Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
IMPROVED OIL FREE SCROLL VACUUM PUMP
Document Type and Number:
WIPO Patent Application WO/1995/021329
Kind Code:
A1
Abstract:
The invention relates specifically to a simplified and subsequently improved method to produce a scroll type vacuum pump that is capable of achieving vacuum pressures below 1 torr through the placement of at least one dynamic orbital vacuum seal (32) between the two scroll halves (22 and 23) at the outside diameter of the scroll spirals to prevent atmospheric gas from entering. Prior to this invention, in order to achieve vacuum pressures less than 1 torr with a scroll pump it has been necessary to either seal the two scroll halves with a large diameter metal bellows (4) that accommodates the required orbital travel or to locate the orbiting scroll plate or plates and the components that convert the rotary drive to the required orbital motion inside the vacuum space with a dynamic vacuum seal (14) on the rotary drive shaft (17). Both ot these designs have been expensive to produce, limiting the application of scroll technology in the vacuum industry. The invention further relates to a method to produce an equally economical scroll type vacuum pump (Fig. 16) with a dynamic orbital vacuum seal that is capable of achieving pressures below .01 torr.

More Like This:
Inventors:
GRENCI CHARLES (US)
CLAYTON R DALLAS (US)
Application Number:
PCT/US1995/001401
Publication Date:
August 10, 1995
Filing Date:
February 01, 1995
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GRENCI CHARLES (US)
CLAYTON R DALLAS (US)
International Classes:
F01C17/00; F04C18/02; F04C23/00; F04C27/00; F04C29/00; F16J15/32; (IPC1-7): F04C18/04; F04C27/00; F16J15/02; F16J15/48
Foreign References:
US3994633A1976-11-30
JPH02275084A1990-11-09
GB566214A1944-12-19
US4718836A1988-01-12
US4883413A1989-11-28
Download PDF:
Claims:
WHAT WE CLAIM IS:CLAIM
1. In an oilfree, scroll vacuumpump comprising a first platehalf having a first, interior, spiral pathway, and a second platehalf having a second, interior, spiral pathway in operative engagement with said first, spiral pathway, at least one of said first platehalf and said second platehalf being capable of orbital motion; an inlet, and an exhaust, whereby, during the orbital motion of said at least one platehalf, a volume of gas is compressed along said spiral pathways until it is exhausted at said exhaust; said first platehalf having a first, annular surfaceface, and said second platehalf having a second, annular surface face for contact against said first, annular surfaceface of said first platehalf, wherein the improvement comprises: said first platehalf having an annular groove formed in said first, annular surfaceface, and vacuumseal means in said annular groove for creating a vacuum seal to prevent ambient air entering into said spiral pathways, said vacuum seal means in said annular groove comprising an annular, elastomeric, sealing member; said annular, elastomeric, sealing member comprising a cutout formed therein, said cutout being bounded by a first, radiallyexterior, narrow lipsection which is contact with a section of said annular groove to form a static seal, and a second, narrow lipsection; whereby the pressure differential between the interior and exterior of the pump loads said sealing member against said second, annular surfaceface.
2. CLAIM.
3. The oilfree, scroll vacuumpump according to claim 1, wherein said first platehalf is a fixed platehalf, and said second platehalf is an orbital platehalf.
4. CLAIM.
5. The oilfree, scroll vacuumpump according to claim 1, wherein said cutout is triangular in shape; said first section tapering to a narrowest portion in a direction from the interior of said groove toward said second, annular surfaceface of said second platehalf.
6. CLAIM.
7. The oilfree, scroll vacuumpump according to claim 1, wherein said cutout is located in said groove closer to said second, annular surfaceface of said second platehalf.
8. CLAIM.
9. The oilfree, scroll vacuumpump according to claim 1, wherein said sealing member is a onepiece, elasto¬ meric ring; said second section tapering to a narrowest portion opposite said second, annular surfaceface of said second platehalf in a direction from the radially innermost annular surface forming said groove toward the radiallyoutermost annular surface forming said groove.
10. CLAIM.
11. The oilfree, scroll vacuumpump according to claim 1, wherein said sealing member comprises a first, outer, annular ring, and a second, inner, annular ring; said first annular ring being in facetoface contact wtih said second annular surfaceface; said cutout being formed in said second annular ring; said cutout being located in said second annular ring groove closer to said first annular ring, whereby said second annular ring loads said first annular ring against said second annular surfaceface by means of said cutout.
