US2927181A - Fluid blast circuit interrupter - Google Patents

Description

M r 1, 1 H. N. SCHNEIDER 2,927,181

FLUID BLAST CIRCUIT INTERRUP'IER Filed Feb. 27, 1958 9 Fig.4.

CLOSKP FULL Y-DPEA POS/ T/0N 0F V/I/VE Inventor:

Harold N. Schneider,

b9 W His torneg.

FLUID BLAST CIRCUIT INTERRUPTER Harold N. Schneider, Springfield, Pa., as'signor to General Electric Company, a corporation of New York Application February 27, 1958, Serial No. 717,892

14 Claims. (Cl. 200-150) This invention relates to an electric circuit interrupter of the fluid-blast type and, more particularly, relates to an interrupter of this type which relies upon pressure-responsive valve means for controlling the flow of exhaust fluids through its exhaust passages during and immediately after a circuit-interrupting operation.

For improving the ability of a fluid blast interrupter successfully to interrupt low currents, it has been proposed heretofore that the exhaust passages of the interrupter be provided with one or more valves responsive to the pressure built up within the interrrupter during an interrupting operation. These valves have been arranged to severely restrict the exhaust passages during low current interruptions and, thus, have acted to increase the pressures developed within the interrupter during low current interruptions, as compared to those pressures developed without the valves. These increased pressures have considerably improved the ability of the interrupter successfully to interrupt those low current arcs which generate relatively small quantities of gases.

For high current interruptions, however, a much greater quantity of arcing gases is generated, and it is most important that these gases be quickly vented from the interrupter in order to prevent excessive pressure rises therewithin. Prior pressure responsive exhaust valves have unduly impeded this required venting.

Accordingly, a general object of the present invention is to provide, for an interrupter, a highly-compact pressure-responsive exhaust valve which is capable of providing a near-maximum in exhaust area for a given amount of space occupied by the valve.

Another object is to construct such a pressure-responsive valve in such a manner that it is capable of opening at exceptionally high speeds.

Another object is to construct a pressure-responsive exhaust valve in such a manner that its operation is not impaired by repeated exposure to the hot exhaust gases produced by arcing.

In application S.N. 717,893, Barkan and Schneider, filed February 27, 1958 and assigned to the assignee of the present invention, an interrupter employing a pressure-responsive exhaust valve is disclosed and claimed. The valve of that application is so constructed that it has a negative gradient characteristic, enabling its movable valve member to be maintained in an open position by pressures within the interrupter substantially below the predetermined value required to initiate valve opening movement. As a result of the valve member remaining open despite a pressure drop within the interrupter, the valve member has less of a tendency to interfere with any scavenging of the interrupter that might take place after such pressure drop has occurred.

Another object of the present invention is to construct such a negative gradient,pressure-responsive exhaust valve in a manner such that it otters a nearminimum of impedance to scavenging action taking place after the valve has opened.

In carrying out my invention in one form, a pressurenited States Patent responsive exhaust valve is provided for controlling the flow of fluid through an exhaust passage of an interrupter. The valve comprises a tubular valve body containing a flow passage forming an outlet for the exhaust passage. A movable vane of a near-balanced construction is pivotally-mounted within the body for controlling flow through the flow passage. This vane is urged toward a substantially-closed position by negative-gradient resilient means located outside the valve body and coupled to the vane. This negative-gradient resilient means provides an effective force on the vane which decreases as the vane moves away from the closed position toward a fully-open position. When the pressure developed within the interrupter exceeds a predetermined value, it overcomes the bias of the resilient means and forces the vane out of its closed position and toward its fullyopen position.

For a better understanding of my invention, reference may be had to following specification taken in connection With the accompanying drawing, wherein:

Fig. 1 is a side elevational view, partly in section, showing an electric circuit interrupter embodying one form of my invention. Y

Fig. 2 is a sectional view taken along the line 22 of Fig. 1 and illustrating a pressure-responsive exhaust valve used in the interrupter of Fig. 1.

Fig. 3 is a sectional view taken along the line 33 of Fig. 2. The valve is depicted in a closed position.

Fig. 4 is a graphical representation of certain operating characteristics of the pressure-responsive exhaust valve of Figs. 2 and 3.

