GB2454127A

GB2454127A - Seal

Info

Publication number: GB2454127A
Application number: GB0902053A
Authority: GB
Inventors: John Angelosanto; Joseph A Luongo; Frank Rubino
Original assignee: Waters Investments Ltd
Current assignee: Waters Investments Ltd
Priority date: 2005-08-17
Filing date: 2005-08-17
Publication date: 2009-04-29
Anticipated expiration: 2025-08-17
Also published as: GB0902053D0; GB2454127B

Abstract

A seal for a high pressure fluidic device comprises a main body having a through bore 49 for sealingly engaging about a shaft. The main body comprises a deformable seal body 55 having an outer sealing surface 51 and a larger diameter cap 57 which has a rigidity greater than that of the seal body 55 to transmit compressive force to the seal body 55 when the seal is under axial compression. Radial fluid relief passageways 21a are formed in the end face of the cap 57 between the through bore 49 and the external surface of the cap 57.

Description

HIGH PRESSURE SEAL WITH DEFINED LEAK PATH

FIELD OF iNVENTION

The present invention relates to a seal for a high pressure fluidic device.

BACKGROUND OF THE INVENTION

The present invention is directed to a seal for use in devices for handling fluids under pressure. For example, without limitation, embodiments of the present invention have application for pumps and valves that produce or control fluids under pressure.

Devices for handling high pressures are built with parts and components with closely controlled tolerances. Such parts and components are also expensive to manufacture.

It is desirable to be able to design components and parts which exhibit wear such that the worn parts and components can be replaced. And, it is desirable to reuse parts and components with closely controlled tolerances.

Unfortunately, worn parts and components may cease functioning prior to replacement. The function of many parts and components of fluid handling devices is to contain fluid under pressure. For example, the failure of seals in a valve or pump * : 20 may release fluid into sections of the device which can not withstand the pressure * and/or pulsation of the fluid. The parts and components to which a pressurized fluid is *.Sa * inappropriately applied may work free or change alignment from other components and parts. Specialized pumps for performing chromatography often have sapphire pistons.

*r' Mis-aligned pistons may gouge precision surfaces of such pumps. The pistons may be scratched or otherwise damaged. Parts and components to which inappropriate pressure is applied may permanently deform.

In the field of chromatography, there is an interest in operating at elevated pressures. Conventional pressures for performing high performance liquid chromatography are up to approximately 3,000 pounds per square inch (psi). Pressures for performing ultra performance liquid chromatography may reach 15,000 to 20,000 psi. With greater pressure, the potential for seal failure is greater and the potential for damage is greater.

It would be desirable to have parts and components of fluid handling devices convey fluids to the exterior of the device in a manner that does not allow inappropriate pressure to be applied to parts and components.

SUMMARY OF THE INVENTION

The invention provides a seal for high pressure fluidic device which seal comprises a main body having a through bore for sealingly engaging about a shaft, the main body comprising a deformable seal body having an outer sealing surface and comprising a larger diameter cap which has a rigidity greater than that of the seal body to transmit compressive force to the seal body when the seal is under axial compression and a radial fluid relief passageway between the through bore and the external surface ofthe cap.

According to a feature of the invention the radial fluid relief passageway may ** .. : be provided in an end face of the larger diameter cap. S' *.**

* 20 According to another feature of the invention, a plurality of fluid relief passageways may be provided between the through bore and the external surface of

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said cap. S. *S

* * According to a still further feature of the invention said deformable seal body :.** may comprise spring means to create a radial force when the seal is under compression.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, by way of example, with reference to, and as shown in the accompanying drawings, in which:-Figure 1 depicts, in cross section, a device incorporating features of the present invention.

Figure 2 depicts, in cross section, the pump assembly of a device depicted in Figure 1.

Figure 3 depicts, in cross section, a seal incorporating features of the present invention.

Figure 4 depicts an angled view of the seal depicted in Figure 3.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to Figure 1, a device, in the form of a pump, generally designated by the numeral 11 is depicted. The device 11 has a housing 13, a seal 15, a cap 17, shaft 19 and passage means 21a, 21b, and 21c as best seen in Figure 2. Returning now to Figure 1, device 11, as a pump, produces fluids under pressure. However, features of device 11 may be modified such that the device could direct fluids to different fluid paths in the nature of a valve or fitting.

The housing 13 is part of a pump assembly 25 having a motor 27 and spindle mechanism 29. Those skilled in the art will recognize that housing 13 could be described as a housing for a valve [not shown] in which the spindle mechanism 29

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* : would normally comprise suitable gearing and the like. As depicted, spindle mechanism 29 is mechanically linked to a shaft 19.

Housing 13 is depicted in greater detail in Figure 2. Housing 13 has a housing **II exterior 31, a cap abutment surface 33, a chamber 35 and a bore opening 37. The cap abutment surface 33 comprising an area of the housing 13, separate from the exterior 31, surrounding the bore opening 37, forreceiving a cap 17. The housing 13 has a cap recess 39 to align the cap 17.

Chamber 35 is for containing fluid under pressure. As a pump, the shaft 19 moves in and out of the chamber 35 causing fluids to move. As a valve, it would be more common that the shaft 19 rotate and turn a rotor [not shown] fitted to a stator [not shown]. As depicted, chamber 35 has an inlet 43 and an outlet 43 for receiving and discharging fluids.

