Static structures (e.g. – buildings) – Cover with projecting restrainer; e.g. – snow stop – Rod-type with plural supports
Reexamination Certificate
2001-09-11
2003-11-18
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Cover with projecting restrainer; e.g., snow stop
Rod-type with plural supports
C052S024000, C052S025000
Reexamination Certificate
active
06647671
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a roof-mounted snow guard assembly to retain accumulated snow and prevent damage and injury caused by snow sliding off the roof surface, and more particularly, to an improved mounting block for securing such snow guard assemblies to a metal roof seam.
Snow guard assemblies have long been used for inhibiting and directing the movement of snow and ice across selected or pitched areas of roofs, as a preventive measure to mitigate the damage caused by migrating and falling snow and ice accumulations. An early application of snow guard assemblies is taught in U.S. Pat. No. 42,992 to Howe, which issued May 31, 1864. Recently, snow guard assemblies have increased in popularity, and currently several snow guard mounting assemblies serve to hold snowloads on roofs. Relevant examples include U.S. Pat. Nos. 5,613,328, and 5,732,513, each to Alley, each of which is herein incorporated in its entirety by reference.
Changing weather conditions, such as high winds or cyclically varying temperatures, create an environment that can induce physical changes in the accumulated snow, and give rise to the conditions tending to cause a snowpack to slide off of a sloped roof. Dislocated snow and ice often cause damage to surrounding property and, in some cases, the sliding snow can cause serious bodily injury; The problem of sliding snow is particularly prevalent on metal roofs. Metal roofs offer many structural advantages, such as strength and durability. However, because metal tends to absorb environmental heat, even a minimal amount of panel expansion or contraction exacerbates the conditions leading to snow slides. Furthermore, metal roofs generally afford little surface friction, which is also conducive to snow slides.
The increasing popularity of construction incorporating metal roof materials also poses particular problems with respect to attaching snow guard assemblies. A typical metal roof comprises a plurality of juxtaposed metal panels typically having substantially perpendicular edges that abut to form a joint therebetween. The perpendicular edges of the abutting panels are each crimped together and/or bent downwardly over each other forming a sealed seam which both connects the roofing panels and prevents fluid communication in between the panels and to the area beneath the roof panels,.
In snow guard assemblies for seamed metal roofs, the mounting block assembly is typically secured to the roof seam using a coupling element, such as screws or bolts. These screws or bolts generally pass through a sidewall of the mounting block seated around the seam, and extend inwardly, to contact the roof seam. However, screws and bolts tend to puncture, abrade, or otherwise damage the surface coating of the metal roof seam seal when tightened to securely fasten the mounting assembly. Holes or fissures thusly created during installation and use, and which remain after removal of the mounting assembly, destroy the hermeticity of the metal roof, and allow water to permeate the seam even while the snow guard is still attached. The water tends to attack the exposed metal beneath the damaged surface coating, creating stains, such as rust stains. This water damage weakens the metal and diminishes the intrinsic aesthetic qualities of metal roofs.
Prior attempts to address this problem include using a mounting block capable of being attached to a metal roof, as described U.S. Pat. No. 5,613,328. In order to attach the mounting block to the seam, a ball and set-screw is provided, such that the curved surface of the ball, rather than the threads of the screw, engages a portion of the roof seam. As the screw is tightened to attach the mounting block, the ball forms a pocket in the engaged portion of the seam such that the mounting block can be secured to the roof without piercing or tearing the seam.
Although this method of attachment is an improvement over the prior art attaching means, drawbacks remain. For example, the entire holding force per coupling means is limited to the contact area between the seam and each ball, which is only a singular, independent contact surface. Because such a design requires that the entire contact force be applied through a single contact surface on each ball, the total amount of static holding force (which is equal to the summation of the holding forces of each individual contact surface) is determined by the number of balls engaging the roof seam. Thus, the net holding force available for holding the mounting block in place is significantly limited, and sliding will occur if the force of the snow load exceeds the friction force at that singular point of contact.
Yet another drawback of the ball and set-screw assembly relates to the occasional rotation of the ball in conjunction with the turning of the set screw instead of gripping to form a stationary contact surface with the metal seam. This unwanted turning gives rise to damage on the contact surface of the seam, and effectively reduces the benefits of employing a ball and set-screw coupling means.
Another attempt to attach the mounting block to a metal roof seam involves the cam-like gripping means disclosed in U.S. Pat. No. 5,613,328 to Alley, the entirety of which is incorporated by reference herein. The cam is a small gripping member, whose length is not significantly greater than its width, which is positioned in a chamber on an internal side of the groove of the securing block and secured at one end. In one case, the securing block is slid along the roof seam in a direction that causes the unsecured end of the cam to catch the seam, swing out from the chamber and deform the metal roof seam, at which point the cam is locked in place using a screw. In this manner, the dented seam is gripped between the cam and a cavity located on the opposite side of the groove of the securing block therefrom. In another case, a set-screw and ball bearing configuration engages the unsecured end of the cam within the chamber, forcing the cam out of the chamber and into the groove, such that the dented seam is gripped between the cam and an opposing cavity on the other side of the groove.
While the cam, rather than a set-screw or ball bearing, contacts the metal roof seam and offers some protection for the metal roof seam, there is still room for improvement with respect to increased protection and gripping power. First, the effective gripping force is somewhat limited by the cam configuration. That is, damage can occur at the point of contact between the roof seam and the cam if too much force is used on the cam, or under the stress of a heavy snow load, because the pressure applied by the cam on the metal roof seam is essentially concentrated at that point of contact. Second, no substantial mechanical advantage with respect to gripping power is offered over the standard ball and set-screw assembly because the length of the cam is not significantly greater than its width.
Another drawback associated with prior art mounting block assemblies for snow guard assemblies relates to corrosion caused by the contact between the metal roof seam and the metal groove of the mounting block, in conjunction with the normal exposure to high degrees of moisture experienced by roofs. The corrosion is a result of a galvanic reaction between the metal roof, which is typically copper, and the metal of the mounting block, which is typically aluminum. This can lead to many harmful conditions, both cosmetic and structural, including unsightly deposits on the roof panels and a weakened coupling between the seam and snow guard assembly. Additionally, corrosion and moisture infiltration eventually degrade the hermeticity of the metal roof.
Efforts to combat corrosion caused by galvanic reactions include fabricating the mounting block using a non-reactive metal, such as stainless steel. However, using stainless steel instead of aluminum significantly increases overall manufacturing and consumer costs, and does not address the problem of moisture communication and physical harm to the surface of t
Burr & Brown
Friedman Carl D.
Varner Steve
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