Patent Publication Number: US-6981440-B2

Title: High-speed cylinder apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a high-speed cylinder apparatus and in particular, it relates to a cylinder apparatus in which a piston is reciprocally movable at high speed. 
   2. Description of the Related Art 
   In general, in a conventional unidirectional or bi-directional cylinder apparatus, working fluid on a discharge side is returned to a reservoir during the movement of a piston so as to allow smooth movement of the piston. However, if the working fluid on the discharge side is positively reused as working fluid for moving another piston, the pistons are moved synchronously, so that the stroke of the pistons is prolonged. Namely, the moving speed of the pistons as a whole is increased, thus resulting in reduction in time of one cycle (one reciprocal movement) and in enhancement of the productivity. 
   Moreover, the reuse of the working fluid on the discharge side makes it possible to reduce the amount of working fluid necessary to actuate the conventional cylinder apparatus, thus leading to reduction the capacity of a pump for feeding the working fluid. Consequently, the space for accommodating the apparatus and the energy necessary to actuate the cylinder apparatus can be advantageously reduced. 
   The inventor of the present invention has conceived an improved high-speed cylinder apparatus in which a movable cylinder having an inner cylinder element and an outer cylinder element is moved is provided and a piston of the outer cylinder element is moved by the working fluid discharged from the inner cylinder element. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a highly productive cylinder apparatus in which a piston is movable reciprocally in opposite directions at high speed. Another object of the present invention is to provide a highly effective cylinder apparatus in which requires less space for accommodating the same and consumes less energy. To this end, according to the present invention, there is provided a high-speed cylinder apparatus comprising a machine bed ( 11 ) which is comprised of a front stationary table ( 12 ), a front stationary member ( 13 ), a rear stationary member ( 14 ) and a rear stationary table ( 15 ), arranged in this order, stationary rods ( 18 ) which are secured between the front stationary member and the rear stationary member, and a movable cylinder ( 20 ) through which the stationary rods extend, said movable cylinder being provided with an inner cylinder chamber ( 21 ) and an outer cylinder chamber ( 31 ) which surrounds the inner cylinder chamber, said inner cylinder chamber being provided with an inner piston ( 22 ) inserted therein, which is integrally secured to the stationary rods, said inner cylinder chamber being provided with an inner front inlet ( 25 ), an inner rear inlet ( 26 ), an inner rear outlet ( 27 ) and an inner front outlet ( 28 ), for working fluid to move the movable cylinder, said outer cylinder chamber being provided therein with an outer piston ( 32 ) having a front operation member ( 33 ) which is moved close to or away from the front stationary table and a rear operation member ( 34 ) which is moved close to or away from the rear stationary table, said outer cylinder chamber being provided with an outer rear inlet ( 35 ) which is connected to the inner rear outlet and an outer front inlet ( 36 ) which is connected to the inner front outlet, for the working fluid to move the outer piston. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be discussed below in detail with reference to the accompanying drawings, in which 
       FIG. 1  shows schematically a longitudinal sectional view of a high-speed cylinder apparatus according to an embodiment of the present invention in a forward position; 
       FIG. 2  shows schematically a longitudinal sectional view of a high-speed cylinder apparatus according to an embodiment of the present invention, in a rearward position; 
       FIG. 3  shows a cross sectional view of a movable cylinder; 
       FIG. 4  shows a hydraulic circuit diagram for actuating a cylinder apparatus shown in  FIGS. 1 and 2 ; 
       FIG. 5  shows a graph showing a relationship between the displacements of a movable cylinder and an outer piston and time; and, 
       FIG. 6  is a graph showing a relationship between the displacement of a piston and time in a known cylinder apparatus. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As can be seen in  FIGS. 1 and 2 , a high-speed cylinder apparatus  10  is comprised of a machine bed  11 , stationary rods  18 , and a movable cylinder  20 . The machine bed  11  is provided thereon with a front stationary table  12 , a front stationary member  13 , a rear stationary member  14 , and a rear stationary table  15 , arranged in this order from the front side (bottom side in FIG.  1 ). The front stationary table  12  and the rear stationary table  15  opposed thereto constitute working stations of the cylinder apparatus  10 . In this embodiment, stationary dies  16  and  17  for metal pressing are mounted to the stationary tables  12  and  15 , respectively. In the illustrated embodiment, the bottom side in the drawing is referred to as a front side and the upper side is referred to as a rear side. Namely, the cylinder apparatus illustrated is a vertical type. However, the invention is not limited thereto and can be equally applied to a horizontal type cylinder apparatus. The stationary rods  18  extend between the front and stationary members  13  and  14  of the machine bed  11 . The stationary rods  18  are provided with an inner piston  22  secured thereto. In general, a plurality of stationary rods  18  (four rods in the illustrated embodiment. See  FIG. 3 ) are provided. 
