US3008294A - Fluid actuator - Google Patents

Description

Filed May 19, 1960 W. L. CARLSON, JR

FLUID ACTUATOR 2 Sheets-Sheet 1 INVENTOR. WILLIAM L. CARLSON, JR.

ATTORNEY Nov. 14, 1961 Filed May 19, 1960 FIE.

w. 1.. CARLSON, JR 3,008,294

FLUID ACTUATOR 2 Sheets-Sheet 2 INVENTOR.

WILLIAM L. CARLSON,JR.

a a/WW A TTORNEY United States Patent 3,008,294 FLUID ACTUATOR William L. Carlson, Jr., Bloomington, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed May 19, 1960, Ser. No. 30,211 8 Claims. (Cl. 60-52) The present invention is broadly directed to a novel type of hydraulic actuator which is particularly adapted for use with conductive fluids such as liquid metals. More specifically, the present actuator utilizes a double bellows sealed shaft and a dump valve that allow the unit to operate rapidly on a return stroke without the impedance of flow of the fluid through the pump that originally supplies the operating pressure to the actuator.

The use of conductive fluid pumps and actuators is progressively becoming more common and is typified by US. Patent No. 2,897,650 and the British Patent No. 810,697. Both of these patents are assigned to the assignee of the present invention and disclose the use of electromagnetic conductive fluid pumps with actuators that supply mechanical outputs whenever the conductive fluid pumps are energized, and which allow the conductive fluid to flow back through the open passage of the conventional electromagnetic conductive fluid pumps on their return stroke. Actuators of this general type are generally somewhat slow in returning due to the impedance to flow of the conductive fluid through the channel of an electromagnetic conductive fluid pump. In order to overcome this impedance, the present invention'is directed to a dump valve which operates on a pressure differential in the actuator to allow for the pump to be bypassed on the return stroke, thereby allowing for rapid return of the conductive fluid from a pressure chamber of the actuator to a reservoir chamber of the actuator. Since this type of unit utilizes a conductive fluid that normally must be hermetically sealed, the present invention is directed to a double bellows sealing arrangement for the reservoir chamber that allows for the rapid response of the unit without adding a separate reservoir chamber as might be needed otherwise.

In the present case, it is the primary object to disclose a dump valve arrangement which is pressure operated and does not rely on fluid flow as does the ordinary check valve or dump valve.

Another object of the present invention is to disclose a dump valve that can be made to operate on power failure to the conductive fluid pump and thereby acts as a safety control.

Yet another object of the present invention is to disclose a dump valve that is subject to both pressure control and to selective electric control for use in actuators where a modulation of the actuator is developed by modulating the pressure input to the actuator from the pump.

Still a further object of the present invention is to disclose a dump valve that can be put into a hermetically sealed unit compatible with conductive fluids of the liquid metal type, such as sodium, potassium, or an alloy of sodium-potassium referred to as NaK, and which is exceedingly simple and reliable.

Yet a further object of the present invention is to dis close a dump valve that is exceedingly inexpensive to build into an actuator.

' Another object of the present invention is to disclose a hermetically sealed actuator that can be used with "ice tion, the invention has been disclosed schematically in FIGURE 1, wherein the dump valve is disclosed;

FIGURE 2 is asimilar schematic representation of the invention, but includes an electrical means of operating the dump valve which is shown in the form of a solenoid; and,

FIGURE 3 is a cross section of a production version of an actuator of the type disclosed in FIGURE 1, with the additional feature of the double bellows seal on the output shaft.

Disclosed in FIGURE 1 is a pump 10, preferably an electromagnetic conductive fluid pump having a continuously open fluid flow channel. This type of pump is sometimes referred to as a Faraday type pump and is well known in the art. Electric current is supplied through conductors 11 and 12 from any convenient power source. The pump 10 has an outlet 13 schematically disclosed as supplying a conductive fluid to two conduits or pipes 14 and 15. The pipe 14 passes into an actuator disclosed at 16 to a pressure chamber 17. The pipe or conduit 15 passes into a valve chamber means 20 that houses the novel dump valve that controls the actuator 16.

