US1813097A - Automatic musical instrument - Google Patents

Automatic musical instrument Download PDF

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US1813097A
US1813097A US116787A US11678726A US1813097A US 1813097 A US1813097 A US 1813097A US 116787 A US116787 A US 116787A US 11678726 A US11678726 A US 11678726A US 1813097 A US1813097 A US 1813097A
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exhaust
valve
chest
chamber
pneumatic
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US116787A
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Charles F Stoddard
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AMERICAN PIANO Corp
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AMERICAN PIANO CORP
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    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10FAUTOMATIC MUSICAL INSTRUMENTS
    • G10F1/00Automatic musical instruments
    • G10F1/02Pianofortes with keyboard
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S251/00Valves and valve actuation
    • Y10S251/901Curtain type valves

Description

July 7, 1931. c. F. sToDDARD AUTOMATIC MUSICAL INSTRUMENT 1926 9 Sheets-Sheet l Filed June 18 NVENTOR.
*n BY D l; ATTORYS.
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Quinn/woz Y D n v lll l' 4 l July 7, 1931. c. F. STODDARD AUTOMATIC MUSICAL INSTRUMENT Filed June 18, 1926 9 Sheets-Sheet 3 July 7, 1931. c. F. sToDDARD 1,813,097
AUTOHTIC MUSICAL INSTRUMENT Filed June 18, 1925. 9 sheets-'sheet 4 I il iup* IIHHII ,Mimik ili if lJuly 7, 1931. c. F. STQDDARD 1,813,097
AUTOMATIC MUS ICAL INSTRUMENT Filled June 18, 1926 9 SheetS-Sheet 5 July?,` 1931. 1c. F.sKToDDAR'D v 1,813,097
` AUTOMATIC MUSIGL INSTRUMENT Filed June 18I 1926 9 Sheets-Sheet 6 July 7, 1931- c. F. STODDARD 1,813,097
Y AUTOMATIC MUSICAL INSTRUMENT Filed June 18, 1926 9 Sheets-Sheet 7l l Snantoz (flor/nur' l July 7, l931 c. F. sToDDARD 1,813,097
' AUTOMATIC MUSICAL INSTRUMENT Filed June 18, 1925 9 sheets-sheet 'e Tracker 733.
l I -25 "Hefe 20 ames aff/1ere AUTOMATIC MUS ICAL INSTRUMENT Filed June 18,1926 9 sheets-sheet 9 @fg-9,15 Z
f2 I@ 30'6 f l vwewboz @Uf/tom Y Mwj Patented July. 7, 1931 UNITED -s'm'rus PATENT .o1-FICE CHARLES F. STODDARD, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, T0
AMERICAN '.PIANO CORPORATION, OF-EAST ROCHESTER, NEW YORK, A CORPORA- TION .OF DELAWARE Applicationfled J une 18,
to mechanisms and methods for improved.
expression control, or for improving the control of the dynamic forces with which indvidual notes or groups of notes of a given composition are sounded.
The apparatus illustrated in the drawings and described more particularly hereinafter relates especially to that class of instruments now known to the trade and general public as reproducing pianos, because they are intended to reproduce, automatically, under control of 'lt-perforated note sheet, the manual performances of artists or other pianists.
The problem of controlling the instrumentalities of a piano by automatic means in such manner as to simulate manual playing brings with it the problem of coordinating such instrumentalities as they are coordinated by the artists in manual playing in order that those subtle refinements and delicate nuances which distinguish the playing of the artist may not be lost, but may be accurately reproduced by the automatic mechanisms. Accurate reproduction of these delicate effects implies more than the mere transmission to the hammer mechanism for striking each note of the composition of a dynamic force equal or proportional to that transmitted to the hammer or key by the artist in the manual performance. There are, for instance, progressions of notes occurring one after another which possess their characteristics as a group and must be treated as a group for proper reproduction; there are pedaling effects which must be accurately coordinated with the playing of the notes themselves; and there are variations within individual instruments which are compensated unconsciously by the artist who is familiar with the feel of his instrument which must be compensated for to secure accurate reproduction by an automatic instrument.
It is an object of the present invention to provide mechanisms which shall cooperate in such manner as to reproduce manual play-- ing automatically with the results just de- AUTOMATIC MUSICAL. INSTRUMENT i 1926. Serial. No. 116,787.
scribed in addition to other results hereinafter more particularly described.
It is a further object of the invention to improve various parts of the expression mechanism in order that the coordinated result of the whole may be correspondingly improvedl Other objects and advantages of the invention will appear hereinafter.
A preferred embodiment of the invention selected for -purposes of illustration is shown in the accompanying drawings, in which,
Figure 1 is a diagrammatic view showing the pneumatic connections between the cooperating units of the apparatus.
Figure 2 is a semi-diagrammatic sectional View taken through the stack and expression mechanism.
Figure 3 is a longitudinal section taken on the line 3-3 of Figure 2.
Figure 4 is a section through the bass expression valve mechanism.
Figures 5 and 6 are top plan and front elevational views respectively of the stack.
Figure 7 is a longitudinal section taken on the line 7--7 of Figure 2.
Figure 8 is a section through the stack showing in section one of the dummy 'valves for controlling the lost motion pneumatica Figure 9 is an enlarged sectional view illustrating the construction and operation of the regulator.
Figure 10 is a rear elevation of the stack showing the pneumatics adjusted to compensate fordiiierences between individual notes.
Figure 11 is a top plan View of the crescendo mechanism. f l
Figure 12 is a front elevation of the same, the valve mechanism and certain other parts being shown in section to better illustrate the construction and operation thereof.
Figure 18 is a semi-diagrammatic view illustrating the construction and operation of the pump pressure controlling mechanism.
' Figure 14 is asectional view of the pedal pressure regulator.
Figures 15, 16, 17 and 18 are sectional views illustrating the construction of the stack and the arrangement of the valve units and striker pneumatics thereon. i
For purposes of convenience in description,
and in order that the construction and mode of operation' of the preferred embodiment of the invention may be more easily understood, the pneumatic regulator will be first described, and then, in the order named, the in- The regulator Referring to thel drawings, the striker or player pneumatics 1 are provided which are connected by rods' 2 to levers 3 pivoted at 4 to a fixed part of the piano structure. The outer ends of the levers 3 lie underneath the rear ends of the keys 5 of the piano and are adapted to actuate the keys through the adjustable screws 6 mounted in the end of the levers 3. Movement of the keys operates the usual hammer act-ions 7 to actuate the hammers 8 to strike the piano strings 9 in the same manner' that the hammers are actuated when the piano is played manually. Upward movement of the keys 5 also actuates the levers 10 to lift the dampers 11 from the strings to permit free vibration thereof in the usual manner. As will be understood, a sufficient number of striker pneumatics 1 are provided to operate the entire piano action.
