US2369063A - Evacuated coolant containing valve - Google Patents

Description

Feb. 6, 1945. R DE Q McD|| A EVAGUATED cooLANT CONTAINING VALVE Filed July 13, 1942 Patented Feb. 6, 1945 EVACUATED COOLANT CONTAINING VALVE Rex De Ore McDill, Cleveland, Ohio, assigner to Thompson.y Products, Inc., a corporation of hlo n Application July 13, 1942. Serial No. 450,685

9 claims. (c1. 12s-177) This invention relates to a hollow evacuated poppet valve or the like for use in internal combustion engines. More particularly. the invention pertains to a valve of the type indicated containing a liquid or liqueiiable coolant such as metallic sodium.

It has heretoforev been proposed to fabricate hollow valves partially filled with a liquid or liqueflable coolant having a vaporlzing temperature greatly in excess of the usual operating temperature of the valves. -Valves of this typ'e are disclosed in the patents to Heron Nos. 1,670,965 and 1,823,452 as containing metallic sodium, the internal space above the sodium being lled with air. When such valves are operated, the temperature rises from the relatively cold starting temperature and the sodium is gradually melted but is not vaporized due to the high internal pressure within the valve. The liqueed sodium functions as a coolant by being heated in the valve head cavity and, on being bodily transferred to the valve stem when the valve reciprocates, delivering the heat picked up in the valve head to the valve stem whence the heat is dissipated.

It is highly desirable to conduct heat away from the valve head as rapidly as possible, because high temperatures cause corrosion of the valve metal in the presence of exhaust gases. Metallic sodium is an excellent coolant, being characterized by a high specific heat, high thermal conductivity and` no tendency to expand greatly at elevated temperatures.

When conventional sodium filled valves are fabricated, the included air effects an initial internal pressure amounting to 15 pounds per square inch. Of this pressure,- 3 pounds are due io the oxygen of the air and 12 pounds are due to the nitrogen of the air. When the valves are heated, thevoxygen combines with the sodium to reduce the pressure by 3 pounds. But the expansion of the nitrogen at the elevated valve operating temperatures causes an internal-valve pressure greatly in excess of the ambient pres sure, as shown by the fact that when a conventional valve operating at an elevated temperature is pierced, the sodium is blasted out. As will be shown more clearly hereinbelow, the vapor pressure of metallic sodium is so low as-to preclude any appreciable vaporization of the sodium in conventional valves.

Conventional sodium lled valves on the order of those disclosed by Heron are formed with a relatively large, cavity in the valve head and with a relatively constrlcted hollow passage through the stem. The sodium must flow from the valve head cavity through a restricted aperture into the stem in order to transfer heat to the valve stem for dissipation therefrom. The small aperture into the valve stem may become gas pressure locked," for the liqueed sodium has a fairly high viscosity even at elevated temperatur. The situation presented by the conventional sodium lled valves is simply one of a viscous liquid and a gas under pressure attempting to reach a state of stability and equilibrium through a constricted orice, and is similar to the pouring of cold molasses out of a jug.

It should also be noted that high internal pressures decelerate the melting of the sodium, as indicated by the following table.

Melting point of Further. the air present in the internal cavities of conventional valves is a poor conductor of heat. The agitation andthe high temperatures tend to cause increased adsorption of air by the sodium, thus reducing the heat transfer to the valve stem surface due to the insulating characteristics of the sodium-air foam'generated when the valves are operated.

In brief, the air present within conventional sodium lled valves impedes the transfer of heat frdm the valve head to the valve stem by delayying liquefaction of the sodium, by forming a eas lock Within the valve and otherwise interfering with the free movement of the sodium, and by acting as an insulating medium, particularly in the form of an air-sodium foam.

I have nofw found that the disadvantages pointed out can vbe eliminated by evacuating sodium filled hollow valves. The evacuation should preferably be extended to a .degree where the sodium can be volatilized. Thus evacuated valves dissipate heat' much more rapidly than conventional sodium fllled valves. Aside from the fact that the liqueiaction of the sodium is notdelayed,

that no gas locks are formed, and that no insulation is effected by air, the eiliciency of the valve is greatly enhanced by volatilization of sodium in the valve head and condensation of sodiuation as possible is shown by the data tabul lated hereinbelow:

Vapor Temperature pressure of sodium 222. 8 4. 575X10" 241. 2 i. 137 X10-l 271. 2 4. 27 X l0'a 271. 3 4 144x104 296. 7 1 06x10-I 303. 6 1. 217x10-I 331. 2 0. 0438 341. 6 0. 0628 360. 2 0. 1074 376. 1 0. 1760 376. 2 0. 1702 366. 7 0. 3025 401. 95 0. 371 428. 06 0. 716 451. 1. 2155 498. 2 3. 653 663. 7 67. 37 706. 7 110. 1 738. D 165. 767. 7 228. 1 797. 4 v 317. 4 840. 1 482. 5 858. 0 760. 0

Conventional sodium lled valves operate at from 1100 F. (593 C.) to 1600 F. (871 C.). Still lower operating temperatures are obtainable with the evacuated valves of the present invention. 'I'he importance of complete evacuation for eiiecting vaporization of sodium at low temperatures is evident.

Clt is, then. an object of this invention to provide a hollow evacuated coolant-containing valve. A further object of the invention is to provide an evacuated hollow valve containing a liqueable coolant such as metallic sodium.

A still further objectvof the invention is to provide a sealed hollow Doppet'valve lled to about 50 to 60% of its capacity with a coolant such as metallic sodium and having the remainder of the interior thereof exhausted.

vA still further object of the invention is to.

provide a hollow poppet valve containing a coolant capable of being vaporized in the valve at the valve operating temperature.

IAnother object of the invention is to provide a coolant-filledvalve wherein the coolant has been reacted with oxygen to form a solid oxide operating in an evacuated space.

in a manner below. y

K Figure 4 is a diagrammatic vertical cross sectional view similar to Fig. 3 but showing a later stage oi' the process illustrated in F18. 3.

As shown in the drawing:

A valve according to this invention is indicated generally in Fig. 1 by the referencen umeral i0 and includes a head Ii and a stem I2. This 0 valve is formed with a mushroom-shaped cavity including a head cavity portion I3 and a stem cavity portion I4 intercommunicating through a constricted aperture I6 formed in the neck of the valve. The h'ead chamber I3 forms about of the total internal capacity of the valve I0, with the stem cavity accounting for the remainder. The contents of the valve cavities include at ambient temperature fiom 50 to 60% sodium indicated by the reference numeral I9 with the valve at rest in non-operating condition.

The valve i0 is formed -with a tapered aperture I6 at its top 'through which the valve is illled. I'his aperture is closed, after iilling. with a tapered plug or pin i1.

As shown in Fig. 1, the sodium I9 is broken up into globules when the valve is operated, due to theshaking or oscillation of the sodium eiected by the movement of the valve and due to yboiling of the sodium. The sodium vapor generated will rise inside the valve stem and will tend to be condensed on the sides ot the valve stem cavity, when the condensed sodium will tend to iiow downwardly, as indicated by the arrows.

" teri-al 23 of a thickness such that the plug i1 may be held'thereby while the interior of the `valve lil as well as the conduit 22 are evacuated A' still further object of the invention is to i provide a coolant-containing valve -having the hollow interior thereof filled with a gas-liquid system formed byasingle coolant.v Y

Evacuation to produce valves oi' 'this invention may be eilected either chemically or mechanical# ly, as illustrated in the appended drawing, in.L

which:

Figure 1 is a diagrammatic vertical cross sectionalview of an evacuated sodium containing valve according to this invention.

Figure 2 is a fragmentary diagrammatic vertlcal cross sectional view o! a valve being evac-V uated by mechanical means.

Figure 3 is a diagrammatic vertical cross sectional view showing 'the initial stage of a process for illling a valve with sodium and oxygen dium is'then extruded into the valve cavity by through a conduit 24 piercing the tubular member 20 near its bottom and connected to a. source of vacuum. When evacuation is completed, the plug I1 may be rammed down into the aperture I6 to Vseal the valve. The tubular memberl 20 .is then removed from the valve.

Evacuation may also be eilected chemically. as by filling the valve with sodium and with oxygen and then sealing the valve. When thevalve is heated, the sodium will then combine with the oxygen to form sodium oxide and to exhaust the valve to an extent determined by the purity of the oxygen. Even in a large cavity valve, the

. amount of sodium oxide formed would not exceed 35 miligrams. If nitrogen and other inert gases are completely excluded, the interior space in .the valve can be, very completely exhausted.

