Patent Publication Number: US-6992256-B1

Title: External disconnect mechanism integrated with an electrical system enclosure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable 
   FEDERALLY SPONSORED RESEARCH 
   Not Applicable 
   REFERENCE TO SEQUENCE LISTING 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   This invention has been devised in the process of developing a photovoltaic inverter which is connected to the utility grid. Some utility companies require equipment which is so connected to include an external disconnect mechanism for easy and rapid disconnection by utility service personnel. In the past, this requirement has been met by adding, to the outside of the photovoltaic inverter main enclosure, a second enclosure containing a switch assembly with an external disconnect lever and terminal lugs which allow wiring connections to the photovoltaic system main enclosure. The disconnect enclosure is costly, bulky, and requires additional assembly at the time of system installation. 
   Photovoltaic inverters, which are connected to the utility grid, are also required to have circuit protection for the output wires. This protection may be in the form of fuses or circuit breakers. Circuit breakers are generally also manually operable as a switch, so that when they are designed into the inverter, the external disconnect is a redundant switching element. The circuit breakers are generally protected from exposure to weather by a watertight enclosure, however, and so are not accessible from outside the inverter. If they were externally operable, then the disconnect enclosure would not be needed. 
   There exist inventions with a circuit breaker in an enclosure, which are operated by an external lever, but none of them directly address the needs of the above application in a simple, cost-effective, reliable manner. U.S. Pat. No. 3,752,947 has an external lever and a mechanism that gives a mechanical advantage that allows large multi-pole circuit breakers to be manually operated with ease. This mechanical advantage is unnecessary for the photovoltaic inverter and would therefore increase cost unnecessarily. 
   U.S. Pat. No. 3,422,238 and U.S. Pat. No. 2,231,072 is mainly concerned with snap action to ensure that the disconnection process is not slowed by manual operation. To achieve the snap-action, their mechanisms have a large number of parts, including bulky springs. Modern circuit breakers have a self-contained snap-action mechanism that makes these intricate mechanisms unnecessary. Again, including this unnecessary feature is undesirable. 
   Further complexity is introduced in the disconnect mechanisms represented in U.S. Pat. No. 2,849,555 and U.S. Pat. No. 5,286,934 both of which involve cover-mounted handles designed to efficiently re-engage the inner mechanisms after opening and closing of the cover for maintenance. A mechanism not mounted to the cover will be simpler and thus more desirable. 
   U.S. Pat. No. 2,938,096 incorporates a design intended for flexibility in installation and a conversion of movement from rotation of the handle to movement on a perpendicular axis within the actuating mechanism. U.S. Pat. No. 3,287,514 contains a similar conversion. Again, a mechanism that did not require this motion conversion will be more desirable and economical. 
   In general, all of the above inventions are more complicated than required for this application. They will therefore be more expensive and more difficult to manufacture. They will also have an increased likelihood of breakdown and increased cost of maintenance. 
   Accordingly, several objects and advantages of the present invention are:
         (1) to provide an externally accessible disconnect mechanism that allows circuit breakers inside the enclosure of a photovoltaic inverter or other electrical system to be switched on or off, eliminating the need for the external disconnect enclosure heretofore used in such systems;   (2) to provide an assembly whose simplicity of design reduces the chance of breakdown and the need for maintenance and makes any required maintenance extremely simple;   (3) to provide a mechanism that indicates by the position of the lever whether the electrical system is turned off or on;   (4) to provide a disconnect mechanism for a watertight enclosure;       

   Further objects and advantages are:
         (1) to provide a disconnect assembly wherein system overload would cause the actuating handle to move to the off position through the force of gravity and without any help of an external preloaded spring or similar mechanism attached to the invention;   (2) to provide a disconnect assembly that is compatible with any generic single- or multi-pole circuit breaker;   (3) to provide a disconnect assembly that is protected from the application of excessive manual force;   (4) to provide a disconnect assembly whose handle is lockable in the off position.       

   Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is an addition to the enclosure of a photovoltaic inverter or other electrical system, which already contains circuit breakers to meet overcurrent protection requirements. A simple mechanism allows external manual switching of the breakers, thus eliminating the need for a separate external disconnect switch and enclosure. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  shows the invention installed in the enclosure of an electrical system, with the walls of the enclosure cut away and the invention viewed from an elevated point. 
