Patent Publication Number: US-7900448-B2

Title: Pulse generator and impulse machine for a cutting tool

Description:
TECHNICAL FIELD 
     The present invention relates to a pulse generator in an impulse generator for a cutting, for example a rock breaking, tool, and an impulse machine comprising a pulse generator. 
     BACKGROUND 
     In traditional machines with striking mechanisms a piston which pneumatically or hydraulically is made to move back and forth in a propulsion chamber is used, where the piston strikes directly or indirectly via for example a drill steel shank against the end of a drilling steel which in turn bears on the rock via a drill bit. The stress pulse provides forces at the contact with the rock that makes the rock break. 
     Efforts have been made with rock breaking machines which contrary to the traditional machines with striking mechanisms have a piston that does not move as far back and forth in the propulsion chamber for transfer of the impact force which brings about a possibility to increase the impact frequency. 
     WO 2005/002801 shows a striking device such as a rock drill, where a stress pulse is generated in a tool by means of the striking device by that pressure fluid is fed to the striking device and is fed out from the striking device. The pressure fluid that is fed to the striking device is pulsed to a working chamber in the striking device. 
     If one in a device of the above mentioned type wants to adapt the energy in the stress pulse which is generated in a tool to that which is required to work the rock, one can vary the level of the pressure which is fed to the striking device. However, the pump and the hoses limit the range within which the pressure can be varied. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The problem to adapt the energy in the delivered pulse is solved according to the invention by arranging a pulse generator in an impulse generator for a rock breaking tool, which pulse generator is designed to transfer energy from a propulsion device to impulses in the tool, where the pulse generator comprises a rotatable cylinder drum comprising at least one piston cylinder, in which piston cylinder is arranged at least one piston, which piston is arranged to compress fluid during rotation of the cylinder drum, and that the cylinder drum is arranged to at the discharge position of the piston to discharge the fluid to the propulsion chamber via at least one into the piston cylinder leading opening in order to produce an impulse in the tool. 
     By that the pulse generator comprises the characteristics in claim  1 , the advantage of producing an impulse generator where the energy in the to the tool delivered pulse can be adapted in a simpler way is attained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention will be described below in greater detail with reference to the attached drawings, in which: 
         FIG. 1  shows schematically a longitudinal section of a first embodiment of an impulse generator, 
         FIG. 2  shows schematically a longitudinal section of a first embodiment of the pulse generator in the impulse generator according to  FIG. 1 , 
         FIG. 3  shows a valve disc with openings, 
         FIG. 4  shows a cylinder drum with low pressure channels, openings and piston cylinders, and 
         FIGS. 5-8  show the valve disc and the in  FIGS. 5-8  behind and against the valve disc bearing cylinder drum in different relative positions. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows schematically a longitudinal section of a first embodiment of an impulse generator  2  comprising a housing  4  with a propulsion chamber  6  for receiving of a pressurizeable fluid volume  8 , and an in the propulsion chamber  6  received impulse piston  10 , where the impulse piston  10  is arranged for direct or indirect transfer of pressure peaks in the fluid volume  8  to impulses in a tool  12 . If the impulse piston  10  is arranged adjacent to the tool  12 , the impulses are transferred directly, but the impulses may also be transferred indirectly via for example an intermediate adapter  16 . In the figure, the propulsion chamber  6  is shown in a position where the pressure in the fluid volume  8  in the propulsion chamber  6  is so low that the impulse piston  10  is situated in its rest position. The return movement of the impulse piston  10  to this rest position is effected for example by pressurizing a chamber  9  on the side of the impulse piston  10  opposite the side of the propulsion chamber  6  with air or fluid or by arranging a spring (not shown) in this space, or by moving the whole drilling rig with the thereon mounted impulse generator  2  forward against the rock in which case a damper  26  may be arranged to regulate the rest position. Optionally, a shoulder (not shown) may be arranged as a stop in the propulsion chamber  6  which however may be difficult in those cases where one obtains large reflections. Another conceivable solution is to use the impulse piston  10  as a part in a system for damping reflections and/or part in a system for rest position restoration. Further is shown a pulse generator  18 , which is driven by the propulsion device  14  via a propulsion mechanism  20 , which propulsion mechanism  20  preferably is a drive shaft. The propulsion device  14  may be arranged outside of the impulse generator  2 , but is preferably arranged inside the impulse generator  2 , which impulse generator  2  may for example be a drilling machine. The propulsion device  14  may for example be electrically or hydraulically driven, i.e. the propulsion device may for example be an electric motor or a hydraulic motor. For rock drilling, the impulse generator  2  may be cooled down with e.g. hydraulic fluid or drilling water via channels in the housing  4  of the impulse generator  2  or via on the outside of the housing  4  of the impulse generator  2  arranged hoses or the like (not shown). Further, a channel  22  leading in to the propulsion device  14  and a channel  24  leading out from the propulsion device  14  are shown that are used if the propulsion device  14  is hydraulically driven. The channel  24  leading out from the propulsion device  14  is connected to the low pressure side  25  (low side). If the propulsion device  14  is driven with electricity, these channels  22 ,  24  are instead replaced by wires for electricity that may be located in the channels  22 ,  24 . 
