Abstract:
A housing for electrical equipment has first and second halves. An electrical connecting plug between the housing halves is arranged to require halves of the plug to be separated before the housing halves can be separated.

Description:
BACKGROUND OF THE INVENTION 
     There are many types of electrical devices operating on line power whose housing must be opened at times for servicing and replacing parts. There is always a concern that these devices will be opened without first removing the power by unplugging the power cord or tripping the circuit breaker. Television sets for example having removable back covers incorporate plugs in the back covers. The plug in the cover is designed to mate with a plug in the chassis when the cover is assembled to the set. In this way, power automatically disconnects when the cover is removed. In such a device, power is supplied to the back cover by the power cord but no electrical component is present in the back cover which uses this power. 
     There are other devices though whose housings are formed of two halves, where it is a design convenience to supply line power directly to the half which has a component operated by line power. As one example, some humidifiers designed for permanent attachment in ductwork have in a removable housing cover, a fan which operates on line power. A base with which the cover mates is permanently installed in the duct. A transformer in the cover steps down line voltage to 24 v. to operate a solenoid valve in the base for regulating water flow to the humidifier, and for connection to the humidistat. The humidistat completes the 24 v. circuit, powering the solenoid and operating a relay which controls fan power. It is necessary to regularly replace a pad onto which the water is dispensed while the humidifier is operating. Replacing this pad requires the humidifier housing to be opened. This operation is safer if the fan is disabled while the housing is open. 
     U.S. Pat. No. 5,252,260, which issued to Schuman on Oct. 12, 1993, describes a humidifier including an internal connector plug having first and second halves which are integrated into the humidifier&#39;s cover and base respectively. When the cover is mated to the base, the two connector plug halves are mated automatically to form the electrical connections which allow operation of the humidifier. I hereby incorporate by reference the &#39;260 patent into this application. 
     BRIEF DESCRIPTION OF THE INVENTION 
     I have developed a variation on the Schuman design which uses externally accessible plug halves and housing halves which do not allow the plug halves to be mated until the housing halves have been properly mated. Such an electrical equipment housing has conventional first and second housing halves. The second housing half is conformed to mate with the first housing half to define an enclosed space. An electrical device is mounted on one of the housing halves so as to be within the enclosed space when the housing halves are mated. A power terminal mounted on one of the housing halves and exterior to the enclosed space when the housing halves are mated, allows connection of the electrical device to a power source. The power terminal may be no more than a power cord for plugging into a conventional receptacle. The device and the power terminal will be defined in the following description on occasion as first and second electrical components. 
     The housing includes a power supply assembly for conditioning supply of power from the power terminal to the component on proper mating of the housing halves. This assembly comprises an interconnection plug comprising first and second plug halves. These plug halves each carry a number of individual conductors which are intended to electrically connect when the plug halves are mated with each other. A flexible first power cable is electrically and mechanically connected at a first end to the first plug half and at a second end, mechanically to the exterior of the first housing half. The first plug half dangles freely on the flexible power cable from the exterior of the first housing half. A second power cable is mechanically and electrically attached to the second plug half. The second plug half is mechanically attached to the second housing half and accessible from the exterior of the second housing half. The first power cable length and the attachment of the first power cable to the first housing half and the attachment of the second plug half to second housing half allows mating of the plug halves when the housing halves are properly mated. The first and second power cables and the first and second plug halves cooperatively form electrical connection between the first and second electrical components when the first and second plug halves are mated. 
     In one form of this invention, the second plug half is mounted in the second housing half and accessible from the exterior of the housing. The first housing half includes a surface carrying an aperture in alignment with the second plug half when the housing halves are mated, and wherein the plug halves are mated with the first plug half passing through the aperture. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation view of a humidifier incorporating the invention. 
     FIG. 2 is a bottom elevation view of a humidifier incorporating the invention. 
     FIG. 3 is a side section view of a humidifier incorporating the invention. 
     FIG. 4 is a magnified perspective view of a preferred configuration for a plug half. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although my invention is suitable for a wide range of electrical equipment housings, I will describe it as deployed in a powered humidifier  10  shown in FIGS. 1-3. Humidifier  10  is designed for mounting in the wall of a conventional air plenum. In such a conventional form, humidifier  10  comprises a cover  12  forming a first housing half and a base  15  forming a second housing half. FIGS. 2 and 3 show these housing halves in a mated position defining an enclosed space as at  13 . A series of tabs at  17  (FIG. 3) and a machine screw  27  (FIGS. 1 and 2) cooperate to lock cover  12  and base  15  together. Screw  27  is carried in a projecting flange  28  completely external to the enclosed space  13 . Base  15  also includes a projecting flange  52  which is intended to enter and mount more or less permanently in an opening cut in the wall of a furnace plenum. The part of the enclosed space  13  indicated at  50  is in direct flow communication with such a furnace plenum once the humidifier  10  is so mounted. FIGS. 1 and  3  show humidifier  10  in its necessary mounting orientation. 
