US3866156A - Overload relay indicating means - Google Patents

Abstract

An overload relay having a conventional replaceable heater is provided with an auxiliary bimetal secured to the deflectable end of the main bimetal and arranged to deflect in a direction opposite to deflection of the latter. Tripping results from the net deflection of these bimetals. The main bimetal shields the auxiliary bimetal from direct heat radiating from the heater, so that upon rapid heating of the latter the initial result is that the main bimetal deflects rapidly and there is essentially no reverse deflection of the auxiliary bimetal whereby tripping takes place very rapidly. A contact position-indicating lever is biased to follow the movable contact to its open position. When the contacts are closed, this lever is accessible for manual opening of the overload relay.

Description

United States Patent [191 DiMarco et al.

[ OVERLOAD RELAY INDICATING MEANS [76] Inventors: Bernard DiMarco, Bellefontaine;

Andrew J. Kralik, Marysville, both of Ohio [22] Filed: July 18, 1974 [21] Appl. No.: 489,807

Related U.S. Application Data [62] Division of Ser. No. 428,097, Dec. 26, 1973.

[451 Feb. 11,1975

Primary Examiner-Arthur T. Grimley Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb & Soffen [57] ABSTRACT An overload relay having a conventional replaceable heater is provided with an auxiliary bimetal secured to the deflectable end of the main bimetal and arranged to deflect in a direction opposite to deflection of the latter. Tripping results from the net deflection of these bimetals. The main bimetal shields the auxiliary bimetal from direct heat radiating from the heater, so that upon rapid heating of the latter the initial result is that the main bimetal deflects rapidly and there is essentially no reverse deflection of the auxiliary bimetal whereby tripping takes place very rapidly.

A contact position-indicating lever is biased to follow the movable contact to its open position. When the contacts are closed, this lever is accessible for manual opening of the overload relay.

3 Claims, 6 Drawing Figures PATENTEB FEBI 1 I975 SHEET 10F 3 PATENTEB FEBI 1 I975 SHEET 2 0F 3 1 OVERLOAD RELAY INDICATING MEANS This is a division of application Ser. No. 428,097, filed Dec. 26, 1973.

This invention relates to motor starter overload relays in general and more particularly relates to an improvement of the overload relay disclosed in U.S. Pat. No. 3,562,688, issued Feb. 9, 1971, to F. W. Kussy et al. for Quick Trip Overload Relay Heaters.

As noted in the aforesaid U.S. Pat. No. 3,562,688, conventional overload relays utilizing indirectly heated bimetal tripping elements are satisfactory for opening of the relay contacts under normal fault conditions. However, these conventional overload relays often prove unsatisfactory where extreme faults must be cleared very rapidly in order to prevent irreparable damage to electric motors.

The solution provided by the aforesaid U.S. Pat. No. 3,562,688 is the utilization of a directly heated bimetal as an element of a replaceable heater unit which generates heat for operating the tripping bimetal of the overload relay. Upon heating, the heater bimetal moves toward the tripping bimetal so that the heat source for the latter is moved closer thereto, bringing about more rapid heating. Upon extremely rapid heating of the bimetal heater, the latter physically engages and moves the tripping bimetal toward its tripping position even before the latter has heated sufficiently to deflect to this tripping position.

In accordance with the instant invention, a nonbimetal type conventional heater is utilized to furnish heat for the tripping bimetal. The tripping bimetal is a strip having one end fixed and the other end free to deflect in a tripping direction. An auxiliary bimetal is mounted on the free end of the tripping bimetal and upon heating thereof moves opposite to the tripping direction. The overload relay trips when the bimetals reach a predetermined deflection obtained by the net movement of the main and auxiliary bimetals combined. The main bimetal is so positioned between the heater and auxiliary bimetal that the latter is substantially, if not entirely, shielded from radiant energy emanating from the heater. Thus, upon the occurrence of extreme fault conditions, radiant energy from the heater will cause rapid deflection of the main bimetal and essentially zero deflection of the auxiliary bimetal so that the net deflection in the tripping direction is essentially the entire deflection of the main bimetal which occurs very rapidly.

In addition to the improved fast acting tripping mechanism, the overload relay of the instant invention is provided with an indicator lever which provides a positive visual indication that the overload relay has tripped. One end of the lever is biased to follow the movable contact arm as it moves from circuit closed to circuit open position. That is, when the overload relay contacts are closed, the indicator lever bias acts in opposition to the closing force exerted by the operating spring of the overload relay. Because of this, even if the indicator lever jams, it will not interfere with opening of the overload relay contacts. The other end of the lever extends externally of the overload relay housing to provide a visual indication of contact position. This end of the indicator lever is also accessible for operation to manually open the overload relay contacts.