Chemical exhaustion carried out in Athis manner may even be more emcient than mechanical exdescribed in greater detail hereinl means of an internally threaded pressure gun 32 having a bent nozzle 33 and a threaded piston operated by means 'of a handle 3l. As shown in Fig. 4, the tube 30 is raised as the level of the sodium in the valve cavity rises. A current of oxygen is kept owing through the valve cavity as long as sodium is being introduced thereinto. When enough sodium has been introduced, the-nozzle 33 is withdrawn from theaperture I6, the tube 30 is likewise withdrawn, and

the plug Il is rammed down into the aperture I6 to seal the same.

When a sealed valve llecl with sodium and oxygen in the manner disclosed hereinabove is exposed to valve operating temperatures, the oxygen combines with the sodium to leave the space above the sodium almost completely exhausted.

In the nished valve there is no oxygen present which would tendto cause corrosion. The sodium present in the valve also reduces any metal oxide iilms coating the internal valve cavity, whereby any evolution of oxygen from such oxide films is prevented.

The sodium used as a coolant may be replaced by potassium, suitable eutectic alloys, salts, mercury or other compositions having suitable thermal characteristics. I

It will thus be seen that in the novel evacuated valves of this invention, the mobility of the liquid coolant has been greatly enhanced and the heat dissipating capacity therefore greatly increased while at the same time a coolant vaporization-condensation cycle has been set up to still further increase the rate of heat transfer from valve head to valve stem.

Many details of construction and procedure may be varied within a wide range without departing from the principles of this invention and it is therefore not my purpose to limit the patent granted on this invention otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A poppet valve having an interior hollow space extending through the head andv thestem of theA valve and having a tapered aperture through the end of the stem aording access to said space, sodium partially filling said space, the4 remainder of said space being evacuated, and a tapered pin seated in said aperture to seal the space.

2. A sealed hollow poppet valve having a stem, a neck and a head, said stem being formed with a tubular cavity and said head being formed with an enlarged cavity forming about of the hollow space within said valve, said head cavity and said stem cavity intercommunicating through a restricted aperture at the neck of said valve, said hollow space being lled to about 50 to 60 per cent of its capacity with metallic sodium and theremainder of said space being exhausted.

3.' A poppet valve having a hollow head adapted to be exposed to high temperature conditions and a tubular stem adapted to be exposed to relatively lower temperatu'res than said head, said head and stem deilning a closed continuous interior'valve space adapted to contain a coolant for dissipating heat from said valve head through y the walls of said valve stem, sodium partially lland a tubular stem adapted to be exposed to reloperating temperature with the ing said space, the remainder. of said space being evacuated for facilitating heat dissipation by said sodium.

5. A poppet valve having a hollow head adapted to be exposed to high temperature conditions and a tubular stem adapted to be exposed to relatively lower temperature conditions than said head, said head and stem deilning a closed continuous interior valve space adapted to contain a coolant for dissipating heat from said valve head through the walls of said valve stem, a liqueilable coolant partially illling said space, the remainder of said space being evacuated for facilitating liquefaction of said coolant.

6. A poppet valve having a hollow head adapted tobe exposed to high temperature conditions and a tubular stem adapted to be exposed to relatively lower temperature conditions than said head, said head and stem defining a closed continuous interior valve space adapted to contain a coolant for dissipating heat fromsaid valve4 head through the walls of said valvestem, a coolant capable of being vaporized in said valve space4 at the operating temperature of the valve, the remainder of the valve being evacuated at the -valve for facilitating vaporization of said coolant.

7. A poppet valve having a hollow head adapted to be exposed to high temperature conditions and a tubular stem adapted to be exposedto relatively lower temperature conditions than said head, said head and stem defining a closed continuous interior valve space adapted to contain coolant for dissipating heat from said valve head through the wallsfof said valve stem, a liquid coolant partially filling said space, the remainder of said space being occupied exclusively by the vapor of said coolant for facilitating heat dissipation by saidv coolant.

8. A poppet -valve having a hollow head adapted to be exposed to high temperature conditions and a tubular stem adapted to be exposed to rel'- atively lower temperature conditions than said head; said head and stem defining a closed continuous interiorvalve space adapted to contain a coolant for'dissipating heat from said valve head through the walls of said valve stem, a single liquid coolant partially lling said space, said space being fllled at the operating temperature of said valve exclusively with a gas-liquid system formed by said single coolant for facilitating heat dissipation by said coolant.

9. An 'elongated hollow metal part adapted to operate back and forth with one end subjected to high operating temperature and with another end at a lower temperature, said part having a closed chamber extending therein from one end to the other end, a liqueiiable vaporizable cool- REX DE ORE MCDILL.

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