US3469318A - Dental handpiece instrument - Google Patents

Description

Sept. 30, 1969 J A. SAFFIR DENTAL HANDPIECE ms'rnumnm Filed Oct. 28, 1964 INVENTOR J4me 14. SIP/IR United States Patent C) US. C]. 32-27 6 Claims This invention relates primarily to improvements in dental handpiece instruments such as are used by the dental profession for drilling in the oral cavity. Similar instruments also are used by the medical profession for trephinging and other bone surgery. Some of the basic requirements of instruments of these types are high speed, small size, suitable torque, and reasonable durability.

More particularly, this invention relates to a novel construction of the power unit for energizing handpieces of the foregoing type which comprises a bladed or finned impeller turbine situated in the head of the handpiece and driven by compressed gaseous fluid.

Dental handpieces and similar instruments presently available primarily achieve high speed by the employment of substantial volumes of air, part of which is discharged through the bearings for the turbine to cool the bearings and also lubricate them by an oil mist entrained in the driving air. To obtain suitable lubrication by such means, it is common practice at present to discharge driving air through the bearings and then through ports or other means at opposite ends of the head of the instruments. Thus, in the normal use of a dental handpiece, a substantial amount of air is discharged into the oral cavity, not infrequently causing discomfort to the patient.

The principal object of this invention is to provide a dental handpiece or similar instrument with considerably more torque than is available in present air-turbine type handpieces, yet using less air pressure per ounce of torque than in such present handpieces.

Another object of this invention is to provide a dental handpiece or similar instrument operable at speeds up to 475,000 r.p.m. produced by air pressures substantially less than pressures now required to develop corresponding speeds in available similar instruments.

A further object of this invention is to provide a dental handpiece or similar instrument which produces only a low pitched hum which is not offensive or objectionable to either a patient or doctor as compared with the high pitched, shrill, piercing and unpleasant noise that now disturbs patient and doctor during the use of presently available turbine handpieces.

Still another object of this invention is to provide more efiicient engagement of the driving air with the rotor, in contrast to the conventional bucket-type turbine widely used in this art at present. Bucket-type rotors are inefficient and wasteful in converting the energy of the compressed air into torque for the rotor, primarily because the driving air in a bucket-type turbine engages said individual bucket but once and then is discharged.

A still further object of the invention is to provide a multi-stage axial type turbine rotor receiving driving air from one end and provided with a plurality of sets of axially arranged finned turbine members to utilize continuous expansion of the compressed driving air between each member until discharged from the opposite end of the turbine.

Still another object of the invention is to utilize a turbine of the type in which the air enters the turbine chamber from a plurality of inlet ports situated adjacent one end of the turbine and the driving air, in passing through the turbine, energizes a plurality of sets of impeller fins before it is exhausted and expelled, whereby about half the air pressure utilized in conventional air-turbine type "ice handpieces produces highly satisfactory torque for dental and other medical purposes, and if greater torque is re quired, increasing the air pressure to the limits required at present by such conventional handpieces will produce completely adequate increased torque when required, such as for bone surgery.

Details of the foregoing objects and of the invention, as well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawing comprising a part thereof.

In the drawing:

FIG. 1 is a side elevation of an exemplary dental handpiece of the air-turbine type embodying the principles of the present invention.

FIG. 2 is a fragmentary vertical sectional elevation of the head end of the handpiece shown in FIG. 1, on a much larger scale than in the latter figure.

FIG. 3 is a side elevation, partly broken away, showing the turbine cartridge per se.

FIG. 4 is a top plan view of the turbine cartridge of FIG. 3.

Referring to the drawing, there is illustrated in FIG. 1 a side elevation of a typical dental handpiece of the type to which the present invention is applicable. It will be understood, however, that while a dental handpiece has been selected for specific illustration and description of the present invention, such election is not intended to restrict the invention solely to incorporation in dental handpieces since wider uses are possible in other medical fields, such as in bone surgery and, more particularly, as a more effective instrument than the hand-operated devices presently employed in trephining.

