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Description  |
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This invention relates to bulb sockets and, more specifically, to an
improved socket for receiving a wedge base bulb.
BACKGROUND OF THE INVENTION
Lamp bulbs of the type commonly known as wedge base bulbs are in wide use
in many environments including in automobiles wherein they are used for
panel lighting and for other purposes. Wedge base bulbs have a glass
envelope containing the filament with the base of the envelope itself
being designed to be wedged into a receiving socket. Of particular
significance is the fact that such bulbs do not have a metallic base like
many other forms of lamps. Instead, the connections to the internal
filament are made through conductors which extend through the base end of
the envelope and are bent backwards over the exterior surface of the wedge
base thereof. Electrical energy is then supplied to the bulb by bringing
contact elements into engagement with those conductors in various ways.
Wedge base bulbs and bulbs of similar types and sockets for use therewith
are shown in a number of issued U.S. Pat. Nos. including 3,143,301;
3,208,032; 3,253,249; 3,339,172; and 3,617,984.
The wedge base bulb has many advantages over screw and bayonet base bulbs,
including lower costs for the bulb and the socket to receive it, and
increased reliability, both as to the bulb itself and also as to the use
of the bulb. For example, the probability of a screw base bulb working
itself loose as a result of vibration in an automobile is somewhat greater
than with either a bayonet base type or a wedge base type, and bayonet
bases tend to corrode in their sockets, rendering replacement more
difficult.
Thus, there is considerable increased interest in wedge base bulbs and
attention has turned to developing inexpensive and reliable sockets for
them. One such approach which has been used is to fabricate leaf type
contact elements to engage the conductors of the bulb and to then mold a
non-rigid material around the contacts to form the socket into which the
bulb can be inserted. The outside configuration of the socket is typically
designed to snap into a mounting hole. Experience has shown that there are
several difficulties with this approach. For one, the mounting holes
formed in an automobile body commonly have sharp edges which can easily
slice through the relatively soft non-rigid material, seriously damaging
the socket. However, it is not possible to simply make the material harder
and more rigid because the socket must be sufficiently resilient to permit
insertion of the bulb without excessive force and to press the molded-in
contact members against the bulb conductors. Such sockets for use in
automobiles must meet rather rigid SAE specifications as to insertion
force, etc.
An additional problem with molded-in contacts is the difficulty of keeping
the contact surfaces of the molded-in contacts free of the socket material
which, of course, is an electrical insulator. Even a small amount of
material on that surface renders the socket inoperative.
Still further, the sockets with molded-in contacts involve costly
manufacturing processes involving the loading of the electrical contacts
into the mold cavities, and there is substantial difficulty in maintaining
dimensional characteristics due to the soft molding material.
In addition, it is not presently possible to make a flexible socket with
thermoforming materials which can withstand temperatures exceeding about
125.degree. F. (52.degree. C.).
Attempts to overcome these problems have resulted in the use of contact
members which snap into pre-molded sockets. However, these efforts have
not been fully successful and have resulted in sockets with exposed
terminals, light leaks through the rear ends of the sockets, high molding
costs as a result of complex molds with slides, cams and the like, or
terminals which fail to lock properly and securely into the pre-molded
housings.
BRIEF DESCRIPTION OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
improved socket for a wedge-base bulb which can be formed using a rigid
material which can be inserted into mounting holes without damage or
difficulty and which is capable of withstanding relatively high
temperatures, e.g., over 400.degree. F. (205.degree. C.).
A further object is to provide such a socket which can be molded in a
simple open-close mold and which receives pre-assembled wire and contact
assemblies, thereby eliminating any possibility of molding material
existing between the bulb conductors and the contacts.
Yet another object is to provide such a socket which is compact and fits
into minimum space requirements, which completely encloses and insulates
the electrical terminals, and which can be opened easily for inspection or
servicing of the contacts.
A still further object is to provide a socket which can receive
preassembled contacts and retain them in a "floating" fashion so that no
stress is exerted on the contacts and so that the configuration thereof,
and the initial insertion force characteristics thereof, are reliably
predictable.
Briefly described, the invention includes a socket for releasably receiving
a wedge base bulb of the type having an envelope and a pair of exposed
conductors on the exterior of the base thereof, and for releasably
receiving preassembled conductive wire and clip means for engaging said
conductors, said socket comprising first and second socket halves molded
from a relatively rigid polymeric material, a hinge member integrally
formed with said socket halves and interconnecting said halves so that
they can be relatively moved between an open position and a closed
position, each of said halves having means defining a recess extending
between opposite ends thereof so that, when said halves are moved to said
closed position, said recesses form a panel through the socket, one end of
said channel being dimensioned to enclose said clip means and to receive
the base of said bulb, one of said halves having means at the other end of
said channel for receiving a pair of wires and for maintaining said wires
in spaced relationship, said one of said halves having means in said
recess intermediate the ends of said channel and extending toward the
other one of said halves for maintaining said clip means in spaced
relationship and in proper position when a bulb is inserted into said one
end of said channel to engage said clips, and latch means integrally
formed on said halves for retaining said halves in said closed position.
