GB2349679A

GB2349679A - Nuts for use with rock bolts

Info

Publication number: GB2349679A
Application number: GB9910488A
Authority: GB
Inventors: Graham Laurence Warwick-Adkins
Original assignee: MAI SYS UK Ltd; SAT SYS UK Ltd
Current assignee: MAI SYS UK Ltd; SAT SYS UK Ltd
Priority date: 1999-05-07
Filing date: 1999-05-07
Publication date: 2000-11-08
Anticipated expiration: 2019-05-07
Also published as: GB2349679B; GB9910488D0

Abstract

A nut (10), which is suitable for use with rock bolts, comprises a main body (12) having a bore (14). The bore has a threaded section (14A) which corresponds with a threaded section of a bolt (18). The nut (10) also has a torque transmission member (20) which extends at least partially across the bore (14) and which is suitable for transmitting torque to the bolt (18). The torque transmission member (20) is removable from the bore (14) by an applied force. The main body (12) of the nut (10) may have a receiving section (22 - see figure 2) for receiving at least some of the removed torque transmission member (20).

Description

Improvements in or Relating to Nuts This invention relates to nuts. In particular, but not exclusively this relates to torque nuts for use with bolts in the tunnelling and other similar engineering industries.

The use of metallic bolts to hold up tunnels is well known. A hole to receive a bolt is first drilled in the wall of the tunnel and then a resin capsule is inserted into the hole. The bolt is then inserted into the hole to pierce the capsule and is then"spun"about its longitudinal axis until the resin cures to secure the bolt in place.

Various ways are utilised in order to"spin"the bolt. One way involves the use of a torque nut having a pin across one end. As the nut is screwed into the bolt, the pin engages the end of the bolt, whereby torque is transmitted from the nut to the bolt via the pin, thereby spinning the bolt about its longitudinal axis. When the resin sets, the bolt is prevented from further spinning and further torque applied to the nut results in the force applied against the pin by the end of the bolt being sufficient to break the pin so that the pin becomes detached from the nut, and the nut can then be screwed down the bolt to hold the bolt in place with a suitable plate.

One disadvantage of the use of such nuts is that the pin tends to shatter when broken and the shattered pieces can fall into the threads thereby causing the nut to jam or the bolt.

According to this invention there is provided a nut comprising a main body defining a bore providing a path for a bolt, said bore having a threaded section to threadably receive a correspondingly threaded section of the bolt, and said nut further including a torque transmission member extending at least partially across the bore and being suitable to transmit torque to the bolt from the nut, the torque transmission member being removable from the path provided for the bolt by a force applied thereto. Preferably the main body defines a receiving section to receive at least some of the torque transmission member so removed, said receiving section being out of the path provided for the bolt.

Preferably, the receiving section comprises a recessed portion or rebate in the main body communicating with the path provided for the bolt. The receiving section may be unthreaded.

The receiving section may comprise a step extending inwardly of the main body from said path to define said recessed portion or rebate. The step desirably extends substantially wholly around the bore. The receiving section preferably extends wholly around the bore. Preferably, the bore extends longitudinally of the body.

In one embodiment, the receiving section extends transversely of said path inwardly of the main body. Advantageously, the diameter of the receiving section is equal to or greater than the largest diameter of the threaded section.

Preferably, the receiving section is provided at one end region of the nut and may extend longitudinally inwardly from said one end region of the nut for a suitable distance, for example substantially one quarter of the length of nut.

The torque transmission member may be provided at the receiving section and may be so provided such that it overlaps the threaded section of the bore. The torque transmission member is advantageously detachable from the main body by said force applied thereto. Preferably the torque transmission member is breakable by said force.

The torque transmission member conveniently comprises an elongate member which may extend substantially wholly across the bore. The elongate member may be in the form of a pin, which may be substantially cylindrical in configuration.

Preferably, opposite end regions of the elongate member are received into suitable apertures in the main body. The elongate member is provided with at least one weakened region, preferably two weakened regions. The, or each, weakened region is preferably provided adjacent a respective end region of the elongate member. The, or each, weakened region, may comprise a region of reduced thickness or diameter of the elongate member.

