AU2014101357A4 - Improved Washer - Google Patents

Abstract

Abstract A washer for a rock bolt, the washer comprising a body having a leading end and a trailing end and an internal aperture extending between the leading end and the trailing end for receiving the rock bolt; and a coupling disposed on the body and arranged to receive an attachment having a complementary coupling so as to couple the attachment to the washer. U-00 (N 00 Q0 (NN 0m rQ 0N( b.0

Description

IMPROVED WASHER Technical Field The present invention relates generally to a washer for a rock bolt, a rock bolt assembly including a washer, and a method of assembling a rock bolt assembly including such a washer. 5 Background of the Invention Rock bolt assemblies provide roof, wall and floor support. Roof and wall support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts, which may be in the form of rigid bolts, .0 or flexible cable bolts, are widely used for consolidating the rock strata by securing a rock bolt in a bore within the rock strata. Reinforcement of the strata occurs through various bolting support mechanisms, including bolts bonding multiple layers or blocks together and tension placed across joints and bedding mobilising frictional resistance to rock movement. .5 The end of the bolt may be anchored mechanically to the rock formation by engagement of an expansion assembly on the end of bolt with the rock formation. Alternatively, the bolt may be adhesively bonded to the rock formation with a resin bonding material inserted into the bore hole. Alternatively, a combination of mechanical anchoring and resin bonding can be employed by using both an expansion assembly and resin bonding material. -O Additionally, rock bolts may be able to receive attachments, such as hangers for supporting mining services. In this regard, rock bolts can be installed to leave a tail portion protruding from the rock surface. The hangers may be attached to the tail portion of the rock bolt which may include a threading to receive said attachment. However, underground mines are typically limited for space, 25 and the protruding tails and attached hangers are sometimes unwanted, easily damaged, or cause damaged to mining equipment. The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also 30 not intended to limit the application of the method and system as disclosed herein 1 Summary of the Invention According to a first aspect, a washer for a rock bolt is disclosed, the washer comprises a body having 5 a leading end and a trailing end and an internal aperture extending between the leading end and the trailing end for receiving the rock bolt; and a coupling disposed on the body and arranged to receive an attachment having a complementary coupling so as to couple the attachment to the washer. In some forms, the coupling is in the form of a male thread extending along an external surface of the .0 body for receiving the attachment. In some forms, the male thread has a minor thread diameter larger than maximum dimensions of an end of the rock bolt. Advantageously, this feature facilitates coupling of the attachment to the washer, as the end of the rock bolt does not impede coupling of the attachment. .5 In some forms, the washer further comprises an internal recess extending from the trailing end, the body further comprises an internal surface that defines the recess, and the coupling is in the form of a female thread extending along the internal surface. In some forms, the female thread has a major thread diameter larger than the maximum dimensions of the end of the rock bolt to facilitate coupling of the attachment to the washer. .0 In some forms, the thread extends to the trailing end. The thread may be in the form of the male thread and/or the female thread. In some forms, the leading end is convex. In some forms, the internal aperture is smooth. 25 According to a second aspect, a rock bolt assembly is disclosed comprising: a rock bolt configured to be at least partially located in a bore formed in a rock substrate, the rock bolt having a shaft extending between opposite first and second ends; an end fitting fixed or mounted to the rock bolt proximal the second end; and 2 a washer mounted on the rock bolt and being retained on the rock bolt by the end fitting and the washer being in any form as described in respect of the washer of the first aspect. In some forms, the rock bolt assembly further comprises an attachment, the attachment is received by 5 the coupling. In some forms, the attachment is in the form of a hanger to allow mining services to be attached to the rock bolt assembly. For example, the coupling may be used to hang power or water lines. In some forms, the attachment is in the form of a load testing apparatus. For