This invention pertains to special arrangements of harmonic reciprocating heat engines, pumps and compressors. Such engines and pumps are characterized by the presence of at least one piston that reciprocates, essentially, harmonically into its cylinder when its crank rotates with constant angular speed and its corresponging connecting rod mechanism moves with slider free motion.

This invention is actually an evolution of the PCT Application No. PCT/GR91/00004 (WO 17694) which is the prior art as well as the DE-A-2432 197.9 Patent Application.

Fig. 1 is the basic module of harmonic engines prior to Patent Appl. DE-A-2432 197.9. Every cylinder has its own Cardan or Straight Line Mechanism.

Fig. 2 is the basic module according to Appl-. No. DE- A-2432 197.9. Each couple of opposite cylinders (which have common cylinder axis) have common Straight Line Mechanism ("Doppelkurbeltriebwerk") As clearly stated in Appl. No.DE-A-2432 197.9:

Page 1, Line 31: "Beim Bau einer mehrzylindrigen... " that is: "For the fabrication of ^' a multicylinder engine, should, (in prior art of Appl. No. DE-A-2431 197.7), for each further cylinder, e.g. 2, 3, 4 or more, each time a new additional similar mechanism be placed beside (next), which means labor cost ."

Page 1 at the end line: "Dadurch wird bei mehrzylinder...", that is: "So in mylticyl nder engines will be the cost (for Straight Line Mechanisms) half". Page 2, Line 20: "Bei Vierzyl ndermotoren steht... ", that is: "In 4-cylinder engines the main journal (d) of the second secondary crank, with regard to the respective journal

of the first secondary crank, is spaced 180 degrees apart, in 6-cylinders the three main journals are spaced 120 degrees each two and so on.

Note the words: "the expense for Cardan Mechanisms according to Appl. No. DE-A-2432 197.9 was half than prior art" and "in prior art of Appl. No. DE-A-2432 197.9 every single cylinder uses its own Cardan mechanism".

Fig. 3 is the before Appl. No. DE-A-2432 197.9 four cylinder harmonic engine arrangement. Note that there are four Cardan mechanisms and it is even firing when four stroke cycle.

Fig. 4 is the four cylinder harmonic engine according Appl. No. DE-A-2432 197.9. Here it needs only two Cardan mechanisms (that is half than the number used in fig. 3). The engine now is a four cylinder flat harmonic engine. Note that the "secondary" cranks (or connecting rod mechanisms) are spaced 180 degrees apart and that they are independent, that is they cannot be "welded" together (or equivalently the two "secondary" cranks or connecting rod mechanisms are necessarily two different pieces (parts)).

Fig. 5 is an eight cylinder flat harmonic engine according to Appl. No. DE-A-2432 197.9. It uses the same number of Cardan mechanisms as the four cylinder engine of fig. 3, but it has twice as many cylinders. The arrangement is for even firing order when it is of four stroke.

Fig. 6 is a six cylinder engine according to Appl. No. DE-A-2432 197.9. The "secondary" cranks or Connecting rod mechanisms are located in 120 degrees angle distance. The engine has 6 cylinders and uses only three Cardan mechanisms. The arrangement is for even firing when four stroke.

Fig. 7 is the engine of figure 6 from another point of view. The location of the "secondary" cranks is seemed. There are three independent "secondary" cranks (necessarily they are three separate pieces (parts)). There are also three double pistons.

Fig. 8 is the basic mechanism of a V-2, 90 degrees or of a radial-4 engine in six different crank angles. The

