US1973252A - Switch contact arc extinguishing means - Google Patents

Description

Sepo'l, 934. M E, HENNING 3,973,252

SWITCH CONTACIl ARC EXTINGUISHING MEANS Filed' Jan. 26, 1931 CURRENT SUPPLY Q Magg@ f Patented Sept. 11,1934

PATENT OFFICE SWITCH CONTACT ARC EXTINGUISHING MEANS Malcolm E. Henning, Des Moines, Iowa, assigner to Penn Electric Switch Co., Des Moines, Iowa, a

corporation of Iowa Application January 26, 1931, Serial No. 511,350

` iclaim.

The purpose of my present invention is to provide a means for extinguishing the arc formed between separable contacts of a switch, such means being of simple, durable and inexpensive construction.

A further object is to provide such a means for the purpose of considerably increasing the capacity of the switch structure without the necessity of making any of the parts more complicated, but by merely adding effective arc extinguishing means to the switch structure as' already manufactured.

A further object is to provide an arc extinguishing means for a pair of separable switch contacts in the form of a magnet mounted adjacent the contacts whereby the arc formed between them is effectively extinguished or blown out due to the iield of the magnet.

Still a further object is to provide an arc extinguishing means of this character for use with a pressure actuated automatic type of switch and one which may be used with a combination control switch and air compressor unloader valve as well as with the switch alone.

Still another object is to provide such an arc extinguishing means in combination with a iioat actuated switch structure.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claim, and illustrated in the accompanying drawing, in which:

Figure 1 is a side elevation of a switch structure embodying my invention, the cover of the casing being removed for showing the interior details of the structure.

Figure -2 is a sectional View on the line 2--2 of Figure `1 showing the magnet and its securing means also partly in section. y

Figure 3 is a view similar-to Figure 1 showing a float actuated switch rather than a pressure actuated one; and

Figure 4 is an electrical diagrammatic view showing the manner in which the arc between the separable contacts is extinguished.

On the accompanying drawing I have used the reference numeral 10 to indicate generally a casing of a switch structure. The casing 10 has a back wall 12 and a cover plate 14. On one end of the casing 10 a diaphragm housing 16 is provided. A pipe connection 18 communicates with the housing 16 for admitting air or the like under pressure tc a dphragm 20. The diaphragm (Cl. .2M-147) 2O is positioned between the diaphragm housing 16 and an end plate 22 of the casing 10.

A diaphragm arm 24 of bell crank shape is pivoted at 26 to ears 28 extending from the end plate 22. A thrust pin 30 contacts with the diaphragm 20 and with the diaphragm arm 24 for imparting movement from the diaphragm to the arm depending on pressure changes within the diaphragm housing 16. A main spring 32 retains the diaphragm arm 24 in contact with the thrust pin 30 and the thrust pin in contact with the diaphragm 20. By means of a ,screw 34 and a nut 36, the tension of the main spring 32 may be adjusted for thus changing the range of operation of the arm 24 with respect to the pressure introduced into the diaphragm housing 16.

A switch arm 38 is pivoted on a pivot bolt 40 and serves ask an operative means of connection between the diaphragm arm 24 and a movable switch block 42. The diaphragm arm 24 and the switch arm 38 are operatively connected together by means of a link 44. The link 44 has a V-cam end 46 coactable with a roller 48. The roller 48 is rotatably mounted on a pin 50 carried by the diaphragm arm 24, the link 44 being received through a slot 52 formed in the arm.

To maintain the cam end 46 of the link 44 in engagement with the roller 48, I provide a spring 54 having one end connected with the link 44 and its other end connected with a stationary pin 56. The upper end of the link 44 is connected by means of a pin 58, links and a pin 62 with the switch arm 38. Enlarged openings 64 are formed in the switch arm 38 for limited movement of the pin 58 relatively to the switch arm. The switch arm 38 is formed of a pair of bars spaced apart, as best shown in Figure 2, the links 60 being interposed between these bars and the link 44 which is located between the links 60.

The movable switch block 42 is pivoted on a pin 66 carried by the switch arm 38 andis guided relative to a stationary switch block 68 by means of a guide pin or rod 70 secured to the switch block 42, and slidable through the switch block 68.

