US3626148A - Electric engine coolant heater - Google Patents

Abstract

A heater for warming coolant in a liquid-cooled engine, including a reservoir for coolant, the reservoir having an inlet and an outlet, a one-way inlet valve to permit coolant to enter the reservoir, a one-way outlet valve to permit coolant to leave the reservoir, a heating element in the reservoir, and a thermostat for controlling the heating element. The thermostat cuts out when the temperature of the coolant in the reservoir is above the boiling point of the coolant, so that the coolant is vaporized. After the heating element is turned off, the remaining vapor in the reservoir condenses, and the resulting partial vacuum draws in a fresh charge of coolant through the inlet, some of which proceeds immediately through the outlet to ram the heated coolant through the cooling system. The heating element is again energized and the cycle is repeated.

Description

United States Patent [72] Inventors Walter J. Woytowleh Deep River, Ontario; Charles G. Shepherd, Oakville, Ontario, both of Canada [21] Appl. No. 827,767

[22] Filed May 26, 1969 [45] Patented Dec. 7, 1971 [73] Assignee Bardon Research and Development Limited Toronto, Canada a part interest [541 ELECTRIC ENGINE COOLANT HEATER 56] References Cited UNITED STATES PATENTS 1,492,153 4/1924 Van Hise et a1 103/255 2,440,610 4/ 1948 Kimberlin 219/208 2,505,286 4/1950 Gratsinger 123/1425 X Primary Examiner-A. Bartis Attorney-Rogers, Bereskin & Parr ABSTRACT: A heater for warming coolant in a liquid-cooled engine, including a reservoir for coolant, the reservoir having an inlet and an outlet, a one-way inlet valve to permit coolant to enter the reservoir, a one-way outlet valve to permit coolant to leave the reservoir, a heating element in the reservoir, and a thermostat for controlling the heating element. The thermostat cuts out when the temperature of the coolant in the reservoir is above the boiling point of the coolant, so that the coolant is vaporized. After the heating element is turned off, the remaining vapor in the reservoir condenses, and the resulting partial vacuum draws in a fresh charge of coolant through the inlet, some of which proceeds immediately through the outlet to ram the heated coolant through the cooling system. The heating element is again energized and the cycle is repeated.

ELECTRIC ENGINE COOLANT HEATER This invention relates to a heater for prewarming the coolant of a liquid-coolant engine during cold weather when the engine is at rest.

Reliable starting of internal combustion engines (particularly automobile engines) in cold weather often requires the use of an auxiliary heater for warming the engine coolant. Such heaters employ electrical heating elements and they are energized by connecting them to the usual electrical mains. The heat provided by the auxiliary heater helps to lower the viscosity of the engine lubricant and to improve the vaporization of the fuel so that the engine is easier to crank and the fuel is easier to ignite. There are two types of such heaters which are in fairly general use: l) the block heater, and (2) the tank heater. The block heater is designed to be inserted directly into the cooling system of the engine, for example through a frost plug. Although this type of heater is reasonably efficient, installation frequently poses difficulties even for mechanics having proper tools. Also, the block heater normally operates continuously, and frequently more power is consumed than actually is needed. The installation of tank heaters is relatively time consuming, particularly for the average car owner, and conventional tank heaters rely mainly on convection to heat the engine block. The resulting circulation of coolant does not always uniformly warm the engine.

The heater of the present invention is of the tank type. It is simple to install (the cooling system need not be drailed in most cases) and it provides a relatively strong flow of coolant to adequately heat the engine block. Furthermore, the supply of electricity to the heater is regulated so that only enough power is consumed to keep the engine coolant at a predetermined temperature.

A preferred form of the invention includes a reservoir having an inlet and an outlet, a one-way inlet valve to permit coolant to enter the reservoir, a one-way outlet valve to permit coolant to be expelled from the reservoir, a heating element in the reservoir and a thermostat electrically connected to the heating element. The thermostat has upper and lower temperature limits; at the upper limit the heating element is turned off, and at the lower limit the heating element is turned on. The upper limit is selected so that the coolant in the reservoir is vaporized. whereupon it is expelled forcibly through the outlet. The heating element turns off after much of the coolant in the reservoir has vaporized, and the remaining vapor in the reservoir condenses, creating a partial vacuum which draws in a fresh charge of coolant into the reservoir. The fresh charge enters the reservoir with considerable force, and a substantial portion of it passes through the outlet and tends to ram the heated coolant through the cooling system. When sufficient incoming coolant has entered the reservoir so that the temperature sensed by the thermostat has dropped to the lower limit, the heating element is again turned on and the cycle is repeated. An advantage of the present invention is that the reservoir can be connected in the cooling system of an automobile engine by simply cutting an existing hose leading from the interior heater and connecting the cut ends of the hose to the inlet and outlet of the reservoir. The time required for installation is comparatively short, and only simple tools are needed.

