Abstract: A wind turbine unit for generating electricity in a confined space includes a pair of sails carried at either end of a pair of spaced, axially aligned rotatable arms mounted to the drive shaft of an electrical generator. As the prevailing wind strikes the sails in opposite directions, one of the sails is moved to a vertical position while the other sail is moved to a horizontal position. The wind incident on the then vertical sail causes the arms to rotate about the longitudinal axis of the generator and the sails are alternatively raised and lowered between a vertical and a horizontal position so that one of the sails is vertical while the other is horizontal.

Abstract: A blade for a wind turbine includes a device for causing air at an increased velocity and/or pressure to escape from exit openings in the blade, thereby to apply a force. Pressure and diameter adjustable valves may be provided at each exit opening or orifice to allow the air to exit from the blade only when the air pressure within the blade exceeds a preset level. Also disclosed is the provision of valves at the exit openings or orifices on an opposite edge of the blade that allows air to escape from the blade to slow down but not stop rotation of the blade when a dangerous wind condition is detected.

Abstract: A blade for a wind turbine includes a means for causing air at an increased velocity and/or pressure to escape from exit openings in the blade, thereby to apply a force that increases the rotational velocity of the blade. In one embodiment of the invention described a fan or vacuum in the blade causes an increase in the air velocity within a hollow air chamber in the blade. In another embodiment of the invention described, a compressor or one-way valve is used to increase the pressure of the air within the interior hollow air chamber. Pressure and diameter adjustable valves may be provided at each exit opening or orifice to allow the air to exit from the blade only when the air pressure within the blade exceeds a preset level. Also disclosed is the provision of valves at exit openings or orifices on an opposite edge of the blade that allows air to escape from the blade to slow down but not stop the rotation of the blade when a dangerous wind condition is detected.

Abstract: An easily opened envelope includes a cutting filament extending across at least one interior edge of the envelope. A tear line that terminates adjacent one end of the cutting filament is torn to expose and thereby permit the user to grasp the thus-exposed end of the cutting element. The edge of the envelope along which the cutting filament extends is severed by pulling the cutting filament along the edge, thereby to provide access to the interior of the envelope.