Abstract:
A plug having a screw-down feature to securely connect to a socket of fixed, existing design. The plug includes flanges with screw receiving bores. Plug screws inserted through the bores deliver a coupling force for a variable compression seal that makes the connection waterproof. The screw-down connection includes upgrading the existing socket machine screws to a socket retaining member. The screw-down feature prevents the plug from accidentally disconnecting from the socket.

Description:
BACKGROUND 
     1. Technical Field 
     The invention relates to a screw down connector. 
     2. Description of the Related Art 
     Various connectors are utilized to couple electronic components, power sources, communications equipment and portable devices. Different connectors are designed to accommodate multiple conductors, avoid accidental disconnection from vibration or other forces, or achieve a degree of moisture resistance or waterproofing. 
     Connectors for computer peripherals such as monitors and printers include multiple conductors to carry low voltage signals. The connectors have a straight-line configuration with the cable extending out the back of the connector, in-line with the conductors and the plug and un-plug direction. For example, U.S. Pat. No. 5,921,801 provides a retention system where the thumb screws are adjacent the rear of the connector housing and threaded members are separate from the device housing. U.S. Pat. No. 7,901,244 discloses a stacked connector which provides an analog and digital video jack on the back of a personal computer with removable fastening posts 128, 148. Neither of these computer connectors addresses moisture resistance or waterproofing. 
     U.S. Pat. No. 7,632,124 discloses a connector having individual O-ring seals 25 on each male conductor pin 27. The connector is secured with screw fasteners 30 that extend through the contact carrier and are disposed adjacent the connector housing. U.S. Pat. No. 6,139,359 discloses a connector incorporated into a battery pack for portable tools having two conductors. The connector includes an O-ring 87 and a friction clip to secure the battery to the tool. The connector lacks a locking mechanism, and rather is designed to uncouple upon application of sufficient pull force in order to swap a fully charged battery into the tool. 
     Advanced power systems and portable batteries have multiple high voltage contacts that are present in their power couplings or connectors. In certain applications, such as military applications, the portable battery utilizes a standard connector and is deployed in the field. These two factors limit the ability of engineers to modify the configuration of the standard connector. Due to the rugged service conditions of these battery connectors there is a need for the connectors to have a locking feature that resists unintentional disconnection. In addition, certain environmental conditions require that these connectors be waterproof. Prior art solutions have provided a large rubber boot that fits over the entire top surface of the unit. This solution has several drawbacks. When the top surface is covered, the user does not have access to the controls and indicators located thereon. In addition, the boot only adds a small incremental advantage in pull tests. 
     Accordingly, it would be desirable to provide a multi-conductor connector that retrofits to existing portable batteries and provides a waterproof seal with high pull test scores. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a multi-conductor connector that retrofits to existing power systems and portable batteries. 
     It is another object to provide a connector with a waterproof seal. 
     It is a further object to provide a connector with an easily operated screw down lock. 
     It is another object to provide a connector with a right angle housing so that the thumb screws are readily accessible. 
     These and other objects are achieved according to an embodiment of the invention including an apparatus for securely connecting a plug having contacts. The apparatus has a plug housing enclosing a contact carrier and including outwardly extending flanges having screw-receiving bores. A plug screw extends through each bore, wherein each screw includes a male thread on a proximal end that is adapted to engage a female thread on an upper portion of a socket retaining member that retains a socket on an electrical device by attaching to a stationary insert that is disposed within an electrical device housing. 
     Male contact pins are supported by the contact carrier, which is a circular disk. The portion of the housing which encloses the contact carrier is a cylindrical tube. Two flanges are disposed in diametrically opposed locations about the cylindrical tube. The flanges and housing are integrally-molded as a single piece. The plug includes a multi-conductor cable, and the housing includes a strain relief integrally-molded around the cable. The strain relief is integrally-molded around the cable and extends laterally outwardly from the plug at a right angle. 
