US2734972A - Circuit interrupters - Google Patents

Description

Feb. 14, 1956 A. VAN RYAN ET AL 2,734,972

' CIRCUIT INTERRUPTERS Filed Jan. 1:5. 1951 5 Sheets-Sheet l INVENTORS finlfiony Van Fyan y 1071/0112 1?. Harry M H W/ -v/L fitlorney Feb. 14, 1956 A. VAN RYAN ET AL CIRCUIT INTER RUPTEIRS Filed Jan. 13, 1951 5 Sheets-Sheet 4 Feb. 14, 1956 A. VAN RYAN ET AL 2,734,972

CIRCUIT INTERRUPTERS Filed Jan. 15, 1951 5 Sheets-Sheet 5 w l I I O /4 I Q? I. d M

I i 6 A? i a 40 4// 5 u YA 40 V V 4 i I INVENTORS finl/zpny Van 2 412 J E BY MY/Jam 2. Harry itarnez United States Patent @fiice 2,734,972 Patented Feb. 14, 1956 CIRCUIT IN TERRUPTERS Anthony Van Ryan, South Milwaukee, and William R. Harry, Hartland, Wis., assignors to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application January 13, 1951, Serial No. 205,842 4 Claims. (Cl. 200-450) This invention relates to circuit interrupters.

In circuit interrupters it has been found that the energy liberated upon operation of the circuit interrupter increases as the length of the arc increases. It is, therefore, clear that in an enclosed circuit interrupter, such as one submerged in oil and enclosed in a metal tank, frequently the pressure rises within the tank to a dangerous degree when the arc is relatively long. Further it has been found that a certain interval of time is required to extinguish the are. In other words, the arc is not instantly extinguished. In prior devices it is frequently the case that this interval is not sufiiciently long to insure the extinguishing of the arc prior to undue elongation thereof.

This invention is designed to overcome the above noted defects and objects of this invention are to provide an enclosed circuit interrupter in which the switch means is submerged in oil and in which the arc is extinguished with certainty and without creating undue pressure in the tank or container and without undesirable elongation of the arc.

In greater detail, further objects are to provide a circuit interrupter in which the arc is prevented from becoming unduly extended and in which the arc is acted upon by a blast of oil which escapes at a plurality of separate points, the construction being such that the outward bowing or elongation of the are at the separate points is very small indeed, so that the total length of the arc is kept relatively short even under very heavy overloads.

Further objects are to provide a circuit interrupter in which the contacts are caused to dwell after they have been separated and while they are enclosed within insulating members, and in which means are provided which is active during this period for projecting a blast of oil across the arc to extinguish the arc during the dwell before the contacts have passed from their enclosing insulating members to thereby insure extinguishing of the arc while it is confined, the movable contacts subsequently passing completely away from the insulating members.

Further objects are to provide a construction of circuit interrupter in which the contacts are separated with minimum retardation on very slight overloads and in which the retarding force increases and persists for a varying length of time proportioned to the severity of the overload, so as to insure a dwell at the correct time and of sufficient duration to insure extinguishing of the arc while the are is confined.

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

Figure l is a sectional view through the circuit interrupter with parts broken away and parts in section.

Figure 2 is an enlarged fragmentary view of the operating mechanism.

Figure 3 is an enlarged sectional view of the contact assembly.

Figure 4 shows the curves for different overload conditions showing the relation between stroke and time.

Figure 5 is an enlarged fragmentary view of the contact rod and valve.

Figure 6 is a sectional view ure 5.

Figure 7 is a sectional viewon the line 77 of Figure 5.

Figure 8 is a fragmentary view of the contact rod and dashpot at the upper limit of its stroke.

Figure 9 is a view of the contact rod and dashpot just at the instant that the piston of the contact rod begins to enter the dashpot, the piston valve being still partly open.

Figure 10 is a view showing the piston passing into the dashpot and the valve closed.

Figure 11 is a view showing the parts in the position they occupy just after the contact rod has started back upwardly on its return stroke.

