US3624329A - Operating mechanism for a circuit interrupter with toggle means continuously in underset condition - Google Patents

Abstract

An operating mechanism for a circuit breaker is provided having a rotatable main lever, which is rotated to a closed position by an actuator, such as a piston, movable within a cylinder, and is maintained in the closed position by a latching device, such as a collapsible linkage maintained in its extended position by a magnetic trip device. The arrangement functions, during an opening operation, to actuate the tripping device, which permits collapse of the linkage and opening rotative motion of the main lever. During a subsequent closing, the piston device provides the energy for rotating the main lever to its closed position against the opposition provided by accelerating springs, and the collapsible linkage maintains the main lever in the closed position by the magnetic trip.

Description

United States Patent William 11. Fischer Pittsburgh; Wayne S. Aspey, Monroeville, both of Pa. [21] Appl. No. 776,510 [22] Filed Nov. 18,1968 [45] Patented Nov. 30, 1971 [73] Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

[72] Inventors [54] OPERATING MECHANISM FOR A CIRCUIT INTERRUPTER WITH TOGGLE MEANS CONTINUOUSLY IN UNDERSET CONDITION 7 Claims, 14 Drawing Figs.

3,334,202 8/1967 Tognella 200/153 (.8) X

2,562,147 7/1951 Kuwayama 335/174 X 3,023,285 2/1962 Favre .1 335/191 X FOREIGN PATENTS 846,527, 9/1939 France 200/148 (.6)

Primary ExaminerRobert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorneys-A. T. Stratton, Clement L. McHaIe and Willard R.

Crout ABSTRACT: An operating mechanism for a circuit breaker is provided having a rotatable main lever, which is rotated to a closed position by an actuator, such as a piston, movable within a cylinder, and is maintained in the closed position by a latching device, such as a collapsible linkage maintained in its extended position by a magnetic trip device. The arrangement functions, during an opening operation, to actuate the tripping device, which permits collapse of the linkage and opening rotative motion of the main lever. During a subsequent closing, the piston device provides the energy for rotating the main lever to its closed position against the opposition provided by accelerating springs, and the collapsible linkage maintains the main lever in the closed position by the magnetic trip.

TO HIGH PRESSURE TO LOW PRESSURE COMPRESSOR HIGH PRESSURE LOW PRESSURE TO AUXILIARY CONTACTS OPEN PATENTED NUVSO I97! SHEET u 0F 6 FIG. 5.

CLOSED POSITION PATENTEB unvso :97:

SHEET 5 0F 6 OPEN POSITION FIG.6.

OPERATING MECHANISM FOR A CIRCUIT INTERRUPTER WITII TOGGLE MEANS CONTINUOUSLY IN UNDERSET CONDITION CROSS-REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION As well known by those skilled in the art, in a circuit breaker mechanism it is desirable to provide for a straight closing operation, a straight opening operation, and for various duty cycles, such as open-close, close-open, and openclose-open. These functions must be provided quickly for opening the circuit in the order of two cycles. This is necessary to prevent continuous flow of fault current through the line, and to prevent a loss of synchronism of associated equipment.

Not only must the operating mechanism for a circuit breaker perform the aforesaid duty cycles, but, in addition, it must be reliable, preferably simple, require little maintenance, and be completely safe to protect operating personnel.

SUMMARY OF THE INVENTION According to a preferred embodiment of the invention, there is provided a rotatable main lever, which is stationarily mounted between the side plates of a main frame. The main lever has an arm portion which is connected to the several phases of the circuit-breaker structure to cause the actuation of either the contact structure thereof, or of control valves associated, with the respective phases. In addition, the main rotatable operating lever has a latching-arm portion, which is maintained in the closed position by a collapsible toggle linkage which, in turn, is.maintained in a slightly underset condition by a trigger actuated by a magnetic tripping device. To effect the closing rotative motion of the main operating lever, there is provided anactuator, such as a piston, movable by gas pressure within an operating cylinder to cause abutment with another arm-portionof the main operating lever to cause the closing rotation thereof.

Accelerating springs associated with either the contact structure, or with the control valves bias the operating lever to the open position, but it is maintained in its closed biased position until release of the tripping magnet by energization of tripping coils.

