US3593247A

US3593247A - Trigger fuse switch assembly

Info

Publication number: US3593247A
Application number: US819020A
Authority: US
Inventors: James D Collins; Ralph B Immel
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1969-04-24
Filing date: 1969-04-24
Publication date: 1971-07-13
Anticipated expiration: 1988-07-13

Abstract

A trigger fuse switch assembly wherein a trigger fuse may only be inserted into the assembly in its correct operative position being held in place by a spring terminal. When the fuse is tripped, the striker pin thereof engages a pushrod of the assembly to cause a movable contact to either make or break a circuit therebetween. The stationary contacts may be selectively placed to provide normally open or closed operation of the switch assembly.

Description

D United States Patent ml 3,593,247

[72] Inven Jam" D- (Yollins; 2,965,873 12/1960 Sindelar. 337/195 X Ralph D. lrnmel, both 01 Bultalo, NY. 2,882,369 4/1959 Bauer 1, 337/ 198 X 1211 Appl. No 819,020 2.581.308 1/1952 Smith 337/186 X 1221 Filc p 2 1969 2,405,929 8/1946 Wald 337/147 X 1451 Patented J ".1 2,306,153 12/1942 Biermanns et al. N 337/142 X 1 1 Assignee wrstinshwsl Electric Corporation |,054,7|1 3/1913 Schramm 337/208 x FOREIGN PATENTS 791,584 12/1935 France 337/225 16 4 7 .4 337 148 541 TRIGGER ruse SWITCH ASSEMBLY 9/195 Germany I 1 Claim, 6 Drawing Figs. Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorneys-1 H. Henson,C. F. Ron: and A. S. Oddi [SI] ..ll0lh85/S0 i 1 sum. 377/5 ABS'IRAC'I': A trigger fuse switch assembly wherein a trigger 143,145, I47, I48, 186, I87, 190, 194, 195, 193, fuse may only be inserted into the assembly in its correct HQ 244 operative position being held in place by a spring terminal. When the fuse is tripped, the striker pin thereof engages a [56] Rehnnm cued pushrod of the assembly to cause a movable contact to either UNITED STATES PATENTS make or break a circuit therebetween. The stationary contacts 3,274,358 9/1966 Hallerberg 337/148 may be selectively placed to provide normally open or closed 3,263,048 7/1966 Hicks 337/142 X operation of the switch assembly.

TRIGGER FUSE SWITCH ASSEMBLY BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to switch assemblies and, more particularly, to switch assemblies adapted to be operative with trigger fuses.

2. Discussion of the Prior Art Trigger fuses are commonly utilized to monitor the condition of main power fuses which are connected in series with semiconductor power devices utilized in high-power rectifier equipment. In such high-power conversion equipment employing semiconductor diodes or thyristors, 400 to 500 power fuses may be utilized in conjunction with the semiconductor devices. If a semiconductor device should fail by shorting, the power fuse will blow open that particular circuit. The blowing of the power fuse applies voltage to a trigger fuse which is connected in parallel with the power fuse causing the trigger fuse to blow and mechanically operate a pair of contacts to activate a circuit which will be indicative of the specific location of the semiconductor device failure and the main power fuse that has blown. In typical application the trigger fuse when activated will cause an indicator light to be turned on or off or to cause an audible-signal-generating device to be energized.

A commonly used method of mounting the trigger fuse is to place the fuse between a pair of fuse clips which are mounted on an insulator board. A microswitch is mounted on the insu lator board adjacent the striker in end of the trigger fuse so that when the trigger fuse is blown the contacts of the microswitch will either opened or closed to activate an indica tor circuit. The use of such a trigger fuse mounting has a number of serious disadvantages. The use of a microswitch is expensive, and care must be taken to accurately place the fuse between the fuse clips to insure that the striker pin end of the trigger fuse is disposed in position to activate the microswitch when the fuse is blown. Also care must be taken to insure that the trigger fuse is not placed into the fuse clips backwards since no inherent protection is provided against such a possibilityv Additionally, when a large number of trigger fuses are to be utilized for monitoring main power fuses, the use of fuse clips and microswitches requires a large amount of space as well as presenting difficult wiring problems due to the large number of microswitches required. Moreover, the microswitches utilized may not be readily adaptable to either normally open or normally closed operation which may be highly desirable in certain applications.

