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DESCRIPTION

The present invention concerns a hydraulic pressure multiplication process. The invention is particularly suitable for increasing the pressure of the oil or other fluid and has been made with particular reference to oil-hydraulic applications, even if this does not rule out any type of hydraulic fluid used or any type of application. The invention also concerns a hydraulic pressure multiplication device and a pressure multiplication hydraulic circuit comprising such a device .

In the field of oil-hydraulics it is often necessary to have high pressures of the hydraulic oil intended to feed actuator devices or motors of high power. Some examples, given for non-limiting purposes, are applications for the parts of earth-moving machines, agricultural machines, lifting machines, etc..

In these fields the hydraulic oil must often have a continuous pressure, i.e. it should not have undesired reductions or interruptions. Moreover, the pressure of the oil should be easy to adjust, always without undesired reductions or interruptions.

However, this is not easy to obtain, and often high power hydraulic pumps are used to have high pressures, but they have a high cost and consumption.

Alternatively, systems are used that comprise lower power pumps to generate oil at a first predetermined pressure, where such oil enters into continuous pressure multipliers that bring it to the desired value.

However, current multipliers do not have the ability to make the oil perform a very high pressure jump .

A general purpose of the present invention is therefore to entirely or partially solve the problems of the prior art by fulfilling the requirement indicated above .

In particular, a purpose of the present invention is to obtain a high pressure multiplication.

A further purpose of the present invention is to obtain a continuous multiplied pressure.

A further preferred purpose of the present invention is to cool the hydraulic fluid used in the pressure multiplication.

Another further purpose of the present invention is to provide a hydraulic circuit with a scheme that is simple, easy to make, low-cost and highly efficient. According to a first aspect thereof the invention concerns a hydraulic pressure multiplication process, characterised in that it comprises the following steps:

- generating a first continuous hydraulic pressure;

- using the first continuous hydraulic pressure to generate a plurality of periodic hydraulic pressures of higher value than the continuous pressure;

- combining the periodic hydraulic pressures to generate a second continuous hydraulic pressure of greater value than the first continuous hydraulic pressure .

Advantageously, through the concept of decomposition and recomposition of the pressure, it is possible to obtain substantially higher continuous pressures with respect to the starting continuous pressures .

According to some particularly preferred embodiments the process comprises the following steps:

- bringing a hydraulic fluid to the first continuous hydraulic pressure;

- using the fluid at said first pressure to exert alternate linear thrusts on first predetermined areas of first slider means;

- transferring the alternate linear thrusts to second slider means; - exerting alternate linear thrusts on a hydraulic fluid with predetermined areas of the second slider means smaller than the first predetermined areas to obtain alternate pressures of greater value than the first continuous pressure;

- combining the alternate pressures to obtain hydraulic fluid at the second continuous pressure.

Advantageously, through the linear thrusts it is possible to obtain a high pressure multiplication and the multiplied pressures, i.e. the second continuous pressures can be easily adjusted by simply adjusting the first continuous pressure.

The predetermined areas are for example given by the thrusting surfaces of pistons, dependent on the bores, like those of the examples described hereinafter.

According to a second general aspect thereof the invention concerns a hydraulic pressure multiplication device comprising at least one driving hydraulic cylinder and at least one hydraulic cylinder guided by the driving hydraulic cylinder, where the driving cylinder has a greater bore than the guided cylinder.

In this way advantageously it is possible to actuate a linear thrust capable of generating a high pressure multiplication.

Preferably, the greater bore is double the smaller bore. According to some preferred embodiments of the invention the driving cylinder is double-acting and the guided cylinder is also double-acting, or the driving cylinder is double-acting and actuates at least two single-acting guided cylinders both of smaller bore than the driving cylinder.

In this way it is possible to use a low value continuous pressure to feed the driving cylinder, to generate periodic pressures of much higher value and combine them to obtain a new multiplied continuous pressure. Since the double-acting cylinders can operate continuously, there are no interruptions of the continuous multiplied pressure.

Preferably, the driving cylinder and the guided cylinder are coaxial for the sake of simplicity and cost- effectiveness of construction.

According to a preferred general characteristic, the driving cylinder comprises at least one guide piston connected to at least one guided piston of the at least one guided cylinder through a stem, so as to form a single slider.

