Paper feed roller

A paper feed roller for delivering and feeding paper, which has a high coefficient of friction that is not affected by changes in temperature or humidity, good hardwearing properties, and is low in ink transferability. The paper feed roller includes a coating layer formed of an elastic material such as rubber which is formed on a surface of a core material molded of a foamed material such as sponge. A bonding agent having an elasticity such as denatured silicon is coated on the surface of the coating layer. Ceramic particles are embedded and fixed in the bonding agent In an alternative embodiment the bonding agent is directly coated on the surface of core material which is molded from a pliable material such as soft rubber and sponge.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a paper delivery mechanism for deliverying 
sheet by sheet, sheets of paper, notes, and various other sheet-like 
members in copying machines, printers, facsimiles, scanners, classifiers, 
presses, note issuing machines, cash dispensers, etc., and to a paper feed 
roller which is a component of a paper feed device for feeding paper. 
2. Description of the Prior Art 
As materials for a delivering or feeding roller, various kinds of rubber 
(natural rubber and synthetic rubber) have been heretofore used. Further, 
for an application requiring a roller having a higher elasticity, sponges 
or the like obtained by foaming rubber have been used. 
Characteristics required for the materials for the delivering or feeding 
roller are listed below: 
1 There should have a coefficient of friction necessary for imparting a 
sufficient feeding force to paper. 
2 The coefficient of friction is not lowered due to the change in 
temperature and humidity (low temperature and low humidity), change after 
passage of year or contaminations such as chemicals (oils and fats), ink, 
dust, etc. 
3 Hardwearing properties are high. 
4 When ink adhered to paper is transferred, the other portions of paper are 
not stained. 
5 Elastic modulus can be adjusted in a wide range according to uses. 
The performance of existing roller materials with respect to the 
requirements of the above-described five characteristics is as follows: 
With respect to the 1, since the coefficient of friction of rubber is in 
inverse proportion to hardness, it is necessary to lower the hardness in 
order to obtain a high coefficent of friction. When the hardness is 
lowered, the performances in connection with other items 2, 3, 4, and 5 
lowered on the other side, which is inconsistent. 
Withe respect to the 2, this is a matter of a weak point in terms of 
properties of rubber itself. At a low temperature and a low humidity, the 
coefficient of friction is extremely lowered, giving rise to a trouble in 
feed and an inferiority in delivery. Further, since rubber is a high 
polymer, the characteristic thereof is unavoidably deteriorated as time 
passes. The average life of rubber is approximately 2 years. Thus, it is 
necessary to periodically replace it with new one. Further, since 
synthetic rubber is an organic substance, there are many rubbers which are 
low in chemicals-resistance. Thus, when oils and fats are adhered thereto, 
the coefficient of friction is lowered, and further, the deterioration in 
characteristic due to denature is accelerated. Further, since the 
coefficient of friction is .left brkt-top.Sticky.right brkt-bot. in other 
words, ink, dust or the like tends to be adhered to a roller having a 
higher coefficient of friction. 
With respect to the 3, rubber is low in hardness so that the rubber is 
shaved by paper and carbon particles (such as pencil, ink, etc.) adhered 
to paper as time passes to reduce its outside diameter. Replacement of 
rubber with new one is necessary in case where frequency of use is high. 
With respect to the 4, since rubber is high in affinity with oils and fats, 
ink after printing is adhered to a roller in the press, and the ink is 
transferred to other portions of paper, resulting in an unavoidable 
occurrence of stain of paper. 
With respect to the 5, the elastic modulus can be adjusted by varying the 
hardness of rubber, but other characterisitcs are simultaneously changed, 
making it necessary to keep balance. 
In the case where a sponge is used, the above-described problems in 
connection with the 2, 3, 4 and 5 further becomes prominent. 
As described above, materials satisfied with all the requirements described 
above do not exist, and in addition, the respective characteristics are 
mutually affected. In the past, therefore, a designer takes the most 
important characteristic into consideration and at the same time 
compromises in other aspects to determine various characteristics. 
Simultaneously, the designer devises a mechanism for covering the 
characteristics in the inferior portions for use of materials. 
In explaining the conventional technique which uses a normal rubber roller, 
an example will be described herein in detail of a feed mechanism in which 
a one-side shaft is movable and upper and lower shafts are fixed, out of a 
double-side driving system used when paper for single slip/double slip are 
fed. 
For the purpose of feeding a sheet of a single slip, one-side drive for 
imparting a drive force to only one roller out of upper and lower rollers 
will suffice. However, in order to stably feed a double-slip in which a 
plurality of sheets are placed one over another, double-side drive for 
imparting a drive force to the upper and lower rollers is essential. This 
is because of the fact that in the one-side drive system, paper feed on 
the side in which no feed force is imparted is delayed, and therefore, a 
deviation between the upper and lower sheets occurs, causing a trouble in 
feed. 
