Support arm for optical accessories

An optical support arm comprising:

• a base portion including means defining an elongated aperture for receiving a support post such that said base portion may be rotated about a longitudinal axis of said aperture;
• an arm portion having first and second ends, said first end being located adjacent to said base portion and said second end being located distal from said base portion, and said arm portion being mounted for pivotal movement about an axis angularly displaced from the longitudinal axis at said first end;
• a mounting shaft mounted at said second end of said arm portion for rotation about a longitudinal axis of said shaft;
• a locking lever mounted to said arm portion for movement relative to said arm portion such that movement of said lever to a locking position simultaneously locks said base portion against rotation about the longitudinal axis of said aperture, locks said arm portion against pivotal movement about said first end and locks said shaft against rotation about the longitudinal axis of said shaft, and
• linkage means extending between said first and second ends whereby the angular relationship between the longitudinal axis of said aperture and the longitudinal axis of said shaft remains substantially constant during pivotal movement of said arm portion.

A counterbalanced optical support arm comprising:

• an elongated hub casing defining an elongated arm structure having opposing ends and including a first front hub half at one end and a second front hub half at an opposite end, said hub casing being formed as an integral structure such that said first and second front hub halves are stationary relative to each other;
• a first rear hub half positioned adjacent to said first front hub half, said first rear hub half being substantially cylindrically shaped and including upper and lower link attachment points on diametrically opposed sides thereof;
• a second rear hub half positioned adjacent to said second front hub half, said second rear hub half being substantially cylindrically shaped and including upper and lower link attachment points on diametrically opposed sides thereof oriented along a line substantially parallel to a line passing through said link attachment points on said first rear hub half;
• upper and lower links extending substantially parallel to each other and attached to respective ones of said upper and lower link attachment points on said first and second rear hub halves to thereby form a parallelogram structure, said links being mounted for pivotal movement relative to said rear hub halves such that said second rear hub half may be moved relative to said first rear hub half;
• said first rear hub half including a first hub plate having means defining a threaded aperture therethrough, and a first hub ring having opposing front and rear sides wherein said hub plate is positioned adjacent to and spaced from said rear side of said hub ring and a substantially circular peripheral lip extends outwardly from said front side of said hub ring;
• said second rear hub half including an outwardly extending substantially circular peripheral lip on a front side thereof;
• first and second substantially circular grooves formed in respective ones of said first and second front hub halves for receiving said peripheral lips of said first and second rear hub halves, said first front and rear hub halves being rotatable relative to each other and said second front and rear hub halves being rotatable relative to each other to allow said movement of said second rear hub half relative to said first rear hub half;
• an elongated cylindrical mounting shaft positioned within said second rear hub half, said mounting shaft extending diametrically across said second rear hub half and oriented substantially parallel to a line through said second rear hub upper and lower link attachment points;
• a substantially rectangular locking block including means defining a first aperture therethrough and means defining a second aperture oriented substantially perpendicular to and intersecting said first aperture, said first aperture including a smooth interior surface and being sized to receive said mounting shaft such that said mounting shaft may be rotated relative to said locking block, said second aperture including threads along an interior surface thereof;
• a support block attached to said mounting shaft adjacent to an exterior portion of said second rear hub half;
• a support shaft attached to said support block and extending perpendicular to said mounting shaft for supporting an optical accessory;
• a substantially cylindrical split collar formed integrally with said first rear hub half including first and second opposing edges, said first hub plate extending from said first edge and said first hub ring extending from said second edge;
• a lower recess formed in an end of said split collar;
• a substantially cylindrical ring bearing for attachment to a support post, said ring bearing being sized to be received within said split collar, said ring bearing having a flange portion sized to be received within said lower recess in said split collar wherein said ring bearing may support said support arm in pivotal movement about the post;
• first and second sprocket wheels mounted for rotation within said first and second front hub halves;
• an endless chain extending around said first and second sprocket wheels;
• a first bolt rigidly attached to said first sprocket wheel, said first bolt having a head engaging an outer portion of said first front hub half and a threaded shank engaged within said threaded aperture in said first hub plate whereby said front and rear first hub halves are held in position adjacent to each other;
• a second bolt rigidly attached to said second sprocket wheel, said second bolt having a head engaging an outer portion of said front hub half and a threaded shank engaged within said second aperture in said locking block whereby said front and rear second hub halves are held in position adjacent to each other;
• a lever positioned adjacent to said second front hub half and rigidly attached to said second sprocket wheel such that said lever may be rotated to cause said second bolt to draw said locking block and said second rear hub half toward said second front hub half;
• a high friction material positioned within said substantially circular groove in said second front hub half for engaging said peripheral lip of said second rear hub half;
• a first mounting bracket attached to said upper link adjacent to said first hub halves and extending between said upper and lower links;
• a second mounting bracket attached to said lower link adjacent to said second hub halves and extending between said upper and lower links;
• a tension spring having opposing ends attached to said first and second mounting brackets to provide a counterbalancing force to said support arm;
• a cover attached to and extending along said elongated arm structure from said first to said second hub halves to enclose said links and said tension spring;
• and
• wherein said lever may be located in a first rotational position which permits said mounting shaft to rotate about its longitudinal axis, said second rear hub half to move relative to said first rear hub half, and said split collar to rotate relative to said ring bearing mounted on a support post for supporting said arm, and a second rotational position of said lever in which said locking block and said second rear hub half are drawn toward said second front hub half to cause said locking block to be forced sideways against and prevent rotation of said mounting shaft and to cause said peripheral lip of said second rear hub half to engage said high friction material to prevent relative rotation between said front and rear second hub halves and thereby lock the parallelogram structure formed by said hub halves and said links in position, and movement of said lever to said second position being transferred from said second sprocket wheel to said first sprocket wheel through said chain whereby said first hub plate is drawn toward said first hub ring to thereby draw said opposing edges of said split ring together and lock said arm against rotation relative to said ring bearing.