In order that the manner in which the foregoing and other objects are
attained in accordance with the invention can be understood in detail, a
particularly advantageous embodiment thereof will be described with
reference to the accompanying drawings, which form a part of this
specification and wherein:
FIG. 1 is a side elevation of a socket according to the invention in its
closed assembled condition;
FIG. 2 is an end elevation of the socket of FIG. 1;
FIG. 3 is a side elevation of the socket of FIGS. l and 2 in open position;
FIG. 4 is an end elevation of the socket of FIG. 3 in open position;
FIG. 5 is an end elevation in partial section along lines 5--5 of FIG. 3;
FIG. 6 is a side elevation of a bulb with a pre-assembled clip and wire
assembly usable in the sockets of FIGS. 1-5; and
FIGS. 7 and 8 are end elevation and plan views, respectively, of the clip
assembly shown in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIGS. 1 and 2, it will be seen that the socket generally
indicated at 10 superficially resembles sockets of the prior art and
includes an annular flange 11 and forwardly protruding circularly spaced
finger members 12 dimensioned to pass through an opening in a panel member
shown in phantom lines at 13. The finger members are formed with an
inwardly tapering forward portion 14 and an outwardly tapering rear
portion 15, the forward portion being designed to have a minimum diameter
smaller than the diameter of a preformed hole in panel 13 so that the
finger members are radially inwardly distorted, slightly, until the
portion of largest diameter at 16 passes through the opening, after which
the finger members can radially expand to their former position to hold
the forwardly facing shoulder of flange 11 against the back of panel 13.
The body 17 of the socket is, in the embodiment shown, formed in an L
shape so that the bulb to be inserted through the circular opening defined
by fingers members 12 is perpendicular to electrical conductors 18 and 19
emerging from the opposite end of the socket body. It will be recognized,
however, that this perpendicular relationship need not exist, and that a
socket in accordance with the invention can be made in such a way that the
conductors extend parallel with the direction of insertion of the bulb, or
at some other angular relationship.
A major feature of the socket of the present invention is that it is made
so that it consists of two halves which are similar, although not
identical, to each other, the two halves being hinged together so that
they can be moved between open and closed positions. The socket is shown
in the open position in FIGS. 3-5, and will be seen to include first and
second halves 20 and 21 each of which has formed thereon one-half of
flange 11 and one-half of fingers 12. A web 22 extends between the two
halves and forms a hinge permitting the described motion. Each of the
halves is provided with means defining a generally L-shaped recess, half
20 having a recess 25 and half 21 having a recess 26. Each of these
recesses is provided with a substantially identical pad 27 which protrudes
into the recess and has a concave arcuate inner surface, this surface
being provided to receive an enlargement at the base of the bulb to more
accurately position the bulb. Pads 27 also serve to separate the
attachhment clips, as will be described. It will be seen in FIG. 3 that
each half has flat faces, which, in the closed position, are in paralell
abutting relationship, half 20 also including alignment posts 28 which
protrude from that surface and which are positioned to enter alignment
holes 29 in the face of half 21 in the closed position.
The recesses 25 and 26 define, in the closed position of the socket, a
channel which extends through the socket to receive, properly position,
and contain clip members 30 and 31 which are shown in phantom lines in
FIG. 3. The clip members are provided with integrally formed tab members
frictionally engaging the stripped ends of insulated wires 18 and 19 which
extend out of the socket. The bulb 32, also shown in phantom lines in FIG.
3 to permit illustration of the socket itself, is inserted into the end of
the channel containing the clips to engage those clips and provide
electrical contact with the conductors. Within recess 25 are post-like
members 35 and 36 which protrude from the flat inner surface of recess 25
toward half 21 of the socket when the socket is in the closed position.
The distal ends of posts 35 and 36 can be arranged to closely approach, or
to contact, the inner surface of recess of 26 in that closed position.
Socket half 20 is also provided with latch members 38 and 39 which have
hook-like sloping faces adapted to engage similar latch members 40 and 41
on socket half 21, the engagement of latch members 41 and 39 being visible
in FIG. 2. Members 38 and 40 can be seen in FIG. 5. As will be observed,
latch members 38 and 39 are spaced from flange 11 to permit members 40 and
41 respectively, to enter between the flange and the latch members for
positive engagement thereof. Within the circular insertion opening defined
by finger members 12 are molded elements having sloping surfaces 43 in
each half of the sockets. These sloping surfaces slope toward each other
when the socket is in the closed position and engage the bulbous portion
of the bulb 32 when it is fully inserted to maintain the bulb in the
desired position.
