FR2499661A1 - Piston assembly for internal combustion engine - has separate compression and oil scraper rings with radial, elastic, thin abutting flaps - Google Patents

Abstract

The piston (11) of a compressor or internal combustion engine is fitted with dual compression rings (12) and a separate scraper ring (13). One compression ring is made of metal and with its radial width considerably greater than its axial thickness. The ring has a number of notches around its inner edge to increase its elasticity. The ring is fitted in the piston groove with a circular lip abutting against the cylinder together with a flat ring of PTFE. The scraper ring (13) is of L shaped cross-section and made of spring steel. The surface abutting against the cylinder wall (14) is divided into a number of circumferentially abutting thin elastic flaps.

Description

 The pistons of internal combustion engines or compressors are generally equipped with a set of segments whose missions are to prevent, between pistons and cylinders, the gas passages towards the crankcase and the oil passages towards the piston head.

 The segments of these currently known games interfere with each other in operation and together perform, more or less completely, the aforementioned missions, each of these segments not entirely ensuring its own.

 The compression segments allow gases to pass from the combustion or compression chamber to the crankcase, and the scraper segments scrape in both directions, i.e. they work against their mission in the upward strokes of the piston. .

 Thus, their roles are not exactly delimited; this results in development difficulties, instabilities, insufficiencies and operating uncertainties.

 Finally, all these segments are applied with force against the cylinder and are heavy, which results in an appreciable expenditure of energy by friction and inertia.

 The present invention relates to an assembly comprising, in a cylinder with a high level of finish, a lightened piston provided with a new simpler segmentation, with very high efficiency, with very low tension against the cylinder, and lighter than the known segmentations at this day, and in which each of the missions assigned to the segmentation is entirely ensured by the segment dedicated to it.

It is composed, by engine or compressor piston - of a compression segment, consisting on the one hand by at
minus a cut, thin, steel ring, with a circu
air is applied against the cylinder by its tension
regularly distributed elastic, the cut of which has a
means of closing the gas passage along the cylinder by the
cutting clearance and on the other hand, by at least one ring
cut, thin, of plastic material with circular lip
is applied against the cylinder by the effect of its
diameter, the two edges of its cut being joined, these
rings being arranged with a slight clearance in a groove of the
piston, the ring, of plastic material, being inter
placed between the groove face of the piston located on the side of the
housing and a steel ring, - of a one-piece spring steel scraper segment, consisting of
by a circular row of contiguous lateral tabs
and very thin elastic bands, connected to each other and to the piston
tightly by the edge of their row located on the side
of the piston head and applied against the cylinder by the
edge of their row located on the side of the housing, using the
elastic force of each tab, their lateral faces
external following the shape of the cylinder and presenting with
its wall a very acute circular angle, open towards the head
piston, said tabs together constituting a skirt
closed and tight circular elastic on the side of the head of the
piston and open towards the casing, - arrangements for receiving said segments and for perfec
operation of the piston and cylinder.

 Such an assembly has great simplicity of segmentation t it takes up less space and weight than the currently known segmentations. The compression segment provides high-efficiency control of the passage of gases between the combustion or compression chamber and the crankcase, and the scraper segment presents two new very high-efficiency actions: one, single-effect scraper, during races descending from the piston, the other from single-acting recycling, during the upward strokes of the piston.

 Indeed, in descending strokes, the lower edge of its thin and elastic external face, almost parallel to the cylinder, constitutes a device for scraping the oil which is ideal, although its force of application on the cylinder is minimal and, in upward strokes, the low angle with the cylinder of the wall of its outer face constitutes another ideal device, although its force of application on the cylinder is still minimal, for recycling towards the casing, by dynamic effect, the oil remaining on the cylinder wall.

