GB2081399A

GB2081399A - Improvements in rotary sealing devices

Info

Publication number: GB2081399A
Application number: GB8024634A
Authority: GB
Original assignee: WOODVILLE POLYMER ENG
Current assignee: WOODVILLE POLYMER ENG
Priority date: 1980-07-28
Filing date: 1980-07-28
Publication date: 1982-02-17
Also published as: GB2081399B

Abstract

A rotary pump for forcing the cooling water to circulate through the cooling system of an i.c. engine is driven by a rotary drive shaft (14) which extends into the pump through a bearing (22). A rotary sealing device (24) between the rotary drive shaft (14) and the stationary housing (23) of the pump prevents water escaping from the pump through the bearing (22). The rotary sealing device (24) has a stationary annular face seal member 26 which is sealingly mounted in the pump housing so as to be coaxial with the rotary drive shaft (14), and an annular counterface member 25 sealingly mounted on the drive shaft (14). The face seal member 26 and the counterface member 25 are held resiliently together at respective opposing sealing faces 28,29. A coaxial shroud 37 is secured to the counterfoil member 25 to shield the faces 28 and 29 from approaching abrasive particles and is equipped with an outwardly extending flange 38 arranged to accelerate water and particles away from the sealing device (24). Water for cooling the members 25 and 26 is allowed to flow within the shroud 37, leaving the shroud 37 through apertures in portion 39 thereof. <IMAGE>

Description

SPECIFICATION Improvements in rotary sealing devices This invention relates to rotary sealing devices.

It is usually found necessary to provide a water-cooled internal combustion engine with a pump for forcing the cooling water to circulate through the cooling system. The pump used is driven by the engine itself which is coupled to a drive shaft which extends into the pump through a suitable bearing. The pump is usually a rotary pump and the drive shaft is then a rotary drive shaft. A rotary sealing device is therefore required between the rotary drive shaft and the stationary housing of the pump to prevent water escaping from the pump through the bearing.Typically the rotary sealing device has a stationary annular face seal member which is sealingly mounted in the pump housing so as to be coaxial with the rotary drive shaft, and an annular counterface member sealingly mounted on the shaft or a rotary member of the pump which the shaft drives directly and which, with the shaft, stops the passage of water through the annular counterface member. The face seal member and the counterface member are held resiliently together at respective opposing sealing faces thereof so that the sealing face of the counterface member rotates against the sealing face of the face seal member when the pump is operating.

These sealing faces, to be effective in sealing, must be parallel to one another to within a few light wavelengths. For example, for flat, annular radial sealing faces, each face is lapped flat to within three light wavelenths. The rotary sealing device then acts as a satisfactory seal for many hours, provided there is no damage to the opposed sealing faces of the face seal member and the counterface member.

It is now found that in some circumstances, sand is washed out of castings forming parts of the cooling system and that the abrasive sand particles quickly destroy the effectiveness of the opposed sealing faces when the pump is working.

According to the present invention there is provided a rotary sealing device including a first seal member adapted to be sealingly mounted on stator structure, and a second seal member adapted to be sealingly mounted on a rotor structure so as to rotate therewith, means for holding the seal members against one another over respective opposing sealing faces which are coaxial with the axis of rotation of the rotor structure, and a shroud which is coaxial with and sealingly secured to the second seal member and is so shaped as to include a shield portion shielding the said sealing faces from material moving with substantial radially inward motion towards the said axis and to provide a flange extending outwardly from the said shield portion, the flange being such that during rotation of the shroud with the second seal member, material which approaches the flange is driven away from the shroud by the rotation of the flange therewith.

Preferably the shroud is adapted to define an outer wall of a cooling space surrounding the seal members adjacent their sealing faces and to allow fluid to flow through the cooling space.

In a preferred embodiment of the invention, intended for use where the stator structure is part of a pump housing and the rotor structure is a rotary drive shaft which extends into the pump housing through a bearing mounted in the said part of the pump housing, the first seal member is a face seal member having an annular radial sealing face held resiliently against an opposing annular radial sealing face on the second seal member which is a ring-like counterface member mounted coaxially on the rotary drive shaft within the pump housing. The shield portion of the shroud is cylindrical and coaxial with the drive shaft, and the flange is flat and extends in a radial plane. A flow-limiting annular gap is defined between the flat flange and an adjacent stationary surface to allow a small flow of water into the shroud for cooling the seal members.A set of holes in the shroud which are distributed around the axis of rotation and allow flow parallel to the axis are provided as outlet holes for water from within the shroud.

The invention will now be described in more detail, solely by way of example, with reference to the accompanying drawings, in which: Figure lisa view, partly in section in an axial plane, of part of a radial flow centrifugal pump for an engine cooling system of a motor vehicle; Figure 2 is a sectional view in an axial plane of part of a seal assembly embodying the invention, and Figure 3 is a sectional view in an axial plane of part of another seal assembly embodying the invention.

