Pressurized fluid flow system for percussive mechanisms

Abstract

A pressurized fluid flow system for percussive mechanisms comprises a cylinder coaxially disposed in between an outer casing and a piston which reciprocates due to the changes in pressure of the pressurized fluid contained inside a front chamber and rear chamber located at opposites sides of the piston. The discharge of fluid from these chambers being conducted through a set of discharge channels and the supply of fluid to the front chamber being conducted through a set of supply channels and a front set of recesses. The supply of fluid to the rear chamber being conducted through a piloted valve.

Claims

1. A pressurized fluid flow system for percussive mechanisms comprising: a cylindrical outer casing having a rear end and a front end; a driver sub mounted to the front end of said outer casing; a rear sub affixed to said rear end of the outer casing for connecting the mechanism to a source of pressurized fluid; a piston slidably and coaxially disposed inside said outer casing and capable of reciprocating due to changes in pressure of the pressurized fluid contained inside of a front chamber and a rear chamber located at opposites ends of the piston, the piston having a rear thrust surface, a front thrust surface, a front outer sliding surface and a rear outer sliding surface; a cylinder coaxially disposed in between the outer casing and the piston, the cylinder having an inner and an outer surface; a valve carrier disposed rear of the rear chamber, the valve carrier having a rear valve support surface; a probe carrier disposed rear of the valve carrier, the probe carrier having a front valve support surface, one or more longitudinal fluid passageways, an inner valve sliding surface, one or more pressure transmitting radial passageways and one or more fluid supply through holes; a valve mounted in a space created in between the valve carrier and the probe carrier, the valve able to slide longitudinally on the inner valve sliding surface of the probe carrier for moving between a front-located closed position and a rear-located open position, the valve further having a front support surface, a rear support surface, a front thrust surface, a rear thrust surface and a biasing thrust surface, the rear support surface and the rear thrust surface of the valve creating together with the inner valve sliding surface and the front valve support surface of the probe carrier a pressurized volume; and a drill bit slidably mounted on the driver sub, wherein the sliding movement of the drill bit is limited by a drill bit retainer mounted on the driver sub; a pressurized fluid supply chamber defined by an annular recess on an external surface of the piston, the pressurized fluid supply chamber longitudinally limited at each end by the front and rear outer sliding surfaces respectively and being in permanent fluid communication with the source of pressurized fluid for supplying pressurized fluid to the front chamber; a set of longitudinal supply channels created in between the outer surface of the cylinder and the inner surface of the outer casing for conveying pressurized fluid from the rear sub to the pressurized fluid supply chamber, the longitudinal supply channels being in permanent fluid communication with the source of pressurized fluid and filled with said fluid when the percussive mechanism is operative; a set of longitudinal discharge channels created in between the outer surface of the cylinder and the inner surface of the outer casing for discharging pressurized fluid from the front chamber and the rear chamber, the longitudinal discharge channels being disposed longitudinally in parallel with respect to the longitudinal supply channels and being in permanent fluid communication with the outside of the percussive mechanism; multiple pressurized fluid intake ports, multiple front pressurized fluid exit ports and rear and front sets of discharge ports provided in said cylinder respectively facing the sets of longitudinal supply and discharge channels, the pressurized fluid intake ports provided in said cylinder for connecting the longitudinal supply channels with the fluid supply through holes in the probe carrier and ultimately with the source of pressurized fluid, the front pressurized fluid exit ports provided in said cylinder for connecting the set of longitudinal supply channels of the cylinder with the pressurized fluid supply chamber and permanently filling it with pressurized fluid; the front set of discharge ports provided in said cylinder for discharging the front chamber into the set of longitudinal discharge channels; the rear set of discharge ports provided in said cylinder for discharging the rear chamber into the set of longitudinal discharge channels; a front set of recesses provided on said cylinder and being disposed longitudinally in series with respect to the longitudinal supply channels for connecting the pressurized fluid supply chamber with the front chamber in cooperation with the front outer sliding surface of the piston when the rear chamber supplied with pressurized fluid in each piston's reciprocating cycle; and a set of longitudinal sensing channels created in between the outer surface of the cylinder and the inner surface of the outer casing for intermittently connecting, in cooperation with the rear outer sliding surface of the piston and a probe carrier's pressure transmitting radial passageways-connecting port and one or more rear chamber-connecting ports in each sensing channel, the rear chamber with the pressurized volume for allowing the opening of the valve when the rear chamber must be supplied with pressurized fluid in each piston's reciprocating cycle, the sensing channels being disposed longitudinally in series with respect to the longitudinal discharge channels.

