US2794095A - Striker pin structures - Google Patents

Description

y 1957 F. J. KOZACKA STRIKER PIN STRUCTURES Filed Nov. 15, 1954 2,794,095 Patented May 28, 1957 STRIKER PIN STRUCTURES Frederick J. Kozacka, South Hampton, N. 1]., assignor to The Chase-ShaWmut Company, Newlnlrypurt. Mass.

Application November 15, 1954, Serial No. 468,798

9 Claims. (Cl. 200-417) This invention relates to means for indicating blowing of fuses and for operating mechanisms such as, for instance, circuit breakers, responsive to blowing of fuses.

One way of indicating whether or not a fuse has blown is to shunt its fuse link or fuse links by an indicator wire or tell-tale wire restraining a loaded spring. Upon fusion of the fuse link or fuse links as a result of an excessive current. the indicator wire or tell-tale wire is subjected to a relatively high current flow and consequently fuses, thus releasing the loaded spring which had been restrained by it. The energy stored in the spring may be used to operate any device having a relatively small mass that can easily be moved from one position to another. Attempts made in the past to apply such devices for moving relatively large masses, or overcoming substantial amounts of friction, e. g. for tripping automatic switches or circuit breakers, were generally unsuccessful. Increasing the force of the wire-restrained springs calls for stronger spring-restraining wires, having larger cross-sections and larger masses, and thus being conducive to more severe interrupting conditions upon fusion thereof and initiation of arcing. Since the spring-restraining wires ought to be of steel to provide sufficient tensile strength, the interrupting conditions resulting from their fusion and vaporization are more onerous than those resulting from fusion and vaporization of wires of say, silver or copper. Silver and copper give rise to less onerous interrupting conditions when they fuse and vaporize than steel. Using relatively thick spring-restraining wires makes interrupting conditions even more onerous. Since in structures of this kind the wire-biasing spring is arranged outside, and the spring-restraining wire inside, of a casing, and since one end of the spring-restraining wire must be threaded through a hole in the fuse structure to be attached to the wire-biasing spring outside of the casing, there is a danger of escape of the hot steel vapors resulting from the vaporization of the spring-restraining wire through the hole provided for the passage of the wire. Such an escape of hot ionized metal vapors may cause destruction and vaporization of the wire-biasing spring. This, in turn, may result in more serious troubles, even in major faults and consequent shutdowns. For these reasons devices of the aforementioned character are now generally used as blown fuse indicators only, in which case the wire-biasing spring may be light and the spring-restraining wire may have but a small mass. In other words, there is a tendency against the application of such devices for tripping circuit breakers and automatic switches.

It is, therefore, one object of this invention to improve devices of the aforementioned character to enable their safe use as striker pin devices, i. e. for the purpose of performing operations requiring a relatively large amount of mechanical energy such as, for instance, tripping of circuit breakers or automatic switches.

Where it is necessary to release a relatively large amount of mechanical energy upon blowing of a fuse, sufficient to overcome the latch friction of a circuit breaker and to trip a circuit breaker, or to perform a similar mechanical task, the required mechanical energy is generally derived from a combustible or explosive charge which is ignited upon blowing of a fuse, and in turn impels a striker pin against a tripping latch, or the like mechanism. In quite a number of instances it requires relatively large combustible or explosive charges to release the amount of energy called for by the striker pin device, and in many applications it is not desirable to resort to the use of relatively large highly combustible or explosive masses.

It is, therefore, another object of this invention to provide a so-called striker pin device capable of releasing relatively large quantities of mechanical energy upon blowing of a fuse by which it is controlled without resorting to the use of relatively large combustible or explosive charges.

In recent years users of striker pin devices have become increasingly apprehensive of. the use of relatively large highly combustible and explosive charges. This resulted in the development of striker pin devices capable of releasing relatively large quantities of mechanical energy but requiring relatively small combustible charges. In the striker pin devices having but a relatively small combustible charge, a relatively strong spring is normally restrained by a relatively strong steel wire; the latter is destroyed upon blowing of the fuse by the action of a relatively small combustible mass. Ignition of this relatively small combustible mass in response to blowing of the fuse is effected by means of an igniter which shunts the link, or the links, of the fuse. This arrangement is quite complicated and expensive to manufacture, and is also open to other objections.

