US1921005A

US1921005A - Electric oil cut-out

Info

Publication number: US1921005A
Application number: US396976A
Authority: US
Inventors: Edmund O Schweitzer
Original assignee: Individual
Current assignee: Individual
Priority date: 1929-10-03
Filing date: 1929-10-03
Publication date: 1933-08-08
Anticipated expiration: 1950-08-08

Description

1933- E. o. SCHWEITZER 1,921,005

ELECTRIC OIL CUT-OUT Filed Oct. 5, 1929 l s Sheets-Sheet 2 J na Aug. 8, 1933. E. o. SCHWEITZER 1,921,005

ELECTRIC OIL CUT-0UT Filed Oct. 3, 1929 3 Sheets-Sheet 3 MKM Patented Aug. 8, 1933 UNITED STATES PATENT OFFICE J ELECTRIC OIL CUT-OUT Edmund 0. Schweitzer, Chicago, Ill. Application October 3, 1929. Serial No. 396,976

38 Claims. (Cl. 200-116) This invention relates in general to electric circuit interrupters and more particularly to interrupters of the kind employing a fuse.

The invention is particularly applicable to circuit interrupters known as fused cut-outs wherein a fuse is mounted in a chamber containing oil or other-insulating liquid, although the invention is not limited to such an arrange ment. A cut-out of this type is shown in the 19 Patent #1,479,558 of January 1, 1924 granted to myself and Alfred Herz.

Briefly, this cut-out comprises a fuse link which is mounted between two compression .blocks of wood or other suitable insulating material and the whole submerged in a bath of oil or other suitable insulating liquid. When the current flowing through the fuse becomes excessive the fuse blows to interrupt the circuit, the oil being relied upon to quickly quench the 20 are that may be formed upon the blowing of the fuse.

When a fuse blows in oil it not only spoils the oil but it also coats the inside of the cut-out and everything therein with a layer of carbon which is highly objectionable in that it constantly breeds trouble. It is an object of the present invention to provide a cut-out which overcomes this dufliculty. This may be accomplished by mounting a certain rated fuse in a bellows, of

metal or other suitable material, and mounting the bellows in an oil tank. The bellows is substantially filled with oil, but the oil content of the bellows should be a small percentage of the total oil in the tank. When the load carried by the fuse is excessive the heat of the fuse will expand the oil in the bellows to trip a catch holding a small quick acting switch blade that is connected in series with the fuse. Should the load reach a certain predetermined value, which is greatly in excess of the maximum instantaneous load to be carried by the circuit the fuse will blow to immediately interrupt the circuit without delaying until the oil within the bellows should heat'sufflciently to bring about the trip- 5 ping of the switch.

The fuse may be mounted within the bellows, or it may be mounted within a receptacle outside of the bellows and a connection provided for permitting the expanding oil within the recep- 0 tacle to expand the bellows ,to trip the switch.

If desired the fuse may be mounted outside of the bellows and arranged, with respect to the bellows, so that the heat of the fuse brings about a heating of the oil in the bellows to expand the same to cause it to trip the switch.

Most of the oil cut-outs are employed in the protection of transformers to promptly disconmeet a defective transformer so that it may not interfere with the service of the remaining apparatus on the same circuit. Certain apparatus which may be connected to the transformer,- such as motors or the like, maytake a starting current of from two to five times the continuous current carrying capacity of the transformer.

In order to-prevent interruption of the transformer circuits when a motor drawing such heavy current is being started it is necessary to employ fuses whose continuous capacity is from two to five times the capacity of the transformer. Transformers are, naturally, not designed to stand even as much as a 50% overload for two or three hours, hence when an overload of 100% is connected to a transformer for any appreciable period of time the transformer burns up since the fuse affords no protection.

To avoid the destruction of a transformer upon the occurrence of such an overload, on the theory that such overloads are unavoidable, thermometers, semaphored thermal indicators, or other indicating devices have been installed in each transformer and an inspector travels the line to see which transformers are running too hot. It is obvious that the inspector cannot be at each transformer when an unexpected load is thrown on due to some customer failing to notify the company of his new load. Therefore, thermal indicators cannot be relied upon to produce the desired results. In addition thermal indicators are of themselves a source of trouble. It is one of the objects of my p'resent invention to not only provide a device which will function as a fuse Ol'ctl'l oil switch upon the occurrence of an overload but which will in addition cut off the transformer when .the temperature of the oil in the-transformer reaches an excessive value, which may be in the neighborhood oj, 901; 1.00 degrees centigrade. This is accomplished in one of the embodiments of my invention, by emersing an oil containing bulb in the transformer casing and connecting this bulb so that upon the expansion of the oil in the bulb, due to a rise in temfrom the following specification taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figure 1 is a plan view of my improved cutout, the cover being removed, said view being taken substantially along the line 1-1 of Figure 2;

