Abstract:
An interlock mechanism for preventing or enabling the operation of a handle operator or a contactor in certain circumstances comprises a system of mechanical linkages which interact to determine whether a lock-out mode or an enabling mode exists with respect to the electric motor being controlled. In the handle assembly, the lock-out bar has a circular aperture that receives a push rod in the enable mode and blocks the push rod in the lock-out mode. The push rod is connected to a blocking bracket which must be depressed by a human operator prior to cycling the handle operator. If the blocking bracket cannot be fully depressed by the human operator because the push rod is blocked by the lock-out bar, then the human operator can not cycle the handle operator between its OFF and ON positions, thus a first half of the interlock is achieved. Conversely, the interlock is also designed to prevent the contactor from supplying power to the electric motor if the handle operator is being cycled. If the switch has been closed (handle operator is in the ON position) and power has been supplied to the contactor but not yet to the electric motor, and the blocking bracket has been activated successfully such that the push rod has engaged the lock-out bar, then the contactor pawl assembly is unable to move and thus the contactor cannot be command to supply power to the electric motor. Thus a two way mechanical interlock is achieved.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional of U.S. patent application Ser. No. 09/206,489, filed on Dec. 7, 1998, pending, which is herein incorporated by reference in it&#39;s entirety. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    The present invention is generally directed to the method and design of mechanical interlock linkages for electrical equipment. More particularly, the present invention is directed to an improved interlock linkage for use in a handle/switch/contactor combination as applied to high powered electric motors. The improved interlock design and method greatly improves reliability, defects per million opportunities, part count, and manufacturing costs.  
           [0003]    The present invention is an improvement over the prior art. Specifically U.S. Pat. No. 5,424,911 to Joyner et al. disclosed a compact motor controller assembly. Motor controller equipment generally includes so-called “high voltage” motor contactors such as described within U.S. Pat. No. 3,198,910 entitled “Electromagnetic Relay Having Removable Contact and Coil Assemblies” as well as “low voltage” equipment in the form of relays and the like. One such relay being that described within U.S. Pat. No. 5,057,962 entitled “Microprocessor Based Protective Relay System”.  
           [0004]    The motor controller equipment is interlocked with the externally accessible handle operator to prevent access to the high voltage equipment when the operating handle is in the ON position. U.S. Pat. No. 4,760,220 entitled “Operator Mechanism Having Reduced Handle Throw and Improved Handle Lock” is one example of such an interlock.  
           [0005]    The state of the art of such motor controller equipment is to mount the low voltage equipment in cabinets having a separate access door from that of the high voltage contactor within a separate compartment to allow ready access to the low voltage equipment without having to turn off the contactor. U.S. Pat. No. 3,621,339 entitled “Modular High Voltage Electrical Components Cooperating Within Cabinet Housing to Provide Electrical Insulation and Cooling Air Passage” describes the separate arrangement of the high voltage contactors and low voltage equipment.  
           [0006]    Therefore it has been determined that a need exists for an improved design of the interlock which increases reliability, lowers part count and manufacturing costs, all while improving operability.  
         SUMMARY OF INVENTION  
         [0007]    In accordance with a preferred embodiment of the present invention, an interlock mechanism for preventing or enabling the operation of a handle operator or a contactor in certain circumstances comprises a system of mechanical linkages which interact to determine whether a lock-out mode or an enabling mode exists with respect to the electric motor being controlled. A handle operator controls a switch which makes or breaks power to the contactor. Once the contactor has been supplied power by the switch, the contactor may then be commanded to supply and remove electric power to and from the electric motor. If the contactor is supplying power to the electric motor, the contactor activates a contactor pawl assembly to initiate a handle lock-out mode. The contactor pawl assembly displaces a lock-out bar in a linear manner which causes the handle operator to be locked-out. In the handle assembly, the lock-out bar has a circular aperture that receives a push rod in the enable mode and blocks the push rod in the lock-out mode. The push rod is connected to a blocking bracket which must be depressed by a human operator prior to cycling the handle operator. If the blocking bracket cannot be fully depressed by the human operator because the push rod is blocked by the lock-out bar, then the human operator can not cycle the handle operator between its OFF and ON positions, thus a first half of the interlock is achieved. Conversely, the interlock is also designed to prevent the contactor from supplying power to the electric motor if the handle operator is being cycled. If the switch has been closed (handle operator is in the ON position) and power has been supplied to the contactor but not yet to the electric motor, and the blocking bracket has been activated successfully such that the push rod has engaged the lock-out bar, then the contactor pawl assembly is unable to move and thus the contactor cannot be command to supply power to the electric motor. Thus a two way mechanical interlock is achieved.  
