GB2323648A

GB2323648A - Adhesively secured bolt and method of manufacture

Info

Publication number: GB2323648A
Application number: GB9706111A
Authority: GB
Inventors: Graham Lawrence Warwick-Adkins
Original assignee: MAI SYS UK Ltd
Current assignee: MAI SYS UK Ltd
Priority date: 1997-03-25
Filing date: 1997-03-25
Publication date: 1998-09-30
Also published as: GB9706111D0

Abstract

A bolt 10 comprises a first portion 12 with a helical groove 20 and a pointed end 16, and a second screw threaded portion 14. The first portion 12 is insertable into a hole such that the point 16 punctures a resin capsule in the bottom of the hole, the resin then forms a bond with the hole wall and the helical groove 20 in the bolt. When the resin is cured, a plate and nut are secured on the screw threaded portion and tightened against the wall. In manufacture, a bolt blank (42, Fig 3) is guided (44) through a grinding wheel (48) and is advanced and rotated by rollers (34,36). A control system lifts the grinding wheel (48) away from the bolt blank (42) in areas where the second screw threaded portion 14 is to be formed by a further grinding system.

Description

A bolt for stabilising a wall This invention relates to bolts for stabilising walls.

In the mining industry, it is known to manufacture rock bolts from an appropriate plastics material. The bolts have a first portion which is insertable into a wall. The first portion of the bolts can be provided with suitable mottled pattern to provide keying of the bolt to the wall. This has the disadvantage that the bolt is expensive to manufacture and wasteful of resources and, further, its properties cannot be varied.

According to one aspect of this invention there is provided a bolt for stabilising a wall comprising a first elongate portion insertable into the wall and a second portion including securing means to assist in securing the bolt to the wall, the first portion having or defining an elongate member extending at least a major proportion of the length thereof. Preferably, the elongate formation is a groove defined by the first portion. The groove may extend substantially the whole length of the first portion.

Thus, the first portion can be inserted into the wall to be secured therein by an appropriate curable material known in the art wherein the groove acts to key the curable material to the first portion.

Preferably, at least some of the formation defined by or on the first portion is helical. Advantageously, the formation is a helical groove extending substantially the length of the first portion.

The depth of the groove may be between 0.5 and 5mm, preferably between 1 and 3mm, more preferably between 1.5 and 2mm. For example the depth may be substantially 2mm.

The pitch of the groove may be between 5 and 75mm, preferably between 15 and 50mm, more preferably between 15 and 30mm. For example, the pitch may be substantially 19mm.

The width of the groove may be between 1 and 30mm, preferably between 1 and 15mm, more preferably between 2 and 6mm. For example, the width may be substantially 5.5mm.

The first portion may be cylindrical in configuration and may have a diameter of between 18 and 35mm, for example substantially 25mm.

The groove may have a buttress profile1 preferably an inclined buttress profile. Although it will be appreciated that the groove may be of any appropriate profile.

The securing means may be in the form of securing formations, preferably comprising threads to receive a nut thereon.

According to another aspect of the invention there is provided a method of producing a bolt for stabilising a wall, the method comprising feeding an elongate bolt blank through formation forming means, forming of an elongate formation along at least a major proportion of the length of a first portion of the bolt blank, and providing a second portion of the bolt blank upon which securing means can be provided.

Preferably, the formation forming means comprises groove forming means to form a groove in the first portion. The groove forming means advantageously comprises grinding means and the groove is formed in the first portion by grinding. Preferably, the formation is formed along substantially the whole length of the first portion.

Advantageously, the formation is formed helically on the bolt blank.

Preferably, the bolt blank is rotated about its longitudinal axis as the groove is formed on the first portion.

The grinding means may comprise a grinding wheel adapted to engage the bolt blank, desirably at an angle to the direction of feed of the bolt blank of between 50 and 850, preferably between 200 and 800, more preferably between 300 and 750. For example, the grinding wheel may be at an angle of between 700 and 750 to the direction of the feed of the bolt blank.

The step of feeding the bolt blank through the groove forming means may comprise engaging the bolt blank with a rotary member.