Figure 2 is a .view in partial section taken along the line 22 of Figure 1, certain of the parts being shown in section and others being shown in elevation;

Figure 3 is a bottom view of the fuse block with the cover for the fuse'removed;

Figure 4 is a diagrammatic view of a modified form of my invention;

Figure 5 is a diagrammatic view of still another form of my invention; and

the cables extending. into the casing and insulated therefrom. The conductor within the cable 2 is insulated from the body of the casing 1 by the insulation 4. The conductors 5 and 6 within the respective cables 2 and 3 are connected to terminal members 7 and 8 respectively, said terminal members being mounted within the casing. Blocks of bakelite or other suitable insulating material 9 and 10, of a U-shape, are secured to the casing 1 by means of

screws

11 and 12 which pass through the vertical portion of the U. The terminal members 7 and 8 are formed of copper or other suitable metal of high electrical conductivity and are secured to the bottom portion 'of the

insulators

9 and 16 by means of screws 14.

A cover member 20 is adapted to be secured to the top of the casing l. by means of six bolts indicated at 21, said cover member closing the top of the casing and providing a snug fit to prevent theentrance of moisture or other foreign material. into the casing. A block 25 of suitable insulating material is suspended from the cover 20 by means of four bolts 26 which are threaded into the cover member and are locked in place by means of nuts 27. To strengthen the cover at the point where the bolts are threaded into it there are formed a number of ridges 28 at the point where the bolts thread into the cover member.

The studs 26 are threaded into corresponding holes in the block ofinsulation 25 and are locked against turning by nuts 29. Two threaded studs 46 extend through openings in the block 25, on opposite sides of .the center thereof and are locked thereto by lower nuts 41 and a pair of upper nuts 42 and 43. The studs 40 are made of copper or other metal of high electric conductivity. Laminated spring contacts 45 are mounted between the two lock nuts 42 and 43 and are held in firm electrical contact with'the stud '40 by means of these nuts. A pivot member 48 is secured to the left hand contact spring 45 and a similar member 49 is secured to the right hand contact spring 45. The member 68 is pivoted between two arms of a forked link 51 by means of a pin 52 which extends through a circular hole in the arms of the forked member 51 and through a similar hole in the member 48, said member 48 being rotatable with respect to the link 51. The member 49 is similarly pivoted between two arms of a forked link 55 similar in construction to the link 51. The two links 51 and 55 are pivotally connected together by means of 'a pin 56 that extends through holes in, the adjacent ends of both of the links. The links 51 and 55 are made of suitable electrical insulating material so as not to constitute a short circuit between the contact springs 45. The links 51 and 55 constitute a toggle which is illustrated as being in its dead center position.

The pin 56 extends through a nut 57 which is pivoted between the links 51 and 55 so that it may remain horizontal when the toggle comprising the links breaks. It is to be noted that this toggle breaks upwardly. An actuating or tripping rod 58 is secured to the under side of this nut and an operating or resetting rod 59 is secured to the upper side. These two rods may constitute one continuous member, or they may be two separate members. The ends 60 and 61 of the spring contact 45 bear against the flat surfaces 62 and 63 of the terminal members 8.and '7, respectively, when the springs are in the switch closed position, which is the position shown in the drawings. A block 65 of insulating material is suspended from the studs 40 and a fuse link 66 is removably mounted on the bottom side of the block 65 by means of two screws 67. In the construction herein shown, the block 65 has a channel-shaped groove 68 formed on its under side. A metal block 69 of copper or other suitable. conducting material is mounted on. the left hand side of the groove, the stud 40 threading into the block 69 and holding it in wition. A similar block 70 is similarly mounted in the right hand end of the groove. The studs 40 thread into taped holes in the blocks 69 and '20 and thus hold these blocks and the block 65 of insulation in place. The screws 6'? thread into tapped holes in the

blocks

69, 70 and thus hold the fuse link 66 in place and in electrical contact with the blocks.

