Patent Description:
A dental turbine handpiece includes a barrel with an air turbine received therein. The air turbine is blown by compressed air to rotate within the barrel and generate power. The air turbine is attached around a central shaft, and a dental tool, such as a bur, is mounted at one end of the central shaft that extends out of the barrel. The rotating air turbine drives rotation of the central shaft, which in turn drives the bur to rotate. For the dental turbine handpieces currently available on the market, during operation, their central shafts are driven by the air turbines to rotate at a speed up to <NUM>,<NUM> to <NUM>,<NUM> RPM.

However, during treating patients, doctors often need to stop the turbine handpiece to replace the bur or observe patient's oral condition. After shutdown, the central shaft and the air turbine will keep rotating for <NUM>-<NUM> seconds due to inertia, which causes a negative pressure to be generated inside the air cylinder of the turbine handpiece, such that blood, water, and various sundries produced by grinding of teeth are sucked back into the barrel. On one hand, the sucked sundries may enter into a bearing of the handpiece, which may seriously affect safety and service life of the bearing; on the other hand, the blood and water may enter into the cylinder and cause pollution, which may result in cross-infection among patients even if disinfection is subsequently performed.

<CIT> discloses a high-speed gas turbine handpiece, which includes a handpiece and a needle. The handpiece comprises a plurality of dust-proof components provided between a machine head and the needle to prevent foreign matter from entering the machine head.

In view of the above, a dental handpiece that can effectively prevent suck-back after shutdown is provided.

According to the invention, a dental handpiece includes a barrel, an air turbine, a central shaft, a bearing, and a seal. The barrel defines an accommodating cavity therein and includes an axial open end in communication with the accommodating cavity. The air turbine is rotatably arranged in the accommodating cavity of the barrel. The central shaft is secured to the air turbine to rotate with the air turbine. The bearing is mounted in the barrel adjacent the axial open end of the barrel and supporting the central shaft for rotation. The seal is trumpet-shaped and includes a sealing portion sleeved over an outer cylindrical surface of the central shaft and a mounting portion surrounding the sealing portion, the mounting portion being arranged and flattened between the open end of the barrel and the bearing.

According to the invention, a bearing seat is provided in the barrel, the bearing seat is formed with a bearing hole and an annular groove at an axial end of the bearing seat facing the air turbine, the bearing is disposed in the bearing hole, the mounting portion is received in the annular groove and sandwiched between the bearing and the bearing seat.

According to the invention, a depth of the annular groove in an axial direction of the barrel is smaller than a thickness of the mounting portion in the natural state.

In one embodiment, the mounting portion has a circular or elliptical cross section, and the annular groove has a square or rectangular cross section.

In one embodiment, a flat gasket is provided between an axial end of the bearing and the bearing seat, and the mounting portion is sandwiched between the flat gasket and the bearing seat.

In one embodiment, the aforementioned bearing is a first bearing, the aforementioned bearing seating is a first bearing seat, the dental handpiece further comprises a second bearing and a second bearing seat, the first bearing and the second bearing are respectively arranged at opposite axial sides of the air turbine, the first bearing is disposed in the first bearing seat and close to the open end of the barrel while the second bearing is disposed in the second bearing seat and away from the open end of the barrel, and an elastic member is provided between an axial end of the second bearing and the second bearing seat.

In one embodiment, an outer edge of a front end of the first bearing seat and an inner edge of the front end of the barrel form matching steps, which axially abut against each other to form a limiting arrangement.

In one embodiment, an outer wall surface of the second bearing seat and an inner wall surface of the rear end of the barrel form matching threads, which are screwed and fixed to each other.

In one embodiment, inner rings of the first bearing and second bearing clamp the air turbine, and the elastic member is compressed and deformed to generate a forward pre-tightening force, which acts on the seal via the second bearing, the air turbine, the first bearing and the flat gasket, such that the seal is clamped and flattened.

According to the invention, the sealing portion is deformable to separate from the outer cylindrical surface of the central shaft or closely contact the outer cylindrical surface of the central shaft depending on a pressure difference between interior and exterior of the barrel.