Fig. 5 illustrates the valve of Fig. 3 in a fully-open position.

Referring now to Fig. 1, the interrupter 1 shown therein is of the general type described and claimed in Patent No. 2,749,412 McBride et al., assigned to the assignee of the present invention. This interrupter l is mounted, along with another similar interrupter (not shown) inside a'relatively large oil-filled enclosing tank. The two interrupters are electrically connected by a reciprocable blade contact 2 of conventional form, such as shown for example in US. Patent 1,548,799 Hilliard, assigned to the assignee of the present invention.

The interrupter It is supported within the oil-filled tank from an insulating bushing structure 3 having a conductor stud to which an adapter 4 is suitably secured in a known manner. Adapter 4 is arranged to cooperate with suitable tie bolts (not shown) which structurally interconnect the interrupter unit 1 and the adapter 4.

The interrupter 1 comprises an insulating casing 5 enclosing a plurality of pairs 8, 9 of separable interrupting contacts which are electrically connected in series. The upper pair 8 or" separable contacts comprises a relatively fixed contact assembly 16 and a relatively movable rod type contact 11. The fixed contact assembly 10 is preferably of the conventional cluster-type comprising a plurality of fingers urged radially inwardly by suitably resilient means. In a corresponding manner, the lower pair 9 of contacts comprises a similar fixed contact assembly 12 and a relatively movable contact 13. The pairs of interrupting contacts 8 and 9 are electrically connected in series by means of suitable current transfer contacts 14and the transversely extending contact support casting 15. For supporting the movable contacts 11 and 13 and for interrelating them for simultaneous movement so as to draw a pair of simultaneously-occurring arcs, there is provided a common crosshead 16 of conducting material to which the lower rod contact 13 is directly secured and to which the upper rod contact 11 is suitably fixed by means of an interconnecting insulating rod 17.

In order to complete the electrical circuit through the interrupter and to provide an isolating contact arrangement for the interrupter, there is provided on the crosshead 16 an external contact button 18 which cooperates with an isolating contact 19 secured to the movable switch blade 2 to form a pair of isolating contacts. From the above description, it will be apparent that the electrical circuit through the interrupter extends from the adapter 4 through the conductor 20, through the upper interrupting contacts 10, 11, through the current transfer contacts 14 and the casting 15, then through the lower interrupting contacts 12, 13, the crosshead 16, the contact button 18, the isolating contact 19, and finally through the switch blade 2 and to the cooperating interrupter (not shown), which is disposed at the opposite end of the switch blade 2.

A circuit-opening operation is produced by driving the switch blade 2 rapidly downward. This allows suitable compression springs 6 to force the crosshead 16 together with the contacts 11 and 13 rapidly downward so as to draw a pair of circuit-interrupting arcs in the regions where these contacts part from their mating stationary contacts. After a predetermined downward movement, the crosshead 16 is blocked by suitable stop means (not shown) from following the switch blade 2. The switch blade 2 however, continues moving downwardly and, as a result, establishes an isolating break between the contacts 18 and 19 in a conventional manner.

The compression springs 6, it will be noted, bear at their upper end against a stationary plate 7. This plate 7 and the adapter 4 act to enclose the interior of the interrupter 1 at its respective lower and upper ends.

Adjacent to the serially-related interrupting contacts 8 and 9 are a pair of arc-extinguishing units in the form of baffle stacks 21 and 22. Bafile stack 21 is formed of a plurality of superposed apertured baflle plates 23 of insulating material which together provide a central interrupting passageway 24 and a plurality of vertically-spaced, angularly-aligned exhaust passages 25 radiating therefrom. The exhaust passages are preferably formed by slotting certain of the baffle plates 23 in a well-known manner. When a high current are is drawn within the passageway 24 in response to separation of contacts 10 and 11 pressure is produced within the oil filled casing and is effective to force a highly concentrated blast of dielectric fluid across the arc through the slots or exhaust passages 25 and out the registering exhaust port 26 formed in the adjacent wall of casing 5. This blast action will be described in greater detail hereinafter. The lower baffle stack 22 generally corresponds to the baffle Stack 21 except that baffie stack 22 is provided with an opening 27 through which reciprocates the insulating portion of the upper rod contact 11.

