Patent Publication Number: US-2019167520-A1

Title: Air pressure massager

Description:
TECHNICAL FIELD 
     The present invention relates to a massager that continuously pressurizes body parts to which massages need to be applied by means of the expansion force and compression force of an air bag, which are produced when air in a cylinder is supplied into the air bag and recovered from the same while a piston moves upward and downward. 
     DESCRIPTION OF THE RELATED ART 
     Korean Patent No. 10-0835755 titled “a high technical skill kyungrak (acupuncture meridians) massage machinery” relates to machinery that forcibly transfers air in a cylinder into an air bag through a hose when an eccentric cam rotates and moves a piston downward, so as to use expansion force produced in the air bag. 
     The above-described massage machinery is configured to move a piston upward by means of the elasticity of a return spring after pressurizing a body part using the expansion force. However, the air having been supplied into the air bag is almost recovered into the cylinder, and very little air is left in the air bag. When air to be sucked into the cylinder is not enough at the time of moving the piston upward, air pressure inside the cylinder is low. Thus, the piston moves upward slowly due to pressing force of the atmospheric pressure applied on the piston, and noise is made when the piston moves upward. 
     When the piston moves up to the top dead center, all the air having been supplied into the air bag is recovered into the cylinder. At this moment, a valve has to be replaced such that 100% of the supplied air may be recovered and then supplied into the air bag, and constant expansion force has to be produced in a plurality of air bags so as to perform massages effectively. However, the piston may not move up to the top dead center rapidly only by using the force of the return spring. When the valve is replaced and new air is supplied in the state where all the air is not recovered, air as much as the air remaining in the air bag is short in the air bag. Thus, expansion force is weak. 
     Therefore, when a return spring is used to move a piston upward, a limited amount of air may not be used completely, and noise is made when a piston starts to move upward. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problems 
     The present invention is directed to providing an air pressure massager which can be operated forcibly so as to move a piston upward, move the piston up to the top dead center rapidly without making noise, and supply a predetermined amount of air alternately to a plurality of air bags without losing the air, in the process of supplying a predetermined amount of air in a cylinder into an air bag and recovering the air from the air bag. 
     Technical Solutions 
     As a means to achieve the above-described purposes, an air pressure massager according to the present invention, which includes a cylinder, a piston vertically reciprocating inside the cylinder, a main hose connected to the cylinder so as to be a passage for supplying and recovering air by the vertical reciprocation of the piston, a valve connected to the main hose so as to supply and cut off air pressure, an air bag connected to the valve so as to perform an acupressure function by using the transferred air pressure, and a driving part for providing rotational power, may include a rotary shaft coupled to the driving part, a first eccentric cam coupled to the rotary shaft, a first press bar the upper end portion of which comes into contact with the lower end portion of the first eccentric cam and the lower end portion of which is coupled to the upper end portion of the piston, a second eccentric cam coupled to the rotary shaft, a second press bar the lower end portion of which comes into contact with the upper end portion of the second eccentric cam, a link for connecting the first press bar and the second press bar, a circular container coupled to the rotary shaft and having a bar on both surfaces thereof for controlling a noise prevention valve, a circular disc cam opening and closing a valve piston while alternately rotating left and right by the rotation of the circular container, a valve piston the upper end portion of which comes into contact with the lower end portion of the circular disc cam, and a hose for connecting a hole configured as an air passage of the valve piston and the cylinder such that air passes, wherein when the first press bar moves downward by the eccentric rotation of the first eccentric cam, the second press bar connected to the first press bar by the link also moves downward, and when the second press bar moves upward by the eccentric rotation of the second eccentric cam, the first press bar connected to the second press bar by the link also moves upward. 
