US2145154A - Fuse block - Google Patents

Description

Jan. 24, 1939. CQRBETT 2,145,154

FUSE BLOCK Original Filed March 22, 1955 3 Sheets-Sheet 1- INVENTOR 4621M g ymwm Jan. 24,1939. CORBETT 2,145,154

FUSE BLOCK Original Filed March 22, 1935 3 iset' 2 Patented Jan. 24, 1939 UNITED STATES PATENT OFFICE FUSE BLOCK Delaware Application March 22, 1935, Serial No. 12,426 Renewed April 2, 1938 12 Claims.

This invention relates to a fuse block, or more properly to a composite assembly comprising :all the essential elements of a fuse block uti-lizable as such, or in building up assemblies such as panel boards.

An object of the invention is to provide a fuse mounting assembly, performing the functions of a fuse block, in which contact-carrying frames are readily mountable on and demountable from the bus bars, to make firm and adequate contact between the contact elements carried by individual frames and the bus :bars to which the icontact-carrying frames are mounted.

Another object of the invention is to provide y a fuse block assembly in which the required quantity of insulation is minimized by the form and arrangement of the insulating elements, constituting a base structure upon which the bus bars are mounted; and to provide an assembly in which the several insulating elements of the base structure are of such structural simplicity as to minimize molding operations requisite in their production.

Another object of the invention is to provide in combination a base structure, and one or more individual contact-carrying frames for mounting on the base structure, so arranged that the base structure is discontinuous in the regions in which contacts carried by the frames mounted to the base make contact with the bus bars, and such arrangement of contact-carrying frames and contacts thereon that the fuse contact structures on the frames are unhoused, and are subjected to air circulation therearound; thus utilizing as an insulating medium air which serves also to prevent overheating in the fuse contacts and fuses, thus preserving a true rating of the fuses.

A further object of the invention is to provide contact frames readily and separately mountable on and demountable from a base structure, each of said frames carrying contacts for fuses of different rating adapted to the several circuits in which the fuses are to be associated, the contact-carrying frames severally comprising contacts, each adapted to receive fuses appropriate to the circuit in which the contacts are connected.

A further object of the invention is to provide an assembly of the nature above indicated, mountable and demountable contact-carrying frames, each comprising a deck having the circuit contacts arranged and mounted on the upper face of the deck with the center contacts of the fuse contact assembly extending beneath the deck and upwardly beyond the upper face of the deck into cooperative association with the circuit contacts carried thereon; thus minimizing possibility of short-circuit during mounting and demounting of the contact-carrying frames.

A still further object of the invention is to provide a contact-carrying frame, as immediately above described, in which means are so mounted in relation to the fuse contacts that the center contact of the assembly is screened from electrical contact with any conductive instrument, save a fuse suitably constructed to establish connection with the center contact of the assembly.

In fuse blocks as made up for mounting in fuse boxes, and in panel boards and the like, it is generally desirable that the fuse block be formed of a plurality of separable elements, since such unit construction facilitates wired installation of the fuse block, and facilitates changes in wiring. Also such division into separable elements permits an open construction, utilizing air as an insulating and cooling medium in the manner noted as an object of my present invention. It further is advantageous that an element of the fuse block may be removed or replaced without disturbing the position, or interrupting the electrical connection, of other separable elements of the fuse block.

Since fuse boxes and panel boards usually are arranged to provide a safety factor in a plurality of circuits capable of carryingcurrent of different amperage,- the fuse block necessarily comprises contacts for fuses constructed to tolerate a variety of amperages. If then, a fuse block is to be so made up that the several contact structures comprised thereby are made compatible, by

contouring or otherwise, only with fuses so limited in capacity that an appropriate safety factor is provided in each circuit, it becomes highly advantageous to provide an arrangement in which a plurality of separable fuse-carrying elements are individually mountable and demountable to make or break contact with the bus bars of the fuse block assembly.

It is highly desirable that the fuse contacts of a contact block comprise structures for preventing tampering with the fuse contacts. That is, it is highly desirable that means should be provided to prevent establishment of a circuit at a fuse contact in the absence of an operable fuse in the circuit. It frequently happens that, a fuse having blown, a person deriving current at the fuse box will, either ignorantly or recklessly, establish a substantially infusible connection at the base of the fuse contact socket, thus depriving the circuit of the protection provided by the ill) grooved longitudinally outward from the socket I to provide a channel 1a for receiving a contact bar 8, connecting the socket with a binding post 3. Desirably, each of the contact-carrying frames has thereon vertical posts H), which support an insulating cover 1! perforated in the regions I 2, to give access to the shells, or sockets, l.

