Title:
Variable inside diameter blowout preventer
United States Patent 3897039


Abstract:
A variable inside diameter blowout preventer, wherein each of a pair of blowout preventer rams has anti-extrusion means, preferably metallic, for preventing any substantial longitudinal extrusion of yieldable sealing material such as rubber when the inside diameter of the preventer is reduced to seal with a pipe or other object in a well bore or with the opposite ram, whereby sealing off of the well bore may be accomplished even at high well pressures and with the elimination of one or more of the conventional blowout preventers customarily arranged in a stack at a well head. The blowout preventer also provides a convenient means for hanging off pipe on the rams during certain conditions and well operations, and it further makes possible high pressure stripping of tubing or well pipe as it is withdrawn from a well. In the preferred embodiment, upper and lower anti-extrusion means are provided for each ram, each of which is independently operable for effecting a seal with a tubing or other object that has different diameters or external dimensions in the length thereof which is sealingly engaged by the rams.



Inventors:
LE ROUAX ROBERT K
Application Number:
05/412677
Publication Date:
07/29/1975
Filing Date:
11/05/1973
Assignee:
HYDRIL COMPANY
Primary Class:
Other Classes:
277/324
International Classes:
E21B33/06; (IPC1-7): E21B33/06
Field of Search:
251/1,212 277
View Patent Images:
US Patent References:
3572628BLOWOUT PREVENTER1971-03-30Jones
3416767Blowout preventer1968-12-17Blagg
3038542Tester apparatus for oil wells or the like1962-06-12Loomis
2846178Conical-type blowout preventer1958-08-05Minor
2780294Packer assembly1957-02-05Loomis
2609836Control head and blow-out preventer1952-09-09Knox
2368928Packing device1945-02-06King
2246709Blowout preventer1941-06-24Allen
2218093Blowout preventer1940-10-15Penick et al.
2035925Casing head equipment1936-03-31Seamark
0778591N/A1904-12-27



Primary Examiner:
Schwadron, Martin P.
Assistant Examiner:
Gerard, Richard
Attorney, Agent or Firm:
Pravel & Wilson
Parent Case Data:


CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No. 190,972 filed Oct. 20, 1971 copending herewith and now abandoned.
Claims:
I claim

1. A blowout preventer ram, comprising:

2. The structure set forth in claim 1, including:

3. The structure set forth in claim 1, including:

4. The structure set forth in claim 1, wherein said upper anti-extrusion means includes:

5. The structure set forth in claim 4, wherein said lower anti-extrusion means includes:

6. The structure set forth in claim 1, wherein:

7. The structure set forth in claim 4, wherein said upper anti-extrusion means includes:

8. The structure set forth in claim 5, wherein said lower anti-extrusion means includes:

9. The structure set forth in claim 7, including:

10. The structure set forth in claim 8, including;

11. The structure set forth in claim 4, including:

12. The structure set forth in claim 5, including:

13. The structure set forth in claim 5, wherein:

14. The structure set forth in claim 13, including an upper wedge shaped guide member disposed adjacent each of said upper secondary segments in said upper anti-extrusion means; and

15. The structure set forth in claim 4, wherein said sealing means comprises:

16. In a blowout preventer having a pair of blowout preventer rams, the improvement residing in each ram, wherein each ram includes:

17. The structure set forth in claim 16, wherein said anti-extrusion means includes means for substantially preventing longitudinal extrusion of said sealing means in both upward and downward longitudinal directions.

18. The structure set forth in claim 16, wherein said blowout preventer has a housing with a recess for receiving each of said rams, and including:

19. The structure set forth in claim 18, wherein said housing includes:

20. The structure set forth in claim 19, including:

Description:
BACKGROUND OF THE INVENTION

The field of this invention is blowout preventers for oil wells and the like.

Annular blowout preventers made by the Hydril Company an example of which is shown on page 2745 of the "Composite Catalog" for 1970-71, have been in extensive commercial use for a number of years. Such blowout preventers provide a fully-open bore therethrough so that drill bits, reamers, casing hangers and other large diameter tools can freely pass therethrough, but when actuated to the closed position, such preventers are forced inwardly to reduce its bore and automatically adjust its size and shape in sealing contact with whatever object happens to then be in the bore of the preventer, thereby closing off the annular space around such object to prevent a blowout of the well pressure from below. If no tool is in the well, the bore of the preventer can be fully closed to prevent a blowout.