2. The pressurized fluid flow system of claim 1, wherein the set of longitudinal supply channels are disposed in the outer surface of the cylinder.

3. The pressurized fluid flow system of claim 1, wherein the set of longitudinal supply channels are disposed in the inner surface of the outer casing.

4. The pressurized fluid flow system of claim 1, wherein the set of longitudinal discharge channels are disposed in the outer surface of the cylinder.

5. The pressurized fluid flow system of claim 1, wherein the set of longitudinal discharge channels are disposed in the inner surface of the outer casing.

6. The pressurized fluid flow system of claim 1, wherein the set of sensing channels are disposed in the outer surface of the cylinder.

7. The pressurized fluid flow system of claim 1, wherein the set of sensing channels are disposed in the inner surface of the outer casing.

8. The pressurized fluid flow system of claim 1, wherein the front set of recesses are extended through all holes in the cylinder.

9. The pressurized fluid flow system of claim 1, wherein the front set of recesses are formed in the inner surface of the cylinder.

10. The pressurized fluid flow system of claim 1, wherein the front set of recesses are formed in the outer surface of the cylinder and comprises one or more pressurized fluid supply chamber-connecting ports and one or more front chamber-connecting ports that fluidly connect the recesses with the cylinder's inner surface.

11. The pressurized fluid flow system of claim 1, wherein the cylinder has a buffer undercut in its inner surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 depicts a longitudinal cross section view of the pressurized fluid flow system of the invention, specifically showing the disposition of the piston with respect to the outer casing, cylinder, valve and drill bit when the rear chamber is discharging pressurized fluid into the discharge channels.

(3) FIG. 2 depicts a second longitudinal cross section view of the pressurized fluid flow system of the invention, where this second longitudinal cross section view is perpendicular to the longitudinal cross section view shown in FIG. 1, specifically showing the disposition of the piston with respect to the outer casing, cylinder and drill bit when the front chamber is being supplied with pressurized fluid.

(4) FIG. 3 depicts a longitudinal cross section view of the pressurized fluid flow system of the invention, specifically showing the disposition of the piston with respect to the outer casing, cylinder, valve and drill bit when the rear chamber is being supplied with pressurized fluid and the front chamber is discharging pressurized into the discharge channels.

(5) FIG. 4 depicts an isometric view of the cylinder of the pressurized fluid flow system of the invention.

(6) FIG. 5 depicts a cross section view of the cylinder of FIG. 4 for a best understanding of the different features of this element.

(7) FIG. 6 depicts a cross section view of the cylinder of FIG. 4 wherein an undercut on its inner surface has been added as a buffer for the inward elastic deformation.

(8) FIG. 7 depicts the valve of the pressurized fluid flow system of the invention.

(9) FIG. 8 shows two graphs labeled A and B. These graphs represent the typical behavior of power and efficiency (power to mass flow rate of pressurized fluid ratio) of a percussive mechanism.

(10) In graph 8A, the power of the mechanism is plotted as a function of the front chamber's maximum feeding area for several level curves where each of these curves represents a different fixed rear chamber maximum feeding area. The x-axis labels and the level curves values are parametrized as multiples of a set value A.

(11) In graph 8B, the efficiency of the mechanism is plotted as a function of the front chamber maximum feeding area for several level curves where each of these curves represents a different fixed rear chamber maximum feeding area. The x-axis labels and the level curves values are parametrized as multiples of a set value A.

(12) The maximum feeding area is defined as the minimum fixed area (as opposed to variable areas originated by the porting transitions) in the whole path traveled by the fluid from the source of pressurized fluid to the respective chamber.

(13) FIG. 9 shows two graphs labeled A and B. These graphs represent the typical behavior of the mass flow rate into the front chamber and into the rear chamber, respectively, in one single piston's reciprocating cycle starting from the position in which the piston is in contact with the drill bit and ending in the same position.

(14) In graph 9A, the mass flow rate into the front chamber is plotted as a function of time for three different values of the fixed rear chamber maximum feeding area: (labeled Optimum), 2A (labeled Degraded) and A (labeled Very Degraded) when the front chamber maximum feeding area is equal in value to A.

(15) In graph 9B, the mass flow rate into the rear chamber is plotted as a function of time for three different values of the fixed rear chamber maximum feeding area: (labeled Optimum), 2A (labeled Degraded) and A (labeled Very Degraded) when the front chamber maximum feeding is equal in value to A.

