Abstract: A manually operable fluid level indicator as illustrated for indicating at a location remote from a reservoir whether the fluid level in the reservoir has fallen below a predetermined level. A hollow dip stick having an aperture through a side wall of a lower end thereof depends into the reservoir and is normally covered by fluid within the reservoir. An indicator housing has chamber communicating with the interior of the dip stick and has a piston moveable therein by a friction drive connection with a manually moveable plunger. On moving the plunger outwardly of the housing, the piston remains stationary if a vacuum condition exists in the conduit communicating between the dip stick and housing. If the fluid level falls below the orifice and allows air or gas to enter the conduit running to the chamber of the housing, the piston will move with the plunger when the latter is pulled outwardly of the housing and the movement of the piston is visually observed to indicate a low fluid level.

Abstract: A vertical take-off and landing (VTOL) aircraft is disclosed. In one embodiment designed for manned flight, the aircraft employs an aerodynamically-shaped body carrying a pair of lifting elements disposed longitudinally along the body on opposite sides thereof. The lifting elements extend outwardly and curve smoothly downward from a horizontal to a vertical orientation at the outboard edge. Lifting air is flowed over them transverse to the direction of flight. In a second embodiment designed for unmanned use such as cropdusting, military surveillance, or the like, the body is a single circular lifting element of parabolic cross-section. In both embodiments, a turbine is carried within the body to provide forward thrust and, primarily, a supply of pressurized air which is flowed through a nozzle slit opening outwardly over the tops of the lifting element(s) in confined segments.

Abstract: A tire cap pressure gauge for mounting upon a tire valve stem and measuring tire pressure has a housing, a manually operated plunger extending axially through the housing, a spring extending about the plunger, a piston biased by the spring and having indicia, and a transparent insert member containing said spring, piston and plunger within the housing and having an internally threaded bore for mounting about the periphery of a threaded valve stem. The housing has multiple windows with indicia proximate thereto for viewing the translational position of the piston through the transparent insert member. Two embodiments show a lightweight, compact and easily assembled pressure measuring cap having sealless construction which utilizes close clearances and sharp corners to minimize leakage airflow. A small but insignificant amount of air leaks past the piston, providing an audible signal that the plunger is sufficiently depressed to provide an adequate pressure reading.

Abstract: A pressure differential indicator for indicating a change in a fluid pressure differential across a component in a fluid system, such as an oil filter, has piston means, means for communicating fluid pressures of said system upstream and downstream of said component to opposite sides of said piston means, respectively, and differential means associated with the piston means for normally balancing the resultant forces of said pressure on opposite sides of said piston means at a given predetermined pressure differential across said component whereby said piston means is responsive to an increase or decrease in the pressure differential above or below said predetermined differential pressure to indicate a clean or clogged filter condition. Means are provided for holding the piston means in its last position upon relief of said first and second pressures to indicate the operating filter condition when the system is not operating.