US2129638A - Quick starting vapor motor - Google Patents

Description

Sept. 13, 1938. J. 5. BAKER 2,129,638

QUICK STARTING VAPOR MOTOR Filed NOV. 10, 1934 Patented Sept. 13, 1938 UNITED STATES PATENT oFFlCE QUICK STARTING "APOR MOTOR John s. Baker, Chicago, 111., assignor to 060k Electric Company,-Chicago, 111., a corporation of Illinois Application November 10, 1934, Serial No. 752,416

2 Claims. (01.50-25) My invention relates to heat motors or thermally controlled vapor motors, and more particularly to motors of the type adapted to be influenced by a volatile liquid or like means.

It has heretofore been proposed to provide in a- 1,885,285 granted to Lawrence M. Persons on November 1, 1932 and assigned to the present" assignee. In vapor motors of this type, an electrical resistance coil is located adjacent'to andusually in contact with the wall to influence the volatilev liquid by the'conduction of the heat through the wall.- I have found, however, that one of the chief difflculties in the design and operation of vapor motors generally is that a rapid transfer of this heat, and thereafter a rapid expansion or volatilization of the volatile fluid, cannot be obtained so that operation of the motor can be obtained practically co-instantaneously with the flow of current through the heating element. In the type of motor disclosed and claimed in the aforesaid patent, a closer approach to this rapid v operation has been obtained than in other types, say .where the heat is applied to influence the entire body of volatilellquid in the motor.

providing a heating zone or chamber communibe vaporized, circulation of the volatile liquid.

in the heating zone begins as soon as the heat is applied, the warm liquid next to the wall of the heating chamber rising tothe' top and flowing toward the center and then downwardly through the center. Such circulation continues until substantially all the volatile liquid is hot before any vaporization will occur, with the result that vaporization is considerably delayed:

Moreover, where the heating element is wound about the exterior of the heating chamber, the wall of this heating chamber is engaged by the heating element by only a line contact. This method of applying the heating element results 7 heating element.

in a loss of a. high percentage of heat-by exterior radiation and convection. Furthermore, a large portion of the heat actually transmitted through the wall is absorbed through the heating of substantially all the volatile liquid in the 5 heating chamber to a relatively high temperature before vaporization. I have found, however, that it is not essential 'to heat substantially all'the volatile liquid in the heating chamher to secure rapid vaporization capable of producing the required Working stroke.

Moreover, I have found that a greater heating efficiency may be obtained by arranging the resistance coil in more intimate; contact with the wall of the heating chamber, which not only has for its 1 advantage the conduction of ahigh percentage of the heat, but also .a construction within the heating chamber which permits rapid vaporizain United States Letters Patent No. 1,902,260, 25

granted to Lawrence M. Persons on March 21, 1933, and likewise assigned to the present assignee. In this structure the starting period is reduced to aboutone third of the time formerly required. It is the purpose of the present invention, however, to reduce the starting period to vapor motor embodying the'present invention has obtained a capacity for work that could not be heretofore obtained, and has a speed. of operation that vapor motors inherently lacked.

An object of my invention is, therefore, to provide a vapor motor of a construction that will 40 operate practically co-instantaneously with the flow of current or application of heat by the heating element.

A further object of the invention is to provide a vapor motor having a heating element capable of rapidly transferring the heat to the volatile liquid so that the volatile liquid may immediately vaporize to secure quick operation of the vapor motor.

A further object of the invention is to provide a-vapor motor having a heating zone adjacent the heating. element which, by virtue of its construction, pockets or recesses small quantities of volatile liquid in close proximity to this The invention further provides" for the rapid heating and volatilization of the aforesaid small quantity of volatile liquid to effect quick operation of the vapor motor without requiring the heating of substantially all the volatile liquid in the heating zone. In this respect the invention broadly contemplates eliminating the slow warm ing of the volatile liquid in the heating zone which necessarily causes a'slow circulation of the volatile liquid throughout the same until the liquid reaches the temperature vaporizing a sum-- cient quantity to eifect operation of the motor.

