US2658969A - Hydraulic circuit breaker actuating mechanism - Google Patents

Description

Nov. 10, 1953 Filed April 17, 1.950

D. M. UMPHREY HYDRAULIC CIRCUIT BREAKER ACTUATING MECHANISM 3 Sheets-Sheet l a Q e \1 O l \0/ s & I 1 mfiv 1 9 20 a: a1 %I 0 /7 a7 IN VEN TOR DONALD M. UMPHREY.

Nov. 10, 1953 D. M. UMPHREY 2,653,969

HYDRAULIC CIRCUIT BREAKER ACTUATING MECHANISM Filed April 17, 1950 3 Sheets-Sheet 2 INVENTOR DONALD M. UMPHREY.

ATTORNEYS.

Nov. 10, 1953 D. M. UMPHREY HYDRAULIC CIRCUIT BREAKER ACTUATING MECHANISM 3 Sheets-Sheet 3 Filed April 17, 1950 INVENTOR.

DONA L'D M. UMPHREY.

I ATTORNEYS Patented Nov. 10, 1953 HYDRAULIC, cmggg gng an ACTUAT- n saiirigc phrey, Palo Alta, can, assi nbr to Patiflc Electric Manufacturing Cori, a certs iati'on 6f uniforms Application April 17, 1950, Serial No. 156,469

(cl. etc-s2) '14 claims. 1 a

'This invention relates to mechanisms for actufauna circuit breakers, and while it is pa-rues larly applicable is circuit breakers or the largest size, as utilized for breaking high voltage circuits or large power-carrying capacity, is also applicable to breakers or smaue types. I

Among the objects of this invention are to provide a mechanism which close a circuit reaker quickly and positively span the spin atlo'n of either a local oifr'e'r'note control, to proviae a 'fiieehafiisifi wherein thebr'e'ak be accoifiplished with estreme rapidity, i. e, from the and ofie-half to two cycles renewing the 15'- iilicatibh of a fault current tr 's'uffi'cleii't tli' to cause the nearer to trip instead "of reqmr g three cycles as success in cenonar breakers, 15c prcv e a 'han srn w ch will trip fr ear the tlosih'g rn'ethanisrn and break circuit with substantially equal 'S'ped pdsitivefie's's case a shblt circuit or other ramt is either arreauy present or occurs at the nstant when the breake s being erased, to provide a circuit breaker which will cperate n secure if aaaannpt is made to 're-crose it wane the tacit sir-11 -egists, to pro de a circuit breaker mechanism annoying lave rag meeha= 'i Slil er the toggle type having a lfa-f'ge in'echi v dram-trace, but wine has, at the sa'inti aeirecuve i s are de a circuit Ere er mechanism of maxi= reliabilityand "p lici ty.

"The bpfati-iig of this invention may be iid substantially any the 6f circuit breakers, g'e'n co is, and-, restrain, to

Trip mechanisms, operatic either manually response to an ove'ri'oad or fault curr nt, release means to separate the stationary and movable contacts, the separation usually beingacccmpl is'hed by means of a powerful spring in truer that, the circuit may be broken as rapidly as possible.

V The equipment whichis thesubiect of the present invention is for the purpose of closing the breaker'against the action of the spring and ineludes the latch and trip elements referred toi Broadly speaking it comprises a source of hydraulic pressure, referably a nigmp essure pump runs a hydraulic accumulator. The latter may be of the type comprising a aha per to which the pump is acted, h chamber contains a bag in balloon e ably, ani'nert gas such as nitr V I? or oil-resistant sy-atheticrubtercr eldst'omers'uch as neoprene, since the actuating fluid is'irequently an oil. By the use of the accumulator the primary pressure source may be a high pressure pump of small capacity, the normal function of which is merely to maintain the proper pressure in the accumulator which acts as a secondar pressure Source.

The operating element for compressing the opening spring and thus closing the circuit breaker comprises a hydraulic cylinder and piston, the cylinder being connected by a conduit system both to the pressure source and to a sump into which the cylinder discharges the fluid contained therein when the circuit breaker opens, the fluid thus discharged being recirculated back to the accumulator. A hydraulically-operated valve in the conduit system connects the cylinder alternatively to the pressure source or, through an exit port, to the sump, this valve being so constructed that when hydraulic pressure is applied thereto it operates first to cut off the passage from the cylinder to the sump and then to open the conduit from the pressure source into the cylinder and thus operate the piston.

Where a breaker of the type here under con-1 sideration is used it is obvious that the possibility always exists that an attempt may be made to close it when a fault, such as a short circuit, exists on the line which it feeds. When this occurs it is important that the breaker should trip open as positively and substantially as rapidly as would be the case if the fault occurred with the breaker in its latched-closed condition and no hydraulic pressure applied thereto. This is particularly the case in self-reclosin'g circuit breakers which are designed to attempt to reclose the circuit automatically one or more times after a fault occurs, in the hope that such fault may be of a purely transient nature which will clear itself.

The mechanism for aetu'atit 1a the main valve while permitting the breaker to trip free when closed under a faulty line c'on'ditio'n comprises a pilot valve interposed in a connection from the pressure source to the hydrauucauyaperat a main valve and a dump valve which normally closes a bypass to the sump" positioned between the pilot valve and the main valve, the dump valve being so constructed that it tends to open when pressure is applied through the pilot valve to the main valve line but is normally prevented from operating in response to such pressure by mechanical means which may be disabled by the operation of trip mechanism operating ccordinately with the trip of the latch holding the circuit breaker closed.

The pilot valve, besides controlling the appli cation of pressure from the source to the main valve, is preferably operated by pressure from the same source. It is, however, externally operable either by direct manual or by remote control. In its preferred form the pilot valve comprises a moveable valve element which, when subjected to pressure on one side, tends to close the pilot valve and when subject to pressure on the other side tends to open it, the area exposed to the closing pressure being greater than that exposed to the opening pressure so that when pressure is applied to both sides the valve tends to remain closed. The pressure is applied continuously and at full force to the side which tends to open the valve, but there is a leak or highresistance passage to the closing side. Accordingly, under static condtions when there is no flow from the pressure source, the hydrostatic pressure on the two sides of the valve equalizes 'and because of the larger area tending to close the valve it remains tightly shut.

