"LINER BOLT ASSEMBLY AND LINER SECURING SYSTEM"
Field of the Invention
[001 ] The present invention relates to a liner bolt assembly and a system for securing a liner within a grinding mill.
Background to the Invention
[002] Grinding mills use liners which are secured to the inner surface of the mill. The liners provide both a protective surface which wears and is replaced over time, as well as surface features to assist with the grinding process.
[003] Aside from the periodic replacement of the liners, the bolts holding the liners can also require replacement due to breakages. Wear and movement over time can result in movement of the bolt relative to the liner. This movement can ultimately lead to the head or the nut of the fastener cracking or breaking off. As the bolts are secured by passing outwardly through the liner to engage with an external nut, replacement requires personnel to enter the mill. The mill will need to be shut down for this to occur which can be costly. Further, having personnel enter the grinding mill creates a range of safety issues which must be addressed.
[004] The present invention relates to a liner bolt assembly and a system for securing a liner which aims to address the abovementioned issues.
Summary of the Invention
[005] According to one aspect of the present invention there is provided a liner bolt assembly comprising:
a bolt having a head adjacent a first end of a shaft and a threaded portion adjacent a second end of the shaft, the bolt being receivable through an
aperture in an outer wall of a mill and an aligned opening in a liner from outside the mill such that the head is innermost;
a collar receivable over the second end of the shaft;
a sleeve receivable over the second end of the shaft; and
a nut engageable with the threaded portion to engage with an outer surface of the outer wall of the mill;
wherein rotation of the nut relative to the bolt causes the head to engage with the collar such that the collar is pulled into a first end of the sleeve to expand the sleeve such that the sleeve engages against an inner surface of the opening in the liner.
[006] Preferably the head and the shaft are generally cylindrical in shape and the bolt includes a tapered shoulder portion between the head and the shaft to engage with the collar in use.
[007] Preferably a washer is provided such that the washer is engaged between an outer surface of the outer wall of the mill and the nut, the diameter of a hole in the nut being less than the external diameter of the sleeve such that the second end of the sleeve engages with the nut in use.
[008] Preferably the sleeve comprises a first cylindrical tube dimensioned to receive the shaft of the bolt and includes a plurality of longitudinal slots adjacent a first end thereof.
[009] In a preferred embodiment, there is provided a pair of slots on opposed sides of the sleeve extending longitudinally from the first end of the sleeve.
[010] In a preferred embodiment, the collar comprises a second cylindrical tube of the same diameter as the sleeve but shorter in length than the sleeve.
[01 1 ] Preferably the collar includes a tapered end portion at a second end thereof and the first end of the sleeve includes a tapered recess therein, such that the tapered end portion is received into the tapered recess between the sleeve and the shaft as the collar moves towards the sleeve to expand the first end of the sleeve.
[012] Preferably the shaft of the bolt includes a tool engagement at the second end thereof to allow engagement of the shaft by a tool.
[013] In one embodiment, the tool engagement comprises a protrusion extending outwardly beyond the threaded portion for engagement by a suitable tensioning tool.
[014] In accordance with a second aspect of the present invention, there is provided a liner securing system comprising:
a liner having an opening alignable with an aperture in an outer wall of a mill; a bolt having a head adjacent a first end of a shaft and a threaded portion adjacent a second end of the shaft, the bolt being receivable through the aperture in the outer wall of the mill and the aligned opening in the liner from outside the mill such that the head is innermost;
a sleeve receivable over the second end of the shaft; and
a nut engageable with the threaded portion to engage with an outer surface of the outer wall of the mill;
wherein rotation of the bolt relative to the nut causes the head to engage with the sleeve to expand the sleeve such that the sleeve engages against an inner surface of the opening in the liner.
[015] Preferably a collar is provided being receivable over the bolt between the head and the sleeve such that the head pulls the collar into the first end of the sleeve to expand the sleeve.
[016] Preferably the shaft and the head are cylindrical and the head includes a tapered shoulder portion to engage with the collar in use.
