1. Field of the Invention
This invention relates to upright keyboard musical instruments such as upright pianos, which are equipped with top boards having opening and closing functions.
This application claims priority on Japanese Patent Application No. 2004-97533, the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally, keyboard musical instruments such as grand pianos and upright pianos are equipped with top boards, which are attached to top positions of main bodies and are free to be opened or closed. During musical performance, top boards are appropriately opened so that musical tones are emitted to the outside of the cases and are thus increased in tone volume. Japanese Patent Application Publication No. H11-305761 discloses an example of a keyboard musical instrument, which is equipped with a support rod for supporting the lower portion of a top board to be opened, and a buffer device for preventing the top board from rapidly rotating when it is closed. Conventionally known keyboard musical instruments control tone volumes by opening and closing top boards, wherein they prevent user's fingers from being caught between cases and top boards, which are opened or closed.
Conventionally known keyboard musical instruments (particularly, upright pianos) allow top boards to be opened or closed only for the purpose of tone volume control. When users play keyboard musical instruments such as grand pianos with top boards in the open condition, for example, they can directly view movements of hammers included in actions, which demonstrate entertaining effects in musical performance. In contrast to grand pianos, upright pianos cannot demonstrate such entertaining effects in musical performance.