Patent Document

FIELD OF THE INVENTION 
   The present invention relates to a disposable dental appliance and more particularly to a dental prophylaxis angle (or “prophy angle”) used for cleaning and polishing teeth, especially to the prophylaxis angle for holding a disposable polishing/cleaning cup-head that is disposed after each application to a patient to prevent potential cross infections. 
   BACKGROUND OF THE INVENTION 
   A prophy angle is a dental appliance employed by a dentist or dental hygienist in a dental treatment to remove the plaque and polish the surface of the dentin of teeth. A prophy angle includes a prophy cup that is secured to the angle and is rotated by a drive mechanism, typically a gear drive. The prophy cup is shaped to retain a desired amount of prophy paste, which is used to polish and clean a patient&#39;s teeth. 
   In order to rotate a prophy cup to perform the teeth cleaning and polishing task, a dental prophy angle includes a driving mechanism that is typically implemented with a gear connection between a driving gear shaft and a driven gear rotor with a right angle. The driving rotor is rotated by a dental handpiece with a speed of about 2,000 to 5,000 rpm, then the rotation is transferred to the driven rotor by the gearing mechanism resulting in rotating the attached prophy cup at a right angle. 
   However, since the prophy angle includes the moving parts connected by driving gears while the gear connections and the prophy cup are continuously operated with high speed rotation, the long term reliability and consistent performance of the gear connection and the rotational prophy cup become a technical challenge. Poor long-term reliability often becomes a problem, particularly for the components made of plastic. The plastic components may be implemented either as moving parts or as part of the gear connections between the moving parts and these plastic components often cracks or break off when subject to tearing forces if these the moving parts or the gear connections are not tightly engaged. In order to improve the reliability by reducing the material wear and degradation under constant use and to eliminate potential weak links, many patented inventions have been disclosed. These disclosures provide new gear material, gear shape, gear position and novel lubrications. These previous patents include U.S. Pat. Nos. 6,203,322, 5,964,590, 5,749,728, 5,730,595, 5,645,426, 5,120,220, and 5,040,978. However, in the present market, many of the prophy angle products still exhibit operating life problem because of the insecure gearing connection, which leads to unreliable performance and causes inconvenience for dentists and hygienists 
   Therefore, a need still exists in the art of designing, component manufacturing and assembling the prophy angles to provide new and improved configuration implemented with better engagement contacts between the moving components to enable a more secure retaining of the driving shaft and driven rotor to assure reliable and high performance operations of a prophy angle. 
   SUMMARY OF THE PRESENT INVENTION 
   It is therefore an object of the present invention to provide a new and improved design and configuration to securely maintain the lateral positions of the driving shaft and the driven rotor such that tight engagements between the driving shaft and driven rotor can be continuously maintained. By minimizing lateral shifts and maintaining tight engagement between the rotating gears, unnecessary wears and damages caused by unreliable gear engagement can be reduced. Secure retaining of the driven rotor and the prophy cup further improve the convenience of operation to allow better performance in patient treatments. The above-mentioned problems and difficulties are therefore resolved. 
   In order to accomplish the object of secure connection, the present invention provides a secured horse-shoe-shaped driven-gear-retainer which retains the neck of the driven gear so as to secure the head portion of the driven-gear member in position, as well as a secured driving shaft locking element to ensure the driving gear is engaged to the driven gear properly during operating. 
   Specifically, the invention is directed to a dental prophy angle that has an integrally formed housing, which incorporates two gears (driving gear and driven gear) with a removable prophylaxis head attachment, also called the prophylaxis cup (or “prophy cup”), and translates rotation from a dental power source to the head attachment through both driving and driven gears. More specifically, the driving gear rotor, which receives the dental power source on one end and engages with the driven gear on the other end, translates the rotation to the driven gear rotor in an angled axis. The angle is made of inexpensive plastic and can be discarded after each treatment, thus preventing cross-infection and reducing the expense and inconvenience of sterilization as well. 
   One aspect of the invention is the two gears are engaged perpendicular to each other on their inner sides of contact, instead of their outer sides, so that the rotation direction of the prophy cup will be the same, instead of opposite, as that of the driving gear and of other dental treatment devices connected with the driving gear. The consistency in rotation direction makes practitioners feel more comfortable. 
   Another aspect of prominent benefit of the present invention lies in the mating of the gears. Due to the existence of necessary operating tolerance, as the prophy angle operates the inner-contact-engagement makes the mating of gears closer when the driven gear rotor is pressed toward to the driving gear rotor by the force from the prophy cup. Contrarily, if the engagement uses the outer-side-contact, that arrangement will reduce the mating area when the driven gear rotor is pressed away from the driving gear rotor by the prophy cup as the prophy angle operates. 