     As a means to achieve the above-described purposes, an air pressure massager according to the present invention, which includes a cylinder, a piston vertically reciprocating inside the cylinder, a main hose connected to the cylinder so as to be a passage for supplying and recovering air by the vertical reciprocation of the piston, a valve connected to the main hose so as to supply and cut off air pressure, an air bag connected to the valve so as to perform an acupressure function by using the transferred air pressure, and a driving part for providing rotational power, may include a rotary shaft coupled to the driving part, a grooved cam coupled to the rotary shaft and having a groove corresponding to a curved outline of the cam on the flat surface of one side thereof, and a press bar for a grooved cam whose lower end portion is coupled to the upper end portion of the piston and which vertically reciprocates by means of changes in the height of the groove of the grooved cam according to the rotation of the grooved cam by inserting a bearing protruding from the upper end portion of the press bar for a grooved cam in the lateral direction thereof into the groove of the grooved cam. 
     Additionally, as a means to achieve the above-described purposes, an air pressure massager according to the present invention, which includes a cylinder, a piston vertically reciprocating inside the cylinder, a main hose connected to the cylinder so as to be a passage for supplying and recovering air by the vertical reciprocation of the piston, a valve connected to the main hose so as to supply and cut off air pressure, an air bag connected to the valve so as to perform an acupressure function by using the transferred air pressure, and a driving part for providing rotational power, may include a rotary shaft coupled to the driving part, a pinion coupled to the rotary shaft, a cylindrical grooved cam configured as a cylinder-shaped member having flat upper and lower surfaces, having saw teeth which are formed along the edge of the upper surface thereof and engaged with the pinion, and having a groove which is formed and gives a turn along a curved surface on the lateral surface of the cylindrical grooved cam and whose height is continuously changed, and a press bar for a cylindrical grooved cam whose lower end portion is coupled to the upper end portion of the piston and which vertically reciprocates by means of changes in the height of the groove of the cylindrical grooved cam according to the rotation of the cylindrical grooved cam by inserting a bearing protruding from the upper end portion of the press bar for a grooved cam in the lateral direction thereof into the groove of the cylindrical grooved cam. 
     Additionally, as a means to achieve the above-described purposes, an air pressure massager according to the present invention, which includes a cylinder, a piston vertically reciprocating inside the cylinder, a main hose connected to the cylinder so as to be a passage for supplying and recovering air by the vertical reciprocation of the piston, a valve connected to the main hose so as to supply and cut off air pressure, an air bag connected to the valve so as to perform an acupressure function by using the transferred air pressure, and a driving part for providing rotational power, may include a rotary shaft coupled to the driving part, an eccentric cam coupled to the rotary shaft, a press bar the upper end portion of which comes into contact with the lower end portion of the eccentric cam and the lower end portion of which is coupled to the upper end portion of the piston, and a return spring built into a spring box in a space at the lower side of the piston inside the cylinder and applying pushing force so as to move the piston upward when the return spring is compressed. 
     Additionally, the piston is preferably further provided with a through hole vertically penetrating the piston, a pressure valve installed inside the through hole and opened when air pressure inside the cylinder is lower than air pressure in a space at the upper side of the piston so as to settle differences in the air pressure at the upper and lower sides of the piston, and an air suction valve installed on the lateral wall of the upper portion of the cylinder and opened when air pressure inside the cylinder is lower than air pressure outside the cylinder. 
     Advantageous Effects 
     The present invention has the advantage of being operated forcibly only with a cam, moving a piston up to the top dead center rapidly without making noise, enabling the expansion force of an air bag to remain constant, thereby making it possible to continuously perform messages, instead of removing a return spring that is a means to move a piston up in the process of moving the piston upward and downward so as to supply and recover air in the cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of an air pressure massager provided with a noise prevention valve which prevents noise while forcibly driving a piston with first and second eccentric cams according to an embodiment of the present invention. 
         FIG. 2  illustrates the structure of a noise prevention valve. 
         FIG. 2A  is a front view of the structure of a noise prevention valve,  FIG. 2B  is a right side view thereof, and  FIG. 2C  is a reference view illustrating changes in the height of the bottom surface of a circular disc cam as lines. 
