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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to organ systems, and more particularly to a stop
tablet control system for an organ for providing convenient visual
indication of what stops are being played.
Over the many years of organ development, a wide variety of systems for
controlling organ stops have been devised, perhaps the earliest of which
was a form of draw knob which, in the case of a pipe organ, required the
exertion of considerable energy to accomplish the mechanical result
necessary to achieve the desired stop effect. Such draw knobs have in more
recent times been electrified and provided with switches which are
actuated by movement of the knobs to activate electrical or pneumatic
systems for accomplishing the required mechanical work involved in setting
the stops. Another system now in common use is the so-called tablet
control, which consists of a multiplicity of stop tablets pivotally
supported above the keyboard of the organ and typically arranged to toggle
between an up "off" position and an "on" down position. Another type of
system is the tilting tablet, used to some degree in pipe organs, and
quite commonly on spinet electronic organs, which consists of a small
tilting tablet, pivoted in the middle, which when the upper part is pushed
turns on the stop and when the lower part is pushed the stop is turned
off.
In all of these systems the "on" and "off" condition of each stop is
visually indicated by the mechanical position of the draw knob or stop
tablet. Although such systems have long been in use, indicating that their
performance is generally satisfactory, they do have limitations,
particularly when used with so-called "combination actions" in which many
stops are changed en masse. With combination actions, of which several
types are known, pushing a single button called a piston automatically
changes the registration of all of the stops (which sometimes number 100
or more) en masse, or at least all of the stops in a particular division
of the organ. Several preset combinations are stored in some form of
temporary memory so that the organist can alter which stops are played in
response to actuation of a given piston as requirements change from time
to time. Sometimes during a concert, the organist will find it desirable
to change the combination between selections so that a given piston will
give a particular tonal effect in one case and a different tonal effect,
appropriate to another selection, in the other case. Usually, however, the
pistons in a church organ, of which typically there are six, ten or
sixteen pistons per keyboard, would be set up in their most generally used
combinations, but adapted to be changed from time to time.
A drawback of combination actions, which has largely limited their use to
large, expensive organ systems, is their cost. Even the simple hard-wired
combination system, in which the stops that are actuated by a given piston
are pre-wired at the factory, and thus not subject to variation, require
physical movement of several tablets, which is difficult to accomplish
silently. For example, if the toggle action of the tablets is designed to
have a "positive" feel when operated manually, a multiplicity of tablets
will offer considerable spring resistance that must be overcome by the
motor mechanism that actuates the tablets, thus generating a certain
amount of undesirable noise as they all toggle from one position to
another. Moreover, a large amount of power is required to operate
combination actions of the kinds in current use. If, for example, the stop
tablets, in the combination action mode, are actuated by respective
magnets, which may number as many as 200, and it is desired to move all
200 tablets from their "on" to their "off" position at the same time, a
relatively large amount of power is required which, in turn, necessitates
the provision of a large and expensive power supply. Because of these
costs and complications, low priced electronic organs are not equipped
with combination actions. Some available organs have a system of preset
combinations wherein pushing a given piston button disables all of the
conventional stop controls and substitutes some factory pre-wired
combination. Such organs normally have an indicator lamp installed
somewhere on the organ which when illuminated tells the organist that he
is not using the manual stops but is instead using a factory preset
combination. Unless the organist is totally familiar with the organ, he
has no way of knowing which stops are on when a particular pre-wired
combination is selected. There is nothing to tell the organist that stops
are being played, thereby making it difficult to manually "tailor" the
combination should he decide that the stops being played are less than
satisfactory for the selection he is playing. Thus, it is evident that a
non-indicating system, particularly in the case of combination actions, is
very limited and leaves much to be desired.
Although it is known to employ illuminated switches on electronic organs to
indicate when a stop or stops are actuated, such systems suffered from the
mechanical difficulties discussed above and lacked aesthetic appeal. For
example, in the early 1900's the Estey Company of Brattleboro, Vermont,
manufactured what was known as the "cash register" organ which had an
array of buttons having lamps therein that would be selectively
illuminated upon momentary depression of a respective button to indicate
that a given stop had been actuated. A more recent application of the
general concept of utilizing an energized lamp to indicate the actuation
of a stop control device is in certain organ models manufactured by the
Rodgers Organ Company in which draw knobs used for stop control have lamps
mounted therein which are energized in response to operation of the draw
knob of the "on" position and are extinguished when the draw knob is
returned to its normal unoperated position.
