Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
A liquid injection type screw compressor
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a liquid injection type
screw compressor comprising a pair of male and female screw
rotors that are installed in a space surrounded by a bore face
within a casing of the compressor, while a liquid such as oil
or water is injected to the bore face; whereby, a lip part is
provided so as to prevent the liquid from flowing-back to a
working gas inlet side, being placed on the bore face, within
a range from a suction seal line (a suction closure line or a
suction containment boundary locus) to a line parallel thereto
apart from the suction seal line, by a distance equal to one
screw pitch (a tooth groove distance in the rotor axis
direction) of the rotors.
[0002] In hitherto known liquid injection type screw
compressors, a pair of a male screw rotor and a female screw
rotor within a casing of the compressor are engaged in each other,
so as to form a working/operation space inside which a liquid
such as oil or water is injected whereby a working substance
of a gas-liquid mixing phase is pressurized. The liquid
injection brings the screw compressor a cooling function, a
sealing function, and a lubricating function; thus, the
compressor of the type obtains high efficiency even during a
low speed operation, becoming widespread in the industry.
[0003] The bore faces forming the working space within the
casing of the compressor are important elements so as to secure
gas/liquid tightness, when the working space is under a
compression process where a gas seal across adjacent tooth
spaces is required; consequently, it is a prerequisite to keep
the clearance between the addendum circles of the rotors (tooth
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tip surfaces of the rotors) and the bore faces as small as
possible. In this specification, the bore faces in the part as
mentioned are called main bore faces.
On the other hand, a gas leakage between adjacent tooth
spaces does not effect on the performance of the compressor when
working spaces are under gas suction process; therefore, the
bore faces in the associated part as mentioned are expanded
toward outside in comparison with the main bore faces so that
a power consumption is reduced by evading useless possible
friction between the bore faces and the tooth tips; thus, the
bore faces in the part as mentioned are called expanded bore
faces.
[0004] In conventional liquid injection type screw compressors
as described above, a weir (a lip part) is provided therein so
as to prevent oil from scattering through a suction side end
face of the rotor casing toward a gas inlet side; thus, it is
intended to preserve the compressor volumetric efficiency and
reduce the compressor power loss.
Conventional screw compressors with such a weir as
mentioned are disclosed, for instance, in a patent literature
1 (JP patent: 1967-10027), a patent literature 2 (JP:
1991-194183) and a patent literature 3 (JP: 1999-13661).
[00051 The figures 1 and 2 in the patent literature 1 disclose
that a lip (weir) 44 is provided between a gas inlet 24 and an
expanded bore part 40 so as to lessen a heat exchange between
a hot back-flow gas from a compression space formed in a rotor
tooth space, and a flow-in gas from the gas inlet 24.
On the other hand, the figure 1 in the patent literature
2 discloses a lip (weir) 39 that is provided at a suction side
end-face of a casing 3 so that the lip 39 prevents a back-flow
oil from flowing from expanded bore parts 7 and 8 back to a gas
inlet side, from warming-up an inhaled gas, and also from
deteriorating a charging efficiency of the inhaled gas to be
charged into a rotor teeth space.
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[0006] Moreover, the patent literature 3 discloses that the oil
injected into a working space flows back to a gas inhaling space;
thereby, an oil mist generated from the back-flow oil suspends
in the gas inhaling space, while the oil mist heats up the inhaled
gas under a suction process; namely, a phenomenon, what is
called inhaled gas heating, occurs; thus, the phenomenon
increases a temperature of the gas to be compressed as well as
expands a volume thereof ; as a result, in a displacement type
compressor that needs to inhale a gas of a constant specific
volume, not only a reduction of mass-throughput but also a
deterioration of volumetric efficiency are brought.
In order to evade the above-mentioned difficulties,
according to the patent literature 3, as shown in Fig. 2 of the
patent literature 3 a lip part 5 is provided at a suction side
end-face of a casing 3 that accommodates the rotors, so that
the lip part 5 protrudes inside, i.e. toward screw rotors;
further, a heat-up prevention wall (a baffle plate) 8 to close
a gap between the screw rotors and the lip part 5 is provided
so as to prevent an inhaled gas from leaking toward a gas inlet
side.
[0007] Figs. 9a and 9b that are attached to this application
shows a casing for conventional screw rotors; for explanatory
convenience, Fig. 9a shows a divided upper half and Fig. 9b shows
a divided lower half. In Figs. 9a and 9b, a space that
accommodates a male rotor and a female rotor is formed inside
the casing 01; thereby, the boundary of the space comprises:
a male rotor side main-bore-face 02a that faces a male rotor
tooth tip with a slight clearance Al,
a female rotor side main-bore-face 02b that faces a female
rotor tooth tip with a slight clearance A2,
a male rotor side expanded-bore-face 03a that faces a male
rotor tooth space during a gas suction process, and a male rotor
tooth tip with a clearance Bl greater than the mentioned
clearance Al, and
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a female rotor side expanded-bore-face 03b that faces a
female rotor tooth space during a gas suction process, and a
female rotor tooth tip with a clearance B2 greater than the
mentioned clearance A2.
Further, a lip part 04 is provided along a suction side
end-face of a casing 01 so that the lip part 04 of the casing
01 protrudes inside, toward screw rotors; on the other hand,
a suction seal line (a suction containment boundary locus) 05
is formed on a boundary between the male rotor side
main-bore-face 02a and the male rotor side expanded-bore-face
03a as well as between the female rotor side main-bore-face 02b
and the female rotor side expanded-bore-face 03b.
[0008] In the configuration as stated above, a working space
is formed with a tooth space of the male rotor and another working
space is formed with a tooth space of the female rotor, the pair
of tooth spaces being independent; whereby, the tooth spaces
are engraved on an outer periphery of rotors along a screw tooth
spiral. While the working spaces are communicated with the
expanded-bore-faces 03a or 03b, the working spaces are
gradually expanded to a maximum volume, inhaling a gas through
a gas inlet; then, the working spaces pass through the suction
seal line (the suction containment boundary locus) 05, and the
working spaces form a closed space the boundary of which
includes a male rotor side main-bore-face 02a and a female rotor
side main-bore-face 02b. Thus, after the working space becomes
a closed space, the volume of the working spaces is gradually
reduced and a confined gas within the space is compressed; at
a last stage of compression, the gas inside the spaces is
discharged through a discharge opening.
