Abstract:
A terminal connector ( 10, 60, 80, 100, 120, 142 ) for connecting a lead wire to a terminal which is a component of a current path so that the current path will be established. The terminal connector has a lead wire attachment portion ( 12, 62, 82, 102, 122, 144 ) which is fixed to the terminal connector with continuity maintained with respect to the lead wire, a terminal mounting portion ( 13, 63, 83, 103, 123, 143 ) mounted on the terminal, a fuse portion ( 14, 64, 84, 104, 124, 145 ) which electrically connects the lead wire fixing portion and the terminal mounting portion to each other and which melts at a predetermined overcurrent, and a reinforcement portion ( 15, 85, 105, 125, 146 ) which protects the fuse portion against external forces.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to terminal connectors for connecting a lead wire that forms a current path to a terminal and more particularly to terminal connectors suitable for mounting on a glass sealed terminal provided in the casing of a sealed electromotive compressor. 
     BACKGROUND OF THE INVENTION 
     It is well known to provide protection devices, such as motor protectors, for electromotive compressor motors employed in air conditioners and the like (hereafter also referred to as motor protection device). The motor protection device typically includes movable contacts controlled by a current carrying bimetal element which is actuated by elevated environmental temperatures and/or overcurrents. The motor protection device is typically attached to a motor coil of the compressor motor mounted inside the casing of the electromotive compressor. The motor is connected to an external alternating current power source through the motor protection device, lead wires and glass sealed terminals provided in the casing. 
     If the electromotive compressor is subjected to an overload or a locked rotor condition due to abnormal circumstances, the environmental temperature inside the casing rises and/or the amount of electric current that passes through the motor protection device rises, the motor protection device then opens the power source circuit by actuation of the bimetal element, thereby preventing possible damage in the compressor caused by excessive temperature or overcurrent. When the temperature and current value are restored to the normal state, the motor protection device closes the power circuit once again and restores the power supply to the compressor. 
     However, if the motor protection device has been used beyond its useful product life, its contacts could weld together with a result that there are cases where an electrically conductive state continues to be maintained even when the electromotive compressor happens to be in a fault condition. In such cases, the temperature of the motor winding rises further and the electrically insulating material on the winding conductors melts, thereby causing short-circuiting between the windings or the glass of the glass seal melts, with the terminal being blown out by the internal pressure in the sealed casing. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is the provision of an apparatus which overcomes the prior art limitation described above and which prevents concomitant trouble that the electromotive compressor would encounter in the event that the motor protection device, by exceeding its useful product life, ceases to perform normally. 
     Briefly, in accordance with the invention, a terminal connector for connecting a lead wire to a terminal in a current path comprises a lead wire attachment portion for attachment to the lead wire in electrically conductive relationship therewith, a terminal mounting portion for mounting on the terminal and a fuse portion which electrically connects the lead wire attachment portion and the terminal mounting portion and which melts at a predetermined overcurrent with a reinforcement member disposed adjacent to the fuse portion to protect the fuse portion against external forces. In certain embodiments, the reinforcement member is formed of electrically insulating material. According to a feature of a preferred embodiment, the reinforcement member is interposed between facing selected surfaces of the lead wire attachment portion and the terminal mounting portion. According to another feature of a preferred embodiment, the reinforcement member is integrally formed by insert molding the lead wire attachment portion and the terminal mounting portion. According to a feature of the invention, the lead wire attachment portion, the terminal mounting portion and the fuse portion are formed integrally. 
     Although useful with various electrical equipment, preferably the mounting portion is configured to be mounted on a glass sealed terminal provided through the casing of a sealed electromotive compressor. If desired, the terminal mounting portion can be configured to be mounted on the terminal portion that protrudes outwardly from the casing of a glass sealed terminal and the lead attachment portion can be configured to be attached to the lead wire from the alternating current power source of the sealed electromotive compressor. The terminal mounting portion can also be configured to be mounted on the glass sealed terminal part that protrudes inwardly into the interior of the casing and the lead wire attachment portion can be configured to be attached to the lead wire from the electromotive compressor inside the casing. In the latter instance, it is preferable that the lead wire attachment portion be attached to the lead wire from the motor protection device provided in the electromotive compressors inside the casing. 
