A review of early Coriolis patents
There were a number of patents filed in the 1950s and 1960s for Coriolis or Coriolis-like flowmeters. Even earlier, in 1917, Ernest F. Fisher on behalf of General Electric Company filed a patent called “Fluid Flow-Indicating Mechanism.” As part of this patent, it is claimed: “It is an established principle that vibrations will be set up in fluid flowing past a statuary object and that the periodicity of the vibrations will be proportional to the velocity of flow of the fluid.”
While this sounds somewhat like the formula for a vortex flowmeter, and it attempts to measure velocity rather than mass flow, it does introduce the idea of vibration of the fluid.
In a patent approved in July 1952, Paul Kollsman presented an “Apparatus for Measuring Weight Flow of Fluids.” While it does not mention a Coriolis force, it does introduce the idea of measuring the weight or mass of a fluid. To quote from the patent:
The present invention provides an apparatus for measuring the flow of fluids and provides, more particularly, an apparatus for determining the actual weight flow of a fluid which may be a gas, a liquid, or a mixture of both, the measurement being accurate within a wide range of density and viscosity of the fluid, and uninfluenced by the pressure of the fluid.
The following year, in January 1953, John M. Pearson, on behalf of the Sun Oil Company, patented a meter using a gyroscopic principle. This patent is simply called “FLOWMETER,” and the meter was designed to measure mass flow: “This invention relates to a flow meter designed to measure flow in terms of mass of the fluid.”
While this patent does not mention the Coriolis force, it does describe the following mechanism: “A curved conduit, means for leading fluid to and from said conduit, means for imparting to said conduit angular movement about an axis transverse to an axis about which there exists angular momentum of the flowing fluid through the conduit, and means, including a device sensitive to gyroscopic couples of said conduit transverse to the axis of movement of the conduit, for indicating mass flow through the conduit.”
Interestingly, this patent cites no previous patent references. In addition to its use in meteorological circles, Coriolis’ theory came to be applied to the development of flowmeters. The earliest patent that proposed setting up vibrations in flowing fluid was published by Ernest Fisher on behalf of the General Electric Company in 1917.
The term “Coriolis Force” introduced
The earliest patent that includes the term “Coriolis Flowmeter” was granted in 1958 to Roby White. This patent was called CORIOLIS MASS FLOWMETER and it proposed subjecting the fluid to tangential acceleration in a whirling tube. This patent was filed on behalf of American Radiator & Standard Sanitary Corporation. This appears to be the earliest patent that mentions the “Coriolis force.” The flowmeter is described as follows: “The present invention relates to instruments for measuring the mass rate of flow of fluids and in particular to an improved flowmeter of the type in which mass flow rate is made responsive to Coriolis force… In instruments of the class described the fluid to be measured is subjected to tangential acceleration in a whirling tube, or impeller, the torque exerted on the tube in reaction to the Coriolis force of the accelerated fluid being measured as an indication of the mass flow rate.”
Roby White – 1958
Patent Title: Coriolis Mass Flowmeter
Patent Number: US2,832,218
Filing Date: July 9, 1954
Issue Date: April 29, 1958
Roby White was the first to use the term ‘Coriolis Mass Flowmeter’ in a patent. His design used actual rotation of fluid through a curved path. The Coriolis force was invoked directly by the angular motion of the fluid. Though the mechanism differs from modern vibrating-tube designs, this was the earliest application of Coriolis physics in flow measurement.
Historical Note: This was the first patent to use the Coriolis name in relation to flow measurement. It relied on actual rotation of the conduit.
Yao Tzu Li – 1960
In May 1960, Yao Tzu Li patented an invention called “MASS FLOWMETER” that involves rotating the flow:
The present invention operates by causing the fluid to be rotated as it flows radially outward from an axis. This produces a Coriolis acceleration in the fluid, and therefore a Coriolis force is applied by the fluid to the member through which the fluid flows. This force is measured, and the mass rate flow of the fluid is obtained.
Interestingly, Yao Tzu Li cites Fisher (1917), Kollsman (1952), and Pearson (1953) as references, but does not cite White (1958), who specifies a mechanism for rotating the fluid and also mentions the Coriolis force.
Neither this patent nor the Roby White patent were developed into products. Apparently the idea of producing Coriolis acceleration in a flowmeter by rotating fluid proved to be challenging from a practical point of view.
Patent Title: Mass Flowmeter
Patent Number: US2,934,951
Filing Date: September 9, 1952
Issue Date: May 3, 1960
Yao Tzu Li, a renowned MIT professor and aerospace engineer, developed an improved version of White’s rotational design. His patent refined the mechanics of rotating conduits to more accurately measure mass flow using Coriolis principles. Though it still relied on mechanical rotation, Li’s work demonstrated the feasibility and engineering maturity of Coriolis-based flow metering.
