Technical Field

The present invention relates to a sealing member for providing sealing between components of a rotary machine. The invention has particular application to sealing between stationary components and one example described involves sealing between the strainer of a sump pump and the sump pump body.

Background Art

A rotary machine typically comprises a rotor mounted inside a casing. The rotor is mounted on a rotatable shaft which is in turn mounted to the casing. Some form of sealing is usually required between components of the machine, such as between components of the casing. To effect this sealing, a sealing member may be used which is fitted between casing components. The casing components are typically formed by a casting process which results in a relatively rough surface finish. In order to provide effective sealing, it is necessary to firstly machine the surfaces of the casings to provide a smooth surface that will contact the sealing members. This machining may have to be repeated following subsequent heat treatment steps.

Summary of the Disclosure

In a first aspect, a sealing member is provided for sealing between components of a rotary machine, the member being in the form of a ring; the sealing member is formed from a homogenous, deformable material; the member including a web and inner and outer flanges which extend from the web, the inner flange extends from the web for a greater distance than the outer flange; the member further including a series of ribs spaced about the ring, each of the ribs being at least partially disposed between the inner flange and the outer flange; wherein the outer flange terminates in a lip about substantially the entire periphery of the sealing member.

In use, pressurised fluid enters the space between the flanges. This pressure causes the lip to be deformed outwardly to provide an enhanced sealing effect against a component of the machine. Such an effect can be thought of as pressure activation of the sealing member. Throughout this specification when the term 'homogeneous material ^' is used in relation to a sealing member it means that the member is made from of a substantially uniform material throughout, and is of substantially uniform density and hardness.

The lip may have a length of at least 20% of the distance between the inner and outer flanges.

The lip may have a length of at least 50% of the distance between the inner and outer flanges.

The lip may have a length of about the distance between the inner and outer flanges.

In a second aspect, a sealing member is provided for sealing between components of a rotary machine, the member being in the form of a ring of a homogeneous, deformable material; the member including a web and inner and outer flanges which extend from the web; the inner surfaces of the web and the inner and outer flanges define an internal volume; the member further including a series of ribs disposed in the internal volume and spaced about the ring; and wherein less than 50 percent of the internal volume is occupied by the ribs.

When the sealing member is installed for use, it is compressed between components of a machine. The degree to which the internal volume is occupied by ribs affects the stiffness of the sealing member, and its behaviour under compression. It has been found that where less than 50% of the volume is occupied by ribs, the sealing member can be deformed to provide suitable sealing performance even when the actual exterior dimensions of individual components of the machine vary to a significant degree. It has been found that such variations can be encountered where components are cast, and not subsequently machined before assembly.

Between 5 and 40 percent of the internal volume may be occupied by the ribs.

Between 5 and 20 percent of the internal volume may be occupied by the ribs.

In one embodiment, about 10 percent of the internal volume may be occupied by the ribs. In a third aspect, there is provided a rotary machine including at least two casing members which meet to define an annular sealing volume therebetween; a sealing member is provided in the annular sealing volume; wherein the surfaces of the casing members against which the sealing member bears are tapered.

During assembly, the sealing member may be stretched about one of the casing surfaces. This may be achieved using some type of lubricant, such as oil, surfactant or soapy water. By providing a tapered surface, the job of fitting the seal by stretching is made easier.

The casing members may meet concentrically.

One of the casing members may be a machine body and the other casing member may be a machine end cap.

The surface of the machine body against which the sealing member bears may taper outwardly in a direction away from the machine.

The surface of the machine end cap against which the sealing member bears may taper outwardly in a direction away from the machine.

Brief Description of the Drawings

An embodiment will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure l is a perspective view of a sealing member according to one embodiment; Figure 2 shows detail A of Figure 1 ;

Figure 3 is a plan view of the sealing member of Figure 1;

Figure 4 is a cross sectional view along line B-B of Figure 3;

Figure 5 shows detail B of Figure 4;

Figure 6 is a cross sectional view along the line A-A of Figure 3; Figure 7 shows detail C of Figure 6;

Figure 8 is an exploded perspective view of a sump pump including the seal of Figure 1; and Figure 9 is a cross sectional view of the sump pump of Figure 8.

Detailed Description of Specific Embodiments

Referring to Figures 1 to 7, a sealing member is shown in the form of a seal 10.

The seal 10 is generally in the form of a ring and is formed in one piece by injection moulding using a resilient, homogeneous, elastomeric material.

In another embodiment, the seal can be provided in a strip-like form which can be bent into the form of a ring when used, as will be described later.

A number of grades of proprietary elastomeric material can be acceptable for use, such as rubber.

The seal 10 includes a web 12 from which extends an inner flange in the form of a skirt 14 and an outer flange in the form of a collar 16. A series of ribs 18 are spaced about the ring, each rib 18 being at least partially disposed between the skirt 14 and the collar 16 and extending from the skirt 14 to the collar 16.

Referring particularly to Figures 5 and 7, it can be seen that the collar 16 is joined to each rib 18 only for a portion of the height of the collar 16 thus defining a lip portion 20 which extends about the entire periphery of the seal 10. The lip has a length being about the same as the internal distance between the skirt 14 and the collar 16. The significance of this lip will be described in due course.

