Plug for heat exchanger tubes

A tube plug kit for sealing the end of a tube is provided. The tube plug kit includes a tube plug having a housing member and a locking member, an insert member having a threaded end portion received within the threaded portion of the bore and an enlarged portion positioned to be drawn within the smooth portion of the longitudinal bore in response to rotation of the insert member in the longitudinal bore. The tube plug kit also includes an actuating tool and a tapered member between the enlarged portion of the insert member and the longitudinal bore of the housing member. The enlarged portion has a recess therein for receiving the actuating tool.

BACKGROUND OF THE INVENTION

The present invention relates to improvements for a plug used to form a seal for tubes, pipes and similar conduits which transport steam, liquid or gases under pressure.

An earlier version of this type of plug commercially exploited by the present Applicant is disclosed in previous U.S. Pat. Nos. 4,653,540 and 5,289,851, the specifications of which are hereby incorporated by reference. The plug disclosed in U.S. Pat. No. 4,653,540 comprises a hollow housing member which has at one end a relatively large open bore surrounded by a thin wall, and a relatively smaller threaded bore which communicates with the larger bore. An insert member is provided which, in use, is threaded into the smaller bore thereby causing a tapered member, which may be formed on the insert member, to engage the open end of the large bore causing it to expand and bear against the wall of a heat exchanger tube into which the heat exchanger tube plug has been inserted. During use, the housing member is prevented from rotating relative to the heat exchanger tube by means of an eccentric assembly which is mounted on the end of the housing member. At the other end, the insert member has a cylindrical portion and a centrally disposed, integrally formed nut portion. The nut is proportioned to be grasped by a wrench for screwing the insert member into the housing member. The disclosure also suggests that instead of the projecting nut portion, a hexagonal recess may be formed in the end of the cylindrical portion for insertion of a hex wrench or similar tool. The insert member is specified as being integrally formed. A coil spring34surrounds the eccentric ring36to provide locking engagement against the inner surface of the heat exchanger tube.

The clutch spring on the eccentric ring was abandoned in the production model of this plug. Instead, a knurled outer surface for the eccentric  ring and also short axial grooves on the plug body were added in order to prevent slipping when the eccentric cam actuated.

Also, annular grooves were added to the plug body to increase the sealing potential of the plug. If the plug was installed in a tube that had corrosion, then the raised portion of the serration would cut through any scale and would be stored in the groove thereby enhancing the mechanical contact seal.

Early on during manufacture of the plug defined in U.S. Pat. No. 4,653,540, the plugs had a machined male hex that would accommodate a {fraction (11/32)} inch socket. This, however, proved unsatisfactory because the sockets split and could not be turned down to a diameter in order to fit in any tube smaller than ½ inch. This would be necessary when the plug is recessed within the end of a tube to be sealed. The next design evolution entailed broaching a ¼ inch female square drive in plugs from 460 inches to 0.610 inches in diameter and a ⅜ inch square drive in all plugs 0.620 inches and larger.

U.S. Pat. No. 5,289,851 describes a tube plug that can be provided in dimensions down to 0.420 inches, yet which permits installation torque values of up to 700 inch pounds. In this improved plug, the insert member as disclosed in U.S. Pat. No. 4,653,540, has been replaced with a T45 Torx® socket head screw combined with a separately machined cone having an internal passage threaded to match the threads of the screw. A T45 Torx® drive can be torqued to 764 inch pounds before failure which permits a recommended installation value of up to 700 inch pounds to be utilized.

In both U.S. Pat. Nos. 4,653,540 and 5,289,851 a tool is required to engage the insert member, and specifically, the recess portion or nut of the insert member, in order to screw the insert member into the housing member. Typically, the insert member includes a recess, such as a T45 Torx® socket head recess or a hexagon socket head recess, to engage the tool. However, such an arrangement creates a fair amount of slippage which can complicate the process of screwing the insert member into the housing member, especially in light of the high torsional forces that are being used. Thus, in order to reduce slippage between the tool and the recess of the insert member, an adhesive, such as a drive holding  compound, may be applied to the recess or the end of the tool that engages the recess. However, applying such an adhesive is cumbersome and messy.

