Tip seal supporting structure for a scroll fluid device

A tip seal supporting structure for use in a scroll fluid device includes intermeshing involute scroll elements mounted for relative orbital movement. Each of the scroll elements includes an involute spiral wrap which is secured to a respective wrap support plate at one axial end thereof. Each involute spiral wrap is provided with a tip seal in the other axial end thereof which engages with the wrap support plate of the other scroll element. One of the wrap support plates includes a substantially, centrally located fluid passage into which the innermost end of the involute spiral wrap of the other scroll element extends during a predetermined portion of the relative orbital movement between the scroll elements. In one embodiment of the invention, a tip seal supporting structure in the form of a bridge extends across a predetermined portion of this central fluid passage and functions to axially support the innermost portion of the tip seal that extends into this fluid passage during relative orbital movement of the scroll wraps to thereby prevent destructive vibrational effects, to permit the tip seals to extend into the center of the involute scrolls as much as possible, and to maximize the efficiency of the scroll fluid device. In other embodiments, the tip seal is attached to the involute spiral wrap by a fastener. In an additional embodiment, the end of the tip seal is supported by a shelf member formed integral with the involute spiral wrap.

BACKGROUND OF THE INVENTION 
The present invention pertains to a tip seal supporting structure for use 
in a scroll fluid device. The tip seal supporting structure includes a 
bridge which extends across a portion of a fluid flow port located at an 
orbit center of one of the involute scroll members of the scroll device 
and functions to support an end portion of a tip seal carried by the other 
scroll device during a predetermined portion of the relative orbital 
motion of the scroll members. 
In scroll fluid devices having a pair of meshed axially extending involute 
spiral wraps defining at least one fluid chamber between them that moves 
radially between an inlet zone and an outlet zone when one wrap is orbited 
along a circular path about an orbit center relative to the other wrap, 
tip seals are widely used in the art to axially seal this fluid chamber. 
These tip seals are arranged to engage wrap support plates to which the 
involute spiral wraps are respectively fixedly secured. Whether the scroll 
fluid device functions as a compressor or an expander, one fluid port 
typically will be substantially centrally located at the center of one of 
the involute spiral wraps and extend through the respective support plate. 
If the tip seals extend substantially the entire length of the involute 
spiral wraps, as is highly desirable in order to maintain proper sealing 
of the fluid chamber, the tip seal portion at the inner end of the spiral 
wrap that does not have the fluid port associated therewith will extend 
beyond the edge of the fluid passage and will therefore be cantilevered 
for a predetermined portion of the relative orbital movement of the 
scrolls. Under these circumstances, the tip seal can vibrate which results 
in wear and/or destruction of the tip seal. 
In order to alleviate this problem, some prior art scroll devices, such as 
that represented by U.S. Pat. No. 4,824,343, utilize tip seals which do 
not extend to the innermost end of the involute spiral wrap and therefore 
will not extend into the centrally located fluid port. Although in these 
prior known arrangements the tip seal will not be cantilevered during a 
predetermined portion of the relative orbital movement between the 
involute spiral wraps, during that portion of the relative orbital 
movement in which the innermost end of the spiral wrap does not extend 
into the fluid passage, there is no tip seal to provide for axial sealing 
at the innermost end of the involute wrap. This can result in some leakage 
of the fluid, a pressure loss and a decrease in the efficiency of the 
scroll device. 
Therefore, to maximize efficiency, there exists a need in the art for a 
scroll fluid device which enables the use of tip seals which extend to the 
innermost end of the involute spiral wraps of the scrolls as much as 
possible and wherein the tip seal can be axially supported during that 
portion of the relative orbital movement between the scroll fluid wraps 
when the innermost end of one of the involute wraps extends beyond the 
edge of the fluid port. 
