WO1998004809A1

WO1998004809A1 - A rotary positive-displacement machine

Info

Publication number: WO1998004809A1
Application number: PCT/IT1997/000178
Authority: WO
Inventors: Giovanni Morselli
Original assignee: Giovanni Morselli
Priority date: 1996-07-29
Filing date: 1997-07-21
Publication date: 1998-02-05
Also published as: ITMO960104A0; ITMO960104A1; IT1287464B1; AU3862497A

Abstract

The rotary positive displacement machine comprises a body (1) provided with a cavity delimited at least in part by a surface of revolution (2) internally of which body a rotor (3) is arranged, having a blade (5) which projects radially and the peripheral end of which is very close to the surface of revolution (2). An annular chamber (4) is afforded between the surface of revolution (2) and the external surface of the rotor (3). Internally of the body (1) a rotary sealing element (6) is arranged, tangential to the external surface of the rotor (3) and rolling thereon undraggingly. The rotary sealing element (6) exhibits a chamber (7) sized and shaped such as to receive internally thereof the blade (5) during relative motion. An inlet mouth (8) for a fluid and an outlet mouth (9) are situated on opposite sides in proximity of the tangential zone between the rotor (3) and the sealing element (6).

Description

Pescπption

A Rotary Positive-Displacement Machine

Technical Field

The invention relates to a rotary positive displacement machine. It can be applied as a drive machine, a machine tool and as a measuring instrument for a quantity of fluid. In particular, it can be used as a hydraulic motor, a pneumatic motor, a hydraulic pump, a pneumatic pump, a vacuum pump, a compressor, a ventilator, a counter, and other applications. Background Art

The invention relates to a machine which, by means of the relative motion of its organs, one of which is rotary, sets in communication a predetermined volume filled with a fluid with two chambers which are separate and at different pressures.

The prior art teaches a vast number of different kinds of machines of this type. Purely by way of example, to obtain effective vacuum pumps rotary machines are used (having mobile radial blades) which however present numerous drawbacks and limitations, such as wear in the mobile mechanical parts in dragging contact, the need to lubricate and to filter the lubricants, and last but not least a not outstanding performance.

An aim of the present invention is to overcome the above-mentioned drawbacks and limitations in the prior art by providing a rotary positive displacement machine having no moving parts in dragging contact. An advantage of the invention is that it is constructionally simple and economical. A further advantage is that it is compact and not massive. The above aims and advantages and others besides are all obtained with the machine of the invention, as it is described in the appended claims. Disclosure of Invention

Further characteristics and advantages of the present invention will better emerge from the detailed description that follows of a preferred but non-exclusive embodiment of the invention, illustrated purely by way of non-limiting example in the accompanying figures of the drawings, in which: figure 1 is a schematic section according to line I-I of figure 2, relating to a first embodiment of the invention; figure 2 is a schematic section according to line II-II of figure 1 ; figure 3 is a transversal schematic section of a second embodiment of the invention; figure 4 is a transversal schematic section of a third embodiment of the invention.

With reference to figures 1 and 2 above, in a first embodiment, the positive displacement machine - which can be used, for example, as a compressor or vacuum pump - comprises a body 1 provided with a cavity delimited at least in part by a cylindrical surface of revolution cylindrical 2 internally of and coaxially to which a rotor 3 is arranged, so that between the surface of revolution 2 and the external surface of the rotor 3 there is an annular channel 4 of constant radial breadth.

The rotor 3 is provided with a blade 5 which projects radially, exhibiting a peripheral end which is very close to the surface of revolution 2. The rotor 3 is keyed on a shaft 42 which is rotatably coupled to the body 1 and which is driven by an external motor of known type and not illustrated. The rotation direction of the rotor 3 is indicated by an arrow 41.

Internally of the body a rotating sealing element 6 is mounted, whose external surface is cylindrical, and which has an axis that is parallel to that of the rotor 3. The sealing element 6 is keyed on a shaft 43 which is rotatably coupled to the body 1 and which is driven by the shaft 42 of the rotor 3, through a mechanical gear transmission 40 external of the cavity of the body 1. The sealing element 6 is tangential to the external cylindrical surface of the rotor 3 and is predisposed to roll on said cylindrical surface with no dragging, in the direction indicated by the arrow 44. For this purpose the diameter of the external cylindrical surface of the rotor 3 is equal to the diameter of the external cylindrical surface of the sealing element 6 and the gear rapport of the transmission 40 is 1. The tangential zone between the rotor 3 and the sealing element 6 is in fact a sealed zone, as will better be explained herein below.

