Low extraction force connector interface

A male connector interface which requires a low extraction force to remove the male interface from a mating female connector interface. The male connector interface has a tubular housing with an inner surface with a first inner diameter region having an inner diameter and an increased inner diameter region having a first end disposed directly adjacent the first inner diameter region and extending to the distal end of the housing for an axial length, wherein the first inner diameter region and the first end of the increased inner diameter region define a shoulder facing the distal end of the housing, and the increased inner diameter region has a first tapered portion disposed at the first end and increasing in diameter toward the distal end, the first tapered portion defining a first frustoconical portion of the longitudinal bore.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to push-on Radio Frequency (RF) coaxial connectors, and more particularly to a male RF coaxial push-on connector used for mating with female RF coaxial push-on connectors.

2. Technical Background

Coaxial cable and coaxial cable connectors are often used for transmitting radio-frequency (RF) signals. Examples of standard RF push-on connector interfaces can be found in MIL-STD-348 under SMP and SMPM series interfaces. Typically, male and female push-on connector interfaces are constructed to matingly engage a male and a female with a secure physical connection and a reliable electrical connection.

As illustrated inFIG. 1, to test a device10having one or more male smooth bore connector interfaces, such as inFIG. 4, with blind mate connectors14having female connector interfaces12or so-called female-female bullets, a test connector16is provided with a male connector interface (not shown) to engage a corresponding female connector interface12. Coaxial cables18are connected to the test connector16and terminate in the male connector interface which is exposed externally on a surface19that is capable of engaging the device under test10. One end of a representative connector14with a known female interface12is schematically illustrated inFIG. 2as having a tubular outer housing20comprising a tubular body22and a plurality of fingers24that extend from the tubular body to a leading end26, and a center terminal28disposed within the longitudinal bore30of the outer housing20and adapted to receive a central terminal of a male connector interface.

Referring again toFIG. 1, a plurality of male connector interfaces, such as shown inFIG. 4, with blind mate connectors14is provided on the device under test10. The test connector16and the device10are brought together to engage the male and female interfaces. At the conclusion of testing, the test connector16and device10are moved apart. For known interfaces, even for interfaces which are not mutually locking, the male interface of the device under test10and the blind mate connectors14of the device under test10may not disengage from each other when the test connector16and device10are moved apart after electrical testing is completed, due to the snug fit between the male and female interfaces.FIG. 3shows the undesirable condition of three blind mate connectors14disengaged from the device under test10at the conclusion of testing. In some situations, all of the blind mate connectors could become dislodged from the device under test. This undesirable situation can be exacerbated during rapid testing or automated testing. The situation can occur even for male connector interfaces with a smooth bore, such as the known SMPM male smooth bore interface1found on page 328.3 of MIL-STD-348, a portion of which is reproduced inFIG. 4. Increasing the diameter of the smooth bore of the male connector interface to create less spring finger deflection and therefore less force and less friction when the connectors are mated and unmated does not entirely address this issue, because sufficient electrical connection must also be maintained between the interfaces during testing.

SUMMARY OF THE INVENTION

A male connector interface is disclosed herein which requires a low extraction force to remove the male interface from a mating female connector interface. The male connector interface has a tubular housing with an inner surface with a first inner diameter region having an inner diameter and an increased inner diameter region having a first end disposed directly adjacent the first inner diameter region and extending to the distal end of the housing for an axial length, wherein the first inner diameter region and the first end of the increased inner diameter region define a shoulder facing the distal end of the housing, and the increased inner diameter region has a first tapered portion disposed at the first end and increasing in diameter toward the distal end, the first tapered portion defining a first frustoconical portion of the longitudinal bore. The combination of the male connector interface and a female connector interface is also disclosed, as well as a method for testing a device utilizing the interfaces.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5illustrates one preferred embodiment of a male connector interface80of the present invention which, in the present example, forms part of a connector90which also has a female interface92opposite to the male interface.FIG. 6illustrates a preferred embodiment of a male connector interface100of the present invention in mating engagement with a female connector interface.