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pistons are not shown, but the piston pin bearings are. The "secondary" cranks or connecting rod mechanisms (as they w ll be called in the following) are embodied in a single piece for the whole engine, and there is one and only Cardan mechanism used for all the four cylinders (when radial-4) or for two cylinders not having parallel cylinder axes (in case of V-2) . With (1) and (2) are named the two piston pin bearings and as shown in the figure they reciprocate along different directions. The same are shown in the figures 9 and 10 but more clearly. The whole arrangement together with the pistons is shown in figures 14 and 15 (a V-2 90 degrees harmonic engine with a single Cardan mechanism and a single piece connecting rod mechanism) . The important here is not only that the used Cardan mechansims are even fewer than those used in the arrangement of Appl. No. DE-A-2432 197.9, but also (and this is the important) that we can use a single piece connecting rod mechanism for at least two cylinders with no parallel cylinder axes. And this is important because such arrangement offers smaller weight and in the same time lower or even zero inertia loads on the Cardan mechanism: Every piston (double or single) as passes through ■ top dead center has zero speed and so zero kinetic energy. As this piston passes through the middle of its stroke, its speed is maximum and so its kinetic energy is maximum. That is, there is an amount of energy which reciprocates between piston mass and the flywheel mass two times for every crank rotation. This amount increases with speed squared. This energy reciprocation takes place through the Cardan mechanism. The gears have to suffer these forces and this not only increases engine friction loss but also limits the life of Cardan mechanism. Now let see what happen in the V-2 of the Fig. 14 and 15. As the one piston has the minimum kinetic energy (because it passes TDC or BDC) then the other has its maximum kinetic energy. The total amount of kinetic energy of the two pistons is always constant (as the engine rotates with constant speed) . This means that there is no reciprocation of energy between flywheel anf pistons, so the Cardan mechanism

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stays always free from inertia load. This fact not only decreases the total friction loss and increases the life of Cardan mechanism, but also gives to the engine the chance to be better (fully) balanced: the assembly "connecting rod - pistons" is dynamically equivalent with their mass concentrated on connecting rod axis.

Fig. 11 and Fig. 12 is the presentation of the kinematic mechanism of a radial-6 or of a W-3 engine. The pistons are not shown, but the piston pin bearings are: (1), (2), (3) . Again -as in 8, 9. 10, 14, 15 figures- one single connecting rod mechanism serves all the cylinders. Also there is only one Cardan mechanism for six cylinders.

Fig 13. shows - from another point of view- the arrangement of fig. 11 and fig. 12. The pistons (double here) are shown too. There is only one Cardan mechanism for all the pistons, and the total inertia load on it is zero. Compare this with the arrangement in figure 6 and 7. Because the number of Cardan mechanisms in fig. 6 and 7 is three and because these mechanisms are loaded with high inertia loads, the friction loss is much more than the friction loss in engine of fig 13, and also the life of the Cardan mechanisms in fig. 6 and 7 is much smaller than that of Cardan mechanism in fig. 13. With a few words we can say that selecting the proper arrangement we can get lower cost and lower weight and lower friction loss and improved reliability and also smaller stresses .

In figures 8 to 15, due to the offset of the pistons there is an inertia moment and so the engine is not completely balanced. To balance this inertia moment we can locate proper counterweights on the connecting rod mechanism or we can cancel this moment with the use of multistem pistons as this shown in the figure 16 and 17. These figures represent a V-2 90-degrees engine with a simple stem (2C) piston (2A) and a multistem ((lC) and (ID)) piston (1A) . With proper counterweights on crankshafts (8A) the engine can be absolutely perfect balanced (neither forces, nor moments, nor torques) .

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In the typical electric power station, the periodic apply of torque pulses to the electric generator (we deal with periodic engines and not with turbines) results in the inevitable reaction on the base (mounts or foundation) . As the number of cylinders increases, things get better but the problem remains. A good solution seems to be the twin engines which rotate in opposite directions. The neccesary synchronizing gearing is a big problem in this case as well as the inertia vibrations, the simultanious ignition in two cylinders and the demand for similar operation of independent cylinders.

The Patent Application PCT/GR91/00004 and especially the engine of figures 17 and 18 is very close to the next.

In our case (single harmonic), fig. 18 and 19 we have: 1: cylinder wal1 2: cooling liquid 3: piston 4: left connecting rod mechanism. It consists of: 41: piston pin of left connecting rod 42: first crankshaft pin of left connecting rod 43: gear fixed on left connecting rod mechanism 44: second crankshaft pin of left connecting rod 5: right connecting rod mechanism

51, 52, 53, 54 as 41, 42, 43. 44 for right conn, rod 6: left crankshaft 61: big counterweight on left crankshaft 62: small counterweight on left crankshaft 63: final shaft of left crankshaft

64: bearing fixed on left crankshaft (it keeps the 42 crankshaft pin of left connecting rod mechanism) 65: bearing fixed on left crankshaft (it keeps the 44 crankshaft pin of left connecting rod mechanism) 8: right crankshaft

81, 82, 83. 84, 85 as 61, 62, 63. 64. 65 for right crankshaft.

