Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-conductor electrical cable connector and, more particularly, to a connector assembly for connecting the center conductor and outer shield of a coaxial cable to the inner and outer electrically conductive connectors, respectively, of an electrode assembly.
2. Description of the Prior Art
A wide variety of electrochemical electrode assemblies exist which require removable socket caps for making electrical connection between the connectors of the assemblies and multiconductor electrical cables such as coaxial cables. Such electrode assemblies include, for example, pH electrodes, oxygen sensors and specific-ion electrodes. Electrode assemblies of these types typically include an inner, male, electrically conductive connector which is connected via a conductor to the sensing portion of the electrode assembly and an outer, male, electrically conductive connector which is connected to an electrostatic shielding member included within the electrode assembly housing. Available socket caps, therefore, typically include an inner female connector which is electrically connected to one of the conductors of the cable such as the center conductor of a coaxial cable, the inner connector of the cap adapted to contact the inner connector of the electrode assembly, and an outer female connector which is electrically connected to another of the conductors of the cable such as the shielding of a coaxial cable, the outer connector of the cap adapted to contact the outer connector of the electrode assembly.
Several problems exist with presently available, removable, socket caps. In the first instance, the conventional method for connecting the inner female connector of the cap to the center conductor of the coaxial cable, which must be designed to prevent the inner connector from slipping within the connector assembly, is to swage the inner connector which tends to open up the hole therein which receives the center conductor and makes soldering more difficult, especially if the center conductor is of very small diameter. Secondly, in order to make electrical connection between the outer connector of the electrode assembly and the shield of the coaxial cable, it is common to use a metal sleeve. This is not only expensive, but makes it necessary to use solder or some other mechanical means for making electrical connection between the metal sleeve and the cable shield. The resulting configuration requires slow, cumbersome assembly methods which further increase the total cost of the cable connector.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a novel cable connector which not only eliminates the problems present in the prior art but also adds several unique features. The present method and means of construction eliminates the need for expensive metal parts and slow, cumbersome assembly methods. The present cable connector has a substantially simpler construction than prior cable connectors and can be made in substantially smaller sizes. The present cable connector can be made at low cost and with the cable at any angle to the axis of the connector. The present cable connector utilizes a conductive molding compound instead of the conventional metal sleeves to make electrical connection to the outer connector of the electrode assembly. By using a conductive molding compound, the need for solder or some other mechanical means for making electrical connection to the cable shield is eliminated. In addition to providing electrical connection to the cable shield, the conductive molding compound can be molded into any convenient shape to provide a finished configuration which functions as a handle, all in a single operation.
Briefly, the present method and means for connecting a multi-conductor electrical cable such as a coaxial cable to an electrode assembly having inner and outer electrically conductive connectors first requires the coaxial cable to be stripped to expose its shield, its center conductor and the insulation between the shield and the center conductor. Thereafter, a connector pin may be inserted into a pin holder and a washer is slipped over the exposed end of the pin. The center conductor of the coaxial cable is inserted into the pin and the entire assembly is soldered thereby connecting the washer, the center conductor and the pin. The washer, soldered to the connector pin, is used as a lock to prevent the pin from slipping out of the pin holder and breaking the electrical connection to the coaxial cable in the event that the connector pin sticks too tightly to the inner connector of the electrode assembly when disconnecting the cable. A piece of shrink tubing is slipped over the pin, washer and exposed center conductor, but not the exposed shield, and the tubing is shrunk down to insulate the pin, center conductor, washer and solder joint from the exposed shield as well as strengthening the joint so that the soldered electrical connection cannot be damaged in handling of the assembly. The subassembly is then put into a mold and a conductive molding compound is used to form the outer cap, the coaxial cable being imbedded within the cap whereby a permanent connection is made between the exposed shield of the cable and the conductive molding material. The cap is molded to include a bore which is coaxial with the connector pin. Therefore, as the completed cable connector is slipped over the end of the electrode assembly, electrical contact is completed between the center conductor of the cable and the inner connector of the electrode assembly via the connector pin and between the shield of the cable and the outer connector of the electrode assembly via the electrically conductive cap.
It is therefore an object of the present invention to provide a novel multi-conductor electrical cable connector.
It is a further object of the present invention to provide a method and means for removably connecting a multi-conductor electrical cable to an electrochemical electrode assembly.
It is a still further object of the present invention to provide a method and means for connecting the center conductor and shield of a coaxial cable to the inner and outer electrically conductive connectors, respectively, of an electrode assembly.
It is another object of the present invention to provide such a cable connector which eliminates the need for expensive metal parts and slow, cumbersome assembly methods.
It is still another object of the present invention to provide a cable connector which can be made in a relatively small size with the cable at any angle to the axis of the connector.
Another object of the present invention is the provision of a cable connector which utilizes a conductive molding compound in constructing the socket cap thereby eliminating the need for a mechanical means for making electrical connection to the shield of a coaxial cable.
