US3067760A - Volume-controlled actuator for bistable valve mechanisms - Google Patents

Description

Dec. 11, 1962 w. HAVERLAND ETAL 3,067,760

VOLUME-CONTROLLED ACTUATOR FOR BISTABLE VALVE MECHANISMS Filed June 12, 1961 2 Sheets-Sheet 1 INVENTORS W/LL/AM H. HAVE/PLA/VD BIRCH/7RD M. BRUSH ATTORNEYS Dec. 11, 1962 w. H. HAVERLAND ET AL 3,067,760

VOLUME-CONTROLLED ACTUATOR FOR BISTABLE VALVE MECHANISMS Filed June 12, 1961 2 Sheets-Sheet 2 INVENTORS W/LL/AM H, HAVE/PLAND B/RCHARD M. BRUSH B Y Kym A T TORNE Y5 3,067,760 VGLUME-CUNTROLLED ACTUATDR FfiR BISTABLE VALVE MECHANISMS William H. Haverland and Birchard M. Brush, Denver, (1010., assignors to The .I. .I. Monaghan Company, Inc.,

Denver, Colo, a corporation of Colorado Filed June 12, 1961, Ser. No. 116,398 22 (Zlaims. (Cl. 137-63) This invention relates to a volume-controlled actuator for bistable valve mechanisms operative to close the latter upon delivery therethrough of a pre-determined quantity of a gaseous medium on an intermittent basis.

Gaseous flow-controlled systems of the type associated with respiratory equipment for medical use require the delivery of accurately predetermined quantities of a gase ous medium on an intermittent basis. The volume of gas delivered to the patients lungs during each inhalation phase of the breathing cycle will vary with each patients lung capacity. Also, the pressure of the gas within the lungs must be maintained below a pre-set maximum or there is danger that the lungs may burst or rupture.

As far as volume-controlled systems in the prior art are concerned, about the only one that has ever been used causes the gaseous medium from a pressurized source thereof to be delivered into an inflatable bag of some type which is then deflated to force the volume of gas contained therein into the patients lungs. The many deficiencies of such a system become readily apparent when it is realized that there is no assurance all of the gas contained in the bag is used during each inhalation of the patient and any residual quantities will be left in the bag to combine with subsequent full volumes delivered thereto. Such a unit is also bulky and, therefore, cumbersome to use even in hospitals. Furthermore, inherent in such a system are the inaccuracies occasioned from the use of flexible rubber bags or bellows arrangements that can stretch when expanded. As a result, most of the prior art systems are pressure, rather than volume, controlled.

Having little in the way of volume-controlled respiratory systems in the prior art for use as a basis of comparison, it will be well to examine briefly the criteria upon which the design of such a system must be predicated. First of all, some kind of mechanical counter capable of accurately measuring the quantity of gas delivered to the patient is desirable. The counter should be actuated by the flow of pressurized gas being delivered to the patient rather than some electrical or electromechanical energy source which have proven to be most difficult to isolate to the extent required for use in an explosive atmosphere such as may exist in an operating room. In this same connection, it follows that the counter, if it is to be flow-actuated, must be responsive to a relatively low-level energy source such as is found in a pressure-regulated bottle of compressed gas.

Under ideal conditions, the counter should reset automatically at the end of each inhalation phase of the breath ing cycle in order to eliminate cumulative errors that. are diflicult, if not impossible, to remove from an additive system. To accommodate the different volumetric requirements of the human lungs, adjustment of the volume being delivered by the system is certainly desirable. Furthermore, because the volume-controlled system is not the complete answer to the problem of respiratory equipment in and of itself, it is preferably usable in combination with a pressure-controlled system capable of overriding the volume-controlled unit Whenever the gas pressure within the lungs reaches a pre-set maximum.

Incidental, but significant, features would be, of course, a unit which is compact, relatively free of service difficulties and convenient to use. Other advantages such 3,057,760 Patented Dec. 11, 1962 as low initial cost and a decorative appearance could, if necessary, be sacrificed in order to realize the aforementioned characteristics of a more functional nature.

