Expanded – threaded – driven – headed – tool-deformed – or locked-thr – With means to indicate application of predetermined...
Reexamination Certificate
1999-09-24
2001-06-12
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
With means to indicate application of predetermined...
C411S014000, C073S761000, C116S212000
Reexamination Certificate
active
06244804
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to fastening devices and, in particular, to tension-indicating fasteners.
FIELD OF THE INVENTION
Bolts, nuts and washers are common parts of any fastening system for securing two or more metal members together, for securing a tension cable to an anchor or base metal or any of a wide variety of elements that must reliably secure two elements together under a predetermined load. Heretofore the monitoring of the clamp load force has been dependent upon sophisticated bolt load analyzers using personal computers or even personal workers who periodically “torque” a nut to ensure that it is exerting the proper clamping load. In commonly assigned U.S. Pat. No. 5,722,807, issued Mar. 3, 1998, entitled “CLAMP LOAD INDICATOR”Ser. No. 08/729,203, filed Oct. 15, 1996, there is disclosed an indicator utilizing a phenomenon generally referred to as “dishing” to monitor the clamp load of a fastener which invention permits an all mechanical indicator if desired. Moreover, the usual technique is to monitor bolt tension and elongation rather than compression of the jointed surface. Nonetheless, portions of that application are incorporated herewith when necessary to complete the description.
Co-pending application Ser. No. 09/102,408, filed Jun. 22, 1998 and entitled “FASTENER TENSION INDICATOR”describes several fasteners equipped with tension-indicator devices. The devices comprise indicator arms that are mounted to the fastener head and configured to remain in contact with the surface of the substrate in which the fastener is secured at points regularly remote from the fastener head. Differences in the degree of deflection caused by the tension of the fastener on the substrate affect the position of the indicator arms, which move in radial directions relative to the fastener. The disclosure of this pending application is hereby incorporated herein by reference as background information.
SUMMARY OF THE INVENTION
The present invention provides several embodiments of tension-indicating fasteners. Generally speaking, fasteners according to the present invention comprise a shank, a fastener head on the shank and a tension indicator on the fastener. In one embodiment of the present invention, the tension indicator is configured to have an indicating arm and a laterally-extending contact member. In use, the fastener is secured to a substrate against which the fastener head bears, and at least the contact member of the tension indicator is configured to contact the substrate surface. The contact member is connected to the indicating arm and extends therefrom in a tangential direction relative to the fastener head. The indicating arm is secured to the fastener and the contact member provides laterally-distant contact points on the substrate surface so that deflection in the substrate to which the fastener is secured causes a distal free end of the indicating arm to move with amplified magnitude.
In another embodiment of the invention, a plurality of tension indicators may be secured to the fastener head. According to still another embodiment of the invention, the contact member is connected to the fastener at a point above the surface of the substrate and vertical movement of the fastener head (relative to the “horizontal” surface of the substrate) causes the indicating arm to move or is at least a partial component of such movement. In still other embodiments of the invention, the improved fastener comprises means for indicating a target degree of substrate deflection.
In particular embodiments, the present invention provides a fastener comprising a shank having two ends, a fastener head on one end of the shank, and a tension indicator on the fastener. The tension indicator comprises an indicating arm having two ends and being connected to the fastener head at one end and extending along the fastener head with a space therebetween and further comprising a laterally-extending contact member connected to the indicting arm above where the indicating arm is connected to the head.
According to one aspect of the invention, the indicating arm may comprise a gauge portion configured to extend over the top of the fastener head. Optionally, there may be tension indicia on the fastener head.
According to another aspect of the invention, the fastener may further comprise a second tension indicator attached to the head opposite the first tension indicator.
Optionally, the laterally-extending contact member may have an A-frame configuration.
The present invention also relates to an improved washer configured to rest on the surface of a substrate wherein the improvement comprises an indicating arm connected to the washer and configured to extend away from the surface of the substrate on which the washer may rest. Preferably, the indicating arm is configured to contact the surface of the substrate at a point distant from the washer.
An alternative embodiment of the invention relates to a fastener comprising a shank having two ends, a head at one end of the shank and a tension indicator comprising an indicating arm having two ends and being connected to the head with one end extending away from the shank and the other end extending in an opposite direction to provide a foot portion for contact with a surface of a substrate beneath the fastener head. Optionally, there may be a shim between the indicating arm and the fastener head. The foot portion may be configured to extend to within the periphery of the fastener head or outside the periphery of the fastener head.
Any of the devices described herein may optionally include a filler in the space between the indicating arm and the fastener head.
In various embodiments, the fastener may comprise an induction coil through which the tension indicator moves as the fastener is tightened onto a substrate, or a potentiometer strip wherein the tension indicator comprises a wiper in contact with the strip, or a resistor strain gauge.
The present invention further provides a fastener having a central axis and a tension indicator disposed alongside the head of the fastener and configured to move towards the central axis when the fastener is tightened to a substrate, wherein the fastener head defines a recess sized and positioned to accommodate the tension indicator in an untightened position and in a tightened position whereby a tightening tool can bear upon the fastener head to tighten the fastener without contacting the tension indicator. Optionally, the fastener head may comprise windows that open to the recess and through which the tension indicator may become visible as the fastener is tightened against a substrate.
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Libert Victor E.
Libert & Associates
Spaeth Frederick A.
Wilson Neill
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