(16) Again, the maximum feeding area is defined as the minimum fixed area (as opposed to variable areas originated by the porting transitions) in the whole path traveled by the fluid from the source of pressurized fluid to the respective chamber. The values 2A and A were chosen among the values A, 2A, 3A, 5A and 10A based on the performance shown by the different level curves in graphs 8A and 8B. For example, the power and efficiency values shown by the level curves with values 5A and 10A for the fixed rear chamber maximum feeding area differ marginally. In this case the value 5A can be considered Optimum because a value of 10A implies increase the cylinder's sectional area and reduce, consequently, the piston's thrust areas (reducing the power and efficiency levels). The front chamber maximum feeding area was set to a value of A this value shows an optimum or close to optimum performance in graphs 8A and 8B.

DETAILED DESCRIPTION OF THE INVENTION

(17) Referring to FIGS. 1 to 9, an exemplary embodiment of the pressurized fluid flow system for percussive mechanisms according to the invention is shown that comprises the following main components:

(18) a cylindrical outer casing (1) having a rear end and a front end;

(19) a driver sub (110) mounted to said front end of the outer casing (1);

(20) a rear sub (20) affixed to said rear end of the outer casing (1) for connecting the mechanism to the source of pressurized fluid;

(21) a piston (60) slidably and coaxially disposed inside said outer casing (1) and capable of reciprocating due to the changes in pressure of the pressurized fluid contained inside of a front chamber (240) and a rear chamber (230) located at opposites ends of the piston (60), the piston (60) having a rear thrust surface (62), a front thrust surface (63) and front and rear outer sliding surfaces (64, 67);

(22) a cylinder (40) that is coaxially disposed in between the outer casing (1) and the piston (60), the cylinder (40) having an inner (47) and an outer surface (48);

(23) a valve carrier (300) disposed rear of the rear chamber (230) and mounted on the inner surface (47) of the cylinder (40), the valve carrier (300) having a rear valve support surface (301) and the valve carrier's (300) frontmost external surface defining partially the rear limit of the rear chamber (230);

(24) a probe carrier (310) disposed rear of the valve carrier (300), the probe carrier (310) having a front valve support surface (311), one or more longitudinal fluid passageways (312), an inner valve sliding surface (313), one or more pressure transmitting radial passageways (315) and one or more fluid supply through holes (21);

(25) a valve (320) mounted in a space created between the valve carrier (300) and the probe carrier (310). The valve (320) able to slide longitudinally on the inner valve sliding surface (313) of the probe carrier (310) for moving between a front-located closed position and a rear-located open position. The valve (320) further having a front support surface (322), a rear support surface (323), a front thrust surface (324), a rear thrust surface (325) and a biasing thrust surface (326). The rear support surface (323) and the rear thrust surface (325) of the valve (320) creating together with the inner valve sliding surface (313) and the front valve support surface (311) of the probe carrier (310) a pressurized volume (314); and

(26) a drill bit (90) slidably mounted on the driver sub (110), wherein the sliding movement of the drill bit (90) is limited by a drill bit retainer (210) mounted on the driver sub (110);

(27) The rear chamber (230) of the percussive mechanism is defined by the valve carrier's (300) frontmost external surface, the valve (320), the cylinder (40) and the rear thrust surface (62) of the piston (60). The volume of the rear chamber (230) is variable depending on the piston's (60) position. The front chamber (240) of the hammer is defined by the drill bit (90), the cylinder (40), a drill bit guide (150) (which is an element that can be skipped) and the front thrust surface (63) of the piston (60). The volume of the front chamber (240) is also variable and depending also on the piston's (60) position.

(28) The piston (60) further comprises an annular recess (68) on its external surface that defines, in cooperation with the inner surface (47) of the cylinder (40), a pressurized fluid supply chamber (66). This pressurized fluid supply chamber (66) is respectively longitudinally limited at each end by the outer sliding surfaces (64, 67) of the piston (60).

(29) The cylinder (40) has a set of longitudinal supply channels (2) and a set of longitudinal discharge channels (3) defined by respective longitudinal recesses or grooves on its outer surface (48), the longitudinal supply (2) and discharge (3) channels being disposed around said outer surface (48) for in the first case conveying pressurized fluid from the rear sub (20) to the pressurized fluid supply chamber (66) and therefrom to the front (240) chamber and in the second case discharging the pressurized fluid from the front (240) and rear (230) chambers. When the percussive mechanism is operative, the longitudinal supply channels (2) are in permanent fluid communication with the source of pressurized fluid and they are filled with said fluid while the longitudinal discharge channels (3) are in permanent fluid communication with the outside of the percussive mechanism.

