US1980811A - Cooling system for internal combustion engines - Google Patents

Description

Nov. 13, 1934. F. LJUNGSTROM COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES 4 Sheets-Shet 1 Filed March 1'7. 1933 Nov. 13, 1934. F. LJUNGSTROM COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed March 17, 1933 4 Sheets-Sheet 2 Nov. 13, 1934. F. LJUNGSTROM 1,980,811

COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed March 17, 1933 4 Sheets-.Sheet 5 7 {1; ATTORNEY Nov. 13, 1934. F. LJUNGSTROM COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES I Filed March 17. 1933 4 Sheets-Sheet 4 INVE TOR g FW-m? Patented Nov. 13, 1934 UNITED STATES COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Fredrik Ljungstriim, Lidingo, Sweden, assignor to Aktiebolaget Spontan, corporation of Sweden Stockholm, Sweden, a

Application March 17, 1933, Serial No. 661,251 In Germany June 20, 1932 37 Claims.

The present invention relates to cooling systems for internal combustion engines and has particular reference to cooling systems of the type adapted to utilize a cooling fluid of high boiling point and low freezing point, such as oil, which is circulated in a closed path of flow in which it absorbs heat from the parts of the engine to be cooled and dissipates this heat in a cooler or radiator over which cooling air is passed.

The usual cooling systems employing water as a cooling medium are subject to numerous disadvantages such as freezing at low temperatures and evaporation of the water at high temperatures, while, on the other hand, oil and like fluids of high boiling point and low freezing point not only avoid such disadvantages but provide other distinct advantages, such, for example, as that of permitting the engine to be operated at a higher temperature and consequently with 20 greater efliciency than is possible with water cooling.

Heretofore, however, in spite of the known advantages of oil and like fluids for cooling purposes, systems employing such fluids have not been successful, due largely to the high viscosity and low specific heat with consequent low heat conductivity of oil as compared with water.

The present invention has for a principal object the provision of an improved cooling system adapted to employ oil as a cooling medium. More specifically, the invention contemplates the provision of novel radiator structure with the cooling fan and circulating pump elements of a system of the character under discussion, by means of which novel structure eflicient cooling may be obtained and practical advantages with respect to compactness and ruggedness of design, simplicity and low cost, be secured, as will hereinafter more fully appear in conjunction with the ensuing description of suitable examples of apparatus for carrying the invention into effect.

In the accompanying drawings forming a part of this specification and illustrative of the examples of apparatus to be described:

Fig. 1 is a horizontal cross-section of the principal elements of a cooling system according to the present invention as applied to an automobile or like engine;

Fig. 2 is a section taken on the line 22 of Fig. 1;

Fig. 3 is a section taken on the line 33 of Fig. 1;

Fig. 4 is a front elevation, on a reduced scale, of the right hand half of the fan and radiator. shown in Fig. 1;

Fig. 5 is a more or less diagrammatic illustration, on a still further reduced scale, of one form of radiator tube, in elevation;

Fig. 6 is a view similar to Fig. '5 and taken at right angles thereto;

Fig. 7 is an enlarged longitudinal cross-section of a portion of one form of tube;

Fig. 7a is a cross-section of the tube shown in F 7;

Fig. 8 is a side elevation of a portion of one form of radiator tube;

Fig. 8a is a view taken at right angles to Fig. 8;

Fig. 8b is a cross-section taken on the line 8b8b of Fig. 8; i

Fig. 9 is a front elevation showing a portion of another form of radiator;

Fig. 10 is a longitudinal section of the part of the radiator shown in Fig. 9;

Fig. 10a is a section taken on the line 10a-10a of Fig. 10;

Fig. 11 is a more or less diagrammatic front elevation of a part of a radiator employing still another form of tube;

Fig. 11a is a perspective view of one of the tubes shown in Fig. 11;

Figs. 12 to 19 inclusive show the several steps employed in making still another form of radiator tube;

Fig. 20 is a front elevation, partly in section, of a radiator having tubes of the form shown in Figs. 12 to 19;

Fig. 21 is an axial section of the structure shown in Fig. 20;

Fig. 22 is a plan view of part of the radiator shown in Fig. 20;

Fig. 23 is an axial section of an aviation engine having a cooling system embodying the invention, and

Fig. 24 is a section taken on the line 24-24 of Fig. 23.

