CA2595360A1 - Multi-shaft vacuum pump with circular translation cycle - Google Patents

Abstract

This vacuum pump comprises: - a fixed disc (8) integral with a fixed body (2) and having a spiral (14), - a movable disk (4) facing the fixed disc (8) and having a spiral (16) interposed with the spiral (14) of the fixed disk (8), - a connection between the fixed body (2) and the mobile disk (4), this link having at least two cranks (18) each comprising two shafts (26, 28) offset by the same eccentricity, - motor means (6) for driving the mobile disk (4) in a translation movement circular, these motor means comprising a motor (6) having a shaft of output (30) parallel to the axes of the disks, and the output shaft (30) of the motor (6) being centered on the axis of the movable disk (4) and driving it by means of a coupling piece (32) having the same eccentricity as the cranks (18).

Description

Vacuum pump with circular cycle with several shafts The present invention relates to a vacuum pump with a translation cycle circular with several trees.
A pump of this type generally comprises a fixed body with a fixed disc having on one of its faces a projection in the form of a spiral so mobile disk, facing the fixed disk and presenting on the side of the disk fixes a corresponding projection in the form of a spiral. The two spirals, one fixed and a mobile, are of the same angular amplitude and intercalated one in the other.
A mechanism for driving the moving disk in a movement of circular translation with respect to the fixed disk. The connection between the disk mobile and the fixed body of the pump is provided by several trees, most often three.
Such a pump is for example described in the document FR-A-2 141 402. As indicated in this document, such a pump can be an entirely dry and waterproof pump. It gives excellent results But has the disadvantage of having many parts and being cumbersome. It is also noted that the pump described in this document uses a coolant to cool the parts.
The present invention therefore aims to provide a new pump to empty, dry, watertight and clean (that is, without the risk of pollution fluid pumped), of simple structure and which is also compact. Preferably, this pump will discharge at atmospheric pressure the aspirated gaseous fluid to create vacuum at atmospheric pressure. In addition, the maintenance of this new pump will be facilitated compared to the pumps of the prior art known.
For this purpose, the invention proposes a translational cycle vacuum pump.
circular comprising:
- a fixed disc fixed to a fixed body and having on one of its faces a projection in the form of a spiral, a mobile disk facing the fixed disk and presenting on the disc fixes a spiral-shaped projection interposed with the projection in made of spiral of the fixed disk, a link between the fixed body and the mobile disk, this connection having at least two cranks, each crank having two shafts parallel but offset from the same eccentricity,

two - motor means for driving the mobile disk in a translational movement circular relative to the fixed disk.
According to the invention, the motor means comprise an engine having an output shaft parallel to the axes of the fixed and mobile disks; the tree of exit the engine is substantially centered on the axis of the movable disk and drives the ci to by means of a coupling piece having an eccentricity corresponding to the eccentricity of the cranks; the two spiral-shaped projections are without contact with each other and have an axial clearance controlled by the assembly of the cranks, and the axial forces exerted on the pump are resumed essentially at the cranks.
This new structure of a multi-shaft vacuum pump is very interesting because it allows for a better distribution of efforts at within the pump, especially at the level of the various rolling bearings. Such a pump is clean because a gaseous fluid pumped through the pump does not come into contact no wear parts such as a seal or the like.
In a preferred embodiment of a vacuum pump according to the invention, the motor is fixed on a plate parallel to the mobile disk, and this platinum has housing for a shaft of each crank. Of this platinum is placed at the heart of the pump and carries both the engine and the mobile disk. This allows on the one hand to simplify the structure of the pump and on the other hand to make it more compact. In this embodiment, the platinum form for example the bottom of a cylindrical tube in which is housed the engine. The fixed body then comprises for example an outer casing connecting the cylindrical tube to the fixed disc.
In a vacuum pump according to the invention, a metal bellows can be used to tightly connect the periphery of the moving disk to body fixed vacuum pump. Such a bellows makes it possible to ensure a seal between a mobile part in translation (circular) and a fixed body. In case the pump to vacuum comprises a cylindrical tube, the metallic bellows then surrounds preferably the cylindrical tube. In this way, the bellows can be relatively large size and the stresses exerted on it are of this made less than for a small bellows.
Advantageously, the invention provides that a second bellows metal, also sealingly mounted between the periphery of the disk

