U.S. patent number 3,924,977 [Application Number 05/408,912] was granted by the patent office on 1975-12-09 for positive fluid displacement apparatus.
This patent grant is currently assigned to Arthur D. Little, Inc.. Invention is credited to John E. McCullough.
United States Patent |
3,924,977 |
McCullough |
December 9, 1975 |
Positive fluid displacement apparatus
Abstract
A positive fluid displacement apparatus employing scroll members
having interfitting spiroidal wraps angularly and radially offset
such that as the spiral centers experience an orbiting motion, they
define one or more moving fluid pockets of variable volume. The
zones of lowest and highest pressure are connected to fluid ports.
Radial sealing is accomplished with minimum wear by linking the
orbiting scroll member to the driving mechanism through a radially
compliant mechanical linking means which also incorporates means to
counteract at least a fraction of the centrifugal force exerted by
the orbiting of the orbiting scroll member. If essentially all of
the centrifugal force is counteracted, then the compliant
mechanical linking means is designed to supply the necessary radial
sealing force. Coupling means, which are separate from the driving
means, and hence from the radial constraining force, are provided
to maintain the desired angular relationship between scroll members
and to provide one opposing force for axial sealing. The other
opposing axial sealing force is a combination of biasing means and
fluid pressure. The apparatus may serve as a compressor, expander
or pump.
Inventors: |
McCullough; John E. (Carlisle,
MA) |
Assignee: |
Arthur D. Little, Inc.
(Cambridge, MA)
|
Family
ID: |
27004380 |
Appl.
No.: |
05/408,912 |
Filed: |
October 23, 1973 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
368907 |
Jun 11, 1973 |
|
|
|
|
Current U.S.
Class: |
418/55.2; 418/14;
418/55.6; 418/55.5; 418/57 |
Current CPC
Class: |
F01C
21/003 (20130101); F01C 1/0215 (20130101); F04C
23/008 (20130101); F05B 2250/50 (20130101); F04C
2250/10 (20130101) |
Current International
Class: |
F01C
21/00 (20060101); F01C 1/00 (20060101); F01C
1/02 (20060101); F04C 23/00 (20060101); F04C
001/02 () |
Field of
Search: |
;418/57,55 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Assistant Examiner: Smith; Leonard
Attorney, Agent or Firm: Lepper; Bessie A.
Parent Case Text
This application is a continuation-in-part of U.S. Pat. application
Ser. No. 368,907 filed June 11, 1973, in the names of Niels O.
Young and John E. McCullough.
Claims
I claim:
1. In a positive fluid displacement apparatus into which a fluid is
introduced through an inlet port for circulation therethrough and
subsequently withdrawn through a discharge port, in which two
scroll members being maintained at a desired angular relationship
and having wraps which make a plurality of moving line contacts to
seal off and define at least one moving pocket of variable volume
and zones of different fluid pressure when one of said scroll
members is driven by driving means to orbit within said other of
said scroll members while maintaining a fixed angular relationship
therewith, and wherein said driving means associated with said one
of said scroll members includes means to provide a centripetal
radial force adapted to oppose a fraction of the centrifugal force
acting upon said one of said scroll members, the improvement
comprising radially compliant mechanical linking means between said
driving means and said one of said scroll members, said radially
compliant mechanical linking means including said means to provide
said centripetal radial force of a magnitude to control the radial
sealing force between said scroll members at a level to minimize
both wear and internal fluid leakage.
2. A positive fluid displacement apparatus in accordance with claim
1 wherein said radially compliant mechanical linking means includes
means to provide a centripetal radial force less than said
centrifugal force and the difference of said forces comprises said
radial sealing force.
3. A positive fluid displacement apparatus in accordance with claim
2 wherein said radially compliant mechanical linking means
comprises swing-like means.
4. A positive fluid displacement apparatus in accordance with claim
3 wherein said swing-link means includes compression spring means
to provide said centripetal radial force.
5. A positive fluid displacement apparatus in accordance with claim
2 wherein said radially compliant mechanical linking means
comprises sliding-block linking means.
6. A positive fluid displacement apparatus in accordance with claim
5 wherein said sliding-block linking means includes compression
spring means to provide said centripetal radial force.
7. A positive fluid displacement apparatus in accordance with claim
1 wherein said radially compliant mechanical linking means includes
means to provide a centripetal radial force essentially equal to
said centrifugal force and means to provide a separate adjustable
radial sealing force.
8. A positive fluid displacement apparatus in accordance with claim
7 wherein said radially compliant mechanical linking means
comprises swing-link means having compression spring means to
provide said centripetal force and counterweight means as said
means to provide a separate controllable radial sealing force.
9. A positive fluid displacement apparatus in accordance with claim
7 wherein said radially compliant mechanical linking means
comprises sliding-block linkage means having compression spring
means to provide said centripetal force and counterweight means as
said means to provide a separate controllable radial sealing
force.
10. A positive fluid displacement apparatus into which fluid is
introduced through an inlet port for circulation therethrough and
subsequently withdrawn through a discharge port, comprising in
combination
a. an orbiting scroll member and a fixed scroll member each having
end plate means to which are affixed wrap means which, when said
orbiting scroll member is orbited with respect to said fixed scroll
member, make moving line contacts to seal off and define at least
one moving fluid pocket of variable volume and zones of different
fluid pressure and develop radial constraints;
b. drive means to effect orbital motion of said orbiting scroll
member;
c. radially compliant mechanical linking means between said
orbiting scroll member and said drive means;
d. centrifugal force counterbalancing means associated with said
mechanical linking means and adapted to counterbalance at least a
fraction of the centrifugal force acting upon said orbiting scroll
member; and
e. coupling means adapted to prevent relative angular motion of
said scroll members, said coupling means being separate and
distinct from said scroll drive means whereby said radial
constraints within said apparatus are limited to said moving line
contacts between said wraps and are controlled through said
radially compliant mechanical linking means.
11. A positive fluid displacement apparatus in accordance with
claim 10 wherein said centrifugal force counterbalancing means
counterbalances less than all of said centrifugal force and that
fraction of said centrifugal force which is not counterbalanced
constitutes the radial sealing force between said wraps.
12. A positive fluid displacement apparatus in accordance with
claim 11 wherein said radially compliant mechanical linking means
is a swing-link and said centrifugal force counterbalancing means
are compression spring means.
13. A positive fluid displacement apparatus in accordance with
claim 11 wherein said radial compliant mechanical linking means is
a swing-link and said centrifugal force counterbalancing means is a
counterweight.
