Abstract:
A rock splitter of oil hydraulic piston type includes a housing having a plurality of cylinder chambers on the upper portion and first and second paths communicated with the cylinder chambers for supplying and discharging oil; a piston in the cylinder chamber of the housing; and a cap capable of a vertical movement, the cap being connected to the upper surface of the housing in such a manner that the inner surface thereof is in contact with the upper surface of the housing. The cap moves vertically depending on the movement of the piston. The rock splitter further comprises: a cylinder detachably mounted inside the cylinder chamber of the housing; a collapsible member having a locking member detachably mounted in the cylinder chamber, a plurality of extension members capable of a vertical extension; and an elastic member supporting the lower end of a central extension member. The entire front surface area of the cap touches the rock to maximize the power applied to the rock. Repair to the cylinder is effected by replacing only the cylinder.

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a rock splitter of oil hydraulic piston type, and more particularly, a rock splitter of oil hydraulic piston type, in which a piston inserted into a hole perforating through rock rises and falls depending on a supply of oil. 
     2. Description of Prior Art 
     In general, a rock splitter of oil hydraulic piston type splits rock through a procedure by which a housing is inserted into a hole perforating through the rock and a piston rises and falls to split the rock when oil is supplied to the housing. 
     Referring to the drawings, the conventional rock splitter will be described hereinafter. 
     FIG. 1 is an exploded perspective view of the conventional rock splitter. FIG. 2 is a sectional view of an assembled state of the conventional rock splitter before operation. FIG. 3 is a sectional view of an assembled state of the conventional rock splitter after operation. 
     As shown in the drawings, The rock splitter  100  includes a housing  110  for inserting into a hole perforating through rock. 
     The housing  110  has an arch-shaped surface at the lower portion thereof for preventing the formation of gaps between the hole formed in the rock and the housing  110 . The housing  110  further has a plurality of cylinder chambers  111  formed in the upper portion of the housing  110  at prescribed intervals, and has first and second paths  114  and  115  formed at one side portion thereof for supplying and discharging oil. 
     When the first path  114  is supplied with oil, a piston  130 , which will be described hereinafter, is extended, and when the second path  115  is supplied with oil, the piston  130  is retracted. 
     Each of the cylinder  111  of the housing  110  includes a folding and unfolding means  120  capable of folding and unfolding to prevent excessive oil from being supplied inside the cylinder chamber  111  of the housing  110 , thereby preventing damage to the housing  110  by overload. The folding and unfolding means  120  includes a fixing member  121  coupled with piston  130 , a locking member  123  having a threaded portion  124  formed on the outer surface of the locking member  123  for engaging to a threaded portion  113  formed on the inner surface of the cylinder chamber  11 , and a connecting member  122  for connecting the fixing member  121  to locking member  123 . 
     The piston  130  is located on the folding and unfolding means  120  which is inserted into the cylinder chamber  111 . The piston  130  includes a stepped portion  132  formed on a lower portion of the outer circumference thereof, a pair of grooves  133  formed on the outer surface of the stepped portion  132 , first and second O-shaped rings  134  and  135  inserted into grooves  133  for preventing the outflow of oil from the cylinder chamber  111 , and a hole  131  formed upper center portion of the piston  130  in which a screw  140  is inserted for connecting the piston  130  to the fixing member  121  of the folding and unfolding means  120 . 
     In order to seal the hole  131  after screw  140  is inserted therein, a sealing member  150  is mounted on the end of the hole  131 . 
     In order to prevent separation of the rising piston  130  from the cylinder chamber  111 , a threaded portion  161  of a cylinder chamber  160  is engaged to a threaded connecting portion  112  of the cylinder chamber  111 . 
     The cylinder chamber  160  includes a sealing member  162  which is inserted into the upper end portion from the lower end portion preventing the inflow of alien substances into the cylinder chamber  111  and a third O-shaped ring  163  inserted within the cylinder cover  160  for preventing the outflow of oil from cylinder chamber  111 . 
     The piston  130  is formed in an arc shape at the upper end surface to facilitate maximum contact with the rock. 
