US 3411210 A
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Description (OCR text may contain errors)
M. STAUNT Nov. 19, 1968 AIR DRIVEN TURBINES FOR DENTAL HANDPIECES AND THE LIKE 4 Sheets-Sheet 1 Filed Dec. 5, 1958 INVENTOR- //z/"ZZ;f 5142025 wrzeyu Nov. 19, 1968 M7 STAUNT 4 Sheets-Sheet 2 Filed Dec. 5, 1958 @W l u M HM Mn N H l l u H I l H H I I |H.WI H NJ INVENTOR.
(w g/X4223? ay/( a Nov. 19, 1968 M. STAUNT 3,411,210
AIR DRIVEN TURBINES FOR DENTAL HANDPIECES AND THE LIKE Filed Dec. 5, 1958 4 Sheets-Sheet 5 M. STAUNT Nov. 19, 1968 AIR DRIVEN TURBINES FOR DENTAL HANDPIECES AND THE LIKE 4 Sheets-Sheet 4 Filed Dec. 5, 1958 R. m E V m BY Wdrdka 522%?6 Wrqy United States Patent 01 fice 3,411,210 Patented Nov. 19, 1968 3,411,210 AIR DRIVEN TURBINES FOR DENTAL HANDPIECES AND THE LIKE Martin Staunt, Des Plaines, Ill., assiguor, by mesne assignments, to American Hospital Supply Corporation, Evanston, Ill., a corporation of Illinois Continuation-impart of application Ser. No. 494,607, Mar. 16, 1955. This application Dec. 5, 1958, Ser. No. 778,526
16 Claims. (Cl. 3227) The present invention relates to air driven turbines for dental handpieces or the like, and is particularly concerned with the provision of an improved air turbine assembly which is adapted to form the power source of an improved air driven dental handpiece, but which is of general application and may be used for driving many other devices.
The present application is a continuation-in-part of each of my following prior applications. Ser. No. 494,607, filed Mar. 16, 1955Dental Handpieces, and now abandoned; Ser. No. 620,434, filed Nov. 5, 1956Dental Handpieces, and now Patent No. 2,988,815 issued June 20, 1961; Ser. No. 633,067, filed I an. 8, 1957Self-Lubricating and Self-Cleaning Dental Handpieces and now Patent No. 2,923,060 issued Feb. 2, 1960; Ser. No. 633,069, filed Jan. 8, 1957Dental Handpieces and now Patent No. 2,911,- 721 issued Nov. 10, 1959; Ser. No. 633,068, filed Jan. 8, 1957Contra Angles for Dental Handpieces and now Patent No. 3,197,869 issued Aug. 3, 1965.
One of the objects of the invention is the provision of an improved air driven turbine assembly which is adapted to be installed or removed as a complete operative unit in the head housing of a contra angle handpiece.
Another object of the invention is the provision of an improved air driven turbine which produces a maximum torque at the driving spindle with the use of a minimum amount of air, and which operates at high rotary speeds, such as between 100,000 r.p.m. to 200,000 r.p.m. and over smoothly and with a minimum vibration and more quiet operation than any of the devices of the prior art.
Another object of the invention is the provision of an improved air driven dental handpiece in which the air path through the turbine is reduced in length to a minimum and graduated in size, increasing in volume as it progresses, and smoothly directed with minimum turbulence to an enlarged outlet for the purpose of reducing the sound level, increasing the torque, and reducing the volume and pressure of air required.
Another object of the invention is the provision of an improved unit assembly for air driven turbines, including a stator and a shell which engage the outer races of a pair of ball bearing assemblies and a rotor and tubular shaft which engage the inner races of the ball bearing assemblies, in which the ball bearing assemblies themselves are adapted to hold the parts in assembled relation.
Another object of the invention is the provision of an improved turbine assembly which is so constructed that the air supplied to it for driving the turbine may be provided with lubricant in the form of a mist adapted to pass out of the turbine unit between the balls and races, which are coated with lubricant and constantly lubricated during the operation thereof.
