Abstract:
A bayonet electrical connector has a spring loaded safety pin for locking the bayonet coupling. The pin projects into a recess, and a sleeve surrounds the part having the recess. The sleeve has a tab which projects into the recess, the sleeve being slidable to make the tab depress the pin against the spring bias of the pin, thereby to enable subsequent disconnection of the bayonet coupling. This design maintains a locking mechanism to prevent accidental decoupling of the bayonet connection, but makes the decoupling process simpler, by using, sliding of the sleeve and twisting to release the bayonet coupling.

Description:
CROSS-REFERENCE 
   This is a Continuation-In-Part of PCT/GB2005/000291 filed 27 Jan. 2005 which designated the US and which claimed priority from British patent application GB 0404280.0 filed 26 Feb. 2004. 

   BACKGROUND OF THE INVENTION 
   This invention relates to electrical connectors, and more particularly to high power safety connectors. 
   The terminals of high current electrical connectors are typically much larger than for domestic electrical connectors, and it can be possible for a person to insert a finger or other object into a socket opening and touch electrically live components within the socket. 
   There are various designs of electrical connector which provide a safety feature, to reduce the risk of live contacts being accessible when the connector is disconnected. 
   U.S. Pat. No. 6,309,231 discloses an electrical connector in which the mating surfaces of the male and female connectors present only insulating components to the user. Furthermore, to separate the male and female parts of the connector, a tool must be used in order to depress a release pin. This provides the advantage that accidental release of the coupling is not easily achieved. 
   For some applications, the need for an additional release tool is appropriate, and may be required for insurance or other purposes. For other applications, the need for a release tool may not be appropriate or required, but the other safety advantages of the connector are still worth while. When a release tool is provided, it will often be mislaid, and users will still attempt to separate the connection, using other implements or using their fingernails. 
   There is therefore a need for an improved release mechanism in this type of electrical connector. 
   SUMMARY OF THE INVENTION 
   According to the invention, there is provided an electrical connector comprising: 
   a male part and a female part; 
   a bayonet coupling between the male part and the female part; 
   a spring-loaded pin projecting from one of the male part and the female part, and a recess in the other of the male part and the female part for receiving the pin, 
   wherein the pin is received in the recess when the bayonet coupling is fully engaged, thereby to limit relative rotation between the male part and the female part and to prevent disconnection of the bayonet coupling while the pin is engaged in the recess, 
   wherein the connector further comprises a sleeve surrounding a portion of the part having the recess, the sleeve having a tab which projects into the recess, the sleeve being slidable to make the tab depress the pin against the spring bias of the pin, thereby to enable subsequent disconnection of the bayonet coupling. 
   This design maintains a locking mechanism to prevent accidental decoupling of the bayonet connection, but makes the decoupling process simpler, by using a sliding and twisting operation rather than needing a specific additional tool. 
   The male part preferably has a connection portion comprising an outer insulating sleeve and an inner conducting sleeve, and wherein a spring-loaded insulating cover is mounted within the inner sleeve, which is biased by the spring to substantially block the open end of the outer sleeve. 
   The contacts are thus inside the sleeve behind the cover, so that no live contacts are exposed when the connector is separated. The inner sleeve defines the electrical connector contact of the male part. 
   The outer insulating sleeve is preferably provided with at least one channel for defining the bayonet coupling. 
   The female part preferably comprises a second outer insulating sleeve and a connector pin housed within the insulator sleeve. This receives the connection portion of the male part, and the connector pin acts to depress the insulating cover. An end of the connector pin, proximate to the open end of the second outer insulating sleeve, is formed from an insulator, so that again no live contacts are exposed by the disconnected female part. 
   The connector pin may also comprise a contact which is radially outwardly spring biased. This presses against the inner sleeve of the male part to define a high current electrical connection. The inner surface of the second outer insulating sleeve preferably comprises at least one projection for defining the bayonet coupling, inn conjunction with the channel of the male part. 
   The sleeve may be releasably connected to the part having the recess, so that the connector can be configured either as a component needing a release tool or as one in which release is simplified. 
   A coupling may be provided between the sleeve and the part having the recess, the coupling comprising a lug in one of the sleeve and the part and a closed channel for receiving the lug in the other of the sleeve and the part. In this way, the sleeve remains attached when the connector parts are separated. 
   The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a known connector in a separated state; 
       FIG. 2  shows the female part of the connector of  FIG. 1  in cross section; 
       FIG. 3  shows the male part of the connector of  FIG. 1  in cross section; 
       FIG. 4  shows the connector of  FIG. 1  in a connected state; 
       FIG. 5  shows the connector of  FIG. 1  in a connected state in cross section; 
       FIG. 6  shows a component of the invention for use with the connector of  FIGS. 1 to 5 ; and 
       FIG. 7  is a cross section of the component of  FIG. 6  in position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Before describing the improved connector of the invention, the operation of the connector of U.S. Pat. No. 6,309,231 will first be described. 
     FIG. 1  shows the power connector assembly of U.S. Pat. No. 6,309,231, generally indicated at  10  in an uncoupled position. 
   The assembly  10  has a male connector  12  and a female connector  14 . The male connector  12  has a body  16  formed from an electrically insulating material, such as plastic. The male connector  12  has a cylindrical male portion  18 , a flange  20  and a rear part  22 . The male connector is for connection to a source of high voltage using a conventional threaded connector  24 . 
   The male connector has an end face  26 , and an insulating engagement pin  28  projects slightly beyond the end face  26  and engages end piece  56  on the female connector when the connector mate. The male portion  18  has two slots  30 , which are used to define a bayonet type coupling with the female connector  14 . 
