Abstract:
The invention provides an environmental shroud ( 190, 290, 390 ) and a camera assembly ( 10, 20, 30 ) including the shroud. The environmental shroud ( 190, 290, 390 ) absorbs and dissipates heat energy that is not reflected and heat energy that is generated by the contents of the camera housing so that the camera housing temperature does not exceed the maximum rated temperature. In one embodiment, the camera assembly includes a camera housing ( 130 ) having a mounting cap ( 140 ) attached to sidewalls ( 126 ) to which is attached an optical surface ( 135 ), the camera housing enclosing a camera system; and an environmental shroud ( 190 ) attached to the camera housing. The shroud has a lower section ( 100 ) having sidewalls ( 126 A) that descend to a drip edge ( 108 ), and at least one vent ( 105 ) in a top portion; and an upper section ( 120 ), at least the lower section having means that reflects or deflects radiant heat energy and means to remove unreflected or undeflected heat from the camera housing ( 130 ) through said vent ( 105 ), the upper section ( 120 ) covering the vent ( 105 ) and having a lower edge ( 125 ) situated below the vent and over the sidewalls ( 126 A) to provide a tortuous path which prevents the penetration of water into the camera housing ( 130 ).

Description:
FIELD OF THE INVENTION 
     This invention relates to indoor/outdoor surveillance equipment and systems, and more particularly, to an improved camera assembly which has a housing that includes an environmental shroud. 
     BACKGROUND OF THE INVENTION 
     Closed-circuit surveillance equipment is well established and can include fixed-position cameras and zoom lenses mounted on pan and tilt mechanisms which are typically controlled by security personnel. In outdoor locations, an enclosure for the camera housing is usually employed and domed housing for such cameras are desirable due to their appearance as well as the fact that the camera itself is not easily visible, though the camera can scan a wide area. 
     In a typical outdoor camera enclosure, a single main housing part is utilized, wherein a top thereof is connected to a pipe. Electrical connections are generally routed from a main power source through the pipe and into the housing. In addition, a hemispheric dome and additional internal components, such as the camera power supply, camera body, lens, pan &amp; tilt mechanism, and controller electronics, are removably attached to an inside of the single housing part. Such camera assemblies are subject to damage and require means to protect the camera from moisture and precipitation, extremes in temperature, and unauthorized tampering. For example, some conventional housings permit rain water or other moisture to accumulate and run down the conical side of the housing and onto the dome itself. Another concern is with the heat caused by sunlight or generated in the housing during use of the camera and the need to deflect such heat energy and/or to dissipate the same from the camera housing to prevent damage thereto. 
     Prior attempts to address some of these problems include U.S. Pat. No. 4,320,949 which, for example, in one embodiment provides a housing with a cover with a skirt over which rainwater may flow, form pendant drops, and fall, and a camera mount adapted to carry a camera and a camera positioning motor. A dome unidirectionally transparent to light is secured to the cover. The cover and dome form an air space between them. A fan is disposed in a side wall of the upper support housing to provide forced cool air circulation in the housing to cool the housing when the temperature reaches a certain predetermined level. The assembly also includes heaters which are operated when the temperature in the housing approaches freezing. In a second embodiment, air is brought into the assembly by natural circulation, i.e. a space or inlet area is provided at the interface of the support housing and cover member so that air can naturally enter the support housing about the circumference of the housing. This air is circulated downwardly adjacent the inner wall of the cover member and then up into the support housing where it is exhausted through an air exhaust port. 
     In U.S. Pat. 5,689,304, commonly assigned herewith, there is disclosed a surveillance housing assembly which comprises an outer shell having a top wall portion and side wall portion, wherein the side wall portion extends in a downward direction from the top wall portion to thereby define a first cavity. An inner shell comprises a top wall portion for mounting engagement with an underside of the top wall portion of the outer shell within the first cavity. The inner shell further comprises a top wall portion and a side wall portion, wherein the side wall portion extends in a downward direction from the top wall portion to thereby define a second cavity. The top wall portion  18  of the outer shell  12  has an exhaust aperture  32  positioned off-center from a central axis  34  of the outer shell; a generally circular aperture  36  is centered on the central axis and is provided in the top wall portion  18  to enable cable to pass through; and the top wall portion  22  of the inner shell  14  has an air exhaust aperture designed to be coincident with the air exhaust aperture  32  of the top wall portion  18  of the outer shell  12 ; and still further, the top wall portion  22  of the inner shell  14  has a generally circular aperture which is coincident with the aperture  36 . Air inlet apertures  44  define an air flow to exhaust  32 . The housing also has a decorative cap  70  which has a plurality of notches along its bottom edge which, cooperate with other parts to provide a path for an exhaust air flow and provides for protection against an ingress of unwanted water. This assembly also comprises various combinations of heaters and blowers. Further in this arrangement, a sequence of wall surfaces and plateau surfaces are arranged for securing components of the surveillance equipment thereto in a prescribed manner such that first components of the surveillance equipment are disposed in between the underside of the outer shell and an outerside of the inner shell, and second components of the surveillance equipment are disposed within the second cavity. 
