Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to fluid displacement apparatus
and more particularly to apparatus for handling fluids to com-
press, expand or pump them.
The need for gas compressors and expanders and for
fluid pumps is well known and there are many different types of
such apparatus~ In these apparatus a working fluid is drawn into ~ ;
an inlet port and discharged through an outlet port at a higher
pressure; and when the fluid is a gas its volume may be reduced
before delivery through the outlet port, in which case the appara-
tus serves as a compressor. If the working fluid is a pressurizedgas when it is introduced and its volume is increased, then the
apparatus is an expansion engine capable of delivering mechanical `
energy and also if desired of developing refrigeration. Finally,
a fluid may be introduced and withdrawn at different pressures
but without any appreciable change in volume, in which case the ~;`
apparatus serves as a fluid pump.
In the following description of the fluid displacement
apparatus of this invention it will be convenient to refer to it,
and to the prior art, as a compressor. However, it is to be
understood that the apparatus of this invention may also be used
as an expansion engine and as a pump and its use as such will be
described for the various apparatus embodiments.
It is not necessary to discuss the prior art in detail
as it pertains to such dynamic apparatus as centrifugal compressors
and pumps, or as it pertains to the more commonly used positi~e~
displacement devices of the vane, gear or other rotary types. How-
ever it is of interest to note some of the features which charac- -
terize these general types of prior art apparatus as a ~asis for
comparison with the fluid displacement apparatus of this invention. ~
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Those pumps, compressors and blowers which may be
termed "dynamic" apparatus must operate at high speeds to achieve
large pressure ratios and they typically have efficiencies of
less than 90~ in terms of mechanical energy converted to flow
and compressional energy. Apparatus of the dynamic type find
their widest application in large sizes in such applications -~
as gas turbine compressors, stationary power plant steam expanders,
and the like.
The positive displacement pumps or compressors of the ~`
vane type have rubbing speeds proportional to the radius of the
vanes and the vanes rub at varying angles. Furthermore, the vanes
operate within a housing of fixed axial length so that any wear
upon their flat surface ends will always act to increase the clear~
ance, and hence, the blow-by or leakage of the apparatus. The
positive-displacement pumps and compressors of the rotary type
are typically constructed to have the rotating components movable -~
between end plates, an arrangement which demands close tolerances ~ -~
to reduce blow-by while permitting free rotation. Wear between
the rotating components and end plates increases blow-by, a fact
which requires the adjustment of the spacings of the end plates
through the use of screws and very precisely constructed gaskets -~
in the form of shims. The gaskets, in turn, may not be able to
withstand corrosive fluids or fluids at extreme temperatures, e.g.,
cryogenic liquids or hot gases. Furthermore, these gaskets require
precisely located edges to prevent injury by the moving vanes, a
fact which adds to the delicacy of assembling the apparatus.
In most industrial applications, particularly those of `~
large scale, the fluid pumps and compressors now being used are
adequate for the uses for which they are employed. However, there
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remains a need for a simple, highly efficient a~paratus, essen-
tially unaffected by wear which can handle a wide r~nge of fluids
and operate over ~ wide range of conditions to serve as a pump,
compressor or expansion engine. The apparatus of this invention
which meets these requirements is based on the use of scroll mem-
bers, having wraps which make moving contacts to define moving
isolated volumes, called "pockets", which carry the fluid to be
handled. The contacts which define these pockets formed between
scroll members are of two types: line contacts between spiral cylin-
drical surfaces, and area contacts between plane surfaces. Thevolume of a sealed pocket changes as it moves. At any one instant
of time, there will be at least one sealed pocket. When there are
several sealed pockets at one instant of time, they will have dif- ~;
ferent volumes, and in the case of a compressor, they will also
have different pressures.
There is known in the art a class of devices generally
referred to as "scroll" pumps, compressors and engines wherein `
two interfitting spiroidal or involute spiral elements of like `~
pitch are mounted on separate end plates. These spirals are
angularly and radially offset to contact one another along at
least one pair of line contacts such as between spiral cyclinders.
The pair of line contacts will lie approximately upon one radius
drawn outwardly from the central region of the scrolls. The
fluid volume so formed therefore extends all the way around the
central region of the scrolls. In certain special cases the
pocket or fluid volume will not extend the full 360 but because
of special porting arrangements will subtend a smaller angle about
the central region of the scrolls~ The pockets define fluid
volumes which vary with relative orbiting of the spiral centers
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while maintaining the same relative spiral angular orientation.
As the contact lines shift alon~ the scroll surfaces, the pockets
thus formed experience a change in volume. The resulting zones of
lowest and highest pressures are connected to fluid ports.
An early patent to Creux (U.S. Patent 801,182~ descr;bes
this general type of device. Among subsequent patents which have
disclosed scroll compressors, and pumps are U.S. Patents 1,376,291,
2,809,779, 2,841,089, 3,560,119, and 3,600,114 and British
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Patent 486rl92. -
Although the concept of a scroll-type apparatus has
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been known for some time and has been recognized as having some
distinct advantages, the scroll-type apparatus of the prior art ~ ~'
has not been commercially successful, primarily because of seal~
ing, wearing and to some extent porting problems which in turn `~
have placed severe limitations on the efficiencies, operating
life, and pressure ratios attainable. Thus in some of the prior
art devices the apparatus components have had to ~e mac~ined to
accurate shapes and to be fitted with very small tolerances to !;
maintain axial sealing gaps sufficiently low to achieve any use-
ful pressure ratios. This is difficult to do and resembles the
problem of constructing apparatus with a reciprocating piston
~ithout the use of sealing rings. In other prior art devices,
radial sealing has been achieved through the use of more than one ~ ~ ~
form of radial constraint, each being imposed by separate appa- ~!ij'' .''~.. :
ratus components requiring precise interbalancing to attain ef-
ficient radial sealing. If during extended operation of such ~ `
devices this interbalancing is disarranged by one component ex
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periencing more ~ear, or by an~ other mechanism, the problem of
wea~ of other components may grow progressively ~orse unt~
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satisfactory radial sealing is no longer possible.
In place of ports, delivery of the compressed fluid
in a number of the prior art scroll apparatus has been made through
the scroll passages, and compression ratios have previously been
limited to approximately the ratio of the radius to the outermost
pocket to the radius to the innermost pocket at the moment fluid
delivery begins, i.e., the moment the inner pocket opens. There-
fore, in the design of prior art scroll-type apparatus another
important approach to the obtaining of compression ratios greater
lG than about two has been to construct the scrolls and their end
plates to resemble very large flat pancakes. In contrast, the
scroll apparatus of this invention possesses features making it
possible to reduce the outside diameter of the scroll members
while attaining desired compression ratios. Among such features
are wraps which are configured at their inner ends to delay de-
livery of fluid into a receiver, wraps having a transition be-
tween a double scroll to a single scroll pattern, and special
types of porting.
The resulting solutions to the sealing, wearing and
porting problems through these and other approaches have not been
satisfactory. Thus in the prior art devices, the inherent advan
tages of scroll-type apparatus ~similicity, high efficiency, ~ -
flexibility, reversibility, and the like~ have not ~een attained
and have, in fact, been usually outweighed by sealing, ~earing
and porting problems. It would therefore be desirable to be
able to construct scroll-type fluid displacement devices which
could realize the inherent advantages of this type of apparatus
and which could be essentially free of sealing, wearing and
porting problems heretofore encountered.
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It is therefore a primary object of this invention to
provide improved practical and useful fluid-displacement apparatus
which may serve as compressors, expanders or pumps. It is another
object of this invention to provide apparatus of the character
described ~hich are of the so-c~lled scroll type and which achieve
ef~icient a~ial and radial sealing over extended operating periods.
It is a further object to provide a fluid displacement apparatus
which is simple and relatively inexpensive to construct, which
has relatively few moving parts and a limited number of rub~ing
surfaces, and which experiences less friction and wear than other
types of apparatus designed for the same purpose. Still another
object is to provide such apparatus wherein ~ear is essentially
self compensating.
