Patent Publication Number: US-11661960-B2

Title: Pressure-booster output stabilizer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-058079 filed on Mar. 27, 2020, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a pressure-booster output stabilizer combined with a fluid pressure booster. 
     Description of the Related Art 
     Conventionally, there has been known a pressure booster that pressure-boosts air of a primary pressure supplied from a compressor and outputs the air at a predetermined secondary pressure. 
     As a pressure booster of this kind, for example, Japanese Laid-Open Patent Publication No. 2018-084270 discloses a configuration in which drive cylinders are arranged on both sides of a pressure boosting cylinder. As described in the same document, the pressure-boosted fluid output from the pressure booster is usually stored in an external tank and used in such a form as to be supplied from the tank to a fluid pressure device. 
     SUMMARY OF THE INVENTION 
     However, when the amount of fluid used in the fluid pressure device greatly exceeds the discharge rate of flow from the pressure booster, the pressurized fluid stored in the tank is rapidly consumed, so that the pressure in the tank drops sharply in a short time. Therefore, it is likely that the fluid with a sufficient pressure becomes unable to be supplied to the fluid pressure device. In addition, there is a concern that the pressure booster is operated at higher speed, resulting in increased consumption of the pressurized fluid, and that the life of the pressure booster is shortened. 
     The present invention has been devised in view of the circumstances described above, and it is an object of the present invention to provide a pressure-booster output stabilizer capable of outputting the secondary pressure of a pressure booster in a stable condition. 
     A pressure-booster output stabilizer according to the present invention is connected to a fluid pressure booster that outputs a predetermined secondary pressure from a primary pressure, and includes: a first cylinder having therein a first chamber and a second chamber separated by a first piston; a second cylinder having therein a third chamber and a fourth chamber separated by a second piston; and a piston rod configured to couple the first piston and the second piston. In this configuration, the primary pressure is supplied to the first chamber, the secondary pressure is supplied to the fourth chamber, and a pressurized fluid is taken out from the fourth chamber. 
     According to the above pressure-booster output stabilizer, the pressurized fluid taken out from the fourth chamber of the second cylinder can be kept at a pressure close to the secondary pressure set by the pressure booster and output at a stable pressure. Further, since the operating speed of the pressure booster can be slowed down, the consumption of the pressurized fluid can be reduced and the life of the pressure booster can be extended. 
     Since the pressure-booster output stabilizer according to the present invention has a configuration in which the first piston on which the primary pressure of the pressure booster acts and the second piston on which the secondary pressure of the pressure booster acts are connected, and the pressurized fluid is taken out from a chamber to which the pressurized fluid of the secondary pressure is supplied, the secondary pressure of the pressure booster can be output in a stable condition. In addition, since the operating speed of the pressure booster becomes slower, the consumption of pressurized fluid is reduced and the durability of the pressure booster is enhanced. 
     The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram showing an example of a pressure booster combined with the pressure-booster output stabilizer according to the present invention; 
         FIG.  2    is a plan view of a pressure-booster output stabilizer according to a first embodiment of the present invention; 
         FIG.  3    is a side view of the pressure-booster output stabilizer of  FIG.  2   ; 
         FIG.  4    is a sectional view taken along a line IV-IV of the pressure-booster output stabilizer of  FIG.  2   ; 
         FIG.  5    is a diagram corresponding to  FIG.  4    when the pressure-booster output stabilizer of  FIG.  2    is in a predetermined operating position; 
         FIG.  6    is a diagram corresponding to  FIG.  4    when the pressure-booster output stabilizer of  FIG.  2    is in a different operating position; 
         FIG.  7    is a diagram showing the relationships between the flow rate of fluid output from the pressure-booster output stabilizer of  FIG.  2    and the pressure; 
         FIG.  8    is a front view of a pressure-booster output stabilizer and a pressure booster according to a second embodiment of the present invention; and 
         FIG.  9    is a sectional view taken along a line IX-IX of the pressure-booster output stabilizer according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, an example of a fluid pressure booster to be used in combination with a pressure-booster output stabilizer according to the present invention will be described first, and then preferred embodiments of the pressure-booster output stabilizer according to the present invention will be described with reference to the accompanying drawings. The fluid used is a pressurized fluid such as compressed air. 
