US2927182A - Fluid blast circuit interrupter - Google Patents

Description

March 1, 1960 P. BARKAN ETAL 2,927,182

FLUID BLAST CIRCUIT INTERRUPTEIR Filed Feb. 27, 1958 07 czosm ruuraaw SIT/0N O zvz/msms 0 VHL VE OPEN/N6 PREGSU/ff PRES s (IRE TIME CYCLE Inventors:

Philip Bark-an, Harold N. Schneider,

United States Patent r 2,927,182 FLUID BLAST CIRCUIT INTERRUPTER Philip Barkan, Lima, and Harold N. Schneider, Springfield, Pa., assignors to General Electric Company, a

corporation of New York Application February 27, 1958, Serial No. 717,893

14 Claims. (Cl. 200-150) 'ice Accordingly, another object of our invention is to construct the pressure-responsive exhaust valves in such a manner that they do not significantly interfere with those scavenging operations which take place after the pressures produced by high current interruptions have subsided.

Another object is to construct the exhaust valves in such a manner that they allow scavenging to take place through most of the same passages that had received the arcing products during interruption.

In carrying out our invention in one form, a pressure-responsive valve is located in an exhaust passage leading from the interrupter. The valve comprises a movable valve member located to restrict the flow of fluid through the exhaust passage and resilient means urging the valve member into a position of maximum mediately after a circuit-interrupting operation.

\ For improving the ability of a fluid-blast interrupter t to successfully interrupt low currents, it has been proj posed heretofore that the exhaust passages of the interf rupter be provided with one or more valves responsive restriction relative to the exhaust passage. The resilient means is arranged to yield in response to pressures above a predetermined value developed within the interrupter and, thus, allows the valve member to move toward a to the pressure built up within the interrupter during an interrupting operation. ranged to severely restrict the exhaust passages during These valves have been arglow current interruptions and, thus, have acted to in- .jcrease 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 smallquantities of gases. Certain capacitive switching operations involve arcs of this nature, and here particularly these increased pressures have considerably aided the interrupter in effecting successful circuit interruption. v

For certain other light current switching operations, however, the quantity of gases generated can be considerably larger, for example, where the are duration preceding the first attempt to clear is relatively long. For these conditions, we have found that it is much more important to rapidly scavenge the interrupter of ionized gases than it is to maintain high pressures within the interrupter. Otherwise, these gases, which are highly ionized, will lower the dielectric strength of the interruptingmedium to such an extent as to unduly prolong arcing. -With prior pressure-responsive valves, as soon as a slight exhaust flow has occurred, the resulting drop fully-open position, or a position of minimum restriction, in response to such pressures. The resilient means is so constructed that it urges the valve member toward its position of maximum restriction with an effective force that decreases as the valve member moves toward its fully-open position. As a result of this decreasing closing force, once the valve has opened, the resilient means acts to restore the valve member to its position of maximum restriction only after the pressure within the interrupter has fallen to a relatively low value, e.g., a value con siderably below the presstn'e required to initiate valveopening.

For a better understanding of our invention reference may be had to the following description taken in conjunction with the accompanying drawing wherein:

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

Fig. 2 is an enlarged view taken along the line 22 of Fig. l and illustrating a pressure-responsive exhaust valve employed in the interrupter of Fig. 1. The valve is shown in closed position.

Fig. 2a is a sectional view taken along the line 2a2a of Fig. 2.

Fig. 3 is a graphical representation of certain operating characteristics of the valve of Fig. 2 and also the valve in Pressure has tended dose thqvalves i this P T- i g 4 illustrates the valve of Fig. 2 in its fully open tended to interfere with the rapid scavenging action position deslred under these condltlons' Fig. 5 is a graphical representation of certain pressure- With references to these latter types of light current interruption, it is an object of the present invention to construct the pressure-responsive exhaust valves in such a manner that they facilitate scavenging of arc-generated gases from the interrupter, even after those pressures within the interrupter have caused valve-opening have subsided from their peak values reached during interruption.

Effective scavenging is also important in connection with the interruption of relatively high power currents. For such interruptions, the arc itself is usually capable of generating the pressures and velocities required for interruption. But, immediately after interruption, and as soon as the pressures within the interrupter have fallen below a predetermined value, a pump, usually provided for this purpose, automatically operates to force fresh insulating fluid through the interrupter so as to scavenge the interrupter. Prior pressure-responsive exhaust valves have unduly interfered with this scavenging action because they have tended to close immediately after interruption and before the pump could perform the desired scavenging action.

time relationships for the interrupter of Fig. 1.

