Abstract:
A method of installing annular seals on a plunger. A first step involves positioning an annular seal on a seal installation tool adapted to hold the annular seal in an expanded state. A second step involves positioning the annular seal so that the annular seal overlies a body of a plunger. A third step involves transferring the annular seal from the seal installation tool to a seal groove in the body of the plunger.

Description:
FIELD 
     A plunger with annular exterior seals and a method of installing annular seals on an exterior surface of a plunger. 
     BACKGROUND 
     Gas lift plungers have a number of annular exterior seals. A joint is positioned at each seal location to allow the disassembly of the plunger, in order to facilitate installation of the annular seals. Each joint is a potential failure point for the plunger. 
     SUMMARY 
     According to one aspect, there is provided a plunger, which has a cylindrical body. All or at least a portion of the body is in one piece with more than one circumferential exterior seal groove. Replaceable annular seals are positioned in selected ones of the seal grooves. 
     According to another aspect there is provided a method of installing annular seals on a plunger. A first step involves positioning an annular seal on a seal installation tool adapted to hold the annular seal in an expanded state. A second step involves positioning the annular seal so that the annular seal overlies a body of a plunger. A third step involves transferring the annular seal from the seal installation tool to a seal groove in the body of the plunger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein: 
         FIG. 1  is a perspective view of a plunger. 
         FIG. 2  is a perspective view of an elastomer seal being expanded by a truncated conical seal expanding member. 
         FIG. 3  is a side elevation view of the elastomer seal being transferred from the seal expanding member onto a seal installation tool. 
         FIG. 4  is a perspective view of the elastomer seal mounted on the seal installation tool. 
         FIG. 5  is a side elevation view of the seal installation tool overlying a plunger body. 
         FIG. 6  is a side elevation view of the elastomer seal being transferred from the seal installation tool onto the plunger body. 
         FIG. 7  is a perspective view of a seal carrier sleeve. 
         FIG. 8  is a side view in section of a seal carrier sleeve overlying a plunger. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment, a plunger generally identified by reference numeral  10 , will now be described with reference to  FIG. 1 . 
     Plunger  10  has a cylindrical body  12 . Body  12  is machined in one piece with numerous circumferential exterior seal grooves  14 . Replaceable annular seals  16  made from elastomer are positioned in seal grooves  14 . As depicted, annular seals  16  are positioned in every other seal groove  14 . Plunger  10  has the distinct advantage of having no joints. It will be appreciated that it not essential that there be no joints. Benefits could be gained by simply reducing the number of joints. This is done by placing more than one of seal grooves  14  on each portion of more than one portion of body  12 . 
     It would not be possible to make plunger  10 , unless some method were developed for installing annular seals  16  onto a one piece body  12 . 
     Referring to  FIGS. 2 through 6 , there will now be described a preferred method of installing annular seals  16 . Referring to  FIG. 4 , annular seal  16  is positioned on a seal installation tool  20 . Seal installation tool  20  is adapted to hold annular seal  16  in an expanded state. Seal installation tool  20  can take a number of forms. The form selected for illustration is a sleeve-form body  22  with an exterior surface  24  on which is positioned a seal seat  26 . Referring to  FIG. 5 , body  22  is positioned so that annular seal  16  overlies body  12  of plunger  10 . Referring to  FIG. 6 , annular seal  16  is then transferred from seal installation tool  20  to one of seal grooves  14  on body  12  of plunger  10 . 
     It will be appreciated that body  22  of seal installation tool  20  need not be in the form of a sleeve. It will also be appreciated that body  22  need not overlie plunger  10 , as long as annular seal  16  does. It will also be appreciated that seal seat  26  can be discontinuous, as annular seal  16  could be just as effectively held in an expanded condition by a plurality of fingers arranged in a ring. 
     Referring to  FIG. 2 , a seal expanding member  30  has been developed for use in expanding annular seal  16 . Seal expanding member  30  has a truncated conical body  32 . It will be appreciated that body  32  need not be truncated, but only the lower portion of body  32  is needed to perform the expanding operation. An upper portion of body  32 , does not serve a useful function if its outer diameter is smaller than the inner diameter of annular seal  16 . It will be appreciated that the conical form is merely a convenient form of inclined plane shape to accomplish the desired objective. Other forms of inclined plane could be used to expand annular seal  16  onto seal seat  26 . Referring to  FIG. 3 , once annular seat  16  is expanded it is transferred from seal expanding member  30  to seal seat  26  of seal installation tool  20  in preparation for installation, as described above. 
     Variation: 
     Referring to  FIG. 7 , instead of the user providing seal expanding member  30  with an inclined plane to expand annular seal  16  and then transferring it to seal seat  26 , an alternative way of providing expanded seals  16  is to provide an annular seal carrier sleeve  40 , or seal cartridge, that is provided with a number of individual seals  16  positioned on an outer seal carrying surface  42 . Seals  16  can then be slid off sleeve  40  onto the desired position on cylindrical body  12  of plunger  10 . This may be done at a centralized location, such as a factory, which would allow the process to be automated, or to be accomplished using machinery or tools that would otherwise be impractical for economic or other reasons. For example, a supplier may purchase sleeves  40  from a manufacturer, which would then be sold to the individual users. 
     The inner diameter of sleeve  40  is large enough to receive cylindrical body  12 . Referring to  FIG. 8 , in addition to carrying seals  16 , the inner diameter of sleeve  40  may be appropriately sized to be used as a test gauge, where if sleeve  40  is able to pass over the existing seals  16  on body  12 , it is necessary to replace them. For example, when in a contracted state on cylindrical body  12 , seals  16  may have a contoured outer surface, such as concave, convex, ribbed, etc. as is known in the art, such that there are at least two different diameters. As seals  16  are worn, the larger outer diameter is reduced to a point where the seals no longer operate in the desired manner. The inner diameter of sleeve  40  may be appropriately sized between the two outer diameters to properly determine when this point has been reached. This feature may also apply to seal installation tool  20  discussed above. 
     In this patent document, the word “comprising” is used in its non-liming sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.