Blowout preventer packing unit with slanted reinforcing inserts

An annular blowout preventer packing unit having a longitudinal axis incorporates metallic inserts having webs that extend both longitudinally and about that axis to define surfaces which have longitudinally facing extents to anchor and resist longitudinal displacement of packer elastomeric material. The webs may typically have upper and lower portions with oppositely directed curvatures, respectively.

BACKGROUND OF THE INVENTION 
This invention relates generally to well blowout preventers, and more 
particularly concerns packer units and inserts used in such equipment. 
U.S. Pat. No. 2,609,836 to Knox describes annular type blowout preventer 
packing units which incorporate like metal inserts spaced about the packer 
central axis, and embedded by an elastomeric, such as rubber, body. Upon 
inward constriction of the unit about a well drill pipe, or upon itself, 
the rubber is squeezed radially inwardly with resistance imposed by the 
inserts to which the rubber is anchored. Well pressure exerted upwardly 
upon the stretched or extended rubber also tends to displace it upwardly, 
so that the material is subjected to strain both radially and vertically. 
This causes fatigue and weakening of the material, particularly after 
repeated closure of the preventer unit, so that each unit is normally 
rated as to its capability to safely sustain or withstand a certain number 
of closures. Efforts have been made to increase this number of closures, 
but the problem of extreme stretching of the rubber has limited the 
success of such efforts. 
SUMMARY OF THE INVENTION 
It is a major object of the invention to provide an improved blowout 
preventer unit characterized in that the capability of the metal inserts 
to effectively anchor the rubber under extreme well pressure is 
substantially enhanced, with the result that stretching of the rubber is 
substantially reduced, and with the result that the life of the preventer 
unit is materially enhanced. 
Basically, the packing unit of the invention employs improved metallic 
inserts having webs that extend both longitudinally and laterally in 
directions about the packer axis, to define surfaces which have 
longitudinally axially facing extent. The webs may be regarded as 
extending generally helically, and such surfaces act effectively to retain 
or anchor the elastomeric material against longitudinal displacement, 
particularly as the packer is closed about well pipe, or to seal off open 
hole, as will be seen; on the other hand, such surfaces do not inhibit 
required radially inward displacement or extrusion of the rubber material 
for well seal off purposes. 
As will be seen, the insert webs typically include upper and lower portions 
with oppositely directed curvatures, and joined at a zone of inflection; 
and the upper portion may be concave in one direction about the packer 
axis, and the lower portion convex in that direction. Further, the insert 
includes upper and lower end plates, the lower plate offset relative to 
the upper in a direction about the packer axis, and the web upper and 
lower portions are elongated toward an inner region associated with the 
unit axis. In one form of the invention, such portions are laterally 
parallel, whereas in another form such portions have lateral skew 
angularity, relative to one another, as will be described. As a result of 
the foregoing, the webs, become nested when the packer is constricted, so 
that the packer material between the webs is more effectively anchored or 
captured, assuming the curvature of the webs themselves. In addition, 
ribbing on the webs enhances this effect. Consequently, the rubber is 
subjected to materially less stretching and strain, particularly in an 
axial direction, and the life of the preventer is enhanced. 
These and other objects and advantages of the invention, as well as the 
details of illustrative embodiments, will be more fully understood from 
the following description and drawings, in which:

