Flange Bolt Hole Alignment Pin

This invention relates generally to mating and aligning piping or rod flanges, and more particularly to a bolt hole alignment tool for assisting in the alignment process of piping flanges prior to final installation of bolts and nuts. This invention allows the alignment of mating flanges with a greater precision and without the use of leveraging tools typically required in the prior art. It gives the individual user the ability to quickly fit-up most joints without additional assistance even in confined spaces, thereby minimizing delays, especially those resulting from waiting for support personnel.

The bolt hole alignment pin of the present invention eliminates much of the difficulty encountered using the prior art methods of aligning flanged joints. The preferred embodiment of this tool is especially useful when joints require the insertion of gaskets which must be properly centered between two mating flanges. The bolt hole alignment pin includes a head, shaped for engagement by a wrench; a first portion of sufficient diameter to allow a slip fit with the bolt holes of the flanges; a second portion of smaller diameter for centering the gasket; a third portion of even smaller diameter which is offset from the second portion and tapered to a blunt point. This offset configuration causes the third portion to act as a cam when the head is turned, thus bringing the two mating flanges into alignment.

FIG. 1 is a side view of the preferred embodiment of the present invention.

FIG. 2 is a cross-sectional end view showing the non-concentric diameters of the embodiment of FIG. 1.

FIG. 3 is a cross-sectional view of the alignment tool inserted in the bolt holes of mating flanges with the tool in the locked position and the flanges aligned.

FIG. 4 is a side view of an alternate embodiment of the present invention.

FIG. 5 is a cross-sectional end view of the embodiment of FIG. 4.

Referring to the drawings, and particularly FIG. 1, the bolt hole alignment pin of the present invention is generally indicated by numeral 10 and is shown in a free standing position. Alignment pin 10 is generally round in cross-section and comprises a head 12, successive longitudinal portions 14, 16, and 18, conical end portion 20, and central axis 22. In the preferred embodiment, head 12 is of hexagonal cross-section but may be of any cross-section which can be rotated around central axis 22 of alignment pin 10. Longitudinal portion 14 is a pilot portion which provides the primary contact surface when alignment pin 10 is initially inserted through the bolt holes of mating flanges. Portions 14, 16, and 18 have successively decreasing diameters, pilot portion 14 being the largest and portion 18 the smallest. Pilot portion 14 is concentric with and extends from head 12 to longitudinal portion 16. Longitudinal portion 16 is concentric with and extends from pilot portion 14 to portion 18. As can be seen in FIGS. 1 and 2, portion 18 is a cam means comprising surface 24 which is offset from central axis 22 thereby operating as a cam when head 12 is rotated about central axis 22 to force misaligned flanges into alignment. Conical end portion 20 facilitates insertion of alignment pin 10 into a bolt hole of a flange.

FIG. 3 shows alignment pin 10 disposed in one pair of a plurality of pairs of corresponding bolt holes 26 and 28 disposed in circles around the circumference of mating flanges 30 and 32. Each bolt hole circle has an inside diameter D corresponding to the inner edges of bolt holes 26,28. When alignment pin 10 is inserted through a pair of corresponding bolt holes 26,28 of mating flanges 30,32, the diameter of pilot portion 14 is sufficient to slip fit bolt hole 26. The diameter of head 12 is larger than the diameter of bolt hole 26 so that full insertion of alignment pin 10 in a pair of bolt holes 26,28 is achieved when the inner face 36 of head 12 adjacent pilot portion 14 contacts the outer face 38 of mating flange 30. Pilot portion 14 and cam means 18 have lengths substantially equal to the thicknesses of mating flanges 30,32. With alignment pin 10 fully inserted, pilot portion 14 is disposed in bolt hole 26, longitudinal portion 16 is disposed between the inner openings 40,42 of bolt holes 26,28, and cam means 18 is disposed in bolt hole 28. Longitudinal portion 16 has a diameter smaller than pilot portion 14 to allow for the outer diameter of gasket 44 which is slightly larger than the inside diameter D of the bolt hole circle of mating flanges 30,32. Longitudinal portion 16 is a gasket centering means which is used to center gasket 44 on the inner faces 48,50 of mating flanges 30,32. When mating flanges 30,32 are initially brought together, temporary bolts (not shown) are inserted into the lower bolt holes along with nuts loosely screwed on. When required, gasket 44 is then inserted between the flanges and the temporary bolts and nuts are tightened to hold mating flanges 30,32 in substantially parallel relationship. Two bolt hole alignment pins 10 of the preferred embodiment are then inserted into two pairs of corresponding bolt holes 28,30 substantially 90.degree. apart along the bolt hole circle of mating flanges 30,32. As alignment pins 10 are successively rotated through substantially 360.degree., longitudinal portions 16 of each pin engage the outer edge 49 of gasket 44 forcing it to a centered position on the inner faces 48,50 of mating flanges 30,32. The temporary bolts are then tightened to prevent further movement of gasket 44.