     The conventional rock splitter  100  with the above structure is assembled into the configuration depicted in FIG.  2  through the following procedure. 
     The folding and unfolding means  120  comprised of the fixing member  121 , the connecting member  122  and locking member  123  is inserted into cylinder chamber  111  of housing  110 . The threaded portion  124  of the folding and unfolding means  120  engages the threaded portion  113  formed on the inner surface of cylinder chamber  111 . The screw  140  is inserted into hole  131  of the piston in which the first and second 0-shaped rings  134  and  135  are inserted. The screw  140  is fixed to the fixing member  121  of the folding and unfolding means  120 , so that the piston  130  is connected with the folding and unfolding means  120 . The hole  131  of the piston  130  is sealed by this sealing member  150 . After that the sealing member  162  and the third 0-shaped ring  163  fasten to the cylinder cover  160 . The threaded portion  161  of the cylinder cover  160  connects to the threaded connecting portion  112  of the cylinder chamber  111 , which is located on its inner circumference. 
     FIG. 2 a sectional view of the assembled state of the conventional rock splitter before operation. FIG. 3 a sectional view of the assembled state of the conventional rock splitter after extension of the piston  130  from the cylinder chamber  111 . 
     When oil is supplied through the first path  114  of the housing  110 , the supplied oil flows into cylinder chamber  111  through gaps formed between the members  121 ,  122  and  123  of the folding and unfolding member  120 . 
     The piston  130  inserted into the cylinder chamber  111  extends due to the rising oil pressure and the extending piston  130  discharges the oil supplied inside the cylinder chamber  111  between the piston  130  and the cylinder cover  160  through the second path  115  of the housing  110 . 
     Meanwhile, the pressure on the rock caused by the extending piston  130  splits the rock. After that, the folding and unfolding means  120  (including the fixing member  121 , the connecting member  122  and the locking member  123 ) is expanded by the fixing member  121  connected to the piston  130  as shown in FIG.  3 . 
     In the expanded state of the folding and unfolding means  120 , as shown in FIG. 3, the gaps  125  (See FIG. 2) formed between members  121 ,  122  and  123  are sealed, so that oil supplied through the first path  114  is no longer supplied to cylinder chamber  111 , thereby limiting the amount of oil supplied inside the cylinder chamber  111 . 
     After splitting the rock, when oil is supplied to the second path  115  of the housing  110 , the oil flows into the cylinder chamber  111  between the cylinder cover  160  and the piston  130 , and thereby the rock splitter  100  is returned to its original condition. At this time, the expanded folding and unfolding means  120  is folded by retraction of the piston  130  such that the gaps  125  are again formed between the members  121 , 122  and  123 . The oil, which is supplied within the cylinder  111  of the lower end of the piston  130  through the first path  114 , is discharged through the gaps  125  to the first path  114 , so that the rock splitter  100  is returned to its original condition. 
     However, because the piston  130  of the conventional rock splitter  100  extends inside the cylinder chamber  111  of the housing  110  by virtue of the high pressure of the oil supplied through the first and second paths  114  and  115 , the piston  130  often deviates from its original position inside the cylinder chamber  111  due to the repetitive extension and retraction operation. The deviated piston  130  scratches the inner surface of the cylinder chamber  111  when the piston extends, and thereby the cylinder chamber  111  is damaged and oil leakage occurs through the gap  125  formed between the cylinder  111  and the piston  130 . Therefore, the rock splitter  100  cannot perform its function, at which time the housing  110  must be replaced. Therefore, there are several disadvantages which decrease efficiency of work, while component expenses and maintenance fees increase. 
     It was explained that the piston  130  has the arch-shaped surface for maximizing the contact area to the rock. However, since the contact area is limited to the area of the piston  130 , it is restricted to maximize the power applied to the rock. 
