Abstract:
A flow rate control device includes a needle valve mounted within a body section and is configured such that the needle valve is advanced and retracted within the body section by the rotation of a handle, thereby adjusting the flow rate of fluid flowing between a first port and a second port. The handle is surrounded by a cover to prevent a change in the adjusted flow rate.

Description:
TECHNICAL FIELD 
     The present invention relates to a flow rate control device, which is capable of controlling the flow rate of a fluid such as a pressure fluid or the like by displacement of a valve body. 
     BACKGROUND ART 
     The present applicant have proposed a flow rate control device, which is connected via a tube to a fluid pressure device such as a cylinder or the like, and which is capable of controlling operations of the fluid pressure device by adjusting, with the position of a valve body, the flow rate of a fluid that is supplied to and discharged from the fluid pressure device (see, Japanese Laid-Open Patent Publication No. 2011-149488). 
     SUMMARY OF INVENTION 
     The present invention has been devised in relation to the aforementioned proposal, and has the object of providing a flow rate control device, which is capable of avoiding a flow rate that has been preset beforehand from becoming changed, due to a displacement in the position of a valve body which has once been set. 
     For achieving the aforementioned object, the present invention is characterized by a flow rate control device, which by displacement of a needle valve is configured to control a flow rate of a fluid that flows between a couple of a first port and a second port. In particular, the flow rate control device comprises: 
     a first body including the first port, and which includes a joint mechanism to which a tube is connected that supplies or discharges the fluid; 
     a second body connected to the first body, and which includes the second port through which the fluid is discharged or supplied; and 
     a handle connected to the needle valve, and which is configured to adjust the flow rate of the fluid by causing axial displacement of the needle valve under a rotary action of the handle. 
     The flow rate control device further comprises a cover that surrounds the handle in a removable manner. 
     According to the present invention, since the cover is provided, which surrounds the handle in a removable manner, after the cover has been installed thereon, the handle is prevented from being touched. Consequently, the flow rate of the fluid, which has been set beforehand by the handle, can be prevented from being changed. 
     Further, in the present invention, a projection may be provided on the cover, the projection engaging with the handle to thereby attach the cover to the handle. 
     In accordance with such a structure, since a locked state between the projection and the handle can be obtained, a further operation of the handle, which has been used to set the flow rate of the fluid, can be prevented by the presence of the cover, and thus the flow rate of the fluid in a stable condition can be assured. 
     Furthermore, the present invention is characterized by providing a release member on the cover, and by providing the projection on an inner surface of the release member. 
     As a result of such a structure, the cover can be removed from the handle as needed, and a desired flow rate for the fluid can be set by readjusting the handle. 
     Still further, the present invention is characterized in that a shoulder portion, with which the projection of the cover engages, is disposed on an outer side of the handle. 
     In accordance with this structural feature, dislodgement of the cover from the shoulder portion of the handle is prevented. 
     Further still, the present invention is characterized in that the release member, which is disposed on the cover, is formed by a groove provided on the cover, the release member being flexed outwardly by the groove, such that engagement of the projection with the handle is released. 
     In this manner, since the release member is formed integrally with the cover, and the cover can be separated from the handle by flexing the release member, there is not the slightest difficulty when the flow rate of the fluid is reset. 
     Further still, the present invention is characterized in that an arcuately shaped opening configured to insert therein a leg member of a jig is provided in the cover. In addition, by insertion of the jig into the arcuately shaped opening, the jig flexes the release member outwardly, such that engagement of the projection with the handle is released. 
     In this manner, since the cover can be separated from the handle upon flexing of the release member by insertion of the jig into the arcuately shaped opening of the cover, there is not the slightest difficulty when the flow rate of the fluid is reset. 
     Further, the present invention is characterized in that the cover is equipped with a handle portion configured to attach a binding member thereto. 
     In this manner, by attaching a binding member such as a wire or the like with respect to the handle portion, separation between the cover and the flow rate control device can be avoided. 
     Still further, the present invention is characterized in that the first body includes a main body section extending in an axial direction, and a connecting section arranged perpendicularly to the axial direction. In addition, the cover includes a cutout that is fitted over a proximal end portion of the connecting section on a side of the main body section. 
