Information
-
Patent Grant
-
6336790
-
Patent Number
6,336,790
-
Date Filed
Friday, October 17, 199727 years ago
-
Date Issued
Tuesday, January 8, 200223 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Frishauf, Holtz, Goodman, Langer & Chick, P.C.
-
CPC
-
US Classifications
Field of Search
US
- 415 1994
- 415 1995
- 415 189
- 415 190
- 415 191
- 415 2082
- 415 2091
- 415 2092
- 415 2093
- 415 2094
- 415 903
- 415 904
- 029 557
- 029 558
- 029 8892
- 409 131
- 409 132
- 409 143
- 409 199
- 409 200
- 451 51
- 451 61
-
International Classifications
-
Abstract
An axial flow power tool turbine motor for operation with an elastic fluid, like pressured air, includes a housing (12), a rotor (11) rotatively journalled in the housing (12) and formed in one piece with drive blades (24) arranged in axially spaced circumferential rows (C, A, C, E, G, I, K), and a stator (10) in the form of a tubular body (22) which is immovably supported in the housing (12) and which carries internal guide vanes (23) arranged in circumferential rows (B, D, F, H, J), wherein the tubular stator body (22) is divided into three longitudinal sections (22a, 22b, 22c) with which the guide vanes (23) are integrally formed, and a retainer (27, 29) for fixing and mounting the longitudinal sections (22a, 22b, 22c) in accurately defined relative positions to form the tubular stator body (22).
Description
This invention relates to an axial flow turbine machine for operation with an elastic fluid.
In particular, the invention concerns an axial flow turbine machine comprising two or more expansion or compression stages, i.e. having a rotor carrying drive blades arranged in two or more axially spaced circumferential rows and a stator carrying guide vanes arranged in one or more circumferential rows, wherein each one of the rows of guide vanes is disposed between two adjacent rows of drive blades.
BACKGROUND OF THE INVENTION
In prior art, it is well known to produce multi-stage turbine machines by forming both the rotor and the stator in a number of sections to be assembled into a complete rotor and a complete stator. In bigger turbines, the guide vanes are formed as separate parts for mounting in rows in the stator, and the stator is divided into two longitudinal halves to be put together around the rotor, whereby the guide vane rows are introduced between the drive blade rows.
However, when producing small size turbines having a diameter of only 30-40 mm, it is not practically possible to use separate guide vanes in the stator. The radial size of the guide vanes in the high pressure stage may be as small as a fraction of a millimeter. Such small vanes have to be formed integral with the stator by machining or molding.
In British Patent No. 1 287 850, there is described a small size two-stage turbine in which the rotor is formed in one piece, including two rows of drive blades. Since the drive blades extend from an outer cylindrical surface, there is no problem machining them from the rotor body. The stator of this known turbine comprises one row of guide vanes which is located between the drive blade rows and which is formed by two semicircular ring elements provided with guide vanes on their outside. This means that the guide vanes are easily machinable from the outer surface of the ring elements.
On the other hand, this prior art guide vane arrangement means that the turbine is rather complicated as it comprises not only separate ring elements to form the stator but also separate sleeve elements for accomplishing an axial clamping of the ring elements in the housing. This also means that there is a nonfavourable air flow path through the turbine, because the guide vanes have a bigger radial extent than the drive blades for enabling the axial clamping of the stator ring elements. Thus, the air flow path is locally enlarged in the stator, which causes an undesirable turbulent air flow therethrough.
OBJECT OF THE INVENTION
The primary object of the invention is to accomplish an axial flow turbine machine having two or more expansion or compression stages and which is inexpensive and easy both to manufacture and to assemble and which is suitable for production in small sizes.
A preferred embodiment of the invention is below described in detail with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE INVENTION
FIG. 1
shows a longitudinal section through a turbine according to the invention.
FIG. 2
shows a cross section along line II—II in FIG.
1
.
FIG. 3
illustrates a machining process in which the guide vanes of a stator section are formed by milling.
FIG. 4
shows, on a larger scale, a fraction of the longitudinal section in FIG.
1
.
DETAILED DESCRIPTION
The turbine illustrated in the drawing figures is a six stage pneumatic motor comprising a stator
10
, a rotor
11
and a cylindrical housing
12
. The stator
10
is immovably secured in the housing
12
, whereas the rotor
11
is rotatively journalled in the housing
12
by means of two roller bearings
13
,
14
. The rotor
11
also comprises a splined output end
15
for connection to a reduction gearing (not shown).
