Abstract: A mixer for first and second fluids, e.g. fresh air and return air respectively, has an outlet for the first fluid which is contiguous to outlet for the second fluid. A first flap is able to move from a position wherein the fresh air outlet is closed to a position wherein the fresh air outlet is open. A second flap is able to move from a position wherein the return air outlet is closed to a position wherein the return air outlet is open. The first and second flaps are connected to move in unison from a position wherein the fresh air outlet is open and the return air outlet is closed to a position wherein the fresh air outlet is closed and the return air outlet is open. Preferably, there is a plurality of alternating fresh air and return air outlets, and the first and second flaps are fixedly joined substantially at right angles to one another.

Abstract: A centrifugal fan apparatus for installation in an air plenum adapted to provide pressurized air to a ventilating system includes a centrifugal fan rotor having front and rear sidewalls and a number of blades extending between these sidewalls. The platform has a horizontal base frame on which wheels are rotatably mounted. The front sidewall has a central opening for receiving air while the rear sidewall is attached to a rotatable drive shaft that extends rearwardly from the rotor. A motor is connected to the shaft in order to rotate it and the rotor. A linearly movable platform supports the rotor, shaft and motor and an actuator moves this platform forwardly or rearwardly in order to control the volume of air flowing out of the rotor. An air inlet member is mounted rigidly at the central opening and has a generally cylindrical section that can extend into the rotor when the rotor is moved to a forward position.

Abstract: A fan unit for a building's air handling system comprising a support structure including a front wall with an air inlet opening formed therein and a bladed fan wheel rotatably mounted on the support structure about its central axis and having an axial air intake on a front side thereof confronting the inlet opening. The fan wheel has an annular air outlet extending about its circumference. A fixed centerbody directs air flow into and within the fan wheel and extends along the central axis from a relatively narrow front end located in the air inlet opening to a wider rear end located within the fan wheel. This centerbody has an annular exterior surface which curves outwardly in a section thereof adjacent the wider rear end. The centerbody extends through the axial air intake of the fan wheel. Support struts rigidly support the centerbody in a fixed position. Preferably the centerbody is filled with sound attenuating material.

Abstract: Combined air duct apparatus and silencer for attachment to both the inlet and the outlet of a fan unit for a building wherein each silencing apparatus has an exterior housing with an air inlet and an air outlet, one of which is adapted for connection to the fan unit. The inlet and outlet are connected by an airflow passageway defined by interior walls of the housing. First and second series of splitters are also provided in the outlet duct unit. The splitters in each series are spaced apart to form smaller air passageways and mounted side-by-side in a row. In the outlet duct unit, the air inlet is circular or annular while the outlet is rectangular. In one embodiment, the outlet lies in a plane at a substantial angle to the plane of the annular inlet and the main airflow passageway is substantially curved in its lengthwise direction.

Abstract: Combined air duct apparatus and silencer for attachment to both the inlet and the outlet of a fan unit for a building wherein each silencing apparatus has an exterior housing with an air inlet and an air outlet, one of which is adapted for connection to the fan unit. The inlet and outlet are connected by an airflow passageway defined by interior walls of the housing. A resonator chamber for reducing noise created by the fan unit extends around or is adjacent to the inlet or the outlet that is connected to the fan unit. The chamber is enclosed by chamber walls including a peripheral wall perforated with a number of holes and facing the airflow passageway. First and second series of splitters are also provided with those in each series being spaced apart to form smaller air passageways and mounted side-by-side in a row. The second series is positioned downstream of the first series. In the outlet duct unit, the air inlet is preferably circular while the outlet is rectangular.

Abstract: A non-fibrous acoustic silencing duct member capable of attenuating noise associated with a gaseous medium passing through it. Perforated sidewalls define a gas flow passageway and include at least two opposing walls, each perforated with a number of small holes distributed over its surface. Exterior sidewalls are positioned on the outside of the perforated sidewalls and are spaced therefrom. Enclosed chambers are formed between the perforated and exterior sidewalls, which chambers are of selected depths. One or more screen layers extend along and adjacent to outer surfaces of the perforated sidewalls, these screen layers being located in the chambers. Each screen layer is covered with an array of very small holes that are substantially smaller than the holes in the adjacent perforated sidewall. Internal dividers extend between each perforated sidewall and its respective exterior sidewall in order to divide the space between the sidewalls.

Abstract: Combined air duct apparatus and silencer for attachment to both the inlet and the outlet of a fan unit for a building wherein each silencing apparatus has an exterior housing with an air inlet and an air outlet, one of which is adapted for connection to the fan unit. The inlet and outlet are connected by an airflow passageway defined by interior walls of the housing. A resonator chamber for reducing noise created by the fan unit extends around or is adjacent to the inlet or the outlet that is connected to the fan unit. The chamber is enclosed by chamber walls including a peripheral wall perforated with a number of holes and facing the airflow passageway. First and second series of splitters are also provided with those in each series being spaced apart to form smaller air passageways and mounted side-by-side in a row. The second series is positioned downstream of the first series. In the outlet duct unit, the air inlet is preferably circular while the outlet is rectangular.

Abstract: Combined air duct apparatus and silencer for attachment to both the inlet and the outlet of a fan unit for a building wherein each silencing apparatus has an exterior housing with an air inlet and an air outlet, one of which is adapted for connection to the fan unit. The inlet and outlet are connected by an airflow passageway defined by interior walls of the housing. A resonator chamber for reducing noise created by the fan unit extends around or is adjacent to the inlet or the outlet that is connected to the fan unit. The chamber is enclosed by chamber walls including a peripheral wall perforated with a number of holes and facing the airflow passageway. First and second series of splitters are also provided with those in each series being spaced apart to form smaller air passageways and mounted side-by-side in a row. The second series is positioned downstream of the first series. In the outlet duct unit, the air inlet is preferably circular while the outlet is rectangular.