U.S. patent application number 10/448104 was filed with the patent office on 2003-12-18 for sheet feed roller.
This patent application is currently assigned to BRIDGESTONE CORPORATION. Invention is credited to Miyashita, Morihiro, Shikahama, Shigeru.
Application Number | 20030230847 10/448104 |
Document ID | / |
Family ID | 29727517 |
Filed Date | 2003-12-18 |
United States Patent
Application |
20030230847 |
Kind Code |
A1 |
Shikahama, Shigeru ; et
al. |
December 18, 2003 |
Sheet feed roller
Abstract
A sheet feed roller capable of achieving highly accurate sheet
feed distance has an outer peripheral surface including a feed
surface that extends at least locally in an axial direction of the
roller over an entire circumference of the roller. The feed surface
of the roller is provided with a plurality of projections,
including microscopic spikes that can be pierced into the sheet,
and stoppers for limiting a piercing depth of the spikes in the
sheet.
Inventors: |
Shikahama, Shigeru;
(Adachi-Ku, JP) ; Miyashita, Morihiro; (Yokohama
City, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
1010 El Camino Real
Menlo Park
CA
94025-4345
US
|
Assignee: |
BRIDGESTONE CORPORATION
|
Family ID: |
29727517 |
Appl. No.: |
10/448104 |
Filed: |
May 30, 2003 |
Current U.S.
Class: |
271/264 |
Current CPC
Class: |
B65H 2404/5213 20130101;
B65H 27/00 20130101 |
Class at
Publication: |
271/264 |
International
Class: |
B65H 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2002 |
JP |
2002-157,556 |
Claims
1. A sheet feed roller having an outer peripheral surface, said
outer peripheral surface including at least one feed surface region
that extends at least locally in an axial direction of the roller
and over an entire circumference of the roller, said feed surface
being provided with a plurality of projections, said plurality of
projections being comprised of microscopic spikes that can be
pierced into the sheet, and stoppers for limiting a piercing depth
of the spikes in the sheet.
2. The sheet feed roller according to claim 1, wherein each of said
plurality of projections comprises one of said spike and said
stopper.
3. The sheet feed roller according to claim 1, wherein each of said
projections comprising said spike further comprises said
stopper.
4. The sheet feed roller according to any one of claims 1 to 3,
wherein each of said projections is arranged in that region of said
feed surface, which is defined by first helices extending in
parallel with each other on the outer peripheral surface, and
second helices extending in parallel with each other on the outer
peripheral surface, said second helices crossing said second
helices.
5. The sheet feed roller according to claim 4, wherein at least one
projection comprising said spike is arranged alternately with at
least one projection comprising said stopper, along said first
helices or said second helices.
6. The sheet feed roller according to any one of claims 1 to 3,
wherein each of said projections is arranged in that region of said
feed surface, which is defined by generatrices extending along the
outer peripheral surface in parallel with an axial direction of the
roller, and circumferential lines extending in parallel with each
other on the outer peripheral surface, said circumferential lines
crossing said generatrices.
7. The sheet feed roller according to claim 6, wherein at least one
projection comprising said spike is arranged alternately with at
least one projection comprising said stopper, along said
generatrices or said circumferential lines.
8. The sheet feeder according to any one of claims 1 to 7, wherein
said stopper has a flat surface that is substantially at right
angles to a radial direction of the roller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an improved sheet feed
roller for feeding various types of sheets in imaging machines,
such as printers, copying machines or facsimile machines, so as to
print information onto the sheet or read out information from the
sheet.
[0003] 2. Description of Related Art
[0004] Sheet feed rollers are generally classified into two types.
A first type makes use of rollers having an outer peripheral
surface with a high friction coefficient. In this instance, the
sheet is sandwiched between the feed roller and a pinch roller and
transferred primarily by friction force. The feeding of the sheet
relies upon unstable friction force, and it is often difficult to
achieve a sufficient feeding accuracy. For overcoming such
difficulty associated with the feed rollers of the first type and
improving the feeding accuracy of the sheet, there has been
proposed a second type wherein the outer peripheral surface of the
roller is provided with a plurality of microscopic spikes that can
be pierced into the sheet. In this instance, the sheet is
positively transferred under engagement of the spikes and
corresponding microscopic recesses formed in the sheet by the
spikes. The latter type of sheet feed rollers are disclosed, for
example, in JP 08-310703A, JP 10-109777A, JP 10-203675A, JP
10-236683A, JP 2000-159377A, JP 2000-159378A and JP
2000-159379A.
[0005] However, it has been found by the inventors that even the
sheet feed rollers with the microscopic spikes may not realize a
satisfactory feeding accuracy, depending upon the material of the
sheet to be transferred, or the pressure under which the spikes are
pierced into the sheet. Here, the feeding accuracy is typically
represented by the difference between the desired feeding distance
and the actual feeding distance, per unit rotation of the feed
roller.
[0006] The inventors conducted thorough research and investigations
to seek measures for improving the feeding accuracy of the feed
rollers, and found the mechanism whereby unsatisfactory feeding
accuracy occurs, as follows. That is to say, the feeding accuracy
of the feed roller provided with the microscopic spikes is degraded
by fluctuation of the piercing depth of the spikes, which occurs
depending upon the material of the sheet to be fed and/or the
pressure for urging the feed roller against the sheet. When the
piercing depth of the spike is insufficient, there occurs
fluctuation of the sheet feeding between the spike and the recess
formed in the sheet by the spike. Fluctuation of the piercing depth
of the spike also causes fluctuation of the sheet feeding. On the
other hand, when a required piercing depth of the spike is achieved
by a sufficient urging force of the roller against the sheet, in an
attempt to avoid occurrence of fluctuation of the sheet feeding,
the sheet feeding radius changes depending upon the piercing depth
and inevitably causes fluctuation of the sheet feeding. The
above-mentioned mechanism will be more fully explained below with
reference to FIGS. 1(a), 1(b) and 1(c) and FIG. 2.
