Abstract:
The present invention is a portable door lock which comprises a bracket having a protrusion capable of insertion into a lock chamber of a doorframe. The bracket is connected by means of a hinge to a threaded bolt, upon which a hinged brace is slidably mounted. The hinged brace comprises a first member, which is adapted to be pressed against the door, pivotally connected to a second member, which is adapted to be pressed against the doorframe. A spring is mounted upon the first member and engages the second member, urging the second member away from the first member. The second member is provided with a stop which engages the first member. A thumbwheel is mounted upon and threadably engages the threaded bolt, effectively retaining the hinged brace upon the threaded bolt.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to door locks and, more particularly, to portable door locks for use independently of the lock generally provided on a door. 
     BACKGROUND OF THE INVENTION 
     Portable door locks, for use in addition to or in place of the conventional lock and key generally provided on a door, have been known in the prior art for sometime. However, many such locks are relatively weak and may be easily damaged when an intruder attempts to break in through the door. In addition, many portable door locks are difficult to apply to and remove from the door, making it hard for an occupant to quickly exit the room in the event of an emergency. There thus remains a need in the art for a portable door lock that is both strong and convenient to use. 
     SUMMARY OF THE INVENTION 
     The present invention is a portable door lock for use in securing an inward-opening door, thereby preventing intruders from entering an occupied room. The lock of the present invention may be folded when not in use for convenient carrying and storage. 
     The lock of the present invention comprises a flat bracket having a protrusion which can be inserted into a lock chamber of a doorframe. In a preferred embodiment, the protrusion is U-shaped. The bracket is connected by means of a hinge to a threaded bolt, upon which a hinged brace is slidably mounted. The hinged brace comprises a first member, or leg, which is adapted to be pressed against the door, pivotally connected to a second member, or leg, which is adapted to be pressed against the doorframe. A spring is mounted upon the first member and engages the second member, urging the second member away from the first member. The second member is provided with a stop which engages the first member and prevents the first and second members from pivoting away from each other at an angle greater than about 60°. A thumbwheel is mounted upon and threadably engages the threaded bolt, effectively retaining the hinged brace upon the threaded bolt. 
     When the protrusion is inserted in the lock chamber and the door is closed, the thumbwheel can be screwed down the threaded bolt towards the bracket. This urges the hinged brace towards the door and doorframe, pressing the first member against the door and the second member against the doorframe. The thumbwheel can then be tightened by hand, effectively locking the door. The inventive door lock can be quickly removed from the door by simply loosening the thumbwheel and spinning it up the threaded bolt away from the door. 
     The first member of the hinged brace is sized to fit within the second member and is also recessed to accept the threaded bolt when the hinged brace is closed by urging the first and second members together. In addition, the first and second members are shaped to form a slot positioned to accept and retain the protrusion in the bracket when the hinged brace is closed and the bracket is folded towards the threaded bolt. The inventive door lock can thus be folded simply by closing the hinged brace and folding the bracket towards the threaded bolt. The lock can then be held in this folded position by tightening the thumbwheel against the closed hinged brace. 
     In an alternative embodiment, the threaded bolt and thumbwheel may be replaced by a rod and locking member, the locking member being mounted upon the rod and being capable of locking to the rod at multiple positions along the rod. 
     The door lock of the present invention offers several advantages over previous portable door locks. As detailed below, due to the design of the lock, the force exerted on the door by someone attempting to enter the room is transferred to the doorframe where it counters the force exerted by the protrusion on the lock chamber. Furthermore, due to the hinge linkage between the bracket and the threaded bolt, no torsional stresses are placed on any of the components of the lock. The inventive lock is thus able to withstand the application of large forces to the outside of the door. 
     The lock is easy to use and can quickly be applied to or removed from a door. Due to the pivotal connection between the first and second members of the hinged brace, the lock is able to automatically adapt to differences in depth between the door and door frame. The lock may also be easily folded and held in a folded position for convenient carrying. 
     The above-mentioned and additional features of the present invention and the manner of obtaining them will become apparent, and the invention will be best understood by reference to the following more detailed description, read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the inventive lock in an open position. 
     FIG. 2 is a side view of the inventive lock in a fully closed position. 
     FIG. 3 is a exploded view of the bracket and threaded bolt. 
     FIGS. 4A and 4B are side views of the bracket and threaded bolt, respectively. 
     FIGS. 5A and 5B are top and side views, respectively, of an inner leg, or first member, of the hinged brace. 
