Fig. 28. Diaphone in the Auditorium, Ocean Grove, N. J.
In Fig. 28 we give an illustration of the form of Diaphone used in the Hope-Jones Unit organ at the Auditorium, Ocean Grove, N. J.
P is a pallet controlling the admission of air into the body of the pipe P1. M is a motor adapted for plucking open the pallet P through the medium of strap s. The box B is permanently supplied with air under pressure from the bellows. When the valves V and V1 are in the position shown in the drawing, the Diaphone is out of action, for the wind from the box B will find its way through the valve V (which is open) into the interior of the motor M.
When it is desired to make the note speak, the small exterior motors M1 and M2 are simultaneously inflated by the electro-pneumatic action operated by depressing the pedal key. The valve V will thereupon be closed and the valve V1 be opened. As the pressure of air inside the motor M will now escape into the pipe or resonator P1, the motor will collapse and the pallet P will be opened in spite of the action of the spring S which tends to keep it closed.
The wind in the box B will now suddenly rush into the lower end of the pipe P1, and by causing a compression of the air at that point will again raise the pressure of the air inside the motor M. The pallet will thereupon close and the cycle of operations will be repeated—thus admitting a series of puffs of wind into the foot of the pipe P1 and thereby producing a musical tone of great power.
As the valve V1 is open, the sound waves formed in the pipe P1 will govern the speed of vibration of the motor M. It will thus be obvious that the Diaphone will always be in perfect tune with the resonator or pipe P1, and that the pitch of the note may be altered by varying the length of the pipe.