In addition, the high and independent efficiency of each of these segments creates more favorable conditions for the functioning of the other than the interaction previously known. Thus, the tasks incumbent on segmentation are fulfilled with a higher efficiency than that of traditional segmentation with less wear and energy saving. Finally, this better efficiency of each of the segments and their lower friction, results in a lubrication regime between piston, segments and cylinder, fully movable, which brings several new operating conditions. the possibility of adopting a level of polishing of the walls
of cylinder much higher than their usual level of which it
results, on the one hand, from other reductions in friction and
of the wear of all the organs of these new assemblies which
are an additional contribution to savings
of energy and on the other hand, a reduction in the wear of the
outer lip of the plastic ring, advantage
important as will be explained later.

. the possibility of establishing the mechanical portage between cylinder
and piston up to the piston head, which improves
heat exchanges between cylinder and piston and, added to
fact that it has only two segments, allows shortening
cir and thus lighten the piston substantially.

Other characteristics and advantages of the present invention will emerge from the following description of an assembly according to the invention, made with reference to the appended drawings in which - FIG. T represents, in a cut cylinder, a piston
provided with a segmentation composed of a compression segment
and a scraper segment; - Figures 2 and 4 are each a sectional view to another
scale, of a part of the piston showing an example of
compression segment, in a cylinder; - Figure 3 shows a means of closing the gas passage by
cutting a compression segment; - Figures 5, 6 and 7 are plan views of three rings
component of the compression segment of Figure 4 - Figure 8 is a sectional view on a larger scale,
along line AA of Figures 5 and 9 ;; - Figures 9 and 10 are plan views of a variant of
the ring of Figures 5 and 6; - Figures 11 and 12 are perspective views of a
scraper segment and a variant of this segment; - Figures 13 and 14 are sectional views of part of
piston each showing the section of the scraper segment of the
Figures 11 and 12 in the operating position - Figure 15 shows in perspective an annular wedge of
scraper segment; - Figures 16 and 18 show two side views of a
scraper segment of Figure ll in the free state; - Figures 17 and 19 are sectional views of Figures 16
and 18; - Figure 20 is a perspective view of cutting stops
added to a scraper segment of Figures 11, 13 and 16.

 Figure 1 shows, on a piston 11 a compression segment 12 and a scraper segment 13; the assembly is arranged in a cylinder 14. After the description of these segments and with an explanation of the operation of the assembly, we will return to the particularities of the piston and of the cylinder which are made possible by the use of these segments.

 FIG. 2 shows, in a partial section of the piston 21 in its cylinder 24, a first example of a compression segment 12, 22. I1 is composed of two thin elements 25 and 26 arranged with a clearance 27 in the groove of the piston 21. This clearance 27 is limited to the minimum necessary to ensure the freedom of movement of the two thin elements as well as the access of the pressure of the combustion or compression chamber by the clearance 27 on the top and on the inner cylindrical face of the segment 22 .

The two thin elements of segment 22 are of a
on the one hand, a cut, thin ring (thickness of about 0.7 mm) made of elastic metal, cast iron or steel for example, and on the other hand, a cut, thin ring 26 (thickness of about 0.5 mm) of material plastic such as annealed copper or polytetrafluoroethylene (Teflon). The plastic ring 26 is always disposed between the elastic metal ring 25 and the groove face of the piston which is on the side of the casing.

 The ring 25 in the free state has a larger diameter than that of the cylinder in order to give it an extension force against the cylinder and the closing of the gas passage by the cutting clearance along the wall of the cylinder is provided by the arrangement shown in Figure 3; the ring 25 is shown there, seen in plan at 35, in the bandaged state in its cylinder 34. The length of the cutting clearance is increased to interpose between its cutting faces 38 and 39 a ring sector 310 of section similar to that of the metal ring 35 but made of plastic, polytetrafluoroethylene (preferably Teflonj.

 This sector 310 is arranged cold without play between the cutting faces 38 and 39 so that by the effect of the extension force of the hot expansion of the ring 35 and of the sector 310 and the pressure of the gas on the inner face of the ring and the sector, these two members are applied against the cylinder and thus cooperate in closing the gas passage between the cutting ring of the metal ring 35 and the cylinder.

