US2954448A - Switch construction - Google Patents

Description

Sept. 27, 1960 c. H. BAKER SWITCH CONSTRUCTION Filed July 16, 1958 4 Shasta-Sheet 1 INVENTOR. Chm-Z5251! flake 7 II. Yrilb Sept. 27, 1960 c. H. BAKER SWITCH CONSTRUCTION 4 Sheets-Sheet 2 Filed July 16. 1958 M500; r/o/v 59 5576/55 Mam/7 7/0 1N VENTOR. C/zarZa5H v[iv/145;; BY M W? W Sept. 27, 1960 c. H. BAKER 2,954,443

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C. H. BAKER SWITCH CONSTRUCTION Sept. 27, 1960 4 Sheets-Sheet 4 Filed July 16, 1958 I 4 R a M a m a Q w n mfl. 3 607% E H WW. 3am wflw. o 7 w a w :1 MW v C M m7 ,7 WM 5 x a g 1 a a 4 N 6 h a 2 1 l m 2 m Z 4 M m m MW i m m W W M f 1! VI 5 il 1. u w :3 M 0 U 2,954,448 SWITCH CONSTRUCTION Charles H. Baker, Arlington Heights, 11]., assignor to S 8: C Electric Company, Chicago, Ill., a corporation of Delaware Filed July 16, 1958, Ser. No. 748,912

10 Claims. (Cl. 200-146) This invention relates, generally, to disconnecting switches and it has particular relation to such switches provided with a load interrupter. It constitutes an improvement over the switch construction shown in U.S. Patent No. 2,621,272, issued December 9, 1952, in the name of John I. Kojis.

The load interrupter described in the patent above referred to is provided with load interrupter contacts between which the circuit is opened after the switch blade has been moved out of engagement with a stationary contact. The are that may be drawn under these conditions is interrupted by the interrupter and there is no external arcing. When the switch blade is closed, the arrangement is such that the circuit is completed by closing of the contacts of the load interrupter followed by engagement of the switch blade with the stat-ionary contact. When such an arrangement is employed, the circuit is both broken and made by opening and closing of the contacts of the load interrupter. Under certain operating conditions where the load interrupter switch closes on a faulted circuit, the flow of current which takes place momentarily through the closed contacts of the load interrupter may be such as to injure them. As the contacts of the load interrupter approach the closed position, there may be some arcing therebetween which results in severe erosion thereof. A limited amount of erosion would likewise occur when the switch is closed under load conditions which would tend to limit the useful life of the switch. It is to avoid the completion of the circuit on closing of the load interrupter switch at the contacts of the load interrupter that the present invention is particularly directed.

Accordingly, among the objects of this invention are: To provide for completing the circuit between the switch blade and the line contact which it engages before the contacts of the load interrupter are closed or are brought close enough together to permit arcing therebetween; to avoid completing the circuit through the load interrupter; to open the circuit by separation of the contacts of the load interrupter after the switch blade has moved toward the open position a sufficient distance to avoid restriking of the are between it and the line contact and to close the contacts of the load interrupter only after the circuit has been initially completed by arcing over a gap between the switch blade and the line contact on closure of the switch blade or by mechanical engagement of the switch blade with the line contact; to delay the closure of the contacts of the load interrupter until after the switch blade has initially closed the circuit; and to mount a closing cam on the switch blade spaced therefrom in the direction of opening movement of the switch blade for closing the contacts of the load interrupter after the switch blade has initially closed the circuit.

