Tristable bending mechanism

Abstract

Actuation system (100) comprising: a locking assembly (186) configured to be releasably engaged with a cradle (116); a movable arm (110); an elastic component (150) having a first end with a pivot joint (152) on the cradle (116) and a second end connected to the movable arm (110), the elastic component (150) being elastically deformed and stores elastic deformation energy in either a first state or a second state when the locking assembly (186) is engaged with the cradle (116), and wherein the elastic component (150) is in a third state in which it is not substantially elastically deformed and stores substantially no elastic deformation energy when the locking assembly (186) is not engaged with the cradle (116); and an input link engaged with the elastic component (150) between the first end and the second end, wherein movement of the input link between a first position and a second position, when the locking arrangement (186) is engaged with the cradle (116), the elastic component (150) transitions between the first state and the second state.

Description

[0001] Embodiments illustrated herein relate generally to electrical circuit breaking with circuit breakers, and more particularly to circuit breaker mechanisms constructed as tristable planar flexure mechanisms with compliant components for use in molded case circuit breakers (MCCBs). BACKGROUND

[0002] MCCBs are used to interrupt electrical DC or AC, single-phase or multi-phase circuits to protect electrical infrastructure when an electrical fault condition occurs. The electrical fault condition may include an instantaneous current in the circuit that exceeds a predefined instantaneous current limit (i.e., an electrical short circuit) or a continuous current that exceeds a predefined continuous current limit (i.e., an overload condition). A single-break MCCB typically has one pair of electrical contacts for each phase, with each pair consisting of a stationary contact mounted on a stationary current loop and a movable contact mounted on a contact arm. A double-break MCCB has two pairs of electrical contacts per phase. There are two stationary contacts and one contact arm with two movable contacts per phase.A circuit breaker mechanism interrupts the flow of electrical current by separating the moving contacts from the stationary contacts, thereby changing it from a closed to a tripped state.

[0003] In conventional approaches, the circuit breaker mechanism moves from the closed to the tripped state by releasing stored elastic deformation energy from a helical tension spring and converting it into kinetic energy of the mechanism's connecting links. The release of elastic deformation energy is initiated by disengaging a cradle from a locking assembly, which helps maintain tension on the spring during normal operation when the circuit breaker mechanism is closed. The locking assembly can be released by an automatic trip unit that detects and responds to an electrical fault, or manually by an operator pressing a "push trip" button.

[0004] The energy to separate the moving contact and contact arm from the stationary contact can also come from an electromagnetic field created around the stationary current loop and contact arm due to the short-circuit currents flowing through these components. The interactions between the electromagnetic field and the short-circuit current result in a repulsive force between the stationary current loop and contact arm, causing them to move away from each other (i.e., be "blown open"). The strength of the repulsive force decreases as the current and electromagnetic field strength decrease as the contacts begin to separate. The circuit breaker mechanism must be able to prevent the contact arm from resealing with the stationary contact.

[0005] Once tripped, the circuit breaker mechanism remains tripped and indicates this condition to an operator. The circuit breaker mechanism can usually be reset after it has been tripped by moving a handle from the tripped position to the open (i.e., off) position. This increases the elastic deformation energy of the spring and engages the cradle with the locking assembly. Once reset, the electrical circuit can be closed by moving the handle from the open position to the closed (i.e., on) position. MCCBs can also be used to break and close electrical circuits in the absence of electrical faults by moving a handle between the closed and open positions.

[0006] The movement of the contact arm from the closed position to the tripped position should be rapid to minimize the formation of arcs that can affect the contacts and thereby increase the overall electrical resistance of the circuit breaker. Likewise, if a handle is used to transition the circuit breaker mechanism between the closed and open states, the contacts must move quickly, even if the handle movement is slow. This characteristic is referred to as "rapid break." The circuit breaker mechanism must be appropriately sized to fit within a predefined circuit breaker enclosure or control panel. The circuit breaker mechanism should be resistant to wear, contamination, long-term fatigue, vibration, temperature, and humidity to prevent inadvertent nuisance tripping or a no-trip situation.

[0007] Due to these design criteria, conventional circuit breaker mechanisms have multiple moving components. Consequently, they are difficult to assemble and have a high number of failure modes, sources of friction, and other uncertainties that affect their performance characteristics. Furthermore, conventional circuit breaker mechanisms can be larger than desired and still not meet all the design criteria regarding opening speed or the repeatability of the input displacement or force input at which they can trip.

[0008] Consequently, there is a need for circuit breaker mechanisms that are less complex, have more repeatable performance characteristics, are easier to assemble, are smaller in size, have faster opening times, and have more repeatable input displacements or force inputs at which they can be triggered. US Pat. No. 4,472,701 A discloses an electrical circuit breaker. Furthermore, US Pat. No. 3,147,353 A describes means for breaking a contact weld. SHORT DESCRIPTION

[0009] In a first embodiment, an actuation system is disclosed. According to the embodiment, the actuation system includes a locking assembly configured to releasably engage a cradle. The actuation system further includes a movable arm and a resilient component having a first end with a pivot on the cradle and a second end connected to the movable arm. The resilient component is elastically deformed and stores elastic deformation energy in either a first stable state or a second stable state when the locking assembly is engaged with the cradle. The resilient component is in a third stable state in which it is not substantially elastically deformed and stores substantially no elastic deformation energy when the locking assembly is not engaged with the cradle.The actuation system further includes an input linkage engaged with the resilient component between the first end and the second end. Movement of the input linkage between a first position and a second position when the locking assembly is engaged with the cradle transitions the resilient component between the first stable state and the second stable state.