Although such Hydril blowout preventers are very satisfactory for relatively low well pressures in the range of from about 2,000 p.s.i. to 5,000 p.s.i., it is generally desirable to use a ram type blowout preventer above such pressures, and above 10,000 p.s.i. well pressure, it is generally considered essential to use a ram type blowout preventer. Ram type preventers heretofore known have had to be stacked, usually in a vertical group of at least three, to seal off a well bore from the fully closed bore position to relatively large diameter pipe which might be in the bore when it is necessary to close off the bore. The three blowout preventers have been required because one had to be a "blind" ram for fully closing the bore by the rams itself and the other two had to specifically fit the outside diameter of at least two pipe strings or tool sizes used in the well. If the inside diameter of one of the blowout preventers did not conform to the outside diameter of the pipe or tool in the well, then there was the danger of the well blowing out, unless of course the Hydrill preventer could seal around the object and hold the amount of well pressure involved.

SUMMARY OF THE INVENTION

The present invention relates to a blowout preventer of the ram type which has the advantages of both the ram type and the Hydril annular blowout preventer in providing a variable inside diameter as in the Hydril preventer and at the same time providing for sealing the well bore even at the high pressures normally handled by ram type preventers. With the blowout preventer of this invention, the number of blowout preventers in a stack may normally be reduced by at least one, and by more than that in some instances.

The blowout preventer of the present invention has anti-extrusion means for preventing longitudinal extrusion of the resilient sealing material of the preventer over a variable range of inside diameters. In the preferred embodiment, upper and lower anti-extrusion means are provided, each of which is independently movable to effect a seal with a tubing or other object that has different diameters or external dimensions in the length thereof which is sealingly engaged by the rams.

Further, the present invention provides a convenient means for hanging off pipe on the rams during certain conditions and well operations, and it additionally makes possible high pressure stripping of tubing or well pipe as it is withdrawn from a well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view, partly in elevation, illustrating the blowout preventer of this invention, and in particular the blowout preventer ram construction of this invention;

FIG. 2 is a partial plan view of the blowout preventer of FIG. 1, illustrating the rams in the open position so that the full normal bore through the housing of the blowout preventer is open;

FIG. 3 is a view taken on line 3--3 of FIG. 1 to illustrate the rams in the inner stop position prior to sealing with the pipe or other object in the bore of the preventer;

FIG. 4 is view similar to FIG. 3, but illustrating the rams in the sealing position with respect to the pipe or other object extending through the bore of the preventer;

FIG. 4A is a view illustrating the sealing action which occurs with a Kelly or other object having a cross-sectional area which is not circular;

FIG. 5A is a plan view, partly in section and with certain parts removed for purposes of illustration, showing a ram of this invention in detail;

FIG. 5B is a view of a portion of the ram of FIG. 5B, or the ram opposite thereto, but showing the yieldable sealing member and the non-extrusion elements in the innermost position for that particular form of the invention;

FIG. 6 is a view taken on line 6--6 to illustrate details of the end mounting of the ram of FIG. 5B;

FIG. 7 is a view taken on line 7--7 to further illustrate details of the ram of this invention;

FIG. 8 is a vertical sectional view taken on line 8--8 of FIG. 5A and it further illustrates details of the ram;

FIG. 9 is a sectional view taken on line 9-9 of FIG. 1, illustrating one of the rams of the preventer in the stop position with the ram carrier at its innermost point of travel but with the rubber or other yieldable sealing means still undistorted with the non-extrusion segments still in their retracted position; and

FIG. 10 is a view corresponding to FIG. 9, but showing the rubber or sealing material after it has been urged inwardly and distorted into sealing engagement with the external surface of a pipe disposed in the bore of the preventer, and also illustrating the position of adjacent segments for the anti-extrusion means with the sealing means of the ram.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawing, the letter B refers generally to the blowout preventer of this invention which is formed with a pair of rams R of this invention. The rams R are disposed in a conventional blowout preventer body or housing 10 having a longitudinal bore 10a therethrough, through which well pipe P or other objects such as well tools may pass in the normal operations conducted with the blowout preventer B in the fully open position (FIG. 2). Each of the rams R is suitably connected to a conventional power means generally indicated by the letter M (FIG. 1), the details of which will be explained hereinafter.

