Internal combustion engines are known. Internal combustion engines typically include a piston/cylinder arrangement in which a fuel/air mixture is combusted in a cylinder to cause a force to be exerted on a piston located in the cylinder, thereby causing linear displacement of the piston to exert a force on a crank of a crankshaft to provide for rotation of the crankshaft. Typically, such piston/cylinder arrangements comprise at least one separate piston which is displaceable within a cylinder and which is in engagement with a crank of a crankshaft via a connecting rod to permit a force which is exerted on the piston by combustion processes in the cylinder, to be transmitted to the crank of the

crankshaft to provide for rotation of the crankshaft.

Such internal combustion engines operate on four-stroke or two-stroke cycles. As such, a four-stroke cycle comprises four piston strokes to complete a cycle, the strokes comprising an induction stroke in which the piston is displaced to the operative bottom end of the cylinder to facilitate the induction of a fuel-air mixture into the cylinder, a

compression stroke in which the piston is displaced to the operative top end of the cylinder to compress the fuel-air mixture, a power stroke in which the fuel-air mixture is ignited, thereby resulting in a build-up of pressure in the cylinder causing operative

displacement of the piston to the operative bottom end of the cylinder, and an exhaust

stroke in which the piston is displaced towards the operative top end of the cylinder to provide for exhausting of the combustion products from the cylinder. Thus, for every completed cycle of a four-stroke internal combustion engine, the crankshaft is caused to rotate through 720°.

In a two-stroke cycle, the induction and compression strokes and the power and exhaust strokes respectively, are combined into one piston stroke, thereby providing for rotation of the crankshaft of a two-stroke internal combustion engine through 360° for every

completed two-stroke cycle.

It is an object of this invention to provide an improved internal combustion engine.

Any reference to a four-stroke or two-stroke cycle must be interpreted to mean a four stroke or a two-stroke cycle of an internal combustion engine, as defined hereinabove.

According to the invention there is provided an internal combustion engine including

at least one crankshaft defining an axis of rotation and having at least one crank

on which a force can be exerted to cause rotation of the crankshaft for performing work;

at least one pair of cylinders defined in an engine body and arranged in spaced opposed relationship with respect to one another, the cylinders permitting a fuel/air

mixture to be combusted therein to exert a force on pistons which are operatively located therein; and

a piston member comprising a piston body having two opposite ends, the piston body having at least one piston located at each end, each piston being displaceably

located in a cylinder of the pair of cylinders in an arrangement in which controlled combustion of a fuel/air mixture in the cylinders causes forces to be operatively exerted on the pistons, thereby causing reciprocating linear displacement of the piston member, the piston member having a floating bearing that is freely rotatably located in the piston body, in which the crank of the crankshaft is eccentrically located to permit the crank to

revolve around the axis of rotation of the crankshaft, thereby permitting said forces to be

transmitted to the crank of the crankshaft, via the floating bearing of the piston member,

to provide for rotation of the crankshaft.

The floating bearing of the piston member may be in the form of a disc having a main

journal bearing located around its periphery, with the piston member defining a housing in which the main journal bearing of the disc is seated, the disc defining an eccentrically-

disposed aperture and including a big-end journal bearing seated in the aperture, in which the crank of the crankshaft is located.

The pistons of the piston member may be formed integrally with the piston body.

The piston member may define elongate extension portions having the pistons located at ends thereof.

Further features of the internal combustion engine of the invention, including the mode of use thereof, are described in more detail hereinafter with reference to an example of

the invention, illustrated by way of the accompanying diagrammatic drawings. In the

drawings:

Figure 1 shows a partly sectioned side view of an internal combustion engine, in

accordance with the invention, showing hidden detail;

Figure 2 shows a partly sectioned side view of the internal combustion engine of

Figure 1, with the crank rotated through an angle of 90° with respect to the crank position shown in Figure 1 ;

Figure 3 shows a partly sectioned side view of the internal combustion engine of

Figure 1 , with the crank rotated through an angle of 180° with respect to the crank

position shown in Figure 1 ;

Figure 4 shows a front view of the crankshaft and cylinders of the internal combustion engine of Figure 1 ;

Figure 5 shows a front view of the crankshaft and cylinders of another embodiment of an internal combustion engine in accordance with the invention;

Figure 6 shows a front view of the crankshaft and cylinders of yet another embodiment of an internal combustion engine in accordance with the invention; and

Figure 7 shows a partly sectioned, schematic side view of a further embodiment of an internal combustion engine in accordance with the invention.

With reference to Figures 1 to 4 of the drawings, an internal combustion engine, in

accordance with the invention, is designated generally by the reference numeral 10. The internal combustion engine 10 comprises, broadly, a crankshaft 12 having a crank 14, a piston member designated generally by the reference numeral 16, and two pairs of

cylinders 18 defined in an engine body 19, which are arranged in spaced opposed relationship with respect to one another.

