Rotary expansible chamber devices – Apertured bypass to pressurize or relieve working chamber...
Reexamination Certificate
1998-03-13
2001-01-23
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Apertured bypass to pressurize or relieve working chamber...
C418S206400
Reexamination Certificate
active
06176693
ABSTRACT:
DESCRIPTION
The present invention relates to a volumetric blower comprising an internally hollow body forming a compartment which houses a pair of rotors and which is connected to an intake manifold and a delivery manifold, the opposite openings in the longitudinal direction of said compartment being closed by an associated cover having, formed on its internal surface, at least one duct arranged on the delivery side so as to allow connection of said chamber to the delivery manifold itself.
In the technical sector relating to compressors so-called volumetric blowers which are also referred to by the term “Roots” are known, said blowers being designed to deliver a gas throughput which is practically constant with variations in the pressure and operation of which does not involve a compression phase inside the compressor.
Said blowers essentially consist of a body having, formed inside it, a cylindrical compartment inside which two shafts comprising several lobes with a correlated profile rotate in opposite directions, said shafts, during rotation, cyclicly forming chambers delimited by two adjacent lobes of the same rotor and by the internal wall of said compartment.
Said chambers, as a result of the rotation of the lobes which delimit them, draw fluid from an intake manifold extending outside the body of the blower and placed in communication with said internal compartment and convey the volume of fluid contained in the chamber to a delivery manifold located opposite the intake manifold and in turn placed in communication with the blower compartment on th e opposite side of the rotors.
It is also known that the fluid compression phase occurs at the moment when the said chamber opens out towards the delivery manifold inside which a fluid with a pressure greater than the intake pressure is present, causing a flowback towards the chamber which is a conveying the fluid from the intake to the delivery, causing compression of the fluid itself.
At the moment when the chamber opens out towards the delivery, however, in addition to the said compression, the flowback of the fluid al so causes the generation of shock waves and violent pressure pulsations which result in rapid dissipation of energy in the form of heat and noise.
In order to reduce drastically this noise phenomena, it is therefore necessary to make the compression phase as gradual as possible, by advancing and graduating opening of the chamber towards the delivery manifold.
For this purpose it is known, in the art of the sector, to form grooves of increasing depth in the direction of rotation of the rotors, in the internal wall of the said compartment housing the rotors.
Examples of this known art are described, for example, in DE 35 27 292 and in IT-1,264,069 which also envisage similar grooves, but having a smaller angular breadth, in the region of the intake manifold.
These grooves on the intake side essentially allow a delay in closing of the chamber formed by the lobes of the rotor with a consequent improvement in the volumetric efficiency of the blower. In addition to this, the specific angular extension of the grooves on the intake side and on the delivery side—the latter being much longer than the former—results, for a short period of time, in a direct connection between intake and delivery which is able to reduce further the said pulsations effects.
Despite the measures taken, the blowers of the known type still have drawbacks arising from the high noise level due to a poor distribution of the flows passing from the intake manifold to the delivery manifold, said poor distribution of the flows also being due to the interference effect caused by said grooves for advancing opening and delaying closing of the chambers.
In addition to this, the practical formation of said grooves on the internal surface of the compartment housing the rotors involves technical difficulties due to the machining difficulty and tolerances required which increase the overall cost of the blower and do not allow easy adaptation of the latter to the specific working conditions since, in order to vary the aperture of said grooves, it would be necessary to change the compressor body.
The technical problem which is posed, therefore, is that of providing a volumetric blower which, while maintaining a high efficiency and low manufacturing cost, is provided with means designed to reduce considerably the noise level and the pressure pulsations which are typical of blowers of the known type.
Within the scope of this problem, a further requirement is that said means for reducing the noise level should result in an improved distribution of the fluid flows from the intake to the delivery and should be easy to apply to blowers of the conventional type as well without the need for structural modifications of the body of the blower itself and, if necessary, should be able to be replaced in an easy and low-cost manner so as to adapt the blower to different working conditions.
These technical problems are solved according to the present invention by a volumetric blower comprising an internally hollow body for defining a compartment which is placed in communication with an intake manifold and a delivery manifold and which has, arranged inside it, two rotors which are parallel to a longitudinal axis of the blower, counter-rotating and shaped in the manner of radial lobes with a correlated profile and which are designed to produce, together with the internal wall of said compartment, the periodic formation of a chamber containing the fluid to be conveyed to the delivery manifold, the opposite openings in the longitudinal direction of said compartment being closed by an associated cover, wherein, the internal surface of said covers has, formed in it, at least one duct arranged, with respect to the longitudinal axis (X—X), on the side corresponding to the delivery manifold so as to allow connection of said chamber to the delivery manifold itself and designed to be closed by the front surface of the lobes of the associated rotor whenever each lobe passes opposite the duct itself.
REFERENCES:
patent: 2111568 (1938-03-01), Lysholm et al.
patent: 2489887 (1949-11-01), Houghton
patent: 4215977 (1980-08-01), Weatherston
patent: 865864 (1953-02-01), None
patent: 3238015 (1984-04-01), None
patent: 3318519 (1984-11-01), None
patent: 309685 (1929-04-01), None
Finder Pompe S.p.A.
Ladas & Parry
Vrablik John J.
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