The dump valve includes a diaphragm 21 that carries a valve member 22 against a valve seat 23. The valve member 22 is disclosed in its open position which occurs when the pump 10 is deenergized. The diaphragm 21 is sealed at its edge 24 to a plate 25 that forms part of the upper wall of chamber 17 and to valve seat 23. This plate has a number of openings 26 that allow free communication of fluid from the pressure chamber 17 to the underside of the diaphragm 21.

The valve seat 23 is connected to a pipe 30 that returns to the inlet 31 of the pump 10. The upper part of the pressure chamber 17 has its walls sealed to the main walls of the actuator '16 in a fluid tight manner, such as by welding. The pipe 30 is sealed also in a fluid tight manner as it passes through the upper wall of the actuator.

With the arrangement described thus far, the actuator 16 has a pressure chamber '17 that communicates with the underside of the diaphragm 21. The underside of the diaphragm 21 and the fluid chamber are in communication with the pipe 30 through the valve seat 23 which, in turn, allows fluid flow to pass through the pipe 30 to the inlet of pump 10. A second chamber, that is, the valve chamber means 20, is completely sealed firom the pressure chamber 17 and is in communication with the outlet of pump 10 through the pipe 15. In order to complete the chamber 17, a piston means 32 is provided to separate the actuator. 16 into two pressure chambers. The piston means 32 has a shaft 33that is used as output means for the actuator 16. A simple fluids of the corrosive type, as mentioned previously, and I gasket 34 is shown as a sealing means around shaft 33 but itis' understood that this is for simplicity in explanation of the operating principles of the unit. A more practical seal is disclosed in FIGURE 3 and will be described in detail inthe discussion directed to that figure.

The piston means 32 provides a reservoirv chamber 35 between the piston means 32 and the side and bottom walls of the actuator 16. A pipe 36 is connected through a lower wall of the actuator 16 to communicate with the reservoir chamber 35. The pipe 36 connects back to the inlet 31 of the pump 10 and also provides a direct communication between the valve seat 23 and the reservoir chamber 35.

The operation of the device disclosed in FIGURE 1 can best be understood by considering the pressure in chambers 17 and 35 as being equal when the pump 10 is deenergized. At this time, the diaphragm 21' holds the valve 22 off the valve seat 23 to allow a free communication of the fluid that fills the chambers 17 and 35 along the outlet 13 into the conduits 14 and 15. The fluid flowing from outlet 13 through the conduits 14 and 15 supplies a fluid pressure to the pressure chamber 17 and to the valve chamber means 20. -The conduits 14 and 15 are arranged so that a pressure drop occurs in the conduit 14, thereby creating a slightly lower pressure in the pressure chamber 17 than occurs in the valve chamber means 20. Since there is little or no flow involved in conduit 15, a larger pressure drop develops in conduit =14 than in conduit 15 due to the frictional flow losses in conduit 14 and this pressure drop moves the diaphragm 21 in a downward direction. The dia phragm carries the valve 22 against the valve seat 23 which immediately seals the pressure chamber 17' and allows a pressure to build up in the pressure chamber to apply a driving force against the piston means 32. It will be understood that the 'full pump pressure is applied to the diaphragm 21 at this point, whereas a slightly lower pressure is applied to the underside of diaphragm 21 from the pressure chamber 17 via the holes 26. A difference in force across the diaphragm 21 occurs due to a diiierence in efiective areas createdby the area of the valve seat '23 being removed from the efiective area of the underside of diaphragm 21 due to valve 22 seating on seat 23.

With the pump pressure thus applied and the valve 22 seated against valve seat 23, the full pump pressure operates against the piston means 32 to move the piston means 32 in a downward direction. The movement of piston means 32 downward decreases the volume of the reservoir chamber 35, foncing fluid through con duit 36 into the inlet side 31 of pump 10. When the piston means 32 reaches the bottom of the actuator 16 or operates against a load (not shown) that causes the piston means 32 to stall against the pumping pressure of pump 10, the unit will remain in equilibrium with the pump '10 supplying continuous pressure to hold the piston means 32 in its downward position. Since the pump is of 'the'electromagnetic conductive fluid type, stalling the pump creates no serious problem from a mechanical or electrical standpoint. 7