         FIG. 3  illustrates a state where a first eccentric cam according to an embodiment of the present invention moves a piston downward while rotating. 
         FIG. 4  is a side view of a second eccentric cam according to an embodiment of the present invention. 
         FIG. 5  is a view of an air pressure massager according to an embodiment of the present invention, provided with a valve having plurality of valve holes connected to a hose the end of which is connected with two air bags so as to massage acupuncture meridians. 
         FIG. 6  is a front view of an air pressure massager which is driven using a grooved cam and a press bar therefor according to another embodiment of the present invention. 
         FIG. 7  is a side view of a grooved cam according to another embodiment of the present invention. 
         FIG. 8  is a front view of an air an air pressure massager using a gear and a cylindrical grooved cam according to another embodiment of the present invention. 
         FIG. 9  is a perspective view of the gear and cylindrical grooved cam of the air pressure massager in  FIG. 7 . 
         FIG. 10  is a front view of an air pressure massager using a pressure valve and a return spring according to another embodiment of the present invention. 
         FIG. 11  is a front view of an air pressure massager using a return spring, a valve cam for opening and closing a valve, and a valve according to yet another embodiment of the present invention. 
         FIG. 12  is a front view of a valve cam assembled with the air pressure massager in  FIG. 11 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     According to the present invention, an air pressure massager, which includes a cylinder, a piston vertically reciprocating inside the cylinder, a main hose connected to the cylinder and configured as a passage for supplying and recovering air by the vertical reciprocation of the piston; a valve connected to the main hose so as to supply and cut off air pressure; an air bag connected to the valve so as to perform acupressure by using the transferred air pressure; and a driving part for providing rotational power, includes a rotary shaft coupled to the driving part; a first eccentric cam coupled to the rotary shaft; a first press bar the upper end portion of which contacts the lower end portion of the first eccentric cam and the lower end portion of which is coupled to the upper end portion of the piston; a second eccentric cam coupled to the rotary shaft; a second press bar the lower end portion of which contacts the upper end portion of the second eccentric cam; a link for connecting the first press bar and the second press bar; a circular container coupled to the rotary shaft and having a bar on both surfaces thereof for controlling a noise prevention valve; a circular disc cam opening and closing a valve piston while alternately rotating left and right by the rotation of the circular container; a valve piston the upper end portion of which contacts the lower end portion of the circular disc cam; and a hose connecting a hole configured as an air passage of the valve piston and the cylinder such that air passes, wherein the second press bar connected to the first press bar by the link also moves downward when the first press bar moves downward by the eccentric rotation of the first eccentric cam, and the first press bar connected to the second press bar by the link also moves upward when the second press bar moves upward by the eccentric rotation of the second eccentric cam. 
     MODE FOR CARRYING OUT THE INVENTION 
     The present invention is specifically described with reference to the attached drawings as follows. 
       FIG. 1  is a front view of an air pressure massager which forcibly drives a piston upward and downward with first and second eccentric cams according to an embodiment of the present invention and is provided with a noise prevention valve. 
     A base block  40  coupled to the upper end of a cylinder  10 , a main block  50  erected upward on the base block, and an assistant block  90  erected at a predetermined distance away from the main block  50  are assembled. A geared motor and a speed reducer are coupled to the main block  50 , and a first eccentric cam  180  and a second eccentric cam  200 , a circular container  270  having a bar on both surfaces thereof for controlling a noise prevention valve are fixedly coupled to a rotary shaft  116  which rotates by means of the operation of the geared motor and is rotatably supported by the main block  50  and the assistant block  90 . Both end portions of a guide  70  are respectively coupled to the upper end portion of the main block  50  and the upper end portion of the assistant block  90 , and the guide is installed so as to horizontally cross the upper end portion of the main block and the upper end portion of the assistant block. 
