| 摘要 |
An injector valve (10) for injecting a charge of a substance such as a plug or a ball into a flow line (12). The injector valve (10) comprises a valve cylinder (20) and a piston (18) which is displaceable in the valve cylinder (20). The valve cylinder (20) has an inlet channel (28) and an outlet channel (30) for connection into a flow line (12) for fluid flow through the valve cylinder (20) between the inlet and outlet channels (28 and 30). The valve cylinder (20) has a loading port (14) for loading a charge of a substance into the injector valve (10). The piston (18) has an injection passageway (22) which is positioned for the piston (18) to be displaceable in the valve cylinder between a loading position where the injection passageway (22) is in register with the loading port (14), and an injection position where the injection passageway (22) is in register with the inlet and outlet channels (28 and 30). An intermediate seal (78) is provided to provide a seal between the piston (18) and the valve cylinder (20), the intermediate seal (78) being positioned to be between the loading port (14) and the injection passageway (22) when the piston (18) is in its injection position; and a pressure balancing cavity area (82) is provided between the valve cylinder (20) and the piston (18) and is positioned to communicate with the intermediate seal (78) when the piston (18) is displaced between its injection and loading positions. |