[0010] In the aforementioned actuation system, the input linkage may comprise a yoke cam in association with a yoke follower, wherein movement of the input linkage from a third position to the second position transitions the mechanism to the second condition in which the resilient component is under tension and the locking arrangement is engaged.

[0011] In the actuation system of any type mentioned above, the input link may have a slot, and the elastic component may have a projection by which a complementary engagement structure is formed between the elastic component and the input link.

[0012] In one configuration, the input linkage includes a pair of cross bars in contact with the elastic component and through which the elastic component is configured to move.

[0013] The elastic component can be rigidly attached to the respective movable arm.

[0014] Alternatively, the elastic component can be connected to the respective movable arm via an offset pivot joint.

[0015] In the actuating system of any type mentioned above, the respective movable arm may be a contact arm arranged to move between a contact position and a non-contact position with a stationary contact.

[0016] In one variant, the respective movable arm may be a contact arm assembly comprising a contact arm, a lever, a contact arm pivot, a torsion spring, and a contact arm stop, and configured to move between a contact position and a non-contact position with a stationary contact.

[0017] In a further variant, the respective movable arm may be a contact arm assembly comprising a lever rotor, two contact arms, two contact arm pivots and contact arm torsion springs and configured to move between a contact position and a non-contact position with stationary contacts.

[0018] In the actuating system of any type mentioned above, the at least one movable arm may comprise two or more movable arms mounted on a common torsion bar connected to the mechanism.

[0019] In the actuation system of any type mentioned above, the first state may comprise a closed state in which the respective movable arm contacts a stationary contact, and the second state may comprise an open state in which the respective movable arm does not contact the stationary contact.

[0020] Additionally or alternatively, the third state may comprise a triggered state in which the respective movable arm does not touch the stationary contact.

[0021] In one application, the actuation system includes an electrical circuit breaker.

[0022] In the actuation system of any type mentioned above, the input connection may be a handle yoke.

[0023] Additionally or alternatively, the elastic component may comprise one of a leaf-shaped flexure, a buffer spring, a ringed flexure, or a helical compression spring.

[0024] In another embodiment, a method for actuating a movable arm is disclosed. The method includes: maintaining an elastic component under a condition having elastic deformation energy in a first stable state or a second state; maintaining a movable arm in a first stable position while the elastic component is in the first stable state; responsive to an input displacement or force input, releasing the elastic deformation energy from the elastic component such that the elastic component is in a third stable state corresponding to a relaxed state; responsive to the released elastic deformation energy, rotating the movable arm such that it is no longer in the first stable position; and responsive to the released elastic deformation energy, moving an input linkage to a triggered position.

[0025] The aforementioned method may comprise: in response to the input link being moved from a first position to a second position, transitioning the elastic component to the second state while maintaining the elastic component elastically deformed such that the elastic component stores elastic deformation energy; and in response to the elastic component assuming the second state, rotating the movable arm so that it is no longer in the first position.

[0026] Additionally or alternatively, the method may comprise: in response to the input link being moved from the triggered position to a second position, transitioning the elastic component from the third state in which substantially no elastic deformation energy is stored to the second state in which elastic deformation energy is stored.

[0027] In the method of any type mentioned above, releasing the elastic deformation energy from the elastic component may comprise disengaging a cradle from a locking arrangement such that the cradle rotates about a cradle pivot.

[0028] In a specific embodiment of the method, the movable arm breaks contact with a stationary contact in response to a repulsive electromagnetic force while the elastic component is maintained under the elastic deformation energy state.

[0029] In another embodiment, a circuit breaker assembly is disclosed. According to the embodiment, the mechanism includes a locking assembly configured to releasably engage a cradle. The mechanism further includes a movable arm configured to move between a closed-circuit position and an open-circuit position. The mechanism further includes a leaf-shaped flexure having a first end with a pivot on the cradle and a second end connected to the movable arm.