It is, therefore, another object of the invention to provide a striker pin device capable of releasing relatively large quantities of mechanical energy upon blowing of the fuse with which the striker pin device is associated consisting of a combination of parts which is easy and simple to manufacture, reliable in operation, and which does not require any combustible or explosive charge for its operation, nor igniter means for controlling the operation of such a charge.

Another object of the invention is to provide a striker pin device having highly effective heat resistant means for precluding the escape of products of arcing from the space where the spring-restraining wire is located to the outside of that space, and more particularly to the region where the Wire-biasing operating spring of the device is located.

Other objects and advantages of my invention will become apparent as this specification proceeds, and the features of novelty which characterize my invention are being pointed out with particularity in the claims appended to and forming part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing wherein:

Fig. 1 is a longitudinal section of a striker pin device embodying the present invention and a side elevation of a current-limiting fuse with which the striker pin device is associated;

Fig. 2 is an end view of the structure shown in Fig. l, and

Fig. 3 is a longitudinal section of another embodiment of my invention comprising a high current-carrying-capacity current-limiting fuse and a striker pin device integrated into a unitary structure.

In Figs. 1 and 2 reference character A has been applied to generally indicate a fuse and reference character B has been applied to generally indicate a striker pin device. The fuse has been shown in a diagrammatic fashion only. It may be a fuse of any desired type, for instance, a fuse of the type disclosed in United States Patent 2,670,418 to Frederick J. Kozacka, February 23, 1954, Fuse and Fuse Holder. The striker pin device B comprises a tubular casing 9 of insulating material which is closed on both ends by inner terminal caps or ferrules 2. The steel wire 7 is arranged along the geometrical axis of easing 9 and immersed in a pulverulent arc-quenching filler 8, e. g. 50/60 grain size quartz sand. The outer ferrules or terminal caps 6 are mounted under pressure upon the inner ferrules or terminal caps 2. The outer ferrule or terminal cap 6 on the left side of the striker pin device is provided with a central aperture 12 for the passage of a striker pin. The striker pin comprises an axially outer portion 3 having a relatively small diameter and an axially inner portion 3a having a relatively large diameter. A collar 3b is arranged between the portions 3 and 3a. Collar 3b has a diameter which is larger than the relatively wide portion 3a. Helical spring 4 is arranged around the relatively wide portion 3a of the striker pin device and rests with its left end upon collar 3b and with its right end upon the left inner ferrule 2. The portion 3a of the striker pin is provided with a recess 3c into which the left end of spring-restraining steel wire 7 is inserted and fixedly held in position by means of a mass of solder 11. Both ends of casing 9 are countersunk. The inner ferrule 2 on the right end of easing 9 is drawn into the countersunk portion of easing 9 whereby an enclosed space S is formed between the inner right ferrule 2 and the outer right ferrule 6. The inner right ferrule 2 is provided with a fine hole 14 through which the spring-restraining wire 7 is threaded. The space S between the inner ferrule 2 and the outer ferrule 6 on the right end of the striker pin device is filled with a mass of solder 11 fixedly holding in position the right end of spring-restraining steel wire 7. The left end of spring-restraining steel wire 7 is threaded through a hole or aperture 14' in the left inner ferrule 2 and through a pair of washers 1 and 5. Washer 1 may be made of fiber and washer is made of a resilient heat resistant elastomer, preferably silicone rubber. Silicone rubbers known by the trade name Silastic have proven to live up to the exacting requirements as to resiliency and heat resistance which must be imposed upon the washer or sealing body 5. Both washers 1 and 5 are provided with fine bores for the passage of steel wire 7. The bore 15 in the silicone rubber washer 5 is sufiiciently large to permit sliding of steel wire 7 therein in a direction longitudinally of steel wire 7 under the action of spring 4, yet bore 15 is sufficiently narrow to establish a substantially gas-tight fit between the lateral sides of bore 15 and the lateral sides of wire 7. The silicone rubber washer 5 is arranged in physical contact with the inner end surface and with the lateral cylindrical surface of the inner ferrule 2 on the left side and held in position by the fiber washer 1 arranged in a plane parallel to that of silicone rubber washer 5.

