HK1215939B - Fastener system with stable engagement and stick fit - Google Patents

Description

Fastener system with stable engagement and snap fit

This application is a divisional application entitled "fastener system with stable engagement and snap fit", filed on 9/15/2010, international application No. PCT/US2010/048846, national application No. 201080065022.6.

Technical Field

The present application relates generally to drive systems for threaded fasteners, tools for making the drive systems, and drivers for applying torque to such fasteners. More particularly, the present application relates to fasteners configured with straight-walled recesses. In particular, a fastener system is constructed in which the driver and fastener engage to improve axial alignment and stability of the gripping fit.

Background

Threaded fasteners commonly used in industrial applications are typically driven by power tools under high speed and high torque loads. This situation presents difficult design considerations, particularly with respect to the drive system, and more particularly with respect to the following threaded fasteners: the threaded fastener has either a driver-engageable recess in the fastener head or a driver-engageable outer profile of the fastener head. Ideally, such a drive system would need to be easy to manufacture with respect to the recess and head geometry as well as the associated tools used to form the fastener head and drivers used to engage the recess or head geometry. The strength of the fastener head should not be adversely affected by the recess. The driver should distribute the stress load evenly when mated to avoid creating high local stress areas that may cause deformation of the driver surface, or the driver, or both, causing premature failure of the drive system.

The fastener system should resist the driver from slipping out of the recess when the fastener is driven. In many applications, it is very important that the fastener must be able to withstand several cycles, as in applications where the fastener must be removed to repair or replace parts or to remove and replace access panels. The fastener driving system should ideally be capable of such repeated cycling, particularly in environments where the recess may become contaminated, painted, corroded, or otherwise adversely affected during use. In these cases, it is important that the drive system maintain driving engagement while applying torque in the disassembly direction. It may be necessary for the drive system to be able to apply higher levels of torque when the fastener is disassembled, as occurs when the fastener is over-tightened during initial makeup, or when corrosion develops at the interface of the engaged threads, or when thermal cycling of the makeup components has placed increased stress on the fastener. These and other features often present competing considerations; and one may have to be compromised in favor of the other.

A variety of recess and driver configurations are commonly used, including a variety of cross recesses, such as those described in U.S. patent re.24,878 (Smith), et al), U.S. patent 3,237,506 (munuchinger), and U.S. patent 2,474,994 (Tomalis). Other fastener geometries include multi-lobe geometries of the type described in us patent 3,763,725 (Reiland) and ribbed drive systems as described in us patent 4,187,892 (Simmons). The "Allen" system, which is basically a straight-walled hexagonal socket adapted to receive a similarly shaped driver, is also in a common recess configuration. U.S. patent 5,957,645 (Stacy) describes a fastener system having multiple lobes with driving surfaces of helical configuration.

In addition to the ribbed system, the walls and faces of the driver and recess are typically designed to mate with each other in an effort to achieve face-to-face contact of the driving surface with the driven surface. With a cross-recess fastener, this face-to-face engagement (if any) can only occur when the driver is properly aligned and seated within the recess. However, as a practical matter, in order for the driver to be able to be inserted into the recess, some clearance must exist between the driver and the recess.

The necessity of such clearance is even more critical for grooves having substantially axially aligned (straight) drive walls (as in the liland' 725 patent and the Allen head system). In all these systems, the practical consequence of the necessity of such a gap is: substantial face-to-face wide area contact between the driver and recess surfaces is rarely achieved, if at all. For most drive systems for threaded fasteners, the driver mates with the recess in the head in a manner that results in point or line contact rather than wide area face-to-face contact. The actual area of contact is generally significantly less than full face-to-face contact. Thus, when torque is applied by the driver, the force applied to the threaded head tends to concentrate in a localized area resulting in high localized stresses and unstable axial alignment. Such localized high stresses can plastically deform the recess, thereby forming a chamfer or other deformation that results in premature and unintended disengagement of the driver from the recess.

The sitaxi' 645 patent, which is commonly owned with the subject application, describes a fastener system for maximizing the engageable surface area between a driver and a driving surface. The disclosure of the' 645 patent is incorporated by reference into this application. The recess and driver of the' 645 patent are configured with a helical configuration of engagement surfaces arranged substantially parallel to the axis of the fastener, and may be generally categorized as a straight-walled fastener system. A more robust embodiment of a screw-driven fastener system is described in U.S. patent application publication 2009-. The disclosure of the Dilin application is also incorporated herein by reference.

The advantages of the invention described in the' 645 patent are achieved by: the drive surface of the driver and the driven surface of the fastener are respectively configured to conform to the helical section, and in particular to a helical configuration that allows for significant and greater clearance between the driver and the recess during insertion and removal of the driver, but allows for the fully seated driver to rotate to take up the clearance. The helical configuration of the driver engageable wall of the driver and the recess is such that when the helical walls are engaged they engage over a wider area thereby applying and distributing stress over the wide area. The helical configuration of the driving and driven walls is oriented to direct a substantial portion of the applied torque substantially perpendicular to the radius of the fastener so that friction dependence on near tangential engagement is minimal, if any.