     In accordance with this structure, since the cutout is fitted over the main-body-side proximal end portion of the connecting section, an increase in the size or scale of the flow rate control device by mounting of the cover thereon can be avoided. 
     Further still, the present invention is characterized in that the handle portion is disposed directly above a cutout that is fitted over the proximal end portion on the side of the main body section. 
     By providing such a structure, the binding member can easily be connected, for example, to a tube. 
     According to the present invention, the following advantageous effect is obtained. 
     In the flow rate control valve, which controls the flow rate of a fluid that flows between the first port and the second port by causing the needle valve to be displaced, by surrounding the handle, which carries out a displacement operation of the needle valve, with the cover, any change in the flow rate of the fluid that has once been adjusted can be avoided. 
     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 a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing the overall structure of a flow rate control device according to an embodiment of the present invention; 
         FIG. 2  is a partially exploded perspective view showing a condition in which a cover has been removed, in the flow rate control device shown in  FIG. 1 ; 
         FIG. 3  is a vertical cross sectional view taken along line III-III of the flow rate control device shown in  FIG. 1 ; 
         FIG. 4  is a vertical cross sectional view taken along line IV-IV of the flow rate control device shown in  FIG. 1 ; 
         FIG. 5  is a perspective view with partial omission of a needle valve of the flow rate control device shown in  FIG. 1 ; 
         FIG. 6  is a cross sectional view taken along line VI-VI of the flow rate control device shown in  FIG. 4 ; 
         FIG. 7  is a partially exploded perspective view showing a modification of the cover in the embodiment of the present invention; 
         FIG. 8  is a partially exploded perspective view, as seen from below, of a jig and the flow rate control device shown in  FIG. 7 ; 
         FIG. 9  is a vertical cross sectional view taken along line IX-IX of the flow rate control device shown in  FIG. 7 ; and 
         FIG. 10  is a vertical cross sectional view showing a condition in which a tool for enabling removal of the cover from the handle is inserted into an opening of the cover, in the flow rate control device shown in  FIG. 7 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment of a flow rate control device according to the present invention will be described in detail below with reference to the accompanying drawings. 
     In  FIGS. 1 through 4 , reference numeral  10  indicates the flow rate control device according to the embodiment of the present invention. 
     As shown in  FIGS. 1 through 4 , the flow rate control device  10  includes a first body  14  including a first port  12  through which a pressure fluid is supplied, a second body  18  including a second port  16  through which the pressure fluid is discharged and which is assembled with respect to a lower part of the first body  14 , a handle (operating member)  20  used for adjusting the flow rate and which is disposed rotatably on an upper part of the first body  14 , a needle valve  22 , which is inserted into the handle  20 , and which controls the flow rate of the pressure fluid (e.g., compressed air) that flows between the first port  12  and the second port  16  by advancing and retracting the needle valve  22  in an axial direction (the directions of arrows A and B) in the interior of the first body  14  under a rotary action of the handle  20 , and a cover  24  that surrounds the handle  20  in a removable manner. 
     The first body  14  is constituted from a hollow main body section  26  formed from a resin material, for example, which extends a predetermined length in the axial direction (the directions of arrows A and B), a connecting section  28  that extends perpendicularly to the axial direction of the main body section  26  and includes the first port  12  in the interior thereof, and a first coupling part  30  formed on the outer circumferential side of the main body section  26  and which is coupled to the second body  18 . 
     The main body section  26  includes a first cylindrical portion  32  formed on a bottom portion thereof, a second cylindrical portion  34  formed integrally with an upper part of the first cylindrical portion  32  and which is expanded in diameter with respect to the first cylindrical portion  32 , and a third cylindrical portion  36  formed integrally with an upper part of the second cylindrical portion  34  and which is expanded in diameter with respect to the second cylindrical portion  34 . In addition, a penetrating hole  38  is formed in the interiors of the first through third cylindrical portions  32 ,  34 ,  36 . 