A passageway leads from the closing side of the valve element into the sump, this passage being normally blocked by an auxiliary valve which can be externally operated to actuate the mechanism. When this latter valve opened 'the pressure tending to hold the valve closed is relieved and the pilot valve at once opens, actuating the main valve and closing the circuit breaker. If, however, the trip is actuated this condition obtains the dump valve operates,

relieving the pressure both upon the main valve and the opening side of the pilot valve element, the latter closes and the breaker trips free. Such process is speeded and made more positive by the fact that the operation of the dump valve also closes the passage into the sump from the c1os- 1 their actual sizes are not large and their masses M are relatively small. It will have been noted from the foregoing general description that differential pressures operate throughout will be seen in the more detailed description which follows, the areas over which these pres-- sures act are so computed that even the dir r" ential pressures are large and, acting upon the relatively small masses of the moving parts, operate them with extreme rapidity.

Speed of operation is, of course, of primary importance in circuit breakers. In order to obtain high operating speeds high rates of aeceleration are necessary, which means either that the masses moved must be small, their velocities must be small or the actuating forces must be large. In high power circuit breakers the breaking mechanisms themselves have to be sturdy and to move through considerable distances and since this involves a considerable mass, large operating forces, 1. e., powerful springs, are required, and this in turn necessitates that large forces be used to compress (or extend the springs. In the past either mechanical methods have been used to close the circuit breakers, or, alternatively, pneumatic methods. The forces used to trip the circuit breakers, however, must be relatively small since these devices should be sensitive and therefore the control equipment must be light in weight and move through reasonably small distances so that the accelerating forces do not become too high. Owing to the low inertia of gases and their relative ease of control, pneumatic circuit breaker operation is, on the surface, quite attractive and hydraulic methods have not been generally used because of the greater masses which must be moved. A careful examination of the problem, however, develops the fact that because of the compressibility of gases and their necessity of expanding into the operating cylinders or other equivalent chambers where they can exert their forces, a material lag is introduced in pneumatic de vices. No such time for expansion is necessary when hydraulic actuation is usecLChanges in pressure are propagated between control valves and any mechanism which such valve operate with the speed of sound in the medium which may well be several times that of the sound in air. The passages through which the pressure acts may be made short and the friction losses correspondingly low so that much quicker operation may be achieved through hydraulic means than through pneumatic.

Pneumatic breakers are, moreover, subject to a number of disadvantages which do not at first appear. Gases are hard to retain, leaks readily occur and are hard to detect, and therefore closed pneumatic systems are not used. With an open pneumatic system, losses due to leakage or to the release of gas when the pressure rises above the desired limit due to expansion from changing temperature, are supplied from the surrounding air by a pump which is electrically driven under the control of an electrically-operated switch. There is also, in such cases, inevitably a loss of compressed air every time that the breaker is actuated, which loss must also be made up by the pump. The power required for make-up of this character is not particularly important, but what is important is the fact that the air to be compressed always contains some water vapor and almost always is contaminated by carbon dioxide, sulphur dioxide, and frequently other even more corrosive materials. The water vapor condenses in the receiver of the system and must be blown out from time to time. It is always carried, to some extent, into the connecting lines and valves. Corrosion always takes place within the air receiver and frequently within the control valves. Particles of rust or other corrosion products may be carried through the air passages of the system into the valves causing them to stick, and because of the chances of actual perforation of the receivers or the pipes connecting the latter with the operating mechanism the whole device must be subject to constant inspection. Therefore, although the pneumatic operating system may be simpler and lighter in weight than the mechan-- ical system and cheaper than a hydraulic system in first cost, it is, in the long run, more expensive and less reliable as well as slower in operation than the hydraulic system which is the subject of this application.

The above considerations may be more fully appreciated, and the invention and its various objects and advantages more fully understood, from the following detailed description of a preferred embodiment thereof, taken in connection with the accompanying drawings wherein:

Fig. 1 is a diagrammatic representation of a 5 circuit breaker embodying a preferred form of the invention;

Fig. 2 is a sectional view of the closing, latchihg and release mechanism of such a breaker, the accumulator and main valve mechanism being shown, for the purposes of illustration, as being rotated 120 degrees from their actual position in order that the entire operating mechanism may be illustrated in a single diagram;

Fig. 3 is a schematic circuit diagram of the electrical portion of the trip mechanism;

Fig. 4 is a drawing on a larger scale than Fig. 2 of the pilot and dump valve mechanism; and

Fig. 5 is a detailed View showing the latched mechanism in its released position.

Figure 1 is a schematic diagram of one form of circuit breaker which may be operated by the subject mechanism of this invention. The type of breaker shown is merely illustrative since the invention maybe modified to actuate almost any of the known types of breaker, of which there are many. In the figure the block A represents the mechanism more fully illustrated in Figure 2, the projecting plunger I representing the operating member which is driven downward hydraulically in order to close the breaker contact. The plunger l connects through a link 3 to a bell crank 5, the bell crank in turn operating a pull rod 1 which moves towards the left of the diagramand compresses an opening spring 9 when the plunger 1 is retracted or pulled downward. Bell crank 5 and pull rod 1 are mounted upon a suitable supporting framework I l.

Pivoted to the frame I l and the pull rod 1 is a parallel motion linkage l3 of known type to which is connected a vertical bar IS. A transverse drop bar l1, carrying the moveable contacts of the breaker, is secured to the lower end of the bar IS. The latter, as well as the pull rod 1, is preferably made of insulating material such as impregnated wood, porcelain, Bakelite, or other material having the requisite dielectric strength. When in the closed position shown in the diagram the moving contacts carried by the drop bar I! make contact with fixed contacts IS in the transmission line 20 which is to be controlled by the breaker. Connection between the fixed and moveable contacts is made within interrupter structures 2| for extinguishing the arc. contacts, moving contacts, and interrupter are all preferably immersed in oil or other arc-quenching dielectric liquid within a tank 22.

Means are provided for tripping the breaker, either manually or in response to an overload, such means comprising, for example, a current transformer 23 in the line 20 which actuates a marginal relay 24, closing the relay contacts and completing a circuit, including a storage battery 25, to the trip mechanism of the breaker which will be described later. Alternatively the trip circuit may be actuated by closing a manuallyoperated switch or key 21. i

As has been indicated, all of the parts referred to, with the exception of the mechanism A itself, are well-known in the art and might be taken for granted, but are shown here for the sake of completeness. It is to be noted that the one mechanism may operate a number of drop bar elements, for example, one set in each leg of a three-phase line. Under other circumstances separate mechanisms may be used in each phase so that if a fault occurs in one line only that particular line may be deenergized and the load carried, at least in part, by the other two phases.

