Patent Publication Number: US-2015064648-A1

Title: Dental handpiece having a rolling bearing

Description:
TECHNICAL FIELD 
     The invention relates to a dental handpiece or an angle piece having a drive for a tool situated in a head housing as well as at least one media-carrying line arranged in the head housing and having an outlet opening toward the tool and having a tool receptacle arranged in a drive chamber, said tool receptacle being supported on one side of the drive chamber facing the tool by means of a rolling bearing, so it can rotate in an abutment of the head housing. 
     PRIOR ART 
     EP 0 630 620 B1 discloses a dental turbine drive, in which the drive unit is secured in the head housing with O-rings and with vibration damping. In the outer race, the bearings have a shoulder with which the O-ring is in contact radially and on the transition of which the O-ring is supported axially. 
     DE 100 25 416 A1 discloses a dental handpiece in which an elastic radial support of a rotor shaft is provided by means of an O-ring and the elastic axial support is provided by means of a wave spring. 
     DISCLOSURE OF THE INVENTION 
     The dental handpiece according to the invention has a drive for a tool, said drive being situated in a head housing, and at least one media-carrying line arranged in the head housing with an outlet opening toward the tool, and a tool receptacle, which is arranged in a drive chamber and is supported on one side of the drive chamber facing the tool by means of a rolling bearing, so that it can rotate in an abutment of the head housing. The rolling bearing has an outer race, which is supported radially against the head housing in the abutment in the region of a raceway and has a sub-area, whose outside diameter is reduced in comparison with the outside diameter in the region of the raceway. The head housing has a housing extension, which extends into the region of the reduced outside diameter, and the media-carrying line runs at least partially through this housing extension. 
     This has the advantage that the outlet opening of the media-carrying line can be carried closer to the tool without increasing the overall height and/or causing a reduction in the overall volume. 
     One advantageous refinement may consist of the outer race being supported against the head housing so that it is axially displaceable and has a cover disk connected thereto, extending from the outer race in the direction of an inner race arranged on the tool receptacle, wherein a prestressing means acting in the axial direction is arranged between the cover disk and the head housing, acting with an axial prestress on the outer race by means of the cover disk such that the head housing has another housing extension connected to the first housing extension, this housing extension extending radially in the direction toward the longitudinal axis in comparison with the outer race on its end, which supports the cover disk, and the media-carrying line also runs at least partially through this second housing extension. 
     This has the advantage that even in the event of an axial prestressing means of the bearing, the overall height need not be increased and, in particular, space is created for cooling equipment such as a spray. 
     The outside diameter of the extension may, in particular, be reduced in comparison with the outside diameter in the region of the raceway by an amount t1 of 0.1 mm to 0.5 mm, preferably 0.2 to 0.3 mm. The outside diameter is thus reduced by 0.2 mm-1.0 mm, preferably by 0.4 mm-0.6 mm, in the region of the extension in comparison with the outside diameter in the region of the raceway. 
     It has been found that such a reduction already results in an improvement in manufacturability and placement of the outlet opening of the media-carrying line. 
     In addition, it may be advantageous if the outer race is supported against the head housing such that it is axially displaceable and has a cover disk connected to it, which extends from the outer race in the direction of an inner race arranged on the tool receptacle such that a prestressing means acting in the axial direction is arranged between the cover disk and the head housing and acts upon the outer race with an axial prestress by way of the cover disk such that the cover disk has an extension extending in the axial direction and forming a sealing gap on its inside with the inner race and its outside is designed as an axial guide for the prestressing means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive handpiece will now be explained with reference to the drawings, in which 
         FIG. 1  shows a dental handpiece having a media-carrying line in the form of a spray according to the prior art; 
         FIG. 2  shows a section from  FIG. 1  of a head housing in the region of a tool having an inventive design of the rolling bearing and of the head housing; 
         FIG. 3  shows an enlargement from  FIG. 2  in the region of the support of the tool in the head housing; 
         FIG. 4  shows an alternative design of the rolling bearing and of the head housing; 
         FIG. 5  shows the embodiment according to  FIG. 4  in detail; 
         FIG. 6  shows another embodiment of the head housing. 
     