Accordingly, a primary object of the instant invention is to provide an overload relay having improved means for effecting extremely rapid operation under severe fault conditions.

Another object is to provide an overload relay having novel indicator means.

Still another object is to provide an overload relay having novel means to effect manual opening thereof.

A further object is to provide an overload relay having main and auxiliary tripping bimetals positioned for opposing deflections, the net result of which is utilized to trip the overload relay.

A still further object is to provide an overload relay of this type in which the main bimetal shields the auxiliary bimetal from radiant energy emanating from the load current carrying heater.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIG. 1 is an end view of an overload relay constructed in accordance with teachings of the instant invention.

FIG. 2 is a side elevation looking in the direction of arrows 22 of FIG. 1.

FIG. 3 is a side elevation looking in the direction of arrows 3-3 of FIG. 1, with the casing cover removed.

FIG. 4 is a plan view looking in the direction of arrows 4-4 of FIG. 3.

FIG. 5 is a fragmentary perspective looking generally in the direction of arrows 55 of FIG. 4.

FIG. 6 is an exploded perspective of the electrical elements and operating mechanism for the overload relay of FIGS. 1-5.

Now referring to the figures. Overload relay unit 10 includes a molded housing divided along line 11 to form base 12 and cover 13 joined by rivets 14. In a manner well known to the art, base 12 and cover 13 are provided with internal depressions and protrusions which engage the electrical and active mechanical elements of unit 10 to operatively position these elements.

Opening 15 at the top of housing 11, 12 forms an entrance to main cavity 16 in base 12. Disposed externally of housing 12, 13 at the edge of opening 15 are spaced-apart main circuit terminals 17, 18, each of which is generally L-shaped. U-shaped heater unit 99 is disposed within main cavity 16 and is provided with out-turned legs 97, 98 having clearance apertures which receive screws 19 for removably securing heater 99 to terminals 17, 18. Auxiliary wire grip 96 is mounted to extension of terminal 17.

Disposed within cavity 16 is main tripping bimetal 20. The latter is a strip-like member having its upper end 21 welded to the offset upper end of formed stiff resilient support strip 22. Bimetal 20 is interposed between heater 99 and support 22 with the main central portion of support 22 extending generally parallel to heater leg 94. The central portion of support 22 is provided with a threaded aperture that receives the threaded portion of adjusting screw 23 having enlarged head 24 disposed outside of casing 12 at one end thereof. Rotation of adjusting screw 23 is effective to draw the ends of support 22 against casing abutments 26, 27 positioned on opposite sides of adjusting screw 23. Thus, as screw 23 is turned to draw the central portion of support 22 to the right with respect to FIG. 3, the upper end 21 of main bimetal 20 will pivot counterclockwise about abutment 27 as a center, thereby moving lower end 31 of main bimetal 20 to the right with respect to FIG. 3.

Reversely bent auxiliary bimetal 35 is secured by rivets 34 to the lower end 31 of main bimetal 20. Free end 36 of auxiliary bimetal 35 is operatively engaged with the right end 42 of translator bar 41 through notch 44 bounded by bar ends 42, 43. Notch 44 also provides clearance for stationary contact member 45 and main operating spring 46. The latter is operatively engaged by the left end 43 of bar 41.

One end of member 45 extends externally of housing l2, 13 at the bottom thereof to constitute plug-in stab 47, and the other end of member 45 is reversely bent and mounts stationary contact 51. The latter is engageable by movable contact 52 mounted at the upper end of movable contact arm 50. The lower end of contact arm 50 is bifurcated and is seated in notches 53 in the upper surface of bifurcated extension 54 of conducting element 55. The lower end 48 of element 55 constitutes a plug-in stab positioned externally of casing 12 at the lower end thereof. Main operating spring 46 is a coiled tension member secured at its upper end to contact arm 50 just below movable contact 52. The lower end of spring 46 is secured to extension 56 of member 55, positioned well below the lower end of contact arm 50. It should be obvious to those skilled in the art that main operating spring 46 and movable contact arm 50 are connected and operatively positioned to form an overcenter toggle mechanism for opening and closing cooperating contacts 51, 52 with a snap action.