Contact between sockets I and bus bars 2 is provided by center contacts, which serve, additionally, firmly to position each contact-carrying frame on the base assembly. Each center contact comprises a screw l3, the .head of which projects above the upper surface of deck 6, within its associated shell socket 1. Each of the screws l3 also makes electrical contact with, and secures to the under side of the deck 6., a U- shaped contact element [4, which has one leg engaged by the screw l3 and lying against the under face of the deck of the contact-carrying structure, the other leg of the U forming a blade for engagement with jaw contact l5. Jaw contact l5 comprises, as is shown, a base, and two jaws which extend horizontally outward from the base, and are brought into a position of close parallelism to each other, to receive and engage the blade Me of contact element l4. Jaw contacts #5 are held in close and firm contact with a side face of each of the bus bars 2 by means of mounting screws I6.

In assembly of a fuse block comprising the elements described, the contact-carrying frames are placed one at a time in the channels formed by the shoulders 50 of the two base elements I, with the contact blade Ma of element I4 in alignment with the jaws l5a and [5b. In this position a contact-carrying frame lies to the left of the position illustrated in Figs. I and II, and, by moving the contact element to the right, it is brought into the position shown in Figs. I and II; in which position the blades Ma are closely and firmly engaged by the contact jaws, to make connection of each center contact with one of the bus bars, and to firmly position the contact-carrying frame on the base assembly.

It will be observed that each of the contactcarrying frames may be removed from its mounted position, making contact with the two bus bars, simply by moving the frame to the left from the position shown in Figs. I and II, and lifting it from the base assembly. Obviously, this may be done without disturbing the mounting of any other contact-carrying frame of the fuse block either physically or electrically.

In the modified assembly shown in Figs. III to VI, inclusive, of the drawings, the bus bar supports, or base elements, are ties of a form still simpler than the form of those shown in Figs. I and II. These ties I! are mere rectangular and elongate blocks of insulating material, which are secured by screws l8 to an underlying structure, such as the inner wall of a fuse box. The bus bars l9 lie upon these blocks, in bridging relation to the tie block assembly, and are secured to the tie blocks by screws 20. It will be noticed that the blocks I! and the bus bars 19 define, by their arrangement, spaces 2| of rectangular configuration. As will be explained, these spaces 2| are useful in positioning the contact carrying frames, and in positively preventing shifting of the contact-carrying frames when mounted.

In this modification, the contact-carrying frames comprise each a deck 22, from which depends a. seating boss 23, which is of rectangular cross-section, fitting the rectangular spaces 2| defined by the ties l1 and bus bars l9. Upstanding from the deck 22 is a center post 24, which overlies the seating boss 23, and which has a bore 24a extending longitudinally therethrough. Posts 25, for supporting an insulating canopy or cover 26, also extend upwardly from deck 22. The entire structure of deck, mounting boss, center post, and cover-supporting posts is desirably made, as shown, of a single block of molded insulating material.

1 In Figs. III and IV, the frame is shown as carrying two screw shell sockets 2'! which are electrically connected with binding posts 28, by means of strips, or bars, 29 of conducting material. At the base of each shell socket 2'! lies the head of a contact screw 30, the shank of which projects through the deck. Terminally, the shank of screw 30 carries a contact nut, or threaded washer, 3|, to provide a relatively extended contact area.

In mounting the contact frames on the base structure, the frame assembly is brought into position with its seating bosses 23 extending into the spaces 2l of the base assembly, and with the contact nuts 3| contacting the upper surfaces of bus bars i9. In order, however, that the frames may be firmly mounted on the base assembly, and that close electrical contact with the bus bars may be continuously maintained, means are provided for forcing the contact-carrying frame toward the base assembly, and for firmly engaging it thereto.

The positive engaging means of the assembly comprises an elongate screw 32, which is headed upwardly of center post 24, and the threaded shank of which, passing through the bore of the center post and downwardly beyond seating bosses 23, enters a threaded socket 33.

When any contact-carrying frame has been positioned on the base assembly, it is positively engaged by passing its associated center screw 32 through the center post and into the socket 33 which is in alignment with the bore through the center post. By tightening down on its associated screw 32, each contact-carrying frame is therefore drawn positively to the base assembly, and the contact nuts 3| of the frame are pressed firmly and positively into contact with bus bars l9. lhe contact-carrying frame is freed, for removal from mounted position, merely by releasing screw 32 from its engaging socket 33.

