AU2019101267A4 - Tubular Nut for a Rock Bolt - Google Patents

Abstract

The invention provides a tubular nut for use with a rock bolt which includes a tubular body, defining an axis, having a leading end and a trailing end, a 5 passage which extends along the axis, opening at each of the ends, the passage having a threaded portion which is adapted to engage formations on a trailing end of the rock bolt and which extends, at least partially, along the passage from the leading end, wherein the tubular body has a first portion of a first diameter which ends at the leading end and which is sized to be received 10 in a rock hole and a second portion which ends at the trailing end and which extends to a second diameter which is larger than the first diameter, wherein the second portion includes an abutment surface which ends at the first portion, and wherein the second portion has a plurality of formations on an exterior surface which are adapted to engage with complementary formations on a drive 15 means. Lak

Description

TUBULAR NUT FOR A ROCK BOLT

FIELD OF INVENTION [0001] The invention relates to a tubular nut for use with a rock bolt.

BACKGROUND OF THE INVENTION [0002] Rock bolts used in the reinforcement of underground excavations commonly use a threaded fixture, such as a nut, to transfer load from a faceplate, positioned against the rock face, to the installed rock bolt. This load will change over the life of the excavation, as the rock mass deforms, imposing greater load on the rock bolt as the rock face closes towards the foot wall.

Conversely, the rock bolt can be pretensioned by application of load, via the nut, on the faceplate and the rock bolt.

[0003] More specifically, during installation of the rock bolt, tension is applied to the rock face by rotation of the threaded fixture along the axis of the rock bolt which is installed within the rock hole, anchored at its distal end or along its length using any of the well know mechanical or adhesive anchoring methods in the industry. During the tensioning process the length of rock bolt protruding from a proximal end of the threaded fixture increases. In an instance of poor installation, such as for example when the rock hole has been drilled insufficiently deep, the resultant protruding length of the bolt poses a safety risk to personnel and increases the chance of damage to moving machinery

2019101267 18 Oct 2019 passing by the installed bolt.

[0004] In order to address this problem, several solutions have been developed, including an end coupling which is described in WO2016/065398.

[0005] Whilst the end coupling may have addressed the problem of excessive 5 rock bolt protrusion, the means by which the coupling is rotated is limiting.

WO2016/065398 describes how a driver tool is inserted into a passage through the coupling. The inserted drive tool blocks the passage to movement of the rock bolt, movement which is sometimes necessary for an installation.

[0006] The invention at least partially solves the aforementioned problem.

SUMMARY OF INVENTION [0007] The invention provides a tubular nut for use with a rock bolt which includes a tubular body, defining an axis, having a leading end and a trailing end, a passage which extends along the axis, opening at each of the ends, the passage having a threaded portion which is adapted to engage formations on a trailing end of the rock bolt and which extends, at least partially, along the passage from the leading end, wherein the tubular body has a first portion of a first diameter which ends at the leading end and which is sized to be received in a rock hole and a second portion which ends at the trailing end and which extends to a second diameter which is larger than the first diameter, wherein the second portion includes an abutment surface which ends at the first portion,

2019101267 18 Oct 2019 and wherein the second portion has a plurality of formations on an exterior surface which are adapted to engage with complementary formations on a drive means.

[0008] The second portion may be shaped as a bulbous formation.

[0009] The abutment formation may be a leading end facing surface of the bulbous formation, adapted to engage a faceplate on the rock bolt on installation.

[0010] Each formation of the plurality of formations may be a recess, a slot, a notch or a planar surface which is formed on or cut into an outer surface of the bulbous formation.

[0011] Alternatively, the plurality of formations may be apertures which are formed at least partially through the bulbous formation, each extending in an axial direction and each opening at the proximal end.

