Spring counterbalanced support arm system

An articulated support arm system including:

• a base bracket;
• means for mounting said base bracket to a supporting structure;
• a rear arm including:
• a pair of elongate parallel rear arm links;
• means pivotally connecting one end of each of said rear arm links to said base bracket;
• an elbow bracket;
• means pivotally mounting the other end of each of said rear arm links to said elbow bracket;
• a forward arm including;
• a pair of forward arm links;
• means pivotally mounting each of said forward arm links to said elbow bracket;
• a nose bracket and means pivotally mounting the other end of each of said forward arm links to said nose bracket to create parallelogram linkages constituting respectively said forward and rear arms;
• whereby said forward and rear arms are articulated by means of said common connection to said elbow bracket, and said rear arm is mounted for movement down and away from said base bracket and said forward arm mounted for swinging movement up and away from said elbow bracket;
• rear arm spring tension means associated with said rear arm acting on at least one of said rear arm links to produce a countering moment acting about said link pivotal connections resisting movement of said rear arm in response to the weight carried thereby;
• said rear arm spring tension means including means applying said spring force with an increasing extent of outward movement of said rear arm assembly away from said base bracket to thereby countereffect the increasing moment exerted by said weight carried with an increasing extent of swinging movement away from said base bracket;
• forward arm spring tension means connected at one end to a point on one of said forward arm links and connected at its other end to a point beyond the pivotal connection of said link to either said elbow bracket or said nose bracket and at a point laterally displaced away from the direction of rotation of said link occurring with said forward arm swinging away from said either said elbow bracket or said nose bracket for exerting a spring force acting on at least one of said forward arm links resisting rotation of said links in directions corresponding to downward swinging movement of said forward arm towards said elbow bracket, said forward arm spring tension means including means increasing the leverage of said spring force acting to create said counter moment in increasingly advanced positions of said forward arm away from said elbow bracket to thereby provide a means for counterbalancing the weight of an attached load secured to said nose bracket;
• adjustable friction brake means associated with at least one of said pivotal connections in said forward or rear arms introducing an adjustable amount of friction braking force acting to resist rotation of an associated link with respect to the associated bracket affording said associated link a pivotal support;
• whereby unbalances between the moments exerted in said pivotal connection by the associated arm between said spring tension means and the weight of said arms and attached load is at least partially absorbed by said friction brake means.

A method of stabilizing a counterbalanced parallelogram arm linkage, the linkage comprising a pair of parallelogram links each pivotally supported at each end to respective brackets to form a parallelogram linkage and supplied with spring tension means exerting a countering force on at least one of said links so as to establish a counter moment on said links countering said rotation about one of said pivotal connections in a sense opposite to the rotation of said connection under the weight of a supported load and wherein said spring tension means produces increasing leverage of a spring force acting on said pivotal connection with positioning of said linkage in position so as to exert a greater moment than the weight of an attached load to produce a countering force offsetting the increased leverage of said supported load, the spring tension means being connected at one end to a point on one of said links and at the other end to one of said brackets at a point beyond the pivotal connection of said links and laterally displaced therefrom in a direction away from the direction of rotation of the link as it moves away from said one bracket, said connection producing less than perfect equilibrium at all positions thereof, the method of eliminating said instability comprising the steps of:

• introducing a frictional force into the pivotal connection of said linkage arms to just absorb the unbalanced moments experienced by said linkage in undergoing said swinging movement of said linkage.

In a counterbalanced arm including a parallelogram linkage including a nose bracket of generally U shape and including a pair of sidewalls and a bottom portion thereof, and a pair of parallelogram links pivotally connected to said nose bracket, the improvement comprising:

• an attachment feature securing an attached load to said nose bracket, comprising:
• a cover configured to be fit over the front and top of said nose bracket;
• means for detachably securing said cover to said nose bracket, said cover further including a lip portion disposed extending across said slot in said installed position;
• whereby a flange support fixture may be slid into said slot and secured therein by an installation of said cover means.

In a counterbalancing parallelogram linkage arrangement consisting of nested U-shaped elongated channel links, a first bracket pivotally mounted to one end of each of said U-shaped channel links by pivotal connections;

• a second bracket pivotally mounted to the other end of each of said channel links by pivotal connections, each of said brackets being generally U-shaped in configuration and each having a pair of sidewalls and connecting wall to form said U-shape wherein each of said pivotal connections is provided by pivot means extending transversely through said respective sidewalls and wherein said counterbalancing parallelogram linkage means further includes spring tension means including at least a pair of tension springs, both of which are mounted within said nested U channel means, each of said tension spring means being connected at one end to a respective U channel link and extending along the length thereof, each connected at the opposite end to a respective one of said first and second brackets by means including a transverse pin mounted to the respective sidewalls of said first and second brackets;
• a pair of hex headed bolts, one each extending through one of said transverse anchoring pins and means for threadably engaging each of said hex headed bolts and with the other end of a respective one of said pair of tension springs;
• whereby rotation of said bolts causes a corresponding increase or decrease in tension of said tension spring means;
• access opening means formed in at least one of said brackets including an opening in registry with said hex head of one of said hex headed bolts, whereby exterior access thereto is afforded for adjustment of said spring tension means.