It will be observed in connection with both modifications of my apparatus that the positive mounting of a contact-carrying frame on the base assembly also makes, and maintains, good electrical connection between bus bars of the assembly and contact structures carried by the frame.

In each of the modifications shown and decribed, the contact-carrying unit is a frame carrying two contact structures for the connection of fuses. It will be understood that the structure of either form of contact-carrying frame may readily be so modified that each frame carries but a single contact structure; or, if desired, each unit may consist of a frame carrying more than two contact structures.

Referring to Fig. VIII of the drawings, a selective contact-making, and selective fuse-receiving, structure is shown as associated with a contact structure mounted on the deck 6 of a contactcarrying frame, made in accordance with the showing of Figs. I, II, and VII. This added structure comprises a barrel 34 of insulating material, having a centrally disposed bore 35 therethrough.

The lower region 35a of bore 35 -is constricted, and an annular rib 31 projects into the bore between the upper region thereof and the lower constricted region thereof. Traversable in bore 35 is a plunger 38 of conductive material, having at the upper extremity thereof an integral collar 38a, and at the lower extremity thereof a washer 38b riveted, or otherwise suitably secured, to the lower terminal of the plunger. A coil spring 39 lie in the main portion of bore 35, surrounding plunger 38 and bearing respectively against collar 38a and the annular inwardly extending rib 31. This coil spring 39 exerts a constant force tending to maintain plunger 35 in its uppermost position, with collar 35?) abutting the under face of rib 31, and spaced a substantial distance from the head of screw [3.

It will be apparent that this structure, inserted within screw shell 1, screens contact screw it from contact in the region thereof which projects above the deck 5. In order, therefore, that electrical communication be established between a bus bar engaged by the bus bar contact structure and the screw shell I, it is necessary that conductive plunger 38 be forced downwardly against the resistance of coil spring 39 into a position abutting contact screw [3, and that a conductor be maintained between it and the screw shell. In inoperative condition of the contact structure, therefore, the bus bar contact is screened from direct contact with a conductor. This arrangement prevents the establishment of electrical communication between the bus bar contact and the screw shell, in the absence of a fuse, and thus prevents establishment of a circuit which lacks the protection afforded by a fuse. Also, as applied to the mountable and demountable contact frame, it prevents the establishment of an accidental short, in the absence of a fuse, and in mounting, or demounting, the contact-carrying frame from the base structure upon which it is mountable. This provides a safety factor, rendering it safe to mount the contact-carrying frames, without deenergizing the bus bar.

A form of fuse 4D, suitable for use in conjunction with the fuse-receiving contact structure is shown in position to be inserted into the screw shell 7. It will be noted that the fuse 41! comprises an elongate terminal 4!, which is surrounded by a skirt 62, carrying a threaded, conductive, terminal element '13 adapted to make contact with screw shell I.

When fuse 59 is screwed into the contact shell, as shown with relation to the contact shell 27 of Fig. IX, skirt d2 enters the annular region 3 lying between the exterior surface of barrel 3::- and the interior surface of the screw shell. -As the fuse is screwed into position, terminal 4!, bearing against conductive plunger 38, forces the plunger downwardly in bore 35;. Terminal 1! is of such length that, before the limit of move ment of fuse 4G in the screw shell has been reached, conductive plunger 38 is brought into contact with the upper face of the head of screw it. This establishes electrical communication between the bus bar contact and the screw socket, through the fuse.

In order that fuses of predetermined capacity may be associated only with contact structures which in turn are associated with circuits of no lesser electrical capacity, the thickness of barrel 34 of the selective contact-making structure, and the thickness of fuse skirt 52, may be mutually apportioned. Thus, the contact structure, or structures, on an individual contact-carrying frame are arranged to provide an annular space M of a width apportioned to the skirt width of fuses to be associated on the contact-carrying frame. By'making the skirt 42, of the fuses of greatest capacity, of the greatest thickness, and by progressively decreasing the thickness of this skirt within decreased capacity of the fuse, assurance may be had that a fuse of capacity too great for that of the circuit in which it is to be incorporated cannot be associated with the contact-carrying frame for that circuit.

As above noted, the use of separately mountable and demountable contact frames gives a highly desirable accommodation to selectivity in the capacity of the fuse, or fuses, associated with the frames. Change in the capacity of any individual circuit, safeguarded by my fractionated fuse block assembly, can thus be readily accommodated by removal of a contact-carrying frame with contacts inappropriate to the changed circuit, and by the mounting of substituted frame-carrying contacts and fuses appropriate to the changed circuit. This may be done, and done safely, without deenergizing the bus bars, or interfering with the active condition of other circuits safeguarded by connection contact-carrying frames.

