Patent Application
20170363130
The disclosed embodiments generally relate to fastener systems including fastener, driver, method of manufacture and related tooling, and in particular to fasteners having spiral drive and removal surfaces that enable high seating torques to be applied without excessive stress on the fastener and driver.
Fasteners having driver engageable surfaces that are, at least in part, defined by spiral segments have been used with good results. Fastener systems of this type are described in U.S. Pat. Nos. 5,957,645, 6,234,914, and 6,367,358 issued to Stacy (the Stacy patents), and U.S. Pat. Nos. 7,891,274, 8,171,826, and 8,387,491 issued to Dilling (the Dilling patents), all of which are commonly owned with this application. The disclosures of these patents are incorporated herein by reference in each of their entireties. The drive surfaces of the Stacy patents are constructed to maximize torque transmission, during installation and removal, while spreading the driving load over a broad driver/fastener interface. The thrust of these teachings is to enlarge the area of the drive surfaces. The Dilling patents discuss increases in driver strength and seating torque capability through the use of an increased core diameter.
More recently certain applications have been found that require the application of high seating torques to the fastener. Such torques may exceed the strength limits of the drivers used to seat the fastener and thus result in breaking the driver or damaging the fastener. Therefore, improvements are needed to provide an improved driver/fastener interface to increase the available seating torque characteristic of the fastener system without detrimental impact to the fastener or driver.
Embodiments disclosed herein include fasteners, drivers, fastener systems, and methods of forming fasteners and drivers. In one example, a fastener system may include a fastener having a head, a shank, and a recess, and the recess includes driver engageable surfaces that define a plurality of wings radially extending from a central core. In one example, a fastener system may include a driver having an end constructed with mating surfaces for engagement with driver engageable surfaces of a fastener recess, and the mating surfaces define a plurality of projections radially extending from a central core matching the wings. And in yet another example, each of the wings of a recess include a cross sectional shape comprising an installation surface, an outer transition surface, and a removal surface that define the wing, and each of the wings are connected by an inner transition surface extending between the installation and removal surfaces of adjacent wings. And in one example, a cross sectional shape comprises a wing having a width and a height and the ratio of the wing height to the wing width is approximately equal to or less than 0.4 In one example, the driver engageable surfaces of the recess are constructed to receive the mating surfaces of the driver.
Embodiments disclosed herein include fastener systems, an example of which includes a recess central core having a first radius and the outer transition surface having a second radius and the ratio of the first radius to the second radius is greater than 0.70. In one example, a recess central core has a first radius and the outer transition surface has a second radius and wherein the ratio of the first radius to the second radius is greater than 0.77. And in another example, the recess central core has a first radius and the outer transition surface has a second radius and wherein the ratio of the first radius to the second radius is within the range of about 0.77 to about 0.78. An in another example, driver engageable surfaces are constructed in the shape of a spiral segment and mating surfaces have a matching shape. And in yet another example, the wings are arranged in a pentalobular configuration.
In one example, the recess and/or driver includes five wings. And in another example, the shank is a threaded shank having a shank tip on an opposite end of the fastener from the head, and the recess is recessed in the shank tip. In one example, mating surfaces are external surfaces on a driver end. And in yet another example, the driver engageable surfaces are external surfaces of the shank tip and the mating surfaces are recessed in a driver end. In one example, an inner transition surface conforms to a circumference of the central core. And in yet another example, a threaded shank comprises external threads having a major diameter at a thread crest and a minor diameter at a thread root, the fastener has a central core diameter at the inner transition surface, and the ratio of the central core diameter to the major diameter is greater than about 0.3.
In one example, the ratio of the central core diameter to the major diameter is between about 0.3 to about 0.45. In another example the ratio of the central core diameter to the major diameter is greater than about 0.38 and less than about 0.50. In another example the threaded shank has a threaded portion and an unthreaded portion, the unthreaded portion being between the threaded portion and the head. An in yet another example, driver engageable surfaces are countersunk from the shank tip in a longitudinal direction toward the head.
In one example fastener, a countersink is chamfered from a first diameter to a second diameter, the first diameter being larger than the second diameter and the first diameter being closer to the shank tip than the second diameter. In another example, a chamfer has a chamfer angle of about 100 degrees. And in yet another example the driver end is chamfered to a point, the chamfer having an angle of between about 16 degrees and about 17 degrees. In one example, the driver comprises a shaft. And in another example, the driver shaft is chamfered toward the mating surfaces at an angle of about 30 degrees with respect to a longitudinal axis of the driver. And in yet another example the driver further comprises a countersink region corresponding to a countersink of the recess, the driver countersink being chamfered at an angle less than the chamfer angle of the recess countersink. In a further example, the chamfer angle of the driver countersink is about 80 degrees and a chamfer angle of the recess countersink is about 100 degrees.