     Each of the plug screws has a distal end remote from the proximal end and a central section disposed between the distal and proximal ends. The central section is sized to allow axial movement within the screw-receiving bores. A clip snaps onto a neck located between the central section and the proximal end to retain the central section of the screw within the screw-receiving bore. The distal end has a diameter larger than the screw-receiving bore and a length extending beyond the housing to provide manual access to the distal end which comprises a thumb screw. 
     Male contact pins are supported by the contact carrier which is a circular disk. The housing includes a cylindrical tube section that encloses the contact carrier. The screw-receiving bores and the central section of said plug screws are located radially outwardly of the contact carrier. A sealing O-ring is disposed about the periphery of the contact carrier. The plug housing includes a cylindrical tube that extends beyond the contact carrier to form a skirt disposed radially outwardly of the contacts which comprise male contact pins. The skirt is adapted to surround the socket of the electrical device. 
     A male thread on the proximal end of the plug screw is disposed radially outwardly of the male contact pins and the skirt. Tightening of the plug screws places an axial force on the flanges, ring and contact carrier which compresses the O-ring. The axial force on the contact carrier compresses the O-ring which is adapted to form a water-tight seal against the socket. The plug screws are adapted to unscrew from the socket retaining member with a lesser force than required to unscrew the socket retaining member from the stationary insert. 
     As a retrofit kit, the kit includes socket retaining members to replace machine screws. Plugs equipped with an O-ring, flanges and plug screws are provided to attach to the socket retaining members. The screw down plug compresses the O-ring to form a water-tight seal. The kit is installed by removing machine screws 12 from the socket and installing socket retaining members with a high torque T to secure the socket to the battery. A new plug is plugged into the socket and screwed-down by hand-tightening plug screws to a low torque t. Rotating the plug screws compresses newly provided O-ring to form a waterproof seal between the plug and socket. The plug screws can be removed and installed with torque t many times without effecting socket retaining members that are installed with torque T that is greater than t. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The advantages, nature, and various additional features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with accompanying drawings. In the drawings wherein like reference numerals denote similar components throughout the views: 
         FIG. 1  is a side schematic view of the prior art connector and boot cover. 
         FIG. 2  is an exploded view of an embodiment of the screw down connector according to the invention. 
         FIG. 3  is a perspective view of the screw down connector housing and modified socket retaining member. 
         FIG. 4  is a perspective view of the connector screwed down into the socket retaining member to form a waterproof seal. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
     The present invention provides an electrical connector that retrofits to existing power supplies and portable batteries with a screw down locking feature which provides excellent pull test results and a waterproof seal. In summary, one embodiment of the invention illustrated in  FIG. 2  provides a plug  20  having a flange  26   a  on a right angle housing  26  to carry a plug screw  28 . The existing machine screw is replaced by a socket retaining member  60 , which is modified to include a female thread  60   b  in its top  60   a . An O-ring  30  is disposed around the periphery of the contact carrier  22 . The thumb screw  28   e  is easily accessible to screw down the plug  20  to avoid accidental disconnection and provide a waterproof connection. 
     According to the prior art configuration as shown in  FIG. 1 , male connector  10  was devoid of outwardly extending flanges and the corresponding plug screws. In addition the socket  12  did not have a mechanism that would allow connector  10  to latch or lock on to. Socket  12  was secured to the device  16  by conventional machine screws  12   a . Plug  10  was retained in socket  12  by a friction fit, which made the coupling susceptible to accidental disconnection. To provide a degree of moisture resistance, a large boot  14  was used to cover the entire top surface  16   a  of the portable battery  16 . While in place, boot  14  restricts access to controls and indicators, generally illustrated by reference numeral  16   b.    
     Accordingly, there is a need to provide a more robust connection that is waterproof and allows access the top surface of battery  16 . Many batteries  16  with installed sockets  12  have already been manufactured. As a result the configuration of socket  12  cannot be changed. The challenge to engineers is to improve the connection between plug and socket where only the plug can be modified. The batteries and their original sockets cannot be redesigned or replaced since they are relatively expensive pieces of equipment, and many batteries are already out in the field in continuous use. 
