Valve actuating apparatus and method

A fluid pressure actuator is moved in one direction by fluid pressure and returned in the other direction by a compressed spring. With the method and apparatus embodied in the disclosure, a plurality of additional energy storage storing devices are compressed by only the initial movement of the actuator in response to the application of fluid pressure thereto. Such energy is applied to the energy storage devices by an annular cam surface provided on the actuator shaft. During the return movement of the actuator, the stored energy is returned in the form of an additional axial force applied to the actuator shaft just prior to its return to its original position. When such actuator is applied to a valve, the additional force imparted to the shaft by the energy storing devices may be designed to cause the severing of a wire line trapped in the opening of the valve at the instant that closing of the valve is required.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a fluid pressure actuator for valves, which are 
opened through the application of fluid pressure, but closed by the 
relaxation of compressed springs, and which require a maximum force to be 
exerted at the end of the valve closing movement in order to effect the 
severing of any wire line or similar obstruction that may remain in the 
valve opening. 
2. Description of the Prior Art 
Many valves are of the type that are actuated to their open position 
through the application of a control fluid pressure. The opening movement 
of the valve under the influence of such fluid pressure compresses one or 
more springs which are employed to assist in the return the valve to its 
closed position. This particular arrangement is desirable because of the 
fact that any failure of equipment in the well, or any other accidental 
occurrence which requires that the valve be closed, could very well affect 
the fluid pressure line transmitting control fluid pressure to the valve. 
Therefore, it is desirable that the energy required to effect the closing 
of the valve be stored in the valve and be independent of any control 
lines. 
When such accidents or failures occur, it may often happen that a wire 
line, for example, from which a well tool may be suspended, is traversing 
the opening of the valve. It is very important to the protection of the 
well and the personnel at the well head, that the closing of the safety 
valve be accomplished with sufficient force to effect a severing of such 
wire line. This necessarily requires that a substantial force be exerted 
by the compressed springs at the end of their closing stroke, and, due to 
the known characteristics of springs, it necessarily means that excessive 
fluid pressure forces would be required to compress such springs during 
the movement of the valve from its closed to its fully open position. What 
is required is an actuating system wherein the energy for effecting the 
final closure of the safety valve is stored in a suitable mechanism within 
the valve only during the initial opening movements of the valve and is 
then not released until the valve approaches its closed position. 
SUMMARY OF THE INVENTION 
The invention provides an improved method and apparatus for operating 
valves wherein the closing of the valve is effected by compressed springs 
and the energy required to effect the final closing of the valve is 
substantially greater than that required to move just the valve elements 
to a closed position. 
In accordance with this invention, a unidirectional fluid pressure actuator 
is provided having a shaft which is connected to the movable element of a 
valve by a lost motion connection. Conventional helical springs or the 
like oppose the opening movement of the actuator shaft and effect the 
storage of sufficient energy to return the operating element of the valve 
to its closed position under normal conditions. To provide an additional 
closing thrust to the actuator shaft as its approaches the fully closed 
position of the valve, this invention provides a plurality of energy 
storing devices which are generally radially disposed with respect to the 
actuator shaft and are energized to an energy storing condition by a cam 
surface carried by the actuator shaft. Such cam surface operates on the 
energy storage devices only during the initial movement of the shaft in a 
valve opening direction. A lost motion connection between the actuator 
shaft and the valve operating element permits such energy storage to be 
accomplished prior to effecting any opening movement of the valve, thus 
reducing the amount of fluid pressure force required during the energy 
storage step. 
The energy storage devices may comprise an ordinary helical spring, a stack 
of Belleville springs, an elastomeric mass, a piston cooperating with a 
cylinder containing a trapped compressible fluid, or any combination of 
the aforementioned energy storing devices. 
As the actuator shaft returns the valve to the closed position under the 
influence of the conventional axially disposed springs, the energy stored 
in the energy storing devices is released in the form of an additional 
axial thrust on the actuator shaft toward the fully closed position. Such 
thrust is imparted by the cooperation of the energy storage devices with 
the same cam surface that effected the storage of energy therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a schematic diagram illustrating the basic construction and 
method of operating of a valve actuator embodying this invention. A 
cylinder C defines a fluid pressure chamber PC in which a piston P is 
mounted for sliding, sealable movement relative to the bore surface of 
cylinder C. A conventional return spring RS opposes pressure produced 
movement of piston P. Piston P is suitably secured to a shaft S which in 
turn is secured by a T slot T to the operating element of a valve, such as 
a safety valve for an oil well. A large diameter portion S1 of shaft S is 
mounted for sliding sealing movement in a bearing B defined in one end 
wall of the cylinder C. A smaller diameter portion S2 of shaft S is 
connected to the larger diameter portion by an annular cam surface CS. One 
or more generally radially disposed plungers PL having roller R on the end 
thereof engage the outer surface of the shaft S. 