     While air circulation via fans and exhaust ports and/or air-intake valves and air-exhaust valves is satisfactory to compensate for environmental temperature changes in some surveillance systems, it has its limitations, most notably in terms of added cost and complexity, size and power constraints occasioned by the need to incorporate such components into the surveillance assembly. 
     There remains a need in the art for a camera surveillance system which does not suffer from the disadvantages set forth above and which provides protection to the camera from moisture and heat without imposing undesirable size and power constraints. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a camera housing with an environmental shroud which is designed to deflect or reflect the radiant heat energy generated by the sun or any other heat source so that the heat does not penetrate the camera housing. 
     Another object of the invention is to provide a camera housing having an environmental shroud which absorbs and dissipates heat energy that is not reflected from radiation and heat energy that is generated by the contents of the camera housing so that the camera housing temperature does not exceed the maximum rated temperature. 
     Another object is to provide such an environmental shroud which protects the camera housing from rain or any other type of moisture by providing a tortuous path which prevents water penetration inside the environmental shroud. 
     Yet another object of the invention is to provide an environmental shroud having a “drip edge” so that the water has a means of falling off the environmental shroud to avoid obstructing the optical surface of the camera housing. 
     These and other objects of the invention are accomplished by a camera assembly having a housing which comprises an environmental shroud having a configuration which reflects and/or deflects heat energy, dissipates heat energy not reflected and/or deflected, protects the camera from water or other moisture, and enables a high level of heat dissipation even when the camera is operated in sunlight at high ambient temperature. 
     Preferably, the environmental shroud includes a coating to deflect the heat energy and a vent to dissipate the heat energy. In the most preferred embodiments, the shroud also includes a drip edge for water or moisture to run off of the camera housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows an external view of a first embodiment of a camera assembly of this invention; 
     FIG. 1B is a vertical cross-section of the embodiment illustrated in FIG. 1A taken along line A—A; 
     FIG. 2A shows an external view of a second embodiment of a camera assembly of this invention; 
     FIG. 2B is a vertical cross-section of the embodiment illustrated in FIG. 2A taken along line A—A; 
     FIG. 2C is a bottom view of the embodiment of the invention illustrated in FIGS. 2A and 2B; 
     FIG. 2D is a top view of the embodiment illustrated in FIG. 2A; 
     FIG. 2E is a vertical cross-section similar to FIG.  2 B and showing an alternative embodiment of the invention; 
     FIG. 3A shows an external view of a third embodiment of a camera assembly of this invention; 
     FIG. 3B is a vertical cross-section of the embodiment illustrated in FIG. 3A taken along line A—A; 
     FIG. 4A shows an external view of a fourth embodiment of a camera assembly of this invention; 
     FIG. 4B is a bottom view of the embodiment of FIG. 4A; 
     FIG. 4C is vertical offset cross-section of the embodiment of FIG. 4B taken along the line C—C; 
     FIG. 4D is a sectional view taken along line F—F of FIG. 4A; 
     FIG. 4E is a sectional view of an alternative embodiment of the invention illustrated in FIG. 4A; 
     FIG. 5A is a vertical cross-section of a fifth embodiment of the a camera assembly of this invention; and 
     FIG. 5B is a top cross-section of the embodiment illustrated in FIG.  5 A. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIGS. 1A and 1B, there is illustrated a camera assembly  10  which comprises a mounting cap  140  attached to sidewalls  126  which are in turn attached to an optical surface  135  to form a camera housing  130  which surrounds a camera or lens assembly, not shown, all as is well known in the art. Attached to the camera housing  130  is an environmental shroud  190  which is effective to deflect heat energy, dissipate heat energy not reflected, protect the camera from water and/or other moisture, and enables a high level of heat dissipation even when the camera is operated in sunlight at high ambient temperature. According to a first embodiment of the invention illustrated in FIG. 1A, a two-piece environmental shroud  190  surrounds the camera housing  130  substantially completely and comprises a lower section  100  and an upper section  120 . The lower section  100  of the environmental shroud provides the protection from radiant heat energy for the camera housing  130  and may include a coating on a surface thereof or the surface itself may be specified so that the emissivity is such that it reflects or deflects most of the radiant heat energy from the sun or any other hot body. Suitable coatings may include polyester, polyurethane, epoxy, transparent metallized polycarbonate coatings, aluminum foil inside various transparent materials, galvanized steel, powder coatings, etc. 
