Patent Publication Number: US-2004041323-A1

Title: Clamping device for work pieces, with scraping member

Description:
BACKGROUND OF THE INVENTION  
       [0001] This invention relates to a clamping device, for clamping work pieces, in particular for locking, centring and/or positioning sheet metal parts in the motor vehicle construction, or for other similar uses.  
       STATE OF THE ART  
       [0002] Clamping devices are generally usued for positioning and/or centring work pieces, clamping them along edges or through appropriate holes for locking the work pieces against a shoulder surface of the clamping device, or an external supporting structure.  
       [0003] A clamping device of the aforementioned type, for example is described in DE 39 36 396; the device comprises a box-shaped body having a longitudinal axis, and a clamping member supported by the aforesaid box-shaped body to perform a rocking and a longitudinal movement between a forward non-operative position and a backward operative position for restraining a work piece.  
       [0004] The clamping device is also provided with control means operatively connected to the clamping member by a thrust member sliding parallel to the longitudinal axis of the box-shaped body, an intermediate toggle-lever mechanism and an articulated lever system.  
       [0005] The articulated lever system, in the form of an articulated quadrilateral system which in turn comprises a first and a second connecting links supported by the box-shaped body to rotate according to respective pivotal axes, said links being connected to the clamping member by means of respective articulation axes.  
       [0006] The clamping member protrudes from an aperture at the front end of the box-shaped body; since the clamping member performs a rocking movement, said aperture has to be large enough compared to the dimension of the clamping member, to allow the rocking movement, thereby causing dirt and dust to penetrate inside the clamping device.  
       [0007] A solution of this kind involves the need to frequently carry out maintenance and cleaning operations to remove the dirt accumulated into the clamping device, in order to prevent operative problems, thereby prolonging the working life of the device.  
       [0008] A partial solution to this problem is proposed in DE 201 00 701, which describes a clamping device comprising a box-shaped body and a clamping member moved by means of a different and more complex control system comprising a thrust member to which the clamping member is pivotally connected; the clamping member is provided with a cam shaped aperture, into which a guide pin penetrates, in such a way as to achieve the aforesaid rocking and sliding movement of the clamping member.  
       [0009] The clamping device also comprises two flexible thin plates inside the box-shaped body, urging against a respective longitudinal edge of the clamping member to prevent entering of the dirt.  
       [0010] The use of simple flexible plates still does not entirely prevent the dirt to penetrate from the front end of the box-shaped body, causing accumulation which in time could give rise to operative problems in the device.  
       OBJECTS OF THE INVENTION  
       [0011] The object of this invention is to provide a clamping device for work pieces, of the aforementioned kind, comprising at least one clamping member, which is structurally simple and whereby it is possible to prevent the passage of dirt inside the device, thereby increasing its reliability and reducing maintenance costs.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0012] More specifically, according to the invention a clamping and positioning device for work pieces, has been provided of the type comprising:  
       [0013] a box-shaped body having a longitudinal axis;  
       [0014] at least one clamping member which partially protrudes from an aperture at the front end of the box-shaped body, said clamping member having fore and rear edges extending in the longitudinal direction of the box-shaped body, said clamping member being supported to perform a rocking and a sliding movement between a forward non-operative position and a backward operative position in which restrains a work piece;  
       [0015] control means operatively connected to the clamping member; and  
       [0016] means for preventing passage of dirt through the front end aperture of the box-shaped body, said means comprising:  
       [0017] a closing plate secured to the front end of the box-shaped body, said closing plate being provided with an elongated aperture for protrusion of the clamping member, said elongated aperture having fore and rear cross edges; the fore edge of the clamping member having in turn a shaped profile designed to slide in contact with one of said cross edges of the elongated aperture in the closing plate, during the movement of the clamping member;  
       [0018] a tiltably supported closing member on the rear side of the elongated aperture, said closing member being provided with a scraping head which extends from the rear edge of the clamping member, towards and beyond the other one of said cross edges of the elongated aperture; and  
       [0019] biasing spring means acting on said closing member to urge and constantly maintain the scraping head in contact with the rear edge of the clamping member to prevent passage of dirt. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020] These and further features according to this invention, will be more clearly evident from the following description with reference to the accompanying drawings, in which:  
     [0021]FIG. 1 shows a longitudinal cross-sectional view of a clamping device according to the invention, having a clamping member in an advanced position disengaged from a work piece, and a centring element;  
     [0022]FIG. 2 shows the clamping device of FIG. 1, with the clamping member in a retracted position in which it restrains a piece, without the centring element;  
     [0023]FIG. 3 shows a top view of the device of FIG. 2;  
     [0024]FIG. 4 shows a second embodiment of the clamping device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0025] The general features of this invention will be illustrated hereunder by means of several embodiments.  
