US2125201A - Circuit breaker - Google Patents

Description

July 26, 1938. R. N. ROWE CIRCUIT BREAKER Filed May 16, 1936 2 Sheets-Sheet 1 INV'ENTOR RAYM mm N Row I E v Q P N R CIRCUIT BREAKER Filed May 16, 1936 2 Shee'ts slmel 2 atented July 26, 1938 UNITED STATES PATENT OFFICE CIRCUIT BREAKER necticut Application May 16,

4 Claims.

My invention relates to circuit breakers. In arc interruption, particularly for circuit breakers, a principle of'arc extinction known as compression interruption has been used. The present invention is an improvement in devices in this field of arc interruption.

One object of this invention is to simplify the structure used in arc interrupters of the compression type.

Another object is to strengthen the compresslon chambers in these breakers.

Still another object is to improve the action of compression chamber seals in these arc interrupters.

A further object is to make a chamber seal that is comparatively inexpensive when com pared to the seals now known to me.

These objects, and others, are accomplished by making a circuit breaker in which the contacts are separated within a closed chamber. As is usual in breakers of the compression are interruption type, the separated contacts draw an are which heats the gases enclosed in the compression chamber. The heating of these gases causes them to expand, until the increased gas pressure in the chamber produces an increase in the arc drop suflicient to extinguish the arc.

Because this whole action depends upon a close sealing of the chamber, it is important that-the wall of the chamber through which any movable contact is projected be provided with a strong and eihcient packing or the like, to prevent escape of the gases under pressure. Leather, or other flexible, semi-resilient material, has been used for this packing. According to the present invention I make the seal for the movable contact member out of metal or other strong and substantially inflexible and non-resilient material. However, the mere close fitting of this seal around the moving member is insufiicient eflec- 'tively to prevent escape of the heated gases. To overcome this detect, the wall of the sealing member, or the wall of the movable contact carrier, or both, is provided with a series of coarse circumferential corrugations or serrations which, as explained below, prevent escape of enough gas under pressure to affect the circuit-breaking operation.

In the accompanying drawings I have illustrated several forms that my improved seal may take, and have shown one form of switch and circuit breaker which may be used in connection therewith.

In these drawings- Pig. 1 is a plan view of a two-pole ganged 1936, Serial No. 80,030

switch and circuit breaker utilizing my invention. The parts are in on position.

Fig. 2 is a vertical section along line 2-2 of Fig. 1.

Fig. 3 is a side elevation of some of the switch parts.

Fig. 4 is a sectional view of the switch and circuit breaker parts in ofi" position.

Fig. 5 is a similar view of these parts in tripped position.

Fig. 6 is an enlarged sectional view of a compression chamber and contact carrier illustrating the preferred form of my invention.

v Fig. 7 is an enlarged section of a modified form of seal for the contact carrier.

Fig. 8 shows another form of seal according to my invention.

Fig. 9 shows still another form of seal for the contact carrier.

In order to illustrate a completely operative device I have shown a novel form of switch and circuit breaker in which my improved chamber seal is used. It should be understood that many other suitable types of switch and breaker mechanism could be used without departing from the spirit of the present invention.

In the device shown, the switch has an insulating base l0 which may be connected to other bases of identical switches by means of screws or rivets II which pass through connecting straps l2 and i3. As shown, two of these switches are ganged together. It is obvious that they may be used singly or in combinations greater than two when desired.

Mounted on the base is a frame piece ll, U-shaped in cross section, each arm of the U carrying an extended leg I 5. Straddling the frame is a switch yoke l8, pivoted as at H in a recess of the base. The yokes of a plurality of ganged switches are connected together by an insulating connecting bar it, operated by a bandle l9.