[0030] In the aforementioned circuit breaker, the leaf-shaped flexure may be in either a first state corresponding to the closed-circuit position or a second state corresponding to the open-circuit position when the locking assembly is engaged with the cradle, and the leaf-shaped flexure may be in a third state corresponding to a tripped position when the locking assembly is not engaged with the cradle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] These and other features, aspects and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying figures, in which like reference numerals represent like parts throughout the figures, in which: Fig. 1 is a schematic view of a single-phase, single-break MCCB mechanism having a leaf-shaped flexure and a contact arm assembly in a closed state, in accordance with aspects of the present disclosure; Fig. 2 is a schematic view of a single-phase, single-break MCCB mechanism having a leaf-shaped flexure and a contact arm assembly in an open state, in accordance with aspects of the present disclosure; Fig. 3 is a schematic view of a single-phase, single-break MCCB mechanism at the bifurcation point of the leaf flexure during transition from the closed to the open state, in accordance with aspects of the present disclosure; Fig. 4 is a schematic view of a single-phase, single-break MCCB mechanism at the bifurcation point of the blade member during transition from the open to the closed state, in accordance with aspects of the present disclosure; Fig. 5 is a schematic view of a single-phase, single-break MCCB mechanism having a leaf-shaped flexure and a contact arm assembly in a tripped state, in accordance with aspects of the present disclosure; Fig. 6 is a schematic view of a single-phase, single-break MCCB mechanism in the closed state and having a leaf-shaped flexure connected to a contact arm assembly via an offset pivot, in accordance with aspects of the present disclosure; Fig. 7 is a schematic view of a single-phase, single-break MCCB mechanism in the closed state, with a coil spring connected to a contact arm assembly via an offset pivot, in accordance with aspects of the present disclosure; Fig. 8 is a schematic view of a single-phase, double-break MCCB mechanism in the closed state and with a ringed flexure according to aspects of the present disclosure; Fig. 9 is a schematic view of a single-phase, single-break MCCB mechanism with a coil compression spring collapsed to provide a closed condition, in accordance with aspects of the present disclosure; Fig. 10 is a schematic view of a single-phase, single-break MCCB mechanism having a helical compression spring collapsed to provide an open condition, in accordance with aspects of the present disclosure; Fig. 11 is a schematic view of a single-phase, single-break MCCB mechanism having a helical compression spring extended to create a tripped condition, in accordance with aspects of the present disclosure; and Fig. 12 is a perspective view of a three-phase single break circuit breaker in a closed state according to aspects of the present disclosure. DETAILED DESCRIPTION

[0032] Embodiments illustrated herein relate generally to the interruption of electrical circuits, and more particularly to the use of tristable planar flexure mechanisms employing elastic components. The mechanisms illustrated herein are, in one embodiment, intended for use in MCCBs. In some such embodiments, the mechanisms illustrated herein are constructed to move an electrical contact arm assembly in a single-phase breaker or multiple contact arm assemblies in a multi-phase breaker to achieve electrical circuit interruption. The MCCB may be configured with single break, with a single stationary contact and a single movable contact per phase, or with double break, with two stationary contacts and two movable contacts per phase.

[0033] As explained herein, separation of the electrical contacts may be achieved by releasing elastic deformation energy stored in an elastic component and converting it into kinetic energy of the linkages of the mechanism. The elastic component may be provided as a leaf-shaped flexure or other suitable component having a first end pivoted to a cradle and a second end connected to the contact arm assembly. Release of the elastic deformation energy may be initiated by disengaging a cradle from a locking assembly that helps retain the elastic component during normal operation when no electrical fault is present.The locking assembly can be disengaged by an input displacement or force input from a trip unit that detects and responds to an electrical fault, or by an operator pressing a "push trip" button. In some embodiments discussed herein, the trip unit may utilize a bimetallic strip that heats and deforms in an overcurrent situation and a magnetic flap that flexes in the presence of electromagnetic fields generated in the presence of short-circuit currents.

[0034] The energy to separate the movable contacts from the stationary contacts can also come from electromagnetic fields created around the stationary current loop and contact arm due to the short-circuit currents flowing through these components. The result is a repulsive force between the stationary current loop and the contact arm, causing it to move away (i.e., to be "blown open"). The strength of the repulsive force rapidly decreases as current levels drop when the electrical contacts begin to separate. As explained herein, the disclosed mechanisms are capable of preventing the movable contact arm from re-closing with the stationary contact after the repulsive force decreases by being triggered by a trip unit and by releasing elastic deformation energy to rotate the contact arm assembly such that it can no longer contact the stationary contact.

[0035] Taking into account the understanding, the planar flexure mechanisms as explained herein may be suitable for use in MCCBs in residential, commercial, or industrial applications at operating voltages of up to 1 kV DC or 1 kV AC at 50 Hz or 60 Hz and at operating currents between 5 A and 2 kA. The nominal short-circuit interrupting current may be more than ten times higher than the rated operating current. The MCCB mechanisms as explained herein may be suitable for contact arm assembly opening times between 1 ms and 100 ms and contact forces of 0.1 N to 100 N between the stationary and movable contacts. As explained herein, various embodiments of the mechanism are described which utilize elastic components that can serve both as devices capable of storing and releasing elastic deformation energy and as structural components (i.e.Connecting links) in the kinematic chain (i.e., mechanical linkage) of the mechanism. As explained herein, such resilient components may be leaf flexures, collapsible helical compression springs, coil springs, or ringed flexures used to maintain a contact arm assembly and handle yoke in either a first stable closed position or a second stable open position while exhibiting high elastic strain energy. In a third condition, with the cradle disengaged from the latch assembly and the resilient components in a relaxed condition with lower elastic strain energy, the circuit breaker mechanism may be in a tripped condition, different from the closed and open conditions.The elastic components discussed herein can enable a reduction in the number of components in the circuit breaker assembly and consequently reduce the complexity of the circuit breaker, improve the reliability and scalability of the design, and result in a lower mass or moment of inertia than a mechanism with conventional components, enabling higher operating speeds.

