In operating diesel powered equipment in cold weather, problems arise with starting cold engines. When the temperature drops below 40.degree. F. approximately (about +4.degree. to 5.degree. C.), starting the engine may become difficult. If the temperature is significantly lower than that, starting engines by conventional means may become essentially impossible, and damage to starters and internal mechanical components may result from forced starting. There is the additional problem that it is common practice in railroad diesel equipment to use water without anti-freeze (there may be other additives, but the freezing characteristics are still those of plain water) as the coolant for the engine, so that the temperature of the coolant must not be allowed to drop very far below 32.degree. F. (0.degree. C.), if at all.
Particularly in severe weather areas, then, it has been common practice to continuously run standby or layover diesel equipment at idle or low speeds. This has number of obvious disadvantages: not only is the cumulative expense of the wasted fuel a very significant cost item; the useless waste of precious petroleum resources is of great concern; long periods of running at low speeds can result in internal damage from improper lubrication of the cylinder walls; combustion is relatively inefficient, so that there is a disproportionate increase in the generation of atmospheric pollutants, and finally of course there is the noise factor which may be of considerable concern, as the incessant beat of a large diesel engine at idle can be most irritating.
There have been many devices proposed to provide auxiliary energy supply for standby or parked vehicles of all sorts. Among the approaches taken have been heaters fired by propane/butane type fuels, heaters with separate fuel supplies of liquid fuel, auxiliary electrical generating equipment which then provides energy to electrical heaters, and other methods. Another form has been the use of a second engine or vehicle, which in one application (U.S. Pat. No. 4,305,354 Dec. 15, 1981, to Majkrzak) uses quick coupling connections to interconnect the liquid coolant systems of the two engines, so that the operating engine will pump its heated coolant into the cold engine on an interchange basis, and the cold engine can then be started. A variation of this same approach is taught in U.S. Pat. No. 4,051,825, Oct. 4, 1977, to Elder. A still further variation is described in U.S. Pat. No. 3,373,728, Mar. 19, 1968 to Collins, in which the second or starter engine provides thereon a heat exchanger, to which the coolant system of the cold engine is connected, to heat up its coolant without actual interchange of fluids between the two engines. In this patent to Collins, it is envisioned that a tow truck or similar vehicle will have the heat exchanger mounted thereon.
A United States Patent issued Feb. 14, 1967 to Hraboweckyj describes an auxiliary heater fueled by butane, to be permanently mounted on the frame of a highway tractor, which provides for cab heat as well as a heat exchanger for the engine coolant. Advantages claimed for this particular approach include simplicity, operation essentially without moving parts, use of natural draft, quiet operation and lower pollution. There are, however, some restrictions on movement through tunnels and other places applicable to vehicles with butane or propane tanks.
In recent years, two U.S. Patents have issued for devices which provide complete units, designed to use the main vehicle diesel fuel supply, and separate thermal generators, to provide auxiliary heat, each intended to be permanently affixed to the subject vehicle. In U.S. Pat. No. 3,758,031, to Moran, a small boiler is provided, with a conventional furnace type pressure fuel burner, to provide heated fluid, which is then interconnected with the vehicle engine coolant system, as well as with a radiator system in the cab. This unit is designed for highway diesel rigs, to be mounted on the tractor frame. In U.S. Pat. No. 4,192,274, Mar. 11, 1980, to Damon, the system layout is essentially the same as taught in Moran, except that the heater system provided is an element of the novelty claimed, being a specially designed oil pressure burner design. A principal focus of this patent is the control system for operation of the system.
There has been recent development interest in systems to provide for maintaining the coolant of standby or non-operating engines at a temperature above the ambient. The escalation of fuel prices over the past few years has heightened the activity in this field, and there are several small auxiliary systems being offered which tend generally to be small motor-generator systems allied with immersion or wrap-around electric heaters.
One of these is the LTP system, (for low temperature protection), being offered by Microphor, Inc, of Willits, Calif., on which U.S. Pat. No. 4,424,775 has issued. The patent teaches a small auxiliary diesel engine providing thermal energy to the coolant and engine oil of a main engine by means of a heat exchanger denominated as "triaxial flow". The heated coolant is then pumped through the main engine system by electrical pumps. A generator is also driven by the auxiliary engine for battery charging, etc. It is stated this system will transfer 50 KBTU/hr of thermal energy to the primary engine.
Still another approach being pursued is the use of an automatic start device which will start the inoperative engine automatically based on temperature sensing devices, or on a time cycle to preserve engine lubricants. One proposed device of this nature is reported as being under development by Maxson Corporation of St. Paul, Minn.