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(11) | EP 3 315 782 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | VACUUM PUMP |
| (57) The invention provides a vacuum pump (1) for lowering pressure in a device (120),
the vacuum pump (1) comprising a vacuum chamber (2), a rotor (3) comprising slots
(31), vanes (4, 41, 42), a fluid inlet (5), a primary fluid outlet (61) and a secondary
fluid outlet (62). A volume of the chamber wall defined by a first virtual outlet
vane (601) in contact with the first secondary outlet point (621) and a second virtual
outlet vane (602) which is subsequent to the first virtual outlet vane (601) is at
least the 66% of a volume of the chamber wall defined by a third virtual outlet vane
(603) in contact with the second primary outlet point (612) and a fourth virtual outlet
vane (604) which is preceding to the third virtual outlet vane (603). The primary
fluid outlet (61) comprises primary blocking means (71) adapted for sealing the fluid
communication between the primary fluid outlet (61) and the first outside fluid zone
(100) if the pressure in the primary fluid outlet (61) is lower than a first predetermined
value. |
TECHNICAL FIELD
[0001] This invention belongs to the field of vacuum pumps comprising a rotor with one or more vanes inserted in it, the rotor being in turn contained in a vacuum chamber, where subspaces are created between the vane or vanes and the chamber wall when the rotor is moved.
STATE OF THE ART
[0002] Some applications need a vacuum pump which may help magnifying the effect of a force. Vacuum pumps usually comprise a pump chamber and a rotor housed inside the pump chamber. This rotor comprises one or more slots, so that a vane is at least partially introduced in each one of said slots. The pump chamber houses this rotor, but the inner volume of the pump chamber is greater than the volume occupied by the rotor and the vanes. Thus, when the rotor rotates, the vane or vanes have some space to exit the rotor due to centrifugal force or any other force provided in the pump. But this inner volume of the vacuum chamber is designed such that the vane or vanes go in and out the rotor alternatively, in such a way that the chambers which are created between two consecutive vanes and the corresponding portion of the chamber wall have a variable volume, depending on the position of the rotor. In the event of one single vane with a single slot, the slot allows the single vane exiting the rotor in two diametrically opposed locations, so that the vane divides the vacuum chamber in different chambers. A fluid inlet located in the chamber wall is in fluid connection with a device where pressure is intended to be lowered and feeds the vacuum chamber in an inlet point with a compressible fluid, such as air or any other gas. As this inlet point is fixed, but the vanes move with the rotor, this inlet point feeds different chambers while the rotor rotates. A fluid outlet is in turn located in an outlet point of the chamber wall, and is in fluid connection with an outside fluid zone, such as the atmosphere or a different device. When the pressure in this outlet point is greater than the pressure in the outside fluid zone, fluid exits the chamber.
[0003] These pumps work relatively well when pressure in the device where pressure is intended to be lowered is far from vacuum, but when the pressure in the device lowers, the pressure in the fluid outlet point can be lower than pressure in the outside fluid zone of the chamber. Thus there is a risk that fluid from the outside fluid zone enters the chamber by the fluid outlet point, increasing the pressure in the chamber which is in fluid connection with the outlet point, and thus penalizing the efficiency of this pump.
DESCRIPTION OF THE INVENTION
[0004] The invention provides a solution for this problem by means of a vacuum pump according to claim 1. Preferred embodiments of the invention are defined in dependent claims.