The thread may comprise alternating helical ridge and through portions wherein at least one of the ridge and trough portions comprises a flat region extending substantially parallel to the longitudinal axis of the nut. Preferably, each of the ridge and trough portions comprises a flat region.

The width of the flat region on the ridge portion may be such that the corresponding trough portion on the thread on the bolt is wide enough such that the trough portion of the nut can receive a broken piece of the torque transmission member. The receiving section, thus, can receive said broken portions of the torque transmission member so received in the thread of the bolt, thereby preventing the jamming of the nut and the * In one embodiment, the flat region on the ridge portion is wider than the flat region on the trough portion.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a section side view of a nut; Fig. 2 is a view along the lines II-II of Fig. 1 ; Fig. 3 is a side view of the nut about to be screwed onto a bolt, this Fig. also showing a torque transmission member separate from the nut; Fig. 4 is a part-sectional view showing a side section of the nut and a bolt threadably received by the nut; Fig. 5 is a side view of the torque transmission member; and Fig. 6 is a sectional side view of a part of the thread of the nut.

Referring to the drawings, there is shown a torque nut 10 comprising a main body 12 defining a bore 14 therethrough. The bore 14 comprises a threaded section 14A and a non-threaded section 14B. The bore 14 is provided longitudinally of the nut 10 and provides a path for a correspondingly threaded bolt 18.

A torque transmission member in the form of a pin 20 extends across the path of the bolt 18. When the bolt 18 and the nut 10 are screwed together such that the pin 20 is tightened against the end 19 of the bolt 18, further tightening of the nut 10 by screwing it onto the bolt 18 transmits torque applied to the nut 10 to the bolt 18 via the pin 20.

The non-threaded section 14B of the bore 14 comprises a receiving section in the form of a recess 22 and a step 23 extending from the threaded section 14A to the recess 22. The recess 22 and the step 23 extend substantially wholly around the bore 16. The diameter of the recess 22 is greater than the largest diameter of the threaded section 14A of the bore 16.

The pin 20 extends across the bore 16 at the step 23.

A pair of diametrically opposed apertures 24 receive end regions 26,28 of the pin therein to hold the pin in its position over the bore 16. The apertures 24 are appropriately sized and shaped to be a tight fit for the end regions 26,28 of the pin 10. Regions of weakness, in the form of regions of reduced diameter 30,32 in the pin 20 are provided adjacent the respective end regions 26,28 (see Fig. 5 for a drawing of the pin 20). Thus, the pin 20 can be broken at the regions of reduced diameter 30,32 when a large enough force is applied thereto, as will be explained below.

The above described embodiment is suitable for use in, for example, tunnels where it is desired to use the bolt 18 to hold up the tunnel wall. An elongate hole is initially drilled into the tunnel wall, and a capsule of a curable resin is inserted into the hole which, when pierced by the bolt, cures to form a rigid substance holding the bolt in place. This is standard procedure and would be understood by any person skilled in the art.

In the present situation, after the capsule of resin has been inserted into the hole, the bolt 18 is then inserted into the hole, the bolt 18 having a sharp end which is intended to pierce the resin capsule. The nut 10 is then screwed onto the threaded section of the bolt 18 until the end 19 of the bolt 18 is tightened against the pin 20. Further tightening of the nut 10 on the bolt 18 results in the torque applied to the nut being transmitted via the pin 20 to the bolt 18. This causes the bolt to"spin"about its longitudinal axis, thereby piercing the capsule of resin which cures to secure the bolt 18 in place. As the resin cures, the bolt 18 can continue to be spinned until, when the resin cures, the bolt 18 is prevented from further spinning. Consequently, further tightening of the nut 10 onto the bolt 18 results in the rection force applied by the bolt 18 against the pin 10 increasing until it reaches such a level that the pin breaks at the regions of reduced diameter 30,32, thereby enabling the nut to be screwed down the threads of the bolt to engage a plate (previously placed over the bolt) which acts as a washer to enable the nut 10 to tighten the bolt 18 against the wall of the tunnel.

As the pin 20 breaks, it has a tendency to break or shatter and small pieces of the broken or shattered pin 20 are received in the recess 22 defined at the unthreaded section 14B in the end of the nut 10. Since this recess is wider than the thread of the bolt 18, the nut 10 can be screwed onto the bolt 18 without the shattered or broken pieces of the pin jamming between the threads of the nut 10 and the bolt 18. The pieces of the pin 10 are received in the recess 22 and kept free of the threads of the nut 10 and the bolt 18.

