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06:; 29, '1946.
Filed May 51, 1941
v 3 Sheets-Sheet 1
~Y Oct‘._29,1946.
Filed May 31, 1941 _
s Sheets-Sheet 2. '
3 ,
3 She'ets-Sheet 3
laatented 6a. 279, 1946
ROTARY scREzv‘ltig’lllglii.
mesne assignments, to Jarvis 0. Marble, Leslie
M. Merrill, and Percy H. Batten, as trustees
Application May 31, 1941, Serial No. 396,030
10 Claims. (01. 230-143)
The present invention relates to apparatus of
the rotary screw wheel'type and has particular
will operate with piston speeds su?iciently low to
reference to compressors of this type as disclosed
of operation.
in my United States Patents No. 2,174,522 and
No. 2,243,874 granted October 3, 1939 and June
3,1941, respectively. More particularly my in
I have further discovered that in the operation
of high speed compressors of the kind with which
the present invention is concerned, certain pres
vention relates to compressors of the aforesaid
type adapted to be constructed in large sizes for
sure variation or pressure wave phenomena occur
avoid excessive dynamic losses due to this factor
in the ?eld chambers both during the ?lling
periods and during compression which can be
10 made use of to increase the capacity and effi
gaseous ?uid.
ciency of operation of a compressor of given size,
Apparatus of the kind under consideration em
and in another of its aspects the present inven
bodies working chambers de?ned by relatively
tion has for further objects the improvement
moving rotor and casing parts which are out of
of ‘compressor performance through improved
contact with each other and the leakage from
whichvis minimized by close clearances between “ port arrangement and construction by means of
which such phenomena may be turned to useful
the moving parts which may conveniently be '
referred to as “space packing.” In order for
- The manner in which the above general ob
such apparatus to operate with acceptable e?'i
ject and other and more detailed objects which
ciency, the volume of ?uid leaking from the
working chambers through the space packing 20 wil1 hereinafter appear, are attained, may best
be understood from a consideration of the en
must be relatively small compared with the vol
suing portion of this speci?cation, taken in con
ume of ?uid passing through the apparatus and
junction with the accompanying drawings, in
this is essentially accomplished in the type of
which by way of example but without limitation
apparatus under consideration by operating the
rotors at very high speeds, since the volume of 25 'suitableapparatus for carrying the invention into
effect is described and illustrated.
?uid handled is substantially a direct function
In the drawings:
of the speed of operation while the volume of
the compression of relatively large volumes of
leakage through the space packing is relatively
constant with respect to speed.
Fig. 1 is a longitudinal section of a compressor
of Fig. 4;
The very high rotor speeds required to secure
Fig. 2 is a section taken on the line 2—2 of
Fig. 1;
working chambers result in relatively high veloc
ities of fluid ?ow, which in turn involve dynamic
Fig. 3 is a section taken on the line 3-—-3 of
I have discovered that a major factor pro
ducing such dynamic losses is- the high speed of
flow of the ?uid along the length of the grooves
embodying the invention, taken on the line l—-I
a sufficiently low percentage of leakage from the
Fig. 4 is a section taken on the line .4—4 of
Fig. 1;
Fig. 5 is a fragmentary view taken from the
line 5—5 of Fig. 1;
Fig. 6 is a fragmentary plan view looking from
are ?lled during the inlet phase of the cycle of
operation, this being particularly true when the 40 the line 6—6 of Figs. 1 and 4; and
Fig. 7 is a diagrammatic development illustra
apparatus operates as a compressor. This speed
tive of certain features of construction.
of ?uid ?ow during the ?lling period may con
Referring now to the drawings, the compres
veniently be referred to as piston speed since
sor comprises a casing in consisting of a central
the moving ?uid column is analogous to a piston.
barrellportion Illa and end closures “lb and 100.
Considerations such as required speed of oper
In the embodiment illustrated, the central casing
ation for acceptable e?iciency, proper relation of
portion is shown with a jacket space 12 for
diameter to length of rotors and otherpractical
cooling ?uid. In the case of small compressors
design factors result in very high piston speeds
such j acketing may in some instances be omitted
in compressors of the kind under consideration
when they are designed for large capacity, such 50 but ordinarily with large capacity compressors
some form of cooling of the casing is desirable
for example as 10,000 cubic feet per minute, and
in order to prevent unequal expansion which ad
in one of its aspects the invention has for an
versely affects the maintenance of the. desired
object the provision‘ of improved structure ca
close clearances.
pable of embodiment in units of large capacity
The male rotor I4 is mounted for rotation‘ in
for high speed operation, which at the same time 55
which form the Working spaces, as these spaces
bearings l6 and I8 in the casing structure, For
As will be observed from Fig, 1, timing gear 44
is carried by a hollow sleeve-like extension of the
rotor core which is carried in the bearing l6.
