US3119646A

US3119646A - Electric lampholders

Info

Publication number: US3119646A
Application number: US166105A
Authority: US
Inventors: Adie Kenneth Scott
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-01-15
Filing date: 1962-01-15
Publication date: 1964-01-28
Anticipated expiration: 1981-01-28

Description

Jan. 28, 1964 K. s. ADIE ELECTRIC LAMPHOLDERS 2 Sheets-Sheet 1 Filed Jan. 15, 1962 United States Patent 3,119,646 ELECTRIC LAMPHOLDERS Kenneth Scott Adie, One Oak, Dove House Lane, Solihull, England Filed Jan. 15, 1962, Ser. No. 166,105 4 (llaims. (Cl. 33967) This invention relates to screw lampholders for screwcap electric lamps said holders each comprising a socket provided with electric supply contacts and with a screwthread so that the socket can receive and retain a screwthreaded plug on the lamp, such a holder being hereinafter referred to as a screw lampholder of the kind specified.

It is one object of the present invention to provide a screw lampholder in which a screw-threaded plug of an electric lamp can be resiliently gripped both in a radially inward and axially inward direction so that the lamp cannot be pulled out of the lampholder and will not become loosened when vibrated.

It is a further object of the present invention to provide a screw lampholder which is capable of receiving screwthreaded plugs having different thread forms.

It is a still further object of the present invention to provide a screw lampholder which does not cause a screw-threaded plug to be made alive until the plug is almost completely within the socket.

It is a yet further object of the present invention to provide a screw lampholder which is inexpensive to produce.

The invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of a screw lampholder,

FIGURE 2 is a top-side plan view of FIGURE 1,

FIGURE 3 is an underside plan view of FIGURE 1,

FIGURE 4 is a cross-sectional view similar to FIG- URE 3,

FIGURE 5 is a diagrammatic side elevation of the lampholder but only showing the resilient bar-like members in full lines and in positions occupied when not deformed,

FIGURE 6 is a similar view to FIGURE 5 but showing the resilient bar-like members deformed as a result of a screw-threaded plug of a lamp being located therein,

FIGURE 7 is a fragmentary cross-sectional view of the holder on an enlarged scale and showing the positions assumed by the resilient bar-like members when deformed as a result of the screw-threaded plug of a lamp being located in the socket and,

FIGURE 8 is a sectional view of FIGURE 7 on the lines 38 thereof.

The screw lampholder comprises a body 10 which is made of porcelain or may be made of any other suitable rigid electrically insulating or non-conductive material and includes a flange 11 formed with gaps 12 to receive fixing screws whereby the lampholder can be secured in a required position.

The body of the lampholder also comprises a cylindrical socket 13 to receive the single start screw-threaded plug 14 of an electric lamp 15 and said socket is formed by an irnperforate cylindricalside wall 16 and a rear end wall 17 and said socket at its forward end is formed with an internal chamfer 18 to facilitate insertion of the plug 14 of the lamp into the socket. The diameter of the internal cylindrical surface 19 of the socket is greater than the major diameter, i.e. the crest diameter of the screw-thread on the plug 14 of the lamp intended for use with the holder.

Disposed centrally within the socket and projecting from the rear end wall 17 is an electrical contact 20 ice adapted to co-operate with the normally provided central contact 21 at the end of the plug 14 of the lamp and said central contact 20 is stationary but may be spring loaded so as normally to be urged axially of the socket towards the forward open end thereof.

Disposed at one side of the socket and thus olfset from the centre thereof is a further electrical contact 22 which is resilient and is adapted to co-operate with the normally provided contact of the lamp formed by a metal screwcap of the plug 14 and the contact 22 extends only a short distance from the end wall 17 so as to be engaged by the metal screw-cap only during final axial movement of the plug of the lamp into the socket. The

contacts

20 and 22 are connected respectively with

terminals

23 and 24 at the rear of the flange 11 and adapted to receive electrical power supply wires.

