Technical Field

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 telephone 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 lightweight, light-duty telephone cords rather than high voltage, high current electrical cable systems.

Background Art

A thorough search of the prior art was made, and no patents were found relating to rotatable electrical connectors for coiled telephone cords. Most, if not all, of the prior art described heavy-duty commercial or industrial electrical connectors, which will now be described. The Mohr 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 cylin- drical 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 polyphase 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 corre¬ sponds to the number of electrical phases.

The Wendell et al Pat. No. 3,599,165 describes an electrical coupling device providing a series of con- tinuous, 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 Pat. No. 3,847,46a 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 sub¬ scribers' television sets.

The Charles et al Pat. No. 3,972,577 describes rotating electTical 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 watertight. 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 wipe 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 the opposite member.

Disclosure of Invention

The present invention provides a low friction rotatable electrical connector for use with coiled tele¬ phone cords, where the connector has a hollow housing with a first plurality of electrical terminal means at one end and a circular opening in the end wall at the opposite end of the housing for supporting a rotor assembly to rotate freely relative to the connector housing, there being a second plurality of electrical terminal means associated with the rotor assembly. The inner end of the rotor assembly has a transverse face supporting a plurality of concentric electrical contact -rings, where each ring is connected to a separate one of the second plurality of electrical terminal means. A plurality of spring -fire ■ contact elements is mounted within the housing in a paral¬ lel array, where each spring wire contact element has a portion biased into continuous wiping contact with a separate one of the concentric rings. The housing includes partitions between adjacent spring wire contact elements for stabilizing them and separating them apart.

Brief Description of Drawings

This invention will be better understood from the following description taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended Claims.

FIG. 1 is a top perspective view of a standard telephone set provided with a coiled telephone cord between the base and the handset, where the low friction rotatable electrical connector of the present invention is interposed between one end of the coiled telephone cord and the handset.

FIG. 2 is a fragmentary perspective view, similar to a portion of FIG. 1, showing the rotatable electrical

connector of the present invention plugged into the base of the telephone set, while the lower end of the coiled telephone cord is plugged into the other end of the connector housing. FIG. 3 is a fragmentary perspective view, similar to that of FIG. 2, showing the rotatable electrical connector of the present invention mounted intermediate the length of the telephone cord.

FIG. 4 is an exploded perspective view, on an enlarged scale, showing the low friction rotatable elec¬ trical connector of the present invention separated into its individual parts and arranged in the manner in which they are joined together, where the hollow cover member is illustrated at the top of the Figure, the rotor assembly is shown just below the cover, then the circuit board is shown supporting a first plurality of spring wire contact elements at one end, as well as supporting a second plural- ity of spring wire contact elements at the opposite end, and finally the hollow base member is shown at the bottom of the Figure.

FIG. 5 is a cross-sectional elevational view of the rotatable electrical connector of the present invention showing the parts completely assembled together with the longitudinally split insulating housing having the female electrical socket at the left end and the male phone plug mounted on the free end of the rotor assembly.

FIG. 6 is a fragmentary cross-sectional view through the enlarged head of the inner end of the rotor assembly that is drawn to illustrate the shallow groove formed in the surface of each concentric electrical contact ring to serve as a track for receiving the mating surface of the spring wire contact element.

FIG. 7 is a top plan view, on an enlarged scale, of the base portion of the housing with the rotor assembly removed, but the circuit board in place along with its first plurality of spring wire contact elements at the right side for engagement with the concentric electrical

contact rings of the rotor assembly, as well as the second plurality of spring wire contact elements at the opposite end of the circuit board for use in the female electrical socket for engagement with the contacts of a male phone Plug.

FIG. 8 is a bottom plan view of the circuit board of FIG. 7 showing the printed circuit elements which are present on the underside of the circuit board as compared with those that are present on the top side of the circuit board.

FIG. 9 is an exploded left end view of the connector housing with the circuit board and rotor assembly in place, and the raised cover portion partly in cross section to show some of its details of construction. FIG. 10 is a fragmentary exploded perspective view of a second modification of the present invention, where the circuit board is designed to support a single plurality of spring wire contact elements which perform the same function as the two pluralities of spring wire contact elements of FIGS. 5-9.

FIG. 11 is a fragmentary front elevational view of the telephone set of FIG. 1 showing the rotatable elec¬ trical connector of the present invention built into the handset, where the telephone cord either plugs into the connector or is permanently fixed to one of the rotatable portions of the connector.

