Rotary-percussive hydraulic perforator provided with a stop piston and a braking chamber

Abstract

The rotary-percussive hydraulic perforator includes a body; a shank; a striking piston configured to strike the shank and provided with a braking surface; a braking chamber configured to hydraulically brake the striking piston; a stop piston configured to apply a pushing force on the shank and provided with a bearing surface configured to abut against a stop surface provided on the body, so as to limit the stroke of displacement of the stop piston towards the shank. The rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart by a predetermined spacing distance simultaneously when (i) the shank bears on the stop piston and is in contact with the striking piston, and (ii) the braking surface is located at an inlet edge of the braking chamber.

Claims

1. A rotary-percussive hydraulic perforator comprising: a body; a shank mounted in the body and intended to be coupled to at least one drill bar equipped with a tool; a striking piston slidably mounted inside the body according to a striking axis and configured to strike the shank, the striking piston including a braking surface which extends transversely to the striking axis; a braking chamber configured to hydraulically brake the striking piston when the striking piston exceeds a predetermined striking position, the braking chamber being configured to be partially closed by the braking surface of the striking piston when the striking piston exceeds the predetermined striking position; a stop piston which is tubular and which is slidably mounted inside the body along an axis of displacement substantially parallel to the striking axis, the stop piston being configured to apply a pushing force on the shank, the stop piston comprising a bearing surface configured to abut against a stop surface provided on the body, so as to limit a stroke of displacement of the stop piston towards the shank; a main hydraulic supply circuit configured to control an alternating sliding of the striking piston according to the striking axis, the main hydraulic supply circuit including a high-pressure fluid supply conduit and a low-pressure fluid return conduit, wherein the body and the striking piston delimit at least partially a first control chamber permanently connected to the high-pressure fluid supply conduit and a second control chamber which is antagonistic to the first control chamber; a control distributor configured to fluidly connect the second control chamber alternately to the high-pressure fluid supply conduit and to the low-pressure fluid return conduit so as to control striking and return strokes of the striking piston; wherein the braking chamber extends from a bottom surface of the first control chamber and towards the shank; and wherein the rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart from each other by a predetermined spacing distance simultaneously when: the shank bears on the stop piston and is in contact with the striking piston, and the braking surface of the striking piston is located at an inlet edge of the braking chamber.

2. The rotary-percussive hydraulic perforator according to claim 1, wherein the predetermined spacing distance, measured substantially parallel to the striking axis of the striking piston, is greater than or equal to 2 mm.

3. The rotary-percussive hydraulic perforator according to claim 2, wherein the braking surface extends in a plane substantially perpendicular to the striking axis.

4. The rotary-percussive hydraulic perforator according to claim 3, wherein the striking piston includes a first piston portion having a first diameter, and a second piston portion having a second diameter which is greater than the first diameter, the braking surface connecting the first and second piston portions.

5. The rotary-percussive hydraulic perforator according to claim 4, wherein an inner wall of the braking chamber and an outer surface of the second piston portion are configured to define a radial functional clearance when the second piston portion is disposed in the braking chamber.

6. The rotary-percussive hydraulic perforator according to claim 1, wherein the braking surface extends in a plane substantially perpendicular to the striking axis.

7. The rotary-percussive hydraulic perforator according to claim 1, wherein the striking piston includes a first piston portion having a first diameter, and a second piston portion having a second diameter which is greater than the first diameter, the braking surface connecting the first and second piston portions.

8. The rotary-percussive hydraulic perforator according to claim 7, wherein an inner wall of the braking chamber and an outer surface of the second piston portion are configured to define a radial functional clearance when the second piston portion is disposed in the braking chamber.

9. The rotary-percussive hydraulic perforator according to claim 1, wherein the main hydraulic supply circuit is also configured to control sliding of the stop piston according to the axis of displacement.

10. The rotary-percussive hydraulic perforator according to claim 1, wherein the bearing surface is inclined with respect to the axis of displacement.

11. The rotary-percussive hydraulic perforator according to claim 10, wherein the body includes a main body and an inner sleeve which is fastened in the main body and which extends around the stop piston, the inner sleeve including the stop surface.

12. The rotary-percussive hydraulic perforator according to claim 1, wherein the body includes a main body and an inner sleeve which is fastened in the main body and which extends around the stop piston, the inner sleeve including the stop surface.

13. The rotary-percussive hydraulic perforator according to claim 1, which further includes a stop ring which is axially disposed between the shank and the stop piston and which is configured to apply the pushing force on the shank.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The present invention will be better understood from the following description with reference to the appended figures, wherein identical reference numerals correspond to structurally and/or functionally identical or similar elements.

