US3587234A - Electrohydraulic mechanical actuator - Google Patents

Abstract

AN ACUTATOR SYSTEM IS DISCLOSED EMPLOYING A RECIPROCATING SOLENOID COUPLED THROUGH AN APPROPRIATE TRANSMISSION SYSTEM FOR MOVING AN ACTUATED MEMBER IN INCREMENTAL STEPS BETWEEN ALTERNATIVE ACTUATED POSITIONS WITH HIGH TORQUES AT LOW SPEEDS. THE SOLENOID HAS AN ARMATURE SLIDABLY ENGAGED AT ONE END FOR RECIPROCATING MOVEMENT THROUGH THE CENTRAL OPENING IN A SOLENOID COIL. A BODY STRUCTURE OF HIGH PERMEABILITY MANGETIC MATERIAL ABUTS THE SURROUNDING OUTER SURFACE OF THE COIL AND SLIDABLY ENGAGES THE END OF THE ARMATURE TO PROVIDE A LOW INDUCTANCE ELECTRICAL PATH AND LOW RELUCTANCE MAGNETIC PATH FOR THE FLUX PRODUCED BY THE COIL SO THAT MAXIMUM DYNAMIC RESPONSE AND OUTPUT FORCE ARE ACHIEVED. IN ONE EMBODIMENT, THE RECIPROCATING SOLENOID ARMATURE OPERATES AS A PUMP PISTON TO FORCE HYDRAULIC FLUID IN A SELECTED PATH TO MOVE AN ACTUATOR VANE IN A DESIRED DIRECTION. IN THE ALTERNATIVE, A MECHANICAL TRANSMISSION SUCH AS A RATCHET AND PAWL ARRANGEMENT IS EMPLOYED TO MOVE THE ACTUATED MEMBER IN THE DESIRED DIRECTION BY AN INTERMENTAL AMOUNT DURING EACH ENERGIZATION OF THE SOLENOID COIL.

Description

United States Patent [72] Inventor Malcolm M. McQueen Northridge, Calif. [2]] Appl. No. 750,039 [22] Filed Aug. 5, 1968 [45] Patented June 28, 197 l [54] ELECTRO-HYDRAULIC MECHANICAL 1'0 ROTARY VALVE STEM Primary Examiner Edgar W. Geoghegan Attorney-Fraser and Bogucki ABSTRACT: An actuator system is disclosed employing a reciprocating solenoid coupled through an appropriate transmission system for moving an actuated member in incremental steps between alternative actuated positions with high torques at low speeds. The solenoid has an armature slidably engaged at one end for reciprocating movement through the central opening in a solenoid coil. A body structure of high permeability magnetic material abuts the surrounding outer surface of the coil and slidably engages the end of the armature to provide a low inductance electrical path and low reluctance mag netic path for the flux produced by the coil so that maximum dynamic response and output force are achieved.

In one embodiment, the reciprocating solenoid armature operates as a pump piston to force hydraulic fluid in a selected path to move an actuator vane in a desired direction. In the alternative, a mechanical transmission such as a ratchet and pawl arrangement is employed to move the actuated member in the desired direction by an incremental amount during each energization of the solenoid coil.

PATENIED JUN28 I971 sum 1 or 3 INVENTOR.

MALCOLM M. MOOUEEN FPASEE r; BOG'UCK/ ATTORNEYS 1 PATENTEU JUN28 l9?! sum 2 0F 3 INVENTOR.

MALCOLM M. MoOUEEN Hansel? BOGUCK/ A TTORNEYS PATENT ED JUN28 I971 SHEET 3 OF 3 INVENTOR. MALCOLM M. McOUEEN T0 VALVE STEM Fknsg? 7' FOGUCKI ATTORNEYS LEQ'IRQJIYQRAULIC.MECHANIQALACIUAT BACKGROUND OF THE INVENTION This invention relates to an improved electrical signal operated actuator for producing bidirectional linear or rotational mechanical movement with relatively high torques at low speeds, and in particular to actuators of this type used to fluid control valves for aircraft or spacecraft. In these instances, efficiency is sacrificed to low weight and simplicity.

Control actuators are presently available in a variety of forms for different purposes, as set forth in the article entitled Control Actuators" beginning on page 165 of the Jan. I967 issue of the monthly trade publication Power, Volume Number I, published by McGraw-Hill of New York, NY. Control actuators presently used in aircraft employ for the most part ordinary electric drive motors that are by nature high speed, low torque devices and thus require complex and costly reduction gear arrangements to obtain the high torques at relatively low speeds used in opening and closing large valves. In the usual case, the valve must also be manually actuatable, and a clutch must be included to permit the motor to be disengaged during manual actuation. This further adds to the cost and complexity of present actuators. In addition, the DC motors most commonly used in these actuators have brush-type commutator systems. These generate broad frequency electromagnetic noise that can seriously interfere with radio communications. All of these-the gears, the clutch and the commutator system-are subject to constant mechanical wear and constitute sources of possible failure. These numerous moving precision parts are sensitive to vibrational stresses and must also be properly lubricated if excessive wear and failure are to be avoided. Adequate lubrication over the wide ranges of operating temperatures frequently encountered can be very difficult. As a result, such previous actuator systems, though very complex and costly, were difficult to maintain and liable to sudden failure from any number of causes, sometimes with disastrous results.

