Patent Publication Number: US-10774589-B2

Title: Mast with hydraulic circuit for assist cylinder

Description:
TECHNICAL FIELD 
     This disclosure relates to mast drilling machines. More particularly, to a hydraulic circuit for controlling the angle of the mast drilling machine. 
     BACKGROUND 
     Mast drilling machines are utilized in surface mining operations where the mast drilling machine drills bores in rocks and other materials in desired locations. The mast is movably coupled to a vehicle such as a truck for transportation. In operation, a lift system moves the mast from the transport position to an operation or drilling position. When in a drilling position the vehicle functions as a counterweight or base for the mast to prevent the mast from tipping over, causing significant damage and danger. 
     The lift system rotates the mast about a pivot axis from the transport position to the drilling position. The drilling position can occur when the mast is perpendicular (at 90°) to the ground. Alternatively, during operation, drilling is desired at an angle, not only at angles less than 90° degrees, where the machine is disposed between the mast and the ground, but also at angles past 90° degrees such as up to 105° degrees when the mast is angled away from the vehicle. Specifically, linkage is proved to hold the mast in such position without tipping as a result of vibrations during the drilling process. 
     Japanese Patent Publication No. 4880642B2 provides a vehicle mounted mast device with framework supporting the device on the vehicle. Linkage, including a hydraulic system is utilized to support the mast and move the mast into desired locations. Still, hydraulic systems can be complicated, expensive to manufacture, and prone to fatigue and wear. Specifically, the hydraulic device or cylinder responsible for supporting and rotating the mast is subject to significant forces resulting in wear, fatigue, strain, malfunction, and the like. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention a mast assembly is provided that includes a mast and a hydraulic circuit coupled to the mast. The hydraulic circuit includes a primary hydraulic cylinder coupled to the mast to rotate the mast about a pivot axis and a secondary hydraulic cylinder extending from a rod end to a cap end, fluidly coupled to the primary hydraulic cylinder. The hydraulic circuit also includes a directional valve fluidly coupled between the primary hydraulic cylinder and secondary hydraulic cylinder to maintain pressure on the cap end of the secondary hydraulic cylinder greater than a pressure on the rod end of the secondary hydraulic cylinder in a first position and in a second position. 
     In another aspect of the invention, a hydraulic circuit is provided. The hydraulic circuit includes a primary hydraulic cylinder and a secondary hydraulic cylinder extending from a rod end to a cap end, fluidly coupled to the primary hydraulic cylinder. A directional valve is fluidly coupled between the primary hydraulic cylinder and the rod end of the secondary hydraulic cylinder. The hydraulic circuit also includes a relief valve coupled between the directional valve and the cap end of the secondary hydraulic cylinder. 
     In yet another aspect of the invention, a method for pivoting a mast through working positions is provided. A primary hydraulic cylinder is activated to move a mast through a first arc. A secondary hydraulic cylinder is engaged by the mast as the mast moves through a second arc and reduces load on the primary hydraulic cylinder as the mast moves through the second arc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagrammatic illustration of an exemplary mast assembly; 
         FIG. 2  shows a diagrammatic illustration of an exemplary mast assembly; 
         FIG. 3  shows a schematic diagram of a hydraulic circuit for an exemplary mast assembly; and 
         FIG. 4  shows a schematic diagram of a hydraulic circuit for an exemplary mast assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate a mast assembly  100  with a mast  105  that extends from a first end  106  to a second end  108  and moves from a 90° operating position, relative to a horizontal surface, in  FIG. 1  to a 105° operating position in  FIG. 2 . While only the mast assembly  100  is illustrated, the mast assembly  100  is coupled to a vehicle such as a truck, or other counterweight that is omitted from the figures to provide better detail related to the mast assembly  100 . While illustrated as positioned at 90° and 105° degrees, the mast  105  also moves from a transport position and rotates about a pivot axis  110  from 0° to 105° degrees. Specifically, the mast rotates through a first arc  112  that in one example is between 0° and 90° and a second arc  114  that in one example is between 90° and 105°. The mast  105  includes a support framework  115  that supports an operational implement that in one example is a drill. A mast pivot system  120  is coupled to the mast  105  and pivots the mast  105  about the pivot axis  110  from a transportation position to a drilling position that includes a range of 0° to 105°. 
     The mast pivot system  120  includes a support base frame  125 , leg members  130 , an arcuate plate  135 , and linkage  140  including a hydraulic support system  145 . The support base frame  125  receives the leg members  130  and is coupled to the vehicle to provide counterbalance for the mast  105 . 