Another object of the invention is the provision of an improved turbine assembly including an improved form of ball bearings, which are without filling openings, so that the balls cannot get out of the races, and in which the balls are held in spaced relation by an improved form of ball retainer, which snaps over the balls and is thereafter retained by the balls as long as they are located in the races.
Another object of the invention is the provision of an improved air driven turbine for dental handpieces and other purposes which operates at a high speed, such as thousands of revolutions per minute, for the purpose of expediting the grinding operations, but with a minimum amount of noise and vibration, since the reduction of vibration and the reduction of the noise level is of the greatest importance to both the patient and the operator in the employment of such a tool for dental operations.
Another object of the invention is the provision of an improved dental handpiece assembly which is adapted to be used with tungsten carbide or diamond burs at high speeds to produce effective cutting in a minimum time and to reduce the heat at the cutting surface and in the bearings of a handpiece to a comfortable level for the purpose of providing less trauma and greater comfort to the patient and lessening the strain and tension of the operator.
Another object of the invention is the provision of an improved air driven dental handpiece in which the air is employed not only for driving the air turbine, but for cooling the parts of the mechanism and for lubricating the bearings and cooling the bur, at which point the cooling of the air is supplemented by a combined air and water spray directed toward the bur and into the cavity, the control of the cooling medium being automatic and simultaneously applied with the operation of the handpiece.
Another object of the invention is the provision of an improved construction of an air driven dental handpiece which is adapted to be lubricated effectively at speeds over 200,000 r.p.m. and so constructed that dirt and grindings are excluded and driven out of the housing containing the ball bearings and other moving parts by employing a combined air and lubricant mist, with a minimum amount of the lubricant reaching the interior of the mouth, where it might be breathed, and practically all of the exhaust air being carried back through suitable conduits to a point away from the patient and the operator.
Another object of the invention is the provision of an improved air driven handpiece contra angle so constructed that it is adapted to be used with a supply of air under pressure and a supply of water under pressure, both of which are controlled by the foot of the operator so that a dental bur cutting at a high speed is automatically cooled by a jet of water combined with atomizing air directed toward the point of grinding, and the grinding may be stopped without removing the handpiece from the mouth, and air at room temperature or elevated temperature momentarily directed into the cavity to blow out the chips and grindings and dry the cavity while it is still being inspected, after which the grinding may continue, if necesar y, and brought to completion with repeated periods of grinding and clean-out, without ever removing the handpiece from the mouth of the patient to reach for the hot air syringe, as is done with devices of the prior art.
Another object of the invention is the provision of an improved turbine assembly which is simple in construction, which has a minimum number of parts, which is adapted to be operated at high speeds, over 200,000 r.p.m., which is provided with bearings that are adequately lubricated so that they may be used for a long period of time, and which may be manufactured economically.
Another object of the invention is the provision of an improved air driven turbine unit adapted to be operated with as little air as possible and at air pressures lower than the devices of the prior art, while producing a maximum torque.
Another object of the invention is the provision of an improved turbine assembly in which the rotor operates with a more uniform torque, without having any dead center positions, and in which the air thrust on the rotor is equally distributed about all sides of the rotor.
Another object of the invention is the provision of an improved turbine assembly having a sustained power output, which eliminates the need for a wiping or brushing technique, as is practiced with the cutter in the practice of the prior art.
Another object of the invention is the provision of an improved turbine assembly in which there is no tendency for the rotor to run at excessive speeds when the turbine is without load because the present turbine has bearings provided with a plastic ball retainer that places a slight drag on the rotation of the rotor.
Another object of the invention is the provision of improved ball bearings, which are without filling notches in the races, so that the balls cannot produce impacts by striking in filling notches, and in which the balls are prevented from impinging upon each other, and in which the balls and races are suitably cooled so as to eliminate any temperatures which would decompose oil and produce carbon deposits.
Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters indicate similar parts throughout the several views.
