CIRCUIT BREAKER OPERATING MECHANISM WITH HIGH-SPEED LOW-ENERGY TRIPPING MEANS
United States Patent 3835277
A circuit breaker operating mechanism comprises two toggle links pivotally interconnected at a knee. One of the toggle links is coupled to a contact-actuating member, and the other is pivotally supported on a pivot pin spaced from the knee. Latching means normally holds the pivot pin in a fixed position but is releasable to release said pivot pin and thus render the toggle links incapable of holding the contact-actuating member in its closed position. The latching means comprises a piston, a cylinder in which the piston is reciprocable, means for mounting said pivot pin on the piston, and a ring latch around the outer periphery of the piston normally latching the piston to the cylinder. The ring latch is operable to release the piston from latching relationship with the cylinder, thus releasing the pivot pin and initiating circuit-breaker opening.
US Patent References:
Switch operating mechanism
Thumim - October 1931 - 1827626
CIRCUIT BREAKER WITH MAGNETIC DEVICE RELEASABLE TO EFFECT OPENING OF THE BREAKER
Johnson - June 1969 - 3450955
HIGH-VOLTAGE ELECTRIC CIRCUIT BREAKER WITH HIGH-SPEED TRIPPING MEANS
Barkan - February 1972 - 3646292
MEANS FOR CHARGING A STORED ENERGY CIRCUIT BREAKER CLOSING DEVICE
Baskerville - April 1973 - 3729065
Switch operating mechanism
Thumim - October 1931 - 1827626
CIRCUIT BREAKER WITH MAGNETIC DEVICE RELEASABLE TO EFFECT OPENING OF THE BREAKER
Johnson - June 1969 - 3450955
HIGH-VOLTAGE ELECTRIC CIRCUIT BREAKER WITH HIGH-SPEED TRIPPING MEANS
Barkan - February 1972 - 3646292
MEANS FOR CHARGING A STORED ENERGY CIRCUIT BREAKER CLOSING DEVICE
Baskerville - April 1973 - 3729065
Application Number:
05/397242
Publication Date:
09/10/1974
Filing Date:
09/14/1973
View Patent Images:
Export Citation:
Assignee:
General Electric Company (Philadelphia, PA)
Primary Class:
Other Classes:
200/401, 335/171, 335/21
International Classes:
H01H3/30; H01H3/00; H01H9/20
Field of Search:
200/82R,82B,82C,148F,153G,153H,153SC,169R,169C 335/21,165-168,171
Primary Examiner:
Schaefer, Robert K.
Assistant Examiner:
Tolin, Gerald P.
Attorney, Agent or Firm:
Haubner, Wesley Freedman William J.
Claims:
What I claim as new and desire to secure by U.S. Letters Patent is
1. In an operating mechanism for a circuit breaker comprising a movable contact-actuating member,
2. The operating mechanism of claim 1 in which:
3. The circuit breaker operating mechanism of claim 1 in which:
4. The circuit breaker of claim 1 in which:
1. In an operating mechanism for a circuit breaker comprising a movable contact-actuating member,
2. The operating mechanism of claim 1 in which:
3. The circuit breaker operating mechanism of claim 1 in which:
4. The circuit breaker of claim 1 in which:
Description:
BACKGROUND
This invention relates to an operating mechanism for an electric circuit breaker and, more particularly, relates to a mechanically trip-free operating mechanism which includes tripping means capable of being operated at exceptionally high speeds by small amounts of tripping energy.
A typical mechanically trip-free operating mechanism for a circuit breaker comprises a toggle linkage that has one end coupled to the movable contact-actuating member of the circuit breaker and its opposite end supported on a pivot pin which is normally latched in a fixed position by a trip latch. If the latch is tripped to release the pivot pin, the toggle becomes ineffective to transmit closing force or hold-closed force to the movable contact-actuating member, thus allowing the circuit breaker to open under the influence of its opening spring.
