Abstract:
A snow-retaining device comprises a detachable upper member attached to a base anchor. The base anchor is adapted to be coupled to a roof. The upper member prevents snow from sliding off the roof during regular snow conditions. In order to prevent catastrophic damage to the roof, if a snow load on the roof exceeds a maximum threshold, the upper member detaches from the base anchor to allow some or all of the snow to slide off the roof. The device optionally integrates a snow melting device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/148,903 filed on Jan. 30, 2009 which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to snow barriers or guards that are coupled to a roof to inhibit the sliding of accumulated snow from the roof up to a pre-determined load, thereby preventing damage to the roof due to excessive accumulation of snow. 
       BACKGROUND 
       [0003]    It is well known in the art to apply brackets, stops, or fences to a roof in order to prevent snow that has accumulated upon the roof from sliding from the roof. These devices help to keep snow from damaging eavestroughs, landscaping on the ground below, etc., or falling dangerously onto pedestrians or vehicles. Nonetheless, the devices serve to maintain snow loads on the roof itself, thereby contributing to the roof caving in or causing undue stress to the roof when the snow load is excessive. 
         [0004]    There have been some attempts to address the problem of excessive snow load accumulation in the prior art. 
         [0005]    U.S. Pat. No. 5,522,185 to Cline discloses a snow stop for attachment to a metal roof seam, comprising a flat, rigid blade formed with curved upper and lower edges. There are openings extending through the blade that permit the passage of air and fluids, and in particular, water. The device described in Cline is restricted to seams of metal roofs. In addition, the openings of the flat blade are not designed to allow for the flow of solids such as snow or ice. Consequently, the snow stop cannot effectively reduce the snow load on a roof in order to prevent a roof from caving in. 
         [0006]    U.S. Pat. No. 6,357,184 to Alley discloses a device capable of being attached to a roof as part of a snow guard system to better restrain snow or ice from falling off the roof. The device includes flags attached to pipes that run longitudinally along the edge of the roof. The flags are designed not to rotate, and extend below the bottom-most pipe in order to restrain snow from sliding off a roof. Alley further discloses prior art devices comprising flags attached to pipes, wherein the bottom of the flags is spaced from the roof. In addition, these prior art flags are secured to the pipes using screws, thereby providing essentially a grid-like snow stop at the edge of the roof. According to Alley, such a prior art device allows a portion of the snow load to fall from the roof, thereby preventing snow from accumulating to dangerous levels. However, there are a number of drawbacks generally associated with these snow guards. In particular, the securing means to attach flags to the pipes do not entirely prevent rotation of the flags when subjected to disturbances such as wind gusts. In addition, the securing means are expensive to manufacture and difficult to install. Furthermore, while the device may haphazardly permit a small portion of the snow load to fall from the roof, it is not designed to fail under the weight of dangerous snow load. 
         [0007]    U.S. Pat. No. 6,536,166 also to Alley discloses a snow guard assembly adapted to be attached to a metal roof seam by a mounting assembly. The mounting assembly includes a mounting block having a seam-receiving groove formed in its bottom surface, and at least one coupling element, which can function as a shear pin, extending through a first side portion of the mounting block. This coupling element provides the snow guard assembly with a break-away feature, wherein the second member of the coupling element is enabled to shear at a predetermined location under a force exceeding a predetermined threshold force to release the entire snow guard assembly from the metal roof seam. The break-away feature is meant to prevent portions of the metal roof itself from lifting and loosening under the weight and force from an excessive snow load on the snow guard attached thereto. The material selection is an important consideration when engineering the coupling member as a shear pin, since some materials are known to shear under more or less force than others. This device, for use with metal roofs only, is designed to prevent roof damage at the point of attachment only, and does not prevent the dangerous accumulation of snow on the entire metal roof. 
         [0008]    U.S. Patent Publication No. 2007/0245636 to Ayer et al. discloses a snow guard for roofs that comprises a plurality of slotted brackets, which are permanently installed atop the roof. A snow fence is removably installed in the slots of the brackets, permitting the user to remove the fence as needed for the deliberate removal of snow from the roof in a safe and predetermined manner. This device requires the user to monitor the snow accumulation and manually remove the device before a significant snow load should threaten damage to the roof. 
