Abstract:
A terminal assembly for a hermetic compressor having a shell includes a terminal block secured to the shell. A terminal fence surrounds the terminal block and is also fixedly secured to the shell. An intermediate gasket sealingly engages both the shell and the terminal block. A power plug is electrically connected to the terminal block and sealingly engaged by the intermediate gasket. A terminal block cover is secured to the shell in order to retain the connection between the various components. The terminal assembly once properly installed is capable of sealing the electrical connection for the compressor from direct contamination by high humidity and salt water spray normally experienced during trans-oceanic shipping.

Description:
This a continuation of U.S. patent application Ser. No. 08/489,803, filed Jun. 13, 1995. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a sealed terminal assembly including the electrical cable for use with hermetic compressors. More particularly, the present invention relates to a sealed terminal assembly which effectively seals the connection between the electrical terminal and the cable from moisture and debris including the moisture which the terminal assembly experiences during trans-oceanic shipping. 
     BACKGROUND OF THE INVENTION 
     Prior art terminal assemblies have included both electrical terminals with covers and/or fences which are designed to protect the terminals from physical damage, electrically isolating the terminals for safety concerns and sealing the terminal assemblies from moisture and debris which the terminal assembly is exposed to during its normal operating life. While these prior art terminal assemblies have been effective, there is always a need to improve the sealing of these terminal assemblies. This is especially true for the terminal assemblies on compressors which are shipped by sea. On some trans-oceanic voyages, the compressors are shipped in open crates positioned on the open decks of the cargo vessel. In this shipping position, the compressors and thus the terminal assemblies are subjected to the high humidity of the sea air as well as periodic spraying of salt water on the compressors due to the wave action of the cargo vessel as it proceeds across the ocean. 
     Typically, a prior art hermetic terminal assembly consists of an electrical terminal and a corresponding electrical cable. The electrical terminal is installed in a hole formed in the hermetic shell of a hermetic compressor so that current may be carried to the motor of the compressor from an external source of power through the corresponding cable where the cable is attached to the electrical terminal. The prior art electric terminals comprise a body welded or secured to the shell of the compressor and a plurality of conductor pins extending through the body. In order to seal and electrically insulate the conductor pins relative to the body, a glass to metal seal is employed, having an epoxy and/or silicone rubber overcoating. A fence normally extends from the hermetic shell and can be integral with the body or it can be a separate component secured to the shell. The fence is designed to protect the electrical terminal and to interface with the corresponding cable to seal the electrical connection between the cable and the electrical terminal from the effects of the external environment. 
     While these prior art terminal assemblies have been effective in sealing the electrical connection between the cable and the terminal during normal operation of the compressor, a more effective sealing configuration is required for the compressors which are subjected to the open deck shipping environment described above. 
     SUMMARY OF THE INVENTION 
     The present invention provides the art with a terminal assembly which is capable of protecting the electrical connection between the electrical terminal and the corresponding cable when the compressor is exposed to the environment normally experienced during open deck trans-oceanic shipping. The present invention includes an electrical terminal block which includes a plurality of conductor pins. The terminal block is welded or otherwise secured to a shell of the compressor. A terminal fence is secured to the exterior of the shell in surrounding relationship to the terminal block. An intermediate gasket is placed over the terminal block to provide a seal at the interface with the shell, a seal around the external surface of the terminal block as well as a seal around each individual conductor pin. A power cable is assembled into the terminal bock which makes the necessary electrical connections with the conductor pins and also sealingly engages the power cable with both the intermediate gasket and the terminal fence. Finally, a terminal box cover is placed in sealing relation to the shell and is fixedly secured to the terminal fence. The terminal box cover, the power cable, the terminal fence and the intermediate gasket all cooperate to form a plurality of seals which effectively protect the electrical connections from marine environments. 
     Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
     FIG. 1 is a side elevational view, partially in cross-section, of a hermetic motor compressor incorporating the sealed terminal assembly according to the present invention; 
     FIG. 2 is an enlarged side elevational view of the sealed terminal assembly shown in FIG. 1; 
     FIG. 3 is a cross-sectional view of the sealed terminal assembly of the present invention taken in the general direction of line  3 — 3  shown in FIG. 2; 
     FIG. 4 is a side elevational view of the terminal block and terminal fence of the present invention; 
     FIG. 5 is a cross-sectional view of the terminal block and terminal fence of the present invention taken in the general direction of line  5 — 5  shown in FIG. 4; 
     FIG. 6 is a view similar to FIG. 4 with the addition of the intermediate gasket in accordance with the present invention; 
     FIG. 7 is a cross-sectional view similar to FIG. 5 but taken the general direction of line  7 — 7  shown in FIG. 6; 
     FIG. 8 is a view similar to FIG. 6 with the addition of the power cable in accordance with the present invention; and 
     FIG. 9 is a cross-sectional view similar to FIG. 7 but taken in the general direction of line  9 — 9  shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1, a hermetic compressor assembly which is designated generally by the reference numeral  10 . Compressor assembly  10  can be a scroll compressor, a piston compressor or any other type of compressor. Compressor assembly  10  comprises a hermetic shell  12  which defines a sealed chamber  14  within which a motor  16  and a compressor  18  are disposed. A terminal assembly  20  is sealingly associated with compressor assembly  10  and provides for the electrical connection between an external source of power (not shown) and motor  16  disposed within sealed chamber  14 . 
