GB2134983A - Fluid operated, axially reciprocating actuator - Google Patents

Abstract

A blowout preventer has opposed rams, each of which is moved between opened and closed positions by a fluid- operated actuator having a rod 18 adapted to be axially reciprocated by fluid pressure within a cylinder and extending from the cylinder for connection to the ram. Each ram is locked in closed position by locking elements 27 carried by the rod for movement into locking position within the cylinder automatically in response to movement of the ram with the rod into closed position. The elements initially are pushed with low friction along the cylinder wall by an annular piston 24 and ring 29 on the rod. At a tapered end cylinder portion 25, the ring forces the elements outwardly by a surface 35A for locking. Upon pressure release, the elements stay in the locked position. Only upon pressure for rod retraction are the elements released by retraction of the ring and piston. <IMAGE>

Description

SPECIFICATION Fluid operated, axially reciprocating actuator This invention relates in general to afluid operated actuator having a rod extending from an inner end of the cylinderthereoffor axial reciprocation between inner outer positions in response to the supply and exhaustofoperatingfluid to and from outer and inner sides, respectively, of piston means within the cylinder.More particularly,this invention relates to improvements in actuators of this type wherein the rod is locked'against return movement to its outer position autamatically in response to movement into its inner position, whereby operating fluid may be exhausted from the outer side ofthe piston means, following whichitherod may be unlocked for return movement automatically in response to the end-forend reversal ofthesupply and exhaustofoperating fluid to and from.opposite sides ofthe piston means.

In one of its aspects, the actuator ofthis invention is well suited for use in moving the rams oft blowout preventer between opened and closed positions, particularly when the preventer is underwater or at some other remote lacation.

In the operation ofablowout preventer, one ram will normally move inwardly into the bore ofthe preventer housing priorto inward' movement of the other ram. In orderto insuretightsealing engagement between the front faces ofthe rams, and about a pipe which might be in the bore, the one ram is allowed to travel beyond the position itwould occupy if both rams moved in simultaneouslyto engage along the centerline of the bore of the housing. Furthermore, as the packing on thefrontface of one or both ram wears, it may be necessaryto move the rams inwardly additional compensating distances, thus requiring adjustment in the operating system andlorstopsfor limiting inward movement ofthe rams.

On page 1432 ofthe 1980-81 issue of the Composite Catalog of Oil field Eq.uipment & Services, a ram operating system isshown in which the rams may be locked in closed position by a wedge-shaped locking element arranged to slide laterally overa com plementarysurfaceontheouterendoftheram control rod in responseto supplyof of operntingfluid to the outer side of a piston on the locking element These locking surfaces form an angle with' mspectto a plane perpendiculartothe rod axis whichis less than the friction angle, so thatthe locking element will remain in locking position upon exhaustion of operating fluid from the outer side ofthe piston, and despite forces tending to open the rams, and will also automatically compensate for packing wear by sliding further over the end of the rod. Over and above the fact that it is not automaticjn the sense that it requires manipulation of suitable controls in proper sequence with opening and closing of the rams, this device is of such construction that, upon the exhaustion of operating fluid, it may develop load paths due to outward forces on the rod which include previously unloaded elements, and, as a result,the rams may be permitted to back offfrom their closed positions an excessive amount.

Patent No.3,242,826 shows a device in which locking elements carried by the control rod for operating a blowout preventer ram or other valve member are moved with the rod into locking engagementwith a locking shoulder in a cylinderautomatically in response to the supply of operating fluid to the outer side of piston means within the cylinderfor moving the ram to closed position. The locking elements are wedged outwardly into and held in locking position by means of a locking ring or sleeve on an inner piston slidable over the rod and within an outer piston on the rod. Thus,the ring has an outer cylindrical surface slidable within inner cylindrical surfaces ofthe locking elements so that operating fluid may be exhausted from the outer side ofthe piston means.Operating fluid may then be supplied to the inner side of the piston means to move the locking ring outwardlyfrom within the locking elements, and thus permitthemto be withdrawn from locking position with the rod.