Stationary contacts 72 and rI4 are mounted on the stationary switch block 68. Movable contacts 72a and '74a are mounted on and carried by the movable switch block 42. Terminal screws 76 and '78 are provided for connection in the circuit to be controlled by the switch structure. Flexible leads 80 and 82 extend from the contacts 72a and 74a respectively and are alsoadapted for connection in the circuit to be controlled.

The means for extinguishing an arc formed between the contacts 72 and 72a upon their being separated consists of a magnet 84 having a pole 86 located adjacent the contact 72 and `a lpole 86a located adjacent the contact 72a. The magnet 84 is retainedin position with respect to the back wall 12 of the casing 10 by means of a screw 88. A base plate of insulation 90 which is usually provided back of the switch blocks 42 and 68 is extended between the magnet 84 and the back wall 12 of the casing. A retainer plate 92y is positioned underthe head of-the screw 88 with a sheet of insulation 94 between the plate 92 and the magnet 84. An insulating sleeve 96 surrounds ythe screw 88 between the poles 86 and 86a of the magnet. Thus the magnet is lentirely insulatedl from the contacts'and the casing.

The arc extinguishing means may be used on the automatic switch structure thus far described or on such a switch structure in combination with an air compressor unloader valve 98. The pin 62 carried by the switch arm 38 projects through an enlarged opening 100 in the back wall 12 for engaging and moving the valve stem 102 of the `unloader valve, whereby operation of the switch structure to open circuit position raises the Valve stem 102 and operation of the switch structure to closed circuit position allows it to be lowered. The valve, of course, is connected with the unloader tank of the air compressor for unloading the tankwhenever the circuit is open and the air compressor at rest.

In Figure 3,'I have shown a iioat arm 104, in place of the diaphragm arm 24 which is actuated by a iloat 106.' The float rod 108 is connected with the float 106 and is slidable through an eye 110 on the end of the iioat arm 104. A slot 112 is provided in the wall of the casing 10 for the float arm 104 to swing in. The top and the bottom of the slot 112 limit the upward and downward movement of the oat arm 104. Adjustable stops 114 are provided on the float rod 108 for thus adjusting the switch to operate to open and closed circuit positions at any desired liquid level. The parts 38 to 94 are the same in the float switch structure shown in Figure 3 as they are in thek pressure actuated switch structure shown in Figure 1.

. Practical operation maintained constantly, while in alternating current the cycles or pulsations of the current cause the current pressure or voltage at times to be zero. yDirect current readily iiows across an air gap caused by separating switch contacts, the contacts acting as electrodes. With alternating current, due to its pulsations, there is a tendency to extinguish the arc whenever the current value is at zero. The obvious result is that a switch which has a maximum capacity for alternating current without undue arcing at the switch cont'acts can not carry the same amount of direct current because the arcing would be excessive. Therefore a switch structure as disclosed without the magnet 84 has a certain maximum capacity on alternating current, but its maximum capacity on direct current is considerably lower.

As a simple means of increasing the capacity of the switch so that it can be rated the same for direct as for alternating current, I have used the magnet 84 placed in the position illustrated so that the arc formed between the contacts upon their being separated, occurs in the magnetic eld of the magnet. Since the magnetic eld of a magnet repels or attracts an arc formed between contacts, the formation of an arc will be as illustratedv in Figure 4 between the contacts 72 and 72a. Without the magnet, the arc would be straight as shown between the contacts 74 and 74a. (The contacts being illustrated greatly enlarged in this figure.)

A bent arc as shown between the contacts 72 and 72a is obviously longer than a straight onev and therefore for a givenv current pressure, the arc will be extinguished while the contacts are still close together, instead of when they are farther apart as when no magnet is used. As soon as one arc is extinguished, the circuit is broken and therother one will, of course, immediately be extinguished.

From the foregoing description, it will be seen that I have provided a very simple arrangement for increasing the capacity of a switch structure without the necessity of changing any of the parts, by merely adding the guishing mean: to the structure.

The device may be applied to any type of switch device with equal eiectiveness and if it is desired to more greatly increase the maximum capacity of the switch, a second magnet can be provided for the contacts 74 and 74a.

Some changes may be made in the construction I and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my clam, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within its scope.

I claim as myinvention:

In a structure of the character disclosed, a pairv of separable switch contacts and a horse-shoe magnet having one pole adjacent one of said contacts and its other pole adjacent the other of said contacts, said contacts lying in the plane of said magnet,- being separable in a direction at right angles to the poles thereof and both being positioned beyond said poles.

MALCOLM E. I-IENNING.

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