Each of the striker pneumatics 1 is connected by a passage 12 to the valve chamber 13 of a valve unit 14 which may be connected to the tracker bar 15 by a suitable duct 16. The valve units 14 and the-striker pneumatics 1 may be convenientl mounted on opposite sides of a board 18 w ich is provided with a series of vertical passages 19 to which the exhaust chambers 20 of the valve units are connected through the passages 21. Each of the passages 19 is connected with a compartment which may be conveniently divided by the partition 22 into two sec-tions 23 and 23', one for the base and one for the treble section of the piano. Each section of this compartment, together with the passages 19 leading therefrom to the valve units, may be referred to as a regulated exhaust chest, since, as will be hereinafter explained, the exhaust therein is regulated by the mechanisms provided to control playing intensities.
As will be understood, the force of the blow delivered by a hammer to a string by the collapse of a motor pneumatic will depend largely upon the degree of exhaust maintained in the regulated exhaust chest. That is, if a high degree of exhaust is maintained in said chest, the collapse of any given pneumatic, when its controlling valve is operated to subject the pneumatic to exhaust, will be more rapid than when the degree of exhaustmaincontrolling mechanism designate vided for governing the degree of exhaust v maintained in the regulated exhaust chest and for thereby governing the force of the blows applied to the strings of the piano. v For purposes of explaining the general character of the regulator and to exemplify one ractical embodiment thereof for controlhng the degree of exhaust maintained in the wind chest. the apparatus particularly shown in Figures 2 and 9 of the drawings has been selected in which the high exhaust chest 25 is connected by a conduit 26 to a reservoir bellows 27' which is connected, as will be hereinafter more fully explained, through conduit 28 to a suitable source of exhaust 29. Any of the well-known forms of exhaust means may be employed in connection with the present invention, that shown herein comprising the ordinary bellows type pump driven by an electric motor 30. As will be hereinafter explained, a pum pressure d) generally by reference numeral 31 may be operatively connected to the conduit 28 through conduit 32, the said mechanism serving to control the exhaust supplied by the pump to the reservoir 27.
Means are provided for controlling the degree of exhaust maintained in the regulated exhaust chests 23 and 23', as for example by restricting more or lessr communication between said chests and the high exhaust chest 25. In the specific illustrative embodiment of the apparatus shown in the drawings, this restrictive action is performed by a movable member of very little weight, influenced, as will be hereinafter explained, by the pneumatic forces to which it is exposed. This movable member is arranged to cooperate with a fixed supporting member which comprises, in the present embodiment, a plate or screen 33 provided with a multiplicity of perforations 34 to permit the ypassage of air.
In the embodiment illustrated, the movable member comprises a diaphragm or membrane 35 of leather, rubber cloth, or other suitable flexible material. Preferably, this movable member is arranged to have one side exposed partly to the high exhaust maintained in the chest 25 and partly to the regulated exhaust maintained in the chest 23. As shown, the diaphragm 35 in operation extends along the plate or screen 33 in position to cooperate therewith to control the passage of air therethrough from the chest 23 to the chest 25, thus forminor in eii'ect a valve controlling the How of air from the action or regulated exhaust chest to the high exhaust chest.
Means are provided to act upon the movable member, herein the diaphragm 35, in such manner as to increase the effect of high exhaust upon regulated exhaust,.as for example, to tend to peel the diaphragm away from the screen or plate 33 to thereby increase the effective opening between the chests. The said means herein includes a chamber 36, which may be known as a controlled exhaust chest, separated from the regulated exhaust chest 23 and the high exhaust chest 25 by the diaphragm 35, and means to maintain in said chamber a certain degree of exhaust, which for the present may be assumed to be constant, although as will appear later, this degree of exhaust may be changed for the purpose of securing expression variations.
In the specific embodiment of the invention illustrated the chamber 36 is connected through a conduit 37 to the reservoir 2T, a bleed opening 3S being interposed in the passage to constrict the communication therebetween. As will readily be understood, any desired degree of exhaust less than high exhaust may be maintained in the chamber 36 by the relative adjustment of the sizes of the bleed opening 38 and certain atmosphere vents opening into chamber 36 hereinafter described, and preferably said degree of exhaust is maintained at a somewhat higher level than the desired degree of regulated exhaust, the precise degree depending upon the particular design and arrangement of the parts. The passage 37 leading to the reservoir 27 may preferably enter the same at a point near the hinged end thereof in order that the exhaust communicated to the controlled exhaust chest 37 may be influenced as little as possible by the aspirative effect of currents of air which may pass through other portions thereof, for, as will hereinafter ap pear, it is desirable to maintain controlled exhaust as far as possible without fluctuation.
The differential between high exhaust in chest 25 and controlled exhaust in chest 36 acting on that part of the diaphragm exposed to high exhaust will exert an upward force urging the diaphragm against the screen 33 to thereby cover the perforations of the screen to prevent the passage of air therethrough and to restrict communication between high and regulated exhaust chests. On the other hand, the differential between regulated exhaust in chest 23 and controlled exhaust in chest 36 acting upon that part of the diaphragm exposed to regulated exhaust exerts a downward force urging the diaphragm in a downward direction. As will be apparent, this downward force will tend to peel a portion of the diaphragm subjected to high exhaust away from the screen 33, thus serving to open certain perforations to permit the passage of airtherethrough. Thus' the area of the diaphragm exposed to high exhaust may be divided into two portions. That portion which is forced against the screen by the differential of pressures acting thereon may be termed an inactive or dead area, and that portion which is drawn away from the screen by the action of pneumatic forces thereon may be termed an active area. As will be observed, the active area subjected to high exhaust may vary as the diaphragm is peeled away from the screen or returned thereto in operation. i
Assuming that the forces exerted on the diaphragm by high exhaust and controlled exhaust remain substantially constant, a condition of equilibrium is established such that regulated exhaustwill also be maintained substantially constant, because if, for example, regulated exhaust tends to increase then the downward force of the differential bei tween regulated exhaust and controlled exhaust is decreased and a tendency toward an upward movement of the diaphragm results. This in turn tends to further restrict communication between the high and regulated exhaust chests by closing certain of the perforations 34, permitting regulated exhaust tobe decreased by the iniiux of air until the condition of equilibrium is restored. On the other hand, if regulated exhaust tends to decrease, then the differential between regulated exhaust and controlled exhaust tends to increase with the result that there is a tendency toward a downward movement of the diaphragm to open additional perforations 34 to thereby increase the effecive opening between the high and regulated exhaust chests, thus permitting additional air to be withdrawn from the regulated exhaust chest to thereby increase the degree of exhaust maintained therein until the condition of equilibrium is restored. Thus there is a. constant tendency on the part of the diaphragm to maintain a position such that the balanced condition sha-ll always prevail.
