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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application claims priority on U.S. Provisional Patent Application No. 60/891,803, filed on Feb. 27, 2007, by the present applicant. 
     
    
     BACKGROUND OF THE APPLICATION 
       [0002]    1. Field of the Application 
         [0003]    The present application relates to portable shelters used as alternatives to garages for vehicles, and more particularly to a door assembly for such portable shelters. 
         [0004]    2. Background Art 
         [0005]    Portable shelters for vehicles have been developed as an alternative to garages. For car owners who do not have access to a garage, a portable shelter allows the car to be protected from snow and from the sun, amongst other elements. In severe winter climates, a portable shelter conveniently protects the car from snow, saving the car user some time, as the time required to shovel the driveway and brush the snow off the car is greatly reduced. 
         [0006]    However, a garage has the advantage of being closeable. As such, snow cannot be blown into the garage in windy and snowy conditions, the garage can be heated, and items can be concealed in the garage. 
       SUMMARY OF APPLICATION 
       [0007]    It is therefore an aim of the present application to provide a portable shelter that addresses issues associated with the prior art. 
         [0008]    Therefore, in accordance with the present application, there is provided a retractable door assembly for an entrance/exit of a portable shelter comprising: a door having a panel of flexible material with a first edge and a second edge; at least one support rod, the door being connected to the support rod at the first edge and rolled onto the support rod; supports operatively connected to ends of the support rod and adapted to connect the support rod on a structure of the portable shelter with respect to the entrance/exit of the portable shelter, such that the support rod is rotatable about its longitudinal axis; and an actuator system operatively connected to the support rod to actuate a rotation of the support rod to deploy the door to close the entrance/exit and retract the door to free the entrance/exit of the portable shelter. 
         [0009]    Further in accordance with the present application, there is provided a retractable door assembly in combination with a portable shelter comprising: a portable shelter having a structure and flexible panels secured to the structure to define a volume for accommodating at least one vehicle and at least one entrance/exit; and a retractable door assembly comprising a door having a panel of flexible material defining a first edge and a second edge, at least one support rod, the door being connected to the support rod at the first edge and rolled onto the support rod, supports operatively connected to ends of the support rod and adapted to connect the support rod on a structure of the portable shelter with respect to the entrance/exit of the portable shelter, such that the support rod is rotatable about its longitudinal axis, and an actuator system operatively connected to the support rod to actuate a rotation of the support rod to deploy the door to close the entrance/exit and retract the door to free the entrance/exit of the portable shelter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a portable shelter in accordance with the prior art; 
           [0011]      FIG. 2  is a structure of the portable shelter of  FIG. 1 ; 
           [0012]      FIG. 3  is a schematic view of a retractable door assembly in accordance with a first embodiment of the present application, as used with the portable shelter of  FIG. 1 ; 
           [0013]      FIG. 4  is a perspective view of a structure of a portable shelter in combination with a retractable door assembly in accordance with a second embodiment of the present application; 
           [0014]      FIG. 5  is an enlarged view of the structure and retractable door assembly of  FIG. 4 ; and 
           [0015]      FIG. 6  is an enlarged view of the structure and retractable door assembly of  FIG. 4 , with a tool for manually retracting the door. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring now to the drawings, and more particularly to  FIG. 1 , a portable shelter or vehicle shelter in accordance with the prior art is generally shown at  10 . The portable shelter  10  has a structure  12  upon which a covering  13  is tautened, so as to define the enclosure or volume in which the vehicle is stored. It is pointed out that the shelter  10  can be of different dimensions, for instance to be used to accommodate more than one car, lengthwise or widthwise. The covering  13  is typically made of panels of flexible material (e.g., plastic sheets, reinforced panels, tarp, etc.). The shelter  10  defines an entrance/exit  14  providing access to the portable shelter  10 . 
         [0017]    Referring to  FIG. 2 , a typical configuration for the structure  12  of the shelter  10  is illustrated. Amongst structural members, the structure  12  has columns  15 , longitudinal beams  16  and transverse beam  18 . 
         [0018]    Referring to  FIG. 3 , a retractable door assembly in accordance with a first embodiment is generally shown at  20 . The retractable door assembly  20  is suitably used with portable shelters such as the portable shelter  10  of  FIGS. 1 and 2 . 
         [0019]    In the embodiment of  FIG. 3 , the retractable door assembly  20  has a support rod  22 . A door  24  consisting of a panel of flexible material is rolled around the support rod  22 , such that rotations of the support rod  22  about its longitudinal axis retract/deploy the door  24 , as illustrated by directions A. 
         [0020]    Supports  26  are provided on opposed ends of the support rod  22 . In the embodiment of  FIG. 3 , the supports  26  each enclose bearings so as to allow the rotation of the support rod  22  about its longitudinal axis, as illustrated by directions B. The supports  26  are secured to the structure  12  of the shelter  10 , and are, as an example, illustrated as being hooked to the longitudinal beams  16 . Fasteners are typically used to ensure that the supports  26  are removably anchored to the structure  12 . In another example, the supports  26  are secured to the transverse beam  18  or atop the columns  15 , with the rod  22  being spaced enough from the beam  18  to be operable. 
         [0021]    An actuation system incorporates the motor  28  that is positioned adjacent to the support rod  22 , on the longitudinal beam  16  as well. The motor  28  actuates the rotation of the support rod  22 , by way of transmission  30 , in either direction. The transmission  30  is, in the embodiment of  FIG. 3 , a belt with pulleys on the shaft of the motor  28  and on the rod  22 . Other transmissions are considered, such as gears or a chain with sprockets, amongst other possibilities. Considering the forces between the motor  28  and the rod  22 , the motor  28  must be anchored to the structure  12  to withstand the transmission of forces. 
