Патент USA US3099714код для вставки
July 30, 1963 H. NAxMER 3,099,704 THREADED PLASTIC ROD WITH MOLD BURR FOR LOCKING FUNCTION Filed April 19, 1957 . 3K lr-lIrF/g l FNÉ’Í’ b. \ 4 3 1 .f5 Í I F192 7 Ia , 15 1 Í „4 3 É INVENTOHSI HUBERT NA! MER ..1 dts zi " mi 3,099,704 Patented July 30, 1963 I 2 3,099,704 6 in 'order rto ensure suthciently «long electrical creep paths. Because the danger residing »in the formation of creep paths can never be entirely precluded it is `often neces THREADED PLASTIC ROD WITH MÜLD BURR FOR LOCKING FUNCTIÜN sary to arrange the bolts in such a manner that they can Hubert Naimer, Schumanngasse 35, Vienna XVIII, Austria Filed Apr. 19, 1957, Ser. No. 653,794 Claims priority, application Austria Apr. 23, 1956 be earthed. In many cases only the fultilling of these requirements necessitates the electrical apparatus to be 1 Claim. (Cl. 174-138) sons or in View of the electrical power to be handled. In that case a certain «alleviation can be provided by sur made larger than would be required tor mechanical rea In the construction of electrical apparatus it is often 10 rounding the bolts with lan insulating tube but that meas ure renders also the construction yof the device more gether and to hold them together by tie rods. The lami complicated. nated core of an electromagnetic device or a switch as is In order to avoid said disadvantages it is proposed ac diagrammatically shown in FIGS. 1 and 2 of the drawing cording to the invention that the tension element con may be referred to as` examples. In that drawing FIG. l sists exclusive-ly of -a thermoplastically deformable, elec is a side View, partly in section, ot a switch composed of trically-insulating plastic, which is of high tensile strength four identical units, and FIG. 2 is a top plan view of and is moderately ilexible and tough `at normal temper a switch unit. The problem with which the invention is atures, and is equal to or better than polyamide-base plas concerned may be set forth iirst with reference to the tic in all said propenties. Superpolyamides have proved necessary to force a plurality of structural elements to latter iigure. The switch apparent from FIGS. l and 2, which is 20 particularly satisfactory in that connection. Superpolyamides have a melting point of about 200° shown in the left-hand part of FIG. l in a sectional view C. and a strength which is suiiìcient for the present pur taken on line l--l of FIG. 2 and in the right-hand pant poses in a temperature range of _20° to at least +l30° of FIG. l in a sectional View taken on line Ia-Ia of C. In that temperature range their tensile strength is FIG. 2, whereas the latter is a sectional view taken on 25 50G-600 lig/sq. cm., which is less than that of iron. line II-~II of FIG. l. The switch which is apparent trom This can easily be compensated by the fact that owing said iigures has an operating shaft 1 provided with cams to the excellent insulating properties of said plastics no 2, which coact with rollers 3 acting by means of forks consideration has to be given Iany longer to creep paths. 4 on plungers `5, with which the jumper bridges 6 are Thus the diameter of the plastic tie bolt can be increased connected, which can be lifted against the action of the 30 and yet the bolt can be disposed more closely to the live «closing springs 7 from the countercontacts t5 having parts. It must also be considered that tension members terminals 9‘. The shaft 1 extends through the bottoms of iron are generally overdimensioned in a high degree. of casing parts 10, lila, ltlb, 10c and a cover 11 and may Because such plastics are thermoplastic they can be be rotatably supported in known manner. The shafts 12 of the rollers 3 extend through the prongs of the forks 35 made by injection moulding in multiple moulds, with head and screw thread, so that the separate forming of the 4 and are guided in slots 13l formed in the casing part screw thread is eliminated as well as any surface iinish lû-liic and in the cover 11. The casing parts 1ti~1ilc ing treatment. Owing to the elastic properties of such and the cover 11 are held together by four tie bolts 15. plastics, split locking rings and the like are eliminated and Such a switch construction is known. The number of it is easily possible to connect the nut and bolt by local casings 10 may vary within wide limits. 40 welding with the aid of a soldering iron or the like to The invention is concerned more particularly with a special construction of tie rods of substantial length, illustrated by the bolts 15, which are found wherever several or many structural parts must lbe held together by tie rods, the length of which is a multiple of their 45 diameter. These tie rods consist in practice generally of metal and owing to their considerable length are not designed permanently and perfectly secure them against undesired opening, particularly if the nut consists also of thermo plastic material. It is thus «apparent that the Substitution of the usual tie rods of metal by tie rods of thermoplas tically shaped suitable plastics ensures important advan tages not only from manufacturing but also from the design aspect. `Electrically non-conductive screws have already been as headed screws but represent bolts having screw threads at both ends for threaded engagement with a nut with 50 proposed which consist of a metal core «and a plastic cover ing which forms the screw thread and the screw head. locking ring or with a double nut. S-uch a -bolt is ap~ parent from FIG. 3. The construction and arrangement of such metal t-ie rods in electrical