Turning now more particularly to Figs. 1 to 4 of the drawings, reference numeral 10 indicates one end of a cylinder block of an internal combustion engine having one or more cylinders, one being indicated at 12, jacketed to provide spaces for circulation of cooling fluid. As used herein the term cylinder block isintended to include the cylinder block structure generally which includes the cylinder head portion of the structure in the case of engines having cylinder heads separable from the main block structure in which the barrel portions of the cylinders are located. At the end or the cylinder block there are provided flanges 14 and 16 having passages 18 and 20, respectively, for flow of cooling fluid to and from the jacket spaces in the cylinder block. The specific construction and arrangement of the cylinder block for providing the spaces for cooling fluid form no part of the present invention, but in conjunction with the use of oil or the like for cooling fluid, I prefer to use a form of construction such as that disclosed in my copending application, Serial No. 661,250 filed March 1'7, 1933.

The radiator of the cooling system is of the closed or surface type and comprises a casing 22 in the form of a body of revolution, preferably circular in cross-section and providing two central chambers 24 and 26, chamber 24 being an inlet chamber for receiving heated cooling fluid from the engine and for distributing this fluid to the cooling tubes of the radiator and chamber 26 being a collecting chamber for receiving cooled fluid from the tubes. Chambers 24 and 26 constitute headers connected by a plurality of bent cooling tubes 28 which extend outwardly from the central casing 22. The form and arrangement of these tubes constitutes an important feature of the invention and will be described in detail later.

Casing 22 is closed at one end by a member 30 which comprises arms 32 and 34 cored to provide passages 36 and 38, the passage 36 providing an inlet conduit for conducting cooling fluid from the passage 18 to the inlet chamber 24 and passage 38 providing an outlet conduit connecting the outlet chamber 26 of the radiator with the passage 20.

The opposite side of casing 22 is closed by a casing member 40. Members 30 and 40 have central aligned passages therethrough and mounted in said members by means of ball bearings 42 and 44 is a shaft 46 which projects at each end through the casing. Shaft 46 is packed against leakage past member 40 by means of a stufling box comprising packing 48 compressed by spring 50 around the shaft between the packing and bearing 44 and leakage around the other end of the shaft past member 30 is prevented by a similar stufling box comprising packing 52 compressed by spring 54.

Chambers 24 and 26 are separated axially by means of a web 56 and chamber 24 is divided into an inner chamber 24a and an outer chamber 24b by means of a circular web or flange 58 which is advantageously formed as a part of member 40.

Fixed to shaft 46 in chamber 24a is the pump for circulating cooling fluid through the system. In the form shown, the circulating'pump comprises an impeller member 60 of the centrifugal type having a ring of impeller blades 62. Radially outside of the discharge ends of the impeller blades 62, the flange 58 carries a ring of diflusor blades 64, the passages between these blades providing communication between the portions 24a and 24b of the inlet chamber. One or more by-pass openings 66 provide for relatively restricted communication between chamber 24b and chamber 26.

The end of shaft 46 projecting through member 40 has secured thereto the hub 68 of the cooling fan 70, which preferably comprises a relatively large number of radially extending blades 72.

The opposite projecting end of shaft 46 has secured thereto the pulley 74 adapted to be driven by belt 76.

In case the engine is used in an automobile or like automotive vehicle, the unitary assembly comprising the radiator, circulating pump and fan is mounted at the forward end of the en gine and belt 76 may be readily driven from a pulley (not shown) on the forward end of the engine crank shaft, in the usual manner. The two arms or branches 32 and 34 of member 30 are preferably flanged as shown at 78 in Fig. 2 and removably secured, respectively, to flanges 14 and 16 on the cylinder block by means of studs 80.

It will be observed that the assembly comprising all of the major elements of the cooling system, other than the engine jackets, forms a selfcontained unit which is supported from the cylinder block by means of the inlet and outlet conduits connecting the radiator with the cylinder block and readily removable from the engine as a unit, upon removal of the studs 80.

The cooling tubes 28 in the present embodiment, as shown in Figs. 1 and 4 to 6, comprise two sets or series of tubes 28a and 28b, the latter set being arranged outside of the former and both sets comprising tubes, one end of which communicates with chamber 24b and the other end of which communicates with chamber 26. The preferred shape of these tubes is shown more clearly in Figs. 5 and 6, the former showing a single tube in frontal elevation and Fig. 6 showing the same tube in side elevation.