12. CLAIM.
13. The oilfree, scroll vacuumpump according to claim 6, wherein said second section tapers to a narrowest portion opposite the interior surfaceface of said first annular ring in a direction from the radiallyinnermost annular surface forming said groove toward the radially outermost annular surface forming said groove.
14. CLAIM.
15. The oilfree, scroll vacuumpump according to claim 7, wherein said cutout is triangular in shape.
16. CLAIM.
17. The oilfree, scroll vacuumpump according to claim 7, wherein said cutout is threesided, and comprises a third interior section against the interior surface of said groove, said third section tapering to a narrowest portion in a direction from the radiallyinnermost annular surface forming said groove toward the radiallyoutermost annular surface forming said groove.
18. CLAIM.
19. In an oilfree, scroll vacuumpump comprising a first platehalf having a first, interior, spiral pathway, and a second platehalf having a second, interior, spiral pathway in operative engagement with said first, spiral pathway, at least one of said first platehalf and said second platehalf being capable of orbital motion; an inlet, and an exhaust, whereby, during the orbital motion of said at least one platehalf, a volume of gas is compressed along said spiral pathways until it is exhausted at said exhaust; said first platehalf having a first, annular surfaceface, and said second platehalf having a second, annular surface face for contact against said first, annular surfaceface of said first platehalf, wherein the improvement comprises: said first platehalf having an annular groove formed in said first, annular surfaceface, and vacuumseal means in said annular groove for creating a vacuum seal to prevent ambient air entering into said spiral pathways, said vacuum seal means in said annular groove comprising an annular, elastomeric, sealing member; said annular, elastomeric, sealing member comprising a first, outer annular ring having an outer, dynamic sealing contactsurface for contact against second, annular surface face of said second platehalf, and an inner contactsurface in an interior portion of said groove; a second, interior annular ring comprising an interior tapering surface that tapers to a narrowest portion opposite said inner contactsurface of said first annular ring in a direction from the radiallyinnermost annular surface forming said groove toward the radiallyoutermost annular surface forming said groove, and a peripheral surfacesection in con¬ tact with, and secured to, a wall section of said groove for providing a static sealing surface. CLAIM 11 The oilfree, scroll vacuumpump according to claim 10, wherein said groove comprises a first exterior portion in which are mounted said first and second annular rings, and a second interior portion having lateral cross section, measured from the outer annular surface to the inner annular surface thereof less than that of said first exterior portion in order to form an inner, stepped, annular surface to which is fixedly secured a radiallyinward section of said interior tapering surface of said second annular ring for providing said static seal. CLAIM 12 In an oilfree, scroll vacuumpump comprising a first platehalf having a first, interior, spiral pathway, and a second platehalf having a second, interior, spiral pathway in operative engagement with said first, spiral pathway, at least one of said first platehalf and said second platehalf being capable of orbital motion; an inlet at the center of the pump, and an exhaust at the outer por¬ tion of the pump, whereby, during the orbital motion of said at least one platehalf, a volume of gas is compressed along said spiral pathways until it is exhausted at said exhaust; said first platehalf having a first, annular surfaceface, and said second platehalf having a second, annular surface face for contact against said first, annular surfaceface of said first platehalf, wherein the improvement comprises: said first platehalf having an annular groove formed in said first, annular surfaceface, and vacuumseal means in said annular groove for creating a vacuum seal, said vacuumseal means in said annular groove comprising an annu¬ lar, elastomeric, sealing member; and a vacuumsupport pump operatively coupled to said outer exhaust of said pump, whereby the vacuumpressures at said outer exhaust may be more greatly reduced, and whereby said pump operates more efficiently and quieter.
Description:
IMPROVED OIL FREE SCROLL VACUUM PUMP

