WO1999014513A1

WO1999014513A1 - Hemispherical seal for a universal joint

Info

Publication number: WO1999014513A1
Application number: PCT/US1998/016911
Authority: WO
Inventors: Steven L. Cunningham
Original assignee: Robbins & Myers, Inc.
Priority date: 1997-09-15
Filing date: 1998-08-14
Publication date: 1999-03-25

Abstract

The present invention is a seal mechanism (36) for a universal joint, where the universal joint is coupled to at least one pivotable or angle, rotatable shaft such as a connecting rod (16) in the drive mechanism of a progressing cavity pump. The seal mechanism comprises a housing (32) for retaining the universal joint therein, where the housing includes a substantially dome-shaped outer wall (38) and an aperture (40) extending therethrough for receiving the shaft; and a substantially annular seal support component (42), encircling the shaft, and mounted adjacent the dome-shaped outer wall. The seal support component includes a substantially annular sealing ring (44), encircling the aperture and abutting a curved (inner or outer) surface (50) of the outer wall. Preferably, the seal support component is slidingly mounted to the shaft and is biased towards the curved surface of the outer wall such that the sealing ring is pressed against the curved surface of the outer wall so as to provide a seal between the sealing ring and the outer wall. The seal support component also preferably includes an O-ring component (52) extending therefrom and abutting the shaft so as to provide a seal between the seal support and the shaft. Furthermore, the curved surface of the outer wall has a radius whose center is substantially at the pivot point of the universal joint, the pivot point being the approximate point about which angular movement of the shaft is centered.

Description

HEMISPHERICAL SEAL FOR A UNIVERSAL JOINT

BACKGROUND

The present invention relates to seals for universal joints and, in particular, to a seal for a gear ball joint utilized in a driving mechanism for a progressing cavity pump.

A typical helical gear pump, or progressing cavity pump, comprises an externally threaded rotor co-acting with an internally threaded stator, where the stator has one more helical lead or start than the rotor. Pumps of this general type are typically built with a rigid metallic rotor and a flexible, resilient stator. The rotor has an effective diameter that is slightly larger than the effective diameter of the stator bore, such that when the rotor is present within the stator bore, a compressive fit between the rotor and stator is formed. This compressive fit results in seal lines where the rotor and stator contact, the seal lines defining or sealing off definite cavities bounded by the rotor and stator surfaces. The rotation of the rotor within the stator bore causes these cavities to progress from the suction end of the pump to the discharge end of the pump, thereby pumping the product from the suction end to discharge end.

The rotor of a progressing cavity pump is typically driven by a drive mechanism that consists of a drive shaft, a pair of universal or gear-ball joints and a connecting rod. A first gear-ball joint is coupled to the rotating drive shaft while the second gear ball joint is coupled to the rotor of the progressing cavity pump. The two gear-ball joints are interconnected by the connecting rod. Because, the centerline of the rotor orbits as the rotor turns within the stator bore, the connecting rod must be able to pivot between the two gear-ball joints as it is being rotatably driven by the first gear-ball joint and as it is driving the second gear-ball joint, and in turn, the rotor. The gear-ball joints are therefore types of universal joints that are suited to allow simultaneous rotation and pivoting of the connecting rod.

U.S. Patent No. 4,639,200 to Baumgardner, et al. discloses a seal for a gear-ball joint that includes a flexible seal member having a flange portion with five sealing surfaces for sealing against mating parts of the gear ball joint assembly. While such a seal is advantageous under typical operating conditions, it may be desirable to include a secondary- seal for the gear-ball joint in case this or a similar seal tears or rips. A secondary seal may also be provided to ensure that grease from the gear ball joint does not enter the product being pumped. For example, if a progressing cavity pump is pumping titanium dioxide for paper products, or is pumping paint products, contamination of the product being pumped with grease from the gear ball joint would likely ruin much of the product being pumped.

Additionally, under extreme operating conditions, grease in the gear joint may at times form gas that causes the Baumgardner seal to deform or tear in such "de-gas" conditions. Therefore, it may be desirable to replace the Baumgardner or similar seal with a universal joint seal that would not fail under such de-gas conditions.