As soon as it is desired to return the piston means 32 in an upward direction, it is only necessary to deenergizethe pump 10 by removing power from con- ;du'ctors 11 and 12 The load (not shown) connected to shaft 33 is biased in an upward direction by a. spring orrother suitable means and causes the piston meanst32 to want to'move upward. Since the pump is 'deenergized, pressure in chamber means 20 goes to zero while 4 described in detail. The pump '10 again is energized through conductors 1'1 and 12 to provide a pumping pressure at outlet 13 and through conduit 14 and conduit 15. For convenience in operation, a check valve 40 has been inserted in conduit 14 and prevents fluid from returning to the outlet 13 of the pump during operation of the unit. The actuator 16 is divided by piston means 1 32 into a pressure chamber 17 and a reservoir chamber 35. The reservoir chamber is connected by pipe 36 back to the inlet 31 of the pump and communicates by pipe 39 with the valve seat 23. The valve seat 23 has a valve 22 cooperating therewith and is'carried by the diaphragm 21 which is sealed at 24 as was disclosed in FIGURE 1. Holes 26 again provide communication between the pressure chamber 17 andthe underside of the diaphragm 21 so that the fiuidpressure in chamber 17' can readily be communicated and permits flow of the conductive fluid in the unit from the pressure chamber 17 to the pipe upon opening of the valve 22.

A valve chamber means 41 is provided which is larger than the valve chamber means 20 of FIGURE 1, to incorporate a solenoid plunger 42 that is supported by a column 43 that is connected to the top of the valve 22 and operates the valve 22 under certain circumstances. Externally mountedto the valve chamber means 41 is a solenoid coil 44 that has a pair of energizing leads 45 and 46 that can be connected to a suitable source of power to energize the coil 44 and thereby create a r the additional weight of the solenoid plunger 42. ,It

pressure in pressure chamber 17 remains substantially constant since, as stated previously, shaft 33' and its attached piston 32 are biased upwardly by means not shown. a This allows the valve 22 to move slightly ofi the valve seat 23, and opensa direct communication between the pressure chamber 17 and the reservoir chamber 35 through the tube 30. The fluid in pressure chamber 17 is thus immediately dumped through tube 30 into tube 36 and back to the reservoir chamber 35, thereby allowing the piston means 32 to move in an upward direction unimpeded by the fluid passage through the pump 10 from the outlet 13 to the inlet 31 It can thus be seen that a unique type of dump valve that is pressure operated has been supplied to a hermetically sealed conductive fluid system and provides for a unique form of operation.

The device disclosed in FIGURE 1 has been modified in FIGURE 2 to add an electr-iecontrol for the system. This allows for modulation of the unit by pulsing or by varying the pumping pressure created by pump 10. Similar numbers will be utilized for similar parts, and the basic mode of operation of the device in FIGURE 2 is the same as that in FIGURE 1 with the additional features necessary, spring means (not shown) could be added for this purpose. This spring means (not shown) has been left ofi for clarity in disclosing the present invention.

In operation, the basic principles described in FIG- URE 1 apply to FIGURE 2. When the pump 10 is energized by supplying power to conductors 11 and 12, a pressure is applied to the upper side of the diaphragm 21through the conduit 15 and the valve chamber means 41. Since the valve 22 is off its valve seat 23, the fluid initially flowing from the outlet 13 of the pump when it is first energized flows through the conduit 14, into the pressure chamber 17 from where it flows through ports 26 into the conduit or pipe 30. The pressure thus applied would normally cause the diaphragm 21 to move down and seal the valve seat 23 by applying the valve 22. This action is immediately aided by energizing the conductors 45 and 46 to supply power to the solenoid coil 44. V This solenoid coil applies to force to the plunger 42, thereby causing a definite and direct seating of the valve 22 on valve seat 23, regardless of the pressures. With this arrangement it should be understood that the pressure alone on theunit may not be suiiicient to operate the diaphragm valve depending on the mode of operation of the unit. It will be noted that if the pump .10 is then deenergized but the solenoid coil 44 is kept energized, the pressure in the pressure chamber 17 cannot be released since the solenoid plunger 42 2 to be locked in any position regardless of whether or not the pump is energized. By deenergizing the conductors 45 and 46, thereby removing the power to the solenoid coil 44, the valve 22 can be opened by the pressure on the underside of the diaphragm 21 increasing due to a movement in an upward direction of the piston means With the arrangement disclosed in FIGURE 2, it is possible to obtainmodulation of the actuator 16by utilizing either oil-on operation or by modulating the power to the pump 10. A definite power failure control is also provided since the deen'ergization of the conductors 45 and 46 will cause the solenoid 44 to allow the solenoid plunger 42 to rise, thereby dumping the valve upon power failure. With the combination of the pumping pressure and the pressure applied by the solenoid plunger 42, it is possible to operate the actuator 16 in various control functions that will be obvious to anyone working in the hydraulic and related arts.