The operation of the device shown in Figs. 1 and 2 is as follows: When the fuse A is connected into an electric circuit the link or links of the fuse are shunted by steel wire 7. Since steel wire 7 has an ohmic resistance which is high compared to the resistance of the link or links in the fuse, but a very small cunrent will normally flow through steel wire 7, and consequently the heat generated therein will be small. Fuse A being a. highcurrent-carrying-capacity fuse tends to generate a substantial amount of heat which will be transmitted by radiation and conduction, possible also by convection, to the striker pin device B. Hence the latter tends to assume relatively high temperatures, particularly if fuse A and the striker pin device B are enclosed with other fuses in a common housing. Hence the requirement that all constituent parts of the striker pin device B be made of materials capable of resisting elevated temperatures during long periods of time without substantial deterioration. Resilient heat resistant silicone rubbers retain their resiliency even if subjected during the average life of fuse A to the heating action of fuse A and to that of other fuses tending to increase the ambient temperature way above 100 C.

Since wire 7 is normally shunted by the fuse link or fuse links of fuse A, the difference in potential between the ends of wire 7 is normally virtually zero, and the current flow through wire 7 correspondingly small. Upon blowing a fuse A the gap between the terminals thereof previously shunted by the fuse links turns into an insulator of electricity, the difference in potential between the ends of wire 7 increases, and the current flow through wire 7 increases in proportion therewith. As a result, wire 7 is caused to fuse, formation of a break being accelerated by the action of spring 4. The initial break in steel wire 7 is generally formed adjacent the center, mid- Way between the ends thereof. Washer 5 engages steel wire 7 under pressure along its entire periphery, and the pressure of washer 5 upon wire 7 is sufliciently high to preclude the vapors resulting from arcing of wire 7 from escaping along wire 7 through bore 15 to the space out side of casing 9. In other words, bore 15 is sufiiciently narrow to cause rubber body 5 to exert a transverse or radial pinching action upon the entire periphery of wire 7, sulficient to provide a substantially gas-light seal between the lateral sides of wire 7 and the lateral sides of bore 15. After the spring-restraining action of wire 7 has ceased, a break therein having been formed, the pressure exerted by the silicone rubber body 5 upon wire 7 and the friction between both is sufficiently small to permit sliding of the left end of wire 7 (as seen in Fig. 1) relative to washer 5 under the action of spring 4. Hence the striker pin 3. 3b, 3a is impelled with the considerable force inherent in spring 4 from right to left. and its im pact upon a tripping mechanism of a circuit breaker or an automatic switch is suflicient to cause instant positive tripping of the circuit-breaker or switch.

