Device for rock and-concrete machining

Abstract

The invention concerns a hydraulic striking tool for application in rock and/or concrete cutting equipment containing a machine housing (100;200) with a cylinder (115;215) with a moveably mounted piston (145;245) which during operation performs a repetitive forward and backward movement relative to the machine housing (100;200) and directly or indirectly strike a rock and/or concrete cutting tool (155;255), and where the piston (145;245) includes a driving part (165;265) which separates a first (120;220) and a second (105;221) driving chamber formed between the piston (145;245) and the machine housing (100;200) and where these driving chambers are arranged to include a pressurized working fluid during operation. The total volume V of the first and second driving chambers is inversely proportional dimensioned to the square of a for the striking tool recommended maximal pressure p, as well as proportional, by a proportionality constant k within the interval 5.3-21.0, to the product of the pistons energy E during the strike against the tool and compression module β of the working fluid.

Claims

1. A valveless hydraulic impact mechanism for use in equipment for at least one of rock and concrete machining, said valveless hydraulic impact mechanism comprising a machine housing with a cylinder bore, a piston mounted to move within the cylinder bore and arranged to carry out repetitively reciprocating motion relative to the machine housing during operation, said reciprocating motion delivering impacts directly or indirectly onto a tool connectable to the equipment for machining at least one of rock and concrete, a driving medium at a predetermined impact mechanism pressure p, and wherein the piston includes a driving part that separates a first and a second drive chamber formed between the piston and the machine housing, and wherein the first and second drive chambers are arranged such that they include during operation the driving medium under pressure, and wherein the machine housing further includes channels that open out into the cylinder bore and are arranged such that the channels include the driving medium during operation, and that with the aid of the piston, during said reciprocating motion in the cylinder bore, the channels open onto and close from one of the first and second drive chambers such that said one of said first and second drive chambers acquires a periodically alternating pressure for maintaining the reciprocating motion of the piston, and that positions for the opening of the channels axially in the cylinder bore and for opening and closing of the channels along parts of the piston are adapted to maintain said one of said first and second drive chambers closed for the supply or drainage of the driving medium that is present in the one of said first and second drive chambers along a distance between an opening of a first said channel associated with a first turning point of the piston and an opening of a second said channel associated with a second turning point of the piston, and that the motion of the piston along said distance continues during the compression or expansion of the volume of said one of said first and second drive chambers, wherein said volume has been further adapted in order to achieve a predetermined change in pressure along the said distance, wherein the total volume V of the first and second drive chambers, including volumes that are in continuous connection with one and the same drive chamber during a complete cycle of a stroke, has been dimensioned to be inversely proportional to the square of the impact mechanism pressure p, and further proportional, with a constant of proportionality k, that has a value in the interval 5.3-21.0, to the product of the energy E of the piston in the impact against the tool and the modulus of compressibility β of the driving medium, according to the equation V=k*β*E/p.sup.2.

2. The hydraulic impact mechanism according to claim 1, with the constant of proportionality k in the interval 6.2<k<11.

3. The hydraulic impact mechanism according to claim 2, where the volume of one of the first and second drive chambers is greater than the volume of the other of said first and second drive chambers.

4. The hydraulic impact mechanism according to claim 2, where one of the drive chambers has a constant pressure during the complete stroke cycle.

5. The hydraulic impact mechanism according to claim 2, where one of said first and second drive chambers are alternately set under pressure.

6. The hydraulic impact mechanism according to claim 2, where the volumes of the chambers extend symmetrically around the cylinder bore.

7. The hydraulic impact mechanism according to claim 2, where the volumes of the chambers extend concentrically around the cylinder bore.

8. The hydraulic impact mechanism according to claim 1, with the constant of proportionality k in the interval 7.0<k<9.5.

9. The hydraulic impact mechanism according to claim 8, where the volume of one of the first and second drive chambers is greater than the volume of the other of said first and second drive chambers.

10. The hydraulic impact mechanism according to claim 8, where one of the drive chambers has a constant pressure during the complete stroke cycle.

11. The hydraulic impact mechanism according to claim 8, where one of said first and second drive chambers are alternately set under pressure.

12. The hydraulic impact mechanism according to claim 1, where the volume of one of the first and second drive chambers is greater than the volume of the other of said first and second drive chambers.

13. The hydraulic impact mechanism according to claim 1, where one of the drive chambers has a constant pressure during the complete stroke cycle.

14. The hydraulic impact mechanism according to claim 13, where the drive chamber with alternating pressure extends into the cylinder bore.

15. The hydraulic impact mechanism according to claim 1, where one of said first and second drive chambers are alternately set under pressure.

16. The hydraulic impact mechanism according to claim 1, where the volumes of the chambers extend symmetrically around the cylinder bore.

17. The hydraulic impact mechanism according to claim 1, where the volumes of the chambers extend concentrically around the cylinder bore.