In considering the paper feed in the feed mechanism, paper obtains a feed 
force from a feed roller owing to a frictional force. This force F is 
determined by the product of a coefficient of friction.mu. between paper 
and the roller and a pinching force P. In order to stably feed paper 
having a variety of thicknesses, it is necessary to weaken the pinching 
force P for a thin sheet of paper and gradually increase it as the 
thickness increases. In the prior art, this has been realized by using a 
mechanism described hereinbelow. 
One-Side Roller Shaft Movable System 
In this system, mounting of a roller on one side is made movable, and the 
roller is pressed by the force of a spring. The pinching force P is 
determined by a spring constant and a deviation amount of a spring (see 
FIG. 7). 
This system has the drawbacks as follows: Since the distance between upper 
and lower roller shafts is varied, it is necessary to use, for 
transmission of power, several timing belts or trains of gears, thus 
increasing the number of parts and thus increasing the cost accordingly. 
Intershaft (Upper and Lower) Fixed System 
In the case where there is a restriction in terms of cost, a soft elastic 
substance (such as soft rubber, sponge, etc.) is used for one-side roller, 
and a difference between thicknesses of paper is absorbed by a collapse of 
the roller whereby the roller shafts on both sides are fixed to simplify 
the construction. The pinching force P is determined by the elastic 
modulus of a roller and an amount of deviation of a roller (see FIG. 8). 
This system has the drawbacks as follows: In order to set a pinching force 
suitable for a thickness of paper, when a soft material is used to 
increase an amount of deviation, an amount of a collapse of a roller 
becomes excessively large so that a peripheral speed becomes changed, 
resulting in occurrences of a slip between the upper and lower rollers, an 
oblique feed of paper, etc., which should be most avoided. 
Further, particularly in a roller using a sponge, absorbency of ink is 
large, and when it is used for a printer, ink not dried completely after 
printing is transferred to the roller, which is further transferred to 
paper to stain the latter. 
These problems are directly related to the lowering in peformance of the 
machinery and the lowering in quality of print. The lower cost is charming 
for the machinery for aiming at a high quality. However, the intershaft 
fixed system has not been widely applied in terms of the restriction of 
the present roller material. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a paper feed roller 
capable of being used for delivering and feeding paper, which is high in 
coeffeicient of friction, has sufficient hardwearing properties with the 
coefficient of friction not affected by the change in environment of 
temperature and humidity, is low in ink transferability and is small in 
change in passage of year of the coefficient of friction of the surface. 
For achieving the aforementioned object, the present invention provides a 
paper feed roller in which a coating layer formed of an elastic material 
such as rubber is formed on an surface of a core material molded of a 
foamed material such as sponge, and a bonding agent having an elasticity 
such as denatured silicon is coated on the surface of the coating layer so 
that ceramic particles are fixed without clearance. 
Alternatively, a bonding agent having an elasticity such as denatured 
silicon is coated on a surface of a core material molded of a pliable 
material such as soft rubber, sponge, etc. so that ceramic particles are 
fixed without clearance.

DETAILED DESCRIPTION OF THE INVENTION 
The embodiments of the present invention will now be described with 
reference to the drawings. 
As shown in FIG. 1, a plurality of paper feed rollers 1 are fitted at 
predetermined intervals in an axial direction of a roller shaft 2, as 
shown in FIG. 1, for use as a roller mounting member 3. 
The paper feed roller 1 is formed with a coating layer 5 which is obtained 
by bonding an elastic material such as rubber to a surface of a core 
material 4, which in turn is obtained by polishing a foamed material such 
as sponge and being formed into a cylindrical shape after which it is 
polished to have a predetermined dimension, by means of an adhesive or the 
like, as shown in FIG. 2. Then, a bonding agent 6 having a viscoelasticity 
such as denatured silicon is coated on the surface of the coating layer 5, 
and ceramic particles 7 having 3 to 300 micro m of particle diameter are 
fixed by the bonding agent 6. 
In fixing the ceramic particles 7, the denatured silicon is first coated on 
the surface of the coating layer 5, and the ceramic particles 7 are 
adhered by their own weight or by pressing them and then set. In this step 
of process, the particles assume a state where about 15% of particle 
diameter is embedded. 
Subsequently, surplus ceramic particles 7 on the surface are removed, and 
after this, denatured silicon is further coated on the temporarily fixed 
ceramic particles 7. Then, the denatured slicon present in the top portion 
of the particles is removed before setting. In this step of process, the 
particles assume a state where about 60% of particle diameter is embedded. 