It is, therefore, the principal object of the invention to provide a volume-controlled actuator for bistable valve mechanisms adapted to deliver predetermined quantities of a gaseous medium on an intermittent basis.

A second objective is the provision of a device of the class described which incorporates a gas-flow actuated nutating plate as the motor mechanism for the counter assembly.

Another object of the invention is to provide a fluidactuated clutch operative to engage the gear train or similar mechanism of the counter assembly for the purpose of operating the spring-biased reset unit that shuts off the gas flow to the patient once the pre-determined volume of gas has been delivered.

Still another object is the provision of an adjustable stop capable of controlling the volume of gas passed to the patient through the nu-tating plate before the fluid actuated clutch functions to disengage the counter assembly.

An additional objective is to provide a volume-controlled gaseous delivery system which is compatible for use in combination with a pressure-controlled system, the latter providing an overriding safety feature preventing excessive gas pressure in the lungs arising from a malfunction.

Further objects are the provision of an invention of the type aforementioned which is versatile, easily operated by even relatively unskilled personnel with a minimum of training, ideally suited for use as a gaseous flowcontrol system for a number of different commerciallyavailable respiratory devices, and one that does not interfere or diminish the eifectiveness of other units used in combination therewith.

Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follows, and in which:

FIGURE 1 is a schematic view in section showing the volume-controlled valve actuating mechanism of the present invention'with the counter unit thereof engaged to furnish a predetermined quantity of gaseous medium received from a pressure-controlled bistable valve used in combination therewith and in overriding relation thereto;

FEGURE 2 is a fragmentary detail of the counter mechanism and automatic reset unit thereof as it appears during the inhalation phase of the respiratory cycle;

FIGURE 3 is a fragmentary detail similar to FIGURE 2 except that the fluid-actuated clutch has disengaged the elements of the gear train permitting the spring-actuated reset unit to return the counter mechanism to its starting position which occurs during the exhalation phase of the respiratory cycle;

FIGURE 4 is a schematic sectional view similar to FIGURE 1 showing the pressure-controlled gas delivery system of the combination at a time slightly farther advanced during the inhalation phase of the breathing cycle; and,

FIGURE 5 is a schematic view shown in section similar to FIGURE 4 except that the elements of the pressure-controlled system of the combination have been shown moved to the inoperative position corresponding to the exhalation phase of the breathing cycle due to the action of the counter mechanism of the volume-controlled system.

Referring now to the drawings for a detailed description of the gaseous flow control system of the present invention and in particular to FIGURE 1 for this purpose, it will be seen to comprise basically a valve assembly which has been indicated in a general way by numeral and a volume-controlled actuating system therefor that has been designated broadly by reference character 12. The valve assembly 10 can be any one of a number of different bistable type connectable to a source of a gaseous medium under pressure for purposes of delivering same at a relatively uniform flow rate on an intermittent basis. In other words, the instant invention is useful in any apparatus for delivering a gaseous medium on an intermittent basis Where such apparatus includes as an element thereof a valve mechanism stable in both the open and closed positions which when moved from closed into open position by some external force acting thereon must be closed again following delivery of a predetermined gaseous volume preparatory to the receipt of a second actuating impulse. For the purposes of the present description it will be assumed that the initiating force used to move the valve mechanism from its stable closed position into a stable open position is the beginning of the inhalation phase of a patients breathing cycle although it is to be clearly understood that the par-ticular means by which the valve mechanism is opened is entirely immaterial. As a specific example of one type of bistable valve that is ideally suited for use with the volume-controlled actuator which forms the subject matter hereof, the pressure-controlled valve that is disclosed and claimed in United States Patent 2,881,757 has been illustrated somewhat schematically and reference should be made to the aforesaid patent for details concerning its construction and operation. Later on in this description an explanation will be given concerning the manner in which this particular bistable valve and other pressure-responsive ones can perform an important added function in combination with the instant volume-controlled actuator therefor; however, for immediate purposes it is desirable to restrict the descriptive material to an. analysis of the actuator assembly 12. For this pur pose, reference will be made to FIGURES 1, 2 and 3.