(2) FIG. 1 is a longitudinal sectional view of a rotary-percussive hydraulic perforator according to a first embodiment of the invention, showing a striking piston, a stop piston and a shank in a first operating configuration.

(3) FIG. 2 is a longitudinal sectional view of the rotary-percussive hydraulic perforator of FIG. 1, showing the striking piston, the stop piston and the shank respectively in a second operating configuration and a third operating configuration.

(4) FIG. 3 is a longitudinal sectional view of a rotary-percussive hydraulic perforator according to a second embodiment of the invention.

(5) FIG. 4 is an enlarged scale view of a detail in FIG. 1.

DETAILED DESCRIPTION

(6) FIGS. 1 and 2 represent a rotary-percussive hydraulic perforator 2 which is intended for drilling blast holes. The rotary-percussive hydraulic perforator 2 includes more particularly a body 3 which is configured to be slidably mounted on a slide (not represented in the Figures) provided on a carrier machinery. According to the embodiment represented in FIGS. 1 and 2, the body 3 includes a main body 3.1, and also an inner sleeve 3.2 and an additional inner sleeve 3.3 slidably or forcibly mounted in the main body 3.1.

(7) The rotary-percussive hydraulic perforator 2 comprises a striking system 4 including a striking piston 5 slidably mounted alternately in a piston cylinder 6, which is defined by the body 3, according to a striking axis A. The striking piston 5 and the piston cylinder 6 delimit a first control chamber 7 which is annular, and a second control chamber 8 which has a cross-section larger than that of the first control chamber 7 and which is antagonist to the first control chamber 7.

(8) The striking system 4 further comprises a control distributor 9 arranged so as to control an alternating movement of the striking piston 5 inside the piston cylinder 6 alternately along a striking stroke and a return stroke. The control distributor 9 is configured to set the second control chamber 8, alternately in connection with a high-pressure fluid supply conduit 11, such as a high-pressure incompressible fluid supply conduit, during the striking stroke of the striking piston 5, and with a low-pressure fluid return conduit 12, such as a low-pressure incompressible fluid return conduit, during the return stroke of the striking piston 5. The first control chamber 7 is advantageously permanently supplied with high-pressure fluid by a supply channel 13 connected to the high-pressure fluid supply conduit 11.

(9) The high-pressure fluid supply conduit 11 and the low-pressure fluid return conduit 12 belong to a main hydraulic supply circuit with which the striking system 4 is provided. The main hydraulic supply circuit may advantageously include a high-pressure accumulator 14 connected to the high-pressure fluid supply conduit 11.

(10) The striking system 4 also includes a braking chamber 15 configured to hydraulically brake the striking piston 5 when the striking piston 5 exceeds a predetermined striking position. Advantageously, the braking chamber 15 is annular and extends in the continuation of the first control chamber 7 and towards the front of the rotary-percussive hydraulic perforator 2. The braking chamber 15 includes an inlet edge 15.1 which is annular and a bottom surface 15.2 which is also annular and which is located opposite the inlet edge 15.1.

(11) The braking chamber 15 is more particularly configured to: be partially closed by a braking surface 16 provided on the striking piston 5, and therefore to be partially fluidly isolated from the first control chamber 7, when the striking piston 5 exceeds the predetermined striking position, and be supplied with high-pressure fluid by the first control chamber 7 when the braking surface 16 of the striking piston 5 is away from the braking chamber 15.

(12) Advantageously, the braking surface 16 is annular and extends transversely to the striking axis A and preferably in a plane substantially perpendicular to the striking axis A. Nonetheless, according to a variant of the invention, the braking surface 16 could have an angle comprised between 30 and 90? with respect to the striking axis A. The braking surface 16 is configured to abut against the bottom surface 15.2 of the braking chamber 15 of so as to limit the striking stroke of the striking piston 5.

(13) According to the embodiment represented in FIGS. 1 and 2, the striking piston 5 includes a first piston portion 5.1 having a first diameter, a second piston portion 5.2 having a second diameter which is greater than the first diameter, and a braking shoulder which defines the braking surface 16 and which connects the first and second piston portions 5.1, 5.2. Advantageously, an inner wall of the braking chamber 15 and an outer surface of the second piston portion 5.2 are configured to define a radial functional clearance when the second piston portion 5.2 is disposed in the braking chamber 15. According to an embodiment of the invention, the radial functional clearance is comprised between 10 and 120 ?m.

