AU2013231169A1 - A method for securing lagging to the exterior surface of conveyor pulley - Google Patents

Abstract

The present invention provides a method for securing lagging of the type that includes wear resistant inserts, to the exterior surface of a conveyor pulley (18). The method including the step of adhering two or more lagging strips (14) to the exterior surface of the pulley in an abutting formation. Each lagging strip being defined by an uncured rubber layer (10) adhered to a cured rubber layer (12). The method further including the step of subjecting the pulley and lagging strips to an increased temperature thereby curing the uncured rubber layers and securing the lagging strips to the pulley surface. __e5 :w

Description

- 1 A METHOD FOR SECURING LAGGING TO THE EXTERIOR SURFACE OF A CONVEYOR PULLEY Technical Field [0001] The present invention relates pulley lagging and in particular to a methods for securing lagging material to conveyor pulleys. [0002] The invention has been developed primarily with reference to an improved method of securing lagging material including wear resistant inserts to the outer surface of a conveyor pulley and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use. Background [0003] The following discussion of the prior art is intended to place the invention in an appropriate technical context and enable the associated advantages to be fully understood. However, any discussion of the prior art throughout the specification should not be considered as an admission that such art is widely known or forms part of the common general knowledge in the field. [0004] Lagging material is used to cover drive and terminal pulleys of belt conveyor systems in order to minimise conveyor belt slippage, the build up of material on the circumferential face of the pulley and to reduce wear and corrosion of the cylindrical steel shell of the pulley. This use of rubber lagging in conveyor systems is particularly common in the mining industry, where very long conveying belts are used and debris is common. The most common type of lagging material used is natural rubber or Styrene Butadiene Rubber (SBR). [0005] Lagging used in this application typically includes an outer, or belt contact, surface having a series of channels or drains defining a surface pattern acting to shed water from the surface of the pulley when operating in wet conditions. In this way, it is possible to significantly reduce slippage between the conveyor belt between the conveyor belt and the pulley when operating in wet conditions. In order to further increase friction and reduce wear, the raised areas in between the drains may include wear resistant inserts in the form of polyurethane or ceramic tiles, adhered to the outer surface.

-2 [0006] For belt conveyor systems operating in dry and dusty conditions, lagging materials must have good abrasion resistance in order to cope with dust and other debris which becomes trapped between the pulley surface and the belt and which may affect the grip of the conveyor belt or damage the lagging surface. In this regard, it is known for the drains to also assist in the removal of general debris. [0007] For background it is known that when the lagging material does not include drains or wear resistant inserts, the lagging can be applied to the pulley surface in any number of ways. In one method, uncured rubber is adhered to the conveyor pulley surface using conventional liquid adhesive. The pulley and lagging is then placed in an autoclave or oven and subjected to an increased temperature so as to cure the uncured rubber and further secure the lagging to the pulley surface. [0008] It will be appreciated, however, that these known processes are not suitable for securing lagging that includes drains, or wear resistant inserts on the top surface, due to dimensional changes that occur in the uncured rubber as it approaches its liquid state when at high temperatures. Also, for the same reason, the bond between any wear resistant insert pre adhered to the uncured rubber, would be lost at these high temperatures. [0009] When the lagging does include drains and wear resistant inserts, the lagging is typically applied to the pulley surface by securing a plurality longitudinal lagging strips of cured rubber, having the drains and inserts, in an abutting formation to the steel exterior cylindrical pulley surface using an adhesive. A liquid adhesive is normally used and the pulley surface is sufficiently primed and cleaned prior to the application of the adhesive resulting in a cold chemical curing process. It is possible to overhaul the entire pulley drum or, in the case where minor repair and maintenance is required, only replace an individual strip of lagging. This procedure may be carried out in a pulley workshop or in situ at the conveyor site. [0010] Any aligned configuration of lagging strips may be used in accordance with desired properties and known advantages. Once the lagging strips cover the pulley surface, the lagging top surface is normally hammered with a soft head hammer to remove any air gaps and provide pressure to ensure good contact with the pulley surface. The assembly of lagging strips and pulley is then left for the adhesive to dry resulting in a chemical bond forming between the cured rubber and pulley surface.