The switch throw piece 20 is pivoted on axis 2| between the arms of the frame and has a cross bar 22 which connects the sides of the piece together. At its lower end, the throw piece carries a rod 23, which extends on either side outside of the confines of the switch frame It. Between each end of this rod 23 and ears 24 on yoke ii are stretched springs 25. The rod 23 passes through the contact-carrying plunger 26 which has a contact 21 at one end. The position of the yoke pivot I l is so arranged with respect to the pivot axis 2! of the throw piece and the ends of the springs 25 that movement of the yoke produces a snap action of the plunger and contact in each direction.

A tri piece 28 is also pivoted on axis 2i in the switch frame. This trip piece has a catch roller 29 rotatablymounted between its sides. A resetting bar 38 connects the sides of the piece together.

Arms ti, on the trip piece 28, carry a crossrod of catch 32 which extends outward far enough to engage one edge of the switch throw piece 2b to' prevent clockwise rotation of the throw piece beyond the catch. The free ends of the arms 3i are engaged by a cross-head 33 on a bar 34!. This bar; is slidably mounted in a pressure plate 35 which in turn ispivotally held at its ends byseats in the ends of legs 85 of the switch frame. A spring 3b surrounds bar Sl and presses against head 33 and plate 35. These parts areso positioned with respect to the pivot axis of trip piece 2t that the spring 36 always exerts a pressure tending to turn trip piece it in a counter-clockwise direction.

A catch piece 3? is pivotally mounted in frame id as at 38 by ears or pivot lugs 59. One end of this catch piece normally abuts against roller 29 on trip piece 28, thus preventing spring 36 from pushing the trip piece to releasing position. See Figs. 2 and a. To insure normal engagement with the roller 29, a small, light spring ill is secured between the opposite end of the catch piece and a fixed part of the switch base or frame. An adjusting or calibrating screw ll is threadedly engaged with the outer end of catch piece El and is held in its adjusted positions by lock-spring 62. This catch piece is actuated upon a short circult or overload by any suitable electro-responsive device. As shown, the electro-responsive device consists of a bimetallic strip d3, fixedly mounted at one end with respect to the switch base by conducting support dd.

The free end of the bimetallic strip is attached to one end of a flexible current-carrying cable 35, the other end of the cable being secured to one end of the contact plunger 26. This free end of the thermostatic element will flex upwardly when the strip is heated, thus engaging the end of adjusting screw ii and tripping the catch piece 3? by overcoming theslight pressure of counterbalancing spring QB. To prevent unnecessary current fiow through the switch parts, a strip of mica or other flexible insulating material lfi is secured to the top surface of the thermostatic strip 33 between the end of. screw tit and strip at.

Current is supplied to the electro-responsive element through support 65. Terminal d? makes connection with a. strap 18, which in turn is electrically connected to support 365 by means of a screw or the like 439.

When a plurality of switches are ganged together, adjacent catch pieces iii are connected for simultaneous movement by means of an insulating bar it, held to the catch pieces as by screws 5!.

The opposite current side of the switch preferably contains the compression chamber. This chamber is composed of acup-shaped piece 52 which has a stationary contact piece 53 in its bottom. The cup andcontact are electrically connected to terminal 58 by means of a strip The walls of this sealing member fit closely around the surfaceof the movable contact carrier 2% but not tightly enough to bind the parts together. As shown' in Fig. 6, the walls of the sealing member are provided with a serrated surface in the'form of a coarse screw thread surrounding the movable contact carrier. the preferred form of sealing means by which the compression within the chamber is maintained-sufiiciently high to aid in arc extinction.

The operation of the switch is as follows, assuming the parts to be in the off position of Fig. 4: the switch handle is and yokes it are moved to the left, the springs 25 being put under increasing tension. When' the springs have stretched their maximum amount they start tocontract, pulling the rod 23 to the left. This rod swings the switch throw piece 29 clockwise and pushes the contact-carrying plunger rod 26 against stationary contact 53. The trip piece 28 and catch piece it do not move. The parts are then in the on position of Figs. 1, 2 and 3. Movement of the handle in the opposite direction causes the above mentioned parts to function in a reverse manner, throwing the switch into normal off position. Stops or lugs 5t on of the switch yokes.

