US1993273A - Electric switch - Google Patents

Description

March 5, 1935. J HAMMERLY 1,993,273

ELECTRIC SWITCH Filed Dec. 30, 1950 H I llllllllllllllllllllllml Patented Mar. 5, 1935 A UNITED STATES PATENT OFFICE ELECTRIC swrrcn of Connecticut Applicationnccember 30, 1930, Serial No. $5,482

Claims.

My invention relates to electric switches of the knife blade type and particularly to such switches as are necessarily or preferably provided with means for breaking up or. interrupting the are '5 which occurs in the opening movement of the switch,- extending from the tips of the stationary contact Jaws to the movable switch blades.

The movable blades and the co-related stationary contact jaws in switches of this type are of such forms and the relative position of the switch blades, with respect to the tips of the contact jaws, in the opening movement of the switch, is such that it is very difllcult to entirely prevent the formation of an arc when heavy currents and/or high voltages are to be interrupted.

Should the arc be of considerable magnitude and/or repeated many times it results in the burning, pitting and oxidizing ofthe respective contact members, thus reducing if not entirely destroying the effectiveness of the switch.

It has been the practice, in some instances, to provide an insulating member which would be moved between the contact jaw and the blade simultaneously with the opening movement of the switch, but such construction is not entirely satisfactory in all cases for the reason that it is usually impracticable to fully interpose the insulating member between the metal members until the blade has been moved away from the contact jaw sufllciently to permit the full movement of the insulating member and this is the period during which the arcing occurs.

The Getchell Patent #1,407,852, February 28, 1922 is an example of the last mentioned type of switch but the arc interrupting barrier 20 of the Getchell patent I have found not to be. as effective as desirable in some cases.

' I have discovered that superior results may be obtained by providing a metal roll supported by insulating side plates and so arranging the opening movement of the switch that it will simultaneously move the metal roll to such a position that the arc, in order to continue, must jump from the contact Jaws to the roll and, in turn, from the roll to the switch blade thus making two breaks in each pole of the circuit. It is well known to the art that two breaks of a given length are much more effective in disrupting an arc than a single break of double the given length. l

I have further found that aluminum is much better adapted for the material of the roll than brass or copper probablyfor the reason that it has a higher electrical resistance which-tends to retardthearc. Ithasfarleastendencytooxidize through atmospheric conditions and, when subjected to the electric arc, it gives ofi a form of oxide which is particularly effective in smothering the arc. However I do not claim that this is the sole reason for the unusually effective operation of my invention which is not limited to the use of aluminum at this point.

Another peculiar property of aluminum, on account of which I prefer its employment, is that the electric arc tends to draw particles of the metal away from the body thus tending to keep the contact surfaces clean and free from oxidition.

I have-found in practice and tests that a switch provided with an aluminum or other suitable metallic arc interrupter as herein disclosed is unusually efiective in disrupting the electric arc and that a switch of given dimensions or rated capacity will safely open or break a circuit of much greater capacity thana similar switch provided with an arc interrupter composed of any form of insulating material.

One of the principal objects of my invention is to provide means for increasing the amount of electrical energy that can safely be interrupted by a switch of given over-all dimensions.

Another object of my invention is'to provide means for effectively extinguishing an arc carrying a greater amount of electrical energy and produced at the point of interruption of the circuit, than would otherwise be possible with a circuit breaking device of a given size.

A further object is to disrupt electrical arcs produced by the breaking of electrical circuits by automatically breaking them up into arcs of shorter length.

Another object of this invention is to temporarily introduce into the path of an electric current are an intermediate metallic member which will subdivide the are into shorter arcs in order to more readily quench-the same.

Another purpose of my invention is to minimize the extent of spread of an electric are produced at an undesired spot, by changing one long are into a series of shorter ones, thereby reducing the distance to which it will rise vertically.

Another purpose of my invention is to utilize the quenching properties of aluminum or similar metals to favor the more rapid extinguishment of arcs produced at undesired points, by the temporary introduction of such metals into the path of such arcs.

Another object of my invention is to provide a knife switch construction including a metallic arcinterruptingmemberhavingasurfaceadaptll ed to be moved between the contact jaw and the switch blade in the opening movement of the switch.

Another object is to provide a. knife switch construction including a metal arc interrupting member adapted to be moved into the arcing area in the switch opening movement in such a manner that the arcing points of the interrupting member will be changed as the operating movement is continued.

Another object is to provide a switch construction including an aluminum arc interrupting member adapted to be moved into the arcing area when the switch is opened to break the circuit.

Another object is to provide a switch construction including an aluminum roll adapted to be moved to a position between the stationary and movable contacts when the switch is being opened.

Another object is to provide a switch construction including a pivotally mounted and freely rotatable metallic arc interrupting member adapted to be moved into a position to intercept the arc in the opening movement of the switch.

Fig. 1 is a side view of a switch unit embodying the improvements of my invention, the parts being shown in the completely open position.

Fig. 2 is a front view of the same.

Fig. 3 is a fragmentary view showing the contact parts of the arc interrupter in the position which they occupy as the circuit is being opened.

Fig. 4 is a similar view showing the parts at a point intermediate the positions of Figs. 1 and 3.