     When power is supplied to the motor, the first eccentric cam  180  rotates. In this case, a first press bar  30   a , and a second press bar  37  which is connected with a piston  20  coupled to the lower end of the first press bar by a link  190  simultaneously move downward. 
     When the piston  20  moves downward, air in the cylinder  10  below the piston  20  is forcibly transferred into a valve  140  through a main hose  225  and then transferred into two air bags  210  connected with only one opened valve among twelve valve holes  230  so as to expand the air bags  210 . 
     The second eccentric cam  200  moves the second press bar  37  upward while rotating, as the rotary shaft  116  continues to rotate after body parts are pressurized by means of the expansive force. In this case, the first press bar  30   a  connected with the second press bar by the link  190 , and the piston  20  coupled with the first press bar  30   a  move upward. 
     When the piston  20  moves upward, the space where air rarely exists is created in the cylinder  10 . Thus, the air having been supplied into the air bag  210  is recovered, and the expansive force of the air bag  210 , applied to the body parts, ceases to exist, thereby making pressure cease to exist. 
     Massages are continuously performed through the above-described process. As a first passive gear  101 , coupled with a gear shaft  115  that is engaged with a first single-tooth gear  100  and is rotatably supported by the assistant block  90 , rotates as first single-tooth gear  100  coupled with the rotary shaft  116  rotates, a second single-tooth gear  102  coupled with the gear shaft  115  rotates as the first passive gear  101  rotates, and a second passive gear  103 , engaged with the second single-tooth gear  102  and coupled to a circular disc cam shaft  110 , rotates as the second single-tooth gear  102  rotates so as to operate only one valve. Twelve valve holes  230  are opened consecutively one by one, and air having been supplied into the cylinder  10  is supplied to the air bag  210  connected to the opened valve through the opened valve such that massages are performed on the body part contacting the air bag. Massages are performed as illustrated in  FIG. 5 . 
     Details on the valve that operates by means of the rotation of the first single-tooth gear  100 , the first passive gear  101 , the second single-tooth gear  102 , the second passive gear  103  and the circular disc cam  160  are disclosed in South Korean Patent No. 10-0835755 and will be omitted herein. 
     Meanwhile, the circular having a bar on both surfaces thereof for controlling a noise prevention valve is coupled to the rotary shaft  116 , rotates the circular disc cam  271  left to right while rotating, opens a valve piston  273  under the circular disc cam right before the piston  20  moves upward so as to discharge compressed air from the air bag and remove air pressure, and then starts to move the piston upward so as to prevent noise that is made while the piston pops out by means of air pressure supporting the piston. Air is sucked into the cylinder  10  through the opened valve while the piston moves upward. Thus, when the piston  20  rapidly move up to the top dead center and then moves downward in the state where the valve piston  273  is closed right before the piston moves downward, massages may be continuously performed while air in the cylinder is supplied and recovered into the air bag through the valve. 
       FIG. 2  illustrates the structure of a noise prevention valve. When the circular container  270  having a bar on both surfaces thereof pushes the projection  276  of the circular disc cam while being coupled to the rotary shaft  116  and rotating in the direction of the arrow, the circular disc cam rotatably supported by the circular disc cam shaft  277  alternately rotates left and right so as to open and close the valve piston. 
     Specifically, when a bar A pulls the projection of the circular disc cam while rotating, the circular disc cam rotates left, and the high portion of the lower surface of the circular disc cam stops over the valve piston  273 . In this case, a horizontal hole of the valve piston  273  moves over a valve cylinder  272  so as to discharge air from the air bag and remove air pressure. Then, when the piston  20  moves upward by means of the rotation of the second eccentric cam  200  in the state where air pressure is removed, noise is not made, and when the valve is opened while the piston  20  moves upward, enough air is sucked into the cylinder  10 . 