It is a primary object of the present invention to provide a true
indicating combination action for an organ which overcomes the
above-described problems of present systems. Another object of the
invention is to provide an indicating combination action that is silent in
operation, is easy to manufacture and adjust, requires a minimum of power
for its operation, and gives the organ a certain visual appeal.
SUMMARY OF THE INVENTION
Briefly, the stop tablet control system according to the invention includes
a multiplicity of stop tablets pivotally supported on a tablet rail and
springbiased to assume a neutral position from which they can be
momentarily moved up or down against the action of the spring, and an
electrical latching circuit adapted to be latched into one or the other of
two stable states by a pulse produced upon momentary movement of the stop
tablet. When a tablet is momentarily pushed downwardly from the neutral
position the circuit is latched into a first state and energizes a light
emitting diode mounted on the operated stop tablet and also turns on the
associated stop. When the tablet is momentarily moved upwardly from the
neutral position, the associated stop is turned off and the light emitting
diode is extinguished. Each stop tablet has an associated latching circuit
whereby one can tell at a glance from the illuminated light emitting
diodes which of the stops are in the "on" condition.
The system according to the invention further includes a plurality of
combination pistons, each having circuit means associated therewith for
toggling a pre-selected plurality of latching circuits to their "on"
states for as long as the piston is held, thereby to energize the light
emitting diodes on the preselected stop tablets, and circuit means
operative when a piston is momentarily depressed to toggle all of the
non-selected stops to their "off" condition.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will become
apparent, and its construction and operation better understood, from the
following detailed description taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is an elevation view, partly in section, of a stop tablet mechanism
according to the invention;
FIG. 2 is a top plan view of two stop tablets of the type shown in FIG. 1;
FIGS. 3 and 3A are fragmentary elevation views illustrating the
construction and function of a modification of the stop tablet mechanism
of FIG. 1; and
FIG. 4 is a circuit diagram of latching circuitry useful with the
illustrated stop tablet mechanism.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2, the present stop tablet control system includes
a multiplicity of stop tablets or more or less conventional design, one of
which is shown in elevation at 10 in FIG. 1, and two of which are shown at
10 and 12 in FIG. 2. The tablets, which are shown approximately full size,
are typically molded of a suitable plastic material, and have a
cross-section as indicated in FIG. 1. The illustrated tablet, which has
been used on Gulbransen organs for several years, has a transverse groove
14 therein defined by a pair of upstanding lips 16 and 18 of a depth of
about one-quarter inch, for receiving a tablet rail 20 which, in turn, is
supported on a stop tab mounting bracket 32 secured to the cabinet of the
organ, as diagrammatically illustrated at 24. The mounting bracket has a
multiplicity of flanges 26 disposed perpendicularly to the axis of the
rail 20 and spaced apart a distance so as to receive a stop tablet between
adjacent brackets as shown in FIG. 2. The mounting bracket 22 and the rod
20 are sufficiently flexible to permit its being mounted in a horseshoe
configuration, as is typical on many organ consoles. The stop tablet 10 is
urged upwardly (so that rod 20 engages the bottom of the groove 14) by a
flat spring 28, preferably formed of phosphor-bronze, secured at its lower
end to the mounting bracket 22 by a fastener, such as the illustrated stud
30. The spring, which may have a thickness of the order of 0.020 inch and
a width of about one-half inch, is curved at its upper end to conform to
the curved under-side 32 of the right-hand 32 of the right-hand end of the
tablet, as viewed in FIG. 1. A thin strip of felt 34 is adhesively joined
to the upper surface of the spring over the region of contact with the
stop tablet to ensure smoothness and quietness of relative movement
between the spring and tablet as the tablet is actuated. The spring 28 is
designed to urge the bottom of the groove 14 against the rod 20 and to
maintain the tablet in the neutral position shown in FIG. 1. When the
left-hand end of the tab is depressed, a protuberance 36 at the lower
extremity of the curved surface 32 urges the spring 28 to the right,
causing it to bend at a point somewhat above the fastening means 30; when
pressure on the tab is released, the spring returns the tablet to its
neutral position. When the tablet is moved upwardly, the upper extremity
of the curved surface 32 tends to bend the spring to have a sharper radius
of curvature and, again, when the upward pressure is released the spring
returns the tablet to its neutral position. The spring 28 is sufficiently
stiff to give a "positive" feel to the tablet operation, and to return and
maintain the tablet in its pre-determined neutral position with relative
firmness. Thus, if all of the tablets and springs are manufactured to the
same tolerance, which is relatively easy to accomplish, the tablets all
assume the same neutral position and give the stop tablet assembly an even
and neat appearance.
