1. Field of the Invention
The present invention relates to self-locking threads and threaded connections, and more particularly to self-locking threaded connection devices that may be discrete fasteners intended to secure two or more work pieces together and comprised of a combination of a threaded bolt, cylinder, stud, shank or screw mated with a complimentary threaded nut or hole, or that also may be an integral part of some other device, such as the threads on the end of the arm that screws into the threaded complimentary hole in the torso of a toy soldier.
2. Description of the Related Art
Locking threaded fasteners and threaded connecting devices of a wide variety of types are available which reduce the tendency of male, generally cylindrical, threaded components from altering their position in relation to their corresponding female threaded component, thereby reducing the tendency of such threaded fasteners and threaded connecting devices to loosen and come apart in response to vibration, expansion, contraction and other movement. Many such fasteners function in this regard by increasing friction between the otherwise mated threads of the male and female components or between the fastener and the parts joined by the fastener. Examples include: lock washers, tooth washers, blind thread bores filled with resilient inserts such as disclosed in U.S. Pat. No. 5,078,562 issued to DeHaitre on Jan. 7, 1992, and screw thread profiles that jam or deform when tightened such as disclosed in U.S. Pat. No. 5,242,252 issued to Harle on Sep. 7, 1993. Other such fasteners and connections function by increasing the friction between the engaging surfaces of the head of the male component and work piece, or between the female component and work piece such as disclosed in U.S. Pat. No. 4,290,469 issued to Nakae on Sep. 22, 1981. In all such arrangements, the increased friction makes rotation more difficult between the male and female components, thereby preventing inadvertent release or loosening of the male and female components. A drawback of all these approaches is that the male and female components can loosen at any axial pressure or tension less than that required to strip the male component out of the female component. Since the threads in each case fall away in the direction of axial pressure or tension, a portion of such pressure or tension is translated into a rotational force tending to loosen the components. Also, fasteners using these approaches generally require high or increased torque to install, or mar the joint surface, or are not reusable, or require greater loads to be effective than is desirable to apply to some joints. Self-locking accessories such as cotter pins, lock wires, and nut assemblies comprising a first working nut and a second locking nut part as disclosed in U.S. Pat. No. 5,154,560 issued to Copito on Oct. 13, 1992, have the drawback of requiring additional installation effort.
Therefore, there is a need for threads, threaded fasteners, and threaded devices: (i) that will not come loose under loads equal or less than the fastener supports, (ii) that can be easily installed using conventional tools, (iii) that employ torque values appreciably closer to those torque values only necessary to clamp together the workpieces (as opposed to requiring higher torque values to provide increased resistance against loosening), and (iv) that can be installed as easily as standard fasteners. The present invention addresses these drawbacks in known prior threaded fasteners and threaded devices and meets these needs with a novel thread design which can be forged, rolled, stamped, or otherwise applied to threaded fasteners and threaded devices using conventional techniques. Improved threaded fasteners and threaded devices may therefore be manufactured at close to the cost of traditional locking threaded fasteners and devices.
USPTO Backgrounds
USPTO Backgrounds