Patent Publication Number: US-7905056-B2

Title: System and method for transferring shear forces in garage door openings

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 60/797,147, “System And Method For Transferring Shear Forces In Garage Door Openings” filed May 2, 2006. 
    
    
     BACKGROUND 
     During earthquakes, large man made structures such as houses are frequently damaged and collapse as a result of the structural damage caused by the earthquake ground movement. People trapped in the fallen structures are often severely injured or killed. While many newer structures are built to withstand earthquakes up to a certain predicted magnitude, many other existing structures must be retrofitted with additional support to prevent failure in the event of a large earthquake. 
     An area of particular weakness is the garage door, which is typically a large rectangular opening in the wall of the garage structure. The door normally includes a frame that has two side posts and a horizontal member that spans the two posts. The space between the posts must provide enough space to drive one or more cars through. The door area is weak because of this large unsupported opening. In contrast, the walls of the garage may comprise closely spaced posts and beams or may even be solid materials such as poured concrete. 
     The garage door itself typically is positioned behind the door frame and is attached to an opening mechanism such as a track or beam actuator. During a large earthquake, the top of the door frame sways from side to side while the base is typically bound to the foundation and does not move. Because the door is behind the door frame, both will move independently during the earthquake and the door will not provide any structural support for the door frame. 
     The door frame is particularly vulnerable to the earthquake movement that is in line with the plane of the frame. As the ground moves below the garage, the posts of the door frame sway which causes stress at the upper corners of the door frame. If the corners of the frame are broken, the frame can easily collapse. Because of this inherent weakness, garage door frame need to be heavily reinforced to prevent failure during a strong earthquake. Unfortunately, many garage doors are not reinforced and are susceptible to failure during an earthquake. What is needed is a system that improves the strength of the garage door frame that can be retrofitted onto existing garage doors. 
     SUMMARY OF THE INVENTION 
     The inventive system improves the structural strength of a garage door frame in the event of an earthquake. During an earthquake, the garage door frame sways in response to the ground movement. The garage door is typically mounted behind the door frame and does not provide strength to the frame or garage structure. The inventive system uses coupling mechanisms to attach the garage door to the garage door frame during the earthquake. This allows the strength of the door to be transferred to the frame which significantly enhances the strength of the garage door frame and may prevent the collapse of the garage structure. 
     In an embodiment, the inventive system uses “L” brackets mounted to the corners of the garage door with a planar portion extending forward into the plane of the door frame. The planar portions are parallel to the frame posts closely spaced to the inner edges. While the garage is stationary, there is no contact between the brackets and the door frame and the garage door can be opened and closed normally by sliding along tracks that extend into the ceiling. During an earthquake, the door frame will sway from side to side with the upper posts of the frame alternately moving towards the door and away from the door and the lower posts remaining stationary in the foundation. When a post moves towards the door it contacts the upper bracket which transfers the shear force to the door and helps to stop the swaying movement of the post. In a larger earthquake, the upper post movement may cause the door to slide horizontally and the lower brackets may contact the lower frame posts to further resist the movement of the posts. 
     When the brackets at opposite corners of the frame the door simultaneously contacts the frame posts, the door is compressed and provides shear strength to the door frame. A solid door transfers the shear force through the door structure which may be reinforced with structural diagonal members. A panel or sectional door will transfer the shear forces from the upper panel to the lower panels through the hinges that connect the panels. The panel or sectional door and other door types may be reinforced with flexible members such as wires or cables that are coupled to opposite corners of the door. When a shear force is applied to the door, one of the flexible members mounted will be pulled tight and will provide tension resistance to shear deformation of the door. 
