US2003954A

US2003954A - Over voltage protective device

Info

Publication number: US2003954A
Application number: US689632A
Authority: US
Inventors: Ralph R Pittman
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-09-15
Filing date: 1933-09-15
Publication date: 1935-06-04
Anticipated expiration: 1952-06-04

Description

June 4, 1935. IR. R. PlTTMAN 2,003,954

OVER VOLTAGE PROTECTIVE DEVICE Filed Sept. 15. 1953 fl/l.

INVENTOR W4 2, VFW

Patented June 4, 1935 UNITED STATES PATENT OFFICE ovaa VOLTAGE rao'rsc-nva navrcs Ralph a. Pittman, rm Bluif, Ark.

Application September 15, 19:3. Serial No. esaesz 110mm. (01. 175-80) This invention relates generally to devices for the purpose of preventing an excessive superimposed voltage rise on a conductor vor connected apparatus, such as might be caused by lightning,

and particularly to the type of devices described in my co-pending application Serial No. 617,585,iiled' June 16, 1932.

It is an object of this invention to provide an improved structure embodying the device abovementioned in which: (a) the flame incident to a circuit-interrupting arc is prevented from impinging upon the insulating housing; (b) the impact due to the operation of the device is reduced; (c) a separate series gap is provided within the insulating housing; (d) the spring or other biasing mean's urging the insulating elements together is shielded from the flame attending a circuiting arc; (e) an improved arrangement for venting the device is provided; (I) a metallic housing is provided for relieving the insulating housing of any pressure due to the expansion or generation of gas within the device; (g) an improved arrangement for centering, supporting and biasing the insulating elements is provided; and (It) means is provided for limiting the discharge current through the device.

A further object of this invention is to provide a simple, in'expensive and 'eil'ective discharge device embodying the objectsv above described.

With the above and other objects in view which will appear from the description, my invention resides in a novel construction, combination and arrangement of parts for providing spark gaps and are extinguishing means associated therewith 'substantially as hereinafter described and more particularly defined in the appended claims,

' it being understood that such changes as come within the scope of the claims may be made in the embodiment herein disclosed.

In the drawing, Figure 1 is a side elevational view of the device, shown in section.

Figure 2 is a plan view ofthe device, as viewed from below.

Figure 3 is a fragmentary view v of the device, as modified to include a resistor.

Referring now in detail to the drawing, Darticularly to Figures 1 and 2, the housing It andthe outer cap H are of any suitable insulating material, as porcelain. The terminal lead I2 is electrically connected to the inner metallic cap [1, as by soldering. The inner cap I! may be conveniently made from sheet copper or brass, and consists of a cylinder having vone end closed, the portion closing the end being provided with a central downwardly extending portion to form one electrode of a spark gap. The insulating cap I I may be cemented to the housing Ill, thereby rigidly securing both the inner cap I! and the outer cap I I thereto.

The housing III is provided with an upper and a lower chamber or recess, and an opening extending therebetween. A conducting member it, here shown as a metal bolt, over which is placed 10 a tube of insulating material 2|, is arranged so that its head 20 engages a centrally located recess in a disk of insulating material 21; the head 29 of the bolt I! in this manner forming a first conducting electrode of the device. This recess is substantially the same depth as the thickness of the head 29 of the bolt l8. An opening is provided through the disk 21 to permit the passage of the body portion of the bolt IS, the latter also passing coaxially through a disk 25, this disk being somewhat larger in diameter than the disk 21.

The upper, or threaded end of' the bolt It extends through the opening between the two chambers of the housing ll, and supports the disks 21 and 25 by means 01' the washer 20, and the nut it. The threaded end of the bolt is also arranged in spaced relation with the centrally located downwardly extending portion of the inner metallic cap II, to form a spark gap. The washers or gaskets 22 and 26, located re- 'spectively between the disk 25 and the wall separating the chambers of the housing II, and between the disks "and 21, are provided to seal the joints between the respective members against the passage therebetween of gas or flame, and at the same time to absorb some of the impact occasioned by the operation of the device when discharging heavy currents. These washers may be made of rubber, cork or any insulating material meeting the above requirements.