The centrifugal pump shown partially in Figure 1 has a rotary impeller 11 with vanes 12, one of which is seen in Figure land a hub 13 by means of which the impeller 11 is mounted on a rotary drive shaft 14. The pump has a housing consisting of an inlet side 15 and an outlet side 16 secured together to form a fluid-tight pump chamber within which the impeller 11 rotates in operation.

The inlet side 15 ofthe pump housing includes an inlet passage 17forwaterwhich isto be circulated as a cooling medium by the pump through an engine cooling system (not shown). The inlet passage 17 directs water towards the annular central region, known as the eye 18 of the impeller 11, surrounding the hub 13 at the low pressure side of the inmpeller 11.A ring of stator vanes 19, one of which can be seen in Figure 1, mounted in the inlet side 15 of the pump housing surrounds the eye 18.

The direction of flow of the water when the pump is working is indicated in the inlet passage 17 and the eye 18 by arrows 20 and 21. The rotation of the impeller drives the water radially outwards in the outlet side 16 of the pump housing where a high pessure is established. Water leaves the outlet side 16 through an outlet passage not shown.

The rotary drive shaft 14 enters the pump housing through a bearing 22 mounted in a socket 23 formed in the inlet side 15 and is coupled outside the pump housing to a driving arrangement by a rotary drive member (not shown) which may be a drive pulley arranged to engage a suitable drive belt. The socket 23 extends inwardly of the inlet side 15 of the pump housing and provides an annular location for an annular seal assembly 24 for sealing the shaft 14 to the pump housing so as to prevent water from escaping from the pump through the bearing 22.

The annular seal assembly 24 embodies the present invention so that opposing sealing faces of a rotating counter face member 25 and a stationary seal face member 26 are provided with protection against abrasive particles which may be carried in the water entering through the inlet passage 17.

The counterface member 25 of the assembly 24 is annular, is mounted coaxially and sealingly on the drive shaft 14 by means of a resilient sleeve 27 which grips the shaft 14 and seals the fitted inner surface of the hub 13 and outer surface of the shaft 14 at the end of the hub 13 remote from the impeller vanes 12. One annular radial face of the counterface member 25 bears against the radial end face of the hub 13. Another annular radial face 28 of the counterface member 25 serves as a sealing face against which a smaller annular radial face 29, which is the sealing face of the seal face member 25, bears with a pressure substantially determined by a compression spring 30 held in compression between an annular shell 31 and part of a reinforcing shell 32 which reinforces a resilient seal assembly body member 33 which is sealingly located in the inner end of the socket 23.The reinforcing shell 32 is substantially in the form of a cup having a radially outwardly turned lip 34 at its mouth and an aperture in its base through which the shaft 14 passes with considerable clearance.

The resilient body member 33 covers the inner and outer surfaces of the reinforcing shell 32 and has a substantially co-extensive coaxial flexible inner skirt portion 35 sealingly attached to inner sufaces of the seal face member 26 so that sealing of the seal face member 26 to the inner end of the socket 23 is complete. The rim of the skirt portion 35 is sandwiched between the annular shell 31 and an annular radial face of the seal face member 26. Part of the skirt portion 35 is within a cylindrical tubular portion 36 of the seal face member 26 which has on its outer surface axially extending ridges which engage in axially extending grooves provided in the inner cylindrical surface of that portion of the resilient body member 33 which covers the inner cylindrical surface of the reinforcing shell 32.The flexibility of the skirt portion 35 allows the seal face member 26 some axial movement relative to the reinforcing shell 32, but relative rotary movement is prevented by the engaging ridges and grooves. Thus the spring 30 is able to press the seal face member 26 against the counerface member 25 but rotation of the counterface member 25 does not result in rotation of the seal face member 26.

Thus the seal assembly 24 has the sleeve 27 and the counterface member 25 which rotate with the shaft 14 and the impeller hub 13 and prevent water from passing along the shaft 14 towards the bearing 22, and the reinforced body member 33 and the seal face member 26 which prevent water from passing aiong the inner surface of the socket 23 to the bearing 22 and are stationary with the pump housing.

The opposing sealing faces 28 and 29 of the counterface and seal face members 25 and 26 are held together by the spring 30 and prevent water from passing between these to members 25 and 26. However, since the face 28 rotates against the face 29, rapid wearing and resultant failure of sealing of these two faces to one another occurs if abrasive particles reach their junction region. The water flowing into the pump through the inlet passage 20 may contain abrasive particles such as grains of sand washed out of the walls of castings in which parts of the engine cooling system (not shown) may be formed.