[0005] In a first inventive aspect, the invention provides a vacuum pump for lowering pressure in a device, the vacuum pump comprising
a vacuum chamber with a chamber wall; wherein the chamber wall comprises a minor point, which is the point of the chamber wall where the distance between the chamber wall and the rotor is minimum, and a maximum point, which is a point where a first virtual size vane is placed so that the volume enclosed by the first virtual size vane and, a second virtual size vane preceding to the first virtual size vane is maximum;
a rotor housed in the vacuum chamber, this rotor comprising at least one slot;
at least one vane, each vane being at least partially introduced in one slot of the rotor;
at least one fluid inlet being located between a first inlet point of the chamber wall and a second inlet point of the chamber wall, the first fluid inlet being suitable for being in fluid communication with the device where pressure is aimed to be lowered; and
a primary fluid outlet being located between a first primary outlet point of the chamber wall and a second primary outlet point of the chamber wall, the primary fluid outlet being in fluid communication with a first outside fluid zone of the vacuum pump;
a secondary fluid outlet being located between a first secondary outlet point of the chamber wall and a second secondary outlet point of the chamber wall, the secondary fluid outlet being in fluid communication with a second outside fluid zone of the vacuum pump, the distance between the first secondary outlet point and the minor point being lower than the distance between the first primary outlet point and the minor point;
wherein a volume of the chamber wall defined by a first virtual outlet vane in contact with the first secondary outlet point and a second virtual outlet vane which is subsequent to the first virtual outlet vane is at least the 66% of a volume of the chamber wall defined by a third virtual outlet vane in contact with the second primary outlet point and a fourth virtual outlet vane which is preceding to the third virtual outlet vane;wherein the chamber wall comprises a minor point, which is the point of the chamber wall where the distance between the chamber wall and the rotor is minimum;
wherein the primary fluid outlet comprises primary blocking means adapted for sealing the fluid communication between the primary fluid outlet and the first outside fluid zone if the pressure in the primary fluid outlet is lower than a first predetermined value.
[0006] Just as a definition, and without any limitation purposes, a compression zone is defined in the vacuum chamber, the compression zone being limited by
a first virtual compression vane located in contact with a major point; the major point being either the second inlet point or a maximum point, wherein a first virtual size vane placed in the maximum point causes that the volume enclosed by the first virtual size vane, a second virtual size vane preceding to the first virtual size vane and the portions of the chamber wall and the rotor between these virtual size vanes is maximum;
a second virtual compression vane located in contact with the minor point;
a portion of the rotor comprised between these two first and second virtual compression vanes, considered in the direction from the first virtual compression vane to the second virtual compression vane; and
a portion of the chamber wall between the major point and the minor point, considered in the direction from the first virtual compression vane to the second virtual compression vane.[0007] In the whole document, the term "chamber wall" includes every surface that limits the vacuum chamber, not only its lateral walls, but also includes the cover or the base of the vacuum chamber.
[0008] The concepts of "preceding" and "subsequent" should be understood in the advance direction of the rotor. In this sense, the preceding vane of a first vane is the vane which is more advanced in the advance direction than said first vane, the vane that "sees" the points before than this first vane. The subsequent vane of a first vane is therefore the vane which is more retarded in the advance direction than said first vane, the vane that "sees" the points later than this first vane.
[0009] In the vacuum pumps which has only one vane which crosses the rotor and exits the rotor in two different points, the concepts of "preceding" and "subsequent" refers to the halves of said vane: one half of the vane would be the preceding and the subsequent vane with respect to the other half of the vane.
[0010] This vacuum pump has an improved efficiency with respect to those of the state of the art, since the presence of fluid outlets allows the fluid exit during the first phase of pump operation, avoiding an unnecessary compression of the fluid before its exit through the fluid outlet. During the second phase of pump operation, the first blocking means in the primary fluid outlet avoids the entering of air into the vacuum chamber and only the secondary fluid outlet allows the exit of fluid without reaching overpressure. Further, the distance between the primary and secondary fluid outlets makes that, although if these blocking means are closed, no high pressure is reached until the fluid volume reaches the secondary fluid outlet. In some particular embodiments, the primary fluid outlet and the secondary fluid outlet are located within the compression zone.
[0012] In some particular embodiments, the vacuum pump further comprises a final fluid outlet, being located between a first final outlet point of the chamber wall and a second final outlet point of the chamber wall, wherein
the distance between the first primary outlet point and the minor point is greater than the distance between the first final outlet point and the minor point;
the distance between the first final outlet point and the minor point is lower than the length of the portion of the chamber wall between the first virtual outlet vane and the second virtual outlet vane; and
the first and second final outlet point are located in the compression zone of the vacuum chamber.
