GB2348895A

GB2348895A - Compressible roof support

Info

Publication number: GB2348895A
Application number: GB9928300A
Authority: GB
Inventors: James Eric Marianski; Andrew James Marianski
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-04-14
Filing date: 1999-11-30
Publication date: 2000-10-18
Also published as: AU766090B2; GB9928300D0; AU2773200A

Abstract

A roof support 10 comprises a post 12 and a collar 14. The post 12 has at one end a threaded portion 20. The collar 14 has an internal thread 38 for engaging the thread 24 on the post. The collar 14 is manufactured of harder material than the thread 24 such that thread 24 will deform when a compressive force above a determined level is applied to the support 10. Said downward deformation will accommodate settling of the roof under gravity.

Description

COMPRESSIBLE SUPPORT COLU J Background of the Invention 1. Field of the Invention The present invention relates to support columns for mine roofs and the like. More specifically, the present invention relates to a compressible support column.

2. Brief Description of the Prior Art Support columns are used to counteract the force that gravity exerts on the mass of an object. For example, vertical support columns are positioned between two horizontal objects to keep the objects spaced away from one another.

In underground mining vertical support columns are used as primary or secondary supports for mine roofs.

Due to the tremendous forces exerted on the vertical support columns by the earth and rock above the mine roof, including forces resulting from shifting and settling of the overhead earth and rock, rigid vertical support columns can bend or break. Complete failure of a vertical support column can cause an isolated collapse of the mine roof.

Therefore, compressible support columns, which yield during settling or shifting of the mine roof, are often used.

In mining operations, compressible vertical support columns are generally positioned perpendicularly between a mine roof and a mine floor. One type of compressible support column is disclosed in United States Patent No. 4,052,029 to Townsend. The Townsend patent uses telescoping members and compressible materials to reduce the overall length of the support column as the earth and rock above the mine roof settles or shifts. Specifically, the Townsend patent discloses a support column having a hollow lower steel member and a hollow upper steel member, where the upper steel member fits over and slidably telescopes toward the lower steel member. The hollow cavity within the lower steel member is completely filled with wood positioned with the grain of the wood oriented parallel to a vertical axis of the assembled column. The hollow cavity in the upper steel member is only partially filled with wood, with the grain of the wood also aligned with the vertical axis of the assembled column. The space left between the wood in the upper and lower steel members is filled with discs, as needed, to adjust the length of the assembled compressible support column between a mine roof and a mine floor.

When earth and rock above the compressible support column disclosed in the Townsend patent shift, settle, or are otherwise subjected to additional force, the wood inside of the upper and lower steel members compresses. The compression reduces the overall length of the assembled compressible support column, easing the force being exerted on the column. Additional settling or shifting of the mine roof further compresses the load resisting material, until the lower steel member is telescoped to its full extent inside of the upper steel member. At this point, the upper and lower steel columns begin to compress, causing the upper and lower steel members to bulge outwardly, away from the vertical axis of the assembled upper and lower steel columns.

One disadvantage of the prior art collapsible support columns is that they are expensive to make.

Another disadvantage is that adjusting the length of the columns during installation is time consuming. Therefore, one object of the present invention is to provide a compressible support column that is inexpensive to manufacture. Another object of the present invention is to make a compressible support column that can be installed quickly.

SUMMARY OF TEE INVENTION The present invention relates to a compressible support column generally including a post and a collar. A cap and a base may also be provided. The post has a first end, a second end, and a longitudinal axis. The post also includes ridges and grooves, generally in the form of threads, positioned adjacent the first end of the post.

The collar has a first end, a second end, an internal surface, and an external surface. The second end of the collar is positioned adjacent the first end of the post during installation. Corrugations generally in the form of screw threads, made from a material harder than the ridges and grooves of the post, are positioned adjacent the internal surface of the collar. The corrugations adjustably engaging the ridges and grooves of the post, which are also generally in the form of screw threads. The corrugations and threads allow the collar to be adjustable along a longitudinal axis of the post, essentially by threading the collar onto or off of the first end of the post. An optional cap and an optional base may be positioned adjacent the ends of the post and collar to distribute the force applied to the post and collar over a greater surface area.