     When a bar B pulls the projection of the circular disc cam  276  by means of the continuous rotation of the circular container  270  having a bar on both surfaces thereof, the inclined surface and low portion of the lower end of the circular disc cam move over the valve piston  273  while the circular disc cam rotates right, and when the valve piston  273  is pressed downward, a horizontal hole  275  moves downward into the valve cylinder  272 . In this case, when the piston  20  moves downward by means of the rotation of the first eccentric cam  180  in the state where air is blocked, 100% of air in the cylinder  10  is supplied into the air bag. Thus, the expansive force of the air bag remains constant such that massages may be performed without noise. 
       FIG. 2C  is a reference view illustrating changes in the height of the lower end of a circular disc cam according to the central angle thereof as straight lines. 
       FIG. 3  illustrates a configuration in which a first eccentric cam  180  moves a first press bar  30   a  downward contacting the lower end of the first eccentric cam  180  while rotating around a rotary shaft  116 . 
     A needle bearing  35   a  is assembled onto the upper portion of the first press bar  30   a , and the piston  20  is screw-coupled to the lower end portion of the first press bar  30   a.    
     While the portion where the central angle of the eccentric cam is 0° rubs against the bearing  35   a  at the upper portion of the first press bar  30   a , the first press bar  30   a  and the piston  20  are positioned at the top dead center. When the first eccentric cam  180  rotates in the direction of the arrow, passes through the central angle of a° where the radius of the eccentric cam becomes long, and the portion of b° rubs against the bearing  35   a , the piston  20  moves downward to the bottom dead center. While the section from b° to c° rubs against the bearing  35   a , the radius of the cam remains the longest. Thus, the piston stays at the bottom dead center. 
     The radius of the first eccentric cam becomes short from the portion of c°. Thus, the first press bar  30   a  and the piston  20  connected by the link  190  move upward while the second press bar  37  moves upward by means of the second eccentric cam  200 . When the portion of e° rubs against the bearing  35   a , the first press bar  30   a  and the piston  20  connected to the lower end of the first press bar move up to the top dead center again. 
       FIG. 4  illustrates a second eccentric cam  200 , and the second eccentric cam  200  moves the piston  20  upward and downward in cooperation with the first eccentric cam  180  while moving the second press bar  35  upward. 
     The second eccentric cam  200  is used to move the piston  20  upward. As opposed to the first eccentric cam  180 , the second eccentric cam  200  moves the second press bar  37  upward and simultaneously moves the first press bar  30   a  connected with the second press bar by the link  190  and the piston  20  coupled to the lower end of the first press bar while the second press bar  37  is positioned over the second eccentric cam  200 , and the second eccentric cam  200  rotates below the second press bar  37 . 
     The first press bar  30   a  and the second press bar  37  are engaged by the link  190  so as to be simultaneously moved upward and downward. The piston  20  moves upward and downward by means of the rotation of the first  180  and second  200  eccentric cams. The second press bar  37  extends upward and penetrates a guide hole formed at the guide  70  such that the guide  70  may guide the upward and downward movements of the second press bar  37 . 
     Specifically, when the first eccentric cam  180  moves the first press bar  30   a  downward while rotating, the piston  20 , coupled to the lower end of the first press bar  30   a , and the second press bar  37 , connected with the first press bar  30   a  by the link  190 , simultaneously moves downward, and when the rotary shaft  116  continuously rotates, and the second eccentric cam  200  moves the second press bar  37  upward, air in the cylinder is supplied and recovered into the air bag, while the first press bar  30   a , connected with the second press bar  37  by the link  190 , and the piston  20 , coupled to the lower end of the first press bar  30   a , also move upward, such that massages may be continuously performed. 
       FIG. 5  illustrates a state where massages are performed with a belt  215  and an air bag  210 . A hose  220  is inserted into each of the plurality of valve holes provided to the valve  140 , an air bag  210  is connected to the opposite end of the hose  220 , the air bag  210  is attached to a body part to which massages need to be applied, and then, a belt  215  is fastened around the air bag  210  such that massages are performed. 