     In other embodiments, the coupling mechanisms may reduce or prevent vertical movement between the door and frame. The coupling mechanism may use brackets that have holes that engage protrusions extending inward from the door frame. When an upper post sways towards the door in an earthquake, one or more protrusions engage corresponding holes in the brackets mounted to the door. The right beam of the frame moves towards the door to engage the holes in the upper right brackets while the protrusions in the left beam move away from the door and are free from the holes in the upper left bracket. As the garage sways back in the opposite direction, the protrusions in the left beam engage the holes in the upper left bracket while the protrusions in the right beam are freed. The coupling mechanism prevents vertical movement between the door and frame and transfers vertical forces from the post to the door. This vertical coupling further improves the strength of the door frame. 
     In another embodiment, the door to frame coupling mechanism includes plates having a series of ramped surfaces. These ramped plates are mounted to the corners of the door and the corresponding inner surfaces of the door frame. The ramped surfaces are configured to face each other and become coupled to each other in the same way as the protrusion/hole mechanism described above. While the protrusion and hole embodiment resists all vertical and inward horizontal forces, the ramped surfaces may only transfer downward vertical forces and inward horizontal forces from the frame to the door. The ramped surfaces may require less alignment of the door within the frame and also release or decouple more easily that the protrusion/hole embodiment. 
     Alternatively, the inventive system may actuate a coupling mechanism to lock the door to the door frame when it is in its closed position. In an embodiment, the inventive system uses the brackets with holes that are mounted at the upper corners of the garage door. When the door is closed or when an earthquake is detected, the system actuates rods that extend inward from the frame through the holes in the brackets. The coupling mechanisms remain engaged to the garage door throughout the earthquake. The coupling mechanisms remain engaged until the system is reset. This engagement of both corners further improves the transfer of strength from the door to the frame and enhances the earthquake resistance of the garage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates the movement of a garage in an earthquake; 
         FIG. 2  illustrates a solid garage door; 
         FIG. 3  illustrates a panel or sectional garage door; 
         FIG. 4  illustrates an “L” bracket; 
         FIG. 5  illustrates a panel or sectional garage door with brackets; 
         FIG. 6  illustrates door frame protrusions and corresponding bracket with holes; 
         FIG. 7  illustrates a panel or sectional door with frame protrusions and brackets; 
         FIG. 8  illustrates a protrusion with a screw end; 
         FIG. 9  illustrates a plate having a plurality of protrusions; 
         FIG. 10  illustrates a door plate and a frame plate having ramped surfaces; 
         FIG. 11  illustrates a panel or sectional door with ramped surface coupling mechanisms; 
         FIG. 12  illustrates an active coupling mechanism; and 
         FIG. 13  illustrates a panel or sectional door with an active coupling mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is a device and system for improving the structural strength of a garage door. In the event of an earthquake, the ground will move which causes the garage to sway. This swaying force is increased in proportion to the height of the structure. The movement is typically horizontal and absorbed by the vertical beams in the structure. If the beams fail, the structure can collapse. The garage door frame is an area of weakness because the large opening requires the vertical posts to be spaced far apart and must support much higher loads than a normal wall posts. Similarly, the beam that spans the garage posts must also support higher loads than a cross beam in a normal wall. 
       FIG. 1  illustrates forces that are applied to the inventive garage door during an earthquake. The ground shakes in the plane of the earth surface and may be represented by movement in both the X-direction  103  and Y-direction  105 . As the ground shakes, the garage  107  responds by also shaking. The garage  107  is typically a heavy structure that responds to the earthquake by also moving in the X-direction  103  and Y-direction  105 . A horizontal force in one direction applied to the upper edge of the door frame  115  which is applied to upper edge of the door  100  and opposed by a force in the opposite direction applied to the bottom edge of the door  100 . The ability to oppose this force is known as the shear strength. The shear strength can also be thought of as the resistance to diagonal forces that are applied between the opposite corners of the door  100 . A force towards the left applied to the top of the door  100  is transmitted through the door to the bottom surface. In order for the door  100  to support the door frame  115 , the bottom of the door  100  resists horizontal movement within the door frame  115 . 
