WO2001014692A1

WO2001014692A1 - Yielding mine prop

Info

Publication number: WO2001014692A1
Application number: PCT/ZA2000/000139
Authority: WO
Inventors: Jan Hendrik Woller
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-08-20
Filing date: 2000-08-18
Publication date: 2001-03-01
Anticipated expiration: 2002-02-20
Also published as: AU7886100A

Abstract

A mine prop (10) includes a tubular member (12) of circular cross-section and a timber prop (14) having a co-axially arranged bore (16) of circular cross-section defined therein, the bore (16) being dimensioned and/or configured to receive snugly and guide the tubular member (12) co-axially into the timber prop (14) initially and thereafter during yielding accommodated by the movement of the tubular member (12) into the timber prop (14).

Description

YIELDING MINE PROP

Field of the Invention

This invention relates to mine props and to yielding devices to be used with mine props.

Background to the Invention

The inventor is aware of prior art in the field wherein mine props including tubular members and timber props are disclosed which are used to increase the distance which a mine prop yields when placed under a load. However, the prior art brings with it numerous problems.

When such a mine prop is in use and is subjected to a load, the force distribution within the mine prop is often uneven due to the unpredictable deformation of the mine prop's elongate timber member or timber prop, which in turn causes the prop to buckle and fail thereby creating a dangerous situation.

This is mainly caused by the tubular member (which is mounted onto an end of the timber prop) not remaining co-axially aligned with the timber prop when being forced into said prop due to a load being exerted on the mine prop as it has no guiding means to keep it in its desired alignment.

Also, the tubular member has to force its way through a large amount of timber when the mine prop is subjected to a load, which makes the timber prop's deformation under a load unpredictable due to the fact that the material properties of the timber prop are not the same throughout its length. This often causes the tubular member to yield into the timber prop in a skewed fashion which in turn causes the tubular member to lose some of its effect as a yielding aid.

Furthermore, in the case of conventional mine props as described above the tubular member used is typically 500 mm long and the total yield distance of the mine prop is typically 300 mm. Since the tubular member is one of the main cost contributors in the manufacture of a mine prop, it would be desirable to decrease its length whilst retaining the same total yield distance.

Summary of the Invention

According to the invention there is provided a mine prop which includes:- a tubular member; a timber prop having a co-axially arranged bore defined therein, the bore being configured initially to receive the tubular member complementally therein and thereafter to guide the tubular member co-axially into the timber prop during yielding. One or more cavities or holes may extend substantially parallel the bore, the cavities or holes being defined in a zone intermediate the bore and an outer surface of the timber prop. The cavity may be in the form of a slot that is configured to circumscribe or surround a substantial portion of the bore.

The slot may be of generally annular form or configuration. The outside diameter of the slot may fall within the region of 100 mm to 125 mm, preferably 114 mm whilst its width may fall within the region of 4 mm to 12 mm, preferably 8 mm.

The ratio of the cross-sectional areas of the timber prop to the tubular member and/ or bore may fall within the region of 1 ,5:1 to 20:1 , preferably 16:1.

The length of the bore may be substantially equal to the length of the tubular member and may be variable according to the length of the tubular member used. Typically, the bore may have an axial length of between 250 mm to 500 mm.

The bore may be circular in cross-section and may have a diameter which is slightly greater or at least corresponds to the diameter of the tubular member, so as to facilitate snug sliding engagement between the outer surface of the tubular member and a wall of the bore. Alternatively, the cross-section of the bore may be selectable from any conventional shape, preferably square, rectangular, hexagonal, oval, elliptical or the like, the dimensions of which are slightly greater or at least correspond to the dimensions of the tubular member, so as to facilitate snug sliding engagement between the outer surface of the tubular member and a wall of the bore.

The diameter of the timber prop may be about 180 mm to 220 mm.

The timber prop is a Eucalyptus prop or any other suitable ligneous material and is typically about 0,7 to 3m long. The timber prop may be "Micon Dip" treated before use.

The tubular member may be circular in cross-section and may have an outside diameter of about 45 to 55 mm, preferably 50 mm and a wall thickness of about 1 to 5 mm, preferably 3 mm. The length of the tubular member may be about 300 mm to 500 mm.

