IL22281A - Method of securing connector terminals to a ribbon cable - Google Patents

Description

This invention relates to a method of securing connector terminals to a ribbon cable. More particularly it relates to a new and improved method of this general class. - Ribbon eables are widely used in the electrical and electronic industries since they possess several desirable characteristics including flatness and flexibility.

As used in the present specification and claims, a ribbon cable is basically an elongated strip of plastic having conductive wires or members embedded or printed therein. As many methods of producing ribbon cables involve a softening or embedding process, the plastic strip is generally a'thermoplastic material, such as a vinyl plastic or polyethylene.

There are several methods of making the ribbon cable, such as positioning or printing a plurality of spaced conductors upon a first elongated plastic strip and then applying a second plastic layer thereover so that the elongated conductors are sandwiched between two of the plastic strips. Heat and pressure are then applied to the thermoplastic strips in order to consolodate the superimposed members and produce an integral ribbon cable. Another technique for producing the ribbon cable involves a simultaneous extrusion of a plastic strip with a carrying of a plurality of parallel conductors into and away from the extrusion area.

Yet another technique includes the heating of the conductiTe members and the forcing of the same into the thermoplastic ribbon.

In order that the ribbon cable may be effectively-used with or incorporated into circuitry, it is necessary that electrical and mechanical conection may be made between the various conductors of the ribbon cable and outside circuits. Towards this end various techniques have been developed in order to secure connector terminals to the conductors of the ribbon cable. One such technique involves the removal of insulation along a narrow area of one or both sides of the ribbon cable with the connector terminal then being soldered to the bared conductors or printed lines. This method, however, presents problems since the removal of the plastic is a cumbersome procedure which is time consuming and unreliable. Another suggested method involves the use of connector terminals with piercing ^fingers which may be directly forced through the plastic of the ribbon cable and into electrical and mechanical contact with the conductive members of the ribbon cable* This method also presents problems since it requires accurate alignment between the piercing member and the conductive member.

It is therefore an object of the present invention to provide a method of securing a connector terminal to a ribbon cable which is simple and yet reliable.

Yet another object of the present invention is to provide a method for securing a connector terminal to a ribbon cable which is economical in practice and which involves the use of a minimum amount of equipment of machinery.

Still another object of the present invention is to provide a method for securing a connector terminal to a ribbon cable which minimizes alignment problems and automatically gives an indication when the connector terminal has been properly joined to the conductive member of the ribbon cable.

The foregoing as well as other objects of the present invention are achieved by providing a method of securing a connector terminal to a ribbon cable which involves the establishment of a welding connection. The method of the present invention basically includes the positioning of the ribbon cable between a source of heat in the form of an electrode and the connector terminal which is to be secured to the ribbon cable.

The electrode heat source is positioned directly against the ribbon cable and because the ribbon cable is of a thermoplastic material the electrode heat source will rapidly penetrate into the ribbon cable until it reaches a conductive member of the ribbon cable. The heat from the electrode heat source then penetrates to the connector terminal adjacent opposing surface of the ribbon cable.

The connector terminal easily forces its way through the heat softened insulation until it too makes physical contact with the conductor of the ribbon cable to form a tri-partite metallic junction. At this point a condenser discharge is sent through the foregoing metallic junction in order to establish a weld. The condenser discharge may be controlled by a timing device to occur after a predetermined time sufficient to guran-tee that the junction between the heat source and the ribbon cable contact is established. As an alternate form of the invention, the timing device may be replaced with an electric sensing device which measures the resistance between the connector terminal and the electrode heat source or between the connector termiial and the particular ribbon cable involved. In this form of the invention the condenser discharge occurs when the resistance becomes low enough to warrant the making of a weld. This also indicates when the weld has been made.

