Fastener having multiple-bossed lead

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ITWO:0004 12984 FASTENER HAVING MULTIPLE-BOSSED LEAD

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In the Sold of fasteners, particularly threaded fasteners, a wide range of configurations are known and currently available. Jh general, threaded fasteners present a threaded shank on which one or more leads are formed. The leads create a helical inclined plane which contacte mating surfaces of one or more mechanical components as thefastener is rotated for insertion or removal. Various threaded fastener designs have been specifically adapted for use with various materials* such as wood, metals, composite materials, concrete, and so forth.

In most conventional threaded fasteners, ahead is formed at the end of the threaded shank to facilitate rotation of the fastener into and out of an ^plication. The 20 shank itself presents a lower tip opposite the head* with the lead of the thread being formed around the shank. The characteristics of the lead determine both the torque required to insert the festener into the application, the torque required to remove the fastener, and the force which resistspullout of the fastener once in place. In most conventional applications, the thread is uniform in shape over the entire shank, with a 25 reduction in height being provided in certain applications, such as for wood or metal screws.

Specialty listeners have bean developed that present a variety of features along the lead, For example, screws having ridges or depressions along the lead have been

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ITWO:0004 12984 developed, such as for penetrating into certain materials during insertion, hi general, however, these designs have presented less flexibility and less than optimal performance in use, There is still a need, therefore, for improved fasteners which can be adapted for particular purposes and materials, through creative lead design. There is a particular need 5 for fasteners which present relatively uniform or constant insertion torque characteristics, with excellent pullout resistance, and which, can be manufactured in straightforward and inexpensive ways.

SI

SUMMARY OFTHEINVE ix*ie

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needs. The fastener presents a lead which includes multiple bosses separated try recesses, In a particularly favored embodiment, two leads of similar geometry are provided. The bosses may be identical to one another along the entire length of the lead, or may be varied to provide the desired characteristics. For example, the lead-in of the bosses need not be identical to die lead-out, and the lead-in and lead-out of bosses along the Length of the leads may vary. Similarly, the length, height and foimofthe bosses may vary along the length of the leads. Where more than one lead is provided, overlap between the bosses formed on the leadmay beprovided so as to maintaingenerallyuniform torque during insertion of the fastener in an application. The recesses between ths bosses also offers locations in which certsan materials maybe allowed to collect, such, as cold-flow plastics, plaster or concrete, or so forth. The lead-out of the bosses may he formed so as to provide enhanced pullout resistance.

The fasteners designed in accordance with the present techniques may be used in a wide variety of applications. They are particularly well suited, however, to applications in

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metals, plastics, wood, concrete, and other composite materials. The overall configuration of the leads and bosses can be adapted specifically to such materials, and to the desired level

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12984 of msertion torque pullout resistance, aud so forth. The fasteners are particularly adapted, moreover, for mass production, such as through roll thread fonning operations.

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reading the following detailed description and upon reference to the drawings in which:

Figure 1 is a prospective view of a threaded fastener in accordance with aspects of the present technique;

Figure 1A is a sectional view through the festœer illustrated in Figure 1 showing the configuration of bosses formedin the two leads of the embodiment of Figure 1;

Figure 2 is a diagram illustrating an exemplary lead of a fastener suchas that illustrated in Figure 1;

Figure 3 is a diagram illustrating an exemplary configuration of two leads far a fastener such as that illustrated in Figure 1 in accordance with particular aspects of the present teriFmîqne;

Figure 4 is a diagram illustrating evolution ofcharacteristics of a lead for a fastener of the type illustrated in Figure 1 inaccordance with aspects of the present technique;

Figure 5, is diagram similar to that of Figures 2,3 and 4, illustrating a particularly preferred configuration of a double-leadfastener in accordance with aspects of the present technique;

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Figure 6 is a plan view of two leads, shown extended vertically, ilustraling overlap between portions of the leads;

Figure 7 is apian view of a portion of a tool used in forming a die for machining the fasteners, such type illustrated in Figure 6, in a roll threading operation;

Figure 8 is an elevations! view of a face of an exemplary die fanned through the use of a tool such as that illustrated in Figure 7;

Figure 9 is a flow chart illustrating exemplarysteps in a manufacturing process far creating fasteners in accordance with foe present technique ihrotigh electric-discharge

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Figure 10 is a perspective view of an alternative configuration for a fastener in accordance with aspects of the present technique having a single leach and

Figure 11 is a graphical representation oftorques encountered for insertion of a double-lead fastener in accordance with the aspects of the present technique.