The block 65 has a cylindrical bore 75 formed therein at its center, and extending about half way through the block.. A smaller cylindrical bore which is internally threaded is formed for the rest of the way through the block. An internally and externally threaded sleeve 76 is threaded into the smaller upper bore and is locked in place by means of a lock nut 77. An expansiblev chamber 7-8 which may be of any suitable-construction and which in the modification herein shown comprises a bellows is mounted on the block 65. A circular plate 79 seals the bottom of the bellows, said plate having an "stud 80 is formed preferably of a material which is-a good conductor of heat for a purpose which will be apparent as this description proceeds. A cylindrical sleeve 83 of suitable insulating material surrounds the bellows 78 being spaced therefrom and extending between the

blocks

25 and 65. The purpose of this sleeve is to prevent the oil or other insulating liquid within the casing 1 from freely circulating around the bellows 78. In addition, this casing prevents the establishment of a contact between the bellows and either of the studs 40., In order to permit the entrance or egress of oil or other suitable insulating medium into. the sleeve 83 the block 65 is provided with a number of holes 84 which extend therethrough.

A cover block 86 of suitable insulation is bolted or otherwise suitably secured to the bottom of the block 65 and provides a' cover for the fuse. The cover block 86 is provided with depressions into which the screws 67 seat and is secured to the block 65 by means of two screws that pass into tapped holes 87 in the block 65. The cover block 86 is provided with a number of holes in alignment with the holes 84 whereby the holes 84 are not plugged up by the cover block.

An explanation will now be given of the manner of operation of my improved circuit interrupter. When the switch is in the closed position a circuit extends from the conductor within the cable 2, through the terminal 7 and the end 61 of the right hand spring contact 45, thence through the stud 40 on the right hand side of the cut-out as seen in Figure 2, thence by way of the block 70, fuse 66 and block 69 to the left hand stud 40, thence through the left hand spring switch 45 to the terminal 8 and the conductor 6 within the cable 3. As previously stated the casing 1 is filled with an insulating oil or other insulating liquid, the liquid level being indicated at 90. The fuse 66 is of a capacity greatly in excess of the continuous capacity of the circuit in which it is connected. Should the load current exceed the rated amount the fuse will over-heat and should the over-load continue for" an extended period of time the liquid adjacent the fuse will be appreciably heated. The bulk of the heated liquid will rise within the cylindrical casing 83 and will act to heat the insulating liquid within the bellows '78. In addition the stud which is in close proximity to the fuse link and therefore in the region of the hottest liquid, will conduct heat to the liquid within the bellows.

This will cause an expansion of the liquid within the bellows with a resulting expansion of the bellows. It is to be understood that the liquid within the entire casing 1 will also be heated but due to the construction of the cut-out as shown the temperature gradient will be such that the liquid in the region of the bellows. will be heated sooner and to a higher temperature than will be the rest of the body of liquid in the casing 1. Upon the expansion of the liquid within the bellows the top of the bellows comes into engagement with the bottom of the actuating or tripping rod 58. Upon further expansion of the bellows the rod 58 is moved upward thereby moving the pin 56 connecting the toggle link 51 and 55 upwardly. A slight upward movement of the pin 56 moves the toggle comprising these links out of dead center. The springs 45 being under stress now act through the

members

48 and 49 to force the center pin 56 of the toggle upwards, the

members

48 and 49 pivoting about the respective links 51 and 55 at the pins 52. The brush ends 60 and 61 of the switch springs 45 are thereby moved out of engagement with the terminals 7 and 8, thus breaking the circuit between the conductor within the conduit 2 and that within the conduit 3. It is to be seen that the tripping of the switch is dependent upon the expansion vof the liquid within the bellows 78 which expansion is not dependent upon the existence of a temperature difference between the liquid within the bellows and that outside of the bellows.

Thus, even if there should be a circulation of the liquid outside of the bellows, that is the liquid within the casing 1, the switch would nevertheless be tripped upon the occurrence of a continuing overload. When the switch trips; the plunger 59 is moved upwardly, said plunger extending through an opening in the top of the casing 1. A sleeve 91 is threaded into the cover member 20, the plunger 59 extending through the sleeve. A covering tube 92 threads onto the sleeve thus closing the top of the casing. To reset the switch the cover portion 92 is unscrewed and the operating rod or plunger 59 is pushed downwardly. Should an exceedingly heavy overload such as a short circuit occur upon the line the circuit is interrupted instantly by the blowing of the fuse. This is necessary because under such circumstances it would be poor practice to permit the short circuit to continue until the liquid within the bellows 78 has heated sufliciently to cause the tripping of the switch. 7T0 replace the fuse the entire mechanism must be removed from the casing 1. To accomplish this end the bolts 21 are unscrewed and, the cover 20 is lifted upwardly. The entire mechanism within the casing is secured to the cover 20 and upon lifting of'the cover that mechanism is drawn upwardly and out -of the casing. It is to be noted that the diameter of the block 25 and the diameter of the block 65 is such as to permit its withdrawal past the insulating members 9 and 10 and through the open top of the casing.

