Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a hermetic
motor compressor unit, particularly to such a unit
which is intended for use in small capacity applica-
tions, such as small refrigerators.
This is a division of copending Canadian Patent
Application Serial No. 373,678, filed March 23, 1981.
One of the primary concerns in designing refriger-
ation compressors for use in small capacity applications
i5 that of minimizing the overall size of the unit
without sacrificing efficiency or the capacity which
is required. ~ further design consideration is that
of minimizing the number of parts required and the
assembly time. This is particularly important in
small compressors because the manufacturing volume of
such compressors is normally quite high and even
small savings in material and labor reaches considerable
proportions when high production levels are attained.
One of the assembly operations performed in
manufacturing such a compressor is that of assembling
the connecting rod to the crankshaft and piston.
Because the connecting rod articulates about the
piston wrist pin only in directions transverse to the
axis of;the crankshaft, it is impossible, when using
most conventional techniqlles, to insert the connecting
rod over the end of the crankshaft when the connecting
rod is attached to the piston. One technigue for
assembling the connecting rod to the crankshaft is
the use of a spllt sleeve-type~connecting rod wherein
the sleeve halves are assembled around the crankshaft
and secured together by means of bolts. The problem
with this technique is that additional parts are
required and there is a sub~tantial amount of labor
in assembling the connecting rod around the crankshaft.
:~ Furthermore, the split sleeve is a difficult part to
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manufacture due to the necessity for accurate machining
of the mating surfaces thereof.
A urther solution to the problem would be to
initially install the piston and connecting rod
assembly into the crankcase and then insert the
crankshaft through the open loop bearing end of the
connecting rod. This solution is not feasible in the
case of the compressor in question, however, wherein
the crankshaft is disposed vertically and must have a
relatively large bearing surface in contact with the
supporting surface of the crankcase. This would
require a correspondingly large opening in the
connecting rod, which is not practical in very small
compressors wherein the connecting rod is generally
small. Although the connecting rod could be lengthened
to accommo~ate the larger opening, this would increase
the overall size of the compressor in the direction
of the connecting rod. As mentioned earlier, mini-
mizing the overall size of the unit is one of the
design criteria of compressors of this type.
U.S. Patent 3,903,752 discloses yet another
solution to the problem of assemhling the piston,
connecting rod and crankshaft. The ~rist pin and
connecting rod form a unitary assembly, which is
inserted into the cylinder through a slot in the
sidewall thereof at the same time that the integral,
open loop bearing end of the connecting rod is
slipped over the end of the crankshaft. There is a
corresponding slot in the piston which enables the
connecting rod-wrist pin assembly to be inserted.
The primary difficulty to this technique is that the
wrist pin portion of the connecting rod-wrist pin
assembly is not per~litted to bear fully on the
openings in the piston. Because a slot in the piston
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is necessary to permit insertion of the assembly, the
wrist pin assembly bears only on the top and sides of
the opening in the piston, rather than around the
entire periphery of the wrist pin as in conventional
designs. This presents a serious problem in low
temperature compressors wherein the compression ratio
is much higher and, consequently, the forces between
the wrist pin and piston are high. It will be
appreciated that the loss of part of the bearing
surface will result in higher forces per unit area on
the remaining bearing surfaces. Another difficulty
is the complicated structure of the connecting rod
and wrist pin assembly, which makes machining more
dificult. Moreover, maintaining squareness of the
connecting rod relative to the crankshaft and piston
is much more difficult to achieve than in the case
where the connecting rod is joined to the piston by a
separate, cylindrical wrist pin.
In prior art compressors of this type, the
; 20 crankcase typically has been secured to the stator
laminations by means of four bolts or screws posi-
tioned at the four corners of the stator. Although
this provides a very stable support, it necessitates
a crankcase which extends la-terally over the full
area of the top surface of the stator. This increases
the amount of material which is required to produce
the crankcase, and necessitates a generally larger
crankcase.
In Patent 4,115,035, a compressor utili~ing a
two point support is disclosed. Ln this case, the
crankshaft extends through a central sleeve portion
and downwardly extending legs at the opposite end
thereof are secured to the stator by means of screws
extending through the stator. It has been found that
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this provides a very weak support resulting in a loss
of stability between the crankcase and stator. Since
the rotor is secured to the crankshaft, which in turn
is supported within the crankcase, any loss of
stability will result in loss of integrity of the air
gap. In order to maintain optimum efficiency, it is
extremely important that the air gap be maintained
within very precise limits around the entire periphery
of the rotor.
In hermetic compressors, the motor-crankcase
assembly is generally resiliently supported within
the outer housing by means of spring support~. This
not only isolates vibration and noise generated by
the compressor, but provides some degree of isolation
between the motor-crankcase assembly and shocks
imparted to the housing during shipping and use.