In certain circuit breakers, the latch that holds the above-described pivot pin in place can be a simple latch member acting directly on the pivot pin (as shown, for example, at 31 in U.S. Pat. No. 2,794,181-Frank), but release of such a latch member requires a large amount of tripping energy, particularly if the circuit breaker is a large one. To reduce the energy required for tripping, it has been customary to provide a latching toggle or a series of latching toggles for normally holding the pivot pin in its latched position. (An example of such a latching toggle appears in U.S. Pat. No. 1,827,626--Thumim,) While the presence of such a latching toggle or series of latching toggles reduces the energy required for tripping, it also results in a relatively complex tripping mechanism which is still not as fast as sometimes required. A factor detracting from the speed of a latching toggle is that its effective mass is high when in or near its usual latching position near toggle-center.
The mechanisms illustrated in the above noted Frank and Thumim patents contain still another toggle which must be moved out of a position near center to effect tripping. This toggle (25, 24, 23, 15 in Frank and 18, 17, 7, 6 in Thumim) is one constituted by the usual guide link for the above-described pivot pin, one of the links of the main toggle, and the connecting pivot pin acting as the knee of this toggle. While the presence of this toggle contributes to reduced tripping force requirements, it also reduces the speed of opening because of the time required for moving this relatively massive toggle out of its latching position near center.
SUMMARY
A general object of my invention is to provide tripping means for a mechanically trip-free operating mechanism which can be operated at exceptionally high speed by small amounts of tripping energy.
Another object is to construct the operating mechanism in such a way that circuit-breaker opening can be effected with small amounts of tripping energy without the need for moving any toggles out of a position near toggle-center during tripping or initial opening movement.
In carrying out the invention in one form, I provide latching means that comprises a piston, a cylinder in which said piston is reciprocable, and a ring latch around the outer periphery of the piston normally latching the piston to the cylinder. The above-described pivot pin that supports one link of the main operating toggle is mounted on the piston and is carried thereby. The ring latch comprises a split ring seated in a groove in the periphery of the piston and a latching element normally fitting between the ends of the split ring for holding the ring in an expanded condition for blocking movement of the piston with respect to the cylinder. This latching element can be withdrawn from its normal position to allow the ring to contract into a disabled position where the ring is ineffective to continue blocking movement of the piston with respect to the cylinder, thus releasing the piston and the pivot pin carried thereby and initiating circuit-breaker opening.
BRIEF DESCRIPTION OF DRAWINGS
For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic view of a circuit-breaker operating mechanism embodying one form of the invention. The operating mechanism is depicted in its circuit-breaker closed position.
FIG. 2 shows the operating mechanism in two separate positions through which it passes during opening. One position is depicted in solid lines, and a later position is depicted in dotted lines.
FIG. 3 is a detailed view of a ring latch constituting a part of the operating mechanism of FIG. 1.
FIG. 4 is a sectional view along the line 4--4 of FIG. 3.
FIG. 5 shows the operating mechanism of FIG. 1 in its fully-open position.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to FIG. 1, the circuit breaker depicted therein comprises a set of spaced-apart stationary contacts 10 connected in a power line 12. Bridging the stationary contacts 10 is a movable bridging contact 14 shown in its closed position. For actuating the bridging contact, an actuating rod 16 of insulating material is connected thereto. Opening of a circuit breaker is effected by driving rod 16 upwardly from its position of FIG. 1, and closing is effected by returning the rod in a downward direction to its position of FIG. 1. Opening force is derived from a compression-type opening spring 18 which, upon release, drives the rod 16 upwardly.
For closing the circuit breaker and also for holding it closed, an operating mechanism 20 is provided. This operating mechanism 20 comprises a toggle 21 which comprises two toggle links 24 and 26 having their adjacent ends pivotally interconnected by a connecting pin 28 that forms a knee for the toggle. One of the toggle links 26 is coupled to the actuating rod 16 by means of an operating crank 29 that is pivotally mounted on a fixed pivot 30. The right hand end of toggle link 26 is pivotally connected to crank 29 by a pivot pin 31, and the right hand end of crank 29 is connected to the actuating rod 16 through a suitable pivotal connection 33.