All such expedients are well known and need not be further considered here.

The block A of Fig. 1 represents a tank-like housing within which the actual operating mech anism i-s encased. Within this housing is a high pressure motor-driven pump P, controlled by e, pressure-actuated switch, which develops the hydraulic pressures for operating the device. The pump P withdraws hydraulic fluid from it tank or sump Z8 and delivers it to the accumulator through a conduit 29. For protectiuh against excess pressures a bypass 30, controlled by a relief valve (not shown) returns excess fluid to the sump.

The hydraulic operating mechanism itself is preferably mounted on and (in part) encased within a base block 3! which may conveniently be a single casting. The bottom of this casting is bored or otherwise recessed to form a h'ydr'aii lic cylinder generally indicated by the reference character 33, the cylinder being provided with a steel liner 35 of high tensile strength ma terial to withstand the hydraulic pressures used. Within the cylinder 2. piston 31 is mounted on a piston rod 39 to which the breaker mechanism is connected through a linkage which will be described in detail later. Suitable means are used for sealing the piston against the hydraulic pressure which it is required to bear, a pre= ferred means being a seal comprising a ring M, of neoprene or other oil resisting' synthetic rubber, within a groove 43 formed in the periphery of the piston. A conduit 45 opens axially from the top of the cylinder 33; if the baseblock 3| is cast the conduit may be cored in the casting. Piston rod 39 runs through the axial opening into the cylinder, this port being of ample size to admit the oil or other hydraulic fluid around the piston rod. Above where the conduit 45 opens into the cylinder the block is accurately machined to size to form a bearing for the rod and a ring seal 4'! is provided to prevent leaking of the hydraulic fluid around the piston rod.

The bas'eblock Si is provided with a bore or other accurately-sized opening, whose axis is parallel to that of the cylinder 33, for receiving a main valve housing 49, the bore intersecting the conduit 45 and also an exhaust conduit 5| which opens into the sump 52 in which almost the entire baseblock 3! is submerged.

The main valve housing 49 is accurately fitted within its bore in block 3! and for additional security against leakage is provided with ring seals. At its upper end it carries, upon a flanged bushing 53, an accumulator reservoir 55, seals again being provided to prevent loss of pressure around the bushing and past the flange. The accumulator opens, through channel 56 through the bushing into the interior of the generally cylindrical main valve housing 49. A centrally ported septum e1 partially closes the housing 49 above the conduit a conical poppet valve seat being formed in the upper side of the port through the septum. v H

Above the septum the housing is provided'with ports 59, one of these ports leading through a high pressure pipe or other connection 29 to the outlet of the high-pressure pump P; the

other port leads through a similar connection (which may be bored or cored in the block 3!) to the pilot and dump-valve mechanism which will later be described, this second connection being indicated schematically as a pipe 6i. These connections are open at all times;

A poppet-valve 63 is seated in septum 51. This valve has a cylindrical section 65 rising above its conical valve face and terminating in a flange which slides in and is guided by the valve housing 49. A spring 59 bears against the upper portion of this flange, tending to keep the valve seated. The cylindrical portion of the valve is provided with ports ll to permit the how of liquid past the flange and through the septum port into the lower body of the housing when the valve is open as well as to permit the flow of oil into and out of the accumulator through the ports 59. The stem of the poppet-valve 63 is of relatively large size and is provided with a longitudinal channel 13 therethrough, and has an enlarged foot T5.

The foot l5 fits within a recess formed in the top of a floating valve piston Ti and is provided with a ring seal which prevents leakage through the stem and recess.

Below the septum 57 the housing as is supplied with ports 13 connecting to the conduit 45. Below these ports, again, the opening within the housing is enlarged slightly to permit the formation of a conical valve-face ill between the portion of the housing connecting to the conduit 45 and its lower-most portion which forms a cylinder within which the valve-piston ll slides. Immediately below the valve-face Bi ports 83 open into the discharge conduit 5| and the sump.

The lower end of the housin. ill is closed by a sealed plug 85 upon which the valve-piston rests when in its lower-most position. Piston TI is generally cylindrical, and is sized to an easily sliding fit within the cylinder formed by the lower portion of the valve housing. At its upper end, however, there is a portion of reduced diameter to form a shoulder 31 whicl. i rrns a valve-face sea-ting against the valve'face 8i when the piston in its raised position. Above the shoulder S'l the piston sized to a sliding fit within the housing bore, so that as the piston rises it closes oi? the passage to the conduit sufficiently well to prevent the escape of any material amount of hydraulic fluid even under the pressures applied from above until the conical faces BI and G7 engage and complete a tight seal.

The lower end of the piston has formed within it a recess or counterbore es. The outer diameter of the piston is also somewhat reduced at the lower end to form a channel surrounding it, and a small notch st in the bottom of the piston connects this channel with the recess 89 to admit an initial flow of fluid thereto when pressure applied. Channel 8% through port 92 in the housing 49 through a lead schematically indicated as a pipe 93 to pilot valve mechanism through which pressure for operating the mechanism supplied.

It will be seen that when the valve piston I! is in the position shown, poppet-valve 63 is held closed both by the hydraulic pressure from the accumulator and the spring 69. The effective area through which this pressure is applied is the diameter of the valve seat in the septum, minus the diameter of the enlarged foot on the valve stem, since other portions of the valve are subjected to an equal opposing pressure. As pressure is applied through the connection 93 below the valve piston, however, it acts on the full diameter of the piston and therefore raises it very rapidly until the piston strikes the foot 15 of the poppet-valve. The parts are so proportioned that this occurs at the same instant that the reduced upper end of the pisconnects ton enters the smaller bore above it and closes off the connection between the conduit 45 and the discharge conduit 5| into the sump. At this instant the piston starts to raise the poppetvalve also, opening it fully when the valve faces Bl and ill engage and admitting the full hydraulic pressure from the accumulator to the conduit G5 and to the cylinder 33, thereby forcing the piston 3! down to the position shown in the drawing, and closing the breaker. At no time is the area upon which the operating pressure acts to force the main valve piston l! downward greater than that referable to the reduced diam eter of the upper portion of the piston, while the area below piston fl is always equal to the full piston diameter and is therefore enough greater to cause positive operation of the valve.