In the drawings which illustrate a preferred embodiment of the invention:

FlG. l is a perspective view, partly broken away, showing a heater;

FIG. 2 is a sectional view of a one-way outlet valve used in the heater of FIG. 1; and

FIG. 3 is an exploded view of an inlet valve used with the heater of HG. 1.

Referring to FIG. 1, atank heater 10 is designed to be installed in the cooling system of a liquid-cooled internal combustion engine, particularly an automobile having an interior heater of the heat exchanger type. The interior heater is usually connected to the cooling system by a hose leading from the water pump of the engine. Theheater 10 is conveniently installed by cutting said hose as near to the water pump as practicable and connecting the ends of the cut hose to theheater 10. as will be explained in more detail below.

Theheater 10 includes a two-piece housing 12, a one-way inlet valve 14, a one-way outlet valve 16, aheating element 18, and athermostat 20.

Thehousing 12 is of noncorrosive material, such as zinc or aluminum and it comprises acylindrical shell 22 having anend wall 24 in which an outlet opening is formed, and anend member 26 which can be secured to theshell 22 by any conventional means (not shown) to provide a liquidtight seal. Theshell 22 and theend member 26 when joined together form a reservoir into which coolant is drawn, heated until it vapourizes and then expelled, as discussed below. Theend wall 24 of theshell 22 is formed with a generally cylindrical, tubular, open-ended boss 28 which extends both inwardly and outwardly of theend wall 24. Theboss 28 constitutes an outlet for thetank 10. The outer end of theboss 28 is internally threaded to receive anadapter 30 for accommodating hoses which will not fit onto theboss 28 directly. Theboss 28 and theadapter 30 are respectively provided withgrooves 32, 34 in their outer surfaces to facilitate the attachment of a hose with a conventional hose clip. The inner end of theboss 28 is shaped to receive thevalve 12, as shown in FIG. 2, and explained more fully below.

Theend member 26 of thehousing 12 has an outwardly projecting, cylindrical, tubular, open-ended boss 36 the axis of which is preferably in line with the axis of theboss 28. Theboss 36 constitutes an inlet for thetank 10. The outer end of theboss 36 is provided with internal threads for receiving anadapter 38 that is similar to theadapter 34, and likewisegrooves 40, 42 are respectively provided in the outer surfaces of theboss 36 and theadapter 38 to facilitate attachment of a hose by means of conventional hose clamps. The inner end of theboss 36 is formed to receive thevalve 14, as shown in F IG. 3 and explained more fully below.

Theend member 26 includes an outwardly projecting generallysemicylindrical portion 44 that is integral with anend wall 46. Theportion 44 of theend member 26 opens outwardly, but it is closed by aremovable cover plate 48 which can be held in place by screws or other conventional means. Thecover plate 48 has a central opening through which an electrical cable (not shown) can be inserted. Theinlet valve 14 includes a generallycircular disc 50 the center of which is slightly dished, and which is preferably of aluminum or cadmium plated steel. Thedisc 50 is formed with two opposed, outwardly projecting tabs 52 (HO. 3), and the inner end of theboss 36 is formed withrecesses 54 for receiving the tabs 52 so that thedisc 50 can hang downwardly with the tabs 52 in therecesses 54. The inner end of theboss 36 is further formed with acircular recess 56 that is slightly larger in diameter than the diameter of thedisc 50, and therecess 56 terminates at its inner end in a shoulder 58 against which thedisc 50 is seated when it is in its closed position. Thedisc 50 is held in place by a washer 60 (also preferably of aluminum or cadmium plated steel) that is frictionally engaged in acircular recess 62 formed in the outer end of theboss 36, and the internal diameter of the washer 60 is larger than the diameter of thedisc 50 so that thedisc 50 can freely swing upwardly through the washer 60 to an open position, where there is relatively little restriction to the flow of incoming coolant. Thedisc 50 fits rather loosely in place, but when the pressure in the reservoir builds up thedisc 50 is pressed firmly against the shoulder 58 to thereby prevent any vapor from being expelled through the inlet of theheater 10.

