Abstract:
An air cylinder apparatus equipped with a fall prevention mechanism, wherein the air cylinder apparatus includes a cylinder body and a piston rod which advances and retreats by supplying and discharging pressurized air to and from the cylinder body, and wherein the fall prevention mechanism includes a fixed member which is immovable with respect to the cylinder body; a plurality of brake members which are supported by the fixed member to be capable of coming into and out of contact with the fixed member; a biasing member which presses the plurality of brake members against the piston rod to lock the piston rod to the fixed member; and a lock-release air mechanism which holds, against a biasing force of the biasing member, the brake members in a non-contact position with the piston rod, the lock-release air mechanism operating by a pressurized air source that is common with that of the air cylinder apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is entitled to the benefit of and incorporates by reference subject matter disclosed in International Patent Application No. PCT/JP2013/077302 filed on Oct. 8, 2013 and Japanese Patent Application 2012-230403 filed Oct. 18, 2012. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an air cylinder apparatus equipped with a fall prevention mechanism. 
       BACKGROUND OF THE INVENTION 
       [0003]    Air cylinder apparatuses are used as a power source for various devices. Among them, in an air cylinder apparatus such as a depositor, a bonder or a precision polishing machine that is used in a manner to move a workpiece up and down by a piston rod that is slidably fitted into a cylinder body, an apparatus which locks the piston rod to the cylinder body at an ascending position (specific position) of the piston rod so that the workpiece does not fall upon an occurrence of an air leakage, an air shortage, or the like, in the air cylinder apparatus has been proposed. See Japanese Unexamined Utility Model Publication No. H05-75503. 
       TECHNICAL PROBLEM 
       [0004]    However, conventional fall prevention (safety) mechanisms are provided between the cylinder body and the piston rod in advance, thus being difficult to be applied to an air cylinder apparatus, once the air cylinder apparatus has been installed. In other words, the conventional fall prevention mechanism cannot be made to function for an air cylinder apparatus that has been installed unless modifications are made to the cylinder body and the piston rod. 
         [0005]    Based on the awareness of the above described issues, an object of the present invention is to obtain an air cylinder apparatus equipped with a fall prevention apparatus which can prevent the piston rod from falling, without modifying the cylinder body or the piston rod of the air cylinder apparatus themselves, upon occurrence of a malfunction in the pressurized air supply system. 
       SUMMARY OF INVENTION 
     Solution to Problem 
       [0006]    The present invention is characterized by an air cylinder apparatus equipped with a fall prevention mechanism, the air cylinder apparatus including a cylinder body and a piston rod which advances and retreats by supplying and discharging pressurized air to and from the cylinder body, wherein the fall prevention mechanism includes a fixed member which is immovable with respect to the cylinder body; a plurality of brake members which are supported by the fixed member to be capable of coming into and out of contact with the fixed member; a biasing member which presses the plurality of brake members against the piston rod to lock the piston rod to the fixed member; and a lock-release air mechanism which holds, against a biasing force of the biasing member, the brake members in a non-contact position with the piston rod, the lock-release air mechanism operating by a pressurized air source that is common with that of the air cylinder apparatus. 
         [0007]    The fixed member can be shaped into a frame which surrounds an outer periphery of the piston rod. 
         [0008]    The frame-shaped fixed member can include a pair of brake member support bars which face each other and support the brake members, and a pair of air-mechanism support bars which face each other and are orthogonal to the pair of brake member support bars, the pair of air-mechanism support bars including the lock-release air mechanism. 
         [0009]    It is practical for the lock-release air mechanism to include an output member which is engaged with and disengaged from the brake members, and a pressure chamber which holds the output member in a disengaged position from the piston rod by engagement with the brake members. The pressure chamber is connected to the pressurized air source that is common with that of the air cylinder apparatus. 
         [0010]    It is desirable for a power-assisted mechanism, which reduces and transfers an amount of movement of the output member to the brake members, to be interposed between the output member and the brake members. 
         [0011]    For example, the power-assisted mechanism can include the output member which is supported to be capable of moving in a direction that intersects an advancing/retreating direction of the brake members, pressed surfaces which are formed on the brake members to be inclined to an advancing/retreating direction of the output member, and force applying portions which are formed on the output member and engaged with the pressed surfaces. 
