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RELATED APPLICATION DATA 
       [0001]    This application claims priority under 35 U.S.C. §119 to EP Patent Application No. 13154608.7, filed on Feb. 8, 2013, which the entirety thereof is herein incorporated by reference. 
       BACKGROUND 
       [0002]    The disclosure relates to a rock drilling unit, and particularly to an arrangement for changing drill rods in the rock drilling unit. The rock drilling unit includes a feed beam and a rock drilling machine arranged movably on the feed beam. The rock drilling machine has a shank for connecting drill rods to the drilling axis. Further, at least one retainer device is arranged on the feed beam. 
         [0003]    The disclosure further relates to a method of changing drill rods in the rock drilling unit. 
         [0004]    In mines and other work sites rock drilling rigs are used for drilling bore holes on rock surfaces. Typically the rock drilling rig includes one or more drilling booms which are provided with drilling units. In many cases drill holes having a greater length than one drill rod need to be drilled. Then two or more drill rods need to be connected to each other in order to form an extension rod. This is called extension rod drilling. Typically several drill rods are stored in a rod magazine which is arranged in the drilling unit. However, the rod magazine is large and heavy, whereby it may hamper the drilling. 
       SUMMARY 
       [0005]    An aspect of the invention is to provide a novel and improved rock drilling unit provided with change means and a method of changing drill rods. 
         [0006]    The rock drilling unit is provided with at least one clamp allowing one single drill rod at a time to be retained at a predetermined side position, which is parallel to the drilling axis and is located at a transverse distance from the drilling axis; and the retaining feature of the clamp is independent of the driving force external to the clamp. 
         [0007]    The method is characterized by supporting one single drill rod at a time at the side position by means of at least one clamp. 
         [0008]    The present rock drilling unit has at least one clamp device allowing one single drill rod at a time to be retained at a predetermined side position, which is parallel to the drilling axis defined by a drilling machine and is located at a transverse distance from the drilling axis. The clamp device includes at least one clamp for holding the drill rod. Further, the retaining feature of the clamp is operable without any driving force external to the clamp. Thus the clamp may be without any connection to a pressure fluid or electric circuit. 
         [0009]    An advantage of the disclosed solution is that the clamp is simple in structure and operation, whereby it is reliable and inexpensive. Since the clamp does not need any external driving power, it is operable while the drilling unit is shut down. Thereby it is safe to place a drill rod manually in the clamp or to remove it. 
         [0010]    According to an embodiment, the rock drilling unit is without any drill rod magazine or storage device for storing more than one single drill rod. Instead, the present solution relates to a holder which influences only one single drill rod at a time. Thanks to the disclosed solution, more than one drill rods can be drilled successively, and still, there is no need to provide the rock drilling unit with any conventional rod magazine. Thus, the rock drilling unit may be lightweight. The reach of a drilling boom may be dimensioned extensive when a lightweight rock drilling unit does not limit the range of the boom. 
         [0011]    According to an embodiment, the clamp is provided with an inside space for receiving a drill rod. The shape of the inside space may be substantially cylindrical, which is beneficial since the outer surfaces of the drill rods are typically cylindrical, too. The dimensions of the space enlarge when a drill rod is placed inside the space. Thus, the space has initial first dimensions and second dimensions when a drill rod is placed inside the space, the second dimensions being larger than the first dimensions. 
         [0012]    According to an embodiment, the clamp includes contact surfaces which are pressed against an outer surface of a retained drill rod when the rod is placed between the contact surfaces. Thanks to the continuous press force, the retained drill rod holds its position firmly and does not vibrate and cause noise. A further advantage is that outer dimensions of the drill rod may vary and the clamp still holds drill rods properly. 
         [0013]    According to an embodiment, the clamp is spring-actuated, comprising one or more spring elements for producing the needed press force. Because of the spring element, the clamp is independent and operable without any driving force external to the clamp. Further, the clamp adjusts itself automatically according to the outer dimensions of the retained drill rod. The spring may be spiral spring, leaf spring or any other suitable spring type. Alternatively, the spring actuation may be formed by a pressure-medium-operated actuator, such as a pressure air cylinder. 
         [0014]    According to an embodiment, the clamp is made of resilient material for producing the needed press force. Because of the spring actuation achieved by the resilient material, the clamp is independent and operable without any driving force external to the clamp. The resilient material may comprise polyurethane (PUR) or other plastic material, for example. Alternatively, the resilient material may comprise rubber or polymeric material. 