To prevent such particles reaching the junction of the faces 28 and 29, the counterface member 25 has fixed thereto a cylindrical shroud 37 provided with a radially outwardly extending flange 38.

The shroud 37 is secured to the counterface member 35 by tight fitting of the inner edge region of an inwardly radially extending flange 39 of the shroud 37 in an annular recess formed in the counterface member 25 adjacent the hub 13. Eight holes (not shown) are formed theinwardly extending flange 39 at positions distributed around the axis of rotation of the shaft 14 to allow water to pass out of the shroud 37.

With the seal assembly 14 installed as shown in Figure 1,the outwardly extending flange 38 lies parallel and close to an annular radial surface at the mouth of the body member 33. The annular gap thus formed between the flange 38 and the body member 33 allows a small flow of water into the shroud 37. The flow of water through the shroud 37 from the annular gap to the holes (not shown) in the inwardly extending flange 39 is sufficient to prevent overheating of the faces 28 and 29 of the members 25 and 26 in operation.

The cylindrical part of the shroud 37 extends axially through the radial plane in which the sealing faces 28 and 29 oppose one another and thus the shroud 37 is able to shield the junction of the faces 28 and 29 from direct impingement by abrasive particles carried by the incoming water. Furthermore, since the shroud 37 rotates with the shaft 14, the outwardly extending radial flange 38 accelerates water and particles in contact therewith away from the seal assembly 24. With the shaft 14 rotating at a rate suitable for pumping the water through the engine cooling system, the protection given by the rotating flange 38 against abrasive particles is sufficient to allow a useful working life for the sealing faces 28 and 29 of the seal assembly 24.

Figures 2 and 3 show partialiy axial sections of two other seal assemblies similar to the seal assembly 24 of Figure 1 and intended to be used for the same purpose, i.e. to seal the drive shaft of a centrifugal water pump of an engine coo ling. system where the drive shaft passes into the pump housing. Component parts of the seal assemblies of Figure 2 and 3 which are the same as or very similar to corresponding component parts of the seal assembly 24 of Figure 1 are given the same reference numbers as the corresponding parts in Figure 1.

The seal assemblies of Figure 2 and 3 are shown in the state which the spring 30 is substantially relaxed, the respective assembly not being installed and the axial extent of the assembly being determined by an engagement between rotor and stator portions of the assembly.

In the assembly shown in Figure 2, the resilient sleeve 27 is longer than the sleeve 27 in the assembly 24 and has at its end remote from the counterface member 25 an external rim 40 which catches on an internal lip 42 formed on an axially inwardly extending cylindrical portion 42 defining the aperture in the base of the cup-shaped reinforcing shell 32.

The inwardly extending flange 39 of the shroud 37 is again provided with holes distributed around the axis of the assembly. A constricted entry for water to enter the shroud 37 is provided by a region 43 of axial overlap between the cylindrical portion of the shroud 37 and the cylindrical portion 36 of the seal face member 26, and, when the assembly is installed and therefore axially compressed, by an annular gap between the outwardly extending flange 38 and the opposing annular face at the mouth of the body member 33. The inwardly extending flange 39 is provided with an integral annular seating recess portion 44 in which the counterface member 25 is fixed.

In the seal assembly of Figure 3, the entry constriction to the shroud 37 is in the form of a gap between region of the shroud 37 at which the outwardly extending flange 38 joins the cylindrical portion of the shroud 37 and an annular recess 45 provided in the face seal member 26.

The inwardly extending flange 39 of the shroud joins integrally with a gripping sleeve 46 shaped to grip a drive shaft (not shown), and extending axially within the seal assembly to engage, by means of a flared end 47 thereof, a retaining ring 48 which also engages the internal lip 41 of the axially inwardly extending portion 42 of the reinforcing shell 32. Holes are again provided in the flange 39 to allow water to escape from within the shroud 37. Sealing between the counterface member 25 and the gripping sleeve 46 and the flange 39 is provided by a flanged resilient sleeve 49.

It is found that the provision of eight holes in the inwardly extending flange 39 of the shroud 37 is satisfactory. The holes need not be strictly uniformly angularly arranged around the rotary axis and they can be of any shape and may extend through the shoulder of the shroud 37 where the flange 39 joins the cylindrical part of the shroud. These holes (not shown) are required simply to allow a more or less axial flow path by which water can come out of the shroud 37, and flow towards the eye 18 of the impeller 11. The cylindrical portion of the shroud 37 in each seal assembly shown in the drawings shields the sealing faces 28 and 29 from direct access by abrasive particles in the water flowing in through the inlet passage 17.The spacing of the outwardly extending flange 38 and/or an adjacent part of the shroud 37 from a stationary member of the seal assembly defines a restricted inlet for a small flow of water into the shroud 37, this flow being induced by the rotation of the impeller 11. The space between the shroud 37 and the counterface member 25 and the seal face member 26 acts as a cooling jacket for the sealing faces 28 and 29.