BACKGROUND OP THE INVENTION

Field of the Invention (Technical Field)

The invention relates specifically to a simplified and subsequently improved method to produce an oil free scroll type vacuum pump which is capable of achieving vacuum pres¬ sures below 1 torr through the application of the invention dynamic orbital vacuum seal between the opposing scroll halves in order to prevent atmospheric pressure from entering into the pump. Background Art

Scroll type vacuum pumps are pumps that consist of two plate halves which have involute archimedes spiral walls formed into each plate half. The plates are placed together with the spirals interleaved. An orbiting motion is employed to either or both plates in order to trap a volume of gas from the outside diameter of the scroll spiral walls and then compress the gas along the spiral walls in a crescent shaped chamber that becomes smaller until the gas is expelled to atmosphere at the outlet port located a the center of the spiral walls. In order to achieve vacuum pressures less than 1 torr, it has previously been necessary to seal the orbiting outside diameter mating joint between the two scroll halves with a large diameter bellows. This bellows is welded to each scroll half in a configuration that can accommodate the required orbital travel and prevent atmospheric pressure from

entering the pump. Another method locates one or both scroll plates, along with the components that convert the rotary drive to the required orbital motion, inside the vacuum space. Both of these designs are more expensive to produce than the invention improved scroll vacuum pump which utilizes the invention dynamic orbital vacuum seal to seal the orbit¬ ing outside diameter mating joint between the scroll halves. This expense has limited the application of scroll technology in the vacuum industry to special applications. Another prior art method uses reverse orbital rotation to pump gas from the center of the scroll spirals to the outside diameter eliminating the requirement for the invention dynamic orbital vacuum seal against atmosphere. It has been discovered that this reversed operation method can be significantly improved with a second source of vacuum and application of the inven¬ tion dynamic orbital vacuum seal against atmosphere.

SUMMARY OF THE INVENTION We have found that an economical oil free scroll vacuum pump capable of vacuum pressures below 1 torr can be produced utilizing our discovery that it is possible to create a dynamic orbital vacuum seal at the orbiting outside diameter mating joint between the two scroll halves as one or both halves travel in the orbital motion required to trap a volume of gas at the outside diameter of the scroll spiral walls and compress it along the spiral walls in a crescent shaped chamber which becomes smaller until the gas is expelled at the outlet port located at the center of the spiral walls. This discovery eliminates the requirement of an expensive

metal bellows seal between the scroll halves as a seal against atmosphere or the complex placement of the orbiting scroll components inside the process vacuum space. These savings make our improved oil free scroll vacuum pump de¬ signed economical to produce with greater potential applica¬ tion within the vacuum industry. We have further discovered that it is possible to create an economical scroll vacuum pump capable of vacuum pressure is below .01 torr through the addition of a second vacuum source to the invention scroll vacuum pump with dynamic orbital vacuum seal against at¬ mosphere where said scroll pump is operated with reverse orbital rotation to pump gas from the center of the scroll spiral to the outside diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a part of the specification, illustrate the pre¬ ferred embodiment of the invention and, subsequently, are not to be construed as limiting the invention.

Fig. 1 is a cross-sectional plan view of a prior art, bellows type scroll vacuum pump.

Fig. 2 is a cross-sectional elevation side view of a prior art, enclosed orbiting scroll type vacuum pump.

Fig. 3 is a side elevation view of the invention oil free scroll vacuum pump.

Fig. 4 is a cross-sectional front elevation view taken on line 4-4 of Fig. 3 that shows the orientation of the interleaved scroll spiral walls when the primary gas volume is trapped in the primary crescent shaped chamber that is

formed when the example orbiting scroll half is in the left most position of its orbital travel.