Patent No.4,304,565 shows a device ofthis latter type in which locking surfaces between the inner sides ofthe locking elements and the outer side of the locking sleeve form an angle with respect to the rod axis which is less than the friction angle, so as to hold the rod in its inner position, butwhich nevertheless permitsthe locking elements to slide inwardly and outwardly along the locking shoulder of the cylinder to a variety of locking positions, depending on the extent to which the rod moves inwardly and thus regardless of wear on the ram packing.Since the locking surfaces between the locking elements and the locking sleeve ofthe last-described device form such a small angle with respect to the rod axis, the sleeve transmits a relatively large radial component of the force which is due to operating fluid supplied to the outer side of the piston, to the locking elements as they are moved with the rod from its outer position to its inner position.As a consequence, it was apparently through necessary to reduce this force on the locking elements and, thus, frictional drag ofthe locking elements with the inner diameter of the cylinder during inward movement withthe piston and rod, by an arrangement of pistons with the cylinder including an outer annular piston on the locking sleeve having a relatively small crosssectional area for moving the locking elements axially inwardly, and an inner piston sealably slideable in the outer annular piston and having a relatively large cross-sectional area for moving the rod inwardly.

More pa rticularly, the locking elements are carried by means of a cage aboutthe rod so that if the locking elements act as a brake as they slide along the inner diameter ofthecylinder,the rod will,through the cage, transmitthe force due to the large piston to the extent it is necessary to move the locking elements inwardly along the cylinder diameter and into position opposite the locking shoulder.

Because of its complex construction,theactuator of Patent No.4,304,565 is also particularly unsuited for use in a preventer ofthetype such as shown in copending application, Serial No. 337,383, filed by Marvin R. Jones on January 6,1982, and entitled "Hydraulically Operated Valves". Thus, as shown and described therein, the ram control rod is hollow and extendsthroughthe outer end ofthe cylinder into a chamber in its bonnet so asto substantially balance forces acting in opposite directions on opposite ends ofthe rod, and thereby reduce the force required to move the rams to closed position.Considerable difficultywould be expected in fitting the dual piston arrangement of such patent within the relatively small annular space between the hollow rod and inner diameterofthe cylinder.

It is therefore an object of thins invention is to provide an actuator of this lattertype which is also operable to move the rod and locking elements axially inwardly toward a variety of locking positions, but which is of a relatively simple construction and which does not cause excessive frictional drag between the locking elements and inner diameter of the cylinder ofthe actuator.

It is a more particular object ofthis invention to provide such a device which is well suited for an disposal within an annular space about a hollow control rod whose outer end extends into a balance chamber.

These and other objects are accomplished, in accordance with the illustrated embodiment of the invention, by an actuator of the type described in which means are provided fortransmitting to the locking elements, and thus to the control rod, a relatively large axial component of the axially inward ly directed force due to operating fluid supplied to the outer side ofthe piston means in order to move the rod axially inwardly with the locking elements until the conical surfaces ofthe locking elements are radially opposite the cylinder shoulder, and then transmitting tothe locking elements, and thus to the rod, a relative large radial component of such force in orderto cause the locking elements to move radially outwardlywith respectto the rod and the conical surfacesthereofto slide radially outwardly along the cylinder shoulder as the rod continues to move axially inwardly with the locking elements to its inner position. More particularly, the rod is locked against return movementfrom its innerto its outer position, upon exhaustion of operating fluid from said outer side of the piston, and means are also provided fortransmitting to the rod the axially outwardly directed force due to the supply of operating fluid to the inner side of said piston means and causing the locking elements to slide radially inwardly along the shoulder and then axially outwardlywith the rod as the rod is returned to its outer position.