     (Example of Pressure Booster) 
     As illustrated in  FIG.  1   , the fluid pressure booster (pressure booster)  70  combined with the pressure-booster output stabilizer according to the present invention includes a center body  72 , a pair of cylinders  74   a  and  74   b  connected respectively to both sides of the center body  72 , pistons  76   a  and  76   b  sliding in the respective cylinders  74   a  and  74   b , and a rod  78  connecting the pistons  76   a  and  76   b . The center body  72  has an inlet port  80 , an outlet port  82 , and a discharge port  84 , and the inlet port  80  is connected to an unillustrated fluid supply source (compressor). 
     The cylinders  74   a ,  74   b  are divided into inner boost chambers  86   a ,  86   b  and outer drive chambers  88   a ,  88   b  by pistons  76   a ,  76   b . The boost chambers  86   a  and  86   b  communicate with the inlet port  80  via inlet check valves  90   a  and  90   b  provided in the center body  72 , and also communicate with the outlet port  82  via outlet check valves  92   a  and  92   b . The drive chambers  88   a  and  88   b  are connected to a switching valve  94  installed in the center body  72 , and push rods  96   a  and  96   b  for switching the switching valve  94  are projected into the boost chambers  86   a  and  86   b , respectively. The pressure booster  70  also includes a governor  98  for adjusting the secondary pressure of the fluid at the outlet port  82 . 
     In this pressure booster  70 , when the piston  76   a  moves to the left in  FIG.  1    by the pressurized fluid supplied to the first drive chamber  88   a  via the switching valve  94 , the pressurized fluid in the first boost chamber  86   a  is pressure-boosted, and output from the outlet port  82  through the outlet check valve  92   a . During this process, the pressurized fluid in the second drive chamber  88   b  is discharged from the discharge port  84  via the switching valve  94 . Then, when the piston  76   a  moves and pushes the push rod  96   a  near a stroke end thereof, the switching valve  94  is changed over, so that the pressurized fluid is supplied to the second drive chamber  88   b.    
     As a result, the piston  76   b  moves to the right in  FIG.  1   , so that the pressurized fluid in the second boost chamber  86   b  is pressure-boosted, and output from the outlet port  82  through the outlet check valve  92   b . During this process, the pressurized fluid in the first drive chamber  88   a  is discharged from the discharge port  84  via the switching valve  94 . Then, when the piston  76   b  moves and pushes the push rod  96   b  near a stroke end thereof, the switching valve  94  switches to a state shown in the figure. The pressure booster  70  repeats the above series of operations until the pressure of the fluid at the outlet port  82  reaches a set secondary pressure. 
     First Embodiment 
     Next, a pressure-booster output stabilizer  10  according to the first embodiment of the present invention will be described with reference to  FIGS.  2  to  7   . 
     As shown in  FIG.  4   , the pressure-booster output stabilizer  10  includes a first cylinder  12  and a second cylinder  14  connected in series. The first cylinder  12  has a rectangular parallelepiped first cylinder tube  12   a  and a circular first piston  12   b  slidably arranged in a circular cylinder hole formed in the first cylinder tube  12   a . The second cylinder  14  has a rectangular parallelepiped second cylinder tube  14   a  and a circular second piston  14   b  slidably arranged in a circular cylinder hole formed in the second cylinder tube  14   a.    
     The first piston  12   b  is connected and fixed to one end side of the piston rod  16  by a first nut  17   a , and the second piston  14   b  is connected and fixed to the other end side of the piston rod  16  by a second nut  17   b . Therefore, the first piston  12   b  and the second piston  14   b  move together with the piston rod  16  in the axial direction. The outside diameter of the first piston  12   b  is greater than the outside diameter of the second piston  14   b.    