[0036] As used herein, elastic components are integrated into the mechanism such that these components have a higher elastic strain energy mode, and such that the mechanism has a first stable state and a second stable state while the cradle remains engaged with the locking assembly. In the embodiments illustrated herein, when the mechanism is in the first stable state, reaction forces and reaction moments of the elastic components create a moment about a pivot of the contact arm assembly such that the movable contacts contact the stationary contacts and such that the handle yoke is held in the closed position.When the mechanism is in its second stable state, reaction forces and reaction moments of the elastic components generate a moment about a pivot of the contact arm assembly to separate the movable contacts from the stationary contacts and to maintain the handle yoke in the open position. Transition between the first stable state and the second stable state of the mechanism can be accomplished by means of the handle yoke, which is mechanically connected to the elastic component. The opening and closing of the stationary contacts and the movable contacts occurs quickly and almost independently of the handle yoke speed once the elastic component passes through an unstable bifurcation point. This behavior is referred to as "mechanism snapping" and results in a "quick break" characteristic.Furthermore, in a third stable state, in which the elastic components exhibit a mode of lower elastic deformation energy, the cradle is separated from the locking assembly, and the mechanism is in a tripped state. The mechanism can transition from the first stable state to the third stable state by releasing the cradle from the locking assembly, and from the third stable state to the second stable state by moving the handle yoke from the tripped to the closed position.

[0037] As an example, and as explained in more detail below, in a first embodiment, the resilient component is a leaf flexure mounted between two ends, one of which is rigidly fixed to a lever that is part of a contact arm assembly and that forms a pivot with the mechanism frame. The rigid connection between the leaf flexure and the lever is at the pivot of the lever. The other end of the leaf flexure has a pivot on a cradle. A handle yoke, which has a pivot on the mechanism frame, is connected to the leaf flexure via a slot and projection on the flexure that forms a pivot, and a prismatic pair between the handle yoke and the leaf flexure. In this example, the cradle is held stationary during normal operation by the locking assembly engaging it.As the handle yoke is moved from the closed position to the open position, the blade flexure eventually reaches a bifurcation point and transitions from the first stable position to the second stable position. Mechanism snapping occurs rapidly and virtually independent of the handle yoke's speed. Likewise, mechanism snapping behavior occurs when the handle yoke is moved from the open position to the closed position. Furthermore, as the cradle disengages from the locking assembly, it rotates about a pivot on the mechanism frame due to the reaction forces exerted on it by the blade flexure. The rotation of the cradle causes the pivot between the cradle and the blade flexure to translate with respect to the mechanism frame, and the blade flexure achieves its unloaded shape with low elastic deformation energy content.As a result of the transition of the blade flexure element from a high elastic strain energy mode to a low elastic strain energy mode, the lever and contact arm assembly as well as the handle yoke are accelerated from the closed position to the triggered position.

[0038] Taking into account the above and now referring to Fig. Referring to Figure 1, a schematic view of certain components of the embodiment of an MCCB mechanism 100 provided in accordance with the present disclosure is illustrated. In this embodiment, and as shown, the mechanism 100 is in the closed state, as can be seen from the contact between the movable contact 108 and the stationary contact 106. Additionally, an electrically conductive current path may exist between the stationary current loop 104, the stationary contact 106, the movable contact 108, the contact arm 110, the flexible conductor 191, and the stationary terminal 190. The contact arm assembly 154 includes a lever 118 having a lever pivot 117 on the mechanism frame 102, a contact arm 110 having a contact arm pivot 155 on the lever 118, and a torsion spring 156 connected to both the lever 118 and the contact arm 110.The leaf flexure 150 exerts a moment on the lever 118, which is transmitted via the torsion spring 156 to the contact arm 110, resulting in a contact force perpendicular to the contact junction between the movable contact 108 and the stationary contact 106.

[0039] In the illustrated example, the blade flexure 150 is in a first stable closed position, held in a loaded and deformed state with high elastic strain energy by the cradle 16, which is secured to the locking assembly 186. One end of the blade flexure 150 has a flexure pivot 152 connected to the cradle 116 (i.e., relative rotational movement can still occur between the cradle and the blade flexure). The other end of the blade flexure 150 forms a rigid flexure connection 151 with the lever 118 (i.e., no relative movement is possible between the lever and the blade flexure). The lever pivot 117 is located in close proximity to the rigid flexure connection 151. In one embodiment, the leaf flexure 150 is made of a 65 mm × 15 mm × 1 mm unidirectional fiberglass composite material having a rigid flexure connection 151 with the lever 118.The rigid bending connection 151 is arranged less than 10 mm away from the lever pivot joint 117.

[0040] In the illustrated embodiment, the mechanism 100 includes a connection in the form of a handle yoke 114 connected to a handle switch 112 and having a handle yoke pivot 113 on the mechanism frame 102. The handle yoke 114 has a handle yoke slot 122 that engages a flexure projection 153, creating a prismatic pair or pivot between the handle yoke 114 and the blade flexure 150 (i.e., forming a pivot point that can move linearly with respect to the handle yoke). In this way, a change in the state of the blade flexure 150 can be transmitted to the other connected parts by actuating either the latch assembly 186, the contact arm assembly 154, the cradle 116, or the handle yoke 114 to change the positions of those connected parts.