     Referring now to FIGS. 2 and 3, terminal assembly  20  comprises a terminal block  22 , a terminal fence  24 , an intermediate gasket  26 , a power cable  28  and a terminal box cover  30 . 
     Referring now to FIGS. 4 and 5, terminal block  22  is sealingly disposed within an aperture  32  which extends through a flattened portion of shell  12 . The sealing relationship between terminal block  22  and shell  12  maintains the integrity of sealed chamber  14  and provides for the electrical connection through shell  12 . Terminal block  22  is shown comprising a plurality of conductor pins  34 , a terminal block body  36 , a plurality of fused glass insulators  38 , a plurality of ceramic insulators  40  and a silicone rubber molding  42 . Terminal block body  36  is a cup shaped metal member defining a plurality of holes  44 . Terminal block body  36  is sealingly disposed within aperture  32  by resistance welding or other methods known well in the art. 
     Each of the plurality of holes  44  is adapted for receiving a respective fused glass insulator  38  which is sealingly fused to both terminal block body  36  and a respective conductor pin  34 . Each conductor pin  34  extends through a respective fused glass insulator  38  to provide for the electrical communication between the exterior and interior of shell  12 . Each conductor pin  34  includes a reduced diameter section  37  which acts as a fuse-like link in the event of an internal short circuit. 
     Each conductor pin  34  has a respective ceramic insulator  40  secured to the end of pin  34  extending into chamber  14  and a flat male connector  45  fixedly secured by brazing or other means known well in the art to the end of pin  34  extending out of chamber  14 . Ceramic insulators  40  insulate conductor pins  34  and their associated connection to motor  16  from contact with terminal block body  36  as well as providing insulation between adjacent pins  34 . Silicone rubber molding  42  is located on the outside of shell  12  and includes a plurality of upstanding jackets  46  which extend from a base  48  having an external sealing surface  50 . The plurality of upstanding jackets  46  are equal to and arranged in the same pattern as the plurality of conductor pins  34 . Each of jackets  46  defines an aperture  52  extending through molding  42  and adapted to receive a respective conductor pin  34 . The relationship between apertures  52  and conductor pins  34  serves to both seal and provide an over-surface insulation protection for conductor pins  34 . 
     Terminal fence  24  is fixedly secured to the outside of shell  12  by resistance welding or other means known well in the art. A pair of tabs  54  extend from the upper and lower wall of fence  24  to facilitate the resistance welding of terminal fence  24  to shell  12 . Terminal fence  24  is generally rectangular in shape and includes a pair of internally threaded tubes  56 . Tubes  56  are fixedly secured to terminal fence  24  at opposing corners of terminal fence  24  by brazing or other means known well in the art. The threaded bores of tubes  56  are utilized for securing terminal box cover  30  to terminal fence  24  as will be described later herein. Terminal fence  24  defines a cavity  58  within which terminal block  22  is disposed. Terminal fence  24  also defines an opening  60  which is adapted for sealingly receiving power cable  28  as is shown in FIGS. 8 and 9. A portion of the wall of terminal fence  24  is cut out and bent generally perpendicular to the wall as shown in FIGS. 4 and 5 to form a grounding lug  62 . Grounding lug  62  defines an aperture  64  which is adapted to receive a self tapping screw  66  which holds a grounding lead  68  extending from power cable  28 . Terminal fence  24  protects conductor pins  34  from inadvertent damage due to the handling of compressor assembly  10  by the manufacturer of the compressor, the manufacturer of the apparatus utilizing compressor assembly  10  and any service personnel involved with servicing compressor  10 . 