-3 [0011] One of the more common modes of failure for pulley lagging installed using this method is due to water ingress at the joins between contacting lagging strips. Once this occurs, corrosion of the outer surface of the pulley shell ensues, which in turn, degrades the adhesive bond between the rubber lagging and the metal pulley. The end result is a loss in adhesion between the lagging and the outer surface and a potential for the lagging to lift away from the pulley surface. [0012] Another cause of the lagging lifting away from the pulley surface is non-uniform bonding strength resulting from uneven pressure being applied during the bonding process. The uneven bonding strength can also possibly be the source of a complete lagging failure given the cyclic loads being applied during conveyor drive belt operation. Whilst not wishing to limit the cause of the uneven bonding strength to one theoretic postulation, it is thought that one reason for the uneven bonding strength is due to the above-mentioned hammering process, which may inadvertently act to loosen the areas immediately adjacent the hammer contact points. [0013] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. [0014] It is an object of a preferred form of the present invention to provide an improved method of securing lagging including wear resistant inserts to the outer surface of a conveyor pulley that minimises the possibility of the lagging material coming away from the pulley surface during use. Summary of the Invention [0015] According to one aspect, there is provided a method for securing lagging of the type that includes wear resistant inserts to the exterior surface of a conveyor pulley, the method including the steps of: (i) adhering two or more lagging strips to the exterior surface of the pulley in an abutting formation, each lagging strip being defined by an uncured rubber layer adhered to a cured rubber layer; and (ii) subjecting the pulley and lagging strips to an increased temperature thereby curing the uncured rubber layers and securing the lagging strips to the pulley surface.

-4 [0016] In one embodiment, in step (i) each uncured rubber layer extends past, and is adhered to, two or more edges of the corresponding cured rubber layer. [0017] In one embodiment, the edges of the corresponding cured rubber layer are the lateral edges of the corresponding cured rubber layer. [0018] In one embodiment, during step (ii), two or more contiguous uncured rubber layers bond to each other such that no physical gap is present between contiguous lagging strips. [0019] In one embodiment, during step (ii) each uncured rubber layer bonds to the corresponding cured rubber layer. [0020] In one embodiment, a plurality of lagging strips is adhered to the exterior surface of the pulley in an abutting formation in step (i). [0021] In one embodiment, during step (ii), the pulley and lagging strips are placed in an oven. [0022] In one embodiment, during step (ii) the pulley and lagging strips are placed in an autoclave. [0023] In one embodiment, during step (ii) the pulley and lagging strips are subjected to a temperature sufficient to cure each uncured layer. [0024] In one embodiment, during step (ii) the pulley and lagging strips are subjected to a temperature of between 100 and 200 degrees Celsius. [0025] In one embodiment, during step (ii) the pulley and lagging strips are subjected to a temperature of 150 degrees Celsius. [0026] In one embodiment, during step (ii) the pulley and lagging strips are subjected to a pressure substantially sufficient to ensure a uniform bond between each lagging strip and pulley surface. [0027] In one embodiment, prior to step (ii) the pulley and lagging strips are wrapped in a wet nylon cloth.