It would therefore be highly desirable ifa trigger fuse switch assembly could be provided which is of low cost, requires small physical space for mounting, permits mounting of a large number in a minimum amount of space, requires that the trigger fuse be inserted into the assembly in the correct position, insures that the striker pin end of the trigger fuse is disposed in position to activate contacts of the switch assembly and permits easy modification of the assembly for normally open or normally closed operation ofthe switch.

SUMMARY OFTHE INVENTION Broadly the present invention provides a trigger fuse switch assembly wherein the trigger fuse may only be properly inserted to the assembly and is held to insure operation of the contacts thereof when activated, with the assembly being readily adaptable for either normally open or normally closed operation.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a pictorial diagram of the fuse assembly of the present assembly in its normally open position;

FIG. 2 is a side view of the fuse assembly having a partially cut away portion; I

FIG. 3 is a partial top view showing the fuse mourning;

FIG. 4 is a bottom sectional view taken along the line IV-IV of FIG. 2 with the trigger fuse blown;

FIG. 5 is a bottom view taken along the line IV-IV of FIG. 2 with the trigger fuse in its unblown condition; and

FIG. 6 is a partial side view of the contact portion of the assembly in its normally closed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the switch assembly includes a base member [0 which may be formed by molding from a high-strength molded glass polyester insulating material for example. A trigger fuse I2 is shown inserted in the assembly and comprises a long ferrule 14, a short ferrule I6, and a tubu lar portion I8 therebetween. The outer end of the long ferrule 14 defines the striker pin end 20 of the fuse and the outer end of the short ferrule I6 defines the base end 22 of the fuse I2. When the fuse I2 blows, a striker pin 24 (see FIG. 4) is ejected from the striker pin end 20 of the trigger fuse 12. In the normal unblown condition of the fuse I2, the striker pin 24 is recessed within the long ferrule I4 as shown in FIG. 5.

The fuse I2 is held in place by a spring clip terminal 26 and a fuse terminal 28. The spring clip terminal 26 may, for example, be made of beryllium copper, which provides a good electrical connection to the short ferrule 16. The spring clip 26 is mounted in a slot 27 of the base member 10. The spring clip 26 has a top portion 30 which extends above the base I0 so that it may be moved away from the short ferrule I6 to permit the insertion or removal of the fuse I2. The spring slip 26 has a U-shaped portion 32 which extends downwardly into the slot 27. A flat portion 34 of the spring clip 26 has a hole disposed therein which rests over a shoulder portion 36 of the base 10 so that the spring clip 26 may be securely mounted to the base I0 via a screw 38. Adjacent the flat portion 34 of the spring clip 26 is a portion 40 which rests on an inside surface 42 of the base I0. A hole is provided in the portion 40 through which a terminal screw 44 is inserted and secured into the base I0. A contact washer 46 is placed between the head of the terminal screw 44 and the portion 40 of the spring clip 26. The contact washer 46 has two concave portions thereon adapted to receive up to two round electrical conductors so as to insure good electrical and mechanical connection thereto. The terminal screw 44 thus serves as one terminal point, for example, for connection to a main power fuse of semiconductor power equipment.

The spring clip 26 also includes a projection 48 thereon disposed directly behind the base end 22 of the fuse I2 which abuts there under the tension of the spring clip 26 to force the striker pin end 20 of the fuse 12 against the fuse terminal 28. The use of the spring clip terminal 26 thus provides good electrical contact to the short ferrule 16 of the fuse and moreover insures that the striker pin end 20 of the fuse 12 is held under tension against the fuse terminal 28. This arrangement adequately takes care of the relatively large variation in trigger fuse length.

