Abstract: A circuit breaker characterized by a movable contact on a contact-carrying arm movable between open and closed positions of a stationary contact mounted on one leg of a U-shaped conductor with another leg secured to the circuit breaker housing, a U-shaped brace between the legs and having a first support supporting and insulated from the other leg and having second supports on opposite sides of the one leg for retaining it against opposing repulsion magnetic forces due to current overloads.

Abstract: A reverse loop circuit breaker characterized by a movable contact mounted on a contact-carrying arm movable between open and closed positions of a stationary contact that is mounted on one leg of a U-shaped conductor with another leg secured to the circuit breaker housing, an insulating block between the legs and including a pair of separable block portions having oppositely facing grooves for receiving edge portions of at least one leg to restrain its deflection, and means for securing the block portions together.

Abstract: A circuit breaker with a shock-absorbing mechanism characterized by a movable contact arm operable between open and closed positions of separable contacts, a stop member for stopping movement of the contact arm which member is integral with a housing for the circuit breaker, and a shock-absorbing plate on the member for spreading the energy released when the contact arm collides with the stop member.

Abstract: A bridging contact is arranged across two fixed contacts with a pair of parallel, closely spaced conductors serving as the bridging contact carrier. A high current pulse in opposite direction within the parallel conductors generates electrodynamic forces rapidly propelling the conductors further apart. The bridging contact carried by the parallel conductors is rapidly driven out of contact relation with the fixed contacts to interrupt the circuit.

Abstract: A current limiting type circuit breaker includes first and second contact arms each pivotally mounted so as to be driven to an open position by an electromagnetic repulsive force, a trip device responsive to an output from a means for detecting a fault to drive the second contact arm to the open position, magnetic substances placed at opposite sides of the contact arms so that the magnetic resistance for magnetic fluxes occurred around the contact arms is decreased, and an attracting stationary conductor placed near the free end of the second contact arm in the open position. The attracting stationary conductor is connected in series with the first contact arm. When an excessive current flows through the contact arms, an electromagnetic attractive force is generated between the attracting stationary conductor and the second contact arm, which force increases the rate at which the second contact arm is moved to the open position.

Abstract: A molded case circuit breaker includes a movable upper electrical contact carried by a movable arm having an end portion with an arcuate cam surface formed thereon for engaging an outwardly projecting cam surface of a spring-loaded clip that is disposed in a recess formed in a rotatable cross-bar of an operating mechanism of the circuit breaker. At least one compression spring is retained within the recess between the cross-bar and the spring clip. The spring clip is configured to transfer sufficient biasing force to the end portion of the movable upper electrical contact end to enable the upper electrical contact arm to move in unison with the cross-bar when the circuit breaker is tripped. Upon the occurrence of a high level short circuit or fault current of sufficient magnitude, the upper electrical contact arm and contact rotate independently of the cross-bar and the arcuate cam surface of the arm is moved against the then stationary spring clip cam surface.

Abstract: An electric circuit breaker with blow open contact arm characterized by a pair of separable contacts one of which is mounted on a contact arm that is rotatably mounted on mounting bracket. The contacts maintain a repulsion magnetic force which operates to separate the contacts when a predetermined current overload occurs. A trip mechanism is connected to the mounting bracket or automatic opening of the contacts in response to a predetermined current overload condition. The contact arm comprising a cam and the mounting bracket comprising a cooperable cam follower whereby the contact arm is movable to an open contact independently of the mounting bracket.

Abstract: A low voltage circuit breaker with remote switching function characterized by an insulating housing containing manually actuator for opening and closing separable contacts and a remotely controlled solenoid for opening the contacts, and the solenoid means being spring biased in the closed contact position only when the manually actuator is in the closed contact position.

Abstract: A contact assembly for electrical circuit breakers has a contact lever and a lever support with the contact lever mounted thereon in an articulate fashion. The support lever is flexibly positioned around a fixed pivot bearing by a drive linkage device for on- and off-switching cycles. A pressure lever is used to introduce a current-dependent force onto the contact levers in order to increase the contact force. The pressure lever is similarly flexibly mounted onto the lever support. The contact lever and the pressure lever operate jointly via their working surfaces which permit a conveyance of force in terms of an increase of the contact force. When switching on the contact assembly, the pressure lever is decoupled from the contact lever so that the tendency to bounce is reduced.