Although it is not essential with respect to certain
features of the invention, the power for driving
the apparatus is preferably transmitted to the
male rotor, for reasons which will hereinafter be
the same reasons that the casing is jacketed it
is also desirable in the case of large units to cool
the rotors and this is conveniently accomplished
by circulating a ooo1ing ?uid through the central
or core portions of the respective rotors. One
suitable arrangement for accomplishing this is
tube 20 is mounted at the axis of the rotor and is
more fully explained, and the power is preferably
'ransmitted directly to the power receiving rotor
through the shaft is which advantageously has
provided with one or more openings 22 adjacent
some torsional and radial ?exibility.
to the end of the tube to provide communication
ing shaft, which is suitably keyed as at 48 to the
shown in Fig. 1 wherein the male rotor I4 is
shown provided with a hollow core [4a. A hollow
This driv
between its interior and the hollow core space
rotor, extends through the sleeve carrying gear
of the rotor surrounding the tube. One end of
134 'to an outboard driving connection 50.
the tube 20 extends axially beyond the end of the
It will be noted that by means of this construc
rotor and is carried by a bearing 24 mounted in
tion'the timing gears are not in the path of power
the casing structure. A Venturi tube 26_ is pro
transmission from the source of power to the
vided at this latter end of the tube 20 and cooling
main body of the rotor and consequently the only,
?uid is supplied through the stationary nozzle
torsional force tending to deflect the relatively
28 mounted in the casing structure, The injected 20 small diameter journal part connecting the main
cooling ?uid travels through the hollow tube 2!]
body of the rotor with the‘timing gear is the
and passes into the hollow rotor core through
torque transmitted through the timing gear' in
the ports 22, leaving the rotor through the annu
order to keep the rotors in'properly ‘synchronized
lar channel 30 between the tube 20 and the end
of’the hollow core structure. Fluid discharged 25
The outer diameters of the rotors and the lobes
from the channel 30 passes to the chamber 32
thereon ‘are made so that clearance is provided
from which it may flow to any‘ suitable cooling
between the rotors and the inner surfaces of the
device for cooling and return through nozzle 28;
casing which encloses them and'also between the
Obviously other speci?c means for circulating
intermeshing portions of the rotors. This‘clear
cooling ?uid may be employed, but the above de
anoe is made as small as practical to provide What
scribed means provides a simple and effective way
maybe conveniently termed space packing for
ofracc'omplishing the desired cooling of the mov
the compression spaces formed between the co
ing. rotor. It is to be noted that in effecting such
operating parts, andv a primary function of the
cooling it is advantageous to have one end of the
timing or synchronizing gears is ‘to maintain the
rotor free’ of other mechanism so as to permit 35 rotors in such properly timed‘r'elation'ship that
the advantageous placing of the cooling connec
' clearance between them is maintained. Due to
tions at the axis of the rotor. It will be’ under
the space packing andv resultant lack of rolling
stood that where such cooling is employed a
or sliding contact between the relatively moving
similararrangement will. be used for cooling the
rotor and casing parts, the rotors may ‘be oper
female ‘rotor. The female rotor 3llis'mounted
ated, and in accordance with the present inven
in "bearings similar to bearings ldand [8 but
tion are intended to be operated'd'ry and at rela—
not shown on the drawings, for rotation about
tively very high speeds of rotation. When space
an axis ‘parallel to that of the male rotor.
packing is employed, high rotating speeds are
The male rotor in the embodiment illustrated
required 'in order to obtain suitably high efficiency
is provided with two sets of spiral lobesseparated
from each other at the center of the rotorby a
space 36. One set of lobes 38, seen 'in‘Figs. l and
2, is inclined in one direction with respect to'an
axial plane while the other set of- lobes, 46, seen
in Fig. l, is inclined in the opposite direction, in
the. manner of theteeth of a herringbone ‘gear.
In the embodiment illustrated, each set of' lobes
on the male rotor comprises four. lobes and the
pro?les of these lobes are preferably in accord‘
ance with'the' disclosure of my‘ aforesaid Patent
No. 2,174,522.
The female rotor is provided with two sets. of
of operation.
