U.S. patent number 3,767,215 [Application Number 05/285,943] was granted by the patent office on 1973-10-23 for multi-ring hydraulic seal for irregular bore surfaces.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Army. Invention is credited to Bruce B. Brown.
United States Patent |
3,767,215 |
Brown |
October 23, 1973 |
MULTI-RING HYDRAULIC SEAL FOR IRREGULAR BORE SURFACES
Abstract
The sealing of irregular bore surfaces against the leakage of
high pressure ydraulic fluid is accomplished by a multi-ring unit
including an elastomer ring supported between a pair of teflon
rings which also provide respective support for a rearward and a
forward oversize leather ring, a steel cam ring adjacent the
forward face of the forward leather ring, and an aluminum alloy
wedge ring cooperating with the cam ring to provide an unsupported
area therebetween. When the sealing unit is mechanically compressed
after insertion thereof into the bore, the elastomer and the wedge
rings are each partially extruded into circumferential obturating
contact with the irregular bore surface to effect adequate sealing
thereof until the sealing rings as well as the support rings are
fully deformed into the final sealing configuration.
Inventors: |
Brown; Bruce B. (Latham,
NY) |
Assignee: |
The United States of America as
represented by the Secretary of the Army (Washington,
DC)
|
Family
ID: |
23096360 |
Appl.
No.: |
05/285,943 |
Filed: |
September 1, 1972 |
Current U.S.
Class: |
277/638; 73/167;
89/31; 277/650 |
Current CPC
Class: |
F16J
15/021 (20130101); F41A 33/00 (20130101); F41A
31/00 (20130101) |
Current International
Class: |
F16J
15/02 (20060101); F41A 31/00 (20060101); F41A
33/00 (20060101); F16j 015/24 () |
Field of
Search: |
;277/102,117,125 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rothberg; Samuel B.
Assistant Examiner: Smith; Robert I.
Claims
I claim:
1. A multi-ring seal for obturating a relatively rough and
irregular bore surface against the leakage of hydraulic fluid under
high pressure comprising,
a pair of leather rings of slightly larger diameter than the bore
surface to be sealed,
an elastomer ring,
a pair of support rings of molded plastic straddling said elastomer
ring and disposed between said leather rings,
a cam ring of steel in adjacent contact with one of said leather
rings, and
a wedge ring of aluminum alloy cooperating with said cam ring to
form an unsupported area therebetween for increasing the extrusion
imparted thereto under hydraulic pressure to a greater extent in
the direction at right angles to the surface to be sealed than in
the direction parallel thereto.
2. The seal defined in claim 1 wherein said elastomer ring is
formed with a convex face tapering to an opposite annular face of
smaller diameter whereby the extrusion thereof in response to the
application of hydraulic pressure is greater in the direction
perpendicular to the bore surface to be sealed than in the
direction parallel thereto.
3. The seal defined in claim 1 wherein the face of said wedge ring
adjacent to said cam ring is of substantially frustoconical
configuration in order to provide the unsupported area which
permits limited sealing orientation thereof prior to the
application of the hydraulic pressure.
4. A multi-ring seal for obturating a relatively rough and
irregular bore surface within a tube against the leakage of
hydraulic fluid under high pressure comprising,
a pair of spaced leather rings of sufficient diameter to fully
engage the bore surface to be sealed upon initial insertion thereof
into the tube,
a pair of support rings of molded plastic of lesser diameter than
said leather rings and respectively in contact with adjacent
surfaces thereof,
an elastomer ring having a portion of its diameter equal to said
plastic support rings and seated therebetween,
a steel cam ring adjacent one of said leather rings,
an aluminum alloy wedge ring having an end face adjacent to said
cam ring to form an unsupported area therebetween, and
means for mechanically compressing each of said rings in the seal
whereby said elastomer ring and said wedge ring are extruded into
partial obturating contact with the bore surface to effect positive
sealing thereof during the period in which the hydraulic pressure
is extruding the seal into final maximum sealing obturation.
5. The seal defined in claim 4 wherein one face of said elastomer
ring is supported along a greater surface area than the opposite
face to minimize the extrusion thereof in the direction parallel to
the bore surface to be sealed.