Other objects of this invention will, in part, be obvious and in part appear hereinaften invention is disclosed in the embodiment thereof shown in the accompanying drawings and it comprises United States Patent "ice the features of construct-ion, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention reference can :be had to the following detailed description, taken together with the accompanying drawings, in which:

Figure 1 is a view, in side elevation, showing one pole of a three phase load interrupter switch installation in which the present invention is embodied, certain parts being broken away and others being shown in section in order to illustrate more clearly the details of constr-uction;

Figure 2 is a view, partly in side elevation and prin-v cipally in vertical section, showing the details of construction of the load interrupter, the illustration showing the contacts of the load interrupter in the closed position;

Figure 3 is a view, similar to Figure 2, but showing the load interrupter contacts in the open position;

Figure 4 is a view of the switch construct-ion shown in Figure 1 with the switch blade in an open circuit position; and

Figure 5 is a view, in side elevation, of the switch construction shown in Figure 1 with the pants in the relation that they occupy when the switch blade first engages the stationary switch contact on movement to the closed position.

Referring now particularly to Figure 1 of the drawing it will be observed that the reference character 10 designates, generally, a frame formed of structural rolled steel sections that may include frame uprights 11 and'12 on which insulating barriers are mounted, one being indicated at 13. Between adjacent insulating barriers 13 there are located load interrupter disconnecting switches, one of which is indicated, generally, at 14. It will be understood that three load interrupter switces 14 are employed for a three phase installation and that provision is made for operating them simultaneously. Since the present invention is embodied in each of the disconnecting switches 14, only one of them is shown and will be described herein.

The load interrupter disconnecting switches 14 are mounted on upper and lower transverse angle members 15 and 16 which are secured suitably to the frame uprights 11 and 12. It will be understood that other mounting means can be employed if desired. Upper and lower insulators 17 and 18 are secured by bolts 19 and 20 to the upper and lower transverse angle members 15 and 16, as shown.

At their outer ends the upper and lower insulators 17 and 18 have secured thereto upper and lower line terminals that are indicated, generally, at 21 and 22, respectively. The terminal members 21 and 22 are provided with terminal pads 23 and 24 to permit connection of line conductors. The upper line terminal 21 has a contact tongue 25 formed integrally therewith and projecting outwardly therefrom while the lower line terminal 22 has a hinge member 26 formed integrally therewith and projecting outwardly therefrom. The upper and lower line terminals 21 and 22 are arranged to be interconnected by a switch blade that is indicated, generally, at 27 and is pivoted at 28 to the hinge member 26. The switch blade 27 preferably is formed by a pair of switch blade members 29 and 30 that are spaced apart a substantial distance for the principal portion of their length and engage opposite sides of the hinge member 26 at their lower ends. Each switch blade member near its upper end is bent inwardly as indicated at 31 in Figure 1 to provide a contact section 32 at the upper end with these contact sections being arranged to engage opposite sides of the contact tongue 25 which is relatively thin as compared to the width of the hinge member 26. It will be understood that the insulators 17 and 18 mounted on the frame 10 in'the manner described serve to position the upper and lower line terminals 21 and 22 in insulated spaced relation and that the switch blade 27 is arranged to interconnect them when it is in the closed position shown in Figure 1.

Any suitable means can be employed for moving the switch blade 27 into and out of the closed position. As shown in Figure 1 a link 35 can be employed, It is formed of insulating material and is pivoted at 36 to the switch blade 27 and at its other end it is pivoted at 37 to an arm 38 which is secured to a horizontally extending shaft 39 that is journaled on the frame 10 in suitable bearings one of which is indicated at 40. Any suitable means can be employed for rotating the shaft 39 in one direction or the other to move the switch blade 27 through the link 35 out of and into the closed position.

When the switch blade 27 is moved to the open position, it is undesirable that any arc be formed between it and the upper line terminal 21. More specifically, it is desired that no are be formed under these conditions between the contact sections 32 and the contact tongue 25. Accordingly, the upper line terminal 21 is provided with a depending contact plate 43 and an integrally formed socket 44 with respect to which a load current interrupter, shown generally at 45, is detachably secured by a bolt 46 as described in the patent referred to hereinbefore.