[0007] FIG. 1(a) is a sectional view of a sheet feed roller 10,
wherein the projection 11 is in the form of a spike 12 having a
height H, and the spike 12 is pierced into the sheet 21A under an
urging force F.sub.1. It is assumed that the sheet 21A is
relatively hard, and the piercing depth of the spike 12 into the
sheet 21A is D.sub.1 and the feeding radius of the sheet 21A is
R.sub.1. In this instance, the piercing depth D.sub.1 of the spike
12 is insufficient so that the spike 12 moves as shown by imaginary
line 12', without being synchronized with the recess 22 in the
sheet 21A, thereby causing fluctuation in sheet feeding. The actual
feeding distance of the feed roller 10 deviates from the desired
feeding distance and reduced by an amount corresponding to the
fluctuation of the sheet feeding.
[0008] When the urging force F.sub.1 is increased so as to increase
the piercing depth D.sub.1 from the state shown in FIG. 1(a), it is
possible to decrease fluctuation in sheet feeding. As shown in FIG.
1(b), an optimum piercing depth D.sub.0 is achieved under an
increased urging force F.sub.0, with which the fluctuation in sheet
feeding is decreased to a negligible level. In this instance, the
sheet feeding radius R.sub.0 is a predetermined, optimum value and
the slipping rate between the feed roller and the sheet is
substantially zero so that a predetermined sheet feeding distance
2.pi.R.sub.0 is achieved for each rotation of the feed roller.
[0009] In this way, it is possible to achieve a predetermined
feeding distance 2.pi.R.sub.0 under an increased urging force
F.sub.0, insofar as a relatively hard sheet 21A is concerned. When,
however, a relatively soft sheet 21B is to be fed by the feed
roller under the same urging force F.sub.0, there arises a tendency
that the predetermined sheet feeding distance 2.pi.R.sub.0 is not
achieved. Thus, as shown in FIG. 1(c), when the spike 12 of the
feed roller 10 is pierced into the relatively soft sheet 21B, the
piercing depth D.sub.2 is larger than the optimum depth D.sub.0
since the sheet 21B exhibits a relatively small piercing
resistance. In this instance, because the distance between the
center axis of the feed roller and the tip end of the spike 12 is
not changed, the sheet feeding radius R.sub.2 is smaller than the
predetermined value R.sub.0. Therefore, when a relatively soft
sheet 21B is to be fed under an increased urging force F.sub.0 that
is made optimum for feeding a relatively hard sheet 21A without
noticeable fluctuation in sheet feeding, the sheet feeding distance
per unit rotation of the feed roll is decreased to 2.pi.R.sub.2
that is smaller than the predetermined distance 2.pi.R.sub.0.
[0010] In order to eliminate the above-mentioned problems, it is
necessary to achieve a constant piercing depth D.sub.0 irrespective
of the hardness of the sheet. To this end, there may be used a feed
roller 30 as shown in FIG. 2, wherein microscopic projections in
the form of spikes 32 having a triangular section are provided on
the outer surface 30A of the roller 30. In this instance, as with
the case of the spikes 12 shown in FIG. 1(b), the spikes 32 under
the same urging force F.sub.0 are not only pierced into a
relatively hard sheet 21A with the desired piercing depth D.sub.0,
but also pierced into a relatively soft sheet 21B with a piercing
depth that is not increased beyond the desired depth D.sub.0, due
to a contact of the lower surface of the sheet 21B with the outer
surface 30A of the roller 30.
[0011] However, the feed roller 30 of the type shown in FIG. 2 is
not easy to produce efficiently and at reasonable cost, since it
would be necessary either to subject the outer surface 30A of the
roller 30 to grinding or the like machining so as to remove
materials and thereby leave the microscopic spikes 32 on the outer
surface 30A, or to join separately prepared microscopic spikes 32
to the flat outer surface 30A of the roller 30.
[0012] An alternative method for producing the feed roller 30 of
the type shown in FIG. 2 is disclosed in the patent documents cited
above, wherein a round rod is subjected to roll forming so that the
material at the outer surface of the rod is raised to form the
spikes. While such a method makes it possible to produce the feed
roller 30 efficiently and at low cost, there arises a problem that
even when it is desired to form a microscopic spike 32 having
exactly triangular section and height D.sub.0, limitations imposed
on the production technology make it inevitable that a spike 32
having a somewhat flared root portion is formed. As a result, it is
still impossible to maintain substantially constant the piercing
depth of the spike 32 as it is pierced into a relatively soft
sheet, since the piercing depth depends on the hardness of the
sheet and the piercing resistance of the spike at its flared root
portion. Therefore, the problem of fluctuation in sheet feeding
radius or sheet feeding distance remains unsolved.
SUMMARY OF THE INVENTION
[0013] It is therefore an object of the present invention to
eliminate the problems of the prior art mentioned above, and to
provide an improved sheet feed roller capable of achieving a highly
precise sheet feeding distance without fluctuations, irrespective
of the hardness of the sheet, and suitable for production at high
manufacturing productivity and at low cost.
