COOLANT LOSS VALVE FOR ENGINE PROTECTIVE SYSTEM

Abstract: A valve (10), response to the loss of coolant under pressure for example in a diesel engine, to open and allow fluid flow downstream with a consequent loss in fluid pressure, which is recognised by a pressure sensitive fuel valve supplying fuel flow to the engine. The coolant loss valve (10) includes a three-part housing (11, 12, 14) having the periphery of an elastomeric rolling diaphragm (44) trapped between two housing parts (12, 14) and forming a coolant chamber (45). A spring-loaded piston (50) and a pin (55) assembly tranmits diaphragm movement, the pin (55) forming a valve controlling fluid flow through a die cast aluminium head structure (11) which is the third part of the housing. The pin (55) is a stainless steel pin used for corrosion resistance and is supported for axial movement in a dual quad ring seal (62) and sleeve (60) structure.

Description: The invention relates to a coolant loss valve for an engine protective system. The invention has particular but not exclusive application to diesel engines. In an engine protective system as shown in Patent Specification US-A-3 877 455, fuel is supplied to a master valve and then routed to an engine so long as specific conditions are met. Among these conditions are sufficient oil pressure, coolant pressure and a lack of excessive engine heat, and devices are provided for sensing these parameters and controlling the flow of fuel to the engine. In a typical system as shown in the patent specification, the master control valve includes an oil pressure responsive piston which serves to hold the fuel valve open so long as sufficient oil pressure exists in the engine. The downstream side of the pressurized oil system supplied to the piston is routed in a parallel connection to a heat valve and a coolant loss valve. Both of the valves remain in a closed condition to prevent dumping of the oil under pressure to the sump of the system, which maintains the master control valve in an open position. The master control valve will be closed upon loss of oil pressure, either due to a failure in the engine itself or due to the opening of the coolant loss valve or the heat sensor valve, under predetermined excess or loss conditions. In coolant loss valves of this kind, a metal or elastomeric diaphragm is used for responsiveness to coolant pressure to provide linear motion to a valving element which then controls fluid flow, such as oil under pressure, through a main valve orifice. Normally, the valve is closed by coolant pressure and spring means are used to bias the valving element to a normally open position so that upon loss of coolant pressure, the valve will be opened and the fluid at the main valve routed to the sump. In the above-noted patent specification the actual valve element is a elastomeric disc which is resiliently biased by means of a separate spring to accommodate variable positioning and tolerance variations. Since the coolant loss valve usually operates in a closed condition under coolant pressure it is necessary that the valve operate consistently and repeatedly in this situation and under loss of pressure to move to an open position under the spring bias. Any contamination of the valve could prevent proper operation and failure to move to an open condition when appropriate could be costly and possibly contribute to a dangerous condition. Since the oil under pressure being controlled is usually contaminated to some degree, even though filters are used throughout a typical engine system, this problem is accentuated and it is difficult to design a reliable and consistently operable valve. Further, it is necessary to have a valve design which is efficient and functional and yet be relatively inexpensive as the engine systems are subject to close scrutiny and periodic maintenance. Another form of coolant loss valve known as the Sentinel Model CL-79 has been widely used in the past. This valve uses a square elastomeric diaphragm and a spring-loaded disc holder assembly, such assembly being a relatively complex structure comprising a moulded plastics stem and valve cup having a snap-in elastomeric seal disc and requiring a nylon washer retainer and specially configured elastomeric seal for sealing the stem of the assembly. The stem is slidably supported in an internal bore of the housing but is subject to contamination in spite of the seals and is subject to premature failure. Further, the main valve seat in this unit is a special relatively expensive stainless steel grommet pressed in place during assembly and chosen to avoid contamination buildup at this critical location. A pneumatically operated valve is known from US-A-3 593 958. According to one aspect of the invention there is provided a coolant valve for an engine protective system comprising; a valve body having an inlet port, an outlet port and a main valve seat to transmit fluid between the inlet and outlet ports, the valve body having a recess therein with the valve seat disposed at the end of the recess, a valve housing supported on the valve body, an elastomeric diaphragm sealingly received in the valve housing and forming an expansible pressure chamber, a coolant pressure port in the valve housing in fluid communication with the pressure chamber, a piston adjacent the diaphragm, spring means biasing the piston into engagement with the diaphragm to follow the movement of the diaphragm, a pin slidably received in the housing and fixed at one end of the piston for support thereof, and a valve member engageable with the valve seat to control fluid flow from the inlet port to the outlet