14. A positive fluid displacement apparatus in accordance with
claim 11 wherein said radial compliant mechanical linking means is
a sliding-block link and said centrifugal force counterbalancing
means are compression spring means.
15. A positive fluid displacement apparatus in accordance with
claim 11 wherein said radial compliant mechanical linking means is
a sliding-block link and said centrifugal force counterbalancing
means is a counterweight.
16. A positive fluid displacement apparatus in accordance with
claim 10 wherein said centrifugal force counterbalancing means
counterbalances essentially all of said centrifugal force and
includes radial sealing force means to provide a separate
controllable radial sealing force.
17. A positive fluid displacement apparatus in accordance with
claim 16 wherein said radially compliant mechanical linking means
is a swing-link and said centrifugal force counterbalancing means
and said radial sealing force means are compression spring
means.
18. A positive fluid displacement apparatus in accordance with
claim 16 wherein said radial compliant mechanical linking means is
a swing-link, said centrifugal force counterbalancing means is a
counterweight and said radial sealing force means are compression
spring means.
19. A positive fluid displacement apparatus in accordance with
claim 16 wherein said radial compliant mechanical linking means is
a sliding-block link and said centrifugal force counterbalancing
means and said radial sealing force means are compression spring
means.
20. A positive fluid displacement apparatus in accordance with
claim 16 wherein said radial compliant mechanical linking means is
a sliding-block link, said centrifugal force counterbalancing means
is a counterweight and said radial sealing force means are
compression spring means.
21. A positive fluid displacement apparatus into which fluid is
introduced through an inlet port for circulation therethrough and
subsequently withdrawn through a discharge port, comprising in
combination
a. an orbiting scroll member and a fixed scroll member each having
end plates affixed to wrap means which, when said orbiting scroll
member is orbited with respect to said fixed scroll member, make
moving line contacts through a radial sealing force to seal off and
define at least one moving fluid pocket of variable volume and
zones of different fluid pressure and develop radial
constraints;
b. axial sealing means adapted to force said wrap means into
sealing contact with said end plates;
c. main drive shaft means, the axis of which is the axis of said
fixed scroll member and is parallel to and spaced from the axis of
said orbiting scroll member, the distance between said axes being
the operational orbit radius of said orbiting scroll member;
d. radially compliant mechanical linking means joining said
orbiting scroll member and said main drive shaft means;
e. centrifugal force counterbalancing means associated with said
mechanical linking means adapted to counterbalance at least a
fraction of the centrifugal force acting upon said orbiting scroll
member;
f. coupling means adapted to prevent relative angular motion of
said scroll members, said coupling means being separate and
distinct from said orbiting scroll member driving means whereby
said radial constraints comprising said radial sealing force within
said apparatus are limited to said moving line contacts between
said wraps and are controlled solely through said radially
compliant mechanical linking means and its associated centrifugal
force counterbalancing means; and
(g) housing means, including frame support means, defining a fluid
chamber within which said scroll members are located.
22. A positive fluid displacement apparatus in accordance with
claim 21 wherein said radial compliant mechanical linking means is
a swing-link and the axis of said swing-link is oriented
perpendicular to said eccentricity radius of said orbiting scroll
member.
23. A positive fluid displacement apparatus in accordance with
claim 21 wherein said radial compliant mechanical linking means is
a swing-link and the axis of said swing-link is oriented to make an
angle of less than 90.degree. with the eccentricity radius of said
orbiting scroll member.
24. A positive fluid displacement apparatus in accordance with
claim 21 including crank means joining said main drive shaft means
to said radially compliant mechanical linking means.
25. A positive fluid displacement apparatus in accordance with
claim 21 including counterweight means attached to said crank means
to minimize or eliminate vibration in said apparatus.
26. A positive fluid displacement apparatus in accordance with
claim 21 including means to circulate a coolant within the end
plate of said fixed scroll member.
27. A positive fluid displacement apparatus in accordance with
claim 21 wherein the contacting surface of the wrap means of said
fixed scroll member has shallow lubricant channel means therein,
and said apparatus includes means to introduce a lubricant into
said channel means.
28. A positive fluid displacement apparatus in accordance with
claim 21 including locking means to lock said fixed scroll member
to said housing means, said locking means being adjustable whereby
the angular orientation of said scroll member may be adjusted
within said housing.
29. A positive fluid displacement apparatus in accordance with
claim 21 having fluid inlet port means associated with the zone of
lowest pressure and fluid discharge port means associated with the
zone of highest pressure and means to rotate said main drive shaft
means, whereby said apparatus is a compressor.
30. A positive fluid displacement apparatus in accordance with
claim 21 having fluid inlet port means associated with the zone of
highest pressure and fluid discharge port means associated with the
zone of lowest pressure and work absorbing means connected to said
main drive shaft means, whereby said apparatus in an expansion
engine.
31. A positive fluid displacement apparatus in accordance with
claim 21 wherein said coupling member is an annular ring,
positioned between the endplate of said orbiting scroll member and
said frame support means, having oppositely disposed keyways on
each surface thereof and wherein said endplate of said orbiting
scroll member and said frame support means have keys slidably
engageable with said keyways of said coupling means.
32. A positive fluid displacement apparatus in accordance with
claim 31 wherein said coupling means is further characterized by
having shallow lubricant channels on each of its surfaces and
passage means providing fluid communication between said
channels.
33. A positive fluid displacement apparatus in accordance with
claim 31 including sets of roller means, each comprising a
plurality of rollers, interposed between one surface of said
coupling means and said end plate of said orbiting scroll member
and between the other surface of said coupling means and said frame
support means, said roller means being so oriented that the axes of
said rollers contacting any one surface of said coupling means are
normal to the axis of said keyways on that surface.
34. A positive fluid displacement apparatus in accordance with
claim 21 wherein said centrifugal force counterbalancing means
counterbalances less than all of said centrifugal force and that
fraction of said centrifugal force which is not counterbalanced
constitutes said radial sealing force.
35. A positive fluid displacement apparatus in accordance with
claim 34 wherein said radially compliant mechanical linking means
is a swing-link and said centrifugal force counterbalancing means
are compression spring means.
36. A positive fluid displacement apparatus in accordance with
claim 34 wherein said radial compliant mechanical linking means is
a swing-link and said centrifugal force counterbalancing means is a
counterweight.
37. A positive fluid displacement apparatus in accordance with
claim 34 wherein said radial compliant mechanical linking means is
a sliding-block link and said centrifugal force counterbalancing
means are compression spring means.
