US1968465A - Circuit breaking receptacle - Google Patents

Description

July 31, 1934. w. 1 PADGET-r 1,968,465

C IRCUIT BREAKING RECEPTACLE Filed Nov. 19, 1950 gmmgwgg 27 'frm/mln l Patented July 3l, 1934 omourr BREAKING nncmaom William L. Padgett, Brooklyn, N. Y. Application November 19, 1930, serial No. 496,811

7 Claims.

The present invention relates to control devices and more particularly to devices for controlling the ilow of current in electrical transmission lines.

.1 An object of the invention is to provide a selfcontained control device for electrical circuits which will be simple and compact in construction,

and efllcient and safe-in operation.

In a preferred embodiment, the invention con- 10 templates the provision, in an electric circuit, of a pin plug receptacle or base receptacle, in the interior of which is mounted, in juxtaposition, a heating element and a bimetallic element. The heating element is connected on one side of the conductor with a spring leaf conductor, which is normally held in position to close the circuit. When the load on the line becomes excessive, the heating element causes the bimetallic element to bend, permitting opening of the circuit. Upon cooling of the parts, the circuit may be re-closed by means of a manually operated resetting pin which restores the spring leaf and blmetallic element to engagement.

In a modiiied form, a latch having a projection to engage the bimetallic element is slidably mounted in the receptacle and is normally held by means of a spring in engagement with the bimetallic element. A flexible contact member of the receptacle is secured to the latch and is held thereby in electrical contact with a binding post of the receptacle when the latch is engaged by the bimetallic element. Upon bending of the bimetallic element from the projection, the latch moves the flexible contact memberl away from the binding post. When the bimetallic member has cooled, the latch may be manually restored to permit engagement o1' the contact member with the post.

In another modincation one end of the bimetallic member is normally in connection with a conducting member in the circuit and with a spring pressed latch. When the bimetallic member bends, the latch forces and holds it away from the conducting member. When the bimetallic member has cooled, the latch may be depressed manually to permit the bimetallic member to resume contact with the conducting member. In this form the bimetallic member forms part of the circuit and the heating element is obviated.

In another and simpliied form the bimetallic member forms the only auxiliary piece part in the receptacle, being so positioned as to normally connect with a connector in the circuit and adapted, when heated as by excess current, to

(Cl. 20o- 116) bend away and break the circuit, and when cool to automatically close the circuit by resuming contact with the connector.

The invention includes a thermostatic cut-out or circuit breaker designed primarily for use in 604 a base receptacle though it can be used -ln a switchboardcombination. The object of the invention is to safeguard insulation on conductors and the conductors, whether in master service or in a branch service.

It is well known that a frequent cause oi lires is the destruction of insulation used to cover conductors, that is, wires used to carry electric current in homes and in public buildings. Standard capacity fuses are required by the National Electrical Code and the Regulations of the National Board of Underwriters to prevent overloading oi.' conductorsbut it has been frequently round that fuses of regulation capacity have been removed and fuses of much greater capacity have been substituted when regulation fuses blow out, this being sometimes done in order that a greater amount of current can be used in given localities. Such substitution is usually the result of ignorance or indiiierence with the result, fre- 'a0 quently, that current increase has heated the conductor to such degree as to destroy its insulation and frequently results in the destruction of the structures in which the wiring was placed. In many instances buildings have been re-wired 35 throughout because of the destruction of con- 4ductor insulation thus caused. Many appliances such as nat-irons, etc. have been equipped with thermal cut-outs to prevent heating the appliance or current consuming equipment, xed or portable, for example, small heating, cooking or motor-operated equipment. The present invention relates to means for the protection of insulation and conductors covered thereby which are usually concealed, that is, rendered inaccessible by the structure or `finish of the building and usually between the base receptacle or outlet and the fuse-box, whether as preferably, in a lighting circuit, or in a circuit supplying appliances of various kinds. f

It is an advantage to place a conductor current overload preventing device in a base receptacle in a hotel room, as such receptacles are usually at the base board and are readily accessible though not so conspicuously so as to suggest unlawful or 105 unauthorized tampering at that locality. To that end ,the present invention is especially well adapted tofbe enclosed in the outlet box or base receptacle commonly found in indoor service and into which can be tapped the conventional pin no Fig` 1 is a fragmentary plan view, generally schematic, illustrating the control device located in a multiple receptacle circuit, which for convenience is shown as a bank of outlet receptacles.