3 mobile and the fixed body, surrounds the first metal bellows. We gets from so a space between the two metal bellows. By monitoring the pressure within this space, it is possible to immediately detect a failure of one of the bellows. In this way, it is possible to ensure perfect control of the pump seal.
In the embodiment in which the vacuum pump comprises a cylindrical tube, it can be provided that the opposite side to the plate, the tube cylinder receives a fan, and that orifices are provided in the platinum to allow ventilation of the motor housing.
The vacuum pump may also comprise ventilation means to cool the face of the fixed disk opposite the moving disk.
When the pump is equipped with such ventilation means, it is not necessary to provide a coolant circuit to avoid a overheating of the pump during operation. This avoids a source of possible pollution of the gaseous fluid pumped by the pump according to the invention.
For even better cooling of the pump discs, can provide that at least one projection forming a spiral on a disc is hollowed out at near the heart of the spiral.
For the delivery of gaseous fluid pumped under pressure atmospheric, the fixed disk presents, for example, substantially in the center of the spiral, a discharge orifice opening on the face opposite to the spiral, and this discharge orifice is optionally provided with a valve of discharge.
To promote the discharge at atmospheric pressure of the pumped fluid, the thickness of the spiral projections present at the heart of the spiral an increasing thickness so as to form a shaped spiral end of bulb.
Details and advantages of the present invention will emerge more clearly from the description which follows, made with reference to the attached schematic drawings sure which :
FIG. 1 is a longitudinal sectional view of a vacuum pump according to the invention, FIG. 2 is a sectional view along section line II-II of FIG.
figure 1, and FIG. 3 is a sectional view along section line III-III of FIG.

4 figure 1.
FIG. 1 shows a vacuum pump with a translation cycle circular. This pump comprises in particular a fixed body 2, a mobile disc 4 and a motor 6.
In the preferred embodiment shown in FIG.
fixed body 2 consists essentially of three elements: a fixed disk 8, a casing 10 and a cylindrical tube 12.
The fixed disk 8 has on its inner face a projection in the form of 14. The shape of the latter is visible in FIG.
mobile 4 facing the fixed disk 8. On its face facing the fixed disk 8, the disk mobile also has a spiral-shaped protrusion 16. The spiral 16 of the mobile disk 4 is nested with the spiral 14 of the fixed disk 8, as can see also in Figure 2 (to simplify the view, Figure 3 does not represent not the spiral 14 fixed, or the housing 10). The spirals 14 and 16 are separated one of the other by a constant axial play, whatever the position of the disc mobile 4 by relative to the fixed disk 8. This game is for example of the order of 5/1 00th of mm. We also finds a radial play between the spirals. This radial game is the same order of magnitude than the axial clearance (about 0.05 mm).
The movable disc 4 is supported by the fixed body 2 via of three cranks 18 of equal eccentricity E and coupled and acting of way synchronized with each other to obtain a translation movement circular of the mobile disc 4 relative to the fixed body 2, and more particularly its fixed disk 8, during operation of the pump.
The cranks 18 connect the mobile disc 4 to the fixed disc 8 of such so on the one hand that the mobile disk 4 is perfectly guided to get a almost perfect control of the axial play at the level of the projections in the form of spiral 14, 16 and on the other hand that the axial forces between these two disks are resumed at level of these cranks. The axial play in question here at the level of projections spiral-shaped 14, 16 indicates that between the top of a spiral 14, 16 and the disc 4, 8 which faces him is a game 19 substantially constant (of order 0.05 mm).
The cylindrical tube 12 has a shaft of longitudinal axis parallel to the axis of the fixed discs 8 and mobile 4 as well as a transverse bottom 20 and therefore situated in a plane parallel to those of the disks. This bottom 20 has three bores 22, each of which receives a crank 18. Each crank 18 comprises a trunnion 24, a lower shaft 26 and an upper shaft 28. The trunnion 24 is at each time disposed at the interface between the bottom 20 and the disk mobile 4.
The lower shaft 26 of each crank 18 is housed with bearings

