Abstract:
A hand power tool selected from the group consisting of a drill hammer and an impact hammer has an exchangeable tool holder, a guide pipe which receives the tool holder at its free end, a locking device arranged on the guide pipe and operative manually for fixing the tool holder on the guide pipe in a defined locking position assumed by the tool holder on the guide pipe, so that the locking position is arranged before a mounting position in a displacement direction of the tool holder, in which mounting position the tool holder is held unlocked on the guide pipe, the locking device being provided with means activatable by a release of the locking device and providing a displacement of the tool holder to the mounting position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a hand power tool, in particular a hammer drill or an impact hammer.  
           [0002]    In a known hand power tool disclosed for example in the German patent document DE 28 20 128 A1 the tool holder is connected of one piece with a rotary sleeve which is supported rotatably on a guide pipe and can be rotated by means of a rotary drive. The guide pipe is arranged fixedly on the machine housing and receives a drive piston of a so-called impact mechanism which is reciprocatingly axially movable by a wobble drive, and an axially displaceable impact piston or anvil. Between the drive piston and the anvil, an air cushion is provided. When the impact mechanism is turned on, the drive piston strikes through the air cushion on the anvil, and it gives an impact energy directly to the tool which is clamped axially displaceably and non rotatably in the tool holder. If in addition the rotary drive is turned on, the tool holder is rotated and the tool is rotated through it.  
           [0003]    A known exchangeable tool holder for a hand power tool, in particular for a drill hammer and/or impact hammer as disclosed in the German patent document DE 32 05 063 C2 is fixed to be displaceable to a limited degree and to be non rotatable, by a locking device directly on the drive spindle which performs a rotary and a stroke movement. For this purpose the tool holder has an end region which is fittable on the drive spindle and is in a rotary connection with the drive spindle through a spline profile. In this end region at least one radial opening is provided, in which a ball is arranged radially displaceably as a locking body. The ball engages in a circumferential longitudinal groove formed in the drive spindle and locks the tool holder with an axial clearance from pulling out in an axial direction. A displacement sleeve which serves for clamping the tool in the tool holder engages the ball and blocks its radial displacement. When the displacement sleeve is manually displaced by force toward the front end, the at least one ball is released and the tool holder can be pulled from the guide pipe by displaceably held displacement sleeve.  
           [0004]    In a known hand power tool with a rotatable guide pipe supported in the machine housing and an exchangeable tool holder arranged on the guide pipe in its end region extending outwardly beyond the machine housing (hammer drill Type No. 0611 249 700), the end portion of the tool holder which engages the guide pipe has four radial openings which are spaced from one another by a rotary angle of 90°, and a ball representing a locking body is radially displaceably inserted in the corresponding radial opening and secured from falling out of the radial opening. In the locking position of the tool holder the balls are located in troughs which are offset by the same rotary angle in the guiding pipe. A rotatably movably held displacement sleeve engages the balls with a radially inwardly projecting ring web and thereby prevents any radial displacement of the ball. When the displacement sleeve is manually placed rearwardly by a rotary-/displacement movement in direction of the machine housing, the ring web releases the balls and the tool holder can be removed from the guide pipe with the displaceably held displacement sleeve.  
         SUMMARY OF THE INVENTION  
         [0005]    Accordingly, it is an object of the present invention to provide a hand power tool of the above mentioned general type, which is a further improvement of the existing hand power tools.  
           [0006]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a hand power tool selected from the group consisting of a drill hammer and an impact hammer, comprising an exchangeable tool holder; a guide pipe which receives said tool holder at its free end; a locking device arranged on said guide pipe and operative manually for fixing said tool holder on said guide pipe in a defined locking position assumed by said tool holder on said guide pipe, so that the locking position is arranged before a mounting position in a displacement direction of said tool holder, in which mounting position said tool holder is held unlocked on said guide pipe, said locking device being provided with means activatable by a release of said locking device and providing a displacement of said tool holder to said mounting position.  
           [0007]    When the hand power tool is designed in accordance with the present invention as defined in claim  1 , it has the advantage that the exchange, or in other words the mounting and dismounting of the tool holder identified also as an exchange chuck, can be possible with one hand operation. The operator holds the power tool with the guiding hand, and with the other hand can remove the tool holder from the power tool or place it on the power tool. The placement is performed by a simple fitting of the tool holder onto the guiding pipe, wherein at reaching the locking position, the locking device is automatically activated and fixes the tool holder non rotatably and axially displaceably on the guide pipe.  
