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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to valves. More specifically, the invention is a relievable check valve assembly for oil or water wells comprising a check valve with a pin, a guide and triggers of various shapes. 
     2. Description of the Related Art 
     The relevant art of interest describes various check valve assemblies, but none discloses the present invention. There is a need for an efficient and inexpensive check valve for use in wells in order to drain fluid out of a plunger type pump and a string of tubing prior to pulling them out of a well. Removing the fluid, water or oil, and entrained debris from inside the tubing will greatly reduce the weight of the string of tubing and thus make the whole operation easier and safer. The relevant art will be discussed in the order of perceived relevance to the present invention. 
     U.S. Pat. No. 1,543,179 issued on Jun. 23, 1925, to Andrew Miller et al. describes a valve trip mechanism for bleeding the tubing of a deep well while the tubing is being extracted. When the working barrel is pulled toward the surface, an edge of the barrel contacts the head of a rod which shifts a lever. The lever operates a lift rod which pushes a ball valve out of its seat within the working barrel and allow fluid within the tubing to drain back into the ground and lessen the weight of the tubing being pulled out. The valve trip mechanism is distinguishable for utilizing a ball valve motivated by a pivoting lift rod consisting of three segments and a spring. 
     U.S. Pat. No. 1,314,070 issued on Aug. 26, 1919, to William H. McKissick describes a drainage valve for deep well pumps comprising a first embodiment of FIGS. 1 and 2 drawn to two spaced collars on bowed springs which cause the opening of a ball valve in a thick coupling by pushing down a perforated sleeve against the ball and its compression spring. The second embodiment of FIGS. 3 and 4 entails a standing ball valve resting on an apertured coupling in contact with a sliding double collared and outwardly bowed springs element and having an internal T-shaped bolt with extending arms. The arms immobilize the upper collar member having L-shaped arms by twisting prior to removal to cause the shaft of the T-shaped bolt to push up the ball and open the drain pipe. The drainage valves are distinguishable for requiring ball valves. 
     U.S. Pat. No. 4,856,756 issued on Aug. 15, 1989, to Linsey L. Combs describes a well bottom release valve assembly comprising a well bottom release valve axially aligned just above a down hole pipe. A short pipe section with a spring biased tight fitting sleeve is manually controlled from the surface by a cable to open drainage ports in the sleeve that allow the water contained within to drain out of the tubing above the down hole pump. The valve assembly is distinguishable for its above ground manual cable control element. 
     U.S. Pat. No. 1,660,486 issued on Feb. 28, 1928, to John A. Friend describes a drain valve for an inner tube of deep well pumps for drainage during removal of the inner tube from the well casing. A casing integrated with the tubing contains an elaborate mechanism which causes the opening of a drainage hole by movement of a plunger attached to a lever (and leaf spring) having a projection which catches in the space between two casings connected by a coupling. A cam lug of the lever pushes down the plunger against a ball valve under spring compression away from its seat. The drain valve mechanism is distinguishable for its numerous parts involving a lever, a plunger, a ball valve, and a lever. 
     U.S. Pat. No. 3,995,691 issued on Dec. 7, 1976, to Floyd R. Hedgecock et al. describes a tool for draining fluids in an oil well while removing a well conduit. An enclosure of an apertured tubular housing connected to a well conduit by two couplings permits drainage from the second bottom coupling when the pushrod attached to the fluid pump is uplifted. The tool is distinguishable for its apertured housing and couplings. 
     U.S. Pat. No. 4,637,471 issued on Jan. 20, 1987, to Paul B. Soderberg describes a tubing drain valve device useful with heavy sand-bearing oil and its method of use in a borehole. A first tubular member of a sub is connected to a pipe string in a casing with three dogs which engage the casing. A second tubular member surrounds an upper portion of the first tubular member and is attached by three shear pins and supported by a compression spring. As the pipe string is pulled up, the dogs contact the casing wall and cause the spring to compress for approximately three feet before the shear pins break and open slots for drainage of the fluid in the pipe string. The tubing drain valve device is distinguishable for its required dogs and shear pins. 
     U.S. Pat. No. 4,645,007 issued on Feb. 24, 1987, to Paul B. Soderberg describes a sub including a tubing drain valve and its method of use in a borehole. The sub comprising a tubular member is inserted in a pipe string by an upper connector and a lower connector and includes a tubular piston connected to a sucker rod. The tubular member has a C-spring with six bosses contacting the tubular member. Three dogs located inside the tubular member are positioned for contacting two semi-circular members on a lowermost position of the sucker rod to hold the uplifted pipe string in place to allow the fluid to drain through aligned ports in the tubular piston and the tubular member. The sub and tubing drain valve are distinguishable for requiring a C-spring with bosses, semi-circular holding members, a hollow piston, and dogs. 