38. A positive fluid displacement apparatus in accordance with
claim 34 wherein said radial compliant mechanical linking means is
a sliding block link and said centrifugal force counterbalancing
means is a counterweight.
39. A positive fluid displacement apparatus in accordance with
claim 21 wherein said centrifugal force counterbalancing means
counterbalances essentially all of said centrifugal force and
includes radial sealing force means to provide a separate
controllable radial sealing force.
40. A positive fluid displacement apparatus in accordance with
claim 39 wherein said radially compliant mechanical linking means
is a swing link and said centrifugal force counterbalancing means
and said radial sealing force means are compression spring
means.
41. A positive fluid displacement apparatus in accordance with
claim 39 wherein said radial compliant mechanical linking means is
a swing-link, said centrifugal force counterbalancing means is a
counterweight and said radial sealing force means are compression
spring means.
42. A positive fluid displacement apparatus in accordance with
claim 39 wherein said radial compliant mechanical linking means is
a sliding-block link and said centrifugal force counterbalancing
means and said radial sealing force means are compression spring
means.
43. A positive fluid displacement apparatus in accordance with
claim 39 wherein said radial compliant mechanical linking means is
a sliding-block link, said centrifugal force counterbalancing means
is a counterweight and said radial sealing force means are
compression spring means.
44. A positive fluid displacement apparatus in accordance with
claim 21 wherein said axial sealing means comprise in combination
(1) mechanical and fluid force applying means providing a first
axial force acting on said fixed scroll member and (2) said
coupling means positioned between said orbiting scroll member and
said frame support means adapted to oppose said first axial force
with a second axial force.
45. A positive fluid displacement apparatus in accordance with
claim 44 wherein said mechanical force applying means comprises a
wave spring washer.
46. A positive fluid displacement apparatus in accordance with
claim 44 wherein said fluid force applying means comprises a fluid
chamber positioned to exert fluid pressure upon the end plate of
said fluid scroll member and means to deliver high-pressure fluid
to said fluid chamber.
47. A positive fluid displacement apparatus in accordance with
claim 46 wherein said means to deliver high-pressure fluid to said
fluid chamber comprises conduit means providing fluid communication
between an external source of a high-pressure fluid and said fluid
chamber.
48. A positive fluid displacement apparatus in accordance with
claim 46 wherein said means to deliver high-pressure fluid to said
fluid chamber comprises conduit means providing fluid communication
between the zone of highest pressure and said fluid chamber.
Description
This invention relates to fluid displacement apparatus and more
particularly to apparatus for handling fluids to compress, 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 apparatus serves as a
compressor. If the working fluid is a pressurized gas 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
positive-displacement devices of the vane, gear or other rotary
types. However, it is of interest to note some of the features
which characterize these general types of prior art apparatus as a
basis for comparison with the fluid displacement apparatus of this
invention.
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 percent
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 clearance, 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 may not, however, 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 remains a need for
a simple, highly efficient apparatus, essentially unaffected by
wear which can handle a wide range of fluids and operate over a
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 members 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 cylindrical wrap surfaces, and
area contacts between plane surfaces. The volume of a sealed pocket
changes as it moves. At any one instant of time, there will be at
least one sealed pocket.
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 curved surfaces. A 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.degree. but because of special porting
arrangements will subtend a smaller angle about the central region
of the scrolls. The pockets define fluid volumes the angular
position of which varies with relative orbiting of the spiral
centers; and all pockets maintain the same relative angular
position. As the contact lines shift along 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. Pat. No. 801,182) describes this
general type of device. Among subsequent patents which have
disclosed scroll compressors, and pumps are U.S. Pat. Nos.
1,376,291, 2,809,779, 2,841,089, 3,560,119, and 3,600,114 and
British Patent No. 486,192.
Although the concept of a scroll-type apparatus has 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 sealing, 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 be machined to accurate shapes and
to be fitted with very small tolerances to maintain axial sealing
gaps sufficiently low to achieve any useful pressure ratios. This
is difficult to do and resembles the problem of constructing
apparatus with a reciprocating piston without 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 constraints, each
being imposed by separate apparatus components requiring precise
interbalancing to attain efficient radial sealing. If during
extended operation of such devices this interbalancing is
disarranged by one component experiencing more wear, or by any
other mechanism, the problem of wear of other components may grow
progressively worse until satisfactory radial sealing is no longer
obtained.
The resulting solutions to the sealing, wearing and porting
problems through these and other prior art approaches have not been
satisfactory. Thus in the prior art devices, the inherent
advantages of scroll-type apparatus (simplicity, high efficiency,
flexibility, reversibility, and the like) have not been attained
and have, in fact, been usually outweighted by sealing, wearing 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 to sealing, wearing and porting problems
heretofore encountered.
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. Therefore, in the
design of prior art scroll-type apparatus an important approach to
the obtaining of compression ratios greater 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 may be
configured to control delivery of fluid into and discharge of fluid
from the apparatus.
In copending application Ser. No. 368,907 filed in the names of
Niels O. Young and John E. McCullough there is disclosed a novel
scroll apparatus in which radial sealing is accomplished with
minimum wear by using a driving mechanism which provides a
centripetal radial force adapted to oppose a fraction of the
centrifugal force acting on the orbiting scroll member. This
requires a flexible linking of the orbiting scroll with its driving
or orbiting means while the fixed scroll remains rigidly fixed with
respect to the housing as well as to the orbiting scroll. In
specific embodiments of the improved scroll apparatus described in
U.S. Pat. application Ser. No. 368,907, the required flexible
linking of the orbiting scroll with its driving means comprises
means defining a cylindrical drive surface associated with the
orbiting scroll member having an orbit radius R.sub.or and a scroll
driving means defining a cylindrical driving surface with an orbit
radius R.sub.od. The driving surface is designed to drive the
orbiting scroll member through line contact with the cylindrical
drive surface by virtue of the fact that R.sub.od is less than
R.sub.or. Thus, when the scroll driver is orbited to develop a
drive force acting upon the orbiting scroll, a centripetal radial
force is provided to oppose a fraction of the centrifugal force
acting on the orbiting scroll member, and the difference between
this centirpetal radial force and the normal centrifugal force
acting upon the orbiting scroll member appears as the only contact
force, e.g., radial sealing force, between the scroll members. This
embodiment of a flexible linking of orbiting scroll member to the
driving mechanism is particularly suitable for smaller-size,
relative low-load machines where simplicity of construction and
minimization of the number of parts is desirable.
