Rotatable electrical connector for telephone cord

This low friction rotatable electrical connector is for use with coiled telephone cords to prevent the cord from becoming twisted and knotted-up. This connector is generally of insulating material formed by a hollow inner cylindrical member telescoped within a hollow outer cylindrical member. A pair of ball bearing members support the outer member on the inner member for rotation about a central longitudinal axis. The inner member has a single longitudinal split in one side for receiving a plurality of continuous conductive rings on the outer surface when the inner member is squeezed, and a first set of flexible insulated conductors extend through the interior of the inner member and then through this split for connection to these rings. A plurality of apertures are formed in the wall of the outer member in alignment with the conductive rings, and these apertures contain spring-biased balls in rolling contact with the rings. The exterior of the outer member supports a plurality of split conductive rings that are in alignment with the continuous rings of the inner member as well as with certain of the spring-biased balls so as to maintain good electrical continuity between the innermost continuous rings and the outermost split rings. A second set of flexible insulated conductors are joined to these split rings at one end and to a male electrical plug at the outermost end of the outer member. An insulated sleeve is fitted over the outer member, and it may include a hollow ball and socket joint that supports the male plug when the connector is fixedly mounted to the telephone base or hand set.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
This invention relates to the art of rotatable electrical connectors for 
use with flexible electric cables, and particularly for use with coiled 
cords that are widely used today on telephone receivers for connecting the 
handset to the telephone base. One of the advantages of coiled cords is 
that they are able to stretch for convenient use, while they retract into 
a compact length when not in use. This rotatable connector of the present 
invention is mainly for use with light-weight, light duty telephone cords 
rather than high voltage, high current electrical cable systems. 
2. Description of the Prior Art: 
A thorough search of the prior art was made, and only one patent was found 
relating to rotatable electrical connectors for coiled cords of telephone 
receivers. Most, if not all, of the prior art described heavy-duty 
commercial or industrial electrical connectors. 
The Larrabure U.S. Pat. No. 2,414,957 describes a swivel connector for 
electric cables and cords for electric lamps, irons, vacuum cleaners and 
telephone sets. One end of the connector comprises a turning head that is 
shown fixed to a telephone handset. The main connector body has a closed 
end and a central socket or bore. The turning head has a ball bearing 
raceway with contacts with the adjacent rim portion of the body. The 
internal electrical conductors comprise a central rod and two concentric 
insulated tubes, with a grooved roller on the innermost end of each 
conductor. The main body has a plurality of radial, spring-biased ball 
contacts, each cooperating with a grooved roller. These spring-biased ball 
contacts are each provided with a wire conductor external of the main 
body, and cooperating with a tubular loop member. 
The Mohr U.S. Pat. No. 3,195,094 relates to an electric cable coupling 
comprising mutually concentric, rotatable units that are capable of 
transmitting electrical current therethrough. Each electrical circuit has 
an internal ring member surrounded by a plurality of cylindrical rollers 
which are confined by an external ring member, and this unit is held 
together by split rings or helical springs. This design appears to have an 
excessive amount of friction to restrain an easy turning action between 
the movable parts. 
The Norwegian Pat. No. 106,382, issued in 1965, appears to be derived from 
the above-cited Mohr patent, or vice versa. 
The German Pat. No. 1,152,459 describes a cable connector with mutually 
concentric and rotatable parts for poly-phase current in which a series of 
ball bearings is provided inside an insulating housing. These ball 
bearings are under spring pressure, and they carry the electrical current. 
An internal tube is provided which holds a compact bundle of conductors 
that reach inside the insulating housing. The number of conductors 
corresponds to the number of electrical phases. 
The Wendell et al U.S. Pat. No. 3,599,165 describes an electrical coupling 
device providing a series of continuous, unbroken, unsliding electrical 
connections between two relatively rotatable members over a limited 
angular displacement. There is a spiral strip connector that is made of 
thin material having a relatively low spring constant, that is capable of 
cyclic operation for a sufficient large number of rotative displacements 
as desired without excessive fatigue and rupture. 
The Hayward et al U.S. Pat. No. 3,847,463 describes a cable connector for 
electrically connecting a coaxial cable to a fixed device, such as a 
coupler or amplifier, for use in a cable antenna television system CATV 
which is adapted to accommodate drop leads to individual subscribers' 
television sets. 
