Pipe plugging device

A method of releasably plugging the interior of a pipe section comprising the steps of:

• inserting a releasable plugging device lengthwise into said pipe section, said releasable plugging device comprising:
• (a) an elongated cylindrical central support member;
• (b) a pair of flexible sealing means, each sealing means defined by a pair of thin, flexible disks with each disk having a concavo-convex surface, said disks mounted in coaxially spaced relation to one another on said central support member terminating in an outer circumferential edge having an effective diameter greater than that of the internal diameter of said pipe section so as to be movable into sealed engagement with the inner wall surface of said pipe section when said releasable plugging device is fully inserted lengthwise into said pipe section;
• (c) said central support member including means for slidably mounting one of said sealing means for independent axial sliding movement on said central support member with respect to the other of said disks;
• and
• (d) limit stop means for limiting slidable movement of said one sealing means, each of said disks being flexible in opposite axial directions such that their concave surfaces alternately will face in the same or opposite directions to one another in response to lengthwise movement of said support member through said pipe section;
• initially advancing said releasable plugging device lengthwise into said pipe section until said plugging device is fully inserted into said pipe section and the concave surfaces of said disks face in the same direction but opposite to the direction of initial advancement into said pipe section;
• moving said releasable plugging device in the direction of withdrawal from said pipe section until said disk of said other sealing means is reversed to cause its concave surface to face the concave surface on the disk of said one sealing means as said disk of said one sealing means slides away from said disk of said other sealing means;
• continuing to move said releasable plugging device in the direction of withdrawal until the disk of said one sealing means reaches its limit of slidable movement and is reversed to cause its concave surface to face in the same direction as the disk of said other sealing means;
• and
• followed by once again advancing said releasable plugging device in the direction of insertion to cause the disk of said other sealing means to reverse its concave surface to face away from the direction of advancement as the disk of said one sealing means slides toward the disk of said other sealing means with its concave surface remaining in a direction facing away from said concave surface on the disk of said other sealing means.