Figures 2 and 3 of the drawings show the details of construction of the load current interrupter 45. There it will be observed that it includes a contact plate 47 which is arranged to overlie the depending contact plate 43 and to be secured thereto by the bolt 46. Threaded into the lower portion of the contact plate 47 is a metallic plug sleeve 48 which is provided at its inner end with a stationary load interrupter contact 49. Since the contact plate 47 is secured to the contact plate 43 which is formed integrally with the upper line terminal 21 and since the plug sleeve 48 is threaded into the contact plate 47, the stationary load interrupter contact 49 is connected directly to the upper line terminal 21.

The load current interrupter 45 also includes a movable load interrupter contact 50 which, as shown in Figure 2 of the drawings, is in contact engagement with the stationary contact 49 when the load interrupter 45 is in the closed position and the switch blade 27 also is in the closed position. The movable contact 50 is carried at one end of a contact rod 51 that is pivoted at 52 at its other end to an operating mechanism that is indicated, generally, at 53. The operating mechanism 53 is contained within a metallic housing 54 and it includes a link 55 to which the contact rod 51 is pivoted at 52. The other end of the link 55 is pivoted at 56 to one end of a link 57 the other end of which is pivoted at 58 to the housing 54. Formed integrally with the link 57 is a stop 59 which limits the movement of the operating mechanism 53 in either the closing or opening direction.

Pivoted at 60 intermediate the pivots 52 and 56 on the link 55 is an arm 61 the other end of which is fastened to a rock shaft 62 that is journaled on the housing 54 with its ends projecting therethrough to opposite sides. At one end of the rock shaft 62 there is fastened a closing trigger 63 which is shown by full lines in Figures 1, 4 and of the drawings and by broken lines in Figure 2. At the other end of the rock shaft 62 there is an opening trigger 64 which is angularly spaced, as shown in Figure 2, from the closing trigger 63. A toggle spring 65 interconnects the pivot 56 and the rock shaft 62 for the purpose of providing a snap action in the movement of the contact rod 51 and for holding it in either the closed 47 while. the other end is threaded into a tubular exten-.

sion from the metallic housing 54. Additional insulation is provided between the contact plate 47 and the metallic housing 54 by a tubular porcelain insulator 69'. The are is confined within the bore 66 by a trailer 70 that is formed of suitable insulating material and is connected to the contact rod 51 and moves simultaneously with it and with the movable contact 50.

Since the only time that current flows through the contact rod 51 is during the circuit opening operation, it

is unnecessary to provide an extremely low resistance path to the switch blade 27. Accordingly, the circuit extends from the contact rod 51 through the links 55 and 57 and arm 61 to the metallic housing 54. The circuit to the switch blade 27 is completed by a bow contact 73 that is carried thereby, as indicated in Figure 1, and which is arranged to engage projections 74 on the metallic housing 54 during the time that the switch blade is moving away from or toward the contact tongue 25 of the upper line terminal 21.

It will be recalled that the arrangement of the load. current interrupter 45 is such that the circuit is opened.

between the contacts 49 and 50 when the switch blade 27 is swung to the open position. In order to accomplish this an opening cam 75, Figure 4, is secured by rivets 76 to the switch blade member 30. The opening cam 75 has a cam surface 77 that faces away from the pivot axis 28 of the switch blade 27 and is arranged to engage the left side of the opening trigger 64 as the switch blade 27 is swung to the open position. The continued movement of the switch blade 27 in the opening direction brings the bow contact 73 into engagement with the metallic housing 54 with the result that, before the contact sections 32 of the switch blade members 29 and 30 disengage the contact tongue 25, a shunt circuit is provided therebetween through the load interrupter 45. After a sufficient gap has been introduced between the switch blade 27 and the contact tongue 25, the opening cam 75 engages the opening trigger 64. This positively causes the rock shaft 62 to be rotated in a counterclockwise direction as viewed in Figure 2 with the result that contact 50 cannot fail to move out of engagement with the stationary contact 49 and the arc is drawn and extinguished within the bore 66. Figure 3 of the drawings shows the relative positions of the movable parts of the load current interrupter 45 when it is in the open posi tion. It will be noted that the opening trigger 64 has been swung in a counterclockwise direction from its position shown in Figure 2 and that a corresponding movement of the closing trigger 63 has taken place.