It is noted that denatured silicon is used as the bonding agent 6 because 
it has a strong contact strength with rubber constituting the coating 
layer 5. Alternatively, other suitable bonding agents can be used as long 
as they have a strong contact strength. 
The ceramic particles 7 are fixed by the bonding agent 6 having the 
viscoelasticity. Therefore, the indvidual ceramic particles 7 can behave 
freely to some extent despite the fact that the relatively large-diameter 
ceramic particles 7 are fixed on the surface of the core material 4 
without clearance. Even if the core material 4 is deformed, the ceramic 
particles 7 are never peeled off from the core material 4. 
In fixing the ceramic particles 7 to the surface of the core material 4, 
there is a contemplated method in which a ceramic layer or a ceramic 
dispersion layer 8 is formed by flame spray method as disclosed in 
Japanese Patent Laid-Open No. 61(1986)-23045. In this case, however, since 
the individual ceramic particles 7 cannot behave freely, when the core 
material 4 is deformed, a crack occurs in the ceramic layer or the ceramic 
dispersion layer 8, or the ceramic particles 7 are peeled off from the 
core material 4, as shown in FIG. 4. 
Since the coating layer 5 formed of an elastic material is formed on the 
surface of the core material 4, it is possible to realize the paper feed 
roller 1, which is high in accuracy in outside diameter and strong in the 
bonding force of the ceramic particles 7, by polishing the coating layer 
5. 
It is to be noted that the coating layer 5 may comprise a unfoamed skin 
layer (without being modified) formed in a portion in contact with the 
inner surface of a mold when a foamed material such as sponge is molded. 
Sharp ends of the ceramic particles 7 are bitten into paper to thereby 
obtain a feed force (which is equivalent to a coefficient of friction) 
enough to feed paper. Further, since the hardness of the ceramic particles 
7 is extremely high, the wear caused by paper is also extremely small. 
Further, if the extreme ends of the ceramic particles 7 are polished by 
diamond to thereby remove the sharp ends thereof, it is possible to 
minimize a damage to paper resulting from the slip between the paper feed 
roller 1 and the paper, to enhance the accuracy of outside diameter and to 
enhance the accuracy of feed. 
Alternatively, a paper feed roller 9 may be constructed such that as shown 
in FIG. 3, the bonding agent 6 having the viscoelasticity such as 
denatured silicon is directly coated on the surface of the core material 4 
obtained by polishing a pliable material such as soft rubber or sponge and 
forming it into a cylindrical shape, and the ceramic particles 7 having 3 
to 300 micro m of particle diameter are fixed by the bonding agent 6. 
However, this paper feed roller 9 is simple in construction but somewhat 
inferior in accuracy of outside diameter to that of the paper feed roller 
1 formed with the coating layer 5. The paper feed rollers are therefore 
suitably selected for use in consideration of the feed accuracy, the 
manufacturing cost and the like. 
Next, a case will be described where the paper feed roller 1 according to 
the present invention is applied to a paper feed device 10 of an 
inter-roller shaft fixed system. 
The paper feed device 10 uses, as shown in FIG. 5, the roller mounting 
member 3 having the paper feed roller 1 according to the present invention 
fitted in the roller shaft 2, and a roller mounting member 13 having a 
paper feed roller 11 made of rubber fitted in a roller shaft 12. 
The transmission of a drive force between the roller mounting member 3 and 
the roller mounting member 13 is achieved by direct engagement between a 
gear 14 secured to the roller shaft 2 and a gear 15 secured to the roller 
shaft 12. 
As shown in FIG. 5, a pulley 16 is secured to the other end of the roller 
shaft 12, and a belt 18 is extended over between the pulley 16 and an idle 
pulley 17. Further, a belt 19 is extended over between the idle pulley 17 
and a pulley (not shown) secured to a motor shaft to transmit the drive 
force of a motor 20. 
As shown in FIG. 6f since as the core material 4 for the paper feed roller 
1, a foamed material such as sponge is used, in the case where as shown in 
(A), a thin paper a is fed, the paper feed roller 1 is not much deformed, 
whereas in the case where as shown in (B), a thick paper a is fed, the 
paper feed roller 1 is greatly deformed so that an adequate pinching force 
F is imparted to the paper a by the repulsion caused by the deformation. 
The coating layer 5 is formed of unfoamed rubber, which is small in elastic 
modulus and the outer circumference thereof is hard to elongate. Thus, the 
force generated due to the deformation is consumed to compress the sponge 
which is the core material. Accordingly, the length of the outer 
circumference of the paper feed roller 1 remains unchanged and the paper 
feed accuracy is not lowered. 