As best seen in FIG. 2, the upper surface of that portion of the tablet
that has the curved underside 32 is formed to receive a contact wire 40,
which is secured to the tablet by a screw 42. The wire is shaped to have a
U-shaped bend under the head of the screw and to extend rearwardly at 40'
and to be engaged in a longitudinal groove 42 formed in lips 16 and 18,
and is bent at right angles at points 40" and 40"' to provide a portion
40a disposed substantially parallel to the rod 20. The section 40' of the
wire passes with clearance over the rod 20, and each of the wires 40 is
grounded, as shown, for reasons that will become evident from the
description of the circuit of FIG. 4. When the tablet is depressed the
section 40a of the wire moves upwardly, and when the tab is moved up the
section 40a of the wire moves downwardly. The shaped wires 40 constitute
movable contactors which, as shown in FIG. 1, engage a first fixed contact
46 when the tablet is depressed and engage a second fixed contact 48 when
the tablet is moved upwardly from its neutral position. Typically, the
contacts 46 and 48 take the form of small coil springs supported on an
insulative panel diagrammatically illustrated at 50, and in the present
system are connected to an associated latch circuit 52.
In a manner to be more fully described in connection with FIG. 4, when the
tablet is depressed the latch circuit is operative to turn on the
associated stop and also to energize a light emitting diode (L.E.D.) 54
mounted in an opening through the tablet so as to be visible from the
upper side thereof. The particular placement of the L.E.D. on the tablet
is a matter of choice, but the illustrated location near the free end of
the tablet, between the conventional printed identification of the stop
tablet, has been found to be aesthetically pleasing as well as readily
visible to the organist.
Turning now to FIG. 4, each of the stop tablets of the organ system has an
associated latch circuit 52 wherein the portion 40a of the wire on the
stop tablet is the movable contact of a single-pole double-throw switch of
the momentary contact type. As has been noted earlier, when the stop
tablet is pushed downwardly, the movable contact 40a momentarily engages
the "on" contact 46, and when the tablet is pushed up from its neutral
position it momentarily engages contact 48. Each of contacts 46 and 48 is
connected to one input of a NAND gate 60 and 62, respectively, each of
which may be one section of the commercially available integrated circuit
SN7400. Each of these input terminals are returned to a source of positive
potential, typically having a value of 5 volts, represented by terminals
64 and 66, respectively, through pull up resistors 68 and 70,
respectively. The output of NAND gate 62 is connected to the other input
of NAND gate 60, and the output of NAND gate 60 is connected to the other
input of NAND gate 62. The two NAND gates thus comprise a DC flip-flop
circuit which will remain in which ever stable condition into which it is
set. The output terminal of NAND gate 60 is connected through a resistor
72 to the base electrode of a transistor 74, the emitter electrode of
which is connected to ground. When the base electrode of transistor 74 is
made positive, the collector electrode, which is connected to the organ
stop with which the latch circuit is associated, is connected to ground
through the collector-emitter junction of the transistor, thus actuating
the associated organ stop. It is to be understood that the described
circuit for actuating the stop is by way of example only, and that a
different arrangement would be used in an organ system in which the stops
are actuated by application of a positive potential rather than by
connection to ground potential.
The light emitting diode 54, which is physically mounted on the stop tablet
10, has one of its terminals connected to a source of positive potential,
typically having a value of 5 volts, represented by terminal 76, and its
other terminal is connected through a resistor 78 to the output terminal
of NAND gate 62. Thus, whenever the stop switch contact 40a is moved into
contact with the "on" terminal 46, the output terminal of NAND gate 62
will be at substantially ground potential, thereby causing the light
emitting diode 54 to become illuminated, with its current limited by
resistor 78 to give the desired brightness.
When the contact 40a is caused to momentarily engage the "off" contact 48,
the described latch circuit is toggled to the condition where the
potential at the output terminal of gate 62 is high, thereby extinguishing
the light emitting diode, and the potential at the output of NAND gate 60
is low, thereby to open the collector-emitter junction of transistor 74
and causing the associated stop to be turned off. If the organ system does
not have a combination action, the circuitry described thus far, one latch
circuit for each stop tablet, is all that is required to provide visual
indication of which stops are being played.