In FIG. 1, the shaft S is illustrated as being in the position 
corresponding to the closed position of the valve element that it is 
intended to operate. When fluid pressure is applied to the pressure 
chamber PC, it acts on the piston P to move the shaft S to the left toward 
its valve open position. In the initial movement of the shaft S, the cam 
surface CS engages the roller R and forces the plunger PL radially 
outwardly. This radial outward movement is utilized to store energy in a 
compressible energy storing device ED. Typical of such devices is an 
ordinary helical spring, a stack of disc spring washers, an elastomeric 
mass, or a compressible fluid that is trapped between the outer end of the 
plunger PL and the surrounding portions of the cylinder C to effect a 
compression of the trapped compressible fluid. 
Thus, in the initial movement of the shaft S in a valve opening direction, 
the primary resisting force is that required to effect a compression of 
the energy storing device ED. After the plunger roller R rides up the cam 
surface CS to rest on the large diameter portion S1 of the shaft S, no 
additional energy is required for the energy storing device, and all of 
the fluid pressure derived energy applied to the piston P may be utilized 
to effect the opening of the valve and the compression of the conventional 
valve return spring RS. 
When it is desired to close the valve, the fluid pressure is exhausted from 
the pressure chamber PC and the piston P and the shaft S are moved toward 
the right to their valve closing position by the compressed return spring 
RS. When, however, the cam surface CS reaches a point of alignment with 
the roller R of the plunger PL, the stored energy in the energy storage 
device ED is released in the form of a substantial additional axial thrust 
imparted to the shaft S in the valve closing direction. Due to the 
mechanical advantage of the inclined cam surface, it is readily apparent 
that a substantial additional axial force may be applied to the shaft S 
during the last stages of its travel to a valve closing position. Thus, 
sufficient force may be readily generated to effect the severing of a wire 
line or other form of obstruction that may be traversing the valve opening 
at the time that it is required to close the valve. The ability to apply 
such additional force only during the final stages of the closing movement 
of the valve is of inestimatable value in improving the dependable 
operation of safety valves for wells. 
Referring now to FIGS. 2 and 3 there is shown in detail the actual 
construction of a valve actuator 1 embodying this invention. Valve 
actuator 1 comprises a hollow body portion 10 having an annular mounting 
element 12 suitably secured to one end thereof. Securement of element 12 
may be effected by a C-ring 13 which is mounted in a suitable groove in 
the interior bore surface 10a of the hollow body member 10. Ring 13 abuts 
an external radial shoulder 12a provided on the mounting element 12. A 
clamping ring 14 overlaps the end face of the mounting member 12 and the 
end face of the hollow body member 10 and is secured thereto by a 
plurality of peripherally spaced bolts 14a. 
Annular mounting member 12 is additionally provided with an axially 
extending, relatively small diameter flange 12b which is conventionally 
secured to the bonnet (not shown) of a housing of a valve to be operated, 
such as a safety valve for an oil well. Such securement may be effected by 
a plurality of bolts (not shown) passing respectively through a plurality 
of peripherally spaced radial holes 12c provided in the extension 12b. 
The other end of body member 10 is provided with a relatively thick annular 
end wall 10b which, at its inner end, has an axially extending annular 
bearing portion 10c formed thereon. Bearing portion 10c defines a bore 10d 
for slidably receiving the shaft portion 21 of a piston assemblage 20. 
Suitable seals 10e are provided in annular extension 10c for effecting a 
slidable and sealable engagement of the bore bearing portion 10c with the 
shaft portion 21. 
An annular piston element 25 is assembled to a medial portion of the shaft 
21 that lies within the hollow bore 10a of the body housing 10. While the 
piston element 25 may be secured to the shaft 21 in a variety of manners, 
it is illustrated as being snugly engaged with a cylindrical surface 21c 
formed on the piston shaft 21 and abutting a radial shoulder 21d. A 
retaining ring 26 is threaded onto threads 21e formed on the piston shaft 
21 and locked in snug engagement with adjacent face of the piston element 
25 by set screws 26a. 
A seal 25a prevents fluid leakage between the annular piston element 25 and 
the shaft 21. The outer surface of piston element 25 is provided with a 
peripheral groove 25b which mounts a seal 25c which engages the interior 
bore 10a of the cylinder body 10. Thus, a fluid pressure chamber 30 is 
defined between the thickened end wall 10b of the hollow body 1 and the 
adjacent face of the annular piston element 25. Pressured fluid may be 
supplied to such pressure chamber 30 through one or more inlet ports 28 
which are formed in the thickened end wall 10b of the body housing 10. 
Thus, the application of fluid pressure to pressure chamber 30 will effect 
a movement of the piston element 25 and the piston shaft 21 from the valve 
closed position, illustrated in FIG. 2, to the left to the valve open 
position illustrated in FIG. 3. Such movement of the piston assemblage 20 
is opposed by a pair of concentric helical springs 31 and 32 which engage 
the left hand face of the piston element 25 and abut a spring seat ring 33 
which is mounted against an internally projecting shoulder 12d provided in 
the end of the annular flange extension 12b of the mounting element 12. 
