Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/06—Means for driving the impulse member
  • B25D9/12—Means for driving the impulse member comprising a built-in liquid motor, i.e. the tool being driven by hydraulic pressure
  • B25D9/125—Means for driving the impulse member comprising a built-in liquid motor, i.e. the tool being driven by hydraulic pressure driven directly by liquid pressure working with pulses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/04—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously of the hammer piston type, i.e. in which the tool bit or anvil is hit by an impulse member
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/06—Means for driving the impulse member
  • B25D9/12—Means for driving the impulse member comprising a built-in liquid motor, i.e. the tool being driven by hydraulic pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/14—Control devices for the reciprocating piston
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/14—Control devices for the reciprocating piston
  • B25D9/145—Control devices for the reciprocating piston for hydraulically actuated hammers having an accumulator
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/14—Control devices for the reciprocating piston
  • B25D9/16—Valve arrangements therefor
  • B25D9/18—Valve arrangements therefor involving a piston-type slide valve
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B1/00—Percussion drilling
  • E21B1/38—Hammer piston type, i.e. in which the tool bit or anvil is hit by an impulse member
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B4/00—Drives for drilling, used in the borehole
  • E21B4/06—Down-hole impacting means, e.g. hammers
  • E21B4/14—Fluid operated hammers

Definitions

• the present invention concerns hydraulic impact mechanisms of the type known as “slideless” or “valveless” to be used in equipment for machining at least one of rock and concrete, and equipment for drilling and breaking comprising such impact mechanisms.
• Equipment for use in rock or concrete machining is available in variants with percussion, rotation, and percussion with simultaneous rotation. It is well-known that the impact mechanisms that are components of such equipment are driven hydraulically .
• a hammer piston mounted to move within a cylinder bore in a machine housing, is then subject to alternating pressure such that a reciprocating motion is achieved for the hammer piston in the cylinder bore.
• the alternating pressure is most often obtained through a separate switch-over valve, normally of sliding type and controlled by the position of the hammer piston in the cylinder bore, alternately connecting at least one of two drive chambers, formed between the hammer piston and the cylinder bore, to a line in the machine housing with driving fluid, normally hydraulic fluid, under
• valveless manufacture slideless hydraulic impact mechanisms, also known sometimes as “valveless” mechanisms.
• the hammer pistons in valveless impact mechanisms perform also the work of the switch-over valve by opening and closing the supply and drainage of driving fluid under pressure during the motion of the piston in the cylinder bore in a manner that gives an alternating pressure according to the above
• pressurisation and drainage of a chamber open out into the cylinder bore such that the openings are separated in such a manner that direct short-circuited connection between the supply channel and the drainage channel does not arise at any position during the
• the units of the modulus of compressibility are Pascal.
• US 4 282 937 reveals a valveless hydraulic impact mechanism with two drive chambers, where the pressure alternates in both of these chambers. Both drive chambers have a large effective volume through them being placed in permanent connection with volumes that lie close to the cylinder bore.
• One disadvantage of the prior art technology revealed in this way is that it has turned out to give a surprisingly low efficiency, given that one mobile part has been removed compared with conventional impact mechanisms with a switchover valve. In this document we define "efficiency", unless
• One purpose of the present invention is to demonstrate a design of a valveless hydraulic impact mechanism that offers the opportunity of improving the efficiency without at the same time reducing the service interval. This is achieved in the manner that is described in the independent claims. Further advantageous embodiments are described in the non-independent claims.
• the effective volume of the drive chambers as the sum of the drive chamber volumes that have an alternating pressure during one stroke cycle, including volumes that are in continuous
• the effective volume of the drive chambers is of crucial significance for the efficiency of the impact mechanism with respect to valveless impact mechanisms.
• factors that influence the efficiency such as play and the length of gap seals, friction in bearings, etc. It is not possible, however, to achieve the desired efficiency without a correctly adapted effective volume of the drive chambers, no matter how such play and bearings are designed.
• Factors that influence the optimal effective volume of the drive chambers with respect to efficiency are: the impact mechanism pressure used, the compressibility of the driving medium and the energy of the piston in its impact against the tool or against a part that interacts with the tool.
• the effective volume of the drive chambers is influenced in inverse proportion to the square of the impact mechanism pressure and proportionally to the product of the effective modulus of compressibility of the driving medium and the energy of the hammer piston when it impacts the tool or a part that interacts with the tool, such as the part known as an "adapter" .
• V k * ⁇ * E/p 2