In the illustrated embodiment ofthe invention, the piston means includes an annular piston having an inner diametersealably slidable along the rod and an outer diameter sealably slidable along the inner diameterofthecylinder. Preferably,theouterend of the rod is hollow and extends sealablythrough the outer end of the cylinder into a chamber outwardly of the cylinder and so asto be substantially pressure balanced, and the inner diameter ofthe annular piston is greater than the outer diameter of the outer end of the rod, so that the piston means also has a piston on the rod which is responsive to control fluid to urge the rod axially inwardly.

In the preferred embodiment ofthe invention,there is a stop on the rod on the inner side ofthe locking elements, a locking ring on the annular piston, and means on the locking ring and locking elements for transmitting to the locking elements, and thus tothe rod, the above-described inwardly directed force due to the supply of operating fluid to the outer side of the piston. More particularly, there is another stop on the rod outwardly ofthe piston for transmitting to the rod the above described outwardly directed force due to the supply of operating fluid to the inner side ofthe piston.As illustrated, this means on the locking ring and locking elements comprises afirstsurface about the ring which is engageable with substantially complementary first surfaces on the locking elements to move the locking elements against the inner stop on the rod and thereby move the rod axially inwardlywith the locking elements, and which is than slidable over said first surfacesto wedgethe locking elements radially outwardly with respectto the rod for sliding along the cylindershoulderasthe rod and locking elements move further axially inwardly, in response to the supply of operating fluid to the outer side of the piston, and a second surfacethereaboutwhich is slidable over substantially complementary second surfaces on the locking elements, upon sliding of said first surface out of engagement with said first surfaces ofthe locking elements, so as to continue to wedge the locking elements radially outwardly for sliding further along said cylindershoulderasthe rod and locking elements continue to move axially inwardly and until the rod reaches its inner position, in response to the continued supply of operating fluid to the outer side of the piston.

More particularly, said first surfaces form a relatively large angle with respectto the rod axis so asto transmit a relatively small radial component of force to the locking elements, wherebythere is a minimum offrictional drag between the locking elements and the inner diameter of the cylinder asthe locking elements move toward locking position, and said second surfaces form a relatively small angle with respect thereto so as to transmit a relatively large radial component offorce thereto as the locking elements are wedged outwardly along the locking shoulder.When operating fluid is supplied to the inner side ofthe piston, the second surface of the locking ring slides out of engagementwith the second surfaces ofthe locking elements as the locking ring is moved axially outwardly to release the locking elementsforsliding axiallyoutwardlywith-the rod and radially inwardly along the cylinder shoulder.

As illustrated, the inner ends of the locking elements have conical surfaces which extend in a direction toward the inner end ofthe cylinder for sliding along a substantially complementary conical surface ofthe inner stop of the rod, during radial expansion and contraction into and out of locking position. Also, the locking ring comprises circumferentially spaced-apart fingers which are pressed tightly about the rod as the second surfaces ofthe ring move into sliding engagementwith the second surfaces ofthe locking elements. Duetothe resulting axially directed frictional forces between fingers and both rod and locking elements, the second surfaces of the fingers may extend at an angle with respect to the rod axis which is substantially largerthan would be permissible if, as in prior devices ofthis type, there was substantially no frictional engagement ofthe locking ring with the rod Consequently, the locking elements are moved into locking position at an accelerated rate.Still further, bolts connect the locking elements to the rod for guided radial movementwith respectthereto, and one or more pins on the rod extend into one or more ofthe splits between the fingers so as to align the splits with the bolts for movementthereover asthe locking ring moves within the locking elements.