One prior art mounting arrangement comprises a
plurality of mounting spuds pressed over the heads of
the screws or bolts extending through the stator
laminations and resiliently retained within a plurality
of respective coil springs secured to the lower
surface of the outer housing. The springs are
mounted to the housing by means of metal mounting
spuds welded or brazed to the housing and extending
axially withln the coils springs. In addition to
serving as the connectors to the coil springsj the
spuds serve as shipping stops to limit the vertical
movement o~ the motor-crankcase assembIy within the
housing.
Generally, the sockets in the upper spuds that
are pressed over the heads of the connecting bolts or
screws are concentric with~the central axis of the
spud. Because the connecting bolts or screws are
necessarily disposed inwardly of the sides of the
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stator laminations to provide the re~uired degree of
structural integrity between the bolts and laminations,
the support base for the assembly, as defined by the
four support spuds, is also disposed inwardly of the
sides of the laminations to the same extent. If the
geometrical centers of the spuds could be relocated
outwardly, then a more stable support base for the
motor-crankcase assembly could be provided.
The mounting spuds and their associated coil
springs present a problem in that they often interfere
with the end turns of the field windings, which -~
extend out of the slots of the stator and form a mass
on the lower surface thereof. This necessitates that
the end turn configuration for the field winding be
carefully controlled so that the end turns do not
come into contact with the springs, which may result
in wearing through of the insulation and shorting of
the winding.
Generally, compressors of this type are designed
such that there will be no contact between the
motor-crankcase assembly resiliently supported within
the housing and the inner wall of the housing during
normal use. During shipping of the unit, however, it
is often sub~ected to severe shocks thereby causing
the motor-crankcase assembly to strike the inner wall
of the housing and cause damage to the compressor or
rupturing of the hermetically sealed housing. Undue
movement of the motor-crankcase assembly is also
necessary to prevent overstressing of the mounting
springs and discharge gas shock loop.
The above-discussed disadvantages and problems
of prior art compressoxs are overcome by the compressox
according to the present invention.
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Regarding the difficulty of assembling the
connecting rod to the piston and crankshaft without
resorting to a two-piece, split end connecting rod is
accomplished by inserting the connecting rod over the
free end of the crankshaft and at the same time
inserting the opposite end of the connecting rod in
the cylinder through a slot in the sidewall thereof.
Rather than forming the connecting rod and wrist pin
as a separate assembly which is then inserted throuyh
a slot in the cylinder side wall and through a slot
in the piston, the present invention provides for
first insertiny the connecting rod and then inserting
the piston over the top of the connecting rod.
Following this, this wrist pin is inserted through
the same slot in the cylinder wall through the
aligned openings in the piston and connecting rod
end. A wrist pin is secured in place by means of an
internally disposed spring clip.
This arrangement is advantageous because it
permits the wrist pin to bear;against the surfaces of
the aligned openings in the piston about is entire
periphery at all times, as opposed to one of the
prior art techniques wherein a slot in the piston to
accommodate the connecting rod and wrist pin assembly
reduces the bearing surface. This is particularly
important in low temperature compressors of this~type
wherein the compression ratio and, accordingly, the
loading of the wrist pin, is quite high. This
arrangement is also advantageous because it utilizes
simply constructed parts which are easy to manufacture
and assemble and squareness of the connecting rod
relative to the piston and crankshaft can be maintained
without difficulty. Additionally, the crankshaft
eccentric on whlch the connecting rod is journaled
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can be made small and can be positioned very close to
the main bearing.
In accordance with one aspect of the compressor,
the crankcase is supported on the stator of the motor
by means of three downwardly depending mounting legs,
which are connected to the stator by three screws
extending through the stator and received in threaded
sockets in the mounting legs. This arrangement
provides the smallest crankcase size possible yet
n without sacrificing the stable support which is
necessary to en~ure integrity of the rotor-stator air
gap around the entire periphery of the rotor at all
times~ It is advantageous over the four point
support utilized extensively in prior art compressors
because the crankcase can be much smaller thereby
reducing weight and amount of material required.
In a specific embodiment of the invention, the
three supporting legs are spaced apart by 90 about
the central axis of the compressor with the two end
legs being separated by 180. It~has been found
that, by positioning the cylinder between two of the
legs which are angularly separated by 90, very
stable mounting of the crankcase can be achieved even
without the fourth supporting point which has cus-
tomarily been~employed in the past.~
The hermetic~motor compressor uni~ according tothis aspect of~the invention comprises an outer
housing, a stator disposed within the outer housing
and including a central opening therethrough, an
electrical field winding disposed within slots of the
stator, a crankcase including a cylinder, and a
piston slidably received in the cylinder. A crankshaft
is rotatably mounted in the crankcase and includes a
rotor secured thereto r which is concentrically
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disposed within the central opening of the stator. A
connecting rod is journaled over the crankshaft and
is connected to the piston. The crankcase includes
three only mounting legs having respective lower
surfaces which are in engagement with the stator and
are secured to the stator by means of three threaded
connecting members which extend through the stator
and are secured to the mounting legs. The crankcase
is resiliently mounted within the outer housing in
order to isolate vibration and shocks.
