Oval Corporation

Katsuichi Uchida

Seigo Ono

Seiji Kobayashi

Yutaka Ogawa

Yuichi Nakao

Norio Sukemura

Shingo Gomi

Flowmeter with a pair of helical gears using an oval pitch curve as a reference rack tooth profile. The tooth height ratio of the reference rack tooth profile is &#x3c0;/4. The reference rack tooth profile is an oval pitch curve of two or less leaves. The moving radius of the oval pitch curve is expressed by &#x3c1;=a/(1&#x2212;b cos n&#x3b8;), where &#x3c1; is a moving radius which is a distance between the center of rotation and the oval pitch curve, 'a' is a similarity factor, 'b' is a degree of flatness, n (n&#x2266;2) is the number of leaves, and &#x3b8; is an argument. The tooth height ratio is h=a/(1&#x2212;b)&#x2212;g, where gis a distance between poles of the oval pitch curve and pitch line, wherein g=a cos &#x3b8;/(1&#x2212;b cos n&#x3b8;). Values for the similarity factor &#x201c;a&#x201d;, degree of flatness &#x201c;b&#x201d;, and distance gare determined so that the tooth height ratio may be &#x3c0;m/4.

Positive displacement flowmeter and helical gear

A position displacement flowmeter having a pair of non-circular gears in a rolling contact on a pitch line without slippage. The positive displacement flowmeter comprises a casing and a pair of rotors provided in the casing and rotatable around its center axes. The pair of rotors, have a tooth profile curve which is an oval pitch curve itself having a trajectory of contact points on the pitch line, and they satisfy a condition of rrK=const rd&#x3b8;=rd&#x3b8;, and a moving radius of the oval pitch curve is given by ri=a/(1&#x2212;b cos n&#x3b8;i) (i=1, 2), where 'ri (i=1, 2)' is the moving radius that is a distance from a center of rotation to the oval pitch curve, 'a' is a homothetic coefficient, &#x201c;b&#x201d; is a flattening, &#x201c;n&#x201d; is a number of lobes, and &#x201c;&#x3b8;i (i=1, 2) is a moving angle.

Positive displacement flowmeter

Each of two flow tubes assumes an arcuate shape consisting of a central arcuate segment and two linear segments located on opposite sides of the central arcuate segment. The inside diameter of the flow tubes and the linear distance between end points of each of the flow tubes are determined on the basis of a target pressure loss arising from passage of a fluid to be measured through a manifold and the flow tube at the maximum flow rate, a target time phase difference between sine wave outputs from vibration sensors at the maximum flow rate, and a target natural frequency of the flow tubes. The length of the linear segments is selected so as to reduce thermal stress induced from an abrupt change in the temperature of the fluid to be measured, and the shape of the flow tubes is determined so as to reduce the vertical height of the flow tubes, so long as the thermal stress is substantially constant even when the length of the linear segments is varied. Thus, the shape of the flow tubes is determined in such a manner as to suppress, to a predetermined low value, stress arising upon abrupt change in the temperature of the fluid to be measured and as to be most compact.

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Tokyo, Japan

Katsuichi Uchida