IMPROVEMENTS TO ROTARY PUMPS

Abstract: A sealless coolant pump (10) comprising a pulley assembly (14) having a pulley (18) for co-operation with a drive belt B and a driving magnetic member (22), a pump body (12) housing a driven pump member (26) attached to a driven magnetic member (30), which co-operates with the driving magnetic member (22) through a static container (16) attached to the pump body, wherein the pulley assembly and driven pump member are rotatable about a common axis, and the pulley, driving magnetic member, and driven magnetic member are substantially radially aligned or superpositioned with respect to said common axis.

Description: IMPROVEMENTS TO ROTARY PUMPS This invention relates to improvements to rotary pumps, and in particular coolant pumps for combustion engines. In a rotary pump it is common practice to provide a rotating mechanical seal at the point where the drive shaft enters the body of the pump. In the internal combustion engine field where a rotary pump is employed as the engine coolant pump, mechanical seals are by no means wholly reliable. The sealing faces may film over with deposits from chemicals held in solution - a situation familiar to the industry known as filming which subsequently leads to sealing breakdown and coolant leakage. The faces may fail prematurely and leak due to excessive shaft run-out. The faces may also fail due to vibration transmitted from ailing bearings which have been overloaded by over zealous tightening of the drive belt. Additionally the faces may wear out prematurely due to scoring caused by hard particles in the pumped medium. Quite apart from the reliability question, it is well known that leakage past a mechanical seal cannot be eliminated entirely even when the seal is in an as new condition. A mechanical seal consists of two polished radial surfaces running adjacent to each other. Since the pressure of the pumped medium at the seal is different from the pressure of the air outside the seal a pressure gradient is set up across the seal faces between which slow leaking or weeping is apt to occur. It is therefore evident that a slightly weeping mechanical seal is not always indicative of a failed seal. However, a common misconception is that any signs of weeping indicates a failed seal. A perfectly serviceable coolant pump assembly is thus often needlessly replaced. However, it is also known to provide a sealless pump which employs a magnetic coupling comprising a driving and a driven magnetic member which couple with one another through a static, hermetically sealed container or containment shroud. Accordingly, the static container prevents leakage since it is a non-moving part. The disadvantage with conventional magnetic couplings is that they are bulky. Because of an ever- in creasing need to reduce the space occupied by the internal combustion engine in its engine compartment, is has not been feasible to accommodate a known magnetic coupling between the pulley or the gear drive system and the coolant pump. Accordingly, the invention seeks to avoid or at least mitigate the problems in the known art. An object of the invention is to provide a sealless coolant pump of the type described comprising a magnetic coupling suitable for use with an internal combustion engine. One aspect of the invention provides a sealless coolant pump comprising a pulley assembly having a pulley for co-operation with a drive belt and a driving magnetic member, a pump body housing a driven pump member attached to a driven magnetic member, which co-operates with the driving magnetic member through a static container attached to the pump body, wherein the pulley assembly and driven pump member are rotatable about a common axis, and the pulley, driving magnetic member, and driven magnetic member are substantially radially aligned or superpositioned with respect to said common axis. Beneficially, a sealless coolant pump having a reduced axial length is thereby provided compared to known pumps. The driving magnetic member can be radially outward of the driven magnetic member. In another form, the driving magnetic member can be radially inward of the driven magnetic member. In this form, the pulley assembly can comprise an annulus for carrying the driving magnetic member. The annulus can carry part of a bearing for co-operating with part of the bearing carried by the static container. Preferably the static container comprises a centrally protruding portion which operably carries a bearing for co-operating with the pulley assembly. Also, the driven pump member can comprise a shaft which is rotatable about the common axis which shaft protrudes axially in to said centrally protruding portion of the static container. A second aspect of the invention provides a sealless coolant pump comprising a pulley assembly having a pulley for co-operating with a drive belt and a driving magnetic member, a pump body housing a driven pump member attached to a driven magnetic member which co-operates with the driving magnetic member through a static container attached to the pump body, wherein the driving magnetic member and driven magnetic member are substantially radially aligned and the driving magnetic member is radially inward with respect to the driven magnetic member. Beneficially, this configuration enables the pulley assembly to comprise a bearing which co-operates with the static container and a pump shaft assembly attached to the driven pump member. Another aspect of the invention provides a sealless coolant pump comprising a pump body housing a driven pump member attached to a driven magnetic member and a shaft assembly rotatable about a rotation axis, a pulley assembly comprising a pulley and driving magnetic member which co-operates with the driven magnetic member through a static container attached to the pump body, wherein the driving magnetic member