EP0728948A1 - Scroll vacuum pump - Google Patents

Abstract

Vacuum pump with circular translation cycle comprising a fixed body (100) having a fixed disc (114) which has on at least one of its sides a spiral-shaped projection (123), a movable disc (131) opposite the disc fixed (114) and also having at least one spiral-shaped projection (133) interposed with the spiral-shaped projection (123) of the fixed disc (114) and of the same angular amplitude, a mechanism by which the movable disc (131 ) is connected to said body (100) and supported by it, to control a circular translational movement of the movable disc (131) relative to said body (100), motor means (120) for driving the movable disc (131) by the intermediary of a pump shaft (140), said pump also comprising a device for limiting circular translation travel: said mechanism comprises two bearings (182,190) carried by the pump shaft (140), which is in the central position by relative to the fixed body (100); the circular translation movement limiting device consists of a crown (201) having fixed teeth (202) between which teeth (212) are interlocked with the movable disc (131) <IMAGE>

Description

The present invention relates to a pump, in particular a vacuum pump, with a circular translation cycle.

More specifically, it relates to a vacuum pump with circular translation cycle comprising a fixed body having a fixed disc which has on at least one of its sides a spiral-shaped projection, a movable disc opposite the fixed disc and also having at least a spiral-shaped projection interposed with the spiral-shaped projection of the fixed disc and of the same angular amplitude, a mechanism by which the movable disc is connected to and supported by said body, to control a circular translational movement of the movable disc by relation to said body during operation of the pump, motor means for driving the movable disc via a pump shaft and causing it to effect said movement of circular translation, said pump also comprising a device for limiting the movement of circular translation guiding the mobile disc in its circular translational movement, avoiding any twisting.

A pump of this type is for example described in FR-A-2 141 402. If such a pump according to this document gives excellent results, it nevertheless has the disadvantage of comprising numerous parts and of being bulky, in particular radially. due in particular to the fact that said mechanism consists of three cranks coupled in a synchronized manner with each other and arranged at the periphery of the pump, these cranks ensuring by themselves the limitation of the circular translation movement.

The object of the present invention is to produce a pump of the above type which does not have these drawbacks.

Thus, according to the invention, a vacuum pump with circular translation cycle comprising a fixed body having at least one fixed disc which has on one of its sides a projection in the form of a spiral, a movable disc opposite to the fixed disc and also having at least one spiral-shaped projection interposed with the spiral-shaped projection of the fixed disc and of the same angular amplitude, a mechanism by which the movable disc is connected to and supported by said body to control movement of circular translation of the movable disc with respect to said body during the operation of the pump, motor means for driving the mobile disc via a pump shaft and causing it to effect said circular translation movement, said pump also comprising a circular translation movement limiting device, said mechanism comprising at least one bearing carried by the pump shaft, characterized in that said pump shaft is in central position relative to the fixed body, and the translation movement limiting device circular consists of a crown having fixed teeth between which interlocking teeth of the moving disc.

A limiting device thus designed is capable of ensuring the travel limitation or anti-torsion function, even when the pump is dimensioned to generate large volumes which can go up to 100 m ³ / h, or even 500 m ³ / h, and even beyond.

Preferably, the fixed teeth are limited by cylindrical surfaces with an axis parallel to the axis of the pump and the section of which, by a plane perpendicular to said axis, is composed of arcs of circles of radii R and r, respectively, whose centers are on a circle of radius R _p centered on said axis, arcs extending inside and arcs extending outside said circle of centers.

Advantageously, the movable teeth are limited by cylindrical surfaces with an axis parallel to the axis of the pump and the section of which, by a plane perpendicular to said axis, is composed of arcs of the same circles extending outside and within, respectively, said circle of centers.

Preferably, α being the angle between two fixed or mobile teeth and E the eccentricity, which corresponds to the radius of the cylinder described by the mobile axis around the fixed axis of the pump, $${\text{R = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{+}\frac{\mathit{\text{E}}}{\text{4}}{\text{and r = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{-}\frac{\mathit{\text{E}}}{\text{2}}\text{.}$$

Advantageously, the radius of the crank is adjustable.

Preferably, the axis of the passage which receives the end of the pump shaft is slightly offset with respect to the axis of the external surface of the bearing in which said passage is formed and which supports the movable disc via bearings received by said outer surface; advantageously, the eccentric bearing of the pump shaft has its axis offset with respect to the axis of a ring which surrounds it and which receives a bearing for a bearing hub.

Preferably, said mechanism comprises two bearings both carried by the pump shaft, and spaced axially.

