Patent Description:
Torque transmission drivers for torque transmitting systems and fasteners used in those systems are well-known in the art. The bit of the driver had a recess or a projection of a particular shape which fit a complimentary shaped projection or recess in the fastener. One of the more commonly known torque transmitting systems was the cruciform type drive system commercialized as the PHILLIPS® drive system. See for example, <CIT>. Numerous forms and shapes of torque transmitting drive systems have been proposed. See for example, <CIT>. In addition, some prior drive systems included three blades or lobes. See for example, <CIT>, and <CIT>.

Spline-type torque transmitting systems of four-lobe, five-lobe and six-lobe have been well-known. Examples of these four-lobe, five-lobe and six-lobe torque transmitting systems, with their fasteners and drivers, are described in <CIT>; <CIT>; <CIT>; <CIT> and <CIT>. Early versions of such spline-type torque transmission drive systems had square corners, for which corresponding fastener recesses were difficult and expensive to make and resulted in stresses in the fastener and/or driver which lead to fatigue failure with repeated use. Later versions of five and six lobe spline type torque drive systems had a plurality of intersecting oppositely curved surfaces evenly positioned about the <NUM>° circumference of the fastener head or driver bit to form an alternating series of lobes and flutes. These latter torque drive systems overcame some of the problems inherent in the earliest spline type systems, but were not generally capable of retaining a lobe drive angle less than five degrees. Upon application of higher torques, force components would rise causing failure or strip out of the lobes from the fasteners or the drivers. One version of these later spline type torque drive systems, known commercially as the TORX@ drive system, had six-lobe and five-lobe configurations based on mating arcuate surfaces designed to attain drive angles within the range of <NUM>° to <NUM>°.

A later version of this spline type torque transmission drive system reduced the drive angle to zero by having both the driven surfaces of the fastener head and the drive surfaces of the torque driver formed by a first series of elliptically curved surfaces with a second series of elliptically curved surfaces alternating there between. One series of these elliptically curved surfaces was convex, while the alternating series of elliptically curved surfaces was concave. The alternating concave and convex elliptically curved surfaces merged smoothly and tangentially to define a series of alternating flutes and lobes extending about the <NUM>° circumference of the fastener head or the driver bit. Both the lobes and the flutes of the fastener head and driver bit were elliptically curved in section. Also, the centers of the elliptically curved lobes and corresponding centers of the elliptically curved flutes were disposed at the apexes of a regular hexagon, although not the same hexagon, due to the alternating nature of these components. An arrangement of this lobular torque transmission drive system has been commercially marketed as the TORX PLUS® drive system.

Certain prior torque transmission drivers have been limited by their dedication to one or a limited number of sizes of fastener having drive surfaces, with recess or projections, corresponding to the size of the driver. For example, the lobular fastener marketed under the brand name TORX@ required a separate driver of a diameter to match each size of corresponding fastener. This meant that a set of the drivers had to be maintained on site by assemblers, and each time a different size fastener was installed a different size bit was retrieved from the set and installed in a torsion gun. For example, a T-<NUM> TORX@ driver was required to drive a T-<NUM> TORX@ fastener, and a T-<NUM> TORX@ driver was required to drive a T- <NUM> TORX@ fastener, and so on. Other fastener systems, such as a cruciform type system sold under the brand name PHILLIPSO, could drive more than one size fastener, but these systems were susceptible to driver cam-out from the fastener. Cam-out is a rotational lifting movement by which the driver lifts out of the fastener recess, caused when the fastener and the driver have angled surfaces that enable sliding movement between the surfaces. Cam-out by the prior torque transmission systems caused damage to the fasteners and drivers, prevented fasteners from being tightened to a proper torque, as well as generated shavings and burrs that damaged components in the assembly.

The prior systems created inefficiency for assemblers who install fasteners of different sizes who have to pick up one driver to install one size fastener and pick up another driver to install another size fastener, or alternatively attempt to drive a fastener with the wrong size driver or a driver that cams out, which added to the difficulty where not impossible. Driving a fastener with a driver that was too large or too small for the fastener prevented the driver from seating properly increasing the prospect of cam-out of the driver from the fastener, strip-out or shearing of the fastener recess or projections, and/or improperly torqued fastener installation. This presented inefficiency and waste in installation and an increased incidence of mis-installed fasteners in assemblies and failure of the assemblies. Tapered drive systems in the past of the cruciform type, e.g. PHILLIPS® drivers, were well know to cam out of fasteners under torque, causing damage to and waste of fasteners or drivers, with decreased efficiency and increased incidence of mis-installed fasteners and misassembly of products, devices and machines. Additionally, the prior spline- type systems were less effective with thread forming and thread cutting fasteners because the drivers tended to cam out of the fastener and the drivers wobbled in the fasteners not maintaining axial alignment. All of these problems were accentuated in extremely small size fastener heads and torsion drivers, particularly for fasteners with a major thread diameter smaller than about <NUM> millimeter (<NUM> inch), and more particularly for fasteners with a major thread diameter smaller than about <NUM> millimeter (<NUM> inch). In addition to the problems discussed above, such small fasteners tended to deform when in use because of the small size of the fasteners, the sizes of the lobes, and the clearance tolerances involved. A three-lobe system is disclosed in <CIT>. The document discloses a fastening system according to the preamble of claim <NUM>. <CIT> discloses a system in which a plurality of lobes are provided whereby in the system the taper of the side walls is <NUM>°.