When an initial or preloading force is exerted on the assembled post and the collar, referred to hereafter as the column, the column provides an equal and opposite force. As the force on the column increases, the ridges adjacent the first end of the post crush, yield, fracture, or strip, allowing the collar to move toward the second end of the post, decreasing the overall length of the column.

Additional force causes additional crushing of the grooves adjacent the first end of the post, until the movement of the collar toward the second end of the post is arrested.

At this point, further force causes the first end of the post and the collar to compress, further decreasing the overall length of the column.

These and other advantages of the present invention will be clarified in the description of the preferred embodiments taken together with the attached drawings in which like reference numerals represent like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a compressible support column according to a first embodiment of the present invention ; Fig. 2 is a bottom view of the collar shown in Fig. 1; Fig. 3 is a side view of the compressible support column shown in Fig. 1, with a collar adjustably attached to a first end of a post thereof; Fig. 4 is a side view of the compressible support column shown in Figs. 1 and 3, with the collar adjustably extended away from a second end of the post; Fig. 5 is a side view of a compressible support column with threads attached to the first end of the post fractured; Fig. 6 is a side view of the compressible support column shown in Fig. 5, where the first end of the post and the collar are compressed; Fig. 7 is a side view of a compressible support column according to a second embodiment of the present invention; Fig. 8 is a bottom view of the collar shown in Fig. 7 ; Fig. 9 is a side view of the compressible support column shown in Fig. 7, with a collar adjustably attached to a first end of a post thereof; Fig. 10 is a side view of the compressible support column shown in Figs. 7 and 9, with the collar adjustably extended away from a second end of the post; Fig. 11 is a side view of a compressible support column with threads attached to the first end of the post fractured; Fig. 12 is a side view of the compressible support column shown in Fig. 11, where the first end of the post and the collar are compressed; Fig. 13 is a cross-sectional side view of standard buttress threads; Fig. 14 is a cross-sectional side view of the modified buttress threads shown in Figs. 7-10; Fig. 15 is a-side view of a collar according to a third embodiment of the present invention; and Fig. 16 is a cross-sectional side view of a first end of a post, structurally weakened with slits, and having ridges and grooves that engage the ridges and grooves of the collar shown in Fig. 15.

DETAILEI) DESCRIPTION OF TFIE PREFERRED EMBODIMENTS Fig. 1 is one preferred embodiment of the compressible support column 10 according to the present invention. The column 10 generally includes a post 12, a collar 14, a cap 16, and a base 18. The post 12 has a first end 20, a second end 22, a longitudinal axis L, and ridges and grooves forming screw threads 24 positioned adjacent to the first end 20 of the post 12. As shown in Figs. 1 and 2, the collar 14 has a first end 26, a second end 28, an internal surface 30, an external surface 32, the internal surface 30 forms an internal cavity 34. The internal surface 30 has adjacently positioned corrugations 38 in the form of screw threads that adjustably engage the threads 24 positioned adjacent the first end 20 of the post 12. The external surface 32 forms a lever cavity 36.

The post 12 is preferably made from hardwood, such as poplar, oak, or other material capable of supporting an applied force of 50 to 100 tons parallel to the longitudinal axis L of the post 12. The post 12 is preferably one piece, but may also be a combination of different pieces and different materials. Moreover, the post 12 can be made into any shape which permits the threads 24 adjacent the first end 20 of the post 12 to adjustably engage the corrugations 38 adjacent the internal surface 30 of the collar 14. However, as shown in Figs. 1, 3-7, and 9-12, a cylindrical-shaped post 12 with a ten-inch diameter is preferred.

The threads 24 positioned adjacent the first end 20 of the post 12 preferably extend six to eighteen inches from the first end 20 of the post 12 toward the second end 22 of the post 12, along the longitudinal axis L of the post 12. The threads 24 are made from a material softer than the corrugations 38 positioned adjacent to the internal surface 30 of the collar 14. Generally, the threads 24 are made from the same material as the post 12, such as hardwood or other suitable material. However, the threads 24 could also be formed of a material different from the post 12.