[0041] Further illustrated in the illustrated example is a locking assembly 186 which, when engaged, maintains the mechanism in either the closed or open state. The illustrated locking assembly includes a primary lock 182 engageable with the cradle 116 at a primary locking interface 172 and a secondary lock 178 engageable with the primary lock 182 at a secondary locking interface 174.In the illustrated example, a locking bias spring 180 is provided between the primary latch 182 and the secondary latch 178 such that, when disengaged from each other, the locking bias spring 180 can bias the primary latch 182 and the secondary latch 178 toward each other such that the cradle 116 can be re-engaged by moving the handle yoke 114 after the mechanism has been triggered. As will be appreciated, the illustrated locking assembly 186 is a double locking assembly (i.e., there are two engagement connections, the first between the primary latch 182 and the secondary latch 178, and the second between the primary latch 182 and the cradle 116).In other embodiments, the locking arrangement may differ, for example, by being a single locking arrangement between a primary lock and a cradle, or a triple or multiple locking arrangement having more than two locks.

[0042] The contact arm assembly 154 includes a contact arm 110 having a contact arm pivot 155 disposed on the lever 118. A contact arm torsion spring 156 creates a moment between the lever 118 and the movable contact arm 110. In the illustrated closed state of the MCCB mechanism 100, the lever 118 is oriented to rotate the contact arm 110 away from a contact arm stop 162, resulting in a contact force between the movable contact 108 and the stationary contact 106. The displacement of the contact arm 110 relative to the contact arm stop 162 is referred to as "contact arm drop." In other embodiments discussed herein, the torsion spring 156, the contact arm pivot 155, and the contact arm stop 162 may be omitted, and the resilient component may be attached directly to the contact arm 110.In this case, the elastic component directly generates the moment required for a contact force between the movable contact 108 and the stationary contact 106. Also in this case, the blade flexure 150 can directly provide the required elastic compliance for an open burst event to occur.

[0043] In Fig. 2, the mechanism 100 is illustrated in the second stable state, or "open" position. The contact arm assembly 154 consists of a contact arm 110, the movable contact 108, a contact arm pivot 155, the lever 118, a contact arm torsion spring 156, and the contact arm stop 162. The contact arm 110 is rotated counterclockwise about the contact arm pivot 117 with respect to the lever 118 due to the moment applied by the contact arm torsion spring 156 such that the contact arm 110 contacts the contact arm stop 162. This orientation of the contact arm assembly is typically always when the contact arm assembly is not in contact with the stationary contact 106.

[0044] In general, it may be desirable to position the circuit breaker mechanism 100 between the Fig. 1 shown closed position and an open position as shown in Fig. 2, without tripping it. That is, it may be desirable to allow an operator to open the electrical circuit in a manner other than tripping the circuit breaker mechanism. For example, the MCCB mechanism 102 is Fig. 2 in an open position, as illustrated by the contact arm assembly 154 being separated from the stationary contact 106. The MCCB mechanism 100 can thus be opened or closed by a user or operator removing the handle yoke 114 from the Fig. 1 to the position of the handle yoke 114 as shown in Fig. 2. It may also be desirable to allow an operator to open the electrical circuit by moving the handle yoke 114 from the position shown in Fig. 2 shown position to that in Fig. 1 shown position.

[0045] By now on Fig. 3, the MCCB mechanism 100 is illustrated in a mode between the first and second stable states when the handle yoke 114 and the switch 112 are moved from the closed to the open position. Because the locking assembly 186 is unchanged, unmoved, and remains engaged, the end of the leaf flexure 150 connected to the cradle 116 by means of the flexure pivot 152 remains secured and stationary with respect to the mechanism frame 102. Movement of the handle yoke 114 causes a force to be applied to the flexure projection 153 through the handle yoke slot 122. As a result of the force, the leaf flexure 150 begins to bend from its first stable closed position toward its bifurcation point between the first and second stable states. Upon still further movement of the handle yoke 114 toward the Fig. 2, the bifurcation point of the sheet bending element 150 is reached and the transition to the position shown in Fig. 2. This transition occurs suddenly and quickly and is almost independent of the speed at which the handle yoke is moved by the operator, resulting in a "quick break" of the electrical circuit and minimal electrical arcing. Movement at the prismatic pair and the rotating pair can take the form of sliding and rotation of the blade flexure 150 with respect to the handle yoke 114. With reference to Fig. 4, the MCCB mechanism 100 is illustrated in a mode between the first and second stable states when the handle yoke 114 is moved from the open to the closed position. This scenario is the reverse of the operation described above and the transition to the Fig. The state of the mechanism illustrated in Figure 1 results in a “rapid establishment” of the electrical circuit.

[0046] As in Fig. 5, in addition to the open state and the closed state, the MCCB mechanism 100 may further be in a third stable state (i.e., a tripped state) in which there is no contact between the movable contact 108 and the stationary contact 106 and in which the leaf flexure 150 has low elastic deformation energy. This state may be achieved from the closed position when the leaf flexure 150 has high elastic deformation energy and such that there is a reaction force acting on the cradle 116, causing counterclockwise movement of the cradle 116 about the cradle pivot 158. The trip event is initiated when a trip unit or "push trip" button pressed by an operator initiates clockwise rotational displacement of the secondary latch 158 about the secondary latch pivot 176.This causes the secondary locking joint 154 to lose contact with the secondary lock 158, and the reaction force at the primary locking joint 152 between the cradle 116 and the primary lock 182 causes the primary lock to rotate clockwise. This causes the primary lock 116 to lose contact with the primary locking joint 172, leaving the cradle 116 free to rotate counterclockwise about the cradle pivot 158.