There remains a need for fastening systems including drivers and fasteners that address the foregoing problems.

In particular, it is provided a system having the features defined in claim <NUM>. A fastener system according to the present invention includes a fastener having a head with a recess, and a threaded shank, the recess defined by a series of three alternating lobes and troughs about a rotational axis, each of the alternating lobes and troughs defined by in series an outer radius portion, a drive side transition, an inner transition radius, and a reverse drive portion, the recess having a side wall defined by the outer radius portion with a taper angle of about <NUM>° from the rotational axis; and a driver comprising a shaped tapered bit defined by a series of three alternating lobes and driver troughs about the rotational axis, each of the alternating lobes and troughs defined by in series an outer radius portion, a drive side transition, an inner transition radius, and a reverse drive portion, wherein each lobe has a tapering height and width with a substantially constant ratio of lobe width to lobe height, and wherein the driver lobes have a side wall defined by the outer radius portion with a taper angle relative to the rotational axis less than or equal to the taper angle of the recess side wall, and the reverse drive portion of the driver comprises a concave portion and a catch portion, wherein the catch portion defines a reverse drive angle of about <NUM>°.

In some embodiments, the driver side wall has a taper angle of about <NUM>° from the rotational axis. In some embodiments, the driver side wall has a taper angle of about <NUM>° from the rotational axis. In some embodiments, the taper angle of the driver side wall is at least <NUM>° less than the taper angle of the recess side wall.

In some embodiments, the drive side transition is linear and defines a drive angle relative to a radial line extending from the rotational axis and tangent to the inner transition radius. In some embodiments, the drive angle is between about <NUM>° and <NUM>°. In some embodiments, the drive side transition has a length between about <NUM>% and <NUM>% of the lobe height.

In some embodiments, the inner transition radius comprises a first segment defined by a first radius and a second segment defined by a second radius greater than the first radius.

In some embodiments, the driver comprises a tip portion and the outer transition radius is tapered at about <NUM>° in the tip portion.

In some embodiments, the fastener system further includes a plurality of additional fasteners of different sizes, each of the plurality of fasteners having at least one cross section of a recess that is substantially the same as a cross section of the recess of the fastener, wherein the driver is configured to transmit torque to each of the fasteners.

In some embodiments, the fastener has a major thread diameter smaller than (<NUM> inch) <NUM> millimeter. In some embodiments, the fastener has a major thread diameter smaller than (<NUM> inch) <NUM> millimeter.

In some embodiments, the drive side transition of the driver is adapted to engage the drive side transition of the fastener at a lift angle less than <NUM>° to reduce cam out.

In the following figures, the arrangement shown in <FIG> is an embodiment of the present invention. The further arrangements shown are helpful for understanding the present invention.

Referring now to <FIG> - ID, a diagrammatical representation of a torque transmission driver <NUM> is shown engaging corresponding recesses of similar shape and taper in a plurality of fasteners <NUM>, <NUM>, <NUM> with differing recess sizes <NUM>, <NUM>, <NUM>. The tapered drive surfaces of the bit, such as shown in <FIG> - ID, may comprise a first tapered portion <NUM> operable to engage a first sized recess <NUM> in a first fastener <NUM>, a second tapered portion <NUM> operable to engage a second sized recess <NUM> in a second fastener <NUM>, and a third tapered portion <NUM> operable to engage a third sized recess <NUM> in a third fastener <NUM>. As shown in FIG. ID, in this application the third sized recess <NUM> of the third fastener <NUM> is larger than the second sized recess <NUM> of the second fastener <NUM>, which is larger than the first sized recess <NUM> of the first fastener <NUM>. As such, the torque transmission driver <NUM> is adapted to effectively drive more than one size fastener. While the torque transmission driver <NUM> shown in <FIG> - ID is operable to effectively engage and drive three different size fastener recesses, the torque transmission driver <NUM> may be adapted for a desired plurality of fastener recess sizes and fastener sizes. The torque transmission driver typically may effectively engage and drive between <NUM> and <NUM> different fastener drive surfaces, such as recesses or projections, as discussed below.