     The invention further relates to a motor protection device that is to be mounted in the casing of a sealed electromotive compressor, the device comprising a lead wire for connection to the glass sealed terminal through the terminal connector at the distal tip end of the lead wire. The invention further relates to a glass sealed terminal that is to be mounted in the casing of a sealed electromotive compressor that is equipped with the terminal connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings which are incorporated in and constitute part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings: 
     FIG.  1 (A) is a front elevational view of a terminal connector made in accordance with a first embodiment of the invention; 
     FIG.  1 (B) is a cross sectional view taken on line  1 (B)— 1 (B) in FIG.  1 (A); 
     FIG.  1 (C) is a cross sectional view taken on line  1 (C)— 1 (C) in FIG.  1 (A); 
     FIG.  2 (A) is a front elevational view of the terminal connector body prior to its completion; 
     FIG.  2 (B) is a perspective view of a reinforcement member used in the FIG.  1 (A) terminal connector; 
     FIG. 3 is a front elevational view of the FIG.  1 (A) terminal connector mounted on a terminal within a compressor casing showing the broken away casing and glass terminal assembly in cross section; 
     FIG. 4 is a schematic diagram showing a power source circuit of a sealed electromotive compressor that contains the terminal connector of FIG.  1 (A); 
     FIG. 5 is a view similar to FIG. 4 but showing a modified mounting arrangement; 
     FIG.  6 (A) is a front elevational view and FIG.  6 (B) is a cross sectional view taken on line  6 (B)— 6 (B) of FIG.  6 (A), respectively, of a terminal connector made in accordance with another embodiment of the invention; 
     FIG. 7 is a front elevational view similar to FIG.  2 (A) showing the FIG.  6 (A) terminal connector body prior to completion; 
     FIG.  8 (A) is a front elevational view and FIG.  8 (B) is a side elevational view, respectively, of a terminal connector made according to still another embodiment of the invention; 
     FIG.  9 (A) is a front elevational view and FIG.  9 (B) is a side elevational view, respectively, of the FIG.  8 (A) terminal connector body prior to completion; 
     FIG. 10 is a front elevational view of a terminal connector made in accordance with still another embodiment of the invention; 
     FIG. 11 is a front elevational view of the terminal connector body shown in FIG. 10 prior to the installation of the reinforcement member; 
     FIG. 12 is a front elevational view of a terminal connector made according to still another embodiment of the invention; 
     FIG. 13 is a cross sectional view of the terminal connector of FIG. 12; and 
     FIG. 14 is a cross sectional view of a broken away portion of a compressor casing and glass terminal assembly showing an embodiment in which a terminal connector made in accordance with the invention is formed integrally with a glass sealed terminal of the compressor casing. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The embodiments of the invention to be described below refer to mounting the terminal connector made in accordance with the invention on a glass sealed terminal of a sealed electromotive compressor. However, it is within the purview of the invention that the terminal connector can be used for various other equipment which will become clear in the following description. 
     With reference to FIGS.  1 (A) through  4  which relate to a terminal connector according to the first embodiment, terminal connector  10  basically comprises a terminal connector body  11  made of suitable electrically conductive material and a reinforcement member  15  made of an electrically insulative material. Terminal connector body  11  makes it possible to connect the lead wire from a motor protection device to a glass sealed terminal inside the casing of a sealed electromotive compressor as will be described below. Connector terminal body  11  is made by punching a sheet of metal such as brass or the like, with various portions being suitably bent. It comprises a lead wire attachment portion  12  for clamping a lead wire, such as a Freon resistant wire from the motor protection device, a terminal mounting portion  13  for mounting on the glass sealed terminal, and a fuse portion  14 . Lead wire attachment portion  12  attaches terminal connector  10  to a lead wire  31  from motor protector  30 . For this purpose, lead wire attachment portion  12  has a lead clamping portion  12   a  that clamps and attaches to the electrically insulative covering of lead wire  31  and a lead wire clamping portion  12   b  that clamps the electrically conductive part that is exposed at the distal tip end of the lead wire, thereby guaranteeing electrical connection with the lead wire, as illustrated in FIG.  3 . Known F clamps, O clamps, etc., can be employed for clamping lead wire  31 . Terminal mounting portion  13  has a terminal insertion space  13   a  formed by bending opposing sides of portion  13 , as shown in FIG.  1 (C) so as to receive the terminal blade portion of the glass sealed terminal provided in the casing of the sealed electromotive compressor. As the terminal blade portion is pressed into insertion space  13   a  from the end of the terminal mounting portion  13 , terminal connector  10  is electrically and physically connected to the glass sealed terminal. It will be understood that the particular configuration of the lead wire attachment portion  12  and terminal mounting portion  13  can be varied as long as it is attachable to the lead wire and can be mounted on the glass sealed terminal. Fuse part  14  comprises that portion that has been designed to have a prescribed current capacity and is serially connected in the current path connecting lead wire attachment portion  12  and terminal mounting portion  13 . If the electric current that passes through the fuse portion  14  exceeds the current capacity, the fuse portion  14  will melt, thereby electrically separating lead wire attachment portion  12  and terminal mounting portion  13 . Fuse portion  14  according to this embodiment is bent into a generally U-shaped configuration with lead wire attachment portion  12  having a portion spaced from and facing terminal mounting portion  13 . 