Referring now to Fig. 3, the structure shown therein comprises a pair of terminal elements each including a recessed metal block 20. Each metal block 20 is substantially cylindrical and the juxtaposed faces of blocks 20 are provided with radial grooves 21. Ribbon-type fuse links 22 are inserted into grooves 21 and conductively connected to metal blocks 20 by means of solder joints (not shown). Each link 22 is provided with one or more portions of reduced cross-section, generally rcferred-to as necks. Tin rivets 23 or an overlay of a low fusing point metal may be arranged close to the points of minimum cross-section of links 22 to initiate the interrupting process on occurrence of relatively small protracted overloads. Links 22 are made of a metal having a relatively low fusing energy and a relatively low tensile strength, e. g. of silver. A substantially tubular spacing post 24 arranged in coaxial relation to cylindrical terminal blocks 20 maintains terminal blocks 20 during the assembly of the fuse structure in their proper spaced positions. Spacing post 24 supports a metallic closing cap 25 at each end thereof. Both closing caps 25 are inserted under pressure into recesses in terminal blocks 20, and thus conductively connected with terminal blocks 20. A casing 26 of insulating material encloses the link means 22 as well as the spacing post 24. Transverse steel pins 27 provide a firm tie between casing 26 and metal blocks 20. A body 28 of pulverulent arcquenching filler, preferably pure quartz sand, within casing 26 effects rapid extinction of the parallel arcs formed upon fusion of links 22. Wire 29 arranged within spacing post 24 consists of a metal having a relatively high tensile strength and a relatively high fusing energy, e. g. steel. Wire 29 interconnects conductively the two caps 25 arranged at the end of spacing post 24, and consequently also the terminal blocks 20. A body of pulverulent arc-quenching filler provided within spacing post 24 and surrounding steel wire 29 quenches the are formed upon formation of a break in it. The right end of wire 29 is secured to the right cap 25. The left cap 25 is provided with a bore for the passage of steel wire 29 from the space inside to the space outside of spacing post 24. The left end of spacing post 24 is also closed by two washers 31 and 32 of which the axially inner washer 31 may consist of fiber and the axially outer washer 32 of a heat resists nt elastomer, preferably a suitable silicone rubber. Washers 31 and 32 each have a fine bore for the passage of wire 29 and washer 32 engages wire 29 under pressure along its entire periphery. Striker pin means arranged in substantially coaxial relation with regard to terminal blocks 20 and spacing post 24 comprise the axially outer striker pin portion 3, the axially inner striker pin portion 3a of relatively large diameter, and the intermediate or collar portion 311. The left end of wire 29 is secured to portion 3a and portion 3a is surrounded by a helical spring 4' of which one end rests against the collar portion 3b of the striker pin device and the other end rests against the axially outer surface of one of blocks 20. Spring 4' biases wire 29 in a direction longitudinally thereof and biases the striker pin 3', 3b, 3a away from the center portion of wire 29, i. e. away from the portion thereof situated midway between caps 25.

Both terminals of the fuse shown in Fig. 3 are provided with tubular connectors 33 of which each is closed by a metal disc 34. The tubular connector on the left side of the fuse houses the entire striker pin mechanism, which is thus well protected against any possible damage. The left closing disc 34 is provided with a bore 35 through which the axially outer portion 3' of the striker pin is impelled upon fusion of links 22 and rupture of steel wire 29.

The operation of the device shown in Fig. 3 is as follows: Upon fusion of links 22 steel wire 29 is rapidly heated and ruptured by the joint action of heat and of the spring 4. As a result, an arc is initiated between the ends of the wire where a break has been formed. Washer 32 of silicone rubber, or another suitable elastomer having properties sufficiently similar to silicone rubber, engages wire 29 under pressure along its entire periphery. The pressure between parts 29 and 32 is sufficiently high to preclude the escape of steel vapors, and of other products of arcing, from spacing post 24 through the bores in washer 32 and in the adjacent cap 25, both provided for the passage of steel wire 29. On the other hand, the pinching action, or pressure, exerted by rubber body 32 upon wire 29, and the friction between rubber body 32 and wire 29, are sufficiently low to permit sliding under the action of spring 4' of the left ruptured end of Wire 29, including striker pin 3', 3b, 3a, relative to rubber body 32.

The structure shown in Figs. 1 and 2 and the structure shown in Fig. 3 have different advantages and limitations; each of them is suited and intended for different applications. In Figs. 1 and 2 the fuse proper A and the striker pin device proper B have been shown as being tied together by suitable bracket means. It is, however, possible to substitute any desired kind of electric conductor for these bracket means, e. g. a flexible cable which may be of considerable length, if desired. This enables to arrange the striker pin device proper B at a point remote from the fuse proper A. The striker pin device may be arranged, for instance, close to the tripping latch of a load break disconnect switch which is serially connected with current-limiting fuses, the current-limiting fuses being arranged at a point relatively remote from the lead break disconnect switch and the tripping latch thereof. The structure shown in Fig. 3 excels on account of its compactness, which is primarily due to the close integration of the fuse and the striker pin device, the spacing post of the former being used to accommodate the spring-restraining wire of the latter and one of the electrical connectors of the former being used as a housing for accommodating the striker pin and the operating spring thereof. The arrangement of parts shown in Fig. 3 is particularly desirable where severe space limitations are imposed, e. g. where the fuse is to be accommodated in a circuit breaker housing.

