Note: Descriptions are shown in the official language in which they were submitted.
~6~
SUCTION TUBE SEAL FOR A ROTARY COMPRESSOR
.
This invention pertains to hermetic rotaxy
compressors for compressing refrigerant in refrigera-
tion systems such as air conditioners, refrigerators,
and the like. In particular, the invention relates
to the manner of sealing the suction tube to the
cylinder in a rotary hermetic compressor.
In general, prior art hermetic rotary compres-
sors comprise a housing which is hermetically sealed.
Located within the housing are an electric motor and
a compressor mechanism. The electric motor is
connected to a crankshaft which has an eccentric
portion thereon. The eccentric portion of the crank-
shaft is located within a bore of the compressor
cylinder. A roller located within the bore is mounted
on the eccentric portion of the crankshaft and is
driven thereby. The roller cooperates with a sliding
vane to compress refrigerant within the bore of the
cylinder.
Rotary hermetic compressors of the type herein
disclosed generally have a pressurized or high side
sealed housing. The compressor is connected into a
refrigeration circuit by means of suction and dis-
charge tuhes. In the prior art compressors the motor
stator may be secured to the interior wall of the
housing by shrink fitting and the compressor cylinder
is generally welded to the housing. A motor rotor is
journalled in a bearing and drives the crankshaft.
The suction tube extends through the housing and is
sealingly connected thereto. The end of the suction
tube which extends into the housing is connected to
the cylinder and conducts low pressure refrigerant
directly to the cylinder bore for compression therein.
The connection of the suction tube to the cylinder is
usually made by press fitting or swedging the tube
into an aperture in the cylinder wall. To that end,
the suction tube outside diameter is made larger than
the inside diameter of the cylinder aperture so that
a good friction fit can be achieved.
The tolerances to which the cylinder, roller and
vane must be manufactured are generally very exacting,
such as ten thousandths of an inch. The reason for
such very tight tole~ances is that leakage of refriger-
ant in compressors must be minimized in order to
achieve acceptable efficiencies of the compressor
pumps. Since the assembl~ operations of welding the
cylinder to the housing and pressing or swedging the
suction tube into the cylinder aperture tend to
distort the cylinderj thereby causing vane slot
distortion and misalignment between the cylinder and
the bearing, the prior art cylinders have generally
been designed with a relatively large axial dimension
so as to be of relatively heavy construction. By
providing a thick, heavily constructed cylinder the
press fitted suction tube i5 surrounded by sufficient
cylinder material so that distortion is minimized,
vane slot geometry and alignment of the bearings are
preserved, and close tolerances are maintained. If
distortion were not minimized and the dimensional
tolerances could not be held during the welding and
swedging operations, leakage in the compressor would
become excessive.
In one prior art compressor having a low side
housing the sealed connection of the suction tube to
~;~g~i5~3
the suction muffler was made by means of an O ring.
In this application of an O ring to a compressor
structure the O ring did not provide a sealing
connection between compressor areas of high pressure
differentials such as the suction and discharge gas
areas. Furthermore, this prior art compressor was of
the reciprocating rather than the rotary variety so
; that there was no need for a thin cylinder to which
the suction tube had to be sealingly connected and in
which a large pressure drop existed across the sealed
connection.
The prior art solution to the problem of providing
a suitable sealed suction tube connection to the
cylinder in a high side rotary compressor by using a
thick cylinder and having the suction tube pressed
therein has the disaavantage that it tends to increase
the length of the refrigerant leakage paths and heat
transfer surface thereby tending to decrease the
efficiency of the compressor. During operation of
the compressor there are areas of various pressure
levels within the compressor. For instance, the bore
of the compressor cylinder has both an inlet portion
at suction pressure and a high pressure portion
wherein the gas is compressed. Furthermore, the
compressor housing itself is at high pressure because
compressed refrigerant is expelled from the cylinder
bore directly into the housing. As pointed out
above, it is important to keep leakage of refrigerant
from high pressure areas to low pressure areas to a
minimum, since such leaked refrigerant represents
lost work and reduces the efficiency of the compressor.
