Method Of Making A Terminal

Abstract

An improved method of making a terminal connector, having a barrel at one end for mechanical deformation or crimping about a conductor and a snap spade blade at the other end that locks over threads of screws or studs.

Description

SUMMARY OF THE INVENTION

This invention is in the field of electrical terminal connectors and is concerned with an improved method for making a terminal.

A primary object is a method of making a terminal that has a relatively soft barrel that can be easily crimped while also having a hard tang or tongue portion.

Another object is an improved method for making the terminal.

Another object is a method of making a terminal that does not require an additional sleeve portion over the barrel.

Another object is a method of making a terminal having locking spade tines that fit over the threads of screws or studs by deformation of the tine beam.

Another object is a method of making a terminal that has improved ease of installation.

Other objects will appear from time to time in the ensuing specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the flat T-shaped blank for the terminal;

FIG. 2 is a view of the terminal blank of FIG. 1 with the extending portions or barrel surfaces rolled inwardly;

FIG. 3 is a view of the terminal in FIG. 2 after a brazing operation;

FIG. 4 is a view of the terminal in FIG. 3 during a pressing operation;

FIG. 5 is a view of the terminal in FIG. 4 after a die operation;

FIG. 6 is an alternate form of the terminal shown in FIG. 4;

FIG. 7 is an enlarged detail view in section of the tines;

FIG. 8 is the same as FIG. 7 after a screw has been inserted in the terminal;

FIG. 9 is a view of the terminal in FIG. 2 during a pressing operation;

FIG. 10 is a view of the terminal in FIG. 9 after a die operation;

FIG. 11 is a view of the terminal in FIG. 10 after a sleeve has been added; and

FIG. 12 is a view of an alternate form of the terminal shown in FIG. 9.

BRIEF DESCRIPTION OF THE INVENTION

The basic method for making the terminal will be described along with two preferred embodiments of the terminal, although the invention should not be limited to the precise structures shown.

The first step of a method for making an improved electrical terminal is shown in FIG. 1, where a generally T-shaped blank 10 is cut from a metal stock. The metal used will exhibit properties of work hardening, such as copper.

The tongue 12, the bottom portion of the blank, is a generally flat planar surface. The upper portion of the blank 10 has two extending portions 14 and 16. At the junction of the top and lower portions of the T-shaped blank there may be material removed at 18 from the edges so as to form rounded indentations in order to facilitate the barrel forming operation.

The next step, shown in FIG. 2, includes rolling up the extending portions 14 and 16 of the top of the T-shaped blank so as to form a generally cylindrical surface or barrel portion 20. The cross section of the barrel may be any closed curve and should not be limited to that of a circle or an ellipse.

In FIG. 3 the terminal blank 10 with barrel portion 20 is shown after a brazing operation. During this operation the rolled up edges 14 and 16 forming the barrel portion are joined so as to completely close the barrel along seam 22. The brazing operation also softens the entire terminal blank which has now become annealed.

The tongue portion 12 of the terminal blank 10 opposite the barrel is now work hardened by compressing it somewhat beyond its elastic limit. This is accomplished as shown in FIG. 4 by a pressing operation. A force, as represented by arrow 8, is applied in a direction normal to the tongue 12 while the tongue is positioned against a support represented by plane 26. The pressing operation reduces the thickness of the tongue portion and also increases its hardness or tensile strength.

The resultant terminal blank 10 now can be seen to have a barrel portion 20 which is relatively soft and can be easily crimped over an inserted conductor or wire due to the annealing or brazing operation. At the same time the tongue portion 12 after the pressing operation has become work hardened such that it is harder than the barrel portion and of a higher tensile strength. This also results in greater resiliency of the tongue portion 12 as contrasted with the soft barrel portion 20.

Other methods for making this type of terminal do not combine the advantages of one piece construction, a fully annealed soft copper crimp barrel, and a hard tongue portion. One method is to use a harder grade of copper for the terminal so that after the crimp barrel is rolled up and brazed, the tongue portion is still hard enough to function properly. However, this results in an inferior crimp barrel even though it is brazed since the material is harder than soft annealed copper and tends to spring back after crimping. Although this spring back may not be discernible to the naked eye, it is undesirable since the crimp barrel tends to pull away from the crimped conductor after crimping which results in an inferior electrical connection. This difference can be detected with a standard temperature rise test whereby the difference in crimp joint temperature and ambient air temperature is measured while the crimp joint is conducting a specified amount of electrical current. Another method is to use a soft copper sleeve over the crimp barrel just mentioned or a similar crimp barrel which has not been brazed, thereby improving crimp joint quality. This approach however, has the disadvantage of a two piece construction and the crimp joint quality is still inferior to that of a fully annealed soft copper crimp barrel. Another method of making this type of connector is to use soft copper, roll up the barrel and braze the seam. However, this results in a soft tongue portion as well as a soft crimp barrel. The importance of a hardened tongue portion can be more easily seen by discussing the two forms of the terminal.

