[0001] THIS INVENTION relates to improvements in or in relation to mine roof cribs and associated joiners and in particular but not limited to joiners used to secure chocks in mine support cribs.

BACKGROUND

[00Q2j Applicant has considered existing mine support cribs and has invented a number of improvements and alternatives to the prevailing norm.

[0003] Mine support cribs are made up from timber planks layered horizontally and stacked vertically. The planks are known as chocks. In the simplest form two chocks are laid parallel and then two chocks are laid on top of them at right angles and this is repeated in "pigsty" fashion until it reaches the mine roof and then wedges are driven in to lock the crib in place. Three or more parallel chocks may be used in each layer. Load is transferred through the chock's crossover points,

[0004] This arrangement had two problems, first the point loading and second the chocks are prone to slide sideways. These probferns were solved by the introduction of notched chocks. In this arrangement each chock had spaced pairs of opposed notches top and bottom with respective pairs of notches spaced just in from each end of the chocks with the depth of the notches equal to one quarter the depth of the chock. This meant that the chocks were locked against sliding and the load-bearing surface was along the entire length of the chocks rather than just at the crossover points. There was thought to be a saving in timber volume due to the improved load-bearing capability enabling thinner Umber to be used. However, more layers of the same width timber are required in the notched version to get to the same height.

[0005] Additional pairs of notches could be evenly spaced so that extra chocks coufd be used in each layer. Generally, the crib is in the form of a rectangle or square in this form and also in the earlier forms as the chocks are set at right angles.

[0006] Applicant has devised a number of inventions some of which are, in preferred applications, are specifically directed to the mine roof support cribs but could be used in other applications. This will be clear from the description. Consequently, each of these inventions have been described generally below and also in specific application and combination as applied to a mine roof support crib. Applicant reserves the right to divide each invention in one or more divisional applications.

[0007] Even though the inventions described herein were developed after the prior art referred to above, the mine support cribs are all based on the notion of alternating and overlapping timber chocks and in this sense the art has become crowded but without any new developments over many years in relation to what is essentially a very simple idea. Consequently, there is a requirement for a fresh look at the general problems and to look "outside the box" through new eyes in an effort to provide an alternative to the efforts made over the last twenty years. It would be desirable to have something that is simple and easy to assemble yet effective.

[0008] All the above chocks work and are generally made to the prevailing standards so in this sense there is nothing wrong with them and they do not in any way lead to the conclusion that there is a specific obvious problem in need of solution.

OUTLINE

[0009] In one invention there is provided a triangular prism shaped mine roof crib comprising layers of chocks, each chock having at least two narrow sections so that the chocks are interconnected at the narrow sections forming a triangle in profile. Preferably, the narrow sections join to comprise lap type joints which can be mitred lap joints spaced from the ends of the chocks to prevent sliding thereof or mitred end lap joints using dowels to secure the joints against sliding. The joints can be mitred at 45 degrees or at other acute angles still forming a triangle. The shoulders and cheeks of the joints need not be straight.

[0010] In another invention there is provided a chock for a mine roof crib, the chock comprising a rail having a joint portion at or adjacent each end and being adapted to form joints with other similar chocks, the joints so formed resulting in a triangular prism shaped mine roof crib.

[001 1] Applicant made another invention, being a dowel type joiner having an automatic alignment feature to lead chocks into position and particularly suited to the end lap joint type chocks. One end of this joiner has a cone top to lead a chock onto the joiner while the other end is substantially absent a similar cone. The cone top is substantially more than a bevel. The end opposite the cone typically has rows of circumferentially spaced teeth.

[0012] Applicant made another invention, being a dowel type joiner based on the joiner referred to in the last paragraph but omitting the automatic alignment feature so in a preferred form this joiner substantially mirrors the end opposite the cone but on both ends.

[0013] in one invention, in a preferred form, there is provided a dowel type joiner having a first end and a second end opposite the first end, the ends being joined by a shaft, at least one end having a tapered lead in, the tapered lead in commencing adjacent a central axis of the shaft and diverging to an outer extremity of the shaft, the shaft being of substantially uniform cross-section in terms of its outer periphery and being adapted to slide into a cylindrical hole. Preferably, the tapered lead-in is generally of a cone configuration.

[0014] Typically, the lead-m includes a generally cone shaped body meeting the shaft at a juncture between the cone shaped body and a cylindrical portion of the shaft, the cylindrical portion extending to a medial flange extending radially and axially about the shaft, the shaft continuing to the opposite end of the joiner, the opposite end of the joiner having circumferentially spaced radially extending rows of teeth adapted to bias the joiner against removal from a cylindrical hole. The flange is optional.

[0015] Preferably, the shaft or sections of the shaft include axially extending rigid or semi-rigid ribs spaced around the periphery of the shaft, the ribs being so made and arranged as to enhance frictional engagement between the shaft and an inner wall of a cylindrical hole.

