TECHNICAL FIELD
The present invention relates to a vacuum pump as defined in the preamble
of claim 1. Such a pump is known e.g. from US-A-4 549 854.
More specifically, the subject invention relates to an ejector type
vacuum pump, comprising a rotationally symmetric ejector body that is housed to
be surrounded by a vacuum chamber that extends axially to open through the house
wall. A dust filter runs concentric about the ejector body, and has a tube shaped,
porous filter body that is circumferentially supported in a frame such that the
filter body and the frame together form a self-containing, rotationally symmetric
unit that runs substantially about the total length of the ejector body. A muffler
comprising a rotationally symmetric body has an inner end that is shaped to be sealingly
seated in the mouth of the vacuum chamber. The inner section of the muffler is dimensioned
to receive and enclose the nozzle end of the ejector body, and tapers towards the
mouth of the muffler. The muffler is inserted in the mouth of the vacuum chamber
and engages the dust filter for axial fixation of the filter in the vacuum chamber.
OBJECT OF INVENTION
The object of the invention is to provide a vacuum pump of non-complex
structure, and which by simplified structural measures may be incorporated in systems
or assemblies where vacuum or negative pressure is desired for running a process.
Specifically, the vacuum pump of to the invention is designed to meet
the object of facilitating assembly and disassembly in maintenance, when cleaning
the dust filter or ejector, e.g. in industrial or otherwise polluted environments,
service interrupts often is considered to be a technical and economic problem.
The object of invention is met in a vacuum pump as defined in the
characterizing part of claim 1.
SUMMARY OF THE INVENTION
Briefly, the invention suggests a rotationally symmetric ejector body
with one or several nozzles axially aligned and connected in series, and valve elements
that are accommodated in the ejector body. The ejector is received in a vacuum chamber,
formed in a house and opening axially in the house wall. The vacuum chamber is connected
to a system, operated by negative pressure, and a compressed air supply is connected
to the ejector so as to generate a negative pressure in the vacuum chamber through
the ejector effect, as is known per se.
A separate attachable unit having a vacuum chamber and inlet for supply
of compressed air, feeding the ejector, may form the vacuum pump house mentioned
herein. Alternatively, the house is a vacuum chamber formed in the structure material
of a system assembly, operated by negative pressure. The rotationally symmetric
configuration of the ejector body allows a vacuum chamber to be formed in the structure
material through boring and internal milling, so that a chamber of circular section
is provided.
The vacuum chamber opens in a wall of the house or the structure material.
The mouth of the vacuum chamber receives the circular sectioned muffler body, which
occupies the annular space between the wall of the vacuum chamber and the nozzle
end of the ejector body.
A dust filter is axially secured inwardly of the muffler. The filter
runs concentric about the ejector body, substantially the whole length about the
ejector body so that the forward end of the filter abuts the inner end of the muffler.
The dust filter is a tube formed filter body of porous material. In the shown embodiment,
the filter body is circumferentially enclosed by a frame having a perforated cylinder
wall. Assembled, the filter and frame form a rotationally symmetric, self-containing
unit that is manually attachable and detachable from the ejector body as the muffler
is removed from the mouth of the vacuum chamber.
DRAWINGS
The invention is further disclosed below, reference being made to
the accompanying drawings wherein
- Fig. 1 is a diagrammatic longitudinal section view of a house of the vacuum
pump according to the invention, equipped with an ejector body, a muffler and a
dust filter illustrated in broken lines;
- Fig. 2 illustrates a frame associated with the dust filter;
- Fig. 3 illustrates a filter body of the dust filter, and
- Fig. 4 is a longitudinal section view showing the muffler of fig. 1.
DETAILED DESCRIPTION
According to this invention, the vacuum pump 1 comprises an ejector
pump 4 arranged in a housing 2, and more specifically arranged in a vacuum chamber
3, formed in the house. Said ejector pump 4 has a rotationally symmetric body and
comprises one or several, internally arranged nozzles arranged in a series, as well
as valve means 5 accommodated in the circumferential wall of the ejector body. Preferably,
the ejector body is a multi stage ejector having valve seats integrally formed in
the ejector body, and the ejector reaches through an inner end or bottom 6 of the
vacuum chamber for fluid flow communication with a compressed air inlet 7. The ejector
is operated by the compressed air to generate a negative pressure in the surrounding
vacuum chamber 3. The latter communicates via a connection 8 with a system assembly
(not shown), which is operated by negative pressure.
The sectional shape of the vacuum chamber is not essential to the
invention, but is preferably circular at least in the area of the mouth 9, where
the vacuum chamber opens axially through the housing wall 10. The vacuum chamber
3 may be formed in a separate housing 2 that is attachable to the pressure operated
assembly, and may alternatively be integrally formed in the material of the assembly
in the shape of a blind bore having a depth adapted to the length of the ejector
body.
A muffler 11 is received in the mouth of the vacuum chamber. An O-ring
12, e.g., seals muffler to the vacuum chamber wall in the mouth area. The muffler
11 has a rotationally symmetric section and extends into the vacuum chamber by an
inner end 13. The inner end 13 is formed to enclose the forward end, i.e. the nozzle
of the ejector pump 4, from where the air is discharged through the muffler. Outwardly
of the ejector pump, the internal section of the muffler tapers in a frusto-conical
shape towards the muffler mouth, as can be seen in fig. 4.
The internal section, formed by a porous and silencing material is
provided by a separate insert 14 that is mounted in a muffler casing made from a
resistant material. The skilled man will understand how the muffler may be formed
and dimensioned in order to hold the muffler in the mouth of the vacuum chamber
by the negative pressure generated therein. Alternatively, threads or other fixations
may be used for holding the muffler in place.
In the vacuum chamber 3, the ejector body 4 is circumferentially enclosed
by a concentrically about the ejector body extended dust filter 15, see also fig.
2, that runs substantially about the whole length of the ejector body. The dust
filter 15 comprises a tube formed filter body 16 made from a porous material, and
may be externally supported by a cylindrical frame 17. In the attached position,
the frame and the filter body provides a self containing, rotationally symmetric
unit that extends from the bottom 6 of the vacuum chamber to the inner end of the
muffler 11, situated in the mouth of the vacuum chamber.
Alternatively, the filter body alone is self containing, and may be
formed from a ceramic material, e.g. a sintered ceramic material, a synthetic material
or formed as a sintered metal body, that is supported on the ejector body to be
extended substantially about the whole length of the ejector body.
Preferably, the frame 17 is formed from a synthetic material, e.g.
plastic or a nylon material. In the cylinder wall, the frame is formed to have areas
18 of perforations or apertures, as well as longitudinal and transversal reinforcements
19,20 with no perforations or apertures. Collar formed shoulders 21 are formed in
the ends of the frame, adapted to abut the bottom 6 of the vacuum chamber and the
inner end of the muffler 11, respectively, in the attached position.
The frame and the filter may alternatively be integrally formed. Such
embodiment may be achieved by incorporating a cylindrical filter body with the frame
in a moulding process.
Above, the invention is disclosed by way of example, to which modifications
are possible within the scope of the appended claims without leaving the inventive
teachings. A central feature of the invention is the cylindrical filter body, running
concentrically about substantially the whole length of the ejector body.
