Patent Application
20100037524
This invention relates to a tilt latch mechanism for use in a pivotable sash window, and more particularly to a latch bolt designed to efficiently withstand high wind loading while simplifying installation into a window.
One of the most valuable and cherished possessions, for many people, is unquestionably his or her own home, which is reflected by the fact that home improvement beyond the traditional contractor renovation has become a major industry. These home improvements include upgrades in older homes in the form of upgraded electrical service, copper plumbing, and particularly replacement windows. A longstanding reason for window replacement, in addition to improved curb appeal, had been the dramatic improvements in thermal efficiency of the double-paned window arrangement, which had already been incorporated into most new construction.
However, windows to be utilized for either new construction or as replacements have seen further improvement as a result of advances in building technology. Improvements to fenestration products have in part been driven by the need to meet more demanding national standards, and in some locations, local building codes which are even more stringent.
A major factor in devising such strict requirements is the ability of the windows to resist damage caused by storms, where storm damage to homes is typically attributable to the storm surge, flood damage, and wind damage. Damage attributed to hurricane Katrina striking the New Orleans area is estimated to be $81.2 billion dollars, and although much of that amount had been due to the flooding which resulted from the levee breaks, shattered windows from hurricane force winds is a significant contributor. Katrina had reached category five in intensity on the Saffir-Simpson Hurricane Scale, but then dropped to category three intensity once it made landfall, and maintained sustained winds between 110-130 mph. Hurricane Andrew, which in 1992 actually struck the Miami-Dade part of Florida at category five, had been the most costly natural disaster in American history, at roughly $26 billion. Victims of hurricane Andrew reported trying to ride out the storm while listening to the category five winds in excess of 156 mph shatter windows, with the glass being dispersed everywhere.
There were similar reports when hurricane Hugo struck South Carolina in 1989, devastating parts of historic Charleston. While the problem may be more often faced by residents of the southern and gulf states, it is not limited to those geographic areas. The “Great September Gale of 1815” was a category three hurricane that struck Long Island, New York, and broke through the barrier beach to create the inlet that still isolates Long Beach. Also, the New York Hurricane of 1893 directly struck New York City, and the Great New England Hurricane in 1938 killed over 682 people and cause over $4.7 billion in damage (2005 U.S. dollars). On average, a hurricane will make landfall in New England every 10-20 years, with last such case being Hurricane Bob in 1991, which killed ten people and caused 2.8 billion dollars in damage (2005 U.S. dollars). Window damage caused by weather phenomena, although very costly and common because of coastal hurricanes, is also problematic for many parts of the country that experience similar risk of damage during tornado season.
However, many if not most coastal areas now mandate that the windows installed be constructed to be both impact resistant and to satisfy other standards. One such standard includes a requirement that the window be able to withstand, for a set period of time, a certain design pressure (DP). A window with a DP30 rating, which would permit the window to maintain its integrity throughout the sustained winds of a category three hurricane, is rated to a pressure level equivalent to 110 mph wind speed, but is tested structurally at a pressure equivalent to 164 mph. Similarly, a window with a DP40 rating is rated to a pressure level equivalent to a 127 mph wind speed, but is tested at a pressure equivalent to a wind speed of 190 mph, and a DP50 rating requires satisfaction of even higher load requirements. Under high wind loading, it is not uncommon to see a window convex a couple of inches, but when properly designed, the window will regain its original form within the window frame. But this deformation under high wind loads creates another design consideration relating to the hardware.
A typical latch for a slidable sash window is shown by U.S. Pat. No. 4,901,475 to Simpson. A latch bolt is spring-loaded relative to its housing, and capable of movement between a retracted or unlatched position, and an extended or latched position. Only a relatively short throw is needed to retract the latch bolt and permit movement of the sash window.
Similarly, another latch for a tilt window is shown by U.S. Pat. No. 7,171,784 to Eenigenberg. The Eenigenberg latch has the same characteristic short throw to retract the latch bolt within the housing, but additionally offers structure permitting its use as a right-hand or a left-hand latch bolt.
Although the short throw characteristic of these tilt-window latches is very desirable, in terms of convenience to the user, and is satisfactory as far as the utility required for personal security, it is deficient maintaining latch integrity during severe weather conditions. Under the high wind loads experienced during a hurricane, the associated deformation to the window may cause the latch bolt to twist and thus the flat face of the bolt will not remain fully engaged with the jam. Also, the deformation, due to the convexing of the window from the winds, may reduce the amount by which any portion of the latch bolt remains engaged with the jam.
A simple solution to the problem would of course be to use a longer latch bolt, and to design the arrangement to have a longer throw, or travel distance, between the engaged and disengaged positions. However, that approach dilutes the advantageous nature of a quick release latch, where any user is able to easily open the window or rotate the window for cleaning, which generally occurs with far greater frequency than that for which such improved hurricane resistance characteristics are normally needed. This invention discloses a tilt latch capable of maintaining its integrity during high wind loading, while maintaining the convenience and overall utility of a short-throw latch bolt.