     A rectangular plate-shaped middle cover  18  is provided between the first cylinder tube  12   a  and the second cylinder tube  14   a . A rectangular plate-shaped first end cover  20  is provided on an end side of the first cylinder tube  12   a  that is farther away from the middle cover  18 , whereas a rectangular plate-shaped second end cover  22  is provided on an end side of the second cylinder tube  14   a  that is farther away from the middle cover  18 . The assembly formed of the first piston  12   b , the second piston  14   b , and the piston rod  16  (hereinafter referred to as “piston assembly”) is configured to be able to move between a position where the first piston  12   b  abuts against the first end cover  20  (see  FIG.  5   ) and a position where the first piston  12   b  abuts against the middle cover  18  (see  FIG.  6   ). 
     The first cylinder tube  12   a  is sandwiched and held between the first end cover  20  and the middle cover  18  by four bolts  23   a  being inserted from the first end cover  20  side and screwed into the middle cover  18 . The second cylinder tube  14   a  is sandwiched and held between the second end cover  22  and the middle cover  18  by four bolts  23   b  being inserted from the second end cover  22  side and screwed into the middle cover  18  ( FIG.  3   ). 
     The inside of the cylinder hole of the first cylinder tube  12   a  is partitioned into a first chamber  24   a  on the first end cover  20  side and a second chamber  24   b  on the middle cover  18  side by the first piston  12   b . The inside of the cylinder hole of the second cylinder tube  14   a  is partitioned into a third chamber  26   a  on the middle cover  18  side and a fourth chamber  26   b  on the second end cover  22  side by the second piston  14   b.    
     As shown in  FIGS.  2  and  4   , one side surface of the first end cover  20  is formed with a primary pressure supply port  28  connected to the aforementioned fluid supply source. The pressurized fluid from the fluid supply source is supplied to the inlet port  80  of the pressure booster  70  and also to the primary pressure supply port  28 . Therefore, the pressure of the fluid supplied to the first chamber  24   a  of the first cylinder  12  via the primary pressure supply port  28  is the same as that of the fluid supplied to the inlet port  80  of the pressure booster  70  (i.e., the primary pressure of the pressure booster  70 ). 
     The middle cover  18  includes, formed on one side surface thereof, a first breathing port  30  that opens to the atmosphere. A second breathing port  32  that opens to the atmosphere is formed on the other side surface of the middle cover  18  opposite to the one side surface. The second chamber  24   b  of the first cylinder  12  is opened to the atmosphere through the first breathing port  30 , and the third chamber  26   a  of the second cylinder  14  is opened to the atmosphere through the second breathing port  32 . 
     The second end cover  22  includes, formed on one side surface thereof, a secondary pressure supply port  34  that is connected to the outlet port  82  of the pressure booster  70  by an unillustrated tube. The pressurized fluid output from the pressure booster  70  is supplied to the fourth chamber  26   b  of the second cylinder  14  via the secondary pressure supply port  34 . The pressure of the fluid at the secondary pressure supply port  34  is the same as the pressure of the fluid at the outlet port  82  of the pressure booster  70  (i.e., the secondary pressure of the pressure booster  70 ). An output port  36  is provided on the other side surface of the second end cover  22  opposite to the one side surface where the secondary pressure supply port  34  is provided, and the pressurized fluid in the fourth chamber  26   b  of the second cylinder  14  can be taken out from the output port  36  and supplied to an unillustrated fluid pressure device. 
     The first end cover  20  is provided with a hollow  20   a  that allows the primary pressure supply port  28  to communicate with the first chamber  24   a  of the first cylinder  12  and that is capable of accommodating the first nut  17   a  therein. The second end cover  22  is provided with a hollow  22   b  that allows the secondary pressure supply port  34  and the output port  36  to communicate with the fourth chamber  26   b  of the second cylinder  14 . 
     Now, the pressure of the first chamber  24   a , that is, the primary pressure of the pressure booster  70 , is denoted by P 1 , the pressure of the fourth chamber  26   b  at which the forces acting on the piston assembly are balanced is denoted by P 2 ′, and the secondary pressure set by the pressure booster  70  is dented by P 2 . P 2 ′ can be determined based on P 1 , the cross-sectional area of the first piston  12   b , and the cross-sectional area of the second piston  14   b.    
