| 摘要 |
A rotary valve and a method of forming a sleeve for such a valve. The valve for controlling fluid pressure to a power assisted steering gear has a rotor 3 mounted in the bore 2 of a sleeve 1 so that relative rotation between the rotor and sleeve controls fluid flow through ports 5, 6a, 6b and 7 to actuate the power assistance means. The port 7 is in the form of an axially extending slot in the bore 2, one end 18 of the slot 7 terminating within the bore and the other end opening into an end face 19 of the sleeve to alleviate the requirement for an annular recess (such as 8, 9 or 10) on the sleeve for supply of fluid to the slot 7 and thereby permitting a reduction in length of the sleeve. The slot 7 may be flat bottomed and inclined relative to the sleeve axis and the method comprises rectilinearly machining such a slot-preferably as a single pass with a broaching tool inclined relative to the sleeve axis. In a modification two diametrically opposed slots 7 are provided which open into opposite end faces 19, 27 of the sleeve and have parallel and inclined flat bottoms, and the method comprises forming both said slots simultaneously or consecutively by rectilinear broaching as a single machining operation with the broaching tool inclined relative to the sleeve axis.
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