Патент USA US3079978код для вставки
.Ma_rch 5, 1963 T. J. BUCKLEY 3,079,968’ SELF—LOCKING SELF-TAPPING SHEET METAL SCREWS Filed Aug. 26, 1959 FIGJ. , FIGZ. FIG.3. FIGS. FIG.6. w". INVENTOR TIMOTHY J. BUCKLEY BY (514.16% EQ/rao-QFM HIS ATTORN EYS United tates Fatent ice 3,0?9,968 Patented Mar. 5, 1963‘ 2 FIGURE 8 is a view in cross-section taken on line 8—8 £79,968 SELF-LGCKING SELF-TAPFING §IPIEET R/IE'I‘AL SCRE‘WS Deiaware Filed Aug. 26, 1959, Eel‘. No. 836,108 7 (Ilaims. (El. 151-—7) of FIGURE 1; and FIGURE 9 is a view in cross-section taken on line 9-9 of FIGURE 2. Referring to the drawing, FIGURE 1 discloses a tapered self-tapping screw 2 having a sharp point or tip 4 and an elongated cylindrical shank portion 6 adjacent the head 8 of the screw. A portion 10 of the shank adjacent to the tip of the screw 4 is greater in diameter than the shank This invention relates to improvements in self-tapping 10 portion 6. Threads 12 which extend around the shank portion of enlarged diameter also have somewhat greater sheet metal screws and relates more particularly to self root and crest diameters than elsewhere along the shank. tapping sheet metal screws which are also self-locking. The illustrated shank and thread portions of enlarged Machine screws, bolts, and the like have been rendered diameter are shown in exaggerated fashion in the draw— self-locking by providing them with resilient inserts as ings for the purpose of description, but in actuality the disclosed in the Brutus US. Patent No. 2,520,121 and the increase in diameter over shank portion 6 and thread por Boots Patent No. 2,539,887. The resilient inserts provide tion 14- adjacent screw head 8 is preferably less than .005 a locking action by forcing together the threads of the inch. mating threaded elements at the opposite sides thereof Located in the upper shank portion 6 is a radial cylin from the insert. Attempts have been made to use such in drical hole 16 (FIGS. 1 and 8), in which is mounted a serts in self-tapping sheet metal screws but these attempts resilient locking plug 18, formed of “nylon” or its equiva have failed for the reason that when the screw is driven lent. The insert 18 is of such length with respect to the into the sheet metal the outer portion of the insert invari hole, that its outer end projects beyond the root line of ably is sheared off or damaged to the extent that its lock the threads and may extend ?ush with or slightly beyond ing action is destroyed. Damage occurs to the insert even the crest of the threads 12 adjacent thereto. As explained when an expansion space is provided in the insert-receiv above, the plug is deformed when the screw is driven into ing recess of the screw as shown, for example, in the a hole or an upset portion around a hole in a sheet of Brutus U.S. Patent No. 2,520,121. metal and due to its resiliency reacts to urge the screw Study of the difficulty encountered with the use of sideways into increased cohesive frictional engagement resilient inserts in self-tapping screws leads to the con with the metal diametrically spaced from the insert or clusion that the zero clearance between the sheet metal plug. and the screw driven into the hole causes the projecting When the screw is driven into a drilled or punched hole portion of the insert to be abraded or sheared away as in a piece of metal which may or may not be upset to the screw was driven into the metal. As a result, the part provide additional thickness, the thicker portion 10 of the of the insert, if any, left projecting beyond the roots of shank and threads of greater crest diameter slightly en the threads of the screw is of insu?icient size to produce large the hole in the metal to provide a slight clearance the reaction e?ect required to lock the screw in the metal. between the shank portion 6 of the screw and the side of In accordance with the present invention, self-tapping the hole and to enable the resilient insert to be deformed screws are provided which, as they are driven into the between the screw threads, screw shank and the side of the sheet metal, tap threads therein and a clearance for the hole without abrading or shearing off the projecting por resilient insert su?icient to prevent the portion of the in tion of the insert. The .005 inch diameter clearance, or sert extending beyond the roots of the screw threads from .0025 inch radius clearance or less