Another primary object of this invention is to provide
fluid displacement apparatus which, as a compressor or an expan-
sion engine, is capable of handling a wide variety o~ fluids over
a large temperature range. Yet another object of this invention ;
is to provide a small, versatile, compact and quiet compressor
to achieve compression ratios up to about ten to supply compressed ; - ;
air for such uses as dentist's drills, garage requirements, auto~
mobile air conditioner etc. Still another object is to provide an `~
efficient, simple, liquid pump usa~le in hydraulic systemsj and
the like. Other objects of the invention will in part be obvious
and ~ill in part be apparent hereinafter. -
The scroll apparatus of this invention incorporates a
unique driving means which permits reducing the radial constraints
within the apparatus to only those imposed by the moving line
contacts bet~een the surfaces of the wraps forming the fluid
pockets. The unique driving means is characterized in part by
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including means to courteract a fraction of the centrifugal ~orce
on the moving scroll member with an inwardly directed radial
(centripetal~ force. There is thus provided a contacting, i.e.,
radial sealing, force which minimizes wear and which is indepen-
dent of the functioning of such other apparatus components as the
means to maintain the desired angular relationship between the
scroll members and the axial sealing means. Axial sealing is
preferably attained through pressurized fluid withdrawn from the
zone of highest pressure and a spring ~iased to exert a force on
one of the scroll members to urge it against the other scroll
member.
An exemplary embodiment of the apparatus of this inven-
tion incorporates a unique scroll driver as the driving means.
The scroll driver is fixed through bearings to the main drive
shaft while the moving scroll member is free to float axially to
respond to fluid pressure acting upon its outer surface to atta;n ~ -
axial sealing. The scroll driver effects the orbiting of the
movable scroll member by making a rolling line contact between
its cylindrical surface and a drive surface associated with the
movable scroll. By maintaining the orbit radius of the scroll
driver less than the orbit radius of the movable scroll, the
required opposing centripital force is provided in the driving -
means.
Valved porting where required is provided in the fluid ~ ;
displacement apparatus of this invention to better control the flow
of fluid in and out. Valved porting generally need not be re-
quired for liquid pumps or for gas compressors and expanders
wherein the pressure ratios are small or when a "pancake" geo-
metry is acceptable. A wide range of scroll designs may be used
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to achieve a variety of desired results such as different com-
pression ratios, control of fluid volume at the time of dis-
charge, overall size of the apparatus and the like. The appara
tus of this invention is readily reversible from a compressor
to an expansion engine and it is capable of handling a wide
variety of fluids over a wide temperature range. Many of the
embodiments illustrated may also be used as pumps for liquids. ~;;
Broadly, the invention relates to a positive fluid
displacement apparatus, comprising in combination
(a) two scroll members having wrap means which,
when one of said scroll members is orbited with respect to
the other, ma~ce moving line contacts to seal off and define at
least one moving fluid pocket of variable volume and zones of
different fluid pressure; ~`
(b) scroll orbiting means associated with said
one of said scroll members, adapted to effect orbital motion
of said one of said scroll members, said scroll orbiting
means comprising means defining a cylindrical drive surface ~
associated with said one of said scroll member and having an ~-
orbit radius Ror, and scroll driver means defining a cylindrical ;
driving surface and adapted to orbit said one of said scroll
member through line contact with said cylindrical drive surface
associated with said one of scroll members and having an orbit
radius Rod less than Ror, whereby when said scroll driver means
is orbited to develop a drive force acting upon said one of
said scroll members a centripetal radial force is provided to
oppose a fraction of the centrifugal force acting on said one ;~
of said scroll members and the difference between said centri-
petal radial force and said centrifugal force appears as the -
only contact force between said scroll members;
~ c) coupling means adapted to prevent relative
angular motion of said scroll members;
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(d) axial sealing mean~ including means to define
a sealing volume in pressure applying relationship with said
one of said scroll members and means to conduct fluid from the
zone of highest pressure into saicl sealing volume, whereby
said one of said scroll members is forced into axial sealing
relationship against the other of said scroll members; and .
(e) porting means associated with the zones of ..
lowest and highest pressures.
The invention accordingly comprises the features ~ .
10 of construction, combinations of elements, and arrangement of ~-
parts which will be exemplified in the constructions herein- -
after set forth, and the scope of the invention will be indica- .
ted in the claims.
For a fuller understanding of the nature and
objects of the invention, reference should be had to the follow-
ing detailed description taken.in connection with the accompany-
ing drawings in which ~
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Figs. 1-4 are diagrams of exemplary spiral wraps, one
moving in a circular orbit with respect to the other, illustrat-
ing the manner in which a device incorporating such spiral
members can achieve compression of a gas,
Fig 5 is a combination of a top plan view and two
side elevational views of spiral member illustrating the princi~
pal forces to which the scroll is subjected; ~ -
Figs. 6A and 6B are diagrams showing forces in the
radial-tangential plane which act upon a spiral member and
illustrating the mechanism by which radial sealing forces are
developed,
Fig. 7 is a cross section through the scroll driver ~ `
and the moving and stationary scroll members illust~ating the `
manner in which axial sealing is attained;
Fig. 8 is a side elevation view, partly in cross
section, of one embodiment of a compressor constructed in ``
accordance with this invention;
Fig. 9 is a cross section of the compressor of Fig. 8 -
through the plane 9-9 of Fig. 8, Fig. 9 is on the same sheet as
Fig. 7
Figs. 10 and 11 are top planar and bottom planar
views of the fixed spiral member of the compressor of Fig. 8,
Fig. 12 is a top planar view of the moving spiral
member of the compressor of Fig. 8, -
Figs. 13, 14 and 15 are top planar, cross sectional
and end views of one embodiment of a coupling member designed `-~
to prevent the relative angular motion of the scroll members
during the orbiting of the movable scroll member, `~
Figs. 16 and 17 are top planar and bottom planar views
of the frame of the compressor of Fig. 8,
Fig. 18 is a cross section of the main shaft and bear-
ng spacer taken through plane 18-18 of Fig. 8; ;`~
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Fig. 19 is a cross section of the main shaft and
balance weights taken through plane 19-19 of Fig. 8;
Fig. 20 is a partial side elevation view, partly in
cross section, of another embodiment of a compressor constructed `~
in accordance with this invention, ``
Fig. 21 is a cross sect:ion of the compressor of Fig.
20 through the plane 21-21 of Fig. 20;
Figs. 22 and 23 are top planar and cross sectional
views of another embodiment of a coupling member such as used
in the compressor of Figs. 20 and 21,
Fig. 24 is a cross section through the scroll members ~
of an embodiment of a compressor constructed in accordance with ~ `
; this invention in which each scroll member has two wraps;
Fig. 25 is a cross section through the scroll members
of an embodiment of a compressor constructed in accordance with ~ ;
this invention in which each scroll member has two outer wraps ~`
- which are transformed into single inner wraps;
; Fig. 26 is a cross section through the scroll members
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of an embodiment of a compressor constructed in accordance with
this invention in which the innermost ends of the wraps are
configured to use a cross-shaped coupling; ~` `-
Fig. 27 is a perspective view of a cross-shaped
coupling. -
Fig. 28 is a perspective view of a portion of the
innermost end of a wrap of Fig. 26 showing the channel which -~
engages one arm of the cross-shaped coupling; `A~
Fig. 29 is a cross section through the scroll members `~
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of an embodiment of a compressor constructed in accordance with
this invention in which the wraps are configured to provide a
modified porting arrangement;
Figs. 30 and 31 are perspective and cross section views ;-
of the coupling used in the ap ~ratus embodiment of Fig. 29, ~
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Fig. 32 is a cross section through the scroll members
of an embodiment of a compressor constructed in accordance with
this invention in which the wraps are circular arcs rather than
involute spirals, Fig. 32 is on the same sheet as Figs. 35, 36
and 37, ~
Fig. 33 is a cross section through the scroll members - --
of an embodiment of a compressor constructed in accordance with
this lnvention in which the wraps are configured so that the
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clearance volume at the start of delive~ of compressed gas is
under control of a central port to clttain intermittent porting;
Fig. 34 is a cross seCtiQrl across plane 34-34 of the
apparatus of Fig. 33;
Figs. 35-37 are cross sections through the wraps of
the scroll members of Fig. 33 illustrating the operation of the
apparatus;
Fig. 38 is a cross sectional view of a compressor con-
structed in accordance with this invention in which the scroll
members rotate on parallel axes;
Fig. 39 is a cross section through the driving
scroll of Fig. 38 taken through plane 39-39 of Fig. 38; and `
Fig. 40 is a side elevational view of a compressor con- ;
structed in accordance with this invention including housing, heat
transfer means, etc.
Before describing specific em~odiments of the apparatus
of this invention, the principles of its operation may be discussed
briefly in order to understand the way in which positive fluid
displacement is achieved. The scroll-type apparatus operates by
moving a sealed pocket of fluid taken from one region into another
region which may be at a different pressure. If the fluid is -
moved from a lower to higher pressure region, the apparatus
serves as a compressor; if from a higher to lower pressure region
it serves as an expander; and if the fluid volumes remain essen-
tially constant, then the apparatus serves as a pump.