   A further aspect of the invention is that the horse-shoe-shaped driven-gear-retainer is arranged in the short leg of the housing by retaining the neck of the driven gear to secure the head portion of the driven-gear member in position. Because of the inner-contact-engagement, a retaining mechanism is always adopted to prevent the driven gear rotor from falling out of the housing during operation. The arrangement of the horse-shoe-shaped driven-gear-retainer in this invention provides a secure means for retaining the prophy cup member from falling out of the passageway and keeping the prophy cup member rotating freely without much friction simultaneously. The inner-side contact gearing arrangement tends to eject the prophy cup-rotating member from the housing because the gear on the driving shaft applies an outward force to the rotating driven gear. Thus, the reliability of the driven-gear-retainer is an important aspect of the present invention. The horse-shoe-shaped driven-gear-retainer ensures in a simple way that the driven-gear rotor remains in position securely with much less cost in comparison with other similar products in market. 
   Yet another aspect of the invention is a secured driving shaft locking mechanism to ensure the driving gear is engaged to the driven gear properly without being pushed out during operation. Specifically, in the present invention, a paw-like disc with a several of axially aligned slots forming a locking positioner is placed in the long leg of the housing. The driving gear tail passes through the central hole of the locking positioner, so that when the locking positioner is snapped on the inside wall of the housing it will be held strongly at the exact position, to secure the driving-gear member axially in position. Rather than a plastic positioner, a metal one can better grasp the plastic housing. Preferably, a washer can be interposed between the retaining lock and the shoulder on the driving gear member to increase stability and reduce friction. 
   As an alternative to the paw-like disc type shaft locking mechanism in the present invention, a horse-shoe-like positioner is held firmly on the inside wall of the housing, with the driving gear tail passing through its fork-like legs, so as to secure the driving-gear member axially in position. 
   The last aspect of the present invention is directed to a pair of, or more, sharp pointed splinters arranged circumferentially on, and pointing outward from the neck of the cup end of the driven gear rotor, upon which the snap-on prophy cup sits. After the prophy cup is attached, the base of the prophy cup is pierced and thus securely anchored by the splinters arising from the neck of the driven gear rotor. These splinters pierce the rubber base of the snap-on prophy cup and force it to rotate with the driven gear rotator, eliminating the free spinning of the rotor within the cavity of the snap-on prophy cup. 
   These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various drawing figures. Other details and features of the invention will become apparent and described hereinafter with the following drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will be readily apparent from the following detailed description. The detailed description will be better understood in relation to the accompanying drawings as: 
       FIG. 1  shows the perspective view of the assembled prophy angle. 
       FIGS. 2A and 2B  are cross sectional views of a prophy angle with a paw-like positioner and a horse-shoe-like positioner respectively. 
       FIGS. 3A and 3B  are perspective views of the assembled driving shaft and driven rotor for placement inside a housing with a paw-like positioner and a horse-shoe-like positioner respectively. 
       FIG. 4  is a perspective view of the parts inside the housing implemented with paw-like positioner before assembly. 
       FIG. 5  is a perspective view of the parts inside the housing implemented with horse-shoe-like positioner before assembly. 
       FIGS. 6A and 6B  are perspective views of a driven-rotor-retainer for positioning the driven rotor at a fixed position, showing top and bottom views respectively. 
       FIG. 6C  is a perspective view of a horse-shoe-like positioner for locking the driving shaft at a fixed position. 
       FIG. 7A  is a cross-sectional view of a housing with horse-shoe-like positioner on for enclosing the gears. 
       FIGS. 7B and 7C  show a top perspective view and a bottom perspective view of the housing for enclosing the horse-shoe-like positioner and the horse-shoe-like retainer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring first to  FIG. 1  for a perspective view of a prophy angle  10  as a preferred embodiment of present invention. The prophy angle includes a driving shaft  30  that engages and driving a driven rotor  40 . The prophy angle includes a long leg and a short leg wherein the driving shaft  30  extends along a longitudinal direction inside the long leg of the housing  20  and the rotator  40  extends along a perpendicular direction inside the short leg of the prophy housing  20 . A powered dental handpiece (not shown) is provided to couple to the tail of the driving shaft  30  to rotate the shaft  30  and a snap-on rubber prophy cup with prophy paste (not shown) is provided to connect to the cup holder head of the driven rotor for rotate with the rotator  40  when driven by the rotating shaft  30 . 
