Abstract:
A mechanical interlock of a lever operated receptacle with a shaft operated switch is disclosed and provides mechanically interlocked electrical service to cord-connected equipment such as wheeled gantries, vehicles docked at port terminals, heavy manufacturing, and mining equipment. The power transmission safety system locks a plug into a receptacle until a main power switch has been disengaged and a grounding switch has been engaged. Only if the receptacle is switched off and grounded will the receptacle allow a plug to be inserted. The power transmission safety system is mechanically prohibited from being engaged or ungrounded until a plug has been inserted into the receptacle and locked into place. To again unlock and remove the plug from the receptacle, the power transmission safety system must be deactivated and grounded.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally directed to an apparatus and a method for providing a mechanical interlock of a lever operated receptacle with a shaft operated switch. More specifically, a mechanically interlocked ground switch, main power switch, receptacle, and receptacle handle lever prevents energizing the receptacle or disconnecting the ground switch without the plug being inserted and locked into the receptacle. Further, the unlocking or disengaging of the plug while the switch is on and ungrounded is mechanically and reliably prevented. In other words the power switch cannot be turned on without a properly inserted plug and the plug cannot then be removed with the switch remaining in the on position. 
     2. Prior Art 
     Interlock systems of other lever operated receptacles in use in modern electrical systems may employ an electrically interlocked system using logic to disallow potentially dangerous or undesirable conditions. However, if the electrical system fails for any reason, the electrical interlock system would also fail—potentially resulting in casualty or damage to powered systems. 
     Another strategy is to use a key interlock system where a key is used to restrict access to and limit potential states of the system. However this faces the drawbacks of heightened expense, complicated key logistics, key access accounting, access control, and secure storage balanced with accessibility. If a key should be lost, the system is rendered inoperative until a replacement key can be identified and procured. In an emergency situation, this can result in catastrophic losses and delay costs brought about by lost productivity, late deliveries, missed deadlines, locksmiths, as well as key administration costs. 
     More importantly, the system is able to be undermined through the use of duplicate keys or neglecting to re-lock the systems appropriately. Such a system is entirely dependent on users remembering and choosing to relock the system each and every time. 
     Another conventional means to ensure proper operation of an electrical receptacle and switch is operator training. Operators are simply trained to perform operations in a specified sequence so as to reduce harm to components and personnel. However, this is difficult to enforce and exposes personnel and hardware to great risks should the procedures not be followed correctly. Again, such a system is entirely dependent upon voluntary compliance each and every time by users. 
     Thus, one problem associated with conventional power switches and receptacles is the exposure of technicians or ordinary users to potentially dangerous and even life threatening situations where interlock systems are susceptible to failure and lack assured enforcement of safety procedures. Such systems are easily undermined, omitted, or broken. 
     Yet another problem associated with conventional power switches is the ease with which one can overcome the previous protection schemes either maliciously, through laziness, or improper user/technician education. 
     SUMMARY OF THE INVENTION 
     An enclosure is provided in which is contained a main power switch and a ground switch. Each of the main power switch and the ground switch are coupled to a respective actuating shaft. The two shafts are disposed in a substantially parallel arrangement. The enclosure has at least one access door which, when opened, provides access to two through holes through at least one obstructive member that blocks the operating shafts of the inner switches and the interlocks. Initially, these two through holes are at least partially occluded by two large disks or another movable obstructive member or assembly. 
     On an outer face of the enclosure a receptacle is provided which is operable to receive an electric plug. The electric plug is preferably a medium voltage push-and-pull-type plug connector for providing power to ships, gantries, or other machinery which requires a connection to provided power. When the electric plug is inserted into the receptacle a first push rod protruding into or around the plug receptacle is displaced. This first push rod is coupled to one of the two disks. The push rod receives a linear force from the insertion of the plug into the receptacle and transmits it to an off-center portion of a first disk which converts the linear force into to a torquing or torquative rotary force which angularly displaces the receiving disk. Through holes are provided through the disk, and through the angular displacement of the disk, these through-holes are brought into registration with two through holes provided on the enclosure. 
