Patent Application
20080145185
1. Field
The present disclosure relates to an improved torque nut fastener. In exemplary embodiments, the present disclosure relates to a two-piece torque nut having a threaded nut member and a base member, the torque nut having a prevailing torque feature when installed.
2. General Background
Threaded fasteners are utilized in variety of applications. Such fasteners include bolts and nut members having a matching threaded form for attachment. In particular applications, for example, aerospace applications, these fasteners are subject to vibration and load fluctuations causing fasteners to lose retention torque causing loosening. Frequently, a prevailing torque feature is accomplished by deforming a portion of the internal thread to cause a certain level of friction between the nut and the bolt. This will hold together the bolt and nut resisting loosening of the fastener.
In standard fasteners having two-piece nut engagements, there are variations in the tolerances between the nut and the bolt. For example, a bolt may possess a thread tolerance that resides at the low end of the range while the nut thread tolerance may be at the high end. As a result, the torque on the fastener is inconsistent and may not reach the required torque specifications.
Another problem may occur if the bolt thread is at the high end of its permissible range and the nut thread is at the low end of its permissible range. As a result, the maximum torque on the fastener can be exceeded. In these previous designs, higher torque values could freeze the nut at any given position on the bolt. Therefore, the fastener would not meet the preload requirements.
To offset this problem, fasteners have been manufactured with small variances in tolerances, raising costs. Additionally, the performance of standard threaded fasteners may vary with the material type of the mating component and performance can only be guaranteed if the material type of the mating component is controlled. Accordingly, there must be separate designs utilized for every different application.
Thus, there is a need to provide a locking torque nut that may be utilized with a variety of different pins and bolts, the bolts having different variations in thread pitches and tolerances.
There is also a need to provide a nut member having two pieces that may be joined together. By attaching the threaded member to the base member, the ease and speed of the installation is increased.
Additionally, there is a need to provide a fastener having a two-piece torque nut that is constructed from different materials, allowing for more flexibility and cost effective use with different types of bearing surfaces.
In one aspect of the present disclosure, a nut member is disclosed. The nut member includes two separate pieces, a threaded member and a base member. The base member has a throughbore, cylindrical counterbore portion and a transition portion. The transition portion has an increased diameter as it extends from the cylindrical through bore portion to the outer surface of the base member.
The threaded member of the nut member has a neck portion and a body portion, and the threaded bore extends through the threaded member. The outer diameter of the neck portion is less than the diameter of the transition portion of the base member at its outer surface allowing the nut member to be fitted with the base member prior to installation.
Upon installation of the nut member, the neck portion of the threaded nut member is moved into the transition portion and then the through bore portion of the base member. As the leading edge of the neck portion moves into the base member, the neck portion moves radially inward into a compressive engagement with the engaged threads of the bolt. As a result, the fastener is held together with a high prevailing torque.
In another aspect, the threaded member is attached to the base member for ease and increased speed of installation. The threaded member may be attached to the base member in a number of different ways, including adhesives, friction, and staking, as well as other attachment techniques.
In another aspect, a fastener is disclosed having a bolt and a two-piece nut member to secure together a plurality of workpieces. The fastener is installed in holes located in the plurality of workpieces. The bolt includes a shank having a smooth shank portion and a thread portion.
In a further aspect, a fastener is disclosed that has the capability of being installed in composite, metallic, or composite/metallic structures. For example, the disclosed fastener could be installed in steel, composites, titanium, aluminum, or a mixture of these components.
In another aspect, the disclosed nut member may be utilized with a variety of existing bolts and pins and a variety of thread forms, including low, medium and high thread pitch diameters.
In another aspect, the threaded portion and the base member of the nut member can be constructed from dissimilar materials. In exemplary embodiments, the threaded nut member may be constructed of a material that is stronger to maximize physical performance of the fastener.
Additionally, the base member may be constructed of lighter and less expensive materials. As a result, the weight of the fastener is reduced, making the fastener more cost-effective for use with aerospace applications.