For pivotally supporting the left hand end of the other toggle link 24, a pivot pin 35 is provided. This pivot pin 35 is mounted on a piston rod 38 which is normally held in its position of FIG. 1, as will soon be described. When the circuit breaker is in its closed position, as shown in FIG. 1, the toggle 21 occupies a slightly undercenter position and has a tendency to collapse downwardly at its knee 28. For preventing such collapse, a conventional prop 40 is provided. This prop is pivotally supported on a stationary pivot 42 and is biased into its position of FIG. 1 against a stop 45 by a torsion spring 43. A roller 48 on the knee pin 28 bears against the upper surface of the prop 40 and thus prevents the toggle from collapsing downwardly while in its position of FIG. 1.
So long as the toggle-supporting pivot pin 35 is held in its position of FIG. 1, the circuit breaker is prevented from opening. Thus, in its condition of FIG. 1, the toggle is able to transmit closing or hold-closed force to the actuating rod 16. When, however, the pivot pin 35 is released, the opening spring 18, acting through output crank 29, drives toggle 21 bodily to the left, thus allowing circuit-breaker opening to proceed. After an initial amount of opening has occurred and the parts have entered their solid line position of FIG. 2, the knee roller 48 has moved off the prop 40 and the toggle 21 is free to collapse downwardly at its knee toward its position of FIG. 5 to permit further opening travel of the operating rod 16. The dotted lines of FIG. 2 illustrate the parts shortly after such collapse has begun.
For releasably holding the pivot pin 35 in its position of FIG. 1, I rely upon a ring latch 50 similar to that shown and described in U.S. Pat. No. 3,646,292--Barkan. This ring latch cooperates with a cylinder 52 and a piston 54 to effect the desired holding or latching action. Cylinder 52 is a stationary element, and piston 54 is reciprocable within the cylinder. The previously-mentioned piston rod 38 is fixed to piston 54.
The ring latch 50, which is shown in more detail in FIGS. 3 and 4, comprises a split ring 60 of circular cross section that is carried in an annular groove 62 in the piston 54. This piston ring 60 is a resilient member that has a tendency to expand in diameter, but its expansion is limited by the internal wall of cylinder 52 and specifically by a conical shoulder 63 on the internal wall of cylinder 52. Referring to FIGS. 1 and 4, a leftward force on piston 54 is transmitted to the piston ring through groove surface 64 and urges the piston ring against conical shoulder 63. The reaction force developed on the ring by the conical shoulder tends to contract the ring. The ring is normally prevented from contracting beyond the position shown in FIG. 4 by a latching member 68, shown in FIGS. 1 and 3, that fits between the ends of the split ring. When latching member 68 is withdrawn radially outward from this position, the reaction force from conical shoulder 63 on the cylinder forces the ring to contract completely into groove 62, thus releasing the piston for leftward movement. When the piston is so released, it allows piston rod 38 and the entire toggle 21 to move rapidly to the left under the bias of opening spring 18, thereby allowing the output crank 29 to pivot at high speed about point 30 in a counterclockwise circuit-breaker opening direction.
In a ring latch such as shown at 50, the latching force on the piston is well distributed around the periphery of the piston, which is a very large area compared to the active area in most latches; and, partially as a result of this, a relatively small releasing force can be used to release a very large force on the piston. In a typical ring latch such as illustrated, the force being released may be 100 or more times the releasing force, as compared to a typical maximum of about five times with a simple prop type latch. (The ratio of the force being released to the releasing force is referred to herein as the mechanical advantage of the latch.)
In the illustrated operating mechanism, I capitalize on the high mechanical advantage of the ring latch by having it act directly on the pivot pin 35 without any intermediate toggle or series of toggles. In some prior mechanisms, prop latches have been provided acting directly on the pivot pin 35, but because of the low mechanical advantage of such a latch, large amounts of tripping energy, too high for many applications, have been needed.