Another example of a straight-wall fastener system is the system described in U.S. patent 3,584,667 to yland. This reference is incorporated herein by reference. The riland' 667 patent describes a fastener system wherein the geometry of the driving surface comprises a series of semi-cylindrical surfaces arranged substantially in a hexagonal shape. The yulan fastener system is generally referred to as a hexalobe and has a driving surface parallel to the axis of the fastener.

While straight wall fasteners are generally used successfully in many applications, they may encounter difficulties arising from axial misalignment between the driver and the fastener. In addition, it has been difficult to obtain a reliable frictional engagement that provides a snap fit feature. A snap fit feature is desirable to hold the fastener in alignment on the driver while initially installing the fastener. This is particularly useful in high volume assembly line operations that use a motorized driver head to apply torque to a fastener. Axial alignment and a snap fit are also important as the fastener length is extended.

In many applications using a straight wall drive system, the driver may be electrically driven or need to be inserted in a location with limited access. In this case, it is necessary to have the fastener detachably engaged to the driver before installation so that the driver can be used as an insertion tool as well as a driver. This "snap fit" feature has been attempted in many different types of fasteners, such as in fastener/driver systems having a cruciform shape (cross-shaped geometry), several of which are shown in U.S. patents 6,199,455 and 4,457,654. Fastener systems having square drive geometries are described in U.S. patent 4,084,478. It was observed that the efforts of the snap fit were focused on the driving surface.

The "snap fit" feature allows the fastener to be removably engaged to the driver to allow the driver and fastener to be handled as a unit in difficult to reach, automated, and other applications. Once installed, the fastener and driver can be disengaged with minimal effort.

Reference U.S. patent 4,269,246 to Larson (Larson) is of interest in that it employs a partially tapered driver to enhance engagement. In larsen, the inner radius of the driver recess is set parallel to the axis of the driver, while the crown of the blades tapers inwardly toward the tip. The clear purpose of this construction is to avoid premature interference between the driver bit and the recess. It is observed that this configuration results in circumferential and axial line contact between the driver and the recess and will not enhance stability or frictional engagement. Only the screwdriver bit is tapered without a change in the geometry of the groove.

Also of interest is us patent 5,461,952 in the reference Goss (Goss). In goss, the tail sidewall of the driver is tapered to provide a progressively thicker blade geometry that creates a frictional engagement on the driving surface. Since only one side wall is tapered, the engagement with the straight-side drive surface becomes circumferential line contact. Also, only the driver head is reconfigured. This is due to the reluctance to change the geometry of the recess, which would result in a loss of compatibility with existing drivers. Backward compatibility is a design advantage in any fastener system, particularly in straight wall systems.

U.S. patent 7,293,949 to dilin, referenced herewith (commonly owned with the present application), describes a fastener system configured to provide a snap fit in a straight-wall fastener. In dilin, the interference surface is configured on an inner non-driving transition surface between the wings of the fastener recess. It has been found that improved snap fit features can be obtained using a standard driver for this type of fastener system, using an interference surface located in the so-called "B" dimension of the recess.

Disclosure of Invention

Various embodiments described herein provide a fastener system with straight-walled driving surfaces that provides a reliable snap-fit feature while also improving stability of engagement between system components. An important feature of the new system is to allow existing standard straight wall drivers to be engaged into the new system. To achieve this goal, the new driver and recess system is constructed as follows.

The straight wall fastener system of the present application is generally configured with a recess having a plurality of wings extending radially outward from a central axis and a driver having a plurality of mating blades that mate with the wings of the recess. Each of the wing and blade has a drive surface comprising a mounting surface and a dismounting surface depending on the direction of the applied torque. These drive surfaces are configured in substantially parallel alignment with respect to a central axis of the fastener system. Adjacent airfoils or blades are separated at the outer diameter by non-driving transition surfaces. The diameter formed by the outer diameter will be referred to herein as the "a" dimension, as shown in the figures.

To create an interference fit and provide a snap fit, a substantially flat interference profile is formed on the "a" dimension surface of the driver blade, while a matching interference profile is formed on the opposite "a" dimension surface of the recess wing. The recess is enlarged relative to a standard straight-walled recess to provide space for a standard straight-walled driver to engage without interference from the recess wing interference profile. The skilled person will understand that references herein to "standard" drivers and recesses refer to industry accepted popular sizes in the relevant market. It should be noted that the advantages of a snap fit and alignment are not obtained when a standard driver is used in conjunction with a fastener, but this provides a rearward capability to allow a standard driver to be used in the recess for such an application.