During the mentioned compression process, a liquid such
as oil or water is injected into the working space, for the
purpose of cooling, sealing, and lubricating.
[0009] Figs. l0a and 10b schematically depicts bore faces of
a conventional screw rotor casing. Fig. 10a shows a
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t I
transparently perspective view seen from the top, depicting a
suction seal line and a lip part. Fig. 10b is a development of
Fig. 10a.
In Figs. 10a and 10b, the reference numeral Ola denotes
a male rotor side casing, and the numeral Olb does a femamale
rotor side casing Olb; a suction seal line 05 is formed on a
boundary between a male rotor side main-bore-face 02a and the
male rotor side expanded-bore-face 03a as well as between the
female rotor side main-bore-face 02b and the female rotor side
expanded-bore-face 03b; a lip part 04 of the casing 01 protrudes
inside, toward screw rotors.
[0010]The Theworking (operatispaces formed with the male rotor
and the female rotor face the male rotor side expanded-bore-face
03a and the female rotor side expanded-bore-face 03b, while the
working spaces gradually increase during a suction process,
inhaling a gas through a gas inlet. After the volume of the
working spaces reaches a maximum volume and the working spaces
cross the suction seal line 05, the spaces form a sealed space,
being surrounded by the main-bore-faces 02a and 02b.
Subsequently, as the volume of the working spaces is reduced,
the gas confined in the spaces is compressed. And the compressed
gas is discharged through a discharge opening at a discharge
side end face 07 of the rotor casing.
In the above situation, the liquid such as oil or water
injected into the working spaces leaks toward a lower pressure
suction side and accumulates in the concaved expanded bore faces
03a/03b. The lip part 04 prevents the liquid from leaking and
scattering toward the gas suction end face 06 of the rotor
casing.
[0011] Patent literatures:
Patent literature 1, JP 1967-10027;
Patent literature 2, JP 1991-194183;
Patent literature 3, JP 1999-13661.
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Disclosure of the invention
Problem to be solved by the invention
[ 0012 ] In spite of the disclosure according to the configuration
such as in the patent literature 3, the conventional
technologies are insufficient in sealing a liquid within the
working spaces as well as in preventing deterioration as to
volumetric efficiency; the insufficiency is caused on the
ground that great distances remain between rotor tooth tips and
the lip part 04 (04a and 04b in Figs. 10a and lOb) placed at
the suction side end face of the rotor casings.
[00131 As just mentioned above, the lip part is provided at the
suction side end face of the rotor casings in conventional
liquid injection screw compressors; thus, a gas inlet has to
be placed outside across the suction side end face; moreover,
the lip part lessens a gas inlet passage area (opening area)
around the suction side end face of the rotor casings; therefore,
in case of manufacturing a mono-block casting of the rotor
casings and the gas inlet casing, it becomes difficult to
allocate a casting core for rotor casing bores.
Further, in conventional ways, only by means of
lengthening rotor space in the axial direction, it is possible
to secure a sufficient gas inlet passage for inhaling a gas into
the working space; in addition, insufficient inlet passage area
enhances suction resistance during a high-speed operation.
Because of the above-mentioned situations, it is
conventionally difficult to obtain a mono-block casting of the
rotor casings and the gas inlet casing. That is, in casting,
it is necessary to manufacture the rotor casing and the gas inlet
casing separately; further, it becomes necessary to provide
each casing with an essentially useless part such as an
additional flange that is needed for assembling the parts. Thus,
an increased whole weight and an intricate production process
are brought; further, as mentioned above, in a high speed
operation, there arise difficulties such as an increased gas
suction resistance as well as a lessened volumetric efficiency.
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[0014] In view of the mentioned subjects in conventional liquid
injection type screw compressors, the goals of the present
invention are:
preventing a liquid such as oil or water from leaking
outside the working spaces of high compression, which are formed
by screw rotors, toward the gas inlet side during a compression
process, more effectively than conventional ways;
lessening a gas suction resistance of a gas flow into the
rotor casings from an outside gas inlet so as to improve
volumetric efficiency of the inhaled gas, as a result; and
realizing an liquid injection type screw compressors of
a simplified structure so as to bring manufacturing cost
reduction.
Further, the invention aims at realizing a liquid
injection type screw compressor provided with a variable
compression ratio mechanism, that is, an internal volume ratio
adjusting valve; wherein, the compressor has a compact
structure so as to not prolong a manipulation mechanism of the
internal volume ratio adjusting valve, making manufacturing
cost be further reduced.
Means to solve the problem
[0015] In order to attain the mentioned goals, the present
invention proposes a liquid injection type screw compressor
comprising of:
a pair of a male rotor and a female rotor,
a rotor casing comprising a pair of bores that accommodate
the pair of the male rotor and the female rotor,
a gas inlet and a gas outlet that are connected to the pair
of the bores, the gas inlet being provided at a first end part
of the rotor casing, while the gas outlet being provided at a
second end part of the rotor casing, and
a lip part that is provided on a surface of the bores and
protrudes inside so as to prevent the liquid on the surfaces
of bores from back-flowing toward the gas inlet, the lip part
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, '
being located at a gas upstream side of a suction seal line of
the rotor casing;
wherein the lip part is placed within a range between the
suction seal line and a line that is apart from the suction seal
line, by one screw pitch distance of the screw rotors, toward
the expanded-bore-face side of the male rotor side casing and/or
the female rotor side casing (namely, toward the gas inlet
side).