The crankcase includes a central opening through
which the crankshaft ext~nds, and the three mounting
legs are preferably positioned to intersect three
coplanar radii perpendicular to the axis of rotation
of the crankshaft and spaced 90 apart. The cylinder
may be positioned such that its central axis is
perpendicular to the axis of rotation of the crankshaft
and is angularly spaced equidistantly from two of the
mounting legs by 45.
In accordance with an illustrated embodiment of
the compressor of the invention, the mounting spuds
are designed such that the sockets which are pressed
over the heads of the four screws extending through
the stator laminations are eccentric relative to the
central axis of the generally circular cross-section
fingers extending downwardly and received within the -
mounting springs. This permits the center of gravity
of the supporting spuds to be moved radially outwardly
relative to the central axis of the compressor so as
to broaden the base of support therefor. It has been
found that this provides a much more stable config-
uration than does the prior art arrangement wherein
the spuds are concentric with the axes of the screws
. or bolts connecting the crankcase to the stator.
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Furthermore, by moving the spuds radially outward,
the respective coil springs are also mo~ed further
away from the slots of the stator thereby providing
more room for the field winding end turns. Thus~ the
configuration of the end turns is not as critical as
is the case with prior art compressors wherein the
mounting spuds and springs are much closer to the
stator slots. In order to prevent rotation of the
spuds, there are provided stop collars which extend
upwardly along a portion of the side of the stator.
Specifically, the compressor according to this
aspect of the invention comprises an outer housing, a
a stator disposed within the outer housing and
including a central opening therein wherein the
stator includes an upper surface, a lower surface and
sides defining a peripheral surface. An electrical
field winding is disposed in the stator and a crankcase
is supported on the upper surface of the stator and
includes a cylinder. A crankshaft is rotatably
mounted in the crankcase and includes a rotor secured
thereto, which is disposed in the central opening of
the stator and is rotatable about an axis extending
through the opening. A piston is slidably received
in the cylinder and~connected to the crankshaft. At
least three Plongated connecting elements extend
upwardly through the stator and are distributed
around the stator central opening near the perlphsral
surface of the stator. The connecting elements are
secured to the crankcase and include heads protrudin~
beyond the lower surface of the stator. At least
three upwardly extending coil springs are secured to
the outer housing, and a mounting spud is sacured to
each of the connecting element heads and is in
abutment with the lower surface of the stator. Each
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of the spuds comprises a downwardly extending retainer
finger disposed axially in a respective coil spring
and retained therein, and further comprises a socket
in which the head of a respective connecting element
is received. The socket is eccentric relative to the
finger and the axis of the respective spring whereby
the major portion of the spud is disposed radially
outward of the head relative to the axis of the
rotor. Preferably, the connecting elements are
screws and the heads of the screws are press fit in
the sockets of the respective spuds. In a preferred
embodiment, a further set of spuds are secured to the
lower surface of the housing and project upwardly
such that they are axially received in the coil
springs. The lower spuds are of such a length that
they abut the respective first mentioned spuds when
the crankcase and stator assembly is pressed down-
wardly, thereby serving as shipping stops to prevent
overstressing of the springs or damage to the com-
pressor or housing.
It is a further object of the present inventionto provide a small hermetic motor compressor unit
wherein the size of the crankcase can be reduced, yet
the crankcase is rigidly connected to the stator in ~-
such a manner that the integrity of~the rotor~stator
air gap is maintained about the entire periphery of
the rotor.
Yet another object of the present invention is
to provide a small, quiet, efficient and relatively
inexpensive~hermetic compressor for use in small
capacity-refrigeration applicati~ns.
These and other objects of the present invention
will become apparent from the detailed description of ~ -~
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a preferred embodiment considered together with the
accompanying drawings.