In one embodiment, the seal is an elastic component with a Shore A hardness of <NUM>-<NUM> degrees.

In one embodiment, the sealing portion extends from an inner edge of the mounting portion radially inward and axially toward the open end of the barrel.

In one embodiment, a radially inner side surface of the sealing portion defines a through hole at a center of the sealing portion, the central shaft passes through the through hole, the radially inner side surface is a cylindrical surface, and the cylindrical surface is in close contact with the outer cylindrical surface of the central shaft when the dental handpiece is shutdown.

In one embodiment, the mounting portion having a greater thickness along an axial direction of the barrel than the sealing portion; wherein, along the axial direction of the barrel, the mounting portion has a thickness of <NUM>-<NUM> while the sealing portion has a thickness of <NUM>-<NUM>.

In one embodiment, the dental handpiece includes a handle connected to the barrel, a main air passage and an exhaust passage are formed in the handle corresponding to the air turbine, and both the main air passage and the exhaust passage are communicated with the accommodating cavity for inflow and outflow of compressed air, respectively.

In summary, the dental handpiece of the present application includes a seal that can expand outwardly or contract inwardly by corresponding deformation of the seal under the action of a pressure difference between interior and exterior of the barrel, such that during operation, the seal is separated from the central shaft to facilitate the rotation of the central shaft, and after shutdown, the seal and the central shaft closely contact each other to form a good braking and sealing effect, thereby preventing foreign matters from being sucked back into the barrel. This on one hand ensures the safety and service life of the bearing, and on the other hand avoids cross-infection among patients.

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The accompanying drawings exemplarily show one or more embodiments of the present invention so as to make the understanding of the technical solutions disclosed in the present invention more accurate and thorough. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments described below.

As shown in <FIG>, a dental handpiece according to an embodiment of the present invention includes a head <NUM> and a handle <NUM> connected to the head <NUM>. The handle <NUM> is convenient for users, such as a dentist, to hold. The head <NUM> includes a barrel <NUM> to which the handle <NUM> is connected, an air turbine <NUM> rotatably provided in the barrel <NUM>, a central shaft <NUM> secured to the air turbine <NUM>, a bearing <NUM> supporting the central shaft <NUM> for rotation, and a seal <NUM>.

The barrel <NUM> generally has a hollow cylindrical structure, and is formed with an accommodating cavity <NUM> therein for installing the air turbine <NUM>. Opposite axial ends (i.e. front and rear ends) of the barrel <NUM> are formed with openings respectively, and a rear cover <NUM> is provided at a rear end of the barrel <NUM>. The central shaft <NUM> is fixedly inserted through a center of the air turbine <NUM>, and its front and rear ends each extend out of the air turbine <NUM>. The rear end of the central shaft <NUM> is rotatably supported at the center of the rear cover <NUM>, and the front end thereof extends out of the barrel <NUM> through the opening located at the front end of the barrel <NUM>. A medical tool such as a bur <NUM> is connected to the front end of the central shaft <NUM>. Corresponding to the air turbine <NUM>, a main air passage <NUM> and an exhaust passage <NUM> are formed in the handle <NUM>, and both the main air passage <NUM> and the exhaust passage <NUM> are communicated with the accommodating cavity <NUM> for inflow and outflow of compressed air, respectively.

When the dental handpiece operates, the compressed air is delivered into the accommodating cavity <NUM> through the main air passage <NUM> to drive the air turbine <NUM> to rotate at a high speed, thereby driving the central shaft <NUM> to rotate, which in turn drives the medical tool, such as the bur <NUM>, to grind teeth. Usually, during operation, the central shaft <NUM> may rotate at a speed up to <NUM>,<NUM> to <NUM>,<NUM> RPM. The compressed air flows along wall surfaces of the accommodating cavity <NUM> to drive the air turbine <NUM> to rotate, and finally flows out of the accommodating cavity <NUM> through the exhaust passage <NUM>. In order to ensure effectiveness of torque transmission between the air turbine <NUM> and the central shaft <NUM>, a circumferentially limiting arrangement may be formed between the air turbine <NUM> and the central shaft <NUM> by means of keying, snapping, etc., such that the air turbine <NUM> and the central shaft <NUM> can rotate synchronously under the driving of the compressed air.