Abstract: An electric circuit breaker with high interrupting capacity characterized by a multi-phase circuit breaker including a crossbar rotatable on its longitudinal axis and having an enlarged portion; a contact carrying arm pivotally mounted on the enlarged portion in response to an overload current at a positions paced from the axis; and a spring biased retainer contacting the arm for yieldingly retaining the arm in a contact closed position below a predetermined current rating.

Abstract: The electromagnetic forces tending to force open the contacts of an electromagnetic contactor are reduced by providing a current flow path having a geometry that tends to minimize the magnetically produced forces acting upon the movable contact of an electromagnetic contactor. A contactor has a frame, a stationary contact attached to the frame, a first conductor supplying the stationary contact, an armature rotatably mounted in the frame, a movable contact attached to the armature, and a second conductor supplying the movable contact. An arm has a first arm end supporting the movable contact and a second arm end attached to the armature.

Abstract: Individual movable contactors of a circuit breaker are made up of a pair of conductors. The first conductor has one end bifurcated to form a pair of legs separated by a slit. At the open end each leg has a curved inner portion the opposed curved portions of the two legs defining a receptor space which is substantially circular in cross section. The second conductor has one end whose cross section is substantially circular and which fits within the receptor space and makes a good slidable contact therewith, and the other end which supports the main contact. Provision is made for rotating the second conductor about its circular end for opening or closing connection to the main contact.

Abstract: A current limiting circuit breaker is provided which has a stationary contact assembly and a movable contact bridge. A contact carrier is connected to the contact bridge and biases the contact bridge toward the closed position. The downward biasing force on the contact bridge is mechanically reduced in response to a preselected amount of opening movement of the contact bridge.

Abstract: A stationary contact assembly is provided for a current limiting circuit breaker. The contact assembly includes a curved input arm which has a contact fastened thereon and a generally straight output arm which also has a contact fastened thereon and which has an opening for receiving the contact end of the input arm. The contacts are encapsulated in an insulating material which separates the contact arms from each other. A magnetic element is also embedded in the encapsulation material between the input and output contact arms. As current flows through the contact arms, a field is developed about the magnetic element which draws in an armature which reduces the opening force of the contacts.

Abstract: The gap distance separating the contacts of a low-voltage circuit breaker in the tripped position is increased by utilizing resilient stop means which is located at the bottom wall of the breaker housing rather than at the top wall (or on the handle of the breaker) in accordance with prior art practice. The movable contact arm is pivotally mounted and structured to strike the stop means as the contacts are separated and being blown open during short circuit conditions and, after the circuit breaker is tripped, the collapsed toggle assembly of the operating mechanism shifts the movable contact arm away from the stop means and allows the arm to move an additional distance away from the fixed contact and thus increase the gap distance between the opened contacts.

Abstract: A contact arrangement for a current limiting circuit breaker wherein two movable contact arms are interconnected by means of a pair of connecting arms and a manually operable push rod. An electromagnet is operatively coupled with one of the contact arms for holding in an open condition when the electromagnet is de-energized. The disclosed contact arrangement allows the circuit breaker to be multifunctionally employed as an integrated combination motor starter.

Abstract: An anti-rebound latch having a generally U-shaped housing which defines a central blade path opening between first and second side legs. The housing supports a pivotally mounted generally crescent shaped drive-arm which includes a kicker portion at one end positioned adjacent the top of the blade path opening and a pusher portion at its opposite end. The drive-arm is operatively associated with a blade catcher carried by the first side leg which is reciprocally movable between a first position in which no part of the blade catcher extends into the opening and a second position in which the catcher extends across the opening to the second side leg. The catcher is spring biased to its first position.

Abstract: A circuit breaker contact configuration reduces the occurrence of contact bounce by providing a reverse force to the contacts during contact closure. This reduces the contact closing shock energy, while keeping the contact bias force constant. In one embodiment, the reverse force is obtained by means of a counteracting spring which engages one of the contact arms at a point along the rebound path. Another embodiment comprises transferring the pivot point of one of the contacts from a first to a second position at a point along the rebound path.