Fig-2 shows a fragmentary cross section taken on the line 2-2 of Fig. 1;

Fig. 3 shows an enlarged fragmentary section taken on the line 3-3 of Fig. 1;

Fig. 4 is a corresponding fragmentary view taken on the line 4 4 of Fig. 3;

Fig. 5 is a bottom plan view showing the circuit connections visible on the bottom of the receptacle with the base cover removed;

Fig. 6 is a sectional detailed view taken on the line 6-6 of Fig. 5 and showing the heating device in relation to the bimetallic strip;

Fig. 'I is a sectional view of the receptacle corresponding with that shown in Fig. 4, but illustrating an open circuit therein;

Fig. 8 is a schematic sectional view showing the first modified form; v

Fig. 9 is a sectional View corresponding to Fig. rshowing the second modified form, and

Fig. 10 is a view corresponding to Fig. 9 but showing the third modified form.

Referring to the drawing, wherein similar parts are indicated by identical reference numerals throughout the several views, a compartment or enclosure, as a room in a house or a circuit generally designated by the numeral 20 is provided with any desired number of outlet receptacles 21, 21, in the particular instance six such being shown. It will be understood that the receptacles are suitably interconnected in such conventional manner that lamps or electrical appliances attached thereto may be supplied with current from a conductor 22 leading to any suitable source of electrical energy (not shown). Interposed in the line between the source and the receptacles is a current controlling device 24 (Figs. 2 to 7, inclusive) which is adapted to be engaged in the circuit by means of a pin plug 25 of any conventional type. The pin plug is connected in the circuit by a conductor cord 26 and is provided with any conventional type of contacting pins 27-27 (Figs. 2 and 3). The controlling device 24 resembles the conventional pin plug receptacle or base receptacle exteriorly, being composed (Figs. 3 and 4) of a cylindrical body portion 28 of non-conducting material, having detachably secured thereto a non-conducting top plate 29 and a non-conducting base or bottom plate 30. The body portion 28 is suitably apertured internally to receive a pair of spaced flexible contact bars 31 and 32 (Figs. 3 and 5) which may engage in a well known manner the contacting pins 27.

Secured on the bottom lof the body portion of the receptacle at the periphery and on opposite sides thereof as shown in Figs. 3 and 5, are a pair of binding posts 33 and 34, respectively. The contact bar 31 is secured to the binding post 33 and the bar 32 is secured to an auxiliary post 35 secured in the receptacle body. The bar 32 is normally indirectly connected to the binding post 34 in a manner to be described hereinafter so that when the receptacle is connected by attaching opposite sides of the line to the posts, the circuit may be completed through the plug pins l2?--2'7 in the well known manner. As shown in Figs. 4, 6 and 7, the body portion is additionally suitably apertured to receive a heating' element 36 which may be of any suitable character, preferably of a folded piece of highly resistant, wire, and a heat responsive bimetallic strip 37 is suspended from one end therein and closely adjacent to the heating element, by a screw and insulating block. It will be understood that the heating element 36 forms part of the circuit, one end thereof being connected to the binding post 34 and the other end thereof being connected to a conducting post 39 suitably embedded in the body material. Mounted on the post 39 and in electrical contact with the heating element is a spring leaf or resilient conducting member 40, the end opposite the post 39 of which normally presses against the lower edge of the bimetallic strip 37 (Fig. 4). vIt will be understood that under normal conditions, when no over-load in ,a conductor exists to heat said conductor and thence theheating element 36 and the bimetallic member is cold, the latter is relatively rigid and serves to maintain the resilient member 40 immovable. A rigid conducting connector 4l is secured at one end to the post 35 and extends across the bottom of the body portion to normally contact with the resilient conductor 40.