     In the event the motor protection device has been short circuited due to use beyond its useful product life and if excess current flows through the power source circuit so as to cause trouble to the sealed electromotive compressor, fuse portion  14  performs its function (of melting), thereby de-energizing the power source circuit. In designing fuse portion  14 , there is a need to take into consideration the time required for the excess current passage to cause melting of the fuse. By adjusting the length and the cross sectional area of fuse portion  14 , a suitable fusing time can be chosen for the sealed electromotive compressor. In one example, when the length of the fuse portion made of brass is selected somewhere between three and five millimeters and its cross sectional area is selected in the range between 0.4 and 0.5 square centimeters, fuse portion  14  melts approximately one minute at a current of 100 A and in less than one second at a current of 200 A. 
     Terminal connector  10  made according to the invention further comprises a reinforcement force isolation member  15  made of electrically insulative material. The reinforcement force isolation member  15  is a recessed block member, as shown in FIG.  2 (B), interposed between facing surfaces of lead wire attachment portion  12  and terminal mounting portion  13 , as shown in FIGS.  1 (A) and  1 (B). Reinforcement force isolation member  15  is fixed by suitable means such as by clamping engagement with the opposing surfaces so that it is integral with terminal connector body  11 . As a result of this, fuse part  14 , whose strength is comparatively low, is protected from possibly damaging forces during assembly or the like. The force isolation capability is enhanced by placing fuse portion  14  inside the recessed portion  15   a  of the reinforcement force isolation member  15 . Because of this arrangement, fuse portion  14  is protected from external physical forces. For example, the force applied when terminal fitting  10  is mounted on the glass sealing terminal can be received by reinforcement force isolation member  15 . In a suitable example, the reinforcement member  15  is formed of heat-hardenable resin. In another suitable example, it is formed of ceramic material. 
     As noted above, FIG.  2 (A) shows terminal connector body  11  prior to its completion. From this state, fuse portion  14  is bent so that a surface of lead attachment portion  12  faces a surface of terminal mounting portion  13 . The reinforcement force isolation member  15 , as shown in FIG.  2 (B), is interposed between the opposing surfaces, thereby resulting in the completed terminal fitting  10  shown in FIG.  1 . 
     FIG. 3 illustrates terminal connector  10  as it is connected for use in a sealed compressor casing. In other words, this figure shows how the terminal connector is used for the connection of lead wire  31  that comes from motor protection device  30  to glass sealed terminal assembly  33 . Motor protection device  30  is mounted in or on the motor windings (not shown in the figure) in the casing of a sealed electromotive compressor. One end of lead wire  31  is connected to terminal  30   a  of motor protection device  30 , with terminal connector  10 , made according to the invention, being attached at the opposite tip end thereof. A lead wire  32  is connected to the other terminal  30   b  of the motor protection device fixed to a steel housing and this is connected to the windings of the motor. Glass sealed terminal assembly  33  closes an opening formed in casing  36  of a sealed electromotive compressor  38  and includes a terminal  34  for connecting the motor in the casing to an alternating current power source (not shown in the figure) disposed outside the casing. Glass sealed terminal assembly  33  includes terminals such as terminal  34  mounted within the assembly and electrically isolated therefrom by glass  35 . 
     Terminal  34  has an inner blade terminal part  34   a  on the interior side and an external pin terminal part  34   b  on the exterior side. Terminal connector fitting  10  is mounted on the inner terminal part  34   a . The motor protection device  30  is actuated when the electric current that passes through it or when its environmental temperature has exceeded certain selected values. When a large electric current passes through terminal connector  10 , its fuse portion  14  is heated. Because of the physical distance between the motor protection device  30  and terminal connector  10 , however, the affect by the heating of the fuse portion on motor protection device  30  is minimal. 
     FIG. 4 is a schematic of the motor drive circuit of a sealed electromotive compressor  40  that includes terminal connector  10  and motor protection device  30 . One terminal  30   b  of motor protection device  30  is connected between the main winding  41  and auxiliary winding  42 . Terminal connector  10  made according to the invention is connected through lead wire  31  to the other terminal  30   a  of motor protection device  30 . Terminal connector  10  is connected through glass sealed terminal assembly  33  and lead wire  43  to an alternating current power source  44  located outside of the casing. 
     FIG. 5 shows a similar circuit relating to an alternate arrangement for terminal connector  10 . In this example, terminal connector  10  is placed outside of sealed electromotive compressor  40 . In other words, the lead wire attachment portion  12  of terminal connector  10  is fixed to the lead wire that is connected directly to the alternating current electric power source  44 . Terminal mounting portion  13  is mounted on the outside terminal part  34   b  (see FIG. 3) of glass sealing terminal assembly  33 . This arrangement becomes possible when there is no problem in exposing the fuse portion  14  outside of the casing of sealed electromotive compressor  40 . 
