Each of the mechanical seal devices of a rotary joint includes a first shaft side seal ring attached to a shaft body and a first case slide seal ring attached to one side of the first shaft side seal ring as well as a second case side seal ring attached to a case body and a second shaft side seal ring attached to the second case side seal ring. A first communication flow passage is formed between a first sliding portion of the first seal rings and a second sliding portion of the second seal rings. A second communication flow passage is formed between the first sliding portion of a mechanical seal device disposed on one side in the axial direction and the second sliding portion of a mechanical seal device disposed on the other side in the axial direction in mechanical seal devices adjacent to each other.

A water transferring device is provided and comprises a body having a water passage chamber, a first water inlet joint having a first water inlet passage and connected to the body, and a water outlet joint having an outer water passage and an inner water passage. The first water inlet joint and the water outlet joint enable the inner water passage to be in communication with the first water inlet passage. The water passage chamber is in communication with the outer water passage. At least one of the first water inlet joint or the water outlet joint comprises a connection structure connected to the body and enabling the at least one of the first water inlet joint or the water outlet joint to be at least rotated for a specific angle around an axis of the at least one of the first water inlet joint or the water outlet joint.

A water transferring device is provided and comprises a body having a water passage chamber, a first water inlet joint having a first water inlet passage and connected to the body, and a water outlet joint having an outer water passage and an inner water passage. The first water inlet joint and the water outlet joint enable the inner water passage to be in communication with the first water inlet passage. The water passage chamber is in communication with the outer water passage. At least one of the first water inlet joint or the water outlet joint comprises a connection structure connected to the body and enabling the at least one of the first water inlet joint or the water outlet joint to be at least rotated for a specific angle around an axis of the at least one of the first water inlet joint or the water outlet joint.

A rotating manifold includes an axle, a hub rotatable relative to the axle about an axis of rotation, and a compressed air line in fluid communication housed in the axle. The rotating manifold further includes a vacuum line in fluid communication with the hub. The rotating manifold further includes a plurality of conduits connected to the hub. Each conduit of the plurality of conduits is in fluid communication with the vacuum line and houses a compressed air line arm in fluid communication with the compressed air line.

A compressor assembly for a portable oxygen concentrator includes a first compressor chamber having a first connector, a second compressor chamber having a second connector, and a tube having a first end having a first connection interface configured to connect to the first connector and a second end having a second connection interface configured to connect to the second connector. The first connection interface is shaped to maintain the connection between the first connector and the first connection interface in a fixed orientation and the second connection interface is shaped to maintain the connection between the second connector and the second connection interface in a fixed orientation. One or more of the first connector, the second connector, and the tube are compliant.

A compressor assembly for a portable oxygen concentrator includes a first compressor chamber having a first connector, a second compressor chamber having a second connector, and a tube having a first end having a first connection interface configured to connect to the first connector and a second end having a second connection interface configured to connect to the second connector. The first connection interface is shaped to maintain the connection between the first connector and the first connection interface in a fixed orientation and the second connection interface is shaped to maintain the connection between the second connector and the second connection interface in a fixed orientation. One or more of the first connector, the second connector, and the tube are compliant.

A rotary union includes a housing having a shaft rotatably mounted in a bore. A plurality of annular plates is mounted on the shaft in spaced relation, and a plurality of spools is disposed in alternating fashion between the plurality of annular plates on the shaft. Each spool includes two seal rings creating mechanical face seals with adjacent annular plates. The shaft, the plurality of annular plates and the plurality of spools are arranged to assemble in a stacked arrangement, which is insertable as a whole into the cylindrical bore of the housing.

A rotary union includes a housing having a shaft rotatably mounted in a bore. A plurality of annular plates is mounted on the shaft in spaced relation, and a plurality of spools is disposed in alternating fashion between the plurality of annular plates on the shaft. Each spool includes two seal rings creating mechanical face seals with adjacent annular plates. The shaft, the plurality of annular plates and the plurality of spools are arranged to assemble in a stacked arrangement, which is insertable as a whole into the cylindrical bore of the housing.

A method of operating a compressor system includes determining an efficiency of a compressor configured to operate at a plurality of output flow settings, including one or more of measuring, calibrating, calculating, or modeling motor efficiency over a range of supply voltage and pulse width modulation duty cycle combinations, each combination including a supply voltage of a plurality of supply voltages and a pulse width modulation duty cycle of a plurality of pulse width modulation duty cycles. The method further includes selecting a supply voltage and a pulse width modulation duty cycle for use at at least one output flow setting of the plurality of output flow settings based on the determined efficiency of the compressor, generating the selected supply voltage by maintaining, reducing, or increasing a nominal supply voltage, and applying the selected pulse width modulation duty cycle.

A method of operating a compressor system includes determining an efficiency of a compressor configured to operate at a plurality of output flow settings, including one or more of measuring, calibrating, calculating, or modeling motor efficiency over a range of supply voltage and pulse width modulation duty cycle combinations, each combination including a supply voltage of a plurality of supply voltages and a pulse width modulation duty cycle of a plurality of pulse width modulation duty cycles. The method further includes selecting a supply voltage and a pulse width modulation duty cycle for use at at least one output flow setting of the plurality of output flow settings based on the determined efficiency of the compressor, generating the selected supply voltage by maintaining, reducing, or increasing a nominal supply voltage, and applying the selected pulse width modulation duty cycle.