In FIGURE 3, pump is energized through conductors 11 and 12 to supply a fluid pressure at outlet 13 to pipes 14 and 15. Pipe 14 leads directly into the pressure chamber 17 of the actuator generally shown at 16. the pipe leads into the valve chamber means 20 which has a flexible diaphragm 21 that supports the valve chamber 22. The valve member 22 cooperates with valve seat 23 which is formed in the dividing plate 25. Dividing plate 25 has a hole 26 that allows free communication of fluid from the pressure chamber 17 to the underside of the diaphragm 21. The structure described is substantially identical to the structure schematically represented in FIGURE 1.

The valve seat 23 opens onto a tube 30 which is connected to a return tube 36 to the inlet 31 of the pump 10. In the more refined version of FIGURE 3, the piston means 32 is formed of a piston-like member 50 that is encapsulated in a rubber 5 1 that forms a tight but sliding seal at 52 to the wall 53 of the actuator 16. Attached by any convenient method to the top 54 of the piston 50 is a stem or shaft 33. Surrounding shaft 33 is a spring 55 that extends to a stop member 56 that is joined at 57 to the outer wall 60' of the actuator 16. The stop 56 acts as a guide for the shaft 33 and also provides a mounting means to a plate 61 that can be a separate mounting plate for the actuator '16 or an integral part of a device to be controlled.

Surrounding the shafts 33 there is a bellows 62 that is attached at 63 between the top of the shaft 33 and the piston top 54 so that the bellows 62 moves in compressiOn whenever the shaft 33 is caused to move in a downward direction. The bellows 62 is sealed at 64 to a cup-like member 65 that forms the lower end of a second concentric bellows 66. The second or concentric bellows is attached to the outer wall 60 of the actuator 16 at 67. The attachment of bellows 66 at 67 is such that the pipe 36 connects into the volume between the bellows 66 and 62 to form the reservoir chamber 35. The area between the bellows 66 and the outer wall 60 of the actuator 16 is utilized to assemble the unit and to form a protective wall for the thin bellows members that actually retain the conductive fluid utilized in the present device.

In considering the operation of the device disclosed in FIGURE 3, its operation is identical to that of FIG- URE 1. This operation is that upon energization of pump 10 fluid is caused to flow through pipes 14 and 15. A pressure differential is developed between the pressure chamber 17 and the valve chamber means 20 to cause the valve member 22 to lower against valve seat 23 to cut off a return path for the fluid. The return path would be from the pressure chamber 17 through opening 26 through the valve seat 23, into tube 30, and back to the inlet 31 of pump 10. As soon as valve 22 seats on valve seat 23, the full pump pressure is applied to the top of diaphragm 21 thereby locking the diaphragm in a down position and applying the full pumping force of pump 10 to the top or outer surface of the piston means 32. Since the piston means 32 is sealed at 52 to the walls 53 of the actuator 16, the piston means 32 is caused to move in a downward direction. The movement in a downward direction compresses the spring 55 and also begins to collapse the bellows 62 which forms one wall of the. reservoir chamber 35. As the bellows 62 collapses, fluid is withdrawn from the reservoir chamber through the pipe 36 to the pump 10. Due to the physical size of the pressure chamber 17 there is required, at this time, more fluid than the smaller chamber 35 could supply if it were merely sealed with a single bellows. As this volume of fluid is pumped through pump 10, the bellows 66 is also caused to collapse, causing an upward movement of the cup-shaped member 65 which also reduces the volume of the reservoir chamber 35.