     If the propulsion device  14  is mechanically driven, i.e. if the propulsion device for example is a mechanical gear such as for example a gear drive, these channels  22 ,  24  are replaced instead by a drive shaft (not shown). 
     If the pulse generator  18  is hydraulically driven, the low pressure side  25  of the pulse generator  18  may as shown in the figure be connected to the low pressure side  25  of the hydraulic propulsion device  14  and with that chamber  9  which is situated on the side of the impulse piston  10  opposite the side of the propulsion chamber  6 . 
       FIG. 2  shows schematically a longitudinal section of a first embodiment of the pulse generator  18  in the impulse generator  2  according to  FIG. 1 , where the pulse generator  18  comprises a rotating cylinder drum  28  with at least one piston cylinder  30 , preferably more than one piston cylinder  30 , and at least one piston  32 , preferably more than one piston  32 . The pulse generator  18  further comprises a valve disc  34  and an angled plane preferably arranged as a tilted disc  38 . The pulse generator as shown in the figure extends thus between the valve disc  34  and the angled plane  38 . The number of piston cylinders  30  is thus optional but has to be at least one. The generation of pulses will however to begin with be exemplified below using only one piston cylinder  30  and one piston  32 , where the piston cylinder  30  and the piston  32  preferably have, but do not have to have, a circular cross section. Thus, the impulse generator  2  shown in  FIG. 1  with the in  FIG. 2  shown, preferably hydraulic, pulse generator  18  creates local pressure levels in at least one piston cylinder  30  by compression by means of the piston  32 . The energy in each pressure peak is determined by the degree of compression in the piston cylinder  30 . A relative to the housing  4  of the impulse generator  2  fixed valve disc  34  regulates via one or more therein arranged openings  36  one or more passages between the propulsion chamber  6  and an against the piston cylinder  30  connecting opening  31  in the cylinder drum  28 , as well as one or more passages between the propulsion chamber  6  and the low pressure side  25  (see further below). When the piston cylinder  30  has been compressed due to the movement of the piston  32  against the volume confined in the piston cylinder  30 , the in the piston cylinder  32  confined fluid is discharged rapidly towards the propulsion chamber  6  and thus towards the impulse piston  10  which experiences a pressure pulse. After the discharge, the propulsion chamber  6  is connected to the low pressure side  25  (see further below). As long as the piston  32  in the piston cylinder  30  decreases the volume of the piston cylinder  30 , one may by introducing more openings  36  in the valve disc  34  create more pressure pulses in the propulsion chamber  6 . In connection with each discharge, the passage/passages between the propulsion chamber  6  and the low pressure side  25  closes (see further below). When the piston  32  executes increase of the volume in the piston cylinder  30 , the connection from the piston cylinder  30  to the low pressure side  25  is open, via the opening  36 /openings in the valve disc  34  to the propulsion chamber  6  and the opening/openings between the propulsion chamber  6  and the low pressure side  25 , with the exception of the short periods when pulses are discharged to the impulse piston  10 . 