For controlling the flow of fluid through the exhaust passages 25, 25, there is provided a pressure-responsive exhaust valve 100 for each of the arc extinguishing units 21 and 22. Referring to Figs. 2 and 3, each of these exhaust valves 100 comprises a tubular valve body 102 which is suitably clamped to the casing 5, as by means of a nut 104 on the exterior of the tubular body 102. When the nut 104 is tightened, it forces a shoulder 106 formed on the tubular housing 102 into clamping engagement with a recessed portion 107 formed in the interior of easing 5. Preferably a suitable washer 108 is interposed between the nut 104 and a casing 5 to provide for better distribution of the clamping forces. For preventing rotation of the valve body 102 relative to the casing S, the shoulder 106 is preferably eccentric with respect to the outer periphery of the remainder of the valve body. An are resistant lining 109, formed of a suitable fibre material or the like, is preferably provided. about the inside of the valve body 102 to prevent carbonization by the hot exhaust flowing through the valve.

For controlling the flow of fluid through the hollow valve body, there is disposed therewithin a pivotallymounted valve member in the form of a metallic vane or flapper 110. This vane is fixed to a pivotally mounted shaft 112 which extends horizontally across the bore of the valve body at an off center location, which, in Fig. 1, is shown as being closer to the bottom inner surface of the valve body than to the top inner surface. Preferably, the shaft 112 is of a rectangular cross section, and the shaft-receiving opening in the valve member 110 is of a similar shape so as to preclude relative rotation between these parts. For providing smooth bearing surfaces for rotatably supporting the shaft 112, on the valve body 102 two sleeves 113 are fitted about opposite ends of the shaft 112. Each of these sleeves 113 is anchored to the shaft for rotation therewith and has a cylindrical outer periphery journaled in a suitable opening 114 in the valve body 110. These sleeves 113 allow the shaft 112 to rotate freely within the openings 114.

Located externally of the valve body 102 are crank arms 115 which are suitably fastened to the shaft 112 at opposite ends thereof. In this regard, each of these crank arms is preferably welded or otherwise attached to an adjacent sleeve 113 and each arm is prevented from shifting axially of the shaft 112 by means of a nut 115a suitably threaded on each end of the shaft.

The vane 110 is urged into its closed position of Fig. 3 by means of a tension spring 11s which interconnects the outer ends of the crank arms 115. This tension spring 116 extends about the top exterior of the valve body 102 and is suitably anchored to the valve body 102 adjacent the top surface of the valve body. The means for anchoring the spring 116 to the valve body preferably comprises a lug 118 which is fastened to the valve body 102, as by screws 11%. The lug comprises a curved flange 120 extending about a portion of the spring periphery, as shown in Fig. 3, and thereby preventing movement of the top portion of the spring 116 axially along the valve body 102.

When the pressure within the interrupter exceeds a predetermined value, it forces the valve member 110 counterclockwise about the axis of pivot shaft 112 thereby opening the central exhaust passageway through the valve body 102 and allowing fluid to flow therethrough. As will soon be pointed out more clearly, the resilient means 115, 116 exerts a generally decreasing force on the valve member 110 as it travels away from its closed position toward its fully-open position. This follows from the fact that the effective moment arm through which tension spring 116 acts on the vane 110 becomes progressively smaller as the vane 110 moves from its closed position toward its fully open position. This moment arm is the effective distance between the axis of the shaft 112 and a plane n containing the lines of action of the tension spring, this distance being measured normal to the plane n. This moment arm is represented at m in Fig. 3. As the vane moves toward its open position, the plane n approaches the axis of shaft 112, or stated otherwise, approaches an in-line position relative to the crank 115, and the moment arm m accordingly decreases. In the disclosed valve, this decreasing moment arm more than offsets the increasing force resulting from lengthening of the tension spring, and accordingly, the net or effective spring closing force on the vane generally decreases as the vane moves from its closed to its fully-open position. This decreasing effective force relationship is occasionally referred to hereinafter as the negative gradient characteristic of the valve. The terms effective force and effective closing force, as used in this application, are intended to be synonymous with the torque or moment which the resilient means 115, 116 exerts on the vane 110. Fig. 4 is a graph representing a typical manner in which this effective closing force exerted by the resilient means 115, 116 on the vane varies as the vane moves from its closed to its fully open position. It will be noted that this effective closing force decreases more sharply as the vane approaches its fully-open position.