     In order to maintain the pressure of the fluid taken out from the fourth chamber  26   b  at a value close to the secondary pressure P 2  set by the pressure booster, it is preferable that P 2 ′ be a value as close to P 2  as possible. Further, P 2 ′ needs to be P 2  or lower in order that the volume of the fourth chamber  26   b  can be restored after the piston assembly has moved until the volume of the fourth chamber  26   b  is minimized. 
     The pressure-booster output stabilizer  10  according to the present embodiment is basically configured as described above, and its operation will be described below. The initial state is assumed such that the pressures of the first to fourth chambers  24   a  to  26   b  are all equal to the atmospheric pressure and the piston assembly stands still at the position shown in  FIG.  4   . In this initial state, the pressure booster  70  is not operating. It is also assumed that the unillustrated flow path connecting the output port  36  and the fluid pressure device is closed by an unillustrated solenoid valve. 
     By switching an unillustrated switching valve from the above initial state, the pressurized fluid is supplied from the fluid supply source to the pressure booster  70  and the pressure-booster output stabilizer  10 . As a result, the pressurized fluid having the primary pressure P 1  is supplied to the inlet port  80  of the pressure booster  70 , and at the same time, the pressurized fluid having the primary pressure P 1  is also supplied to the primary pressure supply port  28  of the pressure-booster output stabilizer  10 . The pressurized fluid is supplied from the primary pressure supply port  28  to the first chamber  24   a  of the first cylinder  12 . 
     As (fluid having) the primary pressure is supplied to the inlet port  80  of the pressure booster  70 , operation of the pressure booster  70  is started, and the pressure-boosted fluid is supplied from the outlet port  82  of the pressure booster  70  toward the secondary pressure supply port  34  of the pressure-booster output stabilizer  10 . When the pressure booster  70  operates for a certain time period or more, the pressure in the fourth chamber  26   b  of the second cylinder  14  to which the pressurized fluid has been supplied through the secondary pressure supply port  34  reaches the secondary pressure P 2  set by the pressure booster  70 , and exceeds the pressure P 2 ′ at which the aforementioned piston assembly maintains balance. As a result, the piston assembly moves until the first piston  12   b  abuts against the first end cover  20 , and the pressurized fluid having the secondary pressure P 2  set by the pressure booster  70  is stored in the fourth chamber  26   b  of the second cylinder  14  (see  FIG.  5   ). 
     When the flow path connecting the output port  36  and the fluid pressure device is opened from the state in which the pressurized fluid having the secondary pressure P 2  has been stored in the fourth chamber  26   b  of the second cylinder  14 , the pressurized fluid stored in the fourth chamber  26   b  is supplied through the output port  36  toward the fluid pressure device. As the pressurized fluid stored in the fourth chamber  26   b  is taken out from the output port  36 , the piston assembly, to maintain the balance of the forces applied to the piston assembly, moves in such a way that the first piston  12   b  moves away from the first end cover  20  and the second piston  14   b  moves close to the second end cover  22 . 
     As a result, the volume of the fourth chamber  26   b  is reduced to thereby suppress the pressure drop. The pressure of the fourth chamber  26   b  is maintained so as not to fall at least below P 2 ′. When the pressure in the fourth chamber  26   b  falls below the secondary pressure P 2  set by the pressure booster  70 , the pressure booster  70  operates, but its operating speed is relatively moderate. In this way, the piston assembly moves to reduce the volume of the fourth chamber  26   b . Moreover, the pressurized fluid having the secondary pressure P 2  is replenished to the fourth chamber  26   b  from the outlet port  82  of the pressure booster  70  and the pressurized fluid is drawn out from the fourth chamber  26   b . Thus, it is possible to send out the pressurized fluid to the fluid pressure device at a stable pressure. 
     When the fluid pressure device stops using the pressurized fluid in a state where the first piston  12   b  is located at an intermediate position between the first end cover  20  and the middle cover  18 , since the pressurized fluid having the secondary pressure P 2  is supplied from the outlet port  82  of the pressure booster  70  to the fourth chamber  26   b , the piston assembly moves until the first piston  12   b  abuts against the first end cover  20 . As a result, the volume of the fourth chamber  26   b  is restored to the maximum. 