In the ordinary operation of the piano, several factors may act separately or may combine tending to cause variations in regulated exhaust. For example, there may be more or less constant leakage of atmospheric air to the regulated exhaust chest, which, even though slight, tends to reduce regulated exhaust. By the action just described, however, this would result in a movement of the dia.- phragm suiicient to permit a corresponding leakage to the high exhaust chest through the perforations 34, thus permitting regulated exhaust to remain substantially constant.
As a further example, in the normal operation of the piano by the motor pneumatics 1 under control of the usual note sheet, each of the motor pneumatics before collapse is filled with air at atmospheric pressure. Immediately that the valve 14 is operated to collapse the pneumatic l there is an inrush of atmospheric air'into the wind chest past the valve as it travels from one seat to another, followed immediately by the air that is withdrawn from the pneumatic as it collapses.
Due to the action just described, whenever such an inrush of air occurs, the force of regulated exhaust acting upwardly on the diaphragm thereby tends to decrease thus permitting the diaphragm to be peeled away from the plate 33 to thereby open additional perforations 34 to permit a corresponding quantity of air to be withdrawn to the high exhaust chest. Consequently, there is a tendency to increase regulated exhaust until a condition of equilibrium is again reached.
Such action may take place so promptly and quickly, that, in effect, .the action is to maintain the degree of exhaust in the regulated exhaust chest substantially constant, or, in other words, the practical ei'ect is that of maintaining rather than correcting. And this capacity of the apparatus to maintain a constant degree of regulated exhaust rather than to correct changes in regulated exhaust is increased over prior art structures having a similar capacity due to the fact that the diaphragm 35 is substantially without inertia. In other words, such action as occurs results almost wholly from the action of juxtaposed pneumatic forces upon each other, and there is no lag or overthrow such as would otherwise occur with parts having substantial weight.
This capacity of the apparatus to maintain a constant degree of regulated exhaust is also increased over prior art structures due to the construction and arrangement of the parts whereby the regulator is placed in close proximity to the player pneumatics. Due to this provision the waves of pressure or change of pressure have a less distance totravel than in prior art structures in which the regulator and action wind chest have been arranged as separate units connected by suitable conduits or wind trunks and consequently an increase in the speed of theregulating action is noted. It will also be observed that in the embodiment of the invention illustrated herein the regulator extends for a substantial distance along the bottom of the Wind chest and thereby provides direct communication between .the regulator and the most frequently used player pneu-matics in the middle range of the instrument.
Thus, in the playing of a single note there may be several contributing factors tending to reduce regulated exhaust below its normal level which, if not compensated for, might reduce the force with which the blow is struck. As has been explained, however, the restoring action operates so quickly due to the absence of inertia that in practical effect regulated exhaust is maintained substantially l constant.A
Obviously, in the operation of a piano the number of motor pneumatics operated during the playing of a musical composition varies Widely from time to time., As will be ap arent, however, due to the action just descri d, the degree of exhaust maintained in the regulated exhaust chest and the wind chest will tend to remain substantially constant no matter how many motor pneumatics are operated at any given time and the effective opening between the high and regulated exhaust chests will be automatically varied to permit the effectual removal of the air admitted to the regulated exhaust chest.
\ Incremental epressz'on control Thus far it has been assumed that the degrec of exhaust maintained in the controlled exhaust chest 36 remains substantially constant, and ythat it thus exerts a substantially constant downward pull on the diaphragm 35. That is, the apparatus thus far has been considered purely as a regulator. Means are provided,` however, acting in conjunction with the regulator for changing the degree of exhaust maintained in the controlled exhaust chest to thereby change the degree of elxhust maintained in the regulated exhaust c es Before passing t0 a'consideration of the means illustrated to accomplish this purpose, it may be convenient to consider the effect of a change in controlled exhaust on the operation of the apparatus, and particularly on regulated exhaust. As has been explained, regulated exhaust and high exhaust exert an upward pull `on the diaphragm, while controlled exhaust exerts an opposed downward pull thereon. Consequently, assuming that high exhaust remains substantially constant, an increase in controlled exhaust must result in an increase in regulated exhaust in order that the condition of equilibrium may be maintained.` That is, having increased the force acting downwardly on the diaphragm, the force acting upwardly must also increase in order to maintain the condition of-equilibrium. As a specific example of what may occur under these conditions, if controlled exhaust is increased, there first results a tendency to peel the diaphragm 35 away from the plate 33 thus opening additional perforations to permit a larger quantity of air to be withdrawn from the regulated exhaust chest whereby the exhaust therein is increased. -This increase in turn exerts an increased upward pull on the diaphragm tending to return somewhat toward the plate to restore a condition of equilibrium at the higher level of regulated exhaust. Inlike manner any decrease in controlled exhaust will cause a decrease in regulated exhaust and in the degree of power applied to the strings by the hammers.
As has been set forth before, the particular degree of exhaust maintained in the controlled exhaust chest 36 depends on the relative sizes of the separate vents leading from this chamber to the reservoir and to the atmosphere. Obviously, if the size of the vent to atmosphere is increased controlled exhaust will be decreased and conversely if the size of the vent to atmosphere is decreased, controlled exhaust will increase. Means are proi vided for varying the size of the vent to atmosphere by distinct increments in order that controlled exhaust and hence regulated exhaust may be varied to thereby obtain incremental expression variations in playing.
For this purpose there are provided, lead? ing into the chamber 36 a plurality of vent passages 40, 40a and 406 in which may be placed bleed cups 4l, 41a and 416, the cups elng provided with openings of progressively increasing areas, the opening in the cup 41 being the smallest opening, the opening in the cu 41a being somewhat larger and the opening in the cup 416 being the largest. When all of the passages 40, 40a and 406 are opened to permit the passage of atmospheric air to the controlled exhaust chest 36, playing intensities will be at their softest, because the large inflow of atmospheric air relative to the small outflow through the constricted passage 37 causes only a slight degree of exhaust to be maintained in chest 36` and as before explained, a relatively low degree of exhaust will be maintained in the regulated exhaust chest 23. On the other hand, as one or more of the passages 40, 40a and 406 are closed to prevent the passage of atmospheric air to the controlled exhaust chest 36 the degree of exhaust maintained therein is increased with corresponding increases in the exhaust maintained in the regulated exhaust chest 23.
In order to close the passages 40, 40a and 406, the pouches 42, 42a and 426 are provided having relatively flat stilfened portions 43, 43av and 436 serving as valves to cover the outer ends of the passages. The pouches 42, 42a and 426 are mounted within a chamber 44 having a conduit 45 leading to atmosphere and are provided with light coil springs 46, 46a and 466 which assist in returning and holding the valves 43, 43a and 436 on their seats. Leading to the inside of each of the pouches is a duct 47 47 a and 476 which may be connected to a valve mechanism hereafter described for supplying either exhaust or atmosphere to the pouches. As will be apparent, when the pouches are subjected to exhaust, a differential of pressure is .created which forces the pouches downward away from the passages 40, 40a and 406 thereby opening the same. On the other hand, when atmosphere is admitted to the pouches, the
pressure differential is reversed, the pouches are returned to their seats under the influence of the springs 46, 46a and 466 and are retained thereon under the combined influence of the springs and the pressure differential;
In order that the pouches may be controlled automatically from the tracker bar the valve mechanism 50 is provided having a chest 5l connected to high exhaust through the conduit 52.
Ina-smuch as the valve mechanisms for controlling the base and treble sections of the piano are` duplicates only one will be described in detail herein, it being understood that a valve mechanism 50 is provided for controlling the treble section of the piano in a manner similar to that in which the valve action 50 controls the base section of the action.
The valve action 50 includes three valve units 53, 53a and 536 connected to the pouches 42, 42a and 426 by the ducts 47, 47 a and 476 respectively. Inasmuch as each of these valve units Aare of the same construction only one will be described in detail herein. The duct 47 is connected to a valve chamber 54 controlled by a duplex valve 55 arranged to control a port 56 to atmosphere and a port 57 leading to the exhaust chest 58, said exhaust chest 58 being connected to the chest 5l through the passage 59.
rlhe valve 55 is controlled and operated by a diaphragm 60 covering the diaphragm chamber 6l into which opens the duct 62 leading to the tracker bar l5. Then the tracker bar vent 63 controlling the admission of atmosphere to the duct 62 is opened, the differential of pressure between the diaphragm chamber 6l and the exhaust chest 58 causes the valve 55 to be raised to close the port 57 to thereby cut off exhaust from the chamber 54 and to open the port 56 to thereby admit atmospheric air to the chamber 54. Thus, under normal conditions with the tracker bar vent 63 closed and the valve 55 lowered the chamber 54 is maintained under exhaust from the exhaust chest 58 and when the valve 55 is raised atmospheric air is admitted to the chamber 54 and exhaust is cut olf.
Then the valve 55 is once raised by venting the tra-cker duct 62 the valve preferably remains in raised position even though the tracker ventmay be immediately closed. In the specific apparatus illustrated, this results from the fact that once the valve 55 is opened to admit atmosphere to the valve chamber 54 said valve 55 is held in that position by atmosphere admitted past the valve 55 into a duct 64 from which it passes through a bleeder vent 65 through the duct 66 which communicates with the diaphragm chamber 6l. Thus so long as atmosphere is admitted through the duct 64 the diaphragm .60 will remain lifted and atmosphere will continue to be admitted to the chamber 54,
time 1n a manner such as that about to be described. x
v f In the preferred embodiment ofthe apparatus illustrated in the drawings, a single valve mechanism controlled by a single tracker vent is employed to cooperate with all or any of the three above described valve mechanisms to nega-tive the effect of opening one or more-tracker vents 63, 63a and 636. Such valve mechanism is designated in the drawings by 71. This valve mechanism comprises a Dvalve chamber 72 controlled by a duplex valve 73 arranged to open the port 74 to atmosphere and to close the port 75 to exhaust from the chest 76 connected to the exhaust chest 51 by means of the duct 77. The valve is opera-ted by diaphragm 78 mounted over the diaphragm chamber 79 which communicates by means of the duct 80 with a tracker vent 81.
When the tracker vent 81 is opened by a suitable opening in the note sheet, atmosphere is admitted to the diaphragm chamber 79 and the differential of pressure between the diaphragm chamber and the exhaust chamber 76 causes. the valve 73 to be raised to cut oil' exhaust from the valve chamber 72 and to permit atmospheric air to enter the chamber.
`As already stated, the valve 55 is held in raised positlon by the atmosphere which is admitted to the diaphragm chamber 61 through the ducts 66 and 64. As'will be apparent, if communication between these ducts is cut off and suction applied to the duct 66 the differential of pressures which causes the valve 55 to be raised would be equalized and the valve 55 would return to its normal position. Means are provided for performing this operation, such means comprising the valve 85 which normally remains in seated position covering the port 86 leading to the exhaust chamber 58. If this valve is raised, the port 86 will be closed thus cutting ofi' communication between the ducts 64. and 66. At the same time the valve chamber 87 will be subjected to exhaust through the port 86 and this exhaust communicated through the bleed vent 65 and duct 66 will cause the valve 55 to return to normal position as before described.
