GB2321280A - Engine driven by expansion and contraction of elongate member, which may be bimetallic, or fluid filled, possibly with change of state of fluid - Google Patents

Abstract

A heat engine is disclosed in which an expandable member 12, which lengthens or contracts when heated, is engaged by two discs 10 of different diameters, but constrained to rotate at the same angular speed by sprockets 6 and chain 8. When part of member 12 is heated or cooled, the difference in length causes discs 10 to rotate. Member 12 may comprise a zig-zag length of bimetallic material (fig. 3), or a series of pistons 20 in cylinders 22 driven by fluid 18. In this case, change of state may lead to change of volume. Figure 5 shows a series of fluid-filled cylinders where heating leads to contraction, and figure 6 a wheel with bendable, bimetallic spokes. Figs. 11 to 14 show lever arrangements for amplifying expansions of fluids; figure 15 shows baths of hot and cold liquids for heating and cooling member 12. Heat may be supplied by combustion, or from the sun.

Description

Heat engines This invention relates to heat engines, by which term is meant devices for converting thermal energy into kinetic energy.

The present invention aims at providing a heat engine which can convert heat, produced by the combustion of fuel or from the sun, into mechanical motion.

Accordingly the present invention provides a heat engine which is as claimed in the appended claims.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side elevation of one form of heat engine of this invention; Figure 2 is a diagrammatic plan view of the engine shown in Fig. 1; Figure 3 is a diagrammatic side elevation of part of a force-transmission member used in the device of Fig. 1; Figure 4 is a diagrammatic cross-section of a force-transmission member alternative to that shown in Fig. 3; Figure 5 is a view similar to Fig. 4, showing a member intended to transmit tension Figure 6 is a side elevation of a second form of heat engine of this invention; Figure 7 is a side elevation of a third form of heat engine of this invention; Figure 8 is a side elevation of a fourth form of heat engine of this invention; Figure 9 is a diagrammatic side elevation of two conical drive wheels engaged by a common force-transmission member; Figure 10 is a side elevation of a device of the present invention comprising an endless loop of force-transmission member supported between four wheels; Figures II and 12 are side elevations, part in section, showing two different forms of force-transmission member employing liquid; Figures 13 and 14 are views similar to Figs. 11 and 12 employing a gas as the working fluid, and Figure 15 is a view of another form of the Fig. 1 heat engine using heated andlor cooled baths to transmit heat to and/or from the force-transmission member.

In the accompanying drawings, parts which are similar in different figures retain their original references.

In the embodiment of Fig. 1, shafts 2 and 4 are mounted for rotation about horizontal axes. Fast to the ends of each shaft are differently-sized discs. A pair of small discs 6, which may be of the same or different sizes, are coupled together by means of a chain 8 so that both discs and their shafts are forced to rotate in unison. A pair of larger discs 10 are coupled together by means of a force-transmission member 12. For convenience and differentiation, chain 8 may be termed the inactive connector, while member 12 is active, in the sense that it is member 12 which is selectively heated and/or cooled to bring about the desired rotation of both shafts. It needs to be emphasised here that member 12 engages its respective discs in a non-slip manner. This may be achieved by the use of friction coatings on the member 12 and/or the cylindrical surface of each disc 10. Alternatively, the member 12 may have non-planar surfaces which key into complementary recesses in the outer surface of each disc 10.

With the Fig. 1 embodiment, member 12 is adapted to change its dimensions when parts of it are selectively heated. When all parts of the Fig. 1 device are at the same temperature, it cannot move, because the chain 8 constrains discs 6 to rotate in unison at the same speed, whereas, were this to happen, the speeds of the peripheries of the discs 10 would be different from each other, which is not permitted by the member 12.

It is envisaged that there are two modes of operation of the Fig. 1 device. In one mode, the member 12 would be constructed of bimetallic material such that it would expand when heated. If the upper run as viewed of member 12 is heated, and/or if the lower run has heat removed from it by cooling, then the tension in the upper run would be reduced, while that in the lower run would increase. This would lead to the turning moment on the larger disc 10 applied by the upper run of member 12 being significantly less than that applied by the lower run, and these differences would lead to the larger disc starting to rotate, with the increase of length of the upper run, and the reduction of length of the lower run, allowing the smaller disc 10 to rotate at a lower peripheral speed than the larger disc 10, so that both rotate at the same angular speed.

In the other mode, the member 12 is designed to contract when heated, and to expand when cooled, leading to rotation in the opposite direction when the same stretches of it are heated andlor cooled.

Fig. 3 shows the locations of the layers 14 of the more-expansible material, and the layers 16 of the less-expansible (when heated) bimetal strips 17 making up the member 12, to achieve the two modes of operation just discussed. When these layers are located as shown in Fig. 3, the member is designed to expand when heated, whereas when their relative locations are reversed, the strips 17 will contract when heated.

Figs. 4 and 5 show an alternative construction of member 12. In that shown in Fig.

