US2908786A - Overload relay switch with ambient temperature compensation - Google Patents

Description

Oct. 13, 1959 H; Eo SCHLEICHER 2,908,786

OVERLOAD-RELAY SWITCH WITH AMBIENT TEMPERATURE COMPENSATION Filed Jan. 4, 1957 A INVENToR. F/ 6 5 HfO/dESm/@fc/ye/ BY h/s afforneys www.

United States Patent Ciice OVERLOAD RELAY SWITCH WITH AMBIENT TEMPERATURE CMPENSATION Harold E. Schleicher, West Hartford, Conn., assignor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation of Connecticut Application January 4, 1957, Serial No. 632,460 12 Claims. (Cl. 200-116) This invention relates to switch mechanism. More particularly, it relates to a snap switch mechanism of the type in my prior Patent 2,322,161 of June 15, 1943, which is particularly useful as a relay in controlling electromagnetic contactors, as may be seen by reference to said patent. The mechanism of the relay disclosed therein is operable in response to overload conditions to automatically move into open-circuit position. It can also be set either to automatically reset itself or to require manual resetting from open-circuit position. Only so much of the mechanism as will be helpful in understanding the present invention will be described herein.

Although the relay switch as illustrated in my prior patent has proved very satisfactory in usage over a considerable period, there are times and conditions where greater accuracy could be achieved if said mechanism were provided with ambient temperature compensation. Under some circumstances, the ambient temperature will vary over such limits as to alter the predetermined setting of the relay and cause the relay to operate at a higher or lower current value than desired.

Therefore, it is an object of the present invention to provide ambient temperature control means for the overload relay switch of the type in my prior patent.

Another object is to provide such ambient temperature control without alteration in the operating mechanism as a whole or the desirable characteristics of operation of the relay in my pn'or patent.

Other objects and advantages of the invention will become apparent as it is described in connection with the accompanying drawing.

Although the invention will be described as applicable to my prior patent, it will be understood that its principles are not limited in that respect.

In the drawing:

Fig. 1 is an end elevation view of the invention.

Fig. 2 is a vertical section view along the line 2-2 of Fig. l.

Fig. 3 is a perspective view of the component elements of the ambient temperature controlling means employed n my invention.

Referring to vthe drawing, the parts are mounted in a base of molded insulating material. The base is generally of the same rectangular form and the same configuration as in my prior patent. The base has a longitudinal horizontal dividing wall 12 in the midportion of the base to separate the switch mechanism from the load responsive elements of the device. The switch mechanism is located below the dividing wall and the load responsive elements, comprising a heater coil 14 and bimetal strip 16, are located above the dividing wall.

The heater 14 may be in the form of a coiled wire or a strip having proper characteristics of resistance for the current to be regulated. The ends of the resistance element 14 preferably are secured by screws 17 to terminal plates 18 which in turn are screwed to the top of the base by screws.

The bimetal is shielded from the heater 14 by a ash 2,908,786 Patented Oct. 13, 1959 plate 22 which extends below the heater from one end of the base toward the other and is attached at one end to the terminal element 18.

The bimetal 16 is pivotally and movably mounted at one end as will hereinafter be more fully described. As the bimetal bends upon the generation of heat by the heater 14, the free end of the bimetal engages a roller 40 upon an integral axle 42 which is guided for vertical movement in the walls of the base. The opposite ends of the roller axle 42 are rotatably mounted in a pair of insulating bars 46, only one of which is visible, which are connected at their lower ends by a transverse pin 48 to one end of an operating stamped sheet metal lever 50.

As the operating lever moves in a vertical plane about its pivot pin 52, it is biased in clockwise direction by a restoring spring 54 which is wound about the pin 52 and has one end pressing against the lever and the other against a wall of the casing.

The right end of the lever 50 has a hook formation to receive a loop on one end of the coiled tensioned switch spring 56, the other end of which is attached to a U- shaped movable contact member 58, near one end thereof. Parallel side arms of the movable contact member are notched at their free ends to receive coaxial pivot pins 60. On the transverse portion of the contact member is a downwardly facing contact button in position to engage and disengagc a Contact button 66.