The valve 85 is operated by diaphragm 88 covering the diaphragm chamber 89 which is in communication with the valve chamber 72 before described through the duct 90. Accordingly, when the valve173 is in its lowered sition the diaphragm chamber 89 is sub- Jectedto exhaust and the valve 85 remains in lowered position. When the valve 73 is raised by the admission of atmospheric air through the tracker vent 81, atmospheric air is also admitted to the diaphragm chamber 89 with the result that the valve 85 is raised and the valve 55 is returned to normal position. In this manner by opening the tracker vent 81 any of the chambers 54, 54a and 546 which have been opened to atmospheric air are again subjected to exhaust. f
The operation just described so far as it concerns the specific illustrative mechanism depends upon bleeding the diaphragm chamber 61. If the tracker duct` 62 be opened through its vent 63 at the same time the vent 81 is opened to initiate the bleeding' of the diaphra m chamber 61, atmosphere will enter the c amber 61 more rapidly than it can be exhausted therefrom by the described bleeding, and, therefore, the effect of opening the vent 81' is negatived and under such circumstances the valve 55 will remain in raised position and atmosphere will continue to be admitted to the chamber 54.
Also, if the tracker vent 63, for instance, be opened simultaneously with the tracker vent 8l, the latter will inaugurate a tendency to bleed the chamber 61 and keep the 'valve 55 lowered in the position shown, but the simultaneous opening of the tracker vent 63 will admit atmosphere to the chamber 61 more rapidly than it can be exhausted by the bleeder vent and, therefore, the valve 55 will be lifted in spite of the opening of the tracker vent 81.
From the above description it will be understood that whether or not the tracker vent 81 be opened, the opening of any of the vents 63, 63a and 636 will have its normal and usual effect to admit atmosphere to the appropriate chamber 54, 54a `or 546. This will be true if any vent 63, 63a or 636 be opened with or without simultaneously opening the tracker vent 81.
On the other hand, if the vent 63 be opened and then closed atmosphere being thereby admitted to the chamber 54, and the vent 81 be thereafter opened, the previous effect of opening vent 63 will be negatived and the chamber 54 will be opened to exhaust.
In the operation of the apparatus thus far described it may be desirable under certain conditions to vent atmospheric air to the regulated exhaust chest, For example, this might be particularly desirable in making sudden changes in regulated exhaust from a condition of relatively high exhaust t0 one of relatively low exhaust in order that the condition of high exhaust may be immediately relieved. For this purpose means are provided for venting atmospheric air to the regulated exhaust chest and such means are preferably controlled by the automatic valve mechanism which controls the degree of exhaust maintained therein.
In the preferred embodiment illustrated, the regulated exhaust chest 23 is provided With a vent 91 to atmosphere, said vent being controlled by the diaphragm 92 mounted on the block 93. The block 93 is recessed to provide a chamber 94 behind the diaphragm and 'the chamber 94 is connectedby duct 95 with the duct 476 leading to the diaphragm chamber 546' controlling the vent 406. Thus, when the duct 476 is subjected to exhaust to operate the diaphragm 426 the duct 95 is likewise subjected to exhaust to raise the diaphragm 92. It will, therefore, be apparent that at any time When vent 416 is open or that in making any change in regulated exhaust involving the opening of the vent 416, the Vent 91 will also be opened to permit the entrance of atmospheric air to the regulated' exhaust chest. It will also be apparent that while the opening of the vent 91 permits an inrush of atmospheric air to relieve any temporary undesirable condition of exhaust, the continued flow of atmospheric air through the vent will not aect the operation of the instrument for the leakage of air will be compensated by a corresponding leakage past the diaphragm 35 as hereinbeiore explained.
Indeed the flow of air through the vent 91 and through the regulator past the diaphragm 35 while playing/the lower inensities which prevail whenever the vent 416 is open may be of positive advantage, for it has been found that the regulator sometimes operates more sensitively with an appreciable fiow of air than is the case when little or no air is flowing therethrough.
The apparatus thus far described has the capacity of maintaining in the regulated exhaust chest al substantially constant degree of exhaust regardless ot the number of motor pneumatics operated at Iany given time, and regardless of the varying amounts of air admitted to the regulated exhaust chest therel'rom. It likewise has the capacity of varying the degree of exhaust maintained in the regulated exhaust chest by a series of substantially distinct steps or increments which produce similar distinct steps or increments in the intensity of the successive notes played by the instrument due to the varying force of the blows imparted to the strings bythe hammers. As has also been noted, the degree of exhaust established in the regulated exhaust chest will be maintained substantially constant at any of the several degrees at which it may be set by changing .the degree of exhaust in the controlled exhaust chest.
Orescemio and diminuendo cont/rol Means are also provided for varying the degree of exhaust maintained in the regulated exhaust chest not only by distinct increments or steps, as has previously been described, but also for varying the degree of regulated exhaust by substantially continuous progression in order to reproduce the crescendo and diminuendo eii'eets which form a part of the artof skilled pianists, such means being designated generally by reference numeral 100. In the present embodiment this desideratum is attained by varying the degree of exhaust maintained in the controlled exhaust chest by substantially continuous progression just as in the previous description incremental changes in regulated exhaust Were obtained by varying controlled exhaust by substantially distinct increments. And such changes in controlled exhaust are obtained in the present embodiment by progressively throttling the conduit 45 leading from :the chamber 44 to atmosphere. Re-
ferring particularly to Figure 12, the conduit f 45 terminates in a mouth piece 101 pivotally mounted on the brackets 102 by means of trunnions 103. Mounted to cooperate with the open end of the mouth piece 101 is a needle valve 104 pivotally secured to the bracket 105 mounted o-n the movable leaf 106 of the crescendo pneumatic 107.
As will be observed, any relative movement between the mouth piece 101 and the needle valve 104 will vary the effective opening to atmosphere and the pressures maintained in the controlled exhaust chest 36 will be correspondingly varied. Consequently, it the mouth piece 101 is held in a stationary position and the needle valve 104 is moved with respect thereto with a substantially uniform movement,`the degree of exhaust maintained in the controlled exhaust chest will likewise be varied with substantial uniformity. It the needle valve is moved further into the mouth piece 101 in this manner, the amount of atmospheric air permitted to enter is progressively decreased, the degree of exhaust maintained in the controlled exhaust chest is progressively increased, and playing intensities are progressively increased, this progressive increase ot playing intensities being known as a crescendo. On the other hand. it the needle valve is withdrawn from the mouth piece at a uniform rate the amount of atmospheric air entering the mouth piece is progressively increased, the degree of exhaust in the controlled exhaust chest decreases progressively and playing intensities decrease progressively whereby diminuendo effects are'secured.