Springs 31 and 32 are thus compressed by the fluid pressure induced 
movement of the piston shaft 21 toward its valve opening position, and, 
when fluid pressure is released from chamber 30, the piston element 25 and 
the connected piston assemblage 20 will be moved to the right from the 
position shown in FIG. 3 toward the closed position of the valve shown in 
FIG. 2. 
A plurality of generally radially disposed energy storing devices are 
provided in the thickened end wall 10b of the body housing 10. Such energy 
storing devices comprise a plurality of plungers 40 mounted in slidable 
relationship in radial holes 10f provided in the thickened body end wall 
10b. Each plunger is backed up by a compressible energy storing device, 
here shown as a simple helical spring 41, but it should be understood that 
a stack of disc springs could be employed or a compressible column of 
elastomeric material, or, through the addition of appropriate sealing 
rings to the plungers 40, a compressible fluid, such as a gas could be 
utilized either alone or in combination with the springs as an energy 
storing device. The springs 41 are respectively backed by sealing plugs 44 
which are respectively threadably secured in the ends of the radial holes 
10f. The inner ends of plungers 40 each mount a roller 46 which rides upon 
the adjacent exterior surface of the shaft 21. Shaft 21 is provided with 
an axially extending cylindrical surface 21b which connects with the 
normal bearing diameter portion 21a of shaft 21 through an abrupt 
outwardly inclined annular camming surface 21f. In the closed position of 
the valve actuator illustrated in FIG. 2, the plunger rollers 46 are 
resting against the reduced diameter cylindrical surface 21b. 
When fluid pressure is introduced into the pressure chamber 30 to effect 
the movement of the piston assemblage 20 to the left, the energy storage 
devices have no significant effect on such movement until the inclined cam 
surface 21f contacts the rollers 46. Then at this point, a substantial 
amount of energy is required to concurrently force all of the plungers 40 
outwardly and thus store energy in the energy storing springs 41. Once the 
cam rollers 46 ride up on the bearing diameter portion 21a of the shaft 
21, then no significant energy will be absorbed from the opening movement 
of the shaft assemblage 20 by the plungers 40 and their associated energy 
storing devices 41. 
On the return movement of the shaft assembly 20 from the open position, 
shown in FIG. 3, back to the closed position shown in FIG. 2, a 
significant additional axial thrust is imparted to the piston shaft 
assemblage 20 through the cooperation of the plungers 40 with the inclined 
annular cam surface 21f. In this case, the plunger rollers 46 ride down 
such surface under the forces imposed thereon by the energy storing 
devices 41 and drive the piston shaft 21 to the right, to the fully closed 
position of the valve being actuated, with a substantial additional 
impetus. In fact, by utilization of a sufficient number of plungers 40 and 
associated energy storing devices 41, the additional axial force imparted 
to the piston shaft 21 can effect the severing of a wire line that may be 
traversing the opening of a safety valve at the time that it is desired to 
effect a complete closure of such safety valve. 
To further reduce the energy requirements involved in the opening movements 
of an actuator embodying this invention, a lost motion connection is 
preferably employed between the piston shaft 21 and the shiftable valve 
element (not shown) of the safety valve or other type of valve which is to 
be operated by the actuator. Such lost motion connection may conveniently 
comprise an annular connector 50 which has a reduced diameter 50a slidably 
mounted in an appropriate recess 21g formed in the end of the shaft 21. A 
pin and slot connection is then provided between the cooperating slidable 
portions of the piston shaft 21 and the connector 50. Obviously, either 
one of the mentioned elements may be provided with an axially extending 
slot and the other with a radial pin cooperating with the slot. In the 
construction illustrated in the drawings, an axially extending slot 21h is 
formed in the end of piston shaft 21 and a radially extending pin 52 is 
mounted in the reduced diameter end of the connector 50 and slidably 
cooperates with the slot 21h. 
With this arrangement, the initial movement of the piston shaft 21 to the 
point where the energy storing devices 41 are fully compressed is 
accomplished within the limits of the lost motion connection so that no 
force is required to be applied to opening the valve until after all of 
the energy storing devices 41 have been compressed. This reduces the total 
amount of fluid pressure force required and permits either the design of 
the actuator to a smaller overall diameter, or the utilization of a lower 
fluid pressure force to effect the opening movements of the valve. 
Although the invention has been described in terms of specified embodiments 
which are set forth in detail, it should be understood that this is by 
illustration only and that the invention is not necessarily limited 
thereto, since alternative embodiments and operating techniques will 
become apparent to those skilled in the art in view of the disclosure. 
Accordingly, modifications are contemplated which can be made without 
departing from the spirit of the described invention.