is insufficient to result being sheared or abraded away. in a “loose ?t” of the screw and the resiliency of the in More particularly, the new screws have enlarged por sert and its reaction force securely locks and retains the tions between the tips or points of the screws and the screw against rotation in the metal. resilient inserts therein to render the hole into which the FIGURE 2 is a modi?cation of the invention in which screw is threaded slightly oversize and thereby provide the self-tapping screw has a threaded shank provided with the necessary clearance enabling the projecting portion of a tip 4-’, a shank portion 6’ of generally uniform diameter the insert to be deformed and compressed, without shear adjacent head 8', a thickened portion 10', and threads 12' ing or abrasion, between the screw and the wall of the conforming to the shank 10’ as described above. The mating hole, and without however producing a loose ?t shank contains a rectangular slot or recess 20 (FIGURES of the screw in the hole. 2 and 9) for receiving a strip 22 of resilient material The insert may be in the form of a cylindrical plug, a such as “nylon” or its equivalent. The slot 20 may be rectangular or tapered strip, or the like, seated in a slot formed by a milling operation with a circular cutter to of general complementary shape. form concavely curved bottom portions 24 in the recess For a better understanding of the invention, reference at the ends thereof. The strip 22 may be shaped to be may be had to the accompanying drawings, in which— press ?tted in the slot but is somewhat shorter in length FIGURE 1 is a side view of a typical self-tapping screw than the slot to provide expansion areas 24 at each end embodying the present invention; of the slot formed by the milling cutter. As shown in FIGURE 2 is a side view of an embodiment of the FIGURE 9, the resilient insert extends about flush with present invention, containing a modi?ed form of locking or slightly above the crests of the threads 14'. In the area insert; where the threads 12’ are of greater crest diameter, the FIGURE 3 is a side view of a modi?ed form of self outer surface of the insert is slightly below the crest of tapping screw utilizing the present invention; the threads. When the screw is screwed into a hole in a FIGURE 4 is a side view of another form of self tapping screw according to the invention; FIGURE 5 is a side view of still another form of the piece of metal, some of the insert at the thickened portion of the shank may be abraded or sheared away, but the self-tapping screw; part of the insert strip in the shank portion 6' will be FIGURE 6 is a side elevational view of a self-tapping screw utilizing a modi?ed form of locking element of essentially intact and will provide the desired locking the type shown in FIGURE 2; FIGURE 7 is a side elevational view of a modi?ed self tapping screw having a locking strip mounted thereon; action. FIGURE 3 illustrates another type of self~tapping screw having a ?at tip which is of a type used in sheet metal, plastics and the like. This screw has threads 26 and a 3,079,968 id, substantially in excess of .005” greater in diameter than the shank portion having said- recess and insert-1 member therein. 3 shank‘ portion 28 of ‘greater diameter than the remainder of the- threads, and. shank. of the screw. A; resilient insert 32 is located between the head of the screw and the en larged portion of the shank. 3. A self-tapping screw as claimed in claim 1 wherein “FIGURE 4f.'illustratesl'ai screw similar to the screw CI said recess is substantially cylindrical and extends radially shown in FIGURE 3 except that the thread 341is- inter of the screw shank, and said resilient insert member is rupted to improve its tapping action.