The casing is provided with a drain plug 94 for permitting the draining of the oil or other insulating liquid within the casing.

Reference may now be had to Figure 4 showing a modified form of my invention. My 'im-- which a bottom portion 103 is threaded, is

mounted within the casing 100. The receptacle 101 includes a cover 104 having a handle 105 for removing the receptacle from the casing. A lower fuse terminal 106 is mounted at the bottom of the receptacle and an upper fuse terminal 107 is mounted at the top of the receptacle, with a fuse 108 interposed therebetween. The receptacle 101 is liquid tight and is adapted to contain a suitable insulating liquid such as insulat ing oil, carbon tetrachloride or the like. All expansible bellows member 110 is also mounted within the casing, said bellows being connected to the receptacle 101 by means of a tube 111 121, said contact ,beingopened upon expansion of the bellows.

A member 125 is provided for resetting the switch. The member 125 may constitute a -5 spring, a reclosing solenoid, or any other approved means. A fuse 130 which may be of any preferred construction is likewise mounted within the casing 100. In the embodiment herein shown the fuse is of a construction such as is .shown in thepatent to Nicholas J. Conrad, Serial No. 1,889,424 of October 30, 1928, although any other preferred form of fuse may be used if desired. An incoming line conductor 131 extends into the casing 100 through a suitable bushing 132 which is fluid tight to prevent the leakagebf liquid out of the casing 100. The conductor 131 extends to the terminal 107 of the fuse casing- 101 and from there the circuit extends through the fuse link 108 to the conductor 135, thence to the terminal 120 and the switch" 115 to the terminal 121, thence by the way of conductor 136 to the load. The conductor 136 enters the casing 100 through a bushing 137 which maintains a fluid tight seal. A second line conductor 141 extends into the casing 100 through a fluid tight bushing 142, said conductor extending the circuit through the fuse 130 to the conductor 146 which extends outside of the casing. A bushing 147 is provided for maintaining a liquid tight seal at the point where the conductor 146 extends out of the casing. The

conductors

131 and 141 are connected to a source'of power whereas the conductors 136 and 146 are connected to the load. A suitable cover 149 is provided for the casing. As previously stated the casing 100 is filled with a suitableinsulating material, the liquid level extending above the top of the contact 121.

;The manner of operation of the embodiment shown in Figure 4 is substantially the same as that of Figures 1, 2, and 3 previously described. Upon the occurrence of an overload of a value insufiicient to blow the fuse 108 or the fuse 130 the liquid within the casing 102 will .be heated by the fuse link. Should this overload continue "-then the liquid within the receptacle 102 will be 'heated to such an amount that the expanding liquid which is forced into the bellows 110 by way of the tube 111 will cause a sufficient expansion of the bellows to bring about a tripping of the switch 115 to interrupt the circuit between the

contacts

121 and 120. Should a very severe overload occur, such as that due .to a short circuit or the like, the fuse link 108 will blow to instant- -ly interrupt the circuit. The fuse 130 is pro- ,vided as an added precaution to provide circuit interrupting means in the event that the fuse 108 fails to function.

Reference maynow be had to Figure 5 showing a modified form of my invention. In this figme, I illustrate a manner whereby my improved cut-out may be adapted to interrupt the circut to a transformer, or any other electrical translating means, when the same tends to overheat, and this regardless of whether or not the overheating is brought about by the flow of an excessive current-or is brought about by 6 a defect in the apparatus. In this figure, the cut-out is indicated diagrammatically at 160. The cut-out comprises a casing 161 within which the various switching parts are mounted said casing being adapted to be filled with an insulating liquid and provided with a cover indicated at 162. A fuse link 163 is mounted in a chamber the primary of this transformer. The secondary current upon starting of the load. Should 9.

164 of suitable insulating material, the chamber being suitably mounted within the casing 161 and being provided with a tight fitting cover I 165. A bellows 166 is mounted within the casing 161, said bellows being of any approved construction. A communicating connection 167 connects the chamber 164 with the bellows 166, so that upon expansion of the fluid in the chamber 164 the fluid causes the expansion of the bellows 166. J The bellows is fixed at its upper end and is provided with an operating member or rod 168 for actuating a switch 169. The switch 169 is of the multiple break typeand comprises a number of contacting fingers 170 which are spaced apart by suitable insulation 171 and are adapted to be short circuited by a conducting arm 172 which swings about the pivot point 173. The circuit through the switch extends from the arm 172 through the uppermost contact finger 170 to a conductor 174.