Therefore, it is important that the lengths of the
S(~8
borders dividing low and high pressure areas are made
as small as possible. It can be reaclily understood
that the height of the cylinder is a critical dimen-
sion affectiny leakage since it is directly related
to the border length dividing the high and low
pressure areas in the compressor cylinder bore. For
instance, the ]ength of the tip of the sliding vane
which contacts the roller and the cracks between the
vane and vane slot form a border dividing the high
and low pressure cylinder bore areas. By using a
thin cylinder this critical dimension can be kept
small and the refrigerant leakage past the vane as
well as other borders can be reduced.
An added disadvantage of the prior art thick
cylinder construction is that the weight of the
compressor is increased which is undesirable since
the compressors are used in household appliances
which are preferably of lightweight construction.
~ Accordingly, a thin cylinder is desired.
;~ 20 Another disadvantage of prior art compressor
structures has been that special shock absorbing
structures had to be provided for the suction tube
end extending into the compressor housing and located
between the housing and the cylinder. Pressures in
compressor housings tend to fluctuate and tend to
rise as the compressor is shut down. Such pressure
variations cause flexing of the housing. Since prior
art suction tubes were secured to hoth the cylinder
and the housing, the flexing of the housing due to
varying pressures had to be accommodated to prevent
rupturing of the suction tube seals with the housing
and the cylinder. Thus, prior art structures provided
$~3
shock tubes and other means to accommodate the stresses on the
suction tube. It is, therefore, desired to accornmodate the
stresses on the suction tube in a simple manner while ensuring
proper seals between the suction tube, the housing and cylinder.
The heavy construction of the cylinders of prior art
compressors tended not only to increase the length of the leakage
paths but also tended to increase the surface area available for
heat transfer to incoming suction gas. Such heat transfer is
undesirable and tends to decrease the efficiency of the compres-
sor. It is, therefore, desirable that the heat transfer surface
areas are minimized in order to optimize the efficiency of the
compressor.
Another disadvantage of prior art rotary hermetic compres-
sors is that in the sealing of the suction tube to the cylinder
the use of fittings is necessitated thereby increasing the cost
of the compressors d~le to the cost of parts and the cost oE
assembling the parts.
One further disadvantage of thick cylinders is that it tends
to increase the size of the compressor. Since hermetic compres-
sors~ are used in articles such as home appliances it is desirable
that the size of the compressors is minimized.
The present invention overcomes the disadvantages of the
above described prior art hermetic rotary compressors by provid-
ing an improved sealed connection between the suction tube and
the compressor cylinder.
The invention provides in one form thereof a hermetic
compressor including a housing, a cylinder secured to the inside
wall of the housing and a suction tube having one end extending
through a wall of the housing and sealingly secured to the
-- 5
. . .
~: ~
. ~,
., ,~ ~. ..1
;2 4~;S08
housing. A suction tube seal for the compressor comprises an
aperture in the cylinder, the aperture having an inside diameter
larger than the outside diameter of the tube. The tube end is
axially slidably received in the aperture and a sealing means is
interposed between the tube end circumference and the wall of the
aperture for sealing the tube to the aperture.
It is an objec~ of the present invention to provide an
improved seal for a suction tube connection with the cylinder of
a rotary hermetic compressor.
It is also an object of the present invention to eliminate
the need to press fit or swedge a suction tube to the cylinder of
a hermetic compressor whereby thin cylinders can be used thereby
keeping refrigerant leakage losses to a minimum.
It is another object of the present invention to provide a
compressor which is efficient, simple to construct and
lightweight due to the ability to utilize a thin cy~inder by
means of a sliding suction tube seal.
It is yet another object of the present invention to provide
d compressor which is energy efficient.
Another object of the present invention is the reduction of
heat transfer in a compressor by means of a suction tube seal
which permits the use of a thin cylinder thereby increasing the
efficiency of the compressor.
Yet another object of the present construction is the
elimination of a variety of fittings for connecting the suction
tube to a compressor.
It is still another object of the present invention to
provide a sliding seal between the cylinder and the suction
-- 6
;
..... .
i5013
tube whereby leakage in the compressor due to the flexing of the
housing is prevented.
According to one aspect of the invention there is provided a
hermetic rotary compressor which has a housing, an electric motor
operatively disposed within the housing and having a rotatable
rotor, and a unitary suction tube sealing secured to the housing
and having an end portion thereof extending into the housing.