[0014] In some particular embodiments, the final fluid outlet comprises final blocking means, adapted for sealing the fluid communication between the final fluid outlet and a third outside fluid zone if the pressure in the final fluid outlet is lower than a third predetermined value.
[0016] In some particular embodiments, the secondary fluid outlet comprises secondary blocking means adapted for sealing the fluid communication between the secondary fluid outlet and the second outside fluid zone if the pressure in the secondary fluid outlet is lower than a second predetermined value.
[0018] The first and/or the second and/or the third predetermined value may be either a pressure value which may depend on the pressure in the corresponding outside fluid zone or a constant value.
[0019] In some particular embodiments, the volume of the chamber wall defined by a first virtual outlet vane in contact with the first secondary outlet point and a second virtual outlet vane which is subsequent to the first virtual outlet vane is substantially equal to the volume of the chamber wall defined by a third virtual outlet vane in contact with the second primary outlet point and a fourth virtual outlet vane which is preceding to the third virtual outlet vane.
[0020] In these embodiments, the primary and the secondary fluid outlets are close enough for a first volume comprised between two consecutive vanes not to compress in the time between ceasing being in fluid communication with the primary fluid outlet and starting being in fluid communication with the secondary fluid outlet.
[0021] In some particular embodiments, the volume of the chamber wall defined by a first virtual outlet vane in contact with the first secondary outlet point and a second virtual outlet vane which is subsequent to the first virtual outlet vane is greater than the volume of the chamber wall defined by a third virtual outlet vane in contact with the second primary outlet point and a fourth virtual outlet vane which is preceding to the third virtual outlet vane.
[0022] In these embodiments, the primary and the secondary fluid outlets are close enough for a first volume comprised between two consecutive vanes to be in fluid communication with both the primary and the secondary fluid outlets at the same time.
[0023] In some embodiments, primary and/or secondary and/or final blocking means comprises a one-way valve.
[0024] In some embodiments, the vacuum pump comprises more than one vane and wherein the angle formed between two consecutive vanes is comprised between 55° and 95°.
[0026] Although in some embodiments, the first, the second and the third outlet fluid zones correspond to different zones (open atmosphere, another device, a channel interconnecting some other parts of the vehicle), in other embodiments, at least some of the outlet fluid zones are the same zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:
Figure 1 shows a vacuum pump according to the state of art, in a first operating position.
Figure 2 shows a vacuum pump according to the state of art, in a second operating position.
Figure 3 shows a schematic representation of the vacuum pump according to the present invention.
Figure 4 shows a compression zone in a vacuum pump according to the present invention.
Figure 5 shows a vacuum pump according to the present invention in a first position during operation.
Figure 6 shows a vacuum pump according to the present invention in a second position during operation.
Figure 7 shows a vacuum pump according to the present invention in a third operating position.
Figure 8 is a comparative graphic showing the torque needed to operate the vacuum pump of the present invention and the vacuum pumps of the state of art.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Through the entire description, the vacuum pump is deemed to operate with an ideal gas, not taking into account thermal or fluid-dynamic phenomena or state changes in this gas, for the sake of clarity in the explanation of the invention. Some simplifications have been carried out in this sense, without losing the main scope of the invention.