SUMMARY OF THE INVENTION Actuators in accordance with this invention employ a reciprocating solenoid as prime mover in conjunction with a mechanical or hydraulic arrangement for storing either the rotational or linear work done on each solenoid stroke. The solenoid develops a relatively high force per unit weight but only over a relatively short distance. However, the solenoid is recycled repetitively to drive the actuator in quick steps through larger operating distances in either direction. In a preferred embodiment of the invention, which is intended for actuating rotary fuel valves in aircraft, a unique solenoid pump delivers pressurized fluid flow through a hydraulic system to force rotation of an actuator vane in the desired direction. In this case, the entire system is immersed in oil which, in addition to being the working media, provides lubrication to all parts and suppresses any vibration movement of the parts. A solenoid operated control valve arrangement controls the direction of fluid flow from the pump outlet and inlet so that the pressurized fluid is applied to one side of the actuator vane, while the fluid on the other side is permitted to return to the pump inlet.

In the solenoid pump, the solenoid armature itself operates as the pump piston to deliver the hydraulic fluid through the system with maximum force at high efficiency. The cylindrical piston is slidably engaged at one end in a cylinder formed in a body structure of magnetic material with high permeance that also encloses the annular solenoid coil. The forward end of the piston is slidably received in a cylindrical opening defined through the center of the coil. Only a thin layer of insulation and/or nonmagnetic material separates the cylindrical piston surface from the inner coil windings so that maximum coupling of the coil flux is maintained through the magnetic material ofthe piston for increased magnetic efficiency.

In the preferred embodiment, a selection switch is closed to deliver a control signal from a direct current source through an operating circuit that repetitively energizes and deenergizes the pump solenoid coil, while at the same time actuating current is delivered to the solenoid operated control valve arrangement to establish the desired flow path through the hydraulic system. In the preferred embodiment, the operating circuit includes a sensing coil responsive to flux variations produced by actuating the pump solenoid coil. Initially, the current flow to the solenoid pump coil is limited through a current control element, preferably a power transistor. The buildup of an initial small current flow through the current control element and to the solenoid pump coil induces a voltage in the sensing coil which is fed back to increase conduction through the current control and the solenoid pump coil. As current through the solenoid pump coil further increases, the current control element is driven further into conduction by the increased feedback voltage from the sensing coil until it reaches saturation. At saturation, the current flow is no longer increasing so no feedback voltage is induced in the sensing coil to maintain the current control element in its conducting state. As the control element begins to return to its limited conductive state, the decreasing current through the solenoid coil induces a signal of opposite polarity in the sensing coil which ultimately drives the power transistor into a nonconducting state cutting off current flow through the solenoid coil. This cycle is again repeated as a small amount of current is again allowed to flow through the solenoid coil, and continues repetitively until operating power is removed.

When the coil is not energized, the solenoid armature is maintained in a rear position by a spring-loaded return mechanism. Each time full operating current pulses through the pump coil, the armature is driven forward against the spring force of the return mechanism, to be returned to its initial rearward position when current flow through the pump coil ceases. With the hydraulic system, the armature operates as a pump piston with a pair of check valves controlling flow from an inlet behind the piston to the outlet ahead of it so that the reciprocating movement of the piston forces fluid through the system to the actuator vane.

In another form, the reciprocating solenoid movement is mechanically linked to produce rotary or linear movement in either of two directions in accordance with the setting of the selection switch. In this arrangement, a control solenoid is actuated by closing a selection switch to bring one of a pair of pawls into operative engagement with a ratchet element, so that the reciprocating movement of the piston produces a step-by-step movement in the desired direction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, cross section view of a rotary valve actuator system in accordance with the invention;

FIG. 2 is a cross section view of the valve actuator system of FIG. 1 taken along the plane 2-2 of FIG. 1;

FIG. 3 is a cross section view of the valve actuator system of FIG. 1 taken along the plane-3-3;

FIG. 4 is a schematic circuit and fluid flow diagram illustrating a preferred form of operating arrangement for a valve actuator system in accordance with the invention;

FIG. 5 is a schematic circuit diagram showing an alternative form of circuit arrangement in accordance with the invention; and

FIG. 6 is a schematic, perspective view illustrating a mechanical arrangement that may be employed in another form of valve actuator system in accordance with the inven- IIOI'I.

