Abstract:
A connection connecting two tool parts includes a first tool part and a receptacle for receiving a second tool part. A clamping device clamps the tool parts together in a joined state. The connecting point further includes a retaining device that is independent of the clamping device and holds the tool parts together in the joined state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 National Stage of International application No. PCT/EP2006/005010, filed May 25, 2006. This application claims the benefit of DE 20 2005 008 389.5, filed May 25, 2005, DE 20 2005 008 461.1, filed May 27, 2005, DE 20 2005 013 572.0, filed Aug. 27, 2005, and DE 10 2005 049 615.6, filed Oct. 15, 2005. The disclosures of the above applications are incorporated herein by reference. 
     FIELD 
     The invention relates to a connection for connecting two tool parts. 
     BACKGROUND 
     Connecting points of this type are known, and are used to join two tool parts to one another. The connecting point may be provided directly on one machine tool, so that a tool part is formed by the receiving spindle of the machine tool. However, this tool part may also be formed by a spacer element, adapter, or portion of a tool. The other tool part may be a tool holder, spacer element, adapter, or the like. Overall, in the present case the term “tool part” refers to elements of various designs which are joined to one another in the region of a connecting point. It is known that the tool parts of a connecting point are clamped together. This is achieved by means of a clamping device which may be actuated by manual or mechanical means, or also automatically. It has been shown that when two tool parts are joined in the region of a connecting point, immediately after the tool parts are joined there is a risk that the two tool parts may come apart before the clamping device is actuated. This may result in damage to the tool and/or the machine tool, as well as injury to the operator. In particular when the two tool parts associated with a connecting point are clamped together manually, the problem frequently arises that the operator must insert one tool part with both hands into the other tool part of the connecting point, and then has difficulty actuating a manual clamping device while securing or holding himself stationary. 
     SUMMARY 
     The object of the invention, therefore, is to provide a connecting point comprising two tool parts which avoids injury to the operator and also prevents damage to one or both tool parts of a connecting point. 
     The connecting point is characterized in that a retaining device is provided which, after the joining, holds the tool parts together in the region of a connecting point, independently of the actuation of a clamping device associated with the connecting point. After being joined, the two tool parts are thus held against one another by the retaining device, even if the clamping device has not yet been actuated. In this manner an operator can manually join two tool parts, and then, without the tool parts being able to come apart, can also actuate a manual clamping device in order to securely clamp the tool parts together in the region of the connecting point. 
     One particularly preferred exemplary embodiment of the connecting point is characterized in that the retaining device is automatically actuated when the two tool parts are joined in the region of a connecting point. Thus, there is no need for additional handling steps to actuate the retaining device. When the two tool parts are joined, in a manner of speaking they are automatically held together by the retaining device, so that the operator has both hands free in order to secure himself and also actuate the clamping device. 
     Further embodiments result from the subclaims. 
    
    
     
       DRAWINGS 
       The invention is explained in greater detail below with reference to the drawings, which show the following: 
         FIG. 1  shows a first exemplary embodiment of a connecting point in the longitudinal section; 
         FIG. 2  shows portions of a retaining device for the connecting point according to  FIG. 1 , in an exploded illustration; 
         FIG. 3  shows a second exemplary embodiment of a connecting point in the longitudinal section; 
         FIG. 4  shows an enlarged section of a retaining device for the connecting point according to  FIG. 3 ; and 
         FIG. 5  shows portions of the retaining device according to  FIGS. 3 and 4 , in an exploded illustration. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a first exemplary embodiment of a connecting point  1  in the longitudinal section. The connecting point comprises a first tool part  3 , illustrated here in truncated form, which forms a receptacle in which a second tool part  5  is inserted in places. To this end, the first tool part has a recess  7  in which a section of the second tool part  5 , also referred to as a shaft  9 , is inserted. 
     The recess  7  may have a cylindrical, polygonal, or also a conical shape, as illustrated in  FIG. 1 . The recess expands in the direction of the second tool part  5 , the shaft  9  of which has a corresponding conical shape. When the two tool parts  3  and  5  of the connecting point  1  are inserted one inside the other, they are concentric to the center axis  11  of the connecting point  1 , which thus also forms the center axis of the first tool part  3  and the second tool part  5 . 
