Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates generally to pressure
responsive compressor valve assemblies and more particularly
to such assemblies employing disc type valve members and
c particularly adapted for use on reErigeration compressors.
The present invention is particularly well suited
for use in combiantion with the disc like lightweight valves
of the type disclosed in assignee's copending Canadian appli-
; cation Serial No. 341,333, filed December 6, 1979 and the
head and valve plate of assignee's U.S. Patent No. 4,385,872
! 10 and represents an alternative to the coil spring biasing
arrangements of assignee's U.S. Patent No. 4,329,125. It
may be used in both rotary and other types of compressors
including single and multi-c~vlinder reciprocating piston
type compressors of either hermetic or accessible hermetic
type.
Valve plates and cylinder head assemblies can
become relatively complex in configuration for certain valve
arrangements and as a result may be quite costly to manu~acture
and sometimes to assemble.
The present invention resides in a valve having
means defining a fluid passage for increasing cross-sectional
- area in the direction of fluid flow, the sidewalls of the
passage defining a valve seat and there being a v~lve member
having a peripheral edge adapted to sealingly engage the
valve seat when the valve is closed.
According to the present invention, there is
provided a valve assembly for use in compressors and including
a valve plate adapted for controlling fluid from a compression
chamber of the compressor and having a discharge opening
therethrough. The opening may be circular and provided with
milh /\ ~
` -
sidewalls defining a valve seat with an increasing diameter
in a direction away from the compressor chamber. The valve
member is engageable with the valve seat to close the discharge
opening, a specific form of this member being disc-shaped
and formed of a compliant material such as polymeric material.
A leaf spring, which may be a bowed leaf spring formed of
metal, is positioned in alignment with the valve member with
the convex center portion thereof acting against the valve
member and biasing into a closed position. A bridge member
overlies the discharge opening and is fixed in position with
respect to the valve plate, the bridge member having means
defining guide surfaces extending into the opening and surrounding
the peripheral edge of the valve member and the leaf spring
so as to maintain the leaf spring and the valve member generally
in alignment with one another and the discharge opening.
The guide surface is normally radially spaced from the peripheral
edge of the leaf spring when the valve member is in a closed
position, and the means defining the guide surfaces being
spaced from the sidewalls of the opening so as to define
a discharge passage therebetween.
In one embodiment of the invention, the bridge
member, which is mounted in a fixed position with respect
to the valve plate, includes a stop surface formed of a relatively
hard material engaging the outer periphery of the bowed leaf
spring to urge the valve member into the closed position,
the guide member having guide surfaces normally radially
spaced from the peripheral edge of the leaf spring a sufficient
distance so as to accommodate radial movement of the leaf
spring and the means defining the guide surfaces being spaced
~ ~ - 2 -
- ~Z1475B
from the sidewalls of the opening whereby a discharge gas
flow path is provided therebetween.
Additional advantages and features of the present
invention will become apparent from the subsequent description
and the appended claims taken in conjunction with the accompanying
drawings.
Brief Description of the Drawinqs
Figure 1 is a fragmentary section view of a
portion of a refrigeration compressor showing a valve plate
assembly in accordance with the present invention;
Figure 2 is a fragmentary plan view of the valve
plate assembly of Figure l;
Figures 3 and 4 are section views of the valve
plate assembly of Figure 1, the sections being taken along
lines 3-3 and 4-4 respectively thereof;
Figure 5 is a perspective view of a leaf spring
member designed for use in the valve plate assembly of the
present invention;
Figure 6 is a graph plotting the relationship
between biasing force and lift for both the leaf spring forming
a part of the present invention and a conventional coil spring;
and
2a -
, ! )
75~3
Figu~e 7 is a p~rspective view of the discharge valve shown in
Figure 1.
Description of the Preferred ~mbodiment
~ eferring ncw to the drawings and in particular tD Figure 1
thereof, there is shcwn a valve plate as~embly 10 in accordance wi~h
the present invention and cc~prising a valve plate 12 having a ring
valve seat n~mber 14 positioned within a generally conically shaped
opening provided therein so as to define ~ubstantially concentric
suction and discharge gas pRssages 16 and 18 respectively therethrough.
lQ A second plate nEmber 30 is positicned on the upper surface o~ valve
plate 1~ ~ith a suitable seal mg gasket 22 dispDsed therebetween ~o
as 1~D isolate suctian and discharge gas passages 16 and 18. An cq?en-
ing 24 iq provided extending thrcugh plate 20 which is adapted to
allow discharge gas to pass upwardly tas shown) therethrough. The
Yalve plate assembly as described thus far is substantially identical
tD the vzlve pla~e assembly described in detail in as~ignee's-
U.S. Patent No. dl,385,872.
A lightweight compliant polymeric discharge valve member 26is also provided seated against conical surfac~ 28 which defines a
valve seat wit n discharge passage 18. Discharge valve 26 is pre-
ferably of the gener~l type described in detail in assignee's
Canadian Patent 1,179,575, issued December 18, 1984.
A bridge nEmber 30 is prcvided having a generally ~ylindri-
cally ~haped central portion 32 positioned approximately coaxially
with cFening 24 and a pQir of dia~.etrically outwardly eKtending arms
34 ana 36 are secured to the upper surface 38 of plate ~e~ber 20
by means of bolts 40 and 42 extending through openings provided in
axms 34 and 36 and into thread~d engayement with suitably position~1
......