The tubular member may have one or more projections extending radially outwards the tubular member. The projections may be in the form of extension arms that extend radially outwards the tubular member.

The extension arms may be arranged towards an end of the tubular member that in use receives a prestressing device. The extension arms may be in the form of metal plates attached to the tubular member by welding or any other suitable attachment method. The dimensions of the plates may be as follows: thickness between about 3 mm to 8 mm, preferably 5 mm, length about 40 mm to 60 mm, preferably 50 mm and width about 30 mm to 50 mm, preferably 35 mm.

In a preferred embodiment, four metal plates may be attached to the tubular member at substantially 90 degree angles to each other.

Furthermore, a metal strip may be arranged co-axially interior or exterior the tube in the form of a wave so as to define spaces and/or passages between the longitudinal side wall of the tubular member and the strip.

Alternatively or in addition to the above, a metal strip may be arranged co- axially interior or exterior the tube, there being provided connecting members which extend radially the tubular member to connect the metal strip to the tubular member. A support band having dimensions slightly exceeding those of the tubular member so that it may slide onto the tubular member may be attached to said member above the metal strip.

Projections of generally "V" - shape configured to extend outwardly or inwardly the inner and outer walls of the tubular member may further be provided on a wall of the tubular member. The "V" - shaped projections may be formed from angle iron.

In yet a further embodiment, the tubular member may be of a frusto- conical shape, with the larger radius being at that end of the tubular member that will be forced into the timber below the bore first.

A valve protection means in the form of an extension arm that extends outwardly the tubular member near to its free end may be provided on the tubular member. The extension arm may be aligned with a valve of a setting device positioned on the timber member in use so as to split and urge the timber away from the valve during yielding as the setting device moves through the timber member in use.

One or more retaining bands which may be in the form of rings manufactured from any suitable metal may be provided to fit snugly around the timber prop to inhibit lateral or transverse expansion of the timber prop during yielding or displacement of the tubular member from its co-axial position into the timber prop in use.

A first retaining band may be located towards an end of the timber prop wherein the bore is defined. The first band may be arranged about 30 mm to 70 mm, preferably 50 mm from the end of the timber prop wherein the bore is defined. Further bands may be arranged at intervals of about 80 mm to 120 mm, preferably 100 mm along a portion of the length of the prop, the last of which bands is preferably a double wind. A further retaining band may be provided at a distance of about 180 mm to 220 mm, preferably 200 mm, from that end of the timber prop that has no bore defined in it.

Another band may be provided at a distance of about 360 mm to 440 mm, preferably 400 mm, from that end of the timber prop which has no bore defined should the timber prop exceed 1 ,4 m in length.

The retaining bands may manufactured from fencing rod having a diameter of about 3 mm to 8 mm, preferably 5,5 mm.

One or more carry handles may be attached to the mine prop to facilitate handling thereof. The carry handles may typically be in the form of loops of woven polyester attached to the retaining bands.

According to a further aspect of the invention there is provided a yielding device which includes:- a tubular member as claimed in any one of the preceding claims having one or more projections extending radially outwards thereof having a cross section dimensioned so as to allow the tubular member to be received by a complementary co-axially defined bore in a timber prop configured to guide the tubular member co-axially into the timber prop initially and thereafter during yielding facilitated by the movement of the tubular member into the timber prop wherein the ratio of the cross-sectional areas of the timber prop to the bore and/ or tubular member is between 1 ,5:1 and 20:1 preferably 16:1 ; and a prestressing or setting device which is mounted on the free end of the tubular member to permit prestressing of the timber prop in use.

Detailed Description of the Invention

The invention will now be described by way of the following non-limiting examples as illustrated in the accompanying drawings.