           [0008]    The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.  
         BRIEF DESCRIPTION OF DRAWINGS  
         [0009]    Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
           [0010]    [0010]FIG. 1 is a perspective view of a handle assembly illustrating the internal structure including several mechanical linkages;  
           [0011]    [0011]FIG. 2 is a side elevation view of a handle assembly illustrating the internal structure including several mechanical linkages and position switches;  
           [0012]    [0012]FIG. 3 is a top plan view of the handle assembly of FIG. 2 taken along line AA;  
           [0013]    [0013]FIG. 4 is a bottom plan view of the handle assembly of FIG. 2 taken along line BB;  
           [0014]    [0014]FIG. 5A is a perspective view of a lock-out bar which is the mechanical link between the handle assembly and the contactor assembly.  
           [0015]    [0015]FIG. 5B is a side elevation view of a lock-out bar showing the z-bracket and the adjustment pin;  
           [0016]    [0016]FIG. 5C is a top plan view of a lock-out bar showing the rectangular aperture in the z-bracket and the circular aperture in the lock-out bar head section;  
           [0017]    [0017]FIG. 5D is a top plan view of a z-bracket showing the rectangular aperture in the z-bracket and other preferred dimensions;  
           [0018]    [0018]FIG. 5E is a side elevation view of a z-bracket showing the z-shape and other preferred dimensions;  
           [0019]    [0019]FIG. 6A is a perspective view of a the top section of the lock-out bar in the enable position allowing the push rod end to travel laterally through the left support bracket;  
           [0020]    [0020]FIG. 6B is a perspective view of FIG. 6A along line CC illustrating how the push rod end has traveled through the left support bracket;  
           [0021]    [0021]FIG. 6C is a perspective view of a the top section of the lock-out bar in the lock-out position blocking the push rod end from traveling laterally through the left support bracket;  
           [0022]    [0022]FIG. 6D is a perspective view of FIG. 6C along line DD illustrating how the push rod is blocked from travelling laterally by the vertically raised lock-out bar;  
           [0023]    [0023]FIG. 7A is a perspective view of a contactor pawl assembly illustrating a mounting bracket and the rotating plate;  
           [0024]    [0024]FIG. 7B is a rear elevation view of a contactor pawl assembly illustrating a mounting bracket and a rod attachment block;  
           [0025]    [0025]FIG. 7C is a top plan view of a contactor pawl assembly illustrating a mounting bracket, rod attachment block, pin hole, rotating plate and bolt assembly;  
           [0026]    [0026]FIG. 7D is a side elevation view of a contactor pawl assembly illustrating a mounting bracket, rotating plate, mouth and bolt assembly. 
       
    
    
     DETAILED DESCRIPTION  
       [0027]    Referring now to FIG. 1, a perspective view of a handle assembly illustrating the internal structure including several mechanical linkages is shown. The handle operator  3  is currently shown in an ON position. When the handle operator  3  is moved downward to its lowest allowed position, it is in the OFF position  3 A (dashed handle). When the handle operator  3  is moved from one position to the other, it is said to have “cycled.” A mechanical interlock circuit (described below) either allows or prevents, depending certain conditions, the handle operator  3  to be cycled, or (as later described) the contactor to supply power to the electric motor. The lock-out bar  17  should be noted as it extends in a downward fashion from the handle assembly  1 . The adjustment pin  105  of the lock-out bar  17  is mechanically connected to and operated by a contactor pawl assembly  150  (not shown) as described in detail below.  