Brief Description of the Drawings
[017] The invention will now be described, by way of example, with reference to the following drawings, in which:
[018] Figure 1 a is a side view of a bolt of a liner bolt assembly in accordance with the present invention;
[019] Figure 1 b is a first end view of the bolt of Figure 1 a;
[020] Figure 1 c is a second end view of the bolt of Figure 1 a;
[021 ] Figure 2 is a side view of components of the liner bolt assembly;
[022] Figure 3 is a side view of a liner bolt assembly prior to connection with the nut;
[023] Figure 4 is a side view of the assembled liner bolt assembly;
[024] Figure 5 is a side view of the liner bolt assembly showing partial tensioning of the bolt;
[025] Figure 6a is a side view of the liner bolt assembly showing the bolt fully tensioned;
[026] Figure 6b is an end view of the liner bolt assembly showing the bolt fully tensioned;
[027] Figure 7 is a side cross sectional view of the liner bolt assembly inserted into a mill liner;
[028] Figure 8 is a side cross sectional view of the liner bolt assembly in the mill liner and partially tensioned;
[029] Figure 9a is a side cross sectional view of the liner bolt assembly in the mill liner fully tensioned;
[030] Figure 9b is an end view of the liner bolt assembly of Figure 9a;
[031 ] Figure 10 is a side view of a second embodiment of components of a liner bolt assembly in accordance with the present invention; and
[032] Figure 1 1 is a side cross sectional view of the sleeve of the liner bolt assembly of Figure 10 in place in a mill liner.
Detailed Description of Preferred Embodiments
[033] Referring to the Figures, there is shown a liner bolt assembly 10 comprising a bolt 12 to be provided for securing a liner 1 1 to an outer wall 13 of a mill. The liner 1 1 comprises a standard mill liner securable to an inner surface of the outer wall 13 of the mill. The liner 1 1 includes openings 15 alignable with apertures 17 in the outer wall 13 through which the bolt 12 of the liner bolt assembly 10 is passed.
[034] The bolt 12 comprises an elongate shaft 14 and a head 16 at a first end thereof. The shaft 14 includes a threaded portion 18 adjacent a second end thereof remote from the head 16. The head 16 is generally cylindrical in shape and includes a tapered shoulder portion 20 provided between the head 16 and the cylindrical shaft 14. The shoulder portion 20 tapers inwardly from the head 16 to the shaft 14.
[035] Unlike a conventional liner bolt, the head 16 of the bolt 12 of the liner bolt assembly 10 is dimensioned to be slightly smaller than the diameter of the apertures 15 in the liner 1 1 and openings 17 in the outer wall 13 of the mill. The bolt 12 may therefore be inserted through the outer wall 13 and the liner 1 1 from the outside of the mill.
[036] The liner bolt assembly 10 is provided also with a sleeve 22, a collar 24 and a nut 26. The nut 26 is provided to engage with the threaded portion 18 at the second end of the bolt 12. A washer 28 is also provided such that the washer 28 is engaged between an outer surface of the outer wall 13 of the mill and the nut 26.
[037] The sleeve 22 comprises a first cylindrical tube dimensioned to receive the shaft 14 of the bolt 12. As can be seen in Figure 3 the sleeve 12 may be received over the second end of the shaft 14 such that the sleeve 12 extends around a portion of the length of the shaft 14. The internal diameter of the sleeve 22 is less than the external diameter of the head 16.
[038] The sleeve 22 includes a plurality of slots 30 adjacent a first end thereof. In the embodiment shown, there is provided a pair of slots 30 on opposed sides of the sleeve 22. The slots 30 each extend longitudinally into the sleeve 22 from the first end of the sleeve 22. The slots 30 are provided to allow expansion of the first end of the sleeve 22. In the embodiment shown, the slots 30 include widened inner ends 32 to further aid in expansion of the first end of the sleeve 22.
[039] The collar 24 comprises a second cylindrical tube of a similar diameter to that of the sleeve 22. That is, the internal diameter of the collar 24 is greater than that of the shaft 14 but less than that of the head 16. The collar 24
however is shorter than the length of the sleeve 22. The collar 24 is provided to be received around the shaft 14 from the second end thereof. The collar 24 is received over the shaft 14 prior to the sleeve 22 such that the collar 24 is located in use between the first end of the sleeve 22 and the head 16 of the bolt 12. The external diameter of the sleeve 22 and the collar 24 are equal to or less than that of the head 16.