The torque transmission driver <NUM> as shown in <FIG> includes a main body <NUM> having a first end portion <NUM> and a second end portion <NUM>. The first end portion <NUM> is adapted to receive and transmit torque from a torque generation source, such as a power driver, a manually operated driver handle, a drill motor, or other torque generation source as desired. As shown in <FIG>, the second end portion <NUM> is opposite the first end portion <NUM> and includes a shaped tapered bit <NUM> having a series of six lobes <NUM> and troughs <NUM> about a rotational axis, shown as A in <FIG>. The six lobes <NUM> and troughs <NUM> are symmetrically arranged about the rotational axis having a taper angle Θ between <NUM>° and <NUM>° from the rotational axis as shown in <FIG>. In one application, the taper angle Θ is about <NUM>°. Alternatively, the taper angle is about <NUM>°. In yet another application, the taper angle is a selected angle between <NUM>° and <NUM>°. In yet another application, the taper angle is a selected angle between <NUM>° and <NUM>°. In yet other applications, the taper angle is a selected angle between <NUM>° and <NUM>°, between <NUM>° and <NUM>°, or between <NUM>° and <NUM>°. In yet other applications, the taper angle is approximately <NUM>° or approximately <NUM>°. An increased taper angle may provide greater strength to the recess reducing wear and failure of the fasteners and driver.

The torque transmission driver <NUM> as shown in <FIG> is a six- lobe driver. In one alternative, the torque transmission driver <NUM> and corresponding fasteners may include a five-lobe torque transmission system shown by example of the cross-section in <FIG>, or may be a four-lobe torque transmission system shown by example of the cross-section in <FIG>. In one application, a small fastener having a major thread diameter less than about <NUM> millimeter (<NUM> inch) may utilize a four- lobe torque transmission system. Alternatively, a small fastener having a major thread diameter less than about <NUM> millimeter (<NUM> inch) may utilize a four-lobe torque transmission system. In another application, a small fastener having a major thread diameter less than about <NUM> millimeter (<NUM> inch) may utilize a five- lobe torque transmission system. In yet another alternative, a small fastener having a major thread diameter less than about <NUM> millimeter (<NUM> inch) may utilize a five-lobe torque transmission system.

At any cross section through the tapered bit <NUM>, such as the cross-section shown in <FIG>, the outermost tip of each lobe <NUM> forms a lobe outer diameter <NUM>, and the root of each trough <NUM> forms an inner diameter <NUM>. The difference between the radius of the lobe outer diameter <NUM> and the radius of the inner diameter <NUM> is the lobe height <NUM>. Additionally, each lobe has a width <NUM>. As the bit <NUM> tapers toward the second end, each lobe has a tapering height and width. For each tapering lobe, the ratio of the lobe width to height is substantially the same for each lobe as it tapers along the axis.

The main body <NUM> may be a hexagonal shank having a length and cross-sectional size operable to be mounted in or otherwise engage the torque generation source such as a power driver. For example, in a common application, the main body may have a <NUM> millimeters (<NUM>/<NUM> inch) hexagonal cross-section. Alternatively, the main body may have a <NUM>/<NUM> hexagonal cross- section. The main body <NUM> may have any cross-sectional shape and size as desired corresponding to the torque generation source needed for the application. Alternatively, the main body may include a socket (not shown) for receiving a corresponding engagement on the torque generation source.

