US2207160A - Overload switch - Google Patents

Description

July 9, 1940. D. s. RIVERS 2,207,160

OVERLOAD SWITCH Filed May 18, 1938 2 Sheets-Sheet 1 J8 fi l0 1 [771 677 ?o7;- Durwamd Efren;

H2 Zornega July 9, 1940. D. s. RIVERS OVERLOAD SWITCH Filed May 18. 1938 2 Sheets-Sheet 2 in van fo r @atented July 9, 1940 ham-:1) STATES QATENT orr ce OVEBLOAD SWITCH Durward s. Rivers, Indianapolis, Ind; Kathryn ratrix Rivers Rivers, deceased of said Durward 8.

Application May 18, 1938. Serial No. 208,521

"lClaims.

a simple and yet a very dependable working combination of members wherein releasing springs and the like do not carry current. By confining the current conducting members to non-springing members, or, in other words, employing a spring to eflect a quick break of current in a manner in which the spring does not enter into the electrical circuit, there is no tendency for any change to occur in the predetermined rated overload current interruption point. Where an electric current is carried by a spring member, it has been observed that the normal resiliency of that spring will in time vary due to some efiect of the current.

Further primary objects of the invention consist of forming the device in a very compact arrangement and forming it in the unique manner and combinations as will be set forth in the following description and the-appended claims.

, One particular form of the invention is illus trated in the accompanying drawings in which Fig. 1 is a side elevation in partial section of a device embodying the invention;

Fig. 2, an opposite side elevation in partial section;

Fig. 3, a transverse section on the line 3-3 in Fig. 1;

Fig. 4, a central vertical section on the line 4-4 in Fig. 3;

Fig. 5, a transverse section on the line 5-5 in Fig. 4;

Fig. 6, a modified form of the invention in central vertical section;

Fig. '7, a rear elevatiomand Fig. 8, a detail in bottom plan elevation.

Like characters of reference indicate likeparts throughout the several views in the drawing.

A generally rectangular body i is formed to have longitudinal slots ll, i2, i3, and I4 on the respective faces. Positioned in the slot II is a length of bi-metal I! of that type which will bend outwardly in the slot I4 when a predetermined current fiow through the bi-metal I is reached. This length of bi-metal i5 has a foot is which is turned around across the upper end of the body iii.

In the next slot ii, Fig. 3, is located a brass bar H. The upper end of this bar I! is turned across the upper end of the body it across the bimetal foot I. A. screw it is carried through the bar foot. the bi-metai foot i6, and is screwthreadedly engaged in the body ID. The bar I! I fits snugly throughout the length 0! this slot H whereas the bi-metal I5 is preferably placed outwardly a slight distance.

Continuing on around the body ll in a clockwise direction, Fig. 3, there is a terminal bar it I.

positioned in the slot I2. This bar I! has a length of a flexible conductor engaged under its lower end and there secured by means of a screw 2| which passed through the lower end of the bar I! and screw-threadedly engages the body ID. The upper end of the bar I! is provided with a hole to receive therethrough a terminal screw 22, under the head of which a wire 23 leading from the cord 24 may be engaged.

The screw 22 screw-threadedly engages the bar 99 I! through the hole provided and provision is made in the side 01' the body II to receive freely the inner end or this screw.

In the slot II, is positioned another brass bar indicated by the numeral 25. This bar, as in- 25 dicated in Fig. 2, has its upper end spaced downwardly from the top end of the, body It so as to be in spaced relation from the end of the overturned foot extending from the bar ll across the body end. This bar 25 is secured to the ,9

body II by means of a screw 26 which passes through the bar and screw-threadedly engages the body II. The bar 25 also carries a terminal screw 21 which screw-threadedly engages the bar 25 to receive the other conductor 28 under its '5 head.

On the lower end oi the body i0 is a head 29 generally cylindrical in shape. The respective slots ll, l2, IS, and I4 are carried on across the head 29 and the opposing bars l1 and 25 ex- 0 tend on down below the head 29 an appreciable distance to serve as the engaging prongs to be received in the usual and well-known type of receptacle (not shown).