The described latch circuit is readily adapted for use with combination
actions, a simple diode matrix type of which is shown by way of example in
FIG. 4, to provide visual indication of the stops being played. The
combination action typically incorporates a plurality of pistons, the
circuitry for one of which is contained in the dotted line enclosure 80,
consisting of a plurality of diodes 82, 84, 86, 88, and 90 through which
the "on" terminal of the latching circuit associated with the stop tablets
of a given division of the organ (such as solo, accompaniment or pedal)
are each connected to a conductor 92 which, in turn, is connected to one
terminal 94 of a piston switch 96, and other terminal 98 of which is
connected to ground potential. In the drawing, the "on" terminal 46 of
latching circuit 52 is connected through diode 90 to piston switch
terminal 94. Preferably the connection from terminal 46 additionally
includes a single-pole single-throw switch 100 in series with the diode to
enable the organist to preselect, in advance, simply by closing or opening
certain of the switches, the registration that will result when the piston
is depressed. When the piston 96, typically a small thumb-operated button,
is momentarily depressed, contacts 94 and 98 are momentarily
short-circuited and connect conductor 92 to ground potential. Conductor 92
is connected through a diode 102 to one input of an inverter 104 whose
input potential is held high by a pull-up resistor 106 connected from both
inputs of the inverter to a source of positive potential, typically having
a value of 5 volts, represented by terminal 108. When the potential at the
input of inverter 104 is lowered by closure of switch 96, the potential at
its output terminal will go high and charge a capacitor 110 through a
diode 112, and thereby apply current to one input of a NOR gate 114 for a
brief period. Since both inputs of the NOR gate are normally held low,
application of current to one of its inputs produces a pulse at the output
terminal having a time constant determined by the value of capacitor 110.
This pulse is applied via conductor 116 and an "off" common bus 118 and a
diode 120 to one input of NAND gate 62, causing the flip-flop to be set to
the "off" condition. It will be understood that the "off" common bus 118
will be connected to the same point in the latching circuits associated
with the other stops controlled by piston 96 through respective diodes.
Thus, any stop connected to conductor 92 will automatically be turned off
when the piston 96 is initially depressed.
The circuit operates as just-described to set all of the stops associated
with piston No. 1 to their "off" condition, but is also effective, as
follows, to turn "on" those stops selected by switches 100. The pulse
produced at the "off" common bus 118 upon initial depression of piston 96
is relatively short compared to the time that the organist will hold the
thumb operated piston depressed; since it is virtually impossible to hold
the piston (or a stop tablet) in its depressed position for less than
fifty or one hundred milliseconds, a pulse of a few milliseconds duration
will with certainty be completed before the piston is released. Thus, even
as the short pulse produced by the initial short-circuiting of contacts 94
and 98 is trying to toggle the flip-flop to the "off" condition, the "on"
input of NAND gate 60 is being held at ground potential through switch
100, diode 90, conductor 92 and the piston switch 96. In other words, the
command telling the flip-flop to toggle to the "on" condition is retained
long after the momentary pulse that would otherwise toggle the flip-flop
to the "off" condition has passed, thus assuring that the latch is toggled
to its "on" condition. Resistors 122 and 124 serve to reset the capacitor
110 so that in the event another piston is operated shortly after piston
No. 1 has been operated, the circuit will again function to supply another
"off" pulse to the common bus 118.
The circuit also includes a "cancel" piston 126 which has contacts 128 and
130 respectively connected to one terminal of capacitor 110 and to a
source of positive potential, typically 5 volts, represented by terminal
132. When contacts 128 and 130 are momentarily shorted together by
depression of the cancel piston to apply a positive potential to capacitor
110, a short pulse is produced at the output of NOR gate 114 which toggles
the flip-flop to its "off" condition. It will be noted that the "cancel"
piston does not affect any aspect of the system which would tend to toggle
the latch circuit to the "on" condition and accordingly simply cancels any
stops that were previously set to the "on" condition.
In order to guarantee that all of the stops are set to the "off" condition
when the organ is initially turned on, one of the inputs of NOR gate 114
is connected through a capacitor 134 to a source of positive potential,
typically having a value of 5 volts, represented by terminal 136, it being
understood that there will be no potential at terminal 136 when the organ
is turned off. A pull-down resistor 138 is connected from one terminal of
capacitor 134 to ground, and a reset resistor 140 is connected from the
other terminal of the capacitor to ground. When the organ power is
initially turned on the potential from source 136 charges capacitor 134 to
produce a momentary pulse at the output of gate 114 which is applied to
the "off" common bus 118, thereby to turn all of the stops "off". Although
not essential, this is a desirable feature because without it there is a
possibility that some stops would be "on" and others "off", in a random
manner, every time the organ is turned on.