(30) The cylinder (40) further has one or more pressurized fluid intake ports (41) bored therethrough which connect the longitudinal supply channels (2) with the fluid supply through holes (21) in the probe carrier (310) and has front pressurized fluid exit ports (42) bored therethrough which fluidly and uninterruptedly communicate the set of longitudinal supply channels (2) of the cylinder with the pressurized fluid supply chamber (66), therefore permanently filling it with pressurized fluid. The cylinder (40) also has rear (43) and front (44) sets of discharge ports bored therethrough which allow the pressurized fluid to respectively flow from the rear chamber (230) and front chamber (240) into the set of longitudinal discharge channels (3).

(31) The cylinder (40) further has a front set of recesses (45) bored therethrough in its wall for allowing the pressurized fluid which flows from the rear sub (20) to the pressurized fluid supply chamber (66), through the set of longitudinal supply channels (2), to be diverted to the front (240) chamber in cooperation with the front outer sliding surface (64) of the piston (60). The front set (45) of recesses being disposed in series longitudinally with respect to the longitudinal supply channels (2) for reducing and making an optimal use of the cylinder's (40) sectional area.

(32) Moreover, the cylinder (40) also has a set of sensing channels (330) defined by respective longitudinal recesses on its outer surface (48), wherein the sensing channels (330) are disposed in series longitudinally with respect to the longitudinal discharge channels (3) for reducing and making an even more optimal use of the cylinder's (40) sectional area.

(33) In this regard, each of the sensing channels (330) has a probe carrier's (310) pressure transmitting radial passageways (315)-connecting port (331) and one or more rear chamber-connecting ports (332), see FIG. 6, where at least one of the rear chamber-connecting ports (332) is not plugged with plugs (334), to transmit the pressure inside the rear chamber (230) to the pressurized volume (314) through the pressure transmitting radial passageways (315) of the probe carrier (310) when the rear chamber-connecting ports (332) are not covered by the rear outer sliding surface (67) of the piston (60).

Control of the State of the Front Chamber (240)

(34) When in the hammer cycle the impact face (61) of the piston (60), which is part of the front thrust surface (63), is in contact with the impact face (91) of the drill bit (90) and the drill bit (90) is at the rearmost point of its stroke, i.e. the hammer is at impact position (see FIG. 2), the front chamber (240) is in direct fluid communication with the pressurized fluid supply chamber (66) through the front set of recesses (45) of the cylinder (40). In this way, the pressurized fluid is able to freely flow from the pressurized fluid supply chamber (66) to the front chamber (240) and start the movement of the piston (60) in the rearward direction.

(35) This flow of pressurized fluid to the front chamber (240) will stop when the piston (60) has traveled in the front end to rear end direction of its stroke until the point where the front outer supply edge (73) of piston (60) reaches the rear limit of the front set of recesses (45) of the cylinder (40). As the movement of the piston (60) continues further in the front end to rear end direction of its stroke, a point will be reached where the front outer discharge edge (72) of the piston (60) reaches the front limit of the front discharge ports (44) of the cylinder (40). As the movement of the piston (60) continues even further, the front chamber (240) of the hammer will become fluidly communicated with the set of longitudinal discharge channels (3) through the front set of discharge ports (44) of the cylinder (40) (see FIG. 3). In this way, the pressurized fluid contained inside the front chamber (240) will be discharged into the set of longitudinal discharge channels (3) and from the set of longitudinal discharge channels (3) it is able to freely flow out of the percussive mechanism.

(36) Normally, the drill bit (90) is aligned to the outer casing (1) of the hammer by the drill bit guide (150). However, the invention is not limited to the use of a drill bit guide (150) and alternative alignment solutions may be used or skipped. Also, the final flow path from the set of longitudinal discharge channels (3) out of the mechanism will depend on the application of the percussive mechanism: pave breakers, down-the-hole hammers (normal circulation or reverse circulation), rotary percussion drilling systems, etc. In the embodiments described in FIGS. 1, 2 and 3 the flow of fluid is channeled out of the mechanism through ports (4) in the outer casing (1) as would occur in a pave breaker.