A suitable instrument of the type to which the present invention is applied comprises a handle 10. In FIG. 1, the handle 10 has attached to the forward end thereof a neck 12, the outer end of which is fixedly connected to a substantially cylindrical head or housing 14 having an internal, preferably cylindrical cavity 16 extending inwardly from the threaded opening 18 in the normally upper end of the head 14. Such opening normally is closed by a threaded cap 20. The lower end of the head 14 has a preferably integral bottom 22 provided with a central opening 24 for purposes to be described. Though the bottom 22 preferably is integral with the head 14, it is to be understood that, within the spirit of the invention, such bottom can be removably connected to the lower end of the head, if desired, by any appropriate means, such as screw threads.

The handle 10 and the extension comprising neck 12 include continuous conduit means between opposite ends thereof, these being fragmentarily illustrated in vertical sectional manner in FIG. 2. As shown, the neck 12 comprises solid material having conduit bores 26 and 28 therein, which terminate at one end by communicating with cavity 16 and the other ends thereof respectively are connected to preferably tubular conduits 30 and 32, the outer ends of which are shown in FIG. 1. The outer ends of the conduit means comprising bore 26 and conduit 30 are connectable to a source of compressed air or other suitable gas, under pressure, for purposes of delivering driving gas or air to the cavity 16 of the handpiece, while conduit means comprising bore 28 and conduit 32 are arranged to receive and discharge exhaust air or gas from cavity 16. If desired, the handle 10 may be of a tubular nature and the opposite end of the bore 28 from that shown in FIG. 2 may discharge directly into the tubular handle in lieu of employing conduit 32 for purposes of removing exhaust air or gas from cavity 16. Further, dental handpieces in particular usually are provided with means for discharging a jet or spray of water from the lower portion of the head 14 and, to this end, the present construction illustrates a suitable tubular conduit means, illustrated specifically in the form of a bore 34 having a discharge opening 36 and the opposite end thereof being connected to the inner end of a water supply tube 38 provided in handle 10, the outer end of which is shown in FIG. 1. Said outer end is connectable to any appropriate source of water at desired pressure.

In association with the above-described structure, the present invention primarily contemplates the employment of an insertable and removable cartridge unit or assembly 40 which is removably positioned within the cavity 16 and includes all the movable elements of the handpiece. The cartridge unit 40 is composed of a preferably cylindrical shell 42, the upper portion of which has an outer diameter provided with sufficient clearance relative to the inner diameter of cavity 16 as to permit ready reception but accurate positioning of the cartridge unit within the cavity 16. The lower portion of the shell 42 has a reduced outer diameter portion 44 for purposes of providing between the exterior of said portion and the walls defining the cavity 16 an exhaust plenum space 46 which is annular and the upper portion of which communicates with the adjacent end of the conduit bore 28 for exhaust air.

The upper end of shell 42 abuts an annular air inlet and distributing member 48, the abutting surfaces of the member 48 and shell 42 preferably telescopically interlocking, as shown in FIG. 2, to insure axial alignment of the same at all times. Arranged around the member 48 at evenly spaced distances circumferentially and adjacent the periphery of the member is a plurality of air distributing ports 50 which, as is particularly apparent from FIGS. 2 and 3, extend downwardly and inwardly toward the bottom of the head 14, and also are disposed otherwise at an angle to the axis of the cartridge unit 40, as is clearly shown in FIG. 3, for purposes of suitably directing the air from the annular air-distributing space 52 between cap 20 and member 48 to the upper portion of the interior of shell 42. Space 52 communicates with and receives driving air under pressure from conduit bore 26.

Member 48 also serves additionally as a bearing seat and, in this regard, is provided with an annular seat 54, which receives the outer race of the upper antifriction bearing 56, preferably with a relatively snug fit. It is preferred that the bearing 56 be of the self-lubricating, sealed type and the sectional view thereof shown in FIG. 2 is intended to illustrate said type of bearing, though the invention is not to be restricted to the use of that particular type bearing.