The fully-open position of the vane is depicted in Fig. 3. The vane is prevented from moving past this fullyopen position by means of a stop 121 adapted to engage the vane in this position. It is to be noted that in the fully-open position, the crank arms 115 are still short of a dead-center, or in-line, position with respect to the spring 116. As a result, the spring 116 is still exerting a closing bias on the vane 110. Accordingly, when the pressure within the interrupter falls below a predetermined value, the spring 116 is capable of restoring the vane to its closed position of Fig. 2.

When a high current are is established within the interrupter 1, the arc generates suflicient pressure to force each of the valve members lit) out of its closed position into its fully-open position. As a result of these high pressures, liquid is impelled at high velocity through the region of the arc and out of the open valve. This high velocity flow which accompanies the interruption of high currents is effective to rapidly extinguish the high current are, and the valves, in opening widely, pre vent excessive pressure rises within the interrupter.

There are a number of important factors which render the valve of the present application most effective in preventing excessive pressure rises within the interrupter. One of these factors is that the movable valve member or vane is capable of moving into its fully open position at a higher speed than is the case with most valve members of comparable mass heretofore proposed for such use. Another factor is that the valve of the present application, when fully-open, offers an exceptionally low impedance to flow therethrough.

With regard to the first of these factors, there are a number of features contributing to the high speed opening characteristics of my valve. One feature is the negative gradient characteristic of the resilient means 115, 116 urging the valve closed. In this regard, once the vane is forced out of its fully closed position, the forces opposing valve-opening quickly decrease, thereby allowing increased opening speeds, as compared to those valves which are biased closed by positive-gradient means tending to offer increasing resistance to opening movement. A second feature contributing to the high operating speeds attainable with my valve is the fact that the valve is so constructed that the vane 110 is of a near-balanced construction, i.e., the fluid pressure forces tending to drive the vane open are nearly balanced by the fluid pressure forces tending to hold the vane closed when the valve is closed. In this regard, the effective area of the vane above the axis of the shaft 112 (which is the area upon which fluid pressure forces act in a valve-opening direction) is only slightly larger than the effective area below this axis (which is the area upon which fluid pressure forces act in a valve closing direction). Hence, only a relatively weak spring 116 is needed to hold the vane closed against relatively large pressures acting on a large overall area of the vane. Since the spring 116 is relatively weak, it becomes relatively ineffective in opposing opening movement once such movement is underway, thus allowing such opening movement to take place at a relatively high speed. Moreover, because .the spring forces involved are relatively small, the spring 116 and the cranks 1.15 may be relatively light in weight and low in mass. This relatively low mass also contributes to higher opening speeds. Still another feature contributing to the high opening speeds obtainable with my valve is the presence of the tail 134), which constitutes the outer end of the vane. Since this tail 13%? is located beyond the seating surface 131 against which the vane seats or abuts, the tail 139 is unexposed to pressures from within the interrupter when the vane is in its closed position of Fig. 3. But as soon as the vane begins to open, the pressurized fluid flowing through the valve. is free to act upon this tail 130, abruptly increasing the ratio of vane area exposed to opening pressure to that exposed to closing pressure, thus providing a quick increase in the valve-opening forces. The fact that the extreme outer end of the tail projects transversely into the flow stream gives added impetus to the ability of the pressurized fluid to force the vane open. This outer end of the tail may be thought of as projecting from the remainder of the vane in a direction generally opposite to the direction of valve opening movement.

With respect to the low impedance characteristic of my valve, it should be noted that when the valve is fully open, the relatively thin vane is disposed substantially parallel to the direction of flow. This leaves a very large unobstructed area through the valve, through which flow can take place with little impedance. The fact that the resilient operating linkage 115, 116 is disposed outside the valve body 1'02 and therefore offers no obstruction to flow through the valve also contributes to very low fluid impedance of the valve when in its fully open position. The fact that the tail 130 is located outside, rather than inside, the valve body 10.2 when the vane is in its fully-open position of Fig. 5 also lessens the obstruction or impedance to fluid flow through the fullyopen valve.