To form a mating interface for the driver and fastener, the driver blade interference surface and the recess wing interference surface taper inwardly. The mouthpiece tapers radially outward from the bottom of the groove to a distance slightly below the height of the groove. The interference profile may be substantially straight to maximize surface-to-surface engagement. However, for ease of construction, these profiles will have a slightly curved portion with a larger radius to allow the use of a turning process.

In this way a snap fit is provided, while the stability of the engagement of the driver and the recess is enhanced. In addition, by slightly enlarging the size relative to the standard recess of a straight wall fastener system, standard drivers are permitted. However, as noted above, when a standard driver is used, there will be no snap-fit engagement.

In one embodiment of the present application, a straight-wall fastener system is configured with a driving surface geometry of a six-bladed fastener system as described in the above-cited reference, yland.

In another embodiment of the present application, a straight wall fastener system is configured with a helical drive surface geometry as described in the above-cited reference stauximab.

In another embodiment of the present application, a straight wall fastener system is configured with a helical drive surface geometry as described in the above-referenced Dilin published application.

In another embodiment of the present application, the fastener is configured with an externally accessible driver surface, and the driver is configured with a mating socket.

In another aspect of the invention, there is provided a punch for forming a recess in a head of a fastener blank, wherein the punch comprises: a body having an end contoured to form a portion of the fastener head; and a tip adapted to form the groove of the present invention in conventional two-hit forging techniques. The radially extending wing of the tip may comprise one or two helical surfaces adapted to form complementary surfaces when impacting the head end of the fastener.

These and other features and advantages of the present invention will be more clearly understood from the following detailed description of the embodiments of the present application and the accompanying drawings.

Drawings

FIG. 1 is a perspective view of a fastener having a driving surface with a helical configuration according to the prior art.

FIG. 2 is a schematic illustration of the engagement geometry of a six-bladed drive system constructed in accordance with a first embodiment.

Fig. 3 is a top view of a driver configured to drive the fastener of fig. 2.

Fig. 4 is a side view of the driver of fig. 2.

Fig. 5 is a top view of a fastener having a recess according to the embodiment of fig. 2.

Fig. 6 is a view taken along section line VI-VI of fig. 5.

Fig. 7 is a perspective view of the special driver and fastener of fig. 2.

FIG. 8 is a schematic illustration of the engagement geometry of a screw drive system constructed in accordance with a second embodiment.

Fig. 9 is a top view of a driver configured to drive the fastener of fig. 8.

Fig. 10 is a side view of the driver of fig. 8.

Fig. 11 is a top view of a fastener having a recess according to the embodiment of fig. 8.

Fig. 12 is a view taken along section line XII-XII of fig. 11.

Fig. 13 is a perspective view of the special driver and fastener of fig. 8.

FIG. 14 is a perspective view of the third embodiment showing a six lobe drive system with a fastener having an outer drive surface.

FIG. 15 is a perspective view of the fourth embodiment showing a helical drive system in which the fastener has an outer drive surface.

Fig. 16 is a schematic view of a fifth embodiment of the fastener system of fig. 2 with jamming interface surfaces on the four blades and wing portions.

FIG. 17 is a schematic view of a sixth embodiment of the fastener system of FIG. 2 with snap-fit interface surfaces on three blades and wing portions.

Figures 18-21 are perspective views of embodiments showing a hex head drive system in which the fastener has an outer drive surface.

Detailed Description

Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention may have alternative forms. In addition, any suitable size, shape or type of elements or materials could be used.

FIG. 1 illustrates an example of a prior art threaded fastener having a straight-walled driving surface. The term "straight-walled drive surface" is used herein to refer to a fastener system in which the drive surface is substantially aligned with, i.e., parallel to, the longitudinal axis of the fastener. It is accepted in the fastener industry that expressions such as "parallel alignment" produce some tolerance for misalignment, as it is understood that such alignment produces manufacturing tolerances and may vary slightly in actual implementation. Specifically, FIG. 1 illustrates a fastener as described in the above published application of the Dilin reference. Typically, this type of fastener system is configured with a fastener 2 and a mating driver head (not shown). The fastener 2 is configured with a head 4 and a threaded shank 5. In this example, a groove 6 of helical configuration is formed in the head 4 with the driving surface aligned parallel to the axis of the fastener 2 (straight wall). The driver head is configured with a driving surface of helical configuration that mates with a corresponding surface of the fastener recess 6. The head 4 may be formed in a conventional two-headed forging machine in which the end of the wire or other material from which the fastener is made is supported in the die of the forging machine and its head end is struck first using a punch (which partially forms the head) and then using a trimming punch (which trims the head and forms a recess engageable with a driver). The overall construction of the fastener is well known and will not be further described in this application. A classification of these well known methods can be used to construct the fastener system of the present subject matter.

