Patent Application
20180292149
The present disclosure relates generally to a cooling system for a machine, and more particularly to a cooling system separating functions of coolant pressure relief and recovery from radiator capping.
Cooling systems are used across virtually all fields of modern machinery. In one known application, a cooling system equipped with one or more liquid-to-air heat exchangers is provided for cooling an internal combustion engine. A pump driven from the engine gear train circulates coolant between the engine block and a heat exchanger in the nature of an air-cooled radiator. The circulated coolant exchanges heat with material of the engine block, and rejects the heat to ambient air conveyed across exterior surfaces of the radiator in a well-known manner. It is common for such cooling systems to include one or both of an engine oil cooler and a transmission fluid cooler each of which transfers heat into the circulated coolant. A great many different configurations and combinations of cooling system components have been produced for more than a century. Outside of the context of engine systems, cooling systems for machinery are used to cool pumps, compressors, electric motors, milling and cutting tools, and all manner of industrial and commercial equipment.
One feature common to most liquid cooling systems for machinery is the use of a liquid coolant that changes in volume relatively substantially with changes in temperature. It is well known that an engine coolant, such as glycol, water, mixtures of glycol and water, and other materials can increase in temperature sufficiently to increase volume of the coolant greater than a closed volume of the cooling system. So-called “recovery bottles” are commonly used in conjunction with radiators to accommodate the increased volume of coolant produced in response to an increase in temperature, and store the coolant for eventual return into the system as temperatures decrease.
A fluid pressure of coolant is commonly raised apace with increases in temperature. As temperatures decrease the fluid pressure of course decreases along with it. The up-and-down pressure cycling produced by increases and decreases in coolant volume can result in coolant being pushed out of a radiator and sucked back into the radiator many times during the course of a typical cooling system duty cycle. This near-constant change in pressure and temperature and in-and-out flow of fluid can make certain components of the cooling system susceptible not only to thermal and/or structural fatigue, but also to seal failure.
It is necessary to provide relatively robust sealing in the plumbing that connects all parts of the cooling system, and in particular between the radiator and the recovery bottle. A typical design employs a radiator cap having integrated valve structures that enable pressure relief to flow coolant to a recovery bottle, and return when appropriate. U.S. Pat. No. 4,167,159 to Warman is directed to a pressurized liquid cooling system for an internal combustion engine, and discloses a radiator cap of generally conventional design that provides fluid paths for expansion and contraction of coolant. As described in Warman, the pressure cap has pressure and vacuum relief valve components for limiting the maximum operating pressure of the system and for limiting negative pressures to avoid damage during cooling after engine shutdown. A lower system relief pressure for lower-temperature conditions is provided by way of a second, temperature-responsive, pressure relief valve. While Warman perhaps provides advantages in some applications, certain of the components are still likely susceptible to leakage or other problems.
In one aspect, a cooling system for a machine includes a radiator assembly including a radiator tank having formed therein a tank access port, an overflow port, and a plurality of coolant circulation ports, for connecting with a coolant circulation loop. The radiator assembly further includes a cap coupled with the radiator tank to seal the tank access port, and a valve mechanism. The valve mechanism includes a valve body coupled with the radiator tank and having formed therein an inlet fluidly connected with the overflow port, and an outlet structured to fluidly connect with a recovery bottle. The valve mechanism further includes a pressure relief valve positioned fluidly between the inlet and the outlet and having a first valve opening surface, and a coolant return valve positioned fluidly between the inlet and the outlet and having a second valve opening surface. The first valve opening surface is exposed to a fluid pressure of the inlet, such that the pressure relief valve opens in response to a pressure drop from the inlet to the outlet, to convey coolant from the radiator to the recovery bottle. The second valve opening surface is exposed to a fluid pressure of the outlet such that the coolant return valve opens in response to a pressure drop from the outlet to the inlet, to convey coolant from the recovery bottle to the radiator.
In another aspect, a radiator assembly includes a radiator tank having an inner surface defining an internal fluid space, and an outer surface, and having formed therein a plurality of coolant circulation ports, a tank access port, and an overflow port. The assembly further includes a cap coupled with the radiator tank at the tank access port and blocking fluid flow through the tank access port, and a valve mechanism coupled with the radiator tank at the overflow port. The valve mechanism includes a valve body having formed therein an inlet fluidly connecting with the overflow port, and an outlet structured to fluidly connect with the recovery bottle. The valve mechanism further includes a pressure relief valve having a first valve opening surface, and a coolant return valve having a second valve opening surface. The valve mechanism is in a first state where the first valve opening surface is exposed to a fluid pressure of the inlet and the second valve opening surface is exposed to a fluid pressure of the outlet and the valve mechanism blocks fluid flow through the overflow port. The valve mechanism is adjustable to a second state to permit fluid flow through the overflow port by way of opening the pressure relief valve responsive to a pressure drop from the inlet to the outlet or to a third state to permit fluid flow through the overflow port by way of opening the coolant return valve in response to a pressure drop from the outlet to the inlet.