Advantageously, the pump also comprises a metal sealing bellows surrounding the pump shaft and one end of which is integral with the movable disc and the other of the fixed body.

Preferably, the pump comprises only a single spiral projection on the fixed disc and a single spiral projection on the movable disc.

Advantageously, the spiral projections of the fixed disc and the spiral projections of the movable disc are separated by a small constant play regardless of the position of the movable disc.

• la figure 1 est une vue en coupe longitudinale partielle d'une pompe selon l'invention ;
• la figure 2 est une vue en coupe selon ll-ll de la figure 1 ;
• la figure 3 est une vue en coupe selon III-III de la figure 1 ;
• les figures 4 et 5 sont des schémas géométriques montrant la construction des dents du dispositif de la figure 3 ;
• les figures 6 et 7 sont des coupes, à plus grande échelle, selon les lignes VI-VI et VII-VII, respectivement, de la figure 1.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of example with reference to the appended drawings in which:

• Figure 1 is a partial longitudinal sectional view of a pump according to the invention;
• Figure 2 is a sectional view along II-II of Figure 1;
• Figure 3 is a sectional view along III-III of Figure 1;
• Figures 4 and 5 are geometric diagrams showing the construction of the teeth of the device of Figure 3;
• Figures 6 and 7 are sections, on a larger scale, along lines VI-VI and VII-VII, respectively, of Figure 1.

Referring to Figures 1 to 7, a pump according to the invention comprises a fixed body 100 consisting of a sleeve 111, a spacer 112 and a flange 114, assembled by screws such as 115, with interposition of seals 116, 117; the flange 114 has, on the side directed towards the inside, that is to say towards the sleeve 111, a projection in the form of a spiral 123, with which is inserted a projection in the form of a spiral 133 of the same angular amplitude presented by a movable plate 131 on one side of this plate 131; on the other side of this movable plate, this supports, thanks to screws 171, a barrel 170 of generally cylindrical shape.

The spiral projections 123 and 133 are separated by a small constant play regardless of the position of the movable disc 131; in FIG. 3, this play, generally of the order of tens of microns, has been exaggerated to be visible.

On the side of its end by which it is fixed to the plate 131, the barrel 170 has a radial rim 181 extended towards the inside of the barrel 170 by a ring 182 supporting rolling means 148 installed inside the ring 182; the rolling means 148 surround a bearing 147 on which they are mounted, said bearing 147 having internally a passage 183 of frustoconical shape whose opening of larger diameter is located towards the inside of the barrel 170.

On the side opposite to that which cooperates with the spacer 112, the sleeve 111 has radial arms 177 directed towards the inside of the sleeve 111, for example three radial arms 177 spaced 120 degrees apart, only one being visible in FIG. 3; from the inner end of the arms 177 extends axially, along the axis 155 of the pump, and inside the sleeve 111, a barrel 180 of generally cylindrical shape, the barrel 180 also extending inside the barrel 170; in the vicinity of its innermost end with respect to the sleeve 111, the barrel 180 supports from the outside rolling means 184.

Externally, the radial fingers 177 of the sleeve 111 support by screws 176 a casing 174 connecting the pump to a motor 120 partially shown of which the end of the motor shaft is seen at 121; the casing 174 has an inner wall 175 carrying a rolling bearing 173.

The pump includes a pump shaft 140; the pump shaft 140 has a frustoconical end 144, the shape of which is complementary to that of the passage 183 of the bearing 147; the bearing 147 is secured to the end 144 of the pump shaft 140 by interlocking and tightening in 185; the other end 172 of the shaft 140 is intended for driving the shaft 140 in rotation by the motor 120; to do this, the motor shaft 121 is secured, thanks to a key 122, in rotation with a driving nut 129, the end 172 of the pump shaft 140 being secured, thanks to a key 188, in rotation d 'a walnut led 186; the leading nuts 129 and led 186 carry fingers respectively 128, 187 connected by a flexible coupling 149.

The pump shaft 140 has two cylindrical bearing surfaces having the axis 155 of the pump as axis: a bearing surface 179 in its central region cooperating with the rolling means 184 and a bearing surface 189 close to its end 172 and supported by the bearing at bearing 173; the frustoconical end 144 of the shaft 140 has as its axis the axis 165 which is offset with respect to the axis 155 while remaining parallel to it, and which is the axis of the barrel 170.

To ensure rigorous parallelism between the axes 155 and 165, it is possible, as shown in the variant shown, to provide another bearing 178 eccentric with respect to the axis 155; this bearing 178 of axis 165 supports a bearing means 190 connected to the barrel 170 by radial arms 191 interposed circumferentially between the radial arms 177 integral with the sleeve 111.