When the pressure below the valve-piston I1 is relieved, however, the pressure from above it immediately forces it downward with the result that the poppet-valve E53 first closes, and the passage from the conduit 45 into the dis charge conduit 5i next opens relieving oil pressure upon the operating piston 37 so that the circuit breaker may open under the full force of the spring 9 and Without being subjected to any material retarding force from the hydraulic system during the major portion of its stroke. As the stroke approaches its end, however, an enlarged portion 39 of the piston rod enters the port into channel 45, restricting the flow of liquid and bringing the mechanism to rest without excessive shock.

It is to be noted that hydraulic pressure within the cylinder 33 is not relied upon to hold the circuit breaker in the operative position; instead a latch mechanism is provided together with means for relieving the pressure beneath the valve-piston '1'! as soon as the closing operation is complete. The means for accomplishing this will next be described, first the hydraulic pilot and dump valves, finally the latching and tripping mechanism.

Both of the latter two valves are mounted in bores formed within a block 95 which may either be integral with the block 3| or may be separate and secured thereto. The pilot valve bore consists of a lower portion 9! of minimum diameter which connects, through a coupling 99 and a suitable hydraulic conduit $3 already mentioned, with the port 92 in the main valve cylinder. Above the portion 91' is a cylindrical bore liil of somewhat larger diameter which connects with the bore 9? through a conical valve seat 163. The lower portion of the bore it! communicates directly through the schematically indicated connection ti and the port 59 with the high pressure source.

A loosely fitting piston H35 slides within the bore llll. No seals are provided for this piston, as it is intended to have the high pressure hydraulic fluid leak past it. The piston H15 has at its lower end a reduced portion terminating in a valve face engaging the valve seat 103 and forming, above it, a shoulder immediately above the port into the cylinder from the connection 6!. Hydraulic pressure from the ac-- cumulator therefore operates against this shoulder and tends to raise the piston and open the passage from the connection 6! into the passage 93 and the main valve piston. Normally, however, this pressure is more than counterbalanced by pressure from the hydraulic fluid flowing past the piston and operating against 9 the full area thereof, thus tending to close the valve.

The upper end of the cylinder IUI is closed by a valve block III! which is axially apertured for a ring-sealed needle valve I09. The needle valve is normally held closed by a spring HI of sufficient strength to hold the needle valve closed against pressure on its point from the cylinder IIII. The needle valve may, however, be externally operated either by manipulation of a handle H3 or by remote control through the lever H5 and a solenoid HT (which is schematically indicated) or by other suitable means.

A dump valve bore is formed in the block 85 parallel to the pilot valve bore and two connections exist between the two bores. The first of these connections passes through the valve block Hi1 and connects the bores above the needle valve. The second of the two connections is below the valve I [33.

Like the pilot valve bore, the dump valve bore has a minimum diameter portion H3 at its lower end, this portion opening above into a valvecylinder portion of somewhat larger diameter and below into the sump. A tubular piston I23 slides within the cylinder. The lower end of the piston is reduced in diameter to form a sliding fi-t within the bore I I9, forming a shoulder I 21 above the reduced portion, and the passage I28 from the outlet of the pilot valve enters the dump valve bore below the shoulder, so that when the pilot valve is open pressure is applied beneath the shoulder tending to raise the piston and open the dump valve. The upper end of the piston is supplied with a flange I29 which limits its downward motion and, when the valve is closed, lies within an annular channel communicating through the connection I3I with the outlet side of the needle valve I69. Above the flange I29 the piston is provided with extension lugs I33 which bear against a flange I35 on a push-rod I31.

The push rod I3'I slides in a ring-sealed bearing in a cap I39 which fits into the upper end of the dump valve bore. A compression spring I4I located within a recess in this cap bears against the flange I35 and thus tends to hold the valve piston I23 in its lower position and close the passage between the pilot valve bore and the sump. Moreover, during the interval when the breaker is being closed, the push rod is normally mechanically locked in this position unless the breaker trips. As will be seen from the drawing, when the dump valve is closed a passage exists from the channel I3I between the lugs I33 and down through the hollow center of the piston into the sump. When the piston rises, however, the flange I23 enters a closely-fitting portion of the bore above the channel and closes off this passage.

Turning now to the more purely mechanical parts of the apparatus including the latch and trip mechanism, the piston rod 39 connects to the breaker plunger I through a strut I50. A compression link I5! is hinged at one end to the strut; its other end is pivoted to one arm I53 of a bell crank which is so mounted that when the switch is in a closed position, as shown, the arm makes approximately a 45-degree angle with the axis of the piston rod 39. As the breaker opens and the piston rises the axis X, about which the link I5I turns, moves up into the position indicated in the drawing by the point X. The link I5I swings in a counterclockwise direction during this motion, moving the bell crank in a, counterclocks wise direction up to the point at which the link? is horizontal, after which it reverses the bell crankmot'ion, moving it very slightly clockwise and bringing it to rest at an angle of between ten and fifteen degrees from the vertical. At this point the other arm I53 of the bell crank is approxi-;

mately horizontal.

It is the aim in all circuit-breaker design toseparate the breaker contacts and open the cir-' cuit as rapidly as is possible. In high-power breakers the necessity of opening a wide gap to insure rupture of the arc, of large insulating members to withstand the high voltages employed, and of relatively heavy conductors to carry the currents involved require that rather heavy masses be moved. To move such masses rapidly requires very large accelerations and a spring of great power. to release such breakers must, however, be sensitive; i. e., small tripping forces must be used to control heavy springs.

a linkage system in which the mechanical advantages change rapidly as soon as any motion takes place. Such a system is a toggle formed of compression links; theoretically, the mechanical advantage of such a system varies between infinity when the toggle links are perfectly straight to zero when the links are fully buckled. In practice, however, no such wide range is possible, since at the position of infinite advantage the linkage is unstable and slight mechanical inaccuracies may prevent its operating in the manner intended. Gains up to a maximum of from (say) 8 to l5-fold may be obtained with a toggle linkage without incurring instability, or requiring undue accuracy of machining or adjustment.

