ELECTRICAL CURRENT SWITCH APPARATUS WITH ARC EXTINGUISHING MECHANISM
BACKGROUND OF THE INVENTION This invention relates to apparatuses for interrupting electrical current, such as direct current (DC) electric power, and more particularly to apparatuses such that they have a mechanism for extinguishing arcs formed between the contacts of the breaker during separation. DC power is used in a variety of applications, such as battery-powered systems, transmissions for DC motors and DC accessory circuits. Contact devices are typically provided between the DC source and the load, to apply and remove electrical energy to the load. The weight, the reliability and the capacity of interruption and switching of high DC voltage are important considerations to develop the contact device. Furthermore, in many applications relatively high continuous currents must be interrupted, which produce arcs when the contacts of the contact device are opened, thus requiring a mechanism to extinguish the arcs. For example, contact devices are used to control the application of direct current to a motor in electric vehicles. Although the current conducts in a direction between the source and the electric motor when the electric motors are driving the wheels, electric-powered vehicles also have a regeneration mode in which the current drives in the opposite direction when the wheels are not running. being driven by the engine. Regenerative braking is used in other engine systems, such as overhead cranes and transit cars, to reduce the speed of the apparatus by directing energy to an absorbent or dissipating device. In this way, it is preferred that the contact device between the DC power source and the motor be able to handle currents in both directions at a high DC voltage and extinguish the arcs that may occur, regardless of the direction of that current. SUMMARY OF THE INVENTION A general objective of the present invention is to provide an improved switching device for electric current. Another objective is to provide a current breaking apparatus with a mechanism that extinguishes arcs that are formed while separating the contacts from the switch. An additional objective is to carry out the interruption without any arc secondary product, such as flames, that extends beyond the housing of the apparatus. Still another objective is to provide an apparatus for interrupting direct currents of any polarity.
These and other objects are achieved by means of an electric current breaking apparatus that includes a pair of terminals with a stationary contact electrically connected to an energy terminal. A movable contact is electrically connected to the other power terminal and is located on one side of the stationary contact. An arc chute has a plurality of spacer plates that extend radially from a central point in a geometric arc that extends around the stationary contact on a side that is opposite the first mentioned side. In essence, the arc chute is bent around the remote side of the stationary contact from the movable contact. In the preferred embodiment, a D-shaped stationary arc runner has a straight portion of the D connected to the stationary contact and a curved portion facing the plurality of spacer plates. The curved portion is aligned so that an electric arc is capable of traveling between the stationary arc runner and the rounded edges of the plurality of spacer plates. Further, a movable bow runner is preferably connected to the movable contact and has arms extending towards each end of the geometric arc of the spacer plates so that an electric arc can travel between the arms and the spacer plates at the ends of the arc. geometric. L-shaped end conductors can be used to assist the electric arc to travel to the separator plates at the ends of the geometric arc. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an isometric view of a DC contact device in accordance with the present invention; Figure 2 is a vertical cross-sectional view along line 2-2 of Figure 1; Figure 3 is a horizontal cross-sectional view along line 3-3 of Figure 1; Figure 4 is an exploded isometric view of the electrical contacts and an insulator used within the contact device; Fig. 5 is a vertical cross-sectional view similar to Fig. 2, with the switch contacts in an open state; and Figures 6A-6D sketch the cleaning action of the switch contacts in four positions, when closing the contacts. Detailed Description of the Invention With reference to Figure 1, a sealed, electromagnetic single-pole contact device 10 has a plastic housing 12 formed by two substantially identical bushes (mirror images) 14 and 16 formed of insulating plastic material. The bushes are held together by four rivets 17 to encapsulate a bi-directional DC switch mechanism within the housing. The first bushing 14 has a first power terminal 18, while the second bushing 16 has a second power terminal 20 and a pair of recessed terminals 22 for a solenoid, which opens and closes the contacts of the electrical switch inside the housing 12. With the switch closed, the direct current between the power terminals 18 and 20. With reference to FIGS. 2 and 3, within the contact device 10 there is an electromagnetic solenoid 30, which nests in grooves in the interior surfaces of the devices. caps 14 and 16 of the housing. The solenoid 30 has an annular coil 32 within a U-shaped metal frame 34, which is closed by an end metal plate 36. Solenoid coil wires 32 are connected to the lowered terminals 22. The The solenoid coil 32 has a central opening 33 with a non-magnetic sleeve 31 which prevents the magnetic bonding of an armature 35 located within the central opening. The armature 35 has an arrow 40 with a