Under normal conditions, a current will flow on one side of the line through the post 34 and through the heating element 36, through the post 39, resilient member 40, connector 4l, post 35, to the flexible contact arm 32, pin 27, and through the conductor of the pin plug; and on the other side in the conductor, pin 27, flexible contact member 3l, and post 33. If it be assumed that the system shown in Fig. 1 is set for control at 110 500 watts, when five watt lamps or less are burned in flve of the receptacles shown, the circuit is normal and closed. However, if a sixth lamp is placed in the remaining receptacle and lighted, the conductor vline becomes overloaded, causing its temperature and the temperature of the heating element to rise, thus heating the bimetallic element. This is so positioned in the assembly that a rise in temperature will cause it to bend to the left as shown in Fig. '7, and away from the resilient member 40. 'I'he resilient member accordingly is released and moves upwardly separating from the connector 41 and breaking the circuit. l

, When the heating element cools, subsequent to the circuit having been opened, the bimetallic member straightens out, but is prevented from resuming its former position atop the resilient member because the latter member is sprung in the return .path of the strip and must be moved 13g into position to contact with the connector before the strip may become entirely straight again.

To permit this adjustment, .the body portion 28 is provided with a central vertically extending aperture, 43, in which is slidably disposed a pin 44 which may be of 4insulating material. The pin is formed witha shoulder 45 and the wall of the aperture with a coacting shoulder 46 for limiting the downward travel of the pin in the aperture, while permitting the pin suiilcient travel M0 therein and beneath the top plate 29 to equal the travel of the free end of the resilient member 40. The lower end of the pin rides on the upper surface of the resilient member 40 and is lifted thereby when the resilient member is .145 released by the strip 37. The top plate 29 of, the `receptacle is provided with an aperture 4'1 coaxially aligned with the aperture 43 through which a common match stem or similar instru- 'ment (not shown) may be inserted to depress the 150 pin, causing the free end of the resilient member to be lowered beneath the bottom end of the bimetallic strip. The strip is then free to become straight, and acts to retain the resilient strip in normal contact with the connector 41 when the match is removed from the pin.

In case it is desired to be able to close the circuit without removing the plug from the receptacle, or for any other reason, the modified form shown in Fig. 8 may be used. This embodiment consists of a somewhat larger though unitary receptacle 49, having therewithin two contact bars, the one being. conventional and connected to a binding post 51, and the other 52 having an elongated flexible connector portion 53 which normally rests upon a pcst 54. The receptacle is provided with a second binding post 56, to which is connected a heating element 36. A bimetallic strip 37 is mounted on but insulated from the post 54 and the heating element is also connected thereto. A latch or notched pin 57 is mounted in the receptacle so as to be vertically slidable therein, and is provided at its lower extremity with a projection 58 and at the upper end with a push button 59. The receptacle is recessed-at 60 to receive a compression spring 61, and near the top with an annular rim 62, which projects between the push button 59 and the latch proper. In the assembly the spring 61 engages the lower end of the latch 57 causing the projection 58 to bear upwardly upon the lower end of the bimetallic strip 37, the strip restraining further upward movement of the latch and insuring that the connector portion 53 is in electrical contact with the post 54.

When an over-load is placed on the line in which this receptacle is connected the temperature of the conductor and the heating element 36 rises and the bimetallic strip 37 bends to the left as viewed in Fig. 8, and moves away from the projection 58. The spring 61 is then operative to thrust the latch upwardly against the rim 62, this traverse beingsulcient to lift the connector portion 53 from contact with the post 54, thus breaking the circuit. After the heating element and the bimetallic strip cool, and when it is desired to close the circuit again, the push button 59 may be manually depressed; the projection 58 is thereby brought down below the end of the strip 37, which' moves thereon, thus causing the connector to be held in contact with the post 54 against the tension of the spring 61. It will be noted that by mounting all of the auxiliary parts shown in Fig. 8 within the body of the receptacle, they are safely enclosed therewithin a face plate or cover, not shown, completing the assembly and necessity for top and bottom plates for the receptacle is obviated, thus making for a more simpliiied construction and reduced costs of assembly in many cases.