The Charles et al U.S. Pat. No. 3,972,577 describes rotating electrical 
contacts in a device that is intended to be used on apparatus submerged 
underwater at great depth where it would be subjected to a high 
hydrostatic pressure. One example of such a device would be a rotary 
antenna of panoramic sonars intended to operate at great depth. This 
device also must be water-tight. This patent uses mercury or an alloy of 
gallium and indium as the conductive liquid. 
The British Pat. No. 331,997 describes swivel connections for electric 
cables using ball bearing rings. One metal ring has spring whip contacts 
that are adapted to press lightly on the face of the opposite ring and 
provide continuous electric contact therebetween. Apparently, the ball 
race is not an electrical conductor. There is a ball and socket joint 
between the spindle of one member and the spindle of opposite member. 
OBJECTS OF THE PRESENT INVENTION 
The principal object of the present invention is to provide a low friction 
rotatable electrical connector for use with telephone cords so as to 
prevent the cord from becoming twisted and knotted-up. 
A further object of the present invention is to provide a connector of the 
class described with a hollow inner cylindrical member telescoped within a 
hollow outer cylindrical member with a novel system of conductive rings on 
the inner and outer members for maintaining electrical continuity through 
the connector. 
A further object of the present invention is to provide a rotatable 
electrical connector of the class described with a low friction rolling 
contact between a pair of conductive rings for each circuit through the 
connector. 
A further object of the present invention is to provide a connector of the 
class described with a ball and socket joint supporting one of the 
electrical terminal means at one end of the connector. 
SUMMARY OF THE INVENTION 
The present invention provides a low friction rotatable electrical 
connector for use with telephone cords where the connector is mainly of 
insulating material having a hollow inner cylindrical member telescoped 
within a hollow outer cylindrical member. The inner member is provided 
with low friction bearing means for supporting the outer member thereon 
for rotation about the central longitudinal axis of the connector. 
Electrical terminals are formed at the opposite ends of this connector for 
joining the connector to electric circuit means. A plurality of continuous 
conductive rings are mounted on the exterior of the inner member, and 
flexible insulated conductors are fed through the center of the inner 
member for joining with these conductive rings. A plurality of split 
conductive rings are mounted on the exterior of the outer member to be in 
alignment with the continuous rings. Apertures are formed in the wall of 
the outer member for receiving spring-biased balls that make electrical 
connection between the related continuous ring and the split conductive 
ring for maintaining the continuity of the circuit through the connector. 
These split rings are furnished with flexible insulated conductors that 
extend out the other end of the connector. An insulated sleeve is fitted 
over the outer member and held thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to a consideration of the drawings, and, in particular, to the 
top perspective view of FIG. 1, there is shown a typical example of a 
telephone set 10 as for use on a table or desk top. This telephone set 10 
has a base 11 which includes the detailing mechanism 12. Separate from the 
base is a handset 13 having an earpiece 14 at one end and a microphone 16 
at the opposite end. This handset is shown resting in a cradle 18 when not 
in use. The handset 13 is joined electrically to the base 11 by means of a 
coiled telephone cord 20, as is conventional in this art. One of the main 
advantages of using coiled telephone cords is that they are stretchable to 
lengths several times greater than their normal, unextended length. Also, 
when the handset 13 is in its rest mode, the telephone cord 20 is of its 
shortest length. One generally uniform disadvantage of the use of coiled 
telephone cords is that they become twisted and knotted-up until they 
reach a condition where they will not expand as originally designed, and 
such cords become an annoyance rather than a convenience. 
The present invention relates to the discovery of a low friction rotatable 
electrical connector 26 for joining with the coiled telephone cord 20 by 
being connected at one end 28 to the end of the cord 20, while being 
connected at its other end 30 to the microphone end 16 of the handset 13. 
Of course, there are two other options for locations to mount this 
rotatable connector 26, and these are shown in FIGS. 5 and 6. In FIG. 5, 
the rotatable connector 26 has its end 30 mounted directly to the 
telephone base 11, while the end 28 of the connector is joined to the end 
of the telephone cord 20. 
In FIG. 6, the rotatable connector 26 of the present invention is shown 
mounted intermediate the length of the telephone cord 20. 
The construction of this low friction rotatable electrical connector 26 of 
the present invention can best be understood from the exploded perspective 
view of FIG. 2. There are three main elements; namely, a hollow inner 
cylindrical member 34 of insulating material, a hollow outer cylindrical 
member 36 of insulating material which is telescoped over the inner member 
34, and an insulated sleeve 38 which telescopes over the outer member 36. 
