Patent Publication Number: US-2013228070-A1

Title: Hydraulic cylinder with variable cushion orifice

Description:
TECHNICAL FIELD 
     The present invention relates to a hydraulic cylinder having a variable cushion orifice. More particularly, the present invention relates to a hydraulic cylinder having a variable cushion orifice, which can adjust the size of a cushion orifice hole that is provided to mitigate an impact generated at a stroke end of a cylinder rod from the outside of the hydraulic cylinder. 
     BACKGROUND ART 
     In general, a hydraulic cylinder is provided with a cushion device which can minimize breakage of the hydraulic cylinder and damage of a hydraulic system through mitigation of impact generated due to high-pressure hydraulic fluid that is formed in a pressure chamber between a piston and a head cover at a stroke end of the cylinder. The cushion device may include a cushion ring and a cushion plunger mounted on a cylinder rod, and a cushion orifice formed on the head cover. The cushion orifice performs cushion function through adjustment of an amount of hydraulic fluid that is discharged through the orifice at the stroke end of the cylinder rod. 
     As illustrated in  FIG. 1 , a hydraulic cylinder in the related art includes a head cover  2  on which a cylinder rod  1  slides; a cylinder tube  4  which is integrally formed to extend from the head cover  2  and on which a piston  3  reciprocates; a cushion orifice  6  controlling an amount of hydraulic fluid that is discharged through a hydraulic flow pat  5  formed on the head cover  2  to mitigate impact due to high-pressure hydraulic fluid formed in a pressure chamber  8  at a stroke end of the cylinder rod  1 ; and a cushion ring  7  mounted on an end portion of the cylinder rod  1 . 
     In the case of the hydraulic cylinder as described above, the cushion orifice  6  is formed inside the hydraulic cylinder. Due to this, it is not possible to change the hole size of the cushion orifice  6  after the hydraulic cylinder, in which the hole size of the cushion orifice has been determined, is assembled and mounted on construction equipment. That is, the construction equipment mounted with the hydraulic cylinder has the same cushion performance regardless of operator&#39;s preference or a change of use state of the construction equipment. 
     Further, in manufacturing hydraulic cylinders that are suitable to respective construction equipment, the hydraulic cylinders may be unable to be commonly used due to the characteristics of cushion performance even in the case where the mounted hydraulic cylinders have similar specifications. 
     DISCLOSURE 
     Technical Problem 
     Therefore, the present invention has been made to solve the above-mentioned problems occurring in the related art, and one embodiment of the present invention is related to a hydraulic cylinder having a variable cushion orifice, which can variably adjust the size of a cushion orifice hole to change the cushion performance in a state where the hydraulic cylinder that is mounted on construction equipment is not replaced or disassembled. 
     One embodiment of the present invention is related to a hydraulic cylinder having a variable cushion orifice, which can unitarily use various kinds of hydraulic cylinders having different cushion performances, and can perform cushion tuning while confirming the cushion performance so as to improve the characteristics or operability of the equipment through the cushion performance change. 
     Technical Solution 
     In accordance with one aspect of the present invention, there is provided a hydraulic cylinder having a variable cushion orifice including a head cover on which a cylinder rod slides, a cylinder tube which is formed to extend from the head cover and on which a piston reciprocates, and a cushion device that mitigates impact occurring at a stroke end of the cylinder rod, which includes a first cushion orifice formed on the head cover; a second cushion orifice communicating with the first cushion orifice and having an inlet formed on an outer side surface of the head cover; a third cushion orifice making the second cushion orifice communicate with a hydraulic flow path formed on the head cover; and a plug for a variable orifice replaceably engaged with the second cushion orifice and having an orifice formed thereon so as to adjust an amount of hydraulic fluid discharged to the hydraulic flow path through the first cushion orifice during the stroke end of the cylinder rod. 
     In the hydraulic cylinder having a variable cushion orifice in accordance with the aspect of the present invention, it is preferable that the orifice formed on the plug for the variable orifice includes a first orifice communicating with the second cushion orifice, and a second orifice communicating with the first orifice and making the second cushion orifice and the third cushion orifice mutually communicate with each other. 
     Advantageous Effects 
     As described above, the hydraulic cylinder having a variable cushion orifice according to the aspect of the present invention has the following advantages. 
     The size of the cushion orifice hole can be variably adjusted in a state where the hydraulic cylinder mounted on construction equipment including an excavator is not replaced or disassembled, and thus workability and convenience can be provided. 
     Further, various kinds of hydraulic cylinders having different cushion performances are commonly used to improve the productivity, and cushion tuning can be performed while the cushion performance is confirmed to improve the characteristics or operability of the equipment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects, other features and advantages of the present invention will become more apparent by describing the preferred embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view of a hydraulic cylinder in the related art; 
         FIG. 2  is a schematic view of a hydraulic cylinder having a variable cushion orifice according to an embodiment of the present invention; and 
         FIG. 3  is a view of a plug having a variable cushion orifice in a hydraulic cylinder having the variable cushion orifice according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS IN THE DRAWING 
     
         
           1 : cylinder rod 
           2 : head cover 
           3 : piston 
           4 : cylinder tube 
           5 : hydraulic flow path 
           7 : cushion ring 
           8 : pressure chamber 
           10 : first cushion orifice 
           11 : second cushion orifice 
           12 : third cushion orifice 
           13 : orifice 
           13   a:  first orifice 
           13   b:  second orifice 
           14 : variable orifice plug 
       