Theoutlet valve 16 is very similar to theinlet valve 14, except that it is arranged so that the fluid is permitted to flow only out of the heater l0 and not into it. Thevalve 14 includes adisc 64 that is identical to thedisc 50, and it hangs inside a recess formed in theboss 28 in a manner similar to thedisc 50. ln its open position, as shown in FIG. 2, thedisc 64 can swing upwardly in the same direction as thedisc 50. Thedisc 64 is held in place by awasher 66, but in this case thewasher 66 has an internal diameter that is smaller than the diameter of thedisc 64 so that thewasher 66 constitutes a valve seat for thedisc 64. In its closed position, as shown in solid lines in F IG. 2, thedisc 64 is pressed against the outer surface of thewasher 66.

Theheating element 18 is conventional, and it may be in the from of a loop of one or more turns, which preferably is positioned near the bottom of thehousing 12. Theheating element 18 is provided with ends 68, 70 that are engaged in openings formed in theend member 26 of thehousing 12, and the ends 68, 70 can be retained in place by swagging the surrounding metal of theend member 26 to provide a firm and leak proof seal.Electrical terminals 72, 74 respectively protrude from the ends 68, 70 of theheating element 18, and they are of course electrically insulated from thehousing 12. Theheating element 18 can be designed to operate at the usual main voltages (eg 1 l or 220 volts AC).

Thethermostat 20 is rigidly attached to theend wall 46 of theend member 26, between the ends 68, 70 of the heating element. The inner surface of theend wall 46 directly opposite thethermostat 20 is formed with a recess 75 which receives a portion of theheating element 18, so that there is reasonably good thermal contact between the outer surface of theheating element 18 and thethermostat 20. Thethermostat 20 has twoterminals 76, 78 and is connected in series with theheating element 18 by a lead (not shown) so that the heating element is controlled by thethermostat 20. Thethermostat 20 has an upper limit at which the thermostat turns off theheating element 18 and a lower limit at which the heating element is turned on. The upper limit is such that coolant in the reservoir is vaporized before theheating element 18 is turned off; the lower limit determines the average temperature of the coolant in the cooling system. In a prototype of theheater 10, an upper limit of 250 F. and a lower limit of l70 F. was used; these limits were found to be satisfactory in a six cylinder engine with a 50 percent glycol antifreeze mixture, which was kept at an average temperature of 70 F.

The heater is most conveniently installed in a horizontal position, as this position usually involves little or no .sharp bends in the connecting hoses. in addition, theheater 10 should be installed at about the upper level of the coolant in the engine block. if theheater 10 is installed too low, the coo lant tends to circulate continuously by convection and the desired vapourization does not'take place to the same extent. It is conceivable that theheater 10 could be installed vertically, with the inlet at the top, but this is not as desirable as the horizontal position in most automobile installations because the heater hose to which connection is made is most frequently horizontally disposed in most cases the installation of the heater l0 simply entails cutting the hose leading from the water pump to the interior heater and attaching the cut ends of the hose to therespective bosses 28 and 36, with the hose leading from the water pump connected to the outlet of theheater 10. The hose should be raised to at least the level of the top of the radiator to avoid loss of coolant. Hose clamps can then be installed to secure the hoses on thebosses 28 and 36. The engine should then be idled for several minutes to fill theheater 10 with coolant. Alternatively, theheater 10 could be filled with antifreeze before installation.

In operation, theheater 10 is connected with a suitable source of electrical power. When the temperature of the coolant n the reservoir of thehousing 12 falls below the low limit of thethermostat 20, theheating element 18 is energized and it remains energized until most of the coolant in the reservoir is vaporized. The hot vapor is expelled through theoutlet valve 16, and eventually condenses and mixes with the coolant downstream from theheater 10. When the high temperature limit of thethermostat 20 has been reached, the heating element is disconnected from the power source and remains disconnected until the temperature has again dropped to the low temperature limit. The remaining vapor in the reservoir condenses and the resulting partial vacuum draws in a fresh charge of coolant through theinlet valve 14. The fresh charge of coolant enters the reservoir with considerable force, and a considerable portion of it continues directly through the reservoir and the outlet valve. As explained above this action tends to ram the heated coolant through the cooling system. When the temperature drops to the low limit of thethermostat 20, the heating element again is energized and the cycle is repeated. It will thus be noted that the operation of theheating element 18 is not continuous, but instead is periodic. The average amount of power consumed depends on the ambient temperature, wind, etc., for example it was determined in a prototype heater that power consumption varies from about 850 watts at 20 F. to watts at +32 F., to maintain an engine temperature of about 50 F.

