US2231081A - Circuit breaker - Google Patents

Description

CIRCUIT BREAKER Filed April 5, 1937 2 Sheets-Sheet l /N VENTO/e Olav 456175 Feb. 11, 1941. o, MASENG 2,231,081

CIRCUIT BREAKER Filed April 5, 19,37 2 Shorty-Sheet 2 fren/f@ O 55-9 O l 1515 4T/f :L 54* .54 G Eff@ "I C@ C@ @o ff m62 fg-f E- E. TQ @D w l l1 L Panarea Feb. 11, 1941 UNITED STATES PATENT OFFICE D Company, Detroit,

Michigan Mich., a corporation of Application April s, 1937, serial No. 134,979

llOlaims.

This invention relates to thermostatic current responsive elements Afor automatic circuit controlling devices and has for its object the provision of a thermostatic means responsive to circuit current which shall have increased sensitivity and be less affected by changesin ambient temperature.

`Another object of this invention is to provide a current responsive thermostatic means for elecl tric circuit controlling devices with a surface on its heat dissipating portions which shall reduce the emission of heat from these portions.

Another object of' the invention is to provide current responsive thermostatic means for eleci tric circuit controlling devices which shall be more uniform in their operation.

Other objects and features of this invention will be readily apparent to those skilled in the art from the following specification and v appended drawings illustrating certain preferred embodiments of the invention in which:

Figure i is a partial front elevational view of an automatic electric circuit breaker utilizing a current traversed bimetallie element according to ,26 the present invention and in which portions are cut away to show internal parts.

Figure 2 is a vertical sectional view taken on the line II-II of Figure i.

Figure 3 is a detailed sectional view of the bimetallic element taken on the line IIIj--m of Figure 2.

' Figure 4 is a view similar to Figure 3 but showing another embodiment of the invention.

Figure 5 is a front elevational view with parts 38 vcut away of a motor starting switch utilizing the solder pot type current responsive overload means.

Figure 6 is an enlarged detailed view of one of the solder pot type thermostatic means' used in the switch of Figure 5. I

Figure 'I is a sectional view on the line VII--VII of Figure 6.

Figure 8 is a view similar to` Figure 7 showing another embodiment of the invention.

Figures 1 to 4 inclusive are directed to the invention as applied to a current traversed bimetallic4 member used in an automatic electric circuit breaker. As disclosed, this circuit breaker is of the type disclosed and claimed in the copending applications of John G. Jackson, Serial No. 36,247, filed August 15, 1935, Serial No. 72,035, filed April 1, 1936, Serial No. 77,519, filed May 2, 1936, all ventitled Circuit breakers, and in the divisions and continuations of these applications. The circuit breaker embodies a metallic mounting (ci. zoo-11a) plate I which may be the back wall of an outer enclosing box against which is mounted a cupshaped insulating base 2. Generally centrally of this base is mounted a stationary contact plate 3 as by means of a stud 4 and carrying stationary '5 contacts adapted to cooperate with movable contacts 5 on the ends of contact blades l. At end ledges at the ends of the base are rigidly supported connectors l as by means of spun over portions of metallic inserts 8 which also receive `l0 terminal studs 3. To the interior end of each of the connectors I is rigidly secured one end of a bimetallic member I I as by means of an adjusting means designated generally at I2. The free end of the bimetallic member I I and the contact blade l5 8 are electrically connected by means of a flexible lead Il. A compression spring I4 biases the blade against the stationary contact and the free end of the birnetallic member II. A U-shaped member I5 having legs of dissimilar length is 20 guided by formations in the base for rectilinear movement at right angles thereof. The longer leg of the member I5 is slottedto receive the blade 6 and the blade at its top edge is provided with a notch I6 received within the top edge of 25 the slot. A second notch I'I is provided in the front edge of the blade and is adapted to engage a shorter leg of the member I5 to serve as a stop for the blade upon rotation as hereinafter described. An operating handle I8 pivotally mount- 30 ed on a shaft I9 has an interior cam surface 4which effects rectilinear movement of the member I5, which cam surface includes a fiat stable portion 2i and a resetting tip 22.

