Patent Publication Number: US-9409282-B2

Title: Clamp apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a clamp apparatus, which is driven under the supply of a pressure fluid, for clamping a workpiece on an automated assembly line or the like. 
     BACKGROUND ART 
     Heretofore, in an automated assembly line for automobiles, for example, clamping by a clamping apparatus is carried out, in a state in which pre-formed body panels are overlapped and positioned, and an assembly step is carried out whereby the body panels are welded together. 
     Such a clamp apparatus, for example, as disclosed in U.S. Pat. No. 4,905,973, is equipped with a body, a drive unit which is made up from a cylinder connected to the body, and a clamp arm that projects externally with respect to the body. In addition, by displacing a piston of the drive unit by supplying air to the cylinder, a piston rod is displaced together with the piston, whereby the clamp arm, which is connected to a link mechanism constituted from a plurality of arms, is rotated through a predetermined angle. Consequently, a workpiece or the like can be clamped by the clamp arm. 
     SUMMARY OF INVENTION 
     With the aforementioned clamp apparatus, for example, in the case that a malfunction occurs in the drive unit including the piston and the piston rod, the drive unit must be detached from the body and maintenance carried out thereon. However, in such a case, the piston rod of the drive unit and the link mechanism provided on the side of the body are connected by bolts or the like, and after the connection between such components has been released, the drive unit becomes detached from the body. Such an operation is difficult to perform and leads to an increase in the number of process steps and man-hours required to carry out such maintenance. 
     Further, in the case one wishes to increase the clamping force applied to the workpiece, it is necessary to prepare a different clamp apparatus having a drive unit that produces a different output, and since it is necessary to secure a large storage space for the different clamp apparatus, a single clamp apparatus has been desired, which enables a change in output of the apparatus to easily be implemented. 
     A general object of the present invention is to provide a clamp apparatus which facilitates and improves ease of maintenance, and which enables a change in output of the apparatus to easily be implemented. 
     The present invention is characterized by a clamp apparatus for clamping a workpiece by rotation of a clamp arm, comprising: 
     a body; 
     a drive unit having a piston that is displaced along an axial direction upon supply of a pressure fluid; 
     a driving force transmission mechanism disposed in an interior of the body and connected to the drive unit, the driving force transmission mechanism converting linear displacement of the drive unit along the axial direction into rotational displacement, and transmitting a driving force of the drive unit to the clamp arm; and 
     a connection mechanism for switching a state of connection of the drive unit with respect to the driving force transmission mechanism, 
     wherein the drive unit is disposed detachably with respect to the driving force transmission mechanism through the connection mechanism. 
     According to the present invention, in the clamp apparatus, which is equipped with the drive unit having a piston displaced by supply of a pressure fluid thereto, a driving force transmission mechanism is provided, which converts linear displacement of the piston along an axial direction of the drive unit into rotational displacement, whereby a driving force of the drive unit is transmitted to the clamp arm. In addition, a state of connection of the drive unit with respect to the driving force transmission mechanism can be switched by the connection mechanism. 
     Accordingly, in the case that a maintenance operation such as exchange of the drive unit or the like is to be carried out, since the connection between the driving force transmission mechanism and the drive unit can easily be released by the connection mechanism, for example, in comparison with the conventional clamp apparatus in which a drive unit and a link mechanism (driving force transmission mechanism) are connected by bolts or the like, it is unnecessary to carry out complicated operations such as removal of bolts or the like. Owing thereto, ease of maintenance of the clamp apparatus can be enhanced. Further, by removal of the drive unit from the body and replacement thereof with a different drive unit, a change in the output of the drive unit in the same clamp apparatus can be implemented. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall cross sectional view of a clamp apparatus according to a first embodiment of the present invention; 
         FIG. 2  is an overall cross sectional view showing a clamped state of the clamp apparatus of  FIG. 1 ; 
         FIG. 3  is a cross sectional view taken along line III-III of  FIG. 1 ; 
         FIG. 4  is a partially exploded perspective view from a drive unit side of the clamp apparatus, and showing a condition in which a displaceable body is projected with respect to a body of the clamp apparatus; 
         FIG. 5  is a partially exploded side view showing a condition in which the drive unit is detached from the clamp apparatus of  FIG. 1 ; 
         FIG. 6  is a partially exploded perspective view showing the clamp apparatus of  FIG. 5  as viewed from the drive unit side; 
         FIG. 7  is an overall cross sectional view of the clamp apparatus having a drive unit according to a modified example, which includes first and second pistons; 
         FIG. 8  is an overall cross sectional view of a clamp apparatus according to a second embodiment of the present invention; 
         FIG. 9  is an overall cross sectional view of the clamp apparatus of  FIG. 8 , showing a condition in which the clamp arm is rotated through a predetermined angle; and 
         FIG. 10  is an overall cross sectional view showing a clamped state of the clamp apparatus of  FIG. 8 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     As shown in  FIGS. 1 and 2 , a clamp apparatus  10  includes a hollow body  12 , a drive unit  14  provided on one end of the body  12 , a clamp arm  16  disposed rotatably with respect to the body  12 , and a driving force transmission mechanism  18  that transmits a driving force, along an axial directions (the directions of arrows A and B) of the drive unit  14 , to the clamp arm  16 . 