Referring to the drawings, of which there are five sheets:
FIG. 1 is a fragmentary side elevational view of an air driven contra angle handpiece, full size, embodying the invention;
FIG. 2 is an enlarged side elevational view of the removable turbine unit;
FIG. 3 is an enlarged fragmentary bottom plan view of the head of the handpiece on a scale of six to one;
FIG. 4 is a fragmentary top plan view of the handpiece head;
FIG. 5 is a similar end elevational view of the handpiece head;
FIG. 6 is a fragmentary sectional view of the handpiece head and its supporting neck and elbow, taken on the plane of the line 66 of FIG. 4, looking in the direction of the arrows;
FIG. 7 is a fragmentary sectional view showing a continuation extending from the right end of FIG. 6, being the lower end of the 'handle of the handpiece;
FIG. 8 is a fragmentary sectional view, taken on the plane of the line 88 of FIG. 6, looking in the direction of the arrows, and showing the ends of the inlet and outlet conduits in the neck of the handpiece;
FIG. 9 is a fragmentary sectional view, taken on the plane of the line 99 of FIG. 6, looking in the direction of the arrows, and showing the shape of the inlet and outlet conduits in the spacer shell of the turbine unit;
FIG. 10 is a fragmentary sectional view, taken on the plane of the line 10-10 of FIG. 6, looking in the direction of the arrows;
FIG. 11 is a sectional view, taken on the plane of the line 11-11 of FIG. 6, looking in the direction of the arrows, with the top cap removed;
FIG. 12 is a sectional view taken on the plane of the line 12-12 of FIG. 6, looking in the direction of the arrows;
FIG. 13 is a fragmentary sectional view, taken on the plane of the line 1313 of FIG. 6, showing the stator slots in plan;
FIG. 14 is a fragmentary sectional view, taken on the plane of the line 1414 of FIG. 6, showing the upper ends of the rotor slots;
FIG. 15 is an end elevational view of one of the ball bearing assemblies;
FIG. 16 is a sectional view, taken on the plane of the line 1616 of FIG. 15, looking in the direction of the arrows;
FIG. 17 is a side elevational view of one of the nylon ball retainers;
FIG. 18 is a fragmentary sectional view similar to FIG. 6 on a larger scale.
Referring to FIGS. 1-6, the air driven handpiece 30 embodying the invention is shown full size in FIG. 1.
It preferably comprises a handle tube 31 carrying an elbow fitting 32 at its lower end, which supports the neck tube 33 at an obtuse angle to the handle 31; and the neck tube 33 carries a handpiece head 34, comprising a housing member made of stainless steel, as are all the other metal parts of the handpiece 30 (FIG. 1); and the head 34 may be substantially cylindrically shaped, having a cylindrical wall 35, which is rounded and tapered at its lower portion 36 to remove as much as possible of that portion of the housing which might obscure the view of the end of a dental bur mounted in the head 34.
The lower end of the head 34 has a generally plane surface 37, which is provided with a central circular aperture 38 that is slightly spaced from the circular end 39 of a rotating bur shaft, leaving an annular clearance 40 serving as an annular air escape and air spray nozzle for air issuing from the housing of the handpiece.
It is this escaping air which is so restricted at the annular nozzle 40 that it maintains an air pressure inside the handpiece housing and excludes the ingress of dirt and grindings by the outward fiow of air from the handpiece housing under operation.
The end of the bur shaft or spindle 39 is shown at 41; and the bur shaft has a cylindrical bore 42, which contains a plastic =bur tube 43, having a cylindrical bore 44 for frictionally gripping the cylindrical portion of the shank of a bur or other tool to be driven by the handpiece, as shown in FIG. 6.
The head 34 is open at its upper end, being provided with a cylindrical bore 45 (FIG. 18) having an internally threaded counterbore 46 at its upper end for receiving the externally threaded portion 47 of a top cap 48, which covers the upper end 49 of the housing, except for the central aperture 50 in the cap that is used for inserting a tool employed in pushing out the shank of a dental bur when it is to be removed, and for permitting exit of air-oil mist from bearings 57.
The cap 48 has a pair of diametrically opposite circular sockets 51 for receiving the lugs of a spanner wrench used in tightening the cap. The cap is rounded at its outer edge portion 52 and may be threaded so far into the head 34 that its edge merges with the top of the head, forming a smoothly rounded upper corner without projections that might injure the month.