Other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Fig. 1 is a schematic view showing a ribbon cable in section positioned between an elevated electrode heat source and a connector terminal with a condenser discharge circuit being associated with the connector terminal ; Fig. 2 is an enlarged fragmentary vie based on Fig. 1 and illustrating an initial step in the present process invention wherein the electrode heat source is brought into contact with the ribbon cable such that the heat source penetrates the front or forward Surface of the ribbon cable and comes in contact with a ribbon cable conductor member; Fig. 3 is a view similar to Fig. 2 but showing a further step in the method of the present invention wherein the heat from the heat source has penetrated beyond the ribbon cable conductive member to soften the insulation on the opposing surface of the ribbon cable and also to heat the connector terminal and particularly a projection extending therefrom so that it will penetrate through the insulation and come incontact with the ribbon cable conduc tive member; Fig. is a schematic view partially in section showing the completed secureraent of the connector terminal to the ribbon cable; Pig. 5 la a. view somewhat similar to Fig. 1 but showing a modified electrode heat source with the connector terminal having a slightly different projection extending therefrom; Fig. 6 is a view showing the final step in the method of Fig. 5 and is somewhat similar to Fig. 3; and Fig. 7 is an enlarged view of the weld produced by the method of Fig. 5» Turning now to the various figures of the drawing wherein like reference characters refer to like parts the basic setup illustrating the method of the present invention is generally illustrated at 10 in Fig. 1.

As shown in Fig. 1 a connector terminal 12 having an extending projection lh is about to be electrically and mechanically united to a ribbon cable 16 having conductor members 18 as also illustrated in Fig. 7.

The projection Ik of the connector terminal 12 facilitates the penetration of the connector terminal into thermoplastic insulation of the ribbon cable. In a preferred embodiment of the invention the projection Ik is approximately 0.030 inches in diameter and 0.020 inches in height.

In order to carry out the process of the present invention, it is necessary to employ a heated electrode or heat source 20 which is of well known construction and essentially comprises a vase 22 from which depends a heating finger 2k. Means for conducting heat to the heating finger 2k (not shown) are associated with the heat surface 20 and, for instance, may be comprised of electric resistance heating means, induction heating or other techniques well known to the art. A thermocouple 26 with an appropriate thermostat arrangement to maintain the heating finger 2k at a precise temperature is associated with the heating finger as illustrated in Fig. 1 .

As also shown in Pig. 1 , a condenser discharge circuit is associated with the connector terminal 12 and ribbon cable conductor member 16. The conductor discharge circuit basically involves a regulated power supply, a resistor 28, a switch 30 which may incorporate a timer or a resistance measuring device via switch 31 and three 100 m.f.d. capacitors 32 , jk, and J6 connected in parallel. A conductor J8 connects the switch 30 to the terminal 12 and conductors kO and kl connect the electrode heat source 20 and the switch 1 to the resistor side of the regulated power supply. Capacitors 32 , 3k and 36 are connected to the resistor side of the regulated power supply by means of conductor k2 and are connected to the switch side of the regulated power supply by means of conductor kk.

In carrying out the process of the present invention the electrode heat source 20 is brought to a desired temperature depending upon (a) the softening and scorching point of the thermoplastic insulation of the ribbon cable, (b) the thickness of the cable, (c) the pressure to be applied to the heat source and (d) the desired In a preferred embodiment of the invention the ribbon cable is comprised of a polyethylene insulation material with a total thickness of 0.010 inches including a conductor thickness of 0.004 inches. The heat source 20 was maintained at approximately 250 C which will not cause scorching of the polyethylene in the relatively short contact time of five seconds with a pressure of seven pounds being applied by the electrode heat source.

As shown in Fig. 1 , the heat source 20 is moved downwardly in the direction of arrow 46 so that the nose 48 of the hot finger is about to come in contact with the insulation on the outer face 50 of the ribbon cable 16.

As shown in Pig. 1 , the nose 46 of the hot finger 24 may be of a bifurcated nature in order to provide two penetrating points.

As the hot ose 46 of the hot finger 24 comes in contact with the outer surface 50 of the ribbon cable 16 , it immediately heats the neighboring insulation with the combination of heat and pressure of the hose 46 causing the insulation to move sideways under the pressure of finger 24. This permits the heat source 20 to readily penetrate through the outer surface 50 until it reaches the ribbon cable conductive member as illustrated in Fig. At this point the heat source continues to emit heat which penetrates through the conductive member 18 and then finally to the inner face 52 of the ribbon cable thereby softening the insulation adjacent the projective 14 of the contact 12. The combination of the softened insulation adjacent the inner surface 50 and the pressure imposed by the electrode heat source 20 enables the projec until it comes in contact with the ribbon cable conductive member 18. When this occurs a metallic junction between the metallic heat source 20 , the ribbon cable conductive member 18 and the connector terminal 12 is established.

At this point a condenser discharge is sent through the foregoing metallic junction in order to establish a weld. The condenser discharge is produced through the combination of the regulated power supply, the capacitors 32 , 3 and 36 and the other circuitry of Fig. 1.

