Abstract:
In an air-type shock absorber, a piston is sealing situated in a cylinder chamber. A vacuum state occurs in a piston bearing side of the cylinder chamber when a piston is pushed. Also, an air reservoir is provided at a side opposite to the piston bearing to have a sealed structure, so that a force of absorbing a shock can be increased to have the same effect as in an oil-type shock absorber. The shock absorber can be used not only at a place requiring cleanness but also in adverse environment in which the shock absorber is exposed to water or coolant, and durability of the shock absorber is also improved.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to a shock absorber for absorbing a shock of a moving member in case the moving member, such as work, is transferred from a moving state to a stopping state. 
     In a conventional shock absorber, oil is used, as shown in FIG. 8 of Japanese Patent Application No. 2000-153832 (corresponding U.S. patent application Ser. No. 09/571,593). Thus, there is a disadvantage of oil stain due to the oil leakage and oozing out of oil. 
     In order to eliminate the above disadvantage, a shock absorber using air has been invented, as shown in, for example, FIG. 1 through FIG. 3 of Japanese Patent Application No. 2000-153832. 
     FIGS. 7 through 9 generally correspond to FIGS. 1 through 3 of Japanese Patent Application No. 2000-153832, and as an example of a prior shock absorber, a shock absorber in FIGS. 7 through 9 will be briefly explained based mainly on operations thereof. From a state shown in FIG. 7, a moving member W is moved rightward, and a piston shaft  102  pressed by the moving member W slides in a piston bearing  101   a  to be displaced rightward, so that a piston  103  provided integrally with the piston shaft  102  compresses air in a cylinder  101  (refer to FIG.  8 ). 
     In this case, in order to prevent a space between a left end side of the piston  103  and an inner wall of a left side of the cylinder  101  from becoming a vacuum state, air flows to the left side of the piston  103  through an air extracting hole  109 . 
     As shown in FIG. 8, air compressed by the piston  103  passes through a first air passage  116 , and flows in an arrow direction for a flow quantity determined by a flow quantity control valve formed of a flow quantity control shaft  113   b  and a flow quantity control shaft hole  114  of a speed controller section B, and air flows backward to outside or a compressed air tank, not shown, through a second air passage  117  and a tube  118 . 
     Furthermore, when the piston  103  reaches an inner end portion of the cylinder  101  such that the right end of the piston  103  abuts against a cylinder wall  106  or a contact  105  abuts against a left end of the piston bearing  101   a , the moving member W stops while receiving cushions of air and a compressing coil spring  108 . 
     When the pressing force of the moving member W against the piston  102  is removed, the piston  103  starts moving leftward by a reactive force of the compression coil spring  108  and an air pressure from the compression air tank (refer to FIG.  9 ). 
     In this case, as shown in FIG. 9, since air in the second air passage  117  opens a check valve  115  by resisting against the pressing force of the compression coil spring  115   a  such that the air in the second air passage  117  is directly sent to the first air passage  116 , a large quantity of air flows in a short time regardless of the flow quantity of air determined by a slit formed by the flow quantity controlling shaft  113   b  and the flow quantity controlling shaft hole  114 . Thus, the piston  3  is quickly displaced leftward to restore to the state shown in FIG.  7 . 
     Incidentally, reference numeral  116   a  denotes a groove connecting the first air passage  116  and an air chamber  115   b , and the check valve  115  can be opened without compressing air in the air chamber  115   b.    
     In the shock absorber using air as described above, as compared to the shock absorber using oil, there might be a case that the force of absorbing a shock is insufficient in order to absorb a movement of the detecting member, and in this case, a larger-scaled shock absorber has to be used. 
     In view of the foregoing, an object of the invention is to provide a shock absorber, in which a force of absorbing a shock is increased to be equivalent to the shock absorber using oil, and air inside the shock absorber is airtightly confined irrespective of outside air, such that dustproof and waterproof functions are made perfect, and the shock absorber can be used in a clean room. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     To achieve the aforementioned objects, the present invention provides a shock absorber, which comprises: a cylinder having a cylinder chamber; a piston bearing integrally formed at one end of the cylinder to be arranged coaxially therewith; a piston slidably provided in the cylinder chamber and having a piston shaft including a distal end projecting from the piston bearing; a flow quantity control valve disposed at the other side of the cylinder; a check valve disposed at the other side of the cylinder; a through hole bored through a piston to penetrate from a piston bearing side to a side located opposite to the piston bearing; and valve means provided in the through hole. The piston shaft slidably moves in the piston bearing when the distal end thereof is pressed by a moving member, and the piston compresses air in the cylinder chamber when the piston is pushed toward the other end of the cylinder, so that a portion of the cylinder chamber located at a side of the piston bearing is made into a vacuum state. 
