US2089387A - Protector for electric circuits - Google Patents

Description

Aug. 10, 1937. G. N. LEMMON PROTECTOR FOB ELECTRIC CIRCUITS Filed Oct. 1, 1934 2 Sheets-Sheet 1 INVENTOR Filed Oct. 1, 1934 2 Shee ts-Sheet 2 .ENVENTOR F ii. l l l I I mi i Waienteti Aug. 16, 193'? UNITED STATES EATENT GZFFW PROTECTOR FOR ELECTRIC CIRCUITS George N. Lcmmon, Homewood, Ala.

Application mm 1, 1934, Serial No. 746,384

9 Claims. (Cl. 200l26) The purpose of this invention is to prevent single-phase operation of a three-phase circuit which is protected by fuses.

On such a three-phase circuit, when one line is opened by the blowing of a fuse, the two other lines still carry single-phase current to such motors as are then in operation. This is undesirable, and my device causes the blowing of the fuses in both of the other lines in case any one of the three lines becomes open-circuited by the blowing of a fuse.

This invention can be used when there is but one fuse for each'line but it is particularly useful when used in conjunction with repeater fuses, such as are shown in my Patent No. 1,954,634 issued April 10, 1934. On such a repeater fuse. the No. 1' tube with its fuse-link is normally in circuit while the No; 2 and No. 3 tubes are in reserve position. When the No. 1 fuse blows, its 20 tube drops open and then the No. 2 fuse closes up into circuit-closing position. Similarly, blowing the No. 2 fuse brings No. 3 into circuit. If the No. 3 fuse also blows the circuit remains open until refused. A three-phase circuit pro- 25 tected by reepated fuses becomes single-phased only after the third fuse has blown in one of the three lines. Therefore my protector device is preferably arranged so that it operates upon the blowing of the No. 3 fuse in any one of the lines.

High voltage circuits cannot be opened successfully in free air; but when a fuse blows inside of an expulsion tube the explosive efiect stops the flow of current. When one of the No. 3 fuses has ruptured, my protector device places a 35 short-circuit across all three lines of the circuit.

This causes all the other fuses to blow and so leaves the circuit fully opened instead of leaving it single-phased. The short-circuiting arms of the device are preferably connected solidly to- 40 gether and all grounded; but if desired one or more resistance elements, properly insulated, can easily be included to limit the overload imposed when the device operates.

Referring to the drawings, Fig. 1 shows part 45 of a three-phase circuit with three repeater fuses installed, together with my protector. Fig. 2 is a side view of the same from the right side; Fig. 3

is a partial section, in larger scale, of the operating mechanism of the protector; and Fig. i 50 is a similar front view of the mechanism, while Fig. 5 shows the grounding bar in operating position.

In Fig. 1 three incoming lines are indicated b i, 2 and 3, while lines to the load are indi- 55 cated at i, ii and ii. Dotted lines are used avoid interference with parts of the protector itself. The three fuses normally in service are l, 6 and 9. The fuse link 9' is in service, the fuse link i6" is in reserve position, and I6 shows a portion of the blown fuse link. Near the fuses is the grounding shaft Hi, to which are attached three ground-arms, H, H, II.

The trip-shaft I2 is near the ground-shaft, and both shafts are supported by the housings ll, [3, l3. Near one end of the trip shaft is the control-arm l4. Each housing also carries a tube I!) which has a projecting plunger ll, so placed that the plunger will be struck whenever one of the No. 3 fuse tubes, i6, I6, l6 blows its fuse-link and drops to the open position l6. The ground-shaft I0 is partially rotatable and when so rotated moves all three ground-arms from the position ii to H. Inside each housing If the shaft l2 has secured to it an arm I! and adjacent to this arm is twist-arm i9, supported on a stud and biased towards I6 by the spring 21.

The arm I! has an end 22 which is held by the latch 23. A spring 24 biases the latch 22 against release, and the extension 25 of the latch arm 23 is in line with the inside end ll of the plunger ll.

Inside the housing l3, the shaft i0 has secured to it an arm 26 which is biased by the spring 21 to move the ground-arms H up to the position ll. Inside of one or more of the housings, the

arms l6 and 26 are connected by the link 28. A.

suitable stop 29 allows, the linkage ill-28 to come somewhat beyond the straight-line. position. When in this position this linkage forms a positive toggle-lock to prevent rotation of 26 and iii. A latch 30 pivoted on the pin 3| is biased by the spring 32 so that it can engage with the stud 33 in the arm l8, thereby preventing backward rotation of the arm l8 and the shaft l2.