   The movable cylinder  20  is provided with an inner cylinder chamber  21  and an outer cylinder chamber  31  surrounding the inner cylinder chamber  21 , as shown in FIG.  3 . The inner piston  22  secured to the stationary rods  18  is inserted in the inner cylinder chamber  21 . The inner cylinder chamber  21  is provided with an inner front inlet  25 , an inner rear inlet  26 , an inner rear outlet  27  and an inner front outlet  28 , for the working fluid (pressurized oil in this embodiment) to move the movable cylinder  20 . 
   In the outer cylinder chamber  31  is inserted a front piston  32  which is integrally provided with a front operation member  33  which is moved with respect to the front stationary table  12  of the machine bed  11  and a rear operation member  34  which is moved with respect to the rear stationary table  15 . In the drawings, numerals  33 R and  34 R designate the rod portions of the front operation member  33  and the rear operation member  34 , respectively. The outer cylinder chamber  31  is provided with an outer rear inlet  35  connected to the inner rear outlet  27  for the working fluid to move the outer piston  32  and an outer inlet  36  connected to the inner outlet  28 . 
   Although no independent outlet for the working fluid is provided in the outer cylinder chamber  31  in the illustrated embodiment, the outer rear inlet  35  and the outer front inlet  36  serve as outlets due to switching valves  55  and  56  provided therein, as can be seen in the hydraulic circuit diagram shown in FIG.  4 . As a matter of course, independent outlets may be provided. 
   The high-speed cylinder apparatus  10  of the present invention operates as follows. 
     FIG. 4  shows a hydraulic circuit diagram for actuating the cylinder apparatus  10 , according to the embodiment. Note that the working fluid is not limited to pressurized oil. Numerals  41 ,  42  and  43  designate the advancing circuit and numerals  44 ,  45  and  46  designate the retracting circuit. In  FIG. 4 , numeral  50  designates the pump,  51  the switching valve,  51 A the advancing switch thereof,  51 B the retracting switch,  53 ,  54  and  57  the check valves,  55  the (advancing) switching valve,  56  the (retracting) switching valve, and  61 ,  62  and  63  the unloaders. 
   The advance movement shown in  FIG. 1  is discussed below. To this end, the advancing circuits  41 ,  42  and  43  in the circuit diagram in  FIG. 4  are in an operative position. Namely, the advancing switch  51 A of the switching valve  51  is turned ON, the switching valve (for the advance movement)  55  it turned ON, and the switching valve (for the retracting movement)  56  is turned OFF. The pressurized oil fed from the pump  50  is introduced to the front portion of the inner cylinder chamber  21  from the inner front inlet  25  of the movable cylinder  20 , through the circuit  41 . The inner piston  22  inserted in the inner cylinder chamber  21  is secured to the stationary rods  18  and the opposing ends of the stationary rods  18  are secured to the front stationary member  13  and the rear stationary member  14 , respectively. Therefore, when the pressurized oil is introduced into the front portion of the inner cylinder chamber  21 , the movable cylinder  20  is moved forward in the direction indicated by an arrow F 1  in FIG.  1 . 