The free ends of the fingers 170 may be connected together by means of a suitable resistor so that upon opening of the switch by movement of the contactor arm 172 sections of the resistor are gradually inserted in the circuit to reduce the current fiow and when the contacting arm 172 leaves the lowermost contact finger the circuit is broken. If desired, the resistor may be omitted so that as the contact arm 172 leaves the uppermost contact finger 170 but is still in contact with the contact finger below it an arc is established between the two uppermost contact fingers. 'As the contact arm 172 continues to move, arcs are successively formed between the next fingers, and-when the circuit is ultimately broken by the contact arm leaving the lowermost contact finger 170 there are a number of series connected small arcs between the respective contact fingers. 'It is well recognized that a better current interrupting action is obtained by establishing a large number of.small arcs in series than could be obtained by the establishment of a single arc of the equivalent length. The arm 175 is integral with the arm 172 but is formed of insulating material rather than of conducting material. A member 176 is provided for reclosing the switch. This member 176 may constitute a spring or itmay be a solenoid.

A line conductor 180 which extends to a source of power enters the cut-out 161 and is connected to the fuse link 163.

From the fuse link the circuit extends through a conductor 181- to-the switch arm 172, thence by way of the uppermost contact finger 170 to a conductor 174 which extends to the primary side of an oil transformer 185.

The opposite line conductor 186 extends from the source of power to the opposite terminal of side of the power transformer is indicated at 187.

The transformer 185 is of the usual construction and is filled with oil in the customary manner. It is of course, understood that the transformer. may be filled with a different insulating liquid or it may be an air cooled'transformer. As iswell understood in-the art the secondary 187 of the transformer is connected to furnish current to a predetermined load. This' load may consist of one or more devices which take an exceedingly heavy current momentarily when starting. For this reason it is necessary for the fuse to be at a capacity of from 2 to 5 times the continuous capacity of the transformer in order to avoid blowing of the fuse due to a rush of thermal indicators of various kinds and an inspector is detailed to travel the lines to see what transformers are operating too hot. It is obvious that the inspector cannot be at each transformer when a new or unexpected load is thrown on due to some customer failing to notify the power company of his new load. Therefore,

thermal indicators are not satisfactory. In the embodiment of the invention herein shown I have provided means for disconnecting the primary side of the transformer when the temperature of the transformer rises above a predetermined value, and this regardless of whether the rise in temperature is due to an overload on the secondary side or due to some defect within the transformer that causes excessive heating thereof. A bulb 190 containing oil or other insulating liquid is emersed in the transformer casing, said bulb being connected by means of a thin tube 191 to the receptacle 164 within which the fuse 163 is mounted. The bellows 166, the casing 164, the tube 191 and the bulb 190 are all filled with insulating liquid. Should a small but continuing overload be connected to the system the fuse 163 will heat the oil within the casing 164 thereby forcing the expanding oil into the bellows 166 which expands so that thelowermost operating member 168 of the bellows actuates the arm 175 of the switch 169 to actuate the switch to open the circuit. In addition, the overload causes a heating of the oil in the transformer casing 185 thereby heating the liquid within the bulb 190.

The liquid within the bulb 190 expands and flows into the casing 164 and then into the bellows 166 thereby further expanding the bellows.

It is apparent that should the transformer overheat due to a defect in the transformer and not due to an overload, the expanding liquid in the bulb 190 will bring about a tripping of the switch 169. It .is obvious that the principles of my inventions as illustrated in Figure 5, are applicable to other translating apparatus than oil filled transformers as shown since it is apparent that the bulb 190 may be located adjacent any part of an'electric device which is liable to overheat. Should a very great overload occur the circuit will be instantly interrupted by the blowing of the fuse 163. It is to be noted that the fuse is mounted in a separate receptacle within the casing 161. As a result the blowing of the fuse does not spoil the liquid within the receptacle 161.

When a fuse blows in' oil or other insulating liquid it spoils the liquid and also it coats the inside of the receptacle and everything else around it with a carbon coating that breeds trouble. In my improved cut-out the oil within the fuse chamber is a small proportion of the total oil in the casing 161 hence only a small portion of the total oil in the cut-out is spoiled eration of the system and during the time that the fuse blows.

Reference may now be had to Figure 6. showing a modified form of switch which may be used in place of the switches shown in the cut-outs of Figure 2, Figure 4, or Figure 5.