The theory of the rapid change of mechanical advantage in a toggle link system is that the lever arm through which the restrained force acts to buckle the links when the toggle is released increases rapidly. The use of this principle in latching mechanism is old per se. In the present mechanism, however, this effect is multiplied by two expedients; first. a plurality of toggle linkages is used in cascade, and, second, compound toggle linkages are used where in the force which is used to buckle the originally nearly straight toggle links is itself applied through a pair of links which are buckled at the start of the action but which straighten as the latching links buckle. Through this latter expedient the mechanical advantage is very rapidly transferred from the latch mechanism to the breaker and breaker spring with the result that the inertial load of the latch is dropped still more rapidly and the motion of the latch mechanism itself becomes very small in spite of its initial mechanical advantage. The transfer of inertia, as regards the final links of the series may, in fact, be made so rapid, that it is only at the initial instant of the trip that it contributes to the inertia,

Trip mechanisms used' In order that this may be done, the actual latch mechanism must be; given a very great mechanical advantage with respect to the spring. The inevitable result of this its velocity actually decreasing while the breaker is still accelerating.

In the present device three linkages are employed in cascade, the principle of each of the three linkages being the same. Each linkage comprises three elements, a driving link, a connecting link, and a driven link, pivotally connected end-to-end with the outer ends of the linkage turning on fixed pivots, plus a latch mechanism to prevent the toggle from buckling until it is released. In the first of the linkages used the driving link is the arm I53 of the bell crank already described, the connecting link is link I54, and the driven link is link I55, the outer end of which turns upon a shaft I56 fixed to the frame of the device. As may be seen from the drawing the driving link I53 acts at an initial angle of somewhere in the neighborhood of to compress the nearly straight linkage comprising the connecting link I 54 and the driven link I55. Owing to the very slight angle between the connecting and driven links the lever arm against which the connecting link I54 thrusts is small; the result is a mechanical advantage of approximately 12 /2 to 1 in favor of the latch mechanism which prevents the driven link from rotating.

The latch mechanism in this case is another linkage of the same type, with the driven link of the first linkage forming the drivin link of the second and thrusting, at a fairly large angle, against the nearly straight connecting link I58 and driven link I59. The latter forms one arm of a bell crank mounted on a fixed shaft I60 on the frame of the equipment.

The second arm, I 60', of the last mentioned bell crank forms the driving link of a third and similar linkage, which constitutes a latch for the second linkage. This last linkage comprises a connecting link I6I and a driven link I62 which turns on a fixed shaft IE3. The final driven link extends beyond its pivot on the shaft and is provided with a face I64 which is engaged by a hooked end I65 on a catch or latch member I61 and comprises the final latching element.

It will be seen that in each of the linkages mentioned the driving link has a relatively large lever arm with respect to a very small lever arm on the driven link. Each of the drivin links is disposed at an angle of approximately 45 with the other two links in their nearly-straightened position, although this angle is not critical. It might appear that a greater advantage could be obtained by making the angle between the driving link and the connecting link approach 90, This is, in fact, the case, but in the 90 position the change in lever arm, for a small rotation of the link, is small, while beyond the 45 position it becomes increasingly rapid. The purpose of the entire linkage is to transfer the advantage from a latching mechanism to the driving mechanism as rapidly as possible and this is achieved better by decreasin the lever arm of the driving link simultaneously with the increase of lever arm of the driven link. Moreover, it will be noted that while the driving and driven links are never permitted to straighten fully, the driving and connecting links in each case may pass through the dead center position and it is, in fact, desirable that they do so since this results in minimum total motion of the succeeding linkage. Since the drive is always supplied from the breaker end of the linkage and never from the latch end, the passage of the driving linkage through the dead center position does not result in any uncertainty or instability of action.

In the linkage which has been shown for illustration the mechanical advantage of the second linkage, when locked, is 8.15 to 1, while that of the third is 9.25 to 1. The overall mechanical advantage of the catch is therefore the product of that of the three linkages taken separately, or slightly over 942 to l. The multiplication of the inertia of the final link is, however, the square of this, or nearly 890,000 so that an efiective mass of one ounce applied at the lever arm of the final link becomes the equivalent of 55,000 pounds added to the mass of the breaker arms themselves. Mechanical advantage due to the linkage is so rapid, however, that by the time the latch face has moved only M of an inch when it is released from the hook I65, the mechanical advantage has dropped by a factor of nearly 9 and its inertial effect by a factor of 80. Furthermore, owing to this shift in mechanical advantage the breaker mechanism can accelerate without any acceleration of the final link and with only moderate accelerations of the intervening links. The result is that in practice circuit breakers may be made to open in 1; of a second or of a cycle where this release mechanism is used, in comparison to a half-cycle or more where conventional types of trip are employed.

The release latch 561 is centrally suspended from a pivot ill on an arm I13 which, in turn, is pivoted on a shaft I15 on the frame of the apparatus. The end I 11 of the latch member which is opposite to the hook IE5 is flattened to form a sear the use of which will be explained later. A spring I19 attached to a depending arm I on the latch and to a fixed point on the frame tends to rotate the latch around its pivot ill in a counterclockwise direction, this motion being limited by a fixed pin I8I on the frame. It will be seen that the effect of the spring I19 is to tend to hold the hook I65 in engagement with the latch face I64 of the link I52. A second fixed pin I83 limits the clockwise rotation of the latch.

The tripping mechanism for the breaker comprises a moving-coil type movement which is schematically illustrated as including a permanent magnet I85 having its moving coil I81 connected by a tension link I89 to the pin I1 I When the moving coil I81 is excited it raises the lever I13, causing the latch I61 to rotate against the pin IBI as a fulcrum and disengage the hook I65 from the face I64, thus releasing the latch. When this has occurred and the excitation is removed from the coil I81 the lever arm I13 carrying the pin I1I drops. Under these circumstances, however, the end of the hook I65 rests upon a circumferential face formed at the end of the link IBI, so that the latch I61 now pivots around this contact and drops the sear end I11 into position to engage the face I93 of a pivoted link I55 and prevent counterclockwise rotation thereof. This serves to lock the dump valve as will be described shortly.

An additional safety trip is provided in addition to the moving-coil type which has just been described. A second lever I91 is pivoted from the pin I15 and extends under the pin I'II, so that when the lever I91 is raised it carries with it the pin, the lever I13, and the latch I61 irrespective of the action of the moving-coil trip. The end of the lever I91 is connected through a link I99 with the plunger 28% of a solenoid, schematically indicated at the reference character 2H3.

solenoids of this character are generally used for the trips of devices of the kind described.

have, however, a, considerable inductance and hence their operation is not very rapid. The inductance of the moving coil [.81 can, however,, be practically entirely neutralized and therefore their action maybe made very fast, Normally and in every case which has been encountered practice) the moving coil magnet will tripthe breaker a measurable time before the solenoid cancome into: action, but case. it should be. incapacitated for any reason, the solenoid will back it up and trip the breaker.