The contact button 66 is mounted on one end of a short piece of resilient sheet metal 68, the other end of which is secured by a screw to a terminal vplate for the purpose of connection of the relay switch contact to and outside the terminal.

The amount of upward travel of the movable contact member as it is actuated by the overcenter spring 56 during the movement of the line of action of that spring across the axis of the pivot pin 60 is limited by a stop pin which extends transversely of the casing from a vertically reciprocative resetting plunger 92 and whose position is adjustable as described in my prior patent.

The operation of the structure illustrated herein is similar under overload conditions to that described in my prior patent. As the bimetal becomes heated by the excess current passing through the heater 14, the bimetal will bend down until its end presses upon the roller 40 causing the insulating bars 46 to act on the operating lever 50 to rotate the lever counterclockwise. As the switch spring 56 moves upwardly across the axis of the pivot pin 60 that overcenter movement will cause the movable contact member 58 to move in clockwise direction to cause contact separation. Manual resetting 1s accomplished by pushing down on the resetting button or plunger 92.

Provision for ambient temperature compensation is made by mounting the main bimetal 16 in a novel fashion. Near one end of that bimetal, the right end as illustrated in Fig. 2, a small bearing plate 81 is ixedly secured to the bottom surface by riveting or otherwise. A portion 81a of the bearing plate is pressed to form a semi-cylindrical bearing or seat for a pivot pin 82 whose axis is parallel to and extends transversely with respect to the bimetal 16. The ends of the pin extend beyond the sides of the bimetal and are journalled in an inverted U-shaped stamped sheet metal supporting bracket 83 which is held in a recess in the top of one end of the base 10, by the terminal plate 18.

Parallel to the main bimetal 16 and located at the bottom of the casing in a position where it is accessible by removal of a bottom plate is a compensating strip bimetal 80 which is identical in dimensions and material' itsy right end on a pin in the same way as the main bimetal except that its supporting bracket 86 faces oppositely from the main bimetal supporting bracket and has the endser of its, side arms 86s turned outwardly and screwedzagainst downwardly facingledges inthe bottom part of the base 10.

i-E'aclr bimetal has a; iingerllrY and 80x) extending from rits pivotedend. These ngersft snugly in upper and lower; apertures, respectively, in a tie-bar or strip 85 which may conveniently be stamped from sheet metal of suiciently heavy gauge to provide a substantially rigid bar.l

Inordertoy adjust the position of the compensating bimetal; an adjustment screw or bolt87 is mounted in its free or llexingend. A reduced neck is formed near the end of the adjustment screw which is assembled by lateral slidinginto a slot 88s formed in the. olset. end of a llexiblev strip 88A of sheet metal which at this other end is held against a downwardly facing ledge in the bottom part of the base by a screw bolt or in any suitable fashion. This strip 88 is stiff enough so that upon turning of the adjustment screw 87 the position of the compensatingbimetal may be varied, but is resilient enough not to bind theV bimetal. The slot 88s extends in the samedirection as the bimetalto avoid binding of the adjustment screw and bimetal.

. The resilience of the mounting ofthe adjustment means also avoids unwanted stress on the compensating bimetall when the main bimetal is heated and is acting to open the switch contacts. During such action, the compensating vbimetal might otherwise on some occasions be caused to move and be subjected to unwanted stress.

y.From the `foregoing, it will be clear that by manipulating the adjustment screw the compensating bimetal is caused to pivot about its mounting pin 84 and consequentlywill cause movement of. the tie bar 85 which in turn will cause pivoting of the bracket and rnain bimetal When the` parts are arranged as illustrated in the` drawing, the compensating bimetal will bow inwardly of the casing as the ambient temperature rises. The main bimetal will bow outwardly on any temperature rise, thus causing its free end (left) to deflect toward the bottom of the casing.