 The length of the sector 310 must be sufficient so that its elasticity (which is of the order of 4% of its length for Teflon) is b at the sum of the expansions of the ring 35 and of the sector 310, in order to avoid that this sector undergoes a permanent reduction in its length.

 Figure 4 shows, in a partial section of the piston 1 in its cylinder 44, a second example of compression segment 12, 42; it is composed of three thin elements 45, 46, 411 arranged with a clearance 47 in the groove of the piston 41.

This clearance 47 is limited to the minimum necessary to ensure the freedom of movement of the three thin elements as well as the access of the pressure of the combustion or compression chamber by the clearance 47 on the top and on the inner cylindrical face of the segment 42 .

FIGS. 5 to 7 separately show a plan view of each of these three elements of segment 42 which are, on the one hand, two rings 45, 55 and 411, 611 joined, cut,
thin (thickness about 0.7 mm) in elastic metal, cast iron or steel for example and, on the other hand, a ring 46, 76 cut, thin (thickness about 0.5 mm) in plastic material such as annealed copper or polytetrafluoroethylene (Teflon); the plastic ring 46, 76 is always disposed between the two elastic rings 45, 55 and the groove face of the piston which is on the side of the casing.

 The rings 45, 55 and 411, 611 have, in the free state, a larger diameter than that of the cylinder in order to give them an extension force against the cylinder and their cutting clearance is just necessary for their hot expansion. when mounted on their piston in the cylinder.

The ring 46, 76, without elasticity, is approximately the size of the cylinder and sGn cutting clearance 715 is approximately zero when cold, so that under the combined effect of thermal expansion and the pressure acting by the clearance 47 of the segment on its inner cylindrical surface, the ring 46, 76, as the rest of the rings 45, 55 and 411, 611 are applied against the cylinder all the more that the pressures in the combustion or compression chamber are more high.

 In this example, the means of blocking the passage of gas along the cylinder by the clearance of the cup is to prevent the rings 45, 55 and 411, 611 from rotating with respect to each other, in order to 'prevent their cuts from overlapping, but without restraining them so that everyone remains free to move in their plane and to apply against the cylinder without stress received either from the other or from the piston.

 Figure 8 is a section AA of the rings 55 and 95; it shows a good example of embodiment of this retention: place on the lower ring 45, 55, 85, 95, a lug 512, 812, 912 slightly lower than the thickness of the upper ring 411, 611, 1011. In this upper ring, a housing is provided to receive the lug 512, 812, 912 with sufficient play so as not to clamp the two rings 45 and 411, 55 and 611, 95 and 1011. A good example of embodiment of this housing consists of the two notches 613 and 614, 1013 and 1014; this position of the notches is advantageous because it allows, by first mounting the ring 45, 55, 95 in the groove of the piston, to then mount the ring 411, 611, 1011 by aligning its cut opposite the lug 512, 912.

 Figures 9 and 10 show the plan views of an alternative embodiment of the rings 45 and 411. On the rings 95 and 1011, there are the lug 912 and the notches 1013 and 1014, but notches 916 have been added. and 1016 distributed over the inner periphery of each ring.

Here is the reason and the role:
The width of a thin cut ring is opposed to obtaining sufficient radial elasticity to obtain a light and well distributed contact between the outer edge of the thin ring and the cylinder. With the notches 916 and 1016, it is possible both to keep the width of the thin ring which is necessary for it to be properly held in the groove of the piston and to regain the radial elasticity which the wide thin ring lacks.

 In addition, it is known that to manufacture segments of normal thickness cast iron or steel, it is necessary to resort to irregularities in the width of the segment in order to obtain a good distribution of the extension force over the entire periphery of the segment. in contact with the cylinder, in particular avoiding the stiffness of the vicinity of the cut. The number and the location of said notches is a good inexpensive means of influencing this distribution, for example by regularly distributing the notches in the sector RR shown in FIG. 10 which is opposite to the cut and by tightening them in the vicinity of the cut.

