Apparatus and method for re-tensioning a loose roof plate in an underground mine

1. An apparatus for retensioning a loose roof plate held by a roof bolt, comprising:

a main spacer for occupying a space between a head of the roof bolt and the loose roof plate, the main spacer having a threaded circumferential outer surface and a radially extending slot for inserting a shaft of the roof bolt therein;

a washer for occupying a space between the main spacer and the loose roof plate, the washer having a radially extending slot for inserting the shaft of the roof bolt therein; and

a nut having a threaded hole for passing the head of the roof bolt therethrough, for threading onto the threaded spacer and for tightening onto the threaded spacer until the roof plate is firmly pressed against the roof,

wherein rotation of the main spacer relative to the washer is limited by a tab extending from one of the main spacer and the washer into a recess in the other of the main spacer and the washer.

2. The apparatus of claim 1 , wherein the tab extends from the washer into the slot of the main spacer.

3. The apparatus of claim 2 , wherein the tab protrudes from a bottom end of the washer a distance less than a height of the main spacer.

4. The apparatus of claim 3 , further comprising an additional main spacer having a threaded circumferential outer surface and a radially extending slot for inserting the shaft of the roof bolt therein, wherein each main spacer has a different height, and

wherein the tab protrudes from the bottom end of the washer a distance less than a height of the shortest main spacer.

5. The apparatus of claim 1 , wherein the nut includes a plurality of flat outer surfaces forming a periphery around the threaded hole of the nut.

6. The apparatus of claim 1 , wherein the washer has a domed-shaped top surface.

7. The apparatus of claim 1 , wherein an outer diameter of the washer is greater than an outer diameter of the main spacer.

8. The apparatus of claim 1 , further comprising one or more supplemental spacers for occupying a space between the main spacer and the roof bolt head.

9. The apparatus of claim 8 , wherein the one or more supplemental spacers each have a radially extending slot for inserting the shaft of the roof bolt therein.

10. The apparatus of claim 9 , wherein the one or more supplemental spacers have an outer diameter that is less than an inner diameter of the nut.

11. A method for retensioning a loose roof plate held by a roof bolt to a roof, comprising:

placing a main spacer having a threaded circumferential outer surface between a head of the roof bolt and the loose roof plate by inserting a shaft of the roof bolt into a radially extending slot of the main spacer;

placing a nut between the main spacer and the head of the roof bolt by passing the head of the roof bolt through a threaded hole of the nut;

threading the nut onto the main spacer while rotation of the main spacer is limited; and

tightening the nut until the roof plate is firmly pressed against the roof.

12. The method of claim 11 , further comprising selecting one main spacer from a plurality of main spacers having different heights depending on the amount of space between the loose roof plate and the head of the roof bolt.

13. The method of claim 11 , further comprising placing a washer adjacent to the roof plate by inserting a shaft of the roof bolt into a radially extending slot of the washer, and wherein a tab of the washer extends into the slot of the main spacer to limit rotation of the main spacer relative to the washer.

14. The method of claim 11 , further comprising placing one or more supplemental spacers between the main spacer and the head of the roof bolt.

15. The method of claim 14 , wherein the one or more supplemental spacers are placed between the main spacer and the head of the roof bolt by inserting a shaft of the roof bolt into a radially extending slot of the supplemental spacers.

16. The method of claim 15 , wherein the one or more supplemental spacers are placed between the main spacer and the head of the roof bolt before the nut is placed between the main spacer and the head of the roof bolt, and wherein the supplemental spacers are passed through the threaded hole of the nut after the head of the roof bolt is passed through the threaded hole.