     Next, when the plug is locked into the receptacle, a handle lever on the outside of the plug receptacle is engaged into a locked position; this locking rotates a rammed portion of the handle lever to impart another linear displacing force on a second push rod. This second push rod itself transmits another linear force to a second disk. An off-center portion of the second disk receives the displacement of the second pushrod and converts this to a torquative or rotary force acting to angularly displace the second disk contained in the enclosure. The second disk also contains two through-holes that are brought into registration with the through-holes of the first disk and preferably the through-holes of an obstructive member of the enclosure when the second disk is angularly displaced. 
     Therefore, in a preferred embodiment, when the plug is inserted and the plug is locked, both the first and second disks are rotated such that two through holes contained in each disk are brought into registration with two through holes contained on the obstructive member of the enclosure. This registration of each respective through-hole provides access through the through-holes to the two shafts which are each respectively coupled to the ground switch and the main power switch. 
     When the plug is inserted and locked, the user is now able to unground the connection and then make the main power connection, or transition the main power connection into an on position. 
     These two shafts contained in the enclosure may be operably coupled together through a power interlock bar. The ends of the two shafts where the power interlock bar is coupled may have different cross-sectional diameters and cammed or ramped transitional portions. These differing cross-sectional diameters may act as a cam where a rotational displacement causes the radius of the shaft to increase and laterally displace the power interlock bar. When the first shaft is rotated to an “ON” position, an increasing cross-sectional radius impinges on the power interlock bar, thus displacing it laterally to a furthest lateral extreme. As this power interlock bar has been displaced laterally to a maximum extent in one direction, this prevents the other shaft from being rotated to an “ON” position as the second shaft&#39;s cam structure prohibits rotation due to the inelasticity of the power interlock bar and tolerances which have been minimized. 
     While the grounding switch is in the “OFF” position, the receptacle handle lever is prohibited from being actuated. The grounding switch is operably coupled through a ground switch linkage to a large gate wheel. This ground switch linkage can be coupled to the grounding switch itself, an arm/blade thereof, or directly to the grounding switch operating shaft. When the grounding switch operating shaft is rotated into an “OFF” position, a rotary movement of the grounding switch operating shaft imparts a linear displacement on the ground switch linkage which is pivotally coupled to the large gate wheel and imparts a rotational movement thereto. A small gate wheel is fixedly coupled through a shaft to the large gate wheel. The small gate wheel therefore mirrors the angular displacement of the large gate wheel. The small gate wheel may then be pivotally coupled to a ground gate member. Thereby, when the small gate wheel rotates the ground gate member is displaced in an upward or downward linear motion responsive thereto. When the grounding switch is engaged, or in the “ON” position, the ground gate member is raised to its highest point of travel. 
     Conversely, when the grounding switch is “OFF”, the grounding gate member is displaced to its lowest point of travel. In the lowest point of travel, the grounding gate occludes or restricts the travel of a locking push rod. The locking push rod is preferably biased to a distal position (outwards) through the use of a resilient member which could be a spring. However, the resilient member is able to be overcome by actuation of the receptacle lever when not locked. In contradistinction, when the lever receptacle is actuated a cam-like structure of the receptacle handle lever imparts a force, thereby achieving a displacement on the locking push rod towards the ground gate. In the event the ground switch is engaged the locking push rod travels freely or elastically. 
     However, in the event that the grounding switch is ungrounded, or in the “OFF” position, the ground gate, being in its lowest travel, blocks or restricts the free movement of the locking push rod. Inasmuch as the locking push rod is arrested and cannot travel to its furthest extent, the lever receptacle is also restricted from travelling. 
