Mechanically balanced tapered plug valve

The invention is a novel hermetic tapered plug valve having a spring-like resilient mechanism for providing axial balance to the plug and thereby prevent valve lock up.

BACKGROUND OF THE INVENTION 
These valves usually comprise a tapered plug located within a similarly 
tapered housing or valve seat; said plug has a passageway for allowing 
fluid flow when in an open position. 
These valves work in two positions: "closed" when the walls of the tapered 
plug shut-off the flow of the fluid through the valve and "open" when 
rotating the plug 90.degree. (one quarter of a turn), to provide for the 
passageway to become aligned with the coaxial passageway of the pipeline, 
thus allowing the continued flow of the fluid. 
The space between the tapered plug and its tapered seat is minimum to 
provide for hermetism and high pressure lubrication. The thickness of the 
lubricant film between the plug and seat is of thousands of an inch. 
Therefore, a failure in lubraication will produce contact between both 
parts. When the failure in lubrication exceeds certain limits, the plug 
gets tightened with its seat. To prevent this, the development of this 
kind of valve has aimed toward the following objectives: 
(1) To provide a pressurized lubrication; (2) to obtain precise control of 
plug axial movements to prevent contact between the plug and its seat by 
unbalancing; (3) to provide an identical pressure in upper and lower ends 
of the plug by means of a system that compensates the excess pressure at 
one end with the lack of pressure at the other end; (4) do not reduce the 
life nor the quality of the valve when solving the above mentioned 
problems. It is also desirable to provide a valve which is long-lasting 
and efficient as well as easy to manufacture at the lowest possible cost. 
The development of related valves is specified as follows: 
U.S. Pat. No. 1,584,699--Mar. 5, 1925 Non-lubricanted valve (present 
concept). It discloses a bronze bushing which serves as a jacket for the 
plug to rotate, keeping the plug in place by means of an helicoidal 
spring, it is a bottom entry plug valve. It has grooves for lubrication in 
the walls. It has a check valve that allows the pressure to flow to the 
bottom (larger diameter tapered side) in openning position and pushing the 
plug to its seat, the same than the spring, both providing tightening. 
U.S. Pat. No. 1,680,812--Aug. 14, 1928 Non-lubricated valve, directional at 
90.degree.. It refers to a dynamic balance mechanism similar to the idea 
of the present dynamic balance (see U.S. Pat. No. 4,174,092) by means of 
two holes which connect the port with upper and lower chambers of the 
plug, it has an helicoidal spring to keep the plug pisitioned with respect 
to the body, causing tightening and a excentric cam type system for 
closing the valve. 
U.S. Pat. No. 1,671,603--May 29, 1928 Lubricated valve. Dynamic balace 
patent, obtained when the pressure of the plug's upper and lower chambers 
is made even. The communication of the upper chamber is obtained through a 
hole in the body, preventing sealant leakage by means of a check valve. 
This, in part, is similar to the new dynamic balance design. (see U.S. 
Pat. No. 4,174,092). 
U.S. Pat. No. 2,079,774--May 11, 1937 Lubricated valve. It discloses plug 
balance through the action of 2 pistons connected to the plug mechanism 
(equalizer type), the reciprocating action of the pistons is obtained by 
the fluid pressure which helps separation and minimizes the tightening 
rotating force. 
U.S. Pat. No. 2,286,689--June 16, 1942 Lubricated valve. It discloses the 
plug balance by balancing the pressure in both ends of the plug which is 
obtained by the flow of fluid pressure, first to the lower chamber (larger 
side) and then through a lateral hole in the plug which carries the 
pressure to the sealant chamber, and to prevent the sealant from leaking 
there is a check valve. 
U.S. Pat. No. 2,945,668--July 19, 1960 Lubraicated valve. Bottom entry plug 
valve which has a sealant chamber similar to the present one. It discloses 
a dynamic balance produced by pressure difference between fluid and 
atmospheric pressures. Both plug ends are exposed to atmospheric pressure. 
It has no adjustable screw, instead it has a spring which positions the 
plug and allows its movement. 
U.S. Pat. No. 3,115,151--December 24, 1963 Lubricated valve. It discloses a 
pressure balance between the fluid side valve, the plug passageway in 
closed position and the plug chamber at the larger diameter side, it uses 
a sling valve placed in the plug, thus making pressures even, and the plug 
balance is complemented with the sealant at the chamber. 
U.S. Pat. No. 4,135,544--June 23, 1979 Lubricated valve. (Dynamic balance 
1st option). The balance is provided by an helicoidal spring in the 
sealing chamber, and the larger diameter of the tapered plug is exposed to 
the atmospheric pressure, obtaining the balance by pressure difference. 
U.S. Pat. No. 4,174,092 discloses an hydraulic balance valve which 
compensates the variations in the line pressure. When the pressure in the 
upper chamber diminishes to a pressure below to that of the line pressure, 
a check valve opens and thereby allows passage of the line pressure to 
said upper chamber, thus conpensating both pressures and thereby 
preventing valve lock up. 
SUMMARY AND OBJECTS OF THE INVENTION 
According to the above, it is clear that the object of this invention is to 
provide a lubricated and hermetic tapered plug valve with mechanical 
balance by means of a resilient mechanism. 
This technical improvement is aimed to obtain a hermetic valve whose plug 
is in axial balance with a predetermined position, in order that, during 
the operation it never gets tightened to its tapered seat, thereby the 
plug always has an easy rotation. 
In order to achieve this object of the invention, it is necessary that 
following conditions be met: 
(a) That the valve have a mechanism that actuates as a resilient element 
concentric to the longitudinal axis of the plug. 
(b) That there always be a predetermined plug position in respect to the 
body such that a small separation between the tapered walls of the body 
and the plug is guaranteed. 
(c) That the mechanism which actuates as the resilient element be of the 
spring type, in which the deflecting piece is a plane washer which 
actuates between two parts having slopping walls in order to attain a 
spring effect. 
(d) That the stem which drives the plug be always in contact with the 
valve's body, so that no displacement of the plug's axis is allowed. 
(e) When assembling the plug, consideration is given to the fact that the 
plug is first driven to a first adjustment position with respect to the 
body by means of a screw located in the larger side of the plug, 
therefore, a deflection in the spring washer is produced; at this moment a 
maximum separation between the tapered walls of the body and the plug 
exists. 
(f) When the line pressure actuates, a hydraulic force is produced on the 
larger side of the plug, whereby the plug will be driven to a second 
position with respect to the body and, consequently, the resilient 
mechanism keeps the balance and position of the plug, even though said 
mechanism would tend to solidify into forming one single piece, also, a 
minimum separation between the tapered walls of the body and the plug will 
prevail. 
In order to balance the hydraulic force described above, there is an axial 
force in the longitudinal axis of the plug, which is generated by the 
pressure of the sealant at the lower side chamber of the plug. Would the 
force caused by the sealing pressure be reduced to a level lower than the 
line's pressure, it will fill the sealant chamber, whereby the plug will 
continue to be in a static balance. 
The resilient mechanism will also prevent the tightening caused by the 
effect of the plug's weight when changing the valve's position, or, by 
changes in volume caused by temperature variations of the fluid controlled 
by the valve.

