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Патент USA US3073523

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Jan.‘ 15, 1963
Filed April 26, 1960
4 Sheets-Sheet 1
‘0M M A?!”
Jan. 15, 1963
Filed April 26, 1960
4 Sheets-Sheet 2
Jan. 15, 1963
Filed April 26, 1960
4 Sheets-Sheet 3
Jan- 15, 1963
Filed April 26, 1960
4'Sheets-Sheet 4
United States Patent 0 “cc
Patented Jan. 15, 1963 .
to the other has been effected by means of‘intermeshing _ f
timing gears the arrangement according to the invention
is such that such gears will be rendered‘ unnecessary and
the rotor driven by the shaft 13 will be effective directly ,
‘Wilfred Bailey, Glasgow, Scotland, assignor, by mesne
assignments, to Svenska Rotor Maskiner Aktiebolag,
to drive the other rotor or rotors.
Naclra, Sweden, a corporation of Sweden
Filed Apr. 26, 1960, Ser. No. 24,803
4 Claims. (Cl. 230-143)
In the embodiment shown in FIG. 1 the arrangement
is such that a liquid such as an oil or other liquid havingv
the necessary lubricating qualities is introduced into the
This invention relates to rotary compressors of the
compressor casing. The liquid acts as a sealing medium -
positive displacement type including two or more rotors 10 for the clearances between the interengaging lobes and
disposed within a housing and formed with interengaging
grooves of the rotors, as a coolant for the air or gas being
helical lobes and grooves, which, however, are not in
compressed and also as a lubricant for the anti-friction
physical contact with one another, but engage with small
bearings supporting the rotors. Referring now speci?cally > .
‘ clearances. correspondingly. the rotors do not contact the
to FIG. 1, 1'7 denotes a pressurized tank from which oil
housing'but rotate with small clearances betweenv the lobe 15 is fed both to the interior of the compressor casing to act
'tips and the inner surface of said housing which is pro
as a sealing medium and also as a coolant and also to the
vided with a discharge port proportioned to cause the pres
rotor bearings. The pump 16 on the shaft 14 is adapted
sure of the gas being compressed to be raised Within
on operation of the compressor to draw oil from the
the compressor before the gas is discharged. The com
tank 17 through a pipe 18 and to deliver such oil via a
, pressor has a working chamber into which a liquid is in
pipe 19, cooler'20 and pipe 21 into the compressor casing
jected to seal the clearances between the rotors, and be
adjacent the air inlet where it enters the clearances be- ,
tween the rotors ,and casing, and to cool the gas being
tween the rotors and between the rotors and the casing
and also enters the rotor bearings.
The present invention is an improvement in or modi?
The majority of the oil thus supplied to the compressor
dation of that forming’the subject of my prior copending 25 is discharged with the compressed air or gas, after acting
application Serial Number 696,349, ?led November 14,
as a sealing and cooling medium, through the duct 12‘
1957, now abandoned, of which this application is a con
and hence to a separator 22 wherein the oil is separated
from the air or gas and returns through a pipe 23 to the
The invention herein has for its chief object to' provide
tank 17, the compressed air or gas being discharged
a compressor of a more simpli?ed andcompact construc
through a conduit 24.
tion, than that disclosed in the aforesaid prior copendin
. application.
bearings through ducts 25 and 26 and it will be returned '
by the pump 15 on the shaft 14 via the duct 27 to the
. the, type referred to above in which a liquid is introduced
into the compressor in su?icient amounts'to seal the small
clearances and also to enableone rotor which is' driven
compressor for repassage through the latter.
vAlthough in thepforegoing the arrangement is such that
from an‘ external source to drive the other or others
the rotor bearings‘ are‘ pressure fed with lubricant it would
without the necessity for the usual intermeshing timing
nevertheless be possible to employ splash lubrication , 1
The liquid may be a-lubri'cat- .
from the injection.
ing oil or any other suitable liquid having the necessary
‘ In Fl'G.§2 is shown a diagrammatic arrangement of a _ '7
In order that thernature of the invention may be clear
ly understood and readily carried into effect the same
‘will be hereinafter more fully described with reference to
the accompanying drawings in which:
FIG. 1 is a diagrammatic arrangement of one form
‘FIG. ‘3 shows in side elevation one construction of a
. .
