GB2112746A - Coil bobbin - Google Patents

Abstract

A coil bobbin comprises an outer bobbin (2) and an inner bobbin (3) that inserted in said outer bobbin. A plurality of plate-like terminals (8) are studded on a flange (5) of said outer bobbin (2) and a ribbed support piece (10) is perpendicularly protruded from said flange (5). A plurality of elongated support holes (21) are formed in a flange (19) of said inner bobbin (3) to support said plurality of plate-like terminals (8), and a plurality of plate-like terminals (26) are studded on said flange (19), said plurality of plate-like terminals (26) being supported by said support piece 10 carried by the outer bobbin (2) from the outer side. The plate-like terminals are T-shaped and inserted in mounting holes in the lower surfaces of the flanges. <IMAGE>

Description

SPECIFICATION Coil bobbin This invention relates to a coil bobbin for small transformers consisting of an outer bobbin and an inner bobbin for winding a primary coil and a secondary coil.

The outer bobbin and the inner bobbin of coil bobbins of this type have so far been made of a synthetic resin in such sizes that they can be fitted to each other. Further, a plurality of rod-like pin terminals are attached to the outer bobbin and to the inner bobbin from the direction in which the bobbin is fitted, and lead wires of the transformer is directly attached and soldered to the root portions of the pin terminals.

In the bobbins of the above-mentioned construction, however, the pin terminals formed in the shape of a rod tend to turn relatively easily. When the pin terminals are turned, the lead wires attached to the terminals may break or may give rise to the occurrence of short-circuiting in the wiring portion.

Therefore, it has been proposed to insert a protector in the rod-like pin terminal to which the lead wire is attached in order that the external force will not be directly exerted on the portion where the lead wire is attached, and in order to prevent the heat from being concentrated at the portions where the pin terminals are studded.

The above construction, however, does not help eliminate the problem of turn of the pin terminals, but rather requires increased number of parts and, hence, increased manufacturing cost.

Under the above-mentioned circumstances, this invention cheaply provides a coil bobbin which has a plurality of plate-like terminals studded on an outer bobbin and on an inner bobbin, which supports the root portions of the platelike terminals of the outer bobbin and of the inner bobbin relative to each other to reliably support the plate-like terminals without using protectors, and which prevents any accident that may stem from the turn of the terminals.

Other objects and features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which: Figure 1 is a perspective view showing a coil bobbin in the assembled condition; Figure 2 is a perspective view of the coil bobbin in the disassembled condition; Figure 3 is a perspective view showing the back side of the inner bobbin; Figure4 is a perspective view showing the back side of the outer bobbin; Figure 5 is a section view of Figure 1 on an enlarged scale; and Figure 6 is a perspective view of a plate-like terminal.

In the drawings, reference numeral 1 denotes a coil bobbin consisting of a square cylindrical outer bobbin 2 and a square cylindrical inner bobbin 3 which is inserted in the outer bobbin 2, both of the bobbins 2 and 3 being made of a synthetic resin.

The outer bobbin 2 consists of a square cylindrical bobbin body 4 on which the coil will be wound and which has an upper flange 5 formed as a unitary structure at the upper circumference thereof. A rectangular engaging plate 6 is formed as a unitary structure on one side portion 5a of the flanges, and a plurality of mounting holes 7 are formed to open outwardly between the engaging plate 6 and the side portion 5a. Plate-like terminals 8 are inserted and studded through the mounting holes 7. A support piece 10 is attached to the outer side of an opposing side portion 5b, which is opposed to the plate-like terminals 8, via a stepped portion 9 to protrude perpendicularly. A plurality of ribs 11 are formed on the inner side of the support piece 10 to run in the upper and lower directions in parallel with each other.Further, engaging grooves 12 are formed in the other side portions, 5c, 5d of the upper flange 5 over nearly the full length thereof running in parallel with each other. The bobbin body 4 further has a lower flange 13 which is formed as a unitary structure and which protrudes toward the outer and inner sides. An engaging protuberance 15 of nearly a ]-shape is formed on the inner surface of an inner projection 14 of the lower flange 13, and a stepped portion 16 and a plurality of protrusions 17 are formed in the corresponding back surface of the lower flange 13.