18. A rock drill comprising impact mechanisms according to claim 1.

19. A rock drilling rig comprising the rock drill according to claim 18.

20. A hydraulic breaker comprising impact mechanisms according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a sketch of the principle of a valveless hydraulic impact mechanism with alternating pressure in drive chambers not only on the upper surface of the piston but also on its lower surface.

(2) FIG. 2 shows a sketch of the principle for a corresponding impact mechanism with alternating pressure on only one surface, and with constant pressure on the second.

(3) FIG. 3 shows a diagram, actually known, for the calculation of the effective modulus of compressibility for a pressure medium that consists of gas and hydraulic fluid.

(4) FIG. 4 shows an impact mechanism according to FIG. 2 with the hammer piston at four different positions: A—the braking is starting at the upper position; B—the upper turning point; C—the braking is starting at the lower position; D—the lower turning point.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) A number of designs of the invention will be described as examples below, with reference to the attached drawings. The protective scope of the invention is not to be regarded as limited to these embodiments, instead it is defined by the claims.

(6) FIG. 1 shows schematically a hydraulic impact mechanism with alternating pressure not only on the upper surface of the piston but also on its lower surface.

(7) In a similar manner, FIG. 2 and FIG. 4 show an impact mechanism with constant hydraulic pressure throughout the stroke cycle on the lower surface of the piston, i.e. on that surface that is located most closely to the tool 155, 255 onto which the hammer piston is to transfer impact energy, and with alternating pressure during the stroke cycle on the upper surface of the piston.

(8) Hydraulic fluid at impact mechanism pressure P is supplied to the impact mechanism through supply channels 140, 240, which pressure often lies within the interval 150-250 bar. The system pressure, i.e. the pressure that the hydraulic pump delivers, is often equal to the impact mechanism pressure.

(9) The hydraulic fluid is set in connection with a hydraulic tank R through return channels 135, 235, in which tank the oil normally has atmospheric pressure.

(10) The hammer piston 145, 245 executes a reciprocating motion in a cylinder bore 115, 215 in a machine housing 100, 200. The hammer piston comprises a driving part 165, 265 that separates a first driving area 130, 230 from a second driving area 110, 210. The pressure that acts on these driving areas causes the piston to execute reciprocating motion during operation. The piston is controlled radially by piston guides 175, 275. In order to avoid pulsation in connecting lines, gas accumulators 180, 280 and 185, 285 may be arranged on supply channels 140, 240 and return channels 135, 235, respectively, which gas accumulators even out rapid variations in pressure.

(11) In order for it to be possible for the hammer piston 145, 245 to move sufficiently far into a drive chamber 120, 220, 221 with alternating pressure, with the aid of its kinetic energy, after the driving part 165, 265 has closed the connection to the return channel 135, 235, such that a connection between the supply channel 140, 240 and the chamber 120, 220, 221 can be opened, it is necessary that the chamber have a sufficiently large volume that the increase in pressure in the chamber as a consequence of the compression by the piston of the volume of fluid that has now been enclosed within the chamber is not so large that the piston reverses its direction before a supply channel 140, 240 has been opened into the chamber, such that the pressure can now rise to the full impact mechanism pressure, and the piston in this way be driven in the opposite direction. The drive chamber for this purpose is connected to a working volume 125, 225, 226. Since this connection between the drive chamber and the working volume is maintained throughout the stroke cycle, we will denote the sum of the volume of the drive chamber and the working volume as the “effective drive chamber volume”. It has proved to be the case, as has been described earlier in this application, that this volume is critically important to achieving high efficiency.

(12) A functioning design involves an effective volume of 3 liters for a system pressure of 250 bar, impact energy of 200 Joules, a hammer piston weight of 5 kg, an area of the first drive surface 130 of 16.5 cm.sup.2 and an area of the second drive surface 110 of 6.4 cm.sup.2. The length of the driving part 70 mm and the distance between the supply channel and the return channel for the drive chamber 120 at their relevant connections to the cylinder bore is 45 mm.

(13) At an impact mechanism pressure or system pressure of 250 bar, giving a β value, as is made clear by FIG. 3, equal to 1500+7.5×25=1687.5 MPa. These values together with an effective volume of 3 liters and impact energy of 200 Joule give, as an example, the constant of proportionality:
k=(3.Math.10.sup.−3/200.Math.1687.5.Math.10.sup.6).Math.(250.Math.10.sup.5).sup.2=5.55.

(14) The drive chamber volume and, in particular, the working volume with its large volume can be located in the machine housing in various ways.

(15) It is advantageous that the volumes be placed symmetrically around the cylinder bore.

(16) It is further advantageous that they be placed concentrically around the cylinder bore.

(17) It may be advantageous, as an alternative, that they be placed in the extension of the cylinder bore.

(18) It is appropriate that an impact mechanism according to the principles described above be integrated in a rock drill or, alternatively, in a hydraulic breaker.

(19) A rock drilling rig with equipment for the positioning and alignment of such a rock drill or hydraulic breaker should comprise at least one rock drill or at least one hydraulic breaker according to the invention.