FIG. 12 is a fragmentary exploded view of a third modification of the present invention, which is related to the rotatable electrical connector of FIG. 11 which is built into the handset, where the coiled telephone cord is attached to the outer end of the rotor assembly and the circuit board has been eliminated by mounting the plurality of spring wire contact elements directly to the base portion of the connector housing.

Best Mode for Carrying Out the Invention

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 12 which includes the dialing mechanism 14. Separate from the base is a handset 16 which, of course, has the earpiece 18 at one end and a microphone 20 at the opposite end. This handset 16 is shown resting in a cradle 22 when it is not in use. Of course, this is only one configuration of a standard telephone set, ^' and it is well recognized that there are many variations of this con- figuration and that the number of such configurations are growing rapidly, but most of them have the relationship of a fixed base element and a movable handset. The handset 16 is joined electrically to the base 12 by means of a coiled telephone cord 26, as is conventional in this art, because they are compact when the handset 16 is at rest in its cradle 22, and it is capable of stretching to several times its normal length for the convenience of the user in moving the handset 16 away from the base unit 12. One frequently heard complaint in the use of coiled telephone cords, such as 26, is that they become twisted and knotted-up during normal use until they reach a condition where they will not expand or stretch as originally designed, and then such cords become an annoyance rather than a convenience.

The present invention relates to the discovery of several modifications of a low friction rotatable elec¬ trical connector 28 for cooperation with the coiled telephone cord 26 to ensure that the movement of the hand¬ set 16 away from the base 12 will not cause a kink or twist to occur in the coiled telephone cord 26. In FIG. 1, the rotatable electrical connector 28 of the present invention is connected at one end 30 of the connector to a standard male phone plug 32 that is formed at one end of the coiled cord 26. The opposite end of. the connector 28 is fitted with a standard male phone plug 34 which is mounted into a standard female receptacle 36 built into the microphone end 20 of the handset 16. Notice, the

opposite end of the coiled telephone cord 26 also has a standard male phone plug 38 which connects into a standard female receptacle 36.

Before going into a detailed description of the construction of this rotatable electrical connector 28, mention will be made of other possible locations for the connector, starting with FIG. 2. The same elements shown in FIG. 2 will be given the same reference numerals as appear in FIG. 1 for those elements. In the modification of FIG. 2, the rotatable electrical connector 28 has its standard male phone plug 34 at one end connected into a standard female receptacle 36 in the base 12 of the phone, and the other end 30 of the connector receives a standard male phone plug 38 on the adjacent end of the coiled tele- phone cord 26. Notice, the opposite end of the cord 26 has its standard male phone plug 32 connected into the standard female receptacle 36 in the microphone end 20 of the

» handset 16. Thus, the connector 28 is merely connected into the base 12 rather than into the handset 16, as in FIG. 1.

In the third modification of FIG. 3, the rotat¬ able electrical connector 28 of the present invention is shown mounted intermediate the length of the telephone cord 26 rather than to the handset 16, as in FIG. 1, or connected into the base, as in FIG. 2. In FIG. 3, the length of coiled cord 26 between the connector 28 and the handset 16 could be furnished with a female socket (not shown) at the left end for receiving a standard male phone plug 34 on the adjacent end of the connector 28, or that left end of the cord could be connected permanently into the connector 28 when the connector was constructed as original equipment.

In the fourth modification of FIG. 11, the rotatable electrical connector 28 of the present invention is built into the microphone end of the handset 16, and the upper end 40 of the coiled cord 26 is connected permanently

into the rotor assembly 44 of the connector 28, as will best be understood during the explanation of FIG. 12. The construction and operation of this low friction rotatable electrical connector 28 of the present invention can best be understood from the exploded per¬ spective view of FIG. 4. There are four main elements; namely, a hollow housing 46 of insulating material which is molded of Delrin or Teflon, or some equivalent self- lubricating type thermoplastic material. This hollow housing 46 is split longitudinally into a lower base portion 48 and an upper cover portion 50; although it will be understood that these parts are only upper and lower depending upon the orientation of the parts. In the drawing, they have been positioned so that one half of the housing is a base and the other half is a top cover for purposes of clarification. Cooperating with the hollow housing 46 is the rotor assembly 44 to be in rela¬ tive rotation therewith. The fourth main element of the connector 28 is a circuit board 52 for supporting the internal circuit elements, as will be explained shortly.