As indicated in Fig. 5, the tube is preferably bent so as to provide-two end portions a connected by curved intermediatev portions 5 to a middle curved portion 0. Portions a are bent so that ends of the tube join the casing 22 radially and the sections b are curved to involute form. Section 0 is preferably arcuate. As indicated in Fig. 6, the connected sections a and b form two legs 25 and 2'7 situated in planes normal to the axis of shaft 46, which may be considered as the axis of the radiator, and spaced apart axially of the radiator. These legs are connected by the arcuate portion 0 of the tube which lies in a plane oblique with respect to the axis of the radiator.

As will be evident from Fig. 5, each of the tubes provides a loop having relatively closely adjacent ends and, as shown in Fig. 4, the several loops in each set are uniformly spaced peripherally of the radiator.

Due to the bending of the sections b of the tubes to the form of involutes, the distance between adjacent tubes in the same set is maintained constant between the radially inner portions of the tubes and the radially outer portions thereof, and this arrangement, as is clearly illustrated in Fig. 4, provides for spaces of uniform area between the tubes for flow of cooling air.

Furthermore, as shown in Fig. 4, the ends of tubes in axially adjacent transverse planes and lying in the same axial plane are bent outwardly from the casing 22 in opposite directions so that the tubes in adjacent planes cross each other as viewed in Fig. 4, that is, frontally of the radiator.

The tubes 28 are preferably of steel having relatively thin wall thickness and are, as shown in Fig. 1, preferably secured at their ends to the casing 22 by rolling the ends into suitable openings formed in the casing wall.

The operation of the cooling system just described is largely obvious from the drawings. Assuming the system to be filled with a suitable cooling fluid, actuation of the shaft 46 from the crank shaft of the engine or other suitable source of power causes operation of the pump 60 which draws cooling fluid from the engine block through the inlet conduit 36 and delivers it through the diflusors 64 to the chamber 24b from which it passes through the cooling tubes, giving up its heat during its passage through these tubes to the air which is forced over the tubes by fan '70 which is simultaneously operated upon actuation of shaft 46. The cooled fluid is returned to chamber 26 and from this chamber passes by way of the outlet conduit 38 to the cooling jackets of the engine where it again absorbs heat and is again withdrawn through conduit 36 by pump 60, thus completing the cycle of circulation.

In this connection, it is desired to point out that lubricating oil of the same character as that used to lubricate the working parts of the engine is a desirable medium to use as cooling fluid since the use of such oil provides numerous advantages. In the first place, fluid tight construction of the means forming the jacket spaces in the engine is not required, since leakage of a portion of the oil used for cooling purposes into the crank case or other parts of the engine containing lubricating oil is not harmful and the cooling fluid in the cooling system may readily be maintained under pressure, which is desirable in a closed circuit oil cooling system to prevent formation of gas due to heating of the oil to comparatively high temperatures, by interconnecting the cooling system with the pressure side of the pump for circulating lubricating oil through the engine. Also, this interconnection may be employed to maintain the cooling system filled with cooling fluid, replacing any fluid which may leak from the cooling circuit. An arrangement suitable for utilizing lubricating oil as the cooling medium and for maintaining the cooling system under pressure and for automatically replacing fluid lost from the system due to leakage is disclosed in my copending application Serial No. 513,335. Obviously, other suitable means may be employed for maintaining the cooling circuit fllled with cooling fluid under pressure and for replacing fluid lost from the system due to leakage.

I have found that the placing of the ring of diffusor blades between the chamber in which the circulating pump works and the inlet ends of the cooling tubes increases the efliciency of operation of the system and I have further found and regard as important the provision of the bypass opening between the inlet and outlet chambers of the radiator. This latter is particularly important when oil or other cooling fluid having the viscosity characteristics of ordinary lubricating oil is used, especially under cold starting conditions. Assuming the system to be filled with lubricating oil and that the engine is started at low temperature, it will be evident that the comparatively long passages through the cooling tubes will provide considerable resistance to flow of the oil which is comparatively viscous under the conditions assumed. Consequently, there will be a considerable flow of oil through the bypass opening, since, due to the comparatively short length of the by-pass passage, the resistance to flow therethrough is not materially greater under ,cold starting conditions than under normal running conditions. Thus, in starting, an initial bypass flow is established which enables circulation to be set up immediately and which permits comparatively rapid warming up of a portion of the I oil in the system. This in turn gradually causes heating of the radiator structure and of the oil in the tubes, with consequent lowering of viscosity of the oil in the tubes and diminished resistance to flow therethrough. As the oil becomes warmer and less viscous, the resistance to flow through the cooling tubes becomes materially less than under the cold starting-conditions, while theresistance to flow through the comparatively short by-pass passage remains relatively constant and normal circulation through the cooling tubes is gradually established as the system warms up.