The sealed pocket of fluid is bounded by two parallel
planes defined by end plates, and by two cylindrical surfaces
defined by the involute of a circle or other suitably curved con-
figuration. The scroll members are aligned on parallel axes. A
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sealed pocket moves along between these parallel planes as the ~
two lines of contact between the cylindrical surfaces move. The ~ ;
lines of contact move because one cylindrical element, e.g., a
scroll member, moves over the other~ This may be accomplished by
maintaining one scroll fixed and orbiting the other scroll or by
rotating both of the two scrolls on their parallel axes. In the ;~
detailed discussion which follows, it will be assumed for the sake
of convenience that the positive fluid displacement apparatus
is a compressor and that one scroll member is fixed while the ;
other scroll member orbits in a circular path. The embodiment in
which both of the scroll members rotate on parallel axes is show~ ~
in Fig. 38. - :
Figs. 1-4 may be considered to be end views of a com-
pressor wherein the end plates are removed and only the wraps of
the scroll members are shown. In the descriptions which follow,
the term "scroll member" will be used to designate the component
which is comprised of both the end plate and the elements which
define the contacting surfaces making movable line contacts. The
term "wrap" will be used to designate the elements making movable
line contacts. These wraps have a configuration, e.g., an involute
of a circle (involute spiral), arc of a circle, etc., and they have
both height and thickness. The thickness may vary over the length ~;
of the wrap.
In the diagrams of Figs. 1-4, a stationary scroll member
,
wrap 10 in the form of an involute spiral having axis 11 and a
movable scroll member wrap 12 in the form of another involute
spiral of the same pitch as spiral 10 and having axis 13 consti-
tute the components which define the moving sealed fluid pocket 14
which is crosshatched for ease of identification. The involute
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spirals 10 and 12 may be generated, for example, b~ wrapping a
string around a reference circle having radius Rg. The distance ~ ~
between corresponding points of adjacent wraps of each spiral is ~ ~ ;
equal to the circumference of the generating circle. This dis- -
tance between corresponding points of adjacent wraps of any scroll
member is also the pitch, P. As will be seen in Fig. 1, the two
scroll members can be made to touch at a num~er of points, for
example in Fig. 1, the points A, B, C and D. These points are
of course, the line contacts between the cylindrical surfaces pre-
viously described. It will be seen that line contacts C and D of
Fig. 1 define the cross-hatched pocket 14 being considered. These
line contacts lie approximately on a single radius which is drawn `
through point 11, thus forming pocket 14 which extends for approx-
imately a single turn about the central region of the scrolls.
Since the spiral wraps have height (normal to the plane of the
drawings3 the pocket becomes a fluid volume which is d~creased
from Fig. 1 to Fig. 4 as the movable scroll member is orbited
around a circle 15 of radius (P/23-t, where t is the thickness of
the wrap. Since wrap 12 does not rotate as it or~its, the path
traced out by the walls of wrap 12 may be, in addition, represented
as a circle 16. As illustrated in Figs. 1-4, wrap 10 has a shape
characterized by two congruent involute spirals 17 and 18 and wrap ;~
12 has a shape characterized by two congruent involute spirals 19 -
and 20. The thicknesses, t, of the spiral walls are shown to be
identical, although this is not necessary. As will be shown in
the description below of Figs. 21, 24-26, 29, 32 and 33, the wraps
may take a number of different configurations and may vary in the
number of turns used.
The end plate (not shown in Figs. 1-43 to which station~
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ary wrap 10 is fixed has a high-pressure fluid port 21 and as the
moving wrap 12 is orbited the fluid pocket 14 shifts counterclock-
wise and decreases in volume to increase the fluid pressure. In
Fig. 3, the fluid yolume is opened into port 21 to ~e~in the dis-
charge of high-pressure fluid and this discharge of the high-
pressure fluid is continued as shown in Fig. 4 until such time as
the moving wrap has completed it orbit about circle 15 and is
ready to seal off a new volume for compression and delivery as
shown in Fig. 1.
If high-pressure fluid is introduced into the fluid
port 21, the movable scroll 12 will be driven to orbit in a
clockwise direction under the force of the fluid pressure and will
delivery mechanical energy in the form of rotary motion as it
expands into flulid pockets of increasin~ volume. In such an ar-
rangement the devicë is an expansion engine.
Although this principle of the operation of scroll appa-
ratus has long been known as evidenced by the prior art, the ~ ;
attainment of practical scroll equipment in a form ~hich would
permit the use of such apparatus on a commercial scale has so far
not been realized. The failure of prior art scroll equipment to ~ -~
attain its potential has, at least in part, been due to pro~lems
of sealing and wearing. More particularly, the scroll devices
of the prior art, as far as is known, have not provided an effi-
cient combination of continuous axial and radial sealing, and ;
they have in many cases sought to impose radial constraints on
the scroll members by mechanisms other than the line contacts of
the wraps themselves while usin~ such mechanisms also to control
angular phase relationships bet~een the scroll members. Failing
to provide efficient continued axial and radial sealing can
materially decrease the efficiency of the apparatus to the point
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~379~
where it is no longer economical to operate. Imposing radial
constraints through means other than through the line contacts of
the wraps of the scroll members eventuall~ leads to the wearing of
the contacting surfaces and then to leakage. Generally such wear
will vary from surface to surface and will not ~e self-compensating,
a fact which only serves to aggre~ate the problem of wear with con-
tinued operation. Combining mechanisms to achieve a desired angu-
lar phase relationship between the scroll members with such means ~ ;~
to impose radial constraints can add to the problem of wear so that -
extended operatlon becomes impractical.
In the apparatus of this invention the disadvantages
associated with scroll apparatus of the prior art are eliminated
or minimized by limiting the radial displacement constraints to
only those imposed by the line contacts of the wraps themselves,
by providing a drive force on the movable scroll which has an
inwardly directed radial component which opposes at least a
fraction of the centrifugal force acting on the movable scroll,
and by providing coupling means to control the angular phase
relationship of the two scroll mem~ers which function independently -
of any constraint imposing means. T~e operation of the scroll ap-
paratus remains independent of any pressure events within the
scroll; wear of the line contacts between the wraps of the scroll
members is essentially self-compensating and ~ence efficient con-
tinued radial sealing is attained over extended periods of opera- ~
tion. Axial sealing is preferably accomplished by using gas from ~ -
the highest pressure zone of the apparatus ln combination with a
suitably biased spring to continuously force the scroll members
to make axial contact.
To understand the problem of sealing a scroll-type appa-
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ratus and to describe the mechanism hy which axial and radi~l
sealing is achie~ed in the apparatus of this invention, it is
helpful to examine the principal axial and radial forces acting
upon a scroll mem~er. Referrlng to Fig. 5, it can be shown that
in the axial direction, the total external axial force Fa on a
scroll pair is the sum of an involute contact sealing force and ~ ~
an internal gas load. Therefore, if an external force is provided ~ `
which is always greater than the internal axial gas force, axial
sealing is accomplished. In the apparatus of this invention,
:
this desired condition is achieved by withdrawing fluid from the
`highest pressure zone and using it to generate an axial sealing
force substantially proportional to the highest pressure ~ithin
the fluid pockets. Referring to Fig. 5, there must then be a ;~
surplus axial force acting upon the scroll which is directed
along the arrow Fa. This surplus force performs sealing of the
edges of one scroll member against the other, and is opposed by
a gas force directed against the force Fa shown in Fig. 5.
Fig. 7 illustrates one exemplary embodiment of an ap-
paratus which attains continued axial sealing through the use of
gas withdrawn from the highest pressure zone of the apparatus
supplemented by the use of a spring ~iased to force the scroll ~
.:
members toward axial sealing contact. In the embodlment of Fig.