     As can be seen in  FIG. 2 , one embodiment of the invention includes a flange-equipped plug, a plug screw and a socket retaining member which are designed to retrofit onto an existing battery  80  and socket  70 . Compared to the prior art plug  10  shown in  FIG. 1 , the plug  20  according to the invention of  FIG. 2  includes a screw down, variable compression seal. The electrical components of plug  20  include a contact carrier  22  that supports contacts  24  in the form of male pins. Contact carrier is a circular disk, having extended therethrough, for example, six male contact pins to carry several high voltage circuits. In addition, small pogo or stationary pins may be included to carry low voltage signals to and from the battery in the case of a smart battery. The contact carrier  22  brings contacts  24  into mating connection with the female contact slots on socket  70 . An O-ring  30  is disposed around the periphery of contact carrier  22  to provide a waterproof seal to the periphery of socket face  70   c . When O-ring  30  is subject to sufficient compression between contact carrier  22  and socket face  70   c  external moisture and liquid is effectively prevented from seeping into the electrical contacts. 
     The plug housing  26  is designed with a low profile height and a generally cylindrical tube  26   c  surrounding contact carrier  22 . A section of the housing extends below the tube and is formed as a skirt  26   d . O-ring  30  is set within the corner where contact carrier  22  meets skirt  26   d . Skirt  26   d  keeps the O-ring from expanding beyond the edge of face  70   c . The interior of skirt  26   d  may be provided with slots or keyways at locations that correspond to ridges or keys  70   d  on the exterior, cylindrical surface of socket  70 . The keys and keyways are set at irregular intervals so that the plug can only couple to the socket in one configuration. This insures that the different functions of the contacts are properly assigned to the mating connector when a coupling is made. 
     Flanges  26   a  extend laterally off the side of the housing  26 . More particularly, two flanges are disposed in diametrically opposed locations outside of cylindrical tube  26   c . Flanges  26   a  are positioned radially outwardly of contact carrier  22 . The plug housing  26  and flanges  26   a  are integrally-molded as a single piece. For example, the plug housing may be manufactured by placing the contact carrier, contacts and cable into a mold and then overmolding the plug, flanges and strain relief in one molding cycle. Radially inwardly of the flanges, a ring  26   r  is formed that sits on top of the edge of contact carrier  22 . Ring  26   r  is axially positioned above O-ring  30 . As the plug screws are tightened on opposite sides, ring  26   r  exerts a downward force on contact carrier  22 . The circular shape of the ring and contact carrier provides even pressure along the entire length of the O-ring. This insures that O-ring forms an even seal between the inner corner where the contact carrier  22  meets the skirt  26   d  and the outer corner where deck  70   c  meets exterior cylindrical surface (where keys  70   d  reside). 
     Flanges  26   a  include screw-receiving bores  26   b . A plug screw  28  is fitted into each bore. From the bottom up plug screw  28  includes a proximal male thread  28   a , a central section  28   b , and a distal end  28   e . The proximal end is inserted through the bore with central section  28   b  residing within the bore. Central section  28   b  is longer than the bore so as allow some axial movement of plug screw  28  within the bore. Bore  26   b  is of sufficient length to maintain plug screw  28  in alignment with its mating female thread. Between central section  28   b  and proximal end  28   a  is a narrow neck  28   d . A clip  28   c  attached to neck  28   d  after the screw is inserted through the bore. Clip  28   c  prevents the screw from being removed from the bore. At the other end, the diameter of the distal end  28   e  is larger than the bore. Accordingly, the bore effectively captures the central section  28   b  of the plug screw  28 , and supports it for limited axial travel during threading. 
     In the prior art connector of  FIG. 1 , socket  12  was configured to only retain the plug  10  by frictional engagement. Socket  12  was bolted to electrical device, e.g. battery  16  by a machine screw  12   a . The battery is equipped with a well that is formed by a depression in the top surface of electrical device housing. Socket  12  sat in the well and machine screws  12   a  passed through ears and threaded into the female threads of inserts. 