Due to the form and arrangement of the cooling tubes in the radiator, substantially uniform spaces for flow of cooling air over the tubes are provided which aids in the uniformity of cooling and, due to the .oppositely curved arrangement of the legs of the tubes in adjacent planes, the turbulence of flow of air over the tubes is enhanced, which contributes to maximum rate of heat transfer from the tubes to the air passing thereover. Also, in the arrangement disclosed, the rapidity of the rate of heat transfer is enhanced because of the placing of the cooling tubes of the radiator on the discharge side of the cooling fan where the flow of air is more turbulent in character than is the flow of air on the suction side of the fan which comprises the usual location for radiators of the character under discussion.

By employing the arrangement described, heat transfer at substantially maximum rate is obtained over the entire area of cooling surface and as a consequence a given cooling capacity may be obtained with a minimum amount of cooling surface, which is provided, in the construction according to the present invention, by structure which is compact and relatively rugged as compared with the usual cellular radiator and which can be manufactured at relatively low cost.

It is further to be noted that by forming the cooling tubes as described, the resulting radiator structure is in the form of a body of revolution or circular in frontal area and air is forced over substantially the entire frontal area of the radiator directly from the blades of the cooling fan, which preferably, as shown, has a diameter substantially the same as that of the radiator.

While the invention is not limited to this specific form of radiator, the general form of radiator shown is to be preferred.

In the case of the ordinary cooling system employing water as a cooling fluid, a high rate of heat transfer is obtained between the water and the inside surface of the cooling elements of the radiator as compared with the rate of heat transfer from the outer surfaces of the radiator to the air passing thereover. For this reason it is customary to increase the outside area of radiators by the use of fins, flanges, and the like.

On the other hand, when oil is used as the cooling fluid, the rate of heat transfer from the oil to the inside surfaces of the radiator cooling elements is relatively lower compared to the rate of heat transfer from the external radiator surfaces to the air, due to the relatively higher viscosity and lower specific heat of oil as compared with water. Therefore, if in the case of oil cooling systems, a conventional type of radiator with extended external cooling surfaces were employed, the radiator would operate normally at a temperature not much above that of the cooling air. This in turn would lead to the formation of a relatively cold and viscous oil film on the inside surfaces of the radiator, so that transfer of heat to the walls of the radiator would be greatly reduced because of the relatively high viscosity of the oil at the low temperature.

This difl'iculty with respect to heat transmission to the walls of the radiator from the oil is avoided in accordance with the present invention by utilizing a radiator construction in which the internal and external areas for the transmission of heat are of about equal size. It will be apparent that in the radiator illustrated in Figs. 1 and 3, the plain tubes provide inside and outside heat transfer surfaces of substantially equal area. With this arrangement the greatest resistance to transfer of heat is between the outside surfaces of the tubes and the air, and as a result the cooling tubes operate normally at a temperature considerably above that of the surrounding air and approaching that of the oil circulated therethrough. This relatively high operating temperature of the tubes prevents the formation of a cold and relatively viscous oil film on the inner surfaces of the tubes so that a relatively good rate of heat transfer is obtained between the oil and the tubes. It is for this reason that, when oil is used as a cooling medium, plain steel tubes having relatively thin walls provide the most satisfactory construction.

1 In some cases it may be advantageous to in crease the rate of heat transfer between the cooling fluid and the inside surfaces of the cooling tubes. This may be accomplished most advantageously by means which tend to increase the turbulence of flow of the cooling fluid passing through the cooling tubes. By way of example, there is shown in Figs. 7 and 7a means for creating turbulence of flow comprising a corrugated strip 82 of thin sheet metal inserted in a cooling tube 28.

Figs. 8, 8a and 8b illustrate another means for creating tubulence of flow comprising a cooling tube which at intervals along its length is flattened as at 84 so as to provide more or less regularly spaced portions of oval or elliptical crosssection as shown in Fig. 8b.