[0016]In a screw compressor according to the present invention,
a lip part for preventing liquid from back-flowing toward a gas
inlet is provided on a casing bores, within a range between a
suction seal line and a line that is apart from the suction seal
line, by one screw pitch distance of the screw rotors, toward
the expanded-bore-face side of the male rotor side casing and/or
the female rotor side casing; hence, the lip part is placed
nearer to the suction seal line in comparison with conventional
ways ; as a result, a liquid leakage from the compressed working
spaces toward the gas inlet side is effectively prevented;
further, the lip part placed nearer to the suction seal line
makes it possible to eliminate a part of bore faces that is
located at the gas inlet side from the lip part. So can be
realized a simplified configuration of rotor casings with a
reduced bore surface as well as a reduced suction resistance
and a reduced manufacturing cost which are attributable to the
simplification.
[ 0017 ] A preferable configuration of the present invention may
comprise:
a straight development-line portion of the suction seal
line in a development view, lying at right angles to a bore
intersection line that is defined as a common generating line
of a male rotor bore and a female rotor bore,
a lip-entering-edge of the lip part that is placed apart
from the suction seal line toward the gas inlet side in a rotor
axis direction, whereby the lip-entering-edge in response to
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the above-mentioned straight-line portion is bent so as to
protrudes toward the suction seal line, and
a lip ending ( trailing ) edge of the lip part whereby the
lip ending edge in response to the straight-line portion is
placed parallel thereto so as to form a straight line portion
of the lip ending edge in a development view, and
a thickened (wide in the rotor axis direction) lip part
in response to the straight-line portion.
The above preferable configuration can surely prevent a
liquid leakage around a neighborhood along the bore
intersection line.
[0018] According to a further preferable aspect of the above
configuration,
the straight line portion of the suction seal line in a
development view lies at right angles to the bore intersection
line, and starts from a cross-point of the bore intersection
and the suction seal line on the male bore surface as far as
a point on the suction seal line on the female bore surface,
the lip-entering-edge of the lip part is placed apart from
the suction seal line toward the gas inlet side in the rotor
axis direction, and the lip-entering-edge in response to the
above-mentioned straight-line portion is bent so as to
protrudes toward the suction seal line; wherein, a part of the
lip-entering-edge in response to the straight line portion
starts from a cross-point of the bore intersection line and the
lip-entering-edge on the male bore surface, as far as a point
on the lip-entering-edge on the female bore surface,
the lip ending ( trailing ) edge of the lip part in response
to the straight-line portion is placed parallel thereto so as
to form the straight line portion of the lip ending edge in a
development view, and
the thickened (wide in the rotor axis direction) lip part
is provided in response to the straight-line portion, whereby
a straight line portion of the ending edge starts from a
cross-point of the bore intersection and the lip-ending-edge
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= '
on the male bore surface, as far as a point on the lip-ending-edge
on the female bore surface.
The above configuration can surely prevent a liquid
leakage around the bore intersection line.
[0019] Another preferable aspect of the invention according to
the mentioned configuration is the liquid injection type screw
compressor, wherein the rotor casing with the gas inlet casing
is formed in one piece or a plurality of divided-pieces from
the lip ending edge toward a gas downstream side. Thus, the gas
inlet side bore surface of the rotor casing can be omitted in
a way that the lip part is located nearer to the suction seal
line; as a result, it becomes possible to form a gas inlet casing
and a rotor casing in one body.
Consequently, the invention realizes a smaller rotor
casing, saving an installation space; in addition, the
invention greatly relieves restrictions concerning a position
where a gas inlet casing is disposed in a rotor casing; in this
regard, the degree of freedom as to the gas inlet casing design
can be greatly expanded.
[ 0020 ] According to a further preferable aspect of the invention,
a labyrinth structure is embodied on the inner surface which
faces rotor tooth tips in the lip part. For example, a pertinent
roughness of the surface (e. g. a pertinent casting surface
roughness) or an intended uneven surface can realize lesser
liquid leakage.
According to another preferable aspect of the invention,
different outer diameters are applied to a pair of the male rotor
and the female rotor so that the outer diameter of the male rotor
is greater than that of the female rotor, and the number of the
male rotor teeth is fewer than that of the male rotor teeth in
a case when the same outer diameter is applied to a pair of the
male rotor and the female rotor.
In this way, a screw pitch distance of the male rotor
can be shortened and the lip part can be located nearer to the
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suction seal line; thus, the liquid leakage can be further
surely prevented; in addition, the geometry of the casings can
be simplified.
[0021] According to another preferable aspect of the invention,
the lip part is provided at the lower side of the casing bore
surfaces. In this configuration, the liquid accumulated by
gravity at the bottom of the bore surfaces can be easily
prevented from scattering toward the gas inlet side; thus, a
simple structure can be realized.
[0022] Another preferable aspect of the invention according to
the mentioned configuration is a liquid injection type screw
compressor comprising:
a slide valve (capacity control valve), and
an internal volume ratio (ui) adjusting valve;
whereby, the slide valve has
a cut-out part, at a discharge end thereof, which
regulates a gas discharge throat between a discharge end part
(of gas discharge side) of the slide valve and an end face (of
gas discharge side) of the rotor casing, and
a valve driving rod (a pushrod) that is prolonged toward
the gas inlet casing on a rotor end face so that the valve driving
rod protrudes across the gas inlet casing, through a storage
space of the internal volume ratio adjusting valve that is
provided on a side of the gas inlet casing which comes in contact
with the rotor end face, the valve driving rod being connected
to a drive source i. e. a hydraulic cylinder in order that the
slide valve can move forward and backward along an axis of the
driving rod by means of the drive source and the driving rod,
while the internal volume ratio ( v i) adjusting valve in the
storage space is placed adjacent to a gas inlet side end face
of the capacity control valve (a slide valve), with a
positioning means that adjusts variably the position of the
internal volume ratio ( U 2) adjusting valve, along a direction
to/from a gas discharge side,
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wherein an internal volume ratio ( u i) is adjusted such that
the positioning means shifts the internal volume ratio (Ui)
adjusting valve to a predetermined position, while an internal
gas capacity (that is equivalent to a gas density at a
compression commencement) is adjusted by by-passing an inhaled
gas back to the gas inlet side through a gap between the internal
volume ratio (Ui) adjusting valve, and the capacity control
valve (a slide valve) that slides to and fro along the driving
rod direction by means of the drive source, through the driving
rod.