The latch of this invention is designed to be able to resist the “twist-out” effect that occurs when a window undergoes substantial deformation, which may occur as a result of the high sustained winds found in a hurricane, as well as the winds that may be found around the periphery of a tornado. The latch features disclosed herein may be utilized on any number of different latch types, but they are particularly useful for the sash window of a tiltable double hung window assembly.
The latch of this invention features a latch bolt, which is biased relative to the sash window, and is capable of resisting twist out effect without requiring large-scale changes to the latch bolt, which would affect its size and ease of use, particularly with regard to the throw of the latch. The throw of the latch bolt is unaffected by incorporation of the features of this invention.
The latch of this invention comprises a couple of different features. In order to successfully counter twist-out effect without modifying the size of the latch bolt and its throw, the nature of engagement of the face of the latch bolt tongue with the window jam becomes critical. Improvements to that engagement may be accomplished herein through a number of different embodiments. In one embodiment, an angled groove passes across the face of the latch bolt tongue in a direction roughly in line with the direction of the jam. The groove may begin at either the upper or the lower edge of the tongue, or may also alternatively begin at some position in between the upper and lower edges of the tongue. The angled groove feature has a combined effect, the first of which involves the creating an angled face on the tongue face, where the angle of the face may be designed for a particular size window so as to become flush with the jam, when the window and latch are experiencing high wind loads and deformation leading to twisting of the latch. In addition, the angled groove also creates lateral faces which may catch upon the window jam flange to aid the latch in resisting disengagement from the jam.
This angled groove may also, in another embodiment, be utilized in two places on the latch tongue. The tongue may have one angled groove beginning at some mid-point on the latch tongue front face and running towards the upper edge with progressively increasing depth, while another angled groove begins just below the first angled groove and runs down towards the lower tongue edge with progressively increasing depth. This tongue configuration would permit the latch bolt to be utilized in either a left-hand or a right-hand installation.
Another possible embodiment would have a groove which is not angled but rather parallels the front face of the latch bolt tongue. This parallel groove, similar to the angled groove, could run from top to bottom, bottom to top, or may alternatively run in either direction while beginning at some intermediate point between the upper and lower edge of the tongue. Additionally, the tongue of the latch bolt could have two such parallel grooves where one runs towards the top edge of the tongue, and the other runs down to the bottom edge of the tongue, with both grooves beginning at some intermediate point between the upper and lower edge of the tongue.
It should be apparent to one skilled in the art that although such a latch may typically be used for a tiltable sash window which rotates downward and inward (see
It is an object of this invention to provide a latch to be installed on the top rail of a sash window of a tiltable double hung window assembly.
It is a further object of this invention to provide a latch in which the latch bolt may be toggled from the latched to the unlatched position with a short throw.
It is another object of this invention to provide a latch that can maintain positive contact with a window jam during sustained winds of a hurricane.
It is another object of this invention to provide a latch that can maintain positive contact with a window jam during sustained winds associated with the periphery of a tornado.
It is another object of this invention to provide a latch that can maintain positive contact with a window jam during load conditions imposed by pressure testing to simulate hurricane force winds.
It is another object of this invention to provide a latch that can maintain positive contact with a window jam under conditions in which the window experiences severe deformation.
It is another object of this invention to provide a window latch that can resist latch “twist-out” effect during high wind loading.
The latch design features of the present invention may be incorporated for use into any one of the various different latch configurations of the prior art, as well as others which may be created. The advantageous nature of these design features, which may be incorporated in whole or in part, are best described in terms of one of the particular latch embodiments, which may be utilized in many different applications, but are particularly useful for a tiltable sash window of a double-hung sash window assembly.
The tongue 91 of the latch 90 normally prevents the window from rotating inward, because, until the latch bolt is toggled, the front face 92 of the tongue 91 bears up against the bearing surface 75 of the side jam flange 74. It is this connection, as previously discussed, which is critical to withstand the high wind loads. When substantial deformation to the window occurs as a result of high wind loading, causing the latch bolt to twist, the flat front face 92 of the tongue 91 will not remain fully engaged with the jam. The twisting will tend to result in only one edge of the front face 92 making contact with the bearing surface 75 of jam flange 74, and additionally, the deformation due to the convexing of the window may further cause the tongue to be angled with respect to a vertical axis, such that only a portion of the bottom edge of the tongue maintains contact with the jam flange at the inner edge of the jam flange. These deformations make the latch subject to “twist-out” effect whereby the jam does not positively restrain the latch tongue, and the window may rotate under such loading.
A series of design modifications to the latch tongue found in this invention negate this effect, and are shown by the various exemplary embodiments of
The latch 4 embodiment (
The latch body 420 (
The latch body 420 may further comprise a latch bolt housing 430 that may be either attached to or integral to the top plate 421. The housing 430 may have a first side wall 451, a second side wall 452, and a bottom wall 453, and the housing 430 has a first end 447 that may facilitate biasing of the latch bolt body relative to the window top rail 87, as will be seen later, and a second end 448 which terminates in latch bolt tongue 432. The housing 430 may also have a plurality of protrusions 431 which may assist in retaining the latch bolt body within the top rail 87. Latch bolt tongue 432 may be attached to or integral to the housing 430 and top plate 420.
