Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Having separate expander means – Including sleeve and distinct tapered expander
Reexamination Certificate
2000-01-27
2001-04-24
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Having separate expander means
Including sleeve and distinct tapered expander
C411S071000, C411S383000, C411S396000, C411S399000
Reexamination Certificate
active
06220802
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
NOT APPLICABLE
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to spreading the clamping load of a bolt which holds an inner liner to an outer shell used in ore milling operations, sealing the shell so that the wet ore slurry in the inner lining does not leak out of the shell through the mounting holes, and repairing enlarged mounting holes which go through the liner and shell to re-establish the ability of the bolt to maintain its designed and desired preload.
2. Description of the Related Art
a. Prior Mill Liner Bolting Techniques and Problems
Because of individual geometry, the head shape of a conventional tapered or spherical head, counter sunk mill liner bolt, presents a poor load bearing contact with the liner and its mating surface. This condition is due primarily to clearance and manufacturing tolerances between the liner, which is cast, and the radiused, tapered, load bearing area of the bolt, which is forged. This poor load area contact always causes early embedment with subsequent loss of bolt clamp load soon after assembly. It requires repeated, expensive mill shut downs, for bolt tightening, before an adequate surface contact can be formed to support the required bolt clamp load. In a majority of instances, bolts never establish enough surface area contact to stay tight and have to be periodically tightened through the life of the liners. Often, loose bolts fatigue and break with expensive consequences if the liners fall out.
While it is known to provide round headed bolts with a plurality of hard metal protrusions of various types, i.e., wings, keys, or fins, formed along the neck and shank of the bolt which embed themselves in the softer work piece to prevent the bolt from turning when a load is applied to the bolt, such structures are unnecessary when a non-round bolt head is supported in a non-round recess and, moreover, will not work in the environment of the present invention where the work piece, i.e., the mill liner, is made of harder steel than the bolt of the fastener.
Accordingly, it is an object of the present invention to provide improved bolt tightening features and processes which provide improved mating surfaces and preload holding ability which overcomes the problems of the prior art.
Moreover, running with loose bolts is also the cause of bolt holes in the mill shell becoming enlarged, which encourages further loosening and leaking problems eventually leading to expensive repair. Typically, the bolt holes in the liners are cast approximately ⅛″ larger, all around the bolt head, for a standard 1½″ liner bolt.
FIG. 3
shows how inadequately the bolt load surface mates with the liner in a horizontal (radial) plane.
FIGS. 1
,
2
show loss of vertical (axial) contact face with small neck angle differences.
Accordingly, it is an object of the present invention to provide improved bolt tightening mechanisms which prevent loosening and enlargement of the holes through which the bolt passes thereby overcoming the problems of the prior art.
b. Prior Liner Bolt Sealing Problem
Prior sealing systems used with liner bolts are designed to give good sealing characteristics, but in doing so, sacrifice jointing efficiency. Typically rubber is introduced between the joint surfaces so that a hard joint, i.e., metal-to-metal, is never attained. This condition then becomes a gasketed joint and will never hold bolt preloads adequately.
While it is known to provide a repair washer with a metal-to-metal contact using a two- or three-piece metal and rubber washer combination atop a repair washer to effect an outboard seal at the outer circumference of the bolt of the fastener and the outboard end of the central bore of the repair washer, such structure ignores the further need for a simultaneous metal-to-metal contact with a resilient member beneath the repair washer to effect an inboard seal at the inborad end of the central bore of the repair washer.
Accordingly, it is an object of the present invention to provide an improved sealing system without sacrificing joint efficiency by providing metal-to-metal contact with simultaneous adequate sealing thereby overcoming the problems of the prior art.
BRIEF SUMMARY OF THE INVENTION
Set forth below is a brief summary of the invention in order to achieve the forgoing and other benefits and advantages in accordance with the purposes of the present invention as embodied and broadly described herein.
A first aspect of the invention is a bolt including a head of predetermined shape, a shank, a neck integral with the head and shank, and a plurality of raised contact surface portions uniformly positioned adjacent the neck and constructed and configured for spreading an applied bolt load.
Another feature of this aspect of the invention is the raised contact surface portions include a base portion contiguous the neck, and a ridge portion raised above the base portion and constructed and configured to contact a congruent wall portion of a bolt bore in a support structure.
Still other features of this aspect of the invention include the bolt is a forged bolt, the head shape may be round, elliptical, square, oblong, spherical, or rectangular, and has an axially extending portion of predetermined thickness having a constant circumference, and a tapered neck portion between the head and shank.
Still other features of this aspect of the invention include the neck having a circumference either intermediate the circumferences of the head and shank or greater than both said circumferences.
Another feature of this aspect of the invention is the raised contact surface portions are elongated V-shaped ridges raised above the base portion and are forged integrally with the neck.
Still other features of this aspect of the invention include the raised portions are symmetrically placed relative to the neck, extend substantially an entire length of the neck, may also extend substantially along an entire length of the head, extend axially and radially relative to the longitudinal axis of the bolt, and are deformable and fay to an adjacent bore wall portion whereby when a load is applied to the bolt the load is spread more uniformly over a surface of the neck.
A second aspect of the invention is an insert including a base portion having a width, a length and a thickness, and a plurality of surface contact portions raised above and extending along a length of the base portion.
In this aspect of the invention the plurality of surface contact portions are short relative to a width of the insert, are coterminous with a length of the base portion, and are formed as parallel, symmetrically placed, V-shaped ridges, the height and width of which vary relative to each other according to the amount of a clearance of an adjacent wall portion of a bore hole in a support structure.
A further feature of this aspect of the invention is the insert has a flat shape in one stage of its production and an arcuate shape in its final form which is self-aligning relative to the neck of the bolt when a load is applied to the bolt whereby the load is spread onto the raised contact surfaces.
A third aspect of the present invention is a repair washer for enlarged holes including a shaped body having a top major surface and a bottom major surface and a central bore therethrough, an annular groove in the top major surface constructed and configured to receive an o-ring seal, an annular groove in the bottom major surface constructed and configured to receive an o-ring seal, and a plurality of teeth integral with the bottom major surface constructed and configured for gripping a surface which is to be sealed.
In this aspect of the invention the annular groove in the top major surface is located near the central bore and is constructed and configured to cooperate with a bolt through the central bore and through an overlying fastener to seal the central bore at the top surface, while the annular groove in the bottom major surface is located near the periph
Lisa Donald J.
Wilson Neill
LandOfFree
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