When contacts 51, 52 are open and reset slide 60 is in its raised or manual position, casing protrusion 59 provides a stop to limit the open circuit position of contact arm 50. When reset slide 60 is held in its depressed or lowered position, cam surface 61 at the lower end thereof limits movement of movable contact 52 to the right with respect to FIG. 3, so that the toggle operating mechanism always stays to. the left of its overcenter position and spring 46 always acts in the closing direction. Reset slide 60 is held in its lowered position by moving end 62 of wire spring 63 upward from MAN" notch 63 to AUTO notch 64, thereby lowering spring end 65 that is entered into reset slide notch 66.

Indicator lever 70 is pivotally mounted in casing 12 on pin 71. The lower end 72 of lever 70 is biased to the right with respect to FIG. 3 by coiled compression spring 73. Lateral extension 74 of lever 70 is thereby engaged with the left or contact carrying side of movable contact arm 50 so that spring 73 tends to open cooperating contacts 51, 52. However, the force exerted by biasing spring 73 is negligible as compared to the force exerted by main operating spring 46 so that insofar as bringing about separation of cooperating contacts 51, 52 the force of biasing spring 73 may be ignored. However, when cooperating contacts 51, 52 are open, spring 73 pivots lever 70 counterclockwise with respect to FIG. 3 so that the upper end 77 thereof, which is visible externally of casing 12, 13, moves to the left with respect to FIG. 3 to indicate that contacts 51, 52 have separated. To facilitate making this observation, end 77 of indicator lever 70 is of a color that contrasts with the color of housing 12, 13. End 77 is accessible for manual opening of contacts 51, 52.

Automatic opening of contacts 51, 52 is a result of heat generated by current flowing through heater 99. Under many overload conditions heat generated by heater 99 gradually elevates the temperature within the entire compartment 16 so that the temperatures of main and auxiliary bimetals 20, 35 rise together by convection heating. Under these circumstances the free end of main bimetal 20 moves to the right with respect to FIG. 3, and simultaneously there is a reverse deflection of auxiliary bimetal 35. However, the net deflection of bimetals 20, 35 moves translator arm 41 to the right, moving main operating spring 46 to the right until its line of action moves to the right of the toggle knee, at which point the movable contact arm pivots rapidly in a clockwise direction to open cooperating contacts 51, 52. Under severe fault conditions initial rapid heating of main bimetal 20 is due to radiation from heater 99, with deflection of bimetal 20 being substantial and very rapid. However, during this period there is very little deflection of auxiliary bimetal 35, since main bimetal 20 serves as a shield which prevents heat being radiated from heater 99 from impinging upon auxiliary bimetal 35. Thus, under severe fault conditions, the net deflection of bimetals 20, 35 is substantially the same as the deflection of bimetal 20, so that opening of cooperating contacts 51, 52 comes about very rapidly.

Although in the foregoing preferred embodiments have been discussed, many variations and modifications will now become apparent to those skilled in the art, and it is therefore understood that this invention is not limited by the disclosure but only by the appending claims.

The embodiments of our invention in which an exclusive privilege or property is claimed are defined as follows:

l. A switch device including a stationary contact, a movable contact engageable with said stationary contact, first spring means biasing said movable contact toward said stationary contact when said contacts are engaged, first means for indicating contact position, said first means including a portion engageable with said movable contact and second biasing means urging said portion into engagement with said movable contact, said second biasing means being substantially weaker than said first biasing means and acting in opposition thereto when said contacts are engaged.

2. A switch device as set forth in claim 1 also including a housing wherein said contacts, said first and second biasing means, and said portion of said first means are disposed, said first means including another portion extending outside of said housing to provide a visible indication of contact position, said another portion also being accessible for operation to move said portion in the direction urged by the second biasing means to open said contacts.

3. A switch device as set forth in claim 2 in which the portion and the another portion are sections of a pivoted member.

Claims (3)

1. A switch device including a stationary contact, a movable contact engageable with said stationary contact, first spring means biasing said movable contact toward said stationary contact when said contacts are engaged, first means for indicating contact position, said first means including a portion engageable with said movable contact and second biasing means urging said portion into engagement with said movable contact, said second biasing means being substantially weaker than said first biasing means and acting in opposition thereto when said contacts are engaged.

2. A switch device as set forth in claim 1 also including a housing wherein said contacts, said first and second biasing means, and said portion of said first means are disposed, said first means including another portion extending outside of said housing to provide a visible indication of contact position, said another portion also being accessible for operation to move said portion in the direction urged by the second biasing means to open said contacts.

3. A switch device as set forth in claim 2 in which the portion and the another portion are sections of a pivoted member.

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