Patent ID: 7300482

Claim:
A particle separation apparatus comprising a cyclone particle separating means, particle collecting chamber and a fan driven by an electric motor for drawing particle laden air into and through the apparatus wherein a valve is provided, upstream of the suction fan driving motor and downstream of the cyclone particle separating means, which includes a valve closure and a valve seat against which the valve closure is normally resiliently urged to prevent air flowing through the valve, and the valve is mounted so as to communicate with a passage between the cyclone particle separating means and the fan so that air pressure within the passage acts on one side of the valve closure while the other side of the valve closure is exposed to ambient air pressure, whereby in use if the air pressure in the passage leading from the cyclone particle separating means to the fan falls below ambient by more than a predetermined amount, the pressure differential acting on the valve closure creates a force sufficient to overcome the resilient force acting thereon and the valve closure will become displaced from the valve seat and allow air to enter the passage to maintain an air flow to and around the fan motor, wherein the valve seat is a circular opening and the valve closure is a hollow ball with its convex curved surface towards the valve seat and the radius of curvature of the curved surface of the valve closure is greater than the radius of the circular opening forming the valve seat, and wherein the valve closure is urged into the closed position by a spiral spring acting on the one side of the valve closure, and wherein the valve closure is located within a hollow housing and the spiral spring acts between the rear of the valve closure and one end of the housing and an opening is provided in the opposite end of the housing defining the valve seat, and the area of the opening is less than the area of the valve closure, and wherein an elongate guide extends rearwardly from the valve closure and the said one end of the housing has an opening therein within which the guide is a sliding fit, and wherein the guide is hollow and open at both ends to communicate between the interior of the ball and the passage, whereby ambient air released into the housing due to a pressure differential acting on the ball sufficient to unseat the ball from the valve seat, can pass from the housing via the ball and interior of the guide to the passage between cyclone and fan, to increase the air flow to and around the motor.