It will be evident that many different sectional forms of cooling tubes may be employed and that the specific shape of the tubes may be varied within the scope of the invention. In Figs. 9, 10 and 10a is illustrated a cooling tube arrangement similar to the arrangement shown in Fig. 4. In this arrangement, the cooling tubes 28' throughout their length, except for the end portions where they are rolled into the casing 22, are flattened to elliptical form in cross-section as shown in Fig. 10a, the major axis of the crosssectional area of the tubes being axial so that the tubes present the least resistance to flow of air axially past the radiator. With this arrangement the ratio of the area of cooling surface to the cubic capacity of the radiator is increased as compared with the ratio of area to capacity in a radiator using tubes of circular cross-section.

Figs. 11 and 11a illustrate another method of bending the cooling tubes to form a radiator of substantially the same frontal outline as that shown in Fig. 4. In this arrangement, the two legs of each cooling tube, instead of being curved oppositely as are the portions b of the tube shown in Fig. 5, are curved in the same direction, the portion 0 of the tube being in the nature of a return bend and the two legs of the tube, when the tube is secured in position in the radiator being axially in alignment. In Fig. 11 only one set or series of tubes is shown, but it will be evident that with this arrangement a plurality of series of tubes may be employed as in the arrangement shown in Fig. 4 and it will further be evident that where a plurality of series of tubes is employed, the tubes in different series may be curved in opposite directions rotationallyso as to cross each other when viewed frontally of the radiator. In

order to support the cooling tubes against vibration, the outer portions of the tubes may be advantageously connected by means of a circular band 86 secured to the tubes in any desired manner, but preferably welded thereto by means of spot welds 88.

In Figs. 12 to 18 inclusive, there is illustrated the successive steps of manufacture of a form of tube of flattened cross-section having the gen eral shape of the tubes shown in Figs. 4 to 6. In making this form of tube a plain cylindrical tubular steel blank 90 is drawn at its ends to provide end portions 92 and 94 of circular cross-section and of reduced diameter as shown in Fig. 13. The drawing of the end portions increases the length of the tube somewhat and the tube is then bent at its central part to provide two similar and axially offset portions. As shown in Fig. 14, this bending operation reduces the length of the tube to substantially its original length and the portion of the tube intermediate the ends 92 and 94 is then flattened to provide a tube the shape of which in plan and elevation is as shown in Figs. 15 and 16. The tube is then bent into loop form and the ends rolled into the central casing 22, as shown in Figs. 18 and 19.

In Figs. 20 to 22, a radiator arrangement employing tubes of the form just described is shown, the radiator illustrated comprising but one series or set of tubes. As shown in Fig. 22, the tube structure is advantageously stiffened and held against vibration by spot welding the outer portions of adjacent tubes together as indicated at 96. It will be evident that any suitable arrangement for bracing the outer portions of the tubes, such, for example, as the means shown in Figs. 11 or 22 may be employed in the form of radiator construction shown in Figs. 1 and 4.

In Figs. 23 and 24 is illustrated another form of apparatus embodying the invention and adapted to be employed with an aviation engine. In the example illustrated, the engine, indicated generally at 100, is of the radial type, one cylinder thereof being shown at 112. The cylinders are provided with the usual cooling jackets which are each connected by means of suitable passages to the conduit 136 leading to the inlet side of the circulating pump member 160 situated in the inlet chamber 124 formed by the central casing 122 of the radiator. Casing 122 also provides a central outlet chamber 126 from which the outlet conduit 138 supplies cooling fluid to the jackets of the several cylinders by means of suitable connections, not shown.

The central casing 122 of the radiator is, in this instance, arranged around the crank shaft 102 which constitutes the main shaft of the engine and which extends through the casing 122 in the same manner as does the shaft 46 in the arrangement shown in Fig. 1. The pump member 160 is fixed to the main shaft 102 of the engine. This shaft may also be considered as the propeller shaft and the projecting end provides a suitable mounting for the propeller 104 which in addition to its primary function as a propeller, also acts as and may be considered as a cooling fan for the radiator.

In the example illustrated, the cooling tubes comprise a single set or series 128 and it will be evident that more tubes may be employed if desired. It will further be evident that any of the several specific forms and arrangements of tubes, hereinbefore described, and others, may

be employed. It is also to be noted that in this is radially outside of theinlet chamber rather than axially to one side thereof. This arrangement provides an axially compact radiator and it will be evident that the arrangement shown in this figure or the arrangement shown in Fig. 1 may be used in accordance with the requirements for any given engine design.