The housing
12
comprises a forward section
16
and a rear section
17
which are rigidly interconnected by a thread connection
18
. A pressure air inlet passage
19
extends coaxially through the rear housing section
17
, and a number of parallel air exhaust passages
20
in the rear section
17
communicate with a tubular exhaust chamber
21
formed between the forward housing section
16
inner wall and the stator
10
. The air flow through the turbine is illustrated by arrows in FIG.
1
.
The stator
10
comprises a tubular body or sleeve
22
carrying inwardly directed guide vanes
23
which are arranged in five axially spaced circumferential rows B, D, F, H, and J, whereas the rotor
11
is provided with drive blades
24
arranged in six axially spaced circumferential rows A, C, E, G, I, and K. See FIG.
1
. In a common manner, the drive blades
24
and the guide vanes
23
are disposed in alternating positions, viewed in the direction of the motive pressure air flow through the turbine. This means that between adjacent rows of drive blades
24
there is a row of guide vanes
23
for linking the pressure air flow into an optimum direction before entering the next row of drive blades
24
.
In the drawings, the reference numerals of the drive blades
24
and the guide vanes
23
are combined with the reference letters of the circumferential rows A, C, E, G, I, and K and B, D, F, H, and J, respectively, in which they are arranged.
In order to simplify this specification, however, these suffix letters are omitted in the text, which means that all the drive blades are simply referred to as
24
and all the guide vanes are referred to as
23
. Apart from the differences in size, all of the drive blades
24
have the same functional features. All of the guide vanes
23
also have the same functional features.
The stator
10
further comprises a forward mounting sleeve
27
, forming an outer support for the sleeve
22
, and a rear cup shaped nozzle piece
28
. The latter has a forwardly directed tubular skirt portion
29
for radial support of the sleeve
22
and a rear air inlet portion
30
. This portion is formed with an air inlet opening
31
communicating at its one end with the air inlet passage
19
and at its other end with radially directed air feed passages
32
. These air feed passages
32
communicate motive pressure air from the inlet portion
30
to a number of air nozzles
33
by which the motive high speed air flow through the turbine is generated. The nozzle piece
28
also comprises a socket
34
forming a support for the rear rotor bearing
14
.
At its front end, the stator
10
also comprises a ring element
35
which forms a radial as well as an axial support for the mounting sleeve
27
. The ring element
35
is formed with a number of exhaust openings
36
communicating with the exhaust chamber
21
.
The motor turbine illustrated in the drawings is intended to be produced in small dimensions, i.e. having a rotor diameter from about 30-40 mm. Accordingly, the rotor drive blades
24
as well as the guide vanes
23
on the stator sleeve
22
are of such small sizes that it is not possible to produce them as separate details for mounting on the respective carrier. Instead, the drive blades
24
and the guide vanes
23
are machined out as integrated parts of the rotor
11
and the stator sleeve
22
, respectively. Since the drive blades
24
are located on the outer surface of the rotor body
11
, there is no problem to carry out the necessary machining work, for instance by a shank end mill.
However, to be able to form the guide vanes
23
on the inside of the stator sleeve
22
, the latter is divided into three separate shells
22
a
,
22
b
and
22
c
. See FIG.
2
. These shells are divided along three cylinder generatrices located at 120 degrees intervals, which means that each shell has a circumferential extent of 120 degrees.
As the turbine is assembled, the shells
22
a
,
22
b
and
22
c
are kept together in a fixed radial relationship by the forward mounting sleeve
27
and the tubular skirt portion
29
of the nozzle piece
28
. The mounting sleeve
27
and the skirt portion
29
surround the shells
22
a
,
22
b
,
22
c
with a tight fit such that the positions of the shells
22
a
,
22
b
and
22
c
are accurately defined so as to form the tubular sleeve body
22
. The stator shells
22
a
,
22
b
and
22
c
are secured relative to the housing
12
by axial clamping between a shoulder
38
on the forward mounting sleeve
27
and a shoulder
39
on the nozzle piece skirt portion
29
. The clamping force is obtained by the thread connection
18
between the two housing sections
16
and
17
.
Scattering of the detail dimensions within the production tolerances is compensated for by a Belleville-type spring washer
37
which is disposed in the socket
34
behind the rear bearing
14
to ensure a correct axial load on the rotor bearings.
In
FIG.3
, there is illustrated a machining situation wherein one of the stator shells
22
a
is firmly clamped against a part cylindrical surface of a fixture
40
, and a milling spindle
41
fitted with a shank end mill
42
is in a position for machining a guide vane at the longitudinal edge of the shell. The shell is clamped in this position by means of screws
43
,
44
and clamp rules
45
,
46
carried on the fixture. This illustrated machining situation intends to show that machining of the guide vanes close to the edges of a stator shell would not be possible with a 180 degree two part divided stator. Each shell has to have a circumferential extent well below 180 degrees to give access to a machining tool.
