Abstract:
A percussion drill, and methods of using the same, including a shank in mechanical alignment with a piston-hammer and a valve in fluid communication with the piston-hammer. The percussion drill further includes an internal hydraulic dampening system for reducing the velocity of the piston-hammer when the shank is forward of a power position relative to the velocity of the piston-hammer when the shank is in a power position. Preferably, the internal hydraulic dampening system includes mechanical alignment of a portion of the piston-hammer with a port in fluid communication with the valve, operable to reduce fluid flow into an area surrounding the valve when the piston-hammer is forward of its position relative to its normal operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/034,472 filed Mar. 6, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a pressure fluid actuated reciprocating piston-hammer percussion rock drill including an internal dampening system for reducing the power output of the piston-hammer when the shank is forward of the impact position. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the art of pressure fluid actuated reciprocating piston-hammer percussion rock drills and similar percussion tools, it is known to provide the general configuration of the tool to include a sliding sleeve type valve for distributing pressure fluid to effect reciprocation of a fluid actuated piston-hammer. There are many applications of these types of drills including, for example, drilling holes having a diameter ranging from about 4 centimeters to about 30 centimeters. 
         [0004]    Examples of such drills are generally disclosed and claimed in U.S. Pat. No. 5,680,904, issued Oct. 28, 1997. The percussion rock drill disclosed in the &#39;904 patent includes opposed sleeve type valves disposed on opposite reduced diameter end portions of the reciprocating piston-hammer, respectively, for movement with the piston-hammer and for movement relative to the piston-hammer to distribute pressure fluid to opposite sides of the piston-hammer to effect reciprocation of same. Another advantageous design of a fluid actuated percussion rock drill is disclosed and claimed in U.S. Pat. No. 4,828,048 to James R. Mayer and William N. Patterson. The drill described and claimed in the &#39;048 patent utilizes a single sleeve type distributing valve disposed at the fluid inlet end of the drill cylinder. 
         [0005]    In such drills the shank may be moved forward, out of its power position, when drilling is no longer required. Such is the situation when the drill is being pulled out of the hole. During this time, however, the sliding sleeve type valve permits the high pressure fluid to continuously drive the piston-hammer. Accordingly, unless impeded, a front landing of the piston-hammer will strike the forward moved shank. Moreover, as the shank is moved forward there is additional length in which the piston-hammer may gain speed. Thus, in some cases the front landing of the piston-hammer strikes the forward moved shank with a force greater than that experienced during operational drilling. Such excessive impact causes components such as the shank to wear unnecessarily. Accordingly, it is desirable to reduce or eliminate such excessive impact. Prior methods of doing so having included the use of shock absorbers, cushions and/or springs to absorb the energy of the piston-hammer. These devices and methods, however, wear themselves and require replacement. 
         [0006]    Therefore, what is needed is an improved internal dampening system that is wear resistant. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention provides an improved pressure fluid actuated reciprocating piston-hammer percussion tool, particularly adapted for rock drilling. The invention contemplates, in particular, the provision of an internal dampening system for reducing the velocity of the piston-hammer when the shank is forward of a power position relative to the velocity of the piston-hammer when the shank is in a power position. 
         [0008]    In another important aspect of the present invention the piston-hammer includes a front landing, a trip section, and a rear landing; the trip section has a forward shoulder, a center area, and a back shoulder; and the center area is of a lesser diameter than the diameter of the forward shoulder and back shoulder. 
         [0009]    In a still further important aspect of the present invention, the fluid communication between the valve and piston-hammer includes at least a first and second port; the internal hydraulic dampening system includes mechanical alignment of the center area and back shoulder of the trip section with the second port to reduce fluid flow into the valve when the piston-hammer is forward of its position relative to its normal operation. 
         [0010]    Those skilled in the art will further appreciate the above-mentioned features and advantages of the invention together with other superior aspects thereof upon reading the detailed description which follows in conjunction with the drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]    The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness, wherein: 
           [0012]      FIG. 1  is a schematic view of a piston-hammer in contact with a shank while the shank is in a power position; 
           [0013]      FIG. 2  is a schematic view of the piston-hammer moving away from the shank while the shank is in a power position; 
           [0014]      FIG. 3  is a schematic view of the piston-hammer moving toward the shank while the shank is in a power position; 
           [0015]      FIG. 4  is a schematic view of the piston-hammer moving toward the shank while the shank is out of a power position; 
           [0016]      FIG. 5  is a schematic view of the piston-hammer moving at a forward most point while the shank is out of a power position; and 
           [0017]      FIG. 6  is a schematic view of the piston-hammer moving and shank in an intermediate position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    In the description which follows like parts are marked throughout the specification and drawing with the same reference numerals, respectively. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. 
         [0019]    Referring to  FIG. 1 , there is illustrated a schematic of one preferred embodiment of a percussion drill  100 . The percussion drill  100  preferably includes a piston-hammer  110  and a shank  115  in mechanical alignment therewith, as well as a valve  150  in fluid communication with the piston-hammer  110 . The piston-hammer  110  preferably includes a front landing  120 , a trip section  125 , and a rear landing  130 . And, the trip section  125  itself preferably includes a front shoulder  135  a center area  140  and a back shoulder  145 . Preferably, the piston-hammer  110  and its component segments are cylindrical. Preferably, the front shoulder  135  and the back shoulder  145  are of a substantially uniform diameter, and the center area  140  is of a smaller diameter as compared to the front shoulder  135  and back shoulder  145 . In an embodiment, the front shoulder  135  and the back shoulder  145  are of a substantially uniform height, and the center area  140  is of a smaller height as compared to the front shoulder  135  and back shoulder  145 . 