There may also be operating conditions when the Baumgardner or similar seal does not provide a sufficient pressure capability. Under such conditions, therefore, it would be desirable to provide a universal joint seal with greater pressure capability.

SUMMARY

The present invention is a seal mechanism for a universal joint, where the universal joint is coupled to at least one pivotable or angled shaft such as a connecting rod in the drive mechanism of a progressing cavity pump. The seal mechanism comprises a housing for retaining the universal joint therein, where the housing includes a substantially dome-shaped outer wall and an aperture extending therethrough for receiving the shaft; and a substantially annular seal support component, encircling the shaft, and mounted adjacent the dome-shaped outer wall. The seal support component includes a substantially annular sealing ring, encircling the aperture and abutting a curved (inner or outer) surface of the outer wall. Preferably, the seal support component is slidingly mounted to the shaft and is biased towards the curved surface of the outer wall such that the sealing ring is urged towards, and is pressed against the curved surface of the outer wall so as to provide a seal between the sealing ring and the outer wall. The seal support component preferably includes an O-ring component extending therefrom and abutting the shaft so as to provide a seal between the seal support and the shaft. Furthermore, the curved surface of the outer wall has a radius whose center is substantially at the pivot point of the universal joint, the pivot point being the approximate point about which angular movement of the shaft is centered. It is, therefore, an object of the present invention to provide a universal joint seal mechanism that provides secondary seal protection to universal gear joints in progressing cavity pumps. It is further an object of the present invention to provide a universal joint seal mechanism that provides increased pressure capability than typical universal joint seals used in progressing cavity pumps and the like. Finally, it is an object of the present invention to provide a universal joint seal that allows the release of pressurized gas from within the universal joint housing when de-gas occurs under extreme operating conditions. These and other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevational view of the driving end of a progressing cavity pump;

Fig. 2 is a cross-sectional, side elevational view of a universal gear-ball joint and the universal joint seal mechanism of the present invention;

Fig. 3 is a cross-sectional view of an alternate embodiment of the universal seal mechanism of the present invention;

Fig. 4 is a cross-sectional view of another alternate embodiment of the universal seal mechanism of the present invention; and

Fig. 5 is a cross-sectional view of another alternate embodiment of the universal seal mechanism of the present invention.

DETAILED DESCRIPTION

As shown in Fig. 1, a progressing cavity pump 10 includes a rotor 12, rotatably driven within a stator 14 by a connecting rod 16 coupled between a pair of gear-ball type universal joints 18, 20. As known to those of ordinary skill in the art, the rotor 12 is typically a single lead helical screw and the stator is typically in the form of a double lead helical nut having an internal bore extending longitudinally therethrough. Accordingly, as the rotor 12 turns inside the stator bore, cavities are formed between the rotor and stator which progress from the suction end 21 of the rotor/stator assembly to the discharge end (not shown) of the rotor/stator assembly. In one revolution of the rotor, two separate sets of cavities are formed, one set of cavities opening at exactly the same rate as the second set of cavities is closing. This results in a predictable, pulsation-less flow. As one of ordinary skill in the art will recognize, the present invention will also be for use with more complex progressing cavity pumps such as 9:10 designs, where the rotor has nine leads and the stator has ten leads. As is commonly known in the art, many combinations are possible so long as the stator has one additional lead than the rotor. For additional information on the operation and construction of progressing cavity pumps, reference can be made to U.S. No. 2,512,764 and U.S. No. 2,612,845.

Referring again to Fig. 1 , one of the gear-ball joints 20 is coupled to a rotating drive shaft 23 while the other gear ball joint 18 is coupled to the rotor 12. The two gear-ball joints 18, 20 are interconnected by the connecting rod 16. Because, the axial centerline of the rotor moves or orbits as the rotor turns within the stator bore, the connecting rod 16 must be able to pivot between the two gear-ball joints 18, 20 as it is being rotatably driven by gear-ball joint 20 and as it is driving gear-ball joint 18, and in turn, the rotor 12. The gear-ball joints 18, 20 are therefore types of universal joints that are suited to allow simultaneous rotation and pivoting of the connecting rod 16.