Preferably, the rotary member is so arranged to feed the bolt blank said motion through the groove forming means, and to impart thereto said rotation about the longitudinal axis of said bolt blank.

The rotary member may be arranged to engage the bolt blank upstream of the groove forming means. Alternatively, the rotary member may be arranged to engage the bolt blank downstream of the groove forming means. In the preferred embodiment, two of said rotary members are provided, one being downstream of the groove forming means, the other being upstream thereof.

The, or each, rotary member is preferably angled relative to the direction of feed of the bolt blank through the groove forming means. Said angle of the, or each, rotary member may be between 50 and 850, preferably between 200 and 800, more preferably between 300 and 750. In one embodiment, the, or each, rotary member is arranged at angle of between 700 and 750 to the bolt blank, and may be substantially parallel to the grinding wheel.

The process may further include the step of providing securing means on the second portion of the bolt blank to assist in securing the bolt formed therefrom to the wall. Preferably, the securing means so provided on said second portion are in the form of threads which may be cut or ground thereon.

Each bolt blank is preferably of a length that a plurality of bolts may be formed therefrom. After the step of forming the groove on one, or each, first portion, the bolt blank may be cut to form a bolt, or a plurality of bolts.

According to another aspect of this invention, there is provided apparatus for producing a bolt comprising feed means for feeding a bolt blank and formation forming means to form an elongate formation extending along substantially the length of a first portion of the bolt blank, the feed means being adapted to feed the bolt blank through the groove forming station.

Preferably, the groove forming means comprises grinding means which may be in the form of a grinding wheel. Preferably, the grinding wheel is angled relation to the direction o of feed of the bolt blank. Said angle of the grinding wheel may be between 50 and 850, preferably between 20 and 800, more preferably between 30 and 750. In one embodiment, the grinding wheel is angled to the direction of feed of the bolt blank at between 70 and 750.

The feed means may be adapted to rotate the bolt blank about the longitudinal axis of the bolt blank. The feed means may comprise a rotary member so arranged to impart said rotary motion to the bolt blank. The rotary member may be arranged upstream of the groove forming means.

Alternatively, the rotary member may be arranged downstream of the groove forming means. In a preferred embodiment, the feed means comprises two of said rotary members, one provided upstream of the groove forming means and the other provided downstream thereof.

The, or each, rotary member is preferably angled relative to the direction of the bolt blank. Said angle of the, or each, rotary member may be between 50 and 850, preferably between 20 and 80 , more preferably, between 30 and 750.

In one embodiment, the, or each, rotary member is angled at between 70 and 750 relative to the direction of feed of the bolt blank. Preferably, the, or each, rotary member, is arranged substantially parallel to the grinding wheel.

Cutting means may be provided downstream of the groove forming means to cut the bolt blank into desired lengths.

The apparatus may further include means for providing securing means on the or each, second portion. Said securing means providing means preferably comprising thread forming means to form threads on the, or each, second portion of the bolt blank.

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 side view of a port; Fig. 2 is a close up view of the formation of the groove in the port of Fig.

1; and Fig. 3 is a schematic top plan view of apparatus for manufacturing a bolt as shown in Fig. 1.

Referring to Fig. 1, there is shown a bolt 10 for use in stabilising a wall.

In this specification the word wall is intended to include walls of buildings, mine shafts, tunnel walls and the like.

The bolt 10 comprises an elongate first portion 12 and an elongate second portion 14. The first portion 12 is inserted into a pre-drilled hole in the wall into which hole has been inserted a suitable resin capsule or other curable means known in the art. The bolt 10 is inserted into the wall in the direction of the arrow A as shown in Fig. 1. As can be seen, the first portion 12 has a free end 16 which defines a point. The purpose of this configuration of the free end region 16 is to puncture the resin capsule in the wall to enable the resin to harden. On hardening the resin secures the first portion in the hole, thereby securing the bolt to the wall. The second elongate portion 14 is provided with threads 18 to receive thereon an appropriate nut (not shown). When the bolt 10 has been secured in the wall by the resin, a plate (not shown) defining an aperture therein is first mounted over the second portion 14 and a nut is then screwed onto the threads 18 to tighten the plate against the wall thereby further securing the bolt 10 to the wall.