         [0015]    According to an embodiment, changing drill rods includes the following actions: connecting the drilling unit to an inoperational state; feeding the drill rod manually to the clamp when the drilling unit is off; and retaining the drill rod in the clamp by an internal spring force. 
         [0016]    According to an embodiment, at least two clamps are arranged at a distance from each other as seen in the longitudinal direction of the feed beam. This embodiment enables secure and stabile support for a retained drill rod. A first clamp and a second clamp may be located at distances from the distal ends of a feed beam. 
         [0017]    According to an embodiment, the clamp has a relatively large axial extent in the direction of the drill rod to be handled, whereby one single clamp may be sufficient to support and retain the drill rod. The clamp may be dimensioned to be relatively wide. This embodiment may be beneficial in situations when there is no space for several clamps. 
         [0018]    According to an embodiment, the clamp is supported to the feed beam by means of at least one support element. The support element may be solid or movable. 
         [0019]    According to an embodiment, the clamp is immovably supported to the feed beam by means of at least one support element. Thus, the clamp is stationary in the mentioned side position. 
         [0020]    According to an embodiment, the clamp is movable in the transverse direction of the feed beam from the side position towards the drilling axis. Thanks to this embodiment, the clamp can be extended closer to an operator, which facilitates placing drill rods in the clamp and removing the rod from the clamp. Safety and working conditions are also improved. 
         [0021]    According to an embodiment, the clamp is movable in the trans- verse direction of the feed beam from the side position to the drilling axis, and vice versa. 
         [0022]    According to an embodiment, the rock drilling unit includes a support arm connected to the feed beam by means of articulation. The clamp is arranged at a distal end portion of the support arm. The support arm is provided with a turning device for turning the support arm in the transverse direction relative to the feed beam from the side position to the drilling axis and vice versa. 
         [0023]    According to an embodiment, the rock drilling unit has at least one changing device. The changing device includes: a body connected movably to the feed beam; and gripping means allowing the drill rods to be gripped and released. Further, the changing device includes one or more transfer devices for moving the changing device in the transverse direction relative to the feed beam and positioning the gripping means at the side position and the drilling axis. The changing device may be controlled by the operator or it may execute the needed transfer operations under automatic control of one or more control units. The changing device may be connected to the feed beam by means of articulation, whereby the distal end of the changing device can be turned between the side position and the drilling axis. 
         [0024]    According to an embodiment, the rock drilling unit includes at least one changing device provided with openable and closable gripping jaws. The gripping jaws serve as gripping means so that rotation of gripped drill rods can be prevented when opening and closing connecting threads, for example. 
         [0025]    According to an embodiment, the clamp is arranged to support the drill rod at the side position and the changing device is arranged to move the drill rod between the side position and the drilling axis. 
         [0026]    According to an embodiment, the clamp is supported to the changing device, whereby it is transversally movable together with the changing device. Thus, changing drill rods may comprise the following actions: moving the drill rods between the drilling axis and the side position by means of a changing device arranged movably relative to the feed beam; and moving the clamp between the drilling axis and the side position together with the changing device. 
         [0027]    According to an embodiment, the clamp is arranged on the changing device pivotably so that the clamp can pivot relative to the body of the changing device. The clamp may have an initial position where it is kept by means of spring means. If necessary, the clamp may turn relative to the body of the changing device when the drill rod is handled. The spring means turn the clamp back to the original position after the external force directed to the clamp is terminated. An advantage of the pivoted connection is that it allows some inaccuracy in the transfer movements, and inaccuracy between the clamp and the drill rod. 
         [0028]    According to an embodiment, the clamp serves as gripping means of the changing device. 
         [0029]    According to an embodiment, the changing device includes the gripping jaws and the clamp. The gripping jaws serve as gripping means, whereas the clamp is mainly for holding the rod at the side position when the gripping jaws are open. The clamp allows the operator to place the drill rod in a correct position in the side position. The drill rod is held in that position until the operator leaves the vicinity of the drilling unit and switches the drilling unit to an operable state. Then the changing device is powered and the gripping jaws may be closed. The operator controls the operation of the changing device from a safe distance. 
         [0030]    According to an embodiment, the rock drilling unit includes at least one additional support, which is rigidly fastened to a feed beam. The additional support may serve as an aid to guide a drill rod. The additional support is located in such a way that it is at a distal end of the drill rod. The additional support may include a protrusion so that a tubular drill rod can be first pushed around the protrusion. Secondly, the drill rod can be pushed laterally towards the one or more clamps for retaining the drill rod. The additional support facilitates handling of long drill rods. 