In still another aspect, a method of operating a cooling system for a machine includes conveying a coolant between a radiator and a coolant circulation loop structured to exchange heat with a machine, and increasing a temperature and a pressure of the coolant within the cooling system by way of the exchange of heat. The method further includes opening a pressure relief valve in a valve mechanism coupled to the radiator at an overflow port in response to the increase in pressure, and venting an excess volume of the coolant produced in response to the increase in temperature to a recovery bottle by way of the pressure relief valve. The method further includes decreasing the temperature in the pressure of the coolant such that a volume of the coolant is reduced, and opening a coolant return valve in the valve mechanism in response to the decrease in pressure. The method still further includes returning coolant to the radiator by way of the coolant return valve, and inhibiting leakage of coolant and air through a tank access port during the venting of the excess volume of coolant and the returning of the coolant to the radiator by way of a solid cap fluidly sealing the tank access port.
Referring to
Referring also now to
Cooling system 10 may further include a recovery bottle 34 having a bottle inlet 35, and a vent line 36 fluidly connecting valve mechanism 48 to recovery bottle 34. Valve mechanism 48, more particularly valve body 50, may have formed therein an inlet 52 fluidly connected with overflow port 26, and an outlet 54 structured to fluidly connect with recovery bottle 34. Cooling system 10 may further include a thermostat assembly 38 having a recirculation valve 40, and a recirculation line 42 extending between recirculation valve 40 and one of the plurality of coolant circulation ports 28 and 30. Thermostat assembly 38 may be operable to direct coolant to circulate through machine 12 and an additional heat exchange mechanism 44 such as an engine oil cooler, until the coolant has reached a certain temperature, at which point recirculation valve 40 may be adjusted to enable coolant to be conveyed through a supply line 43 to radiator tank 16.
Referring now to
Valve mechanism 48 may further include a pressure relief valve 56 within valve body 50 and positioned fluidly between inlet 52 and outlet 54 and a coolant return valve 58 positioned fluidly between inlet 52 and outlet 54. Pressure relief valve 56 and coolant return valve 58 may each be pressure-operated, based upon a pressure difference between inlet 52 and outlet 54 in a manner further described herein. To this end, pressure relief valve 56 may include a first valve opening surface 62 and a first valve closing surface 66. Coolant return valve 58 may include a second valve opening surface 64 and a second valve closing surface 68. Each of pressure relief valve 56 and coolant return valve 58 may be positioned at least partially within a fluid space 82 defined by valve body 50 and structured to fluidly connect inlet 52 and outlet 54 depending upon the state of pressure relief valve 56 and coolant return valve 58.
Each of pressure relief valve 56 and coolant return valve 58 may be movable between an open position and a closed position, and may be biased towards the respective closed position. In an embodiment, valve mechanism 48 includes a first biaser 92 biasing pressure relief valve 56 towards the respective closed position, and a second biaser 94 biasing coolant return valve 58 towards the respective closed position. Each of first biaser 92 and second biaser 94 may include a biasing spring. First biaser 92 may be held in compression between pressure relief valve 56 and coolant return valve 58, and second biaser 94 may be held in compression between coolant return valve 58 and pressure relief valve 56.
It can be further noted from
It can also be seen from
In the illustrated embodiment, each of the various ports formed in tank wall 18 extends by way of a bore between inner surface 22 and outer surface 20. In the case of overflow port 26 a portion of the bore through tank wall 18 may be threaded by way of a second set of threads 99 engaged with a first set of threads 98 formed on a connector 51 of valve body 50. It can be seen that connector 51 has a tapered shape such that the set of threads 98 forms a tapered profile, which tapered profile is complementary to a tapered profile formed by the set of threads 99. In the case of tapered threads a fluid seal between valve body 50 and radiator tank 16 can be accomplished by way of metal-to-metal wedging amongst the mating threads. It can further be seen from
Referring now to
Referring to the drawings generally, but with particular reference to cooling system 10, during operating cooling system 10 coolant may be conveyed between radiator tank 16 and coolant circulation loop 32 to exchange heat with machine 12. The exchange of heat will tend to cause an increase in a temperature and a pressure of the coolant within cooling system 10. In response to the increase in pressure, pressure relief valve 56 in valve mechanism 48 is opened to enable venting of an excess volume of the coolant that is produced, in response to the increase in temperature, to recovery bottle 34. At a later time during operation, or potentially during or after shutting down machine 12, the temperature and the pressure of the coolant can decrease, causing coolant return valve 58 in valve mechanism 48 to open in response to the decrease in pressure. It has been observed that the cooling and contracting of coolant within radiator tank 16 can cause a vacuum to develop within space 60. Coolant is returned by way of the opening of coolant return valve 58 to radiator tank 16. During conveying coolant into and out of radiator tank 16 in the manner described, leakage of coolant and air through tank access port 24 can be inhibited by way of cap 46.
It has been observed that certain earlier radiator cap designs included structure for enabling pivoting of the cap body relative to components of the radiator cap including a pressure relief valve and/or a coolant return valve, for instance which necessitated a breach in the otherwise fluidly sealed body of the cap. Those skilled in the art will appreciate the thermally dynamic conditions under which machine cooling systems must operate. Components expand and contract in response to changes in temperature, experience thermal fatigue, and can be corroded or otherwise degraded in performance by the relatively harsh conditions. The pivot pin or other structure in a radiator cap and the associated breach in the otherwise fluidly sealed barrier had a tendency in response to the changes in temperature and pressure, to form a leak path enabling air to be drawn into the coolant system. The present disclosure provides for separating pressure relief and coolant return functions between the radiator cap and other apparatus, eliminating or at least reducing the possibility of air entering the system and causing a host of known problems.
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.