Accordingly, it is a general purpose of the present invention to provide an improved operating mechanism for a circuit interrupter, preferably one of the high-voltage type.

Another object of the present invention is the provision of an improved high-speed operating mechanism for a circuit interrupter, which is reliable in operation and composed of relatively few parts.

Still a further object of the present invention is the provision of an improved operating mechanism for a circuit interrupter, which requires littlemaintenance and provides fast opening and closing operations.

Further objects and advantages will readily become apparent upon readingthe following specification taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevational view of a 3-phase circuit interrupter, of the high-voltage type, utilizing the improved operating mechanism of the present invention;

FIG. 2 is a side elevational view of the 3-phase circuit interrupter ofFIG. 1;

FIG. 3 is a top plan-view of the 3-phase circuit interrupter of FIGS. 1 and 2; K

FIG. 4 is a diagrammatic view illustrating the interconnecting mechanical linkage between the operating mechanism, or

ground potential operator. and the control valves associated with each of the phase-units of the circuit interrupter;

FIG. 5 is an enlarged side elevational view of the improved operating mechanism of the present invention, the parts being indicated in the closed position;

FIG. 6 is a view similar to that of FIG. 5, but illustrating the disposition of the several parts in the fully open-circuit position;

FIG. 7 is a detailed view of the tripping lever for the mechanism;

FIG. 8 is a plan view of the tripping lever of FIG. 7;

FIG. 9 is a side elevational view of the tripping magnet of the operating mechanism;

FIG. 10 is atop plan view of the tripping magnet for FIG. 9;

FIG. II is a side elevational view of the magnet structure of the electromagnetic tripping mechanism, with the armature being shown in the released position;

FIG. 12 is a diagrammatic view illustrating the cooperation between the operating mechanism of the present invention through the interconnecting linkage to the 3-way control valves associated with each of the phase units, and a diagrammatic representation of the manner of contact operation;

FIG. 13 is a diagrammatic view showing the utilization of 5 the operating mechanism of the present invention in conjunction with a simple actuation of contact structure for a 3phase circuit interrupter; and,

FIG. 14 is a wiring diagram suitable for use with the improved operating mechanism of the present invention, and adapting the same to reclosing operations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, and more particularly to FIGS. 1-3 thereof, it will be observed that there is illustrated a 3- phase circuit interrupter of the high-voltage type, generally designated by the reference numeral 1. With particular reference being directed to FIGS. 2 and 3 of the drawings, it will be noted that there is provided three circuit-interrupting phase-units designated by the reference letters A, B and C. The three phase-units are mounted upon a stationary sturdy frame support composed of heavy structural channel members, generally designated by the reference numeral 3, and comprising upstanding supporting members 4 and and lateral braces 5.

It will be noted that each phase-unit generally, comprises a grounded housing structure 7 and slantingly upwardly extending arc-extinguishing assemblages 9 and terminal-bushing structures 10. As a result, the electrical circuit extends in a general U" manner from the line terminal 11 downwardly through the arc-extinguishing assemblage 9, and through a pressurized conduit (not shown) disposed within the housing structure 7, and then upwardly toward the right through the terminal-bushing structure 10. This structure is more detailed in US. Pat. application filed Dec. 9, 1968, Ser. No. 782,365, by Richard Kane and Frank Reese, and assigned to the assignee of the instant application.

Since the present invention is directed to the operating mechanism 13 for the circuit-interrupting structure 1, it does not appear necessary to go into a detailed description of the various parts within the arc-extinguishing assemblage, and, if desired, reference may be had to the aforesaid US. Pat. application Ser. No. 782,365.

Each of the arc extinguishing assemblages 9 includes one or more pairs of separable contacts, which are pressure actuated by a piston device. This is designated by the reference numeral 15 in FIG. 12 of the drawings. Tocontrol the opening and closing operations of the piston device 15, and hence to effect the opening and closing movement of the several contact structures 17 disposed within the arc-extinguishing assemblages 9, 3-way control valves 18 areassociated with each of the arc-extinguishing assemblages 9. The valve rods 19 for controlling each of the 3-way control valves I8 are mechani cally interconnected, generally horizontally, along the stationary'frame structure 3 in a manner somewhat indicated by FIGS. 4 and 12 of the drawings. With reference to FIG. 4, it will be seen that each valve-control rod 18 is connected to a bellcrank operator 20, which is moved by horizontally interconnecting rods 21, 22 which are, in turn, actuated by the main operating lever 24 of the improved operating mechanism 13 of the present invention.