7, which is a cross section through the scroll members and scroll
driver, there is illustrated the use of a scroll driver along ~;
with a "floating" movable scroll member to achieve continuous
self-adjusting axial sealing. The wrap lO forming the line-
contacting surfaces of the stationary scroll member, generally
indicated at 25, is integral with or affixed to a stationary ;~
scroll end plate 26 terminating around Its peripheral edge in an
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annular housing 27 which has an annular sealing surface 28. The ~-
wrap 12 forming the line-contactin~ surfaces o~ the mova~le
scroll member, generally indicated at 30, is integral with or `-~
affixed to a movable scroll end plate 31, the peripheral sealing
surface 32 of which is adapted to contact annular sealing surface
28 of stationary scroll member 25 to achieve axial sealing of the
internal volume 33 defined between end plates 26 and 31. It will `
be appreciated that rubbing contact must be completely and co~
tinually achieved between sealing surfaces 28 and 32 even as
these surfaces experience wear during operation. Furthermore,
and more importantly, the axial sealing force is used to force
the end plates to make sealing contact with the end surfaces of
the wraps of the opposing scroll member such as at 41 and 42 to
seal the pockets at these areas of contact. This desired axial
sealing is attained through the use of a scroll driver, generally
indicated at 35, in conjunction with movable scroll member 30
which is allowed to "float" under the influence of forces upon
it. That is, movable scroll member 30 moves under the influence
of the forces upon it until there is sufficient contact to seal
the pockets. -
Movable scroll member 30 includes, in the embodiment of
Fig. 7, a scroll driver annular housing ring 36 defining a cylin~
drical volume 37 in which scroll driver 35 is located. Internally,
annular ring 36 had a wall 38 normal to the plane of end plate 31,
an annular shoulder 39, and a pressure sealing surface 40 which is,
in effect, the central external surface of the movable scroll mem-
ber 30. The scroll driver 35 is generally configured as a piston,
and in this embodiment, comprises a ring 45 having an internal an-
nular shoulder 46 for seating a bearing 47 and a central closure
--1~-- ,. .
. . .
37~
plate 48, the external wall 49 of which faces thè drivin~ surface
40. The ring 45 of the scroll driver has a diameter, Dd, slightly
less than the diameter, Ds, of internal wall 38,,thereby definin~
with it a clearance 50. The difference in diameters may be expressed
as (Ds-Dd~/Ds and it may range from about 0.001 to about 0.2,
Ring 45 is contoured to define a peripheral groove 51 suitable for ~-
positioning an elastomeric sealing ring 52 between the scroll '~
driver and internal wall 38 of scroll driver housing ring 36. A
preloading spring 53 is designed to exert an axial force on the
movable scroll member at those times when the delivery pressure
and hence the gas loading force is zero. Preloading'spring 53 is
positioned to cbntact annular shoulder 39 and t~e periphery of ;'
scroll driver end plate 48 thereby defining a shallow axial seal-
ing fluid volume 54 between the scroll driver end plate 48 and
driving surface 40 of the movable scroll member. Some means, such ~
as hole 44 in spring 53, must be provided so that the spring does ` ~ ;
not adventitiously seal off volume 37 from 54,,for these volumes
must be in fluid communication at all times. A fluid port 55 pro~
vides fluid communication between the zone of highest fluid pres- ~;
sure in volume 33 and sealing yolume 54. Scroll driver 35 is ' ~;
fixed to driver shaft 56 through bearing 47 and the mechanism by
which it drives the movable scroll member 30 will be described
beIow. ''~
Inasmuch as the movable scroll member 30 is not rigidly ,~
connected to the scroll driver it will be seen that it is ~ree ~'
to move axially, i.e., to float. By bleeding high pressure fluid ``
through port 55 into sealing ~olume 54,,a force Fa which is essen- -~
tially equal to the internal gas force is provided as the axial '
sealing force so long as the area of t~e force applying surface ~ `
-20- ,
,~.
:, ~ '- . :
of the scroll driver is sufficiently large. In effect, the fluid
pressure within sealing volume 54 fc)rces the movable scroll member
away from the scroll driver and against the fixed scroll member
to achieve sealing between surfaces 28 and 32, as well as to
effect sealing contact between the wrap edges and scroll member
end plates. As these sealing surfaces wear, sealing contact is -
maintained because of the ability of the movable scroll member
to float under the force of the pressure of the fluid in sealing
volume 54. In practice, it is desirable to bias the total end
force Fa by means of spring 53 so that Fa does not go to zero even
should the differential pressure in the system go to zero. Thus
spring 53 provides an axial sealing force at start up and some
additional axial sealing force during operation.
Whereas axial sealing is required to seal the end sur-
fa~es of the wrap edges to the end plate of the opposing scroll
member, radial sealing is required to maintain a seal along the
line contacts made by the cylindrical surfaces of the wraps of
the scroll members as the movable scroll member is orbited (See
for example points A, B, C and D of Figs. 1-4 which illustrate
the shifting positions of such line contacts~. The principal ` -~
forces which determine radial sealing of the scroll members are
sketched out in simplified manner in Fig. 5 which deals with
the forces on the moving scroll having a single wrap 12a affixed
to an end plate 31a. As the scroll member is orbited a~out a ;
path with radius Ror it experiences a tangential force Ft and a
normal contacting force which is, of course, the centrifugal ` `
force, m~ Ror, where m is the scroll member mass and ~ is its
angular velocity. This centrifugal force is in excess of that
which is required to attain efficient radial sealing, and the
', , .
-21-
'`' '
~L~37~
magnitude of such excess centrifugal ~orce determines the e~tent
of wear experienced by the contacting cylindrical surfaces of
the wraps. In the apparatus of this invention, the driving means
associated with the orbiting of the movable scroll member incor-
porates means to counteract, or oppose, a ~raction of the centri-
fugal force to provide a contacting force which is of a magnitude
sufficient to attain effective radial sealing and at the same
time is not conducive to excessive wear. Thus the driving
means of the apparatus of this invention includes means to pro-
vide a centripetal radial force Fr to oppose a fraction of thecentrifugal force acting upon the orbiting scroll member. This
is in direct contrast to prior art teaching which discloses the
use of an augmented centrifugal force to attain radial sealing
(See for example British Specification 486,192.)
In the practice of this invention the actual fraction of
centrifugal force which is counteracted by the centripetal radial
force applying means will depend upon several factors which may
be interrelated. The optimum balance between centrifugal force,
which is never reduced to zero, and centripetal force can be
detèrmined for any scroll apparatus by consideration of such
factors as the specific application for which the scroll appara- .
tus is used, the use or nonuse of lubricants, the material
from which the wraps are made, the speed of operation, the de-
sired life of the apparatus, and the like. For example, a com-
pressor running dry will generally require that a greater fraction :
of the centrifugal force ~e opposed than one operating with a suit-
able lubricant; and a compressor having wraps formed of materials
conducive to wear will require that a larger fraction of the
centrifugal force be opposed than one having wraps formed of
-22-
:
, ~,. : . . - :
~379'~ ~
materials which are not as subject to ~ear. In general, higher
operational speeds and lonyer operational lives dictate that a
greater fraction of the centri~ugal force be opposed by a centri-
petal force.
In conjunction with the providing of means to oppose
a fraction of the centrifugal force on the orbiting scroll member,
the apparatus of this invention is characterized by additional
features which make ît possible so to regulate the contacting force
as to continuously maintain the radial sealing force between the
scroll members at a level consistent with minimum wear and mini-
mum fluid leakage. One of these features is the limiting of the
radial constraints within the scroll apparatus to the moving line
contacts between the wraps. Thus these radial constraints, con-
trolled solely through the centripetal force providing means, -
not only minimi2e wear but impart a flexibility to the operation ;
of the apparatus such that a great part of any wear that does ;
occur is self-compensating. The limiting of the radial constraints
to only the moving line contacts between the wraps is contrary to
teaching in the prior art as exemplif~-ed~by U.S. Patent 3,600,114.
Another important feature of the apparatus of this in-
vention is the use of a coupling means, adapted to maintain a `~ ;
fixed angular relationship between the scroll members, which is
separate and distinct from the driving means. By using such a
coupling means in combination with the unique driving means of
this invention, and by limiting the radial contraints to the
moving line contacts between the cylindrical surfaces of the
wraps, the apparatus of this invention overcomes, at least to a
very large extent, the radial sealiny and wear problems of the - ~ 9.
prior art apparatus. ~ ~
:: :
-23-
,....... . . . ~ , , , :
1~;379;~S
In the embodiments of the ~pparatus of this inYention
illustrated in Figs. 7-40 the unique driving means, provid~ng a
centripetal force to oppose a fraction of the centrifugal force
to give the desired contact force and radial sealing, is exempli-
fied by a combination of means to define a cylindrical drive
surface associated with the movable scroll member and a scroll
driver which defines a cylindrical driving surface adapted to
orbit the movable scroll member through line contact with the
drive surface. By choosing the orbit radius, Ror, of the movable
scroll member to be greater than the orbit radius~ Rod, of the
scroll driver, the desired ce~tripetal, inwardly directed radial
force opposing a fraction of the centrifugal force is attained.
