Locking mechanism for the support arm elbow of a selectively adjustable multipurpose support stand

A locking mechanism for an elbow swivel joint of a support arm for selectively locking a lower arm section and an upper arm section of said support arm relative to each other, said lower arm section having a swivel head disposed between corresponding end flanges of said upper arm section, said swivel head and said corresponding end flanges hinged about a common hinge member threaded through centrally-located coplanar screw holes respectively in said swivel head and said corresponding end flanges, said locking mechanism comprising:

• at least one spring-biased locking pin disposed in at least one corresponding open-ended guide channel in said at least one corresponding end flanges of said upper arm section;
• a plurality of corresponding locking pin receiving notches on the engagement surface of said swivel head of said lower arm section abutting said end flanges of said upper arm section and in registry with said at least one spring-biased locking pin, said corresponding locking pin receiving notches adapted to receive said at least one spring-biased locking pin in mating relationship;
• and,
• locking means for releasably forcing said at least one spring-biased locking pin into locking relationship with said plurality of corresponding locking pin receiving notches, wherein a guide plate with a central hole for said common hinge member is fixedly attached to an exposed side of said end flanges of said upper arm section, said guide plate having at least one corresponding guide hole for receiving said at least one spring-biased locking pin,
• said elbow swivel joint having a ratchet adjustment mechanism, comprising:
• a plurality of ratchet recesses on said engagement surface of said swivel head of said lower arm section;
• at least one ratchet ball bearing occupying said ratchet recesses, said ratchet recesses being made so that said at least one ratchet ball bearing is able to shift to an adjacent ratchet recess when said lower arm section and said upper arm section of said support arm pivotally move relative to each other;
• and,
• at least one ratchet spring corresponding to said at least one ratchet ball bearing and biased there against, said at least one ratchet spring located in a corresponding ratchet spring channel and held in place and in a biased relationship with said at least one ratchet ball bearing by abutment against said fixed guide plate,
• wherein, in operation, a torque exceeding a predetermined threshold magnitude causes said at least one ratchet ball bearing pressing against a corresponding biasing ratchet spring to move out of the ratchet recess it is occupying and enter into the adjacent ratchet recess and, thereby causing said lower arm section to pivot in a step-wise ratchet movement relative to the upper arm section of said support arm in a ratchet movement.