Pressure accumulator with anti-extrusion gas charging valve assembly

The present invention is directed to a pressure accumulator of the type which includes a rigid container or casing having substantially axially aligned ports in the ends thereof, and having a deformable open mouth bladder therein dividing the casing into a liquid chamber and a gas chamber in communication respectively with said ports, the port in communication with the gas chamber having a rigid fitting associated therewith, with a gas charging passageway extending therethrough and leading into the gas chamber, deformable closure member being associated with said fitting, automatically to seal the end of the passageway leading into the gas chamber upon discharge of gas from said gas chamber, to preclude extrusion of said bladder into said end of the passageway in said rigid fitting with consequent failure of the accumulator.

As conducive to an understanding of the invention, it is noted that where 
in a pressure accumulator of the type comprising a cylindrical container 
formed from two cup-shaped shells, the mouths of which are juxtaposed and 
secured together and the closed ends of which each has a port, a bladder 
of resilient deformable material, having a large mouth, is mounted in the 
container by means of a rigid annular supporting member so that the 
bladder intervenes between said ports to define a liquid chamber and a gas 
chamber in communication respectively with said ports, when such 
accumulator is charged with liquid under pressure, the side wall of the 
gas charged bladder may deform and fold over the inner end of a passageway 
in a rigid gas charging fitting secured in one of said ports with 
consequent extrusion into said passageway, resulting in puncture of the 
bladder with consequent leakage of gas and failure of accumulator. 
Leakage of gas may also occur through the usual gas charging valve which 
may be of the "Schrader" type, mounted in the rigid gas fitting. As a 
result, the gradual bleeding of gas from the bladder will result in 
inoperativeness of the accumulator to serve its intended purpose. 
It is accordingly among the objects of the invention to provide an 
accumulator which employs a conventional wide mouth bladder assembly 
supported, for example, on the side wall of the accumulator, in 
combination with an anti-extrusion cap longitudinally spaced from the 
mouth of the bladder and maintained in position by the gas charging valve 
fitting, which anti-extrusion cap will permit free communication of gas 
under pressure into the bladder to charge the latter, but will 
automatically close to prevent extrusion of the bladder through the 
passageway in the gas fitting. 
The anti-extrusion cap, according to the invention, is associated with a 
pressure accumulator of the type comprising a cylindrical container, 
formed from two cup shaped shells, the mouths of which are juxtaposed and 
secured together and the closed ends of each of which has a port. A 
bladder of resilient deformable material, having a large open mouth, is 
mounted in the container by means of a rigid annular supporting member, 
one edge of which is secured, for example, between the juxtaposed mouths 
of the shells and the other edge of which is molded in the mouth of the 
bladder, said bladder intervening between said ports and defining a liquid 
chamber and a gas chamber in communication respectively with said ports. A 
gas charging fitting is secured in one of the ports, said gas fitting 
having a central passageway therethrough, the outer end portion of which 
mounts, for example, a conventional "Schrader" valve. The inner end of the 
passageway defines the inlet into the gas chamber defined by the bladder. 
The gas charging fitting has a base portion extending into the gas 
chamber, and such base portion mounts a cap formed of an elastomeric 
material which preferably is of lower durometer than the durometer of the 
material forming the bladder, so that the cap may readily be deformed by 
engagement of the bladder thereagainst. The cap is substantially 
frusto-conical and the truncated end thereof which extends over the inner 
end or inlet of the gas passageway in the rigid fitting has an axial 
passageway aligned with and normally in communication with the inlet of 
the gas passageway and designed so that upon pressure of the bladder 
against such truncated end of the cap, the cap will deform to close the 
axial passageway therein, thereby preventing extrusion of the bladder into 
the inlet end of the passageway with resultant picking out of such bladder 
and consequent failure thereof.