Thus, with the thin rings of elastic metal have notches 916 and 1016 judiciously established and distributed, this new behavior is obtained for thin rings - elasticity, flexibility and conformation allowing contact
light and equally distributed, around their entire periphery, between the rings and the cylinder.

 Figures 11 and 12 show in perspective two examples 113 and 123 of the scraper segment. I1 comprises a single piece, made of spring steel, composed of a frustoconical crown of very thin elastic strips 1117, 1217, for example 0.2 mm thick. These strips are separated from one another on the side of the large base of the frustoconical crown and connected together on the side of the small base of said crown, for example by a flat washer 1118 or a cylinder 1218.

 The metal of these scraper segments is subjected, either to the state of raw material, or to the state of the part being executed, to a heat treatment which gives it optimum elasticity. The ends of the elastic strips 1117, 1217, can be hardened by an additional localized heat treatment in order to form a contact line with the cylinder of high hardness and thus to increase its protection against wear. This protection already results from the fact that the lamellae which make up this contact line are applied against the cylinder under very slight force, which is explained below.

 FIGS. 13 and 14 are partial views, in section, of a piston 131 or 141 mounted in its cylinder 134 or 144 and carrying in 133 a scraper segment of FIG. 13 and in 143 a scraper segment of FIG. 14.

 The scraper segment 133 is held in a groove 1320 of the piston 131 by its part forming a flat washer 1118, 1318 with a minimum clearance 1321 and an annular shim 1322 is used, if necessary, in order to give the groove 1320 a easily executable width greater than the thickness of the washer 1118, 1318 which may be 0.2 mm for example. This annular wedge 1322 is presented in FIG. 15 in 1522. It includes a section 1523 to allow its mounting; its outside diameter is smaller than that of the piston because it has no mission to rub against the cylinder and at rest, its cut 1523 is contiguous; its thickness is represented in 1524; this will be discussed below, Figure 20; it can be made of metal, preferably light, or better of plastic, for example polytetrafluoroethylene (Teflon) in this case, it adds to its role of annular wedge that of annular seal.

 The scraper segment 143 is held on the piston 141 by its cylindrical part 1218, 1418 by gluing (by anaerobic resins, or cyanoacrylates, for example) in a circular housing 1425 formed in the piston. Between the strips 1317 or 1417 and the piston 131 or 141, an annular chamber 1326 or 1426 can be provided in the piston, the mission of which is to collect the oil scraped by the strips 1317 or 1417 in the descending strokes of the piston.

The return to the sump of this oil can be done by the following means, used as required, together or separately. during the upward strokes of the piston
- a frustoconical shape 1327 connects the chamber 1326 and the
top of the skirt 1328 of the piston; this form presents a
angle with the cylinder wall favorable for driving
dynamics of the oil, for example 70, and produces the return
oil to the crankcase via the clearance between the piston and the
cylinder.

- a row of radial holes 1429 oriented towards the bottom of the
piston, making the bottom of the annular chamber communicate
1426 (or 1326) with the center of the piston, produced by its
orientation a dynamic effect driving the oil towards the
center of piston.

. during descending strokes of the piston
a row of radial holes 1330 perpendicular to the axis of the
piston, or holes 1431 oriented towards the piston head,
connecting the top of the annular chamber 1326 or
1426 with the center of the piston, leads the oil to the center
of the piston, the holes 1431 adding thereto by their orientation a
dynamic effect.

 Figures 16 and 17 show from the front and in profile, in the free state, the segment 113, 133, of Figures 11 and 13, with sections between lamellas 1632 perpendicular to the radial plane of the segment.

 Figures 18 and 19 show in the same way a variant of the same segment comprising sections between blades 1833 inclined relative to the radial plane of the segment. Taking into account the difference in contact between the lamellae and the cylinder during the downward scraper strokes and the upward recycling strokes, these inclined cuts rotate the segment, which is favorable to the perfect conformation of the segment in the cylinder, therefore its efficiency.

