Electronic keyboard musical instruments and the like keyboard musical instruments generally employ playing keys made of resin or plastics. A key made of resin is generally formed in a shape of a hollow box having a horizontal upper wall to be pressed by the finger of the player and vertical walls including a front wall, two side walls and a rear wall extending downward from the periphery of the upper wall to surround an open space therein. A plastic key can therefore be manufactured easily and inexpensively when compared with a traditional key (such as of a piano) which comprises a core bar made of wood and surface plates made of plastics or ivory adhered on the wooden core.
However, a plastic key of a hollow box shape has a drawback, in comparison with a wood-core key of a solid body, of generating harsh click noises caused by the clashes between the key top (horizontal upper wall) and the nail and resonating in the hollow box structure when the key is struck by the player's finger. In particular, a white key which has a larger surface area for key depression than a black key tends to generate louder click noises, much more does a white key having thinner plastic walls for the purpose of decreasing the weight and the manufacturing cost of the keyboard assembly.
A keyboard is a main input device for playing music on a keyboard musical instrument, and accordingly the keys constituting the keyboard are required to be of high quality and a high grade. But a harsh or ear-annoying clash noise between the key top and the nail would give an impression of a cheap musical instrument. Further, in the case of an electronic musical instrument on which the player is playing music using a headphone or an earphone, the musical tones can be heard only by the player and not by the persons near the player, and consequently only the clash noises would reach conspicuously to the ear of the persons present nearby.
Unfortunately, however, there has been known no technique of taking countermeasures against such nail clashing noises. The technique disclosed in an unexamined Japanese patent publication No. 2000-132168 is to utilize cushion materials disposed between the screw heads and the key bed when the keyboard assembly is fixed to the key bed in the electronic piano in order to absorb the vibration of the keyboard assembly generated by the key depression and to prevent the vibration from being propagated to the key bed. The technique is for suppressing the noises produced by the vibrations of the key bed at the times the keys are depressed, and does not work as a countermeasure against the clash noises between the key and the nail.
The technique disclosed in a registered Japanese patent publication No. 3758590 is to manufacture a key by forming the portion which serves as a swing fulcrum of the key by resin and forming the front body part by wood in order to increase the preciseness of the connecting portion to serve as the swing fulcrum as well as obtain the appearance and the rigidness of the wood material. As this technique utilizes wood material, the manufacturing cost will be almost the same as the conventional wooden key.