Control of the State of the Rear Chamber (230)

(37) When in the hammer cycle the impact face (61) of the piston (60), which is part of the front thrust surface (63), is in contact with the impact face (91) of the drill bit (90) and the drill bit (90) is at the rearmost point of its stroke, i.e. the hammer is at impact position, the valve (320) is in its closed position (see FIG. 1 and FIG. 2) and the rear chamber (230) is in direct fluid communication with the set of longitudinal discharge channels (3) through the rear set of discharge ports (43) of the cylinder (40). In this way, the pressurized fluid contained inside the rear chamber (230) will be discharged into the set of longitudinal discharge channels (3) and from the set of longitudinal discharge channels (3) it is able to freely flow out of the percussive mechanism. Again, the final flow path from the set of longitudinal discharge channels (3) out of the mechanism will depend on the application of the percussive mechanism.

(38) This flow of pressurized fluid will stop when the piston (60) has traveled in the front end to rear end direction of its stroke (see FIG. 3) until the point where the rear outer discharge edge (70) of piston (60) reaches the rear limit of the rear set of discharge ports (43) of the cylinder (40). Beyond this point, pressure will start building-up inside the rear chamber (230) due to compression in a close to isentropic like process.

(39) As the movement of the piston (60) continues further in the front end to rear end direction of its stroke, a point will be reached where the rear outer discharge edge (70) of the piston (60) reaches the rear limit of the rearmost ports (332) that are not plugged with plugs (334). At this point, the sensing channels (330) and the pressurized volume (314) will become isolated from the rear chamber (230) by the rear outer sliding surface (67) of the piston (60) and become pressurized at the pressure level existing in the rear chamber (230) at that point of the piston's reciprocating cycle. As the movement of the piston (60) continues even further, pressure will continue building-up inside the rear chamber (230) due to the compression process until the pressure inside the rear chamber (230) is high enough to cause the valve (320) opening (FIG. 3 shows the valve in its open position). In this way, the rear chamber (230) will be supplied with fluid coming directly from the source of pressurized fluid through the longitudinal fluid passageways (312) of the probe carrier (310).

(40) The high pressure of the pressurized fluid acting on the rear thrust surface (62) of the piston (60) will drive it frontward. As the movement of the piston (60) continues in the rear end to front end direction of its stroke, again a point will be reached where the rear outer discharge edge (70) of piston (60) reaches the rear limit of the rearmost ports (332) that are not plugged with plugs (334). At this point, the sensing channels (330) and the pressurized volume (314) will become again in fluid communication with the rear chamber (230) and become pressurized at the higher pressure level existing in the rear chamber (230) at that point of the piston's reciprocating cycle causing the valve (320) closing due to the force acting on its rear thrust surface (325).

Valve Operation

(41) When the valve (320) is closed (see FIG. 1 and FIG. 2, see also FIG. 7 to identify all the valve's surfaces), the pressure acting on the biasing thrust area (326) is equal to the stagnation pressure (this is a well stablished concept in thermodynamics and fluid mechanics as well) of the fluid coming from the source of pressurized fluid through the longitudinal fluid passageways (312) of the probe carrier (310). The force exerted on the biasing thrust area (326) is added to the forces exerted on the rear support surface (323) and the rear thrust surface (325) due to the pressure that exists inside the pressurized volume (314) and all these forces act in the rear end to front end direction. Simultaneously, the only forces that act in the front end to rear end direction (without considering the friction, which are negligible, and reaction forces) are the forces due to the pressure inside the rear chamber (230) acting on the front thrust surface (324) and on the partially exposed front support surface (322).

(42) In a similar fashion, when the valve (320) is open, the pressure acting on the biasing thrust area (326) is equal to the stagnation pressure of the fluid coming from the source of pressurized fluid through the longitudinal fluid passageways (312) of the probe carrier (310). The force exerted on the biasing thrust area (326) is added to the force exerted on the rear thrust surface (325) due to the pressure that exists inside the pressurized volume (314) and both forces act in the rear end to front end direction. Simultaneously, the only forces that act in the front end to rear end direction are the forces due to the pressure inside the rear chamber (230) acting on the front thrust surface (324) and on the front support surface (322), this late being fully exposed to the rear chamber (230) when the valve (320) is open. Reaction forces should not be considered in the calculations of the valve's (320) areas (322, 323, 324, 325, 326) which ultimately determine the close-open and open-close states transitions.

