US2904658A - Drop-out delayed action fuse constructions - Google Patents

Description

Sept. 15, 1959 G.R.M CLOUD DROP-OUT DELAYED ACTION FUSE CONSTRUCTIONS Filed April 4, 1958 l o 26 -L 2 Sheets-Sheet 1 INVENTOR.

Geoaee R. MCwuo BY Fma. gal/2W Awtonuzi Sept. 15, 1 s. R. M CLOUD DROP-OUT DELAYED ACTION FUSE CONSTRUCTIONS 2 Sheets-Sheet 2 Filed April 4, 1958 7. w F U q 3 \w m 2 I U W. W m

0 Km mu n M 3 R I E 6 m m CI m m o 3 w \o 2 8 2 ill A-r-roancv Patented Sept. 15, 1959 iiRoP-oU'r DELAYED ACTION FUSE CONSTRUCTIONS Application April 4, 1958, Serial No. 726,554 Claims. c1. 200 414 This invention relates to dropout delayed action fuse constructions. In drop-out fuse constructions, as heretofore made, it is the usual practice after the fuse blows, to allow the drop-out fuse tube to slide downwardly or move in some manner to break contact between the upper contact of the fuse tube and the upper stationary contact so that there can be no leakage current along the inner surface or even along the outer surface of the fuse tube after the fuse link has been ruptured. This construction is very desirable and is almost universally followed in this general type of drop-out fuse construction. However, it has certain defects one of which is the tendency of the apparatus to operate too rapidly. Extremely rapid mechanical operation of the device following melting of the fusible element causes the upper movable contact of the fuse tube to move away from the upper stationary contact before the overcurrent has been entirely interrupted by the complete extinguishing of the are within the fuse tube itself.

Extremely rapid mechanical operation of the device following melting of the fusible element causes the upper movable contact of the fuse tube to move away from the upper stationary contact before the overcurrent has been entirely interrupted by the complete extinguishing of the are within the fuse tube itself, thus initiating an are between the movable contact and the stationary contact. This arcing outside the fuse tube is not desirable as it causes pitting and burning of the cont-acts which eventually causes overheating of the current carrying parts. Further, this are externally of the fuse tube, causes ionization of the gases and vaporizing of the metal often resulting in flashover between the upper and lower terminals of the cutout and failure of the cutout to interrupt the current.

This invention is designed to overcome the above noted defects, and objects of this invention are to provide a delayed action drop-out fuse construction which is so made that a slight delay is provided between the time that the fuse link is ruptured on overload or while it is carrying a load, and the time at which the contact at the upper end of the fuse tube and the upper stationary contact are separated, thus preventing flashover and burning of the contacts. Broadly stated, objects of this invention are to provide a drop-out fuse construction which will not produce flashover or burning and pitting at its upper separable contacts.

Further objects are to provide a drop-out fuse construction which is so made that use is made of the usual flip-out lever for withdrawing any remaining portion of the fuse link after rupture of the fuse link and to so arrange a mechanical construction operatively positioned between the flip-out lever and the fuse tube as to provide a delay in the release of the fuse tube for downward motion after rupture of the fuse link. This delay allows the fuse tube to completely extinguish the arc within itself before the upper contacts are separated.

Further objects are to provide a time delay construction for drop-out fuse tubes which is so made that bellows, pistons or other devices of this type are not employed but instead, in which a very simple delayed action lever mechanism is employed.

Further objects are to provide a mechanical delay means for drop-out fuse construction which does not necessitate the use of a ratchet or clockwork mechanism but instead which is so constructed that it provides the small needed delay in a simple manner by very simple lever mechanism. 7

Further objects are to provide a delayed action dropout fuse construction which is very cheap to manufacture and which does not require any additional room at the lower portion of the drop-out fuse construction over that provided in the usual well-known fuses of this general type.

An embodiment of the invention is shown in the accompanying drawings in which:

Figure 1 is a vertical section through the device showing the fuse tube in operative position.

Figure 2 is a fragmentary sectional view of the lower portion of Figure 1 showing the fuse tube after it has dropped downwardly under the influence of its spring and gravity.

Figure 3 is a fragmentary bottom view of the structure shown in Figure 1 with parts omitted for the sake of clearness.

Figure 4 is a line section on the line 4-4 of Figure 1.