The cylinder is disposed within the housing in axial alignment
with the rotor and is connected to the interior wall of the
housing, the cylinder having a cylindrical bore therein. A
rotatable crankshaft is received within the bore and is driven by
the motor for driving a piston means inside the bore and com-
pressing the refrigerant therein. A discharge port in the
cylinder is provided for discharging compressed refrigeran-t from
the bore, and an aperture in the cylinder wall of the cylinder is
in communication with the bore. The suction tube end portion has
a smaller outside diameter than the inside diameter of the
aperture, the tube end being axially slidably disposed within the
aperture. Resilient sealing means is provided for sealing the
suction tube end of the cylinder aperture and preventing the
refrigerant from leaking past the suction tube sealing means
while permitting axial movement of the tube end in the aperture.
The suction tube adapter means is provided for securing the
suction tube to the cylinder housing, -the adapter means including
a first cylindrical flange member adapted to fit over the tube
and in contact with the tube~ the adapter including a second
cylindrical portion having a diameter greater than the outside
diameter of the suction tube, and a third transition portion for
connecting the first and second portions, the second portion
being in intimate contact with the housing of the compressor.
:
In a specific embodiment of the invention, there is provided
a resilient neoprene O-ring for sealing the suction tube end of
the cylinder aperture and preventing refrigerant from leaking
. ~ .
... .
z~o~
past the suction tube sealing means while permitting the axial
movement of the tube end in the aperture when the suction tube
moves with the housing wall.
According to ano-ther aspect of the present invention there
is provided a hermetic compressor of a type which may be utilized
to compress refrigerant, the compressor including a hermetically
sealed housing with an electric motor located in the housing and
secured to an inside wall thereof. A suction tube is provided
which has an end thereof extending through the wall of the
housing and is sealingly connected thereto for conducting
refrigerant to the compressor. A crankshaft is connected to the
motor and is rotatably driven thereby, and a cylinder means is
secured to the housing and has a bore therein. An aperture is
provided in the~wall of the cylinder which communicates with the
bore, and the suction tube end is slidably received in the
aperture. Flexible sealing means is interposed between the
aperture and the outside wall of the tube for forming a seal
between the suction tube and the wall of the aperture while
permitting slidable axial movement of the tube in the aperture.
Adapter means fixedly connects the tube to the housing to prevent
relative movement therebetween, the adapter means including a
first cylindrical flange, the tube extending through the flange
and secured thereto, and a second cylindrical flange portion
secured to the housing, the firs-t and second portions being
joined by a frustoconical portion.
~,
According to another aspect of the invention there is
provided a compressor for compressing refrigerant, the compressor
having a flexible housing, an electric motor secured to an inside
wall of the housing and a crankshaft within the housing rotatably
connected to the motor. A main bearing is secured to the inside
of the housing, and a cylinder is located inside the housing and
connected to the main bearing, at least a portion of the cylinder
-- 8
:
...
. ...
1~4~i5~8
being radially spaced from the housing, the housing wall being
movable with respect to a side wall in the cylinder, the cylinder
having a compression chamber therein. A piston means is operably
connected to the crankshaft for compressing the refrigerant
within the chamber, and discharge means is provided in the
cylinder in operative association with the chamber for discharg-
ing compressed refrigerant. An aperture is provided in the
cylinder wall in communication with the cornpression chamber, a
suction tube has an end extending into the housing, the tubing
sealingly and rigidly connected to the housing whereby the tube
end moves relative to the cylincler when the housing flexes, the
tube end being axially slidably received within the aperture. A
suc~ion tube adapter means is provided for securing the suction
tube to the housing, the adapter means including a cylindrical
flange member adapted to fit over the suction tube, the adapter
having a first portion secured to the suction tube and a second
portion spaced away from the suction tube, the second portion
being in contact with the housing. An O-ring which is con-
structed of oil resistant resilient material is interposed
between the wall of the aperture and the tube wall for sealing
the tube end in the cylinder aperture while permitting axial
movement of the tube in the aperture whereby the suction tube end
moves with the housing and slides axially in the aperture upon
movement of the housing.
