US2304606A - Electric switch - Google Patents

Description

Dec. 8, 1942.

J. J. SHOEMAKER ETAL ELECTRIC SWITCH Original Filed March 4, 1939 2 Sheets-Sheet 1 INVENTORS Jfasaph J'j/Jaernarer and flagYrarup'eege ATTORNEY WlTNESgES: fw

1942- 4. 4. SHOEMAKER ETAL 2,304,606

ELECTRIC SWITCH Original Filed March 4, 1939 2 SheetS -Sheet 2 WITNESSES: h INVENTORS osep .fhoemaxerand HOWOBQOI -fee/ye [21/ g2; %ORNEY Patented Dec. 8, 1942 UNITED STATES PATENT OFFICE ELECTRIC SWITCH Original application March 4, 1939, Serial No. 259,846, which is a division of application Serial No. 3,225, January 24, 1935. Divided and this application October 31, 1940, Serial No. 363,646

7 Claims.

This invention relates in general to alternating-current distribution systems, and is more particularly concerned with improved switching means therefor.

The present application is a division of our copending application Serial No. 259,846 filed March 4, 1939 (now Patent 2,253,400), which in turn is a division of parent application Serial No. 3,225, filed January 24, 1935, now Patent 2,152,445. The present application is directed primarily to the switch structure employed in the system covered in the current application.

In the usual type of distribution systems, utilizing a sectionalized loop, it has been the custom in the past to provide sectionalizing switches in the form of circuit breakers which are arranged so as to isolate a faulty section by opening during the flow of fault current. Such operation necessitates that the circuit breakers have sufiicient interrupting capacity to open the fault current, thereby not only necessitating the use of an expensive device, but in addition requiring the use of auxiliary relay equipment, etc., for controlling the operation of the circuit breakers.

With the foregoing in mind, the presqant invention seeks to provide an economical system, wherein the expensive circuit breakers and auxiliary devices may in a large measure be dispensed with, and in which switches of the disconnecting type have little or no interrupting capacity may be used. In the novel switch to be hereinafter described, novel switching means are provided, whereby the opening of the switch contacts is delayed until the circuit in which the switches are disposed is deenergized.

It is an object of the present invention to provide a switch having improved actuating means which functions to trip the switch upon current flow changes from its normal amount or direction, but which will maintain the switch contacts closed until current ceases to flow, due to the circuit being deenergized elsewhere.

It is a further object of the present invention 'to provide in a switch of the character described,

means to preset the switch for the tripping operation upon current flow changes, but which does not function to open the switch contacts until the current ceases to flow.

It is another object of the invention to provide an electrical switch having improved means for providing adequate contact pressure.

It is a still further object of the invention to provide an electrical switch having contact blades articulated to form a toggle mechanism.

Other objects of this invention will more fully appear from the following detailed description taken in connection with the accompanying drawings, which illustrate several embodiments thereof, and in which:

Figure 1 is a vertical sectional view through the housing of a switch utilized in the present invention, this view showing the operative relationship of the switch parts, when the switch is innormal closed position;

Fig. 2 is a plan view on an enlarged scale of the tripping and latching mechanisms of the switch shown in Fig, 1;

Fig. 3 is an enlarged fragmentary view in vertical section of the tripping and latching mechanism, illustrating the relative positions of the parts just after the switch has been preset, and prior to the latch releasing operation;

Fig. 4 is a similar view showing the operative relationship of the parts when the latch is released, and just before the switch door has opened to open the switch contacts; and

Fig. 5 is a schematic wiring diagram showing a distribution system and illustrating an application of the present invention.

Referring to Figures 1 through 4, the illustrated embodiment discloses the switch as comprising a box-like structure, generally indicated at III, which is formed by a back member II, a pair of'side members I2I2 (only one being shown), and top and bottom members I3 and I4, respectively. The box is open on its forward side and is arranged to be closed by means of a cover l5 which is inwardly secured to the side members l2--l2 by means of hinge brackets 16.

