Music Trade Review

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THE MUSIC TRADE REVIEW
Being the Third Instalment of a Talk on the Fundamentals of Player
Design Discussed in Plain Language for Benefit of Salesman and Non-
Technical Reader—The Subject This Month is "How do the Bellows Work?"
Everybody is familiar with the bellows system
of a. player so that in order to understand what
follows it is only necessary to go to a player-piano
and examine the bellows carefully. Stripped of all
non-essentials, then, such a system will be seen to
consist of two large exhausting bellows or units,
each connected with a foot treadle, and one or two
equalizers (often erroneously called "reservoirs").
These comprise the bellows system on its operative
side, any and all other boxes, bellows, rods or
levers belonging to the control department. Let
us examine this structure, thus stripped to es-
sentials.
Apart from the fact that the exhausters are con-
nected up with foot treadles, or to some form of
power like an electric motor (as is the case with
the coin-operated and similar instruments), the
one outstanding difference between them and the
equalizers is that although both are furnished with
springs the exhausters are held shut thereby,
while the equalizers are held open. The exhauster
springs press the exhauster bellows shut, normally,
and keep them so until the pressure of the feet on
the treadles opens them. On the contrary, the
equalizers are normally held open and remain so
until caused to close in a manner hereinafter
described.
If we now examine the exhausters more closely,
we shall see that each of them consists of a bellows
with one wall fixed and the other movable. The
fixed wall is attached to the general framework
of the system, and if we were to look inside we
should see that this framework is hollow and pro-
vides channels within it whereby communicating
passages are maintained between the equalizer or
equalizers and the exhausters. The fixed walls of
the exhausters are pierced with holes so that they
may be in pneumatic communication with the
channel ways and the latter in turn communicate
with the equalizers through their fixed walls in the
same way. Thus the whole system is interde-
pendent, each part being bound up with the others.
Air, in fact, is free to flow from one part into
another without hindrance, except as now to be
noted. This exception is of the utmost importance
in making the player practical.
If we examine the outside of the moving wall of
the exhauster we shali see a leather strip extend-
ing over part of it, and held in place by a wire
spring. By bending the strip backwards we see
that it covers a series of holes extending through
the movable wall. If now we could look inside
the exhauster we should see that the fixed wall is
also provided with a leather strip covering the
series of holes leading into the channel ways in
the framework. This strip is situated on the side
of the fixed wall nearest to the movable wall.
The reader who wishes to make this clear to him-
self will find a drawing on page 19 of "The Player-
Piano Up-to-Date, 1 ' published from the office of
this paper, which illustrates clearly the above
description. In fact, from the above, it should be
easy to make a sketch which would fix in '.he
reader's tnisd the above-mentioned facts. These
may be summarized as follows:
The exhauster communicates with the channel
ways of the main framework. So does the equal-
izer, or equalizers. The doorway thus opened be-
tween exhauster and channels is kept closed by a
spring-held leather strip. Also the doorway which
is provided between the interior of the exhauster
and the atmosphere through the moving wall there-
of is kept shut by a spring-held leather strip. The
equalizers, however, open direct into the channels
of the frame work and thus are always in com-
munication with the rest of the system. Exhausteis
are normally held shut by a spring. Equalizers
are normally held open by a spring.
The operation of this system is simple. Imagine
that what has been described above is in existence
and brought into connection with the pneumatic
stack or top action of a player by means of a large
suction tube running from the top action to a con-
venient place in the channel board of the bellows
system. Now. suppose that the tracker-bar of the
player is dosed by a sheet of blank paper, so that
every perforation is shut off. Now, let the foot be
placed on one of the treadles. Then press down
the treadle. What happens? The exhauster is
opened. What does this imply? That air is drawn
out of the top action. But how? Listen for a
moment to an explanation scientifically correct and
exceedingly simple.
When the exhauster was opened by the down-
ward push to the foot of the treadle the result
was simply to increase the interior size of the
player. By that is meant that if we consider the
whole player, including its bellows, as a great
closed box it is plain that the opening of a bellows
is just like the stretching out, or otherwise en-
larging, of a part of this box. Or to put the matter
still in another way, it means giving more space
for the air contained in the player to occupy. Sup-
posing, then, that the whole player is scaled against
further air entering it, the result of opening the
bellows naturally is to cause the contained air to
expand, following its inherent property of expan-
sion, until the newly opened space is filled. But
we remember that there is a spring-held flap, be-
tween the exhauster and the channels which com-
municate with the rest of the player. Well, is it
not plain that, since there is no air at first in the
closed exhauster, the pressure of the air inside the
player will be sufficient, as that air rushes forward
in its effort to expand, to force open the flap
against its light spring and thus cause the newly
opened space to be filled with air until the pres-
sure of air in the new space is equal to that of
the air in the rest of the player?
But, of course, now that the contained air in the
player has expanded, it follows that the pressure
thereof is somewhat lowered, for that air has been
stretched out a little, as it were, and, like a rubber
band, the more it is stretched the thinner it be-
comes. Therefore, the whole body of contained
air is now in this artificial condition of stretched-
ness and therefore, while the whole amount weighs
just as much as it did before, any given cubic inch
of it, for example, is lighter than it was before, for
there are more cubic inches occupied by the same
quantity. It will be observed that once the air from
the player has rushed into and filled up the ex-
tended bellows or exhauster it becomes securely
trapped therein, for the leather strip will snap
shut and block off any chance of its getting back
into the player, as soon as enough air has flowed
into the exhauster to balance the pressure on
either side of the strip. Thus the air that gets
into the exhauster finds itself trapped therein. It
.can get neither in nor out.
Now, suppose that we release the foot pressure
and allow the spring of the exhauster to begin
closing it up. The air trapped in the exhauster is
squeezed until its pressure becomes normal once
more, and before the exhauster is closed up en-
tirely the air trapped in it will be so compressed
that it will overcome the spring pressure on the
leather strip which guards the way to the outer air
and will force the strip back, allowing a passage
into the atmosphere. In other words the air
trapped in the exhauster will be squeezed out into
the atmosphere through the closing of the ex-
hauster. Thus each stroke of the exhauster means
(Continued on page 12.)
Mr. Manufacturer and Dealer:
A Player Action at a reasonable price, easy to install and that
has already given satisfaction to hundreds of customers is what you
have been looking for. We have it in the
Sonorus Player Action
Write for particulars or visit us at our Display Room and judge for
yourself.
T h e
S o n o r u s
Company
—Incorporated—
FACTORY
706 Townsend St.
CHICAGO, ILL.
DISPLAY ROOMS
606 Shops Bldg., 17 N. Wabash Avenue