To reduce the amount of tripping energy required, it has been customary to provide a single latching toggle or a series of latching toggles between the latching member and the pivot pin. While such an arrangement does have reduced tripping energy requirements, it has the disadvantage of being complex and not as fast as sometimes required. As already pointed out hereinabove, a factor detracting from the operating speed of a latching toggle is that its effective mass is high when in its normal latching position near toggle center. By using a ring latch such as 50 with its high mechanical advantage, I am able to dispense with the heretofore-used latching toggles and still trip rapidly with only a small amount of tripping energy.
Another feature which many prior mechanisms have relied upon to reduce the tripping energy requirements is to mount the toggle-supporting pivot pin (e.g., my pin 35) on a guide link which is pivotally mounted so as to form a latching toggle with an adjacent link of the main toggle. Such a latching toggle is illustrated at 25, 24, 23, 15 in the aforesaid Frank U.S. Pat. No. 2,794,881. The presence of such a toggle detracts from opening speed because when the circuit breaker is closed, such toggle is typically latched in a position near dead center, where it has a high effective mass opposing initial opening movement of the toggle away from dead center. I am able to dispense with this additional toggle and its retarding effect inasmuch as my high mechanical-advantage latch does not require the assistance of such a toggle to reduce tripping energy. The absence of this toggle effect will be apparent from FIG. 1, where it can be seen that the reference line 90 along which the piston 54 is movable is substantially in line with the line of action 92 of the opening force applied by opening spring 18. Initial opening motion of both the toggle link 24 and piston rod 38 occurs along this line 90, 92, with no toggle effect being present between these parts to delay such opening movement. Although I prefer to arrange the parts so that reference lines 90 and 92 are substantially in line or parallel, a moderate degree of angularity between them is permissible. In neither case is any significant toggle effect present between the parts 38 and 24. The more in-line or parallel these lines are, the more reduced will be the transverse force on piston 54 and piston rod 38, thus reducing any tendency for them to bind within their surrounding guide surfaces, such as 93.
After the opening movement has proceeded beyond its initial stage, the knee roller 48 has moved off the prop 40, thus allowing the toggle 21 to collapse downwardly at its knee in a conventional manner. FIG. 2, in solid lines, shows the mechanism at the instant when such initial movement has occurred and at the point where the toggle 21 is starting to collapse. In dotted lines, FIG. 2 shows the parts at a later stage after the toggle has partially collapsed and additional leftward motion of piston 54 has occurred.
In FIG. 5 the piston 54 has been reset and toggle 21 has fully collapsed so that the breaker is fully open. Resetting of the piston 54 to its position of FIG. 5 is effected by a compression type resetting spring 95 (FIG. 1) located between the piston and the left hand end wall of cylinder 52. This resetting spring 95 is weak compared to the opening spring 18 and cannot effectively oppose initial opening.
For assuring that the toggle 21 will not enter an overcenter position and collapse in an upward direction, a suitable buffer indicated schematically at 96 (FIG. 1) is provided. This buffer is positioned to prevent entry of the knee roller 48 into an overcenter position. To assure prompt collapse of the toggle 21 during an opening operation, a torsion spring 97 is provided about pivot 31. This torsion spring biases the toggle link 26 in a counterclockwise direction about pivot 31.
Closing of the circuit breaker is effected by driving the operating mechanism from its position of FIG. 5 back into its position of FIG. 1. In the illustrated embodiment, this is done with a suitable fluid-actuated closing operator 100 comprising a cylinder 103 and a piston 106 reciprocable therein. Piston 106 carries an upwardly projecting plunger 104. When the operator is energized, the piston 106 and plunger 104 move upwardly, driving a roller 102 on the toggle link 24 in an upward direction to extend the toggle 21. At the end of this closing operation, the closing operator 100 is deenergized, and its driving parts 106, 104 rapidly return to their reset position of FIG. 5 under the bias of a suitable reset spring 105. It is to be understood that other conventional types of closing operators, e.g., spring-type or solenoid-type, can equally well be used with my mechanism.