DETAILED DESCRIPTION Referring now to FIGS. 1, 2 and 3, a compact structure embodying a preferred embodiment of the invention is illustrated in somewhat simplified form to assist in understanding the invention. The particular actuator system is of a type that might be mounted in aircraft or space vehicles for opening and closing rotary valves. For this purpose, a rotary mechanical output is transmitted by the actuator system to the rotary valve stem (not shown) by means of an output shaft 12 journaled for rotation in a bearing 14. Within the system, the end of the shaft 12 is fixedly coupled to be rotated by movement of an actuator vane 18. if desired, a handle 16 is affixed to the shaft 12 to permit manual operation of the valve.

In this embodiment, a unique solenoid operated pump produces the required high torque rotational forces in one direction or the other through the application of hydraulic pressure to one side of the actuator vane 18 while releasing pressure on the other side by permitting the fluid to escape back to the pump inlet. A cylindrical armature 20 is made ofa magnetic material capable of sustaining very high flux densities, such as the iron alloy known as Vanadium Permandur." The armature 20 is slidably received within a smooth cylinder bore that is closed at one end and formed in a cup-shaped rear body member 22, preferably made of the same high permeability magnetic material. The forward interior portion of the rear body member 22 is coaxially counterbored, to form an annular recessed shoulder surrounding the armature 20 for receiving the solenoid coil 24 and a separate coaxially disposed sensing coil 26. A circular disc-shaped body member (also called a front closure member) 28 of high permeability magnetic material covers the forward open end of the member 22 to complete the enclosure and has a cylindrical central boss portion 30 with substantially the same diameter as the cylindrical armature 20 that is inserted into the center of coil 24. Together, the rear body member 22 and the disc-shaped body member 28 comprise a solenoid housing of high permeability magnetic material. The coils 24 and 26 are insulated from the members 22 and 28 and from the armature 20, and from each other, by thin layers of insulating material 32 surrounding the coil windings. The insulation layer on the inside of the coil 24 has a relatively smooth, hard surface surrounding the armature 20 with adequate clearance to permit its free reciprocating movement through the central opening in the coil. The cylinder engaging the back end of the armature 20 and the central opening in the coil behind the boss 30 define an elongated, close fitting bore that is slightly longer than the armature and permits its' free reciprocating movement over a short distance. The close fit promotes magnetic efficiency and effects a low friction, low leakage seal. Because the solenoid coil windings are separated from the armature 20 only by a thin insulating nonmagnetic layer, the coupling of high flux densities produced by the coil through the magnetic material of the armature is maximized. In this way, very high driving forces can be exerted on the armature with maximum magnetic efficiency even though the system is relatively small and light.

The rear cover member 22 is attached to a main body member 36 with a metal attachment ring 38 and bolts, or by other suitable means. A fluidtight seal between the members 22 and 36 is maintained with a resilient O-ring 40. Although the main body member 36 has been shown herein as a unitary construction in order to simplify the illustration, as a practical matter it could most readily be constructed in several different parts to permit insertion and ready access to the various internal elements. In this instance, the various internal parts would be housed in asingle enclosure and the entire outside of the enclosure would be filled with oil. This form would have the advantage of not requiring O-rings and other seals between the several parts.

A spring-loaded push rod 42 extends from the main body member 36 through an aperture in the cylindrical boss portion of the member 28 to bear against the armature 20 urging it toward a normal position at the rear of the bore against the closed end of the cylinder in the rear body member 22. A unidirectional flow path is defined through the armature 20 from an opening 44 at the rear of the bore to a plurality of regularly spaced openings 46 at the front through a springloaded, ball-type, inlet check valve 48 that permits flow only in the forward'direction so that as it is moved backward fluid is transferred from the inlet at the rear of the cylinder to fill the volume vacated .in front. As the armature 20 is moved forward, the fluid in front is expelled through a plurality of outlet passages regularly arranged about the center of and extending through the central boss portion of the member 28 into an annular outlet manifold 50. A springloaded, ball-type outlet check valve 52 at the outlet prevents reverse flow. Flow through the outlet check valve 52 is routed in either of two flow paths in accordance with the setting of a pair of solenoid actuated, two position, three- way control valves 54 and 56, both of which are spring-loaded to a normally closed position that blocks flow from the pump outlet, as illustrated by valve 54 in FIG. 1. When opened, the control valves 54 and 56 deliver fluid from the pump outlet to a respective side of the actuator vane 18, while when not actuated they permit the escape of fluid from the other side of the vane back to the pump inlet. Thus, when power is applied to either Operating solenoid 58 or 60, the armature pulls in to shift the control valve 54 or 56 to its alternate position, as illustrated by valve 56 in FIG. 1, to shut off flow back to the pump inlet and establish a flow path from the pump outlet to the appropriate side of the actuator vane 18.