The tail 130 at the end of the vane serves the additional function of preventing the vane from fluttering or oscillating when in its fully-open position. So long as the interrupter pressures are sufficient to hold the vane fully open, fluid flowing past the upper surface of the vane acts on the tail to provide a component of force urging the vane against the stop and preventing valvefluttering. Without the tail, there would be no appreciable force for holding the vane in its fully open position parallel to the direction of flow. As a result, under such conditions, the spring would urge the vane into the fluid stream until some substantial opposition forces were encountered. There would be a certain amount of overshoot, and this would lead to oscillations or flutter of the vane, assuming the tail were omitted. Such oscillations would tend to effect an undesirable increase in the impedance of the fully open valve. Since these oscillations are largely eliminated as a result of the tail, the disclosed valve is largely free from those undesirable increases in valve impedance which tend to result from such oscillations.

The tail 130 also serves to provide some diffusion of the ionized fluid streaming through the valve body 102. In this regard, when the blade is in its fully-open position of Fig. 5, streams of fluid are flowing along its two major surfaces i.e., its upper and lower surfaces. The tail 136 at the downstream end of the vane tends to divert the upper stream upwardly away from the lower stream as the two streams leave the vane. This diffusion helps to increase the dielectric strength of the oil in the region external to the interrupter.

Locating the resilient operating linkage 116 external to the valve body 102 is advantageous not only be cause it reduces the obstruction to flow through the valve, as pointed out hereinabove, but also because it renders the resilient means less likely to have its operating charaoteristics adversely affected by the hot exhaust gases which flow through the valve. The valve body 102, in effect, shields the spring 116 from these hot gases and thus prevents impairment of the spring 116 by heating or erosion.

It should be understood that even apart from the negative gradient characteristics of my valve, the other important features set forth hereinabove are capable of contributing in a highly effective manner toward the desired high opening speeds and the desired minimum impedance characteristics.

As soon as the interrupting operation for relatively high currents has been completed, a pump 36 operates to scavenge the interrupter 1 of any ionized gases remaining after the interruption so as to prepare the in terrupter for possible reclosure followed by another inter- 7 ruption. To this end, the pump 39 forces a flow of fresh insulating liquid through the arc extinguishing unit via the passageways 31 and 25', 2.6 and the exhaust valves 1%, all in a manner soon to be described in greater detail.

The pump 30, which is structurally similar to a corresponding pump described in the aforementioned Mc- Bride patent, comprises a cylinder 32 suitably secured to the interrupter casing and connected with the passageways 31 by means of ducts 53 and 43a. The pump 3% also comprises an impulse piston 35 which is spring biased downwardly by a compression spring 36. The compression spring 36 is mounted between a stationary part 37 and a stop 39 fixed t0 the piston rod 49, which in turn is fixed to the piston 35. The compression spring 36 held charged during the time the interrupter is closed by means of a plunger 39a fixed to the switch blade 2 and abutting against the stop 39. However, when the switch blade 2 is driven downwardly to open the interrupter, the restraint of the plunger is removed and the spring 36 is free to begin driving the piston 35 downwardly against the opposition of the oil disposed therebeneath.

During high current interruptions the spring 36 is ineffective to produce substantial downward movement of the piston 35 until after the high current arcs are extinguished. This is the case because these high current arcs generate sufficient pressure to overcome the action of the spring 36. It is only when these pressures subside that the pump becomes effective to impel liquid through the arc extinguishing unit.

For protecting the pump 36 from high arc-generated pressures, the ducts 43 and 43a are preferably provided with check valves 44 and 44a disposed in the ducts 43 and 43a respectively. These check valves are adapted to cooperate with valve seats 45 and 45a respectively located within the ducts. The valves are free to slide on their centrally disposed spindles 46 and .6a, which are supported from the valve seats by suitable spiders. These valves freely permit fluid flow therethrough from the pump 30 except when the pressure produced by the arcs drawn by the contacts 11 and 13 predominates. Under such conditions, the valves close automatically to protect the pump from objectionable arc-generated back pressures.