; l'axe 155 est fixe et l'axe 165 décrit un cylindre, autour de l'axe 155, dont le rayon correspond à l'excentration E ; dans ce mouvement, en choisissant les rayons R et r en sorte que R = r + E, les dents 212 suivent le profil des dents 202 en sorte que le fût 170, donc le plateau 131, est guidé dans son mouvement de translation circulaire, sans aucune torsion. Comme cela ressort des figures 4 et 5, on voit que E, α, R_p, R et r sont reliés par la relation R_p. Sin $\frac{\text{α}}{\text{4}}$

= $\frac{\text{1}}{\text{2}}$

(R+r) qui combinée à la précédente donnant l'excentration conduit à $${\text{R = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{+}\frac{\mathit{\text{E}}}{\text{2}}{\text{, r = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{-}\frac{\mathit{\text{E}}}{\text{2}}$$

According to an important feature, there is provided a device for limiting the movement of circular translation 200 which, according to the invention, consists of a ring 201 having teeth 202 integral with the frame 100 between which nests 212 teeth formed at the 'free transverse end of the movable barrel 170; as is better visible in Figures 3 to 5, the fixed teeth 202 and mobile 212 have semi-circular profiles constructed from circles of radii R and r whose centers are on a so-called primitive circle of radius R _p ; more precisely, the fixed teeth 202 are limited by cylindrical surfaces with an axis parallel to the axis 155 and the section of which, by a plane perpendicular to the axis 155, is composed of arcs of circles 203, 204 of radii respectively R and r, the centers of which are on a circle 205 of radius R _p and centered on the axis 155, the arcs 203 extending inside the circle 205 and the arcs 204 outside; the movable teeth 212 are limited by cylindrical surfaces with an axis parallel to the axis 165 or 155 and the section of which, by a plane perpendicular to these axes, is also composed of arcs of circles 203, 204, the arcs 203 s 'extending outside the circle 205 and the arches 204 inside; the angle α between two teeth 202, or 212, depends of course on the number N of teeth: α = $\frac{\text{2π}}{\mathit{\text{NOT}}}$

; the axis 155 is fixed and the axis 165 describes a cylinder, around the axis 155, whose radius corresponds to the eccentricity E; in this movement, by choosing the radii R and r so that R = r + E, the teeth 212 follow the profile of the teeth 202 so that the barrel 170, therefore the plate 131, is guided in its movement of circular translation, without any twist. As shown in Figures 4 and 5, we see that E, α, R _p , R and r are connected by the relation R _p . Sin $\frac{\text{α}}{\text{4}}$

= $\frac{\text{1}}{\text{2}}$

(R + r) which combined with the previous one giving the eccentricity leads to $${\text{R = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{+}\frac{\mathit{\text{E}}}{\text{2}}{\text{, r = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{-}\frac{\mathit{\text{E}}}{\text{2}}$$

The invention also provides for allowing adjustment of the offset, as shown in Figures 6 and 7; according to FIG. 6, the axis of the frustoconical end 144 of the pump shaft 140, and therefore the axis of the passage 183 which receives it, is slightly offset with respect to the axis 165 of the outer surface 192 of the bearing 147 which receives the bearings 148 which support the barrel 170; the eccentricity E being the transverse distance between this axis 165 and the axis 155 of the cylindrical bearing surface 179 of the pump shaft 140, mechanically linked to the frustoconical part 144, it can be seen that it suffices to turn the bearing 147 relative to it so that the distance between the axis 165 and the axis 155, that is to say the eccentricity E, varies.

A similar arrangement makes it possible to adjust the eccentricity E at the same level as the bearing means 190; as seen in Figure 7, the eccentric bearing 178 of the pump shaft 140 has its axis offset from the axis of a ring 193 which surrounds it and which receives the bearing of the bearing hub 190; here again, by rotating the ring 193 relative to the shaft 140, the distance between the axes 155 and 165 is modified.

The pump which has just been described has an arrangement such that the plane of inertia of the moving masses is located axially in line with the spacer 112; thus, a single dynamic balancing mass 197 located in this region, secured to the bearing 147, is sufficient for balancing the assembly.

The suction 156 of the pump is provided radially in the spacer 112 and the discharge 157 is axial, downstream of a non-return valve 159.

As soon as the pump is put into service, the pumped fluid is subjected to the continuous and progressive compression effect due to the movement in circular translation of the movable spiral projections relative to the fixed spiral projections.