     When the folding and unfolding means  120  spreads with the rising piston  130 , as shown in FIG. 3, the fixing member  121  is forcibly inserted into the connecting member  122 , and the connecting member  122  into the locking member  123 . At this time, too much power is required to fold the members  121 ,  122  and  123 , so that the members  121 , 122  and  123  do not fold smoothly and the falling operation of the piston  130  is not performed smoothly. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to overcome the disadvantages in the prior art by providing a rock splitter of oil hydraulic piston type, which includes an extra cylinder and cap, such that when the cylinder is damaged only the damaged cylinder is replaced, thereby improving efficiency of the work and reducing the maintenance fees. 
     It is another object of the present invention to provide a rock splitter of oil hydraulic piston type, which has a cap of an arc shape, such that the entire front surface of the cap touches the rock, thereby increasing the contact area to the rock and maximizing the power applied to the rock. 
     It is another object of the present invention to provide a rock splitter of oil hydraulic piston type, in which a connecting structure of members of a folding and unfolding means is improved, so that when returning to its normal state after operation, the collapsible member can be easily folded to its original condition, thereby preventing malfunction of the folding and unfolding means. 
     The foregoing objects are accomplished in one embodiment by providing a rock splitter of oil hydraulic piston type, which comprises a housing having a plurality of cylinder chambers formed on the upper portion and first and second paths communicated with the cylinder chambers for supplying and discharging oil; a piston inserted into the cylinder chamber of the housing, the piston rising and falling depending on the inflow of oil; and a cap being capable of vertical movement, the cap being connected to the upper surface of the housing in such a manner that the inner surface thereof is in contact with the upper surface of the housing, the cap moving vertically depending on the movement of the piston. The rock splitter further comprises: a cylinder detachably mounted inside the cylinder chamber of the housing in a sealing state; a collapsible member having a locking member detachably mounted in the cylinder chamber of the lower end of the piston, a plurality of members capable of a vertical extension, which are connected inside the locking member, inner and outer circumferences of the members having a gap for flowing the oil, and an elastic member supporting the lower end of the central member of the members and providing the elasticity to contacting the upper end of the member to the lower surface of the piston; and a plurality of stepped portions formed on the inner and outer circumferences of the members, each upper surface or lower surface of the stepped portion being in close contact with each lower surface or upper surface thereof to stop the gaps between the members and to prevent the flow of oil when the collapsible member spreads completely. 
     The cap is moveably mounted on the piston and has a pair to guide holes formed on opposite sides thereof. The housing has a pair of guide pins, which are formed on opposite sides thereof and slidingly inserted into the guide holes. 
     The cylinder includes a concave portion formed along the entire outer circumference thereof and communicated with the second path of the housing and a plurality of oil paths formed within the concave portion for allowing the oil supplied to the second path of the housing to flow into the cylinder. The piston has a concave portion formed on the upper end of a stepped portion thereof, the concave portion forming a space between the cylinder and the piston for allowing the oil to flow into the cylinder through the oil paths easily and for allowing the oil pressure to be applied to the stepped portion of the piston. 
     A plurality of rings are rearranged on the outer and inner surfaces of the cylinder and on the outer surface of the piston to maintain the sealing state between the cylinder chamber and the cylinder between the cylinder and the piston. Wear rings are arranged on the outer surface of the piston and on the inner surface of the cylinder to prevent lateral movement of the piston when the piston rises. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
     FIG. 1 is an exploded perspective view of a conventional rock splitter; 
     FIG. 2 is a sectional view of the conventional rock splitter before operation; 
     FIG. 3 is a sectional view of the conventional rock splitter after operation; 
     FIG. 4 is an exploded view of the rock splitter according to the present invention; 
     FIG. 5 is a sectional view of the rock splitter according to the present invention before operation; 
     FIG. 6 is a sectional view of the rock splitter according to the present invention after operation; 
     FIG. 7 a  is a view of the folding and unfolding means in a folded state and 
     FIG. 7 b  is a view of the folding and unfolding means in an unfolded state. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described in detail hereinafter with reference to the accompanying drawings, wherein the same reference characters designate corresponding parts throughout several views. It is to be understood that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting in its scope. 
     FIG. 4 is an exploded view of the rock splitter according to the present invention; FIG. 5 is a sectional view of the rock splitter before operation; FIG. 6 is a sectional view of the rock splitter after operation. FIG. 7 a  is a view of the folding and unfolding means of the present invention in a folded state, and FIG. 7 b  is a view of the folding and unfolding means in an extended state. 
