Patent Abstract:
The present invention relates to a seal in the tool side of a straight or contra angle handpiece head for sealing the interior of straight or contra angle handpieces. The seal is characterised by a spring, which prestresses a gasket of compressible elastic material against a fixed component and a rotating disk located in the immediate vicinity of the seal. Moreover, the present invention relates to a straight or contra angle handpiece with such a seal.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims priority from pending Austrian Patent Application No. A 1214/2003, filed Jul. 31, 2003, which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field  
         [0003]     The present invention relates to a seal in the tool side of a straight or contra angle handpiece head for sealing the interior of straight or contra angle handpiece.  
         [0004]     2. Description of Prior Art  
         [0005]     The necessity for sealing exists due to the danger of transferring pathogens between patients, which pathogens are transported into the straight or contra angle handpiece via bodily fluids such as blood or saliva, and for protection of the components within the straight or contra angle handpiece, such as the clamping device, the bearings and the drive shafts, against soiling and damage from tissue during treatment, such as pieces of bone, or from substances employed during treatment, such as pastes, for example. Retainment of lubricating agents from bearings within the straight or contra angle handpiece must also be guaranteed by the seal, particularly during treatment.  
         [0006]     The fundamental problem in sealing the straight or contra angle handpieces against the environment is that tools, which are actuated by a drive, for example rotating drills, brushes, Prophy Cups, protrude from the head. In order to ensure safe operation of the straight or contra angle handpieces with low wear, low noise, the rotating tools and associated components, such as, for example, the drive shaft and the spindle, operate with a clearance to the non-rotating, fixed components, such as the outer sleeve and the bearings. The particles and soiling described above can enter into the straight and contra angle handpieces through gaps between the fixed and moving parts.  
         [0007]     To keep soiling entry to a minimum, a variety of devices are known that are employed in a number of application areas, such as implantology, prophylaxis or the mechanical removal of tissue; very often, labyrinth seals are used to seal the gaps between the fixed and moving parts; see EP 997 110 A2, for example. Disadvantageous here is once again the existence of gaps between the components of the labyrinth seal, through which small particles, fluids, and substances dissolved and dispersed within them, can penetrate the interior of the straight or contra angle handpiece.  
         [0008]     By means of rotating disks (splash guards), an attempt has been made to keep particles and soiling out of the head area of the straight or contra angle handpiece, or to hurl them away. These rotating disks are therefore attached to rotating components, for example to the drive shaft or to the tool itself; see U.S. Pat. No. 6,350,124 B1,  FIGS. 7A-7C . Here, too, however, there is clearance between the rotating disk and the fixed components, through which soiling can penetrate the interior of the straight or contra angle handpiece.  
         [0009]     In prophylaxis contra angle handpieces used for polishing the tooth surface, a particularly good seal is necessary, because the polishing treatment pastes are distributed especially close to the contra angle handpiece head by the tool (a so-called Prophy Cup). In patent U.S. Pat. No. 3,436,830, a sealing ring rotating with the tool is proposed, the cylindrical extension of which protrudes into the tool side of the contra angle handpiece head. The sealing ring is pressed against the contra angle handpiece head through a Prophy Cup apron.  
         [0010]     In the patent U.S. Pat. No. 5,642,995, a cap with a cutting tool, which cuts into a cylindrical extension of the Prophy Cup when the cup is screwed into the tool coupling, is fitted to the head of the contra angle handpiece.  
         [0011]     Disadvantageous in both documents is that specially formed Prophy Cups with extensions are required in each case. In particular, the seal described in the &#39;830 patent requires extremely high manufacturing precision (low tolerance) for the apron in order to exercise correct sealing force on the sealing ring.  
         [0012]     The present invention therefore has the aim of creating an improved seal. In particular, the seal can be utilized universally in various straight or contra angle handpieces, for example for implantology, prophylaxis or for mechanical removal of tissue, achieving a reduction in production costs. For prophylaxis contra angle handpieces, the seal must be designed such that special Prophy Cups are not necessary, giving the user greater choice in the selection of Cups.  
       SUMMARY OF THE INVENTION  
       [0013]     In one embodiment of the present invention, a seal is provided that is adapted for substantially universal use with a variety of straight or contra angle handpieces.  
         [0014]     In order to achieve the greatest possible sealing effect in an embodiment of the present invention, a gasket, preferably of the grommet type, is prestressed against a fixed component by a spring. The gasket consists of an elastically compressible material, preferably rubber. This allows the dimensions of the gasket to be selected such that it can be slightly compressed by the surrounding components and so that when installed it fits very tightly to the fixed components in particular, thereby achieving a very good sealing effect. The spring holding the gasket against the fixed components also increases the sealing effect of the gasket, in particular in the direction of the tool side of the straight or contra angle handpiece head.  
         [0015]     In yet another embodiment of the invention, a splash guard is located in the immediate vicinity of the gasket, preferably in direct contact with the gasket. Because of the direct contact with the gasket and the resulting extremely small spacing to the head of the straight or contra angle handpiece, a rotating disk already prevents entry of a large proportion of soiling elements. Particles or fluid droplets penetrating as far as the gap between the rotating disk and the head of the straight or contra angle handpiece are hindered in entering the interior of the straight or contra angle handpiece by the gasket, which lies tightly in contact with the surrounding components. In addition, the spring automatically compensates for any wear of the gasket by increasing the travel of the spring and in this way guarantees a uniform quality sealing effect.  