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71: rotor of left electric generator 72: coil on the rotor 71 of left generator 16: coil on the stator of the left electric generator 91: rotor of right electric generator 92: coil on the rotor 91 of right generator

17: coil on the stator of the right electric generator 14: body of the engine 15: base of the construction

18 and 19: immovable gear of the two Cardan Mechanisms (they cooperate respectively with 53 and 43 gears of right and left connecting rod mechanisms) 10, 11, 12, 13: bearings between crankshafts and the body of the engine 14

The fig. 19 gives the successive locations of the main moving parts of the above engine for 0, 30, 60, 90, 120 and 150 degrees of crank rotation. The main characteristic here is the opposite direction of rotation of the two cranks. The two electric generators are twins (identical), that is, their operating characteristics are as close as possible,, and they are connected to their load in a way that ensures the balanced absorption of torque (power), every moment. For example they could be connected in parallel to their load, also they could be connected in line to their load (but it is not clever to connect different -in size or time- loads to the two generators: although the whole construction continues to work, the advantage of absence of power vibrations is lost) . The left electric generator (driven by left crank) rotates in opposite direction than the right one. (This happens if we start the engine in this way. The initial rotation direction of every crankshaft stay unchanged untill the engine is stopped. That is, it is enough to start the engine rotating one crank in a direction and the other crank in the opposite direction.)

The selection of the counterweights is such that the

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sum of the action of the 61 and 62 counterweights (located with 180 degrees angle distance) to be equivalent to the action of one only counterweight rotating with the crankshaft 6 on a plane containing piston axis and normal (at right angle) to crank axis. To achieve this it is enough the proper selection of the 61 and 62 masses according to their distances from the cylinder axis and from the crankshaft axis: basically the torque of the centrifugal force of the 62 counterweight -as regards the section point of crankshaft axis and cylinder axis- has to be equal and opposite to the torque of the centrifugal force of the 61 counterweight as regards the same point. Also the centrifufal force of the 61 counterweight less that of the mass of the 62 counterweight has to be equal and opposite to half the maximum inertia force that the total reciprocating mass of the engine needs (it is the mass of the piston 3 and of the piston pins 41 and 51) . Using these two relations, the selection of the location and of the mass of the 61 and 62 counterweights can be done. Remember that in our case the reciprocation is a harmonic reciprocation, also that the counterweights are to cancel the vibrations from the reciprocating masses. The rest masses which rotate with constant speed are balanced with the typical way: a proper mass in antidiametrical direction of the rotating shaft. The two pairs of counterweights on the two crankshafts (a big counterweight close to piston and another smaller away from the piston) offer complete balance of inertia forces, inertia moments and inertia torques. The symmetric location of the two similar electric generators and their motion in opposite direction, makes the torque pulses (produced by the engine) to be equally distributed to the two electric generators, and the total reaction on the base of the construction to be zero. The result is that the base or^ foundation of the arrangement is completely free of any kind of vibrations (inertia vibrations and power vibrations) .

We said that the two crankshafts rotate in opposite direction and are synchronized. This is acheived either by

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the use of some synchronizing mechanism (e.g. like that mechanism used in the typical differential with bevel gears) or just using the action of piston and of piston pin bearing. When a synchronizing mechanism is used, it takes no loads in operation, so we can use this mechanism only when the engine is to start and when the engine is to stop. Another way to synchronize the two cranks is to have one more bearing into the piston pin 41, where a suitable subpin of the piston pin 51 rotates (in this way the piston is not loaded with synchronizing work) .

In the same arrangement, if the rest stay unchanged and the piston becomes a single piece double one (that is the engine becomes a two cylinder flat or boxer engine, see prior art) again the base of the construction stay unaffected from both inertia vibrations and gass pressure vibrations.