     [0026] According to a first embodiment of the invention, shown in figures from  1  to  3 , the clamping device for work pieces, comprises a box-shaped body  10  having a longitudinal axis, and at least one clamping member  11 , in this case one.  
     [0027] The clamping member  11  partially protrudes from a front end of the box-shaped body  10 , and is supported to perform a rocking and a sliding movement in respect to the aforesaid longitudinal axis, between a forward or disengaged position and a backward or retracted position in which it restrains a work piece against a closing plate  12 , secured to the front end of the body  10  of the clamping device.  
     [0028] The clamping device can be provided with a centring element  13 , which can be secured to the front end of the box-shaped body  10  for example by means of a counter plate  14 ; in such case, the work piece is restrained in the backward position of the clamping member  11  against the aforesaid counter plate  14 .  
     [0029] The centring element  13  is provided with a cavity for housing the clamping member  11  in its forward position, and a lateral slit from which the hook shaped end of the clamping member  11  protrudes to restrain a work piece. This is necessary, for example, whenever, in addition to the clamping function, the device must carry out a centring function for centring the work piece.  
     [0030] The device also comprises control means operatively connected to the clamping member  11 , which in turn comprise a thrust member  15 , sliding parallel to the longitudinal axis of the box-shaped body  10 , operatively connected to an appropriate control member, such as for example a pneumatic or electric linear actuator  16  having a rod  17  movable with the thrust member  15 , or to a manual control lever, not shown.  
     [0031] The thrust member  15  extends with a fork  15 ′ to which is connected, by means of a pivot  18 , an intermediate toggle rod  19 , preferably of controlled elastical yielding type.  
     [0032] Disposed coaxially to the pivot  18  of the intermediate toggle rod  19 , are guide rolls  20  movable along longitudinal guides  21  inside the box-shaped body  10 .  
     [0033] The intermediate toggle rod  19  is in turn connected in  22  to an extension  23 ′ of an L-shaped or first connecting link  23  of an articulated lever system, preferably in the form of an articulated quadrilateral system, supporting the clamping member  11  of the device.  
     [0034] In particular, the articulated quadrilateral system comprises the aforesaid first connecting link  23  supported by the box-shaped body  10  to rotate according to a first pivotal axis  24 , the link  23  being in turn connected to the clamping member  11  by means of a first hinge axis  25 .  
     [0035] The articulated quadrilateral system also comprises a second connecting link  26  supported by the box-shaped body  10  to rotate according to a second pivotal axis  27 , the link  26  being connected to the clamping member  11  by means of a second hinge axis  28 .  
     [0036] During movement, the intermediate toggle rod  19  reaches its dead centre when its pivotal and hinge points  18 , 22  are aligned with the contact points between the rolls  20  and the guides  21  inside the box-shaped body  10 ; when the clamping member  11  is disposed in a backward or retracted position for restraining a work piece, the pivot pin  18  of the intermediate toggle rod  19  comes to rest slightly beyond its dead centre, in a condition of irreversibility, thereby preventing the accidental disengagement of the work piece caused by any external force.  
     [0037] The clamping device also comprises sealing means to prevent the entrance of dirt through the front end of the box-shaped body  10 ; the sealing means comprise the aforesaid closing plate  12 , which is provided with an elongated aperture  12 ′ for protrusion of the clamping member  11 , said aperture  12 ′ having a first and a second cross edges  29 , 30  at the fore and rear sides.  
     [0038] The clamping member  11  has in turn a fore edge  11 ′ and a rear edge  11 ″ which extend in the direction of the longitudinal axis of the box-shaped body  10 .  
     [0039] The fore longitudinal edge  11 ′ of the clamping member  11  has a shaped profile designed to slide in contact with a first cross edge at the fore side of the elongated aperture  12 ′ in the closing plate  12 , during the rocking and sliding movement of the clamping member  11 ; the profile of the fore edge  11 ′ in particular will be defined in relation to the movement of the clamping member  11 , in turn determined in relation to the position of the pivotal and hinge points  24 , 25 , 27 , 28  of the aforesaid articulated quadrilateral system.  
     [0040] The sealing means also comprise a closing member  31 , for the aperture  12 ′, tiltably supported in this case in the box-shaped body  10 ; the closing member  31  is provided with a scraping head  32  which extends from the rear longitudinal edge  11 ″ of the clamping member  11  towards and beyond the second cross edge  30  of the elongated aperture  12 ′ for protrusion of the clamping member  11 .  
     [0041] The scraping head  32  of the closing member  31  is urged and constantly maintained in contact with the rear edge  11 ″ of the clamping member  11  by a biasing spring means  33  acting on the closing member  31 .  
     [0042] The closing member  31  preferably comprises an L-shaped lever having a first arm  31 ′ pivoted in  34  to the box-shaped body  10 , and a second arm  31 ″ which extends in the direction of the longitudinal axis of the box-shaped body  10 , ending at its upper end with the scraping head  32 .  
     [0043] The spring means  33  comprise a spring member  35  disposed between the first arm  31 ′ of the closing member  31  and a seat  36  for housing the spring member  35  in the box-shaped body  10 .  
     [0044] The elongated aperture  12 ′ of the closing plate  12  preferably is provided with fore and rear sharped edges  29 , 30  to limit the frictional forces due to the sliding movement of the clamping member  11 .  
     [0045] The scraping head  32  of the closing member  31  is preferable T-shaped and has an upper rounded surface sliding along a corresponding arched lower surface of the closing plate  12 , so as to ensure a more efficient seal against dirt.  
     [0046] Moreover, in correspondence with the point  34  in which it is pivoted to the box-shaped body  10 , the arm  31 ′ of the closing member  31  defines a stop for the clamping member  11  in its backward or retracted position.  
     [0047] The pivotal point  34  of the closing member  31  is preferably positioned rearwardly to the aforesaid articulated quadrilateral system, with respect to the direction of the longitudinal axis of the box-shaped body  10 .  
     [0048] The clamping device according to the invention consequently enables a reduction in maintenance costs and offers greater reliability, due to the fact that the scraping head  32  of the closing member  31  prevents the passage of dirt inside the box-shaped body  10 .  
     [0049] A second embodiment of the clamping device according to the invention is shown in FIG. 4, in which the same reference numbers have been used to indicate similar or equivalent parts.  
     [0050] This embodiment of the clamping device differs from the previous one in that the closing member  31  is pivoted coaxially to one of the connecting links  23 , 26  of the articulated quadrilateral system, in this case to the first connecting link  23 ; moreover, the scraping head  32  of the closing member  31  is maintained in contact with the rear edge  11 ″ of the clamping member  11  by a tensioning spring  37  connected between the scraping head  32  and the connecting link  23  of the articulated quadrilateral system, for example by means of two respective hooks  38 , 39 .  
     [0051] The device comprises a stop element  40  to stop the clamping member  11  in its backward position, secured to the box-shaped body  10 .  
     [0052] According to a further embodiment of the invention, the clamping device may comprise a first and a second opposite clamping members, each having a longitudinal fore edge designed to slide in contact with a respective cross edge of the elongated aperture  12 ′ of the closing plate, and a rear longitudinal edge.  
     [0053] The device also comprises a closing member coplanary arranged to each clamping member, each closing member having a scraping head constantly maintained in contact, by means of relevant spring, with the rear longitudinal edge of the respective clamping member.  
     [0054] In this way it is possible to prevent the infiltration of dirt into the box-shaped body also whenever there are several clamping members.  
     [0055] What has been described and shown with reference to the accompanying drawings, has been given purely by way of example in order to illustrate the general principle of the invention, and some preferential embodiments; consequently, other modifications and variations to the clamping device are possible, without thereby departing from the scope of the claims.