Consequently, there is no jamming of the nut against the bolt caused by the pieces of the broken pin.

Referring to Fig. 6 there is shown a sectional view of part of the threaded section 14A of the nut 10. The threaded section 14A is dependent upon the thread of the bolt 18. The bolts 18 are produced from long iron bars which are formed during their production with the thread. The thread on the nut 10 comprises a helical ridge portion 34 and a helical trough portion 36 alternating therewith. Helical sloping regions 38,40 join the ridge portion 34 to the trough portions 36. Each of the ridge and trough portions 34,36 comprise flat regions 42,44 respectively.

The flat region 42 of each ridge portion 34 is wider than the flat region 44 of the trough portion 36. The width of the flat region 42 of each ridge portion 34 is such that the flat region of the corresponding trough portion of the thread on the bolt is wide enough to receive a broken piece of the pin 20.

However, as described above, the unthreaded recess 22 is provided to receive any of the broken pieces of the pin 20 that would otherwise fall between the threads of the nut 10 and the bolt 18, thereby preventing the jamming of the nut 10 and the bolt 18 together.

Various modifications can be made to the invention without departing from its scope.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims :1. A nut comprising a main body defining a bore providing a-path for a bolt, the bore having a threaded section to threadably receive a correspondingly threaded section of the bolt, and said nut further including a torque transmission member extending at least partially across the bore and being suitable to transmit torque to the bolt from the nut, the torque transmission member being removable from the path provided for the bolt by a force applied thereto.
2. A nut according to claim 1 wherein the main body defines a receiving section to receive at least some of the torque transmission member so removed, the receiving section being out of the path provided for the bolt.
3. A nut according to claim 1 wherein the main body defines a receiving section in the form of a recessed portion communicating with the path for the bolt to receive at least some of the torque transmission member so removed.
4. A nut according to claim 3 wherein the receiving section comprises a step extending inwardly of the main body from said path to define said recessed portion or rebate.
5. A nut according to claim 4 wherein the step extends substantially wholly around the bore and the bore extends longitudinally of the body.
6. A nut according to any of claims 2 to 5 wherein the receiving section is in the form of an annular rebate around the bore.
7. A nut according to any of claims 2 to 6 wherein the diameter of the receiving section is equal to, or greater than, the largest diameter of the threads in the threaded section.
8. A nut according to any of claims 2 to 7 wherein the receiving section is provided at one end region of the nut and extends lengthwise of the nut from said one end region.
9. A nut according to any preceding claim wherein the torque transmission member comprises an elongate member extending substantially wholly across the bore, and the main body defines opposed apertures and opposite end regions of the elongate member are received in the apertures.
10. A nut according to claim 9 wherein the elongate member is in the form of a substantially cylindrical pin.
11. A nut according to claim 9 or 10 wherein the elongate member is provided with at least one weakened region and the, or each, weakened region is provided adjacent a respective end region of the elongate member.
12. A nut according to claim 11 wherein the, or each, weakened region comprises a region of reduced thickness or diameter of the elongate member.
13. A nut according to any preceding claim wherein the thread comprises alternating helical ridge and trough portions wherein at least one of the ridge or trough portions comprises a flat region extending substantially parallel to the longitudinal axis of the nut.
14. A nut according to claim 13 wherein the flat region has a width which is such that a broken piece of the torque transmission member can be received between the threads of the nut and bolt.
15. A nut and bolt arrangement comprising a nut as claimed in any preceding claim and a bolt adapted to be threadably received therein.
16. A nut and bolt arrangement according to claim 15 wherein the bolt has a thread comprising alternating helical ridge and trough portions wherein at least one of the ridge and trough portions comprises a flat region extending substantially parallel to the longitudinal axis of the bolt.
17. A nut and bolt arrangement according to claim 16 wherein the width of the flat region on the trough portion of the bolt is such that the trough portion of the bolt can receive a broken piece of the torque transmission member.
18. A nut substantially as herein described with reference to the accompanying drawings.
19. A nut and bolt arrangement substantially as herein described with reference to the accompanying drawings.
20. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.