FIGURE 3 shows the actuator mechanism 12, in its disengaged or inoperative position which is the one which it occupies when the valve assembly 14 is closed; whereas, as soon as the valve opens and the gas is admitted into conduits 14 and 16 of FIGURE 1, said mechanism moves into the operative position of FIGURE 2. Fluid-actuated clutch mechanism indicated generally by numeral 18 is responsible for shifting the actuator assembly between its operative and inoperative positions. This clutch mechanism comprises a cylinder 2i connected to receive gas through conduit 16 whenever the valve mechanism It) is open. Piston 22 mounted for reciprocal movement within the cylinder is extended against the action of compression spring 2.4 to shift rocker arm 26 connected to the free end of piston rod 28 from the disengaged position of FIGURE 3 to the engaged position of FIGURE 2.

Rocker arm 26 is pivotally attached to the piston rod 28 at one end and the other end thereof is mounted for pivotal movement about the axis of rotation of shaft 30. Intermediate the ends of the rocker arm 26, a stub shaft 32 is carried upon which are mounted for conjoint rotation, elements 34 and 36 of the drive mechanism that has been designated broadly by numeral 38 and which, in the particular form shown, comprises a gear train although it could quite obviously constitute friction rollers or the latter in combination with a belt and pulley arrangement or some other equivalent power transmission system.

Shaft is mounted for rotation on a suitable support 46 and carries on oneend thereof drive element 42 of the gear train that, forms a permanent driving connection with element 34 thereof. Element 36, on the other hand, provides only an intermittent driving connection with driven element 44 of the gear train which is mounted on shaft 46 for rotation therewith between supports 48 and 50.

Also mounted on shaft 30 is an arm or kicker 52 that is, engaged by the stem 54 that projects from the spherical hub 56 of nutating-plate 58 placed in the path of the gas the nutating plate 58 is divided bya web 72 which fits into;

corresponding slots (not shown) in the piate that prevent the latter from turning thus restricting its action, to a wobbling motion as the flowing air impinges thereupon. The spherical hub 56 rests within a correspondingly shaped seat in the center of the cavity 70 in housing 62. The action of the plate as it wobbles within housing 62 is to turn stem 54 around in a direction depending upon the direction of the flow of gas through the cavity. As this stem turns it, in turn, turns shaft 30 by means of kicker 52 thus activating the elements 34, 36 and 42 of the gear train whenever gas is flowing and also driven element 44 when the piston is extended to move the rocker arm 26 into the operative position whereby a driving connection is formed between elements 36 and 44.

Shaft 4-6 carrying the driven element 44 of the drive mechanism 33 is biased in a direction opposite to that at which it is rotated by said drive mechanism when the fluid-actuated clutch assembly moves element 34 into driving relationship therewith. The biasing means comprises a loose-wound spiral spring 74 having one end thereof connected to shaft 46 while the other end is attached to fixed abutment '76. A pusher element 78 projects from shaft 46 in position to engage adjustable stop 8% at one extremity of its travel with shaft 46 and push-rod 82 which closes the bistable valve assembly 10 at the other.

In the particular form shown, adjustable stop 8-0 com prises a crank-like element in which the offset leg portion forms the stop while the other leg portion 84 parallel thereto is mounted for frictional rotation within a supporting plate 86 in substantial coaxial alignment with the axis of rotation of shaft 46. The free end of leg portion 84 of the crank-like stop element carries a knob 88 by means of which the offset leg portion thereof is adjusted angularly. Leg portion 84 also carries a pointer adapted to swing therewith across a scale (not shown) provided on the supporting plate 86 that is calibrated in units of volume. Spring 74 continuously biases pusher element 78 against the adjustable stop 8t) although the action of the nutating plate assembly 60 through the drive mechanism 38 is sufiicient to overcome the action of the spring whenever gas is flowing through main conduit 14 and conduit 16 to place the fluid-operated clutch into engagement.