     In the exemplary embodiment illustrated here, the shaft  9  of the second tool part  5  has a hollow design, the cavity  13  of the shaft  9  having a circumferential groove  15  with a clamping shoulder  17 . Clamping elements (not illustrated here) engage in the groove, and in the clamped state rest against the clamping shoulder and brace the first tool part  3  against the second tool part  5 . The clamping elements may be externally actuated through openings extending perpendicular to the center axis  11 , or through a central opening  19  in the first tool part  3 . 
     In the exemplary embodiment illustrated here it is seen that the two tool parts  3  and  5  contact one another in the region of the connecting point  1 , and preferably have annular surfaces  21  and  23  which are situated concentrically with respect to the center axis  11  and which lie in a plane perpendicular to the center axis  11 . The annular surface  21  is associated with the first tool part, and the annular surface  23  is associated with the second tool part  5 . 
     This design of the connecting point  1  is basically known, and therefore is not discussed in greater detail here. 
     The connecting point  1  illustrated here is characterized by a retaining device  25  which holds the two tool parts  3  and  5  of the connecting point  1  together in the joined state, even when the clamping device (not illustrated here) has not yet been actuated. 
     For this purpose the retaining device has at least one locking element  27  which is displaceably supported in one of the tool parts, in this case the first tool part  3 , and in a functional position, namely, the locked position illustrated here, engages in the other tool part, in this case the second tool part  5 , when the tool parts  3  and  5  are joined together. In this manner, as described above, the two tool parts  3  and  5  are held together after being joined. 
     In the exemplary embodiment illustrated here, in the locked position the locking element  27  projects slightly into the recess  7  and engages in a recess  29  provided in the other tool part, in this case the second tool part  5 . Viewed in the direction of the center axis  11 , this recess is situated such that the locking element  27  with its right (as shown in  FIG. 1 ) outer surface rests against the right inner surface of the recess  29 , so that the second tool part  5  cannot fall out of the first tool part  3  after the two tool parts  3  and  5  have been joined in the region of the connecting point  1 . 
     In the exemplary embodiment illustrated here, the second tool part  5  is designed in such a way that the recess  29  is formed by a hole, preferably a borehole, extending essentially perpendicular to the center axis  11 . However, individual depressions in the outer surface of the second tool part, and thus support surfaces for the locking element  27 , may also be provided on the second tool part  5 , or a circumferential groove may be provided in the exterior of the shaft  9  in which the locking element  27  is able to engage in the joined state of the tool parts  3  and  5 . In the latter case, the rotational position of the two tool parts  3  and  5  is irrelevant when they are joined, because the locking element  27  is always able to engage in the annular groove. As illustrated here, when a recess  29  designed as a borehole is provided in the second tool part  5 , a specified rotational alignment of the two tool parts  3  and  5  with respect to one another is required in the region of the connecting point  1  to ensure that the locking element  27  is able to engage in the recess  29 . 
     In the exemplary embodiment illustrated in  FIG. 1 , the locking element  27  is guided in a borehole extending essentially perpendicular to the center axis  11 . This borehole may also extend at an angle relative to the center axis  11 . It is crucial that the locking element  27  in its locked position engages in a recess  29 , thus holding the second tool part  5  in a predetermined position as viewed in the direction of the center axis  11 . 
     In the exemplary embodiment illustrated here, the retaining device  25  is situated in the front region of the first tool part  3 , i.e., close to the annular surface  21 . The locking element  27  thus engages in the recess  7  and is able to grip the second tool part  5  in the region of the shaft  9  thereof. The locking element  27  is thus situated inside the connecting point  1  and is therefore protected from contaminants. 
     The locking element  27  cooperates with an actuating element  31  of the retaining device  25 . The actuating element is displaceably supported in the tool part in which the locking element  27  is provided, i.e., in the first tool part  3  in this case. In the exemplary embodiment illustrated here, the center axis  33  and thus also the displacement path of the actuating element  31  extend essentially parallel to the center axis  11  of the connecting point  1 , and thus parallel to the center axis of the first tool part  3 . 
