JP2005344587A - Uniaxial eccentric screw pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a uniaxial eccentric screw pump capable of smoothly transferring liquid objects which have a wide temperature range from high temperature to low temperature or have low viscosity to high viscosity, having high discharge performance, enabling stable use for a long time, having a simple structure and capable of reducing the entire weight. <P>SOLUTION: In this uniaxial eccentric screw pump 1, a stator 5 with a female threaded hole 7 having an oval opening cross section and spirally continuing in the longitudinal direction is formed of a rigid resin material, and a male thread shaped rotor 3 is loosely inserted into the female threaded hole 7 of the stator 5, leaving a slight clearance. An end stud 15 is arranged in one end open side of the stator 5, and a tip part of a pump casing 16 connecting the other end open side of the stator 5 and the end stud 15 are connected and fastened by a plurality of staybolts 19. Due to this constitution, both stator 5 and end stud 15 are connected integrally with the pump casing 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stator in which a main body portion of a uniaxial eccentric screw pump for liquid transfer is configured with a male screw type rotor, and more particularly to a rigid resin stator having an oval cross section and a female screw hole penetrating in the longitudinal direction. .

  A uniaxial eccentric screw pump stator is generally made of rubber, resin, or metal. Each of the rubber stator and the resin stator has a metal outer cylinder, and has a drawback that it expands toward the inner diameter side due to an increase in the temperature of the stator, such as when a high-temperature liquid is transferred, and the diameter of the female screw hole is reduced.

  On the other hand, in the case of a metal stator, a cast molded product takes days and costs to manufacture a mold in the same manner as a rubber stator, and in a machined product, a female screw hole is formed by electric discharge machining or cutting from a round bar-shaped metal material. However, the machining is complicated and difficult, and it is necessary to use expensive special processing machines such as electric discharge machines and compound lathes. Difficult and expensive. In addition, the stator is very heavy and inconvenient to handle, and it is particularly difficult to manufacture a large-sized stator.

In other prior art, as a stator of a uniaxial screw pump for powder transfer, a structure formed of thermoplastic plastic, provided with a flange around one end of the stator, and the stator is accommodated in a cylindrical holder together with the flange Have been proposed (see Patent Document 1).
Japanese Patent Laying-Open No. 2001408349 (paragraph number 0010 and FIG. 1)

  However, the stator described in the above publication has the following disadvantages. That is, it is a uniaxial eccentric screw pump for powder transfer, and it is unclear whether liquid material can be transferred. Also, when the stator is made of plastic, it does not have elastic properties like rubber, so it is necessary to make a gap between the two in engagement with the rotor. In general, since the dimensional accuracy on the inner diameter (inner peripheral surface of the female screw hole) side is poor, it is necessary to increase the gap between the stator and the rotor. For this reason, the discharge performance of a transfer liquid is low, and discharge performance falls, so that the viscosity of a liquid becomes low. Furthermore, when transferring a high-temperature liquid material, the resin stator has a high coefficient of thermal expansion and is likely to expand. In addition, when the stator temperature rises and expands, a holder (usually made of metal) is placed on the outer peripheral surface side. Therefore, thermal expansion to the outer diameter side of the stator is restricted and obstructed, so that it expands to the inner diameter side, that is, the female screw hole side, and deformation occurs. As a result, the outer peripheral surface of the rotor contacts the inner peripheral surface of the female screw hole, the rotor contacts under a high pressing force, and both the rotor and the stator wear in a short period of time, the rotor does not rotate smoothly, The resin-made stator may be worn or damaged, and the worn or damaged portion may be mixed into the transfer liquid injection and cause liquid discoloration. In the worst case, the inner surface of the female screw hole peels off. It may be damaged. Therefore, conventionally, a problem is avoided by selecting and using a rotor having an outer diameter smaller than the inner diameter of the stator (during expansion) according to the temperature of the transfer liquid.