As best seen by reference to FIG. 2, the actuator vane 18 is journaled at its upper end for rotational movement with the output shaft 12 to sweep through a limited arc within a pieshaped cavity 62 defined in the forward part of the main body member 36. The cavity 62 has a substantially constant, radial cross section matching that of the vane 18 throughout its arc of movement so that the vane serves as a movable fluidtight partition between the fluid volumes on either side. A fluid passage 64 from the control valve 56 terminates in an opening through one of the radial sidewalls of the cavity 62 on one side of the vane 18, while on the other side a fluid passage 66 from the control valve 54 terminates at the other radial sidewall on the opposite side of the vane. With the control valve 54 open and valve 56 closed, as shown in FIG. 1, fluid flow from the solenoid pump proceeds in the direction shown by the arrow 68 to move the vane 18 in a clockwise sweep, as shown by the arrow 70 in H6. 2.

In many applications, the actuator system must provide for a manual actuation of the valve or other actuated device. In this arrangement, with the system deenergized, both control valves 54 and 56 are maintained in the open position and the actuator vane 18 is held in place by friction with the sidewalls of the cavity 62, or if desired by some sort of detent arrangement (not shown) included in the mechanical linkage. in this condition, the actuator vane 18 can be moved manually to any desired position by applying sufficient force by means of a handle 16 to overcome the friction force or detent. As the vane is moved, fluid is simply transferred from one side of the vane to the other through the passages 64 and 66 and the open control valves 54 and 56 past the outlet of the check valve 52. Thus, the actuator is effectively decoupled from the system prime mover without the necessity of a clutch to permit manual operation.

Referring now to FIG. 3, a pair of conventional pushbutton switches 72 and 74 are mounted at an angie to one another within a cavity 76 immediately behind the cavity 62. The end of the output shaft 12 extends into the cavity 76 and has a finger member 78 afi'ixed for rotation with the actuator vane 18. A flat metal strip is formed into a V-shaped contact element 80 that is rotatably mounted at its apex on a dowel 82 between the switches 72 and 74 with the two arms extending radially outward adjacent the pushbuttons on opposite sides of the finger member 78. The outer end portions of the anns are angled inwardly. The length of the finger member 78 is slightly less than the distance from the shaft 12 to the pushbuttons on switches 72 and 74. As the output shaft 12 rotates in one direction or the other, the end of the finger member 78 passes freely along the flat inner surface of the arms past the pushbuttons until it reaches the inwardly directed end portion of one arm of the element 80. Further rotation of the finger member 78 along the inwardly directed end portion forces the intermediate portion of the leg adjacent the pushbutton to be pushed outward against the respective pushbutton to depress it and actuate the switch. Rotation in the opposite direction releases the pushbutton and continues until the finger member 78 reaches the end of the other arm to depress the other pushbutton. This indicates the shaft 12 has reached a position in which the rotary valve is fully opened or fully closed and opens the circuit supplying-the solenoid to stop its operation.

A further cavity 84, located within the mainbody structure 36 above the cavities 62 and 76, houses the electronic components of the system to provide a compact unitary structure. In most instances, the cavity 84 need not be vented to permit escape of heat generated by the electronics, since components can be mountedin heat exchange relationship with the surrounding metal that thus serves as an adequate heat sink.

Connections to an outside power source, and to external indicators and selection switches, are made through connector fitting 86 with wire leads 88 from the internal circuitry being connected to metal plugs 89 mounted by an insulative end plug 90 sealing the'open end of the fitting 86. The hollow interior of the fitting 86 is partially filled with the hydraulic fiuid used in the hydraulic pump system and serves as a reservoir. A hydraulic fluid having a high dielectric constant and good lubricating and heat transfer properties, such as silicon oil, permits the inner elements of the system, including the electrical circuitry, to be entirely immersed so that the unit need only be sealed against exterior leakage and against transfer between different fluid paths. In this way, the fiuid serves as a lubricant for moving parts, as a heat transfer and spark retarding agent for the electrical elements and asa damping medium to suppress vibrational movement of the parts relative to one another.

Referring now to H6. 4, which is a schematic illustration of the preferred form of the electric circuit and hydraulic system, a high current capacity external power supply 92 supplies preferably direct current'at a preselected voltage through a single pole, double throw selection switch 94. For the purposes of this explanation, the selection switch 94 is shown with its movable contact in an upper position for actuating the system to open the valve, whereas the actuator vane 18 is shown in an intermediate position being moved in a counterclockwise direction from the closed to the opened position. With the selection switch 94 in the upper position as shown, direct current flows from the positive terminal of the source 92 through the closed selection switch contacts and a set of normally closed contacts of the pushbutton switch 72 to actuate the valve control solenoid 58, causing the control valve 54 to be shifted upwards from its normal position to its alternate position against the upper valve seat. This opens the flow path from the pump outlet through the passage 64 into the chamber 62 on the upper side of the vane 18. Since no current is applied to the solenoid 60, except in the event the selection switch 94 is moved to the closed position, the other control valve 56 remains in its normal position against the upper valve seat to vent fluid on the other side of the actuator vane 18 through the passage 66 back to the pump inlet.