FIG. 12 diagrammatically illustrates the interconnection between the main operating lever 24 of the improved operating mechanism 13 and the horizontally extending interconnecting links 21, 22. A simplified wiring diagram is shown in FIG. 12, but for adapting the circuit breaker l to quick opening and reclosing operations, use may be made of a more sophisticated diagram, as illustrated in FIG. 14 of the drawings.

A low-pressure tank 26 is suspended below the main frame support 3 and provides a reservoir for the low-pressure sulfurhexafluoride (SF gas, which is used in the particular structure. It will, of course, be obvious to those skilled in the art that other gases could be used, such as compressed air. In addition, the present operating mechanism 13, being described, is not restricted to a compressed-gas circuit interrupter, but may be used to actuate the contacts directly, as indicated in FIG. 13 of the drawings; and, in fact, the contacts 17 associated therewith could be disposed in an oil tank, (not shown) and the structure, therefore, could be termed an oilcircuit breaker. In other words, the operating mechanism 13 of the present application has universal application, either to actuate control valves 18 associated with a compressed-gas circuit interrupter, or it could be used to actuate the contacts 17 directly in any type of a circuit-interrupting structure, such as oil, compressed gas, or even an air-break device.

In the structure being described, and as particularly set forth in the aforesaid application Ser. No. 782,365, sulfur-hexafluoride (SF gas is utilized. Since this is an expensive gas, it is desirable to conserve it, and, therefore, a circulating system is provided, in which the used gas is stored in the low-pressure tank 26, recompressed by a compressor structure, not shown, and then the high-pressure gas is stored in suitable reservoirs associated with the arc-extinguishing assemblages 9. It is then used for opening the contact.structures and simultaneously effecting an arc-extinguishing flow across the resultant arcs established between the pairs of separated contacts. Reference may be had to the aforesaid application Ser. No. 782,365 for a description of the manner of circuit interruption utilizing a flow of compressed SF gas. For the purposes of understanding the present invention, however, such a description is deemed unnecessary.

The operating mechanism 13 of the present invention is closely associated with the middle phase unit, as designated by the reference letter B" in FIG. 2 of the drawings. Also FIG. 4 generally shows the association of the operating mechanism 13 with the interconnecting linkage 21, 22 so as to efiect simultaneous operation of all of the control valves 18 associated with the 3-phase-units A, B, and C.

FIGS. and 6 show, in a more detailed manner, the several components of the improved operating mechanism 13 of the present invention, FIG. 5 showing the disposition of the several parts in the closed position, whereas FIG. 6 shows the parts in the fully open-circuit position. It will be noted that, generally, there is provided the rotatable main operating lever 24, which is stationarily pivoted on an operating shaft 29, which extends between two side plates 30, 31 of a main stationary frame support 32. -In fact. although the main rotatable lever 24 is indicated as being a single-plate configuration, in fact, it comprises two spaced plates welded together for strength, and having a sleeve bearing 33 welded thereto, which is used as a bearing structure for the stationary operating shaft 29.

As shown in FIGS. 5 and 6, it will be noted that the main rotatable operating lever 24 has an actuating-arm portion 24a, which has pivoted thereto an operating link 34 which extends generally laterally, and is connected to the previously mentioned horizontal linkage structure 21, 22.

In addition, the rotatable main operating lever 24 has an actuating-a-rm portion 24b, which supports a roller 35, which is actuated by a piston rod 36, the piston 37 being disposed interiorly of an operating cylinder 38 and operated by high-pressure gas passing through a 3-way control valve 40 to the lefthand face of the operating piston 37 to force the same to the right, and hence to effect a closing rotative motion of the main operating lever 24. This is indicated by the dotted lines in FIGS. 5 and 6 of the drawings. A retracting spring 41 is disposed to the right of the aforesaid piston structure 37 and effects a retraction thereof following a reduction of the gas pressure at the left-hand end of the operating cylinder 38 following a closing operation.

