Coolant pump

Abstract: A water pump has a bowl (24) like body and a seal (30,32) across the rim of the body. Coolant leakage through the seal (30,32) is used to wet the rubbing faces of the seal (30,32). Superfluous leakage is collected in the bowl (24) so that it may be evaporated by engine heat.

Description: This invention relates to coolant pumps for use in I.C. engines, and of the kind comprising a body adapted to be fixed to an engine block as a cover for a cavity therein, an impeller mounted on a shaft journalled in said body for location in said cavity, bearing means in the body journalling said shaft, drive means for the shaft for example a pulley or gear on the end of the shaft opposite to that provided with the impeller, and a seal between the impeller and the body which may, and often does, according to the design of the seal allow minute bleed or leakage of coolant from the cavity to wet the seal surfaces. It will be appreciated that the cavity forms a pump chamber, and has appropriate passages communicating with the cavity as inlet and outlet for the pump. Thus, the pulley is outside the body, the bearing is between the pulley and impeller, and the seal is between the bearing and the impeller. DE 3931938A (Figure 2) shows a pump of this kind. The body has a tubular extension in which the bearing and seal are located, with a space therebetween. A drain passage opens through the wall of this tubular part to allow leaked fluid to run directly out so that it does not accumulate. The leaked fluid inevitably runs down the external surface of the pump body and may leave a visible trace for example a water stain. GB 1461901 shows another design which is effectively similar. Figure 1 of the said DE 3931938A shows a version in which the drain passage leads to a collection chamber formed by a bore closed by a plug. This is to prevent venting of the leaked fluid and allow it to accumulate. However this solution is subject to its own problems because of the inevitable temperature and pressure cycling with the risk of leakage from the area of the plug. The problem with pumps of the mentioned kind is that the minute leakage of coolant is apt to be misinterpreted by mechanics. This leakage is inherent, as is mentioned, in order to wet the seal faces, and excess leakage of coolant evaporates due to engine heat. When the engine is cold, and evaporation does not occur, the leakage may be seen. The object of the invention is to solve the problem. According to the invention, a coolant pump for use in I.C. engines is of the kind comprising a bowl-like body adapted to be fixed to an engine block as a cover for a cavity therein, an impeller is mounted on a shaft journalled in said body, bearing means for the shaft are on the end of the same opposite to that provided with the impeller and in the base of the bowl-like body, and a seal is provided between the impeller and the body which allows minute bleed or leakage of coolant to wet the seal surfaces, and a space is provided between the said seal and the bearing for said bleed or leaked coolant and a drain passage extends from the space, characterised in that the seal extends as a cover plate substantially in the plane of the rim of the bowl, said space for coolant is formed in the bowl, and said drain passage opens through the base of the bowl above the lowermost point of the bowl interior in ordinary usage. This solves the problem, because the leaked coolant can accumulate in the bowl below the drain passage and be evaporated by engine heat so that in normal usage there is no overflow leaving a trace, and additionally the presence of the coolant will not be noted by the mechanic. It is only in the event that the leakage exceeds the possible volume of the pool that flow will occur through the drain passage and hence a genuinely failed pump will be detected. In ordinary usage of a pump which has not failed, the pool will be evaporated by engine heat without ever reaching sufficient volume to overflow through the drain passage. According to a feature of the invention the seal comprises a sheet metal pressing fixed and sealed in relation to the body for example as an interference fit in the rim of the bowl. Preferably the periphery of the pressing is arranged to extend out of the bowl into the engine block cavity: it may then serve as the primary or possibly the only pump location means. One embodiment of the invention is now more particularly described with reference to the accompanying drawing wherein the sole figure is a sectional elevation of a water pump for an I.C. engine. Referring to the drawing, the engine block 10 has a cavity which communicates with inlet port 11 and outlet ports 12, 14 for circulating coolant. The cavity houses vaned impeller 16 mounted on shaft 18 which is journalled in bearing 20 and carries a drive pulley or like 22 at the free outer end of the shaft. The pump body comprises a bowl 24 having a flange 26 extending radially outwardly at its rim. The flange is adapted to be bolted to the engine block with an interposed O ring 28 trapped in a rebate in the rim. The body or bowl may be a casting. Conventional water pump bodies have a drilled hole for drainage, or a cored hole provided by adding a hole-forming core to the mould impression, but in this invention the hole 44 (described below) extends generally axially parallel to the axis of shaft 18 and can thus be cored integrally with the impression without needing a separate added core piece. A seal is diagrammatically indicated by the reference 30,32. This seal is of conventional construction essentially comprising component 30 rotatable with the shaft and part 32 which is stationary with the bowl, and rubbing surfaces located between the parts 30,32. It will be appreciated by those skilled in the art that the space 36 between the impeller and the seal 30,32 is in effect part of the pump cavity and hence is filled with coolant which may be a water based mixture. Flow to the rubbing surfaces is required but only in minute amounts. Excess fluid collects in the bowl after passing through the seal and may form a pool 40. If the level in the pool were to arise above the chain-dot line 42, which represents a horizontal plane when the pump is in its normal position of use, excess liquid escapes via vent or drain passage 44. The latter is shielded from view by the drive pulley 22 as a further safeguard against coolant escape being misinterpreted. The outer seal component 32 has an upstanding peripheral flange 46 which could be continuous. Hence, if the cavity and body are circular in a plane normal to the shaft axis, the flange is cylindrical: alternatively the flange could be a series of separate prongs for location. The flange or prongs enter the body cavity at 48 and position the pump relative to the cavity. It will also be appreciated that the periphery of the seal adjacent the flange or prongs 46 needs to seal with the body 24 to prevent fluid flow at that interface. This may be achieved by a press fit of the parts and/or the use of a sealant, but alternatively O ring 28 may have a dual function of sealing the interface of the pressing 32 and the body 24 as well as preventing leakage out of the pump between the body and the block 10.

Claims: A coolant pump for use in I.C. engines and of a kind comprising a bowl-like body (24) adapted to be fixed to an engine block (10) as a cover for a cavity (11,12,14,36) therein, an impeller (16) mounted on a shaft (18) journalled in said body, bearing means (20) for the shaft on the end of the same opposite to that provided with the impeller and in the base of the bowl-like body, and a seal (30,32) between the impeller and the bearing which allows minute bleed or leakage of coolant to wet the seal surfaces, a space between the said seal and the bearing for said bled or leaked coolant and a drain passage (44) opening from said space, characterised in that the seal extends as a coverplate substantially in the plane of the rim of the bowl, said space for coolant is formed in the bowl, and said drain passage (44) opens through the base of the bowl above the lowermost point of the bowl interior in ordinary usage. A pump as claimed in Claim 1 wherein the seal comprises a sheet metal pressing (30) having a cylindrical flange (46) which is a press fit in the bowl-like body. A pump as claimed in Claim 2 wherein the periphery of the seal extends out of the bowl into the cavity as a location means. A pump as claimed in any of Claims 1-3 wherein said drain passage is parallel to the shaft axis.

Inventors: FREEMAN RICHARD ROBERT, FREEMAN, RICHARD ROBERT
Applicants: CONCENTRIC PUMPS LTD, CONCENTRIC PUMPS LIMITED
Application year: 1991
Main classification: F04D29
IPC codes: F04D29, F01P11, F16J15, F01P5