Referring to the drawings it will be seen that a housing 1 of porcelain or other insulating material provided with a door 2 of plastic or other insulating material has been shown. The housing 1 is provided with an upper stationary contact assembly indicated generally by the reference character 3 and provided with a line terminal clamping means 4 adapted to receive a line wire which may be passed through the upper opening 5 in the side wall of the housing. The housing also carries a lower stationary contact assembly indicated by the reference character 6 and provided with a line terminal receiving member or clamping member 7 adapted to receive a line wire after it has been passed through the lower opening 8 in the housing wall.

The door 2 is provided with a lower contact consisting of an outer member 9 to which is welded or otherwise secured an inner sleeve 10 through which the fuse tube 11 is adapted to freely slide. The guiding sleeve 10 need not be of metal, but could be molded as an integral part of the door. It is to be noted that the lower stationary terminal 6 of the housing has a pair of spring arms 12 which engage opposite sides of the lower .contact 9 of the door 2, see Figure 4.

It is to be understood that the invention could be followed for open types of drop-out fuse constructions.

It is to be noted that the lower terminal 9 on the door is provided with side walls 17 which have grooved or indented portions 13, see Figures 1 and 4, and that the arms 12 of the lower stationary contact have inwardly bent, or indented portions 14 which yieldinglv interlock with the grooves or portions 13. This construction holds the door closed but allows it to be pulled open by means of the handle 16 formed integrally with the door 2.

The side walls 17 are each provided with a slanting slot 19 for a purpose hereinafter to appear. Also it is to be noted from reference to Figures 1 and 3 that the side walls 17 are provided with outwardly projecting pins 18 which are removably received in notches 15 formed in the hooklike portions 20 supported from the inner walls of the housing.

It will be seen from the description thus far given that the door 2 is pivotally-carried by the housing 1 and is normally held in its upright closed position, but may be rocked downwardly if so desired, or may be lifted from the housing for refusing.

The fuse tube 11 is provided with an upper terminal indicated generally by the reference character 21, see Figures 1 and 2. This upper terminal consists of a portion 22 carried by the fuse tube 11 and a cap 23 screwed on the portion 22 and arranged to clamp a disklike head of the fuse link, not shown, between the metal members 22 and 23 in accordance with the usual practice.

The upper terminal 3 of the housing is provided with a contact spring finger 24 which bears against the upper metal cap 23 of the upper terminal 21 of the fuse tube.

The leader portion 25 of the fuse link projects through the bottom open end of the fuse tube and is clamped by means of the fastening means 26 to the lower terminal 9 of the door or fuse tube assembly.

The device is provided with a flip-out lever 27, see Figure 1, which is pivotally mounted at 28, and is urged in a clockwise direction by means of the spring 29. This flip-out member 27 is in reality a fuse link extracting lever, and is adapted to quickly extract any remaining portion of the fuse link after the fuse link has been ruptured by overload.

This flip-out lever 27 is roughly channel shaped and pivotally supports links 30 located on opposite sides thereof and extending outwardly beyond the flip-out lever as may be seen from Figure 3. The outer end of the links 30 are joined by means of a transverse pin 31 which normally holds the fuse tube 11 against downward sliding motion. The fuse tube 11 is provided with a groove 32 into which is spun a collar or retaining member 33 which is engaged by the transverse pin 31 of the links 30. The collar or restraining member 33 also acts as a stop against which the lower end of a coiled spring 34 bears, such spring being loosely coiled about the fuse tube 11 and bearing at its upper and against the bottom portion of the sleeve and urging the fuse tube downwardly in a positive and effective manner. Gravity also urges the fuse tube downwardly and completes the downward travel of the fuse tube though obviously the spring may be so proportioned as to be effective throughout the entire downward motion of the fuse tube 11.

The fuse tube 11 is normally retained in its uppermost or service position as shown in Figure 1 by the engagement of the transverse pin or rod 31 with the collar 33. However, when the rod or pin 31 moves downwardly out of engagement with the collar 33, the fuse tube is free to drop or slide downwardly under the influence of the springs 34 and 24 and of gravity.

Obviously other ways of making the collar 33 either as a separate member or as an integral member could be followed.

It has been found that with fuse constructions of this general type that the downward motion of the fuse tube frequently occurs so quickly after rupture of the fuse link that the fuse tube does not have an opportunity to thoroughly clear itself and thus interrupt the are which is formed when the fuse link is ruptured under load. Under these conditions it also frequently happens that an arc is formed between the upper movable contact of the fuse tube and the stationary upper contact of the housing, thus pitting these members and causing heating of the current carrying portions of the device and ionizing of the gases within the housing. This sometimes causes flashover between the stationary contacts followed by complete destruction of the entire device.