As will be evident from Figs. 23 and 24, the radiator and pump comprise a single unitary assembly connected to the engine by means of conduits 136 and 138 and removable therefrom as a unit upon disconnection of these conduits from the engine and removal of the propeller from the end of shaft 102. .1

In case the engine is of the type in which the propeller is mounted on a separate shaft geared to the crank shaft of the engine, the radiator casing 122 is preferably mounted on the separate propeller shaft so that its relation to the propeller will be as shown in Fig. 23.

The present'invention is of particular advantage in connection with aviation motors since the relatively small amount of radiating surface required and the arrangement thereof according to the invention provides a radiator giving minimum air resistance and in this connection it is to be noted that this characteristic of the invention makes favorable its use with aviation engines of the in-line type as well as with engines of the radial type.

It will be apparent to those skilled in the art that many changes and variations may be made in the specific form of apparatus for carrying the invention into effect without departing from the spirit or scope of the invention as defined in the appended claims, in connection with which, I wish to point out that the term oil as therein employed is to be considered generically as embracing fluids other than lubricating oil but having the same general characteristics as lubricating oil with respect to cooling properties, that the term closed circuit cooling system as therein employed is to be understood as embracing, but without limitation, systems such as that shown in my copending application Serial No. 661,250, hereinbefore referred to, in which provision is made for release of fluid from the closed circuit and for the introduction to the circuit of fluid to replacelosses due to leakage or other causes, and that the term positive circulation as therein employed, is not to be considered as limited in sense to positive displacement but is to be considered as including all types of systems in which circulation is effected by mechanical means in contradistinction to the so-called thermo-siphon circulation.

What I claim is:

1. In a closed circuit cooling system for internal combustion engines, a unitary assembly comprising a radiator, a cooling fan, a pump for circulating cooling fluid and. means for driving the fan and pump, said assembly being adapted to be secured to and to be removed from an engine as a single unit.

2. In a closed circuit cooling system for ining tubes connecting said chambers and. extending outwardly therefrom, a cooling fan adjacent to said radiator, a pump for circulating cooling fluid through the radiator, means for driving said fan and said pump and inlet and outlet conduits for conducting cooling fluid to and from said radiator, said radiator, said fan, said pump and said driving means comprising a unitary assembly and said inlet and outlet conduits providing means for supporting said assembly from an engine.

4. In apparatus of the character described, the combination with an internal combustion engine having spaces for circulation of cooling fluid in a closed circuit, of a radiator comprising inlet and outlet chambers and bent cooling tubes connecting said chambers and inlet and outlet conduits connecting said chambers and said spaces, said radiator being supported by said conduits at the forward end of the engine.

5. In apparatus of the character described, the combination with an internal combustion engine having spaces for circulation of cooling fluid in a closed circuit and having a main shaft, of a radiator comprising central inlet and outlet chambers and bent cooling tubes connecting said chambers and extending outwardly therefrom and conduits for connecting said chambers with said spaces, said chambers and cooling tubes being arranged around said shaft.

6. Apparatus of the character described comprising, in combination, an internal combustion engine including cylinders having spaces for circulation of cooling fluid in a closed circuit and a main shaft extending laterally of said cylinders, a propeller mounted on said shaft, a radiator located between the engine cylinders and the propeller comprising inlet and outlet chambers around said shaft and bent cooling tubes connecting said chambers and extending outwardly therefrom and conduits connecting said chambers and said spaces for circulation of cooling fluid in a closed path of flow.

7. In apparatus of the character described, in combination, a radiator comprising central inlet and outlet chambers, a plurality of cooling tubes connecting said chambers and extending out wardly therefrom, said tubes being bent to provide a radiator of substantially circular frontal ,form, a cooling fan mounted for rotation coaxially with the axis of the radiator and conduits for supplying cooling fluid to and withdrawing cooling fluid from said chambers.

8. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a rotatably mounted shaft extending through said casing centrally thereof, a

cooling fan mounted on one projecting end of said shaft, a centrifugal pump for circulating cooling fluid through said tubes mounted on said shaft within said casing and means for driving said shaft.

