Method and apparatus for locking a manhole cover

Abstract

A manhole cover lock includes a lock body which is mounted to the cover and a lock arm mounted for rotation relative to the lock body. The lock arm is mounted to a pin which is positioned in a passage through the lock body. The pin has a specially shaped head for engagement by a special tool. A nut is threaded onto a bottom end of the lock body at a bottom side of the cover. The lock arm can be rotated with the pin from an unlocked position to a locked position, the arm in the locked position rotated under or into engagement with a support or other structure which underlies the manhole cover. The lock arm is retained in its locked position by being biased upwardly to a position where tabs on the lock arm fit into a slot in the lock body.

1 . A locking device for use with a manhole cover comprising: 
 a lock body for mounting to a manhole cover, said lock body having a first end and a second end, said lock body having a passage there through and defining at least one slot at said second end thereof;    a pin having a first end and a second end, said pin defining a head at said first end;    a lock arm, said lock arm mounted to said pin at said second end of said pin and said lock arm located at said second end of said lock body when said lock arm is connected to said pin, said lock arm rotatable relative to said lock body, said lock arm including at least one outwardly extending tab for engagement with said at least one slot in said lock body; and    a spring positioned between said head of said pin and said lock body, whereby said pin is biased upwardly, causing said at least one tab of said lock arm to engage said at least one slot of said lock body when aligned therewith.    
   
   
       2 . The locking device in accordance with  claim 1  wherein said lock body has a threaded exterior portion at said second end thereof and including a nut for selectively engaging said threaded portion of said lock body.  
   
   
       3 . The locking device in accordance with  claim 1  wherein said lock body defines a cap at said first end thereof, said cap being generally cylindrical in shape and having a diameter which is greater than a diameter of a remaining portion of said lock body.  
   
   
       4 . The locking device in accordance with  claim 1  wherein said head of said pin is generally triangular in shape.  
   
   
       5 . The locking device in accordance with  claim 1  wherein said pin defines at least one slot at said second end of said pin and wherein said lock arm has at least one second tab extending therefrom which engages said at least one slot in said pin when said lock arm is mounted to said pin.  
   
   
       6 . A locking manhole cover comprising: 
 a generally circular manhole cover having a top side and a bottom side and a generally circular perimeter, said manhole cover having a passage there through; and    a cover lock connected to said manhole cover, said cover lock comprising:    a lock body, said lock body located at least partially within said passage through said manhole cover, a top end of said lock body located at said top side of said manhole cover and a bottom end of said lock body located at said lock body side of said manhole cover;    a pin located in a passage through said lock body, said pin having a head located at said top end of said lock body and accessible from said top side of said manhole cover; and    a lock arm connected to a bottom end of said pin opposite said head thereof, said lock arm located at said bottom end of said lock body at said bottom side of said manhole cover, said lock arm rotatable relative to said lock body between a first position and a second position.    
   
   
       7 . The locking manhole cover in accordance with  claim 6  wherein said lock body defines a cap at said top end thereof, said cap supported by said manhole cover and positioned in a portion of said manhole cover such that a top of said cap is generally flush with said top side of said manhole cover.  
   
   
       8 . The locking manhole cover in accordance with  claim 6  including a nut having threads engaging mating threads on an exterior of said lock body, said nut located on said lock body at said bottom side of said manhole cover.  
   
   
       9 . The locking manhole cover in accordance with  claim 6  wherein said lock body defines at least one slot in said bottom end thereof and where said lock arm includes at least one outwardly extending tab configured to engage said at least one slot when said lock arm is in said first position, and to not engage said at least one slot when said lock arm is in said second position.  
   
   
       10 . The locking manhole cover in accordance with  claim 6  wherein said head of said pin is generally triangular in shape.  
   
   
       11 . The locking manhole cover in accordance with  claim 6  wherein said pin defines a slot in said bottom end thereof and wherein said lock arm defines at least one outwardly extending tab which is positioned in said slot in said pin, preventing rotating of said lock arm relative to said pin when said lock arm is connected to said pin.  
   
   
       12 . The locking manhole cover in accordance with  claim 6  including means for biasing said pin upwardly relative to said lock body.  
   
   
       13 . A method of selectively locking a manhole cover to a frame comprising the steps of: 
 providing a cover with a cover lock, said cover having a top side and a bottom side and a generally circular perimeter, said cover having a passage there through and said cover lock comprising a lock body, said lock body located at least partially within said passage through said cover, a top end of said lock body located at said top side of said cover and a bottom end of said lock body located at said lock body side of said cover, a pin located in a passage through said lock body, said pin having a head located at said top end of said lock body and accessible from said top side of said cover, and a lock arm connected to a bottom end of said pin opposite said head thereof, said lock arm located at said bottom end of said lock body at said bottom side of said cover, said lock arm rotatable relative to said lock body between a first position and a second position;    locating said cover on a supporting structure, said supporting structure having at least one portion located under said cover which extends outwardly;    engaging said head of said pin with a tool;    rotating said pin from a first position to a second position, causing said lock arm to rotate from a first unlocked position to a second locked position in which at least a portion of said pin is located beneath said at least one outwardly extending portion of said supporting structure; and    permitting said lock arm to move upwardly into engagement with said lock body.    
   
   
       14 . The method in accordance with  claim 13  wherein said lock body has at least one slot located at a bottom thereof and said lock arm has at least one tab extending outwardly therefrom and said step of permitting said lock arm to move upwardly includes said at least one tab moving into said at least one slot.