The switch blade 7 is hinged or supported on a base 8 in the usual manner and its movable or swinging end is adapted to coact with stationary jaws consisting preferably of two parts 9 and 10, the part 9 having its edge substantially parallel with the edge of the blade when the blade is just contacting with the tip. The base 8 and the stationary contact are supportedin a suitable manner on a base or panel 11 and provided with suitable cable connections or circuit terminals as customary.

It should be understood that any number of the switch units may be used and that suitable means for moving the switch blades will be employed. I have shown in the drawing a simple type of handle connected to the blade for moving it.

The are interrupter of the former Getchell patent includes two insulating side plates 13, which are hinged at 14 to the stationary contact and adapted to swing around the ends of the stationary contact jaws.

These insulating plates are connected to the switch blade or its operatinghandle by means of links 15 so that as the switch blade is moved toward and from the stationary jaws the plates are oscillated on the axis of the pin 14.

Between the plates 13 I mount a member 16, which constitutes an arc interrupter or deflector. This member is of metal and is preferably in the form of a roller rotatably mounted on the tubular rivet 17 which connects the two side plates. This roller is located so that it just clears the tips of the contacts 9 and 10 as the plates are swung on the axis of the pin 14. The roller is also located with respect to the path of movement of the swinging switch blade so that the roller is interposed between the tip of the switch blade and the stationary contact as the switch is being opened. This conducting member being introduced into the path of the are which tends to form between the stationary and movement contacts, causes the arc to be deflected outwardly to the roller 16 and thus divides the arc into two parts and so reduces the effect of the are as to avoid continuation of the arc.

As the blade is moved toward the open circuit position the arc travels outwardly toward the tip of the blade where it is deflected to the roller 16 and to the tip of the contact 10. The possibility of pitting or burning is thus restricted to the tips of the blade and the contact and to the roller. Obviously even if there should be a burning of the metal at the tip of the contact or of the blade it will have no deleterious effect upon the normal contact making portions of them. On the other hand the movement of the roller also tends to break the arc and even if there should be a pitting of theroller due to working it would have, no effect upon the normal conductive action of the switch.

It should be understood that the arc deflector 16 may be made in various forms and that more than one might be employed if desired. I have shown an additional member 18 connecting the insulating plates 13 of the interrupter which reinforces the plates.

While these switch units are complete in themselves, it will be understood that the are interrupter is useful in laterally confining the arc to the individual unit so that where such a switch unit is mounted in a metal box or adjacent another unit there is no tendency for the arc to jump from one unit to another or from one unit to the enclosing box or receptacle.

It should be understood that this invention is applicable to various types of switches, both of the hand operated and snap action or quick makeand-break types. The invention is especially useful however, in switches of the slow movement type which are more subjected to arcing than the snap action switches. My invention enables one to interrupt circuit with safety even with a hand operated or slow moving switch blade.

I claim:

1. A switch including a stationary contact, a hinged contact blade coacting therewith, a pair of insulating plates connected to the blade and hinged to swing on opposite sides of the stationary contact to laterally confine an are which tends to form as the blade is moved to open the circuit and a conducting member carried by and between said plates and movable bodily in an arcuate direction toward the end of the stationary contact and the blade and then away from the contact while the blade moves away from the contact and from the conducting member to intercept the arc as the circuit is opened.

2. In an electric switch a stationary contact, a hinged blade co-acting therewith, an insulating plate pivotally mounted at each of the opposite sides of said contact and connected by a rivet to move about the stationary contact, and a conducting roll member vrotatably mounted on said rivet and between said plates and adapted to be moved adapted to be moved bodily in an arcuate direction over the contact making end of the stationary contact without engagement therewith, and manually operated means of connection between said side plates and the movable blade, whereby the metallic member swings first toward the contact between the contact blade and the stationary contact and then away from the contact as the side plates swing alongside of the contact and the blade recedes from the metallic conducting member.

4. In an electric switch, an insulating base, a stationary hinge post and a stationary contact jaw supported by the base and spaced apart from each other, a blade hinged to said hinge post at one end and adapted at the other end to engage said contact jaw, a pair of insulating plates pivotally hinged so as to move on opposite sides of the contact jaw and the blade and connected to the blade to swing therewith, a rivet connecting said plates, and a conducting arc arresting roller carried by said rivet and between said plates in such a position as to move toward the end of the contact jaw as the circuit is first opened and to move away from the contact jaw as the switch blade is moved to the fully open circuit position and away from said roller so as to attenuate any are which may tend to form.

5. An electric switch including a contact post and a hinge post, a movable blade pivotally mounted on said hinge post and engageable with said contact post, an insulating plate pivotally mounted at each of the opposite sides of said contact post, a metal conducting member mounted on and between said insulating plates, a link connecting each of the said insulating plates to said blade whereby the operating movement of said blade will move said insulating plates simultaneously and will move said conducting member bodily in an arcuate direction adjacent and around the end of the contact breaking tip of said contact post with a constantly changing position with respect to any given point of the contact breaking portions of said contact post and said blade and whereby the blade recedes from the conducting member and from the contact post as the switch is fully opened.

HERMAN J. HAMMERLY.

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