(14) The rotary-percussive hydraulic perforator 2 also comprises a stop piston 17 which is tubular and which is slidably mounted inside the body 3 along an axis of displacement parallel to the striking axis A and preferably coinciding with the striking axis A. According to the embodiment represented in FIGS. 1 and 2, the stop piston 17 is slidably mounted around the striking piston 5, and extends coaxially to the striking piston 5.

(15) The stop piston 17 includes a bearing surface 18 which is annular and which is configured to abut against a stop surface 19, also annular, provided on the body 3 and for example on the inner sleeve 3.2, so as to limit the stroke of displacement of the stop piston 17 towards the front of the rotary-percussive hydraulic perforator 2.

(16) According to the embodiment represented in FIGS. 1 and 2, the bearing surface 18 is inclined relative to the axis of displacement according to an angle of inclination comprised between 30 and 60?, and for example of about 45?, and the sop surface 19 is also inclined with respect to the axis of displacement according to an angle of inclination comprised between 30 and 60?, and for example of about 45?. Advantageously, each of the bearing and stop surfaces 18, 19 diverges in the direction of a rear end of the stop piston 17. Nonetheless, according to another embodiment of the invention represented in FIG. 3, each of the stop surface 19 and the bearing surface 18 could extend substantially perpendicular to the axis of displacement.

(17) The rotary-percussive hydraulic perforator 2 further includes a shank 21 intended to be coupled, in a known manner, to at least one drill bar (not represented in the figures) equipped with a tool, also called bit. The shank 21 extends longitudinally along an axis of extension which advantageously coincides with the striking axis A, and includes a first end portion 22 facing the striking piston 5 and provided with an end face 22.1 against which the striking piston 5 is intended to hit during each operating cycle of the rotary-percussive hydraulic perforator 2, and a second end portion (not represented in the figures), opposite the first end portion 22, intended to be coupled to the at least one drill bar.

(18) The shank 21 also includes a front bearing surface 24 configured to abut against a front stop surface 25, which is annular and which extends around the shank 21, so as to limit the stroke of displacement of the shank 21 forwards. The front bearing surface 24 may for example be annular, or be discontinuous if the female and male coupling splines provided on the shank 21 extend up the front bearing surface 24. The front stop surface 25 may be provided directly on the body 3 and in particular the main body 3.1, or may be provided on an annular stop ring which is disposed in the main body 3.1. Advantageously, the front bearing surface 24 is inclined with respect to the striking axis A and diverges in the direction of the striking piston 5.

(19) The stop piston 17 more particularly includes a front face 26 which is facing the shank 21 and which is configured to apply a pushing force directly on the shank 21 or indirectly on the shank 21 through a stop ring 27 interposed axially between the shank 21 and the stop piston 17.

(20) The operation of a stop piston is well known to those skilled in the art and is therefore not described in detail in this description. In addition, the hydraulic supply of a stop piston may be carried out in various ways well known to those skilled in the art. Different examples of hydraulic supply of the stop piston 17 are however described hereinafter.

(21) According to the embodiment represented in FIGS. 1 and 2, the body 3 and the stop piston 17 delimit, with the striking piston 5, a primary control chamber 28 which may for example be permanently connected to the high-pressure fluid supply conduit 11 and which is configured to urge the stop piston 17 forwards, that is to say towards the shank 21.

(22) The body 3 and the stop piston 17 delimit, with the striking piston 5, also a secondary control chamber 29 which is antagonist to the primary control chamber 28 and which may for example be connected to the low-pressure fluid return conduit 12 or to a dedicated drain line. Advantageously, the bearing surface 18 and the stop surface 19 partially delimit the secondary control chamber 29.

(23) According to the embodiment represented in FIGS. 1 and 2, the body 3 and the stop piston 17 delimit an additional control chamber 31 which is antagonist to the secondary control chamber 29 and which is for example connected to a low-pressure accumulator 32 connected to the low-pressure fluid return conduit 12 and belonging to the main hydraulic supply circuit of the striking system 4. Each of the aforementioned low-pressure and high-pressure accumulators may be a membrane accumulator, such as a hydropneumatic accumulator, a piston accumulator, a bladder accumulator or any other type of accumulator. Nonetheless, according to the embodiment represented in FIG. 3, the additional control chamber 31 could be connected to an outer drain 30. According to another variant of the invention, the additional control chamber 31 could be connected directly to the low-pressure fluid return conduit 12, that is to say without the presence of a low-pressure accumulator.