In the example of <FIG>, the transition between each lobe <NUM> and the trough <NUM> on at least one side of each lobe <NUM> forms a drive side transition <NUM> extending between an outer transition radius <NUM> and an inner transition radius <NUM>. A drive angle a is measured between the drive side transition <NUM> and a radial line <NUM> extending from the rotational axis A and tangent to the inner transition radius <NUM> as shown in <FIG>. The drive side transition <NUM> is adapted to engage a corresponding fastener surface for transferring torque from the driver to the fastener. The drive side transition is typically between about <NUM>% and <NUM>% of the lobe height. Alternatively, the drive side transition is between about <NUM>% and <NUM>% of the lobe height. In yet another alternative, the drive side transition is between about <NUM>% and <NUM>% of the lobe height. As shown in <FIG>, the drive side transition <NUM> forms a drive angle a between <NUM>° and <NUM>°. Alternatively, as shown in <FIG>, the transition between each lobe and the trough on at least one side of each lobe <NUM> form the drive side transition <NUM> having a negative drive angle, where the drive angle a is between <NUM>° and -<NUM>°. In one application, the drive angle a is between - <NUM>° and -<NUM>°. Alternatively, the drive angle a is between -<NUM>° and - <NUM>°. In yet another alternative, the drive side transition may form a drive angle between <NUM>° and -<NUM>°. As used herein, a positive drive angle is defined as a drive side transition surface angled outwardly such that a line extending perpendicularly from the surface is directed toward the outside of or away from the inner diameter <NUM>. Conversely, a negative drive angle is defined as a drive side transition surface angled inwardly such that a line extending perpendicularly from the surface is directed toward the inside of or toward the inner diameter <NUM>. A zero degree drive angle provides a line perpendicular to the drive side transition surface that is parallel to a tangent of the inner and/or outer lobe diameters. Typically, the fastener drive angle is approximately the same as the bit drive angle to provide surface to surface contact. Alternatively, the fastener drive angle may be greater or less than the bit drive angle to accommodate clearances between the fastener and the driver as desired.

The tapered driver <NUM> is operable to drive corresponding drive surfaces in a fastener in a male-female engagement. In one application as discussed above and shown in <FIG>, the fastener <NUM> has a drive end portion <NUM> and a lead end portion <NUM>. The drive end portion <NUM> is operable to engage a torque transmission driver and the lead portion <NUM> is operable to fasten the fastener, such as by threads. The drive end portion <NUM> has drive surfaces <NUM> comprising a series of five or six fastener lobes <NUM> and fastener troughs <NUM> about a rotational axis having tapered drive surfaces γ of between <NUM>° and <NUM>° from the rotational axis. The fastener lobes <NUM> and fastener troughs <NUM> are operable to engage corresponding drive surfaces of similar shape and taper on the driver. Each fastener lobe <NUM> has a tapering height and width, where the ratio of lobe width to height is a constant. In the fastener recess, the lobes <NUM> project into the recess to engage the driver troughs <NUM> on the driver. Similarly, the driver lobes <NUM> on the driver engage the fastener troughs <NUM> in the fastener recess.

In another alternative, such as shown in <FIG>, the fastener drive surfaces <NUM> comprise a projection of four, five, or six lobes and troughs to engage a corresponding recess in the driver (not shown). It is intended that discussion and references in the present application describing drive surfaces of the driver bit corresponding to a recess in the fastener such as shown in <FIG> also apply to drive surfaces as a projection on the fastener such as shown in <FIG>. Similarly, discussion and references in the present application describing drive surfaces of the recess in the fastener such as shown in <FIG> also apply to drive surfaces in a recess in a driver for use in driving projections on a fastener such as shown in <FIG>.

The lobes and troughs taper into the recess at least to a bottom plane, identified in <FIG> as "P". The bottom plane P as used herein is the approximate depth to which a corresponding driver is insertable into the recess. Below the bottom plane P, the bottom of the recess may be conical, hemispherical, hemispheroidal, flat, or any other arcuate or angled shape as desired for forming the recess. From the bottom plane P, the cross-sectional lobular shape of the recess tapers outwardly toward the top of the fastener recess having a taper angle γ. The recess taper angle γ may be approximately the same as the driver taper angle Θ. Alternatively, the recess taper angle γ may be slightly larger than the driver taper angle Θ for manufacturing tolerances. In another alternative, the recess taper angle γ may be between <NUM>° and <NUM>° larger than the driver taper angle Θ. As one example, the recess taper angle γ may be specified between <NUM>° and <NUM>°, and the driver taper angle Θ specified between <NUM>° and <NUM>°, where nominally the recess taper angle γ and the driver taper angle Θ are <NUM>°. In another example, the recess taper angle γ may be specified between <NUM>° and <NUM>°, and the driver taper angle Θ specified between <NUM>° and <NUM>°, where nominally the recess taper angle γ and the driver taper angle Θ are each <NUM>°. In another example, the recess taper angle γ may be specified between <NUM>° and <NUM>°, and the driver taper angle Θ specified between <NUM>° and <NUM>°, where nominally the recess taper angle γ and the driver taper angle Θ are <NUM>°. However, the recess taper angle γ and the driver taper angle Θ may be any angle between <NUM>° and <NUM>° from the rotational axis as desired.