- 'The '?rst three frictiona'lly engaged within said recess and has a‘ portion threads are shown as interrupted so as to provide‘ a cut extending substantially to the crests of the thread adja surfatce 3810111 the third thread‘ which‘: is one of the cent thereto. threads of enlarged" diameter- The leadingend: of thread‘ 4. A self-tapping screw as claimed in claim- 1 wherein 40 is double thread of reduced height. This enables the said recess is a slot in and extending lengthwise of one complementali threads: to be tapped‘ in thev sheet metal or side of said screw’ shank and said resilient insert member is substantially complemental to and ?ts Within said slot with its? outer‘ edge extending beyond th’e'roots‘ of the the: likerwith‘out undue; strain on‘. any one or' any portion of the“ threads; of the screw:. thread’ adjacent thereto: FIGURE 5 isv a: modi?cation‘- of the‘ embodiment of 3 showing at longer screw having the‘ enlarged‘ or' thickened! portion of the’ shank. and‘ the‘ larger diameter threads spaced‘ farther' from the free end' or tip‘ of- the screw/than‘ in the screws‘ described above. The expansion‘ tovmaximumr diameter in they FIGURE‘ 5" embodiment is more gradualgiresulting'in easier'driv-ingof the'screw‘int'o the sheet metal. 5.v A-self-tapping screw as claimed‘ in‘ claim' 4' wherein said slot- extends parallel to the axis of the: screw and substantially.v the full length‘ thereof. ‘ 6'. A self-tapping screw as‘ claimediin‘ claim 4' wherein said‘ slot comprises end portions- permitting- expansion of saidr'esilient insert’ member. ' 'Ii'he screw/shown i?‘FIG'UR-E‘G istsimilar to thetscrew 7‘. A self-tapping sheet’ metal screw comprising a head; a- shank ?xed'to said head‘ and having: an outer end2 of shown‘. i111~ FIGURE 3‘ but having? therein av slot 44? and' smaller diameter than‘ the remainder o?said shank‘ps'aidi resilient locking-t strip‘ 46 similar to?- the locking’ strip'iil shank having ar-?rst shank-‘portion adjacent said h‘eatl'fptir2 lust'ratedl in‘: FIGURE‘, 2'.’ tion‘» and1 a second shank portionbetweenl said-‘outer end and‘ said ?rst shank portion‘,-a1r'e‘cess'- in‘ said’ shank exi-v tending. into said ?rst shank portion; a resilient locking"? insert inlsaidirecess, said second‘ shank portion being of greater diameter than said‘ ?rst'nameds'hank portion; and‘ The“- screw: shown: in: FIGURE7 i‘sisimilar'to‘ithat shown ' in FIGURE; 6‘ with the‘ exception? that~ the threads‘ are in terrupted as: at 48'. Although. the" resilient, insertsi arev preferably made" of’ 0 nylon,‘ other.’ materials resilient‘: or‘ elastic in nature and c'a‘pab'lef'of providing-a“ grippin'gvsurface with theimetal-or oth'er‘composi'tion of the: female member can be utilized; I claim: 1 a plurality of convolution's'of‘ a helical~ screw threadio'n said shank, said- tliread' being" of substantiallyvv uniform cross-section throughout‘ themajor portion of its length? for tappingithreads'in sheet metal, said?thread'havingianl e 1. A self-tapping, self-locking sheet metal screw com 35 axial root' dimension‘ at least as great as the axial base prising; a; shank having: a: plurality‘ offc'o‘nvolu‘tions'v of? a dimension of said thread,is'aid second named slia'nk‘rporl helical screw thread: thereontfor' tapping; threads in: sheet tion'havin'g' thread portions thereonl of slightly" enlarged metal, said: thread being;off'substantially‘uniform cross; section. throughout: the major: portion 0f'its1 length and root and crest‘ diameters adapted to- form-haul enlarged female’ socket thread‘ providing clearance- for expansion» having an axial: rootl dimension; at: least as-Lgreat'! a's-th'ei 40 of said resilient‘ insert‘, s'aid'insert' extending radially! be; axiallb'as‘e:dimensioniofi'th'e thread; said“ shankihavin'g 'a'tip' yond the root line ofsaid‘thr'ead onls‘a'id ?rstshankiphr tion. smaller- tharn said‘ shank‘ and: a head: a‘ti the end- of said shankt opposite said tip; . a portion - of said‘ shank: between'ry References Gited-in’the ?le of this patent saidih'ea'diandi tip having‘; threads of greater! root-diameter‘ thanithe-remainder'of sa'idi shank, a- recesslinith'e' side of 45 the‘ s'crew shank,- at=v leastI av part1 of- which‘ is positioned between said? portion of greater‘ root diameter and said head,’ and~a resilient‘insert-member, in‘saidirece'ss extend UNITED‘STA'TES PATENTS . 192,636 ‘1',064§93'4 Collins et all __________ _>__ July» 1877' Ryan .; _______________ “June 17,1913‘ 2,407,160 Kahn ________________ .._. Sept. 3, 1946 2.409538’ Lyon ___-_ ____________ __ Oct. 22, 1946 portion. 2,520,121 Brutus _______________ __ Aug. 29, 1950v 2; A‘ selfita'ppingiscrew as claimed'in claim 1', in‘which said'sh'ank andlthread portionof greater diameter‘ are not 2,539,887 Bo'ots' _____ _-____- ______ __ Jan. 3'0,.1951~ 2,796,906‘ Buckley.‘ ____________ __,__ June 25, .1957} 2,956,293 McKay et al..__'_ _______ __ Oct; 18,1960 ingradially beyond the root’: line, o'f‘sai'd" portion of said‘ thread b‘e'tweeri'said head'an'd ‘said’ enlarged ‘root diameter 50 at".