There are, however, a number of applications for compressors,
expanders and pumps where large horsepower sizes are required that
can carry large drive loads with good wear life, operate over
extended periods of time and be easily started up and shut down.
For such applications, a positive mechanical linkage between scroll
members to achieve radial sealing through balancing of centrifugal
forces with centripetal forces has advantages over the use of
cylindrical driving surfaces relying on line contacts to provide
force control. The apparatus of this invention comprises a unique
combination of elements which achieve such a positive mechanical
linkage in a scroll type apparatus.
It is therefore a primary object of this invention to provide
scroll-type apparatus particularly suited for large housepower
sizes and where drive forces on the scroll members are significant.
It is another object of this invention to provide apparatus of the
character described which has radial compliance permitting the
orbiting scroll member to move inwardly and outwardly relative to
the machine axis in response to initial component misalignment or
gradual wear or to compensate for the temporary presence of
noncompressible material such as a slug of liquid, accumulated wear
debris or ingested dirt.
Another object of this invention is to provide scroll-type
apparatus of the character described which places no load on the
drive motor when used as a compressor or pump during start-up and
shut-down and which permits the use of conventional journal or ball
bearing elements to carry the drive loads with acceptable wear
life.
This invention has as yet another object the providing of a
scroll-type compressor which is capable of achieving near
isothermal compression by virtue of relatively large internal heat
transfer capability, which has excellent volumetric efficiency,
which is capable of operating at relatively low noise levels, which
has a sealed inlet volume, and which is suitable for high- and
low-speed operation and for mounting directly to a motor to utilize
the drive motor's bearings.
Other objects of the invention will in part be obvious and will in
part be apparent hereinafter.
The scroll apparatus of this invention provides means to control
the radial contacting forces such that radial sealing is
continuously and effectively attained even with wear or when
noncompressibles are temporarily present. This means to control
radial contacting comprises means to counterbalance at least a
fraction of the centrifugal force acting upon the orbiting scroll
member and radially compliant mechanical linking means between the
orbiting scroll and its drive means. In one embodiment, the
radially compliant mechanical linking means is capable of providing
a centripetal force to counterbalance a fraction of the centrifugal
force thereby having a portion of the centrifugal force available
for achieving controlled radial sealing. In this embodiment the
compliant mechanical linking means incorporates mechanical springs
to counteract a portion of the centrifugal force.
In another embodiment, means separate from the radially compliant
mechanical linking means, e.g., counterweights, are provided to
counterbalance all or nearly all of the centrifugal forces acting
upon the orbiting scroll member and the radially compliant linking
means, i.e., mechanical springs, are incorporated to provide the
desired radial sealing forces. In this embodiment, the radial
sealing force may be made independent of changes in pressure at the
inlet and outlet of the machine and of variations in operational
speed.
The scroll members are angularly positioned by a coupling of the
sliding friction type or rolling element type; the radially
compliant linking means may be a slide-link or swing-link; either
one or both of the scroll members may be cooled and the contacting
surfaces may be lubricated if desired.
The invention accordingly comprises the features of construction,
combinations of elements, and arrangement of parts which will be
exemplified in the constructions hereinafter set forth, and the
scope of the invention will be indicated in the claims.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed
description taken in connection with the accompanying drawings in
which
FIGS. 1-4 are diagrams of exemplary spiral wraps, one moving in a
circular orbit with respect to the other, illustrating the manner
in which a device incorporating such spiral members can achieve
compression of a gas;
FIG. 5 is a longitudinal cross section of a compressor constructed
in accordance with this invention incorporating a sliding friction
type coupling, a swing-link and springs to counterbalance a
fraction of the centrifugal force acting on the orbiting scroll
member;
FIG. 6 is a fragmentary cross section of the fixed scroll member
illustrating in detail one embodiment of an axial sealing force
generating means;
FIG. 7 is an end view of the fixed scroll member showing the back
or external side of the end plate and the location of coolant
passages drilled in the end plate;
FIG. 8 is an end view of a portion of the front or internal side of
the end plate of the fixed scroll member illustrating the lubricant
groove in the wrap end and the introduction of a lubricant into the
groove;
FIG. 9 is a cross section through plane 9--9 of FIG. 7 showing the
lubricant inlet line;
FIG. 10 is a cross section through the scroll wraps taken through
plane 10--10 of FIG. 5;
FIG. 11 is a fragmentary end view of the front or external side of
the end plate of the orbiting scroll member showing the coupling
key;
FIG. 12 is a top plan view of one embodiment of a scroll coupling
member;
FIG. 13 is a cross section of the coupling member of FIG. 12 taken
through plane 13--13 of that figure;
FIG. 14 is a cross section of the coupling member of FIG. 12 taken
through plane 14--14 of that figure;
FIG. 15 is a plan view of the inside surface of the housing frame
support member showing the coupling member keys and lubricant
channels;
FIG. 16 is a cross section through plane 16--16 of the housing back
plate of FIG. 15;
FIG. 17 is a top plan view of another embodiment of a coupling
member designed to make rolling contact with the housing frame and
orbiting scroll member;
FIG. 18 is a fragmentary cross section showing the coupling member
in place between the housing frame and the orbiting scroll
member;
FIG. 19 is a plan view of a swing-link assembly serving as the
compliant mechanical linking means between the orbiting scroll
member and the driving means;
FIg. 20 illustrates a modification of the swing-link of FIG.
19;
FIGS. 21-23 are cross section, end and side views of a sliding
block assembly serving as the complicant mechanical linking means
between the orbiting scroll member and the driving means; and
FIG. 24 is a cross section through the main drive shaft through
plane 24--24 of FIG. 5 showing the configuration of the centrifugal
force counterbalancing weights used to eliminate vibration.
Before describing specific embodiments of the apparatus of this
invention, the principles of the operation of scroll apparatus in
general 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 compressed while being 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 volume remain essentially constant independent of
pressure 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 configuration.
The scroll members have parallel axes since in only this way can
the continuous sealing contact between the plane surface of the
scroll members be maintained. A sealed pocket moves 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 is
accomplished, for example, by maintaining one scroll fixed and
oribiting the other scroll. 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.