The first portion 12 defines a helical groove 20 extending substantially the length of the first portion 12. The purpose of the helical groove 20 is to provide keying means to improve the adhesion of the resin to the first portion 12 of the bolt 10.

Referring to Fig. 2, there is shown one example of the profile of the groove 20 defined in the first portion 12. The groove 20, as shown in Fig. 2, is of a buttress configuration having a first sloping side 22 at a first angle to the surface of the first portion 12, and a second sloping side 24 at a second angle to the surface of the first portion 12, where the second angle is shallower than the first angle.

The groove 20 has a pitch designated by the letter X, a width designated by the letter Y and a depth designated by the letter Z. By varying one or more of these valves, as well as, it desired, the diameter of the second portion 12 of the properties of the bolt can be varied.

In one embodiment of the invention, the second portion 12 of the bolt 10 may be substantially 25mm in diameter, in which case, referring to Fig. 2, the pitch X can be substantially in 19mm, the width Y can be substantially 5.5mm, and the depth Z can be substantially 2mm. It will be appreciated, however, that the pitch, depth, and width will vary from diameter to diameter of the bolt and will depend upon uses to which the bolt is to be put and its properties (for example yield strength). The skilled person will be able easily to work out the appropriate diameter of the first portion 12, and the pitch, width and depth of the groove, for example, by trial and error, for any desired application.

Referring to Fig. 3, there is shown apparatus 30 for use in the manufacture of bolts 10. The apparatus 30 comprises feed means 32 comprising a first roller 34 and a second roller 36. The rollers 34,36 have an appropriate high friction surface to be able to feed a bolt blank, as will be explained below. Such high friction surface is, for example, rubber or an appropriate synthetic rubber. Suitable positioning members 38,40 act to hold the rollers 34,36 in position to ensure smooth feeding of the bolt blank.

A bolt blank 42 is arranged to extend through guides 44 on an appropriate channel 46. The bolt blank 42 is an elongate cylindrical member formed from a suitable plastics material from which a plurality of bolts will be formed. The bolt blank is formed by a process known in the art and is several metres in length. The rollers 34,36 engage the bolt blank 42 and, being arranged at an angle of between 700 and 750 to the bolt blank 42 impart thereto a motion in the longitudinal direction of the bolt towards the left hand edge of the paper, and also impart thereto a rotational motion about the longitudinal axis of the bolt blank 42. Thus, the bolt blank 42 is fed by the feed means 32 while rotating about its longitudinal axis. The apparatus 30 further includes grinding means comprising a grinding wheel 48, mounted on a movable arm 50 which is adapted to move the grinding wheel 48 into, and out of, engagement with the bolt blank 42.

As the bolt blank 42 is fed past the grinding wheel 48, the grinding wheel 48 grinds the groove 50 to regions of the bolt blank 42 destined to become first portions 12 of a plurality of bolts formed from the bolt blank 42.

In operation, a bolt blank 42, past through the guides 44 on the channel 46 from the right hand end of the apparatus, as shown until the left hand end of the bolt blank 42 engages the first wheel 34. If the wheels 34,36 are rotated at an appropriate speed, the bolt blank 42 will be fed towards the left hand edge of the paper to come into engagement with the grinding wheel 48 and, thereafter, the second wheel 36. At this point, the bolt blank 42 is fed through the apparatus 30 by both wheels 34,36.

When the bolt blank 42 comes into engagement with the grinding wheel 48, a helical groove 20 is ground into the region of the bolt blank 42 in engagement with the grinding wheel 48.