FIG. 4 is a horizontal ‘section along-the ._1ine'IV-—I:V
FIG. '5 is a .view corresponding to FIG. .3 with the
casing partially cut- away showing the positionof the out
FIG. 1 is supplied by the pump 16 through pipe 19,;
The liquid discharged with the compressed'air or gas
compressor according to the‘ invention.
system wherein the sealing and cooling medium is a liquid
other than the lubricant for the rotor hearings. in this
‘case the sealing and cooling medium is contained in a
pressurized tank 17 and similarly to'the arrangement in
'cooler 26 and pipe 21 to the interior of the compressor.~ ~ ' ’
FIG. 2 is a diagrammatic arrangement of a modi?ed
form of the invention}
inlet and outlet ends ofthe rotors will drain from such
A further object is to provide a rotary [compressor of _
gears hitherto employed.
A proportion of the oil passing to the bearings at the
FIG. 6 is a section along "the line -vi_vi of FIG, 5.‘.
FIG. 7 is a section through the working chamber along .
through they duct; 32 is ‘delivered as before to the septarator 22 and after separation returns via pipe 23 to the
tank 17, the air or gas being discharged through the pipe _}
1 > The lubricating systemv comprises a ventilated-tank 28‘
from which oil is suppliedrby the pump 1S'through a
pipe 29', acooler 3t? and a pipe 31 to the outlet end '
bearingsand through a‘branch'pipe 32 to theinlet end
bearings. , Oil draining from these two bearings passes
through pipes 33 and 34 back to the tanklh.
‘ "
It will be appreciated that with an arrangement such as
the line Vii-VII of FIG. 5.‘
‘is shown in FIG. I wherein the rotors are supported inf
Referring now to FIGS. 1 and,»2, 10. denotes a rotary 60iantifrictionbearings and a portion of the liquid injected
compressor of the positive displacementv typevhaving two 1 ‘into the working chamberot the compressor is permitted
or more rotors disposed. within an outer ‘casing and “to pass to such hearings to provide for lubrication and a‘
formed with interengaging.helicallobes and grooves en
gaging with smallclearances ashereinafter described .with
cooling thereof, the‘resultant construction will be simpler
’ . sincethere is no necessityfor external or‘additional :lub
reference toFIG. 3.- As is well known in the operationjof . 65 rication supplies such, for example, as isthecase with th
such a compressor air or gas entering byiway of an inlet '
arrangement shown in F1G.2_
duct lliis compressedand thereafter discharged ‘through
> _ Theia‘mount of liquid injected into the uworkingichan'le
an outletductlZ. One of the rotorsis driven through a " ber of‘ the‘ compressor'will depend on the'cha'r'acteris'tic ,.
driving shaft 13v and serve'sto'drivetlie other frotor'which ' ofthe compressor. for example tests have shown,that!v
. carries on its shaft 14 two pumps ,15 andlo, the purpose
the vvolumetric r'aito between the liquid introduced for,
of which will be'hereinaft'er described. .Itmay 'be‘ men
tioned here that while hitherto the ,drive fromone rotor
‘ example in the formbf oil has varied between 0.24%.
liquid to‘
at maximum speedand.l.1% liquid to gas
The male rotor 43 is ?tted with an overhung pinion 49
forming part of the speed increasing gear and, on applica
tion of the casing part 39 to the ?ywheel housing 37, mat
ing directly with the gear 38 secured to the ?ywheel.
low speed of the compressor, these ?gures being given
merely by way of example only and without limitation
thereto. These volumetric ratios correspond to mass
ratios of liquid to gas of 1.5/1 and 10/ l. The optimum
Thus the male rotor 43 is driven from the engine and as
indicated above by virtue of the introduction of the liquid
into the working chamber of the compressor said rotor 43
is effective to drive the female rotor 44 without the neces
or preferred mass ratio appears to be about 4/ i at max
. imum compressor speed.
