Патент USA US2126280

‘ Aug. 9, 1938.
sis. REDFIELD
2,126,280
AIR COMPRESSOR
Filed March 17, 1937
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2,126,280
Patented Aug. 9, 1938 I
UNITED STATES PATENT ‘OFFICE
Snowden B. Red?‘eld, Bethlehem, Pa., assignor
to Fuller Company, Catasauqua, Pa., a. corpo
ration of Delaware
Application March 17, 1937, Serial No. 131,305
8 Claims. (Cl. 230——152)
This invention relates to rotary compressors
and vacuum pumps, and more particularly to an
apparatus for improving ef?ciency by reducing
air or gas slippage losses between the ends of the
5 rotating element or. elements'and the casing or
cylinder heads.
The invention has especially to do with modi?
cations and improvements of the apparatus of
my Patent No._1,994,'786. ’ Similarly to that apé
10 paratus, it may be applied with advantage to
compressors'and pumps having various types of
rotary elements, to maintain substantially con
stant minimum clearances between the ends of
the rotary elementsand adjacent surfaces of the
15 casing, and is of especial utility in its application
to compressors and pumps of the multi-vane type.
For simplicity in description, the apparatus will
be referred to as an air compressor and speci?
cally described in its application to multl-vane
20
compressors.
_
'
‘
The rotors of compressors of this type, designed
for relatively high discharge pressures, expand
longitudinally a. considerably greater distance
than the stator casings or cylinders, as the latter
above, and comprises a compressor preferably
having one end of the rotor ?xed against sub
stantial axial movement, with a predetermined
minimum safe running clearance, and a movable '
or ?oating, internal cylinder head at the expan
sion end of the rotor, the ?oating head clearing
the surface of the rotor by at least the distance
of a running ?t. This ?oating head is of simpli
?ed and less costly design and is provided with a
bearing surface located so as to provide a positive
seal against air slippage around or along the rotor
shaft. The bearing‘surface is lightly held against
an annular'shoulder, on therend of the rotor sur
rounding the shaft, preferably by air pressure on
the outer surface of the ‘floating head slightly 15
above the average pressure on its inner surface.‘
‘As the rotor expands longitudinally, the ?oating
‘head is moved axially by the force of the‘ shoulder
against the bearing ‘surface. The head is pro
vided with a rearwardly extending sleeve sur
rounding the shaft, and preferably having an
inner surface of bearing metal, the sleeve pre
venting angular displacement of the head due to
the unequal pressures on its inner surface. A
rotating collar on the shaft serves to return the
ciencies. As the rotors are vdriven at high speeds, ' head when the rotor contracts, by bearing against
the end of the sleeve.
‘
'
it is essential that adequate clearances be pro
It will be seen, as the description proceeds, that,
vided between the ends of the rotor and the inner ?oating
heads of similar design may be used at
surfaces of the cylinder heads to prevent actual
each end of the rotor, whereby the rotor and
30 contact, and consequent burning or welding of
?oating heads may ?oat axially in either direction
the parts. It is common practice to “fix” a con
until
contact is made with one ?xed head. This
stant clearance at one‘end of the rotor, as by duplication
does not materially increase the oper
supporting the rotor shaft at that end in a thrust
bearing, so that as the rotor is heated it expands ating advantages, and as it is more costly than
the arrangement described, the‘latter is preferred.
35 longitudinally in the direction of the other or
For a better understanding of the invention,
“expansion end”.
reference
is made to the accompanying drawing,
The shaft at the‘expansion end of the rotor is
supported in a plain. ‘radial roller bearing, the in which:
25 . are water-cooled to provide for satisfactory e?i
" inner race of which is displaced axially as the
40 rotor expands or contracts.
The "?xed end"
clearance is established principally with relation
to the axial play of the thrust bearing plus a
. running fit, and in machines of average size will
be about .004 of an inch. The expansion end
45 clearance is determined with relation to the tem
perature of the rotor corresponding to the highest
expected operating pressure, the largest volume
and lowest, temperature of the cooling water and
the maximum duration of continuous loading.