The fasteners are configured in a number of different configurations and the application of the subject matter of the present application is not intended to be limited to any particular type. For example, some fasteners do not have a head that clamps the workpiece to the base. Alternatively, they may engage the workpiece using the second threaded section. Although the illustrated fastener has a clamping head, the advantages provided by the illustrated configuration may be obtained in other fastener types, such as non-clamping fasteners and the like.

The features of the first embodiment are illustrated in fig. 2, where the profile geometries of the recess 10, the special driver 11 and the standard driver 12 are shown in an engaged relationship. For purposes of illustration, cartesian axes V and S perpendicular to the central longitudinal axis are shown in fig. 2 and the other figures. The profile of the standard driver 12 is shown in broken lines in fig. 2 at a portion where the profile of the standard driver 12 is different from that of the special driver 11. Although the geometry in this particular illustration is similar to the six-lobe type fastener system of the above-cited yulan reference, it is intended to be merely exemplary of the use of the subject invention in a straight-walled fastener system. Fig. 2 is of course not intended to indicate that both drivers may be used simultaneously, but merely to illustrate the relative positions of the special driver and the standard driver when engaged into the fastener recess. The gap is exaggerated for illustrative purposes. There is no gap at the interface 19 between the special driver and the recess. Frictional engagement will occur slightly inward of the top 27 of the fastener recess 10.

As shown in fig. 2, the driver 11 is configured with an interference profile 13 formed on an "a" -sized surface of a driver blade 14. Fastener recess 10 is configured with mating interference profiles 15 formed on opposing "a" sized surfaces of recess wings 16. The recess is enlarged relative to a standard six-bladed recess (not shown) to provide sufficient clearance 18 for receiving a standard six-bladed driver 12 in the recess 10 without interference with the recess wing interference profile 15. In one embodiment, only the "a" size profile is enlarged, while the "B" size profile remains a standard recess size for a fastener of the type illustrated in fig. 2. This improves the stability of the alignment of the special driver and the standard driver. The geometry of the standard recess 30 is shown according to an embodiment in which only the "a" dimension is expanded. The contour of the standard groove 30 is shown in fig. 2 with a dotted line at a position where the contour of the standard groove 30 is different from the contour of the exclusive groove 10. When engaged, the driver 11 and recess 10 form an interface 19 between the driver blade interference surface 13 and the fastener wing interference surface 15. It should be noted that the interference surfaces 13 and 15 thus formed are non-driving surfaces.

The interference surfaces 13 and 15 are configured to provide a significant face-to-face engagement at the interface 19. The contours match to further facilitate this engagement. In the construction of the interference profile, a machining process will be carried out, by means of which a slightly curved portion will be formed. These profiles may be considered "substantially" straight because of the larger radius of curvature used in the preferred embodiment, however, the interface profiles may be more curved and still achieve the advantages of the subject fastener system.

Details of the improved driver 11 of fig. 2 are shown in fig. 3 and 4, where like reference numerals refer to like elements. The driver 11 is constructed as described above, with an interference profile 13 formed at the crown of each blade 14 at the "a" dimension of the driver geometry. These surfaces are non-driving surfaces providing transition profiles between the mounting driving surface 20 and the dismounting driving surface and 21, respectively. The interference profile 13 tapers inwardly at an angle θ with respect to the central longitudinal axis x of the driver 11 towards the tip 22 of the driver 11. Depending on the angle of the groove interference surface (or wedge) 15, the angle θ may preferably be about 1 ° to about 3 °.

As shown in fig. 5 and 6, the groove 10 is configured on the top surface 27 of the fastener with matching interference profiles 15 located at the relative "a" dimension of each of the wings 16 of the groove 10. These surfaces are respectively non-driving surfaces providing a transition profile between the mounting driving surface 23 and the dismounting driving surface 24. The groove wing interference profile 15 tapers inwardly (toward the central longitudinal axis y) toward the bottom 25 of the groove 10. The interference profile 15 starts at a position 26 slightly below the top 27 of the groove 10 and continues for a depth d which for small angles approaches the taper length. This provides a small gap between the driver 11 and the recess 10 at initial insertion. The interference profile 15 tapers inwardly at an angle Φ about the central longitudinal axis y of the fastener. Depending on the angle of the driver blade interference profile 13, the angle Φ may preferably be about one degree (1 °) to about three degrees (3 °).

To ensure that an effective snap fit feature is established, the interference profiles 13 and 15 taper inwardly from about the top to the bottom of the groove at an angle preferably of about one degree (1 °) to about three degrees (3 °), but it has been found that the angles Φ and θ should not be exactly the same, but rather that the angle θ should be slightly larger than the angle Φ. Preferably, the difference between the angle θ and the angle Φ is from about one-quarter degree (0.25 °) to about three-quarter degree (0.75 °), and more preferably about one-half degree (0.5 °). Depending on the size of the thread and thus on the depth of its groove, it may be desirable to make the angle θ and the angle Φ larger or smaller. For one to three size recesses and drivers, which are currently prevalent in the building supply market, approximately three degrees (3 °) is preferred. For larger size drivers and recesses, about four degrees (4 °) may be more preferred. And as the thread recess and driver size become larger, larger angles may be preferred. For standard recess and driver sizes on the building supply market, angles θ and Φ from about half a degree (0.5 °) to about seven degrees (7 °) are preferred. As the angle becomes larger, the taper length becomes shorter. Advantageously, the taper is inward or outward beyond the "a" dimension by about ten percent (10%) of the depth d of the taper length.