Control means (not shown) may be provided to control the lifting of the arm 50 to disengage the grinding wheel 48 from the bolt blank 42. Thus, the control means can be programmed such that the grinding wheel 48 is in engagement with the bolt blank 42 for an appropriate period of time which corresponds to the length of the first portion 12 of the bolt to be formed, to define a helical groove therein. The control means then lifts the grinding wheel away from the bolt blank 42 for a period of time which corresponds to the length of the second portion 14. The control means then lowers the grinding wheel 48 into engagement with the bolt blank 42 to define therein the groove 20 on the region which will become the first portion of the next bolt to be produced. The process then repeats itself for the length of the bolt blank 42 thereby producing a bolt blank having a plurality of alternating grooved and non-grooved regions. The bolt blank 42 so formed can then be passed to a suitable cutter to cut the bolt blank into appropriate lengths to form the bolts and thereafter to further grinding means to grind the thread 18 on the second portion 14 of each bolt. Further cutting means can then be used to cut the end portion 16 into the first portion 12 of each bolt.

The control means can be appropriately programmed to raise or lower the grinding wheel 48 at any desired intervals depending upon the length of the first portion of each bolt required.

The preferred embodiments of this invention provide advantages that the bolts formed by the process have determinable variable bonding characteristics, i.e. as the load on a bolt secured in the wall is increased, the bond between the resin and the bolt will eventually fail. The load at which this failure occurs can be varied by varying the profile, the pitch1 the depth and the width of the groove cut into the bolt. The embodiment shown has the further advantage that when the bolt is pushed into the hole, it is normally done about its longitudinal axis. The helical groove provides an advantage of even resin flow around the bolt, because the smooth sections allow the bolt to be pushed in more easily and the helical groove causes the resin to spread evenly about the first portion 12. The preferred embodiment of the process has the further advantage that it is less expensive than known processes for producing bolts.

The preferred embodiment has the further advantage that the smooth surface of the first portion into which the groove is cut, may facilitate installation.

Various modifications can be made with departing from the scope of the invention.

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

1. A bolt for stabilising a wall comprising a first elongate portion insertable into the wall and a second portion including securing means to assist in securing the bolt to the wall, the first portion having or defining an elongate formation extending at least a major proportion of the length thereof.

2. A bolt according to claim 1, wherein the elongate formation is a groove defined by the first portion.

3. A bolt according to claim 1 or 2, wherein the elongate formation extends substantially the whole length of the first portion.

4. A bolt according to any of claims 1 to 3, wherein at least some of the formation defined by, or on, the first portion is helical.

5. A bolt according to any of claims 1 to 3, wherein the formation is a helical groove extending substantially the length of the first portion.

6. A bolt according to claim 5, wherein the depth of the groove is between 0.5 and 5mm.

7. A bolt according to claim 6, wherein the depth of the groove is between 1 and 3mm.

8. A bolt according to claim 6 or 7, wherein the depth of the groove is between 1.5 and 2mm.

9. A bolt according to any of claims 6 to 8, wherein the depth is substantially 2mm.

10. A bolt according to any of claims 5 to 9, wherein the pitch of the groove is between 5 and 75 mum.

11. A bolt according to claim 10, wherein the pitch of the groove is between 15 and 50mm.

12. A bolt according to claim 10 or 11, wherein the pitch of the groove is between 15 and 30mm.

13. A bolt according to any of claims 10 to 12, wherein the pitch is substantially 19mm.

14. A bolt according to any of claims 5 to 13, wherein the width of the groove is between 1 and 30mm.

15. A bolt according to claim 14, wherein the width of the groove is between 1 and 15mm.

16. A bolt according to claim 14 or 15, wherein the width of the groove is between 2 and 6mm.

17. A bolt according to any of claims 14 to 16, wherein the width is substantially 5.5mm.

18. A bolt according to any of claims 5 to 17, wherein the groove has a buttress profile.

19. A bolt according to claim 18, wherein the groove has an inclined buttress profile.

20. A bolt according to claim 18 or 19, wherein the groove may be of any appropriate profile.

21. A bolt according to any of the preceding claims, wherein the first portion is cylindrical in configuration.

22. A bolt according to claim 21, wherein the first portion has a diameter of between 18 and 35mm.

23. A bolt according to claim 22, wherein the first portion has a diameter of substantially 25mm.

24. A bolt according to any of the preceding claims, wherein the securing means are in the form of securing formations.

25. A bolt according to claim 24, wherein the securing formations comprise threads to receive a nut thereon.

26. A method of producing a bolt for stabilising a wall, the method comprising feeding an elongate bolt blank through formation forming means, forming of an elongate formation along at least a major proportion of the length of a first portion of the bolt blank, and providing a second portion of the bolt blank upon which securing means can be provided.