[0016] The joiner is typically moulded from a relatively hard plastics material. In one embodiment the plastics material can be hard, in another it can be made such that the ribs and teeth deform slightly as the joiner shaft is being pushed into a cylindrical hole. In another case the material used may be nylon or other rigid material so that the material in the wall of the cylindrical hole is deformed as the joiner shaft is being pushed into the cylindrical hole.

(001 7] In another case the first end of the joiner can include a relatively smooth cone section leading into a shaft section comprising circumferentially spaced projections adapted to improve frictional engagement with the inner wall of a cooperating cylindrical hole.

[00181 The opposite end is typically an extension of the shaft so that the joiner resembles a pointed object at one end and terminating at a relatively flat end at its opposite end, this extension can include projections to improve frictional engagement with a cylindrical hole. The projections can include rows of teeth, or be barb like, each tooth or barb having a resilient tang function mechanically connecting the teeth or barb to the remainder of the joiner such that upon insertion of the joiner into a cylindrical hole, the resilient tangs are biased against removal of the joiner from the cylindrical hole. [0019] In another aspect there is provided a mine roof cib chock having opposite ends, each end having a hole and a separate cock joiner'fitted into the hole. In this case built from these chocks is a still further aspect comprising joined together mine roof crib chocks of any configuration, joined using a joiner as described in any of the preceding paragraphs where all the chocks are provided with upwardly facing joiners at each end with upwardly facing chock lead-in top sections.

[0020J In still another invention there is provided a three part mine roof crib chock comprising a rail and two rail joiner elements connected to the rail, at least one of said elements being a separable joiner, and being adapted to be inserted into a mating element of another rail for form a joint. The separable joiner may comprise dowel type joiner insertable into a hole in the rail as described in any one of the preceding paragraphs. Alternatively, the joiner may be formed as part of an add-on rail extension with a projection effectively operating as the cone shaped lean in for the next chock. Typically, the add-on is moulded as a half lap joint fitting securable to the end of the rail.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order that the present invention may be more readily understood and be put into practical effect reference will now be made to the accompanying drawings which illustrate preferred embodiments of the inventions and wherein:-

Figure 1 is a drawing illustrating the use of a mine roof crib behind a mining operation; Figure 2 is a drawing illustrating the relative widths of two types of mine cribs, both made according to one invention as set out herein;

Figure 3 is a perspective part exploded view of a triangular crib according to one invention as described herein;

Figures 4A and 4B show a part section through chocks showing operation of a chock joiner according to one invention as described herein;

Figures 5 to 7 are drawings illustrating another embodiment of a chock and a chock joiner; Figures 8A-8E illustrate in a joiner according to another invention;

Figure 9 illustrates application of a joiner similar to the joiner illustrated in Figures 8A-8E; and

Figure 10 illustrates application of a joiner similar to the joiner illustrated in Figures 8A-8E to construction of a raised timber garden bed.

METHOD OF PERFORMANCE

[0022] Referring to the drawings and initially to Figures 1 and 2 there is illustrated application of the present invention to a mining operation 10 where a long wall 1 1 or other similar wall is being mined in the usual way.

[0023] A roof 12 of the line is supported on mine roof cribs 13 between floor 14 and roof 12. Cribs 13 maybe of the two types illustrated in Figure 2 being either a triangular crib 15 or a square crib 16 to be in described in greater detail below. The triangular crib is made up from chocks 17 and the square crib is made up from chocks 18. In both cases end lap joints are used with interconnecting joiners to be described below. It will be noted that in Figure 2 the relative width of the triangular crib for a comparable chock length is narrower than the square crib, it will also be noted that the triangular crib users a less timber than square crib.

[0024] Referring to Figures 3, 4A and 4B the triangular crib is illustrated in more detail. Each chock 17 comprises a length of timber typically about 750mm to 1000mm long, 75mm to 100mm thick and 100mm to 200mm deep and typically 150mm deep. Each chock has a first end 19 and a second end 20. Three chocks 17 form a layer 21 with mitred half lap joints at ends of the chocks. The chocks are held in place by a joiner 22. The lap joint cheek is reversed at each end of each chock, and each cheek has a through hole 23 and the joiner is a dowel type joiner 22 inserted into the hole 23 as shown. It will be appreciated that in order to save on mine inventory that the chocks will arrive onsite with the joiners in place so that mine workers do not have to worry about the joiners and due to the particular form of the chocks they can be easily assembled with automatic alignment as the chocks are stacked to form the crib,

[0025] The joiner 22 is shown in section in Figure 4A and in side view in Figure 4B. The joiner projects up at each end from each chock as the chock is laid and includes a cone top 24 which serves to lead the hole of the next chock into position. The cone at its widest is at the juncture with a cylindrical barrel or shaft 25 with a medial flange 26 locating in a rebate 27 in the chock cheek. The opposite end poVtion 28 includes four rows of teeth or barbs 2S to grip the interior wall 30 of the hole 23. The teeth or barbs are circumferentially spaced around the shaft 24. As the joiner barrel is substantially uniform in cross-section it is designed to work in a simply drilled hole, the drilling tool may be fitted with blade so that it cuts the rebate for the flange 26. The joiner can be of any suitable size for the application, in the case of a mine crib a suitable size would be 10 -15 mm wide by 40-60 mm long.