As pointed out in the abovementioned Barkan and Schneider application, the ability of a pump such as 30 to produce effective scavenging action is dependent to a large extent upon the particular paths through which the pump impels the fresh insulating liquid and upon the size of the exhaust opening. In general, with respect to the first of these factors, the fresh insulating liquid should be impelled through those same passages which had received the arcing products during arcing. It is these passages which tend most to collect and retain the gaseous arcing products, and it is therefore these passages which most requi e flushing. With egard to the second of these factors, generally speaking, the larger the exhaust opening, the easier it is for the pump to displace the ionized arcing gases from the interrupter. The smaller the exhaust openings, the greater is the tendency for gas pockets to be bypassed by the stream of scavenging liquid and thus to remain behind within the interrupter.

The negative-gradient characteristics of my valve enable scavenging to be effected in accordance with these ideals. For example, a a result of these negative-gradient characteristics, the pressure-responsive valves do not close as soon as the pressures within the interrupter fall from their peaks reached during arcing. Since only a relatively small pressure is required to maintain the valve members in their open position, as indicated hereinabove, the valves remain fully-opened, even though the pressure within the interrupter drops appreciably when the arc is extinguished. More specifically, the

valves of the present application are so constructed that.

the pressure produced by the pump alone, as it operates after arc-extinction, is suificient to maintain the valve-members in their fully open position until effective scavenging has been completed. With the valve members fully-open, the fresh insulating fluid can be impelled through most of the same passageways as had previously received the arcing products, and the residual arcing products can be effectively displaced from these passageways through the unimpeded exhaust openings without significant hindrance from the valve members.

If, on the other hand, the exhaust valves had been closed immediately after arcing, as has been the case with prior inter-rupters, liquid from the pump would be dissipated inelfectively through miscellaneous leakage openings in the interrupter and would bypass many of the normal exhaust passages, where residual arcing gases would most likely have been left behind.

When the piston 32 has approached the end of its operating stroke and has substantially ceased to pressurize the fluid within the interrupter, the valve members 110 are restored to their closed position by their resilient closingbias means 115, 116.

A basic function of the exhaust valves is to restrict the exhaust ports during those low-current interruptions which generate relatively small quantities of gases. Without the valves, these gases would be dissipated so quickly through the large exhaust ports that no appreciable pressure build-up would occur within the interrupter, which is a condition that would render interruption extremely diflicult. Although the pump 30 would provide some pressure build-up, its effectiveness in this regard would also be substantially impaired by the absence of any material downstream restriction in the exhaust ports.

With the exhaust valves 100 present, however, the arcing gases, even though of a small quantity, are not ineffectively dissipated but are temporarily retained within the interrupter to produce, in cooperation with the pump 30, a pressure build-up which greatly aids in interrupting the low-current arc. For those low-current interruptions which generate insuflicient pressure to open the valves 100, the temporary retention of the arcing gases tends somewhat to reduce the dielectric strength of the insulating fluid, but any losses in dielectric strength resulting from the presence of arcing gases are more than offset by the increases resulting from increased pressure.

In connection with certain light current switching operations, the negative gradient characteristics of my exhaust valves are especially advantageous in assisting the Interrupting process. In particular, where the arc-duratron is relatively long and the amount of gases generated is relatively large, the valves are capable of opening and remaining open to permit the required scavenging of the interrupter by the pump 30 during the interrupting process. In this particular connection, the valve of the present application acts in a manner corresponding to the valve of the aforementioned Barkan and Schneider application, where it is pointed out that scavenging of the interrupter under these light current, long arc-duration conditions is important in order to build-up dielectric strength in the interrupter at a rate high enough to substantially prevent harmful restrikes across the arcing gap. Reference may be had to this Barkan and Schneider application for a more complete description of how the valve performs under such conditions.

It has been found that a slight amount of flow through the exhaust passages 25 is desirable, even during the interruption of very low currents. Such flow is obtained in the disclosed interrupter by providing a small opening, such as 132, in the vane 110. Although this opening allows some flow through the exhaust passages during low current interruptions, this flow is not sufiicient tointerfere with the desired pressure build-up under such that have their exhaust passages restricted by pressureresponsive valves is that liquid entrapped within the interrupter tends to impede circuit-breaker closing action. In conventional interrupters having no such exhaust valves, the liquid displaced by the contacts, as they move into the interrupter during closing, is freely vented through the unrestricted exhaust passages. No appreciable pressure build-up occurs within the interrupter and, as a result, the liquid does not significantly interfere with closing action. But with exhaust valves restricting such venting action, the interrupter housing acts, during closing, in a manner analogous'to a dashpot. In this regard, pressures built up within the interrupter tend to retard closing movement of the contacts and tend to very substantially increase the forces required to close the contacts at the desired speed.