The blade shown at the top of Figure 2 is in the 35 normal on position.' To move the parts to the manual off position the handle is rotated counterclockwise until the flat surface 2| engages the top surface of the member I5 which produces a stable position in which the member I 5 has been 40 moved toward the bottom of the base and has separated the movable contact at the end of the associated blade l from its cooperating stationary contact. The movable contact and blade are then in the position shown partially adjacent the 45 bottom of Figure 2. In automatic release upon the occurrence of an overload through the circuit breaker mechanism shown at the top of Figure 2 its bimetal will become heated and will flex upwardly until it releases the latched end oi.' con'- 50 tact blade 6 whereupon this blade rotates in a counterclockwise direction about the engagement of the notch I6 with the member I5 and under the bias of spring I4 into a contacts disengaged position, thus interrupting the circuit through the breaker mechanism. To reset the parts after an automatic release the handle is rotated past the oiTposition until the latching tip 22 is on the top surface of the member l5 in which position the contact blade 6 will have engaged the bottom of the arc chamber and moved back into position to engage the bimetallc latch Il. If this latch has cooled suiiiciently to assume its normal position, release of the handle will then place the parts in the normal off position whereupon clockwise rotation of the handle will again permit the parts to assume the position shown in Figure 2, the closed circuit position.

rllhe bimetal il embodying the features of the present invention is shown in greatly thickened scale in order to denote the layers thereof. These are more fully shown in Figure 3 in which again the proportion of the parts has not been retained. The bimetal is formed of two metals 23 and 2l having dissimilar thermal coefficients of eXpansion which are integrally bonded together to form a single strip which will bend in well-known manner upon changes in temperature. About this bimetallic strip is plated or otherwise disposed a surface coating 25 which will serve to decrease the transmission of heat to or from the birnetal. Figure 4 is similar to Figure 3 but here the bimetal formed of the strips 23 and 24 is provided with a double coating 26 and 2l as has been found desirable and as will be more fully explained hereinafter.

Figures 5 to 8 inclusive illustrate the features of applicants invention applied to a motor control switch using a solder pot type overload release. This is illustrated in connection with the switch which is more fully disclosed in Patent No. 1,912,109 granted May 30, 1933 to H. L Van Valkenburg, et al., and reference is made thereto for the parts not shown herein. This includes an enclosure 5i within which is mounted a base 52 supporting stationary contacts 53 and movable contacts 54 which are carried on an insulating block 55 reciprocable at right angles to the base 52.- As more fully explained in the patent disclosure, means is provided for holding the contacts engaged and for releasing the holding the block 55 in response to melting of the holding metal in the overload relays indicated generally at 56. The overload relays 56 are more particularly shown in Figures 6 and '7 and embody end terminals 51 between which extend a heater strap 58 insulated at the front by means of a plurality of thin mica strips 59. At the back of the heater strap 58 are placed one or more thin sheets of mica insulation SI whose number determines the heat lag to the holding metal alloy to be described. Against the mica plate 6I is disposed a metallic block 62 having a cylindrical chamber 63 therein in which is disposed a shaft 64 and an alloy metal E5 surrounding and holding the shaft 64. At the end of the shaft 64 is disposed a ratchet Wheel 66. A clamp 61 is disposed about the unit and serves to hold the metal block 62 in heating conducting relation with `the heater 58. The metallic alloy 65 is chosen to have a fusion point at a certain desired temperature and its softening will permit ratchet wheel 66 to yturn and this operates as described in the previously cited patent to initiate operation of the switching parts to open the circuit therethrough. The metallic block B2 and other heat dissipating metallic portions are here provided with a coating 68 serving to reduce the emission or transmission of heat from the thermostatically sensitive parts. The solder pot overload relay shown in Figure 8 is the duplicate of that shown in Figure 7 with the exception that here two coatings 69 and 1I are shown for the heat dissipating parts.

While applicants inventive concept iinds its greatest advantages in bimetallic current traversed members it is also advantageously used in the solder pot type relay of Figures 5 to 8 inclusive and applicants invention is to be broadly construed asapplying to any current responsive thermostatic member wherein there are heat absorbing or heat dissipating surfaces.