When the rotor pro?les are made in accord
ance with the preferred design disclosed in my
aforesaid Patent No. 2,174,522, the torque trans
mitted through the timing‘ gears is relatively only
a small fraction of the total torque, amounting
inmost instances to not over about 15% of the
latter. For'reasons not germaneto the present
invention, the‘ torque transmitted ‘through the
timing gears is negative rather than positive,
when the input power‘ is applied'tothe male rotor,
since‘ the *?uid forces acting'on the sides of the
grooves ‘and lobes when th'ecompressor is in ‘op
eration .tend to make the female rotor rotate at
grooves separated axially by a space 35, these
grooves also being spiral and inclined so’ that the
a higher speed, or overrun, the male rotor. _ Since
two sets cooperate‘ in’ intermeshing relation with 60 the driving torque is transmitted directly to the
the lobes 38 and '46; respectively. ‘In the embodi
main body of ‘the rotor in accordance with the
ment illustrated- the grooves, of. which the set
present construction, it will be evident that the
cooperating with‘ the lobes ‘38'are shown at 42 in
clearance between the rotors may be most effec
Fig, 2,rare ?ve‘ in number in each set, the pitch , tively maintained since the parts connecting the
of the grooves being different from that of the co
rotors to effect synchronization therebetweenare
operating. lobes in order to permit the ‘four. lobes
subject to very little torque and consequently'are
of each set to properly intermesh with the ?ve
not subject to such torsional de?ection as might
grooves of ‘the cooperating set. The pro?le of
permit the rotors'to turn relative to each ‘other
the'grooves isalsopreferably in accordance with
to an‘ extent destroying the clearance therebe
the disclosure in my aforesaid Patent No.
tween." The speci?c feature of ‘construction just
described forms the claimedsub'ject matter of my
The: cooperating rotors are synchronized or’
copending divisional application Serial No.
timed by suitable timing gears mounted on the
479,429, ?led March 17, 1943. I
rotor shafts, of which the gear for the male rotor
will be noted from Fig. 2, the pitch lines
isfshown'at 4.4;inEFi’g-.‘1.
75 of'the rotors lie on‘t‘he root circle of the 'I'nalel
rotor; andyat the cylindrical envelope of the fe
male rotor, respectively, or closely adjacent there
to;l_'a_ned as employed inl-this speci?cation and the
appended, claims the terms male-rotor and fe
male. rotor are intended to de?ne rotors having
is angularly related to the line 42a de?ning the
edge of the female rotorgroove. These port edges
this general characteristic withirespect to their
pitch. circles- as‘ distinguished: from rotors of» the
are ‘so varranged that the portions of the port
wellknown Roots or similar type which have their
pitch lines; located intermediate the 'apexes and
roots of. the lobes and which may be characterized
generallyvas twin rotors.
' edgesthatiare ?rst passed by the apexes of the
male rotor; lobes and'theedges of the female
rotor grooves to openlup communication between
the working spaces ‘and'the outlet port, are ad
__Referring now more particularly to Fig. 1,3,
and -5,;the casing ends are provided with inlet
jacent to the outlet ends of the working spaces,
and radial communication between the'working
passages 52and .54‘ which terminate in inlet ports
56i'and‘z58jrespectively, in the two end walls at
ment of therotor grooves and lobes will be as
indicated by the arrows in Fig. 6 as they pass
the outlet port and it will be noted that the port
line k,—r is angularly related to the apex line 38a
of the male rotor and further that the line s——p
15 spaces and the outletport is opened up progres
sively as the rotors revolve, from the outlet ends
of. the working spaces axially toward their inlet
ends, until full communication between the work
to provideflor substantially axial admission of, air
ing spaces and the outlet port for radial dis
to the ends of the grooves in the rotor-s as the
latteripas's these ports.
, _
20v charge from such spaces is established. In the
position of the rotors shown in Fig. 6, the port
“IAs will be seen more particularly from Fig. 3,
has been opened for radial discharge along the
.the'portion’of the inlet port 56 for direct axial
entire length of the port from the groove space
admission of ?uid is de?ned by line a--b--c-d;
42 lying behind the edge 42a and from the space
e-l-f-d, the area of the ‘port portionv de?ned‘by
this line in the end wall constituting the major 25 38b lying behind the apex line 38a. Obviously
the action is similar with respect to the port edges
area of the port. 'ItTis not essential, however,
15-10 and 11-10 which cooperate with the working
that this constitute the entire inlet’ port area
spaces formed on the axially opposite side'of the
andi'as will be seen from Fig. '1‘,‘ it may be de
sirable in the interests of ‘providing a smoothly
central partition 60.‘
V y
curved’inletfpassage to. have a small portion of 30 . Inthe operationof the ‘hereinbefore described
the‘ opposite endsv of the rotors.’ These ports
and theirfcooperating inlet passages are. formed
the inlet port extend axially‘ inwardly from .the
' apparatus as a compressor, the working spaces
end‘wall. 'In the embodiment illustrated there
are ?lled substantially axiallyof their length and
is a small axiallyextending port ‘portion de?ned
by the lines'g’ .andfh in Fig.‘ 5, but it‘will be ap
parentfrom a'consideration or Figs. 1, 3 and 5
that this'frelativ'elyj small lport portion’will. not
materially affect the generalcharacter of ?ow of
progressively from the inlet vtoward the outlet
ends thereof ‘as the inlet ends of the spaces pass
their respectively‘ cooperating inlet port. More
over, these spaces, increase in volume to their
maximum from their inlet ‘toward their outlet as
therotors revolve during the portion of the cycle
the'?uid mm the? apparatus, "which flow can be
said tobeaxialin natures.’ ?
