Patent GB-190009912-A (GB)
Title: Improved Automatic Playing Attachment for Key Musical Instruments.
Inventor: BIRKBECK HENRY
Filed: 1900-05-29
Granted: 1900-08-04
Abstract: 9912. Birkbeck, H., [Ludwig, J. H., and Ericsson, C. A.]. May 29. Automatic instruments.-Relates to keyboard instruments played by means of a tune-sheet. The tune-sheet a is perforated, and passes underneath a removable rail C<6>, the underside of which is recessed to accommodate the heads C<2> of a series of levers C. The tune-sheet operates in the usual way the levers which control resilient valves B<2>, Fig. 7, which thus open and close holes b in a tracker-board B. The rail C<6> can be shifted when it is required to change the tune-sheet, which is wound from a roller D on to another roller D<5>, which is driven by a train of wheels D<7>, D<8>, and D<10> from the shaft E of a compressed-air motor. At the conclusion of the piece, the wheel D' is shifted from the wheel D<8> to the wheel E<2>, which operates the roller D and thus re-winds the tunesheet. The holes in the tracker-board communicate by tubes n with orifices J<5>, Fig. 3, in corresponding chambers J, thus operating pistons K<2> which cause flanges H<4> to strike the keys of the musical instrument. The plunger devices are arranged in two rows corresponding to the white and black keys of the musical instrument. They connect with wind-chests G, and contain supply and exhaust valves L, N connected by a central spindle. A spring J<3> tends to keep the supply closed. When the wind is released from the chamber J by uncovering a hole in the trackerboard, the pressure of wind in the chest G forces the valve L open and reaches the piston K<2> through a space round the central spindle, the exhaust valve N being closed at the same time. When the hole in the tracker-board is closed, the chamber J fills again through a port L', which can be regulated by a screw L<3>, and the parts return to their former positions, the plunger H<4> being acted on for the purpose by a spring. At the end of a tune the mechanism is automatically reversed by transferring the pinion D<8> from the wheel D' to the wheel E<2>. For this purpose the pinion D<8> is carried by an arm D<9> which is operated by a lever T<2> actuated by apparatus h<3>, h<4>. These last are set in operation by the tune-sheet in the same way as the plunger apparatus for striking the keys, and two of them are used, one for forward and the other for backward movement of the apparatus. When the sheet is to be rewound, the lever T<2> also tilts a half-round rail C<5>, which depresses the levers 0 and moves them out of the way of the tune-sheet. At the same time a wedge F<5> is moved so as to relieve friction, which is normally applied to a governor F, causing the motor to rewind the tunesheet at an increased rate. During the performance of a tune, the effective diameter of the roller D<5> increases through the tune-sheet being wound upon it. To prevent increase of tempo from this cause, another wedge F<6>, actuated by an arm t, is moved so as gradually to increase the friction on the governor. The tempo can also be regulated by a lever F<7> operated by hand. The apparatus also comprises the following parts :-(1) A water motor of any suitable description for supplying compressed air ; (2) a pressure regulator controlled by the tune-sheet for augmenting the air pressure in forte passages ; (3) means similar to those used for striking the keys are used for operating the pedals ; the soft pedal mechanism is capable of automatic graduation ; (4) means for reversing the tune-sheet at will on pressing a button W<1> ; (5) a button W for starting ; (6) a three-way cock I, which either stops the compressed-air supply, or causes the tunesheet to be rewound at the end of a tune and the instrument to cease playing or to repeat the tune ; (7) a brake to prevent the tune-sheet from unwinding too readily from the roller D.