         [0031]    According to an embodiment, the drilling unit includes several clamps arranged in such a way that at least two drill rods can be retained. However, each clamp influences one drill rod only. This embodiment allows placing 2 to 4 drill rods in the vicinity of drilling axis without a need to provide the drilling unit with a complicated, large-sized and heavy rod magazine. 
         [0032]    Above-disclosed embodiments can be combined in order to form suitable solutions provided with necessary features. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0033]    Some embodiments are described in more detail in the accompany- ing drawings, in which: 
           [0034]      FIG. 1  is a schematic side view showing a rock drilling unit. 
           [0035]      FIGS. 2   a  and  2   b  are schematic views showing two alternative rock drilling units at position A-A. 
           [0036]      FIG. 3  is a schematic side view showing a clamp formed of resilient material. 
           [0037]      FIG. 4  is a schematic side view showing a clamp provided with a spring element. 
           [0038]      FIG. 5  is a schematic view showing a rock drilling unit and two transfer devices arranged on a feed beam. 
           [0039]      FIG. 6  is a schematic view showing a transfer device which is provided with a clamp. 
           [0040]      FIG. 7  is a schematic view showing a drill rod supported to the drilling axis by means of a clamp and gripping jaws of a transfer device. 
           [0041]      FIG. 8  is a simplified chart showing features relating to changing of drill rods according to principles disclosed above. 
       
    
    
       [0042]    For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements. 
       DETAILED DESCRIPTION 
       [0043]      FIG. 1  shows a rock drilling unit  1  which may be connected by means of a boom  3  to a movable carrier, which is not shown. The drilling unit  1  includes a feed beam  2  provided with a rock drilling machine  4  that can be moved on the feed beam  2  by means of a feed device  5 . The rock drilling machine  4  has a percussion device  6  for generating impact pulses on a tool  7 , and a rotating device  8  for rotating the tool  7 . 
         [0044]    At a drilling site, one or more drill holes are drilled with the drilling unit  1 . The drill holes may be drilled in the vertical direction, as shown in  FIG. 1 . 
         [0045]    When a drill hole having a length longer than one single rod needs to be drilled, then an extension rod system is formed by connecting two or more drill rods successively. Typically the extension system formed of two drill rods is sufficient. Then, the tool  7  includes a drill bit  9 , a first drill rod  10  and a second drill rod  11 . At the beginning of drilling the drill bit  9  is connected to the distal end of the first drill rod  10 , and the opposite end of the first drill rod  10  is connected to a shank  12  of the drilling machine  4 . After the drilling of the first drill rod  10  is completed, the second drill rod  11  is connected to the shank  12  and the first drill rod  10 . Between the first and second rods  10 ,  11 , between the first rod  10  and the drill bit  9 , and between the second rod and the shank  12 , there are connecting means, such as connecting screws  13 . The connecting screws  13  can be closed and opened by means of the rotating device  8 . When connecting and disconnecting components of the tool  7 , a retaining device  14  may be utilized for preventing rotation of tool components. The retaining device  14  is mounted on the feed beam  3  so that it is located on the drilling axis D. The retaining device  14  has retaining jaws or corresponding means for gripping the tool component. The retaining device  14  further includes one or more actuators for generating the needed retaining force. 
         [0046]    The rock drilling unit  1  is provided with one or more clamps  15 , which are arranged at the transverse direction from the drilling axis D. As it is shown in  FIG. 1 , one single clamp  15  may be adequate to hold a drill rod  11  a at a side position  16  in a parallel direction relative to the drilling axis D. The clamp  15  is dimensioned relatively wide, whereby sufficient support is achieved for the second drill rod  11   a  placed in the clamp  15 . Alternatively, two or more clamps may be arranged at a selected distance from each other for supporting the same drill rod  11   a  in the side position  16 . The second drill rod  11   a  can be placed in the clamp  15  manually. During the manual operation, the rock drilling unit  1  may be shut down for safety reasons. The clamp  15  can operate independently of the drilling unit  1 , whereby the drill rod  11   a  may be left in the clamp  15 . Thereafter the operator may close a feasible safety cage and switch on the rock drilling unit  1  by means of a control unit  17 . The operator controls the drill rod change operations manually by means of the control unit  17 , or alternatively the control unit  17  may have one or more automatic control programs for controlling the drill rod changing measures. 
