The present invention relates to a disposable dental appliance and more particularly to a dental prophylaxis angle (or “prophy angle”) used for cleaning teeth, and more especially to those to be disposed of after each patient to avoid cross infection.
A conventional prophy angle is used in dental treatment to remove plaque and to polish the surface of the enamel of teeth. A prophy cup 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 clean a patient's teeth.
A typical drive mechanism is a gear connection between a driving gear shaft and a driven gear rotor at a right angle of 90 degrees. The driving shaft is rotated by a dental drive means of a dental tool (such as a dental handpiece) with speeds typically ranging from 2,500 to 4,500 rpm. The rotation is transferred to the driven rotor by the gearing mechanism resulting in rotation of the attached prophy cup at an angle, conventionally at a right angle.
To improve the stability, performance and feel and hand fatigue of the operator, an operating angle other than 90 degrees has been studied by the disclosures of previous patents such as U.S. Pat. 2008/0064007, 2008/0003537, 2006/0127844, U.S. Pat. Nos. 6,916,176, 5,902,107, 5,749,728, 5,571,012, 5,531,599, 5,503,555, 5,433,605, 5,423,679, 5,374,189, 5,328,369, 5,074,788, 4,681,540, 4,460,337 and 4,382,790. However, in the present market, those products exhibit cost weakness or vibration/noise problem because of the complicated mechanical structure used to transfer the rotation.
Thus, the present invention provides a non-90-degree gear structure with features that ensure the driving gear remains properly engaged to the driven gear while reduce the hand fatigue of the dental practitioner during operation.
The invention is directed to a dental prophy angle that has an integrally formed housing, which incorporates two gears (driving gear and driven gear) and a removable prophylaxis head attachment, also called the prophylaxis cup (or “prophy cup”), and which translates rotation from a dental power source to the head attachment through these gears. More specifically, the driving gear shaft, 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 at an angle. The entire prophy angle is made of plastic and is discarded after a single treatment, thus avoiding cross-contamination as well as the expense and inconvenience of sterilization.
One aspect of the invention is that the axes of the driving gear shaft and the driven gear rotor are not perpendicular to each other, facilitating teeth cleaning operations by allowing the prophy angle to easily reach all areas of the mouth and making practitioners feel more comfortable because the smaller bend in the body of the prophy angle allows them to maintain an ergonomically correct neutral wrist position to prevent the possible repetitive stress injuries, or cumulative micro trauma disorders, of the forearm, wrist and hand. The U.S. Government Bureau of Labor Statistics reported in 1994 that there were 92,576 cases annually involved days away from work due to repetitive motion and 55% affected the wrist.
Another aspect of prominent benefit of the present invention lies in the mating of the gears. Due to the necessary existence of operating tolerances in the sizing of the gears, there is some play in the gear contact. However, during operation, the inner contact engagement makes the mating of the gears closer as the driven rotor is pressed toward to the driving shaft by the force transmitted from the prophy cup.
A further aspect of the invention is a horseshoe-like positioner which acts as a driving shaft locking means. It consists of two forks perpendicular to the central axis of the tail-section passageway of the housing, where the separation gap between the forks is greater than the diameter of the driving shaft tail, and the horseshoe-like positioner is permanently located through a slot on the housing next to the shoulder of the driving shaft to ensure a secure assembly and to locate the driving shaft axially.
Similarly, the rotor head portion is held by another horseshoe-like retainer within the rotor neck to ensure that the rotor gear stays connected with the driving shaft gear head. The diameter of the rotor head is greater than the separation gap of the forks of the horseshoe-like driven rotor retainer to ensure that the rotor cannot come out, while the diameter of the rotor neck is smaller than the separation gap to ensure low operating friction and accurate rotation around the rotor axis during operation.
Thus, the arrangement of the horseshoe-like retainer provides a secure means for preventing the driven rotor from coming out while allowing it to rotate freely without much extra friction. Without it, the inner-side contact gearing arrangement would tend to eject the driven rotor from the housing because the gear on the driving shaft applies an outward force to the rotating driven gear.
Other details and features of the invention will be in part apparent and in part pointed out hereinafter.
The invention will be further described in conjunction with the attached drawings of which:
After assembly, the relative positions of the driving shaft 20 and the driven rotor 30 are shown in
The driving gear shaft 20 and the driven gear rotor 30 have tooth-matched gears that tranlate rotation of the driving gear shaft into rotation of the driven gear rotor.
In view of the above, it will be seen that the objects of the invention are achieved.
Although specific examples of the present invention and its application are set forth herein, they are not intended to be exhaustive or limiting of the invention. These illustrations and explanations are intended to acquaint others skilled in the art with the invention, its principles, and its practical application, so that others skilled in the art may adapt and apply the invention in its numerous forms, as may best suit the requirements of a particular use.