   The female connector  14  has a cylindrical electrically non-conductive body  40  with a portion  41  having a slot, or recess  42  extending inwardly from an end face  44  of the housing  40 . The female connector  14  is also connected to a source of electrical power. 
   A locking pin  45  projects from a face at the end of the male portion  18 , and as will be described below, this provides a safety locking mechanism. 
     FIG. 2  shows the female connector  14  in cross section. The female connector houses a contact assembly  50  which is pinned to the body  40  using a pin  52  to prevent relative movement. A forward part of the contact assembly  50  includes connector pin  51  with a louver band  54 . The louver band  54  is a single, double or multi-louver spring band depending on the voltage applied. Beyond the louver band  54  is an insulating end piece  56 , so that all exposed parts of the female connector  14  are insulating. 
   The inner surface of the housing  40  has two tabs  57 , which engage with the slot  30  to form the bayonet coupling. As shown in the end view of  FIG. 2 , the tabs  57  are not diametrically opposite, so that there is only one relative angular orientation in which the male and female connectors can be joined. 
     FIG. 3  shows the male connector  12  in cross section. The threaded connector  24  is also pinned to the housing  22  using a pin  60  to prevent relative movement. The engaging pin  28  is biased by a compression spring  62  into the projecting position shown, so that all exposed parts of the male connector are insulating. The engaging pin  28  has a rear shoulder  64  to limit outward movement of the pin  28 . 
   The spring biased engaging pin  28  slides back and forth within the male portion  18  to enable the louver  54  to make electrical connection to the conductive inner sleeve  66  of the male portion  12 . The electrical connection is thus made between the louver  54  and the inner sleeve  66 , by means of the louver spring bands. 
     FIG. 4  shows the connected coupling and  FIG. 5  shows the connected coupling in cross section. 
   To mate the male and female connectors, the tabs  57  are aligned with the slots  30 . The end piece  56  engages with the engaging pin  28  which is depressed as the male and female parts are moved together. When fully engaged, the end face  44  of the female connector comes into contact with the locking pin  45 . The pin  45  is fully compressed when the male and female connectors are fully pushed together. The male connector  12  is then rotated (clockwise), until the slot  42  reaches the pin which then projects into the slot  42 . This prevents any further rotation of the two parts relative to each other. The shape of the slot  30 , having a shaft and a head, ensures that in this relative orientation, the male and female connectors cannot be separated, as the tabs  57  are then trapped in the head portions of the recesses  30 . 
   In order to release the connection, the pin must be depressed, and at the same time, the male and female parts are rotated relatively to each other to release the bayonet coupling. 
   The locking pin is housed in a small enclosure defined by the slot  42 , so that this depression is deliberately not a straightforward operation. A tool is provided for insertion into the slot  42 , and having a width to fill the slot, and thereby depress the pin, so that the male and female parts can be rotated and released. While this provides an additional level of safety which may be desirable or required, for example if the connectors are in public areas, it can be a nuisance when the level of safety is not required. 
   The connector above is described in more detail in U.S. Pat. No. 6,309,231, to which reference is made. 
   The invention provides a modification to the connector described above, which provides similar levels of safety but without requiring additional tools. 
   In a first embodiment, the invention provides an extra component which can be added to the design described above to avoid the need for a tool. In this way, the—connector can have a single design, and the additional component is then optional, so that use of the connector in some applications will require use of a tool to disconnect the male and female parts, whereas use of the connector in other applications, for example where there is no public access, does not require use of the tool. 
     FIG. 6  shows the additional component, comprising a sleeve  70  having an inwardly projecting tab  72  designed to fit inside the slot  42 . 
   In use, the sleeve  70  is fitted over a portion  71  of the end  44  of the female connector  14 , with the tab  72  sliding into the slot  42 . The engagement of the tab  72  with the slot  42  may be the only coupling between the sleeve and the female connector  14 , so that a choice of whether or not to use to sleeve  70  can be made when making the electrical connection, and in dependence on the requirements at that location. 
     FIG. 7  shows how the tab  72  engages with the slot  42  in the housing  40 , so that the slot limits the sliding and rotational movement of the sleeve  70 . 
   In order to release the connector, the sleeve is pushed towards the male connector as shown by arrow  74 , and the tab  72  pushes the pin  45  inwardly against the spring bias of the pin. When the pin is fully depressed, the male and female connectors can be rotated to release the bayonet coupling. 
   In another version, the sleeve is mounted on the housing  40  with a coupling in addition to the engagement of the tab  72  and slot  42 . For example, a lug and slot arrangement between the inside of the sleeve  70  and the outside of the housing  40  may hold the housing  40  and sleeve  70  together even when the male and female connectors are separated. Even with this additional coupling between the sleeve and housing, the sleeve may still be removable from the housing by applying sufficient force, but the additional coupling is sufficient that the sleeve does not fall off when the connector is disconnected. 
   Alternatively, the sliding sleeve can be securely mounted over the housing, so that the connector is supplied only in the format in which it is to be used. 
   No biasing arrangement for the sleeve is required, as the spring force of the pin  45  is used to push the sleeve away when the male and female connectors are joined. 
   The connector provided by the invention can be released more easily and without the need for an additional tool. However, the release operation is still a two stage operation, of axial force and simultaneous rotation. The invention also enables a connector to be formed with two possible levels of safety, so that the connector can be used in different ways for different applications. 
   The sleeve can have a ribbed or other outer surface to improve grip and to make the release operation easier in confined spaces. An end section of the housing  40  can be recessed to house the sleeve, without increasing significantly the total volume of the connector. 
   Various other modifications will be apparent to those skilled in the art. 
   Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.