The negative-gradient characteristics of the valves 100 enable this problem to be readily overcome. In this regard, the interrupter of the present invention has its interior enclosed to such an extent that initial closing movement of the contact structures 11, 13, 17, abruptly builds-up within the interrupter pressure exceeding the value required to initiate valve-opening movement. The slight valve-opening which follows immediately produces a pressure drop within the interrupter, but despite this pressure drop, valve opening continues, inasmuch as the pressure required to hold the valve open decreases as the vane 110 travels away from its closed position, due to the negative gradient characteristics of the valve. The vane 110 is maintained in an open, and preferably a fully-open, position until near the end of the closing stroke, thus maintaining the pressure within the interrupter at a comparatively low value which does not materially interfere with closing action.

Another advantageous feature of my disclosed interrupter is that the valves 100 are structurally separate from their respective bafile stacks, instead of being incorporated directly into the stacks and relying upon the stacks for support, as have some prior designs. By

virtue of this separateness, the location of the baifie stacks is not closely fixed by the exhaust openings in the casing but may be adjusted either vertically or horizontally, within limits, relative to these openings. Also by virtue of this separateness, various minor structural changes may be made in either the baflle stacks or the valves without changing the construction of the other. Still further, by virtue of this separateness, the valve is rendered fail-safe. For example, if it should be blown oh. due to a possible material defect, or some other cause, the bafile stack wouldremain intact and the high-current interrupting ability of the interrupter would remain unchanged.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

i. In an electric circuit interrupter, means for establishing an are within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage and comprising a tubular valve body containing a flow passage forming an outlet for said exhaust passage, 21 near-balanced vane pivotally mounted within said body for controlling flow through said flow passage, negative-gradient resilient means located externally to said valve body and coupled to said vane for urging said vane toward a substantially closed position with an effective force on said vane that decreases as said vane moves away from said closed position toward a fully-open position, said vane having a first area against which pressures internally of said interrupter act in a direction to force said vane open and a second area against which said internal pressures act in a direction to hold said vane closed, the size of said second area being slightly smaller than that of said first area whereby pressures developed within said interrupter above a predetermined value force said vane open against the opposition of said resilient means.

2. In an electric circuit interrupter, means for establishing an arc within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage and comprising a tubular valve body containing a flow passage forming an outlet for said exhaust passage, a near-balanced vane pivotally mounted Within said body for controlling flow through said flow passage, resilient means located externally to said valve body and coupled to said vane for biasing said vane toward a substantially closed position, said vane having a first area against which pressures internally of said interrupter act in a direction to force said vane open and a second area against which said internal pressures act in a direction to hold said vane closed, the size of said second area being slightly smaller than that of said first area whereby pressures developed within said interrupter above a predetermined value force said vane open against the opposition of said resilient means, said vane being so constructed that the ratio of the effective size of said first area to the eitective size of said second area abruptly increases upon initial opening of said vane.

3. In an electric circuit interrupter, means for estab lishing an are within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said are, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage and comprising a tubular valve body containing a flow passage forming an outlet for said exhiust passage, a near-balanced vane pivotally mounted Within said body for controlling flow through said flow passage, resilient means located externally to said valve. body and coupled to said vane for biasing said vane toward a substantially closed position, said vane having a first area against which pressures internally of said interrupter act in a direction to force said vane open.

and a second area against which said internal pressures act ina direction to hold said v-ane closed, the size of said second area approximating that of said first area but being slightly smaller whereby pressures developed within said interrupter above a predetermined value force said vane open against the opposition of said resilient means, said vane including a tail portion upon which pressures within said interrupter act when said tail portion is exposed to said pressures to provide supplementary valve-opening force, said tail portion being unexposed to said pressures when said vane is in said closed position but becoming exposed to said pressures in response to movement of said vane out of said closed position.