     The shroud also includes means to remove heat either absorbed from radiated heat energy or convected from the camera housing  130  through a vent  105  included in the top of the lower section  100 . The upper section  120  of the environmental shield covers the vent  105  in the lower section  100 . The lower edge  125  of the upper section is below the vent  105 , thus providing a tortuous path that prevents water from penetrating and adhering to the camera housing  130 . Instead the water is lead away from the housing via the environmental shroud to a drip edge  108  from which water, rain, melted snow, or other moisture will run off the environmental shroud. This configuration prevents water from adhering to the optical surface  135  and impairing optical performance. In a preferred version of this embodiment, a ridge or a valley  103  is formed in front of the vent  105  to further assist in preventing the egress of water or other moisture into the vent. This is particularly preferred when the difference in height between the lower edge  125  of the top portion  120  and the vent  105  is not great enough to establish a tortuous path which prevents water penetration of the camera housing  130 . 
     The embodiment of the invention illustrated in FIGS. 3A and 3B is substantially the same as the FIG. 1 embodiment described above except that it of a one-piece construction. Thus the environmental shroud embodiment of this figure achieves the same function as that achieved by the FIG. 1A embodiment except that it is a one piece design. The single piece of the environmental shroud  390  prevents water from entering the cavity between the shroud and the camera housing, protects the camera housing from radiant heat energy, and provides a drip edge  308  to prevent water from running on to the optical surface  135 . Louvres  305  are located on the sides near the top let the hot air escape and also provide protection from rain penetrating and adhering to the camera housing  330  and impairing the optical surface  135 . 
     In the embodiment of the invention illustrated in FIGS. 2A,  2 B, and  2 C, the environmental shroud  290  achieves the same function as shroud  190  illustrated in FIG. 1A but has a different mode of operation. Shroud  290  is a two piece design having an inner shroud  220  and an outer shroud  200  where the outer shroud  200  performs multiple functions. The outer shroud  200  provides protection for the camera housing  230  by reflecting and removing radiant heat energy. It prevents rain from penetrating the camera housing  230 . The outer shroud  200  also provides the means of preventing water from adhering to the optical surface  135  by providing a drip edge  208 . The outer shroud  200  has vents  205  in a top portion that not only allow hot air to escape, but also allow the water to penetrate inside the outer shroud  200 . The inner shroud  220  then collects the water that penetrates the vent  205  and redirects it along the inside surface  202  of the outer shroud  200  through water channels  225  located on the inner shroud  220 . The inner shroud also has vents  228  in the top that let the hot air escape. These vents are above and/or offset to the vents  205  in the outer shroud  200 . Thus, the water does not penetrate the inner shroud  220  and does not adhere to the camera housing  230  and impair the optical surface  135 . 
     In an alternative embodiment illustrated in FIG. 2E, at least a pair of bimetallic strips  241  are positioned over or under the vents  205 . These strips are actuated to close the vents when the temperature falls below a certain level such that warm air cannot escape from the assembly during colder weather. These strips also provide insulation to keep the contents of the camera housing  130  from dropping below a certain temperature level. It will be understood that such bi-metallic strips may be used in combination with any embodiment of the invention that includes vents and function as described above. It will also be understood that vents may be included in any embodiment of the invention including the embodiments described in FIGS. 4A-5B below. 
     With reference to FIGS. 4 and 5, the embodiments illustrated therein are different from the embodiments discussed and illustrated in the preceding figures in several aspects. First, these environmental shrouds do not present a largely smooth surface appearance. This is to promote enhanced convection heat transfer from a larger portion of the surface of the housing than is obtained by the natural convection to produce a lower internal housing temperature at the maximum ambient temperature. These embodiments also avoid a large cavity in which insects or other pests might be likely to take up residence. Secondly, these embodiments are of modular construction which allows for smaller tooling and part shipping volume prior to assembly. As will be seen, the overall outer profile need not be a “bell” or domed shape and allows for a the multi-piece construction that “wraps” around the housing to give design appearance alternatives. Thirdly, since convection plays a larger heat transfer role than conduction, the various parts of these embodiments may preferably be constructed of weather-resistant non-metallic materials, resulting in considerable cost savings. 