[0047] Around the MCCB mechanism 100 in Fig. 1 from a closed state in which the leaf bending element 150 has a state with high elastic deformation energy, to a triggered state of the mechanism 100 in Fig. 5, in which the leaf flexure 150 is in a low elastic deformation energy state, it is necessary for the deformation energy to be converted into kinetic energy of the various components of the mechanism that move during the transition, including, for example, the handle yoke 114, the contact arm assembly 154, the latch assembly 186, the leaf flexure 150, and the cradle 116. Relaxation of the leaf flexure 150 results in a moment that accelerates the lever 118 from the rest state, allowing the contact arm assembly 154 to rotate away from the stationary contact 106 and thus open the electrical circuit.The MCCB mechanism 100 comes to a stop in the tripped configuration once the blade flexure 150 has converted its elastic deformation energy into kinetic energy of the moving components, and once this kinetic energy has been absorbed by friction or losses due to inelastic impacts at the various stops, e.g., between the yoke cam 120 and the yoke follower 160. It should be noted that the torsion spring 156 may also contribute elastic deformation energy in the tripping event.

[0048] In the triggered state of the MCCB mechanism 100, and as in Fig. 5, the handle yoke 114 is in a tripped position between the closed position and the open position, indicating to an operator that the MCCB mechanism 100 has tripped. In the tripped state, the leaf flexure 150 is illustrated in an undeformed configuration, which is due to the flexure pivot 152 no longer being held stationary with respect to the mechanism frame 102 by the cradle 116. Generally, in order to return the contact arm assembly 154 to contact with the stationary contact 108 after a tripping event, the MCCB mechanism 100 must be moved (i.e., reset) to the open configuration before being moved to the closed configuration. That is, because the latch assembly 186 is disengaged when the MCCB mechanism 100 is tripped, the act of moving the handle yoke 114 from the position shown in Fig. 5 shown triggered position to that shown in Fig. 2, the yoke cam 120 exerts a force on the yoke follower 160, causing the cradle 116 to rotate clockwise toward the primary lock 182. Simultaneously, the handle yoke slot 122 exerts a force on the flexure projection 153 to move the leaf flexure element 150 from the released state with low elastic deformation energy to the open state with higher elastic deformation energy, as shown in Fig. 2. When the open state of the MCCB mechanism 100 is reached, the primary locking connection point 172 contacts the cradle 116, and the secondary locking connection point 174 contacts the secondary lock 178.

[0049] The mechanical movements of the components, as described above, are determined by various kinematic pairs provided as part of the assembly. For example, certain kinematic pairs may be rotary joints (i.e., pivot points), prismatic pairs (i.e., sliding devices), or cam followers (i.e., surface-to-surface contacts). Referring to Fig. 1, the kinematic pairs may or may not be fixed in position with respect to the mechanism frame 102. Fixed kinematic pairs include pivots that rely on extensions or hole features of the mechanism frame 102, the circuit breaker housing wall, or surface. For example, the cradle pivot 158, about which the cradle 116 rotates, is fixed with respect to the mechanism frame 102, the lever pivot 117, about which the lever 118 rotates, is fixed with respect to the mechanism frame 102, the secondary lock pivot 176, about which the secondary lock 178 rotates, is fixed with respect to the mechanism frame 102, and the handle yoke pivot 113, about which the handle yoke 114 rotates, is fixed with respect to the mechanism frame 102.The primary locking slot 181 and the primary locking pin 184 form a prismatic pair and a pivot joint that allow the primary lock 178 to translate and rotate relative to the mechanism frame 102. This is utilized in resetting the locking assembly 186 after it has been triggered.

[0050] Conversely, different kinematic pairs move with respect to the mechanism frame 102, and they are determined by the Fig. 1, which includes the flexure pivot 152, which is defined by the interaction between the blade flexure 150 and the cradle 116. Another moving kinematic pair is the contact arm pivot 155, which is defined by the interaction between the contact arm 110 and the lever 118 (as mediated by the torsion spring 56). The handle yoke slot 122 and the flexure projection 153 form a prismatic pair and a pivot joint that allows the blade flexure 150 to rotate and translate with respect to the handle yoke 114. In the example shown, the various kinematic pairs shown define the available movements and ranges for the illustrated components in response to both internally and externally applied forces and displacements. As mentioned above, the Fig. The MCCB mechanism 100 illustrated in Figure 1 also includes higher-order kinematic pairs formed between surfaces of the illustrated components that may be in contact with each other. For example, the yoke cam 120 may engage the yoke follower 160 when the cradle 116 and the handle yoke 114 are in the tripped position to reset the mechanism from the tripped to the open configuration.

