Electrical coil assembly and terminal therefor

An electrical coil assembly includes a bobbin having a pair of generally parallel end plates with a pair of terminals inserted into holes in an edge in one of the end plates. A wall is attached to that one of the end plates and extends radially outward therefrom, being formed with a pair of crossholes each aligned with one of the blind holes. A pair of terminals are partially inserted into the blind holes. Each of the terminals includes an elongated slot of reduced width at the end remote from the end plate. A portion of the terminal slot material is lanced out to form a tab at that remote end of the terminal. The close in ends of the terminal slots are lined up with the crossholes. Magnet wire is then wound on the bobbin hub and the two ends of the magnet wire are dressed through respective terminal tabs and then resistance welded thereto. A layer of protective tape is then applied over the surface of the wound coil. Prestripped lead wires are inserted through the crossholes of the wall and through the lower end of the terminal slots. Finally, the terminals are driven in the remainder of the blind hole depth. As a result, the reduced terminal slot widths cut into the lead wires, creating both electrical and mechanical connections.

BACKGROUND OF THE INVENTION 
This invention relates to electrical coil assemblies. 
It is an object of the present invention to provide an electrical coil 
assembly which may be manufactured either manually or completely 
automatically. 
It is another object of this invention to provide such an assembly with a 
minimum number of parts. 
It is a further object of this invention to provide an extremely reliable 
electrical coil assembly. 
It is yet another object of the present invention to provide such an 
assembly having a very low cost. 
It is still a further object of this invention to provide an improved 
terminal for connecting a lead wire to the magnet wire forming the coil. 
SUMMARY OF THE INVENTION 
The foregoing and additional objects are attained in accordance with the 
principles of this invention by providing an electrical coil assembly 
adapted for connection to at least one lead wire comprising a bobbin 
having a coil receiving central portion and a pair of generally parallel 
end plates at either end of the central portion defining a coil receiving 
channel, a coil wound on the central portion of the bobbin within the 
channel, and at least one terminal fixed on one of the end plates, each of 
the terminals comprising a unitary member having a coil wire receiving tab 
and a lead wire receiving slot, the slot being elongated in a radial 
direction with respect to the bobbin, the radially inward end of the slot 
being dimensioned sufficiently to receive a lead wire therethrough, and 
the lateral dimension of the slot decreasing therefrom to a region of 
lateral dimension smaller than the diameter of the lead wire.

