Coil spring engagement construction of a high tension terminal in an engine ignition apparatus

Abstract: The invention provides apparatus for connecting a high tension terminal (11) to a plug of an engine ignition apparatus by means of a coil spring (10) which is operatively engageable in the terminal (11). The terminal (11) comprises a cylindrical wall defining an insertion chamber (11a) receiving the coil spring (20) therein and holes and/or grooves (11b) cooperable with an insertion end portion (10a) of the coil spring (10) to captively retain the coil spring (10) in the terminal (11). The insertion end portion (10a) of the coil spring (10) has diammetrically opposed projections (10b) engageable in the holes and/or grooves (11b). The coil spring (10) is inserted into the insertion chamber (11a) by tilting the insertion end portion about the helical axis to reduce the effective external diameter of the coil spring (10) without changing the actual diameter of the spring.

Description: The present invention generally relates to a high tension terminal in an engine ignition apparatus to be directly connected with an ignition plug of an engine, and more particularly, to improvements in the engagement construction of the coil springs to be inserted into the interior of the high tension terminal. Conventionally an ignition apparatus of the engine is provided wherein a high tension terminal 2 is buried within the high tension power supply 1, conductive coil springs 5 for electrically connecting the high tension terminal 2 with the top terminal 4 of the ignition plug 3 are inserted into the interior of the high tension terminal 2, as disclosed within Japanese Patent Laid-Open Publication No. 3-47475, and represented in Fig. 14. The above described coil springs are required to engage the insertion end portion 5a with the high tension terminal 2 to an extent so that the coil springs may not naturally drop. As shown in detail in Fig. 15 (A), an annular engagement concave groove 2a is provided on the peripheral face of the cylindrical portion of the high tension terminal 2, and also, the outer diameter dl of the insertion end portion 5a of the coil spring 5 is made larger in diameter (d1 > d2) than the outer diameter d2 of the coil spring 5. The insertion end portion 5a is inserted into the interior of the high pressure terminal 2 while the insertion end portion 5a is being contracted in diameter by rotation reverse to the winding direction so that the insertion end portion 5a is adapted to be engaged with the engagement concave groove 2a. It is difficult to insert the insertion end portion 5a of a larger diameter of the coil spring 5 into the interior of the high tension terminal 2, making it harder to fit the spring. Also, it could not be recognised visually that the insertion end portion 5a of the coil spring 5 was engaged into the engagement concave groove 2a of the high tension terminal 2. As shown in Fig. 15 (B), there is also a method of inserting the coil spring 5 into the interior of the high tension terminal with the inserting end portion 5a of the coil spring 5 being made the same in diameter as the outer diameter d2 of the coil spring 2, thereafter drawing out and erecting inwardly one portion of the outer peripheral wall of the high tension terminal 2, engaging the insertion end portion 5a with the drawn out, erected portions 2b, 2b. When the insertion end portion 5a is engaged with the above described drawn out, erected portions 2b, 2b, it is necessary to effect a drawing out, erecting working operation as another step after the insertion of the coil spring 5. When the bending onto the inner portion side of the drawn out, erected piece portion is small, and plays and so on exist in the vertical direction of the spring, springs are often invisible from the gaps of the drawn out, erected portion, with a problem that the spring engagement is hard to visually confirm from the outside. US 1933304 relates to a connector terminal for electrical conductors for use in ignition systems. The device comprises a cylindrical terminal having an annular latch recess in which a portion of the coil spring can engage. A portion of the coil spring is formed into an elliptical shape so that it is slightly larger on at least one diameter than the diameter of the terminal. Consequently, the edges of the coil on the longest diameter may engage in the latch recess to retain the coil in the terminal. Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent in the prior art, and has for its essential object to provide an improved coil spring engagement construction of a high tension terminal in an engine ignition apparatus. Another important object of the present invention is to provide an improved coil spring engagement construction of a high tension terminal in an engine ignition apparatus which can be easily inserted and engage the coil springs into the high tension terminal, in which the engagement condition can be seen from the outside, and besides, can be manufactured at a lower price. The present invention provides a coil spring engagement construction for a high tension terminal of an engine ignition apparatus comprising a terminal comprising a cylindrical wall defining an insertion chamber receiving a conductive coil spring therein, the wall also defining at least one engagement portion cooperable with an insertion end portion of the coil spring to captively retain the coil spring in contact with the terminal, the insertion end portion comprising a pair of diammetrically opposed radial projection portions operatively engageable with the engagement portion, characterised in that the engagement portion comprises at least one hole, through which hole the coil spring may be seen from the exterior of the terminal. The apparatus is advantageous because the coil spring can be engaged in the terminal without the need to reduce the actual diameter of the coil spring by twisting it as was necessary in the prior art. In another aspect of the invention there is provided a method of assembling a coil spring engagement construction for a high tension terminal of an engine ignition apparatus comprising a terminal having a cylindrical wall defining an insertion chamber for receiving a coil spring therein and defining an engagement portion cooperable with an insertion end portion of the coil spring to captively retain the coil spring in contact with the terminal, the insertion end portion having a pair of diammetrically opposed projection portions operatively engageable with the engagement portion, the method comprising the steps of tilting the insertion end portion to reduce the external diameter of the insertion end portion, inserting the insertion end portion into the insertion chamber and allowing the insertion end portion to relax into a captive position with the projection portions engaged in the engagement portion. When the insertion end portion of the coil spring is inclined so that the projection portion may become respectively upper and lower in position in the coil spring engagement construction of the present invention, the outer diameter of the projection portion becomes approximately the same in diameter as the outer diameter of the coil spring, so that the insertion end portion can be easily inserted into the high tension terminal. The inclined insertion end portion is changed in the inclination angle and is engaged by the engagement portion of the high insertion terminal or is restored horizontally and engaged. The coil spring is inserted, and engaged with one touch operation in this manner so as to improve the ease of fitting the spring. As the engagement portion of the above described high tension terminal comprises at least one hole, it can be confirmed visually from the outside that the insertion end portion of the coil spring has been engaged with the engagement portion. When the insertion end portion of the coil spring is kept inclined in advance, the operation of inclining before the insertion is made unnecessary. These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which; Fig. 1 is a side sectional view of the coil spring engagement construction of the present invention; Fig. 2 is a plan view sectional view of Fig. 1; Fig. 3 is a side sectional view of a high tension terminal; Fig. 4 is a plan view of the coil spring in Fig. 1; Fig. 5 is a sectional view taken along a line A-A of Fig. 4; Fig. 6 is a sectional view taken along a line B-B of Fig. 4; Fig. 7 is a side sectional view showing a condition at the terminal insertion time of the above described coil spring; Fig. 8 (A), (B) are plan views each showing a modified embodiment of the insertion end portion of the coil spring; Fig. 9 (A), (B), (C) are side views each showing a modified embodiment of an engagement portion to be provided in the terminal; Fig. 10 (A), (B) are side sectional views each showing an outwardly embossed engagement portion provided at a terminal; Fig. 11 is a side sectional view showing a modified embodiment of the engagement portion of the terminal; Fig. 12 (A), (B) are side sectional views each showing an inwardly embossed engagement portion in a terminal; Fig. 13 is a side sectional view showing a modified embodiment of the engagement construction of a coil spring; Fig. 14 is a side sectional view of the conventional engine ignition apparatus; and Fig. 15 (A), (B) are side sectional views each showing the conventional coil spring engagement construction. Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Fig. 1 through Fig. 7 show a first embodiment of the present invention. Fig. 1 and Fig. 2 show a condition where coil springs 10 are engaged with terminals 11. Fig. 3 shows terminals 11, Fig. 4 through Fig. 6 show coil springs 10, Fig. 7 show a condition where the coil springs 10 are not inserted into the terminal. The above described coil spring 10 is wound in a true circle helical shape with a given pitch and a given outer diameter d2 as in the conventional coil spring 5. Projection portions 10b, 10b which are projected outwards to a larger diameter dl than the outer diameter d2 of the coil spring 10 are provided, on both the sides in the axial orthogonal direction of the insertion end portion 10a seen from the plan view of Fig. 4, in the insertion end portion 10a of the coil spring 10. The insertion end portion 10a becomes oval as shown in Fig. 4 by projection portions 10b, 10b. The insertion end portion 10a may be made a diamond shape as in Fig. 8 (A), or a projection shape as in Fig. 8 (B) as an alternative to the above described oval shape. The insertion end portion as in Figure 8 (A) having projection portions on both the side portions will do without restriction. As shown in Fig. 3, a high tension terminal 11 is of a cylindrical shape having an insertion chamber or hole lla of a diameter larger slightly than the outer diameter d2 of the coil spring 10 as in the conventional high tension terminal 2. Engagement holes 11b, 11b which engage the projection portions 10b, 10b of the insertion end portion 10a of the above described coil spring 10 are opened in the given position of the outer peripheral wall of the high tension terminal 11. The engagement holes 11b, 11b may be of a true circle as shown in Fig. 9 (A), an oval shape as shown in Fig. 9 (B), or a slit shape as shown in Fig. 9 (C). When the coil spring 10 is inserted for engagement into the terminal 11 composed of the above described construction, the insertion end portion 10a of the coil spring 10 is inclined so that the projection portions 10b, 10b may become respectively upper and lower in position before the coil spring 10 is inserted. Thus, the outer diameter dl of the insertion end portion 10a with respect to the outer diameter d2 of the coil spring 10 becomes smaller by the inclined portion as shown in Fig. 7. As the outer diameter d3 becomes approximately the same as the outer diameter d2 of the coil spring 10, the insertion into the insertion hole lla of the high tension terminal 11 can be effected easily. When the projection portions 10b, lob of the insertion end portion 10a of the coil spring 10 inserted obliquely into the insertion hole lla of the above described high tension terminal 11 are adjacent with the engagement holes 11b, 11b, the projection portions 10b, 10b are restored into a horizontal condition from the inclined condition with the elastic force as shown in Fig. 1 and Fig. 2 so as to engageably fix the projection portions 10b, 10b into the engagement holes 11b, 11b so that the coil spring 10 will not drop out of the high tension terminal 11. The ease of fitting the spring is improved, because the coil spring 10 can be inserted and engaged into the high tension terminal 11 with one touch operation. It can be confirmed visually from the engagement holes 11b, 11b of the high tension terminal 11 from the outside that the projection portions 10b, 10b of the insertion end portion 10a of the coil spring 10 have been engaged with the engagement holes 11b, 11b. The high tension terminal 11 in the above described first embodiment has engagement holes 11b,11b which can be seen from the outside. The projection portions 10b, 10b of the insertion end portion 10a of the coil spring 10 inserted obliquely can be restored in a horizontal condition especially if the high tension terminal has a long engagement concave groove llc shown in Fig. 10 (A). The visual sight can also be effected if an engagement hole llb, and an engagement concave groove lld are provided respectively on one side of the high tension terminal 11 and on the other side thereof as shown in Fig. 11, according to a second embodiment of the invention. The engagement concave groove 11d of the high tension terminal of the above described Fig. 11 is formed by the outward embossing operation of the inner face of the peripheral wall. The outer face of the peripheral wall can be inwardly embossed so that the engagement concave groove 11d can be formed as shown in Fig. 12 (A) and Fig. 12 (B). It is preferable for the coil spring 10 to be accommodated in a sleeve shaped jig 15 of a diameter smaller than the inner diameter of the embossed projection so as to effect an inserting operation to prevent the projection portions 10b, 10b of the insertion end portion 10a from being caught in the embossed projection as the coil spring 10 is inserted. By keeping the insertion end portion 10a of the coil spring 10 inclined in advance so that the projection portions 10b, 10b may become respectively upper and lower in position as shown in the above described Fig. 7, the bother of inclining the insertion end portion 10a is made unnecessary before the insertion, so that the inserting operation can be quickly effected. The engagement holes 11b, 11b of the high tension terminal 11 need only be shifted to upper and lower positions respectively as shown in Fig. 13 in accordance with the inclined angle of the projection portions 10b, 10b in its no-load condition. The projection portions lob, lob of the coil spring need only