In the embodiment shown in Fig. 9, a unitary receptacle 63 is apertured to receive two conventional oppositely disposed contact bars 64 and 65 respectively, the former of which is connected to a binding post 66 and the latter with a post 67. Securely mounted on a binding post 68 and in electrical connection therewith is a bimetallic strip 37 disposed vertically in the receptacle. Slidably mounted in the receptacle and parallel with the strip 37 is a latch 69 of insulating material, having a projection 71 which is normally held against a portion of the lower edge of the stripby a compression spring 72. A resilient conductive connector 73, has an enlarged and angularly disposed end 73 which extends breaking p the circuit.

through the projection 71 and normally contacts with` the strip 37 and contact bar 65 to close the circuit between the posts 67 and 68.

When an over-load is placed on the line in which this receptacle is connected the bimetallic member becomes hot and it bends to the right as viewed in Fig. 9. The `spring 72 causes the latch to slide upwardly and the projection 71 to press the bimetallic strip away from the connector and against Ian insulating wall 74, thus Its upward movement causes the latch to project above the toplof the `receptacle and the projecting portion is convenient to be manually depressed when the overload has been removed. The bimetallic member cools and may then resume its normal position on the projection 71 and in contact with the connector 73, thus restoring the closed circuit.

A very simple form of circuit breaking receptacle is the modification shown in Fig. 10. Two conventional contact bars 75 and 76, respectively, are shown, the first connected to a binding post 77, and the other to a post 78. A rigid conductive connector 79 is also connected to post 78. A bimetallic strip 37 is electrically connected to and mounted on a binding post 80, and extends to normally contact with the connector 79. The metallic elements of the strip 37 are so arranged that when an over-load is placed in the line, and the strip becomes heated, it bends to the left as viewed in Fig. 10, and away from the connector, opening the circuit. Upon removal of the over-load, the strip cools and automatically closes the circuit by resuming contact with the connector 79. i

From the foregoing it will be observed that by using a receptacle of the type shown in either of the iirst three forms described, in the circuit shown in Fig. 1 or other similar apparatus, the circuit is instantly opened upon an overload being suiilciently excessive as to raise the temperature in or around the bimetallic strip, and since those types must needs be reset manually, there is no possibility of an accidental resumption of the over-loaded condition pending inspection and correction by a custodian of the box. It will obviously be his duty before resetting the control device to remove one of the lamps from the circuit, orv take whatever other steps which may be necessary to correct the condition. Where inspection is unnecessary, the construction shown in Fig. 10 may be advantageously employed since the circuit there is re-closed automatically upon cooling of the strip 37.

By the use of bimetallic strips which may be set at any predeterminedl point in the receptacle, dependent upon the particular type of receptacle desired to be employed, the thermostatic elements of the receptacle occupy only a small space, are easily accommodated 'in the ordinary receptacle and are readily sheltered therewithin.

Thermostatic controlling devices of the type described are especially adapted for use as fuse protectors or current savers in public buildings such as hotels, apartment houses and dormitories, and in all lines where a maximum current load should not be exceeded. Furthermore a device of the type described may be used as a protection against high fusing on ordinary home circuits, thus preventing the use of apparatus requiring heavier loads than desired.

It will be understood that various details of the structures described above may be modified and many substitutions and eliminations made without departing from the spirit and scope of the invention as defined in the appended claims.

What'I claim is:

1. A pin plug receptacle having slidably disposed therein a spring pressed latch member having a projection, a resilient connector in the receptacle circuit, and a heat-responsive member adapted to electrically engage the connector and contact with the projection when cool.