5 corresponding in a bore 22 of the bottom 20 while the trees higher 28 are each housed with corresponding bearings in housing provided for this purpose in the movable disk 4. The axes of the lower shafts 26 and upper 28 are parallel and offset by a distance corresponding to Eccentricity E.
Each bore 22 has a shoulder against which come releasing ball bearings guiding the lower shaft 26 of a crank 18. The trunnion 24 comes to rest on these ball bearings on the opposite side to the aforementioned shoulder. A similar arrangement is made at the housing level provided in the mobile disk 4. Each of these dwellings has a shoulder against which abut ball bearings receiving the tree upper 28 of the crank 18 and the opposite side to this shoulder, the trunnion 24 comes to rest on the ball bearings. These bearings are maintained in their housing, both at the mobile disk 4 and the bottom 20, using a ring held by screws 29.
This type of assembly corresponds to a vacuum pump in which the mobile disk 4 tends to approach axially fixed disk 8.
The translational movement of the mobile disk 4 relative to fixed disk 8 is controlled by the motor 6. The latter is disposed to interior of the cylindrical tube 12 and is fixed on the bottom 20 thereof. In the form of preferred embodiment of the invention shown in the drawings, the output shaft 30 of motor 6 is connected to the movable disc 4 by a coupling piece 32. This last presents here the shape of a sleeve with two dwellings cylindrical circular, one in the extension of the other and staggered a value corresponding to the eccentricity E. The cylindrical housing being of motor side receives the output shaft 30 of the motor while the housing cylindrical located on the side of the movable disc 4 receives a crank pin 34 making protrusion of the face of the movable disc 4 opposite the spiral 16 and a rolling with needles. In this embodiment shown in the figures, the pin 34 is centered with respect to the movable disc 4. The needle bearing resumes

6 essentially radial forces at the motor shaft. We notice sure the figure a ball bearing near the output shaft 30. This rolling only for the purpose of holding the motor shaft when the motor is disassembled for to be maintained, repaired, or changed.
We note in Figures 1 and 3 the presence of a mass balancing device 36 around the coupling piece 32 at the crankpin 34.
This mass is calculated and positioned to perform a balancing dynamics of the pump during operation thereof.
The housing 10 of the fixed body connects, in the embodiment visible on FIG. 1, the periphery of the fixed disc 8 with the free edge of the tube cylindrical 12, free edge which is opposite the bottom 20.
We also note the presence of two bellows 38, 38 'metal in Figure 1. Each of these bellows 38, 38 'is mounted in a sealed manner on the one hand on a peripheral edge of the mobile disc 4 and on the other hand on the box 10. The fastening bellows 38, 38 'is for example made by welding.
The two bellows 38, 38 'thus surround the cylindrical tube 2 (fixed) to inside which is the word 6, the bellows 38 'surrounding the bellows 38. The presence of a single bellows is sufficient to allow a bon_fonctionnement of the vacuum pump according to the invention. The second bellows is planned here for of the security reasons. A pressure sensor connected to the free space between two bellows can immediately detect any leakage at the level of one of the bellows, the other bellows still sealing the pump.
The bellows 38, 38 'are used to make a metal complete sealing of the pump. They are protected against any effect of twist of the makes the kinematics of the drive system. To limit the constraints exercised on these bellows, they extend over almost the entire height of the pump, as can be seen in Figure 1. Bellows (or only one bellows) less length, could also be suitable.
The housing 10 has an inlet opening 42 which allows realize, in the example shown, a radial admission of gaseous fluid, proximity of the fixed discs 8 and mobile 4. An enclosure to empty (no represented in the drawings) is connected to the pump (by means not shown) to the inlet opening 42. As soon as the pump is put into operation, the fluid gaseous to pumping is subjected to the continuous and progressive effect of compression obtained through at