In a prototype of the heater, the separation between the valves was about 2 three-quarter inches, the diameter of thediscs 50 and 64 was about one-half inch. Theheating element 18 was rated at 850 watts.

What we claim as our invention is:

1. A heater for warming liquid coolant in a cooling system of an engine and for forcing said coolant through the cooling system without creating any appreciable convection current in said heater, said heater comprising:

a. an enclosed reservoir for containing liquid coolant, said reservoir having a fluid inlet and a fluid outlet to permit said reservoir to be connected in said cooling system with said coolant substantially filling said reservoir;

b. a one-way inlet valve in communication with said fluid inlet to permit coolant to flow into said reservoir and to prevent coolant from leaving said reservoir through said fluid inlet;

c. a one-way outlet valve in communication with said fluid outlet to permit heated coolant to leave said reservoir and to prevent coolant from entering said reservoir through said fluid outlet; 7

d. an electrical heating element coupled to said reservoir for heating said coolant; and

e. a thermostat having an upper limit and a lower limit, said thermostat being electrically connected to said heating element to control the supply of electricity to said heating element, said thermostat being positioned so that it is in thermal contact with the contents of said reservoir and is responsive to the temperature of said coolant in said reservoir in both its liquid and vapor states, the supply of electricity to said heating element being interrupted when the temperature sensed by the thermostat reaches said upper limit, and being resumed when said temperature falls to said lower limit, said upper limit being such that at least a portion of the liquid coolant in said reservoir is vaporized when said heating element is energized and heated coolant is expelled through said outlet, the heating element being disconnected from its supply of electricity by said thermostat when said upper limit has been reached, whereupon the temperature in said reservoir falls so that the vapor pressure in said reservoir drops substantially thereby drawing a fresh charge of liquid coolant into said reservoir through said fluid inlet.

2. A heater as claimed in claim 1 wherein said fluid inlet and said fluid outlet are substantially in alignment and said heating element is in said reservoir.

3. A heater as claimed in claim 2 wherein said inlet valve comprises a first disclike member positioned at the inner end of said fluid inlet against an end wall of said reservoir, said first disclike member being pivotally mounted and the inner end of said fluid inlet being shaped to provide a seat for said first dis clike member when said first disclike member is pressed against said fluid inlet inner end.

4. A heater as claimed in claim 3 wherein said outlet valve comprises a second disclike member positioned at the inner end of said fluid outlet against an opposite end wall of said reservoir, said second disclike member being pivotally mounted, and a washer secured to said opposite end wall and positioned inwardly of said second disclike member to provide a seat for the same.

5. A heater as claimed in claim 2 wherein a portion of said heating element is adjacent to an inner surface of a wall of said reservoir. and said thermostat is in contact with an outer surface of said wall opposite said portion of said heating element, said wall being thermally conductive.

6. in combination with an engine cooling system containing liquid coolant, a heater for warming the liquid coolant and for forcing said coolant through the cooling system. the heater being positioned at about the upper level of coolant in the system so that the heater is substantially full of coolant; the heater comprising an enclosed reservoir for containing liquid coolant, said reservoir having a fluid inlet and a fluid outlet to permit said reservoir to be connected in said cooling system with said coolant substantially filling said reservoir; a one-way inlet valve in communication with said fluid inlet to permit coolant to flow into said reservoir and to prevent coolant from leaving said reservoir through said fluid inlet; a one-way outlet valve in communication with said fluid outlet to permit heated coolant to leave said reservoir and to prevent coolant from entering said reservoir through said fluid outlet; an electrical heating element coupled to said reservoir for heating said coolant; and a thermostat having an upper limit and a lower limit,

said thermostat being electrically connected to said heating element to control the supply of electricity to said heating element, said thermostat being positioned so that it is in thermal contact with the contents of said reservoir and is responsive to the temperature of said coolant in said reservoir in both its liquid and vapor states, the supply of electricity to said heating element being interrupted when the temperature sensed by the thermostat reaches said upper limit, and being resumed when said temperature falls .to said lower limit, said upper limit being such that at least a portion of the liquid coolant in said reservoir is vaporized when said heating element is energized and heated coolant is expelled through said outlet. the heating element being disconnected from its supply of electricity by said thermostat when said upper limit has been reached whereupon the temperature in said reservoir falls so that the vapor pressure in said reservoir drops substantially thereby drawing a fresh charge of liquid coolant into said reservoir through said fluid inlet.

