JPS6229781A - Eccentric screw pump - Google Patents

Abstract

PURPOSE:To enable a ceramic made stator, providing an excellent property resisting against heat, wearing and corrosion, for an eccentric screw pump to be easily manufactured, by molding an inner surface into an internal thread shape copying the smooth surface of a core metal mold subsequently performing sintering. CONSTITUTION:A core metal mold 14 has a smooth surface prepared estimating a contracting margin by firing of ceramic, and a stator base body, placing a dust material 16 of ceramics between the core metal mold 14 and a rubber mold 15 to be hermetically sealed thereafter in fluid 18 serving as a pressure medium in a high pressure vessel 17, is molded by applying pressure to the fluid 18. Subsequently, said base body, performing firing, can obtain a high accurate ceramic made stator for an eccentric screw pump with no necessity for grinding the internal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eccentric screw pump suitable for pumping highly abrasive and corrosive fluids and high-temperature fluids.

[Conventional technology]

A male threaded rotor with a circular cross section that is eccentric with respect to the rotational axis is connected to a stator that has an oval cross section consisting of a semicircular part and a straight part, and has a female threaded inner surface with a pitch twice that of the rotor. Eccentric screw pumps, which are configured so that the rotor rotates around the rotational axis and performs eccentric movement with respect to the stator axis, are widely used as pumps suitable for transporting highly viscous fluids. It is being

In such eccentric screw pumps, the stator has conventionally been made of rubber or metal.

[Problem that the invention seeks to solve]

However, conventional eccentric screw pumps using rubber stators are not suitable for high-temperature fluid pumping because their maximum operating temperature is limited by the characteristics of the stator's rubber material, and their physical properties deteriorate as the operating temperature rises. It also had poor solvent resistance (and could not be used for pumping solvents such as lacquer).

Furthermore, mechanically, eccentric screw pumps rotate with the rotor strongly pressed against the inner surface of the stator, so if a rubber stator is used, solid particles in the pumped fluid can cause the stator to wear or tear in a short period of time. damage. Particularly in the case of pressure-feeding food, there is a problem in that worn pieces of the stator get mixed into the food. On the other hand, when the stator is made of metal to prevent wear and damage, the internal threaded inner surface has a complicated shape and requires precision, making cutting extremely difficult and expensive.

This invention solves these problems in eccentric screw pumps.

Therefore, the stator of this invention has excellent heat resistance, solvent resistance, abrasion resistance, and corrosion resistance, can withstand long-term use, can be safely used for food pressure conveyance, and is relatively inexpensive. The purpose is to provide an eccentric screw pump.

[Means for solving problems]

The eccentric screw pump of the present invention has a stator made of ceramics whose inner surface is formed into a female thread shape by removing the smooth surface of a middle mold, and which is sintered.The stator is connected to a suction portion at one end and a discharge portion at the other end. A male-threaded rotor is attached to the stator.

[Effect]

In this invention, the stator is molded with high precision by the ceramics transferring the smooth surface of the inner mold, so there is no need to grind the inner surface of the stator after sintering, and the rotor rotates smoothly. Therefore, the stator is heat resistant, corrosion resistant,
Since it is made of highly wear-resistant ceramic, there is no risk of wear or damage, and it prevents wear debris from entering the pumped fluid, allowing long-term operation.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an eccentric screw pump which is an embodiment of the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1.
This pump has a driving part 1. It is composed of a suction section 2, a pump section 3, and a discharge section 4.

A drive shaft 5 is supported in the drive section 1, and the drive shaft 5 is rotated by a motor (not shown).

It will be done. As shown in FIG. 2, the pump part 3 includes a male threaded rotor 6 whose center 0 of its circular cross section is eccentric by a predetermined distance e with respect to the rotational axis R, which has semicircular parts 7a and 7b and a straight part. The stator 8 has an internally threaded inner surface 7 having an oval cross section with a pitch twice that of the rotor 6, and has an elliptical cross-section 7c and 7d. R is mounted so that it is eccentric by a distance e.