     FIG. 6A is an exploded side view of an outer leg, of second member, of the hinged brace. 
     FIG. 6B is a side view of an outer leg. 
     FIG. 7 is a front view of the hinged brace in an open position. 
     FIG. 8 is a top view showing application of the inventive lock to a door. 
     FIG. 9 is a top view of the inventive lock applied to a door. 
    
    
     DETAILED DESCRIPTION 
     A portable lock of the present invention in the open position is shown in FIG.  1 . The lock comprises a flat bracket  1 , having at one end a narrow U-shaped protrusion  2  formed at 90° to its length. Protrusion  2  is preferably formed by folding bracket  1  over on itself in a double U bend. Bracket  1  is preferably constructed from high quality steel plate. However, other materials having similar strength, weight and rigidity to steel plate may also be employed to form bracket  1 . Bracket  1  is hingably connected to threaded bolt  5 . As shown in FIGS. 3 and 4, in a preferred embodiment, the end of bracket  1  is cut and rolled to form two hinge loops  3  and  4 , the end of each loop  3  and  4  being welded to main bracket  1  to prevent loops  3  and  4  being unraveled under tensile stress. Threaded bolt  5  has a hole  6  bored through it at one end, with flats  7  and  8  being located on each side of threaded bolt  5  at 90° to the axis of hole  6 , so that bolt  5  fits snugly between hinge loops  3  and  4  on main bracket  1 . A pin  9 , preferably formed from high tensile steel, is inserted through hole  6 , connecting main bracket  1  to threaded bolt  5  and forming a swivel joint. Preferably, threaded bolt  5  is made of steel. 
     Over threaded bolt  5  slides a hinged brace  10  formed of two main parts, inner leg, or first member,  11  and outer leg, or second member,  12 . Preferably, both inner leg  11  and outer leg  12  are formed from steel, or another material of similar rigidity and strength. As shown in FIGS. 5A and 5B, inner leg  11  has a recess  13  formed by base  14  and parallel sides  15  and  16 , which extends along the entire length of inner leg  11  and within which threaded bolt  5  can rest when the lock is not in use. At the rear end of inner leg  11 , sides  15  and  16  extend vertically to a height greater than that along the remaining length of inner leg  11 , to form opposing protrusions  17  and  18 . Preferably, protrusions  17  and  18  extend along approximately 25% of the length of inner leg  11  and are approximately twice the height of sides  15  and  16  at the opposing end of inner leg  11 . Threaded holes  19  and  20  are drilled in line through protrusions  17  and  18 , respectively. In a preferred embodiment, reinforcing plates  15 A and  16 A may be placed on the inner surfaces of sides  15  and  16 , in order to increase the strength of inner leg  11 . Reinforcing plates  15 A and  16 A preferably extend along the inner surfaces of protrusions  17  and  18 . A similar reinforcing plate may be placed on the inner surface of base  14 . Such plates exactly match the internal profile of inner leg  11  and have corresponding holes to match holes  19  and  20  in protrusions  17  and  18 . 
     An abutment cap  23  is permanently attached to, and connects, the upper edges of protrusions  17  and  18 . Preferably, abutment cap  23  is formed from solid steel and is welded to protrusions  17  and  18 . Immediately below abutment cap  23 , is located a spring  24 . Spring  24  is retained in place by a pin  25  which passes through spring  24  and which extends at 90 degrees between protrusions  17  and  18 . A flange plate  26  is rigidly connected to the front end of inner leg  11 . A buffer pad  27  formed from compressible, non-slip material, preferably rubber, is connected to flange plate  26 . 
     As shown in FIGS. 6A and 6B, outer leg  12  comprises parallel vertical sides  28  and  29  connected by base  30 , which preferably extends along approximately 50% of the length of sides  28  and  29 . Outer leg  12  is sized to fit closely over sides  15  and  16  of inner leg  11  when hinged brace  10  is folded. Holes  31  and  32  are located at the rear ends of sides  28  and  29  to match holes  19  and  20  in inner leg  11 . Hinge pivot screws  21  and  22  pass through holes  31  and  32  and into threaded holes  19  and  20  on protrusions  17  and  18 , thereby pivotably connecting outer leg  12  to inner leg  11 . 