 When the piston is mounted in the cylinder, the elastic strips 1317 and 1417 are held tight by the cylinder; they have an angle a with its wall, FIGS. 13 and 14 and the two faces 1119 and 1219 of the section of the segment are in abutment against one another. In this position, by construction and except very small clearances for the needs of the operation that is to say mainly of thermal deformations or expansions and lubrication, the strips 1317 and 1417 are contiguous, as shown in Figures ll and 12 which show them joined, as they are in the cylinder. Their edge on the casing side which is in the scraping position in the descending strokes and in recycling in the ascending strokes, has a continuous line in contact with the cylinder. In the free state outside the cylinder, the sections 111 and 1219 are construction, preferably closed, in order to facilitate their retention in place on the piston before its mounting in the cylinder, but the elastic strips 1117 and 1217 are open, that is to say that their outside diameter is larger and that they are no longer joined; they have spaces between them 163-2 and 1833 and they form with the axis aj segment, which is parallel to the wall of the cylinder when the piston is mounted, an angle 8 which is greater than the angle a. It is the difference between the angles ss and a which gives rise to the elastic force which applies each strip against the cylinder when the segment is mounted inside the cylinder.

 The variation in the difference between these two angles and that of the thickness of the elastic strips makes it possible, during manufacture, to adjust the elastic pressure with which each strip is pressed against the cylinder as desired.

The angle of the slats 1317 and 1417 with the wall of the cylinder is very small, an angle of 70 for example, known as favorable to the effects of entrainment of the oil between moving walls and indicated as favorable for the recycling of the oil during upward strokes of the piston, as well as during scraping during its downward strokes.

 Figure 20 shows in perspective the section of a segment of the type presented in Figure 11, to which is added to each side of the section a small rim at right angles 2034 and 2035 disposed at each end of the flat washer 2018 of the segment. The height of this rim is at most equal to the thickness of the annular shim or of the joint 1322, 1522. It has the advantage of ensuring that the segment is cut, the two ends of which are pressed one against the other in service, a positive stop which protects them against any risk of overlapping that their thinness can make possible.

The functions and the advantages of this new cylinder, piston and light segmentation assembly are as follows
The compression segment comprising at least one thin elastic metal ring, the cut of which is provided with a means for shutting off the gas passage along the cylinder assisted by a wTeflon seal for example, ensures: by eliminating the cut passage , by well distributed pressure against the cylinder and by assistance of the seal, a very high seal against the passage of gas, with a friction force on the cylinder reduced by the fact that the extension force of thin rings, at regularly distributed pressure , is much weaker than that of conventional segments which are thicker.

 On the other hand, it is known that a segment sealed against the passage of gas has the drawback of producing an oil pumping effect towards the top of the cylinder. Cooperation with the scraper segment, the very high efficiency of which will be seen below, provides a remedy for this drawback.

 We also know that the service life of the plastic material seal (Teflon in particular) is excellent; it can reach the life of the engine, with the sole exception of the attack on its outer edge by the roughness of the cylinder which is necessary, in the current state of technology, to build up oil reserves on the cylinder walls , to avoid "scuffing".

However, the very high reduction of the gas passage and that of the friction of the compression segmentation, by eliminating the entrainment of abrasive combustion residues, the hot spots of the segment and the burning of the oil on the cylinder and around the segment of compression, create new lubrication conditions which make it possible to resort to two new means - on the one hand, the prolongation of the contact between the piston and the
cylinder up to the piston head, whereas generally
this contact is limited to the piston jacket, below the
scraper segment; - on the other hand, the use for interior surfaces
cylinders with a high degree of polishing.

 These two measures reduce friction, improve the heat exchange between cylinder and piston and, added to the fact that the piston can be taller by having only two segments, they make it possible to reduce its height, therefore to lighten it substantially. In addition, they eliminate the lateral wear of the seal of plastic material iTéflon, in particular).