50 Under the less extreme conditions of normal oper
ation, the expansion end clearance is excessive
and the increasing air slippage is detrimental to
e?iciency.
}
In general, the present apparatus has among its
' purposes to overcome the difficulties described
Fig. 1 is a cross-sectional elevation of the com- '
pressor, and
‘
Fig. 2 is a cross-section, on a reduced scale, with
the vanes shown in their normal running posi
tions.‘
.
Referring to the drawing, the apparatus will-be ,
seen to consist of a stator casing or cylinder I, 45
having an intake port 2‘, a discharge port 3, and
a generally ‘cylindrical bore 4. The bore is pref
erably counter-bored and broached at 5, and as
shown by the arrows, between the intake and dis
charge ports, to minimize air slippage, the 50
counter-bore being concentric to a‘ cylindrical
rotor 6, arranged eccentrically within the bore 4,
' the rotor being provided with a plurality of pref
erably radial, equally spaced slots ‘I, the depths of
which are indicated by the dotted lines 8, in which ‘ ' /
2
2,126,280
vanes or blades 9 are arranged to move out
wardly and into contact with the inner wall of
the cylinder, due to the effect of centrifugal force.
The rotor is carried by trunnion shafts l0 and
H in hearings, to be described in detail herein
after, in cylinder heads l2 and It. The cylinder
is provided with water-jackets H which com
municate, as at I5 and IS, with water-jackets in
the ‘cylinder heads'l2 and I3, and it will be evi
10
dent that this arrangement provides for adequate
cooling of the stationary parts and that the longi
tudinal expansion of the cylinder will be relatively
less than the uncooled rotor. The “fixed end" of
therotor is carried by'the cylinder head H, the
head having a smooth inner face or surface I1
and a bore l8 through which the shaft H) ex
tends. The ?xed end is also preferably the driven
and of the rotor, so that accidental thrust due to
the driving mechanism may be absorbed in the
thrust bearing to be described hereinafter, and
the shaft In is accordingly further extended
through a packing gland IS in a bearing cover
20, the shaft- being provided with a key-seat 2|
for the usual ?exible coupling (not shown). The
25 head I2 is provided with a chamber 22 to receive
the outer race of a radial and thrust bearing 23,
which is preferably of the roller type, one edge of
this race abutting one or more shims 24 which
fix the axial po?tion of the bearing, the race be
30 ing secured by the bearing cover 20. The inner
race abuts a shoulder 25 on the shaft I 0, the race
being secured to the shaft by a lock-washer and
nut 26 threaded thereon and which bear against
the retaining ring 21. The number and thickness
85 of the shims 24. in ?xing the axial position of the
bearing, accordingly ?x the clearance between the
loading, as su?icient clearance is provided be
tween the sleeve and the bore of head I3 to per
mit substantial radial displacement, whereby the
actual radial load of the rotor is carried by roller
bearing 3|. The inner surface of the head 31 is
recessed to receive an annular bearing surface 4|
preferably of babbitt, surrounding and adjacent
to shaft II, the bearing surface 4| abutting va
shoulder 42 forming a complementary bearing
surface on the end of the rotor below the bottom 10
of the vane-slots, as indicated by the dotted lines
8 ," the contact of the bearing surface 4| and‘ that of
shoulder 42 serving as an effective seal to prevent
air slippage around and along shaft ||. The
sealing effect is improved by the admission of lu
bricating oil through a duct 43 which opens into
the bore through the bearing surface 42.