In the present embodiment automatic means are provided for securing uniform progressive movement of the needle valve with respect tothe mouth piece 101, such means comprising in part the pneumatic 10T previously referred to. Pneumatic 107 is connected by means of the conduit 108 with the valve chamber 109 formed in the crescendo valve unit 110. The chamber 109 is connected through the bleed 111 to duct 112 leading to the valve chamber 113 which is normally open to atmosphere through the passage 114. Mounted in the valve chamber 113 Yis a valve 115 cooperating with the diaphragm 116 having a diaphragm chamber 117 connected to the tracker bar through duct 118. The valve mechanism is also provided with a chamber 119 connected to high exhaust or in the preferred embodiment illustrated to a substantially constant exhaust less than high exhaust through the conduit 120 and a bleed 121 is provided to maintain the duct 118 and diaphragm chamber 117 normally under exhaust. When the tracker vent 122 is uncovered to admit atmosphere to the duct 118, valve 115 is raised to close the passage 114 to atmosphere and to connect the passage 112 through the port 123 with the exhaust maintained in the chamber 119. This exhaust being communicated through the bleed 111, chamber 109, and conduit 108 to the crescendo pneumatic 107, collapses the pneumatic slowly, the particular rateof collapse being determined by the size of the bleed opening 111, this bleed ordinarily being of a size to collapse the pneumatic 10-7 rather slowly.
It is sometimes desirable, however, to 'collapse the pneumatic 107 more rapidly in order to secure a more rapid crescendo effect. For this purpose the duplex valve 124 is provided having a head sufficiently large to cover the vent 125 connecting the passage 112 to the valve chamber 109. The lower end of the valve 124 cooperates with the diaphragm 126 having a. diaphragm chamber 127 connected to the tracker bar through the duct 128 and to the exhaust chest 119 through the bleed 129. If, during the operation of. the instrument, tracker vent 130 is opened while the tracker vent 122 is also open, valve 124 will be raised to uncover the vent 125 to permit a more rapid exhaust of the pneumatic 107 than was -previously permitted through the bleed 111. l
Thus it will be apparent that 'by collapsing the pneumatic 107 at two different uniform speeds, fast and slow crescendo effects may be secured. Fast and slow diminuendo effects may like-wise be secured by controlling the rate of expansion of the pneumatic 107 under the influence of the spring 131 by controlling the rate at which atmospheric air is admitted thereto. As will be apparent, if both of the valves 115 and 124 are lowered, as when both tracker vents 122 and 130 are closed, the flow of atmospheric air to the pneumatic is controlled by the bleed 111 and a relatively slow expansion of the pneumatic is permitted and a slow diminuendo effect is thereby secured. On the other hand, if the valve 115 remains lowered While the valve 124 is raised, atmospheric air is permitted to enter the pneumatic 107 through the vent 125 and a fast diminuendo effect is thereby secured. Thus by properly controlling the valves 115 and 124 by suitable perforations in the note sheet controlling vents y122 and 130, both fast and slow crescendo effects and fast and slow diminuendo effects may be secured.
As will be observed from Figures 1 and 12, duplicate crescendo mechanisms are provided for the base. and treble sections of the wind chest. Inasmuch as the crescendo mechanisms are in all respects the same, only one has been described in detail herein.
Referring to Figure 12 the fixed leaf 135 of the pneumatic 107 is mounted on a block 136, while the corresponding. fixed leaf 135 of the treblecrescendo pneumatic 107 is pivotally mounted on the block 136 by means of the hinge 137. The two leaves 135 and 135 are attached by a relatively stiff coil spring 138. As will be observed, the bracket 102 carrying the mouth piece 101 is mounted on the bracket 139'having an adjusting screw 140 forming a limit stop for the pneumatic 107. Corresponding brackets 102 are provided for holding the mouth piece 101', said brackets being mounted on the brackets 139 provided with the adjusting screw 140 forming a .limit stop for the pneumatic 107. Mounted on the fixed lea-f 135 of the pneumatic 107 is an eccentric disk 141 having a handle 142 and adapted to contact with the leaf 13,5 of the pneumatic 107.
As will be observed, movement of the eccentric disk 141 caused by turning the handle 142 serves to displace the entirey pneumatic 107 and serves to simultaneously adjust both of the vents to atmosphere as desired. For instance, moving the handle 142 to the right would cause the leaf 135 to move to the left and brackets 139 and 102 carrying the mouth piece 101 would be moved to withdraw the mouth piece somewhat from the needle valve 104, thus permitting a greater quantity of atmospheric air to enter through the vent. At the same time the leaf 106 would be moved to the left to the same extent and would withdraw the needle valve 104 from the mouth piece 101 to secure a corresponding increase in the size of this vent to atmosphere. This adjustment may be used to adjust the playing of the instrument as desired to meet the taste of the individual owner or operator. If the piano is to be used in large rooms or forconcert work the handle 142 may be moved to the right to thereby raise the normal scale of playing intensities, while if the instrument is to be used in a small room, the handle 142 may be moved to the left to thereby lower the general range of playing intensities.
Pump pressure control In the -preceding description it has been explained that playing intensities are governed and controlled by opposed pneumatic forces acting on the area of the diaphragm 35 exposed thereto, such opposed forces comprising the force of regulated exhaust in the chest 23, the force of controlled exhaust maintained in chest 36 and the force of high exhaust in the chest 25. It has also been explained that variations in controlled exhaust acting on the diaphragm 35 produce Variations in regulated exhaust; thatby causing controlled exhaust to be varied by substantially distinct increments, regulatedrexhaust and playing intensities were likewise varied by substantially distinct increments; that by varying the'force of controlled exhaust by substantially continuous progression, regulated exhaust and playing intensities were varied by substantially continuous progression: p
It is also proposed herein to govern and control the pressure applied by the source of exhaust, herein the pump 29, to thereby additionally govern and control playing intensities. Before passing to a consideration of the means illustrated for governing and controlling pump pressures it may be convenient to consider the effect of changes in pump pressure on regulated exhaust and playing intensities.
as has been set forth before, during the operation of the specific apparatus illustrated and described herein the diaphragm 35 is constantly under the control of opposed forces tending always to balance each other and to hold the diaphragm 35, as it were, in suspension between them; that is to say, the specific apparatus tends constantly to establish a balancing equation between the opposed forces acting upon the diaphragm 35.