The rotating sealing element 6 exhibits a niche 7 sized and shaped with large tolerances in order to receive therein the blade 5 of the rotor 3 during relative motion, without there being any contact. The rotor 3 and the rotary sealing element 6 must be properly relatively timed so that the blade 5 inserts uncontactingly into the niche 7. The gear transmission 40 has in this case the function of maintaining the rotation movements of the rotor 3 and the sealing element 6 in correct time. An inlet mouth 8 and an outlet mouth 9 communicate with the annular chamber 4, being situated in proximity of and on opposite sides of the tangential zone between the rotor 3 and the sealing element 6. Note that the two mouths 8 and 9 are arranged in such a way that the blade 5 runs, from the inlet 8 to the outlet 9, through an arc of circumference which is considerably greater than the arc that the blade 5 travels through from the outlet mouth 9 to the inlet mouth 8. The two mouths 8 and 9 are connected to two respective chambers kept at different pressures. In particular, when the machine is being used as a compressor, the outlet mouth 9 can be connected to the high-pressure chamber by means of a conduit, not illustrated, on which there is a no-return valve preventing the fluid from flowing back into the annular chamber 4.

The functioning of the machine will now be described, starting from the configuration of figure 1 in which the blade 5, rotating in the annular chamber 4, is passing in front of the inlet mouth 8. In this phase a volume of the fluid present in the low-pressure chamber, communicating with the inlet mouth 8, has occupied the annular chamber 4; the no-return valve situated between the outlet mouth 9 and the high-pressure chamber, is closed. As soon as the blade 5 has passed the inlet mouth 8, a volume of fluid is isolated between said inlet mouth 8 and the outlet mouth 9, which fluid begins to be compressed by the rotating blade 5. At a certain point during the arc of the blade 5, as a predetermined fluid pressure is reached, the no-return valve opens automatically, so that the trapped compressed fluid in the annular chamber 4 begins to the transferred from the high-pressure chamber through the outlet mouth 9. During this phase the two mouths 8 and 9 are sealedly isolated from each other by the sealing action of the sealing element 6 which is tangentially in contact with the external cylindrical surface of the body 3. Furthermore, the part of the annular chamber 4 which the blade 5 has passed through is progressively filled though the inlet mouth 8, by effect of the aspiration created by the movement of the blade 5.

As soon as the blade 5 has travelled past the outlet mouth 9 the no-return valve automatically closes; the blade 5 continues its journey without interfering with the sealing element 6 thanks to the presence of the niche 7, up until it returns to the initial configuration and begins a new work cycle. It is worth stressing that before the blade 5 passes the outlet mouth 9 the sealing element 6 must act in contact with the rotor 3 in order to create a seal, while after the blade 5 has passed the outlet mouth 9 and until it has once more passed the inlet mouth 8, the sealing element 6 does not have to contact the rotor 3. This means, in other words, that the tangential zone (and therefore the sealing zone) can be in communication with the niche 7 immediately after the blade 5 has passed the outlet mouth 9. Furthermore, the insertion of the blade 5 in the niche 7 not only happens with no contact between the blade 5 and the sealing element 6, but happens without any seal being established, that is, with the blade 5 at a distance from the surface of the sealing element 6 delimiting the niche 7. An advantageous consequence of this fact is that the niche 7 can be constructed very simply and economically, without any special tolerances having to be considered. For this reason the peripheral breadth, in the circumferential direction, of the niche 7 can be at most equal to (but not greater than) the circumferential distance between the two mouths 8 and 9, without compromising the functionality of the machine, as long as contact (and seal) is guaranteed in the tangential zone between the rotor 3 and the sealing element 6 during the journey that the blade 5 makes from the inlet mouth 8 to the outlet mouth 9.

When used as a vacuum pump the inlet mouth 8 is connected with a closed environment from which fluid is aspirated. The outlet mouth 9 can be set in direct communication with the outside environment. Turning to figure 3, in a second embodiment the rotary positive displacement machine of the invention - here too preferably used as a vacuum pump or compressor - comprises a body 11 provided with a cavity delimited at least in part by a surface of revolution 12, cylindrical in shape, internally of which a rotor is arranged coaxially and has a cylindrical external shape so that between the surface of revolution 12 and the external cylindrical surface of the rotor 13 there is an annular chamber 14 of a constant radial breadth. The rotation direction of the rotor 13 is indicated by arrow 45. The rotor 13 is provided with two identical blades 15, situated on diametrically opposite sides and projecting radially, with their peripheral ends very close to the surface of revolution 12.

