Compositions – Electrically conductive or emissive compositions – Elemental carbon containing
Reexamination Certificate
2000-03-29
2001-02-06
Kopec, Mark (Department: 1754)
Compositions
Electrically conductive or emissive compositions
Elemental carbon containing
C428S312800, C033S023010
Reexamination Certificate
active
06183667
ABSTRACT:
This invention relates to a titanium- and copper-containing carbon composite material and to a process for the production thereof.
A current collection installation mounted on a locomotive roof for supplying electric current to the locomotive on a track from an overhead conductor extending along the track is called pantograph.
FIG. 1
schematically depicts such a pantograph generally designated as
500
. The pantograph
500
has a base
506
secured to insulators
507
on a locomotive roof (not shown) for supporting a frame
509
thereon. The frame
509
has a lower pantograph arm
501
pivoted obliquely upward about a horizonal shaft
508
rotatably received in bearings and an upper pantograph arm
502
pivoted obliquely downward about a shaft (not shown) received in bearings. The upper and lower arms
501
and
502
are pivotally connected to each other. Secured to an apex portion of the upper arm
501
are bows
503
to which sliding plates
504
are fixed by, for example, screws. Designated as
505
is a spring operatively connected to the shaft
508
for urging the shaft
508
to rotate in a direction so that the sliding plates
504
on the bows
503
are maintained in contact with an overhead conductor (not shown) generally made of hard-drawn copper. Thus, the pantograph
500
collects electric power from the overhead conductor by sliding contact of the sliding plates
504
therewith.
Such a sliding plate
504
is required to be made of a material having the following characteristics:
(1) good electrical conductivity;
(2) low frictional resistance;
(3) high wearing resistance;
(4) small tendency to cause wearing of overhead conductor;
(5) high toughness;
(6) high resistance to arc.
With a view toward obtaining a sliding plate which meets with the above criteria, JP-A-H7-126713 proposes a sliding plate made of a shaped body of a carbon fiber-reinforced carbon composite (C/C composite) in which copper is impregnated. The production of the Cu-containing C/C composite body is carried out in an impregnation furnace maintained under a pressure of 2 torr by immersing a carbon shaped body in a melt of oxygen-free copper at 1,150° C. or more while applying a pressure of 130 atm thereto. This process must use a large apparatus and a long process time and, therefore, has a problem that the productivity is low and production costs are high. The Cu-containing C/C composite body has an additional problem because the mechanical strengths such as toughness is unsatisfactory. Thus, a sliding plate made of the Cu-containing C/C composite is apt to be broken when the thickness thereof is reduced during use.
SUMMARY OF THE INVENTION
It is, therefore, the prime object of the present invention to provide a composite material which meets with the above-described requirements and which is suitable for use as a sliding plate for a pantograph.
Another object of the present invention is to provide a composite material which is devoid of the drawbacks of the conventional technique.
It is a further object of the present invention to provide a composite material which has good electrical conductivity, low frictional resistance and high mechanical strengths, which is light in weight and which can be produced by a simple process.
It is yet a further object of the present invention to provide an economical process for producing a composite material.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a composite material comprising:
a carbon matrix, and
a titanium-copper alloy dispersed in said carbon matrix and containing 1-80% by weight of titanium and 14-99% by weight of copper, said titanium-copper alloy being present in an amount of 2-85% based on a total weight of said carbon matrix and said titanium-copper alloy.
In another aspect, the present invention provides a process for the preparation of a composite material, comprising the steps of:
(a) forming a shaped body of a carbon; and
(b) impregnating said shaped body with a melt of titanium and with a melt of copper or a copper alloy.
The present invention also provides a process for the preparation of a composite material, comprising the steps of:
(a) forming a shaped body of a carbon in which metal components including titanium and copper are dispersed, and
(b) heating said shaped body at a temperature sufficient to melt said metal components.
The present invention further provides a process for the preparation of a composite material, comprising the steps of:
(a) forming a shaped body of a carbon in which titanium is dispersed, and
(b) impregnating said shaped body with a melt of copper or a copper alloy.
The present invention further provides a process for the preparation of a composite material, comprising the steps of:
(a) providing a preformed yarn comprising a core of a multiplicity of carbon fibers, fine powders of carbon and titanium provided in interstices between said fibers, and a flexible sleeve of a thermoplastic resin surrounding said core;
(b) forming said yarn into a shaped body;
(c) incorporating copper or a copper alloy into said shaped body; and
(d) heating said shaped body so that said titanium forms an alloy with said copper or said copper alloy.
The present invention further provides a pantograph for collecting electric current from a conductor and supplying the electric current to a vehicle, comprising a frame secured to the vehicle, and a contact member supported by a frame for sliding contact with the conductor, said contact member being formed of the above composite material.
It has been found poor wettability of carbon with a melt of copper is ascribed to the difficulty in impregnating the C/C composite with copper and unsatisfactory toughness of the Cu-containing C/C composite in the above-described known technique. More particularly, carbon is not wetted with but repels a melted copper. Thus, when a melted copper is impregnated into voids, pores or interstices of a shaped carbon body, the melted copper does not coat the carbon walls but forms droplets or spheres therein. Upon solidification by cooling, the copper particles are not tightly bound by or bonded to the carbon walls but are present in a free state. Moreover, the copper is not uniformly distributed in the carbon shaped body. Therefore, it is necessary to apply a high pressure of more than 100 atm in order to uniformly impregnate the carbon body with melted copper. The Cu-containing C/C composite thus obtained by forcibly impregnating the carbon body with melted copper is still low in mechanical strengths.
When copper is used in conjunction with titanium, on the other hand, wettability of carbon with copper is much improved. As a result, a carbon shaped body is easily impregnated with melted copper uniformly. The melted copper and titanium form an alloy and are tightly bound to carbon walls, so that the Ti- and Cu-containing C/C composite material has excellent physical properties such as high mechanical strengths.
The term “wettability” herein may be expressed in terms of contact angle between a liquid and a solid. When the contact angle is acute, the wettability is good and the solid (carbon) is well wetted with the liquid (melted copper and titanium). The liquid contacts well with the solid surface and is widely spread thereon. On the other hand, when the contact angle is obtuse, the wettability is not good.
REFERENCES:
patent: 3869259 (1975-03-01), Lindsey
patent: 4772502 (1988-09-01), Okura et al.
patent: 5206085 (1993-04-01), Nakagawa et al.
patent: 6059847 (2000-05-01), Farahmandi et al.
patent: 01270512 (1989-10-01), None
patent: 01270571 (1989-10-01), None
Ikeuchi Jitsuji
Kubo Shun-ichi
Morita Yoshinobu
Nakagawa Takao
Saito Kojiro
Kopec Mark
Lorusso & Loud
Railway Technical Research Institute
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