The threads 24 are preferably screw-type modified buttress threads. A buttress thread is designed to take exceptionally high stresses in one direction (i. e., on the load resisting or flank-vertical side). An example of a typical buttress thread is shown in Fig. 13. To make a modified buttress thread, and utilize the buttress principal as a yielding element, the loading is reversed and one of the threads 24 is cut into a material which will yield rather than fail in shear. For this type of application, as shown in Fig. 14, the buttress angle a is reduced from the normal 45 to 50 degree angle to an angle P between 15 and 30 degrees. The pitch P of the threads is also modified, preferably resulting in threads 24 having a two-inch pitch P'and a one inch depth D. It is understood that decreasing the buttress angle reduces the load resisting properties of the modified buttress thread 24 and that while modified buttress threads 24 having buttress angles of 15 degrees to 30 degrees are preferred, other types of ridge and groove configurations, including other types of yieldable threads, are also suitable.

The collar 14 is preferably made from harder material than the post 12 threads 24 such as a harder wood, metal, or any other suitable material or combination thereof. The collar 14 is preferably a one-piece machined or formed section extending the same distance as the threads 24 positioned adjacent the first end 20 of the post 12. However, collars 14 with two or more pieces or different lengths are also contemplated. For example, Fig.

15 shows a two-piece collar 14 having a hinge 40 and secured together by pins 42 and pin holders 44, or other suitable devices. This collar engages the ridges and grooves on the first end 20 of the post 12 shown in Fig.

16.

The corrugations 38, like the collar 14, are preferably made from materials that are harder than the material used to make the threads 24 positioned adjacent to the first end 20 of the post 12. The corrugations 38 positioned adjacent to the internal surface 30 of the collar 14 preferably form modified buttress-type threads 24 that adjustably engage the modified buttress threads 24 positioned adjacent the first end 20 of the post 12, and are preferably formed by the internal surface 30 of the collar 14. However, the corrugations 38 may also be formed by welding seams or by inserting a pipe segment or other device adjacent the internal surface 30 of the collar 14.

Alternatively, as shown in Figs. 7 and 8, corrugations 38' and corresponding ridges and grooves 24' (in place of threads 24) adjacent the first end 20 of the post 12 can be perpendicular to the longitudinal axis L of the post 12.

To help distribute an applied force over a greater area, a cap 16 and a base 18 may be added to the collar 14 and post 12, respectively. The cap 16 has a planar shape and is positioned adjacent the first end 26 of the collar 14, perpendicular to the longitudinal axis L of the post 12. The base 18 also has a planar shape and is positioned adjacent the second end 22 of the post 12, perpendicular to the longitudinal axis L of the post 12 and parallel to the cap 16.

In one example of operation shown in Figs. 3 and 9, the column 10, formed by adjustably engaging the collar 14 to the first end 20 of the post 12, is inserted perpendicularly between two objects, such as a mine roof and a mine floor. As shown in Fig. 4, the column 10 length is varied by adjusting the collar 14. If the post 12 and collar 14 have threads 24, the length of the column 10 is adjusted by turning the collar 14, moving the collar 14 along the longitudinal axis L of the post 12. A turn lever 46 may be inserted into the lever cavity 36 in the collar 14 and rotated about the longitudinal axis L of the post 12 to aid in adjustment. If the post 12 and collar 14 have a different configuration, such as corrugations 38 and corresponding ridges and grooves 24 (in place of screw-type threads 2a), the collar 14 is positioned adjacent the first end 20 of the post 12 and is adjusted by moving the collar 14 toward or away from the second end 22 of the post 12, along the longitudinal axis L of the post 12.

When an initial or preloading force is exerted on the column 10, the column 10 provides an equal and opposite force. As shown in Figs. 5 and 11, as the force on the column 10 increases, the threads 24 adjacent the first end 20 of the post 12 yield, crush, or strip, allowing the collar 14 to move toward the second end 22 of the post 12, and decreasing the overall length of the column 10.