Li describes his meter as follows: “The present invention operates by’ causing the fluid to be rotated as it flows radially outward from an axis. This produces a Coriolis acceleration in the fluid, and therefore a Coriolis force is applied by the fluid to the member through which the fluid flows. This force is measured and the mass rate flow of the fluid is obtained. The present invention operates by’ causing the fluid to be rotated as it flows radially outward from an axis. This produces a Coriolis acceleration in the fluid, and therefore a Coriolis force is applied by the fluid to the member through which the fluid flows. This force is measured and the mass rate flow of the fluid is obtained.”
Historical Note: Li helped formalize the mechanical and theoretical basis for early Coriolis meters using rotating tubes.
Anatole Sipin – 1965 and 1967
In November 1965, July 1967, and December 1967, Anatole J. Sipin patented three separate devices designed to measure mass flow. These designs by Sipin were designed to improve on earlier designs (described above) that involved rotating the flow or using an oscillating gyroscope. Sipin’s objection to rotating gyroscopic designs was that they required rotating fluid seals, which introduced potential leakage and friction problems. His objection to oscillating gyroscopic designs was that they introduced bends and turns that made the meter difficult to clean. Meter size was also an issue. According to Sipin, “the diameter of the loop must be ten to twenty or more times as large as the diameter of the flow passage…(making) the apparatus large and cumbersome for the flow range.” This problem of meter size is one that Coriolis manufacturers have never fully solved, except for meters two inches or less in diameter.
In 1965, Anatole Sipin was granted a patent called Mass Flowmeter Systems. He was critical of previous patents that called for rotating the fluid, saying these were too large to be practical. Instead, he proposed oscillating the fluid.
Patent Title: Mass Flow Measuring Device
Patent Number: US3,218,851
Filing Date: May 24, 1961
Issue Date: November 23, 1965
Anatole Sipin was the first to propose using oscillation instead of rotation in a mass flowmeter. His design involved vibrating a fluid-carrying tube and detecting the inertial effects of the moving fluid, which anticipate the key principles of modern Coriolis meters.
Historical Note: Sipin’s concept of using vibrating tubes to detect mass flow by inertia laid the foundation for all subsequent Coriolis flowmeter designs.
James E. Smith
Jim’s patents
In August 1972 James (Jim) E. Smith patented a “Balanced Mass-Moment Balance Beam with Electrically Conductive Pivots.”
Beginning in June 1975, Jim began patenting a series of devices that became the basis for the flowmeters produced by Micro Motion. His patent filed in June 1975 was granted in August 1978. This patent and subsequent flowmeter patents explicitly evoke the Coriolis force. Jim’s patents substituted a vibrating and oscillating tube for a rotating tube (following Sipin, 1965), which worked better than the earlier ones and is still used today in many different forms.
When Jim Smith applied for his patent in 1975, he continued with the oscillation method introduced by Sipin in 1965. Even though this was a departure from the mechanical rotation of motion described by Coriolis, he kept the name “Coriolis,” probably because of the 1958 Roby White patent called CORIOLIS MASS FLOWMETER.
U.S. Patent 4,109,524 – Method and Apparatus for Mass Flow Rate Measurement
Filed: June 30, 1975; Granted: August 29, 1978
Continued with vibrating tube design (from Sipin; oscillation, not rotation)
Retained the ‘Coriolis’ name
1977 – Micro Motion founded
In 1977, James E. Smith founded Micro Motion out of his garage and commercialized his design. the term ‘Coriolis Flowmeter’ became standard in industry. Today, the name persists for historical and mathematical reasons, even though ‘inertial mass meter’ might be a more accurate descriptor.
Micro Motion’s first Coriolis flowmeter debuted that year — an “A” meter for laboratory use — was followed by the “B” meter in 1978. In 1981, Micro Motion introduced the first single-bent tube Coriolis meter, the “C “meter. Then in 1983, the company added the first dual-bent tube Coriolis meter, the “D” meter, which had a 2-inch diameter. In 1984, Emerson acquired Micro Motion in what proved to be one of the most successful acquisitions in flowmeter history.
A little known story about Jim Smith, as related by Dr. Mark Bell of Emerson, is that at the same time he developed the Coriolis meter, he invented another technology: an automatic nail gun. Mark relates the story as follows: “He invented two technologies and put them both for sale, and said whichever one sells, he’s going to develop the other one. He developed the first automatic nail gun. I got pictures of the it. And he was like, for sure one of these chemical companies is going to buy the Coriolis meter patent, and I’m going to buy it, I’m going to develop the nail gun, and I’m going to become rich. Black and Decker bought the nail gun. It was a terrifying thing. You know how they throw baseballs with two spinning wheels? It was a two spinning wheel nail gun shooter… Black and Decker bought it, and it was almost immediately displaced by pneumatics, and then, electrodynamics, and some other things.”