         [0022]    The motor  28  is connected to a power source, such as an adjacent power network. As alternatives, it is considered to provide the actuation system of the retractable door assembly  20  with a rechargeable battery, with for instance solar panels positionable on the outside of the shelter  10  to recharge the battery. The battery is selected so as to provide enough storage to be used as the single source of power for the actuation system. 
         [0023]    The motor  28  is preferably provided with a remote control, such that the retraction/deployment of the door  24  can be performed from the vehicle. A remote control using RF signals can suitably be used for wireless communication with the motor  28 , such that the door  24  can be retracted from the vehicle. 
         [0024]    A ballast  32  is optionally positioned on a bottom edge of the tarp door  24 . The ballast  32  provides stability to the door  24  once the door  24  is unrolled to close the entrance  14  of the shelter  10 . As an alternative, releasable connectors  34  in the form of Velcro™ strips are provided on the lateral edges of the door  24 , to releasably secure the door  24  to complementary strips on the periphery of the entrance  14 . The presence of connectors  34  must be taken into consideration if a remote control is used with the retractable door assembly  20 . More specifically, all necessary precautions must be taken so as to ensure that the door  24  is not retracted while being secured to the shelter  10 , or that the connection forces can be overcome by the action of the motor  28  without damaging the door  24 . The ballast  32  advantageously overcomes this problem. 
         [0025]    When the ballast  32  is used, the selection of the sizing of the motor  28  must take into account the additional weight of the ballast  32 . The anchoring of the retractable door assembly  20  to the structure  12  of the shelter  10  must also be capable of sustaining this additional weight. The ballast  32  typically consists of a pocket in which a readily-accessible material is accommodated (e.g., sand, ice). 
         [0026]    Referring concurrently to  FIGS. 4 and 5 , a shelter in accordance with another embodiment is generally shown at  10 ′. The shelter  10 ′ is similar to the shelter  10  of  FIGS. 1 and 2 , but is expandable/retractable in directions B. Accordingly, the shelter  10 ′ is readily deployed or put away in storage, or kept permanently on site in the retracted configuration. Anchoring devices are illustrated at C in  FIG. 4 , so as to anchor the shelter  10 ′ to the ground or alternatively to surrounding structural walls. It is considered to have the roof be removable from a remainder of the structure, to facilitate storage of the shelter  10 ′. It is also considered to provide casters at the bottom of the structure  12  to facilitate the expansion or retraction of the shelter  10 ′. 
         [0027]    The shelter  10 ′ is used in combination with retractable door assembly  20 ′. The retractable door assembly  20 ′ is similar to the retractable door assembly  20 , whereby like reference numerals represent like elements. The retractable door assembly  20 ′ has supports  26 ′ by which it is anchored atop the columns  15 , for instance by being bolted to the columns  15 . The supports  26 ′ support the rod  22 , the electric motor  28 , as well as gears  30 ′ which will transmit motion from the electric motor  28  to the rod  22 . The supports  26 ′ support the rod  22  by way of bearings or like member enabling rotation of the rod  22 . 
         [0028]    A PCB controller  36 , a transformer  38  and emitter  40 /receiver  42 , and a manual switch are provided as part of the actuation system of the retractable door assembly  20 ′. More specifically, the PCB controller  36  controls the signals received from the remote control and from the detectors (i.e., the emitter  40 /receiver  42 ), so as to control the closing/opening of the door  24 . The transformer  38  is provided to ensure a suitable voltage is provided to the motor  28  and to the PCB controller  36 . For instance, the motor  28  preferably runs on 24 V voltage. It is pointed out that the transformer  38  may enclosed in the casing of the PCB controller  36 . 
         [0029]    The retractable door assemblies  20 / 20 ′ may be provided in the form of retrofit kits that can be used with existing temporary shelters. In such a use, the support rod  22  is sized as a function of the width of the entrance  14 , or may be a telescopic rod adapting to different widths. 
         [0030]    As the interior of the portable shelter  10  can be concealed with the door  24 , it is considered to provide heating in the portable shelter  10 . In such a case, all necessary precautions must be taken, considering that the tarp of the shelter  10  is made of a flammable material. 
         [0031]    The retractable door assembly  20 / 20 ′ may suitably be used with other types of shelters that have an opened entrance. Moreover, the retractable door assembly  20  may be sold with the shelter  10 . Although the retractable door assemblies  20 / 20 ′ have been described with the door  24  moving upward/downward in retraction/deployment ( FIG. 3 ), it is considered to provide a retractable door assembly in which the door deploys from one side to another (e.g., left to right), similar to the lateral movement of an elevator door. In such a case, a rail is provided to support a free upper end of the door, so as to guide the door in its movement. 
         [0032]    As illustrated in  FIG. 6 , a manual override is optionally provided to actuate the motor  28  without the remote control. For instance, in the case of a power outage, the ratchet  44  or similar tool is used to open or close the door. 
         [0033]    In another embodiment, the door (or doors) is a hinged door, pivoting about a vertical or horizontal axis as actuated by a motor. In the case in which the retractable door assembly has a hinged door, a frame is provided on the periphery of the door to maintain the tarp of the door tautened.

Summary:
A retractable door assembly for an entrance/exit of a portable shelter comprises a door having a panel of flexible material. The door is rolled onto the support rod. Supports are operatively connected to ends of the support rod and are adapted to connect the support rod on a structure of the portable shelter with respect to the entrance/exit of the portable shelter, such that the support rod is rotatable about its longitudinal axis. An actuator system is operatively connected to the support rod to actuate a rotation of the support rod to deploy the door to close the entrance/exit and retract the door to free the entrance/exit of the portable shelter.