     The arcuate support plate  135  is coupled to the support base frame  125  and linkage  140  and includes a plurality of openings  150  at its periphery  155  for receiving a pin to lock the mast at predetermined angles. Specifically, each opening  150  represents a pre-determined angle and by connecting the end of the mast to the arcuate plate  135 , undesired movement of the mast  105  during operation is prevented. 
     The hydraulic support system  145  includes a first primary hydraulic cylinder  160 , a second primary hydraulic cylinder  165 , and a secondary hydraulic cylinder  170  that is coupled to the linkage  140  to pivot the mast  105  about the pivot axis  110 . The first and second primary hydraulic cylinders  160 ,  165  are coupled to the support base frame  125 . In one embodiment, the cylinders are spaced apart and positioned parallel to one another. While first and second primary hydraulic cylinders  160 ,  165  are provided in this example, in other examples only a single primary hydraulic cylinder is utilized. Each hydraulic cylinder  160 ,  165  extends from a rod end  172  that secures to first end  106  of the mast  105  to a cap end  175 , or piston end that is coupled to the support base frame  125 . Each primary hydraulic cylinder  160 ,  165  also includes a rod element  180  that secures to the framework  115  and is disposed within the cylinder body  185  to extend or retract from the cylinder body  185  based upon the fluid pressure within the cylinder body  185 . 
     The secondary hydraulic cylinder  170  extends from a rod end  190  to a cap end  195  that is coupled to the support base frame  125  between the first primary hydraulic cylinder  160  and second primary hydraulic cylinder  165 . The secondary hydraulic cylinder  170  includes a rod element  200  and head or piston element (not shown) that are disposed within the cylinder body  205  to extend or retract from the cylinder body  205  based upon the fluid pressure within the cylinder body  205 . The rod element  200  extends from the cylinder body  205  and is coupled to a plate element (not shown) that is supported by linkage. Specifically, the secondary hydraulic cylinder is only provided to supplement the first and second primary hydraulic cylinders  160 ,  165  when the mast  105  is positioned in a predetermined range that in one example is between 90°-105°. Consequently, the secondary hydraulic cylinder  170  is positioned adjacent the second end  108  of the mast  105  and does not engage the mast  105  until the mast  105  rotates to a predetermined angle, such as the 90° position. At this point the second end  108  of the mast  105  engages the plate element (not shown) to place a force on the rod element  200  inwardly into the cylinder body  205 . The plate element and support linkage allow some movement of the mast  105  against the plate element, but prevents undesired movement. 
       FIGS. 3-4  illustrate a hydraulic circuit  300  of a hydraulic support system for a mast when the mast moves between a 90° degree position to a 105° degree position. In one example, the hydraulic circuit  300  is the hydraulic circuit  300  of the hydraulic support system  145  for mast  105  of  FIGS. 1-2 . 
     The hydraulic circuit  300  includes a primary hydraulic cylinder  305 , secondary hydraulic cylinder  310 , first counterbalance valve (CBV)  315 , second CBV  320 , relief valve  325 , directional valve  330 , and relief valve  335 . In one example, the primary hydraulic cylinder  305  is either of first primary hydraulic cylinder  160  or second primary hydraulic cylinder  165  of  FIGS. 1-2 , while the secondary hydraulic cylinder  310  is the secondary hydraulic cylinder  170  of  FIGS. 1-2 . 
     The primary hydraulic cylinder  305  includes a rod element  340  secured to a head or piston (not shown) and extends within a primary hydraulic cylinder body  342  from a rod end  345  to a cap end  350 . Adjacent the rod end  345  is a first port  352  while adjacent the cap end  350  is a second port  355 . Each port  352 ,  355  is fluidly coupled to a fluid line  360 ,  365  wherein the first fluid line  360  if fluidly coupled to the first CBV  315  while the second fluid line  365  is fluidly coupled to the second CBV  320 . The first and second CBVs  315 ,  320  function as a relief valves to set up back pressure to prevent load runaway when the piston is retracting. 
     The secondary hydraulic cylinder  310  also includes a rod element  380  secured to a head or piston (not shown) and extends with a secondary hydraulic cylinder body  382  from a rod end  385  to a cap end  390 . Adjacent the rod end  385  is a first port  395  while adjacent the cap end  390  is a second port  400 . Each port  395 ,  400  is fluidly coupled to a fluid line  405 ,  410  extending from the secondary hydraulic cylinder  310  to the directional valve  330  where the directional valve  330  controls the direction of fluid flow within the fluid lines  405 ,  410 . 