In the drawings, wherein like reference characters are usedthroughoutto designate like parts: Fig. is is a vertical sectional view of a blowout preventer having rams which are operated by means of actuators constructed in accordance with the present invention, the right-hand ram being shown moved to its inner position to engage about a pipe in the bore of the preventer housing and the left-hand ram being shown in its withdrawn position; Fig. 2 is a vertical sectional view, on an enlarged scale, ofthe upper half of the actuatorforthe right-hand ram, but with the rod shown in its outer position to withdrawthe ram to open position;; Fig. 3 is a viewsimilarto Fig. 2, but upon inward movement ofthe rod and locking elements of the actuatorto a position to which the locking elements are wedged outwardly along the locking shoulder of the cylinder as the ram is moved toward its closed position; Fig. 4 is still anotherview similarto Fig. 3, but upon further inward movement of the rod to its innermost inner position to wedge the locking elementsfurther outwardly along the locking shoulder as the ram is moved further inwardly to the closed position of Fig.

1;and Fig. 5 is a cross-sectional view ofthe upper half of the actuator, as seen along broken line 5-5 of Fig. 4.

With reference now to the details ofthe drawings, the blowout preventer shown in Fig. 1, and indicated in its entirety by reference character 10, comprises a housing 11 having a vertical bore 12 and adapted to be installed upon a wellhead, which may be at an underwater location, in the customary manner. A pipe P extending through the bore 12 may be a string of drill pipe extending from the water level into the well bore and having a bit on its lower end for drilling the well.

For this purpose, drilling mud would ordinarily be circulated downwardly th rough the pipe, out the bit, and up the annulus between the pipe and bore 12.

Rams RR and RL are mounted within chambers 13 in the housing intersecting opposite sides ofthe bore 12 for movement between outer positions to open the bore (see the left-hand ram LR) and inner positions to engage one another and aboutthe pipe P (see the right-hand ram RR)to close the bore. One ram normally moves inwardly before the other to a position which is limited either by engagement of the ram with a pipe in the bore, as in Fig. 1, orwith a stop, or by engagement of parts ofthe operating system to be described. When both rams are moved to closed position, they seal with respectto one another and the housing chambers to contain pressure within the well, as will be described.

As shown, each ram has a vertical recess in its front faceforfitting aboutthe pipe Pwhen moved into engagement therewith, as well as a packing 14 extending laterally across its frontface, so that when both rams are moved to closed position, the packings sealably engage about the pipe as well as with one another on both sides of the pipe. As well known in the art, additional packing along the sides of each ram connect the ram face packing with a top packing 15so as to form a continuous seal with one another and the chambers 13 when the rams are closed. As well known in the art, however, the rams may instead be "blind" rams for closing the bore when empty.

As also shown in Fig. 1, each ram has a groove 16 formed in its lower side to connect the bore 12 with the chamber 13 behind it, whereby well fluid is able to act over portions ofthe outer ends ofthe closed rams to supplement the force of the operating system in maintaining them in tight sealing engagementwith one another and the pipe P. As also shown in the aforementioned copending patent application, each ram is moved between opened and closed positions by means of a control rod 18 axially reciprocable within a cylinder C in the housing outwardly ofthe ram chamber.More particularly, each ram has a passageway 17 formed therein which connectsthechamber 13 behind the ram with its top side above the packing 14,andtheinnerendofthecontrol rodhasalost motion connection with the rod which enables a valve head 19 thereon to open and close the outer end of the passageway. Thus, as the ram is moved inwardly with the rod to its closed position, a surface on the inner end ofthevalve seatengages a seat on the backofthe ram surrounding the passageway so as to close the passageway, and thus enable well fluid to supplement the force of the operating system to maintain the ram closed.However, as the control rod is withdrawn or moved outwardlyto return the rams to open position, so as to vent well fluid within the chamber behind the closed ram to the annulus of the bore 12abovethe closed rams.

The operating system for each ram includes piston means 24 carried by the control rod and axially reciprocable within the cylinder C in order to recipro catethe rod and thus move the rams between closed and open positions in response to the supply and exhaust of operating fluid to and from opposite sides ofthe piston means. Fluid may be supplied through a port P1 connecting with the outer end of the cylinder and exhausted through a port P2 connecting with its inner end in order to close the ram, or, alternatively, supplied through the inner port and exhausted through the outer port to open the ram.