     As shown in the drawings, a rock splitter  2  of oil hydraulic piston type includes a housing  10  which has an arch-shaped lower surface and a plurality of concave cylinder chambers which has threaded portions  12  and  13  on its upper side. 
     The housing  10  further includes first and second paths  14  and  15  formed on a side surface thereof and communicated with the cylinder chambers  11  for supplying and discharging oil, and a pair of guide pins  16  protruding from opposite portion thereof. 
     A folding and unfolding means  30 , which is comprised of a fixing member  33 , a connecting member  32  and a locking member  31 , is inserted into each cylinder chamber  11 . The threaded portion  13  of the cylinder chamber  11  engages a threaded portion  31 , and thereby the folding and unfolding means  30  is detachably mounted to the cylinder chamber  11 . When the folding and unfolding means  30  is connected to the cylinder chamber  11 , the folding and unfolding means  30  is inserted into the cylinder chamber  11  through the center of an elastic member  20  of a spring. The elastic member  20  is substantially formed in a conical shape wherein the upper end portion with a small diameter is in contact with the lower end of the fixing member  33  of the folding and unfolding means  30  and a lower end portion with a large diameter is placed in the cylinder chamber  11  in a compressed state. 
     As shown in FIG. 7 a,  the folding and unfolding member  30  has gaps  30   a  formed between the members  31 ,  32  and  33  for passing oil therethrough. When the folding and unfolding means  30  is expanded, the gaps  30   a  are sealed as follows. The locking member  31  has a stepped portion  31  bent inward at the upper portion. The connecting member  32  has a stepped portion  32   a  bent inward at the upper portion and a stepped portion. Also, the fixing member  33  has a stepped portion  31   a  bent outward at the lower portion. When the folding and unfolding means  30  is expanded, the stepped portions  31   a,    32   a,    32   b,    33   a  of the members  31 ,  32 , and  33  are in contact with each other to thereby seal the gaps  30   a  between the members  31 , 32 ,and  33 . 
     In the meantime, a hollow cylinder  50  is detachably mounted on the folding and unfolding means  30  inside the cylinder chamber  11  by engaging a threaded portion  51  formed on the outer circumference of the hollow cylinder  50  to the threaded portion  12  of the cylinder chamber  11 . The cylinder  50  has a plurality of rings on the inner and outer circumferences for sealing, an upper grove  54  and a lower grove  55 . 
     In the upper groove  54  are a back-up  56  for preventing the outflow of oil and an O-shaped ring  57  for sticking the back-up ring  56  to the upper end of the upper groove  54 . In the lower groove  55 , an O-shaped ring  62  is located between two back-up rings  63 . The back-up rings  63  are stuck to the upper and lower end of the lower groove  55  by the elasticity of the O-shaped ring  62 , thereby preventing any oil leakage. 
     The rings inserted into the inner circumference the cylinder  50  are comprised of a (1) scraper  61  for preventing the entrance of alien substances from the outside into cylinder  50 , (2) a step seal  59  arranged at the inner lower portion apart from the a scraper  61  through the center of an O-shaped ring  60  for preventing the outflow of oil from cylinder  50 , and (3) a wear ring  58  attached to a piston  40  by the resilient force of the O-shaped ring  60  and arranged at the inner lower portion apart from the step seal  59  for preventing lateral movement of the piston  40  which extends and retracts within the cylinder  50 . 
     The wear ring  58 , which is made of a solid material resistive to contraction, is provided not to the seal but to guide the lifting of the piston  40 , and to prevent lateral movement of the piston  40 . 
     The piston  40  has a concave portion  52  formed on the outer circumference and communicated with the second path  15  of the housing  10 . The concave portion  52  has a plurality of oil paths  53  for allowing the oil provided to the second path  15  to flow into the cylinder  50 . 
     As shown in FIG. 4, the piston  40  is arranged inside the cylinder  50 . The piston  40  has a stepped portion  41  formed at the lower portion of the outer circumference thereof and a plurality of grooves  43  and  44  formed at the outer circumference of the stepped portion  41 . 