As has been noted earlier, an organ may have any number of pistons, ranging
from perhaps a minimum of four up to perhaps 100 or more in the case of
large theater organs, divided up into divisional pistons and general
pistons. That the system of FIG. 4 may employ a plurality of pistons is
indicated by the dotted enclosures 142 and 144 which would each contain
circuitry for pistons #2 and #3 similar to that described in connection
with piston circuit 80. It is significant to note, however, that
regardless of the number of pistons provided in the organ it is necessary
to have but one control circuit (i.e., the circuit including inverter 104
and NOR gate 114) to control all of the piston circuits. Thus, since each
piston would require a relatively small number of inexpensive diodes, and
it is not necessary that the control circuit be duplicated for each
piston, it will be evident that a rather comprehensive combination action
can be realized at relatively low cost.
Although the invention has been described in association with a diode
matrix type of combination action, the inventive concepts and principles
are equally applicable to other known types of combination actions. For
example, a full capture type combination action, wherein by manually
setting selected tablets to the desired registration and then holding the
associated piston as a set button is pushed, one can capture that
combination on a given piston for later recall whenever that piston is
pushed, can be used. Accordingly, it is to be understood that the
invention is not limited to the specific circuitry that has been
illustrated and described.
An important advantage of the overall system described herein is that there
has not been a major change from the familiar appearance of organs: the
stop tablets look the same as they do in conventional organs and the
action taken by the organist is the same as with conventional organs. That
is, when it is desired to turn a given stop on, he reaches up and
depresses the appropriate stop tablet, and when he wants to turn off a
given stop he pushes the tablet upwardly in the same way as he is
accustomed. Organists who have used the described system have remarked
that while the illuminated light emitting diodes give the organ a uniquely
different appearance than a conventional organ, none has had to ask how
the stop tablets are to be used. The aesthetic appeal of the array of stop
tablets may be enhanced by using light emitting diodes of distinctive
colors to indicate different classes of stops, much as different colored
tablets are currently used for this purpose. For example, red L.E.D.'s
might be used to indicate reeds, green ones to indicate flue stops, and
amber ones to indicate strings, these three colors now being commercially
available.
The described construction of the stop tablet mechanism and the described
circuit can with minor modification provide another desirable feature to
an organ having a combination action. It is sometimes desirable when
playing a given registration of stops to select another stop, for example,
a single melody stop, and cancel any other stops in the division that were
previously sounding. Referring to FIG. 3, this function may be added to
the present system by adding an additional spring 150 to each stop tablet
assembly which is spaced from the spring 28 and is somewhat shorter than
spring 28. The two springs have such relative lengths that when the tablet
is pushed to its "on" position the bent spring 28, shown in dotted line,
will come in contact with the upper curved end of spring 150, the latter
thus offering resistance to further downward movement of the stop tablet.
The modulus of spring 150 is such that upon further depression of the stop
tablet, i.e., beyond the point of increased resistance provided by spring
150, the upper end of spring 150 is deflected, as shown in FIG. 3A,
allowing further downward movement of the tablet. When in its fully
depressed position, the wire contactor 40a on the tablet contacts an
additional contact 152 (while at the same time also engaging contact 46)
supported on the panel 50 (FIG. 1) and connected to the latch circuitry
52. As seen in FIG. 4, the additional contact 152 is connected through a
diode 154 to the input of inverter 104. Consequently, when the stop tablet
is depressed to the point where contact 40a engages both of contacts 46
and 152, the input to inverter 104 is grounded causing its output terminal
to go high and to produce a cancelling pulse at the output of NOR gate 114
to turn off any other stops in the division that were previously sounding.
Then, as the stop tablet is released, first breaking contact between
contactor 40a and contact 152, while still maintaining contact between
contactor 40a and contact 46, the latch circuit associated with that stop
tablet will toggle the flip-flop to the "on" condition and turn on the
single stop associated with the tablet. This feature would usually be
employed only on the solo divisional pistons, and its utility lies in the
fact that when playing a given registration it is possible to substitute a
single melody stop and to cancel any other stops in the division that were
previously playing.
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