The fuse terminal 28 is generally L-shaped and includes a bottom portion 50 which has a hole therein through which a mounting screw 52 is extended into the base I0 to secure the fuse terminal 28 thereto. The fuse terminal 28 also includes a fuse-receiving portion 53 having a slot 54 therein through which the striker pin 24 of the fuse 12 may extend when the fuse I2 is blown. The portion 53 also includes a pair of wing portions 56 which prevent the fuse 12 from flipping out of the assembly or working its way out under the force of the spring clip terminal 26. A second terminal screw 58 is provided which extends through the portion 50 of the fuse terminal 28 into the base I0. A contact washer 60 similar to the contact 46 is provided between the head of the screw 58 and the portion 50 and is adapted to receive electrical wire for connection, for example, to the other side ofa main power fuse so that the terminal screws 44 and 58 are connected in parallel across a main power fuse. A shoulder portion 62 is provided in the base 10 which has a semicircular top Indentation 64 thereof which serves to seat the fuse I2 at the large ferrule I4 diameter. An aperture 66 is provided through the base 10 from the inner surface 42 to the bottom surface 68 of the base III. This aperture may be utilized for mounting the assembly to any suitable surface from either end of the aperture 66 with any suitable form of securing device. A mounting lug 70 is provided on the bottom surface 68 so as to aid in seating the assembly on a mounting surface and is useful when a plurality of assemblies are mounted side by side.

FIG. 3 demonstrates the feature that the fuse 14 cannot be mounted in the assembly in the backwards position. For proper mounting of the fuse 12 between the

terminals

26 and 28, it is necessary that the long ferrule I4 abut against the fuse terminal 28 so that the striker pin 24 thereof will be in the proper position. FIG. 3 shows the diameter of the long ferrule I4 to be DI. The diameter of the short ferrule I6 may also be D] or may vary from this value slightly. However the diameter of the tubular insulating portion I8 between the ferrules I4 and 16 is of a smaller diameter D2. As shown in FIG. 3 the base 10 is designed to have stop portions 72 which extends into the slot 27 so as to define the distance D2 thcrebetween. The distance D2 is smaller than the distance DI, but it is of sufficient width to permit the passage ofthe tubular portion 18 of the fuse I2 therethroughv The short ferrule I6 fits within the slot 28 with the tubular portion I8 fitting between the stop portions 72 when the fuse I2 is in its normal operating position between the

terminals

26 and 28. If it were attempted to reverse the fuse so that the long ferrule portion 14 were to be inserted to contact the spring clip terminal 26, this would not be possible since the long ferrule I4 would have to extend through the stop portions 72 which is too small of a gap D2 therebetween to permit the passage of the larger diameter DI of the long ferrule I4. Thus the fuse I2 could not be inserted backwards into the fuse assembly of the present invention and must be disposed between the

contacts

26 and 28 so that the long ferrule abuts against the fuse terminal 28 and the striker pin 24 is disposed in position to be ejected when the fuse is tripped.

Referring now to FIGS. 4 and 5, along with FIG. 2, a pushrod 74 having a large-diameter section 75 is disposed in a passageway 76 in the base III. The passageway 76 extends laterally from behind the slot 54 of the fuse terminal 28 to a rest portion 78 of the base 10. The pushrod 74 may, for example, comprise a plastic insulating material and may ideally be made of a different color than the base 10. An opening 79 is provided in the base It) behind the fuse terminal 28 so that an observer may view the osition of the pushrod 74 to determine visually whether the trigger fuse I2 has been blown or not. The pushrod 74 has a small-diameter portion 80 which extends through a contact opening 82 in the base I into a passageway 84 in the base I0 which is of a smaller diameter than the passageway 76 however on the same axis.

A movable contact 86 which may comprise a suitable electrically conductive material, such as, brass or beryllium copper coated with silver, and which may have a substantially rectangular shape is provided with a hole therein of sufficient diameter to just fit over the small-diameter portion 80 of the pushrod 74. As shown in FIGS. 2 and when the fuse I2 is in its unblown state the movable contact 86 abuts against the end of the larger diameter section 75 of the pushrod 74 and against the rest portion 78 of the base I0. A coil spring 88 is disposed around the small section 80 of the pushrod 74 and is disposed between the movable contact 86 and a shoulder 90 at the inside edge of the passageway 84. The coil spring 88 thus holds the movable contact 86 under spring tension against the rest portion 78 when the fuse I2 is in its unblown condition as shown in FIGS. 2 and 5.