With the present arrangement the collapse of the two bellows, which are in concentric relationship with one another and have a common lower sealed edge, there is provided a reservoir that is capable of supplying all of the fluid needed for the upper or pressure chamber 17 without supplying an external reservoir of any type for the present unit. With both bellows 62 and 66 collapsing the fluid in the lower portion of the reservoir chamber 35 is utilized even though this portion of the chamber is not occupied by the piston means 32 when it has reached its most downward position. The movement of the shaft 33 and the compressing of bellows 62 compresses the spring 55. The compressed spring 55 is the return force utilized to cause the piston means 32 to move in an up ward direction upon deenergization of the pump 10.

As was pointed out in connection with FIGURE 1, when pump 10 is deenergized the spring 55 will tend to move the piston means 32 upward slightly. This slight upward movement applies a greater pressure to the underside of diaphragm 21 than exists on the upper side of the diaphragm since the pump 10 no longer is the pressure source. This change in pressure allows the diaphragm to assume its normal position which opens a free fluid passage from the pressure chamber 17 through the opening 26 and the valve seat 23 to the pipe 30. This allows fluid to flow directly back through pipe 30 and pipe 36 into the reservoir chamber 35 thereby completely bypassing the limited passage of the pump channel.

The present invention has been disclosed as operable with a conductive fluid when utilized with an electromagnetic conductive fluid pump. The device is considered to be hermetically sealed at all joints by any convenient means, as welding or soldering; It is under stood that the applicant does not Wish to be limited to this arrangementsolely, but wishes to be limited only by the scope of the appended claims. There are many modifications of the present invention that would be adaptable to various forms of pumps and actuators and the schematic representation along with one preferred embodiment has been presented as an example of one usable embodiment of the present invention.

I claim as my invention:

1. In a pressure operated hermetically sealed actuator particularly adapted to be filled with a liquidmet'al and connected to an electromagnetic liquid metal pump: a pressure chamber and a reservoir chamber separated by piston means with said pump connected to move said liquid between said chambers; said piston means biased to a first position; said pressure chamber including valve means capable of opening a liquid return conduit to said reservoir chamber; said valve means including apressure actuated diaphragm member which carries a valve member; valve chamber means connecting one side of said diaphragm to an outlet of said pump; and the other side of said diaphragm being exposed to the pressure in said pressure chamber; said diaphragm holding said valve member in-a cooperable position to a valve seat controlling liquid flow to said liquid return conduit; upon energization, said pump creating a pressure diiferential across said diaphragm to hold said valve member on said valve seat and thereby apply full pump pressure to said piston means; said valve means operating upon deenergization of said pump to open said valve member and permit said liquid to return from said pressure chamber to said reservoir chamber to thereby allow said piston means to return to said first position without the impedance of flow of the liquid metal through said pump.

2. In a pressure operated actuator particularly adapted to be filled with a. conductive fluid and connected to an electromagnetic conductive fluid pump: a pressure chamber and a reservoir chamber separated bypiston means with said pump connected to move said fluid between said chambers; said piston means biased to a first position; said pressure'chamber including'valve means capable of opening a fluid return conduit to said reservoir chamber; said valve means including a pressure actuated diaphragm member which carries a valve member; valve chamber means connecting one side of said diaphragm to an outlet of said pump; and the other side of said diaphragm being exposed to the pressure in said pressure chamber; said diaphragm holding said valve member in a cooperable position to a valve seat controlling fluid flow to said fluid return conduit; upon energization, said pump creating a pressure difierential across said diaphragm'to' hold said valve member on said valve seat and thereby; apply full pump pressure to said piston means; said valve means operating upon deenergization of said pump to open said valve member by said biased piston means moving toward said first position to allowsaid fluid to return from said pressure chamber to saidreservoir chamber.

3; In a pressure operated actuator particularly adapted to be filled with a conductive fluid and connected to an electromagnetic conductive fluid pump: a pressure chamber and a reservoir chamber separated by piston means with said pump connected to move said fluid between said chambers; said piston means biased to a first position; said pressure chamber including solenoid valve means capable of opening a fluid return conduit to said reservoir chamber; said valve means including a diaphragm member which carries a valve member; valve chamber means including solenoid means connecting one side of said diaphragm to an outlet of said pump; and the other side of said diaphragm being exposed to the pressure in said pressure chamber; said diaphragm holding said valve member in a cooperable position to a valve seat'controlling fluid flow to said fluid return conduit; upon energization of said pump and said solenoid means there is created a force on said diaphragm to hold said valve member on said valve seat and thereby apply full pump pressure to said piston means; said solenoid valve means being deenergized to open said valve member and said biased piston means moving toward said firstposition to allow said fluid to return from said pressure chamber to said reservoir chamber.

