US2574888A - Protective device - Google Patents

Protective device Download PDF

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US2574888A
US2574888A US154093A US15409350A US2574888A US 2574888 A US2574888 A US 2574888A US 154093 A US154093 A US 154093A US 15409350 A US15409350 A US 15409350A US 2574888 A US2574888 A US 2574888A
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ground
bimetal
contact
serrations
base
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US154093A
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Theodore C Riebe
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Automatic Electric Laboratories Inc
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Automatic Electric Laboratories Inc
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T1/00Details of spark gaps
    • H01T1/14Means structurally associated with spark gap for protecting it against overload or for disconnecting it in case of failure

Description

Nov. 13, 1951 T. c. RIEBE PROTECTIVE DEVICE Filed April 5, 1950 TO LINE IN V EN TOR.
THEODORE C. RIEBE %Z 4 ATTORNEY Patented Nov. 13, 1951 2,574,888 rnoracnva nmca Theodore C. Biebe, Automatic Electric Laboratories, Inc.,
111., a corporation of Delaware Application April 5, 1950, Serial No. 154,093 8 Claims. (Cl. 200-115) This invention relates in general to protective devices and more particularly to the thermal type of protective device for arresting abnormal voltages, lightning and the like, likely to prove dangerous to life or destructive to property.
Accordingly, it is an object of the present invention to provide an improved thermal abnormal voltage protector which is reliable and test inoperation and which is operative to complete a direct ground circuit 01 fixed low resistance.
Another object of the invention is to provide an improved thermal abnormal voltage protector which is simple in construction and compact in $128.
A further object oi the invention is to provide in an abnormal voltage protector including in combination, serrated discharge members, an improved thermal member, a ground element and. a ceramic insulator for maintaining the aforementioned members in a given spaced relationship.
These and other objects and features will be more particularly pointed out and described in the ensuing specification and appended claims taken in conjunction with the accompanying drawings in which:
Fig. 1 is an exploded view of the protective de- V109.
Fig. 2 is a plan view of the protective device.
Fig. 3 is a cross sectional view of the device taken along line 33 in Fig. 2.
In the preferred form as shown in the accompanying drawings, the abnormal voltage arrestor construction contemplates the use in combination of a carbon block type ground element I, serrated metallic discharge members 2, a thermal bimetal member 3, refractory insulating member 4 and contact member 5. The serrated member 2 and bimetal member 3 are positioned in spaced relationship with ground element I by means of a refractory insulating member 4, and held in place by means of projections on a contact member 5, which projections are in registry with apertures in said other members for receiving them.
In general, the contact member 5 is in electrical contact with a line or lead of the equipment that is desired to be protected, and abnormal voltages then travel through said contact member 5 to the serrated discharge member 2 and bimetal member 3 by way of the projections G and 1 on contact member 5. These voltages, if sufiiciently great to. create a hazardous condition, will are from the tips of the serrated discharge member 2 to the ground element I which is as its name implies, connected to ground.
ground, and in the event In this manner the voltages are dissipated to that these abnormal voltages are sustained, the heat created by the arcing to the ground element causes the bimetal member 3 to flex into contact with ground element I, thereby providing a direct path of fixed low resistance for said voltages to travel to ground. This path eifectively shorts out the arcing occurring from the serrated members and as cooling occurs the bimetal member will return to its normal position. Electrical equipment is in this manner positively and quickly protected for the duration of the abnormal voltage, the pro tective device removing itself from the circuit when the necessity for protection has ceased, namely, when the voltage has been dissipated. The construction of the preferred embodiment shown will now be described in detail.
The refractory insulating member l is com posed of a ceramic material which has been subjected to heat, and a particular material meeting these requirements which may be used is known as Steatite. However, other forms of composttions of insulating material may be employed as weli.
Insulating member 4 is somewhat elongated. and rectangular in shape. The upper portion evenly recessed at 8 and the bottom of the recess is designated at 9 and upper edges H! are some what fiat and parallel. In the under portion, a groove ll runs longitudinally therethrough. In the bottom 9 of recess 8 and extending from bottom 9 to groove H are two holes 12 and i3. Contact member 5 having projections 6 and "l con nected to either end thereof is placed in groove it with the projections 6 and I extending upwardly through holes 12 and i3. On the flat bottom 9 of recess 8 is placed the somewhat elongated serrated discharge member 2.
The base Id of the serrated member 2 has two apertures therein which are in registry with holes l2 and 13 so that projections 6 and T of contact member 5 extend upwardly therethru. Along the lateral edges of discharge member 2, connected to and extending upwardly therefrom are saw tooth-like serrations l5 and IS. The tips of these serrations are pointed and somewhat sharp. At one end of the serrated member and connected thereto is an upraised hook IT.
