Data processing: generic control systems or specific application – Generic control system – apparatus or process – Plural variables
Reexamination Certificate
1999-02-16
2001-05-22
Lee, Thomas (Department: 2182)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Plural variables
C700S017000, C418S150000
Reexamination Certificate
active
06236897
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention describes the precision processing of curved surfaces of the cardiocle and expanded cardioid casing in springless eccentric rotor vane pumps.
2. Description of the Prior Art
In general, vanes used in eccentric rotor vane pumps are fitted with springs so that their length can vary in line with casing surfaces. However, the eccentric rotor vane pump discussed here has a solid vane of constant length. For this type of eccentric rotor vane pump, the key technology is the accuracy of the casing surface curvatures, to allow the edges of a sliding vane match the surface curves as closely as possible no matter what the rotation angle and the eccentricity of the rotor may be.
However, the exact mathematical descriptions which accurately represent the curves drawn by the movements of the vane edges in an eccentric rotor vane pump have not been found until now. Thus processing of curved casing surfaces has been possible only via the recopy method. This method has several significant weaknesses: (1) Curved surfaces have to be retraced and remodelled each time eccentricity or casing size needs to be changed. (2) Precision processing is not quite possible, especially for large-sized casings. (3) The entire surface of the casing has to be processed at one time. (4) The edges of scraping, sliding vanes make poor contact with casing surfaces.
Moreover, with this recopy method, the accuracy of casing surface processing varies with the eccentricity of the pump, the angle of rotation of the vane, and the distance the vane travels. As there have been no geometrical equations which exactly describe the curves drawn by the vane rotation, such advanced manufacturing techniques as CNC, and processing in sections, have not been available. The only possible manufacturing method was the recopy method, using a prototype curved action.
SUMMARY OF THE INVENTION
In this invention, however, the following equations (A) and (B), which represent the curves drawn by the movement of vanes of fixed length in eccentric rotor vane pumps, are derived on the basis of these curves always falling into two categories, cardiocle and expanded cardioid curves, regardless of rotor eccentricity and vane length:
P
=
2
a
{
1
+
(
R
-
r
)
sin
θ
2
a
-
R
2
-
(
R
-
r
)
2
cos
2
θ
2
a
}
for
cardiocles
(
A
)
P
=
2
a
{
1
+
(
R
-
r
)
sin
θ
2
a
}
for
expanded
cardioids
(
B
)
Nomenclature in the equations will be discussed in detail later, in reference to
FIGS. 1
,
3
,
5
and
6
.
These two equations represent in terms of analytic geometry the curved surfaces of eccentric rotor pump casings, and thereby alow the precision processing of casings using CNC techniques. As the equations do not depend on rotor eccentricity and vane length, casings of any size can be manufactured to the highest levels of accuracy current engineering technology permits; and even further, more processing in sections is now possible.
As a result, not only precision processing, but also mass production, of large-sized springless eccentric rotor vane pumps of 1-meter or larger diameter is now possible, thus making feasible the supply to customers of eccentric rotor vane pumps at more reasonable prices.
In other current eccentric rotor vane pumps, the center of eccentricity of the rotor is set at the upper section or sides of the casing center for better ventilation and smooth valve movement. But the movement of a vane causes friction with the casing surfaces, as the centrifugal force generated by the rotating vane is in the same direction as the gravitation force exerted on the rotor. Therefore the rotation speed of the rotor has to be kept low. However, the vane of the eccentric rotor vane pump being discussed here makes large-area contact with the casing surfaces when sliding on surfaces; and thus the center of eccentricity of the rotor can be placed in the lower section of the casing center. Additionally, the centrifugal force produced by the rotation of the vane is reduced by the weight of the vane. Therefore the rotation speed of the rotor can be sped up.
In particular, as shown in
FIG. 10
, existing thrust bearings may be used for the processing of large-sized casings of 1-meter or greater diameter, so that the rotor axis can be designed vertically, reducing gravitational pull due to the weight of the rotating vane and increasing operational life.
As the casing diameter increases, the weight of the vane increases and so, too, does the friction produced by the vane when sliding and scraping along the casing surface. For this reason the manufacture of large-sized eccentric rotor vane pumps was regarded as impractical in the past.
By positioning the rotor shaft vertically, it is possible to reduce the friction between the ends of the vane and the casing surface, and thus to increase the size of eccentric rotor pumps. Furthermore the mathematical descriptions of cardiocle and expanded cardioid curves derived and shown in this invention allows the implementation of CNC techniques in the manufacture of casings, and subsequent increase in casing surface accuracy. CNC processing makes possible both mass production and cost reduction.
REFERENCES:
patent: 1442198 (1923-01-01), Utley
patent: 1626510 (1927-04-01), Chase
patent: 3877851 (1975-04-01), Komiya et al.
patent: 3922114 (1975-11-01), Hamilton et al.
patent: 4133617 (1979-01-01), Reynaud
patent: 4300874 (1981-11-01), Georgiev
patent: 5511525 (1996-04-01), Jirnov et al.
patent: 595639 (1947-12-01), None
Lee Dae Sung
Park Yong Hee
Du Thuan
Lee Thomas
Morgan & Lewis & Bockius, LLP
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