Figure 1 is a top view of the compressor according
to the present invention wherein the upper portion of
the outer housing has been removed;
Figure 2 is a sectional view taken along line
2-2 of Figure 1 as viewed in the direction of the
arrows;
Figure 3 is an eleva~ional view of the compressor
viewed from the left end of Figure 1 wherein a
portion of the outer housing has been removed;
Figure 4 is a bottom view of the compressor
wherein a lower portion of the outer housing has been
removed;
Figure 5 is an elevational view of the crankcase
viewed from the cylinder end;
Figure 6 is a bottom view of the crankcase shown
in Figure 5t
Figure 7 is an inverted sectional view taken
along line 7-7 of Figure 6 and viewed in the direction
of the arrows;
Figure 8 is a fragmentary, exploded view of the
: piston and connecting rod assembly being assembled
wh~rein the connecting rod is partially inserted into
the cylinder and over the free end:of the crankshaft;
Figure:9 is a view similar to Figure 8 but:
wherein the connecting rod and counterweight have
been completely assembled and the:piston is being
: slid over the end of the connecting rod;
Figure 10 lS a view similar to Figures 8 and 9
wherein the wrist pin is now being inserted through
the piston and connecting rod;
Figure 11 is a fragmentary, top view OL the
:: assembled piston aod connecting rod assembly wherein
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a portion of the piston has been removed to illustrate
the details of construction;
Figure 12 is a bottom view of the cylinder head;
Figure 13 is a top view of the valve plate and
leaf plate asse~ly;
Figure 14 is a sectional view taken along line
14-14 of Figure 13 and viewed in the direction of the
arrows;
Figure 15 is a sectional view taken along line
15-15 of Figure 13 and viewed in the direction of the -
arrows;
Figure 16 is a top view of the retainer cage for
the lubricant pickup tube;
Figure 17 is a bottom view of one of the mounting
spuds;
Figure 18 is a sectional view taken along line
18-18 of Figure 19 and viewed in the direction of the
arrows;
Figure 19 is a top view of one of the mounting
spuds;
Figure 20 is a sectional view taken along line
20-20 of Figure 3 and viewed in the direction of the
arrows, and
Figure 21 is a detail of the discharge valve.
Referring now to the drawings~in detail,
Figures 1-4 illustrate various views of the assembled
compressor. The compressor is mounted within a
hermetically sealed outer housing ~6 comprising upper
and lower halves 27 and 28, respectively, which are
welded or brazed together along seam 30. A pair of
mounting ears 32 and 34 are welded or brazed to the
bottom of housing lower half 28 and include openings
36 to enable mounting to the frame of the refrigerator
or other device in which the compressor is incorporated.
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A conventional multiple pin terminal 38 (Figure 2)
provi.des for electrical connection between an external
source of supply to the field winding 40 in a manner
well known in the art. Terminal 38 includes a cup
member 41 which extends through and is brazed or
welded to the lower housing half 28.
Suction tube 42 and discharge tube 44 extend
through the housing lower half 28 and are welded or
brazed in place. Suction tube 42 connects to the
evaporator ~not shown) of the refrigeration system
and discharge tube 44 connects to the condenser (not
shown) thereof.
The motor-pump unit of the compressor comprises
an induction motor 46 to which is secured crankcase
48. Motor 46 comprises a stator 50 made up of a .
stack of laminations having a generally circular
array of vertical slots (not shown) therethrough
within which are wound the coils making up the field
winding 40. Extending out of the upper surface 52
and lower surface 54 of stator 50 are the end turns
55 of the field winding, and these are configured in .: ~:
a generally toroidal shape concentric with the axis ~ ;
: : of the motor 46. Preferably, the slots in stator 50
in which the field windings 40 are disposed extend
radially i~ward to the circular central opening 56 of
stator 50. A conventional rotor 58~is~press fit over
crankshaft 60, which is rotatably supported within :
crankcase 48 in a manner to be described below, and
is concentrically disposed within the central opening
30 56 of stator 50. A very uniform, concentric air gap ~:
is defined between rotor 58 and stator 50
Referring now to Figures 5, 6:and 7, crankcase
48 is of integral construction made of 30,000 UTS
gray cast iron. It comprises an upper web portion
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62, a central crankshaft beari.ng portion 64 depending
from web portion 62, and three mounting legs 66, 68
and 70 depending from web portion 62. Crankshaft
bearing portion 64 includes a cylindrical opening 72
therein, and the axial centers of legs 66, 68 and 70
intersect radii at points equidis~ant from the axis
of crankshaft opening 72 wherein the center of leg 68
is spaced 90 from the center of leg 66 and 180 from
the center of leg 70. The center of leg 70 is spaced
90 from the center of leg 66. Threaded sockets 74
are provided in the lower surfaces 76 of legs 66, 68
and 70 at the respective centers thereof.
