Air Conditioner Auto-Locking Window Guard

Most people install an window air conditioner in the summer. Whether it is a full-size air conditioner unit or a floor air conditioner unit with a window vent adapter. The security of these installations is poor as a burglar can easily raise the window and push in the A/C to gain access to the home's interior. And if they cannot raise the window then they will try to push in the A/C and raise the window to enter.

This design uses a simple ratchet device that prevents the window from being raised at all. And if it is lowered slightly it will adjust to the new height and prevent any widening of the opening. And a simple trick closes the window automatically if the A/C is pushed in.

Simply affix a cord to the top of the A/C and the bottom of the window on it. If the A/C is pushed in it will hang on the cord and lower the window with it's entire weight. The Window Guard will ratchet down and prevent any attempt to lift and raise the window.

This is a easy solution to risky installations of air conditioners such as first floors, fire escapes and a second story if the burglar uses a ladder and a ruse such as disguising as a handyman or repairman so as not to raise attention to himself.

You will need the .stl files for the "Window Guard" parts and a 3D printer or access to one. You will also need appropriate wood screws and a cordless drill. Best to use PLA filament in a darker color. Use 0.2mm "Draft" resolution mode and an infill density that is about 60+ percent for added strength. Try recommended "Grid" infill for rigidity. If the window is thick, use the "Thick hinge.stl" file. And if the window is thin use the "Narrow hinge.stl" as it will work better for it. Arrange parts on the print bed strategically for fit on the bed and for most efficient placement. A part where that "Grid" infill is diagonal inside it is stronger than one where they are parallel to the inside/outside walls. So plan ahead. Feel free to modify any part to suit your window dimensions.

Although the "Window Lock" will rest against the "Window Rack" it needs something to ensure that it stays engaged to it when the window is lowered. That is why attaching a rubber band to the lock is recommended. Use some clamps and adhesive to glue one end of a cut rubber band to the underside of the "Window Hinge" and the other end to the "Window Lock". Ensure that the rubber band is stretched while the adhesive dries so that it will be tight when installed on the window.

Open your window to a height necessary to install your window air conditioner and mark where the "Window Rack" should go. You may need to pre-drill a hole for a small wood screw which should do the job.

Set the "Window Lock" with it's large "tooth" set in the matching inset tooth in the "Window Rack" and the highest point.

Pre-drill some holes on the top of the window and install it with small wood screws. Make sure that the rubber band snaps the lock back into the rack when separated and released.

Set your air conditioner in the window like usual and lower the window onto the top of the A/C allowing the "Window Lock" to ride down the "Window Rack" to the lowest tooth on the rack. Your window is now locked onto the air conditioner. Try to raise it. Can't be down.

Should the burglar push in the A/C into the room to raise the window, you should attach an eyelet screw to the lower part of the window and run a strong cord from the eyelet to a hole on top of the air conditioner's metal window ledge. So if the air conditioner falls it will pull the window down and make a space too small for the burglar to fit through.

Although this idea has been tested by the publisher it has not yet to have proven itself in a real world event of preventing a forced entry through the window with a air conditioner in it. The publisher does not guarantee that a successful break in through the window will not happen. It just might be thwarted or inhibited by the "Window Guard" mechanism. So keep your usual methods of guarding your home, like alarms and timed lights, on and working.

Keep alternate escape exits such as doors and other windows ready in case of fire or emergency or leave a screwdriver near the A/C window to remove the "Window Guard" in case of emergency exit requirement.

Good Luck.