Fig. 5 is a moved position of Fig. 4 that shows the orientation of the interleaved scroll spiral walls when the primary trapped gas volume has been compressed and moved along the spiral walls from the right side of the spiral walls outside diameter to the bottom spiral outside diameter when the example orbiting scroll half is in the top most position of its orbital travel.

Fig. 6 is a moved position of Fig. 4 that shows the orientation of the interleaved scroll spiral walls when the primary trapped gas volume has been further compressed by moving further into the scroll spiral and a secondary gas volume is trapped in the secondary crescent shaped chamber which is now opposite the primary crescent shaped compression chamber when the example orbiting scroll half is in the right most position of its orbital travel.

Fig. 7 is a cross-sectional front elevation view taken on line 7-7 of Fig. 3 that shows the orientation of the interleaved scroll spiral walls when both the primary and secondary gas volumes are trapped in the primary and second¬ ary crescent shaped chambers have been further compressed by moving further into the scroll spiral towards the center of the scroll spiral walls where both the primary and secondary gas volumes will be expelled through the scroll pump outlet.

Fig. 8 is a cross-sectional side elevation view taken on line 8-8 of Fig. 7 with an enlarged view of the invention preferred dynamic orbital vacuum seal configuration.

Fig. 9 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate dynamic vacuum seal configuration.

Fig. 10 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate delta pressure operated dynamic/static vacuum seal configuration.

Fig. 11 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate delta pressure operated dynamic orbital vacuum seal configuration.

Fig. 12 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate compressed elastomer dynamic orbital vacuum seal configuration.

Fig. 13 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate delta pressure operated dynamic orbital vacuum seal configuration.

Fig. 14 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an

invention alternate delta pressure operated dynamic orbital vacuum seal configuration.

Fig. 15 is the cross-sectional side elevation view with enlarged view of Fig. 8 where the invention preferred dynamic orbital vacuum seal configuration has been replaced by an invention alternate delta pressure operated dynamic orbital vacuum seal configuration.

Fig. 16 is a schematic diagram of an invention oil free scroll vacuum pump configuration that is capable of vacuum pressures below .01 torr through the addition of a second vacuum source to the invention scroll vacuum pump with dyna¬ mic orbital vacuum seal against atmosphere where said scroll vacuum pump is operated with reverse orbital rotation to pump gas from the center of the scroll spiral to the outside diameter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Fig. 1, a prior art bellows type scroll vacuum pump 1 is shown with a bellows type fixed scroll half 2 and a bellows type orbiting scroll half 3. This type of scroll pump incorporates a nutating bellows 4 with a welded bellows connection to fixed scroll half 5 and a welded bel¬ lows connection to orbiting scroll half 6 as a vacuum seal against atmospheric pressure. The bellows is of sufficient length to reliably accommodate the orbital motion that is imparted to the bellows type orbiting scroll half 3 by a bellows type rotary drive shaft 7 connected to a bellows type orbital drive crank shaft 8. The bellows insures that the bellows type scroll pump inlet 9 is the sole point of entry

for gas that will be compressed by the pump and expelled through the bellows type scroll pump exhaust 10.

Referring to Fig. 2, a prior art enclosed orbiting scroll type vacuum pump 11 is shown. This type of scroll pump has an enclosed type fixed scroll 12 that incorporates a process vacuum orbiting scroll assembly vacuum cover 18 that encases the enclosed type orbiting scroll 13, the enclosed type orbital drive crank shaft 15, the idler crank bearing assembly 16 and other associated mechanisms that convert the rotary motion of the enclosed type rotary drive shaft 17 to the orbital motion that scroll type pump require to compress and expel gas. A dynamic rotary vacuum seal 14 and several static seals insure that the sole point of entry for gas into the put is through the enclosed type scroll pump process vacuum inlet 19. The gas is then compressed and expelled through the enclosed type scroll pump outlet 20.