It would therefore be an improvement in this art if a tube plug having an insert member were provided with a tool for securely engaging the insert member without the need for an adhesive.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a tube plug kit is provided. The tube plug kit includes a tube plug, an insert member, an actuating tool, and a tapered member. The tube plug has a housing member and a locking member. The housing member has a longitudinal bore that has a smooth portion communicating with a threaded portion. The locking member is mounted on the housing member. The insert member has a threaded end portion received within the threaded portion of the bore and an enlarged portion positioned to be drawn within the smooth portion of the longitudinal bore in response to rotation of the insert member in the longitudinal bore. The actuating tool including a head. The head has a compression member for engaging the insert member. The tapered member is between the enlarged portion of the insert member and the longitudinal bore of the housing member. The enlarged portion has a recess therein for receiving the head. This new design allows for a tube plug that can be provided in dimensions down to 0.250 inches in diameter, yet which permits installation.

In one aspect of the present invention, a tube plug kit for sealing an end portion of a tube is provided. The kit includes a tube plug, an insert member, an actuating tool, and a tapered member. The tube plug has a housing member and a locking member. The housing member is sized for insertion within the end portion of the tube. The housing member has a longitudinal bore comprising a smooth portion communicating with a threaded portion. The locking member connects with the housing member for locking the inserted housing member against rotation relative to the tube. The insert member has a threaded end portion received within the threaded portion of the bore and an enlarged portion positioned to be drawn within the smooth portion of the bore in response to  rotation of the insert member in the housing member. The tapered member is between the enlarged portion of the insert member and the longitudinal bore of the housing member. The enlarged portion has a recess therein for receiving the actuating tool. The tapered member is formed separately from the insert member in the form of a truncated cone with a bore therethrough for receiving the threaded end portion of the insert member. The tapered member and the enlarged portion are sized to cause the smooth portion of the bore to expand, thereby providing a seal between the housing member and the tube.

In one aspect of the present invention, a tube plug kit for sealing an end of a tube is provided. The tube plug kit includes a body portion, locking means, an insert member, an actuating tool, and a separately formed tapered member. The body portion is sized to be received within the tube with a minimum of clearance. The body portion has a friction enhancing outer surface and a central bore therein with a portion of the bore having a smooth inner surface and a smaller radiused portion having an internal thread. The locking means comprises an eccentric ring rotatably mounted on a post projecting axially from an end of the body portion to prevent the body portion from rotating within the tube. The ring has a friction enhancing external cylindrical surface. The insert member comprises a headed screw having a threaded portion threadingly received within the threaded bore portion of the body portion. The actuating tool includes a head, wherein the head includes a compression member for engaging the insert member. The tapered member is for engaging with the smooth bore portion of the body portion. The tapered member has a frustoconical member with a bore therethrough for engaging with the threaded portion of the insert member. The insert member has a driving recess in an end thereof opposite the threaded portion for receiving the head. The the tapered member and the enlarged portion are sized to cause the smooth portion of the bore to expand upon threaded insertion of the insert member into the body portion, thereby providing a seal between the body portion and the tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a tube plug kit. The tube plug kit includes a tube plug having a housing member and a locking member. The  housing member has a longitudinal bore that has a smooth portion in communication with a threaded portion. The locking member is mounted on the housing member for locking the inserted housing member against rotation relative to a tube. The tube plug kit also includes an insert member having a threaded end portion received within the threaded portion of the bore and an enlarged portion positioned to be drawn within the smooth portion of the longitudinal bore in response to rotation of the insert member in the longitudinal bore. The kit also includes an actuating tool and a tapered member between the enlarged portion of the insert member and the longitudinal bore of the housing member. The enlarged portion has a recess therein for receiving the actuating tool. Since the tube plug kit uses an actuating tool, the kit does not require the use of an adhesive for securely engaging the insert member.