Now, let us think of a rubber ring only for the coating layer 5 without 
sponge of the core material 4 as shown in FIG. 9. 
This rubber ring is hollow, and is very weak against the bending force, as 
shown in FIG. 9(A), since the coating layer 5 is thin, and the rubber ring 
becomes readily deformed. However, it is readily imaginable that an 
extremely great force is required to stretch the rubber ring to elongate 
the length of the outer circumference as shown in FIG. 9(B). Turning now 
back to FIG. 6(B), the deformation of the roller 1 is taken into 
consideration. The roller 1 is compressed by the thickness d of paper to 
generate the pinching force F. The roller 1 subjected to the pinching 
force F absorbs the force as a result that the length of the outer 
circumference of the coating layer 5 is not elongated and the core 
material 4 of the sponge is contracted. As just mentioned above, an object 
has properties that when the object receives a force from outside, it 
keeps balance in the state where a deformation energy within the object is 
minimum. 
Since the paper feed roller 1 has the ceramic particles 7 fixed to the 
surface thereof without clearance, the paper feed roller 1 is provided 
with the characteristics of ceramic materials, without modification, which 
are excellent in the hardwearing properties, chemicals resistance, 
change-in temperature and humidity resistance, change-after passage of 
time resistance, heat resistance, non-ink transferability, etc. 
The paper feed roller 1 further exhibits the cleaning effect such that dust 
or the like adhered to the surface of the paper feed roller 11 made of 
rubber is scraped off by the ceramic particles 7 fixed to the surface 
thereof without clearance. 
Since ceramic is inorganic, the change in temperature and the change after 
passage of year are not at all involved. The ceramic is not affected by 
chemicals (oils and fats) due to the characteristics thereof. Further, 
since the ceramic repels ink, the transfer of ink is also very less. 
The ceramic particles are fixed to the core material or to the surface of 
the coating layer formed on the surface of the core material by the 
bonding agent having the viscoelasticity whereby the paper feed roller as 
a whole is freely deformed and the ceramic particles are not peeled off 
from the core material. 
The paper feed roller 1 according to the present invention can be applied 
to the feeding of paper, notes, and various sheet-like members, and 
further can be applied as various feed rollers such as a paper feed 
roller, a paper ejection roller, etc. 
The above-described various properties are given in Table 1 comparing the 
paper feed roller 1 according to the present invention with the 
conventional paper feed roller. 
The properties given in Table 1 result from the execution of the life 
acceleration test under the following testing condtions: 
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*Testing Conditions 
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Environment Room temperature 
Printing device IBM9056 bankbook . form printing 
device 
Ink ribbon IBM 9056 dye ink 
Paper Bankbook (10 pages) 
Printing pattern 
See FIG. 10 
Paper feed amount 
70000 pages 
Dimension of roller 
.phi.16.79 .times. 12 .times. 6 (mm) 
(OD .times. Width .times. Shaft Dia.) 
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As a core material for a roller, a pliable material such as soft rubber or 
sponge is used, to the surface of which are fixed ceramic particles which 
function to feed paper, thereby making it possble to utilize various 
excellent properties of the ceramic as a paper feed roller, and being 
capable of solving all the problems involved in conventional rubber 
rollers and sponge rollers. 
According to the paper feed roller of the present invention, the 
hardwearing properties are high; no lowering of the coefficient of 
friction due to the change in temperature and humidity occurs; less 
adhesion of dust or the like occurs; the paper feed can be effected in a 
stable manner for a long period; the ink absorbency is low; and 
unnecessary ink is not transferred to paper. 
Furthermore, material and hardness for the core material are suitably 
selected to thereby impart a flexibility to the roller, and the hardness 
of the roller can be freely set without affecting on the coefficient of 
friction of the surface and others. 
By applying the paper feed roller according to the present invention, it is 
possible to effect the paper feed in a stable manner for a long period 
even in the intershaft fixed system and provide a paper feed device which 
is simple in mechanism and inexpensive. 
TABLE 1 
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CONVEN- FEED ROLLER 
TIONAL OF PRESENT 
PROPERTIES FEED ROLLER INVENTION 
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Coefficient of friction 
1.2 1.02 
(room temperature) 
Lowering rate of 
coefficient of 
friction 
Temperature -21% -6% 
and humidity 
(5.degree. C., 8%) 
Change after -80% -14% 
passage of 
year 
Chemicals Poor Good 
resistance 
Hardwearing rate 
5% or more 0% 
(volume rate) 
Ink transfer-ability 
Poor Excellent 
Accuracy of outside dia. 
.+-.0.20 mm .+-.0.10 mm 
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