Security lock for door

Abstract

A security lock for a door is provided having a bracket on the interior side of the door with a locking bolt mounted in the bracket. The bolt is adapted for movement between a raised, unlocked position above a cavity on the floor below the bracket and a lowered, locked position where the bolt is in the cavity to prevent the door from being opened. A bolt restraint is mounted on the bracket and cooperates with the bracket to maintain the bolt in its unlocked position. The bolt restraint, for example, a spring-loaded ball that engages an annular recess in the bolt, releases the bolt into its locked position when a downward force is applied to the bolt. The locking bolt has an enlarged flange that stops movement of the bolt into the cavity beyond a predetermined location on the bolt.

Claims

1. A security lock for a door, comprising; (a) a bracket for being secured to an interior side of the door proximate a bottom of the door; (b) a locking bolt for being mounted in the bracket and adapted for manual movement between a raised, unlocked position above a cavity positioned below the bracket in a floor without the use of a force multiplier, and a lowered, locked position without the use of a force multiplier, with the bolt positioned in the cavity to prevent the door from being opened; (c) a laterally-operating bolt restraint mounted on the bracket and laterally-engaging a sidewall of the bolt for maintaining the bolt in the unlocked position above the cavity and adapted to release the bolt for movement into its lowered, locked position upon a downward force being applied to the bolt; (d) the locking bolt including an enlarged flange adapted to stop movement of the bolt into the cavity beyond a predetermined location on the bolt; (e) a protective bushing adapted for being fitted into the cavity in the floor for receiving the bolt; and (f) an unlocking tool having a thin, curved strip including an opening in a first end of the strip and adapted to fit onto the bolt at a location below the flange and adapted for being inserted under and through an existing space between floor and the door from a position proximate to an exterior side of the door and manually operated to engage the enlarged flange of the locking bolt to lever the bolt upwardly out of the cavity into the unlocked position without damage to the lock or the door.

2. A security lock for a door according to claim 1, wherein the bolt includes an annular recess in the bolt at a location along a length of the bolt such that the annular recess communicates with the laterally-extending bolt restraint to maintain the bolt in the unlocked position and is adapted to release the bolt by downward pressure applied to the bolt sufficient to overcome interference between the bolt restraint and the annular recess.

3. A security lock for a door according to claim 1, wherein the bolt restraint comprises a spring carried by the bracket and a ball urged by the spring to partially reside in the annular recess and apply a perpendicular interference force to the annular recess for maintaining the bolt in the unlocked position.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The present invention is best understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which:

(2) FIG. 1 is an environmental perspective view showing the safety stop in an unlocked position;

(3) FIG. 2 is an exploded perspective view of the security lock, showing the manner of installation;

(4) FIG. 3 is an enlarged perspective view of the security lock shown in FIG. 1 in an unlocked position;

(5) FIG. 4 is a partial vertical cross sectional view of the security lock in an unlocked position;

(6) FIG. 5 is an enlarged perspective view of the security lock shown in FIG. 1 in a locked position; and

(7) FIGS. 6-8 are sequential perspective views showing the security lock being unlocked from outside of the door.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(8) Referring now to the drawings, a security lock 10 is shown in FIG. 1 installed on an interior side of a classroom door in its preferred embodiment. The security lock 10 is in a raised, unlocked position allowing the door to open and close freely. A bracket 40 is mounted on a lower portion of the door and allows a locking bolt 20 to slide through the bracket 40 in a perpendicular orientation to the floor. When in the unlocked position, the bolt 20 is held above a bushing 50 installed into the floor beneath the door.

(9) The assembly of the security lock 10 is shown in FIG. 2. The bracket 40 is affixed to the inside of the door by two threaded bolts 62. These threaded bolts 62 pass through a mounting plate 64 located on an outside of the door and through two corresponding holes 66 in the door. The threaded bolts 62 then fasten the bracket 40 to the inside of the door with two nuts 60. The bushing 50 is inserted into a cavity 52 in the floor which is positioned below the bolt 20 so that the bolt 20 can slide into the bushing 50. The bolt 20 has a pointed lower end 32 that enables proper location on the floor of the cavity 52 prior to the installation of the bushing 50.

(10) FIGS. 3 and 4 also show the bolt 20 in its raised, unlocked position. The bolt 20 has a lower end 32 with a diameter that fits into the bushing 50 and a bolt head 30 on the opposite end. Proximate to the lower end 32 is an enlarged, downwardly-tapered annular flange 22 that serves as a stop to prevent the bolt 20 from sliding further into the bushing 50. The flange 22 also functions as a gripping surface for unlocking the door from the outside, as described below. An annular recess 24 is located in the surface of the bolt 20 between the flange 22 and the bolt head 30.

(11) As shown in FIG. 4, the bolt 20 is held in place by a bolt restraint that includes a ball 28 and a spring 26. The spring 26 is embedded in a recess 27 inside of the bracket 40 and provides an force that is perpendicular to the bolt 20. The ball 28 is positioned between the spring 26 and the annular recess 24 and fits partially inside of the annular recess 24. Interference between the ball 28 and the annular recess 24 due to the force being applied by the ball 28 against the spring 26 perpendicular to the direction of movement of the bolt 20 holds the bolt 20 in its unlocked position.

(12) Referring now to FIG. 5, the security lock 10 is shown in a lowered, locked position preventing the door from being opened. The lower end 32 of the bolt 20 is inside of the bushing 50 due to the application of a downward force on the bolt head 30 sufficient to overcome the interference between the annular recess 24 and the ball 28 caused by the perpendicular force applied to the spring 26 by the ball 28.

(13) In the event of an emergency, the downward force can be quickly applied to the bolt head 30 by a foot, for example. Note that when the bolt 20 is in the locked position the annular recess 24 is no longer engaged with the ball 28 and is visible below the bracket 40.

(14) FIGS. 6-8 show the process of unlocking the security lock 10 from outside of the door. An unlocking tool 80 is used to raise the bolt 20 until the ball 28 engages with the annular recess 24 and holds the bolt 20 in the unlocked position. The unlocking tool 80 is a thin, curved strip with a hand gripping end 82 and a two pronged flange gripping end 84, The flange gripping end 84 is thin enough to slide under the door from the outside and engage with the flange 22 between the two prongs. The bushing 50 has an upward flare that cooperates with the flare of the flange 22 to form a “V” that guides the unlocking tool 80 into position. Once the flange gripping end 84 of the unlocking tool 80 is under the door and engaging with the flange 22 of the bolt 20 manual downward force is applied to the hand gripping end 82 of the unlocking tool 80. When a sufficient downward force is applied on the hand gripping end 82, the flange 22 is levered out of the bushing 50 and raised until the annular recess 24 and the ball 28 engage and hold the bolt 20 in its unlocked position enabling the door to open and close freely.

(15) A security lock according to the invention has been described with reference to specific embodiments and examples. Various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description of the preferred embodiments of the invention and best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation, the invention being defined by the claims.