       FIG. 2  shows the invention from the bottom, along with its connection to the circuit breaker. 
       FIG. 3  is an exploded diagram of the preferred embodiment of the invention as viewed from the bottom. 
       FIG. 4  shows the preferred embodiment of the invention installed in the enclosure of an electrical system, with the walls of the enclosure cut away and the invention viewed from the front, with the breaker in the on position and the actuating handle at the end of its travel. 
       FIG. 5  shows the preferred embodiment of the invention installed in the enclosure of an electrical system, with the walls of the enclosure cut away and the invention viewed from the front, with the breaker in the on position and the actuating handle at a position of gravitational equilibrium. 
       FIG. 6  shows the preferred embodiment of the invention installed in the enclosure of an electrical system, with the walls of the enclosure cut away and the invention viewed from the front, with the parts in the off position and the system locked. 
       FIG. 7  shows an alternative embodiment of the invention with reduced component count. 
   

   DETAILED DESCRIPTION—FIGS.  1  THROUGH  6 —PREFERRED EMBODIMENT 
   As illustrated in  FIG. 2  of the drawings, extension pin  10  is a cylindrical rod inserted into the hollow chamber of switch arm  11  of the electrical system&#39;s circuit breaker  12 . Extension pin  10  is similar to pins used by the breaker manufacturer to gang multiple pins together. When one breaker in the gang trips the other breakers in the gang will also trip. The present invention makes new use of existing circuit breaker construction features in extending the gang connection to a mechanism for manual operation of the breaker. An advantage of this method of connecting to the circuit breaker is that the small mass of the connection will not disrupt the proper operation of the circuit breaker. An additional advantage of the connection method of the present invention is that extension pin  10  may be properly sized and shaped so that it will shear before allowing excessive force to be applied to the circuit breaker  12 , thus preventing damage. It should be apparent to one skilled in the art that various other shapes could be used instead of a cylinder. 
   Actuating arm  13  is comprised of two vertical plates formed from sheet metal, their upper sections joined flush and containing an upper opening  14 . The lower sections, containing a pair of identically shaped openings, are slightly separated, with a flat horizontal surface  15  of  FIG. 3 , joining them at the bottom. Extension pin  10  passes through upper opening  14  in actuating arm  13 . Opening  14  is shaped and sized so as to accommodate variable positions of switch arm  11  in any of the major brands of circuit breakers currently on the market. The shape of opening  14  gives actuating arm  13  freedom of motion between the points where the extension pin  10  touches the forward edge  16  of opening  14  and where extension pin  10  touches the back edge  17  of opening  14 . Actuating arm  13  and opening  14  comprise a lost motion actuating means, as will be clear from the following discussion and figures. 
   As shown in  FIG. 3 , both sides of the lower half of actuating arm  13  are keyed with identical holes that are largely circular but flat on the bottom, shaped to accommodate the correspondingly keyed inner end  19  of actuating shaft  18 . Actuating arm retaining screw  21  is fastened to threaded hole  22  on the flat bottom surface of actuating arm  13 , securing actuating arm  13  to keyed inner end  19  of actuating shaft  18 . 
   Actuating shaft  18  passes through the hollow core of flanged bearing  23 , which in turn passes through hole  26  in bearing-mounting bracket  25  so that flange  24  of flanged bearing  23  lies flush against bracket  25 . Retaining clip  27  is inserted into retaining clip groove  28  near the center of actuating shaft  18  to prevent lateral movement of actuating shaft  18  within flanged bearing  23 .  FIG. 1  shows actuating shaft  18 , flanged bearing  23 , and bearing-mounting bracket  25  assembled, with retaining clip  27  in place, flush with flange  24  of flanged bearing  23 . Actuating shaft  18  passes through a hole in the wall of enclosure  29  before attaching to the end of actuating handle  31 .  FIG. 3  shows watertight seal  30 , which encircles actuating shaft  18  at the point where the shaft passes through enclosure wall  29 , as illustrated in  FIG. 1 . 