(43) In situations where increase the efficiency is also important, which means improve the percussive mechanism power to pressurized fluid consumption ratio, or the flow rate coming from the source of pressurized fluid is limited, a retarded opening of the valve (320) can be accomplished unplugging ports (332) closer to the rear end of the mechanism.

Design Considerations

(44) The embodiment of the percussive mechanism described previously and depicted in FIGS. 1 to 7 is only one of many obvious variations that can be envisioned, including for example longitudinal passageways equivalent to the sensing channels (330) but on the inner surface (or even in the wall) of the outer casing (1). Likewise, channels (2,3) are described as longitudinal because the fluid flow through them is mainly longitudinal (in the mechanism axis direction), but they can have a helical shape.

(45) Similarly, recesses (45) are showed in the embodiment as through all holes letting the inner surface of the outer casing (1) act as the sealing bottom of the channels or passages that they create. It is obvious that different approaches can be used to create these channels, including but not limited to recesses on the inner surface (47) of the cylinder (40) or recesses on the outer surface (48) of the cylinder (40) together with ports at the recesses' ends to communicate them with the cylinder's (40) inner surface (47).

(46) In a similar fashion, the probe carrier (310) and the valve carrier (300) don't need to be separated parts and can be built in in the rear sub (20) and in the cylinder (or sleeve) respectively. These kinds of changes must be considered obvious.

(47) It will be appreciated by those skilled in the art that other changes, besides the ones mentioned above, could be made to the embodiment described without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention.

(48) In the figures, the probe carrier (310) has a surficial undercut to avoid the need of angular alignment with respect to the cylinder (40). Because this is an obvious design solution, that undercut is not considered a critical feature of the invention and it is not numbered.

(49) In a different matter, observing FIG. 8A and 8B, several conclusions can be drawn:

(50) The mechanism generates maximum power at a low value of the front chamber (240) maximum feeding area (in between ? A and A). A similar behavior can be observed for efficiency.

(51) The mechanism generates higher power for higher values of the rear chamber maximum feeding area, but the effect in power of a fixed percentual increment decreases with the base value of the rear chamber maximum feeding area. A similar behavior can be observed for efficiency.

(52) Optimum values of power and efficiency are achieved for values of the rear chamber's (230) maximum feeding area several times higher (five to twenty) than the values of the front chamber's (240) maximum feeding area.

(53) The last point reveals another advantage of not supply the rear chamber (230) with pressurized fluid through the cylinder (40). Because in the present invention only the front chamber (240) is supplied, through recesses (45), with pressurized fluid coming from the longitudinal supply channels (2) and the pressurized fluid supply chamber (66), making possible a design where the recesses (45) are disposed in series longitudinally with respect to the longitudinal supply channels (2), the cylinder (40) can have a very reduced sectional area because the longitudinal supply channels (2) and recesses (45) don't need to have a high sectional area, allowing it be even more compact and allowing increase the piston (60) thrust areas even further.

(54) In a similar fashion, observing FIG. 9A and 9B, several conclusions can also be drawn:

(55) The main effect of a reduction in the size of the rear chamber's (230) maximum feeding area is a degraded filling process of this chamber when the feeding of the rear chamber (230) with pressurized fluid starts during the rearward stroke. Also, the filling process slows down during the frontward stroke (after the reflow, which is identifiable by negative mass flow rate values), but at a less extent.

(56) The filling process of the front chamber (240) stays almost unchanged despite a small increment in the piston's (60) reciprocating cycle period.

(57) Finally, the elastic inward deformation of the cylinder (40) observed empirically in the realization of the pressurized fluid flow system described in U.S. Pat. No. 10,316,586 due to the permanent high pressure fluid acting on the thin bottom of the longitudinal supply channels (2) (main feed fluid passages (28) in U.S. Pat. No. 11,174,679) occurs precisely on the bottom of the longitudinal supply channels (2) between the rear discharge ports (43) and the front pressurized fluid exit ports (42) (in the longitudinal direction or the mechanism's axis direction). FIG. 6 shows a buffer undercut (49) that acts as a buffer for keeping the deformation far from the sliding surfaces (64,67) of the piston (60). This solution can be used to keep a thin bottom of the longitudinal supply channels (2) and make the cylinder (40) even thinner, considering that in practice this undercut should have only a few tenth of millimeters in depth. Should also be noted that this solution can't be used in the fluid flow systems described in U.S. Pat. No. 10,316,586 and U.S. Pat. No. 11,174,679 because it would create cross flows through the inner surface (47) of the cylinder (40).