     The movement of the piston  32  is exact and known, preferably of sinus shape see further description below. The location of the opening  36  in the valve disc  34  and the piston stroke of the piston  32  in the piston cylinder  30  determines the compression which may be achieved in the piston cylinder  30 . The piston stroke of the piston  32  may for example be varied using a tilted disc  38  which changes the degree of compression in the piston cylinder  30  whereby the pulse energy may be controlled. The pulse frequency is determined by the rotation speed of the cylinder drum  28  which is controlled by the propulsion device  14 . Thus, there is no connection between pulse energy and pulse frequency. If the pulse generator  18  is driven by a propulsion device  14  in the form of a hydraulic motor arranged on the same shaft  42  as the pulse generator  18 , the rotational speed may be determined by the flow in the hydraulic motor. The size (displacement) of the feeding hydraulic motor which is used determines what pressure and flow is needed to feed the motor. The motor may be adapted to available pressure—and flow levels in for example a drilling rig. If the motor is variable, one can instead obtain a flexible impulse generator  2 , i.e. a drilling machine, with regard to the pressure—and flow levels in the drilling rig. 
       FIG. 2  thus shows an angled plane  38 , preferably arranged as a tilted disc, against which the piston  32  bears via a sliding support  40 . A device  39  which keeps the sliding supports against the tilted disc in those positions where the piston forces are small may be needed. The piston  32  performs a sinus shaped movement when the cylinder drum  28  and thereby the piston cylinder  30  rotates around the rotating shaft  42  of the cylinder drum  28 . One half of the revolution, the piston  32  moves to the left and compresses confined fluid, or delivers flow pulses to the propulsion chamber  6 . The second half of the revolution, the piston  32  moves to the right and is then connected to low pressure  25  (low side) via the propulsion chamber  6  (with the exception of the short periods when pulses are created in the propulsion chamber  6 —see further below). 
       FIGS. 3-8  show an embodiment of a valve disc  34  fixed relative to the housing  4  of the impulse generator  2 . 
       FIG. 3  shows a valve disc  34  with seven openings  36 ,  41 ,  43 ,  45 ,  42 ,  48 ,  50 , which openings form passages between the cylinder drum  28  and the propulsion chamber  6 . 
       FIG. 4  shows the cylinder drum  28  with in this embodiment eight low pressure connections  54 ,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68  and eight openings  31 ,  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 , which openings  31 ,  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84  each open into a separate piston cylinder  30 ,  86 ,  88 ,  90 ,  92 ,  94 ,  96 ,  98  in the cylinder drum  28 . Pistons  32 ,  87 ,  89 ,  91 ,  93 ,  95 ,  97 ,  99  are each located in a separate piston cylinder  30 ,  86 ,  88 ,  90 ,  92 ,  94 ,  96 ,  98 . 
       FIGS. 5-8  shows the valve disc  34  and the in  FIGS. 5-8  behind and against the valve disc  34  beating cylinder drum  28 . The cylinder drum  28  rotates to the left in the figure whereas the valve disc  34  is removably fixed in its position. During the rotation of the cylinder drum  28  compression takes place on the left half of the valve disc  34  and expansion on the right half of the valve disc  34  as mentioned above. In the embodiment shown in  FIGS. 5-8 , four pistons  87 ,  89 ,  91 ,  93  located in separate piston cylinders  86 ,  88 ,  90 ,  92  cooperate. By that a number of pistons cooperate by simultaneous discharges, more energy is obtained in the produced pulse. Optionally, the piston cylinders may be discharged one at a time which provides less energy in the produced pulse, but on the other hand a higher pulse frequency. 
       FIG. 5  shows the valve disc  34  and the cylinder drum  28  in a position where the piston cylinders  86 ,  88 ,  90 ,  92  for the four cooperating pistons  87 ,  89 ,  91 ,  93 , after having been exposed to compression have discharged to and created a pressure pulse in the propulsion chamber  6 . As can be seen, eight openings towards the low pressure channels  54 ,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68  of the cylinder drum  28  have just opened between the valve disc  34  and the cylinder drum  28  which makes the propulsion chamber  6  to connect to low pressure  25 . 