FIGS. 1-4 may be considered to be end views of a compressor wherein
the end plates are removed and only the wraps of the scroll members
are shown. In the descriptions which follows, 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 arc 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 constitute the components
which define the moving sealed fluid pocket 14 which is
crosshatched for ease of identification. The involute spirals 10
and 12 may be generated, for example, by wrapping a string around a
reference circle having radius R.sub.g. The distance between
corresponding points of adjacent wraps of each spiral is equal to
the circumference of the generating circle. This distance 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 number 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 previously 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 approximately a single turn about the
central region of the scrolls. Since the spiral wraps have height
(normal to the plane of the drawings) the pocket becomes a fluid
volume which is decreased from FIG. 1 to FIG. 4 as the movable
scroll member is orbited around a circle 15 of radius (P/2)-t,
where t is the thickness of the wrap. Since wrap 12 does not rotate
as it orbits, 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. In this illustrative example
of scroll wraps, congruency results from the fact that one scroll
pattern can be brought into coincidence with the other by a simple
rotation of one-half turn or less about its axis, followed by a
small translation to bring their centers together. The thicknesses,
t, of the spiral walls are shown to be identical, although this is
not necessary. As will be discussed in the following description
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. 1-4) to which stationary wrap 10
is fixed has a high-pressure fluid port 21 and as the moving wrap
12 is orbited the fluid pocket 14 shifts counterclockwise and
decreases in volume to increase the fluid pressure. In FIG. 3, the
fluid volume is opened into port 21 to begin the discharge 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, delivering mechanical energy
in the form of rotary motion as the fluid pockets expand to
increasing volume. In such an arrangement the device is an
expansion engine and may be used, if desired, to develop
refrigeration.
Although this principle of the operation of scroll apparatus has
long been known as evidenced by the prior art, the attainment of
practical scroll equipment in a form which would encourage 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 problems of sealing
and wearing. More particularly, the scroll devices of the prior
art, as far as is known, have not provided an efficient combination
of continuous axial and radial sealing; and they have in many cases
sought to impose radial constraints on the scroll members by
mechanism other than the line contacts of the wraps themselves
while using such mechanisms also to control angular phase
relationships between the scroll members. Failure to provide
efficient continued axial and radial sealing permits blow-by and it
can materially decrease the efficiency of the apparatus to the
point 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 eventually leads to the wearing of
the contacting surfaces and then to leakage. Generally such wear
will vary from surface to surface and will not be
self-compensating, a fact which only serves to aggravate the
problem of wear with continued operation. Combining mechanisms to
achieve a desired angular phase relationship between the scroll
members with such means to impose radial constraints can compound
the problem of wear so that extended operation becomes
impractical.
To understand the problem of sealing a scroll-type apparatus and to
describe the mechanism by which axial and radial sealing is
achieved in the apparatus of this invention, it is helpful to
examine the principal axial and radial forces acting upon a scroll
member. The total external axial force on a scroll pair is the sum
of a contact sealing force acting between plane surfaces 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.
Whereas axial sealing is required to seal the end surfaces 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 orbiting scroll 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 inherently determine radial
sealing of the scroll members comprise tangential forces due to the
reaction of the fluid within the scroll volume which is resolved by
mechanical radial constraints and centrifugal forces due to the
orbiting of the orbiting scroll member. In addition to these
inherent forces, other external forces may be supplied.
In the apparatus of this invention the disadvantages associated
with scroll apparatus of the prior art are eliminated or minimized
by counterbalancing all or a portion of the centrifugal forces
acting upon the orbiting scroll and by linking the orbiting scroll
to the drive means through a radially compliant mechanical linkage.
If all of the centrifugal forces are counterbalanced, then the
compliant mechanical linkage is designed to provide a radial force
component of a desired magnitude to achieve radial sealing. If less
than all of the centrifugal forces are counterbalanced, that
fraction which is not counterbalanced is used to provide radial
sealing. Axial sealing is accomplished by two opposing forces
acting on the scroll members. The first of these forces is a
biasing means, including fluid pressure acting on the fixed scroll
member and the second force acts upon the orbiting scroll through
the coupling means located externally of the scroll pockets and
arranged to oppose the force of the biasing means. The coupling
means, which maintains the desired angular relationship of the
scroll members functions independently of the radial sealing forces
which are independently controlled to minimize wear of the line
contacts between the wraps of the scroll members and to be able to
compensate for noncompressible contaminants which may accidentally
enter the fluid pockets.
A compressor constructed in accordance with this invention is shown
in longitudinal cross section in FIG. 5. Reference should also be
had to FIGS. 6-16, 19 and 24 where indicated. In all of the
drawings like reference numerals are used to refer to like
elements. As seen in FIG. 5 the fixed scroll member, generally
indicated at 10, is comprised of an end plate 11; a wrap 12, which
makes more than three revolutions (see FIG. 10) and terminates in
an enlarged peripheral section 13; an annular sealing ring member
14; and a central ported extension 15. Within extension 15 is a
high-pressure fluid passage 16 and extending into it is an
connector tube 17, aligned on the machine axis 18, for connecting a
high-pressure line, not shown.
The orbiting scroll member, generally indicated at 20, comprises an
end plate 21 and a wrap 22, which makes more than three revolutions
and terminates in an enlarged peripheral section 23 (FIG. 10). In
order to achieve axial sealing the end surface 25 of the fixed
scroll member wraps 12 and 13 must make sealing contact with the
internal surface 26 of the end plate 21 of the orbiting scroll; and
in like manner, the end surface 27 of the orbiting scroll member
wraps 22 and 23 must make sealing contact with the internal surface
28 of the fixed scroll member. In order to achieve radial sealing
the wraps of the two scroll members must make rolling line
contacts, e.g., 29, 30 and 31 of FIG. 10. Innermost fluid pocket 35
defines the zone of highest pressure while plenum chamber 36,
defined around the wraps, comprises the zone of lowest pressure.
The fluid pockets, e.g., 37, 38 and 39 are at intermediate
pressures increasing toward the center pocket 35. This zone of
highest pressure communicates with a high-pressure line through
fluid passage 16 and connector tube 17. The low-pressure plenum
chamber 36 communicates through one or more low-pressure ports 40
with a low-pressure fluid source or reservoir. If the apparatus is
a compressor, low-pressure fluid is brought in through low-pressure
port 40 and compressed fluid is delivered through a suitable
conduit connected to connector tube 17. If, on the other hand, the
apparatus is used as an expander, high-pressure fluid is brought in
through passage 16 and expanded low-pressure fluid is discharged
through one or more low-pressure ports 40.
