Liquid-filled electrical circuit interrupter having a fluid pressure-resistant insulating coating

Claim 2

In an oil-filled cutout comprising an oil-confining metal container at least partially filled with arc-quenching oil, arcdeveloping means mounted in said container and electric circuit means connected to supply electric power to said arc-developing means, the improvement comprising a coating of insulating material of predetermined thickness bonded to an inner surface of said container adjacent the arc-developing means to insulate the container from an arc developed by said arc-developing means, said coating being prevented by its bonding with the container from moving relative to said container responsive to rapid movement of oil therein, said coating of insulating material being formed of a heat-cured epoxy resin that is resistent to water absorption, said predetermined thickness exceeding 4 mils over substantially the entire area thereof, and said coating being formed of a Composition that has its insulating properties improved by being subjected to repeated contact by electric arcs and the effect of very high liquid pressures being created on the coating surface by said rapid movement of oil responsive to arcs being formed in the container, whereby the dielectric capability of the coating is improved during normal operation of the cutout.

Claim 3

A device as defined in claim 1 wherein said container comprises a cup-shaped body portion and an end cap member secured in position on said body portion to seal it, and wherein said inner surface said container coated by said coating of insulating material comprises substantially all of the inner walls of said cup-shaped body portion of the container.

Claim 4

The invention defined in claim 1 wherein said coating of insulating material is bonded directly to said container, and said predetermined thickness is in a range from 4 to 50 mils over substantially the entire area thereof.

Claim 5

The invention defined in claim 2, including a preformed member of organic insulating material mounted over the inner bottom surface of said cup-shaped portion above said coating, thereby to further insulate said bottom surface from an arc formed by said arc-developing means.

Claim 6

An oil-filled electric circuit interrupter comprising a hollow metal housing, an arc-developing circuit interrupting means operably mounted in said housing, said interrupting means being operable to develop an arc adjacent an inner surface of said housing thereby to suddenly generate a substantial volume of gas and cause oil to move rapidly at very high liquid pressures along said surface of said housing, a coating of insulating material bonded to said surface to insulate it from such an arc, said coating being formed of a composition of matter comprising; an epoxy resin comprising the reaction product of a polyhydric phenol and an epihalohydrin, a polyvinyl acetal resin and a polyacrylate resin selected from the group consisting of homopolymers and copolymers of esters selected from the group consisting of methylacrylate, methylmethacrylate ethylacrylate, ethylmethacrylate, butylacrylate, isobutylacrylate, butylmethacrylate and isobutylmethacrylate, whereby the dielectric capability of the coating is improved during normal operation of the cutout due to the improvement of the insulating properties thereof resulting from the coating being subjected to burning contact with electric arcs developed by said circuit and the effect of very high liquid pressures being created on the coating surface by said rapid movement of oil responsive to arcs being formed in the container.

Claim 7

An oil-filled electric circuit interrupter comprising a hollow metal housing, an arc-developing circuit interrupting means operably mounted in said housing, said interrupting means being operable to develop an arc adjacent an inner surface of said housing thereby to suddenly generate a substantial volume of gas and cause oil to move rapidly at very high liquid pressures along said surface of said housing, a coating of insulating material bonded to said surface to insulate it from such an arc, said coating being formed of a composition of matter comprising; an epoxy resin comprising the reaction product of a polyhydric phenol and an epihalohydrin, a polyvinyl acetal resin and a polyacrylate resin selected from the group consisting of homopolymers and copolymers of esters selected from the group consisting of methylacrylate, methylmethacrylate ethylacrylate, ethylmethacrylate, butylacrylate, isobutylacrylate, butylmethacrylate and isobutylmethacrylate, whereby the dielectric capability of the coating is improved during normal operation of the cutout due to the improvement of the insulating properties thereof resulting from the coating being subjected to burning contact with electric arcs developed by said circuit and the effect of very high liquid pressures being created on the coating surface by said rapid movement of oil responsive to arcs being formed in the container.