4, the member is made up of a series of fluid-filled expansion chambers 18, with the piston 20 of each chamber being fast with the cylinder 22 of the next chamber, to form a member which expands when heated. While the change in volume of the fluid is preferably effected by changing its temperature, it is within the purview of this invention to cause the change in volume by changing its state. When the fluid in effect acts on the other face of each piston, as shown in Fig. 5, the member shrinks in length when heated.

In that embodiment shown in Fig. 6, a hollow cylinder 24 is connected to an eccentric cylinder 26, movable about a shaft 28, by an angularly-spaced series of bent 'spokes' 30 of bimetal material. A belt 32 of inactive material supports the mass of a drum 34 from the periphery of cylinder 24. When the upper left-hand quadrant of cylinder 24 is heated, and/or the lower right-hand quadrant is cooled, the spokes 30 react, in one construction of the bimetal spokes, to push the cylinder 24 to the right (as viewed) of the shaft 28. As the tensions in both runs of the belt 32 are equal, that which applies a greater turning moment about shaft 28 is effective to rotate the cylinder 24 clockwise, as shown by arrow 36.

In that embodiment shown in Fig. 7, the belt 38 supporting the lower drum 40 from the upper one is active. When using the expand-on-heating form of active member and heating the left-hand side (as viewed) more than the right-hand side, the expansion of the former side and the contraction of the latter side means that the mass of the member on the cooler side becomes greater than that on the hotter side, so that the assembly is constrained to rotate in the direction shown by the arrow. The converse would be true if the member 38 were of the contract-onheating construction.

It will be appreciated that the heat engine shown in Fig. 8 is a combination of the Figs. 1 and 7 embodiments, so that the differential heating of the upper and lower runs of member 12, and the right-hand and left-hand sides of the lower run, combine to produce rotation of the assembly in the respective direction.

In the Fig. 9 embodiment, conical wheels 40 and 42 are used, with the active member 12 being entrained with part of both of their frustoconical driving surfaces 44 and 46. The shafts 48 of the wheels are connected together by means (which are not shown) so that both shafts rotate in unison.

In the Fig. 10 embodiment, the member 12 is generally in the shape of a circle which is engaged by two pairs of wheels. The pair of wheels 50 are mounted for free rotation by their engagement with member 12, while the pair of wheels 52 are positively connected together for rotation only in unison. In both these embodiments, the active member is in compression rather than in tension.

Figs. 11 and 12 show alternative constructions of links in the active chain. Each link 58 is intended to be connected to two similar links by pins through apertures 60 in the ends of lever arm 62 and cylinder 64, with the complete member having perhaps ten such links. Associated with the cylinder is a reservoir 66 for the working fluid 68.

A strut 70 interconnects the lever arm and cylinder so that the piston 72 may travel in a straight line independently of the state of contraction of the link 58. Fig. 11 shows the link in its distended condition, while Fig. 12 shows it in its contracted condition.

Figs. 13 and 14 show alternatives to the link of Figs. 11 and 12, showing two different classes of lever, with the cylinder 64 of Fig. 11 being replaced by a lever arm 74 carrying a bellows 76 containing the working fluid 68.

In the embodiment of Fig. 15, the run of the active member 12 is extended by running it around two freely-mounted wheels 54, each having part of its circumference immersed in liquid in a bath 56. In this form, the liquid is used to transfer heat to or from the active member, allowing close control of the temperature to which the active member is raised or lowered.

The source of the heat used to make the heat engines of this invention work is immaterial. While any fuel could be used to produce the heat by which part of the length of the active member is caused to expand or shrink, and while the cooling of any other part of the active member which is to shrink or expand, respectively, may be natural or forced, the invention encompasses the use of solar heating. The actual means by which the active member is selectively heated and/or cooled is not part of the subject-matter of this invention, and so will not be described herein in any further detail. The same comments apply to the means whereby the active and inactive members are held in contact with the rotatable members with which they are in frictional contact.

Accordingly it will be seen that the present invention provides a heat engine in which heat from any source may be used to heat a force-transmission member differentially to rotate an output member.

Claims (2)

1. Claims

   A A heat engine adapted to produce rotary motion of an output member by the selective application of heat to, and/or the extraction of heat from, heat-responsive force-transmitting components, the engine comprising: two rotary members coupled together for rotation in unison, the members also being connected together by an endless length of a force-transmitter in such a way that there is a differential ratio in their movements under the action of the force-transmitter, in which engine the forcetransmitter is adapted to change its length by the application of heat to, and/or the extraction of heat from, an incremental part of its length which is not in frictional contact with the rotary members, whereby, upon the differential heating and/or cooling of the force-transmitter, the said differential ratio is at least partially compensated for, leading to rotation of the coupled members.
2. 2 A heat engine substantially as described herein with reference to, and as shown in, Figs. land 2; Fig. 6; Fig. 7; Fig. 8; Fig. 9; Fig. 10 or Fig. 15 of the accompanying drawings.