US3251969A - Criss-cross heater for motor starter overload relay - Google Patents

Description

May 17, 1966 v. MITCHNICK Em. 9,251,969

CRISS-CROSS HEATER FOR MOTOR STARTER OVERLOAD RELAY Filed June l5, 1963 2 Sheets-Sheet l May 17, 1966 v. MITCHNICK ETAL 3,251,969

CRISS-CROSS HEATER FOR MOTOR STARTER OVERLOAD RELAY Filed June 13, 1963 2 S1'1eecs--SheerI 1 United States Patent t O 3,251,969 CRISS-CROSS HEATER FOR MQTOR STARTER OVERLGAD RELAY Victor Mitchnick, Southfield, and Alva ll. Powell, Jr., Roseville, Mich., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed .lune 13, 1963, Ser. No. 287,726 3 Claims. (Cl. 20o-122) Our invention relates to an overload relay and, more particularly, is directed to a novel construction for the heater element whereby the parts are positioned and constructed to gain maximum lbenefit from the inherent characteristics of the components.

The contactor to which our invention can be applied is described in detail in copending application U.S. Serial No. 189,915 tiled April 24, 1962 in the names of John B. Cataldo et al., entitled Electrical Device and assigned to the assignee of the instant invention. An overload relay, in which our invention is particularly applicable, is illustrated and described in copending application U.S.

Serial No. 225,044 tiled September 20, 1962, in the names.

of Robert W. Thomas and Elwood T. Platz, entitled Overload Relay for Motor Starter, also assigned to the assignee of the instant invention.

In an overload relay for a contactor, the sensing element consists of a bimetal which is actuated by a heater. In many overload relays there are ranges of current which pass directly through the heater where the temperatures of the terminals to the heater and overload relay become excessive even though the heater does not radiate sufficient heat to actuate the bimetal. That is, the permissible temperature rise of the overload relay terminals is exceeded even though there is insufficient heat generated by the heater to actuate the bimetal. This condition can exist because the temperature of the overload relay terminals is iniiuenced byv at least two factors, namely, the actual heat generated by the heater itself, as well as the particular temperature distribution along the whole thermal path including the heater.

Commercial contactors and overload relays have limitations with regard to the allowable temperature rise of the terminals which usually permits the temperature rise of the line terminals to be higher than the allowable temperature rise for the load terminals. In one typical standard, the load terminal is permitted a temperature rise of only 50 C., whereas the line terminal is permitted a temperature rise of 65 C. Thus, if the line and load terminals are exposed to the same temperature conditions, the severe temperature rise limitation for the load terminal will result in an extreme limitation on the construction and materials to be used in the overload relay. In the prior art, means have been provided to modify the temperature distribution in order to partially eliminate the aforementioned problem. In these prior art constructions in which the heater is directly heated and of a U-shaped configuration, the heater is constructed with each leg of the U made of a different material, wherein the leg adjacent the bimetal is of high electrical and thermal resistance material and the leg furthest from the bimetal being of low electrical and thermal resistance and being essentially a heat sink.

With this arrangement, a given current magnitude through the heater will heat the leg adjacent the bimetal to a higher temperature and thus permit actuation of the bimetal at a current magnitude in which the temperature rise in the leg of the heater removed from the bimetal is low. In other words, in some instances actuation of the bimetal is permitted with terminal temperatures remaining within allowable temperature rise standards. However, this desired result is obtainable only when the construction of the overload relay issuch that the load 3,251,969 Patented May 17, 1956 terminal can be connected to the low resistance leg of the U-shaped heater since the permissible temperature rise of the load terminal is substantially less than the permissible temperature rise of the line terminal.

Unfortunately, some overload relays are constructed such that the load terminal is adjacent the bimetal and, thus, with a U-shaped heater, the load terminal would be connected to the high resistance leg of the heater and, thus, the desired results would be either substantially reduced or eliminated. A typical prior art construction in which the load terminal is mounted adjacent the bimetal is shown and described in the aforementioned copending application U.S. Serial No. 225,044. Thus, in this prior art arrangement there are ranges of current magnitude where it is possible that even though the U-shaped heater, including the high resistance leg adjacent the bimetal, would not generate suii'cient heat to actuate the bimetal and still exceed the allowable temperature rise of the load terminal.