     The body  12  is formed, for example, with an elongate rectangular shape in cross section, and is formed in the interior thereof with a housing chamber  20  in which the driving force transmission mechanism  18  is accommodated. The housing chamber  20  opens downwardly (in the direction of the arrow A), and the drive unit  14  is connected to the body  12  so as to close the opening of the housing chamber  20 . 
     A support member  22  is provided on the body  12  which projects in a sideways direction. More specifically, the support member  22  projects horizontally at a predetermined length with respect to the body  12 , and is formed on a distal end thereof with an adjustment pin  24 , which projects upwardly (in the direction of the arrow B). In addition, as shown in  FIG. 2 , as will be described later, at a time of clamping when the clamp arm  16  is rotated, a workpiece W is clamped between the clamp arm  16  and the support member  22 . The adjustment pin  24  is screw-engaged with respect to the support member  22 , and is movable in vertical directions (the directions of arrows A and B) by rotating the adjustment pin  24 . 
     Further, roller grooves  26  are formed in both side surfaces of the body  12 , which extend in the vertical direction (the direction of arrow A or B) substantially in the center of both side surfaces. Rollers  28 , which are disposed on a later-described displaceable body  58 , are inserted in and guided by the roller grooves  26 . 
     The drive unit  14  includes a cylinder tube  30  having a bottom, a piston  32 , which is disposed displaceably in the interior of the cylinder tube  30 , a piston rod  34  connected to the piston  32 , and a rod cover  36  that displaceably supports the piston rod  34 . 
     An open end of the cylinder tube  30  is disposed in abutment against an end surface  12   a  of the body  12 . Fastening bolts  40 , which are inserted through a pair of penetrating holes  38  (see  FIG. 4 ) that penetrate in the axial direction of the cylinder tube  30 , are screw-engaged and connected with respect to the body  12 . 
     Further, a first port  42 , which is provided in one end side (in the direction of the arrow B), and a second port  44 , which is provided in another end side (in the direction of the arrow A) and separated a predetermined distance with respect to the first port  42 , are formed in a side surface of the cylinder tube  30 . A cylinder chamber  46  formed in the interior of the cylinder tube  30  communicates with the exterior through the first and second ports  42 ,  44 . The first and second ports  42 ,  44  are connected through non-illustrated tubes to a non-illustrated pressure fluid supply source. In addition, pressure fluid is supplied selectively to the first port  42  or the second port  44 , and is introduced into the cylinder chamber  46  from the non-illustrated pressure fluid supply source. 
     The piston  32  is formed in the shape of a disk, for example, and a piston packing  48  is installed via an annular groove on the outer circumferential surface of the piston  32 . Additionally, by abutment of the piston packing  48  against the inner wall surface of the cylinder chamber  46 , leakage of pressure fluid between the piston  32  and the cylinder tube  30  is prevented. 
     One end of the piston rod  34  is connected integrally by caulking to a hole that is formed in the center of the piston  32  in a state of being inserted through the hole. Further, a connector  54  having an annularly recessed neck part  50 , and a head part  52 , which is expanded in diameter with respect to the neck part  50 , is formed in the other end of the piston rod  34 . In addition, the neck part  50  and the head part  52  are connected integrally through engagement with respect to the later-described displaceable body  58  of the driving force transmission mechanism  18 . Moreover, the neck part  50  and the head part  52  are formed with circular shapes in cross section having different diameters, respectively. 