So why is it called a Coriolis meter?
Gaspard Gustave de Coriolis wrote a very influential paper in 1835 that eventually became the basis for what is known today as the Coriolis force. While some commentators have stated that this article was about waterwheels, Coriolis does not mention waterwheels in his paper. Instead, he limits his discussion to rotating frames of reference. His main point is that in order to account for motion around a rotating frame of reference, it is necessary to introduce what he calls compound centrifugal forces. These compound centrifugal forces are what later became known as Coriolis forces.
It is also important to be aware that Coriolis did not discuss meteorology or what is now known as the “Coriolis effect” on weather systems in his article. So, how did the term ‘Coriolis’ become attached to a certain type of flowmeter? The following timeline outlines the main steps that led to this result, as discussed above:
• This timeline illustrates how the term ‘Coriolis’ became associated with mass flowmeter technology, even as the physical mechanisms shifted significantly.
• In 1958, Roby White patented a device that rotated the fluid flow and relied on the actual Coriolis force arising from angular motion. He explicitly called it a ‘Coriolis Mass Flowmeter.’
• In the 1960s, other designs continued this trend of using mechanical rotation to invoke the Coriolis effect.
• In 1965, Anatole Sipin substituted oscillation for rotation and described achieving “Coriolis-like” forces.
• In 1975, Jim Smith applied for a new patent that build on Sipin’s design. He described using oscillating tubes instead of rotating flow. Despite the lack of true rotation, he retained the term ‘Coriolis,’ likely due to continuity with earlier patents. This patent was granted in 1978.
• By 1977, with the founding of Micro Motion and commercialization of Smith’s design, the term ‘Coriolis flowmeter’ was fully established in industry—even though the underlying physics was better explained by fluid inertia than by true Coriolis forces.
Today, the name persists for historical and mathematical reasons, even though ‘inertial mass meter’ might be a more accurate descriptor.
The patents granted in the 1950s and 1960s that described flowmeters that rotated the flow were not commercialized and were most likely not practical. This was the criticism of Anatole Sipin, who had three different patents approved from 1965 to 1967. He makes the following comments in his 1965 patent:
“Other mass flowmeters that have obstruction-free flow passages are the rotating or oscillating gyroscopic meters of which several types are known. The gyroscopic meter has the disadvantage of requiring at least one and sometimes several loops with associated bends and turns between the flow inlet and outlet. For accurate flow measurement, moreover, the diameter of the loop must be ten to twenty or more times as large as the diameter of the flow passage (assuming circular cross-sections); and this requirement makes the apparatus large and cumbersome for the flow range… In addition, the rotating gyroscopic type of meter requires rotating fluid seals, introducing serious leakage and friction problems.”
In place of earlier designs, by Anatole Sipin in Patent 3,218,851 proposes using an oscillating design. This patent was filed in 1961 and approved in 1965. Sipin proposes the following:
The mass flow measuring principle used in the embodiments of this invention is that where an oscillatory motion is applied by a member to a bounded stream of material and there is a changing difference between a transverse momentum, that is momentum orthogonal to the axis of flow, or the fluent material entering the oscillating member and that leaving the oscillating member, mechanical energy is removed from the oscillating member and added to the stream at a rate directly proportional to the mass rate of flow.
In discussing his invention, Sipin does not claim to be employing the Coriolis force, though he says that what he is doing is “equivalent to the Coriolis force” and “equivalent to the Coriolis acceleration.” Furthermore, he called his patent “Mass Flowmeter Systems,” not making an explicit reference in the title to Coriolis flowmeter.
When Jim Smith applied for his patent in 1975, built on Sipin’s idea of oscillation instead of rotation and proposed using the difference in phase shift between the incoming fluid and the outgoing fluid in a bent pipe to measure mass flow. Jim Smith in his patent, which was approved in 1978, called his invention “Method and Apparatus for Mass Flow Measurement.” He cited three previous patents by Anatole Sipin as supporting documents. However, he drops Sipin’s more cautious phrasing of “equivalent to the Coriolis force” and “equivalent to the Coriolis acceleration.” In Smith’s abstract, he appeals directly to the Coriolis force, saying that his device measures “the torque generated by the Coriolis force.” At this point, the move from rotation to oscillation was complete, and Coriolis flowmeters were born as devices that oscillate the flow