According to a third aspect thereof the invention comprises a pressure multiplication hydraulic circuit comprising at least one pressure multiplication device of the type indicated above, at least one continuous pressure generator, at least one tank of hydraulic fluid, at least one hydraulic user, and a plurality of hydraulic connection lines between them.

Preferably, the at least one driving cylinder is double acting and the circuit comprises a hydraulic distributor connected to the at least one driving cylinder to alternately feed its chambers with the hydraulic fluid at the continuous pressure generated by the generator, the driving cylinder moves at least one double-acting guided cylinder or at least two single- acting guided cylinders, where in inlet and outlet from the active chambers of such guided cylinders valves are arranged to allow or deny the flow of fluid to at least two hydraulic connection lines intended to contain fluid at periodic pressures, the two lines being joined in the user or before it to generate an area intended to contain fluid at continuous pressure, multiplied with respect to the pressure of the generator.

According to some simpler and more cost-effective embodiments the driving cylinder and the guided cylinder, or the guided cylinders each comprise at least one opening in connection with the tank of fluid.

According to a fourth aspect thereof, the invention concerns a pressure multiplication hydraulic circuit comprising at least one hydraulic pressure multiplication device comprising at least one hydraulic drive cylinder and at least one hydraulic cylinder guided by the hydraulic drive cylinder, where the drive cylinder has a larger bore than the guided cylinder,

the drive cylinder is double acting and the guided cylinder is also double acting, or the double acting drive cylinder actuates at least two single acting guided cylinders both of smaller bore than the drive cylinder .

The hydraulic circuit comprising at least one tank of hydraulic fluid, connected simultaneously to all of the chambers of said cylinders to send hydraulic fluid to those that are in a suction step and to receive the fluid from those that are in a discharge step, where the circuit comprises a cooling device of said hydraulic fluid .

Advantageously, the circuit system is particularly simple and referring to one same tank for all of the cylinders manages to effectively cool the oil used in the pressure multiplication.

Preferably, said chambers are connected to a single hydraulic connection line that leaves from and goes back to said tank and along which said cooling device is arranged.

In this case, preferably, the chambers of the cylinder of larger bore are connected to said hydraulic line through a four-way slide valve. This allows the circuit to remain with a simplified scheme by dividing the connection line into a high pressure part and into a part at another pressure suitable for feeding the chambers of the cylinder of larger bore in an active step and in a low pressure part suitable for receiving the hydraulic fluid from the chambers of the cylinder of larger bore and of the cylinders of smaller bore in the discharge steps.

According to some preferred embodiments of the invention the slide valve divides said connection line into a part at a first pressure between the tank and the slide valve and into a part at a second pressure between the slide valve and the tank, where the first pressure is greater than the second and where the cooling device is connected to the part at the lower pressure. Basically therefore the slide valve allows the existence of a very simple circuit where the cooling is arranged in a low pressure area suitable for its operation.

Preferably, the cylinder (s) with smaller bore is/are connected in suction to the part at lower pressure.

Even more preferably, the cylinder (s) with smaller bore is/are connected in discharge to a second hydraulic connection line that gives hydraulic fluid to at least one load.

In this case, preferably, the load discharges the hydraulic fluid received by the cylinder (s) of smaller bore in said tank, so that by going in a circle it has the possibility of being cooled by the cooling device.

In addition or alternatively, it is possible to foresee a connection between the discharge of the load and the hydraulic connection line along which said cooling device (76) is arranged, where the connection is arranged downstream of the slide valve.

In this case it is preferable for the connection to be upstream of the cooling device, so that the fluid coming from the load is immediately cooled.

According to a preferred general characteristic the circuit comprises at least one continuous pressure generator arranged between said tank and the four-way slide valve.

Further characteristics and advantages of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings and given for indicating and not limiting purposes. In such drawings :

- figure 1 schematically shows an oil-hydraulic pressure multiplication device according to the present invention in longitudinal section;

- figure 2 shows an alternative embodiment to the device of figure 1; - figure 3 schematically shows a pressure multiplication hydraulic circuit comprising the device of figure 1, and

- figures 4a to 4d show the progression over time of the hydraulic pressures in the circuit of figure 3.

