US2591949A - Fuse housing construction - Google Patents

Description

April 8, 1952 s. 1. LINDELL ETAL FUSE HOUSING CONSTRUCTION 3 Sheets-Sheet 1 Filed June 4, 1948 [7206722 5715 J/gardfluzdeld Carl E 56mm 41M m mam, M I

April 8, 1952 1. LINDELL EI'AL FUSE HOUSING CONSTRUCTION 3 Sheets-Sheet 2 Filed June 4. 1948 April 8, 1952 s. l. LINDELL ETAL FUSE HOUSING CONSTRUCTION 3 Sheets-Sheet 3 Filed June 4. 9 8

Qzzfcz Z 1547262 62, @rZ 555k Patented Apr. 8, 1952 FUSE HOUSING CQNSTRUCTION Delaware Application June 4, 1948, Serial No. 31,094

'7 Claims.

This invention relates, generally, to circuit interrupter housings, and it has particular relation to housings for bayonet type fuse devices and constitutes an improvement over that disclosed in Patent No. 2,108,993 which is assigned to the assignee of this application. The housing disclosed herein is for use with the bayonet type fuse tube assembly which is shown in copending application Serial No. 16,179, filed March 22, 1948, now Patent No. 2,531,949, issued November 28, 1950, and assigned to the assignee of this application. However, it will be understood that the housing construction disclosed herein can be employed interchangeably with the housing shown in said patent and can be employed in combination with the bayonet type fuse devices disclosed therein.

Among the objects of this invention are: To avoid the two step counterbore in the porcelain housing shown in said patent; to make it unnecessary to mask the line conductor openings in the counterbores preparatory to roughening the alloy receiving surface of the housing; to provide a central longitudinal bore of uniform diameter in the porcelain housing counterbored at the ends with the inner end surfaces of the central bore roughened to receive cement or alloy for holding line terminal contact assemblies in place therealong; to guide the fuse tube assembly through the housing and its lower ferrule into engagement with the lower contact assembly; to reduce the amount of cement or alloy required for cementing the line contact assemblies in place and also the amount of metal in said contact assemblies over the amounts required for the construction shown in said patent; to prevent the flow of molten alloy into the bore of the housing; to limit the maximum possible outward movement of the spring contact fingers of the contact assemblies as when the fuse tube is being inserted forcefully into the housing and the fuse tube ferrules are thrust into the contact assemblies somewhat eccentrically, such movement outwardly being limited Within the elastic limits of the material in order to prevent individual contact fingers from taking a permanent set resulting in reduction in contact pressure; and to reenforce the portion of the upper contact assembly which is subject to shock incident to operation of the fuse device in interrupting heavy overload currents.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiments thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention, reference can 7 be had to the following detailed description, taken together with the accompanying drawings, in which:

Figure 1 is a view in side elevation of a circuit interrupter housing constructed in accordance with this invention and mounted on a cross-arm by a suitable cross arm bracket;

Figure 2 is a longitudinal sectional view throughthe housing of the circuit interrupter shown in Figure 1, the showing being at full scale and including a showing of the bayonet type fuse device illustrated in the copending application above referred to;

Figure 3 is a view, similar to Figure 2, illustrating only the housing and showing the terminal assemblies and the insulating guide sleeve in elevation;

Figure 4 is a longitudinal sectional view, at-a reduced scale, of the porcelain housing shownin the preceding figures;

Figure 5 is a top plan View of the upper line contact assembly shown in Figure 6;

Figure 6 is a view, in side elevation, of the upper line contact assembly;

Figure 7 is a view, in side elevation, of the lower line contact assembly;

Figure 8 is bottom plan view of the lower line contact assembly shown in Figure 7;

Figure 9 is a plan view of a soft rubber gasket that is employed in conjunction with each of the line terminal contact assemblies for preventingthe flow of molten alloy into the bore of the housing;

Figures 10 and 11 are side elevational views of a modified form of upper line contact assembly showing a modified form of gasket engaging shoulder and also a modified form of. gasket; and

Figure 12 is a detail sectional view showing how the contact assembly shown in Figures 10 and 11 is positioned in the porcelain housing Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character l0 designates, generally, a cylindrical housing that is formed of wet process porcelain. The housing It] has corrugations II in its outer surface to increase th leakage distance between its ends. It has a central clamp portion l2 to which a metallic mounting bracket [3 can be secured. As shown, the bracket I3 can be attached to a cross arm clamp M which is secured to a cross arm [5 in conventional manner. At the upper end of the housing l there is a handle l6 which also is formed preferably of wet process porcelain.

