US2180976A - Film cut-out - Google Patents

Description

Nov. 2l, 1939..v H. E. BUTLER' FILM CUT-OUT Filed March 18, 1936 a. wv .w.

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Fatenied Nov. 2i, ig

t UNITED STATES FILM QUT-our Henry E. Butler, Scotia, N. Y., assignor to' General Electric Company, a corporation of New York Application March is, 193e, semina. 59,494 l "12 Claims.

My invention relates to .dielectric illm cutouts and more particularly to cutouts for series connected lamps.

This application is a'continuation in part oi my'application Serial No. 32,043, filed'July 17,

One application oi my invention is in co'nnection with strings of series connected lamps such as are used in the lighting of Christmas trees or for other decorative purposes wherein it is common practice to connect eight or nin'e lamps in series across the usual 115 volt house lighting circuit. When one of these lamps burns out, each one of the lamps in the string is extinguished and it becomes necessary to try each lamp to determine which one is burned out. It is also found at times, after duly testing each lamp in a circuit, that the lamps are all good but that one oi' the lamps had become loose in its socket and thereby broke the circuit.

It is one oi' the objects of my invention to provide an improved cutout device for shunting the circuit around a burned-out lamp in a series circuit.

Another object of my invention isto provide a cutout which will simultaneously act as a locking device for locking the lamp. in its socket.

' Another object of my invention is to provide a method of .manufacturing cutouts whereby only a. single film of oxide is placed between the two terminals of a circuit.

Another object of my invention is to provide a cutout for series connected lamps which will establish a circuit when the voltage across the lamp contacts -reaches a predetermined value and will again' interrupt the circuit when the current in said circuit rises to a predetermined value.`

Other objects and the advantages of my in- 40 vention will be apparent and the invention itself In the accompanying drawing, Figs. 1 and 2- illustrate respectively a plan view and a side view of an oxide film cutout made in accordance with my'invention; Fig. 3 illustrates one'of the cutouts illustrated in Figs. 1 and 2 mounted on the base of an incandescent lamp; Fig. 4 illus-- trates the lamp of Fig. 3 assembled in Va socket; Fig. 5 is an enlarged sectional view of a lamp base having thereon a cutout made in accordance (c1. zoo-118) with my invention; Fig. 6 illustrates a method of manufacturing the cutouts; Fig. 'I is a circuit diagram illustrating the us'ual series string of eight lamps connected to a plug cap through a fuse, and Figs. 8, 9, 10. 11 and 12 are m'cdifica- 5 tions of my invention.

Referring to the drawing in detail, Figs. 1 and 2 illustrate a thin metal concave disk I0, having attached thereto ears II and I2 projecting in opposite directions from the disk. Thel disk I0 is provided with a concentric truncated cone portion I3 having anl outwardly rolled edge I4. This metal disk is covered with a layer. I5 of metal oxide which forms the dielectric iilm. 'Ihe metals most generally used for this purpose are copper or aluminum. Other suitable metals may, of course, be used. The process of applying an oxide coating to this metal is important, since the thickness of the oxide determines the breakdown potential. It is also necessary to provide an oxide which will not ilake oi when the cutout is bent while being assembled on the lamp base. One satisfactory process for producing this oxide iilm on copper is disclosed in United States Patent 1,982,384, to Edgar H. Harty and assigned to the assignee of the present invention.

As stated above, the metal of the cutout, illustrated in Figs. 1 and 2, is thin and easy to bend. In placing the cutout on the .base of an incandescent lamp, lamp I6 for example, the truncated cone section I3 is fitted against the similarly-shaped insulation section I'I of the lamp base extending between the metal screw shell I8 and the center contact I9. The ears II and I2 are then bent at right angles to the disk I0 downwardly along the'screw shell I8 and a rubber band 20 is rolled over the base so as to hold the cutout onto the basey until the lamp is screwed into a socket 2l. This is clearly illustrated in Figs. 3 and 4.

