Load skidding vehicle having a positionally biased grapple

A load skidding vehicle (10) comprising:

• a vehicle chassis (12);
• a boom (24) pivotally attached to said chassis (12) and extending rearwardly relative to said chassis (12);
• a fluid boom ram (44) pivotally connected to said boom (24) and to said chassis (12);
• a grapple assembly (28) including a grapple (50) having a pair of tongs (56), said grapple assembly (28) providing load grasping capability and being subjectable to skidding forces induced by said grasped loads during vehicle movement, said grapple assembly (28) being pivotally connected about a pivot axis (30) to said boom (24);
• means (32) for pivoting said grapple assembly (28) about said pivot axis (30) between a rearwardly extending position and a forwardly extending, skidding position, said grapple assembly pivoting means (32) having first and second positions which respectively correspond to said grapple assembly's rearwardly extending position and said skidding position, said pivoting means (32) including
• a fluid equalizing ram (36) constituting a cylinder (36b) and a piston (36a) displaceably disposed in said cylinder (36b), one of said piston (36a) and said cylinder (36b) being connected to said grapple assembly (28), the remaining one of said piston (36a) and cylinder (36b) being connected to one of said boom (24) and said chassis (12), said piston (36a) separating said cylinder (36b) into a first (36c) and a second (36d) fluid tight portion;
• selectively actuatable means (66,68,70,72,78,62',68') for biasing said grapple assembly pivoting means (32) toward said second position with a predetermined force, said biasing means (66,68,70,72,78,62',68') permitting movement of said grapple assembly pivoting means (32) away from said second position when the skidding force acting on said grapple assembly (28) about said pivot axis (30) is greater than said predetermined force, said biasing means (66,68,70,72,78,62',68') inducing movement of said grapple assembly pivoting means (32) toward said second position when the skidding force acting on said grapple assembly (28) is less than said predetermined force, said biasing means (66,68,70,72,78,62',68') including
• a fluid reservoir (66);
• means (68,68') for supplying pressurized fluid at a discharge pressure;
• means (70,72,62') for selectively providing fluid communication from said pressurized fluid supply means (68,68') to said first cylinder portion (36c);
• and
• means (78,62') for selectively providing fluid communication between said second cylinder portion (36d) and said reservoir (66) when fluid communication between said pressurized fluid supply means (68,68') and said first cylinder portion (36c) is provided;
• means (58) for moving said grapple tongs (56) between an open and a closed configuration, said tong moving means (58) having a first and a second configuration which respectively correspond to said open and closed configuration, said tong moving means (58) constituting
• a grapple cylinder (58b) and a grapple piston (58a) displaceably disposed in said grapple cylinder (58b), said grapple cylinder (58b) and grapple piston (58a) being connected to different grapple tongs (56), said grapple piston (58a) separating said grapple cylinder (58b) into a third (58c) and a fourth (58d) fluid tight portion;
• and
• means (74,96,64') for biasing said tong moving means (58) toward said second configuration, said tong moving means' biasing means (74,96,64') including
• means (74,64') for providing fluid communication between said pressurized fluid supply means (68,68') and said third cylinder portion (58c) and
• means (96,64') for providing fluid communication between said fourth cylinder portion (58d) and said reservoir (66).