To align mating flanges 30,32, the two alignment pins 10 are now successively rotated until surface 24 of cam means 18 frictionally engages inner surface 60 of bolt hole 28. Rotation of alignment pins 10 causes surface 24 of cam means 18 to sweep through a circle having a diameter substantially the same as or slightly larger than the diameter of pilot portion 14, thereby forcing mating flanges 30,32 into alignment. In practice it has been found that the diameter of the circle swept by surface 24 of cam means 18 can be adjusted by changing the offset of cam means 18 to meet whatever tolerances may be required for flange alignment. The frictional forces between surface 24 of cam means 18 and inner surface 60 of bolt hole 28 and between pilot portion 14 and inner surface 34 of bolt hole 26 lock alignment pins 10 in bolt holes 26,28. In this locked mode, alignment pins 10 prevent any transverse movement of mating flanges 30,32 relative to each other, but allow limited rotation of mating flanges 30,32 relative to each other. The difference between the diameters of pilot portion 14 and bolt hole 26 is sufficient to allow this limited movement which facilitates fit up at the opposite end of pipes which may be connected to either mating flange. Allowable rotation of the flanges relative to each other is approximately 2.degree. or less in the locked mode without affecting alignment of the mating flanges.

After mating flanges 30,32 are in alignment, the temporary bolts are removed and permanent bolts (not shown) installed in their places. With the permanent bolts installed, mating flanges 30,32 are in a fixed relationship relative to each other and alignment pins 10 are removed and replaced by permanent bolts, Alignment pins 10 are taken out of their locked mode by rotating each pin 10 until surface 24 is no longer in frictional engagement with inner surface 60. Each pin 10 is then easily removed from bolt holes 26,28.

FIGS. 4 and 5 show an alternate embodiment of the present invention that is used to align mating flanges when a gasket is not required. In FIG. 4, the bolt hole alignment pin of this alternate embodiment is generally indicated by numeral 80 and is shown in a free standing position. Alignment pin 80 is generally round in cross-section and comprises a head 82, successive longitudinal portions 84 and 86, conical end portion 88, and central axis 90. As shown in FIG. 5, head 82 is preferably of hexagonal cross-section but may be of any cross-section which can be rotated around central axis 90 of alignment pin 80. Portion 84 is a pilot portion of diameter sufficient to slip fit a bolt hole of a flange and provides the primary contact surface when alignment pin 80 is initially inserted through the bolt holes of mating flanges. Pilot portion 84 is concentric with and extends from head 82 to longitudinal portion 86. Portion 86 is a cam means having a smaller diameter than pilot portion 84, an outer surface 92, and is offset from central axis 90. Conical end portion 88 facilitates insertion of alignment pin 10 through the bolt holes of mating flanges. When alignment pin 80 is inserted through a pair of corresponding bolt holes of misaligned mating flanges and head 82 is rotated around central axis 90, the surface 92 of cam means 86 sweeps through a circle having a diameter substantially the same as or slightly larger than the diameter of pilot portion 84, thereby forcing the mating flanges into alignment.