Compressed-gas electric circuit breaker
[ Apr. 29, 1975 COMPRESSED-GAS ELECTRIC CIRCUIT BREAKER Inventor:  
 Primary Examiner-Robert S. Macon [73] Assignee: Siemens Aktiengesellschaft, Munich.  
 Germany [57] ABSTRACT A compressed-gas electric circuit breaker is equipped [22] Filed: Oct. 25, 1973 [21] Appl. No.: 409,705  
 with a gas-blast assembly having a blast piston and a cylinder between which relative motion takes place to produce a flow of quenching gas directed toward the [30] N l 9 pnomy Dam gap between the switching contacts. An ancillary pis- 335455 ton is arranged in the cylinder and is controlled in dependence upon the relative motion of the blast piston and the cylinder in such a manner that the effective piston area is decreased in a self-acting manner in the Field of Search.....................  
  0 n 3 U3 mm 0 ;H A&#34; 8 4 l l 0 0 2 V C sMt Uh ll zll 55 200/148 6 course of the compression stroke. The ancillary piston is coupled to the blast piston or cylinder by a latch switchable in dependence upon the stroke.  
 [56] References Cited UNITED STATES PATENTS 4 Claims, 1 Drawing Figure 3.739.l24 6/l973 Richter..........v.,.............. 200/148 A COMPRESSED-GAS ELECTRIC CIRCUIT BREAKER BACKGROUND OF THE INVENTION From Deutsche Offenlegungsschrift Pat. No. 1,913,969 an electric circuit breaker is known which includes a stationary switching contact, a movable switching contact and a blast cylinder rigidly connected with the movable switching contact. When the breaker is opened, the blast cylinder is pulled over a stationary piston. The blast cylinder has an end-face directed toward the stationary contact and forms with this endface a nozzle for a flow of gas which is set in motion by the piston and the cylinder. In this known configuration the movable contact pin 8 is made hollow and functions to remove the gas. The movable contact pin and the stationary contact form a sliding contact arrangement whichis closed during one-half of the stroke of the contact pin to improve the pre-compression of the quenching medium.  
  Deutsche Offenlegungsschrift Pat. No. 2,014,101 discloses an electric circuit breaker of the same type wherein the blast piston consists of two parts. The two parts are formed by ring pistons of which the one is relatively stationary and the other is controlled in dependence upon the relative stroke between the blast cylinder and the stationary blast piston in such a manner that the effective piston area is decreased in a selfacting manner in the course of the compression stroke. In this way, it is possible to reduce the mechanical stroke of the blasting device without reducing the blast effect.  
  In principle, the switching time attainable with blast piston breakers is longer, because of the unavoidable pre-compression time, than in pressurized-gas circuit breakers in which during the interruption process quenching medium is fed from a high-pressure reservoir to the switching gap via a controlled valve. In order to shorten the switching time in blast piston breakers, one can either choose a low pre-compression ratio or, as will be seen, for instance, from the Deutsche Offenlegungsschrift Pat. No. 2,014,101, one can use a controlled ring piston for changing the cross-section of the blast cylinder.  
  In the configuration disclosed in Deutsche Offenlegungsschrift Pat. No. 2,014,101 the additional piston is controlledin dependence upon the relative stroke between the blast cylinder and the blast piston and is supported by a spring. This spring is tensioned in the course of the opening motion. The force required for tensioning the spring also increases here the required actuating force and energy.  
 SUMMARY OF THE INVENTION The invention is based on the realization that it is possible to reduce the actuating energy for the same pre-compression time if the ring piston can be controlled without springs during the pre-compression phase of the blasting assembly.  
  It is an object of the invention to provide an electric circuit breaker of the above-mentioned type wherein small switching times are achieved. Subsidiary to this object it is an object of the invention to provide such a circuit breaker wherein the driving force required for the opening operation of the breaker is not increased.  
  The electric compressed gas circuit breaker of the invention is switchable between open and closed positions and includes a switching chamber wherein two switching contacts are disposed. These contacts mutually define an open gap when the breaker is switched to the open position. Switching means are provided for electrically joining the switching contacts in the closed position of the breaker and for electrically disconnecting the same in the open position of the breaker. The circuit breaker further includes as a feature a gas-blast assembly for blasting a stream of gas through the above-mentioned gap when the breaker is switched to the open position. The gas-blast assembly includes a blast piston member. A blast cylinder member is pulled over the blast piston member and is disposed in surrounding relation to the switching contacts. Drive means are provided for moving one of the members relative to the other one of the members in a first direction to define a compression stroke when the breaker is switched open and for moving the one member relative to the other member in a direction opposite to the first direction when the breaker is switched closed. An ancillary piston is arranged in the blast cylinder so as to be movable along a portion of the stroke. The ancillary piston and the blast piston conjointly define a compression surface against which the gas is compressed in the cylinder member during the compression stroke. The invention includes as a feature, latching means for coupling the ancillary piston to the one member in the course of the stroke to cause the ancillary piston to move along with the one member relative to the other member whereby the effective area of the compression surface is reduced.  
  According to a preferred embodiment, the latch of the latching means has a preferred position which can be obtained by spring force and from which position the latch can be transferred by the action of the blast cylinder into a position preparatory to switching over.  
  In a preferred embodiment of the invention, the latch is configured as a pin which is supported in the ancillary piston so as to be radially movable in a direction transverse to the movement of the ancillary piston. The length of the pin is selected here so that it engages either a recess of the blast piston or a recess of the cylinder.  
  Although the invention is illustrated and described herein as compressed-gas electric circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.  
 BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic diagram, partially in sec tion, illustrating the compressed-gas electric circuit breaker according to the invention. The embodiment shown is suitable for operation at KV for example.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Reference numeral 1 designates a switching chamber 1 fabricated from a cylinder porcelain tube. Two switching contacts 2, 3 are arranged in the chamber and can be electrically separated from each other. A gaseous insulating medium, preferably sulfur hexafluoride (SP surrounds the switching contacts 2, 3. In the illustrated embodiment, the two contacts 2, 3 are arranged stationary and are made hollow for the removal of switching gases. The free end-faces 4, 5 are mutually adjacent and are disposed on a common axis. The two switching contacts 2, 3 are electrically connected in the position shown by a switching element 6 which coacts with a drive 7 and bridges the contacts.  
  To move the electric circuit breaker into the open position, the switching member 6 is moved by the drive 7 in the direction of the arrow 8. Coupled with the switching member is a blast cylinder 9 which is pulled over a relatively stationary piston part 10. By the relative motion between the blast piston 10 and the blast cylinder 9, compressed SF is directed as a quenching medium into the gap between the two end-faces 4, 5 of the switching contacts 2, 3 as soon as the switching member 6 slides off of the stationary contact 2 in the course of the opening movement. Up to this point in time, the sulfur hexafluoride enclosed in the space 11 surrounded by the blast cylinder 9 is compressed (precompression phase).  
  In the blast cylinder 9 is arranged an ancillary ring piston 12. The piston 12 is controlled in dependence upon the relative stroke between the blast cylinder 9 and the blast piston 10 in such a manner that the effective piston area is decreased in the course of the compression stroke. For this purpose, the ancillary ring piston 12 has a latch 13, which can be switched over in dependence upon the stroke and which is coupled with 4 the blast piston 10 or with the blast cylinder 9.  
 I The latch 13 is constructed as a pin and is supported in the ring piston 12 so as to be movable in the radial direction transverse to the direction of motion 8 of the piston 12. The latch 13 has a length selected so that it engages selectively with a recess 14 of the blast piston 10 or with a recess 15 of the blast cylinder 9.  
  The latch 13 has a preferred position obtained by the force of a spring 16. The latch 13 can be switched over by means of a leaf spring 17 operating in the manner of a toggle spring. For this purpose, the spring 17 braces with its end 18 against a piston part 22 which, in turn, is guided in the ring piston 12 and is damped as to its movability; whereas, the end 19 is connected with a release slide 20. The release slide 20 is actuated from the end face 21 of the blast cylinder 9.  
 The operation of the pressurized-gas circuit breaker according to the invention will now be described.  
  In the course of the opening motion, the switching member 6 and the blast cylinder 9 coupled therewith are moved in the direction of the arrow 8. The gas in the interior 11 is thereby compressed against the stationary blast piston 10 and so also against the ring piston 12, which is firmly locked by the latch 13. In the course of the further movement of the blast cylinder 9 in the direction of the arrow 8, the end face 21 of the blast cylinder comes into engagement with the free end i of the slide 20. By means of the actuation of the slide 20, the toggle spring 17 is bent through and reverses the latch 13 so that the ring piston 12 travels along with the blast cylinder 9. The recess 15 is opposite the recess 14 at the time of the latch reversal. Because the ring piston 12 now is taken along with the blast cylinder 9, the effective piston area of the blasting assembly is decreased. The ring piston 12 acts, in effect, as the blast cylinder with respect to the stationary blast piston 10. In this manner the switching time of an electric pressurized-gas circuit breaker with a blast-piston arrangement can be reduced effectively without the need to increase the actuating forces during the opening movement.  
  In the course of the closing movement the recess 15 gets into a position relative to the recess 14, which drives the latch 13 into the recess 14 through the force of its spring 16, and thereby secures the ring piston with respect to the blast piston 10.  
 What is claimed is:  
  1. An electric compressed-gas circuit breaker switchable between open and closed positions comprising: a switching chamber two switching contacts defining an open gap therebetween when the breaker is switched to the open position, said contacts being disposed in said chamber; switching means for electrically joining said switching contacts in the closed position of the breaker and for electrically disconnecting thesame in the open position; and, a gas-blast assembly for blasting a stream of gas through said gap when the breaker is switched. to the open position, said gas-blast assembly including: a blast piston member, a blast cylinder member pulled over said blast piston member and disposed in surrounding relation to said switching contacts, drive means for moving one of said members relative to the other one of said members in a first direction to define a compression stroke when the breaker is switched open and for moving said one member relative to said other member in a direction opposite to said first direction when the breaker is switched closed, an ancillary piston arranged in said blast cylinder so as to be movable along a portion of said stroke, said ancillary piston and said blast piston member conjointly defining a compression surface against which the gas is compressed in said cylinder member during said compression stroke, and latching means for coupling said ancillary piston to said one member in the course of said stroke to cause said ancillary piston to move along with said one member relative to said other member whereby the effective area of said compression surface is reduced.  
  2. The electric compressed-gas circuit breaker of claim 1, said latching means comprising: a latch movable between first and second positions for alternately coupling said ancillary piston to said other member and to said one member, respectively, in dependence upon the movement of said one member relative to said other member; and resilient means for holding said latch in one of said first and second positions.  
  3. The electric compressed-gas circuit breaker of claim 2, said latch means comprising release means for actuating said latch during the course of said compression stroke to cause the same to move from said first position to said second position thereby coupling said ancillary piston to&#39;said one member whereby said ancillary piston moves along with said one member.  
  4. A The electric compressed-gas circuit breaker of claim 2, each of said members having a recess formed therein for receiving said latch, said latch being a pin mounted in said ancillary piston so as to be movable in a direction transverse to the movement of said ancillary piston, said pin having a longitudinal dimensionselected so as to enable said pin to engage said recess of said other member in said first position and to engage said recess ofsaid one member in said second position.&#34;  
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