     With reference to FIG. 4, there is illustrated a modified aero-foil environmental shroud  490 , which, like the previous embodiments, has no moving parts. As illustrated in FIGS. 4A and 4B, a camera assembly  40  has a camera housing  430  having a mounting cap  440  attached to sidewalls  426  which are attached to an optical surface  135 . As best seen in FIGS. 4B and 4D, two rings of vertical strips  441  and  445  are placed concentric with the housing  430 . The inner ring of strips  441  is placed at some distance from the housing  430 , and the outer ring of strips  445  at some distance from the inner ring of strips  441 , such that air can circulate between all three, i.e. in the gaps between  430 ,  441  and  445 . The inner strips  441  are positioned at the gaps (x) between the outer strips  445  so an air stream  413  traveling to the housing surface  430  must turn and flow tangentially for some distance after radially entering the outer gap (x). Therefore precipitation moisture entering radially through the outer gap (x) will strike the inner strips  441  and drain downward without reaching the camera housing  430  or the optical dome surface  135 . 
     The strips  441  and  445  are secured at top and bottom by structural cap  407 ,  408  and ring  409 ,  410  parts such that they maintain their relative alignment. In addition, the mounting cap piece  440  mates with the camera housing  430  to prevent water ingress at the top of the environmental shield  490 . In one embodiment, the external vertical strips  445  are partial cylinder shapes attached to the inside lip of a circular top cap  407  such that the overall shape is cylindrical. The internal vertical strips  441  are also attached to the lip of another smaller circular cap  408  attached underneath the larger cap. 
     The internal strips  441  preferably have a central out-facing vertical ridge profile  411  to direct the air stream behind the external strips when wind impinges normal to the outer gap, and set up a circulating venturi effect when the wind impinges normal to the center of the external strip  445 . In a variation thereof, outwardly facing radial edges  412  on both sides of the inner strips  441  are turned to further prevent precipitation from blowing into contact with the camera housing  430 . 
     FIG. 5 illustrates an embodiment of the invention in which the camera assembly  50  comprises an environmental shroud  590  which is a modified turbine with moving parts. The shroud includes a bearing  507  which is centrally positioned at the top of the camera housing  530 . This bearing is large enough to permit camera power supply, video, and control wires (not shown) to pass through the center bore. In the case of a ball bearing, the center race is firmly attached to the camera housing  530 . An example of a turbine blade assembly  505  is illustrated in FIG.  5 B. 
     The turbine blades  506  are attached firmly to the outer race of the bearing  507  and is coupled to the camera housing  503  and the mounting cap  540  via a coupling plate  504 , thus forming a structure that protects the bearing from the elements and prevents water ingress at the top. The turbine blades  506  consist of strips of metal that are formed into arcs and overlapped at an angle to the radial direction such that they form vanes to catch the wind and rotate the turbine irregardless of the wind direction. Any wind threatening to force precipitation into the gaps between blades will also rotate the assembly, generating centrifugal force to push the moisture away from the interior. 
     When no breeze is blowing, the gaps between the blades provide significant area for natural convection. When a breeze is blowing, the stirring action of the turbine blades will promote forced convection at the camera housing surface, further increasing heat transfer. In addition, as a result of this construction, heat transfer conditions around the entire housing are very uniform. The sun shining from one direction will not heat just one side, but the heat will be distributed evenly. 
     In an alternative embodiment thereof, a continuous ridge or depression running down the center of the blade is added to channel moisture down to the bottom where a taper is provided for a drip edge  508 . A ring may be attached at the bottom circumference to provide structural support and is also configured to facilitate the movement of moisture away from the camera housing window  135 . 
     The aesthetic appearance of the moving turbine blades can be modified as desired. For example, strips similar to those illustrated in the FIG. 4 embodiment may be attached over the blades to minimize this effect. In this instance, with no wind, the area available for natural convection is somewhat decreased and when the breeze is blowing, less energy will reach the vanes to turn the turbine assembly. However, the blades will be protected from damage and will be effective to remove heat and protect the camera housing as contemplated herein. It is also contemplated that other combinations of the FIG.  4  and FIG. 5 embodiments may be realized. For example, inner and outer vertical strips may be employed to partially or completely cover the turbine blades. 
     While the invention has been described for convenience in the context of an environmental shroud for a camera assembly, and particularly when used to protect outdoor surveillance cameras, it will be understood that the invention is not limited to these embodiments. The environmental shrouds of the invention may be used in any context where it is necessary to protect the contents of a housing from moisture and heat, for example enclosed lighting, electronic equipment, other surveillance equipment such as switches, multiplexers, etc. Additionally, the invention may be embodied in other specific forms without departing from the spirit and scope or essential characteristics thereof, the present disclosed examples being only preferred embodiments thereof.