In one disclosed example, a driver shaft bit includes at least one notch. In another example a driver comprises a shaft. And in yet another example, driver engageable surfaces extend a length from the shank tip, and the mating surfaces of the driver extend a length from the shaft, the length from the shank tip being greater than the length from the shaft.
In one disclosed fastener example, a fastener may include, a head, a shank, and a recess, and the recess comprises driver engageable surfaces that define a plurality of wings radially extending from a central core. In one example, each of said wings of the recess include a cross sectional shape having an installation surface, an outer transition surface, and a removal surface that define the wing, and each of the wings are connected by an inner transition surface extending between the installation and removal surfaces of adjacent wings. In one example fastener, at least one of the installation and removal surfaces are configured to define a segment of a spiral, and in yet another example, the driver engageable surfaces of the recess are constructed to receive mating surfaces of the driver. In a further example, the shank has a shank tip on an opposite end of the fastener from the head, and the recess is recessed in the shank tip.
Disclosed herein are methods of manufacturing fasteners. In one example, the method includes a method of manufacturing a fastener having a head, a shank, and a shank tip on an opposite end of the fastener from the head. In one example, the method includes forming a starter hole. In another example, the method includes, forming driver engageable surfaces that define a plurality of wings radially extending from a central core, and each of said wings of the recess comprise a cross sectional shape comprising an installation surface, an outer transition surface, and a removal surface that define the wing, and each of the wings are connected by an inner transition surface extending between the installation and removal surfaces of adjacent wings. And in yet another example, at least one of the installation and removal surfaces are configured to define a segment of a spiral. In one disclosed example, forming driver engageable surfaces includes broaching. And in yet another example, forming driver engageable surfaces comprises punching.
Additional details will be provided in the accompanying figures and the detailed description below.
An example fastener, according to the present application is shown in
Threaded portion 20 includes threads 26 having a major diameter 28 and a minor diameter 29. In one example, a spirally configured recess 6 is formed in a shank tip 24 opposite the head 4. Such a pin may be used, for example, in a number of machining or assembly applications where the threads and driver can be accessible from the same side of the pin. For example, in the assembly of aircraft, or any other application that could utilize one-sided installation of a threaded fastener. The pin 2, may be used for example, in conjunction with a torque nut or any other female threaded receiver known in the art. The recess 6 may be formed, for example, via broaching, punching, or any other method known to a person of ordinary skill after reading this disclosure.
The recess 6, in one example, includes driver engageable surfaces for cooperation with the driver bit 3 to apply torque to the pin 2. These driver engageable surfaces will be discussed in more detail below. The recess 6 may also include additional non-driving features including an extended portion 30 and recess tip 32, which in one example, function as a starter hole for forming the wings of the recess via broaching. Extended portion 30 and recess tip 32, in another example, provides a location for the material removed during forming the recess wings to settle during manufacturing. In, one example of broaching, the pin 2 is started with a hole and the wings/recess are broached or formed by shaving the material into the end of the starter hole. In certain example applications (or customer specifications), the shaved materials (commonly known as petals) are required to be removed to avoid FOD (Foreign Object Debris) in, typically, an airframe assembly, or other highly sensitive industries. This remove can be carried out by a post process drilling process. The recess 6 may also include a countersink 34. The countersink 34 may be chamfered from the top of the recess in a direction towards the bottom of the recess, as shown for example in
With reference to
A cross section of the recess is provided in
The overall shape of the recess 6 and driver bit 3 is similar, except the bit 3 is smaller to provide a clearance between driver and fastener to promote engagement and removal of the driver bit 3 from the recess 6. In addition, the driver bit installation and removal walls are slightly different from the corresponding recess walls so rotation of the bit will provide a full face to face engagement on both the removal and installation wall. As indicated above, the driver/fastener interface surfaces are configured in the general shape of a segment of a spiral on both of the installation and removal surfaces.
The driver may include a countersink region 54 between the shaft 50 and the mating surfaces corresponding to the countersink of the recess. The countersink region 54, in one example may be chamfered at an angles (
The mating surfaces 56 of the driver extend a length H from the shaft 50. In one example, the bit 3 includes a bit point 58 extending beyond the mating surfaces 56 from the shaft 50. The bit point 58, in one example, is chamfered at an angle δ (
The bit 3 may include notches 62 in the bit 50 for use with a quick release bit holder (not shown). The notches may have any shape or location in accordance with an appropriate quick release holder. In one example, the notches 62 have an angle γ and are positioned a length 64 from a back end of the shaft 50. In one example γ is about 90 degrees with a curve radius of about 0.010 inches and length 64 is about 5/16 of an inch with a notch angle offset of about 30 degrees.
