| 摘要 |
<p>Reaction force limiting means and a steering gear including such means. A valve includes a spool assembly (100) having first (5) and second (10) spool parts and which is axially displaceable in a spool housing (101) to control flow of fluid under pressure from a pressurised port (1) to an actuating port (8) intended for communication with a ram. The first and second spool parts (5,10) form a reaction chamber (105), the volume of which is variable. The spool parts (5,10) can be connected by a pin and slot mechanism (108,14) so that the chamber (105) has maximum and minimum volumes. Control means (4) acts on one (5) of the spool parts for manually displacing the spool assembly in one axial direction to open communication between said pressurised port (1) and the actuating port (8). A biasing spring (12) opposes axial displacement of the other (10) of the spool parts in the one axial direction. The reaction chamber (105) communicates with the actuating port (8) when that port (8) communicates with the pressurised port (1) and upon pressurisation of the reaction chamber (105) by its communication with the pressurised port the other spool part (10) reacts against the biasing spring (12) to oppose and provide a reaction to the manual force which is applied to displace the spool assembly (100) in one axial direction. …<??>A secondary spring (9) which is weaker than the biasing spring (12) biases the reaction chamber (105) to its expanded condition. The valve can be double acting to be displaceable from a neutral condition and in either sense of axial direction to control fluid flow to one or the opposite sides of a ram; in the neutral condition both sides of the ram may communicate through the valve with exhaust.</p> |