The lower end of the reduced diameter portion 44 of shell 42 abuts a lower bearing seat 58, which has a diameter similar to member 48 and is axially aligned therewith. Such alignment is maintained by an interfitting relationship with the lower end of shell 42, as is shown in sectional detail in FIG. 2. The lower bearing seat 48 has an annular seat 60 extending thereinto from the lower end thereof for purposes of receiving the outer race of lower antifriction bearing 62, which preferably is identical with the upper bearing 56, both of said bearings having inner and outer races respectively provided with opposed raceways receiving therebetween rotatable antifriction members, such as the balls shown in FIGS. 2 and 4. The outer race of the lower bearing 62 also preferably is received snugly within the annular seat 60 of the lower bearing seat 58.

Extending between and rotatably supported by the upper and lower bearing 56 and 62 is a turbine rotor 64 comprising a shaft 66 having an enlarged intermediate hub 68 and one end of the shaft 66 has a threaded bore 70 for purposes of receiving the shank of a dental tool directly or, if desired, any suitable type of chuck may be inserted within the bore, either in addition to or in lieu of the threads, for purposes of removably connecting a dental tool to the shaft of the rotor. From FIG. 2, it also will be seen, in the fragmentarily illustrated portion of the upper end of shaft 66, that the bore 70 extends substantially to the upper end of the shaft and terminates in an air escape hole 72 for purposes of preventing a piston effect when inserting a tool shank within the bore. In this regard, it will be seen that there preferably is a seat 74 within the inner face of the cap 20 to engage the upper end of the outer face of upper bearing 56, said seat also having a relieved central area 76 provided with a central opening 78, primarily to permit the insertion of a pushout member in the event a dental tool should become broken off within the bore 70 and require removal.

In opposition to the seat 74 within the cap, the bottom 22 of head 14 is provided with an annular seat 80 which receives and accurately positions the lower end of the outer race of the lower bearing 62, said seat likewise being provided with a relieved central area 82.

The hub 68 of the turbine rotor is provided with a plurality of circular rows of turbine blades 84 which are relatively thin and the same havevanes on the peripheries thereof which are twisted from a plane at the roots thereof which extends transversely to the axis of the rotor so that the outer ends thereof are disposed, uniformly at the same angle with respect to said transverse plane, said angle being within the range between 15 and 30 and the gaps between adjacent edges of successive vanes being quite small. Also, the inner surface of shell 42, being stationary with'respect to head 14, functions as a stator with respect to the tips of the vanes on blades 84. To produce a satisfactory stator etfect, it is preferred that the space between the tips of the vanes and the inner surface of he shell 42 be minimum and preferably not substantially in excess of .0005 inch in view of the fact that in a satisfactorily operated rotor of the type illustrated and described, the outer diameter of the vaned portion of the rotor is only approximately .250 inch and the length of the hub is only slightly in excess of such dimension.

One expedient for forming the rotor, and especially the vaned portion thereof, is to form the shaft and hub integrally from a single piece of metal, and machine the same to provide a series of evenly spaced and parallel flanges having an outer diameter slightly in excess of that desired for the length of the vanes. Said flanges then are slit by a very narrow milling cutter, radially and parallel to the axis of the rotor, followed by uniform twisting of each of the projecting vanes thus formed. Accordingly, it will be seen that each vane, in plan view, is of a so-called butterfly wing shape, being substantially wider at the tip than at the root. Following the twisting of the vanes, the entire rotor then is ground carefully so that the periphery of all of the vanes lies substantially exactly within a common cylindrical configuration outlined by the ends of the vanes and corresponding to the cylindrical inner surface of shell 42, but slightly less in diameter than such inner surface.

Another expedient for forming the vaned rotor 64 is to press-fit onto the shaft 70 a series of collars of uniform outer diameter equal to that of hub 74 with a series of blades discs disposed therebetween of a thickness equal to that of the vanes on the blades or discs 84. The vanes could be either formed on the blades or discs 84 prior to assembly or after assembly, as desired, followed by grinding to provide an outer periphery on each vane disposed within a common cylindrical outline as described above with regard to the foregoing expedient.

By reference to FIG. 2, it also will be seen that the length of the vanes of blades 84 preferably is less than half the diameter of the hub 68 of the rotor 64, whereby, in view of such arrangement, together with the relatively small gap between adjacent vanes and the very close space tolerance between the tips of the vanes and the inner surface of cylindrical shell 42, a high moment arm is, provided to develop the force exerted by the turbine, thereby resulting in high efiiciency of operation for the amount of air consumed to drive the turbine and substantial economy in the amount and pressures of the driving air required.

