| 摘要 |
<p>A first fluid passageway (A) can be opened or closed by movement of a shut-off valve (10), whilst a parallel second passageway or by-pass channel (40) is provided with a one-way valve, e.g. a spring loaded ball (41), which permits flow of fluid in one direction only (indicated by arrows). When the shut-off valve (10) is closed, application of hydraulic or pneumatic pressure via the second passageway (40) is possible, whereas release of such pressure is prevented. In this way, when the arrangement is applied to vehicle hydraulic or pneumatic systems, brakes can be applied but not released, or clutches or automatic transmissions can be disengaged yet not re-engaged, whenever the shut-off valve (10) is closed, and this prevents unauthorized use.</p> |