Returning now to, the link 195-, this link is, loosely pivoted upon a fixed pin 2,05 mounted on the frame of the device. It is pivotally connected with a long link 201, the lower end of; which pivots on a fitting 2!. I fixed to the end of the dump valve push rod ['31. The upper end of the link 2-01 is constrained to move in an arcuate path by a uide crank 2J3 mounted rotatively on a fixed shaft 2| 5 carried by the frame. It will be seen that when the dump valve is seated the linkage consisting of the elements Hi5, 2.0.1., and the push rod [31 is nearly but not quite straight, all of the various t ggles comprised in this linkage therefore being broken but barely broken. When the cireuit breaker is open the dump valve hook I65 rests on link I62 and the linkage is locked in its position by the engagement of the face [9 3 with the sear end I." of the latch until and unless one of the trip coils operates to break this contact, when a suincient upward force applied on the push rod will flex the linkage and permit the rod to. rise.

We can, now trace the operation of the device. The breaker, in the first instance, is in its open position, with the piston 31 at the top of the cylinder 33 The. main valve mechanism within the h 4 is n the p i ion shown, wi h he paa sages from the cylinder into the sump completely open so that, no pressure can exist: within the yl nd r h r an. the. normal hydrostati head of t flu d n the sump. Hi h pre sure in the ac umul to is, ow ve at u l alu o a th usand or more pounds per square inch, being main-. tained in this condition by the pump P under the control of the pressure-actuated switch. This, pressure is available in the pilot valve and is off. fective both above and below the floatin piston I05 tending to hold it against the valve face $03.

To, operate the breaker the needle valve .13 is opened, either by hand or by the remote control equipment already described. This; relieves the pressure above the piston, offering; free egress of the hydraulic fluid through the channel I3! and the tubular dump, valve piston I23 into the sump. The pressure below the shoulder on the piston H35 immediately raises it, opening a direct passage through the connection 9.3 to the main. valve. When this occurs, the piston Hi5, being forced u t ght y a ainst the block I0 it. lar ely uts off the flow of hydraulic fluid through this pasage- As soon as the pilot valve opens the full; pressure from the source is admitted under the main, valve piston 17, lifting it until its redueed upper end enters the bore above it and closes off the passage from the conduit 45 into the sump. At e, nstant that this oc rs the p ton strik s th f t 5 of the p ppet-va 63. d start to raise. it, th s action c tinuin unti he va ve fa e 81. on the piston engages the seat ill and completes the; sealing of the exhaust port. As soon as the. poppet-valve 63 starts to lift the oil pressure from the source is effective through the conduitv 45 in.- to. the cylinder 33 and forces. the piston down until reac e substantially e botto of he eviinder This straightens out the toggles latch mechanism until the hook [6.5, of the latch l6! drops, simultaneously locking the circuit breaker closed and releasing the end [1-1 of the latch from the push rod mechanism which holds the dump valve closed. Since at the instant of; opening the latch link I62 loses acceleration rapidly, at the instant of closing itgains acceleration with equal rapidity, and a spring stop 2!! is therefore provided to absorb the shock of its; final closing and prevent snapping past dead center.

It may be noted here that because of the large magnitude of the forces acting upon the piston the closing action is quite violent and might be destructive were not some means provided of cushioning the final movement. Such a cushion effect can be provided by a projecting tapered end 2:20 on the piston 31 which projects through a ring 22 I, the ring being held in place by a cylinder head 223 secured to the lower end of the cylinder, The internal periphery of the ring 22! is dimensioned so that when the breaker is nearly closed there is a very small clearance between the ring and the larger end of the taper. When the breaker is open, however, and the small end of the taper lies within the ring there is a wide oil passage pro vided. As the breaker closes there is therefore a continually increasing dash pot action as the channel between the taper and the ring is con.-, striated, and the final closing of the breaker is, fairly gentle. When the breaker trips, however, the ring I2l rises with the piston, permitting oil to flow around the ring and through a plurality of ports 225 and 221 into the cylinder.

As soon as the latch l6! engages; with link I82 the sear end I11 disengagesv from the link, 195., thus releasing the lock on the dump valve. Pressure through the channel I28 then becomes efctive to raise the. dump valve piston, opening a free passage from, below the main valve through the connections 93, 91-, and H9 into the sump. The pressure below the main valve piston beingreleased. the direct. pressure from the source, acting through the poppet-valve on the smaller diameter above the piston 11, becomes effective to force it down, the flow of liquid from beneath it. continuing to hold the dump valve open. As soon as the poppet-valve has closed the passage between conduits 45 and 5| opens, relieving the pressure within the main cylinder 33, but the motion, of the piston 11 continues until it has bottomed due to the continued flow of liquid through the hollow stem of the poppet-valve into the recess, in the piston head.

In the meantime, however, the pilot valve has closed, its piston, I05 dropping under its own weight, the pressure drop through the valve below it and the increasing pressure of liquid above it. This will occur whether or not the needle valve I'll has. been closed in the meantime, since as soon. as. the dump. valve rises its flange 129 will have risen into the cylinder above it to cut off the flow through the tubular dump valve piston.

In case an attempt is made to close the breaker upon a. fault the trip coil will raise the lever I13 and the latch l6! will pivot around its hooked end to release the contact between the face I93 and the end ll! of the latch, permitting the dump valve to lift. The effect is then the same as; that already described at the end of the normal closing operation; the pressure on the main valve piston is immediately relieved into the sump; and. as the main latch is not engaged the main breaker spring opens the breaker in the same manner as though no attempt was being made to close it. As soon as the dump valve opens the pilot valve closes, as has already been described. Very little loss of fluid into the sump therefore occurs, so that a one gallon accumulator will effect eight or ten closures even when the accumulator is not replenished by the pump.

If a failure in the hydraulic system should ocour the system will in all cases fail safe, i. e., the breaker can always trip free, and the worst failure which can occur is an inability to close it and not the maintenance of a destructive fault.