• V the effective drive chamber volume (by which we mean the sum of the volumes of the two drive chambers, including volumes that are in continuous connection with one and the same drive chamber during a complete stroke cycle) .
• the volume of this chamber is normally totally dominating in comparison with that of the chamber that has a constant pressure. It then becomes possible to regard the effective drive chamber volume as the volume solely of the drive chamber that has alternating pressure together with the volume that is continuously connected to this, ⁇ in the equation constitutes the effective modulus of compressibility of the driving medium as it has been previously defined.
• the effective modulus of compressibility is calculated as the resultant ratio between the change in pressure and the relative change in volume.
• Figure 3 presents values of ⁇ for hydraulic fluids with different levels of air content.
• the accumulators are directly connected to the effective volumes, as is described in, for example, SU 1068591 A, these are also to be included in the calculation of effective volume.
• the existing gas volume that is present in these, normally consisting of nitrogen gas will be included in the calculation of the effective modulus of compressibility. It is appropriate in this case that the gas volumes of the accumulators when the impact mechanism is in its resting condition, i.e. the condition that normally prevails before the impact mechanism is started, be used.
• the said gas accumulators here are not to be confused with those that are normally connected to the supply line and return line for the impact mechanism.
• accumulators are connected to the drive chamber only intermittently, and are thus not to be included in the calculation of the effective volume or the effective modulus of compressibility.
• E denotes the impact energy of the piston in its impact with the tool or with a part that interacts with the tool.
• p is the impact mechanism pressure that is used.
• mechanism pressure is normally between 150 and 250 bar.
• k is a constant of proportionality, that it has become apparent most suitably lies in the interval 7.0 ⁇ k ⁇ 9.5, but where a good effect for the efficiency can be achieved in the larger interval 6.2 ⁇ k ⁇ 11.0 and even up to the interval 5.3-21.0.
• One preferred embodiment constitutes an impact mechanism, where the volume (by which we refer to the effective volume as defined above) of one of the drive chambers is much larger than that of the second drive chamber, i.e. that the volume of the second drive chamber is negligible, for example 20% or less than the volume of the first drive chamber, and where the smaller drive chamber has essentially constant pressure during the complete stroke cycle. Constant pressure in this chamber is normally achieved by the chamber being connected to a source of constant pressure during the complete stroke cycle, or at least during essentially the complete stroke cycle, most often being directly connected to the source for the system pressure or alternatively impact mechanism pressure.
• Impact mechanisms of the type that has been described above can be an integrated component of equipment for the machining of at least one of rock and concrete, such as rock drills and hydraulic
• breakers These machines or breakers during operation should most often be mounted onto a carrier that can comprise means for their alignment and position together with means for the feed of the drill or breaker against the rock or concrete element that is to be machined, and further, means for the control and monitoring of the process.
• a carrier may be a rock drilling rig.
• Figure 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.
• Figure 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.
• Figure 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.
• Figure 4 shows an impact mechanism according to Figure 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 .
• Figure 1 shows schematically a hydraulic impact mechanism with alternating pressure not only on the upper surface of the
• Hydraulic fluid at impact mechanism pressure 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.
• the hydraulic fluid is set in connection with a hydraulic tank through return channels 135, 235, in which tank the oil normally has atmospheric pressure.
• 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.
• 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.
• the hammer piston 145, 245 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
• 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.
• a functioning design involves an effective volume of 3 litres 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 2 and an area of the second drive surface
• 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.
• the drive chamber volume and, in particular, the working volume with its large volume can be located in the machine housing in various ways.
• 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.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• Geology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Percussive Tools And Related Accessories (AREA)
• Earth Drilling (AREA)
• Portable Nailing Machines And Staplers (AREA)
• Fluid-Pressure Circuits (AREA)

Priority Applications (8)

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Publications (1)

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Cited By (2)

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Citations (3)

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• 2011
  • 2011-04-05 SE SE1100252A patent/SE536289C2/sv unknown
• 2012
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  • 2012-04-03 AU AU2012240637A patent/AU2012240637B2/en active Active
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• 2013
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