A primary purpose of this invention is to provide means to guard against the destructive flashover as well as burning or pitting of the normal current carrying contacts. This result is obtained by slightly delaying the downward motion of the fuse tube after rupture of the fuse link, thus allowing the fuse tube to clear itself completely before the upper fuse tube contact moves away from the upper stationary contact of the housing. The delay in the 4 downward motion of the fuse tube is obtained by the construction hereinabove described.

It is to be noted that the transverse pin 31 of the links 30 rides in the slots 19 formed in the side walls 17 of the lower contact assembly of the door. The length of the slots 19, therefore, determines the length of time that the pin 31 remains in engagement with the restraining collar 33 of the fuse tube 11, and thus provides the necessary delay to insure complete and perfect clearing of the fuse tube before the upper contacts of the housing and fuse tube separate. It is apparent that the longer the transverse pin 31 remains in engagement with the collar or stop 33 of the fuse tube, the longer contact is maintained between the upper movable contact of the fuse tube and the upper contact of the housing, since the spring finger 24 of the upper contact of the housing, see Figure 1, will follow the upper movable contact 21 of the fuse tube downwardly a considerable distance before con tact is broken. It is also to be understood that the, time delay depends primarily on the length of the slots 19 and the diameter of the collar 33 and the diameter of the pin 31, but also depends to a lesser extent on the strength of the springs urging the fuse tube downwardly and the mass of the moving parts.

It has been found that this delay is sufiicient to allow adequate clearing time, or in other words to insure perfect clearing of the fuse tube internally before contact is broken between the upper movable contact of the fuse tube and the upper stationary contact of the housing. It will also be noted that the flip-out lever is not dependent for its motion on the downward motion of the fuse tube. Instead the flip-out lever is actuated by its own spring independently of the spring which acts on the fuse tube and urges the fuse tube downwardly.

It will be seen further that the primary purpose of this invention is obtained by providing this time delay mechanism which is a very simple construction, and which does not depend upon any dashpot or bellows action whatsoever, or upon any type of escapement mechanism. Instead the slight amount of time delay needed to insure clearing of the fuse tube before parting of the upper movable contact and the upper stationary contact, is obtained by a simple lever construction or lever mechanism and a guiding slot whose length and association with other parts of the lever mechanism determines the length of the delay.

Further, it is to be noted that this delay is obtained by a very small and simple type of mechanism which does not materially increase the cost of the device, and does not require any additional room at the lower portion of the fuse structure. These are very important and desirable features in drop-out fuses.

The guiding collar through which the fuse tube slides need not be a part of the lower contact of the fuse tube, but could be formed as an integral portion of the door. Further than this, the flip-out lever need not be pivoted on the lower contact of the fuse tube and the guiding slots need not be formed in such lower contact. Instead, some other member could have the guiding slots and the flip-out lever could be pivoted on such other member. All the above detailed alternate constructions are shown in my copending application, S.N. 726,787, executed March 24, 1958. Other changes in the details of this invention could be made without departing from the spirit of the invention.

Therefore, although the invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. A drop-out fuse construction comprising a fuse tube, means slidably supporting said fuse tube, a contact adjacent one end of said fuse tube and carried by said fuse tube, a stationary contact engaging said first mentioned contact, a second contact adjacent to the other end of said fuse tube and carried by said fuse tube, a stationary contact engaging the contact carried by said fuse tube adjacent said other end thereof, a flip-out lever, a fuse link Within said fuse tube normally joining the contacts of said fuse tube and passing around said flip-out lever, spring means urging said flip-out lever towards flip-out motion, restraining means for restraining said fuse tube against motion, and mechanism operatively connecting said restraining means and said flip-out lever and delaying and restraining said fuse tube against motion and delaying the separation of said first mentioned contact of the fuse tube from the first mentioned stationary contact after rupture of said fuse link, said restraining means including a movable member temporarily operatively engaging said fuse tube and having a relatively long path of motion while operatively engaging said fuse tube and having a final relatively shorter path of motion away from said fuse tube to release said fuse tube, and guiding means for first guiding said movable member along its longer path and subsequently guiding said movable member along its shorter path.