As illustrated in
FIG. 4
, the extreme free ends of the drive blades
24
and guide vanes
23
form clearance seals with cylindrical surfaces
50
and
51
on the stator
10
and the rotor
11
, respectively. The drive blades
24
in each circumferential row A, C, E, G, I, and K cooperate sealingly with a corresponding cylindrical surface
50
on the stator
10
. It is to be noted that the drive blade and sealing surface reference numerals in
FIGS. 1 and 4
are provided with the suffix letter of the corresponding circumferential row.
In the same way, the extreme free ends of the guide vanes
23
in each circumferential row B, D, F, H, and J cooperate sealingly with a cylindrical surface
51
on the rotor
11
. The reference numerals of the guide vanes and sealing surface in the drawing figures are provided with the suffix letter of the corresponding circumferential row. Although, the last three stages only of the turbine are shown in
FIG. 4
, i.e. the drive blade rows G, I and K and the guide vane rows F,H, and J, the clearance seal arrangement with cylindrical sealing surfaces
50
and
51
on the stator
10
and the rotor
11
, respectively, is similar in all turbine stages.
By having the drive blades
24
and guide vanes
23
form clearance seals together with cylindrical surfaces
50
and
51
, respectively, there is obtained the advantage of allowing a certain axial adjustment of the rotor
11
relative to the stator
10
without influencing on the clearance seals.
It is to be noted that the embodiments of the invention are not limited to the shown and described example but can be freely varied within the scope of the claims.
For example, the circumferential extent of the stator shells does not have to be exactly the same. The important thing is that the guide vanes
23
are formed in one piece with and on the inside of the tubular stator body formed by the shells. To enable this, the tubular body
22
has to be divided into three or more sections or shells each having a circumferential extent well below 180 degrees.
In an alternative embodiment of the invention the stator shells
22
a
,
22
b
,
22
c
are fixed and mounted relative to each other by joints engaging external flanges located at the longitudinal edges of the shells. This method for fixing and mounting the stator shells is well known per se at bigger two-part turbine stators.
Claims
- 1. A small-size axial flow power tool turbine rotor or operation with an elastic fluid, said turbine motor comprising:a housing; a rotor journalled in said housing and carrying a plurality of drive blades, said drive blades being integrally formed with said rotor as a one piece -member, and said drive blades being arranged in three or more axially spaced circumferential rows; and a stator supported in said housing, said stator comprising a tubular body having a number of guide vanes formed therein which are arranged in two or more circumferential rows on an inside surface of said tubular body such that each one of said two or more circumferential rows of guide vanes is disposed between adjacent ones of said three or more axially spaced circumferential rows of drive blades; wherein said tubular body is cylindrical in shape and divided along at least three cylinder generatrices into at leas three longitudinal sections which each extend along an axial length of said tubular body over all of said two or more circumferential rows of guide vanes; wherein said guide vanes are integrally formed on said at least three longitudinal sections; and wherein a retainer is provided for fixing and mounting said at least three longitudinal sections in accurately defined relative positions; and wherein free ends of said drive blades and said guide vanes form clearance seals with cylindrical surfaces on the stator and the rotor, respectively.
- 2. A turbine motor according to claim 1, wherein each one of said at least three longitudinal sections extends over a circumferential angle which is less than 180 degrees of the stator circumference.
- 3. A turbine motor according to claim 2 wherein said tubular body is divided into exactly three longitudinal sections, and each one of said longitudinal section extends over a circumferential angle of 120 degrees of the stator circumference.
- 4. A turbine motor according to claim 3, wherein said retainer comprises at least one sleeve element which is tightly fitted around said tubular body.
- 5. A turbine motor according to claim 2, wherein said retainer comprises at least one sleeve element which is tightly fitted around said tubular body.
- 6. A turbine motor according to claim 1, wherein said retainer comprises at least one sleeve element which is tightly fitted around said tubular body.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9603835 |
Oct 1996 |
SE |
|
US Referenced Citations (11)
Foreign Referenced Citations (13)
Number |
Date |
Country |
383734 |
Jan 1965 |
CH |
661678 |
Aug 1987 |
CH |
560836 |
Sep 1932 |
DE |
732767 |
Mar 1943 |
DE |
91048 |
Aug 1961 |
DK |
0 718 469 |
Jun 1996 |
EP |
630558 |
Dec 1927 |
FR |
633074 |
Jan 1928 |
FR |
817957 |
Aug 1959 |
GB |
909058 |
Oct 1962 |
GB |
1 287 850 |
Sep 1972 |
GB |
1390979 |
Apr 1975 |
GB |
2250782 |
Jun 1992 |
GB |