Date Filed February 21, 1916
' In most of the machinery universally employed for the development, transmission an transformation of mechanical energy,

fluid impulses are made to pass, more or less free y, through suitable channels or conduits in one direction while their return is effectively checked or entirely prevented. This function is generally performed by devices designated as valves, comprising carefully fitted members the precise relative movements of which are essential to the efficient and reliable operation of the apparatus. The necessity of, and absolute dependence on these, limits the machine in many respects, detracting from its practical value and adding greatly to its cost of manufacture and maintenance. As a rule the valve is a delicate contrivance, very liable to wear and get out of order and thereby impel-i1 ponderous, complex and costly mechanism and, moreover, it falls to-meet the requirements when the impulses are. extremely sudden or rapid in succession and the fluid is highly heated or corrosive.' -Read more here