Expansion shell assembly

A bolt and anchor assembly for securing a mine roof bolt, comprising:

• an elongated bolt;
• an expansion shell having an aperture for receiving the elongated bolt;
• an expansion member disposed on one end of the elongated bolt for expanding the expansion shell;
• and
• a shell support having a shell engaging portion radially disposed between and in contact with the elongated bolt and the expansion shell the shell engaging portion generally maintaining the axial position of the expansion shell relative to the elongated bolt while the expansion member forces the shell to engage a rock formation and moving axially relative to the expansion shell when the elongated bolt is tensioned after engagement to the rock formation.

A method for anchoring an elongated threaded member to a rock formation, comprising the steps of:

• (a) providing an elongated member having a threaded end portion that is to be anchored to a rock formation,
• (b) providing an expansion shell assembly on the threaded end portion of the elongated member, the expansion shell assembly comprising an expansion shell, a plug for expanding the expansion shell, and a support member for supporting the expansion shell;
• (c) forming a blind drilled hole in the rock formation for the elongated member and the expansion shell assembly;
• (d) advancing the elongated member with the expansion shell assembly carried thereon into the blind drilled hole;
• (e) rotating the elongated member to effect a gripping of the rock formation by the expansion shell assembly within the blind drilled hole, the support member generally axially fixed relative to the expansion shell and generally maintaining engagement between the plug and the expansion shell while the expansion shell expands to engage the rock formation;
• (f) further rotating the elongated member to tension the elongated member after the expansion shell has sufficiently engaged the rock formation, the support member axially traversing within the expansion shell to permit the tensioning only after the expansion shell has sufficiently engaged the rock formation.

A method of installing a mine roof bolt assembly, comprising the steps of:

• inserting a mine roof bolt assembly into a hole of a rock formation, the mine roof bolt assembly comprising a mine roof bolt, an expansion member threadingly engaged to the mine roof bolt, an expansion shell, and a support, the expansion shell having fingers engaged with expansion member and a base portion engaged with the support, the hole appropriately sized to frictionally prevent rotation of the expansion shell and the engagement of the fingers restricting rotation of the expansion member;
• anchoring the mine roof bolt assembly to the rock formation within the hole by rotating the mine roof bolt, said rotation causing the support to force the expansion shell against the expansion member thereby forcing the fingers of the expansion shell to move radially outwardly and grip the rock formation;
• and
• tensioning the mine roof bolt by continuing to rotate the mine roof bolt, said continued rotation causing the support to forcibly move within the base portion of the expansion shell.

An expansion shell assembly for mine roof bolts, comprising:

• an expansion member threaded onto an associated bolt;
• a support device annularly disposed around the associated bolt, the support device having an outer transition surface that includes a straight portion generally parallel to an axis of the associated bolt and a tapered portion;
• and
• a shell annularly disposed on the bolt between the expansion member and the support device, the shell having a base ring for engaging the support device and fingers for engaging the expansion member wherein the base ring engages the tapered portion while the fingers of the shell are expanded by the expansion member and engages the straight portion after the fingers have expanded and while the associated bolt is tensioned.