Still another object of the present invention is the provision of a cable connector including a washer to prevent breakage of the electrical connection between the cable and a connector pin within the assembly.
An additional object of the present invention is the provision of a cable connector which utilizes a piece of shrink tubing to insulate various electrical connections.
Still other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment constructed in accordance therewith, taken in conjunction with the accompanying drawings wherein like numerals designate like parts in the several figures and wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view of the present cable connector in a first stage of construction;
FIG. 2 is a longitudinal sectional view of the present cable connector in a second stage of construction; and
FIG. 3 is a longitudinal sectional view of the present cable connector when completed, with the electrode assembly for use therewith also being shown in cross-section but detached from the cable connector.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, the present invention relates to a cable connector, generally designated 10, for connecting a multi-conductor electrical cable 11 to an electrode assembly, generally designated 12. Electrode assembly 12 may be, for example, a pH electrode, an oxygen sensor or a specific-ion electrode. For an example of one type of electrode assembly which may be used with the present invention, reference should be made to U.S. Pat. No. 3,476,672. Electrode assemblies of these types typically include an internal half cell (not shown) positioned within a tube 13 of non-conductive material. A cap assembly 14, as disclosed, for example, in said U.S. Pat. No. 3,476,672 may be included for providing a hermetic seal so that no leakage will occur between the parts of electrode assembly 12. An electrical lead 15 is connected between the internal half cell and an inner, male, electrically conductive connector 16. A foil shield 17 is usually positioned within body 13 to electrostatically shield the sensing portion of electrode assembly 12. Shield 17 is electrically connected to an outer, male, electrically conductive connector 18 which is coaxial with inner connector 16 and insulated therefrom by means of a non-conductive body 19.
Connector 10 is required for making a removable electrical connection between connectors 16 and 18 and cable 11. In this example, cable 11 would have two conductors corresponding to connectors 16 and 18. It will be understood, however, that the present invention is equally suited for use in any application wherein electrical connection is desired to any number of conductors. For example, connector 16 might be a female connector or there could be more than one, spaced, inner connectors similar to connector 16.
Also for purposes of example, connector 11 will be described as being a coaxial cable having a center conductor 20 (see FIG. 1) which is surrounded by a braided electrical shield 21. Conductors 20 and 21 are insulated from each other by an electrically non-conductive tubular element 22, cable 11 also including an outer insulator 23. According to the present invention, cable connector 10 is operative to connect inner conductor 20 and shield 21 of cable 11 to inner connector 16 and outer connector 18, respectively, of electrode assembly 12.
Referring now primarily to FIG. 1, the present method and means for connecting cable 11 to electrode assembly 12 first requires that cable 11 be stripped to expose, in the following sequence, center conductor 20, insulation 22, and shield 21. A female, tubular connector pin 24 is provided having an inner diameter of essentially the same dimension as the outer diameter of connector 16. Connector pin 24 may include a plurality of slots 25 to provide flexibility in the connector for friction fit with male connector 16. According to a preferred embodiment of the present invention, connector pin 24 is inserted into a pin holder 26 which is made from an electrically non-conductive material such as plastic. Pin holder 26 is an elongated member having first and second coaxial bores 27 and 28 therein. The diameter of bore 27 is essentially the same as the outer diameter of connector pin 24, thereby providing a friction fit between connector pin 24 and pin holder 26. The diameter of bore 28 is greater than the diameter of bore 27 to provide for a slight flare at the open end of connector pin 24 for ease in seating connector 16 in connector pin 24. Alternatively, a single bore may be provided through pin holder 26 which would exactly correspond to the outer dimensions of connector pin 24. In addition, pin holder 26 includes an annular flange 29 adjacent the open end of connector pin 24 for reasons which will appear more fully hereinafter.
After cable 11 is stripped as described previously, connector pin 24 is inserted into pin holder 26. A metal washer 30 is slipped over the closed end of pin 24. The inner diameter of washer 30 is such that washer 30 will only partially extend over pin 24, as shown. A piece of heat shrinkable tubing 31, to be described more fully hereinafter, is slipped over the stripped end of cable 11 and, at the present time, positioned away from the stripped end of cable 11, as shown in FIG. 1. Tubing 31 is formed with an elongated slot 33 adjacent to its upper end, through which cable 11 extends. Center conductor 20 is then inserted into a small hole at the apex of connector pin 24 and bent at any desired angle.
The subassembly consisting of cable 11, connector pin 24, pin holder 26 and washer 30 is then inverted and dip soldered. During the dip solder operation, the solder 32 simultaneously, electrically connects washer 30 and center conductor 20 to connector pin 24.
Referring now to FIG. 2, shrink tubing 31 is generally cylindrical and open at both ends thereof. According to the preferred embodiment of the present invention, shrink tubing 31 is a double layer structure, an inner layer 40 being formed of polyethylene and an outer layer 41 being formed of polyolifin. The piece of shrink tubing 31 is slipped into place over the subassembly including pin 24, washer 30 and center conductor 20, but not enclosing the exposed shield 21. Shrink tubing 31 also does not cover flange 29 of pin holder 26.