A fastening system may be provided whereby one torque transmission driver <NUM> is operable to drive a plurality of different sized fasteners <NUM>, <NUM>, <NUM>. The tapered driver <NUM> may be configured to drive two or more different sized fasteners with the same size of bit <NUM>. In the example of <FIG> - ID, the tip portion of the tapered bit has a cross-sectional size forming the first tapered portion <NUM> operable to engage fasteners corresponding to the size of the first tapered portion. The second tapered portion <NUM> may be adjacent the first tapered portion <NUM> in a position on the tapered bit having a cross-sectional size larger than the first tapered portion. The second tapered portion <NUM> is operable to engage fasteners corresponding to the size of the second tapered portion. Similarly, a third tapered portion <NUM> is adjacent the second tapered portion <NUM> operable to engage fasteners corresponding to the size of the third tapered portion. For example, one driver may be adapted to drive associated sizes <NUM>, <NUM> and <NUM> screws, in which the first tapered portion <NUM> of the bit is adapted to the #<NUM> screw, the second tapered portion <NUM> is adapted to the #<NUM> screw, and the third tapered portion <NUM> is adapted to the #<NUM> screw. In other alternatives, one driver may be adapted to drive associated sizes <NUM>, <NUM> and <NUM> screws, and another driver adapted to drive associated <NUM> millimeters (<NUM>/<NUM> inch), <NUM> millimeters (<NUM>/<NUM> inch), and <NUM> millimeters (<NUM>/<NUM> inch) screws. Alternatively, a driver may be adapted to drive a plurality of small fasteners, such as size #<NUM> and #<NUM> fasteners, or smaller, associated to the driver. The driver may be adapted to drive two or more sequentially-sized associated fasteners as desired.

For one driver <NUM> to drive a plurality of fasteners <NUM>, <NUM>, <NUM> of differing sizes, each fastener has drive surfaces <NUM> corresponding to the driver such that the differing sizes of drive surfaces have at least one cross-section substantially the same in size and shape. Specifically, with reference to <FIG> - ID, the size and shape of the cross-section of the recesses <NUM>, <NUM>, <NUM> at the bottom plane P is the approximately the same for each fastener associated with the desired drive bit <NUM>. Additionally, the corresponding cross-sectional size and shape of the driver <NUM> at the second end <NUM> is approximately the same as the fastener size and shape at the bottom plane P. For certain applications, the cross-sectional size and shape of the driver <NUM> at the second end <NUM> is smaller than the fastener size and shape at the bottom plane P for ease of insertion of the driver into, and removal from, the recess. Alternatively, the cross-sectional size and shape of the driver <NUM> at the second end <NUM> is slightly larger than the fastener size and shape at the bottom plane P such that interference between the driver and fastener cause the fastener to releasably stick to the driver so that an assembler does not have to hold the fastener onto the driver.

The drive surfaces of the fastener and the correspondingly configured bit drive surfaces are configured for the fastener drive surfaces to engage the corresponding bit drive surfaces an engagement depth sufficient to permit good application of torque from the driver bit to the fastener. For example, a small fastener having a major thread diameter less than about <NUM> millimeter (<NUM> inch) may have an effective engagement depth of the drive surfaces of less than <NUM> millimeter (<NUM> inch). For larger fasteners, such as having a major thread diameter greater than about <NUM> millimeter (<NUM> inch), the effective engagement depth may be <NUM> millimeter (<NUM> inch), or greater.

For certain larger fastener applications, the tapered fastener drive surfaces and associated driver may be manufactured using traditional cold-heading and/or machining techniques. However, smaller fasteners tend to require increased precision. In one application the fastener drive surfaces are impressed or embossed onto the fastener by stamping. For certain applications, such as for small fasteners having a major thread diameter less than about <NUM> millimeter (<NUM> inch), or alternatively having a major thread diameter less than about <NUM> millimeter (<NUM> inch), the drivers may be made by electrical discharge machining (EDM) or electrochemical machining (ECM). It is contemplated that hobbing may also be used for certain suitable geometries.

The present torque transmission drivers may be steel or aluminum as desired for the application. In one alternative, the steel is a medium carbon steel, such as AISI S2, <NUM>, <NUM>, <NUM>, or other tool steel compositions or alloy steel compositions as desired for hardenability and strength. The medium carbon steel may be hardened after the driver is made. After the torque transmission driver is formed, the steel driver may be hardened to a hardness of <NUM>-<NUM> HRC. Alternatively, the steel driver may be hardened to a hardness greater than <NUM> HRC.

As discussed above, the lobes <NUM> of the driver shown, for example, in <FIG>, taper as the bit <NUM> is tapered. In these arrangements, when the size of the cross sectional bit (see <FIG>) is reduced, the proportions of the lobes <NUM> to troughs <NUM> will remain substantially the same. Because the lobes are tapered, the reaction force exerted against the driver lobe from the fastener, schematically represented as "FR" in <FIG>, includes a lift angle β. The reaction force FR includes a component along the driver axis, schematically represented as "Fy" in <FIG>, in a direction tending to lift the driver <NUM> and reduce driver engagement in the fastener recess during driving of the fastener. This process is known as "cam out" because as driving torque increases and the component force Fv increases, when a force opposing the component force Fy is not applied the driver may lift in a direction away from the fastener recess, and in some instances the driver may lift enough to disengage from the fastener recess.

