GB2162379A

GB2162379A - Electrical connector for a spark plug stem

Info

Publication number: GB2162379A
Application number: GB8513433A
Authority: GB
Inventors: A D Jeffery; N Mitchener
Original assignee: AMP Inc
Current assignee: TE Connectivity Corp
Priority date: 1984-07-27
Filing date: 1985-05-28
Publication date: 1986-01-29
Also published as: GB8513433D0; GB8419179D0; GB2162379B

Abstract

The connector comprises an insulating housing (4) and an electrical terminal (10) slidably received therein and having a crimping ferrule (22) for connection to an ignition cable (C), and a receptacle (24) for mating with a spark plug stem (S). A spring arm (36) projecting from the terminal (10) has a stem (S) engaging surface (44) which is pressed against the stem (S) by a ramp (56) in the housing (4) which acts against the arm (36) when the terminal (10) is pushed inwardly of the housing (4) by engagement with the ceramic insulator (1) of the spark plug, thereby to secure the terminal (10) to the stem (S). The surface (44) can be released from the stem (S) by pulling the housing (4) in a direction away from the spark plug. <IMAGE>

Description

SPECIFICATION Electrical connector and an electrical terminal for mating with a spark plug stem Electrical connectors for mating with a spark plug stem usually comprise an electrical terminal having a connecting portion for connection to an ignition cable so as to make electrical connection to the conductor of the cable and a receptacle formed integrally with the connecting portion, for receiving the spark plug stem.

Although it is known to provide the receptacle with internal teeth for engaging the spark plug stem, such teeth and the stem are subject to considerable wear as a result of the receptacle being repeatedly mated with, and disengaged from, a spark plug stem. Since the connection between the receptacle and the stem will, in practice, be subjected to considerable vibration when the engine served by the spark plug is in use, and since the cable may be accidentally pulled, for example when the engine is being serviced, it is important that the receptacle should be securely attached to the spark plug stem when it has been mated therewith.

According to one aspect of the present invention, an eiectrical connector for mating with a spark plug stem comprises a tubular insulating housing and an electrical terminal therein having a portion for connection to an ignition cable so as to make electrical connection with the conductor of the cable and a receptacle for receiving the spark plug stem, a spring arm projecting from the terminal into the housing, having a plug stem engaging surface in register with an opening in the wall of the receptacle, the terminal being slidable in the housing by engagement with the spark plug stem, to cause the spring arm to engage a cam surface in the housing and the stem engaging surface of the spring arm to be forced against the spark plug stem, the stem engaging surface of the spring arm being readily retractable from the spark plug stem by pulling the housing in a direction away from the spark plug.

Since the plug stem engaging surface of the spring arm exerts a positive pressure against the spark plug stem, the connection between the receptacle and the spark plug stem is restrained from relaxation by reason of vibration. Also, the receptacle pulled from the spark plug stem only by exerting a substantial pulling force on the ignition cable.

According to another aspect of the invention, an electrical terminal for mating with a spark plug stem comprises a portion for connection to an ignition cable so as to make electrical connection with the conductor of the cable, and a receptacle formed integrally with the connecting portion, for receiving the spark plug stem through an end of the receptacle remote from the connecting portion, a spring arm projecting from the terminal, having a spark plug stem engaging surface positioned in register with an opening in the receptacle, the receptacle having an internal rib opposite to the stem engaging surface, for engaging between screw threads on the spark plug stem.

For a better understanding of the invention, reference will now be made by way of example to the accompanying drawings in which: FIGURE 1 is a perspective view of an electrical connector for mating with a spark plug stem; FIGURE 2 is an exploded perspective view of the connector; FIGURES 3 and 4 are longitudinal sectional views of the connector illustrating the manner in which it is mated with a spark plug stem; and FIGURES 5 and 6 are enlarged views of details of Figures 3 and 4 respectively.

As best seen in Figures 1 and 2, the connector, which is generally referenced 2, comprises an insulating housing 4 in the form of a tube which is open at both ends, an electrical terminal 10 which is received in the housing as shown in Figures 3 and 4, a spring cam member 1 2 which is also received in the housing, and a tubular, expansible insulator sleeve 1 5 made of rubber or a rubber-like material.