2. In an electric conductor-overload preventing device, a xed terminal receptacle, a conductor including a resilient terminal securedin said receptacle, a reciprocable plunger in said receptacle having the terminal engaged therewith, a bimetallic thermostat adapted to secure the plunger-in a set position and make contact with the resilient terminal, the thermostat when overheated moving out of contact with thev resilient terminal and releasing said plunger, and a spring adapted to actuate the plunger when said engagement is broken and move the plunger into position to prevent the thermostat from engaging the resilient terminal as it cools.

3. In an electric conductor-overload preventing device, a fixed terminal receptacle, a conductor including a resilient terminal secured in said receptacle, a plunger movable longitudinally into and out of a set position and provided with a shoulder, a bimetallic thermostat normally in engagement with the resilient terminal to hold the plunger in its set position, and a spring adapted to move said plunger out of its set position when said engagement is broken by ilexing of the thermostat when overheated, said shoulder preventing return of the thermostat into engagement with the resilient terminal as it cools.

4. A device for preventing overloading comprising a receptacle, contact bars in said receptacle, one having a resilient extension, a plunger slidable in the receptacie into and out of a set position and having a side arm formed with an opening, the resilient extension having a portion received in the opening of the side arm, a heat responsive strip mounted at one end for connection with a conductor and having its other end normally bearing against the portion of the resilient extension engaged therein and serving as a latch to retain the plunger in its set position .and make contact with the resilient extension, said strip when overheated moving outA of latching engagement with the side arm, and a spring to move the plunger when released to a position in which the side arm prevents engagement between the strip and resilient extension.

5. A device for preventing overloading of a circuit comprising a receptacle, contact bars in said receptacle, a plunger slidable in said receptacle and having a side arm, one bar having an extension engaging a portion of the plunger,

a heat responsive strip in said receptacle normally having its free end bearing against the side arm to retain the plunger in a set position in which the circuit is closed, and a spring to slide the plunger out of its set position when the strip is distorted by overheating -and moved out of latching engagement with the side arm, said side extension being moved with the plunger to a position in which now oi' current is interrupted when the plunger moves out of its set position and an end of the side arm engaging the strip to prevent complete return of the strip to its normal position as it cools until the plunger is manually restored to a set position.

6. A device for preventing overloading of a circuit comprising a receptacle having conductor engaging posts, a heat responsive strip in said receptacle connected with one post, contact bars in said receptacle, one beingconnected with the second post, a barrier of insulation between the strip and second bar "to prevent direct contact of the strip with the second bar, a plunger o! insulation slidable in said receptacle and having a side arm engaged by said strip to releasably secure the plunger in a set position, the second contact bar having an extension engaging the side arm and contacting with said strip when the strip is in latching engagement with the arm, the strip when overheated moving towards the barrier out of latching engagement with said arm to release the plunger, and a spring to move the plunger out oi its set position when released, the plunger when released having its arm positioned to engage the strip and prevent return thereof into engagement with the side extension as it cools.

'7. A device for preventing overloading oi' a circuit comprising a receptacle having conductor engaging posts, a heat responsive strip in said receptacle connected with one post, contact bars in said receptacle, one bar being connected with the second post, a barrier of insulation between the strip and second bar to-prevent direct contact o! the strip with the second bar, a plunger of insulation slidable in said receptacle between the strip and first contact bar andv having a side arm extending towards said barrier -and normally engaged by the free end of said strip whereby the strip serves as a latch to retain the plunger in a set position, the second contact bar having an extension extending towards the plunger below said barrier and having an end ilxed in an opening formed in the side arm and contacted by the free end of the strip when the strip is in latching engagement with the side arm, and a spring to slide the plunger out of its set position when the strip is distorted and moved out of latching engagement with' the side arm by overheating of the strip, the strip when so moved having its free end confined between the barrier and side arm to prevent contact between the strip and extension as the strip cools until the plunger is manually restored to its set position.

WILLIAM L. PADGE'I'I'.

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