FIG. 10 illustrates but one design of the scroll wraps which may be
used in the apparatus. It is also within the scope of this
invention to use, for example, wraps of more or less than three
revolutions, wraps which are configured as other than true spiroids
(e.g., arcsoof circle) and wraps which have their innermost ends
configured to control the volume of the highest-pressure pocket. A
number of such suitable wrap design variations are included in
copending application Ser. No. 368,907.
The scroll apparatus is contained within a housing, generally
indicated at 45, which in the embodiment of FIG. 5 comprises a
front housing cover plate 46 affixed through screws 47 to housing
back plate 48 which in turn is covered by a back cover 49.
Low-pressure port 40 is cut through the front cover plate 46.
The fixed scroll member 10 is mounted on and aligned in front
housing cover plate 46 through annular sealing ring member 14 and
central ported extension 15 which are affixed to, or preferably
integral with, the external surface 55 of end plate 11. Front
housing cover plate 46 has an internally disposed mounting ring 56
and a central opening 57, each of which are grooved to hold
elastomeric sealing rings 58 and 59, these sealing rings providing
a seal with ring member 14 and extension 15. As seen in the detail
drawing of FIG. 6, the annular sealing ring member 14 terminates
short of the inner surface 60 of front cover plate 46 to define a
shallow annular spacing 61 into which is placed a wave spring
washer 62 biased to apply an axial force on the fixed scroll member
10. The force thus applied constitutes a portion of the axial
sealing force required. An additional axial sealing force is
provided by introducing a high-pressure fluid into spacing 61 and
into annular fluid sealing chamber 63 (defined between ring 14 and
extension 15) through fluid port 64 which is, in turn, connected to
a source of high-pressure fluid, not shown. This source of
high-pressure fluid may be an external one, e.g., nitrogen from a
storage tank, or it may be the zone of highest pressure of the
apparatus, e.g., high-pressure pocket 35. In the latter case,
suitable fluid communication means (not shown) must be provided
between pocket 35 and fluid sealing chamber 63. If the
high-pressure fluid is to be supplied from the zone of highest
pressure within the machine (i.e., from pocket 35) then the axial
force provided by the wave spring washer 62 must be sufficient to
provide sealing during start-up since little, if any, high-pressure
fluid will be available from pocket 35 during this period of
operation. If, however, as in the case of the embodiment of FIGS. 5
and 6, the high-pressure axial sealing fluid is applied from an
external source, the sealing fluid may be introduced into sealing
chamber 63 prior to start-up and continued subsequent to
shut-down.
The fixed scroll member is angularly positioned relative to the
front housing cover plate 46 and is thereby maintained fixed with
respect to the housing frame. This is accomplished through the use
of locking means generally indicated at 70. The locking means of
FIG. 5 permits minor adjustments to be made during assembly or
operating in angularly locating the fixed scroll so that it may be
placed at the optimum angle. This locking means comprises a bolt 71
with threads 72 and a head 73 to which a pin 74 is fixed eccentric
to the bolt axis. A nut 75 engaging threads 72 serves to hold the
bolt in the front plate. Pin 74 engages a notch 76 cut into the
back of end plate 11 (See FIG. 7). Because of the eccentricity of
pin 74 relative to the axis of the bolt, turning of bolt 71 causes
pin 74, and hence fixed scroll end plate 11, to undergo small
angular excursions to find the optimum position for the fixed
scroll member. Alternatively, the locking means may be a simple
constant-diameter pin extending from within front cover 46 into
notch 76, in which case the angular position of the fixed scroll
member is not adjustable.
In the embodiment of FIG. 5, the scroll members are cooled by
circulating a coolant through end plate 11 of the fixed scroll
member as can best be seen in FIG. 7 which is an end view of the
external surface 80 of end plate 11. A series of interconnecting
passages 81 forming a conduit network are drilled in end plate 11
and they are connected through suitable connectors 82 and 83 to
fluid conduits (not shown) capable of introducing a coolant into
and withdrawing it from the coolant passage network.
In the embodiment illustrated, a lubricant is provided to lubricate
the contacting ends 25 of the fixed scroll member wraps. As seen in
the fragmentary detail drawings of FIGS. 8 and 9, the contacting
spiraling end surface 25 of the continuous wraps 12 and 13 have an
oil channel 84 cut into it. A suitable lubricant is delivered to
the outermost part of the channel through a line 85 connected to a
passage 86 drilled into enlarged wrap 13 and extending to channel
84. The lubricant is forced through channel 84 which follows the
entire wrap and any excess eventually drains by gravity to the
bottom of the housing to be withdrawn through oil drain port 87.
Lubrication of the contacting wrap ends may not be required,
particularly in such cases where the wrap and end plate surfaces
are of a self-lubricating nature or are not subject to intolerable
wear, or where the size and mode of operation either does not
require or even prohibits the introduction of lubricants into the
system.
The orbiting scroll member must be prevented from moving angularly
with respect to the fixed scroll member and with respect to the
frame of the housing; and it must be driven in an orbit in a way to
counteract all or a portion of the centrifugal force developed in
its orbiting while providing the required radial sealing
forces.
The maintaining of the desired angular relationship between the
oribiting scroll and the fixed scroll member and housing is
accomplished through the use of a coupling member generally
indicated by the numeral 90. As will be seen in FIGS. 12-14, this
coupling member comprises an annular ring 91 with an "H"-shaped
cross section. What may, for convenience, be designated the front
surface 92 faces the orbiting scroll; and in keeping with this
terminology, the opposite surface, called the back surface 93,
faces the inside wall 94 of an internal supporting frame member 95
of the housing. Front surface 92 has two oppositely disposed
keyways 96 and 97 cut into it (FIG. 12); and back surface 93 also
has two oppositely disposed keyways 98 and 99 cut into it. The axes
of the keyways on the front and back surfaces are at right angles.
The keys which slidingly engage these keyways are attached to the
orbiting scroll and the housing frame member 95. As will be seen in
FIGS. 5 and 11, keys 100 and 101 are fastened, such as by
countersunk screws 102 into shallow recesses 103 and 104 cut into
external surface 105 of the orbiting scroll member end plate. These
keys slide in keyways 96 and 97 of the coupling member,
respectively. FIG. 15, which is a plan view of internal surface 94
of housing frame member 95 shows the position of keys 106 and 107
mounted through countersunk screws 108 (FIG. 16) into recesses 109
and 110, respectively, cut into surface 94. These keys 106 and 107
slidingly engage keyways 98 and 99.