For tripping the ring latch 50 to initiate an opening operation, I provide a suitable solenoid 110 preferably of the repulsion type. This solenoid, which is best shown in FIG. 3, has its stationary coil structure 112 mounted on the stationary cylinder 52 and an armature 114 coupled to the latching element 68. When the coil structure is appropriately energized, the armature 114 is repelled therefrom, and it moves at high speed to rapidly withdraw the latching element 68 from between the ends of the piston ring 60 to release the ring latch. A suitable compression spring 116 resets the armature to its normal position of FIG. 3 after such a releasing operation.
Another advantage of the ring latch in a circuit-breaker operating mechanism is that the ring latch can readily be made insensitive to the mechanical shocks typically encountered in such an application. Such shocks have a tendency to jar the armature of a tripping solenoid out of its normal position, thereby producing unintentional tripping on certain rare occasions. Such shocks usually act in the plane of movement of the parts of the operating mechanism or parallel to this plane. By positioning the latching element 68 in a plane that is disposed at a substantial angle to the plane of movement of the parts of the operating mechanism such as pivot pin 35, I can materially reduce the sensitivity of the ring latch to these shocks, thereby decreasing the chances for such unintentional tripping. In a ring type latch, the split in the latching ring and, hence, the latching element 68 can be located at any circumferential point about the piston periphery. Although the drawing shows the latching element 68 in the same plane as the plane of movement of the operating mechanism, this has been done merely to simplify the drawing. In a preferred form of the invention, the latching element 68 is disposed in a plane approximately perpendicular to the plane of movement of the operating mechanism.
While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.
This invention relates to an operating mechanism for an electric circuit breaker and, more particularly, relates to a mechanically trip-free operating mechanism which includes tripping means capable of being operated at exceptionally high speeds by small amounts of tripping energy.
A typical mechanically trip-free operating mechanism for a circuit breaker comprises a toggle linkage that has one end coupled to the movable contact-actuating member of the circuit breaker and its opposite end supported on a pivot pin which is normally latched in a fixed position by a trip latch. If the latch is tripped to release the pivot pin, the toggle becomes ineffective to transmit closing force or hold-closed force to the movable contact-actuating member, thus allowing the circuit breaker to open under the influence of its opening spring.
In certain circuit breakers, the latch that holds the above-described pivot pin in place can be a simple latch member acting directly on the pivot pin (as shown, for example, at 31 in U.S. Pat. No. 2,794,181-Frank), but release of such a latch member requires a large amount of tripping energy, particularly if the circuit breaker is a large one. To reduce the energy required for tripping, it has been customary to provide a latching toggle or a series of latching toggles for normally holding the pivot pin in its latched position. (An example of such a latching toggle appears in U.S. Pat. No. 1,827,626--Thumim,) While the presence of such a latching toggle or series of latching toggles reduces the energy required for tripping, it also results in a relatively complex tripping mechanism which is still not as fast as sometimes required. A factor detracting from the speed of a latching toggle is that its effective mass is high when in or near its usual latching position near toggle-center.
The mechanisms illustrated in the above noted Frank and Thumim patents contain still another toggle which must be moved out of a position near center to effect tripping. This toggle (25, 24, 23, 15 in Frank and 18, 17, 7, 6 in Thumim) is one constituted by the usual guide link for the above-described pivot pin, one of the links of the main toggle, and the connecting pivot pin acting as the knee of this toggle. While the presence of this toggle contributes to reduced tripping force requirements, it also reduces the speed of opening because of the time required for moving this relatively massive toggle out of its latching position near center.
SUMMARY
A general object of my invention is to provide tripping means for a mechanically trip-free operating mechanism which can be operated at exceptionally high speed by small amounts of tripping energy.
Another object is to construct the operating mechanism in such a way that circuit-breaker opening can be effected with small amounts of tripping energy without the need for moving any toggles out of a position near toggle-center during tripping or initial opening movement.