[0029] Figures 1 and 2 show a vacuum pump 101 according to the state of the art. This vacuum pump 101 is intended to lower pressure from device 120, and comprises
a pump chamber 102 with a chamber wall 121;
a rotor 103 housed in the pump chamber 102, this rotor 103 comprising a plurality of slots 131;
a plurality of vanes 104, each vane 104 being at least partially introduced in one slot 131 of the rotor 103;
a fluid inlet 105 being located in and inlet point of the chamber wall 121; and
a primary fluid outlet 161 being located in a primary outlet point of the chamber wall 121;
wherein the primary outlet point is intended to be in fluid communication with an outside fluid zone 100.[0030] Figure 1 shows the vacuum pump 101 in a first position during operation. In this position, a fluid enters the pump chamber 102 through the fluid inlet 105, and is kept in a first volume 110 defined by two consecutive vanes 104, the chamber wall 121 and a portion of the rotor 103. While the rotor rotates, the first volume 110 is made smaller (and the fluid pressure increases), as the portion of the chamber wall 121 which is comprised between the two consecutive vanes 104 limiting the first volume 110 is nearer the rotor 103 as the rotor 103 rotates.
[0031] Figure 2 shows the vacuum pump 101 in a second position during operation. In this position, the pressure of the fluid which is kept in the first volume 110 has increased, as the first volume 110 has been reduced by the rotation of the rotor 103. In this second position, the first volume 110 reaches the primary outlet point, where the pump chamber 102 comprises the primary fluid outlet 161. This primary fluid outlet 161 is in fluid communication with an outside fluid zone 100. If the pressure of the fluid contained in the first volume 110 is greater than the pressure in the outside fluid zone 100, fluid will exit the first volume 110 when the first volume 110 is put into fluid communication with the outside fluid zone 100, which is achieved by the rotation of the rotor 103, as shown in this second position.
[0032] But it may happen that the fluid enters the pump chamber 102 with a low pressure, and the pressure of the fluid when reaching this second position is still lower than the pressure in the outside fluid zone 100. In this case, when the first volume 110 is put in fluid communication with the outside fluid zone 100, fluid from the outside fluid zone 100, with higher pressure, will enter the first volume 110. This will worsen the efficiency of the vacuum pump 101.
[0033] Figure 3 shows a vacuum pump 1 according to the invention. This vacuum pump 1 comprises
a pump chamber 2 with a chamber wall 21;
a rotor 3 housed in the pump chamber 2, this rotor 3 comprising a plurality of slots 31;
a plurality of vanes 4, each vane 4 being at least partially introduced in one slot 31 of the rotor 3;
a fluid inlet 5 being located between a first inlet point 51 of the chamber wall 21 and a second inlet point 52 of the chamber wall 21, the fluid inlet 5 being in fluid communication with a device 120, where pressure is intended to be lowered; and
a primary fluid outlet 61 being located between a first primary outlet point 611 of the chamber wall 21 and a second primary outlet point 612 of the chamber wall 21; the primary fluid outlet 61 being intended to be in fluid communication with a first outside fluid zone 100;
a secondary fluid outlet 62 being located between a first secondary outlet point 621 of the chamber wall 21 and a second primary outlet point 622 of the chamber wall 21; the secondary fluid outlet 62 being intended to be in fluid communication with a second outside fluid zone 100';
wherein the primary fluid outlet 61 comprises primary blocking means 71 which only allow fluid communication between the primary fluid outlet 61 and the first outside fluid zone 100 if the pressure in the primary fluid outlet 61 is equal or higher than a first predetermined value which depends on the pressure in the first outside fluid zone 100.[0034] The distance between the first secondary outlet point 621 and the minor point 22 is lower than the distance between the first primary outlet point 611 and the minor point 22.
[0035] A volume of the chamber wall defined by a first virtual outlet vane 601 in contact with the first secondary outlet point 621 and a second virtual outlet vane 602 which is subsequent to the first virtual outlet vane 601 is at least the 66% of a volume of the chamber wall defined by a third virtual outlet vane 603 in contact with the second primary outlet point 612 and a fourth virtual outlet vane 604 which is preceding to the third virtual outlet vane 603. This means that, when moving from a first point where fluid communication ceases with the primary fluid outlet to a second point where fluid communication starts with the secondary fluid outlet, the volume in the second point is greater than a 66% of the volume in the first point. In some embodiments, this is the same volume, as the point where fluid communication ceases with the primary fluid outlet is the same as the point where fluid communication starts with the secondary fluid outlet. In other embodiments, such as the one shown in figures 4 to 7, it is even greater, as the volume becomes in fluid communication with the secondary fluid outlet even before fluid communication with the primary fluid outlet ceases.