In operation, pointer 9t? is first set to the point on the scale carried by plate 556 which indicates the desired volume of gas to be delivered during each cycle. This action, of course, sets stop 8%? in adjusted angular relation to push-rod $2 and determines the sweep of pusher element 78 needed to close the bistable valve assembly. With the bistable valve assembly closed, compression spring 24 of the fluid-actuated clutch assembly 313 is effective to retract the piston 22 thereof thus disengaging elements 3-6 and 44 of the drive mechanism so that spring '74 can freely bias the pusher element 73 into engagement with the stop 8%. Then, immediately upon the receipt of an actuating impulse of a character adapted to open the bistable valve assembly, gas under pressure enters conduits 14 and 16 simultaneously actuating the fluidoperated clutch mechanism 18 to engage elements 36 and 4-4 of the drive assembly 38 and nutating plate mechanism 649 to drive the latter. As the fluid flows past the nutating plate, it functions through the drive mechanism to turn pusher-element away from the stop 89 in the direction of the arrow in FIGURE 2 until said pusher element contacts the push-rod 82 (dotted line position of FIGURE 2) closing the bistable valve assembly once again. In the meantime, spring 74 has been wound more tightly and a pre-determined volume of gas has been delivered through conduit 68. As soon as the bistable valve is moved into closed position, the fluid-pressure behind piston 22 of the clutch mechanism is bled from the cylinder 20 to the atmosphere through port 92 thus again disengaging elements 36 and 44 of the drive mechanism and permitting spring 74 to reset the pusher element 78 against the stop preparatory to receiving another initiating impulse.

From the foregoing, it should be apparent that the volume-controlled actuator of the present invention, when used in combination with a bistable valve, is effective to deliver an accurately predetermined quantity of gas on an intermittent basis. The automatic reset feature assures the fact that each quantity of gas delivered will be independent of that dispensed during a prior or subsequent operating cycle thus eliminating the errors inherent in an additive system. Also, the positive mechanical linkage between the nutating plate and pusher element makes it possible to control the quantity of gas delivered during each cycle of operation with considerable precision. Up to the present, the instant valve actuator has been described as it would function in coordination with any bistable valve; however, when used for certain applications, particularly as a control system for respiratory equipment, it is desirable to supplement the actuator with a pressure-responsive type of bistable valve assembly connected thereto in a manner to override the volume-controlled function whenever the pressure in the system exceeds a preset value. A bistable valve assembly of the aforesaid pressure-responsive type has been illustrated in FIGURES 1, 4 and to which reference will now be made.

The basic bistable valve assembly shown used with the actuator mechanism 12 is that which forms the subject matter of US. Patent 2,881,757 although it has been modified slightly to accommodate and cooperate with the actuator and has been illustrated schematically for the purposes of simplicity. The inlet conduit 94 is connected to receive gas under pressure from a suitable source thereof (not shown) and deliver same to the interior of spool valve housing 96 wherein lies spool 98 that is stable in both the closed position of FIGURE 5 and the open position of FIGURE 4. Assume for the moment that spool 98 is closed as in FIGURE 5 preparatory to receiving an impulse of a character adapted to open same initiating the operating cycle. Such an initiating impulse can be impressed manually by pushing plunger 100 which acts through the hub 102 of diaphragm 104 to engage the end of spool 98 moving the latter to the left so as to uncover the inlet to gas passage 106 as in FIGURE 1. A second method of initiating the operating cycle is to lower the pressure in chamber 103 at the left of disk 110 by sucking gas through delivery conduit 14 as. would be the case if a patient were connected to receive gas from tube 63 downstream of the nutatiug plate and said patient inhaled. Whenever the fluid pressure in the adjoining chamber 112 on the right side of plate 110 exceeds that in chamber 108, the differential across the plate will lift same off of its seat 114 allowing the gas to pass from passage 106 into venturi 116 and into chamber 112 where it passes the plate and enters the delivery conduit from chamber 108. At the beginning of the cycle, chamber 112 is at ambient pressure being open to the atmosphere through port 92 in the venturi 116.