As an example, an angle Φ of one and a half degrees (1.5 °) and an angle θ of two degrees (2 °) will provide effective interference. It is also possible to reliably construct a snap fit during manufacture by maintaining the driver "a" dimension within a positive tolerance range of, for example, plus zero (+0) to plus two thousandths (+0.002) of an inch, while forming the recess "a" dimension with a negative tolerance of, for example, minus zero (-0) to minus two thousandths (-0.002) of an inch. As another example, geometric tolerances can be specified as follows: positive quarter-degree (+0.25 deg.) and negative zero (-0.0 deg.) for the groove angle phi; and positive zero (+ 0.0) and negative quarter-degree (-0.25) for driver angle theta. The mouthpiece tapers radially outward from the bottom of the groove to a distance slightly below the height of the groove. To facilitate the gripping fit of the driver and recess, as described above, the taper angle θ of the driver blade interference profile can be configured to be slightly greater than the taper angle Φ of the recess wing interference profile.

Another embodiment of the profile geometry is illustrated in fig. 8. In fig. 8, the recess 110 is shown as having a straight walled driver surface with a helical profile. The special driver 111 and the standard driver 112 are shown in an engaged relationship. The gap is exaggerated for illustrative purposes. Similar to the first embodiment, there is no gap at the interface 119 between the dedicated driver 111 and the recess 110. Frictional engagement will occur slightly inward of the top of the fastener recess 110.

As shown in fig. 8, the driver 111 is configured with an interference profile 113 formed on an "a" size surface of the driver blade 114. Fastener recess 110 is configured with mating interference profiles 115 formed on opposing "a" sized surfaces of recess wing 116. The recess is enlarged relative to a standard six-bladed recess (not shown, but similar to that shown in the embodiment of fig. 2) to provide sufficient clearance 118 for receiving a standard screw driver 112 into the recess 110 without interfering with the recess wing interference profile 115. In one embodiment, only the "a" size profile is enlarged, while the "B" size profile is maintained at the standard recess size for fasteners of the type illustrated in fig. 8. When engaged, the driver 111 and the recess 110 form an interface 119 between the interference profiles 113 and 115, respectively. It should be noted that the interface surfaces 113 and 115 thus formed are non-driving surfaces.

The interference profiles 113 and 115 are configured to provide a significant face-to-face engagement at the interface 119. The contours match to further facilitate this engagement. In the construction of the interference profile, a machining process will be carried out, by means of which a slightly curved portion will be formed. These profiles may be considered "substantially" straight because of the larger radius of curvature used in the preferred embodiment, however, the interface profiles may be more curved and still achieve the advantages of the subject fastener system.

Details of the improved driver 111 of fig. 8 are shown in fig. 9 and 10, where like reference numerals refer to like elements. The driver 111 is constructed as described above, with an interference profile 113 formed at the crown of each blade 114 at the "a" dimension of the driver geometry. These surfaces are respectively non-driving surfaces providing a transition profile between the mounting surface 120 and the dismounting surface 121. The interference profile 113 tapers inwardly toward the tip 122 of the driver 111 at an angle θ relative to the central longitudinal axis x of the driver 111. The angle θ may preferably be about one degree (1 °) to about three degrees (3 °), depending on the angle of the groove wing interference surface 115.

As shown in fig. 10, the groove 110 is configured on the top surface 127 of the fastener with matching interference profiles 115 located at the relative "a" dimension of each of the wings 116 of the groove 110. These surfaces are respectively non-driving surfaces providing a transition profile between the mounting driving surface 123 and the dismounting driving surface 124. The interference profile 115 tapers inwardly (toward axis y) toward the bottom 125 of the groove 110. The interference profile 115 begins at a location 126 slightly below the top 127 of the groove 110 and continues for a depth d. This provides a small gap between the driver 111 and the recess 110 at initial insertion. The interference profile 115 tapers inwardly at an angle Φ relative to the longitudinal axis y of the fastener. Depending on the angle of the driver interference profile 113, the angle Φ may preferably be about one degree (1 °) to about three degrees (3 °).