It will be observed that the bottom It is upwardly spaced fromthe lowermost edges of the back and side walls of the box, and that the hinge brackets of the cover are pivoted to the side walls at a point below the bottom It. With this arrangement, when the box cover is swung to open position, it may assume a natural hanging position below the box.

Mounted centrally in the middle of the cover or door I5 of the box is a bracket l'l which projects rearwardly from the door at substantially right angles thereto to form a support for a pair of pivotally mounted switch blades l8 and I9 which are oppositely disposed relative to a pivotal connection 20.

Between the switch blades I8 and I9 and the rear face of the door, there is mounted a leaf spring 2| which is arranged with its free ends bearing against the respective switch blades and normally tending to cause the outer ends of the blades to be moved away from the rear face of the door. This movement of the switch blades is limited by means of a stop which is formed by a plate 22 secured at the outer end of the bracket 1. The switch blades form a movable bridging contact which is moved out of and into bridging relation with an upper stationary contact 23 and a lower yieldingly mounted contact 24 by opening and closing the door of the switch box.

The switch blades are interconnected by means of a flexible jumper 25. The upper and lower contacts are respectively supported on the top and bottom of the box. The lower contact is provided with a threaded stem 26 which is supported for axial movement in the bottom l4. A compressing spring surrounds the stem 26, one end of this spring bearing against the contact head and the other end against the bottom l4, whereby the tendency of the contact is to move upwardly. Upward movement of the contact by the spring is limited by nuts 2828 on the stem below the bottom member l4.

In Fig. 1, there is shown in dotted lines, the positions assumed by the switch blades l8 and I9 when the door is in open position. The blades are angularly disposed, and rest against the stop 22. If the door is now closed, the ends of the blades engage deflected portions 29 and 30 of the upper and lower contacts respectively, these portions serving as stops, so that as the door I is moved into fully closed position, the blades are moved into axial alignment, with the result that the blades function as a toggle and are forced against the contacts 23 and 24.

The door I5 is manually operable to closed position and is provided with a pull ring 3| which is adapted to receive an operating switch hook. Threaded into the body portion of the pull ring is a stem 32 having a head portion 33 which is extended outwardly beyond the stem and shaped to form a cam surface 34. Adjacent the head 33, the stem is provided with an upwardly extending boss 32a, the purpose of which will shortly be evident. Cooperatively associated therewith is a pair of spaced arms 35 and 36 which are secured together to form a latching lever. This lever is provided intermediate its ends with a trunnion 31, the ends of which are supported in aligned elongated arcuate openings 38 respectively disposed in the spaced legs 39 and 40 of a U-shaped bracket 4|.

A compression spring 42 is connected at one end to the latching lever and at its other end bears against a plate 43 on a stem 44 which is threaded into the bracket 4| for axial movement, to enable the adjustment of the pressure exerted by the spring. The stem 44 may be locked in. adjusted position by means of a lock nut 45. It will be observed that the compression spring is off center relative to the pivotal support of the latching lever and so disposed thatthere is a tendency for the latching lever to be rotated about the trunnion 31 in a counter-clockwise direction. The forward end of the latching lever is provided with a roller 46 for cooperation with the cam surface 34 of the head 33.

Pivotally mounted on a pivot pin 41 for swinging movement between the arms 35 and 36 is a trigger 46 having arms 49 and 50 which are substantially at right angles to each other. The arm 59 has one end thereof formed as a cam surface 5| which terminates near the end of the arm 50 in a swell 52.

The arm 56, when the switch is in closed position, is disposed so that the swell 52 engages a roller 53, as shown in Fig. 1. In this position, the arm 56 opposes the counterclockwise movement of the latching arm under the influence of the compression spring 42 to unlatch the door. Also, when the arm 50 is so disposed, the arm 49 'projects slightly below the associated end of the latching lever.

Mounted on the rear surface of the switch box is a tripping coil 54 which is surrounded by a frame 55. This frame is secured to a pair of spaced angle iron legs 56 and 51 which depend from a base plate 58 upon which the bracket 4| is mounted.