     As shown in FIG. 7, one end  24 A of spring  24  abuts and pushes against base  30  of outer leg  12 , thereby opening hinged brace  10 . Stops  33  and  34  are positioned on the inner surfaces of sides  28  and  29 , respectively, adjoining the edge of base  30 , and contact abutment  23  when hinged brace  10  is open thereby limiting the opening of hinged brace  10  to an angle less than about 80°, preferably less than about 75°. In one embodiment, stops  33  and  34  consist of nuts retained by screws  35  and  36  passing through holes  37  and  38  in sides  28  and  29 . However, stops  33  and  34  made also be formed of rigid material, such as steel, securely fixed to sides  28  and  29  by, for example, welding. Flange plates  39  and  40  are rigidly connected to the front ends of sides  28  and  29 , with buffer pads  41  and  42  of compressible, non-slip material, being connected to plates  39  and  40 . 
     Threaded bolt  5  passes between protrusions  17  and  18  of inner leg  11 , under abutment cap  23  and spring  24 , with the end connected to bracket  1  being positioned at the front end of inner leg  11 , so that hinged bracket  10  is movably positioned on threaded bolt  5 . Hinged bracket  10  is retained on threaded bolt  5  by circular thumbwheel  43  which has a hole  44  passing through its axis. Hole  44  is sized and threaded to match the thread of threaded bolt  5 , whereby, when turned, thumbwheel  43  moves down threaded bolt  5  and connects with the end  45  of hinged brace  10 . Thumbwheel  43  preferably has a non-slip outer surface, for example knurled, in order to aid in griping it. In a preferred embodiment, thumbwheel  43  is formed from aluminum. As shown in FIGS. 3 and 4B, thumbwheel  43  is preferably retained on threaded bolt  5  by means of a small diameter split ring  46  which passes through a hole  47  in the rear end of threaded bolt  5 . In the embodiment shown in FIG. 3, small depression  48  is provided in the upper surface of thumbwheel in which split ring  46  rests. It will be clear to one of skill in the art that thumbwheel  43  may be replaced by other locking means, such as a nut or screw. 
     With reference to FIGS. 8 and 9, in order to place the inventive lock on the inside of a door  49 , inner leg  11  is held in one hand and door  49  is opened. U-shaped protrusion  2  on bracket  1  is placed in the lock chamber  50  in door frame  51 . Hinged brace  10  is closed, preferably by pinching with the thumb and forefinger, swung away from door  49 , and door  49  is closed. Hinged brace  10  is released, allowing it to spring open. Hinged brace  10  is then pushed forwards along threaded bolt  5  until buffer pad  27  on inner leg  11  touches door  49 , and buffer pads  41  and  42  on outer leg  12  touch door frame  51 . Thumbwheel  43  is rotated down threaded bolt  5  until it contacts end  45  of hinged brace  10  and is tightened by hand. 
     To remove the inventive lock, thumbwheel  43  is loosened and rotated back up threaded bolt  5  until it contacts spilt ring  46 . Hinged brace  10  is pulled away from door  49  until it contacts thumbwheel  43 , pinched closed and swung away from door  49 . Door  49  is opened and the lock is removed. The lock may then be folded, as shown in FIG. 2, as follows. While keeping hinged brace  10  closed, bracket  1  is folded over the top of outer leg  12  towards threaded bolt  5  and U-shaped protrusion  2  is engaged in slot  53  formed in closed hinged brace  10  between abutment cap  23  and the end of base  30 . Thumbwheel  43  is then tightened against end  45 , holding the lock in a compact form. 
     With reference to FIG. 9, when an attempt is made to open door  49  from the outside with the lock installed as described above, force is applied at point A to inner leg  11 . This causes hinged brace  10  and threaded bolt  5  to pivot with respect to bracket  1  via hinge pin  9 . The force is then applied through outer leg  12  directly into door frame  51  at point B. 
     The door lock of the present invention is stronger than previous portable door locks for two main reasons. First, by transferring the force on door  49  directly to door frame  51 , it prevents any bending stresses from being applied to either bracket  1  or threaded bolt  5  and instead puts them both under tensile stress, which they are better able to withstand. Secondly, the force applied inwards to door frame  51  at point B opposes the force exerted outwards by U-shaped protrusion  2  on the inner edge of lock chamber  50  at point C. It is thickness X, between lock chamber  50  and the outer edge of door frame  51 , that is the weakest point in most door and frame sets, and that is most likely to fail if a door is forced. Therefore, any force opposing that applied at point C will act to strengthen the door and frame set. 
     While in the foregoing specification this invention has been described in relation to certain preferred embodiments, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein may be varied considerably without departing from the basic principles of the invention.