To ensure that an effective snap fit feature is established in this embodiment, the interference profiles 113 and 115 taper inwardly from top to bottom relative to the groove at an angle preferably ranging from about one degree (1 °) to about three degrees (3 °), but it has been found that the angles Φ and θ should not be identical, but rather the angle θ should be slightly larger than the angle Φ. As an example, an angle Φ of one and a half degrees (1.5 °) and an angle θ' of two degrees (2 °) will provide effective interference. It is also possible to reliably construct a snap fit during manufacture by maintaining the driver "a" dimension within a positive tolerance range of, for example, plus zero (+0) to plus two thousandths (+0.002) of an inch, while forming the recess "a" dimension with a negative tolerance of, for example, minus zero (-0) to minus two thousandths (-0.002) of an inch. The mouthpiece tapers radially outward from the bottom of the groove to a distance slightly below the height of the groove. To facilitate a snap-fit engagement of the driver and the recess, the taper angle θ of the driver may be configured to be slightly greater than the taper angle Φ of the recess, as described above.

The above features can be applied to other straight wall fastener systems with similar results. As another example, the screw drive system of the cited reference stasie can be improved by constructing the interference interfaces on the opposing "a" sized recessed wing and driver blade, respectively. Since the operation and configuration thereof can be obtained from the above description, this embodiment will not be further described.

In a preferred embodiment, the interference profiles will be configured on each of the driver blade interference profiles and on each of the recess wing interference profiles to avoid the need for alignment of the driver and fastener, particularly in the opposite direction, and to facilitate manufacture. However, in some applications it may be advantageous to construct interference profiles on selected pairs of driver blades and fastener wings, and it will be appreciated that certain misalignments may often occur. This can be avoided to some extent in the six-lobe configuration by configuring the interference profiles on the opposing pairs of wings 40 and 41 and lobes 42 and 43 as shown in fig. 16. As in fig. 2, the profile portion of the standard driver is shown in broken lines at a portion where the profile portion of the standard driver is different from the profile portion of the special driver, and the profile portion of the standard groove is shown in broken lines at a portion where the profile portion of the standard groove is different from the profile portion of the special groove in fig. 16.

In another embodiment of a six-lobe configuration, as shown in FIG. 17, a balanced distribution interference profile is configured on three spaced apart wings 50, 51, 52 and lobes 53, 54 and 55. This configuration will allow the user to selectively use or not use the snap fit feature by aligning or misaligning the snap interface of the driver with the interface of the recess. Optionally, (not shown), three interface profiles may be asymmetrically spaced, two in adjacent recess blades and corresponding driver wings and a third in non-adjacent blades and corresponding wings, to provide engagement of at least one pair of wing and blade interference profiles when engaged regardless of how the driver is rotationally positioned relative to the recess. As in fig. 2, in fig. 17, the profile portion of the standard driver is shown in broken lines at a portion where the profile portion of the standard driver is different from the profile portion of the special driver, and the profile portion of the standard groove is shown in broken lines at a portion where the profile portion of the standard groove is different from the profile portion of the special groove.

The embodiments described above are illustrated as a common form of fastener system involving a female recess and male configuration driver on the fastener. However, the interference profiles of the subject fastener system can be applied in the reverse arrangement as shown in fig. 14 and 15. A fastener system having a six-bladed, straight wall driving surface is shown in fig. 14. In this embodiment, the fastener is configured with a protrusion 211, the protrusion 211 extending axially outward from the fastener head for engagement with the driver 210. The driver 210 is configured with a female socket having a mating drive surface for engaging the drive surface of the protrusion 211. In this embodiment, the protruding interference profile 213 is configured on the "a" dimension surface of the blade 214 of the fastener protrusion 211, while the recessed interference profile 215 is configured on the opposite "a" dimension surface of the wing 216 of the driver socket 210.

An additional embodiment of an out-drive version of the subject fastener system is shown in FIG. 15, in which a screw-drive fastener system is illustrated. In the screw-driven, straight-walled fastener system of fig. 15, the projection 311 is configured to extend axially outward from the fastener head for engagement with the driver socket 310. The driver socket 310 is configured with a mating drive surface for engagement with the drive surface of the protrusion 311. In this embodiment, the protruding interference profile 313 is configured on an "a" sized surface of the blade 314 of the fastener projection 311, while the recess interference profile 315 is configured on an opposite "a" sized surface of the wing 316 of the driver socket 310. In this manner, alignment stability and a reliable snap fit are achieved in an externally driven fastener system.

A further embodiment of an externally driven fastener system is shown in fig. 18-21, in which a hex head driven fastener system is illustrated. In the hex head driven, straight wall fastener system of fig. 18, the protrusion 411 is configured to extend axially outward from the fastener head for engagement with the driver socket 410. The driver socket 410 is configured with a mating drive surface for engagement with the drive surface of the protrusion 411. In this embodiment, fastener interference profile 413 is configured on a surface of side 419 of protrusion 411, while groove interference profile 418 is configured on an opposite surface of side 415 of socket 410. In this manner, alignment stability and a reliable snap fit are achieved in an externally driven hex head fastener system. In fig. 19, profile 413 is shown disposed on a lower portion of surface 419, but portion 413 can be disposed higher, can be sized to extend over a larger or smaller portion of surface 419, with profile 418 correspondingly matingly disposed and sized.