     A gliding ring  46  is inserted into the upper grove  43  through the center of an O-shaped ring  45  to prevent the oil leakage between the cylinder  50  and the piston  40 . The gliding ring  46  is closely attached to the inner surface of the cylinder  50  by the resilient force of the O-shaped ring  45 . A wear ring  47  is inserted into the lower groove  44  to guide stable vertical movement of the piston  40  without any lateral movement. 
     The oil supplied to the second path  15  of the housing  10  flows into the cylinder through the oil paths  53  of the concave portion  52  of the cylinder  50 , which causes the piston  40  to retract. Therefore, a prescribed space is formed between the cylinder and the piston  40  to allow the oil to flow into the cylinder  50  easily. In order to easily apply the oil pressure, which flows into the cylinder  50 , to the stepped portion  41  of the piston  40 , a concave portion  42  is formed along the outer upper circumference of the stepped portion  41 . 
     The rock splitter  2  with the above structure includes an arc-shaped cap  70  which is arranged in the upper portion of the piston  40 . Since the cap  70  is formed in the arc shape, the entire front surface of the rock splitter  2  can touch the rock, thereby maximizing the power applied to the rock. The cap  70  has a pair of guide holes  71  formed vertically on the opposite sides of the cap  70  for inserting the guide pins  16  of the housing  10 . 
     When the piston  40  with the arc-shaped upper surface is in contact with the inner surface of the cap  70 , the cap  70  rises, and when the piston  40  retracts, the cap  70  falls by the force of gravity. 
     The rock splitter  2  is assembled as follows. After the large diameter portion of the elastic member  20  is seated in the cylinder chamber  11  of the housing  10 , the fixing member  33  of the folding and unfolding means  30  is arranged on the upper end of the elastic member  20  in the cylinder chamber  11  and the threaded portion  31  of the locking member  31  engages the threaded spiral portion  13  of the cylinder  11 . 
     The scraper  61 , the O-shaped ring  60 , the step seal  59  and the wear ring  58  are arranged on the inner surface of the cylinder  50 . The back-up ring  56  and the O-shaped ring  57  are inserted into the outer upper groove  54  of the cylinder  50  and the back-up ring  63 , the O-shaped ring  62  and the back-up ring  63  are inserted into the lower groove  55  of the cylinder  50  respectively. 
     The cylinder  50  is inserted into the cylinder chamber  11 , after the piston  40  is inserted into the cylinder  50 , which piston  40  has the O-shaped ring  45 , the gliding ring  46  and the wear ring  47  inserted into the grooves  43  and  44  of the stepped piston  41 . At this time, the threaded portion  51  formed on the outer surface of the cylinder  50  engages the threaded portion  12  formed on the inner surface of the cylinder chamber  11 . 
     The upper portion of the piston  40  protrudes through the upper end portion of the cylinder  50 . The cap  70  is situated on the upper portion of the piston  40  and the guide pins  16  of the housing  10  is inserted into the guide holes  71  of the cap  70 . Through the above procedure, the rock splitter  2  is completely assembled as shown in FIG.  5 . 
     When the oil is supplied through the first path  14  into the rock splitter  2 , as shown in FIG. 7 a,  the oil flows into the cylinder  50  through the gaps  30   a,  formed between the members  31 ,  32  and  33  of the folding and unfolding means  30 , which are placed inside the cylinder chamber  11  of the housing  10 . 
     When the oil is continuously provided into the cylinder  50  through the gaps  30   a  of the folding and unfolding means  30 , the piston  40  is raised in a state such that the piston  40  is sealed by the rings placed between the cylinder  50  and the piston  40  and prevented from moving laterally by virtue of the wear rings  47  and  58 . When the piston  40  rises, the folding and unfolding means  30  is expanded by the elasticity of the member  20 , and at this time, the upper surface of the fixing member  33  keeps the contact state with the bottom surface of the piston  40 . 