The viscosity of the oil or other medium employed will
depend on the clearances between the lobes of the rotors
sity for any intermeshing timing gears such as have hither
and the smaller the clearance the thinner the oil or other
to been employed. It may be pointed out here that the
medium which may be used. The clearance will vary
mounting of the rotors is such that the small clearances
with the rotor diameter but not however in direct propor
between the lobes 50, 51 of the respective rotors will be
tion and the clearances employed in practice will be a
maintained without possibility of direct contact of said
compromise between what is desirable and what is pos
sible in production. Purely as examples only the clear
Located outside the compressor casing and mounted
ances used between the rotor lobes, measured on the end 15 on the end plate 52 and driven by the shaft of the female
face may be .0024-—.O04" in the case of 5" diameter
rotor 44 are the pumps, denoted diagrammatically at 53,
rotors and 0035-006” in the case of 8” diameter rotors.
injecting the liquid sealing and cooling medium into
It is to be understood that due to the smaller tempera
compressor casing and for supplying lubricant to the
ture rise obtained when using liquid as a sealing medium
bearings of the rotors.
and coolant, the clearances between the rotors and be 20 endFrom
the above description it will be understood that
tween the latter and the housing, may initially be made
43, 44 are mounted within a casing which is
smaller without fear of rubbing contact on expansion,
divided longitudinally along the diametrical plane of the
due to temperature, than in the case of “dry” air ma
This enables the rotors to be inspected on re
chines. However, the outlet end clearance, that is, the
moval of the upper casing parts and to be withdrawn from
clearance between the rotors and the housing at the high 25 the casing without drawing the same axially through the
pressure delivery end, is believed to be of considerable
casing after removal of the end plate 52 of the casing.
importance, and in order to limit leakage across the high
In operation the driving members 35, 36 drive the male
pressure ends of the rotors, the clearance between the
rotor 43 through the intermediary of the meshing gears
rotors and the housing should not exceed 0.010 inch. In
38, 49 and air enters the compressor through the air
general higher viscosity oil decreases the back leakages 30 inlet
duct 77 and through the inlet port 82 (FIG. 6) at
giving greater volumetric efficiency but increased churn
the inlet end of the easing into the working chamber
ing loss. For rotors less accurately produced, i.e. with
83 formed by the bores 75, 76 of the casing and the end
larger local clearances for the same backlash it would be
walls 84, 85 thereof. The air in the working chamber
preferable to use higher viscosity oil.
passes into the grooves 86, 87 of the intermeshing rotors
Since the rotational speed of a compressor varies with 35 43, 44 and is compressed therein by the progressive en
the size of the machine, a governing factor in obtaining
gagement of the rotor lobes within said grooves and is
good results will be the tip speed which should be ap
moved to the outlet end of the working chamberv to ex~
proximately constant for all sizes of machines. Tests
through the compressed air outlet port 78. During
have shown that satisfactory results are obtained with tip
40 rotation of the rotors 43, 44 the pump 72 on the shaft of
speeds of between 60 and 145 feet per second.
the female rotor 44 draws the sealing and cooling medium
FIGS. 3 to 7 show a preferred construction of the com
from a supply of, for example, lubricant (not shown in
pressor according to the invention. The compressor illus
FIGS. 3-7) and delivers said medium to the apertures
trated is intended to form a portable compressor unit with
81 where it enters the grooves 86, 87 of the rotors and
a diesel or other internal combustion engine. The en
seals the clearances 80 between the intermeshing elements
gine shaft 35 carries a ?ywheel 36 enclosed within a ?y 45 of the rotors and also seals the clearance shown diagram
wheel housing 37 and carrying an externally toothed gear
matically in FIG. 7 at 88 between the rotor lobes 70,
33. The compressor includes a main casing comprising
71 and the walls of the bores 75, 76. Said medium passes
parts 39, 40, the part 39 being bolted to the ?ywheel hous
through the outlet port 78, together with the compressed
ing 37.
air or other gaseous medium and is separated from the
The casing part 39 supports the rotor bearings at the 50 compressed air outside the compressor in the manner
inlet end of the compressor and forms a housing for the
described with reference to FIG. 1 or FIG. 2.
