Патент USA US2300858код для вставки
N°V~ 3, 1942- E. E. ARNOLD ETAL 2,300,858 BUSHING CAP Filed Jan. 29, 1941 2 Sheets-Sheet l l” WITNESSES: 2 QMm/i/i/y , 9M" 7% /Z 4 > INVENTORS MW»? 6 Arno/0’ & 4' Harry J. Z/ngcr/ / W ATTORNEY NOV- 3, 1942- _E. E. ARNOLD ETAL 2,300,858 "BUSHING CAP Filed Jan. 29, 1941 2 Sheets-Sheet‘ 2 > /4' n 50 6 8 ‘ g . 6 \ 28 _ ivy/414% Z5 26 \ § WITNESSE : my, 3, -—/6 _. @dwrép 20 § “T : 5. INVENTORS Patented Nov. 3_, 1942 2,300,858 vUNITED STATES PATENT OFFICE 2,300,858 BUSHING CAP Edwin E. Arnold, Pittsburgh, and Harry J. Lingal, Forest Hills, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pitts burgh, Pa., a corporation of Pennsylvania Application January 29, 1941, Serial No. 376,424 5 Claims. (01. 174-142) The present invention relates to high tension insulating bushings, and it has particular rela tion to a cap structure for such a bushing. Be cause of the difference in temperature coeflicients of expansion of parts of such bushings, it has ?at upper end surface l2, and annular surface creepage ?anges of a usual type (not shown). The conductor 4, which may be either solid or tubular, as illustrated, extends axially through the casing 2 and may be provided within the eas ing with a condenser structure (not shown) of the type well known in condenser bushings. It will be understood that the position of this con ducting stud. This problem presents particular ductor is ?xed with respect to the lower end di?iculty in the numerous cases where it is re 10 of the casing by means of the mounting ?ange quired that the cap or terminal member com or in some other manner well ‘known in the art. pletely close the end of the bushing without the Referring particularly to Fig. 1, the terminal conductor passing therethrough. According to cap 6 is of a hollow construction and de?nes a the present invention, a proper uniform electrical substantially cylindrical interior chamber M ‘at contact between the conductor and the cap is its upper end and a somewhat larger chamber obtained despite any relative movement due to I6 therebelow. The conductor stud is screw expansion by means of a spring device biased be threaded at 18 and a nut 20 disposed thereon, tween the two members. while the end of the cap 6 is closed around the It is accordingly an object of the present in conductor by means of a plate or flange 22 which vention to provide a novel and improved cap 20 is secured to the main cap structure by means of structure for high tension electrical insulating bolts 24. A collar member 25 having vertical bushings. ?anges at 28 is disposed around the conductor 4 Another object of the invention is to provide below the nut 20 and a helical spring designated a bushing that shall permit relative movement by 28 is compressed between it and the plate between the sealed Darts thereof without ad 22 to supply a uniform sealing pressure to the versely affecting the seal between such parts or gasket 8. An insulating washer 29 is preferably the electrical contact between the cap and the disposed between the spring 26 and the plate conductor. 22 to prevent electrical contact therebetween. A further object of the invention is to provide Another resilient gasket member may be dis an. insulating bushing cap in which uniform 30 posed between the main cap structure and the electrical contact is insured between the conduc plate member 22, as indicated at 30. tor and the cap by means of a spring device of To the upper end of the conductor 4 is secured high conductivity material biased between the a spring retaining clip 32 while a spring member two members. 34 is disposed in the upper chamber l4 between Other objects and advantages of the invention its surface and the surface of the conductor. will appear from the following detailed descrip The spring 34 is preferably of a good electrical tion taken in accordance with the accompanying cond-ucting material and its helical turns are in drawings in which the same reference characters a conical form. This spring is compressed be designate corresponding parts throughout. In’ tween the upper retaining clip 32 and a similar always been a diflicult problem to obtain a proper seal at the cap and to obtain uniform electrical contact between the cap structure and the con the drawings: Figure 1 is a side view partially in section and partly in elevation of a terminal cap in accord ance with the invention secured to an insulating bushing; and Figs. 2 and 3 are similar views of modi?cations of the invention. The device comprises, in general, an insulating casing 2, a conductor 4 extending axially there through and a terminal cap designated by 6 seated on the end of the bushing with a two piece re silient gasket structure 8 disposed therebetween. A screw-threaded terminal I0 is disposed on the upper end of the cap 6. The dielectric casing member 2, only the upper end of which is shown, is preferably constructed of porcelain having a 40 clip 33 located just above the threaded portion [8 of the conductor 4 so as to be biased against both the surface of the chamber l4 and that of the conductor. This spring may be readily formed by winding the resilient strip material upon a conical shaped helical mandrel and inner and outer-edges thereof are preferably machined to eliminate the corners and provides ?at en gagement with the surfaces in question. as indi cated at 3B and 38, respectively. It will be un 50 derstood that while retaining clips 32 and 33 are particularly satisfactory with applicants’ structure, other retaining means may be sub stituted therefor under some circumstances. The assembly of the unit is preferably made by securing the spring 34 in place on the end of 2 2,300,858 the stud before placing the cap 6 thereover while the remainder of the structure may be assembled ture expansion characteristics of the stud and easing. 