[0014] To this end, according to the present invention, there is
provided a sheet feed roller having an outer peripheral surface,
said outer peripheral surface including at least one feed surface
region that extends at least locally in an axial direction of the
roller and over an entire circumference of the roller, said feed
surface being provided with a plurality of projections, said
plurality of projections being comprised of microscopic spikes that
can be pierced into the sheet, and stoppers for limiting a piercing
depth of the spikes in the sheet.
[0015] With the sheet feed roller according to the present
invention, since the projections on the feed surface of the feed
roller are comprised of microscopic spikes that can be pierced into
the sheet, and stoppers for limiting a piercing depth of the spikes
in the sheet, it is always possible to maintain the optimum
piercing depth of the spikes by the stoppers even when the hardness
of the sheet changes from time to time. In this way, the desired
sheet feeding radius or distance can be maintained without causing
fluctuations, thereby realizing a highly precise sheet feeding.
[0016] In the case of a sheet feed roller for ink jet printers, for
example, due to limitations in machine design, the total urging
force applied to the sheet feed roller in use is made relatively
low. In order to achieve an optimum piercing depth for each spike,
it is sometimes necessary to reduce the number of the spikes that
are simultaneously in engagement with the sheet. Thus, it is
preferred that each of the projections comprises one of the spike
and the stopper. In this instance, it is possible to reduce the
number of the spikes that are simultaneously in engagement with the
sheet since projection comprising the stoppers may be arranged
adjacent to the projections comprising the spikes, and the distance
between the adjacent spikes can be increased. Such an arrangement
may also be advantageous when the distance between the adjacent
projections cannot be readily reduced due to roll forming
conditions or the like.
[0017] Alternatively, each of the projections comprising the spikes
may further comprise the stopper. In this instance, it is possible
to ensure that each spike can be pierced into the sheet by a
constant, optimum piercing depth since the stopper of the
projection limit the radial position of the sheet relative to the
feed roller.
[0018] It is preferred that each of the projections is arranged in
that region of the feed surface, which is defined by first helices
extending in parallel with each other on the outer peripheral
surface, and second helices extending in parallel with each other
on the outer peripheral surface, wherein the second helices are
crossed with the first helices. Here, the term "helices" signifies
helical lines that extend in the axial direction of a cylindrical
body, along the outer peripheral surface thereof. In this instance,
it is possible to efficiently form the projections by a roll
forming device comprising a first roll forming die for forming
grooves on the outer surface of the feed roller so as to extend
along the first helices, and a second roll forming die for forming
grooves on the outer surface of the feed roller so as to extend
along the second helices, thereby minimizing the production cost of
the sheet feed roller.
[0019] In the arrangement described above, at least one projection
comprising the spike may be arranged alternately with at least one
projection comprising the stopper, along the first or second
helices. Such an arrangement of the spikes and the stoppers makes
it readily possible to ensure that each spike can be pierced into
the sheet by a constant, optimum-piercing depth.
[0020] It is alternatively preferred that each of the projections
is arranged in that region of the feed surface, which is defined by
generatrices extending along the outer peripheral surface in
parallel with an axial direction of the roller, and circumferential
lines extending in parallel with each other on the outer peripheral
surface, wherein the circumferential lines are crossed with the
generatrices. Here, the term "generatrices" signifies straight
lines that, in the case of a cylindrical body, extend axially along
the outer peripheral surface of the cylindrical body. In this
instance also, it is possible to efficiently form the projections
by a roll forming device comprising a first roll forming die for
forming grooves on the outer surface of the feed roller so as to
extend along the circumferential lines, and a second roll forming
die for forming grooves on the outer surface of the feed roller so
as to extend along the circumferential lines, thereby minimizing
the production cost of the sheet feed roller.
[0021] In the arrangement described above, at least one projection
comprising the spike may be arranged alternately with at least one
projection comprising the stopper, along the generatrices or the
circumferential lines. Such an arrangement of the spikes and the
stoppers makes it readily possible to ensure that each spike can be
pierced into the sheet by a constant, optimum piercing depth.
[0022] It is further preferred that the stopper has a flat surface
that is substantially at right angles to a radial direction of the
roller. The flat surface of the stopper serves to positively
maintain the desired optimum piercing depth of the spikes, in
highly accurate manner
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention will be more fully explained below
with reference to some preferred embodiment shown in the
accompanying drawings.
[0024] FIGS. 1(a) to 1(c) are sectional views showing a
conventional sheet feed roller.
[0025] FIG. 2 is a sectional view showing another conventional
sheet feed roller.
[0026] FIG. 3(a) is a perspective view showing a sheet feed roller
according to a first embodiment of the present invention, and FIG.
3(b) is a perspective view showing a modification thereof.
[0027] FIG. 4 is a developed view of the sheet feeding surface
region of the feed roller shown in FIG. 3(a) or 3(b).
[0028] FIG. 5 is a sectional view corresponding to section 5-5 in
FIG. 4, but showing the feed roller in use.
[0029] FIG. 6 is a view showing the arrangement of a roll forming
device for forming the feed roller according to the first
embodiment.
[0030] FIG. 7 is a perspective view showing a first die of the
roll-forming device shown in FIG. 6.
[0031] FIG. 8 is a perspective view showing a second die of the
roll-forming device shown in FIG. 6.
[0032] FIG. 9 is a perspective view showing a sheet feed roller
according to a second embodiment of the present invention.
[0033] FIG. 10 is a developed view of the sheet feeding surface
region of the feed roller shown in FIG. 9.
[0034] FIG. 11 is a view showing the arrangement of a roll forming
device for forming the feed roller according to the second
embodiment.
[0035] FIG. 12 is a perspective view showing a first die of the
roll-forming device shown in FIG. 11.
