Abstract:
A positioning and clamping device or tools and/or workpieces, comprising a base body, a piston arranged such as to be displaceable in the base body, a pin which may be connected to the piston and at least one locking mechanism, for locking the positioning and clamping device relative to a tool or workpiece holder which has a complementary form to the base body. The base body has a cylinder housing for housing the piston with a clamping cone between the piston and the pin with control surfaces formed on the clamping cone and the piston, with further control surfaces on the locking mechanism, cooperating with the control surfaces of the clamping cone and the piston and the locking mechanism is arranged to be radially displaceable in the base body.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a positioning and clamping device for tools and/or workpieces, comprising a basic body, a piston arranged such as to be displaceable in the basic body, a pin arranged such that it can be connected to the piston, and at least one locking means for locking the positioning and clamping device relative to a work or tool holder designed to be complementary to the basic body. 
         [0002]    In the machine tool industry, workpieces are machined with computer-controlled tools in a “machining center”. In order to accurately position the workpiece and hold it in place with respect to the tool, or vice versa, quick-action clamping systems are used. A quick-action clamping system ensures that the position of the tool or of the workpiece can be reproducible and accurately defined in the three-dimensional coordinate system which forms the basis for the control by the computer. If the tool or the machine tool has to be changed frequently in the course of the machining of the workpiece, it must be ensured for the computer control that the workpiece is always located again at the same place in the coordinate system. 
         [0003]    A device of the generic type for the releasable retention of workpieces on machine tools is known from DE 10116229 A1. A cylindrical receptacle for a matching piston is formed in a basic body. The piston is moved in the Z direction against a spring force by a hydraulic or pneumatic medium. A clamping pin, which is connected to a pallet, is mounted in a ball sleeve such as to be movable in the Z direction. In the ball sleeve, a plurality of balls are arranged in a radially movable manner at the circumference of the clamping pin. Due to specially designed clamping surfaces on the clamping pin and on the piston, the clamping pin is centered and clamped in place by the movement of the piston. 
         [0004]    Proceeding from this prior art, the object of the invention is to specify a positioning and clamping device which has an accuracy within the micrometer range, is composed of as few parts as possible and ensures a long service life and has as high a clamping and retaining force as possible. 
       SUMMARY OF THE INVENTION 
       [0005]    The object is achieved by a positioning and clamping device for tools and/or workpieces, comprising a basic body, a piston arranged such as to be displaceable in the basic body, a pin arranged such that it can be connected to the piston, and at least one locking means for locking the positioning and clamping device relative to a work or tool holder designed to be complementary to the basic body, wherein the basic body is formed with a cylindrical receptacle for accommodating the piston, wherein a clamping cone is arranged between the piston and the pin, wherein control surfaces are formed on the clamping cone and on the piston, wherein further control surfaces interacting with the control surfaces of the clamping cone and of the piston are formed on the locking means, and wherein the locking means is arranged so as to be radially displaceable in the basic body. 
         [0006]    It is advantageous that the positioning and clamping device ensures the highest possible reproducibility. This is achieved by Z seatings being formed on the outer circumference of the basic body. This is also achieved by the basic body having a conically designed centering surface on the outer side. This is also achieved by the conically designed centering surface being designed to be concentric to the cylindrical outer surface of the basic body. The basic body, which can be made in one piece, takes over all the functions that are necessary for precise clamping and centering of the workpiece. 
         [0007]    It is also advantageous that the positioning and clamping device can easily be cleaned. This is achieved by horizontal and slot-shaped blow-out openings being formed in the basic body adjacent to the Z seating. This is also achieved by lines for the scavenging air which lead to the cylindrical receptacle being provided in the basic body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    An exemplary embodiment of the invention is described with reference to figures. In the drawing: 
           [0009]      FIG. 1  shows a section through a positioning and clamping device according to the invention, 
           [0010]      FIG. 2  shows a perspective view of the positioning and clamping device of  FIG. 1 , 
           [0011]      FIG. 3  shows a further view of the positioning and clamping device of  FIG. 1 , 
           [0012]      FIGS. 4   a, b  show a perspective view of a locking means for the positioning and clamping device of  FIG. 1 , 
           [0013]      FIG. 5  shows a perspective view of a piston for the locking means of  FIG. 4 , 
           [0014]      FIG. 6  shows a perspective view of a work or tool holder designed to be complementary to the positioning and clamping device, and 
           [0015]      FIG. 7  shows a perspective view of a further work or tool holder of complementary design. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    A positioning and clamping device  1  is shown sectioned along the Z axis in  FIG. 1 . The Z axis in this case refers to the perpendicularly running axis in a coordinate system having three axes X, Y and Z. The positioning and clamping device  1  consists of a basic body  2 , which can be fastened with the underside to a plate (not depicted here) or to a work table. Belonging to the positioning and clamping device  1  is a work or tool holder  30  which is designed to be complementary thereto and is shown in  FIGS. 6 and 7 . The basic body  2  has an essentially rotationally symmetrical shape. A cylindrical receptacle  3  for a piston  4  is formed in the basic body  2 . The piston  4  can be moved in the direction of the Z axis. A hydraulic or pneumatic means is used for a movement of the piston  4  in the positive direction of the Z axis. Springs  5  and/or the pressure of the hydraulic or pneumatic medium serve for the movement in the opposite direction. Feed lines for the hydraulic or pneumatic medium are provided in the plate. For sealing relative to the plate, the basic body  2  has an O ring  6  at a cylindrical surface  61 . The sealing between the piston  4  and the basic body  2  is ensured by special seals  7  having an X-shaped profile. 