As shown more clearly in Figure 2 of the drawings, a threaded insert I! is cemented, as by alloying, into the under side of the handle l6 for threaded attachment to a bayonet type fuse tube assembly which is indicated generally at l8 and which is described in more detail in the copending application above referred to. For present purposes, it is pointed out that the fuse tube assembly l3 includes a fuse tube 19 having upper and lower fuse tube ferrules 20 and 2| at its ends which are arranged to make contact engagement with upper and lower line terminal contact assemblies that are indicated, generally, at 22 and 23 respectively. The upper fuse tube ferrule 20 has a garter spring 24 which, as described in more detail in the aforesaid patent, is arranged to be expanded radially together with an underlying convolutely wound leaf spring when the fuse link within the fuse tube l9 blows as a result of the gas pressure incident to the circuit interruption of heavy currents. The expansion of the garter spring 24 and the underlying leaf spring under these conditions serves to lock the fuse tube assembly [8 in the housing! and to prevent it from being expelled therefrom when the circuit interrupter is required to interrupt relatively heavy overload currents. This locking effect is accomplished by the cooperation of the expanded garter spring 24 with the upper contact assembly 22 which is particularly adapted and formed, as will be described hereinafter, to accomplish this purpose.

The construction of the porcelain housing [0 constitutes an important feature of the present invention. As illustrated more clearly in Figure 4 of the .drawings, the housing [0 has a central longitudinal bore 2'! of uniform diameter which has counterbores 23 and 29 at its upper and lower ends. The lower counterbore 29 is flared outwardly slightly as shown. Transverse line conductor openings 30 and 31 are provided in the counterbores 28 and 29 for receiving line conductors for connection to the contact assemblies 22 and 23. The inner end surfaces 32 and 33 are roughened, as by glazing and sanding, to pro- Vide a suitable surface for receiving an alloy which is employed for securing the contact assemblies 22 and 23 in position at the ends of the housing It].

The particular configuration of the porcelain housing ill just described eliminates the undercutting or two step counterbore that is employed in the housing shown in the patent referred to above. This construction permits the housing I!) to be made from a pug in which the central longitudinal bore 21 is formed by the pug mill. Because of the reduction in the required operations for forming the housing In in contrast to those required for the housing shown ,in the patent, the expense involved in manufacturing the housing ID has been reduced considerably.

Furthermore, the spacing of the contact assemblies can be determined accurately by suitable fixtures with their spacing being generally independent of variations in the length of the housing Ill within conventional tolerances for porcelain.

In Figures 2, 3, and 6 of the drawings, the details of construction of the upper line terminal contact assembly 22 are shown more clearly. It will be noted that the upper contact assembly 22 includes a metallic contact sleeve 36 which has integrally formed downwardly extending contact fingers 31 the lower ends of which are flared outwardly. The contact fingers 31 are arranged to engage the upper fuse tube ferrule 20, as shown in Figure 2, and they are urged into good contact engagement therewith by a garter spring 38 which surrounds them in a suitably grooved portion thereof removed slightly from the lower outflared ends. Near its upper end the contact sleeve 36 has an annular groove 39 which registers with the garter spring 24 that constitutes the locking means previously referred to. On the generation of sufficient pressure within the fuse tube H! on blowing of the fuse link therein, the garter spring 24 is expanded thereby and moves into the groove 39. The upward thrust of the fuse tube [9 is transmitted by the expanded garter spring 24 to the upper edge of the annular groove 39 in the contact sleeve 36. In this manner the fuse tube [9 is prevented from being expelled under these operating conditions. As soon as the pressure is relieved in the fuse tube IS, the garter spring 24 is retracted, thereby permitting the bayonet type fuse assembly l8 to be withdrawn from the housing Ill. The contact sleeve 38 has an outflared upper edge 40 against which the lower face of the insert ll reacts to limit the downward movement of the fuse tube assembly l8 in the housing I0.