BRIEF DESCRIPTION OF DRAWINGS [0012] The invention is described with reference to the following drawings in which:

Figure 1 illustrates, in longitudinal section, a rock bolt assembly installed in a rock hole with a tubular nut in accordance with the invention, engaged with the rock bolt in a first relative position;

2019101267 18 Oct 2019

Figure 2 is a view in elevation of the rock bolt assembly of Figure 1;

Figure 3 illustrates, in longitudinal section, the rock bolt assembly of Figure 1 installed in a rock hole with the tubular nut engaged with the rock bolt in a second relative position;

Figure 4 is a view in elevation of the rock bolt assembly of Figure 3;

Figures 5 illustrates the tubular nut in longitudinal section; and

Figure 6, 7 and 8 are isometric illustrations of a first, second and third embodiment of the tubular nut respectively.

DESCRIPTION OF PREFERRED EMBODIMENTS [0013] Figure 1 and 3 illustrate a rock bolt assembly 10, inserted in a rock hole

12, in a first and a second configuration respectively. The rock bolt assembly includes a resin-anchored rock bolt 14, having a shaft 16 which extends between a distal end 18 and a proximal end 20, a tubular nut 22 in accordance with the invention, engaged with the shaft of the rock bolt, and a faceplate 24.

[0014] The shaft 16 has a threaded proximal end section 26, which ends at the proximal end 20. It is to this section that the tubular nut is engaged.

[0015] The shaft is adapted with features that provide for efficient resin adherence of the rock bolt within the rock hole 12. These features are not limiting to the invention and include a ribbed outer profile, as illustrated in

Figures 2 and 4, a penetrating formation 28 on the distal end 18, and a plurality of paddle formations 30 formed in the outer surface of the shaft. The

2019101267 18 Oct 2019 functionality of these features will be described below.

[0016] The tubular nut 22, as best illustrated in Figure 5, includes a tubular body 32, defining an axis (illustrated as a dotted line on Figure 5 and designated X), having a leading end 34 and a trailing end 36 and a passage 38 extending along the axis, opening at each of the ends. The passage has a threaded portion 40, which is adapted to engage the threads of the threaded proximal end section 26 of the shaft 16, and which portion extends, in this example, only partially along the passage from the leading end.

[0017] The tubular body 32 is divided into a first elongate tubular portion 42 of 10 a first diameter (designated Y on Figure 5) and a second bulbous portion 44 which ends at the trailing end 36 and which extends to a second diameter (designated Z on Figure 5) which is substantially larger than the first diameter. The bulbous portion defines a sloping leading-end facing abutment surface 46, a convex median surface 47 and a back surface 48 which terminates at the trailing end 36. Within, or on, the bulbous portion, a plurality of drive-receiving formations 50 are provided. The shape or configuration of these formations are dependent upon the particular embodiment illustrated in Figures 6, 7 and 8.

[0018] In use of the tubular nut 22, as part of the rock bolt assembly 10, the tubular nut 22 is attached to the rock bolt 14 by inserting the proximal end 20 of the shaft 16 into the passage 38 of the nut, from its leading end, so that the threaded proximal end section 26 can threadedly engage the passage’s threaded portion 40. This assembled, pre-inserted, assembly is illustrated in Figure 1.

2019101267 18 Oct 2019 [0019] The faceplate 24 is passed over the rock bolt, to abut up against the abutment surface 46 of the bulbous portion 44 of the nut 32.

[0020] Alternatively, the bolt 14 can be inserted into the hole 12, the faceplate placed against the rock face 52, about the hole, and the tubular nut 22 can be partially inserted into the hole tubular first portion 42 leading, as it is sized to be received in the hole without the need to re-bore the hole, to reach, and threadedly engage with, the rock bolt which proximal end 20 is recessed within the hole.

[0021] The assembly 10 can be grouted or adhered within the rock hole 12 by 10 any suitable method, using any suitable grout or adhesive. Typically, a number of resin-containing capsules (not shown) are pushed into the hole 12 prior to rock-bolt insertion.

[0022] The assembly 10 is then inserted into the hole 12, with the distal end 18 penetrating formation 28 leading, pushing through and puncturing the pre15 installed capsules, until the faceplate 24 abuts the rock face 52.

[0023] The insertion is performed by either a mechanised or hand-held (rockdrill) drive means. Either way, the bulbous portion 44 of the tubular nut 22 is received in a chuck or socket-end (hereinafter referred to as a chuck) of the drive means before an axial driving force is exerted on the tubular nut, and the attached rock bolt 14 by or via the drive means to push the assembly 10 into the hole.

