Abstract:
There is provided a cable connector ( 10 ) comprising a body ( 12 ) joined to a connector ring ( 14 ) tor securing to a female connector ( 20 ), wherein a seal ( 26 ) is placed between the body ( 12 ) and the connector ring ( 14 ). The use of the seal or gasket ( 26 ) prevents electromagnetic leakage from and into the connector. The connector ring can be provided with an inner recess ( 28 ) housing a ring spring ( 30 ) so as to grip a female connector tightly and prevent electromagnetic leakage where the connector mounts to the female connector.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a cable connector such as is used to mount a cable onto a female connector associated with a device. 
       BACKGROUND TO THE INVENTION 
       [0002]    Cable connectors are joined to the end of cables so that the cable can engage with a connector on an electrical device. Normally a male connector is secured to the cable, with a female connector on the device. To mount the cable to the device, the male connector is screwed or pushed onto the female connector. With screw connectors, it is very important that the male connector is screwed with the correct torque to the female connector as otherwise the connection is not sufficiently secure to prevent electromagnetic signals leaking from the device or external signals entering the device and introducing noise into the electrical system. Even if the male connector is screwed into position correctly with no electromagnetic leakage occurring, over time a connector will slowly loosen due to the different thermal conductivity of materials used, vibrations, cold flow and the like. Thus over time the connector is likely to leak or receive electromagnetic radiation. 
       SUMMARY OF THE INVENTION 
       [0003]    In accordance with the first aspect of the present invention, there is provided a cable connector comprising a body formed with a central channel and joined to a connector ring for securing to a female connector, wherein a sealing means is positioned between adjoining faces of the body and connector, the faces of the body and the connector being substantially perpendicular to a longitudinal axis of the body. The use of the sealing means or gasket reduces electromagnetic leakage from and into the connector. 
         [0004]    Preferably the connector ring has an internal thread, such that the connector is of a screw type. 
         [0005]    The sealing means may be deformable to fill any space between the body and connector ring. 
         [0006]    Preferably the sealing means acts to urge the connector ring away from the body whilst remaining in permanent contact with both the body and the connector ring. 
         [0007]    Typically the body and connector ring are substantially cylindrical and thus the sealing means is preferably annular so as to completely surround a region where the body and connector ring adjoin. The sealing means may be a rubber o-ring or a metal gasket. 
         [0008]    Desirably the annular sealing means has a greater internal diameter than the central channel of the body, such that the sealing means is external to the internal channel. 
         [0009]    The connector may further comprise a resilient member surrounding an internal metal collar positioned within the central channel of the body. The resilient member may comprise an electrically conductive ring spring. 
         [0010]    In accordance with second aspect of the invention, there is provided a cable connector comprising a body joined to a connector ring for securing to a female connector, wherein the connector ring comprises at least one resilient member. As a female connector is screwed into the connector ring, the at least one resilient member urges against the female connector and when the female connector is fully inserted, the resilient member firmly grips the female connector such that leakage of electromagnetic signals is prevented. The resilient member also has the advantage of absorbing vibrations and so ensures the connector stays firmly connected for longer. 
         [0011]    In accordance with a third aspect of the present invention, there is provided a cable connector comprising a body joined to a connector ring for securing to a female connector, wherein a sealing means is placed between the body and connector ring and the connector ring is formed with an inner recess means in which at least one resilient member is seated. 
         [0012]    For all aspects, the resilient member is preferably an electrically conductive resilient material which is substantially annular in shape, such as a ring spring, gasket or equivalent such as resilient plastics material loaded with conductive particles, resilient metal materials or similar resilient materials that can be formed into an annulus or toroid. 
         [0013]    For the second and third aspects, the recess means may be in the form of a circumferential groove with the resilient member having a co-operating annular shape so as to locate securely in the recess means. 
     
    
     
         [0014]    The invention will now be described, by way of example, with reference to the following drawings: 
           [0015]      FIG. 1  shows a section through a cable connector in accordance with a first aspect of the invention; 
           [0016]      FIG. 2  shows a section through a cable connector in accordance with a second embodiment; 
           [0017]      FIG. 3  shows a section through a cable connector in accordance with a third embodiment; 
           [0018]      FIG. 4  shows a section through a cable connector in accordance with a fourth embodiment; 
           [0019]      FIG. 5  shows a section through a cable connector in accordance with a fifth embodiment; 
           [0020]      FIG. 6  shows a graph illustrating signal leakage for a prior art connector; and 
           [0021]      FIG. 7  shows a graph illustrating signal leakage for a connector in accordance with the present invention. 
       