     The actuating element  31  is coupled to the locking element  27  in such a way that when the actuating element is displaced in the direction of its center axis  33  tensile or pressure forces are exerted on the locking element  27 , so that the locking element is moved in the direction of the center axis  11  by pressure forces and is moved in the opposite direction by tensile forces. 
     The conversion of the motion of the actuating element  31  to a displacement of the locking element  27  is achieved by means of a coupling device  35 . In the exemplary embodiment illustrated here, the actuating element  31  has a slot  37  extending at an acute angle relative to the center axis  33  of the actuating element  31 , and thus has two support surfaces, namely, an upper support surface  39  and a lower support surface  41 . These support surfaces likewise extend at an acute angle relative to the center axis  33  of the actuating element  31 , and thus also at an acute angle relative to the direction of motion thereof. The two support surfaces  39  and  41  are preferably situated essentially parallel to one another, as illustrated here. 
     A pin  43  extending perpendicular to the image plane of  FIG. 1  engages in the slot  37 ; the diameter of the pin is adapted to the width of the slot  37  so that the pin is able to make contact at the upper support surface  39  and the lower support surface  41 . The diameter of the pin  43  is preferably selected so that the pin is guided in the slot  37  essentially without play. The pin  43  is fixedly connected to the locking element  27 . 
     The actuating element  31  is acted on by a pretensioning force which pushes the actuating element into its first functional position, namely, to the left. The pretensioning force is provided by a spring element  45 , which in this case is designed as a helical spring. This spring encloses a pin-shaped tapered region  46  of the actuating element  31  and on one side is supported on same, and on the other side is supported at the base of a borehole  47  which accommodates the actuating element  31  and the spring element  45 . 
     The path of motion of the actuating element  31  is limited by a stop so that the actuating element cannot slide to the left out of the borehole  47 . In the present case this stop is formed by a screw  49  which engages in a groove, extending in the direction of the center axis  33 , in the outer surface of the pin-shaped tapered region  46 . 
     The pretensioning force exerted on the actuating element  31  is transmitted via the coupling device  35  to the locking element  27 . The actuating element  31  is moved to the left by the spring element  45  until the stop is reached. The lower support surface  41  on which the pin  43  rests pushes the pin upward, thereby displacing the locking element  27  into its locked position in which it is closest to the center axis  11 . 
     The spring element  45  via the coupling device  35  exerts a pressure force on the locking element  27  which pushes same into the recess  29  in the second tool part  5 . 
     On its end facing the center axis  11  the locking element has a stop bevel  51 , which in  FIG. 1  ascends from left to right in the direction of the center axis  11 . When the second tool part  5  is inserted into the first tool part  3 , the shaft  9  is able to push the locking element  27  against the pretensioning force of the spring element  45 . When the second tool part  5  is inserted far enough into the first tool part  3 , the elastic force causes the locking element  27  to snap into the recess  29 . 
     When the second tool part  5  is inserted, a force is exerted on the locking element  27  from above so that the locking element is pushed downward away from the center axis  11 , and the pin  43  presses against the lower support surface  41  of the slot  37  so that the actuating element  31  is displaced against the pretensioning force of the spring element  45  (to the right in  FIG. 1 ). 
     In order to separate the two tool parts  3  and  5  of the connecting point  1 , a pressure force acting from left to right is exerted on the externally accessible actuating element  31 , causing the actuating element to be displaced to the right against the pretensioning force of the spring element  45 . In this case, the upper support surface  39  acts on the pin  43  which extends in the slot  37 , perpendicular to the image plane. Since the slot  37  ascends from left to right, this causes the upper support surface  39  to push the pin  43  downward in this displacement direction of the actuating element  31 , so that the locking element  27  is likewise pulled downward and exits the recess  29  in the second tool part  5 . The tool parts  3  and  5  of the connecting point  1  are unlocked in this manner. 
     When the actuating element  31  is displaced to the left or right in the direction of the center axis  33 , the support surfaces  39  and  41  of the slot  37  act on the pin  43  in such a way that the locking element  29  coupled thereto is acted on by tensile or pressure forces. 