     When the piston  40  rises, the oil, which flows into the space between the cylinder  50  and the stepped portion  41  of the piston  40 , is discharged though the oil paths  53  of the cylinder  50  to the second path  15  of the housing  10 . The cap  70 , which is located on the upper portion of the piston  40 , rises with the rising piston  40  through the guidance of the guide pins  16  inserted into the guide holes  71  of the cap  70 . 
     After rising to a prescribed extent, the stepped portion of the rising piston  40  engages the inside of the cylinder  50  and thereby the piston no longer rises, the cap  70  also does not rise any more. At this time, the entire front surface of the arch-shaped cap  70  can easily split the rock by the contact area and the power applied to the rock, which are larger than that of the conventional rock splitter, thereby splitting the rock more easily. At this time, the folding and unfolding means  30  is completely expanded by the piston  40 , as shown in FIGS. 6 and 7 b.    
     The completely expanded folding and unfolding means  30  is in the following state. The threaded portion  31  of the locking member  31  is engaged to the threaded portion  13  of the cylinder chamber  11 , the lower stepped portion  32   b  of the connecting member  32  is in contact with the upper stepped portion  32   a  of the connecting member  32 , such that the gaps  30   a  between the members  31 ,  32  and  33  are sealed. Therefore, the oil supply through the first path  14  into the cylinder  11  blocked, thereby preventing any overload damage to the housing  10 . 
     Meanwhile, after splitting the rock, in order to return the rock splitter  2  to its original condition, when the oil is supplied to the second path  15  of the housing  10 , the oil supplied to the second path  15  flows into the cylinder  50  through the oil paths  53  of the cylinder  50 . When the oil continuously flows through the concave portion  42 , the piston  40  drops with the oil pressure applied to the concave portion  42 . 
     When the piston  40  drops, the fixing member  33 , being in contact with the bottom of the piston  40 , is inserted into the connecting member  32  and the connecting member  32  is inserted into the locking member  31 , thereby the folding and unfolding means is folded and the elastic member  20  is again compressed. When folded, the stepped portion  31   a,    32   a,    32   b  and  33   a,  are separated from each other and thereby, the folding and unfolding means  30  has the gaps  30   a  between the members  31 ,  32  and  33 . Through the gaps  30   a,  the oil staying inside the lower portion of the piston  40  is discharged through the fist path  14  of the housing  10 . 
     When the piston  40  falls down in the above manner, the cap  70  which is located on the upper end of the piston  40  is returned to its original position, being guided by the guide pins  16  inserted into the guide holes  71 . 
     When the piston  40  rises within the cylinder  50 , the wear rings  58  and  47 , which are placed on the inner surface of the cylinder  50  and the outer portion of the piston  40  respectively, prevent lateral movement of the piston  40 . 
     The rock splitter  2  according to the present invention includes another cylinder  50  inserted into the cylinder chamber  11  of the housing  10 . In the conventional rock splitter  2 , if the cylinder  50  is damaged by the piston  40 , the entire housing  10  must be replaced. However, in the rock splitter  2  according to the present invention, only the damaged cylinder  50  is replaced without necessitating replacement of the entire housing  10 , thereby reducing the maintenance fees considerably and improving the efficiency of work. 
     Additionally, in the conventional rock splitter, the power applied to the rock is limited to the area of the piston  40 , but in the present invention, the power applied to the rock is applied to the entire front surface of the cap  70 , so that the rock can be easily split, while the rising pressure of the piston  40  is maintained in the same intensity as the conventional rock splitter. 
     Furthermore, the folding and unfolding means  30  is expanded while the gaps  30   a  between members  31 ,  32  and  33  are sealed by the engagement of the stepped portions  31   a,    31   b,    32   b  and  33   a.  When returning to its original position, the members  31 ,  32  and  33  are easily returned to their original positions by a small amount of oil pressure passing through the stepped portions, thereby preventing malfunction of the folding and unfolding means  30 . 
     Those skilled in the art will readily recognize that these and various other modifications and changes may be made to the present invention without strictly following the exemplary application illustrated and described herein, and without departing from the true spirit and scope of the present invention, which is set forth in the follow claims.