I > .
‘ _
It‘Will'be understood tha't'fth'e port 58 at the
opposite end of the compressor will‘ have the same
outline-as port 56.
when the spaces-are in communication with the
40 inlet port, as willbe more readily apparent from
a considerationvor, Fig. 7 in which a Working
space 38byjlying ‘between two apex lines 38a, and
iniie casing: is" provided :‘with a. partition ‘60
intermediate’. its
:wh'ich ' ,proje'cts radially
inwardly‘tc‘?llthespace‘36 between thetwo sets
‘ a female rotor working space 42, are shown in
of “the working ‘chambers incertain positions of
inlet port are indicated-at a—_—b and e-f, respec
tively, these lines corresponding to the similarly
designated. lines appearing in Fig. 3. At the
opposite endsof ‘the working spaces, the outletv
end closingv wall is indicated which? corresponds
to the portion of the partition 60 lying below the
rotation of. the rotors, 'lI‘hi's partitiontdoes not
extend‘peripherally; entirely‘ around the rotors asv
will be moreclearly seen from, Fig. 4 in which the
edge de?ning the" peripheral extent of. this par-;
in this view;iS.;as' indicated-"by the arrows ~68;
Therlines de?ning the peripheral limits ofv the
of'lobes IOnJeachrotor and to provide end wall
surfaces I62 and 54 which de?nethevoutlet'ends’
tition is‘ indicated?by the
_ Theodirection of rotation of the rotors as seen
o—p—q. The outlet port isiindicated generally
at‘, 6.5,this' port beinglocated in theocasing inter- .
mediate'its ends and. as will beobservedjrom.
line Z—m—--n—o in Fig- 4.
As seen in Fig. ‘Lethe working spaces open up
progressively fromleft; to right'as the male rotor
Figs’. 1 and 4; this‘po'rt‘ extends axially alongeach
lobes progressively roll out of their cooperating
of.-the t'wolsets of rotor-lobes. and is further in
’ grooves and the ?ow of air or other working ?uid
directfcommunication with vthe portionlofg the
scariest lying" above thepartition 60 so that the
ontlet. port is in .both radial’, and axial com
riiunication with the working spaces.
hev atureot-the portion of~vthe port whichii-sl
int-radial "communication;withutheworking spaces
into these spaces is generally in the direction of
Because of the fact that the speed”
of. rotation is relatively veryhigh, a depressed
pressure is created due, to suction as the working
spaces open up and this in turn induces a rela
60 the arrows ‘ID.
tively high velocity of-?ow generally axially of the
is important. in'respect'of one or the. aspects of_ 65 working spaces. As these spaces progressively
open up ‘to their full‘ volume, the ends of the
the'present invention and in Fig. 6 the 'edgesde
?ningthe radially communicating portions of the
portgareindicated by the lines k—r_-¢-s—p—,.and
spaces are; determined by the end wall at their
outlet ends ‘and this wall may be said to extend
generally transversely of the axes of the spaces,
t._—i-uI-'v-:w, respectively.
ti'Asi'viewed in Fig.6, the apex line of ‘one of 70 although as will be observed from Fig. 7 the wall
does not extend transversely at right angles to
themalerotor lobes 38 appears at 38a and that of
these axes. The high velocitycolumn of fluid
one .of the _rotor globes [It appears at*40a.- Like
moving into theworkingspaces from the gener
wise>,~_42a_ (see _alsg,sFig._;4) indicates; the edge of
ally axially directed inlet produces what is in ef
onea-lofithe female grooves :41. ; In-the normal
operationofthe apparatusythe direction of mover.‘ 75 iect;;_an;elasti¢ Piston moving toward the outlet
for obtaining-an appreciable! ramming effect-is‘
endsof the spaces and when’. the spaces open‘u'p
t0 their'full axial‘ length,-this'~lnoving column?
high velocity operation-and
StOppedTby the dliltl'et'uelfldlwall. ‘ Due; no'wevenltc
but without'lin'iitation itinay- ‘besta't'ed that ‘the
minimum peripheral velocity” forfthe' working
the fact that the rcolum?‘is“ e'la'Stri'c",~?OW thfoligh
the’ inlet’ port continues ‘ arterrnow has ceased’ at}
the outlet ends‘ of the spaces.‘ Ihave‘ disc'o'vered'
spaces in- order to: achieve a ramming effectjvof
su?icient magnitude to be of material ‘practical
importance is of the order‘o-f‘150feet per second;
that if‘ the ‘speed of" operationZ of the rotors and‘
the'peripheral extent’ ofthe-"in1et‘port‘ar‘e prop; .
