Spa cover lift system

Apparatus for aiding removal and replacement of a spa cover on top of a spa tub, said apparatus comprising lifting assemblies adapted to be secured relative to said spa tub, each said lifting assembly comprising:

• a lifting arm mounted for rotation relative to said spa tub and including a cover-engaging end adapted to be coupled to the spa cover and a pivot end mounted for pivotal movement about a pivot axis, wherein said lifting arm is rotatable through a range of motion about the pivot axis from a covering position and an uncovering position;
• a lifting system for exerting a lifting force on said arm tending to lift said arm as the arm moves from the covering position toward the uncovering position, and for exerting a resistance force on the arm tending to resist movement of the arm from the uncovering position toward the covering position, the lifting system including (i) a link lever having a pivot end pivotally mounted to said lifting arm at a link pivot location disposed between said arm pivot end and said cover-engaging end, and a slider end constrained for sliding movement along a slider path of travel, and (ii) a spring structure connected to said link lever at a spring pivot location between said link lever pivot end and said slider end, said spring structure further coupled to said lifting arm at a spring connection point between said arm pivot end and said cover-engaging end, wherein said spring structure is under compression when said lifting arm is at said covering location.

A lifting assembly for applying a lifting force to a pivoting structure, comprising:

• a lifting arm including a distal end and a pivot end mounted for pivotal movement about a pivot axis, wherein said lifting arm is rotatable through a range of motion about the pivot axis from a first position and a second position;
• a lifting system for exerting a lifting force on said arm tending to lift said arm as the arm moves from the first position toward the second position, and for exerting a resistance force on the arm tending to resist movement of the arm from the second position toward the first position, the lifting system including a force applying structure having a first end coupled to said lifting arm at a location between said arm pivot end and said distal end, wherein said force applying structure exerts a force substantially parallel with a longitudinal axis of said lifting arm when said lifting arm is in said first position, so that relatively little force is exerted by the force applying structure in a vertical direction, and wherein as said lifting arm moves from the first position toward the second position, said force applying structure exerts a force having a substantial force component in the vertical direction, thereby tending to assist in moving the lifting arm to the second position, and wherein said force applying structure has a second end which translates along a constrained path from a first path location as said lifting arm moves from said first position to said second position.