         [0016]     In a preferred embodiment, in order to minimize gasket wear in the area of contact with the rotating disk and thus ensure effective sealing after prolonged seal use, and to achieve optimum force transmission from the spring to the gasket, washers, preferably of metal, are situated between the gasket and the rotating disk and/or between the gasket and the spring.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The invention is described below based on preferred embodiments and with reference to the drawings provided:  
         [0018]      FIG. 1  shows the head of a prophylaxis contra angle handpiece with a seal according to an embodiment of the invention.  
         [0019]      FIG. 2  shows the seal of  FIG. 1  enlarged in sectional representation.  
         [0020]      FIG. 3  shows the head of a contra angle handpiece for mechanical removal of tissue with a seal according to another embodiment of the invention. 
     
    
       [0021]     In all figures, the same components are labelled with the same numbers.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     The head  1  of a prophylaxis contra angle handpiece represented in  FIG. 1  consists of an outer sleeve  2  with a handle sleeve section  2 A and an adjacent contra angled head sleeve section  2 B. A drive shaft  3  is located in the handle sleeve section  2 A and is set rotating by a motor (not represented), for example an air motor. In a bore  12  in the head sleeve section  2 B, a driven shaft  5  is located in two bushings, or bearings,  10 ,  15 . The distal end of the driven shaft  5  is developed as a rotatable tool carrier  9 , into which a prophylaxis tool can be inserted by means of a screw thread. At the distal end of the tool carrier  9  is a rotating disk  11 , preferably removable from the tool carrier  9 , for example by means of a screw or push connector. The rotary action of drive shaft  3  is transmitted to the driven shaft  5 , the tool and the rotating disk  11  by means of gear wheels  4  and  6 .  
         [0023]     Parts of a seal  20 , according to an embodiment of the invention, are located in a recess  13  in the bushing, or bearing,  10  ( FIG. 2 ). The driven shaft  5 , the two bearings  10  and  15  and the seal  20  are fixed in a bore  12  by means of a ring nut  7 , which is screwed by a thread  8  into the head sleeve section  2 B. It can be seen in  FIG. 2  that the ring nut  7  has a radially inwardly directed interior shoulder  14  on the tool carrier side, which accepts a gasket  22 , which is part of the seal  20 . The gasket  22 , which may be formed of an elastic material, comprises a ring that encircles tool carrier  9 . The gasket is clamped against the shoulder  14  by means of a dog  17  on the lower bushing, or bearing,  10 , which is a press fit in ring nut  7 . A spring  21  and a washer  24  are located in the recess  13  in the lower bushing  10 . The spring  21 , preferably a leaf spring, exerts a force on the gasket  22  in the direction of the distal end of the tool carrier  9  and presses the gasket  22  against a further washer  23 . The rotating disk  11  is affixed to the top drive  5  via threads  16 ,  18  on the outside of the top drive  5  and the inside of the rotating disk  11  and, simultaneously, by screwing on the rotating disk  11 , the washer  23  is pressed against the gasket  22 .  
         [0024]     Because of the compressible elastic material properties of the gasket  22  and the distal and proximal forces exercised, the gasket  22  engages all fixed, non-rotating components (ring nut  7 , bushing  10 , washers  23  and  24 ), without a gap. The washer  23  does not rotate, because the frictional resistance between the elastic gasket  22  and the metal washer  23  is greater than between the metal rotating disk  11  and the metal washer  23 . Both washers  23 ,  24  are preferably manufactured from metal, in particular washer  23  is preferably manufactured from hard alloy. None of the components of seal  20  (spring  21 , gasket  22  and washers  23 ,  24 ) contact the outer surface  19  of the rotating driven shaft  5 , circumventing wear or noise generation. The only contact between a rotating and a fixed component is between the washer  23  and the rotating disk  11 . The contact surface between these two components is, however, very small, so that noise generation is also small. By the sound choice of materials, in particular the hard alloy washer  23 , wear can be kept extremely low, ensuring no gap occurs through which soiling elements can penetrate into the interior of the contra angle head  1 , even after prolonged use of the seal  20 . The seal  20  thus represents, in particular in combination with the rotating disk  11 , a simple, durable and economical seal.  
         [0025]     The configuration of another embodiment of seal  20 A represented in  FIG. 3  in the head  100  of a contra angle handpiece for mechanical removal of tissue corresponds somewhat to those shown in  FIGS. 1 and 2 . However, a substantially higher speed is required for such contra angle handpieces, so that the driven shaft  5  in the head  100  is supported in ball bearings (due to the only partially cut away outer sleeve  101 , only one bearing  102  is visible). In this embodiment, the bushing  10  serving as a seat for at least part of the seal  20  in the embodiment of  FIG. 2  is missing. Instead, a fixation disk  104  is located at the proximal end of seal  20 A, the shoulder  104 A of which clamps the gasket  22  against the shoulder  14 A of the ring nut  7 A. The extension  104 B serves as a seat for spring  21 . A spring  105 , which prestresses the ball bearing  102  by means of a distance piece  103 , is located in a recess  106  in the fixation disk  104 . It can be recognized from this embodiment that, by simple modification, the seal of the invention can be adapted for universal use in straight and contra angle handpieces in a variety of applications.  
         [0026]     The invention is not restricted to the represented applications and embodiments, but encompasses all possible embodiments that do not alter the basic design principle of the invention and analogous functions. In particular, the type and shape of the gasket and the washers, as well as the location and type of bearing of the invented seal, are variable and shall be adapted to the variety of spatial relationships in the different straight and contra angle handpieces.

Technology Classification (CPC): 0