and driven magnetic member are substantially radially aligned with respect to the rotation axis but the pulley is axially displaced therefrom, the pulley assembly comprising a bearing which co-operates with the pump shaft assembly and wherein the static container encloses the whole of the shaft assembly and the driven magnetic member. Beneficially the pulley can be axially outermost from the pump. A further aspect of the invention relates to sealless coolant pump comprising a pump impeller such as the pump disclosed in European Patent specification EP-A-0331288 to Concentric Pumps Limited. The sealless coolant pump comprising a pump body housing a driven impeller pump member attached to a shaft assembly and a driven magnetic member, and a pulley assembly comprising a driving magnetic member for co-operating with the driven magnetic member through a static container attached to the pump body, the pump further comprising a radially inward fluid inlet region and radially outward fluid outlet, an axial or thrust, bearing for co-operating with the shaft assembly, and a duct for communicating fluid from the outlet region to a position proximal the thrust bearing. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- FIGURE 1 is a schematic sectional side elevation view of a pump according to the invention; FIGURE 2 is a schematic sectional side elevation view of a second embodiment of a pump according to the invention; FIGURE 3 is a schematic sectional side elevation view of a third embodiment of a pump according to the invention; and FIGURE 4 is a sectional side elevation view of a fourth embodiment of a pump according to the invention. Referring to Figure 1 there is shown a pump 10 according to the invention comprising a pump body 12 and pulley assembly 14. The pulley assembly and pump body are separated by a static container 16 which hermetically seals the pump body to prevent loss or leakage of fluid in this region. The container 16 is attached to body 12 by bolts which clamp an annular ring against the container 16 and body 12. Pulley assembly 14 comprises a pulley or pulley ring 18 which in use is engaged by a belt B which drives the pulley. The assembly further comprises an annular flange 20 which provides an annular bore radially inward of the pulley 18. Flange 20 carries a driving magnetic member 22 which can consist of an annular series of spaced bar magnets. The pulley bore engages a bearing 24 for example of the double row angular contact ball bearing type. A spacer 25 can be used to position pulley assembly 14 with respect to container 16 and pump body 12. The pump body 12 houses a driven member 26 comprising impeller blades 28. The driven member carries a driven magnetic member 30 which also can comprise an annular series of spaced bar magnets. Preferably, there is a 50% overlap between the bar magnets of the driven and driving magnetic members. The driven magnetic member 30 is carried on an axial extension 32 which can comprise a series of radial apertures to enable fluid communication around the pump body for lubrication purposes. The driven member 26 is attached to a shaft assembly 34 which comprises a hollow shaft 35 having first and second journal ends 36 and 38. First journal end 36 is journalled in a bearing 40 which abuts an axial spacer 42. Second journal end 38 is journalled in a bearing 44 which together with journal end 38 abuts an axial bearing 46 which acts as a thrust bearing for hollow shaft 35. The pump body 12 also defines a fluid inlet region 38 and fluid outlet region 50. In use, belt B drives pulley assembly 14 about rotational axis A which causes the driving magnetic member 22 also to rotate and transfer kinetic energy to driven pump member 26 due to magnetic coupling with driven magnetic member 30. This causes rotation of blades 28 which drive fluid from inlet region 48 to outlet region 50 thereby providing a pressure differential between these regions. Fluid passes from the pump 10 through an outlet (not shown) for example for communication with an internal combustion engine. Fluid can be supplied to an inlet (not shown) from a radiator within a vehicle having such an internal combustion engine. Beneficially, pump 10 has a reduced axial extent compared to known sealless coolant pumps, due to the positioning of the pulley substantially radially in line with magnetic members 22 and 30. Beneficially also, bearing 24 provides a dynamically stable system since it compresses container 16 on to bearing 40. Preferably bearing 40 can comprise a ceramic material such as silicon carbide which is strong in compression. In another form, driven magnetic member 30 can comprise an induced magnetic drive coupling comprising a ring of axially placed copper rods suitably embedded in an appropriate matrix. Referring to Figure 2 there is shown a pump 110 according to the invention wherein components which are in common with those shown in Figure 1 are given the same two digits reference number prefixed with the number 1. In this embodiment, a static hermetic seal is provided by container 116 which can for example be made of a non-magnetic stainless steel. The container comprises a series of folded regions as shown in Figure 1. However, in this embodiment the driving magnetic member 122 is radially outside the driven magnetic member 130 with respect to the rotation axis A. Bearing 124 is carried on the outside radial face of angular flange 120 for co-operating with housing 116 and extension 132. Referring to Figure 3 there is shown a third embodiment of a pump 210 according to the invention. In this embodiment components in common with the earlier two embodiments are given the same two digit reference number prefixed with the number 2. In this embodiment pulley 218 comprises an annular flange 220 at approximately the same radial position with respect to axis A and therefore axially