[0023] The installation of an internal volume ratio ( Ui)
adjusting valve makes a whole compressor compact, realizing a
compressor of three kinds of compression ratios, namely, of
lower/medium/higher compression ratios, without changing a gas
inlet casing, only by replacing a rotor casing. Thus, a gas inlet
casing can be applied to these kinds of compressors in common.
On the other hand, conventional compressors are apt to
be of a large size, as a positioning means to position the
internal volume ratio ( U i) adjusting valve is prolonged toward
a gas discharge side, penetrating a gas discharging casing so
as to be used for setting (positioning) the valve.
In order to solve the difficulty, according to a further
preferable aspect of the present invention, the positioning
means comprises:
a hollow shaft which is placed concentric to the driving
rod, having a screw part on an outer surface of the hollow shaft
so that the screw part is engaged into a corresponding screw
part inside the internal volume ratio adjusting valve, and
a rotation rod that is placed so as to intersect with
the hollow shaft in order that the rod can transmit a rotational
driving movement of the rod to the hollow shaf t, via a connection
part; whereby, the rotational movement transmitted to the
hollow shaft is transformed into a to-and-fro movement of the
internal volume ratio adjusting valve, through the mentioned
screw engagement, so that the internal volume ratio adjusting
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valve is positioned to a predetermined position.
According to the above aspect, there is no need to prolong
a positioning means as in conventional approaches; a driving
mechanism to position the internal volume ratio-adjusting valve
can be formed as a compact one. The mentioned connection part
between the hollow shaft and the rotation rod may be a bevel
gear pair or a crossed helical gear pair.
Effect of the invention
[0024] In a screw compressor according to the disclosed
invention, a lip part for preventing liquid from back-flowing
toward a suction inlet is provided on a casing bores, within
a range between a suction seal line and a line that is apart
from the suction seal line, by one screw pitch distance of the
screw rotors, toward the expanded-bore-face side of the male
rotor side casing and/or the female rotor side casing.
Therefore, a liquid leakage scattering during a
compression process from the compressed working space formed
by the screw rotors toward the gas inlet side can be effectively
prevented.
Moreover, the lip part placed nearer to the suction seal
line makes it possible to eliminate a part of the rotor casing
at the gas inlet side from the lip part. So can be realized a
simplified configuration of rotor casings with a reduced bore
surface as well as a reduced suction resistance of an inhaled
gas and an enhanced volumetric efficiency of the compressor.
[0025] Further, the lip part placed nearer to the suction seal
line makes it possible to eliminate a part of the rotor bore
faces at the gas inlet side from the lip part. Hence, the rotor
casing can be formed in one body with a gas inlet casing. As
a result, manufacturing processes can be simplified and a
manufacturing cost can be reduced. Consequently, the disclosed
invention greatly relieves restrictions regarding
installation position of a gas inlet casing in a rotor casing.
Further, the degree of freedom as to the gas inlet casing design
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can be greatly expanded; in addition, a compact casing can be
realized and a compressor installation space can be reduced.
[0026] Also as already explained, in a screw compressor
according to the disclosed invention, the compressor comprises:
a straight development-line portion of the suction seal
line in a development view, lying at right angles to a bore
intersection line that is defined as a common generating line
of a male rotor bore and a female rotor bore,
a lip-entering-edge of the lip part that is placed apart
from the suction seal line toward the gas inlet side in a rotor
axis direction, whereby the lip-entering-edge in response to
the above-mentioned straight-line portion is bent so as to
protrudes toward the suction seal line, and
a lip ending ( trailing ) edge of the lip part whereby the
lip ending edge in response to the straight-line portion is
placed parallel thereto so as to form a straight line portion
of the lip ending edge in a development view, and
a thickened (wide in the rotor axis direction) lip part
in response to the straight-line portion.
Thus, the above configuration can surely prevent a liquid
leakage around a neighborhood along the bore intersection line.
Further, in a screw compressor according to the disclosed
invention, the compressor comprises:
the straight line portion of the suction seal line in
a development view lies at right angles to the bore intersection
line, and starts from a cross-point of the bore intersection
and the suction seal line on the male bore surface, as far as
a point on the suction seal line on the female bore surface,
the lip-entering-edge of the lip part is placed apart
from the suction seal line toward the gas inlet side in the rotor
axis direction, and the lip-entering-edge in response to the
above-mentioned straight-line portion is bent so as to
protrudes toward the suction seal line; wherein, a part of the
lip-entering-edge in response to the straight line portion
starts from a cross-point of the bore intersection and the
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lip-entering-edge on the male bore surface, as far as a point
on the lip-entering-edge on the female bore surface,
the lip ending (trailing) edge of the lip part in
response to the straight-line portion is placed parallel
thereto so as to form the straight line portion of the lip ending
edge in a development, and
the thickened (wide in the rotor axis direction) lip
part is provided in response to the straight-line portion,
whereby a straight line portion of the ending edge starts from
a cross-point of the bore intersection and the lip-ending-edge
on the male bore surface, as far as a point on the lip-ending-edge
on the female bore surface.
Thus, the above configuration can surely prevent a liquid
leakage around a neighborhood along the bore intersection line.
[ 0027 ] Further, in a screw compressor according to the disclosed
invention, different outer diameters are applied to a pair of
the male rotor and the female rotor so that the outer diameter
of the male rotor is greater than that of the female rotor, and
the number of the male rotor teeth is fewer than that of the
male rotor teeth in a case when the same outer diameter is applied
to a pair of the male rotor and the female rotor.
In this manner, a screw pitch distance of the male rotor
can be shortened and the lip part can be located nearer to the
suction seal line; thus, the liquid leakage can be further
surely prevented; in addition, the geometry of the casings can
be simplified.
