| 摘要 |
<p>A bulb (36) for a hydraulic unit is formed by placing two layers (28, 30) of thermoplastic sheet material over a cavity (12) in a tool (20) base (10), locating an annular clamping member (22) at a distance from the surface of the tool (20) base (10) surrounding the cavity (12) such that the thermoplastic material is a sliding fit therebetween, pressing on to the thermoplastic material bridging the cavity (12) the convex end (18) of a mandrel (16) shaped to substantially conform to the concave shape of the cavity (12), applying an annular welding tool (20) to the thermoplastic material surrounding the cavity (12) so as to weld the two layers (28, 30) together round all of the cavity (12) except for a hydraulic fluid inlet opening, and withdrawing the mandrel (16), clamping member (22) and welding tool (20) from the tool (20) base (10). Such a hydraulic unit forms part of a hydraulic remote control system for adjusting the orientation of a controlled member in which the bulb (36) is located between a first contact member (38) of concave hemispherical shape and a second contact member (40) of convex hemispherical shape dimensioned to nest within the first contact member (38).</p> |