Formed in the internal cylindrical surface 19 of the socket are two

sets

25 and 26 of openings said sets being spaced apart axially of the socket a distance equal to twice the pitch of the screw-thread on the plug 14 of the lamp. Each set of openings comprises four slots 27 and one blind hole 28 and three of the said four slots 27 are of right-angular formation when the socket is viewed in end elevation, see FIGURE 7, and these four slots are spaced apart substantially equi-angularly relative to a central longitudinal axis of the socket. The blind hole 28 is disposed substantially radially of the socket. The openings extend only partially through the thickness of the side wall 16 which, as previously stated, is imperforate.

The length of the mouth of each slot 27 opening onto the internal cylindrical surface 19 of the side wall 16 and in a circumferential direction is equal approximately to of the circumference of said internal cylindrical surface and the thickness of each slot, i.e. in a direction axially of the socket is much narrower than this, it being slightly larger than the diameter of wire to be used in the socket and hereinafter to be more particularly described. Thus as viewed in front elevation the mouth of each slot is of rectangular elongated formation, see FIGURE 1.

Adjacent but spaced a small distance circumferen-tially from one slot is the blind hole 28 hereinbefore referred to which is of circular cross-sectional shape and is slightly larger in diameter than the thickness of each slot 27.

The five openings in a set are positioned so as to define a helix having the same pitch as vthe screw-thread on the plug 14 of the lamp and the blind hole 23 land the closely adjacent slot 27 are disposed an axial distance apart corresponding to the pitch of the screw-thread. Each slot 27 as viewed in front elevation is inclined at the helix angle aforesaid.

The sets of

openings

25 and 26 are adapted respectively to receive loops 2? and Sil made of resilient metal wire. The wire is preferably made of stainless steel and is circular in cross-section and the diameter of the wire is such as to enable said wire to have an easy push-fit engagement with the sets of openings. By way of example the wire may be 0.048 inch in diameter and t e thickness of the slots may be 0.056 inch and the diameter of the blind hole 28 may be 0.62 inch.

The

wire loops

29 and 30 are each of angular and of substantially square formation when not deformed, see FIGURES 3 and 4 so as to provide three corners 3 1 which are rounded and are spaced Iapart relative to a central axis of the loop and at a position opposite the middle corner of the three corners, the two ends 32 and 3-3 of the wire are spaced apart to form a gap 34 to permit of expansion and contraction of the loop and the end 32 is disposed substantially radially outwardly.

Each of the wire loops 29' and 30 are conveniently planar in their undeformed condition and the distance across opposite corners of each loop is approximately equal to or slightly less than the distance between radially outermost parts of a pair of opposed slots 27 and each wire loop can beinserted and located in the socket by radially compressing the loop and engaging the one end 32 in the blind hole 28 so that said end is positively anchored against axial movement in and rotary movement around the socket and the other end in the closely adjacent slot 27 and the three corners 31 of the loop are engaged with the other three right-angular slots 27 in the appropriate set of openings and when the loop is permitted freely to expand said loop is retained in the socket by the openings.

Whilst the

free ends

32 and 33 of a loop and the corners 31 thereof are disposed within the openings in the socket, straight resilient bar-like, i.e., elongated, members 35 of the loop extending between the corners are disposed in :a chord-like manner across the side wall 16 of the socket and are spaced from the inner cylindrical surface 19 of the socket and owing to the helical formation of the openings the four chord-like bars 35 of the loop are constrained into a somewhat helical formation corresponding to one convolution of a screw-thread the pitch of which is the same as that of the screw-thread on the plug 14 of the electric lamp. Thus two sets of resilient bar-like members are provided at positions'axially spaced apart along the socket.

Prior to insertion of the screw-threaded plug 14 of the lamp into the socket, when the chord-like bars 35 are thus substantially straight and in an undeformed condition, pairs of opposed chord-like bars are spaced apart a distance equal to or slightly less than the minor diameter, i.e., the root diameter of the screw-thread on the plug 14 of the lamp.