Abstract: It is the main object of this invention to provide a circuit breaker in which the movable contacts have sufficient opening force and opening distance, and in which the breaking time is short. In order to attain the object, the circuit breaker of this invention is provided with a dead center link mechanism comprising a movable contact link which is rotatably supported by the arms of a cross bar which is operated so as to be capable of opening-closing the circuit and tripping by means of a trip-free mechanism, and a toggle spring which is bridged between the cross bar and the movable contact link. When a large current such as a short-circuit current flows, a movable steel plate attracted by an electromagnet for instantaneously tripping hits a rod for supporting the movable contacts which is connected to the movable contact link, whereby the dead center link mechanism makes the movable contacts open at high speed from the fixed contacts.

Abstract: A latching mechanism is arranged to engage one of the movable contact arms upon magnetic repulsion of the contact arms independent of the operating mechanism to prevent the contact arm from re-closing until the operating mechanism has responded. An operating lever reacts with the contact arm latching mechanism to articulate the operating mechanism to trip the breaker after the latching mechanism has fully engaged the contact arm.

Abstract: A movable contact arm assembly is provided for a circuit breaker. The contact assembly includes a carrier which has first and second guide plates with aligned roller guides and bracket supports and a roller which has a middle portion extending between the guide plates and the end portions and engaging the roller guides. A bracket extends between the guide plates and engages the bracket supports. A spring is positioned between the bracket and roller which urges the roller along the roller guide. The contact arm has first and second cam surfaces and is positioned between the guide plates and pivotally connected thereto. The roller rides in the guide on the first and second cam surfaces and the roller moves from the first cam surface to the second cam surface as the contact arm moves from a closed position to an open position in response to preselected electromagnetic repulsion forces.

Abstract: An improved remotely controllable circuit breaker comprises a manually operable switching mechanism for opening and closing a single set of first and second contacts, a trip mechanism for opening the contacts upon occurrence of predetermined overload current conditions, and a remotely controllable switching mechanism for selectively opening and closing the contacts in response to a control signal remote from the breaker. The manually operable switching mechanism includes a movable contact arm carrying the first contact to be brought into and out of contacting engagement with the second contact by manipulation of a manual handle. The second contact is operatively connected to the remotely controllable switching mechanism to be driven thereby for movement between an operative position where the second contact is engageable with the first contact and an inoperative position where it is prohibited from being engaged with the first contact independently of the position of the first contact.

Abstract: A circuit breaker for high-speed current-limiting breaking of a three-phase current in the event of a short-circuit condition. The breaker has three pairs of fixed and movable contactors, the latter being arranged for pivoting movement on a common shaft. The center movable contactor is biased against an opposing holder, such that in the event of a short-circuit, the bias is overcome and the movable contactors separate in unison from the fixed contactors.

Abstract: A current limiting circuit breaker utilizes a first pair of contacts for carrying continuous current and controlled by an operating mechanism. A second pair of contacts is arranged on a pair of movable contact arms ahead of an arc chute for rapid repulsion under high current fault conditions.

Abstract: A blow open contact arm assembly is provided for a molded case circuit breaker. A ferromagnetic carrier is attached to the movable contact arm and is positioned thereabout for creating a magnetic field about the movable contact arm which attracts the contact arm to the open position during severe fault conditions. The molded case housing has reinforced walls to withstand the pressures exerted on the walls of the houses during a blow open operation of the contacts.

Abstract: A contact that has two fixed contact elements and a mobile contact bridge actuated by a switching assembly and is urged by a pole spring. The connection between the mobile contact bridge and switching assembly is provided by a magnetic compensator connected to the switching assembly by means of a magnetic coupling device adapted so that, when the compensating forces rise above a given threshold, the magnetic compensator is disengaged from the switching assembly and becomes inoperative.

Abstract: In a current-limiter electric switch having fixed contacts, movable contacts, remote control means active upon the movable-contact-carrier against spring bias, thermomagnetic protection means being also provided, the remote control means is a solenoid the core of which is directly connected to the movable-contact-carrier and in the excitation circuit of the solenoid contacts are provided, which are opened when controlled by the thermomagnetic protection devices to have the solenoid dropped in the case of overcurrents which cause said protection devices to enter action.

Abstract: Several braids (26) to connect a moving contact (10) to a lug (14) for the current lead are attached to the lug by welding under pressure, the ends (32) of the braids (26) being placed in slots (34, 36, 38) made in the face of the lug (14). The welding occurs without any need of hard solder.