Briefly, the construction of each ram B provides for a sealing with the opposite ram R and with an object such as the well pipe P which is disposed in the bore of the preventer B. By reason of the particular construction of the present invention, extrusion of the yieldable sealing means is prevented throughout a variable inside diameter range of sealing positions, whereby the benefits of both the ram type and the annular type of preventer are made possible with the preventer of this invention.

Although the blowout preventer housing 10 of this invention may be constructed in any manner suitable for receiving each of the rams R, as best seen in FIG. 1, the housing 10 has a lateral opening or recess 10b for each of the rams R. The ram housing 10 is preferably made with an upper annular flange 10c (FIGS. 1 and 2) having bolt openings 10d therethrough and a lower flange 10e having similar openings therethrough so that such housing 10 may be connected in a stack of blowout preventers or in the string of well casing or pipe in the conventional manner. A seal ring groove 10f is provided in the flange 10c and a similar seal ring groove 10g is provided in the flange 10e for receiving seal rings which serve to seal with the adjacent well casing or other blowout preventer to which the housing 10 is connected, as will be well understood.

A conventional head or bonnet 12 is connected to each side of the body or housing 10, and each of such heads or bonnets has a recess 12a (one of which is shown in FIG. 1), and each of which is aligned with the lateral openings 10b in the housing or body 10 so as to form a continuation thereof. The rams R are received in their respective recesses 12a when they are in the retracted position. A piston rod 14 extends through a suitable seal in an opening 12b of each head or bonnet 12. Each piston rod 14 extends to a piston 16 of conventional construction which is disposed in a cylinder 17 having an end cap or closure 18 therewith in any known manner. For purposes of illustration, a fluid inlet line 18a is shown for introducing air, hydraulic fluid or other operating fluid into the cylinder 17 for moving the piston 16 inwardly towards the center of the bore 10a. Another fluid line 12c is provided for introducing air, hydraulic fluid or other fluid into the cylinder 17 for moving the piston 16 outwardly (to the right as viewed, in FIG. 1) to retract the ram R connected therewith through the piston rod 14. It will be understood that various systems for the power means M may be employed and the invention is not limited to the specific form illustrated in FIG. 1. It should also be understood that a power means is provided for the left-hand ram R as viewed in FIG. 1, in the same manner as the power means illustrated for the right-hand ram R in FIG. 1.

For ease of description, the details of only one of the rams R will be described hereinafter, at least for the most part, and only when it is necessary to show the interaction of the two rams will the other ram be specifically identified. However, it will be understood that the two rams R are preferably made in the same manner, but they are provided with interfitting portions as will be more evident hereinafter so that they fit together and cooperate with each other in the sealing action.

Thus, each ram R has a ram carrier 20 which is connected to the piston rod or stem 14, preferably in the conventional releasable manner, utilizing a button 14a on the rod 14 fitting into a suitable slot in the ram carrier 20. In the preferred form of the invention, the ram carrier 20 is formed of steel or other relatively rigid material and is preferably substantially semi-cylindrical in cross-sectional shape (FIGS. 9 and 10). The ram carrier 20 is provided with an internal recess or surface 20a which is likewise substantially semi-cylindrical in crosssectional shape and which is adapted to receive a seal element 21, preferably having an external convex surface 21a which substantially conforms with the internal surface or recess 20a (FIGS. 9 and 10). The seal member 21 is formed of rubber or other yieldable material and it has therewith side anti-extrusion plates 22 formed of steel or other metal which are adapted to engage the inside surface of an inwardly extending lip 10h on the housing or body recess 10b. During movement of the carrier 20 from the position of FIG. 9 (stop position) to the sealing position of FIG. 10, there is also a sliding movement between the carrier 20 and the side plates 10h as is evident from a comparison of FIGS. 9 and 10 and as will be more evident hereinafter.