[0036] FIG. 13 is a perspective view showing a second die of the
roll-forming device shown in FIG. 11.
[0037] FIG. 14 is a perspective view showing a sheet feed roller
according to a third embodiment of the present invention.
[0038] FIG. 15 is a developed view of the sheet feeding surface
region of the feed roller shown in FIG. 14.
[0039] FIG. 16 is a sectional view corresponding to section 16-16
in FIG. 15, but showing the feed roller in use.
[0040] FIG. 17 is a view showing the arrangement of a roll forming
device for forming the feed roller according to the third
embodiment.
[0041] FIG. 18 is a perspective view showing a die of the
roll-forming device shown in FIG. 17.
[0042] FIG. 19 is a graph showing the deviation of sheet feeding
distances obtained by performance tests under various surface
pressure conditions.
[0043] FIG. 20 is a developed view similar to FIG. 4, showing the
sheet feeding surface region of the modified feed rollel
[0044] FIG. 21 is a graph showing the deviation of sheet feeding
distances obtained by further performance tests under various
surface pressure conditions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] A first embodiment of the present invention is shown in FIG.
3(a), wherein the sheet feed roller is generally denoted by
reference numeral 101. The feed roller 101 may be suitably used in
an imaging machine, such as printers, copying machines or facsimile
machines, for feeding a sheet S on which image information is
printed. The feed roller 101 includes a cylindrical roller body 102
provided on both axial ends with shaft end portions 103 for
rotatably supporting the feed roller 101 in the imaging machine.
The feed roller 101 has an outer peripheral surface provided with
at least one feed surface region 104 that extends at least locally
in an axial direction of the roller 101 and over an entire
circumference thereof. In the embodiment shown in FIG. 3(a), there
are provided three feed surface regions 104 that are spaced from
each other in the longitudinal direction of the feed roller
101.
[0046] A modification is shown in FIG. 3(b), wherein the sheet feed
roller is generally denoted by reference numeral 101A includes a
cylindrical roller body 102A provided on both axial ends with shaft
end portions 103A for rotatably supporting the feed roller 101A in
the imaging machine. The feed roller 101A differs from that shown
in FIG. 3(b) essentially in that the outer surface of the roller
101A as a whole constitutes a feed surface region 104A.
[0047] The sheet feed rollers 101, 101A are rotatably mounted in
the imaging machine with their feed surface regions 104, 104A in
pressure contact with pinch rollers PR so that the sheet S
sandwiched between the feed surface regions 104, 104A and the pinch
rollers PR is highly accurately fed toward the downstream side of
the feed roller 101, 101A.
[0048] As mentioned above, FIG. 4 is a developed view of the sheet
feeding surface region 104, 104A of the feed roller 101, 101A shown
in FIG. 3(a) or 3(b), and FIG. 5 is a sectional view corresponding
to section 5-5 in FIG. 4, but showing the feed roller 101, 101A in
use. It can be seen that the entire feed surface region 104 of the
roller 101 is comprised of a number of diamond-shaped microscopic
areas defined by a plurality of first helices L.sub.1 that are in
parallel with each other, and a plurality of second helices L.sub.2
that are also in parallel with each other but arranged so that they
are crossed with the first helices L.sub.1. Each of such
microscopic areas is provided with a microscopic first projection
105 or a microscopic second projection 106, which are combined with
each other such that the first and second projections 105 and 106
are arranged alternately with each other along the first helices
L.sub.1, and either the same first projections 105 or the same
second projections 106 are arranged continuously along the second
helices L.sub.2.
[0049] In FIG. 4, reference character R denotes a direction
parallel to the circumferential direction of the sheet feeding
region 104, and reference character W denotes a direction parallel
to the center axis of the roller 101. The first helices L.sub.1 are
oriented so as to form an angle of 45.degree. with reference to the
axial direction W of the roller 101 and spaced from each other by a
pitch P.sub.1. The second helices L.sub.2 are oriented so as to
form an angle of -45.degree. with reference to the axial direction
W of the roller 101 and spaced from each other by the same pitch
P.sub.1. Thus, as shown in FIG. 5, the projections 105 and 106 are
arranged alternately with each other in the axial direction W of
the roller 101 so as to be spaced from each other by a pitch
P.sub.2. It is to be noted, however, that the directions and the
pitches of the first and second helices L.sub.1, L.sub.2 are not
limited to those of the embodiments shown in FIG. 4.
[0050] The first projection 105 is in the form of a microscopic
pyramid having a height H.sub.1. The first projection 105 has a
spike 105A at it top portion, which can be pierced into the sheet S
so as to feed the sheet, and four facets 105B, 105C of which two
facets 105B are opposed to the first helices L.sub.1 and the other
two facets 105C are opposed to the second helices L.sub.2. The
first projection 105 forms an angle .theta. between opposite edges
of each facet 105B, 105C. The second projection 106 is in the form
of a frustum of a microscopic pyramid having a height H.sub.2 that
is lower than the height H.sub.1 of the first projection 105. The
second projection 106 has a flat top surface 106A, which can be
brought into engagement with the surface of the sheet S as a
stopper for limiting the piercing depth D of the spike 105A of the
adjacent first projection 105, and four facets 106B, 106C, of which
two facets 106B are opposed to the first helices L.sub.1 and the
other two facets 106C are opposed to the second helices L.sub.2.
The second projection 106 forms an angle .theta. between opposite
edges of each facet 106B, 106C.