Abstract: The switch comprises a stationary contact (2) and a moving contact (3) subjected to the action of a magnetic component (12). The moving contact (3) is carried by a rocker-arm (4) which pivots about a pin (10) rigidly fixed to a control device (6). The extremity (4a) of the rocker-arm carries a second pivot-pin (15) which is connected to a mechanical threshold device (18). The second pivot-pin is capable of displacement between a normal position in which the contacts (2, 3) can be closed and opened by the control device and a trip position in which the contacts are permanently separated. The magnetic component (12) occupies a position such as to exert on the rocker-arm (4) a torque which increases the contact pressure prior to tripping of the threshold device and produces a pivotal displacement of the rocker-arm about its pivot-pin (10) in the direction of opening of the contacts after tripping of the threshold device (18).

Abstract: A circuit interrupter which comprises a pair of separable contact structures each including a contact element, at least one of the contact structures being movable between a closed position and an open position relative to the other contact structure for opening and closing an electric circuit extending through the circuit interrupter, the movable contact structure having an arm support that is pivotable about an axis, a movable contact arm pivotally supported on the arm support and extending in a parallel and an opposite direction to the other contact structure for generating an electromagnetic repulsive force therebetween, and a biasing means connected between the arm support and the movable contact arm for biasing the movable contact arm to a predetermined position with respect to said arm support, and an operating mechanism connected to the arm support of the movable contact structure for separating the movable contact structure from the stationary contact structure in response to an overcurrent flowing t

Abstract: An electric circuit breaker having fast short circuit response along with reduced arc energy is provided by means of a current limiting contact arm arrangement. The contact arm is arranged to pivot independently of the circuit breaker operating mechanism under the influence of magnetic repulsion forces. A contact spring configuration controls the rate at which the contacts separate, thereby limiting the energy of the arc created upon contact separation.

Abstract: The invention concerns a very simple and effective current limiting circuit breaker of great versatility which is especially adaptable for motor control centers and combinations starters. That breaker can be used with various interchangeable trip units always with the same basic mechanism.(a) for instantaneous trip type circuit breakers of various current ratings having high interrupting capacity and low I.sup.2 t value to protect control equipment at high fault currents.(b) for high interrupting capacity thermal magnetic circuit breakers at various current ratings.(c) for circuit breakers with solid state tripping units to protect against overloads, short circuits, single phasing, underloads, etc.

Abstract: High speed trip facility is provided within a molded case circuit breaker used within industrial applications. The movable contact arm is pivotally arranged to open independently of the trip unit-driven operating mechanism. A "latch kicker" arrangement interfaces between the mechanism trip bar and the circuit breaker intermediate latch whereby rotation of the trip bar causes the latch kicker to immediately displace the intermediate latch from the circuit breaker cradle thereby allowing the interrupter mechanism to untoggle the mechanism and open the breaker contacts.

Abstract: A current-limiting electric switch for low-voltage has a contact device with a contact finger and an elongated fixed contact arranged side by side. The contact finger is rotatably arranged and forms at one end a break together with the fixed contact and is at the other end provided with a flexible current connection conductor. The contact finger has its bearing point located between the two ends of a movable arm. Through the influence of electrodynamic forces from short-circuit currents, the contact finger is first rotated in one direction of rotation while maintaining the galvanic contact at the break, whereby the movable arm is displaced so that the distance between the bearing point of the contact finger and the fixed contact is increased. A stop means limits the movement of the contact finger in the first direction of rotation and brings about a continuation of the rotational movement in the opposite direction of rotation resulting in an instantaneous contact opening.

Abstract: A residential or commercial circuit breaker of the narrow width type, typically having a width of 3/4 inch or 1 inch, is provided with a magnetically permeable slot motor 102 mounted within the case 2 and around both current carrying conductors 8 and 12 for concentrating magnetic repulsive force and boosting the contact separating force.

Abstract: A residential or commercial circuit breaker of the narrow case type, typically having a width of 3/4 inch or 1 inch, is provided with a single-piece nonlaminated slot motor 102 mounted within the case 2 and around current carrying conductors 8 and 12 for concentrating magnetic repulsive force and boosting contact separation force. A dramatic increase in short circuit interruption capacity is achieved, at minimal cost.