erly‘ related to the length of thewerking spaces,
the volumetric e?iciency-of the apparatu'slmayio'e
enhanced by taking a‘dvanta‘geiof a phenomeii'orrv
way" of » examine;
In! an actual-compressoreinbbdying the above
described‘ feature of construction which _I have
built‘ and tested, I have been able to;- secure an
increase of as much as 12% in'lpres‘su're‘ above
resulting froin' the impact of the" highl velocity
atmospheric in the‘ working spaces‘ ' due‘ to ram
ming effect,- by operating rotors approximately 12
piston striking the Outlet end-'Vwfall as the
inches long at peripheral velocities of approxi-'
mately“285"feet per‘ second‘ and" Witlrthe pe
ripheral extent of the inlet port proportionediso
that they working spaces 'remainincommunica
spaces open up to theiriful-llength. 3' When? this
occurs under high velocity conditions; a nun»
pressure wave is created‘which mcves in the
Working spaces tact:- toward their inlet" ends in
the direction of the arrows7'l2‘.‘ This ‘pressure
tion: with the-inlet portforapp‘rOximately 20
wave moves approximately» with the velocityio'f
degrees of angular travel ofthemale‘rotor after
sound and if the Working spaces are kept in com; 20 the position of the male rotoris reached at‘ which
munication until approximately the time when
the working: space‘ therein has attained its‘maxi
this pressure wave reaches the inlet'ends of the
spaces-the net result is to produce what may'con
In the operation of compressors" of the kind
veniently be termed a ramming re?ect which en
‘under consideration,‘the'working' spaces, after
ables‘t'he spaces to be‘?lle'd with ?uid'at aprés 25 they have opened up to their full‘ volume and
sure as high or higher than’ the pressure'of ‘the
atmosphere or other fluid'hody from" which the
after they have passed out of communication
with the inlet port are rotated through a‘ certain
?uid ent'eringlthe spaces is derived. As a con;
amount of angulartravel at‘ constant ‘volume.
Thereafter, due to the entrance of 'a'male'i rotor
be packed into the working spaces than corre 30 lobe into a cooperating female rotor‘groovei and
sponds to their'actual volumetric displacement at
before the spacesconie into communication with
inlet pressure andathuslthe- capacity of a com
the outlet port, the'volumes offthe spaces are
pressor of given size/may be increased as com
progressively decreased ‘and thisjdecrease' is ef
pared'iwith the capacity’ of'a compressor which
fected by the progressiveshortening‘of the work.
sequence of this, a greater weight of‘ ?uid" may
n is not» designed to make‘1 use of this ramming
effect. The‘ex'act peripheral extent of the axi
ally“ opening inlet required to achieve this de
sired're'sult Willbe different with-diiferent spe
c'i?c compressor designs‘ but in each in'stance,_
having in mind‘thesub'stanti'aHy ?xed speed of
travel of the‘p'ressure wave created during the‘
inlet periddthe'r'equired peripheral extent of the
inlet port is'readily determinableifor rotors hav
35 ing spaces, due‘to thejintermeshing l‘obesand
grooves; from the___inlet~t'oward the" outlet‘ ends
of the‘ spaces. 7 Ini‘connection witnthisa'ction it‘v
may conveniently be‘ said thatv the wo’rkirfg'sp'aces‘
are axially displaced toward their outlet 'Vends'
during the compressionanddischarge phases of
the cycle; With‘ the high] speed'ofivope‘ration'
contemplated by the presentinvention; this'axial
ing working spaces of given length and design to
operate with a given normal peripheral speed.