Two bearings <NUM> are provided, which are referred to as a first bearing 14a and a second bearing 14b hereinafter for ease of description. The first bearing 14a and the second bearing 14b are respectively sleeved over the front end and rear end of the central shaft <NUM>, and are respectively located on the front and rear sides of the air turbine <NUM> in the axial direction, to ensure balance and stability of the rotation of the air turbine <NUM> and the central shaft <NUM>, thereby reducing the generation of noise. In this embodiment, both the first and second bearings 14a, 14b are ball bearings, which form rolling friction during the rotation of the central shaft <NUM>, thereby effectively reducing wear. It should be understood that the first and second bearings 14a, 14b may also be sliding bearings, ceramic bearings, etc.; in addition, the first and second bearings 14a, 14b may also be different types of bearings, which are not limited to the specific embodiments described herein.

The first bearing 14a is assembled into the barrel <NUM> via a first bearing seat <NUM>, and the second bearing 14b is assembled into the barrel <NUM> via a second bearing seat <NUM>. In this embodiment, an outer edge of a front end of the first bearing seat <NUM> and an inner edge of the front end of the barrel <NUM> form matching steps, which axially abut against each other to form a limiting arrangement; an outer wall surface of the second bearing seat <NUM> and an inner wall surface of the rear end of the barrel <NUM> form matching threads, which are screwed and fixed to each other; the rear cover <NUM> is hooked and connected to an end of the second bearing seat <NUM>. It should be understood that the first bearing seat <NUM> and/or the second bearing seat <NUM> may be integrally formed in the barrel <NUM>, or the second bearing seat <NUM> and the rear cover <NUM> may be a unitary structure.

A first bearing hole is formed at a center of a side of the first bearing seat <NUM> facing the air turbine <NUM> for assembling the first bearing 14a. Preferably, a flat gasket <NUM> is provided between the first bearing seat <NUM> and a front axial end of the first bearing 14a. A seal <NUM> is sleeved over the central shaft <NUM> and located on the front side of the first bearing 14a, particularly, in this embodiment, sandwiched between the flat gasket <NUM> and the first bearing seat <NUM>, for providing sealing between the first bearing 14a and the front end of the barrel <NUM> during the shutdown of the dental handpiece. It should be understood that the flat gasket <NUM> provided between the first bearing seat <NUM> and the first bearing 14a may be omitted, and then the seal <NUM> is sandwiched between the first bearing 14a and the first bearing seat <NUM>.

A second bearing hole is formed at a center of the second bearing seat <NUM> for assembling the second bearing 14b. An elastic member <NUM>, such as an elastic washer, is provided between the second bearing seat <NUM> and a rear axial end of the second bearing 14b. In assembly, the first bearing seat <NUM>, the seal <NUM>, the flat gasket <NUM>, the first bearing 14a, the central shaft <NUM> and the air turbine <NUM> are sequentially assembled into the barrel <NUM>; the elastic member <NUM> and the second bearing 14b are assembled into the second bearing seat <NUM>, and then the second bearing seat <NUM> is screwed to the barrel <NUM>. During the process of screwing, inner rings of the first bearing 14a and second bearing 14b clamp the air turbine <NUM>, the elastic member <NUM> is compressed and deformed to generate a forward pre-tightening force, which acts on the seal <NUM> via the second bearing 14b, the air turbine <NUM>, the first bearing 14a and the flat gasket, such that the seal <NUM> is clamped and flattened.