     The relief valve  325  is disposed within the second fluid line  365  to allow fluid flow from the second CBV  320  to the directional valve  330  and provide pressure relief when fluid is flowing from the directional valve  330  to the second CBV  320 . Meanwhile, the first CBV  315  is fluidly connected to the directional valve  330 . In addition, the first CBV  315  and second CBV  320  are both fluidly connected to a hydraulic engine via a directional valve (not shown). 
     In one example, the directional valve  330  is a piloted directional valve or pilot valve. The directional valve  330  in a first position  412  allows fluid to flow from the secondary hydraulic cylinder  310  to the second CBV  320  while fluid from the first CBV  315  flows to the secondary hydraulic cylinder  310 . In the second position  414  the directional valve  330  allows fluid to flow from the secondary hydraulic cylinder  310  to the first CBV  315  while fluid from the second CBV  320  flows to the secondary hydraulic cylinder  310 . 
     The relief valve  335  is fluidly disposed between the directional valve  330  and the secondary hydraulic cylinder  310 . The relief valve  335  includes a free flow bypass  415 , and is also fluidly connected to a tank  425  to provide a vented spring chamber such that when relief flow occurs it is vented to the tank  425 . 
     INDUSTRIAL APPLICATION 
     When at a worksite, the mast  105  is transported to a desired location. The mast  105  is pivoted from the vehicle into a drilling position to drill at a desired location. When pivoting from the transportation position to a drilling position, up to a predetermined angle such as in one example 90° degrees, the primary hydraulic cylinders  160 ,  165 ,  305  are activated and move the mast  105  along a first arc  112  without supplementation. In one example, the first arc  112  is in a range between 0° to 90°. The mast  105  continues to rotate about the pivot axis  110  in the first arc  112  until the mast  105  engages the secondary cylinder  170 ,  310 . At this point the mast rotates about a second arc  114 , during which the secondary cylinder reduces the load on the primary cylinder  160 ,  165 ,  305 . The load is reduced regardless of the direction the mast is rotating along the second arc  114 . In one example, the second arc  114  is in a range including and between 90° and 105°. 
     When moving from 90° degrees to 105° degrees, the directional valve  330  and relief valve  335  of the hydraulic circuit  300  are positioned as provided in  FIG. 3  with the directional valve  330  in a first position  412 . In particular, when the mast  105  is moving from 90° to 105° degrees, the rod element  180 ,  340  of the primary hydraulic cylinder(s)  160 ,  165 ,  305  moves in the direction of the force the mast  105  is placing on the rod element  180 ,  340  while the rod element  200 ,  380  of the secondary hydraulic cylinder  170 ,  310  similarly moves in the direction of the force the mast  105  is placing on the rod element  200 ,  380 . 
     In this example, as the rod element  200 ,  380  of the secondary hydraulic cylinder  170 ,  310  is pushed into the cylinder body  205 ,  382  of the secondary hydraulic cylinder  170 ,  310  the piston of the secondary hydraulic cylinder  170 ,  310  compresses the fluid at the cap end  195 ,  390  of the secondary hydraulic cylinder  170 ,  310 . Meanwhile, compressed high pressure fluid (at least 140 pounds per square inch—psi) exists the secondary hydraulic cylinder  170 ,  310  through port  400  and flows through relief valve  335 , through the directional valve  330 , to relief valve  325 , then second CBV  320 , to finally provide fluid pressure into the primary hydraulic cylinder(s)  160 ,  165 ,  305  at the second port  355 . This pressurized fluid assists in the movement of the piston(s) within the primary hydraulic cylinder(s)  160 ,  165 ,  305  such that the rod element  180 ,  340  extends out of the cylinder body  185 ,  342  to a desired position. 
     As a result of the movement of the piston(s) of the primary hydraulic cylinder(s)  160 ,  165 ,  305  the fluid within the primary hydraulic cylinder(s)  160 ,  165 ,  305  increases such that high pressure fluid exits the first port  352  of the primary hydraulic cylinder(s)  160 ,  165 ,  305 . This high-pressure fluid then flows to the first CBV  315  that provides pressurized fluid to the second CBV  320  as required. Otherwise, return pressure fluid flows from the first CBV  315  to the hydraulic motor or pump and through the directional valve  330  to supply fluid to the secondary hydraulic cylinder  170 ,  310 . 
