Check valve

1. A check valve comprising:

a valve housing defining an opening; and

a plurality of flapper elements each having a proximal end and a distal end, the flapper elements being pivotally mounted to the valve housing at their proximal ends for pivotal movement between a closed position, in which they block the flow of fluid through the opening and an open position in which they permit the flow of fluid through the opening;

wherein each flapper element is rigid and is generally triangular or trapezoidal in shape having a distal end, a proximal end, a first straight side edge extending from the distal end to the proximal end and an opposed second straight side edge extending from the distal end to the proximal end such that the flapper elements create a generally conical or frustoconical shape when in the closed position;

wherein the first side edge of one flapper element overlaps the second side edge of an adjacent flapper element when in the closed position, the overlap between the adjacent flapper elements being such as to draw the flapper elements towards the closed position due to gravity.

2. The check valve of claim 1 , wherein the proximal ends of the flapper elements engage the valve housing to effect a seal therebetween when in the closed position.

3. The check valve of claim 1 , wherein the flapper elements are generally triangular in shape and wherein the distal ends of adjacent edge portions of adjacent flapper elements contact each other when in the closed position.

4. The check valve of claim 1 , wherein the flapper elements are generally trapezoidal in shape, the check valve further comprising a plug element mounted to the valve housing and spaced from the opening, the plug element engaging the distal ends of the flapper elements to close an opening formed at the distal ends of the flapper elements.

5. The check valve of claim 4 , wherein the plug element is a disc.

6. The check valve of claim 4 , wherein the plug element is mounted axially forward of the valve housing by a plurality of circumferentially spaced supports.

7. The check valve of claim 1 further comprising: one or more biasing elements for biasing the flapper elements towards the closed position.

8. The check valve of claim 7 , wherein the biasing elements comprise one or more springs.

9. The check valve of claim 1 , wherein the proximal end of each flapper element further comprises a bumper element for engagement with the valve housing when in the open position.

10. The check valve of claim 9 , wherein the respective bumper elements are configured to receive a hinge pin, wherein said hinge pin pivotally mounts the flapper elements to the valve housing.

11. The check valve of claim 1 , wherein the valve housing is a generally annular member.

12. A check valve comprising:

a valve housing defining an opening; and

a plurality of flapper elements each having a proximal end and a distal end, the flapper elements being pivotally mounted to the valve housing at their proximal ends for pivotal movement between a closed position, in which they block the flow of fluid through the opening and an open position in which they permit the flow of fluid through the opening;

wherein each flapper element is rigid and is generally triangular or trapezoidal in shape, having a distal end, a proximal end, such that the flapper elements create a generally conical or frustoconical shape when in the closed position; wherein an edge portion of one flapper element overlaps an edge portion of an adjacent flapper element when in the closed position, the overlap between the adjacent flapper elements being such as to draw the flapper elements towards the closed position due to gravity, and wherein opposed overlapping surfaces of the overlapping edge portions are curved to provide a curved sealing interface between the flapper elements.