example, the load testing apparatus may check the quality of ground support provided by the rock bolt assembly. .0 In some forms, the rock bolt assembly further comprises a plate, the plate being configured to be located between the surface of the rock substrate and the washer. In some forms, the leading end of the washer is convex to allow, in use, the leading end to be received by a complementary aperture in the plate. In some forms, the plate is in the form of a volcano plate. The convex leading end of the body may be advantageous by effectively self-locating the washer to the plate during compression of .5 the plate against the rock face. The convex leading end of the body accommodates angled loading from the plate to transmit a purely axial load to the bolt end fitting for maximum load capacity. In some forms, the trailing end of the washer is substantially flat. This feature is advantageous as it facilitates retention of the washer by the end fitting. The substantially flat surface may reduce friction .0 losses during rotation of the end fitting in relation to the washer. According to a third aspect, a method of mounting an attachment to a rock bolt assembly installed in a bore formed in rock substrate, the method comprising the steps of: providing a washer on a protruding end of the rock bolt assembly, the washer being retained 25 thereon by an end fitting and the washer including a coupling; providing the attachment with a complementary coupling on the body of the washer; and coupling the attachment to the washer via the coupling. In some forms, the coupling is in the form of a male thread extending along an external surface of a 30 body of the washer, and the method further comprises threading the attachment on the male thread. In 3 some forms, the washer further comprises an internal recess extending from the trailing end, the body further comprises an internal surface that defines the recess, and the coupling is in the form of a female thread extending along the internal surface, the method further comprises threading the attachment on the female thread. 5 Brief Description of the Drawings Embodiments of the present disclosure will now be described with reference to the following drawings by way of example only, where Fig. 1 is a bottom isometric view of one embodiment of a washer; .0 Fig. 2 is atop isometric view of the washer of Fig. 1; Fig. 3 is a side view of one embodiment of a rock bolt assembly including the washer of Fig. 1; Fig. 4 is a top isometric view of the rock bolt assembly of Fig. 3 and an attachment mounted thereon; Fig. 5 is a side view of the rock bolt assembly and the attachment of Fig. 4 mounted thereon; Fig. 6 is a cross-sectional view of the rock bolt assembly of Fig. 4 and along the line A-A of Fig. 5; .5 Fig. 7 is a cross-sectional view of the rock bolt assembly of Fig. 5 in use; Fig. 8 is a top isometric view of a second embodiment of a washer; Fig. 9 is a cross-sectional view of the washer of Fig. 8; Fig. 10 is a side view of an installed rock bolt assembly incorporating the washer of Fig. 8; Fig .11 is a cross-sectional view of the rock bolt assembly and the washer along the line A-A of Fig. 20 10; Fig. 12 is a side view of the rock bolt assembly and the washer of Fig. 8 and an attachment mounted thereon; and Fig. 13 is a cross-sectional view of the rock bolt assembly along the line A-A of Fig. 12, the washer and the attachment along the line A-A of Fig. 13 25 4 Detailed Description of the Embodiments Referring to the Figures disclosed are some illustrative embodiments of a rock bolt assembly and a washer for a rock bolt assembly. The washer allows coupling of embodiments of an attachment to enhance the functionality of the rock bolt assembly. 5 The disclosed rock bolt assembly is suitable for use in hard rock applications as well as in softer strata, such as that often found in coal mines, and it is to be appreciated that the term "rock" as used in the specification is to be given a broad meaning to cover both these applications. The following description relates to assemblies for reinforcement of rock strata through various bolting support .0 mechanisms, including bolts bonding multiple layers or blocks together and tension placed across joints and bedding mobilising frictional resistance to rock movement.. Although, the washer is discussed in relation to a rock bolt assembly in the form of a rigid bolt, embodiments of the washer may be used with either a rigid bolt or a cable bolt, and are not limited to a rigid bolt. The rigid bolt generally works in connection with a threaded end fitting disposed at an exterior surface of the rock .5 strata, and the cable bolt generally works in connection with a barrel and wedge end fitting disposed at an exterior surface