6. The seal defined in claim 4 wherein said means for mechanically
compressing said rings comprises,
a cylinder having a reduced diameter portion for mounting said
rings to permit the insertion thereof into the tube,
a closure member threaded on said cylinder in adjacent contact with
said wedge ring,
means for preventing rotation of said closure member relative to
the tube, and
a closure ring between the reduced diameter portion of said ring
mounting cylinder and the other of said leather rings whereby
rotation of said cylinder relative to said closure member advances
said closure ring to compress the remaining rings in the seal.
7. A multi-ring seal mounted on a mandrel adapted to be inserted
into the breech end of a rifled gun tube for circumferentially
obturating the lands and grooves therein against the forward
leakage of hydraulic fluid being cycled therethrough to simulate
the stresses ordinarily encountered in the firing of a round
therein, comprising,
a pair of spaced leather rings of sufficient diameter to fill the
rifling grooves in the gun tube during the insertion of the mandrel
therein,
a pair of support rings of teflon of lesser diameter than said
leather rings and respectively in contact with adjacent surfaces
thereof,
an elastomer ring having a portion of its diameter equal to said
teflon rings and seated therebetween,
a steel cam ring having a frustoconical front face and a rear face
in contact with the forwardmost of said leather rings,
a wedge ring of aluminum alloy having a rear face cooperating with
said front face of said cam ring to provide an unsupported area
therebetween,
a pilot rotatably secured to the forward end of the mandrel and
engageable in the rifling grooves in the gun tube, and
means for longitudinally advancing said mandrel relative to said
pilot to reduce the space occupied by the seal whereby said
elastomer and wedge rings are partially extruded into
circumferential sealing engagement in the bore of the gun tube.
8. The seal defined in claim 7 wherein said pilot comprises an
internally threaded hollow cylinder having a plurality of helically
inclined lugs spaced about the exterior periphery thereof to permit
insertion of the mandrel into the gun tube and yet prevent rotation
of the cylinder in response to rotation of the mandrel.
9. The seal defined in claim 7 wherein said wedge ring includes a
front face inclined at a relatively small angle to the rear face of
said pilot whereby the partial extrusion of said wedge ring is
attained without eliminating the unsupported area provided thereby
in cooperation with said cam ring.
10. The seal defined in claim 7 wherein said elastomer ring
comprises an arcuate rear face tapering to an annular front face of
lesser diameter and wherein said teflon ring in contact with said
rear face of said elastomer ring is correspondingly contoured to
provide full support thereto against axial extrusion parallel to
the rifled surface to be sealed.
Description
BACKGROUND OF THE INVENTION
This invention relates to the sealing of high pressure fluids and
is more particularly directed to a multi-ring seal for use in a
hydraulic pressure technique which simulates the stresses produced
within the bore of a gun tube during the firing of a round of
ammunition therein.
In the past, the establishment of the safe fatigue life for the
type of gun tube employed in large caliber artillery weapons has
generally been accomplished by the actual firing of one or more
representative tubes to the point of actual failure. Since a firing
program of such magnitude is extremely expensive and
time-consuming, considerable effort has been directed to developing
a technique capable of simulating the stresses produced in the gun
tube during actual firing. Relatively recent successes have
demonstrated that it is possible to achieve the desired simulation
by cycling hydraulic fluid through the gun tube in repetitive
pulses equivalent in pressure and duration to those encountered in
the firing of successive rounds of ammunition.
However, in view of the difficulties encountered in sealing the
relatively irregular rifled interior of a fired gun tube against
the leakage of high pressure hydraulic fluid, the simulation of
firing stresses has heretofore been limited to sections cut from
tubes which had been subjected to sufficient firing to fully
develop the cracks which are ultimately responsible for the fatigue
failure of the tube. In order to positively seal the tube section
during the firing simulation, it has been found necessary to
machine finely finished pockets at each end thereof to properly
seat the conventional seals. While effective insofar as sealing is
concerned, the machining of these pockets is both costly and
time-consuming and, in conjunction with the required sectioning of
the gun tube, frequently resulted in the loss of important portions
of partially worn rifling. Of even greater concern has been the
considerable difficulty experienced in correlating the growth rate
of the cracks propagated during the simulated firing with those
developed under actual firing conditions. Obviously, the firing of
even one gun tube to the point of failure introduces the same
costly and time-consuming procedure the simulated firing is
specifically intended to eliminate. Moreover, in view of the
statistical nature of gun tube fatigue life and the inherent
variability of the materials from which the tubes are fabricated, a
fairly extensive testing program is required to provide a
meaningful comparison of the crack growth rate under actual and
simulated conditions.