     The rod cover  36  is provided in an opening of the cylinder chamber  46  facing the body  12 , thereby closing the opening, and a piston rod  34 , which is inserted through the center of the rod cover  36 , is supported displaceably along the axial directions (the directions of arrows A and B). A rod packing  56  is installed through an annular groove on an inner circumferential surface of the rod cover  36 . The rod packing  56  slides in contact with the outer circumferential surface of the piston rod  34 , whereby leakage of pressure fluid to the exterior from the cylinder chamber  46  is prevented. 
     The driving force transmission mechanism  18  includes the displaceable body  58 , which is disposed in the housing chamber  20  of the body  12  and is connected to the other end of the piston rod  34 , a pair of rollers  28  provided rotatably on an upper part of the displaceable body  58 , a link arm  60  supported pivotally on the displaceable body  58  together with the rollers  28 , and a sub-arm  62  connected to the link arm  60  and the clamp arm  16 . 
     The displaceable body  58  is formed with a substantially rectangular shape in cross section, with a connecting recess  64 , which is connected to the connector  54  of the piston rod  34 , being formed on a lower end of the displaceable body  58 . 
     As shown in  FIGS. 1 through 6 , the connecting recess  64  includes a small diameter part  66 , which is formed on one end surface, so as to open on the end surface side (in the direction of the arrow A) and on one side surface side (in the direction of the arrow C1 in  FIG. 4 ) of the displaceable body  58 , and a large diameter part  68  adjacent to the small diameter part  66 , which is formed in a direction (the direction of the arrow B) separated from the end surface. Further, the small diameter part  66  and the large diameter part  68  are recessed with semicircular shapes in cross section, respectively, such that the large diameter part  68  has a diameter that is greater than that of the small diameter part  66 . 
     In addition, the neck part  50  of the piston rod  34  is engaged with the small diameter part  66 , whereas the head part  52  of the piston rod  34  is engaged with the large diameter part  68 . More specifically, the radius of the small diameter part  66  is set to correspond with the diameter of the neck part  50 , and the radius of the large diameter part  68  is set to correspond with the diameter of the head part  52 . 
     On the other hand, as shown in  FIGS. 1 and 2 , an inclined member  70  that tapers gradually toward the upper end, is formed on an upper portion of the displaceable body  58  on a side surface facing toward the clamp arm  16 . When the clamp arm  16  is rotated from an unclamped state (see  FIG. 1 ) into a clamped state (see  FIG. 2 ), a sub-roller  72 , which is pivotally supported on the sub-arm  62 , abuts against the inclined member  70 . 
     The rollers  28  are inserted into the roller grooves  26  that are formed along the axial direction of the body  12 , such that upon movement thereof, the displaceable body  58  is guided in the vertical directions (the directions of arrows A and B), and rotational displacement of the displaceable body  58  is restricted. 
     Further, a shaft of the rollers  28  is inserted in a link groove  73  formed on an upper part of the displaceable body  58 , such that the rollers  28  are movable by a predetermined distance in a direction perpendicular to the axial direction (the direction of the arrow A or B) of the displaceable body  58 . An end of the link arm  60 , which is pivotally supported together with the rollers  28  on the displaceable body  58 , also is movable in a direction perpendicular to the axial direction of the displaceable body  58 . 
     The link arm  60  is connected between the sub-arm  62  and an upper part of the displaceable body  58 . The link arm  60  is pivotally supported together with the rollers  28  with respect to the displaceable body  58 , and is supported mutually and rotatably with respect to the sub-arm  62  through a link pin  74 . In addition, the link arm  60  converts linear motion of the piston rod  34  into rotational motion of the clamp arm  16  via the displaceable body  58 . 
     The sub-arm  62  is connected to ends of the link arm  60  and the clamp arm  16 , and the sub-roller  72  is axially supported rotatably in the middle of the sub-arm  62 . On the other hand, the sub-arm  62  is connected to the clamp arm  16  through support pins  76  having a rectangular shape in cross section. Additionally, upon rotation of the sub-arm  62 , the sub-roller  72  rotates in abutment against the inclined member  70  of the displaceable body  58 . 
     The clamp arm  16  is disposed on an outer part of the body  12  having a U-shape in cross section, such that one end thereof is connected to the pair of support pins  76 , which project externally of the body  12 . In addition, by being connected to the sub-arm  62  via the support pins  76 , the clamp arm  16  is axially supported rotatably through the sub-arm  62 . 