-5 [0028] In one embodiment, during step (ii) the wet nylon cloth dries and shrinks thereby applying a substantially equal force to each lagging strip surface. [0029] In one embodiment, each cured rubber layer includes a plurality of longitudinally extending drain formations disposed on its outer surface. [0030] In one embodiment, prior to step (ii) removable infill strips are placed in the drain formations to ensure that uniform pressure is applied to each lagging strip step (ii). [0031] In one embodiment, the infill strips are substantially formed from any heat resistant material. [0032] In one embodiment, the infill strips are substantially formed from silicon. [0033] In one embodiment, the wear resistant inserts are in the form of ceramic or polyurethane tiles. [0034] According to one aspect, there is provided a method for securing lagging of the type that includes drains and wear resistant inserts to the exterior surface of a conveyor pulley including the steps of: (i) adhering a lagging strip to the exterior surface of the pulley; the lagging strip being defined by an uncured rubber layer adhered to a cured rubber layer; and (ii) subjecting the pulley and lagging strip to an increased temperature thereby curing the uncured rubber layer and securing the lagging strip to the pulley surface. [0035] According to one aspect, there is provided a lagging strip in accordance with any of the above aspects. [0036] Reference throughout this specification to "one embodiment", "some embodiments" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment", "in some embodiments" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or -6 characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. [0037] It will be appreciated that in the present context, the terms "adhere" or "adhering" refer to the process of using an adhesive, and the term "securing" or "bond", as in securing to the pulley surface, refers to bonding due to the curing, or vulcanization, of uncured rubber. Brief Description of the Drawings [0038] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: [0039] Figure 1 is a perspective view of a plurality uncured and cured rubber layers in accordance with the present invention; [0040] Figure 2 is a perspective view of the uncured and cured rubber layers of Figure 1, adhered to each other to define a plurality of lagging strips; [0041] Figure 3 is a perspective view of a conveyor pulley without lagging; [0042] Figure 4 is a perspective view of the conveyor pulley of Figure 3 with one of the lagging strips of Figure 2 partially adhered to the pulley surface; [0043] Figure 5 is a perspective view of the conveyor pulley of Figure 3 with a plurality of the lagging strips of Figure 2 completely covering the pulley surface; [0044] Figure 6 is a perspective view of the pulley and lagging strips of Figure 5 being hammered with a soft head hammer in order to remove any air gaps; [0045] Figure 7 is a perspective view of an infill strip in accordance with a second aspect of the present invention; [0046] Figure 8 is a perspective view of the pulley and lagging strips of Figure 5 with a number of in fill strips about to be engaged in the drains on the outer lagging surface; -7 [0047] Figure 9 is a perspective view of the pulley and lagging strips of Figure 5 with all the drains on the outer surface filled with the infill strips and further covered with a wet nylon cloth; [0048] Figure 10 is a schematic view of the pulley, lagging strips and cloth wrap assembly of Figure 9 being placed into an oven; [0049] Figure 11 is a perspective view of a fully lagged pulley; [0050] Figure 12 is a cross-sectional view of the pulley and lagging strips of Figure 5; [0051] Figure 13 is a cross-sectional view of the pulley of Figure 9 prior to being wrapped with a cloth wrap; [0052] Figure 14 is a cross-sectional view of the pulley of Figure 9; [0053] Figure 15 is a cross-sectional view of the fully lagged pulley of Figure 11 showing the removal of the infill strips; and [0054] Figure 16 is a cross-sectional view of the fully lagged pulley of Figure 11. Description of Preferred Embodiments [0055] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals throughout. In the following description, detailed descriptions of known functions and configurations incorporated herein have been omitted for conciseness and clarity. [0056] Referring to the accompanying drawings, there is provided a method for securing lagging to the exterior surface of a conveyor pulley. As those familiar with the art will appreciate, lagging material is used in order to minimise conveyor belt slippage, build up of material on the circumferential face of the pulley and to reduce wear and corrosion of the pulley. This type of conveyor system is typically known in the mining industry. The lagging is typically formed from a resilient rubber material and the outer pulley surfaces have a uniform diameter along the entire face or can vary in diameter to create crowned faces.