  The present invention has been made in view of the above points, and has a wide temperature range from a high temperature to a low temperature without selecting and using the outer diameter of the rotor according to the temperature of the transfer liquid, and from a low viscosity to a high viscosity. It is intended to provide a uniaxial eccentric screw pump for liquid transfer that can smoothly transfer liquid material, has high discharge performance, can be used stably over a long period of time, has a simple structure, and can reduce the overall weight .

  In order to achieve the above object, a uniaxial eccentric screw pump according to the present invention includes a stator having a female screw hole that is oval in an opening cross section and spirally continuous in a longitudinal direction, and is formed of a hard resin material. A uniaxial eccentric screw pump in which a male screw type rotor is loosely inserted in a hole with a slight gap, and an end stud is arranged on one end opening side of the stator, and a pump casing connecting the other end opening side of the stator The stator and the end stud are integrally connected to the pump casing by connecting and tightening the tip portion and the end stud with a plurality of screw rods (stay bolts).

  According to the single-shaft eccentric screw pump having the above-described configuration, since it is provided with a rigid resin stator and is integrally attached between the pump casing and the endstat with a screw rod, the structure is simple and the weight can be reduced. Because it can be attached with the outer peripheral surface exposed without being accommodated in the casing such as the outer cylinder or holder, the stator expands to the outer diameter side even when transferring a liquid or viscous liquid having a relatively high temperature, for example, No expansion or deformation occurs on the female screw hole side. For this reason, the gap between the rotor and the stator is properly maintained, and the transfer amount is proportional to the rotational speed of the rotor.

  According to a second aspect of the present invention, the stator is integrally formed of a high-performance engineering plastic such as PEEK or PPS resin or a hard resin imparted with excellent sliding characteristics obtained by compounding at least carbon fiber to the engineering plastic. be able to.

  All of the above engineering plastics are thermoplastics, high strength and high rigidity, excellent chemical resistance and wear resistance, and their properties do not easily change even at high temperatures, making them suitable for transferring various solutions at high temperatures. In addition, since high dimensional accuracy is ensured in terms of material, by setting the gap between the rotor and the stator small, the discharge performance can be improved and a low-viscosity liquid such as water can be transferred. Furthermore, a highly viscous liquid can be used for a long time even under a high pressure of 5.0 MPa.

  According to a third aspect of the present invention, the gap between the inner peripheral surface of the female screw hole of the stator and the outer peripheral surface of the rotor can be set to 0.2 mm or less (for example, 0.05 mm).

  With this configuration, for example, when the rotor outer diameter is 20 mm and the stator length is 210 mm, water discharge performance with a maximum discharge pressure of 0.5 MPa can be obtained at a rotor rotation speed of 450 r.p.m.

  Since the stator for a uniaxial eccentric screw pump according to the present invention has the above-described configuration, the rigid resin stator can be incorporated into the pump casing without covering the outer peripheral side with an outer cylinder or a holder. For this reason, even when a high-temperature liquid material is transferred, for example, the stator expands to the outer diameter side and does not expand to the inner diameter side, so that the gap with the rotor is maintained properly, and the stator and the rotor are worn in a short time. The inner surface of the stator is not peeled off or damaged. Accordingly, the gap between the stator and the rotor can be set small, and the discharge performance is improved. Therefore, even a low viscosity liquid such as water can be reliably transferred.

  Embodiments of a uniaxial eccentric screw pump according to the present invention will be described below with reference to the drawings.

  Fig.1 (a) is a top view which shows the uniaxial eccentric screw pump concerning the Example of this invention, FIG.1 (b) is the sectional view on the AA line of Fig.1 (a).

  2A is an enlarged longitudinal sectional view showing the stator of FIG. 1, and FIG. 2B is a transverse sectional view for explaining the relationship between the stator and the rotor.