2. A drop-out fuse construction comprising an upper and a lower stationary contact, a supporting means supporting said contacts, a downwardly slidable movable drop-out fuse tube having an open lower end and having an upper contact and a lower contact normally in engagement with the upper and lower stationary contacts, a fuse link within said fuse tube projecting from the lower open end of said fuse tube and electrically connecting the upper and lower contacts of said fuse tube, said fuse tube being arranged to slide downwardly away from the upper stationary contact upon rupture of said fuse link, a flip-out lever for withdrawing any remaining portion of said fuse link upon rupture thereof, links pivoted on said flip-out lever and having projecting ends provided with a transverse pin, said fuse tube having a collar adapted to be engaged by said transverse pin under normal conditions and released when said flip-out lever operates and moves said pin out of engagement with said collar, guiding means having an elongated slot within which the transverse pin of said link mechanism is arranged to slide, said slot extending generally away from said fuse tube and gradually guiding the pin away from the collar of said fuse tube, whereby a time delay is provided after rupture of said fuse link before said fuse tube is released and allowed to move its upper contact away from said stationary upper contact.

3. A drop-out fuse construction comprising an upper and a lower stationary contact, a supporting means supporting said contacts, a downwardly slidable movable drop-out fuse tube having an open lower end and having an upper contact and a lower contact normally in engagement with the upper and lower stationary contacts, a fuse link within said fuse tube projecting from the lower open end of said fuse tube and electrically connecting the upper and lower contacts of said fuse tube, said fuse tube being arranged to slide downwardly away from the upper stationary contact upon rupture of said fuse link, a flipout lever for withdrawing any remaining portion of said fuse link upon rupture thereof, links pivoted on said flipout lever and having projecting ends provided with a transverse pin, said fuse tube having a collar adapted to be engaged by said transverse pin under normal conditions and released when said flip-out lever operates and moves said pin out of engagement with said collar, said lower contact of said fuse tube having an elongated slot within which the transverse pin of said link mechanism is arranged to slide, said slot extending generally away from said fuse tube and gradually guiding the pin away from the collar of said fuse tube, whereby a time delay is provided after rupture of said fuse link before said fuse tube is released and allowed to move its upper contact away from said stationary upper contact.

4. A drop-out fuse construction comprising a casing having an upper and a lower stationary contact, a fuse tube within said casing having upper and lower contacts normally in engagement with said upper and lower stationary contacts, means for guiding said fuse tube for downward sliding motion, a fuse link normally electrically joining the upper and lower contacts of said fuse tube and projecting from the lower end of said fuse tube, a flip-out fuse link extracting lever pivotally mounted on the lower contact of said fuse tube and spring urged towards flip-out motion to withdraw any remaining portion of the fuse link upon rupture thereof, a projecting member carried by said fuse tube adjacent its lower end, lever mechanism pivoted to said flip-out lever and projecting from said flip-out lever towards said fuse tube and provided with a portion adapted to engage the projecting portion of said fuse tube under normal conditions to hold said fuse tube in operative position as long as said fuse link is unbroken, an elongated slot for guiding the outer end of said link mechanism upon motion of said flip-out lever, whereby a time delay is provided between the time of the rupture of said fuse link and the movement of the upper contact of said fuse tube away from the upper stationary contact.

5. A drop-out fuse construction comprising a fuse tube, means slidably supporting said fuse tube, a contact adjacent one end of said fuse tube and carried by said fuse tube, a stationary contact engaging said first mentioned contact, a second contact adjacent to the other end of said fuse tube and carried by said fuse tube, a stationary contact engaging the contact carried by said fuse tube adjacent said other end thereof, a flip-out lever, a fuse link within said fuse tube normally joining the contacts of said fuse tube and passing around said flip-out lever, spring means urging said flip-out lever towards flip-out motion, restraining means for restraining said fuse tube against motion, and mechanism operatively connecting said restraining means and said flip-out lever and delaying and restraining said fuse tube against motion and delaying the separation of said first mentioned contact of the fuse tube from the first mentioned stationary contact after rupture of said fuse link, said restraining means including a movable member temporarily operatively engaging said fuse tube, and time delay means directly engaging said movable member and producing a delay in the operation of said movable member from an engaged position with said fuse tube, to a disengaged position, and being independent of any initial or delaying action of any other portion of the restraining means and acting solely upon said movable member.

References Cited in the file of this patent UNITED STATES PATENTS 2,138,255 Schultz et a1 Nov. 29, 1938 2,203,928 Schultz June 11, 1940 2,231,510 Schultz Feb. 11, 1941 2,313,364 Schultz Mar. 9, 1943 2,423,258 Schultz July 1, 1947 2,458,743 Schultz Jan. 11, 1949 2,513,822 Schultz July 4, 1950

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