Further, providing a plurality of rows of vanes on the axially spaced blades 84 produces a multi-stage turbine embodying a plurality of expansion stages respectively between each pair of adjacent rows of vanes. As a result, as compared with existing dental handpieces and the like employing an air turbine either of the axial or radial type, considering one of such existing turbines of comparable size to the turbine illustrated and described herein, substantially equal speeds are developed by the latter when consuming air at less pressure than that required by conventional air-turbine type handpiece's. Further, highly improved torque values are attainable by the multi-stage type turbine of the present invention than by the conventional tangential type rotors or single stage axial type rotors in conventional air-turbine type handpieces. Of substantial further importance is the fact that the multi-stage type of turbine employed in the present invention produces only a very low pitched hum, as distinguished from a high pitched, shrill and piercing unpleasant noise produced by substantially all air-turbinetype conventional handpieces presently in use.

Part of the efiieiency of the multi-stage type turbine of the present invention is attributed to the fact that as the air enters the turbine cavity within shell 42 at evenly spaced locations and at substantially even pressures from the plurality of inlet ports 50, it successively engages the vanes of the various circular rows thereof on plates 84, expanding continuously between each row of vanes, whereby maximum work is derived from such air before the same emerges from the lowermost vane's on the blade 84, following which the air discharges simultaneously through the plurality of exhaust ports 86 adjacent the lower end of the reduced diameter portion 44 of shell 42. In view of the capacity of the annular exhaust plenum chamber or space 46 and its ready accessibility to the discharge ports 86, the spent driving air readily is exhausted from the head 14 by the exhaust air directly passing from the space 46 to the conduit bore 28 which, as will be seen especially from FIG. 2, is preferably of a greater diameter than inlet air conduit bore 26.

In view of the bearings 56 and '62, respectively adjacent opposite ends of head 14, preferably being of the sealed and self-lubricating type, very little if any air from the turbine chamber within shell 42 escapes either from the bore 78 in cap 20 or through the preferably slight clearance space between the central opening 24 in the bottom of the head 14 and the exterior surface of the lower end of shaft 66. However, in the event it is not desired to use sealed and self-lubricated bearings, so-called open type radial antifriction bearings may be employed and, under such circumstances, a certain amount of the air within the rotor cavity will escape through the space between the concentric races of each of the bearings for discharge through the bore 78 and space between opening 24 and the lower end of shaft 66. Under such circumstances, lubrication of the bearings can be effected by an oil mist being dispersed within the driving air, similar to the kind of lubrication now employed in most conventional airturbine type handpieces and the like.

The inner races of each of the bearings 56 and 62 preferably are press-fitted onto the shaft 66 from the opposite ends thereof, in such manner that the raceways within the concentric races of each bearing are transversely opposite each other and are so maintained due to the frictional engagement of the inner races of the bearings upon the opposite ends of the rotor shaft, and the spacing of the outer races by means of the seat members 48 and 58, and shell 42, which engages said seat members at the opposite ends thereof to maintain a constant axial dimension between the bearing seats 54 and 60 which receive the outer races of said upper and lower bearings.

In view of the further fact that the driving air enters the turbine cavity within shell 42 adjacent the upper end thereof and expands progressively toward the lower end of such cavity, a certain amount of thrust resistance is afforded by the air under pressure, thereby aiding the inherent thrust effect of the anti-friction bearings 56 and 62, which is provided to resist axial movement of the rotor shaft 66 when using the dental tool or other type of medical instrument carried by the projecting lower end of the turbine shaft 66.

Although the bearing antifriction members, as viewed in FIG. 4, are illustrated as comprising a full complement, without the employment of a spacer, it is to be understood that, if desired, a lesser number of antifriction members may be employed, together with an appropriate spacer ring or the like.

In view of the particular direction at which the air inlet ports 50 are arranged, as readily can be visualized from FIGS. 2-4, it will be seen that the incoming air engages the vanes of the uppermost row thereof upon the turbine in a direction to effect maximum driving force for the turbine.

