Rod packing

Abstract

A tangentially cut rod packing ring is provided. The tangentially cut rod packing ring comprises a first ring formed from a plurality of segments. Each of the segments has a portion of two interfaces where each interface slidably engages an interface of an adjacent segment. One interface terminates at a leading surface. One interface has a stop surface. The leading surface is originally separated from the stop surface by a gap. As the interfaces slidably move, the gap lessens until the leading surface abuts the stop surface. The tangentially cut rod packing ring also comprises a second ring formed from a plurality of segments. The second ring has a first portion and a second portion. The first portion forms as shelf on which the first ring sits. The second portion surrounds the first ring. An elastic member in a groove on the outer surface of the second portion provides a compressive force on both the second ring and the first ring.

1 . A packing ring set for a rod, comprising:
 a first ring comprising a plurality of segments formed by tangential cuts along a first ring segment interface between each of the plurality of segments wherein each of the plurality of segments is slidably movable along the first ring segment interface, the first ring having a first ring inner diameter and a first ring outer diameter;   a second ring having an outer surface comprising a plurality of segments formed by tangential cuts along a second ring interface between each of the plurality of segments wherein each of the plurality of segments is slidably movable along the second ring segment interface, the second ring comprising:   a first portion having a first portion inner diameter and a first portion outer diameter   a second portion having a second portion inner diameter substantially equal to the first ring outer diameter and a second portion outer diameter substantially equal to the first portion outer diameter such that the first portion and second portion together form a shelf sized to accommodate the first ring;   a groove formed on the outer surface of the second ring; and   an elastic member disposed in the groove providing a compressive force on the second ring and the first ring.   
     
     
         2 . The packing ring set of  claim 1  wherein the elastic member comprises a spring. 
     
     
         3 . The packing ring set of  claim 1  wherein the elastic member comprises an o-ring. 
     
     
         4 . The packing ring set of  claim 1  wherein the first ring segment interface each have a leading surface and a stop surface such each leading surface has a corresponding stop surface such that the plurality of segments slidably move with respect to each other until at least one leading surface abuts at least one stop surface. 
     
     
         5 . The packing ring set of  claim 1  wherein the second ring segment interface each are through cuts. 
     
     
         6 . The packing ring set of  claim 4  wherein the second ring segment interface each are through cuts. 
     
     
         7 . The packing ring set of  claim 1  wherein the first portion inner diameter is substantially equal to the first ring inner diameter. 
     
     
         8 . The packing ring set of  claim 1  wherein the first portion inner diameter is greater than the first ring inner diameter. 
     
     
         9 . The packing ring set of  claim 4  wherein a gap initially separates the leading surface from its corresponding stop surface. 
     
     
         10 . The packing ring set of  claim 9  wherein the gap initially separating the leading surface from its corresponding stop surface is between 1 and 10 millimeters. 
     
     
         11 . The packing ring set of  claim 9  wherein the gap initially separating the leading surface from its corresponding stop surface is greater than 4 millimeters. 
     
     
         12 . The packing ring set of  claim 9  wherein the gap initially separating the leading surface from its corresponding stop surface is between 4 millimeters and 10 millimeters. 
     
     
         13 . The packing ring set of  claim 9  wherein the gap initially separating the leading surface from its corresponding stop surface is between 6 and 8 millimeters. 
     
     
         14 . The packing ring set of  claim 9  wherein the gap initially separating the leading surface from its corresponding stop surface is about 8 millimeters. 
     
     
         15 . An apparatus comprising:
 a piston rod moving between a high pressure and a low pressure; and   a packing ring set for the rod, comprising:   a first ring comprising a plurality of segments formed by tangential cuts along a first ring segment interface between each of the plurality of segments wherein each of the plurality of segments is slidably movable along the first ring segment interface, the first ring having a first ring inner diameter and a first ring outer diameter;   a second ring having an outer surface comprising a plurality of segments formed by tangential cuts along a second ring interface between each of the plurality of segments wherein each of the plurality of segments is slidably movable along the second ring segment interface, the second ring comprising:   a first portion having a first portion inner diameter and a first portion outer diameter   a second portion having a second portion inner diameter substantially equal to the first ring outer diameter and a second portion outer diameter substantially equal to the first portion outer diameter such that the first portion and second portion together form a shelf sized to accommodate the first ring;   a groove formed on the outer surface of the second ring; and   an elastic member disposed in the groove providing a compressive force on the second ring and the first ring.