     As a result of the coupling device  35  it is sufficient when, as illustrated here, a pretensioning force is exerted on the actuating element  31  which presses same into a specified functional position. The pretensioning force is transmitted to the locking element  27 . However, a pretensioning force may also be exerted directly on the locking element  27 , the force then also acting on the actuating element  31  via the coupling device  35 . However, the implementation illustrated here allows a relatively small, compact design of the connecting point  1 . Viewed in the axial direction, i.e., in the direction of the center axis  11 , there is sufficient space in the first tool part  3  to accommodate the actuating element  31  and the spring element  45  in the borehole  47 . In the direction perpendicular to the center axis  11  only a relatively small space is necessary for accommodating the locking element  27 . 
     With reference to the explanations of  FIG. 1 , it has been assumed that the retaining device  35  is provided close to the annular surface  21  of the first tool part  3 . If the shaft  9  of the second tool part  5  should have a design that is longer than that illustrated in  FIG. 1 , or, as is common in known tools, is provided with an extension, the retaining device could also be provided at a distance from the annular surface  21 , and act on the rear end of the shaft  9  or on an extension connected thereto. 
     It is further noted that more than one of the retaining devices  35  described here may be provided over the periphery of the connecting point  1 , in particular for very large and heavy tools. 
       FIG. 2  shows portions of the retaining device  25  in an exploded illustration. Identical parts are provided with the same reference numerals, so that in this regard reference is made to the preceding description. 
     The top right portion of  FIG. 2  illustrates the locking element  27  in the same position as shown in  FIG. 1 . The stop bevel  51  is clearly shown. 
     A slot  53  is provided in the end region of the locking element  27  oppositely situated from the stop bevel  51 , thereby forming two connecting arms  55 ,  55 ′ spaced at a distance from one another, of which the connecting arm  55  is illustrated in the top right portion of  FIG. 2 . The top left portion of  FIG. 2  shows the locking element  27  rotated by 90°, thus showing the slot  53  and the other connecting arm  55 ′. 
     In the respective end region of the connecting arms  55 ,  55 ′ facing away from the stop bevel  51   a  hole  57  or  57 ′ is provided in which the pin  43 , explained with reference to  FIG. 1  but not illustrated here, is inserted. This pin may be fastened in any given manner. 
     The lower right portion of  FIG. 2  illustrates the actuating element  31  in the side view. In this case the actuating element is situated in the same manner as in  FIG. 1 . The actuating element has a pin-shaped region  46  having a groove  59 , extending in the direction of the center axis  33  of the actuating element  31 , in which the screw  49  explained with reference to  FIG. 1  engages. This screw basically does not hinder the motion of the actuating element  31 . The actuating element  31  may be freely moved back and forth in the borehole  47 . However, the path of motion is limited by the fact that the right flank of the groove  59  in  FIG. 2  abuts against the screw  49 , thus preventing the actuating element  31  in  FIG. 1  from being arbitrarily displaced far to the left. 
     The slot  37  in the actuating element  31  is clearly shown in the lower right portion of  FIG. 2 . The slot is provided in a region  61  in which the actuating element  31  has a thinner design. At this location a wall region  63 , for example, may be provided which is perpendicular to the center axis  33  and which is so thin that it is able to engage in the slot  53  in the locking element  27 . In the assembled state, the connecting arms  55  and  55 ′ of the locking element  27  are thus situated on opposite sides of the wall region  63 . 
       FIG. 2  clearly shows that the slot  37  has an upper support surface  39  and a lower support surface  41  which extend essentially in parallel to one another, and at an acute angle relative to the center axis  33  and thus relative to the path of motion of the actuating element  31 . 
     The lower left portion of  FIG. 2  shows a cross section of the actuating element  31  which is guided through the region  61 . Clearly shown here is the wall region  63 , which is able to engage in the slot  53  in the locking element  27  illustrated in the top left portion of the figure. The thickness of the wall region  63  is selected such that relative motion between the locking element  23  and the actuating element  31  may be achieved with the least possible friction. The actuating element  31  moves back and forth, as explained with reference to  FIG. 1 , in the direction of the center axis  33 , whereas on account of the coupling device  35  the locking element  27  undergoes a motion perpendicular to the center axis  33  or to the center axis  11  of the connecting point  1 . From the interaction of the parts of the coupling device  35  it is apparent that the locking element  27  may be positioned not only perpendicular to the center axis  11 , but also at an angle thereto. As a result of the pin  43  in the slot  37 , motion of the actuating element  31  in the direction of the center axis always causes displacement of the locking element  27  relative to the center axis  11 . 
