Patent ID: 7337499

Claim:
A knuckle arm adapted to be connected to a machine body and a top cover of a machine, said knuckle arm comprising: a base including a mounting plate adapted to be disposed fixedly on the machine body, and two pivot plates extending respectively from two opposite sides of said mounting plate, each of said pivot plates being formed with a pivot hole; a pivot seat including two wing plates located respectively to two opposite sides of an assembly of said pivot plates of said base, and a connecting plate interconnecting said wing plates of said pivot seat and adapted to be attached to the top cover of the machine, each of said wing plates of said pivot seat being formed with a first pivot hole; a first pivot rod extending through said pivot holes in said pivot plates of said base and said first pivot holes in said wing plates of said pivot seat so as to allow for pivoting of said pivot seat about said first pivot rod; a biasing unit disposed between said base and said pivot seat so as to bias said pivot seat to pivot upwardly about said first pivot rod; and a friction assembly disposed between said pivot seat and said base so as to impart a resistance to pivoting of said pivot seat about said first pivot rod, thereby maintaining said pivot seat at any position, wherein each of said pivot plates of said base is formed with a curved guide slot, each of said wing plates of said pivot seat being formed with a through hole, said frictional assembly including a frictional block disposed fixedly on said base and having a frictional surface, and a frictional rod extending through said through holes in said wing plates of said pivot seat and said curved guide slots in said pivot plates of said base and movable to press against said frictional surface of said frictional block.