In this particular embodiment of the invention sealing means made of a material other than a resilient heat resistant elastomer may be substituted for washer 32, though the use of a silicone rubber washer, or of a sealing means made of a similar material, is generally dcsirabie because it enables the combined fuse and striker pin structure to be arranged at any desired point, irrespective of whether the ambient temperature at the location of the structure is relatively high or low, and irrespective of whether or not emission of hot products of arcing from the striker pin device is permissible at the location of the structure or not.

It will be understood that I have illustrated and described two preferred embodiments of my invention and that various alterations may be made in the details thereof without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A striker pin fuse comprising a substantially tubular casing, a striker pin arranged coaxially to said casing. a fusible link arranged within said casing, one end of said link being attached to said striker pin, substantially gastight closing means for said casing arranged at spaced points thereof, passage means for the passage of at least one end of said link through said closing means, spring means adjacent to said one end of said link biasing said striker pin and said link in a direction longitudinally thereof, said closing means including casing sealing means made of a heat resistant elastomer engaging said link under pressure along the entire periphery thereof, said pressure being sufficiently low to permit sliding of said one end of said link relative to said sealing means under the action of said spring upon formation of a break in said link.

2. A striker pin fuse according to claim 1 wherein said sealing means is made of a resilient heat resistant silicone rubber.

3. A striker pin fuse comprising a substantially tubular casing, a striker pin arranged in coaxial relation to said casing, a fuse link of steel arranged within said casing, one end of said link being attached to said striker pin, substantially gas-tight closing means for said casing arranged at the axially outer ends thereof, passage means in said closing means for the passage of at least one end of said link from the inside of said casing to the outside thereof and to said striker pin, spring means arranged on the outside of said casing biasing said striker pin and stressing said link in a direction longitudinally thereof, said closing means including sealing means made of a heat resistant elastomer capable of withstanding continuously temperatures in excess of C. engaging said link under pressure along the entire periphery thereof, and said pressure being sufficiently low to permit sliding of said one end of said link relative to said sealing means under the action of said spring means upon formation of a break in said link.

4. A striker pin fuse according to claim 3 wherein said sealing means consists of a heat resistant silicone rubber.

5. A fuse comprising a pair of terminal elements, a pair of spaced recessed metal blocks each forming an integral part of one of said pair of terminal elements, a plurality of fuse links of a metal having a relatively low fusing energy and a relatively low tensile strength conductively interconnecting said pair of blocks, a substantially tubular spacing post for said pair of blocks arranged in coaxial relation thereto, a pair of metallic closing caps for said spacing post each supported by one end thereof and each inserted into a recess in said pair of blocks, a casing of insulating material enclosing said plurality of links and said spacing post, a first body of pulverulent arcquenching tiller within said casing surrounding said plurality of links, a fusible link made of a metal having a relatively high tensile strength and a relatively high fusing energy arranged within said spacing post conductively intercom necting said pair of caps, a second body of pulverulent arc- 7 quenching filler within said spacing post surrounding said fusible link, means providing a passage for one end of said fusible link from the space inside to the space outside of said spacing post, a striker pin arranged in coaxial relation with respect to said pair of blocks and said spacing post attached to said one end of said fusible link, and a helical spring arranged in abutting relation to one of said pair of blocks and to said striker pin biasing said striker pin away from said one of said pair of blocks.