Inasmuch as there is sliding friction contact between the front and
back surfaces of the coupling and the surfaces of the orbiting
scroll member end plate and the support frame, it may be desirable
to lubricate these surfaces. In the embodiment of FIG. 5, this is
accomplished by injecting oil through oppositely disposed passages
115 and 116 (FIG. 15) drilled into frame member 95 to communicate
with arcuate channels 117 and 118 cut into surface 94 of the frame
member. Oil flowing through these arcuate channels is introduced
into oil groove 119, cut into back face 93 of the coupling, and
then transferred to oil groove 120, cut into front face 92 of the
coupling, through short arcuate channels 121 and 122 by way of
passages 123 and 124 (FIGS. 12 and 14) cut through the coupling.
Excess oil discharged from the coupling eventually flows out
through oil drain port 87.
In some apparatus it may not be desirable to use a lubricant or to
tolerate the losses developed by the friction between the coupling
member and the surfaces it contacts as in the embodiment of FIG. 5.
It is possible to eliminate the use of a lubricant and at the same
time materially reduce friction losses by the use of a rolling
coupling member as illustrated in FIGS. 17 and 18. The coupling
member 130 is an annular ring constructed with essentially the same
cross section as the coupling member 90 of FIGS. 12 and 13, and it
has keyways 96-99 as described above. It is, however, supported on
three sets of rolls 131, 132 and 133, each set comprising a
plurality of rolls 134 contacting the front face 135 of the
coupling and surface 105 of the orbiting scroll member, and a
plurality of rolls 136 contacting the back face 137 of the coupler
and surface 94 of the support frame member 95. Rolls 134 and 136
are oriented at right angles to each other and their axes are
oriented to be normal to the axis of the keyway cut in the surface
which they contact. Thus each roll is positioned to travel with the
coupling member as it moves in the directions indicated by the
arrows.
Although the embodiments of the coupling means illustrated in FIGS.
12-18 show keyways in the coupling means and slidingly engageable
keys in the orbiting scroll member and housing frame, it is also
within the scope of this invention to reverse this arrangement and
affix the keys to the coupling means and locate the keyways in the
orbiting scroll member and the housing frame.
Several embodiments of suitable mechanisms for driving the orbiting
scroll member with the desired radial compliance to attain a
predetermined sealing force are illustrated in FIGS. 5 and 19-23.
As will be seen in the detailed description of these drawings, the
radial compliant means may take one of several forms. Moreover, it
is possible to choose between several operating modes, i.e.,
counterbalancing a fraction of the centrifugal force and using that
fraction which is not counterbalanced as a radial sealing force, or
counterbalancing essentially all of the centrifugal force and
incorporating into the mechanical compliant linkage, means to
provide a radially outward force which can alone serve as the
radial sealing force.
In the embodiment of FIGS. 5, 19 and 20 the radially compliant
mechanical linkage is a swing-link, while in FIGS. 21-23 it is a
sliding-block linkage. Both of these embodiments may use springs in
compression to counteract all or a part of the centrifugal force,
or they may use counterweights in place of or in addition to the
springs.
In order to attain radial compliance, the orbiting scroll member
must have the ability to move inwardly or outwardly relative to the
machine axis in response to gradual wear of the scroll wraps or to
encounter noncompressible objects such as a slug of liquid,
accumulated wear debris or ingested dirt particles. This radial
compliance feature also allows the use of less perfect geometry
scrolls in that it allows the orbiting scroll member to ride inside
of the fixed scroll member and adjust its trajectory, as required,
to suit the geometries of the wraps of the two scrolls. In the
embodiments of FIGS. 5, 19 and 20, a ball bearing is mounted on the
axial drive shaft of the orbiting scroll member and the outer
periphery of this ball bearing is connected to a crank mechanism
with a swing-link. The axis of the swing-link in FIG. 19 is shown
to the nominally perpendicular to the eccentricity radius of the
orbiting scroll member. During rotation of the drive crank, the
orbiting scroll member swings radially outward under the action of
centrifugal force acting on its center of mass. The orbiting scroll
member is confined to a given locus of motion by virtue of contact
with the wrap of the fixed scroll member. The radial contact force
between the orbiting and fixed scroll members is adjusted by the
use of mechanical springs, or equivalent devices, to counteract
some predetermined fraction of the centrifugal force exerted on the
orbiting scroll member.
Turning now to FIGS. 5 and 19, the orbiting scroll is driven by the
main drive shaft 140 which is mounted in the back cover plate
through a bearing 141. Affixed to main drive shaft 140 is a crank
142 to which a connecting rod 143 is pivotally mounted through
connecting rod pin 144. This connecting rod is affixed to the
orbiting scroll member through a stub shaft 145 by means of snap
ring 151 and ball bearing 146 retained by an inner race 147 and
outer race 148 mounted on ring 149 of the connecting rod. The axis
of shaft 145 is designated in FIG. 19 by the numeral 150. The axis
of the main shaft and of the machine is the same as that of the
fixed scroll member and is therefore designated by the numeral 18.
The distance between the orbiting scroll axis 150 and the machine
axis 18 is R.sub.or, the orbit radius.
Since the description of the apparatus is, for convenience,
presented in terms of its serving as a compressor, main shaft 140
is shown attached to a motor 152 of a type suitable to rotate shaft
140. However, it is also, as previously noted, within the scope of
this invention to use this apparatus as an expansion engine, in
which case the element 152 may be considered to be any suitable
work absorbing means, e.g., another compressor, or a brake in the
case of an expansion engine used to develop refrigeration.
The swing-link, which is comprised of the connecting rod, ball
bearing assembly, and pin is connected to the crank through one or
more springs in compression as shown in FIG. 19. A T-bolt 155 is
attached to connecting rod 143 and extends through the wall of
crank 142 which has a shallow well 156 on its external surface to
seat concentric springs 157 and 158 held in compression by means of
a spring retainer 159 adjustably affixed to T-bolt 155 by means of
nut 160. Springs 157 and 158 are preloaded to a desired force
through turning nut 160. The number of springs and the degree of
preloading may be so chosen as to overcome a predetermined fraction
of the centrifugal force exerted on the orbiting scroll member
while it is achieving full running eccentricity. Thus the springs
in effect pull back on the swing-link and thereby exert a
centripetal force on the orbiting scroll member, the difference
between the centrifugal and centripetal forces being in essence
equal to the radial sealing force. This in turn means that the
radial sealing force may be adjusted by adjusting the degree of
preloading of the springs.