At the same time, the DC power from the source 92 is applied to operate the solenoid pump. The large solenoidpump coil 24, which consists of numerous turns of heavy gauge wire such as copper, is coupled to the positive terminal of the source 92 through a diode 96 and the switches 72 and 94. The pump coil 24 is also connected through the collector-toemitter circuit of a controlled power transistor 98 to ground potential. More specifically, the emitter of power transistor 98 is connected directly to ground potential, while its base terminal receives a control signal from the emitter of an amplifier transistor 100 that is coupled to ground potentialthrough a biasing resistor 102 and a reverse connected diode 103 connected in parallel. In the particular circuit illustrated, both transistors 98 and 100 are NPN-type transistors, but equivalent circuits using other solid state and even electronic tube elements may also be used. The base terminal of the transistor 100 is connected to the junction between a pair of resistors 104 and 105 to receive an input signal. Theopposite terminal of the resistor 104 receives the positive voltage from the source 92 through a diode 107, whereas the opposite terminal of the other resistor 105 is connected through the sensing coil 26 to ground potential. The resistor 104* preferably has a resistance value approximately 10 times larger than that of the resistor 105, so that these two resistors form a voltage divider circuit for applying to the base terminal of transistor a signal voltage approximating the voltage in duced in the sensing coil 26, plus a small proportion of the dif ference between the induced voltage and the positive supply voltage. The collector terminal of the transistor 100 receives a positive voltage from a tap on the solenoid coil 24 that is placed to include only about one-tenth of the total turns in the pump coil, the voltage at this point being only slightly below the positive supply voltage.

Initially, upon closing the switch 94, no voltage has been induced in the sensing coil 26' so that the voltage at the base terminal of the transistor 100 is only slightly above ground potential. Thus, conduction through amplifier transistor 100 is limited to a relatively low value to hold the power transistor 98 in a low conduction state also. As the initial small current flow permitted by transistor 98 begins to build up through the pump coil 24, a small positive voltage is induced across the sensing coil 26 that increases the signal voltage applied to the base of the transistor 100. As conduction through transistor.

100 increases, the increased voltage developed across resistor 102 results in more conduction through the power transistor 98 and the pump coil 24. The greater current flow permitted through the pump coil 24 generates a further increase in the positive voltage induced in the sensing coil 26 with the result that the regenerative process continues at an increasing rate driving the power transistor 98 into saturation to maximum current flow through the pump coil 24. As the power transistor 98 approaches saturation, the rate of increase of current flow through pump coil 24 drops, causing a corresponding decrease in the rate of increase for the flux generated. Since the voltage induced in the sensing coil 26 is directly proportional to the rate of change in the flux generated by the pump coil 24, the induced voltage drops, reducingithe feedback signal to the transistor 100, and ultimately causing the power transistor'98 to be returned from saturation towards its nonconducting state. As flux produced by the pump coil 24 decreases, a negative voltage is induced in sensing coil 26 to cause both amplifying transistor 100 and power transistor 98 to cut off. At this point, the circuit is ready to repeat another operating cycle. This sequence occurs repetitively as long as the selection switch 94 remains closed, or until the actuator vane 18 reaches the fully open position whereupon switch'72 changes position interrupting current to the solenoid.

Since the large current pulses through pump coil 24 can result in arcing problems, a thyristor device 109 is connected as an arc suppressor between the collector and base terminals of the transistors 98. Also, the emitter terminal of the transistor 100 is coupled through the reverse connected diode 103 to ground potential. This protects the circuit against voltage and current surges and possible arcing problems when current flow through the pump coil 24 is suddenly switched off.

As will be evident to those skilled in the art, other types of oscillatory current pulsing may be employed. For example, the sensing coil can be replaced with a normally closed magnetic reed switch and a timing device. The reed switch is set to open and'shut off the current to the solenoid coil in the presence of amagnetic field corresponding with the one anticipated when the plunger has completed its stroke. After the reed switch opens, the timing device permits the plunger to move back to its rest positionbefore the current is turned on again prior to the next power stroke. In another version, an ordinary limit switch may be employed to either cause the power transistor to begin conducting or it can be connected directly to the main solenoid coil. In either case, it is in the normally closed position when the plunger is at the beginning of the power stroke. his a hysteresis characteristic of this type of switch to hold the contacts closed during the power-stroke motion. The switch will be arranged to break contact just prior to the end of the power stroke. This action interrupts the current flow and permits the return spring to move the plunger back to the, rest position. Another hysteresis characteristic of the limit switch is to remain in the open position while the plunger is moving back to its rest position. Again by proper selection of switches and arrangement thereof, the current will be caused to begin to flow just prior to the time when the plunger reaches its furthest excursion.

