Abstract:
An improved annular seal assembly and packless stuffing box for an oil pumping unit of the type having a polished rod reciprocatingly extending therethrough and downhole to a pump located at the lower end of a borehole. The stuffing box has a main body that terminates in a tubing adaptor at the lower end thereof by which it can be mounted to the upper end of the tubing of a wellhead. The main body houses the annular seal assembly that includes a pressure set seal pack for sealingly engaging the polished rod. The polished rod reciprocatingly extends through the seal assembly and main body. The seal assembly includes paired metal annular cones which are capable of sealing under conditions present in the stuffing box. The seal assembly withstands such conditions far longer than traditional seal assemblies, thus reducing cost and downtime of the pumping unit.

Description:
RELATED U.S. PATENT DOCUMENTS 
       [0001]    This patent application is an original patent application in the United States. No federal funding was used in the development of this invention. 
       DESCRIPTION 
     Summary of the Invention 
       [0002]    The present invention provides a stuffing box having an improved design of a pressure active seal assembly consisting of pairwise arrangements of hollow cones, which adds unexpected long life to the seals thereof. 
       BACKGROUND OF THE INVENTION 
       [0003]    Standard oil pumping units, also known as pumpjacks, have several components that are essential for operation. One such unit is the polished rod, which is visible from the exterior of the unit. The polished rod moves up and down in a vertical plane, when the unit is in operation. 
         [0004]    The polished rod moves through a stuffing box, which contain seals that lubricate the polished rod, and yet seal the unit to prevent oil leaks. These seals are often constructed of graphite or other soft, malleable material, in order to closely conform to the motions of the polished rod. 
         [0005]    The difficulty with graphite seals, or seals of other soft material, is that they are not durable. Seals must be replaced frequently, at high replacement cost, due to manpower needs, replacement materials, and down time of the pumping unit. Yet, prior to the present invention, it was difficult to engineer hard materials to produce seals of long life and duration. 
         [0006]    A primary object of this invention is the provision of an improved stuffing box for a unit, or the like, having a seal assembly mounted within a main body thereof. There is a seal pack included within the seal assembly which is supported within a seal holder therefor. The seal assembly includes a series of pairwise mounted metal hollow conical seals, so configured to fit tightly around the polished rod. 
         [0007]    Another object of this invention is the provision of slots in the cones, which allow for expansion and contraction of the cones, according to ambient temperature and pressure conditions. This allows the cones to maintain their function of sealing the rod. 
         [0008]    Another object of this invention is to provide a sealing mechanism for a polished rod, which mechanism is comprised of hardened steel or other hard material. 
         [0009]    A significant object of the current invention is to provide a sealing mechanism for an oil producing unit that is significantly more durable than current devices of the same service. Thus, an important objective is to provide more time between replacement services for seals in an oil pumping unit. 
         [0010]    The above objects are attained in accordance with the present invention by the provision of a combination of elements which are fabricated in a manner substantially as described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
           [0012]      FIG. 1  is a longitudinal side view of the current invention, with partial translucency of the outer surface in order to indicate the presence of interior components. 
           [0013]      FIG. 2  is a longitudinal side view of the current invention, with the head cap removed. 
           [0014]      FIG. 3  is a longitudinal, cross-sectional, side view of the current invention, with interior components displayed. 
           [0015]      FIG. 4  is a side view of a single truncated annular hollow cone of the current invention. 
           [0016]      FIG. 5  is a cross-sectional, view form below of the base of a single truncated annular hollow cone of the current invention. 
           [0017]      FIG. 6  is a side view illustrating details of a single truncated annular hollow cone of the current invention. 
           [0018]      FIG. 7  is a perspective lower side view illustrating details of a single truncated annular hollow cone of the current invention. 
           [0019]      FIG. 8  is a side view of the cap of the housing cylinder of the current invention. 
           [0020]      FIG. 9  is a side view of the base element of the housing cylinder of the current invention. 
           [0021]      FIG. 10  is a view of a pumping unit, or ‘pumpjack’, embodying the current invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
         [0023]      FIG. 1  discloses the overall structure of the novel packless stuffing box  100  of the current invention. The ‘box’ is actually a cylindrical tube, with sealing elements inside the tube. 
         [0024]    The main body of the outer tube  200  has upper and lower end caps,  20  and  40 , respectively. The entire unit is designed to fit snugly around a polished rod, at the lower end thereof, near the borehole exit. 