7 relative movement between the two spirals 14 and 16. In a known manner (cf.
example FR-2 141 402) the gaseous fluid in the space between the bellows 38 'outside and the housing 10 is driven to a discharge port 44 himself located in the center of the spiral 14 of the fixed disk 8. This orifice of repression 44 is provided with a valve 46 allowing the discharge of the gaseous fluid at the pressure atmospheric.
During this operation, the spirals tend to heat up. A
first ventilation group 48, represented very schematically on the figure 1, is disposed on the face of the fixed disk 8 opposite the face carrying the spiral 14.
An arrow 50 represents an example of air movement allowing the ventilation of the fixed disk 8.
A second ventilation group 52 is disposed in the cylindrical tube 12 for cooling the motor 6 and the mobile disk 4. This second ventilation group 52, very schematically represented, draws air to the outside of the pump to make it run inside of it according to a illustrated by way of example by arrows 54. To allow such a passage of air, orifices are provided on the one hand in the bottom 20 of the cylindrical tube and on the other hand in the fixed body 2 so as to allow outside air of penetrate between the outer surface of the cylindrical tube 12 and the interior of the bellows interior 38.
To further promote the cooling of the fixed disk 8 and mobile 4, a recess 56 is formed in each of the spirals 14 and 16, as can be notice it on the drawings. The spirals 14 and 16 each have their own end located substantially in the center of the corresponding disc shape of a bulb 57 due to the widening of the projection forming the spiral corresponding towards the center of the disc. So the air set in motion by the groups of ventilation can enter the recesses 56 and thereby achieve a better cooling the spirals 14 and 16 and thus the disks 8 and 4 correspondents.
The vacuum pump described above is a vacuum pump in its entirety dry, which works without oil or coolant. This pump is also completely sealed with, thanks in particular to the two bellows, a perfect control of this tightness.
The pump described here is a so-called clean pump. The pumped fluid does not no wear parts Qoints, etc ...) from the inlet opening WO 2006/07732

8 PCT / FR2006 / 000132 until it exits through the discharge port 44. Control of the axial clearance between the protrusions in the form of a spiral 14, 16 makes it possible to remove the joints that are find usually between each spiral and the disc facing the said spiral.
The absence of wear parts along the path of the pumped fluid makes it possible to preserve it from any pollution.
A pump such as the one described above can be used for relatively low flow rates. As a non-limitative example but only illustrative example, such a pump may have, for example, a generated volume of the order of 30 m3 / h.
A vacuum pump according to the invention can find applications by example in the field of nuclear, in the manufacture of components in the pharmaceutical, food, etc. industry.
listing of applications is of course not exhaustive. This type of pump can be in use wherever great attention is needed to avoid pollution a fluid transported.
While for pumps of equivalent sizes of the prior art it is usually necessary to provide a coupling to a primary pump, the pump described can flow back directly to atmospheric pressure. This rejection direct to the atmospheric pressure can be realized here thanks to the presence of a valve 46 at the outlet but also at the bulb shape 57 to ends of the spirals. The good ventilation of the pump also favored by the recesses 56 made at the level of said bulbs, is also an element important to allow such rejection. Indeed, given the variation of pressure, the heating in the pump is relatively suitable cooling must be provided.
The structure of the pump described is simple, even if it comprises four trees. In addition, it allows to have a compact pump. In addition, the maintenance of this pump is simplified. The number of joints and parts wear is very limited.
An important advantage of the structure presented above with a central motor shaft and peripheral trees is the resumption of efforts radial.
These are essentially cashed by the described needle bearing. The bearing load at the level of the peripheral shafts is limited and allows the use of bearings with higher axial stiffness compared to bearings