     When air is supplied into the air bag  210  through the valve  140 , a flat air bag  210  is inflated, the belt  215  is pulled, and the body part fastened by the belt  215  is pressurized. When the piston  20  moves upward again, air having been supplied to the air bag  210  is sucked into the cylinder  10  again, and pressure is dealt with. This process is repeated such that massages are continuously performed. 
       FIGS. 6 and 7  illustrate another embodiment of the present invention. 
     According to the embodiment illustrated in  FIG. 1 , a first eccentric cam  180 , a first press bar  30   a , a second eccentric cam  200  and a second press bar  37  are used to move a piston  20  upward and downward. However, according to this embodiment, a grooved cam  185  and a press bar for a grooved cam  30   b  are used to move a piston  20  upward and downward. As in the case of the massager in  FIG. 1 , the massager in  FIGS. 6 and 7  uses only cams so as to move a piston  20  upward and downward without s spring. 
       FIG. 7  is a side view of the grooved cam  185  of the embodiment illustrated in  FIG. 6 . 
     When a grooved cam  185  rotates in the direction of the arrow in the state where the bearing  35   b  of a press bar for a grooved cam  30   b  is fitted into the groove  186  of the grooved cam  185 , the press bar for a grooved cam  30   b  moves upward and downward according to the height of the groove  186 . When the groove  186  corresponding to the portion where the central angle of the grooved cam  185  is 0° rubs against the bearing  35   b , the groove  186  is positioned closest to a shaft hole  187 . In this case, the press bar for a grooved cam  30   b  is moved uppermost. Thus, the bearing  35   b  fitted into the groove  186  moves up to the top dead center, and the piston  20  coupled to the press bar for a grooved cam  30   b  also moves up to the top dead center. 
     The press bar for a grooved cam  30   b  is always positioned in the vertically downward direction of the shaft hole  87 . Thus, when rotating, the grooved cam  185  moves upward and downward according to the height of the groove  186 . 
     When the grooved cam  185  rotates in the direction of the arrow, the groove  186  becomes gradually farther from the shaft hole  187  while the groove  185  from the central angle of 0° to the central angle of a° rubs against the bearing  35   b . Thus, the press bar for a grooved cam  30   b  moves downward gradually. Thus, the press bar for a grooved cam  30   b  moves downward gradually. The press bar for a grooved cam  30   b  stops at the bottom dead center while the section from b° to c°, where the groove  186  is positioned farthest from the center of the shaft hole  187 , rubs against the bearing  35   b.    
     The press bar for a grooved cam  30   b  starts to move upward from the moment when the portion of c° rubs against the bearing  35   b  by means of the continuous rotation of the grooved cam  185 , and when the portion of e° rubs against the bearing  35   b , the press bar for a grooved cam  30   b  moves up to the top dead center again. 
     Thus, when the grooved cam  185  continuously rotates, the press bar for a grooved cam  30   b  and the piston  20  continuously move upward and downward, and air in the cylinder is supplied and recovered such that massages may be continuously performed. 
     The press bar for a grooved cam  30   b  has a different shape from the first press bar  30   a . Because the bearing  35   b  rotates in the state where the bearing is fitted into the groove  186  of the grooved cam  185 , the press bar for a grooved cam  30   b  moves upward and downward according to the height of the groove  186  of the grooved cam  185  and moves the piston  20  coupled to the lower end thereof upward and downward. 
       FIG. 8  illustrates an embodiment configured to move a press bar for a cylindrical grooved cam  30   c  upward and downward while the cylindrical grooved cam  65 , a variation of the grooved cam  185  of the embodiment in  FIG. 6 , rotates. 
