Bullet Seal

A bullet seal tail section is reconfigured from a groove flanked by tapered surfaces that engage an o-ring seal to an end design on the bullet seal that has tapered surfaces that meet at a first angle and a pin with an end taper that has counterpart surfaces that slope more with respect to an axis of the seal. The o-ring is on an opposite side of the pin from the tail of the bullet seal. Large differentials evenly push out the bullet seal tail and uniformly compress the o-ring for a larger contact area at greater contact force than previously known. The o-ring is reformed into a generally quadrilateral shape from round due to the applied loading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 11-17it can be seen that the bullet seal40has been redesigned to eliminate the deep groove with parallel walls in favor of a more open chevron shape which is defined by end walls42and44. An adjacent pin46has a flat back48that faces the o-ring50and is preferably perpendicular to the axis52as better seen inFIG. 18. Surface48may have a slight slope or can be formed of multiple surfaces or an arcuate shape without departing from the scope of the invention. Included angle54is smaller than included angle56formed by surfaces58and60on the pentagonal shaped pin62leaving a gap64between the pin62and the bullet seal40at axis52under low load conditions such as100PSI that is illustrated inFIG. 18. This angular difference in opposing surfaces that is preferably in the order of about 5 degrees but can vary between 1 and 10 degrees ultimately accounts for even loading on surfaces42and44in response to a radial force represented by arrow66branches into components represented by arrow groups68and70to result in closing the gap64and uniform outward loading to enhance contact stress and contact area. At the same time with the differential at only1000PSI note how the o-ring72has taken the shape of surface48of the pin62. The o-ring72has also started to form an enlarging contact surface74and76on opposed sealing surfaces78and80. Arrows82and84respectively represent the loading force from the o-ring72and the reaction force from the opposing sealing surfaces.FIGS. 20-22show what happens at higher pressure loading. The contact stress inFIG. 22is somewhat higher than the known design shown inFIG. 10and the contact area is dramatically larger in the order of twice as large. What this means is the present invention results in more reliable sealing as the contact area has doubled for identical loading conditions of 500 degrees F. and 20,000 PSI.

The performance improvement comes from one or more new features not found in the old design. The deep groove with parallel walls such as20or22has been eliminated in favor of a more broadly open chevron shape using surfaces40and42. There is now a pin with leading surfaces58and60preferably at a slightly greater angle from the axis52than opposing surfaces42and44on the bullet seal40. This provides uniform outward loading as shown inFIG. 19and prevents or minimizes the collapsing of the bullet seal which would otherwise reduce contact sealing area.

FIGS. 11-17illustrate the mirror image layout with an o-ring90straddled by mirror image pins92and94and further out the opposed bullet seals40and96. As the loading at 500 degrees F. increases the o-ring90is reformed into more of a quadrilateral or square shape confined as it is on radially opposite sides by sealing surfaces98and100. In the axial direction the confining surfaces are102and104of pins92and94respectively. Here the symmetrical o-ring deformation contributes to a greater sealing contact area when the differential pressures get to the level of 20,000 PSI as illustrated inFIG. 17.

Those skilled in the art will also appreciate that the pins92and94are annular ring shapes as are the bullet seals such as40and of course the o-rings72or90. All fit in an annular gap defined by opposed circular surfaces such as98and100. An assembly can be a mirror image as inFIGS. 11-17or it can be one directional such asFIGS. 18-21.