At its lower side the cap 48 has the plug formation 53, which is provided with a bore 54, large enough to receive the upper outer race of the ball bearing assembly; and the plug is formed with a smaller counterbore 55 for receiving the upper end of the spindle and its associated parts, with a clearance so that the spindle may rotate without contacting the cover.
The plug formation 53 has an annular shoulder 56 for engaging the outer race of the upper ball bearing assembly 57 to secure the removable turbine unit 58 in the head 34.
The head 34 has a frustoconical inner surface 59 toward its lower end and a reduced counterbore 60 for receiving the outer race of the lower ball bearing assembly 61 against an annular shoulder 62. From the annular shoulder 62 the interior of the head 34 has a frustoconical inner surface 63, providing a clearance with respect to an external frustoconical surface 64 on an enlargement 65 of the bur shaft 39, thereby forming the annular nozzle clearance 40, which is slightly enlarged at its lower end by forming a flaring crack 66 of annular shape.
This annular crack or nozzle permits air to escape from the interior of the head housing 34, but maintains sulficient resistance to its escape to provide a pressure inside the housing, to exclude dirt and grindings from the housing.
The air turbine constitutes a removable unit 58 because all of its parts are carried by a cylindrical stainless steel shell 67. This shell 67 has an outer cylindrical surface 68 and an inner cylindrical bore 69.
At its lower end it has an inwardly extending frustoconical flange 70, terminating in an annular end surface 71 that engages the outer race of the lower ball bearing assembly 61 to secure it in the head 34.
The shell 67 fits in the bore 45 of the head 34 and is secured against rotation therein by an outwardly turned tab or lug 72 pressed out of its upper edge to extend into a rectangular groove 73, which extends upwardly across the threads 46, and is open at the top end 74 so that the turbine unit may be slid downward into the bore 45 when the lug 72 registers with the groove 73; but thereafter it cannot rotate.
The upper end of the shell 67 is indicated at 75, presenting an annular surface which engages the lower surface 76 of the upper enlargement 77 of the stator 78. The stator 78 comprises of cylindrical body or enlargement 77 integrally joined to a central tubular portion 79 and a lower cylindrical body 80, which forms a floor or lower wall of an annular rectangular groove 81, serving as a stator air manifold.
The tubular portion 79 of the stator 78 has a central through bore 82, clearing the parts of the rotor 83; and there is a cylindrical counterbore 84 in the top of the stator, terminating at an annular shoulder 85 engaging the lower edge of the outer race of the upper ball bearing assembly 57, which is located in the counterbore 84. The stator 78 and shell 67 together from a separate cylindrical inner casing which spaces the outer races from each other.
The stator enlargement 77 closes the upper end of the stator manifold 81 by engaging the shell 67; and the lower floor 80 of the stator engages in the shell bore 69 with its outer cylindrical surface 86 and closes the lower side of the air manifold 81, except that the floor 80 of the stator has a multiplicity of nozzle slots 87, which form nozzle apertures in combination with the inner surface 69 of the shell 67.
The slots 87 in the stator floor are at an acute angle to the upper and lower stator surfaces 88, 89 so that the air issuing from the surface 89 of the stator may have an axial component to move the air out of the stator may have an axial component to move the air out of the stator and into the rotor; but the major component is in a peripheral direction and in the direction of rotation of the rotor.
The angularity may vary; and I have found that an angle of 60 degrees to the axis of the turbine produces a driving torque which is stronger than the devices of the prior art and that performance is improved at an angle of 65 degrees.
The slots 87 in the stator are made by means of a milling cutter; and while a suitable torque has been produced by using slots fifteen thousandths of an inch in width, the torque is improved by employing slots ten thousandths of an inch in width, this being the width of the milling cutter.
This results in slots which are parallel walled and substantially rectangular and complementary in shape to the cutter. A multiplicity of such slots is provided, there preferably being sixteen slots in the stator of this size, with twice as many slots in the rotor. Using eight slots of this size also increases the torque.