' 4; 'In a pressure operated actuator particularly adapted to be filled with a conductive fluid and connected to an electromagnetic conductive fluid pump: a pressure chamher and a reservoir-chamber separated by piston means with said pump connected to move said fluid between said chambers; said piston means biased to a first position; said pressure chamber including valve means capable of opening a fluid return conduit'to said reservoir chamber; said valve means including a pressure actuated diaphragm member which carries a valve member; valve chamber means connecting one side of said diaphragm to an outlet of said pump; and the other side of said diaphragm being exposed to the pressure in said pressure chamber; said diaphragm holding said valve member in a cooperable position to a valve seat controlling fluid flow to said fluid return conduit; upon energization of said pump a force is created-across said diaphragm to hold said valve. member on said valve seat and thereby apply full pump pressure to said piston means; said valve means operating upon deenergization of said pump to open said valve member by said biased piston means moving toward said first position to allow said fluid to return from said pressure cham her to said reservoir chamber. 7 V

5. In a pressure operated actuator filled with a fluid and connected to a pump: a pressure chamber and a reservoir chamber separated by piston means with said pump connected to move said fluid between said chambers; said piston means biased to a first position; said pressure chamber includingvalve means capable of opening a fluid return conduit to said reservoir chamber; said valve means including a pressure actuated diaphragm member; valve chamber means connecting one side of said diaphragm to an outlet of said pump; and the other side of said diaphragm being exposed to the pressure in said pressure chamber; upon energization of said pump a pressure differential is created across said diaphragm to hold said valve means closed prevent-ing fiuid flow to said fluid return conduit to thereby apply full pump pressure to said piston means; said valve means opening upon deenergization of said pump by said biased piston means moving toward said first position to allow said fluid to return from said pressure chamber to said reservoir chamber.

6. In a pressure operated hermetically sealed actuator particularly adapted to be filled with a corrosive liquid metal and connected to an electromagnetic liquid metal pump: a pressure chamber and a reservoir chamber separated by piston means; said pump having an outlet connected to said pressure chamber and an inlet connected to said reservoir chamber; and said reservoir chamber being hermetically sealed by two concentric metallic bellows having an inner common sealed portion to allow each said bellows to contract upon movement of said piston means upon application of pressure from said outlet of said pump; said'pump pressure simultaneously causing movement of said piston means and a compatible variance in the volume of said reservoir chamber to move said liquid metal from said reservoir chamber to said pressure chamber.

7. In a pressure operated actuator particularly adapted to be filled with a conductive fluid and connected to an electromagnetic conductive fluid pump: a pressure chamber and a reservoir chamber separated by piston means; said pump having an outlet connected to said pressure chamber and an inlet connected to said reservoir chamber; and said reservoir chamber being sealed by two concentric bellows h'a'v ing an inner common sealed portion to allow each said bellows to contract upon movement of said piston means upon application of pressure from said outlet of said pump; said pump pressure simultaneously causing movement of said piston means and a compatible variance in the volume of said reservoir chamber to move said conductive fluid from said reservoir chamber to said pressure chamber.

8. In a pressure operated actuator filled with a fluid and connected to a fluid pump: a pressure chamber and a reservoir chamber separated by piston means; said pump having an outlet connected to said pressure chamber and an inlet connected to said reservoir chamber; and said reservoir chamber being sealed by two concentric bellows having an inner common sealed portion to allow each said bellows to contract upon movement of said piston means upon application of pressure from said pump; said pump pressure simultaneously causing movement of said piston means and a compatible variance in the volume of said reservoir chamber to move said fluid from said reservoir chamber to said pressure chamber.

References Cited in the file of this patent UNITED STATES PATENTS 337,118 Belden Mar. 2, 1886 1,836,813 Rankin Dec 15, 1931 2,072,481 McNair'y Mar. 2, 1937 2,399,294 Ray Apr. 30, 1946 2,584,431 Dearsley Feb. 5, 1952

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