     When the fluid pressure device has continuously used an extremely large amount of pressurized fluid and the pressurized fluid stored in the fourth chamber  26   b  has been rapidly consumed, the piston assembly moves until the first piston  12   b  abuts against the middle cover  18 , so the volume of the fourth chamber  26   b  is minimized (see  FIG.  6   ). In this case, substantial operation is performed by the pressure booster  70  only, but when the amount of the pressurized fluid used in the fluid pressure device decreases or becomes zero, the volume of the fourth chamber  26   b  is restored again. 
       FIG.  7    is a diagram showing the relationship between the pressure and the flow rate of the pressurized fluid taken out, for two pressure boosters having different sizes, each with and without the pressure-booster output stabilizer. The horizontal axis represents the flow rate, and the vertical axis represents the pressure. A graph of circle points joined with a dotted line shows a case where a small pressure booster is used alone, and a graph of circle points joined with a solid line shows a case where the small pressure booster is used in combination with the pressure-booster output stabilizer. A graph of triangular points joined with a dotted line shows a case where a medium-sized pressure booster is used alone, and a graph of triangular points joined with a solid line shows a case where the medium-sized pressure booster is used in combination with the pressure-booster output stabilizer. 
     As can be understood from  FIG.  7   , use of the pressure-booster output stabilizer in combination suppresses the pressure drop when the flow rate increases. Further, combined use of the pressure-booster output stabilizer enables even a small pressure booster to have a capacity equivalent to a pressure booster of one size higher. 
     According to the pressure-booster output stabilizer  10  of the present embodiment, the first piston  12   b  on which the primary pressure of the pressure booster  70  acts and the second piston  14   b  on which the secondary pressure of the pressure booster  70  acts are coupled, and the pressurized fluid is taken out from the fourth chamber  26   b  to which (the fluid having) the secondary pressure is supplied. Thus, the pressurized fluid can be output at a stable pressure close to the secondary pressure of the pressure booster  70 . Further, since the operating speed of the pressure booster  70  is moderate, the amount of pressure fluid discharged from the discharge port  84  is reduced, whereby it is possible to reduce the consumption of pressure fluid and improve the durability of the pressure booster  70  as well. 
     Second Embodiment 
     Referring next to  FIGS.  8  and  9   , a pressure-booster output stabilizer  40  according to a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in that the pressurized fluid from the fluid supply source is supplied to the first chamber of the first cylinder and also to the third chamber of the second cylinder. The second embodiment will also be described as being used in combination with the pressure booster  70  described above in the first embodiment, but the combined pressure booster is not limited to the above-described pressure booster  70 . 
     The pressure-booster output stabilizer  40  includes a first cylinder  42  and a second cylinder  44  connected in series. The first cylinder  42  has a rectangular parallelepiped first cylinder tube  42   a  and a first piston  42   b  slidably arranged in a cylinder hole formed in the first cylinder tube  42   a . The second cylinder  44  has a rectangular parallelepiped second cylinder tube  44   a  and a second piston  44   b  slidably arranged in a cylinder hole formed in the second cylinder tube  44   a.    
     The first piston  42   b  is fixed to one end side of the piston rod  46 , and the second piston  44   b  is fixed to the other end side of the piston rod  46 . The first piston  42   b  and the second piston  44   b  move together with the piston rod  46  in the axial direction. The outside diameter of the first piston  42   b  is the same as the outside diameter of the second piston  44   b.    
     A middle cover  48  is provided between the first cylinder tube  42   a  and the second cylinder tube  44   a . A first end cover  50  is provided on an end side of the first cylinder tube  42   a  that is farther away from the middle cover  48 , whereas a second end cover  52  is provided on an end side of the second cylinder tube  44   a  that is farther away from the middle cover  48 . The pressure booster  70  is attached to the second end cover  52 . The piston assembly formed of the first piston  42   b , the second piston  44   b , and the piston rod  46  is configured to be able to move between a position where the first piston  42   b  abuts against the first end cover  50  and a position where the first piston  42   b  abuts against the middle cover  48 . 