Also referring to <FIG>, the seal <NUM> is made of fluorine rubber, hydrogenated nitrile rubber or other materials, and preferably has a Shore A hardness of <NUM>-<NUM>, which may provide advantages of oil resistance, abrasion resistance and high temperature resistance, and also can be fabricated directly by injection-molding and thus have low production cost. For example, the seal <NUM> has a Shore A hardness of <NUM> degrees. The seal <NUM> generally has a ring shape, and includes a mounting portion <NUM> located on an outer edge thereof, and a sealing portion <NUM> located inside the mounting portion <NUM>. A radially inner side surface of the sealing portion <NUM> defines a through hole <NUM> at a center of the sealing portion <NUM>, for the central shaft <NUM> to pass therethrough. The radially inner side surface serves as a working surface <NUM>, and is in close contact with the outer cylindrical surface of the central shaft <NUM> when the dental handpiece is shutdown. Preferably, the through hole <NUM> is a cylindrical hole, and the working surface <NUM> is a cylindrical surface. The working surface <NUM> has a diameter D1 of preferably <NUM>-<NUM>, which is slightly smaller than the diameter of the central shaft <NUM>.

The mounting portion <NUM> may be generally annular with a circular or elliptical cross section, and resembles an O-ring. In this embodiment, the cross section of the mounting portion <NUM> is circular in a natural state, and the circular cross section has a diameter D2 of <NUM>-<NUM>, that is, a thickness of the mounting portion <NUM> in the axial direction of the barrel <NUM>/central shaft <NUM> is <NUM>-<NUM>. Preferably, an annular groove <NUM> is formed in the first bearing seat <NUM> at a side of the first bearing seat <NUM> facing the air turbine <NUM>, for receiving and positioning the mounting portion <NUM> of the seal <NUM>. As shown in <FIG>, the annular groove <NUM> has a square or rectangular cross section, which is different from the cross section of the mounting portion <NUM> and can provide a space for the deformation of the mounting portion <NUM>. An axial depth of the annular groove <NUM> is smaller than the thickness D2 of the mounting portion <NUM> in the natural state. In an assembled state, the mounting portion <NUM> is sandwiched between the flat gasket <NUM> and the first bearing seat <NUM> and is flattened, such that the mounting portion <NUM> has a roughly elliptical cross section, as shown in dashed lines in <FIG>. After being flattened, the mounting portion <NUM> has a thickness D3 equivalent to the axial depth of the annular groove <NUM>, and thus has a difference of <NUM>-<NUM> from its original thickness D2.

The sealing portion <NUM> is generally trumpet-shaped, and extends radially inward from the inner edge of the mounting portion <NUM> and axially toward the front end of the barrel <NUM>. The sealing portion <NUM> is tapered from back to front in the axial direction of the seal <NUM>. Preferably, the thickness of the sealing portion <NUM> in the axial direction of the barrel <NUM> is smaller than the diameter of the mounting portion <NUM>, so that the sealing portion <NUM> may have better elastic deformation ability while the mounting portion <NUM> may be fixed better. Preferably, the thickness T of the sealing portion <NUM> in the axial direction of the barrel <NUM>/the central shaft <NUM> is <NUM>-<NUM>. In this embodiment, the sealing portion <NUM> is a curved structure arched toward the central shaft <NUM>, which corresponds to an arc surface radius R of <NUM>-<NUM>.

As shown in <FIG>, when the dental handpiece of the present invention does not operate, the working surface <NUM> of the sealing portion <NUM> closely contacts the outer cylindrical surface of the central shaft <NUM>. Since the diameter of the working surface <NUM> is slightly smaller than that of the central shaft <NUM>, the seal <NUM> may generate elastic deformation when the seal <NUM> and the central shaft <NUM> are assembled. In the assembled state, the working surface <NUM> of the seal <NUM> closely contacts the outer cylindrical surface of the central shaft <NUM>. The close contact between the working surface <NUM> and the outer cylindrical surface of the central shaft <NUM> form a seamless connection therebetween, which isolates the components inside the barrel <NUM>, especially the first bearing 14a and the second bearing 14b, from the outside, and ensures cleanness of the components inside the barrel <NUM>. It should be noted that the outer cylindrical surface of the central shaft <NUM> mentioned in the present application refers to an outer circumferential wall surface of the central shaft <NUM>, which is different from an axial end surface or a chamfered surface of the central shaft <NUM>, and generally has a cylindrical shape. However, it is not excluded that the outer circumferential wall surface of the central shaft <NUM> may be formed with any small notch and other structure, that is, the outer cylindrical surface of the central shaft <NUM> mentioned in the present invention is not limited to a complete cylindrical surface.