27. A method according to claim 26, wherein the formation forming means comprises groove forming means to form a groove in the first portion.

28. A method according to claim 27, wherein the groove forming means comprises grinding means.

29. A method according to claim 27 or 28, wherein the groove is formed in the first portion by grinding.

30. A method according to any of claims 26 to 29, wherein the formation is formed along substantially the whole length of the first portion.

31. A method according to any of claims 26 to 30, wherein the formation is formed helically on the bolt blank.

32. A method according to claim 31, wherein the bolt blank is rotated about its longitudinal axis as the groove is formed on the first portion.

33. A method according to claim 28, wherein the grinding means comprises a grinding wheel adapted to engage the bolt blank.

34. A method according to claim 33, wherein the grinding wheel is adapted to engage the bolt blank at an angle to the direction of feed of the bolt blank of between 50 and 850.

35. A method according to claim 34, wherein the grinding wheel is adapted to engage the bolt blank at an angle to the direction of feed of the bolt blank of between 200 and 800.

36. A method according to claim 34 or 35, wherein the grinding wheel is adapted to engage the bolt blank at an angle to the direction of feed of the bolt blank of between 300 and 750.

37. A method according to any of claims 34 to 36, wherein the grinding wheel is at an angle of between 700 and 750 to the direction of the feed of the bolt blank.

38. A method according to any of claims 27 to 37, wherein the step of feeding the bolt blank through the groove forming means comprises engaging the bolt blank with a rotary member.

39. A method according to claim 38, wherein the rotary member is so arranged to feed the bolt blank said motion through the groove forming means, and to impart thereto said rotation about the longitudinal axis of said bolt blank.

40. A method according to claim 38 or 39, wherein the rotary member is arranged to engage the bolt blank upstream of the groove forming means.

41. A method according to claim 38 or 39, wherein the rotary member is arranged to engage the bolt blank downstream of the groove forming means.

42. A method according to any of claims 38 to 41, wherein two of said rotary members are provided, one being downstream of the groove forming means, the other being upstream thereof.

43. A method according to any of claims 38 to 42, wherein the, or each, rotary member is angled relative to the direction of feed of the bolt blank through the groove forming means.

44. A method according to claim 43, wherein the angle of the, or each, rotary member is between 50 and 850.

45. A method according to claim 44, wherein the angle of the, or each, rotary member is between 20 and 800.

46. A method according to claim 44 or 45, wherein the angle of the, or each, rotary member is between 300 and 750.

47. A method according to any of claims 44 to 46, wherein the, or each, rotary member is arranged at angle of between 700 and 750 to the bolt blank.

48. A method according to any of claims 43 to 47, wherein the, or each, rotary member is arranged substantially parallel to the grinding wheel.

49. A method according to any of claims 26 to 48, wherein the process further includes the step of providing securing means on the second portion of the bolt blank to assist in securing the bolt formed therefrom to the wall.

50. A method according to claim 49, wherein the securing means so provided on said second portion are in the form of threads which cut or ground thereon.

51. A method according to claim 26 to 50, wherein each bolt blank is of a length that a plurality of bolts may be formed therefrom.

52. A method according to claim 51, wherein after the step of forming the groove on one, or each, first portion, the bolt blank is cut to form a bolt, or a plurality of bolts.

53. A method according to any of claims 28 to 52, wherein control means are provided to disengage the grinding wheel from the bolt blank.

54. A method according to claim 53, wherein the control means is programmed such that the grinding wheel is in engagement with the bolt blank for an appropriate period of time which corresponds to the length of the first portion of the bolt to be formed, to define a helical groove therein.

55. A method according to claim 54, wherein the control means lifts the grinding wheel away from the bolt blank for a period of time which corresponds to the length of the second portion.

56. A method according to claim 54 or 55, wherein the control means then lowers the grinding wheel into engagement with the bolt blank to define therein the groove on the region which will become the first portion of the next bolt to be produced.