With reference to figure 1 the oil-hydraulic pressure multiplication device is wholly indicated with reference numeral 1 and comprises:

- a double-acting primary cylinder 10, in which a piston 15 slides, called driving piston,

- two secondary cylinders 20 and 30, in which a second piston 25 and a third piston 35 respectively slide, moved by the primary piston, and for this reason also called guided pistons.

The multiplier device 1 has a longitudinal axis X coinciding with the stroke direction of all three pistons 15, 25 and 35. For example, the secondary cylinders are arranged at opposite axial ends of the primary. In particular in the illustrated embodiment the driving piston 15 is connected to the middle of a stem 16 at the distal ends of which the guided pistons 25 and 35 are arranged. Preferably, the three cylinders are coaxial.

In general, the bore of the primary cylinder 10 is greater than the bores of the secondary cylinders 20 and 30, for which reason the first is also called larger cylinder and the second are called smaller cylinders. Figure 1 shows the particularly preferred case in which the bores of the smaller cylinders 25 and 35 are the same, where a particularly preferred bore value for each of them is half the bore of the larger cylinder 15.

The driving piston 15 divides the primary cylinder 10 into two chambers 11 and 12, both equipped with at least one distal opening 13, 14 for the entry and/or exit of the hydraulic oil. Preferably, there is at least one opening 13, 14 per chamber that acts both as entry and as exit, as indicated in the example of figure 1, but this does not rule out the possibility of there being many openings with differentiated entry and exit functions .

The guided pistons 25 and 35 divide the relative cylinders into a distal chamber 21, 31 with respect to the primary cylinder and a proximal chamber 22, 32. Only the distal chambers are equipped with at least one distal opening 23, 24, 33, 34 for the entry and/or exit of the hydraulic oil. Preferably there are at least one inlet opening 23, 33 and at least one outlet opening 24, 34 that are distinct, as indicated in the example of figure 1, but this does not rule out the possibility of there being a single opening with double inlet and outlet function.

In use, hydraulic oil at a first pressure is sent alternatively in one or the other chamber of the primary cylinder 10 so that the driving piston 15 is moved to exert a thrust alternately in the two stroke directions according to the axis X. When the driving piston 15 slides in a first direction it pushes one of the two guided pistons 25, 35 in the direction of the relative distal end stop and pulls the other in the direction of the relative proximal end stop. The consequence is that the guided piston 25, 35 pushed in the distal direction exerts a pressure on the oil contained in the distal chamber 21, 32 of its cylinder, with relative expulsion from it at multiplied pressure with respect to the first pressure. The expulsion takes place through the relative opening 24, 34. In the distal chamber 21, 32 of the other guided piston 25, 35 hydraulic oil is sucked, generally at a lower pressure than the first pressure. The suction takes place through the relative opening 23, 24, 33, 34.

When the driving piston 15 has reached the end stop it reverses its motion and the operation of the two guided pistons reverses, so that the one that previously was sucking now pushes and the one that was pushing now sucks .

According to a practical example, hypothesising as an example that the oil at the first pressure enters into the chamber 11, the piston 35 compresses the oil in the chamber 32 and pushes it in expulsion from the relative outlet 34, whereas the piston 25 sucks oil into the chamber 21 from the relative opening 23. At the end stop of the piston 15, the pressurised oil starts to enter into the chamber 12 and pushes the piston 15 in the opposite direction to the previous one. The oil in the chamber 11 is thus expelled, but particularly the piston 25 compresses the oil in the chamber 21 while the piston 35 sucks it in the chamber 32. The chambers 22 and 31 are in this example inactive, in the sense that they neither suck nor compress oil.

Although up to now an embodiment has been described in which the double-acting primary cylinder guides two single-acting secondary cylinders with aligned strokes arranged at the opposite axial ends thereof, this is not the only possible configuration. For example, it is possible to replace the two secondary cylinders with a single double-acting cylinder of smaller bore than the primary, or it is possible to arrange the secondary cylinders all on the same side of the primary, coaxial or with parallel axes. More generally, any arrangement of the secondary cylinders, provided that they are guided by the primary, is possible. It is even possible for the double-acting driving cylinder to be replaced by two single-acting cylinders, each of which guides one of the two secondary ones, although this is a less preferred solution, since the return of these cylinders does not exploit an oil-hydraulic principle and thus less guarantees the quick inversion of motion and therefore the continuity of the multiplied final pressure.