     Further, a gripping pin  78  for gripping a workpiece W is provided on the other end of the clamp arm  16 . The gripping pin  78  projects with respect to the other end, and is screw-engaged therein so that the projecting height with respect to the other end can be changed. Further, when the workpiece W is clamped as shown in  FIG. 2 , the gripping pin  78  is disposed so as to confront the adjustment pin  24  on the support member  22 . Thus, in a clamped state in which the clamp arm  16  is rotated through a predetermined angle, the workpiece W is clamped and gripped between the gripping pin  78  and the adjustment pin  24 . 
     The clamp apparatus  10  according to the first embodiment of the present invention is constructed basically as described above. Next, operations and effects of the clamp apparatus  10  will be described. In the following descriptions, the unclamped state shown in  FIG. 1  shall be treated as an initial position. 
     In the initial condition, pressure fluid is supplied to the first port  42 , and by lowering of the piston  32 , via the driving force transmission mechanism  18 , the clamp arm  16  is placed in a state of being separated substantially perpendicularly with respect to the support member  22 . Further, a thin plate shaped workpiece W is mounted beforehand with respect to the support member  22  of the body  12 . 
     At first, in the initial position of the clamp apparatus  10  shown in  FIG. 1 , under a switching operation of a non-illustrating switching device, the pressure fluid which had been supplied to the first port  42  is supplied instead to the second port  44  from the pressure fluid supply source, while the first port  42  is placed in a state of being open to atmosphere. Consequently, by action of the pressure fluid, which is introduced from the second port  44  into the cylinder chamber  46 , the piston  32  is pressed upwardly toward the side of the body  12  (in the direction of the arrow B), and the piston rod  34  is displaced integrally with the piston  32 . 
     In addition, accompanying displacement of the piston rod  34  and under a guiding action of the rollers  28  with respect to the roller grooves  26 , the displaceable body  58  is moved in an upward direction (in the direction of the arrow B), whereupon the link arm  60  starts to rotate clockwise about a location where the link arm  60  is pivotally supported on the displaceable body  58 . Together with rotation of the link arm  60 , the sub-arm  62  rotates, and by rotation of the sub-arm  62 , the clamp arm  16  is rotated through a predetermined angle clockwise about the support pins  76 . 
     Consequently, as shown in  FIG. 2 , the gripping pin  78  of the clamp arm  16  abuts against the workpiece W, and a clamped state is brought about in which the workpiece W is gripped between the gripping pin  78  and the support member  22  of the body  12 . 
     At this time, accompanying rotation of the clamp arm  16 , the rollers  28  are moved via the link arm  60  along the roller grooves  26  in a direction to approach the clamp arm  16 , and together therewith, the sub-roller  72  abuts against the inclined member  70  of the displaceable body  58 , whereby the clamp arm  16  is pressed, and a locked state is brought about in which rotation of the clamp arm  16  is locked. As a result, the clamped state of the workpiece W by the clamp arm  16  is maintained. 
     On the other hand, in the event that the clamped state of the workpiece W shown in  FIG. 2  is released, under a switching operation of the non-illustrated switching device, the pressure fluid which had been supplied to the second port  44  is supplied instead to the first port  42 , while the second port  44  is placed in a state of being open to atmosphere. 
     By action of the pressure fluid, which is supplied to the first port  42  and introduced into the cylinder chamber  46 , the piston  32  is pressed downward in a direction to separate from the body  12  (in the direction of the arrow A), and the piston rod  34  is lowered integrally with the piston  32 . 
     In addition, accompanying displacement of the piston rod  34 , the displaceable body  58  is moved in a downward direction under a guiding action of the rollers  28  with respect to the roller grooves  26 , and along therewith, the link arm  60  is rotated counterclockwise about a location where the link arm  60  is pivotally supported on the displaceable body  58 . Together with rotation of the link arm  60 , the sub-arm  62  rotates, and by rotation of the sub-arm  62 , the clamp arm  16  is rotated through a predetermined angle counterclockwise about the support pins  76 . Consequently, the gripping pin  78  of the clamp arm  16  separates from the support member  22 , and the clamped state of the workpiece W is released (see  FIG. 1 ). 