Similarly, when the movable contact of the selection switch 94 is placed in its alternate position to actuate the system to close the valve, operating power from the direct current source 92 is delivered through the normally closed contacts of the pushbutton switch 74. In that case, actuating current is applied to the solenoid 60 to move the valve 56 from its normally closed position to' its lower valve seat, establishing a flow path from the pump outlet through the passage 66 to the chamber 62 on the lower side of the vane 18. In this case, the control valve 54 is held in its normally closed position to establish the flow path from the opposite side of the vane 18 through the passage 64 to the pump inlet. Power from the source 92 is also applied through a diode 110 to the pump coil 24 and through a diode 111 to the biasing resistors 104 and 105 to initiate the desired circuit operations, as previously described.

Once the selection switch 94 is operated to either open or close the valve, high power current pulses are delivered through the pump coil 24 until the valve reaches the desired open or closed position. At that time, the finger member 78 has been rotated on shaft 12 to a position to actuate the appropriate pushbutton switch 72 or 74, lifting the movable contact from its normally closed position. This interrupts the power supply to the circuit from the source 92, thus preventing further operation and returning the actuated control valve 54 (or 56) to its normal position. Diodes 113 and 114 are connected in parallel across the control solenoids 58 and 60, respectively, in the conventional manner for surge suppression.

Frequently, it is desirable or necessary to positively indicate when the valve is in the fully opened or fully closed position. For this purpose, the pushbutton switches 72 and 74 may have an alternative contact position, as shown, to which a movable contact is switched by toggle action after it is moved from its normal position by the finger member 78. In the alternative contact position, power from the source 92 lights an indicator lamp 116 or 117, most conveniently located near the selection switch 94 on the control panel, to signal that the valve is in the fully opened or fully closed position.

In some instances, particularly in aircraft or spacecraft where severe vibrations can produce unexpected short circuits, safety requires that the system provide protection against accidental simultaneous application of control signals to the circuit for both opening and closing the valve. Most commonly a requirement is made that in this situation the actuator maintain the valve in its last position until the condition is corrected. With the circuit of FIG. 4, simultaneous actuation of the solenoids 58 and 60 would move both valves 54 and 56 to their alternate positions to establish parallel flow paths from the pump outlet through passages 64 and 66 to both sides of the actuator vane 18, and there would be no return path back to the pump inlet. Although the circuit would continue to deliver current pulses through the pump coil 24, the armature could not move forward against the fluid filling both outlet passages. In addition, a flow path is established between the cavity volumes on opposite sides of the actuator vane 18 through the fluid passages 64 and 66. While random movement of the actuator vane is prevented and the valve would remain in the last position selected, pulsing of the pump coil 24 would continue and could cause unnecessary wear. Should such an occurrence take place, it would be desirable to alert the operator to the condition so that early corrective action could be effected.

To provide for this, and to meet the requirements where established, the basic circuit illustrated in FIG. 4 is modified, for example, as shown in FIG. 5 to prevent the operation of the pump should both inputs be mistakenly energized. In this particular arrangement, a pair of normally closed magnetic reed switches 120 and 121, each disposed in proximity to a respective one of the valve solenoids 58 and 60, are connected in parallel with one another between the sensing coil 26 and ground. When one of the solenoids 58 or 60 is energized, a magnetic element on the movable contact is attracted by the solenoid flux so that the switch is changed from its normally closed position and held open. In the preferred arrangement, should both valve solenoids 58 and 60 be mistakenly energized simultaneously, both switches 120 and 121 are opened to disconnect the sensing coil 26 from ground, thereby preventing any feedback signal from being induced in the coil 26. However, when only one switch 120 or 12] is open, the ground connection is established through the other so that the signal can be induced in the sensing coil 26 as previously explained. Thus, should both control valves 58 and 60 be mistakenly energized, lack of a feedback signal from the sensing coil 26 prevents pulsing of the pump coil 24, since the power transistor 98 remains in a state of low conduction. The low current flowing through the pump coil 24 can continue indefinitely without overheating or otherwise damaging the coil. As will be obvious to those skilled in the art, similar switching arrangements can be employed elsewhere in the circuit to interrupt normal operation of the pulsing circuit should both valve solenoids 58 and 60 become simultaneously energized.

Actuator systems of this type can be readily designed to meet the requirements of the valve or other device to be actuated. For example, assuming that the valve requires a torque of 100 inch pounds and is rotated 90 between the fully open and the fully closed positions with an actuation time of I second, the system might be as follows. The pump solenoid circuitry may be designed to pulse the pump coil at the rate of 50 pulses per second, with the repetition rate primarily being determined by the inductive values of the pump coil 24 and the sensing coil 26 and the bias values selected for the transistor elements 98 and 100. With a small actuator vane extending 1% inches outward from its center of rotation and having a width of less than one-half inch, a pressure differential of approximately 180 psi. would provide the desired torque. With a solenoid stroke of only 0.045 inch at 50 strokes per second, the piston area need only be approximately 0.4 square inch to move the required volume of fluid for sweeping the actuator vane through the full 90 within 1 second. Typically, the return spring force on the armature may be 2 pounds. Assuming the voltage supply source is a standard 27 volts DC capable of providing a maximum of 3 amperes through the pump coil 24 during each pulse cycle, the required pump force can be achieved using a solenoid having on the order of 900 turns of a 22-gauge wire.