         [0009]    None of the cited prior art disclose a snow barrier having a load sensitive mechanism to prevent large snow deposits from damaging roofs or even causing them to cave in. 
         [0010]    There is a need for a snow guard or barrier device that prevents snow from sliding off a roof in regular or normal snow conditions, yet automatically collapses once a given snow load threshold is reached in order to prevent catastrophic damage to the roof. The device should not require cumbersome reattachment of the entire device to the roof. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention keeps snow from sliding off a roof during regular snow conditions, while allowing excessive snow to safely slide off once a given snow load threshold is reached in order to prevent catastrophic damage to the roof. 
         [0012]    In one aspect of the present invention, there is provided a snow-retaining device or barrier comprising an upper member attached to a base anchor which is coupled to a roof. The upper member retains snow accumulated on the roof during regular snow conditions. Once an allowable snow load against the upper member is attained, the upper member collapses to allow some or all of the snow to slide off the roof. The maximum allowable snow load against the upper member may be set to, for example, 750 lb, although this threshold may vary in accordance with the location and expected snow conditions. 
         [0013]    The device is designed to allow the upper member to be flexibly attached to the base anchor, preferably by a spring-load means; or the upper member may comprise a fold-away means. 
         [0014]    Alternatively, the upper member can be removably attached to the base anchor and detaches from the base anchor when the maximum allowable snow load is attained. 
         [0015]    The base anchor is attached to the roof using adhesive or mechanical means. Furthermore, the snow-retaining device may comprise a mechanism to assist in melting the snow and ice. 
         [0016]    The upper member and base anchor are comprised of a suitable material such as polycarbonate. The upper member may be of any shape, so long as it can function as a snow barrier during normal snow conditions. In one embodiment, the upper member has a flat surface that has a shape of a polygon, circle, or an area defined by a combination of lines and curves. In another embodiment, the upper member can have a recognizable shape such as an eagle or star silhouette. 
         [0017]    In another aspect of the present invention, there is provided a method of protecting a roof from damage due to excessive snow accumulation, comprising placing a plurality of the snow-retaining devices described herein on the roof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIGS. 1(   a ) and  1 ( b ) illustrate first and second perspective views, respectively, of a snow barrier device of one embodiment of the present invention. 
           [0019]      FIG. 2  illustrates a perspective view of another embodiment of the present invention. 
           [0020]      FIG. 3  illustrates a rear view of an upper member of another embodiment of the present invention. 
           [0021]      FIG. 4  illustrates the upper member of  FIG. 3  in relation to a base member of the snow barrier of one embodiment of the present invention, prior to assembly. 
           [0022]      FIG. 5(   a ) illustrates a side view of the assembled snow barrier of  FIG. 4 . 
           [0023]      FIG. 5(   b ) illustrates a perspective side view of the partially-assembled snow barrier of  FIG. 4 . 
           [0024]      FIG. 6  illustrates a perspective view of another embodiment of the present invention attached to a roof, along with the integration of a heating cable. 
           [0025]      FIG. 7  illustrates a side view of another embodiment of the present invention that folds back under an excessive snow load. 
           [0026]      FIG. 8  illustrates examples of shapes of the flat face of the upper member of the snow barrier of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    General features of the present invention are shown in  FIGS. 1(   a ) and  1 ( b ). The base anchor ( 10 ), which may be made of a polycarbonate material, is attached to a roof using bolts or screws that are inserted through holes ( 20 ) and ( 25 ). Base anchor ( 10 ) optionally includes a base surface ( 45 ) that serves as a waterproof seal. The upper member ( 30 ) is removably attached to the base anchor ( 10 ) at an attachment assembly junction ( 35 ). The upper member ( 30 ) may also be made of polycarbonate material. 