Fig. 6 illustrates a modification of the valve shown in Fig. 2.

Referring now to Fig. l, 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 1 is mounted, along with another similar interrupter (not shown) inside a relatively large oil-filled enclosingtank. The two interrupters are electrically connected by a reciprocable blade contact 2 of conventional form, such as shown for example in U.S. Patent 1,548,799 Hilliard, assigned to the assignee of the present invention.

The interrupter 1 is supported within the oil-filled tank from an insulating bushing structure 3 having a conductor stud to which the 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 interrupt.-

ing contacts which are electrically connected in series. The upper pair 8 of separable contacts comprises a relatively fixed contact assembly 141 and a relatively movable rod-type contact 11. The fixed contact assembly 19 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 14 and 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 simultaneouslyoccnrring 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 complet 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 13 which operates 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 23, through the upper interrupting contacts 16, 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 contactslS and 19 ion conventional manner.

The compression springs 6, it will be noted bearat 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. Baffle stack 21 is formed of a plurality of superposed apertured baiile plates 23 of insulating material which together provide a central interrupting passageway 24 and a plurality of verticallyspaced, angularly-aligned exhaust passages 25 radiating therefrom. The exhaust passages 25 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 1% and 11, pressure is produced within the oil filled casing and is eifective to force a highly concentrated blast of dielectric fluid across the arcing region 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. he lower bafiie stack 22 generally corresponds to the baffle stack 21 except that bafiie 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, 26, there is provided a pressure-responsive exhaust valve for each of the arc extinguishing units 21 and 22. Referring to Fig. 2, 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 1tl2. When the nut 16-?- is tightened, it forces a shoulder 106 formed on the tubular housing 162 into clamping engagement with a recessed portion 167 formed in the interior of casing 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.

Disposed within the valve body 102 is a movable valve member 110 pivotally mounted at its lower end upon a shaft 111. This shaft 111 is suitably fixed to the valve body 102 and projects across the lower portion of the bore of the valve body. Preferably, the ends of the shaft 111 are of a rectangular cross-section and are tightly fitted within suitable rectangular holes in the valve body 102 in order to prevent rotation of the shaft. The valve member 110 is normally maintained in its closed position shown in Fig. l by resilient means comprising a compression spring 112 and a prop lever 114. The prop lever 114 is pivoted on the valve member by means of a pivot pin 115, and the compression spring 112 urges the prop lever in a clockwise direction about the pivot pin 115. Preferably, suitable guides 112a and 11217 are I provided at opposite ends of the spring 112 to provide for correct positioning of the spring. The guide 112a is shown pivotally joined to the prop lever 114, whereas the guide 11% is secured to the shaft 111. When the pressure within the interrupter exceeds a predetermined value, it overcomes the action of spring 112 and forces the valve member 111 counterclockwise about its pivot 111, thereby opening the central exhaust passageway throughthe valve body 110 and allowing fluid to flow therethrough.

"'For reasons which will soon be pointed out in detail, the resilient means 112,114 exerts a generally decreasing effective closing force on the valve member 110 as it travels away from its closed position toward its fully open position. The terms efieotive force and effective closing force, as used in this application, are intended to be synonymous with the torque or moment exerted by the resilient means 112, 11-4 on the valve member 110. The manner in which this eflective closing force decreases can be more clearly understood by referring to the graphical representation of Fig. 3. As depicted in the solid line curve of Fig. 3, the resilient means 112-114 exerts on the valve member an effective closing force 1 when the valve rnember is in its closed position, but this force declines along the solid line curve as the valve member moves toward its fully open position indicated on the abscissa of the graph. When the valve member has moved into its fully open position, the effective closing force exerted by the resilient means has decreased to a value g, which is only a fraction of the original effective closing force f. This decreasing force relationship is referred to hereinafter as the negative gradient characteristic of the valve.