From the foregoing, it will be seen that the present invention provides an air-driven turbine-type dental handpiece or other form of appropriate medical instrument, such as may be used for bone-cutting or the like, in which more etficient use is made of the driving air, both with respect to volume and pressure, than has been possible in contemporary and previous air-turbine type handpieces, or the like, resulting not only in economy of operation, but also far more quiet and agreeable sound results than has been evident in contemporary air-turbine type handpieces. Further, these benefits are available at no sacrifice in convenience with respect to the moving elements of the handpiece being embodied in a readily removable and insertable cartridge movable into and out of the interior of head 14 after the cap 20 has been removed. Ready seating of the cartridge is achieved automatically by the reception of the lower bearing 62 in seat 80, followed by securing of the cap 20 within threaded opening 18 to dispose the upper bearing 56 within the seat 74 of the cap.

Another very substantial advantage of the present invention over at least certain contemporary dental handpieces of the air-turbine type is that no indexing of the cartridge with respect to the interior of the head 14 is required in that the annular air distributing space 52 in the upper end of the head equally serves all air inlet ports 50 and receives driving air from conduit bore 26, regardless of any relative rotary position of the cartridge within the head 14. Similarly, the annular nature of the air exhaust plenum space 46 and its accessibility to the exhaust conduit bore 28 makes it unnecessary to dispose the cartridge at any particular angular position about the axis of the cartridge-receiving cavity 16 within head 14.

While the invention has been described and illustrated in its several preferred embodiments, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as described herein.

I claim:

1. A dental handpiece comprising in combination, a handle, a contra-angle hollow head on one end of said handle having a first bore of uniform diameter extending inward from one end thereof, a plurality of conduit means in said handle arranged respectively to deliver driving air under pressure to said head and exhaust at least a portion thereof from said head, bearings mounted within said head adjacent the upper and lower ends of said first bore, a turbine rotor supported rotatably by said bearings and having a second bore extending axially from one end to receive a dental tool shank for rotation by said turbine, a series of similar circular disc-like turbine blades in excess of two each having radial vanes on the peripheries thereof all sloping in similar angular directions relative to the axis of the rotor and mounted upon said turbine rotor between said bearings, said blades being closely spaced axially therealong in stacked multi-stage relationship, sleeve-like stator means extending axially within said first bore of said head and surrounding said blades in closely spaced relationship to the peripheral edges of said vanes of said blades and terminating adjacent the opposite ends of said stack of blades, the outer surface of the lower portion of said sleeve-like stator being reduced in diameter to provide an annular plenum exhaust chamber between said stator and the housing surface which defines said first bore, air delivery means in one end of said stator means adjacent one end of said turbine communicating with said air delivery conduit to receive air therefrom and operable to discharge air in a generally axial direction against the vanes of the blade nearest said air delivery means and then successively and directly engage the vanes of the succeeding blades and expand between said blades to effect driving rotation of said rotor, and means on the opposite end of said stator means to direct at least a substantial portion of spent driving air from the opposite end of said rotor to said plenum exhaust chamber for passage to said exhaust conduit means in said handle.

2. The dental handpiece according to claim 1 further including air delivery means adjacent the opposite end of said stator means and said air delivery means having circumferentially spaced ports directed at an angle toward the vanes of said rotor blades.

3. The dental handpiece according to claim 1 further including bearing seat means positioned in the opposite ends of said sleeve-like stator and respectively receiving said bearings.

4. The dental handpiece according to claim 3 further characterized by one of said bearing seat means having air inlet ports therein arranged radially outward from said seat therein and extending in directions to direct air against the vanes in the blade at the end of the turbine rotor adjacent said one of said bearing seat means.

5. The dental handpiece according to claim 3 in which said rotor, stator means, bearing seat means and bearings are interconnected in a manner comprising a cartridge insertable within and removable from said head as a unit, one of said bearing seats having air inlet ports extending at least partially in an axial direction therethrough and the end of the stator means adjacent the opposite bearing seat having a plurality of air exhaust ports spaced circumferentially therearound and extending therethrough.