There are other modes of rendering difficult the use of an overecapacity fuse in a contact structure on the contact-carrying frame. For example, the diameter of the bore 35 in barrel 34 of the contact screening insert may be made too smallto receive the terminal 4! of any fuses save those of adequately low capacity. Also the length of conductive plunger as, with respect to the effective seated length of fuse terminal at, may be varied in accordance with corresponding variation in the length of the fuse terminal. A combination of these two limiting factors may be employed.

I claim as my invention:

with 7 other 1. In a fuse block assembly the combination of a base structure comprising spaced bars of insulating material secured to an underlying wall and a bus bar bridging between said insulating bars, with a contact-carrying frame comprising a deck, a bus bar contact extending beneath the deck in position to make direct electrical contact with the said bus bar, and means for mounting the contact-carrying frame on the base structure with the bus bar contact thereon in electrical communication with the bus bar in an interval between insulating bars of the base structure.

1 2. In a fuse block assembly the combination of a base structure comprising spaced bars of insulating material secured to an underlying wall and a bus bar bridging between said insulating bars, with a contact-carrying frame comprising a deck, a bus bar contact extending above the deck and extending beneath the deck in position to be brought into direct electrical communication with the said bus bar, means for mounting the contact-carrying frame on the base structure with the bus bar contact thereon in direct electrical communication with the bus bar in an interval between insulating bars of the base structure,v a circuit contact carried at the upper side of the deck in spaced relation to said bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, and selective contact-making means associated with the contact structure carried by the said selective contact-making means bein arranged normally to screen the upward extension of the bus bar contact from the establishment of electrical communication therewith and being operable by a fuse to establish electrical connection between the fuse and said bus bar contact.

3. In a fuse block assembly the combination with an underlying supporting wall of a structure comprising spaced bars of insulating material secured to said underlying wall bus bar bridging between said insulating bars, a contact-carrying frame comprising a deck having a positioning boss adapted to lie between adjacent insulating bars of the base assembly, a bus bar contact extending beneath the said deck in position to make direct electrical contact with the said busbar in an interval between insulating bars, and a member adapted to pass through the positioning boss of the contact-carrying frame and regulably to engage in said underlying sup-- porting wall thereby to force the contact-carrying frame to said base structure and to force the contact element carried thereby into electrical contact with said bus bar.

4. In a fuse block assembly the combination with anunderlying supporting wall of a structure, comprising spaced bars of insulation secured to said underlying wall and a bus bar bridging between said insulating bars, a contactcarrying frame comprising a deck having a positioning boss adapted to lie between adjacent insulating bars of the assembly, a bus bar contact extending above said deck and extending beneath the said deck in position to make direct electrical contact with the bus bar in an interval between insulating bars, a circuit contact carried at the 1 upper side of the deck in spaced relation to upward extension of said bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, selective contactmaking means associated with said bus bar contact, said selective contact-making means being arranged normally to screen the upward extension of said bus bar contact from the establishment of electrical communication with the bus bar therethrough and being operable by a fuse to establish electrical communication from the bus bar by way of the bus bar contact and the fuse to the circuit contact, and a member adapted to pass through the positioning boss of the contact-carrying frame and regulably to engage in said underlying structure thereby to force the contact-carrying frame to said base structure and to force the bus bar contact carried thereby into electrical contact with said bus bar.

5. In a fuse block assembly the combination with an underlying wall of a base structure comprising spaced bars of insulating material secured to said underlying wall and a bus bar bridging between said insulating bars, a contact-carrying frame arranged to rest upon said insulating bars and carrying a depending contact positioned to make electrical contact with said bus bar in an interval between insulating bars in mounted positioning of the contact-carrying frame thereon, and an engaging member mounted in the contactcarrying frame and adapted to engage in said underlying wall, thereby to hold the contactcarrying frame to said base structure and to hold the contact element depending therefrom in electrical contact with said bus bar.

6-. In a fuse block assembly the combination a base structure comprising spaced bars of insulating material secured to an underlying wall and a bus bar bridging between said insulating bars, with a contact-carrying frame comprising a deck, a bus bar contact extending above the deck and extending beneath the deck in position be brought into direct electrical communica tion with the said bus bar, means for mounting the contact-carrying frame on the base structure with the bus bar contact thereon in electrical communication with the bus bar in an interval between insulating bars of the base structure, a screw shell forming an element of the contact structure carried by the frame and surrounding the upward extension of said bus bar contact, and means in said shell adapted to limit the space therewithin and thereby to limit the receptivity of the shell to fuses formed in accordance with the space limitation within the shell effected by said space limiting means.