When the switch is in on position, current flows from terminal to terminal through the fol? lowing parts: terminal 6?, strap it, screw connection 69, support dd, bimetallic strip as, cable d5, plunger 26, contact 27!, contact 53, compression chamber wall 52, connecting strip 55, and terminal 56.

On a short circuit or overload the thermostatic strip d3 will be heated and, flex upwardly. This will trip the switch mechanism to separate the contacts. Action is as follows: when strip 43 flexes upwardly it lifts screw ll upward, tilting catch piece 37 counter-clockwise around its pivots 39. f The other end of the catch piece will then become disengaged from catch roller 29 and spring 36 isable to push trip piece 28 in its counter-clockwise direction. As soon as cross rod or catch 32 engages the edge of the switch throw .under surface of this resetting piece will engage resetting bar 36 of trip piece 28 and the pressure of spring 36 will prevent springs 25 from pulling the yoke any farther. The parts are now in the tripped position of Fig. 5.

To reset the switch, after the bimetallic strip has cooled down and assumed normal position,

it is merely necessary for the operator to force the handle to full 01f position.

This is the switch frame limit the extent of movement When-the handle is so forced, resetting piece 59 bears against resetting bar 30 and pushes trip piece 28 (against the action of spring 36) clockwise into the position of Fig. 4. Counterbalance spring 30 will pull one end of catch piece 31 downwardly and the other end will engage catch roller 29 to hold the tripfpiecie in place. Resettingbar 3!! will also engage the upper surface of catch piece 37 to insure proper resetting at the end of the switch handle movement; The parts are now all in the position of Fig. 4 because the switch throw piece 20 and plunger 26 were al- 75 ready in off" position and have been held there by tension of the spring 25.

When the contacts 21 and 53 are separated under load or short circuit, arcing will take place within the compression chamber. Because the chamber is sealed, the pressure, built up by the expanding gases heated by the arc, will act to extinguish the arc. To seal the moving contact carrier at its place of entry into the chamber 1- have provided the structure described above in connection with Fig. 6. Other forms are illustrated in Figs. 7, 8 and 9.

It is theorized that the expanding gases, because of the serrations in the wall, are alternately expanded and contracted. It is believed that this alternate expansion and contraction in rapid succession creates an obstruction to the escape of the'gases and that this is why the proper compression is maintained in the chamher.

In Figs. 6 and 7 the serrations are in the form of coarse screw threads, in the first case on the inside of the aperture of the chamber wall, and in the second case on the outer walls of the contact carrier. These two forms are preferred mainly because of the extreme ease of their manufacture.

In Figs. 8 and 9 are illustratedother forms of serrations, namely, a series of adjacent circumferential grooves. In Fig. 8 these grooves are within the aperture of the chamber wall, and in Fig. 9 they are around the outer surface of the contact carrier. The spiral arrangement of the grooves in these forms does not seem to affect the efliciency of the seal produced, probably because thearc pressure is explosive in nature and tends to act equally in all directions.

It should be understood that the contact carrier of Fig. 6 may be used with the sealing tube of either Fig. 6 or Fig. 8. The contact carriers of Figs. '7 and 9, however, may be used with the sealing tubes of Fig. 6, Fig. 7, or Fig. 8.

Note that although I have shown a switch with a contact carrier that reciprocatesthrough one wall of the compression chamber, other forms of switches utilize contact carriers which have a twisting or rotary movement through one wall of a chamber. My improved sealing means is equally eifective in this other mounting of the contact carrier and the appended claims should be read with this in mind.

Because of the use of metal instead of other material in my seal, the structure is extremely strong and durable.

The tendency of ordinaryseals to cause sticking between the chamber wall and the moving contact carrier is obviated by my improved structure.