In‘ all cases, “however??- if the desired’ eifect is to
displacement toward the ‘outlet ends ofth'e work
ing-spaces results in-another phenomenon; ad
vantage-v of- which-may be" taken‘; to "improve the‘
performanceof'the compressorby‘suitable’ design‘
be oht‘ain'ed,‘ the ‘peripheral exten't'rof the inlet
portirnustbe suchitha’t the‘ working space: in the
' ofthe‘peripherally' limitingedge's‘of the outlet‘
male" rotor remains in communication with'thev
male~ rotor lobes and the edges of‘ the'female'
port, which ‘when-passed‘ byjthé apexe's' of the
inlet port-untilafter such-space has opened up
to its full vaxial extehtFand- full volume; By ref
rotor ‘grooves determine the opening of’ communi-j
cation between’ the working 'spacesand the outlet
erence to Fig '7 it‘ will’bel seen’ that the working’
space aeb'iin-‘the malero'tor comes into'com‘muni
part; The‘ aiiia-l'nisplacementduring the com;
préssio'n" phasef"creates'- aj' pressuretwave“ in the
cation at the outlet end‘w'ith the "working space
form'ed'by groove’ 42 in‘the female rotor- before
male lobe hasiirolled‘completehr"v outof the‘
end" of
working"spacesi'which travels'itowardthe outlet;
groove and thereby opened up‘ the groove to its full volumetric capacity.’ Due to this open com
s'u're' within the’v'vork'irig spaces‘ themselveswith'
angnerfpressiireiat the outlet end than'a'tlthe
inlet- end} Thi _ 1‘ condition ' within ‘ the? working"
spaces obtains’ at about‘ the-timefwlien‘the' spaces‘
_munication hetweenfthe two ‘spaces, the pressure
wave ' created by impact ‘against the end wall
moves‘ toward the‘ let ends‘of both of the‘ com
municating spaces. Therefore, inorder to secure
are brought into :fcommuriication with ' the’ outlet"
the’ desired result it is not essential "that the
' iii " thd hernia‘? operand; of‘ the-"apparatus
groove in the female’rotor befkept" incomrnuni;
and v1n order-“5th s'e
in this rotor has reached’ its‘ mammum volume;v
Also,'it isde’sirable to 'sorlocate the lines ‘ct-J7~
pl'ie'ndnie'rion;'1adv'ahtageousv to open‘ commun'ia cation between ‘ thebutlet port and 'the‘working’
and e'—f de?ning the peripheral lir'n'it'sfofthe
on simultaneously as‘indiea‘ted by; the relative
positions of these'line's-in Fig; 7‘W'ith respect to
the ‘edges of the working-‘spaceswformed in the:
v‘A's hereinbefore notedponefcr the" requisites?
e more e?icientljoperationl
of the ‘a'p‘palr'atusi with less "throwing? loss at-tne
outlet pengr have" found that it‘ *due" ‘to this
cation with‘ the'inle't port until after the'g'roove
inlet port that communication between‘ the‘ inlet
port'and the worliinglspaic'es inhoth'rot'ors is cut
spaces ' and impacts v"against/the‘ w'all'
de?ningfthejoutlet- ends of the spaces.’ This pres:
sure ‘wave operates'to' createjai differential vpres
70 7
spaces progressively from the-outlet- toward the’
inlet ends of? theii'latt'e‘ra Iris-for thls~reason
that‘inlaecordarice'iwith’thisip'l séiof" ‘ yfi‘n'v‘enf
tioniI provide Yaj'“ outlet 'pOrtQWith iliniiting edges‘
such-as k'—r‘-'a_nd"
of" Fig‘. '6; the‘ pitch" of
wl'i'ich‘v is» greater ithaln‘l'theiipitc ‘ of, ‘ the: rotor
lobes‘? and '- g‘rdo‘ve's1 which? respectively cooperate"
therewith. ; By ‘reference to Fig. 6 it‘will [readily
be seen that with the rotors turning ‘in the di
tudinally of said grooves during saidinlet- phase
rections indicated ,by'the ' arrows therein, the
and impacting the outlet end wall as the grooves
open up toytheir maximum volumtefthe periphe
eral extent of said inlet port means causing the
same to'remain in direct axial communication
with'the grooves of said‘ male rotor for'a sub-_
working spaces will open progressively into com
munication with the outlet port from their cute
let ends toward their inlet ends until communi
cation over the full axial length of the port is
stantial period after such grooves have come into
In the embodiment ofnapparatus herein shown
and described, the two sets of working spaces
are separatedby an intermediate partition wall
60 the purpose of which is to provide for both
axial and radial ‘ discharge from the working
spaces in order to reduce throttling losses and
in this connection it is to be noted that the lines
full communication with said outlet end wall,
whereby‘ to create a ramming e?ect in such
grooves due'to said impacting. '
' '
kind having intermeshing spiral lobed and
grooved rotors rotating in a casing structure be
15 tween inlet and outlet casing end walls and‘in
which workingspaces open up from theinlet
ends tothe outlet ends ofthe grooves during the
inlet phase of the cycle .of operation; inlet'port
'means in the inlet end wall for directing ?uid
into said grooves in generally axial direction dur
ing said inlet phase, means for driving said ro
which communicates with the axial ends of the
working spaces are located with reference to the
' lines k-r and s-p which de?ne the peripheral
extent of the portion of the po'rtwhich com
municates radially with the working spaces, so
that the working spaces are opened for axial
communication with the outlet port simultane
ously with the time when the'port begins to pro
gressively come into communication with the
spaces in radial direction. Thus, the point k
of Fig. 6 corresponds with point k of Fig. 4 and
point p of Fig. 6 corresponds with point p of
3. In a rotary screw wheel compressorof the
k-Z and o—p (Fig. 4), which de?ne the periph
eral extent of the portion of the outlet port
Fig. 4.