When the two

loops

29 and 30 of resilient wire'are positioned in the socket the bar-like members collectively provide two axially spaced apart screw-thread-like convolutions formed of resilient bar-like members, the effective diameters of which convolutions are equal 'to or slightly less than the minor diameter of the screw-thread on the screw-threaded plug 14 of the lamp and it should be appreciated that the two convolu-tions are arranged so as to for-m part of a single start helix.

By inserting the screw-threaded plug 14 of an electric lamp into the socket 13 and at the same time rotating the lamp about the longitudinal axis of the socket the screw-threaded plug makes screw engagement with the chord-like resilient bar-like members of the two loops and screws into the socket until the central contact on ;the lamp 21 abuts the central contact in the socket and final tightening rotation of the lamp is applied until substantial resistance to rotation is felt. The engagement of the end 32 of a wire loop in the blind hole 28 anchors the loop against movement circumtferentially in the socket and each resilient bar-like member is supported adjacent its ends at 36 by the slots 27 against movement both axially and radially outwardly of the socket so that when the final tightening rotation of the lamp is effected up to a stop provided by the contact 20 in the socket the resilient bar-like members 35 are deformed, between their ends, radially outwardly of the socket against the surface 19 as shown in FIGURE 7 to exert radially inward resilient pressure on the screw- :threaded plug 14.

It should be appreciated that the four resilient bar-like members 35 in each loop provide four-point contact with the plug 14 at positions spaced 90 apart and thus said bar-like members are collectively disposed around a major circumferential part, i.e., more than 180, of the side wall whereby the plug is positioned centrally in the socket.

Whilst four resilient bar-like members 35 are provided in each loop it will be appreciated that three or more resilient bar-like members may be employed provided they are collectively disposed around a major circumferential part of the side wall so as to position the plug centrally in the socket.

As a consequence of each resilient bar-like member 35 being deformed radially outwardly of the socket against the surface 19, each member, between its ends is caused by continued tightening rotation of the lamp to be deformed axially outwardly of the socket as shown in FIGURE 8 whereby said bar-like members exert axially inward resilient pressure on the plug. Thus the plug is effectively locked centrally in the socket in a. manner preventing accidental unlocking, by for example, vibration and alternate heating and cooling of the members.

As considered from another aspect the screw-thread in the socket is formed of one or more rings, as hereinbefore defined, of triangular or other polygonal form made of resilient wire or rod with their sides forming resilient bar-like members 35 extending as chords relative to the internal cylindrical surface of the side wall 16 of the socket and supported therefrom at their ends. As shown in FIGURE 3 in the rings of polygonal form the successive sides formed by the members 35 are gapped between their ends.

If desired the offset contact 22 may be omitted and the inner loop 30 may be connected to the terminal 24 so that said inner loop 30 forms the offset contact in the socket.

Whichever of the two forms the offset contact of the lampholder may take, for cooperation with the screwthreaded plug of the lamp, .this offset lampholder contact is positioned adjacent the inner end of the socket so that the plug only connects with said offset contact when the plug is entirely or substantially within the socket to such an extent that the plug of the lamp is then inaccessible to a person inserting the lamp into the socket so that it is impossible for that person to receive an electric shock from the screw-threaded plug.

As it is virtually impossible for a person inserting a lamp into the lampholder to receive an electric shock there is no need for the open end of the socket to be provided with an outwardly flared skirt such as is normally provided and as the provision of a skirt tends to 'cause'the socket to become overheated due to collection of the uprising current of heated air from the lamp, the lampholders'according to the invention remain relatively cool.

The lampholders according to the present invention provide the further advantage that the resilient bar-like membersformingthe screw-thread in a single lampholder are readily self-adaptable to the different thread forms employed, for example, by British, American and Continental or other manufacturers of screw-cap electric lamps so that the different screw-threaded plugs, but in which the screw threads have the same pitch and lead, can each be inserted in an efiicient manner in the single lampholder according to the present invention.