port; characterised in that the pin slidably received in the housing is a small diameter pin and the other end of the pin to said one end is of the same small diameter, forms the valve member and is engageable into the valve seat. A coolant loss valve according to the invention can avoid many of the limitations of prior art devices and yet be a relatively simple structure which provides repeatable and reliable valve openings and closures. This is achieved by the three-part body structure valve housing in which the main valve is formed in a die cast aluminium housing portion and the remainder in injection moulded plastics housing parts. A circular elastomeric diaphragm is employed which is secured between the housing parts and which helps to seal the body parts, avoiding further body seals. The simplified piston and pin assembly reduces the number of parts required which increases the reliability of the unit while reducing the cost thereof. A stainless steel pin is preferably used as the main valving element connected directly to the piston which in turn engages and follows the diaphragm movement. The piston is biased to a normally open position in engagement with the diaphragm, while the pin is supported in a central bore in the housing for movement toward and away from the valve seat in the die cast housing structure. By this arrangement, a metal to metal valving structure can be achieved obviating many of the problems encountered in prior art devices which relied on elastomeric sealing elements. A double seal arrangement for the shaft of the pin can isolate the chambers but allow fairly unrestricted travel of the pin in part to its relatively small diameter and ease of sealing. The housing parts can be bolted together as an assembly which can be readily disassembled for service. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Figure 1 is an elevation of a coolant loss valve according to the invention; Figure 2 is a bottom view of the coolant loss valve of Figure 1; and Figure 3 is a sectional elevational view of the coolant loss valve of Figures 1 and 2. Referring to the drawing, a coolant loss valve 10 comprises a three-part housing made up of an aluminium head 11, a main valve housing 12 and a housing cap 14, all of which are secured together as a unit by means of bolts 15 passing through the housings 12, 14 and threaded into apertures in the aluminium head 11. The housing is generally square in configuration as best seen in Figure 2 and includes a coolant port 20 located in a boss on the outer side of the housing cap 14. The aluminium head 11 is a die casting also generally in a square configuration including an inlet port 21 at one side thereof and an outlet port 22 opposite thereto. The head 11 further includes an inlet bore 24 and an outlet bore 25 extending end to end in a horizontal direction and a transverse central bore 26. The bore 26 extends vertically and terminates in a bottom wall 28, having a central orifice or main valve seat 30 therein, joining the inlet and outlet bores 24, 25 respectively. The inlet port 21 and the outlet port 22 are internally threaded and can receive conduits to transmit fluid flow through the coolant valve 10. Typically, the inlet port 21 is connected to the oil pressure line at the downstream side of a master control valve in a diesel engine protection system, while the outlet port 22 may receive conduit which lead to the sump of an engine lubrication system. The main valve housing 12 is preferably formed of injection moulded plastics and is also generally square in configuration having four substantially identical side walls 32 extending between the housing cap 14 and the head 11. A generally circular funnel 35 is located in the centre of the housing 12 and has its wide end joined to the side walls 32 to support the funnel. The funnel 35 further supports, at the narrow end thereof, a central boss 35 which extends vertically both upwardly of funnel 35 and downwardly within the funnel structure itself. The boss 36 is slidably received as a friction fit in the bore 26 of the head structure 11 and is sealed therein by means of o-ring 38 trapped between shoulders of the bore 26 and the boss 36 respectively. The housing cap 14, is preferably also formed of injection moulded plastics and, although having a square outer periphery, includes a raised circular boss 41 therein, having an annular groove 42 at its outer periphery. The edge of a circular elastomeric diaphragm 44 is received in the groove 42 and is trapped therein between the boss 41 and the side walls 32 of the main housing 12 which are internally formed in a circular configuration at this location. The diaphragm 44 thus is in fluid communication with the coolant inlet port 20 and forms, together with the end cap 14, an expansible chamber 45. The diaphragm 44 is of the rolling diaphragm type and includes a reversely folded peripheral edge 46 thereon, which allows elongation extension of the diaphragm 44 into the main housing 12 with substantially little resistance to such elongation. A circular plastics piston 50 comprising a flat circular disc having a raised edge and a central hub 52 is supported adjacent the diaphragm 44 for movement therewith. A stainless steel cylindrical pin 55 is pressed into the hub 52 and extends vertically from the piston 50 forming a pin and piston assembly which moves together with the elastomeric diaphragm 44. The pin 55 is slidably received in a vertical bore 58 in the boss 36 of the housing 12 for movement toward and away from the main valve seat 30. The pin 55 is a relatively slender pin being approximately 4mm (0.156 inches) in