The lower side of the coil supporting frame is apertured to receive a solenoid core 58s. and the upper side is apertured as shown at 59 to receive a stem 60 which is connected to and movable with the solenoid. The upper end of the stem 60 carries an abutment plate 6|. The pick-up point of the solenoid is adjusted by means of adjusting screw 62 which is threadedly supported in a stirrup 63 which is secured to the frame 55. Associated with the screw 62 is a plate 64 which forms a seat for the solenoid, and which may be raised or lowered by means of the screw to vary the pick-up point of the solenoid.

Interconnecting the legs 39 and 40 of the bracket 4| is a web 65 which is apertured to receive a rod 66 for axial movement. The rod is guided by means of .guide rollers 61, 68 and 69 (Figs. 3 and 4). The forward end of this rod is provided with a head portion 10 which is held in abutment with the head 33, when the door of the switch is closed, by means of an expansive spring 1| having one end bearing against the head.10 and its other end bearing against the web 65. I

The other end of the rod 66 carries an outwardly projecting plate 12 which is arranged to contact the outer end of the arm 50 of the trigger, when the rod 66 is permitted to move under the influence of spring 1|, by opening the switch door.

The operation of the tripping and latching mechanism will now be explained.

With the switch in closed position, the latching and tripping mechanism will be as shown in Fig. l, the latching lever being locked against movement to release position by the trigger 46, since the swell 52 is in engagement with the roller 53.

Assuming that the coil 54 is now energized by connecting it to an electric circuit, the solenoid core 58a picks up and the abutment plate 6| strikes the arm 49 of the trigger and rotate the same in a clockwise direction to bring the arm 50 to such a position that the roller 53 is in engagement with the cam surface 5|. So long as the coil is energized, the solenoid will oppose and will supersede the action of the trigger in opposing movement of the latching lever to release position, as the plate 6| also engages the associated arm of the latching lever, as shown in Figs. 2

and 3.

Referring to Fig. 4, it will be observed that when the coil is deenergized, the solenoid drops and permits the counter-clockwise movement of the latching lever under the influence of the spring 42 about its trunnion 31 as a pivotal axis. This movement of the latching lever to release position causes the roller 46 to disengage the head 33 and at the same time, the engagement of the cam surface 5| on the trigger causes the trigger arm 49 to assume a position substantially at right angles to and above the associatedend of the latching lever.

Movement in this direction is arrested by a stop pin 58a.

Assoon as the head 33 is released, the expansion spring H moves the rod 88 to the right, as viewed in Fig. 4, to automatically open the door of the switch box to disengage the switch contacts. As soon as the door is released-randkicked outwardly by the action of spring H, it continues by virtue of gravity to assume a depending position below the box. Simultaneously with this action, the plate 12 will be moved into engagement with the outer end of arm 58 and will rotate the arm in a counter-clockwise direction. This movement and the action of the cam surface on the roller 53 will reset the latching lever to normal position, as shown in Fig. 1.

The switch may be reclosed and latched in closed position by simply manually closing the door of the switch. As the door comes to fully closed position, the cam surface 34 engages the roller 46 and raises the roller, the latching lever in this case being pivotally rotated about the pivot 41 a limited amount as determined by the length of the arcuate openings 98. As soon as the door has seated, the roller will drop behind the head 33 striking the boss 32a and latch the door in closed position. The boss 32a is of such height that it will prevent lever 35 from pivoting about trunnion 31 when the roller 46 is at its lowermost position, and also prevents the lever 35 from kicking up when the door [5 is closed. Such kicking would tend to release the trigger arm 58.

The entire tripping and latching mechanism is enclosed within a suitable housing 120.

A typical'installation in which a switch as described may be used is shown in Fig. 5, comprising a distribution system which includes a primary source of supply, as 13, which represents a substation bus. Connected to this bus is a feeder I4 in which is mounted a main circuit breaker 15. This circuit breaker is arranged to trip an overload, and is provided with a trip coil I6 which is connected in the usual manner to a current transformer 11. The feeder 14 may be an underground cable or overhead main and is connected to an overhead main 18 which, in this instance, has its ends connected through switches such as described in connection with the present invention to a bridging underground cable I9, whereby a primary loop is formed, this loop having an underground section of cable which it is desirable to protect against internal short circuit.