         [0012]    In addition, the present invention is characterized by an air cylinder apparatus, equipped with a fall prevention mechanism, including a frame member; a plurality of brake members which are supported by the frame member to be movable toward a center of the frame member; a biasing member which biases and moves the brake members in a direction toward the center of the frame member; and a lock-release air mechanism which operates by a pressurized air source to move the brake members in a direction away from the center of the frame member. 
       Advantageous Effects of Invention 
       [0013]    According to the present invention, a fall prevention apparatus is achieved which can prevent the piston rod of an air cylinder apparatus from falling, without modifying the cylinder body or the piston rod themselves, upon occurrence of a malfunction in the pressurized air supply system. Accordingly, a useful fall prevention apparatus which can also be relatively easily installed, by a “retrofit”, onto an already-existing air cylinder apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a front elevational view of an air cylinder apparatus equipped with a fall prevention apparatus according to the present invention, showing an example of the outward appearance thereof; 
           [0015]      FIG. 2  is a side elevational view of the same; 
           [0016]      FIG. 3  is a perspective view of only the fall prevention apparatus, according to the present invention; 
           [0017]      FIG. 4  is a sectional view taken along the line IV-IV line (plane) shown in  FIG. 3 ; 
           [0018]      FIG. 5  is an exploded perspective view of a pair of mutually opposed air-mechanism support bars of a rectangular frame member of the fall prevention apparatus shown in  FIG. 3 ; and 
           [0019]      FIG. 6  is an exploded perspective view of the pair of mutually opposed air-mechanism support bars, viewed from the opposite direction. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]      FIGS. 1 and 2  show an example of the outward appearance of an air cylinder apparatus  20  equipped with a fall prevention mechanism  10  according to the present invention. The air cylinder apparatus  20  is provided with an air cylinder body  21 , the axis of which extends in the vertical direction, and a piston rod  22  which is supported by the air cylinder body  21  to be movable up and down. As schematically shown, the piston rod  22  is coupled to a piston  23  which is slidably fitted into the air cylinder body  21 , and pressurized air is selectively (alternatively) supplied and exhausted to and from cylinder pressure chambers P 1  and P 2 , which are partitioned as upper and lower partitions by the piston  23  (and a sealing member or a rolling diaphragm), via a compressed air source  31 , a regulator  32 , a switching valve  33  and air flow channels  34  and  35 . 
         [0021]    A support base  24  which supports the air cylinder apparatus  20  is in the shape of a letter U and is provided with a bottom wall  24   a,  an upper wall  24   b  and a connecting wall  24   c.  The air cylinder body  21  is fixed to the upper wall  24   b,  and the piston rod  22  extends downward from the upper wall  24   b.  A movable work-tool W 1  is mounted to the lower end of the piston rod  22 , and some work is performed between the movable work-tool W 1  and a fixed work-tool W 2 , mounted on the bottom wall  24   a,  by moving the movable work-tool W 1  up and down with the piston rod  22 . 
         [0022]    The fall prevention mechanism  10  is for preventing the piston rod  22  from falling from the air cylinder body  21  (the upper wall  24   b ) when the supply of pressurized air to the air cylinder  20  stops due to some reason; the fall prevention mechanism  10  is fixed to the lower surface of the upper wall  24   b.    FIGS. 3 through 6  show an embodiment of the fall prevention mechanism  10 . The fall prevention mechanism  10  is provided with a frame member (fixed member)  11  which is fixed to the upper wall  24   b  with the piston rod  22  inserted through the frame member  11 , brake members  12  which are movable relative to the frame member  11  and come into and out of contact with the piston rod  22 , compression coil springs (biaser)  13  which bias the brake members  12  toward the piston rod  22 , and lock-release air mechanisms  14  which hold the brake members  12  at a disengaged position (unlocked position) from the piston rod  22  against the biasing forces of the compression coil springs  13 . 
         [0023]    The piston rod  22  in this embodiment is rectangular in a cross section, and the frame member  11  is in the shape of a rectangle which surrounds the piston rod  22  to correspond to the rectangular cross sectional shape of the piston rod  22 . Two opposite sides of the rectangular frame member  11  and the other two opposite sides of the rectangular frame member  11  that are orthogonal to the aforementioned opposite sides are formed as a pair of brake member support bars  11 A and a pair of air-mechanism support bars  11 B, respectively. 