The housing 4 comprises an enlarged portion 6 and a reduced cross section portion 8.

At a position back from its spark plug stem receiving end 14, the portion 6 of the housing is formed with an internal stop rib 1 6 as best seen in Figures 3 and 4 near the junction between the portions 6 and 8 of the housing 4. The side of the portion 6 opposite to that on which the rib 1 6 is formed defines a channel 1 8 for receiving the spring cam member 12, each sidewall of the channel 1 8 being formed with a through opening 20 (only one of which is shown) to allow latching of the cam member 1 2 in the channel 1 8.

The terminal 10 comprises a crimping ferrule 22 which, as shown in Figures 3 and 4, can be crimped about an ignition cable C so that an insulation piercing lance 23 struck inwardly of the ferrule 22 makes eiectrical contact with the conductor C1 of the cable C.

Formed integrally with the ferrule 22 is a substantially semi-circular cross-section tubular receptacle 24 for receiving a screwthreaded spark plug stem S extending from the ceramic insulator I of a spark plug. The upper part (as seen in Figures 2 to 4) of the wall of the receptacle 24 has struck out therefrom a stop lance 26 adjacent to which is formed, between the lance 26 and the plug stem receiving end 28 of the receptacle 24, a rib 30 which projects internally of the receptacle as shown in Figures 3 to 6. A divided collar comprising a series of stop projections 32 is radially outstanding from the plug receiving end 28.At a position opposite to the lance 26 and adjacent to the ferrule 22, the receptacle 24 is formed with an arcuate support 34, from which projects, outwardly of the receptacle 24, a cantilever spring arm 36 having a rectilinear part 38 projecting obliquely away from the receptacle 24 and which merges with a bight 40 bowed generally away from the receptacle and being surmounted by a substantially S-shaped spark plug stem engaging portion 42 extending towards the receptacle 24. The portion 42 has adjacent to its free end a spark plug stem engaging surface 44 which is substantially parallel with the longitudinal axis of the terminal 10. The surface 44 is positioned in register with an opening 46 in the lower (as seen in the drawings) part of the wall of the receptacle 24. The opening 46 extends from the end 28 of the receptacle 24 towards the ferrule 22.

The spring member 1 2 (which is best seen in Figure 2) comprises two arms 48 connected by a bight 50 which is sufficiently resilient to allow the arms 48 to be pressed towards one another, each arm 48 being provided in the vicinity of its free end with a latch member 54 projecting laterally outwardly of the arm 48. On its upper (as seen in Figure 2) surface, each arm 48 has a camming ramp 56 which merges in the direction of the bight 50, with a thicker portion 58 of the arm 48, and towards the free end 52 of the arm 48, with a thinner portion 60 of the arm 48. Outwardly of the ramp 56, each arm 48 is formed with a longitudinal guide rib 62.

In order to assemble the connector for use, the spring member 1 2 is inserted, with the bight 50 leading, into the channel 1 8 of the housing portion 6 until the latching members 54 of the arms 48 engage in the openings 20 in the sides of the channel 18, the arms 48 having initially been pressed towards one another against the spring action of the bight 50 to allow the insertion of the spring member 1 2 into the channel 18. The insulator sleeve 1 5 is then threaded onto the cable C so as to lie a substantial distance back from the cable end, after which the cable end is threaded through the housing 4 to an extent sufficient to allow the terminal 10 to be crimped to the cable end.After the terminal 10 has been crimped to the cable end, the cable C is withdrawn to insert the terminal 10 into the housing 4, whereby the lance 26 is depressed by the rib 16 and thereafter resiles to as to latch behind the rib 1 6 as shown in Figure 3, the spring arm 36 being guided between the ribs 62 on the cam member 1 2.

The insulator sleeve 1 5 is then mated with the portion 8 of the housing 4, and is thereafter restrained from axial movement relative thereto by means of a circular rib 64 on the portion 8.