In a further aspect a fastener is disclosed that includes a free running nut which also provides a prevailing torque feature upon installation. The nut member is free running along the threaded portion of the bolt prior to the neck portion of the nut member entering the base member.
Other objects, features, and advantages of the present disclosure will become apparent from the subsequent description and the appended claims.
The foregoing aspects and advantages of present disclosure will become more readily apparent and understood with reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
A fastener for securing together a plurality of workpieces 105, 110 and adapted to be located in holes 115, 120 in such workpieces is disclosed. In exemplary embodiments, the fastener includes a bolt 15, and a two-piece nut member 20. In exemplary embodiments, the workpieces 105, 110 can be formed with a plurality of different materials, the materials including composite, metallic, or composite/metallic structures, any combination thereof. In particular embodiments, the workpieces 105, 110 may be constructed from steel, titanium, aluminum, composites, or any combination thereof.
As depicted in
The base member 30 of the nut member includes a counterbore 45 that is adapted to allow the bolt of the fastener to extend through. At one end of the base member 30 is an outer surface 40 for engagement with an outer surface 125 of the workpieces 105, 110. On the opposite end of the base member 30 is a beginning engagement transition segment 50 that engages the threaded nut member 35.
The transition segment 50 extends axially and radially inward from the outer surface 57 of the base member 20 to a cylindrical through bore portion 55 of the base member 20. The diameter of the transition portion of the base member decreases as it moves axially towards the cylindrical through bore portion 55 of the base member.
In exemplary embodiments, the transition portion 50 may be tapered and have an angle of less than or equal to 40° from the throughbore as the diameter decreases radially from the outer surface 57 to the through bore 55. In the embodiment illustrated, the diameter of the transition portion 50 is tapered and decreases in a uniform fashion.
However, the transition portion can be any shape as long as the diameter decreases as it moves axially toward the cylindrical through bore portion of the base member. For examples, the transition portion could be a decreased shape such as a convex curve, a concave cure, or an s-shaped curve, or be any configuration that would cause a reduction in the diameter of the neck portion of the mating threaded nut member.
Following the cylindrical through bore portion 55 is cylindrical counterbore portion 45. The counterbore portion 45 may have a diameter greater than that of the cylindrical through bore portion 55. The counterbore portion 45 of the base member 30 extends from the cylindrical through bore portion 55 to the outer surface 40 of the base member 30 that is in bearing with the outer surface 125 of the workpieces 105, 110.
The diameter of the cylindrical through bore portion 55 is fabricated with very close tolerances to provide consistency in deformation and to not exceed pre-described torque loads. As a result, over loading is controlled during installation and pre-load targets are achieved.
The threaded nut member 35 has a neck portion 65 and a body portion 70. The body portion 70 includes a threaded throughbore 75 through the body portion 70 and neck portion 65 and can readily be applied to the threaded part of the bolt 15. The body portion 70 has a hexagonal shape 80 on its outer surface to facilitate engagement of the head of a standard socket tool (not shown) whereby torque may be applied to the nut member 20. However, the shape of the body portion is not limited to a hexagonal shape. In other embodiments, the shape may be a square or other suitable shape to apply torque.
The neck portion 65 has an outer diameter less than the diameter of the transition portion 50 at the outer surface of the base member. This allows the neck portion to fit into the base member 30 of the nut prior to installation. This allows the two pieces of the nut member 20 to be fitted together prior to installation.
In particular embodiments, the surface finish of the threaded nut member 35 and base member 30 can be independently adjusted. As a result, the torques and preload characteristics of the fastening assembly can be optimized.
In some embodiments, it is advantageous to attach the base member 30 to the threaded nut member 35. In a particular embodiment, the base member 30 is attached to the threaded nut member 35 by means of an adhesive 85. The attachment can also be accomplished in several other techniques. The threaded nut member 35 may also be attached to the base member 30 by friction, staking and other suitable methods known by those skilled in the art.