     Cover  12  carries a motor  42  driving a fan  43  which draws air from the plenum into space  50  and then through a porous block or pad  47  into the enclosed space  13 . A nozzle  20  receiving water under the control of a solenoid valve  30  provides a slow flow of water to the top surface of block  47 . This water flows slowly under the influence of gravity through block  47  saturating it. Air flowing through block  47  under the force of fan  43  vaporizes some of this water, and thereby gains humidity. Fan  43  forces this humidified air back into the plenum through areas of space  13  adjacent to block  47 . This air returned to the plenum mixes with other air flowing in the plenum, increasing the overall humidity of the plenum air flow. Water provided to block  47  and not vaporized by the air flow through block  47  eventually drains to the bottom of block  47  and leaves the enclosed space  13  through a drain  53 . 
     Motor  42  operation is controlled by a circuit board  40 . Motor  42  typically operates on line voltage, whereas valve  30  operates on 24 v. provided by a transformer  41  carried on circuit board  40 . Circuit board  40  receives line voltage from a power cord  25  which is routed through the interior space of cover  12 . Power cord  25  enters cover  12  through an opening  24  in cover  12 . Power cord  25  is terminated at the outside end by a standard electrical plug  23  for connecting to a standard 110 v. receptacle. A relay carried on circuit board  40  switches power to motor  42 . The relay winding operates on the 24 v. transformer output. The transformer  41  primary and motor  42  are the only components within humidifier  10  which operate at line voltage. 
     It is necessary on occasion to replace block  47  because minerals carried in the water supplied by nozzle  20  accumulate in block  47 , reducing its efficiency. Replacing block  47  of course requires that cover  12  be separated from base  15 . Recall that humidifier  10  is placed in service by mounting base  15  in the wall of a plenum, from which wall base  15  is extremely inconvenient to remove. Cover  12  is on the other hand, quite easy to detach from base  15 . However, when cover  12  is removed, the blades of fan  43  are exposed. These blades could pose a hazard should the motor  42  run or start to run while the cover  12  is separated from base  15 . Accordingly, it is useful to provide some sort of interlock or disconnect which disables motor  42  from operating while cover  12  is separated from base  15 . ′ 260  solves this problem with an interconnection plug whose halves are mounted in the cover and base, so that separating the cover from the base automatically removes power from the winding of the relay controlling power flow to the motor. 
     In my embodiment, I use an external interconnection plug comprising a first plug half  32  electrically connected to circuit board  40  through a flexible electrical cable  35 , only the two ends of which are shown. Cable  35  is routed through the interior space of cover  12 . Cable  35  also mechanically connects plug half  32  to cover  12 , with plug half  32  dangling from the end of cable  35 . A second plug half  33  is mounted on the exterior of base  15  adjacent to a flange  28  of cover  12 . In my embodiment, there are first through sixth separate conductors in cable  35  and first through sixth connection elements in each of the plug halves  32  and  33 . Plug halves  32  and  33  are configured to mate with each other so that the first through sixth connection elements in first plug half  32  are connected to the respective connection elements in plug half  33 . When cover  12  is mated with base  15 , an aperture  37  in flange  28  is aligned with second plug half  33 . Plug half  32  can mate through aperture  37  with plug half  33  to form the connection between the individual connection element pairs. Two of these connection element pairs control flow of power to motor  42  by controlling flow of power to the control winding of the relay. These two connection elements in plug half  33  are connected to wires  38  in FIG.  2 . Wires  38  are intended for connection to a humidistat, whose switch when closed allows power to flow to the relay control winding. Plug half  32  is designed with a feature to be described later which interferes with the edges of aperture  37  to oppose any attempt to separate cover  12  from base  15  until plug half  32  is unmated from plug half  33 . 
     While plug half  33  is shown as integral with or mounted on base  15 , this is not necessary. Plug half  33  can be electrically connected by a flexible cable as is plug half  32 , and the two plug halves  32  and  33  simply mated and allowed to dangle. The flexible cables should be of a length which opposes any separation of cover  12  and base  15  until the plug halves  32  and  33  are separated. No matter what the specifics are for the design of plug halves  32  and  33  and their electrical connection, the cable for plug half  32  and the mounting for plug half  33  should be designed to make the mating of plug halves  32  and  33  as inconvenient as possible when cover  12  and base  15  are not normally mated. This deters people from providing power to motor  42  by mating plug halves  32  and  33  while cover  12  and base  15  are separated. 
     The embodiment of plug half  32  shown in FIG. 4 shows two holes  36  of six total in the commercial embodiment, which house the first plug half  32  connection elements. Plug half  33  includes projecting conductors intended to enter these holes  36  to form the connections between the respectively conductors. Plug half  32  also includes four similarly profiled shoulders  39  which are intended to extend over the flange  28  in interfering relationship with the edges of aperture  37  when plug halves  32  and  33  are mated. The intent is to prevent separating cover  12  from base  15  without first completely separating plug halves  32  and  33 . 
     In further variations on this design, it is possible to orient plug halves  32  and  33  and flange  28  in a variety of ways so that plug half  32  can actually serve to pin or lock cover  12  in its mated position with base  33 . In such an arrangement, a flange is oriented perpendicular. Thus configured, cover  12  and base  15  cannot be separated until plug halves  32  and  33  are separated.