The seal member 21 is confined at its upper end between the ram carrier 20 and an upper ram confining and alignment plate 24 (FIG. 1) which plate 24 is secured to the carrier 20 by one or more cap screws 26 or other suitable securing means. It is to be noted that the upper surface 20b of the ram carrier 20 engages and slides relative to the upper surface of the recess 10b and the recess 12a. Similarly, the upper surface 21b of the seal member 21 engages and seals with the wall or upper surface of recess 10b. The configuration of the upper alignment plate 24 can be seen in FIGS. 1 and 3 and it includes an alignment finger 24a which is adapted to interfit with a corresponding alignment recess 24b on the opposite ram R when the rams R are in their innermost stop position, as will be more evident hereinafter.

The ram R also has a lower ram confining and alignment plate 25 which preferably extends for the full depth of the ram and which is provided with an alignment finger 25a which fits into an alignment recess 25b on the opposite alignment plate 25 of the other ram R in the same manner as illustrated with respect to the upper alignment plate 24. The lower alignment plate 25 is engaged by the ram carrier 20 by means of a shoulder 25c or other suitable engaging means for enabling the carrier 20 to retract the plate 25 outwardly therewith, but permitting inward movement of the carrier 20 relative to the plate 25 after the inward movement of the plate 25 is stopped by engagement with the opposite plate 25.

It is to be noted that the vertical or longitudinal area between the upper alignment plate 24 and the lower alignment 25, and inwardly of the seal member 21, forms a pocket or recess which is generally semi-cylindrical for receiving the parts of the ram R of this invention which are normally the primary replaceable parts. Such parts may be preassembled and inserted initially into position, as will be more evident hereinafter. Also, replacement assemblies including such parts may be used when necessary.

Such replaceable assembly of the ram R includes a yieldable sealing element or member 30 formed of rubber or other similar yieldable material. An upper anti-extrusion means 31 is provided with the seal member 30, and a lower anti-extrusion means 32 is also provided with the seal member 30, as will be more fully explained. The seal member 30 is actually a part of the entire sealing means for providing sealing engagement with the pipe P, or other object in the well bore or with the opposite ram R. Such seal member 30 is distorted in coaction with the seal member 21 and therefore the two seal members 21 and 30 together form the sealing means, as will be more fully explained.

The upper anti-extrusion means 31 is identical to the lower anti-extrusion means 32 in the preferred form of the invention, except that they are upside down with respect to each other. Therefore, the details of the anti-extrusion means 31 will be hereinafter explained and the same parts will be identified and explained briefly with respect to the anti-extrusion means 32.

The upper anti-extrusion means 31 includes a plurality of primary segments 35 formed of metal or other similar relatively rigid material which are secured to the upper part of the rubber or other yieldable material of the sealing member 30. Preferably, such primary segments 35 are embedded and are molded into the rubber or other yeidable material of the sealing member 30. The sealing member 30 is preferably formed with an inner surface 30a which is generally semi-cylindrical in shape although it is also prferably dished out as best seen in FIG. 1. Such dished out surface 30a is merely illustrative, as will be more fully explained. The primary segments 35 are arranged in a generally semi-circular manner as best seen in FIG. 9 and they are positioned so that their inner ends 35a are arranged in a semi-cylindrical manner of alignment with the semi-cylindrical surface 30a therebelow. The radius of such semi-cylindrical surface which is thus formed may be varied, depending upon a particular range of well pipe or objects which are to be sealed, as will be more evident hereinafter. The inner surface 35a of each of the primary segments 35 is adapted to engage the pipe or other object P when the yieldable material of the seal member 30 has been moved into sealing position so as to prevent upward longitudinal extrusion of the yieldable material (FIG. 10). Since the primary segments 35 are secured to and are preferably molded with the seal member 30, they move radially inwardly and outwardly as the seal member 30 is urged or distorted inwardly and outwardly as will be more fully explained.

Although the primary segments 35 may have various configurations, the preferred configuration is shown in detail in FIG. 8 and it includes a plurality of grooves 35b which facilitate the embedding and holding action of each of the segments 35 in the rubber or other yieldable material of the seal member 30. The outer portion of each segment 35 is formed with an enlargement 35c having a key-receiving pocket 35d formed therein for receiving one leg of a generally T-shaped key 36 (FIGS. 5A and 8). Each primary segment 35 is also formed with a threaded opening 35e for receiving a retaining screw or bolt 37 having an enlarged head 37a, the purpose of which will be explained.