         [0028]    As illustrated, upper member ( 30 ) preferably has a generally flat face ( 32 ), that may be of any shape. The illustrated shape is generally octagonal. Other contemplated geometrical shapes for the flat face ( 32 ) of upper member ( 30 ) are depicted in  FIG. 8 . Further shapes for the flat face ( 32 ) of upper member ( 30 ) are contemplated (not shown), and include shapes with or without holes, screens and other barrier shapes. Such shapes may also be of recognizable silhouettes including an eagle, star or other known shape. 
         [0029]    The base anchor ( 10 ) can be mounted to the roof using adhesive, mechanical or other known coupling means. When mounted, in normal operating conditions, upper member ( 30 ) is about perpendicular to base anchor ( 10 ). 
         [0030]    The device of the present invention may be installed on roofs where the average snow accumulation per year is known. 
         [0031]    When there is heavy snow accumulation on the roof, once the horizontal load against upper member ( 30 ) exceeds a certain threshold, the upper member ( 30 ) fails, such as by detaching from anchor base ( 10 ), thereby allowing for some or all of the snow in proximity to the device to slide off the roof. By failing at the given threshold, the device fails as a snow barrier but succeeds in preventing the dangerous load of snow from causing damage to the roof by allowing a path to fall off the roof. Conditional failure of upper member ( 30 ) is therefore a safety mechanism. 
         [0032]    A device with a failed upper member ( 30 ) may be repaired or replaced on the same base member ( 10 ), typically after the dangerous accumulation of snow is no longer present. If repaired, the broken-away upper member ( 30 ) may be used if it was not damaged during the failure. Alternatively, a new upper member ( 30 ) may be coupled to the base member ( 10 ). While upper member ( 30 ) must be attached subsequent to failure in order to continue using the device, the base anchor ( 10 ) of the present invention remains coupled to the roof, and does not need to be re-anchored. 
         [0033]    In another embodiment, upper member ( 30 ) is flexibly attached to the base anchor by using, for example, a spring-load mechanism. Once the snow load reaches a certain threshold, upper member ( 30 ) fails by receding or falling back, thereby allowing some or all of the snow to slide off the roof. Once the excessive snow has fallen, the upper member ( 30 ) may be biased back to its original operating position, typically about perpendicular to base anchor ( 10 ). Alternatively, after the excessive snow has fallen, upper member ( 30 ) may be manually adjusted to its operating position. 
         [0034]    The base anchor ( 10 ) assembly also functions as a lesser snow brake in the event snow loads exceed a certain threshold per anchor, which can be set as the same threshold required for the upper member ( 30 ) to give way. 
         [0035]    Whether the upper member ( 30 ) is attached flexibly or removably to the base anchor ( 10 ), an optional means for melting the snow, such as a heating cable, can be integrated into the snow barrier of the present invention, such as at groove ( 40 ) in base anchor ( 10 ). 
         [0036]      FIG. 2  illustrates an example of a snow barrier of the present invention designed to operate without an optional means for melting the snow. Upper member ( 42 ) is attached to base anchor ( 44 ) at assembly junction ( 46 ), while base anchor ( 44 ) comprises a hole ( 48 ) for attaching the snow barrier to a roof by use of a screw or other equivalent fastening means. Unlike the base anchor ( 10 ) of  FIGS. 1(   a ) and ( b ), base anchor ( 44 ) of  FIG. 2  does not incorporate a groove for incorporation of a heating element. 