6. A fuse comprising a pair of terminal elements, link means of a metal having a relatively low fusing energy and a relatively low tensile strength conductively interconnecting said pair of terminal elements, a substantially tubular spacing post for said pair of terminal elements arranged in coaxial relation thereto, a pair of metallic closing caps one supported by each end of said spacing post and each conductively engaging one of said pair of terminal elements, a casing of insulating material accommodating said link means and said spacing post, a first body of pulverulent arc-quenching filler within said casing surrounding said link means, a wire of a metal having a relatively high tensile strength and a relatively high fusing energy arranged within said spacing post conductively interconnecting said pair of caps, a second body of pulverulent arc-quenching filler within said spacing post surrounding said wire, means in one of said pair of closing caps providing a passage for one end of said wire from the space inside to the space outside of said spacing post, a striker pin arranged in substantially coaxial relation with regard to said pair of terminal elements and said spacing post attached to said one end of said wire, a helical spring surrounding a portion of said striker pin biasing said striker pin away from the center portion of said wire, and sealing means of a heat resistant elastomer engaging said wire under pressure along the entire periphery thereof, said pressure being sufficiently low to permit sliding of said one end of said wire relative to said sealing means under the action of said helical spring upon formation of a break in said wire.

7. A fuse comprising a pair of spaced parallel metal plates, a pair of connectors each projecting from one of said pair of plates into the space outside of said pair of plates, at least one of said pair of connectors being of substantially tubular shape, link means conductively interconnecting said pair of plates, a substantially tubular spacing post for said pair of plates arranged in coaxial relation with respect to said pair of connectors, a pair of closing caps of metal one on each end of said spacing post each in conductive relation with one of said pair of plates, a casing of insulating material enclosing said link means and said spacing post, a first body of pulverulent arcquenching filler within said casing surrounding said link means, a fuse link having a relatively high tensile strength arranged within said spacing post conductively interconnecting said pair of caps, a second body of pulverulent arc-quenching filler within said spacing post surrounding said fuse link, passage means situated at one end of said spacing post for the passage of one end of said fuse link from the space inside to the space outside of said spacing post, a striker pin attached to said one end of said fuse link arranged inside of said one substantially tubular con nector in coaxial relation thereto, and spring means biasing said striker pin away from said spacing post in a direction longitudinally of said one substantially tubular connector.

8. A fuse comprising a pair of spaced substantially parallel metal discs, 21 pair of connectors each projecting from one of said pair of discs into the space outside of said pair of discs, at least one of said pair of connectors being of substantially tubular shape, link means conductively interconnecting said pair of discs, a first casing extending between said pair of discs enclosing said link means, a first body of pulverulent arc-quenching filler within said first casing surrounding said link means, a second casing of relatively smaller diameter within said first casing arranged in coaxial relation with respect to said one of said pair of connectors, a pair of closing caps of metal each arranged on one end of said second casing and each in conductive relation with one of said pair of discs, a fuse link having a relatively high tensile strength arranged within said second casing conductively interconnecting said pair of caps, a second body of pulverulent arc-quenching filler within said second casing surrounding said fuse link, means providing a passage for one end of said fuse link from said space within to the space outside of said second casing, a striker pin attached to said one end of said fuse link arranged within said one substantially tubular connector in coaxial relation thereto, spring means biasing said striker pin away from said second casing in a direction longitudinally of said one substantially tubular connector, and sealing means of a heat resistant elastomer engaging said fuse link under pressure along the entire periphery thereof, said pressure being sufficiently low to permit sliding of said one end of said fuse link and said striker pin relative to said sealing means under the action of said spring means upon formation of a break in said fuse link.

9. A fuse according to claim 8 wherein said sealing means comprising a resilient heat resistant body of silicone rubber.

References Cited in the file of this patent UNITED STATES PATENTS 1,152,148 Davis Aug. 31, 1915 2,071,435 Saudicoeur Feb. 23, 1937 2,405,929 Wald Aug. 13, 1946 2,572,901 Yonkers Oct. 31, 1951 FOREIGN PATENTS 370,092 Great Britain Apr. 7, .1932 580,462 Great Britain Sept. 9, 1946

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