The inner bobbin 3 has an upper flange 19 formed as a unitary structure at the upper circumference of a square cylindrical bobbin body 18 on which the coil will be wound. A plate-like support member 20 is protruded from a side portion 19a of the upper flange 19, and a plurality of elongated support holes 21 are formed in the outer portion of the support member 20 so that the plurality of platelike terminals 8 are allowed to pass therethrough and are supported. Further, stoppers 22 protrude upwardly at both end portions of the support member 20.

Further, a pair of protrusions 23 are formed as a unitary structure on another side portion 19b that is opposed to the stoppers 22, a support wall 24 is studded as a unitary structure on the outer end portion of the pair of protrusions 23 and on the outer end portion of the side portion 19b, a plurality of mounting holes 25 that open outwardly are formed between the pair of protrusions 23 and the side portion 19b starting from the base portion of the support wall 24, and plate-like terminals 26 are inserted and studded in the mounting holes 25.

Upwardly protruded stoppers 27 are formed at both ends of the support wall 24, and an engaging step 24a is formed at a lower portion in the middle of the support wall 24 to engage with the stepped portion 9 of the outer bobbin 2. Engaging protuberances 28 are formed on the back side of the side portions 19c, 19d of the upper flange 19 nearly over the whole length thereof in parallel with each other to engage with the grooves 12 that are formed in the upper flange 5 of the outer bobbin 2. Stepped portions 29 and a plurality of protrusions 30 are formed in the middle portion in the surface of the side portions 19c, 19d of the upper flange 19.Moreover, a lower flange 31 is formed as a unitary structure at the lower end of the bobbin body 18, and an engaging groove 32 is formed nearly in a ]-shape in the back surface of the lower flange 31 to engage with an engaging protuberance 15 which is formed on the inner projection 14 of the lower flange 13.

Next, the plate-like terminals 8, 26 mounted on the outer bobbin 2 and on the inner bobbin 3 are formed as shown in Figure 6. That is, a slender terminal piece 33 is folded nearly in aT-shape, and a plurality of escape-preventing engaging pieces 36 are formed on both sides of a superposed piece 35 of a folded and superposed portion 34. The folded and superposed portion 34 is inserted and engaged in the mounting holes 7 of the outer bobbin 2 and in the mounting holes 25 of the inner bobbin 3.A terminal piece 37 branched at right angles from the folded and superposed portion 34 is fitted and supported at its base portion in an engaging recess 38 which is formed at the end portion of the engaging plate 6 of the outer bobbin 2, or fitted and supported at its base portion by an engaging groove 39 which is formed in the outer surface of the support wall 24 of the inner bobbin 3. In the outer bobbin 2, an engaging piece 40 to which the lead wire of the transformer will be fastened and which is stretched straight from the folded and superposed portion 34, is drawn on a guide groove 41 which is formed in the side portion 5a of the upper flange 5 of the outer bobbin 2, and is folded and is engaged in the guide groove 41.In the inner bobbin 3, the engaging piece 40 is folded nearly at right angles in the direction opposite to the terminal piece 37, and is folded and is engaged in a guide recess 42 which is formed in the side portion 19b of the upper flange 19.

In the thus constructed device, a coil 43 is wound on the periphery of the bobbin body 4 of the outer bobbin 2, lead wires of the coil 43 are connected to engaging pieces 40 of the plate-like terminals 8, and the engaging pieces 40 are downwardly folded at their root portions along the guide grooves 41, and are disposed at positions adjacent to the coil 43 which is wound. Further, a coil 44 is wound on the periphery of the bobbin body 18 of the inner bobbin 3, lead wires of the coil 44 are connected to the engaging pieces 40 of the plate-like terminals 26, and the engaging pieces 40 are downwardly folded at their root portions along the guide recesses 42 and are disposed at positions adjacent to the coil 44 which is wound.

Then, the bobbin body 18 of the inner bobbin 3 is inserted in the bobbin body 4 of the outer bobbin 2 as shown in Figure 1.

Therefore, the plurality of plate-like terminals 8 of the outer bobbin 2 are inserted in the elongated support holes 21 of the inner bobbin 3, the middle portion of each of the plate-like terminals 8 is supported by each of the support holes 21, and the back surface of the support member 20 is fitted onto the engaging plate 6. The plurality of plate-like terminals 26 of the inner bobbin 3 descend being guided by ribs 11 formed on the support piece 10 of the outer bobbin 2, the middle portion of each of the plate-like terminals 26 is supported by the ribs 11 of the support piece 10 and by the outer surface of the support wall 24 of the inner bobbin 3, and the engaging step 24a of the support wall 24 engages with the stepped portion 9.Moreover, the engaging groove 32 formed in the back surface of the lower flange 31 of the inner bobbin 3 engages with the engaging protuberance 15 formed on the lower flange 13 of the outer bobbin 2, so that the lower flange 13 and the lower flange 31 are joined to each other. Further, the engaging proturberance 28 formed on the back surface of the upper flange 19 of the inner bobbin 3 engages with the engaging groove 12 which is formed in the upper flange 5 of the outer bobbin 2, so that the upper flange 5 and the upper flange 19 are joined to each other.

