Abstract:
A blast arrangement for gas-blast circuit breakers including a blast cylinder and a blast plunger, the blast plunger being designed in two pieces, arranged axially, the two pieces being rigidly coupled via spacers parallel to the axis and holding between them the sealing rings which form a return valve.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a gas-blast circuit breaker with a blast arrangement associated to the contact system. 
     Gas-blast circuit breaker of this type are known as shown in U.S. Pat. 4,293,750 corresponding to the German Patent 2,907,691, wherein a one piece ring plunger holds the sealing rings in annular grooves. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention provides for a gas-blast circuit breaker with a blast arrangement associated to the contact system, comprising a ring plunger and a movable cylinder, in which the ring plunger is sealed off tightly by a sealing ring against the cylinder, on one side and by a sealing ring against the movable cylindrical contact member of the contact system on the other side, and a return valve closed during the pressure phase and open during the suction phase, which is formed by the two flush-lying sealing rings arranged with axial play in the recesses of the ring plunger, in the line of the flow paths for the compressed gas. 
     An object of the present invention is to facilitate the manufacture of the ring plunger and to simplify the assembly of the sealing arrangement. Accordingly, the plunger is designed in two pieces arranged along an axis and its two pieces are rigidly connected via spacers arranged parallel to the axis to hold the sealing rings between them. 
     An advantage of the present invention is that the two plunger parts can be made of different materials. For example, the first plunger piece, which faces away from the compression chamber can be made from a metallic material, while the second plunger piece, which is turned toward the compression chamber, can be made from an insulating material, a casting resin, or a metallic material. Spacer bolts with surrounding spacing tubes are used as spacing devices to establish the distance between the two plunger parts. 
     Another advantage of the invention is that the outer sealing ring, which operates upon a pushing force in the circumferential direction, can have a coil spring operable within a ring separation. The spring can be positioned in aligning bored holes of the ring body located at the ring separation, wherein the spring can be enveloped by a sliding tube that bridges the ring separation. 
     Another advantage of the invention is that the inner sealing ring operates upon a pulling force in the circumferential direction, and an annular groove can be provided in the sealing ring opposite the sealing surface, wherein the annular groove is designed to receive an annular spring. The annular spring may take the form of a cylindrical coil spring. 
     Further details and advantages of the embodiment in accordance with the invention are described with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows section-view through an electrical gas-blast circuit breaker with a ring plunger arrangement in accordance with the invention; and 
     FIGS. 2 and 3 show details of FIG. 1 on an enlarged scale and in section. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, a gas-blast power circuit breaker of the blast plunger circuit breaker type is shown in longitudinal section, in the switched-on position. Within a circuit breaker chamber 1 of porcelain, two hollow, tubular contact members 3, 4 are separated and arranged along an axis in a gas-filled interior space 2. By way of example, the gas can be SF 6  under a pressure of 6 bars. The distance A between the frontal surfaces of the contact members 3 and 4 constitutes the separation gap of the circuit breaker in the switched-off state. 
     In the switched-on state, the two contact members 3, 4 are bridged by the movable bridging contact member 5, which is designed in tubular form and contains several spring-loaded contact blades 6 distributed evenly over the circumference. The movable contact member 5 is mechanically coupled with a blast cylinder 7 which is moved in the direction of the arrow 8 by bars 9 via a drive (not shown herein) when the circuit breaker is moved from the illustrated switched-on state to the switched-off state. During this process, the blast cylinder 7 is pulled over a relatively stationary ring plunger 10, which compresses the extinguishing and insulating means contained in the cylinder space 7a until it becomes effective, after the contact separation, to extinguish the arc. 
     As shown schematically and in detail in FIG. 2, the ring plunger 10 is designed in two pieces, arranged axially, wherein the two parts 10a and 10b rigidly coupled parallel to the axis via spacers 11. The sealing rings 12, 13 are held between the two plunger parts 10a and 10b such that the rings have axial play. The spacers 11 include spacing bolts 11a, encircled by spacing tubes 11b. The length of the spacing tubes 11b relative to the thickness of the sealing rings 12, 13 determines the axial play of the two sealing rings 12, 13. 
     The first plunger piece 10b, which is turned away from the compression chamber 7a, is made of a metallic material in the illustrated embodiment, while the second plunger piece, 10a, turned toward the compression chamber 7a, is made of an insulating material. The plunger piece 10a can also be made of a metal such as aluminum. The two plunger pieces 10a, 10b are fastened together by means of bars 14 which keep the plunger 10 fixed in place relative to the blast cylinder 7. 
     FIG. 3, in a section view rotated 90° , along the Line III--III of FIG. 2, illustrating the outer sealing ring 12, operating upon a pushing force in the circumferential direction, and having, within the range of a ring separation 12a, aligned bored holes 15, 16 located in the ring body. A compression spring in the form of a coil spring 17 is located within the aligned bored holes 15, 16. The spring 17 is enveloped by a sliding tube 18 that bridges the ring separation 12a. 
     The inner sealing ring 13, which operates upon pulling force in the circumferential direction, has an annular groove 20 opposite the sealing surface 19, designed to receive an annular spring 21, which in the illustrated embodiment is a cylindrical coil spring. 
     In FIGS. 1 through 3, the same parts are marked with the same reference symbols.