     FIG. 2A  is a cross-sectional view of the prophy angle shown in  FIG. 1 , where a driving rotating shaft  30  is enclosed in the housing  20 .  FIG. 2A  represents the paw-like driving shaft positioner structure while  FIG. 2B  represents the horse-shoe-like driving shaft positioner structure. The prophy angle  20  further includes a driving shaft locking means  60  to retain the driving shaft at a fixed horizontal location. The driving shaft  30  is engages a driven rotator  40  to translate first rotation of the driving shaft  30  along a horizontal rotational axis to a second rotation of the driven rotor along a vertical rotational axis. The driven rotator  40  is maintained in a vertical position by a driven rotor retainer  50 . At the lower end of the driven rotator  40 , a pair of splinter is further provided to more securely attached to a disposable prophy cup (not shown) that is snapped onto the lower end of the rotor  40 . The details structure of the driving shaft locking means  60  and the driven rotator retainer  50  will be further described below. 
     FIGS. 3A and 3B  are a perspective views of the parts assembled inside housing for a paw-like driving shaft positioner structure and a horse-shoe-like driving shaft positioner structure respectively. In order to enclose the driving shaft  30  and the driven rotor inside the housing  20 , the housing  20  has a hollow space as that shown in  FIG. 2A  or  2 B. The housing  20  is hollow to provide a longitudinal passageway  21  and a transverse passageway  22  inside the short and long legs of the housing such that the driving shaft  30  and the driven rotor can be placed therein to engage each other for generating a gear-driving mechanism. The driving shaft  30  is placed along the longitudinal passageway  21  with a locking system  60  are preferably perpendicular to the transverse passageway  22  for placing the driven rotor  40  with the vertical position fixed by a driven rotor retainer  50  along the transverse passage  22 . 
   It is desirable to fix driven rotor  40  with respect to driving shaft  30  to ensure constant gearing action during operation. At the near end of transverse passageway  22  of housing  20 , there exists a driven rotor-positioning hole  23  centered on the axis of transverse passageway  22 . The diameter of driven rotor positioning hole  23  is loosely fit to the diameter of rotor head  41  as shown in  FIGS. 4 and 5  below of driven rotor  40  to ensure the concentricity of rotation of driven rotor  40 . The depth of driven rotor positioning hole  23  is designed such that the gearing action between gear head  31  of driving shaft  30  and gear shoulder  43  of driven rotor  40  stays constant during rotation, and such that cup flange  44  stays slightly in contact with open end  29  of housing  20 . 
   In order to prevent axial movement of driving shaft  30  from its position relative to driven rotor  40  within longitudinal passageway  21  of housing  20 , there exist two longitudinal positioning steps  25 ,  26  on the wall of longitudinal passageway  21  of housing  20 . The longitudinal positioning step  25  controls the axially forward position of driving shaft  30  by blocking the head side of shaft shoulder  33  in position when axially forward directed forces are exerted on driving shaft  30 . Longitudinal positioning step two  26  positions driving shaft locking means  60  which controls the axially backward position of driving shaft  30  by blocking the tail side of shaft shoulder  33  in position when axially backward directed forces are exerted on driving shaft  30 . There are slots  27  and  28  provided on the housing  20  for adapting the driving shaft locking means  60  as will be further described below. 
     FIGS. 4 and 5  are perspective views of the parts of  FIGS. 3A and 3B  respectively before these parts are assembled for showing the details of paw-like and horse-shoe-like positioners, respectively, e.g., the structural details of the driving shaft locking means  60  and the driven rotor retainer  50 . Two kinds of retaining mechanism are presented for this invention to achieve the retaining function of driving shaft locking means  60 : the paw-like mechanism as shown in  FIG. 3A  and  FIG. 5 , and the horse-shoe-like mechanism as shown in  FIG. 3B  and  FIG. 6 . 
   Referring to  FIG. 4 , the driving shaft locking means  60  includes a washer  61  and paw-like positioner  62 . The head side of washer  61  is blocked by longitudinal positioning step  26  of longitudinal passageway  21  of housing  20  after final assembly. The diameter of washer  61  is slightly greater than the diameter of longitudinal positioning step  26  of longitudinal passageway  21  of housing  20  so that, after assembly, washer  61  provides an axially forward directed retaining force to driving shaft  30 . Paw-like positioner  62  tightly presses the tail side of washer  61  after final assembly. The diameter of paw-like positioner is slightly greater than the diameter of longitudinal positioning step  26  of longitudinal passageway  21  of housing  20  so that, after assembly, paw-like retainer  62  provides an extra axially forward directed retaining force to driving shaft  30 . Paw-like positioner  62  may be made of a metal material, retainer toes  63  are bent backwards and splintered into the wall of housing  20  to provide a strong axially backward directed retaining force during operation of prophy angle  10 . 