In carrying out the invention in one form, I provide latching means that comprises a piston, a cylinder in which said piston is reciprocable, and a ring latch around the outer periphery of the piston normally latching the piston to the cylinder. The above-described pivot pin that supports one link of the main operating toggle is mounted on the piston and is carried thereby. The ring latch comprises a split ring seated in a groove in the periphery of the piston and a latching element normally fitting between the ends of the split ring for holding the ring in an expanded condition for blocking movement of the piston with respect to the cylinder. This latching element can be withdrawn from its normal position to allow the ring to contract into a disabled position where the ring is ineffective to continue blocking movement of the piston with respect to the cylinder, thus releasing the piston and the pivot pin carried thereby and initiating circuit-breaker opening.
BRIEF DESCRIPTION OF DRAWINGS
For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic view of a circuit-breaker operating mechanism embodying one form of the invention. The operating mechanism is depicted in its circuit-breaker closed position.
FIG. 2 shows the operating mechanism in two separate positions through which it passes during opening. One position is depicted in solid lines, and a later position is depicted in dotted lines.
FIG. 3 is a detailed view of a ring latch constituting a part of the operating mechanism of FIG. 1.
FIG. 4 is a sectional view along the line 4--4 of FIG. 3.
FIG. 5 shows the operating mechanism of FIG. 1 in its fully-open position.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to FIG. 1, the circuit breaker depicted therein comprises a set of spaced-apart stationary contacts 10 connected in a power line 12. Bridging the stationary contacts 10 is a movable bridging contact 14 shown in its closed position. For actuating the bridging contact, an actuating rod 16 of insulating material is connected thereto. Opening of a circuit breaker is effected by driving rod 16 upwardly from its position of FIG. 1, and closing is effected by returning the rod in a downward direction to its position of FIG. 1. Opening force is derived from a compression-type opening spring 18 which, upon release, drives the rod 16 upwardly.
For closing the circuit breaker and also for holding it closed, an operating mechanism 20 is provided. This operating mechanism 20 comprises a toggle 21 which comprises two toggle links 24 and 26 having their adjacent ends pivotally interconnected by a connecting pin 28 that forms a knee for the toggle. One of the toggle links 26 is coupled to the actuating rod 16 by means of an operating crank 29 that is pivotally mounted on a fixed pivot 30. The right hand end of toggle link 26 is pivotally connected to crank 29 by a pivot pin 31, and the right hand end of crank 29 is connected to the actuating rod 16 through a suitable pivotal connection 33.
For pivotally supporting the left hand end of the other toggle link 24, a pivot pin 35 is provided. This pivot pin 35 is mounted on a piston rod 38 which is normally held in its position of FIG. 1, as will soon be described. When the circuit breaker is in its closed position, as shown in FIG. 1, the toggle 21 occupies a slightly undercenter position and has a tendency to collapse downwardly at its knee 28. For preventing such collapse, a conventional prop 40 is provided. This prop is pivotally supported on a stationary pivot 42 and is biased into its position of FIG. 1 against a stop 45 by a torsion spring 43. A roller 48 on the knee pin 28 bears against the upper surface of the prop 40 and thus prevents the toggle from collapsing downwardly while in its position of FIG. 1.
So long as the toggle-supporting pivot pin 35 is held in its position of FIG. 1, the circuit breaker is prevented from opening. Thus, in its condition of FIG. 1, the toggle is able to transmit closing or hold-closed force to the actuating rod 16. When, however, the pivot pin 35 is released, the opening spring 18, acting through output crank 29, drives toggle 21 bodily to the left, thus allowing circuit-breaker opening to proceed. After an initial amount of opening has occurred and the parts have entered their solid line position of FIG. 2, the knee roller 48 has moved off the prop 40 and the toggle 21 is free to collapse downwardly at its knee toward its position of FIG. 5 to permit further opening travel of the operating rod 16. The dotted lines of FIG. 2 illustrate the parts shortly after such collapse has begun.