The operation of this rotatable electrical connector 28 can best be understood in the assembled view of FIG. 5, which is partly in cross section in a front elevational view. The same elements described in FIG. 4 -that are illustrated in FIG. 5 will be identified by the same reference numerals. The hollow insulating housing 46 Is of cylindrical form, having one end 30 provided with a rectangular opening 56 which leads into a female socket 58 for receiving a standard male phone plug 32, as illustrated in FIG. 1. The upper edge of the rectangular opening 56 includes an indexing slot 60, as best seen in FIG. 4, that is adapted to receive the finger-operated locking means 62, which is illustrated at the right side of FIG. 5, as part of the standard male phone plug 34 which is assembled on the free end of the rotor assembly 44. Of course, this male phone plug 34 is not the one that fits into the female socket 58 at the other end of the housing 46. This male

plug 34 is merely representative of a standard male phone plug of the type that would mate into the female socket 58 at the other end of the housing.

The opposite end of the housing 46 has an end wall 64 with a central circular opening 66 for receiving the rotor assembly therethrough, where this circular opening 66 serves as a bearing in which the rotor assembly is supported and is designed to rotate freely relative to the connector housing 46. The rotor assembly 44 is molded of a thermoplastic material, such as Delrin or Teflon or other compatible material, to the insulating material of the hollow housing 46. The rotor assembly 44 is also of hollow material having an enlarged head 68 at its inner¬ most end. The innermost end of the enlarged head 68 has a circular opening which is closed by a wafer 72 that is formed by a plurality of concentric electrical contact rings 74 which are spaced apart by rings of electrical insulation 76. Thus, the innermost end of the rotor assembly 44 has a transverse face presenting a plurality of concentric electrical contact rings 74, which are four rings in number, which are spaced apart by a series of three rings of insulation 76, as is best seen in FIG. 4. Each contact ring 74 is fitted with a tab terminal 78 on its unexposed side to which is soldered an insulated conductor 80 which extends through the hollow rotor assembly 44 for connection to the circuit elements within the standard male phone plug 34, as seen in FIG. 5. The rear face 82 of the enlarged head 68 of the rotor assembly 44 is furnished with a thrust bearing surface 84 which acts against the innermost peripheral edge of the circular opening 66 in the end wall 64 of the housing 46 to retard the removal of the rotor assembly 44 from the housing 46 and serve as the only bearing surfaces between the rotor and housing. Turning back to a consideration of the exploded perspective view of FIG. 4, the circuit board 52 is also of insulating material, and it is fitted with a first

plurality of spring wire contact elements 88 at one end of the board adjacent the plurality of concentric electrical contact rings 74, and a second plurality of spring wire contact elements 90 at the opposite end of the board so as to be disposed within the female socket 58 and being in a position to automatically engage with the circuit elements carried by a mating standard male phone plug when it is coupled in the female socket. The first plurality of spring wire contacts 88 is arranged in a parallel vertical array, as viewed in FIG. 4. Each spring wire contact 88 is identical, and it has a fixed terminal end 92 at one end that is inserted into a mating hole 94 adjacent the edge 96 of the circuit board 52. The intermediate portion of each spring wire contact 88 is formed in a hairpin shape 98, while the other end 100 of the spring wire contact termi¬ nates at about mid-height of the spring wire contact, and it is fitted with a smooth convex wiping surface _102 that will be positioned in engagement with a separate one of the plurality of concentric electrical contact rings 74. The circuit board 52 is provided with a plurality of printed circuit elements 106 and 108, where each printed element is connected to a separate one of the first plural¬ ity of spring wire contact elements 88. There are two printed circuit elements 106 on the top side of the circuit board 52 and two printed circuit elements 108 on the bottom side, as is clear from FIGS. 4, 7 and 8.

The second plurality of spring wire contact elements 90 is generally V-shaped, as seen in a side view looking along the plane of the circuit board 52, as best seen in FIG. 5. The lower leg 110 of the spring wire contact 90 is positioned horizontally against the underside of the circuit board 52, and its free end 112 is turned up slightly to form a vertical terminal that is adapted to fit into a mating hole 114 and soldered in place, as seen in FIG. 4. Notice that the printed circuit elements 106 and 108 each have a mating hole 114 at one end and a mating

hole 94 at its opposite end for completing the circuit between the first and the second plurality of spring wire contacts 88 and 90. The apex 116 of the V-shaped spring wire contact 90 is adapted to slip into a shallow notch 118 5 formed in the edge of the end of the circuit board 52 to help to retain and stabilize this spring wire contact 90. The upper leg 120 of the V-shaped spring wire contact 90 is formed at an acute inclined angle of about 25 degrees, and it is longer than the lower leg 110. This second

10 plurality of spring wire contact elements 90 is likewise arranged in a vertical parallel array, but they are closer spaced than the spring wire contacts 88 of the first plurality.