Referring now to FIG. 3, heat is applied to tubing 31 by means of a suitable tool which pinches the upper end of tubing 31. The applied heat seals such upper end of tubing 31 as well as the material near slot 33. In addition, the heat applied is sufficient to cause the polyethylene inner layer 40 to flow and fill the entire space surrounding center conductor 20, washer 30 and solder 32. In this manner, shrink tubing 31 insulates pin 24, center conductor 20, washer 30 and solder 31 from the exposed shield 21.
Shrink tubing 31, together with washer 30, also serves another purpose. Since connector 16 makes a friction fit with connector pin 24, there is a possibility, when removing cable connector 10 from electrode assembly 12, that connector pin 24 will firmly hold connector 16 and move therewith. Without washer 30, pin 24 could slip through and out of pin holder 26, thereby breaking the electrical connection with center conductor 20. Washer 30, however, has an outer diameter which is greater than the diameter of bore 27 in pin holder 26 and effectively prevents pin 24 from being pulled out of pin holder 26 if it sticks too tightly to connector 16 of electrode assembly 12. In addition, since inner layer 40 fills the entire space surrounding conductor 20, washer 30 and solder 32, it also functions to prevent pin 24 from being pulled out of pin holder 26.
The cable subassembly, as shown in FIG. 2, with tubing 31 shrunk down, is then put into a mold, such mold having any desired shape. A conductive molding compound is injected into the mold to form a socket cap, designated 35. During the molding operation, cable 11 is imbedded within the molding compound, cable 11 being positioned at any desired angle relative to the axis of connector pin 24. In addition, because of the manner in which cable 11 is stripped, a permanent electrical connection is made between the exposed shield 21 of cable 11 and the conductive molding material of cap 35. Flange 29 of pin holder 26 is also imbedded in the molding material to firmly position the subassembly of FIG. 2 in socket cap 35.
Socket cap 35 functions, in the first instance, as the outer housing of cable connector 10 and the outer configuration, therefore, may have any desired shape. In addition, socket cap 35 also serves to make electrical connection between shield 21 of cable 11 and outer connector 18 of electrode assembly 12. More specifically, socket cap 35 includes a bore 36, the axis of which is parallel to the axis of connector pin 24. In the present example, bore 36 and connector pin 24 are coaxial. Bore 36 extends from the open end 37 of socket cap 35 to a plane which includes the open end of connector pin 24 and the adjacent end of pin holder 26. This distance is substantially equal to the length of connector 18 of electrode assembly 12. In addition, the diameter of bore 36 is essentially equal to the outer diameter of connector 18 whereby connector 18 may frictionally engage socket cap 35 along the walls of bore 36.
The completed cable connector is shown in FIG. 3. As cable connector 10 is slipped over the end of electrode assembly 12, inner connector 16 extends into and frictionally engages connector pin 24 whereas outer connector 18 extends into bore 36 and frictionally engages socket cap 35. In this manner, electrical contact is simultaneously completed between inner connector 16 of electrode assembly 12 and center conductor 20 of cable 11 via connector pin 24 and between outer connector 18 of electrode assembly 12 and shield 21 of cable 11 via the conductive molding material of socket cap 35.
It can therefore be seen that in accordance with the present invention, there is provided a novel cable connector 10 which not only eliminates the problems present in the prior art but also adds several unique features. The present method and means of construction completely eliminates the need for expensive metal parts to make connection between shielding 21 and connector 18 since the molded socket cap 35 provides such electrical connection directly. The slow, cumbersome assembly methods are also entirely eliminated. More specifically, it is no longer necessary to swage connector pin 24 since washer 30 in combination with shrink tubing 31 is operative to prevent connector pin 24 from slipping out of pin holder 26 and breaking the electrical connection between pin 24 and center conductor 20. The construction process is also considerably simplified by the elimination of a mechanical means for making an electrical connection between a metal sleeve and the cable shield. Such conventional metal sleeve is entirely replaced by the conductive molding compound which may be molded into any convenient shape to provide these advantages as well as providing the finished configuration. The piece of shrink tubing 31 insulates the center connections from the conductive molding compound as well as strengthening the joint so that the soldered electrical connection cannot be damaged in handling prior to the molding operation.
While the invention has been described with respect to the preferred physical embodiment constructed in accordance therewith, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, cable connector 10 may be fabricated with various configurations for pin 24, with or without pin holder 26, and with cable 11 at any angle to pin 24. With minor variations, cable connector 10 may be used in any application where an electrical connection is desired on coaxial or multi-conductor cables. Socket cap 35 may be made of a flexible, semi-flexible or rigid material. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrative embodiment, but only by the scope of the appended claims.