The third method by which the cycle may be initiated is by means of the automatic cycler that has been indicated broadly by numeral 118. Assume that the valve assembly 10 has been manually triggered to shift the spool and unseat plate 110, whereupon, the gas will begin to flow into chamber 112 from the venturi and across the seat 114. When this takes place, the flow of the gaseous medium will function to shift the spool and associated plate into the stable open position of FIGURE 4 wherein the inlet of conduit 120 that opens into the spool valve casing 96 is uncovered thus admitting gas to cylinder 122. The fluid pressure in this cylinder causes piston 124 to retract in opposition to the action of compression spring 126 biasing the latter into extended position. Now, as long as the spool remains open and the fluid continues to flow, piston 124 will remain retracted although gas is continuously being bled from ahead of the piston through line 128 and exhaust ports 130 in needle valve housing 132 at a rate controlled by adjustable needle valve 134 which is substantially slower than the rate at which the gas enter the system. As soon as the spool is shifted to the stable closed position of FIGURE 5, however, the supply of gas to cylinder 122 is cut off and piston 124 extends under the influence of spring 126 as gas is slowly bled off ahead of said piston past the needle valve. As the piston approaches its fully extended position, an externally-located member 136 carried on the piston rod 138 contacts one end of a rocker arm 140 pivotally mounted within the main valve body 142 in position to engage plate 110 and move the latter off of its seat 114 thus automatically initiating the next cycle by pulling the spool to the left and admitting fluid to passage 106. Ordinarily, when the above-described valve assembly is used as a part of a respiratory device, the rate at which the gas is bled past the needle valve 134 is selected such that the system automatically cycles at a slower interval than the patients natural breathing cycle. Thus, the system will normally be triggered by the natural inspiratory efforts of the patient lowering the pressure in chamber 108 rather than automatically by means of the automatic system 118 above-described. This is especially useful in breathing patients recovering from anaesthesia as they are able to override the automatic cycle feature as soon as they are able to initiate an inspiratory response thus substantially reducing the recovery time.

Valve assembly 10 is pressure-responsive and capable of overriding the volume-controlled actuator therefor whenever the fluid pressure in chamber 112 equals or exceeds a pre-set value determined by the position of adjustable spring abutment 144 in internally-threaded collar 146 of main valve casing 142. As the fluid pressure within chamber 112 rises, diaphragm 104 will shift from the position shown in FIGURES 1 and 5 to the extended position of FIGURE 4 carrying with it the hollow hub 102 that is attached by means of a lost-motion connection to the projecting stem 148 of spool 98. Plate 110 is mounted on a section of reduced diameter 150 at the opposite end of the spool 98 which also carries a compression spring 152 biasing said plate against shoulder 154 thus providing a yieldable mounting.

Now, during normal operation of the bistable valve assembly 10, the spool is shifted into the stable open pos tion of FIGURE 4 and the fluid passing between seat 114 and disk or plate 110 forces the latter to the left against the bias of spring 152 as shown. A further increase in pressure within chamber 112, however, will move the hollow hub 102 and diaphragm 104 supporting the latter more to the right than shown in FIGURE 4 compressing spring 156 against adjustable abutment 144 and, at the same time, shifting the spool into the closed position of FIGURE 5. Of course, as soon as the spool shifts into closed position shutting off passage 106, the flow of fluid past disk 110 stops permitting spring 152 to snap the latter into place against its seat 114 while exhausting the fluid within chamber 112 through exhaust port 92 adjacent the venturi. The location of adjustable spring abutment 144 within the internally-threaded collar of main valve casing 142 determines the fluid pressure within chamber 112 that is required to overcome spring 156 and shift the spool to closed position. Note also that the above-described pressure-responsive mechanism is operative to override the automatic cycling assembly 118 which might conceivably be in the position shown in FIGURE 1- holding the disk 119 off its seat 114- at the instant the pressure in chamber 112 actuates diaphragm 1% to shift the spool into closed position as this would merely hold the lower edge of said disk to the left against the bias of spring 152, the flow of fluid having already been shut off.