of the rock strata. Referring to Figs. 1 and 2, disclosed is a first embodiment of a washer 10 for a rock bolt 12. The washer 10 includes a body 14 which has a leading end 16 and a trailing end 18. A coupling 22 is 0 disposed on the body 14. The coupling 22 is arranged to receive an attachment 24 having a complementary coupling so as to couple the attachment 24 to the washer 10. The body 14 also has an internal aperture 20 extending between the leading end 16 and the trailing end 18 for receiving the rock bolt 12. In the illustrated embodiment, the internal aperture 20 is of the 25 body 14 smooth which allows for the washer 10 to be easily received by the rock bolt 12. In the illustrated embodiment, the coupling 22 is in the form of a male thread 28 that extends along an external surface 30 of the body 14 for receiving the attachment 24. The leading end 16 is convex and the male thread 28 extends to the trailing end 18. The convex leading end may also be in the form of 30 a dome-shaped end. The dome-shaped leading end 16 facilitates alignment of the washer in use in a rock bolt assembly 32, as well as connection to the assembly 32. The thread 28 extends to the trailing end 18 to be accessible and visible for facilitating receipt of the attachment 24. 5 Now turning to Figure 3, the rock bolt assembly 32 is shown including the washer 10 of Figs. 1 and 2. The rock bolt assembly 32 generally includes the washer 10, the rock bolt 12, an end fitting 34, and in the illustrated embodiment, a plate 44. In use, the rock bolt 12 is configured to be at least partially 5 located in a bore formed in a rock substrate (as shown in Fig. 6). The rock bolt 12 has a shaft 36 that extends between opposite first and second ends 40. The washer 10 is retained on the rock bolt 12 by the end fitting 34. The end fitting 34 is fixed or mounted to the rock bolt 12 proximal the second end 40. In the illustrated embodiment, the shaft 36 .0 of the rock bolt 12 has an external thread 42. The end fitting 34 has an internal thread and is arranged to be coupled to the external thread 42 of the shaft 36. The end fitting 34 is adapted to allow tensioning of the shaft 36 when it is located in the bore by being rotated along the shaft 36. Advantageously, the same size washer may be used on various sized bolts and in combination with various types of end fittings. This provides cost effective and flexible manufacturing options. .5 The male thread 28 of the washer 10 has a minor thread diameter d larger than maximum dimensions of the end fitting 34 and the second end 40 of the rock bolt 12. This allows for easy assembly and removal of the attachment, and facilitates unobstructed coupling of the attachment 24 to the thread 28. 0 In the illustrated embodiment, the rock bolt assembly 36 also includes the plate 44. The plate 44 is located between the surface of the rock substrate and the washer 10 (as shown in Fig. 6). The plate is in the form of a volcano plate 44, but may be in the form of any suitable plate. The volcano plate 44 and the dome-shaped the leading end 16 are designed to work together to facilitate alignment and assembly of the washer 10 and the end fitting 34 on the shaft of the rock bolt 12 by accommodating 25 angled loading from the plate 44 to transmit a purely axial load to the bolt end fitting for maximum load capacity. Attachments may be used with rigid bolts or cable bolts, and when installed, are generally used to hang mining services from the rock bolt assembly, such as power or water lines. However, an 30 attachment in the form of a load testing apparatus may be used for testing the quality of ground support provided by the rock bolt assembly. Another embodiment of an attachment may be in the form of mesh to inhibit crumbling and breaking rock from falling on workers. 6 Now referring to Fig. 4, a first embodiment of the attachment 24 is shown assembled on the rock bolt assembly of Fig. 3. In the illustrated embodiment, the attachment is in the form of a hanger 48. The hanger 48 is received by the coupling 22 on the body 14 of the washer 10. The hanger 48 is used to 5 hang mining services from the rock bolt assembly 32. The hanger 48 includes an attachment portion 50, and a hanging portion 52. The attachment portion 50 is in the form of a hex nut having a coupling 26 that corresponds to the male thread 28. In the illustrated embodiment, the coupling on the hanger 48 is in the form of a female thread for mating .0 with the male thread 28 of the washer 10. The hanging portion 52 is in the form of a U-shaped member that is fixed to opposing sides of the hex nut to form a closed loop. The mining services are threaded through the closed loop to secure them to the rock bolt assembly. The hanging portion may be in any