As the sleeve 39 is eccentric to the head 31, a
dowel 44 is provided to prevent partial rotation
and consequent jamming against the wall of bore 20
36. The head 31 is provided with a hole 45 to
communicate pressure from the cylinder to the
outer surface of the disc. The hole 45 is located
so as to communicate pressure slightly above the
average pressure of the cylinder, whereby the
?oating head is pressed toward the rotor and the
bearing surface 43 lightly held against the sur
face of shoulder 42. The outer end of sleeve 29
coincides with a shoulder 46 on shaft II, the
sleeve being secured for inward movement, as the 80
rotor contracts, by a lock-washer and nut 41
threaded to the shaft and which bear against a
rotating collar 48;
The operation of the apparatus 'will be appar- I
ent from the foregoing, and it will be understood 85
that the ?oating head 31 is freely displaced
end of the rotor and the surface I‘! of the head . axially as the rotor expands, and that the bearing
l2. The bore I8 is sealed against substantial air
slippage by a split hub-collar 28, secured to the
40 shaft by a continuous ring and garter spring 29,
between the inner race and the end of the rotor.
The expansion end of the compressor consists
of the ?xed head I‘, the head having an eccentric
bore of two diameters, that of the larger diameter
45 forming a chamber to receive the outer race 3|!
of a plain radial roller bearing II, the outer race
being secured in the chamber by ?ngers II in the
bearing cover 32. The inner race 28 abuts a
shoulder 34 on the shaft II and is secured by a
lock-washer and nut 35 threaded to the shaft.
As the rotor expands or contracts, the race 33
is displaced axially. without ‘~ damage to the
bearing
Beyond the end of rotor 8, the cylinder is pro
vided with a shallow cylindrical bore 36 to ac
commodate the disc-shaped ?oating head 31, the
' bore having a diameter slightly greater than that
of bore 4 to extend beyond the bottom of the
counter-bore 5. It will be understood that in
.60 compressors having a
‘ bore 28 is unnecessary.
true cylindrical bore, the
The ?oating head 31 consists ‘of a disc loosely
:‘?tted in the bore 36, the periphery of the disc
being sealed against air slippage by sealing rings
65 ll, preferably piston ‘rings of the snap type such
as those used in internal combustion engines, but
ordinary packing has been found to be satisfac
tory. ‘The head is provided with a rearwardly
surface 42 is not subjected to substantial wear
as the thrust necessary to move the head does not
exceed substantially that represented by the 40
slightly increased air pressure on its outer surface.
I claim:
'
1. A rotary compressor comprising the combi
nation of a stator casing, having a central bore
‘and an' air intake and a discharge port com 45
municating therewith, a rotor within the bore
having shafts mounted in bearings in ?xed heads
closing the casing at each end of the bore, said
bearings supporting the entire radial load of the
rotor, the casing having a length greater than 50
that of the rotor, at least one ?oating head
within the bore between an end of the rotor and
the adjacent ?xed head, the ?oating head having
a bore through which the rotor shaft passes, an
nular ?at sealing and thrust bearing surfaces on
the rotor and ?oating head near and encircling 55
the shaft, the annular bearing surfaces being in
contact in a plane perpendicular thereto and
separating said head and rotor at least the dis
tance of a running ?t, said head being provided
with a hole opening into the bore of the casing
at a location where the pressure on its inner sur
face is slightly above the average to apply pres
sure to its outer surface to maintain the annular
bearing surfaces in contact as the rotor expands 65
longitudinally, and means secured to the shaft
beyond and engaging the ?oating head to force
said head inwardly when the rotor contracts.
extending sleeve ll loosely ?tted in the bore of
2. A rotary compressor comprising the combi
70 cylinder head ll, the sleeve surrounding shaft || - nation of a stator casing, having a central bore
and being lined with hearing metal, such as and an air intake and a discharge port com 70
babbitt, as indicated at 40, to form a sleeve bear
municating therewith, a rotor within the bore
ing for the shaft to prevent scoring of the parts. having shafts mounted in bearings in ?xed heads
It is to be understood; however, that the bearing closing the casing at each end of the bore, said
75 surface 40 is not subjected to substantial radial bearings supporting the entire radial load of the
75
2,126,280
rotor, the casing having a length greater than
3
surface of the ?oating head to maintain its‘
that of the rotor, at least one ?oating head with-' annular bearing surface in contact with the
in the bore between an end of the rotor and the annular surface of said shoulder.