     There are many types of garage doors. With reference to  FIG. 2 , some doors are solid structures that are generally mounted within the door frame  115  so that the planar strength can be used to support the door frame  109 . These solid doors  111  typically have a single solid layer  113  of material that spans the entire door surface. In an earthquake the horizontal shear force is distributed across the solid layer  113  through the height of the door  111 . A solid door  111  may be further strengthened by attaching the solid layer  113  to a support members  109  that runs along the perimeter of the door  111  and cross beams  117  that run between opposite corners of the door  111 . 
     A stronger door  111  will result in more support for the door frame  115  and the garage  107  in an earthquake. Because these cross beams  117  are aligned with the shear forces they are able to enhance the shear strength of the door  111 . This strengthening will also cause the door  111  to be much heavier making it more difficult to open and close. The perimeter members  109  and cross beams  117  of the door also resist the horizontal shear forces in compression as the upper edge of the frame  115  sways from side to side. Thus, the solid door  101  is strong in shear and can provide resistance against horizontal forces directed in opposite directions. 
     Another type of garage door are panel or sectional doors. With reference to  FIG. 3 , the panel or sectional door  121  is typically made of many horizontal planar panels  123  that are coupled together with hinges  125  that allow the door  121  to travel along a track  124  mounted behind the frame into an open space in the ceiling. The panel or sectional door  121  is flexible out-of-plane at the bending sections hinges  125  but has strength in the plane of the door  121  when it is closed. If the horizontal force is applied to the top panel, the force is transmitted sequentially through the hinges  125  to the adjacent lower panels. The hinges  125  typically allow for some horizontal movement, thus all of panels  123  will shift towards the left until the hinge  125  will not allow any additional movement. 
     There are also many ways for reinforcing the panel or sectional garage door  121  to improve its resistance to shear forces. Because the perimeter  115  and cross beam  117  members are not be flexible discussed with reference to  FIG. 2  are not flexible, they are unsuitable for use with panel or sectional doors that roll or slide along curved tracks. Wire, rod or cable members  129  that are run diagonally across the door  121  and attached to the opposite corners may be used to support a panel or sectional door  121  in order to oppose shear forces. These flexible members  129  are tight when the door  121  is closed and able to resist tensile forces but will not provide strength in compression. In the example above, when the top panel  123  shifts horizontally to the left out of vertical alignment, the members  129  running between the upper left and lower right corners will be pulled tight and will prevent additional horizontal movement. Similarly, members  129  mounted to the opposite corners between the upper right and lower left corners will prevent horizontal movement in the opposite direction. These members  129  may be attached to the inner surface of the door so that when the door  121  is opened, the bending at the hinges  125  will shorten the distance between the corners providing slack to the members  119 . Thus, the members  129  can bend with the door  121  as it slides into the overhead track. 
     A problem with panel or sectional garage doors  121  as shown in  FIG. 3  is that the tracks  124  that hold the door  121  are generally mounted behind the door frame  115  and is not rigidly attached to the door frame  115  in a secure structural manner. Thus, even if the door  121  is strong in shear strength, it may not provide any structural support to the garage  107  structure. In an earthquake, the door tracks  124  may easily bend away from the door frame  115  so that the door move independently from the garage structure. Once separated, the shear strength of the door  121  does not help to prevent failure of the garage door frame  109  and the garage  107  structure as shown in  FIG. 1 . The garage door tracks  124  can be more securely attached to the frame  115 , however a simpler method for improving the strength would be to couple the door frame  115  to the door  121  during an earthquake. 
     The inventive system improves the strength of the garage  107  by coupling the panel or sectional door  121  to the door frame  115  during an earthquake. This coupling is particularly useful with panel or sectional doors  121  but may also be used to keep the solid door  111  within the door frame  115  and to reduce horizontal motion during the earthquake. The door frame  115  by itself is normally fairly weak in shear strength because the frame  115  spans a large open area and has weak connections at the post-to-beam location. However, when the door  121  is closed and physically coupled to the frame  115 , the shear strength is dramatically enhanced. In an embodiment, the door  121  supports the door frame  115  with coupling mechanisms mounted at each of four corners. These coupling mechanisms strengthen the frame  115  by attaching the door  121  to the structure in order to resist shear forces that are applied to the door frame  115  during an earthquake. 