Surrounding and closely fitting with the upper portion of the contact sleeve 36 is a retainer sleeve 42. It has an outfiared upper edge 43 which conforms to the shape of the outfiared upper edge 40 of the sleeve 35. Also it conforms to the shape of the upper end of the sleeve 36 where the annular groove 39 is provided and serves to reinforce the same for resisting the upward thrust applied thereto by the fuse tube I!) when the fuse link therein blows as described. Near its lower end the retainer sleeve 42 has a gasket engaging shoulder 44 which is formed by suitably shaping this portion of the sleeve 42 by providing an inwardly opening annular groove therein. The function of the shoulder 44 will be described presently.

As illustrated more clearly in Figure 6, the lower portion of the retainer sleeve 42 is spaced, as indicated at 45, outwardly of the outer surfaces of the contact fingers 31. The purpose of the space 45 is to permit the contact fingers 3l to flex outwardly when the fuse tube ferrules 2i and 20 are passed therethrough. At the same time because of the presence of the retainer sleeve 42 surrounding the contact fingers 31, the outward flexing thereof is limited so that they cannot be stressed beyond their elastic limits and acquire a permanent set which would reduce the contact pressure that they would be capable of applying against the fuse tube ferrules. This construction also distributes the impact stresses applied to the contact fingers 31 when the fuse tube ferrules 2| and 20 are thrust thereinto somewhat eccentrically.

The intermediate portion 46 of the retainer sleeve 42 is externally knurled for receiving an anchoring cement or alloy between it and the upper cement or alloy receiving surface 32 in the housing In previously described. The manner in which the cement or alloy is applied will be described presently.

The contact sleeve 35 and retainer sleeve 42 are formed of relatively thin walled tubing of brass or other suitable metal. They are individually shaped toprovide the desired configuration of the-contact fingers 31, the shoulder 44 and the portions forming the groove 33. Thereafter they are telescoped, with a press fit between the parts which form the groove 39, and are rolled con jointly to form the upper edge of the annular groove-39 for receiving the garter spring 24 which constitutes the tube locking means. .Also the upper edges 40 and 43 are flared outwardly together to provide a unitary construction. The telesoped sleeve arrangement, anchoring the contact assemblies in the bore 21, avoids the necessity for employing a relatively heavy casting and thus effects a material reduction in the weight of the contact assembly over that required for the construction-shown in the aforesaid patent and a reduction in the amount of cement or alloy needed to hold it in place.

A line conductor fitting 41 may be secured by rivets 48 to the assembled contact and retainer sleeves 36 and 42; The fitting 4! may be cut from a length of brass bar which has been extruded to the desired shape. It may be provided with an aperture 49 which, as shown in Figures 2 and 3 of the drawings, registers with the transverse line conductor openings 35. The line conductor may be secured in the aperture 49 by screws 58.

In Figures 2, 3, 7 and 8 of the drawings, the details of construction of the lower line terminal contact assembly 23 are shown more clearly. Like the upper contact assembly 22, the lower contact assembly 23 includes a metallic contact sleeve 53 which is provided with upwardly extending contact fingers 54 the upper ends of which are flared outwardly, as shown, for receiving and guiding the lower fuse tube ferrule 2| into alignment when the fuse tube assembly I8 is thrust into the housing I5. A garter spring 55 surrounds the contact fingers 54 and urges them into good contact engagement with the outer surface of the lower fuse tube ferrule 2|. The contact sleeve 53 has an outfiared lower end 56 which facilitates the escape of the products of the are that is formed on blowing of the fuse link in the fuse tube l9. Also the outflared lower end 58 protectsthe inner surface of the lower counterbore 29 from the heat of the arc or the incandescent particles blown out of the lower end of the fuse tube l9.