6. The dental handpiece according to claim 1 in which said vanes are fan-shaped segments in plan view, the widest portion being at the periphery, thereby providing very limited spacing between the edges of adjacent vanes on said blades to provide maximum efiiciency in the expansion of the air between the vanes on each blade.

References Cited UNITED STATES PATENTS 3,055,112 9/1962 Borden 32-27 3,364,576 1/1968 Kern 32-27 3,325,899 6/ 1967 Staunt 32-27 751,261 2/ 1904 Clarke. 2,799,934 7/ 1957 Kern. 2,983,519 5/1961 Staunt. 3,175,293 3/ 1965 Borden.

ROBERT PESHOCK, Primary Examiner.

US. Cl. X.R. 253-3

Claims (1)

1. A DENTAL HANDPIECE COMPRISING IN COMBINATION, A HANDLE, A CONTRA-ANGLE HOLLOW HEAD ON ONE END OF SAID HANDLE HAVING A FIRST BORE OF UNIFORM DIAMETER EXTENDING INWARD FROM ONE END THEREOF, A PLURALITY OF CONDUIT MEANS IN SAID HANDLE ARRANGED RESPECTIVELY TO DELIVER DRIVING AIR UNDER PRESSURE TO SAID HEAD AND EXHAUST AT LEAST A PORTION THEREOF FROM SAID HEAD, BEARINGS MOUNTED WITHIN SAID HEAD ADJACENT THE UPPER AND LOWER ENDS OF SAID FIRST BORE, A TURBINE ROTOR SUPPORTED ROTATABLY BY SAID BEARINGS AND HAVING A SECOND BORE EXTENDING AXIALLY FROM ONE END TO RECEIVE A DENTAL TOOL SHANK FOR ROTATION BY SAID TURBINE, A SERIES OF SIMILAR CIRCULAR DISC-LIKE TURBINE BLADES IN EXCESS OF TWO EACH HAVING RADIAL VANES ON THE PERIPHERIES THEREOF ALL SLOPING IN SIMILAR ANGULAR DIRECTIONS RELATIVE TO THE AXIS OF THE ROTOR AND MOUNTED UPON SAID TURBINE ROTOR BETWEEN SAID BEARINGS, SAID BLADES BEING CLOSELY SPACED AXIALLY THEREALONG IN STACKED MULTI-STAGE RELATIONSHIP, SLEEVE-LIKE STATOR MEANS EXTENDING AXIALLY WITHIN SAID FIRST BORE OF SAID HEAD AND SURROUNDING SAID BLADES IN CLOSELY SPACED RELATIONSHIP TO THE PERIPHERAL EDGES OF SAID VANES OF SAID BLADES AND TERMINATING ADJACENT THE OPPOSITE ENDS OF SAID STACK OF BLADES, THE OUTER SURFACE OF THE LOWER PORTION OF SAID SLEEVE-LIKE STATOR BEING REDUCED IN DIAMETER TO PROVIDE AN ANNULAR PLENUM EXHAUST CHAMBER BETWEEN SAID STATOR AND HOUSING SURFACE WHICH DEFINES SAID FIRST BORE, AIR DELIVERY MEANS IN ONE END OF SAID STATOR MEANS ADJACENT ONE END OF SAID TURBINE COMMUNICATING WITH SAID AIR DELIVERY CONDUIT TO RECEIVE AIR THEREFROM AND OPERABLE TO DISCHARGE AIR IN A GENERALLY AXIAL DIRECTION AGAINST THE VANES OF THE BLADE NEAREST SAID AIR DELIVERY MEANS AND THEN SUCCESSIVELY AND DIRECTLY ENGAGE THE VANES OF THE SUCCEEDING BLADES AND EXPAND BETWEEN SAID BLADES TO EFFECT DRIVING ROTATION OF SAID ROTOR, AND MEANS ON THE OPPOSITE END OF SAID STATOR MEANS TO DIRECT AT LEAST A SUBSTANTIAL PORTION OF SPENT DRIVING AIR FROM THE OPPOSITE END OF SAID ROTOR TO SAID PLENUM EXHAUSTT CHAMBER FOR PASSAGE TO SAID EXHAUST CONDUIT MEANS IN SAID HANDLE.

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