It is possible, if desired, to completely isolate the pump enclosure, where the vacuum is created, from the outside and from the rest of the pump; it suffices to have, as shown in FIG. 1, a metal bellows 160 around the was 170; one end of the bellows 160 is fixed to a flange 196 formed on the outer surface of the barrel 170 in line with its radial rim 181; the other end of the bellows 160 is fixed to a ring 194 secured to the fixed body 100 by the screws 176 and screws 195. Such an arrangement increases the number of possible applications of the pump which thus forms part of the so-called dry pumps whose active parts are isolated from the outside and free from any lubricant, oil or grease.

The metal bellows 160 used to achieve the complete sealing of the pumping system is thus positively protected against any functional or accidental torsional force due to the limiting device 200; the life of the bellows 160 is therefore practically unlimited.

Such a pump intended to generate volumes of up to 500 m ³ / hour or more is advantageously provided with a cooling oil circuit, the entry of which can be seen in 198 in FIG. 1.

Claims (11)

Vacuum pump with circular translation cycle comprising a fixed body (100) having at least one fixed disc (ll 4) which has on one of its sides a projection (123) in the form of a spiral, a movable disc (131) opposite the fixed disc (114) and also having at least one spiral-shaped projection (133) interposed with the spiral-shaped projection (123) of the fixed disc (114) and of the same angular amplitude, a mechanism by which the movable disc ( 131) is connected to said body (100) and supported by it, to control a circular translational movement of the movable disc (131) relative to said body (100) during operation of the pump, motor means (120) for driving the movable disc (131) by means of a pump shaft (140) and causing it to perform said circular translation movement, said pump also comprising a device for limiting circular translation travel, said mechanism comprising at least one bearing (182,190 ) p orted by the pump shaft (140), characterized in that the said pump shaft (140) is in the central position relative to the fixed body (100), and the device for limiting the displacement in circular translation consists of a crown (201) having fixed teeth (202) between which nest teeth (212) integral with the movable disc (131). Pump according to claim 1, characterized in that the fixed teeth (202) are limited by cylindrical surfaces with an axis parallel to the axis (155) of the pump and whose section, by a plane perpendicular to said axis (155 ), is composed of arcs of circles (203, 204) of radii R and r, respectively, whose centers are on a circle (205) of radius R _p centered on said axis (155), arcs (203) s extending inside and arches (204) extending outside said circle of centers (205). Pump according to claim 2, characterized in that the movable teeth (212) are limited by cylindrical surfaces with an axis parallel to the axis (155) of the pump and the cross section of which, by a plane perpendicular to said axis (155), is composed of arcs of the same circles (203, 204) extending outside (203) and inside (204), respectively, of said circle of centers (205). Pump according to claims 2 and 3, characterized in that a being the angle between two fixed (202) or mobile (212) teeth and E the eccentricity, which corresponds to the radius of the cylinder described by the mobile axis (165 ) around the fixed axis (155) of the pump, $${\text{R = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{+}\frac{\mathit{\text{E}}}{\text{2}}{\text{and r = R}}_{\text{p}}\text{Sin}\frac{\text{α}}{\text{4}}\text{-}\frac{\mathit{\text{E}}}{\text{2}}\text{.}$$

Pump according to one of claims 1 to 4, characterized in that the crank radius is adjustable. Pump according to claim 5, characterized in that the axis of the passage (183) which receives the end of the pump shaft (140) is slightly offset from the axis (165) of the outer surface ( 192) of the bearing (147) in which said passage (183) is formed and which supports the movable disc (131) by means of bearings (148) received by said external surface (192). Pump according to claim 5, characterized in that the eccentric bearing (178) of the pump shaft (140) has its axis offset with respect to the axis of a ring (193) which surrounds it and which receives a bearing for a bearing hub (190). Pump according to one of claims 1 to 7, characterized in that the said mechanism comprises two bearings (182, 190) both carried by the pump shaft (140), and axially spaced. Pump according to one of claims 1 to 8, characterized in that it further comprises a metal bellows (160) sealing surrounding the pump shaft (140) and one end of which is integral with the movable disc (131 ) and the other of the fixed body (100). Pump according to one of claims 1 to 9, characterized in that it comprises only a single spiral projection (123) on the fixed disc (114) and a single spiral projection (133) on the movable disc (131). Pump according to one of claims 1 to 10, characterized in that the spiral projections (123) of the fixed disc (114) and the spiral projections (133) of the movable disc (131) are separated by a small constant play regardless of the position of the movable disc (131).

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