Figure 2 illustrates a multiplier device 101 according to an alternative embodiment to that of figure 1 that is more compact, where elements that are the same as or similar to the previous ones are indicated with the same reference numeral increased by 100. Here there is only one secondary cylinder 130 arranged on a side of the primary cylinder 110. Also in this case the secondary cylinder is double-acting, i.e. both of its chambers 131 and 132 are active, both having the possibility of expelling and sucking oil through relative openings (in the previous example the two cylinders 20 and 30 was single-acting) . In the example an inlet opening 133 and an outlet opening 134 of the oil are shown for each chamber .

When the primary cylinder 110 has oil at a first pressure that enters from the opening 113 into the chamber 111, it pushes the piston 115 towards the secondary cylinder 130 in this way guiding the piston 135 of smaller bore to compress the oil in the chamber 132 and to expel it from the relative opening 134 at a greater pressure than the first pressure. At the same time, the chamber 131 sucks oil from the relative opening 133 at a lower pressure than the chamber 132.

When the piston 115 is at the end stop the oil at the first pressure starts to enter into the chamber 112 from the opening 114 reversing the thrusting direction of the piston. Consequently, the pressurised chamber of the secondary cylinder 130 becomes 131 and the sucking chamber becomes 132.

With reference to figure 3 an example of hydraulic circuit comprising the device 1 of figure 1 is now described and illustrated.

The circuit is wholly indicated with reference numeral 50 and comprises:

- a device 1;

- a continuous hydraulic pressure generator group 55

- a hydraulic user 60 (for example an actuator or a hydraulic motor intended to be moved by the oil at multiplied pressure by the device 1;

- various hydraulic connection ducts between the part and valves as explained better hereinafter;

- a tank of hydraulic oil 65.

The inlet and outlet openings 13 and 14 of the chambers 11 and 12 of the double-acting primary cylinder 10 are alternatively operatively connected to the pressure generator group 55 and to the oil tank 65 through a hydraulic distributor 70. In general, the hydraulic distributor 70 is capable of simultaneously placing a chamber of the primary cylinder in communication with the pressure generator 55 and the other with the tank 65, so that the pressurised oil moves the piston 15 in a first direction. When it has reached the end stop, the hydraulic distributor 70 controls the inversion of the connections of the two chambers, for which reason the one that had previously been connected with the pressure generator 55 is now connected to the tank 65 and the one that was connected to the tank 65 is now connected to the generator 55.

The hydraulic distributor 70 in general is preferably of the type controlled automatically by the pressure of the oil in the chambers of the primary cylinder 10, like for example a distributor 70 of the four-way drawer type indicated in the figures with the letters T P A B. The connection is such that in a first configuration it respectively places P in communication with B allowing oil to flow at a first pressure from the generator group 55 to the chamber 12, and T in communication with A allowing oil to flow at low pressure from the chamber 11 to the tank 65. When the piston 15 is at the end stop the pressure increase automatically reconfigures the distributor 70 so that P is in communication with A allowing oil to flow at the first high pressure in the chamber 11, and T is in communication with B allowing oil to flow at low pressure from the chamber 12 to the tank 65.

In order to do this there is a first part of connection line 72 (which is at high pressure) from the generator group 55 to the inlet P to the hydraulic distributor 70, and a second part of connection line 74 (which is at low pressure) from the outlet T from the hydraulic distributor 70 to the tank 65.

In general, it should be observed that the parts 72 and 74 are therefore parts of a single hydraulic connection line that starts from the tank 65 and goes back to it feeding the chambers 11, 12, 21, 22, 31, 32 that are in active (suction) step and receiving oil from those that are inactive (discharge) . The four-way slide valve allows the existence of such a single connection line since it divides it into the high and low pressure parts, and allows such a connection line to be connected to a cooling device of the oil 76, which as illustrated hereinafter is preferably connected to the low pressure part 74.

Going back to the detailed description, it should be observed that in the illustrated example unidirectional valves associated with the openings 13 and 14 are not necessary, so that as seen they are advantageously exploited both as inlets and outlets of the oil from the primary cylinder 10.

It should be observed that the generator group 55 preferably takes the oil from the tank 65.

