Patent ID: 8779256
Filing Date: 2014-07-15
Classification: G01C,G10C,G10H

Abstract:
1. A keyboard apparatus comprising: keys each having a front portion located forward of a key fulcrum and each configured to pivot about the key fulcrum when the front portion thereof is operated to be depressed or released; whippens each configured to be driven and pivoted by a rear portion of a corresponding one of said keys, the rear portion being located rearward of the key fulcrum; jacks each configured to be pivotable relative to a corresponding one of said whippens; hammer assemblies each having a butt including a base portion and a struck portion driven by a tip end portion of corresponding one of the jacks, and a hammer shank extending from the base portion of the butt, and each configured to pivot exclusively about a single corresponding pivot center; back checks each located below an axis of the hammer shank of the corresponding one of the hammer assemblies and fixed to the corresponding one of the whippens; and back check-catching portions each disposed on the base portion of the butt of the corresponding one hammer assembly, and configured to catch the corresponding back check when the corresponding one hammer assembly is pivoted in a key release direction, wherein a first acute angle of a straight line passing through a center of gravity of and the pivot center of the corresponding one hammer assembly relative to a horizontal plane is less than 45 degrees during an entirety of a key depression and a key release stroke, and a second acute angle of the axis of the hammer shank relative to the horizontal plane is less than 45 degrees during the entirety of the key depression stroke and the key release stroke, wherein the axis of the hammer shank is offset relative to the pivot center of the corresponding one hammer assembly, and an offset amount of the axis of the hammer shank is set so that the hammer shank always does not contact the back check, and wherein the back check, the struck portion, and the pivot center of the corresponding one hammer assembly are arranged in this order with respect to a front-rear-direction.