         [0024]    The pair of brake member support bars  11 A are mutually identical in structure. Linear ball bearings  11   c  which are orthogonal to the lengthwise direction of the brake member support bars  11  A are embedded in the brake member support bars  11 A, and the brake members  12  are fixed to linear members  11   c ′ of the linear ball bearings  11   c  by set screws  12   a.  In addition, a spring support hole  11   d  is bored in each brake member support bar  11 A to be positioned between the pair of linear ball bearings  11   c  thereof, and the compression coil springs  13  that are inserted into the spring support holes  11   d  are supported between spring adjust screws  11   e  which are screw-engaged in the spring support holes  11   d  and the brake members  12 . 
         [0025]    The pair of air-mechanism support bars  11  B are also mutually identical in structure and are each provided with a pair of split boards  11   f  and  11   g  and a stopper plate  11  h which is fixed by screws to the split board  11   g  that is positioned on the inner side. The stopper plates  11  h restrict the jutting ends of the brake members  12  that jut due to the compression coil springs  13 . The pair of brake members  12  come in contact with the piston rod  22  at positions before the pair of brakes members  12  come in contact with the stopper plates  11  h to fix the piston rod  22  to the fall prevention mechanism  10 . The forces of the compression coil springs  13  have been set large enough to prevent the piston rod  22  from falling. 
         [0026]    Two lock-release air mechanisms  14  are supported between one pair of split boards  11   f  and  11   g  of each air mechanism support bar  11  B so that two pairs of lock-release air mechanisms  14  operate to act on both ends of the brake members  12 , respectively. Each lock-release air mechanism  14  is provided with a diaphragm  14   b  which is sandwiched between the pair of split boards  11   f  and  11   g , an output rod (output member)  14   d  which is coupled to the diaphragm  14   b  via a joining member  14   c,  and a compression spring  14   e  which biases and moves the output rod  14   d  toward the brake member  12 ; each lock-release air mechanism  14  is provided with an air discharging chamber  11   i  and a pressure chamber  11   j  which are partitioned by the diaphragm  14   b  and formed in the associated pair of split boards  11   f  and  11   g.    
         [0027]    The output rods  14   d  project into the inside of the frame member  11  through through-holes  11   k  formed in the split boards  11   g , and spherical force applying portions (force applying portions)  14   d ′ are formed at the ends of the output rods  14   d.  The brake members  12  are provided with pressed surfaces  12   b  which are formed to be inclined to the advancing/retreating direction of the output rods  14   d  and with which the spherical force applying portions  14   d ′ come in contact, and movements of the output rods  14   d  in directions toward the brake members  12  (the presses surfaces  12   b ) against the forces of the compression coil springs  13  cause the brake members  12  to retreat. The inclined surfaces of the pressed surfaces  12   b  constitute a power-assisted mechanism which moves the brake members  12  in directions orthogonal to the output rods  14   d  by an amount of movement that is smaller (e.g., 0.2 through 0.5) than a unit amount of movement ( 1 ) of the output rods  14   d  when the output rods  14   d  move by this unit amount of movement. With this power-assisted mechanism, the pressure of the pressurized air supplied to the pressure chambers  11   j  can be boosted and transferred to the brake members  12 . 
         [0028]    Air supply holes  11   m  and  11   n  which are communicatively connected to the pressure chambers  11   j  are formed in the split boards  11   f,  and the air supply holes  11   m  are connected to the compressed air source  31  via an air flow channel  36  between the regulator  32  and the switching valve  33 . The air supply holes  11   m  and  11   n  are formed as through-holes, and ends (one end of each) thereof are closed by closing members. 
         [0029]    The output rods  14   d  jut in the direction toward the brake members  12  against the forces of the compression springs  14   e  and press the pressed surfaces  12   b  via the spherical force applying portions  14   d ′ to make the brake members  12  retreat in a state where pressurized air of the compressed air source  31  is supplied to the pressure chambers  11   j  via the air flow channel  36  and the air supply holes  11   m  and  11   n.  In other words, the output rods  14   d  are each held in a non-contact position with the associated brake member  12 . In a state where the supply of pressurized air to the pressure chambers  11   j  is stopped, the compression springs  14   e  make the output rods  14   d  retreat to positions at which the output rods  14   d  are in non-contact with the brake members  12 . 
         [0030]    The split boards  11   f  and  11   g  are fixed to each other via set screws  11   p , and the split boards  11   f  and  11   g  (the air-mechanism support bars  11 B) thus fixed are fixed to the brake member support bars  11 A via set screws  11   q  to complete the rectangular frame member  11 . The frame member  11  is fixed to the lower surface of the upper wall  24   b  of the support base  24  via bolt insertion holes  11 X ( FIGS. 3  and  4 ) which are formed between the brake member support bars  11 A and the air-mechanism support bars  11 B. 