‘ate columns of'said ?uid'?owing generally longi
tors at a normal operating speed providing a pc
ripheral velocity of said working spaces within a
range the lower limit ofwhich isv of the order of
150 ft. per second, whereby to create high velocity
columns of said, ?uid ?owing generally longitudi
nally ofsaid grooves during said inlet phase and
impacting the outlet end wall as the grooves open
up to their maximum-volume, the peripheral ex
tent of said inlet port means causinglthe same to
It will be apparent that in so far as the features
remain in direct ‘axial'communication with at
of the invention involving ramming and exhaust
least certain of said grooves for a substantial pe+
port con?guration are concerned. such features
riod after such'grooves have come into full com;
are equally applicable to single as well as double
munication with saidoutlet end wall, whereby
ended compressors and it will further be ap
to create a" ramming 'effectin such grooves due
to'said impacting. -'
' '
parent that without departing from the scope of
the invention.‘ many‘ changes in speci?c design
1 4'. In a rotaryscrew wheel compressor of the
may be made and certain features ‘of the inven-é
kind having intermeshing male and female spiral
lobed 'andfgrooved'rotors rotating in a casing
tion used to the exclusion of others. It is ac
cordingly to be understood that the invention 40 structure‘ between inlet and outlet casingend
walls and in which working spaces open up from
embraces all forms and modi?cations of appara
tus 'falling within the scope of the appended
What is claimed:
1. In a rotary screw wheel compressor of the
kind having intermeshing spiral lobed and
' 4
the inlet ends to the outlet ends of the grooves
during the inlet phase of the‘ cycle of operation,
inlet port means in the inlet end wall for di-i
recting ?uid into said grooves in‘ generally axial
direction during said inlet phase, means for driv-j
inggsaid rotors at a normal operating speed pro;
viding a peripheral velocity of said working}
grooved rotors rotating in a casing structure be
tween inlet and outlet casing end walls and in
spaces within a range the lower limit ofwhich‘
which working spaces open up from the inlet
ends to the outlet ends of the grooves during the 50 is of the order of 150 ‘ft. per second; whereby to
inlet phase of the cycle of operation, inlet port
means in the inlet end wall for directing ?uid
into said grooves in generally axial direction dur
create high velocity columns of said ?uid ?owing
generally longitudinally of said grooves‘ during
said inlet phase and impacting the outlet end
wall as the grooves open up to their maximum
ing sald inlet phase, whereby to create columns
of said ?uid ?owing generally longitudinally of 55 volume, the peripheral extent of said inletv port
said grooves during said inlet phase and impact
means causing the same to remain in direct, ax
ing the outlet end wall as the grooves open up to
ial communication with the grooves ‘of said, male
their maximum volume the peripheral extent of
rotor for a substantial period after‘such grooves‘
said inlet port means causing the same to re
have come into full communication with said out
main in direct axial communication with at least 05 O let end wall, whereby to create a ramming effect
certain of said grooves for a substantial period
in such grooves due to said impacting.
after such grooves have come into full communi
5. In a rotary screw Wheel compressor of the
cation with said outlet end wall, whereby to cre
kind having intermeshing spiral lobed and
ate a ramming effect in such grooves due to said
grooved rotors rotating in a casing structure be
tween inlet and outlet casing end walls and in
2. In a rotary screw wheel compressor of the
which working spaces open up from the inlet
kind having intermeshing male and female spiral
ends to the outlet ends of the grooves during the
lobed and grooved rotors rotating in a casing
inlet phase of the cycle of operation, inlet port
structure between inlet and outlet casing end
means in the inlet end wall for directing ?uid
walls and in which WOI‘kiIlg spaces open up from
into said grooves in generally axial direction dur
the inlet ends to the outlet ends of the grooves
ing said inlet phase, whereby to create columns
during the inlet phase of the cycle of operation,
inlet port means in the inlet end wall for direct
ing fluid into said grooves in generally axial di
of said ?uid ?owing generally longitudinally of
said grooves during said inlet phase and impact
ing the outlet end wall as the grooves open up to
rection during said inlet phase, whereby to cre-l 75 1711131!‘ maximum volume, said inlet port means in
remote from said wall is established.