5. A rotary compressor comprising the combi
adjacent ?xed head, the ?oating head having ‘a
bore through which the rotor shaft passes, means nation of a stator casing, having a central bore
and an air intake and a discharge port communi
to separate said head and rotor at least the dis
tance of a running ?t comprising an annular ?at cating therewith, a rotor within the bore having
sealing and‘thrust bearing surface on the end of shafts mounted in bearingsin ?xed heads closing
the casing at each end of the bore, said bearings
the rotor near and surrounding the shaft, a com
‘10 plementary sealing and thrust bearing‘, surface supporting the entire radial load of the rotor, the
on the inner surface of the ?oating head and casing having a length greater than that of the
surrounding its bore, said annular ?at bearing rotor, at least one ?oating head within the bore
between an end of the rotor and the adjacent ?xed
surfaces being in contact in a plane perpendicu
lar to the shaft, the ?oating head being provided head, said ?xed head having a bore concentric to
with an oil duct opening into the bore of the the shaft, the ?oating head having a sleeve ex
casing through its annular bearing surface, and tending rearwardly into said head bore and sur
‘means to apply pressure to the outer surface of rounding the shaft to prevent angular displace-‘
ment of the ?oating head, means to separate the
said head to maintain said annular bearing sur
rotor and ?oating head at least the distance of a
faces in contact.
running fit comprising annular ?at sealing and
'3. A rotary compressor comprising the combi
nation of a stator casing, having a central bore thrust bearing surfaces on the rotor and ?oating
and an air intake and a discharge port com--.v head near and encircling the shaft, the annular
bearing surfaces being in contact in a plane per
' municating therewith, a rotor within the bore
having shafts mounted in bearings in ?xed heads pendicular to the shaft, means to apply pressure
- ', closing the casing at- each end of the bore, said against the outer surface of the ?oating head to
bearings supporting the entire radial load of maintain said annular surfaces in contact and
the rotor, the casing having a length greater than means secured to the shaft and bearing against
that of‘ the 'rotor, at least one ?oating head the end of the sleeve to move the ?oating head
within the bore between an end of the rotor and inwardly as the rotor contracts.
the adjacent ?xed head, the ?oating head having
6. A. rotary compressor comprising the combi
a bore through which the rotor shaft passes. nation of a stator casing, having a central bore
means to separate said head and rotor at least and an air intake and a discharge port communi
the‘ distance of a running ?t comprising an an
cating therewith, a rotor within the bore having
nular shoulder forming a ?at sealing and thrust shafts mounted in hearings in ?xed heads closing
35 bearing surface carrying no radial load, saidv the casing at each end of the bore, said bearings
shoulder being on the end of the rotor nearland supporting the entire radial load of the rotor, the
10
15
20
30
35
surrounding the shaft, a complementary sealing
casing having a length greater than that of the
and thrust bearing surface of bearing metal se
cured in a recess provided in the inner surface of
rotor, at least one ?oating head within the bore
between an end of the rotor and the adjacent
?xed head, said ?xed head having a bore concen 40
tric to the shaft, the ?oating head having a sleeve
40 the ?oating head and surrounding its‘ bore, said
annular surfaces being in‘a plane perpendicular
to the shaft, means to apply pressure to the outer
surface of the ?oating head to maintain its annu
lar bearing surface in contact with the ?at sur
45 face of said annular shoulder, and means secured
to the shaft beyond and engaging the ?oating
head to force said head inwardly when the rotor -
contracts.