     The inventive reinforcement system is particularly useful with panel or sectional garage doors  121  that slide through tracks  124  that are loosely mounted behind the plane of the door frame  115 . The tracks  124  guide the door  121  but do not provide any significant strength to the garage door frame  115 . In an earthquake, the tracks are easily bent away from the door frame  115 . Door  121  will move independently of the garage door frame  115  and does not provide any structural support to the garage  107 . 
     There are various ways to modify the door  121  to support the door frame  115 . These support devices should provide a temporary support mechanism that can be released so that the door  121  can easily be opened when access to the garage  107  is needed. In some embodiments, the support device may only be engaged when there is ground movement from an earthquake. In other embodiments, the support device may also include a coupling mechanism that has a coupled setting that locks the door to the frame and an uncoupled setting that releases the door  121  from the frame  115 . This mechanism may be manually actuated or automatically triggered in the event of an earthquake. 
       FIG. 4  illustrates an “L” bracket  141  that is used with the present invention. The bracket  141  has a mounting surface  146  which is attached to the door  121  and an extended portion  148  which is perpendicular but not attached to the frame  143 . The mounting surface  146  maybe attached to the door with screws, bolts, slotted fittings or any other fastener. The mounting surface  146  may be welded to a compatible metal door or attached with an adhesive or any other secure adhesive means. The extended portion  148  provides a contact surface that transfers force from the contact to the door  121  in the event of an earthquake. Although the contact surface  148  is shown as being planar, it may have various alternative surfaces as described below. 
     For example, with reference to  FIG. 5 , in a first embodiment, the support device is a plurality of L brackets  141  that are mounted to garage door  121  at the four corners adjacent to the frame  115  when the door is closed. Because these brackets  141  are not attached to the frame  115 , the garage door  121  opens and closes normally while the structure is stationary. In an embodiment, the brackets  141  are positioned so that one planar surface is attached to the door  121  and the perpendicular surfaces protrude forward into the plane of the door frame  115 . The protruding sections of the brackets  141  have planar surfaces that are parallel to the frame  115 . During an earthquake, the garage structure shakes as the ground moves. The door frame  115  is susceptible to movement in line with the plane of the frame. As the garage moves, the garage and door frame sway together. One side of frame  115  sways inward towards the door  121  and then away from the door  121  in the opposite outward direction. 
     When the frame  115  sways towards the left, the right side of the frame  115  moves inward and contacts the bracket  141  at the upper right side of the door  121 . The bracket  141  and door  121  resist the inward movement of the right side of frame  115  and are therefore able to strengthen the door frame  115 . In a strong earthquake, the force of the frame  115  against the bracket  141  may cause the door  121  to slide to the left side of the frame  115 . When the door  121  moves to the left, the bracket  141  at the bottom left corner of the door  121  contacts the lower side of frame  115 . Although the upper portions of frame  115  sway, the lower portions remain stationary within the foundation. Thus, the lower frame  115  provides a strong structure to resist any further horizontal movement of the door  121 . 
     Once the frame  115  simultaneously contacts the brackets  141  at opposite (upper right and lower left) corners of the door  121 , the door frame  115  is structurally supported by the compression and shear strength of the door  121 . The door  121  transfers the force diagonally in shear across to the lower left corner which stops against the lower left side of frame  115  to help further resist the inward movement of the right side of frame  115 . Thus, the upper left and lower right brackets  141  strengthen the door frame  115  as it sways right. As discussed, the shear forces are transferred through the hinges  125  in  FIG. 3  across the door  121 . The door  121  may also be strengthened by diagonal tension members  129  that is attached to the upper left and lower right corners of the door  121 . As the upper panels are moved left, the force attempts to tilt the door  121  to the left making it a parallelogram. This movement causes the diagonal member  129  shown in  FIG. 3  to be pulled tight and resist the side movement and strengthening the door frame  115 . 