     The penetrating hole  38  is formed such that inner diameters thereof become greater respectively in a stepwise manner corresponding to the first through third cylindrical portions  32 ,  34 ,  36 . The needle valve  22  protrudes into the penetrating hole  38  displaceably in the axial direction. 
     On an outer circumferential surface of the first cylindrical portion  32 , a check valve  44  made from a synthetic rubber material or the like is installed through an annular groove  40 . The check valve  44  includes a flange  46  that projects in a radial outward direction. The flange  46  is formed with a downwardly opening V-shape substantially in cross section, and the distal end thereof abuts resiliently against the inner wall surface of the second body  18 . 
     Plural fins  48 , which are directed radially outward and are separated at equal intervals along the circumferential direction, are formed on a lower end of the first cylindrical portion  32 . The plural fins  48  serve to rectify the fluid that flows between the first port  12  and the second port  16 . 
     On a peripheral wall of the second cylindrical portion  34 , a pair of communication holes  50   a ,  50   b  are formed (see  FIG. 4 ), which communicate with a space on the inside of the penetrating hole  38  and the first coupling part  30 . The communication holes  50   a ,  50   b  are substantially rectangular shaped. 
     A seat  52  on which the needle valve  22  can be seated is formed at a boundary site between the first cylindrical portion  32  and the second cylindrical portion  34 . Actually, a later-described shoulder portion  42  of the needle valve  22  is seated on the seat  52 . An illustrated O-ring may be mounted on the shoulder portion  42 . 
     The first coupling part  30  is formed integrally on an outer circumferential surface between the second cylindrical portion  34  and the third cylindrical portion  36 . Together therewith, the connecting section  28  that extends in a radial outward direction is formed integrally on a part of the peripheral wall of the first coupling part  30 . 
     A first meshing portion  56 , on which a plurality of cross-sectional triangular shaped teeth  54  project at equal intervals along the outer circumferential surface thereof, is disposed on an upper part of the third cylindrical portion  36 . As will be discussed later, the first meshing portion  56  is placed in meshing engagement with a second meshing portion  110  of the handle  20 . 
     Furthermore, below the first meshing portion  56 , a first projection  58 , which projects radially outward, and a second projection  60 , which is formed further below the first projection  58  and has a smaller diameter than the first projection  58 , are disposed respectively. 
     In this case, a first annular groove  57  is formed in the vicinity of the lower end of the first coupling part  30 , and a second annular groove  59  is formed above the first annular groove  57 . An O-ring  62  is installed in the first annular groove  57 . The O-ring  62  is pressed in contact against an inner circumferential surface of a later-described tightening member  90  of the second body  18 . On the other hand, a pawl  92  that projects outward annularly from a distal end inner circumferential wall of the tightening member  90  is fitted into the second annular groove  59 . This serves to prevent the main body section  26  from becoming dislodged from the second body  18 . 
     A nut  66  is installed in the interior of the third cylindrical portion  36 . As shown in  FIGS. 3 and 4 , female threads that make up the nut  66  are screw engaged with male threads  122  of the needle valve  22 , as will be described later. 
     On a proximal end side of the first port  12 , a connecting hole  70  is formed through a stepped portion  68 . The connecting hole  70  communicates with a flow path  72  provided between the outer periphery of the main body section  26  and the first coupling part  30 . A joint mechanism  76  for connecting a tube  74  through which a pressure fluid is supplied is formed in the first port  12 . 
     The joint mechanism  76  includes a chuck  78  that engages with the tube  74  that is inserted into the first port  12 , a guide  80  that surrounds the chuck  78 , a release bush  82  displaceable along the guide  80 , and which expands or widens the distal end of the chuck  78 , and thereby releases the engaged condition with the tube  74 , and a packing  84  that abuts against an outer circumferential surface of the tube  74 . 
     The second body  18  is formed from a resin material, for example. An attachment member  88  on which threads  86  are engraved is formed on the outer circumference of one end of the second body  18 , and is formed with the cross-sectional hexagonal shaped tightening member  90  on the other end thereof. Reference numeral  94  indicates a flow path, which is formed between the first cylindrical portion  32  and the inner circumferential wall of the second body  18 . The flow path  94  communicates with the flow path  72 . 
