Safety device for a cantilevered beam and boom assembly incorporating the same

Abstract

A safety device ( 100, 200, 300, 400, 500, 600 ) for a cantilevered beam ( 86 ) pivotally mounted adjacent one end thereof to a support surface is adapted to bridge the beam and the support surface ( 84 ) and is structured so that when coupled to the beam and support surface, the safety device maintains the beam in a substantially fixed cantilevered condition until a downward force exceeding a threshold is applied to the beam and thereafter controls downward pivoting of the beam.

1 . A safety device for a cantilevered beam pivotally mounted adjacent one end thereof to a support surface, said safety device being adapted to bridge said beam and said support surface and being structured so that when coupled to said beam and support surface, said safety device maintains said beam in a substantially fixed cantilevered condition until a downward force exceeding a threshold is applied to said beam and thereafter controls downward pivoting of said beam. 
     
     
         2 . A safety device according to  claim 1  wherein said safety device comprises first structure to maintain said beam in said substantially fixed cantilevered condition and second structure to control downward pivoting of said beam. 
     
     
         3 . A safety device according to  claim 2  wherein said first structure is physically altered when a downward force exceeding said threshold is applied to said beam. 
     
     
         4 . A safety device according to  claim 3  wherein said first structure is at least one elongate link. 
     
     
         5 . A safety device according to  claim 4  wherein said at least one elongate link breaks when a downward force exceeding said threshold is applied to said beam. 
     
     
         6 . A safety device according to  claim 4  wherein said at least one elongate link stretches to a point of non-recovery when a downward force exceeding said threshold is applied to said beam. 
     
     
         7 . A safety device according to  claim 5  wherein said at least one elongate link has a region of weakness formed along its length. 
     
     
         8 . A safety device according to  claim 7  wherein said region of weakness is a region of reduced dimension. 
     
     
         9 . A safety device according to  claim 5  wherein said second structure comprises at least one beam-pivoting resisting element. 
     
     
         10 . A safety device according to  claim 9  wherein said at least one beam-pivoting resisting element is selected from (i) at least one chain-link element, (ii) at least one spring element, and (iii) at least one dashpot. 
     
     
         11 . A safety device according to  claim 10  comprising a plurality of beam-pivoting resisting elements. 
     
     
         12 . A safety device according to  claim 10  wherein said beam-pivoting resisting elements comprise a combination of at least two of (i) a chain-link element, (ii) a spring element, and (iii) a dashpot. 
     
     
         13 . A safety device according to  claim 10  further comprising a plurality of elongate links. 
     
     
         14 . A safety device according to  claim 1  wherein said safety device is a metal strap comprising said first and second structure. 
     
     
         15 . A safety device according to  claim 14  wherein said first structure is at least one elongate link and said second structure is at least one beam-pivoting resisting element. 
     
     
         16 . A safety device according to  claim 15  wherein said at least one elongate link has a region of weakness formed along its length. 
     
     
         17 . A safety device according to  claim 16  wherein said region of weakness is a region of reduced dimension. 
     
     
         18 . A safety device according to  claim 15  wherein said at least one beam-pivoting resisting element is selected from (i) at least one chain-link element, (ii) at least one spring element, and (iii) at least one dashpot. 
     
     
         19 . A safety device according to  claim 18  comprising a plurality of beam-pivoting resisting elements. 
     
     
         20 . A safety device according to  claim 1  wherein said first structure comprises a shear pin and retainer assembly. 
     
     
         21 . A safety device according to  claim 20  wherein said second structure comprises at least one beam-pivoting resisting element selected from (i) at least one chain-link element, (ii) at least one spring element, and (iii) at least one dashpot. 
     
     
         22 . A safety device according to  claim 21  comprising a plurality of beam-pivoting resisting elements. 
     
     
         23 . A safety device according to  claim 22  wherein said beam-pivoting resisting elements comprise a combination of at least two of (i) a chain-link element, (ii) a spring element, and (iii) a dashpot. 
     
     
         24 . A boom assembly comprising:
 a boom pivotally coupled adjacent one end to a support surface; and   a safety device acting between said boom and said support surface, said safety device maintaining said boom in a substantially horizontal orientation but failing when a downward force exceeding a threshold is applied to said boom thereby to permit said boom to pivot downwardly, after failure said safety device controlling downward pivoting of said boom.   
     
     
         25 . A boom assembly according to  claim 24  wherein said safety device comprises first structure coupling said boom and support surface that is physically altered when subjected to a downward force exceeding said threshold and second structure coupling said boom and support surface that controls downward pivoting of said boom. 
     
     
         26 . A boom assembly according to  claim 25  wherein said first structure breaks when subjected to the downward force exceeding said threshold. 
     
     
         27 . A boom assembly according to  claim 26  wherein said first structure and second structure are integrally formed on a strap extending between and secured to said boom and support surface. 
     
     
         28 . A boom assembly according to  claim 27  further comprising a mounting bracket to which the one end of said boom is pivotally coupled, said mounting bracket being fastened to said support surface. 
     
     
         29 . A boom assembly according to  claim 28  wherein said strap is fastened adjacent one end thereof to said boom and adjacent an opposite end thereof to said mounting bracket. 
     
     
         30 . A boom assembly according to  claim 29  wherein said first structure comprises at least one elongate link having a region of weakness thereon and wherein said second structure comprises at least one beam-pivoting resisting element. 
     
     
         31 . A boom assembly according to  claim 30  wherein said at least one beam-pivoting resisting element is selected from (i) at least one chain-link element, (ii) at least one spring element, and (iii) at least one dashpot. 
     
     
         32 . A boom assembly according to  claim 31  comprising a plurality of beam-pivoting resisting elements. 
     
     
         33 . A boom assembly according to  claim 29  wherein said first structure comprises a shear pin and retainer assembly and wherein said second structure comprises at least one beam-pivoting resisting element. 
     
     
         34 . A boom assembly according to  claim 33  wherein said at least one beam-pivoting resisting element is selected from (i) at least one chain-link element, (ii) at least one spring element, and (iii) at least one dashpot. 
     
     
         35 . A boom assembly according to  claim 34  comprising a plurality of beam-pivoting resisting elements. 
     
     
         36 . A boom assembly according to  claim 26  further comprising a mounting bracket to which the one end of said boom is pivotally coupled, said mounting bracket being fastened to said support surface. 
     
     
         37 . A boom assembly according to  claim 36  wherein said first structure comprises a shear pin and retainer assembly coupling said boom and mounting bracket. 
     
     
         38 . A boom assembly according to  claim 37  wherein said shear pin is affixed to said boom and said retainer is affixed to said mounting bracket. 
     
     
         39 . A boom assembly according to  claim 38  wherein said second structure is at least one dashpot coupling said boom and mounting bracket. 
     
     
         40 . A boom assembly according to  claim 38  wherein said second structure is at least one spring element coupling said boom and mounting bracket. 
     
     
         41 . A boom assembly according to  claim 36  wherein said first structure comprises a rotatable spool and tether arrangement coupling said mounting bracket and boom, said spool being inhibited from rotation prior to failure of said safety device. 
     
     
         42 . A boom assembly according to  claim 41  wherein said spool is locked by a retaining pin that fails when a downward force exceeding the threshold is applied to the boom. 
     
     
         43 . A boom assembly according to  claim 42  wherein said spool is mounted on said mounting bracket, said tether being wound about said spool and affixed adjacent one end thereof to said boom. 
     
     
         44 . A boom assembly according to  claim 43  wherein said second structure is a brake acting on said spool.