US2997701A - Plug-in cap with ground indicating light - Google Patents

Description

Aug- 2. 1961 R. J. COSTANZO 2,997,701

PLUG-IN CAP WITH GROUND INDICATING LIGHT Filed Oct. 16, 1958 2 Sheets-Sheet 1 INVENTOR W1 ATTO RN EYS R. J. COSTANZO PLUG-IN CAP WITH GROUND INDICATING LIGHT Filed 001;. 16, 1958' Aug. 22, 1961 2 Sheets-Sheet 2 '3 M Z? B/ack 6 f II M/ '7 l J f/vfc i l Z? 4 I l 7 KY} W 5/ af w a if? Green 3 LL-I Fig. 6.

INVENTOR ATTORNEY5 United States Patent 2,997,701 PLUG-IN CAP WITIIIIEROUND INDICATING HT Raphael J. Costanzo, Bridgeport, Conn., assignor to Harvey Hubbell, Incorporated, Bridgeport, Conn., a corporation of Connecticut Filed Oct. 16, 1958, Ser. No. 767,704 4 Claims. (Cl. 340-255) This invention relates to a plug-in cap with ground indicating light, and has for an object to provide such a cap with simple and eifective means such as a signal or indicating light so connected that when used for supplying electric current to a grounded electrical power device or attachment, this light will indicate whether the ground is working and in good condition, or whether it has been broken.

Another object is to provide such a device that merely plugging the cap into an outlet receptacle for supplying current to the electrical device will, through this indicating light, show whether the ground from the electrical device or attachment is in good condition and functioning properly.

With the foregoing and other objects in view, I have devised the construction illustrated in the accompanying drawing forming a part of this specification. It is, however, to be understood the invention is not limited to the specific details of construction and arrangement shown, but may embody various changes and modifications within the scope of the invention.

In these drawings:

FIG. 1 is a top view of the lower member of the cap with certain parts in section and the fuses removed, the section being substantially on line 1-1 of FIG. 3;

FIG. 2 is a similar view looking toward the bottom of the upper section taken substantially on line 22 of FIG. 3, and with parts broken away to more clearly show the construction;

FIG. 3 is a longitudinal section of the complete plug-in cap taken substantially on line 3-3 of FIG. 2;

FIG. 4 is a bottom or end view looking toward the bottom of FIG. 3;

FIG. 5 is a diagrammatical view showing the various elements on the plug and electrical connections to an electric attachment or power device, such, for example, as an electric hand drill, and

FIG. 6 is a wiring diagram of the connections involved.

The cap 10 is the regular fused and grounded cap used for plugging into an outlet receptacle or similar connection (not shown) for supplying current to some electrical attachment or power-operated device such, for example, as a motor 11 in a hand drill or similar device, including a grounded frame or casing 12. This cap is provided with means to indicate whether the ground connection from this casing or frame 12, for example, of the motor, is as it should be and functioning properly, or whether it has been broken. This plug-in cap comprises a body including two body sections of insulating material indicated at 13 and 14, and for identification purposes the member 13 will be called the upper member and member 14 the lower member. Mounted in the lower member in a recess or chamber 15 in the inner or top wall thereof are connections for mounting the contacts 16, 17 and 18, one of which (18) is the grounding contact, and 16 may be indicated as the hot contact and 17 the return or neutral wire of the power circuit. The contacts 16 and 17 extend through slots 19 and 20 in the end wall of the member 14 where they terminate in lateral plates or connectors 22 respectively mounted on the bottom of the recess 15 by any suitable means such, for example, as screws 23 threaded through the plates 22 into the material of the body or into threaded inserts molded in this body, or they could be permanently connected by riveted-over inserts. The contacts 16, 17 and 18 are transversely curved and have a wider overhanging end portion 24 at their free ends providing a locking shoulder 25 adapted to lock with shoulders in the body of the receptacle into which they may be inserted, by a limited relative turning movement after they are so inserted in the receptacle. Mounted on each of the base connectors 22 is a spring clip 26 which may be used for holding one end of a fuse cartridge 27 and forms electrical connection from the end contact 28 thereof to the contacts 16 and 17.

Mounting and gripping the other ends of the fuse cartridges 27 are similar spring contacts 29 mounted on the conductor bars or plates 30 and 31 mounted in the recess 32 in the inner or bottom wall of the body member 13 by any suitable means, such, for example, as screws 33 and 34 which may also be binding screws for connecting lead wires to the conductors 30 and 31. The body 13 is provided with a passage 35 leading from the top wall thereof to the recess 32 to which conductor wires of an insulating electric cable may be led for connection t0 the various elements in the cap. In the arrangement shown a hot or black wire 36 is connected to the conductor 30 by the binding screw 33 and through a fuse 27 to the contact 16. Similarly, the return or neutral white wire 37 is connected to the conductor 31 by the binding post 33 and through a similar fuse 27 to the contact 17. The green or ground wire 38 is connected by a binding screw 39 to a plate 40 mounted in the bottom recess 15 in the lower body member and electrically connected by a screw 41 to the base 42 of the grounding contact 18, this base being located in a recess in the lower end wall of the member 14. This screw 41 and similar screw 43 are passed through the lower member 14 and threaded into an insert (not shown) in the upper member 13 to connect these two members together after the various elements have been assembled.