In the drawings:-

Figure 1 is a side view of an embodiment of a tubular member in accordance with the invention;

Figure 2 is a side view of a further embodiment of a tubular member in accordance with the invention;

Figure 3 is a plan view of the tubular member of Figure 2;

Figure 4 is a side view of yet a further embodiment of a tubular member in accordance with the invention;

Figure 5 is a plan view of the tubular member of Figure 4;

Figure 6 is a plan view of yet a further embodiment of a tubular member in accordance with the invention; Figure 7 is a plan view of yet a further embodiment of a tubular member in accordance with the invention;

Figure 8 is a three dimensional view of an end section of a timber prop of a mine prop;

Figures 9 to 11 show sectioned side views of a mine prop in accordance with the invention in an initial, prestressed and yielding condition respectively;

Figures 12 a to c show side views of three timber props provided with retaining rings in accordance with the invention;

Figures 13 to 24 are graphs of load versus yield of mine props of 1 meter length using 500 mm tubular members at a yield rate of 30 mm per minute; Figures 25 to 36 are graphs of load versus yield of mine props of 1 meter length using 500 mm tubular members at a yield rate of 3 meters per second;

Figures 37 to 52 are graphs of load versus yield of mine props of 1 ,6 meter length using 300 mm tubular members at a yield rate of 3 meters per second; and Figures 53 to 62 are graphs of load versus yield of mine props of 1 ,6 meter length using 300 mm tubular members at a yield rate of 30 mm per minute.

In the drawings, reference numeral 10 generally indicates a mine prop in accordance with the invention which includes a tubular member 12 of circular cross-section and a timber prop 14 having a co-axially arranged bore 16 of circular cross-section defined therein, the bore 16 being dimensioned and/or configured to receive snugly and guide the tubular member 12 co-axially into the timber prop 14 initially and thereafter during yielding accommodated by the movement of the tubular member 12 into the timber prop 14.

In particular, an end of the tubular member 12 is forced or pressed into the timber prop 14 below the bore 16 during the said movement thereby compressing and/or splitting timber of the timber prop 14 below the bore 16.

In the embodiments shown in Figures 9 to 11 , the prop includes an annular slot 18 that extends substantially parallel to the bore 16 into the timber prop 14. The slot 18 is defined in an area intermediate the bore 16 and an outer surface 20 of the timber prop 14 and substantially surrounds the bore 16.

The outside diameter of the slot 18 is about 125 mm to 100 mm, preferably 114 mm and its width is about 12 mm to 4 mm, preferably 8 mm.

The ratio of the cross-sectional area of the timber prop 14 to that of the bore 16 is about 1,5:1 to 20:1, preferably 16:1.

The bore 16 has an axial length of about 250 mm to 500 mm and depends on the length of the tubular member 12. It therefore varies according to the length of the tubular member 12 used.

In the embodiments shown, the bore 16 is circular in cross-section and its diameter is slightly greater or at least corresponds to the diameter of the tubular member 12, for example, it may be 50,5 mm for a tubular member having an outside diameter of 50 mm, so as to facilitate snug sliding engagement between the outer surface of the tubular member 12 and a wall of the bore.

The diameter of the timber prop is in the region of between 180 mm and

200 mm and is typically a Eucalyptus. The length of the timber prop varies between about 0,8 m and 3 m as shown in Figures 12a to c, depending on the height of the hanging wall 22 of a mine under which it is to be placed. The timber prop 14 is "Micon Dip" treated before use.

The tubular member 12 shown in Figures 1 and 2 is circular in cross- section and has an outside diameter of 50 mm with a wall thickness of 3 mm. The length of the tubular member 12 varies between about 300 mm and 500 mm, depending on the length of the timber prop 14 in conjunction with which it is to be used.

The yielding characteristics of the mine prop 10 are varied by means of a projections in the form of extension arms 24 which extend radially outwards the tubular member 12 and which are arranged towards an end of the tubular member 12 which in use receives a prestressing device 30.

The extensions arms 24 are in the form of rectangular metal plates which are attached to the tubular member 12 by welding or any other suitable attachment means as shown in Figures 2 to 7. Their dimensions are typically as follows: thickness = 5 mm, length = 50 mm and width = 35 mm. Alternatively, the extension arms could be in the form of square metal plates.

In a preferred embodiment of the invention, four such metal plates are welded onto the tubular member 12 at substantially 90 degree angles to each other as shown in Figures 2 and 3. In use, the metal plates increase the yielding characteristics of the mine prop 10 by virtue of increasing the cross-sectional area of the tubular member 12 which is to be moved through the timber prop 14.