In operation, the seal assemblies being installed, as described with reference to Figure 1, in a cooling system for an internal combustion engine, the impeller rotates at 1.3 x engine speed. Thus the impeller is typically rotating at between 1500 r.p.m. and 6000 r.p.m. Under these conditions, the seal assemblies described obtain considerable protection from abrasive particles entrained in the closed circuit flow through the cooling system by having the shroud 37 and its outwardly extending flange 39.

In the assembly of Figure 2, the following materials can be used: Item Material 37 Zinc plated steel 27 Nitrile rubber 25 Plastic impregnated sintered bronze 31 Zinc plated steel 30 Spring steel 26 Graphite impregnated phenolic resin 32 Zinc plated steel 33 Nitrile rubber The same materials can be used for the corresponding items in the assembly of Figure 3, the spring ring 48 being of spring steel.

For a drive shaft of substantially 12 millimetres diameter, the internal diameter of the sleeve 27 in its relaxed state adjacent the counterface member 25 is 11.5 millimetres in the assembly of Figure 2.

The internal diameter of the narrowest part of the gripping sleeve 46 of Figure 3 for the same drive shaft is 11.98 millimetres. The respective external diameters of the respective cylindrical portions of the shrouds 37 of the assemblies of Figures 2 and 3 are 32.5 millimetres and 30.0 millimetres, and the outside diameters of the respective flanges 38 are 37.5 millimetres and 33.0 millimetres.

The flow limiting gap 43 in Figure 2 and that between the recess 45 and the shroud 37 in Figure 3 are substantially 1 millimetre across in an axial plane. The holes (not shown) provided in the flanges 39 are circular and substantially 1 millimetre in diameter.

CLAIMS (Filed on 25.11.80) 1. A rotary sealing device including a first seal member adapted to be sealingly mounted on stator structure, and a second seal member adapted to be sealingly mounted on a rotor structure so as to rotate therewith, means for holding the seal members against one another over respective opposing sealing faces which are coaxial with the axis of rotation of the rotor structure, and a shroud which is coaxial with and secured to rotate with the second seal member and is so shaped as to include a shield portion shielding the said sealing faces from material moving with substantially radially inward motion towards the said axis and to provide a flange extending outwardly from the said shield portion, the flange being such that during rotation of the shroud with the second seal member, material which approaches the flange is driven away from the shroud by the rotation of the flange therewith.

2. A rotary sealing device according to claim 1, wherein the shroud is adapted to define an outer wall of a cooling space surrounding the seal members adjacent their sealing faces and to allow to flow through the cooling space.

3. A rotary sealing device according to claim 1 or 2, wherein the stator structure is part of a pump housing and the rotor structure is a rotary drive shaft which extends into the pump housing through a bearing mounted in the said part of the pump housing, the first seal member is a face seal member having an annular radial sealing face held resiliently against an opposing annular radial sealing face on the second seal member which is a ring-like counterface member mounted coaxially on the rotary drive shaft within the pump housing.

4. A rotary sealing device according to claim 3, wherein the shield portion of the shroud is cylindrical and coaxial with the drive shaft, and the flange is flat and extends in a radial plane.

5. A rotary sealing device according to claim 4, wherein a flow-limiting annular gap is defined between the flat flange and an adjacent stationary surface to allow a small flow of water into the shroud for cooling the seal members, and holes which are distributed around the axis of rotation and allow flow parallel to the axis are provided in the shroud as outlet holes for water from within the shroud.

6. A rotary sealing device substantially as described hereinbefore with reference to Figure 1 or 2 or 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the respective flanges 38 are 37.5 millimetres and 33.0 millimetres. The flow limiting gap 43 in Figure 2 and that between the recess 45 and the shroud 37 in Figure 3 are substantially 1 millimetre across in an axial plane. The holes (not shown) provided in the flanges 39 are circular and substantially 1 millimetre in diameter. CLAIMS (Filed on 25.11.80)

1. A rotary sealing device including a first seal member adapted to be sealingly mounted on stator structure, and a second seal member adapted to be sealingly mounted on a rotor structure so as to rotate therewith, means for holding the seal members against one another over respective opposing sealing faces which are coaxial with the axis of rotation of the rotor structure, and a shroud which is coaxial with and secured to rotate with the second seal member and is so shaped as to include a shield portion shielding the said sealing faces from material moving with substantially radially inward motion towards the said axis and to provide a flange extending outwardly from the said shield portion, the flange being such that during rotation of the shroud with the second seal member, material which approaches the flange is driven away from the shroud by the rotation of the flange therewith.