In conclusion, it will be desirable to mention briefly the exhaust system and the function of venturi 116 in the combination already set forth in considerable detail. As is Well known in the art relating to the flow of fluids, the velocity of the gas increases as it passes through the throat or orifice 158 of the venturi 116 creating a localized negative pressure zone adjacent thereto which functions to suck air from the atmosphere in port 92. This influx of air effectively blocks port 92 and prevents the gas in line 16 that feeds cylinder 24B and from being exhausted therethrough while the bistable valve mechanism is open and fluid is flowing into the delivery conduit. The gas pressure in conduit 16 that is used to extend piston 22 also functions to expand inflatable exhaust valve 16% into substantially fluid-tight sealed contact with the exhaust branch 162 of delivery tube 68 as shown in FIGURE 1. This exhaust branch 1.62 is located downstream of the nutating plate assembly at and must, therefore, be closed at all times when the fluid isflowing in the direction of the arrow in tube 68 in FIGURE 1; otherwise, the fluid would be vented to the atmosphere before it could be used.

The instant the bistable valve assembly shifts into the closed position of FIGURE and fluid ceases to flow through passage 106 and the venturi 116, the fluid pres sure in line 16 exceeds the ambient pressure due to the bias of spring 24 on piston 22 and also the pressure exerted by the inflatable valve 169 tending to deflate same thus exhausting the fluid from line 16 out port 92. When valve element 164) deflates into the condition illustrated in FIGURE 5, it opens the branch exhaust 162 and allows the gas fed to the patient or other user to escape preparatory to initiation of another cycle.

Having thus described the several useful and novel features of the volume-controlled bistable valve actuator of the present invention and combinations thereof with a bistable valve, it will be apparent that the many worthwhile objectives for which they were developedhave been achieved. Although but a singlespecific embodiment of the invention has been illustrated and described in connection withv the accompanying drawings, we realize thatcertain changes and modifications therein may well occur to those skilled in the art within the broad teaching here,- of; hence, it is our intention that the scope of protection afforded hereby shall be limited only insofar as said-limitations are expressly set forth in the appended claims.

What is claimed is:

1. In combination in a system for controlling the flow of fluids under pressure on an intermittent basis, a valve assembly including a bistable valve having a stable open and a stable closed position and means responsive to the flow of a predetermined volume of fluid operative to automatically close the bistable valve, said means comprising actuating means operatively associated with the bistable valve and adapted upon movement in one direction to close the latter, stop means positioned in the path of movement of the actuating means and adapted to cooperate therewith in controlling the interval during which the bistable valve remains open, reset means operatively connected to the actuating means normally biasing the latter into engagement with the stop, -1 eans and in a direction opposite to that at which it moves to close the bistable valve, nutating plate means connected to receive fluid from the bistable valve and respond to the flow thereof to provide a motor, power transfer means having an engaged and a disengaged position forming a driving connection between the nutating plate means and the actuating means, said power transfer means being operative in engaged position to overcome the bias of the reset means and move the actuating means in the direction to close the bistable. valve, when the nutating plate means is actuated by. fluid: flow ng therethrough, and

said power transfer means functioning in disengaged position to release, the actuating means for return movement into engagement with the stop under the influence of the reset means while freeing the bistable valve for actuation into open position, and fluid-actuated clutch means normally biased into inoperative position connected to receive fluid from the bistable valve when the latter is open, said clutch means being operatively connected to the power transfer means and adapted upon actuation to shift same from disengaged into engaged position.

2. The combination as set forth in claim 1 in which the power transfer means comprises a mechanical train having at least three elements, the first of. said elements being connected to receive power for rotating same about a fixed axis directly from the nutating plate means, a second element of said train carrying the actuating means for rotational movement therewith about a fixed axis, and a third element mounted for rotational movement about a shifting axis responsive to operation of the fluidactuated clutch means, said third element in the disengaged position of the power transfer means being operatively connected to only one. of said first and second elements of the train, and said third element in the engaged position of the power transfer means being operatively connected to both said first and second elements of the train.