   Referring to  FIG. 5  for an alternate driving shaft locking means  60  that is simply made up by a horse-shoe-like locker  64 . The detail structural features of the horseshoe locker  84  is further illustrated in  FIG. 6B . The horse-shoe-like locker  64  is inserted through horse-shoe-like locker head slot  27  on the wall of longitudinal passageway  21  of housing  20  and reaches to horse-shoe-like locker tail slot  28  on the other side of the wall of longitudinal passageway  21  of housing  20 . The front side of horse-shoe-like locker  64  is located at longitudinal positioning step  26  of longitudinal passageway  21  of housing  20  after assembly, and the horse-shoe-like locking means provides a strong longitudinal backward directed retaining force during operation of prophy angle  10 . Transverse locking is achieved by a special structure on the locker legs  65 . There exists a step  66  near the end of both locker legs, which ensures the transverse positioning of the horse-shoe-like locker  64 . The step depth is equal to the wall thickness of the housing so that when assembled, the edge of step  66  will stay against the inner wall of the housing. On the other side, two elastically bendable arms  67  and  69  are formed near the other ends of the legs  65  which ensure transverse positioning of the horse-shoe-like locker  64  on that side. The tip  68  of the locking means  60  is constructed such that, when assembled, the edge of tip  68  will stay against the other side of the inner wall of the housing. That transverse locking mechanism ensures horse-shoe-like locker  64  will not drop out as a result of any accidental forces exerted on it. The dimensions of horse-shoe-like locker  64  are such that horse-shoe-like locker  64  is positioned accurately to avoid any contact with shaft tail  34 . Details of how the parts of this locking means are related to the housing can further be referenced to  FIGS. 7A to 7C   
   Referring to  FIGS. 7A to 7C  for details of the driven rotor retainer  50  to maintain the driven rotor  40  stays in position under any conditions which would tend to pull it out of open end  29  of transverse passageway  22  of housing  20 . The driven rotor  40  is provided with a horse-shoe-like driven rotor retainer  50  that is firmly positioned next to rotor neck  42  of driven rotor  40  by two driven rotor retainer forks  51  through driven rotor retainer slot  24  on the wall of transverse passageway  21  of housing  20 . Thus, driven rotor retainer  50  is able to retain rotor head  41  without it dropping out during operation. In addition, there exists a retaining tongue  52  that can be elastically bent between the two retaining forks  51  in driven rotor retainer  50 . A retaining hook  53  exists at the tip of retaining tongue  52  that further ensures driven rotor  50  is not dropped out by any accidental forces exerted on it. Two retaining shoulders  54  extends out at the curve side of driven rotor retainer  50  that match the shape of driven rotor retainer slot  24  on the wall of transverse passageway  21  of housing  20 . These ensure that driven rotor retainer  50  cannot touch any parts of driven rotor  40  other than rotor head  41 . 
   In order to prevent possible rotational slipping between the prophy cup and the driven rotor during operation, a pair of sharp pointed splinters  46  is arranged circumferentially on the neck of the cup end of the driven gear rotor, upon which the snap-on prophy cup sits. Refer  FIG. 2 . The splinters  46  pierce into the rubber base of the snap-on prophy cup and force it to rotate with the driven gear rotator without the possible free spinning of the rotor within the prophy cup. 
   According to above descriptions, a dental prophylaxis angle enclosing in a housing is disclosed. The dental prophylaxis angle comprises a driving shaft engaging and translating a rotational movement to a driven rotor wherein a constant engagement is maintained between the driving shaft and the driven rotor by a first and second position retainers for retaining the driving shaft and the driven rotor at fixed positions respectively. In a preferred embodiment, the first and second position retainers are securely attached to the housing each at a fixed position. In another preferred embodiment, the first position retainer keeping the driving shaft from a horizontal shift and the second position retainers keeping the rotor from a vertical shift. In another preferred embodiment, the housing further having slits for adapting a part of the first and second position retainers for securely keeping the first and second position retainers at fixed positions. In another preferred embodiment, the housing further includes inner steps for mechanically retaining the first and second position retainers for restricting the first and second position retainers from a lateral movement inside the housing. In another preferred embodiment, the housing further includes inner space for adapting a portion of the driven rotor therein for mechanically retaining the rotor from tilting beyond a certain incline angle. 
   Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is not to be interpreted as exhaustive or limiting. Various alternations and modifications will no doubt become apparent to those skilled in the art after reading the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alternations and modifications as fall within the true spirit and scope of the invention.

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