         [0047]      FIGS. 2   a  and  2   b  illustrate two alternative rock drilling units seen from their front sides. The clamp  15  may be supported on the feed beam  2  by means of a support element  18 . In  FIG. 2   a  the support element  18  is solid. For clarity reasons,  FIG. 2   a  does not show a transfer device by means of which the second drill rod  11   a  can be moved from the side position  16  to the drilling axis D. However, the transfer device may be an articulated manipulator, robot arm or any other suitable device. In  FIG. 2   b  the support element  18  can be turned T from the side position  16  towards the drilling axis D, and vice versa. It is possible to transfer the second drill rod  11  a to the drilling axis D, or alternatively, it is possible to turn T the support element  18  only by a desired distance towards the drilling axis D and simultaneously closer to the operator  19  on the opposite side of the feed beam  2 . In the latter case, the clamp  15  is moved within the reach of the operator, whereby handling of the drill rod is facilitated. The support element  18  is connected to the feed beam  2  by means of one or more pivots  20 . 
         [0048]      FIG. 3  discloses a clamp  15  manufactured of resilient material, such as polymeric material. The clamp  15  has a space  21  where a drill rod  11  can be pushed through an inlet opening or slot  22 . Surfaces of the space  21  serve as contact surfaces against the drill rod  11 . When the rod  11  is inserted into the clamp  15 , the resilient material will allow the clamp  15  to form according to the drill rod  11 , as illustrated by arrows. 
         [0049]      FIG. 4  discloses an alternative clamp  15  which includes two clamp arms  23   a  and  23   b  connected to each other by means of a pivot  24 . The clamp arms  23   a ,  23   b  are pressed towards each other by means of one or more spring elements  25 . The clamp arms  23   a ,  23   b  are provided with curved contact surfaces which form together a space  21  for a drill rod  11 . When the rod  11  is inserted into the clamp  15 , the clamp arms  23   a ,  23   b  will part from each other under the influence of the spring element  25 , as illustrated by arrows. 
         [0050]      FIG. 5  shows a rock drilling unit  1  provided with two changing devices  26  arranged on a feed beam  2  and located at an axial distance from each other. The changing device  26  may be arranged pivotably on the feed beam  2 , whereby it can be turned between the drilling axis D and the side position  16 . The changing device  26  may comprise gripping means or jaws  27  for gripping drill rods  11 . Further, a clamp  15  may be arranged on the changing device  26 , whereby the clamp  15  is arranged to move together with the changing device  26  between the drilling axis D and the side position  16 . 
         [0051]    The rock drilling unit  1  may further include an additional support  28 , which may be mounted on the feed beam  2 . The additional support  28  may be a solid object which may facilitate manual handling of the drill rod and especially serve as a suitable guide for the drill rod when it is placed in the clamp  15 . 
         [0052]      FIG. 5  further shows an example of a structure of a retaining device  14 . The retaining device  14  may comprise retaining jaws  29   a ,  29   b  which are moved by a hydraulic cylinder  30 . 
         [0053]      FIG. 6  discloses a changing device  26  on a side position  16 . Gripping jaws  27   a ,  27   b  are open and a drill rod  11  is in a clamp  15 . A body  31  of the changing device  26  may be turned relative to a pivot  32  by means of a turning cylinder  33 . Further, the clamp  15  may be arranged to the body  31  via a turning member  34 . The turning member  34  has a spring element  35  keeping the clamp  15  in the initial position. The spring element  35  can be seen in  FIG.  7 . 
         [0054]    In  FIG. 7  the changing device  26  is turned to the drilling axis D and a drill rod  11  is supported by gripping jaws  27   a ,  27   b . Also, the clamp  15  is still around the drill rod  11 . After the drill rod  11  has been coupled to a shank of a drilling machine, the gripping jaws  27   a ,  27   b  are opened and the changing device  26  is turned back to a side position. As the changing device  26  is turned back, the clamp  15  releases the drill rod  11 . Similarly, when the changing device  26  is turned towards a drill rod situated in the drilling axis D, the clamp  15  becomes automatically positioned around the drill rod. 
         [0055]    In  FIG. 8 , it is shown a simplified chart of steps relating to changing of drill rods, as discussed above. 
         [0056]    Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.

Summary:
A rock drilling unit and a method of changing drill rods in a rock drilling unit is disclosed. The rock drilling unit includes a feed beam, a retainer device, a rock drilling machine and at least one clamp. The clamp is operable without driving force of the drilling unit. The clamp has a space for receiving one single drill rod. The clamp is positioned at a side position, which is parallel to a drilling axis and is at a transfer distance from the drilling axis.