More particularly, and again as fully described in the aforementioned copending application, the outer end of each rod 18 extends sealablythrough the outer end of the cylinder and into a balance chamber 21 in the housing outwardly ofthe cylinder C, and a hole 20 therethrough connects the inner end of the rod within seating area ofthe valve head 19 with the balance chamber 21. Thus, as shown, the inner end of each rod extends through a seal ring 22 in an opening in the housing connecting each chamber 13 with cylinder C ofthe operating system, and the outer end ofthe rod extends through a seal ring 22A in an opening therein connecting the cylinder with the balance chamber 21.

Assuming that the cross-sectional areas of the control rod extending through the seal rings 22 and 22A are substantially equal, the forces due to fluid pressure acting on opposite ends ofthe rods are at all times substantially balanced.

As previously mentioned, piston means 24 includes an annular piston 30 about rod 18 having an inner seal ring 30Asealablyslidable along the rod and an outer seal ring 30B sealably slidable within the inner diameter of the cylinder. As shown, and as also previously described, the inner diameter ofthe piston 30, and thus the outer diameter ofthe intermediate part of rod over which the piston is sealably slidable, is largerthan the outer diameter ofthe inner and outer ends ofthe rod. Consequently, the piston means also includes a piston area on the rod within the annular piston which is responsive to control fluid to provide a force for moving the rod axially.

Thepreventerhousing includesa main body 11Ain which bore 12 and the inner ends of chambers 13 are formed on opposite sides of the bore 12, and bonnets 11 B in which the outer ends of the chambers, cylinders Cand chambers 21 areformed.The bonnets are hinged or otherwise mounted on the main body asto permitthem to be moved between the closed positions shown in Fig. and open positions which enable the rams to be removed and replaced with respectto the control rods.

A conical shoulder 25 formed in the cylinder adjacent its inner end extends outwardly from the inner diameter of the cylinder in a direction toward its inner end. Aseries of circumferentially spaced-apart locking elements 26 are carried about the rod for radial expansion and contraction between the inner positions shown in Fig. 2, in which they are free to move within the inner diameter of the cylinder, and outer positions, such as shown in each of Figs. 3 and 4, in which a conical surface 27 about each locking element, and substantially complementaryto the cylindershoulder25, is disposed radially outwardly of the inner diameter of the cylinderforsliding along such shoulder into and outof locking position. More particularly, the locking elements are carried about the rod intermediate an innerannularstop 28 about the rod and the piston 30, and the piston 30 is in turn axially reciprocable along the rod intermediate the locking elements and an outer annular stop 31 about the rod.

A locking ring 29 extends inwardlyfrom the piston 30fortransmitting the force due to operating fluid supplied to the outer side ofthe piston to the locking elements, and thus to the stop 28, for moving the rod with the locking elements inwardly from the position of Fig. 2. As the locking elements 26 reach positions opposite shoulder 25, the locking ring will begin to wedgethem outwardly and cause theirouter surfaces 27 to slide along the shoulder as the rod continues to move inwardly with the locking elements.However, when operating fluid is instead supplied to the inner side of piston 30, ring 29 will be moved with the piston 30 outwardly along the rod to release the locking elements for radial inward movement, and the piston engages outer stop 28 to transmit the force due to such fluid to the rod for moving the rod with the piston toward its outer position as the surfaces 27 ofthe locking elements are wedged between inner stop 28 and locking surface 25 backto their inner positions. Of course, in both cases -- i.e.,whether the rod is being moved inwardly or outwardly-the force due to operating fluid acting over piston 30 is supplemented bytheforce due to such fluid acting overthe piston area ofthe rod.

