Method for replacing a tacking fastener
Patent ReferencesInventorAssigneeApplicationNo. 10131629 filed on 03/06/2002US Classes:29/525.11, Threaded fastener29/426.4, By altering or destroying work part or connector29/524.1, Riveting411/43, Frangible mandrel411/69, Expander or sleeve extruded during expansion411/70, Expander having integral pull stem411/501Having plastically flowable or deflectable end, e.g., rivet, etc.ExaminersPrimary: Safavi, MichaelAttorney, Agent or FirmForeign Patent References
International ClassB23P 11/00DescriptionBACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal working and more particularly to a method for assembling that includes disassembling by destroying a temporary connector to create a hole for a permanent separate fastener for temporarily fastening twoadjacent workpieces. 2. Description of Related Art The fuselage of an airplane is constructed from a number of individual panels that are fastened to a frame by a plurality of rivets. Temporary fasteners are typically installed into adjacent parts to insure that the workpieces do not becomeseparated during the installation of the permanent rivets. The temporary fasteners are eventually removed and replaced with a permanent rivet. Some areas of the aircraft are not fully accessible, thereby requiring the use of a blind rivet which can be installed from only one side of a workpiece. Temporary blind fasteners typically contain a shank which extends through a hole drilledthrough the workpieces. The shank has a head which prevents the fastener from falling into the "blind" side of the assembly. The fastener also contains a pull stem which has a stem head located at the blind end of the shank. The stem head is pulledthrough the shank to expand the shank and secure the fastener to the workpieces. The temporary fastener is eventually removed by drilling through the head and the shank with a drill of the proper diameter for the shank of the permanent rivet to beinstalled. It has been found that drilling temporary blind fasteners of the prior art may create splinters and portions of the head that can scratch the surface of the outer workpiece. Additionally, although the head and enlarged shank end prevent thefastener from falling out of the hole, it has been found that the shank may rotate with the drill bit before the head is totally drilled out, preventing further penetration of the drill. Also the rotation of the shank and head remnants spins thesplinters and drill chips to further scratch the surface of the workpiece. It would therefore be desirable to provide a temporary fastener that is easy to remove and does not create scratches on the workpiece surfaces. SUMMARY OF THE INVENTION The present invention is a temporary fastener for fastening two or more adjacent workpieces. The fastener includes a shank that extends through a hole of the workpieces. Extending from one end of the shank is a conical shaped head. Thefastener also contains a pull stem which has a head located adjacent to the blind end of the shank. The stem head is pulled through the shank to expand and tightly fasten the shank to the workpieces. The fastener is removed by drilling through the headand the shank. The present invention is a method of replacing a tacking fastener that temporarily joins two adjacent workpieces with a permanent fastener to permanently join the workpieces. A drill bit is engaged with an inner channel of the temporaryfastener at a head of the fastener. The drill bit has a diameter larger than the head diameter. The head, the shank, the first workpiece, and the second workpiece are drilled through to form a hole through the workpieces. The first workpiece and thesecond workpiece are joined with a permanent fastener through the hole. The diameter of the conical shank head is smaller than the diameter of the drill so that part of the head does not become attached to the drill bit and scratch the workpiece. The conical shape of the head also reduces the volume of fastenermaterial to further reduce the size and amount of chips produced during the drilling process. The tightly engaged shank prevents the fastener from rotating during the drilling operation. BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein: FIG. 1 is a side view of a tacking fastener of the present invention; FIG. 2 is a front end view of the tacking fastener of FIG. 1; FIG. 3 is a rear end view of the tacking fastener of FIG. 1; FIG. 4 is a side sectional view showing the fastener inserted into a hole of two adjacent workpieces; FIG. 5 is a side view similar to FIG. 4 showing a stem pulled through a shank of the fastener; FIG. 6 is an enlarged side view of the shank head pressed into the workpiece; FIG. 7 is a side view showing a drill positioned to initiate drilling; FIG. 8 is a side view similar to FIG. 7 showing the drill drilling through the shank head. DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings more particularly by reference numbers, FIGS. 1 through 3 show a tacking fastener 10 of the present invention. The tacking fastener 10 is typically used to temporarily fasten together two adjacent workpieces. Thefastener 10 includes a shank 12 which has a first end 14, a second end 16 and an inner channel 18 that extends through the shank 12. Extending from the first end 14 of the shank 12 is a conical shaped head 20. The head 20 has an annular lip portion 22that is separated from the first end 14 by a tapered portion 24. The fastener 10 includes a pull stem 26 that extends through the inner channel 18 of the shank 12. The pull