7. Apparatus as claimed in claim 6 wherein said fluid inlet and said fluid outlet are substantially in alignment.

Claims (7)

1. A heater for warming liquid coolant in a cooling system of an engine and for forcing said coolant through the cooling system without creating any appreciable convection current in said heater, said heater comprisIng: a. an enclosed reservoir for containing liquid coolant, said reservoir having a fluid inlet and a fluid outlet to permit said reservoir to be connected in said cooling system with said coolant substantially filling said reservoir; b. a one-way inlet valve in communication with said fluid inlet to permit coolant to flow into said reservoir and to prevent coolant from leaving said reservoir through said fluid inlet; c. a one-way outlet valve in communication with said fluid outlet to permit heated coolant to leave said reservoir and to prevent coolant from entering said reservoir through said fluid outlet; d. an electrical heating element coupled to said reservoir for heating said coolant; and e. a thermostat having an upper limit and a lower limit, said thermostat being electrically connected to said heating element to control the supply of electricity to said heating element, said thermostat being positioned so that it is in thermal contact with the contents of said reservoir and is responsive to the temperature of said coolant in said reservoir in both its liquid and vapor states, the supply of electricity to said heating element being interrupted when the temperature sensed by the thermostat reaches said upper limit, and being resumed when said temperature falls to said lower limit, said upper limit being such that at least a portion of the liquid coolant in said reservoir is vaporized when said heating element is energized and heated coolant is expelled through said outlet, the heating element being disconnected from its supply of electricity by said thermostat when said upper limit has been reached, whereupon the temperature in said reservoir falls so that the vapor pressure in said reservoir drops substantially thereby drawing a fresh charge of liquid coolant into said reservoir through said fluid inlet.

2. A heater as claimed in claim 1 wherein said fluid inlet and said fluid outlet are substantially in alignment and said heating element is in said reservoir.

3. A heater as claimed in claim 2 wherein said inlet valve comprises a first disclike member positioned at the inner end of said fluid inlet against an end wall of said reservoir, said first disclike member being pivotally mounted and the inner end of said fluid inlet being shaped to provide a seat for said first disclike member when said first disclike member is pressed against said fluid inlet inner end.

4. A heater as claimed in claim 3 wherein said outlet valve comprises a second disclike member positioned at the inner end of said fluid outlet against an opposite end wall of said reservoir, said second disclike member being pivotally mounted, and a washer secured to said opposite end wall and positioned inwardly of said second disclike member to provide a seat for the same.

5. A heater as claimed in claim 2 wherein a portion of said heating element is adjacent to an inner surface of a wall of said reservoir, and said thermostat is in contact with an outer surface of said wall opposite said portion of said heating element, said wall being thermally conductive.

6. In combination with an engine cooling system containing liquid coolant, a heater for warming the liquid coolant and for forcing said coolant through the cooling system, the heater being positioned at about the upper level of coolant in the system so that the heater is substantially full of coolant; the heater comprising an enclosed reservoir for containing liquid coolant, said reservoir having a fluid inlet and a fluid outlet to permit said reservoir to be connected in said cooling system with said coolant substantially filling said reservoir; a one-way inlet valve in communication with said fluid inlet to permit coolant to flow into said reservoir and to prevent coolant from leaving said reservoir through said fluid inlet; a one-way outlet valve in communication with said fluid outlet to permit heated coolant to leave said reservoir and to prevent coolant from entering said reservoir through said fluid outlEt; an electrical heating element coupled to said reservoir for heating said coolant; and a thermostat having an upper limit and a lower limit, said thermostat being electrically connected to said heating element to control the supply of electricity to said heating element, said thermostat being positioned so that it is in thermal contact with the contents of said reservoir and is responsive to the temperature of said coolant in said reservoir in both its liquid and vapor states, the supply of electricity to said heating element being interrupted when the temperature sensed by the thermostat reaches said upper limit, and being resumed when said temperature falls to said lower limit, said upper limit being such that at least a portion of the liquid coolant in said reservoir is vaporized when said heating element is energized and heated coolant is expelled through said outlet, the heating element being disconnected from its supply of electricity by said thermostat when said upper limit has been reached whereupon the temperature in said reservoir falls so that the vapor pressure in said reservoir drops substantially thereby drawing a fresh charge of liquid coolant into said reservoir through said fluid inlet.

7. Apparatus as claimed in claim 6 wherein said fluid inlet and said fluid outlet are substantially in alignment.

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