     Thereby a user is unable to remove or unlock the plug until the switch member is regrounded. Further, as the two switch members are mutually exclusive through the use of the mechanical power interlock bar, the main power switch must first be disengaged, and only then will the grounding switch be able to be engaged. Once the grounding switch has been engaged, and only then, is a user able to unlock and remove the plug member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective drawing of an interlock assembly to be used internal to the enclosure; 
         FIG. 2  is a perspective view of a lever operated receptacle and plug; 
         FIG. 3  is a perspective view of an enclosure; 
         FIGS. 4-5  are perspective views of the receptacle lever locking assembly; 
         FIG. 6  is a perspective view of the obstructive disks; 
         FIG. 7  is a perspective view of the obstructive disks from an internal position of the enclosure; 
         FIG. 8  is a plan view of the internal push rod and obstructive disk assembly; 
         FIG. 9  is a perspective view of the obstructive disks and enclosure; 
         FIG. 10  is a perspective view illustrating the plug push rod coupling to an obstructive disk; 
         FIG. 11  is an elevational view of the parallel shafts and switch structures; and 
         FIG. 12  is a perspective view of the grounding switch blades. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a mechanical interlock of a lever operated receptacle with a shaft operated switch. The mechanical interlock of a lever operated receptacle with a shaft operated switch includes a receptacle  20  for receiving a plug and having a pivotally coupled handle lever  22 . A first obstructive enclosure  130  or cabinet shields the internal workings of the interlocking switch assembly from a user—ensuring the user&#39;s safety and the integrity of the internal workings. A first shaft  80  is arranged in parallel relation to a second shaft  90 . Each of the first shaft  80  and second shaft  90  will be respectively coupled to a grounding switch and a main power switch. Initially, while the receptacle is not locked and no plug is inserted, access to the first shaft  80  and the second shaft  90  are obstructed by both an outer disk  60  and an inner disk  70 . Outer disk  60  has two through holes  62  and  64  which are disposed on opposite sides of a central portion of outer disk  60 , substantially the same distance as the distance between the first shaft  80  and second shaft  90 . Inner disk  70  has two through holes ( 72  and  74 ) as well, arranged analogously to the through holes of the outer disk  60 . 
     Initially, when both the handle lever  22  is unlocked and the receptacle is empty (no plug is inserted), the through holes of inner disk  70  and outer disk  60  are preferably unregistered with the through holes  52  and  54  of an obstructive element  50  thereby occluding passage through through-holes  52  and  54  of the obstructive element  50 . The unregistered state of n disk  70  and outer disk  60  blocks access to shafts  80  and  90 . 
     Receptacle  20  has a protective element, preferably a lid that shields off the receptacle. When lever handle  22  is actuated, this protective element shielding the receptacle  20  is opened to allow insertion of a plug. When the plug is inserted, the leading edge of the housing of the plug actuates a plug push rod  30  which protrudes into the receptacle from within the enclosure  130 . The plug&#39;s insertion occasions a linear displacement on push rod  30  which is coupled to an orthogonal disk engaging member which pivotally engages an off-center portion of the outer disk  60 . Thereby, the linear displacement of the plug push rod  30  creates a torquative or rotary force on the outer disk  60  through a disk engaging portion  34  of push rod  30 . This rotary or torquative force results in a rotational movement of outer disk  60  which brings through-holes  62  and  64  into registration with the though-holes  52  and  54  of the obstructive element  50 . 
     The user then clamps down the lever handle  22  thereby locking the plug into the receptacle  20 . This locking action imparts a linear force on the receptacle push rod  40  which is initially biased outwards through a resilient spring-type member  41 . When receptacle push rod  40  is actuated, the linear displacement imparts a rotational movement to the inner disk  70  through means similar to the movement of the outer disk  60 . Inner disk  70  similarly has two through-holes that are also brought into registration with the outer disk through-holes  62 ,  64  and the obstructive element  50 &#39;s through holes  52  and  54 . Thereby, once the plug is inserted and the lever handle  22  is locked, all three pairs of through holes ( 52 , 54 ;  62 , 64 ; and  72 , 74 ) are brought into respective registration (e.g. through hole  52  aligns with  62  and  72 ) thereby allowing full access to the two shaft members  80  and  90 . 