stem 26 has a stem head 28 that is located adjacent to the second end 16 of the shank 12. The stem 26 also has a serrated pull portion30 that can be gripped by a pull gun (not shown) to pull the head 28 through the inner channel 18 of the shank 12. The stem head 28 may have a tapered portion 32 which leads the head 28 into the inner channel 34. The tapered portion 32 extends to anannular tip portion 34. The tip portion 34 typically has a diameter larger than the diameter of the inner channel 18 so that the head 28 expands the shank 12 as the stem 26 is pulled through the channel 18. The stem head 28 may have an inner cavity 36which allows the head 28 to contract as the stem 26 is pulled through the shank 12, particularly as the shank expands tightly into the surrounding hole in the work pieces. In the preferred embodiment, the shank 12 is constructed from an aluminum material and the pull stem 26 is constructed from a steel material. The fastener 10 preferably has the dimensions listed in Table I. Various embodiments are listed, eachembodiment corresponding to a particular size of permanent fastener which will replace the tacking fastener 10. For example, the first row of values provide dimensions for a tacking fastener 10 that corresponds to a permanent fastener which has a 0.1562inch diameter, the second row relates to a permanent fastener diameter of 0.1875 inches and so forth and so on. All dimensions are in inches. TABLE-US-00001 TABLE I PERMANENT SHANK HEAD HEAD DRILL SIZE FOR FASTENER DIAMETER DIAMETER LENGTH INSTALLATION PERMANENT DIAMETER D H L HOLE DIAMETER FASTENER 0.1562 0.093-0.097 0.128 0.036 0.098-0.107 #20 0.1875 0.125-0.128 0.170 0.0420.1285-0.1436 #10 0.250 0.155-0.159 0.212 0.055 0.160-0.178 #F FIGS. 4 through 8 show the installation of a fastener 10 to temporarily attach a first workpiece 40 to an adjacent second workpiece 42. The first workpiece 40 typically has an outer flat surface 44. The second workpiece 42 has a blind surface46. The blind surface 46 is typically inaccessible to the operator installing the fastener 10. As shown in FIG. 4, the hole 48 is initially drilled through the first 40 and second 42 workpieces. The hole 48 is typically larger than the diameter of the shank 12 so that the shank 12 and stem head 28 can be easily inserted into theworkpieces 40 and 42. The stem head 26 and second end 16 of the shank 12 extend from the blind surface 46 of the second workpiece 42. As shown in FIG. 5, the stem 26 is pulled through the shank 12. The stem head 28 initially expands the second end 16 of the shank 12 to create an upset portion 50 which bears against the second workpiece 42. As the head 28 is pulled through theworkpieces, the head 28 expands the inner shank portion 52 into tight engagement with the parts 40 and 42. Movement of the head 28 through the workpieces also contracts the annular tip portion 34 into the head cavity 36 to reduce the diameter of thestem head 28. The resultant inner channel 18 is thus smaller in the shank portion 52 than the upset portion 50. As shown in FIG. 6, the conical head 20 is seated into the first workpiece 40 when the stem 26 is pulled through the shank 12. The tapered surface 24 of the head 20 will center the shank 12 with a hole 48 even when the hole diameter varies froma nominal dimension. The installed fastener 10 typically holds together the first 40 and second 42 workpieces while an operator installs permanent fasteners into the workpieces 40 and 42. The temporary fastener 10 is eventually removed and replacedwith a permanent fastener. As shown in FIGS. 7 and 8, a drill bit 54 drills through the head 20, the shank 12 and the workpieces 40 and 42 to remove the temporary fastener 10 and create a hole for a permanent fastener (not shown). The head 20 has a diameter that issmaller than the diameter of the drill bit 54. The smaller head diameter reduces the possibility of the head material splintering and otherwise sticking to the drill 54 and scratching the outer surface 44. Additionally, the conical shape of the head 20reduces the amount of fastener material that is removed by the drill and thus reduces the amount of drill chips produced during the drilling operation. The expanded shank 12 is in tight engagement with the workpieces so that the fastener does not spin during the drill process. Additionally, the angle A of the conical head 20 is preferably different than the drill angle of the drill bit 54. Thedifferent angles reduce the amount of slippage between the bit 54 and the head 20. In the preferred embodiment, the angle A is 100°, with the corresponding angle of the drill being 120°. This assures that the head will finally drill outfrom outer diameter to inner diameter, thereby preventing the separation of a washer-like section of the head to clog the drill and cause the same to stop drilling, and perhaps to wander to damage the work piece. The present invention thus provides atemporary fastener that does not spin or create scratches on the workpiece when removed by a drill. While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not belimited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art. * * * * * Other References
Field of SearchExpander or sleeve extruded during expansionExpander having integral pull stem Frangible mandrel Having plastically flowable or deflectable end, e.g., rivet, etc. PROCESSES Funnel like work-engaging surface cooperating with protuberance on work By altering or destroying work part or connector Threaded fastener |
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