A conventional jack plug comprises an elongate member divided into several axially spaced electrical conductors separated by insulators. A jack plug of this type is designed to be received in a socket which comprises a number of axially spaced spring biased contacts which establish electrical connection with the axially spaced conductors of an inserted jack plug. A problem exists in that the jack plug can snag on the interior of the socket during withdrawal, leading to undesirable excessive stress on the jack plug. A further problem exists in that if an off-axis force is used to withdraw the jack plug from the socket then the tip of the jack plug will engage the side wall of the socket and the jack plug will attempt to pivot about the opening of the socket and this causes undesirable bending stresses on the jack plug. The present invention attempts to ameliorate these problems.

According to a first aspect, the present invention consists in an electrical connector comprising a series of conductive sections axially spaced apart along its length and adapted to engage respective contacts of a socket into which the connector can be inserted, each conductive section having a maximum radial dimension, and the maximum radial dimension of successive conductive sections along the length of the connector towards its tip being of progressively decreasing radial dimensions.

According to a second aspect, the present invention consists in a socket for a jack plug, the socket containing electrical contacts for establishing a connection to a jack plug, the radial dimension of the socket decreasing from the insertion end of the socket that receives the jack plug.

The decreasing radial dimensions of the connector or socket creates an increasing clearance between the tip of the connector and the socket as the connector is withdrawn. This reduces the likelihood of the inserted connector snagging the interior of the socket on withdrawal. The increasing clearance with withdrawal also provides a reduction in the bending stress experienced by the connector when it is being withdrawn in an off axis manner such that the connector pivots about the opening of the socket and the tip contacts the side of the socket.

Preferably, the electrical connector comprises a tip section and a series of substantially cylindrical sections. In a preferred embodiment, there are two substantially cylindrical sections. The tip section can comprise a substantially rounded portion which tapers into a reduced waist portion spaced away from the tip. The surface of the tip section is preferably part spherical. The tip section and the substantially cylindrical sections are spaced by insulators.

The socket according to the second aspect of the invention preferably has a diameter which decreases in steps or in a continuous taper. Preferably, the edge of the opening at the insertion end of the socket is rounded so that an inserted jack plug can pivot around this edge.

Further advantages and features of the invention will become apparent to readers skilled in the art upon consideration of the following description of embodiments of the invention, the embodiments being described by way of example only, and with reference to the accompanying figures, in which: Figure 1 shows a connector according to a first embodiment engaged in a socket; Figure 2 shows a section of the connector of Figure 1 in more detail; Figure 3 shows a socket according to a second embodiment engaging a connector; and Figure 4 shows a connector pivoting about the opening of a socket such that its tip engages the side of the socket.

Figure 1 shows a jack plug 10 comprising a shank portion 12 for insertion in a corresponding socket 11 and a handle portion 14 which remains outside the socket. The portion 12 comprises a tip contact 16 and two cylindrical contacts 18 and 20. These contacts engage spring-loaded contacts 30,32,34 within the socket in order to establish an electrical connection between the socket and the jack plug. The contact portions 16,18 and 20 are separated by insulating portions 22 and 24. The diameters of cylindrical sections 20,24,18 and 22 decrease successively, and the maximum diameter of tip section 16, indicated 26, is smaller than the diameter of cylindrical section 22. This series of successively reducing diameters means that when the jack plug is withdrawn from the socket, it is less likely to snag upon, or interfere with, the interior surface of the socket or the spring-loaded contact terminals 30,32,34 provided therein.

The series of decreasing diameters can be seen more clearly in Figure 2.

Referring again to Figure 1, the tip section 16 has a waist section, the minimum diameter region of which is indicated 28. When the jack plug is fully inserted in the socket, the spring-loaded contact 30 provided in the socket for engaging the tip section 16 of the jack plug engages the waist section of the jack plug in order to retain the jack plug in the socket.

Figure 3 shows a further embodiment of the invention wherein the jack plug 10 is received in a tapered socket 50. The diameter of the socket decreases with increasing distance from the opening of the socket, and in the embodiment shown, decreases in three steps having successively smaller diameters 52,54 and 56. It will be appreciated that when the jack plug is withdrawn from the socket 50, the increasing diameter of the socket in the withdrawal direction will reduce the chance of the jack plug interfering with, or snagging on, the interior surface of the socket or on the spring-loaded electrical contacts 58,60, and 62 provided therein. This benefit will be produced regardless of whether the jack plug 10 is of the type shown in Figure 1. It will be appreciated that an ordinary jack plug having a shank of uniform diameter would still receive the benefit provided by the socket.

The interior surface of the socket need not be continuous. For example, the space providing the bore of the socket could be defined by a series of circumferentially spaced guide members which extend in the longitudinal direction of the bore or by a series of axially spaced toroidal members arranged about the axis of the bore.

Figure 4 shows a jack plug 100 being withdrawn from a socket 110 using a force which is not coincident with the axis of the socket. It will be appreciated that such a withdrawing action results in a net force F in a direction transverse to the longitudinal access of the jack plug. Therefore, the jack plug will tend to pivot about the opening 112 of the socket such that the tip portion of the jack plug contacts the interior surface of the socket at 114. In this condition, there are undesirable bending stresses on the jack plug.

It will be apparent that the force F induces a turning moment on the jack plug about pivot point 112 and that, when the tip of the jack plug contacts the side of the socket, the socket wall will exert a force G on the jack plug which produces a moment about the pivot 112 to counteract the moment produced by the force F. It is desirable to reduce the force G to reduce the bending stress on the jack plug.

It will be appreciated that if a jack plug as shown in Figure 1, or a socket as shown in Figure 3 is used, then the transverse separation between the wall of the bore of the socket and the tip section will be increased, which means that the lever existing between points 112 and 114 in Figure 4 is longer (since contact point 114 effectively moves further towards the very tip of the curved tip section), thus reducing the effective bending stress on the jack plug.

Furthermore, it is beneficial if the aperture of the socket is rounded as illustrated in Figures 1 and 3 (shown at 19), since this further increases the length of the aforementioned lever increasing the reduction in the force G necessary to produce the counter moment. It is also beneficial if the tip section of the jack plug has a rounded or continuous or smooth surface to reduce the likelihood of it interfering with the interior surface of the socket or the spring loaded electrical contacts provided therein (particularly in the case of off-axis withdrawal as shown in Figure 4).