Referring to Fig. 3, an improved oil free scroll vacuum pump 21 is shown with a fixed scroll half 22, an orbiting scroll half 23, a scroll pump inlet location 24, and a scroll pump exhaust location 25 to illustrate the major components of the invention.

Referring to Fig. 4, a cross-section of the improved oil free scroll vacuum pump 21 in Fig. 3 is shown with the orbit¬ ing scroll half 23 in the left most position of its orbital travel in relation to the fixed scroll half 22. The fixed scroll half 22 has been cross sectioned to show the location of a dynamic orbital vacuum seal 32 that is positioned within a dynamic orbital vacuum seal groove 26 and to show the orien-

tation of the interleaved fixed scroll half 22 spiral walls and the orbiting scroll half 23 spiral walls when the first volume of gas is isolated from the scroll pump inlet location 24 in the primary crescent shaped gas compression chamber 27. The volume of gas will be compressed along the spiral walls in the primary crescent shaped gas compression chamber 27 that becomes smaller with each orbital rotation of the orbit¬ ing scroll half 23 until the gas volume is expelled through the scroll pump exhaust location 25 at the center of the fixed scroll half 22 spiral.

Referring to Fig. 5, the cross section of the improved oil free scroll vacuum pump 21 in Fig. 3 is shown with the orbiting scroll half 23 moved to the top most position of its orbital travel in relation to the fixed scroll half 22. The orientation of the interleaved fixed scroll half 22 spiral walls and the orbiting scroll half 23 spiral walls in this position have further compressed the gas that is trapped in the primary crescent shaped gas compression chamber 27 to¬ wards the scroll pump exhaust location 25 at the center of the fixed scroll half 22 spiral where the gas volume will be expelled. The orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23 does not travel across the boundary formed by the outside diameter of the dynamic orbital vacuum seal groove 26 which allows the dyna¬ mic orbital vacuum seal 32 to maintain contact with the orbiting scroll half vacuum seal contact surface 29 to prev¬ ent atmospheric pressure from entering the improved oil free scroll vacuum pump 21.

Referring to Fig. 6, the cross section of the improved oil free scroll vacuum pump 21 in Fig. 3 is shown with the orbiting scroll half 23 moved to the right most position of its orbital travel in relation to the fixed scroll half 22. The orientation of the interleaved fixed scroll half 22 spiral walls and the orbiting scroll half 23 spiral walls in this position have further compressed the gas that is trapped in the primary crescent shaped gas compression chamber 27 and isolated a second volume of gas from the scroll pump inlet location 24 in a secondary crescent shaped has compression chamber 28 that will be compressed with the primary crescent shaped gas compression chamber 27 towards the scroll pump exhaust location 25 at the center of the fixed scroll half 22 spiral where both gas volumes will be expelled. The orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23 does not travel across the boundary formed by the outside diameter of the dynamic orbital vacuum seal groove 26 which allows the dynamic orbital vacuum seal 32 to maintain contact with the orbiting scroll half vacuum seal contact surface 29 to prevent atmospheric pressure from entering the scroll pump inlet location 24, the secondary crescent shaped gas compression chamber 28 or the primary crescent shaped gas compression chamber 27. This allows the improved oil free scroll vacuum pump 21 to achieve vacuum pressures as low as 5xl0 "3 torr.

Referring to Fig. 7, the cross section of the improved oil free scroll vacuum pump 21 in Fig. 3 is shown with the

orbiting scroll half 23 moved to the bottom most portion of its orbital travel in relation to the fixed scroll half 22. The orientation of the interleaved fixed scroll half 22 spiral walls and the orbiting scroll half 23 spiral walls in this position have further compressed the gas that is trapped in the secondary crescent shaped gas compression chamber 28 towards the scroll pump exhaust location 25 at the center of the fixed scroll half 22 spiral where both gas volumes will be expelled. Again, the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23 does not travel across the boundary formed by the outside diameter of the dynamic orbital vacuum seal groove 26 which allows the dynamic orbital vacuum seal 32 to maintain contact with the orbiting scroll half vacuum seal contact surface 29 to prev¬ ent atmospheric pressure from entering the improved oil free scroll vacuum pump 21.