[0051] It is preferred that the opposite facets 105B or 105C of the
first projection 105 form an angle .phi. that is within a range of
30.degree. to 60.degree.. It is to be noted that the angle .phi.
between the opposite facets 105B or 105C of the first projection
105 is slightly different from the angle .theta. between the
opposite edges of each facet 105B, 105C. If the angle .phi. between
the opposite facets 105B or 105C of the first projection 105 is
larger than 60.degree., there may be instances wherein a sufficient
piercing depth D for a relatively hard sheet cannot be achieved,
thereby causing slipping of the sheet while it is being fed. On the
other hand, if the angle .phi. is smaller than 30.degree., there
may be instances wherein the mechanical strength of the spike 105A
is insufficient, thereby degrading the durability of the feed
roller.
[0052] It is also preferred that the piercing depth D of the first
projection 105 is within a range of 10 .mu.m to 40 .mu.m. If the
piercing depth D is smaller than 10 .mu.m, there may be instances
wherein slipping of the sheet occurs due to insufficient piercing
depth. On the other hand, if the piercing depth D is larger than 40
.mu.m, there may be instances wherein the surface of the sheet S
cannot be properly supported by the stoppers 106A of adjacent
second projections 106 particularly when the sheet S is relatively
hard, thereby causing fluctuation in the sheet feeding radius
depending upon the hardness of the sheet S.
[0053] As for the first projection 105 having a spike 105A to be
pierced into the sheet S, although the tip of the spike 105A may be
sharp from the viewpoint of piercing function, it is often
preferred from the viewpoint of manufacturing technology that the
spike 105A is in the form of a frustum of a pyramid. In this
instance, it is preferred that the spike has a top surface with a
surface area not greater than 400 .mu.m.sup.2, more preferably not
greater than 100 .mu.m.sup.2, and more preferably not greater than
50 .mu.m.sup.2. As for the second projection 106, while it is
desirable for the top surface 106A to have as large a surface area
as possible, from the viewpoint of the stopper function, it is
often preferred from the viewpoint of manufacturing technology that
the tip surface 106A has a surface area within a range of 160-3600
.mu.m.sup.2, more preferably 400-2500 .mu.m.sup.2. Furthermore,
although the first projection 105 in the illustrate embodiment is
in the form of a pyramid, it may be in the form of a cone provided
that it has a spike that can be pierced into the sheet S. Also,
although the second projection 106 in the illustrate embodiment is
in the form of a frustum of a pyramid, it may be in the form of a
frustum of a cone, provided that it has a top surface serving as a
stopper for limiting the piercing depth D of the first projection
105.
[0054] When the roller body 102 is comprised of a metal material,
the sheet feeding surface region 104 can be advantageously formed
by a pair of roll forming dies by a roll forming process to be
described hereinafter. FIG. 6 shows the arrangement of a roll
forming device comprising a first die 120 and a second die 121 for
forming the feed roller according to the embodiment of FIG. 3(a),
and FIGS. 7 and 8 are perspective views showing the first die 120
and the second die 121, respectively.
[0055] The first roll forming die 120 has an outer surface provided
with ridges 120A that are arranged at a constant distance over the
entire periphery thereof. Neighboring ridges 120A are spaced from
each other with a groove 120B therebetween, wherein the groove 120B
is of triangular cross-section. Each ridge 120A is of a trapezoidal
cross-section, and has a cutting surface 120C on its top, for
forming grooves along the first helices L.sub.1 on the sheet
feeding surface region 104. Similarly, the second roll forming die
121 has an outer surface provided with ridges 121A that are
arranged at a constant distance over the entire periphery thereof.
Neighboring ridges 121A are spaced from each other alternately with
a groove 121B and another groove 121C therebetween, wherein the
groove 121B is of triangular cross-section and the groove 120C is
of trapezoidal cross-section. Thus, for example, a groove 121B with
triangular cross-section is arranged between the first and the
second ridges 121A, 121A, and a groove 121C with trapezoidal
cross-section is arranged between the second and the third ridges
121A, 121A, and such an arrangement of the ridges and the grooves
is repeated in the circumferential direction of the second roll
forming die. Here also, each ridge 121A of the second die 121 is
substantially of trapezoidal cross-section, and has a cutting
surface 121D on its top, for forming grooves along the second
helices L.sub.2 on the sheet feeding surface region 104.
[0056] When the sheet feeding surface regions 104 are to be formed
on a roller body 102, the roller body 102 is clamped between the
first and second roll forming dies 120, 121, which are arranged
with their respective center axes in parallel with each other. By
urging the roller body 102 against the first and second roll
forming dies 120, 121 under a predetermined working pressure, and
rotating these dies 120, 121, it is possible to form the desired
feed surface region 104 on the roller body 102.
[0057] As seen in exploded views, the angle formed between the
ridge 120A and the center axis of the first roll forming die 120 is
the same as the angle (e.g., +45.degree.) between the first helices
L.sub.1 on the sheet feeding surface region 104 and the center axis
of the feed roller 101. Similarly, the angle formed between the
ridge 121A and the center axis of the second roll forming die 121
is the same as the angle (e.g., -45.degree.) between the second
helices L.sub.2 on the sheet feeding surface region 104 and the
center axis of the feed roller 101.
[0058] With such an arrangement of the roll forming device, the
facets 105B, 106B of the projections 105, 106 opposed to the first
helices L.sub.1 are formed by the wall surfaces 120D of the
triangular grooves 120B in the first die 120, the facets 105C of
the projections 105 opposed to the second helices L2 are formed by
the wall surfaces 121E of the triangular grooves 121B in the second
die 121, the facets 106C opposed to the second helices L2 are
formed by the wall surfaces 121F of the trapezoidal grooves 121C in
the second die 121, and the stoppers 106A of the second projections
106 are formed by the bottom surfaces 121G of the trapezoidal
grooves 121C of the second die 121.