A cylinder 76 is machined in crankcase 48 and
extends completely through web portion 62 from a
pDsition just radially outward of the crankshaft
opening 72 to the flat, machined surface 78 ill~s-
trated in Figure 5. ~he central axis of cylinder
bore 76 coincides with a radius extending from the
central axis of crankshaft opening 72, and this
radius is spaced angularly 45 from the radii of the
threaded sockets 74 of mounting legs 66 and 68. A
somewhat arcuate slot 80 (Figures 1 and 7) extends
through the sidewall 82 of cylinder 77. The purpose
of slot 80 is to facilitate assembly of the connecting
rod to the piston 84 and crankshaft 60 in a manner to
be described in detail below. An intake muffler --
chamber 86 is formed within web portion 62 and an
intake opening 88 is provided in the side walI 89
thereof. A suction port 90 extends from suction
muffler chamber 86 to the machined surface 78 of
crankcase 48. A discharge muffler 92 is also formed
in web portion 62 of crankcase 48, and a discharge
port 94 extends from chamber 92 to the flat surface
78 of crankcase 48. It will be noted that suction
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muffler 86 and discharge muffler 92 are positioned on
opposite sides of cylinder bore 76 and the centers
thereof are equidistantly spaced from the vertical
plane intersecting the central axis of bore 76.
As shown in Figures 1 and 3, suction tube 96 is
secured to suction inlet 88 and is provided with a
90 bend so that it extends downwardly before ter-
minating in opening 98. The present compressor
includes the feature of semidirect suction, which
means that the opening 98 of the internal suction
tube 96 is in direct alignment with the opening of
the suction tube 42 tFigure 1) that extends through
housing 26 and is connected to the evaporator of a
refrigeration system. This arrangement raduces the
suction gas superheating and results in improved
efficiency of the compressor. Preferably, the
opening 98 of suction tube 96 is cut at a 45 angle
relative to the longitudinal axis of the downwardly
extending portion thereof.
A hollow, generally frustoconical shaped cover
100 is positioned over discharge muffler 92 and i5
secured to muffler 92 by means of a screw 102 extending
therethrough and being threadedly received within
socket 104. The discharge gas shock loop 106 is
connected to and extends through cover 100 into the
interior of muffler chamber 92, and connects to
discharge tube 44 as illustrated in Figure 1. In
order to avoid overstressing of shock loop 106 as the
resiliently mounted pump unit moves within housing
26, shock loop 106 is bent to form~convolutions 108
as illustrated in Figure 4. Suction muffler chamber
86 is also provided with a hollow, generally frusto-
conically shaped covèr 110, and is secured over
chamber 86 by screw 112, which is threadedly received
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within socket 114 (Figure 7). Covers 100 and 110 are
seated on annular shoulders 115 and 116 at the upper
ends of chambers 86 and 92, respectivel~.
As discussed above, crankcase 48 is supported on
three legs 66 ~ 68 and 70, as opposed to prior art
compressors wherein the crankcase has a four point
support, and the legs are angularly spaced by 90.
Leg 70 is joined to the central portion of web
portion 62 by bridge portion 120, and legs 68 and 66
are connected directly to the main part of web
portion 62.
Crankcase 48 is connected to stator 50 by means
of three screws 122, which pass through clearance
openings 124 in stator 50 and are threadedly received
in sockets 74 in legs 66 ~ 68 and 70 (Figure 3).
Screws 122 are preferably cap screws having cylindrical
heads 126 which protrude beyond the lower surface 54
of stator 50. Although not utilized to connect
crankcase 48 to stator 50, a fourth screw 128 also
extends upwardly through clearance openings in stator
50 and is connected thereto by nut 130, which is
tightened down against the upper surace 52 o stator
50. When screws 122 are tightened, crankcase 48 is
drawn downwardly against the upper surface 52 of
stator 50, and the three mounting legs 66, 68 and 70
provide an extremel~ stable connection between
crankcase 48 and stator 50. As will be appreciated,
this results in a substantially smaller crankcase
because of the open area over that portion o~ the
motor 46 around the fourth connecting screw 128 as
illustrated in Figure 1.
The valving arrangement for the suction and
discharge gases will now be described. The cylinder
'~! head 132 illustrated in Figure 12 is made of 30,000
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UTS gray cast iron and comprises a generally tri-
angularly shaped discharge chamber 134 and a smaller,
slightly elongated suction chamber 136 separated from
each other by web 138. Head 132 includes four
clearance holes 140 for bolts 142 (Figures 1, 3 and
4).
Head 132 is disposed over valve plate 144
(Figure 13), which has an outer periphery in the
lateral direction of the same shape as that of head
132. The lower surfaces 146 (Figure 2) of head 132
are sealed against valve plate 144 by means of a
suitably shaped gasket 133 (Figure 1). Valve plate
144, which is made of cast iron, is provided with
four clearance holes 148 for bolts 142, and also
includes a discharge passage 150 communicating with
discharge chamber 134 in head 132 and a suction
passage 152 communicating with suction chamber 136 in
head 132.
