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lever or Z-crank g—h (termed the "hopper") in conjunction with the before-mentioned " roller " attached to the hammer, and the adjustable 6et-off screws q and t.
The operation of the escapement is as follows :—
So long as the key remains unmoved, the Hammer rests, supported through its Roller k, upon the end h of the hopper : this latter being for this purpose passed through an aperture in the lever I—m, the "escapement-lever. ''
When the key is depressed, the whole of the levers concerned in the escapement are raised through the Upright n, and through them, the hopper-supported hammer.
Both the end C of the hammer, and the point p of the lever o—p however remain stationary, owing to their being pivoted to the planks r and s.
To prevent the hammer, on reaching the string, from " blocking " against it, the set-off nut q is so adjusted as to cause the hopper to tilt its g-end against this nut at the right moment. As the levers continue H to rise while g is arrested by q, it follows that h slides from under the Hammer-roller, and as the rise of I S has also been meanwhile arrested by the screw t, the hammer is thus left free to fall back. It cannot however, fall far away from the string, so long as the key is kept fully depressed, owing to its now resting t£ on the lever I—m. m
It is the latter lever that will enable us now to repeat the note without a full ascent of the finger-end of the key being previously required. For if the key is allowed to rise even slightly, then h will d
at once slightly descend, as will also the m end of the escapement-lever I—m ; but as I is under a slight S pressure from the spring underneath, it continues for awhile pressing upward against its screw t and thus B holds the hammer still raised, though not in actual contact with the string. Meanwhile, a moment 1-3
will however soon be reached, when the Hopper (actuated by the same spring that also gives life to the escapement-lever) will again be able to slip into position under the hammer-roller. We 6hall thus be able to repeat the note at will. The neat way in which the escapement-lever (I—m) thus as it were
lifts and replaces the hammer upon the top of the hopper is a real marvel of mechanical ingenuity.
v is the Check ; the u end of the hammer is caught by this on its recoil from the string.
w is the damper, lying on its string ; and y—z is a little crank by which this is lifted through its wire x by the end of the rocker A B when the key is depressed.
At aa we also see the felt pad6 that prevent the key being taken down too far—the "key-beds" as they are here termed.
bb represents the position of the string.
cc, the edge of the sounding-board.
The arrows indicate the direction of the movements resulting from key-depression to |
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