The hollow inner cylindrical member 34 has a single split 40 which extends 
from one end to the other of this member, and it is illustrated in FIG. 2 
at the top of the member 34, and this FIG. 2 is taken on a vertical plane 
that extends through this single split 40. The purpose of this split 40 is 
so that the hollow inner cylindrical member 34 may be slightly compressed 
for receiving thereover a series of four continuous conductive rings 42 of 
copper material or the like. These rings would be slid onto the inner 
member 34 from one end, and they would be spaced from each other a slight 
amount so that they do not touch. Each copper ring 42 has soldered thereto 
a flexible insulated conductor 44, and these conductors extend through the 
single split 40 in the wall of the inner member and extend longitudinally 
through the inner member and exit from the left end of the inner member, 
as is seen in FIG. 2. Notice that slight annular recesses 46 are formed in 
the outer wall of the inner member 34 for receiving one of the copper 
rings 42 therein so that the outer surfaces of these rings are flush with 
the outer surface of the inner member 34. 
Assembled on the left end of the inner cylindrical member 34 is a female 
electrical socket 50, again of insulating material, and it has an end 
cavity 52 fitted with a series of four, generally parallel, separate 
electrical contacts or terminals 54 of standard construction for receiving 
the standard male plug that is furnished with coiled telephone cords 20 on 
the market today. Such a standard male plug would be located at the end 28 
of the cord 20, as shown in FIG. 1, and it would also be located at the 
other end 30 of the connector 26 of FIG. 1. The fact is that the male plug 
at 28 in FIG. 1 is fixed to the end of the telephone cord 20, while the 
male plug at the end 30 of FIG. 1 is carried by the connector 26 of the 
present invention. Turning to the assembly view of FIG. 4, a standard male 
plug 56 is shown on the right end of this rotatable connector 26 for 
fitting into the end of the handset 13 in FIG. 1. Each of the four 
flexible insulating conductors 44 is soldered to one of the electrical 
contacts or terminals 54 within the end cavity 52. 
The female electrical plug 50 is a separate member from the hollow inner 
cylindrical member 34, but the female plug 50 is assembled to the left end 
of the inner member 34 and held in place thereon by friction, or other 
means. A pair of ball bearing raceway members 58 and 60 are also slid onto 
the end of the inner member 34 and widely spaced from each other so that 
each is adjacent the endmost copper ring 42. 
Next to be discussed is the design of the hollow outer cylindrical member 
36 that is adapted to telescope over the inner member 34 and is adapted to 
be rotatably supported from the inner member by the pair of low friction 
ball bearing members 58 and 60, as is best seen in the cross-sectional 
assembly view of FIG. 4. Mounted on the exterior surface of the outer 
cylindrical member 36 is a series of four split conductive rings 64 of 
copper, or the like, which are adapted to be aligned and concentric with 
the four continuous conductive rings 42 mounted on the inner member 34. 
These split rings 64 are split for ease of assembling them to the outside 
of the outer member 36. Annular recesses 66 are formed in the exterior 
surface of the outer member for receiving the split rings 64 therein, so 
that the exterior surfaces of these split rings 64 are flush with the 
exterior peripheral surface of the outer member 36, as is best seen in the 
assembly view of FIG. 4. Now it is necessary to provide a continuous 
electrical circuit means between the continuous copper rings 42 and the 
split copper rings 64. At least two spring-biased metal balls 68 and 70 
are provided to operate between the concentric continuous ring 42 and the 
overlying split ring 64, as is best seen in the assembly view of FIG. 4. 
Each metal ball is furnished with a small helical compression spring 72. 
In order to accommodate each ball and spring, an aperture 74 is formed 
through the wall of the hollow outer member 36 so that the apertures are 
generally diametrically opposed to each other. These apertures 74 are also 
positioned within the recesses 66 so that they underlie the split rings 64 
as well as overlie the continuous rings 42 of the inner member 34. Looking 
at the single split ring 64 in FIG. 2 that is separated to the left from 
the outer member 36, it will be understood that on the interior surface of 
this split ring a pair of diametrically opposed pins 76 are formed 
thereon, and these pins are of such a size that they fit within the end of 
the helical spring 72 for serving as a spring support means. In other 
words, the two pins 76 are aligned to fit within the apertures 74 in the 
recesses 66. Of course, the metal balls 68 and 70 are installed into the 
apertures, as well as the two springs 72, before the split ring 64 is 
assembled over the outer member 36. Another purpose for one of these pins 
76 is to serve as a terminal means for receiving the eyelet terminal 78 
that is crimped on the end of a flexible insulated conductor 80, as best 
seen in FIG. 2. This eyelet terminal 78 would be assembled on one of the 
pins 76 before the split ring 64 is assembled in the recess 66, and that 
same pin engages in one of the helical springs 72 bearing against the 
related metal ball. Thus, the spring 72 not only urges the metal ball in 
reliable rolling contact with the continuous ring 42 of the inner member, 
but it also ensures a good electrical connection between the spring and 
the eyelet terminal 78 as rotational movement occurs between the inner 
member 34 and the outer member 36. 