-8 [0057] With reference initially to Figures 1, the first step in the method according to the invention is to adhere a plurality of uncured rubber layers 10 to a plurality of cured rubber layers 12 in a laminated configuration using a liquid adhesive. This results in a plurality of lagging strips 14 shown in Figure 2. As generally known in the art, the rubber used for the uncured or cured rubber layers may be natural rubber or Styrene Butadiene Rubber. [0058] It should be understood that the effective friction between the lagging material and conveyor belt is optimised when the lagging material efficiently drains any accumulated fluid between the belt and lagging. With this consideration in mind, the lagging strips 14 include a series of drains 22 disposed on the cured rubber layer's outer surface. The drains 22 are used for shedding water and/or debris from the lagging surface during use and especially when operating in wet conditions. The outer surface further includes a plurality of wear resistant inserts in the form of ceramic tiles 24, each including a plurality of dimples 26, housed between the drains 22. These ceramic tiles 24 act to further reduce slippage between the lagging and conveyor belt and reduce wear of the lagging strips. [0059] As best shown in Figure 2, in accordance with a further aspect of the present invention, the uncured rubber layers 10 are sized such that they extend beyond the lateral edges 16 of the cured layers so as to be turned up and adhered to the whole of the lateral edge. As will be discussed below, these turned up portions allow sufficient material for contacting uncured layers to bond during the curing process. [0060] In the embodiment shown, the lagging strips 14 are sized to extend from one end of a conveyor pulley to the other. However, in other not shown embodiments, the lagging strips could be any shape and configuration as long no gaps are present once the lagging strips are adhered to the pulley surface as discussed in more detail below. The drains 22 could also be in a diamond, chevron or herringbone pattern rather than longitudinally extending along the elongate lagging strip. [0061] As shown in Figures 3 to 5, the plurality lagging strips 14 are then adhered to the exterior of a pulley 18 in an abutting formation so as to completely cover the cylindrical pulley surface, again using a suitable liquid adhesive. To assist in correct alignment, it will be useful for the installer to mark a guide line 20 across the pulley face that is parallel with pulley rotational axis as shown in Figure 3, and then align the first lagging strip to that line as shown in -9 Figure 4. The remaining lagging strips are then adhered to the pulley surface in a contiguous and abutting formation as shown in Figure 5. [0062] With reference to Figure 6, as is normal in the art, the lagging strips are then impacted by a soft hammer in order to remove any entrapped air gaps. [0063] The above steps may be altered by creating and adhering one lagging strip 14 to the pulley surface at a time, rather than creating and adhering a plurality of lagging strips to the pulley surface, without departing from the scope of the invention. Similarly, the lagging strips may be applied to the surface by first adhering the uncured layers to the pulley surface and then adhering the cured layers to the uncured layers. However, using this method will require special care to make sure the upturned edges of the uncured layers are retained. [0064] In order to prepare the pulley surface prior to the adhering of the lagging strips, the metal exterior surface of the pulley is preferably sandblasted to a minimum of 16 grit finish and also to be free from oil and grease contamination. Within 15 minutes of sandblasting, a suitable primer such as Chemlok @ 205 is ideally applied to the metal surface and allowed to dry. A liquid adhesive can be then applied to the primed surface so as to apply the first of lagging strips. [0065] Referring to Figures 7 and 8, according to a further aspect of the present invention, subsequent to the adhering of the lagging strips 14 to the pulley surface, removable elongate infill strips 28 are placed in each drain 22. Each infill strip 28 has a cross section that is complementary to each drain cross section such that a generally flush upper surface is defined upon insertion. Since the lagging is made of a resilient rubber material, the infill strips can be pushed into place and gripped in position. [0066] With reference to Figures 9 and 10, the assembly of pulley, adhered lagging strips and infill strips 28 are then wrapped in a wet nylon cloth 30 and placed in an autoclave or oven 32. Whilst in the oven, the assembly is subjected to an increased temperature in order to cure the uncured layers 10 and hot vulcanise the lagging strips to the steel pulley surface. In one embodiment, the increased temperature is approximately 150 degrees Celsius and the assembly remains in the oven for approximately one hour. However, in other embodiments, the temperature may be in the range of 100 to 200 degrees Celsius with the oven duration being adjusted accordingly.

- 10 [0067] It will be appreciated that while the assembly is being subjected to the increased temperature in the autoclave or oven, the wet nylon cloth 30 begins to dry and shrink thereby applying a uniform force to the lagging surface. This will, in turn, create a uniform bonding strength, or more importantly, no areas of weaker bonding strength, between the lagging and the pulley surface. It should be understood that the purpose of the infill strips 28 is to create a generally flat top surface thereby equalising the force applied to the lagging strips 14 and the surface of the pulley 18 by the drying wet nylon cloth during the increased temperature in the oven. Furthermore, since the drains 22 and ceramic tiles 24 are disposed on the cured layers, advantageously there will be no dimensional changes while the assembly is subjected to the increased temperature and the tiles 24 will remain in position. [0068] The pulley is then removed from the oven 32 and the nylon cloth 30 and infill strips 28 are removed. The ends of the lagging can be trimmed if required such that they are flush with the end of the pulley. The process is then essentially complete resulting in the lagged pulley 34 of Figure 11. [0069] As the infill strips 28 are only present while the pulley is subjected to the increased temperature and pressure it is not necessary that they be the exact same length of the pulley. Ideally, they are made of a suitable heat resistant material such as silicon so that they do not deform or bond to the rubber lagging material whilst subjected to the increased temperature and maintain their shape under the increased pressure present in the oven 32 or autoclave. [0070] It will be appreciated that whilst in the oven 32, the plurality of uncured layers 10 approach their liquid state to cure and bond with each other and the cured layers 12, thereby transforming them into a substantially uniform cured rubber lagging sleeve 38 surrounding the pulley 18. Also, upon curing, the lagging sleeve 38 secures to the pulley surface due to a hot vulcanisation process. A relatively stronger and more uniform bond is created between the lagging and pulley surface and no physical gaps will be present in the lagging sleeve. This minimises the possibility of the lagging coming away during use in addition to minimising the potential for corrosion of the pulley surface by moisture ingress. [0071] The end result is more clearly shown with reference to Figures 12 to 16, which illustrate cross sections of the pulley and lagging at various stages of the process.