DETAILED DESCRIPTION 
A major component of the electrical coil assembly according to this 
invention, which assembly is generally designated by the reference 
numberal 10, is the bobbin 12. The bobbin 12 has a coil receiving central 
portion 14 and a pair of generally parallel end plates 16 and 18 at either 
end of the central portion, or hub, 14 which together define a coil 
receiving channel. Preferably, the bobbin 12 is formed as a unitary molded 
plastic piece, illustratively of nylon material. The bobbin 12 further 
includes a wall 20 attached to the end plate 16 and extending radially 
outward from the end plate 16. 
Within the angular extent of the wall 20, the end plate 16 is formed with a 
pair of blind holes 22 and 24 which extend into the end plate 16 generally 
parallel thereto. In addition, the end plate 16 is formed with a generally 
triangular shaped slot 26 which extends down to the level of the coil 
receiving central portion 14 and is open at 28 to the coil receiving 
channel. The slot 26 is a coil starting slot. 
The wall 20 is formed with a pair of openings 30 and 32 therethrough. Each 
of the openings 30,32 is aligned with one of the blind holes 22,24 
substantially at the top thereof. Each of the openings 30,32 is formed as 
a stepped bore having an internal shoulder 31,33 so that when the end of a 
lead wire is stripped of its insulating sleeve, the lead wire can extend 
all the way through the wall 20, within an opening 30,32 but the 
insulating sleeve surrounding the remainder of the lead wire is prevented 
by the internal shoulder 31,33 from passing completely through the wall 
20. 
The coil assembly 10 also includes a pair of terminals 34 and 36 which are 
adapted for insertion into the blind holes 22 and 24, respectively. For 
the sake of uniformity and cost efficiency, the terminals 34 and 36 are 
preferably identical and are constructed as shown in FIG. 4. Preferably, 
each of the terminals 34,36 is stamped from brass stock to have a 
plurality of barbs 38 at one end thereof. The purpose of the barbs 38 is 
to engage the sides of the respective blind holes 22,24 to prevent removal 
of the terminals 34,36 therefrom. Each of the terminals 34,36 has a slot 
40 formed therein. This slot is for the purpose of receiving a lead wire 
therein and is of varying lateral dimension. Thus, the end 42 of the slot 
40 which is radially inward when the terminal 34,36 is inserted in its 
blind hole is dimensioned sufficiently to receive a lead wire 
therethrough. The lateral dimension of the slot 40 at increasing distances 
from the end 42 is decreased to a region of lateral dimension smaller than 
the diameter of the lead wire. At the distal end of the slot 40, some of 
the material removed during formation of the slot 40 is folded over to 
form a tab 44. The tab 44 is for the purpose of receiving coil wire. 
The assembly and construction of the electrical coil assembly 10 will now 
be described. The bobbin 12 is fed to an assembly machine, where the 
terminals 34 and 36 are inserted partially into the blind holes 22 and 24, 
respectively, so that the ends 42 of the slots 40 are aligned with the 
openings 30 and 32 in the wall 20, resulting in the construction shown in 
FIG. 5. Magnet wire is then wound on the central portion 14 of the bobbin 
12, to form a coil 48, as shown in FIG. 6. The starting end 51 of the coil 
48 emerges from the slot 26 and the finish end 52 is held on the surface 
of the coil 48 by a wax dot 50. The operator then dresses the loose ends 
51,52 of the coil 48 through the tabs 44 of the terminals 34 and 36, as 
shown in FIG. 7, and then this assembly is inserted into a welding machine 
which resistance welds the ends 51,52 of the coil 48 to the terminals 34 
and 36. The excess ends of the coil 48 are then cut. A layer of protective 
insulated tape 53 is then applied to the surface of the coil 48, as shown 
in FIG. 8. Next, pre-stripped lead wires 54 and 56 are inserted into the 
openings 30 and 32, respectively, of the wall 20 bottoming out in the 
shouldered openings 30 and 32, with the uninsulated wire portions 58 and 
60 continuing through the openings 30 and 32 and through ends 42 of the 
slots 40 of the terminals 34 and 36, as shown in FIG. 9. Finally, the 
terminals 34 and 36 are driven in the remainder of the depth of the blind 
holes 22 and 24, resulting in the construction shown in FIG. 1. During 
this operation, the reduced width of the slots 40 of the terminals 34 and 
36 cut into the uninsulated wire portions 58 and 60, creating both an 
electrical and mechanically connection. Preferably the terminals 34,36 are 
oriented in the blind holes 22,24 so that the tabs 44 are facing the wall 
20 This provides an extra measure of protection to the connections to the 
coil 48. Thus, there has been constructed an advantageous electrical coil 
assembly without soldering operations that provides a reliable, firm 
connection between the coil winding and the external leads and can be 
automated in manufacturing. 
Although this invention has been illustrated with two lead wires, there are 
applications envisioned where only a single lead wire would be connected 
to the coil. Thus, certain low voltage grounded automotive coils have one 
end of the coil connected to a lead wire and the other end of the coil 
welded to the coil bobbin core which is then fastened directly to the 
automotive frame. Additionally, while this invention has been illustrated 
with pre-stripped lead wires, it is contemplated that the wall openings 
and terminal slots could be dimensioned so that an insulated wire could 
pass therethrough and when the terminals are driven into their blind 
holes, the reduced width slots would cut through the insulation and into 
the wire. 
Accordingly, there has been disclosed an improved electrical coil assembly. 
It is understood that the above-described embodiment is merely 
illustrative of the application of the principles of this invention. 
Numerous other embodiments may be devised by those skilled in the art 
without departing from the spirit and scope of this invention, as defined 
by the appended claims.