   The forward movement of the movable cylinder  20  in the direction F 1  causes the pressurized oil in rear of the inner piston  22  to move from the inner rear outlet  27  into the outer rear inlet  35  of the outer cylinder chamber  31  of the movable cylinder  20  through the circuit  42  in which the switching valve  55  is turned ON. Consequently, the outer piston  32  is advanced in the direction F 2  in FIG.  1 . The pressurized oil in front of the outer piston  32  in the outer cylinder chamber  31  is discharged outside from the outer front inlet (which serves as an outlet in this case)  36  in accordance with the advance movement of the outer piston  32 . As the switching valve  56  is OFF, the pressurized oil is returned from the circuit  43  to the reservoir through the unloader  62 . 
   The backward movement (retracting movement) shown in  FIG. 2  will be discussed below. 
   The retracting switch  51 B is ON, the switching valve (for the advancing movement)  55  is OFF, and the switching valve (for the retracting movement)  56  is ON, so that the retracting circuits  44 ,  45  and  46  are in an operative position. Namely, the pressurized oil from the pump  50  is introduced into the rear portion of the inner cylinder chamber  21  from the inner rear inlet  26  of the movable cylinder  20  through the circuit  44  when the retracting switch  51 B of the switching valve  51  is ON. The inner piston  22  inserted in the inner cylinder chamber  21  is integrally connected to the stationary rods  18  whose ends are integrally connected to the front and rear stationary members  13  and  14 , as mentioned above. Therefore, if the pressurized oil is introduced in the rear portion of the inner cylinder chamber  21 , the movable cylinder  20  itself is moved backward in the direction R 1  in FIG.  2 . 
   In accordance with the backward movement of the movable cylinder  20  in the direction R 1 , the pressurized oil in front of the inner piston  22  is moved from the inner front inlet  28  into the outer front inlet  36  of the outer cylinder chamber  31  of the movable cylinder  20  through the circuit  45  in which the switching valve  56  is ON. Consequently, the outer piston  32  is retracted in the direction R 2  in FIG.  2 . 
   The backward movement of the outer piston  32  causes the pressurized oil in the rear portion of the outer piston  32  within the outer cylinder chamber  31  to be discharged outside from the outer rear inlet (which serves as an inlet in this case)  35 . As the switching valve  55  is OFF, the pressurized oil is returned from the circuit  46  to the reservoir through the unloader circuit  63 . 
   As can be understood from the foregoing, in a high-speed cylinder apparatus  10  of the present invention, the sum (F 1 +F 2 ) of the forward displacement F 1  of the movable cylinder  20  caused by the inner cylinder chamber  21  and the forward displacement F 2  of the outer piston  32  in the outer cylinder chamber  31  is identical to the forward displacement of the front operation member  33  with respect to the front stationary table  12 . Consequently, the workpiece M 1  is pressed by the movable die  37  provided on the front operation member  33  and the stationary die  16  of the front stationary table  12  (FIG.  1 ). 
   Upon backward movement (retracting movement), the sum (R 1 +R 2 ) of the rearward displacement R 1  of the movable cylinder  20  caused by the inner cylinder chamber  21  and the rearward displacement R 2  of the outer piston  32  in the outer cylinder chamber  31  is identical to the backward displacement of the rear operation member  34  with respect to the rear stationary table  15 . Consequently, the workpiece M 2  is pressed by the movable die  38  provided on the rear operation member  34  and the stationary die  17  of the rear stationary table  15  (FIG.  2 ). 
     FIG. 5  shows the displacements of the movable cylinder  20  and the outer piston  32  in connection with time. In this embodiment, the velocity of the forward or backward movement by the pistons is 150 mm/sec. and that at the pressing operation is 50 mm/sec. 
