Fluid flow sensing switch device method of making the same

In a method of making a fluid flow sensing switch device having a housing means provided with a fluid flow passage therethrough defined by an inlet and an outlet separated by a valve seat controlled by a movable valve member that is operated by the pressure differential between said inlet and said outlet acting on a flexible diaphragm carried by said housing means, said device having an electrical switch construction operatively associated with said valve member and having contact means thereof actuated by said pressure differential acting on said flexible diaphragm, the improvement comprising the steps of mounting said contact means of said switch construction in said fluid flow passage so as to be exposed to fluid flow therethrough, forming said contact means to comprise a first part thereof and a second part thereof, said step of mounting said contact means comprising the step of mounting said first part of said contact means on said valve member and mounting said second part of said contact means on said diaphragm in spaced apart relation to said first part of said contact means and being positioned to make contact with said first part of said contact means to close said switch construction upon actuation of said switch construction, operatively interconnecting control means that is operated by said differential pressure to said contact means and to said valve member to operate the same, and forming said control means with means that actuates said contact means before said control means opens said valve member upon sensing a certain pressure drop between said inlet and said outlet.