According t`o applicants invention the surface on the thermostatic element is preferably an electro-plated coating known as bright chromium which consists of an electro-plated coating of nickel directly on the element followed by an electro-plated coating of chromium on top of the nickel coating. B`oth o'fthese coatings are preferablyl made as thin as is consistent with good coating practice. This double coating appears to give the most advantageous results and as it is also relatively permanent and non-tarnishable is selected as the preferred coating. However, it has also been determined tha-t a coating of silver appears to give beneficial results but due to its high conductivity is apt to disturb the resistance of the bimetallic element of the type of Figures 14 to 4 inclusive and it also tarnishes easily which results in a decrease in its effectiveness. A coating of nickel alone has also been found to have some advantageous effects but these are considerably less than the chromium on nickel coating previously discussed. A coating of zinc also appeared to be beneficial but this is undesirable due to its relatively high conductivity when applied as a coating and also to its tarnishabilty. A coating of whi-te paint was also found to have beneficial effects but is undesirable as it darkens and/or chars quickly and is apt to flake due to mechanical stress. Applicants invention is to be construed as covering any surface on the thermal element which decreases the emission or transmission of heat and while the chromium on nickel coating is preferred because of its other properties it is obvious that many other materials including those mentioned above can be used with varying results to produce the desired effect.

Tests of the thermal elements provided with coatings according to the present invention indicate that in the bimetal there is an increased deflection due to an increased internal temperature which is caused by the heat retention since radiation and other heat losses from the bimetal are greatly reduced by the coating. This results in either the use of a heavier bimetal to produce the same deflection or in the use of greater mechanical latching overlap or in the use of a lesser tripping current. One very important result which is perhapsmore important in case of the bimetallic strip although also present in the solder pot type unit is the lessened effect upon the performance Yof changes in the temperature surrounding theelement. As ordinarily the heat emitted from the element will vary with the temperature difference to the surrounding atmosphere it is apparent that if this emission is greatly cut down that the temperature of the element will obviously be less affected by changes in this difference in temperature. Hence the element is less affected by change in the surrounding temperature. Furthermore, in a given bimetallic strip having a given resistance the Coating according to the present invention provides for a higher internal temperature which means that the bimetal for the same current will be calibrated as to latching overlap at a higher temperature and this will result in the bimetal being less affected by ambient temperatures on the ou-tside of its enclosure where there is heat dissipation due to conduction through the connecter to the external terminal and to the circuit wiring. If the bimetal is operating at a higher ltemperature it is obvious that it will be less affected by changes in the ambient temperature about the connecter and the temperature of the circuit wiring to which it dissipates heat. In `the case of the solder pot relay the coating, according to the present invention, permits the use of a heavier and lower resistance heating strip to produce the same temperature for the same overload current in the fusible holding metal and also makes the unit less responsive to changes in surrounding temperature. In the case of the bimetallic strips it is also noticed that the coating appears to reduce variations between individual bimetals which may have been caused by surface variations in the individual bimetals. It also permits an increased standardization by permitting the use of the same cross sectional and resistance bimetals over a wide current range depending upon whether they are plated or not. Furthermore, particularly in devices where the thermostatic units are used in close proximity to other thermostatic units a benecial effect is noted inasmuch as, due to the decreased emission of heat from the units, the internal temperatures of the devices will be lowered sinceA less heat is wasted to them by the units; also should the internal temperature of the device be raised due to the heat emitted from uncoated units or from any other source, this increase in temperature will have a reduced effect upon the units coated in accordance with the present invention as has been explained heretofore.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that .the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation. within the terms of the following claims.

What is claimed is:

l. In an automatically opening'circuit controlling device having cooperating contacts and means for effecting separation of said contacts to open the circuit therethrough, thermostatic means for initiating operation of said first mentioned means in response to the heat generated by the passage of current through the device in excess of a predetermined value, and reflecting, heat retaining surfaces on heat dissipating portions of said thermostatic means.

2. In an automatically opening circuit controlling device, a stationary contact, a contact cooperating therewith and movable to effect opening and closing of the circuit therethrough,

means biasing said movable contact to separated position to open the circuit, thermostatically controlled means holding said contacts in engaged position against the force of said biasing means, the thermostatic means operating to effect the release of said movable contact for movement thereof to separated position under the action of its biasing means in response to the heat generated by the passage of current through the device in excess of a predetermined value, and

surfaces on said thermostatic means inhibiting the normal heat waste therefrom.