The inner surfaces of the web 12, the skirt 14 and the collar 16 bound an internal volume 17 of the seal. It can be seen that some of this volume 17 is occupied by the material of the ribs 18 and the remainder is free space. The ratio of the volume occupied by rib material to free space affects the stiffness of the seal during assembly, as will be later described.

The outer diameter of the seal 10 is approximately 400mm. The distance between the inner surfaces of the skirt 14 and the collar 16 is approximately 14mm. The length of the lip 20 is approximately 16mm. The web 12 is approximately 5mm thick. The skirt 14 is approximately 3 -4mm thick. The collar 16 is approximately 8mm thick at its thickest point where it meets the web 12. The ribs 18 are approximately 5mm thick. These dimensions can of course be varied in other embodiments. Referring to Figures 8 and 9, a seal 10 is shown in combination with a rotary machine in the form of a sump pump 30. The sump pump 30 is suitable for use in industrial applications for removing waste water from low-lying areas such as in a mining pumping installation or a minerals processing plant. The sump pump 30 includes an end cap casing member in the form of strainer casing 34, and a machine body casing member in the form of body casing 32. The strainer casing 34 and the body casing 32 meet to define a sealing volume in which sits the seal 10. The casings 32, 34 are formed by a casting operation and the surfaces of the casings 32, 34 against which the seal 10 bears are not machined following the casting operation. Thus, these surfaces have a cast finish in the pump assembly 30 rather than being fettled or smoothly formed by a separate machining process. As a result, effective sealing can be achieved without expending time and effort in machining sealing surfaces, which gives a manufacturing cost advantage.

The sump pump 30 includes a centrifugal pump impeller 36 mounted on drive shaft 37. When in operation, the impeller 36 operates to draw waste water upwards through holes provided in the strainer 34 and to expel the water through the outlet pipe 40. During its operation, a high pressure fluid zone is created within the impeller housing. The seal 10 is oriented so that the skirt 14 and collar 16 extend from the web 12 towards the high pressure zone. Thus in use, high pressure fluid enters the internal volume of the seal and serves to press the skirt 14 and collar 16 against the respective surfaces of the casings 32, 34 thus increasing the sealing effect. In particular, the lip 20 provided about the seal 10 is free about its circumference to be deformed under pressure of fluid to lie against the sealing face of casing 32 to thereby further enhance the effectiveness of the seal. The seal 10 therefore performs its function when pressure activated.

To assemble pump 30, it is first necessary to select an appropriate size of shim 38. The shim 38 is selected to achieve a close fit between the impeller 36 and the strainer 34 casing at the point indicated by arrow C. To size the shim 38, the impeller 36 is fitted to a drive shaft 37 within the body casing 32. Then strainer casing 34 is brought against the impeller 36 with no seal in place to come into contact with impeller 36 at the point indicated by arrow C. The distance between the casings 32, 34 is then measured and a shim 38 of slightly larger thickness is selected for insertion between the casings 32, 34. The strainer casing 34 is then removed and the seal 10 is stretched about the spigot 41 of the strainer casing 34. Some detergent or other lubricant may be used to assist in fitting the seal 10 about the spigot 41.

In an embodiment of the seal which is provided in a strip-like form, the seal strip can be bent into the form of a ring and then curled tightly around the strainer casing component 34 and the remote ends glued or fused together to form a one-piece ring. Once the glue or joining substance has dried and cured, the assembly of the pump 30 can continue as described.

With the shim 38 in place, the strainer 34 with the seal 10 fitted is then brought against the body housing 32. During assembly, the seal 10 operates to centralise strainer casing 34 concentrically within pump casing 32. The strainer casing 34 is secured in place by tightening a series of bolts inserted through pairs of corresponding holes 42 provided about the periphery of strainer casing 34 and pump casing 32. During tightening, the seal 10 deforms and, in particular, the ribs 18 become deformed as the bolts 42 are tightened. The material that the seal is made of is substantially incompressible, and thus as the ribs 18 become compressed and deform, they occupy volume in the internal volume of the seal that was previously free space. Deformation of the seal 10 serves to allow for variations in the actual sealing volume between different pairs of casings 32, 34 as a result of manufacturing tolerances. Due to the fact that the casings 32, 34 are cast, and not subsequently machined, the variations in sealing volume from one pump to the next can be significant. The seal 10 is intended to allow for variations of up to 8mm in the depth of the shim 38.

The ratio of the volume of the rib material to the free space controls the stiffness of the seal, and consequently the degree of variations in actual casing sizes that the seal 10 can accommodate. A seal with more stiffness will be less accommodating to variations in size, but will have a higher rigidity following assembly and thus a higher maximum operating pressure. Similarly, a seal with less stiffness will be more accommodating to variations in size but will have a lower rigidity following assembly and thus a lower maximum operating pressure.

A degree of leakage from the sump pump 30 can be tolerated as any leaked fluid will simply return to the pool of wastewater that pump 30 is drawing from.

It can be seen that the sealing surface of the casing 32 tapers outwardly in a direction away from pump 30. Although not readily appreciable from the drawings, the sealing surface about spigot 40 of strainer casing 34 also tapers outwardly in a direction away from the pump, albeit to a lesser degree than the pump casing 32.

Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.

Finally, it is to be appreciated that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the present invention.