JPS623691Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a confinement pressure prevention device in a positive displacement flowmeter equipped with a pair of rotors having twisted tooth profiles such as helical gears.

In general, a rotor with a twisted tooth profile such as a helical gear transfers fluid along the torsional direction of the rotor due to its twisted tooth profile, but once the fluid is transferred, it follows the meshing movement of the pair of rotors. As a result, there is a constant tendency to become trapped, and eventually there is a tendency to become trapped by the side portions of the pair of rotors.

This tendency clearly appears as a pressure loss, which has an adverse effect not only on the rotor but also on instrumental error.

As a means to solve this problem, the present applicant has already proposed Utility Model Application No. 55-23031 (Utility Model Application No. 56-126528), in which an end face structure of the measuring chamber is devised.

This device utilizes the prior art described above and also adds a new configuration to the rotor itself to avoid the confining pressure of the fluid to be transferred and to facilitate the inflow of fluid into the expanding side part. An object of the present invention is to provide a confining pressure prevention device in a positive displacement flowmeter.

An embodiment of this invention will be described below with reference to the drawings.

Reference numerals 1 and 1 denote a pair of rotors each having a helical tooth profile 2, 2, which has the same tooth profile as, for example, a helical gear. Although the illustrated rotor is a helical gear having four toothed portions 3, the number of toothed portions 3 can be set as desired. Reference numeral 4 denotes a notch recessed in both end surfaces of the rotors 1, 1, and a notch opening 4a is formed at each tooth portion 3 in the direction of rotation.

Reference numeral 5 denotes a casing constituting the flowmeter a, in which an inlet 6 and an outlet 7 are formed. 8, 8 are the shafts of the pair of rotors 1, 1; 9, 9 are the shafts of the pair of rotors 1, 1
It is an end face portion of the measuring chamber 10 that is provided opposite to the side surface of the measuring chamber 10, and is configured as a separate body or the same body. 1
1 and 11 are bearing parts.

As shown in FIG. 2, this end surface portion 9 is formed into a disk shape, and one side of the central portion through which the rotor shafts 8, 8 pass is formed as a recessed portion 13 having a mounting contour portion 12. Arc surfaces 14, 14 corresponding to the outer radius R _L of both rotors 1, 1 are connected by rotor shaft notch arcs 15, 15, and further arcs corresponding to the pitch circle radius Ri of both rotors 1, 1. 16, 16 are provided to form forked protrusions 17, 17, and finally this circular arc 1
6 and 16 are connected by a curve 18 with an appropriate radius r at a distance L from the center line passing through the rotor shafts 8 and 8 to obtain the cutout part b. That is, it is characterized by a configuration in which the shaded line portion X formed on the outside of the forked protrusions 17, 17 from the point extracted and intersecting by the outer radius R _L of both rotors 1, 1 is omitted. shall be. Incidentally, fan-shaped recesses 19, 19 can be formed outside the rotor shaft notch arcs 15, 15, if necessary. 20 is a mounting hole.

The action will be explained based on the above structure.

When the pair of rotors 1, 1 rotate due to the transfer of fluid, the state in which the fluid is trapped in the meshing teeth 3, 3 of the pair of rotors 1, 1 changes from state A as shown in Fig. 4. It progresses gradually in the process of transitioning to state B.

However, in this embodiment, in the state of A, the notch openings 4a of the notches 4 formed in the side end faces of the rotors 1, 1 are open toward the trapped portion, so that the rotors 1, 1 are about to be trapped. Fluid flows into the cutout 4 through the cutout opening 4a.

In addition, this notch 4 is connected to the end surface 9 of the measuring chamber 10.
The recess 13 formed in the cutout portion b communicates with the portion surrounded by the curve 18 of the cutout portion b, so the cutout portion 4 is immediately connected to the cutout portion b.
There is no risk that the fluid inside will flow into the recess 13 and become trapped.

Next, as the rotation progresses in state C, the notch opening 4a of the notch 4 of the rotor 1 is separated from the teeth 3 and faces the outflow side, so the fluid entrapment phenomenon due to mutual meshing of the teeth 3 disappears. do.

As described above, the fluid after the pair of rotors 1, 1 rotates and is measured is confined on the confinement side formed by the teeth 3, 3 on the outflow side of the pair of rotors 1, 1. Even if the rotor is damaged, the confinement phenomenon can be easily eliminated by the structure of the notch 4 of the rotor and the cutout b of the end face 9.

Also, regarding the expansion effect on the inflow side, the rotor 1,
Due to the notch 4 of 1 and the cutout b of the end face 9, the fluid can be smoothly transferred in the opposite direction, and there is no possibility of negative pressure being generated.

Although one embodiment of this invention has been described above, the invention is not limited to the configuration of this embodiment.

Since this device is constructed as described above, it is possible to eliminate the negative pressure phenomenon caused by fluid confinement and expansion, thereby reducing pressure loss, improving instrumental error accuracy, and eliminating damage to the rotor. In addition, it is particularly suitable for a flow meter for a rotor having a helical tooth profile such as a helical gear with a large number of teeth and a severe confinement phenomenon.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing an embodiment of a positive displacement flowmeter according to the invention, Fig. 2 is a front view showing the end structure of the rotor, and Fig. 3 is an explanatory diagram of the end structure of the metering chamber. , FIGS. 4A, 4B, and 4C are explanatory diagrams of the process of preventing the fluid entrapment phenomenon that occurs as the rotor rotates. DESCRIPTION OF SYMBOLS 1, 1... A pair of rotors with twisted tooth profiles 2, 2, 3... Teeth, 4... Notch, 4a... Notch opening, 9... End surface, 17... Bifurcated projection part, a
...flow meter, b... missing part.

Claims (1)

[Scope of utility model registration request] A volume in which a pair of rotors each having a helical gear-like helical tooth profile are rotatably housed in a measuring chamber formed by a housing having an inlet and an outlet, and an end plate, using a bearing provided on the end plate. In the type flowmeter, a cutout is provided in a part of the end faces of the pair of rotors, and a cutout is formed from the cutout arcs of both rotor shafts by an arc surface and a circular arc corresponding to the outer diameter radius and pitch radius of the rotor. forming a furrow-like protrusion and eliminating the defect;
A positive displacement flow rate system in which fluid that is about to be trapped in the pair of rotors is evacuated by the cutout part and the notch part of the rotor, and the fluid is easily allowed to flow into the part on the expanding side. Confinement pressure prevention device in meters.