To maintain the main operating lever 24 in its closed position, as illustrated in FIG. 5 of the drawings, a collapsible toggle linkage 43 is provided. As shown in FIG. 5, the collapsible toggle linkage 43 comprises a pair of pivotally connected toggle links 45 and 46, the upper toggle link 45 being stationarily mounted upon a stationary pivot pin 48 supported by an upstanding support portion 32a of the main stationary frame 32. The lower toggle link 46 is pivotally connected at 49 to the arm portion 24c of the main operating lever 24. In fact, each of the toggle links 45, 46 comprises a pair of spaced toggle links for strength and for facility in mounting the pins and rollers. To latch the collapsible linkage 43 in a slightly underset position, there is provided a pivotally mounted trigger lever, generally designated by the reference numeral 50. As shown in more detail in FIGS. 7 and 8, the rotatable trigger lever supports an armature 52, which is magnetically maintained to a tripping magnet 54, as illustrated in FIG. 11 of the drawings.

Generally, the tripping magnet 54 is such as to beactuated by an energization of tripping coils 56, 57, which releases the magnetic flux extending through the armature 52 and thereby permits collapse of the toggle linkage 43.

A pair of hydraulic shock absorbers, 59, 60 or snubbers are provided having actuating-stem portion 590, 60a which engage rollers 61 and 62 movable with the main rotatable operating lever 24. This cushions the operating lever 24 at the extremity of its opening and closing motions. Elements 59, 60 also act as the stops at the full open and close positions.

As shown in FIGS. 5 and 6, the arm portion 240 has pivotally connected thereto a link 64, which effects rotation of a rotatably-mounted arm 65, which, in turn, actuates a plurality of auxiliary switches 16 connected into the wiring circuit for the mechanism 13.

FIG. 14 illustrates, in detail, a wiring diagram for the operating mechanism 13 of the present invention, adapting the same for high-speed opening and reclosing operations.

Diagram FIG. 14 is shown in the breaker open position.

To close the circuit breaker the 101 C contact is closed. This completes the circuit through b, I-IPSX, Y, X time delay relay. Both X contacts close. This completes the circuit through X, Y, CC (Close Coil), Y, X. The close coil is energized and the breaker closes. At the end of the close stroke the TI LCH SW contact closes. This completes the circuit through Y relay. Two Y contacts close and three Y contacts open. The CC (Close Coil) is deenergized. The X time delay relay is deenergized and both X contacts open. As long as the C contact is closed the Y relay stays energized and the X relay cannot again be energized. This prevents pumping the circuit breaker contacts. The X relay is time delay in case b should open before TT LCH SW the Y relay will still be energized at the end of the close stroke.

To open the circuit breaker contact 101 T is closed. This completes the circuit through HPSX, RPMS, a, a, TC-l, 7.7r resistor. When the ll-pole switch reaches the breaker open position contacts a, a, open and interrupt the trip current. If reset piston is not reset the micro switch RPMS will prevent tripping.

The function of HPSX is to prevent tripping or closing should the high pressure SF fall below the minimum pressure allowed for safe operation.

FIG. 12 diagrammatically illustrates the association of the operating mechanism 13 of the present invention with the3- way control valves 18 of the individual arc-extinguishing assemblages 9 associated with the phase-units A, B and C. It will be observed that the three control rods 19 are simultaneously actuated, and control the entrance and exhaust of gas pressure below the actuating pistons 15, which, in turn control the moving contacts 17 of the interrupter. By an upward movement of the control valves 18, high-pressure gas is admitted below the pistons to effect an opening operation of the contact structure 17. Correspondingly, an exhausting, or dumping of high-pressure gas below the pistons 15 will efiect a closing of the contact structure 17, as assisted by the closing springs 68.

Generally, the mechanism 13 is biased to the open position by one or more accelerating springs 70, such as diagrammatically indicated in FIGS. 12 of the drawings.

From the foregoing description it will be apparent that to effect an opening operation of the interrupter, energization is had of the tripping magnet 54 to effect release of the rotatable trigger arm 50, and a collapse of the toggle linkage 43. This will permit an opening rotative motion of the main operating lever 24, as biased by the several accelerating springs 70, with a consequent opening of the 3-way valves 18. In the fully open-circuit position, as illustrated in FIG. 6 of the drawings, the trigger arm 50 remains in its upward position, and is not reset until during the subsequent closing operation. As mentioned, during the opening operation, the valve rods 19 are maintained in theirpiston-exhausting position, as illustrated in FIG. 12, and the contact structure 17 is maintained in its open position.