         [0031]    The present apparatus that has the above described structure operates in a manner which will be discussed hereinafter. In a state where the compressed air source  31  and the regulator  32  supply pressurized air at a normal pressure, this pressurized air is supplied to the pressure chamber  11   j  of each lock-release air mechanism  14  via the air flow channel  36  and the air supply holes  11   m  and  11   n . As described above, one pair of lock-release air mechanisms  14  is provided for each brake member  12 , and the pressurized air supplied to each pressure chamber  11   j  causes the spherical force applying portions  14   d ′ to act on the pressed surfaces  12   b  at both ends of each brake member  12  to hold the output rods  14   d  in positions (non-contact positions with the piston rod  22 ) to retract the brake members  12  against the forces of the compression coil springs  13 . Accordingly, without influencing the operation of the air cylinder apparatus  20 , pressurized air can be selectively supplied to the cylinder pressure chambers P 1  and P 2  to freely move the piston rod  22  (the movable work-tool W 1 ) upward or downward or to stop moving the piston rod  22  by selectively connecting ports  33   a,    33   b  and  33   c  of the switching valve  33  to the air flow channels  34  and  35 . 
         [0032]    Whereas, if the pressurized air from the compressed air source  31  and the regulator  32  stops (the pressure drops below a normal value) for some reason, the pressure of the air supplied to the pressure chamber  11   j  from the air supply holes  11   m  and  11   n  likewise drops. Thereupon, the force which holds the brake members  12  in a non-contact position with the piston rod  22  disappears, which causes the pair of brake members  12  to clamp the piston rod  22  with the compression coil springs  13  to prevent the piston rod  22  (the movable work-tool W 1 ) from falling. The output rods  14   d  retreat by the forces of the compression springs  14   e.  Accordingly, an accident, which may occur by the movable work-tool W 1  falling onto the fixed work-tool W 2 , can be prevented from occurring. 
         [0033]    Although the brake members  12 , which come into and out of contact with the piston rod  22 , are provided as a pair and are supported by the rectangular frame member  11  in the above illustrated embodiment, it is possible to increase the number of the brake members  12 ; in addition, the fixed member which supports the brake members  12  does not have to be shaped into a frame. Additionally, the present invention is applicable regardless of the specific structure of the air cylinder apparatus  20 , how the air cylinder apparatus  20  is supported, or the shape of the movable work-tool W 1 . The present embodiment of the fall prevention mechanism  10  is useful for the application thereof to the pre-existing air cylinder apparatus  20  by a “retrofit”. 
       INDUSTRIAL APPLICABILITY 
       [0034]    An air cylinder apparatus equipped with a fall prevention mechanism according to the present invention can also be relatively easily installed, by a “retrofit”, to an already-existing air cylinder apparatus and can be widely used as a low-cost fall prevention mechanism. 
         [0035]    Although various embodiments of the present invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims. 
       REFERENCE NUMERAL LIST 
       [0000]    
       
           10  Fall prevention mechanism 
           11  Frame member (Fixed member) 
           11 A Brake member support bar 
           11 B Air-mechanism support bar 
           11   c  Linear ball bearing 
           11   c ′ Linear member 
           11   d  Spring support hole 
           11   e  Spring adjustment screw 
           11   f    11   g  Split board 
           11   h  Stopper plate 
           11   i  Air discharge chamber 
           11   j  Pressure chamber 
           11   k  Through-hole 
           11   m    11   n  Air supply hole 
           12  Brake member 
           12   a  Set screw 
           12   b  Pressed surface 
           13  Compression coil spring (Biasing member) 
           14  Lock-release air mechanism 
           14   b  Diaphragm 
           14   c  Joining member 
           14   d  Output rod (Output member) 
           14   d ′ Spherical force supplying portion 
           14   e  Compression spring 
           20  Air cylinder apparatus 
           21  Air cylinder body 
           22  Piston rod 
           23  Piston 
         P 1  P 2  Cylindrical pressure chamber 
           24  Support base 
           24   a  Bottom wall 
           24   b  Upper wall 
           24   c  Connecting wall 
           31  Compressed air source 
           32  Regulator 
           33  Switching valve 
           34   35   36  air flow channel