SUMMARY OF THE INVENTION 
The present invention provides a tip seal supporting structure for use in a 
scroll fluid device which solves the problems associated with known prior 
art devices. The tip seal supporting structure of the present invention is 
incorporated in a scroll fluid device having first and second meshed 
axially extending involute spiral wraps having involute centers and 
defining at least one chamber therebetween that moves radially between an 
inlet zone and an outlet zone when one wrap is orbited along a circular 
path about an orbit center relative to the other wrap. At least one of the 
first and second meshed axially extending involute spiral wraps includes a 
tip seal secured within a recess formed in one axial end of the involute 
spiral wrap. This tip seal engages a respective wrap support plate to 
which the involute spiral wrap is secured so as to axially seal the moving 
fluid chamber. The present invention incorporates a tip seal supporting 
structure constituted in one embodiment by a bridge that extends across a 
centrally located fluid passage that extends through one of the wrap 
support plates of the scroll fluid device. The bridge functions to axially 
support the innermost end of the tip seal on the involute spiral wrap that 
extends into this fluid passage during the relative orbital movement of 
the first and second involute spiral wraps. In a second embodiment, the 
supporting structure comprise a screw which extends axially through an 
involute spiral wrap and attaches the tip seal thereto. In a third 
embodiment, a pin and slot arrangement is used to support the end of the 
tip seal. In a fourth embodiment, the involute spiral wrap is integrally 
formed with a shelf member which axially supports the end of the tip seal. 
Since the tip seal supporting structure of the present invention provides 
axial support for the innermost end of the tip seal projecting into the 
central fluid passage, the first and second involute spiral wraps may be 
provided with tip seals which extend into the center of the involute wraps 
as much as possible to thereby maximize the axial sealing between the 
spiral wraps and, due to the additional axial support provided, 
destructive vibrational effects on the tip seal can be prevented. 
A fuller understanding of the nature and objects of the present invention 
will become apparent from the following detailed description of the 
preferred embodiments thereof when taken in conjunction with the drawings 
which depict a scroll fluid device incorporating the tip seal support 
structure of the present invention in a scroll fluid device that functions 
as a compressor.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Although the present invention may be applied to various types of scroll 
fluid devices, it is depicted and described for exemplary purposes 
embodied in a hermetically sealed scroll refrigerant compressor which is 
adapted to be used in a closed-loop expander-condenser refrigeration 
system. 
With initial reference to FIG. 1, a compressor is shown comprising a 
housing assembly 5 including a base plate 7, a lower housing section 9, an 
upper housing section 11 and a cover member 13. The upper end of lower 
housing section 9 includes a radially transversely extending annular 
flange 15 that is either integrally formed therewith or fixedly secured 
thereto by any means known in the art, such as by welding. Annular flange 
15 has various circumferentially spaced apertures 16 extending 
substantially longitudinally therethrough. The lower end of upper housing 
section 11 also includes an annular flange 17 including various apertures 
18 which are longitudinally aligned with apertures 16 for receiving 
fasteners such as bolts 20 and nuts 21 for fixedly securing upper housing 
section 11 to lower housing section 9 as will be more fully described 
herein. 
Located within lower housing section 9 is a motor assembly 26. Motor 
assembly 26 comprises a bottom plate 28 and an upper crosspiece 31. 
Located in bottom plate 28 is a lower central aperture 33 defined by an 
upstanding annular bearing flange 34. Mounted within motor assembly 26 is 
an electric motor 38 including a rotor 39 rotatable about a longitudinal 
central axis, windings 40 and a lamination section 41. The exact mounting 
of motor 38 will be more fully discussed hereinafter. 
As depicted, motor assembly 26 includes a lower skirt section 43 integrally 
formed with bottom plate 28, an upper skirt section 44 formed integral 
with crosspiece 31 and a central skirt section 45 which is part of 
lamination section 41. Lower, upper and central skirt sections 43, 44, 45 
include an aligned, elongated vertical apertures 46 extending therethrough 
at circumferentially spaced locations. Aligned with apertures 46, in upper 
crosspiece 31, is an internally threaded bore 47. Motor housing 26 is 
secured together by various bolts 49 which extend through apertures 46 and 
are internally threaded into bore 47 of upper crosspiece 31. 
Upper crosspiece 31 includes an annular flange 51 which mates with annular 
flange 15 of lower housing section 9 and annular flange 17 of upper 
housing section 11. Annular flange 51 further includes a plurality of 
circumferentially spaced apertures 53 which can be aligned with apertures 
16 and 18 formed in lower housing section 9 and upper housing section 11 
respectively. Bolts 20 are then adapted to extend through aligned 
apertures 16, 53 and 18 and nuts 21 are secured to the bolts 20 in order 
to fixedly secure upper housing section 11 to lower housing section 9 with 
upper crosspiece 31 of motor assembly 26 therebetween. By this 
construction, motor assembly 26 is thereby secured within lower housing 
section 9. 