    
    
     DESCRIPTION 
       [0022]      FIG. 1  is a section through a cylindrical cable connector  10  comprising body  12  secured by metal collar  13  and post plate  13 ′ to connector ring or rotating nut  14 . Connector ring  14  is formed with an internal screw thread  16  for receiving female connector  20  which has a co-operating thread. Body  12  is hollow with an internal channel  21  which receives coaxial cable  22  with central conductive core  24 . The coaxial cable  22  is shown to indicate how the male connector  10  secures such a cable. 
         [0023]    Adjoining faces of body  12  and nut  14  are substantially perpendicular to the longitudinal central axis of body  12  and positioned between these faces is a seal or gasket  26  made of a resilient electrically insulating material such as rubber. The gasket is toroidal, for example a ring, and has a similar annular diameter, to the cross section or wall thickness of hollow body  12 , such that the gasket does not extend into the internal channel  21 . The cross section of material forming the o-ring  26  is typically around 0.5 mm. Due to its resilience, seal  26  urges the nut  14  against post plate  13 ′. The o-ring  26  applies an equal pressure to the nut  14  where the two adjoin and so the nut  14  is always pushed equally to the post plate  13 ′. Thus the nut  14  sits square to the post plate  13 ′ and the adjoining surfaces of the nut  14  and post plate  13 ′ are pushed together with no air gap between the adjoining surfaces. This has the effect of preventing or substantially reducing electromagnetic leakage at the back end of the male connector  10  and gives 90 dB screening up to 1 GHz. 
         [0024]      FIG. 2  shows a second embodiment of the present invention where o-ring  26 ′ is used in combination with ring spring  29  to close the gap between spinning nut  14 ′ and body  12  which as shown in  FIG. 1  typically includes retaining member  13 ″ equivalent to collar  13  and post plate  13 ′. In this arrangement, o-ring  26 ′ has a reduced cross section when compared to o-ring  26  which makes it easier to manually tighten spinning nut  14 ′ with respect to body  12 . However the reduction in cross sectional diameter of the o-ring reduces the effectiveness of sealing in relation to electromagnetic leakage at the back end of the connector when compared to the version shown in  FIG. 1 . Thus in the second embodiment, an internal ring spring  29  is located around collar and post plate  13 ″ and in combination, o-ring  26 ′ and ring spring  29  act to prevent leakage or ingress of electromagnetic signals into the back end of the connector. The ring spring is typically made from a conductive material, such as metal, and in particular copper. 
         [0025]    In a third embodiment of the present invention as shown in  FIG. 3 , connector ring  14  is formed with an internal annular recess  28  within which sits electrically conductive resilient ring spring  30 . The annular ring spring  30  grips female connector  20  as it is screwed into connector ring  14  and when female connector  20  is fully engaged, spring  30  pushes radially inwards towards female connector  20  to grip it tightly. This tight connection ensures that no air gap exists between the connector  20  and ring  14  and prevents leakage as long as the female connector is partially mounted within the male connector. Signal leakage is prevented at this front end of the male connector  10  even after female connector  20  has been loosened by two full turns. Spring  30  is also of advantage as it absorbs vibrations and so reduces the loosening effect these vibrations have on connector  20 , so ensuring that connector  20  remains in a electromagnetic leak free position for longer. 
         [0026]    A fourth embodiment of the dimension is shown in  FIG. 4 , where all features of the invention as disclosed in relation to  FIGS. 1 and 3  are combined in a single connector, in particular rubber o-ring  26  and ring spring  30 . A fifth embodiment is shown in  FIG. 5  where the features of the second and third embodiments are combined. 
         [0027]    The connectors of the present invention are all able to meet Class A screening requirements even when the female connector has been substantially loosened with respect to the nut  14 . 
         [0028]    The improvements with regard to signal leakage can be demonstrated by comparing with a known prior art connector, see  FIGS. 6 and 7 .  FIG. 6  shows a graph comparing signal leakage or noise over a frequency range of 5 MHz to 1 GHz for a prior art connector as it is loosened. The different traces represent the connector tightened to 4 Newton Meter, trace  32 , loosened by 10 degrees, trace  34 , loosened by 20 degrees, trace  36 , and loosened by 30 degrees, trace  38 . Solid stepped line  40  represents acceptable signal leakage levels at given frequencies and represents the characteristics required of a connector classified as a Class A connector. This prior art connector is similar to that disclosed in EP 1207586 and includes an internal o-ring positioned between a seal nut and collar. 
         [0029]    As will be seen from  FIG. 6 , as the prior art connector is loosened with respect to a cable mounted within it signal leakage increases to be in excess of the Class A requirement when the connector is loosed by at least 20 degrees. 
         [0030]    In contrast, the signal leakage of a connector in accordance with the second and third embodiment of the present invention, and as seen in  FIG. 4 , is shown in  FIG. 7  with trace  42  showing the signal leakage characteristics for such a connector when hand tightened and trace  44  showing the characteristics when completely loose by two turns. Even when the connector is completely loosened by two full turns, the signal leakage characteristics are still compliant with the requirements needed for a connector classified as a Class A connector. With a connector according to the present invention, the signal leakage characteristics are very similar from 10 degrees loosened to completely loose at two turns loose.