Leaf plate 154, which is made of bri.ght polished
flapper valve steel, is sandwiched:be~ween val~e
plate 144 and leaf plate gasket 156. JJeaf plate 154
and leaf plate gasket 156 each have the same periph~ral
shape as head 132 and valve plate 144. Leaf plate
1~4 includes an elongaked leaf valve portion 158
stamped therein and joined to leaf plate 154 by an
integral hinge:portion generally in:accordance with
conventional leaf valve design employed in prior art
compressors. ~he end portion of leaf valve 158 is
positioned directly below suction~opening I60 (Figures
13 and 15), and is pressed into sealing engagement
with the lower surface 162 of valve plate 144 by the
compressed gases produced during the compression
stroke of piston 84. On the suction stroke of piston
84, however, the partial vacuum within cylinder bore
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76 will draw leaf valve 158 away from the lower
surface 162 of valve plate 144 and permit refrigerant
within suction chamber 136 to pass through opening
160 into cylinder bore 76. Suction passage 152
(Figure 13) is aligned with a similar opening (not
shown) in leaf plate 154, which, in turn, is in
alignment with suction port 90 (Figures 5, 6 and 7).
Thus, refrigerant is drawn from suction muffler 86
through suction port 90 and passage 152 in valve
plate 144 into suction chamber 136, and from there
downwardly through opening 160 and past leaf valve
158 into cylinder bore 76.
Referring now to Figures 13 and 14, discharge
leaf valve 166 tFigure 21), which is made of the same
material as leaf plate 154, is connected to the upper
surface 168 of valve plate 144 by discharge valve
retainer 170 and rivets 172. It will be noted that
leaf valve retainer 170 includes a curved portion .~`
174, which overlies the movable portion of discharge
leaf valve 166 and limi~s the upward movement thereof.
A discharge opening 176 is positioned directly
beneath discharge leaf valve 166 an.d communicates
with piston bore 76. Discharge gas passage 150
(Figure 13) is in alignment with an opening in leaf
plate 154 and with discharge port 94 (Figures 5 and
6). On the piston compression stroke,~the refrigerant
flows upwardly through opening 176, past open discharge
valve 166 into discharge chamber 134, and from there
back through discharge port 94 into discharge muffler
92. The pressurized refrigerant flows out of discharge
muffler 92 hrough discharge shock loop 106 and
discharge tube 44 to the condenser of the refrig-
eration system.
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Valve plate 144 includes annular grooves 178 and
180 concentric with openings 176 and 160, respectively.
The valve assembly described above is secured to the
flat surface 78 of crankcase 48 by screws 142, which
are threadedly received in four corresponding threaded
sockets 182 in crankcase 48 (Figures 5, 6 and 7).
With reference to Figures 1, 2 and 8-11, the
piston and connecting rod assemhly and the manner of
assel~ling the same will be described. Crankshaft
60, which is best illustrated in Figure 2, is Journaled
within the central sleeve portion 64 of crankcase 48
and includes a bearing portion 184 having a bearing
surface 186 supported on the upper surface 188 of
crankcase sleeve portion 64. The end of crankshaft
60 is formed as a circular eccentric 190, and when
the crankshaft 60 is fully inserted in sleeve portion
64, eccentric 130 will be positioned directly opposite
the central axis of cylinder bore 76. In assembly,
crankshaft 60 is first inserted into crankcase 48 to
20 the position shown in Figure 2, and rotor 58 is then ~- -
pressed over it.
The connecting rod 192 comprises a closed loop -
first end 194 having a circular opening 196 therein,
and a closed loop second end 198 also having a
circular opening 200 therein and connected to the
first end 194 by a shank portion 202. Figure 8
illustrates connecting rod 192 being inserted, and
this is accomplished by slipping the opening 200 over
the eccentric 190 of crankshaft 60. If this is done
with eccentric 190 at the bottom dead center position
illustrated in Figure 8, slot 80 in the side wall of
cylinder 77 will permit end 194 to drop into cylinder
bore 76. It will be noted that slot 80 is generally
the same shape as end 194 of connecting rod 192, and
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is located such that cylinder bore 76 will remain
sealed even when piston 84 is in its bottom dead
center position as illustrated in Figure 2.
After connecting rod 192 has been inserted to
the position illustrated in Figure 9, piston 84 is
inserted through the opposite end of cylinder bore 76
as shown in Figure 9 over the end 194 of connecting
rod 192. It is necessary to assemble piston 84 prior
to the cylinder head and valve assembly. Piston 84
comprises a pair of aligned openings 2G6 and 208
extending through its skirt 210 to the interior 212
thereof. Openings 206 and 208, which are circular in
cross section, have axes which intersect the longi-
tudinal axis of piston 840
When piston 84 has been inserted to the posi~ion
shown in Figure 10, cylindrical wrist pin 214 is
dropped in place through opening 206, then through
the opening 196 in connecting rod 192, and finally
into opening 208 in piston 84. It will be appreciated
that, when crankshaft 60 is in the bottom dead center
position, wrist pin 214 can be inserted through the
slot 80 in the sidewall of cylinder 77. Figures 2
and 11 illustrate the manner in which wrist pin 214
is held in place within piston 84. When wrist pin
214 has been slid to the posi~ion illustrated in
.
