A contactor for medium voltage electric systems including: one or more electric poles; for each electric pole, a fixed contact and a corresponding movable contact reversibly movable between a first position, at which the movable contact is decoupled from the fixed contact, and a second position, at which the movable contact is coupled with the fixed contact; an electromagnetic actuator including a magnetic yoke having a fixed yoke member and a movable yoke member, the movable yoke member reversibly movable between a third position corresponding to the first position of the movable contacts, at which the movable yoke member is decoupled from the fixed yoke member, and a fourth position, corresponding to the second position of the movable contacts, at which the movable yoke member is coupled with the fixed yoke member, the electromagnetic actuator including an excitation circuit assembly including an excitation coil wound around the magnetic yoke and electrically connected with an auxiliary electric power supply to be fed with an excitation current to generate an excitation magnetic flux to move the movable yoke member from the third position to the fourth position or to maintain the movable yoke member in the fourth position; an opening springs operatively coupled with the movable yoke member to move the movable yoke member from the fourth position to the third position; a kinematic chain to operatively connect said movable yoke member with said movable contacts. The electromagnetic actuator including camping circuit assembly comprising a damping coil arranged to form a conductive loop adapted to be at least partially enchained with the excitation magnetic flux generated by the excitation current flowing along the excitation coil, when the auxiliary electric power supply provides the excitation current to the excitation coil, so that a secondary current circulates along the damping coil when the excitation magnetic flux is subject to a transient.

A method for controlling an electromagnetic brake (1) having a coil carrier (2), a solenoid (5), an armature disc (7), and at least one further force-exerting element. The internal and external poles (3, 4) of the coil carrier each have a front surface with a varying gradient that fits, in a complementary fashion, the front surfaces of the respective internal and external poles (8, 9) of the armature disc. The brake has an air gap (11) which varies in size and forms a stroke region (21). When excitation occurs, the solenoid generates a magnetic force, and the force-exerting element generates an opposing force, wherein the ratio of the solenoid's magnetic force and the opposing force varies at least once between greater than and smaller than one during the movement of the armature disc in the stroke region owing to the variation of the excitation of the solenoid.

A method for controlling an electromagnetic brake (1) having a coil carrier (2), a solenoid (5), an armature disc (7), and at least one further force-exerting element. The internal and external poles (3, 4) of the coil carrier each have a front surface with a varying gradient that fits, in a complementary fashion, the front surfaces of the respective internal and external poles (8, 9) of the armature disc. The brake has an air gap (11) which varies in size and forms a stroke region (21). When excitation occurs, the solenoid generates a magnetic force, and the force-exerting element generates an opposing force, wherein the ratio of the solenoid's magnetic force and the opposing force varies at least once between greater than and smaller than one during the movement of the armature disc in the stroke region owing to the variation of the excitation of the solenoid.

A stationary core is in an exciting coil. A yoke covers an outer periphery and an axial end of the exciting coil to form a magnetic circuit and has an opening portion. The movable core faces the stationary core through the opening portion and is attracted toward the stationary core on energization of the exciting coil. A return spring urges the movable core against the attraction direction. A first gap is formed between the stationary core and the movable core on deenergization of the exciting coil. A second gap is formed between the yoke and the movable core on deenergization of the exciting coil. The second gap allows the yoke and the movable core to generate an attractive force therebetween on energization of the exciting coil. The return spring is made of a magnetic material to magnetically bridge the first gap or the second gap.

A servo valve is provided with a first elastic portion, a second elastic portion, and a connecting portion. The first elastic portion extends in an X direction inside a valve body and has a first elastic force exerted on a movable element toward an X2 direction. The second elastic portion extends in the X direction inside the valve body and has a second elastic force exerted on the movable element toward an X1 direction.

The connecting portion is connected to the first elastic portion and the second elastic portion inside the valve body, and is in abutment against a step portion of the valve body and a spool of the movable element at a neutral position of the movable element.

A push-pull solenoid is provided with a cylindrical guide member that is fixed to a case. A circular outer peripheral surface of a plunger is in contact with a friction guide surface formed on a circular inner peripheral surface of the guide member, and slides along the friction guide surface. Frictional force due to contact with the friction guide surface is always acting on the plunger, so it is possible to suppress impact-like contact of the plunger with an object to be manipulated during suctioning, and vibration and noise caused thereby. Moreover, over-recovery and falling-out of the plunger after suction is released can also be prevented.

In a diameter-increasing portion, which includes first to third angle segments, an A-point is defined as an intersection between a radially outer surface of a thin wall portion and the first angle segment, and a B-point is defined as an intersection between a radially outer surface of a thick wall portion and the third angle segment. Radially outer surfaces of the first to third angle segments are located on a radially outer side of a reference conical surface, which is formed by rotating a straight line connecting between the A-point and the B-point about a central axis, throughout an entire range from the A-point to the B-point. A first angle , a second angle , a third angle and a reference angle e satisfy relationships of , , , and .

In a diameter-increasing portion, which includes first to third angle segments, an A-point is defined as an intersection between a radially outer surface of a thin wall portion and the first angle segment, and a B-point is defined as an intersection between a radially outer surface of a thick wall portion and the third angle segment. Radially outer surfaces of the first to third angle segments are located on a radially outer side of a reference conical surface, which is formed by rotating a straight line connecting between the A-point and the B-point about a central axis, throughout an entire range from the A-point to the B-point. A first angle , a second angle , a third angle and a reference angle e satisfy relationships of , , , and .

A shaft outputs a thrust force in an axial direction by using a magnetic flux caused by an electric current flowing through a coil. A housing is made of resin and retains the shaft. The housing has a base portion having an outer circumferential surface, which is configured to be entirely in contact tightly with a sealing member. The housing further has a distal portion having an outer circumferential surface defining a depression. The outer circumferential surfaces of the base portion and the distal portion are substantially equal in diameter and are formed continuously.

A solenoid device includes two electromagnetic coils, two stationary cores, two plungers and a yoke that surrounds the two electromagnetic coils. When a first electromagnetic coil is energized, magnetic flux flows through a first magnetic circuit that includes the first stationary core. When the two electromagnetic coils are energized, magnetic flux of the first electromagnetic coil flows through the first magnetic circuit, and magnetic flux of the second electromagnetic coil flows through a second magnetic circuit that includes a second stationary core. When energization of the first electromagnetic coil is stopped while maintaining energization of the second electromagnetic coil, the magnetic flux of the second electromagnetic coil continues to flow through the second magnetic circuit and a third magnetic circuit that includes the two stationary cores. A magnetism limiting portion is disposed in a portion of the second magnetic circuit that does not overlap the third magnetic circuit.