Patent Document

BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention pertains to an apparatus employed in grounding the stator and end plates of a dynamoelectric device. In particular, the invention pertains to a terminal block constructed of an electrically insulating material and a ground connector constructed of a electrically conductive material that is installed in the terminal block, where the ground connector has a plug projecting from the terminal block at one end and a tab with a fastener hole at its opposite end. Attachment of the terminal block to the stator of the device simultaneously positions the tab of the ground connector with the tab hole aligned with fastener holes of the stator and at least one end plate of the device where assembling the stator and end plate together by a threaded fastener also secures the tab of the ground connector between the stator and end plate. 
     (2) Description of the Related Art 
     A dynamoelectric device is often constructed with a ground system that directs electrical energy away from the device in the case of an electric malfunction in the device that could shock a person touching the device or its supporting equipment. In a typical electrical device the ground is attached to an external frame or housing of the device. This insures that in the event of a power supply wire making contact directly or indirectly with the frame or housing of the device that is accessible to a person using the device, the electric energy can be directed away from the housing of the device. By directing the electric energy to a ground a “short circuit” condition is created where the electric energy is directed away from the device along the path of least resistance, thus preventing any person contacting the device from receiving an electrical shock. The high current flow through the ground in situations such as this will often cause self-actuating protective switches in the device to open the circuit and stop electrical current flow to the device. This protects both the device from a high current surge and also protects people who may otherwise contact the malfunctioning device and receive a shock. 
     In electrical devices such as electric motors installed in household appliances, the external frame of the device is required to be provided with a ground connection to protect persons using the appliance if an electrical malfunction occurs. The ground connection is often directed to a water pipe of the home or the ground pole in a three prong plug electrical socket. Because the electric motor is typically mounted directly to the metallic structure of the appliance, the ground connection is directly to the frame of the motor. In the event of an electric malfunction in the motor, the electric current is directed to the grounding system and people using the appliance are protected from receiving an electrical shock. Grounding of electrical devices in this manner is common. For the purpose of explaining the subject matter of the invention, the example of a small electric motor is used. However, it should be understood that the example is illustrative only and that the grounding system of the invention may be employed in many different types of electrical devices and is not intended to be limited to use with only electric motors. 
     FIG. 1 is a side elevation view of a typical electric motor  10 . The motor is basically comprised of a stator assembly  12 , a pair of end plates  14 ,  16  secured to opposite end surfaces of the stator assembly  12 , and a rotor (not shown) mounted on a rotor shaft  18  which in turn is mounted for rotation in a pair of bearings (not shown) mounted in the two end plates  14 ,  16 . A terminal block  20  constructed of an insulating material is mounted on the stator assembly  12 . The terminal block  20  has a series of electrical plugs  22  projecting from the block that are connected to the wiring of the stator assembly  12  and provide external connections to the circuitry of the appliance or other device with which the motor is used. The motor also comprises a ground connector  24  that is easily accessible for connection to a conductor used to connect the motor to an external ground, such as the earlier example of the water pipe. The ground connector  24  is secured and grounded to both the stator assembly  12  and one of the two end plates  14  of the motor by the bolt  26  and nut  28  threaded fasteners that secure the end plates  14 ,  16  to the opposite end surfaces of the stator assembly  12 . 
     FIG. 2 shows the stator  30  removed from the stator assembly  12  of the motor shown in FIG.  1 . The stator  30  in this example is comprised of a stack of laminate plates that each have the same, generally square peripheral edge  32 . The peripheral edges  32  of each of the plates in the stator stack forms a portion of the motor frame or exterior surface of the motor. The stator has a generally cylindrical center bore  34  surrounded by a plurality of stator poles  36 . Four fastener holes  38  pass entirely through the stator stack adjacent the four corners of the stator. The stator fastener holes  38  are positioned on the stator so that they will align with four fastener holes  40  in each of the end plates  14 ,  16  when the end plates are positioned on the opposite end surfaces of the stator. The stator also has two pairs of terminal block mounting post holes  42  adjacent opposite ends of the stator. The mounting post holes  42  are provided in pairs on opposite sides of the stator to enable a single terminal block to be mounted on either side of the stator or a pair of terminal blocks mounted on the opposite sides of the stator if needed. The mounting post holes  42  are dimensioned to receive mounting posts  44  of the terminal block  20  and to hold the terminal block securely against one of the end surfaces of the stator adjacent the post holes. Typically, the ground connector  24  is also mounted on the end surface of the stator adjacent the terminal block  20 . This provides all of the electrical connections to the motor on one side of the motor. As seen in FIG. 2, the ground connector  24  has a plug  46  at one end that projects from a grounding tab  48 . The tab  48  has a hole  50  therethrough that is dimensioned to be the same size as the stator fastener holes  38  and the end plate fastener holes  40 . 