DETAILED DESCRIPTION 
Referring to FIGS. 1 and 3, a blowout preventer 10 includes a metallic 
housing 11, the lowermost extent of which is flanged at 12 and bolted at 
13 to well head casing flange 14 or other well head equipment. The housing 
contains a piston 15 movable upwardly in chamber 16 in response to fluid 
pressure exertion upwardly against piston face 17, for constricting an 
annular packer unit 18 via pressure exertion from piston cam surface 22 
against packer exterior surface 23. Surfaces 22 and 23 are frusto-conical 
and flared upwardly. The packer when sufficiently radially inwardly 
displaced, seals off about a well pipe 19 shown extending axially 
vertically through the preventer 10; and in the absence of the pipe, the 
packer unit 18 will completely close off the vertical passage 20 through 
the preventer, when the unit is sufficiently constricted by piston 15. 
Upon downward movement of the piston in response to fluid pressure 
exertion against face 24, the packer expands radially outwardly to the 
open position seen in FIGS. 1 and 2. Note that the piston annular surface 
25 may have guided sliding engagement with housing cap bore 26, and that 
the packer unit is normally confined vertically under the housing cap 
lower interior surface 27. Fluid pressure lines 28 and 29 communicate 
external pressure to chambers 30 and 31, respectively. Vertical sleeve 32 
communicates with the well via the casing 33, and the top of the sleeve 
seats the packer when the piston 15 is in down position. 
In accordance with the invention, the packer unit 18 has a longitudinal 
upright axis 36 toward which the unit is adapted to be constricted or 
compressively displaced, radially inwardly. Basically, the unit comprises: 
(a) metallic inserts, as for example at 37, generally circularly spaced 
about axis 36, the inserts having webs that extend longitudinally and in 
directions about the axis 36 (as for example helically) to define surfaces 
(as at 38) which have longitudinally facing extents 38a, and 
(b) an annulus of elastomeric material 39 extending about axis 36 and 
embedding the webs; also, the material 39 extends in contacting relations 
with the surface extents 38a (as seen in FIG. 6, for example) so that the 
webs anchor the material and resist upward longitudinal displacement of 
the material, under extreme well pressure exertion on the packer during 
compressive displacement of the packer, as seen in FIGS. 4 and 5, for 
example. 
More specifically, the inserts 37 shown in FIGS. 1-14 are alike and have 
upper and lower end plates 40 and 41 between which the webs 42 extend. The 
webs have upper portions 42a and lower portions 42b with oppositely 
directed curvature; for example, the upper portions 42a in FIG. 6 are 
concave in one circular direction (indicated by arrow 43) about axis 36, 
and lower portions 42b are convex in that direction. Further, there is a 
region of inflection at 44 between such oppositely curved upper and lower 
portions. In addition, the lower plate 41 is offset relative to the upper 
plate 40, and in the direction 43 about axis 36. 
As is clear from FIGS. 5 and 6, the webs may have upright ribbing 45 
extending therealong and lateral ribbing 46 extending thereabout, such 
lateral ribbing protruding so as to provide additional surfaces to anchor 
the rubber material 39 against longitudinal displacement under extreme 
overall pressure. The longitudinal ribbing 45, which has the described 
curvature of the webs, anchors rubber material against excessive flow 
radially inwardly during radial constriction of the packer. Such 
constriction results in relative nesting of successive of the curved webs, 
whereby the lower portion 42b of each web extends beneath the upper 
portion 42a of a next successive web, with the result that rubber or 
elastomeric packer material between the nested webs is better retained or 
anchored against upward displacement than in prior packers where the webs 
remained vertical and parallel. The FIG. 6 webs 42 move closer together, 
when nested. 
Turning to FIGS. 7-10, it will be seen that the upper and lower web 
portions 42a and 42b are laterally elongated in generally parallel 
directions toward an inner region about axis 36, which region does not 
necessarily coincide with axis 36 but is proximate thereto. This is 
further seen in FIG. 10 wherein horizontal web sections are schematically 
depicted at 50, 51, 52 and 53. Sections 50 and 51 are taken at different 
elevations in upper portion 42a of the web 42, and sections 52 and 53 at 
different elevations in the lower section 42b of the web. Sections 50-53 
are wedge shaped, and have parallel central axes 50a -53a. The bottom 
plate or foot 41 is skewed relative to the top plate and sections 50-53, 
are directed in such relation that when the packer is closed about pipe 
19, or upon itself (in this case of open hole), the axis 41a of 
wedge-shaped plate 41 will be directed toward or close to axis 36. 
Note also the lateral sections seen in FIGS. 11-14, and which are parallel 
and in planes offset slightly from horizontal. Such wedge shaped sections 
have axes 55-58 which are parallel; sections 11 and 12 associated with web 
upper portion 42a and sections 13 and 14 associated with web lower portion 
42b. FIG. 7 also shows that the lower plate 41 is offset inwardly relative 
to upper plate 40. FIG. 8 shows that the upper portion 42a provides an 
additional curved surface extent 60 wherein faces longitudinally 
downwardly to anchor rubber packer material therebeneath. Surface extent 
60 is at the side of the web opposite from surface extent 38a previously 
described, and also facing downwardly. 
The modified insert shown in FIGS. 15-24 bears certain numerals which 
correspond to those applied to the insert 37, a hundred digit numeral "1" 
being added. The modified insert 137 has the same characteristics as those 
described for insert 37, with the following exceptions: in FIGS. 15 and 
18-24 the horizontal sections 169-174 taken along and through web 142 are 
progressively skewed, i.e. have increasing skew angularity along their 
axial lengths, as are defined for example by axes 169a-174a. Such axes 
have extension which meet at points along a common longitudinal axis 200 
parallel to packer axis 136. Axis 200 may coincide with axis 136 for some 
position of the packer, as for example unconstricted, partially 
constricted, or fully constricted. Sections 169-171 are associated with 
the upper portion 142a of the web 142, and sections 172-174 associated 
with the lower portion 142b of the web. 
Lower plate or foot 141 is also laterally elongated toward axis 200, 
despite the fact that it is offset from top plate 140 as seen in plan view 
18. Such offsetting is both circular (relative to axes 136 and 200), and 
lateral or radial. Top plate 140 also is elongated toward axis 200. 
Referring back to FIGS. 1-3, the packer material is seen to define radial 
slots or gaps 250 and 251 at the top and bottom of the unit, such slot 
being subject to narrowing as the packer constricts. The slots are 
circularly spaced and located between the top and bottom plates of 
adjacent inserts. 
Finally, FIG. 6 shows an alternate configuration of inserts 337, with upper 
and lower end plates 340 and 341 located and centered vertically above one 
another. The inserts have webs 342 which are bowed laterally, as shown, 
out of vertical alignment with plates 340 and 341. The webs may be curved, 
as shown, to define surfaces having longitudinally facing extents to 
resist longitudinal (i.e. vertical) displacement of packer material 339 
embedding the webs. Note web convex and concave lateral surfaces 337a and 
337b. This double convolution configuration possesses the advantages 
described above, and also allows use of packer molding tooling previously 
employed for packers wherein the insert top and bottom plates were spaced 
one above the other.