In the usual arrangement, either expensive sectionalizing circuit breakers would be used, which would necessitate expensive auxiliary devices, such as relays, etc.; or in order to cut down the cost, hand operated switches would be used, which require considerable time to operate and cause objectionably long interruption of the entire circuit in case of a cable fault. In the present scheme using switches A, current transformers 88 and 8| are placed at the ends of the cable 19, these current transformers being connected by means of conductors 82 and 83 in such a manner that, when current flow through the current transformers in the same direction, there will be opposing potentials in the conductors 82 and 83. As soon, however, as thereis a short circuit in the cable lying between the current transformers, current will flow in opposite directions through the current transformers, and a potential will be built upbetween the conductors 82 and 83. Advantage is taken of this fact to provide tripping potential for the trip coil 84 of switches A. These trip coils are connected across conductors 82 and 88 by conductors 85 and 86 in each case.

When a short circuit occurs on the cable, the v operation of the switches A is as follows:

The coil 84 being energized picks up the solenoid 81 to cause a spring latch 88 to engage a tripping latch 89. So long, however, as the coil 84 is energized, the switches A will not'be tripped. The short circuit on the cable will cause the circuit breaker 15 to trip out on overload and the primary loop will be deenergized, with the result that the trip coils 8484 of the switches A will likewise be deenergized. This enables a spring 98 to actuate the solenoid in such a direction as to trip the switches A. As soon as the switches have been tripped, a spring 9| will return the tripping latch to normal position, so that when the switch is reclosed it will be latched in closed position.

It will, thereforabe seen that the tripping of switches A, to isolate the bridging cable, will not take plyace until after the primary circuit has been deenergized in response to tripping the main circuit breaker 15. Consequently the switches A do not have to interrupt the fault or load current and consequently do not have to be designed so as to have interrupting capacity characteristics. These switches may, therefore,-

be constructed at materially less cost than in the case of oil circuit breakers for a similar purpose.

As soon as the faulty cable has been cut out, the main circuit breaker 15 may be reclosed in any of the usual ways, such as by an electric operating means, or by automatic reclosing equipment. The primary feeder 14 being energized, the primary main 78 may again reestablish service to branch feeders such as 92, which feed through step-down transformers 93 to energize a utilization circuit 94, which may be a low voltage network.

The switch A, such as described herein, may

also be used for disconnecting a branch feeder such as shown at 95 from the primary loop.

In this case, as shown in Fig. 5, the feeder 95, which may be an underground cable, is connected through a fuse 96, step-down transformer 91 to a utilization circuit 98 which may be a network fed from other sources than the sub-station bus I3. Current transformers 99 and I08 are provided at the ends of the cable 95, the same as in the case of the bridging cable 19, and the tripping coil of the switch is connected in the same manner, and the tripping mechanism of the switch A in this case operates in the same manner, as previously described, upon a short circuit in the cable 95.

From the foregoing description, it will be apparent thairthis invention provides a novel switch for a system of distribution at a very economical cost; which avoids the necessity of providing expensive circuit breakers which must have sufficient interrupting capacity to interrupt fault current; and in which the parts are arranged to preset the switch and delay opening of the switch contacts until after the circuit in which the switch is connected has been deenergized elsewhere.

But, it is of course to be understood that, although we have described in detail the several embodiments of our invention, the invention is not to be thus limited, but only insofar as defined by the scope and spirit of the appended claims.

We claim as our invention:

1. In an electric switch device for: disconnecting portions of an electric circuit, a pair of contact members, bridging means for said contact members comprising a pair of conductive members pivotally related to provide a toggle structure, means mounting said toggle structure for movement between said contact members, said contact members being positioned to engage the ends of said conductive members while said toggle structure is in broken condition, whereby as said toggle structure is straightened said conductive members engage said contact members with increasing pressure, means for actuating said toggle structure relative to said contact members, and means mounting said contact members for opposing displacement of said contact members as said toggle structure is straightened therebetween.