Abstract: A residential or commercial circuit breaker of the narrow case type, typically having a width of 3/4 inch or 1 inch, is provided with a combination slot motor and arc chute 102 mounted within the case 2 and around the current carrying conductors 8 and 12. The combination slot motor and arc chute 102 concentrates the current-induced magnetic repulsive force between the conductors 8 and 12 to boost contact separation force, and also extinguishes the arc. The slot motor portion 106, 108 of the combination structure 102 continues to support the magnetic force which tends to force the arc into the arc chute portion 104 away from the contacts 10, 16 and operating mechanism. The combination slot motor and arc chute 102 is particularly simple and inexpensive, yet very effective within the size constraints of the narrow type breaker case 2.

Abstract: A molded case circuit breaker includes an operating mechanism having an integral or one-piece, rotatable, molded cross bar. The cross bar includes an enlarged section, associated with each phase or pole of the circuit breaker, having a window, pocket or enclosed opening formed therein for the receipt of a base portion of an upper movable electrical contact of a pair of separable electrical contacts. Also disposed in the opening is a compression spring and an associated spring follower positioned between the compression spring and the base portion of the upper electrical contact. The compressive spring force biases the upper electrical contact for movement in unison with the cross bar. Upon the occurrence of a high level short circuit or fault current condition, the spring follower may be downwardly deflected to enable the upper electrical contact to move independently of the cross bar.

Abstract: A molded case circuit breaker includes a movable upper electrical contact having a base portion with a slot formed therein for releasably receiving a portion of an elongated spring biased locking pin disposed in a rotatable cross bar of an operating mechanism of the circuit breaker. The locking pin is biased in the slot by a pair of tension springs secured to the cross bar, enabling the upper electrical contact to move in unison with the cross bar. Upon the occurrence of a high level short circuit or fault current of sufficient magnitude, the pin is displaced from the slot enabling the independent rotational movement of the upper contact arm. During such movement, an elongated leaf spring is downwardly deflected and then released by the base portion. Subsequently, the upper electrical contact is prevented from contacting the lower electrical contact by the engagement of the leaf spring with the base portion.

Abstract: A circuit breaker capable of breaking an associated circuit when an overcurrent higher than a rated current keeps flowing through the breaker or upon a short-circuit current. Electric power path in the breaker is partly inserted through an arm of a magnetic material and holding a movable contactor plate of make-and-break contact means, an armature means is provided as pivoted at one end to the holding arm, and a tension spring means is provided between the other end of the armature means and the movable contactor plate to provide a contact pressure. The overcurrent flowing through the path causes a magnetic force to be induced in the holding arm, whereby the armature means is rotated to change the direction in which the force of the tension spring means acts on the movable contactor plate and the latter breaks the contact means.

Abstract: A current limiting apparatus includes bridging electrical contacts forming a first current path across a gap in a conductor, a trigger for breaking said first current path in response to an excessive or rapidly changing level of current on said conductor, a fast acting fuse forming a second current path across said gap, for maintaining a conductive path across said gap for a predetermined length of time after breaking of said first current path, to allow the bridging electrical contacts to separate a sufficient distance from said gap to preclude arcing thereacross, and an auxiliary resistor connected across said gap to provide a relatively high resistance conductive path for current in the conductor after said fuse has blown.

Abstract: A contactor capable of having a very high breaking power comprises a movable contact carrier bridge (3) having a central part in the form of a blade (3c) and conducting J-shaped pieces (2a-2b) supporting fixed contacts. A non-magnetic blade bent in the form of a U is mounted slidable inside a hollow movable insulating contact holder (1) and guides and holds at its upper end a magnetic plate (8) cooperating with said blade (3c) and forming an air-gap with another U-shaped magnetic piece (6), disposed between the legs of the bent blade (5) and integral (at 7) with the contact holder (1). A contact pressure spring (4) bears on the basis of the U-shaped magnetic piece (6) and on the bottom of the bent blade (5).

Abstract: A so-called blow-off type current limiting circuit breaker includes a stationary contact strap that is divided into three elongated closely spaced coplanar parallel arms that are connected to each other at one end of the strap. The stationary contact is mounted to the interior one of the parallel arms at the end thereof remote from the one end of the strap. A terminal portion of the strap connects exterior ones of the parallel arms to one another at the ends thereof remote from the one end of the strap. A movable contact engageable with and disengageable from the stationary contact is mounted to one end of a movable contact arm that is pivoted at its opposite end in the region of the one end of the strap, extending parallel to the arms of the strap and being aligned with the interior arm. Current in the interior arm flows in a direction opposite to the direction of current flow in the exterior arms and the movable contact arm.