suitable form, for example, a hook, etc. .5 In use, the rock bolt assembly is assembled (as shown in Fig. 3) prior to being inserted into the bore in the rock substrate. Once inserted into the rock substrate, the end fitting 34 is adapted to allow rotation to be imparted about the shaft 36 of the rock bolt 12 to compress the plate 44 against the rock face. The hanger 48 is then coupled to the washer 10 as illustrated in Fig. 4, and mining services are able to 0 be hung through the closed loop. It is understood that in other embodiments of an attachment where the attachment does not inhibit a drive being engaged with the end fitting, the attachment may be pre assembled. A second embodiment of the attachment 24 is illustrated in Figs. 5 to 7. The attachment 24 is in the 25 form of a load testing apparatus 62. The load testing apparatus may also be referred to as a pull test assembly 62. The pull test assembly 62 includes a coupler 64, a pull stem 66, a spacer 68, a hydraulic ram 70, and back nut 72. The pull test assembly checks the quality of ground support provided by the rock bolt assembly. The pull test assembly does this by hydraulically pulling the rock bolt to measure the displacement of the rock bolt. 30 7 The coupler 64 of the pull test assembly 62 is attached to the washer 10 via the male thread 28. The pull stem 66 is also threaded to attach to the coupler at its other end. The spacer 68 fits over the end fittings of the bolt, namely the plate 44, the washer 10, the end fitting 34, the coupler 64 and the pull stem 66. The hydraulic ram 70 is placed over the pull stem 66. The back nut 72 is then screwed onto 5 the end of the pull stem protruding behind the hydraulic ram 70. The hydraulic ram 70 includes an inner cylinder 74 and an outer cylinder 76. In use, the inner cylinder 74 of the hydraulic ram 70 is extended out using a hydraulic pump (as shown in Fig. 7). The inner cylinder 74 loads against the back nut 72, which is attached to the pull .0 stem 66. This transfers tensile load to the washer 10 and the rock bolt 12 via the end fitting 34. The reaction force from the back nut 72 is counteracted by the outer cylinder 76 of the ram 70, which is forced against the spacer 68 and indirectly the surface of the rock substrate. The net result is the progressive loading of the bolt 12, typically up to 75-80% of the bolt yield strength. The displacement of the bolt can also be measured during testing by using a displacement dial indicator .5 resting against the end of the pull stem 66. In non-illustrated alternative embodiments, the washer 10 may be used to attach mesh on a rock face outside of the development sequence of a roadway. During the development of a roadway additional mining induced stress can break the rock surface about a tunnel, especially during the traction of the .0 ore. The mesh may be required for the protection of the workers. The coupling of the washer meets the plate against the rock surface. The mesh can be fixed close to the rock surface by a secondary plate that is coupled to the washer. The secondary plate may be coupled may any suitable means, for example, a threaded nut or fixed by any other means. 25 Now referring to Figs. 8 to 13, a second embodiment of the washer 100 is illustrated. Like reference numerals are used for like features. The primary difference between the first embodiment and the second embodiment of the washer is that the second embodiment includes an internal coupling rather than an external coupling. As best shown in Figs. 8 and 9, the washer 100 includes an internal recess 56 extending from the trailing end 18. An internal surface 58 of the washer defines the recess 56. 30 The internal surface 58 also includes the coupling 22, which extends thereon. In the illustrated embodiment, the coupling 22 is in the form of a female thread 60. It is also understood that the washer may include both an internal and an external coupling. 8 The washer 100 is illustrated in Figs. 10 and 11 assembled on the rock bolt assembly. As best shown in Fig. 11, the washer 100 is able to receive the attachment 24 via its female thread 60. The female thread 60 has a major thread diameter D larger than the maximum dimensions of the end fitting 34 and the second end of the rock bolt 12. 