[0036] In some particular embodiments, any of the first, second or third predetermined values is the result of summing two terms: a cracking pressure and the pressure in the corresponding outside fluid zone. The cracking pressure is a value which may be positive or negative, but, in absolute value, is usually much smaller than the pressure in the corresponding outside fluid zone. The final result is that the corresponding blocking means remains sealed until the pressure in the corresponding fluid outlet is greater than this sum: the cracking pressure (positive or negative) plus the pressure in the corresponding outside fluid zone. Accordingly, if the cracking pressure is negative, fluid communication is allowed even if the pressure in the corresponding fluid outlet is a little lower than the pressure in the corresponding outside fluid zone. The corresponding blocking means remains open until the pressure in the corresponding fluid outlet falls down and becomes lower than this predetermined value.
[0037] A compression zone 11, as shown in figure 4, is defined in the vacuum chamber 2. This compression zone 11 is limited by
a first virtual compression vane 401 located in contact with a major point 23, which is following explained;
a second virtual compression vane 402 located in contact with the minor point 22;
a portion of the rotor 3 comprised between these two first 401 and second 402 virtual compression vanes, considered in the direction from the first virtual compression vane 401 to the second virtual compression vane 402; and
a portion of the chamber wall between the major point 23 and the minor point 22, considered in the direction from the first virtual compression vane 401 to the second virtual compression vane 402.[0038] Regarding the major point 23, depending on the pump layout, the major point can be either the second inlet point 52 or a maximum point. The maximum point of the pump is defined as the point such that when a first virtual size vane 501 is placed in the maximum point, the volume enclosed by the first virtual size vane 501, a second virtual size vane 502 preceding to the first virtual size vane 501 and the portions of the chamber wall and the rotor between these virtual size vanes 501, 502, is maximum. In the case of Figure 4, the maximum point coincides with the second inlet point 52, so the major point also coincides with the second inlet point 52.
[0039] The minor point 22 is the point of the chamber wall 21 with the minimum distance to the rotor 3. The advance direction of the vanes is the direction in which the rotor is moved when the vacuum pump is in operation, so it is the direction in which the vanes advance when the vacuum pump is in operation.
[0040] The vanes of the vacuum pump have one position where the volume between two particular consecutive vanes is maximum. This maximum volume is achieved when one vane is located in a first maximum point of the chamber wall and the preceding vane is located in a second maximum point of the chamber wall.
[0041] If the second inlet point 52 is located nearer the first primary outlet point 611 in the advance direction of the vanes than this first maximum point, the major point 23 is the second inlet point 52. But if the second inlet point 52 is located farther from the first primary outlet point 611 in the advance direction of the vanes than this first maximum point, the major point 23 is the first maximum point. This depends only on the configuration of the vacuum pump and the position of the fluid inlet with respect to the vanes, so this point is always the same for each given vacuum pump, without depending on the operation.
[0042] In some embodiments, the chamber wall 21 may comprise more than one minor point 22 and more than one major point 23, because the rotor may be tangent to the chamber wall in more than one point (e.g., in the case of an elliptic vacuum chamber). In these cases, the vacuum pump comprises more than one compression zone.
[0044] This vacuum pump also comprises a secondary fluid outlet 62 and a final fluid outlet 63, all of them located in the compression zone 11 of the vacuum pump 1.
[0045] Figure 5 shows the vacuum pump 1 in a first position during operation. In this position, a fluid enters the vacuum chamber 2 through the fluid inlet 5, and is kept in a first volume 10 defined by a front vane 41, a rear vane 42 and a portion of the chamber wall 21 as well as a portion of the rotor 3 comprised between these vanes 41, 42. While the rotor 3 rotates, after the rear vane 42 has reached the first maximum point, the first volume 10 is made smaller, as the portion of the chamber wall 21 which is comprised between the two vanes 41, 42, limiting the first volume 10 is nearer the rotor 3 as the rotor 3 rotates.