         [0028]    Referring to FIG. 2, a side elevation view of the handle assembly  1  is shown. The handle assembly  1  is used to open and close a switch (separate assembly, not shown) which supplies electrical power to the contactor (not shown). The handle  3  (shown in the ON position) is coupled to a first fork  5  (see FIG. 4) of horizontal rod  10  and a second fork  9  of the rod  10  is pivotally connected to a bell crank lever  6 . An inclined rod  8  has a first fork  7  pivotally mounted to the bell crank  6  and a second fork  77  which is connected to a switch assembly (not shown). The bell crank  6  is rotatably mounted to the handle assembly support frame  78  at pivot point P 1 .  
         [0029]    Disregarding the interlock mechanism for the moment, and considering only the operation of the handle  3  with respect to the switch, the handle is shown in the ON position. When the handle  3  is cycled to the OFF position  3 A, the horizontal rod  10  is retracted towards the handle housing  2  causing the bell crank  6  to rotate in a counter-clockwise manner, further causing inclined rod  8  to move in an upward manner and imparting such motion to the switch assembly (not shown). When the handle  3  is cycled from the OFF position  3 A back to the ON position  3 , just the opposite occurs with respect to the mechanical linkage. As the handle  3  cycles from OFF to ON, the horizontal rod  10  is forced to extend away from the handle housing  2  causing bell crank  6  to rotate in a clockwise manner, and further causing inclined rod  8  to move in a downward manner and imparting such motion to the switch assembly. This is the manner in which the handle  3  cycles power to and from the contactor.  
         [0030]    Referring to FIG. 2, further, an interlock feature is described. Blocking bracket  4  is slidably mounted on the handle housing  2  and springedly predisposed to rest away from the handle housing  2  in its normal handle lockout position. In the normal handle lockout position, the blocking bracket provides a mechanical interference so that the handle operator  3  cannot cycle. The blocking bracket  4  is connected to a first end  51  of push rod  41  (see FIG. 4) while the opposing or second end  52  of the push rod  41  is laterally restrained by a circular aperture  25  in support bracket  24  which is mounted on the support frame  78  of the handle assembly  1 . The push rod  41  passes through and supports a helical spring  81  which is longitudinally restrained at one end by the support bracket  24  and exerts a repositioning force on the blocking bracket  4 . A companion support bracket  11  is mounted further aft of support bracket  24  and aligned to receive the opposing or second end  52  of the push rod  41 . Between the support brackets  11  &amp;  24 , the lock-out bar  17  is suspended from the push rod  41  as described below. The preferred diameter of the push rod  41  including its second end  52  is 0.500 in. and the preferred diameter of the circular aperture  25  in the right support bracket  24  is 0.560 in.  
         [0031]    Referring to FIG. 3, a top plan view of the handle assembly  1  taken along line AA of FIG. 2 is shown. It can be seen that the handle  3 , horizontal rod  10 , bell crank  6 , and inclined rod  8  all lie in the same vertical plane. It is also shown that the spring loaded push rod  41  operates on a parallel axis to the horizontal rod  10  but in a separate vertical plane. In this drawing the blocking bracket  4  and spring loaded push rod  41  (spring not shown) are at rest with the second end  52  of push rod  41  located between the left support bracket  11  and the right support bracket  24 . In this position, as will be further described below, the lock-out bar  17  may be activated by the contactor pawl assembly  150  (not shown) to either an up or down position.  
         [0032]    Referring to FIG. 4, a bottom plan view of the handle assembly  1  taken along line BB of FIG. 2 is shown. The adjustment pin  105  is shown with an adjusting nut  42  mounted about the pin  105 . The adjustment pin  105  and several adjusting nuts  42  are used to connect the lock-out bar  17  to the contactor pawl assembly  150  as described in detail below.  