In the hex-head driven, straight wall fastener system of fig. 19, the projections 511 are configured to extend axially outwardly from the fastener head for engagement with the driver socket 510. The driver socket 510 is configured with a mating drive surface for engagement with the drive surface of the protrusion 511. In this embodiment, the fastener interference profile 513 is configured on a surface of the side 519 of the projection 511, while the groove interference profile 518 is configured on an opposite surface of the side 515 of the socket 510. The system shown in fig. 19 is similar to that of fig. 18, however, profiles 513 and 518 extend over only a portion of surfaces 519 and 515, respectively. In fig. 19, profile 513 is shown disposed on a lower portion of surface 519, but portion 513 could be disposed higher or disposed to one side and/or could be sized to extend over a larger or smaller portion of surface 519, with profile 518 correspondingly matingly disposed and sized.

In the hex-head driven, straight wall fastener system of fig. 20, the protrusion 611 is configured to extend axially outward from the fastener head for engagement with the driver socket 610. Driver socket 610 is configured with a mating drive surface for engagement with the drive surface of protrusion 611. In this embodiment, the fastener interference profile 613 is configured on the surface of the side 619 of the protrusion 611 at the corner 617 between two adjacent sides 619, while the groove interference profile 618 is configured on the opposite surface of the side 615 of the socket 610 at the corner 614 between two adjacent sides 615.

In the hex-head driven, straight wall fastener system of fig. 21, the protrusion 711 is configured to extend axially outward from the fastener head for engagement with the driver socket 710. The driver socket 710 is configured with a mating drive surface for engagement with the drive surface of the protrusion 711. In this embodiment, the fastener interference profile 713 is configured on a surface of a side 719 of the protrusion 711 at a corner 717 between two adjacent sides 719, while the groove interference profile 718 is configured on an opposite surface of a side 715 of the seat 710 at a corner 714 between two adjacent sides 715. The system shown in fig. 21 is similar to the system of fig. 20, however, the surface 713 begins its taper at a location below the top of the protrusion 711, i.e., at the bottom of the straight wall portion 720.

The driver and recess of the present application can be made in a conventional two-bit forging machine. The punch will typically be formed to include a body and a tip, the tip substantially corresponding to the geometry of the driver illustrated in fig. 4 and 10. The punch may be formed according to conventional stamping forming techniques, for example using a hobbing machine die. Drivers according to the present invention can also be manufactured using conventional techniques, such as by stamping the driver blank using one or more shaping dies to form the desired shaped wings, or by milling out the driver head using a specially shaped milling cutter.

The above description and drawings are only to be considered illustrative of particular embodiments which achieve the features and advantages described herein. Modifications and substitutions for specific conditions and materials can be made. Accordingly, the embodiments are not to be seen as limited by the foregoing description and drawings, but are only limited by the scope of the appended claims.

Claims (26)

1. A fastener system, comprising:

a fastener having a head and a shank, the fastener having a central longitudinal axis, wherein the head is configured with a projection extending axially outwardly from the head, the projection including a central portion and a plurality of fastener straight sides each having a fastener side surface aligned substantially parallel to the central longitudinal axis of the fastener;

a driver having a driver head with a central longitudinal axis, wherein the driver head is configured as a recess socket having a central portion and a plurality of driver straight sides each having a driver side surface aligned substantially parallel to the central longitudinal axis of the driver, and wherein the recess socket is adapted to receive the fastener head protrusion such that the driver driving surface receives the fastener driving surface in mating engagement;

an interference interface, the interference interface comprising:

a fastener interference profile, wherein the fastener interference profile tapers inwardly toward a tip of the fastener head projection at a fastener taper angle relative to a central longitudinal axis of the fastener; and

a driver interference profile, wherein the driver interference profile tapers inwardly toward the bottom of the recess socket at a driver taper angle relative to a central longitudinal axis of the driver,

wherein the fastener taper angle is greater than the driver taper angle, and wherein the driver interference profile and the fastener interference profile are configured to form a friction fit engagement at the interference interface when the fastener head protrusion and the recess socket are matingly engaged.

2. The fastener system of claim 1, wherein the fastener interference profile is formed on at least one fastener straight side surface and the driver interference profile is formed on at least one driver side surface.

3. The fastener system of claim 2, wherein the fastener interference profile and the driver interference profile are located at lower portions of the fastener side surface and the driver side surface, respectively.

4. The fastener system of claim 3, wherein the fastener interference profile and the driver interference profile are located at a central lower portion of the fastener side surface and the driver side surface, respectively.

5. The fastener system of claim 1, wherein the fastener interference profile is formed at a corner between two adjacent fastener side surfaces and the driver interference profile is formed at a corner between two adjacent driver side surfaces.