[0046] The secondary fluid outlet 62 is located between a first secondary outlet point 621 of the chamber wall 21 and a second secondary outlet point 622 of the chamber wall, and the final fluid outlet 63 is located between a first final outlet point 631 of the chamber wall 21 and a second final outlet point 632 of the chamber wall 21. The distance between the first secondary outlet point 621 and the minor point 22 is greater than the distance between the first final outlet point 631 and the minor point 22 but lower than the distance between the first primary outlet point 611 and the minor point 22. As a consequence, in normal operation, the fluid which enters the vacuum chamber 2 finds first the primary fluid outlet 61, then the secondary fluid outlet 62 and finally the final fluid outlet 63. The distance between the first final outlet point 631 and the minor point 22 is lower than the portion of the chamber wall between the first virtual outlet vane 601 and the second virtual outlet vane 602.
[0047] The secondary fluid outlet 62 comprises secondary blocking means 72 which only allows fluid communication between the secondary fluid outlet 62 and a second outside fluid zone 100' if the pressure in the secondary fluid outlet 62 is equal or higher than a second predetermined value which depends on the pressure in the second outside fluid zone 100'. The final fluid outlet 63 comprises secondary blocking means 73 which only allows fluid communication between the final fluid outlet 63 and a third outside fluid zone 100" if the pressure in the final fluid outlet 63 is equal or higher than a third predetermined value which depends on the pressure in the third outside fluid zone 100".
[0048] In particular embodiments, the blocking means are non-return valves, which are designed to prevent fluid from flowing through it in one direction if the fluid pressure value does not reach a predetermined value.
[0049] Figure 6 shows the vacuum pump 1 in a second position during operation. In this position, the pressure of the fluid which is kept in the first volume 10 has increased, as the dimensions of the first volume 10 has been reduced by the rotation of the rotor 3. In this second position, the first volume 10 reaches the first primary outlet point 611, therefore becoming in fluid communication with the primary fluid outlet 61. This primary fluid outlet 61 is in fluid communication with the first outside fluid zone 100 by the interposition of primary blocking means 71, which only allows fluid communication between the primary fluid outlet 61 and the first outside fluid zone 100 if the pressure in the primary fluid outlet 61 is equal or higher than a first predetermined value which depends on the pressure in the first outside fluid zone 100. As the first volume 10 is in fluid communication with the primary fluid outlet 61, the pressure in the first volume 10 and the pressure in the primary fluid outlet 61 is the same.
[0050] If the pressure of the fluid contained in the first volume 10 is greater than the first predetermined value, the primary blocking means 71 allows the fluid communication between the primary fluid outlet 61 and the first outside fluid zone 100. If the pressure of the fluid contained in the first volume 10 is furthermore greater than the pressure in the first outside fluid zone 100, fluid exits the first volume 10 towards the first outside fluid zone 100. As the advance of the rotor leads to a decrease in the dimensions of the first volume 10, pressure in this first volume 10 keeps on increasing, and fluid continues exiting. But at the same time, fluid exits the first volume 10 by the primary fluid outlet 61, so pressure in this first volume 10 decreases until the pressure of the first outside fluid zone 100 or until the primary blocking means 71 is activated. At some point, the rotation of the rotor 3 makes the first volume 10 cease being in fluid communication with the primary fluid outlet 61, when the rear vane 42 of the first volume 10 reaches the second primary outlet point 612.