With the ram withdrawn to open position, and thus with the control rod 18 in its outer position, as shown in Fig. 2, piston 30 is engaged with outer stop 31, and the locking elements 26 are retracted radially inwardly to positions close aboutthe rod, and thus for movement axially within the inner diameter ofthe cylinder. Atthis time, the inner ends 34A ofthe locking elements are adjacent a substantially complementary surface 34 on the outer side of stop 28, nd a conical surface 32 on the inner end ofthe lock g ring is adjacent substantially complementary surfaces 33 on the inner corners ofthe outer ends ofthe locking elements 26.Thus, as the piston 30 begins to move inwardly from the position shown in Fig. 2, the inwardly directed force due to operating fluid acting over its outer side to the piston is transmitted to the stop and thus the rod through the surfaces 32 and 33.

As shown, these surfaces form a relatively large angle with respect to the axis ofthe rod so as to transmit a relatively large axial component, but a relatively small radial component of such force to the locking elements as they move axially inwardly within the inner diameter ofthe cylinder. Thus, although the locking elements may be wedged radially outwardly into engagementwith the inner diameter ofthe cylinderto some extent, there will bea minimum of drag between them and the inner diameter ofthe cylinder, and thus a minimum of resistanceto inward movement of the rod.

As the locking elements are moved into the position shown in Fig. to dispose their locking surfaces 27 opposite the shoulder 25 on the inner end ofthe cyiinder, the relatively small radial component of force will movethem radially outwardly and thus cause them to begin to slide along the shoulder 25.

Preferably, and asshown,the outerside 34 and the complementarysurfaces 34Aon the inner ends ofthe locking elements are conical and extend inwardly and outwardly with respect to the axis ofthe rod at a relatively steep angle, so as to facilitate sliding ofthe locking elements radially outwardly into locking position as well as radially inwardly out of locking position.

Asthelocking elements move radiallyoutwardlyan initial distance, the first surfaces 33 thereon will move out ofengagementwith the surface 32 on the inner end ofthe sleeve 29, and thus permit a surface 35 on the inside of each locking elementto move over and about a substantially complementary second surface 35A on the outside ofthe sleeve 29, More particularly, these second surfaces intersectsurfaces 33 atthe corners ofthe locking elements and also extend outwardly and rearwardly with respect to the rod axis so asto continue to wedge the locking elements radiallyoutwardlyand axiallyinwardlyforsliding along the locking shoulder 25 as rod 2 8 continues to move inwardly. However, theanglewhich these second surfaces 35 and 35Aform with respect to the rod axis is relatively small, so that, at this stage, the locking elements are moved radially outwardly with a relatively large radial component of the force due to operating fluid acting on the outer side of the piston 30. As previously described, the extent to which the locking elements are moved radially outwardly and inwardly, as their locking surfaces 27 slide along locking shoulder 25 and the conical surfaces on their inner ends slide along the conical surface 34 on the inner side of the stop 28, is determined by the extentto which the rod must move inwardly in closing its ram.

As previously described, when the rams have been so moved to closed position, they are locked against return movement bythe locking elements, so that operating fluid may be exhausted from the outer side ofthe piston 30, thereby relieving the overall operating system as long asthe ramsareto be maintained closed. Forthis purpose,the blocking surface of ring 29 preferably comprises a series of circumferentially spaced-apart fingers 29Awhich, upon sliding oftheir outer surfaces 35A within the surfaces 35 on the inside ofthe locking elements, are pressed tightly into frictional engagement with the rod.Thus, there is frictional resistance to outward movement ofthe rod not only along the surfaces 35 and 35A, but also along theinnerdiametersofthefingersandthe rod.

The foregoing description will of course enable the angles which the various surfaces of the locking elements form with respect to one anotherto be selected by one skilled in the art. Thus, in orderto ensure the locking elements' release, the angle formed between surfaces 27 and surfaces 34A must at least substantially equal the sum oftheir maximum anticipated respective friction angles.Also, in order to ensure maintaining a reliable lock during the time the fingers occupy a position blocking the locking ele ments,the angle formed between surfaces 35Aand the axis ofthe rod must not exceed the sum ofthe minimumanticipatedfriction angle between the fingers and the locking elements and the minimum anticipated friction angle between the fingers and the rod. Byway of example, however, the surfaces 35 may form an angle of about 10" and the surfaces 34A an angle of about 60" with respect to the rod axis.Thus, with locking surfaces 27 extending atan angle of about 150 with respect to such axis, they will form with surfaces 34A an included angle of about450 for wedging the locking elementsfrom their outer to their inner positions.

