Applicant: Eutecna

Technical field

The present invention relates to a new percussion oleodynamic machine comprising an on-off hydraulic or slide valve, a pilot piston and a primary hitting tool, that transforms mechanical energy into impact energy.

Conventional percussion oleodynamic machines comprise a housing with a cylinder therein, in which a reciprocating hitting piston repeatedly impact on a demolisher tool. The demolisher tool transfers the impact energy to the material to be crashed. The piston motion is given by a hydraulic circuit, connected to the high- and low-pressure circuits, which sequentially feed the drive chambers of the hitting tool, giving to said piston a uniformly accelerating motion up to the impact on the tool. As a consequence of the immediate deceleration, the impacting piston transmits a compression wave that propagates from the impact area to the material at sound speed. After the impact, reflected wave combines with the compression wave reducing its speed and as a consequence its impact content. This energy transmission model implies a poor impact efficiency and the

dissipated mechanical energy reduces the reliability of the percussion oleodynamic machine and its performances.

Disclosure of the invention The invention solves these technical problems being a new oleodynamic percussive machine characterized by a telescopic pilot piston, which interacts with a small on-off slide valve and controls the distribution timing of the machine hydraulic charge and discharge. Said pilot piston is telescopically inserted in the primary hitting tool, from which it receives the consent signal for the oleodynamic positioning. Said signal acts as a set-point for the opening/closing time of the inlet and outlet ports of the hydraulic circuits of the slide valve. The pilot piston telescopic motion is obtained by injecting a certain amount of the pressurized oil coming from the braking chamber. The amount of the pressurized oil depends on the tool penetration in the material; therefore, controlling the rising stroke of the two hitting tooles, the timing and, consequently, the active displacement. Both pilot piston and primary hitting tool have different mass and inertia, different speed (during both rising and descending) and are never in contact, being separated by a pressurized oil control volume. These features imply that the impact of the primary hitting tool occurs in a rapid sequence:

a) transfer of the impact energy of the initial wave, generated by the first impact of the hitting tool on the demolisher tool; b) before this phase ends and before the expansion wave propagation (related to the bounce) starts, the pilot piston impacts on a hydraulic control volume, having said second impact the same direction of the previous one. This second impact interacts with the return impact wave, thus preventing the expansion phase of the primary mass (having opposite verse) and instantaneously smoothing the cyclic oscillation. The result is the optimization of the impact energy transfer on the tool, due to the absence of oscillatory phenomena and the control of pilot piston axial position.

The energy saving is noteworthy because of the optimization of the active displacement, the work sequence and the volumetric efficiency. The latter increases due to the reduction of the oil consumption by the slide valve, which is small and has a short stroke. The mechanical efficiency also increases, due to the improved energy transfer of the sequential impact. According to another aim of the present invention, the technical solutions used by the percussion machine also reduce the acoustic pollution. Infact, the invention is characterized by a reduced acoustic power, radiated at low-middle frequencies. These and other advantages will be pointed out in the detailed description of the invention that will refer to the figures of the

tables 1/7, 2/7, 3/7, 4/7, 5/7, 6/7, 7/7 in which some preferred embodiments will be disclosed. All of them are examplifying and not restrictive. In particular: • Fig. 1 shows the percussion oleodynamic machine according to the invention;

• Figs 2, 3 and 4 represent the same machine in different working positions;

• Figs. 5, 6, 7 and 8 show some design modifications to realize economic models or components.

Way of carrying out the invention

With reference to Fig. 1, the oleodynamic percussion machine comprises a high pressure oil-nytrogen source (2), a casing (1) accommodating a primary hitting tool (3) with its pushing chambers (12, 5), a pilot piston (4) with its pushing chambers (5, 23) and a demolisher tool (10). According to the invention, the machine comprises an on-off slide valve (7), with inlet (9) and outlet (8) chambers, a service circuit (14) and the high pressure feeding circuits (11, 26) of the two hitting tools (3, 4). The machine also comprises low pressure discharge circuits (25, 27), connected to the chambers (8, 13) and to the exit collector (18), by means of a low-pressure control throttle (100). Lastly, the machine includes the control volume (15) of the primary hitting

tool, the volume (19), the circuits (20, 21) and the volume (22), with different pushing areas: they provide the supplementary translation of the pilot piston (4), controlled by the pilot throttle (16) of the differential stroke (28). The opening and closing of the on-off slide valve (7) is given by the service circuit (14), the volume (32) and the low pressure control throttle (100). The pressurization of the pushing volume (23) and the feeding circuit (29) is provided by the chamber (6) and the start throttle (24). Referring to the same Fig. 1, the working procedure of the percussion oleodynamic machine will be described.

First phase, descending motion. As the chambers (12, 19) are at high pressure, the primary hitting tool (3) is at the top dead center, in contact with the pilot piston (4) and the on-off slide valve (7). The same pressure is present in the chamber (9) as in (8), connected by the control throttle (100), while the moving parts (7) and (4), each other in contact, assure the hydraulic sealing of the chamber (23). The incompressible process fluid, coming from the high-pressure feeding circuit (11), pressurizes the oil-gas source (2) up to the maximum pressure level, feeding the high-pressure chamber (6). The high-pressure oil from the start throttle 24 immediately pressurizes the pushing chamber (23), allowing the pilot piston (4) to move, and feeds the pushing chamber 5 of the primary hitting tool through the feeding circuit (29) and the pilot throttle (16). Being different the high pressure