Press-fit or otherwise secured within upstanding annular bearing flange 34 
of bottom plate 28 is a lower bearing sleeve 56. Rotatably mounted within 
lower bearing sleeve 56 is a lower end 57 of a longitudinal extending 
hollow drive shaft 58. Drive shaft 58 includes an upper hollow section 59 
separated by a partition, as will be explained more fully below, from 
lower end 57. Located within lower hollow end 57 is an oil cup 61 which 
tapers inwardly in a downward direction. Oil cup 61 rotates freely around 
an upstanding central knob 62 formed in an attachment plate 63. Knob 62 
includes a centrally located through-hole 64 communicating between the 
interior of oil cup 61 and a lower sump 65 in order to permit lubricating 
fluid to flow into and out of oil cup 61. Attachment plate 63 is secured 
to bottom plate 28 by means of various bolts 66. 
Upper portion 59 of drive shaft 58 extends through a central opening 70 in 
crosspiece 31 and terminates in an integrally formed drive plate 71. 
Central opening 70 houses an upper bearing sleeve 72 which includes an 
upper transverse flange 73 embedded in a recess 74 formed in an upper 
surface of crosspiece 31. Upper bearing sleeve 72 includes a clearance 
passage 76 for the draining of lubricating fluid bearing medium. Drive 
plate 71 is dish-shaped and includes a substantially horizontal, central 
portion 80 and an upwardly sloping outer portion 81. 
Located above dish-shaped drive plate 71 is a drive scroll 84 that includes 
a central, hollow sleeve portion 86, a wrap support plate 87 and an 
involute spiral wrap 88. Central, hollow sleeve portion 86 is fixedly 
secure to drive shaft 58 through drive plate 71. Intermeshingly engaged 
with drive scroll 84 is a driven scroll 91 having a wrap support plate 92 
with an involute spiral wrap 93 extending downwardly from a lower first 
side 94. As is known in the art, defined between involute spiral wrap 88 
and involute spiral wrap 93 are fluid chambers 95 that, in this example, 
transport and compress gaseous refrigerant radially inwardly between the 
scroll flanks when the scroll is operated. Typically, the scroll fluid 
device would operate at a high speed within a gaseous fluid medium 
surrounding the rotating scroll wraps so that, when the device is operated 
as a compressor, fluid intake occurs at the outer end of each scroll wrap 
and output flow through the device occurs at central output port 96. Of 
course, it should be understood that such scroll fluid devices can be 
operated as an expander by admitting pressurized fluid at port 96 and 
causing it to expand within the radially outwardly moving fluid chambers 
95, to be discharged at the outer ends of the scroll wraps. However, in 
this description, it will be assumed that the scroll fluid device 
illustrated is arranged to function as a compressor. 
The upper, second side 99 of wrap support plate 92 is formed with an 
integral central projection 100. Disposed vertically above driven scroll 
91 is a pressure plate 101 having an upper side surface 102 and a lower 
side surface 103. Formed in lower side surface 103 is a central recess 104 
into which central projection 100 of driven scroll 91 extends and is 
fixedly secured therein. Relatively thin reinforcing ribs 100a extend from 
surface 99 of driven scroll 91 to pressure plate 101. On upper side 
surface 102, opposite recess 104, pressure plate 101 is formed with an 
axially projecting bearing support shaft 105. Bearing support shaft 105 
extends into a central bore hole 108 formed in a fixed support plate 109 
in upper housing section 11. 
In this embodiment, drive scroll 84 and driven scroll 91 co-rotate and 
therefore a bearing sleeve 112 is mounted within bore 108 and extends 
about the periphery of bearing shaft 105. In addition, bearing sleeve 112 
includes a clearance passage 113, analogous to clearance passage 76 
previously discussed, for the draining of a lubricating fluid medium 
between bearing shaft 105 and bearing sleeve 112. It is possible, however, 
to fixedly secure driven scroll 91 and orbit drive scroll 84 about an 
orbit radius relative to scroll 91. 