During start-up and shut-down (as well as periods of nonorbiting)
the springs cause the swing-link to be pulled inwardly, that is
toward the inner surface 161 of the crank so that the small gap 162
shown in FIG. 19 is not present. This means that the eccentricity
radius of the orbiting scroll member is slightly less than the
normal operating orbit radius. As the speed of the machine
increases, the centrifugal force of the orbiting scroll increases,
reaching a point where it balances the restraining spring force and
eventually achieves a value greater than the restraining spring
force. In this fashion, the initial start-up and the final portion
of the shut-down operations of the machine occur without
wrap-to-wrap contact of the scroll members. This in turn means that
the motor 152 which turns main shaft 140 does not have to start
under a load but picks up the load as the speed of the machine
increases. The same desirable condition also, of course, occurs
during shut-down.
It will be apparent that in the embodiment described, the axis of
the swing-link is oriented perpendicular to the eccentricity radius
of the orbiting scroll member. This has the advantage that the
radial sealing force does not vary with changes in the inlet and
outlet conditions of the machine.
Modifications of the swing-link embodiment of FIG. 19 are possible
and within the scope of this invention. Exemplary of one such
modification is the use of a counterweight on the swing-link to
exert a force on the link equal and opposite to the centrifugal
force exerted by the orbiting scroll. Such a counterweight may be
affixed to the spring retainer 159, or alternatively, the spring
retainer itself may be configured to serve as such a counterweight.
In the case where a counterweight is used to counterbalance all of
the centrifugal force, the springs (e.g., 157 and 158 or a single
spring) will be used to generate the radial sealing force. Again,
this modification permits accurate control of the radial sealing
force. Moreover, the combination of springs and counterweight
allows the radial sealing force to be independent of changes in
pressure at the inert and outlet of the machine as well as of
variations in operating speed.
Two additional modifications of the swing-link are illustrated in
FIG. 20. In the first of these, the springs are replaced by a
counterweight 163 which is affixed to or integral with the ring 149
of the connecting rod 143 and extends beyond opening 164 in crank
142. In this modification, counterweight 163 is designed to
counterbalance a fraction of the centrifugal force exerted on the
orbiting scroll member, the remaining fraction being used to
provide a radial sealing force of a predetermined magnitude. Thus
counterweight 163 serves in the same role as springs 157 and
158.
The second modification illustrated in FIG. 20, which is equally
applicable to the swing-link embodiment of FIG. 19, is the
orientation of the axis of the swing-like to form an angle less
than 90.degree. with the eccentricity radius of the orbiting
scroll. This is evident from the shift in position of swing-link
pivot axis 144 relative to axes 18 and 150. Reducing this angle has
the advantage of reducing the size of the counterweight, or spring,
required to counteract the centrifugal force acting upon the
orbiting scroll member; but it does mean that the resulting radial
sealing force is somewhat dependent upon machine inlet and outlet
pressure variations.
It is also possible to form the mechanical, compliant link between
the main drive shaft and the orbiting scroll member through a
sliding block mechanism in place of the swing-link mechanism
illustrated in FIGS. 5, 19 and 20. An exemplary sliding link
mechanism is illustrated in FIGS. 21-23, wherein the same reference
numerals are used to define similar elements identified in FIGS. 5,
19 and 20. In the cross section, end-on and sides views of FIG.
21-23, it will be seen that crank 180 provides a flat contacting
surface 181 adapted for slidable engagement with surface 182 of
sliding block 183 which slides in a groove defined within crank
180, (FIG. 23). Sliding block 183 is affixed to flanged stub shaft
184 or orbiting scroll member 20 through a bearing assembly,
comprised of an inner race 192, an outer race 193 and ball bearings
194, held by retaining member 195 affixed to the back side 196 of
sliding block 183. Crank 180 is preferably linked to sliding block
183 through compression spring 186 (FIG. 21) which is anchored to
the inner wall 187 of a chamber 188 cut into the sliding block and
to a spring support 189 which is an integral extension of crank 180
extending into chamber 188. This spring 186 serves the same role as
springs 157 and 158 of the embodiment of FIG. 19, i.e., the
counterbalancing of a fraction of the centrifugal force exerted on
the orbiting scroll member. As in the case of the swing-link
assembly, it is also possible to use a counterweight in place of or
in addition to the springs in the same manner as previously
described. Thus counterweight 190 is shown affixed to sliding block
183 in FIG. 22. The sliding block linkage of FIGS. 21-23 is
preferably used with the coupling member of FIGS. 5 and 12, i.e.,
where the coupling member makes sliding friction contact with the
housing frame and orbiting scroll member. The advantage of the
sliding block linkage is that it can carry the axial restraining
force to be exerted on the orbiting scroll member so that the
coupling is unloaded in the axial direction and therefore consumes
less power.
As will be seen in FIGS. 5 and 24, the driving mechanism also has
oppositely disposed counterweights comprising a primary
counterweight 170 affixed through screws 171 to the shoulder 172 of
crank 142 and a secondary counterweight 173 affixed through screws
174 to a flanged extension 175 of crank 142. The counterweights are
so configured with respect to size and are so positioned on the
crank to eliminate vibrations in the running of the machine. It
will be noted that the larger, primary counterweight 170 is
positioned to exert a centrifugal force in the same direction as
the centripetal force of springs 157 and 158 (FIG. 19).
The operation of the apparatus of this invention has been detailed
above with respect to the various elements. It is, therefore, only
necessary to briefly review the overall operation of the apparatus,
particularly with respect to its serving as either a compressor or
an expansion engine. In the case where it is to serve as a
compressor, low-pressure fluid, e.g., air at ambient conditions, is
taken in through one or more of the low-pressure ports 40, and
delivered as high-pressure air through high-pressure discharge
conduit 16. During its orbiting, orbiting scroll member 20 is
forced by the coupling member 90, which is interposed between it
and the housing frame 95, against the fixed scroll member 10 to
oppose the force of the wave spring washer 62 and fluid pressure in
fluid sealing chamber 63, thus attaining axial sealing between the
wrap ends and the scroll end plates which they contact. Radial
sealing by forcing the wraps to make moving-line contacts is
controlled to the desired degree by the amount of centrifugal force
which is counteracted by the amount of centripetal force provided
by the radially compliant mechanical linkage used.
If the apparatus is to serve as an expansion engine to develop
mechanical energy and/or refrigeration, the gas to be expanded is
introduced into the high-pressure port 16 and withdrawn into a
low-pressure reservoir through one or more low-pressure ports. The
attainment of axial and radial sealing is the same as when the
apparatus is used as a compressor.
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 interpreted as
illustrative and not in a limiting sense.
* * * * *