The locking elements are guided for limited radial expansion with respect to the rod by means of bolts 36 threadedly connected tothe rod and extending through holes in the locking elements. The bolts have enlarged heads on their outer ends received in counterbores on the outer ends of holes to retain the locking elements on the rods. In orderto permitthe locking ring 29 to move to its innermost position within the locking elements 26, the splits between their fingers are held in alignment with the bolts by means of pins 37 mounted within the rod intermediate adjacentfingers. Obviously, a single such pin may be sufficient.

When the rams are to be moved to open position, operating fluid is supplied to the inner sides of the piston 30 and exhausted from the outer side thereof to move the piston outwardly along the rod until the surface 35A ofthe ring 29 are withdrawn from within the surfaces 35 on the inside ofthe locking elements.

As the piston continues to move outwardly, its outer end engages the innerface of outer stop 31 to transmit a force to the rod which supplements that acting on the piston area ofthe rod to move the rod outwardly with the piston, and thus cause the locking surfaces 27 to slide along the locking shoulder 25 of the cylinder back into the retracted positions shown in Fig. 2. That is, upon sliding ofthesurfaces35Aofthe ring 29from within the locking elements,the locking elements are free to move radially inwardly and thus to be fully withdrawn into a position in which they are free to move axially outwardly within the cylinder C, as surfaces 33 slide radially inwardly along surface 32 as the rod continues to be moved outwardly.This outward movement will continue of course until the stop 30 moves into engagementwith the outer end of the cylinder, atwhich time,the ramsarewithdrawn into the open positions shown in Fig. 1.

As shown, a coil spring 38 is disposed about the outer stop and within an annular recess on the outer side of piston 24so asto yieldably urge the piston in an inward direction with respect to the stop. This may be desirable if there is some tendency for the piston to stickto the rod, ortothe inner diameter ofthe cylinder, orto otherwise not be free to move axially inwardly in orderto move the rod inwardly and the locking elements into locking position.

From the foregoing itwill be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherentto the apparatus.

Itwill be understood that certain features and subcombinationsareofutilityand may be employed without reference to otherfeatures and subcombinations. This is contemplated by and is within the scope

Claims (10)

ofthe claims. As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. CLAIMS

1. An axially reciprocating,fluid-operated actuator, comprising a cylinder with a conical locking shoulder extending radially outwardly from its inner diameter and in an axial direction toward the inner end ofthe cylinder, a rod extending sealablythrough the inner end ofthecylinderforaxial reciprocation between inner and outer positions, piston means axially reciprocable within the cylinder, means by which operating fluid may be supplied to or exhausted from opposite sides of the piston means, locking elements carried about the rod for radial expansion and contraction between inner positions in which they are free to move within the inner diameter ofthe cylinder and outer positions in which conical surfaces on their outer sides which are substantially complementaryto the conical shoulder of the cylinder project outwardly from said diameter, means for transmitting to the locking elements, and thus to the rod, a relatively large axial component of the axially inwardly directed force due to operating fluid supplied to the outer side ofthe piston means in order to move the rod axially inwardly with the locking elements until the conical surfaces ofthe locking elements are radially opposite the cylinder shoulder, and then transmitting to the locking elements, and thus to the rod, a relative large radial component of such force in orderto causethe locking elements to move radially outwardlywith respectto the rod and the conical surfacesthereofto slide radially outwardly along the cylindershoulderasthe rod continues to move axially inwardly with the locking elements to its inner position, said rod being locked against return movementfrom its inner to its outer position, upon exhaustion of operating fluid from said outer side of the piston means, and means fortransmitting to the rod the axially outwardly directed force due to the supply of operating fluid to the inner side of said piston means and to cause the locking elements to slide radially inwardly along the shoulder and then axially outwardly with the rod as the rod is returned to its outer position.

