Link Stacks and Valve Types

(Photograph courtesy of Rusty King)

Link stack with number 2264 die stamped into the wood, from a Link Style R (Schaff #25499; Link #2264). Note the individually removable unit valve blocks, which made servicing a Link piano very simple. All the serviceman had to do to replace a unit was to remove two wood screws and then lift out the valve and pneumatic assembly, replacing it with a new unit.

(Photograph courtesy of Rusty King)

Example of an early Link removable unit valve. The regulating screw (with the head formed into an eye) was used to adjust the bleed, which was integral with the valve unit. Notice the brass screen at the top side of the atmospheric vent, which prevented large dust and lint particles from getting into the valve and stuck on the leather valve seats. This is a feature uncommon on other brands of coin pianos.

(Photograph courtesy of Rusty King)

Pallet valve setup (in the right half of the picture) in a keyboard Link Style AX piano. Each pallet valve controls a single xylophone note (some rubber tubing has been disconnected to better show the pallet valve unit). Here is how it works: There are small wood blocks glued to the piano action's stickers, and each block has an adjustable capstan screw set in it. The capstan screw pushes up on the end of the pallet (held closed by a jack spring) allowing atmosphere to enter a drilled channel beneath it. There is a bleed for each pallet valve channel, covered by the narrow wooden chamber at the top front of the pallet valve unit. The pallet valve channels end in a brass nipple, which is then tubed to a standard valve that in turn supplies vacuum to a pneumatic that plays a xylophone note. The cumbersome pallet valve system was mostly abandoned in late Link keyboard instruments in favor of using what are often termed "reverse valves." These accomplished the same job, but in a simpler manner, whereby a normal stack valve was connected via a rubber tube to a "reverse valve" on the xylophone.

(Photograph courtesy of Rusty King)

This is an example of a late Link removable unit valve. The late unit valve is similar to the early construction, but without the adjustable bleed, or any bleed at all. In the late style coin pianos the stack bleeds were a ganged together in one central place, a block mounted between the tracker and the stack, which made cleaning the bleeds much easier, since all were accessible in one convenient place. The bottom brass nipple connects to the tracker bar, while the upper nipple would be connected to a so-called "reverse valve," which were used for late style xylophones equipped with "reverse-valves," and/or for the 12 octave-coupled-bass notes common in instruments played by the Link 49-note Style A music roll.

(Photograph courtesy of Rusty King)

Two views of identical reverse valves for use with a xylophone. The small brass nipple would be connected to a standard configuration Link unit valve, such as for a piano note operated directly by a music roll perforation (not octave-coupled). Note the small hole directly under the nipple. This is a vent which conducts atmospheric pressure to the underside of the pouch at all times, something common only for Link reverse valves. The xylophone beater actuating pneumatic would be connected to the large brass nipple protruding from the valve unit's bottom block. A "reverse valve" as would be used for the 12 octave-coupled bass notes would be similar in appearance to the Link valves shown in the above picture, but with a pneumatic for playing a piano note glued to the bottom side instead of the block with a nipple for connecting rubber tubing.

(Photograph courtesy of Rusty King)

Reverse valve drawing by Rusty King for an MBSI workshop about 1982, and showing the so-called "reverse valve" in the closed or rest position. When the valve is at rest there is no pressure differential across the lower pouch, and so the valve remains seated against the vacuum in the middle chamber. This valve differs greatly from a normal valve setup, in that the pouch area is separated from the vacuum chamber by a flexible membrane, which must be considerably smaller than the working area of the lower valve seat, otherwise the atmospheric pressure normally above the pouch and pushing up on the small membrane would cause the lower valve seat to unseat, and leak or more or less fully open. When a vacuum is applied to the small tubing connection on the bottom right the pouch raises the valve stem due to atmospheric pressure on the pouch's bottom side pushing it upwards. This, then, connects the vacuum chamber with the pneumatic that plays a piano or xylophone note. It is called a "reverse valve" because in a standard valve a vacuum is applied above the pouch and when atmospheric pressure rushes in under the pouch the valve operates. In this case, atmospheric pressure always exists under the pouch and when a vacuum is applied above the pouch the valve operates.

(Photograph courtesy of Rusty King)

Reverse valve drawing by Rusty King for an MBSI workshop about 1982. This drawing shows the reverse valve in the open or operating position. This occurs whenever a vacuum is applied to the small tubing nipple at bottom right, whereupon atmospheric pressure below the pouch pushes it upwards, likewise lifting the separating membrane (isolating the pouch area from the vacuum chamber) and valve stem, thereby opening the valve to the vacuum chamber (see upper panel for more details). This causes the motor pneumatic in a xylophone or octave-coupled bass note to play.