Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
  • H01F27/306—Fastening or mounting coils or windings on core, casing or other support
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
  • H01F17/041—Means for preventing rotation or displacement of the core
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/02—Casings
  • H01F27/027—Casings specially adapted for combination of signal type inductors or transformers with electronic circuits, e.g. mounting on printed circuit boards

Definitions

• the invention relates generally to inductance elements for electronic circuits and more particularly to choke coils of the type particularly suited for mounting on electronic circuit boards.
• inductance element generally for the performance of some filtering function. Such is the case for circuits in telephone receivers. These circuits are subject to various types of electromagnetic noise which is best filtered out by an inductance.
• the types of inductance elements commonly used for suppressing noise in electronic circuits are generally known as "choke coils". They are preferably designed so that they can be readily mounted on a circuit board along with the other circuit components present on it. Since this mounting procedure is separate from the processes for manufacturing the other circuit portions on the board, it is important that there be a minimum of complexity involved in the assembly process.
• the novel choke coil in accordance with the present invention includes an E-core with a coil member on its central leg.
• the legs and center post of the E-core extend beyond the end of the coil member, so that magnetic flux coupling between the legs and post is sufficient to permit significantly reduced winding turns in the coil member. This makes possible a reduced thickness dimension
• the coil member includes one or more coils wound on a bobbin which slides onto the center post of the core.
• the bobbin includes locking tabs which locks the core in place in its assembled position.
• the coil member is asymmetrically configured to permit ready orientation by automated assembly equipment.
• FIG. 1 is an elevated perspective view of a choke coil assembly in accordance with the preferred embodiment of the invention.
• FIG. 2 is a top view of the choke coil assembly of FIG. 1.
• FIG. 3 is an elevated perspective view of the choke coil assembly of FIG. 1 with the core disassembled from it.
• FIG. 4 is an elevated perspective view of a bobbin of the choke coil of FIGs. 1 and 2 shown separately.
• FIGS. 1 and 2 there is shown a choke coil assembly 10 which includes a bobbin assembly 12 fastened to a core member 14.
• the core member 14 is shown removed from the bobbin asembly 12 in FIG. 3 of the drawings.
• the core 14 is an E-core made of a ferrite ceramic material, such as, for example, a material designated as LRM382-L1 manufactured by the Western Electric Company in North Andover, Mass., in 1983.
• the core 14 includes a base portion 16, two outer legs 18, 20 and a center post 22.
• the vertical edges 24 at the end of the center post 22 are chamfered.
• the bobbin assembly 12 includes a bobbin 26 which is molded of thermoplastic resin material. It is shown separately in FIG. 4.
• the bobbin 26 has a central guide opening 28 for receiving the center post 22 of the core 14.
• the outside vertical edges of 30 of the guide opening 28 are chamfered to facilitate horizontal alignment when the bobbin assembly 12 receives the center post 22.
• Vertical alignment is provided by a pair of tongue-like lead-in members 31 extending out a short distance from the guide opening 28 and flaring out, away from it.
• a pair of axially spaced end flanges 32, 34 are attached to a central cylindrical portion 36 of rectangular cross-section. Spaced midway between the flanges 32, 34 is partition 38 which axially divides the bobbin 26 into two winding spools.
• Each of the flanges 32, 34 is provided with two holes 40 in its plane which each receive a terminal pin 44.
• the terminal pin has a short coil wire wrap leg section 46 bent at a right angle and a mounting stem section 48.
• the mounting stem section 48 includes a swaged segment 50 which deforms the inside wall of the receiving hole 40 to rigidly hold the pin 44 in place after it is assembled to the bobbin 26.
• Four tongue-shaped locking tabs 52 extend from one flange 32. These are designed to engage the outer edges surface of the base 16 of the core 14 when the bobbin assembly is pressed against the base 16 on assembly and to firmly hold the core 14 in place.
• FIG. 2 the bobbin assembly 12 is shown with the terminal pins 44 in place and each of the winding spools wound with a winding 54, 56 of copper wire.
• the completed assembly of FIGS. 1 and 2 shows the ends of the windings 54, 56 wire-wrapped about the terminal legs 46.
• the mounting stems 48 extend from the bottom of the assembly and are designed to readily attach to a circuit board.
• the legs 18, 20 and center post 22 of the core 14 are significantly longer than the length of the guide opening 28 in the bobbin 26, so that they extend beyond the end of the outer winding 56 a distance of about 30% of their total length.
• This provides magnetic flux coupling through the air gaps between the outside legs 18, 20 and the center post 22 which significantly increases the inductance value of the choke coil assembly 10. Without this feature it would be necessary, in order to obtain the same inductance value, to add more turns of wire to the windings 54, 56, thereby increasing the diameter of the windings 54, 56 and giving the entire choke coil assembly 10 a correspondingly greater thickness dimension. Since this thickness dimension is the dimension which determines the protrusion of the choke coil assembly 10 above the level of the circuit board to which it is mounted, this would be undesirable for many applications where space is at a premium.
• the copper wire which forms the windings 54, 56 is of such a thickness that it serves as a fuse link for the circuit in which the choke coil assembly 10 is used. Most typically, this would be a telephone receiver circuit.
• bobbin 26 It is an advantageous feature of the bobbin 26 that its configuration is asymmetrical. It is therefore more readily handled by automated assembly equipment. It is well known that automatic assembly equipment is more readily designed to handle asymmetrical pieces than symmetrical ones because it is easier to orient and align such pieces. The same can be said of the core 14.
• the distance d that the center post 22 and the outside legs 18, 20 of the core 14 extend beyond the end of the outer winding 56 may vary within a range feasible for a particular application. Also, if the distance d is made much greater than about 30% of the total length of the legs 18, 20, and the post 22, no appreciable inductance will be added to the structure, and the core 14 is likely to become much more susceptible to breakage in handling.
• coil assembly 10 includes two windings 54, 56, it will be readily apparent to those skilled in the art that the bobbin 26 could also be wound with a single winding or more than two. Moreover it could be readily modified to be specifically designed for a single winding. ⁇ JRE ⁇ -
• the core 14 of the coil assembly 10 is an E-core having two outside legs 18, 20
• a U-shaped core having only a single outer leg would also provide coupling in the air gap between the outer leg and the center post if these extended sufficiently beyond the outer winding. This would be an alternative structure which might be suitable for some purposes.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Coils Or Transformers For Communication (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=24124554

Family Applications (1)

Country Status (4)

Cited By (4)

Families Citing this family (3)

Citations (9)

Family Cites Families (8)

• 1984
  • 1984-08-28 WO PCT/US1984/001370 patent/WO1985001387A1/en unknown
  • 1984-08-28 JP JP1985600006U patent/JPH051049Y2/ja not_active Expired - Lifetime
  • 1984-08-28 DE DE19848490152 patent/DE8490152U1/de not_active Expired
  • 1984-09-14 GB GB08423273A patent/GB2146847A/en not_active Withdrawn

Patent Citations (9)

Non-Patent Citations (1)

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