axial direction
(namely, the circumferential direction).
Test Example 2
[0053] The outer peripheral surface of the roll in Example 1 was
observed. The results are shown in FIG. 5. The cells of the
lattice, each measuring 1 mm square, are indicated by white lines.
As shown in FIG. 5, concavities and convexities were formed in the
axial direction on the outer peripheral surface of the roll.
Test Example 3
[0054] As shown in FIG. 6, a free roll 12 provided rotatably was
pressed under a load against a separating roll 11 of each of the
Examples and the Comparative Examples, with a sheet 13 being
interposed between the free roll 12 and the separating roll 11.
When the separating roll 11 was rotationally driven, the amount of
movement of the sheet per rotation of the separating roll was
measured by a laser feed monitor (FC2010, KEYENCE CORP.) to
investigate the efficiency of sheet feed and the stability of sheet
feed. The measuring conditions were changed as shown by Nos. 1 to 8
in Table 2. The measuring environment was 2.3.degree. C..times.50%
RH. TABLE-US-00002 TABLE 2 Measuring Load Sheet feed speed
condition No. gf mm/s Type of sheet No. 1 100 125 Type 6200* No. 2
Hammer mill* No. 3 500 Type 6200 No. 4 Hammer mill No. 5 400 125
Type 6200 No. 6 Hammer mill No. 7 500 Type 6200 No. 8 Hammer mill
*Type 6200: 64 g/m.sup.2, RICOH CO., LTD. *Hammer mill: 108
g/m.sup.2, INTERNATIONAL PAPER
[0055] TABLE-US-00003 TABLE 3 Amount of sheet movement per rotation
of sample under each test condition Chipping (mm) Average
Efficiency of end No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8
.sigma. mm % portions Ex. 1 72.74 76.62 71.14 75.15 70.86 75.92
69.66 75.02 2.63 73.39 93.5 Yes Ex. 2 71.55 75.43 71.11 75.04 70.67
73.85 68.81 74.03 2.36 72.56 92.4 Yes Ex. 3 71.96 74.16 71.53 74.39
71.23 73.35 69.20 73.26 1.74 72.38 92.2 Yes Ex. 4 72.58 72.51 71.22
75.20 70.82 75.18 69.53 74.89 2.17 72.74 92.7 No Comp. 70.31 73.44
68.02 70.97 68.43 70.93 63.87 70.33 2.83 69.54 88.6 Yes Ex. 1 Comp.
70.94 72.31 67.72 71.41 67.28 71.13 62.33 69.77 3.27 69.11 88.0 Yes
Ex. 2 Comp. 71.05 74.34 68.98 72.63 65.63 72.19 65.16 71.51 3.35
70.21 89.4 Yes Ex. 3 Comp. 71.40 74.54 68.84 72.98 67.90 73.10
65.87 72.63 3.03 70.91 90.3 Yes Ex. 4 Comp. 68.26 74.38 67.48 74.31
63.30 73.13 61.22 73.29 5.17 69.42 88.4 Yes Ex. 5 Comp. 66.72 71.38
66.31 72.11 62.16 69.31 60.10 68.33 4.21 67.05 85.4 Yes Ex. 6 Comp.
69.00 74.87 68.08 72.38 67.40 72.41 65.19 71.28 3.19 70.08 89.3 Yes
Ex. 7 *Efficiency = (Actually measured amount of sheet
movement/Circumferential length of sample) .times. 100
[0056] In Examples 1 to 4, in which the samples comprised
polyurethane having a hardness of 25 to 50.degree. (JIS A) and
rebound resilience of 50 to 80%, the direction of the concavities
was the axial direction of the roll, the width of the convexities
was 500 .mu.m or less, the width of the concavities was 500 .mu.m
or less, and the height of the convexities was 50 to 150 .mu.m, it
was found that the efficiency of sheet feed was particularly high,
and the sheet feed performance was satisfactory. It was also found
that the samples of Examples 1 to 4 had small standard deviations
.sigma., were not susceptible to load, the sheet feed speed, and
the type of the sheet, and were stable in sheet feed
performance.
[0057] In Comparative Example 3, in which the direction of the
concavities was random, on the other hand, the sheet feed
efficiency was not so good as in Examples 1 to 4, and the sheet
feed performance was not stable. In Comparative Example 1, in which
the width of the concavities was not 500 .mu.m or less, moreover,
such satisfactory characteristics as in Example 1 were not
obtained, even when the other conditions were set to be the same as
those in Example 1 affording satisfactory performance. The same can
be said of Comparative Example 2 in which the width of the
convexities was not 500 .mu.m or less, and Comparative Example 6 in
which the hardness was outside the range of 25 to 50.degree..
Test Example 4
[0058] As shown in FIG. 7, a free roll 22 provided rotatably was
pressed under a load of 200 gf against the separating roll 11 of
each of the Examples and the Comparative Examples fixed so as not
to rotate, with a sheet 23 (color laser OHP sheet TR-3, CANON INC.)
being interposed between the free roll 22 and the separating roll
11. The sheet 23 was pulled out by 120 mm at a rate of 50 mm/sec
with the use of a load cell 24 attached to one end of the sheet 23.
Then, the state of end portions of the separating roll 11 was
observed. The results are shown in Table 3. End portions of the
separating roll of Example 1 were microscopically observed, and the
results are shown in FIG. 8.
[0059] As shown in Table 3, Example 4, in which the opposite end
portions of the separating roll were chamfered to have C-surfaces,
showed no chipping in the opposite end portions of the roll,
demonstrating excellent wear resistance. The separating rolls other
than that of Example 4, on the other hand, underwent chipping in
the opposite end portions, as shown in FIG. 8.
[0060] Although the preferred embodiments of the present invention
have been described in detail, it should be understood that various
changes, substitutions and alterations can be made therein-without
departing from the spirit and scope of the invention as defined by
the appended claims.
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