In use, the connector is pushed home over the ceramic insulator 1 of the spark plug so that the spark plug stem S is received in the receptacle 24 of the terminal 10 (Figures 3 and 5), the projections 32 on the terminal 10 engaging the insulator so that the terminal 10 is caused to slide inwardly of the housing until the projections 32 finally engage the rib 16 (Figures 4 and 6). During the sliding movement of the terminal 10, the spring arm 36 rides up the cam surfaces 56 of the spring member 12, whereby the surface 44 of the arm 36 is driven against the spark plug stem S so that the stem is gripped between the surface 44 and the rib 30, the latter entering between screw threads of the stem S, whereby the connector is firmly secured to the stem S. If the cable C is pulied, the housing 4 maintains its position relative to the terminal 10. However, if the pulling force is sufficiently increased, the stem S is forced to ride away from the rib 30 but meets increasing resistance from the compressed spring arm 36, until the pulling force is great enough to cause the stem S to be pulled away from the terminal 1 0. Nevertheless, said resistance should be sufficient to counteract normal accidental pulling forces exerted on the cable C.

In order to withdraw the connector correctly and readily from the spark plug stem, the housing is pulled in a direction away therefrom so that the arm 36 rides down the cam surfaces 56, thereby retracting the surface 44 from the spark plug stem, whereafter the connector can be pulled from the stem. As shown in Figure 5, the rib 30 does not engage between the threads of the stem in the retracted condition of the surface 44.

Claims

1. An electrical connector for mating with a spark plug stem and comprising an insulating housing and an electrical terminal therein having a portion for connection to an ignition cable so as to make electrical connection with the conductor of the cable, and a receptacle for receiving the spark plug stem, a spring arm projecting from the terminal into the housing having a spark plug stem engaging surface positioned in register with an opening in the wall of the receptacle, the terminal being slidable in the housing by engagement with the spark plug, to cause the spring arm to engage a cam surface in the housing, and the stem engaging surface of the spring arm thereby to be forced against the spark plug stem, the stem engaging surface of the spring arm being readily retractable from the spark plug stem by pulling the housing in a direction away from the spark plug.

2. An electrical connector according to claim 1, in which the receptacle has an internal projection positioned opposite to the spring arm, for engagement between screw threads on the spark plug stem when the stem engaging surface has been forced against the spring arm.

3. A connector according to claim 1 or 2, in which the terminal is slidable in the housing to an extent limited by stop surfaces on the terminal and the housing.

4. A connector according to claim 1, 2 or 3, in which the opening is in the form of a slot extending from the spark plug receiving end of the receptacle towards the connecting portion.

5. A connector according to any one of the preceding claims, in which the cam surface is provided on a spring member which is resiliently received in a channel in the housing and is latched thereto.

6. An electrical connector according to claim 5, in which the spring member comprises a pair of arms connected by a resilient bight, each arm having thereon a latching member which is received in an opening in a wall of the channel, and a longitudinal guide rib for guiding the spring arm, as the terminal is inserted into the housing during assembly of the connector.

7. An electrical terminal for mating with a spark plug stem and comprising a portion for connection to an ignition cable so as to make electrical connection with the conductor of the cable, and a receptacle formed integrally with the connecting portion, for receiving the spark plug stem through an end of the receptacle remote from the connecting portion, a spring arm projecting from the terminal, having a spark plug stem engaging surface positioned in register with an opening in the receptacle, the receptacle having an internal rib opposite to the stem engaging surface, for engaging between screw threads on the spark plug stem.

8. A terminal according to claim 7, in which the spring arm has a first part projecting obliquely away from the receptacle adjacent to the connecting portion and merging with a bight which is bowed generally outwardly of the receptacle and is surmounted by a portion extending towards the receptacle and on which the stem engaging surface is provided.

9. A terminal according to claim 7 or 8, in which the plug stem receiving end of the receptacle is provided with a series of radial projections, a lance extending outwardly of the receptacle at a position spaced from the projections in the direction of the connecting portion, having its free end directed towards the projections.

10. A terminal according to claim 7, 8 or 9, in which the receptacle is of substantially semicircular cross-section, the opening therein being in the form of a slot extending from the stem receiving end of the receptacle towards the connecting portion.

11. An electrical connector for mating with a spark plug stem, substantially as hereinbefore described with reference to the accompanying drawings.

1 2. An electrical terminal for mating with a spark plug stem, substantially as hereinbefore described with reference to the accompanying drawings.