Surrounding the metallic contact sleeve 53 is a metallic retainer sleeve 58 which has a gasket engaging shoulder 59 that is formed therein as described for the shoulder 44 of the retainer sleeve 42. As shown in Figure 7 the upper end of the retainer sleeve 58 is spaced as indicated at 60 slightly from the outer surfaces of the contact fingers 54. The purpose of this, as previously described for the contact fingers 37 of the upper contact assembly 22, is to permit flexing of the contact fingers 54 when the lower fuse tube ferrule 2| is inserted therein. The retainer sleeve 58 likewise limits the extent of flexing of the individual contact fingers 54 to prevent their being over stressed. Also the retainer sleeve 58 distributes the impact stresses that are applied to the contact fingers 54 when the lower fuse tube ferrule 2| enters them slightly off center. The intermediate portion 6| of the retainer sleeve 58 is knurled externally for receiving a cement or alloy in the molten state between it and the lower alloy receiving surface 33 in the housing It! in a manner to be described presently.

The contact sleeve 53 and the retainer sleeve 58 are formed of relatively thin brass tubing in 6; the same manner that the contact sleeve 36 and retainer sleeve 42 of the upper contact assembly 22 are formed. The contact sleeve 53 and retainer sleeve 58 are rolled conjointly to provide a substantially unitary construction.

A line conductor fitting 62, identical with the line conductor fitting 47, is secured by rivets 63 to the sleeves 53 and 58. It is provided with a conductor receiving aperture 64 which, as shown in Figures 2' and 3, registers with the lower transverse line conductor openings 3| in the lower counterbore 29. Set screws 65 extend transversely of the aperture 84 for holding a line conductor therein.

The manner in which the contact assemblies 22 and 23 are secured in the housing It] at the ends of the central bore 2'! is important and constitutes another feature of the present invention. As describedpreviously, the retainer sleeves 42 and 58 of the upper and lower contact assemblies 22 and 23 have knurled surfaces 46 and BI which are arranged to receive an alloy in the spaces provided between them and the sanded surfaces 32 and 33 at the ends of the bore 27. In order to prevent the alloy, which is applied in the molten state, from escaping into the bore 21, a soft rubber gasket 65, shown in Figure 9 as a flat ring, can be applied around the lower and upper ends of the retainer sleeves 42 and 58 respectively adjacent the gasket engaging shoul' ders-44 and 53. The diameter of the opening in the gasket 55 is less than the outside diameter of the retainer sleeves 42 or 58 adjacent the gasket engaging shoulders 44 and 59.

Consider first the manner in which the upper contact assembly 22 is secured in place. It is positioned accurately within the bore 21 so that when it is inserted it occupies the position shown in Figures 2 and 3 of the drawings. It will be noted there that the gasket 66 is wedged between the shoulder 44 and the sanded surface 32. Suitable fixtures are provided for holding the contact assembly 22 in the proper position within the housing 18. Thereafter an alloy 6'1, such as a lead antimony alloy, in the molten state is poured into the space between the knurled outer surface 46 of the retainer sleeve 42 and the sanded surface 32. When it solidifies, the contact assembly 22 is held securely in place in the housing l8 and is capable of resisting the shear forces that are appliedthereto when the fuse tube assembly i3 is inserted or withdrawn or when it is urged outwardly under short circuit interrupting conditions.

The soft rubber gasket 66 provides a substantially liquid tight seal for holding the molten alloy 61 in place. Even though slight amounts of the alloy 67 were to flow through minute spaces between the sanded surface 32 and the rubber gasket 66, the volume of such flows would be extremely small and would be rapidly chilled and attenuated because of the cooling effect provided by the resulting relatively large surface area. 'Experience shows that, when the contact assembly 22 is positioned properly in the housing 18, none of the molten alloy 61 flows into the bore 21 past the rubber gasket 85.

The gasket 66 preferably is formed of sponge rubber which conforms to the irregularities of the sanded surfaces 32 and 33 even at relatively light pressures. Thus the flexing and bonding of the gasket 86 as such is in itself suificient to make a fair seal. Moreover, the gasket 66, when formed as set forth herein, takes care of variations in the diameter of the bore H of the" porcelain housmg I and of the sanded surfaces 32 and 33.

It will be understood, of course, that the upper contact assembly 22 is cemented into place by the alloy 61 with the housing It] in the upright position as shown in Figures 2 and 3 of the drawings. The lower contact assembly'23 is similarly inserted and cemented in place with the housing l0 turned upside down.