Another modification is to use but a single aperture with a spring-biased 
contact member that is not necessarily a conductive ball. It could be a 
conductive brush; as for example a motor brush. 
As is best seen in FIG. 2, longitudinal recesses 82 are formed in the 
exterior surface of the outer member 36, each for receiving one of the 
four insulated conductors 80 therein, so that these same conductors can be 
fed underneath the split conductive rings 64 in the assembled condition so 
as not to interfere with the smooth low friction rotational movement of 
this connector 26. Notice in FIG. 4, that the outer member 36 is longer 
than the inner member 34 at the right end thereof, so that the outer 
member extends beyond the inner member. An aperture 84 is formed through 
the wall of the outer member in the vicinity of the outermost end of each 
recess 82 so that these insulated conductors 80 are fed into the interior 
of the hollow outer member and extend from the end thereof, as best seen 
in FIG. 4. Interestingly enough, the presence of the spring-biased metal 
balls 68 and 70 in the assembled position as shown in FIG. 4 serves as an 
interlocking means between the inner cylindrical member 34 and the outer 
cylindrical member 36 due to the close proximity of the two ball bearing 
members 58 and 60 to the endmost rings 42, 64 and the related metal balls. 
If a force were applied tending to separate the outer member 36 from the 
inner member 34, the metal balls would be unable to slide off of the inner 
member due to the presence of the endmost ball bearing member 60, as seen 
in FIG. 4. 
Means must be provided for protecting these four split rings 64, and this 
is furnished by an insulated sleeve 38, which was mentioned earlier. This 
sleeve is held in place by a forced fit so that it is removable for making 
repairs, but it will ordinarily remain in position and not become 
disassembled inadvertently. 
This outer sleeve 38 has an outermost extension 88 which extends beyond the 
outermost end 90 of the outer member 36. The purpose of this outermost 
extension 88 is to accommodate a hollow ball and socket joint 92 on which 
is supported the standard male plug 56, as was mentioned above. Thus, the 
four flexible insulated conductors 80 extend out of the outer member 36 
and through the hollow ball and socket joint 92 for termination with the 
male plug 56. Exterior threads 94 are formed on the outer end of the 
extension 88 of the sleeve 38 for receiving a threaded collar member 96 
which has a central opening 98 and a semi-spherical socket for mating 
engagement with the hollow ball 92 for holding the ball in place and 
capable of rotational movement in a universal direction with very low 
friction between the moving parts. The interior throat 102 of the 
outermost extension 88 of the sleeve 38 also has a semi-spherical socket 
formation mating with the ball 92 to complement the semi-spherical socket 
formation 100 of the collar 96. 
It should be understood that the use of this ball and socket joint 92 is 
only necessary when one end of the connector 26 is fixedly mounted to the 
handset 13, as shown in FIG. 1; or alternately when one end is fixedly 
mounted to the base of the telephone set, as shown in FIG. 5. The use of 
the ball and socket joint is not necessary when the connector 26 is 
mounted intermediate the length of the coiled cord 20, as shown in FIG. 6. 
In that event, the connector 26 would be furnished with a length of coiled 
telephone cord 20 at each end, and a male plug 56 would be furnished on 
the free end of each such length of cord. 
Another possible modification would be to eliminate the female socket 50 at 
the left end of the inner cylindrical member 34 of FIG. 4, and to 
substitute a length of coiled cord 20, and to install a male plug 56 on 
the free end of this cord length. 
Another possible modification would be to eliminate the ball and socket 
joint 92 at the right end of the connector of FIG. 4 and substitute a 
short length of coiled cord 20 for the joint, and to install a male plug 
56 on the free end of this cord length. 
Modifications of this invention will occur to those skilled in this art. 
Therefore, it is to be understood that this invention is not limited to 
the particular embodiments disclosed, but that it is intended to cover all 
modifications which are within the true spirit and scope of this invention 
as claimed.