The presently disclosed fastener system inhibits cam out, and for certain applications it may be desired to further reduce the forces causing cam out. In one example shown in <FIG>, the drive surface <NUM> of the driver <NUM>' may be modified while the trailing surface <NUM> may be tapered as previously explained. The drive surface <NUM> may be substantially parallel to the axis of rotation of the driver, as shown in <FIG>, reducing the lift angle β to be at or near zero degrees, depending on manufacturing tolerances. In one alternative, the lift angle on the drive surface <NUM> may be between <NUM>° and <NUM>°. The lift angle may be selected to reduce the amount of vertical force imposed on the driver when a torque is applied to the fastener through the driver. As torque requirements increase, it may be desirable for the lift angle to be at or near zero degrees. In low-torque arrangements, the lift angle may not need to be highly constrained, as determined by the application. In the arrangement shown in <FIG> having the angle of the drive side approximately zero degrees, the lift angle β will be near zero when the driver is used to tighten a fastener with a corresponding recess, reducing the potential for cam-out during fastening. When the driver shown in <FIG> is used to loosen a fastener, the lift angle on the trailing surface <NUM>, which drives the removal of the fastener, may be greater than zero. The fastener may be designed to accommodate separate drivers for installation and removal of fasteners, which may be desired for tamper-resistant applications.

The driver <NUM>' shown in <FIG> enables less taper on the corresponding drive side of the lobes in the fastener recess, which increases the amount of material in the lobes of the fasteners making the fastener stronger. The added material in the fastener lobes may cause the difference in the torque between the driver and the fastener to be closer in amounts, further assisting in inhibiting cam-out and improving service of the driver.

Referring now to <FIG>, tests were conducted of the disclosed tapered lobular driver and fastener system. In each instance, a set of tapered lobular drive bits having a selected taper angle were engaged corresponding recesses. As shown in <FIG>, the three tests included a five-lobe drive bit and recess having a taper angle of <NUM>°, a six-lobe drive system having a taper angle of <NUM>°, and a six-lobe drive system having a taper angle of <NUM>°. The drive bits were each torque until the drive system failed to identify the strength of the system. In addition, the drive bits were tested in both a standard fastener recess, as well as a recess formed in high speed steel having significantly increased strength in order to separately analyze the strength of the drive bit. The black reference line indicates the specified drive bit strength of a prior art commercially available six-lobe straight- walled drive bit. As shown, the six- lobe drive bits having taper angles of <NUM>° and <NUM>° both exceeded the drive bit strength of the six-lobe straight-walled drive bit. The tapered lobular driver and fastener thus provide an improvement in drive system strength in combination with the ability to use a single driver with multiple size fasteners, all while reducing the potential for cam-out during fastening.

Referring now to <FIG> also disclosed is a fastener system according to the present invention that includes a fastener and a driver having a three lobe drive surface configuration.

Referring to <FIG>, an arrangement of a driver <NUM> is show in multiple views. The driver <NUM> includes a a shaped tapered bit <NUM> defined by a series of three alternating lobes <NUM> and troughs <NUM> about the rotational axis. Each of the alternating lobes <NUM> and troughs <NUM> are defines by an outer radius portion <NUM>, a drive side transition <NUM>, an inner transition radius <NUM>, and a reverse drive portion <NUM>, as best shown in the cross section illustration. Each lobe <NUM> has a tapering height and width with a substantially constant ratio of lobe width to lobe height. Lobe height and width are measured in the same manner described above with respect to <FIG> and <FIG>. The outer radius portion <NUM> defines the outer diameter of the bit at a given location, and further defines the side wall <NUM> of the driver. The side wall <NUM> of the driver is tapered at a taper angle Θ with respect to the rotational axis of the driver. The taper angle Θ of the side wall of the driver is less than or equal to the taper angle of the side wall of the recess (as discussed further below).