     Generally describing the assembly of a motor such as that shown in FIG.  1  and the attachment of the prior art ground connector  24  to the motor, after the stator poles  36  are wound, the winding connections from the stator poles and other circuitry of the motor are made to the conductor plugs  22  of the terminal block  20 . The terminal block  20  is then mounted on the end surface of the stator assembly  12  by inserting its posts  44  into the mounting post holes  42  of the stator. The rotor assembly is then inserted into the stator bore. The rotor is supported in the stator bore by inserting the opposite ends of the rotor shaft  18  into bearing assemblies mounted into the two end plates  14 ,  16  as the end plates are assembled over the opposite end surfaces of the stator assembly  12 . 
     In assembling the end plates  14 ,  16  to the opposite end surfaces of the stator assembly  12 , the stator fastener holes  38  are aligned with end plate fastener holes  40  provided in each of the end plates. The end plates  14 ,  16  are secured to the opposite end surfaces of the stator assembly  12  by bolts  26  inserted through the aligned fastener holes of the stator and the end plates and by the nuts  28  screw threaded on the projecting ends of the bolts. However, before the bolts  26  are inserted through the aligned holes of the end plates and the stator assembly, the ground connector  24  is first positioned between the stator assembly and one of the end plates in its position shown in FIG.  1 . The ground connector tab  48  is inserted between the stator  12  and the one end plate  14  with its tab hole  50  aligned with a fastener hole  38  of the stator and a fastener hole  40  of the end plate. The bolts  26  are then inserted through the aligned holes and the nuts  28  are screw threaded on the projecting ends of the bolts and tightened down. 
     The installation of the prior art ground connector  24  requires the manual positioning of the connector tab  48  with the tab hole  50  coaxially aligned with one of the stator fastener hole  38  while also manually positioning the two end plates  14 ,  16  on the opposite end surfaces of the stator and inserting a fastener bolt  26  through the aligned holes of the end plates, the stator and the ground connector tab. The positioning of these components while aligning the hole of the ground connector tab with the stator fastener hole and the end plate fastener hole before inserting the bolt through the aligned holes is both time consuming and cumbersome for the motor assembler. 
     SUMMARY OF THE INVENTION 
     The disadvantages in the prior art motor discussed above could be overcome by a ground connector that could be installed in the terminal block. The terminal block would securely hold the ground connector relative to the terminal block and would position the tab hole of the ground connector over a stator fastener hole when the terminal block is attached to the stator. This would eliminate the need for the motor assembler to hold the ground connector tab in position while securing the two end plates to the opposite end surfaces of the stator with the bolt and nut fastener, thus greatly simplifying the assembly of the electrical device and permitting automated assembly of the device. 
     The present invention provides a grounding system for an electrical device where a ground connector is securely held by a terminal block of the device and the ground connector is properly positioned relative to other component parts of the electrical device for making a grounding connection with those other component parts when the terminal block is assembled to one of the component parts. The invention is basically comprised of a modified terminal block and a ground connector that is designed to be assembled to the terminal block and securely held by the terminal block. 
     The terminal block of the invention is, for the most part, similar to prior art terminal blocks in that it is constructed of an electrically insulating material and includes a plurality of plug sockets that securely hold electrically conducting plugs of the electrical device. The terminal block is assembled to a side of the electrical device where it positions the conductive plugs where they can be easily connected to mating receptacles of a separate electrical connector that is attached to the terminal block. The terminal block of the invention differs from prior art terminal blocks in that it is provided with a socket designed to received and securely hold the ground connector of the invention. 