3. In an automatically opening circuit controlling device having cooperating contacts and means for effecting separation of said contacts to open `the circuit therethrough, thermostatic means for initiating operation of said first mentioned means in response to the heat generated by the passage of current through the device in excess of a predetermined value, said thermostatic means being provided with a coating decreasing the normal heat emission from its surfaces.

4. In an automatically opening circuit controlling device, a stationary contact, a contact cooperating therewith and movable to effect `opening and closing of the circuit therethrough,

means biasing said movable contact to separated position to open the circuit, thermostatically controlled means holding said contacts in engaged position against the force of said biasing means, the thermostatic means operating to effect the release of said movable contact for miovement -thereof to separated position under the action of its bi-asing means in response to the heat generated by the passage of current through the device in excess of a predetermined value, said thermostatic means being provided with a bright, reflecting surface coating which reduces its sensitivity to changes in surrounding temperatures.

5. In an automatically opening circuit controlling device having cooperating contacts and means for effecting separation of said contacts to open the circuit therethrough, thermostatic X means for initiating openation of said iirst mentioned means in response to the heat generated by the passage of current through the device in excess of a predetermined value, said thermostatic means being provided with a thin coating formed of layers of chromium on nickel.

6. In an automatically opening circuit controlling device having cooperating swiitching con-l tacts, of which one is stationary and the other is movable to and from engagement therewith to effect opening and closing of the circuit through the device and means for biasing said movable contact for movement to a position separated from said stationary contact, a bimetallic element for effecting release of said movable contact for movement to separated position under the action of its biasing means, said bimetallic element being connected in series circuit with said contacts so as to be traversed by the current flowing therethrough and operating to effect release of said movable contact in response to the heat generated in itself by the passage of current in excess of a predetermined value, and means for increasing the internal operating temperature of said bimetallic element comprising a surface coating reducing the heat emission therefrom.

7. In an automatically opening circuit controlling device having cooperaltlng switching contacts, of which one is stationary and the other is movable to and from contact therewith to effect opening and closing of the circuit through the device and means for biasing said movable contact for movement to a position separated from said stationary contact, a bimetallic element for effecting release of 'said movable contact for movement to separated position under the action of its biasing means, said bimetallic element being connected in series circuit with said contacts so as to be traversed by the current flowing therethrough and operating to effect release of said movable contact in response-to the heat generated in itself by the passage of current in excess of a predetermined value, and a bright, metallic, reflecting coating on said element substantially reducing the heat emission therefrom.

8. In an automatically opening circuit controlling device having cooperating switch contacts and means for effecting separation of said contacts to open fthe circuit through the device, a bimetallic element connected in series circuit With said contacts so as to be traversed by the current passing therethrough and operating to effect initiation of said means in response to the heat generated in itself by the passage of current in excess of a predetermined value, said bimetallic element having a thin coating formed of electro-deposited layers of chromium on nickel. l

9. In an automatically opening circuit controlling device having cooperating switching contacts and means for effecting separation of said contacts fto open the circuit through the device, a. thermostatic unit for initiating operation of said means, said unit including a heater element connected in series circuit with said contacts so as to be traversed by the current flowing therethrough, a fusible metal in heat conducting relation with said heater and an element normally held immovable by said metal when in a solid state but released for movement upon fusion of said metal, and means for increasing the temperature of said fusible metal in response to a given circuit current through the heater element comprising a surface coating on said unit reducing the heat emission therefrom.

10. In an automatically opening circuit controlling device having cooperating switching contacts and means for effecting separation of said contacts rto open the circuit through the device, a thermostatic u nit for initiating operation of said means, said unit including a heater element connected in series circuit with said contacts so as lto be traversed by the current flowing therethrough, a fusible metal in heat conducting relation with said heater and an element normally held immovable by said metal when in a solid state but released for movement upon fusion of said metal, and a. bright, metallic, reflecting coating on heat dissipating portions of said unit substantially reducing the heat emission therefrom.

11. In an automatically opening circuit controlling device, a stationary contact, a. contact cooperating therewith and movable to effect opening and closing of the circuit therethrough, means biasing said movable contact to separated position to open the circuit, a thermostatic unit for effecting release of said movable contact for movement to separated position under the action of its biasing means, said unit including a heater element connected in series circuit -with the contacts so as to be traversed by

Images