The first embodiment of the terminal shown in FIG. 5 is the result of a die operation performed on the terminal blank 10 shown in FIG. 4. In the die operation, the terminal blank 10 is shaped to the desired final terminal configuration 28 by cutting away the unwanted portions of the blank in the tongue portion as shown in FIG. 5. The portion of the material cut away in the center of the tongue portion so as to form a slot 30 is only important within certain limits. The slot must extend far enough from the front of the tongue back towards the barrel portion 20 in order to allow a screw or a stud to be enclosed by the remaining tongue portion. Also, the slot cannot extend so far back towards the barrel portion such that the tongue loses all strength. What is important is that the slot be such as to result in a generally forked shape with two tines 32 and 34.

One of the two tines 32 has a nib portion 36 on its leading edge. The leading edge is that which first engages the screw or stud and is furthest removed from the barrel portion. The requirement of only one tine having a nib results in a substantial ease of tooling manufacture of the die. The importance of the nib 36 is to contribute to the snap action of the terminal when engaging a screw, stud or other bolt. The general shape of the nib 36 is a curved arc along the inward edge of tine 32 pointing towards the second tine 34. This nib 36 can be on either of the tines but not both. The curved arc shape is functional in that it provides an increasing mechanical advantage as the terminal is forced over a screw. As the terminal is forced over a screw, the deflection increases with a resulting stress increase in the tines which in turn increases the insertion force required. The curved arc counteracts this effect by decreasing the slope of the nib surface as the screw is inserted, thereby increasing the mechanical advantage which reduces the force to spread the tines and allows smooth engagement of the screw as it is being inserted into slot 30. The distance between the interior surfaces of nib 36 and the opposite tine 34 is also important. The tines must be forced outward for the screw to be inserted into or withdrawn from slot 30. If the tines are too close together, the deflection of the tines will be too high which will result in a high force required for screw insertion or deflection beyond the elastic limit of the material resulting in permanent distortion or both.

Each of installation is improved by having a single nib since the terminal screw slips in much easier with less regard to force applied in the correct direction as with two nibs. The mechanical advantage in forcing a space terminal over a screw is determined by the arc profile of the nib. It is preferable to maximize the mechanical advantage which will minimize the force required to insert a screw into a spade terminal. The mechanical advantage of a design with one nib is greater than that of a two nib design if the same arc profile is used for the profile of the two nibs.

Now the importance of the hardness and resiliency of the tongue of the terminal can be appreciated. If the tongue area 12 in FIG. 4, later transformed into the tang with two tines in FIG. 5 in the die operation, is fabricated from a soft material and not work hardened, the soft material of the tines would provide no snap-action or tight fit around the screw. The material does have to be work hardened to increase the elastic limit to the point where a minimum amount of deformation beyond the elastic limit takes place. The spread of the tines within the elastic limit will permit the tines to return to the initial position in an unstressed condition after being pressed over the threads of the screw. Increasing the elastic limit of the material increases the amount of deformation which will be regained and minimizes the permanent set of the tines which is determined by the amount of deformation beyond the elastic limit. Still another advantage of increasing the elastic limit is an increased amount of force required to remove the terminal from the screw. Whether the tines 34 and 32 with nib 36 shown enlarged in FIG. 7 are deformed beyond the elastic limit is also dependent on the tendency of the tine areas 40 and 42 in contact with the screw thread to assume a profile like the thread form as shown in FIG. 8. This limits the practical hardness of the tines.