In the embodiment of this invention using a movable
scroll member which provides a cylindrical drive surface in com-
bination with a scroll driver which defines a cylindrical driving `
surface to provide the desired contacting force, an important ;
feature is that the diameter, Dd, of the scroll drive must be ~`
different from the diameter, Ds, of the cylindrical drive surface.
In Fig. 6A, which is, in essence, a cross section taken through
plane 6A-6A of Fig. 7, the diameter, Ds of the internal wall 38
which serYes as the cylindrical drive surface is larger than the
external diameter, Dd, of the ring 45 of scroll driver 35 which
serves as the cylindrical driving surface. The difference between
Ds and Dd is greatly exaggerated in Fig. 6A beLter to illustrate
the forces involved. Due to the difference in these diameters, -
the scroll driver, represented in Fig. 6A by the ring 45, makes
an essentially rolling line contact at L with the movable scroll
member, represented in Fig. 6A by internal wall 38. ~ ~-
The movlng scroll is contained in the radial-tangential
'
-24- ~ ~
'~
7~'~5
plane by forces ~pplied to the internal ~all 38 as sho~n in Fig. ;
6A. (For continuity of presentation, the center, C, of the mov- `
able scroll driving ring is assumed to contain the origin of the
involute of the scroll member as well as the center of gravity of
the movahle scroll member.~ T~ese forces applied to the movable
scroll member through wall 38 are seen to be the centrifugal force,
m~ Ror, and the tangential force Ft. By making the orbit radius,
.: : .
Rod, of the scroll driver less than the orbit radius, ROr, of the
.~
movable scroll member there is developed a centripetal force which
is an inwardly directed radial force Fr. The magnitude of Fr is a
function of the contact angle which in turn is a function of the
difference in orbit radii Ror and Rod as well as of the difference
in diameters Ds and Dd. Thus this contact angle e between the
scroll driver and the movable scroll member can be expressed in
terms of diameters and orbit radii as
sin e = 2(ROr ~ Rod)/~ s d Ua~
For a given operational speed and fluid pressure, e is designed
into the apparatus to provide an adequate, ~ut not excessive, radi~
al sealing force which is always less than the centrifugal force
m~2ROr on the orbiting scroll as discussed previously. j -~
`; . - . .
It is also within the scope of this invention to con- ;; -~ --
struct the movable scroll member, as illustrated somewhat dia-
grammatically in ~'ig. 6B, to have a cylindrical drive surface 38a,
such as a shaft in place of the internal wall 38 of the annular
ring housing and to use a scroll driver which defines an internal
driving wall 45a, having a diameter greater than the drive sur-
face 38a, in place of the external wall of the scroll driver
piston. Thus, in this embodiment Dd is greater than Ds. However,
,.' ', ~
-25- ~
: : : . : .- - ::: . . . : : : . : ; .
. - - , . . - : . .
:.. . . , . : . .
~V;3~ ae~r
Ror remains greater than Rod and the various ~orces which make up
the contacting or radial sealing forces are comparable to the
reverse situation as a comparison oE Fig. 6A and Fig. 6B makes
evident. In the arrangement of Fig. 6B the contact angle e is
defined as
sin e = 2(Ror Rod)~Dd s (lbl
The geometry which regulates the radial sealing force `
also tends to reduce the effects of manufacturing errors and the ~-
wasting away of material through wear. If the full centrifugal
force were exerted on the radial sealing lines, excessive scroll
wear would result. For example in manufacturing the scroll driver,
the orbit center might not precisely coincide with the scroll ~ i
orbit center; in such case e would have a component oscillating
at the fundamental frequency ~. By making the actual values of
the numerator and denominator of equation (la~ or (lb~ some 10 -
times larger, for example, than the expected manufacturing error,
there results less than 10% peak-to-peak a.c. component of radial
sealing force compared to its steady value.
Figs. 8-19 illustrate in detail a compressor constructed
in accordance with this invention directly coupled to an electric
motor as a driving means. The driving means illustrated is that
discuss~d in conjunction with Figs. 5-7. Figs. 8 and 9 clearly
illustrate the absence of any radial constraining means other than " ` -
~
the contacting forces developed along the line contacts of the `~
wraps. A number of different embodiments of coupling means which
are connected only to the scroll members are illustrated. It will
be seen that the scroll members and scroll driver are similar to
-26- ~
-~:
~0;~7~;~5
the components shown in Fig. 7 and like reference numerals are
used to identify like components throu~hout Figs. 7-19
As will ~e seen from Fig. 9, the flxed scroll member 25
has two spiral wraps 60 and 61 defilling the line-contacting surfaces,
and these wraps terminate at their inner ends in enlarged sections
62 and 63 which are configured to define with similar enlarged `~
inner sections 64 and 65 of spiral wraps 66 and 67 of the mo~able
scroll member an essentially rectangular central fluid pocket ;
68 which is, of course, the zone of highest fluid pressure. The
flat inner faces (e.g., face 69 of enlarged inner section 62 of
wrap 60) of the four inner sections of the spiral wraps make ;~
it possible to use a small square-cornered coupling member 70, the
purpose of which is to permit the movable scroll member 30 to
orbit without rotating with respect to the stationary scroll mem- -
ber.
Coupling member 70 is detailed in Figs. 13-15 which
a~e top plan and cross sectional views of the coupling member
and an end view of one of the sealing plates, respectively.
Since the coupling member is located within the highest-pressure
fluid pocket, it must be configured to provide fluid passages
within the pocket to communicate with both fluid ports 21 and 55.
It therefore has relatively large cutouts 80 on each side and
cutouts 81 and 82 on the top and bottom leaving in effect a
solid central piece 83. Right-angled sealing plates 84 are
affixed to each coxner and these sealing plates are beveIed at 85
to permit the opening of fluid communication between an outer ~
fluid pocket and the inner fluid pocket through the two recesses ~ -
86 and 87 cut into the end plate 26 of the fixed scroll member.
:.
-27- ~ ~
~ ,
Thus as shown in Fig. 9, there is established fluid communica-
tion from fluid pocket 90 by way of recess 86 and cutout 80 into
the central pocket. It will be appreciated that ~ith the orbit-
ing of the movable scroll, this fluid communication path shifts
to use each of the recesses 86 and ~7 in turn.
The stationary scroll mem~er 25 of, Fig. 8 ~shown in top
and bottom plan views in Figs. 10 and 11~ is formed to have a
lip 95, which provides the sealing surface 28, and an outer
grooved seating ring 96 for engagement with a frame 97 (Figs. 8, `
16 and 17) to which it is fixed by means of a series of screws
98 (Fig. 11) through holes 99. An inlet fluid port 100 in end `
plate 26 provides for the intake of fluid, e.g., air, into the `
apparatus. It will be seen from Fig. 11 that the bottom of the
stationary scroll member has a series of radially extending fins
101 to dissipate heat to the atmosphere and to contribute strength ~ ;~
to this member. Finally, as will ~e seen in Fig. 8, the high-
pressure fluid port 21 has an adapter ring 102 suitable for in-
ternal threading or other modification to permit ready attach~
ment of a conduit, e.g., flexible hose, thereto. `~
The end-on view in Fig. 12 of the movable scroll
mem~er shows that it has recesses 88 and 89 similar to recesses ~ -
86 and 87 of the stationary scroll member and designed for the
same purpose.
AS Will be seen in Figs. 8, 16 and 17, the frame 97
which serves as a support for the drive motor, shaft ~earings
and stationary scroll member comprises an outer ring 110 engageable
with grooved seating ring 96 through screws in threaded holes 111,
a grooved ring 112 adapted to seat the housing of an electric
motor and an center inwardly-lipped bearing retaining ring 113.
.:
~0379'~
These rings are joined through a plurality o~ radial ribs 114.
The main dri~e shaft 56 which is the shaft of the
rotor 120 of electric motor 121 is mounted in a bearing 122
seated in bearing ring 113. Main shaft 56 ls in axial alignment
~ith the central axis of the stationary scroll mem~er. Shaft 56 `~ -
terminates in an eccentric shaft section 125 which is axially
aligned with the movable scroll member. The two axes are parallel
and the distance between them is, of course, Rod, the radius of
the orbiting circle of the scroll driver. Shaft bearing 47 asso~
ciated with eccectric shaft 125 is held in spaced relationship
with main shaft bearing 122 by means of an eccentric bearing
spacer 126 which is fixed to the main shaft by means of pin 127.