When the Switchblade 27 is in the fully open position it can occupy the position shown in Figure 4. Here the closing trigger 63 is shown in the position that it occupies, as shown in Figure 3, when the load current interrupter 45 is in the open position.

For the reasons o'utlined hereinbefore, it is desirable that the circuit not be closed through the load interrupter 45 on initial engagement of the movable contact 50 with the stationary contact 49 in the load current interrupter 45 or when the blade 27 comes close enough to the contact tongue 25 for an arc to be struck when the switch blade 27 is moved toward the closed position. Accordingly, provision is made for delaying the closing of the load current interrupter 45 until the circuit has been completed between the switch blade 27 and the contact tongue 25 of the upper line terminal 21. For this purpose there is secured by rivets 78 to the switch blade member 29 an arm 79 which extends from the switch blade27 in the direction of opening movement thereof. At the outer end of the arm 79 there is secured by rivets 80 a closing cam 81 which has a cam surface 82 that faces outwardly or away from the'pivot axis 28 and is arranged to engage the right hand side of the closing trigger 63 when the switch blade 27,is swung toward the closed position.

Figure 5 shows the closing action of the switch blade 27 and the consequent operation of the load current interrupter 45. Here the switch blade 27 is shown as having completed the circuit between the upper and lower line terminals 21 and 22 by engagement of the contact sections 32 of the blade members 29 and 30 at 83 with a tip of the contact tongue 25. Since these parts are relatively massive, they are more readily capable of withstanding the flow of short circuit current than are the contacts 49 and 50 of the load current interrupter 45 or the bow contact 73 and the pivoted joints of the operating mechanism 53. At the time that the circuit is closed at 83 between the switch blade 27 and the contact tongue 25 on the upper line terminal 21, the movable contact 50 of the load current interrupter 45 is spaced a substantial distance, as indicated at 84, from the stationary con tact 49. This distance is such that there is no likelihood of any dielectric breakdown and consequent arcing taking place between the contacts 49 and 50 during theclosing operation. The breakdown voltage over the surface of the bore 66 in the arc extinguishing material or stack of fiber washers 67 within the load interrupter 45 is always substantially greater than the breakdown voltage between the switch blade 27 and the contact tongue 25 since the gap between the latter is smaller than through the load interrupter 45. This delayed action is obtained by placing the closing cam 81 at the outer end of the arm 79 and remote from the switch blade 27 with the result that the closing trigger 63 is not operated through "a sufficient extent to move the operating mechanism 53 past the center position until after the circuit has been completed at 83 in the manner described. The continued mo'vement of the switch blade 27 in the closing direction merely causes further engagement between the inner faces of the contact sections 32 of the switch blade members 29 and 30 with opposite sides of the contact tongue 25 and, during the final closing movement, forces engagement of the load interrupter contact 50 with the stationary contact 49.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combinatio'n, a pair of switch contacts in insulated spaced relation, a switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact,

means on said switch blade cooperating with said operat-,

ing means on movement of said switch blade to open position to open said interrupter contacts after said switch blade disengages said one switch contact, means holding said interrupter contacts in open position after operation to open position by said means on said switch blade, and means on said switch blade cooperating with said operating means when said switch blade is swung to closed position to overcome said holding means and close said 6 interrupter contacts after a circuit is completed between said switch blade and said one switch contact thereby avoiding completing the circuit in the first instance through said interrupter contacts.

2. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced re lation, a switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said oneswitch contact, means on said switch blade cooperating with said operating means on movement of said switch blade to open position to open said interrupter contacts after said switch blade disengages said one switch contact, means holding said interrupter contacts in open position after operation to open position by said means on said switch blade, and means on said switch blade cooperating with said operating means when said switch blade is swung to closed position and providing a direct mechanical connection to said other of said interrupter contacts for overcoming said holding means and positively moving said other of said interrupter contacts to closed position after a circuit is established directly fromsaid switch contact to said switch blade.

3. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced relation, a switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact, means on said switch blade cooperating with said operating means on movement of said switch blade to open position and providing a direct mechanical connection to said other of said interrupter contacts and positively moving it to open position only after said switch blade disengages said one switch contact, means holding said interrupter contacts in open position after operation to open position by said means on said switch blade, and means on said switch blade cooperating with said operating means when said switch blade is swung to closed position and providing a direct mechanical connection to said other of said interrupter contacts for overcoming said holding means and positively moving said other of said interrupter contacts to closed position only after a circuit is established directly from said switch contact to said switch blade.

4. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced relation, a switch blade'for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable inter-.

rupter contacts and operating means for opening and closing said interrupter contacts, said operating means including an interrupter contact opening member spaced from said switch blade in closed position, one of said interrupter contacts being connected to said one switch' contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact, means on said switch blade operatively engaging said interrupter contact opening member to open said interrupter contacts after said switch blade disengages said one switch contact and introduces a substantial gap therebetween, means holding said interrupter contacts in open position after operation to open position by saidmeans on said switch blade, and means on said switch blade cooperating with said operating means when said switch blade is swung to closed position to overcome said holding means and close said interrupter contacts after a circuit is completed between said switch blade and said one switch contact thereby avoiding completing the circuit in the first instance through said interrupter contacts.

5. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced relation, a switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts including a pair of triggers on said load current interrupter and spaced from said switch blade when closed in the direction of opening movement thereof, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact, means on said switch blade cooperating with said operating means on movement of said switch blade to open position to engage one trigger to open said interrupter contacts after said switch blade disengages said one switch contact, and means on said switch blade cooperating with said operating means when said switch blade is swung to closed position to engage the other trigger to close said interrupter contacts after a circuit is completed between said switch blade and said one switch contact thereby avoiding completing the circuit in the first instance through said interrupter contacts;

6. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced relation, a switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on the one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts including a pair of triggers on said load current interrupter and spaced from said switch blade when closed in the direction of opening movement thereof, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact, means on said switch blade cooperating with said operating means on movement of said switch blade to open position to engage one trigger to open said interrupter contacts after said switch blade disengages said one switch contact and establishes a substantial gap therebetween, and' means carried by said switch blade and extending therefrom in the direction of openingmovement thereof to engage the other trigger when said switch blade is swung to closed position to close said interrupter contacts after a circuit, is completed directly between said switch blade and said one switch contact thereby avoiding completing the circuit in the first instance through said interrupter. contacts.

7. A switch construction for opening and closing a high voltage. current carrying circuit comprising, in combination, a pair of switch contacts in insulated spaced relation, a. switch blade for bridging said switch contacts and movable into and out of engagement with one of said switch contacts, a load current interrupter mounted on one switch contact and including separable interrupter contacts and operating means for opening and closing said interrupter contacts including a pair of triggers on said load current interrupter and spaced from said switch blade when closed in the direction of opening movement thereof, one of said interrupter contacts being connected to said one switch contact and the other interrupter contact being connected to said switch blade during that portion of its movement into and out of engagement with and adjacent to said one switch contact, an opening cam on said switch blade cooperating with said operating means on movement of said switch blade to open position to engage one trigger to open said interrupter contacts after said switch blade disengages said one switch contact, and a closing cam carried by said switch blade and spaced therefrom in the direction of opening movement of said switch blade to engage the other trigger when said switch blade is swung to closed position to close said interrupter contacts after a circuit is completed between said switch blade and said one switch contact thereby avoiding completing the circuit in the first instance through said interrupter contacts,