 As for the operation of the scraper segment, its elastic lamellae have only linear contact with the cylinder, subjected to very slight pressure and are placed in an absolutely ideal position, both for scraping oil in downward strokes and for recycle in uphill races; they therefore ensure at the highest possible level the control of the oil flows to the combustion chambers and the reduction of friction which is very high with conventional segments since all of them perform scraping by a high pressure of lips having not a line, but a contact surface with the cylinder and working in a perpendicular position against the cylinder, which is as unfavorable as possible for scraping and recycling, since during one race in two, the upward races, the scraping segments perpendicular to the cylinder scrape and return oil in the wrong direction to the side opposite the crankcase.

Thus, the new whole brings together, positively, by new cooperation of its various elements - the reduction to a negligible level or the elimination of the
passage of gases between pistons and cylinders - control of the oil flow control - reduction of most of the friction and
wear between pistons and cylinder - lightening of the piston and its segmentation.

 All this saves energy, oil, mechanical wear and maintenance.

 Still other advantages result therefrom; among them, in particular, the best cold start by improving compression, especially on diesel engines, and reducing pollution by reducing trapped volumes of air and fuel between piston, segments and cylinder.

Finally, it should be specified that the separate use of the compression segment and the scraper segment, described in this set, remains within the scope of the invention because, if such use does not achieve all the effects of the above-mentioned cooperation. -exposed, each of these elements used in isolation brings its own advantages, in particular - for the compression segment: high tightness at
gas passage, reduction of friction, reduction
wear, lighter compression segment, gains in
performance, organ duration and energy saving - for the scraper segment: single-effect oil scraper
very effective in downhill racing in recon
reducing to the crankcase and recycling of the oil film remaining on
the single acting cylinder, very effective in racing
upward by reintroducing it into the casing circuit,
reduction of friction on the cylinder to a very fraction
low friction of all other scraping segments,
reduction of wear, reduction of the scraper segment, gains in
performance, duration of organs and energy saving.

 The two main organs of the invention therefore have an individuality which remains viable when used separately, but their cooperation alone can obtain all the advantages of the invention.

This is indeed, in fact - that the compression segment, if used separately
the scraper segment with very high oil control level,
can't master the oil pumping effect already
reported that incoming consumption of unacceptable oil,
very difficult, if not impossible, to reduce safely and
sufficient in series production.

- that the scraper segment, if used separately from the
compression segment
. on the one hand, is exposed to the gas passages of the segments of
conventional compression, and so it receives with these
gas the abrasive combustion residues they cause
and drive, which is a wear factor - of its
linear contact with the cylinder,
. on the other hand, remains forced to operate in a cylinder
exhibiting the usual degrees of roughness, instead of a
cylinder with high polishing level.

 These two conditions are detrimental to the good conservation without wear of the linear bearing of the elastic lamellae of the scraper segment against the cylinder.

Claims (7)