It is a primary object of our invention to provide a construction for the heater of an overload relay in which, although the load terminal is adjacent the bimetal, the heater will always actuate the bimetal without creating excessive temperature rises at the load terminal.

Essentially we provide a criss-cross arrangement in which the high temperature material is connected to the line terminal which has a larger permissible temperature rise than the load terminal which, in turn, is connected to the low temperature rise leg of the heater. Furthermore, the high temperature portion of the heater is positioned parallel and adjacent to the bimetal so that the maximum benefit can be obtained for actuating the bimetal Without exceeding allowable temperature rises.

Thus, the primary object of our invention is to provide an arrangement whereby the bimetal can be actuated from a heater without exceeding the permissible temperature rises of the load terminal.

Another object of our invention is to provide a heater for an overload relay in which, although the load terminal is positioned adjacent the bimetal, a novel criss-cross arrangement for the heater permits the high resistance material of the heater to be mounted adjacent the bimetal and still be connected to the line terminal.

These and other objects of our invention will be-apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 is an exploded perspective view of an overload relay and, in particular, shows an exploded perspective view of our novel criss-cross heater.

FIGURE 2 is a side view of the overload relay of FIG- URE 1 with the cover removed and shows our novel heater.

FIGURE 2a is a composite side and cross-sectional View similar to FIGURE 2 but illustrates the movement of the bimetal when it is actuated by our novel heater.

FIGURES 3a, 3b and 3c are a side, top and end View, respectively, of our novel criss-cross heater.

Referring now to the FIGURES l through 3, there is shown an overload relay containing our novel electric heater .10. It should be noted that the overload relay to which our heater can be applied and the one illustrated in FIGURES l through 3 is shown and described in the aforementioned copending application, U.S. Serial No. 225,044. The basic elements of the device consists of the control contacts 32-33 and 43-44, the adjustment device including the means 28, the lost motion connectors including the transfer ybar 31, and the external controls including the slide 50.

It is noted that the heater circuit of the overload relay is constructed so that the heater terminals are readily `accessible from the external portion of the casing and the heater 100, therefore, isreadily removable and replaceferably to the load terminals.

The purpose, function and desired .results of our novel crisscross heater is described in detail in the introduction of the instant application. The specific construction is illustrated in the drawings and is as follows.

The heater 100 is comprised of a first member or .section 103 which is a high resistance member and located in a first plane substantially parallel to the bimetal 21. The first member 103 has an end portion 102 which is conne-cted to the frstor line terminal 16 and the second member or section 101 has an end member 104 connected to the load or second terminal 17. A member 105, which is illustrated as an integral part of the second member 101 electrically connects the first member 103 to the second member 101. The connecting means 105 couldbe an integral part of the first member 103 or an independentr connection. The first member 103 has a higher resistance as compared to the second member 101 which has a low resistance. Preferably the member 101 is made of copper so as to serve as a heat sink with respect to the high resistance first member 103.

As seen in the figures, the line terminal 16 is connected to the high resistance member 103 by means of the Vscrew 20 passing through the opening 20a in extension 102 and the low resistance member 101 is connected to the line terminal v17 by means of the screw 19 passing Athrough the opening 19a of the extension 104. Thus,

the first or line terminal 16, which has a high permissible temperature rise, is connected by means of the extension 102 to the first member 103, and the second or load terminal 17, on the other hand, has a low permissible temperature rise and it is properly connected thus to the second or low resistance member 101.

Since the first member 103 is in close proximity to the bimetal 21, the heat generated by current flowing through this high resistance member will immediately be absorbed by the bimetal 21, thereby causing deflection of the bi- `metalaway from the heater as illustrated in the dotted the dotted position seen in FIGURE 2a to the solid position seen in FIGURE 2a thereby closing the cooperating contacts 43, 44 and opening the cooperating contacts 32 and 33. v

The illustration shown in the gures is a preferred embodiment of my invention and, as heretofore noted, arises from the problem that the load terminal 17 is located closer to the bimetal 21 than the line terminal 16 but the temperature rise permitted for the load terminal 17 is lower than the temperature rise permitted for'the line terminal. However, since the high resistance member 103 must be adjacent the bimetal 21, we have provided a novel criss-cross arrangement whereby the high resistance member 103 is located adjacent the bimetal 21 is connected to the line terminal 16 located furthest from the bimetal whereas the low resistance member 101 is connected to the load terminal 17.