The crankshaft 12 is essentially a conventional-type crankshaft with the crank 14 being

off-set to permit a force to be exerted on the crank 14 to cause rotation of the crankshaft 12 for performing work. The crankshaft 12 defines an axis of rotation A and its crank 14 defines a central axis B along its length. The crankshaft 12 further has a pair of spaced opposed locating members 20 which are located at ends of the crank 14 to provide for the secure location of the crank within the piston member 16.

The piston member 16 comprises a piston body 22 having two opposite ends 24, the

piston body 22 having two pistons 26 located at each of the ends 24, and a floating

bearing generally designated by the reference numeral 28, that is freely rotatably located in the piston body. The crank 14 of the crankshaft 12 is eccentrically located within the

floating bearing 28 in an arrangement which permits the crank 14 to revolve around the axis of rotation A of the crankshaft 12. The location of the crank 14 within the floating bearing 28 will be described in more detail hereinafter. The piston member 16 defines

elongate extension portions 30 having the pistons 26 located at ends thereof. As such, the piston member 16 forms a single unit in which the pistons 26 are formed integrally with the piston body 22.

The floating bearing 28 of the piston member 16 permits forces which are exerted on the

pistons and caused by controlled combustion of a fuel-air mixture in the cylinders 18, to

be transmitted to the crank 14 of the crankshaft 12 to provide for rotation thereof. The floating bearing 28 is in the form of a disc 32 having a main journal bearing 34 located around its periphery. The piston body 22 defines a central housing in which the main journal bearing 34 is seated. The disc 32 defines an eccentrically-disposed aperture 36 having a big-end journal bearing 38 seated therein, in which the crank 14 of the crankshaft 12 is freely rotatably located. The configuration of the floating bearing 28 is such that it permits the crank 14 of the crankshaft 12 to revolve around the axis A of the crankshaft 12 within the piston member 16 as a result of forces transmitted to the crank 14 via the floating bearing 28. The floating bearing 28 defines a central axis C about which it is displaceable.

In use, the internal combustion engine 10 permits forces caused by the controlled combustion of a fuel/air mixture in the cylinders 18 to be operatively exert d on the pistons 26 thereby causing reciprocating linear displacement of the piston member 16 which in turn causes the said forces to be transmitted to the crank 14 of the crankshaft

12 via the floating bearing 28 of the piston member 16 to provide for rotation of the

crankshaft 12 to perform work. The internal combustion engine 10 operates on a four- stroke cycle and each of the four pistons 26 of the internal combustion engine 10 undergoes a different stroke in the four-stroke cycle of the engine 10. As such, one

piston undergoes an induction stroke while another piston undergoes a compression stroke while yet another piston undergoes a power stroke while the final piston

undergoes an exhaust stroke.

It must be appreciated, however, that the pistons 26 located in each bank of cylinders disposed adjacent one another, may be synchronised, thereby operating on the same stroke.

With reference to Figure 1 of the drawings, the piston member 16 is shown at one end of its stroke (hereinafter referred to as bottom-dead-centre for the purposes of explanation). The internal combustion engine 10 is shown in a configuration in which the piston 26.2 in the cylinder 18.2 has just completed a power stroke, the piston 26.1

located in the cylinder 18.1 has just completed an exhaust stroke, the piston 26.4 located in the cylinder 18.4 has just completed an induction stroke, and the piston 26.3 located in the cylinder 18.3 has just completed a compression stroke. As such, it can be seen that the strokes required to complete a four-stroke cycle take place in each of the

cylinders 18.1 , 18.2, 18.3 and 18.4 at different times.

With reference to Figure 2 of the drawings, the internal combustion engine 10 is depicted with the crank 14 of the crankshaft 12 rotated through, an angle of 90° with respect to

the position of the crank depicted in Figure 1 of the drawings. In this position, each of

the pistons 26 are disposed mid-way within a particular cylinder 18. In this configuration

of the internal combustion engine 10, the piston 26.2 located in the cylinder 18.2 is in the

process of undergoing an exhaust stroke, the piston 26.3 located in the cylinder 18.3 is

in the process of undergoing a power stroke, the piston 26.1 located in the cylinder 18.1 is in the process of undergoing an induction stroke and the piston 26.4 located in the cylinder 18.4 is in the process of undergoing a compression stroke.

With reference to Figure 3 of the drawings, the internal combustion engine 10 is shown in a configuration in which the crank 14 of the crankshaft 12 is displaced through an angle 180° with respect to the position of the crank 14 as depicted in Figure 1 of the drawings. In this configuration the piston member 16 is displaced through a full stroke

with respect to its bottom-dead-centre position as depicted in Figure 1 of the drawings. (This position shall be referred to as top-dead-centre for the purposes of explanation.)