[040] The collar 24 includes a first end adjacent the head 16 of the bolt 12 and a second end located in use adjacent the first end of the sleeve 22. The second end of the collar 24 includes a tapered end portion 32 such that the collar 24 is thinner at the second end thereof. The first end of the sleeve 22 includes a tapered recess 34 therein. The tapered recess 34 is complementary in shape to the tapered end portion 32 of the collar 24 such that the tapered end portion 32 is received into the tapered recess 34 as the collar 24 moves towards the sleeve 22 in use. That is, the tapered end portion 32 is received inside the first end of the sleeve 22 adjacent the shaft 14. The collar 24 includes also an internal taper to aid in the collar 24 moving over the tapered shoulder portion 20 towards the head 16.
[041 ] The shaft 14 of the bolt 12 includes also a tool engagement 36 at the second end thereof. The tool engagement 36 comprises a protrusion extending outwardly beyond the threaded portion 18 and is provided for engagement by a suitable tool. In the embodiment shown, the tool engagement 36 comprises a protrusion having a square cross section for engagement by a complementary socket on a tool. It will be appreciated however that the tool engagement 36 may comprise other shapes and may also be a recess instead of a protrusion.
[042] Figures 7 to 9 show the process of securing the liner 1 1 with the liner bolt assembly 10. The collar 24 and sleeve 22 are slid onto the shaft 14 of the bolt 12 from the second end. The outer diameter of the sleeve 22 and the collar 24 are less than the inner diameter of the apertures and openings 15 and 17 in the liner 1 1 and the outer wall 13 of the mill such that the head 16, the collar 24 and the sleeve 22 may all pass through the outer wall 13 and the liner 1 1 from the outside of the mill. The liner bolt assembly 10 is inserted
such that the washer 28 and the nut 26 can be provided on the threaded portion 18 to engage against the outer surface of the mill (as shown in Figure 7).
[043] Tension is then applied to the liner bolt assembly 10 by rotation of the nut 26 relative to the shaft 12. A suitable tool engages the tool engagement 36 to secure the bolt 12 and a further tool is engaged with nut 26 to rotate the nut 26 relative to the shaft 14. As the nut 26 is rotated to move the bolt 12 outwardly relative to the liner 1 1 , the second end of the sleeve 22 engages with the washer 28 and longitudinal movement of the sleeve 22 is prevented. That is, the hole in the washer 28 has a diameter less than the external diameter of the sleeve 22. The tapered shoulder portion 20 of the head 16 engages into the collar 24 and moves the collar 24 towards the sleeve 22 such that the tapered end portion 32 engages into the tapered recess 34 in the first end of the sleeve 22 (as shown in Figure 8).
[044] As the bolt 12 is tensioned further, the collar 24 is pulled inside the first end of the sleeve 22 (as shown in Figure 9). The collar 24 and the first end of the sleeve 22 are both thereby expanded to engage against inner surfaces of the opening 15 in the liner 1 1 . The first end of the sleeve 22 is expanded by the collar 24 and the first end of the collar 24 is expanded by the shoulder portion 20. The liner bolt assembly 10 is thereby prevented from being pulled through the opening 15 in the liner 1 1 and tensioning of the liner bolt assembly 10 thereby pulls the liner 1 1 towards the outer wall 13 of the mill. A rubber backing 19 may be provided between the liner 1 1 and the outer wall 13 of the mill.
[045] Figures 10 and 1 1 show a further embodiment of a sleeve 22 of the liner bolt assembly 10 in accordance with the present invention. The sleeve 22 of Figures 10 and 1 1 is similar to the previous embodiment and like reference numerals are used to denote like parts.
[046] The sleeve 22 includes a thinned wall portion 38 adjacent the second end thereof. The thinned wall portion 38 is formed in the embodiment shown
by an annular recess 40 provided in an inner wall of the sleeve 22 adjacent the second end.
[047] As can be seen in Figure 1 1 , the thinned wall portion 38 is located such that it is within the aperture 17 in the outer wall 13 of the mill in use. As the liner bolt assembly 10 is tensioned, the thinned wall portion 38 causes the sleeve 22 to expand outwardly adjacent the thinned wall portion 38. The outer surface of the sleeve 22 around the thinned wall portion 38 therefore engages with an inner surface of the aperture 17 in the outer wall 13 of the mill. This expansion of the sleeve 22 within the aperture 17 thereby acts to provide a seal around the liner bolt assembly 10.
[048] It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention.