Abstract:
A device for clamping a workpiece on tool includes a ram and a clamp, the ram being selectively actuated by a pressurized fluid. The ram includes a body which, when in use, is secured to the tool and a slide mounted such that it can slide with respect to the body. The clamp is hinged with the slide about a pivot axis. The body includes a front face beyond which the clamp projects when it is in a clamping position in order to clamp the workpiece. In addition, the clamp has a release position which it reaches at least partially by pivoting about the pivot axis. The slide includes a piston and a rod that are assembled to one another. The pivot axis is offset by a predetermined distance with respect to the axis of the rod in the direction of the front face.

Description:
BACKGROUND 
       [0001]    The invention relates to a clamping device of a workpiece on a tool, of the type comprising a flange actuated by a cylinder, which retracts and which moves linearly in the clamping phase. 
         [0002]    Such a clamping device is known from document FR 2 863 190, a patent application filed by the present inventor. This device comprises a body comprising a lower part of cylindrical form and an upper part in the form of a clevis. A flange is mounted mobile between the two wings of the clevis and is actuated by the rod of a cylinder housed in the lower part. The flange moves between a gripping position and a release position. Movement from the gripping position to the release position comprises a first translation phase parallel to the axis of the cylinder followed by a rotation phase to give access to the tool to remove the workpiece and place another. Movement from the release position to the gripping position follows the same trajectory, in the reverse direction of the preceding. 
         [0003]    In the positions of the translation phase, the flange is guided by support elements made by heels of the flange and support surfaces of the wings of the clevis. It is also guided by a pivot at the end of the rod. The geometry of the triangle formed by the axis of the pivot, the support elements and the point of contact of the flange on the workpiece determines amplification of forces applied to the workpiece and which are transmitted in the form of torque between the pivot and the support elements. 
         [0004]    Such a device is entirely satisfactory, in particular in terms of quick actuation and compactness, when the support point on the workpiece can be near the device. However, in some configurations, it is preferable, or even indispensable, for this support point to be away from the clamping device due to the stresses of the geometry of the workpiece. This is possible by elongation of the flange, but such elongation increases stresses on the pivot and the support elements or limits the clamping force if said stresses cannot increase. Also, this elongation leads to larger bulk in the release position. In fact, the flange has pivoted by around a quarter turn towards upwards and its length is added to that of the body in the direction of the cylinder. 
         [0005]    A possible solution for increasing admissible forces is to move the support elements away from the position of the pivot in the gripping position. This in turn increases the length of the body and the height of the flange, which increases the bulk of the device both in gripping position and in release position. This solution therefore is not optimal due to this excessive bulk. 
       SUMMARY 
       [0006]    The aim of the invention is a clamping device of a workpiece for a tool which is compact, rapid and powerful, even if the point clamping must be moved away. 
         [0007]    With these aims in focus, the object of the invention is a clamping device of a workpiece on a tool, comprising a cylinder and a flange, the cylinder being selectively actuated by pressurised fluid and in turn comprising a body intended to be fixed to the tool and a slide mounted to slide relative to the body, the flange being hinged about a pivot axis on the slide, the body comprising a front face beyond which the flange projects when it is in a gripping position to clamp the workpiece, the flange also having a release position it reaches at least partially by pivoting about the pivot axis, the device comprising guide members which comprise a fixed guide member relative to the body and a mobile guide member connected to the flange cooperating together to drive the flange in a rotation movement about the pivot axis at least to completion of travel towards the release position and as per translation movement at least to completion of travel towards the gripping position, the device being characterized in that the fixed guide member comprises at least one hollowed groove in the body and the mobile guide member comprises at least one finger engaged in the groove. 
         [0008]    Due to the translation movement during the clamping phase, the workpiece is well clamped without sliding movement being triggered. On the contrary, rotation during the release phase rapidly releases the flange to leave access to the workpiece on the tool to unload it and load a fresh one in a direct movement along the front face. This succession of movements is obtained with simple control by a single cylinder. The finger has the form of a nipple or a roller and is fixed on the flange at a distance from the pivot axis. If the groove were arranged on the flange, it would have the disadvantage of weakening the cross-section of the latter. In the invention, the body can be made with a strong cross-section which is not overly affected by the groove. 
         [0009]    In particular, the groove extends according to a trajectory whereof a first portion is parallel to the direction of translation of the flange and a second portion is oriented obliquely relative to the first portion, the finger located in the first portion when the flange is in the gripping position or near and in the second portion when the flange is driven to pivot. Pushing on the finger during its displacement in the groove guides the movement of the flange, in particular to control pivoting towards the release position and translation towards the gripping position. When the finger is in the first portion of the groove, the relative position of the pivot axis and of the roller is not modified, and the flange retains the same orientation, which determines translation movement. In contrast, when the roller is in the second portion of the groove, the relative position of the pivot axis and of the finger is modified, and the flange pivots on the pivot axis. 
         [0010]    According to a constructive arrangement, the finger is located at a distance from the pivot axis, moved away in the direction of translation of the rod from the gripping position to the release position. It is evident that this arrangement is easier to execute, leaving space between the pivot axis and the cylinder rod without stress to limit the length of the rod. 
         [0011]    According to another characteristic, the slide comprises a piston and a rod joined by assembly and the pivot axis is offset by a predetermined distance relative to the axis of the rod in the direction of the front face. Moving the pivot axis in the direction of the workpiece to be clamped first shortens the distance between the pivoting point and the support point on the workpiece. This increases the force which can be applied to the workpiece. Also, the release position of the flange is offset towards the workpiece, which decreases the bulk in the direction opposite the workpiece. Also, the distance between the end of the flange and that of the pivot axis decreases, in turn decreasing the bulk in height of the device in release position, for a determined distance between the body of the device and the support point on the workpiece. The substantial offset of the pivot axis is possible due to the slide being made in two workpieces. In fact, the size of the upper part of the slide is not limited to the passage diameter of the rod in the body, but can be greater. 
         [0012]    In particular, the piston and the rod are assembled by screwing into each other. 
         [0013]    According to a constructive arrangement, the body comprises a cap for closing a cylinder chamber delimited by the piston and a bore of the body in which the piston slides. The cylinder can be mounted by introducing the piston into the bore, assembling it with the rod, then blocking the bore with the cap to create the cylinder chamber. 
         [0014]    According to another characteristic, the clamping device comprises upper support elements, the upper support elements comprising an upper fixed support element fixed relative to the body, and a mobile upper support element connected to the flange, the fixed and mobile upper support elements cooperating, at least to completion of travel of the flange towards the gripping position, to mutually offer sliding contact parallel to the translation movement of the flange and to oppose pivoting of the flange towards the release position. Direct transmission of forces is made between the flange and the body of the flange, ensuring good rigidity and good capacity for collecting the clamping forces. 
         [0015]    In addition, the clamping device comprises lower support elements comprising a lower fixed support element, fixed relative to the body, and a lower mobile support element connected to the rod, the fixed and mobile lower support elements cooperating, at least on completion of travel of the flange towards the gripping position, to mutually offer sliding contact parallel to the translation movement of the flange. The lower support elements absorb forces transmitted by the flange during clamping by means of the rod. And preferably, the lower mobile support element is at the level of the pivot axis of the flange such that the forces are transmitted without generating torque on the rod. 
         [0016]    According to an improvement, the clamping device comprises a detection conduit terminating on the upper fixed support element and intended to be connected in fluid communication with a device for detecting a fluid leak. When the flange is in gripping position, the upper fixed support element is in contact with the mobile upper support element, blocking the output of the detection conduit. This is a highly compact element for detecting the closing or opening of the flange. The fluid used is typically air. A particular form can also be provided on the mobile support element so that detection is performed only within a very precise range of position. 
         [0017]    Another aim of the invention is a mounting method of a clamping device such as described previously, according to which the rod is placed on the body to have it terminate in the body, and the piston is assembled on the terminating part of the rod. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will be better understood and other particular features and advantages will emerge from the following description, the description making reference to the appended drawings, in which: 
           [0019]      FIG. 1  is a perspective view of the clamping device according to a first embodiment of the invention, in gripping position; 
           [0020]      FIG. 2  is a view similar to  FIG. 1 , in a release position; 
           [0021]      FIG. 3  is a plan view of the device of  FIG. 1 ; 
           [0022]      FIG. 4  is a side elevation of the device of  FIG. 1 , in an intermediate position between the gripping position and the release position; 
           [0023]      FIG. 5  is a view of the detail V of  FIG. 4 , the device being in the gripping position; 
           [0024]      FIG. 6  is a sectional view of the device according to a longitudinal plane in gripping position; 
           [0025]      FIG. 7  is a view similar to  FIG. 6 , in the release position; 
           [0026]      FIG. 8  is a view of the detail VIII of  FIG. 4 ; 
           [0027]      FIG. 9  is a view similar to  FIG. 6  of a flange according to a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    A clamping device according to a first embodiment of the invention is intended to clamp a workpiece on a tool. The device comprises a body  1  fixed on the tool, for example by means of a collar  10  screwed onto the tool. The body  1  essentially comprises a cylindrical part  11  to one side of the collar  10 , and a part in the form of a clevis  12  opposite the cylindrical part  11 . Arbitrarily and for clearer description, it is considered that the bottom of the device is the cylindrical part  11  and the top is the clevis  12 . However, the device can be mounted on the tool in any orientation. 
         [0029]    The clamping device also comprises a flange  2  mounted mobile between two wings  120  of the clevis  12 . The flange  2  comprises an arm  20  at the end of which a support point is intended to clamp the workpiece. The flange  2  has a gripping position in which it projects beyond a front face  13  of the body  1  and in which it is likely to clamp the workpiece on the tool, as shown in  FIGS. 1 ,  4  and  6 . It also has a release position in which the front face  13  is totally released upwards and the arm  20  is raised, as shown in particular in  FIGS. 2 and 7 . The flange  2  projects upwards. 
         [0030]    A cylinder  3  is housed in the cylindrical part  11 . It comprises a bore  31  made in the body  1  and in which a slide  32  is mounted to slide. A cap  33  blocks the bore  31  by being screwed onto the exterior of the cylindrical part  11  of the body  1 . The slide  32  is divided into two parts joined together: a piston  321  and a rod  322 . The piston  321  has the form of a disc from which a threaded part projects  3210  placed at the centre of the disc. The rod  322  comprises a threaded muff  3221 , followed by a smooth part  3222  then a foot  3223  wider than the smooth part  3222 . The smooth part  3222  is adjusted to slide in a neck  14  of the body  1 , succeeding the bore  31 , whereas the foot  3223  is located beyond the neck  14 , in the space between the wings  120  of the clevis  12 . The threaded part  3210  is screwed into the muff  3221  of the rod  322 . A first chamber  35  is delimited in the bore  31  between the piston  321  and the cap  33  while a second chamber  36  is delimited between said piston  321  and the neck  14 . On the outside the cylindrical part  11  comprises two shallow distribution throats  113 ,  114 . Each distribution throat  113 ,  114  is in communication with one of the chambers  35 ,  36  of the cylinder  3  by means a respective supply conduit  1130 ,  1140 . Sealing throats are provided on either side of the distribution throats to insulate the latter when the body  1  of the device is placed in a cylindrical housing of the tool, not shown here. Two channels are to be provided terminating in the housing opposite the distribution throats to supply the cylinder  3  with pressurised fluid such as oil or air via the distribution throats  113 ,  114  and the supply conduits  1130 ,  1140 . 
         [0031]    The flange  2  is hinged about a pivot axis A on the foot  3223  of the slide  32 . Due to the form of the foot  3223 , it is possible to offset the pivot axis A relative to the axis of the slide  32  such that the latter is for example offset in the direction of the front face  13  by a value close to the radius of the smooth part  3222  of the rod  322 . The flange  2  reaches the release position by pivoting about the pivot axis A. The movement of the flange  2  also comprises a sliding phase given by the sliding of the piston  321 . The flange  2  comprises a flange clevis  21  comprising two wings  210  which enclose the foot  3223 . The pivot axis A is made by a trunnion  22  passing through the wings  120  of the flange clevis  21  and the foot  3223 . 
         [0032]    The device comprises guide members which comprise a fixed guide member  15  relative to the body  1  and a mobile guide member  16  connected to the flange  2  cooperating together to cause pivoting of the flange  2  about the pivot axis A to completion of travel towards the release position. The guide members  15 ,  16  also impose translation movement to completion of travel towards the gripping position. 
         [0033]    The fixed guide member  15  is formed by two grooves  150  made respectively in the wings  120  of the clevis  12  passing through. The groove  150  extends according to a trajectory whereof a first portion  1501  is parallel to the direction of translation of the flange  2  and a second portion  1502  is oriented obliquely relative to the first portion  1501 , practically at 90°. The second portion  1502  is oriented towards the rear, opposite the front face  13 . The two portions are connected by a curved portion. The groove  150  is extended downwards to create a passage  1503  opposite the pivot axis A when the flange  2  is in gripping position. This passage enables introduction of the trunnion  22  during assembly of the device. 
         [0034]    The mobile guide member is a finger  16  in the form of a nipple. In practice, the nipple  16  is screwed onto the flange  2  and comprises a cylindrical head of diameter adjusted to the width of the groove  150 . The nipple  16  is placed above the pivot axis A. 
         [0035]    The clamping device comprises also upper support elements  4  and lower support elements  5 . The upper support elements  4  comprise an upper fixed support element  41 , fixed relative to the body I, and a mobile upper support element  42  connected to the flange  2 . The upper fixed support element  41  is formed by two support surfaces substantially vertical in front of the wings  120  of the clevis  12 . The mobile upper support element  42  comprises two stubs projecting from the faces of the flange  2  and offering two vertical support surfaces when the flange  2  is in gripping position. In this way, the upper fixed and mobile support elements  41 ,  42  cooperate to completion of travel of the flange  2  towards the gripping position to mutually offer sliding contact parallel to the translation movement of the flange  2  and oppose pivoting of the flange  2  towards the release position. 
         [0036]    The lower support elements  5  comprise a lower fixed support element  51 , fixed relative to the body  1 , and a lower mobile support element  52  connected to the rod  322 . The lower fixed support element  51  has the form of a groove placed along the foot  3223  of the rod  322  between the wings  120  of the flange clevis  21 . The lower mobile support element  52  comprises a support surface borne by the foot  3223  opposite the groove  51 . The fixed and mobile lower support elements  51 ,  52  cooperate to completion of travel of the flange  2  towards the gripping position to mutually offer sliding contact parallel to the translation movement of the flange  2 . In cooperation with the upper support elements  4 , the flange  2  is retained very rigidly when it is placed supported against a workpiece to be clamped, with support planes which opposing the torque generated by contact with the flange  2  on the workpiece in front of the device. 
         [0037]    A detection conduit  19  is provided terminating on the upper fixed support element  41 , as shown in  FIG. 5 , and intended to be connected in fluid communication with a device for detecting a fluid leak. For this, the detection conduit  19  comprises a joining section terminating in a detection throat  115 , between the collar  10  and the sealing throat closest to the collar  10 . The mobile upper support element comprises an indentation which is opposite the output of the detection conduit  19  when the flange has completed travel towards the gripping position. It could therefore be considered that the flange has not been stopped by the workpiece to be clamped, and therefore the workpiece is absent in this position. 
       Operation of the Device 
       [0038]    It is supposed that the device is initially in the gripping position, as shown in  FIG. 1 . The piston  321  is towards the bottom such that the first chamber  35  has reduced volume. With the flange  2  placed at the very bottom, the fixed and mobile support elements are in contact with each other. The flange  2  is oriented to project beyond the front face  13 . 
         [0039]    The flange  2  is actuated by sending pressurised fluid to the first chamber  35 . The fluid of the second chamber  36  escapes and lets the piston  321  rise. The flange  2 , driven by the foot  3223 , also rises with a translation movement, guided also by the finger  16  which circulates in the first portion  1501  of the grooves  150 . When the finger  16  arrives at the end of the first portion  1501 , the upper support elements  4  are released from each other. The finger releases in the second portion  1502  of the groove  150 , causing pivoting of the flange  2  about the pivot axis A on the foot  3223  of the cylinder  3  in the direction of arrow F 1 . The upper mobile support element passes over the clevis  12 . The flange  2  then reaches the release position in which it does not project beyond the front face  13 , but in which the arm  20  is placed above the clevis  12  pointing upwards. The space before the device is released to remove a workpiece and put one in place. 
         [0040]    To achieve clamping of the workpiece, the cylinder  3  is controlled in the reverse direction, that is, the pressurised fluid is sent to the second chamber  36  and allows it to escape from the first chamber  35 . The piston  321  commences displacement downwards. The finger  16  is forced to traverse the groove  150  in the second portion  1502 , causing pivoting of the flange  2  in reverse of arrow F 1 , that is, towards lowering of the arm  20  above the workpiece beyond the front face  13 . When the finger reaches the first portion  1501  of the groove  150 , the piston  321  continues its sliding course by driving the flange  2  downwards. The upper support elements engage by being opposite. When the arm  20  comes into contact with the workpiece at the level of the support point and exerts clamping force on it, the flange  2  is supported against the clevis  12  at the level of the upper support elements  4 . It also tends to press the rod  322  of the cylinder  3  against the groove at the level of the lower support elements  5 . The flange  2  is held supported rigidly on the workpiece. 
         [0041]    According to a second embodiment, shown in  FIG. 9 , a clamping device is distinguished from the device according to the first embodiment in that the slide  32 ′ is made in a single workpiece comprising the rod  322 ′ and the piston  321 ′. 
         [0042]    To install such a device, the rod  322 ′ of the slide is introduced into the neck  14 ′ by passing it through the chamber of the cylinder. The trunnion  22  id then put in place to assemble the rod  322 ′ with the flange  2 ′. The cap  33 ′ is screwed onto the body  1 ′ to close the chamber  35 ′ of the cylinder. The operation of the device is the same as for the first embodiment. 
         [0043]    The invention is not limited to the embodiments described above.