Since the` end at which the adjustment screw 87 ot the compensating bimetal is located cannot move closer to the casing during bowing, the opposite end will cause pivoting clockwise of the ngerk 80x, thereby moving the bar 85V down. That will pivot the main bimetal clockwise about pivot 82,. The result is to require greater bowingor deflection of the main bimetal before tripping the switch` open, as the main bimetal is heated due to excess current in the heater 14.

\ By manipulating the adjustment screw 87 to move the adjustment end of the compensating bimetal. inwardly,V

both bimetals move together and the main bimetal can be adjusted to act at the precise current setting desired. However, this'adjustment is a iine adjustment as the main current calibration ofthe device is done by substituting heaters l14 of different characteristics, as heretofore.

` Many modifications Within the scope of the invention will occur to those skilled in the art. Therefore, I do not limit the vinvention to the specific form and structure described.v n j iWhat is claimed is: j

l. In an electric switch, separable contacts, means to operate Nsaid contacts including a lirst bimetallic strip one end of which is positioned to move and cause contact separation, a pivot for said strip, an extension rigid with the `strip on the opposite side of said pivot, a strip of bimetalrfor ambient temperature compensation, a pivotalmountingfor said compensating bimetal independent of said,` strip pivot, an extension rigid. withsaid compensatilng bimetal on thef..oppositev side ofA said pivotal mount1ng,.a tie bar connectingsaid extensions and causing said rst bimetal to turn upon its pivot as the temperature of said compensating bimetal rises.

2. In an electric switch, separable contacts, mechanism including an actuating element of which a certain amount of movement operates said contacts, a rst bimetallic strip one end of' which is positioned to move said actuating element, aV pivot for said strip, an extension -rigid with the strip on the opposite side of said pivot, a strip of bimetal for ambient temperature compensation, a pivotal mounting for said compensating bimetal, an extension rigid with said compensatingbimetal on the opposite side of -said pivotal mounting, a tie bar connecting said extensions vand causing said rst bimetal to urn upon its pivot as the temperature of said compensating bimetal rises, means to adjust the position of said compensating bimetal to vary the relation of said first bimetal to said actuating element.

3. In an electric switch, separable contacts, 'mechanism including` an actuating element of which a certain amount of movement operates said contacts, a rst bimetallic strip one end ofy which Yis positionedto move said actuating element, Ia pivotforrsaid strip,`an extension rigid with the strip on the opposite side of said pivot, a strip 'of bimetal for ambient temperature compensation,a pivotal mounting for said compensating bimetal,y an extension rigid with said `compensating bimetal on the opposite side of said pivotal mounting, and a tie bar having linger and slot connections between said extensions and said tie' bar andcausing said rst bimetal to turn upon its pivot as the temperature of said compensatingbimetal rises.

4. In an electric switch, separable contacts, means to operate said contacts including av iirst bimetallic strip one end of which is positioned `to'niove and cause contactseparation, a pivot for said strip, an extension rigid with the rstrip on the opposite side'ot'said pivot, a strip of bimetal identical with said rst bimetallic strip and mounted parallel thereto-for ambient temperature cornpensation, al pivotal mountingfor. said compensating bimetal similar tothe pivotalmounting of said irst bimetal, an extension rigid with said `compensating bimetalsimilar to the extension beyond said'first bimetal, a tie bar connecting said extensions andv causing said first bimetal to turn upon its pivotas the temperature of said compensating bimetal rises. f

5. In an Velectric switch, separablecontacts, mechanism including an actuating element of which a certain amount of movement operates said contacts, a rst Ybimetallic striponeend of which is positioned to` move said: actuating element, a pivot. for .said strip, .an extension rigid with the strip on the opposite4 sideV of said pivot, a strip of bimetal for ambient temperature rcompensation, a pivotalv mountingA for said compensating bimetal, an extension rigid with said compensating bimetall onthe opposite side of said pivotal mounting, a tie bar connecting said extensions and causing said'frstbimetal to-tur-n upon its pivot as the temperatureofV saidvcompensating bimetal rises, an adjustment bolt connected to a lixedpartA of the switch and engaging with the end ofsaid compensating bimetal for moving the latter'- about its pivot providing adjustment for it and said firsty bimetal strip. f