    
    
     EMBODIMENT(S) OF THE INVENTION 
       FIG. 1  shows a dental handpiece  1 , which has a head housing  2  with a drive  3  in the form of a turbine or a gear shaft for a treatment tool  4 . To cool the tool  4  or to illuminate the location being treated with the tool, an outlet  5  for a water stream  6  or for an air stream or beam of light is provided in the head housing  2 . In the event that water, air or light is used as the medium, this outlet location  5  should be as close to the tool  4  as possible in order to reduce shadows of the water jet or of the beam of light and to improve the illumination or cooling, in particular when working in tight cavities. The angle of viewing α is given in relation to a longitudinal axis  18  in accordance with Standard DIN/EN/ISO 7785-1. 
     The tool  4  is set in rotation by means of the drive  3 , so that, as shown in  FIG. 2 , it is supported against the head housing  2  by means of a rolling bearing  11 . The rolling bearing  11  is arranged in a drive chamber  12  and comprises an outer ring  13 , which is supported radially against the head housing  2  in an abutment  14 . The inner race  15  of the rolling bearing  11  is arranged on a tool receptacle  16  in which the tool  4  is secured. Even this diagram shows that the head housing has a media-carrying line  17 , which leads to the outlet opening  5  and is designed as a straight-line bore because of the manufacturing process. The line  17  is inclined by an angle β with respect to the longitudinal axis  18  of the treatment tool  4 , such that, in the present case, the direction of the emerging stream  6  corresponds to this angle β. 
       FIG. 3  illustrates the special embodiment of the head housing  2  in the region of the abutment  14 . This shows that the outer race  13  of the rolling bearing  11  has a sub-area  21 , the outside diameter D2 of which is reduced by a double amount t1 in comparison with the outside diameter D1 in the region of the raceway. 
     In addition, in the region of the abutment  14 , the head housing  2  has a housing extension  23 , which extends into the region of the reduced outside diameter of the outer race and passes at least partially through the media-carrying line  17 . This is indicated by the dashed continuation of the abutment without the housing extension  23 . It is clear here that the line  17  would be open into the abutment itself if there were an abutment without an extension so that fluid could emerge here. 
     The projection  23  thus makes it possible to bring the line  17  closer to the longitudinal axis  18  than would be possible without the projection. If the outlet opening is not so far away from the longitudinal axis, this has the advantage that the shadowing is reduced, vision is improved and the angle of viewing α according to Standard DIN/EN/ISO 7785-1 is smaller. 
     To support the outer race  13  against the head housing  2 , an elastic O-ring  24 , which is deformed with a prestressing force, may be provided in the region of the abutment  14 , with the O-ring  24  lying at approximately the height of the raceway  22 . Therefore, radial mobility of the rolling bearing and/or an equalization of the tolerance of the components relative to one another is/are made possible. 
     In the axial direction, the outer race is displaceable axially beyond the O-ring and may be supported by a prestressing spring  31 , which is supported in the axial direction against the bottom side of the head housing  2 . 
     To permit the prestressing means  31  to be supported on the outer ring [sic, outer race], the outer ring [sic, outer race]  13  may have a cover disk  32  connected to it in the sub-area  21 . The cover disk  32  may extend up to an inner race arranged on the tool receptacle  16 , forming an annular gap  33 . A certain sealing of the rolling bearing can be achieved by means of this annular gap. 
       FIGS. 4 and 5  illustrate another exemplary embodiment, in which another housing projection is also provided in the region of the arrangement of the prestressing means in order to bring the media-carrying line even closer to the longitudinal axis. A slope can be provided (see  FIG. 6  subsequently) instead of several steps. 
     In  FIG. 4 , the head housing  2  is provided with an additional projection  41  in the region of the abutment  14  for the outer race  13 , in addition to the projection  23 , with this additional projection extending in the radial direction to the longitudinal axis  18  beneath the outer race  13 . Unlike the projection  23 , the outer race  13  is not designed according to the projection  41 , i.e., it does not take into account the projection  41 . The outer race  13  of the bearing may also have a chamfer in the region of the projection  23 , because no supporting functions are necessary here with respect to the housing. 
     The projection  41  limits the overall volume available for the prestressing means  31  and, at the same time, forms an axial stop for the outer race  13  and ensures that the prestressing means  31  will not be compressed completely and thereby damaged under the influence of the axial force via the outer race  13 . 
     It can be seen that the line  17  can be brought even closer to the longitudinal axis  18  by the additional radial projection  41 , which is also shown in the details of  FIG. 5 , in which the outer race and the prestressing means have been omitted from the diagram. The outlet location  5  of the line  17  can therefore be moved further toward the longitudinal axis  18  than would be the case if projection  23  or  41  were omitted, which is depicted by the dashed contour  42  in the abutment  14  of the head housing  2 . 
       FIG. 6  shows a head housing  2  with a housing projection  23 , which extends obliquely into the region of the reduced outside diameter of the outer race  13 , such that the outer race  13  also has an inclination. An axial continuation  51 , which serves as a radial inside stop for the prestressing means in the form of a wave spring  31  and guides it axially, is provided on the end of the cover disk  32  facing the longitudinal axis  18 . The gap  33  between the outer race  13  and the inner race  15  is therefore longer, so that the sealing effect is improved. 
     The inclined housing projection  23  again contains a line  17  with the outlet location  5 . Since there is no longer an axial stop on the outer race  13  on this inclined projection, a stop on the outer race  13  with respect to the head housing is established by means of the continuation  51 .