Supported by the end housing I! is the control arm I, which is movable to rotate the shaft 34 and the crank and pin 36 which are inside the housing. This pin 36 engages against the arm I! so that it can rotate l8 clockwise when I4 is moved from H to M as shown in Fig. 2, and when 36 is thereby moved from the position shown in Fig. 3 by full lines to the position shown by dotted lines. When the outside arm is in the position N, the pin 36 is away from l8 and the end 36' is engaged with 30 so that 30 is disengaged from the stud 33. In this position the device is ready to function.

Under such conditions l2 can be rotated, thereby releasing the toggle-lock of the linkage arm It and the shaft II, in clockwise motion.

Operation is as follows: If one of the No. 3 tubes on any of the repeater fuses drops to the 5 position It its strikes I1 and drives l1 against II. This releases 23 from 22, and fl rotates I9 against ll, moving the toggle-joint II and II beyond the center position. 'Ihereupon 21 rotates II to the position 26, and this rotates l0 l0 and brings all the ground arms to the position II, in connection with the conductors l, I, 6. Thereby the remaining fuses in the two other iinesare all blown, and the three-phase circuit is completely open. A contact member I may be used to avoid any burning of the line conductor 8.

When the line trouble has been cleared the equipment is re-fused as follows: With an insulated stick, the operator pulls down, It to It as a far as possible. This rotates It against II, and

10 so rotates the whole shaft l2 until every member II has been pushed back, tensing 2i and engaging 2! with 13. The stop 29 is reached by 28 only after I! and 28 are ensu d. At the same time II has engaged with 3!, locking the protector open. The man then re-fuses the repeaters in the usual way placing the No. 1 tubes all in service and the No. 2 and No. 3 tubes all in reserve position. He then pushes the control ,arm from It up to ll, which lifts 30 away from 33 and ena gages it with the notch, in so. The spring :2 acts to hold ll over 38'. thereby keeping the arm ll up until it is forcibly pulled down.

The equipment is thus again set ready to operate automatically.

I am not limited to the methods of construction here shown. for the details can easily be modified in many ways without departing from the fundamental principle of my invention. Also my invention can beeasily applied to single fuses or to repeater fuseshaving other than three I claim:

i. A protector for electric circuits comprising a conductor, a plurality of fuse containers connected to the conductor, a fuse within each container, an adjacent fuse in 'series with an adiacent conductor, together with automatic means to blow the adjacent fuse. the operation of said last means being initiated by motion of one of 50 the said containers.

2. A protector for an electric circuit comprising automatic means to short-circuit all the conductor-sot the circuit. a fuse in circuit with each 2,089,887 II and II, whereupon the spring 22' rotates the of said conductors, a container for each fuse, together with means operable by the motion of one of the said containers to initiate the operation of the said automatic means.

3. A protector for an electric circuit comprising automatic means to short-circuit all the conductors of the circuit, a plurality of fuses connected to each of said conductors, a container for each fuse, together with means operable by motion of one of said containers to initiate the action of said automatic short-circuiting means.

4. In combination, a conductor, a plurality of fuses connected therewith, another fuse adjacent thereto, automatic means operable upon the rupture of a certain one of the first fuses to rupture the said adjacent fuse.

5. Protection for electric circuits comprising a plurality of circuit conductors, a plurality of fuses associated with one of said conductors, a fuse associated with another of said conductors together with automatic means to blow the last said fuse upon rupture of the last of said plurality of fuses.

6. Protection for electric circuits comprising a plurality of circuit conductors, a plurality of fuses associated with each of said conductors, together with automatic means operable upon the rupture of all fuses associated with any one of the said conductors to rupture all of the fuses associated with one of the other said conductors.

7. Protection for electric circuits comprising a plurality of circuit conductors, a plurality of fuses connected to each of said conductors, together with automatic means operable upon the rupture of all fuses connected to any one of the said conductors to rupture a fuse connected to each of the other said conductors.

8. Protection for electric circuitscomprising a plurality of circuit conductors, a. plurality of fuses associated with each of said conductors. together with automatic means operable upon the rupture of all fuses associated with any one of the said conductors to rupture all of the other said fuses.

9. Protection for electric circuits comprising a plurality of adjacent conductors, circuit interrupting means in series with each conductor and operable independently of each other, together with automatic means operable after a pre-determined number of operations of one of said circuit interrupting means to operate another of said circuit interrupting means.

GEORGE N. LEMMON.

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