InFIG. 1a boiler tube plug10is shown which is made in accordance with the present invention. The plug10comprises a hollow housing member12and an insert member14. The housing member12has a cylindrical body16, the rear portion of which is formed with a large open bore18. The bore18is surrounded by relatively thin wall20, the end portion22of which will expand outwardly to provide a seal for a boiler tube as is shown inFIG. 5, when the insert member14is screwed into the housing member12. The housing member12also includes a relatively smaller internally threaded cylindrical bore28which communicates with the large bore18.

At its front end30, the housing member12is provided with a locking member32which serves to lock the housing member tightly within the boiler tube24, as is shown inFIGS. 4 and 5, so that the insert member14can be screwed into the housing member12. In one embodiment, the locking member32includes an eccentric assembly that comprises a cylindrical post34which projects axially from the front end30of the housing member12, a ring member36which is mounted eccentrically on the post and is rotatable thereon, as shown inFIG. 2. As is shown inFIGS. 1 and 2, the post34is disposed eccentrically relative to a longitudinal axis of the housing member12.

An outer cylindrical surface39of the ring member36is serrated or knurled in order to provide enhanced frictional gripping between the ring36and the tube24. The ring member36has a bore40which fits rotatably over the post34. The post has a groove42near a distal end44thereof for receiving a locking snap ring46. This snap ring retains the ring36on the post34.

The housing member12has a series of axial grooves48at the end adjacent to the ring member36for enhancing frictional gripping of the housing member12to the tube24to prevent continued rotation of the housing member12within the tube. The outer surface of the housing member12also includes a plurality of annular grooves50adjacent to the open bore18of the housing member to enhance the sealing characteristics of the plug as described below.

The insert member14is comprised of a headed cap screw52and a tapered member54. In one embodiment, the screw52is a Torx® socket head screw having a threaded shank56and an enlarged head58with a driving recess60formed in the head. While a Torx® socket screw comprises one embodiment, other types of recess drive apertures are known. In one embodiment, the screw52is a hexagon socket screw152having a hexagon socket recess160, as illustrated inFIG. 6.

An appropriate tool is used to engage driving recess60and to tighten or untighten the screw52. In one embodiment, the tool is an actuating tool101that is used to tighten or untighten the screw52. The actuating tool101includes a socket screw wrench for a fastener with an internal hexagon socket arrangement, particularly a hexagon socket screw. This internal polygon arrangement can of course also have a different number of corners. Preferably, the actuating tool101has a spherical-type tool head. The tool head may of course also be made in the form of a cylinder.FIGS. 7A and 7Bdepicts an actuating tool101. As shown inFIG. 7A, the actuating tool101includes a cylindrical hexagon shank103, which at its one end is provided with a tool head105. The tool head105includes a compression member140that flexes and engages at least a portion of the recess60of the screw52. In this manner, the actuating tool101is able to more securely  engage the recess60than a conventional tool. In one embodiment, the compression member140includes a spring washer121, as described below.

In one embodiment, the tool head105is made as a spherical hexagon head with an external hexagon arrangement107, as illustrated inFIG. 7B. Hexagon tool head105is integrally formed with shank103, whereby shank103comprises beveled faces109that slope toward a center axis of the tool so as to form a constriction111. In the area of constriction111, tool head105adjoins with faces113, which increase toward an end115of tool head105, i.e. their distance to the longitudinal axis of actuating tool101increases. In the further course of tool head105, a recess117is provided, which is realized as a substantially rectangular or U-shaped groove119, also referred to as neck. In the area between constriction111and groove119, tool head105is formed by a first spherical segment120. Groove119accommodates a spring washer121. In the further course of the tool head, toward end115, outwardly curved faces123sloping toward the center axis of actuating tool101adjoin groove119. Faces123are the outer faces of a second spherical segment125of tool head105to which a truncated cone127is attached. The truncated cone127with its truncated face129forms the end115of the actuating tool101. The truncated cone, along its lateral surface131, is provided with a polygon arrangement, particularly a hexagon arrangement133. It is apparent fromFIG. 7Bthat the external hexagon arrangement107, or tool head105, is formed by the first spherical segment120, the second spherical segment125, and the truncated cone127. In other words, faces113of the first spherical segment114, faces123of the second spherical segment125, and the lateral surface131each merge into each other. The actuating tool101is described in further detail in U.S. Pat. No. 6,302,001, the entire specification of which is hereby incorporated by reference.