     A case will now be described in which the drive unit  14  in the clamp apparatus  10  is exchanged. First, in the event that the drive unit  14  is to be exchanged, the clamp arm  16  is placed in the unclamped state shown in  FIG. 1 , in which the clamp arm  16  is separated from the support member  22 . In such a condition, a non-illustrated worker rotates the fastening bolts  40  by which the drive unit  14  is fastened to the body  12 , whereupon the connected state of the drive unit  14  with respect to the body  12  is released (see  FIG. 4 ). 
     Next, the other end of the clamp arm  16  is grasped, and as shown in  FIG. 4 , by further rotating the clamp arm  16  counterclockwise through a predetermined angle, the displaceable body  58 , which is connected via the sub-arm  62  and the link arm  60 , is moved downward (in the direction of the arrow A). Thus, as shown in  FIG. 4 , the end of the displaceable body  58  is made to project a predetermined length with respect to the end surface  12   a  of the body  12 . 
     In addition, after the cylinder tube  30  constituting the drive unit  14  has been moved downward (in the direction of the arrow A) to separate away from the body  12 , the connector  54  of the piston rod  34  is made to slide in a direction (the direction of the arrow C1 in  FIG. 6 ) perpendicular to the axial direction of the piston rod  34  (the direction of the arrow A or B), whereby the connector  54  is separated from the connecting recess  64  of the displaceable body  58 . Consequently, the connected condition between the displaceable body  58  and the piston rod  34  is released, and removal of the drive unit  14  including the piston rod  34  from the body  12  is completed. 
     Next, in the event that a new drive unit  14  is to be assembled with respect to the body  12 , the connector  54  of the piston rod  34  thereof is fitted in engagement with the connecting recess  64  of the displaceable body  58 , which projects from the end surface  12   a  of the body  12 . 
     In greater detail, by the connector  54  being made to approach from the side of the one side surface in which the connecting recess  64  is opened, and having the connector  54  slide in a direction (the direction of the arrow C2 in  FIG. 6 ) perpendicular to the axial direction (the direction of arrow A or B) of the piston rod  34 , the head part  52  of the connector  54  is inserted into the large diameter part  68 , and the neck part  50  is inserted into the small diameter part  66 . 
     In addition, in a state in which the connector  54  of the piston rod  34  is inserted into the connecting recess  64  of the displaceable body  58  (see  FIG. 4 ), the other end of the cylinder tube  30  that makes up the drive unit  14  is slowly made to approach (in the direction of the arrow B) the end surface  12   a  of the body  12 , whereupon the other end comes into abutment against the end surface  12   a . Thereafter, the fastening bolts  40  are inserted through the penetrating holes  38  and screw-engaged with respect to the body  12 , whereby the new drive unit  14  is assembled with respect to the body  12  in a state in which the piston rod  34  and the displaceable body  58  are connected together. 
     At this time, because the connecting recess  64  is open on the one side surface of the displaceable body  58 , the piston rod  34  is in a state of being movable in a direction (the direction of the arrow C1) perpendicular to the axial direction of the piston rod  34 . However, since a thrust force is applied only in the axial direction (the direction of arrow A or B) to the displaceable body  58  and the piston rod  34 , and is not applied in a direction (the direction of the arrow C1) perpendicular to the axial direction, the connected state between the piston  32  and the displaceable body  58  can reliably be maintained. 
     In the foregoing manner, with the first embodiment, in the clamp apparatus  10  having the drive unit  14  including the piston  32  that is displaced upon supply of a pressure fluid, and in which the clamp arm  16  is rotated by a driving force from the drive unit  14 , the connector  54  of the piston rod  34  constituting the drive unit  14  is connectable with the displaceable body  58  of the driving force transmission mechanism  18  that transmits the driving force of the drive unit  14  to the clamp arm  16 . Owing thereto, in the case that a maintenance operation such as exchanging the drive unit  14  or the like is carried out, merely by a simple operation of detaching the piston rod  34  from the displaceable body  58  after the displaceable body  58  has been made to project from the body  12 , an operation can be performed easily to remove the drive unit  14 . As a result, in comparison with the conventional clamp apparatus in which a drive unit and a link mechanism (driving force transmission mechanism) are connected by bolts or the like, it is unnecessary to carry out complicated operations such as removal of bolts or the like. Owing thereto, ease of maintenance of the clamp apparatus  10  can be enhanced. 