The engagement surfaces of the pin 2 shank tip 24 have been shown to be recessed to receive the shown mating male configured driver. However, it is equally possible to provide the engagement surfaces as external surfaces of shank tip 24 for engagement with a female configured driver, as shown in
The details of the shapes of the driver bit and recess shape are shown in
As shown in
Instead of a deficit in performance, these changes have resulted in an increase in corresponding driver strength and a significant rise in seating torque capability for spiral drive fastener systems without detrimental impact to the pin 2. This is particular advantageous to pin configurations in which the recess 6 is within the shank tip 24 of a threaded shank 5, where an increased recess size should result in a decreased wall strength between the outer transition surfaces of the wings and the minor diameter of the threads. The reduction in drive surface area is offset by the improved distribution characteristics from the drive surfaces to the core.
Tables 1 and 2 show example dimensions in inches (unless otherwise marked) for non-limiting example configurations of a five winged recess (table 1) and corresponding five lobed/projection driver (table 2). Also shown are minimum torsional moments applied for successful tests of example pins and driver bits. The indicated dimensions and corresponding strengths, represented in the chart of table 1, are indicative of the significant advantage provided by the fastener system of this application.
The increased strength of the system and the increased seating torque, may be attributed to the recess and driver being constructed with a core diameter that is increased over the prior art spiral fastener system. It would have been logical to try to maintain the area of the drive surfaces by constructing the transition surface as a convex continuation of the installation and removal surfaces 7 and 8. Instead according to subject matter of this application, the drive surfaces 8 and 9 are constructed to intersect the core diameter in a transitional surface 10 between the wings 7 that has a concave form conforming to the core diameter. This adds to core strength, but further truncates the wing cross section and reduces drive surface area. In addition, by truncating the outer tip of the wing cross section and moving the drive surfaces outward in parallel with the prior art configuration, the wing may be enlarged and formed with a blunt tip, the strength of the system maybe further increased. It is observed that the center of mass of the wing will also be moved outward, thereby effecting an improved load distribution.
This is accompanied by a shortening of the radial extension of the wing of both recess and driver cross sections beyond the core diameter. The wing cross section of the driver/recess is further modified by moving the installation and removal surfaces in a parallel manner to form a truncated wing shape with a blunt tip. The blunt tip is constructed to conform to a circle, concentric with the core, with a diameter larger than the core diameter.
In one example, to accomplish this, the cross section of the wing portion of the recess 6 (and therefore also the wing portion of the bit 3) is truncated both outward from the core circumference 12 and inward from the outer transition surface 11. In this manner, the wings 7 are constructed so that the ratio of core diameter øB to the wing outer transition surface to the diameter øA, in one example, is greater than 0.70 and the transition surface 10 between the wings 7 is a concave segment of the core circumference. In another example, the ratio of core diameter øB to the wing outer transition surface to the diameter øA is greater than 0.77. An in yet another example, the ratio of core diameter øB to the wing outer transition surface to the diameter øA is between about 0.77 and about 0.78.
In addition, the width w of the wings 7 (recess), or corresponding projections of the bit, is enlarged while maintaining the profile of the drive surfaces to be consistent with the prior fastener system. The ratio h/w of the height h of the wing cross section to its width w is constructed to be approximately equal to or less than 0.4 in one example. In another example, equal to or less than about 0.35. And in other examples equal to or less than about 0.32 or between about 0.30 and 0.32 (inclusive). In comparison, the prior art faster systems ratio of øB/øA may be calculated to be approximately 0.46 and 0.66, respectively and the ratio of prior art fastener systems (h/w) may be calculated to be approximately 0.9 and 0.5.
In certain described examples, the ratio of the core diameter øB to the corresponding major thread diameter may be calculated to be greater than or equal to about 0.3. In another example, the ratio of the core diameter øB to the corresponding major thread diameter may be calculated to be greater than or equal to about 0.35. In another example, the ratio of the core diameter øB to the corresponding major thread diameter may be calculated to be between (and including) about 0.3 and about 0.45. Or in other examples, between (and including) about 0.38 and about 0.50
These modified dimensions have proven to provide a significant advantageous improvement in bit strength.
Although the subject matter of this application is discussed with reference to a fastener system having spirally configured drive surfaces, it is believed that the construction and method is equally applicable to other cruciform style fastener systems, in particular, a hexalobular style fastener system as described in U.S. Pat. No. 6,017,177 and ISO 10664, titled “Hexalobular internal driving feature for bolts and screws” and available at iso.org.
In this manner a new and unique fastener system is presented that provides an improvement in strength characteristics with respect to the driver without a deficit to the overall performance of the fastener system.
It should be understood that the above description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall with the scope of the appended claims.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 62/351,540, filed on Jun. 17, 2016, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62351540 | Jun 2016 | US |
