Core Member for Platen Roll

The present invention relates to a core member of a platen roll used for an office printer, copier, typewriter, etc.

Recently, along with the development of a hard aluminum alloy and progress in the art of extrusion forming this aluminum alloy, a platen roll having light weight and a high degree of core accuracy can be produced. As an example, such a platen roll is disclosed in U.S. Pat. No. 4,453,848. This platen roll comprises, as shown in FIG. 1 and FIG. 2, a platen roll core member 1 formed by extruding a hard aluminum alloy and a rubber cover layer 2 which is placed over an external circumferential surface of the core member 1, and the shape of the platen roll core member 1 is formed such that it has an axle part 1a, an external tube part 1b and three radially extending webs 1c which connect the external tube part 1b and the axle part 1a, wherein the external tube part 1b and the webs 1c at opposite ends of the core member 1 are cut and removed, further the exposed axle part 1a and each opposite end is fabricated by cutting to form an assembly axle part 2, thus making a platen roll shown in the drawing. A platen roll core member 1 having such a structure with its external tube part 1b, the axle part 1a and the webs 1c formed integrally by an extrusion forming process, has an advantage in the accuracy is enhanced yet the weight thereof can be reduced since it is made of a hard aluminum alloy, but it has the following drawback on the other hand. That is, there is a structural drawback in that a platen roll using this platen roll core member 1 produced noise due to a striking sound from impact on a surface of the platen roll which echoes within an internal hollow part of the platen roll core member 1.

The present invention overcomes the above-mentioned drawback by preventing the noise caused by striking, and further, the platen roll core member can be formed by sintering materials such as alumina, etc., or it can be made of synthetic resin, and compound material comprising synthetic resin and carbon fiber, etc. which when used as the raw materials in place of the aluminum alloy, reduces the cost of the platen roll core member. The core member according to the present invention comprises an axle part, an external tube part concentrically formed with the axle part, and webs which integrate the axle part and the external tube part, and further, a plurality of projections are provided extending in the axial direction on either or both of an external circumferential surface of the axle part and an internal circumferential surface of the external tube part.

FIG. 1 shows part of a conventional platen roll structure.

FIG. 2 shows a cross section of the platen roll shown in FIG. 1.

FIG. 3 is a plan view showing an embodiment of a core member of a platen roll according to the present invention.

FIG. 4 is a cross-sectional view taken along the line A`A of FIG. 3.

FIGS. 5, 6, 7(a) and 7(b) are cross-sectional views showing different embodiments of the core members of the platen rolls according to the present invention.

Now, the present invention will be explained in detail with reference to the embodiments shown in FIGS. 3 to 7.

FIG. 3 is a plan view showing an embodiment of a platen roll core member according to the present invention. Figs. 4 to 7 show several embodiments of cross-sectional views of platen roll core members of the present invention, wherein a platen roll core member 10 is formed by extruding suitable sintering materials, such as alumina, etc., thus forming a core body 11 of a tubular shape having air spaces therein which are open at opposite ends thereof, and after molding assembling axle parts 12, 12 at opposite ends thereof the structure is completed by sintering.

All of the platen roll core members 10 are integrally formed in such a manner that their core bodies 11 comprise axle parts 13 of generally cylindrical shape and extending in an axial direction, each having an axially extending hole 13a, external tube parts 14 of tubular shape coaxially disposed around the axle parts 13 such that a radially inner surface of the external tube part is spaced from a radially outer surface of the axle part, and a plurality of radially extending webs 15 which extend between the inner surface of the external tube part 14 and the outer surface of the axle part 13 at three evenly spaced angular positions. The platen roll core member 11 according to the first embodiment shown in FIG. 4, includes sound dampening means comprising a plurality of projections 16 each of which is formed by at least one surface extending rectilinearly in the axial direction, such as by three surfaces forming a trapezoidal cross-sectional shape taken in a plane which is perpendicular to the axial direction and each being integrally formed on the radially inner circumferential surface of the external tube part 14, the projections 16 being uniformly spaced in the circumferential direction and having a radially innermost part thereof spaced from the outer surface of the axle part.

In a second embodiment, as shown in FIG. 5, in addition to the projections 16 the sound dampening means further includes projections 17 each having a V-shape formed by two surfaces extending rectilinearly in the axial direction and which are integrally formed on the radially outer circumferential surface of the axle part 13, the projections 17 being uniformly spaced in the circumferential direction and having a radially outermost part thereof spaced from the inner surface of the external tube part.

A third embodiment is shown in FIG. 6 wherein the above-mentioned projections 16 of a trapezoidal cross-sectional shape are replaced with projections having a V-shape, and also the projections 17 of the V-shape are replaced with semi-circular projections, each of which is formed by one surface extending rectilinearly in the axial direction. Thus, the above-mentioned projections 16 and 17 are not limited to these particular shapes. Also, as shown in FIGS. 7(a) and 7(b), fins 18 may be integrally provided on the webs 15. As shown in FIG. 7(a) each of the fins 18 has a flat surface facing the axle part 13 and a semi-circular surface facing the external tube part 14, whereas the fins 18 shown in FIG. 7(b) each include a pair of first linear portions extending perpendicularly from the webs and second linear portions, each extending perpendicularly from the first linear portions in a direction towards the axle part 13.

As has been explained above, according to the present invention, the platen roll core member body 11 has sound dampening means comprising a plurality of projections formed by at least one surface extending rectilinearly in the axial direction and integrally formed at either or both the external surface of the axle part 13 and the internal surface of the external tube part 14, whereby striking sounds generated as the platen roll core member is struck from outside make irregular reflections within a cavity of the core member 10 by the above-mentioned projections, thus being absorbed or damped. In addition, when fins 18 are provided on the webs 15 as shown in FIG. 7, the irregular reflections of the striking sounds increase, thus further improving the sound preventing effect, and furthermore when the core member 10 is formed from a porous sintering material, the sound preventing effect is still further improved.

Thus, the platen roll core member 10 can be formed using such sintering materials such as alumina, etc., and after the assembling axle parts 12, 12 are integrally formed at both ends of the core member body 11, the core member is completed by sintering. Since secondary fabrication such as cutting, etc., becomes unnecessary, the invention achieves the effect of reducing cost in production of the platen roll core member.

While the core member body 11 and the assembling axle parts 12, 12 are integrally formed in the above-mentioned embodiment, an assembling axle part 12 which is formed of steel or aluminum, etc., may be inserted into both ends of a core member body 11 after the body 11 is sintered.

Also, the core member 10 of the above-mentioned embodiment may be made by using sintering materials such as alumina, etc., as the raw material thereof which produces a sound damping effect from the material itself while reducing a unit cost of production. However, a synthetic resin such as polyacetal, polycarbonate, polymide, fluororesin, etc., may be used instead for forming the platen roll core member by injection molding, etc., or the platen roll core member may be formed from a composite or compound material which combines these synthetic resins with a reinforcing material such as metallic fiber, carbon fiber, etc.

Therefore, according to the present invention, since striking sounds generated as the core member of the platen roll is struck from outside are damped by the projections, a sound prevention effect as a result of absorbing sound or damping sound can be obtained.

Also, since inexpensive sintering material, synthetic resin or a compound material combining synthetic resin and reinforming material can be used as the raw material for a core member, it is possible to reduce the cost of the product.