     Further, in the clamp apparatus  10 , by exchanging the drive unit  14  with a different drive unit  14  having a piston  32  that differs in cross sectional area, a change in output of the drive unit  14  can easily be carried out using the same body  12  including the driving force transmission mechanism  18 . As a result, in the case it is desired to change the clamping force imposed on the workpiece W by the clamp arm  16 , by exchanging the drive unit  14  with a different drive unit  14  having a different output, the size of the thrust force transmitted to the driving force transmission mechanism  18  through the piston rod  34  can be changed. Owing thereto, simply by exchanging the drive unit, the clamping force applied by the clamp arm  16  can easily be changed in a single clamp apparatus  10 . 
     More specifically since it is unnecessary to prepare a plurality of clamp apparatus that exhibit different clamping forces, equipment investments can be suppressed. 
     Furthermore, since the opening of the housing chamber  20  is closed by the drive unit  14  without being open to the exterior, a fluidtight state can be provided in the interior of the housing chamber  20  of the body  12 . Owing thereto, even in the event that water or the like is used by an assembly line in which the clamp apparatus  10  is employed, such water can be prevented from infiltrating into the interior, and spatter generated on a welding line or the like can be prevented from entering the interior. 
     Further, the drive unit  14  is not limited to a structure having a single piston  32  as in the foregoing embodiment. For example, as shown in  FIG. 7 , a drive unit  80  may be used which is equipped with two first and second pistons  84 ,  86  disposed displaceably in the interior of a cylinder tube  82 . 
     With the drive unit  80 , as shown in  FIG. 7 , on a side surface of the cylinder tube  82 , first and second ports  42   a ,  42   b ,  44   a ,  44   b  are provided in each of respective pairs, and the cylinder tube  82  is formed with a first cylinder chamber  88  in which a first piston  84  is accommodated, and a second cylinder chamber  90  in which a second piston  86  is accommodated. The first cylinder chamber  88  and the second cylinder chamber  90  are separated, and are formed so as not to communicate with each other, and the first cylinder chamber  88  and the second cylinder chamber  90  communicate respectively with the first and second ports  42   a ,  42   b ,  44   a ,  44   b.    
     Further, the first piston  84  and the second piston  86  are connected respectively to a first piston rod  92  and a second piston rod  94 , and by being connected mutually to an end of the first piston rod  92  and an end of the second piston rod  94 , the first and second pistons  84 ,  86  are connected in series through the first and second piston rods  92 ,  94 . 
     In addition, for example, in the case that the clamp apparatus  10  is switched from an unclamped state to a clamped state, a pressure fluid is supplied respectively to the pair of second ports  44   a ,  44   b , whereby the first and second pistons  84 ,  86  are displaced toward the side of the body  12  (in the direction of the arrow B) integrally and simultaneously with the first and second piston rods  92 ,  94 . More specifically, compared to the drive unit  14  equipped with a single piston  32 , a thrust force of roughly two times can be obtained, and accompanying such an increased thrust force, the clamping force applied by the clamp arm  16  can be increased. 
     The piston that constitutes the drive unit  14  is not limited to the aforementioned case in which the two first and second pistons  84 ,  86  are disposed in series, and the thrust force can be increased by connecting two or more pistons in series. 
     Next, a clamp apparatus  100  according to a second embodiment is shown in  FIGS. 8 through 10 . Structural elements thereof, which are the same as those of the clamp apparatus  10  according to the aforementioned first embodiment, are denoted by the same reference characters, and detailed descriptions of such features are omitted. 
     The clamp apparatus  100  according to the second embodiment differs from the clamp apparatus  10  according to the first embodiment, in that a driving force of the drive unit  14  is transmitted to the clamp arm  16  from a toggle link mechanism  102 . 
     The toggle link mechanism  102  is disposed in the housing chamber  20  of the body  12  and includes a link arm  104 , which is supported pivotally together with the rollers  28  on an upper part of the displaceable body  58 . The toggle link mechanism  102  converts linear motion of the piston rod  34 , which is connected to the displaceable body  58 , into rotational motion of the clamp arm  16 . One end of the link arm  104  is supported pivotally on an upper part of the displaceable body  58 , whereas the other end thereof is supported pivotally on an end of a sub-arm  106 . 
     With the clamp apparatus  100  constructed in the foregoing manner, in the initial position shown in  FIG. 8 , by supply of pressure fluid to the second port  44  of the drive unit  14 , the piston  32  and the piston rod  34  are raised integrally, accompanied by the displaceable body  58  being moved upwardly (in the direction of the arrow B) under a guiding action of the rollers  28  with respect to the roller grooves  26 . In addition, accompanying rising of the displaceable body  58 , the link arm  104  starts to rotate clockwise about a location where the link arm  104  is pivotally supported on the displaceable body  58 , and via the sub-arm  106 , the clamp arm  16  is rotated through a predetermined angle clockwise about the support pins  76  (see  FIG. 9 ). 
