Automatic sash safety mechanism

A fume hood comprised of:

• a first side wall and a second side wall, a back wall, a work surface, and a top wall, said first side wall and said second side wall, said back wall, said work surface, and said top wall defining a work area;
• an access opening for providing a user access to said work area;
• a movable sash member, said movable sash member comprised of a bottom surface and disposed for vertical movement across said access opening to vary an effective size thereof;
• a drive motor mechanically coupled to said movable sash member, wherein said drive motor is mechanically coupled to said movable sash member to a chain on a first end of said chain and to a counterweight on a second end of said chain;
• an operator sensor, said operator sensor electrically coupled to said movable sash member for automatically raising said movable sash member when an operator is detected and automatically lowering said movable sash member when an operator is not detected for a specified period of time;
• and
• a pressure-sensitive switch disposed on said bottom surface of said movable sash member and electrically connected to said drive motor via an electrical cable secured to a back side of said chain, wherein upon a pressure being exerted on said pressure-sensitive switch in excess of a threshold limit, said movable sash member is stopped.

An apparatus comprised of:

• a hood portion comprised of:
• a first side wall;
• a second side wall;
• a back wall;
• a work surface;
• a top wall, said first side wall, said second side wall, said back wall, said work surface, and said top wall defining a work area;
• an access opening for providing a user access to said work area;
• a movable sash member, said movable sash member comprised of a bottom surface and disposed for vertical movement across said access opening to vary an effective size thereof;
• a drive motor mechanically coupled to said movable sash member;
• an operator sensor, said operator sensor electrically coupled to said movable sash member for automatically raising said movable sash member when an operator is detected and automatically lowering said movable sash member when an operator is not detected;
• and
• a pressure-sensitive switch disposed on said bottom surface of said movable sash member and electrically connected to said drive motor, said pressure-sensitive switch comprised of a series of upper electrode plates and a series of corresponding lower electrode plates, both of said series substantially encased within an insulating material, wherein upon a pressure being exerted on said pressure-sensitive switch in excess of a threshold limit, at least one of said series of upper electrode plates comes in contact with at least one of said series of lower electrode plates to stop said drive motor and halt movement of said movable sash member;
• and
• a base portion for supporting said hood portion.

A method of controlling a position of a movable sash member within a fume hood unit comprising the steps of:

• mechanically coupling a drive motor to said movable sash member;
• securing a pressure-sensitive switch to a bottom surface of said movable sash member;
• detecting the absence of a user by an operator sensor;
• said drive motor lowering said movable sash member in response to said detecting step after a predetermined time period;
• and
• electrically connecting said pressure-sensitive switch to said drive motor such that when said pressure-sensitive switch contacts an object in excess of a threshold limit, said pressure-sensitive switch sends an electric signal to said drive motor and said lowering step is stopped.