An advantage of the structure of one aspect of the present
invention is that by making a sliding sealed connection between
the suction tube and the cylinder by means of an O-ring arrange-
ment, a thin cylinder can be used because no distortion forces
will be placed on the cylinder during the assembling of the
suction tube thereto. The use of a cylinder which has a small
axial dimension reduces the lengths of the leakage paths formed
by the borders dividlng the low and high`pressure areas of the
compressor. For instance, the tip area of the sliding vane which
~,,"',,.
1246S08
-
contacts the roller and cracks in the vane slot are relatively
small if the height of the compressor is relatively small. Thus,
the amount of refrigerant which can leak from the high pressure
side of the bore to the low pressure side of the bore past the
vane tip and flanks are reduced, whereby the efficiency of the
compressor is improved.
Another advantage of a compressor constructed in accordance
with the present invention is that by using a thin cylinder, the
amount of surface area available for heat transfer is reduced
whereby less heat transfer will take place ancl the efficiency of
the compressor is improved.
Yet another advantage of the structure of the present
invention is that by using a sliding seal between the suction
tube end and the compressor cylinder the need for means to absorb
the flexing stresses of the housing relative to the cylinder due
to varying pressures in the housing is eliminated, since the
sliding seal formed by the O-ring accommodates those stresses.
Still another advantage of a compressor constructed in
accordance with the present invention is the elimination of
special fittings for sealing the suction tube to the cylinder as
weil as the elimination of the swedging or pressing operation for
securing the suction tube to the cylinder.
:
A still further advantage of a compressor constructed in
accordance with a present invention is that by the elimination of
` the pressing or swedging operation the possibility of distortion
of the compressor cylinder is eliminated and better bearing
alignment and slot geometry are maintained, thereby decreasing
leakage in the compressor and reducing excessive wear of the
bearings.
- 10 _
~,.
i, ~,
.. ...
5V8
A yet further advantage of the compressor according to the
present invention is that by the use of a flexible O-ring suction
tube seal and a thin cylinder the size and weight of the compres-
sor is decreased.
The above mentioned and other features and objects of this
invention and the manner of attaining them will become more
; apparent and the invention itself will be better understood by
reference to the following description of an embodiment of the
invention taken in connection with the accompanying drawings,
: wherein:
~: Fig. 1 is a broken away side sectional view of the compres-
sor embodying one form of the present invention;
Fig. 2 is a broken away bottom sectional view of the
compressor taken along the line 2-2 of Fig. l;
:
- I 1 -
.~
L~ :
. ', ..~
~Z~50~
12
Fig. 3 is an enlarged plan view of the cylinder;
Fig. 4 is an enlarged sectional view of the
suction tube connection to the housing and the
cylinder;
Fig. 5 is a plan view of the main bearing
assembly; and
Fig. 6 is a sectional view of the main bearing
assembly taken along line 6-6 of Fig. 5.
Referring to Fig. 1 there is shown a side
sectional view of the compressor with the compressor
disposed horizontally. A casing or housing 10 is
shown having a cylindrical portion 12 and top and
bottom portions 14 and 16, respectively. A flange 18
is shown welded to the bottom porti~n of the compres-
- 15 sor. The flange is used for mounting the compressor
when it is assembled to a refrigeration apparatus
such as an air conditioner or refrigerator.
A terminal cluster 20 is provided for making
electrical connections from a supply of electric
power to the compressor motor. A discharge tube 22
extends through the top portion of the housing and
into the interior of the compressor as shown. The
tube is sealingly connected to the housing as by
soldering. A suction tube 24 extends into the
interior of the compressor housing as further described
hereinbelow. The outer end of suction tube 24 is
connected to an accumulator 26 which has support
plates 28 disposed therein for supporting a filtering
mesh 29.
~n electric motor 30 is disposed within the
compressor housing and includes a stator 31 and a
rotor 32. The electric motor is an induction type of
~24~i0 !3
motor having a squirrel cage rotor. Windings 33
provide the rotating magnetic field for inducing
rotational movement of the rotor. The cylindrical
stator 31 is secured by interference fit to the
interior wall of the housing 10 as by shrink fitting.