  As shown in FIG. 1, a pump body portion 2 of a uniaxial eccentric screw pump 1 includes a male screw rotor 3 having a true circular cross section and a female screw hole 7 having an oval cross section having an opening cross section having a pitch twice that of the rotor 3. As shown in FIG. 2, the rotor 3 rotates eccentrically within the female screw hole 7 by a distance e around the central axis s. The rotor 3 revolves in the female screw hole 7 in the direction opposite to the rotation around the central axis s while rotating in one direction, and the rotor 3 rotates in the cross section at an arbitrary position of the female screw hole 7 while the oblong hole 7b. Are reciprocated in the long axis direction by being guided by the straight portions 7c and 7c.

  The stator 5 of this embodiment is integrally molded using a mold by injection molding using PPS (polyphenylene sulfide). As another manufacturing method, it can be manufactured by machining from a cylindrical hard resin material such as PPS resin using a multi-axis control high-precision machine tool. On the other hand, the rotor 3 is generally made of mild steel such as SUS316. However, for the stator 5 using a hard and rigid engineering plastic such as PPS or PEEK or a general-purpose grade in which the engineering plastic is filled with glass fiber as it is. The surface of the rotor 3 is worn in a short time, and the pump performance is greatly reduced. Therefore, in this embodiment, a PPS resin, which is a hard resin obtained by compounding at least carbon fiber to a PPS resin base polymer and imparting excellent sliding characteristics, is used. By using this good sliding grade for the stator 5, wear of the rotor 3 is eliminated.

  As shown in FIG. 1A, the rotor 3 is made of a metal made of stainless steel or the like, and a rotary shaft 11 connected to a drive shaft 10 a of the electric motor 10 by a pin joint 11 a and a universal shaft at one end of the rotary shaft 11. A coupling rod 13 connected via a joint 12, and one end of the rotor 3 connected to one end of the coupling rod 13 via a universal joint 14. An endstat 15 is attached to the stator 5 on the other end side of the rotor 3 to serve as a discharge port or a suction port. On the other hand, the opposite end of the stator 5 is connected to a pump casing 16, and a flanged opening 16 a that serves as a suction port or a discharge port projects upward at an intermediate position in the longitudinal direction of the pump casing 16.

  The rotating shaft 11 is rotatably supported in the bearing unit 17 via a bearing 17a, and a shaft seal portion 18 such as a mechanical seal is mounted around the rotating shaft 11 on the pump casing 16 side of the bearing unit 17. Since these structures are known, the stator 5 which is a characteristic part of the present invention will be described in detail below.

  The stator 5 shown in FIG. 1 is integrally formed of PPS as described above. The stator 5 is a cylindrical body, and an oval port 7b constituting a part of the female screw hole 7 is opened at the center of both end faces. An inward flange 16b is integrally formed in the tip opening 16c of the pump casing 16, and the outer peripheral edge of one end of the stator 5 is brought into contact with the flange 16b. On the other hand, the base end side opening frame portion 15 b of the end stud 15 is fitted to the outer peripheral edge portion on the opposite end side of the stator 5. Then, one end screw portions 19a of stay bolts 19 as screw rods are respectively screwed into the screw holes 16d at the four corners of the front end surface of the pump casing 16, and are fastened and fixed by nuts 20 screwed into the screw portions. The other end side threaded portions 19b of the four stay bolts 19 penetrate through the through holes 15a at the four corners of the base end face of the end stud 15 and project to the opposite side of the through hole 15a, and the nut 21 is screwed and tightened. Thus, the stator 5 is fixed and attached together with the end stud 15 between the end stud 15 and the pump casing 16.

  With this configuration, the resin-made stator 5 can be attached between the end stud 15 and the pump casing 16 without performing processing for attachment to the stator 5 and without using a holder or the like. Therefore, even if the stator 5 is thermally expanded by flowing in the screw hole 7 of the stator 5 when transferring a high-temperature liquid, the stator 5 expands to the outer diameter side, but does not expand to the inner diameter side. Further, since the stator 5 is in an exposed state, for example, if the stator 5 is formed of a transparent or translucent resin such as a transparent hard urethane resin, the transfer state of the liquid transferred through the screw hole 7 is observed from the outside. be able to.