In use, one of the extension arms 24 is aligned with a valve 28 of a prestressing device 30 to protect the valve 28 of the pre stressing device 30 from damage as the prestressing device 30 moves through the timber prop 14 in use by splitting and urging the timber away from the valve 28 during yielding.

Referring now to Figures 4 to 7, projections in the form of metal strips 32 which are connected to and arranged around the tubular member 12, are provided to increase the yielding characteristics of the mine prop 10 by virtue of increasing the cross-sectional area of the tubular member 12 which is to be moved through the timber prop 14.

In Figures 4,5 and 7 the metal strip 32 is arranged co-axially the tubular member 12, in the form of a wave so as to define spaces and/or passages 34 between the longitudinal side wall of the tubular member 12 and the strip 32.

In Figure 6 the strip 32 takes the form of a ring 35 and connecting members 36 which extend radially the tubular member 12 to connect the ring 35 to the tubular member 12. A support band in the form of support ring 38 of a diameter slightly larger than that of the tubular member 12 is attached to the tubular member 12 above the ring 35 so as to further increase the yield characteristics of the mine prop by providing a narrowing of the passages 40.

In Figure 7 generally "V" - shaped projections 42 are provided to extend inwardly the tubular member 12 to aid guidance of the tubular member 12 into the timber prop 14 and to increase the yield characteristics of the mine prop 10.

In use, the first step is to place the tubular member 12 into the initial position as shown in Figure 9, wherein the section of the tubular member below the edges of the extension arms 24 is slideably engaged with the bore 16 of the timber prop 14 .

A prestressing or setting device 30 is mounted on the free end 44 of the tubular member 12 to permit prestressing of the mine prop 10 in use. A block 46, typically of timber or any suitable material having a desired frictional coefficient which is greater than metal, is mounted on the setting device 30 to improve frictional engagement between a hanging wall 22 and mine prop 10 in use.

The mine prop 10 is then prestressed by forcing the tubular member 12 into the timber below the bore 16 as shown in Figure 10, whereafter the mine prop 10 is positioned between the hanging wall 22 and a foot wall (not shown) of a mine and the prestressing device 30 is filled with any suitable pressurised fluid.

When loaded, the timber surrounding the tubular member 12 yields in the predictable mushroom fashion as shown in Figure 11. Since the tubular member 12, as used in accordance with the invention, has to force its way through far less timber than when used in conventional mine props, the timber prop 14 deforms much more predictably, typically in a mushroom fashion as shown in Figure 11 , thereby making use of a mine prop 10 in accordance with the invention safer than the use of conventional mine props.

In use, a tubular member 300 mm in length may permit a yield of approximately between 400 mm and 500 mm. When using a tubular member of 500 mm length, the yield may be 600 mm. It is to be appreciated, that the length of the tubular member may be varied in accordance with the specific conditions which the mine prop will be subjected to. For example, mines which have a high closure rate, say 3 cm per day, would preferably use a tubular member of 500 mm length. Referring now to Figures 12a to c, retaining bands in the form of retaining rings 48 are provided around the timber prop 14 to inhibit lateral or transverse expansion of the timber prop 14 during yielding. It is to be appreciated that the rings 48 in the inoperative condition do not exert a compressive load on the timber prop 14.

In particular, a first retaining ring 48 is located towards an end of the timber prop 14 wherein the bore 16 is defined. The first ring 48 is arranged in the region of about 50 mm from said end of the timber prop 14. Further rings 48 are arranged at intervals of about 100 mm along a portion of the length of the prop 14, the last of which rings 48 is preferably a double wind. The number of rings 48 provided depend on the length of the timber prop 14 as can be seen in Figures 12a to c.

A further retaining ring 48 is typically provided at a distance of about 200 mm, from that end of the timber prop 14 which has no bore defined in it. Another ring 48 is provided at a distance of about 400 mm, from that end of the timber prop 14 which has no bore defined in it in the case of timber props which exceed 1 ,4 m in length as shown in Figures 12b and c. In the case of timber props which exceed 2 m in length as that shown in Figure 12c, additional rings 48 may be added.

The retaining rings 48 are manufactured from fencing rod and have a diameter of about 5,5 mm.