The thermal bimetal member 3 is essentially rectangular in shape and of dimensions somewhat smaller than those of recess 8. The center portion, longitudinally speaking, is cut away with the exception of a cross piece l8 and the end crosspieces thereof. One end has thereon a raised contact is. The other end is then placed under hook I! so that the major portion of the bimetal member normally lies flat on the base ll of the discharge member 2 and between the upwardly extending serrations I and I6.
Projection 6 extends upward through the cutout center portion of the bimetal element and is bent tightly over cross piece l8. The other projection, I, is bent tightly over base ll of discharge member 2 and the hook i1 is pressed tightly down over the end of the bimetal member thereunder thereby firmly holding all of these members together.
The bimetal member is so constructed that heat will cause it to flex upwardly, but as one end is securely held or clamped down to the refractory insulating member 4 by bent over projection 6 and hook l1, only the other end having thereon contact l9 can raise upwardly when the bimetal is heated.
The pointed saw teeth-like tips of serrations l5 and iii are upset so that a predetermined distance exists between a plane including the tips and the plane including the upper edges Ill of refractory insulating member 4.
The device is then completed by placing ground element I, preferably a substantially rectangular carbon block and of the same dimensions in length and width as the insulating'member, upon the flat upper edges Hi. In this position, as shown in the cross section in Fig. 3, only a narrow air gap of predetermined size exists between the now upset tips of serrations i5 and I6 and the under surface of ground element I.
It will also be seen, particularly in this cross sectional view, the normal position of the bimetal member laying flat upon the base H of the discharge member 2 and that its free end with contact l9 thereon is normally out of electrical contact with the under surface of ground element i.
Looking again at the cross section in Fig. 3, it is now readily seen that an abnormal potential on contact member 5 will be transmitted through projections 6 and l to the serrated discharge member 2 as well as the bimetal member 3, and that if this potential is above a predetermined value it will complete a path to ground on ground element 1 from the nearest points thereto, namely, by arcing from the tips of serrations l5 and I6. Any sustained abnormal voltage will seek to perpetuate this path and the arcing will create suflicient heating very quickly to cause bimetal member 3 to flex upwardly so that contact l9 will be in electrical contact with ground element I. A fixed low resistance circuit is thereby traced from the potential on contact member 5 through the projection Ii to the crossarm 18 of bimetal member 3 and therethrough to contact IS on the end thereof to ground element I and ground thereon. This latter low resistance path effectively short circuits the arcing paths previously described and as cooling occurs, the bimetal member 3 will flex back to normal removing the short.
It will be seen therefore that the device will be good for a great many continued repetitions of this protective cycle.
Having described my invention in detail what I desire to be protected by the issuance of Letters Patent of the United States is:
1. A device for protecting electrical equipment from abnormal voltages comprising in combination, a metallic contact member; a metallic serrated discharge member having a base and a pair of oppositely positioned serrations extending upwardly from the lateral edges of said base; and a bimetal short circuiting member normally lying flat on said base and extending longitudinally between said serrations, said bimetal member be ing additionally arranged with relation to said base in a manner such that heat will cause it to flex upwardly therefrom, all of said members connected mechanically and electrically together, a carbon block ground element positioned substantially parallel to the base of said serrated member and separated from the tips of the teeth of said serrations by a small airgap, and ceramic insulator means for maintaining the ground element in said position, whereby an abnormal voltage on said contact member will travel thru said serrated member and discharge thru the serrations thereof to said ground element in a plurality of arcs, and in case said arcing is sustained, the heat generated therefrom will cause said bimetal member to flex upwardly and contact said ground element directly shorting said abnormal voltage to said ground element.
2. A device for protecting electrical equipment from abnormal voltages as claimed in claim 1 wherein one end only of said bimetal member is secured to the base of said serrated member, the other end extending free therebetween and beyond the longitudinal extent of said serrations, said otherend having a wide contact portion on the extremity thereof, said free end rising and said contact portion engaging said ground element when the arcing from the serrations to the ground element are sustained.
3. A device for protecting electrical equipment from abnormal voltages as claimed in claim 1 wherein said bimetal member resumes its position flat on the base of said serrated member when cooling of said bimetal following said short circuiting has occurred.
4. A device for protecting electrical equipment from abnormal voltages as claimed in claim 2, said serrations aligned longitudinally, the tips of said serrations lying in parallel lines which are parallel also to said ground element as well as spaced by a narrow air gap therefrom.