The manner in which the resilient means 112-1 14 operates to provide this negative gradient characteristic will now be explained. Referring to Fig. 2, the degree to which the resilient means 112, 114 restrains the valve member 110 from opening movement depends on the angle h which the prop lever makes with the bottom surface 116 of the valve body 102. In general, the smaller this angle, the smaller is the force tending to oppose opening of the valve member lltl. For example, when sufficient pressure builds up to the right of the valve member 110 to initiate opening, the prop lever is forced counterclockwise about its pivot 115 and more into line with the line of action 117 of spring 112, thus decreasing the angle 11. As this action continues, the spring 112 acts on the valve member 110 through a progressively decreasing lever arm and 'thus'exerts a progressively decreasing closing force on the valve member 110. When the valve member 110 has been urged into its fully-open position of Fig. 4, the angle h has reached its lowest value and the spring means 112, 114 is exerting on the valve member 110 its minimum force in a valve-closing direction. A suitable stop 118 prevents opening travel of the valve member 110 beyond the position of Fig 4. As a result, the resilient means 112. 114 exerts a closing force on the valve member 110, even when the valve member is in its fully-open position of Fig. 4. When the pressure within the interrupter falls below a predetermined value, the closing'force exerted by the resilient means 112, 114 acts to restore the valve member 1 to its closed position of Fig. 2. I

When high current arcs are established within the in iterrupter 1, the arc generates sufiicient pressure to force :each of the valve members 110 out of its closed position into its fully open position. As a result of these high pres- :sures, liquid is impelled at high velocity through the region of the arc and out the open valves. This high velocity fiow which accompanies the interruption of high currents is effective to rapidly extinguish the high current arc, and the valves, in opening widely, prevent excessive pressure rises within the interrupter.

As soon as the interrupting operation for these relatively high currents has been completed, a pump 30 operates to scavenge the interrupter 1 of any ionized gases remaining after the interruption so as to prepare the interrupter for possible reclosure followed by another interruption. To this end, the pump 39 forces a flow of fresh insulating liquid through the arc extinguishing unit via the passageways 31 and 25, '26 and the exhaust valves 100, 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 McBride patent, comprises a cylinder 32 suitably secured to the interrupter casing 5 and connected 'with the passageways '31 by means of ducts 43 and 43a. The pump 30 also comprises an impulse piston 35 which is spring biased downwardly by a compression spring 36. The compres- :sion spring 36 is mounted between a stationary part 3'7 :and a stop 39 fixed to the piston rod 40, which in turn is tfixed to the piston 35. The compression spring 36 is held charged during the time the interrupter is closed by means of a plunger 39a fixed to the Switchblade 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 sufiicient 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 30 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 46a, 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.

We have found that the ability of the pump 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 require flushing. With regard tothe 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.

In prior interrupters the presence of pressure-responsive valves in the exhaust ports has rendered it difiicult, if not impossible, to scavenge the interrupter in accordance with the ideals set forth hereinabove. It is with the object of attaining these ideals that we have constructed our pressure-responsive exhaust valves with the negative gradient closing characteristics described hereinabove. As a re sult 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 fullyopened, even though the pressure Within the interrupter drops appreciably when the arc is extinguished. In ac cordance with one particular aspect of our invention, the pressure produced by the pump alone, as it operates after arc-extinction, is sufficient 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 eifectively 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 interrupters, liquid from the pump would be dissipated inetfectively 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 35 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 112, 114.

A basic function of the exhaust valves is to retrict 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 difficult. 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 insufficient pressure to open the valves 100, the temporaly retention of the arcing gases tends somewhat to reduce the dielectric strength of the insulating fluid, but any losses in dielectric strength re- Y sulting from the presence of arcing gases are more than offset by the increases resulting from increased pressur During such interruptions, it will be noted, the pressures generated by both the pump 30 and by arcing are not sufiiciently high to force the valve members 110 out of their respective closed positions. I

A type of low current interruption which provides an extremely severe test for an interrupter is that encountere when opening predominately capacitive circuits. During such opening operations, it is comparatively easy to effect a temporary interruption of the are at an early current zero, but after an additional one-half cycle, the voltage across the parting contacts of the breaker approaches twice the peak value of the system voltage. Unless the gap between the contacts is then capable of withstanding this double peak voltage, a restrike will occur. Such restrikes can produce seriously high voltages approaching three times the system peak voltage and even higher if they occur on succeeding half cycles.

By employing pressure-responsive exhaust valves constructed in accordance with the present invention, it has been possible to almost entirely prevent such restrikes. For example, consider first the interruption of a low regulation capacitive circuit. Here the arc duration preceding the first attempt to clear is relatively short, and, as a result, the exhaust valves remain closed because the quantity of gases generated is small and the resulting pressure, even though supplemented by the pump 30, is not sufficient to open the valves. The valves in preventing rapid dissipation of this gas causes the confined gas, acting in conjunction with the pump 3%, to build up a pressure which increases the dielectric strength of the gap sufiiciently to withstand double peak voltage. The pressure built up as a result of the valves remaining closed is, however, sufficient to raise the dielectric strength of the gap sufiiciently to withstand the double peak voltage which would cause a harmful restrike.