The anit-extrusion means 31 further includes a plurality of guide members 38 which are generally coincidental with the primary segments 35 therebelow, but of a slightly smaller size so as to receive therebetween secondary segments 40 in overlapping relationship with the edges of the adjacent primary segments 35. For the purposes of illustration, parts of the segments 40 and the guide members 38 have been removed in FIG. 5A. It is to be noted that the vertical sides 40a of each of the secondary segments 40 extend beyond the side edges 35f of the adjacent primary segments 35, at all times, and as the segments 35 and 40 move from the retracted position (FIG. 5A) to the sealing position (FIG. 5B), the overlap of the secondary segments 40 with the adjacent edges of the primary segments 35 increases.

A generally semi-circular or semi-cylindrical upper retainer plate 41 is disposed above the upper guide wedges 38 and the upper secondary segments 40. Such upper retainer plate 41 is preferably formed of steel or other metal and its shape is substantially coincidental with the upper alignment plate 24, at least at its inner semi-cylindrical surface 41a which is likewise generally coincidental with the alignment of the inner edges 35a of the primary segments 35. The ends 41b of each upper retainer plate 41 are adapted to contact each other to limit the travel of the rams R inwardly with respect to each other, which occurs when the rams reach the position essentially shown in FIGS. 1 and 9, and as will be more fully explained. Thus, the two upper retainer plates 41 together form a circular plate when they are in the position in contact with each other. The retainer plate 41 is keyed or is otherwise connected to the alignment plate 24 by suitable key 42 or other connecting means. The guide members 38 are connected to the upper retainer plate 41 by a plurality of dowel pins 43 (FIGS. 5A and 8), and also a plurality of cap screws 44. The dowel pins 43 take substantially all of the forces involved during the movements of the parts of the ram R to and from the sealing position. Because the retainer plate 41 is a unitary member and its movement is stopped when the rams R reach the point at which the plates 41 engage each other, the wedge guide members 38 are likewise moved with the retainer plate 41 until the retainer plate 41 is stopped, and at that time, the wedge members 38 are prevented from further movements inwardly. The primary segments 35 and the secondary segments 40, on the other hand, are free to move inwardly even after the retainer plate 41 and the guide members 38 have been stopped in their inward movement, which results in the yieldable material of the seal member 30 moving inwardly to engage the pipe or other object within the bore of the preventer and with the primary and secondary segments 35 and 40 moving with the yieldable material of the sealing member 30 to prevent longitudinal extrusion of the yieldable material when it is in the sealing engagement with the pipe or other object. During the relative movement of the secondary segments 40 with respect to the wedge members 38, the sides 40a of each secondary segment 40 engage the sides 38a of each wedge member 38 so that the radial inward movement of the secondary segments 40 is assured. The rubber or other yieldable material of the seal member 30 extends upwardly and outwardly behind each of the secondary segments 40 so as to urge them inwardly along with the primary segments 35. To be sure that the upper secondary segments 40 retract with the seal member 30 as it is moved from the sealing position to the retracted position, the keys 36 connect the primary segments 35 to the secondary segments 40. As previously explained, each key 36 is substantially T-shaped with its vertical portion 36a extending upwardly into a suitable slot 40b (FIG. 8) in the secondary segment 40 thereaboove. The lateral legs 36b of each key 36 extends into the slots 35d of the adjacent primary segments 35 (FIGS. 5A and 8).

The retainer screw 37 which are threaded into the primary segments 35 extend upwardly into slots 38b having a shoulder 38c over which the head 37a extends. Such slidable connection between each primary segment 35 and its wedge member 38 thereabove serves to interconnect the primary segments 35 to the wedge members 38 and thus to the retainer plate 41 so that in the event damage occurs in the well to the rubber or other yieldable material of the seal member 30, the segments 35 will not fall into the well. Secondarily, there is some guiding action provided by the cap screws 37 moving in the slots 38b as the primary segments 35 move radially relative to the guide members 38.

It should be noted that the inner curved surface 35a of each of the primary segments 35 has a radius which would perfectly engage only one external radius of a pipe P disposed in the bore of the preventer. To provide some variability with respect to that contact, the inner surfaces 35a of the segments 35 may be coated with Teflon or other yieldable material so that they can more accurately conform to the external surface of pipes P of different diameters. However, in the normal operations, the variations in such surfaces is not sufficient to be concerned about so that there is essentially a steel to steel contact between the segments 35 and the external surface of the pipe P when the rams R are in the sealing position with the yieldable material of the seal member 30 in sealing engagement with the external surface of the pipe P.