Figure 2, a generally U-shaped spring clip 218 is
slipped over wrist pin 214 within a peripheral groove
220 therein. Spring clip 218 comprises legs 222
having arcuate inner edges 224 and tapered edges 226. `
The distal end~228 of clip 218 functions as a hinge
; to permit legs 222 to spread as clip 218 is forced -
~ ~ over wrist pin 214. ~The tapered edges 226 assist in
- ~ spreading legs 222 as clip 218 is inserted, and since
the inner, arcuate edges 224 lie on a circle ha~ing a
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diameter smaller than the outer diameter of wrist pin
214 and approximately the same size as the outer
diameter oE groove 220, spring clip 218 will be
resiliently held in place. Clip 218 is inserted
through the open, lower end of piston 84. Because
spring clip 218 has a larger outer diameter than the
openings 206 and 208 in piston 84, wrist pin 214 will
be retained in place. Figure 2 illustrates that
wrist pin 214 is spaced inwardly from the opposite
sides of piston 84 so as to avoid scoring the walls
of cylinder bore 76.
The feature of providing the slot 80 in the
sidewall of the cylinder to facilitate the assembly
of the piston, connecting rod and crankshaft is also
described and above-identified parent application
373,678.
Counterweight 234 is then connected to the end
of crankshaft 60 by means of cap screw 236. The use
of a detachable counterweight is advantageous because
it allows for differences in counterweight size to
compensate for variations in bore and stroke, the
shaft eccentric 190 can be located adjacent to the
main bearing 184, and it permits the use of a one-
piece connecting rod 192. Counterweight 234 is
attached to crankshaft 60 after the insertion of
~spring clip 218.
Lubrication of the compressor is provided by
means of a conventional aluminum killed, steel pickup
tube 238 having a generally cylindrical upper portion
240 and a tapered lower portion 242. Tube 238 is
pressed into a drilled out portion~239 of crankshaft
60 and extends downwardly into the refrigerant and
: lubricant sump formed within the lower portion of
outer housing 26. Tube 238 is in fluid communication
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with two drilled passages 246 and 248 in crankshaft
60, which are in alignment with an opening 250 in
counterweight 234. A lubricant distrlbution tube 252
is pressed within opening 250 so that lubricant
pumped upwardly by tube 238 will flow through passages
239, 246, 248 and opening 250 and the upwardly and
out through lubricant tube 252. It is noted that
tube 252 is positioned eccentrically with respect to
the axis of rotation of crankshaft 60. Tube 252
preferably extends through opening 250 and is re-
ceived within eccentric 190.
The resilient mounting arrangement for the
compressor to permit relative motion of the pump unit
within outer housing 26 comprises four metal, generally
cylindrical, and slightly tapered mounting spuds 256
welded or brazed to flats 258 formed in the lower
half 28 of outer housing 26 (Figures 2 and 20).
There are four such mounting spuds 256. Coil springs
260 are resiliently clamped over respective spuds 256
and extend upwardly in a general vertical direction
from the bottom of outer housing 26.
Four upper mounting spuds 262 made of a suitable
plastic material are positioned directly above the
lower spuds 256 as illustrated in Figure 20. Each of
: 25 upper spuds 2~2 comprises a lateral flange portion
264, a generally frustoconical depending finger 266,
which is resiliently clamped within coil spring 260,
and a socket or recess 268 r which is press fit over
the heads 126 of the four connecting screws 122 and
30 128. The upper surface 270 of each of the upper
spuds 262 are in abutment with the lower surface 54
of stator 50. Of primary importance is the fact that
the central axis represented by dotted line 272 of
circular sockets 268 is eccentric relative to the
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central axis shown as dotted line 274 of frustoconical
spuds 276 and 256. This permits the support centers
of spuds 262 to be positioned further outward in a
radial direction relative to the axis of rotation of
5 crankshaft 60 than is the case with prior art mounting
spuds of this type wherein the centers of support are
coincident with the a~es of the connecting screws
122. The relationship of mounting spuds 262 relative
to connecting screws 122 is further illustrated in
Figure 4.
This arrangement is important in that it enables
the support base for stator 50 and, therefore, for
the entire compressor, to be larger than is the case
with prior art compressors. Furthermore, the fact
that the mounting spuds 262 and, therefore, springs
260 are further outward, the configuration of the end :-
turns 55 of main winding 40 is not as critical
because more space is available for the end turns 55.
In order to properly position upper spuds 262, stop
20 collars 280 are provided, and these collars have an ~
inner arcuate surface 282 which generally conforms to .~-:
~he outer peripheral side surface 286 of stator 50.