[0028]Further,in a screw compressor according to the disclosed
invention, the compressor comprises:
a slide valve (capacity control valve), and
an internal volume ratio (ui) adjusting valve;
whereby, the slide valve has
a slide valve (capacity control valve), and an internal
volume ratio (vi) adjusting valve;
whereby, the slide valve has
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a cut-out part, at a discharge end thereof, which
regulates a gas discharge throat between a discharge end part
(of gas discharge side) of the slide valve and an end face (of
gas discharge side) of the rotor casing, and
a valve driving rod (a pushrod) that is prolonged toward
the gas inlet casing on a rotor end face so that the valve driving
rod protrudes across the gas inlet casing, through a storage
space of the internal volume ratio adjusting valve that is
provided on a side of the gas inlet casing which comes in contact
with the rotor end face, the valve driving rod being connected
to a drive source in order that the slide valve can move forward
and backward along an axis of the driving rod by means of the
drive source and the driving rod,
whereas the internal volume ratio adjusting valve in the
storage space is placed adjacent to a gas inlet side end face
of the capacity control valve (a slide valve), with a
positioning means that adjusts variably the position of the
internal volume ratio adjusting valve, along a direction
to/from a gas discharge side,
wherein an internal volume ratio is adjusted such that the
positioning means shifts the internal volume ratio adjusting
valve to a predetermined position, while an internal gas
capacity is adjusted by by-passing an inhaled gas back to the
gas inlet side through a gap between the internal volume ratio
adjusting valve, and the capacity control valve (a slide valve)
that slides to and fro along the driving rod direction by means
of the drive source, through the driving rod.
According to the above disclosure, the installation of an
internal volume ratio (vi) adjusting valve can make a whole
compressor compact, realizing a compressor of three kinds of
compression ratios, namely, of lower/medium/higher
compression ratios, without changing a gas inlet casing, only
by replacing a rotor casing. Thus, a gas inlet casing can be
applied to these kinds of compressors in common.
[0029] Still further, in a screw compressor according to the
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disclosed invention, the compressor comprises a positioning
meansfor positioning the internal volume ratio-adjusting valve,
the positioning means comprising:
a hollow shaft which is placed concentric to the driving
rod, having a screw part on an outer surface of the hollow shaft
so that the screw part is engaged into a corresponding screw
part inside the internal volume ratio adjusting valve, and
a rotation rod that is placed so as to intersect with
the hollow shaft in order that the rod can transmit a rotational
driving movement of the rod to the hollow shaft , via a connection
part; whereby, the rotational movement transmitted to the
hollow shaft is transformed into a to-and-fro movement of the
internal volume ratio adjusting valve, through the mentioned
screw engagement, so that the internal volume ratio adjusting
valve is positioned to a predetermined position.
According to the above aspect, there is no need to prolong
a positioning means as in conventional approaches; a driving
mechanism to position the internal volume ratio-adjusting valve
can be formed as a compact one.
BRIEF DESCRIPTION OF THE DRAWINGS
(00301 The present invention will now be described in greater
detail with reference to the preferred embodiments of the
invention and the accompanying drawings, wherein:
Fig. la shows a transparently perspective view seen from
a top as to a first embodiment of the present invention;
Fig. lb is a development view of Fig. la;
Fig. 2a shows a perspective view of an upper side
rotor-casing seen from the inside thereof, as to a first
embodiment;
Fig. 2b shows a perspective view of a lower side
rotor-casing seen from the inside thereof, as to the first
embodiment;
Fig. 3 shows a perspective view of a part of a rotor casing
as to the first embodiment;
Fig. 4 shows a longitudinal plan view of a second
17
CA 02626884 2008-04-22
embodiment of the present invention;
Fig. 5 shows a longitudinal section view concerning the
second embodiment;
Fig. 6 explains a development view showing a suction seal
line (a suction containment boundary locus) as to each of the
male/female rotors that have different tip diameters;
Fig. 7 gives an explanation about the male/female rotors
that have different tip diameters;
Fig. 8 shows a perspective view as to a variation of the
second embodiment;
Fig. 9a shows a perspective view of an upper side
rotor-casing seen from the inside thereof, as to a conventional
compressor;
Fig. 9b shows a perspective view of a lower side
rotor-casing seen from the inside thereof, as to a conventional
compressor;
Fig. l0a shows a transparently perspective view seen from
the top as to a conventional compressor in consideration of a
schematic explanation for bore faces thereof; and
Fig. 10b is a development view of Fig. 10a.
Reference Numerals
[0031]
Ola, la, and lla a male rotor side casing;
Olb, 1b, and llb a female rotor side casing;
02a and 2a a male rotor side main-bore-face;
02b and 2b a female rotor side main-bore-face;
03a and 3a a male rotor side expanded-bore-face;
03b and 3b a female rotor side expanded-bore-face;
04, 4, and 33 a lip part;
4c and 33c a thickened lip part;
4d and 33d a lip entering edge;
4e and 33e a lip ending (trailing) edge
05, 5, and 32 a suction seal line (a suction containment
boundary locus)
5c and 32c a straight line portion of a suction seal
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line in a development view
06 and 6 a suction side end face
07 and 7 a discharge side end face
08, 8, and 34 a bore intersection line (that is defined
as a common generating line of a male rotor bore and a female
rotor bore)
9 and 12 a gas inlet (a suction inlet)
11 a rotor casing
13 a gas inlet casing
14 a male rotor shaft
15 a female rotor shaft
16 and 19 a thrust bearing
17, 18, 20, and 21 a radial bearing (a journal bearing)
22 a male rotor
23 a female rotor
24 a mechanical seal
25 a discharge outlet (a gas outlet)
26 a gas outlet casing
27 and 36 a tightening bolt
28 a slide valve (a capacity control valve)
28a a cut-out part
29 a pushrod (a valve driving rod for
manipulating a capacity control valve)
30 an oil-hydraulic cylinder (for driving a
capacity /displacement-volume control valve)
31 an internal volume ratio (ui) control
device of a manual operation type
35 a casing
37 an internal volume ratio ( ui) adjusting
valve for adjusting compression ratio vi
38 a hollow shaft
39a and 39b a bevel gear (a movement communicating
part)
40 a rotation-rod
41 a discharge opening
"a" in Fig. 4 an intersection point of a suction seal
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CA 02626884 2008-04-22
line and a bore intersection line
"b" in Fig. 4 an intersection point of a lip entering
edge and a bore intersection line
"c" in Fig. 4 an intersection point of a lip ending
(trailing) edge and a bore intersection line
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Hereafter, the present invention will be described in
detail with reference to the embodiments shown in the figures.