(See also Fig. 18
In those embodiments wherein one scroll member remains
stationary and the other orbits, machine vibrations are minimized
by the use of counterweights spinning synchonously in proper phase `~`
~ .. ,
with the scroll drive motor. In the embodiment of Fig. 8, as well
as in Fig. 19 which is a cross section through the drive shafts,
. .:
these counterweights are shown to comprise a smaller mass 130 and
a larger mass 131 clamped to main shaft 56 by means of bolts 132
and nuts 133. Fig. 19 shows the general counterweight configura- -~
tions and means for attachment to the shafts.
The counterweight assembly comprising masses 130 and
131, and the bolts which tie them together onto shaft 56, make up
an eccentric weight. This weight has a mass mb and an effective
radius Rb in the sense described earlier. The purpose of this
counterweight assembly is to provide static ~alancing of the scroll
: .,
-29~
machine due to the orbiting of the ~oYing scroll member. Of cQurse,
there is an unbalanc~d couple, that is, the ~stem of sc~oll
member and counterweight assem~ly i'3 statically but not dyna~ic-
ally balanced. Dynamic balance of the whole apparatus is achieved
nonetheless by means of the high pressure stage in the compressor
unit of Fig. 8. The dynamic unbalance of the high pressure stage
is designed to cancel the dynamic unbalance of the low-pressure
stage. By this means the entire scroll compressor is balanced
-both dynamically and statically. Of course, it is also possible ~-
to achieve full balancing by means of a second counterweight
attached at an angle of 180 to the first. By such means both
the radial inertial force and the rotating moments due to the or-
biting of one moving scroll membex may be balanced out individ- `-
ually.
The motor 121 and its housing 135 may be any suitable
sized commercially available rotary drive mechanism. Although ii ~`
the embodiment of Fig. 8 illustrates the compressor shaft being
connected directly to the motor shaft, it is of course within
the scope of this invention to connect the apparatus through
any suitable mechanism including belts, gears and the like. If ~
the apparatus of this invention is to be used as an expander, `
than shaft 56 will be connected to any suitable energy absorbing - ;
means such as a drive shaft, the shaft of a dynamo, and the like. ~ `
Figs. 20-23 illustrate embodiments of compressors con- ~
structed in accordance with this invention in which the scroll ~ `
members have two complete spiral wraps forming the line-contact-
ing surfaces and a circular coupling member. In Fig. 20, like
reference numerals are used to refer to li~e components shown ;~
in Fig. 8.
-30-
~ ~ - . - .. . - . .. . . . . . .
- - , 7 ~
: - ' - . . . . .
.~ ~ , . .
~ 037~
In Fig. 21 the statlonary scroll member is formed of
two involute spiral wraps 140 and 141 and the mova~le scroll mem- `
ber of two involute spiral wraps 142 and 143. The coupling means
joining the stationary and movable scroll members comprises a
ring 144 which has a diameter which is sufficiently great to per-
mit it to surround the surfaces defining the scroll wraps. As ,
shown in detail in Figs. 22 and 23, this coupling ring 144 has
: oppositely disposed internal flat surfaces which define slightly '~';
thickened wall sections 145 and 146 in the ring. Channels 147 ;' ,~
- 10 and 148 are cut into one side ~e.g., the bottom side as shown in ~
Figs. 22 and 23~ and oppositely disposed channels 149 and 150, the ~ ~;
axis of which is normal to the axis of channels 147 and 148, are
cut into the opposite side of ring 144. As will be seen more ,;
clearly from Fig. 21, wrap 140 of the stationary scroll member
has a radial extension 155 affixed thereto or integral therewith
which is positioned and sized to fit into channel 147 o~ the
ring. In like manner,,radial extension 156 affixed to wrap 141
fits into channel 148,,radial extension 157 affixed to wrap 14
of the movable scroll is adapted to slidably engage channel 149 '~
and radial extention 158 affixed to wrap 143 is adapted to slid~
ably engage channel 150. In orbiting,,the radial extensions are
free to move within the channels while the scroll members are pre-
vented from experiencing relative angular motion. One or more ;
low-pressure fluid ports 159 are located between ring 144 and the
outermost wraps and a central high-pressure port 160 communicates
~ith the high-pressure zone.
Figs. 24-32 illustrate a number of scroll member embod-
iments and coupling members suitable for these scroll members.
In the drawings showing cross sections of the scroll members and
.
-31-
,
7~
couplings the annular housing 28 (see Fig. 8) which is an integral
part of the stationary scroll member, along with the lip ~lange,
(e.g., 95 of Fig. 8~ is omitted since these components will be
identical in cross section to those shown in Fig. 9. Thus Figs.
24, 25, 26, 29 and 32 may be considered to be cross sections
through the plane 9-9 of Fig. 8 terminating with the internal
wall of housing 27 which is lined in and identified ~ that
reference numeral.
The modification of Fig. 24 illustrates one preferred -~
approach to the attainment of a compression ratio of the order of
three. Each scroll member has two wraps, each of which makes about
one and one-half turns. A greater number of turns is of course
possible, but may not be desirable because of the large diameter
of housings required. The stationary scroll member wraps 165 and ~
166 have radial extensions 167 and 168 which engage channels 16~ -
and 170 for slidably engaging the stationary scroll member with ~;
the coupling ring 171; and the movable scroll member wraps 172
and 173 have radial extensions 174 and 175 which slidably engage -~
channels 176 and 177 in ring 171. As in the case of the embodi-
ment of Fig. 21, the porting is simple, comprising a high-pressure
fluid port 140 centrally located in the end plate of the station~
ary scroll member and one or more low-pressure fluid ports 150
located under and outside of the coupling ring. Coupling ring 171 -
in Fig. 24 is configured as a peripheral ring with the channels ~
cut as rectangular slots entirely through it. ~ -
The embodiment of Fig. 25 illustrates one way in which
acceptable compression ratios may be attained without having to
unduly increase the diameters of the scroll members. In this -
embodiment it will be seen that in each scroll member, two
-32-
.. ... ...
: -~ - . .
: - . . . : :
.-.. . , . .. .
:.:. ., : ' ' '
1~75~
outer wraps are transformed into a single, thick-walled inner
wrap. Thus thin-walled stationary scroll wrap 185 makes almost ;
a full turn, ~ut terminates before i~t approaches the center of
the end plate; while stationary thin-walled scroll wrap 186 makes ~;
something more than one full turn and then is transformed into
a thick-walled wrap section 187 which terminates near the center
of the end plate and is cut out to free high-pressure fluid port
140. In like manner, the movable scroll member has a thin-walled
scroll wrap 188 making almost one full turn and a thin-walled wrap ;
189 which is transformed into a thick-walled wrap section 190. The
effect of the thick-walled wrap sections is to materially decrease
the volume of the high-pressure chamber 191 and hence to increase ~
the overall compression ratio. `
The coupling in Fig. 25 is similar to that of Fig. 24
in that it comprises a ring 192 formed to have four cut~outs to
define channels 193-196 through which radial extensions 197 and `
198 at ~he outer ends of wraps 185 and 186 and radial extensions
199 and 200 at the outer ends of wraps 188 and 189 can slide so
that the movable scroll member may orbit but not experience
angular motion relative to the stationary scroll member.
By delaying the opening of the high-pressure fluid
chamber into the high-pressure fluid port, the volume at the
beginning of fluid discharge from a compressor may ~e reduced.
This in turn results in the use of a smaller outside diameter
device for a given volumetric compression ratio. Such an
arrangement is illustrated in Fig. 26. The stationary scroll
member wraps 211 and 212 terminate at their inner ends in enlarged
sections 213 and 214 which define oppositely disposed inwardly
facing flat surfaces 215 and 216. Likewise, movable scroll member
wraps 217 and 218 terminate at their inner end in similarly con~
-33-
.: - . - . . . .::
~3~9~
figured enlarged sections 219 and 220 defining oppositely disposed
inwardly facing flat surfaces 221 and 222 which with surfaces 215
and 216 define a rectangular-like chamber 223 in which the coupl-
ing member 224 is located. This coupling member takes the form
of a cross, (shown in Fig. 27~ each arm 225 of which serves as
a key adapted to slide in a keyway 227 cut through each of the
enlarged wrap sections 213, 214, 219 and 220 as shown in perspec-
tive detail in Fig. 28 which shows the keyway cut into section
219. The high-pressure fluid port 228 lies under a portion of ~he
central solid section of coupling member 224. The diameter of
port 228 is such that a minor area of it is always open to high-
pressure chamber 223. Alternatively, the cross-shaped coupling
member 224 need not extend the full depth of the wraps. ~n this `~
case, the keyway such as channel 227 would not extend all the ` -
way through the wraps. Furthermore, the high-pressure fluid port
228 could be of a smaller diametex and there would still remain
free passage of fluid from the fluid pockets discharging to the `~
delivery port. Low-pressure fluid port 159 is located around
the outer edge of the stationary scroll member end plate 26.