Referring to the drawings, it will be seen that the circuit interrupter comprises a tank 1 or container which includes the cover or top 2 secured thereto in any suitable manner. Within the upper portion of the tank or cover 2, the operating mechanism indicated generally by the reference character 3 is positioned. This operating mechanism is described and claimed in the copending application of William R. Harry, Serial No. 141,336, filed January 30, 1950, for Circuit Interrupter, assigned to the same assignee as the present application.

The operating mechanism includes the main operating lever 4 which is connected to the plunger rod 5 of the magnetic plunger 6, see Figures 1 and 2. The main lever 4 has rolling contact with the contact lever 7. This contact lever at its outer end straddles the contact rod 8 and engages the collar 7 on such rod. Suitable link mechanism and springs are provided for respectively guiding the contact rod 8 and for restoring the parts after they have been moved downwardly to contact open position. In the position shown in Figures 1 and 2 the contacts are closed. The details of the operating mechanism need not be described further.

The operating mechanism is located in the upper portion of the tank or container, as shown in Figure 1, above the oil level indicated by the dotted line 9. The switch mechanism indicated generally by the reference character 10 and the solenoid 11 for the magnetic plunger 6 are located below the oil level.

The operating rod or contact rod 8 extends downwardly and is provided with a combined valve and plunger 12 which is slidably mounted on the operating rod and which normally rests upon the transverse pin 13. A sleeve 14 is rigidly secured to the operating rod 8 and coacts with the combined valve and plunger 12. A spring 15 is partially housed within and seats against the sleeve 14, see Figures 5 and 7, and its lower portion normally bears against an intermediate transverse pin 16. The transverse pin 16 fits within the hollow recessed portion 17 of the combined piston and valve 12, see Figure 6.

The member 12 will hereinafter be referred to either as a piston or as a valve or as a combination of the two. It is adapted to be moved downwardly into the dashpot 18, see Figures 8 through 11. When the piston 12 first enters the dashpot as indicated in Figure 9, it moves upwardly with reference to the rod 8 until its inwardly directed ribs 19, see Figure 6, contact with the lower end of the spring 15. As the combined piston and valve 12 is forced downwardly into the dashpot 8, it may be forced at such a rate as to close the valve. This is accomplished by compressing the spring and moving the member 12 upwardly into engagement with the collar or sleeve 14. This position of parts is shown in Figure 10. When the contact rod 8 moves upwardly the valve immediately opens, as shown in Figure 11, and allows a quick upward stroke of the contact rod.

The contact rod 8 is formed of insulating material and is attached at its lower end to the contact cross-head on the line 6-6 of Fig 29, see Figure 3. This cross-head is of metal and carries the two movable contacts indicated by the reference char acters 21 and 22. These movable contacts are normally positioned within the stationary contacts indicated generally by the reference characters 23 and 24. These stationary contacts are composed of a plurality of arms which are drawn inwardly by means of springs 25 and provided with contact portions 26 at their lower ends. The upper ends of the arms are pivoted to metallic members 27 which are electrically connected to the contact terminals 28 and in series with the solenoid 11.

It is obvious that when an overload occurs that the main operating lever 4 will be drawn downwardly and will depress the contact lever 7 which, in turn, will move the contact rod 8 downwardly, thus moving the movable contacts 21 and 22, see Figure 3, out of engagement with the stationary contacts 23 and 24.

The stationary contacts 23 and 24 are housed within insulating tubular members indicated generally by the reference characters 29 and 30. These tubular members 29 and 30 are connected by means of a transversely extending insulating tube 31. The member 29 is provided with a discharge orifice 32 which opens into the tube 31 and the member 30 is provided with an inlet aperture 33 communicating with the tube 31 and is provided with a plurality of outlet apertures 34. These outlet apertures 34, as may be seen Figure 1, consist of a plurality of spaced holes in the insulating tubular memher or assembly 30. It is to be noted that the insulating tubular member or assembly 29 is provided with a sleeve 35 adjacent its lower end which relatively closely fits the movable contact 21 and thus prevents the major portion of the discharging oil from passing downwardly and causes such discharged oil to pass into the tube 31 and from there through the insulating assembly or member 30 and outwardly through the discharge orifices 34. The lower portion of the tubular assembly 30 is provided with an insulating sleeve 36 which relatively closely fits the movable contact 22.