Mounted in the side wall of the body member 13 is an indicating light 44 which may be a neon glow light, and it is mounted in a recess 45 in a side wall of the member 13, which recess opens through the outer surface of this member. One contact of this light, indicated at 46, is connected through a resistor 47 to the conductor 30, as indicated at 48, and the other lead or conductor 49 from this lamp is connected to a binding screw 50 to a conductor 51 in the cable, which is indicated as a red conductor, and it is connected at the other end of the cable to the frame or casing 12 of the motor or electrical device to be operated, as shown in FIGS. 5 and 6. The hot or black wire 36 and the white or return wire 37 are connected to the motor 11 for supplying power to this motor. The frame or casing 12 of the motor is grounded through the green wire 38, which is connected to this casing at one end, as shown at 38a, and leads to the grounded contact 18 in the cap. The indicating lamp 44 may be covered and protected in its recess 45 by a transparent protective cap 52 which may be screwed into or forced or snapped into a recess 53 at the outer end of the recess 55 or cemented in position.

In operation, as shown in FIGS. 5 and 6, plugging this cap into the grounded outlet receptacle or connector will connect the hot contact 16 to the hot side of the power circuit, the contact 17 connected to the return and 18 connected to the grounded contact in the receptacle. Its ground is indicated at 54. If the grounded connection 38 from the motor frame or casing 12 is in proper working order, current will flow from contact 16 through the resistor 47 to the light 44 and through the red connection 51 to the frame or casing 12 and back through the green connection 38 from this casing to the grounded contact 18. Thus the lamp 47 will glow and indicate that the grounding connection is intact and working properly. The resistor 47 has sufficiently high resistance to protect the lamp 44 and supply proper small current for operation of this lamp. Should the grounding connection 38 from the frame or casing of the motor be broken or not functioning properly, then the lamp will not glow, and will indicate immediately to the operator either that the ground connection is broken or not functioning, and will warn him for safetys sake to see that the proper ground from the motor casing is restored before the motor and the electrical device is operated. The two fuses 27 may or may not be used, and if not used the loads 36 and 37 may be connected directly to the contacts 16 and 17 respectively.

It will be seen from the above that this provides a very simple and effective device which will function from the mere act of inserting the blades of the plug-in cap into the outlet receptacle or other connection, to indicate immediately to the operator whether the ground from the frame or casing of the motor to be operated by power from this receptacle is functioning properly, or should be restored before use of the motor or use of the device operated by it.

Having thus set forth the nature of my invention, I claim:

1. A plug-in cap comprising a body of insulating ma terial, blade contacts projecting therefrom for insertion in an outlet receptacle and including power circuit contacts and a grounding contact, an indicating light mounted in the body, conductor wires connected to the contacts and extending from the body with the wires from the power contacts adapted for connection to a motor of an electrical device to supply power thereto and the wire from the grounding contact adapted for connection to the casing of the motor to ground it, a resistor in the body connected in series with one of the power contacts and the light, and a conductor wire connected to the light and extending from the body so as to be adapted to be connected to the casing of the motor to ground the light through the first ground connection.

2. A plug-in cap comprising a body, blade contacts projecting from the said body for insertion in an outlet receptacle including power circuit contacts and a ground ing contact, said body provided with a recess opening through one side thereof, an indicating light mounted in said recess, conductor wires connected with the contacts and extending from the body where they are adapted for connection to the motor of an electrical device to supply current to the motor and to ground its casing, a resistor in the body, conductor means connecting the resistor in series with one of the power contacts and one side of the light, and a conductor wire connected to the other side of the light and extending from the body adapted for connection to the motor casing to ground the light thereon.

3. In combination, a plug-in cap and an electric motor including a casing, said cap including a body, blade contacts projecting from the body for insertion in an outlet receptacle, said contacts including power circuit contacts and a grounding contact, an indicating light mounted in the body, conductor wires extending from the power circuit contacts-to the motor to supply current thereto, a conductor wire extending from the grounding contact to the motor casing, a resistor mounted in the body, and conductor means connecting the resistor and light in series with one of the power circuit contacts and the motor casing.

4. In combination, a plug-in cap and an electrically operated device including a motor and a casing, said cap comprising a body provided with a recess opening through one side thereof, blade contacts projecting from the body for insertion in an outlet receptacle and including power circuit contacts and a grounding contact, an indicating light mounted in said recess, a resistor mounted in the body, lead wires extending from the power circuit contacts to the motor for supplying current thereto, a lead wire extending from the grounding contact to the motor casing, and conductor means connecting the resistor, the light and the motor casing in series with the hot side of the power circuit.

References Cited in the file of this patent UNITED STATES PATENTS

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