However, the dimensions, materials, shape, the relative
placement and so on of a component described in these
embodiments shall not be construed as limiting the scope of the
invention thereto, unless especially specific mention is
placed.
Fig. la shows a transparently perspective view seen from
the top as to a first embodiment of the present invention; Fig.
lb is a development view of Fig. la; Fig. 2a shows a perspective
view of an upper side rotor-casing seen from the inside thereof,
as to the first embodiment; Fig. 2b shows a perspective view
of a lower side rotor-casing seen from the inside thereof, as
to the first embodiment; Fig. 3 shows a perspective view of a
part of a rotor casing as to the first embodiment; Fig. 4 shows
a longitudinal plan view of a second embodiment of the present
invention; Fig. 5 shows a longitudinal section view concerning
the second embodiment; Fig. 6 explains a suction seal line (a
suction containment boundary locus) as to each of the
male/female rotors that have different tip diameters; Fig. 7
gives an explanation about the male/female rotors that have
different tip diameters; Fig. 8 shows a perspective view as to
a variation of the second embodiment;
[First embodiment]
[0033] Figs. la and lb schematically depict a bore face in a
rotor casing of a screw compressor according to the present
invention; Fig. la shows a perspective view as to a suction seal
line (a suction containment boundary locus) and a lip part on
CA 02626884 2008-04-22
the bore face seen transparently from a top; and, Fig. lb is
a development view of Fig. la; in Figs. 2a and 2b, the
rotor-casing is divided into an upper side part and a lower side
part so that the bore face of the casing is easily explained.
In a male rotor side casing la and a female rotor side
casing lb of Figs. la, 1b, 2a, 2b, and 3, a suction seal line
(a suction containment boundary locus) 5 is formed on a boundary
between main bore faces 2a/2b and expanded bore faces 3a/3b,
whereby the main bore faces 2a/2b are located opposite to
addendum circles of the a male rotor and a female rotor, with
a slight clearance, while a lip part 4 as a protruding part is
provided apart from the suction seal line 5, by a screw pitch
distance to a suction side end face 6. Here, an example of
dimension data is such that a clearance between the main bore
faces 2a/2b and the addendum circles of the a male rotor and
a female rotor is substantially 0.05 mm to 0.125 mm (a clearance
to a diameter c/D = 0.8 to 1. 0/ 1000 ), while a distance between
the expanded bore faces 3a/3b and the addendum circles of the
rotors is substantially 5 mm (a clearance to a diameter c/D =
0.05 to 0.06). It is noted hereby that c and d denote a clearance
and a diameter respectively.
[00341 The suction seal line 5 includes a curved part 5a that
is on a main bore face of the male rotor side casing la, a curved
part 5b that is on a main bore face of the female rotor side
casing 1b, and a curved part 5c that is also on the main bore
face of the female rotor side casing lb; whereby, in the
development figures of Figs. la and lb, the curved part 5c is
seen as a straight line which starts from a point "a" that is
a cross point of the curved part 5a and a bore intersection line
8; further, in Figs. la and lb, the straight line lies at right
angles to the bore intersection line 8, while the straight line
ends a point where the line intersects with the curved part 5b.
On the other hand, in response to the suction seal line
5, the geometry of the lip part 4 comprises:
a lip-entering-edge 4d of the lip part 4c that is placed
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CA 02626884 2008-04-22
apart from the suction seal line, within one screw pitch
distance, toward the gas inlet side along a rotor axis direction,
whereby the lip-entering-edge in response to the
above-mentioned straight-line 5c is bent so as to protrudes
toward the suction seal line; wherein, a part of the
lip-entering-edge in response to the straight line portion
starts from a cross-point "b" of the bore intersection line 8
and the lip-entering-edge on the male bore surface, as far as
a point on the lip-entering-edge on the female bore surface,
a lip ending ( trailing ) edge 4e of the lip part 4c whereby
the lip ending edge in response to the straight-line 5c is placed
parallel thereto so as to form a straight line portion of the
lip ending edge in a development view; wherein, a straight line
portion of the ending edge starts from a cross-point "c" of the
bore intersection line 8 and the lip-ending-edge on the male
bore surface, as far as a point on the lip-ending-edge on the
female bore surf ace , and
a thickened (wide in the rotor axis direction) lip part
4c in response to the straight-line portion 5c.
Liquid such as oil or water injected into a compression
working space is apt to leak toward a lower pressure suction
side and accumulates in concaved expanded bore faces 3a/3b. The
lip part 4 prevents the liquid from leaking and scattering
toward a gas inlet side.
[0035] According to the first embodiment as described above,
the distance between the suction seal line 5 and the lip part
4 is substantially within one screw pitch distance; thus, the
lip part 4 is provided at a location closer to the suction seal
line 5 in comparison with conventional ways. Therefore, in
comparison with conventional ways, is effectively prevented a
liquid leakage that scatters, during a compression process,
from the compressed working space which is formed by the screw
rotors toward the gas inlet side. Moreover, the lip part placed
nearer to the suction seal line makes it possible to eliminate
a part of the rotor casing, located at the gas inlet side from
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CA 02626884 2008-04-22
the lip part. So can be realized a simplified configuration of
rotor casings with a reduced bore surface as well as a reduced
suction resistance of an inhaled gas and an enhanced volumetric
efficiency of the compressor.
[0036]Further, in the above embodiment, a straight line portion
5c of the suction seal line 5 is provided in the neighborhood
of the bore intersection line, the line lying at right angles
with the bore intersection line in a development view. In
addition, a thickened lip part 4c is provided, comprising:
a lip-entering-edge 4d of the lip part 4c that is placed
apart from the suction seal line, within one screw pitch
distance, toward the gas inlet side in a rotor axis direction,
wherein the lip-entering-edge in response to the
above-mentioned straight-line portion 5c is bent so as to
protrudes toward the suction seal line; and
a lip ending (trailing) edge 4e of the lip part 4c,
being placed parallel to the straight line portion 5c so as to
form a straight line portion of the lip ending edge in a
development view; wherein, the straight line portion of the
ending edge is vertical to the bore intersection line 8 in a
development.