     Referring now to FIGS. 6 and 7, intermediate gasket  26  is a generally cylindrical gasket preferably manufactured from Dow Corning  3120  RTV rubber or General Electric RTV  31  rubber. Gasket  26  defines a first cylindrical cavity  70  which is designed to mate with terminal block  22 , a second cylindrical cavity  72  which is designed to mate with power cable  28  and a plurality of apertures  74  extending between cavities  70  and  72 . The plurality of apertures  74  are equal to and are arranged in the same pattern as the plurality of conductor pins  34  in order to allow pins  34  to extend through gasket  26 . The inside diameter of each aperture  74  is designed to sealing engage a respective jacket  46  of silicone rubber molding  42 . Gasket  26  is positioned over terminal block  22  such that pins  34  extend through apertures  74  to mate with power cable  28 . The portion of terminal block body  36  which extends outside of shell  12  is disposed within cavity  70 . The internal surface of cavity  70  is designed to sealingly engage the outside diameter of terminal block body  36  as well as the external sealing surface  50  of molding  42 . In addition, an external face  76  of gasket  26  is designed to sealingly engage the flattened portion of shell  12 . 
     Referring now to FIGS. 8 and 9, power cable  28  includes a molded plug  78  and a plurality of wires  80  which extend between plug  78  and the external supply of electrical power. Each of three wires  80  is electrically connected and secured to a connector  82  which provides a female electrical receptacle  84  for receiving a respective male connector  45 . Connectors  45  and receptacles  84  are well known in the art and will not be discussed in detail here. The fourth wire  80  forms grounding lead  68  which is secured to grounding lug  62  as detailed above. The plurality of wires extend through a radially extending jacket  86  which provides the access for three of the plurality of wires  80  into plug  78  in an orderly manner and for the fourth wire  80  to extend out of jacket  86  to form grounding lead  68 . Preferably, plug  78  and jacket  86  are integrally formed from silicone rubber. Jacket  86  includes an angular surface  88  which sealingly engages opening  60  in terminal fence  24 . The plurality of receptacles  84  are equal in number to and are arranged in the identical pattern to conductor pins  34  of terminal block  22 . A plurality of apertures  90  extend from the plurality of receptacles  84  through plug  78  to allow access to receptacles  84  by conductor pins  34  and male connectors  45 . The orientation of the plurality of conductor pins  34 , the positioning of opening  60  and the angulation of surface  88  cooperate to insure that when male connectors  45  are in registry with and engaged by female receptacles  84 , jacket  86  and angular surface  88  are in alignment with opening  60  in terminal fence  24  to provide the necessary sealing relationship. 
     Once power cable  28  is assembled to terminal block  22  by mating connectors  45  with receptacles  84 , molded plug  78  is disposed within cavity  72  of intermediate gasket  26 . The internal wall of cavity  72  defines a plurality of sealing ribs  92  which sealingly engage the outside of molded plug  78 . In addition, an external face  94  of molded plug  78  sealingly engages the internal surface of cavity  72  to provide an additional face seal for terminal assembly  20 . The connection between connectors  45  and receptacles  84  provides for electrical connection between the two components and helps to retain power cable  28  in place during the remainder of assembly of terminal assembly  20 . 
     Referring back to FIGS. 2 and 3, terminal box cover  30  is a rectangular box shaped component defining an internal cavity  96  within which the components of terminal assembly  20  are disposed. The top of cover  30  defines a pair of holes  98  which align with the pair of threaded tubes  56  of terminal fence  24 . A bolt  100  extends through each hole  98  and is threadingly received within a respective tube  56  to fixedly secure cover  30  to compressor assembly  10 . A seal  102 , preferably made from EPDM sponge rubber is disposed between shell  12  and a flange  104  formed around the open end of cover  30 . The lower wall of cover  30  defines an aperture  106  which allows power cable  28  to extend through cover  30 . The internal surface of the top of cover  30  defines a first pair of parallel ribs  108  which extend between the pair of holes  98  to provide rigidity for the top of cover  30 . The internal surface of the tip of cover  30  defines a second pair of ribs  110  which extend generally parallel to power cable  28  such that tightening of bolts  100  causes engagement of ribs  110  with power cable  28  to hold power cable  28  in place and provide a slight compressive load between intermediate gasket  26  and shell  12  and terminal block  22  as well as between intermediate gasket  26  and power cable  28 . Thus, the assembly of cover  30  to terminal fence  24  completes the assembly of terminal assembly  20  and provides six distinct areas of sealing for terminal assembly  20 . The first seal is provided between external face  76  of intermediate gasket  26  and the flattened portion of shell  12  (FIG.  7 ). The second seal is provided between the external surface of terminal block body  36  of terminal assembly  20  and the internal surface of cavity  70  of intermediate gasket  26  (FIG.  7 ). The third seal is between external surface  50  of molding  42  and the internal surface of cavity  70  (FIG.  7 ). The fourth seal is between the internal surface of apertures  74  and the external surface of jackets  46  (FIG.  7 ). The fifth seal is between external face  94  of molded plug  78  and the internal surface of cavity  72  of intermediate gasket  26  (FIG.  9 ). The sixth and final seal is between the external surface of molded plug  78  and sealing ribs  92  in cavity  72  of intermediate gasket  26  (FIG.  9 ). 
     While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.