8. A swit-ch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of line terminals mounted in insulated spaced relation with a hinge member carried by one terminal and a switch contact member carried by the other terminal, a switch blade comprising a pair of elongated blade members pivoted to opposite sides of said hinge member for movement into and out of engagement with said contact member, an elongated load interrupter mounted on said other terminal and extending between said blade members when said switch blade is closed; said load interrupter including in tandem separable load inteirupter contacts, arc extinguishing means therefor, and operating means for said contacts, and including a conducting housing enclosing said operat ing means having a rock shaft projecting at its ends from opposite sides of said housing, and a trigger secured to each projecting end of said rock shaft and extending radially therefrom in angular spaced relation, one of said interrupter contacts being connected to said switch contact member and the other interrupter contact being connected to said housing; means interconnecting said housing and said switch blade during that portion of its movement into and out of engagement with and adjacent to said switch contact member, means on one of said blade members for engaging one of the triggers when said switch blade is swung to open position to operate said operating means and open said interrupter contacts after said switch blade disengages said switch contact member, and means on the other blade member extending therefrom in the direction of opening movement of said switch blade for engaging the other trigger when said switch blade is swung to closed position to operate said operating means and to close said interrupter contacts after a circuit is completed between said switch blade and said switch contact member.

9. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of line terminals mounted in insulated spaced relation with a hinge member carried by one terminal and a switch contact member carried by the other terminal, a switch blade comprising a pair of elongated blade members pivoted to opposite sides of said hinge member for movement into and out of engagement with said contact member, an elongated load interrupter mounted on said other terminal and extending between said blade members when said switch blade is closed; said load interrupter including :in tandem separable load interrupter contacts, are extinguishing means therefor, and operating means for said contacts, and including a conducting housing enclosing said operating means having a rock shaft projecting at its ends from opposite sides of said housing, and a trigger secured to each projecting end of said rock shaft and extending radially therefrom in angular spaced relation, one of said interrupter contacts being connected to said switch contact member and the other interrupter contact being connected to said housing; means interconnecting said housing and said switch blade during that portion of its movement into and out of engagement with and adjacent to said switch contact member, an opening cam on one of said blade members for engaging one of the triggers when said switch blade is swung to open position to operate said operating means and open said interrupter contacts after said switch blade disengages said switch contact member, an arm secured at one end to the other blade member and extending therefrom in the direction of opening move ment of said switch blade, and a closing cam on the other end of said arm for engaging the other trigger when said switch blade is swung to closed position to operate said operating means and to close said interrupter contacts after said switch blade completes a circuit through said switch contact member.

10. A switch construction for opening and closing a high voltage current carrying circuit comprising, in combination, a pair of line terminals mounted in insulated spaced relation with a hinge member carried by one terminal and a switch contact member carried by the other terminal, a switch blade comprising a pair of elongated blade members pivoted to opposite sides of said hinge member for movement into and out of engagement with said contact member, an elongated load interrupter mounted on said other terminal and extending between said blade members when said switch blade is closed; said load interrupter including in tandem separable ioad interrupter contacts, are extinguishing means therefor, and operating means for said contacts, and including a conducting housing enclosing said operating means having a rock shaft projecting at its ends from opposite sides of said housing, and a trigger secured to each projecting end of said rock shaft and extending radially therefrom in angular spaced relation, one of said interrupter contacts being connected to said switch contact member and the other interrupter contact being connected to said housing; means interconnecting said housing and said switch blade during that portion of its movement into and out of engagement with and adjacent to said switch contact member, an opening cam on one of said blade members having a cam surface facing away from the pivot axis of said switch blade for engaging one of the triggers when said switch blade is swung to open position to operate said operating means and open said interrupter contacts after said switch blade disengages said switch contact member, an arm secured at one end to the other blade member and extending therefrom in the direction of opening movement of said switch blade, and a closing cam on the other end of said arm having a cam surface facing away from the pivot axis of said switch blade [for engaging the other trigger when said switch blade is swung to closed position to operate said operating means and to close said interrupter contacts after said switch blade completes a circuit through said switch contact member.

References Cited in the file of this patent UNITED STATES PATENTS 2,469,203 Palme et -al. May 3, 1949 2,480,622 Warnock Aug. 30, 1949 2,621,272 Kojis Dec. 9, 1952

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