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Turning now to the figures, and referring first to Figure 1, an exemplary fastener formed in accordance with aspects of the present technique is illustrated and designated generally by foe reference numéral 10. Fastener 10 includes a head 12 a tip 14, hnd a threaded shank section 16. Any suitable head and tip portion may be employed in the fastener, such as the hex head illustrated in Figure 1. The tip portion may be similar fo diameter to foe threaded shank portion, or may be profiled, such as to facilitate insertion into certain materials.

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In the illustrated embodiment fastener 10 has one or more leads which are configured in accordance with aspects of the present technique. In the embodiment illustrated in Figure 1, two such leads 18 and 20 are provided and have similar or

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16. As described below, the configurations may also be different between the multiple leads, where such multiple leads are provided, and the configurations may evolve along the length of each lead. Even where a single lead is provided, as discussed below, features formed along the single lead may evolve between tip 14 and head 12. In general, each lead presents a base 22* and a series of bosses 24 rising from the base, The particular forms of the bases and bosses provided on the leads, and presently favored methods for forming these features .«ro described in greater detail below,

Figure 1A illustrates â sectional view through the fastener of Figure I. As shown in Figure 1Λ the bosses 24 formed along the shank of the fastener are positioned with 15 îcspett to one another to provide a desired pattern for entry and exit of the bosses into a material being fastened. In particular, the bosses 24 formed on lead 18 are positioned so as to correspond to recesses formed between bosses on lead 20. As described more folly below, it has been found the illustrated configuration of corresponding locations for recesses and bosses on the doublcdead fastener fodtitaies insertion, enhances resistance 20 to puflout, aod provides locations in which materials may settle or flow. It may also be noted from the illustration of Figure 1A that in the presently preferredconfiguration, two bosses 24 axe located for each revolution of leads 18 and 20, with the bosses being offset from one another by 180 degrees.

Figure 2 illustrates an exeanplaiy thread profile for one of the leads in a fastener of the type illustrated in Figure 1. In the diagram of Figure 2, reference numeral 26 refers to the root of the thread, while reference numeral 28 refers to the thread crest profile itself For the sake of illustration, multiple base profiles are illustrated, including a fust base 30, a second base 32 and a third base 34. Along the length of the thread profile 28, these

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12984 bases may be referred to as successive features N+l, and N+2. Similarly, a series of bosses aie formed between the bases, including a first boss 36 adjacent to base 30, a second boss 38 adjacent to base 32, and a third boss 40 adjacent to base 34. These bosses, too, may be referred to as successive features in, N+l and N+2. In the embodiment illustrated in Figure 2, each of the bases 30,32 and 34 arc generally identical to one another, -while each of the bosses 36,38 and 40 are similarly identical to one another. That is, the length, height, form, andadjacent features of each, of these bases and bosses are similar between the successive N, N+l -andN+2 levels.

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desirable in certain applications, die present technique also permits features to be varied along the length of the lead, In the embodiment illustrated in Figure 2, for example, each boss presents a lead-in profile and a lead-out profile which can be tailored to specific applications, such as to provide a desired insertion torque and pullout resistance. In. the embodiment illustrated in Figure 2, for example, the boss 36 at the N level has a lead-in 42 and a lead-out 44, while bosses 38 and 40 at the N+l and N+2 levels lead-ins 46 and 50 respectively, and lead-outs 48 and 52 respectively. As described in greater detail below, these features can be altered along the length of the fastener to provide differing characteristics, such as for low insertiontorque near the tip of the fastener with greater insertion torque as the fastener is progressively inserted, or vise versa. Similarly, pullout resistance can be varied by altering the same lead-in and lead-out protiles. As will be appreciated by those skilled in the art, in general, thelead-in profile will have a greater effect on the insertion torque, while the lead-out profile will have a greater effect upon the pullout resistance.

