U.S. patent application number 10/380918 was filed with the patent office on 2004-05-13 for turbomolecular vacuum pump with rows of rotor blades and rows of stator blades.
Invention is credited to Adamietz, Ralf, Beyer, Christian, Schutz, Gunter.
Application Number | 20040091351 10/380918 |
Document ID | / |
Family ID | 7656904 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091351 |
Kind Code |
A1 |
Adamietz, Ralf ; et
al. |
May 13, 2004 |
Turbomolecular vacuum pump with rows of rotor blades and rows of
stator blades
Abstract
The invention relates to a turbomolecular vacuum pump comprising
rows of rotor blades (3) and rows of stator blades (4) that
alternately engage with one another at varying angles of attack
(.alpha.). The aim of the invention is to improve the properties of
such a pump. To this end, at least a part of the blades (1 or 2) of
the rows of blades (3 or 4) that are mounted on the pressure side
thickens towards the rim facing the pressure side.
Inventors: |
Adamietz, Ralf;
(Wermelskirchen, DE) ; Beyer, Christian; (Koln,
DE) ; Schutz, Gunter; (Koln, DE) |
Correspondence
Address: |
Fay Sharpe Fagan
Minnich & McKee
Seventh Floor
1100 Superior Avenue
Cleveland
OH
44114-2518
US
|
Family ID: |
7656904 |
Appl. No.: |
10/380918 |
Filed: |
March 18, 2003 |
PCT Filed: |
August 9, 2001 |
PCT NO: |
PCT/EP01/09195 |
Current U.S.
Class: |
415/90 |
Current CPC
Class: |
F05D 2240/304 20130101;
F04D 29/324 20130101; F04D 29/544 20130101; F04D 19/042 20130101;
F05D 2250/70 20130101; F05D 2240/122 20130101 |
Class at
Publication: |
415/090 |
International
Class: |
F01D 001/36 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2000 |
DE |
10046506.4 |
Claims
1. Turbomolecular vacuum pump comprising rows of rotor blades (3)
and rows of stator blades (4) that alternately engage with one
another at varying angles of attack (.alpha.), wherein at least a
part of the blades (1 or 2) of the rows of blades (3 or 4) that are
mounted on the pressure side thickens towards the rim facing the
pressure side.
2. Pump according to claim 1, wherein rim areas (11), (12) forming
the pressure side rim of the thickened blades (1, 2) in each
instance are located in a plane perpendicular with respect to the
rotor axis (9).
3. Pump according to claim 1 or 2, wherein the thickenings (10) of
the thickened blades in the cross section through the blades (1, 2)
are designed conically increasing in the direction of the pressure
side.
4. Pump according to claim 3, wherein the thickenings (10)
increasing in the direction of the pressure side, commence at the
pressure side half of the width of the blades (1, 2).
5. Pump according to claim 3 or 4, wherein the thickenings (10) are
provided on both sides or only on one side of the blades (1,
2).
6. Pump according to claim 5, wherein the thickening (10) commences
at a point of change (14) and where the angle (.beta.) formed by
the pressure side section (1", 2") of the boundary lines (1', 1,";
2', 2") of the blades (1, 2) with a connecting line (15) which
forms the point of change (14) with the bottom rim of the in each
instance opposing blade, is greater than 90.degree..
7. Pump according to one of the above claims, wherein it is
equipped with a filling stage (21) implemented by way of a radial
stage.
8. Pump according to claim 7, wherein the radial stage comprises
ridges (23) extending towards the outside, the width of which
decreases towards the outside.
Description
[0001] The present invention relates to a turbomolecular vacuum
pump comprising rows of rotor blades and rows of stator blades that
alternately engage with one another at varying angles of
attack.
[0002] The pumping capacity in the pumping chamber of a
turbomolecular pump is effected through the interaction between the
rotating rotor blades and the stationary stator blades. Commonly
the angles of attack of the blades become more shallow from the
suction to the pressure side, and the blade increments decrease in
said direction.
[0003] The effective pumping capacity S.sub.eff of the
turbomolecular pump is given through
S.sub.eff=S.sub.theo-S.sub.back
[0004] The effective pumping capacity S.sub.eff.sup.1) is thus
equal to the theoretical pumping capacity S.sub.theo reduced by
backstreaming which is unavoidable owing to the slots present (gap
leakage). Backstreaming increases more and more in the direction of
higher pressures. This applies in particular to light gases. With
increasing molecular mass the probability for backstreaming of the
pumped gases decreases. .sup.1) Translator's note: The German text
states "s" here whereas "S" would be appropriate and in line with
the remaining text. Therefore a capital S has been assumed for the
translation.
[0005] It is the task of the present invention to improve the
pumping properties of a turbomolecular vacuum pump of the kind
mentioned above.
[0006] This task is solved through the present invention in that at
least a part of the blades of the rows of blades that are mounted
on the pressure are designed in the area of their rim facing the
pressure side such that longer covering sections with respect to
the rotor (stator) blades that follow result, so that a higher
density against backstreaming is effected. This results in
thickening of the blades in the direction of the compression side.