           [0008]    For removing of the tool holder from the power tool, the locking device must be first released with one hand, whereby the tool holder is displaced automatically to the unlocked mounting position of the guide pipe, in which it is secured on the guide pipe from falling out. The operator can release the displacement sleeve and with the same hand can remove the tool holder by manual gripping or again lock it, depending on the direction in which the tool holder is displaced. A new release of the locking device or a holding of the locking device in its deactivating position is not needed.  
           [0009]    When the operator neither pulls out nor again locks the tool holder located in the mounting position, its failure is prevented, since with placing the tool clamped in the tool holder at the operational location, the tool holder under the action of the pressing force applied to the tool is displaced from the mounting position to the locking position and is automatically locked by the locking device.  
           [0010]    The axial operating direction of the tool holder and the locking device during exchange of the tool holder is ergonomically optimal. The unlocking of the tool holder by a displacement movement in direction of the operator is understandable and facilitates the handling. Moreover, with the removed tool holder, the components of the locking device are easily mountable on the guide pipe, and in the case of a repair or recycling they are easily dismountable.  
           [0011]    In accordance with a preferable embodiment of the present invention, the tool holder in its region engaging the guide pipe is provided with locking bodies which are offset relative to one another in a peripheral direction, are radially limitedly displaceable, and are held axially non displaceably. The same number of pockets which axially non displaceably receive the locking bodies are provided on the guiding pipe in the locking position of the tool holder, and in the mounting position the same number of concavities each receiving a corresponding locking body are provided. The concavities are adapted to the limited radial displacement of the locking bodies so that the latter are introduced into the concavities with a low but sufficient radial pressing force, so that falling out of the tool holder is reliably prevented. Basically it suffices to provide only one locking body and correspondingly only one pocket and a preceding concavity.  
           [0012]    The displacement means for bringing the tool holder from the locking position to the mounting position with release of the locking device include, in accordance with a preferable embodiment, a pre-tensioned spring which is supported on the one hand against the tool holder and on the other hand against the guide pipe.  
           [0013]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a view showing a portion of the hammer drill with a tool holder in a section in accordance with a first embodiment of the present invention, wherein the tool holder in an upper half of the drawing is shown in its mounting position and in a lower half of the drawing is shown in its locking position; and  
         [0015]    [0015]FIG. 2 is a view showing a hammer drill in accordance with a second embodiment of the present invention, with a tool holder in a section in accordance with a first embodiment of the present invention, wherein the tool holder in an upper half of the drawing is shown in its mounting position and in a lower half of the drawing is shown in its locking position.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    [0016]FIG. 1 shows a longitudinal section of a part of a hammer drill as an example for generally a hand power tool. It has a machine housing  10 , and a guide pipe  11  which is arranged in the machine housing rotatably by means of a radial bearing  12 . The guide pipe  11  has a front end region  111  which extends outwardly beyond the machine housing  10  and has a reduced diameter for receiving a tool holder  13 . The tool holder  13  is known and can be formed for example for receiving a so-called SDS plus tool. Such a tool and a tool holder for clamping the tool are described for example in the German patent document DE 25 51 125 C2, so that their details should not be explained in detail.  
         [0017]    An impact piston or an anvil  14  of a not shown impact mechanism is axially displaceably guided in the guide pipe  11 . It is formed so as to be stricken by a reciprocating drive piston and its impact energy is transmitted to the tool which is clamped in the tool holder  13  so that it is limitedly axially displaceable. A rotary drive engages also with the guide pipe  11  and can turn the guide pipe  11  in rotation. An example for a rotary drive and an impact mechanism is provided for example in the German patent document DE 28 20 128 A1.  
         [0018]    The tool holder  13  is arranged exchangeably on the guide pipe  11 . By means of a locking device  14  it is fixed in its locking position on the guide pipe  11  axially substantially non displaceably and non rotatably relative to it. The locking position of the tool holder  13  is shown in the lower half of FIG. 1. The tool holder  13  in the case of wear or exchange of a tool holder, for example for an SDS plus tool, can be replaced with another tool holder, for example for a normal drill.  