The configuration of the enlarged inner sections of
the wraps, the use of a coupling which is located within the ~ i~
high-pressure fluid chamber and the continual partial covering of
the high-pressure fluid port achieve the desired results of delay- ~ -
ing the opening of the high-pressure fluid chamber and the reduc-
tion in volume of this chamber at the beginning of fluid discharge.
The scroll members of Fig. 29 illustrate what may be
termed an extreme form of porting achieved by a unique configur-
ation of the inner ends of the wraps and by the use o~ a square,
centrally-positioned coupling means. Each of the stationary
-34-
1~379ZS ~
scroll member wraps 231 and 232 and of the movable scroll ~ ;
member ~raps 233 and 234 terminates at its inner or central end
in an enlarged section. Inasmuch as each of these enlarged
sections is identical, section 235, terminating in wrap 231, may ~ ;
be described as illustrative of them. It will be seen that the
end of the enlar~ed section which joins the wrap is configured
to define what ma~ be described as reversed curves 236 and 237.
At its other end, the enlarged section is formed as an extension
238 of the wrap, this extension being faired into flat surface
239 through cur~e 240. By adjustment of the contours of curve
236 and 237 of one enlarged section and curve 240 of the adjacent
enlarged section it is possible to define the range of the size
of the fluid passages 241-244 between the enlarged wrap sections
and to obtain the degree of porting desired.
Since the coupling 245 is square and makes contact with
all four flat surfaces 239, it must be constructed to define
fluid flow paths to provide fluid communications to the high~
pressure fluid port 140 and to the port ~e.g., port 55 of Figs. 7
and 8~ leading to the sealing volume associated with the scroll
driver. This is done through the design of the coupling shown
in perspective and cross sectional views in Figs. 30 and 31. In
essence, this coupling may be described as comprising two pair
of oppositely disposed legs 246 and 247 and 248 and 249 formed
integral with a square plate 250 positioned midway between the
ends of the legs to define a lower fluid passage 251 opening into
port 140 and an upper fluid passage 252 opening into port 55.
As will be seen in the modification of Fig. 32, the
scroll member wraps may be configured as arcs rather than as
involute spirals. In this modification the stationary scroll
member wraps comprise arcs 261 and 262 which vary in thickness
-35-
. . . ., ., , . . . - . :
~.~3~S
throughout their length and which define flat inner surfaces 263
and 264 similar to Fig. 9. Likewise, the movable scroll member
wraps comprise arcs 265 and 266 terminating in flat inner surfaces
267 and 268. The coupling member 70 is identical to that of
Figs. 8 and 9, and detailed in Figs. 13-15. Fluid port recesses
86 and 87 are provided in the end plate of the stationary scroll ~ -
member and fluid port recesses corresponding to 88 and 89 (as in
Fig. 12) in the end plate of the movable scroll mem~er are also '~
used to complete the high-pressure fluid flow path.
The modification of Figs. 33-37 is designed to achieve
high compression ratios with relatively small outside diameters. ;
The porting of this modification is designed to open the high-
pressure fluid port intermittently and the scroll drive is loaded '
by gas pressure intermittently when the high-pressure port is ~;~
opened. Through this arrangment, the axial load can be a func~
tion of the angular position of the scroll driver if desired as '~
well as a function of the delivery pressure.
As will be seen in Fig. 33,,the stationary scroll
member wrap 270 is an involute spiral of one turn with a semicir-
cular skirt 271 having an edge which is an involute curve (shown ~`
by dotted line in Fig. 33~ at its base and two radial extensions
272 and 273 to engage channels in coupling ring 274 which is
similar to the coupling ring 192 of Fig. 25. The end plate 275
of-the stationary scroll member along w~th annular memher 276 and
flange 277 form part of a housing which defines a chamber 278 in
which the movable scroll member and scroll driver are located. An
off-center high-pressure fluid port 279 provides fluid communic-
ation between the highest pressure zone of the apparatus and any
attached fluid conduit (not shown); and a peripherally located
7~
low-pressure fluid port 280 provides fluid communication with the ~;
surrounding atmosphere on some low-pressure fluid reservoir (not
shown).
The movable scroll member has a wrap 281 which terminates
at its inner end in an enlarged section 282, the cross sectional ;
configuration of which is defined by a circle and an involute
curve. Wrap 281 has a skirt 283 of involute outline at its base
and two radial extensions 284 and 285 for engagement with coupling
274. The enlarged central section 282 of the movable scroll ; ;
member wrap has a narrow fluid passage 286 extending throughout
its height and a high-pressure fluid passage 287 which, as is
seen in Fig. 34 extends for a short distance upwardly into en-
larged section 282 from its contacting surface. This fluid pas-
sage 287 has a scalloped edge and a curved edge, the purpose of
which will become clear from the description of the operation
of this apparatus.
The scroll driver 35 and its associated bearing 47,
preloading spring 53, ring seal 52, and sealing volume 54 are ~;
similar to those shown and described in Figs. 7 and 8.
The main housing is completed by housing member 288 -
which is affixed to flange 277 by suitable means such as bolts
289 and which has a central shaft housing extension 290. The
scroll driver shaft 291 with axis 291a terminates in an eccentric
shaft 292 with axis 292a, the distance between these parallel
axes being Rod, the radius of the scroll driver. Shaft 291 is
mounted for rotation in shaft housing 290 through bearings 293
and 294 which are held in spaced relation by bearing spacer ring
295 and rotary shaft seal 296. A bearing retaining ring 298
holds bearing 293 and 294 in place.
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.: .: . . . .
~Q;~7~;~$
In contrast to the arrangement of Fig. 8, the movable
scroll member does not make an orbit:ing rubbing seal with the
housing portion of the stationary scroll member. Rather, the
seals are formed between the end surfaces of the wraps and the
skirts 271 and 281 as shown in Fig. 34. The low-pressure fluid
port 280 opens into chamber 278 and enters the low-pressure `~
pockets defined by the scroll wraps through passages between the
wraps and the skirts, such as passage 299.
Figs. 35-37 along with Fig. 33 illustrate four different
positions occupied by the orbiting movable scroll member relative
to the stationary member. These figures, in which like refer-
ence numerals are used to identify like components, illustrate
the manner in which intermittent porting in attained. It will
be assumed for the purpose of this description of the operation
of the device that it is working as a compressor. Beginning with
Fig. 33, which represents the relative wrap positions shortly
after high-pressure chamber 300 has sealed off a freshly-loaded
pocket of inlet fluid, it will be noted that the enlarged section
282 of the wrap of the movable scroll member covers high-pressure
fluid port 279. In Fig. 35, which represents wrap positions im-
mediately prior to the uncovering of port 279, the voIume 300 has ;
decreased, thus increasing the fluid pressure. ~7olume 300 con-
tinues to decrease as fluid passage 279 begins to uncover port
- ~ 279, then opens it completely (Fig. 36~ until volume 300 reaches
zero volume (Fig. 37~ at which time fluid port 279 is again closed.
After the complete closing of port 279, the orbiting of wrap 281
closes off chamber 301 which is open to the low-pressure side so
as to form high-pressure chamber 300 to begin the cycle anew. -~
The intermittent loading of the high-pressure sealing
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~37~5
volume 54 through passage 286 is achieved during that period of
the cycle when passage 286 is in fluid communication with high-
pressure port 279. Such a condition is shown in Fig. 35. During
the remaining portion of the cycle, high-pressure fluid is
stored in sealing volume 54 until such time as it receives a new
charge of pressurized gas. This intermittent porting into the
sealing volume has the advan'age of making it possible to directly
vary the axial sealing forces with the axial gas forces exerted by
the movable scroll and hence to maintain the difference between
these two opposing forces approximately constant. Moreover, it
will be seen that the phase of the drive shaft with respect to
the open condition of port 286 is subject to choice, thereby
making it possible to achieve a balance between the axial gas
force and the loading force as previously discussed.
The apparatus of Figs. 33-37, although possessing dis- ;~
tinct advantages as a gas compressor or expander, is not suitable
as a liquid pump because of the intermittent porting feature.
