A pressure indicator with a pressure-relief function is disclosed, which can release excessive pressure to the environment. The pressure indicator includes a transparent tube defining therein a first bore and a second bore, and a slider which can be forced by the medium supplied from an external pressure source to move along the first and second bores of the transparent tube. In particular, the first bore has a diameter greater than the second bore, and a tapered annular surface is provided between the first bore and the second bore of the transparent tube. When the pressure of the medium exceeds a predetermined pressure, the slider can be forced by the medium to reach the tapered annular surface, at which excessive medium can be released into the environment via an annular gap between the slider and the tapered annular surface.

A pen-type pressure indicator, which can be detachably connected to an air compressor for measuring the pressure of compressed air produced in the air compressor, includes a transparent tube and a slider. The slider can be moved along a first bore and a second bore of the transparent tube. The motion of the slider in the transparent tube is similar to the motion of a piston in a cylinder. The transparent tube is provided with a tapered annular surface, between the first bore and the second bore. In addition to measuring the pressure of the compressed air delivered to an object, when the pressure of the compressed air exceeds a predetermined pressure, excessive air can be released into the environment, without requiring the air compressor to be installed with a safety valve, so that the object can be protected from damages due to overpressure.

A pressure indicator, which can be detachably connected to an air compressor for measuring the pressure of compressed air produced in the air compressor, includes a tube and a slider. The slider can be moved along a first bore and a second bore of the tube. The motion of the slider in the tube is similar to the motion of a piston body in a cylinder. The tube is provided with a tapered annular surface, between the first bore and the second bore, and defines an elongated opening. In addition, when the pressure of the compressed air exceeds a predetermined pressure, excessive air can be released into the ambient environment, without using a mechanical safety valve, so that an object can be prevented from over-inflation.

A ball mount for measuring tongue weight of a trailer is disclosed. The ball mount can comprise a ball portion for interfacing with a ball configured to couple with a tongue of a trailer, a hitch portion for interfacing with a hitch receiver associated with a vehicle, and a load measurement device associated with the hitch portion. The hitch portion can be configured to pivot relative to the hitch receiver about a fulcrum in response to a downward force on the ball, with the hitch receiver resisting rotation of the hitch portion about the fulcrum thereby inducing a load on the hitch portion. The load measurement device can be configured to determine a magnitude of the downward force on the ball based on the load on the hitch portion.

Embodiments of air admittance valve assembly and piping system incorporating the same are provided herein. In some embodiments, a valve assembly comprising a housing, a first valve comprising a first valve sealing member and a first valve seat, and a second valve comprising a second valve sealing member and a second valve seat, and a pipe, an inlet, an outlet, a first zone, a second zone, a third zone, the first and second valve sealing member is closed by gravity and open based upon the pressure differential between the first zone, second zone and third zone.

A height adjustable hitch receiver is disclosed and described.

A safety device coupled to a fluid end such that the safety device is in fluid communication with at least one of a suction chamber and a discharge chamber of the fluid end. The safety device has an outer housing and a visual indicator. The visual indicator is moveable between a first position where the visual indicator is retracted into the outer housing, and a second position where the visual indicator is extended out of the outer housing.

An air compressor structure includes a cylinder, a piston, a cylinder lid, and a pressure gauge. The piston coupled in the cylinder performs reciprocating motion to generate compressed air, and the cylinder lid is assembled to the cylinder to receive the compressed air. The pressure gauge includes a propelling barrel movably disposed in the cylinder lid and having a gear rack, a value panel disposed on a surface of the cylinder lid, a pointer, and a spring disposed in the cylinder lid and abutting against the propelling barrel. The pointer includes a pointing portion and a pivot, where the pivot is disposed on the cylinder lid and has a gear engaged to the gear rack, and the pointing portion extends from the pivot and is located on the value panel.

Embodiments of air admittance valve assembly and piping system incorporating the same are provided herein. In some embodiments, a valve assembly comprising a housing, a first valve comprising a first valve sealing member and a first valve seat, and a second valve comprising a second valve sealing member and a second valve seat, and a pipe, an inlet, an outlet, a first zone, a second zone, a third zone, the first and second valve sealing member is closed by gravity and open based upon the pressure differential between the first zone, second zone and third zone.

Embodiments of air admittance valve assembly and piping system incorporating the same are provided herein. In some embodiments, a valve assembly comprising a housing, a first valve comprising a first valve sealing member and a first valve seat, and a second valve comprising a second valve sealing member and a second valve seat, and a pipe, an inlet, an outlet, a first zone, a second zone, a third zone, the first and second valve sealing member is closed by gravity and open based upon the pressure differential between the first zone, second zone and third zone.