Afterthe inner bobbin 3 is inserted in the outer bobbin 2, a predetermined core 45 is disposed in the bobbin body 18 of the inner bobbin 3 as shown in Figure 5. A small transformer is thus constructed.

In the above-mentioned embodiment, a primary coil is wound on the outer bobbin 2 and a secondary coil is wound on the inner bobbin 3 to construct a small output transformer. Or, the secondary coil is wound on the outer bobbin 2 and the primary coil is wound on the inner bobbin 3 to construct a small power-supply transformer.

According to this invention, a plurality of plate-like terminals are studded on a portion of the flange that is formed at the upper circumferential edge of the outer bobbin, support pieces are perpendicularly protruded from the other portion of the flange, a flange that engages with the flange of the outer bobbin is formed atthe upper circumferential edge of the inner bobbin that is inserted in the outer bobbin, a plurality of elongated support holes are formed in a portion of the flange of the inner bobbin to support the plurality of plate-like terminals, and a plurality of plate-like terminals are studded on the other portion of the flange of the inner bobbin, the plate-like terminals being supported from the outer side by the support piece.When the inner bobbin is fitted into the outer bobbin, therefore, the plate-like terminals of the outer bobbin and the plate-like terminals of the inner bobbin are simply and reliably supported at their root portions. Further, the platelike terminals provided for the outer bobbin and for the inner bobbin are firmly secured in regard to their positions and are not turned even when external force is exerted. Moreover, since the root portions of the plate-like terminals are supported by the elongated support holes and by the support piece, twisting force is not exerted on the root portions, and the electrodes are more effectively prevented from being turned. Accordingly, lead wires of the coils attached to the plate-like terminals are not broken or short-circuited, and there is no need of using protection means such as protectors. Consequently, it is possible to prevent the occurrence of unexpected accidents that may result from the turn of the terminals.

Furthermore, the plate-like terminals are folded nearly in a T-shape, and the folded and superposed portions are inserted in the mounting holes of the flange from the outer direction. Therefore, the plate-like terminals are raised from the horizontal direction toward the vertical direction, and are not pulled out.

Further, the plate-like terminals have engaging pieces for connecting lead wires, making it easy to connect the lead wires at a position different from the root portions of the terminals; the lead wires do not receive external forces.

According to this invention as mentioned above, coil bobbins can be provided maintaining excellent efficiency of assembling operation and high produceability.

Claims (5)

1. A coil bobbin comprising an outer bobbin of a square cylindrical shape and an inner bobbin of a square cylindrical shape that is inserted in said outer bobbin, wherein a flange is formed at the upper circumferential edge of said outer bobbin, a plurality of plate-like terminals are studded on a portion of said flange, support piece is perpendicularly protruded from the other portion of said flange as a unitary structure, a flange which engages with said flange of said outer bobbin is formed at the upper circumferential edge of said inner bobbin, a plurality of elongated support holes are formed in a portion of said flange to support said plurality of plate-like terminals, and a plurality of plate-like terminals are studded on the other portion of said flange, said plurality of plate-like terminals being supported by said support piece from the outer side.

2. A coil bobbin according to claim 1, wherein the plurality of plate-like terminals mounted on the outer bobbin and on the inner bobbin are folded nearly in a T-shape, and the folded and superposed portions are inserted in the mounting holes that are formed in the lower surface of the flange, the folded and superposed portions being inserted from the outer side.

3. A coil bobbin according to claim 1 or 2, wherein the plurality of plate-iike terminals mounted on the outer bobbin and on the inner bobbin have engaging pieces for connecting lead wires of the transformer.

4. A coil bobbin according to claim 1,2 or 3, wherein the support piece of the outer bobbin has a plurality of ribs to support the plate-like terminals of the inner bobbin.

5. Coil bobbin, substantially as hereinbefore described with reference to the accompanying drawings. ~~~~~~ ~~~~~ ~~~~~~~~~~