4. The interrupter of claim 3 in which at least a portion of said tail portion projects from the remainder of said vane generally in a direction opposite to the direction of valve-opening movement.

5. In an electric circuit interrupter, means for establishing an are within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products haust passage and comprising a tubular valve body containing a flow passage forming an outlet for said exhaust passage, a vane pivotally mounted within said body for controlling flow through said flow passage, negative gradient resilient means located externally to said valve body and coupled to said vane for urging said vane toward a substantially closed position with an efiective force that decreases as said vane moves away from said substantially closed position toward a fully-open position.

6. The interrupter of claim 5 in which said negativegradient resilient means comprises a crank coupled to said vane and spring means coupled to said crank, said crank charging said spring means and moving toward an inline position relative to the line of action of said spring means as said vane moves from said substantially closed position toward said fully-open position.

7. The interrupter of claim 5 in which said negativegradient resilient means comprises angularly movable cranks located at opposite sides of said valve body and coupled to said vane, a tension spring interconnecting said cranks and extending about said valve body, means for anchoring a portion of said tension spring to said valve body in such a location that angular movement of said cranks during valve-opening causes said cranks progressively to approach an in-line position relative to the line of action of said tension spring.

8. In an electric circuit interrupter, means for establishing an are within said interrupter, an arc extinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage and comprising a tubular valve body containing a flow passage forming an outlet for said exhaust passage, a plate-like vane pivotally mounted within said body, said vane having a substantially-closed position severely restricting flow through said flow passage and a fully-open position generally parallel to the direction of flow through said flow passage for allowing substantially unobstructed flow therethrough, negativegradient resilient means located externally to said valve body and coupled to said vane for urging said vane toward a substantially closed position with an effective force on said vane that decreases as said vane moves away from said closed position toward a fully-open position, said vane when in said closed position having an area upon which pressures developed within said interrupter above a predetermined value act to drive said vane out of said closed position toward said fully-open position.

9. The interrupter of claim 8 in which said plate-like vane has two major surfaces on its opposite sides and in which said vane in its fully-open position allows fluid to flow past both of its two major surfaces, said vane having at its downstream end a tail portion which acts to divert the stream of fluid flowing past one of said ma- 12 jo-r surfaces away from the stream flowing past the other of said major surfaces.

' 10. The interrupter of claim 8 in which said vane is provided with a tail portion upon which pressures within said interrupter act when said tail portion is exposed to said pressures to provide supplementary valve-opening force, said tail portion being unexposed to said pressures when said vane is in said closed position but becoming exposed to said pressures in response to move ment of said vane out of said closed position.

11. The interrupter of claim 10 in which at least a portion of said tail portion projects from the remainder of said vane generally in a direction opposite to the direction of valve-opening movement.

12. In an electric circuit interrupter, a casing, means for establishing an are within said casing, an arc-extinguishing unit located within said casing and including at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, a pressure-responsive exhaust valve structurally separate from said arc-extinguishing unit and having a tubular body mounted Within an opening in said casing, means for fastening said tubular body to said casing independently of said arc-extinguishing unit, said tubular body containing a flow passage therethrough communicating with said exhaust passage and forming an outlet for said exhaust passage to the exterior of said casing, said valve further comprising means for controlling the fiow of fluid through said exhaust passage in accordance with the pressures developed within said interrupter as a result of an interrupting operation.

13. The interrupter of claim 3 in which said valve includes a valve seat against which said vane abuts when in said substantially closed position, said tail portion being positioned when said vane is closed beyond said valve seat relative to that region of said vane which is exposed to said internal pressures.

14. The interrupter of claim 3 in which at least a part of said tail portion projects from the remainder of said vane generally in a direction opposite to the direction of valve-opening movement and in which said projecting part of the tail portion is located outside of said valve body when said vane is in a fully-open position.

References Cited in the file of this patent UNITED STATES PATENTS 616,100 Harrison Dec. 20, 1898 2,095,263 Moss Oct. 12, 1937 2,160,673 Prince May 30, 1939 2,345,824 Macbeth Apr. 4, 1944 2,556,277 Hill et al. June 12, 1951 2,749,412 McBride et a1. June 5, 1956 FOREIGN PATENTS 264,043 Great Britain Jan. 13, 1927 394,221 Great Britain June 22, 1933

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