As shown in <FIG>, when the dental handpiece of the present invention operates, compressed air is introduced into the barrel <NUM> to drive the air turbine <NUM> and the central shaft <NUM> to rotate, and a small amount of the compressed air flows through a gap of the first bearing 14a to the seal <NUM>, since the pressure of the compressed air is far more than the pressure of the external environment, the compressed air exerts an outward force on the sealing portion <NUM>, which causes the sealing portion <NUM> to deform and expand outwards, and forms a gap between the working surface <NUM> of the sealing portion <NUM> and the outer cylindrical surface of the central shaft <NUM>, so that the rotation of the central shaft <NUM> is not restricted by the seal <NUM>, which effectively reduces friction and ensures the high-speed rotation of the central shaft <NUM>. During operation of the dental handpiece, due to the pressure difference between the inside and outside of the barrel <NUM>, external blood, impurities, etc. cannot enter the barrel <NUM> through the gap between the seal <NUM> and the central shaft <NUM>.

As shown in <FIG>, when the dental handpiece of the present invention is shutdown during use, the central shaft <NUM> and the air turbine <NUM> will continue rotating due to inertia. During shutdown, firstly, because no compressed air is delivered to the accommodating cavity <NUM> anymore, the air pressure in the barrel <NUM> drops rapidly, and the sealing portion <NUM> recovers from the deformation and tightly wraps around the central shaft <NUM>; after that, due to the continuing rotation of central shaft <NUM> and the air turbine <NUM>, air is discharged out of the barrel <NUM>, and thus a negative pressure is formed in the barrel <NUM> and the external ambient air exerts an inward force on the sealing portion <NUM>, so that the sealing portion <NUM> deforms and contracts inward, and further tightly wrap around the central shaft <NUM> and, as a result, a sufficiently strong force is formed between the working surface <NUM> and the outer cylindrical surface of the central shaft <NUM>. On one hand, the central shaft <NUM> is braked so as to quickly stop rotating. For example, it has been tested for the dental handpiece of the present invention that the shaft <NUM> can stop rotating within <NUM> seconds after shutdown. On the other hand, a sufficiently strong force is provided to prevent foreign matters, including blood, impurities, debris, etc., from entering the barrel <NUM>, that is, to avoid the damage to the internal components, particularly the bearings 14a and 14b, and also avoid cross-infection among patients.

Claim 1:
A dental handpiece comprising:
a barrel (<NUM>) defining an accommodating cavity (<NUM>) therein and comprising an axial open end in communication with the accommodating cavity (<NUM>);
an air turbine (<NUM>) rotatably arranged in the accommodating cavity (<NUM>) of the barrel;
a central shaft (<NUM>) secured to the air turbine (<NUM>) to rotate with the air turbine (<NUM>);
a bearing (<NUM>) mounted in the barrel (<NUM>) adjacent the axial open end of the barrel (<NUM>) and supporting the central shaft (<NUM>) for rotation; and
a seal (<NUM>) being trumpet shaped and comprising a sealing portion (<NUM>) sleeved over an outer cylindrical surface of the central shaft (<NUM>) and a mounting portion (<NUM>) surrounding the sealing portion (<NUM>), wherein the sealing portion (<NUM>) is deformable to separate from the outer cylindrical surface of the central shaft (<NUM>) or closely contact the outer cylindrical surface of the central shaft (<NUM>) depending on a pressure difference between interior and exterior of the barrel (<NUM>);
wherein a bearing seat (<NUM>) is provided in the barrel (<NUM>), the bearing seat (<NUM>) is formed with a bearing hole and an annular groove (<NUM>) at an axial end of the bearing seat (<NUM>) facing the air turbine (<NUM>), the bearing (<NUM>) is disposed in the bearing hole, the mounting portion (<NUM>) is received in the annular groove (<NUM>) and sandwiched between the bearing (<NUM>) and the bearing seat (<NUM>);
wherein a depth of the annular groove (<NUM>) in an axial direction of the barrel (<NUM>) is smaller than a thickness of the mounting portion (<NUM>) in the natural state of the mounting portion (<NUM>).