     The user may then access first shaft  80  through through holes  52 ,  62 , and  72  and rotationally engage the shaft  80  which will impart a rotational force on the grounding member to deactivate the ground, or switch the ground to an “OFF” position. The deactivation of the grounding switch will cause the ground switch linkage  142  to travel linearly which imparts a rotational movement to the large gate wheel  144  of grounding safety lock assembly  140 , which in turn, through a coupling member  146 , rotates the small gate wheel  148 . The small gate wheel  148  in rotating counterclockwise imparts a linear downward motion to the ground gate  149 . The ground gate member  149  will come to rest in the travel path of a locking push rod  24 . The grounding gate member  149  thereby restricts the travel of the locking push rod  24  which thereby prevents the lever handle  22  from becoming disengaged either accidentally or through user intervention. Inasmuch as the lever handle  22  cannot be disengaged the plug cannot be disengaged. Indeed, the plug cannot be unlocked or disengaged until both the main power has been shut off and the grounding switch has been reactivated. 
       FIG. 2  shows a plug inserted into receptacle  20 , the lever handle  22  of the receptacle  20 , and an engaging portion  42  of receptacle push rod  40 . Locking push rod  24  (not shown) is arranged substantially symmetrically to push rod  40 , on the opposite side of the lever handle  22  (far side). 
       FIG. 3  shows a preferred embodiment of the enclosure of the subject Patent Application. In this embodiment, the enclosure is a cabinet  130  (enclosure and cabinet are used interchangeably herein). The cabinet  130  has a technician door  134  which may optionally provide access to the inner workings of the system without obstructive members. Window  136  is preferably transparent allowing inspection of components and proper operation from a distance. The cabinet  130  also provides a workers&#39; door  132 . The workers&#39; door  132  may be used by any worker, or any standard user who has not been trained to the level of a technician. A technician may also use workers&#39; door  132 , however, workers&#39; door  132  only provides limited access to the system whereas the technician door  134  provides for substantially unrestricted access to the system. Preferably, workers&#39; door  132  merely provides access to the through holes  52  and  54  to thereby engage shaft  80  (grounding switch) and shaft  90  (main power switch). Preferably, a socket wrench type tool  133  is provided which may be tethered to the inside of the workers&#39; door  132  to allow a user to manipulate the shafts  80  and  90  through the passage-way created by the alignment or registration of the through-holes of the obstructing member  50 , outer disk  60 , and inner disk  70 . 
       FIG. 4  shows an internal arrangement of the grounding switch interlock. Ground switch linkage  142  couples to the grounding switch on the right most portion and to the large gate wheel  144  pivotally on the left hand side. The large gate wheel  144  is coupled fixedly to the small gate wheel  148  through a coupling member such as a shaft  146 . The small gate wheel  148  is pivotally coupled to the ground gate member  149 . Thereby, when the grounding switch is deactivated, a leftwards linear motion is imparted on the ground switch linkage  142  which rotates the large gate wheel  144  causing the small gate wheel  148  to rotate in a counterclockwise direction imparting a downward linear motion on the ground gate member  149 . 
     As seen in  FIG. 5 , the ground gate member  149  is then displaced downwards to restrict travel of the locking pushrod member  24 . As seen in  FIG. 1  on an outer face of the enclosure  130 , the lever handle  22  of the receptacle  20  has a cam-type surface which engages the handle locking pushrod  24 . When a user would attempt to unlock the lever handle  22 , the cam surface abuts against the locking push rod  24  which is unable to travel further to accommodate the lever handle&#39;s  22  cam surface due to the obstructive element ground gate member  149 . Thereby, the lever handle  22  is unable to be unlocked until ground gate member  149  has resumed an upwards displacement brought about by the regrounding or the engaging of the grounding switch to the “ON” position. As is also seen in  FIG. 5 , plug push-rod  30  is disposed through receptacle  20  and is engaged when the plug is inserted into receptacle  20  thereby displacing plug push-rod  30  in a lateral rightward displacement. 
     As seen in  FIG. 6 , the main power switch shaft  90  is exposed and available and permitted to be accessed by the user. Outer disk  60  has been rotated such that through-hole  64  of the outer disk  60  has been brought into registration with the through-hole  54  of obstructive element  50 . Still further, the inner disk  70  has also been rotated into position such that its through-hole  74  has also been brought into registration with through-hole  64  and  54  thereby allowing access through an unobstructed composite through-hole to main power switch shaft member  90 . 