As previously discussed a timer may be associated with the switch 30 in order to complete the circuit of Fig. 1 after a predetermined time long enough to gurantee that a metallic junction between the heat source, ribbon cable conductive member and connector terminal has been established. This is done by providing switch 31 which is wired (not shown) to switch 30 with the timer closing switch 31. Appropriate relays may be employed if desired In a preferred embodiment of the invention the switch may be closed manually or by a microswitch arrangement whereby downward movement of electrode heat source 20 closes a microswitch. Closing of switch 30 actuates the timer which closes switch Jl after a predetermined time to complete the power circuit. The condenser discharge can occur in a "dumping" arrangement with switches 30 and 31 then opening to complete the cycle.

While a condenser discharge is preferably utilized to establish the weld, it is also contemplated that other power-arrangements may be utilized.

In the embodiment of Figs. 5 » 6 , and 7 the nose lk6 of electrode heat source 120 has but a single tip and is not bifurcated as the nose k6 of Fig. 1. Also, the projection ll is punched as indicated by depression 100. As shown in Fig. 5, the electrode heat source 120 possesses a slightly convex arc so that the center thereof will penetrate more readily into the insulation.

The electrode heat source 120 acts upon ribbon cable 16 with conductors 18 much in the mannei/of the heat source 20. A support base 162 is provided and may also be utilized in the method of Fig. 1. Also, the contact 12 can be secured in an insulating casing 164 although this is usually done subsequent to welding.

The last step in the process is shown in Fig. 6 wherein a depression 166 is created by the action of the electrode 120. Two depressions 166 are also created by electrode 20. However, the depression or depressions may be filed in with epoxy or other sealing materials.

An enlarged view of the underside of a completed assembly is shown in Fig. 7 with welds 168 having been produced by the method of the present invention.

It is clear that the process of the present invention produces a weld connection between the connector terminal and the ribbon «ra¾le conductive member in a simple and efficient manner. Such a weld connection may not be strong enough physically to withstand the stresses imposed upon the ribbon cable in use. Therefore, mechanical means may be associated with the welded joints of the present invention in order to protect them. Such mechanical means may involve well known mechanical strain release techniques or may utilize epoxy materials in orde ito strengthen the weld joints. Epoxy is also used to fill in depression 166 as previously noted.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims (2)

1. HAVING NOW particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we delcare that what we claim is:- 1. A method of securing a connector terminal to spaced embedded electrical conductors of a ribbon cable having thermoplastic insulation, characterized by the steps of positioning said ribbon cable between said connector terminal and an electrode heat source capable of exerting pressure, urging said electrode heat source against a first face of said ribbon cable with said connector terminal being thereby forced against a second face of said ribbon cable, allowing the heat from said electrode heat source to penetrate through said ribbon cable to soften said cable whereby said electrode heat source penetrates through said first face to contact one of said ribbon cable conductors and said connector terminal penetrates through said second face to contact said one ribbon cable conductor thereby forming a metallic junction between said conductor and said connector terminal, and sending an electrical charge through said junction to achieve welding thereof.

2. The method according to Claim 1, characterised in that said electrical charge is a condenser discharge. 3· T e method according to Claim 1 or 2, characterized in that a timing device is associated with said junction to permit the sending of said charge at a given time. k. The method according to any one of the preceding Claims, characterized in that a resistance measuring device is associated with said junction to permit the sending of said charge at a predetermined low resistance value. 5· The method according to Claim 4, characterized in that a signalling device is associated with an actuated by 6. The method according to any one of the preceding claims, characterized in that said electrode heat source is bifurcated. 7. The method according to any one of Claims l-5t characterized in that said electrode heat source includes a nose possessing a slightly convex arc. 8. The method according to any one of the preceding claims, characterized in that mechanical means are employed to strengthen said junction after the voiding thereof. 9· The method according to any one of the preceding claims, characterized in that said terminal includes a projection extending toward said conductor. 10. The method according to Claim 9» characterized in that said projection is punched from said terminal. 11. A method of securing a connector terminal to spaced -embedded electrical conductors of a ribbon cable substantially as described herein and as shown in the accompanying drawings. DATED THIS 18th day of October, 1964. Cohen Zedek & Spisbach P.O.Box 116, Tel-Aviv Attorneys for Applicants.