nut 37 and a spring retainer 39 attached at one end and linking a spring 41 which biases the armature 35 so that the contact device 10 is in a normally open position, as illustrated in FIG. Figure 5. Figure 3 sketches the contact device 10 in the closed state, with the solenoid energized to move the armature 35 to the left. The armature 35 further comprises a metal piston 38 attached together with a disk 42 to an intermediate section of the armature shaft 40. The piston 38 is located at an end portion of the sleeve 31 and is approximately equal to half the length of the piston. length of the central opening 33 of the coil. The armature arrow 40 passes freely through a magnetic core 43 in the other half of the central opening 33. The magnetic core 43 is fixed to the solenoid frame 34 by means of rivets at a reduced diameter end of the extending core through a hole in the frame. The armature arrow 40 projects through that hole in the solenoid frame 34 and ends with the head 44 at the remote end. The head 44 of the armature shaft links an actuator 46 formed of electrically insulating material, such as plastic. Specifically, the head 44 is captured within a slot in an end wall 48 of the hollow actuator 46. The opposite end wall of the actuator 46 has an opening that receives an arrow 52 of a movable contact 54 that is connected by a braided cable copper 56 to the energy terminal 18, as can be seen in Figure 3. The details of the movable contact 54 are also shown as an exploded view in Figure 4. The remote end of the contact arrow 52 is attached to the mean of an elongated copper arch runner 57, with a pair of vertical arms 58 and 59 displaced horizontally on opposite sides of the contact arrow 52 in the orientation illustrated in figure 4. The arms 58 and 59 of the arch runner they have end portions bent towards the solenoid 30 to form the flanges 60. The opposite side of the movable bow runner 57 of the contact arrow 52 has a first contact pad 63., shown in Figures 2 and 3. The movable contact 54 is biased by means of a coil spring 62 away from the end wall 48 of the actuator 46. In the closed state of the contact device 10, the first contact pad 63 of the movable contact 54 is forced by the solenoid 30 against a second contact pad 61 in a stationary contact 64. The armature arrow 40 pushes on the actuator 46, compressing the coil spring 62 and establishing a contact force through wear of the contact pads 61 and 63. The actuator 46 is designed so that this action inherently cleanses the surfaces of the two contact pads 61 and 63. As shown in Figure 6A, when the contacts are opened, a head 49 in the tubular shaft 52 of the movable contact 54 is forced against the inner surface 47 of the actuator 46 by the spring 62. This inner surface 47 is angled so as not to be orthogonal with with respect to the center line of the second fixed contact pad 61. In this manner, the axis of the movable contact arrow 52 is not aligned with the center line of the first contact pad, as indicated by the lines 51. When the solenoid 30 is energized, the actuator 46 and the movable contact 54 they move towards the stationary contact 64 until the first contact pad 63 hits the second contact pad 61, as illustrated in Figure 6B. Subsequently, further movement of the solenoid armature 35 continues to push the actuator toward the second contact pad 61, as shown in FIG. 6C. However, the first contact pad 63 remains relatively motionless due to the stop with the second contact pad 61 fixed. Note that the head 49 of the movable contact arrow 52 has now moved away from the inner surface 47 of the actuator and that a rib 55 in the movable arc runner 57 begins to bump into the actuator. At this point, the movable contact arrow 52 is still out of alignment with the first contact pad center line. However, additional movement of the armature shaft 40 of the solenoid forces the actuator 46 against the rib 55, causing the movable contact 54 to pivot within the opening in the actuator to a position shown in Figure 6D. The pivoting results in the surface of the first contact pad 63 in motion cleaning across the surface of the second stationary contact pad 61. That cleansing action cleans those surfaces. Referring again to Figures 2 and 4, a rigid metal belt 66 connects the second contact pad 61 to the other energy terminal 20. The stationary contact 64 has a stationary arc runner, D-shaped 68 through the which extends one end of the belt 66 and is welded to the straight portion 67 of the D. An isolator 70 has a U-shaped plate 72 extending around the stationary contact 64 with the curved portion 69 of the stationary arc runner. in the form of D 68 being adjacent to a curved inner edge 73 of the insulator. Two straight legs 74 and 76 of the insulating plate 72 project on opposite sides of the movable contact 54 and the actuator 46. With particular reference to Figure 4, the arm 58 of the movable arc runner 57 is located on a first side 78 of the plate 72 of the insulator 70 and the other displaced arm 59 is placed on the second opposite side 84 of the insulator plate. A first series of five walls 86 is on the first side 78 of the insulator plate 72 along the first straight leg 74; and a second series of five walls 88 is on the second side 84 of the plate 72 along the second straight leg 76. The walls 86 and 88 are on opposite sides of the respective plate legs 74 and 76 from the adjacent side to arms 58 and 59 of the movable arch runner 57 (see figure 2). Referring again to FIGS. 2 and 3, a novel arc chute 90 is placed in the housing 12 around the curved outer edge 75 of the insulator 70 to extinguish the arcs formed by separating the contact pads 61 and 63. Arc channel 90 is formed by 21 separator plates 92 of a non-ferrous, electrically conductive material, such as copper. The separator plates 92 are positioned radially in a semi-circular array around a center located at the point of contact between the two contact pads 61 and 63. Note also that this point is the center of the radius for the curved portion of the insulator 70 and the curved portion 69 of the stationary arc runner 68. The spacer plates 92 are J-shaped, with rounded edges 93 facing contacts 54 and 64 and spaced equidistantly from the central surface of the curved portion 69 of the stationary arc runner. 