Internally of the body 11 a rotary sealing element 16 is arranged, whose external surface is cylindrical and whose axis is parallel to that of the rotor 13. The cylindrical surface of the rotary sealing element 16 has a diameter which is exactly equal to half of the diameter of the external cylindrical surface of the rotor

13.

The sealing element 16 is tangential to the external surface of the rotor 13 and is predisposed to roll thereon undraggingly, in the direction indicated by arrow 46. For this reason the sealing element 16 is rotated at a velocity which is double that of the rotor 13, by a gear mechanism (not illustrated) external of the cavity of the body 11.

The rotor sealing element 16 affords a niche 17 sized and shaped to receive internally thereof the blades 15 of the rotor 13 during relative motion, without any contact taking place. The rotor 13 and the rotary sealing element 16 must be specially timed with each other, for the same reason as with the first embodiment of the invention.

An inlet mouth 18 and an outlet mouth 19 communicate with the annular chamber 14 and are situated on opposite sides and close to the tangential zone between the rotor 13 and the sealing element 16.

This machine, when used as a compressor, differently to the first embodiment of the invention illustrated in figure 1, does not necessitate use of a no-return valve on the outlet mouth 19. In this case, however, the niche 17 has to be shaped so that the insertion of the blades 15 in the niche 17 is sealed, i.e. with each blade 15 passing at a very close distance from the surface of the sealing element 16 delimiting the chamber.

The illustrated embodiment can be used, apart from as a compressor and/or a vacuum pump, also as a motor. In this case the inlet mouth 18 would become the inlet mouth of a pressurised fluid.

The third embodiment of the rotary positive displacement machine of the invention, shown in figure 4, can be used as a motor. It comprises a body 21 provided with a cavity delimited at least in part by a cylindrically-shaped surface of revolution 22, internally of which a rotor 23 is coaxially arranged, said rotor 23 having a cylindrical external surface, so that between the surface of revolution 22 and the external surface of the rotor 23 an annular chamber 24 having a constant radial breadth is defined. The rotation direction of the rotor 23 is indicated by an arrow 47.

The rotor 23 is provided with three blades 25 which are identical, angularly equidistanced and radially projecting, having their peripheral ends placed very close to the surface of revolution 22. Internally of the body 21 there are two rotary sealing elements 26, which are situated in diametrically opposite positions and have axes which are parallel to the axis of the rotor 23, and which have cylindrical external surfaces. The cylindrical external surface of each rotary sealing element 26 has a diameter which is exactly equal to a third of the diameter of the external cylindrical surface of the rotor 23. Each sealing element 26 is tangential to the external surface of the rotor 23 and is predisposed to roll undraggingly thereon, in the direction indicated by the arrows 48. For this purpose each sealing element 26 is rotated at a velocity which is three times that of the rotor 23, by a gear mechanism (not illustrated) situated externally of the cavity of the body 21. Each rotary sealing element 26 exhibits a niche 27 sized and shaped to receive internally thereof the blades 25 of the rotor 23 during relative motion, with no contact being made. The rotor 23 and the rotary sealing elements 26 must be correctly timed. In this embodiment, too, the insertion of the blades 25 in the chambers 27 is timed by said geared mechanical transmission. For each rotary sealing element 26 there is an inlet mouth 28 and an outlet mouth 29, which communicate with the annular chamber 24 and which are situated, on opposite sides, in proximity of the tangential zone between the external cylindrical surface of the rotor 23 and the external cylindrical surface of the respective sealing element 26. As can be seen in figure 4, the two inlet mouths 28, one for each sealing element 26, are situated in diametrically opposite positions, as are the outlet mouths 29. The machine of figure 4 comprises means, of known type and not illustrated, for introducing a pressurised fluid into the annular chamber 24 through the inlet mouths 28. A distributor, of known type and not illustrated, is associated to said means for introducing a fluid, which distributor is capable of selectively introducing the pressurised fluid through one or another of the two inlet mouths 28, according to a timed sequence with the positions assumed by the blades 25 with respect to the sealing elements 26, as will be better explained herein below. In the operative configuration illustrated in figure 4, for example, the distributor creates a communication between the source of compressed air and the inlet mouth 28 in the lower position in the figure, while it closes the communication with the upper-situated inlet mouth.