A metallic chamber 22 is rigidly supported by the disk 25, in co-axial relation therewith. A convenient manner of supporting the chamber 23 is by means of a plurality of integral inwardly extending wall portions, spaced vertically apart for a distance substantially equal to the thickness of the disk 25. The outer edges of the disk 2! may be out along a chord, or may. be slotted to facilitate this assembly. The chamber 23 is conveniently substantially cylindrical in shape, having its bottom, or lower end entirely closed except for a plurality of vents II, near the outer edge of the lower end. An integral upstanding cylindrical portion 24 forms a second conducting electrode of the device, and provides a housing for the spring 30. A disk, also of insulating material, is biased toward the disk 21 by the spring .30, the former disk being held in alignment by the cylindrical portion 24. A suitable and inexpensive insulating material for the

disks

25, 21 and 28 is dense hard fiber, as this material is not easily affected by shock. A conductor I3 is electrically connected to the metallic housing Any voltage appearing on the conductor of a character to break down the gaps in the device will cause the resulting current to take a path from the inner cap I! to the upper end of the bolt l8, thence between the disks 21 and 28 from the first electrode 29 to the' second-electrode 24, and thence through the metallic chamber 23'to the ground terminal [3. Should a power are follow the spark or arc caused by the superimposed voltage, it is immediately extinguished by its confinement between the disks 21 and 28. The amount of separation of the disks varies substantially directly with the magnitude of the discharge current.

I I prefer to use insulating elements having the shape of disks, but it will be apparent that other shapes may be used as long as the shortest path between the electrodes and in the space between the elements is of suflicient length to extinguish the arc. In any case the electrodes must be arranged to prevent the creation of an alternate path around the outer edges of the insulating elements, as it is the confinement of the are between the insulating elements which makes possible its extinction. For this reason the conducting member or bolt l8 leading to the first electrode 29 is provided with the insulation 2|, and the

members

22, 25, and 26 are preferably of insulating material.

- In applications where a certain voltage rise due to the passage of discharge current through a resistance in series relation in the circuit may be tolerated, the duty on the disks may be somewhat relieved by employing such a resistance. Such an arrangement is shown in Figure3. In this Iembodimenta resistance element 35, preferably of carborundum, is rigidly supported at its upper end in a recess formed integral with the inner cap 33. The screw 34 is provided for holding the resistance .element in spaced co-axial relation with the bolt end I8, which, as above described, connects to the portion of the device shown 'in detail in Figures 1 and 2.

I claim as my invention:

1. An over-voltage protective device comprising, in combination, a housing of insulating material, a metallic chamber supported within said housing, a pair of coaxial disks of insulating material resiliently supported within said metallic chamber, spaced electrodes forming a radial rial, a metallic chamber supported within said housing, at least two coaxial disks of insulating material resiliently mounted within said metallic chamber, means biasing said disks coaxially one toward the other, means including spaced electrodes for forming radial arc paths between the adjacent faces of said disks, and an opening through a wall of said chamber in communication with the atmosphere for venting the arc-products from said chamber.

3.- An over-voltage protective device comprising, in combination, a housing of insulating material, at least two elements of insulating material supported in face to face relationship within said housing, normally insulated conducting electrodes associated with said elements so as to provide a preferential spark path between the adjacent faces of said elements, and resilient means for biasing said elements one toward the other, one .of said electrodes forming. an arc-shield for said resilient means.

4. An over-voltage protective devicev compris-' ing, in combination, a housing of insulating material having. an upper chamber and a lower chamber and an opening therebetween, a spark gap supported within said upper chamber, a metallic container supported within said lower chamber, at least two coaxial disks of insulating material. resiliently supported within saidmetallic chamber, means biasing said disks coaxially one toward the other, means including spaced electrodes for forming radial arc paths between the adjacent faces of said disks, and means including a metallic member forming one electrode of said spark gap for closing the opening between said upper and said lower chambers, said metallic member also supporting at least one of said disks and forming one of said spaced electrodes.

