An indicator adapted to provide a visual indication of an over pressure situation in a system. The indicator (also referred to as a pop indicator), includes a main body, a piston that is disposed in the main body, and one or more O-rings disposed around the piston. Initially, the piston is in a first position where the piston is retracted into the body. However, when an over pressure situation occurs, the pressure causes the piston to move in a direction out of the main body against a friction force created by the O-ring. When the piston is moved, i.e., popped, then end of the piston extending out of the body provides a visual indication.

An air compressor having a pressure gauge, the pressure gauge contains: a hollow tube, a drive element, an anti-leak spring, a resilient element, and a cap. The hollow tube includes an accommodation chamber, a connector having a conduit, and a display unit. The drive element includes a protection unit, a first open segment, a second distal segment, a receiving portion, a hollow extension, and a protrusion. An anti-leak spring is received in the hollow extension of the drive element, a first end of the anti-leak spring abuts against the protrusion, and a second end of the anti-leak spring contacts with the protection unit. The resilient element is received in the receiving portion of the drive element. The cap includes a seat, a push bolt, and multiple passages. An end of the resilient element contacts with the cap.

An improved air compressor includes a cylinder fitted with a piston body and an air storage container. The cylinder and the air storage container are detachably assembled to define an air chamber. A metal seat with a through hole is provided on top of the cylinder. A valve plug is spring-biased against the metal seat. The air storage container is provided with a pressure indicator, which includes a tube defining therein a first bore and a second bore, between which a tapered annular surface is formed. When the air pressure within the air storage container exceeds a predetermined pressure set for the air compressor, the pressure indicator allows excess air to flow into the first bore of the tube and sequentially pass through the tapered annular surface and an elongated opening to be released to the ambient environment, so that objects can be prevented from damages due to excessive inflations.

A microfabricated pressure transducer is formed in a multilayer substrate by etching a plurality of shallow and deep wells into the layers, and then joining these wells with voids formed by anisotropic etching. The voids define a flexible membrane over the substrate which deforms when a force is applied.

A pressure gauge includes a hollow tube, a drive element, an anti-leak spring, a resilient element, and a cap. The hollow tube includes an accommodation chamber, a connector having a conduit, and a display unit. The drive element includes a protection unit, a first open segment, a second distal segment, a receiving portion, a hollow extension, and a protrusion. An anti-leak spring is received in the hollow extension of the drive element and abuts against the protrusion and the protection unit. The resilient element is received in the receiving portion. The cap includes a seat, a push bolt, and multiple passages. The accommodation chamber has a first fixing section and a second fixing section, a diameter of which is different from that of the first fixing section. The hollow tube further includes a tilted surround section and at least one discharge orifice.

A pressure gauge has a shell, a scale panel, an index pointer, a piston set, and a gear transmission set. The shell has a front end board, a back end board, and a piston base mounted on the inner surface of the back end board. The scale panel is mounted between the front end board of the shell and the back end board of the shell. The index pointer is mounted on a front surface of the scale panel. The piston set is mounted in the piston base of the shell. The gear transmission set is mounted between the back end board of the shell and the scale panel.

An imaging scope includes an internal surface defining an internal cavity, a window permitting visual inspection of the internal cavity, a fluid in the internal cavity having a pressure different than ambient pressure, and a leak indicator transitionable between nonvisible and visible through the window when the pressure of the fluid changes toward ambient pressure.

A height adjustable hitch receiver is disclosed and described.

A pressure indicator includes a body, a piston, first and second biasing elements, and a rotatable disc. The piston is disposed at least partially in a bore of the body at a first longitudinal axial position relative to the body when pressure of fluid acting on the base is below a threshold pressure. The first biasing element is disposed between a base of the piston and a shoulder of the body, wherein a force of the first biasing element is overcome by pressure of fluid acting on the base at or above the threshold pressure, thereby allowing the piston to move to a second longitudinal axial position. The rotatable disc has a first rotational position when the piston is in the first axial position. The second biasing element is configured to urge the disc to a second rotational position when the piston is in the second axial position.

A height adjustable hitch receiver is disclosed and described.