The diameter of the internal cylindrical surface 19 of the socket and the cross-sectional diameter of the resilient bar-like members 35 are such that if said members are deformed radially outwardly so as to abut the internal cylindrical'surface 19 the effective minor diameter of the deformed members is such as to provide an interference fit with the major diameter part of the screw-threaded plug of the lamp which the holder isintended to receive so as to prevent withdrawal of the screw-threaded plug from the socket unless the said plug is screwed out of the socket. In other words the cross-sectional Size of the socket is less than the sum of the major diameter of the screw-threaded plug intended for the socket and twice the cross-sectional thickness of the wire of which the resilient bar-like members are made.

Whilst the lampholder illustrated in the drawings is provided with two sets of resilient bar-like members at positions axially spaced apart along the socket only one set may be provided which is preferably disposed adjacent the open end of the socket and the inner end of the socket may be provided with location means adapted to bear on the side of the screw-threaded plug of the lamp when the plug is inserted fully into the socket so as to locate and centralise the end of the plug at the inner end of the socket.

The invention thus provides an electric screw lamp holder in which the lamp is held so as to be co-axial therewith and in a manner such that the lamp will not accidentally become loosened when tightened in the lampholder and furthermore said lampholder is less expensive to produce than known lampholders and a single lampholder is capable of receiving screw-threaded plugs having different thread forms.

What I claim then is:

1. A screw lampholder comprising a socket made of electrically insulating rigid material to receive a screwthreaded plug of a screw cap electric lamp and Ihaving a rear end wall to close one end of the socket, electrical contacts within the socket, including a central electrical abutment contact at the inner closed end of the socket against which a central electrical contact of the plug can abut, at least one ring of polygonal form disposed in the socket to provide the sole screw-thread therein to receive the screw-threaded plug and the ring being made of resilient wire and affording resilient bar-like members each normally extending as chords relative to an internal surface of a sidewall of the socket and said members being supported by the side wall at their ends against rotary and axial movement in the socket whilst being normally free between their ends to move radially and axially, the cross-sectional size of the socket being less than the sum of the major diameter of the screw-threaded plug intended for the socket and twice the crosscectional thickness of the wire so that after the screw-threaded plug of the lamp has been screwed into the screw thread afforded by the ring up to the central electrical abutment contact in the socket further rotation of the plug firstly deforms the bar-like members of the ring radially outwardly against said internal surface of the side wall and secondly then deforms said members axially to cause said members to exert both radial and axial resilient gripping pressure on the plug and prevent its withdrawal from the socket unless said plug is screwed out of the socket.

2. A screw lampholder according to claim 1 in which the electrical contacts are provided adjacent the inner closed end of the socket so as to be capable of co-operating with the screw-threaded plug of the lamp only during the final axial movement of the plug into the socket so that the normally provided metal screw cap in which the screw is formed is not rendered alive until the plug is almost completely within the socket.

3. A screw lampholder comprising a socket made of electrically insulating rigid material to receive a screwthreaded plug of a screw cap electric lamp and having a rear end wall to close one end of the socket, the internal surface of an imperforate side wall of the socket being formed with a plurality of openings which extend only partially through the side wall, electrical contacts within the socket, including a central electrical abutment contact at the inner closed end of the socket against which a central electrical contact of the plug can abut, at least one ring of polygonal form disposed in the socket to provide the sole screw-thread therein to receive the screwthreaded plug and the ring being made of a loop of resilient metal wire affording a ring of at least three resilient barlike members of which adjacent members together define corners which enter the openings in the side wall of the socket so that said members normally extend as chords relative to the internal surface of the side wall and are supported by the side Wall at their ends against rotary and axial movement in the socket whilst being normally free between their ends to move radially and axially, the cross-sectional size of the socket being less than the sum of the major diameter of the screw-threaded plug intended for the socket and twice the cross-sectional thickness of the wire so that after the screw-threaded plug of the lamp has been screwed into the screw-thread afforded by the ring up to the central electrical abutment contact in the socket further rotation of the plug firstly deforms the bar-like members of the ring radially outwardly against said internal surface of the side wall and secondly then deforms said members axially to cause said members to exert both radial and axial resilient gripping pressure on the plug and prevent its withdrawal from the socket unless said plug is screwed out of the socket.