The rotor 83 comprises a substantially cylindrical metal body preferably made of brass; and the body 90 is integrally joined to a pair of tubular extensions 91, 92 having cylindrical outer surfaces 93 and a cylindrical bore 94.
The cylindrical bore 94 is adapted to receive the tubular body 95 of a bur shaft which has the frustoconical en largement 65 at its lower end. The cylindrical part 95 of the bur shaft may support the inner race 96 of the ball bearing assembly 61 against the annular shoulder 97; and
this race is in turn engaged by the end surface 98 of the tube 92.
The tube 92 and the rotor 83 and upper tube 93 are mounted on the bur tube; and the upper end 99 of the rotor tube 93 engages the bottom of the upper ball hearing race 100. The bur tube 93 is provided at its supper end with inner threads 101 and with a screw plug 102 threaded into the threaded bore.
The screw plug has a laterally extending or radial flange 103, the bottom of which may engage a metal washer 104, which engages the upper race 100. Thus the inner races and the rotor are secured on the bur shaft, on which they may also have a close fit.
There is a clearance between the supper end of the bur shaft 39 and the washer 104 so that the screw plug 102 may clamp the race only. Left hand threads keep plug 102 tight in bore 101.
The cylindrical rotor body has an upper plane surface 105 and a lower plane surface 106, which are spaced farther from each other than the thickness of the stator floor.
The rotor body 93 has a cylindrical outer surface 107, which has a close clearance with respect to the inner surface 69 of the shell, but permits the rotor to rotate freely without contact. The rotor is preferably provided with twice as many slots in its periphery as there are slots in the stator; and the rotor slots are cut by means of a tubular milling cutter, which has a sufficiently large diameter and is used on a rotor of smaller diameter so that one edge of the tubular cutter may cut a curved slot like that indicated at 108 in the rotor 83, there being 32 such slots, for example, in a rotor which produces a high torgue.
The curvature of the slots 108 relative to the upper and lower surfaces of the rotor depends on the location of the tubular cutter, which in FIG. 6 had its axis located midway between the upper and lower surfaces of the rotor. This makes the curvature a circular arc symmetrically located across the rotor.
By employing stator jets only half in number to the number of the rotor slots a more smooth rotating torque is impressed on the rotor; and by employing the specific construction shown, the air passing through the stator and rotor takes the shortest possible path, with a minimum amount of turbulence and a maximum amount of torque.
The air is discharged into a lower expansion chamber 109, from which the air is exhaused out of the turbine at a lateral exhaust port 110. The air is also used to pass through the lower ball bearing assembly 61 at the spaces between the balls; and the air issues through the conical slot 66 and is discharged in a conical spray toward the cutting end 111 of the bur 112 due to the flare 66, which exists at the lower end of the slot 40.
The clearance between the upper surface 105 on the rotor and the lower surface of the stator floor is quite close, in the nature of seven thousandths of an inch; but the rotor and its bearing parts have a limited axial freedom due to a certain looseness of the balls in the ball bearing races.
The structure of the ball bearings employed in the turbine is of the utmost importance; and they are preferably constructed as described herein, because this structure is peculiarly adapted to permit high speed operation at 200,000 to 300,000 rpm. and to permit air and lubricant mist to pass through the ball bearings, depositing lubricant thereon, and the balls are spaced from other other and kept out of contact with each other, reducing friction and wear.
Each of the ball bearing assemblies 57 anrd 61 includes the following parts. The bearing assembly 57 includes the inner race 100, outer race 113, balls 114, and ball retainer 115. The races and balls are preferably made of hardened stainless steel, but carbon steel balls may also be used, FIG. 16.
The outer race 113 has cylindrical outer surface 115a 7 and inner cylindrical surface 116 (FIG. 16). The inner race 100 has the inner cylindrical surface 117 and the outer cylindrical surface 118. The ends or edges of both races are plane; but the corners are preferably chamfered.