       FIG. 3  shows a second exemplary embodiment of the connecting point  1 , comprising a first tool part  3  and a second tool part  5 . Identical parts are provided with the same reference numerals, so that in this regard reference is made to the description for  FIG. 1  in order to avoid repetition. 
     The two exemplary embodiments according to  FIGS. 1 and 3  differ in that  FIG. 3  illustrates a modified retaining device  25  in a partial sectional view. The retaining device has a symmetrical design. The retaining device  25  to the right of a line of symmetry  65  is in the locked state, and to the left is in the unlocked state. 
     In this exemplary embodiment as well, one or more retaining devices  25  may be provided, depending on the size and/or weight of the tool parts. 
     A more detailed description of the retaining device  25  is provided with reference to  FIG. 4 , which illustrates the retaining device in a greatly enlarged view. The following discussion relates to the illustration on the right side of the line of symmetry  65 , showing the retaining device  25  in the locked state. 
     The retaining device  25  has a locking element  27  with a stop bevel  51 , which in this case projects beyond the inner surface of the recess  7  in the first tool part  3 . The locking element  27  thus engages in a second tool part  5  (not illustrated here) of the connecting point  1 , as has been explained with reference to  FIG. 1 . 
     The locking element  27 , the same as for the first exemplary embodiment, may be displaced back and forth, i.e., up and down in  FIG. 4 , perpendicular to a center axis  11  (not illustrated here) of the connecting point  1 . The locking element may also extend at an angle relative to the center axis  11 . 
     The retaining device  25  has an actuating element  31  which, in a departure from the first exemplary embodiment, may likewise be displaced perpendicularly or at an angle to a center axis  11  (not illustrated here) of the connecting point  1 , i.e., up and down in the illustration according to  FIG. 4 . On the right side of the line of symmetry  65  the actuating element  31  is in a lower, first functional position in which, on account of a pretensioning force exerted by a spring element  45   a , the first locking element  27  is situated in its first maximum upwardly displaced position. In this functional position the actuating element  31  rests against a stop  67 , thus preventing it from falling out or being pushed downward from a borehole  47  in the first tool part  3  in which the actuating element  31  and the locking element  27  are accommodated together with the spring element  45   a.    
     In the present case the stop  67  is implemented by an eye bolt, which with an outer thread engages with an inner thread provided on the inner surface of the borehole  47 . The stop may thus be upwardly displaced relative to the line of symmetry  65  in the direction of the center axis  11  of the connecting point  1 , or in the opposite direction. 
     The actuating element  31  has an essentially cylindrical base body  69  which has a hollow design so that it is able to accommodate the spring element  45   a . The floor of the base body forms a support surface for the spring element  45   a , which in this case as well is designed as a helical spring and which is also supported at the underside of the locking element  27 , i.e., on the end of the locking element  27  oppositely situated from the stop bevel  51 . This causes the locking element  27  to be pushed upward into its locked position to the right of the line of symmetry  65 . 
       FIG. 4  shows a coupling device  35   a  which is used to convert an upward motion of the actuating element  31  in the direction of the line of symmetry  65  into tensile forces which pull the locking element  27  downward against the pretensioning force of the spring element  45   a.    
     Pressure forces acting from above on the locking element  27  are thus exerted solely by the spring element  45   a . In this case the actuating element  31  when moved upward exerts tensile forces on the locking element  27  solely via the coupling device  35 , whereas in the first exemplary embodiment the actuating element  31  is able to produce tensile and pressure forces via the coupling device  35 . 
     The coupling device  35   a  has at least one ball  71 . In the present case a number of balls are provided over the peripheral surface of the borehole  47 . At least three such balls are preferably present, which are held in equal circumferential spacing in order to achieve uniform production of force on the locking element  27 . However, a coupling device  35   a  having a plurality of balls  71  is preferred. 