9 used with comparable pumps of the prior art.
The present invention is not limited to the embodiment preferential described above by way of non-limiting example. She concerned also all embodiments within the reach of the skilled person within the scope of the claims below.
For example, the number of trees (cranks) can be changed without departing from the scope of the invention. Other modifications, concerning for example the shape of the fixed body, the cooling of the parts (even possibly with a coolant), the motor assembly, the bellows, etc. can also be made without departing from the invention.

Claims (12)

A circular translation cycle vacuum pump comprising:
- A fixed disk (8) integral with a fixed body (2) and having on one with its faces a spiral projection (14), a mobile disk (4) facing the fixed disk (8) and presenting on the side of the fixed disc (8) a spiral-shaped projection (16) interposed with the protrusion in the form of a spiral (14) of the fixed disc (8), a link between the fixed body (2) and the mobile disk (4), this connection having at least two cranks (18), each crank (18) comprising two shafts (26, 28) parallel but offset by the same eccentricity, - motor means (6) for driving the mobile disk (4) in a translational movement circular with respect to the fixed disc (8), characterized in that the motor means comprise an engine (6) having an output shaft (30) parallel to the axes of the fixed disks (8) and mobile (4), and in that the output shaft (30) of the motor (6) is substantially centered on the axis of the movable disk (4) and drives it with a coin coupling (32) having an eccentricity corresponding to eccentricity of the cranks (18), in that the two spiral projections (14, 16) are without contact with each other and have an axial clearance controlled by the assembly of the cranks (18) and in that the axial forces exerted on the pump are resumed essentially at the cranks (18). Vacuum pump according to Claim 1, characterized in that the motor (6) is fixed on a plate (20) parallel to the mobile disc (4), and what this plate (20) has housing (22) for a shaft (26) of each crank (18). Vacuum pump according to Claim 2, characterized in that the platinum forms the bottom (20) of a cylindrical tube (12) in which is housed the engine (6). Vacuum pump according to Claim 3, characterized in that the fixed body (2) comprises an outer casing (10) connecting the cylindrical tube (12) fixed disk (8). Vacuum pump according to one of Claims 1 to 4, characterized in that a metal bellows (38) sealingly connects the periphery of the disk mobile (4) to the fixed body (2) of the vacuum pump. Vacuum pump according to claims 3 and 5, characterized in that the metal bellows (38) surrounds the cylindrical tube (12). Vacuum pump according to one of Claims 5 or 6, characterized in that what a second bellows (38 ') metal, also mounted so watertight between the periphery of the movable disc (4) and the fixed body (2) surrounds the first bellows (38) metal. Vacuum pump according to Claim 3, characterized in that opposite side to the plate (20), the cylindrical tube (12) receives a group of ventilation (52), and in that apertures are provided in the plate (20) for allow ventilation of the motor housing (6). Vacuum pump according to one of Claims 1 to 8, characterized in that that ventilation means (48) are provided for cooling the face of the disk fixed (8) opposite to the movable disc (4). Vacuum pump according to one of Claims 1 to 9, characterized in that the fixed disk (8) has substantially in the center of the spiral (14), a discharge orifice (44) opening on the face opposite to the spiral (14), and in this discharge port (44) is provided with a discharge valve (46). Vacuum pump according to one of Claims 1 to 10, characterized in that at least one spiral protrusion (14, 16) on a disk (8, 4) is hollowed out near the heart of the spiral (14, 16). Vacuum pump according to one of Claims 1 to 11, characterized in that the thickness of the spiral projections (14, 16) at the level of the heart of the spiral (14,16) an increasing thickness so as to form a end spiral shaped bulb (57).