To effect a closing operation, the 3-way valve 40 associated with the operating cylinder 38 is energized to introduce highpressure gas to the left of the actuating piston 37, which forces the plunger thereof to the right in abutment with the closing roller 35 of the main operating lever 24. This effects a counterclockwise closing rotative motion of the main operating lever 24, until the toggle linkage 43 is extended, and the latching portion 50a of the tripping lever 50 again maintains the toggle linkage 43 in its slightly underset condition. A tension spring 71 biases the tripping lever 50 in a counter- 'clockwise direction, so that during the closing operation, the

armature 52 again confronts the pole plates of the tripping magnet 54. The magnetic force then maintains the armature 52 in its engaged position, as illustrated in FIG. 5, until the next energization of the tripping coils 56, 57.

TRIP MAGNET ASSEMBLY 54 The trip magnet assembly 54 or magnetic holding latch, for releasably magnetically latching the roller 44 of the knee pin 47 in the closed circuit position of the circuit breaker 1 will now be described. Generally, the trip magnet assembly 54 comprises a holding magnet and a trigger lever 50 pivotally mounted about a stationary pivot shaft 51 and carrying a movable armature 52 at one end thereof, and a latch portion at the other end thereof. As shown more clearly in FIG. 11, the holding magnet '54 comprises a generally U-shaped magnet structure, as shown, and a permanent magnet member 58. The U-shaped magnetic structure 54 comprises a base part 54a and two pole pieces, or leg parts 54b, 546. A thin layer 63 of nonmagnetic material separates the pole pieces 54b, 540 from the base part 54a. Each of the pole pieces 54b, 540 is provided with a generally flat pole face against which the armature 52 seats in the closed position, as shown in FIG. 5. The pole pieces 54b, 540, base part 540, and armature 52, are made of a suitable magnetically permeable material, such as soft iron. The permanent magnet 58 is of the ceramic type.

With reference to FIG. 11, which shows the holding magnet 5'4 in the released position, it will be noted that theZ-piece pole assembly provides two parallel magnetic paths for flux from the ceramic permanent magnet 58. With the armature 52 in the reset position, most of the flux concentrates in the lowreluctance path provided by the moving armature 52. The magnet 54 holds this armature with a force of 200 pounds, for example, opposing a pound force as applied by the roller load 44 through the trigger lever 50. Thus, there is provided a [00 percent safety factor, for example, to prevent accidental tripping by mechanical shocks.

To initiate a tripping operation of the pole-unit "A, the trip coil assembly 56, 57 is energized by pressing the manual trip button TB thereby completing the tripping circuit through the battery 112. Or, as well known by those skilled in the art, the tripping may be initiated by means of the trip relay 113 upon the occurrence of an overload current through the line L,L controlled by the breaker l, which overload or fault current causes the relay 113 to close its contacts 114, thus completing the tripping circuit through the battery 112.

There are provided two trip coils 56, 57, one around each pole piece 54b, 54c, which are connected in series and wound so that the magnetomotive force produced by the coils opposes the permanent-magnet flux in the moving armature 52. This opposition decreases the magnetic flux in the moving armature circuit (the permanent-magnet flux transfers from the moving armature loop to the parallel upper airgap loop). The holding force on the armature 52 is reduced, allowing the I00 pound trigger force to initiate motion for release of the armature trigger lever 50.

Trip coil current is cut off by an auxiliary switch after a small movement of the breaker mechanism 13. The armature 52 is reset when the mechanism closes.

As stated hereinbefore, when the trip coil 56 is energized, either by manually pressing the tripping button TB, or by automatic operation of the overload current relay 113, the trip-coil magnetomotive force opposes the magnetomotive force of the permanent magnet 58 in the magnetic path through the armature 52, thereby reducing the flux through the armature 52. The magnetic flux of the permanent magnet itself remains almost constant and transfers" from the armature 52 to the path through the air" gaps 63a, 63b and the base part 540, thereby reducing the force by which the armature 52 is attracted to pole faces 54b and 54c and allowing the armature 52, to be opened by the 100 pound force resulting from the trigger load. The trigger structure 50 will rotate, as a unit, in a clockwise direction about the stationary pivot shaft 51 until the force F" exerted by the latching roller 44 collapses the toggle linkage 43.