Referring to Fig. 8, a cross section of the improved oil free scroll vacuum pump 21 in Fig. 7 is shown with the orbit¬ ing scroll half 23 in the bottom most position. The enlarged detail shows the configuration of the preferred invention dynamic orbital vacuum seal 32 and the elastomer seal loading bladder 33. In this configuration, the dynamic orbital vacuum seal face surface 30 is loaded against the orbiting scroll half vacuum seal contact surface 29 by the pneumatic pressure inside the elastomer seal loading bladder 33 that exerts force against the seal loading bladder inside surface 34 which in turn causes the seal loading bladder outside surface 35 to exert force against the dynamic orbital vacuum

seal back surface 31 and the dynamic orbital vacuum seal groove 26. The force inside the elastomer seal loading bladder 33 creates a reliable static vacuum seal between the dynamic orbital vacuum seal between the dynamic orbital vacuum seal face surface 30 and the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23. We have found that the orbital vacuum sealing perfor¬ mance of the dynamic orbital vacuum seal 32 is related to the type of material used to construct said seal. "GYLON BLUE" from Garlock, Inc. is the preferred material for the purpose of creasing the vacuum seal at the time of this application. It is understood that other material may prove adequate or superior for the purpose. The preferred material for con¬ struction of the elastomer seal loading bladder 33 is cur¬ rently fluorocarbon elastomer. Because the bladder is pneumatically actuated, the type of elastomer used for this component relates more to the longevity of said bladder and less to its ability to load the dynamic seal and create the static seal. We believe that the seal configuration in this figure will improve the performance of the invention scroll pump when the pump is used as a gas compressor instead of a vacuum pump.

Referring to Fig. 9, a cross section of the improved oil free scroll vacuum pump 21 in Fig. 7 is shown with the orbit¬ ing scroll half 23 in the bottom most position. The enlarged detail shows the configuration of the alternate invention dynamic orbital vacuum seal 32 and the elastomer seal loading ring 37. In this configuration, the dynamic orbital vacuum

seal face surface 30 is leaded against the orbiting scroll half vacuum seal contact surface 29 by deformation of the elastomer seal loading ring 37. The deformation exerts force against the dynamic orbital vacuum seal back surface 31 and the dynamic orbital vacuum seal groove 26. The force creates a reliable static vacuum seal groove 26 and an effective dynamic vacuum seal between the dynamic orbital vacuum seal face surface 30 and the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23. We have found that the orbital vacuum sealing performance of the dynamic orbital vacuum seal 32 is related to the type of material used to construct the seal. "GYLONG BLUE" from Garlock Inc. is the preferred material for the purpose of creating the vacuum seal at the time of this application. The preferred material for construction of the elastomer seal loading ring 37 is currently 70 durometer fluorocarbon elastomer. Because the elastomer is not pneumatically actu¬ ated, the type of elastomer used for this component relates to both the longevity of the ring and its ability to load the dynamic seal and create the static seal. It is understood that other material may prove itself to be adequate or supe¬ rior. We believe that the seal configuration in this figure will improve the performance of the invention scroll pump when the pump is used as a gas compressor instead of a vacuum pump.

Referring to Fig. 10 a delta pressure operated dynamic/static orbital vacuum seal 38 configuration is shown. In this configuration the delta pressure operated

dynamic/static orbital vacuum seal dynamic face surface 39 and the delta pressure operated dynamic/static orbital vacuum seal static face surface 42 are located against their op¬ posite surfaces by difference in pressure between the interi¬ or of the pump and the exterior. The delta pressure exerts force against the delta pressure operated dynamic/static orbital vacuum seal dynamic back surface 40 and the delta pressure operated dynamic/static orbital vacuum seal static back surface 41.