The hollow insulated housing 46 of this rotatable

15 connector 28 is generally a circular cylindrical member that is split longitudinally on its center longitudinal axis to form the lower base portion 48 and the upper cover portion 50, as is best seen in FIG. 4. Thus, one half of the rectangular opening 56 is in the base portion 48, and

20 ^" the other half is in the cover portion 50.. The same is true of the circular opening 66. One half of it is in the base portion 48, and the other half is in the cover portion 50. Opposite side ledges 122 are formed near the bottom of the base portion 48, and these serve as support

2.5 ledges for the opposite side edges of the circuit board 52. The circuit board has a tongue portion 124 at one end, which is more narrow than the normal width of the circuit board, to slip down between the opposite vertical sidewalls 126 of the rectangular opening 56. Actually, the top sur-

30 face of the circuit board 52 is flush with the bottom wall of the rectangular opening 56, as is best seen in FIG. 5. The base portion 48 has a central vertical post 132 that is rectangular in plan view. Similarly, the circuit board 52 has a rectangular opening 134, as seen in

35 FIG. 10, so that this opening may be aligned with the post 132 so the circuit board may thereby be indexed on the

post until the board is seated upon the opposite support ledges 122 in the base portion. Thus, this interaction between the post 132 and this opening 134 in the circuit board serves as a precision method of locating the circuit board relative to the housing 46 and the rotor assembly 44. Four, narrow, deep slots 136 are cut vertically in the top end of the post 132; each slot for receiving the free end 138 of the inclined upper leg 120 of the spring wire contact element 90 for retaining and spacing these spring wire contacts and increasing the life expectancy of this rotatable electrical connector. Notice, in FIG. 4, one edge 140 of the top of the vertical post 132 is ground off at an inclined angle. Now, turning to FIG. 5, the upper portion 50 of the housing is provided with a solid section 142 which has a complementary wedge-shaped tip 144 which mates with this inclined top edge 140 of the vertical post 132, as is best seen in FIG. 5. The solid section 142 includes a pair of parallel vertical partitions 146 which are adapted to be located on the opposite sides of the vertical post 132 when the cover 50 is assembled on the base 48, as is clear from FIG. 9. The height of these partitions 146 is such that these partitions bear down on the top surface of the circuit board 52 for holding the circuit board firmly in place in final assembly. Now, looking at FIGS. 4 and 5, it is clear that there is a compartment 148 formed on the right end of the housing 46 between the end wall 64 and the solid section 142 of the cover portion 50. This compartment Is for receiving the enlarged head 68 of the rotor assembly 44. In addition, this solid section 142 includes a series of parallel vertical slots 149, as is best seen in FIG. 9, for receiving the top portions 98 of the individual spring wire contact elements 88 for retaining each spring wire contact element in place as well as to stabilize it to ensure long life expectancy and reliability of function.

As stated earlier, FIG. 6 is a fragmentary cross- sectional view, on an enlarged scale, through the enlarged

head 68 on the inner end of the rotor assembly 44 that has been presented to illustrate a shallow groove 150 that is formed in the contact face of each concentric electrical contact ring 74 to serve as a track for receiving the smooth convex wiping surface 102 at the free end of the first plurality of spring wire contact elements 88.

Also, as stated earlier, FIG. 9 is an exploded left end view of the rotatable connector housing 46 showing the circuit board 52 in dotted lines and the upper portion of the inner face of the rotor assembly 44 in full lines, while the upper cover portion 50 of the housing is raised above the base portion 48, and parts of the cover are broken away to show specific details.

FIG. 10 is a fragmentary exploded perspective view of a second modification of the present invention, where the first plurality of spring wire contact elements 88 is made integral with the second plurality of spring wire contact elements 90, and these new spring wire contact elements are identified by the numeral 156. Compare FIG. 4 with FIG. 10, and notice that the printed circuit elements 106 and 108 have been eliminated from the circuit board 52 of FIG. 10 due to the fact that the new spring wire contact elements 156 include the characteristics of the first plurality 88 of spring wire contacts and the second plurality of spring wire contacts 90.. Very little has to be done to the circuit board 52 in order to accommodate these new spring wire contact elements 156. A series of shallow notches 158 would be formed in the edge of the board 52 opposite the earlier shallow notches 118 that were- used for the second plurality of spring wire contact elements 90. Of course, these notches 158 are not aligned with the notches 118 in view of the nature of the opposite ends of the spring wire contact elements 156.