     The flow quantity control valve is provided for controlling a quantity of air flowing between the cylinder chamber and an outside of the cylinder chamber, to thereby control a force of absorbing a shock in case the piston compresses air in the cylinder chamber. The check valve is opened only when air is fed from the outside of the cylinder into the cylinder chamber in case the piston returns to an original position after the piston compressed air in the cylinder chamber, to thereby send a large amount of air rapidly. The valve means opens and closes in accordance with a movement of the piston in the cylinder chamber, to thereby increase the force of absorbing the shock. 
     Also, the shock absorber includes air storing means provided for storing air passing through the flow quantity control valve outside the cylinder chamber, and the air storing means is sealed to thereby increase the force of absorbing the shock. The sealed air storing means allows air in the shock absorber to be airtightly confined therein. Further, the air storing means has a capacity which is variable. 
     In addition, in the shock absorber as stated above, the valve means is formed of first valve means and second valve means. The first valve means is opened in case the piston approaches an end surface of the cylinder opposite to the side of the piston bearing, and the first valve means includes a valve operation shaft slidably abutting against the end surface of the cylinder opposite to the side of the piston bearing to thereby open the first valve means. The second valve means is opened only when the piston is moving toward an end surface of the cylinder in the side of the piston bearing. 
     Also, instead of having the sealed air storing means inside the shock absorber, the shock absorber can be provided with an air passage passing through the flow quantity controlling valve and extending between the cylinder chamber and an outside of the shock absorber. A portion of the air passage projecting outside the shock absorber can be connected to an external air chamber, or a compressed air tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 ( a ) is a front sectional view showing a first embodiment of the invention in a state before an operation; 
     FIG.  1 ( b ) is an enlarged view of a check valve; 
     FIG. 2 is a front sectional view of the first embodiment showing a state during the operation; 
     FIG. 3 is a front sectional view of the first embodiment showing a state in the course of returning to an original state after the operation; 
     FIG.  4 ( a ) is an explanatory side view of a part of a piston as seen from a section taken along line  4 ( a )— 4 ( a ) in FIG.  1 ( a ); 
     FIG.  4 ( b ) is a cross sectional view taken along line  4 ( b )— 4 ( b ) in FIG.  4 ( a ); 
     FIG.  4 ( c ) is a cross sectional view as in FIG.  4 ( b ), showing a state that a first valve is actuated; 
     FIG. 5 is a front sectional view of a second embodiment of the invention; 
     FIG. 6 is a front sectional view of a third embodiment of the invention; 
     FIG. 7 is a front sectional view of a prior shock absorber showing a state before an operation; 
     FIG. 8 is a front sectional view of the prior shock absorber showing a state during the operation; 
     FIG. 9 is a front sectional view of the prior shock absorber showing a state in the course of returning to an original state after the operation; and 
     FIG. 10 is a front sectional view of a fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG.  1 ( a ) through FIG.  4 ( c ) show structural views of a first embodiment of the invention, wherein FIG.  1 ( a ) is a front sectional view of a shock absorber of the first embodiment in a condition that a moving member is spaced away; FIG.  1 ( b ) is an enlarged view of a check valve; FIG. 2 is a front sectional view showing a state that a piston is pressed by the moving member to compress air in a cylinder; and FIG. 3 is a front sectional view showing a state in the course of returning of the piston to the original state, that is, the state shown in FIG.  1 ( a ). 
     FIG.  4 ( a ) is a side view of a part of the piston seen from a section taken along line  4 ( a )— 4 ( a ) in FIG.  1 ( a ); FIG.  4 ( b ) is a cross sectional view taken along line  4 ( b )— 4 ( b ) in FIG.  4 ( a ); and FIG.  4 ( c ) is a view showing a state that the first valve shown in FIG.  4 ( b ) is actuated. 
     In FIG.  1 ( a ) through FIG. 3, reference numeral  41  denotes a cylinder;  42  is a cylinder head;  43  is a piston bearing;  44  is a piston shaft;  45  is a contact;  46  is a piston; and  47  is a piston ring. The piston  46  and the piston shaft  44  are press-fitted to each other by using a retaining ring  44   a . A ring shape magnet  48  is embedded at a right side of the piston  44 . Reference numeral  49  is a compression coil spring which constantly attracts the piston  46  to a side of the cylinder head  42 . 
     In a cylinder wall  41   a  of a right side of the cylinder  41 , a flow quantity control bearing  50  is fixed by a screw, and a flow quantity control shaft  52  is screwed into a control screw  51  of the flow quantity control bearing  50 . A cone portion  52   a  at a left distal end of the flow quantity control shaft  52  and a hole  50   a  at a left distal end of the flow quantity control bearing  50  form a throttle, and by turning a control knob  53 , the throttle can be controlled. Reference numeral  54  denotes a double nut for fixing the control knob  53 , and  50   b  is an air hole for a bypass. 
