Patent GB-190824185-A (GB)
Title: New or Improved Transposing Mechanism for Pianofortes, Organs and like Instruments.
Inventor: MITCHERD JOHN WALTER
Filed: 1908-11-11
Granted: 1909-01-14
Abstract: 24,185. Mitcherd, J. W., and Mitcherd, A. A. Nov. 11. Pianofortes ; organs ; transposing music.-In transposing - means for pianofortes, organs, &c., a series of levers which operate the playing- mechanism and are themselves operated by the keys are capable of being rotated horizontally, so as to operate the same parts of the playing-mechanism but to be operated by different keys. The movement of the levers is effected by the depression of a key, which by moving a stop allows the rotation of a weight-driven drum, and so through a series of levers releases a slide which is pressed forward by another weight-driven drum. The slide carries a grid which is enmeshed in the series of transposing- levers and gives the necessary rotation to them. The extent of movement of the slide is limited by a stop regulated by a separate keyboard. This keyboard operates a series of stops corresponding to an octave for each movement, and has a number of rows of stops to enable successive transpositions to be made in a determined order. Two series of transposing-levers and corresponding slides and grids are provided, each series being used alternately, and one series being raised out of reach of the keys' action when the other is in use. The weights for driving the several drums are wound up by means of a spindle, and an indicator is provided to show the power yet remaining in the instrument. Fig. 5 is a cross-section of an harmonium through the extra transposition keyboard which is placed at the side of the ordinary keyboard, and Fig. 7 is a cross-section through the ordinary keyboard. The key slide b<1>, Fig. 5, is initially raised, but on the depression of one of the octaves of keys b one of the stops b<4>, of which there is one in each row for each key, is pushed through the slide b<1>, and at the same time the lever b<5> rocks the pawls b<6>, b<7> and the slide falls to the next row of stops b<4>. A stop in this second row is depressed by another key, and so on, the music being written throughout in one key and indicating at the beginning what changes of key are necessary throughout the playing of the piece. The ordinary keys a are shown in Fig. 7. They operate through bars a', a<2> the transposing-levers d, e, which in turn actuate the levers f of the playing-mechanism. One of the series of levers d, e is raised out of action at any time. The operation of the extra key c rocks the levers c<1>, c<2>, c<4> and moves the stop c<8> from the path of the weight driven drum h<1> to allow of a semi-rotation. This rotation operates the bars m<2>, p, which are connected by the pulley 26 and carry the rollers m<3>, p3 to control the levers d, e, thus taking one series cut of action and bringing the other series into action. On the same shaft with the drum h<1> are the cams n, n<2>, one of which on each semi-rotation rocks its connected lever n' or n' and so rocks a lever n<4> or n<6>. These levers carry stops against the movement of weightdriven apparatus carrying the slides l, k and the grids u, v of the transposing-levers d, e. When one of the levers n<4>, n<6> is rocked, the stop is removed, and the levers d or e are rotated until the stop l<3> or k<3> on the corresponding slide l or k is held by the protruding peg b<4> in the row, this peg thus determining the position of the transposing- levers and the key of the instrument. The raising of the slide b<1> at each transposition is effected by arranging for the semi-rotation of the drum h' to operate a series of levers to raise the axis w<4> of the pawl b<6> which pushes up the slide b<1>. A predetermined series of transpositions, corresponding to the successive depressions of the keys b at the beginning of the piece, are thus made by successive depressions of the key c. The various weights for driving the apparatus are wound up from the drum g, and the slide b<4> can be raised by the lever 65. The raising of the slide b<1> also presses the piece 48 against the pegs b<4> to push them all into the inoperative position.