The progressing cavity pump shown in Fig. 1 includes a suction port 22 for receiving the product to be pumped through the rotor/stator assembly. Accordingly, in order to seal the product from gear-ball joint 18, and in turn, to seal the joint lubricants, such as grease, from the product being pumped, a seal assembly is needed.

As shown in Fig. 2, a gear-ball joint for use with the progressing cavity pump 10 may include a gear ball 24 mounted on the connecting rod 16 and enclosed by housing 32. The gear ball 24 is secured on the connecting rod 16 by a nut 26 and is supported by thrust plates 28, 30. The gear ball 24 engages a ring gear 70, which is in turn coupled to the rotor head 72 by a pair of keys 74. Approximately six socket head cap screws 76 secure a rotor head ring 78 to the universal joint housing 32, and in turn pull the whole rotor head and universal gear joint together. A seal 34 is provided between the connecting rod 16 and the universal joint housing 32. Preferably, the seal 34 is a flexible seal member as described in U.S. Patent 4,639,200 to Baumgardner, et al., the disclosure of which is incorporated herein by reference.

As is known to those of ordinary skill in the art, the gear-ball 24 and associated thrust plates 28, 30 allow the connecting rod 16 to pivot as it simultaneously, rotatably drives the rotor 12. Such pivoting of the connecting rod 16 with respect to the thrust plates 28, 30 and housing 32 is centered substantially at pivot point P.

The universal joint seal assembly of the present invention 36 includes a hemispherical or substantially dome-shaped wall portion 38 extending from the universal joint housing 32 having an aperture 40 extending therethrough for receiving the connecting rod 16. The universal joint seal assembly 36 also includes an annular seal support 42 slidably mounted to the connecting rod 16. An annular sealing ring 44 is mounted to the seal support 42 and extends inwardly towards the dome shaped wall 38 of the universal joint housing 32. The annular sealing ring 44 preferably has a substantially concave inner surface 45 adapted to abut and seal against the curved or convex outer surface 50 of the dome-shaped wall 38. A biasing mechanism such as an annular spring 46 is coupled between a fixed annular collar 48 and the seal support 42 to urge the seal support towards the universal joint housing 32, and in turn, to urge the sealing ring 44 against the curved outer surface 50 of the dome shaped wall 38. An O-ring 52 is provided between the inner cylindrical surface of the seal support component 42 and the outer cylindrical surface of the connecting rod 16. Because the inner surface 45 of the sealing ring 44 conforms to the outer surface 50 of the dome-shaped wall, the seal formed by the sealing ring and the dome-shaped wall is maintained throughout all pivoting movement of the connecting rod 16.

The sealing ring 44 may be fabricated from any suitable substance to provide an adequate seal between the annular seal support 42 and the dome-shaped wall 38, such as a hard or soft elastomer or a material such as Stellite. The spring component 46 preferably urges the seal support 42 towards the universal joint housing 32 at a force operatively ranging from 5 pounds to 30 pounds, and preferably ranging from 15 pounds to 18 pounds. The dome-shaped wall 38 of the housing is preferably curved at a radius R with the center being the pivot point P of the gear ball 24. Accordingly, in operation, as the connecting rod 16 rotates and pivots, the abutting surfaces of the sealing ring 44 and the dome-shaped wall 38, under the biasing force of the spring 46, will maintain a reliable seal between the annular seal support 42 and the dome shaped wall 38. Because the universal joint seal assembly 36 can operate at substantially higher pressure capabilities than the flexible seal 34, the seal assembly 36 can be used with or without the flexible seal 34. Additionally, under extreme operating conditions, when de-gas occurs in the grease or lubrication fluid of the universal joint 18, the universal joint seal assembly 36 is adapted to allow the gas to "burp" out if the pressure within the housing 32 builds to an extent sufficient to overcome the biasing force of the spring 46. Therefore, the present invention provides a high performance universal joint seal that has exceptional pressure capabilities and operates under extreme operating conditions.