     FIGS.  6 (A),  6 (B) and  7  show a modified embodiment of terminal connector  10 . Terminal connector  60  comprises fuse portion  64  made of a separate member fixed to lead wire attachment portion  62  and terminal mounting portion  63  of terminal connector body  61  by means of rivets or the like. An advantage provided by the use of a separate member for fuse portion  64  lies in the ability of selecting different materials for terminal body  61  and fuse portion  64  so that it is possible to finely set or change the fuse characteristics of the fuse portion  64 , irrespective of the characteristics of the material for the terminal connector body  61 . 
     FIGS.  8 (A),  8 (B),  9 (A) and  9 (B) show a terminal connector which relates to another embodiment of the invention. Terminal connector  80  of this embodiment has a generally L-shaped terminal connector body  81 , with a fuse portion  84  being formed at the bend of the L-shaped part. Reinforcement force isolation member  85  in this embodiment is a generally block-shaped resin body member integrally formed with terminal connector body  81  by molding in such a fashion as to cover the L-shaped bend but with a window  85   a  exposing fuse portion  84  so that its fused state can be observed through the window. Lead wire attachment portion  82  of terminal connector body  81  and terminal mounting portion  83  are made physically integral with one another and maintained integral even after a melting of the fuse portion by means of the reinforcement force isolation member  85 . In addition, reinforcement force isolation member  85  receives external forces in connection with the mounting of the connector on the terminal. In this embodiment, moreover, the attachment of the lead wire to the lead wire attachment portion  82  is effected by welding. 
     FIGS. 10 and 11 show the terminal connector according to another embodiment of the invention. Terminal connector body  101  of terminal connector  100  according to this embodiment has an external appearance which is similar to the terminal connector body  81  in the previous embodiment; however, it is different in that the arrangement of fuse portion  104  is shifted further toward lead wire attachment portion  102  from the L-shaped bend. Reinforcement force isolation member  105 , made integral with terminal connector body  101  by insert molding, circumscribes the fuse portion  104  and, at the same time, extends over the top of terminal mounting portion  103 . The extended portion of the reinforcement force isolation member  105  functions as that part which receives external forces during mounting of terminal mounting portion  103  on the glass sealed terminal. 
     FIGS. 12 and 13 show a terminal connector relating to yet another embodiment. In this embodiment, the reinforcement force isolation member  125  comprises a casing made of steel for sealing the terminal connector and forms a part of the current path in the terminal connector  120 . In other words, terminal connector  120  forms part of an electric current path by means of a pin-shaped lead wire attachment portion  122 , fuse portion  124 , casing shaped reinforcement force isolation member  125  and terminal mounting portion  123  welded to the outside of reinforcement force isolation member  125 . Reinforcement force isolation member  125  and lead wire attachment portion  122  are electrically isolated from each other by means of glass seal  126 . The casing shaped reinforcement force isolation member  125  completely covers fuse portion  124 , with a result that external influences on the fuse portion  126  is minimized. 
     FIG. 14 shows an embodiment in which a glass sealed terminal is integrally connected to a terminal connector made in accordance with the invention. The glass seal terminal assembly  140  has a terminal connector  142  integrally connected at the tip of an internal terminal part  141 . Terminal connector  142  is fixed thereto by welding terminal mounting blade portion  143  to the inner terminal part  141 . Terminal connector  142  has a lead wire attachment portion  144  as in the previously described embodiments. A fuse portion  145  is formed between lead wire attachment portion  144  and terminal mounting portion  143 . Reinforcement force isolation member  146 , made of an electrically insulating material, covers fuse portion  145  by insert molding as in the FIGS.  8 (A),  8 (B) embodiment and becomes integral with it. The basic operation of the terminal fitting  120  in this embodiment is the same as in the case of each embodiment previously described. 
     According to the invention explained above, protection of a circuit against overcurrent can be realized by using an extremely simple construction. With a terminal connector having a fuse portion protected by the reinforcement force isolation member made according to the invention, it becomes possible to prevent the occurrence of an accident that will change the characteristics of the fuse portion by producing a deformation of the fuse portion when it is mounted onto the terminal. In particular, as a result of the invention, it is possible to prevent various possible problems of the electromotive compressor that could occur when the motor protection device has exceeded its product life and no longer operates as intended. 
     It will be understood that in view of the above description and drawings, variations and modifications will be apparent to those skilled in the art. It is the intention that the appended claims be interpreted as broadly as possible, in view of the prior art, to include all such variations and modifications.