It has therefore been suggested that the necessary correlation
could be achieved more accurately and economically by alternating
selected amounts of actual and simulated firings on the same gun
tube. Such procedure would not only permit a direct comparison of
the rate of growth of the fatigue cracks under the two different
firing modes involved but would also greatly reduce the amount of
actual firing required. However, the successful conduct of this
desirable technique is dependent on the positive sealing against
hydraulic leakage of the relatively rough and unpredictably
irregular surfaces of the alternate lands and grooves present in
the rifled interior of the gun tubes.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an improved
high pressure seal which will fully obturate the annular clearance
between a tube and a cylindrical seal carrier inserted therein
despite the considerable roughness and irregularity of the bore
surface of the tube.
A further object of the present invention is to provide an improved
seal, as aforesaid, wherein a plurality of relatively deformable
rings of different material and configuration are alternated with
supporting rings of a more rigid construction.
Another object of this invention lies in the provision of a
multi-ring seal, as aforesaid, which can be mechanically deformed
to provide an initial sealing action against the leakage of
hydraulic fluid during the first few cycles of hydraulic actuation
required to complete the full sealing deformation thereof.
Still another object of this invention is to provide a multi-ring
seal, as aforesaid, wherein the more rigid rings support the
deformable rings in a manner which minimizes the extrusion thereof
in the direction parallel to the surface to be sealed.
It is a still further object of this invention to provide a
multi-ring seal, as aforesaid, which can be readily and completely
removed from a rifled gun tube to avoid any interference with the
subsequent re-firing thereof.
It has been found that the foregoing objects can be achieved by a
seal assembly carried on a mandrel to be inserted into the bore of
a gun tube. The assembly includes an elastomer ring of modified
O-ring configuration supported between a pair of teflon rings, an
oversized leather ring adjacent each of the teflon rings, a steel
ring adjacent to one of the leather rings and provided with a
frustoconical end face on the side furthest from the leather ring,
and a wedge ring of aluminum alloy having an end face of greater
slope than the angular face of the steel ring to form an
unsupported area therebetween. The opposite face of the wedge ring
is formed at a slight angle to the vertical to provide partial
contact thereof with the end face of the adjacent closure member
utilized to retain the seal assembly in place. Thus, when the
closure member is mechanically advanced to compress the seal
assembly, the wedge ring is subjected to an overturning force which
causes a portion of the exterior periphery thereof to extrude into
initial sealing contact with the bottom of the rifling grooves and
the sides of the adjacent lands in the gun tube. At the same time,
the elastomer ring is bulged outwardly to provide a similar initial
obturating contact with the rifling grooves and lands. As a result,
the elastomer, leather, and wedge rings provide adequate sealing
contact during the first few cycles of hydraulic pressure required
to complete the full deformation thereof into obturating contact
with the rifled interior bore of the gun tube. While the sealing
rings are permitted to readily deform in the direction
perpendicular to the gun tube surface to be sealed, the teflon
rings, the steel ramp ring, and the steel end closures each provide
the support necessary to minimize the extrusion of the sealing
rings in the direction parallel to the rifled surface to be
sealed.
In the case of the wedge ring such limitation is additionally
enforced by the work hardening produced 7 during the extensive
deformation imparted thereto by the high hydraulic pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
The exact nature of the invention, as well as other objects and
advantages thereof, will be readily apparent from consideration of
the following specification relating to the annexed drawings
wherein:
FIG. 1 is a vertical section through the breech end portion of a
rifled gun tube equipped with an arrangement for cycling hydraulic
fluid therethrough in a manner simulating the stresses encountered
during actual firing and shows the means for sealing the opposite
ends of the stressed portion of the tube;
FIG. 2 is an enlarged sectional view of the forward sealing means
of FIG. 1 with the mandrel portion shown in full and the
configuration and the materials of the individual components
thereof shown prior to the application of any pressure thereon;
FIG. 3 is a perspective view of the wedge ring shown in FIG. 2 and
is partially cut away to show the cross-sectional configuration
thereof;
FIG. 4 is a fragmentary sectional view of the sealing means of FIG.
2 which is still further enlarged to show the position of the
individual components following the application of the mechanical
pressure required to provide the desired initial sealing
deformation thereof;
FIG. 5 is a fragmentary section taken along line 5--5 in FIG. 4 to
show the relationship of the partially deformed wedge ring to the
rifling grooves and lands in the gun tube;
FIG. 6 is a view equivalent to that of FIG. 4 but showing the
position and configuration of the individual components of the seal
assembly following the completion of the deformation required to
positively seal the gun tube portion undergoing the hydraulic
cycling designed to simulate firing stresses; and
FIG. 7 is a fragmentary view of FIG. 6 showing the extent of the
sealing deformation imparted to the various rings in the seal where
the surface to be sealed is relatively rough and irregular in
contour.
DESCRIPTION OF A PREFERRED EMBODIMENT
The seal of the present invention is particularly successful in the
type of rough and irregular surface provided by the rifled interior
of a large caliber gun which has been fired to a considerable
extent. As best shown in FIG. 1, such gun generally includes a
breech ring 12 threaded to the breech end of a gun tube 14 and
arranged to seat the slidable breechblock 16 therefor. The bore of
the gun tube 14 is customarily provided with alternate helical
lands 18 and grooves 20. In order to simulate the stresses normally
encountered in firing a plurality of live rounds in the gun,
hydraulic fluid is cycles through a portion of tube 14 in a manner
which will provide a repeated rise and fall in pressure comparable
to actual firing pressure in intensity. This is accomplished by
high pressure tubing 22 passing through breech ring 12 and
breechblock 16 into the rear end of a cylindrical mandrel 24 which
extends forwardly into the bore of gun tube 14. Surrounding the
rear end of mandrel 24 is a conventional O-ring unit 26 arranged to
seal the breech end of gun tube 14 against the rearward leakage of
the hydraulic fluid. Mandrel 24 is also provided with a suitable
forwardly extending passage 28 designed to direct the hydraulic
fluid into the annular clearance between the exterior periphery of
mandrel 24 and the rifled bore surface of gun tube 14. The forward
portion of mandrel 24 is reduced in diameter, as indicated at 30,
and terminates in a threaded end 32 engageable with an internally
threaded cylindrical rifling pilot 34 of hollow configuration
preferably fabricated of a relatively hard bearing metal such as
beryllium copper. Forward movement of pilot 34 relative to mandrel
24 is prevented by a circular plate 36 secured to the front end of
mandrel 24 as by bolts 38. The exterior circumference of pilot 34
is formed with a series of helically oriented spaced lugs 40
arranged to slidably engage in rifling grooves 20 as mandrel 24 is
guided into the breech end of gun tube 14. However, when mandrel 24
is rotated, any accompanying rotation of pilot 34 is prevented by
rifling lands 18 and consequently, mandrel 24 will be threadably
advanced relative to pilot 34 for a purpose to be hereinafter
shown.
Reduced diameter portion 30 of mandrel 24 terminates in an arcuate
rear end wall 42 and cooperates with the rifled bore surface of gun
tube 14 to provide an annular recess for seating a series of
sealing elements of which the rearwardmost is a steel closure ring
44 having an inner periphery conforming to the arcuate curvature of
end wall 42 and an outer periphery of slightly lesser diameter than
that across rifling lands 18. Adjacent to closure ring 44 is an
oversized leather ring 46 arranged to fully conform to the
irregular contour of the rifling in gun tube 14 as mandrel 24 is
inserted therein. A support ring 48 of teflon is seated next to
leather ring 46 and is formed with a concave forward face 50
conforming to the arcuate rear end face 51 of an adjacent ring 52
of elastomeric material. The body of ring 52 is axially tapered to
form a forward annular face 54 of smaller diameter than the
adjacent face of a support ring 56 of teflon. A second oversize
leather ring 46 is positioned between teflon support ring 56 and a
steel cam ring 58 having a frustoconical front face 60.
Between ring 58 and the closure end 61 of rifling pilot 34 is a
wedge ring 62 of aluminum alloy having a rear face 64 of sufficient
slope to contact cam ring 58 only along the inner portion of front
face 60 so as to provide an unsupported area therebetween. The
front face 66 of wedge ring 62 is also sloped relative to the
vertical and is additionally provided with a rounded edge 68
blending into the inner periphery thereof. The outer periphery of
wedge ring 62 is forwardly sloped away from the bore surface of gun
tube 14. Except for leather rings 46, the major diameters of the
other rings are each slightly less than the diametrical distance
between rifling lands 18 in order to prevent scoring or other
undesirable mutilation thereof as mandrel 24 is being inserted into
the bore of gun tube 14.