     The inside of the cylinder hole of the first cylinder tube  42   a  is partitioned into a first chamber  54   a  on the first end cover  50  side and a second chamber  54   b  on the middle cover  48  side by the first piston  42   b . The inside of the cylinder hole of the second cylinder tube  44   a  is partitioned into a third chamber  56   a  on the middle cover  48  side and a fourth chamber  56   b  on the second end cover  52  side by the second piston  44   b.    
     The first end cover  50  is provided with a primary pressure supply first port  58  connected to the fluid supply source, and the middle cover  48  is provided with a primary pressure supply second port  60  connected to the fluid supply source. The pressurized fluid from the fluid supply source is supplied to the inlet port  80  of the pressure booster  70 , and also to the primary pressure supply first port  58  and the primary pressure supply second port  60 . Therefore, the pressure of the fluid supplied to the first chamber  54   a  of the first cylinder  42  via the primary pressure supply first port  58  and the pressure of the fluid supplied to the third chamber  56   a  of the second cylinder  44  via the primary pressure supply second port  60 , are the same as that of the fluid supplied to the inlet port  80  of the pressure booster  70  (i.e., the primary pressure of the pressure booster  70 ). 
     The middle cover  48  is formed with a breathing port (not shown) that is open to the atmosphere, and the second chamber  54   b  of the first cylinder  42  is opened to the atmosphere through this breathing port. The second end cover  52  is provided with a secondary pressure supply port  62  that is directly connected to the outlet port  82  of the pressure booster  70 . The pressurized fluid output from the pressure booster  70  is supplied to the fourth chamber  56   b  of the second cylinder  44  via the secondary pressure supply port  62 . The pressure of the fluid at the secondary pressure supply port  62  is the same as the pressure of the fluid at the outlet port  82  of the pressure booster  70  (i.e., the secondary pressure of the pressure booster  70 ). Further, the second end cover  52  is provided with an output port  64 , and the pressurized fluid in the fourth chamber  56   b  of the second cylinder  44  can be taken out from the output port  64  and supplied to an unillustrated fluid pressure device. The output port  64  is arranged at a position away from the secondary pressure supply port  62 . 
     Here, the pressure of the first chamber  54   a  and the third chamber  56   a , that is, the primary pressure of the pressure booster  70 , is denoted by P 1 , the pressure of the fourth chamber  56   b  at which the forces acting on the piston assembly are balanced is denoted by P 2 ′, and the secondary pressure set by the pressure booster  70  is dented by P 2 . P 2 ′ can be determined based on P 1 , the cross-sectional area of the first piston  42   b , the cross-sectional area of the second piston  44   b , and the cross-sectional area of the piston rod  46 . 
     In order to maintain the pressure of the fluid taken out from the fourth chamber  56   b  at a value close to the secondary pressure P 2  set by the pressure booster  70 , it is preferable that P 2 ′ be a value as close to P 2  as possible. Further, P 2 ′ needs to be P 2  or lower in order that the volume of the fourth chamber  56   b  can be restored after the piston assembly has moved until the volume of the fourth chamber  56   b  is minimized. 
     The pressure-booster output stabilizer  40  according to the present embodiment is thus configured, and its operation is the same as that of the pressure-booster output stabilizer  10  described above, so the description is omitted. 
     According to the pressure-booster output stabilizer  40  of the present embodiment, the primary pressure and the secondary pressure of the pressure booster  70  act on the piston assembly, and the pressurized fluid is taken out from the fourth chamber  56   b  to which (the fluid having) the secondary pressure is supplied. Accordingly, it is possible to output the pressurized fluid at a stable pressure close to the secondary pressure of the pressure booster  70 . Further, since the operating speed of the pressure booster  70  is moderate, the amount of pressure fluid discharged from the discharge port  84  is reduced, whereby it is possible to reduce the consumption of pressure fluid and improve the durability of the pressure booster  70  as well. 
     The pressure-booster output stabilizer according to the present invention is not limited to the above-described embodiments, and may naturally have various configurations without departing from the essence and gist of the present invention.