     According to this embodiment, as illustrated in  FIG. 9 , when a pinion  60  such as a spur gear having a usual involute tooth profile rotates around a horizontal rotary shaft  116 , the pinion is engaged with the saw teeth circularly arranged along the edge of the upper surface of the cylindrical grooved cam  65  and makes the cylindrical grooved cam  65  rotate. A gear with the above-described configuration is similar to a face gear among intersecting axe gears. When the cylindrical grooved cam  65  rotates, the bearing  35   c  moves upward and downward according to the height of the groove  66 , and the press bar for a cylindrical grooved cam  30   c  moves the piston  20  upward and downward while moving upward and downward because the bearing  35   c  is fitted into the groove  66  of the cylindrical grooved cam  65 . 
     In  FIG. 9 , while the portion where the central angle is 0° rubs against the bearing  35   c , the groove  66  is positioned uppermost, and the press bar for a cylindrical grooved cam  30   c  reaches the top dead center. When the cylindrical grooved cam  65  rotates in the direction of the arrow, and the portion of a° moves close to the bearing  35   c , the press bar for a cylindrical grooved cam  30   c  moves downward, and when the cylindrical grooved cam  65  continuously rotates, the press bar for a cylindrical grooved cam  30   c  moves upward and downward according the position of the groove  66 , and air in the cylinder is supplied and recovered such that massages are performed. 
       FIG. 10  is a front view of an air pressure massager using an eccentric cam  180  and a return spring  250  according to another embodiment of the present invention. 
     According to this embodiment, an air pressure massager further includes a return spring  250 , which supports the piston  20  and is built into a spring box  11  at the lower end of the cylinder  10 , instead of a second eccentric cam, a second press bar and a link according to the embodiment in  FIG. 1 , wherein the return spring is compressed when the piston  20  moves downward, and when the portion, where the radius of the eccentric cam  180  is short, rubs against the press bar  30 , the piston  20  moves upward by means of the elasticity of the return spring, a pressure valve  240  provided to the piston  20 , and an air suction valve  241  provided to the side wall of the upper portion of the cylinder  10  are further included. 
     The pressure valve  240  as a check valve plugs the inside of a through hole formed at the piston so as to penetrating the piston in the up-down direction thereof. A spring is provided inside a usual check valve so as to support the valve elastically. When the valve is pressed by an external force stronger than the elasticity of the spring, the valve moves creating a gap and is opened so as to allow air to move. When the external force is weaker than the elasticity of the spring, the gap disappears because the valve is pushed by the spring, and the valve is closed. 
     According to the present invention, when air in the cylinder  10  is forcibly transferred to the air bag  210  while the piston  20  moves downward, the space in the air bag  210  is smaller than the space in the cylinder  10 , and the air is compressed, thereby producing the air pressure of about 200 g per square centimeter (cm 2 ). 
     When the piston  20  moves downward, the pressure of air in the air bag  210  is higher than that in the atmosphere. When some of the air leaks through a connecting portion of a hose for six seconds after the piston moves downward, and the piston  20  moves upward again, air as much as the leaked air is not sucked into the cylinder  10 . Thus, the air pressure in the cylinder  10  is weaker than the atmospheric pressure. 
     For instance, if 5% of air is lost, the pressure of 50 g per square centimeter is weaker than the atmospheric pressure. Suppose that the cross section dimension of the piston  20  moving upward is 200 cm 2 . The piston  20  is pressed by the atmospheric pressure corresponding to 200 kg. Thus, air in the cylinder  10  is short of force for supporting the piston  20  corresponding to 10 kg. 
     When the piston  20  is near the bottom dead center, the return spring  250  is compressed and has high elasticity, and air pressure is applied. In this case, the piston easily moves upward. However, when the piston is near the top dead center, the return spring  250  is almost stretched and has low elasticity, and the pressing force of the atmospheric pressure applied on the piston  20  is stronger than the elasticity of the return spring  250 . Thus, the piston does not move up easily. 
