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Threaded fastener assemblyRelated Patent Categories: Expanded, Threaded, Driven, Headed, Tool-deformed, Or Locked-threaded Fastener, Torque Responsive Nut Or Bolt Driving ConnectionThreaded fastener assembly description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060110232, Threaded fastener assembly. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This is a continuation of application Ser. No. 10/486,118, filed Feb. 6, 2004, which is the national stage application of International Application No. PCT/US02/28382, published in English under PCT Article 21(2), and filed on Sep. 6, 2002, which claims the benefit of U.S. Provisional Application No. 60/318,097, filed Sep. 6, 2001. This application claims the benefit of U.S. Provisional Application No. 60/318,097, filed Sep. 6, 2001. The disclosures of application Ser. No. 10/486,118, International Application No. PCT/US02/28382, and Provisional Application No. 60/318,097 are hereby incorporated herein by reference. FIELD OF THE INVENTION [0002] This invention relates generally to a threaded fastener. It relates particularly to a threaded fastener assembly characterized by its ability to provide incremental tension or clamp load and resistance loosening. BACKGROUND OF THE INVENTION [0003] The physical property by which threaded fasteners perform their clamping function is tension, or clamp load. This clamp load is achieved by the application of rotational force, or torque. Fastener designers rely on empirical data accumulated from tests that plot the relationship of torque vs. tension. This torque-tension relationship can be significantly affected by friction in the joint, both in the thread and at the rotated clamp surface. [0004] Extremely high friction can cause insufficient clamp load, resulting in joint looseness and possibly shear failure of the externally threaded component. Extremely low friction can cause clamp loads that exceed the fastener's tensile load capability at assembly, resulting in stretching to the point of failure. Worse yet, the fastener could be near the tensile limit at assembly and fail in the field due to normal additional loads applied during use. To avoid potential catastrophic tensile failure, designers typically design or use fasteners that have significantly great strength than actually required. [0005] Friction cannot be controlled very well in the typical manufacturing environment. Consequently, assembly processes are designed to identify suspect assemblies. Installation of fasteners is typically controlled by torque with resultant torque angle being monitored to identify potential faulty assembly. However, torque angle alone is less of an indicator of clamp load than torque since a torque value is utilized as a point to begin measuring torque angle. Very high torque angle could be an indicator of high friction that could be detrimentally reduce the clamp load, or some other assembly characteristic that may not affect clamp load adversely. It is necessary to evaluate assemblies with high torque angles to determine if rework is required. This is costly and inefficient use of manufacturing resources. [0006] Another weakness of existing threaded fasteners is the potential for inadvertent loosening of the fastened joint due to cyclic loads or vibration. A cyclic load applied to the helical surface of the thread can result in a torque force inducing a rotation in the direction opposite to the original tightening rotation. SUMMARY OF THE INVENTION [0007] The present invention is embodied in a fastener assembly which achieves a desired clamp load with predictable consistency, and is considerably less affected by frictional variation than conventional fasteners. This clamp load is achieved incrementally, providing for the capability to select any of numerous load values with the same components. It further includes a mechanism that resists loosening due to vibration or cyclic loading. The invention also facilitates simple assembly, either manually or with computerized automation. [0008] The fastener assembly comprises a nut or bolt with a mating washer or other component with which the clamping surface of the nut or bolt engages. The design of the mating surfaces is such that predictable tension can be incrementally applied through control of torque angle. This incremental application of tension by torque is alternated with increments of rotation imparting little or no increase in joint tension. Degree of rotation is identified with this feature and also an anti-loosening effect is achieved. [0009] The mated bearing surfaces between the components consist of a series of alternating right hand and left hand, helically inclined surfaces. Right hand and left hand, in this context, means the same as applied to thread description. The axis of the helix is common with the axis of the threads of the nut or bolt and the hole in the washer or other component. The right hand helically inclined surfaces each have a pitch equal to the thread pitch of the fastener. The pitch of the left hand helical inclined surfaces can be varied to achieve the desired tension vs. torque angle characteristic. There are equal numbers of right hand and left hand surface segments in the bearing surfaces, each defining an equal arc. The sum of the arcs defined by the right and left hand segments is equal to 360.degree.. [0010] In application, the washer or non-threaded component of the assembly must not rotate freely against the surface of the clamped part. Conventional methods to increase friction or mechanically prevent rotation at this interface are employed, as necessary. [0011] As the treaded fastener is rotated, contact between the nut or bolt and the washer is alternated between the right hand and left hand surface segments. When rotation occurs during contact between the right hand segments, tension does not increase. Rotation during contact between left hand segments results in an increase of joint tension. The tension increase vs. the total torque angle of the right hand and left hand segments is the same as the tension applied for the same torque angle of a standard fastener design of the same thread pitch. [0012] The increment of tension increase per rotation through a left hand segment is empirically derived through testing. Each incremental increase in tension corresponds to an increase in torque applied. Torque is easily measurable and incremental increases can be identified. Controlling the count of these increases provides an identifiable and consistent clamp load. Computer of PLC controlled assembly equipment can be programmed to accomplish this. In manual assembly the incremental increases can be identified by "feel" and counted to achieve the same result. [0013] In that the clamp load does not increase during rotation and contact between the right hand helical surface segments, clamp load also does not decrease during opposite rotation when these same surfaces are in contact. It is this characteristic that gives the fastener it's anti-loosening feature. [0014] Computerized assembly equipment can be programmed to compare torque angle to applied torque. For the purpose of this invention, the program is designed to recognize when continuous rotation of the fastener results in alternating between increasing and non-increasing torque angle segments. When the program identifies two cycles of torque increase it identifies the starting point for counting cycles. After a pre-determined count is achieved, the assembly equipment stops rotating the fastener. [0015] The program in its simplest form would require the user to input the cycle count at which to stop rotating. This would be determined by dividing the desired clamp force by a value empirically established for the pitch of the thread being used. Another approach is to have the values tabulated by thread pitch within the program. The user in this case would only be required to input the thread pitch and the desired clamp force. The program would calculate the required number of cycles. BRIEF DESCRIPTION OF THE DRAWINGS [0016] The invention, including its construction and operation, is illustrated diagrammatically and graphically in the following drawings: [0017] FIG. 1 is a side perspective view of a fastener assembly comprising a nut and conical washer and embodying features of the present invention; [0018] FIG. 2 is a bottom perspective view of the threaded nut seen in FIG. 1; [0019] FIG. 3 is a top perspective view of the unthreaded washer seen in FIG. 1; [0020] FIG. 4 is a graphic illustration of the relationship between torque angle and clamp load during application of a fastener assembly embodying features of the invention; and Continue reading about Threaded fastener assembly... Full patent description for Threaded fastener assembly Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Threaded fastener assembly patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Threaded fastener assembly or other areas of interest. ### Previous Patent Application: Retractable tie down and method of using Next Patent Application: Pyromechanical fastening element Industry Class: Expanded, threaded, driven, headed, tool-deformed, or locked-threaded fastener ### FreshPatents.com Support Thank you for viewing the Threaded fastener assembly patent info. 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