         [0037]    An example of a snow barrier with a detachable upper member is shown in  FIGS. 3-6 .  FIG. 3  illustrates the attachment features of an upper member ( 50 ) of another embodiment of the present invention. These attachment features, used to attach the upper member ( 50 ) to the base anchor ( 80 ) (shown in  FIG. 4 ), include snap-in-place lugs ( 55 ) and ( 56 ), and side/twist load lugs ( 60 ) and ( 61 ). The accompanying base anchor ( 80 ) of  FIG. 4  includes an attachment assembly junction ( 105 ), to which a portion of the upper member ( 50 ) attaches as follows: snap-in-place lug ( 55 ) fits into mating slot ( 90 ), snap-in-place lug ( 56 ) fits into a mating slots ( 91 ), and side/twist load lugs ( 60 ) and ( 61 ) fit into mating slot ( 95 ). In addition, base anchor ( 80 ) includes: a groove ( 85 ) for an optional heating cable; holes ( 110 ) and ( 111 ) for bolts/screws for the attachment of the base anchor to the roof; and a base ( 75 ) for a waterproof seal of the base anchor ( 80 ). Alternatively, an adhesive can be applied to the underside of base ( 75 ) in order to secure the base anchor ( 80 ) to the roof. The base anchor ( 80 ) and upper member ( 50 ) are preferably each made of polycarbonate material. 
         [0038]    The upper member ( 50 ) and base anchor ( 80 ) of FIGS. ( 3 ) and ( 4 ) are shown assembled together in  FIG. 5(   a ) and partially assembled in  FIG. 5(   b ). In particular, the perspective view of  FIG. 5(   b ) illustrates the fitting of snap-in-place lugs ( 55 ) and ( 56 ), and side/twist load lugs ( 60 ) and ( 61 ) and into their respective mating slots. In addition, both means for attaching the base anchor ( 80 ) to the roof are shown in  FIG. 5(   b ): holes ( 110 ) and ( 111 ) for bolts or screws, and base ( 75 ) for application of an adhesive. 
         [0039]      FIG. 6  shows another embodiment of the invention comprising upper member ( 50 ) and base anchor ( 80 ) attached to a roof ( 130 ) via screw ( 140 ) (another screw on the other side of the base anchor ( 80 ) is not shown). In addition, a heating cable ( 120 ) passes through a groove ( 85 ) on the underside of the base anchor ( 80 ). 
         [0040]    In this embodiment, upper member ( 50 ) breaks off when the snow load on the face of the upper member exceeds a certain threshold. In this instance, side/twist load lugs ( 60 ) and ( 61 ) detach from mating slot ( 95 ), and snap-in-place lugs ( 55 ) and ( 56 ) detach from mating slots ( 90 ) and ( 91 ) respectively. Once detached, the upper member ( 50 ) can be recovered and attached once again to the base anchor ( 80 ) as described above. 
         [0041]    An example of a snow barrier with an upper member ( 150 ) that is flexibly attached to the base anchor ( 160 ) is shown in  FIG. 7 . The base anchor ( 160 ) includes a groove ( 170 ) for optional inclusion of a heating cable, and an attachment junction ( 180 ) where upper member ( 150 ) is attached to the base anchor ( 160 ). The upper member ( 150 ) includes a notch ( 200 ) that extends across the face ( 190 ); the notch ( 200 ) acts as a failure mechanism allowing a portion of the upper member to fail or fold back when the snow load against the face ( 190 ) of upper member ( 150 ) exceeds a certain threshold, thereby allowing some or all of the snow to slide off the roof. Once the excessive snow has fallen, the upper member ( 150 ) may be replaced or manually adjusted to its operating position. 
         [0042]    Depending on the embodiment illustrated, grooves ( 40 ,  85 ,  170 ) allow a heating cable to be integrated with the snow barrier. For example  FIG. 6  illustrates the snow barrier fixed to roof ( 130 ) wherein heating cable ( 120 ) is integrated in groove ( 85 ). Together, the heating cable ( 120 ) and snow barrier perform the dual task of melting snow and ice deposits on the roof and keeping snow from sliding off the roof. 
         [0043]    For roofs that presently incorporate a heating cable, the device of the present invention can be fixed at a plurality of locations on the heating cable. Alternatively, a heating cable and one or more snow barriers may be attached to a roof. 
         [0044]    A plurality of snow barrier devices of the present invention may be placed at various intervals along one or more sides of a roof. The number of devices and the spatial distance between each device depends on various factors including where the building is located, the average annual snow accumulation in the area, the snow dump area on failure, the size/slope/material composition of the roof, presence of eave troughs or other roofing accessories, etc.