57. A method according to any of claims 53 to 56, wherein the control means is appropriately programmed to raise or lower the grinding wheel at desired intervals.

58. Apparatus for producing a bolt comprising feed means for feeding a bolt blank and formation forming means to form an elongate formation extending along substantially the length of a first portion of the bolt blank, the feed means being adapted to feed the bolt blank through the groove forming station.

59. Apparatus according to claim 58, wherein the formation forming means comprises groove forming means to form a groove in the first portion.

60. Apparatus according to claim 59, wherein the groove forming means comprises grinding means which may be in the form of a grinding wheel.

61. Apparatus according to claim 60, wherein the grinding wheel is angled relation to the direction of feed of the bolt blank.

62. Apparatus according to claim 61, wherein the angle of the grinding wheel is between 50 and 850.

63. Apparatus according to claim 62, wherein the angle of the grinding wheel is between 200 and 800.

64. Apparatus according to claim 62 or 63, wherein the angle of the grinding wheel is between 300 and 750.

65. Apparatus according to any of claims 62 to 64, wherein the grinding wheel is angled to the direction of feed of the bolt blank at between 700 and 750.

66. Apparatus according to any of claims 58 to 65, wherein the feed means is adapted to rotate the bolt blank about the longitudinal axis of the bolt blank.

67. Apparatus according to claim 66, wherein the feed means comprises a rotary member so arranged to impart said rotary motion to the bolt blank.

68. Apparatus according to claim 67, wherein the rotary member is arranged upstream of the groove forming means.

69. Apparatus according to claim 67, wherein the rotary member is arranged downstream of the groove forming means.

70. Apparatus according to any of claims 67 to 69, wherein the feed means comprises two of said rotary members, one provided upstream of the groove forming means and the other provided downstream thereof.

71. Apparatus according to any of claims 67 to 70, wherein the, or each, rotary member is angled relative to the direction of the bolt blank.

72. Apparatus according to claim 71, wherein the angle of the, or each, rotary member is between 50 and 850.

73. Apparatus according to claim 72, wherein the angle of the, or each, rotary member is between 200 and 800.

74. Apparatus according to claim 72 or 73, wherein the angle of the, or each, rotary member is between 300 and 750.

75. Apparatus according to any of claims 71 to 74, wherein the, or each, rotary member is angled at between 700 and 750 relative to the direction of feed of the bolt blank.

76. Apparatus according to any of claims 71 to 75, wherein the, or each, rotary member, is arranged substantially parallel to the grinding wheel.

77. Apparatus according to any of claims 58 to 76, wherein cutting means are provided downstream of the groove forming means to cut the bolt blank into desired lengths.

78. Apparatus according to any of claims 58 to 77, wherein the apparatus further includes means for providing securing means on the or each, second portion.

79. Apparatus according to claim 78, wherein the securing means providing means comprise thread forming means to form threads on the, or each, second portion of the bolt blank.

80. Apparatus according to any of claims 60 to 79, wherein control means are provided to disengage the grinding wheel from the bolt blank.

81. Apparatus according to claim 80, wherein the control means is programmed such that the grinding wheel is in engagement with the bolt blank for an appropriate period of time which corresponds to the length of the first portion of the bolt to be formed, to define a helical groove therein.

82. A method according to claim 81, wherein the control means lifts the grinding wheel away from the bolt blank for a period of time which corresponds to the length of the second portion.

83. A method according to claim 81 or 82, wherein the control means then lowers the grinding wheel into engagement with the bolt blank to define therein the groove on the region which will become the first portion of the next bolt to be produced.

84. A method according to any of claims 80 to 83, wherein the control means is appropriately programmed to raise or lower the grinding wheel at any desired intervals depending upon the length of the first portion of each bolt required.

85. A bolt substantially as described above, with reference to Figs. 1 and 2.

86. A method of producing a bolt substantially as described above, with reference to Figs. 1, 2 and 3.

87. Apparatus for producing a bolt substantially as described above, with reference to Fig. 3.

88. 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.