The Families of Adam Keith

Inventors and their inventions


Measure arterial blood pressure


Rulo Wayne Smith [1897-1985]


Ancestry:  Adam Keith1>Adam Keith2>Lewis Keith3>Rosanna [Keith] m. [John Sleeper] Smith4>Godfrey Jacob Smith5>Rulo Wayne Smith6

From grandson Kerry Smith via email


Rulo was an engineer and a college professor at Ball State. He worked later at the Rieke Corp in Auburn, where he was their plant engineer. He was an inventor, with several patents including one on an innovative method to measure blood pressure. I spent many happy hours with him in his basement workshop. He was responsible for me becoming an engineer. I still have some of his equipment in my workshop. Before Auburn, they lived in Warsaw, IN, and owned two local movie theaters. Grandpa was always ahead of his time; before central air conditioning was popular, to cool the theater he ran water from a nearby lake to a set of car radiators and blew air thru them!


Thesis, Indiana University [1920]


Application of complex quantity to A. C. current computations.

by Rulo Wayne Smith

United States Patent Office




United States Patent 3,769,964  [filed 8/28/1970] Note: Idea originated in 8/1867


Inventor(s) Smith; Rulo Wayne (Auburn [DeKalb Co.], IN)


Abstract: The system includes a sensor with a liquid filled bladder inside of a human body finger clamping device. A transducer connected to the clamping device translates the liquid pressure into an electrical signal. The pressure is adjustable externally and the resulting electrical signal is displayed on an oscilloscope to give an indication of the pressure applied by the liquid to a finger clamped in the finger clamping device. Blood pressure pulses sensed by the sensor produce an alternating current portion of the electrical signal and this is displayed on a chart recorder to give an indication of the pulse pressures. To determine blood pressure, a finger is inserted into the clamp and external pressure is applied to the finger. The external pressure is adjusted to the lowest pressure at which the pulse pressure indications are at a maximum value. The electrical signal will then have a maximum (peak) voltage and a minimum voltage displayed on the oscilloscope. True systolic pressure is represented by the maximum peak voltage and true diastolic pressure is represented by the minimum peak voltage. The device is built to have a minimum of compliance, so that the natural expansion and contraction of the finger arteries is at a minimum. This prevents any stiffness of the artery walls from affecting the blood pressure reading. The difference between the true systolic pressure and a systolic pressure reading taken conventionally by collapsing an artery, is a measure of the stiffness of the artery.


Other patent/patent applications of Rulo Smith


United States Patent Office




Inventor Rulo Wayne Smith Auburn Ind

Assignee Rieke Corporation Auburn Ind

Filed Oct 26 1971 21 Appl No 192,174


United States Patent Office


 2,665,841 Air Circulator


Rulo Wayne Smith, Auburn Ind., assignor of one-half to J. Allen McMeen, Fort Wayne, Ind.