     Numeral  55  is a non-contact switch, which outputs an abutment signal through a lead  55   a  when the magnet  48  approaches the non-contact switch  55 . The magnet  48  and the non-contact switch may be omitted. 
     Reference numeral  56  denotes a check valve, and an enlarged view thereof is shown in FIG.  1 ( b ). Namely, a hole  41   b  is formed at a left side of the cylinder wall  41   a , and a screw  41   c  is provided at a right side of the cylinder wall  41   a . Then, a thin plate spring  57  is held by a valve seat nut  58 . 
     A ball  59  is inserted between a conical hole  58   a  of the valve seat nut  58  with a cross-shaped hole and the thin plate spring  57 , and the ball  59  is always slightly pressed by the plate spring  57  to close the conical hole  58   a.    
     Reference numeral  60  is an air reservoir cover, which is screwed into the cylinder  41  to form an air reservoir  61  between the cylinder wall  41   a  and the air reservoir cover. In the air reservoir  61 , by rotating the air reservoir cover  60 , a capacity of the air reservoir  61  can be changed. 
     Reference numeral  62  is a double nut for fixing the position of the air reservoir cover  60 . Reference numerals  63   a ,  63   b ,  63   c ,  63   d ,  63   e ,  63   f  and  63   g  denote O-rings, which are attached to maintain airtightness. 
     In explaining FIGS.  4 ( a ) through  4 ( c ), FIG.  4 ( a ) is a side view of a part of the piston  46  seen from a section taken along line  4 ( a )— 4 ( a ) in FIG.  1 ( a ), and FIG.  4 ( b ) is a cross sectional view taken along line  4 ( b )— 4 ( b ) in FIG.  4 ( a ). Holes  46   a  and  46   b  are bored in the piston  46 , and an operation shaft  73 , wherein a compression coil spring  71  and an O-ring  72  are fitted, is stored in the hole  46  and fastened by a nut  74  to thereby form a first valve  70 . 
     Further, a hole  46   c , a conical hole  46   d , and a hole  46   f  are bored in the piston  46 , and a ball  75  and a compression coil spring  76  are stored in the conical hole  46   d  and fastened by a nut  77 , to thereby form a second valve  78 . 
     Next, operations of the shock absorber of the first embodiment will be explained. In FIG.  1 ( a ), the moving member W is moved rightward, and the piston  44  pressed by the moving member W slides in the piston bearing  43  to be displaced rightward. Then, as shown in FIG. 2, the piston  46  integral with the piston shaft  44  compresses air in the cylinder  41 . 
     Air compressed by the right end side (pushing side) of the piston  46  passes through the throttle formed by the cone portion  52   a  at the left distal end of the flow quantity control shaft  52  and the hole  50   a  at the left distal end of the flow quantity control bearing  50 , and air enters the air reservoir  61  from the air hole  50   b  as the bypass (refer to the arrow in FIG.  2 ). 
     In this case, since a space between the left end side (pulling side) of the piston  46  and the cylinder head  42  is in a vacuum state, the force of absorbing the shock is increased. Further, when the piston  46  is displaced rightward, the vacuum state between the left end side (pulling side) of the piston  46  and the cylinder head  42  is further intensified, to thereby apply brake on the moving member W. Accordingly, the piston  46  gradually approaches the cylinder wall  41   a , and the operation shaft  73  shown in FIG.  4 ( b ) abuts against the cylinder wall  41   a  to slide inside the piston  46 , so that the first valve  70  is opened as shown in FIG.  4 ( c ). Accordingly, air compressed by the right end side (pushing side) of the piston  46  flows into the space between the left end side (pulling side) of the piston  46  and the cylinder head  42 , which is in the vacuum state, to thereby prevent the brake effect from being excessive, so that a soft contact can be carried out. 
     When the ring magnet  48  of the piston  46  approaches the non-contact switch  55 , the switch  55  outputs the abutment or contact signal to send the contact signal to an outer control device through the lead  55   a.    
     After the contact of the piston  46 , when the moving member W is returned to the position shown in FIG.  1 ( a ), the piston  46  starts to restore (FIG.  3 ), and the ball  59  of the check valve  56  is displaced leftward to push the thin plate spring  57  to the left, so that the check valve  56  is opened. Accordingly, a large quantity of air is sent in a short time from the air reservoir  61  into the cylinder  41 , so as to accelerate the returning time of the piston  46 . 
     Needless to say, air in the air reservoir  61  flowing from the air hole  50   b  of the bypass passes also through the throttle formed by the cone portion  52   a  at the left distal end of the flow quantity control shaft  52  and the hole  50   a  at the left distal end of the flow quantity control bearing  50 , and flows into the cylinder  41 . 