Referring toFIG. 6, the male connector interface100comprises a tubular housing102comprising an inner surface104that defines a longitudinal bore106along a longitudinal axis of the housing102. In this embodiment, the bore106is a through-bore, although in other embodiments the bore may not pass all the way through the body. The housing102has a distal end108. The housing102is made from an electrically conductive material, preferably metal, and serves as an outer conductor. In preferred embodiments, the housing102is made from brass, copper, kovar, or stainless steel. A central terminal110is disposed within the longitudinal bore106of the housing102. The central terminal110is made from an electrically conductive material, preferably metal, and serves as an inner conductor. In preferred embodiments, the central terminal110is made from brass, copper, kovar, or stainless steel. A dielectric support member112is disposed on the inner surface of the housing and holds the central terminal110within the longitudinal bore106and away from the inner surface104of the housing102, such that the central terminal110does not contact (directly contact) the inner surface104of the housing102. The support member112is made from an electrically nonconductive material, such as ptfe (Teflon®) or glass such as Corning 7070 glass. The inner surface104of the housing102comprises a first inner diameter region120having an inner diameter D1, and an increased inner diameter region130having a first end132disposed directly adjacent the first inner diameter region120and extending to the distal end108of the housing102for an axial distance L1. The first end132has an inner diameter D2, and D2>D1. The first inner diameter region120and the first end132of the increased inner diameter region130define a step or a shoulder134facing the distal end108of the housing102. The increased inner diameter region130comprises a first tapered portion140disposed at the first end132, and extending from the first end132for an axial distance L2, and having increasing inner diameters within the axial distance L2with increasing longitudinal distance away from the first end132. Preferably, the shoulder134is substantially orthogonal to the longitudinal axis, even more preferably the shoulder134is perpendicular to the longitudinal axis. The first tapered portion140defines a first generally frustoconical bore portion141of the longitudinal bore106. Preferably, the first tapered portion140has a monotonically increasing inner diameter with axial length in the direction of the distal end108. In other embodiments, the tapered portion140has a series of minute steps, such as steps that have a depth smaller than the depth of the shoulder134.

Preferably, 0.1≦L2/L1≦1.0. In some preferred embodiments, 0.2≦L2/L1≦0.8. In other preferred embodiments, 0.3≦L2/L1≦0.7. In the preferred embodiment illustrated inFIG. 6, L2/L1is about 0.5. In some embodiments, the first tapered portion140extends all the way to distal end108.

The increased inner diameter region130here also comprises an optional second tapered portion150extending axially for a length L3.

The ratio L3/L1is greater than or equal to 0 and less than (1−L2/L1). In some preferred embodiments, 0.2≦L3/L1≦0.8. In other preferred embodiments, 0.3≦L3/L1<0.6. In the preferred embodiment illustrated inFIG. 6, L3/L1is about 0.4, and L4/L1is about 0.1.

The first tapered portion140is disposed directly adjacent to and extending away from the shoulder134. The first tapered portion140defines a first acute angle α1with the longitudinal axis. Preferably 0.5°≦α1≦30°, more preferably 1°≦α1≦25°, even more preferably 2°≦α1≦10°. In the embodiment ofFIG. 6, α1is about 6°. The second tapered portion150defines a second acute angle α2with the longitudinal axis, wherein α2>α1. Preferably α1≦α2≦45°, more preferably α1≦α2≦30°. In the embodiment ofFIG. 6, α2is about 16°. The second tapered portion150is disposed between the first tapered portion140and the distal end108. The increased diameter region130further comprises an optional third inner surface section having a substantially constant diameter D3, and D3>D2>D1. The increased diameter region130further comprises an optional chamfered inner surface section160disposed at the distal end108of the housing102.

FIG. 6illustrates a combination of one preferred embodiment of a male connector interface100and a mating female connector interface200, the female connector interface comprising a tubular outer housing202comprising an inner surface204defining a longitudinal bore206, preferably a throughbore, along a longitudinal axis of the outer housing202. The outer housing202comprises a tubular body203and a plurality of fingers209that extend from the tubular body203to a leading end208. A center terminal210is disposed within the longitudinal bore206of the outer housing202and adapted to receive the central terminal110of the male connector interface100. The outer housing202and the center terminal210are made from electrically conductive material, preferably metal, such as brass, copper, kovar, or stainless steel. A dielectric support member212is disposed on the inner surface204of the outer housing202and holds the center terminal210within the longitudinal bore206and away from the inner surface204of the outer housing202, wherein the center terminal210does not contact (directly contact) the inner surface204of the outer housing202. The support member210is made from an electrically nonconductive material, such as ptfe (Teflon®) or glass such as Corning 7070 glass. The increased inner diameter region130of the male connector interface100is adapted to receive the plurality of fingers209. Each of the plurality of fingers209has a protrusion211disposed at or near the leading end208. The protrusion211may comprise a chamfered or frustoconical outer surface portion as illustrated inFIG. 6, or the protrusion may have a more bulbous or spherical contour. The protrusion211has an outer surface that mates with at least part of the first tapered portion140of the male connector interface100. The contour of at least part of the protrusion211and the contour of the first tapered portion140preferably match. Preferably, the protrusion211contacts the first tapered portion140when the male and female connector interfaces are fully mated together. Alternatively, or in addition, the leading end208of the tubular outer housing202contacts the shoulder134when the male and female connector interfaces are fully mated together. For some embodiments, I have found that the leading end of the tubular outer housing could be spaced away from the shoulder by a small axial gap. Even more preferably, the protrusion contacts both the tapered portion, and the leading end of the tubular outer housing contacts the shoulder, when the male and female connector interfaces are fully mated together, as shown inFIG. 6.