If -using the same figure- the piston and cylinder is a single cylinder pump (compressor), and the two electric generators are electric motors, the result is a pumping installation which has its base completely free of vibrations. Although the fluid in the pump may absorbs power in any specific way, the base is completely free of inertia and power vibrations.

We said that for the complete counterbalance of the above single cylinder is enough a pair of counterweights on each one of the crankshafts. Although the total balance of the engine is complete, the gears of the Cardan or Straight Line Mechanisms suffer from inertia loads produced by the piston's motion. If the construction is for use in low rotation speed where these inertia loads are small, it is all right. But when the rotation speed is increased, then the location of counterweights also on both connecting rod mechanisms (see prior art for details) give not only base free of vibrations, but also Cardan Mechanisms free of inertia loads. Application of the above: In elecric power stations, in robots, in high standards buildings, in ships, in hybrid cars (where a small engine charges the batteries), in pumping

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(compressing) stations (a pump driven by twin electric motors, but also the case that a reciprocating engine drives some pumps e.t.c). In general the above is applicable in case that the torque produced by an engine can be absorbed from two (at least) in opposite direction rotated twin loads.

The absence of inertia forces or forces due to gass pressure on the cylinder wall make possible the connection of cylinder(s) with the crankcase to be such that permiting it (them) a move along its (their) axis (axes) while maintaining the axis (axes) immovable.

Main purpose of this movement which is (generally) small is a variable compression ratio especially when it is controlable while the engine works. This is important for good efficiency especially at part load, at iddl ng operation and at high rotation speed.

Fig. 20 is such an arrangement. The cylinder (1) is located on the crankcase (12) in a proper cylindical guide (11) which although keeps the cylinder axis immovable, permits a small axial motion of the cylinder (or equivalently permits a small change of cylinder head distance from crankshaft axis). There is also a wedge (10) which does not permit the culinder to rotate around its axis. The cylindrical part (6) keeps axialy the cylinder: in cavity (4) of part (6) is kept a proper flange (5) of the cylinder (1). This connection permit the rotation of the part (6) with regard to cylinder (1). but does not permit axial motion of cylinder (1) as regard part (6). The part (6) is also connected to crankcase (12) through thread (7) on (6) and thread (8) on (12). The engine is a typical harmonic engine (the (14) is the two gears of Cardan mechanism, the (13) is the piston pin, the (3) is the piston e.t.c.) and is either four stroke or two stroke. When the engine is in operation, with some kind of servomechanism the intermidiate mechanism (6) is rotated -with regard to cylinder axis-. This rotation just alter the compression ratio of the engine. Since the

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total loads on cylinder are axial, the mechanism can stand them. The same apply also in multicylinders and in pumps.

Owing to the fact that even single cylinder harmonic engine can be fully balanced (prior art Appl. PCT/GR91/00004) an engine can be made of, at least, two independent subengines interconnected or connected to the same load (e.g. gearbox, propeller e.t.c.) by means of connections (clutches, gears e.t.c.) which permit them to work simultaniously or some to be stopped when others in function. It enables the engine to work more effectively at partial loads using fewer cylinders, to have stand by cylinders for safety reasons, to have cylinders of different characteristics e.t.c.)

In Fig. 21, there are two harmonic engines. The right engine (10) has one cylinder (8) and through shaft (6) and clutch (3) transmit power -when desired- to the primary shaft (1) of the gearbox (4). The left engine (11) has two smaller cylinders (9) and through shaft (7) and clutch (2) transmit power -when desired- to primary shaft (1) of gearbox (4). The secondary shaft (5) transmit the power from gearbox (4) to the load. The result is ability to'work the (10) engine only, or the (11) engine only, or both engines (10) and (11).

Fig. 22 shows a separation surface (shell) between crankcase and cylinder wall. It can be there because of the special movement (permanently along its axis) of the piston.

The most important use in 4-stroke of this space between piston and this surface is to help the aspiration and of course to isolate cylinder wall from crankcase. Especially in the case of 2-stroke a movable and/or controlable surface can be of interest because it can affect scavenging procces (prior art PCT/GR91/00004)

Also in four stroke can offer control on the aspiration. The movement can be made just to change possition or be a continuous motion by means of cams e.t.c.

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