Another advantage is the fact that although the present seal effectively holds the pressure within the chamber during arc explosion, there is suflicient communication with the outer air to enable the pressures inside and outside of the chamber to equalize by slow leakage after arc interruption. This aids in cooling the chamber and shortens the periods during which the walls of the chamber are subjected to internal pressure. A further advantage of my invention is the simplicity of the compression chamber structure. The parts of this chamber are easily manufactured and assembled, and produce a rugged, in-

expensive device.

want of better generic terminology to cover both application Serial Number 100,414, filed Septem ber'12, 1936.

I claim: 1. In a circuit breaker, circuit making and breaking means including a cup-shaped member having a contact in the bottom thereof, a metal bushing having an aperture in line with said contact, insulating means interposed between the bushing and the edge of the cup-shaped member and extending inside the wall of the cup-shaped. member from the bushing part way toward the bottom of the cup-shaped member, said cupshaped member, insulating means and bushing together constituting a closed chamber in which an arc may be formed, ,said chamber being of such size that the heat of the arc is suiiicient to raise gas pressure within said chamber to an amount capable of assisting in choking the are, a contact making plunger slidable in said aperture and having its inner end adaptedto make and break contact with the contact in the bottom of the cup-shaped member, the plunger and the bushing having between themgrooves constitu ing substantially the only passage for the relief of gas pressure within said chamber, the fit between said sliding plunger and said bushing being such as to effectively hold gas pressure within the chamber during existence of the are but yet capable of allowing a leakage of gas to substantially equalize the pressure inside and outside of said chamber after interruption of said arc.

2. A circuit breaker having relatively fixed and movable contacts between which an arc may form on opening the circuit, a compression chamber in which said arc is formed, said chamber being oi such size that the heat of the arc is suflicent to raise the pressure of gas within the chamber to an amount capable of assisting in choking the are formed, a. movable contact carrier passing through a wall of said compression chamber, and gas sealing means around said movable contact carrier where it passes through said chamber wall, said sealing means including a close fit between said-wall and carrier and a plurality of circumferential serrations on either the movable contact carrier or on the chamber wall around it and through which it passes, the fit between said movable carrier and chamber wall being such as to eflectively hold the gas pressure within said chamber during existence of said arc but yet capable of allowing leakage of gas to substantially equalize the pressure inside and outside of said chamber after interruption of said arc.

3. In a circuit breaker having a fixed and a movable contact between which an arc may form on separation of the contacts, a compression chamber around said contacts and in which said arc is formed, said chamber being of a size such that the heat of the arc may raise the pressure of gas within the chamber to an amount capable of assisting in choking the arc formed, a carrier for the movable contact passing through a wall of said chamber, the improvement which includes a gas sealing means around the contact carrier where it passes through said chamber wall, said sealing means including a plurality of closely ad jacent circumferential serrations of generally V- shape on either the movable carrier or wall of the chamber around the carri r, the carrier and the contiguous portion of the chamber wall being oi metal and their fit being such as to effectively hold gas pressure within said chamber during existence of said arc but capable of allowing leakage of gas to substantially equalize the pressure inside and outside of said chamber after interruption of said arc. Y

4. A circuit breaker having relatively fixed and movable contacts between which an arc may form on opening the circuit, a compression chamber in which said arc is formed, said chamber being of such size that the heat of the arc is suflicient to raise the pressure of gas within the chamber to an amount capable of assisting in choking the arc formed, a movable contact carrier passing through a wall of said compression chamber, and gas sealing means around said movable contact carrier where it passes through said chamber wall, said sealing means including a close fit between said wall and carrier and a screw thread on either the contact carrier or the chamber wall contiguous thereto, the fit between the movable carrier and the contiguous portion'of the chamber wall being sufllcient to hold the gas pressure within the chamber during existence of said arc but also capable of allowing leakage of gas from the chamber to substantially equalize the pressure inside and outside of said chamber after interruption of said arc.

RAYMOND N. ROWE.

Images