2. In an electric switch device for disconnecting portions of an electric circuit, a pair of spaced contact members each having a surface, said surfaces being substantially parallel and opposed, a separate conductive member for engaging each of said surfaces, means pivotally associating said conductive members intermediate said contact members for providing a toggle structure, means mounting said toggle structure for movement into and out of bridging engagement with said contact members, and biasing means for urging one of said contact members towards the other of said contact members, whereby said contact members yield as said toggle structure is straightened therebetween.

3. In an electric switch device for disconnecting portions of an electric circuit, a pair of spaced contact members each having a surface, said surfaces being substantially parallel and D- posed, a separate conductive member for engaging each of said surfaces, means pivotally associating said conductive members intermediate said contact members for providing a toggle structure, means pivotally mounting said toggle structure for rotation into and out of bridging engagement with said contact members, wherein said toggle structure is straightened between said surfaces, and means mounting said contact members for opposing displacement thereof as said tog e structure is straightened.

4. In an electrical switch device, a supporting structure, a pair of spaced contact. members, means mounting said contact members on said supporting structure, and bridging means for said contact members comprising a pair of conductive members pivotally related to form a toggle structure, said conductive members having free ends for engaging said contact members, means mounting said toggle structure for movement between a first position wherein said free ends engage said contact members and said toggle structure is in substantially extended condition and a second position wherein said toggle structure is displaced from said contact members, and means efiective in said second position for urging said free ends towards said contact members, said mounting means being constructed to oppose movement of said contact members as said toggle structure is extended thereagainst.

5. In an electric switch device for disconnecting portions of an electric circuit, a supporting structure, a pair of contact members, means mounting said contact members on said supporting structure, bridging means for said contact members comprising a pair of conductive members pivotally related to provide a toggle structure, means mounting said toggle structure for movement between said contact members, said contact members being positioned to engage the ends of said conductive members while said toggle structure is in broken condition, whereby as said toggle structure is straightened said conductive members engage said contact members with increasing pressure, stop means carried by said supporting structure and positioned to engage each of said conductive members for preventing movement of said conductive members out of engagement with said contact members as said toggle structure is straightened therebetween, and means for actuating said toggle structure relative to said contact members.

6. In an electrical switch device, a pair of spaced contact members having parallel opposed surfaces and having projections adjacent corresponding edges of said surfaces, and bridging means for said contact members comprising a pair of conductive members pivotally related to form a toggle structure, said conductive members having rounded free ends for engaging said con-' tact members, means mounting said toggle structure for movement between a, first position wherein said free ends engage said contact members in the angles formed by'said parallel sur faces and said projections, and said toggle structure is in substantially extended condition and a second position wherein said toggle structure is displaced from said contact members, biasing means for resiliently urging said contact members towards each other, and means effective in said second position for urging said free ends towards said contact members.

'7. In an electrical switch device, a pair of conductive members; means pivotally connecting said conductive members to form a toggle structure; a pair of contact members; means supporting said contact members for engagement respectively with-the free ends of said conductive members when said toggle structure is in extended condition and said pivotal connecting means is in a first position; means mounting said pivotal connecting means for movement relative to said contact members from said first position towards a second position to break said toggle structure and remove said conductive members from engagement with said contact members, said mounting means also serving to guide said pivotal connecting means from said second position towards said first position for engaging said conductive members with said contact members and for extending said toggle structure to increase the pressure of said conductive members against said contact members, said supporting means including means designed to oppose movement of said contact members under the influence of said pressure; and means carried by said supporting means and positioned in the path of movement of said conductive members for preventing movement of said conductive members beyond said contact members as said pivotal connecting means moves from said second position towards said first position.

JOSEPH J. SHOEMAKER. HOWARD P. SEELYE.

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