Referring now in particular to FIGS. 5A, 5B, 6 and 7, the specific mounting for the ends of the assemblies for each ram R are illustrated in the preferred form of this invention. Thus, at each of the generally semi-cylindrical or semi-circular ends, a half width secondary segment 40' is disposed in sliding engagement with the adjacent wedge member 38. The end secondary segment 40' has a slot 40'a through which extends a retaining screw 45 which is threaded or is otherwise connected to the adjacent guide member 38(FIG. 5A). Also, the end key 36' (FIG. 7) is only a half key, having only one of the legs 36b and it is secured to the end secondary segment 40' by an additional pin 46.

The lower anti-extrusion means 32 is not illustrated in detail since the parts thereof are preferably identical to those described heretofore in connection with the upper anti-extrusion means 31, except that they are upside down with respect to each other. Briefly, as seen in FIG. 1, the lower anti-extrusion means 32 has its parts identified with the same letters and numerals as the upper anti-extrusion means 31, except that the prefix "1" is placed in front of the numbers for the lower anti-extrusion means 32. Thus, the same general arrangement for the lower primary segments 135 is provided as is provided for the upper primary segments 35, and they are interconnected with suitable keys 136 to secondary segments 140. A plurality of wedge guide members corresponding to the guide members 38 are provided between the secondary segments 140 and these are connected to the lower retainer plate 141 which corresponds with the upper retainer plate 41. The lower retainer plate 141 is keyed or is otherwise removably connected to the lower alignment plate 25 by keys or pins 142, or other suitable connecting means.

In the operation or use of the apparatus of this invention, each of the rams R is adapted to be retracted to a fully open position, wherein the bore 10a of the blowout preventer body or housing 10 is fully open as illustrated in FIG. 2. This is of course accomplished in a conventional way by moving the piston 16 or other power means outwardly to retract the rams R into the recesses 10b and 12a. The depth of the recesses 12a in the head or bonnet 12 may be deep enough to receive the entire ram R, as will be well understood, so that when the head or bonnet 12 is removed from the preventer body 10, the ram R may be exposed for the replacement or repair of the ram parts. The details of such construction are not illustrated since they form no specific part of this invention, but are to be understood to be useful in connection herewith.

When the blowout preventer is to be used for sealing around the pipe P or with the opposite rams themselves, the power means P for each of the rams R is actuated to move the piston 16 inwardly towards each other to bring the alignment plates 24 and 25 together into the closed or stop position illustrated in FIG. 3. At that time, the retainer plates 41 and 141 of the pair of rams R are also in engagement with each other at their ends so that they form generally cylindrical or circular plates above and below the wedge members 38 and 138.

At the time the rams R thus move to the stop position shown in FIG. 3, the pipe P is confined, but sealing therewith has not actually been accomplished. Continued inward movement of the ram carriers 20 is then effected by continuing the inward movement of the power means such as the pistons 16, which causes a distortion or inward movement of the sealing means, and in particular the seal members 30 and 21 to force the inner surface 30a of each of the ram sealing members 30 into sealing engagement with the external surface of the pipe P.

At the same time, the primary segments 35 and 135 as well as the secondary segments 40 and 140 move radially inwardly until they engage the external surface of the pipe P. When the primary and secondary segments have thus engaged the pipe P, the rubber or other yieldable material of the seal member 30 is confined and is prevented from extruding longitudinally along the length of the pipe P. This makes it possible to hold extremely high pressures above and below the preventer.

In some instances, it may be possible to use only the upper anti-extrusion means 31, to seal against upward extrusion forces from well pressure, but normally both of the anti-extrusion means 31 and 32 are provided with each of the rams R. .

When it is desired to release the seal members 30 from their sealing position, the pistons 16 are retracted and are moved outwardly to relieve the pressure on the seal members 21 and 30. The elasticity of the materials such as rubber of the seal members 21 and 30 cause them to return to their normal undistorted condition (FIG. 1) as the pressure from the power means M is relieved. The retraction of the seal member 30 causes the primary segments 35 to also retract radially to their non-sealing position (FIG. 9). The secondary segments 40 and 140 are forced to retract with the primary segments 35 and 135 because of the interconnections of the keys 36 and 136, respectively, as previously explained.