Such thickenings needs to be so designed that on the one hand the
thickened rims of the blades on the pressure side significantly
reduce any backstreaming and on the other hand the pumping cross
section is restricted only slightly or to an acceptable extent.
This applies to rotor and stator blades.
[0007] Especially effective with respect to the avoidance of any
backstreaming are the rims on the pressure side of the thickened
blades in such instances where these are located in a plane
perpendicular with respect to the rotational axis of the rotor
blades. Here the thickenings shall restrict the pumping cross
section of the turbomolecular pump by no more than 10%
(corresponding to the compression capacity of one stage).
[0008] So that the thickenings will not impair the pumping
properties of the turbomolecular pump too much, it is expedient
that the thickenings in the cross section through the blades in
creases conically in the direction of the pressure side. Preferably
the increasing thickening will commence in the direction of the
pressure side only on the pressure side half of the width of the
blades.
[0009] Further advantages and details of the present invention
shall be explained with reference to.sup.2) drawing FIGS. 1 to 3.
Depicted are in:
[0010] drawing FIG. 1 sections through some blades of a row of
rotor and a row of stator blades (depicted by way of a developed
view).
[0011] drawing FIGS. 2 and 3 pumping surfaces of a filling stage,
said pumping surfaces being designed according to the present
invention. .sup.2) Translator's note: The German text states " . .
. anhand von in den . . . " here whereas " . . . anhand von den . .
. " would be appropriate. Therefore the latter has been assumed for
the translation.
[0012] Depicted in drawing FIG. 1 are sectional views through
blades 1, 2 of a row of rotor blades 3 and a row of stator blades
4. The angle of attack .alpha. of the blades which are depicted as
an example, amounts to approximately 30.degree.. The direction of
the rotor's movement, the direction of pumping action and the
direction of the backstreaming flow are generally indicated by the
arrows 5, 6, 7. From the arrows 8, the existence of pumping
channels is apparent, these being formed by the blades 1, 2 as well
as the walls of stator and rotor. The rotor axis is designated as
9.
[0013] The pressure side rims of the blades 1 and 2 are thickened
on the pressure side (thickenings 10). In that the rim areas 11, 12
are located in a plane perpendicular with respect to the rotor axis
9, there result relatively large surface sections 11, 12 which
oppose the backflowing gas molecules (arrow 7).
[0014] From drawing FIG. 1, two of the many embodiments for
thickening 10 are apparent. At the rotor blades 1 an increase in
the thickness d (conical) commences at the bottom half of the
blades. It increases in a linear manner in the direction of the
pumping action. In the instance of the stator blades 2 the increase
in thickness d is not linear; the change in thickness also
increases.
[0015] The thickenings are substantially designed on one side since
such embodiments may easily be manufactured by milling. The
fore-running boundary line of the rotor blades 1 depicted by way of
a cross sectional view consists of two straight line sections 1',
1", between which there is located the point of change 14. In the
instance of the stator blades 2 the rear boundary line with respect
to the motion of the rotor is formed by a straight section 2' and a
curve 2", for example.
[0016] In order to substantially maintain the pumping properties of
the pumping channels (arrows 8), the thickenings shall only be
implemented in halves of the blades 1, 2 on the pressure side. The
angle .beta. formed by the boundary lines 1" and 2" at the point of
change 14 with a connecting line 15 which connects the point of
change 14 to the bottom end of the in each instance opposing
blades, shall preferably be greater than 90.degree.. This measure
shall ensure that the pumping cross section, given by the distance
a between the blades (line section perpendicular with respect to
two adjacent blades) is not restricted by the thickenings 10.
[0017] From WO 99/15793 it is known to provide between a
turbomolecular pumping stage and a molecular pumping stage, a
filling stage being designed as a centrifugal stage and which
comprises of ridges extending substantially radially towards the
outside. Filling stages of this kind modified in accordance with
the present invention are depicted in drawing FIGS. 2, 3 by way of
a top view.
[0018] In the drawing figures, the filling stage is designated as
21, the annular pumping channel of the molecular pump as 22, the
ridges modified in accordance with the present invention as 23 and
the thus created peripherally open pockets as 24. In the filling
stage 21 in accordance with drawing FIG. 2, the wedge shaped ridges
23 extend radially whereas in the filling stage in accordance with
drawing FIG. 3 they are inclined backwards with respect to the
direction of rotation (arrow 5).
[0019] In that the width of the ridges 23 increases from outside to
inside, the width of the peripherally open pockets 24 decreases
towards the inside corresponding to the pumped distribution of the
gas volumes. Thus both the rim surfaces of the ridges 23 which
oppose the backflowing molecules and also the axial sealing
surfaces increase.
[0020] The measures detailed all effect an increase in compression
and pumping capacity of a turbomolecular pump, be it with or
without a filling stage 21 upstream of the molecular pumping stage.
This applies in particular to light gases. The surfaces which
effect the pumping action in line with the present invention may be
produced simply by milling, for example. The measures detailed will
be especially effective when being implemented in compression areas
with relatively small angles of attack
.alpha.(.alpha.<30.degree.).
* * * * *