8. In a rotary screw Wheel compressor, casing
groo‘vesin oneof saidrotors, and the peripheral
‘structure having .an inlet port [for fluid, a~plu
location of‘ said closing ledge being related to the
length and to the ncrmal'speed of operation of
the grooves controlled thereby to cut off direct
axialjcommunication between the grooves and
the inlet port only after, an interval following
the time when the grooves controlled thereby
have opened'up to their maximum volume ‘but 10
rality of intermeshing spiral lobedand grooved
rotors cooperating .._with each, other and the cas~
before the pressure wave created in said ?uid by
saidiimpacting can travel tram the outlet ends to
the inlet ends ,of the grooves controlled bysaid
dosing edge
S6. v‘In ,a’ rotary screw wheelcohrnpressor of the
kind havingint'ermeshing ‘male andiernale spiral
,port ,and ‘the ‘portions ,of the respective spaces
‘eluding a closing edge forcutting off communi
cation between said inlet ‘port means, and the
ing structure ‘to-form compression spaces de?ned
at one end by a wall'forming a part of said‘cas
ing structure, said spaces decreasing in volume
toward saidwall ,as-the rotors revolve, and an
outlet .portin said ‘casing structure .extending
axially, fromsaid wall and Jarrangedto ‘be brought
into radial‘ communication with said ‘spaces by
therotationpigaid r0tors,._said outlet port having
(limiting. edges located to progressively open radial
communication between the outlet port and said
spaces in a vdirection.away fromthe wall.
lobed and grooved rotors rotating ,in a casing
;9. In a rotaryscrew wheel compressor, casing
structure between inlet, and outlet casing end
walls and in which workingspaces open upfrom
structure havi?gll-aninlettport ior ?uid, a plu
during the inlet phase of the cycle of operation,
inlet port means in the inlet end wall for direct
ing‘fluid into said grooves in generally axial di
rection?during saidinlet phase, whereby to cre
rotors,cooperatingwithfeach ‘other and thecas
Ling structure toiiforrn eompressiontspaces, de?ned
thexinlet ends to the ‘outlet ,ends of the grooves 20 rality of intermeshing spiral lobedand grooved
ate columns of said ,?uid ?owing generally longi
tudinally-of~ said grooves during said inlet phase
and impacting ,the outletend wall as the-grooves
open “up .to their maximum ‘volume, said inlet
portqmjeans including ‘a closing edge for cutting
O? communicationbetween-said inlet port means
and the grooves in said male rotor, and the pe
atoneendv-by awalliorming a part oflsaid casing
structure, _said.,spa_ces, decreasing in volume to
wardsaid wall ‘as ,therotors revolve, and’ an out,
let- port in saidicasinglstructure extending axially
,igromrsaid wall .and arrangedto be brought into
radial communication Y-With-said spaces byathe
rotationdoif said rotors,,_said outlet'port ,having
30 limiting edges located to be passed by theledges
of the rotor lobes @and, grooves, said limiting edges
ripherallocationof said’ closing edge being re
lated itoithe length [and-to the normal speed ‘of
operation of the grooves controlled thereby to
out off direct axialcommunication?between the
beinginclined toward each ‘other in the. direction
grooves and the inlet port only after an interval
away fro-msaid walland the inclination of said
edgesbeing greatermthan ‘the-pitch angles of the
rotoredges ,with- which they respectively co.
thereby have opened up to their maximum vol
umemhutbefore the pressure wave created insaid
fluidby saidimpacting can travel from theout
let ends v,to the inlet ends of the grooves icon.
trolledby said closing edge.
7. lnuairotarysprlew wheel ,compressonpasing
structure ‘having an,.in1et~port for ?uid, a .plu
‘ lQ. ,In .a rotary-screw v_w_~heel compressor, casing
‘following the time when the grooves controlled
Structure rhayin‘gqan inlet .port ,for fluidpa ,plue
rality, of intermeshing spiral lobed and grooved
rotorscopperating ,with each, other and the cas
ing structure to term compression vspaces de?ned
atone end bye ‘Wall .forming a part ofsaid casing
structure, said spaces decreasing in volume ‘to
ward said wall as the rotors revolve, ‘and ,an
rality ,of intermeshing spiral lobed and grooved 45 outlet port in saidcasing structure, said outlet
pert having portions located to communicate
axially and radially respectively with saldspaces,
structure ‘to ,form compression spaces de?ned ,at
the radially , communicating portion having
one end by-na wall forming a part of said casing
limitingedges located to provide progressive com
structure, said’ spaces decreasing ill-‘volume to
ward saidwall as the rotors -revo1v,e,>,and an out 50 munication between the, spacesand the Wall in
a direction away from the ,outlet port, and the
let :port insaid casing structure extending axially
axially cornmuuipatins portion having limiting
from said wall and ‘arranged robe brought into
edges located to ‘provide communication between
radial eornrnunication with .saidspaces by the
the outlet port and the spaces substantially
rotation ,of said rotors, said outlet, port having
limiting edgesshaped to open radial cornmunicae 55 simultaneously with the commencement of the
progressive radial communication.
tion between the ‘outlet port and the portions of
the compression spaces adjacent tosaidwall be.
fore radial communication between the outlet
rotors ‘cooperating with each other .and'the casing
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