Prior to the insertion of the lower contact assembly 23 in the housing l0, an insulating sleeve 68, preferably formed of fiber, is inserted in the bore 21 and is loosely positioned therein between the contact assemblies 22 and 23. The sleeve 68 is shorter than the distance between the contact assemblies 22 and 23 to provide clearance therebetwen and prevent leakage tracking when the fuse tube I9 is inserted. At its lower end, the sleeve 68 has a reenforcing ring 69 of insulation which also serves to center the fuse tube [9 and to guide its lower ferrule 2| and its upper end is flared outwardly as indicated at 10 by providing longitudinal slots II therein. The insulating sleeve 68 is employed to guide the lower fuse tube ferrule 2| into the lower contact assembly 23. If the sleeve 68 were not provided and if the bayonet fuse tube assembly [8 were not inserted centrally of the housing (0, it is likely that the lower end of the fuse tube ferrule 2! might jam against the upper ends of the contact fingers d and damage them.

Another function of the insulating sleeve 68 is to assist in extinguishing the are that may be drawn between the lower fuse tube ferrule 21 and the lower contact assembly 23 when the fuse tube assembly 18 is withdrawn from the housing [0 while the device is carrying current. The are is drawn inside of the sleeve 68, and, since it is formed of fiber or similar material, it evolves an arc extinguishing medium which assists in deionizing the arc space.

In Figure of the drawings, there is illustrated at 22 a contact assembly which is essentially the same as the contact assembly 22 described hereinbefore except that instead of the gasket engaging shoulder 44 being provided as described, the lower end of the retainer sleeve 42 is flared outwardly as indicated at 12 to provide a gasket engaging shoulder. The shoulder 12 provides a somewhat tighter fit with the gasket 66 than is provided by the shoulder M previously described.

In Figure 11 of the drawings the modified form of upper contact assembly 22' is shown with a gasket l3 in the form of a ring of sponge rubber. It will be observed that the gasket E3 is positioned between the shoulder :2 and the garter spring 38 which surrounds the contact fingers 31. It will be understood that the sponge rubber gasket 73 can be employed, if desired, in lieu of the soft rubber gasket 65 previously described.

When the constructions shown in Figures 10 and 11 are employed for both the upper and lower contact assemblies, the garter spring 38 or 55 is displaced slightly along the outflared contact fingers 31 or 54 from its position of minimum diameter. Thus the spring 38 or 55 acts to hold the gasket 36 or 13 against the adjacent edge of the outflared flange l2 and its inherent resilience holds it against the outer surfaces of the contact fingers 31 or 54. As a result of the coaction of these two forces, i. e. the action of the spring 33 or 55 and the resilience of the gasket '56 or T3, the gasket 56 or 13 8 is gripped securely and is prevented from being pulled over the flange 12 when the contact assembly is inserted into the housing 21, as shown in Figure 12, and seats against the inner end of the retainer sleeve 42 or 58.

When the contact assemblies are positioned in the housing H], as shown in Figure 2, the shoulder 44 or flange 12 bears against the cement or alloy 61. In this manner the contact assemblies are prevented from being moved out of their proper locations.

While the present invention has been described particularly in relation to its use in connection with fuses, it will be understood that the device as shown in the drawings can be employed as a switch by using the fuse tube [9 with a fuse link therein as a switch blade. Alternatively, if desired a rod or tube of conducting material, such as copper, can be substituted for the insulating tube 19 for the purpose of bridging the terminal contact assemblies 22 and 23. In such case the copper rod or tube would constitute the switch blade. An arrangement of this general type is shown in Patent No. 2,316, 17 0.

Since certain further changes can be made in the foregoing constructions and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In a circuit interrupter construction for receiving a bayonet type circuit interrupter assembly having upper and lower contacts near its ends, in combination, a cylindrical porcelain housing having a central longitudinal bore of uniform diameter, the end surfaces of said central bore being roughened, and upper and lower contact assemblies fori receiving said upper and lower contacts, said assemblies being located at the ends of said central bore and secured therein by means solidified between them and said roughened end surfaces.