As pointed out in the general description of this inven-
tion, the desired relative motion of the cylindrical surfaces
defining the variable volume fluid chambers of the positive
fluid displacement device may be attained by maintaining one
scroll member stationary and orbiting the other without effect-
ing any relative angular motion, or by spinning both of the scroll
members about their respective parallel axes without effecting `~`
relative angular motion of the scroll members. The apparatus ;~
illustrated in the preceding figures incorporate the first of
these operational principles.
The apparatus of Figs. 38 and 39 operates using the
second of these principles. Inasmuch as the scroll wraps and
.
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3~Z,S
couplings may take any of the forms previously illustrated, these
components need not be further described. Thus the scroll members
wrap and coupling of Fig. 20 are used to exemplify these com-
ponents in Fig. 38 and the same reference numerals are used to
identify like components as illustrated in Fig. 20.
The stationary scroll member of the previous embodiments
becomes a driving scroll member, generally indicated at 304; and
the movable scroll member becomes a driven scroll member, generally
indicated at 305. Driving scroll member 304 has an end plate 306
and an annular outer ~all 307 which terminates in an annular
sealing surface 308 (identical in function to sealing surface 28
of Fig. 8. End plate 306 of driving scroll member 304 is
affixed to or formed integral with a scroll shaft 309 which has
a central low-pressure fluid passage 310 extending throughout its
length to within the point where the shaft joins end plate 306.
Passage 310 is the low-pressure fluid inlet (or outlet~ conduit ` `
and therefore it is necessary to provide means for passage 310 to
communicate with the outer low-pressure chambers. This is done
through transverse fluid passage 311 located in ~eb 312 on the
underside of end plate 306. Transverse passage 311 terminates
in one or more ports, e.g., ports 313 and 314 drilled in end
plate 306 as seen in Fig. 39.
Driving scroll shaft 309 is mounted for rotation in `~
main frame section 315 and is supported and aligned through bear-
ings 316 and 317 which are separated by bearing spacer 318~ An
externally threaded section 319 of the shaft peLmits a threaded
ring 320 to be used as a bearing retainer ring. A pulley housing
and shaft frame 321 is affixed to frame section 315 and driving
scroll shaft 309 terminates within an extension 322 of this
_ . - . -:
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,:
~37~'~S ;:
housing. An elastomeric ring 323 and a ring retaining member 324
- are provided to seat the shaft. Housing extension 322 has a
threaded fluid passage 325 aligned with shaft passage 310. This
threaded passage is adapted for connection with any suita~le
conduit if such a conduit is required. A pulley 326 is mounted `~
on shaft 309 to drive the shaft and the driving scroll 304. This `~
may be accomplished by a motor 327 through another pulley 328 and
V-belt 329. It is, of course, within the scope of this invention ;~
to use any other suitable means for rotating shaft 309, such as
gearing.
The driven scroll member 305 is identical in construction
with the movable scroll member previously described, having an
end plate 335 with a peripheral sealing surface 336 and an
annular ring extension 337 which defines a volume in which the ~`~
scroll driver, generally indicated at 338, is located. Elastomeric
ring 52 and preloaded spring 53 are identical in function as
previously described and scroll driver 338 differs from that pre-
viously described in that it is affixed to or integral with scroll ;~
driver shaft 339 which has a high-pressure fluid passage 340
extending throughout its entire length. Shaft 339 is mounted
for rotation in main frame section 341 and is supported and
aligned through bearings 342 and 343 maintained in spaced relation
by bearing spacer 344. An externally threaded section 345 of
shaft 339 permits threaded ring 346 to serve as a bearing re~
taining means. A shaft housing 347 is affixed to the end of
frame section 341 and scroll driver shaft 339 terminates within
an extension 348 of this housing. An elastomeric ring 349 and
a ring retaining member 350 are provided to seal shat 339. Hous-
ing extension 348 has a threaded fluid passage 351 aligned with
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':' i ' ' ' ', ' ' ' ' : ' ' ' ' .
1037~ .S
sha~t passage 3~6. This threaded passage is adapted for con-
nection with any suitable conduit. ;
High-pressure fluid passa~e 340 opens into sealing ;
volume 355 which has a function ide~tical with sealing volume 54
of Fig. 7. High-pressure fluid port 356 provides fluid communi-
cation between the high pressure chamber 357 and sealing passage
355 as well as high-pressure fluid pass~ge 340. ~-
The main frame sections 315 and 341 may be constructed
similarily to frame 97 ~Figs. 8 and 20~ with ribs and heat
transfer surfaces and they may be joined in any suitable manner `~ ;
such as with bolts 358. `~
In an alternative arrangement, the low-pressure port ;
into the scroll members may be the volume 359 defined by frame
sections 315 and 341. In such a modification, a low-pressure
fluid port into volume 359 may be defined as a passage between
the frame sections. It will, of course, be necessary to join
the frame sections through a gasket or otherwise make volume 359 ;-
fluid-tight. In this alternative arrangement passage 310 and
311, ports 313 and 314, shaft sealing ring 323 and annular outer `~
wall 307 of scroll member 304 are eliminated. The bearings must `
then operate in the fluid being handled unless appropriate shaft
seals are provided to protect them. In many cases such shaft ;
seals would not be required.
In the operation of the apparatus of Fig. 38 driving
scroll member 304 is rotated about its axis 360 and in tuxn
drives driven scroll member 305 about its axis 361 which is
.. ; .
parallel with axis 360 and spaced therefrom by a distance equal
to the radius Rod of the scroll driver. Contact between the ;
wraps of the two scroll members is through a number of contact
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3~
lines, e.g., A-D of Fig. 1 and the operation o~ the apparatus is
the same as that described in conjunction with Figs. 1-4. It
will be seen that the driven scroll member 335 still "floats"
with respect to scroll driyer 338 to achieve axial sealing by
the same principle described. Likewise, the diameter Dd f
the scroll driver is less than the diameter Ds of the internal
wall of annular ring extension 337 of driven scroll 335 to pro-
vide the radial sealing load required.
Since each scroll member spins in self-balance, no
balance weights (e.g., 130 and 131 of Fig. 8~ are required. This
is an inherent advantage of the embodiment of Fig. 38. Another
inherent advantage of this embodiment is the fact that no iner-
tial forces are transmitted through the bearings so that very ;
high rotational speed and a resulting high capacity can be
attained.
The roles of the two scroll m~mbers may be reversèd if
~: ,
desired. For example, the scroll driver may be connected throug~
any suitable means to the motor, thus in effect making scroll
, - : ~
member 305 the driving scroll and scroll member 304 the driven
scroll.
It is, of course, within the scope of this invention `
to employ the positive fluid displacement apparatus in a multi~
staged device. Exemplary of such a multistaged system in the - ;~
two-staged air compressor illustrated in Fig. 40. No attempt
has been made in Fig. 40 to show the scroll members, scroll
drivers, etc., in detail since these components may be any one
of the embodiments and modifications previously described.
Rather, Fig. 40 shows a complete compressor system with auxiliary
components.
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~ 0;~r;~
In the apparatus of Fig. 40 a first or low-pressure
stage 370, mounted in frame 371 ~hich is in turn supported by
cover 372 of housing 373, has an inta~ce air filter 374 constructed
in accordance with any suitable well-known design. Compressed air `~ -
- is withdrawn from first stage 370 through conduit 375 which com-
municates with the internal passage 376 of a finned heat exchanger
377 serving as an intercooler. The cooled, initially compressed ~
air is then withdrawn from heat exchanger passage 376 via fluid ; ~;
conduit 378 and introduced into the low-pressure side of the `
second-stage compressor 379, mounted in frame 380, by way of in~
take 381. The finally compressed air is withdrawn through the
high-pressure discharge line 382 and fluid conduit 383 for circu-
lation through internal passage 384 of finned heat exchanger 385
serving as an aftercooler. Finally, the cooled compressed air is
withdrawn from heat exchanger 385 by way of conduit 386 into an oil
removal sump 387 from where it is directed into any desired con-
duit (not shown) which may be attached to the compressor discharge
port 388. The oil from sump 387 is recirculated to the first
stage by means of line 389. A single motor 390 drives both stages. ;;
The positive fluid displacement apparatus of this inven-
tion is versatile with respect to its applications ~compressor, -~
expansion engine or pump~ the types of fluids it can handle and
the conditions under which it can operate.
It will thus be seen that the objects set forth above,
among those made apparent from the preceding description, are
efficiently attained and, since certain changes may be made in
the above constructions without departing from the scope of the
invention, it is intended that all matter contained in the above
description or shown in the accompanying drawings shall be inter~
preted as illustrative and not in a limiting sense.
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