As better shown in FIG. 4, when the fuse I2 is blown, the striker pin 24 is extended and passes through the slot 54 of the fuse terminal 28 to strike the outer end of the pushrod section 74 causing it to be moved to the right in the passageway 76. The movable contact 86 abutting against the opposite end of the large-diameter section 75 of the pushrod 74 is therefore moved away from the surface 78 of the base 10. The spring 88 is compressed as the contact 86 moves to the right. The small section of the pushrod 74 extends further to the right into the passageway 84. The movable contact 86 moves to the right against the pressure of the coil spring 88 until the movable contact 86 abuts against a pair of fixed

contacts

92 and 94. The fixed

contacts

92 and 94 are made from a suitable electrically conductive material such as brass or beryllium copper coated with silver, for example. The contact between the movable contact 86 and the fixed

contacts

92 and 94 occurs at contact points 96 and 98 of the fixed

terminals

92 and 94, respectively, with the

points

96 and 98 having sharp points to insure good electrical contact between the fixed

contacts

92 and 94 and the movable contact 86. Both the movable contact 86 and the fixed

contacts

92 and 94 are desirably provided with a relatively heavy silver plating to insure good electrical conductivity.

The base I0 is provided with four contact terminal positions I, 2, 3 and 4. As shown in FIGS. 1 and 2, when the switch assembly is in its normally open state, the fixed contact 92 is disposed in the terminal position 3 and the fixed contact 94 is disposed in the terminal position 2. The fixed contact 92 is secured in the terminal position 2 by a terminal screw 100 which extends through a hole in the fixed contact 92 into the base I0 in a slot I02 which defines the terminal position 2. A contact washer I04 is situated between the head of the terminal screw I00 and the fixed contact 92 similar to the contacts 46 and 60 and is adapted to receive up to two round wire conductors. A terminal screw I06 secures the fixed contact 94 in the terminal position 3 defined by a slot 107, with the screw I06 passing through a contact washer I08 similar to the contact 104 and the terminal 94 into the base 10. The fixed

contacts

92 and 94 have bottom lug portions I10 and 112 which are bent inwardly with respect to sidewalls of the base [0 so that these portions of the fixed

contacts

92 and 94 are projecting over the base 10 adjacent the contact opening 82 of the base It]. The fixed contact 92 has another contact point "4 opposite the contact point 96 and the fixed contact 94 has a contact point I I6 opposite the contact point 98. The contacts points I14 and I16 serve no purpose when the switch assembly is operative in its normally open state, but come into operation when the switch assembly is changed to its normally closed state of operation.

An additional terminal screw I20 is provided in the screw terminal position 4 and serves to secure a fixed terminal 122 which may comprise a sliver-coated electrically conductive member to the base 10. The contact I22 has a substantially U- shape and is secured by the screw which is passed through a contact washer I24 and the fixed terminal I22 into the base I0. The terminal screw I20 in the terminal position 4 is provided to supply an ideal output terminal for the connection of an indicating light such as a neon bulb or other indicator light to the switch assembly.

FIG. 6 shows how the switch assembly of the present invention can be readily converted from a normally open type of switch to a normally closed type of switch. The conversion from the normally open type of switch is shown in FIGS. 1 and 2 to the normally closed type of switch of FIG. 6 may be accomplished in the following fashion. The fixed

contacts

92 and 94 are removed from the

terminal positions

3 and 2, respectively. The fixed contact 92 is then inserted into the terminal 2 position on the same side of the base 10 as it was previously disposed. The fixed contact 94 is disposed in the terminal I position being fixed therein by the terminal screw I06 which previously held this contact in the terminal 2 position. The contact 94 is also disposed on the same side of the base I0 in FIG. 6 as it was in the embodiments of FIGS. 1 and 2.

As can be seen in FIG. 6 the contact point II4 of the contact 92 directly contacts the movable contact 86 with the coil spring 88 insuring good electrical and mechanical contact therebetween. 0n the other side of the base I0, in the embodi ment of FIG. 6, the contact point 116 would also contact the movable contact 86. Thus the switch assembly as shown in FIG. 6 provides a normally closed type of switch assembly and only requires the movement of the two fixed

contacts

92 and 94 to effect this modification.

ln the embodiment of FIG. 6, when the trigger fuse I2 is tripped, the striker pin 24 thereof forces the pushrod 74 against the movable contact 86 thereby driving the movable contact 86 away from the fixed

contacts

92 and 94 opening the closed contacts therethrough. The opening of these contacts is thus indicative that the trigger fuse 12 has been blown.