The functioning of the machine of figure 4 will now be described, starting from the configuration shown in figure 4 itself, where only the lower sealing element 26 is in contact (merely a rolling contact) with the rotor 23. The pressurised fluid introduced through the lower inlet mouth 28 acts on the lower blade 25 on the left, setting the rotor 23 in motion. As it rotates, the upper sealing element 26 enters into contact with the rotor 23, after the upper blade 25 has already passed the upper inlet mouth 28; at this point the distributor introduces the pressurised fluid through the upper inlet mouth 28, and the fluid acts on the upper blade 25.

Then, the lower blade on the right - still referring to figure 4 - passes the lower inlet mouth 28, while the lower sealing element 26 enters into contact with the rotor 23: in this situation the distributor once more intervenes to cause the pressurised fluid to pass through the lower inlet mouth 28. Substantially, the inversion of the distributor occurs at each rotation by a sixth of the round angle of the rotor 23. The functioning of the machine allows an extremely continuous and regular rotation of the rotor 23 and prevents any dead points from occurring.

Obviously it would be possible to create further embodiments with various numbers of blades, rotary sealing elements and chambers on said sealing elements, with the contact between the sealing elements and the central rotor in all cases occurring by rolling and not dragging.

As has been seen, the machines described herein, in all the versions, include no mechanical organs which drag against one another. Obviously numerous modifications of a practical-applicational nature could be brought to the invention without its forsaking the field of protection sought for the inventive idea, as claimed in the following.

Claims

Ctøims,

1). A rotary positive displacement machine, comprising: a body (1, 11, 21) provided with a cavity which is at least in part delimited by a surface of revolution (2, 12, 22); a rotor (3, 13, 23), arranged coaxially internally of the surface of revoltion (2, 12, 22) in such a way that between said surface of revolution and an external surface of the rotor (3, 13, 23) an annular chamber (4, 14, 24) is afforded, the rotor (3, 13, 23) being provided with at least one blade (5, 15, 25) which projects radially and which exhibits a peripheral end very close to the surface of revolution (2, 12, 22); at least one rotary sealing element (6, 16, 26) which is situated internally of said body (1, 11, 21) and which is tangential to the rotor external surface (3, 13, 23) and which is predisposed to roll on said rotor external surface (3, 13, 23) with no dragging, said rotary sealing element (6, 16, 26) exhibiting at least one chamber (7, 17, 27) sized and shaped such as to receive internally thereof said blade (5, 15, 25) during relative motion, with no contact taking place therebetween; an inlet mouth (8, 18, 28) and an outlet mouth (9, 19, 29) communicating with said annular chamber (4, 14, 24), situated on opposite sides of and in proximity of said tangential zone between said rotor (3, 13, 23) and said sealing element (6, 16, 26); means for timing rotation movements of the rotor (3, 13, 23) and the sealing element (6, 16, 26).

2) The machine of claim 1, wherein the surface of revolution (2, 12, 22), the rotor external surface (3, 13, 23) and external surface of the rotary sealing element (6, 16, 26) are cylindrical in shape.

3) The machine of claim 2, wherein the rotor external surface (3) and the external surface of the rotary sealing element (6) have equal diameters.

4) The machine of claim 2, wherein the rotor (13) exhibits two identical blades (15) which are diametrically opposite and wherein the cylindrical surface of said rotary sealing element (16) has a diameter which is exactly equal to half a diameter of the external cylindrical surface of the rotor (13).

5) The machine of claim 1 or 2, wherein the rotor (23) exhibits three angularly equidistanced blades (25), and wherein there are two diametrically opposite rotary sealing elements (26), said two inlet mouths (28) being situated in practically diametrically opposite positions, as are said two outlet mouths (29); there being provided means for introducing a pressurised fluid into the annular chamber (24) through the inlet mouths (28), to which a known-type distributor is associated, which distributor can selectively introduce said pressurised fluid through one or the other of the two inlet mouths (28) according to a timed sequence in accordance with positions assumed by the blades (25) with respect to the sealing elements (26).

6) The machine of an one of the preceding claims, wherein said means for timing the rotary movements of the rotor (3) and the sealing element (6) comprise a mechanical transmission (40) which is external of the cavity of the body (1).