The switch comprises a number of leaf springs of current conducting material, said springs being mounted as cantilevers. The leaf springs are indicated at 200 and are mounted at one end and spaced apart by insulation indicated at 201. The springs are shown in the switch-closed position by the full. lines and in the switchopen position by the dotted lines. A conductor such as the conductor 174 is connected to a terminal block 205 which is connected to the uppermost spring 200. A conductorsuch as 181 is connected to the other terminal of the switch circuit, said terminal being indicated at 2061- When the springs are unstressed the circuit is open. The switch is arranged to be closed by a member 168 of insulating material. This switch closing member is the equivalent of the member 168 of Figure 5, being connected'to the bottom portion of a bellows such as 166 of Figure 5. When a switch such as is shown in Figure 6 is used in connection with a cut-out such as is shown in Figure 5, the member 168' is arranged to be elevated when the bellows is expanded instead of being lowered as is the slight amount the springs 200 separate slightly thus introducing/one or more small arcs in the circuit. Upon further upward movement of the operating member 168' further separation of the springs take place thereby increasing the number of arcs and increasing the size of\ the arcs. The first arc to be formed is formed between the lowermost spring 200 and the terminal 206. Upon further separation of the springs this are is increased in length until the lowermost spring 200 assumes its normal position as shown in the dotted'lines. Further upward movement of the insulating member 168' causes the second spring from the bottom to separate from the bottommost spring thus drawing another arc; When this spring reaches its normal position as is shown by the dotted lines thenext spring separates, this drawing still another arc, andso forth until the current flow through the circuit is interrupted and the arcs go out. The oil or other insulating liquid surrounding the arcs tends to cool the arc quickly and in addition the leaf springs 200 extending into the arc tend to accelerate this cooling action thereby tending to quickly deionize the are causing its extinguishment.

In compliance with the requirements of the patent statutes I have herein shownand described a' preferred embodiment of my invention.

It is however, to be understood that the invention is not limited to the preciseconstruction of the embodiments herein shown but is capable of modification, the embodiments herein shown being merely illustrative of v the principles of my invention. What I consider new and desire to secure by Letters Patent is:

1. A switch comprising a pair of stationary contacts, a pair of spring contacts adapted to engage the stationary contacts, said spring contacts including a pair of leaf springs fixed at one end and flexible about the fixed end to bring the other end from the'normal switch open position into engagement with the corresponding stationary contacts, a toggle for maintaining the contacts in engagement, said toggle being substantially on dead center and maintaining the spring contacts under stress when the switch is closed, means for breaking the toggle, whereby the stress on the spring contacts is released and the contacts snap away from the stationary contacts to open the circuit, and thermal means for actuating said toggle breaking means.

2. A switch comprising a pair of stationary contacts, a pair of spring contacts adapted to engage the stationary contacts, a toggle for maintaining the contacts in engagement, said toggle being substantially on dead center and maintaining the spring contacts under stress when the switch is closed, -means for breaking the toggle, whereby the stress on the spring contacts is released and the contacts snap away from the stationary contacts to open the circuit, and thermal means including an electric fuse for actuating said toggle breaking means.

3; A switch comprising a pair of stationary contacts, a pair of spring contacts adapted to engage the stationary contacts, a toggle for maintaining the contacts in engagement, said toggle being substantially on dead center and maintaining the spring contacts under stress when the switch is closed, and means for breaking the toggle, whereby the stress on the spring contacts is released and the spring contacts move the toggle to its release position and snap away from the stationary contacts by the release of the energy stored in the spring contacts to open the circuit, said switch and said toggle breaking means being immersed in a bath of insulating liquid.

4. A switch comprising a pair of stationary contacts, a pair of spring contacts adapted to engage the stationary contacts, a toggle for maintaining the contacts in engagement, said' toggle being substantially on dead center and maintaining the spring contacts under stress when the switch is closed, means for breaking the toggle, whereby the stress on the spring contacts is released and the spring contacts move the toggle to its release position and snap away from the stationary contacts by-the release of the energy stored in the spring contacts to open the circuit, and thermal means for actuating said toggle breaking means, said switch and said toggle breaking means being immersed in a bath of insulating liquid.

5. A switch comprising a pair of stationary contacts, a pair of sprng contacts adapted to engage the statonary contacts, a toggle for maintaining the contacts in engagement, said toggle being substantially on dead center and maintaining the spring contacts under stress when the switch is closed, means for breaking the toggle, whereby the stress on the spring contacts is released and the contacts snap away from the stationary contacts to open the circuit, and thermal means including an electric fuse .for actuating said toggle breaking means, said switch and said fuse being'immersed in a bath of insulating liquid.

ing means for connecting said fuse in circuit with said terminals, an expansible member heated by the fuse, and means controlled by the expansible member for tripping the switching means.