       FIG. 2  shows that screws  12   a  have been replaced with a socket retaining member  60  having a head  60   c  with a downwardly facing shoulder  60   d  that sits on deck  70   b  of socket ear  70   a . When installed, the middle portion  60   e  resides within ear  70   a , while the male threads of lower portion  60   f  engage female threads  82   a  of insert  82 . When socket retaining member  60  is tightened, shoulder  60   d  presses down on deck  70   b  to secure socket  70  to electrical device  80 . Socket retaining member was previously a slotted head machine screw. 
     Socket retaining member  60  is provided with a female thread  60   b  formed in its upper portion  60   a . The female threads were dimensioned with a diameter smaller than middle portion  60   e  and a length that allows plug screw  28  to thread in about 4 to 15 turns. The length of the female threads may extend between 40% and 90% of the combined height of head  60   c  and middle portion  60   e . Flanges  26   a  are laterally dimensioned to position bore  26   b  axially above, and centrally aligned with, socket retaining member  60 . Bore  26   b  and plug screw  28  are axially dimensioned so that plug  20  can be installed onto socket  70  without interference. Once plug  20  is fully seated, screws  28  will loosely rest on socket retaining member  60 . Screw  28  has a thread pitch that is configured to bring distal end  28   e  down to flange  26   a  after several initial turns. Thereafter, continued turning of screw  28  will provide a downward force on flange  26   a  and the entire plug housing  26  toward socket  70 . This downward force compresses O-ring  30  between contact carrier  22  and socket face  70   c.    
     A perspective view of plug  20  may be seen in  FIG. 3  where housing  26  is a right angle connector having an integrally molded strain relief  26   e  for cable  26   f . The right angle turn at the top of housing  26  provides a low-profile height  26   h . The distal end  28   e  of plug screw  28  has a greater height  28   h  so that the knurled, thumb screw portion of plug screw can be readily accessed for manual turning. According to another embodiment, the invention includes the components shown in  FIG. 3  which comprise a retrofit kit. The kit includes the right angle housing  26  equipped with plug screws  28  and O-ring  30  along with socket retaining members  60 . Socket retaining member  60  includes a slot formed in its upper portion  60   a . To install the screw down waterproof plug kit, the old machine screw  12   a  is removed. Socket retaining member  60  is installed to secure socket  70  to the electrical device housing  80   a . Plug  20  and socket  60  have complementary slots and keys so that the plug can only be inserted into socket  60  in one orientation. Plug housing  26  is configured so that the flanges  26   a  and plug screws  28  will align over the socket retaining members in that one orientation. 
     As can be seen in  FIG. 4  the old machine screw  12  has been replaced with socket retaining member  60  to secure socket  70  to battery housing  80   a . This screw replacement can be carried out in the field with a screw driver, pocket knife, coin, etc. Ideally a screwdriver is used to tightly secure socket retaining member  60  to insert  82 . Insert  82  has a textured or knurled outer surface that allows insert to be held securely in place when electrical device housing is molded to it. Accordingly socket retaining member  60  can be tightened with a high degree of torque. As a result the torque required to unscrew socket retaining member will require mechanical means and will be a high value T. In contrast, plug screws  28  are designed to be hand tightened by gripping the thumb screw portion  28   e . The torque required to unscrew plug screw can be achieved by manual operation and will be a low value t. Use of the invention preferentially uses mechanical means to tighten socket retaining member  60  and manual means to tighten plug screw  28 . In this manner the torque t needed to unscrew plug screw  28  will be significantly less than the torque T required to unscrew socket retaining member  60 . Accordingly, plug screw  28  can be attached and removed many times without causing socket retaining member  60  to loosen. 
     The completed assembly provides a plug housing with screw down capability to retrofit to existing sockets. The plug screws gradually compress the O-ring to form a waterproof seal. The screw down feature improves the pull test performance to avoid accidental or vibration-induced disconnection between the plug and socket. 
     Having described preferred embodiments for (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. The flanges may be of alternate shape or height while still locating the plug screws above the socket retaining members. The plug housing may be formed from a wide array of materials and by various manufacturing methods. The plug screws may be different diameters and lengths while still effectively providing a screw down feature to seal the connection and offer positive pull test results. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope and spirit of the invention as outlined by the appended claims. Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.