An alternate embodiment of the terminal is shown in FIG. 6. In the die operation of the second embodiment, portions of the tongue are cut away but rather than a central area or slot cut from the tongue, a long tab-type tongue or spade is the result. With ring-type tongues or flat tongues, it is still desired that the barrel be of a soft material but the tongue or ring can also be softer or more ductile than in the first embodiment but still harder and less ductile than the barrel. This is true because elastic deformation is not as important in this second application. However, when a terminal of the type of the second embodiment, shown in FIG. 6, is pressed between a screw head and a terminal block, an excessive amount of deformation should not take place. Excessive deformation could result in a broken terminal connector or easily broken connection by a small force applied to the terminal. A terminal made by the process described will yield a soft barrel that is easily crimped as well as reasonably resilient but somewhat harder tongue 38. It can be seen that any number of terminal shapes can be made by this process merely by varying the die in the die-cutting operation. Therefore, it should be noted that the method should not be restricted to the precise structures shown.

The method of making an improved terminal described above may also be accomplished without brazing the barrel so as to join the rolled up edges 14 and 16 along 22 in FIG. 3. The terminal of FIG. 2 with rolled up barrel portion 20 is annealed without brazing. Then the tongue portion 12 of the terminal blank 10 is work hardened by compressing it somewhat beyond its elastic limit. As in the previous method, this is accomplished as shown in FIG. 9 by a pressing operation. A force, represented by arrow 8, is applied in a direction normal to the tongue 12 while the tongue is positioned against a support represented by plane 26. The pressing operation reduces the thickness of the tongue portion and also increases its hardness or tensile strength. As previously described, the resulting terminal blank 10 now has an easily crimped barrel 20 and a work hardened tongue 12.

The terminal shown in FIG. 10 is the result of a die operation performed on the terminal blank 10 shown in FIG. 9. The final tongue configuration 28 is the same as that of FIG. 5 including two tines 32 and 34 separated by a slot 30. One of the tines 32 also has a nib portion 36 on its leading edge.

A sleeve 50 of annealed copper is then added over the barrel portion 20 in FIG. 11. The sleeve 50 closes the barrel portions 14 and 16 along 52. As described above, the terminal of FIG. 11 with sleeve 50 exhibits the same characteristics as the terminal of FIG. 5. The only difference is the annealing without brazing and the addition of the sleeve 50. The easily crimpable barrel and the harder tongue portion are still achieved. As in the method described earlier, the tongue portion 28 could also be stamped in various alternate forms such as that of FIG. 6.

In either of the two forms of the method, with or without brazing, the entire tongue portion does not have to be work hardened as shown in FIGS. 5 and 11. The pressing or spanking may be limited to a portion of the terminal tongue portion 12 so as not to extend completely to the barrel 20. In FIG. 12, the tongue configuration 60 has a raised portion 62 near the barrel 20 that has not been work hardened or pressed while the remainder of the terminal tongue has been work hardened with a similar result as the configuration of FIGS. 5 and 11. The work hardening of a portion of the tongue 12 could be utilized in forming any of the many possible terminal configurations.

Whereas the preferred forms of the invention have been shown and described herein, it should be realized that there may be many modifications, alterations and substitutions thereto.

Claims

I claim:

1. A method for making an electrical terminal connector including the steps of cutting a generally T-shaped blank from a conductive metal stock that exhibits work hardening properties, inwardly curling the extending portion of the top portion of the T-shaped blank to form a tubular barrel, brazing the seal formed by the curling inward of the extending portions such as to anneal the terminal, and compressing the lower portion of the T-shaped blank which forms the plane tongue opposite the barrel end beyond its elastic limit in a pressing operation so as to work harden the tongue portion to increase its hardness and to increase its resiliency.

2. The method of claim 1 further characterized in that the conductive metal that is used for the stock is copper.

3. The method of claim 1 further characterized by performing a die operation resulting in the tongue portion of the terminal being cut to the desired shape for use in making an electrical connection.

4. A method for making an electrical terminal connector including the steps of cutting a generally T-shaped blank from a conductive metal shock that exhibits work-hardening properties, inwardly curling the extending portions of the top portion of the T-shaped blank to form a tubular barrel, annealing the terminal, compressing the lower portion of the T-shaped blank which forms the plane tongue opposite the barrel end beyond its elastic limit in a pressing operation so as to work-harden the tongue portion to increase its hardness and to increase its resiliency.

5. The method of claim 4 further characterized by placing an annealed tube over said barrel.

6. The method of claim 5 further characterized by performing a die operation resulting in the tongue portion of the terminal being cut to the desired shape for use in making an electrical connection.

7. The method of claim 4 further characterized by and including the step of brazing the seam formed by the inward curling of the extended portion at the same time that the terminal is annealed.