displaced with respect to pulley 218. Radially inward of pulley 218 is bearing 224 which co-operates with housing 216 and bearings proximal a first journal end 236 of shaft assembly 234. Axially displaced from pulley 218 is magnetic driving member 222 which co-operates with driven magnetic member 230 carried on extension 232 attached to shaft assembly 234. Beneficially housing 216 encloses the moving driven parts of the pump and in this embodiment shaft 234 protrudes beyond the co-operating magnetic members to enable pulley 218 to engage housing 216 and effectively shaft 235 via a series of bearings thereby providing a dynamically stable pump in which significant radial forces are applied to pulley 218 by belt B. Also, a diametrically compact pump is provided which can use a smaller pulley than other embodiments. In a further embodiment of the invention, a pump 310 comprises many features in common with those shown in Figure 1 in relation to pump 10. Components in common with pump 10 are given the same two digit reference numbers prefixed with the number 3. In this embodiment pump 310 further comprises a duct 352 which passes through pump body 312 between the outlet region 350 and a position proximal the thrust bearing 346. Body 312 also comprises an end plate 354 which locates thrust bearing 346 at the end of shaft 335. The duct 352 can comprise a bore in body 312 as well as a tube passing away from and back to plate 354. Also, shaft 335 can comprise a central bore 356 which only passes from end 336 to a point beyond driven member 326 where a cross bore 358 communicates the lubricating medium with region 348. Beneficially, the lubricant supplied to the thrust bearing 346 is therefore derived from duct 352. Beneficially therefore fluid is drawn from the relatively high pressure region of outlet region 350 to a relatively low pressure region proximal the assembly shaft 334 thereby to lubricate the contact between journal end 238 and thrust bearing 346.

Claims: CLAIMS: 1. A sealless coolant pump comprising a pulley assembly having a pulley for co-operation with a drive belt and a driving magnetic member, a pump body housing a driven pump member attached to a driven magnetic member, which co-operates with the driving magnetic member through a static container attached to the pump body, wherein the pulley assembly and driven pump member are rotatable about a common axis, and the pulley, driving magnetic member, and driven magnetic member are substantially radially aligned or superpositioned with respect to said common axis. 2. A pump according to Claim 1 wherein the driving magnetic member is radially outward of the driven magnetic member. 3. A pump according to Claim 1 wherein the driving magnetic member is radially inward of the driven magnetic member. 4. A pump according to any preceding claim wherein the pulley assembly comprises an annulus for carrying the driving magnetic member. 5. A pump according to Claim 4 wherein the annulus also carries part of a bearing for co-operating with part of a bearing carried by the static container. 6. A pump according to Claim 5 wherein the static container comprises a centrally protruding portion which operably carries a bearing for co-operating with the pulley assembly. 7. A pump according to Claim 6 wherein the driven pump member comprises a shaft which is rotatable about the common axis which shaft protrudes axially in to said centrally protruding portion of the static container. 8. A sealless coolant pump according to Claim 1 or independent thereof, comprising a pulley assembly having a pulley for co-operating with a drive belt and a driving magnetic member, a pump body housing a driven pump member attached to a driven magnetic member which co-operates with the driving magnetic member through a static container attached to the pump body, wherein the driving magnetic member and driven magnetic member are substantially radially aligned and the driving magnetic member is radially inward with respect to the driven magnetic member. 9. A pump according to Claim 2 wherein the pulley assembly comprises a bearing which co-operates with the static container and a pump shaft assembly attached to the driven pump member. 10. A sealless coolant pump comprising a pump body housing a driven pump member attached to a driven magnetic member and a shaft assembly rotatable about a rotation axis, a pulley assembly comprising a pulley and driving magnetic member which co-operates with the driven magnetic member through a static container attached to the pump body, wherein the driving magnetic member and driven magnetic member are substantially radially aligned with respect to the rotation axis but the pulley is axially displaced therefrom, the pulley assembly comprising a bearing which co-operates with the pump shaft assembly and wherein the static container encloses the whole of the shaft assembly and the driven magnetic member. 1 1. A pump according to Claim 10 wherein the pulley is axially outermost from the pump. 12. A sealless coolant pump according to any preceding Claim or independent thereof comprising a pump body housing a driven impeller pump member attached to a shaft assembly and a driven magnetic member, and a pulley assembly comprising a driving magnetic member for co-operating with the driven magnetic member through a static container attached to the pump body, the pump further comprising a radially inward fluid inlet region and radially outward fluid outlet, an axial or thrust bearing for co-operating with the shaft assembly, and a duct for communicating fluid from the outlet region to a position proximal the thrust bearing.

Inventors: TEBBY STEPHEN WALKER, TEBBY, STEPHEN, WALKER
Applicants: CONCENTRIC PUMPS LTD, TEBBY STEPHEN WALKER, CONCENTRIC PUMPS LIMITED, TEBBY, STEPHEN, WALKER
Application year: 1998
Main classification: F04D13
IPC codes: F04D13