Abstract: An air pressure indicator attaches to a manifold and uses air pressure to elide a pressure pin outward. A spring moves the pressure pin inward when pressure decreases in the manifold. A collet and o-ring on the pressure pin prevent the flow of pressurized fluid through the interior of the indicator.

Abstract: An emergency breathing device has a manifold with two threaded receivers for holding compressed air cartridges and two parallel bores. A first bore holds a primary plunger. A collar on the plunger rests on a nylon seal, which is supported on a ledge between the relatively small lower bore and the larger upper bore. A drive spring surrounds an upper portion of the primary plunger and bears against the collar. A housing receives and abuts the spring, and slides an upper part of the plunger through an axial bore in the housing. Detent pins extend through radial bores in the housing. Detent springs urge the detent pins outward. The plunger has a recess which receives semi-spherical inner ends of the detent pins when the plunger is pushed upward against drive spring force. A bell-shaped cap has a bevelled lower edge and a cylindrical inner surface, which presses the detent pins inward against detent spring force.

Abstract: An improved drafting instrument is provided for scribing small dots on a drafting medium comprising a substrate provided with a removable surface coating. The drafting instrument includes a drive motor and rotatable cutter which are slidably mounted as a unit for vertical movement toward and away from the drafting medium. A manually operable actuator is provided for moving the drive motor downward to bring the cutter into engagement with the surface coating of the drafting medium. A control switch responds to downward movement of the drive motor and cutter by a predetermined distance for automatically actuating the drive motor before the cutter is moved into engagement with the drafting medium. The drafting instrument includes an adjustable depth limit feature to control the depth of penetration of the cutter into the surface coating of the drafting medium. The operation of the drive motor and rotation of the cutter are automatically terminated when manual pressure on the actuator is released.