One or more carry handles (not shown) are attached to the mine prop 10 to facilitate handling thereof. The carry handles are typically in the form of loops of woven polyester attached to the retaining rings 48.

The accompanying graphs (Figures 13 to 62) of load sustained by the mine prop 10 vs. hanging wall 22 closure clearly illustrate the advantageous yield characteristics of a mine prop 10 in accordance with the present invention.

It is to be appreciated, that the invention is not limited to the precise constructional details as hereinbefore described. For example, the length of the tubular member may vary according to the amount of yielding required or its dimensions may vary according to the cross-sectional area of the timber prop used.

Claims

Claims:

1. A mine prop including:- a tubular member; a timber prop having a co-axially arranged bore defined therein, the bore being configured initially to receive the tubular member complementally therein and thereafter to guide the tubular member co-axially into the timber prop during yielding.

2. A mine prop as claimed in claim 1 wherein one or more cavities or holes extend substantially parallel the bore, the cavities or holes being defined in a zone intermediate the bore and an outer surface of the timber prop.

3. A mine prop as claimed in claim 2 wherein the cavity is in the form of a slot that is configured to circumscribe or surround a substantial portion of the bore.

4. A mine prop as claimed in claim 3 wherein the slot is of generally annular form or configuration.

5. A mine prop as claimed in claim 4 wherein the outside diameter of the slot falls within the region of 100 mm to 125 mm, preferably 114 mm.

6. A mine prop as claimed in any one of claim 2 to 5 wherein the width of the slot falls within the region of 4 mm to 12 mm, preferably 8 mm.

7. A mine prop as claimed in any one of the preceding claims wherein the ratio of the cross-sectional areas of the timber prop to the tubular member and/ or bore falls within the region of 1 ,5:1 to 20:1 , preferably 16:1.

8. A mine prop as claimed in any one of the preceding claims wherein the bore has an axial length of between 250 mm to 500 mm.

9. A mine prop as claimed in any one claims 1 to 7 wherein the length of the bore is substantially equal to the length of the tubular member and is variable according to the length of the tubular member used.

10. A mine prop as claimed in claim 9 wherein the bore is circular in cross- section and has a diameter which is slightly greater or at least corresponds to the diameter of the tubular member, so as to facilitate snug sliding engagement between the outer surface of the tubular member and a wall of the bore.

11. A mine prop as claimed in claim 10 wherein the cross-section of the bore is selectable from any conventional shape, preferably square, rectangular, hexagonal, oval, elliptical or the like, the dimensions of which are slightly greater or at least correspond to the dimensions of the tubular member, so as to facilitate snug sliding engagement between the outer surface of the tubular member and a wall of the bore.

12. A mine prop as claimed in any one of the preceding claims wherein the diameter of the timber prop is about 180 mm to 220 mm.

13. A mine prop as claimed in claim 12 wherein the timber prop is a Eucalyptus prop or any other suitable ligneous material.

14. A mine prop as claimed in claim 13 wherein the length of the timber prop is about 0,7 m to 3 m.

15. A mine prop as claimed in any one of claims 12 to 14 wherein the timber prop is "Micon Dip" treated before use.

16. A mine prop as claimed in any one of the preceding claims wherein the tubular member is circular in cross-section.

17. A mine prop as claimed in claim 16 wherein the tubular member has an outside diameter of about 45 to 55 mm, preferably 50 mm.

18. A mine prop as claimed in claim 17 wherein the tubular member has a wall thickness of about 1 to 5 mm, preferably 3 mm.

19. A mine prop as claimed in any one of claims 16 to 18 wherein the length of the tubular member is about 300 mm to 500 mm.

20. A mine prop as claimed in any one of the preceding claims wherein the tubular member has one or more projections extending radially outwards the tubular member.

21. A mine prop as claimed in claim 20 wherein the projections are in the form of extension arms that extend radially outwards the tubular member.

22. A mine prop as claimed in claim 21 wherein the extension arms are arranged towards an end of the tubular member that in use receives a prestressing device.

23. A mine prop as claimed in claim 22 wherein the extension arms are in the form of metal plates attached to the tubular member.