Consider next the interruption of those relatively light currents in which the arc duration preceding the first attempt to clear is relatively long. Such currents generate a considerably larger quantity of gases than low-regulation capacitive currents, and the resulting pressures are therefore higher and sufhcient to open the pressure-responsive valves 1%. With the valves open, the pump 3t) operates to flush the arcing gases from the gap between the contacts while the voltage across the contacts is rising toward its peak value. Initial opening of the valve immediately tends to lower the pressures Within the in terrupter. But, in the disclosed interrupter, this pressure reduction ordinarily does not cause the valve memher to begin returning to its closed position because less force is required to hold the valve in an open position than is require to initiate opening, due to the previouslydescribed negative gradient characteristic. Thus, the

valve does not tend to flutter between an open and closed position, as has been the case with certain prior designs, and, accordingly, scavenging is allowed to continue at a high rate without undue interference from the exhaust valves. As a result of this high rate of scavenging under these particular conditions, the dielectric strength of the gap between the contacts is built up at a rate suflicient to prevent breakdowns which might otherwise result from the voltage being built up across the contacts immediately following interruption.

For a better understanding of the manner in which the valve 1th operates during the switching of relatively light currents, reference may be had to the graph of Fig. 5. Curve A illustrates a typical pressure. build-up when the arc duration preceding interruption is short. It

will be noted from this curve A that during such opera' tions the pressure within the interrupter does not reach the value V.O. required to initiate valve-opening. Thus, the valve remains closed as described hereinabove.

When the arc duration is relatively long, as depicted 'in' curve B, the pressure developedwithin the interrupter is sufiicient to open the valve as indicated at point 0. Referring still to curve B, the pressure within the interrupter begins to fall as soon as the valve opens, and continues to fall inasmuch as the valve remains open due to above described negative gradient characteristics. It isassumed that these pressures are measured in the region of the arc, i.e., upstream from the valve itself.

Curve C depicts the type of pressure rise which would be encountered if the valve member were biased closed by a positive gradient spring, as is the case with prior art valves. It is assumed that the arc duration preceding the first attempt to clear is of the same relatively great length as that occurring in connection with curve B. When such a positive-gradient valve opens a short distance, a pressure drop within the interrupter occurs, causing the valve to return toward closed position. This causes a pressure rise within the interrupter, and the valve responds by opening. Such oscillations between a closed and a partially-open position continue (as depicted in the flat region of curve C), while the pump strives to scavenge the interrupter of the arcing products. The fact that the valve during this interval is moving into and out of its closed position impedes flow through the interrupter and, accordingly renders it most difficult for the pump to effectively scavenge the arcing gap. This results in a lower rate of dielectric build-up with a corresponding increase in the likelihood of a restrike, when compared to the performance attainable with the negative gradient characteristic of my valve.

With regard to the disclosed valve, it is to be understood that considerable control over the shape of the characteristic curve shown in Fig. 3 can be obtained by suitably var ing the shape of the sliding surface 116, or by suitably varying the gradient of spring 312, or by suitably varying both of these features. In other words, by resorting to such variations, the nature of the relationship between closing force and valve position can be significantly varied, although still maintaining the desired negative gradient.

As an example of the manner in which the shape of sliding surface 116 can be varied to modify the shape of the characteristic curve of the valve, reference may be had to Fig. 6. Here the surface 116 is provided with a cam surface 116a upon which the lower end of the prop lever 114 slides. This cam surface will act to provide a more abrupt drop in the valve closing force as the valve member 119' moves out of its closed position than is the case with the valve of Figs. l-S. The dotted line curve of Fig. 3 illustrates the approximate manner in which closing force would vary as the valve member of Fig. 6 moved open.

A problem that arises in connection with interrupters 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 our valves 1G0 enable this problem to be readily overcome. In this regard, the interrupter of the present invention has its interiorenclosed to such as extent that initial closing movement of the contact structure 11, 13, 17 abruptly buildsup within the interrupter pressure exceeding the value re- =quircd-to initiate valveopening 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 valve member 110 travels away from its closed position, due to the negative gradient characteristics of the valve. The valve member 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. As will be apparent from Fig. 5, this low value of pressure is only a fraction of the pressure required to initiate valve-openmg.