For releasably holding the pivot pin 35 in its position of FIG. 1, I rely upon a ring latch 50 similar to that shown and described in U.S. Pat. No. 3,646,292--Barkan. This ring latch cooperates with a cylinder 52 and a piston 54 to effect the desired holding or latching action. Cylinder 52 is a stationary element, and piston 54 is reciprocable within the cylinder. The previously-mentioned piston rod 38 is fixed to piston 54.
The ring latch 50, which is shown in more detail in FIGS. 3 and 4, comprises a split ring 60 of circular cross section that is carried in an annular groove 62 in the piston 54. This piston ring 60 is a resilient member that has a tendency to expand in diameter, but its expansion is limited by the internal wall of cylinder 52 and specifically by a conical shoulder 63 on the internal wall of cylinder 52. Referring to FIGS. 1 and 4, a leftward force on piston 54 is transmitted to the piston ring through groove surface 64 and urges the piston ring against conical shoulder 63. The reaction force developed on the ring by the conical shoulder tends to contract the ring. The ring is normally prevented from contracting beyond the position shown in FIG. 4 by a latching member 68, shown in FIGS. 1 and 3, that fits between the ends of the split ring. When latching member 68 is withdrawn radially outward from this position, the reaction force from conical shoulder 63 on the cylinder forces the ring to contract completely into groove 62, thus releasing the piston for leftward movement. When the piston is so released, it allows piston rod 38 and the entire toggle 21 to move rapidly to the left under the bias of opening spring 18, thereby allowing the output crank 29 to pivot at high speed about point 30 in a counterclockwise circuit-breaker opening direction.
In a ring latch such as shown at 50, the latching force on the piston is well distributed around the periphery of the piston, which is a very large area compared to the active area in most latches; and, partially as a result of this, a relatively small releasing force can be used to release a very large force on the piston. In a typical ring latch such as illustrated, the force being released may be 100 or more times the releasing force, as compared to a typical maximum of about five times with a simple prop type latch. (The ratio of the force being released to the releasing force is referred to herein as the mechanical advantage of the latch.)
In the illustrated operating mechanism, I capitalize on the high mechanical advantage of the ring latch by having it act directly on the pivot pin 35 without any intermediate toggle or series of toggles. In some prior mechanisms, prop latches have been provided acting directly on the pivot pin 35, but because of the low mechanical advantage of such a latch, large amounts of tripping energy, too high for many applications, have been needed.
To reduce the amount of tripping energy required, it has been customary to provide a single latching toggle or a series of latching toggles between the latching member and the pivot pin. While such an arrangement does have reduced tripping energy requirements, it has the disadvantage of being complex and not as fast as sometimes required. As already pointed out hereinabove, a factor detracting from the operating speed of a latching toggle is that its effective mass is high when in its normal latching position near toggle center. By using a ring latch such as 50 with its high mechanical advantage, I am able to dispense with the heretofore-used latching toggles and still trip rapidly with only a small amount of tripping energy.
Another feature which many prior mechanisms have relied upon to reduce the tripping energy requirements is to mount the toggle-supporting pivot pin (e.g., my pin 35) on a guide link which is pivotally mounted so as to form a latching toggle with an adjacent link of the main toggle. Such a latching toggle is illustrated at 25, 24, 23, 15 in the aforesaid Frank U.S. Pat. No. 2,794,881. The presence of such a toggle detracts from opening speed because when the circuit breaker is closed, such toggle is typically latched in a position near dead center, where it has a high effective mass opposing initial opening movement of the toggle away from dead center. I am able to dispense with this additional toggle and its retarding effect inasmuch as my high mechanical-advantage latch does not require the assistance of such a toggle to reduce tripping energy. The absence of this toggle effect will be apparent from FIG. 1, where it can be seen that the reference line 90 along which the piston 54 is movable is substantially in line with the line of action 92 of the opening force applied by opening spring 18. Initial opening motion of both the toggle link 24 and piston rod 38 occurs along this line 90, 92, with no toggle effect being present between these parts to delay such opening movement. Although I prefer to arrange the parts so that reference lines 90 and 92 are substantially in line or parallel, a moderate degree of angularity between them is permissible. In neither case is any significant toggle effect present between the parts 38 and 24. The more in-line or parallel these lines are, the more reduced will be the transverse force on piston 54 and piston rod 38, thus reducing any tendency for them to bind within their surrounding guide surfaces, such as 93.