The outer race 113 has a ball groove 119 of partially circular cross section on its inside formed on a radius larger than the radius of the ball 114; and the inner race 100 has an outer groove 120 registering with the groove 119 and formed on a radius which is larger than the radius of the balls 114.
The ball grooves 119 and 120 are uniform in cross section and extend all the way around the inside and outside, respectively, of the outer and inner races; and there are no filling grooves.
The grooves are not filled with a full complement of balls 114, but only include a lesser number, so few that when all the balls are arranged on one side, there is a suflicient crack between the inner race and the outer race to insert or remove balls edgewise into or out of the crack until they reach the groove.
For example, the present bearings include seven balls, which are equally spaced in the grooves by the ball retainer 115. The ball retainer comprises a plastic member of lubricating characteristics, such as nylon or some polyethylene compound; and the ball retainer is made out of a short length of nylon tubing, which forms a closed annulus of such size that it may be received between the inner race and the outer race with a clearance with respect to both of them.
The retainer 115 has seven ball sockets 121, comprising circular bores, the diameter of which may be 0.043 when balls are employed having a diameter of 0.0394". The inner diameter of the inner race 100 may be 0.0125" or 0.0135", depending on the shaft diameter.
The outer diameter of the outer race may be A. The length of the races may be and the ball retainer may be 0.081 in width.
The ball retainer 115 is provided for each ball bore 121 with a longitudinally extending slot 122; and this slot is of smaller size than the diameter of the balls. For balls having a diameter of 0.0394" the slots may be 0.035", or $4 narrower than the balls.
This permits the balls to be pressed into the slots or the slots to be pressed over the balls by exerting a predetermined force. The balls snap into the bores 121, where they are retained by the restricted slots.
The dimensions given in this specification are merely by way of example, and may be varied in devices of different sizes.
The balls being held in the assembly by engagement with the grooves, and the balls being spaced by the retainer, the balls hold the retainer in the position of FIG. 16, where it floats.
The clearance between the outside of the retainer and the outer race is less than the clearance between the inside of the retainer and the inner race for the purpose of making sure that there is no drag between the retainer and the inner race, which rotates rapidly.
For example, the clearance between the inner race and the inside of the ball retainer may be 0.006" and the clearance on the outside of the ball retainer with respect to the outer race may be 0.0035".
When the rotor rotates, the inner race 100 necessarily rotates with it; and the balls roll in the groove 120; but they rotate in the opposite rotative direction. It is believed that the balls are thrown out by centrifugal force, engaging in the groove 119 of the outer race, where they may have less slippage than they have with respect to the inner race.
The nylon retainer floats between the races, engaging neither of them; but it rotates and moves with the balls.
It is believed that the air, entraining a mist of lubricant, which is forced through the bearings, serves to keep the ball retainers concentrically located; and lubricant is deposited on the retainer and races and the balls, which are constantly lubricated thereby.
The structure of the lower bearing assembly 61 is the same; and the inner race is indicated at 96, the outer race 123, and the balls 124.
The air driving the turbine, containing lubricant mist, leaks along the clearances between the rotor 83 and the stator 78 to the upper bearing assembly 57, and may escape through the hole 50. When the air reaches the aperture 50, the amount of lubricant passing has already been reduced to a minimum, being deposited as drops in the bearings.
The lower bearing assembly 61 is exposed to air from the expansion space 109, carrying lubricant mist; and this air is passed through the bearings to the annular slot between the outer frustoconical surface 64 and the inner frustoconical surface 63, lubricating the bearing 61 during its passage.
I have found that it is desirable to increase the amount of air escaping from the annular clearance 40 about the bur shaft head 65, as follows. The bore 60, forming a socket for the outer race 123, has its wall provided with a channel, which may be wide, extending down the cylindrical inner wall at 125. This channel communicates with a radial groove 126 located in the base of bore 60 in the annular shoulder 62, and communicating with the bore 63 below the outer race 123.
The rotation of the head 65 distributes the additional air uniformly and it issues from the annular nozzle clearance 40 in a conical air stream about the bur shaft 112 and converges on the bur 111 to increase the cooling effect.