[0059] In the roll forming device shown in FIGS. 6 to 8, all of the
grooves in the first roll forming die 120 are comprised of
triangular grooves 120B. It is however possible to arrange one or
more trapezoidal grooves between neighboring triangular grooves
120B. As for the second roll forming die 121, it is likewise
possible to arrange two or more trapezoidal grooves 121C between
neighboring triangular grooves 121B. By appropriately selecting the
number of the trapezoidal grooves provided for the roll forming
dies 120, 121, it is possible to realize a desired arrangement of
the microscopic projections 105, 106 on the sheet feeding surface
region 104 wherein the number of the stoppers 106A is optimized for
each spike 105A.
[0060] As mentioned above, the first and second dies 120, 121 of
the roll forming device shown in FIGS. 6-8 are arranged with their
respective center axes in parallel with each other, as mentioned
above. The roller body 102 is oriented in parallel with the dies
120, 121 and urged against the dies 120, 121 under a predetermined
working pressure, while the dies 120, 121 are rotated. In this
instance, it is possible to form the sheet feeding surface region
104 on the roller body 102 without causing an axial movement of the
roller body 102 relative to the first and second dies 120, 121,
provided that the width of the sheet feeding surface region 104 on
the roller body 102 as seen in the axial direction is the same as
the width of the dies 120, 121. This type of roll forming method is
known as infeed roll forming process.
[0061] When such an infeed roll forming process is applied to
formation of the sheet feeding surface region 104A of the sheet
feed roller 101A shown in FIG. 3(b), which extends over the entire
length of the roller body 102A, the roll forming dies 120, 121 must
have a large width corresponding to the axial length of the sheet
feeding surface region 104A, thereby making it difficult to achieve
an uniform roll forming over the entire length of the roller body
102A. In order to eliminate such difficulty, it is preferred to
carry out a thru-feed roll forming process wherein the roll forming
device has a slightly different arrangement in that the center axis
of the first die 120 is inclined relative to the center axis of the
roller body 102B by a predetermined angle, and the center axis of
the second die 121 is oppositely inclined relative to the center
axis of the roller body 102B by the same angle of the opposite
sign, without causing intersection of the center axes of the dies
120, 121 with the center axis of the roller body 102B. In this
instance, the roller body 102 is urged against the dies 120, 121
under a predetermined working pressure, while the first and second
roll forming dies 120, 121 are rotated, so as to feed the roller
body 102 axially relative to the dies 120, 121 under a
predetermined speed, and thereby form the feed surface region 104
uniformly over the roller body 102.
[0062] A second embodiment of the present invention is shown in
FIG. 9, wherein the sheet feed roller is generally denoted by
reference numeral 131. The feed roller 131 includes a cylindrical
roller body 132 provided on both axial ends with shaft end portions
133 for rotatably supporting the feed roller 131 in the imaging
machine. The feed roller 131 has an outer peripheral surface
provided with three sheet feeding surface regions 134 that are
spaced from each other axially and extend over an entire
circumference of the roller 131.
[0063] The sheet feed roller 131 is rotatably mounted in the
imaging machine with its sheet feeding surface regions 134 in
pressure contact with pinch rollers PR so that the sheet S
sandwiched between the feed surface regions 134 and the pinch
rollers PR is highly accurately fed toward the downstream side of
the feed roller 131.
[0064] As mentioned above, FIG. 10 is a developed view of the sheet
feeding surface region 134 of the feed roller 131 shown in FIG. 9,
wherein reference character R denotes a direction parallel to the
circumferential direction of the sheet feed roller 131, and
reference character W denotes a direction parallel to the center
axis of the feed roller 131. It can be seen that each feed surface
region 134 of the roller 131 is comprised of a number of
rectangular microscopic areas defined by a plurality of
circumferential lines L.sub.3 that extend over the sheet feeding
surface region 134, and a plurality of generatrices L4 that extends
axially over the sheet feeding surface region 134. Each of such
microscopic areas is provided with a microscopic first projection
135 or a microscopic second projection 136, which are combined with
each other such that the first and second projections 135 and 136
are arranged alternately with each other along the generatrices
L.sub.4, and either the same first projections 135 or the same
second projections 136 are arranged continuously along the
circumferential lines L.sub.3.
[0065] The first projection 135 is in the form of a microscopic
pyramid having a spike 135A at it top portion, which can be pierced
into the sheet S so as to feed the sheet, and four facets 135B,
135C of which two facets 135B are opposed to the circumferential
lines L.sub.3 and the other two facets 135C are opposed to the
generatrices L.sub.4. The second projection 136 is in the form of a
frustum of a microscopic pyramid having a flat top surface 136A,
which can be brought into engagement with the surface of the sheet
S as a stopper for limiting the piercing depth D of the spike 135A
of the adjacent first projection 135, and four facets 136B, 136C,
of which two facets 136B are opposed to the circumferential lines
L.sub.3 and the other two facets 136C are opposed to the
generatrices L.sub.4.
[0066] When the roller body 132 is comprised of a metal material,
the sheet feeding surface region 134 can be advantageously formed
by a pair of roll forming dies by a roll forming process to be
described hereinafter. FIG. 11 shows the arrangement of a roll
forming device comprising a first die 140 and a second die 141 for
forming the feed roller according to the embodiment of FIG. 9, and
FIGS. 12 and 13 are perspective views showing the first die 140 and
the second die 141, respectively.