Stop collars 280 also serve to provide additional
support in the lateral direction because they are in
engagement with the sides 286 of stator S0.
The fingers 266~of upper spuds 262~extend :
axially within coil springs:260 and have a maximum
outer dimension which is slightly larger~than the
inner dimension of coil spri.ngs 260 in their unde- :
:~ 30 flected states so that fingers 266 are resiliently
and frictionally clamped within springs 260.
The mounting devices described above, which
comprise upper spuds 262, lower spuds 256 and coil
springs 260, are positioned generally at the four
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corners of the stator 50. The ma~or portions of the
spuds 262, 256 and springs 260 are located radially
outward of the heads of the connecting screws 122,
and it will be seen that their respective axes are
located at about the edge of stator 50. The size and
positions of spuds 262 can be varied to adjust the
location of the respective support axes, but it is
generally preferable that the support axes are at or
~ust slightly inward of the outer surface of stator 50.
The resilient mounting devices just described
permit the motor-crankcase assembly to move slightly
relative to outer housing 26. Not only do coil
springs 260 permit a certain degree of upward and
downward movement, but they also permit some lateral
movement as well. This serves to lessen the trans-
mission of shocks and vibration between the compressor
and outer housing.
In order to prevent undue lateral movement of
the motor-compressor unit within outer housing 26, a
cup-shaped cage element 290 (Figures 2 and 16) is
welded or brazed to the lower surface 291 of outer
housing lower half 28. Lubricant pickup tube 238
extends downwardly into cage 290 r and the clearance
between the outer surface of cylindrical portion 240
and the inner surface 294 of cage 290 is selected
such that the cylindrical portion 240 of tube 238
will contact the inner surface 294 of cage 290 before
coil springs 260 and shock loop 106 a~e excessively
deflected and before any of the internal structure
30 can strike the sides of outer housing 26. Thus, cage -~
290 serves as a shipping stop in ~he lateral direction.
The clearance between the lower end 296 of tube 238
and the bottom 297 of cage 290 is slightly greater
than the clearance between the lower end 298 of spuds
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262 and the upper ends 300 of the corresponding lower
spuds 256 (Figure 20) so that spuds 262 and 256 will
engage each other before the lower end 296 of tube
238 strikes the bottom 297 of cage 290. The com-
S bination of lubricant tube 238, cage 290, and spuds262 and 256 function as shipping stops in the lateral
and downwardly vertical directions. The up stop is
accomplished by contact between a portion of the
compressor and the inner surface of the upper housing
half 27.
In order to permit lubricant to flow to pickup
tube 238, openings 304 are provided in the sides of
cage element 290 as illustrated in Figures 2 and 16.
The particular shape of outer housing 26 has
15 been designed so as to minimize the transfer of ~ -
noise, and is disclosed in copending Canadian appli- -
cation entitled Continuous Curvature Noise Suppressing
Compressor Housing, Serial No. 373,627 filed concur-
rently herewith in the name of David C. Lowery and
owned by the assignee of the present application.
In operation, when main windings 55 are energized,
rotor 58 is caused to rotate within the central
opening 56 of stator 50 thereby causing crankshaft 60
also to rotate. This causes piston 84 to reciprocate
within cylinder bore 76. On the suction stroke of
piston 84, the partial vacuum within cylinder bore 76
opens intake leaf valve 158 and draws refrigerant
through intake tube 42, then through the opening 98
and intake tube 96 and into suction muffler 86. From
suction muIfler 86, the refrigerant flows through
passage 90 into intake chamher 136 and downwardly
through opening 160, past leaf valve 158 into bore
76. On the piston compression stroke, leaf valve 158
- closes and discharge valve 166 opens thereby permitting
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the refrigerant to flow through opening 176, into
discharge chamber 134, back through passage 150,
through passage 94 and into discharge muffler 92.
From there, the refrigerant flows outwardly through
the opening in cover 100 through discharge shock loop
106 and discharge tube 44 to the condenser of the
refrigeration system. This same sequence occurs for
each revolution of crankshaft 60.
Lubricant pickup tube 238 is rotated by crank-
shaft 60 and pumps lubricant upwardly by centrifugal
action in a manner well known in the art. The
lubricant flows upwardly through passages 239 r 246
and 248, and then through tube 252 whereby it is
sprayed upwardly and drops by gravity through the
compressor so as to lubricate the sliding parts
thereof. It should be noted that the open configura-
tion of crankcase 48 illustrated in Figure 1 due to
the three point support permits very good lubrication
of the crankshaft bearings and of the piston.
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
seneral principles thereof and including such depar-
tures from the present disclosure~as come within
known or customary practice in the art to which this
invention pertains and fall within the limits of the
appended claims~ ~
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