be projected from the outer diameter in the horizontal direction or the inclined condition at the no-load condition, and the engagement portion to be formed at the terminal where the projection portions are engaged need only be formed in a position where the projection portion to be projected in the above described no-load condition is engaged. The engagement portion to be formed on the terminal will be sufficient if the projection portion of the coil spring is engaged to an extent sufficient to hook the inner edge of the hole with respect to the dropping direction. When the engagement portion is short, it is desirable to provide a stopper on the terminal inner face on the coil spring compression side in the reverse direction. As is clear from the foregoing description, according to the arrangement of the present invention, the insertion end portion of the coil spring is inclined so that the projection portion may have upper and lower portions respectively and is made smaller than the inner diameter of the cylindrical terminal when the coil spring is to be inserted into the high tension terminal of the present invention so that the inserting operation can be effected smoothly. Since the outer diameter of the projection portion of the coil spring is projected in the engagement portion provided on the terminal, the coil spring can be inserted and engaged in the high tension terminal with one touch operation, and the ease of fitting the spring can be improved. As the engagement portion of the high tension terminal comprises at least one hole, it can be confirmed by the visual sight that the insertion end portion of the coil spring has been engaged with the engagement portion. As the high tension terminal can be worked into the cylindrical shape with a conductive plate material, with an advantage that the coil spring engagement construction can be made at lower cost. Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.

Claims: A coil spring engagement construction for a high tension terminal of an engine ignition apparatus comprising a terminal (11) comprising a cylindrical wall defining an insertion chamber (11a) receiving a conductive coil spring (10) therein, the wall also defining at least one engagement portion (11b) cooperable with an insertion end portion (10a) of the coil spring (10) to captively retain the coil spring (10) in contact with the terminal (11), the insertion end portion (10a) comprising a pair of diammetrically opposed radial projection portions (10b) operatively engageable with the engagement portion (11b), characterised in that the engagement portion (11b) comprises at least one hole, through which hole the coil spring (10) may be seen from the exterior of the terminal (11). A coil spring engagement construction as claimed in Claim 1, wherein the insertion end portion (10a) of the coil spring (10) is substantially oval about the helical axis of the coil spring (10), the major axis (d1) of the oval being greater than the external diameter of the remainder of the coil spring (10) and the minor axis (d2) of the oval being equal to the external diameter of the remainder of the coil spring (10). A coil spring engagement construction as claimed in Claim 1 or Claim 2, wherein the engagement portion (11b) comprises two diammetrically opposed holes cooperable with the insertion end portion (10a) of the coil spring (10). A coil spring engagement construction as claimed in any of claims 1 to 3 characterised in that the holes are circular. A coil spring engagement construction as claimed in any of claims 1 to 3 characterised in that the holes are diamond shaped. A coil spring engagement construction as claimed in any of claims 1 to 3 characterised in that the holes are slit shaped. A method of assembling a coil spring engagement construction for a high tension terminal of an engine ignition apparatus comprising a terminal (11) having a cylindrical wall defining an insertion chamber (11a) for receiving a coil spring (10) therein and defining an engagement portion (11b) cooperable with an insertion end portion (10a) of the coil spring (10) to captively retain the coil spring (10) in contact with the terminal (11), the insertion end portion (10a) having a pair of diammetrically opposed projection portions (10b) operatively engageable with the engagement portion (11b), the method comprising the steps of tilting the insertion end portion (10a) to reduce the external diameter of the insertion end portion (10a), inserting the insertion end portion (10a) into the insertion chamber (11a) and allowing the insertion end portion (10a) to relax into a captive position with the projection portions (10b) engaged in the engagement portion (11b).

Inventors: IMANISHI HISAO, NAKAJIMA KEIICHI, IMANISHI, HISAO, NAKAJIMA, KEIICHI, Imanishi, Hisao, c/o Sumitomo Wiring Systems, Ltd., Nakajima, Keiichi, c/o Sumitomo Wiring Syst. Ltd.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1993
Main classification: H01T13
IPC codes: H01T13, H01R13, H01R4