It is to be understood that the desired negative gradient characteristics can be obtained with forms of valves other than that specifically disclosed hereinabove. For another example of an exhaust valve constructed to provide the desired negative gradient characteristics, reference may be had to application S.N. 717,892, Schneider, filed February 27, 1958, and assigned to the assignee of the present invention. ,7 d

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

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

1. In an electric circuit interrupter, means for establishing an arc within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading tor the exterior of said unit for venting arcing products from the region of said are, an exhaust valve member located to restrict the flow of fluid through said exhaust passage, resilient means urging said valve member into a position of maximum restriction relative to said passage and arranged to yield in response to pressures above a predetermined value developed within said interrupter thereby allowing said valve member to move toward a position of minimum restriction in response to said pressures, said resilient means urging said valve member toward said position of maximum restriction with an effective force on said valve member that generally decreases as said valve member moves toward said position of minimum restriction.

2. In an electric circuit inteirupter, means for establishing an are within said interrupter, an arc-extinguishing unit comprising at least one exhaust passage leading to the exterior of said interrupter for venting arcing products from the region of said arm, an exhaust valve member having a generally-closed position providing a maximum restriction to flow through said exhaust passage and a fully-open position providing a minimum restriction to said flo'w, resilient means urging said valve member into said generally closed position and arranged to yield in response to pressures above a predetermined value developed within said unit for allowing said valve member to move toward said fully-open position in response to said pressures, said resilient means urging said valve member toward said generally-closed position with an elfective force on said valve member that generally varies inversely with respect to the opening travel of said valve member from its generally-closed position.

3. In an electric circuit interrupter, separable contacts for establishing an are within said interrupter, an arcextinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, an exhaust valve member having a generally closed position providing a maximum restriction to flow through said exhaust passage and a fully-open position providing a minimum restriction to said flow, resilient means urging said valve member into said generally closed position and arranged to yield in response to pressures above a predetermined value developed within said unit for allowing said valve member to move toward said fully-open position in response to said pressures, said resilient means acting in said fully open position to urge said valve member closed with an effective force on said valve member substantially lower than the effective force with which said resilient means acts when said valve member is in said closed position.

4. The interrupter of claim 3 in which the interior of said interrupter is enclosed to such an extent that initial contact-closing action produces pressures therewithin sufficient to initiate valve opening movement, and additional cont act-closing produces pressures therewithin sufiicient to hold said valve member in an open position until near the completion of contact-closing action.

5. In an electric circuit interrupter, separable contacts for establishing an are within said interrupter, an arcextinguishing unit comprising at least one exhaust passage leading to the exterior of said unit for venting arcing products from the region of said arc, an exhaust valve member having a generally closed position providing a maximum restriction to flow through said exhaust passage and a fully-open positio'n providing a minimum restriction to said flow, resilient means urging said valve member into said generally closed position and arranged to yield in response to pressures above a predetermined value developed within said unit for allowing said valve member to move toward said fully-open position in response to said pressures, said resilient mean-s acting in said fully open position to urge said valve member closed with an effective force on said valve member substantially lower than the effective force with which said resilient means acts when said valve member is in said closed position, a hollow valve body in which said valve member is pivotally mounted, a prop lever forming a part of said resilient means and pivotally connected at one end to said valve member and supported at its other end on an internal surface of said valve body, o'pening movement of said valve member driving said prop lever along said surface in such a manner as to generally reduce the effective angle between said prop lever and said surface, and spring means forming another part of said resilient means opposing opening motion of said prop lever along said surface.

6. In an electric circuit interrupter which is adapted to contain an insulating fluid, 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, pump means operable after predetermined cir cuit interruptions for pressurizing fluid within said arcextinguishing unit and for directing a flow of fluid through said arcing region and said exhaust passage, a movable exhaust valve member located to restrict the flow of fluid through said exhaust passage, resilient means urging said valve' member into a position of maximum restriction relative to said passage and arranged to yield in response to pressures above a predetermined value developed within said unit, thereby allowing said valve member to move toward a position of minimum restriction in response to said pressures, said resilient means urging said valve member toward said position of maximum restriction with an effective force that generally decreases as said valve member moves toward said position of minimum restriction, the pres-sure produced by said pump means during at least a portion of its operating period after circuit interruption being of a sulficient value to maintain said valve member generally in said position of minimum restriction in the event that said valve member hastbeen moved into said position of minimum restriction by a circuitinterrupting operation. 7 p

7. The interrupter of claim 6 in which said pump means operates during low current interruptions to pressurize fluid within said interrupter, the pressure produced by said pump means during and after certain low current operations being insufficient to force said valve member out of said position of maximum restriction.