In this manner, can be surely prevented a liquid leakage
around the neighborhood along the bore intersection line,
toward a gas inlet side, from the working (compression) spaces
which are formed by the male female rotors.
Moreover, it becomes possible to eliminate a part from the
lip part 4 toward a side of the gas inlet 9 in the rotor casing;
in addition, a simplified configuration of rotor casings can
be realized. Further, since the gas inlet casing can be placed
nearer to the rotor casing, the rotor casing can be formed in
one body together with the gas inlet casing. As a result,
manufacturing processes can be simplified and a manufacturing
cost can be reduced.
[Second embodiment]
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CA 02626884 2008-04-22
[0037] A second embodiment of the present invention is now
detailed with reference to Figs. 4 to 8. As shown in Fig. 7,
in the second embodiment a male rotor and a female rotor of
different rotor sizes, namely different outer diameters, are
used; where the outer diameter of the male rotor is larger than
that of the female rotor, and the number of teeth as to the male
rotor is 5, while that as to the female rotor is 6.
In Figs. 4 and 5, the reference numeral 11 denotes the
rotor casing that accommodates both the male rotor and the
female rotor, and the rotor casing 11 together with a gas inlet
casing 13 that forms a gas inlet 12 is made of mono casting.
The rotor casing 11 accommodates the male rotor 22 and the female
rotor 23 shown in Fig. 7, here the detail of the rotors is omitted.
The reference numeral 14 denotes a male rotor shaft that is
supported by a thrust bearing 16 and radial bearings 17/18,
while the numeral 15 denotes a female rotor shaft that is
supported by a thrust bearing 19 and radial bearings 20/21.
[00381 A mechanical seal 24 is provided near a shaft end part
14a of the male rotor shaft 14, the shaft end part 14a being
connected to an output shaft of a drive motor (not shown) as
a power source.
A gas outlet casing 26 that forms a gas outlet 25 is made
of casting; however, the casing 26 is made of different casting
from the rotor casing 11, and the casing 26 is fastened thereto
with tightening bolts 27. At a lower part of the rotor casing
11, is provided a slide valve (a capacity control valve) 28 that
makes it possible to regulate a compressor capacity (an inhaled
gas capacity) by means of sliding-manipulation along an axis
direction of the rotors; thereby, a pushrod (a driving rod) 29
regulates a length as to the sliding-manipulation of the slide
valve 28. In addition, the pushrod 29 is operated through an
oil pressure that is supplied to a left cylinder room 30a and
a right cylinder room 30b in an oil-hydraulic cylinder 30.
[00391 At the middle part of the pushrod 29, is installed a U
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CA 02626884 2008-04-22
i-control device (an internal volume ratio control device) 31
of a manual operation type; hereupon, the device 31 makes it
possible to optimize the internal volume ratio ui. A casing
35 that contains the vi-control device 31 is fastened to the
gas inlet casing 13 with tightening bolts 36, while the
oil-hydraulic cylinder 30 is fitted to the casing 35. The
reference numeral 37 denotes an internal volume ratio (vi)
adjusting valve; thereby, the ui-adjusting valve 37 is engaged
into a screw part 38a that is provided on an outer face of a
hollow shaft 38. Here, the hollow shaft 38 is installed around
the pushrod 29 having a round cross-section, so that a round
hollow cylinder of the hollow shaft 38 and the round
cross-section of the pushrod 29 are concentric, and the hollow
shaft 38 can rotate freely around the pushrod 29. Further, the
ui-adjusting valve 37 moves along the rotor axes with a
rotational movement of the hollow shaft 38.
On the other hand, the reference numeral 39a denotes a
bevel gear that is fitted to a suction-side end part of the hollow
shaft 38, while the bevel gear 39a is engaged in a corresponding
bevel gear 39b that is fitted to an end part of a rotation-rod
40; hereupon, it is noted that the axes of the hollow shaft 38
and the rotation-rod 40 lie at right angles to each other.
[ 0040 ] According to the above-mentioned conf iguration, when the
rotation-rod 40 is rotated, either clockwise or
counterclockwise, a rotational movement is transmitted to the
hollow shaft 38; as a result, the v i-adjusting valve 37 moves
back and forth along an rotor axis, through an engagement of
the screw part 38a and the uj-adjusting valve 37. A steering
wheel (not shown) or the like may be fitted to the rotation-rod
40 so as to enable an operator to turn the wheel by hand in case
of manual control.
When the internal volume ratio (vi) is adjusted, the
following sequence of manipulations is performed: rotating the
rotation-rod 40 under a stop condition of the compressor; making
the U i-adjusting valve 37 move along an rotor axis; as a result,
CA 02626884 2008-04-22
thrusting the slide valve 28 toward the gas outlet 25; adjusting
an opening level of a discharge opening 41 that is formed between
a cut-out part 28a provided at a discharge-front end side of
the slide valve 28, and the gas outlet casing 26; thus,
initializing the internal volume ratio (vi).
[00411 In addition, when a capacity of the compressor needs to
be adjusted, the slide valve 28 is shifted along the axes of
the rotors through a movement of the pushrod 29; thereby, a
by-passed gas flow toward the gas inlet side from a gap between
the slide valve 28 and the pushrod 29 controls the capacity (the
inhaled gas flow quantity).
Fig. 6 shows the male rotor 22, the female rotor 23, and
the suction seal line 32 in the second embodiment, in which the
male rotor 22 and the female rotor 23 of different rotor sizes,
namely, different outer diameters, are used, where the outer
diameter of the male rotor is larger than that of the female
rotor; in addition, the number of teeth as to the male rotor
is 5, while the number of teeth spaces as to the female rotor
is 6.
[00421 Incidentally, in Fig. 4, are shown the suction seal line
32 and the lip part 33, for explanation use. Similar to Fig.