, . ~
7S~ ~
.
.
openings provided in plate member 20. Central portion 32 of bridge
m~ber is of a diameter substantially less than the diameter of op~ning 24
provided in plate n~mber 20 so as to leave a su`bstantially unrestricted
area for passage of discharge gas and also includes a plurality o~
substantially identical circ~nferentially spaced depending guide
fingers 44 projecting through op~mng 24 and into discharge passage lB
in valve plate 12. m e lcwer surface 46 of each of guide fingers 44
is beveled or inclined so as to enaole it to be positioned in very
close, slightly spaced relationship to valve seat surEace 28 of ring
me~ker 14. The inwardly facing surface 48 of each of guide ~ingers
44 has a conrave shape defining segments of a cylinder having a
diam.eter slightly greater than that of valve ne~ber 26 so as to provide
a clearance there~etween. .
A wear plate nemker 50 is also provided positioned in ~ngaging
relationship with under surface 52 of bridge me~ber 30. Wear plate
nY~er 50 has a generally circular shap with a diameter approx~mately
equal to the diameter of the central portion of bridga mem~er and ~-
includes a plurality of flat edge surfaces 54 positioned adjacent each
of the guide fingers 44 and ccoperating therewith so as to prevent
relative rotation of the wear plate.
In order to bias valve member into ~ closed position as ~h~n
a pair of substantially identical leaf springs 56 of the cNrved disc -
type ~-e provided being positioned between upper surEace 58 of valve
nemker 26 and lower s~rface 59 of wear plate 50. As best seen with
reference to Fig~re 5, leaf springs 56 are each in the for~ of rela-
tively thin metal discs having diametrically opposite edges 60 and 62
b~wed upwardly as shcwn therein so as to define a generally arcuate ~.
shape in transverse cross section. As clearly sha~n in Figure 4,
leaf springs 56 do not have any opEnings providea therein and are
-- 4 -- .
.
~, ~ 7~
positioned with ~oncave 6urfa oe 64 ~acing lower surface 59 of waar
plate 50, the convex ~urface 66 forming a piv~tal engagement with
surface 58 of valve nember 26 which is also preferably flat or planar
cver the en_ire extent thereof (Figures 1 and 4, or Figure 7). mi~
orientation ~revents excessive wear on the valve m~mber as well a~
possible wear of the guide fingers during compression of the ~e~f
~pring which coLld result from mGN~ment of edgPs 60 and 6? during
sompression of leaf springs 56. Also, leaf springs 56 will prefer-
ably have a nu~u3mlm diameter ~hen m a flattened fully compressad
condition slightly less than the diameter of wear plate 50 and the
~nner surfaoe s 48 of guide f~ngers 44 will operate to F~event le~E
spring 56 from slipping oNe~ the edge thereof. It is also imço~tant
that the ~Euu~m diameter of leaf spring 56 be selected to prcvide
a slight minimal d earance with g,l de fingers 44 when F~x~rly
centered so as to av~id the possibility of le f springs 56 becoming
locked in a fully comp~essed condition. It should also be noted ~hat
the use of such a continuous planar or flat upper surEa oe 58 on di~- _
charge valve 26 eliminates any Fotential points of stress concentration
~hich could possibly oontribute to val~e failure.
In operation, as the suction gas is campressed by cperation
of the compressor the mcreasing pressure acting on the lower surface
of valve mYnber 26 will cause it to m~ve upwardly (as shown~ ther~ky
o$ening ~he compression chan~er to the discharge passage 18 and comr
pressing leaf spring 56. The inn~r surfaoes 48 of guide fingers 44
~ill oooperate with the cylindrical sidewall 68 of valve nember 26
to restrict or i ~ibit lateral mcvement thereof thereby maintaining
prcper alignment of v21ve mem~er 25. Cbmpressive mDvement of le~f
spring 56 into substantially full surfa oe contact wit'h sur~aoe 59 of '~
wear plate 50 will operate to provide a positive sbop thcr~by limiting
- 5 -
7S~3
the maximum opening of valve member 26. However, because
as shown in Figure 6 the spring rate increases with increasing
lift, the velocity at which the valve member moves into
this maximum open position may be less than with a comparable
fixed rate coil spring. Further, because of the variable
spring rate offered by such leaf springs, it is possible
to reduce the preloading on the valve member as shown on
the graph of Figure 6 below that generally required for
a comparable coil spring valve assembly. This may be particu-
larly desirable for polymeric valve members of the type
disclosed in above-identified Canadian Patent No. 1,179,575.
It should also be noted that it is possible to adjust both
preloading and overall spring rate without altering the
geometry or dimensions of the various components by merely
inserting additional leaf springs 56. Additionally, when
multiple leaf springs are employed such as is shown, there
will be a slight relative movement between the engaged
surfaces thereof during compression and relaxation. The
frictional forces resulting from this movement will provide
a damping action which is particularly desirable at high
frequency operation to inhibit vibration of valve member
26. Also, the use of multiple leaf springs provides redundant
biasing means thereby improving operating reliability.
It also appears that the use of leaf springs offers the
advantage of quieter operation as compared with the use
of coil springs.
While it will be apparent that the preferred
embodiment of -the invention disclosed is well calculated
to provide the advantages and features above stated, it
will be appreciated that the invention is susceptible to
modification, variation and change without departing from
the proper scope or fair meaning of the subjoined claims.
mab/ `~!~