diameter and is engageable with the wall 28 fully to cover the main valve seat 30 which is approximately 2.38mm (0.93 inches) in diameter. The pin 55 is further supported for vertical axial movement in the boss 36 by means of a pair of sleeves 60 and sealed by a pair of ring seals 62. A compression spring 65 is disposed between the narrow end of the funnel 35 and the piston 50 adjacent the central boss 52 to urge the piston 50 into engagement with the diaphragm 44 so that the piston and pin assembly follows the movement of the diaphragm 44 to open and close the main valve seat 30. In Figure 3 the coolant loss valve 10 is shown in a de-energised condition in the absence of fluid under pressure applied at the coolant port 20 with the spring 65 urging the piston 50 and the diaphragm 44 to a lowermost position adjacent the housing cap 14. In this position a free end 69 of the pin 55 is spaced from the valve seat 30 to allow the flow of fluid from the inlet port 21 to the outlet port 22. The end 69 of the pin 55 is flat and transverse to the vertical axis of the pin and is readily formed in this manner to achieve a suitable seal with the main valve seat 30. As pressure is applied at the coolant inlet 20, the elastomeric diaphragm 44 will move to an upper position acting against the bias of the spring 65 and move the pin 55 upwardly into engagement with the valve seat 30 to close the valve seat 30 and prevent the flow of fluid from the inlet port 21 to the outlet port 22. A vent port 70 is included in the housing 12 being located at the junction between the housing 12 and the head structure 11 and communicating with the area enclosed by the housing walls 32. An orifice 72 is included in the funnel 35 to provide communication with the volume between the funnel 35 and the piston 50 so that fluid trapped therein may freely breathe externally of the housing 12 so as not to restrict movement of the piston. By virtue of this design, a more efficient operation of the coolant loss valve 10 is realised. For example, because of the minimal diameter of the pin 55, very little frictional effect is introduced by the seals 62 and the supporting sleeves 60 which could become fouled by contaminants in the fluid being routed between the inlet and outlet ports 21, 22 and which could prevent reliable and repeatable movement of the pin and piston assembly. Further, the diameter of the diaphragm 44 is relatively large in relation to the diameter of the pin 55 providing a significantly large fluid ratio to overcome any frictional effects created by the elastomeric material of the seals 62 or by contamination in the bore 58. Still further, the combination of the stainless steel material in the pin 55 in conjunction with the die cast aluminium structure forming the wall 28 at the main valve seat 30 provides surfaces which are not susceptible to fouling or the accumulation of contaminants resulting in a reliable action of the valving therein.

Claims: A coolant valve (10) for an engine protective system comprising; a valve body (11) having an inlet port (21), an outlet port (22) and a main valve seat (30) to transmit fluid between the inlet and outlet ports, the valve body having a recess (26) therein with the valve seat (30) disposed at the end of the recess (26), a valve housing (12, 14) supported on the valve body (11), an elastomeric diaphragm (44) sealingly received in the valve housing (12, 14) and forming an expansible pressure chamber (45), a coolant pressure port (20) in the valve housing (12, 14) in fluid communication with the pressure chamber (45), a piston (50) adjacent the diaphragm (44), spring means (65) biasing the piston (50) into engagement with the diaphragm (44) to follow the movement of the diaphragm (44), a pin (55) slidably received in the housing (12, 14) and fixed at one end to the piston (50) for support thereof, and a valve member engageable with the valve seat (30) to control fluid flow from the inlet port (21) to the outlet port (22); characterised in that the pin (55) slidably received in the housing is a small diameter pin and the other end of the pin (55) to said one end of the same small diameter, forms the valve member and is engageable into the valve seat (30). A valve according to claim 1, wherein the housing has a boss (36) thereon received in the recess (26) of the valve body (12, 14), the boss (36) having a central bore (58) therein, and means (60, 62) in the bore (58) slidably supporting and sealing the shaft of the pin (55). A valve according to claim 2, wherein the supporting and sealing means comprises a pair of spaced ring seals (62) and a pair of spaced sleeves (60). A valve according to claim 3, wherein the valve housing (12, 14) includes a cap (14) having the coolant pressure port (20) therein, the elastomeric diaphragm (44) being engaged at its periphery between the cap (14) and the remainder of the housing (12) to seal the periphery of the expansible chamber (45). A valve according to claim 4, wherein the cap (14) has a circular boss (41) thereon with an annular groove (42) at its periphery and the elastomeric diaphragm (44) is received in the annular groove (42). A valve according to claim 5, wherein the housing has a funnel structure (35) therein terminating at the narrow end thereof in the housing boss (36). A valve according to any one of claims 1 to 6, wherein the elastomeric diaphragm (44) is a rolling diaphragm having a reversely folded peripheral edge (46) thereon.

Inventors: MACDONALD, ROBIN B., SCHAUPP, RICHARD E.
Applicants: PARKER HANNIFIN CORPORATION
Application year: 1988
Main classification: F01P11
IPC codes: F01P11, F02B3