Attaching the base member 30 to the threaded nut member 35 is an improvement over prior art fasteners having a two piece construction. Previously, the two pieces would be shipped separately or loosely. As a result, parts were easy to lose. Additionally, the installation of the fastener was made much more difficult. The parts would have to be connected by an individual before installation. By attaching the two components prior to shipping, the nut member acts as a single, one-piece part increasing the speed and ease of installation, but also provides the flexibility of the two-piece fastener.
In particular embodiments, as it is preferred that the nut member 20 be of a two-piece construction, the base member 30 and threaded nut member 35 may be formed from different materials. The threaded nut member 35 may be constructed from higher strength materials to maximize the physical characteristics of the fastener. The base member 30 may be constructed of different materials that are lighter or more cost effective or other compatible materials. By constructing the base member 30 of the nut with lighter materials, the unit weight of the fastener is reduced. Accordingly, the fastener is more useful for particular applications, including aerospace applications.
Allowing the threaded nut member 35 and the base member 30 to be constructed from dissimilar materials permits the fastener to be used in many different applications. As a result, the nut member 20 can also be used with a variety of different pins or bolts. For example, the nut member 20 in the present disclosure can be utilized with bolts having low, medium and high thread pitch diameters. The fastener becomes much more flexible in use.
Additionally, the bearing surfaces may be formed from a variety of different materials. For example, the disclosed fastener 10 may be utilized on bearing surfaces including aluminum, composites, steel and many other materials. Prior art fasteners are designed and qualified on only one pin and one bearing surface. The design of this fastener is therefore an improvement over such prior art fasteners.
As illustrated in
Looking now to
During installation of the fastener 10, the nut member 20 can be applied to the bolt 15 by a suitable tool or by hand to initially thread the nut section onto the threaded portion of the bolt shank. With the base member 30 of the nut member 20 in engagement with the outer surface of the workpieces 105, a desired magnitude of initial clamp load is achieved by the application of a first predetermined magnitude of torque. At this point the threaded nut member 35 is essentially free running along the threaded portion of the bolt shank.
With the base member 30 of the nut member 20 in engagement with the outer surface 125 of the workpiece 105, torque is applied to the threaded nut member 35, moving the neck portion 65 of the threaded nut member 35 axially into the transition portion 50 of the base member. As the neck portion 65 of the threaded nut member 35 enters the transition beginning engagement 50 of the base member 30, the leading edge 67 of the neck portion 65 of the thread nut member 35 is moved radially inward along the transition engagement 50 until it reaches the cylindrical through bore portion 55 of the base member 30. As the leading edge 67 of the neck member enters the cylindrical through bore 55, the leading edge of the neck portion 65 is moved into compressive engagement with the threaded portion of the bolt 15.
The threaded nut member 35 will slightly deform to the shape of the threaded portion of the bolt 135 in response to the compressive engagement as the neck portion 65 is moved into the base member 30. The design of the fastener 10 is optimized so that the engaged threads of the shank portion of the bolt 15 remain substantially undistorted.
The result is a fastener 10 holding the workpieces 105, 110 together at under a pre-selected magnitude of final clamp load and with the engaged threads of the nut 20 and bolt 15 of the installed fastener 10 held together under a high compressive load resulting in a high prevailing torque. This provides a desired resistance from removal and loosening of the fastener 10 from vibration or other loading.
In particular embodiments, the workpieces 105, 110 have a total thickness which is the total minimum thickness of the grip range of the fastener 10. In this application, the smooth shank portion of the bolt 15 will extend past the outer surface of the workpiece and partially into the counterbore section 45 of the base member 30. In other embodiments, the workpieces 105, 110 have a total thickness which is the maximum thickness of the grip range of the fastener 10. As can be seen in
While the above description contains many particulars, these should not be considered limitations on the scope of the disclosure, but rather a demonstration of embodiments thereof. The fastener and uses disclosed herein include any combination of the different species or embodiments disclosed. Accordingly, it is not intended that the scope of the disclosure in any way be limited by the above description. The various elements of the claims and claims themselves may be combined any combination, in accordance with the teachings of the present disclosure, which includes the claims.