Other features of the thread profile 28 illustrated in Figure 2 may also be adapted for specific applications. By way of example, each base 30,32 and 34 has a length, such as length 54 illustrated for base 32, which may be altered along the length of the fastener. That is, bases in levels in N+l and N+2 may differ from one another, where desired.

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Similarly, each boss 36,38 and 40 has a predetermined length, represented by reference numeral 56 for boss 38, which may be adapted and varied along th© length of the fastener between the respective lead-in and lead-out profiles. Moreover, the height of the bases, as indicated at reference numeral 58, may be altered, as may the height 60 of the bosses.

Other features, such as fee configuration and shape of the bosses and bases may also be changed or evolve along the length of the fastener as described in greater detail below.

Where more than one lead is provided on the fastener, the features along each lead

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generally be positioned to correspond to one another in predetermined manners along the length of theshank. Figure 3 illustrates, for example, profiles of a pair of leads 62 and 64, each presenting bases and bosses a described above with reference to Figure 2- In addition to allowing for adaptation or tailoring of the bosses and bases along the length of each lead, the positions of these features may be provided in corresponding manners, such as to provide overlap 66 between lead-in and lead-out regions, or other regions of the leads, and separations 68 between such features. For example, where two leads are provided, lead-out portions of bosses from one lead may be positioned tocorrespond to lead-in portions of bosses from the second lead. Thus, relatively uniforminsertiontorque

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between the two leads. At the same time, the multiple lead-outs of the bosses from each lead aide, together, in resisting pullout. '

Figure 4 illustrates an exemplary embodiment of a lead profile wherein features including bases and bosses evolve along the length of the lead. As shown in Figure 4, a 25 first base 30 at a level N along fee lead joins a first boss 36 at the N level by a lead-in 42.

The boss 36then joins a second base 32 at a level N+l by a lead-out 44. As fee lead continues, then, bosses 38 and 40 join bases 32 and 34 by lead-ins 46 and 50 respectively, with bosses 38 and 40 terminating lead-outs 48 and 52 respectively. At each level N,

N+l and N+2, then, differing angles and forms may be provided for tile lead-ins and leadCA 02390967 2002-06-19

ITWO:0004

12984

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above.

As illustrated, in Figure 5, in a particularly preferred present configuration, the lead-in profiles of a double-lead fastener correspond in location about the shank to locations of the lead-out profiles of the second lead. Moreover, as shown in Figure 5, it has been found that a relatively shallow lead-in angle, such as 15 degrees, facilitates insertion of the fastener in applications. Excellent pull-out resistance has been found with lead-out angles which are relatively steep, on the order of 45 degrees in the embodiment illustrated in Figure 5. Thus, as noted above, the lead-in and lead-out profiles need not be identical to one another, and optimized profiles, such as a 15 degree/45 degree configuration of Figure 5, may be found to be optimal for certain applications.

Figure 6 illustrates a pair of leads for a fastener of the type shown in Figure 1, provided with bases and bosses which correspond to one another in location and overlap as fflustrat^gcwrally inFigureB. Reference numeals on the first lead 62 are labeled to correspond to those features illustratedin Figure 2, including bases 30,32 and 34, and bosses 36 and 38. Similar or identical bases and bosses are provided along the second lead ¢4, In the plan view of Figure 6, however, it can be seen that the form, referred to generally by reference numeral 70 of each load can evolve along the length of the lead identical along the length of the lead, or may be varied. Similarly, the lead-in form 74 may be modified to provide the desiredperformance characteriatics, particularly foe insertion torque. The lead-out form16 may be tailored ina similar manner. In general, these features may be contoured, angled, or otherwise adapted, and, as mentioned above, neednot be identical along the length of the leads.

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Various techniques may be employed for manufacturing fasteners in accordance with foe features described above. In a presently preferred method, electric-discharge