Referring to Fig. 11 a delta pressure operated dynamic orbital vacuum seal 43 configuration is shown. In this configuration the delta pressure operated dynamic orbital vacuum seal dynamic face surface 44 is loaded against the opposite surface by difference in pressure between the in¬ terior of the pump and the exterior. The delta pressure exerts force against the delta pressure operated dynamic orbital vacuum seal dynamic back surface 45. In this seal configuration a status seal between the the seal and the host scroll half is created with a delta pressure operated dynamic orbital vacuum seal bond to host scroll half 46.

Referring to Fig. 12 a compressed elastomer dynamic orbital vacuum seal 47 configuration is shown. In this configuration the compression of the seal loads the com¬ pressed elastomer dynamic orbital vacuum seal face surface 48 to establish the dynamic vacuum seal and creates the static seal contact with the seal groove. It should be noted that the single seal configurations rely on special elastomer seal material that incorporates special material characteristics

that give it the ability to withstand the surface speed requirements of the dynamic orbital seal requirement and flexibility to also maintain a static seal with the host scroll half.

Referring to Fig. 13 a cross section of the improved oil free scroll vacuum pump 21 in Fig. 7 is shown with the orbit¬ ing scroll half 23 in the bottom most portion. The enlarged detail shows the configuration of the alternate invention dynamic orbital vacuum seal 32 and a delta pressure operated dynamic/static orbital vacuum seal 38. In this configura¬ tion, the dynamic orbital vacuum seal face surface 30 is loaded against the orbiting scroll half vacuum seal contact surface 29 by pressure deformation of the delta pressure operated dynamic/static orbital vacuum seal 38. The deforma¬ tion exerts force against the dynamic orbital vacuum seal back surface 31 and the dynamic orbital vacuum seal groove 26. The force creates a reliable static seal with the dyna¬ mic orbital vacuum seal groove 26 and an effective dynamic vacuum seal between the dynamic orbital vacuum seal face surface 30 and the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23. In this configu¬ ration the delta pressure operated dynamic/static orbital vacuum seal dynamic face seal 39 and the delta pressure operated dynamic/status orbital vacuum seal static face surface 42 are loaded against their opposite surfaces by difference in pressure between the interior of the pump and the exterior. The delta pressure exerts force against the delta pressure operated dynamic/static orbital vacuum seal

dynamic back surface 40 and the delta pressure operated dynamic/static orbital vacuum seal static back surface 41.

Referring to Fig. 14 a cross section of the improved oil free scroll vacuum pump 21 in Fig. 7 is shown with the orbit¬ ing scroll half 23 in the bottom most position. The enlarged detail shows the configuration of the alternate invention dynamic orbital vacuum seal 32 and a delta pressure operated dynamic/static orbital vacuum seal 38. In this configuration the dynamic orbital vacuum seal face surface 30 is loaded against the orbiting scroll half vacuum seal contact surface 29 by pressure deformation of the delta pressure operated dynamic orbital vacuum seal 43. The deformation exerts force against the dynamic orbital vacuum seal back surface 31. The force creates an effective dynamic vacuum seal between the dynamic orbital vacuum seal face surface 30 and the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23. In this configuration the delta pressure operated dynamic orbital vacuum seal 43 bias loads the dyna¬ mic orbital vacuum seal back surface 31 through difference in pressure between the interior of the pump and the exterior. The delta pressure exerts force against he delta pressure operated dynamic orbital vacuum seal dynamic back surface 45. In this seal configuration a static seal between said seal and the host scroll half is created with a delta pressure operated dynamic orbital vacuum seal bond to host scroll half 46.

