Patent ID: 6350081
Filing Date: 2002-02-26
Classification: E02D

Abstract:
A manhole restraining system set below pavement of a street and used in conjunction with a manhole for venting out explosive gases in the manhole, the system comprising:a. a generally rectangular shaped main support frame having a central opening, an annular flange collar surrounding the central opening and extending downwardly therefrom, and three pairs of spaced apart mounting apertures extending therethrough and located on each opposite side of the central opening, the main support frame being positioned over said manhole such that said central opening is aligned with said manhole; b. a generally rectangular shaped plate member having a central opening, and three pairs of spaced apart mounting apertures extending therethrough and located on each opposite side of the central opening, the plate member positioned on top of said support frame such that the central opening and the three pairs of mounting apertures are respectively aligned with said central opening and said three pairs of mounting apertures of said support frame; c. an annular angle flange positioned and secured to said plate member and surrounding said central opening; d. a manhole cover seated and secured to said annular angle flange and sized to cover said central openings of said support frame and said plate member leading to said manhole; e. a plurality of restraining assemblies, each having an elongated rod, an upper slidable stop plate, a coil spring, a lower fixed support plate and a nut; f. said elongated rod of said each restraining assembly having a head portion and a shaft portion, the shaft portion respectively inserted through said each aperture of said plate member and said support frame such that said head portion abuts against an upper surface of said plate member and said shaft portion extends through a horizontal concrete base ledge of said manhole; g. said nut of said each restraining assembly respectively and threadedly engaged with said elongated rod and secured thereto; h. said lower fixed support plate of said each restraining assembly positioned around said elongated rod and secured to said nut; i. said coil spring of said each restraining assembly surrounding a lowermost part of said rod; j. said upper slidable stop plate of said each restraining assembly secured on top of said coil spring and around said elongated rod; and k. means for allowing said rod of said each restraining assembly to move smoothly up and down without any friction; l. whereby when an explosion occurs in said manhole, the pressure caused by the explosion lifts said plate member away from said support frame which in turn moves said rod of said each restraining assembly upwardly such that said upper slidable stop plate of said each restraining assembly strikes against the bottom of said horizontal concrete base ledge, where said coil spring of said each restraining assembly is compressed such that said plate member is lifted upwardly to a limited predetermined distance to form a gap between said plate member and said support frame to allow the explosive gases to escape from said manhole, and after all of the explosive gases have escaped, said coil spring of said each restraining assembly is uncompressed forcing down said plate member to said support frame back into alignment with said manhole.