To jexplain my invention I have illustrated lamp I6 as being equipped with a base comprising a. screw shell and a raised center contact at the end thereof. This type of base is referred to in the art as an Edison type base. It will be clear to those skilled in the art that my cutout can be equally applied to modiications of this base without departing from the spirit of my invention.

The center contact I9 on the illustrated lamp base comprises a drop of soft metal, siich as solder, which is deposited when the lamp lead is anchored in the base. The rolled edge I 4 of the cutouttouches this center contact along its edges, as is illustrated in Fig. 5, but thecenter portion .of this contact projects above the rolled edge so screwed into the socket, until the last fraction of a turn, shell.

In operation, or actualuse, it is an easy matter for any inexperienced person to place the cutout before it becomes tightly seated in the on a small base of a Christmas tree lamp, as

above explained. When the lamp is then placed into a socket, the ears iI and I2 do not prevent contact between the shells I8 and 23, because they are not wide enough, but they do act in the capacity of a lock washer and prevent the lamp becoming loose in the socket due to a jarring of the socket. In case the lament in the lamp breaks, the circuit between the contact. I9 and the shell I8 is broken, so that thefull line voltage, that is, the full voltage available at theoutlet from which current is drawn for the Christmas tree circuit, is placed across the oxide film between the contact I9 and the rolled edge I4 of the cutout. In the treatment of the cutout, this oxide lm is made of such thickness that it will break down at about one-half of the available voltage. When this film breaks down, the metal of the cutout becomes a conductor between the shell I8 and the center contact I 9 of the lamp, to take the place of the filament. and the circuit through the remainingl lamps is again established. It will be noted that in order to establish this conductive path, current must enter the metal of the ears I I or I2 and again leave at the edge I4. If the entire cutout, including the ears II and I2, is covered with oxide, it will be necessary for the potential to break down two layers of this oxide. This may be desirable in cases where a single layer of oxide is insufiicient to carry the desired voltage.

On lthe other hand, the ears II and I2 need not necessarily be oxidized, and if not, then it is only necessary for the potential to break down the single layer ofi oxide between the rolled edge I4 and the center contact IB of the lamp. In such instances the thickness of the single layer of oxide may be more easily controlled and the breakdown voltage thereby more accurately obtained. f

In the production of oxide-coated cutouts, it

has been found difficult to produce a continuous or dependable oxide. coating along the edges of the thin sheet metal which for the present use is between 2 and 3 thousandths of an inch. In my present cutout I overcomev this difficulty in one instance and make use thereof in another instance. It will 'be noted that the inner edge I4 of the truncated cone section I3 of the disk I0 is rolled, or flared outwardly, and that it is the continuous inner surface of the cone that touches the center contact I9 of the lamp base. 'I'he faulty edge is out of contact. 70

Inmaking the cutouts in large numbers, I prefer to use a large sheet of metal 24, such as shown in Fig. 6, and produce the truncated cone sections I3 and rolled edges I4 spaced from each other at predetermined distances. 'Ihe sheet is then treated to produce the oxide thereon and thereafter is cut along the dotted lines 25, as indicated. This last step leaves an unoxidized edge on both the disk and the strips. When the lamp base having thereon one of these cutouts is screwedinto a socket, the oxide which is weak at the severed edges is suiiiciently displaced to permit the metal of the strips engaging the socket shell. The only insulation between the shells and the center contacts is, therefore, one thickness of oxide between the rolled edge I4 and the center contact I9.

Fig. 7 is a circuit diagram illustrating the manner of connecting the lamps I3 and cutouts I0 in a series circuit to a plug cap 3l. A fuse 32 is placed lin the circuit to prevent the current rising above the safe linut when several of the lamps in the circuit burn out. It is to be noted that since the available voltage remains substantially constant, the voltage across each lamp .rises when one burns out. 'I'he possibility of the other lamps burning out is, therefore, increased. To avoid this difficulty I provide several modifications of the above described cutout.