[0067] The first roll forming die 140 has an outer surface provided
with ridges 140A that are arranged at a constant distance over the
entire periphery thereof. Each ridge 140A has a flat top surface
140D for forming grooves in the sheet feeding surface region 134 so
as to extend along the. Neighboring ridges 140A are spaced from
each other alternately with a groove 140B or another groove 140C
therebetween, wherein the groove 140B is of triangular
cross-section and the groove 140C is of trapezoidal cross-section.
Each ridge 140A is of trapezoidal cross-section, and has a cutting
surface 140D on its top, for forming grooves along the
circumferential lines L.sub.3 on the sheet feeding surface region
134. Similarly, the second roll forming die 141 has an outer
surface provided with ridges 141A that are arranged at a constant
distance over the entire periphery thereof. Neighboring ridges 141A
are spaced from each other alternately with a groove 141B, which is
of triangular cross-section. Here also, each ridge 141A of the
second die 141 is substantially of trapezoidal cross-section, and
has a cutting surface 141C on its top, for forming grooves along
the generatrices L.sub.4 on the sheet feeding surface region
134.
[0068] With such an arrangement of the roll forming device, the
facets 135C, 136C of the projections 135, 136 opposed to the
generatrices L4 are formed by the wall surfaces 141D of the
triangular grooves 141B of the second die 141, the facet 135B of
the projection 135 opposed to the circumferential lines L.sub.3 are
formed by the wall surfaces 140E of the triangular grooves 140B of
the first die 140, the facets 136B of the projection 136 opposed to
the circumferential lines L3 are formed by the wall surfaces 140F
of the trapezoidal grooves 140C of the first die 140, and the
stoppers 136A of the projection 136 are formed by the bottom
surfaces 140G of the trapezoidal grooves 140C of the first die
140.
[0069] In the roll forming device shown in FIGS. 10-12, it is
possible to arrange two or more trapezoidal grooves 140C between
neighboring triangular grooves 140B. By appropriately selecting the
number of the trapezoidal grooves provided for the roll forming
dies 140, 141, it is possible to realize a desired arrangement of
the microscopic projections 135, 136 on the sheet feeding surface
region 134 wherein the number of the stoppers 136A is optimized for
each spike 135A.
[0070] A third embodiment of the present invention is shown in FIG.
14, wherein the sheet feed roller is generally denoted by reference
numeral 151. The feed roller 151 includes a cylindrical roller body
152 provided on both axial ends with shaft end portions 153 for
rotatably supporting the feed roller 151 in the imaging machine.
The feed roller 151 has an outer peripheral surface provided with
three sheet feeding surface regions 134 that are spaced from each
other axially and extend over an entire circumference of the roller
151.
[0071] The sheet feed roller 151 is rotatably mounted in the
imaging machine with its sheet feeding surface regions 154 in
pressure contact with pinch rollers PR so that the sheet S
sandwiched between the feed surface regions 154 and the pinch
rollers PR is highly accurately fed toward the downstream side of
the feed roller 151.
[0072] As mentioned above, FIG. 15 is a developed view of the sheet
feeding surface region 154 of the feed roller 151 shown in FIG. 14,
and FIG. 16 is a sectional view corresponding to section 16-16 in
FIG. 15, but showing the feed roller 151 in use. It can be seen
that the entire feed surface region 154 of the roller 151 is
comprised of a number of diamond-shaped microscopic areas defined
by a plurality of first helices L.sub.5 that are in parallel with
each other, and a plurality of second helices L.sub.6 that are also
in parallel with each other but arranged so that they are crossed
with the first helices L.sub.5. Each of such microscopic areas is
provided with a microscopic projection 155.
[0073] In FIG. 15, reference character R denotes a direction
parallel to the circumferential direction of the sheet feeding
region 154, and reference character W denotes a direction parallel
to the center axis of the roller 151. The first helices L.sub.5 are
oriented so as to form an angle of 45.degree. with reference to the
axial direction W of the roller 151 and spaced from each other by a
pitch P.sub.1. The second helices L.sub.6 are oriented so as to
form an angle of -45.degree. with reference to the axial direction
W of the roller 151 and spaced from each other by the same pitch
P.sub.1. Thus, as shown in FIG. 14, the projections 155 are aligned
in the axial direction W of the roller 151 so as to be spaced from
each other by a pitch P.sub.2. It is to be noted, however, that the
directions and the pitches of the first and second helices L.sub.5,
L.sub.6 are not limited to those of the embodiments shown in FIG.
15.
[0074] The projection 155 includes a lower portion in the form of a
frustum of pyramid, and an upper portion in the form of a pyramid,
wherein the bottom surface of the upper portion is smaller than the
top surface of the lower portion. The upper portion forms a spike
155A that can be pierced into the sheet S so as to feed the sheet.
The top surface of the lower portion can be brought into engagement
with the surface of the sheet S as a stopper for limiting the
piercing depth D of the spike 155A. The lower portion of the
projection 155 has four facets 155C that are opposed to the first
or second helices L.sub.5, L.sub.6. Similarly, the upper portion of
the projection 155 has four facets 155D that are opposed to the
first or second helices L.sub.5, L.sub.6. The first projection 155
forms an angle .theta. between opposite edges of each facet 155C,
155D. The projection 155 has a height H.sub.1, and the lower
portion has a height H.sub.2.
[0075] When the roller body 152 is comprised of a metal material,
the sheet feeding surface region 154 can be advantageously formed
by a pair of roll forming dies by a roll forming process to be
described hereinafter. FIG. 17 shows the arrangement of a roll
forming device comprising a first die 160 and a second die 161 for
forming the feed roller according to the embodiment of FIG. 14, and
FIGS. 18 and 19 are perspective views showing the first die 160 and
the second die 161, respectively.