8. In an electric circuit interrupter which is adapted to contain insulating fluid, 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 are, pump means operable after predetermined circuit interruptions for pressurizing fluid within said interrupter and for directing a flow of fluid through said arcing region and said exhaust passage, a movable exhaust valve member located to restrict the flow of fluid through said exhaust passage, resilient means urging said valve member into a position of maximum restriction relative to said passage and arranged to yield in response to pressures above a predetermined value developed Within said unit, thereby allowing said valve member to move toward a position of minimum restriction in response to said pressures, said resilient means acting in said position of minimum restriction to urge said valve member toward its position of maximum restriction with an efiective force on said valve member substantially lower than the effective force with which said resilient means acts when said valve member is in its position of maximum restriction, the pressure produced by said pump means during at least a portion of its operation after a circuit interruption being of a sufiicient value to maintain said valve member generally in said position of minimum restriction in the event that said valve member has been moved into said position of minimum restriction by a circuit interrupting operation.

9. The interrupter of claim 8 in which said pump means operates during low current interruptions to pressurize fluid within said interrupter, the pressure produced by said pump means during and after certain low current operations being insufiicient to force said valve member out of said position of maximum restriction.

10. 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 are, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage, said valve comprising a movable valve member and resilient means urging said valve member toward a substantially closed position, said resilient means being arranged to yield in response to pressures above a predetermined value developed within said interrupter when said valve member is in said closed position thereby allowing said valve member to move from said closed position toward a fully-open position, said valve being so constructed that said valve member will be maintained approximately in a fully-open position by pressures within said interrupter in said are region substantially below the value required to initiate valve-opening.

11. In an electric circuit interrupter, separable contacts 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 are, a pressureresponsive exhaust valve controlling the flow of fluid through said exhaust passage, said valve comprising a movable valve member and resilient means urging said valve member toward a substantially closed position, said resilient means being arranged to yield in response to pressures above a predetermined value developed within said interrupter when said valve member is in said closed position thereby allowing said valve member to move from said closed position toward a fully-open position, said valve being so constructed that said valve member will be maintained in a fully-open position by pressures within said interrupter in said are region substantially below the value required to initiate valve-opening, the

interior of said interrupter being enclosed to such an extent that initial contact-closing action produces pressures therewithin suflicient to initiate valve-opening and additional contact-closing action produces pressures therewithin suflicient to hold said valve member in an open position until near the completion of contact-closing action.

12. In an electric circuit interrupter which is adapted to contain an insulating fluid, 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, pump means automatically operable after predetermined circuit interruptions for pressurizing fluid within said interrupter and for directing a flow of fluid through said arcing region and said exhaust passage, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage, said valve comprising a movable valve member and resilient means urging said valve member toward a substantially closed position, said resilient means being arranged to yield in response to pressures above a predetermined value developed within said interrupter when said valve member is in said closed position thereby allowing said valve member to move from said closed position toward a fully-open position, said valve being so constructed that said valve member will be maintained in a fully-open position by pressures within said interrupter in said are region substantially below the value required to initiate valve-opening, the pressure produced by said pump means during at least a portion of its operation after a circuit interruption being of a sufficient value to maintain said valve member generally in said fully-open position in the event that said valve-member has been moved into said fully-open position by a circuit-interrupting operation.

13. The interrupter of claim 12 in which operationmf said pump means produces insuflicient pressure within said interrupter during and after predetermined low current interruptions to force said valve member out of said generally-closed position.

14. In an electric circuit interrupter which is adapted to contain an insulating fluid, 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 are, pump means automatically operable after predetermined circuit interruptions for pressurizing fluid within said interrupter and for directing a flow of fluid through said arcing region and said exhaust passage, a pressure-responsive exhaust valve controlling the flow of fluid through said exhaust passage, said valve being constructed to open in response to pressures developed within said interrupter above a predetermined value, the pressure produced by said pump means during at least a portion of its operation after circuit interruption being sufficient to maintain said valve open in the event that said valve has been opened by a circuit-interrupting operation, the pressure produced by said pump means during and after certain low current interruptions being insuflicient to initiate valve-opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,216 Whitney et al Apr. 17, 1934 2,022,241 Kopeliowitsch Nov. 26, 1935 2,160,673 Prince May 30, 1939 2,717,293 Titus et al. Sept. 6, 1955 2,748,788 Duckstein June 5, 1956 2,749,412 McBride et al June 5, 1956 2,806,111 Baker et al. Sept. 10, 1957 FOREIGN PATENTS 264,043 Great Britain Jan. 13, 1927 201,986 Australia May 30, 1956

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