Referring to Fig. 15 a cross section of the improved oil free scroll vacuum pump 21 in Fig. 7 is shown with the orbit-

ESHEET RULE26)

ing scroll half 23 in the bottom most position. The enlarged detail shows the configuration of the alternate invention dynamic orbital vacuum seal 32 and an alternate delta pres¬ sure operated dynamic/static orbital vacuum seal 38 to il¬ lustrated that different geometry's can be used to create the dynamic/static seal. In this configuration, the dynamic orbital vacuum seal face surface 30 is loaded against the orbiting scroll half vacuum seal contact surface 29 by pres¬ sure deformation of the delta pressure operated dynamic/static orbital vacuum seal 38. The deformation exerts force against the dynamic orbital vacuum seal back surface 31 and the dynamic orbital vacuum seal groove 26. The force creates a reliable static seal with the dynamic orbital vacuum seal groove 26 and an effective dynamic vacuum seal between the dynamic orbital vacuum seal face surface 30 and the orbiting scroll half vacuum seal contact surface 29 of the orbiting scroll half 23. In this configuration the delta pressure operated dynamic/static orbital vacuum seal dynamic face surface 39 and the delta pressure operated dynamic/static orbital vacuum seal static face surface 42 are loaded against their opposite surfaces by difference in pressure between the interior of the pump and the exterior. The delta pressure exerts force against the delta pressure operated dynamic/static orbital vacuum seal dynamic back surface 40 and the delta pressure operated dynamic/static orbital vacuum seal static back surface 41.

Referring to Fig. 16 a schematic diagram of an invention oil free scroll vacuum pump configuration that is capable of

vacuum pressures below .01 torr is shown. In this configura¬ tion a second vacuum source 63 is added to an invention scroll vacuum pump with dynamic orbital vacuum seal against atmosphere 21 that employs a reverse orbital operation, to evacuate the scroll outside diameter exhaust port 61. The reverse operation creates reduced pumping speed but provides less leakage between crescent shaped scroll chamber and isolates leakage of the dynamic orbital vacuum seal 62 as the pump operates. The scroll chamber leakage reduction is due to an expansion in the size of the crescent shaped chambers as the pump operates in reverse orbital rotation as opposed to a reduction of the crescent chamber size and compression of gas in the normal rotation configuration. Expanding the size of these chambers as they move along the scroll spiral toward the exhaust minimizes the delta pressure between chambers and creates a reduction in inter chamber leakage. Isolation of the lead associated with the dynamic orbital vacuum seal 62 is related to the seals relationship to the base vacuum at the inlet of the pump. In normal rotation operation which provides maximum pumping speed from the outside of the scroll spiral to the inside, this seal is the only protection against the entry of atmospheric gas into the base inlet vacuum. In reverse operation this seal is only required to prevent atmospheric gas from entering into the exhaust region of the pump and there are multiple scroll chamber stages between the exhaust space sealed by the dyna¬ mic orbital vacuum seal and the base vacuum pressure at the center of the scroll spiral. While this type of reverse

operation scroll pump has been previously disclosed to elim¬ inate the need for a sealed space at the exhaust out diameter region of the scroll spiral, we have discovered that it is possible to significantly reduce the amount of power required to operate this type of pump at its base vacuum pressure, and significantly reduce the base vacuum pressure of this type of pump if a vacuum is maintained in the exhaust region. Though the application of the invention dynamic orbital vacuum seal 62, and a second vacuum source 63, we have reduced the power consumption of a 5 cfm reverse operation scroll pump, at base vacuum pressure, from 14 amps of 110 volt current to 7.5 amps of 110 volt current, and reduced the base pressure from .01 torr to .00009 torr. This was accomplished with a very economical secondary vacuum source with a base pressure of 60 torr and a pumping speed of .5 cfm. If a slow pumping speed is used to evacuate said exhaust region and check valve bypass exhaust 64 can be used to prevent pressurization of the second vacuum source 63 and the scroll outside diameter exhaust port 61.