An important, although apparently minor feature of the device is the electrical trip mechanism. The essential features of the circuit used are shown in Fig. 3. In this figure the battery and pushbutton or key 21 are those shown in Fig. 1, it being apparent that a many other parallel paths as may be desired for closing the circuit may be bridged around this key. In series with the battery and key is a current-limiting resistor 233 connecting to the solenoid coil 2113 and the moving coil trip in parallel, the latter comprising the moving coil I87 already identified and an equal but oppositely-wound fixed coil I81, mounted in the air gap closely surrounding or surrounded by the moving coil. The fixed coil substantially neutralizes the inductance of the moving coil but does not affect its reaction to the flux in the air gap, which is preferably provided by a permanent magnet. This method of inductance neutralization has been used in loudspeaker practice and hence in the diagram the coils only are schematically represented.

Closing the circuit by means of the key 2'1 or otherwise impresses a surge of voltage across the solenoid and the moving-coil trip in parallel. The resistance of the coil I81 and I8? may be equal to or even higher than that of the currentlimiting resistance 233. The resistance of the solenoid 203 should be very much lower than that of the limiting resistance. The inductance of the solenoid is, however, material; it therefore requires time for current through it to build up and therefore in the first instant when the circuit is closed the moving coil carries practically the entire current and exerts a powerful pull which trips the breaker. This action ordinarily occurs so rapidly that under fault conditions the breaker opens and relay 24 releases before the solenoid can trip. If the circuit is closed by the switch 21, however, or if, for any reason, the moving coil device is incapacitated, current builds up in the solenoid and causes it also to trip. Building up of the current in the solenoid increases the drop through resistor 233. This reduces the current through the coils I 81I8l' very rapidly, and because of this quick drop in coil current it is possible to design the circuit so that the initial surge through the moving coils is several times the normal overload value. This makes possible a very high initial acceleration of the moving coil trip and the extremely quick action of the device without danger of damage to the coils. The rapid taking-over of the load by the solenoid permits initial trip currents through the coils which, if continued, would burn them out in a second or less.

The breaker as thus described has been proved to be capable of operating in from one-half to two-thirds of the time required by other breakers capable of rupturing comparable power. Normally circuit breakers for high power lines can be expected to operate in a minimum of three cycles, provided the actual interrupter device itself is capable of functioning to break the are on the first or second passage of the current wave through zero. With the mechanism here described interruption can be accomplished in from one and one-half to two cycles. This improvement in operation is due to a number of factors working together. The first of these is the minimum inductance of the moving-coil trip, which sets the whole release mechanism in operation in from one-half to one cycle less than is possible with the ordinary type of solenoid trip. Use of the moving-coil release is made possible by the sensitiveness of the catch mechanisms, which in turn stems from the combination of high initial mechanical advantage with small overall acceleration and motion provided by the toggle linkages which have been described. Once the trip has been actuated the speed of the break is controlled by the force of the main opening spring, which may be made great because of the very large forces available to operate the closure. When the tripping occurs the passages from the cylinders are so large that the frictional drag of the oil through them is negligible until it is purposely increased to provide a dashpot action at the end of the stroke, the actual inertia of the oil displaced is very small indeed compared to that of the remainder of the equipment. When the trip occurs during normal operation of the circuit the main valve is already open into the sump and no delay is occasioned by it. If the trip occurs during the reclosing of the breaker some slight delay may ensue but it is very small owing to the fact that the latch mechanism has not yet reached the position where it contributes greatly to the inertia of the system, and to the very large pressure available to move the valve piston. Normal pressure in the accumulator may be from 1000 to 2500 pounds per square inch. In the breaker illustrated this pressure operates, at the instant of application, against a cylindrical face of 1 inches diameter, making a force of over 4000 pounds effective to move a main valve piston, weighing a pound or two at most a distance of approximately half an inch before the poppet-valve closes, and the conduit from the cylinder 33 opens into the sump. As it works out, the additional time required by the breaker to trip free from a closing operation, as compared with the time of opening from a latched closed condition is, at most, less than one tenth of a cycle. In spite of this fact the presence of the hydraulic fluid between the faces of the various parts as they reach the ends of their f strokes cushions the final blow. No appreciable peening takes place and the parts do not wear or deform perceptibly under operation.

It should be apparent that while the invention has been described as applied to one representative type of circuit breaker it is capable, with minor mechanical modifications, of actuating substantially all types. Moreover, it is subject to many modifications as to detail; e. g., diaphragms may be used to provide hydraulic chambers with movable walls instead of the equivalent cylinder and piston.

Furthermore, while the various instrumentalities mentioned as contributing to the speed of operation of the equipment are most efiective when combined, they can be used separately in otherwise conventional circuit breakers. The claims in this application are therefore confined to the hydraulic actuating mechanism, claims to the latch and trip features being presented in a companion application filed concurrently. I

17 therefore do not intend to imply limitations not expressedv in the following claims.

I. claim:

1 Hydraulic circuit-breaker operating. mechanism. comprising a source of hydraulic pressure, a circuit-breaker operating hydraulic chamber having a moveable wall. a conduit leading from said source to said chamber and an additional conduit from said chamber leading to a sump; a hydraulically operated main valve connecting said conduits and operative to connect said chamber to said pressure source or said sump alternatively depending on its position,v a hydraulically operated pilot valve connected to said pressure source, said pilot valve including an. element having pressure areas on both sides thereof said areas being unequal and subject to pressure from said source, the pressure on one side thereof tending to open said pilot valve and that on the other to close it, a connection from said pilot valve to said main valve for admitting pressure thereto to operate said main valve and. to connect said source to said chamber, connections from each side of said element for relieving pressure" thereon to permit pressure on the other side thereof to operate said pilot valve, a normally closed externally operated valve in one of said connections operation of which opens said pilot valve to operate said main valve, a dump valve in the other of said connections, means operative by pressure in said last mentioned connection tending to open said dump valve, mechanical means for holding said dump valve closed against said pressure operative means, and electrically operative means for disabling said mechanical means.

2. Hydraulic circuit-breaker mechanism in accordance with claim 1 including. means incorporated. in said dump valve for closing said first mentioned connection to said pilot valve element irrespective of the operation of said ex.- ternall'y operated valve.

3. Hydraulic circuit-breaker mechanism in accordance with claim 1 wherein said pilot valve element comprises a floating piston loosely onclosed within a cylinder, said piston having one end thereof formed to engage a valve seat, said piston having a shoulder theron to form a recess within said cylinder adjacent said end, the connection from said pilot valve to said pressure source opening into said recess, so that pressure against said shoulder will raise said piston from said valve seat when pressure on the other end of said piston is relieved and pressure on said other end will be reestablished by leakage past said loose-fitting piston when the connection from said last mentioned end of said piston is closed.