[0051] When the vacuum pump 1 is starting its operation, and pressure in the fluid inlet 5 is still relatively high, it is easy that the pressure in the first volume 10 is high enough to open the first blocking means 71. But as the pressure in the fluid inlet 5 decreases, due to the pump operation, it is more difficult for pressure in the first volume 10 to reach the first predetermined value required to open the blocking means 71, and there is a point in the operation when the first volume 10 becomes in fluid contact with the first fluid outlet 61 and the fluid in the first volume has not reached pressure enough to open the first blocking means 71. In this case, when the first volume 10 is put in fluid communication with the primary fluid outlet 61, fluid does not exit the vacuum chamber 2, but fluid does not enter the vacuum chamber 2 either, due to the primary blocking means 71, which prevents fluid communication between the primary fluid outlet 61 and the first outside fluid zone 100 if the pressure in the primary fluid outlet 61 is lower than a first predetermined value. As the rotor 3 continues rotating, the pressure in the first volume 10 keeps on increasing, without decreasing due to fluid exit, as the primary blocking means 71 remains sealed until the pressure in the first volume 10 reaches the first predetermined value. In fact, if this pressure increase makes the pressure in the first volume 10 be equal or higher that the first predetermined value while the first volume 10 is still in fluid contact with the first fluid outlet 61, the blocking means 71 will open and fluid will start to exit. If not, the primary blocking means 71 will remain sealed.
[0052] In some embodiments, such as the one shown in these figures 5 and 6, the distance between the tips of two consecutive vanes is greater than the distance between a second outlet point and the first outlet point of the subsequent fluid outlet. As a consequence, it is possible for the first volume 10 that the position of the front vane 41 makes the first volume become in fluid communication with a fluid outlet while the position of the rear vane 42 keeps the first volume in fluid communication with the previous fluid outlet, as shown in Figure 7. In this position, the front vane 41 of the first volume 10 has surpassed the first secondary outlet point 621, while the rear vane 42 of the first volume 10 has not reached the second primary outlet point 612. The first volume 10 is therefore in fluid communication both with the first fluid outlet 61 and with the second fluid outlet 62.
[0053] In these embodiments, when pressure in the first volume 10 is not high enough to open the first blocking means 71 before the front vane 41 reaches the first secondary outlet point 621, the first volume 10 will become in fluid communication with the second fluid outlet 62 with a pressure which is not enough to open the first blocking means 71. If the second predetermined value is the same as the first predetermined value, the secondary blocking means 72 will be closed as well, because pressure in the first volume 10 is not enough to open the secondary blocking means 72. But if the compression of the first volume 10 makes the pressure inside this first volume 10 be equal or higher that the first and second predetermined value while the first volume 10 is still in fluid communication with the first fluid outlet 61, both primary and secondary blocking means will open. If this does not happen, both first 71 and second 72 blocking means will be closed during the whole time that both are at the same time in fluid communication with the first volume. But as the rear vane 42 advances and surpasses the second primary outlet point 612, the first volume 10 is further compressed, and it is possible that the secondary blocking means 72 may open, due to the greater pressure in the first volume 10.
[0054] Operation will continue, progressively reducing the pressure in the inlet 5 and consequently in the first volume 10, until a steady-state flow is reached in the vacuum pump.
[0055] As a consequence, such a vacuum pump will be able to operate more efficiently, without unnecessarily wasting energy in the fluid compression and, collaterally, will not see its operation worsened by fluid entering the vacuum pump by the outlet points.
[0056] A graphic is illustrated in Figure 8 to show the difference between the average torque needed to operate the rotor of three different vacuum pumps throughout their entire performance curve. The dashed line shows the torque needed to move the vacuum pump as known in the state of the art which has a single short outlet. The dotted line shows the torque needed to move the vacuum pump as known in the state of the art which has a single large outlet. The solid line shows the torque needed to move the vacuum pump of the invention. "Short" outlet and "large" outlet refer to the size of the single outlet, the second point of which is placed near the minor point of the vacuum pump (second point and minor point should be understood according to the terminology used in the description for the vacuum pump of the invention). In the particular example of short outlet, the outlet extends along around 18 degrees in the vacuum chamber and in the particular example of large outlet, the outlet extends along around 73 degrees in the vacuum chamber.