In certain uses, a mechanical linkage instead of the hydraulic system may be desirable for transferring the high torque, low speed output from the reciprocating solenoid armature to move the valve or other actuated member. Various methods of accomplishing this purpose will be apparent to those skilled in the art, one of which is schematically illustrated in FIG. 6. In this arrangement, a pair of ratchet wheel segments 125 and 126 having peripheral gear teeth are affixed for rotation on opposite sides of the output shaft 12. Both extend over an angular segment equal to the angle moved by the rotary valve from a fully opened to the fully closed position. A pair of slip pawls 128 and 129 are movably disposed adjacent respective ratchet wheel segments 125 and 126 to selectively engage the peripheral gear teeth. Both pawl arms are rotatably journaled at the opposite end to a reciprocating shaft member 131 that is coupled to move with the solenoid armature 20. As a practical matter, the shaft 131 may simply be an extension of the push rod member 42. The arms of the slip pawls 128 and 129 are slidably engaged for reciprocating movement through movable bearing members 133 and 134, each of which is normally urged upward to hold the pawls out of engagement with the ratchet wheel segments by a spring force, schematically represented at 136 and 137. The movable bearings 133 and 134 are independently coupled to the armature of one of a pair of control solenoids 139 and 140, which are selectively actuated by power from the DC supply source 92 in accordance with the position of the selection switch 94. When actuated, the solenoid 139 or 140 moves its respective pawl arm 128 or 129 down into engagement with the teeth on the I ratchet wheel segment 125 or 126, respectively, to turn the output shaft 12 in the desired direction to open or close the valve. It should be noted that with this mechanical arrangement, should both solenoids 139 and 140 accidentally be actuated simultaneously, both slip pawls 128 and 129 would engage the ratchet wheel segments 125 and 126 on opposite sides of the shaft 12 so that movement in either direction is prevented and the valve is maintained in its last position. Of course, depending upon the particular use of the actuator system, other types of mechanical linkage arrangements may be employed-to suit these needs.

Although preferred embodiments of the actuator system in accordance with this invention have been illustrated and described herein to explain the nature of this invention, it should be understood that various changes, modifications and equivalent arrangements may be employed other than those specifically mentioned. Thus, for example, although the valves 54 and 56 are shown as being actuated by a pair of solenoids 58 and 60, respectively, it will be obvious that other activating means may be employed, such as a pair of bimetallic elements each of which is translated from afirst position to a second position upon'the application of heat to the element by an electrical heater, for example. It will be understood that such changes, modifications and equivalent arrangements may be utilized without departing from the spirit or scope of theinvention as expressed in the appended claims.

lclaim: v

1. An actuator system for providing high torque, low speed movement of an actuated member comprising:

solenoid means including a solenoid coil, a magnetic solenoid housing surrounding said coil and providing a low reluctance path for flux produced by said coil, and a magnetic armature slidably supported by said body member for reciprocating movement along the axis of said coil;

power transmission means linking said solenoid armature for selectively moving said actuated member a fixed amount in a given direction for each reciprocating movement of said-armature in a forward direction from a normal position toward the center of said coil;

control means connected to said transmission means for selectively establishing the given direction of movement of said actuated member; and

circuit means responsive to the operation of said control means for repetitively energizing said solenoid coil to generate a flux forcing said armature in said forward direction.

2. The actuator system of claim 1 wherein:

said solenoid means further includes means for urging said armature away from the center of said coil within said body member for returning said armature to said normal position after each energization of said coil.

3. The system in accordance with claim 2 wherein said transmission means constitutes an hydraulic system including:

a movable actuator vane coupled to move said actuated member in either direction in response to a fluid pressure differential between opposite sides of said vane;

a conduit system for directing flow of hydraulic fl'uH between opposite sides of said actuator vane and the opposite ends of said armature; and

check valve means for permitting fluid flow through said conduit system in the forward direction into the cavity formed during the retreat of said armature only when said armature is being returned to the nonnal position; and

wherein said control means includes control valve means for selectively directing flow through said conduit system to either side of said actuator vane from the forward end of said armature and for directing flow to the other end of said armature from the opposite side of said actuator vane to move saidactuator vane an incremental distance in a selected direction during each forward movement of said armature.

4. The system of claim 2 wherein:

said transmission system constitutes ratchet means coupled for moving said actuated means in either selected direction;

pawl means coupled for reciprocating movement with said armature means and disposed for selectively engaging said pawl means to cause movement in either selected direction; and

wherein said control means comprises means for selectively moving said-pawl means into operative engagement with said ratchet means for producing incremental movement of said ratchet means in the desired direction during each forward movement of said armature.