Accordingly, I contemplate broadly a structure which will hold the volatile liquid inert adjacent the heated surface of the heating zone, and in such quantity or quantities, until sufficient heat is conducted thereto to raise the temperature to that of volatilization that expansion or operation of the motor will be quickly obtained to produce the desired working stroke.

It will be understood that I do not desire to be limited to the specific construction mentioned for accomplishing the result set forth, because I believe that I'am the first to devise a vapor motor capable of operating within several seconds after the heat is applied.

A still further object of the invention is to provide a vapor motor having a heating element which automatically reduces the heat input when reaching a predetermined high temperature. This is accomplished specifically by employing an electrical heating element that has a relatively high coefilcient of resistivity so that the resistance materially increases upon a rise of temperature, thereby reducing the heat input and preventing excessively high temperatures during this on period.

Further objects and advantages will be apparent from the following detailed description when taken in connection with the accompanying drawing which forms a part hereof.

In the drawing:

Figure l is a vertical sectional view of a vapor motor embodying the invention, the heating device being in elevation.

Fig. 2 is a similar sectional view, but showing expansion of the vapor motor instead of contraction in Fig. 1 when the volatile liquid is expanded;

Fig. 3 is an enlarged vertical sectional view of the heating device;

Fig. 4 is a detail sectional view of the heating device, but illustrating a slightly modified construction; and i Fig. 5 is a detail elevational view of a portion of the heating'device, and likewise illustrating a modified embodiment of the invention.

In the drawing, wherein, for the purposes of illustration, there are shown several preferred embodiments of my invention, the vapor heat motor may comprise an expansible and contractible vessel I having a volatile liquid 6 therein, such as benzol, toluene or other suitable liquid, and a source of heat for the volatile liquid. which, in this case, may be carried by a tube I in communication with vessel 5.

Although any suitable form of expansible and contractible vessel may be employed, it is preferably shown as comprising an inverted, rigid cup I and an expansible and contractible wall 9. In the particular form shown, in the drawing, expanaible and contractible wall Q may be any well known form of bellows arranged in nested relation with respect to cup I and hermetically sealed at ll to a rim plate in the form of a rim ii to which cup 8 is also hermetically sealed, as by solder or otherwise. The arrangement provides a closed liquid chamber l2.

Tube 1 may be closed at either end and communicate at the opposite end with chamber 12. As to the specific form of heating device that may be used, it is obvious that the source may be an electric resistance coil conveniently located at or adjacent to tube I. A heating zone will thereby be provided within tube 1 for heating volatile liquid 6. The vapor pressure will be rapidly increased and the liquid driven out of the heating zone and depressed into chamber i2. It is by this means that a predetermined expansion or power stroke of vessel 5 may be effectively obtained and held, without danger of the vapor pressure building up to a point where vessel 5 will burst.

A heating element M, which, in this particular instance, is in the form of an electric resistance coil, suitably'surrounds tube 1. course, electrically insulated from tube 1, as will be hereinafter explained, but is in close proximity thereto to conduct the heat developed by the current flow through the coil to volatilize liquid 6. Terminal bands [6 at each end of coil H receive conductors l1 comprising a control circuit in which'any suitable or desired circuitregulator may be disposed.