The head 28 is provided with a central transa coiled spring 31 the diameter of the spring being such that it will be retained within this slot enlargement so as to prevent displacement along the slot. At that end of the transverse slot 20 which intercepts the slot. l2, there is a hinge pin 32 inserted through the head 2% to carry as around the outer end of the plate 34 and under the lower side thereof to have a rivet unite it and also the bracket cross-member with the plate 34 so that the plate 34 may be rocked freely within the slot 33 about the pin 32. The width of the plate 34 is slightly less than that of the slot 30 so that the plate may be rocked freely within the slot and against the outer end of the spring 3|. 3

The lower end of the bi-metal strip I5 is bent inwardly and around downwardly to form a shoulder 35 to engage over the outer free end of the .plate 34, when that plate is pushed inwardly against the spring 3|, as indicated in Fig. 4. This engagement between the bi-metal 5 and the plate 34 will persist until the bl-metal i5 is heated sufliciently to cause it to bend or travel outwardly a very slight distance suflicient to release the plate 34 which is constantly being urged downwardly by the spring 3|. The spring 3| will, of course, flip the plate 34 downwardly out of engagement with the bi-metal Hi to cause a very quick break in the circuit between those two elements. It is to be notedthat the bi-metal I5 is given an L-shape, the short foot It being anchored by the screw Hi. The bending action may occur throughout the entire length of the bimetal including the length of the foot Hi from the screw I8 to the bend. Thus, a minute deviation from the original form of the bi-metal strip will be greatly magnified by the time that deviation is taken into efiect at the contact line between the shoulder 35 and the plate 34. First there is an upward pull on the .bi-metal l5 by reason of the foot l6 tending to curl away from the end of the body ill. Then there is the tendency for the bend to straighten out as well as a tendency for the major length of the bi-metal l5 below the bend to curl outwardly away from the body ID. All of these tendencies when added together exert an extremely beneficial action in first holding and maintaining good electrical contact between the bi-metal and the plate 34 and then giving an instantaneous break without pere mitting any great degree of arcing. This feature is extremely vital in a circuit protector of this type since the contact areas must be kept smooth and clean and not be permitted to weld together. The movement set up by the structure indicated gives first a wiping movement with the members still in contact and then a quick release in a wiping manner. 3

Also it is to be noted that by employing the flexible conductor 20 the electrical contact is maintained without deterioration of parts between the terminal bar |3 and the rockable plate 34. The spring 3|, which is provided to shift the plate, does not enter into the electrical circuit and, therefore, its resiliency is maintained irrespective of current flow.

Another feature to be noted is that the bar I5 is centrallyslotted substantially throughout its major length along the side of the body l0 as indicated by the slot 36. This slot is pro- I load current has flowed and heated the bi-metal, the slotted arrangement permits a quicker cooling of the bi-metal to enable the device to be re-set quickly after the overload has been re moved from the circuit. A third reason is that by spreading apart the conducting legs of the bi-metal, the contacting shoulder 35 may always be presented in parallel alignment with the contacting end of the plate 34. With the double bar arrangement in place of a single conductor of like current carrying capacity, the bl-metal resists twisting and other distorting influences as would cause an eventual misalignment.

A mounting base 31 is provided to have a cen tral hole therethrough to 'slidingly receive a reset button 38. This button 38 perferably carries a head on its inner end so as to limit outward travel of the button. This button is employed as an external means for pushing inwardly against the plate 34 in opposition to the spring 3| in order to rock the plate 34 into engagement under the shoulder 35 of the bi-metal 5. Whenthe bi-metal releases the plate 34, and the spring 3| kicks the plate 34 outwardly or downwardly, the button 38 will likewise be pushed downwardly to its limit and its shank will thus extend beyond the underside of the base 31.

The base 31 is provided with openings to receive therethrough the terminal prongs l1 and 25 and the head 29 is brought down into engagement with the inner side of the base 31 and there secured by means of detents 39 and 40 projecting respectively from the sides of the prongs l1 and 25 under the base 31.

This structure rigidly attaches the base 31 to the body l0 and its head 29. The base 31 is then carried into the mouth of a bell-like housing 4|, the mouth of this housing being counterbored a suflicient distance as will permit the entrance therein of the base 31 to that position that will carry the button 38 well back in the mouth or at least a sufliicient distance as will permit the outward or downward travel of the button without its contacting the receptacle into which the prongs I 1 and 25 are inserted. That is to say, there must be a sufficient distance between the extended end of the button '38 and the extreme end of the housing as will permit the free outward travel of the button 38 to its limit without interference from the member to which the entire device may be applied.

The base 31 is secured to the housing 4| in any suitable manner, one form as herein shown being a screw-threaded engagement between the base 31 and the housing. The cord wires 23 and 28 joining in the cord 24 are carried into the housing 4| through a suitable opening 42 here shown as in the extreme upper or outer end.