FIG. 4 illustrates the metal-to-metal contact of the secondary segments 40 with the external surface of the pipe P when the seal member 30 of each of the rams R is in sealing engagement with the external surface of the pipe P. In FIG. 4, the secondary segments 40 have been shown in their extreme innermost position, which is the limit of travel and effective sealing action with the particular ram R illustrated in the drawings. It will be understood that effective sealing action may be accomplished from such innermost position of FIG. 4 to any pipe diameter outwardly to the diameter formed by the 24 surfaces 24c of the upper alignment plates 25 (FIG. 4). Thus, there is a variable inside diameter range for effective sealing with the particular ram construction. The extent of such variation depends upon the particular configuration and the radius of curvature of the inner segments of the anti-extrusion means 31 and 32. In fact, the arrangement of the primary and secondary segments of both of the anti-extrusion means 31 and 32 may be constructed so that the diameter of the opening formed by such segments in their innermost sealing position is small enough so that there is sealing and anti-extrusion protection even when nothing is in the bore of the preventer and the sealing is accomplished by the rams themselves as in the case of "blind" rams.

FIG. 4A illustrates the effectiveness of the anti-extrusion means of this invention when sealing with a kelly K or other object which does not have a cylindrical external surface. The rubber or other yieldable material of the seal members 30 is distorted into sealing engagement with the external surface of the kelly K, and the anti-extrusion segments move into contact at some parts of the external surface of the kelly K, but because of the circular arrangement thereof, they cannot contact fully throughout the external surface of the kelly K. However, the area which is left exposed as seen in FIG. 4A is relatively small and therefore the anti-extrusion means 40 provides support throughout substantially the full area in which the seal elements 30 extend for the sealing action.

FIGS. 9 and 10 illustrate the movement of the upper primary segments 35 from the open or stop position (FIG. 9) to the sealing position (FIG. 10) where the inner edges 35a are in metal to metal contact with the external surface of the pipe P to prevent longitudinal extrusion of the rubber or other sealing material of the seal member 30. It will be understood that the lower primary segments 135 move similarly and effect a metal to metal contact with the pipe P also.

However, it should be noted that the upper segments 35 and 40 may move independently of the lower segments 135 and 140 from the stop position of FIGS. 3 and 9 to the sealing position of FIGS. 4 and 10, so that sealing and metal to metal contact by the segments may be effected at a pipe or object even though the diameter of the object is different in proximity to the upper segments than it is in proximity to the lower segments. For example, if a pipe joint or collar is disposed in the bore of the preventer when it is desired to close off the bore, and with the upper edge of the joint or collar below the upper segments 35 and 40 but above the lower segments 135 and 140, distortion and sealing of the seal member 30 with the pipe and collar is effected, metal to metal contact of the upper segments 35 and 40 with the pipe is effected for preventing upward longitudinal extrusion of the seal member 30, and metal to metal contact of the lower segments 135 and 140 with the collar is effected for preventing downward longitudinal extrusion of the seal member 30.

It will also be understood that the same type of sealing action occurs at any intermediate location or radial position of the segments between the stop position of FIG. 9 and the smallest diameter sealing position of FIG. 10. The secondary segments 40 and 140 prevent extrusion of the sealing material of the seal member 30 beyond the radial gaps between the primary segments 35 and 135, respectively.

It will also be understood that the smallest diameter sealing position of FIG. 10 is merely illustrative and may be varied. If desired to provide a blind ram with the anti-extrusion action of this invention the inner edges of all of the segments would essentially meet at the innermost sealing position so that there would essentially be no central opening.

Instead of the dished out or concave surface 30a, the shape of the surface 30a or other portions of the sealing member 30 may be modified, or recesses or the like in the member 30 may be provided, the purpose of which is to compensate, or partially compensate, for the smaller volume of the space available for the rubber of the member 30 when it is in its sealing position (FIG. 10) as compared to the volume of the space available for such member 30 in its retracted position (FIGS. 1 and 9).

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.