In this configuration of the internal combustion engine 10, the piston 26.2 located in the piston 18.2 has completed its exhaust stroke, the piston 26.3 located in the cylinder 18.3 has completed its power stroke, the piston 26.1 located in the cylinder 18.1 has

completed its induction stroke and the piston 26.4 located in the piston 18.4 has

completed its compression stroke.

After the crankshaft has been displaced through an angle of 360°, half of a four-strok cycle will have been completed, with two of the cylinders 18 having undergone a powe

stroke. After the crankshaft 12 has been displaced through an angle of 720° the four- stroke cycle will have been completed. With reference to Figures 1 to 3 of the drawings,

the position of the crank 14 of the crankshaft 12 is clearly indicated at different stages in a four-stroke cycle of the internal combustion engine 10. It can be seen that the central

axis B of the crank 14 revolves around the axis of rotation A of the crankshaft, while the piston member 16 is displaced in linear reciprocating-fashion between the two pairs of cylinders 18. As the crank 14 of the crankshaft 12 is displaced, the floating bearing 28 exhibits a reciprocating seesaw-like motion with respect to the piston body 22 of the piston member 16 and the crank 14 of the crankshaft 12. Thus, as the crank 14 of the crankshaft 12 is displaced past its 180° position, the floating bearing commences its return to the position it occupied when the crank 14 was rotated through 90° as depicted in Figure 2 of the drawings.

With reference to Figure 5 of the drawings, another embodiment of an internal combustion engine in accordance with the invention is depicted by the reference numeral 110. The same and similar reference numerals are used to depict the same and similar

components, respectively, to those of the internal combustion engine 10 depicted in Figures 1 to 4 of the drawings. In this embodiment, the internal combustion engine

includes two banks of cylinders and two opposed pairs of cylinders 18. It must be

appreciated that the configuration of an internal combustion engine, in accordance with

the invention, is greatly variable. As such, an internal combustion engine in accordance

with the invention may comprise a number of banks of cylinders arranged around a crankshaft.

With reference to Figure 6 of the drawings, and in yet another embodiment of the

invention, an internal combustion engine 210 in accordance with the invention comprises two spaced cylinders 18 in opposed relationship with respect to one another. In such an arrangement, the internal combustion engine operates on a two-stroke cycle with the induction and compression strokes and the power and exhaust strokes respectively, being combined into one piston stroke, thereby providing for the rotation of a crankshaft through 360° for every completed two-stroke cycle. The mode of operation of an internal combustion engine operating on a two-stroke cycle is similar to that of the internal combustion engine 10 which exhibits a four-stroke cycle as depicted in Figures 1 to 4 of

the drawings.

With reference to Figure 7 of the drawings, and in a further embodiment of the invention, an internal combustion engine 310 in accordance with the invention, comprises a single cylinder 118. The internal combustion engine 310 operates on a two-stroke cycle and has a crank case 312 having a piston member 116 comprising a piston body 122,

located therein. The piston body 122 has a piston 126 located in the cylinder 118, with

the piston 126 being integrally connected to the piston body 122 via a round extension

shaft 130. More specifically, the crank case 312 defines a sealing formation 132 that

seals off the base of the cylinder 118 and that defines a central aperture 134 in which the extension shaft 130 of the piston body, is slidably located. As such, a seal 136 is located

within the aperture 136 for providing a fluid-tight seal between the extension shaft 130 and the sealing formation 132 of the crank case 312. Furthermore, a pair of sliding pads 138 is located within the crank case 312 along opposite sides thereof for guiding the piston body 122 during operative sliding displacement thereof within the crank case 312. It is believed by the Applicant that in the engine 310, no fuel/oil mixture will be required as is the case with conventional internal combustion engines employing a two stroke cycle. Furthermore, the Applicant believes also that no expensive sealing of the crank case will be necessary with the internal combustion engine 310. In the internal

combustion engine 310, a properly metered volume of fuel can be transferred via a fuel inlet port E into the cylinder 118 and the exhaust gases can be discharged through an exhaust port F. As such, no exhaust pipe extraction methods are required to improve

"breathing" as a metered fuel mixture is transferred to the combustion chamber.

Accordingly, with the extraction of gases not necessary, the exhaust port can be further down in the cylinder thereby providing more complete burning of the mixture and

improved engine efficiency.

It must be appreciated that the invention extends to an internal combustion engine

substantially equivalent to the internal combustion engine 310, but wherein the piston

body comprises a pair of opposed pistons that are located in opposed cylinders.

An advantage of the invention is that the internal combustion engine of the invention

provides a compact engine having a reduced size and weight in comparison to

conventional internal combustion engines of similar power output.

The Applicant believes that friction between working surfaces in the internal combustion engine of the invention will be reduced, when compared to conventional internal combustion engines of similar engine capacity, resulting in a greater power output. Further, the Applicant believes that balancing of the engine shall be simplified as no

centrifugal forces will be created by the piston member as is created by the big-end of the connecting rod of a conventional internal combustion engine.