68. As evident in Figure 3, the separator plates 92 extend on both sides of the insulator plate 72, which is located midway along the rounded edge of each separator plate. L-shaped copper end pieces 94 and 96 are positioned at the ends of the semi-circular array of separator plates 92 and have a leg 97 that forms another element of the array and an orthogonal leg 98 that is parallel to the direction of movement of contacts. In essence, the arc chute 90 is arranged in a geometric arc, a half circle, around the remote side of the stationary contact 64 from the movable contact 54. With reference to Figure 5, a gas vent 112 in each of the spacer plates provide a passage for the arc gases to escape between the separator plates and the back of the arc chute 90, thus relieving the gas pressure and preventing it from interfering with the arc 115 running through the edges rounded 93 of the separator plates. Because the contact device 10 interrupts direct current, a magnetic field is required to move arcs towards the arc chute 90. Referring to Figure 3, that magnetic field is produced through the arc chute 90 by a permanent magnet assembly 100. This assembly comprises a separate permanent magnet 102 and 104 on opposite sides of the arc chute 90 along the inner surfaces of the sockets 14 and 16 of the housing between the contacts 61 and 63 of the raceway. arc 90. Each permanent magnet has a semi-circular shape, as shown by dotted line 105 in Figure 2. The two permanent magnets 102 and 104 are magnetically coupled by means of a U-shaped steel member 106 which it abuts on the outer surface of each permanent magnet and extends around the end of the arc chute 90 that is remote from the contact pads 61 and 63. A pair of plastic clamps 108 and 110, with notches therein, hold the separator plates 92 of the arc chute and the permanent magnets 102 and 104 in alignment within the U-shaped member 106. The engagement of the permanent magnets 102 and 104 establishes a field The magnetic arc through the arc chute 90 (vertically in Figure 3), which directs the arcs formed between the contact pads 61 and 63 towards the separator plates 92, as will be described. With reference to Figure 2, when the contact device 10 opens the electrical contact pads 61 and 63, the plunger 38 moves to the right, outside the solenoid coil 32. This movement is transferred by the armature arrow 40. and the actuator 46 to the movable contact 54, causing the first contact pad 63 to move away from the second contact pad 61 in the stationary contact 64. At the end of this displacement, the movable contact 54 and the armature 35 are positioned as illustrated in Figure 5. Al separating the contact pads 61 and 63, an arc 115 can be formed between them. The force produced by the interaction of the arc current with the magnetic field of the permanent magnets 102 and 104 causes the arc 115 of the first pad to move of contact 63 outwards along the movable arc runner 56 towards one of the L-shaped end pieces 94 and 96 of the arc chute 90. To which of the end pieces 94 or 96 the arc moves it is determined by the direction of current flow between the two contact pads 61 and 63. Assume for example that the arc travels along the arc runner arm 59 towards the end piece 94 in figure 5. At the same time, and the arc 115 moves out of the second contact pad 61 and the stationary arc runner 68. By continuing to separate the contact pads 61 and 63, the arc propagates to the end of the arm 59 of the movable arc runner 57 and is stretched outward until it reaches the arc chute 90. So, subsequently, the arc 115 bridges the gap between the L-shaped end piece 94 and the adjacent separator plate 92. Then, the arc begins to propagate to each subsequent separator plate 92 around the semi-circular array, while remaining established between the movable arc runner 57 and the end piece 94. This action forms a separate sub-arc in the free space between the adjacent separator plates 92. The guide end of the arc travels around the curved outer surface of the stationary arc runner 68. Eventually, arc 115 encompasses a sufficient number of clearances between spacer plates 92, accumulating sufficient arc voltage and extinguishing the arc. As the arc propagates around the entire arcuate arc chute 90 between the two end plates 94 and 96 that accumulate arc voltage, the walls 88 in the insulator 70 act as gas cooling fins, preventing the arc from jumping over the other end of the movable arc runner 57. The walls 88 also prevent the arc voltage from collapsing, inhibiting the arc 115 from restarting its downward movement through the movable arc runner 57 to the end plates 94 and 96. The present chute of Arc is intrinsically unpolarized (bi-directional) due to the symmetry of the arc-corridor arrangement and the separator plates. This design allows a set of separator plates to handle arcs that run in both directions from the contact and allows each separator plate to have sufficient mass to make possible the interruption of inductive load (long arc duration) without damage to the plates.