Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Internally threaded fastener element – e.g. – nut – etc. – Including lubricating means
Patent
1995-02-06
1996-10-15
Wilson, Neill R.
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Internally threaded fastener element, e.g., nut, etc.
Including lubricating means
411149, 411432, 411534, F16B 3700, F16B 3924
Patent
active
055648754
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a locking fastener and relates more particularly to a threaded fastener of this type, having friction reducing means, for reducing friction during tightening and loosening of the fastener, in combination with cam means for inhibiting inadvertent loosening of the fastener due to vibration.
The invention will be described with particular reference to threaded wheel fasteners, such as nuts and bolts, however it will be understood that the locking fastener of the invention can be used in any application where the fastener may be subjected to vibrational or oscillatory loads.
A conventional fastener, such as a wheel nut or bolt comprises a head portion with grip means designed to receive a wheel brace or spanner or fastening machine, a threaded portion to screw onto the thread of a wheel stud or onto the inner flange located on the wheel axle, and a tapered cone portion shaped to engage in a matching recess provided in the wheel. In some arrangements the cone portion is provided separate from the head portion and sometimes the fastener is further provided with a conventional washer behind the cone. In other arrangements, particularly on truck wheels the wheel nuts or bolts have a flat under-surface rather than a cone portion.
Irrespective of the form of the wheel fastener a primary objective during tightening is to pre-load the bolt or wheel stud to the particular tension specified so as to give the desired clamping effect. When a conventional wheel fastener is tightened a high degree Of friction is encountered, comprising friction on the threaded portion, friction on the wheel recess and friction on the cone portion or underside of the fastener contacting the wheel surface or recess. Thus a significant proportion of the torque required to tighten a conventional wheel nut or bolt is expended in overcoming the frictional resistance, whilst the remainder provides the pre-load or clamping pressure. These torque losses due to friction become very significant on heavy vehicles where the torque required to overcome friction and attain clamping pressure is very high. Fastener friction therefore causes wasteful expenditure of energy during both tightening and loosening as is well known. Furthermore, fastener friction also causes inaccurate reading of the torque tension setting during pre-loading of the fastener. In practice it is extremely difficult to distinguish the torque required to overcome friction, (especially underhead friction, where with different fasteners and repeated use the friction varies), from the torque required to attain the necessary pre-load, and this can lead to the wheel not being securely clamped to the wheel flange and therefore more susceptible to loosening. Attempts have been made to overcome the problems of high friction, but have been of limited success.
The problem of conventional wheel fasteners tending to loosen when subjected to vibrational or cyclic loading is significant, particularly on heavy transport vehicles where catastrophic failure resulting in loss of a wheel can cause substantial damage and even loss of life. A loosening force may arise during elongation or compression of the associated threaded stud or bolt when subjected to a working load, that results from a component of the pre-load force on the fastener being directed along the lead angle or helix of the thread series in a loosening direction. A working load that exceeds the pre-load can cause the fastener to rotate in a loosening direction. A number of locking devices designed to overcome this problem are known in the art, one of which comprises a two part lock washer having opposing cam surfaces.
Such a prior art lock washer arrangement is disclosed, for example, in U.S. Pat. No. 3,263,727 by Arthur B. Herpolsheimer. This U.S. Pat. discloses a pair of lock washers received, for example, on a stud or lug between a nut and the object to be fastened. As the nut is tightened, the washer adjacent the nut becomes fixed to the nut due to the frictional contact resistanc
REFERENCES:
patent: 679935 (1901-08-01), Behler
patent: 3263727 (1966-08-01), Herpolsheimer
patent: 3926237 (1975-12-01), Enders
patent: 4134438 (1979-01-01), Frieberg et al.
patent: 4433578 (1984-02-01), Hill
patent: 4619559 (1986-10-01), Norris
patent: 4704058 (1987-11-01), Crunwell
patent: 4969788 (1990-11-01), Goiny
patent: 5080545 (1992-01-01), McKinlay
patent: 5190423 (1993-03-01), Ewing
patent: 5203656 (1993-04-01), McKinlay
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