It is apparent that when the circuit interrupter functions to open the circuit under overload, that gas will be generated within the tubular assembly 29 and will cause oil to be discharged towards the right as viewed in Figure 3 through the are formed between the movable contact 22 and the stationary contact 24 and will thus tend to extinguish the arc.

The transverse tube 31 may, if desired, be provided with apertures 37 on its upper side to facilitate rapid refilling by allowing escape of gas. The tube 31, it is to be noted, is provided with a vertically positioned transverse sleeve 38 through which the contact rod 8 passes.

A particularly important feature of this invention is that the arc is not allowed to bow or project outwardly in a long or extended path. Instead, the apertures 34 are too small to allow the arc to be swept outwardly and consequently the length of the arc is very short indeed and, therefore, the amount of energy liberated is relatively small. As a result of this, there is a relatively small rise of pressure in the enclosed tank or container 1 when the circuit interrupter functions.

A further feature is to be noted which greatly aids in the efficient operation of the circuit interrupter. This feature is particularly concerned with causing the arc to be interrupted before the contacts leave their en closing insulating tubular structures and producing a dwell prior to the time that the movable contacts are withdrawn from their tubular enclosing structures. This desirable mode of functioning is obtained by means of the dashpot and plunger construction which is illustrated particularly in Figures 8 through 11 in conjunction with the construction of the contact assembly as shown in Figure 3.

It is to be understood that the expression dwell is intended to mean either a complete stopping of the motion of the movable contact assembly or a very much slowed down motion thereof. In the structure illustrated and described the dwell is not obtained by actually completely interrupting the motion of the movable contact assembly but is obtained by greatly slowing down its motion.

The dashpot 18 is provided with an upper reduced portion 39 and a lower reduced portion 40 between which an intermediate enlarged portion 41 is located. When the plunger 12 travels through the upper reduced portion of the dashpot indicated at 39 it causes a dwell of the movable contacts. The limit of this dwell, under all conditions, occurs at the time that the plunger 12 passes from the constricted portion 39 into the enlarged portion 41. While the piston is in the enlarged portion the movable contacts can travel rapidly. At the extreme lower portion of the travel, the piston 12 passes into the lower reduced portion 40 of the dashpot 18 and checks the final motion of the contact rod and contact assembly.

In Figure 3 the positions indicated in full lines for the movable contacts 21 and 22 and for the piston 12 are those corresponding to closed position of the circuit interrupter. In the position indicated in imaginary lines at A for the movable contacts and the piston, the piston will be found to have just passed from the reduced portion 39 into the enlarged portion 41 of the dashpot 18. At the position shown in imaginary lines in Figure 3 and indicated by the reference character B for the movable contacts and the piston, it will be seen that the contacts have passed completely downwardly out of their normally surrounding insulating tubular members.

Figure 4 shows a series of curves indicating the relation between stroke and time of the movable contact assembly for light, medium, and heavy overloads. The curve W corresponds to a very light overload. During this operation of the circuit interrupter the valve formed by the piston 12 and sleeve 14 is open. In other words, the contact rod 8 travels downwardly as shown in Figure 9 and the piston 12 moves upwardly and merely contacts the spring 15. It does not compress the spring as there is not sufficient downward force on the contact rod 8 during the time that the piston 12 is passing through the reduced portion 39 of the dashpot 13. Consequently, there is only a small retardation of the contact assembly and the relation between the stroke and time is indicated by the curve W.

Assume now that a heavier overload occurs. This would correspond to the curves shown in Figure 4 and indicated at X or Y. It will be seen that when the piston 12 moves downwardly that the valve closes and the parts occupy the position shown in Figure 10, the piston 12 compressing the spring 15 and coacting with the sleeve 14 of the rod 8 to close the valve. There is, therefore, retardation of the downward motion of the movable contact assembly. This causes a dwell of the movable contacts while they are within their tubular enclosing structures. If the overload is relatively light, the downward motion of the contact assembly is checked to such an extent that the valve again opens. This occurs at the point marked X in Figure 4.

For a heavier overload as indicated by the curve Y, the valve does not reopen until the point Y is reached. There is, therefore, a longer dwell, thus insuring the extinguishing of the arc.