By heating a portion only, a major portion of the liquid remains comparatively cool. The liquid in chamber I2 is not subjected to the heat. After the liquid in tube 1, which is not vaporized, is somewhat expanded and a portion thereof is depressed into chamber l2, there is no possibility of further vaporization or expansion. Accordingly, the vessel will be held at its limit of travel until the thermal balance or equilibrium is destroyed, which occurswhen the current ceases to flow through coil I4. It is preferable that the interior of chamber l2 and tube 1 be substantially filled with the volatile liquid 8 so as to eliminate the presence of an air pocket at the upper end of this tube. The presence of an air pocket tends to cushion the expanding action of the vessel and destroy its positive movement; that is to say, the initial pressure developed by the vapori zation' oi the liquid tends to compress the air instead of immediately depressing the liquid out of the tube to expand vessel 5. With the presence of air the device is not positive, requires a longer time for initial movement and is materially restricted in its power movement. On the other hand, air in the presence of a volatile liquid undergoing constant thermal expansion and contraction causes chemical reactions which tend to liberate a free gas, which, when cbmbined with air, will increase the air pockets and thereby affeet the return movements of vessel 5. It will be understood, however, that, in so far as the present invention is concerned, the presence or absence ofair is immaterial, but its absence above the volatile liquid in tube I greatly aids in securing a more eflicient and longer lived vapor motor. I By referring particularly to Figure3, it will be noted that the exterior surface of tube 1 is formed with a relatively deep helical groove l8. Groove l8 may be formed by corrugating the wall of tube 1 or by any other suitable means, it being preferable that the width of the groove thus formed be substantially close to the diameter of the wire forming the resistance coil H. A substantial portion of the resistance coil will then lie within this groove l8 so that a large surface area of this resistance coil will engage the surface of the This coil is, of

groove as distinguished from a line contact, as heretofore obtained where this resistance coil has been wrapped about the heater.

Any suitable form of insulation may be employed for resistance coil I4. I find, however, that a high thermal conduction may be obtained by employingbare wire Hi. The exterior surface of this tube 1 is first coated, however, with an insulating material, such as enamel 26, the resistance coil I4 being then laid in groove l8 and a second coating of insulating material, say

enamel 21, being preferably applied thereover.

' pockets 2| about the inner wall surface of this tube. Small quantities of volatile liquid 6 will be trapped in these recesses or pockets 2|. I have represented these small quantities of volatile liquid generally as A. These small quantitles of volatile liquid A in pockets 2| are, in effect, subjected to the hottest areas or portions along the wall of the tube. The large surface area of resistance coil M in engagement with the surface of the outer helical groove 18 results in a rapid conduction or transfer of a relatively large percentage of the heat generated in this resistance coil M to the liquid trapped in these recesses or pockets 2|. The heating action is so rapid that the temperature of volatilization of the fluid is obtained almost co-instantaneously with the flow of current through the resistance coil I4.

I have found that the immediatevaporization of the small quantities of volatile fluid trapped inrecesses or pockets 2| causes a vapor pressure in the tube 'l which will drive the unvolatilized fluid out of the tube. through a connecting tube 22. Connecting tube 22 is open at its upper end 23 and passes downwardly through the bottom of tube 1 and communicates with chamber l2 by entering the cup 8 at anysuitable point, there being a hermetically sealed connection provided both where this connection tube leaves tube 1 and 'where it enters the housing 8.

It is my belief that the action of this device includes rapidly vaporizing these small quantities of volatile liquid A trapped in the pockets or recesses 2| and the rising of the vapor to the top of the tube. The volatile liquid next to these vapor pockets is in turn rapidly brought into contact with the hot wall of these pockets for additional vaporization within the tube 1, if found necessary. The vapor which rises will accumulate in the upper portion of tube 1 and thereby drive the unvaporized liquid through opening 23 in tube 22. The action of vaporization and the accumulation of vapor'in tube 7 is so rapid, due to an absence of rapid circulation of thermal currents that little, if any, of the unvaporized Consequently, a heat terior and interior grooves I8 and 2| for the resistance wire I4 and the volatile fluid 6 respectively. It is true that a very rapid and fast heating action of the volatile fluid 8 in tube 1 is obtained so that operation of the vapor motor will be practically co-instantaneous with the flow of current through the resistance coil l4. This single formation of either the exterior or. interior grooves would be obtained where the wall of the tube I is substantially heavy and the formation obtained by machining or by molding the same in the making of the tube.