         [0019]    In order to provide the exchange of the tool holder  13  ergonomically, and in particular by one hand operation during the exchange process, a mounting position for the tool holder  13  is provided on the guide pipe  11 . In the mounting position the tool holder  13  is arranged unlocked on the guide pipe  11  and is held again falling out. In this mounting position, with release of the locking device  14 , the tool holder  13  is automatically brought to this mounting position by a displacement means which becomes operative. For this purpose the tool holder  13 , in its end portion  131  which engages the end portion  111  of the guide pipe  11  and has an increased diameter, is provided with at least one locking body  15 . In the end region  111  of the guide pipe at least one pocket  16  is provided, in which the locking body  15  in the locking position of the tool holder  13  lowers and thereby a non rotatable and axially displaceable connection between the guide pipe  11  and the tool holder  13  is provided. For the mounting position of the tool holder  13 , at least one concavity  17  is formed in the guide pipe  11 , and the locking body  15  can be moved into it by a small radial pressing force. The concavity  17  is supported axially directly before the pocket  16  as considered in the displacement direction of the tool holder  13  of the guide pipe  11 . In accordance with a preferable embodiment of the present invention, several, for example four locking bodies  15 , pockets  16  and concavities  17  are provided, and are offset relative to one another over the same rotary angle. The locking bodies  15  are axially non displaceably received in wall passages of the end portion  131  of the tool holder  13  and secured against radial falling out outwardly.  
         [0020]    In the above described embodiment, the locking bodies  16  are formed as balls, and the pocket  16  are formed as radial openings. The radial falling out of the balls  18  from the radial openings  19  is prevented by a ring disc  20 . The ring disc  20  is fixed on the end portion  131  of the tool holder  13  by a safety ring  21 . The ring disc  20  abuts against the balls  18  so that they are arranged in the radial openings  19  with a certain radial clearance. The concavities  17  have a contour corresponding to the contour of the balls  18 , and in the mounting position the balls  18  are located in the concavities  17  with a little pre-stress by the ring disc  20 .  
         [0021]    The locking device  14  is fixed on the guide pipe  11  and has for example a displacement sleeve  22  which carries a radially inwardly projecting ring web  23 . The displacement sleeve  22  is axially displaceably guided on a guide element  24  which is mounted on the guide pipe  11 . The displacement sleeve  22  engages the machine housing  10  with its end which faces the machine housing. The guide element  24  is formed as a one-piece synthetic plastic injected part. It has a ring  25  which is fixed axially non displaceably on the guide pipe  11 , and a plurality of arms  26  extend axially from the ring  25  and have arresting hooks  27  projecting at their free ends in a peripheral direction. The arresting hooks  27  form a front abutment for the displacement of the displacement sleeve  22 .  
         [0022]    The ring web  23  of the displacement sleeve  22  radially engages a blocking ring  28  of the locking device  14  which is axially displaceably guided by the arms  26  of the guide element  24 . A helical spring  30  is supported between the blocking ring  28  and the ring  25  of the guiding element  24 . It abuts the locking ring  28  against the ring web  23  of the displacement sleeve  22 , so that the ring web  23  is pressed against the arresting hooks  27 . In this locking position of the locking device  14 , the blocking ring  28  is located on the locking bodies  15  or the balls  18 , which are introduced in the pockets  16  and prevent any radial displacement of the locking bodies  15  or the balls  18 .  
         [0023]    Displacement means are integrated in the locking device  14 . They are automatically activated with a release of the locking device  14  and displace the tool holder  13  to the mounting position, in which the locking bodies  15  or the balls  18  are engaged in the concavities  17 . In the embodiment of FIG. 1, this means include a cylindrical pressure spring  29  which is supported against the locking ring  28  and the guide pipe  11 . One embodiment of the pressure spring  19  against the guide pipe  11  is provided by safety disc  31  which is inserted in the ring groove formed in the guide pipe  11  and clamps the ring  25  of the guiding element  24  against a radial shoulder formed in the guide pipe  11 . The other abutment of the pressure spring  29  is formed by a cup bottom of a spring cup  32  which engages with a central opening of the end portion  131  of the tool holder  13  and abuts against a radial shoulder  132  formed at the end portion  131 .  