2. In a bushing for high tension electrical ap paratus including a tubular casing of insulating in the art. The construction of Fig. 2 differs from the U! material and a rigid conducting stud extending axially through said casing in ?xed relationship above in that a pair of helical springs of trian in a manner which will be evident to those skilled gular cross section are employed to provide con tact between the cap and stud. The inner of thereto, a metallic cap engaging an end of said casing to close it, said cap defining a substan— these two springs is designated by 110 and is tially cylindrical chamber about the end of said wound with its flat edge contacting the stud while 10 stud, and a helical spring comprising substan tially conically disposed turns of resilient metal the outer spring 42 is wound with its flat edge strip arranged around said stud with its opposite to the outside and engaging the walls of the chamber Ill. The two springs are compressed by edges biased against the surface of said stud and the upper and lower retaining clips 44 and 46, the surface of said chamber respectively to in respectively, and are so disposed that each turn of one of them falls partly within the space be tween adjacent turns of the other so that a pres sure is exerted both inwardly against the stud 4 sure uniform electrical contact therebetween de spite relative movement between the cap and stud. 3. In a bushing for high tension electrical ap paratus including a tubular casing of insulating and outwardly against the cap. In the modification of Fig. 3, a nut 25’, which 20 material and a conducting stud extending axially through said casing in fixed relationship there is used to compress the spring 28 in the same manner as described with reference to the other to, a metallic cap engaging an end of said cas ?gures of the drawings is provided with split ?n ing to close it, said cap de?ning a substantially cylindrical chamber about the end of said stud, and a pair of helical springs of substantially tri angular cross section disposed within said cham ber about said stud, one of said springs being ar ranged with one of its sides contacting said stud and the other being arranged with one of its sides contacting the surface of said chamber in staggered relationship to the first said spring so that the turns of each spring are partially dis posed within the substantially triangular spaces between turns of the other. 4. In a bushing for high tension electrical ap~ paratus including a tubular casing of insulat ing material and a rigid conducting stud extend gers M3 for engaging the surface of the chamber l4’. These ?ngers may either be themselves re silient with an outward bias, or else, they may be grooved, as indicated at 45, to receive a spring 50. This spring 5!! is of the split ring type which facilitates assembly of .the device in a manner which will appear evident from the foregoing de scription. With the constructions shown in the present invention, the spring devices insure a de?nite and uniform electrical contact between a conduc tor and the terminal cap despite any relative ax~ ial movement therebetween which may result from the different coeflicients of expansion of the casing 2 and the conductor itself. The spring contact arrangement further cooperates with the means for clamping the cap in place on the di electric casing to provide a compact and efficient arrangement. With the insulating washer 29 disposed between the cap and the main sealing spring 25 no current can pass through the lat ter member With the result that no damaging heating thereof can occur. Even when this ing axially through said casing in ?xed relation ship thereto, a metallic terminal cap engaging an end of said casing to close it and de?ning a chamber with an even cylindrical surface about the end of said stud, helical spring means dis posed around said stud in resilient engagement with its surface and the surrounding surface of said chamber, and means projecting from said stud in engagement with the ends of said spring washer is not provided the low resistance path provided by the invention prevents the current through this spring 25 from reaching a value means to con?ne it to a predetermined longitu terpreted in view of the prior art. paratus including a tubular casing of insulating dinal portion thereof, whereby said spring means moves with said stud in sliding electrical contact 50 with said chamber surface in response to rela high enough to impair its strength, tive axial movement between said stud and cap Since various modi?cations of the structure due to the difference in temperature expansion shown in the drawings will appear to those characteristics of the stud and casing. skilled in the art, it is intended that the inven 5. In a bushing for high tension electrical ap tion be limited only by the appended claims, in We claim as our invention: 1. In a bushing for high tension electrical ap paratus including a tubular casing of insulating material and a rigid conducting stud extending material and a conducting stud extending ax ially through said casing in fixed relationship thereto, a metallic cap engaging an end of said casing to close it, said cap de?ning a substantial axially through said casing in ?xed relationship 60 ly cylindrical chamber about the end of said stud, thereto, a metallic terminal cap engaging an end of said casing to close it, said cap de?ning a sub stantially cylindrical interior chamber about the end of said stud, and metallic helical spring means disposed around said stud in resilient en gagement with its surface and the surrounding surface of said chamber and in slidable relation to at least one of said surfaces, whereby said spring means maintains a slidable resilient elec trical contact with one of said surfaces in re sponse to relative axial movement between said stud and cap due to the difference in tempera a ?rst helical spring disposed in said chamber about said stud and having sloping surface por tions defining an outwardly divergent helical space between adjacent turns, and a second heli cal spring disposed in said chamber in engage ment with the surface thereof and having a cross section such that a sloping portion thereof ex tends into said helical space in resilient engage ment with the turns of said other spring defin ing it. EDWIN E. ARNOLD. HARRY J. LINGAL.