     The movement of earthquakes is cyclical and after the left movement the earthquake will cause the garage door frame  115  to move in the opposite direction towards the right and a similar sequence of events will occur. The frame  115  will sway inward and contact the bracket  141  mounted on the upper left side of the door  121 . The door  121  may then slide to the right and the bracket  141  mounted to the lower right side of the door  121  may contact the lower right side of frame  115 . The upper right and lower left brackets  141  strengthen the door frame  115  as it sways left. By resisting shear forces, the inventive bracket system improves the strength of the garage structure during an earthquake. 
     In another embodiment, the brackets have a different design that includes a coupling mechanism that helps to keep the garage door  121  from lifting up as forces are applied horizontally within the plane of the door frame  115  during an earthquake. This feature is important because the garage door  121  can only strengthen the door frame  115  if the door  121  remains in its fully closed position within the plane of the door frame  115  during the earthquake. If the door  121  lifts or becomes misaligned with the frame  115  during an earthquake, the garage structure will be weakened at the door area. 
     There are various coupling mechanisms that can be used to reduce uplift of the door  121  with the frame  115 . 
     The coupling mechanisms may be passive or active devices. A passive device will couple the door  121  to the frame  115  in response to the earthquake movement and then disengage the door  121  after the earthquake has ended. An active device senses or responds to early earthquake forces and actuates a coupling mechanism to lock the door  121  to the frame  115 . When the earthquake has ended, the active device may automatically disengage the coupling mechanisms or may require the mechanisms to be manually reset. 
     With reference to  FIGS. 6 and 7 , the passive coupling mechanism  151  may include a plurality of horizontally aligned protrusions  153  that engage holes  155  in the L brackets  159  mounted at the upper corners of the door. As discussed above, during an earthquake, the frame  115  sways towards the door  121  and contacts the bracket  159 . In this embodiment, one or more tapered protrusions  153  will engage the holes  155  in the brackets  159  coupling the upper right corner of the door  121  to the door frame  115 . This coupling keeps the door  121  from uplifting within the door frame  115 . If the door  121  lifts within the door frame  115  during an earthquake, the door  121  does not add full structural strength. As the frame  115  sways in the opposite direction, frame  115  sways towards the door  121  and the protrusions  153  on the left side engage the holes  155  in the upper left bracket  159 . This opposite motion also causes the right side of frame  115  to sway away from the door  121  and the protrusions  153  disengage from the holes  155  in the bracket  159 . Thus, the coupling mechanisms in the upper right corners engage and disengage throughout the earthquake. Eventually, the earthquake will stop and both coupling mechanisms  153 ,  159  will disengage so that the door  121  can be opened. 
     The protrusion  153  may be tapered so that it will engage the hole  155  more easily. As the frame  115  moves closer towards the door  121 , the hole  155  will slide down to a wider and stronger portion of the protrusion  153 . The hole  155  and protrusion  153  may have corresponding shapes, such as circular or rectangular cross sections. In other embodiments, the protrusions  153  are uniform in cross section rather than tapered. The corresponding shapes provide a larger contact area than mismatched shapes, i.e. a round protrusion engaging a square hole. However, it is contemplated that mismatched protrusions and holes will also provide the described functionality. 
     There are various options for the lower corners of the door  121  when used with the upper protrusion  153  and hole  155  in L bracket  159  configuration. In one embodiment, there are no protrusions extending from the lower corners of the frame  115 , the door  121  slides horizontally and the simple planar bracket  141  shown in  FIG. 5  contacts the door frame  115  which prevents further horizontal movement. 
     In yet another embodiment, there are no brackets at the lower corner of the door. 
     There are many ways in which to attach the protrusions  153  to the door frame  115 . With reference to  FIG. 8 , a screw  157  may be attached to the opposite end of the protrusion  153 . The protrusion  153  may have parallel flat surfaces on the sides which allow a wrench to be used to screw the protrusion  153  into the frame. Alternatively, a screw (straight, Philips slot, etc.) or wrench fitting (Allen, star hole, etc.) may be machined into the exposed tip of the protrusion  153 . Thus, each individual protrusion  153  can be individually mounted in the door frame  115 . Because the screw  157  should be fully inserted into the frame  115 , the cross section of the protrusion is preferably circular to avoid any misalignment problems. 