         [0017]    From the plate arranged below the basic body  2  or from the work table, the hydraulic or pneumatic medium is fed to the basic body  2  and to the underside of the piston  4 . Running in the basic body  2  are lines which constitute an open connection, inter alia, to the space above the piston  4 . Furthermore, lines leading to the receptacles for the springs  5  and to the cylindrical receptacle  3  are provided for the scavenging air, which is necessary for the cleaning of the positioning and clamping device  1 . The piston  4  can therefore also be moved in the opposite direction by the pressure of the hydraulic or pneumatic medium instead of by the force of the springs  5 . A combination of the spring force with the medium pressure for the positioning and clamping operation can also be applied. 
         [0018]    A pin  8  is screwed in place in the piston  4  on the top side. The pin  8  is designed as a body-fit shoulder screw of precisely defined dimensions. The body-fit shoulder screw  8  comprises a threaded region  9 , a shoulder region  10  and a head region  11 . Between the head region  11  of the body-fit shoulder screw  8  and the piston  4 , an annular thrust washer  12  and a clamping cone  13  are arranged one below the other in the shoulder region  10 . The underside of the clamping cone  13  and the top side of the piston  4  run parallel to one another and are arranged at a uniform distance from one another. The thrust washer  12  serves to distribute the force which is exerted by the clamping cone  13  on the head region  11  of the body-fit shoulder screw  8 . 
         [0019]    Radially running apertures  14  are formed in the basic body  2  approximately at the same level as the clamping cone  13 . Locking means  15  are arranged in a radially displaceable manner in these apertures  14 . The locking means  15 , the clamping cone  13  and the piston  4  have respective control surfaces  16 ,  17 ,  18  which are designed to interact with one another. The control surfaces  16 ,  17 ,  18  are designed, for example, as flanks, grooves or ribs which are all formed at the same angle of, for example, about 45° to the Z axis. The control surfaces  16 ,  17 ,  18  are arranged to run parallel to one another. This ensures that the radially moving locking means  15  are positively guided or positively controlled by the movement of the piston  4  and of the clamping cone  13 . The locking means  15  are moved radially inward by the movement of the piston  4  upward, against the force of the springs  5 . Conversely, the locking means  15  are moved radially outward by the movement of the piston  4  and of the clamping cone  13  downward. The clamping cone  13  has a central bore  32  having an inside diameter which is markedly larger than the outside diameter of the shoulder region  10  of the body-fit shoulder screw  8 . As a result, the clamping cone  13  is mounted in a floating manner about the Z axis in the directions of the X and Y axis. This compensates for differences in the movements of the individual locking means  15  and achieves defined, uniform clamping of the complementary work or tool holder  30 . 
         [0020]    The locking means  15  are designed as slides or bolts having a rectangular or round cross section. The locking means  15  have a foot  19  at the end lying inside the basic body  2 . The foot  19  ensures that the locking means  15  are captively arranged in the basic body  2 . At the end lying outside the basic body, the locking means  15  have a profile  20  which is designed precisely for the work or tool holder  30  formed in a complementary manner to the basic body  2 . 
         [0021]    At the top, i.e. in the region having the largest cone diameter, the clamping cone  13  has a first conical surface  31 , which is designed to run at an angle of less than 10° to the Z axis. The steep angle of the conical surface  31  ensures that self-locking can act between the locking means  15  and the clamping cone  13 , said self-locking maintaining reliable and firm retention even if the medium pressure ceases or if the spring force is absent. 