5. A device for protecting electrical equipment from abnormal voltages, in combination, a metallic discharge member having a base, oppositely disposed serrations extending upwardly from the lateral edges of said base; a bimetal shorting member normally lying flat on said base and between said serrations, a ground element and means for positioning said ground element in spaced relation to said members; a contact member connected to said other members and maintaining said discharge member fixed to said positioning means and clamping one end of said bimetal member to said base; the other end of said bimetal member free to move upwardly when heated; and the tips of said serrations being upset to provide a small air gap between said tips and said ground element, whereby an abnormal potential on said contac member will are from the upset tips of said serrations to said ground element, the heat from said arcing causing the free end of said bimetal member to move upwardly to contact the ground element offering a low resistance path therethru to ground, effectively shorting said potential thereby to ground.
6. A device for protecting electrical equipment from abnormal voltages comprising, a ceramic insulating block having a rectangular flat bottomed recess in one surface and a groove in an opposite surface, two holes joining said recess with said groove, a contact member in said groove, two projections connected to either end of said contact member and extending upwardly therefrom thru said holes into said recess, a metallic discharge member having a base and two apertures therein, said discharge member positioned in said recess with its apertures in registry with said holes and said projections extending therethru, a pair of serrations extending upwardly from the lateral edges of said base and a raised hook at one end of said base, a bimetal shorting member having an elongated slot ex tending longitudinally thru the center portion thereof and normally lying flat on said base be tween said serrations; a cross piece near one end of said slot and that end of said bimetal element held down beneath said hook; the other end of said bimetal member free to rise upwardly when heated, one of said projections bent over said crosspiece co-operating with said hook to clamp said one end of the bimetal member and the discharge member Within said recess to said insulating block, the other projection bent over said base additionally securing said discharge mernher to said insulating block, a carbon ground element positioned on the edge of said recess in spaced relation to said members, and the tips of said serrations being upset so that they are in a plane parallel to said grounding element and separated therefrom by a narrow predetermined airgap, whereby an abnormal potential on said contact member will arc to ground from said upset serration tips, the heat from said arcing causing the free end of said bimetal member to move upwardly contacting the grounding element to close a low resistance path ther'ethru from said abnormal potential to ground.
7. In a device for protecting electrical equipment from abnormal voltages as claimed in claim 6, a raised wide contact integrally connected to said free end of said bimetal member for contacting said ground element when said bimetal member is heated.
8. A device for protecting electrical equipment from abnormal voltages, comprising a refractory insulating block having a recess and a groove in opposite surfaces, said groove connected to said recess by two holes through said block; a carbon block for covering said recess; a discharge member lying in said recess having a base, a pair or" oppositely positioned serrations extending upwardly from the edges of said base, a hook at one end of said base and a pair of holes in said base; a bimetallic short circuiting member normally lying flat in said recess and resting on said dis charge member, said bimetallic member being held down at one end by said hook and being so constructed as to flex upwardly at the other end so as to contact said carbon block in the event of an abnormal increase in temperature; and a contact member in said groove having a pair of projections extending upwardly at either end of said member through the holes in said insulating block, said discharge member, and said bimetallic member, and bent over at the ends, thereby securely connecting said members mechanically and electrically together in spaced relation one to another and in relation to said carbon block when said carbon block is set on said insulating member.
THEODORE C. RIEBE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,656,076 Sands Jan. 10, 1928 2,141,490 Sands Dec. 27, 1938 2,463,718 Sands Mar. 8, 1949
US154093A 1950-04-05 1950-04-05 Protective device Expired - Lifetime US2574888A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2695377A (en) * 1950-04-06 1954-11-23 Automatic Elect Lab Protective device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1656076A (en) * 1926-04-16 1928-01-10 Roy G Sands Lightning arrester
US2141490A (en) * 1935-07-29 1938-12-27 Associated Electric Lab Inc Substation protector
US2463718A (en) * 1944-09-18 1949-03-08 Automatic Elect Lab Protective device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1656076A (en) * 1926-04-16 1928-01-10 Roy G Sands Lightning arrester
US2141490A (en) * 1935-07-29 1938-12-27 Associated Electric Lab Inc Substation protector
US2463718A (en) * 1944-09-18 1949-03-08 Automatic Elect Lab Protective device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2695377A (en) * 1950-04-06 1954-11-23 Automatic Elect Lab Protective device

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