     In addition, upon further rising of the piston  32 , the link arm  104  and the sub-arm  106  are rotated under a displacement action of the displaceable body  58 , accompanied by the clamp arm  16  being rotated further in a clockwise direction. Consequently, the gripping pin  78  of the clamp arm  16  abuts against the workpiece W, and a clamped state is brought about in which the workpiece W is gripped between the gripping pin  78  and the support member  22  of the body  12  (see  FIG. 10 ). At this time, the link arm  104  is maintained in a substantially horizontal orientation, whereby the clamped state of the workpiece by the clamp arm  16  is locked. 
     In the foregoing manner, with the second embodiment, in the clamp apparatus  100  having the toggle link mechanism  102 , the connector  54  of the piston rod  34  constituting the drive unit  14  is connectable with the displaceable body  58  of the driving force transmission mechanism  18  that transmits the driving force of the drive unit  14  to the clamp arm  16 . Owing thereto, in the case that a maintenance operation such as exchanging the drive unit  14  or the like is carried out, merely by a simple operation of detaching the piston rod  34  from the displaceable body  58  after the displaceable body  58  has been made to project from the body  12 , an operation can be performed easily to remove the drive unit  14 . As a result, in comparison with the conventional clamp apparatus in which a drive unit and a link mechanism (driving force transmission mechanism) are connected by bolts or the like, it is unnecessary to carry out complicated operations such as removal of bolts or the like. Owing thereto, ease of maintenance of the clamp apparatus  100  can be enhanced. 
     Further, in the clamp apparatus  100 , by exchanging the drive unit  14  with a different drive unit  14  having a piston  32  that differs in cross sectional area, a change in output of the drive unit  14  can easily be carried out using the same body  12  including the driving force transmission mechanism  18 . As a result, in the case it is desired to change the clamping force imposed on the workpiece W by the clamp arm  16 , by exchanging the drive unit  14  with a different drive unit  14  having a different output, the size of the thrust force transmitted to the driving force transmission mechanism  18  through the piston rod  34  can be changed, and along therewith, the clamping force applied by the clamp arm  16  can easily be changed in a single clamp apparatus  100 . 
     Furthermore, since the opening of the housing chamber  20  is closed by the drive unit  14  without being open to the exterior, a fluidtight state can be provided in the interior of the housing chamber  20  of the body  12 . As a result, for example, even in the case that water or the like is used by the assembly line in which the clamp apparatus  100  is employed, such water can be prevented from infiltrating into the interior, and spatter generated on a welding line or the like can be prevented from entering the interior of the housing chamber  20 . 
     With the aforementioned first and second embodiments, a case has been described in which the first and second ports  42 ,  44  of the drive unit  14  are provided on a side surface, which is opposite from the side on which the support member  22  projects from the body  12 . However, by reversing the direction in which the drive unit  14  is assembled, the position of the first and second ports  42 ,  44  can easily be changed to the side of the support member  22 . More specifically, the position of the first and second ports  42 ,  44  can be changed selectively responsive to the work environment in which the clamp apparatus  10 ,  100  are used. 
     Further, by providing a position detecting sensor, which is capable of detecting the displacement position of the piston  32  in the drive unit  14 , the angle of rotation of the clamp arm  16  can be detected based on the position of the piston  32 , thus enabling clamped and unclamped states of the clamp arm  16 , for example, to be confirmed reliably. 
     Furthermore, with the clamp apparatus  10 ,  100  according to the above-described first and second embodiments, a case has been described in which an air driven type of drive unit  14  is applied for displacing the piston  32  upon supply of a pressure fluid. However, the invention is not limited to this feature, and for example, a hydraulically driven type of drive unit  14  may be used in which hydraulic oil is used as the pressure fluid. By using a hydraulically driven type of drive unit  14 , compared to an air driven type, a larger drive force can be obtained, which is suitable for cases in which workpieces W are to be clamped by a large clamping force. 
     The clamp apparatus according to the present invention is not limited to the above embodiments. Various changes and modifications may be made to the embodiments without departing from the scope of the invention as set forth in the appended claims.