5. The system of claim 4 wherein:

said ratchet means comprises a ratchet wheel coupled to rotate said actuated member;

said pawl means comprises first and second pawls, each disposed to selectively engage an opposite side of said ratchet wheel to produce incremental movement of said ratchet wheel in either of said directionswhen one of said pawls is in engagement during each forward movement of said armature; and

said control means comprises selectively operable means for bringing said pawls into engagement with said ratchet wheel.

6. An actuator system for providing high torques at'low speed for moving an actuated member comprising:

an elongated cylindrical armature of high permeability magnetic material having front and rear end surfaces;

an annular solenoid coil having a cylindrical central opening for slidably receiving the front of said armature;

a rear body member of high permeability magnetic material having an annular cavity for receiving said solenoid coil and defining a central cylinder closed at one end for slidably engaging the rear of said armature for reciprocating movement through the central opening in said coil;

1 front closure member of high permeability magnetic material having a central cylindrical boss extending partially through the cylindrical central opening in said coil and with a base portion abutting said rear body structure to enclose said solenoid coil and define a low reluctance and low inductance magnetic path through said boss, said base portion, said base member and said armature, the central cylinder in said body structure and the central opening in said solenoid coil defining an elongated cylindrical bore for permitting reciprocating movement of said armature between said boss and the closed end of said central cylinder;

spring return means for urging said armature to a normal position against the closed end of said central cylinder;

means for repetitively pulsing energizing current through said solenoid coil to drive said armature forward in said bore toward the surface of said boss, said armature being permitted to return to said normal position in the interval between pulses; and

transmission means coupling said armature to said actuated member to move said actuated member an incremental distance in a selected direction in response to each forward movement of said armature.

7. The system of claim 6 wherein said circuit means comprises:

signal controlled current gating means connected in series with said solenoid coil for controlling the flow of current through said coil in response to the value of an input signal;

a sensing coil disposed adjacent said solenoid coil for generating a feedback signal proportional to the rate of increase of the flux generated by said solenoid coil; and

an input signal circuit coupled to provide input signals to said gating means and to said sensing coil for providing an initial bias signal permitting a small flow of current through said solenoid coil for receiving said feedback signal to increase the value of said input signal in response to the increase in flux produced by said solenoid coil.

8. The system of claim 7 further comprising:

control means for selectively operating said transmission means to produce movement of said actuated member in either of two directions in response to applied control signals; and

control signal means coupled to operate said control means for selectively applying control signals in accordance with the selected direction.

9. The system of claim 8 wherein'said second means further comprises:

switching means responsive to the accidental application of both said control signals for interrupting the generation of said feedback signal to said current gating means.

10. A solenoid pump comprising:

an annular solenoid coil having a central cylindrical opening along its central flux axis;

an elongated cylindrical armature of magnetic material;

a body structure of high permeability magnetic material en-, closing said coil and said armature, said body structure having an annular cavity therein for mounting said solenoid coil and a counterbored cylinder concentric with said annular cavity and closed at one end for slidably receiving one end of said armature, said cylinder and said opening through the solenoid coil defining a cylindrical bore permitting reciprocating movement ofsaid armature between a rear position abutting the closed end of said cylinder and a forward position abutting a forward interior surface of said body structure at the front of said bore;

return means for normally urging said armature toward the rear position;

fluid passage means in communication with a cavity formed between the forward interior surface of the body structure and the armature when the armature moves rearward for conducting fluid to said cavity;

valve means for permitting flow only in the forward direction through said passage;-

a fluid outlet defined through said body structure from said cavity, said solenoid coil being adapted to receive high power energizing current pulses for forcing said armature against said return means to the forward position to force fluid from said cavity through said outlet, said armature being returned to its rear position by said return means after cessation of each energizing current pulse to permit flow from the rear of said bore to pass through said valve to the front of said bore, whereby an incremental amount of fluid is forced under pressure through said outlet by said armature during each reciprocating movement.

11. The solenoid pump of claim 10 further comprising:

circuit means responsive to a control signal for delivering high power energizing current pulses repetitively at a given repetition rate to said solenoid coil.

12. The solenoid pump of claim 11 wherein said circuit means comprises:

noid coil to a small portion of the maximum and connected to receive said feedback signal to increase said input signal gradually in response to the increase in flux produced by said solenoid coil to permit maximum flow through said solenoid coil.

13 The solenoid pump of claim 11 further comprising:

control valve means responsive to said control signals for selectively directing the flow of fluid in alternative paths from the outlet and to the inlet in accordance with a desired direction of movement.

g g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIUN Patent No. 3 587 .234 Dated June 22L l97l Inventor(s) Malcolm M. McQueen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 60, "outside" should read --inside. Column 6, line 43, after "induced in" insert --the--; line 54,

"transistors" should be --transis tor--. "turns of" delete "a". Column 12 line 35, after "maximum" and before "flow" insert "current- Signed and sealed this 'H th day of March 1972.

(SEAL) Attest:

EDWARD M-FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents Column 8, line 54, after-

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