Patent ID: 7141729

Claim:
A hammer assembly for a keyboard system having a plurality of keys, the hammer imparting a touch weight by swinging when the keys are pressed or released, the hammer comprising: a hammer main body having three pass-through holes and supported in the keyboard system so that the hammer main body can swing freely; two mass plates attached on both sides of the hammer main body such that the hammer main body is sandwiched between them; and a rivet driven such that the rivet is inserted and passes through a linking hole of one of the mass plates to a linking hole of the other mass plate via a pass-through hole of the hammer main body, wherein the mass plates include two protuberances that can each fit into two of the pass-through holes from among the three pass-through holes when the mass plates are attached to the hammer main body, wherein the mass plates include a linking hole that links with the remaining pass-through hole, and wherein the two protrusions of the mass plates are each formed so that the protrusions protrude by means of half piercing processing, and are arranged in a position that is roughly linearly symmetrical with respect to the imaginary line that passes roughly through the center of the linking hole.