     Supposed that the cross section dimension of the upper surface of the pressure valve  240  is 1 cm 2 . The valve is pressed by the atmospheric pressure corresponding to 1 kg. Thus, the pressure valve  240  is supported by the air pressure in the cylinder  10  corresponding to 950 g that accounts for 95% of the pressing force of the atmospheric pressure. The pressing force of the atmospheric pressure, which is applied to the pressure valve  240 , is 50 g stronger than the supporting force of the air pressure. If the force of the return spring  250  for pushing up the pressure valve  240  corresponds to 20 g, the pressing force of the atmospheric pressure is 30 g stronger than the force of the return spring. The pressure valve  240  is pressed by the atmospheric pressure. In this case, the pressure valve  240  is opened, and air at the upper portion of the pressure valve  240  is sucked into the cylinder  10 . Thus, air pressure inside the cylinder  10  at the lower portion of the piston  20  becomes identical with that outside the cylinder at the upper portion of the piston  20  thereby making it possible to move the piston  20  upward only with the force of the return spring  250 . 
     When the air suction valve  241  as a check valve is attached to any portion that is linked to the inside of the cylinder  10  except for the piston, the air suction valve  241  is automatically opened by means of the difference in air pressure, and air is sucked into the cylinder  10 . As a result, the piston easily moves upward. That is, the atmospheric pressure outside the cylinder  10  is automatically balanced with the air pressure inside the cylinder  10  by means of the air suction valve  241 . In the cylinder  10 , the air pressure at the upper portion of the piston  20  and the air pressure at the lower portion of the piston  20  are automatically controlled and balanced by means of the pressure valve  240 . 
       FIG. 11  is a front view of an air pressure massager using a return spring  250 , a valve, and a valve cam  181  for opening and closing a valve according to yet another embodiment of the present invention so as to easily move a piston  20  upward. According to this embodiment, a return spring  250 , pushing and supporting the piston  20  and built into a spring box  11  at the lower end of the center of the cylinder  10 , and a hose  224 , connecting an air suction valve  241  and a suction mouth at lower end of a cylinder  10 , which are opened and closed by means of the rotation of the valve cam  181  assembled with a rotary shaft  116 , are included instead of a second eccentric cam, a second press bar and a link according to the embodiment in  FIG. 1 . Right before the piston moves upward, the valve cam  181  opens the valve  242  so as to discharge some of the compressed air. Then, air pressure that rapidly moves the piston upward is partially removed, and the piston  20  moves upward only with the elasticity of a spring, when the piston moves upward. Thus, noise caused by the upward movement of the piston  20  significantly decreases. When the valve is opened during the upward movement of the piston  20 , air sucked into the valve is sufficiently sucked into the cylinder through the hose  224  connected to the lower end of the cylinder. Thus, the piston may move up to the top dead center rapidly even though a return spring has low elasticity. 
     The piston then moves downward by means of the rotation of the first eccentric cam  180  in the state where the valve  242  is closed by means of the rotation of the valve cam  181 , right before the piston  20  moves downward. In this case, 100% of air in the cylinder is supplied into the air bag such that pressing force applied on a body part, to which massages will be performed, may remain constant. 
     A return spring illustrated in FIG. 1 in Korean Patent No. 10-0835755 may not be installed, and therefore the piston may not normally move upward because the return spring collides with another part. Thus, the spring box  11  is separately provided at the lower end of the cylinder  10  such that the spring is built into the spring box. In this case, the piston moves down to the bottom dead center and then normally moves upward by means of the elasticity that is caused when the spring is compressed. 
       FIG. 12  is a front view of a valve cam for opening and closing a valve. At the moment when a protruding part that is assembled with the rotary shaft  116  and formed at the portion where the central angle of the valve cam is 355° touches the valve  240 , while rotating simultaneously together with the first eccentric cam, the valve is closed, and at the moment when the protruding part at the central angle of c° touches the valve  240 , the valve is opened. Thus, the protruding part opens the valve right before the piston moves upward while the protruding part closes the valve right before the piston moves downward.