In Fig. 8, I have illustrated one modification of my invention. The cutout illustrated in this figure is suitable for larger lamps), and comprises an oxide-covered disk 26 provided with a hole 21 suitable for the center contact of a lamp base to project through. A pair of straps 28 and 29 are fastened to the edge ofthe disk and are respectively fastened to a resilient split ring 30. This structure is placed on the base of a lamp and the oxide on the edge of the hold 21 constitutes the insulating film. When the filament breaks the coating breaks down andv establishes a circuit, between the screw shell and the center contact,` through the material of the disk 28. This material may be a low resistance metal, such as copper or aluminum, or it may be a high resistance metal or other material so as to take the place of the burnt-out lamp filament. It is to be -noted `that in this construction the disk is manifold the thickness of the disk I0 wherefore the precaution of rolling the edge of hole 21 is not necessary, although it could be done if 'found necessary. The straps 28 and 29 are not oxide coated. Any suitable method may be used to attach the straps to the disk. The method illustrated comprises slotting the disk after. the oxide coating process so that the straps placed through the slots will contact the metal of the disk. In this manner only the single oxide coating at the edge of hole 21 controls the breakdown.

In Figs. 9, 10 and 11 I have illustrated a modification of my invention whereby the cutout serves also as a fuse for interrupting the circuit through the remaining lamps. In Fig. 9 I have illustrated a modification comprising a rectangular portion 33 provided with a hole 34 through which the center contact of a lamp may project.

Y A strap 35 provided with a reduced portion 38 is attached to `the rectangular member 33. The member 33 corresponds to the member I0 of Fig. 1 and the strap 35 corresponds to the strap I2. When thislatter cutout is used the member 33 is cemented to the center contact of the lamp and the strap may either be cemented or held by a rubber band 20. When the lamp burns out the oxide breaks down and if the current rises above the predetermined safe value, the portion 36 will fuse and break the circuit. With this Ymodification I retain the advantage of the strap for locking .the lamp in its socket and obtain the additional advantage of providing a fuse within the lamp socket. In manufacturing thlamcdication I use strip material having a width equal to the width of the rectangular portion 33. This provides a considerable saving of material over the method used for the manufacture of the cutout of Figs. 1 and 2.

Figs. and 1l illustrate another modification in which an oxide coated metal strap, or wire, 31

is attached to the center contact of the lamp and 1o to the shell. The strap 31 is made of such dimensions that it will carry only a predetermined current and will fuse and break the current circuit when a larger current flows. The lower side may be fastened to the upper end of the shell contact. If s o attached the cut-out has the two functions of establishing a current circuit when the lamp burns out and to break the circuit when the current exceds a predetermined value. When this strap extends along the shell and is attached lamp is inserted in the socket, ajlarge strap sim-- ilar to strap 35 may be combined withthe strap l31. In attaching this strap 31 to the center contact of the lamp, this contact is grooved and the oxide-coated strap is soldered therein; In case the lamp burns out the oxide breaks in the solder and permits cur-rent to ilow in the metal of the strap. When the lamp is turned into the socket the oxide film on the strap is rubbed of! sufilciently to permit the current to ow directly to the shell. In manufacturing thisv cut-out, a continuous wire or strip is oxidized and then cut into the required lengths.- One end of this strip is placed into the groove in the metal of the center contact so that the bare end is free of the lamp contact, as shown in Fig. 14; the other end may be connected to the bulb of the lamp or to the shell,` as above described.

In Fig. 12 I have shown a modification wherein a resistance wire 38 is wound in the grooves of the shell. It is attached at its one end to the shell andY at its other end to an oxidized strap 33 which 'is attached to the center contact of the lamp in the same manner as strap 31. In this manner the proper breakdown and fusing strength is obtained. The resistance of the wire is chosen such that the length wound about the shell will have suilicient resistance to take the place of the burned-out lamp. The wire 33 is covered with enamel which insulates the wire and has sufllcient strength to resist abrasion during the turning of the lamp into the socket. In

this manner the current. flows from theoxidecoated strip 39 to the resistance wire 3B, through the wire and to the shell at the end of the wire where it is soldered tothe shell and the insulation removed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. 'A dielectric fum cutout for use with' a lamp having a center contact and a shell, comprising a current conducting member coated with a dielectric iilm, arranged to engage the center contact of a lamp base and to extend over a portion of the shell surface of the said base for establishing a circuit betwen said `contact and said shell upon the breaking of said film due to the occurrence of a predetermined voltage and for locking said base in a socket.

