A backpack dust collector includes a housing, a slit portion, and a noise-absorbing member. The housing includes a suction port, a dust collecting chamber, a motor chamber, and an exhaust port. The dust collecting chamber is connected to the suction port and configured to accommodate a dust collecting bag. The motor chamber is connected to the dust collecting chamber and accommodates a fan and a motor. Through the exhaust port, air from the motor chamber is discharged. The slit portion is disposed in a flow path between the motor chamber and the exhaust port and includes at least one slit-shaped vent through which air from the motor chamber passes. The noise-absorbing member is disposed in at least part of a flow path between the vent and the exhaust port.

A cyclone separation device includes a cyclone chamber for separating dirt from incoming air, a dirt collecting chamber arranged adjacent to the cyclone chamber for collecting dirt particles separated from air, and a dirt duct between the cyclone chamber and the dirt collecting chamber for allowing dirt particles to exit the cyclone chamber into the dirt collecting chamber. To reduce the generation of noise-generating air vortices, the dirt duct has an edge protruding into a direction at an angle to the dirt duct at an exit ridge of the cyclone chamber that is first encountered by the air rotating in the cyclone chamber. Preferably, the edge is formed by a tangential extension of a wall of the cyclone chamber. A vacuum cleaner advantageously includes such a cyclone separation device.

A vacuum clear and an electric motor module (100) therefor are provided. The electric motor module (100) includes an outer casing (1) provided with an air inlet (10) at a front side thereof and an air outlet (11) at a rear side thereof; an electric motor assembly (2) arranged in the outer casing (1), and cooperating with the outer casing (1) to define an air passage in communication with the air inlet (10) and the air outlet (11); and a silencer (3) arranged at the air inlet (10), defining at least one resonant cavity therein, and the at least one resonant cavity having a side wall provided with a throat in communication with the resonant cavity.

The present application discloses dust boxes, dust box assemblies and cleaning devices, wherein the dust box assembly includes a dust box and at least two fans. The dust box is formed with a holding cavity, a dust suction port and at least two air outlets, the dust suction port is connected to the holding cavity, the at least two air outlets are connected to the holding cavity. At least two fans are provided corresponding to at least two air outlets for creating an airflow that passes through the dust suction port, the holding chamber and the air outlet in sequence.

A work machine includes microphones inside the housing. The microphones are configured to collect sound inside the housing, and output sound signals that are electrical signals corresponding to the collected sound. The sound includes an operating noise generated inside the housing due to motion of a machine. The microphones are arranged at different locations inside the housing. The work machine is configured to execute a process related to the operating noise based on the sound signals from the microphones.

A vacuum cleaner comprises: a suction part for suctioning external air; a discharge part through which the sucked air is discharged to the outside; a frame along a flow path between the suction part and the discharge part; and a filter including a filter member which is supported by the frame and which separates dust from the suctioned air, wherein the filter member includes: a first filter part spaced from and to be parallel with an opening formed in the frame; a second filter part having one side supported by the frame and another side extended from the one side thereof toward the edge of the first filter part; and a bent part between the edge of the first filter part and the other side of the second filter part, and the thickness of the first filter part or the second filter part is different from the thickness of the bent part.

The work machine includes a path leading into a housing from an opening. The path is provided to control an airflow generated by motion of a machine. The work machine includes a microphone. The microphone is configured to collect sound in the housing, including operating noise generated in the housing by the motion of the machine. The work machine further includes a structure that defines a receiving space for the microphone along the path through which the operating noise propagates outside the housing. The structure includes an open structure that connects the receiving space with the path and faces downstream in the path. The structure surrounds the receiving space upstream of the open structure in the path.

A cleaning machine may include: a first brush including a first brush shaft and a first brush body held by the first brush shaft; a second brush including a second brush shaft and a second brush body held on the second brush shaft; a first brush attaching member having a first shape, wherein one end of the first brush shaft is detachably attached to the first brush attaching member; and a second brush attaching member having a second shape, wherein one end of the second brush shaft is detachably attached to the second brush attaching member. The one end of the first brush shaft may have a first corresponding shape that corresponds to the first shape. The one end of the second brush shaft may have a second corresponding shape that corresponds to the second shape. Other end of the first brush shaft may have the second corresponding shape.

A blower may include a fan, a casing including a discharge port and housing the fan, and a nozzle attachable to the discharge port. The nozzle may include a nozzle tube in which air flows, and a plate member disposed within the nozzle tube. A rear end surface of the plate member may be inclined to a flow direction in which air flows within the nozzle tube.

A cleaner reduces noise. The cleaner includes a motor, a fan including a number Z of blades and rotatable at a rotational speed N, indicating revolutions per minute, about a rotation axis by the motor, a cover having an inlet located frontward from the fan, and a number V of ribs located in the inlet. The ribs extend in a radial direction from the rotation axis and are arranged in a circumferential direction about the rotation axis. The fan is rotatable to produce noise having a frequency f.sub.NZ of 20,000 Hz or higher, and f.sub.NZ=(m−k×V)×N/60 and m=n×Z+k×V, where n is an order, m is an integer, and k is an integer.