We have shown a single structural arrangement to achieve t-hese results but it should be apparent to those skilled in the art that other structural arrangements could be used in order to achieve the desired results and still be within the con-cept as previously set forth.

Although we have described preferred embodiments of our novel invention, many variations and modifications will now be obvious to those skilled in the art, and we prefer, therefore, to be limited not by the specific disclosure herein but only by the appended claims.

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

What is claimed is:

1. An overload device including'a housing, a first and a second fixed terminal mounted to said housing and positioned externally thereof, a bimetal, a heater, contact means, and additional means exclusive of said heater extending between said bimetal and said contact means for operation of the latter upon a predetermined defiection of the bi-metal; said bimetal, said heater, said contact means and said additional means all mounted within said housing; said heater including a first and a second portion connected to said first and said second terminals,

respectively, said portions connected in series with each other and comprising a series circuit extending between said terminals; said series circuit being exclusive of said contact means; said first portion have a higher electrical resistivity than said second portion; said bimetal posisheet material with said first portion having a major.

portion thereof in a first plane generally at right angles to a second plane wherein a major portion of said second portion is disposed; said bimetal comprising a generally planar strip positioned in a third plane generally at right `angles to said second plane; said heater being connectible to circuitry external of said device solely through said first and second terminals.

3. An overload device as set forth in claim 1 in which said bimetal is spaced from said heater when said predetermined deliection takes place; said device also including means removably mounting said heater to said first and second tenminals.

References Cited by the Examiner UNITED STATES PATENTS 2,824,941 2/.1958 Fry 200-122 2,897,319 7/1959 WolfiF 200-122 2,994,754 8/1961 lWebking 200--138 3,015,007 12/1961 Howard 200--114 3,023,288 2/1962 Bodenschatzet al. 20G-122 3,031,551 4/1962 White et al. 200-122 BERNARD A. GILHEANY, Primary Examiner.

L. A. WRIGHT, Assistant Examiner.

Claims (1)

1. AN OVERLOAD DEVICE INCLUDING A HOUSING, A FIRST AND A SECOND FIXED TERMINAL MOUNTED TO SAID HOUSING AND POSITIONED EXTERNALLY THEREOF, A BIMETAL, A HEATER, CONTACT MEANS, AND ADDITIONAL MEANS EXCLUSIVE OF SAID HEATER EXTENDING BETWEEN SAID BIMETAL AND SAID CONTACT MEANS FOR OPERATING OF THE LATTER UPON A PREDETERMINED DEFLECTION OF THE BIMETAL; SAID BIMETAL, SAID HEATER, SAID CONTACT MEANS AND SAID ADDITIONAL MEANS ALL MOUNTED WITHIN SAID HOUSING; SAID HEATER INCLUDING A FIRST AND A SECOND PORTION CONNECTED TO SAID FIRST AND SAID SECOND TERMINALS, RESPECTIVELY, SAID PORTIONS CONNECTED IN SERIES WITH EACH OTHER AND COMPRISING A SERIES CIRCUIT EXTENDING BETWEEN SAID TERMINALS; SAID SERIES CIRCUIT BEING EXCLUSIVE OF SAID CONTACT MEANS; SAID FIRST PORTION HAVE A HIGHER ELECTRICAL RESISTIVITY THATN SAID SECOND PORTION; SAID BIMETAL POSITIONED IN CONFRONTING RELATIONSHIP WITH SAID FIRST PORTION IN PROXIMITY SO THAT HEAT GENERATED BY CURRENT FLOW THROUGH SAID FIRST PORTION HEATS SAID BIMETAL CAUSING DEFLECTION THEREOF; SAID BIMETAL POSITIONED CLOSER TO SAID SECOND TERMINAL THAN TO SAID FIRST TERMINAL.

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