2. In a circuit interrupter construction for receiving a bayonet type circuit interrupter assem bly having upper and lower contacts near its ends, in combination, a cylindrical porcelain housing having a central longitudinal bore of uniform diameter, the end surfaces of said central bore being roughened, and upper and lower contact assemblies for receiving said upper and lower contacts, said assemblies being located at the ends of and extending outwardly from said central bore and secured therein by means solidified between them and said roughened end surfaces.

3. In a circuit interrupter construction for receiving a bayonet type circuit interrupter assembly having upper and lower contacts near its ends, in combination, a cylindrical porcelain housing having a central longitudinal bore of uniform diameter, the end surfaces of said central bore being roughened to provide alloy receiving areas of limited extent, upper and lower contact assemblies for receiving said upper and lower contacts, said assemblies being located at the ends of said central bore and secured therein by alloy means solidified between them .and said alloy receiving areas, and a gasket interposed between said contact assemblies and the inner ends of said alloy receiving areas to limit the inward flow of said alloy in the molten state.

4. In a circuit interrupter construction for receiving a bayonet type circuit interrupter assembly having upper and lower contacts near its ends, in combination, a porcelain housing having a central longitudinal bore of uniform diameter counterbored at its ends with the surface of said central bore near each end being roughened, upper and lower tubular contact assemblies telescoped with and spaced from the roughened ends of said central bore and projecting into said counterbored ends for receiving therethrough said upper and lower contacts, a resilient annular gasket extending between an inner end portion of each tubular contact assembly and the juxtaposed portion of said central bore to center said contact'assemblies therein and form the bottom of a well the sides of which are formed by said roughened surface and the juxtaposed surface of the corresponding contact assembly, and means solidified in each well to hold said contact assemblies securely in position in said housing.

5. The invention, as set forth in claim 4, wherein each contact assembly is provided with a radially extending shoulder at the bottom of its well, and the gasket is in the form of a flat washer bearing on said shoulder and capable 'of gripping tightly its contact assembly and is wide enough to be turned backwardly when inserted into its end of the central bore.

6. The invention, as set forth in claim 5, wherein a garter spring surrounds each contact assembly and holds the gasket individual thereto against the adjacent shoulder.

7. In a circuit interrupter construction for receiving a bayonet type circuit interrupter assembly having upper and lower contacts near its ends, in combination, a porcelain housing having a central longitudinal bore of uniform diameter counterbored at its ends with the surface of said central bore near each end being roughened, upper and lower tubular contact assemblies tele scoped with and spaced from the roughened ends of said central bore and projecting into said counterbored ends for receiving therethrough said upper and lower contacts, each contact assembly including a metallic contact sleeve having a plurality of resilient outfiared contact fingers for engaging the corresponding circuit interrupter contacts and a retainer sleeve surrounding each contact sleeve and spaced from the contact fingers 0 Number at the base of the outfiared portions thereof to permit their outward flexing and limit their outward movement, the outer surface of each retainer sleeve coextensive with the respective roughened end surface of said bore being roughened, the end of each retainer sleeve adjacent the base of the outfiared portions of its contact fingers having a radially extending shoulder, a resilient annular gasket overlying each shoulder and extending therefrom to engage the juxtaposed portion of said central bore and center said contact assemblies therein and form the bottom of wells the sides of Which are formed by said roughened surfaces of said bore and said retainer sleeves, garter springs surrounding said outfiared portions of said contact fingers to urge them inwardly and to bias the gaskets against their respective shoulders, and means solidified in each well to hold said contact assemblies securely in position in said housing.

SIGURD I. LINDELL. CARL E. SCHULTHEISS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Wagner et a1 Apr. 23, 1895 Austin Nov. 19, 1918 ,Smith Jan. 8, 1929 Nyman Sept. 11, 1931 Heinrich July 18, 1933 Stevens Oct. 24, 1933 Ramsey Feb. 22, 1938 Koehler July 12, 1938 Rorden Nov. 1, 1938 Sagona Aug. 4, 1942 Peltz et al. June 8, 1943 West Oct. 5, 1943 Schultz Oct. 21, 1947 FOREIGN PATENTS Country Date England Aug. 24, 1931 England Oct. 18, 1946 France June 1, 1932 Number

Images