     The tightening member  90  is used when the flow rate control device  10  of the present embodiment is attached to another fluid pressure device S or the like, by a tool such as a non-illustrated spanner that utilizes the cross-sectional shape of the tightening member  90 . 
     The handle  20  is formed in a bottomed cylindrical shape, with a disk-shaped base section  98  formed on one end side thereof, and an annular outer wall  100  being formed to project along an outer circumferential edge on the other end side of the base section  98 , together with an inner wall  102  being formed to project on an inner circumferential side thereof. An adjustment member  107 , which is formed on an end of a shaft  104  that makes up the needle valve  22 , is accommodated in a deformed rectangular space  106  formed by the inner wall  102  (see  FIG. 6 ). As shown in  FIG. 5 , the adjustment member  107  has a deformed rectangular shape as viewed in plan, which as shown in  FIG. 6 , is fitted into the inner wall  102  of the handle  20 . 
     Actually, the inner wall  102  of the handle  20  is inserted along the inner wall of the third cylindrical portion  36 , in a state in which the needle valve  22  has been inserted through the first cylindrical portion  32 , the second cylindrical portion  34 , and the third cylindrical portion  36 . As a result, the outer wall  100  is fitted externally over the third cylindrical portion  36 . 
     As shown in  FIG. 2 , on the outer circumferential surface of the outer wall  100 , there are provided a plurality of gripping members (shoulder portions)  108 , which project radially outward at equal intervals in the circumferential direction and extend in the axial direction. The gripping members  108  serve a function to prevent or stop slippage when the handle  20  is subjected to a rotating operation by a non-illustrated operator. Furthermore, in addition to the gripping members  108 , on the handle  20 , there is provided an origin point unit  109 , which serves as a reference for rotational movement of the handle  20 . In addition, on the surface of the base section  98 , arrows  111   a ,  111   b  are provided, which indicate the direction of rotation thereof. 
     The second meshing portion  110 , which meshes with the teeth  54  of the first meshing portion  56 , is formed to project on an inner circumferential wall of the proximal end side of the outer wall  100 . The second meshing portion  110  is constituted from cross-sectional triangular shaped teeth  113 , which project radially inward from the inner circumferential surface of the outer wall  100 , plural ones of which are provided at equal angular intervals along the circumferential direction of the handle  20 . 
     Hook pieces  112 , which are bent radially inward at a right angle, are disposed on a distal end of the outer wall  100 . The hook pieces  112  are disposed in plurality (e.g., at three locations) and at equal angular distances along the circumferential direction of the handle  20 . When the handle  20  is displaced upwardly, the hook pieces  112  overcome or get over the second projection  60  and come into engagement against the lower surface of the first projection  58 . Thus, by preventing further upward displacement of the handle  20 , the hook pieces  112  function to prevent the handle  20  from being pulled off. 
     The needle valve  22  includes a control section  114  on one end thereof, which is capable of controlling the flow rate of the fluid, the shoulder portion  42  connected to an upper portion of the control section  114  and which can be seated on the seat  52  of the first body  14 , and the shaft  104  that extends integrally in an axial direction from the shoulder portion  42 . 
     The control section  114  includes a cutout groove  118 , which is cut out with a triangular shape in cross section, and extends so as to intersect with the axial direction on one end of the control section  114 . As the cutout groove  118  extends to the side of the shaft  104 , the cross section thereof becomes greater in size (see  FIG. 3 ). 
     An annular groove  119  is provided on the outer circumferential surface of the needle valve  22 , and an O-ring  120  is installed in the annular groove  119 . The O-ring  120  is pressed into contact with the inner circumferential surface of the penetrating hole  38 . 
     The male threads  122  are engraved on the outer circumferential surface of the shaft  104 . The male threads  122  are screw-engaged with female threads of the nut  66  that is fixed to the interior of the main body portion  26 . 