As shown in Fig. 3, an alternate embodiment of the present invention 36' includes an annular seal support 42' slidably mounted to the connecting rod 16 and a sealing ring 44' extending from the seal support 42 and abutting the outer surface 50 of the dome shaped wall 38. The annular seal support 42' also includes an O-ring component 52' mounted to an inner circumferential surface of sealing ring, such that it seals against the outer circumferential of the connecting rod. The spring support or collar 56 is mounted to the connecting rod 16 within the housing 32 and a biasing component 58 is coupled between the collar 56 and the seal support 42 and extends through the aperture 40. The biasing component 58 is biased inwardly such that the concave inner surface of the sealing ring 44' is urged against and mates with the curved outer surface 50 of the dome-shaped wall 38 during rotational and pivotal movement of the connecting rod 16.

As shown in Fig. 4, in a third embodiment of the present invention 36" the entire seal assembly can be housed within the housing 32. As in the previous two embodiments, an annular seal support 42" is slidingly mounted to the connecting rod 16 and includes an annular sealing ring 44" extending therefrom to abut a curved surface of the dome-shaped wall 38 of the housing. But rather than abutting the convex, outer curved surface 50 of the dome shaped wall, the sealing ring 44" substantially convex and is adapted to abut with and seal against the substantially concave, inner curved surface 62 of the dome-shaped wall 38. Accordingly, the biasing member 64 mounted between the collar 56" and the seal support 42" is biased outwardly so as to urge the sealing ring 42" towards the inner curved surface 62 of the dome-shaped wall 38. In this embodiment, an annular wiper component 66 is also mounted to the convex sealing surface of the seal support 42"; and it will be apparent to one of ordinary skill in the art that a similar wiper component can be incorporated into all of the embodiments of the present invention.

As shown in Fig. 5, another alternate embodiment of the present invention 36'" includes an annular seal support component 42'" that is fixed to the connecting rod 16. A plurality of flexible, annular sealing rings 44'", in the form of flexible annular ribs, extend from the seal support component 42'" and abut against the curved outer surface 50 of the dome-shaped wall 38. Each of the annular sealing rings 44'" are preferably longer than the gap 68 between the seal support component 42'" and the dome-shaped wall 38, and each of the annular sealing rings 44'" are preferably naturally biased downwardly towards the dome- shaped wall 38 so that they press themselves against the outer surface 50 of the dome-shaped wall 38. It will also be apparent to one of ordinary skill in the art that a substantially similar structure of this embodiment can be mounted within the housing 32.

Having described the invention in detail and by reference to the drawings, it will be apparent that modification and variations are possible without departing from the scope of the invention as defined by the following claims.

What is claimed is:

Claims

1. A seal assembly for a universal joint, the universal joint being coupled to at least one pivotable or angled rotatable shaft, the seal assembly comprising: a housing for retaining the universal joint therein, the housing including a substantially dome-shaped wall and an aperture in the dome-shaped wall for receiving the shaft; and a sealing ring, linked to the shaft, encircling the aperture and biased against the dome- shaped wall so as to form a seal between the dome-shaped wall and the sealing ring.

2. The seal assembly of claim 1, wherein the sealing ring is carried on a substantially annular support, the support being slidingly coupled to the shaft.

3. The seal assembly of claim 2, further comprising a collar mounted to the shaft and a biasing member coupled between the collar and the support such that the biasing member urges the support towards the dome-shaped wall.

4. The seal assembly of claim 3, wherein the support has an inner cylindrical surface facing the outer cylindrical surface of the shaft and wherein the seal assembly further comprises a second annular sealing ring mounted to the inner cylindrical surface of the seal support, adapted to abut the outer cylindrical surface of the shaft and to form a seal between the support and the shaft.

5. The seal assembly of claim 4, wherein the sealing ring abuts an outer surface of the dome-shaped wall and the biasing member urges the support and sealing ring towards the outer surface of the dome-shaped wall.

6. The seal assembly of claim 5, wherein the collar is mounted to the shaft outside of the housing and the biasing member pushes the support and sealing ring towards the outer surface of the dome-shaped wall.