     U.S. Pat. No. 4,782,895 issued on Nov. 8, 1988, to Jean-Luc Jacob et al. describes a pumped oil well bottom safety valve automatically closing when pumping stops and reopening when pumping resumes. A cylindrical valve body attached at the end of a production tube and below the valve pump has two cylindrical vertical channels. The first channel has a valve seat closed by a flap controlled by a lever and an orifice below the flap. The second channel is plugged on the bottom and the top with the top plug abutting a return spring. A push rod attached to the spring has a transverse second pressure valve and a notch for actuating the lever and flap. The bottom end of the push rod moves a piston closing an admission chamber having an orifice. The valve body is distinguishable for its numerous parts of a two-channelled body. 
     U.S. Pat. No. 5,310,005 issued on May 10, 1994, to William W. Dollison describes a flapper valve assembly with a floating hinge located between two pipe sections and used in oil and gas wells. A semicircular flapper body is supported by two pivoting struts and blocks a flow sleeve or can be folded behind the flow sleeve. The flapper valve assembly is distinguishable for its flapper and strut structure. 
     U.S. Pat. No. 5,425,416 issued on Jun. 20, 1995, to Michael N. Hammeke et al. describes a formation injection tool for down-bore in-situ disposal of undesired fluids. The oil and natural gas are expelled upwards in the upstroke of the pump and the mineral laden water is disposed underground in the lower disposal formations during the down stroke. The injection tool consists of three basic parts comprising an upper intake flow assembly, a middle seal mechanism and a lower discharge control device. The formation injection tool is distinguishable for its extensive structure. 
     Soviet Union Patent Application No. SU 1388-548 A published on Apr. 4, 1988, for Volg Oil Ind. describes an oil well expeller by using strata energy to drive a pump with its cylinder connected to an underground separator. The separator has two chambers with a piston and a poppet valve on a rod in the upper chamber and a compression spring and stop in a perforated lower chamber. Increasing pressure in upper chamber by the rising crude causes the piston to rise to close the poppet valve by the pressure difference. The crude enters the well tubing and up to decrease the pressure in the separator to move the piston down to expel the water through the perforations into the absorbing underground level. The device is distinguishable for its two fluid separating sections, piston and poppet valve structure. 
     Soviet Union Patent Application No. SU 1434-082 A published on Oct. 30, 1988, for Bashkir Oil Ind. describes a production well pump-out equipment with a drain valve comprising a cylinder having a seat for a ball and a piston under it with a rod interacting with the ball when the pump stops operation. The drain valve is distinguishable for its piston structure. 
     None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus, a relievable check valve assembly for oil wells and water wells solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     A relievable check valve assembly for oil or water wells is shown comprising a check valve with a pin, a guide and triggers of various shapes. There is a need for a check valve for controlling the liquid discharge from wells when removing the tubing. 
     Accordingly, it is a principal object of the invention to provide a check valve assembly for oil and water wells. 
     It is another object of the invention to provide a check valve assembly for oil and water wells when removing the in-ground tubing. 
     It is a further object of the invention to provide a check valve assembly for oil and water wells when removing the in-ground tubing for draining the liquid and entrained solids from the tubing back into the well. 
     Still another object of the invention is to provide a check valve assembly for oil and water wells when removing the in-ground tubing comprising a pin, a guide and a trigger. 
     It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational cutaway view of a first embodiment for a relievable check valve assembly for oil or water wells according to the present invention. 
     FIG. 2 is a perspective view of the first embodiment showing a guide inserted in a plate, a pin and a trigger with a conventional valve. 
     FIGS. 3A,  3 B and  3 C are schematic diagrams of the first embodiment showing the sequence of the valve operation. 
     FIG. 4 is perspective view of a second embodiment of a valve assembly having a trigger with an enlarged base. 
     FIGS. 5A,  5 B and  5 C are schematic diagrams of a third embodiment showing the sequence of the valve operation. 
     FIGS. 6A,  6 B,  6 C,  6 D and  6 E are schematic diagrams of a fourth embodiment showing the sequence of the valve operation. 
     FIGS. 7A,  7 B and  7 C are schematic diagrams of a fifth embodiment showing the sequence of the valve operation. 