In order to seal the annular clearance between mandrel 24 and the
rifled bore surface of gun tube 14 during the first few hydraulic
pressure cycles prior to the completion of the deformation incurred
by rings 46, 52, and 62, sufficient mechanical pressure is imparted
to the entire assembly to effect the deformation required to insure
a preliminary seal. This is accomplished by rotating mandrel 24,
preferably from the rear end thereof, to advance forwardly relative
to rifling pilot 34 thereby compressing the resilient rings of the
assembly to partially deform as shown in FIG. 4. Elastomer ring 52
is bulged into an essentially oval configuration which enters into
each of rifling grooves 20 to provide a sealing contact along a
circumferential area in gun tube 14. At the same time, teflon
support ring 48 is extruded in the radial direction to partially
enter into rifling grooves 20 to a progressively increasing depth.
Support ring 56 is also partially extruded into rifling grooves 20
but to a relatively constant depth. In addition, wedge ring 62 is
partially rotated by the reduction in the distance between ring 58
and closure end 61 of rifling pilot 34 so that the outer rear
portion of ring 62 is forced into circumferential sealing contact
with the floor of rifling grooves 20. As best shown in FIG. 4, the
major portion of wedge ring face 64 is still clear of angular face
60 of ring 58 while the major portion of the exterior periphery
thereof is similarly clear of the floor of rifling grooves 20.
However, once a few cycles of hydraulic pressure are applied, all
the rings except closure ring 44 are forced forwardly as shown in
FIG 6 to complete the required sealing deformation. The exterior
peripheries of leather rings 46 and teflon support rings 48 and 56
are each radially deformed into full sealing contact with rifling
lands 18 and grooves 20 with only a slight amount of extrusion in
the direction parallel to the bore surface. Leather rings 46 are
considerably more compressible than teflon rings 48 and 56 and
therefore absorb a greater share of the existing hydraulic
pressure, thereby reducing the amount of extrusion imparted to
rings 48 and 56 in the direction parallel to the bore surface.
While the bulging of elastomer ring 52 has been increased, support
rings 48 and 56 serve to limit the axial extrusion of ring 52 along
rifling lands 18 and grooves 20. The absence of such support has
heretofore been the factor most responsible for the rapid
deterioration of O-ring type seals under the high pressures here
involved, generally in the vicinity of 60,000 psi. The aluminum
wedge ring 62 has also been completely deformed in a radial
direction into full sealing contact with rifling grooves 20 with
considerably lesser axial extrusion into the clearance between lugs
40 on rifling pilot 34 and the rifling lands and grooves in gun
tube 14. It is believed that such desirable result is primarily due
to the unique configurations of cam ring 58 and wedge ring 62 and
the relationship therebetween. As the unsupported area of rear face
64 is progressively reduced, the force tending to deform wedge ring
62 is correspondingly diminished thereby minimizing further
deformation in the axial direction once the exterior surface
thereof is in full sealing contact with the rifling in gun tube 14.
The controlled extrusion of wedge ring 62 may also be partially due
to the work hardening of the aluminum alloy during the deformation
thereof.
Thus, there is here provided an extremely successful sealing
arrangement for obturating the interior of a rifled gun tube
against the leakage of hydraulic fluid under pressures ranging
between 40,000 and 70,000 psi. Adequate sealing is provided
throughout the fatigue life of the gun tube even through the
rifling therein may be partially worn and eroded thereby
substantially increasing the irregularity of the surface to be
sealed in addition to the existing stepped configuration of the
rifling lands and grooves. Furthermore, despite the extensive
deformation of the sealing rings into the gun tube rifling, the
entire assembly may be readily removed from gun tube 14 merely by
retracting mandrel 24 relative to rifling pilot 34 to reduce the
compression on the rings and thereafter breaking the engagement
thereof with the rifling to permit mandrel 24 to be retracted from
gun tube 14. Such procedure is accomplished without any adverse
effect on the interior of the gun tube which may then be subjected
to additional actual firing.
The foregoing disclosure and description of the invention is
illustrative only. Various changes may be made within the scope of
the appended claims without departing from the spirit of the
invention.
* * * * *