| 摘要 |
<p>A valve assembly for controlling the flow of a fluid between a plurality of ports including at least one high pressure port and one low pressure port, includes: a base mounting the plurality of ports; and a valve member rotatable to a selected operational position with respect to the base. The control face of the valve member is formed with a low pressure cavity in the central region, and with an annular high pressure cavity in the outer region completely circumscribing the low pressure cavity. Such an arrangement produces a balanced valve construction which permits the valve member to be selectively rotated to the selected operational position, or to any intermediate position, while substantially isolating the high pressure from the low pressure in all its positions. This permits the valve assembly to be used not only as conventional change-over valve in an air conditioning system to select either a heating mode or cooling mode of operation, but also as a control valve to perform one or more additional control functions, e.g. for temperature or output control purposes, in any operational positions of the valve member.</p> |