     On its upper edge the actuating element  31  has an actuating surface  73  which extends upward conically as viewed from the line of symmetry  65 . The at least one ball  71  contacts this actuating surface. 
     The locking element  27  has an indentation  75  which is provided in the lower end region of the locking element  27 , in the peripheral surface thereof, facing away from the stop bevel  51 , the peripheral surface having an actuating surface  77  extending in the opposite direction from the actuating surface  73  and tapering upwardly from the lower end of the locking element  27 , i.e., extending conically in the direction of the line of symmetry  65 . 
     The mode of operation of the coupling device  35   a  is as follows: 
     When the actuating element  31  is moved upward against the force of the spring element  45  in the direction of the line of symmetry  65 , which is illustrated on the left side of the line of symmetry  65 , the actuating surface  73  of the actuating element  31  presses the ball  71  inwardly in the direction of the line of symmetry  65 , which also represents the center axis of the borehole  47 . The actuating element is therefore designed, in a manner of speaking, as a wedge drive between the actuating surface  37  [sic;  73 ] and the at least one ball  71 . 
     The inwardly directed forces from the ball  71  act on the actuating surface  77  of the locking element  27  in such a way that when the at least one ball  71  moves inwardly, tensile forces are exerted on the locking element  27  which move the locking element downward, i.e, away from the centerline  11 , i.e., in the direction of the line of symmetry  65 . 
     On the left side of the line of symmetry  65 ,  FIG. 4  shows that the upward motion of the actuating element  31  and the effect of the coupling device  35   a  result in a downward motion of the locking element  27 . 
     In the exemplary embodiment illustrated here, the actuating element  31  has a cylindrical shoulder  79  which projects through the open interior space of the stop  67  which is designed as an eye bolt, and is therefore externally accessible by an operator. As described here, the operator is thus able to press the actuating element  31  upwardly against the force of the spring element  45   a , which is illustrated on the left side of the line of symmetry  65  in  FIG. 4 . 
     The two connecting arms  55  and  55 ′ of the locking element  27  described with reference to  FIG. 1  grip the wall region  63  of the actuating element  31 . This design prevents rotation of the locking element  27 , thus ensuring that the stop bevel  51  is always oriented in such a way that the locking element  27  can be pushed back against the pretensioning force when a second tool part  5  is inserted into the first tool part  3 . 
     The exemplary embodiment of the retaining device  25  illustrated in  FIGS. 3 and 4  likewise suitably ensures that the locking element  27  is prevented from rotating and that the stop bevel  51  is oriented as intended. Rotation could be prevented, for example, by a polygonal design of the locking element  27 . In that case, however, a polygonal channel would have to be provided in this region of the borehole  47 . In the exemplary embodiment illustrated here, a groove  81  is provided on the interior of the borehole  47  in which a projection  83 , implemented as a pin or screw, for example, engages, and which protrudes from the outer wall of the locking element  27 . 
     A suitable channel and/or seal is preferably provided in the contact region between the locking element  27  and the first tool part  3 , for example a seal  85 , preferably designed as an O-ring, inserted into a groove  85  in the locking element  27 . 
     A corresponding device such as an O-ring or the like is preferably provided in the contact region between the cylindrical shoulder  79  of the actuating element  31  and the inner surface of the stop  67 . 
       FIG. 5  shows portions of the retaining device  25  as represented in  FIG. 4 , in an exploded illustration. The bottom portion of the figure shows the annular stop  67 , which comprises an open interior  86 , an outer thread  87 , and a circumferential groove  89  in the inner wall of the interior  86  for accommodating a seal (not illustrated here). 
     The actuating element  31  is situated above the stop  67 , concentric with the center axis of the retaining device  25  which coincides with the line of symmetry  65 ; the cylindrical shoulder  79  of the actuating element is designed so that it engages in the interior  86  with the least possible friction. 
     Shown above the actuating element  31  is the actuating surface  73  thereof, which opens conically upward and cooperates with the at least one ball  71  (not illustrated here) of the coupling device  35   a  described in  FIG. 4 . 