     The ground connector socket extends from a back surface of the terminal block to its front surface and is positioned on the terminal block in line with the other plug sockets of the terminal block and adjacent one side of the terminal block. The ground connector socket has a cross-section configuration that resembles two diametrically opposite quarter circles. A recessed slot intersects the ground connector socket at the back surface of the terminal block. 
     The ground connector is formed of a single monolithic piece of electrically conductive material. The ground connector has a length with a ground plug at one end and a connecting tab at its opposite end with a span of the ground connector connecting the ground plug and the tab. The tab is flat and has a hole passing therethrough for receipt of a threaded fastener of the electrical device. The tab projects from one end of the span of the ground connector and is positioned perpendicular to the span of the ground connector. The plug is also flat and projects from an end of the connector span opposite the tab. The plug has a series of barbs adjacent its connection to the span. The plug projects perpendicularly from the span and both the plug and the tab are positioned in parallel, horizontal planes although not in the same horizontal plane. 
     The plug of the ground connector is inserted into the terminal block ground connector socket from the back of the terminal block. However, because the mounting posts of the terminal block are also positioned at the back of the terminal block, the ground connector plug cannot be inserted directly into the ground plug socket of the terminal block due to the length of the span connecting the ground connector plug to the tab. The ground connector plug is first inserted into the ground connector socket of the terminal block from the back of the terminal block with the span of the ground connector positioned generally parallel with the adjacent mounting post of the terminal block. The ground connector plug is inserted a sufficient distance into the ground connector socket of the terminal block until the span of the ground connector is positioned generally between the back of the terminal block and the adjacent mounting post. In this position of the ground connector it can be rotated 90° causing the span of the ground connector to be positioned between the back of the terminal block and the adjacent mounting post of the terminal block. Once in this position the ground connector plug is inserted to its full extent into the ground connector socket of the terminal block. The ground connector plug barbs are inserted into the recessed slot in the back of the terminal block as the ground connector plug is inserted completely into the ground connector socket of the terminal block. The barbs engage in the material of the terminal block as they are inserted into the recessed slot, thereby securely holding the ground connector to the terminal block. 
     With the ground connector plug completely inserted into the ground connector socket of the terminal block and with the barbs of the plug engaging in the material of the terminal block slot, the span extends across the back of the terminal block between the back of the terminal block and the mounting plug of the terminal block to the tab which is positioned by the span to one side of the terminal block. With this positioning of the tab by the span, when the terminal block is attached to the stator by inserting the terminal block mounting posts into the post holes of the stator, the span of the ground connector positions the tab over an end surface of the stator with the tab hole aligned coaxially with a fastener hole of the stator. In this position of the tab it provides a ground connection between the stator and an end plate of the electrical device that is attached to the surface of the stator the tab overlaps. The threaded fasteners passed through the fastener hole of the stator and the end plate hole with which the tab hole is aligned securely holds the tab between the stator and end plate. In this manner, the ground connector provides an electrically conductive ground connection between the stator and the end plate. Furthermore, with the ground connector securely held in the terminal block, the ground connector tab hole is held in alignment with the stator fastener hole and the end plate fastener hole by the terminal block being attached to the stator. Thus, the construction of the terminal block and the ground connector simplifies the prior art connection of a ground connector to an electrical device and also provides for automated assembly of the ground connector to the electrical device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and features of the invention will be revealed in the following detailed description of the preferred embodiment of the invention and in the drawing figures wherein: 
     FIG. 1 is a side elevation view of a prior art electrical device, in this case a prior art electric motor; 
     FIG. 2 is a view of the stator disassembled from the motor of FIG. 1; 
     FIG. 3 is a top plan view of the ground connector of the invention; 
     FIG. 4 is a bottom plan view of the ground connector; 
     FIG. 5 is a front elevation view of the ground connector; 
     FIG. 6 is a side elevation view of the ground connector; 
     FIGS. 7 and 8 show the terminal block ground connector socket of the invention and illustrate steps in attaching the ground connector of the invention to the terminal block; 
     FIG. 9 shows the ground connector of the invention attached to the terminal block; 
     FIGS. 10 and 11 illustrate the assembly of the terminal block and ground connector of the invention to a stator; and 
     FIG. 12 shows the terminal block of the invention assembled to an electrical device such as the motor shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 3 through 6 show an assortment of views of the ground connector  54  of the present invention. In the preferred embodiment of the invention the ground connector  54  is stamped or formed from a single, monolithic piece of metal having good electrically conductive properties. From the stamped blank of metal the ground connector is formed with an intermediate length or span  56  having opposite proximal  58  and distal  60  ends. The proximal end  58  is that closest to the terminal block and the distal end  60  is that closest to the connection to the motor stator  30  and end plate  14  as will be explained. The ground connector intermediate span  56  has opposite front  62  and back  64  surfaces that are flat, and in particular the front surface  62  is flat to lay flush against a back surface of the terminal block as will be explained. 