Extending upwardly from and connected to outer perimeter 118 of drive plate 
71 is an annular torque transmitting member 119. Secured to an upper, 
interior side wall 120 of torque transmitting member 119 is an annular 
bearing plate 121 having a central through-hole 122 therein through which 
bearing shaft 105 extends. An Oldham Coupling or synchronizer assembly, 
generally indicated at 125, is located between annular bearing plate 121 
and upper side surface 102 of pressure plate 101 to maintain the drive and 
driven scrolls 84, 91 in fixed relationship in a rotational sense (i.e., 
so they cannot rotate relative to each other but maintain a fixed angular 
phase relationship relative to each other). Annular bearing plate 121 
includes at least one clearance passage 126 for the introduction of high 
pressure oil to counteract the axial gas force developed and to lubricant 
to the Oldham Coupling. 
In order to drive the compressor, electric motor 38 operates in a 
conventional manner. Lamination section 41 is fixedly secured to upper and 
lower skirt sections 43, 44 of housing assembly 5. Rotor 39, on the other 
hand, is secured to drive shaft 58 such that when motor 38 is activated, 
rotation of rotor 39 causes rotation of drive shaft 58, drive plate 71, 
drive scroll 84, annular torque transmitting member 119, annular bearing 
plate 121 and, in the preferred embodiment, driven scroll 91 through the 
Oldham synchronizer assembly 125 acting through pressure plate 101. 
Formed as part of housing assembly 5, between upper housing section 11 and 
cover member 13, is a housing fluid inlet port 130 which opens up into an 
annular inlet manifold 132. Inlet manifold 132 includes an inlet passage 
133 leading to a scroll inlet port 134 formed in annular torque 
transmitting member 119, adjacent the involute spiral wraps 88 and 93. The 
scroll fluid intake zone is provided inside the torque transmitting member 
119 around the periphery of the scrolls. Another port 130a may be provided 
optionally for instrumentation access. 
When functioning as a compressor, gaseous refrigerant will enter the scroll 
fluid chambers 95 between spiral wraps 88, 93 through housing inlet port 
130, inlet passage 133 and scroll inlet port 134. Upon activation of motor 
38 and rotation of drive shaft 58, drive plate 71 and drive scroll 84, 
gaseous refrigerant will be pumped and compressed through the scroll 
device and will exit from scroll outlet port 96. Since scroll outlet port 
96 opens into the hollow, upper section 59 of drive shaft 58, the 
compressed refrigerant will run downwardly through upper section 59. Just 
above lower end 57, drive shaft 58 includes a partitioning drive shaft 
outlet 141 which opens into motor assembly 26. Thus, refrigerant will be 
conducted through a passage 143 adjacent lower end 144 of rotor 39, 
through passage 145 adjacent windings 40 and into lower sump 65 through 
various outlet holes 147 formed in bottom plate 28. The refrigerant then 
moves along bottom plate 28, through a clearance passage 149 formed 
between lower housing section 9 and motor housing 26, and out through a 
housing outlet port 150. 
With reference to FIG. 3 which shows a mirror-image of driven scroll 91, 
involute spiral wrap 93 includes an inner end 155 and an outer end 158. As 
previously discussed, one axial end (not labeled) of involute spiral wrap 
93 is fixedly secured to lower first side 94 of wrap support plate 92. The 
other or lower axial end 161 of involute spiral wrap 93 is formed with an 
involute recess 164 which extends substantially from inner end 155 of 
involute spiral wrap 93 to outer end 158. Mounted within involute recess 
164 is a tip seal 167 which extends axially beyond axial end 161 as 
indicated in FIG. 2. As known in the art, drive scroll 84 is similarly 
constructed with a tip seal 168 as shown in FIG. 2. During operation of 
the scroll fluid device, the respective tip seals 167, 168 engage with the 
respective wrap support plates 87, 92 so as to axially seal fluid chambers 
95. At this point it should be recognized that the present invention could 
also be used with a scroll fluid device having only a single tip seal as 
well. 
As previously stated, when the scroll fluid device of the present invention 
functions as a compressor, output flow from fluid chambers 95 between 
spiral wraps 88, 93 flows out of scroll outlet port 96 and through hollow 
drive shaft 58. During relative orbital movement between involute spiral 
wraps 88 and 93, inner end 155 of involute spiral wrap 93 will come out of 
contact with upper surface 156 of wrap support plate 87 associated with 
drive scroll 84 and will extend into scroll outlet port 96. Without the 
tip seal supporting structure of the present invention, when inner end of 
involute spiral wrap 93 comes out of engagement with upper surface 156 of 
wrap support plate 87, tip seal 167 would no longer be supported at its 
end in an axial direction but would rather be cantilevered off upper 
surface 156. 