         [0033]    Referring to FIG. 5A, a perspective view of a lock-out bar  17  which is the mechanical and operational link between the handle assembly  1  and the contactor assembly  150  is shown. The bar  17  is formed from an elongated plate having a head  102 , a body  101 , and a base  103 . A slot  104  is formed in the base  103  so as to receive an adjustment pin  105 . The pin  105  is rigidly held in the slot  104  using the preferred method of a mig-weld. A circular aperture  106  is formed in the head  102  of sufficient diameter to receive and allow a second end  52  of push rod  41  to pass through the head  102  of the lock-out bar  17  as further described below.  
         [0034]    A z-bracket  110  having a top leg  111  and a bottom leg  112  is secured to the head  102  of the bar  17  by using well know mechanical means such as spot welding. The z-bracket  110  is dimensioned and positioned such that the perimeter surfaces of the top leg  111  are flush with the perimeter of the head  102  of the bar  17 . A rectangular aperture  113  is formed in the top leg  111  of the z-bracket  110  and through which the push rod  41  will pass and slide in a horizontal manner. Further the rectangular aperture  113  will allow for the bar  17  to move in a vertical manner, up and down, relative to the push rod  41 . The preferred dimensions of the rectangular aperture  113  are 0.560 in. wide and 1.50 in. long. The width of the rectangular aperture is in close tolerance to the diameter of the push rod  41  (0.500 in.) so as to keep the lock-out bar  17  fairly restrained in lateral movement.  
         [0035]    Referring to FIG. 5B, a side elevation view of a lock-out bar  17  illustrating a z-bracket  110  and an adjustment pin  105  is shown. The top leg  111  of the z-bracket  110  is substantially parallel to the head  102  of the bar  17  and the two surfaces are separated by a predetermined gap G 1 . The preferred dimension of the gap G 1  is 0.50 in. and is designed into the bar  17  to allow the push rod  41  and bar  17  to interact in a novel manner more particularly described below.  
         [0036]    Referring to FIG. 5C, a top plan view of a lock-out bar  17  illustrating the alignment of the rectangular aperture  113  in the top leg  111  of the z-bracket  110  with the circular aperture  106  in the head  102  of the bar  17  is shown. As can be seen in this view, a portion of the rectangular aperture  113  and a portion of the circular aperture  106  over lap each other providing a continuous through-hole path  107  in the bar  17 . This dimensions of the continuous through-hole path  107  are predetermined to allow the push rod  41  to slide unimpeded through both the rectangular aperture  113  and the circular aperture  106  during certain configurations of the bar  17  and the push rod  41  as more particularly described below.  
         [0037]    The preferred diameter of circular aperture  106  is 0.750 in. and the center of the aperture  106  is located on the head  102  of the bar  17  such that when the lock-out bar  17  is being supported by the push rod  41 , i.e., when the push rod  41  is in contact with the upper edge of the rectangular aperture  113 , then the center of push rod  41  is axially aligned with the center of circular aperture  106 . This provides a clearance about the push rod  41  with respect to circular aperture  106  when the push rod  41  is activated. When a human operator pushes on the blocking bracket  4 , the push rod (O.D. 0.500 in.) will smoothly pass through circular aperture  106  (I.D. 0.750 in.) as long as the lock-out bar  17  is in the enable position.  
         [0038]    Referring to FIG. 5D, a top plan view of a z-bracket  110  showing the rectangular aperture  113  in the z-bracket  110  and other preferred dimensions is shown. The width of the rectangular aperture  113  is 0.560 in and the length is 1.50 in. The overall width of the z-bracket is 1.0 in. The rectangular aperture  113  is offset from the side edge  114  by 0.220 in. and offset from the top edge  115  by 0.250 in.  
         [0039]    Referring to FIG. 5E, a side elevation view of a z-bracket  110  showing the z-shape and other preferred dimensions is shown. The overall length of the z-bracket  110  is 3.50 in. with a height of 0.50 in. from outside bottom leg  112  to outside top leg  111 . The overall length of the top leg  111  is 2.0 in. The overall length of the bottom leg  112  is 1.50 in.  