         [0024]    The mounting and dismounting of the tool holder  13  is performed in the following manner:  
         [0025]    For mounting, the tool holder  13  with its end portion  131  is placed on the end region  111  of the guide pipe  11  until the balls  18  are located in the mounting position of the tool holder  13  in the concavities  17 . During a further displacement in direction toward the machine housing  10 , the balls  18  abut against the blocking ring  29  which is displaced back so far until the balls  18  in the locking position of the tool holder  13  engage in the pockets  16 . In this moment the blocking ring  28  is displaced again by the helical spring  30  forwardly for abutment against the ring web  23  of the displacement sleeve  22 . In this locking position the blocking ring  28  is placed on the balls  18  and blocks their radial displacement, so that the balls  18  can not move from the pockets  16  and the locking between the guide pipe  11  and the tool holder  13  is reliably maintained (lower part of FIG. 1). The locking during the mounting is therefore automatically performed by simple, one hand displacement of the tool holder  13  on the guide pipe  11 . The power tool can be held with another hand.  
         [0026]    For dismounting, the displacement sleeve  22  is displaced in direction of the machine housing  10  rearwardly. The ring web  23  on the displacement sleeve  22  moves the blocking ring  28  as shown in the upper half of FIG. 1. By the displacement of the blocking ring  28 , on the one hand the balls  18  are released and on the other hand the pressure spring  29  and the helical pressure spring  30  are tensioned. When now the displacement sleeve  22  is released, the pressure spring  29  displaces the tool holder  13  to the left in FIG. 1, while the balls  18  are moved from the pockets  16  as a result of the radial displaceability and fall in the concavities  17  in the mounting position. The pressure spring  29  is designed so that the balls  18  are not displaced by the spring force from the concavities  17 .  
         [0027]    The relaxed helical pressure spring  30  presses the blocking ring  29  and the displacement sleeve  22  until abutment of the ring web  23  against the displacement sleeve  22  against the arresting hooks  27  of the guiding element  24 . The tool holder  13  is now unlocked for removal from the guide pipe  11 . When the operator displaces the tool holder  13  to the right in FIG. 1, the tool holder  13  is automatically locked again as explained herein above. When the operator pulls the tool holder  13  to the left in FIG. 1, the tool holder  13  is removed from the guide pipe  11 . The actuation of the displacement sleeve  22  and the pulling out off of the tool holder  13  from the mounting position is performed one after the other with the same hand, while the other hand holds the machine. The dismounting of the tool holder  13  can therefore be performed with the one hand.  
         [0028]    In the embodiment of the hammer drill with the tool holder  13  as shown in FIG. 2, the locking device  14  is different in that the separate function of the both pressure springs  29  and  30  in the locking device  14  of FIG. 1 is performed by a single conical spring  34 . The end portion  131  of the tool holder  13  which engages the lateral end of the end region  111  of the guide pipe  11  is provided with a cone  133 . The conical spring  34  has a diameter-increased spring end which is located on the blocking ring  28  and a diameter reduced end which is located on a further radial shoulder  113  formed in the guide pipe  11 . The cone  133  and the conical spring  34  are formed with respect to one another so that in the locking position of the tool holder  13  shown in the lower half of FIG. 2 the conical spring  34  is pretensioned by the cone  133  to bulge outwardly.  
         [0029]    When the displacement sleeve  22  is pulled back for releasing the locking device  14 , the conical spring  34  is released from the cone  133  as shown in the upper half of FIG. 2. During release of the rearwardly pulled displacement sleeve  22 , the conical spring  34  is loosened and displaces not only the blocking ring  22  and the displacement sleeve  22  for abutment against the arresting hooks  27  of the guiding element  24 , but the windings of the conical spring  34  also touch the cone  133  and displace the tool holder  13  forwardly to its lock-free mounting position, in which the locking bodies  15  or the balls  18  are introduced into the concavities  17  on the end region  111  of the guide pipe  11 . In other aspects the construction and the operation of the locking device  14  for a tool exchange are identical to that in FIG. 1, so those the same components are identified with the same reference numerals and the description of the embodiment of FIG. 1 is applicable to the description of FIG. 2. The tool holder  13  in the upper half of FIG. 2 is shown in its unlocked mounting position and in the lower half of FIG. 2 is shown in its locking position.  
         [0030]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
         [0031]    While the invention has been illustrated and described as embodied in hand power tool, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
         [0032]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.