1 as to the first embodiment, the lip part 33 is provided apart
from the suction seal line 5, by a screw pitch distance, toward
the gas inlet side.
As shown in Figs. 4 and 6, the suction seal line 32
comprises:
a curved part 32a on the bore in the male rotor casing lla,
a curved part 32b on the bore in the female rotor casing
llb, and
a straight line portion 32c in a development view whereby
the straight part lies at right angles to the bore intersection
line 34; wherein, the straight line starts from a cross-point
"a" of the bore intersection line 34 and the curved part 32a,
as far as a point on the curved part 32b on the bore in the female
26
CA 02626884 2008-04-22
rotor casing lib.
[0043] Further, the lip part 33 comprises a male casing side
lip part 33a on the bore in the male rotor casing lla, and a
female casing side lip part 33b, while the boundary of the lip
part 33 comprises a lip-entering-edge and a lip ending
(trailing) edge; hereupon, the lip part 33 is away from the
suction seal line, within a screw pitch distance.
Still further, the lip-ending-edge comprises:
a straight line portion 33e, in response to the straight
line 32c of the suction seal line 32, and lying at right angles
to the bore intersection line 34 in a development view, while
the line portion 33e starts a cross-point "c" of the bore
intersection line 8 and the lip-ending-edge on the bore in the
male rotor casing lla, as far as a point of the lip-ending-edge
on the bore in the female rotor casing 11b; in addition,
the lip-entering-edge comprises:
a bent curve portion 33d, in response to the straight line
portion 32c of the suction seal line 32, whereby the bent curve
portion 33d protrudes toward the straight line portion 32c of
the suction seal line 32, while the bent curve portion 33d starts
a cross-point "b" of the bore intersection line 8 and the
lip-entering-edge on the bore in the male rotor casing lla, as
far as a point of the lip-entering-edge on the bore in the female
rotor casing llb.
In the above-mentioned manner, a thickened lip part 33c
is formed with the bent curve portion 33d and the line portion
33e, in response to the straight line portion 32c of the suction
seal line 32. So can be surely prevented a liquid leakage around
the neighborhood along the bore intersection line, toward a gas
inlet side, from the working (compression) spaces in the rotor
casing 11.
[0044] According to the second embodiment, in the same way as
the first embodiment, the lip part 33 is provided apart from
the suction seal line 5, by a screw pitch distance, toward the
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CA 02626884 2008-04-22
gas inlet side; thus, can be surely prevented a liquid leakage
around the neighborhood along the bore intersection line,
toward a gas inlet side, from the working (compression) spaces.
Further, since the lip part is provided around the neighborhood
along the bore intersection line as mentioned above, a liquid
leakage around the bore intersection line can be surely
prevented.
Moreover, can be eliminated a part of the rotor casing on
the gas inlet side of the lip part 33. Thus, can be secured a
satisfactory space that communicates the bore faces of the rotor
casing to the gas inlet 12, the space reducing a suction
resistance of the gas inhaled from the gas inlet 12. As a result,
a volumetric efficiency of the compressor can be enhanced.
[00451 On the other hand, by means of eliminating a part of the
rotor casing the part which is located on the gas inlet side
of the lip part, the location of the gas inlet 12 can be shifted
toward the rotor casing 11. Thus, the rotor casing 11 together
with a gas inlet casing 13 that forms a gas inlet 12 can be made
of mono casting. In this way, a compact casing can be realized
and a compressor installation space can be reduced.
Consequently, a compact casing can be realized, a compressor
installation space can be reduced, a compressor manufacturing
cost can be greatly lowered, and the degree of freedom as to
the gas inlet casing design about the rotor axis direction can
be expanded.
Further, it becomes possible to design a compressor casing
of the same kind compressors so that a distance L between an
axis "i" of the gas inlet 12 and an axis "o" of the gas outlet
25 can be kept constant. Therefore, a manufacturing line of the
compressor casings can be streamlined so as to mechanized and
robotized.
[00461 The installation of an internal volume ratio ( ui)
adjusting valve makes a whole compressor compact, realizing a
compressor with three kinds of compression ratios , namely, of
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CA 02626884 2008-04-22
lower/medium/higher compression ratios, without changing
sorts of a gas inlet casing, only by replacing a rotor casing.
Thus, a gas inlet casing can be applied to these kinds of
compressors in common. Namely, even if the rotor-casing is
replaced by another one for constituting a different kind
(capacity) of the compressor, it is not necessary to exchange
the gas inlet casing.
Further, conventional compressors are apt to be of a large
size, as a positioning means to position the internal volume
ratio ( v i) adjusting valve is prolonged toward a gas discharge
side, penetrating a gas outlet casing so as to be used for
positioning the valve. Contrary to the above, the second
embodiment comprises a positioning means for positioning the
internal volume ratio-adjusting valve including:
a hollow shaft 38 , and
a rotation rod 40 that is placed so as to intersect with
the hollow shaft with right angles in order that the rod can
transmit a rotational driving movement of the rod to the hollow
shaft, via a bevel gear pair 39a/39b.
According to the above configuration, there is no need to
prolong a positioning means as in conventional approaches; a
driving mechanism to position the internal volume
ratio-adjusting valve 37 can be formed as a compact one.
[0047] Incidentally, for the connection part between the
rotation rod 40 and the hollow shaft 38, a crossed helical gear
pair may be applied instead of a bevel gear pair; a bevel gear
pair tends to have a play to some extent between meeting gears,
while a crossed helical gear has little play.
Industrial Applicability
[0048] According to the present invention regarding a liquid
injection type screw compressor, a liquid leakage, such as an
oil leakage or a water leakage, that flows back to a gas inlet
side from a compression room which is formed screw rotors is
further effectively prevented in comparison with conventional
29
CA 02626884 2008-04-22
compressors of the same kind. In addition, suction resistance
of the gas inhaled from the gas inlet can be lowered, and
volumetric efficiency as to the inhaled gas can be improved;
further, cast modeling of a rotor casing can be simplified and
a manufacturing cost can be reduced.
Thus, the invention greatly contributes to a practical
compressor industry.