         [0040]    Referring now to FIGS. 6A &amp; 6B, the enabling mode of the lock-out bar  17  is shown. In FIG. 6A, a perspective view illustrating the top section of the lock-out bar  17 , respective left and right support brackets  11  &amp;  24 , helical spring  81  and a push rod  41  is shown. In FIG. 6B a perspective view of FIG. 6A along line CC is shown.  
         [0041]    In the enabling mode as shown in FIGS. 6A &amp; 6B, the push rod  41  has been displaced successfully towards and through the left support bracket  11  by the blocking bracket  4  (not shown) to a handle operational position R 2 . In these figures, the lock-out bar  17  is in the enable position (down) allowing the push rod end  52  to travel laterally through, first, the circular aperture  106  in the head  102  of the bar  17 , and second, through the circular aperture  12  in the left bracket  11 . The preferred diameter of circular aperture  12  is 0.600 in. Once the push rod  41  has traveled through the aperture  12  of the left support bracket  11  so that the second end  52  of the push rod  41  passes through the plane R 2 , the blocking bracket  4  has been displaced a sufficient lateral distance to allow the handle operator  3  to be cycled. When the blocking bracket  4  is not being displaced by human force, it is driven away from the handle housing  2  by the helical spring  81  to a rest position. The push rod  41  and its second end  52  comes to rest inside the gap G 1  at a location shown by dotted line R 1  in FIG. 6B. When the push rod  41  is in this rest position R 1 , it can be seen that the lock-out bar  17  may be displaced up and down in a vertical manner by the contactor pawl assembly  150  because the bar  17  has a rectangular aperture  13  which allows for this movement about the then stationary push rod  41 .  
         [0042]    Referring now to FIGS. 6C &amp; 6D, the lock-out mode of the lock-out bar  17  is shown. In FIG. 6C, a perspective view illustrating the top section of the lock-out bar  17 , respective left and right support brackets  11  &amp;  24 , helical spring  81  and a push rod  41  is shown. In FIG. 6D, a perspective view of FIG. 6C along line DD is shown.  
         [0043]    In the lock-out mode as shown in FIGS. 6C &amp; 6D, the lock-out bar  17  has been vertically raised by the contactor pawl assembly  150  (not shown) so that circular aperture  106  in the head  102  is no longer axially aligned with push rod  41 . The rectangular opening  113  in the top leg  111  of the z-bracket  110  is dimensioned longitudinally so that the bar  17  can move a sufficient vertical distance to misalign circular aperture  106  and the push rod  41 . Thus when the push rod  41  is displaced laterally by the blocking bracket  4  from rest position R 1  towards handle operational position R 2 , the path and movement of push rod  41  are blocked by the head  102  of the bar  17 . Therefore the blocking bracket  4 , which can not now be sufficiently depressed by the human operator, is still blocking the path of the handle operator  3  and the handle operator  3  can not be cycled between ON and OFF positions.  
         [0044]    It will be understood by those skilled in the art that the push rod second end  52  forms a “key” and that circular aperture  106  forms a “keyway” to receive the “key”. It is noted that a key/keyway could be constructed from other matching shapes besides a rod/hole pair and that such shapes would perform the same enabling or blocking functions.  
         [0045]    Referring to FIG. 7A, a perspective view of a contactor pawl assembly  150  illustrating a mounting bracket  151  and a rotating plate  152  is shown. The contactor pawl assembly  150  is mechanically linked to a contactor (not shown) by a linkage member (not shown) having one end confined to a mouth  153 . Thus when the contactor applies power to the electric motor, the linkage member deflects the mouth  153  in a downward manner causing the plate  152  to rotate about arc A 1 . This rotation raises up rod attachment block  154 . Rod attachment block  154  has a through-hole  155  which receives the adjustment pin  105  of lock-out bar  17 . Adjusting nuts  42  are located on the adjustment pin  105  above and below rod attachment block  154  securing the pin  105  to the block  154 . The adjustment nuts  42  are used to bring the linkages into proper alignment.  