         [0020]    The piston-hammer  110  is disposed within a first housing  160 , and the valve  150  is disposed within a second housing  170 . The housings may be of any shape. In a preferred embodiment, the first housing  160  has at least a first port  200 , a second port  205 , a third port  215 , and a fourth port  220  and the second housing has at least a fifth port  225 , a sixth port  230 , and a seventh port  235 . The ports serve to allow fluid flow, preferably high pressure fluid, to enter and exit the housings and drive the piston-hammer  110  and valve  150 . 
         [0021]    The high pressure fluid may be water, oil, glycol, invert emulsions, and the like fluids of at least about 170 atm. In various embodiments, the high pressure fluid may be at least about 68 atm, alternatively at least about 136 atm, alternatively at least about 204 atm, alternatively at least about 272 atm, and alternatively at least about 340 atm. Preferably, the high pressure fluid is hydraulic oil at about 170 atm. 
         [0022]      FIGS. 1 ,  2 , and  3  illustrate the shank  115  in a normal or power position.  FIGS. 4 and 5  illustrate the shank  115  outside of its normal or power position.  FIG. 6  illustrates the shank in an intermediate position. 
         [0023]    Continuing with reference to  FIG. 1 , the piston-hammer  110  is at its forward most position and the front landing  120  is in contact with the shank  115 . The center area  140  of the trip section  125  bridges the second  205  and third  215  ports allowing fluid to flow into the seventh port  235 . The fluid flow into the seventh port  235  increases the pressure differential within the valve  150  and causes it to move in a direction toward the shank  115  within the second housing  170 . At the same time, the piston-hammer  110  moves away from the shank  115 . As the trip section  125  moves away from the shank  115  the center area  140  no longer bridges the second  205  and third  215  ports, and fluid is cut off from the second port  205 . 
         [0024]    Referring to  FIG. 2 , the movement of the valve  150  in a direction away from the shank  115  blocks the fluid flow between the sixth port  230  and the first port  200 . The movement of the valve  150  in a direction away from the shank  115  opens the fluid flow between fifth port  225  and the first port  200 . This will slow the movement of the piston-hammer  110  until it comes to a stop. Thereafter, the pressure differential within the first housing  160  against the piston-hammer  110  will cause the piston-hammer  110  to move toward from the shank  115 , as shown in  FIG. 3 . In an embodiment, the force differential sufficient to actuate the piston-hammer  110  is at least about 111 newtons, preferably the force differential is at least about 222 newtons. In an embodiment, the force differential sufficient to actuate the piston-hammer  110  is at least about 2.22 kilonewtons. 
         [0025]    Referring to  FIG. 3 , the movement of the valve  150  toward the shank  115  allows fluid to flow into the first port  200 . When the pressure differential between the rear landing  130  of the piston-hammer  110  and the front landing  120  of the piston-hammer  110  is great enough, the piston-hammer  110  will move toward the shank  115 . The process will then repeat. Preferably, piston-hammer  110  impacts the shank  115  at least 2500 times in one minute. 
         [0026]    Referring to  FIG. 4 , the shank  115  is moved forward, and out of normal striking position, as shown with respect to  FIG. 1 . In this forward position, however, the back shoulder  145  of the trip section  125  impedes at least a portion of the fluid flow through the second  205  port. The impediment caused by the back shoulder  145  of the trip section  125  preferably decreases the fluid flow into the seventh  235  port an amount sufficient to slow the movement of the valve  150  toward the shank  115 . In this embodiment, the valve  150  moves more slowly toward the shank  115  than in power operation. By movement of front shoulder  135  of the trip section  125  into a dash pot  180 , i.e., a restricted fluid area, the forward movement of the piston-hammer  110  is slowed. 
         [0027]    In an embodiment, the back shoulder  145  causes at least a 10 percent decrease in the fluid flow into the seventh  235  port. In an alternative embodiment, the back shoulder  145  causes at least a 20 percent decrease in the fluid flow into the seventh  235  port. In preferred embodiment, the back shoulder  145  causes at least a 50 percent decrease in the fluid flow into the seventh  235  port. In a still further preferred embodiment, the back shoulder  145  causes at least a 70 percent decrease in the fluid flow into the seventh  235  port. 
         [0028]    Referring to  FIG. 5 , the shank  115  is illustrated forward of power position, and the piston-hammer  110  is in its most forward position. In this manner, the back shoulder  145  of the trip section  125  blocks fluid flow into the second port  205 . Thus, no fluid flows into the seventh port  235 , and the valve  150  remains in its most rearward position, or is alternatively moved to its most rearward forward position. In either event, in this position the valve  150  permits fluid to flow continuously into the first port  200 , and thus the piston-hammer  110  is held in its most forward position. 
         [0029]    Preferably, the dash pot  180  contains high pressure fluid in constant fluid communication with the forward landing  120 . Thus, the dash pot  180  serves to balance the pressure on the front seal between the front landing  120  and the front shoulder  135  of the trip shoulder  125 . 
         [0030]    Referring to  FIG. 6 , the shank  115  is pushed back into power position. Accordingly, the fluid communication between the third port  215  and the second port  205  is opened. Thus, permitting the normal hammer oscillation to resume as described above. 
         [0031]    The construction and operation of the drill  100 , and associated parts, may be carried out using conventional materials and engineering practices known to those skilled in the art of hydraulic percussion rock drills and the like. Although preferred embodiments of the invention have been described in detail herein, those skilled in the art will recognize that various substitutions and modifications may be made to the invention without departing from the scope and spirit of the appended claims.