Referring to <FIG>, an arrangement of a fastener <NUM> is illustrated for use in the disclosed fastener system. The fastener <NUM> includes a head <NUM> with a recess <NUM>, and a shank <NUM>. The shank <NUM> may be threaded. The recess <NUM> is defined by a series of three alternating lobes <NUM> and troughs <NUM> about the rotational axis of the fastener. Each of the alternating lobes and troughs is defined by an outer radius portion <NUM>, a drive side transition <NUM>, an inner transition radius <NUM>, and a reverse drive portion <NUM>. Similar to the driver discussed above, the outer radius portion <NUM> defines the outer diameter of the recess at a given location, and further defines the side wall <NUM> of the recess. The side wall <NUM> of the recess is tapered at a taper angle Θ with respect to the rotational axis of the fastener. In some arrangements, the taper angle of the recess side wall is about <NUM>°.

Referring now to <FIG>, the driver <NUM> and fastener <NUM> combine to form a fastener system. In some arrangements, the three lobe fastener system provides advantages for off-axis drive capability. As used herein, off-axis drive capability means the ability to transmit torque from the driver to the fastener when the rotational axis of the driver is not aligned with the rotational axis of the fastener. In some arrangements, the disclosed fastener system is capable of driving fasteners with up to a <NUM>° different the rotational axis of the fastener and the driver.

In some arrangements, the driver side wall <NUM> has a taper angle Θ that is approximately equal to the taper angle of the recess side wall <NUM>. In one arrangement, the driver side wall <NUM> taper angle Θ is about <NUM>°. In this arrangement, the three lobe configuration of the driver and fastener recess may allow for some off-axis drive capability.

In other arrangements, the driver side wall has a taper angle less than the taper angle of the recess side wall. For example, the driver side wall taper angle maybe at least <NUM>° less than the recess side wall taper. In the arrangement shown in <FIG> and <FIG>, the driver side wall has a taper angle of about <NUM>°. When the driver side wall taper angle is less than the recess side wall taper angle, the driver bit may lean within the recess with the result that the driver's rotational axis <NUM> deviates from the fastener's rotational axis <NUM>. The angle β between the driver's rotational axis <NUM> and the fastener's rotational axis <NUM> indicates the extent to which the driver is "off-axis" relative to the fastener. In some arrangements, the disclosed fastener system is capable of transmitting torque to a fastener with the driver's rotational axis up to <NUM>° off from the fastener's rotational axis. This feature facilitates use of the disclosed fastener system in products where the configuration of a product does not permit on-axis access to the recess of the fastener.

Referring again to <FIG> and <FIG>, the drive side transitions <NUM>, <NUM> may be linear and define a drive angle a. The drive angle a is defined as the angle between the drive side transition <NUM> and a radial line extending from the rotational axis and tangent to the inner transition radius <NUM>, <NUM>. In various arrangements, the driver angle a may be between <NUM>° and <NUM>°. The drive side transitions <NUM>, <NUM> may also have a length, which may be between <NUM>% and <NUM>% of the lobe height. In yet other arrangements, the drive side transition <NUM> of the driver <NUM> is adapted to engage the drive side transition <NUM> of the fastener <NUM> at a lift angle less than <NUM>° to reduce cam out.

The outer radius portion <NUM>, <NUM> is defined by one or more radii which may be constant or varying. The inner transition radius <NUM>, <NUM> is also defined by one or more radii which may be constant or varying. In one arrangement, the inner transition radius comprises a first segment defined by a first radius, and a second segment defined by a second radius larger than the first radius. The reverse drive portion <NUM>, <NUM> extends from the inner transition radius <NUM>, <NUM> to the outer radius portion <NUM>, <NUM>, and is configured to permit rotation of a fastener for removal.

The driver <NUM> also has a tip portion <NUM> at the end of the bit <NUM>. In some arrangements, the tip portion <NUM> includes the three lobe drive surface configuration, however the outer transition radius <NUM> is tapered at a greater taper angle than in the bit <NUM>. In one arrangement, the outer transition radius <NUM> is tapered at about <NUM>° in the tip portion <NUM>. The increased taper of the outer transition radius in the tip portion may improve engagement of the driver in the recess of a fastener, particularly for small fasteners where alignment of the driver and faster recess is can be difficult.

As previously discussed, the fastener system allows one driver to be used with multiple fasteners of different sizes. The multiple fasteners may each have a recess defined by the three lobe configuration and have substantially the same side wall taper angle, such that at least one cross section of the recess of each fastener is substantially the same as one cross section of the recess of the other fasteners. In this manner, a single driver may be used to driver two or more different size fasteners further improving the efficiency of the fastening system. The three lobe fastening system may be particularly beneficial for small fasteners, such as those with a major thread diameter of less than <NUM> millimeter (<NUM> inch), or less than <NUM> millimeter (<NUM> inch).