In the shrink fitting process the housing 10 is
heated so that it expands. Motor stator 31 is then
inserted and positioned and the assembly is allowed
to cool. As the assembly cools, the housing 10 will
shrink and will securely grasp the motor stator 31.
A crankshaft 34 is secured to the hollow interior
aperture of the rotor 32 by shrink fitting. The
crankshaft 34 extends axially through an upper
bearing 36, and a cylinder 37 into a lower or outboard
bearing 38. The crankshaft is journalled in sleeve
bearings 35 and 39. As best illustrated in Fig. 2
the main bearing 36 has three flanges 40 thereon for
securing the bearing to the housing 10 at points 41
such as by welding.
As best illustrated in Figures 5 and 6, the main
bearing 36 comprises a relatively long sleeve bearing
portion 35 for journalling or rotatably supporting
crankshaft 34. Lower bearing 38 has a sleeve bearing
portion 39 for journalling the end portion of crank-
shaft 34. Cylinder 37 and lower bearing 38 are
secured to main hearing 36 by means of six bolts 50
as best illustrated in Figs. 1 and 2. Bolts 50
extend through holes 51 in the main bearing and holes
44 in the cylinder block and are threaded into the
lower bearing 38.
If the cylinder axial dimension permits, the six
bolts 50 could be replaced with twelve bolts, six of
~2~ 5(~8
14
which would secure outboard bearing 38 to the cylinder
and be threaded into the cylinder. q'he remaining six
`~ bolts would secure main bearing 36 to the cylinder
and be threaded into the cylinder.
As best illustrated in Figs. 1 and 2, crankshart
34 has an eccentric portion 52 thereon for revolving
eccentrically around the crankshaft axis. A cylindri-
;~ cal roller member 54 surrounds the eccentric and
rolls around circular bore 55 as the eccentric
revolves around the crankshaft axis. A counterweight
56 for counterbalancing the eccentric 52 is secured
to the end ring 57 of the motor rotor such as by
riveting. A rectangular sliding vane 58 is received
in a vane slot 59. The vane slot 59 is located in
lS the cylinder wall of cylinder 37. A spring 60 biases
the end of vane 58 against the roller 54 for continu-
ous engagement therewith, The spring 60 is received
in a spring pocket 62 machined into the wall of the
cylinder.
A lubrication hole 64 in shaft 34 communicates
with lubrication passage 66 in outboard bearing 38.
Passage 66 receives oil from a lubrication pump 68
disposed centrally in shaft 34. The oil is pumped
upwardly by centrifugal force through the central
opening in the shaft and is spun outwardly into
radial passage 66 in outboard bearing 38. Shaft 34
has an annular opening (not shown) machined therein
for communication of pump aperture 68 with passage
66. An oil passage 70 is provided adjacent vane 58
for lubricating the vane. Therefore, the oil will
travel upwardl~ through passage 66 and through
passage 70 adjacent vane 58 and will then exit on top
.~ -
~L24~
of the cylinder from which it will run down over the
cylinder by gravity back to the oil sump 72 in the
lower portion 16 of housing 10. A raclial oil lubrica-
tion hole 73 is provided in eccentric 52 of shaft 34
for lubricating the roller 54. The hole 73 communi-
cates with pump aperture 68 in shaft 34 and receives
oil therefrom. Another aperture 74 is provided in
cylinder 37 to accommodate the rectangular end of
vane 58.
In operation, as the roller 54 rolls around bore
55 refrigerant will enter the bore through suction
tube 24. As the volume defined by the end of vane 58
and the contact point of the roller 54 with the
outside perimeter of the bore 55 is reduced in size
by the rolling action of the roller the refrigerant
will be compressed. As best shown in Figures 5 and
6, compressed gas is discharged from the compression
chamber through cylindrical relief 76 in cylinder 37,
through opening 78 in the main bearing, past valve 80
and valve retainer 82 and into muffler space 84. A
discharge muffler baffle 86 is shown having an
opening 88 therein for discharging compressea gas
directly from the space 84 into the compressor
housing 10 and around motor 30 for cooling the motor
windings 33.