[0051] As an example, in the embodiment of the MCCB mechanism 100 shown in Fig. 6, the elastic component of the mechanism consists of a leaf flexure 150 mounted such that a first end includes a flexure pivot 152 on the cradle 116 and such that a second end includes a secondary flexure pivot 170 on the contact arm 110. The secondary flexure pivot 170 is offset from the lever pivot 117 by between 2 mm and 100 mm. As the mechanism moves between the closed, open, and tripped states, the curvature of the leaf flexure 150 may or may not remain deflected to one side (i.e., the curvature of the leaf flexure may or may not change from positive to negative or vice versa).

[0052] As a further example, in the embodiment of the mechanism 100 shown in Fig. 7, the elastic component of the mechanism consists of a buffer spring mounted such that a first end has a pivot 152 on the cradle 116 and a second end has a secondary pivot 170 on the contact arm 110. The secondary pivot 170 is offset from the lever pivot 117. As the mechanism moves between the closed, open, and tripped states, the buffer spring contracts primarily in its axial direction and expands primarily in its axial direction (i.e., the curvature of the buffer spring remains small).

[0053] Furthermore, the handle yoke 114 in the Fig. The embodiment illustrated in Figure 7 comprises two separate structures parallel to each other, with the buffer spring 138 positioned between these separate structures. The connection point between the buffer spring 138 and the handle yoke 114 is illustrated as a pair of crossbars 136 that connect the separate components of the handle yoke 114 through which the buffer spring 138 extends.

[0054] In another example, in the Fig. In the embodiment of the MCCB mechanism 100 illustrated in Figure 8, the elastic component of the mechanism consists of a ringed flexure 139 connected at one end to the cradle 116 via a flexure pivot 152 and at the other end to the lever rotor 130 via a rigid flexure connection 151. The mechanism 116 is illustrated as a single-phase, double-break mechanism, with the contact arm assembly consisting of a lever rotor 130, two contact arm stops 162, two contact arms 110, two movable contacts 108, two torsion springs 156, and two contact arm pivots 155. A current flows through the first stationary current loop 104, the first stationary contact 106, the contact arm assembly, the second stationary contact 106, and the second stationary current loop 104.

[0055] As an example, in the embodiment of the MCCB mechanism 100 shown in Fig. 9 in the first stable closed state, the resilient component of the mechanism consists of a collapsible compression spring 140 (shown in cross-section) that is collapsed and compressed, with a first end rigidly connected to a flexure follower 144 that contacts the cradle 116 at a cradle control surface 142. This allows in-plane rotation of the collapsible compression spring 140 with respect to the cradle 116. A second end of the spring 140 is rigidly connected to the contact arm 110.

[0056] Furthermore, in this embodiment, the handle yoke 114 comprises two separate structures parallel to each other, with the collapsible compression spring 140 positioned between these separate structures. The connection point between the collapsible compression spring 140 and the handle yoke 114 is illustrated as a pair of crossbars 136 that connect the separate components of the handle yoke 114 through which the collapsible compression spring 140 extends.

[0057] With reference to Fig. 10, the MCCB mechanism 100 is illustrated in the second stable open state in which the collapsible compression spring 140 is compressed and collapsed, with the contact arm assembly consisting of the contact arm 110, the movable contact 108, and the lever pivot 117 not contacting the stationary contact 106.

[0058] With reference to Fig. 11, the MCCB mechanism 100 is illustrated in its third stable deployed state. In this state, the collapsible compression spring 140 is not collapsed and is less compressed than in the first and second states, exhibiting a state of lower elastic deformation energy. In this example, the locking assembly 186 has been disengaged, as illustrated by the separation or disengagement of the cradle 116 from the primary latch 182. In response to the disengagement of the locking assembly 186, the cradle 116 may rotate with respect to the cradle pivot 158. This rotation allows the collapsible compression spring 140 to release deformation energy and move toward a relaxed state by expanding and recovering from the collapsed state.

[0059] The above examples have, for simplicity and ease of explanation, illustrated planar or other bending mechanisms for MCCBs that may be used in single-phase, single-break configurations. However, it should be recognized that any of the aforementioned approaches may be applied in other configurations, such as multi-phase (e.g., three-phase) or double-break arrangements, as well as in AC or DC circuits. For example, and with reference to Fig.12, a three-phase single-break MCCB mechanism 100 is shown, including a torsion bar 135 connecting three contact arm assemblies to the circuit breaker mechanism. Likewise, various arrangements of interlock assemblies, external trip units, and contact arm assemblies other than those described may be used in conjunction with resilient components that mediate the transition from the open, closed, and tripped states of the MCCB mechanism.

[0060] Technical effects of the invention include the construction and use of an MCCB mechanism including resilient components connecting a cradle to a contact arm assembly. In a first embodiment, the resilient component is a leaf flexure rigidly connected to a contact arm assembly. In a second embodiment, the leaf flexure has a pivot on the contact arm assembly offset from the lever pivot. In a third embodiment, the resilient component is a buffer spring. In a fourth embodiment, the resilient component is a ringed flexure, and in a fifth embodiment, the resilient component is a collapsible compression spring. A handle yoke may also be connected to the resilient component to transition the mechanism from a first stable closed state to a second stable open state when the cradle is held stationary.The handle yoke is moved to a tripped position by the elastic component when the mechanism is tripped, transitioning to a third stable tripped state. The handle yoke can be used to reset the mechanism by re-engaging the cradle with the locking assembly, imparting elastic deformation energy to the elastic component and transitioning the mechanism to the open state. The components of the mechanism can provide a low mass and low moment of inertia, enabling high angular acceleration of the contact arm assembly.

[0061] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be included within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

[0062] Embodiments of a tristable flexure mechanism are described in which an elastic component is present that serves both as a structural component in the mechanism's kinematic chain and as an energy storage component of the mechanism. The elastic component maintains a movable arm and an input link in either a first stable state or a second stable state when the ends of the elastic component are held in position such that the elastic component has a high elastic strain energy state. In a third stable state, in which the elastic elements are in a relaxed state with lower elastic strain energy, the mechanism may be in a triggered state, which is different from the closed and open states.

Claims

[1] Actuation system (100) comprising: a locking assembly (186) configured to be releasably engaged with a cradle (116); a movable arm (110); an elastic component (150) having a first end with a pivot joint (152) on the cradle (116) and a second end connected to the movable arm (110), the elastic component (150) being elastically deformed and stores elastic deformation energy in either a first state or a second state when the locking assembly (186) is engaged with the cradle (116), and wherein the elastic component (150) is in a third state in which it is not substantially elastically deformed and stores substantially no elastic deformation energy when the locking assembly (186) is not engaged with the cradle (116); and an input link engaged with the elastic component (150) between the first end and the second end, wherein movement of the input link between a first position and a second position, when the locking arrangement (186) is engaged with the cradle (116), the elastic component (150) transitions between the first state and the second state. [2] The actuation system (100) of claim 1, wherein the input linkage comprises a yoke cam (120) in communication with a yoke follower (160), and wherein movement of the input linkage from a third position to a second position transitions the mechanism to the second state in which the resilient component (150) is under tension and the locking assembly (186) is engaged; and / or wherein the input connection has a slot and the elastic component (150) has a projection by which a complementary engagement connection structure is formed between the elastic component (150) and the input connection; or wherein the input connection comprises a pair of cross bars which are in contact with the elastic component (150) and by which the elastic component (150) is arranged to be movable. [3] The actuation system (100) of claim 1 or 2, wherein the elastic component (150) is rigidly attached to the respective movable arm (110); or wherein the elastic component (150) is attached to the respective movable arm (110) via an offset pivot joint. [4] An actuation system (100) according to any one of the preceding claims, wherein the respective movable arm is a contact arm (110) adapted to move between a contact position and a non-contact position with a stationary contact (106); or wherein the respective movable arm (110) is a contact arm assembly (154) comprising a contact arm (110), a lever (118), a contact arm pivot (155), a torsion spring (156), and a contact arm stop (162) configured to move between a contact position and a non-contact position with a stationary contact (106); or wherein the respective movable arm (110) is a contact arm assembly (154) comprising a lever rotor (130), two contact arms (110), two contact arm pivots (155) and contact arm torsion springs (156) configured to move between a contact position and a non-contact position with stationary contacts (106). [5] An actuation system (100) according to any one of the preceding claims, wherein the at least one movable arm (110) comprises two or more movable arms (110) mounted on a common torsion bar (135) connected to the mechanism. [6] The actuation system (100) of any preceding claim, wherein the first state comprises a closed state in which the respective movable arm (110) contacts a stationary contact (106), and the second state comprises an open state in which the respective movable arm (110) does not contact the stationary contact (106); and / or wherein the third state comprises a triggered state in which the respective movable arm (110) does not contact the stationary contact (106). [7] Actuation system (100) according to any preceding claim, wherein the input connection is a handle yoke (114); and / or wherein the elastic component (150) comprises either a leaf flexure element (150) or a buffer spring (138) or a ringed flexure element (139) or a helical compression spring (140). [8] A method of actuating a movable arm (110), the method comprising: Maintaining an elastic component (150, 138, 139, 140) in a state having elastic deformation energy in a first state or a second state; Holding a movable arm (110) in a first position while the elastic component (150, 138, 139, 140) is in the first state; Releasing the elastic deformation energy from the elastic component (150, 138, 139, 140) in response to an input displacement or force input such that the elastic component (150, 138, 139, 140) is in a third state corresponding to a relaxed state; Rotating the movable arm (110) in response to the released elastic deformation energy so that it is no longer in the first position; and Moving an input link to a triggered position in response to the released elastic deformation energy. [9] A method according to claim 8, comprising: in response to the input link being moved from a first position to a second position, transferring the elastic component (150, 138, 139, 140) to the second state while maintaining the elastic component (150, 138, 139, 140) elastically deformed such that the elastic component (150, 138, 139, 140) stores elastic deformation energy; and / or in response to the elastic component (150, 138, 139, 140) assuming the second state, rotating the movable arm (110) so that it is no longer in the first position; and / or in response to the input link being moved from the triggered position to a second position, transitioning the elastic component (150, 138, 139, 140) from the third state in which substantially no elastic deformation energy is stored to the second state in which elastic deformation energy is stored. [10] Circuit breaker arrangement comprising: a locking assembly (186) configured to releasably engage a cradle (116); a movable arm (110) configured to move between a closed circuit position and an open circuit position; a leaf flexion member (150) having a first end with a pivot (152) on the cradle (116) and a second end connected to the movable arm (110).

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