    
     BEST MODE 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and the present invention is not limited to the embodiments disclosed hereinafter. 
     According to an embodiment of the present invention as illustrated in  FIGS. 2 and 3 , there is provided a hydraulic cylinder having a variable cushion orifice including a head cover  2  on which a cylinder rod  1  slides, a cylinder tube  4  which is formed to extend from the head cover  2  and on which a piston  4  reciprocates, and a cushion device that mitigates impact occurring at a stroke end of the cylinder rod  1 , which includes a first cushion orifice  10  formed on the head cover  2 ; a second cushion orifice  11  communicating with the first cushion orifice  10  and having an inlet formed on an outer side surface of the head cover  2 ; a third cushion orifice  12  making the second cushion orifice  11  communicate with a hydraulic flow path  5  formed on the head cover  2 ; and a plug  14  for a variable orifice replaceably engaged with the second cushion orifice  11  through the inlet of the second cushion orifice  11 , and having an orifice  13  formed thereon so as to adjust an amount of hydraulic fluid discharged to the hydraulic flow path  5  through the first cushion orifice  10  at the stroke end of the cylinder rod  1 . 
     In this case, the orifice  13  formed in a “T” shape on the plug  14  for the variable orifice includes a first orifice  13   a  communicating with the second cushion orifice  11 , and a second orifice  13   b  communicating with the first orifice  13   a  and making the second cushion orifice  11  and the third cushion orifice  12  mutually communicate with each other. 
     In the drawing, an unexplained reference numeral  15  denotes a plug screw-engaged with the inlet side of the third cushion orifice  12  to prevent leakage of the hydraulic fluid. 
     Since the configuration except for the cushion device including the first cushion orifice  10 , the second cushion orifice  11 , the third cushion orifice  12 , and the plug  14  for the variable orifice is substantially the same as the configuration of the hydraulic cylinder illustrated in  FIG. 1 , detailed description of their configuration and operation will be omitted, and the same reference numerals are used for the duplicate components. 
     Hereinafter, a use example of the hydraulic cylinder having the variable cushion orifice according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     As illustrated in  FIGS. 2 and 3 , hydraulic fluid in the pressure chamber  8  between the piston  3  and the head cover  2  becomes in a high-pressure state at a stroke end of the cylinder rod  1  as the piston  3  moves toward the head cover  2 . The hydraulic fluid in the pressure chamber  8  is discharged to the hydraulic flow path  5  formed in the head cover  2  through the cushion orifice. At this time, as the cushion orifice controls the amount of hydraulic fluid that is discharged from the pressure chamber  8  to the hydraulic flow path  5 , the impact is mitigated, and thus the breakage of the hydraulic cylinder and the damage of the hydraulic system can be minimized. 
     That is, at the stroke end of the cylinder rod  1 , the high-pressure hydraulic fluid that is formed in the pressure chamber  8  is discharged to the hydraulic flow path  5  after passing through the first cushion orifice  10 , the second cushion orifice  11 , the first orifice  13   a  and the second orifice  13   b  formed in the plug  14  for the variable orifice, and the third cushion orifice  12  in order. 
     On the other hand, in the case of changing the cushion performance to improve the specifications or the operation performance of the equipment, the size of the cushion orifice hole can be changed through replacement of the plug  14  for the variable orifice in which the first and second orifices  13   a  and  13   b  are formed. 
     That is, since the plug  14  for the variable orifice is screw-engaged with the inlet of the second cushion orifice  11 , the amount of hydraulic fluid that is discharged from the pressure chamber  8  to the hydraulic flow path  5  at the stroke end of the cylinder rod  1  can be controlled by the first and second orifices  13   a  and  13   b  formed in a “T” shape in the plug  14  for the variable orifice. That is, the cushion performance of the hydraulic cylinder can be changed through replacement of the plug  14  for the variable orifice in which the orifice holes have different sizes with respect to the hydraulic cylinders having the same specifications. 
     As described above, in the case of changing the size of the orifice hole to improve the cushion performance of the hydraulic cylinder, the size of the orifice hole can be easily changed through replacement of the plug  14  for the variable orifice only from the outside of the hydraulic cylinder in a state where the hydraulic cylinder is mounted on the construction equipment. Since the size of the cushion orifice hole can be changed in a state where the hydraulic cylinder is assembled to the equipment, it is possible to tune the cushion performance of the hydraulic cylinder. 
     Further, since the size of the orifice hole is determined regardless of the fastening depth between the second cushion orifice  11  and the plug  14  for the variable orifice, the productivity of the cushion device including the plug  14  for the variable orifice can be improved. 
     Further, since the size of the cushion orifice hole is changed through replacement of the plug  14  for the variable orifice, foreign substances, which are inserted into the cushion orifice to cause the cushion orifice to be clogged, can be easily removed through replacement of the plug  14  for the variable orifice. 
     INDUSTRIAL APPLICABILITY 
     As apparent from the above description, according to the present invention having the above-described configuration, the size of the cushion orifice hole can be variably adjusted in a state where the hydraulic cylinder mounted on the construction equipment is not replaced or disassembled, and thus the workability can be improved. Further, it is good economy to commonly use various kinds of hydraulic cylinders having different cushion performances. 
     Further, since cushion tuning is possible while the cushion performance is confirmed in a state where the hydraulic cylinder is mounted on the equipment, the cushion tuning becomes possible in hydraulic component development stages.