The suction part 2 has a suction port 10 in a housing 9 that connects the pump part 3 and the drive part 1, and inside, the drive shaft 5 and the rotor 6 are connected to each other by universal joints 11 and 12 at both ends.
An intermediate shaft 13 is provided which is connected to.

In the pump having such a configuration, when rotation is applied to the drive shaft 5, the rotor 6 rotates around the rotation axis R (
rotate). However, the center 0 of the cross section of the rotor 6 is eccentric from the rotation axis R by a distance e, whereas the stator 8 is fixed, so the rotor 6 cannot rotate freely and is subject to the reaction force of the stator 8. As a result, the rotational axis R of the rotor 6 is given rotation (revolution) about the axis S of the stator 8 in a direction opposite to the rotation of the rotor 6 . Therefore, the rotor 6
The cross section at an arbitrary point is the linear portion 7c of the internally threaded inner surface 7 of the stator 8, ? It reciprocates within this cross section while being restrained by d.

Due to this movement of the rotor 6, the fluid supplied from the suction port 10 is pressurized and discharged from the discharge part 4. At this time, if the gap between the inner surface 7 of the stator 8 and the rotor 6 is large, leakage may occur. Stator 8 due to reduced pump efficiency
The inner surface 7 needs to be formed into a complex shape with high precision.

In this embodiment, the stator 8 is molded using a rubber press method as shown in FIG.

After placing the ceramic powder raw material 16 between the rubber mold 5 and the inner mold 14 having a smooth surface, which has been manufactured in advance to account for shrinkage due to firing of the ceramic, and sealing the material, It is placed in a certain liquid 18 and molded by applying high pressure (approximately 100,100 O/cd) to this liquid 18. After pressure molding, the inner mold is removed by twisting, taking advantage of the fact that the inner mold has a male thread shape and that the ceramic expands during aging and creates a minute gap between the inner mold and the inner mold. If formed using this method, the particles will be homogeneous, with good clogging between the particles, and deformation and shrinkage due to sintering will be small and uniform, so the shape of the smooth surface of the middle mold will be transferred with high precision, and the inner surface will be easily ground. A high-performance pump stator was obtained without any additional steps.

From the viewpoint of wear resistance and corrosion resistance, silicon carbide and silicon nitride are recommended as materials for stator ceramics.

Silica/alumina materials such as sialon, zirconia, alumina, spinel, and mullite are used.

In this embodiment, a rubber press method was applied to mold the stator, but other molding methods may be used as long as the smooth surface of the inner mold can be removed.

〔Effect of the invention〕

Since the eccentric screw pump of the present invention is constructed as described above, high efficiency can be obtained without the need for internal grinding of the stator, and fluids containing solvents, high-temperature fluids, particles with high H purity, etc., and corrosive fluids There is no risk of wear or damage to the stator even when used for pressure feeding, and it is highly durable and can be operated for a long time. It is non-toxic and does not contain broken pieces, so it can be used with confidence even when used for pressure-feeding food products.It does not require precision mechanical machining of the inner surface of the stator, so it is possible to supply inexpensive products.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an eccentric screw pump according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line nu in FIG. 1, and FIG. 3 is an explanatory view of forming the stator. In the figure, 1 is the drive part, 2 is the suction part, 3 is the pump part, 4 is the discharge part, 6 is the rotor, 7 is the inner surface of the stator, 8 is the stator, 14 is the inner mold, 15 is the rubber mold, and 16 is the It is a powder raw material.

Claims (1)

[Claims] The inner surface of the inner mold is formed into a female thread shape by removing the smooth surface of the inner mold, and sintered ceramic is used as a stator.A suction part is connected to one end and a discharge part is connected to the other end.A male threaded rotor is attached to the stator. Eccentric screw pump.