At the end of the socket through which conductors 18 and 19 extend, the
recess is diminished in size and socket half 20 includes means defining a
pair of generally U-shaped side-by-side openings 44 and 45 separated by an
upstanding member 46 which serves to maintain the conductors in spaced
parallel relationship and, in cooperation with half 21, to maintain the
conductors in their desired position.
The bulb and the clip means are more clearly shown in FIGS. 6-8. The bulb
itself, being conventional in nature, will not be described in detail, but
it will be observed that bulb 32 in FIG. 6 includes electrical wires
extending out of the base of the bulb at its end 47, the wires then being
folded back over the exterior surface of the bulb at 48. The conductor on
the opposite side of the bulb is folded back in a similar fashion either
on the same side or on the opposite side of the bulb base. Which side the
wires exist on is of no particular consequence.
A suitable clip for engaging the wires and making good, reliable electrical
contact therewith is indicated at 31 in FIGS. 6-8, the clip being
generally U-shaped in configuration but having indentations 50 and 51 and
outwardly extending distal end portions 52 and 53 so that the bulb base
can easily slide through between the indented portions, expand them
slightly, and permit good engagement and electrical contact between the
indented portions and the conductors 48. Each clip also has a flat base
surface 54 from which extends an integrally formed metallic tab 55 with
distortable portions which can be folded over and clamped against the
stripped end portion 56 of a conductor to form good frictional engagement
therewith and provide reliable electrical contact. This manner of
connection is, of course, very common.
Referring again to the socket of FIG. 3, it will be seen that clip members
30 and 31 are maintained in substantially parallel spaced-apart
relationship by pad 27 and also by the action of posts 35 and 36, post 36
lying between the connector portions 55 of the clips. While the posts and
pads serve to locate and maintain these elements in their appropriate
positions, it should be observed that the clips are not rigidly held and
are not firmly engaged by the socket. Instead, they are floating to a
degree, even when the socket is closed, until the bulb is inserted.
Indeed, it will be observed from FIG. 5 that the socket is formed with
outwardly sloping surfaces 60 at the locations which will be occupied by
distal end portions 52 or 53 of the clip members to avoid placing any
compressive force on these portions. Thus, at the time of manufacture of
the clips exact spacing between the indentations 50 and 51 can be
established and there is no force imposed by the socket itself on the clip
portions tending to change that relationship. This permits the
establishment and maintenance of a predetermined and reliably predictable
insertion force which will exist when a bulb is inserted into the clips
for the first time. The clips are, of course, produced from a springy
material in the nature of phosphor bronze or the like for good electrical
conductivity and appropriate spring action.
It will also be observed that post 35 serves to maintain clip 30 and its
conductive exposed attachment portion properly located away from the
corner of the L-shaped recess and that the forwardly facing surfaces (in
the direction of the bulb) of posts 35 and 36 lie directly behind the flat
rear surfaces 54 of the clips so that when the bulb is inserted the clips
can move rearwardly very slightly and then abut the posts, thereby
providing a force tending to hold the clips in position so that the bulb
can be fully inserted.
Because of the fact that the side surfaces and configurations of the socket
as illustrated herein are all straight or diverging surfaces, no undercuts
and no complicated mold configurations are needed. Indeed, a simple one
step molding operation is suitable to form the entire socket, the only
separate operation being the formation of the clip and wire assemblies.
These assemblies are then placed into the socket and the socket is snapped
to the closed, latched position shown in FIGS. 1 and 2 and, with the
insertion of a bulb, is a finished assembly ready for attachment to a
wiring harness or installation in the location of desired use.
It will also be observed that any exposed electrically conductive portions
are completely enclosed by the sockets and are exposed only in the
direction of the bulb insertion. After insertion, all conductive portions
are totally enclosed and unexposed. Because of the fact that the socket
itself need not cooperate with the clips in any way to assist in
completing the electrical contact with the base, the clips being in
relatively loose floating relationship therein, the socket itself need not
be made of a resilient material to the same degree as prior sockets in
which clips were integrally molded. Indeed, the socket need only be of
sufficiently resilient material so that fingers 12 can radially inwardly
distort very slightly upon insertion of the socket into panel 13. This
permits the use of polymeric materials such as a rigid polypropylene which
resists cutting and abrasion and which has relatively high temperature
characteristics, being able to withstand temperatures in excess of
200.degree. C.
While one advantageous embodiment has been chosen to illustrate the
invention it will be understood by those skilled in the art that various
changes and modifications can be made therein without departing from the
scope of the invention as defined in the appended claims.
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