| 摘要 |
A limited release manhole cover locking arrangement for a manhole cover normally fit into a manhole opening above a manhole vault including a fixed frame beneath said manhole 5 opening comprising: a slide mounted to said manhole cover and having an end disposed beneath said manhole cover adjacent a perimeter of said manhole cover, said slide selectively movable to extend said end thereof radially outward so as to be engageable with said fixed frame upon a predetermined extent of upward movement of said manhole cover so as to prevent complete 10 removal of said manhole cover from said fixed frame and manhole opening; one or more lugs mounted to the underside of said manhole cover, each including an end normally extending radially out from said manhole perimeter with said manhole cover in position over said manhole opening; a vertical clearance space between said fixed frame and said end of said slide and each 15 of said lugs to allow said limited extent of vertical movement of said manhole cover until said end of said slide and said respective ends of said lugs engages said fixed frame to thereby create a gas venting gap around said manhole cover in the event of an explosion and rising of said manhole cover out of said manhole opening to a limited extent; said slide also movable so as to move said end thereof radially inward sufficiently to clear said 20 fixed frame and allow complete removal of said manhole cover from said frame and manhole opening by lifting said manhole cover out of said manhole opening. 4175683_1 (GHMatters) P80757.AU.1 9/04/13 WO 2007/146256 PCT/US2007/013731 14 16 is10 30 32 18 F/G.d 20 *28 FIG. i32 |