  In the present embodiment, four stay bolts 19 are used. However, as long as the number of the stay bolts is two or more, for example, three, five, or six may be used. Further, a plate-like connecting member can be used in place of the stay bolt 19.

  Although the embodiment of the uniaxial eccentric screw pump of the present invention has been described above, for example, it can be implemented as follows.

  1) The structure other than the pump main body portion 2 and the end stud 15 on the tip side thereof, that is, the structure of the coupling rod 13 in the pump casing 16, the front and rear universal joints 12 and 14, the bearing unit 17 and the like is merely an example. However, other members can be used and can be changed as appropriate. For example, it goes without saying that the position and structure of the opening 16a of the pump casing 16 can also be changed.

  2) In addition to PPS resin, the stator is formed of a high-hardness and high-rigidity engineering plastic such as PEEK. As shown in FIG. 2 (c), male screws 5b and 5c are formed at both ends of the outer peripheral surface of the stator 5 '. Each is processed. And the internal thread corresponding to each external thread 5b * 5c can be formed in the base end part inner peripheral surface of the end stud 15, and the front end part internal peripheral surface of the pump casing 16, and can also be screwed in and attached. As a result, the stay bolt 19 can be omitted.

  3) Stator that uses hard and rigid engineering plastics such as PPS, PEEK, etc. that do not have improved sliding characteristics, wears the outer peripheral surface of the other metal rotor metal such as SUS316. There is aggression. Conventionally, since soft steel such as SUS316 is generally used for the rotor, soft resin such as PTFE resin should be used instead of the stator 5 made of good sliding grade PPS resin as in the above embodiment. However, it is possible to prevent the rotor from being worn. However, when the stator 5 is used alone as in the present invention, that is, it is used without being housed in the metal outer cylinder, the soft resin is inferior in terms of rigidity and cannot be applied.

Fig.1 (a) is a top view which shows the uniaxial eccentric screw pump concerning the Example of this invention, FIG.1 (b) is the sectional view on the AA line of Fig.1 (a). 2A is an enlarged longitudinal sectional view showing the stator of FIG. 1, and FIG. 2B is a transverse sectional view for explaining the relationship between the stator and the rotor. FIG. 2C is a plan view partially showing a stator according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Uniaxial eccentric screw pump 2 Pump main-body part 3 Male thread type rotor 5 * 5 'stator 7 Female thread hole 7a Female thread hole 7b Oval port 10 Electric motor 10a Drive shaft 11 Rotating shaft 12/14 Universal joint 13 Coupling rod 15 Endstat 16 Pump casing 16a Flange opening 17 Bearing unit 18 Shaft seal 19 Stay bolt (Screw)
20.21 Nut

Claims (3)

A uniaxial shaft formed by forming a stator having a female screw hole that is oval in the opening cross section and spirally extending in the longitudinal direction with a hard resin material, and loosely inserting a male screw rotor into the female screw hole of the stator with a slight gap. An eccentric screw pump,
An end stud is disposed on one end opening side of the stator, and a tip end portion of a pump casing connecting the other end opening side of the stator and the end stud are coupled and tightened by a plurality of screw rods, thereby fixing the stator. A single-shaft eccentric screw pump that is connected to the pump casing together with the end stud. 2. The single-shaft eccentric screw pump according to claim 1, wherein the stator is integrally formed of a high-performance engineering plastic such as PEEK or PPS resin or a hard resin imparted with excellent sliding characteristics obtained by compounding at least carbon fiber to the engineering plastic. . The uniaxial eccentric screw pump according to claim 1 or 2, wherein a gap between the inner peripheral surface of the female screw hole of the stator and the outer peripheral surface of the rotor is 0.2 mm or less.

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