     Alternatively, as illustrated in  FIG. 9 , a plurality of protrusions  153  are mounted to a single plate  156 . The plate  156  has a plurality of holes  154  that are used to attach the plate  156  to the frame  115  using screws  158  or any other suitable fasteners. This plate  156  configuration may be stronger and more resistant to shear forces because the forces are distributed over a larger area and more mounting screws. Although the protrusions  153  are illustrated as being attached to the frame  115 , it is also possible to reverse the configuration by mounting the protrusions  153  to the extended surface  148  of bracket  141  that is attached the door  121 . In this embodiment, the frame  115  has the corresponding holes  155  which engage the protrusions  153 . 
     There are other passive coupling mechanisms in addition to protrusions and holes. For example with reference to  FIGS. 10 and 11 , the door  121  has a door brackets  161  and the frame  115  has a frame plates  162 . Both the door brackets  161  and the frame plates  162  have ramped surfaces  163 . The ramps  163  are configured to press the door  121  downward when the frame  115  sways towards the door  121 . Thus, in  FIG. 7 , the ramped surfaces  163  of the door brackets  161  are angled upward and the ramped surfaces  163  are angled downward. The door brackets  161  is attached to the upper corners of the door  121  and the frame plates  162  are attached to the corresponding upper corners of the frame  115 . When the door brackets  161  contacts the frame plate  162 , the ramped surfaces  163  engage each other and prevent uplift of door  121 . When the post  141  sways away from the door  121 , the ramped surfaces  163  disengage freeing the door  121 . The ramped surfaces  163  do not require the alignment to be as accurate as the protrusion and hole mechanism. 
     As an alternative to passive coupling devices the inventive system may also be used with an active system. The active coupling mechanism requires the activation of a coupling mechanism. With reference to  FIGS. 12 and 13 , the active mechanism may have movable horizontally mounted rods  191  that are normally attached to or recessed within the door frame  115 . The L brackets are the same as the brackets described above in  FIG. 6 . When an earthquake occurs, an actuator  197  extends the rods  191  on both sides of the frame inward to engage the holes in L brackets on both sides of the door  121 . The actuator  197  may comprise a compressed spring, a solenoid or any other type of extending actuator mechanism may be used to extend the rods  191 . The sensor  195  may be a motion detector that trips the actuators  197  when a specific earthquake magnitude is exceeded. Alternatively, the sensor  195  may trip the actuators  197  in response to receive earthquake actuation signals from a wired source or a radio wave signal. Since power may be lost during an earthquake, the sensor  195  and actuator  197  may run off of a rechargeable battery. Alternatively, the sensor  195  and actuator  197  may be pure mechanical devices that do not require electrical power. 
     The extended rods  191  remain engaged with the holes of the bracket throughout the earthquake as the frame side to side swaying movement of the frame  115 . Because both sides of the door  121  are coupled to the frame  115 , the active coupling embodiment provides the better structural support than the passive devices. Only after the earthquake has stopped may the rods  191  be retracted so that the door  121  can be opened. The retraction of the rods  191  may be through a manual reset. Although the active coupling mechanism has only been described with reference to movable rods  191 , it is contemplated that various other coupling mechanisms may be used including: clamps, wedges, calipers, blocking or restraints at the top of the door or any other type of friction mechanism to prevent uplift of the door  121  with respect to the frame  115 . 
     While the present invention has been described in terms of a preferred embodiment above, those skilled in the art will readily appreciate that numerous modifications, substitutions and additions may be made to the disclosed embodiment without departing from the spirit and scope of the present invention. It is intended that all such modifications, substitutions and additions fall within the scope of the present invention that is best defined by the claims below.