Double screw rotor assembly

Details Double screw rotor assembly Double screw rotor assembly

1999-08-12

2001-01-23

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

Interengaging rotating members

Each tapered

Reexamination Certificate

active

06176694

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a double screw rotor assembly, and more particularly to such a double screw rotor assembly which is suitable for use in a fluid pressure changer means, such as water or air pumps, compressors, etc.
FIGS. 4 and 5
show a traditional double screw rotor assembly. This structure of double screw rotor comprises a casing
5
defining a compression chamber
51
, two screw rotors
6
meshed inside the compression chamber
51
. Because the thread
60
of each rotor
6
has constant pitch P and same cross-sectional profile, the volume of each transfer chamber
52
does not vary with the operation of the two screw rotors
6
. Because the volume of transfer chamber
52
is not variable, a high pressure difference occurs at the outlet end
512
during the operation of the screw rotors
6
, and this high pressure difference results in a reverse flow of fluid, high noises, and waste of energy.
U.S. Pat. No. 5,667,370 discloses another structure of double screw rotor assembly as shown in FIG.
6
. According to this design, the thread
61
of each screw rotor
60
has an uneven pitch P
1
,P
2
, and the pitch P
1
,P
2
is reduced in proper order from the inlet end
513
toward the outlet end
514
(P
1
>P
2
), therefore the volume of respective chamber
53
or
54
are gradually reduced in same direction. However, the non-uniform pitch type of thread
61
defines different cross-sectional profiles and pressure angles at different elevations. These limitations cause the thread
61
difficult to be produced. When processing the thread
61
, a particularly designed cutting-metal working machine must be used. This complicated thread processing process greatly increases the manufacturing cost of the double screw rotor assembly.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide a double screw rotor assembly which eliminates the aforesaid drawbacks. It is one object of the present invention to provide a double screw rotor assembly which effectively reduces reverse flow at the outlet end, so as to reduce power consumption and operation noises. It is another object of the present invention to provide a double screw rotor assembly which is easy and inexpensive to be manufactured.
According to one aspect of the present invention, the double screw rotor assembly comprises a casing, and two screw rotors. The casing comprises an inside wall defining a compression chamber, an inlet port and an outlet port respectively disposed in communication with said compression chamber. The screw rotors are mounted in the compression chamber inside the casing and meshed with each other. The addendum of screw rotor defines an outside diameter abutted against the inside wall of the casing. The dedendum of screw rotor defines a root diameter. A thread height is defined between the addendum of thread and the dedendum of thread, i.e. between the outside diameter and the root diameter. Further, at least one transfer chamber is defined within the casing and surrounded by the inside wall of the casing and groove of each of the screw rotors. The at least one transfer chamber which's volume gradually reducing in direction from the inlet port toward the outlet port. According to another aspect of the present invention, the gradually reduced design of the volume of the at least one transfer chamber is achieved by gradually and linearly
on-linearly increasing the root diameter, or reducing the outside diameter in direction from the inlet/port toward the outlet port. According to still another aspect of the present invention, the screw rotors can have more than one thread. The thread of each screw rotor can be made defining an equidistant pitch, or having a uniform cross-sectional profile, so that the thread can easily and inexpensively be processed.


REFERENCES:
patent: 3180559 (1965-04-01), Boyd
patent: 5533887 (1996-07-01), Maruyama et al.
patent: 5667370 (1997-09-01), Im
patent: 6019586 (2000-02-01), Liou
patent: 384355 (1932-12-01), None
patent: 401267384 (1989-10-01), None
patent: 406307360 (1994-11-01), None

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