Patent Publication Number: US-7216902-B2

Title: Portable door lock

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to portable door locks. 
   2. Background of the Invention 
   Portable door locks of various designs have been created to secure doors that do not have operable locks, or for travelers or others who wish to personally control access to a room. Such portable door locks can be especially useful in public accommodations, including hotels, dormitories, apartments, and cruise ships. 
   Prior portable door locks possess several disadvantages. Many are complex and not cost effective to manufacture. Others can be picked, and those with securing pins can be wrenched or pried from the outside by intruders. Some portable door locks include notches, teeth or contain rough edges which may cause injury to the user during installation or removal. A number of portable door locks require special tools to install, or can only work with doorknobs or doorknob shanks of a specific size or shape. Still other portable door locks mar the door when installed, or detract from the door&#39;s appearance. Chain locking portable door locks have a low yield strength, and allow the door to be opened several inches, which makes it possible for the chain to be cut by an intruder. Thus, previous portable door locks have not enjoyed large scale commercial acceptance. 
   Therefore, there is a need for an improved portable door lock that does not damage doors or door frames, and that is simple, secure, compact, strong, lightweight, and inexpensive to manufacture. 
   SUMMARY OF THE INVENTION 
   The present invention is a portable door lock comprising a strike plate, a magnet, and a bolt. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental perspective view of a door and door frame with a portable door lock according to an embodiment of the present invention. 
       FIG. 2  is an exploded perspective view of a portable door lock according to an embodiment of the present invention. 
       FIG. 3  is a top cross-section view taken along lines  3 — 3  of  FIG. 1 . 
       FIG. 4  is a side view of a strike plate according to an embodiment of the present invention. 
       FIG. 5  is a side view of a U-bolt according to an embodiment of the present invention. 
       FIG. 6  is a side view of a magnet according to an embodiment of the present invention. 
       FIG. 7  is a front view of a portable door lock according to an embodiment of the present invention, as installed in a door. 
       FIG. 8  corresponds to the view of  FIG. 3 , but shows a portable door lock according to an embodiment of the present invention as configured for a door with a greater displacement between the molding and the door than in  FIG. 3 . 
   

   DETAILED DESCRIPTION 
   The present invention is a portable door lock comprising: a strike plate  10 , a U-bolt  20 , and a magnet  30 . As shown in  FIGS. 1 ,  2 ,  3 ,  4 ,  7 , and  8 , the strike plate  10  is a plate-type structure with apertures ( 12 ,  13 ,  14 ,  15 ) for the U-bolt, and with a protuberance or boss  16  for holding the strike plate  10  in the recess of the deadbeat latch  50  or doorknob strike plate. 
   In one embodiment, the strike plate  10  has two sets of apertures. See  FIG. 2 . The first set of apertures  12 ,  13  can be used when the distance between the molding  70  and the door  40  is relatively small, as shown in  FIG. 3 . The second set of apertures  14 ,  15  can be used when the distance between the door molding  70  and the door  40  is relatively greater, as shown in  FIG. 8 . In alternative embodiments, one set of apertures can be used, or even a single aperture. 
   The strike plate  10  also has a hooked boss  16  at one end that engages the recess within a dead bolt latch  50  of a door frame  60 , see  FIGS. 1 ,  3  and  8 , or the recess of a conventional doorknob strike plate within a door frame  60 . Thus the present invention can work with any door frame that has a recess, whether that recess is part of a dead bolt or conventional door lock. 
   The strike plate  10  also has an arm  17 , and a handle  18 . See  FIGS. 2 ,  3 ,  4 ,  7 ,  8 . Users can grip the handle  18  when inserting the strike plate  10  into the recess of the door frame, thereby making installation easier. 
   The strike plate  10  can be made of many different materials, including metals such as iron and stainless steel, or metal coated plastic, or magnetized ceramic. 
   As shown best in  FIGS. 2 ,  3 ,  5 ,  7 , and  8 , the U-bolt  20  has arms  22 ,  24  for fitting through the strike plate&#39;s apertures  12 ,  13 ,  14 ,  15 . Like the strike plate, the U-bolt  20  can be made of many different materials, including but not limited to metals such as iron and stainless steel, or metal coated plastic, or magnetized ceramic. 
   Although a U-bolt is shown, many different types of bolts or fastening devices can be used with the present invention. For instance, in one alternative embodiment, the U-bolt could have a pin that is placed between slots at the end of the U-bolt, thereby improving the U-bolt&#39;s strength. For purposes of this patent, the term “bolt” shall be used to generically denote any bolt, pin, or other structure that can fit into or through the aperture or apertures of the strike plate. 
   The magnetic bar  30  can be virtually any magnet that is sized and shaped so as to fit in the area between the strike plate  10 , the U-bolt  20 , and the door  40 . See  FIG. 1 . As shown in  FIGS. 1 ,  2 ,  3 ,  6 ,  7 , and  8 , in one embodiment the magnetic bar  30  is rectangular. The magnet can be sized so that when positioned in one orientation, it can accommodate a relatively narrow offset between the molding  70  and the door  40 , and when positioned in a second orientation, it can accommodate a relatively wide offset between the molding  70  and the door  40 . Compare  FIGS. 3 and 8 . The magnet can be made of traditional metallic materials, as well as magnetized ceramic. 
   The magnetic bar  30  also advantageously holds the pieces of the present invention together when the device is in its unassembled state. Thus, the magnet helps prevent loss of either the strike plate  10  or the U-bolt  20 . 
   In one embodiment, both the U-bolt  20  and the strike plate  10  are made of materials that are capable of attracting and holding the magnetic bar  30 . However, it is not necessary that both items be made of magnet-attracting materials—the invention can function so long as one of these items, or even just the appropriate part of one of these items, can hold attract and hold the magnetic bar  30 . 
   In operation, the user grips the portable door lock by the handle  18 , then places the boss  16  into the recess of the deadbeat latch  50  or doorknob strike plate. The door  40  is then closed, and the U-bolt  20  is placed through either set of apertures  12 ,  13 ,  14 ,  15 , and the magnet is placed between the arms  22 ,  24  of the U-bolt, the body of the strike plate  10 , and the door  40 . See  FIGS. 1 ,  2 . The magnet  30  adheres to the arms of the U-bolt  22 ,  24  and/or the body of the strike plate  10  and presses onto the face of the door  40 . See  FIGS. 1 &amp; 2 . The end of the U-bolt  20  opposite to the arms presses firmly against the door frame molding  70 , thus precluding inward opening of the door. The device keeps the door securely closed and cannot be disengaged from the outside by an intruder. 
   The portable door lock of the present invention has many different applications, including use in public accommodations, such as hotels, dormitories, apartments, and cruise ships. The present invention may also be useful to prevent unwanted entry by the holder of a master key. 
   In addition to providing effective security, the device of the present invention is small, lightweight and easily packed. Having only three parts, it is easy and quick to install and uninstall, with no tools required. The device is durable and reliably constructed, as well as easily and efficiently manufactured and marketed. The present invention requires no particular door, handle, or door frame configuration, other than a standard strike plate with a recess. Neither installation nor removal of the device will damage, alter or mar the door, door frame or associated parts. 
   One skilled in the art will appreciate that the present invention can be practiced by other than the preferred embodiments, which are presented for purposes of illustration and not of limitation.