   As shown in  FIG. 3 , the outer end  20  of actuating shaft  18  is keyed with a flattened lower surface for insertion through a pair of correspondingly keyed holes  33  in the base of actuating handle  31 . Actuating handle retaining screw  34  is fastened to the flat bottom surface  35  of actuating handle  31  by threaded hole  36 , which secures actuating shaft  18  in position with respect to actuating handle  31 . It should be apparent to those skilled in the art that the handle described could be replaced by a knob, wheel or other structure, which could be gripped by an operator in order to exert rotational force. 
   As  FIG. 1  illustrates, the midsection of actuating handle  31  angles away from the enclosure wall  29  so that the operator will have sufficient clearance to ergonomically grasp the gripping end  32  of handle  31 . Attached to the handle, as shown in  FIG. 4 , is locking ring  37 . Locking bracket  38  is welded to the enclosure wall  29 .  FIG. 6  illustrates how locking ring  37  and locking bracket  38  align, when actuating handle  31  is in the off position. Aligned at the off position, padlock  39  of up to ⅜ of an inch in diameter is used to secure the handle in the off position to allow the utility to perform maintenance. 
     FIG. 3  shows the bearing-mounting bracket  25 , which supports the assembly by containing flanged bearing  23 . Bearing-mounting bracket  25  is fastened to generic din rail mounting clips  40  by screws  41  through holes  42 .  FIG. 2  shows how din rail mounting clips  40  are attached onto generic din rail  43 , which is fastened to the enclosure. 
   Operation— FIGS. 4 ,  5 , and  6   
     FIG. 4  illustrates how manually pushing actuating handle  31  away from the operator, into the on position, has caused actuating shaft  18  of  FIG. 5  to rotate, moving actuating arm  13  so that the forward edge  16  of opening  14  of  FIG. 2  at the end of actuating arm  13  has pressed against extension pin  10  connected to circuit breaker  12  via switch arm  11 , forcing switch arm  11  to flip upward, thereby closing the electrical circuit. 
     FIG. 5  illustrates how actuating handle  31  will rotate back under the force of gravity to a detent position. The system is still in an on position, but actuating arm  13  has moved so that the back edge  17  of opening  14  at the end of actuating arm  13  rests against extension pin  10 . In the detent position, tripping of the circuit breaker by system overload will move switch arm  111  and thus also extension pin  10 . Gravitational force will keep the back edge  17  of opening  14  in  FIG. 2  of actuating arm  13  in contact with extension pin  10 , thus rotating actuating shaft  18  so that actuating handle  31  moves to the off position, alerting the viewer, by the alignment of locking ring  37  and locking bracket  38 , that the system has been turned off. It should be apparent to those skilled in the art that a gentle spring could also be inserted to effectuate movement of actuating handle  31  to the off position when the system is intended to be installed in a different orientation with respect to gravity, at the expense of additional system complexity. 
     FIG. 6  shows how the same motion may be accomplished by manual operation. Pulling actuating handle  31  toward the operator, into the off position, has caused actuating shaft  18  in  FIG. 5  to rotate, moving actuating arm  13  so that the back edge  17  of opening  14  in  FIG. 2 , at the end of the actuating arm  13  has pressed against extension pin  10  connected to circuit breaker  12  via switch arm  11 , forcing the switch arm to flip downward, thereby opening the electrical circuit. In this position a lock may be inserted through locking ring  37  and locking bracket  38 , preventing the circuit breaker from being turned back on by way of actuating handle  31 . Even if the enclosure were to be opened, giving direct access to the circuit breaker, the position of extension pin  10  against the back edge  17  of opening  14  would prevent the circuit breaker from being turned back on. 
   Alternative Embodiment— FIG. 7   
     FIG. 7  shows that the embodiment eliminates components found in  FIG. 2 . This embodiment eliminates extension pin  10 , replacing opening  14  of actuating arm  13  with opening  44 , set at a right angle to the rest of actuating arm  13 . Opening  44  is sized and shaped so as to fit around switch arm  11  of circuit breaker  12 . 
   Operation of Alternative Embodiment— FIG. 7   
   Opening  44  in  FIG. 7  can contact switch arm  11  of circuit breaker  12  directly. This embodiment has one fewer part, but actuating arm  13  is now more complex due to the setting of opening  44  at a right angle to the main body of actuating arm  13 ; thus there is little or no cost saving over the preferred embodiment. The preferred embodiment also has the advantage, due to the shape of opening  44 , that it more easily accommodates circuit breakers of slightly different dimensions.