After the opening movement has proceeded beyond its initial stage, the knee roller 48 has moved off the prop 40, thus allowing the toggle 21 to collapse downwardly at its knee in a conventional manner. FIG. 2, in solid lines, shows the mechanism at the instant when such initial movement has occurred and at the point where the toggle 21 is starting to collapse. In dotted lines, FIG. 2 shows the parts at a later stage after the toggle has partially collapsed and additional leftward motion of piston 54 has occurred.
In FIG. 5 the piston 54 has been reset and toggle 21 has fully collapsed so that the breaker is fully open. Resetting of the piston 54 to its position of FIG. 5 is effected by a compression type resetting spring 95 (FIG. 1) located between the piston and the left hand end wall of cylinder 52. This resetting spring 95 is weak compared to the opening spring 18 and cannot effectively oppose initial opening.
For assuring that the toggle 21 will not enter an overcenter position and collapse in an upward direction, a suitable buffer indicated schematically at 96 (FIG. 1) is provided. This buffer is positioned to prevent entry of the knee roller 48 into an overcenter position. To assure prompt collapse of the toggle 21 during an opening operation, a torsion spring 97 is provided about pivot 31. This torsion spring biases the toggle link 26 in a counterclockwise direction about pivot 31.
Closing of the circuit breaker is effected by driving the operating mechanism from its position of FIG. 5 back into its position of FIG. 1. In the illustrated embodiment, this is done with a suitable fluid-actuated closing operator 100 comprising a cylinder 103 and a piston 106 reciprocable therein. Piston 106 carries an upwardly projecting plunger 104. When the operator is energized, the piston 106 and plunger 104 move upwardly, driving a roller 102 on the toggle link 24 in an upward direction to extend the toggle 21. At the end of this closing operation, the closing operator 100 is deenergized, and its driving parts 106, 104 rapidly return to their reset position of FIG. 5 under the bias of a suitable reset spring 105. It is to be understood that other conventional types of closing operators, e.g., spring-type or solenoid-type, can equally well be used with my mechanism.
For tripping the ring latch 50 to initiate an opening operation, I provide a suitable solenoid 110 preferably of the repulsion type. This solenoid, which is best shown in FIG. 3, has its stationary coil structure 112 mounted on the stationary cylinder 52 and an armature 114 coupled to the latching element 68. When the coil structure is appropriately energized, the armature 114 is repelled therefrom, and it moves at high speed to rapidly withdraw the latching element 68 from between the ends of the piston ring 60 to release the ring latch. A suitable compression spring 116 resets the armature to its normal position of FIG. 3 after such a releasing operation.
Another advantage of the ring latch in a circuit-breaker operating mechanism is that the ring latch can readily be made insensitive to the mechanical shocks typically encountered in such an application. Such shocks have a tendency to jar the armature of a tripping solenoid out of its normal position, thereby producing unintentional tripping on certain rare occasions. Such shocks usually act in the plane of movement of the parts of the operating mechanism or parallel to this plane. By positioning the latching element 68 in a plane that is disposed at a substantial angle to the plane of movement of the parts of the operating mechanism such as pivot pin 35, I can materially reduce the sensitivity of the ring latch to these shocks, thereby decreasing the chances for such unintentional tripping. In a ring type latch, the split in the latching ring and, hence, the latching element 68 can be located at any circumferential point about the piston periphery. Although the drawing shows the latching element 68 in the same plane as the plane of movement of the operating mechanism, this has been done merely to simplify the drawing. In a preferred form of the invention, the latching element 68 is disposed in a plane approximately perpendicular to the plane of movement of the operating mechanism.
While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.