Vacuum pump switch

A control member comprising:

• a housing having a first chamber connected to a second chamber by a bore and a passage, said first chamber being connected to a reservoir containing a fluid, said second chamber being connected to the surrounding environment through a port;
• a first wall in said first chamber;
• a second wall in said bore;
• linkage means for connecting said first wall with said second wall, said linking means extending into said second chamber;
• a first valve connected to said linkage means and aligned with said port for controlling communication between the surrounding environment and said second chamber;
• a second valve connected to said linkage means and aligned with said passage for controlling communication between said first and second chambers;
• first resilient means for urging said first wall away from said second chamber to bring said second valve into engagement with said housing to seal said passage and disengage said first valve from said port to allow air to flow into said second chamber, said fluid in the reservoir and first chamber creating a pressure differential across said first and second walls with air in the surrounding environment and second chamber, respectively, said pressure differential creating a first force for urging said first movable wall toward said second chamber and a second force in said second wall which with the first resilient means opposes said first force;
• a third wall in said second chamber;
• and
• second resilient means for moving said third wall to activate a switch connected to a device that effects a pressure change in the fluid in said reservoir, said pressure change producing a corresponding change in said pressure differential which allows the resulting first force to overcome said first resilient means and resulting second force to move the first and second walls toward the second chamber and sequentially close said first valve and open said second valve, said reservoir fluid being communicated to said second chamber to eliminate the pressure differential across said second wall and thereafter allow the first force to move the first and second walls toward the second chamber in opposition to said first resilient means while a pressure differential is created across said third wall to develop a third force which overcomes said second resilient means and moves said third wall to deactivate said switch and thereby interrupt the effect of the device on the fluid in the reservoir.