       FIG. 7  shows an internal view of the cabinet  130 . Grounding shaft  80  is coupled to the grounding blade  112  which engages with the grounding point  100 . As is seen, grounding shaft  80  and main power shaft  90  are exposed through the through-holes  72  and  74 . Inner disk  70  is contained on a pivoting rod  76 . Receptacle push-rod  40  has a disk engaging portion  44  having a joined perpendicular bit  46  which engages a slot cut through inner disk  70 . Thereby, when the lever handle  22  is locked into place on the plug receptacle  20 , the push-rod  40  is engaged laterally which imparts a rotational motion to inner disk  70 . Inner disk  70  is disposed in parallel arrangement with outer disk  60 . 
       FIG. 8  shows an alternate view of the receptacle push-rod  40  having a disk engaging portion  44  containing a perpendicular bit  46  which engages a slot  78  of the inner disk  70  to impart a rotational movement responsive to the linear insertion of the plug member. Inner disk  70  is seen to have a pivot point  76  and a first through-hole  72 . 
       FIG. 9  is a possible view that a worker or user of this system would see when accessing the workers&#39; door  132 . More preferably, obstructive element  50  would expand to occlude view of the disks entirely and all other inner mechanisms, ideally providing solely for through-holes  52  and  54 . It is seen that outer disk  60  is rotated such that its through holes are in registration with the obstructive element  50 &#39;s through holes  52  and  54 . Therefore it can be ascertained that a plug has been inserted into receptacle  20  imparting a linear motion on plug push rod  30  which then engages the outer disk  60  imparting the rotational movement to bring the through holes into registration. As shaft members  80  and  90  are visible through the respective through-holes it can also be ascertained that the lever handle  22  of plug receptacle  20  has indeed been locked into a locking position thereby engaging the receptacle push rod  40  to thereby rotate the inner disk  70  thereby resulting in all three respective pairs of through-holes being brought into registration. Cabinet  130  is seen enclosing the remainder of the inner workings. 
       FIG. 10  shows another angle of the plug push-rod  30  being engaged through plug receptacle  20  and thereby rotating the outer disk  60  in relation to the obstructive element  50 . Also seen is the relation of receptacle push-rod  40  to the plug push-rod  30 . 
       FIG. 11  shows a view of the enclosure  130  with the technician door  134  open exposing the innards of the system to a qualified/certified electrician/technician. Fuses  114  may be inserted in-line with the main power switch. Grounding shaft  80  is shown in parallel relation to main power switch shaft  90 . Grounding blades  112  are shown engaged in the grounded position. Workers&#39; door  132  is shown closed. 
     Main power contacts  110  and grounding blades  112  could be circuit breakers or molded case switches or any other switch type known to one of skill in the art. Still further, voltage ranges of up to 5.5 kV, 7.2 kV, or higher could be accommodated. Yet further, three phase, neutral plus ground, or three phase plus ground could be accommodated and color coded for easy access, installation, maintenance, and/or removal. 
     To better withstand adverse conditions, the cabinet  130  may be optionally fabricated from stainless steel or cold rolled steel. To even further prevent corrosion, and withstand adverse environments, a plurality of latches on the side of the cabinet  130  with tightenable screws to exert a further force against the gasketed doors and the cabinet  130  to ensure a sufficient sealing force may optionally be installed. 
     Still further, optionally, the technician door  134 , or even potentially, the workers&#39; door  132  may be locked in a closed position by means known to one of reasonable skill in the art. 
       FIG. 12  shows a perspective view of the grounding blades  112  coupled to grounding shaft  80  within enclosure ( 130  not shown) from the technician door ( 134  not shown). 
     Although this invention has been described in connection with specific forms and embodiments thereof, it will be appreciated that various modifications other than those discussed above may be resorted to without departing from the spirit or scope of the invention as defined in the appended claims. For example, equivalent elements may be substituted for those specifically shown and described, certain features may be used independently of other features, and in certain cases, particular applications of elements may be reversed or interposed, all without departing from the spirit or scope of the invention as defined in the appended claims.