4. Hydraulic circuit-breaker mechanism in accordance with claim 1 wherein said dump valve comprises a hollow piston having a valve face formed on one end thereof engaging a valve seat opening into said sump, said hollow piston being slideably mounted within a cylinder and having a reduced portion on the end thereof adjacent said valve face to form a recess within said cylinder which opens into said connection from said pilot valve to said main valve to permit pressure therein to act against the unreduced portion of said piston and tend to open said valve; the opening through said hollow piston connecting from said second mentioned connection from said pilot valve element beyond said externally operated valve to said sump, said hollow piston having a valve member formed on the other end thereof to close the passage therethrough when the valve face on the first mentioned end of said hollow piston is separated from its seat, and said mechanical means acting to hold said valve face against said seat until released by said electrically operative means.

5. In combination with circuit-breaker mechanism comprising resilient means for opening said breaker, a latch for holding said breaker closed, and electrical means for tripping said latch, a source of hydraulic pressure, hydraulically operated means connected to said source for closing said breaker against the action of said resilient means, a hydraulically operated main valve interposed between said source and said closing means, an externally operable pilot valve connecting said source and said main valve to operate the same and close said breaker when said pilot valve is opened, and a dump valve connected when open to release pressure between said pilot valve and said main valve, said dump valve being normally retained in closed condition by said latch and opening by tripping thereof, thereby permitting said breaker to open irrespective of the condition of said pilot valve.

6. A circuit-breaker comprising a source of hydraulic pressure including a reservoir for holding a liquid and a collapsible gas bag of material substantially impervious to gas and said liquid within said reservoir, a hydraulic pump connected to maintain pressure within said reservoir by forcing liquid therein. to keep said gas under compression, circuit-breaker means including at least one pair of contacts relatively moveable to make or break a circuit, resilient means tending to force said contacts apart, and means for closing said contacts against said resilient means comprising a hydraulic chamber having a moveable wall mechanically connected to move at least one of said contacts, a pressure conduit connecting to said pressure source, an exhaust conduit and a valve connecting said chamber alternatively to said conduits, means for actuating said valve to connect said chamber to said pressure conduit, and independently operable electrical means for disabling said actuating means.

7. In combination with a circuit-breaker having relatively moveable contacts and resilient means tending to separate said contacts, operating means for closing said contacts against said resilient means comprising a reservoir for storing a liquid under pressure, a sump for receiving liquid discharged from said reservoir and a pump for returning liquid from said reservoir to said sump; a hydraulic chamber having a moveable wall, mechanical connections from said wall operative to move said contacts, a conduit from said reservoir to said chamber, a conduit into said sump, a hydraulically operated main valve interconnecting said conduits and operative to direct liquid alternatively from said reservoir to said chamber or from said chamber to said sump, a passage from said reservoir connected to operate said main valve to connect said reservoir and said chamber and close said breaker contacts, a pilot valve in said passage, a by-pass connecting said passage and said sump, a dumpvalve in said by-pass, means for holding said valve closed against the pressure in said passage and electrical means for releasing said holding means.

8. Mechanism in accordance with claim 7 including means interconnected with said dump valve for closing said pilot valve when said dump valve is open.

9. Mechanism in accordance with claim '7 including latching means for retaining said contacts closed, means operating coordinately with the engagement of said latching means for releasing said dump-valve holding means, and means interconnected with said electrical releasing means for releasing said latching means.

10. In combination with a circuit-breaker having relatively moveable contacts and resilient means tending to separate said contacts, operating means for closing said contacts against said resilient means comprising a reservoir for storing a liquid under pressure, a sump for receiving liquid discharged from said reservoir and a pump for returning liquid from said reservoir to said sump; means for applying pressure from said reservoir to close said contacts, means for controlling the application of pressure to said last mentioned means comprising a hydraulically operated main valve connected open and admit pressure thereto when pressure is applied to said main valve and close when such pressure is removed, a pilot valve connected to apply or shut off pressure from said source to operate said main valve, a by-pass connected between said pilot and main valves, a dump-valve in said by-pass, means for holding said dump-valve closed and electrical means for releasing said holding means.

11. The combination in accordance with claim including means operative on release of said latch-retained valve for closing said pilot valve irrespective of external operation of the latter.

12. A circuit breaker mechanism comprising at least one pair of relatively movable electrical contacts, resilient means tending to separate said contacts, hydraulic means comprising a chamber having a movable wall mechanically connected to close said contacts against the action of said resilient means, a sump for receiving actuating liquid for said hydraulic means, a hydraulic accumulator having a liquid capacity at least a plurality of times as great as that of said chamber, conduits connecting respectively to said chamber, accumulator and sump, valve means interconnecting said conduits and operative a1- ternatively to open a passage from said chamber to said sump and close a passage from said accumulator to said chamber in a normal position of said valve means and to close said first mentioned passage and open the other in a second position thereof, actuating means operative to move said. valve means from said normal position to said second position, separate electric means for disabling said actuating means, and a pump connected to return liquid from said sump to said accumulator to maintain the pressure and volume of liquid therein at a normal level suflicient to operate said hydraulic means to close said contacts a plurality of times in the event of failure of said pump.

13. A circuit breaker mechanism in accordance with claim 12 wherein said actuating means comprises a conduit connecting said accumulator and said valve means and a pilot valve operable to open or close passage of liquid through said conduit, external means for operating said pilot valve, and means operative in response to actuation of said disabling means for closing said pilot valve irrespective of the operative position of said external means.

14. Circuit breaker mechanism in accordance with claim 13 including latch mechanism for re taining said contacts in closed position, means interconnected with said separate electrical means for disabling said valve actuating means for simultaneously releasing said latch, and means operative upon engagement of said latch for closing said pilot valve.

DONALD M. UMPHBEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 537,103 Berry Apr. 9, 1895 1,595,755 Brooks Aug. 10, 1926 1,836,813 Rankin Dec. 15, 1931 1,873,787 Rankin Aug. 23, 1932 2,360,687 Johnson m Oct. 16, 19 14 2,411,360 Boden Nov. 19, 1946 2,496,553 Littleiield Feb. 7, 1950

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