Further force causes additional yielding, crushing, or stripping of the threads 24 adjacent the first end 20 of the post 12, until the movement of the collar 14 toward the second end 22 of the post 12 is arrested. At this point, as shown in Figs. 6 and 12, still further force causes the first end 20 of the post 12 to compress, further decreasing the overall length of the column 10, and causing the first end 20 of the post 12, as well as the collar 14, to bulge outwardly away from a longitudinal axis L of the post 12.

This effect can be encouraged by hollowing or cutting slits 45 (shown in phantom in Fig. 16) into the first end 20 of the post 12.

The invention has been described with reference to the preferred embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims and equivalents thereto.

Claims

Claims :

1. A compressible support column comprising: a post having ridges and grooves positioned adjacent one end of the post; and a collar having an internal surface forming an internal cavity, the internal surface having adjacently positioned corrugations that adjustably engage with the ridges and grooves positioned adjacent to the first end of the post; wherein the ridges positioned adjacent the first end of the post are made from a material softer than the corrugations of the collar.

2. The compressible support column as claimed in claim 1 wherein the post is wood.

3. The compressible support column as claimed in claim 2 wherein the wood is a hardwood selected from the group consisting of poplar and oak.

4. The compressible support column as claimed in claim 1 wherein the ridges and grooves positioned adjacent the first end of the post form screw threads.

5. The compressible support column as claimed in claim 4 wherein the threads are formed by a hardwood selected from the group consisting of poplar and oak.

6. The compressible support column as claimed in claim 4 wherein the threads are modified buttress threads having a buttress angle of 15 to 30 degrees.

7. The compressible support column as claimed in claim 1 wherein the first end of the post is structurally weakened.

8. The compressible support column as claimed in claim 1 wherein the first end of the post has a cylindrical shape.

9. The compressible support column as claimed in claim 1 wherein the corrugations form modified buttresstype screw threads having a buttress angle of 15 to 30 degrees.

10. The compressible support column as claimed in claim 1 wherein the corrugations are metal.

11. The compressible support column as claimed in claim 1 further comprising a planar-shaped cap positioned adjacent an end of the collar, generally perpendicular to a longitudinal axis of the post.

12. The compressible support column as claimed in claim 1 further comprising a planar-shaped base positioned adjacent a second end of the post, perpendicular to a longitudinal axis of the post.

13. A method of installing a collapsible support column comprising the steps of: inserting a collapsible support column perpendicularly between two objects, the collapsible support column having a post and an adjustable collar, the post having ridges and grooves positioned adjacent a first end of the post, the collar having an internal surface, forming an internal cavity and having adjacently positioned corrugations; wherein the ridges and grooves positioned adjacent the first end of the post are made from a material softer than the corrugations of the collar and the ridges and grooves adjustably engage with the corrugations positioned adjacent the internal surface of the collar; and adjusting the length of the compressible support column by moving the collar along the longitudinal axis of the post.

14. The method of installing a collapsible support column as claimed in claim 13 wherein the post is wood.

15. The method of installing a collapsible support column as claimed in claim 14 wherein the wood is a hardwood selected from the group consisting of poplar and oak.

16. The method of installing a collapsible support column as claimed in claim 13 wherein the moving of the collar includes inserting a turn lever into a lever cavity formed by an external surface of the collar and rotating the turn lever about a longitudinal axis of the post.

17. The method of installing a collapsible support column as claimed in claim 13 wherein the ridges and grooves are modified buttress threads having a buttress angle of 15 to 30 degrees.

18. A compressible support column comprising: a hardwood post having modified buttress threads positioned adjacent a first end of the post; and a collar having an internal surface forming an internal cavity, the internal surface having adjacently positioned modified buttress threads that threadedly engage the modified buttress threads positioned adjacent the first end of the post, wherein the collar is adjustable along a longitudinal axis of the post.

19. The compressible support column as claimed in claim 18 wherein the modified buttress threads positioned adjacent the first end of the post are made from a material softer than the modified buttress threads positioned adjacent the interior surface of the collar.

20. The compressible support column as claimed in claim 18 wherein the modified buttress threads have a buttress angle of 15 to 30 degrees.