         [0022]    A further central bore  21  is formed at the top in the basic body  2  concentrically to the receptacle  3 . A cap  22  is captively arranged in the bore  21 . To this end, the cap is formed with a hat brim  24 , as can be seen in  FIG. 1 . Instead of the hat brim  24 , the cap  22  can be provided in the marginal region with a groove in which a snap or expanding ring is inserted, which, after insertion through the bore  21 , expands and prevents said cap  22  from being removed again through the central bore  21 . The cap  22  covers the head region  11  of the body-fit shoulder screw  8  and can be moved up and down in the direction of the Z axis. Arranged between the head  11  and the cap  22  is a spring  23  which ensures that the cap  22  is pressed outward from the basic body  2  in the unloaded state, i.e. without coupling to the complementary work or tool holder. Due to the fact that the cap  22  is arranged so as to project upward above the basic body  2 , the complementary work or tool holder  30  can be brought up to the positioning and clamping device  1  and lifted off again as gently as possible. In the loaded state, the piston  4  presses the cap  22  upward until the top edge of the cap  22  is flush with the top edge of the basic body  2 . The hat brim  24  or the clamping ring of the cap  22  is caught by a stop  25  of the basic body  2 . 
         [0023]    The positioning and clamping device  1  is shown in perspective in  FIG. 2 . It can be seen here how four locking means  15  having the profile  20  are arranged at the outer circumference of the basic body  2 . Furthermore, four Z seatings  26  are formed at the bottom on the basic body  2 . A blow-out opening  27  is formed directly above each Z seating  26 . The blow-out opening  27  is inclined slightly downward, i.e. it is arranged so as to be directed toward the Z seatings  26 , and is of slot-shaped design. During the positioning of the complementary work or tool holder  30 , the Z seating  26  is blown clean with compressed air through the blow-out slot  27 . Furthermore, a conically running centering surface  28  is formed on the basic body  2 . The centering surface  28  runs exactly concentrically to the cylindrical outer surface  61  of the basic body  2 . The concentric arrangement of the outer surface  61  and of the centering surface  28  ensures that the positioning and clamping device  1  can be fastened and positioned in a precisely defined place on the plate or on the work table. 
         [0024]    The positioning and clamping device  1  is shown in a side view in  FIG. 3 . The basic body  2  is designed to be rotationally symmetrical and so as to precisely match the complementary work or tool holder  30 , which is shown in  FIGS. 6 and 7 . A presence control  36  is also indicated in  FIG. 3 . Formed in the Z seatings  26  is a small bore  36 , through which the hydraulic or pneumatic medium flows, as long as no work or tool holder  30  is located on the Z seating  26 . If the bore  36  is covered with the work holder  30 , it can be established by means of a flow or pressure monitor that medium no longer flows and that the workpiece has been correctly positioned. 
         [0025]    The locking means  15  is shown on its own in a perspective view in  FIGS. 4   a  and  4   b . The piston  4  is shown on its own in a perspective view in  FIG. 5 . The piston  4  has apertures  29 , into which the locking means  15  can be moved inward or outward in the radial direction. The control surfaces  16 ,  18  can be seen on the locking means  15  and on the piston  4 . Further matching control surfaces  17  are formed on the clamping cone  4 . The control surfaces  16 ,  17 ,  18  ensure that the locking means  15  can be positively guided in both directions in the piston  4  and in the basic body  2 . 
         [0026]    No seals are arranged between the locking means  15  and the basic body  2  and between the cap  22  and the basic body  2 , such that the scavenging air can escape here and the outside of the positioning and clamping device can be cleaned with compressed air right up to the moment when the basic body  2  touches the complementary work or tool holder  30 . 
         [0027]    Two variants of the complementary work or tool holder  30  are shown in perspective in  FIGS. 6 and 7 . More than one positioning and clamping device  1  is required for the positioning of large workpieces. Of said positioning and clamping devices, one is normally a device suitable for the “zero point centering” and one is a device suitable for fixing the workpiece in the X or Y direction. Other devices are not designed for positioning but rather for clamping and retention. The work holder  30  from  FIG. 6  has a centering surface  33  which is designed to be continuously conical all round. The diameter of the conical centering surface  33  is adapted exactly to the diameter of the centering surface  28  of the positioning and clamping device  1 . This ensures that positioning free of play, with minimum deformation of the devices to be coupled, becomes possible. The diameters of the conical centering surfaces  28   33  are designed in such a way that only deformation within the elastic range of the material will occur. 
         [0028]    At the margin directed downward, the work or tool holder  30  has a protective rim  34  located in front of the centering surface  33 . The protective rim  34  protects the centering surface  33  from contamination and damage. The work or tool holder  30  from  FIG. 7  has two centering surfaces  35  arranged opposite one another. The work or tool holder  30  from  FIG. 7  is therefore designed only for centering in the direction of the X or Y axis. 
         [0029]    With the positioning and clamping device  1  according to the invention, a clamping system is offered which can also be used under high loading. Because the centering surfaces  28  of the basic body  2  are relatively large, and because the locking means  15  work without balls, the clamping force is distributed over areas instead over points. Precise positioning is achieved, which can still be reproduced even after a prolonged service life. The retaining force of the locking means  15  can be set substantially higher than in a device having balls without the risk of damage.