7. A cut out including a casing, a pair of conductors extending into said casing and insulated therefrom, a pair of switch terminals to which said conductors are connected within the casing, a block of insulating material in said casing, a fuse mounted on said block, switching means for connecting said fuse in circuit with said terminals, an expansible member heated by the fuse, means controlled by the expansible memher for tripping the switching means, and a cover for said casing, said block of insulation and the switching means and the expansible member being suspended in the casing from the cover.

8. A cut out including a casing, a pair of con minals, an expansible member heated by the fuse; means controlled by the expansible member fortripping the switching means, a cover for saidcasing, said block of insulation and the switching means and the expansible member being suspended in the casing from the cover, and a reset member for the switch, said reset member extending through an opening in the cover.

9. A cut out including a casing, a pair of conductors extending into said casing and insulated therefrom, a pair of switch terminals to which said conductors are connected within the casing, a block of insulating material in said casing, a fuse mounted on said block; switching means for connecting said fuse in circuit with said terminals, an expansible member heated by the fuse, means controlled by the expansible member for ltripping the switching means, a cover forsaid casing, and a reset member for the switch,

ing in the cover.

, 10..A cut out including a casing, a pair of conductors extending into said casing and insulated therefrom, a pair of switch terminals to which said conductors are connected within the casing, a block of insulating material in said casing, a fuse mounted on said block, switching means for connecting said fuse in circuit with said terminals, an expansible member heated by the fuse, and means controlled by the expansible member for tripping the switching means, said casing being filled with an insulating liquid and said expansible member being set to trip the switch upon the occurrence of a continuing overload below that at which the fuse blows, whereby the circuit within which the fuse is connected is protected and the contamination of the insulating liquid bythe fuse upon the occurrence of slight overloads is prevented.

11. A cut out including a casing, a pair of conductors extending into said casing and insulated therefrom, a pair of switch terminals to which said conductors are connected within the casing, a block of insulating material in said casing, a fuse mounted on said block, switching means for connecting said fuse in circuit with said terminals, an expansible member heated by the fuse, means controlled by the expansible member for tripping the switching means, and a cover for said casing, said block of insulation and the switching means and the expansible member being suspended in the casing from the cover, said casing being filled with an insulating liquid and said expansible member being set to trip the switch upon the occurrence of a continuing overload below that at which the fuse blows, whereby the circuit within which the fuse is connected is protected and the contamination of the insulating liquid by the fuse upon the occurrence of slight overloads is prevented.

12. An electric circuit interrupting device including a fuse, a switch, and thermal means actuated responsive to a rise in temperature of the fuse below its circuit interrupting temperatures for actuating the switch. I

13. An electric circuit interrupting device including a fuse surrounded by a body of insulating liquid, a switch, and means actuated responsive to a rise in temperature of the liquid around the fuse for actuating the switch.

14. An electric circuit interrupting device including a fuse surrounded by a body of insulating liquid, a switch, and means actuated responsive to a rise in temperature of the liquid around the fuse for actuating the switch, said fuse and said switch being electrically connected in series.

15. In combination, a receptacle filled with an insulating liquid, a'fuse within the receptacle, an expansible member within receptacle and heated by the fuse, and switching means actuated by the expansion of said member.

16. An electric circuit interrupter including delayed action means for interrupting the circuit upon the prolonged occurrence of a load in excess of a predetermined amount, and means including a fuse for instantly opening the circuit upon the occurrence of a predetermined load in excess of the first mentioned amount, said delayed acting means including thermal responsive means heated by the fuse.

17. In combination, a pair of spaced parallel blocks of insulating material secured together, a fuse mounted on one of the blocks, resilient switching means mounted on the other block, a toggle mechanism mounted on the blocks for maintaining the switching means in its closed insulating material, a fuse mounted thereon,

rupting the circuit upon the occurrence of a predetermined relatively large overload, and

means for interrupting the circuit upon the oocurrence of a relatively smaller but continuing overload, said means comprising a switch connected in said circuit and means controlled in accordance with the heat dissipation of said fuse for tripping the switch.