6. In an electric switch, separable contacts, mechanism including an actuating elementl of which a certa-in amount of movementv operates said contacts, a rst bimetallic strip one end ofwwhich is positioned tomove said actuating element, apivotV for saidl strip, an extension rigid withy thestrip on the opposite side Vof'said pivot, afstrip of bimetal for ambient'- temperat'ure compensation, a pivotal vmounting for said-compensating bimetal, an extension rigid with=said-comp`ensating bimetal onY the opposite side of said pivotal mounting,I a tiebar connecting said extensions and causingvsaidijst bimetal to turn-upon its pivot as thetemperature ofsaid-compensating bimetal rises, an adjustmentbolt connected/with a" xed part oill the switch and'- engaging-withftlie end of said? compensating bimetal for moving the latter about its pivot providing adjustment for it and said rst bimetal strip, said adjustment bolt having a reduced neck permitting exing of said compensating bimetal without binding or unwanted distortion.

7. A device as claimed in claim 6 wherein said fixed [part to which said adjustment bolt is connected comprises a flexible member having a slot therein in which said reduced neck is slidably engaged.

8. In an electric switch, separable contacts, means to operate said contacts including a first bimetallic strip one end of which is positioned to move freely and cause contact operation, a pivot for said strip spaced from said free end, a strip of bimetal for ambient temperature compensation, a pivotal mounting for said compensating bimetal independent of said iirst pivot, means connecting said bimetallic strips causing them to pivot identical amounts about their pivots as the temperature of said compensating bimetal rises thereby to compensate for ambient temperature rise, the connection of said connecting means to said first strip being at a point remote from its free end so as not to impede the movement of said free end.

9. In an electric switch, separable contacts, means to operate said contacts including a rst bimetallic strip one end of which is positioned to move and to cause contact operation, a pivot for said strip spaced from said free end, a strip of bimetal for ambient temperature compensation having the same characteristics as said first strip, a pivotal mounting for said compensating bimetal located in the same position along said compensating bimetal as the pivot of said first strip and independent of said strip pivot, and means connecting said bimetallic strips causing said first bimetal to turn upon its pivot as the temperature of said compensating bimetal rises, t0 compensate for ambient temperature rise, the connection of said connecting means to said first strip being at a point remote from its free end so as not to impede the movement of said free end.

10. In an electric switch, separable contacts, means to operate said contacts including a first bimetallic strip one end of which is positioned to move and cause contact operation, a pivot for said strip spaced from said free end, a strip of bimetal for ambient temperature compensation, a pivotal mounting for said compensating bimetal, said bimetallic strips being identical in character and in relation of their pivots thereto, and means causing said first strip to turn upon its pivot in corresponding amount to the compensating strip as the temperature of said compensating strip rises, the last-mentioned means being connected to said first strip at a point remote from its free end so as not to impede the movement of said free end.

11. An electric switch as claimed in claim 10 in which a rigid connecting member nonrigidly connects said strips and causes turning of the first strip corresponding to the compensating strip on both heating and cooling of the compensating strip.

l2. An electric switch as claimed in claim 8 in which a rigid connecting member nonrigidly connects said strips and causes turning of the first strip corresponding to the compensating strip on both heating and cooling of the compensating strip.

References Cited in the tile of this patent UNITED STATES PATENTS 1,784,450 Klahn Dec. 9, 1930 2,041,511 Pearce May 19, 1936 2,171,895 Sardeson Sept. 5, 1939 2,235,337 Shaw Mar. 18, 1941 2,392,498 Osterheld Ian. 8, 1946 2,416,170 Gano et al. Feb. 18, 1947 2,863,023 Rowe Dec. 2, 1958 FOREIGN PATENTS 436,010 Great Britain Oct. 3, 1935

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