Such movement of the valve. 35 as may occur when that balancing equation is disturbed takes place practically instantaneously so that a new balancing equation appropriate to the newly initiated conditions is immediately set up.
lf, under these conditions, that is, with the diaphragm 35 being held in a condition of equilibrium under the action of the opposed pneumatic forces acting thereon, high exhaust is increased, the exhaust in the reservoir 27 and in the high exhaust chest 25 is likewise increased and the upward pull on the dialihragm 35 is thereby increased. At the same time, however, exhaust in the controlled exhaust chest 36 is also increased somewhat, due'to the communication maintained with the reservoir 27 through the conduit 37, and an increased downward pull 4on the diaphragm 35 results. Inasmuch as the active area of the diaphragm 35 exposed to high exhaust in the chest 25 is very small,
while the areaof the diaphragm exposed to controlled exhaust in chest 36 is somewhat larger, the downward pull exerted by the increase in exhaust in chest 36 predominates over the upward pull exerted by the increase of exhaust in chest 25, the final result being an increase in the downward pull on the diaphragm. Consequently, in order to maintain the diaphragm in equilibrium, regulated exhaust must increase.
t Thus if pump pressures are increased an increase in regulated exhaust results therefrom, and conversely, in asimilar manner, if pump pressures are decreased regulated exhaust is decreased.
The changes before described occur throughout the entire range of playing intensities established by the incremental expression mechanism or by the crescendo and diminuendo mechanism previously described. That is, whatever the pressure of regulated exhaust may be, a change in pump pressure will cause a change in regulated exhaust. It
follows, of course, as a logical consequence that if pump pressures are maintained at any substantially constant level, regu-lated exhaust will also be maintained substantially constant.
For instance, for convenience of description and explanation it may be assumed that playing intensi-ries determined bythe crescendo, diminuendo and incremental or step change mechanism could be measured by an imaginary scale upon which the numeral would indicate the lowest playing intensity, while the numeral would indicate the loudest playing intensity when high exhaust is being maintained at 25 as measured on a water gauge. Therefore, incremental and crescendo or diminuendo changes will be effective within the compass of this scale from 5 to 25. F or instance, it may be assumed that the seven steps would fix the different playing intensities respectively at 5, 6, 7.3, 9, l2, 17 and 25.
It may further be assumed that a crescendo may be inaugurated when the playing intensity is fixed at any one of the seven points in the scale except the last, and will, if continued long enough raise the playing intensities at a greater or less speed as may be determined by the apparatus, from the point at which it is inaugurated to the highest intensity.
Thereafter a diminuendo operation may be inaugurated to decrease playing intensities to any point determined by the said step change mechanism.
lf now high exhaust be decreased from 25 to 20, regulated exhaust would be decreased and playing intensities thereby decreased throughout theentire range of the imaginary scale. For instance, the lowest normal intensity 5 on the imaginary scale might be decreased to 4 and the normal intensity of 6 might be decreased to 4.8 and so on, so that the new scale of playin intensities might be represented by 4, 4.8 5. ,7.2, 9.613.6 and 20.
On the other han if high exhaust should be increased from 25" to say 40, regulated exhaust would be correspondingl increased and playing intensities increase For instance, the imaginary scale under these conditions may be as follows: 8, 9.6, 11.6, 14.4, 19.2, 27.2 and 40. Obviously the foregoing ligures are resented herein for illustrative purposes on y, it being desired merely to show that changes in hi h exhaust tend to .change the entire range 0% playing intensities.
'/In the present embodiment for purposes above described, the spill valve regulator mechanism' 150 is provided having a chamber 151 connected to the conduit 28 through the conduit 32'. On one side of the chamber is mounted the grid 152 having a multiplicity of perforations 153v therein, said perforations being adapted to be covered or uncovered by the flexible curtain 154 of very little weight connected to the sleeve pneumatic 155 also of very little wei ht to control the passage of atmospheric air to the chamber 151. The sleeve neumatic is also connec ed to the reservoir 2 through the conduit 156 so'that a condition of exhaust is constantly maintained therein tending to draw the sleeve pneumatic toward the left as shown in' Figure 7 to thereby uncover certain of the perforations 153 to spill .atmosphere to the chamber' 151.
As will be observed, if the exhaust in res ervoir 27 increases, additional exhaust is communicated to the sleeve pneumatic 155, and the force acting on the valve 154 and tending to move the same to uncover additional perforations is increased. Additional quantities of air are thereby admitted to the chamber 151 reducing the exhaust therein, and due to the communication with the reservoir 27 through conduits 32 and' 28 the ex haust therein is decreased. Conversely, if exhaust in the reservoir 27 tends to decrease the force acting on the sleeve pneumatic 155 tending toopen the valve 154 is decreased, the amount of atmosphere entering through the perforations-153 is decreased and the exhaust in the chamber151 and the reservoir 27 is thereby increased.
As will be seen, the action just described results in maintaining in the reservoir 2,7 a substantially constant degree of exhaust and whatever fluctuations, due to change in pump speed or to other conditions such as the admission-of abnormal quantities of air to the main regulator, may tend to occur therein are automatically compensated by admitting more or less atmospheric air. I
The cooperative effect between the main regulator and the spill valve or pump pres-- sure regulator may be vbriefly referred to herein. For example, if, during the operaally large number of motor pneumatics are operated simultaneously, a large quantity of a1r is admitted to the main regulator and is permitted to pass the throttle valve in the manner previously described in order that playing intensities may be maintained at a substantially constant level. As soon as the air admitted has passed the throttle valve, there is a tendency to reduce the exhaust maintained in the conduit between said valve and the source of exhaust.` This tendency, however, results in disturbing the balance of the forces acting on the spill valve, for the force of .exhaust acting on the sleeve vpneumatic 155 tends to be decreased thereby. Consequently, the spill valve tends to close, cutting offy the normal inlow of atmospheric curs in which none of the motor pneumatics are operated, there is a tendency to increase the degree of exhaust maintained in the system between the throttle valve and the source of exhaust, which tendency, acting on the sleeve pneumatic tends to collapse the same to increase the effective spill valve opening to thereby admit a greater quantity of atmospheric air to counteract the tendency toward increased exhaust.