20. In an electric circuit, a fuse for interrupting the circuit upon the occurrence of a predetermined relatively large overload, and means for interrupting the circuit upon the occurrence of a relatively smaller but continuing overload, said'means comprising a switch connected in saidcircuit and means controlled in accordance with the heat dissipation of said fuse for tripping the switch, said fuse and said switch being both immersed in an insulating liquid of high are quenching properties and said switch interrupting the circuit and preventing blowing of the fuse and contamination of the liquid upon the occurrence of small but continuing overloads.

21. A cutout including a casing, insulating fluid within the casing, switching means immersed in the fluid, a bellows in the casing, means for expanding the bellows upon the prolonged occurrence of an overload flowing through the switching means, and means for opening the switching means upon the expansion of the bellows.

22. In combination, 'a closed fluid. system including an expansible member, means including an electric fuse for heating the fluid in the system, and electric switching means actuatedby the expansible member upon expansion thereof.

23. The method of protecting an electric circuit against overloads which comprises, inserting in the circuit. a fuse of a capacity in excess of the steady current carrying capacity of the circuit, inserting a switch in the circuit, and opening the switch upon a predetermined heating of the fuse which heating occurs upon the continued flow of current in excess of the rated current but below the current value at which the fuse blows.

24. In combination, a switch, a fuse in circuit therewith, a bath of insulating'arc quenching liquid within which both the fuse and the switch are immersed, and an expansible element expanded by the current flowing through the circuit and controlling the switch, said element being outside of the fuse-switch circuit.

25. In combination, a switch, a fuse, a bath of insulating arc quenching liquid within which both the fuse and the switch are immersed, and means controlled by the fuse for opening the switch under predetermined conditions.

26. A fuse cut-out including a fuse, a switch,

and thermal means controlled by the fuse for contacts snap away from the stationary contacts under their own resiliency to open the circuit, and by. their motion move the toggle to its switch open position.

28. A switch comprising a pair of stationary contacts, a pair of spring contacts adapted to engage the stationary contacts, a toggle for maintaining the contacts in engagement and the spring contacts under sufiicient stress when the switch is closed to furnish the power necessary'to open the switch upon release of the toggle, means for breaking the toggle, whereby the stress on the spring contacts is released and the spring contacts snap away from the stationary contacts under'their own resiliency to open the circuit, said last named means including thermal expansive means.

29. In combination, a liquid system containing insulating, arc quenching liquid, and including an expansible member, means for heating the member including a fuse mounted in the liquid, and switching means controlled by the expansion of said member.

30. In combination, a liquid system containing insulating, arc quenching liquid, and including an expansible member, means for heating the member including a fuse mounted in the liquid, and switching means controlled by theexpansion of said member, said switching means being connected in circuit with the fuse.

31. In combination, a liquid system containing insulating, arc quenching liquid, and including an expansible member, a fuse mounted in the liquid, switching means controlled by the expansion of said member, and a bath of insulating liquid surrounding theswitching means and the first mentioned liquid system.

32. In combination, a bellows, a fuse containing casing communicating therewith, and insulating liquid in the bellows and in the fuse casing.

33. In combination, a pair of parallel blocks I secured 'together in spaced relation, a fuse mounted on one of the blocks, switching means mounted on the other block and connected in circuit with the fuse, a thermal element disposed between the blocks, and means controlled by the thermal element for opening the switching means.

34. A switch comprising a pair of spaced blocks, a switch mounted on the outside of one of the blocks and biased to the open position, a toggle for maintaining the switch in its closed position, a thermal expansive member mounted between switching means mounted on one side of the block, a thermal expansive member on the other side of the block, and switch tripping means extending through the block and actuated by the thermal expansive member to trip the switching means.

36. A switch comprising a casing, a cover therefor, a block suspended within the casing, contact means carried by the casing, switching means mounted on one side of the block and movable into and out of engagement with the contact means,,a thermal expansive member'on the other side of the block, and switch tripping means extending through the block and actuated by the thermal expansive member to trip the switching means.

37. A switch comprising an open top cup shaped casing, switch contacts mounted therein, switching means separatefrom the casing and extending therein from'the open top thereof, a cover for the casing, said cover having an aperture therein, means for moving the switching means into engagement with the contacts including a rod extending through the aperture, and a tube closed at its outer end and removably secured to the cover and forming a closure for the aperture.

38. A'switch comprising an open top cup shaped casing, switch contacts mounted therein, switching means separate from the casing and extending therein from the open top thereof, a cover for the casing, said cover having an aperture therein, means for moving the switching means into engagement with the contacts including a rod extending through the aperture, a tube closed at its outer end and removably secured to the cover and forming a closure for the aperture, and means within the casing for mined conditions.

EDMUND O. SCHWEITZER.