9. In apparatusof the character described, in combination, a casing providing central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a rotatably mounted shaft extending through said casing centrally thereof, a cooling fan mounted on one projecting end of said shaft, a centrifugal pump for circulating cooling fluid through said tubes mounted onsaid shaft within said casing and a pulley for driving said shaft mounted on the other projecting end thereof.

10. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a rotatably mounted shaft extending through said casing centrally thereof, a pump for circulating cooling fluid through said tubes mounted on said shaft within said casing, spring loaded packing means between said shaft and said casing at either side of said pump and means mounted on a projecting end of said shaft for driving the same. v

11. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, 'a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a rotatably mounted shaft ex-' tending through said casing centrally thereof, a pump for circulating cooling fluid through said tubes mounted on said shaft within said casing, spring loaded packing means between said shaft and said casing at either side of said pump, a pulley mounted on one projecting end of said shaft for driving the same and a cooling fan mounted on the other projecting end of the shaft.

12. In apparatus of the characterdescribed, in combination, a casing providing central inlet and outlet chambers, said chambers being arranged axially side by side, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a shaft rotatably mounted in said casing centrally thereof, a centrifugal pumpfor circulating cooling fluid through said tubes mounted on said shaft within the inlet chamber and a plurality of difiusors between the outlet of said pump and the inlet ends of said cooling tubes.

13. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, said chambers being arranged axially side by side, a plurality of cooling tubes connecting said chambers, a shaft rotatably mounted in said casing centrally thereof, a pump mounted on said shaft within said casing for causing circulation of cooling fluid through said tubes, said pump being located in one of said chambers and a by-pass providing for direct flow of cooling fluid from one to the other of said chambers.

14. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, said chambers being arranged axially side by side, a plurality of cooling tubes connecting said chambers, a shaft rotatably mounted in said casing centrally thereof, a centrifugal pump for circulating cooling fluid through said tubes mounted on said shaft within said inlet chamber, a ring of diffusor blades located in the inlet chamber between the outlet of the pump and the inlet ends of said tubes and a by-pass opening providing a direct connection between said inlet chamber outwardly of said ring of difiusor blades and said outlet chamber.

15. In apparatus of the character described, in combination, a casing providing central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, a central rotatably mounted shaft extending through the axially opposite sides of said casing, a cooling fan mounted on one projecting end of said shaft and a driving pulley mounted on the other projecting end of said shaft.

16. A positive circulation, closed circuit, oil

cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom.

17. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers, said chambers being in the form of bodies of revolution and having a common axis, and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom.

18. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprisinga radiator having central inlet and outlet chambers and aplurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes being arranged so that the frontal area occupied by the radiator is substantially that of a body of revolution.

19. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central circular inlet and outlet chambers arranged on a common axis and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes being arranged so that the frontal area of the radiator is substantially that of a circle concentric with respect to said axis.

20. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet.and outlet chambers in the form of bodies of revolution having a common axis and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, the ends of said tubes being arranged in a plurality of planes normal to said axis.

21. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers in the form of bodies of revolution having a common axis and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, the ends of said tubes being arranged in a plurality of planes normal to said axis and the inlet and outlet ends of any given tube being situated in different ones of said planes and spaced peripherally of said chambers.

22. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes comprising portions situated in planes normal to the central axis of the radiator.

23. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes comprising involute curved portions situated in planes normal to the central axis of the radiator and said tubes being circumferentially spaced with respect to each other uniformly around said central chambers, said involute curved portions providing interstices of substantially uniform area for flow of air axially of the radiator between adjacent tubes.

24. A positive circulation, closed circuit, oil v cooling system for internal combustion engines ii} comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambersand extending outwardly therefrom in the form of loops, the legs of the loops being located in axially spaced planes normal to the axis of the radiator and being curved in opposite directions in adjacent planes.

25. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, each of said tubes comprising axially spaced legs connected by a return bend tube portion, said legs being curved circumferentially of the radiator and the legs of each tube being in axial alignment with respect to each other.

26. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, each of said tubes comprising axially spaced legs connected by a return bend tube portion, said legs being of involute curved form in planes normal to the axis of the radiator and the legs of each of said tubes being in axial alignment with respect to each other.

2'7. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, each of said tubes being in the form of a loop and means for joining adjacent tubes outwardly of said chambers to provide a relatively rigid tube structure.

28. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, each of said tubes comprising two curved legs opposite with respect to each other axially of the radiator and located in planes normal to the axis of the radiator, the outer ends of said legs being connected by a tube portion oblique with respect to the axis of the radiator and the inner ends of said legs joining the walls of said chambers radially.

29. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, each of said tubes being flattened intermediate its ends so that the flattened portions extend axially of the radiator.

30. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes being of irregular cross-section intermediate their ends to produce turbulent flow of cooling fluid therethrough.

31. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers and a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, said tubes being flattened at intervals along their lengths to produce tur -bulent flow of cooling fluid therethrough.

32. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom and means in said tubes for producing turbulent flow of cooling fluid therethrough.

33. A positive circulation, closed circuit, oil cooling system for internal combustion engines comprising a radiator having central inlet and outlet chambers, a plurality of bent cooling tubes connecting said chambers and extending outwardly therefrom, and means in. said tubes for producing turbulent flow of cooling fluid therethrough, said means comprising corrugated metal strips within the tubes.

34. In a closed circuit cooling system for internal combustion engines, a unitary assembly adapted to be rigidly secured to a cylinder block of the engine and to project therefrom comprising a radiator having central casing structure providing inlet and outlet headers for cooling fluid and a plurality of cooling tubes connecting said headers, a central shaft extending through said headers and projecting at axially opposite sides thereof, a fan for forcing air over said tubes mounted on one of the projecting ends of said shaft, means for rotating the shaft mounted on the other projecting end of the shaft, a pump impeller located within said casing structure for forcing cooling fluid into said cooling tubes, and inlet and outlet conduits for connecting said casing structure to the cylinder block of an engine.

35. In a closed circuit cooling system for internal combustion engines, a unitary assembly adapted to be rigidly secured to a cylinder block of the engine and to project therefrom comprising a radiator having central casing structure providing inlet and outlet headers for cooling fluid and a plurality of cooling tubes connecting said headers, a central shaft extending through said headers and projecting at axially opposite sides thereof, a fan for forcing air over said tubes mounted on one of the projecting ends of said shaft, means for rotating the shaft mounted on the other projecting end of the shaft, a pump impeller located within said casing structure for forcing cooling fluid into said cooling tubes, and rigid inlet and outlet conduits for connecting said casing structure to the cylinder block of an engine, said conduits projecting in generally axial direction from said casing structure and having flanged ends adapted to be bolted to correspondingly flanged portions of the cylinder block of an engine.

36. In a closed circuit cooling system for internal combustion engines, a unitary assembly adapted to be rigidly secured to a cylinder block of the engine and to project therefrom comprising a radiator having central casing structure providing inlet and outlet headers for cooling fluid and a plurality of bent cooling tubes connecting said headers and projecting therefrom in the form of loops, said tubes being arranged to provide a radiator having a generally circular frontal area, a central shaft passing through said casing structure and projecting at each end thereof, a fan mounted on one of the projecting ends of said shaft and having a plurality of propeller type blades for forcing air axially across said tubes, a pulley for rotating said shaft mounted on the other projecting end thereof, a pump impeller located in said central casing structure for forcing cooling fluid through the inlet headers to the inlet ends of said tubes, and means providing inlet and outlet conduits for cooling fluid projecting from the side of said casing structure and embracing said pulley, said means including flanges at the ends of the conduits for detachably securing said assembly to the cylinder block 01' an engine.

37. In a closed circuit cooling system for internal combustion engines, a unitary assembly adapted to be rigidly secured to a cylinder block of the engine and to project therefrom comprising a radiator having central casing structure providing inlet and outlet headers for cooling fluid and a plurality of cooling-tubes connecting said headers, said headers having circular outer walls and said tubes being bent to form loops with the ends of the tubes projecting radially from the circular walls of the headers, a central shaft rotatably mounted in said casing structure and passing through the end walls thereof, a pump impeller on said shaft for forcing cooling fluid from the inlet headers into said cooling tubes, a fan mounted on one projecting end of said shaft comprising propeller blades for forcing air axially across said cooling tubes, a pulley mounted on the opposite projecting end of said shaft, shaft packing means between the pump impeller and said fan, shaft packing means between said pump impeller and said pulley, and means forming a part of said central casing structure extending in generally axial direction from said headers past said fan to provide rigid support for said assembly, said means providing inlet and outlet conduits for conducting fluid to and from the radiator and the ends of said conduits being flanged to provide for detachable connection of the conduits with the cylinder block of an engine.

FREDRIK LJUNGSTRijM.

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