Boring or penetrating the earth – With orienting or racking means for unconnected tools or...
Reexamination Certificate
1999-10-01
2001-11-27
Neuder, William (Department: 3672)
Boring or penetrating the earth
With orienting or racking means for unconnected tools or...
C152S005000, C295S011000, C301S040200, C384S058000
Reexamination Certificate
active
06321859
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to blasthole drills and to rollers for supporting a load and, more particularly, to rollers made of more than one material. Specifically, the present invention relates to a bi-material roller for use in a blasthole drill.
BACKGROUND OF THE INVENTION
There are many known rollers or wheels designed for supporting a load. For example, U.S. Pat. No. 1,408,388 to Reddaway et al. is directed to a tire and rim assembly wherein the tire includes a body portion formed of hard rubber and a central portion constituting a soft rubber resilient core. U.S. Pat. No. 1,687,113 to Stockdale describes a caster wheel formed with a rubber annulus and a tread or wear element in the shape of a disc which is fabricated of fibrous or fabric materials vulcanized to the rubber annulus. U.S. Pat. No. 4,321,727 to Sheiman et al. discloses a luggage roller including a central groove in the form of a V-shaped channel of elastomeric material and a central cylindrical sleeve formed of low friction material, such as polyethylene nylon, Teflon, or similar plastic. In U.S. Pat. No. 4,452,141 to Mistyurik, a roller with a porous surface and a central flange is disclosed. U.S. Pat. No. 5,803,235 to McGinnis et al. is directed to an idler roller which includes an impact shell with a backing layer on the inside of the shell, and a compression ring adapted to expand and engage the inside of the impact shell and an external surface of a main roller body. The load carrying capability of these types of rollers and other rollers varies as a result of their structural construction and intended use.
Blasthole drills are large machines used in mining operations to drill holes for explosives. A conventional blasthole drill comprises a frame supported by crawlers for movement over the ground. A mast which defines a drill hole axis is supported by the frame for movement between a substantially vertical position and a number of angled or non-vertical positions. A rotary head, which engages the upper end of a drill pipe for rotating the drill pipe and driving the drill pipe into the ground, moves relative to the mast along the drill hole axis. The rotary head is supported by rollers which move along appropriate surfaces or grooves in the mast. The rollers are designed to have a load carrying capacity to support, at a minimum, the weight of the rotary head and the weight of the end of the drill pipe supported by the rotary head. As can be appreciated, when the mast is positioned in a vertical or substantially vertical position, a light load is transferred to the rollers. On the other hand, when the rotary head is applying, a downward force for drinking, heavy load is transferred to the rollers.
It is known to make such rollers of an all-steel construction.
It is also known to provide rollers having a steel main body surrounded with an outer covering of plastic.
BRIEF SUMMARY OF THE INVENTION
A roller according to the present invention is adapted to support a load under any number of different applications. However, a roller according to the present invention is particularly useful in a blasthole drill.
Under certain load conditions, it may be advantageous for a roller to have particular load supporting and roller surface characteristics and yet, under other load conditions, it may be advantageous for the roller to have different load supporting and roller surface characteristics. The invention provides a roller which is capable of adapting its load supporting and roller surface characteristics as needed for different applications or changing load conditions.
Many of the known rollers or wheels, while capable of supporting loads under many different conditions, do not provide the desired versatility when it comes to subjecting the rollers or wheels to variable load conditions. In other words, such rollers or wheels do not include load supporting and roller surface characteristics which independently change on an as-needed basis depending on the load to be supported. Thus, a problem with these types of rollers or wheels is that while such rollers or wheels may satisfactorily operate when subjected to a given load, such rollers or wheels may not satisfactorily operate when subjected to a different load.
The known all-steel rollers for blasthole drills are capable of high load carrying capacity. However, a problem which exists for all steel rollers is that during light loading, the steel rollers may skid rather than roll, which may cause flat spots on the rollers, thereby adversely affecting the rollers capability to function properly and support the load. The load supporting and roller surface characteristics of the all-steel rollers do not adjust for changing load conditions.
The plastic covered rollers for blasthole drills were designed to address some of the problems associated with the all-steel rollers by providing a surface with better frictional properties for certain load conditions, particularly light load conditions. Nevertheless, a problem which exists for these types of rollers is that during heavy loading, the large loads may excessively compress the plastic coverings and cause the plastic to flow outward and over the edges or sides of the steel roller main body. Too large of a flow in the plastic can result in high stresses in the bond between the main body of the steel rollers and the plastic outer covering thereby possibly causing the bond to fail.
Accordingly, the present invention provides a roller that alleviates these problems and many other problems common to known rollers or wheels. More particularly, the present invention provides a bi-material roller which is capable of supporting various loads, i.e., light loads or heavy loads, and which is also designed to properly roll, rather than skid, under any given load condition. A bi-material roller according to the present invention is particularly capable of use in a blasthole drill which is notorious for subjecting load supporting rollers to various load conditions.
In one aspect of the present invention, there is provided a roller which is rotatable about its axis, and which is adapted to support a load. The roller includes a roller body having a first substantially non-deformable, generally cylindrical outer surface located radially outward with respect to the roller axis. The roller further includes a second deformable, generally cylindrical outer surface located radially outward with respect to the roller axis.
The outer surfaces are configured and arranged such that under a light load condition, the second deformable surface extends farther radially outward than the first substantially non-deformable surface. Under such a light load condition, the deformable surface of the roller is in contact with and supports the load while the substantially nondeformable surface of the roller is not in contact with and does not support the load. The surface properties of the deformable material allow the roller to roll under light loads whereas, as pointed out, an all steel roller may undesirably skid under such load conditions.
The outer surface of the rollers are further configured and arranged such that under a heavy load condition, the second deformable surface deforms to a point where the second surface does not extend farther radially outward than the first substantially non-deformable deformable surface. Under such a heavy load condition, both the deformable and substantially non-deformable surfaces are in contact with and cooperatively support the load. The non-deformable surface ensures that the roller is capable of supporting the heavy load while, at the same time, the roller is constructed so as to prevent the deformable surface from being overstressed or deformed beyond an acceptable range. A roller according to the present invention is unlike the prior plastic covered rollers which may perform in a less than acceptable manner if subjected to heavy loads as previously discussed.
In a preferred embodiment, the roller body and thus the first substantially non-deformable surface is made of steel and
Harnischfeger Technologies Inc.
Neuder William
Price David R.
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