(24) According to the embodiment of the invention represented in FIGS. 1 and 2, the main hydraulic supply circuit is configured to also control the sliding of the stop piston 17 along the axis of displacement. However, according to a variant of the invention, the rotary-percussive hydraulic perforator 2 could include a secondary hydraulic supply circuit separate from the main hydraulic supply circuit and configured to control the sliding of the stop piston 17 along the axis of displacement.

(25) The rotary-percussive hydraulic perforator 2 also comprises a rotational drive system 33 which is configured to drive the shank 21 in rotation about a rotational axis which is substantially coincident with the striking axis A. The rotational drive system 33 includes a coupling member 34, such as a coupling pinion, which is tubular and which is disposed around the shank 21. The coupling member 34 comprises male coupling splines and female coupling splines which are coupled in rotation respectively with female and male coupling splines provided on the shank 21.

(26) Advantageously, the coupling member 34 includes outer peripheral gearing coupled in rotation with an output shaft of a drive motor 35, such as a hydraulic motor hydraulically supplied by an external hydraulic supply circuit, belonging to the rotational drive system 33. The rotational drive system 33 may for example include an intermediate pinion 36 which is coupled on the one hand to the output shaft of the drive motor 35 and on the other hand to the outer peripheral gearing of the coupling member 34.

(27) When the rotary-percussive hydraulic perforator 2 is in operation, the shank 21 is rotated thanks to the drive motor 35, and the shank 21 receives on its end face 17 the cyclic hits of the striking piston 5, ensured by the striking system 4 supplied by the main hydraulic supply circuit. At the same time, the carrier machinery on which the rotary-percussive hydraulic perforator 2 is mounted applies a pushing force on the drill bar, via the body 3 and the shank 21. Inside the rotary-percussive hydraulic perforator 2, between the body 3 and the shank 21, this pushing force is transmitted through the stop piston 17 and the stop ring 27.

(28) The rotary-percussive hydraulic perforator 2 is more particularly configured such that the bearing surface 18 and the stop surface 19 are axially spaced apart from each other by a predetermined spacing distance D simultaneously when: the shank 21 bears on the stop piston 17, via the stop ring 27, and is in contact with the striking piston 5, and the braking surface 16 of the striking piston 5 is located at the inlet edge 15.1 of the braking chamber 15, that is to say is located radially opposite the inlet edge 15.1.

(29) Advantageously, the predetermined spacing distance D, measured substantially parallel to the striking axis A of the striking piston 5, is greater than or equal to 2 mm.

(30) Such a configuration of the rotary-percussive hydraulic perforator 2 allows, when the pushing force exerted by the slide on the rotary-percussive hydraulic perforator 2 is too small, if any, compared to the striking pressure, the stop piston 17 of to be able to position the shank 21 in an axial position (corresponding to a position of the stop piston in which the bearing surface 18 bears against the stop surface 19) such that the striking piston 5 will have penetrated into the braking chamber 15 with a distance corresponding to the predetermined spacing distance D before being able to strike the shank 21. Thus, the rotary-percussive hydraulic perforator 2 according to the present invention guarantees that the impact between the shank 21 and the striking piston 5 is carried out at a reduced speed when the pushing force exerted by the slide on the rotary-percussive hydraulic perforator 2 is too low, if any, and therefore without generating damage to constituent elements of the striking line of the perforator, and in particular to the shank 21, to the drill bar(s) and to the bit.

(31) Consequently, the rotary-percussive hydraulic perforator 2 according to the present invention makes it possible to define an intermediate impact speed of the striking piston comprised between a maximum impact speed of the striking piston 5 (which corresponds to a position of the striking piston 5 in which the braking surface 16 is located at the inlet edge 15) and a minimum impact speed of the striking piston 5 (which corresponds to a position of the striking piston 5 in which the braking surface 16 is located in contact with the bottom surface 15.2), and thus to definitely limit the energy transmitted to the shank 21, to the drill bars and to the bit when the latter is not resting on the rock de be drilled, and therefore to protect the shank 21, the drill bars, the bit and the entire striking line of the rotary-percussive hydraulic perforator 2.

(32) Such a protection function is integrated in the rotary-percussive hydraulic perforator 2, without the addition of external control blocks or additional internal or external hydraulic circuits, and is therefore obtained without having to guarantee the safety of the perforator by external functionalities subject to hazards.

(33) It goes without saying that the invention is not limited to the sole embodiments of this rotary-percussive hydraulic perforator, described hereinabove as examples, it encompasses on the contrary all variants thereof.