2. An actuatorofthe character defined in claim 1, wherein the piston means is an annular piston about the rod, the locking elements are carried about the rod on the inner side ofthe piston, there is a stop on the rod on the inner side ofthe locking elements, a locking ring on the piston, and means on the locking ring and the locking elementsfortransmitting to the locking elements, and thus to the rod, said relatively large axial and radial components ofthe axially inwardly directedforcedueto operating fluid, and there is another stop on the rod outwardly ofthe piston for transmittingtothe rod said axially outwardly directed force.

3. An actuatorofthe character defined in claim 2, wherein the locking ring on the piston having a first surface thereabout which is engageable with substantially complementaryfirst surfaces on the locking elements to move the locking elements against the inner stop on the rod and thereby move the rod axially inwardly with the locking elements, and which is then slidable over said complementary first surfaces to wedge the locking elements radially outwardly with respectto the rod for sliding along the cylinder shoulder as the rod and locking elements move further axially inwardly, in response to the supply of operating fluid to the outer side ofthe piston, and a second surface thereaboutwhich is slidable over substantially complementary second surfaces on the locking elements, upon sliding of said first surface out ofengagementwith said first surfaces of the locking elements, so as to continue to wedge the locking elements radially outwardlyfor sliding further along said cylinder shoulder as the rod and locking elements continue to move axially inwardly and until the rod reaches its inner position, in response to the continued supply of operating fluid to the outer side ofthe piston, said first surfaces forming a relatively large angle with respectto the rod axis, and said second surfaces forming a relatively small angle with respect thereto, and said rod being locked against return movement from its inner to its outer position, upon exhaustion of operating fluid from said outer side of the piston, said second surface ofthe locking ring sliding out of engagement with the second surfaces of the locking elements, as the locking ring is moved axially outwardly in response to the supply of operating fluid to the inner side of said piston, wherebythe locking elements will be released for sliding radially inwardly along the cylinder shoulder and axially outwardly with the rod and the piston will engage with said outer stop on the rod for moving the rod, and thus the locking elements, axially outwardly with the piston.

4. An actuator ofthe character defined in any one of claims 1,2 or 3, wherein the outer diameter of said piston is sealablyslidable along the inner diameter of the cylinder.

5. An actuator of the character defined in claim 3, wherein the inner ends ofthe locking F-'ements have conical surfaces which extend radial > outwardly in a direction toward the innerend ofthe cylinderfor sliding along a substantially complementary conical surface of the inner stop of the rod, during radial expansion and contraction into and out of locking position.

6. An actuatorofthe character defined in claim 3, wherein the locking ring comprises circumferentially spaced-apartfingers which are pressed tightly about the rod as the second surface ofthe ring moves into sliding engagementwith the second surfaces of the locking elements.

7. An actuator ofthe character defined in claim 6, including bolts connecting the locking elements to the rod for guided radial movement with respect thereto, and pins on the rod extending betweenthefingersso as to axially align the spaces between them with the bolts for movement thereover as the locking ring moves within the locking elements.

8. An actuatorofthe character defined in claims 1, 2 or 3, wherein the rod is hollow and extends sealably through the outer end ofthe cylinder into a chamber outwardly of the cylinder so as to be substantially pressure balanced.

9. As in any one of the foregoing claims, wherein the actuator is connected to a valve member movable within a body of valve apparatus between positions opening and closing aflowwaythroughthebody.

10. As in claim 9, wherein the body is the housing of a blowout preventer and the housing has a bore therethrough and chambers therein intersecting opposite sides ofthe bore, and there is an actuator for moving a ram within each chamber between an outer position to open the bore and an inner position for engaging the other ram to close the bore.