[0076] The first roll forming die 160 each has an outer surface
provided with ridges 160A that are arranged at a constant distance
over the entire periphery thereof. Neighboring ridges 160A are
spaced from each other with a groove 160B therebetween, wherein the
groove 160B is of stepped cross-section defined by a trapezoidal
portion and a triangular portion. Each ridge 160A is of a
trapezoidal cross-section, and has a cutting surface 160C on its
top, for forming grooves along the first helices L.sub.5 on the
sheet feeding surface region 154. Similarly, the second roll
forming die 161 has an outer surface provided with ridges 161A that
are arranged at a constant distance over the entire periphery
thereof. Neighboring ridges 161A are spaced from each other with a
groove 161B therebetween, wherein the groove 161B is of stepped
cross-section defined by a trapezoidal portion and a triangular
portion. Each ridge 161A is of trapezoidal cross-section, and has a
cutting surface 161C on its top, for forming grooves along the
second helices L.sub.6 on the sheet feeding surface region 154.
[0077] As seen in exploded views, the angle formed between the
ridge 160A and the center axis of the first roll forming die 160 is
the same as the angle (e.g., +45.degree.) between the first helices
L.sub.5 on the sheet feeding surface region 154 and the center axis
of the feed roller 151. Similarly, the angle formed between the
ridge 161A and the center axis of the second roll forming die 161
is the same as the angle (e.g., -45.degree.) between the second
helices L.sub.6 on the sheet feeding surface region 154 and the
center axis of the feed roller 151.
[0078] With such an arrangement of the roll forming device, the
facets 155C of the lower portion of the projection 155, which are
opposed to the first helices L.sub.5, are formed by the wall
surfaces 160E, 161E at the trapezoidal portions of the triangular
groves 160B, 161B, the facets 155D of the upper portion of the
projection 155, which are opposed to the second helices L.sub.6,
are formed by the wall surfaces 160F, 161F at the triangular
portions of the groves 160B, 161B, and the stoppers 155B of the
projections 155 are formed by the bottom surfaces 160D, 161D of the
trapezoidal portions of the grooves 160B, 161B.
[0079] Performance Tests
[0080] In order to confirm functional advantages of the sheet feed
roller according to the present invention, performance tests were
conducted as follows. First of all, a sheet feed roller 101 shown
in FIG. 3(a) was used as Example 1, to measure the sheet feeding
distance under various surface pressures of the pinch rollers PR.
Another sheet feed roller was used as Control, wherein the
projections 106 having the stoppers 106A were replaced by the
projections 105 having the spikes 105A, to measure the sheet
feeding distance under various surface pressures of the pinch
rollers PR. The result of the tests is shown in FIG. 19.
[0081] In the next place, a sheet feed roller similar to that shown
in FIG. 3(a) was used as Example 2, to measure the sheet feeding
distance under various surface pressures of the pinch rollers PR.
In this instance, as shown in FIG. 20, the sheet feeding surface
104X of the feed roller as Example 2 has an arrangement of the
projections 105, 106 wherein two projections 106X having stoppers
are arranged between two neighboring projections 105X having
spikes. The sheet feed roller used as Control was the same as that
described above. The result of the tests is shown in FIG. 21.
[0082] It can be seen that FIGS. 19 and 21 are graphs wherein the
abscissa indicates the theoretical feeding distance that can be
obtained by multiplying the moving angle of the feed roller with
the nominal diameter of the feed roller, and the ordinate indicates
the deviation of the feeding distance, i.e., the difference between
the theoretical feeding distance and the actual feeding distance.
It is noted that the surface pressure of the pinch rollers is per 1
mm in the axial direction of the feed roller. The sheets used for
the performance tests were coated sheets for ink jet printers.
[0083] In the sheet feed rollers used in the performance tests as
Examples 1, 2 and Control, the angle of the first helices L.sub.1
relative to the center axis of the roller is +45.degree., the angle
of the second helices L.sub.2 relative to the center axis of the
roller is -45.degree., the distance between the neighboring helices
is 0.35 mm, and the projections with the spikes or stoppers are in
the form of pyramid of which the opposite facets form an angle of
50.degree. relative to each other. The dimensions (.mu.m) of the
projections are as shown in the following Table.
1 Projections Items Example 1 Example 2 Control Projection Height
75 80 75 with spike Top surface 10 .times. 10 7 .times. 7 10
.times. 10 Projection Height 62 49 -- with stopper Top surface 8
.times. 20 40 .times. 40 --
[0084] It will be appreciated from FIGS, 19 and 21 that the sheet
feed rollers of Examples 1 and 2 according to the present invention
exhibit larger average sheet feeding distance due to suppressed
fluctuation in sheet feeding, and stable feeding distance due to
fluctuations relative to the surface pressure of the pinch
rollers.
[0085] With the sheet feed roller according to the present
invention, since the projections on the feed surface of the feed
roller are comprised of microscopic spikes that can be pierced into
the sheet, and stoppers for limiting a piercing depth of the spikes
in the sheet, it is always possible to maintain the optimum
piercing depth of the spikes by the stoppers even when the hardness
of the sheet changes from time to time. In this way, the desired
sheet feeding radius or distance can be maintained without causing
fluctuations, thereby realizing a highly precise sheet feeding.
[0086] While the present invention has been described above with
reference to some preferred embodiments, various modifications or
variations may be made without departing from the scope of the
invention as defined by the appended claims.
* * * * *