 1. - Cylinder assembly of internal combustion engine or compressor, piston and segmentation, characterized in that each element of the segmentation alone provides, while limiting its friction to a small part of their known level, with very effective high, one of the two missions assigned to it to stop the passage of gas and stop oil rises, the means used being - a compression segment 12 consisting on the one hand, by at  minus a thin, elastic metal cut ring (25, 35),  whose circular lip is applied against the cylinder  (14, 24, 34) by its elastic tension regularly  distributed, the cut of which comprises a closure means (38,  39, 310) of the passage of gas through the clearance of the cup and, on the other  part, by at least one cut, thin ring, of material  plastic (26, 76), the circular lip of which is applied  against the cylinder by the effect of its diameter, the two  edges of its cut (715) being contiguous, these rings being  arranged with a small clearance (27) in a groove of the piston and  the aforesaid ring (26, 76) of plastic material being  disposed between the groove face of the piston (21) located on the side  of the casing and the aforesaid steel ring (25, 35), - a scraper segment (13, 113, 123, 133, 143) ensuring  including two new actions, one of which is the simple scraping  very high efficiency during downhill races  piston dantes, the other single acting recycling,  very high efficiency during the upward races of the  piston, which segment is one piece in spring steel,  consisting of a circular row of side slats  (1117, 1217, 1317, 1417) contiguous and very elastic  thin, tightly connected to each other and to the piston  by the common side of their row (1118, 1218, 1318, 1418,  2018) located on the side of the piston head and applied  against the cylinder (134, 144) by the edge of their row  located on the side of the housing, by means of the elastic force of  each lamella, their outer side faces  having a circular angle (a) with the cylinder wall  very sharp, open towards the piston head, said blades  together constituting a closed and waterproof elastic skirt of the  side of the piston head and open towards the housing - the piston comprising on its periphery, at the  lamellae of the scraper segment (1317, 1417), a space  ring 1326, 1426) for receiving the scraped oil and the  means of its return in the casing (1327, 1429, 1330,  1431).  2. - Cylinder assembly of an internal combustion engine or of a compressor, piston and segmentation, characterized in that the compression segment alone provides, with very high efficiency, while limiting its friction to a small part of the known level, the mission assigned to it to stop the passage of gas, the means used being - a compression segment (12) consisting on the one hand by at  minus a thin, cut, steel ring (25, 35), the  circular lip is applied against the cylinder (14, 24,  34) by its regularly distributed elastic tension, the  cut includes a shutter means (38, 39, 310) of the  passage of gas through the clearance of the cup and, on the other hand, through  at least one cut, thin ring of plastic material (26,  763, whose circular lip is applied against the  cylinder by the effect of its diameter, the two edges of its  cut (715) being contiguous, these rings being arranged with  a small clearance (27) in a groove of the piston and the above  ring (26, 76) of plastic material being disposed between the  piston groove face (21) located on the side of the housing and the  aforesaid steel ring (25, 35).  3. - assembly according to one of claims 1 and 2, characterized in that the means for closing the cut is produced by two contiguous rings (45, 411, 55, 611) cut, thin, of elastic metal, including the circular lips are applied against the cylinder (14, 44) by their regularly distributed elastic tension, provided with a means (512, 912, 613, 1013, 614, 1014) respecting the independence of their movements, but imposing a limitation to their rotation relative to each other about the axis of the piston, in order to prevent the alignment of their cuts.  4. - Assembly according to any one of claims 1 to 3, characterized in that, at least one thin ring of elastic metal (25, 35, 45, 411, 55, 611, 95, 1011) of the compression segment ( 12, 22, 42) has notches (916, 1016) distributed around its inner periphery.  5. - Cylinder assembly of an internal combustion engine or of a compressor, piston and segmentation, characterized in that the scraper segment alone ensures, with very high efficiency, while limiting its friction to a small part of the known level, the mission assigned to him to stop the oil rises, the means used being - a scraper segment (13, 113, 123, 133, 143) ensuring in particular  two new actions, one simple scraping  very high efficiency during downhill races  piston dantes, the other single-acting recycling,  very high efficiency during the upward races of the  piston, which segment is one piece in spring steel,  consisting of a circular row of side slats  (1117, 1217, 1317, 1417) contiguous and very elastic  thin, tightly connected to each other and to the piston  by the common side of their row (1118, 1218, 1318, 1418,  2018) located on the side of the piston head and applied  against the cylinder (134, 144) by the edge of their row  located on the side of the housing, by means of the elastic force of  each lamella, their outer side faces  having a circular angle (a) with the cylinder wall  very sharp, open towards the piston head, said blades  together constituting a closed and waterproof elastic skirt of the  side of the piston head and open towards the casing - the piston comprising on its periphery, at the level of the  lamellae of the scraper segment (1317, 1417), a space  1326, 1426) for receiving the scraped oil and the  means of its return in the casing (1327, 1429, 1330,  1431).  6. - assembly according to any one of claims 1 to 4, characterized in that the cylinder (14, 24, 34, 44, 134, 144) comprises an internal wall of a level of polishing much higher than that normally used.  7. - An assembly according to any one of claims 1, 3, 4, 5 and 6, characterized in that the section of the scraper segment comprises a stop (2034, 2035) closing, cooperating with a shim (1322; 1522) of thickness (1524) at least equal to the height of the flanges (2034, 2035) of the stop.