     As described above, the first valve  70  of the piston  46  is opened, and air compressed by the right end side (pushing side) of the piston  46  flows into the space, which is in the vacuum state, between the left end side of the piston  46  and the cylinder head  42 , to thereby ease the vacuum state. Thus, air is introduced into the space between the left end side (pulling side) of the piston  46  and the cylinder head  42 , so that the second valve  78  of the piston  46  is naturally opened at the time of restoring the piston  46 . In case that the piston  46  is restored to the state shown in FIG.  1 ( a ), there is no air between the piston  46  and the cylinder head  42 . 
     FIG. 5 is a front sectional view of a shock absorber according to a second embodiment of the invention. As compared with the shock absorber of the first embodiment in which the air reservoir  61  is provided inside the air reservoir cover  60 , the shock absorber of the second embodiment is provided with an air passage  84 , which is communicated with an outside of the shock absorber and the cylinder chamber through the air hole  50   b  as the bypass, and an air joint portion  85  is attached to an outlet of the air passage  84  projecting outside the shock absorber. A chamber  86  whose capacity is adjustable is provided to the outside of the shock absorber, to thereby form an external air reservoir  87 . 
     Namely, the external air reservoir  87  is detachably attached to the air passage  84  by a tube  89 , and includes a control screw  91  to adjust a capacity of the air reservoir  87 . Since the capacity of the reservoir  87  is adjustable by a controlling screw  90 , the shock absorbing ability when the piston is being moved can be adjusted. 
     Also, other than the aforementioned method of controlling the capacity of the air reservoir, there can be used a method of replacing the chamber with another chamber of a fixed quantity having a different inner diameter and length. Further, without using the chamber  86 , the air joint portion  85  can be opened to the atmosphere, to thereby reduce the force of absorbing the shock. Also, the shock absorber can be connected to a compressed air source, not shown, to thereby increase the force of absorbing the shock. 
     FIG. 6 shows a front, partly sectional view of a shock absorber of a third embodiment of the invention. In the shock absorber of the first embodiment, the flow quantity control shaft  52  and the check valve  56  are used, but a speed controller, which is available in the market, has functions corresponding to the flow quantity control shaft  52  and the check valve  56 . Thus, in the shock absorber of the third embodiment, instead of the flow quantity control shaft  52  and the check valve  56 , a speed controller  91  is attached to the cylinder wall  41   a , to thereby achieve the object of the invention. 
     The speed controller  91  includes therein an air hole corresponding to the air hole  50   b  in the first embodiment at one side of a casing of the speed controller  91 . An air chamber  92  is directly joined to a path communicating with the air hole from the speed controller. The air chamber  92  is formed similar to the second embodiment. Accordingly, the third embodiment operates as in the first embodiment. 
     FIG. 10 shows a front, partly sectional view of a shock absorber  93  of a fourth embodiment of the invention. In the shock absorber of the first embodiment, the flow quantity control bearing  50  is fixed to the cylinder wall  41   a  to adjust the flow quantity from the compression side of the cylinder to the air chamber  61 . However, in the fourth embodiment, a throttle hole  94  is simply formed in the cylinder wall  41   a . Since the cover  60  for the air chamber  61  can be adjusted relative to the cylinder  41 , shock absorbing ability of the shock absorber  93  can be adjusted. The shock absorber  93  operates as in the first embodiment. 
     According to the first to fourth embodiments (FIG.  1 ( a ) to FIG.  6  and FIG. 10) of the invention, the shock absorbers employ an air system while the conventional shock absorber employs an oil system. Since air used in the shock absorber is not given to or received from the outside at all, air can be airtightly confined in the shock absorber. Thus, the shock absorbers of the embodiments are excellent in dustproof and oilproof functions, and can be used in a clean room. 
     There was a case that the force of absorbing the shock in the conventional shock absorber using air is deficient in order to absorb the movement of the detecting member as compared with the conventional oil-type shock absorber. However, in the shock absorber according to the present invention, since the suction force of the piston due to the vacuum state caused between the pulling side of the piston and the cylinder is added to the resistance force of air compressed by the pushing side of the piston and the cylinder, the absorbing force which is sufficient for absorbing the movement of the detecting member can be obtained. 
     Also, in the shock absorber according to the present invention, a degree of absorbing the shock can be controlled by a method of varying both the flow quantity controlling valve and the capacity of the air chamber, or by a method of varying either of them. Accordingly, the shock absorber, in which both the flow quantity controlling valve and the capacity of the air chamber are controllable, can be used widely, and the shock absorber in which either of the above is controllable can be used for an exclusive purpose, so that it can be very handy in some cases. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.