- 11 [0072] Figure 12 shows a cross section of the pulley 18 and laggings strips 12 prior to being placed in the autoclave or oven. In Figure 13, a cross section of the pulley and lagging strips is shown with the infill strips 28 in position and Figure 14 depicts a similar view but with the cloth wrap in place prior to being placed in the autoclave or oven. As is evident with respect to Figures 12 - 14, the uncured and cured rubber layers and the turned up portions are still clearly distinguishable prior to the curing process. [0073] Figure 15 is a cross section of the pulley and lagging sleeve 38 after leaving the oven 32 or autoclave with the removal of the infill strips 28 shown, and Figure 16 is a cross section of the completed lagged pulley. In these Figures, it can be seen that no separate layers or contiguous laggings strips are present at the completion of the process according to the invention, rather a uniform lagging sleeve 38 is shown with no joins is provided. [0074] As should be now self evident, the method of securing lagging to the exterior of a conveyor pulley according to the present invention greatly improves the bonding strength between the lagging material and the pulley surface due the curing or hot vulcanising process that occurs in the oven. The infill strips 28 and the drying wet nylon cloth 30 ensure that an even pressure is applied to the pulley surface whilst in the oven resulting in an even bonding strength. Moreover, upon curing, no physical gaps will be present resulting in no path between lagging strips for moisture ingress. [0075] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (21)

1. A method for securing lagging of the type that includes wear resistant inserts to the exterior surface of a conveyor pulley, the method including the steps of: (i) adhering two or more lagging strips to the exterior surface of said pulley in an abutting formation, each lagging strip being defined by an uncured rubber layer adhered to a cured rubber layer; and (i) subjecting said pulley and lagging strips to an increased temperature thereby curing said uncured rubber layers and securing said lagging strips to said pulley surface.

2. A method according to claim 1, wherein in step (i) each uncured rubber layer extends past, and is adhered to, two or more edges of the corresponding cured rubber layer.

3. A method according to claim 2, wherein said edges of the corresponding cured rubber layer are the lateral edges of the corresponding cured rubber layer.

4. A method according to any one of claims 1 to 3, wherein during step (ii) two or more contiguous uncured rubber layers bond to each other such that no physical gap is present between contiguous lagging strips.

5. A method according to any one of the preceding claims, wherein during step (ii) each uncured rubber layer bonds to the corresponding cured rubber layer.

6. A method according to any one of the preceding claims, wherein a plurality of lagging strips is adhered to the exterior surface of the pulley in an abutting formation in step (i).

7. A method according to any one of the preceding claims, wherein during step (ii), said pulley and lagging strips are placed in an oven.

8. A method according to any one of claim 1 to 6, wherein during step (ii) said pulley and lagging strips are placed in an autoclave.

9. A method according to any one of the preceding claims, wherein during step (ii) said pulley and lagging strips are subjected to a temperature sufficient to cure each uncured layer. - 13

10. A method according to any one of the preceding claims, wherein during step (ii) said pulley and lagging strips are subjected to a temperature of between 100 and 200 degrees Celsius.

11. A method according to any one of the preceding claims, wherein during step (ii) said pulley and lagging strips are subjected to a temperature of 150 degrees Celsius.

12. A method according to any one of the preceding claims, wherein during step (ii) said pulley and lagging strips are subjected to a pressure substantially sufficient to ensure a uniform bond between each lagging strip and pulley surface.

13. A method according to any one of the preceding claims, wherein prior to step (ii) said pulley and lagging strips are wrapped in a wet nylon cloth.

14. A method according to claim 13, wherein during step (ii) the wet nylon cloth dries and shrinks thereby applying a substantially equal force to each lagging strip surface.

15. A method according to any one of the preceding claims, wherein each cured rubber layer includes a plurality of longitudinally extending drain formations disposed on its outer surface.

16. A method according to claim 15, wherein prior to step (ii) removable infill strips are placed in said drain formations to ensure that uniform pressure is applied to each lagging strip step (ii).

17. A method according to claim 16, wherein said infill strips are substantially formed from any heat resistant material.

18. A method according to claim 16 or claim 17, wherein said infill strips are substantially formed from silicon.

19. A method according to any one of the preceding claims, wherein said wear resistant inserts are in the form of ceramic or polyurethane tiles.

20. A method for securing lagging of the type that includes drains and wear resistant inserts to the exterior surface of a conveyor pulley including the steps of: - 14 (i) adhering a lagging strip to the exterior surface of said pulley; said lagging strip being defined by an uncured rubber layer adhered to a cured rubber layer; and (ii) subjecting said pulley and lagging strip to an increased temperature thereby curing said uncured rubber layer and securing said lagging strip to said pulley surface.

21. A lagging strip in accordance with any one of the preceding claims.