Referring now to the drawings, the invention illustratively is incorporated 
in a pressure accumulator which as shown in FIG. 1, comprising a container 
10 of rigid material such as steel capable of withstanding relatively high 
pressure. 
The container comprises two complimentary cup shaped shells 11 and 12, the 
former comprising the cap or cover member for the latter, which defines 
the body portion of the accumulator. 
The rims or mouths, 13 and 14 of the shells are beveled as shown and define 
a V-shaped annular groove when the rims are aligned with their inner 
edges, 15, 16 in juxtaposition. 
Each of the cup-shaped shells, 11, 12, has a rounded end 17, 18, so that 
the accumulator is a substantially cylindrical unit having substantially 
hemispherical ends, each of which has a port 19, 20 therethrough, which 
are axially aligned. 
The port 20 is adapted to receive a fitting 21 which as shown in FIG. 1 may 
comprise a cylindrical sleeve affixed as by welding as at 22, to the end 
18 of shell 12 axially aligned with the periphery of port 20. The inner 
end of the fitting 21 defines a valve seat 23. 
Positioned in the container 10 is a deformable partition, illustratively in 
the form of a bladder 24 of rubber or similar material having like 
characteristics. The bladder is closed at one end as at 25 and said closed 
end has secured thereon and preferably molded integral therewith a rigid 
button or valve member 26 which is axially aligned with the bladder and 
designed to move against the valve seat 23 when the bladder is charged, to 
close the port 20 and thereby prevent extrusion of the bladder. 
The mouth 27 of the bladder 24 has a thickened rim portion to which an 
annular supporting member 29 is affixed by being molded therein as shown. 
The supporting member 29 is of a relatively thin resilient sheet material 
such as sheet steel having an inwardly inclined mounting portion 31 at its 
lower end molded in such thickened rim and an outwardly inclined retaining 
portion 32 at its upper end. As shown in FIG. 1, the junction 33 between 
retaining portion 32 and the cylindrical mid-portion 34 of the supporting 
member 29 is seated on the inner edge 16 of rim 14 of shell 12 and the rim 
13 of shell 11 seats on the top surface of retaining portion 32, the rims 
13, 14, and retaining portion 32 being secured together as by welding at 
35. 
According to the invention, a gas charging fitting 36 is provided which has 
a cylindrical base portion 37 with an axial stem 38 extending outwardly 
therefrom. The axial stem 38 extends through the gas port 19 and is 
positioned so that the top surface of the base portion 37, abuts against 
the inner surface of shell 11, adjacent the periphery of port 19. The 
fitting is secured in said port 19 as by welding at 41. The gas charging 
fitting 36 has a longitudinal bore 42 therethrough of reduced diameter at 
its inner end as at 43, defining a gas passageway, the inlet end 44 of 
which leads into the gas chamber 45 of the accumulator defined by the 
interior of bladder 24. 
A conventional valve member such as a "Schrader" valve 46 is screwed into 
the internally threaded enlarged bore portion 42 of the gas fitting and a 
closure cap 47 may then be screwed on the threaded outer surface of the 
valve stem 38. 
Mounted on the base portion 37 of the gas charging fitting is an 
anti-extrusion cap member 48. The cap member 48, includes an interior 
cavity 49 which has an annular rib 51 formed integral therewith. This rib 
51 is designed to coact with an annular groove 52 in the base portion 37 
of the gas charging fitting 36 dependably to retain the cap member 48 on 
said base portion 37. As is shown in the drawing, the cap member 48 is in 
the form of a truncated inverted cone and the smaller diameter end 53 of 
the cap member 48 has a passageway 54 therethrough axially aligned with 
the inlet 44 at the inner end of the gas passageway 43. Preferably, the 
layer 55 of material defining the small diameter surface 53 of the cap 
member 48 is relatively thick and the axial passageway 54 is also in the 
form of a truncated cone having its base portion 56 of larger diameter 
than the diameter "D" of the inlet 44 of the gas passageway 43, and its 
truncated end "d" of smaller diameter and slightly less than the diameter 
of the inlet 44 of passageway 43. 
The cap member 48 is formed of an elastomeric material which is preferably 
of lower durometer and hence softer than the material of which the bladder 
24 is formed. 
In use of the accumulator, the bladder 24 is charged with gas under 
pressure through the gas charging valve 46 mounted in the fitting 36 in 
port 19 and such gas under pressure will pass through the passageway 43 
and through the normally open axial passageway 54 in cap member 48 into 
the gas chamber 45 defined by bladder 24 to charge the bladder 24 to cause 
it to expand so that the wall of the bladder 24 will engage the inner 
surface of the wall of the container 10 and the valve member 26 will move 
against the seat 23 to prevent extrusion of the bladder 24. 
Thereupon a fluid such as oil under pressure is forced through fitting 21 
to charge the liquid chamber 57 with oil under pressure. As a result of 
the influx of oil under pressure into the accumulator it will cause the 
bladder to deform and possibly fold inwardly so that the side wall thereof 
will press against the under surface of cap member 48 as shown in FIG. 2. 
Due to the fact that the material of the cap member 48 is of lower 
durometer than that of the bladder 24 the force exerted by the bladder 24 
against the cap member 48 will cause the material thereof to deform 
thereby closing the axial passageway 54 as shown in FIG. 2. As a result, 
this will preclude extrusion of the bladder 24 into the inlet end 44 of 
passageway 43 through the rigid gas charging fitting 36 which could cause 
pickout of the bladder with resultant failure thereof. 
In normal operation, the accumulator may be charged with gas under pressure 
under a predetermined precharge and also would contain liquid in the 
liquid chamber thereof which is also under pressure. Under many 
circumstances, the accumulator may be in standby condition for some 
extended periods. As a result, there is a possibility that leakage may 
occur through the "Schrader" valve 46 due, for example, to a defect in the 
valve; or the presence of dirt which prevents complete seating of the 
valve member of the "Schrader" valve, thereby permitting a slight escape 
of gas which, after a long period, may cause complete exhaustion of gas 
from the bladder. As a result, the bladder would press against the inner 
end 53 of the cap member 48 which would cause the axial passageway 54 
therein to close in the manner previously described to prevent damage to 
the bladder 24 with resultant failure of the unit. If not for the presence 
of such readily deformable cap member 48 and if the bladder pressed 
against a rigid opening such as the inlet end 44 of the passageway in the 
gas charging fitting, pickout of the bladder could occur. 
Due to the provision of a deformable anti-extrusion cap member 48 which is 
separate and distinct from the wide mouth bladder 24, which is secured to 
the side wall of the container 10, it is possible to have the durometer of 
the bladder material greater then the durometer of the anti-extrusion cap 
member 48, thereby facilitating deforming of said cap member 48 when the 
bladder 24 presses thereagainst to insure closure of the axial passageway 
54 in the cap member 48 thereby precluding extrusion of the bladder 24. 
As many changes could be made in the above construction and many apparently 
widely different embodiments of this invention could be made without 
departing from the scope of the claims, it is intended that all matter 
containing the above description, or shown in the accompanying drawings be 
interpreted as illustrative and not in a limiting sense.