Referring now to <FIG>, arrangements of a driver for a three lobe fastener system according to the present invention are illustrated. The fastener system also includes one or more fasteners (not shown) each having a recess configured to match the configuration of the driver. For clarity, each driver is shown with a flat tip portion. Some arrangement of the drivers may include a tapered tip portion as previously discussed.

Referring now to <FIG>, a driver <NUM> is illustrated that is similar to the driver shown in <FIG>. The driver <NUM> has three alternating lobes and troughs. For comparison, the driver <NUM> is shown overlaid with the six lobe configuration of the driver illustrated in <FIG>. In this arrangement, the drive side transition of the three lobe driver aligns with the drive side transition of the six lobe configuration. The outer radius portion and reverse drive portion prevent use of the three lobe driver in a six lobe configured fastener.

Referring now to <FIG>, a driver <NUM> is illustrated in which the width of the each lobe increases at a greater angle moving up the length of the driver. The increased lobe width may provide additional strength to the drive bit. In some arrangements, the angle at which the width of the lobes increases may be related to the taper angle of the driver side wall. In one example, a driver may have a reduced side wall taper angle and include a larger angle for increasing the width of the lobe. In this manner, the driver may accommodate a selection of shallow recess fasteners.

Referring now to <FIG>, yet another arrangement of a driver <NUM> for a three lobe fastener system is disclosed. Said arrangement is an embodiment of the present invention. Although the claimed value of <NUM>° for the reverse drive angle and the taper angle of <NUM>° are difficult to be visualized by said 3D view, the scope of protection is defined by the claims. The driver <NUM> includes three alternating lobes and troughs defined by an outer radius portion <NUM>, drive side transition <NUM>, and inner transition radius <NUM>, and reverse drive portion, generally as described above. The reverse drive portion is defined by a concave portion <NUM>' and a catch portion <NUM>". The concave portion <NUM>' is a curved portion defined by a constant or varying radius originating from an origin outside the outer diameter of the driver. The catch portion <NUM>" extends generally radially. According to the present invention, the catch portion <NUM>" defines a reverse drive angle of approximately <NUM>°. The reverse drive portion of the driver <NUM> may provide an improved ability to remove fasteners, which may be beneficial for applications where removal of fasteners is contemplated. The fastener system also includes one or more fasteners (not shown), each having a recess configured to match the configuration of the driver <NUM>.

Referring now to <FIG>, yet another arrangement of a driver <NUM> for a three lobe fastener system is disclosed. The driver <NUM> includes three alternating lobes and troughs defined by an outer radius portion, drive side transition <NUM>, inner transition radius <NUM>, and reverse drive portion, generally as described above. The reverse drive portion of the driver <NUM> may include a concave portion <NUM>' and a catch portion <NUM>" similar to the configuration of the driver <NUM>. The outer radius portion of the driver <NUM> may include two or more segments configured to improve the function of the fastener system. For example, the configuration may improve the forward drive capability, reverse drive capability, off-axis drive capability, seating or engagement of the driver in the fastener recess, or similar functions of the fastener system. In one arrangement, the outer radius portion of the driver <NUM> includes a first convex segment <NUM>', a concave segment <NUM>", and a second convex segment <NUM>"'. At least a portion of the outer transition radius defines the side wall of the driver <NUM>, and tapers at a taper angle as discussed above.

Claim 1:
A fastener system comprising:
a fastener (<NUM>) having a head (<NUM>) with a recess (<NUM>), and a threaded shank (<NUM>),
the recess (<NUM>) defined by a series of three alternating lobes (<NUM>) and troughs (<NUM>) about a rotational axis, each of the alternating lobes (<NUM>) and troughs (<NUM>) defined by in series an outer radius portion (<NUM>), a drive side transition (<NUM>), an inner transition radius (<NUM>), and a reverse drive portion (<NUM>); and
a driver (<NUM>) comprising a shaped tapered bit (<NUM>) defined by a series of three alternating driver lobes and driver troughs about the rotational axis, each of the alternating driver lobes and driver troughs defined by in series an outer radius portion (<NUM>), a drive side transition (<NUM>), an inner transition radius (<NUM>), and a reverse drive portion;
wherein each of the driver lobes and of the recess lobes has a tapering height and width with a substantially constant ratio of lobe width to lobe height,
wherein the driver lobes have a side wall (<NUM>) defined by the outer radius portion with a taper angle relative to the rotational axis less than or equal to the taper angle of the recess side wall, and
characterised in that the recess (<NUM>) having a side wall (<NUM>) defined by the outer radius portion with a taper angle of about <NUM>° from the rotational axis and in that the reverse drive portion of the driver comprises a concave portion (<NUM>') and catch portion (<NUM>"), wherein the catch portion defines a reverse drive angle of about <NUM>°.