Bore opening 37 extends from said cap abutment surface 33 to said chamber 35.

Bore opening 37 may be substantially contiguous with chamber 35. Bore opening 37 has a sealing surface 45 and at least one housing seal compression surface 47. Sealing surface 45 is for creating a seal between the housing 13 and seal 15. Housing seal compression surface 47 is for creating a compressive force on the seal 15 which will compel the seal 15 against the sealing surface 45.

Seal 15 is held in the bore opening 37. As best seen in Figures 3 and 4, the seal has a seal opening 49 and a housing engagement surface 51 The seal opening 49 receives shaft 19 extending axially there-through. The surface of the seal opening 49 sealing engages the shaft to prevent fluid from escaping the chamber 35. The housing engagement surface 51 sealing engages the sealing surface 45 of the bore opening 37 upon axial compression of the seal 15 against the housing seal compression surface 47.

Seal 15 has a seal body 55 and a seal compression pad 57. The seal body 55 is a flexible section that engages the sealing surface 45 of the bore opening 37. The seal body 55 has a canted coil spring 59. Canted coiled spring 59 creates radial force *.

*. : directed inward and outward upon compression of the seal 15 against the housing seal **** compression surface 47. This radial force facilitates the sealing engagement of the housing engagement surface 51 with the sealing surface 45 of the housing 13.

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However, seal 15, holding pressure up to 15,000 psi, may fail. Upon failure, the fluid *55S leaks to areas of the pump until an outlet is reached, or if confronted with a sealed area, the fluids will build up pressure. However, the pressure may build in areas of the device 11 which are pressure sensitive.

Seal compression pad 57 has less flexibility than seal body 55 to compress the seal body 55 against the housing seal compression surface 47. The seal compression pad 57 is made of plastic, such as, by way example, without limitation, polyethylene ether ketone, (PEEK). The seal body 55 is made of rubber or rubber-like materials.

The seal compression pad 57 has a cap engaging surface 61 for engaging the cap 17. It will be recognized by those skilled in the art, that the seal compression pad 57 may represent a area of a seal body that is more rigid than sections of the seal body performing sealing functions. That is, the seal cap 57 may be integral with the seal body 55.

Returning now to Figure 2, shaft 19 has a shaft axis 63 extending lengthwise along the shaft. The shaft 19 is generally cylindrical and shaft 19 and seal 15 are constructed and arranged such that shaft 19 fits seal opening 49. Shaft 19 is mounted in the seal opening 49 of the seal 15 for rotation about said shaft axis 63 or reciprocating movement along a shaft axis 63.

Cap 17 has a cap exterior 67, housing abutment surface 69, a cap opening 71 and a cap seal compression surface 73. The cap exterior 67 is that part of the cap 17 other than housing abutment surface 69, cap opening 71 and cap seal compression surface 73. Cap 17 is affixed to the housing 13 with the housing abutment surface 69 engaging the cap abutment surface 33. The relationship of the housing 13 to the cap 17 is important. The cap 17 is secured to other components as depicted in Figure 1.

Misalignment of the cap 17 with the housing 13 may cause extreme wear of moving components and may alter the shape of components not designed for pressure. **** * S *. S **SS

Returning now to Figure 2, shaft 19 extends through the cap opening 71. Cap *.: 20 seal compression surface 73 is pressed against the seal 15 at the cap engaging surface *..., 61 of the seal compression pad 57. The seal 15 is compelled against the seal compression surface 47 by the seal compression pad 57 to sealingly engage the housing ** S. * engagement surface 51 against the sealing surface 45.

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Device 11 has passage means 21 for receiving and conveying fluid from the housing engagement surface 51 to at least one of the cap exterior 67 or the housing exterior 31 and away from the cap abutment surface 33 and the housing abutment surface 69. Passage means 21 may take several forms. For example, without limitation, one embodiment of passage means 21 is at least one channel 21a in a cap engaging surface 61 of the seal 15, and in particular, the seal compression pad 57 as best seen in Figure 4. e

In the alternative, channels [not shown] can be provided in the cap seal compression surface 72 of the cap 17. As a further alternative, returning again to Figure 2, passage means 21 is a channel 21b in the housing 13. As a further alternative, a channel 21c is provided in the cap 17.

Embodiments of the present device prevent critical wear and damage to parts of a valve and/or pump or other fluid containing device in the event of a seal failure.

These advantages and features may be realized with a seal 15 having a seal body 55 having channels 21a in a cap engaging surface 61 for pumps, valves and fittings. I.

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Claims

1. A seal for high pressure fluidic device which seal comprises a main body having a through bore for sealingly engaging about a shaft, the main body comprising a deformable seal body having an outer sealing surface and comprising a larger diameter cap which has a rigidity greater than that of the seal body to transmit compressive force to the seal body when the seal is under axial compression, and a radial fluid relief passageway between the through bore and the external surface of the cap.

2. A seal according to claim 1, wherein the4 radial fluid relief passageway is provided in an end face of the larger diameter cap.

3. A seal according to claim 1 or claim 2, wherein a plurality of fluid relief passageways are provided between the through bore and the external surface of said cap. S.. * * * .

4. A seal according to any of the preceding claims wherein said deformable seal * 20 body comprises spring means to create a radial force when the seal is under * * * *I compression. ***I

* *

5. A seal substantially as hereinbefore described with reference to and as shown in * : * the accompanying drawings.