4. A screw lampholder according to claim 3 in which the loop of resilient metal wire affords ends which are spaced apart circumferentially of the loop to provide a gap between said ends and one end of the loop is directed substantially radially outwardly and enters a radially disposed opening in the internal surface of the side wall of the socket to support said one end positively against rotary and axial movement in the socket and the other end of the loop enters an opening in said internal surface whereby said other end is supported against axial movement in the socket whilst permitting its rotary movement in the socket to allow for expansion and contraction of the loop.

References Cited in the file of this patent UNITED STATES PATENTS 1,167,473 Benjamin Jan. 11, 1916 1,238,849 Wacker Sept. 4, 1917 1,780,826 Kuhn Nov. 4, 1930 1,881,663 Kennedy Oct. 11, 1932 2,476,071 Spiro July 12, 1949 2,668,278 Avery Feb. 2, 1954 2,874,741 Brancato Feb. 24, 1959 FOREIGN PATENTS 137,562 Australia Jan. 8, 1950 658,761 France Jan. 278, 1929 912,009 France Apr. 8, 1946 981,399 France Jan. 10, 1951 997,233 France Sept. 12, 1951 1,171,784 France Oct. 6, 1958 1,036,971 Germany Aug. 21, 1958 589,357 Great Britain June 18, 1947

Claims

1. A SCREW LAMPHOLDER COMPRISING A SOCKET MADE OF ELECTRICALLY INSULATING RIGID MATERIAL TO RECEIVE A SCREWTHREADED PLUG OF A SCREW CAP ELECTRIC LAMP AND HAVING A REAR END WALL TO CLOSE ONE END OF THE SOCKET, ELECTRICAL CONTACTS WITHIN THE SOCKET, INCLUDING A CENTRAL ELECTRICAL ABUTMENT CONTACT AT THE INNER CLOSED END OF THE SOCKET AGAINST WHICH A CENTRAL ELECTRICAL CONTACT OF THE PLUG CAN ABUT, AT LEAST ONE RING OF POLYGONAL FORM DISPOSED IN THE SOCKET TO PROVIDE THE SOLE SCREW-THREAD THEREIN TO RECEIVE THE SCREW-THREADED PLUG AND THE RING BEING MADE OF RESILIENT WIRE AND AFFORDING RESILIENT BAR-LIKE MEMBERS EACH NORMALLY EXTENDING AS CHORDS RELATIVE TO AN INTERNAL SURFACE OF A SIDEWALL OF THE SOCKET AND SAID MEMBERS BEING SUPPORTED BY THE SIDE WALL AT THEIR ENDS AGAINST ROTARY AND AXIAL MOVEMENT IN THE SOCKET WHILST BEING NORMALLY FREE BETWEEN THEIR ENDS TO MOVE RADIALLY AND AXIALLY, THE CROSS-SECTIONAL SIZE OF THE SOCKET BEING LESS THAN THE SUM OF THE MAJOR DIAMETER OF THE SCREW-THREADED PLUG INTENDED FOR THE SOCKET AND TWICE THE CROSS-SECTIONAL THICKNESS OF THE WIRE SO THAT AFTER THE SCREW-THREADED PLUG OF THE LAMP HAS BEEN SCREWED INTO THE SCREW THREAD AFFORDED BY THE RING UP TO THE CENTRAL ELECTRICAL ABUTMENT CONTACT IN THE SOCKET FURTHER ROTATION OF THE PLUG FIRSTLY DEFORMS THE BAR-LIKE MEMBERS OF THE RING RADIALLY OUTWARDLY AGAINST SAID INTERNAL SURFACE OF THE SIDE WALL AND SECONDLY THEN DEFORMS SAID MEMBERS AXIALLY TO CAUSE SAID MEMBERS TO EXERT BOTH RADIAL AND AXIAL RESILIENT GRIPPING PRESSURE ON THE PLUG AND PREVENT ITS WITHDRAWAL FROM THE SOCKET UNLESS SAID PLUG IS SCREWED OUT OF THE SOCKET.