Under extremely heavy overloads the valve does not open at all after once having closed, while the piston is passing the upper reduced portion of the dashpot. This is indicated by the curve Z in Figure 4. The retardation or dwell of the movable contacts continues until the piston passes clear of the reduced portion 39 of the dashpot into the enlarged portion 41. This, therefore, is the limit of the dwell for maximum overload and corresponds to the position A in Figure 3.

It will be seen, therefore, that there is a direct coaction between the'parts so as to cause the complete extinguishing of the are due to the transverse blast of oil from adiacent the contact 21 past the contact 22 and through the apertures 34. In other words, the movable contacts remain in their enclosing tubular insulating structures until suflicient time has elapsed for the complete extinguishing of the are by the transverse blast of oil. It will be seen from the foregoing that the piston 12, sleeve 14, and dashpot 18, constitute a time delay means or a valve delay piston structure which has the peculiar action of producing a time delay proportional to the velocity of contact separation. In view of the fact that the velocity of contact separation is proportional to the overload, it is also apparent that the time delay is proportional to the magnitude of the overload current.

After the arc has been extinguished, the contacts move to their final position shown at B in Figure 3 clear of their insulating structures so that there cannot be any creepage.

It will be seen that a novel circuit interrupter has been provided by this invention which has means for limiting the length of the arc and for extinguishing the are by a transverse blast of oil while the contacts are caused to dwell within their enclosing insulating structures.

It will be seen further that the above described highly desirable results are obtained by a relatively simple structure which is rugged and compact and independent of delicate parts or other instrumentalities of this order. Instead the contact rod, combined piston and valve, and movable contact assembly constitute a unitary structure which coacts with the enclosing insulating members and other associated parts of the device to produce the results enumerated. By this means, simplicity and ruggedness are obtained and a highly effective and reliable interrupter is secured.

It is to be understood that the expression during the separation of the contacts is intended to mean the period of time between the initial start of the separation of the contacts and the final or end position of the contacts.

Although this 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.

We claim:

1. A circuit interrupter comprising switch means including separable contacts, insulating means normally enclosing said contacts and confining the arc during separation of said contacts under overload, operating means for separating said contacts on overload, delay means for causing a dwell during the separation of said contacts prior to the time that said contacts are fully separated, and means for projecting a blast of oil between said contacts during said dwell while said contacts are within said insulating means, said operating means being arranged 6 to cause at least one of said contacts to move completely away from said insulating means after cessation of said dwell, said insulating means being hollow and having a central open space for said contacts and an oil inlet opening and a plurality of oil outlet apertures opening to the exterior of said hollow insulating means.

2. A circuit interrupter comprising switch means including separable contacts, hollow insulating means normally enclosing said contacts, said insulating means having an oil entrance opening and having a plurality of oil outlet openings which are small as compared with said oil entrance opening, operating means for separating said contacts on overload, means for projecting a blast of oil sequentially through said oil entrance opening and between said contacts and through said oil outlet openings, and delay means for limiting the separation of said c0ntacts during said oil blast to produce a dwell during the separation of the contacts and for subsequently allowing further separation of said contacts.

3. A circuit interrupter comprising switch means including separable contacts, operating means for separating said contacts upon the occurrence of an overload and time delay means responsive to the magnitude of the current interrupted for causing a dwell during the separation of said contacts, said time delay means causing the eifect of said delay means to be proportional to the magnitude of the current interrupted for all overloads.

4. A circuit interrupter comprising switch means including separable contacts, means for separating said contacts, and time delay means responsive to the velocity of separation of said contacts for limiting the separation of said contacts for a period of time to cause a dwell during the separation of said contacts proportional to the velocity of contact separation during that portion of the contact separating stroke before the time delay means comes into operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,289,649 De Camp Dec. 31, 1918 1,344,196 Albrecht June 22, 1920 2,025,549 Prince Dec. 24, 1935 2,196,008 Cole Apr. 2, 1940 2,333,604 Wallace Nov. 2, 1943 2,493,371 Vradenburigh Jan. 3, 1950 2,535,702 Skeats et a1 Dec. 26, 1950 2,606,262 Bartlett Aug. 5, 1952 FOREIGN PATENTS 15,776 Great Britain I Apr. 17, 1913 (1912) 396,190 Great Britain Aug. 3, 1933

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