     When moving the mast  105  back from 105° degrees to 90° degrees, the directional valve  330  and relief valve  335  of the hydraulic circuit  300  are positioned as provided in  FIG. 4  with the directional valve  330  in a second position  414 . In particular, when the mast  105  is moving from 105° to 90° degrees, the rod element  180 ,  340  of the primary hydraulic cylinder(s)  160 ,  165 ,  305  moves in the direction opposite of the force the mast  105  is placing on the rod element  180 ,  340  while the rod element  200 ,  380  of the secondary hydraulic cylinder  170 ,  310  similarly moves in the opposite direction of the force the mast  105  is placing on the rod element  200 ,  380 . 
     Under this condition, high pressure fluid flows to the first CBV  315  into the primary hydraulic cylinder  160 ,  165 ,  305  to retract the rod element  180 ,  340  of the primary hydraulic cylinder  160 ,  165 ,  305  into the cylinder body  185 ,  342  to rotate the mast  105  about the pivot axis  110 . As the piston of the primary hydraulic cylinder  160 ,  165 ,  305  moves toward the cap end  175 ,  350  of the primary cylinder  160 ,  165 ,  305  fluid exits the second port  355  of the primary hydraulic cylinder  160 ,  165 ,  305  to the relief valve  325  to provide return fluid. Contemporaneously, the high-pressure fluid flow also flows through the directional valve  330  to the relief valve  335  to introduce the high-pressure fluid to the cap end  195 ,  390  of the secondary hydraulic cylinder  170 ,  310 . Consequently, the rod element  200 ,  380  of the secondary hydraulic cylinder  170 ,  310  provides a supplemental force on the mast  105  to rotate the mast  105  about the pivot axis  110 . Return fluid is then displaced from the secondary hydraulic cylinder  170 ,  310  at the rod end  190 ,  385  of the secondary hydraulic cylinder  170 ,  310  through port  395 . This return fluid flows through the directional valve  330  to combine with the return fluid from the primary hydraulic cylinder  160 ,  165 ,  305  to a hydraulic pump or motor. 
     Thus provided is a hydraulic circuit  300  with a primary hydraulic cylinder  160 ,  165 ,  305  for pivoting a mast  105  about a pivot axis  110  and a secondary hydraulic cylinder  170 ,  310  for supplementing and reducing forces on the primary hydraulic cylinder  160 ,  165 ,  305 . Within the hydraulic circuit  300 , a directional valve  330  and relief valve  335  are arranged between the primary hydraulic cylinder  160 ,  165 ,  305  and secondary hydraulic cylinder  170 ,  310  to control fluid flow to, from, and between the working cylinders. When the mast  105  is moving from 90° to 105° degrees, the directional valve is in a first position  412  such that high-pressure fluid is provided from the cap end  195 ,  390  of the secondary hydraulic cylinder  170 ,  310  to supplement the primary hydraulic cylinder  160 ,  165 ,  305 . When the mast  105  is moving from 105° to 90° degrees the directional valve  330  is in a second position  414 , again resulting in high pressure at the cap end  195 ,  390  of the secondary hydraulic cylinder  170 ,  310 , only this time flow is reversed and high-pressure fluid is provided to the cap end  195 ,  390  of the secondary hydraulic cylinder  170 ,  310 . In this manner the secondary hydraulic cylinder  170 ,  310  counteracts the force of the mast  105  to supplement the primary hydraulic cylinder  160 ,  165 ,  305 . Therefore, both the primary hydraulic cylinder  160 ,  165 ,  305  and secondary hydraulic cylinder  170 ,  310  provide forces, including hydraulic and mechanical forces, to rotate the mast  105  about the pivot axis  110 . Specifically, the arrangement of the circuit  300  ensures that pressure at the cap end  390  of the secondary hydraulic cylinder  170 ,  310  is greater than the pressure on the rod end  385  of the secondary hydraulic cylinder  170 ,  310 , during all operation conditions. Consequently, the secondary hydraulic cylinder  170 ,  310  reduces and minimizes forces on the primary hydraulic cylinder  160 ,  165 ,  305  reducing wear, fatigue, and malfunction. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic circuit  300  without departing from the scope of the disclosure. Other embodiments of the hydraulic circuit  300  will be apparent to those skilled in the art from consideration of the specification and practice of the methods disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.