         [0046]    As the rod attachment block  154  is raised, the adjustment pin  105  is also raised forcing the lock-out bar  17  to also be raised, thus misaligning the push rod  41  and the circular aperture  106  putting the lock-out bar  17  in the lock-out mode as described above.  
         [0047]    After the contactor has removed electric power from the electric motor, the linkage from the contactor to the mouth  153  rotates the mouth  153  in an upward direction, with the rod attachment block  154  and adjustment pin  105  being moved downward to the enable position. Thus the lock-out bar  17  is lowered and the push rod  41  is axially aligned with the circular aperture  106  which allows for the push rod  41  to be displaced horizontally to the handle operational position R 2 . Now the handle operator  3  can be safely cycled as power has been removed from the electric motor.  
         [0048]    Referring now to FIG. 7B, a rear elevation view of a contactor pawl assembly  150  illustrating a mounting bracket  151 , rotating plate  152 , bolt assembly  156 , rod attachment block  154 , and cylindrical shoulder  157  are shown. It should be noted that the rod attachment block  154  may rotate relative to the plate  152  due to its cylindrical shoulder  157 . This eliminates any rotational motion to be imparted from the plate  152  to the lock-out bar  17  through the adjustment pin  105 .  
         [0049]    Referring to FIG. 7C, a top plan view of a contactor pawl assembly  150  illustrating a mounting bracket  151 , a rod attachment block  154 , a through-hole  155 , a cylindrical shoulder  157 , a cotter pin hole  158 , a rotating plate  152 , and bolt assembly  156  is shown. The rod attachment block  154  is rotatably mounted to the plate  152  by passing its cylindrical shoulder  157  through a hole in the plate  152 , sliding a washer over the shoulder  157  and capturing the shoulder  157  with a cotter pin assembled in cotter pin hole  158  in a manner well know in the art.  
         [0050]    Referring now to FIG. 7D, a side elevation view of a contactor pawl assembly  150  illustrating a mounting bracket  151 , a rotating plate  152 , a cylindrical shoulder  157 , and bolt assembly  156  is shown. It can be seen that when the linkage from the contactor (not shown) drives the mouth  153  of the rotating plate  152 , such motion is inverted with respect to the motion imparted to the adjustment pin  105  captured in the rod attachment block  154 . That is, when the contactor (not shown) drives the mouth  153  upward to the enable mode position, the rotating plate  152  causes the rod attachment block  154  to descend pulling down the lock-out bar  17  and allowing axial alignment of the circular aperture  106  with the push rod  41  so that the push rod  41  may be successfully received by the circular aperture  106  if the blocking bracket  4  is depressed. Finally when the contactor drives the mouth  153  downward to the lock-out position, the rotating plate  152  causes the rod attachment block  154  to rise pushing up the lock-out bar  17 , and causing misalignment of the circular aperture  106  with the push rod  41  so that when the blocking bracket  4  is depressed, it can not be fully depressed as the push rod  41  is blocked by the head  102  of the lock-out bar  17 , thus preventing the handle operator  3  from being cycled between ON and OFF positions.  
         [0051]    It will also be appreciated by those skilled in the art that when the push rod  41  has been activated and passed through aperture  106 , the contactor pawl assembly cannot pull the bar  17  down in response to a demand from the contactor (not shown) to close. Thus, the interlock also prevents the closing of the contactor when the handle operator  3  is about to be cycled. This would occur in a situation where a hot contactor (switch is closed supplying power to the contactor) was being commanded to turn on the motor, but an operator had pushed in the blocking bracket  4  to cycle the operator handle  3 . Thus we are preventing the contactor from closing as the switch is about to be opened, thus preventing the switch from removing power directly from the motor.  
         [0052]    From the above, it should be appreciated that the systems and apparatus described herein provide a reliable interlock system for handle operators, switches, and electric motors. It should also be appreciated that the interlock apparatus of the present invention permits the reduction of parts and adjustment points, increased reliability, and increased safety.  
         [0053]    While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.