       FIG. 6  shows the valve disc  34  and the cylinder drum  28  in a position where the three openings  41 ,  43 ,  45  in the valve disc  34  are closed by that they are blocked by the wall of the cylinder drum  28  whereby the fluid in the piston cylinders  30 ,  86 ,  88 ,  90  located behind the left half of the valve disc  34  are compressed, at the same time as the piston cylinders whose fluid expands now are connected to low pressure  25  via the low pressure channels  54 ,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68  in the cylinder drum  28 , the propulsion chamber  6  and their respective openings  78 ,  80 ,  82 ,  84 . 
       FIG. 7  shows the valve disc  34  and the cylinder drum  28  under similar pressure conditions that are shown in  FIG. 6  with the difference that the cylinder drum  28  has rotated somewhat further in  FIG. 7  than in  FIG. 6 . 
       FIG. 8  shows the valve disc  34  and the cylinder drum  28  in a position just before four cooperating pistons are about to create a pressure pulse in the propulsion chamber  6 . All seven openings  41 ,  43 ,  45 ,  42 ,  48 ,  50 ,  52  in the valve disc  34 , and all eight openings between the valve disc  34  and the cylinder drum  28  towards the low pressure channels  54 ,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68  of the cylinder drum  28  are in this position blocked by the wall of the cylinder drum  28  in order for the pressure pulse in the propulsion chamber  6  to be maximised without losses due to leak flows or compression of the pistons that are located behind the right side of the valve disc  34 . Thus, the valve disc  34  delimits in this position the propulsion chamber  6  from the low pressure side  25 . If all leak flows are directed to the low pressure side  25 , fluid does not have to be fed to the pulse generator  18  which results in that the pulse generator  18  may work in a closed circuit. However, circulation of fluid may be arranged if this is justified in order to attain sufficient cooling of the impulse generator. A gas accumulator (not shown) may be arranged on the low pressure side  25  in order to balance the rapid flow pulses that arise when the propulsion chamber  6  is decompressed. 
     The invention is described above using a valve disc. It is also conceivable to arrange radial openings in the cylinder drum which openings lead to the propulsion chamber via channels. 
     The pistons preferably have matched draining holes and/or draining channels (not shown) of known type for cooling and lubrication. In the fluid volume, i.e. the liquid volume, a fluid from e.g. the group: water, silicone oil, hydraulic oil, mineral oil, and non-combustible hydraulic. fluid, shall be received, but also other fluids may be conceivable. The propulsion chamber has preferably a circular cross section. The pulse generator cylinders are preferably distributed symmetrically, but optionally non-symmetrically, over the cross section area of the propulsion chamber. The impulse generator is designed to be rotationally driven. The pistons are forcedly operated by the tilted disc and the device  39  regarding both their inward-bound and outward-bound movements. Preferably, the inclination of the tilted disc may be manually or automatically altered during operation. 
     The invention thus relates to a pulse generator  18  in an impulse generator  2  for a rock breaking tool  12 , which pulse generator  18  is intended to transfer energy from a propulsion device  14  to impulses in the tool  12 , where the pulse generator  18  comprises a rotatable cylinder drum  28  comprising at least one piston cylinder  30 ,  86 ,  88 ,  90 ,  92 ,  94 ,  96 ,  98 , in which piston cylinder  30 ,  86 ,  88 ,  90 ,  92 ,  94 ,  96 ,  98  is arranged at least one piston  32 ,  87 ,  89 ,  91 ,  93 ,  95 ,  97 ,  99 , which piston  32 ,  87 ,  89 ,  91 ,  93 ,  95 ,  97 ,  99  is arranged to compress fluid  29  during rotation of the cylinder drum  28 , and that the cylinder drum  28  is arranged to discharge the fluid  29  to the propulsion chamber  6  in the discharge position of the piston  32 ,  87 ,  89 ,  91 ,  93 ,  95 ,  97 ,  99  via at least one opening  31 ,  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84  opening into the piston cylinder in order to produce an impulse in the tool  12 . 
     With an impulse machine is intended for example a drilling rig for rock drilling. 
     It is possible to combine that which has been mentioned in the different herein described optional embodiments within the scope of the following claims.