Action for upright piano

Claim 1

An action for an upright piano, said piano having a basic structure, said action comprising a plurality of key-hammer mechanisms and having an at rest position, said key-hammer mechanisms individually comprising: a key having a playing end, a working end, a first fulcrum attached to said basic structure and supporting said key between said playing end and said working end, at least one weight installed between said playing end and said first fulcrum, and a second fulcrum attached to said key between said working end and said first fulcrum, a wippen having a wippen center, a jack center, a jack having a toe and an engaging end, said jack being pivoted at said jack center, a backcheck wire, a backcheck block attached to said wippen by said backcheck wire, said wippen being pivoted to said basic structure at said wippen center and supported by said second fulcrum, a hammer assembly having a hammer butt, a backstop assembly, a hammer shank and a hammer head, said hammer butt being pivoted to said basic structure at a hammer center, said piano having at least one string attached to said basic structure and positioned to be struck by said hammer head, a regulating button attached to said basic structure, a hammer return spring, supported between said basic structure and said hammer assembly, producing a first force and engaging said hammer assembly at a lever arm distance from said hammer center such that said first force produces a first torque on said hammer assembly in a direction to urge said hammer head away from said at least one string, said first torque being in the range of 25% to 150% of the torque which the force of gravity would produce on said hammer assembly about said hammer center with said hammer shank essentially horizontal, said at least one weight producing a second force due to the force of gravity on said weight, said second force being applied to said hammer assembly by said engaging end of said jack, via said wippen and said first fulcrum, at a lever arm distance from said hammer center such that said second force produces a second torque on said hammer assembly opposing said first torque, a repetition spring having first and second ends and producing a third force, said ends being supported between a first point on said hammer assembly and a second point on said jack, said first and second points having an arrangement, said arrangement determining the line of action of said third force, said line of action oriented to urge engagement of said engaging end of said jack with said hammer butt, said line of action also oriented to provide a lever arm distance for said third force about said hammer center such that said third force produces a third torque on said hammer assembly, said third torque also opposing said first torque, said hammer butt having a shape such that engagement of said engaging end of said jack with said hammer butt has a camming action which produces a fourth force on said hammer butt at a lever arm distance from said hammer center such that said fourth force produces a fourth torque on said hammer assembly, said fourth torque also opposing said first torque, said second force being such that, with said engaging end of said jack being engaged with said hammer butt, the sum of said second, third and fourth torques is less than said first torque such that said first torque, via said hammer butt, said wippen and said first fulcrum, produces a net return force urging return of said playing end of said key toward said at-rest position, said arrangement and said shape being such that, with said engaging end of said jack being disengaged from said hammer butt, said sum of said second, third and fourth torques is greater than said first torque such that re-engagement of said engaging end of said jack with said hammer butt occurs before said hammer head reaches said at-rest position and such that said hammer assembly rests on said jack in said at-rest position, whereby, when said playing end of said key is released after play, said backcheck block begins to move away from said backstop assembly allowing return movement of said head toward said at-rest position, whereupon, said first, second, third and fourth torques act upon said hammer assembly such that re-engagement of said jack with said hammer butt occurs before said hammer head reaches said at-rest position, said re-engagement enabling replay, if said playing end of said key is again depressed, said re-engagement also reducing said third and fourth torques to enable said second torque to urge contact between said engaging end of said jack and said hammer butt and to enable said first torque to put said action in said at-rest position due to said net return force, and said re-engagement also assuring that said hammer assembly rests on said jack.