Although the present invention has been described with a certain degree of particularity. it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts and elements can be resorted to without departing from the spirit and the scope of the present invention.

We claim as our invention:

l. A switch asembly operative with a trigger fuse operative to eject a striker pin when blown from one end thereof comprising:

a base member comprising an insulating material:

a fuse terminal mounted on said base member for receiving said one end of said fuse;

a spring terminal mounted on said base member for receiving the other end of said fuse and forcing said one end into contact with said fuse terminal;

a pair of fixed contacts mounted on said base member;

a movable contact;

activating means disposed between said one end of said trigger fuse and said movable contact to move said movable contact with respect to said fixed contacts to either open or close a circuit therebetwcen when said fuse is blown,

said activation means including a pushrod disposed within said base member between said fuse terminal and said movable contact, and biasing means for said movable contact to bias said movable contact to a rest position when said fuse is in its unblown state,

said fuse terminal having an aperture therein permitting said striker pin to pass therethrough when ejected to engage said pushrod and move said movable contact,

said base member including a stop portion thereon preventing said fuse from being disposed between said fuse terminal and said spring terminal except with said one end adjacent said fuse terminal,

said base member also including a plurality of terminal positions for said fixed contacts,

when said pair of fixed contacts are disposed in a first set of said plurality of terminal positions, said assembly being operative as a normally open switch with said movable contact biased away from said fixed contacts by said biasing means,

when said pair of fixed contacts are disposed in a second set of said plurality of terminal positions, said assembly being operative as a normally closed switch with said movable contact being biased against said fixed contacts by said biasing means; and

an auxiliary fixed terminal disposed in one of said plurality of terminal positions for providing an auxiliary electrical connection to said assembly,

said pair of fixed contacts each including a pair of contact points on opposite sides thereof,

when said pair of fixed contacts are disposed in said first set of terminal positions, said contact points on one side of each of said pair of fixed contacts making contact with said movable contact when said fuse is blown,

when said pair of fixed contacts are disposed in said second set of terminal positions, said contact points on the other side of each of said pair of fixed contacts making contact with said movable contact when said fuse in unblown.

Claims

1. A switch assembly operative with a trigger fuse operative to eject a striker pin when blown from one end thereof comprising: a base member comprising an insulating material: a fuse terminal mounted on said base member for receiving said one end of said fuse; a spring terminal mounted on said base member for receiving the other end of said fuse and forcing said one end into contact with said fuse terminal; a pair of fixed contacts mounted on said base member; a movable contact; activating means disposed between said one end of said trigger fuse and said movable contact to move said movable contact with respect to said fixed contacts to either open or close a circuit therebetween when said fuse is blown, said activation means including a pushrod disposed within said base member between said fuse terminal and said movable contact, and biasing means for said movable contact to bias said movable contact to a rest position when said fuse is in its unblown state, said fuse terminal having an aperture therein permiTting said striker pin to pass therethrough when ejected to engage said pushrod and move said movable contact, said base member including a stop portion thereon preventing said fuse from being disposed between said fuse terminal and said spring terminal except with said one end adjacent said fuse terminal, said base member also including a plurality of terminal positions for said fixed contacts, when said pair of fixed contacts are disposed in a first set of said plurality of terminal positions, said assembly being operative as a normally open switch with said movable contact biased away from said fixed contacts by said biasing means, when said pair of fixed contacts are disposed in a second set of said plurality of terminal positions, said assembly being operative as a normally closed switch with said movable contact being biased against said fixed contacts by said biasing means; and an auxiliary fixed terminal disposed in one of said plurality of terminal positions for providing an auxiliary electrical connection to said assembly, said pair of fixed contacts each including a pair of contact points on opposite sides thereof, when said pair of fixed contacts are disposed in said first set of terminal positions, said contact points on one side of each of said pair of fixed contacts making contact with said movable contact when said fuse is blown, when said pair of fixed contacts are disposed in said second set of terminal positions, said contact points on the other side of each of said pair of fixed contacts making contact with said movable contact when said fuse in unblown.