     A connector plug  66  at the proximal end  58  of the span projects perpendicularly from the span. As seen in FIG. 6, the plug  66  is generally flat and is bent outwardly from the proximal end  58  of the intermediate span  56 . A distal end  68  of the plug  66  is formed in the conventional manner with tapered surfaces to facilitate receipt of a mating receptacle on the plug. The connector plug  66  has a sufficient length from the span  56  to enable the plug to pass completely through the terminal block with the span front surface  62  resting against the back of the terminal block as will be explained. The plug is formed with opposed pairs of barbs  70  adjacent the connection of the plug to the span  56 . The barbs  70  project slightly outwardly from the opposite edges of the plug  66  and are employed in securing the plug to the terminal block as will be explained. 
     A grounding tab  72  is formed at the distal end  60  of the ground connector. As seen in FIG. 6, the grounding tab  72  is bent from the distal end  60  of the ground connector so that it projects generally perpendicularly from the back surface  64  of the ground connector span  56 . Where the tab  72  connects with the distal end  60  of the ground connector span it is provided with a bend portion  74 . The bend portion  74  functions as a spring and enables the ground connecting tab  72  to flex resiliently relative to the intermediate span  56  of the ground connector about the bend portion  74 . As seen in FIGS. 3 and 4, the grounding tab  74  extends outwardly from the ground connector span and has a tab hole  76  adjacent a distal end  78  of the tab. The tab hole  76  has an interior diameter that is dimensioned at least as large as the fastener holes  38  of the stator and the fastener holes  40  of the end plate with which the ground connector  54  is to be used. 
     The terminal block  82  of the invention is shown in FIGS. 10 through 12 and the inventive portion of the terminal block is shown in the partial views of the terminal block of FIGS. 7 through 9. The terminal block of the invention is a modification of the terminal block of the prior art and therefore its overall construction will not be described in detail. The terminal block  82  is constructed of an electrically insulating material and has opposite top  84  and bottom  86  surfaces and a back surface  88 . A plurality of plug sockets  90  pass through the terminal block from its back surface  88  to the front of the terminal block. The plug sockets  90  are designed to receive and securely hold various different types of electrical connectors  92  such as those shown in FIG.  12 . Also shown in FIG. 12 are a pair of arms  94  with opposed clasps or pawls  96  that are positioned to receive a receptacle plug therebetween and are configured to grasp the receptacle plug inserted between the arms  94 . Shown to the right in FIG. 12 is the plug socket  102  and the connector plug  66  of the ground connector  54  of the invention. 
     The top surface  84  of the terminal block extends rearwardly across the top of an upper ledge  104  that projects from the terminal block back surface  88 . Extending downwardly from the upper ledge  104  are a pair of terminal block mounting posts  106 . Because the mounting posts  106  extend downwardly from the upper ledge  104  of the terminal block, the terminal block of the invention is mounted on a side of the stator  30  instead of on an end surface of the stator as shown in FIG.  1 . The back surface  88  of the terminal block engages against the side of the stator stabilizing the terminal block on the stator. The terminal block back surface  88 , the upper ledge  104  and one of the mounting posts  106  of the inventive terminal block  82  can be see in the partial views of FIGS. 7 through 9. The inventive plug socket  102  of the terminal block is also seen in FIGS. 7 through 9 as well as FIG.  12 . 