A further advantage of the present invention resides'in making the resistance coil of wire having an especially high coefficient of resistivity. It is found in connection with the present construction that wire of a high coefficient of resistivity will cause a decrease of current flow after a predetermined temperature is obtained. Namely, when a sufficient vapor pressure is obtained in tube 1 to effectoperation of the vapor motor, continued generation of heat at the initial rate is unnecessary in order to maintain this vapor pressure and hold the vapor motor operated. j

Having once obtained the power stroke and a relatively high temperature at tube 1, the resistance of the wire materially increases, thus reducing the heat input and preventing any excessively high temperature being obtained at the tube during the on" period. This type of wire is generally known as ballast wire, and generally has the following characteristics with respect to I temperature and resistance in the'order of:

It will be noted, therefore, that the resistance increases considerably with an increase of temperature which results in the employment of a reduced current, and consequently, a reduced heat input after the desired temperature necessary to maintain the thermal balance to keep the vapor motor in its expanded position is obtained. I

' The device disclosed herein may be constructed of different materials. As a specific example of a preferred embodiment of the invention, it is mentioned that the wall of tube 1 may be of a relatively high heat conducting material such as copper of a thickness of .005 inches. When the circuit is closed across the line l1, current will flow through resistance coil H to generate heat preferably of a temperature of 350 R, which, with the body of volatile fluid in tube 1 and chamber I2, may develop a pressure of approximately 45 to 50 pounds per square inch. It will be understood that these are merely specific examples of characteristics of my vapor motor which may be varied to meet the different conditions without departing from the scope of the invention.

Exterior groove 8 may be helical in formation so that the resistance coil I4 may be continuously wrapped from end to end about tube 1. The helical formation of groove l8 may be eliminated and groove l8 otherwise provided in any desirable way, say by annular grooves 25 shown in Figure 5, the resistance coil I! then being wrapped about these annular grooves 25 in individual turns, the ends of each turn electrically connecting with the ends of adjoining turns, 75

whereby they will be connected in series to provide a continuous flow 01 current between the i6. As previously mentioned, the groove I! or each groove 25 may beend terminal bands made slightly deeper or wider than the diameter of the wire H. And, as previously explained, to insulate each turn 01' the wire it in these grooves, any form of insulation may be provided. I have found that a coating of enamel 26 may be applied to the exterior of the tube 1. After enamel 28 dries the wire may be placed in these grooves plied as I have shown in Figure 4.

Any type of well known expansible and contmctible vessel may be used. In Figure 1 the expansible and contractible vessel is adapted to contract to produce a working stroke. This working stroke may be imparted through a work connection 28 suitably secured at 28 to the expansible and contractible vessel 9. To illustrate the variation in which the expansible and con tractible vessel may be arranged without departing from the spirit and scope of the invention, an alternative embodiment is illustrated in Fig ure 2. In this alternative embodiment, the vessel 30 is adapted to expand to produce a working stroke through the working connection 3i secured at 32 to the base of the vessel 30. The connecting tube 22 between tube 1 and a top plate II of the vessel 30 is preferably arranged to enter the top plate '33 for communication with the interior of vessel 30. It will be apparent that operating connection 22 may be connected in a variety of ways to the chamber of the expansible and contractible vessel of the type shown, both in Figures 1 and 2 of the drawing.

Without further elaboration, the foregoing will so fully exp-lain the gist of my invention that others may, by applying current knowledge, readily adopt the same for use under varying conditions of service, without eliminating certain ieatures, which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to me by the following claims.

I claim:

1. In a heat motor, a work chamber and a communicating heating chamber a closed system, a volatile liquid in said system, the wall or said heating chamber being corrugated, the inner recesses forming pockets in which said volatile liquid may rapidly volatilize in small quantities, and a resistance coil in the outer recesses having a relatively large surface contact with said heating chamber wall.

2. A heat motor comprising a substantially closed body filled with a volatile liquid, a portion of which is adapted to vaporize and create a predetermined vapor pressure producing, a power stroke, and means iorheating a portion of said 'closed body, said heating means including a chamber and a heating element for said chamy

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