[0024] Before pre-tensioning the rock bolt 14 in the hole 12, the resin contents

2019101267 18 Oct 2019 of the punctured capsules require mixing before the resin hardens. This is achieved by rotating the rock bolt, about the axis, bringing the mixing functionality of the paddle formations into action 30. However, the rock bolt must not move relatively to the nut 22 during this action and so a shear pin 54 is provided. This pin, laterally penetrating the body 32 of the nut and the rock bolt, locks the rock bolt against rotation relatively to the nut. Thus, when a rotational drive force is applied to the nut by the drive means, the nut and the bolt rotate in unison up to threshold torque.

[0025] As the resin begins to harden, so the torque on the nut increases until a 10 threshold torque is reached, at which point the shear pin shears, unlocking the nut 22 from the bolt 14 and allowing the threaded portion 34 of the nut to ride along threaded proximal end section 26 to draw the bolt further into the passage 38. In so doing, as the upper part of the bolt adheres within the hole

12, this drawing action axially elongates the bolt, placing the bolt in pretension 15 and reactively forcing the nut against the faceplate and, in turn, in load supportive contact with the rock face 52.

[0026] As the drive means engages exteriorly with the tubular nut 22, the passage remains open, to its full axial extent, to the axial inward ingress of the rock bolt 14. Figure 3 illustrates a second configuration of bolt 14 to nut 22 after this pre-tensioning movement.

[0027] To optimally transfer torque to the nut, to turn the nut on the bolt in pretension, the chuck of the drive means is complementary shaped to the

2019101267 18 Oct 2019 bulbous formation 44 of the nut 22, specifically as adapted by the drivereceiving formations 50.

[0028] There are a number of non-limiting examples of the drive-receiving formations. In Figure 6, a circumferential series of planar surfaces or flats (respectively designated 50A, 50B, ...50N) are provided, by any suitable means, on the convex surface 47 of the bulbous portion 44 in a typical hex-nut configuration. In Figure 7, each drive-receiving formation is radially spaced about the circumference of the bulbous formation and is an in-cut formation (respectively designated 50A, 50B, ...50N). Each such formation provides two perpendicular surfaces, respectively designated 56A and 56B. It is against the radially directed surface 56B that the drive means imparts torque to the nut 22.

[0029] In Figure 8, each drive-receiving formation is a channel (respectively designated 50A, 50B, ...50N) formed through the bulbous formation, each extending in an axial direction, and each opening at the leading-end facing abutment surface 46 and a back surface 48. The channels again are regularly radially spaced. It is through each channel that a pin (not shown) of the drive means inserts to provide the rotational drive/torque.

Claims (5)

1. A tubular nut for use with a rock bolt which includes a tubular body, defining an axis, having a leading end and a trailing end, a passage which extends along the axis, opening at each of the ends, the passage having a

5 threaded portion which is adapted to engage formations on a trailing end of the rock bolt and which extends, at least partially, along the passage from the leading end, wherein the tubular body has a first portion of a first diameter which ends at the leading end and which is sized to be received in a rock hole and a second portion which ends at the trailing end and which extends to a

10 second diameter which is larger than the first diameter, wherein the second portion includes an abutment surface which ends at the first portion, and wherein the second portion has a plurality of formations on an exterior surface which are adapted to engage with complementary formations on a drive means.

2. A tubular nut according to claim 1 wherein the second portion is a bulbous

15 formation.

3. A tubular nut according to claim 1 or 2 wherein the abutment formation is a leading end facing surface ofthe bulbous formation.

4. A tubular nut according to anyone of claims 1 to 3 wherein each formation of the plurality of formations is a recess, a slot, a notch or a planar surface which

20 is formed on, or cut into, an outer surface of the bulbous formation.

5. A tubular nut according to anyone of claims 1 to 3 wherein each formation of the plurality of formations is an aperture which is formed at least partially through the bulbous formation in an axial direction and which opens at the proximal end.

2019101267 18 Oct 2019