speed increasing gears of the rotors. The casing part 40
Rotary compressors of the kind described above are
is formed with the bottom half of the main rotor bores
normally designed for an optimum built-in presure ratio
75, 76 and supports the rotor hearing at the outlet end
,which means that the outlet port of the compressor has
of the compressor. To the casing parts are secured an 55 a de?nite predetermined shape normally substantially tri
inlet casing member 56 formed with an inlet duct 77
angular as shown in FIG. 4, and the delivery starts at a
through which the gas passes to the rotors and an upper
predetermined distance along the rotor axis. The nearer
casing member 57 formed with the top half of the rotor
the location of the point of opening‘ 90 (apex) of the tri
bores‘ 75, 76 and with a suitably shaped delivery port 78
angularly shaped outlet port 78 to the delivery end of the
(see FIGS. 4 and 7). The upper casing members 56, 60 machine, the higher will be the pressure ratio. In deter
57 will be rigidly ?xed to the lower casing para 39, 40
mining the pressure ratio of machines having liquid in
by means of a number of threaded studs 58 passing
troduced into the gas inlet, this would appear to differ
through aligned holes 42 in ?anges on thelrespective
slightly from the theoretical location for machines using
“dry” air. For example, in obtaining an outlet pres
Two rotors 43, 44 are located in the bores 75, 76 of the
sure of 100 lbs. per square inch corresponding to a pres
casing and are carried by suitable bearings. At the inlet
sure ratio of 7.8/1, a built-in‘pressure ratio of between
end the bearings comprise main bearings 45 which in the
7.0/1 and 9.0/1 depending on the speed of the rotors
illustrated construction are of thewhite metal half shell 5’ gifes'optimum results when oil is introduced into the gas
type but may-if desired be anti-friction bearings of the
ball and roller type. ,Similar bearings 46 are-located at 70 While in therabove description reference has been made
to compressors forming part of a portable compressor
the outlet end of the compressor and in addiiton thrust
'unit‘driven by a diesel engine, it is to be understood that
bearings 47 of the tilting pad type are provided at this
end. .Alternatively ball or roller bearings of the axial ’
thrust type may replace the bearings 46, 47. Labyrinth
' seals 48 are ?tted at both ends of the rotors.
‘a compressor constructed,‘ and ‘operating according to'this
invention may, if desired, be installed in a stationary
75 plant driven by an electric motor running at speeds of the
order of 1500 r.p.m. or by any other suitable power
a pinion is a?ixed to said pinion shaft exteriorly of said
casing and engaged with the teeth of said ?ywheel.
Various changes and modi?cations may be made with~
4. A rotary compressor as de?ned in claim 1 wherein a
out departing from the spirit and scope of the present
pump is provided for said ?uid, and wherein said female
invention and it is intended that such obvious changes 5 rotor is provided with a forwardly extending pump shaft
and modi?cations be embraced by the annexed claims.
extending through said casing and connected to said pump,
What I claim is:
wherein a drive shaft is provided for said compressor, a
1. A rotary compressor comprising a casing having a
toothed ?ywheel is a?ixed to said drive shaft, a pinion
working chamber extending longitudinally in said casing
shaft extends from said male rotor rearwardly through
and formed of a pair of intersecting bores, said casing 10 said casing, and a pinion is affixed to said pinion shaft
having an inlet port communicating with one end of said
exteriorly of said casing and engaged with the teeth of
chamber, said casing having an outlet port providing a
said ?ywheel.
discharge from said chamber, a male rotor positioned in
References Cited in the ?le of this patent
one of said bores, a female rotor positioned in the other
of said bores, said male rotor having spiral lobes, said 15
female rotor having spiral grooves each receiving in slight
Kerr ________________ __ Oct. 28, 1919
ly spaced intermeshing relation one of said lobes, said
.Kien ________________ __ Mar. 14, 1922
rotors being slightly spaced from the walls of their respec
Leonard _____________ __ June 5, 1928
tive bores, and separate means operable upon operation
Meston et al. _________ __ June 12, 1928
of the compressor for supplying a lubricating and cooling 20
?uid to said chamber to ?ll the spaces between said lobes
and the walls of said grooves, said ?uid disposed in the
space between said lobes and the walls of said grooves
constituting the sole means for transmitting driving force
from one rotor to the other.
2. A rotary compressor as de?ned in claim 1 wherein a
pump is provided for said fluid, and wherein said female
rotor is provided with a forwardly extending pump shaft
extending through said casing and connected to said pump.
3. A rotary compressor as de?ned in claim 1 wherein a
drive shaft is provided for said compressor, a toothed ?y
wheel is af?xed to said drive shaft, a pinion shaft extends
from said male rotor rearwardly through said casing, and
Meston et al. _________ __ June 12,
Zajac _______________ __ July 3,
DeBije ______________ __ Oct. 10,
Lysholm _____________ __ June 3,
Montelius ____________ __ Oct. 24, 1944
Paget _______________ __ July 26, 1949
Lindhagen et a1. _______ __ Feb. 3, 1953
Nilsson ______________ __ Aug. 12, 1958
Davey ______________ __ Sept. 22, 1959
Great Britain ______________ __ of 1895
Australia ____________ __ Feb. 25, 1959
Germany ____________ __ Dec. 15, 1931
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