     Aligned concentrically with the actuating element  31  is the locking element  27 , which is able to engage in places with the interior  91  of the actuating element  31 , which in this case has a capped shape, thereby allowing relative motion in the direction of the line of symmetry  65  between the locking element  27  and the actuating element  31 . 
     The top portion of  FIG. 5  shows that an indentation  75  having an actuating surface  77  is provided in the peripheral surface of the locking element  27 . This actuating surface tapers upward conically in the direction of the line of symmetry  65 . 
     The stop bevel  51  is shown at the top of the locking element  27 . The groove  84  is also clearly shown. 
     From the explanations of  FIGS. 3 through 5  it is apparent that the retaining device  25  acts automatically in this case as well. When two tool parts  3  and  5  are joined one inside the other in the region of a connecting point  1 , the locking element  27  is first pushed back, but on account of a pretensioning force exerted by a spring element  45   a  is then pushed into a functional position referred to as the locked position. In this position the locking element  27  engages in a recess  29  in the second tool part  5  which may be designed as a borehole, annular groove, or, as described above, as any given depression in the outer surface of a portion of the second tool part  5 . 
     The two tool parts  3  and  5  of the connecting point  1  are thus held together by the retaining device  25 , without actuating a clamping device which is activated for ultimately joining the two tool parts  3  and  5 , whether by manual or mechanical means, in particular automatically. 
     An operator is thus able to manually join the two tool parts, and as a result of the automatic action of the retaining device  25  the two joined tool parts no longer have to be held. The operator thus has both hands free in order to actuate the clamping device and secure himself, i.e., hold himself stationary during the procedure. 
     The two exemplary embodiments show that the locking element  27  may be displaced perpendicular to the center axis  11  but also at an angle thereto, and that an actuating element  31  which cooperates with the locking element  27  via a coupling device  35 ,  35   a  may be displaced essentially parallel to the center axis  11  or perpendicular thereto in order to exert a tensile and/or pressure force on the locking element  27 . 
     In both cases the retaining device  25  has a very simple design and is therefore unsusceptible to malfunction, and is also easy to handle. Manual locking is omitted since the retaining device  25  acts automatically. To unlock the retaining device  25  it is necessary only to exert a pressure force on the actuating element  31 . In this case the clamping device is already loosened, so that the operator is able to grip and unlock the tool parts  3  and  5  anyway due to the pressure force which is exerted on the actuating element  31 . 
     From the above discussions it is clear that the retaining device  25  may be provided in conjunction with many different types of connecting points  1 . In particular, it is irrelevant whether the shaft  9  of the second tool part and the corresponding recess  7  in the first tool part  3  have a cylindrical, polygonal, and/or conical shape. 
     Depending on the length of the shaft  9 , the retaining device may also be situated at a greater or smaller distance from the front side of the first tool part  3 , i.e., from the annular surface  21  thereof. The design of the connecting point  1  may thus be varied over a broad range. 
     The retaining device described here may also be provided with one or more locking elements  27  distributed over the peripheral surface of the connecting point  1 , or even multiple retaining devices  25 . 
     In principle it is possible to combine the exemplary embodiments, as described with reference to the figures, with one another. 
     The connecting point  1  described here is very unsusceptible to malfunction because a simple coupling is possible between the locking element  27  and actuating element  31  via the coupling device  35  or  35   a  described here, and tensile and/or pressure forces may be easily exerted on the locking element  27 . 
     The stop  67  described in conjunction with  FIGS. 3 ,  4 , and  5  may also be provided in the exemplary embodiment according to  FIG. 1 . For example, an element, such as an annular adjusting screw, which is displaceable in the longitudinal direction of the center axis  33  of the borehole may be inserted into the borehole  47 , and is screwed a longer or shorter distance into the borehole to form a displaceable abutment for the spring element  45 . 
     In principle, in the exemplary embodiment according to  FIG. 1  a stop may also be provided at the end of the borehole  47  at which the actuating element  31  may be inserted. For example, an eye bolt may also be provided here which prevents the actuating element  31  from falling out of or being pushed through the borehole  47 .