     As shown in  FIGS. 1 and 2 , the cover  24  is formed in a bottomed cylindrical shape with an insertion opening  24 A at an end opposite the bottom, and into which the handle  20  may be inserted such that the cover is removably attached with respect to the handle  20 . A handle portion  124  (see  FIG. 2 ) is provided on an outer circumferential part on an upper end of the cover  24 . One end of the handle portion  124  resides on the top corner of the cover  24 , and the other end terminates on the outer peripheral wall of the cover  24 . Release members  126 , which are cut in a downwardly oriented U-shape, are formed on a side of the outer peripheral wall at positions that are moved substantially 90 degrees on the left and right along the circumferential direction from the handle portion  124 . The release members  126  are provided as a diagonally symmetric pair. The release members  126  are each formed, respectively, by a pair of vertical grooves  136  provided on the outer circumferential wall of the cover  24 , and a horizontal groove  138  that communicates with upper ends of the vertical grooves  136 , whereby the release members  126  are each supported on the outer peripheral wall of the cover  24  by the support region  126 A where no groove is present. On the other hand, underneath the handle portion  124 , a U-shaped cutout  128  is formed, which is fitted over a circular shaped proximal end portion of the connecting section  28 , such that an outer peripheral wall along a circumferential direction from the cutout  128  serves as a skirt section  130  that surrounds the first body  14 . 
     The handle portion  124  projects outwardly in parallel with the longitudinal direction of the connecting section  28  at the time that the cover  24  is mounted over the handle  20 . A non-illustrated binding member such as a wire or the like is attachable to the handle portion  124 . 
     On inner circumferential surfaces of the release members  126 , and at a portion of the release members  126  spaced from the support regions  126 A, third projections  140  are provided that project toward the axis (see  FIG. 3 ). When the cover  24  is fitted externally over the handle  20 , the third projections  140  engage with bottom surfaces  144  of the gripping members  108  of the handle  20 , thereby preventing dislodgement of the cover  24  from the handle  20 . 
     The flow rate control device  10  according to the embodiment of the present invention is constructed basically as described above. Next, operations and advantages of the flow rate control device  10  will be described below. 
     As shown in  FIG. 2 , a completely closed condition in which the cover  24  is taken off from the handle  20 , and communication between the first port  12  and the second port  16  is blocked, and moreover, a state in which rotational displacement of the handle  20  is restricted (a rotation locked state), will be referred to as an initial condition. 
     More specifically, the completely closed condition indicates a state in which the shoulder portion  42  of the needle valve  22  is seated on the seat  52 , and communication between the first port  12  and the second port  16  is blocked. Further, the condition (rotation locked state) in which rotational displacement of the handle  20  is restricted indicates a state in which the handle  20  is moved downwardly in  FIG. 4 , such that the first meshing portion  56  and the second meshing portion  110  engage with each other, thus restricting any rotational displacement of the handle  20 . 
     In the initial condition, the threads  86 , which are formed on the attachment member  88  of the second body  18  of the flow rate control device  10 , are screw-inserted into the female threads of one of the ports of a non-illustrated fluid pressure device S, for example, an air pressure cylinder. Similarly, a flow rate control device  10  of the same structure is attached under the initial condition to the other port of the air pressure cylinder. Below, since the two flow rate control devices  10 , which are attached to the cylinder, are handled in the same way, as necessary, only one of the flow rate control devices  10  will be described. Next, the tube  74  is inserted up to the stepped portion  68  from the side of the release bush  82  of the joint mechanism  76 . Upon slightly pulling out the tube  74 , the distal end of the chuck  78  bites into the tube  74 , and thus separation of the tube  74  is prevented. 
     Next, when the handle  20  is grasped and pulled upwardly in  FIG. 4 , the hook pieces  112  that are formed on the outer wall  100  of the handle  20  overcome the second projection  60 , and come into abutment against the lower surface that is formed around the first projection  58 . A sensation when the hook pieces  112  overcome the second projection  60  and then come into abutment against the lower surface of the first projection  58  can be confirmed sensorially by the operator. In this manner, under a state in which the hook pieces  112  are in abutment against the lower surface of the first projection  58 , further separation of the handle  20  from the main body section  26  is prevented. In this state, the adjustment member  107  of the needle valve  22  is still retained in its state of abutment with the side surface of the inner wall  102  of the handle  20 . 
