Casing construction for pole type dielectric containing transformer

In an improved overhead pole mounting type of electrical distribution transformer construction, a metal casing defining an operating chamber therein and being of generally hollow cylindrical shape, an oil-immersed transformer within said casing having high voltage input electric leads thereto and having low voltage output leads extending therefrom, a current limiting fuse connected within the high voltage input leads and adapted to cut-off electrical current flow to said transformer after a fault occurs, said transformer casing having securely sealed closing-off top and botton end walls of outwardly curved shape, said top end wall having a substantially circular combined pressure relief and maintenance open portion therethrough, a circumferential seating flange about said open portion, and a pressure-sensitive relief cover assembly adapted to normally close-off said open portion;

• said cover assembly comprising:
• an operating stem having handle means at its upper end and a threaded end portion at its lower end, a domed cover member loosely positioned on said stem, spring and clamping means positioned on said stem and adapted to be tilted for insertion through said open portion and to then be turned to an upright position at which said clamping means extends across the maintenance opening for engagement with the underside of said seating flange, a nut carried on said threaded end portion and retained by said spring and clamping means in a non-rotatable position on said stem and with respect to said seating flange, said spring means being positioned between said nut and said clamping means, whereby manual turning of said handle means will rotate said stem with respect to said nut to, in one direction, apply increasing cover member closing force on said spring and clamping means, and to, in an opposite direction, relieve the application of closing force on and to loosely position said cover members with respect to said stem.

In an improved overhead transformer enclosure construction, a hollow cylindrical casing of metal construction having an outwardly convexly shaped integral enclosing bottom end wall and an outwardly convexly shaped upper end wall integrally secured thereon, said upper end wall having a substantially circular fluid pressure fluid relief and maintenance open portion therethrough and defined by an upwardly offset seating flange thereabout of angular shape, a pressure relief hand-hole cover member for said open portion of outwardly convex shape, said cover member having an angular-shaped sealing flange thereabout, a ring gasket operatively positioned for sealing engagement between said seating and said sealing flanges, an operating stem extending rotatably centrally through said cover member and having an outer handle portion and an inner threaded end portion, a corss-extending clamping member carried substantially centrally on said stem and adapted to extend therefrom to latch-engage an under-portion of said seating flange, a retention bracket member having a nut secured thereon engaging the threaded end portion of said stem, Belleville washer means carried on said stem between said clamping and bracket members, said retention bracket member cooperating with said clamping member to prevent rotation of said nut on said stem, said handle portion being adapted to turn the threaded portion of said stem within said nut and advance said nut upwardly to compress said washer means against said clamping member and secure said cover member in a sealing-off position with respect to the open portion, whereby said cover member will be forced substantially uniformly upwardly to an open position when fluid pressure within said casing becomes greater than the force exerted by said washer means.