5. An over-voltage protective device comprising, in combination, at least two elements of insulating material, each element having at least one substantially fiat surface, means resiliently biasing said elements together, a substantially fiat surface of one being adjacent to a substantially fiat surface of the other, a first electrode extending through at least one of said elements and a second electrode positioned adjacent the outer edge of said elements, the electrodes being so dis posed that the weakest electrical path through the device is from one electrode to the other between said insulating elements, electrically conducting members extending from each electrode to provide a circuit through said device, at least one of said conducting members being insulated whereby an arc path outside of said insulating .elements is prevented; and means including a metallic housing for supporting said elements within a hollow insulator, whereby any flame attending the operation of the device is prevented from impinging upon said hollow insulator;

6. An over-voltage protective device, comprising a housing of insulating material, at least two elements of insulating material supported within said housing, means biasing at least one of said elements toward another of said elements in abutting relation, normally insulated conducting electrodes-associated with said elements for providing a preferential arc path between the abutting surfaces of said elements, and means in-, cluding a wall of noninfiammable material inter posed between said housing and said element for preventing the flame attending the operatioi of the device from impinging on said housing.

7. An over-voltage protective device, comprising a housing of insulating material, at least two elements of insulating material supported within said housing, resilient means biasing at least one of said elements toward another of said elements in abutting relation, normally insulated conducting electrodes associated with said elements for providing a preferential arc path between the abutting surfaces of said elements, one of said electrodes surrounding said resilient means for preventing the flame attending the operation of the device from impinging on said resilient means.

8. An over-voltage protective device, comprising a housing of insulating material, supporting means within said housing for at least two elements of insulating material, resilient means biasing said elements toward each other in abutting relation, at least two normally insulated conducting electrodes associated with said elements so as to provide a preferential spark path between the abutting surfaces of said elements, and means including integral portions of said supporting means for providing said electrodes.

9. An over-voltage protective device comprising a housing of insulating material, means supporting within said housing at least two elements of insulating material, each of said elements having at least one face of substantially the same shape, resilient means for normally maintaining said elements in face to face relationship, said resilient means opposing a divergent movement of said elements, at least two normally insulated conducting electrodes combined with said elements, said electrodes being so disposed that the weakest electrical path through the device is from one elcctrode ,to another between the adjacent faces of said elements, conducting members extending from each electrode, and insulating means for at least one of said conducting members whereby the establishment of an arc in shunt circuit relation with said weakest electrical path is prevented.

10. An over-voltage protective device comprising a housing of insulating material, supporting means within said housing for at least two elements of insulating material, each of said elements having at least one face of substantially the same shape, resilient means associated with said elements for opposing a divergent movement of said elements, at least two normally insulated conducting electrodes combined with said elements, said electrodes being so disposed that the weakest electrical path through the device is from one electrode to another between the ad jacent faces of said elements, means including conducting members extending from each electrode for connecting the device in a circuit, and insulating means for at least one of said conducting members for preventing the establishment of an arc in shunt relation with said weakest electrical path, said resilient means cooperating with an integral portion of one of said electrodes for maintaining said elements in face to face relationship.

11. An over-voltage protective device comprising at least two elements of insulating material, each element having at least one substantially flat surface, means resiliently biasing said elements together, a substantially flat surface of one being adjacent to a substantially flat surface of the other, a first electrode extending through at least one of said elements and a second electrode positioned adjacent the outer edge of said elements, the electrodes being so disposed that the weakest electrical path through the device is from one electrode to the other between said insulating elements, electrically conducting members extending from each electrode to pro vide a circuit through the device, at least one of said conducting members being insulated whereby an arc path outside of said insulating elements is prevented, and a metallic housing for supporting said elements within a hollow insulator, said metallic housing forming said second electrode and being provided with an opening in communication with the atmosphere through which the are products attending the operation 'of the device may-be vented.

RALPH R. PI'I'IMAN.