The present invention contemplates providing a tip seal supporting 
structure in the form of a bridge 172 which extends across a portion of 
outlet port 96 as best shown in FIGS. 4 and 5. Bridge 172 is curvilinear 
as viewed in FIG. 4 and includes a top surface 174 which is located in the 
same plane as upper surface 156 of wrap support plate 87. Bridge 172 
fixedly attached at both ends thereof to inner wall 176 of wrap support 
plate 87. As can be readily seen from FIG. 4, the inclusion of bridge 172 
separates outlet port 96 into a small outlet passage 180 and a larger 
outlet passage 183. 
When the scroll fluid compressor is in operation, involute spiral wrap 93 
will orbit relative to wrap support plate 87 of involute sprial wrap 88. 
During a portion of this relative orbital movement, tip seal 167 will be 
axially supported by upper surface 156 of wrap support plate 87. During 
the remainder of this relative orbital movement, the innermost end of the 
seal 167 will be over outlet port 96 and out of contact with upper surface 
156. However, since bridge 172 extends across outlet port 96 in the 
orbital path of the innermost end of tip seal 167, tip seal 167 is axially 
support throughout the entire range of relative orbital movement. 
In a preferred embodiment, bridge 172 is integrally formed with wrap 
support plate 87 of drive scroll 84, however, it is to be understood that 
bridge 172 could be formed as a separate element and fixedly secured to 
wrap support plate 87 so that upper surface 156 of wrap support plate 87 
is in the same plane with top surface 174 of bridge 172. Furthermore, 
since bridge 172 inherently minimizes the cross-sectional area of outlet 
port 96, it is possible to compensate for this reduction by reducing the 
size of wrap support plate 87 adjacent outlet port 96, such as indicated 
at 187 in FIG. 4, to increase the size of outlet passage 183. The 
necessity of this would depend on the desired output and pressure 
requirements of the compressor which could be readily determined by 
experimentation. 
It should be noted that the bridge structure of the present invention could 
be used on driven scroll 91, as well, in conjunction with a shallow recess 
to insure that discharging fluid from the center of the scroll compressor 
has substantially the same flow passage geometry. 
Reference will now be made to FIGS. 6-8 which depict alternate embodiments 
of the tip seal supporting structure of the present invention. In each of 
these embodiments, the tip seal is supported at its end to a respective 
scroll wrap such that the tip seal will again be supported when located 
over outlet port 96 as fully discussed below. 
In the FIG. 6 embodiment, the inner end 155 of involute spiral wrap 93 of 
driven scroll 91 includes an axially extending bore 190 having a first 
diametric portion 192 extending through wrap support plate 92 and a 
second, reduced diametric portion 194 extending entirely through involute 
spiral wrap 93. A screw 196 extends through bore 190 and is threadably 
secured to an inner end of tip seal 167. 
In the FIG. 7 embodiment, the inner end of tip seal 167 is formed with a 
radially extending slot 200 through which a pin 202 extends. Pin 202 is 
located within a transverse bore (not shown) formed in involute spiral 
wrap 93. By this construction, tip seal 167 is axially secured to involute 
spiral wrap 93 but is permitted, due to slot 200, to expand and contract 
radially a predetermined amount. Of course, involute spiral wrap 93 could, 
alternatively, be formed with the slot and pin 202 secured within a bore 
in tip seal 167. 
In the FIG. 8 embodiment, inner end 155 of involute spiral wrap 93 is 
formed with an integral, radially extending shelf member 210 at the inner 
end of involute recess 164. The inner end of tip seal 167 is formed with a 
notch such that a reduced thickness portion 215 extends above shelf member 
210. Depending upon the axial clearance between shelf member 210 and the 
notch in tip seal 167, a predetermined amount of radial expansion and 
contraction of tip seal 167 is also permitted in this embodiment. 
Although described with respect to particular embodiments of the invention, 
it is to be understood that the description was for illustrative purposes 
only and it is not intended that the invention be limited to the 
particular configurations described. In general, various changes, and/or 
modifications can be made without departing from the spirit of the 
invention as defined by the following claims.