3. The combination as set forth in claim 2 in which the stop means is mounted for arcuate adjustable movement in the path of the actuating means, said stop means cooperating with the actuating means to vary the time internal required for the latter to sweep the are between the stop and the bistable valve thus controlling the volume of fluid delivered while the valve is open. v

4. The combination as set forth in claim 2 in which the reset means comprises a spring operatively connected to the second element of the mechanical train biasing the actuating means carried thereby against the stop means.

5. The combination as set forth in claim 2 in which the nutating plate means comprises a housing connected downstream of the bistable valve to receive fluid therefrom and a nutating plate operatively connected to the first element of the. mechanical train and mounted for wobblingmovement within the housing in a direction responsive to the flow of fluid therethrough adapted to move the actuating means, away from the stop means toward the bistable valve.

6. The combination as set forth in claim 2 in which the fluid-actuated clutch means comprises a cylinder connected to receive fluid downstream of the bistable valve, a piston mounted for reciprocal movement within the cylinder, linking means operatively interconnecting the third element of the mechanical train with the piston and adapted upon the application of fluid pressure to the latter to extend same shifting the power transfer means from disengaged into engaged position, and springmeans biasing the piston into retracted position within the cylinder when the fluid pressure is released therefrom thus returning the power transfer, means to disengaged position.

7. The combination as set forth in claim 1 which includes a delivery conduit having an exhaust opening therein connected to receive fluid from the nutating plate means and a fluid-pressure actuated normally open exhaust valve connected to receive fluid downstream of the bistable valve, said exhaust valve being operative in response to the application of fluid pressure thereto to close and seal the exhaust opening.

8. The combination as set forth in claim 7' in which the the fluidvalve mounted for reciprocating movement within a housing therefor having an inlet and at least one outlet, said spool valve having a portion thereof projecting from the housing into position to be engaged by the actuating means which functions upon actuation to shift said spool into its stable closed position wherein the inlet is sealed ofi from the outlet.

11. The combination as set forth in claim 10 in which the spool valve housing includes a second outlet located in the opposite side of the first outlet from the inlet, and in which the valve assembly includes means operative to automatically open the spool valve, said means comprising a cylinder connected to receive fluid from the second outlet of the spool valve housing when the spool valve is open, a piston mounted for reciprocal movement within the cylinder, an exhaust conduit connected into the same end of the cylinder in which fluid is delivered thereto, a bleed valve connected into the exhaust conduit and adapted to control the rate at which fluid is exhausted therefrom, spring means biasing the piston in a direction to bleed the fluid delivered to the cylinder out the exhaust conduit past the bleed valve at a predetermined flow rate while the spool valve is closed, and an actuating lever mounted for rockable movement in position to provide an operative connection between the piston and spool valve, said actuating lever being adapted to shift the spool valve from stable closed to stable open position when the spring means biasing the piston has caused a predetermined amount of fluid contained in the cylinder to be bled therefrom.

12. The combination as set forth in claim 10 in which the valve assembly includes a hollow valve casing containing the spool valve housing and spool valve, and a manually-operable spool valve actuator adapted upon actuation to shift the spool valve from stable closed into stable open position, said spool valve actuator comprising a push-rod mounted for reciprocal movement in the hollow valve casing in coaxial relation to the spool valve with one end thereof positioned to engage the end of said spool valve opposite the end thereof engaged by the volumecontrolled actuating means.

13. The combination as set forth in claim 10 in which the valve assembly includes pressure-responsive means adapted to override the volume-responsive means and close the spool valve at a pre-determined pressure, said pressure responsive means comprising a hollow cylindrical casing containing the spool valve and housing therefor, said casing having an annular seat encircling the projecting end portion of the spool valve in substantially normal relation to its axis of reciprocal movement and a passage connected to receive fluid from the outlet of the spool valve casing and deliver same on the same side of said seat, a disk carried by the projecting end portion of the spool valve for movement therewith, spring means carried by the projecting end portion of the spool valve biasing the disk into sealed engagement with the seat when said spool valve is closed, a flexible diaphragm mounted in the hollow casing at the opposite end of the spool valve from the disk, hub-forming means carried by the diaphragm and connected to the adjacent end portion of the spool valve with a lost-motion coupling, and conduit means connected into the hollow casing in position to receive fluid therefrom that has flowed past the seat and deliver it to the nutating plate means, said diaphragm and disk cooperating with one another and with the hollow valve casing to define a pressure chamber, said diaphragm being operative when the spool valve is open and fluid is flowing from the chamber past the unseated disk to shift said spool valve into closed position when the fluid pressure in said chamber reaches a pre-determined level.