[0057] Vacuum pumps with short outlets require more torque when starting a full operation, because pressure reaches higher values, and a greater compression rate is achieved. When, with the progressive operation of the pump, the pressure level decreases, the pressure difference between two consecutive chambers is lower and therefore, this pump becomes more efficient in terms of torque.
[0058] Vacuum pumps with a large outlet require, initially, less torque, as the big outlet does not allow fluid to reach high pressure. However, this lack of initial pre-compression in the chamber before communicating with the exit leads to an increased pressure difference between the chamber open to the outlet fluid zones and the previous one which generates a higher resistant torque along the function of the pump.
[0059] With the vacuum pump according to the invention, a low torque is needed when starting operation and a low torque is needed in the second performance phase as well as in the steady state.
[0060] In this text, the term "comprises" and its derivations (such as "comprising", etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.
[0061] The invention is obviously not limited to the specific embodiments described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.
a vacuum chamber (2) with a chamber wall (21); wherein the chamber wall (21) comprises a minor point (22), which is the point of the chamber wall (21) where the distance between the chamber wall (21) and the rotor (3) is minimum, and a maximum point, which is a point where a first virtual size vane (501) is placed so that the volume enclosed by the first virtual size vane (501), a second virtual size vane (502) preceding to the first virtual size vane (501) is maximum;
a rotor (3) housed in the vacuum chamber (2), this rotor (3) comprising at least one slot (31);
at least one vane (4, 41, 42), each vane (4, 41, 42) being at least partially introduced in one slot (31) of the rotor (3);
at least one fluid inlet (5) being located between a first inlet point (51) of the chamber wall (21) and a second inlet point (52) of the chamber wall (21), the first fluid inlet (5) being suitable for being in fluid communication with the device (120) where pressure is aimed to be lowered; and
a primary fluid outlet (61) being located between a first primary outlet point (611) of the chamber wall (2) and a second primary outlet point (612) of the chamber wall (2), the primary fluid outlet (61) being in fluid communication with a first outside fluid zone (100) of the vacuum pump (1);
a secondary fluid outlet (62) being located between a first secondary outlet point (621) of the chamber wall (2) and a second secondary outlet point (622) of the chamber wall (2), the secondary fluid outlet (62) being in fluid communication with a second outside fluid zone (100') of the vacuum pump (1), the distance between the first secondary outlet point (621) and the minor point (22) being lower than the distance between the first primary outlet point (611) and the minor point (22);
wherein a volume of the chamber wall defined by a first virtual outlet vane (601) in contact with the first secondary outlet point (621) and a second virtual outlet vane (602) which is subsequent to the first virtual outlet vane (601) is at least the 66% of a volume of the chamber wall defined by a third virtual outlet vane (603) in contact with the second primary outlet point (612) and a fourth virtual outlet vane (604) which is preceding to the third virtual outlet vane (603);wherein the primary fluid outlet (61) comprises primary blocking means (71) adapted for sealing the fluid communication between the primary fluid outlet (61) and the first outside fluid zone (100) if the pressure in the primary fluid outlet (61) is lower than a first predetermined value; and
wherein a compression zone (11) is defined in the vacuum chamber (2), the compression zone (11) being limited by
a first virtual compression vane (401) located in contact with a major point (23); the major point being either the second inlet point (52) or the maximum point;
a second virtual compression vane (402) located in contact with the minor point (22);
a portion of the rotor (3) comprised between these two first (401) and second (402) virtual compression vanes, considered in the direction from the first virtual compression vane (401) to the second virtual compression vane (402); and
a portion of the chamber wall between the major point (23) and the minor point (22), considered in the direction from the first virtual compression vane (401) to the second virtual compression vane (402).the distance between the first primary outlet point (611) and the minor point (22) is greater than the distance between the first final outlet point (631) and the minor point (22);
the distance between the first final outlet point (631) and the minor point (22) is lower than the length of the portion of the chamber wall (21) between the first virtual outlet vane (601) and the second virtual outlet vane (602); and
the first (631) and second (632) final outlet point are located in the compression zone (11) of the vacuum chamber (2).