DETAILED DESCRIPTION OF THE INVENTION 
The valve consists of a body 11, a fluid passageway 15 which passes through 
tapered seat 14 on which plug 13 is seated. 
Such plug 13 has generally a truncated cone form and a hole 28 for fluid 
flow. When plug 13 is rotated 90.degree. the fluid flow is hermetically 
shut-off. Plug 13 has a groove or slit 23 in its upper side which receives 
the lower projections 22 of equalizer 17. Plane washer 16 fits on the 
upper perimeter 29 of tapered seat of the equilizer 17. Lower projection 
20 of the stem 12 enters the orifice of washer 16 and is placed on seat 
21. This allows conical plate 30 of stem 12 to fit in the bored washer 16. 
Therefore, washer 16 has a deflecting movement and provides a spring 
mechanical balance to plug 13. 
90.degree. rotating movement of plug 13 is produced by rotating movement of 
stem 12. 
Equalizer 17 has an upper perimeter 29 which is the seat of deflecting 
washer 16, said equalizer 17 has a seat 21 for projection 20 of stem 12. 
The wall between seat 21 and upper perimeter 29 is conical or tapered to 
allow deflection or spring movement of washer 16. 
Coupling between projection 20 and seat 21 is a free vertical movement. 
Movement between projection 22 and and groove 23 is vertically free. 
However, in both cases, there is a positive mechanical contact for a 
rotating movement. 
Stem 12 is firmly placed in hole 31 defined by upper cover 26, high 
pressure seal 25, valve body 11 and packing 32. 
Axial rotating movement of stem 12 and plug 13 and intermediate parts 
between them is limited to 90.degree. by flange 33 and stop 34. The safety 
device (pin) 35 of flange 33 fixes it in position. 
Lower cover 27, valve body 11 and plug 13 define a lower chamber 36 where 
plate 37 is located, which is positioned peripherically under pressure of 
gasket 38. Screw 39 is used to adjust plug's position. Cover 40 protects 
screw 39. Atmospheric seal 24 is paused in groove 18 to keep high pressure 
seal 25 from external damage. Although the above description sets forth 
one embodiment of same, it is understood that the scope of the protection 
applied for should be defined only by the following: