| 摘要 |
A differential pressure sensing switch for a motor vehicle has a piston axially slidable in a housing and exposed at each end to the pressure in separate brake circuits. At one end, the piston has a smaller diameter exposed to fluid pressure than at the other end and a sleeve and seal are slidable on said smaller diameter to have a combined diameter greater than that of the other end. A spring biases the sleeve toward the one end so that on cycling, the piston moves first in one direction and then in the other direction to provide positive movement between each seal and its adjacent sealing surface.
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