2. A dielectric film cutout comprising a coated metal disc arranged to engage the center contact ol a lamp base, and current conducting means arranged to extend along the side of the shell of said center contact by said oxide film, said base a said base to hold said disc in engagement with asaid center contact.

3. A dielectric nlm cutout comprising an oxide coated current conducting disc arranged to engage the center contact of a lamp base and pro- 5 vided with an opening through which a said center-contactmay project, and current conducting means attached to said disc arranged to extend alcng the shell of a said base and for holding 1saii disc in engagement with a said center con- 4. In combination. a lamp provided with `a base, comprising a shell and a second contact insulated therefromand projecting above the end of said shell, a dielectric film cutout comprising a coated metal disc in engagement with the said second contact of said base, said disc being provided with an opening through which said sec- `ond contact projects, means for holding said disc 30 comprising a shell and center contact, current conducting straps attached to said disc and adapted to engage the shell of av said base, said straps being free from oxide on their edges whereby contact may be established between a shell and the metal of said straps so that only ,a single film of oxide insulates a said center contact from a said shell. v

6. In combination, a lamp provided with a base comprising a shell and center "contact, a dielectric film cutout comprising `a coated disc of current conducting material in engagement with said center contact, a pair of current conducting straps attached to said disc in engage. ment with the shell of said base, and a rubber band surrounding said shell and straps for holding said straps in engagement with said shell.

7. In combination, a lamp provided with a base comprising a shell and center contact, a socket therefor, a dielectric film cutout for shunting said contacts in case the lament of said lamp breaks comprising a dielectric film coated current conducting disc in engagement with the p center contact of said base, and means for holding said disc in engagement with said base including a exible current conducting strap attached to said disc, said strap being pinched between said base and said socket when saidlamp is inserted whereby said strap acts to lock said lamp in said base. 8 In combination, a lamp provided with a base, contacts in said base vnormally insulated from each other, a cutout comprising a dielectric film covered and fusible current conductor adjacent sald contacts, said cutout being arranged to establish a current conducting circuit be` tween said lamp contactsupon the occurrence of a predetermined rise in voltage between said contacts and to fuse and thereby break said established circuit upon the occurrence of a predetermined increase in current flowingiin said circuit.

9. In combination, a lamp provided with a base, contacts in said base normally insulated from each other, and a cutout comprising a current conducting member provided with an insulating lm for separating it from one ci said contacts and being attached to the other of said contacts, and having a resistance substantially equal to the normal resistance of said lamp.

10. In combination, a lamp provided with a base comprising a center contact and a screw shell contact, said contacts being insulated from each other and comprising the terminals of said lamp, and a cutout comprising an insulated wire having a total resistance substantially equal to the normal resistance of said lamp adjacent at one end to the said center contact being separated therefrom at this end by an insulating film having a predetermined breakdown voltage, said wire being Wound about said Lshell and attached to the shell at its other end.

11. A dielectric lm cutout comprising a coated current conducting member arranged to engagethe center contact of a lamp base, an insulated resistance wire attached to said member at one end and wound in the grooves of the screw shell of a said base, said wire having a resistance substantially equal to the resistance oi? a said lamp and attached at its other end to the said shell whereby this cutout establishes a shunt circuit of equal resistanceto the lamp when a predetermined potential occurs across the contacts thereo f, breaks this circuit upon the occurrence of a predetermined current and locks the said lamp base in a socket.

l2. In combination, a lamp provided with base contacts, an insulating member between said contacts, a cutout comprising a dielectric lm covered and fusible current conductor adjacent said contacts and extending along the surface of said insulating member between said contacts, said cutout being arranged to establish a current conducting circuit between said lamp contacts upon the occurrence of a predetermined rise of voltage between said contacts and to .fuse and thereby break said established circuit upon current owing in said circuit.

HENRY E. BUTLER.

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