In use, a first body (such as a connector) which comprises a male connector interface and a second body (such as another connector) which comprises a female connector interface capable of mating with the male connector interface and moved into mutual engagement. The first body and/or the second body could have a cable mounted opposite its respective interface, or the side opposite to the interface could be configured to attach to a PCB board, a metal panel, a wave guide, or other components. The body (or connector) could comprise two interfaces to form an adapter. The plurality of fingers209of the outer housing202of the female interface200are guided into engagement with the increased inner diameter region130of the male interface100, and the male central terminal110of the male interface is guided into engagement with the female center terminal210of the female interface. In some preferred embodiments, the female center terminal210comprises radially inwardly biased flexible fingers229that form a socket that receives the central terminal110of the male interface100. The fingers229are spread apart by the entry of the central terminal110to allow a snug but releasable physical fit while allowing a good electrical contact to be established therebetween. In some preferred embodiments, the plurality of fingers209of the outer housing202of the female interface200are spread radially outward and are disposed at an angle with respect to the longitudinal axis prior to engagement in a freestanding state, and then engagement between the male100and female200interfaces, and in particular engagement between the protrusions of the fingers209and the increased inner diameter region130of the male interface, causes the fingers209to deflect radially inwardly. Preferably, the increased inner diameter region130and the plurality of fingers209are mutually adapted to allow the inner surfaces of the plurality of fingers209to lie parallel to or at a precise acute angle to an outer surface of the center terminal210when the male and female connector interfaces are fully mated together, as illustrated inFIG. 6.

Referring toFIG. 7, the present invention relates to a method of testing a device-under-test with a test connector comprising the male connector interface of the present invention. The device under test has coaxial connectors each with a male connector interface with a blind mate connector pre-installed. A mating male connector interface for each of the female interfaces is adapted to mate with respective female connector interfaces. For illustration purposes, only one of the male interfaces is shown by cutaway of the test connector. The method comprises the sequential steps of moving the test connector toward the device under test to engage the male connector interface with the female connector interface such that the device under test and the test connector are electrically connected to each other, transmitting test information through the male connector interface and female connector interface, and moving the test connector away from the device under test such that the device under test and the test connector are electrically disconnected from each other, wherein the blind mate connector is disengaged from the male connector interface. The male and female interfaces are temporarily brought together with a sufficient axial force, but the interfaces are easily separable upon termination of the axial force.FIG. 7schematically represents both the “before engagement and testing” and “after testing and disengagement”, wherein all of the connectors that were initially installed on the device under test also remained on the device under test after conclusion of the test. The non-sticking engagement between the male and female interfaces is provided by the male interface of the present invention.

The present invention also relates to a test interface apparatus for interconnecting a device under test with an analyzer and supply for testing the device (which could include one or cables), the device comprising a female connector interface, the apparatus comprising a test structure having an interface surface adapted to receive the device under test and having the male connector interface of the present invention, wherein the male connector interface is adapted to engage the female interface.

The male connector interface of the present invention is particularly suited for testing purposes because it provides a non-locking, temporary connection between male and female interfaces to allow a good physical and electrical contact during a test wherein a sufficient axial force is applied to engage the male and female interfaces, but which also allows rapid and easy disengagement of the male and female interfaces upon removal of that axial force. Thus, the male connector interface is easily separable from the female connector interface upon termination of the axial force that keeps the male and female interfaces in mutual engagement during testing.