Mechanical stabilizer

A device for stabilizing an article on a surface, comprising:

• a supporting unit comprising a first member in the form of a moveable shaft and a second member in the form of a housing for receiving said shaft, said shaft being moveable along an axis for controllably extending and retracting said first member with respect to said second member within first and second regimes, said first regime allowing free extension of said first member relative to said second member while locking said first member against retraction and said second regime allowing said first member to be reversibly, freely extended and retracted,
• a coupling mechanism for automatically enabling said regimes, the coupling mechanism comprising:
• an invertable bistable element associated with said second member, which comprises an annular invertable spring wherein outer radial edge portions of said spring are axially stationary and inner radial edge portions are axially translated in use,
• a rotatable engaging piece disposed about the axis of motion of said first member, and
• a cam surface disposed about and transverse to said axis of motion,
• wherein said bistable element enables said first regime by positioning said engaging piece adjacent said cam surface and first member such that said engaging piece frictionally bears upon said cam surface and first member to prevent retraction of said first member but enables free, continuous extension of said first member, and
• in another, inverted configuration, said bistable element enables said second regime by positioning said engaging piece relative to said cam surface such that said first member is freely retractable and extendable,
• a regime control associated with said first member for controllably and automatically switching between said first and said second regimes by inverting said bistable member at a desired point based on the extension or retraction of said first member, and
• a spring biasing said first member to extended positions wherein said spring is constructed to have a bias force greater than the force needed to switch said bistable element from one to another stable configuration.