The end portion of the suction tube end 24
within the housing 10 is received within an aperture
90 in the cylinder wall. Since it is desirable to
have a thin cylinder 37 as explained hereinabo~e, the
height or axial dimension of cylinder 37 is chosen to
be small. Therefore, the amount of material of
cylinder 37 surrounding the aperture 90 in the axial
~Z9L~i50~
16
direction of cylinder 37 is relatively small. This
material is indicated at numerals 92 and 94 in Figure
4. Cylinder 37 is preferably cons~ructed of cast
iron which is somewhat porous. The porosity of the
cylinder material determines the minimum dimension of
the thic]cness of the material surrounding the aperture
~; 90 such as portions 92 and 94 since it is desired to
prevent leakage of any refrigerant through the walls
of the cylinder 37. If the thickness of the cylinder
material surrounding the aperture 90 is made too
small, compressed refrigerant might escape through
the pores of the cylinder material. The minimum
material thickness to prevent leakage has been found
to be thirty-seven thousandths of an inch. If this
dimension is chosen to be smaller, the likelihood of
leakage i5 increased due to the porosity of the
material.
Unlike prior art structures, the inside diameter
of the aperture 90 is greater than the outside
diameter of suction tube 24. Tube 24 is not friction-
ally engaged by the cylinder walls but is slidable
inside aperture 90. Aperture 60 communicates with
the bore of the cylinder and includes a shoulder
portion 96 to prevent tube 24 from entering too far
into the aperture. The tube end portion 100 also has
a reduced diameter portion 90 at its end to aid the
;~ entry of tube 24 into aperture 90 during assembly.
Aperture 90 is encircled by a circular recess
102. Recess 102 has a sealing ring 104 located
therein. The sealing ring 104 may be an O ring
constructed of a flexible material or any other
suitable flexible sealing ring. The material for the
~2465;~
17
O ring should be resistant to oil as the compressor
contains lubricating oil, which will contact sealing
ring 104. One material which has been found to be
suitable is Bunham which is an oil resistant neoprene
rubber.
As explained above, the suction tube 24 is not
fas~ened into the aperture 90 but is in frictional
; engagement with O ring 104 and is slidably received
within the aperture. The suction tube 24 is secured
to the compressor housing by being attached to a
suction tube adapter 106 as by soldering. Adapter
106 is cylindrical in shape and has a frusto-conical
section 108. The lower portion 110 of adapter 106 is
spaced away from suction tube 24 so that a void or
15 space 112 exists between portion 110 and suction tube
24. Lower portion 110 is soldered to an upstanding
~lange 114 of housing 10. By way of this construction,
when adapter 106 is soldered to suction tube 24 the
heat produced by the soldering process is transferred
away from suction tube 24 by means of frusto-conical
portion 108, cylindrical portion 110 and into the
housing 10 of the compressor thereby preventing
scorching of the O ring 104.
As the compressor housing 10 flexes because of
changing pressures inside the housing, suction tube
24 and end 100 thereof will move axially together
with adapter 106 with respect to the cylinder 37.
Since tube end 100 is slidably received within the
cylinder aperture 90, a proper seal is maintained
between the tube and the cylinder by flexible O ring
104.
~Z~6S~)8
~; 18
By eliminating the need for swedging or pressuring
the suction tube end 100 into the cylinder aperture
90 and thus keeping the distortion forces on the
cylinder 37 to a minimum, a thin compressor cylinder
37 can be used. The leakage paths between vane 58,
roller 54 and cylinder vane slots 59 are thus kept at
a minimum. The efficiency of the compressor is
thereby greatly improved over the efficiency of prior
art structures. In addition~ by using a thin cylinder,
heat transfer between cylinder 37 and the refrigerant
gas is greatly reduced, thus further improving the
efficiency of the compressor.
What has been provided is a rotary hermetic
compressor of simple construction having a high side
housing 10 and a thin cylinder 37 and having a high
degree of efficiency by the utilization of a very
effective seal 104 between the suction tube 24 and
the cylinder 37.
While this invention has been described as
having a preferred design, it will be understood that
it is capable of further modification. This applica-
tion is therefore intended to cover any variations,
uses, or adaptations of the invention following the
general principles thereof and including such depar-
tures from the present disclosure as come withinknown or customary practice in the art to which this
invention pertains and fall within the limits of the
appended claims.
; 30
:
