DESCRIPTION

Technical Field

The present invention relates to a cylinder-piston system, whose piston and cylinder have corresponding rectangular cross-sections, and which comprises sealing elements for avoiding leakages.

In general, the present invention relates to reciprocating engines, pumps or compressors. In particular, the present invention advantageously relates to internal combustion engines, such as a two-stroke engine, four-stroke engine, or other engines.

Background art

In known cylinder-piston systems, the linear movement of a piston is converted into a rotating movement of a shaft, via known cinematic mechanisms. An example of a suitable cinematic mechanism is a connecting rod and a crankshaft. A flywheel is often used to ensure smooth rotation or to store energy to carry the engine through an un-powered part of the cycle. The more cylinders a reciprocating engine has, generally, the more engine vibrations are reduced. Other suitable cinematic mechanisms exist, for converting the linear movement of a piston into a rotating movement of a shaft. A particular example of another mechanism is the so called "scotch yoke" (also known as slotted link mechanism): in this case, the piston is directly coupled to a sliding yoke, with a slot that engages a pin on the rotating part; the location of the piston versus time is a sine wave of constant amplitude, and constant frequency given a constant rotational speed.

Pistons typically have a circular cross-section, on a plane transversal to the direction of linear movement of the piston. A seal must be provided between the sliding piston and the walls of the cylinder, so that the fluid (such as an high pressure gas) above the piston does not leak past it, thus improving the efficiency of the engine. In general, sealing elements are provided, such as piston rings made of hard metal which are sprung into a circular groove in the piston head. The rings fit tightly in the groove and press against the cylinder wall to form a seal.

Since the power of a reciprocating engine is proportional to the volume of the combined pistons' displacement, it is advantageous, under certain conditions, to provide pistons whose cross-section is different from circular.

For example, document DE3039536A1 describes a piston engine employing a scotch yoke mechanism, wherein the piston has a substantially oval shaped cross-section, comprising two straight tracts. Document DE3039536A1 describes that a seal is provided by a plurality of piston rings, which are sprung into an oval groove.

While the solution of DE3039536A1 relates to an oval piston which is advantageous in combination with a scotch yoke mechanism, providing an elongated slot for the pin on the rotating part, the engine displacement according to DE3039536A1 is not yet maximized.

A cylinder-piston system whose piston and cylinder have corresponding rectangular cross- sections, would maximize the engine displacement with respect of comparable overall engine dimensions, and would therefore improve the performances of the engine.

On the other hand, such a piston having a rectangular cross-section would still require sealing elements for avoiding leakages. In fact, in engines or pumps or compressor, sealing elements provide three necessary functions: sealing the piston chamber so that there is no fluid leakage, supporting fluid compression for receiving/extracting power, regulating functioning of the system.

Document US2010319530A1 describes a sealing apparatus for a square piston; such sealing apparatus includes two sealing members, each having four sides and a square hole in contact with the square piston, the sealing apparatus further comprises first and second elastic means disposed on the upper and right-hand sides of the first sealing member and installed in the cylinder housing, and third and fourth elastic means disposed on the lower and left-hand sides of the second sealing member and installed in the cylinder housing.

The sealing members according to US2010319530A1 remain fixed with respect of the cylinder housing, and the piston reciprocates in their inside; the sealing elements are configured for providing a sealing with the outer walls of the square piston.

The solution according to US2010319530A1 still presents some disadvantages. For example, the stationary sealing elements fixed to the cylinder housing would not perform well if the same system was to be applied to reciprocating engines, instead of pumps. Moreover, these sealing elements provide a seal which can withstand only limited pressures, and the piston is adapted for compressing only certain types of fluids.

In general, the state of the art lacks a solution for providing a cylinder-piston system whose piston and cylinder have rectangular cross-sections, wherein an effective and advantageous sealing system is provided, for avoiding leakages between cylinder and piston.

More in general, the state of the art lacks reciprocating engines, pumps or compressors, wherein pistons and corresponding cylinders have rectangular cross-sections, and still exhibit an effective degree of functioning, good performances and mechanical durability. Summary of the invention

It is an object of the present invention to provide a cylinder-piston system which is alternative to known solutions.

It is also an object of the present invention to provide a cylinder-piston system comprising sealing elements which are effective and provide a high degree of sealing between cylinder and piston.

It is a further object of the present invention to provide a cylinder-piston system which exhibits good functioning and achieves mechanical durability.

It is a further object of the present invention to provide a cylinder-piston system which is easy to assemble and to manufacture.

It is a further object of the present invention to provide a cylinder-piston system which is compact and reliable.

It is a further object of the present invention to provide a cylinder-piston system which comprise a piston having rectangular cross-section, whose functioning is smooth and effective.

It is a further object of the present invention to provide a reciprocating engine comprising a cylinder-piston system, which has an improved engine balance and reduced vibrations.

It is a further object of the present invention to provide a reciprocating engine comprising a cylinder-piston system, which has a convenient power/displacement ratio, and is desirable for selected applications.

It is a further object of the present invention to provide a reciprocating engine having reduced weight and compact dimensions, which is more desirable for certain applications.

These and further objects of the present invention are achieved by a cylinder-piston system, and a relative reciprocating engine, which comprise the features of the appended claims which are an integral part of the present description.

An idea at the basis of the present invention is to provide a cylinder-piston system, comprising at least one cylinder, at least one piston configured for a reciprocating linear motion inside the cylinder, and at least one rotating shaft system configured for cinematically converting the reciprocating linear motion of the piston into a rotating motion of the shaft; the piston and the cylinder have corresponding rectangular cross-sections on a plane transversal to the direction of the linear motion, and the piston comprises sealing elements configured for providing a seal between its walls and the walls of the cylinder which surround the piston, so as to avoid leakage in there between; the sealing elements comprise a first series of sealing elements adjacent to each other at first joining zones on the transversal plane, so as to include a complete perimeter of the piston at the transversal plane, and further comprise a second series of sealing elements adjacent to each other at second joining zones on the transversal plane, so as to include a complete perimeter of the piston at the transversal plane; the first series of sealing elements are axially overlaid on, and in contact with, the second series of sealing elements with respect of the direction of the linear motion; the first joining zones are different from the second joining zones with respect of said transversal plane.

The cylinder-piston system comprises a rectangular cross-section piston, which is alternative to known solutions and requires appropriate sealing for proper functioning; the first and second series of sealing elements, including the whole piston's perimeter, are effective and provide a high degree of sealing between cylinder and piston.

Moreover, advantageously, the first and second series of sealing elements are overlaid, having joining zones which are different from each other, so as to avoid any leakage of fluid during the piston's reciprocating motion; the overlaid sealing elements each stop leakages, both at the first and at the second series.

Further aspects and advantageous technical features of the present invention, are set out in the dependent claims. The present invention, according to a further aspect, also relates to a reciprocating engine.

Brief description of the drawings

Further features and advantages of the present invention will become apparent in the detailed description of preferred non-exclusive embodiments, which are described as non-limiting examples with the help of the annexed drawings, wherein:

Figure 1 represents a preferred embodiment of an engine, in assembled state, comprising a cylinder-piston system according to the present invention.

Figure 2 represents a preferred embodiment of a piston according to the present invention.

Figure 3 represents the engine of Figure 1, in disassembled state.

Figure 4 represents a side view of the piston of Figure 2.

Figure 5 represents a first preferred embodiment of sealing elements according to the present invention.

- Figure 6 represents a second preferred embodiment of sealing elements according to the present invention.

Figure 7 represents further preferred embodiments of sealing elements according to the present invention.

Figure 8 represents a preferred embodiment of a rotating shaft in a cylinder-piston system according to the present invention.

Figure 9 represents a preferred embodiment of a sliding element in a cylinder-piston system according to the present invention.

Figure 10 represents a further preferred embodiment of a sliding element in a cylinder- piston system according to the present invention.

Figure 11 exemplifies the cinematic motion of a preferred embodiment of a cylinder- piston system according to the present invention.

Figure 12 represents a cut out section of the head of the engine of Figure 1.

In general, the drawings may illustrate different aspects and embodiments of the present invention and, where appropriate, like elements or components or materials or actions in different figures are indicated by the analogous reference numbers. Certain reference numbers may be omitted for alike elements, in order to improve legibility of the drawings.

Detailed description of embodiments

Figure 1 represents an engine 101 comprising a cylinder-piston system according to the present invention.

The engine 101 is a reciprocating engine, preferably a two-stroke internal combustion engine. The engine 101 comprises a cylinder housing 102, which is adapted for air cooling; in fact, the cylinder housing 102 comprises a plurality of fins, which extend also to the engine head 103.

In a preferred embodiment, the two-stroke engine 101 comprises an intake manifold 104 for a reed valve system (not shown), for controlling the fuel-air mixture admitted into the cylinder 102. The engine 101 further comprise a flywheel system 105.

Figure 2 represents a piston 201 according to the present invention. The piston 201 is configured for being housed inside the cylinder housing 102, as it will become further apparent.

The piston 201 comprises a perimetral groove 202, which is adapted for housing the sealing elements of the piston. The piston 201 further comprise a slot 203, which is transversal to the direction of the linear movement of the piston 201 inside the cylinder 102. As it will be described, the slot 203 is configured for housing a fitted eccentric element of a rotating shaft. The piston 201 preferably further comprises one or more recesses, such as bottom recesses 204 and side recesses 205, which are meant to reduce the piston's 201 weight and inertia. Figure 3 represents the engine 101, in disassembled state. The piston 201 is configured for linearly moving, in a reciprocating manner, inside the corresponding cylinder 102. The cylinder 102 comprises, in this preferred embodiment, a main cylinder body 301 which defines three walls of the cylinder chamber, and an auxiliary cylinder body 302, configured as a cover providing the fourth wall of the cylinder chamber. The cylinder 102 further comprises two cooling elements 303 fixed to its outer walls, the cooling elements 303 comprising fins or similar elements, meant to improve the heat exchange with the environment, in an air cooled engine.

In the cylinder-piston system of the engine 101, a rotating shaft 304 is provided, which constitutes a mechanism for converting the reciprocating linear motion of the piston 201 into a rotating motion of the shaft 304.

The rotating shaft system, in this preferred embodiment, employs a "scotch yoke" or "slotted link mechanism" which will be further described in greater detail with reference to Figure 11. In fact, this mechanism is particularly advantageous in combination with a piston having a rectangular cross section, because the increase in engine displacement, linked to the limited rotational speed of such an engine, and the exactly sinusoidal movement of the piston, provide for an engine which is reliable and effective. Moreover, this particular mechanism allows for a square engine, which has equal or nearly equal bore and stroke dimensions, giving a bore/stroke ratio value of about 1 : 1.

In other embodiments, the rotating shaft system may use a more traditional connecting rod and a rotating crankshaft, or other suitable cinematic mechanisms.

The piston 201 is configured for a linear motion inside the cylinder 102, which is in the "up and down" direction of Figure 3.

The piston 201 has a rectangular cross section on a plane which is transversal to the direction of linear motion. Similarly, the cylinder 102 in assembled state will have a corresponding rectangular cross section on the same transversal plane.

As it is clear, in the present description the term "cylinder" is not meant as "having cylindrical shape", but it is rather used for its mechanical meaning, familiar to the skilled in the art, in order to define the sleeve body inside which the piston, which has a rectangular cross section, linearly moves.

The piston 201 comprises, associated thereto, a plurality of sealing elements 305 configured for providing a seal between the walls of the piston 201 and the walls of the cylinder 102, that will be further described in greater detail. The sealing elements 305 are preferably associated with spring elements 305b, which will be further described.

The rotating shaft system further comprises a sliding element 306, which will be further described as well. The sliding element 306 is preferably associated with roller bearing elements 306b, which will be further described. Moreover the engine 101 comprises, for its functioning, further elements such as a first internal flywheel 307, which houses a small magnetic element used for controlling the ignition of the engine, a flange 308 configured for housing and constraining the rotating shaft 304, a second external flywheel 309 for regulating the engine, and an outer cover 301 for closing the assembly.

The engine 101 further comprise known elements, such as in injection system, fuel lines, and so on which are not depicted nor described for sake of brevity.

Figure 4 represents a side view of the piston 201, from the side (hidden in Figure 3) which comprises the elongated slot 203, and the recesses 205.

The piston 201 comprises the perimetral groove 202, which runs around its perimeter on the four sides. The perimetral groove 202 is proximal to the piston's top 401, and is configured for housing the sealing elements 305, which provide a seal. In this sense, it is advantageous to have the perimetral groove and the sealing elements as close as possible to the piston's top, which faces the cylinder's chamber.

Inside the groove 202, the piston 201 comprises a plurality of slots 402 configured for housing spring elements (305b of Figure 1). The piston comprises at least one, preferably two, spring elements for each side of the slot. The function of such slots 402 and of the respective spring elements will become further apparent.

Preferably, the width (height, in Figure 4) of the groove 202 is 2.0 mm; preferably the groove's depth is more than its width (height, in Figure 4).

The piston 201, inserted in the groove 202, comprises sealing elements which provide a seal surrounding the piston, so as to avoid leakage from the cylinder's chamber during the reciprocating motion.

According to the invention, the sealing elements comprise a first series and a second series of sealing elements, which are overlaid on each other, and in contact with each other. In other words, the first series and the second series of sealing elements are superimposed, so as to provide a sealing system made of more parts. In particular, the sealing system comprises two (or at least two) series of overlaid sealing elements, which are flexible enough to follow the reciprocating motion of the piston while providing sealing on the cylinder's walls.

The first series and the second series of sealing elements have corresponding overall shapes and sizes, so as to be combined to include a complete perimeter of the piston.

Figure 5 represents a first preferred embodiment of a first series 501 of sealing elements according to the present invention.

The first series 501 comprises four sealing elements 502, 503, 504 and 505 which are adjacent to each other at joining zones, in order to complete a perimeter of the piston 201 (which is depicted in section, on an exemplifying transversal plane).

At the joining zones, the elements are not welded nor glued nor constrained, but rather assembled having matching shapes; this improves effectiveness in assembling the engine 101. The joining zones correspond to areas of contact between adjacent elements, and are considered as projected on the transversal plane of reference.

In particular, the joining zones of the first series 501 is at the edges of all four angles of the rectangular cross section of the piston 201.

All elements 502, 503, 504 and 505 are shaped as isosceles trapezoids, having 45° angles toward the outer region of the piston's perimeter, and consequently having 135° angles toward the inner region of the piston's perimeter.

Advantageously, such elements 502, 503, 504 and 505 are configured to include the complete perimeter of the piston 201, being two alike pairs: elements 502 and 504 are alike, and these cover the longer sides of the piston 201; elements 503 and 505 are alike, and these cover the shorter sides of the piston 201; manufacturing costs are thus reduced by providing alike elements.

As mentioned, the piston 201 comprises spring elements 403, housed in respective slots 402, which are configured for pushing outwards the sealing elements 502, 503, 504 and 505 so as to improve their sealing effect.

Such spring elements 403 can be traditional coil springs, or other suitable types of springs or resilient elements.

Preferably, two spring elements 403 are associated to each of the sides of the piston's cross section, so as to exert a uniform force on all four sides.

Figure 6 represents a second preferred embodiment of a second series 601 of sealing elements according to the present invention.

The second series 601 comprises four sealing elements 602, 603, 604 and 605 which are adjacent to each other at joining zones, in order to complete a perimeter of the piston 201 (which is depicted in section, on a further exemplifying transversal plane).

The sealing elements 602, 603, 604 and 605 are different from the sealing elements 502, 503, 504 and 505.

The joining zones of the second series 601, are still at the edges of all four angles of the rectangular cross section of the piston 201, but these joining zones are different from the ones of the first series 501 (i.e. being angled 90° with respect of the piston's sides, instead of being angled 135° with respect of the piston's sides). All elements 602, 603, 604 and 605 are shaped as rectangles, thus having all 90° angles.

Advantageously, such elements 602, 603, 604 and 605 are configured to include the complete perimeter of the piston 201, comprising at least one alike pairs: elements 603 and 605 are alike and manufacturing costs are reduced by providing alike elements.

The elements 602, 603, 604 and 605 are so shaped as to cooperate in including a complete perimeter of the piston 201, in order to provide a sealing effect, as already described.

The spring elements 403 housed in respective slots 402, are sized and configured for pushing outwards also the sealing elements 602, 603, 604 and 605 so as to further improve their sealing effect.

The force exerted by spring elements 403 can be applied to elements both of the first series 501 and of the second series 601 of sealing elements. Other possibilities include providing dedicated spring elements for each series.

In general, the sealing elements have a rectangular cross section with respect of their main direction of development; in particular, these superimposed sealing elements have an overall thickness which is compatible with the one of the groove 202, in order to house two (or more, in case) series of sealing elements. For example, for a groove having thickness of 2.0 mm, the sealing elements of each series will have (an equal) thickness of 1.0 mm, including appropriate tolerances.

Preferably, the sealing elements are made of cast iron, in particular spheroidal graphite iron. Such materials exhibit appropriate properties for flexibility, resistance and friction.

Preferably, the surface roughness of the sealing elements correspond to R _a = 0.2 μπι, preferably obtained by grinding.

Preferably, the sealing elements have sharp outer edges, so as to improve the sealing effect. Other seals conceived without sharp outer edges would not work as well.

In a preferred embodiment, series 501 is overlaid on top of series 601 as shown in Figure 3. In general, a particular order of a "first" and "second" series is not essential, as the mutual disposition of the overlying series can be varied. In fact, the piston moves of a reciprocating motion, so that its direction of motion changes over time: both series then became, at a certain time instant, either "leading" elements, or "trailing" elements.

Figure 7 represents further preferred embodiments of sealing elements according to the present invention, arranged in corresponding series, which are configured for including a complete perimeter of the piston. The sealing elements of each series are adjacent to each other, at adjoining zones which are represented as solid lines.

The pair of series, for each embodiment, is indicated by a "+" sign in Figure 7, and the skilled in the art will be able to derive further embodiments starting from the examples given herein. In a first embodiment, a series 501 of sealing elements as already described, is associated with a series 601b of sealing elements; series 601b comprises four sealing elements of rectangular shape, comprising two alike pairs for the shorter and longer sides of the piston's section, respectively. This first embodiment is an alternative to the preferred embodiment of Figures 5 and 6.

In a second embodiment, a series 501b is associated with a series 601c of sealing elements; series 501b comprises two substantially L-shaped sealing elements, which are symmetric (being the same sealing element reproduced twice, and then rotated in space of 180°) and which comprise at its extremities a 135° inner angle, and a 45° outer angle with respect of the piston's perimeter; series 601c comprises as well two substantially L-shaped sealing elements, which are symmetric (being the same sealing element reproduced twice, and then rotated in space of 180°) and which comprise five 90° angles, both in the inner and outer zones with respect of the piston's perimeter. This second embodiment is an alternative which minimizes the number of sealing elements (four in total) and achieves sealing by providing joining zones which are at the edges of same angles of the piston, but which are different from each other. In a third embodiment, a series 501b as already described is associated with a series 601c' of sealing elements; series 601c' comprises two substantially L-shaped sealing elements, symmetric and comprising 90° angles and corresponds essentially to series 601c rotated of 180° in the space. This third embodiment is a further alternative which minimizes the number of sealing elements (four in total) and achieves a better sealing by providing joining zones which are at the edges of the piston different from each other: this overlaying of the sealing elements further provides a barrier which the fluid cannot cross, without any leakage.

In a fourth embodiment, a series 501b as already described is associated with a series 501b' of sealing elements; series 501b' corresponds essentially to series 501b rotated of 180° in the space. This fourth embodiment is a further alternative which minimizes the number of sealing elements (four in total), requires only one kind of sealing element (L-shaped) and still achieves good sealing by providing joining zones which are at the edges of the piston different from each other.

In a fifth embodiment, a series 601c' as already described is associated with a series 601c of sealing elements as already described. The combination of these sealing elements of this fifth embodiment is a further alternative which still minimizes the number of sealing elements (four in total), requires only one kind of sealing element (L-shaped with 90° angles) and still achieves good sealing by providing joining zones which are at the edges of the piston different from each other.

In general, it is advantageous that the joining zones of the sealing elements of the first series are different from the joining zones of the sealing elements of the second series. Preferably, all of the joining zones of the sealing elements of the first series, are different from and do not have a match in any of the joining zones of the sealing elements of the second series. This improves the sealing, as during the piston's motion small deformation can occur to the sealing elements, that still do not create a passage for the fluid to leak.

Moreover, the joining zones of the sealing elements of either the first or second series, are at the edges of at least two of the angles of the rectangular cross section of the piston.

The solutions wherein each series of sealing elements comprises a sealing element for each of the four sides of the piston is preferred, as it provides the best sealing effect, having a dedicated array of sealing elements for each side of the piston which improve flexibility of the assembly, thus following best the piston's reciprocating motion.

In general, appropriate sealing on the piston's edges is assured by non-overlapping different joining zones between the series of sealing elements. The spring elements pushing outwards the sealing elements further contribute to this sealing effect.

Figure 8 represents a preferred embodiment of a rotating shaft in a cylinder-piston system according to the present invention.

Given the characteristic of the cylinder-piston system according to the present invention, an exemplary preferred embodiment of a best working rotating shaft system is herein provided. The rotating shaft 304 comprises an eccentric element 801 of cylindrical shape, at one sides, which is configured for being inserted inside the slot 203 of the piston 201. Preferably, at the same side of eccentric element 801, the rotating shaft 304 also comprises a balancing mass 802, which can be used for balancing the engine system.

Figure 9 represents a preferred embodiment of a sliding element 901 in a cylinder-piston system according to the present invention. The sliding element 901 is configured to be interposed between the eccentric element 801 and the slot 203 of the piston 201, so as to reduce friction therein.

The sliding element 901 comprises a pair of parallel surfaces 902 and 903 (not visible, below the element) which are configured for sliding each on a respective parallel surface of the slot 203, transversally with respect of the direction of linear movement of the piston 201.

Preferably, the sliding element comprises a plurality of lubricating holes 904, which are configured for adducting lubricating oil inside the cylindrical surface of the sliding element which houses the eccentric element 801, to further reduce friction. Figure 10 represents a second preferred embodiment of a sliding element 1001 in a cylinder- piston system according to the present invention.

The sliding element 1001 comprises a sliding element 901 as already described, and it further comprises a pair of roller bearing elements 1002 and 1003 (306b of Figure 1) which are respectively associated with the parallel surfaces 902 and 903. These roller bearing elements comprise roller bearings which are configured to fit inside the slot 203 of the piston 201, and further reduce friction therein with the parallel surfaces of the slot 203.

Figure 11 exemplifies the cinematic motion of a preferred embodiment of a cylinder-piston system according to the present invention.

Figure 11A schematically depicts a section of engine 101, wherein the piston 201 is near the bottom dead centre (BDC) inside the cylinder 102; the sliding element 801 is near the center of the transversal slot 203.

Figure 11B depicts the piston 201 moving upwards, while the sliding element 801 slides towards the right part of the transversal slot 203.

Figure 11C depicts the sliding element 801 that slides further towards the right part of the transversal slot 203, causing the piston 201 to move further up, and then the sliding elements starts to move towards the center of the slot 203, once again.

Figure 1 ID depicts the piston 201 near the top dead centre (TDC) inside the cylinder 102; the sliding element is again near the center of the transversal slot 203.

Figure HE depicts the piston 201 moving downwards, while the sliding element 801 slides completely towards the left part of the transversal slot 203.

Figure 1 IF depicts the sliding element 801 that begins sliding again towards the right part of the transversal slot 203, causing the piston 201 to move further down, competing the cycle and returning to the position of Figure 11 A, in a reciprocating motion.

As above described, the rotating shaft system is configured for cinematically constraining the linear motion of the cylinder 102 with the rotating motion of the shaft 304. As mentioned, the particular rotating shaft system comprising an eccentric element moving in a transversal slot of the piston, provides for a "square engine" configuration, having equal or nearly equal bore and stroke dimensions, which exhibits particularly advantageous power bands.

By providing a transversal slot 203 in the piston 201, it is possible to constrain the motion with the motion of of an eccentric element 801; the slot 203 allows for a complete transversal range of movement of the eccentric element 801, so as to provide a reciprocating motion of the piston 201 inside the cylinder 102.

The rotating shaft system as above described is particularly advantageous in combination with a cylinder-piston system according to the present invention. In fact, the elements of the engine exhibit good functioning and achieve mechanical durability. Moreover, the engine comprises a limited number of elements and is easy to assemble and to manufacture, easier than engines comprising a traditional crankshaft, especially since the present engine comprises a rectangular piston.

Moreover, an engine comprising a rotating shaft system as described, is advantageous in combination with a rectangular cross-section piston, as the latter exhibits a larger dimension in transversal direction (width), thus increasing the piston's stroke and increasing engine displacement and power.

The engine according to the present invention is also more compact and reliable, has a smooth functioning; in fact the particular rotating shaft system, in combination with a cylinder-piston system as described, improves engine balance and reduces vibrations.

An engine as described has a convenient power/displacement ratio, and is desirable for selected applications wherein lightness and versatility is desirable, especially for two-stroke engines.

As examples, an engine according to the present invention could advantageously be applied to cars, motorcycles, motorized gardening tools (such as chainsaws, lawn mowers, etc.) and could in general be a road or a non-road engine.

Figure 12 represents a cut out section of the head 103 of the engine 101. The cylinder head 103 comprises two cavities 1201 and 1202, each configured for housing a respective sparkplug. According to this embodiment, the hot gases generated by the combustion in the cylinder can act more evenly on the piston's surface, thus providing an improved balance for an engine comprising a rectangular piston.

The system according to the invention, as merely exemplified in the present description with the implementing details herein given, is susceptible to a number of changes and variants, which become apparent to the skilled in the art which considers the present description. Such variants do not depart from the scope of protection of the present invention, as defined by the appended claims.

For example, the cylinder-piston system may comprise three or more series of overlaid sealing elements.

Although the cylinder-piston system has been described with reference to an internal combustion engine, the skilled in the art can readily translate the teachings of the present invention to further mechanical reciprocating system, such as compressors, volumetric or gas compressors, pumps in general. Moreover, even if the exemplified internal combustion engine is a two-stroke engine, the skilled in the art understands that the present invention could be applied to four-stroke engines, Otto or Diesel engines, or other engines, as well. These engines could either be naturally aspirated engines, or supercharged/turbocharged engines. These engines could be air cooled, as described, or liquid cooled.

Even if the exemplified internal combustion engine comprises a reed valve system, other injections system can be provided, such as valves, poppet valves, rotating disc valves, piston ports.

For example, even in the cylinder-piston system has been described with reference to a single- cylinder system, the skilled in the art can envisage the cylinder-piston system applied to systems comprising a plurality of cylinders, such as two, three, four, and so on, having a plurality of configuration (in line, L-twin, V-twin, boxer, etc.).