devices must meet several requirements. In the case of a composite switch of the type shown in 55 FIGS. 1 and 2 these requirements are as follows: >For cost reasons the tie rod consists in most cases of iron but in that case it must be given a surface protection, In that known screws the metal core has a ribbed sur face with which it is embedded in the plastic to ensure a torsion-resistant and tension~resistant connection there with. That prior proposal relates to a countersunk screw rather than to a tie rod; whereas a countersunk screw cooperates with the nut thread, as a rule, over a length which is a multiple of the diameter of the pin, this is not the case with tie bolts acting in the manner of a screw or in most cases by Ielectro-cadn‘iiumplating, electro-galvaniz ing, electro-nickelplating or the like. This is necessary 60 rivet. It was not recognized that tension-stressed struc tural elements of the present type can be made entirely of because the switch (or another electrical apparatus) is thermoplastics and the use of metal cores can be entirely often used in aggressive atmospheres or in moist rooms. eliminated and that it is also possible to provide tension The screw thread is either produced by machining or in elements which combine the advantages of perfect insu a thread rolling machine. This requires in the iirst case tools subject to a particularly high wear and in the second 65 lation with suiiicient strength «and moderate plasticity, and which are formed with force-transmitting surfaces .which case also an expensive machine. Similar requirements are subjected to shearing stress and are not larger or not exist regarding the nuts, the screw thread of which must substantially larger than in the case of a pure metal con in any case be cuit. Thus the making of such bolts takes struction. -It is also not new to use rivets of thermoplas considerable time. As to the arrangement of these bolts in the switch there 70 tics; this applies also to electrical apparatus. This has is the requirement «that the bolts must be sufficiently spaced always concerned only short rivet pins, the length of -which from live parts, e.g. the terminals 9 or the jumper bridges was only a small multiple of their diameter so that a good 3,099,704. heat soaking of the entire rivet shank and thus a good lill ing of the rivet hole was achieved when the rivet pin was aligned parts of an electrical apparatus, said rod having heated in order to form thel second rivet head. Highly stressed tie rods of large length (i.e., of a length which entirely precludes a continuous engagement of the rod of a thermoplastic resin at least equivalent to polyamide periphery with the hole periphery and which is practically unlimited) and which consist of plastics are an entirely new structural element in electrical apparatus. As is shown in FIG. 4 the present tie rod 20 may sub stantially take the form of a headed screw of metal. Contrary to metal tie rods the head 21 may now be pro vided because its formation in an injection mould involves no diñìculties and the mould may easily be adapted to the manufacture of ties of dilîerent length by means of inter mediate mould sections. The screw thread 22 is also pro duced in the mould and is used 'without any subsequent machining. The (exaggeratedly shown) burr 23, which is due to the mould is not removed, for reasons which Will be described hereinafter. Another advantage of the plastic tie rods according to the invention consists in that when constructed as threaded bolts they can easily be made self-locking. 'lf the spontaneously formed burr 23, which is due to the split injection mould, is left on the bolt 20, as is apparent from FIG. 4, the burr will be deformed by the nut 24 when the latter is subsequently applied to the bolt. This has proved an excellent lock for the nut even if the same does not consist of plastics (the invention being not re stricted to the use of plastic nuts). r'That burr need not be thicker than the one which is formed where good 30 moulds are used. -It is obvious that such -a burr may also be provided in the nut itself. I claim: A tension-stressed tie rod interconnecting a plurality of a length which is a multiple of its diameter and consisting plastics in thermoplastic deformability, tensile strength, electrical insulating power, ilexibility and toughness at normal temperatures), said rod being injection molded in a mold having two mold parts with meeting faces and having at least one threaded end portion, and further com prising an axially extending ridge-like burr formed as an integral portion of said threaded end portion at the meet ing faces of the mold and extending radially beyond the threaded crest. References Cited in the ñle of this patent UNITED STATES PATENTS 1,062,000 1,640,433 1,717,287 2,320,947 2,533,894 2,551,834 2,568,640 2,613,397 Hahn _______________ __ May 20, Weldon _____________ __ Aug. 30, Warren et al __________ __ lune 11, Martin et al ___________ __ lune 1, Podell ______________ __ Dec. 12, Ferguson _____________ __ May 8, Kindelberger _________ __ Sept. 18, Borkland ____________ __ Oct. 14, 1913 1927 1929 1943 1950 1951 1951 1952 2,624,916 2,664,023 Persak ______________ __ Tan. 13, 1953 Mugford ____________ __ Dec. 29, 1953 2,754,546 Mason et al. _________ __ July 17, 1956 2,769,202 2,890,845 Thompson ____________ -_ Nov. 6, 1956 Kiekhaefer __________ __ lune 16, 1959 OTHER REFERENCES Product Engineering (published by the lPolychemicals Department, E. I. du Pont de Nemours and Co. Inc.) April 1954, pages 1, 2 and 3. Copy in Division 57.