4. A rotary compressor comprising the com
50 bination of a stator casing,>having a central bore
and an air intake and a discharge port com
municating therewith, a rotor within the bore
having shafts mounted in bearings in ?xed heads
_ closing the casing at each end of the bore, said
bearings supporting the entire radial load of the
rotor, the casing having a length‘ greater than
‘ that of the rotor, the rotor being provided with
vane-slots extending throughout its length, at
least one ?oating head within the bore between
an end of the rotor and the adjacent ?xed head,
the ?oating head having a bore through which
the shaft passes, the rotor being provided with
an annularshoulder having a ?at sealing and
extending rearwardly into the head bore, ‘the
sleeve being lined with hearing metal to form a
sleeve bearing for the shaft to prevent angular
displacement of the ?oating head, means to sepa 45
rate the rotor and ?oating head at least the dis
tance of a running-?tacomprising an annular ?at
sealing and thrust bearing surface on the end of
the rotor near and surrounding the shaft, the
?oating head being provided with an annular re 50
cess in its inner surface, a ?at annular surface of
bearing metal in the recess and complementary
to the annular bearing surface on the rotor, means,
secured to the shaft and bearing against the sleeve
to force the ?oating head inwardly when the rotor 55
contracts and means to communicate air pressure
slightly above the average on the inner surface of
the ?oating head between it and the ?xed head
to hold said annular surfaces in contact.
7. A rotary compressor comprising the combi 60
nation of a stator casing, having a central bore
and an air intake and a discharge port communi—
cating therewith, a rotor. within the bore having
thrust bearing surface surrounding the shaft be
shafts mounted in bearings in ?xed heads closing
the casing at each end of the bore, said bearings 65
rotor and ?oating head at least the distance of a supporting the entire radial load of the rotor, the
running ?t, said thrust bearing surface being in casing having a length greater than that of the
a plane perpendicular to the shaft, a comple» rotor, at least one ?oating head within the bore
65 low the bottoms of the vane-slots to separate the
mentary sealing‘and thrust bearing surface of
70 bearing metal in a recess provided in and se
cured to~the inner surface of the ?oating head
and surrounding its bore, means secured to the
shaft beyond and-engaging the ?oating head to
force said head inwardly when the“ rotor con
75 tracts and means to, apply pressure to the outer
between an end of the rotor and the adjacent ?xed
head, the ?oating. head comprising a disc loosely 70
?tted in the bore, air sealing means for the periph
ery'of the disc, the disc being provided with a
rearwardly extending sleeve lined with bearing
metal and forming a sleeve bearing for the shaft
to prevent angular displacement of the disc, the 75
2,120,280
?xed head being provided with a bore loosely to
receive the sleeve,__ the inner surface of the disc
being provided with an annular ?at sealing and
thrust bearing surface of bearing metal surround
vent angular displacement of the disc, the last
ing the shaft, a shoulder on the end of the rotor
named ?xed head being provided with a bore to
of the disc, the disc being provided with a rear
wardly extending sleeve lined with bearing metal
and forming a sleeve bearing for the shaft to pre
surrounding the shaft, said shoulder having a ?at '
receive the sleeve with su?lcient looseness to
avoid supporting the radial load of the rotor upon
the sleeve bearing surface, the inner surface of
head, said annular surfaces being in contact in a - the disc being provided with an annular ?at bear
annular sealing and thrust bearing surface com
plementary to the annular surface on the ?oating
10 plane perpendicular to the shaft, and means to
ing surface of bearing metal near and surround
apply pressure to the outer surface of the disc to
ing the shaft, a shoulder on the end of the rotor
maintain the annular bearing surfaces in contact.
8. A rotary compressor comprising the combi
surrounding the shaft vand forming a comple
mentary bearing surface, said bearing surfaces
nation of a stator casing, having a central bore
15 and an air intake and a discharge port communi
being in a plane perpendicular to the shaft, means
cating therewith, a rotor within the bore having
shafts mounted in hearings in ?xed heads closing
the casing at each end of‘ the bore, the casing
the inner surface of the ?oating head to the
having a length greater than that of the rotor, at
least one ?oating head within the bore between
an end of the bore and the adjacent ?xed head,
the ?oating head comprising “a disc. loosely ?tted
in the bore, air sealing means for the periphery
1O
to communicate air pressure above theaverage on
space behind the head to hold said bearing sur
faces in contact, means secured to the shaft and
bearing against the sleeve to force the disc in~
wardly when the rotor contracts, and an anti 20
friction radial bearing supporting the shaft
beyond said means.
SNOWDEN B. REDFIELD.