From the foregoing description it will be apparent that there has been provided an improved high-speed simplified type of operating mechanism 13 particularly adapted for high-speed closing and opening operations. In addition, it is adapted for reclosing operations by use of the wiring diagram of FIG. 14. Moreover, the operating mechanism 13 is suitable not only for the actuation of control valves 18, but for a direct connection with the movable contact structures, as diagrammatically represented in FIG. 13 of the drawings.

The solenoid valve 40a is tilted in such a way that any liquid SP that forms or drains back into the high-pressure SF source. A latch check switch 73 cuts off the current to the solenoid valve. In addition, a latch check switch 74 on the closing cylinder prevents the tripping coil from being energized until the piston rod is fully retracted.

The operating mechanism 13 of the present invention is low in cost, meets 2-cycle and duty-cycle ratings, is simple in design, and provides improved contact synchronization by using only one operator 24 for all three poles of the device.

It is to be clearly understood that those skilled in the art could make many changes to the above-described operator without departing from the basic concept. As an example of this, compressed air could be used instead of sulfur hexafluoride gas, or rubber snubbers could be used instead of the hydraulic snubbers 59, 60 as indicated. Other changes would obviously present themselves to one skilled in the art.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

We claim:

I. An operating mechanism for a circuit interrupter including, in combination:

a. supporting means rotatively supporting a main operating lever on a fixed pivot and having rotative opening and closing motions about said fixed pivot;

b. said operating lever having a latching-arm portion;

c. a collapsible toggle linkage pivotally connected between a stationary point and said latching-arm portion and in an underset condition at all times;

d. holding means releasably maintaining said collapsible toggle linkage in an underset condition;

e. mea'ns releasing said holding means;

f. an operating rod interconnecting the operating mechanism with the contact motion and responsive to motion of said operating lever; and,

g. closing means for, at times. effecting the rotative closing motion of said main operating lever about said fixed pivot independently of said toggle linkage.

2. The combination of claim 1. wherein the holding means is a magnetically actuated trigger arm.

3. The combination of claim 1, wherein the closing means is a piston'operated device.

4. The combination of claim 1. wherein said operating rod is connected to a control valve for controlling the operation of piston-actuated contacts of the circuit breaker.

5. The combination of claim 1, wherein a pair of shock absorbers cushion the opening and closing motions of the rotatable main operating lever.

6. The combination according to claim 3, wherein the piston-operated device includes a piston reciprocally movable within an operating cylinder and spring-retracted to its inoperative position.

7. The combination according to claim 2, wherein a fluxshifter magnetically releases an armature attached to the trigger arm.

Claims (7)

1. An operating mechanism for a circuit interrupter including, in combination: a. supporting means rotatively supporting a main operating lever on a fixed pivot and having rotative opening and closing motions about said fixed pivot; b. said operating lever having a latching-arm portion; c. a collapsible toggle linkage pivotally connected between a stationary point and said latching-arm portion and in an underset condition at all times; d. holding means releasably maintaining said collapsible toggle linkage in an underset condition; e. means releasing said holding means; f. an operating rod interconnecting the operating mechanism with the contact motion and responsive to motion of said operating lever; and, g. closing means for, at times, effecting the rotative closing motion of said main operating lever about said fixed pivot independently of said toggle linkage.

2. The combination of claim 1, wherein the holding means is a magnetically-actuated trigger arm.

3. The combination of claim 1, wherein the closing means is a piston-operated device.

4. The combination of claim 1, wherein said operating rod is connected to a control valve for controlling the operation of piston-actuated contacts of the circuit breaker.

5. The combination of claim 1, wherein a pair of shock absorbers cushion the opening and closing motions of the rotatable main operating lever.

6. The combination according to claim 3, wherein the piston-operated device includes a piston reciprocally movable within an operating cylinder and spring-retracted to its inoperative position.

7. The combination according to claim 2, wherein a flux-shifter magnetically releases an armature attached to the trigger arm.

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