     The plug socket  102  passes completely through the terminal block  82  from the back surface  88  through to the front of the terminal block. As seen in FIGS. 7 through 9 and  12 , the plug socket  102  has a cross-section configuration of a pair of connected, diametrically opposed quarter circles. This configuration is best seen in FIG.  12 . This cross-section of the plug socket  102  extends completely through the terminal block  82 . However, adjacent the back surface  88  of the terminal block the plug socket  102  is also formed with a recessed slot  108 . The recessed slot  108  can be seen in FIGS. 7 and 8. The slot  108  is dimensioned to received the opposed barbs  70  of the ground connector plug  66  with the barbs  70  digging into the material of the terminal block at the opposite ends of the slot  108  to securely hold the barbs and the plug  60  in the plug socket  102  as will be explained. 
     FIGS. 7 through 9 illustrate the insertion and attachment of the ground connector  54  to the terminal block  82 . In the initial insertion of the ground connector, the connector plug  66  is inserted into the socket  102  at the back surface  88  of the terminal block with the plug  66  positioned generally perpendicular to the recessed slot  108 . This orientation of the ground connector  54  allows a substantial portion of the connector plug  66  to be inserted through the plug socket  102  without the adjacent terminal block post  106  interfering with the insertion. As can be seen in FIG. 7, a substantial portion of the connector plug  66  can be inserted through the plug socket  102  without the mounting post  106  shown in FIG. 7 contacting the ground connector span  56  and interfering with the plugs insertion. Once the plug  66  is inserted to the extent that is barbs  70  come into contact with the terminal block back surface  88  as shown in FIG. 7, then the ground connector  54  is rotated relative to the terminal block  82  so that the intermediate span or length  56  of the ground connector passes between the terminal block back surface  88  and the adjacent mounting post  106  as shown in FIG.  8 . While the ground connector  54  is rotated in this manner the barbs  70  come into alignment with the recessed slot  108 . When the barbs  70  are aligned with the recessed slot  108  they are inserted into the slot thereby securely holding the ground connector  54  in the terminal block  82  in the relative positions of the ground connector and terminal block shown in FIG.  9 . With the ground connector so assembled to the terminal block, the terminal block  82  can now be assembled to the stator assembly  12  and the particular configuration of the ground connector  54  will position the grounding tab  72  between the stator assembly  12  and the end plate  14  with the tab hole  76  aligned with a stator fastener hole  38  and an end plate fastener hole  40 . 
     FIGS. 10 through 12 illustrate the assembly of the terminal block  82  and the attached ground connector  54  to an electric device such as the motor shown in FIG.  1 . As in the assembly of the prior art terminal block to the stator assembly  12 , the mounting posts  106  of the terminal block are positioned over the mounting post holes  42  of the stator. The mounting posts  106  are then inserted into the stator post holes  42  until the terminal block upper ledge  104  rests against the end surface of the stator onto which the end plate is to be mounted. This attachment of the terminal block  82  to the stator  12  properly positions the grounding tab  72  over the surface of the stator with the tab hole  76  aligned with a stator fastener hole  38  as shown in FIG.  11 . When the end plate  14  is positioned against the end surface of the stator assembly  12 , the end plate fastener hole  40  that aligns with the stator fastener hole  38  also aligns with the tab hole  76  as shown in FIG.  12 . When a bolt  26  connector is then inserted through the aligned end plate fastener hole  40  and stator fastener hole  38  it also passes through the tab hole  76  of the ground connector. Securing the bolt  26  with a nut  28  as was done in the prior art assembly of the electric device provides the grounding connection between the grounding tab  72  of the ground connector  54  and the stator assembly  12  and end plate  14 . 
     The ground connector  54  and terminal block  82  of the invention provide a grounding system in which the need to manually hold a grounding tab relative to a stator and end plate of an electric device as the stator and end plate are assembled together is eliminated. The grounding system of the invention facilitates the manual assembly of a ground connector to an electrical device and also enables automated assembly of the ground connector to the electrical device. 
     While the present invention has been described by reference to specific embodiments, it should be understood that modifications and variations of the invention may be constructed without departing from the scope of the invention defined in the following claims.

Technology Category: 5