Latch bolt tongue 432 may have a top surface 433 and bottom surface 434, which need not be, but is however shown as being generally parallel in the latch 4 embodiment, and the other embodiments. Furthermore, top surface 432 and bottom surface 433 need not be flat, and may conversely be curved in one or more directions. The latch bolt tongue 432 may also have a back face 435 that is slanted with respect to front bearing face 436, which extends between top surface 432 and bottom surface 433. The slanted face 435 and front bearing face 436 may form a sharp edge or may alternatively be formed so as to have a chamfered tip 37, or even a rounded tip. One end of the front face 436, as it meets the tip—either chamfered, rounded or a sharp edge—is its outer end 429, and is opposite the inner end 428. Outer end 429 and inner end 428 need not be parallel, and they need not form a linear edge.
Front bearing face 436, which will normally be flush against the bearing surface 75 of side jam flange 74, may be interrupted by a step feature, which, for embodiment 4 may comprise lower angled groove 438. Lower angled groove 438 may be created by the lower groove face 439 which is angled with respect to front bearing face 436 and thus would also form a first lateral face 440 and second lateral face 441. The groove face in this embodiment is flat, however, it could also be curved in this and any other embodiment. These lateral faces may similarly be flat, or they may be curved, or they may initially be flat and thereafter transition into a curved portion, essentially forming a fillet radius between a flat portion of the lateral face and the groove face. Also, these lateral faces 440 and 441 may be perpendicular to front bearing surface 436, or they may be angled with respect to front bearing surface 436 and may thus be so designed to catch a lip or recess formed at the junction of bearing surface 75 and side bearing surface 76 of side jam flange 74. The lateral faces may also be generally triangular in shape. In other embodiments described in subsequent paragraphs, when the groove face may have a different orientation with respect to the tongue front bearing face, these lateral faces may then be generally rectangular in shape, trapezoidal in shape, or possibly an irregular shape.
The step feature of the latch 4 embodiment may also comprise the front bearing face 436 being interrupted by an upper angled groove 442, which is similarly created by upper groove face 443, and first and second lateral groove faces 445 and 445, respectively. The front bearing face 436 being interrupted by lower angled groove 438 and upper angled groove 442 results in the front bearing surface 436 resembling an “H” shape, where the connecting portion or surface 446 would normally be in contact with the bearing surface 75 of side jam flange 74.
When the window 70, and consequently the latch 4, is subjected to the high wind load conditions, the design of the latch bolt tongue 432 enables the latch to resist the “twist-out” effect and remain positively engaged with the side jam flange 74 for a combination of reasons.
First, as the latch experiences twisting due to the wind loading, the connecting surface 446 that had been bearing upon bearing surface 75 of window 70, is now angled away from the bearing surface 75, but the angled groove face of the tongue 432 may now be flush to bearing surface 75. It can be appreciated by one skilled in the art, that the size and shape of a particular window will affect the magnitude of loading and twisting to the latch 4 installed in such a window, because the increased surface area of a larger window will produce higher loads under a 30, 40, or a 50 pound per square foot wind load condition, than a smaller window, and this load must be reacted by the latch 4. Therefore, the relative angle between the groove face 439 or 443, and the front bearing face of the tongue 436 (and more particularly connecting surface 446) may be increased or decreased for a particular window latch to accommodate such loading and twisting for a particular window design. In fact, that relative angle should necessarily be different and be custom designed for each particular window configuration.
Secondly, and perhaps more significant for the latch 4 to resist the high wind-loading, is the fact that lower angled groove 438 creates the lateral groove face 441, and similarly the upper angled groove 442 creates lateral groove face 445. When high sustained winds would create deformation that would tend to pull the tongue from the opening in the jam and permit the window to unexpectedly rotate, these lateral faces 441 and 445 may engage the side bearing surface 76 (see
While it would be apparent to one skilled in the art that loading of the window 70 will only produce twisting in one particular direction, so that having both the lower and upper angled grooves 438 and 443 on the latch 4 as installed in
The advantageous nature of constructing the tongue 432 of a window latch 4 as shown in
The embodiments 7 and 8, shown in
Embodiments 2 and 3 each have a single angled groove 242 and 328 respectively, and permit a similar response by the latch tongue to wind loading as with embodiment 4. However, embodiments 2 and 3 do not have a bearing surface, comparable to surface 446 of embodiment 4, which normally is flush to the bearing surface 75 of side jam flange 74 of window 70. The angled groove 242 of embodiment 2 begins at the tongue bottom surface, and can have some initial depth or may essentially have no depth or a zero depth where the groove begins at the bottom surface, but in either case the groove will have increasing depth with increasing distance from the bottom surface. Angled groove 328 may be similarly formed, but would actually begin at the tongue top surface and have increasing depth with increasing distance from the top surface.
Embodiment 5, shown in
One additional embodiment that would be advantageous in resisting high sustained wind loading, is shown by embodiment 10 in
Other modifications, substitutions, omissions and changes may be made in the design, size, materials used or proportions, operating conditions, assembly sequence, or arrangement or positioning of elements and members of the preferred embodiment without departing from the spirit of this invention as described in the following claims.