   As may be seen from the drawings, the forward movement F 2  of the outer piston  32  begins slightly behind the forward movement F 1  of the movable cylinder  20 , and thereafter, the workpiece M 1  is subject to press machining under pressure at the low speed. While the workpiece M 1  is pressed, no movement of the movable cylinder  20  occurs, and in this period of time, the supply of the pressurized oil to the inner cylinder chamber  21  is switched. As soon as the pressing of the workpiece M 1  is completed, the pressurized oil is fed to the inner cylinder chamber  21  for the rearward movement, so that the movable cylinder  20  begins the rearward movement R 1 . In accordance with the rearward movement of the movable cylinder  20 , the hydraulic circuit of the pressurized oil in the outer cylinder chamber  31  is switched. Consequently, the outer piston  32  begins the rearward movement R 2  in retard of the rearward movement R 1  of the movable cylinder  20  and thereafter, the workpiece M 2  is subject to press machining under pressure at the low speed. Thus, one cycle is completed and the workpieces M 1  and M 2  are pressed. 
   While the workpiece M 2  is subject to a pressing operation, the movable cylinder  20  does not move. During this period of time, the hydraulic circuit to supply the pressurized oil to the inner cylinder chamber  21  is switched, so that as soon as the pressing of the workpiece M 2  is completed, the pressurized oil is supplied to the inner cylinder chamber  21  for the forward movement. Consequently, the movable cylinder  20  begins the forward movement F 1 . 
   As can be seen from the above discussion, in the high-speed cylinder apparatus  10  of the present invention, as the switching operation of the hydraulic circuit to supply the working fluid to the inner cylinder chamber  21  and the outer cylinder chamber for the forward movement or rearward movement can be effectively carried out during the movement of the outer piston  33  or movement of the movable cylinder  20 , the operation time can be remarkably reduced. Note that in the illustrated embodiment, two workpieces M 1  and M 2  can be produced in one cycle of  3  seconds. 
     FIG. 6  is a graph corresponding to  FIG. 5 , showing a known cylinder apparatus in which the pressing operation is carried out under the same conditions as those of the present invention. The velocity of the forward or rearward movement by the pistons in the known cylinder apparatus J is 150 mm/sec and that at the pressing operation is 50 mm/sec., as in the present invention. However, as can be seen from  FIG. 6 , the velocity of the forward or rearward movement in a known apparatus is identical to that determined by a single piston. Moreover, it takes time (approximately ¼ sec.) to switch the forward and rearward movements. In the known apparatus, it takes approximately 4 seconds to machine one workpiece M. In comparison with the present invention in which two workpieces M 1  and M 2  can be machined in one cycle of 3 seconds, the prior art requires time of more than 2.6 times the present invention. 
   As may be understood from the above discussion, in a high-speed cylinder apparatus according to the present invention, when the movable cylinder is advanced, the outer piston is independently advanced in association therewith, and when the movable cylinder is retracted, the outer piston is retracted in association therewith. Therefore, the operation member provided on the outer piston can be moved by a displacement identical to the sum of the displacement of the movable cylinder and the displacement of outer piston within the substantially same time and hence, operation member can be moved at high-speed within a short space of time, in comparison with the case in which the same displacement is produced by the single piston. 
   Moreover, in a high-speed cylinder apparatus of the present invention, the operation members are moved in opposite directions, the productivity can be enhanced. 
   Furthermore, in the present invention, the movable cylinder is moved by the inner piston secured to the stationary rods which are in turn secured to and between the front and rear stationary members, and the front and rear operation members are provided on the outer piston. Therefore, the operation members can provide a large space between the same and the corresponding stationary tables, as in a common cylinder apparatus. The large space makes it possible to easily load or unload the workpieces or to easily replace the press dies. 
   Furthermore, according to the present invention, not only can the accommodation space of the apparatus be saved but also the energy consumption can be reduced. Thus, a high speed cylinder apparatus which is practically very advantageous can be provided, according to the present invention.