6. The fastener system of claim 5, wherein the fastener interference profile and the driver interference profile are located below the top of the protrusion and the recess, respectively.

7. The fastener system of claim 1, wherein the driver recess socket is enlarged in size such that the enlarged recess can receive a standard fastener projection without binding the driver interference profile or the fastener interference profile.

8. The fastener system of claim 1, wherein the driver taper angle and the fastener taper angle are each in the range of one degree (1 °) to three degrees (3 °).

9. The fastener system according to claim 7, wherein a distance from one transition profile to an opposite transition profile across the driver recess is defined as an "A" dimension of the driver, and the driver recess is enlarged by lengthening the "A" dimension.

10. The fastener system of claim 1 wherein the fastener taper angle is one-half (0.5 °) greater than the driver taper angle.

11. The fastener system of claim 1, wherein the driver taper angle and the fastener taper angle are each in the range of one-half degree (0.5 °) to seven degrees (7 °).

12. The fastener system of claim 1, wherein the fastener system is a hex head driver fastener system.

13. A method of constructing a fastener system, comprising:

forming a fastener having a head and a shank, the fastener having a central longitudinal axis, wherein the head is configured with a projection extending axially outwardly from the head, the projection including a central portion and a plurality of fastener straight sides each having a fastener side surface aligned substantially parallel to the central longitudinal axis of the fastener;

forming a driver having a driver head with a central longitudinal axis, wherein the driver head is configured as a recess socket having a central portion and a plurality of driver straight sides each having a driver side surface aligned substantially parallel to the central longitudinal axis of the driver, and wherein the recess socket is adapted to receive the fastener head protrusion such that the driver driving surface receives the fastener driving surface in mating engagement;

forming an interference interface comprising:

forming a fastener interference profile, wherein the fastener interference profile tapers inwardly toward a tip of the fastener head projection at a fastener taper angle relative to a central longitudinal axis of the fastener; and

forming a driver interference profile, wherein the driver interference profile tapers inwardly toward the bottom of the recess socket at a driver taper angle relative to a central longitudinal axis of the driver,

wherein the fastener taper angle is greater than the driver taper angle, and wherein the driver interference profile and the fastener interference profile are configured to form a friction fit engagement at the interference interface when the fastener head protrusion and the recess socket are matingly engaged.

14. The method of constructing a fastener system according to claim 13, wherein fastener interference profiles are formed on at least one fastener straight side surface and driver interference profiles are formed on at least one driver side surface.

15. The method of constructing a fastener system according to claim 14, wherein the fastener interference profile and the driver interference profile are formed at lower portions of the fastener side surface and the driver side surface, respectively.

16. The method of constructing a fastener system according to claim 15, wherein the fastener interference profile and the driver interference profile are formed at central lower portions of the fastener side surface and the driver side surface, respectively.

17. The method of constructing a fastener system according to claim 13, wherein a fastener interference profile is formed at a corner between two adjacent fastener side surfaces and a driver interference profile is formed at a corner between two adjacent driver side surfaces.

18. The method of constructing a fastener system according to claim 17, wherein the fastener interference profile and the driver interference profile are formed below the top of the protrusion and the recess, respectively.

19. The method of constructing a fastener system according to claim 13, wherein the driver recess socket is enlarged in size so that the enlarged recess can receive a standard fastener projection without binding either the driver interference profile or the fastener interference profile.

20. The method of constructing a fastener system according to claim 13, wherein the driver taper angle and the fastener taper angle are each in the range of one degree (1 °) to three degrees (3 °).

21. The method of constructing a fastener system according to claim 19, wherein the distance from one transition profile to the opposite transition profile across the driver recess is defined as the "a" dimension of the driver, and the driver recess is enlarged by lengthening the "a" dimension.

22. The method of constructing a fastener system according to claim 13, wherein the fastener taper angle is one-half (0.5 °) greater than the driver taper angle.

23. The method of constructing a fastener system according to claim 13, wherein the driver taper angle and the fastener taper angle are each in the range of one-half degree (0.5 °) to seven degrees (7 °).

24. The method of constructing a fastener system according to claim 13, wherein the fastener system is a hex head driver fastener system.

25. The method of constructing a fastener system according to claim 21 wherein the driver and fastener interference profiles are configured such that the "a" dimension of the fastener has a positive tolerance of plus zero (+0) to plus two thousandths of an inch (+0.002) and the "a" dimension of the recess has a negative tolerance of minus zero (-0) to minus two thousandths of an inch (-0.002).

26. The method of constructing a fastener system according to claim 13, wherein the fastener interference profile and driver interference profile are configured to: the driver taper angle has a tolerance of positive quarter-degree (+0.25 deg.) and negative zero-degree (-0.0 deg.); while the fastener taper angle has a tolerance of plus zero (+ 0.0) degrees and minus one-quarter degrees (-0.25).