The tapered member54has an internal passage61which is made to receive the external thread of the shank56of the screw52, as illustrated inFIGS. 1 and 8. In one embodiment, the internal passage61is threaded to mate with the external thread of the shank56of screw52, as illustrated inFIG. 1. In one embodiment, the internal passage61is a smooth surface, as illustrated inFIG. 8.  The tapered member54may either extend up to and abut a surface57of a head58of the screw as shown inFIG. 1, particularly for smaller radius insert members14, or it may have an outer diameter greater than the diameter of the head58such that the tapered member54will surround the head as illustrated inFIGS. 4 and 5. The tapered member54includes an outer surface62that engages the mouth of the large bore18. Preferably, the outer surface62is generally shaped like a frustoconical member, as illustrated inFIG. 1. In one embodiment, the outer surface62has a spiral groove64therein, as illustrated inFIG. 1. In another embodiment, the outer surface62does not have a spiral groove64therein, as illustrated inFIG. 8. In one embodiment, the tapered member54is separate and apart from the housing member12and/or the insert member14, as illustrated inFIGS. 1 and 8. In one embodiment, the tapered member54is integrally formed with the housing member12or the insert member14.

Although the insert member14could be made as an integral part, since these socket head screws are readily available commercial items, machining of the tapered member54permits a substantial savings in machine time over integral formation of the insert member14. The threaded shank56of the insert member14is sized to be received in the threaded smaller bore28of the housing member12.

In use, the assembled insert member14is inserted into the housing member12and the threaded shank56is inserted through the internal passage61and screwed into the threaded bore28until the outer surface62of the tapered member54engages the mouth of the large bore18and the insert member14can no longer be turned by hand. The eccentric ring member36is rotated relative to the post34, by hand, until it is approximately concentric with the body of the housing member12. In this condition, the plug10is sized so that it may be inserted into the end of a heat exchanger tube24to the position shown inFIG. 4, although the clearances between the plug and the tube wall is less than the exaggerated showing inFIGS. 4 and 5.

The driving recess60is then engaged with an appropriate tool, as described above, which causes the ring member36, which engages the sidewalls  of the heat exchanger tube with its knurled surface, to turn on the post34toward the eccentric position shown inFIG. 2. The ring member36thus presses tightly against an inner surface80of the heat exchanger tube24so that the ring member36can no longer turn on the post34and the housing member12is tightly locked against turning within the heat exchanger tube24.

When the drive recess60is further turned by the appropriate tool, the insert member14turns within the housing member12, with the threaded shank56screwing further into the small bore28. At the same time, the outer surface62engages an inner surface82of the large bore18and as the increasing diameter of the tapered member54enters the large bore18, it deforms the surrounding thin wall20of the housing member12outwardly, increasing its diameter as shown inFIG. 5. As the diameter of the thin wall20increases, the expanded end portion22engages the inner surface80of the heat exchanger tube24and makes an effective seal therewith. The annular grooves50increase the sealing potential of the plug. If the tube24has any corrosion on its inner surface80, the raised portions between the annular grooves50would cut through any scale and the scale would be retained in the grooves50, thereby enhancing the mechanical contact seal. Since an actuating tool101is used to securely engage the insert member14, adhesive is not required.