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12984 machining (EDM) is employed to creators which are then used to roll thread fastener blanks. To facilitate creation of the dies, EDM processes aroused to create the features that evolve along the length of a roll thread forming die of the type generally known in the art Figure 7 illustrates an exemplary machining process for an EDM tool used in this 5 technique. As shown in Figure 7, the tool, designated generally by reference numeral 78, may be formed of any suitable material, typically graphite for EDM processes. The tool presents bosses 80 generally similar to the bosses which will he formed oh the resulting fastener, and bases 82 similar to the bases of the leads desired on the fastener. Where evolution of the features is desired along the length, of the threads, these wifi similarly 10 evolve along the length of the bosses and bases formed on the EDM tool. Creation of the bosses and bases is performed in any suitable manner, such as through milling operations as illustrated in Figure 7. In the embodiment of Figure 7, the features are formed by end milling along tool pads 84,86,88 and 90 to form the lead profiles and the spaces separating the leads. Similar machining operations are performed along the entire surface 15 oftheEDMtoolasneeded,dependinguponth«sizeoftheresultingdieFigure 8 illustrates a die for roll threading a fostener formed through the use of a tool such as that shown in Figure 7. As will be appreciated by those skilled in the art, such roll threading dies, designating gcnerafiy by the reference numeral 92 in Figure 8, 20 include a sharpening section 94 and a thrcad formitiK section 96. Grooves or striations are formed along the die, as shown in dashed Unes Figure d; to Xacilïtate drawing the fastener blank along the die. As will alSehe appreciated by those skilled in the art, such dies are typically employed in pairs, with one die being stationary and a second die oscillating to draw and rotate the fastener blank therebetween and to fotin the threads. By 25 a plunge EDM process, then, features are formed along the die corresponding to the bosses and bases of the fastener lead. Through use of a tool 78 as illustrated in Figure 7, ' then, a die as illustrated in Figure 8 will present a series of linear recesses, including relatively deeper recesses 98 corresponding to the desired bosses along the leads, and relatively shallower recesses 100 corresponding to the bases along the lead profile. It has

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ÏTWO:OOÛ4 12984 been found that the use of plunge EDM processes for forming the dies for the present fastener profiles greatly facilitates the production of the dies, and the formation of the desired profiles along the fastener, particularly where these profiles may be varied.

Figure 9 is a flow chart illustrating exemplary steps in a process for forming dies and listeners in accordance with aspects of the technique described above. The method, designated generally by reference numeral 102 in Figure 7, begins with machining of foe EDM tool at step 104. Again, step 104 may include any suitable machining processes, such as milling of foe features desired on foe resulting fastener. As step 106, the thread rolling dies arc formed by plunge EDM processes to create the progressive thread fomfoig recesses as described above with reference to Figure 8. At step 108 fastener blanks are formed. As will be appreciated by those skilled in the art, such blanks

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threads which are upset from the shank during the thread rolling operation- Finally, at step 110 the multi-boss threads are rolled onto foe blanks through foe use of specially adapted dies such as that illustrated in Figure 8.

Figure 10 illustrates an alternative embodiment in accordance with aspectsof the foregoing technique, wherein a single lead is provided. While foe double-lead configuration provides excellent torque characteristics, in certainapplications, aspects of foe present technique maybe incorporaied with a single lead. Thus, in foe embodiment of Figure 10, rather foau separate leads 18 and 20, foe reference numerals refer to turns of the same lead, For enhancing insertion torque and resistance to pull-out, however, We forgoing teachings wifo regards to the presence of bosses 24, and to foe configuration of thë bosses.

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As noted above, the present technique provides for excellent insertion torque and high resistance to pull-out Figure 11 illustrates exemplary insertion torque of a fastener

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ITWO:0004 12984 having two leads with correspoudingly located bosses and recesses as described above. As shown in Figure 11, reference numeral 120 refers to a torque curve for insertion torques as the fastener is inserted into a base material. As illustrated in the Figure, the torque curve begins at a fairly low level 122 as the fastener is begun to be inserted. Thereafter, torque increases somewhatwifhin amicldle range 124, but remams relatively constant as compared to conventional lobed fasteners. While some undulation maybe encountered where bosses begin entry into the material, it has been found that such changes in insertion torque are extremely minimal. As also noted above, the present technique provides a fastener having excellent resistance to pull-out It has been found, in particular, that ratios in excess of 1:1 10 can be obtained through the present technique Ç.e., pullout to insertion torques). While conventional festeuers may obtain ratios on tiw order of 0.8:1, tests have indicated that double-lcad festeuero configured in accxxdance with the foregoing teachings can obtain ratios on the orderof 1.1:1 (in materials such as nylon) end higher.

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forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should, be Understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of 20 the invention as defined by the following appended claims,