[0026] In addition the shaft includes circumferentially spaced axiaily extending ribs 31. As can be seen in Figure 4B the ribs 31 and the teeth 30 are marginally outside the wall 32 of the shaft 24. These teeth are made to deform or flex ever so slightly as the joiner is pushed into the drill hole 23 and bias the joiner against removaf from the hole as the teeth bite into the inner wall 30.

[0027] While Figures 3-4B illustrate the use of an end lap joint and a dowel type joiner the triangular crib form may be accomplished using mitred quarter lap joints or half lap joints that are not at the ends. In this embodiment the joiner would not be required. However, the use of the cone top joiner at the end lap is easier to assemble as the cone top joiner serves as a lead in to easily locate chocks.

[0028] The use of another cone shaped top for a joiner is illustrated in Figures 5-7. In this case the cone shaped top is not formed in a dowel but is moulded as a chock extension. Each chock 33 has each end 34, 35 machined to form a projection 36 and a rebate 37 surrounding the projection 36. A moulded end fitting 38 has a projection 39 which has a cone shaped top portion 40, which is basically the same form as the cone top and shaft section left protruding when using the dowel type joiner of the previous embodiment. The projection illustrated has a shaft portion 41 and a collar 42 formed on a mounting base 43, it has a bracket section 44 fitted to the projections 39 as fitted using screw fasteners as shown in Figure 6.

[0029] The base 43 has and axialiy aligned recess 45 in its underside so that the projection 39 of a lower chock can fit in, so that the chocks stack into a square crib as shown in Figure 7.

[0030] This crib is -formed also with an end lap joint formed using the moulded end extension 38 and this moulded from could be other shapes as in for example, it could be formed into a mitred end to effectively be the same as the mitred lap joint of the embodiment of Figures 3-4A thereby forming a triangular crib.

[0031] In relation to Figure 4B, it will be appreciated that the end portion 26 of the joiner 22 could be mirrored on the opposite side of the flange 26 thus forming a joiner 46 as illustrated in Figures 8A-8E where flange 47 is located in the middle of the joiner 46, each end at 47 and 48 has a bevelled lead in 49 and rows of circumferentially spaced teeth 50 and a barrel section 51 with circumferentially spaced ribs 52. There are seven teeth 50 in each row. There are atso seven ribs 52. It will be appreciated that although separate individual teeth 50 are shown in Figure 8D it may be possible to utilise other arrangements of circumferentially spaced gripping means including a ringlike structure as illustrated in Figure 9 at 53. Figure 9 shows how a joiner of the type illustrated in Figure 8D might be used to join two pieces of timber 54 and 55 together once holes 56 and 57 have been drilled. [0032] Figure 10 illustrates application of the joiner illustrated in Figure 8D or Figure 9 to the assembly of a garden bed frame 58 made from timber sections 59 where the joiners 46 are used in the usual way as dowels would be used to join timber in this type of structure.

[0033J In addition to the use of doweis 46 there is illustrated in Figure 10 a bridging type joiner 60 having a top section 61 and two plugs 62 and 63. These plugs may be in any form but typically also are in the same structure as illustrated by the end 48 as illustrated in Figure SD,

[0034] Joiners according to the present invention may be moulded from any suitable materiaf that works for the particular application. For example, it may be more desirable to have a certain amount of flexibility or softness in some case, while in other cases a more rigid material would be better. For example, in the case of a mine crib it may be desirable to have greater strength in sideways shear in the event a crib is knocked or bumped so as to minimise the risk of the joiner shearing. Suitable materials tested are set out in

Appendices 1 , 2 and 3 copies of which are filed herewith and are incorporated in their entirety by reference. Appendix 1 concerns PP (Polypropylene), Appendix 2 concerns HDPE (High-density polyethylene) and Appendix 3 concerns Nylon 101. As can be seen Nylon 101 has a shear load capability of more than twice that of the PP or HDPE.

(0035] Whilst the above has been given by way of illustrative example of the present inventions many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the inventions as set out in the appended claims. For example, in relation to the respective joiners, the flanges 26 and 47 could be omitted in which case there will be no need to drill a hole with a rebate as would particularly be the case if there was a blind hole drilled to correct depth. In addition in the present specification words "comprised", "comprising", "including" and similar words used herein are non-limiting and are used in the non-exhaustive inclusive sense, that is to say they do not mean "made up of" but rather "include".