         [0025]    A schematic depiction of stuffing box  100  is shown in  FIG. 2 . The hollow nature of the tube  200  is emphasized in this depiction. 
         [0026]      FIG. 3  reveals more details of the current invention  100 . The head  20  is shown at the bottom, with exit ports  25  to vent gases. Interior to the main body are pairs of annular seals  50 , in the form of truncated cones. The cones fit pairwise, base-to-base in each pair. Pairs meet other pairs at top-to-top junctures  70 . Optionally, O-rings or other sealant aid may be used at these junctions  70  to ensure a tight seal. 
         [0027]    When assembled, the cones and main body form a channel  80  into which will fit a polished rod of a pumpjack unit. The rod can move up and down in a vertical plane, or can rotate around its long axis. The present invention will maintain a tight seal and prevent the escape of oil. 
         [0028]    An annular seal cone  50  of the preferred embodiment of the current invention is shown in  FIG. 4 . The cone is hollow, and open at both its top and its base. Preferably the cone is constructed of steel. The cone also has a through slot  54 , and a recessed base  56 . The slot allows for expansion and contraction as temperatures and pressures increase and decrease. The recessed base allows for tight coupling with another seal cone, to form the pairs shown in  FIG. 3 . The hollow area inside the cone is designed to accommodate the shaft of the polished rod in a pumpjack unit. 
         [0029]      FIG. 4  portrays one of the paired metal sealing cones  50  in a perspective view from the side. The cone is truncated at the top, and open at both top and bottom, and is hollow. Preferably the cone is constructed of ⅛ inch carbon steel. The cone has a through slot  54  extending vertically from the top to the bottom of the cone. This allows for thermal expansion of the ring without damaging the walls of the cone. Other slots (no shown in  FIG. 4 ) are desirable, but must not be through slots, in order to preserve the integrity of cone  50 . Also present on the cone  50  is a channel  56  that runs along the lower edge of the cone, at the base. This channel allows for close fitting of two paired cones  50 , base to base. 
         [0030]      FIGS. 5 and 6  display the sealing cone  50  from alternate view angles.  FIG. 5  shows a preferred embodiment of cone  50 , viewed from its base. From this vantage point, through slot  54  and partial slots  58  are clearly seen. The slots are optimally placed at 120-degree intervals around the circumference of the cone. The dashed line  59  represents the wall of the cone  50  rising behind the base in this view. 
         [0031]    Turning now to  FIG. 6 , sealing cone  50  is displayed upright, from a side view. Here the bottom channel  56  is clearly displayed, as is through slot  54 , rising vertically from base to top of truncated cone  50 . Partial slots  58  are also shown, but in the preferred distribution of slots, partial slots  58  would be obscured in this view, as they lie on the rear side of the cone as viewed from the side of through slot  54 . 
         [0032]      FIG. 7  displays the same cone from the base in a perspective view. The depressed base  56  is shown, with through slot  54  and partial slots  56  displayed to advantage. 
         [0033]    The entire stuffing box  100  has a cap and a base. The cap is shown in  FIG. 8 . The cap preferably has various levels of fit, providing microchannels for oil to flow in and around the cones. 
         [0034]      FIG. 9  shows the base of the entire stuffing box. Although not seen in this side view, the base is also hollowing, in order to accommodate the polished rod. Thus, there will be a through hole inside the base, from top to bottom, of the dimensions of the polished rod. 
         [0035]      FIG. 10  shows how the present invention  100  fits into its designed operational environment. The standard oil pumpjack unit comprises a walking beam, a head, and a polished rod or ‘sucker rod. The polished rod extends down to the wellhead of the oil well. At the junction of the polished rod and wellhead, a stuffing box, such as that of the current invention, is placed to create a seal preventing oil leaks, and allowing the unit to pump oil from the ground. 
         [0036]    As shown in  FIG. 10 , the current invention  100  will act as a sleeve, or collar, around the polished rod as it meets the wellhead. The rod moves up and down, forcing oil to the surface, while the stuffing box preserves proper pressure and prevents leaks. 
         [0037]    The new combination of the novel packless stuffing box and pressure set seal packs provides new and unobvious and patentable features that reduce the cost of producing an oil well with a pump jack unit. 
         [0038]    While the invention has been described in connection with a preferred embodiment or embodiments, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.