     Then, the operator turns the handle  20  in the direction shown by the arrow  111   a  in  FIG. 2 . Accordingly, under a screw-engaged action of the male threads  122  of the needle valve  22  with the female threads of the nut  66 , the needle valve  22  moves upwardly in  FIG. 4 . As a result, when the shoulder portion  42  of the needle valve  22  separates away from the seat  52 , the cutout groove  118  that is formed on the one end of the needle valve  22  also moves upwardly, whereupon the first port  12  of the connecting section  28  and the second port  16  disposed in the second body  18  are placed in communication through the communication holes  50   a ,  50   b  formed in the main body section  26 . 
     Furthermore, after the handle  20  has been rotated in the direction of the arrow  111   a , rotational movement of the handle  20  is stopped once at an appropriate position. Consequently, the opening area between the cutout groove  118  of the needle valve  22  and the inner wall of the first cylindrical portion  32  or the second cylindrical portion  34  is determined. In such a condition, when compressed air from a compressed air supply source (not shown), for example, is supplied from the tube  74  that is connected to the flow rate control device  10  disposed on the other side of the cylinder, after the compressed air has flexed the flange  46  of the check valve  44  outwardly in the axial direction, i.e., when passage of the compressed air to the flow path  94  is prevented, the compressed air passes only through the cutout groove  118  whose position has been adjusted, and is discharged to the exterior from the second port  16 . Stated otherwise, the flow rate of the compressed air is throttled by the cutout groove  118 . During this action, movement of the piston inside the non-illustrated cylinder together with the velocity thereof are controlled by the opening passage between the cutout groove  118  and the inner wall of the first cylindrical portion  32  (or the second cylindrical portion  34 ), and can be grasped to a certain extent by the operator. 
     Assuming the operator is satisfied with the velocity of the piston, by carrying out the same operation also in the flow rate control device  10  of the present embodiment that is attached to the one port of the aforementioned cylinder, adjustment of the needle valve  22  therein is performed. At this time, by referring to the position indicated by the origin point unit  109  of the handle  20  of the other flow rate control device  10 , position information of the origin point unit  109  can be made use of. 
     Thus, if a desired flow rate control could not be performed, the operator turns the handle  20  further in the direction of the arrow  111   a , or depending on the circumstances in the direction of the arrow  111   b , and can thereby control the degree of penetration of the needle valve  22  into the interior of the first cylindrical portion  32 . At this time, since the origin point unit  109  formed on the handle  20  indicates the origin of rotation of the handle  20 , the degree by which the handle  20  has been rotated can easily be confirmed. 
     In addition, after adjustments have been made such that the discharge flow rate of the air from the cylinder is at a desired rate, the operator presses downwardly on the handle  20  in  FIGS. 1 through 4 . Consequently, the hook pieces  112  of the handle  20  overcome and move below the second projection  60  formed on the main body section  26 , and as shown in  FIG. 4 , the hook pieces  112  are stopped in front of the connecting section  28 . As a result, in a state in which downward pressing on the handle  20  is completed, the first meshing portion  56  of the main body section  26  is placed in meshing engagement with the second meshing portion  110  of the handle  20 . In this case, since the main body section  26  is assembled together integrally with the second body  18 , further screw-rotation of the handle  20  is restricted. Accordingly, a desired velocity for the piston of the cylinder can be assured. 
     According to the present embodiment, in a state in which the velocity of the piston of the cylinder has been fixed as described above, the cover  24  is fitted over the handle  20  from the outer side thereof. More specifically, using the U-shape cutout  128  of the cover  24 , the cover  24  is mounted onto the proximal end side of the connecting section  28 . At this time, the third projections  140 , which are provided on the inner side of the release members  126 , are moved along the outer circumferential wall of the handle  20 , and ultimately overcome the gripping members  108  of the handle  20 . Since the third projections  140  are formed inwardly of the release members  126 , when the cover  24  is pressed downwardly in  FIG. 3  with respect to the handle  20 , the gripping members  108  of the handle  20  can easily be overcome under an action in which the release members  126  are pressed slightly outward. By the third projections  140  overcoming the gripping members  108 , the cover  24  is prevented from being moved in an upward direction in  FIG. 3 . Consequently, a screw-rotating operation of the handle  20  becomes impossible, and the flow rate of the air, which was set by the handle  20 , can be secured in a stable condition. 
