Coin Switch Mechanism
(Photograph courtesy of Dick Hack.) Overall view of the coin switch mechanism in National piano #348. The coin switch mechanism, although perhaps complicated looking, can be logically divided into three functionally different but interconnected regions. At front is the electrical switch and its associated trip and reset linkages. In the middle is the studded cylinder, which is rotationally synchronized with the revolver magazine. At the very back is the wide die-casting (painted red) containing eight separate coin chutes, each with its own corresponding coin trip lever mechanism. With the wooden multi-slot coin transfer connector removed, the wide open mouths for each of the eight coin trip slots are plainly visible. Normally the size and extent of the slot openings are obscured by the coin transfer connector. |
(Photograph courtesy of Dick Hack.) Coin trip lever mechanism in National piano.#7352. When a coin falls through one of the coin chutes it impinges upon a trigger pawl near the bottom of the chute. When this happens a vertically oriented extension on the trigger pawl rotates toward the rear, which then allows the end of a lever arm resting on top of the pawl extension to slip free and drop. The other end of this lever arm is enlarged and rounded where it swivels around its pivot point. Below the pivot point is a tension spring that works to rotate the lever's trip arm downward, while above the pivot point there is a short projection sticking up that is forced in a rearward direction. This upward projection has two functions. Firstly, it is drilled with a hole to accept a long hooked wire that connects with corresponding linkage that interacts with the studded selector cylinder in the middle of the coin switch enclosure. When this wire is pulled it causes a finger to pop forward toward the studded cylinder, putting it in the path of one of the cylinder studs. Secondly, as the upward sticking projection is rotated to the rear it pushes against a suspended metal bar that is free to swing to and fro (within limits). This bar runs the entire width of the coin switch enclosure, so that any coin chute pawl that has been tripped will cause an affected lever arm to impact this swinging metal bar, pushing it toward the rear of the enclosure. When it is pushed back it comes up against a vertical lever that, in turn, trips the electrical switch at the front of the enclosure, which then makes electrical contact. If this metal bar is kept in the rearward position, such as when multiple tunes have been selected, the coin switch will not open (break the electrical circuit) until all of the coin trip levers have been reset, one by one, as any additionally selected music rolls have been played. |
(Photograph courtesy of Dick Hack.) Close-up of the coin trip lever mechanism in National piano.#7352. Here the upward projecting leg of the trigger pawl can be easily discerned. When a coin impacts the trigger pawl (sticking out into the into the path of the falling coin) its vertical extension rotates toward the rear, which then allows the end of a lever arm resting on top of the pawl extension to slip free and drop. The other enlarged and rounded end of this trip lever arm has two attachment points. Below the pivot point is a tension spring that works to rotate the lever's arm downward, while above the pivot point there is a short projection sticking up that is forced in a rearward direction, and that, through linkages, causes the coin switch to snap closed. |
(Photograph courtesy of Dick Hack.) Studded selector cylinder and associated linkages in National piano.#7352. When one of the wires connected to a coin trip lever pulls the corresponding linkage associated with the studded selector cylinder, a metal finger is caused to move closer to the studded cylinder (each finger is akin to a vertical lever with a projecting tip or finger at the top end that is facing toward the cylinder). When a stud on the rotating cylinder touches the finger it will be pushed downward, and then at some point the finger will automatically disengage from the stud. When a finger is pushed downward it both resets the corresponding coin trip lever, and it also presses down against a heavy-duty metal bar attached at both ends to a steel shaft (partially obscured by the rod above it with the brass colored spacers), which has a simple lever arm on its front facing right end. When this shaft is rotated (perhaps a quarter revolution) a wire connected to a cast bronze bell-crank (near the front of the coin switch enclosure) triggers the player system into the Play mode. |
(Photograph courtesy of Dick Hack.) Plan view of knife switch and associated control linkages in National piano.#7352. The simple electrical knife switch and its connecting terminals, at picture center, are held in place on a typical red fiber insulating block. Forward of the knife switch are various linkages clamped to one of the two long shafts that transverse the "keybed" area, one inside the other, entering the front region of the coin switch enclosure. The larger, and hollow, shaft terminates about midway through the enclosure, to which is clamped the reset linkages for the knife switch. The longer and smaller shaft terminates at the right side of the enclosure, and is fitted with a cast bronze bell-crank used to trip the Rewind/Play camshaft into the Play mode when the selected music roll is positioned under the tracker bar. |
(Photograph courtesy of Dick Hack.) Side view of knife switch and associated control linkages in National piano.#7352. The red fiber insulated block uses copper strips to connect the electrical wiring terminals to the two fixed switch blade contacts. The knife blade itself is electrically neutral, and is connected to but electrically insulated from the steel lever arm that raises and lowers the switch blade. When the player system is off the knife switch blade is raised, breaking the electrical circuit, and it is kept latched in that upward raised position until specifically released. When a coin falls through one of the coin chutes at the back end of the coin switch enclosure, and trips a coin trip lever, the vertical oriented latching lever (at the front of the enclosure but connected by a long metal rod to the coin trip mechanism) is pushed forward. This action forces the latching lever to swivel slightly, which releases the latch pin projecting outward from the knife blade lever arm, allowing the electrical contacts to close. The bearing pin, on which the latching lever swivels, is attached to a horizontal lever that can be raised and lowered by a bell-crank clamped onto the larger hollow shaft that traverses the front of the “keybed” area, and that is further attached to the cam follower lever for the “coin switch reset cam.” When the vertical latching lever is raised, by the action of the reset cam, the latch pin on the switch blade arm can re-engage. Then, when the vertical latching lever is lowered, it pushes down on the latch pin located on the forward end of the knife switch arm, in turn swiveling the knife switch on the opposite end of the lever arm into the open position, breaking the electrical circuit. However, when several tunes have been selected the rod controlled by the coin chute trip levers will keep the vertical latching lever pushed forward. This will prevent the latch pin on the knife blade lever arm from re-engaging the vertical latching lever, until all selected tunes have been successively played and their associated coin trip levers have been reset, whereupon the player system will then be shut down. |
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