exposed areas, both the pilot piston (4) and the primary hitting tool (3) are pushed downward. The pilot piston (4) acceleration is proportional to the feeding pressure and inversely proportional to its mass, while its initial speed is kept lower than the speed of the primary hitting tool (3). Such speed difference is controlled by the pilot throttle (16) of the differential stroke (28). Shape, diameter and length of the pilot throttle influence the separation of the two hitting tooles, the pressure difference between the two pushing chambers (5, 23) and the optimal value of the differential stroke (28) between the primary hitting tool (3) and the pilot piston (4). At the same time, the high pressure, acting on the pushing chambers (5, 12, 19) of the primary hitting tool (3), creates the net force, proportional to the difference between pushing chamber (5) area and pushing chambers (12, 19) areas. In this phase, the circuit (20) is closed and can not be connected with the circuit (21), which feeds the pushing chamber (22) of the pilot piston (4). While impacting, the speed of the pilot piston depends on its stroke, from the start up to the impact against the demolisher tool (10). Therefore, during the descending phase, the primary hitting tool (3) and the pilot piston (4) start at the same timo with different speed, separate themselves, the primary hitting tool (3) preceding the pilot piston (4); at the fixed time, they achieve a position defined by the differential stroke (28), and reach the same speed, keeping it

constant up the rapid sequential impacts. In this phase, the oil- gas source provides the oil to keep the pressure in the pushing chambers (23, 5) almost constant. In the meantime, while descending, the pilot piston (4) closes the start throttle (24) and pressurizes the chamber (32), which feeds the service circuit (14), and the pushing chamber (9) of the slide valve (7). Due to the pressure difference between pushing chamber (9) and discharge chamber (8) (connected to the low pressure circuit (25), the slide valve (J) moves downwards and closes the high pressure feeding port of the chamber (6), as shown in Fig. 2. The rapid opening of the slide valve (7) is determined by the optimal dimensioning of the control throttle (100), which assures the needed pressure differential. Referring to Fig. 3, together with the closing of the high pressure chamber (6), the chamber (32) connects with the chamber (23) and, through the chamber (30), to the chambers (32) and (8), which is also connected with the low pressure discharge circuit (25, 18) of the machine. In this way, both chambers (23, 32) and the pushing chamber (5) are depressurized by means of the pilot throttle ( 16) and the circuit (29).

Under these conditions, due to the pushing chambers (12, 19), being fed by the high pressure channel (26), the upwards force prevails and the rising phase of the primary hitting tool begins. Consequently, even with a translated position, the rising phase of

the pilot piston (4) begins as well. In this phase, with no connection with the high pressure chamber (6), the oil from the high pressure feeeding circuit (11) recharges the oil-gas source

(2) up to its calibrated pressure, making it ready for the next working cycle. During the rising stroke, the primary hitting tool

(3) comes into contact with the pilot piston (4), which pushes the on-off slide valve (7); consequently, the low pressure oil is discharged through the volume (30), whose port is progressively closed. The last discharge phase of the low-pressure oil (which determines the tight contact between the on-off valve (7) and the pilot piston (4) ) is controlled by the low-pressure throttle (100), connected to the chamber (8) and the discharge circuit (25). Under these conditions, the start throttle (24) is disconnected and can activate the next cycle, istantaneously pressurizing the pushing chamber (23) and then energyzing pilot piston and primary hitting tool, so that the descending phase begins. As said before, one important feature of the invention is the control of the differential stroke (28) of the primary hitting tool (3), which determines the telescopic motion of the pilot piston, during the rising stroke. Interacting with the slide valve (7), the piston (4) modulates the intervention timing of the vale itself, thus obtaining the variation of the machine active displacement. In fact, the pilot piston (4) is inserted into the primary hitting tool (3) and can translate with respect of the hitting tool (3)

position, by receiving a hydraulic set point signal. The latter is obtained by injecting a controlled quantity of high-pressure oil (22). This quantity comes from the hydraulic braking chamber (15), which is proportional to the tool penetration and consequently to the material hardness, by means of the hydraulic circuits (20, 21) and the volume (19). Due to the exposed areas difference, the pilot piston (4) telescopically moves inside the primary hitting tool (3) and, when the rising starts, moves on up to the contact with the on-off slide valve (7). In Fig. 5, a second embodiment of the invention is shown. The hydraulic set point signal, controlling the piston (4) translation, can be more precisely obtained by controlling the primary hitting tool (3) motion, when penetrating the material in neutral pressure area. Infact, just before the impact, an oil control volume (35) between the body (1) and the hitting tool (3) is created. Proportionally to its penetration stroke, the mass (3) defines the set point signal, by feeding the volume (36). The latter is constituted by different pressure exposed sections, on the pilot piston (4) connecting channels (34). In this way, two advantages arise: the pilot piston (4) displacement, inside the hitting tool (3), can be everyway amplified, by suitable dimensioning the pressure exposed sections of the volume (36) sections; the set point signal of the pressure in the volume (15) can become independent. In this way, the machine active displacement can

be varied in real time and more precisely, by defining the differential stroke translation in a shot to shot modality, even when the impact mechanical conditions change, because of tool (10) rebounce, material non-homogeneity or real working conditions.

Further design consideration: the impact speed of the hitting tool must be kept inside a defined range, to obtain both an impact optimal efficiency and a high reliability or mechanical resistance of the parts during the impact; moreover, especially for low- medium size machines with lower performances, the invention can be semplified, to reduce the machine production costs. Under these conditions, the oleodynamic percussion machine can show some design modifications, though mantaining the same working principle. In Fig. 6, the modifications are mostly related to the primary hitting tool (3) and pilot piston geometry, the service circuit (14), without the low pressure control throttle (100), and the higher speed of the slide valve (7). Instead, the embodiment in Fig. 7 comprises only one knocking and pilot mass (3), having the two functions. In Fig. 8, the start throttle is inside the slide valve, such solution being suitable for low- medium oleodynamic machines.