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is directed to valves useful in oil or water wells for draining the fluids when removing well tubing from a down hole. FIGS. 1,  2 ,  3 A,  3 B, and  3 C illustrate a first embodiment of a check valve assembly  10 . In FIG. 1, a portion of an upper well tubing member  12  threadingly joined to a lower valve assembly casing member  14  are broken away to expose a conventional traveling valve unit  16  with its valve member  15  and cage  17 , and a modified standing valve unit  18 . A push rod  20  shown in an upstroke or open position is attached to a plunger  22  comprising steel discs  24  with two enclosed neoprene discs  26 . The first embodiment of the check valve assembly  10  in a closed position comprises a bell-shaped valve member  28  with an internally threaded stem  30 . The valve member  28  is configured to abut the valve seat  32  formed inside the valve assembly casing member  14 . An apertured planar steel disc  34  with three apertures  36  has a threaded edge  38  which is engaged by the internal threading  40  at the end of the well tubing  12 . A Teflon bushing  42  is positioned to seat on top of the disc  34  and its narrow portion to extend slightly below the disc through the central throughbore  44  in the disc. A flat headed bolt or guide pin  46  with a washer  47  secures a steel trigger  48  configured with a throughbore  50  and an upturned end  52  to the bushing  42 , the disc  34 , and the valve member  28 . 
     Turning to the diagrammatic partially sectional views of FIGS. 3A,  3 B and  3 C, wherein FIG. 3A depicts the stage when the push rod  20  initially begins a downstroke with the traveling valve unit  16  with its valve member  15  being uplifted from its valve seat  19  by hydrostatic pressure. The valve member  28  in the standing valve unit  18  is seated on the valve seat  32  and the trigger  48  has its upturned end  52  facing up. The fluid trapped in the region between the two valve units is forced through the open traveling valve unit  16  into the upper region. It should be noted that the relievable check valve assembly  10  is unaffected by this operation. 
     FIG. 3B depicts the normal operation of a standard reciprocating plunger type pump on the downstroke of the traveling valve unit  16 . The upstroke motion causes the upper valve member  15  of the traveling valve unit  16  to close and the lower valve member  28  to open temporarily through hydrostatic pressure to force the fluid below the standing valve unit  18  to be pumped up into the tubing. Again, the relievable check valve assembly  10  is unaffected by this operation. 
     FIG. 3C illustrates the operation of the relievable check valve assembly  10  when the well operator desires to pull up the string of tubing or to clear trash out of the standing valve unit  18 . The well operator disconnects the rod string and sets it down on the bottom of the pump. This action causes the traveling valve member  15  to strike the guide pin  46  to raise the trigger  48  of the relievable check valve assembly  10  and the standing valve member  28 , and simultaneously raise the traveling valve member  15  to cause the entrained well fluid to drain from the tubing back into the well. 
     FIG. 4 illustrates a second embodiment for a modification of a check valve assembly  54  comprising an inverted U-shaped frame portion  56  on a body portion  58  having external threading  60  for securing to an end of the well tubing  12 . The frame portion  56  has a throughbore (hidden) to support a guide pin  62  and a trigger  64  configured with a U-shaped cross-section, an aperture  66 , a wide flanged base portion  68  straddling the frame portion  56 , and tapering to a raised tip  70 . The head  46  of the guide pin  62  is seated with a washer  47  on the trigger  64 . The trigger is connected by the guide pin  62  to the bell-shaped standing valve member  28  seated on a valve seat (hidden) in the lower region of the body portion  58 . 
     FIGS. 5A,  5 B and  5 C illustrate a third embodiment  72  utilizing a double curved trigger  74  standing on a raised Teflon bushing  76  in the third standing valve unit  78  in a sequence described above for the second embodiment of FIGS. 3A to  3 C. 
     FIGS. 6A,  6 B and  6 C illustrate a fourth embodiment  80  utilizing a hinged trigger  82  in the fourth standing valve unit  84  in a similar sequence. FIGS. 6D and 6E depict the hinged trigger  82  having two Y-shaped elements  86  joined by a hinge  88 . 
     FIGS. 7A,  7 B and  7 C illustrate a fifth embodiment  90  utilizing a straight, elongated and planar trigger  92  in the fifth standing valve unit  94 . 
     Thus, various configurations of the trigger  62  have been illustrated to function effectively in standing valve units of the present invention. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Summary:
A relievable check valve assembly having various trigger forms for oil wells and water wells adapted to control the liquid flow when inserted tubing is being removed from a well.