Abstract: A check valve construction is provided having: a movable disc with a flat surface on a first side and a convex shaped surface on the opposing side, a first seat on for the flat surface and a second seat for the convex surface, where the narrowest portion of the fluid path is defined by the equation: G 3 = 12 ? ? ? ? W ? ? Q ? ? ? D ? ? ? ? ? P Wherein G: the gap of most narrow passageway between the flat surface of the disc and disc seat; ?: dynamic viscosity of the fluid; D: mean diameter of the flat sealing surface of the disc; Q: desired fluid flow rate; W: breadth of the flat sealing surface of the disc; ?P: pressure differential across the gap (G).

Abstract: A check valve construction is provided in which a moveable a movable ball having a convex surface resides in a cage having a conical frustum chamber and a seat for the ball. A fluid path between the ball and the cage is defined by the equation: G = D ? ? cos ? ( b - a ) 2 ? ? cos ? ? b - d 2 wherein G is the gap of the narrowest passageway of the fluid path, D is the diameter of the small end of the conical frustum chamber of the cage, d is the diameter of the convex surface of the ball, a is the angle between a vertical diameter of the ball and the position of the narrowest gap on the convex surface of the ball, and, b is the angle between the vertical diameter of the movable element and the position of the small end of conical frustum chamber of the cage.

Abstract: A check valve construction is provided having: a movable disc having a convex surface, a flat surface and a raised element on the convex surface, a cage for the disc, a first seat for the flat surface of the disc, and a second seat for the convex surface of the disc. A fluid path is provided between the disc and the cage including a narrowest portion of the fluid path defined by the equation: G = 12 ? ?? ? ? D W ? ? ? ? ? P wherein G: the height of the gap of most narrow passageway between the flat surface of the disc and disc seat. ?: dynamic viscosity of the fluid; D: mean diameter of the flat sealing surface of the disc; Q: desired fluid flow rate; W: breadth of the flat sealing surface of the disc; ?P: pressure differential across the gap (G).

Abstract: A check valve construction is provided having: a movable ball having a convex surface, a cage having a conical frustum chamber for said ball, a seat for said ball, a fluid path between said ball and said cage defined by the equation: G = D ? ? cos ? ( b - a ) 2 ? ? cos ? ? b - d 2 wherein G is the gap of the narrowest passageway of the fluid path, D is the diameter of the small end of the conical frustum chamber of the said cage, d is the diameter of the convex surface of the ball, a is the angle between a vertical diameter of the ball and the position of the narrowest gap on the convex surface of the ball, and, b is the angle between the vertical diameter of the movable element and the position of the small end of conical frustum chamber of the said cage.

Abstract: The present invention produces a combustion simulation of flames, burning logs and embers in a fuel-burning fireplace or like device. One or more light source(s), such as LEDs, are used to transmit light to and through one or more of an artificial log set and an ember bed. A microprocessor-based controller is used to vary one or more of light intensity and color of the LEDs to simulate a naturally varying glow effect of the ember bed and the log set.