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a reservoir that also acts as a cooler. The steering box houses a self neutralizing rotary valve which is part of the worm/valve assy and an hydraulic piston/rack to assist the mechanical operation. The rotary valve which is operated by movement of the steering wheel, directs fluid pressure to the appropriate side of the hydraulic piston/rack to provide assistance. Rotary valve operation Rotary valve at neutral The rotary valve assembly comprises a worm (1), valve sleeve (2), input shaft (4) and torsion bar (5). The valve sleeve is retained inside the worm by a trim screw (3), and incorporates valve ports in its inner bore. The input shaft is attached to the steering wheel via a steering shaft and steering column and incorporates valve ports in its outer diameter to align with those in the sleeve. The torsion bar, which is secured to the worm and input shaft with pins (6) at each end, holds the valve ports in neutral alignment when there is no demand for assistance. When there is no demand for assistance the torsion bar holds the input shaft and sleeve valve ports in neutral relationship to one another, allowing equal pump pressure (A) to both sides of the piston/rack (9). Any excess fluid flow from the pump returns to the reservoir via (B). Rotary valve misaligned |