     For avoiding loss of the cover  24 , one end of a non-illustrated string may be tied to the handle portion  124 , and the other end thereof may be tied to the non-illustrated fluid pressure device S. Further, the one end of the string may be tied to the tube  74 . As a result, loss of the cover  24  can be prevented. 
     Next, a situation will be described in which the non-illustrated fluid pressure device S, for example, the velocity of the piston in the cylinder, is readjusted by the flow rate control device  10  according to the present embodiment. 
     The non-illustrated string that has been applied to the handle portion  124  is untied, and the cover  24  is detached from the handle  20 . At that time, a tapered flat tool such as the distal end of a screwdriver is inserted into the horizontal groove  138  of the release members  126 . In addition, the release members  126  are flexed outwardly. Consequently, the third projections  140  become detached from the gripping members  108  of the handle  20 , and thus the cover  24  can easily be removed from the handle  20 . 
     Next, once again, the handle  20  is pulled upwardly from the main body section  26  in  FIG. 3 , whereupon engagement between the first meshing portion  56  and the second meshing portion  110  is released, and the needle valve  22  can be subjected to a rotational operation in the same manner as described previously. 
     In the foregoing manner, according to the present invention, when the flow rate of the fluid between the first port  12  and the second port  16  has been adjusted by effecting screw-rotation of the needle valve  22 , the cover  24  is disposed with respect to the handle  20  that is used for rotating the needle valve  22 , whereby unexpected rotation of the handle  20  can reliably be prevented. As a result, reliable operation of a non-illustrated fluid pressure device S, for example a cylinder, can be assured over a long period of time in a continuously stable condition. 
     Next a modification of the cover  24  in the aforementioned embodiment is shown in  FIGS. 7 through 10 . 
     According to the modification, for example, two (a pair of) arcuately shaped openings  132  are provided in the cover  24 . Each of the arcuately shaped openings  132  is made up from a wide section  134   a , and a narrow section  134   b , which while communicating with the wide section  134   a , is narrower than and has an arc length that is longer than that of the wide section  134   a.    
     As shown in  FIG. 9 , the arcuately shaped openings  132  extend from the top surface of the cover  24  to the inner circumferential surfaces of the release members  126 , and terminate at upper parts of the third projections  140 . On the upper parts of the third projections  140 , inclined sections  142  are provided, which are inclined downwardly from above, so as to approach toward the axis. 
     Next, a tool (jig)  146 , which is used for detaching the cover  24  from the handle  20 , will be described below. As shown in  FIGS. 7 and 8 , the tool  146  is constituted from a disk-shaped base portion  148 , and a pair of insert legs  150 , which are disposed to project in the axial direction from one end surface of the base portion  148 . The legs  150  have lengths that are slightly longer than the depths of the arcuately shaped openings  132 . Further, the distal ends of the legs  150  are provided with tapered shapes, which are slightly reduced in diameter in a radial inward direction. 
     The two legs  150  of the tool  146  are inserted into the wide sections  134   a  of the arcuately shaped openings  132 , and the base portion  148  is pressed toward the cover  24 . Then, as shown in  FIG. 10 , the legs  150  are guided along the arcuately shaped openings  132  and press upon and at once expand or spread the inclined sections  142  radially outward, so that the release members  126  are flexed outwardly. As a result, the third projections  140  can be separated at once away from the gripping members  108  of the handle  20 . 
     In order to prevent loss of the tool  146 , as shown in  FIG. 7 , an attachment member  152  may be provided on the base portion  148  of the tool  146 . One end of a non-illustrated string may be tied to the attachment member  152 , whereas the other end of the string may be tied to the non-illustrated fluid pressure device S, or alternatively, to the tube  74 . As a result, loss of the tool  146  can be prevented. 
     The flow rate control device according to the present invention is not limited to the above-described embodiment. It should be understood that various additional or alternative structures may be adopted therein without deviating from the essential scope of the present invention.