7. The seal assembly of claim 5, wherein the collar is mounted to the shaft within the housing and the biasing member, coupled between the collar and the support, extends through the aperture and draws the support and sealing ring towards the outer surface of the dome- shaped wall.

8. The seal assembly of claim 4, wherein the sealing ring abuts an inner surface of the dome-shaped wall and the biasing member urges the support and sealing ring towards the inner surface of the dome-shaped wall.

9. The seal assembly of claim 8, wherein the collar is mounted to the shaft within the housing and the biasing member pushes the support and sealing ring towards the inner surface of the dome-shaped wall.

10. The seal assembly of claim 1, wherein: the sealing ring is attached to a substantially annular support, the support being mounted to the shaft; and the sealing ring includes a flexible annular rib extending therefrom and abutting the dome-shaped wall.

11. The seal assembly of claim 10, wherein the flexible annular rib is constructed to be biased towards the dome-shaped wall.

12. The seal assembly of claim 1, wherein: the universal joint includes a pivot about which angular movement of the shaft with respect to the housing is centered; and the dome-shaped wall has a radius centering substantially at the pivot.

13. A seal assembly for a universal joint, the universal joint being coupled to at least one angled or pivotable, rotatable shaft, the seal assembly comprising: a housing for retaining the universal joint therein, the housing including an wall and an aperture in the wall for receiving the shaft; and a substantially annular seal-support component coupled to the shaft adjacent the wall; the seal-support component including a substantially annular sealing ring, encircling the aperture, and abutting a curved surface of the wall so as to form a seal between the wall and the sealing ring.

14. The seal assembly of claim 10, wherein the sealing ring is biased against the curved surface of the wall.

15. The seal assembly of claim 14, wherein the seal-support component is slidingly mounted to the shaft and is biased towards the curved surface of the wall, causing the sealing ring to be biased against the curved surface of the outer wall.

16. The seal assembly of claim 15, wherein the seal-support component includes an o-ring component extending therefrom and abutting the shaft so as to form a seal between the seal- support component and the shaft.

17. The seal assembly of claim 15, further comprising: a collar extending from the shaft; and a biasing component, coupled between the collar and the seal-support component, the biasing component urging the seal-support component towards the curved surface of the outer wall.

18. The seal assembly of claim 13, wherein the sealing ring includes a flexible annular rib, biased towards the curved surface of the wall, extending therefrom and abutting the curved surface of the wall.

19. The seal assembly of claim 13, wherein: the universal joint includes a pivot about which angular movement of the shaft with respect to the housing is centered; and the curved surface of the outer wall has a radius centering substantially at the pivot.

20. A progressing cavity pump comprising: a rotor in the form of a helical gear with at least one lead; a stator having an internal bore in the form of a helical gear including one more lead than the rotor, the rotor being rotationally disposed in the internal bore to form a plurality of cavities between the rotor and stator; a drive assembly, including a connecting rod coupled between first and second universal joints, the first universal joint being coupled to the rotor and the second universal joint being coupled to a drive shaft; a housing for retaining one of the first or second universal joints therein, the housing including a substantially dome-shaped wall and an aperture in the dome-shaped wall for receiving the connecting rod; and a sealing ring, linked to the connecting rod, encircling the aperture and biased against the dome-shaped wall so as to form a seal between the dome-shaped wall and the sealing ring.

21. The progressing cavity pump of claim 20, wherein the sealing ring is carried on a substantially annular support, the support being slidingly coupled to the connecting rod.

22. The seal assembly of claim 21, further comprising a collar mounted to the connecting rod and a biasing member coupled between the collar and the support such that the biasing member urges the support towards the dome-shaped wall.

23. The seal assembly of claim 22, wherein the support has an inner cylindrical surface facing the outer cylindrical surface of the connecting rod and wherein the seal assembly further comprises a second annular sealing ring mounted to the inner cylindrical surface of the seal support, adapted to abut the outer cylindrical surface of the connecting rod and to form a seal between the support and the connecting rod.

24. The seal assembly of claim 20, wherein: the first and second universal joints are gear-ball joints having an approximate center point about which angular movement of the connecting rod with respect to the housing is centered; and the dome-shaped wall has a radius centering substantially at the center point.