24. A mine prop as claimed in claim 23 wherein the dimensions of the plates are as follows: thickness between about 3 mm to 8 mm, preferably 5 mm, length about 40 mm to 60 mm, preferably 50 mm and width about 30 mm to 50 mm, preferably 35 mm.

25. A mine prop as claimed in claim 24 wherein four metal plates are attached to the tubular member at substantially 90 degree angles to each other.

26. A mine prop as claimed in any one of the preceding claims wherein a metal strip is arranged co-axially interior or exterior the tube in the form of a wave so as to define spaces and/or passages between the longitudinal side wall of the tubular member and the strip.

27. A mine prop as claimed in any one of claims 1 to 25 wherein a metal strip is arranged co-axially interior or exterior the tube, there being provided connecting members which extend radially the tubular member to connect the metal strip to the tubular member.

28. A mine prop as claimed in claim 27 wherein a support band having dimensions slightly exceeding those of the tubular member so that it may slide onto the tubular member is attached to said member above the metal strip.

29. A mine prop as claimed in any one of the preceding claims wherein projections of generally "V" - shape configured to extend outwardly or inwardly the inner and outer walls of the tubular member are provided on the wall of the tubular member.

30. A mine prop as claimed in claim 29 wherein the "V" - shaped projections are formed from angle iron.

30. A mine prop as claimed in any one of the preceding claims wherein the tubular member is of a frusto-conical shape, with the larger radius being at that end of the tubular member that will be forced into the timber below the bore first.

31. A mine prop as claimed in any one of the preceding claims wherein a valve protection means in the form of an extension arm that extends outwardly the tubular member near to its free end is provided on the tubular member.

32. A mine prop as claimed in claim 31 wherein the extension arm is aligned with a valve of a setting device positioned on the timber member in use so as to split and urge the timber away from the valve during yielding as the setting device moves through the timber member in use.

33. A mine prop as claimed in any one of the preceding claims wherein one or more retaining bands are provided to fit snugly around the timber prop to inhibit lateral or transverse expansion of the timber prop during yielding or displacement of the tubular member from its co-axial position into the timber prop in use.

34. A mine prop as claimed in claim 33 wherein a first retaining band is located towards an end of the timber prop wherein the bore is defined.

35. A mine prop as claimed in claim 34 wherein the first band is arranged about 30 mm to 70 mm, preferably 50 mm from the end of the timber prop wherein the bore is defined.

36. A mine prop as claimed in any one of claims 33 to 35 wherein further bands are arranged at intervals of about 80 mm to 120 mm, preferably 100 mm along a portion of the length of the prop, the last of which bands is preferably a double wind.

37. A mine prop as claimed in any one of claims 33 to 36 wherein a further retaining band is provided at a distance of about 180 mm to 220 mm, preferably 200 mm, from that end of the timber prop which has no bore defined in it.

38. A mine prop as claimed in any one of claims 33 to 37 wherein another band is provided at a distance of about 360 mm to 440 mm, preferably 400 mm, from that end of the timber prop which has no bore defined should the timber prop exceed 1 ,4 m in length.

39. A mine prop as claimed in any one of claims 33 to 38 wherein the retaining bands are manufactured from fencing rod having a diameter of about 3 mm to 8 mm, preferably 5,5 mm.

40. A mine prop as claimed in any one of the preceding claims wherein one or more carry handles are attached to the mine prop to facilitate handling thereof.

41. A yielding device which includes:- a tubular member as claimed in any one of the preceding claims having one or more projections extending radially outwards thereof having a cross section dimensioned so as to allow the tubular member to be received by a complementary co-axially defined bore in a timber prop configured to guide the tubular member co-axially into the timber prop initially and thereafter during yielding facilitated by the movement of the tubular member into the timber prop wherein the ratio of the cross-sectional areas of the timber prop to the bore and/ or tubular member is between 1 ,5:1 and 20:1 preferably 16:1 ; and a prestressing or setting device which is mounted on the free end of the tubular member to permit prestressing of the timber prop in use.

41. A mine prop and a yielding device according to the invention, as hereinbefore generally described.

42. A mine prop and a yielding device as specifically described with reference to or as illustrated in the accompanying drawings.

43. A mine prop and a yielding device including any new and inventive integer or combination of integers, substantially as herein described.