Abstract: Current limiting stationary (2) and movable (6) contacts are arranged to provide spaced, parallel oppositely directed current paths therein whereby fault currents generate electromagnetic forces for repelling the movable contact (6) from the stationary contact (2). An electrically resistive arc runner (20) has an arc transfer segment (20a) disposed along the path of movement of the movable contact (6) and is biased at one end (20b) into current carrying engagement with a stop (22) on stationary contact (2). The other end of the transfer segment (20a) is connected through a major length of the arc runner (20) to the stationary contact (2) at a point distinct from stop (22). An arc drawn between the contacts (2, 6) at separation initially passes current to the transfer segment (20a) and the stationary contact (2) through stop (22).

Abstract: A current limiting circuit breaker contains a pair of electrical contacts within separate chambers arranged side-by-side and isolated by means of an insulated barrier. The contacts are electrically connected in series such that the arcs formed between the contact pairs are magnetically motivated by the sum of the current paths through both contact pairs.

Abstract: A so-called blow-off type current limiting circuit breaker is constructed with a contact pressure spring that also holds the contact arm in open contact position when the contacts are blown open by electrodynamic forces. A multi-section cam means transmits contact opening and closing forces produced by a spring powered overcenter toggle type operating mechanism to the movable contact arm. A follower on the latter is biased into engagement with the cam means by the contact pressure spring. The cam means is so constructed that during contact blow-off the movable contact arm requires relatively little motion to move overcenter in the opening direction. One section of the cam means is constructed so that when the contact arm moves overcenter in the opening direction during contact blowoff, speed of the contact arm is controlled to an extent that contact rebound does not become a problem.

Abstract: A so-called blow-off type current limiting circuit breaker is provided with an elongated movable contact arm that is pivotally mounted at one end thereof on a pin that projects from opposite sides of a support. The contact arm is constructed of parallel sections that are biased toward one another, by spring means disposed remote from the support, with the support being resiliently clamped between the sections to provide a good electrical connection between the support and contact arm. The pivot pin extends through aligned enlarged pivot apertures in the parallel sections to facilitate weld breaking. A wall of each pivot aperture is disposed to cooperate with the pivot pin to achieve a camming action that moves the contact arm slightly lengthwise after initial butting engagement of the circuit breaker main contacts to wipe the engaged contacts with respect to one another.

Abstract: A thermal magnetic circuit interrupter with instantaneous short circuit current response utilizes a hook-shaped contact arm pivotally mounted on the operating mechanism at the end of the contact arm most distant from the contact. A saddle-type torsion spring proximate the pivot end of the contact arm provides adequate contact pressure while allowing the contact to immediately respond to magnetic forces generated under short circuit conditions. The immediate separation of the contacts reduces the current let-through the operating mechanisms while the tripping mechanism operates to trip the breaker.

Abstract: A mechanically controlled power switch with automatic opening is provided for limiting short circuits. A switch (13), a breaking chamber (30) which is associated therewith, a coil (50), a striker (51) cooperating therewith, and a lock (53) for holding the power switch in open position S after the appearance of a short circuit are placed in a removable cartridge (23) provided with connection terminals (37, 55). This switch cartridge is advantageously used in mechanically controlled protection apparatus or in electromagnetic contactor apparatus having their own protection.

Abstract: A contact structure (40, 44; 62, 63) is arranged to provide oppositely directed parallel current paths within a closed loop magnetic flux amplifier (46) to be directly separable under high overload current conditions, the flux amplifier (46) functioning to arrest the movable contact (62, 63) momentum. Manufacturing economies are realized by subassembling the stationary contact structure (40, 42, 44) and flux amplifier (46) and subsequently trapping one end (42a) of that assembly within the base (4a) and securing the other end with a single screw (68). The movable contact arm (62) comprises a plurality of blanked laminations assembled to provide improved contact (63) mounting and bearing (62d) surfaces. The molded case sidewalls are strengthened in the contact separation area by offsetting the parting line (PL) between cover (6) and base (4) closer to the bottom of base (4) and overlapping the thinner base sidewalls with thicker cover sidewalls at the offset (4e, 6e).