As will have been apparent, the circuit through the device is as follows: The one in -coming wire 28 is connected directly to the extending prong 25. The circuit interrupter is placed in the other side of the circuit.- This side includes the incoming wire 23, the bar l3, theflexible conductor 20, the rocker plate 34, the bi-metal l5, and the bar or prong I 1. The circuit is interrupted, of course, between the plate 34 and the bi-metal 5.

In the other form of the invention, as illustrated in Figs. 6, 7, and 8, no housing is required since the structure is concealed or protected behind the mounting panel 48.. The body In is then mounted upon any suitable base 43 by such means as screws 44 passing through the base 43. The plate or base 43 would carry the reset button 31.

In this form, the terminal prongs l1 and 25 are omitted and in their place, short terminal connections and 48 are secured under the screws I8 and 2!. The terminals of the electrical circuit to be protected are attached to these terminal members if desired or directly under the screws l8 and 2|.

While I have herein shown and described my invention in detail as relating to the one particular form, it is entirely obvious that structural changes may be employed without departing from the spirit of the invention, and I, therefore, do not desire to be limited to that precise form beyond the limitations as may be imposed by the following claims.

I claim:

1. In an automatically opening overload switch, a body member, a bi-metallic bar secured to an end of the body to extend across the end by a foot and then around and along and normally biased toward the side of the body to terminate near the opposite end of the body whereby the bar assumes substantially an L-shape, a switch bar rockably carried by the body, a shoulder on the bi-metal bar under which an end of said switch bar may normally engage and close an electrical circuit through both of said bars, and a spring removed from said circuit normally urging said switch bar against said shoulder, and means for securing said foot to said body end at a distance removed from said body side whereby the foot may bend away from the body end to impart a longitudinal component oi. travel to-said bar as well as a lateral movement upon heating thereof.

2. In an automatically opening overload switch, a body member, a bi -metallic bar secured to an end of the body to extend across the end by a foot and then around and along the side of the body to terminate near the opposite end of the body whereby the bar assumes substantially an L-shape, a switch bar rockably carried by the body, a shoulder on the bi-metal bar under which an end of said switch bar may normally engage and close an electrical circuit through both of said bars, and a spring removed from said circuit normally urging said switch bar against said shoulder, said body having a transverse slot across said opposite end, in which slot said switch bar rocks, means in said body slot retaining said spring in position, a terminal on the body, and a flexible conductor leading from said switch bar to said terminal.

3. In a thermostatic switch, a bi-metal and rockable switch arm assembly, a pair of spaced apart terminal prongs secured to and extending from the assembly, a base receiving said prongs therethrough to have the assembly bear against the base, and means on said prongs engaging the outer side of said base to secure the 4. In athermostatic switch, a bi-metal and rockable switch arm assembly, a pair of spaced apart terminal prongs secured to and extending from the assembly, a base receiving said prongs therethrough to have the assembly bear against the base, and means on said prongs engaging the outer side of said base to secure the base in compressive contact with said assembly, and a housing surrounding said assembly and engaging said L-shape, a switch bar rockably carried by the body, a shoulder on the bi-metal bar under which an endof said switch bar may normally engage and close an electrical circuit through both of said bars, and a spring removed from said circuit normally urging said switch bar against said shoulder, said body having a transverse slot across said opposite end,-in which slot said switch bar rocks, means in said body slot retaining said spring in position, a terminal on the body, a flexible conductor leading from said switch bar to said terminal, a reset button slidably carried through said base and having means limiting its outward travel, and said housing having a petticoat extending beyond the base at least a distance equal to the length of the extending button in its outermost position.

6. In a thermostatically operated switch, a body, a bi-metal bar positioned along one side of the body, a foot on the bar bending around therefrom and over an end of the body, means securing the foot to said body end, said body having a slot across its opposite end and said bar entering said slot by its free end, a switch arm rockably mounted in said slot to have a free end in the path of said bar end, a shoulder formed on said bar end under which said arm may engage, a spring carried by the body to extend into said slot and into the path of said arm whereby said arm will compress said spring when the arm is engaged under said shoulder, and means for carrying said am into said shoulder engagement.

7. In a thermostatically operated switch, a body, a bi-metal bar secured at one end of the body, said body having a slot across its opposite end and said bar entering said slot by its free end,

a switch arm rockably carried by the body to swing in said slot to have a free end in the path of said bar end, an abutment carried by said bar adjacent its free end under which said arm end may engage, a spring carried by the body to extend into said slot into the path of said 'arm, whereby said arm will compress said spring when the arm is engaged under said shoulder, and means for carrying said arm into said abutment engagement.

DURWARD S. RIVERS.

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