FIG. 11 shows a third modification of the present invention, and this Figure is a fragmentary front eleva- tional view of the telephone set of FIG. 1, except it shows the rotatable electrical connector 28 built into the handset

16, where the coiled telephone cord 26 may be permanently attached to the rotor assembly 44 of the connector 28. This would be the preferred embodiment, when the connector is made integral with the handset, as in FIG. 11. Of course, another possibility would be to have the telephone cord 26 fitted with a standard male phone plug, such as element 38 in FIG. 2, to fit into a female socket (not shown) in the built-in rotatable connector 28 of FIG. 11. This third modification of FIG. 11 is best seen in the fragmentary exploded view of FIG. 12, where the rotor assembly 44 is the same as in the previous modifica¬ tions, except its outer end is connected to one end of a coiled telephone cord 26, as distinguished from the arrange¬ ment of FIG. 5 of the first modification of the invention where the outer end of the rotor assembly 44 is fitted with a standard male phone plug 34. This third modification of the connector 28 has a hollow insulated housing 160 that is split longitudinally from one end to the other, thereby forming a base portion 162 and a cover portion 164. This third modification of FIGS. 11 and 12 has a hollow housing 160 that is much shorter than the housing 46 of the early modifications because the circuit board 52 has been elimi¬ nated, and that includes the elimination of the central vertical post 132 as well as any support means for the circuit board as well as clamping means for holding the circuit board firmly in place in final assembly. This housing 160 has one end wall 166 with a central circular opening 168 which is split in two halves by the lower base portion 162 and the upper cover portion 164. This circular opening 168 is for receiving the rotor assembly 44 therein and serves as a bearing. On the interior side of the end wall 166 is a compartment 170, similar to compartment 148 of FIG. 4, for receiving the enlarged head 68 of the rotor assembly which includes the -plurality of concentric elec- trical contact rings 74. The connector housing 160 includes a second end wall 172 which is likewise split into two halves by the longitudinal split of the housing.

The lower base portion 162 includes a plurality of spring wire contact elements 174, which are four in number, and they are related to the plurality of spring wire contact elements 88 of the first modification of this invention. One important difference is that these spring wire contact elements 174 have a fixed terminal end 176 which is encapsulated or molded into the base portion 162 at the time the base portion is formed, so that these spring contact elements 174 become a permanent part of the base portion 162. Moreover, each spring wire contact element 174 has an external terminal end 178 which extends outwardly from the end wall 172 to be in a parallel array. Each external terminal 178 is shown fitted with a sleeve 180, which is hollow, for receiving a mating wire terminal or pin. This sleeve 180 could be crimped onto the wire terminal or pin for making a good electrical connection, as is well-known in this art. Notice that the free end of each spring wire contact element 174 has a smooth convex wiping surface 182 which is similar to the wiping surface 102 of the first plurality of spring wire contact elements 88 as shown in FIG. 4.

What this third modification of the rotatable electrical connector 28 is teaching is that the connector 28 need not have a removable connector means at each end, such as a standard male phone plug or a standard female socket for receiving such a male plug. The present invention can be modified by eliminating the circuit board 52 while retaining the present invention in its simplest form. As in the early modifications, the upper cover portion 164 is provided with a series of parallel vertical slots 184, each for receiving the top portion of a separate spring wire contact element 174 so as to retain the contact f-lement in place and stabilize it so as to increase its life expectancy and reliability. These vertical slots 184 are similar to the series of parallel vertical slots 149 in the cover portion 50, as seen in both FIGS. 5 and 9.

In all of the modifications of this invention that were explained above, the hollow insulated housing was described as a split housing. It will be understood by those skilled in the art that the split housing must be sealed together during use. Adhesives could be used, or a sonic welding technique, or a push-on or wraparound sleeve.

In the final assembly of the modifications of FIGS. 1-10, the rotor assembly 44 would be positioned in the base portion 48, then the circuit board 52 would be lowered onto the vertical post 132 so the spring wire contact elements 88 would be in contact with the plurality of concentric electrical contact rings 74. Then the cover portion 50 would be lowered onto the base portion and the split housing 46 sealed together.

Modifications of this invention will occur to those skilled in this art. Therefore, it is to be under¬ stood that this invention is not limited to the particular embodiments disclosed, but that it is intended to cover all modi ications which are within the true spirit and scope of this invention as claimed.