It is possible to foresee a cooling device 76, like for example a heat exchanger 76, for example arranged along the line 74.

Now moving on to describe the hydraulic connections of the secondary cylinders 20 and 30, it should be observed that each of the outlet openings 24 and 34 are connected to the hydraulic user 60 through a part of oil line 80, 82 at the multiplied pressure. Preferably, the lines 80 and 82 join together in a part of line 84 that carries the oil to the user 60. The user 60 can also discharge the oil in a tank, preferably the tank 65, through a part of discharge line.

The parts 80, 82, 84, 89 are part of a line for conveying oil at the multiplied pressure from the cylinders of smaller bore to the load and from there to the tank 60.

According to a variant, the part 89 could be connected, instead of directly to the tank, to the line 74, more preferably upstream of the cooling device 76. In this way, the oil coming from the load can be immediately cooled and/or there can be a single final part of hydraulic connection line that gives all of the oil to the tank.

Each outlet opening 24 and 34 is associated with a unidirectional valve 86, 88 that allows the oil to flow towards the user 60 and prevents flow in the opposite direction .

Each of the inlet openings 23 and 33 are connected to a low pressure oil line to suck oil from a tank, in the illustrated example they are connected to the line 74 to suck from the tank 65.

Each inlet opening 23 and 33 is associated with a unidirectional valve 90, 92 that allows the oil to flow towards the respective chambers 21 and 32 inside the cylinders 20 and 30 and prevents flow in the opposite direction.

With the configuration just described a single oil tank 65 is advantageously sufficient to serve/receive from all of the cylinders.

In use, when the primary cylinder 10 is controlled in the thrusting direction of the cylinder 30, the unidirectional valve 88 opens and allows the oil to flow in multiplied pressure from the cylinder 30 to the user 60. At the same time, the unidirectional valve 92 is closed. As far as the other secondary cylinder 20 is concerned, its unidirectional valve 86 is closed, preventing oil from coming out, whereas the valve 90 is open, allowing low pressure oil to be sucked from the tank 65. When the primary piston 15 reverses the direction of motion, the previously closed unidirectional valves open and those that were previously open close so that it is the cylinder 30 that sucks and the cylinder 20 that thrusts .

The two pistons 20 and 30 therefore exert a thrust of the oil in an alternate manner, where the alternate pressure combine in a single continuous pressure in the line 84, so that the user 60 is fed with oil at multiplied pressure continuously. The synchronisation of combination is generated by the fact that the hydraulic distributor is controlled hydraulically to automatically reverse the motion of the pistons at each end stop. However, this does not rule out the possibility of other types of hydraulic distributors, like for example distributors controlled electronically based on pressure sensors.

The adjustment of the pressure value does not alter the continuity of pressure at the user, since it depends on the pressure exerted with the generator group 55 and does not alter the operation just described.

As far as an example of possible performance is concerned, it should be observed that in the case in which the bore of the piston 15 is double the bore of the pistons 25 and 35, faced with a pressure in inlet to the cylinder 10 of 100 bar, a multiplied pressure in outlet from the secondary cylinders 20 and 30 of 400 bar was recorded .

The graph 4a shows an example of progression over time of the continuous pressure generated by the generator group 55 and in inlet to the cylinder 10.

The graph 4b shows for example a progression over time of the alternate multiplied pressure in outlet from the cylinder 20 and the graph 4c shows an example of progression over time of the alternate multiplied pressure in outlet from the cylinder 30.

The graph 4d shows the continuous multiplied pressure in the line 84 in inlet to the user 60 and that is obtained by combining the alternate pressures of the cylinders 20 and 30.

These graphs therefore generally show the multiplication concept starting with a first continuous pressure, multiplying it in the form of periodic pressures through alternate thrusting sliders, like for example the pistons of the various cylinders described, and combining the multiplied periodic pressures to obtain a constant multiplied pressure.

In general, it should be observed that in the present document the definitions of "distal" and "proximal" position are given taking the centre of the primary cylinder 10, 110 as reference. Of course, the embodiments and the variants described and illustrated up to now are purely examples and those skilled in the art can bring numerous modifications and variants, in order to satisfy specific and contingent requirements, including for example the combination of said embodiments and variants, all of which are in any case covered by the scope of protection of the present invention as defined by the following claims .