Thus it will be seen that due to the cooperation between the main regulator and the pump pressure regulator the exhaust applied by the source of exhaust is maintained at a substantially constant level, and this in turn assistsin securing accurate regulation by the main regulator as is desirable. v
In the present embodiment the pneumatic force acting on the sleeve pneumatic 155 is opposed by the force of the spring 157, so that in effect the valve 154 is balanced between the two opposed forces. As has been explained, changes in the pneumatic force applied to the sleeve pneumatic automatically regulate the exhaust in the chamber 151 and the reservoir 27 to maintain a substantially constant exhaust therein. On the vother hand, changes in the opposing force, or
tained in the chamber 151 and in the raser-- voir 27 is thereby changed. Specifically, if
lll
the tension of the spring 157 is increased the exhaust in the chamber 151 and reservoir 27 is 1ncreased while if the tension of the spring 157 is decreased the exhaust in the chamber 151 and reservoir 27 is decreased.
For example, 1f we assume an increase m the tension of the spring 157 Without a corresponding immediate increase in the exhaust applied to the sleeve pneumatic 155 the sleeve pneumatic is moved to the right and valve 154 is thereby permitted to cover additional pertorations 153 to thereby additionally restrict the admission of atmospheric air. This additional restriction results in increasing the exhaust maintained in chamber 151 and in the reservoir 274 and consequently the exhaust communicated to the sleeve pneumatic 155 through conduit 156y is increased, and such increase continues until the pneumatic force applied is equal to and balances the tension ot the spring 157. Similarly a decrease in the tension of the spring 157 results in a decrease in the exhaust maintained in the chamber 151 and reservoir 27.
Means are provided for varying automatically the tension applied to the valve 154 by the spring 157 and opposing the exhaust applied to the pneumatic 155. Preferably means are provided for either increasing or decreasing this tension with respect to a predetermined normal tension, and such auto matic mechanisms are preferably controlled from a single opening of the tracker bar.
For this purpose the end of spring 157 is attached to he movable leaf 158 of the pneumatic 159 and the rod 160 which connects the other end of the spring 157 to the valve 154 and pneumatic 155 is preferably slotted to receive one end of the lever 161 which is connected by means of the `spring 162 to the movable leaf 163 ofthe pneumatic 164.
Pneumatic 159 is connected by means o the passage 165 to the exhaust chamber 166 of the outside valve mechanism 167 of usual construction, so that the pneumatic 159 is normally subjected to exhaust, and is therefore normally collapsed to exert a greater tension on the spring 157 than would be the case were the pneumatic 159 in expanded condition. The diaphragm chamber 168 of the valve'mechanism 167 is connected by mea-ns of a duct 169 to a vent 170 in the block 171, said vent normally being closed by means of an arm 172 pivoted at 173. Acting on the arm 172 is a spring 174 tending to raise the arm 172 to uncover the vent 170. The end of the arm 172 engages the movable leaf 175 of the pneumatic 176 and the spring 177 of the pneumaticbeinq stronger than the spring 174 the arm 172 normally remains in position to cover the vent 170, except when the pneumatic 176 is collapsed, at which time the spring 174 raises the arm 172 to uncover the vent 170. As Will be observed, when the vent 170 is uncovered valve 178 is raised to thereby admit atmosphere to the chamber 106 and to the pneumatic 159 to permit the same to expand to thereby decrease the tension of the spring 157.
'Pneumatic 176 ,is connected by means of the passage 179 to valve box 18C having a check valve 181 therein, said check valve being provided with a bleed duct 182. The valve box 180 is connected by means of the duct 183 with the valve chamber 184 of the primary valve mechanism 185 so that the valve box 180 is normally open to atmosphere and the pneumatic 176 is normally in expanded condition. The primary valve 185 is connected tothe tracker bar 15 by means of the duct 186 having a tracker vent 187. Operation of the primary valve 185 by suitable openings in the note sheet cooperating with vent 187 will subject the valve box 180 and the pneumatic 176 to exhaust as the check valve 181 Will be raised by the flow of air as the pneumatic 176 is collapsed. When the vent 187 is closed, however, the check valve 181 will be seated and pneumatic 176 Will expand slowly, the rate of expansion being controlled by the size of the bleed opening 182 in the check valve.
Pneumatic 164 is connected by means of the passage 190 to the valve chamber 191 of the inside valve mechanism 192v so that the pneumatic 164 remains normally in expanded condition. The diaphragm chamber 193 of the' valve mechanism 192 is connected by means of the duct 194 with the vent 195 in block 171, said vent being normally closed by the arm 196 pivoted to block 171 at 197. The pivot 197 is preferably sufficiently tight to cause the arm 196 to remain in any position to which it is moved. When the arm 196 is raised to open vent 195 to atmosphere valve 198 is raised and the pneumatic 164 1s collapsed to thereby tension the spring 162 and through lever 161 to increase the spring tension acting on valve 154 to thereby increase the exhaust maintained in chamber 151 and reservoir 27.
The arm 196 normally remains in position to cover the vent 195, but may be raiced by pneumatic 199 having a movable leaf 200 carrying the lug 201 adapted to engage the end of arm 196, lug 201 being of a length to engage the arm 196 only during the latter partof the collapse of pneumatic 199. 4Pneumatic 199 is connected by means of a passage 202 with valve chamber 203 having a check valve 204 with a bleed opening 205 therein. The valvechamber 203 is connected b v means of the duct 206 with the valve chamber 184 of the primary valve 185 previously described. It will be apparent that valve chamber 203 and pneumatic 199 are normally open to atmosphere and pneumatic 199 is normally expanded; When the tracker vent 187 is open to exhaust by suitable openings in the note sheet, duct 206 is subjected to exhaust but due to the interposition of the check valve 204 pneumatic 199 is exhausted slowly
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2472053A (en) * 1946-10-26 1949-05-31 American Wheelabrator & Equipm Dust collector for shuttle feed conveyers
US3012545A (en) * 1957-09-03 1961-12-12 Goldmann Boleslaw Marja George Machines
US3472110A (en) * 1964-12-11 1969-10-14 W W Kimball Co Player piano

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2472053A (en) * 1946-10-26 1949-05-31 American Wheelabrator & Equipm Dust collector for shuttle feed conveyers
US3012545A (en) * 1957-09-03 1961-12-12 Goldmann Boleslaw Marja George Machines
US3472110A (en) * 1964-12-11 1969-10-14 W W Kimball Co Player piano

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