14. The combination as set forth in claim 13 in which abutment means adjustable along the axis of reciprocal movement of the spool valve is carried by the hollow valve casing at the end thereof in which the diaphragm is mounted, and means comprising a compression spring is mounted between the axially adjustable abutment means and the hub portion of the diaphragm, said abutment means and spring means cooperating to define an adjustable and yieldable abutment operative to vary the fluid pressure required in the pressure chamber to shift the spool valve into closed position.

15. The combination as set forth in claim 13 in which the valve assembly includes a venturi connected to receive fluid from the outlet of the spool valve housing and deliver same to the pressure chamber, said venturi also having a port therein open to the atmosphere positioned to suck in air when the spool valve is open.

16. The combination as set forth in claim 15 in which the venturi is also connected to receive fluid from the fluidactuated clutch means and exhaust same through the port when the spool valve is closed.

17. The subcombination of a fluid-flow-driven volumecontrolled valve actuator which comprises stop-forming means, actuating means mounted for movement toward and away from the stop, reset means normally biasing the actuating means into engagement with the stop-forming means, nutating plate means responsive to the flow of fluid therethrough to provide a motor, power transfer means having a disengaged and an engaged position forming a driving connection between the nutating plate means and the actuating means, said power transfer means being operative in engaged position to overcome the bias of the reset means and move the actuating means away from the stop-forming means when the nutating plate means is opperative, and said power transfer means functioning in disengaged position to release the actuating means for return movement into engagement with the stop-forming means under the influence of the reset means, and fluid actuated clutch means normally biased into inoperative position responsive to the application of fluid thereto to shift the power transfer means from disengaged into engaged position.

18. The subcombination as set forth in claim 17 in which the power transfer means comprises a mechanical train having at least three elements, the first of said elements being connected to receive power for rotating same about a fixed axis directly from the nutating plate means, a second element of said train carrying the actuating means for rotational movement therewith about a fixed axis, and a third element mounted for rotational movement about a shifting axis responsive to operation of the fluid-actuated clutch means, said third element in the disengaged position of the power transfer means being operatively connected to only one of said first and second elements of the train, and said third element in the engaged position of the power transfer means being operatively connected to both said first and second elements of the train.

19. The subcombination as set forth in claim 18 in which the stop-forming means is mounted for arcuate adiustable movement in the path of the actuating means, said stop-forming means cooperating with the actuating means to vary the time interval during which the actuating means moves away from said stop means before the fluidactuated clutch means functions to disengage the power transfer means.

20. The subcombination as set forth in claim 18 in which the reset means comprises a spring operatively connected to the second element of the mechanical train biasing the actuating means carried thereby against the stop-forming means.

21. The subcombination as set forth in claim 18 in which the nutating plate means comprises a housing connectable to receive fluid under pressure from a source thereof on an intermittent basis and a nutating plate operatively connected to the first element of the mechanical train and mounted for wobbling movement within the housing in a direction responsive to the flow of fluid therethrough adapted to move the actuating means away from the stop means.

22. The subcombination as set forth in claim 18 in which the fluid-actuated clutch means cmnprises a eylinder. connectable to receive fluid from a source thereof on an intermittent basis, a piston mounted for reciprocal movement within the cylinder, linking means operatively interconnecting the third element of the mechanical train with the piston and adapted upon the application of fluid pres sure to the latter to extend same shifting the power transfer means from disengaged int engaged position, and spring means biasing the pistonintq cylinder when the fluidpress eis a e ted position within the 'eleased therefrom thus References Cited in the file-of this patent UNITED STATES PATENTS Brayer June: 8;, 1,9,3? McGili Feb. 16,1943

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