Bypass-Type Motor Protecting Device for a Vacuum Cleaner

A bypass-type motor protecting device for a vacuum cleaner, the vacuum cleaner including a body housing which has an intake port, an airflow duct which is disposed within the body housing and which is in fluid communication with the intake port, a filter unit disposed in the airflow duct for trapping dust, a suction motor disposed in the airflow duct and downstream of the filter unit, and a hose which is in fluid communication with the intake port, and which has a suction opening remote from said intake port for sucking up a dust-entraining air stream, the body housing further having a bypass opening, said bypass-type motor protecting device comprising:

• a casing having a tubular wall which includes a mounting end that defines an access bore, and that is adapted to be fitted into the bypass opening, and which surrounds an axis and extends along the axis and inwardly to define a passageway that is communicated with said access bore, said casing further having an inner abutment wall which extends radially to confront said passageway, and which has an internal port that is adapted to communicate said passageway with the airflow duct;
• a seat body extending radially to close said access bore, and having an inner peripheral wall which defines a bypass entry port that is in fluid communication with said passageway, a back pressure being generated at said bypass entry port as a result of clogging of the airflow duct by the trapped dust, thereby creating a reduced pressure upstream of the suction motor;
• a valve body unit which is disposed to be movable in said passageway between a closed position, where entry of air into said passageway through said bypass entry port is denied, and an open position, where, by virtue of the generated back pressure, air is permitted to enter into said passageway through said bypass entry port, and which includes
• to a valve disc configured to be engaged with and disengaged from said seat body when said valve body unit is in the closed and open positions, respectively,
• a plunger body having an operated head which is disposed to be externally accessible through said bypass entry port, and which is mounted on said valve disc to be revolvable about the axis, and a threaded shank which extends from said operated head along the axis into said passageway, and
• an abutment member which is spaced apart from said inner abutment wall along the axis by an axial distance, and which is threadedly engaged with said threaded shank such that rotation of said operated head about the axis results in a change of the axial distance;
• and
• a biasing member which has two ends respectively abutting against said inner abutment wall and said abutment member to provide a biasing force to bias said valve disc to the closed position such that the biasing force is varied in strength by the change of the axial distance.