5 Figs. 12 and 13 illustrate the rock bolt assembly in use having the attachment 24 mounted thereon. In the illustrated embodiment, the attachment is in the form of the hanger 48. The hanger 48 includes a male thread that corresponds to the female thread 30 of the washer 100 for coupling the hanger 48 to the washer 100. As discussed above, the hanger 48 includes an attachment portion 50, and a hanging .0 portion 52. Both embodiments of washers 10, 100 are in the form of a dome-washer. Therefore, the leading end is dome-shaped and the trailing end is substantially flat. These features, that is, the domed leading end 16 and the flat trailing end 18, provide better control on the rock bolt 12. The torque/tension .5 relationship on the rock bolt 12 is affected by friction. The primary contributors to tension on the rock bolt are approximately 10% due to the pitch of the thread, 40% due to the thread friction and 50% due to bearing surface friction. The domed leading end 16 effectively locks to the plate 44. A flat end surface of the substantially flat trailing end 18 allows a complementary substantially flat end surface of the end fitting 34 to rotate against the flat end surface of the trailing end 18. The two flat .0 surfaces end surfaces may also be lubricated to reduce friction losses by 50% in the torque/tension relationship. Whilst the dome and flat ends of the washer provide the above advantages, it is to be appreciated that the ends may take other profiles and therefore the disclosure is not limited to that arrangement. 25 Advantageously, the washer 10, 100 may be used in combination with low profile rock bolts. Low profile rock bolts are used where rock bolt shaft tails are arranged to not protrude excessively from the face of the rock substrate. Shaft tails protruding into a mine tunnel are susceptible to damaging equipment or equipment can hit and damage the ground support provided by the rock bolt assembly. However, low profile bolts do not have a coupling able to receive any attachment. Therefore, the 30 threaded washer 10, 100 is ideal for receiving an attachment 24 as it unlikely to be damaged by or damage equipment because of its proximity to the surface of the rock substrate and fits within the plate such that it is substantially flush with the plate. As a result, the rock bolt 12 protrudes from the face of the rock surface with little or no shaft tail. 9 Conventional rock bolts protrude from the surface of the rock substrate more than the low profile rock bolts. As a result, conventional rock bolts are more susceptible to damage than low profile rock bolts. Known ways to hang services or load test is from the end of end fitting (i.e., nut) or the end or from 5 the second end of the rock bolt. When the conventional rock bolts are hit by equipment both the nut and the second end of the rock bolt are left useless for hanging services or load testing. In these circumstances, the washer 10, 100 is also beneficial, as it is not as susceptible to damage and may still be used for an attachment, for example, to hang services, load testing etc. .0 Further, embodiments according to the present disclosure are advantageous as they are directed to a separate washer and end fitting arrangement rather than a one piece washer and end fitting arrangement. A separate washer and end fitting arrangement is advantageous for at least the following three reasons: 1. Lower comparative manufacturing cost due to simpler forging shapes and automatic .5 threading. 2. Better control on bolt loading provided by the advantageous torque/tension relationship discussed above. 3. Versatile and flexible options in manufacturing (i.e., the same washer may be used for various size bolts). .0 In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e., to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the 25 method and apparatus. 10

Claims (5)

1. A washer for a rock bolt, the washer comprising: a body having a leading end and a trailing end and an internal aperture extending 5 between the leading end and the trailing end for receiving the rock bolt; and a coupling disposed on the body and arranged to receive an attachment having a complementary coupling so as to couple the attachment to the washer.

2. The washer according to claim 1, wherein the coupling is in the form of a male thread .0 extending along an external surface of the body for receiving the attachment.

3. The washer according to either claim 1 or claim 2, further comprising an internal recess extending from the trailing end, the body further comprising an internal surface that defines the recess, and the coupling is in the form of a female thread extending along the internal .5 surface.

4. The washer according to either claim 2 or claim 3, wherein the thread extends to the trailing end. O0

5. A rock bolt assembly comprising: a rock bolt configured to be at least partially located in a bore formed in a rock substrate, the rock bolt having a shaft extending between opposite first and second ends; an end fitting fixed or mounted to the rock bolt proximal the second end; and a washer mounted on the rock bolt and being retained on the rock bolt by the end 25 fitting and the washer comprising the features according to any one of claims I to 4. 11