7. In a fuse block assembly the combination of a base structure comprising an insulating base and a bus bar mounted thereon, a contact-carrying frame comprising an insulating deck, a contact assembly comprising contact elements mounted on the upper surface of the deck and arranged to be bridged by a fuse lying wholly at the upper face of the deck, means projected through the deck arranged to maintain the said deckcarried contact assembly in electrical connection with the said bus bar, and an insulating canopy mounted on the deck and spaced from the upper surface of the deck, said insulating canopy being perforate in a region overlying the said contact assembly.

8. In a fuse block assembly the combination of a base structure comprising an underlying base and a bus bar mounted on said base in insulated relation thereto, with a contact-carrying frame comprising a deck, a bus bar contact extended above the deck and extended beneath the deckin position to make electrical contact with the bus bar, a connecting member projected beneath the deck in a position of electrical separation from the bus bar contact and adapted by engaging the underlying base to hold the downward extension of the bus bar contact in electrical contact with the bus bar, a circuit contact carried at the upper side of the deck in spaced relation to the upward extension of the bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, and selective contact-making means associated with said bus bar contact, said selective contact-making means being arranged normally to screen the upward extension of said bus bar from the establishment of electrical communication with the bus bar therethrough and being operable by a fuse to establish electrical communication from the bus bar by way of the bus bar contact and the fuse to the circuit contact.

9. In a fuse block assembly the combination of a base structure comprising an underlying base and a bus bar mounted on said base in insulated relation thereto, with a contact-carrying frame comprising a deck, a bus bar contact extended above the deck and extended beneath the deck in position to make electrical contact with the bus bar, a mounting screw passed through the deck in electrical separation from the bus bar contact and having a threaded engagement with the underlying base thereby to force the bus bar contact extended beneath the deck into electrical contact with the bus bar, a circuit contact carried at the upper side of the deck in spaced relation to the upward extension of the bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, and selective contact-making means associated with said bus bar contact, said selective contactmaking means being arranged normally to screen the upward extension of said bus bar from the establishment of electrical communication with the bus bar therethrough and being operable by a fuse to establish electrical communication from the bus bar by way of the bus bar contact and the fuse to the circuit contact.

10. In a fuse plug assembly the combination of a base structure comprising an underlying base and a bus bar mounted on said base in insulated relation thereto, with a contact-carrying frame comprising a deck, a bus bar contact extended above the deck and extended beneath the deck in position to make electrical contact with the bus bar, a connecting member projected beneath the deck in a position of electrical separation from the bus bar contact and adapted by engaging the underlying base to hold the downward extension of the bus bar contact in electrical contact with the bus bar, a circuit contact mounted at the upper side of the deck in spaced relation to the upward extension of the bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, and selective contact screening means associated with said bus bar contact at the upper side of the deck and arranged to limit conductive agencies effective to establish electrical communication between the circuit contact and the bus bar contact to a fuse selectively adapted to said contact screening means 11. In a fuse block assembly the combination of a base structure comprising an underlying base and a bus bar mounted on said base in insulated relation thereto, with a contact-carrying frame comprising a deck, a bus bar contact extended above the deck and extended beneath the deck in position to make electrical contact with the bus bar, a mounting screw passed through the deck in electrical separation from the bus bar contact and having a threaded engagement with the underlying base thereby to force the bus bar contact extended beneath the deck into electrical contact with the bus bar, a circuit contact carried at the upper side of the deck in spaced relation to the upward extension of the bus bar contact, said bus bar contact and said circuit contact being arranged to be bridged by a fuse, and selective contact screening means associated with said bus bar contact at the upper side of the deck and arranged to limit agencies effective to establish electrical communication between the circuit contact and the bus bar contact to a fuse selectively adapted to said contact screening means.

12. In a fuse plug assemblythe combination of a base structure comprising an underlying base and a bus bar mounted on said base in insulated relation thereto with a contact-carrying frame comprising a deck, a bus bar contact extended above the deck and extended beneath the deck in position to make electrical contact with the bus bar, and a mounting screw passed through the deck and projected therebeneath in a position of electrical separation from the bus bar contact and having threaded engagement with the underlying base, said mounting screw by its engagement with the underlying base exerting a regulable force to maintain electrical contact between the bus bar contact and the bus bar by forcing the bus bar contact against the bus bar.

ALFRED CORBE'IT.

Images