The bur shaft 39 comprises a stainless steel tube having a cylindrical bore 42 and a plane end 41, and terminating in the threaded counterbore 101 at the top.
The bur shaft has an annular shoulder at 129 and a slightly larger counterbore 130 extending upward from said shoulder, where the bore is enlarged by several thousandths to form the annular shoulder 129.
The bur shaft has a pair of parallel flats 65 on its enlarged head for grip by a wrench.
The hollow threaded plug 102 of stainless steel has a through aperture 131, which terminates in a sharp edge 132 and a beveled end surface 133 engaging the end of the plastic tube 43, which is preferably made of Teflon. The plastic tube 43 has an inner cylindrical bore 44 and an outer cylindrical surface 43b, the outer diameter of which is initially uniform throughout its length, except that a short portion 430, at the lower end, is a few thousandths greater outer diameter. Plug 102 has a larger counterbore 131a which ends in an annular shoulder 131b, accurately centering and seating the upper end of the bur shank.
The purpose of making the lower end slightly larger is to compress the plastic sleeve into the bur tube 39 at its lower end, while a mandrel is inserted in the bore 44, so that the Teflon is under greater compression at that point, Where there is a maximum lateral pressure exerted on the bur shank.
At its upper end the plastic tube 43b is also initially of the same uniform outer diameter throughout; but as the plastic tube 43 is forced into the bore 42 with a mandrel having an annular shoulder engaging the end 137, the upper end engages the beveled end 132 of the plug 102; and the Teflon is forced outward and expanded into the counterbore 130 anchored against the annular shoulder 129 for retaining the plastic tube in the bur shaft.
The plastic tube is adapted to grip the cylindrical portions of shanks of burs and other tools, even though they have flats or slots or other formations beneath their cylindrical surfaces for locking the shank in, in other types of handpieces.
The present application relates to the air driven turbine per se; and the features of the chuck for holding a bur shank are the subject of another application.
The inlet port for the air turbine unit comprises a rectangular aperture 138 in the curved cylindrical wall of the shell 67, as shown in FIG. 1; and the outlet port for the turbine is indicated at 110 (FIG. 1) in shell 67.
The head housing 34 is integrally brazed to a substantially cylindrical neck tube 33, which is formed by brazing together two tubes, one small and the other larger, indicated at 139 and 140, these tubes being initially round, but deformed into substantially D cross section at their left end in FIG. 6, where the flat sides are brazed together at 141.
The ends of these D shaped tubes at the left are curved to fit against the cylindrical side wall of the shell 67 at the inlet 138 and the outlet 110; and the lower tube 140 is flared downward at 142 to meet an aperture 143 below the conical end 70 of the shell.
The two D tubes, when brazed together, form a finished cylindrical neck 33, except that they have also secured to the lower side of the tube 140 a pair of water and air tubes 144 and 145. These two tiny tubes extend along below the neck 33; and each is curved downwardly and brazed to the rounded portion 36 of the head housing 34.
The two tiny tubes for water and air terminate in beveled ends flush with the end 37 of the head housing, as shown in FIG. 1, and pointing toward the grinding bur 111.
The air issuing from the annular nozzle sucks in the water issuing from the water tube 144 so that the water is caused to rotate and is atomized into a blunt conical point at the bur 111, cooling the bur and the cavity by the application of warm water and air.
The control of the supply of air to the turbine is such that both driving air and water are turned on simultaneously and off simultaneously so that the grinding end of the bur and the tooth are always cooled when a bur is running.
The air driven turbine is capable of many different uses, but is preferably employed in a dental handpiece of the type shown in FIGS. 1-4, 6, 7, and 18.
The present application relates to the air driven turbine per se; and the other features of the air driven dental handpiece and of the control unit therefor for supplying drive air, lubricant mist, cooling air, and water are the subject of separate applications.
Such a control unit is adapted to provide drive air which is clean with respect to particles and moisture, and which entrains or contains a mist of lubricant that deposits lubricant on the races, ball bearings, and retainer, in each case, constantly lubricating the bearings and excluding foreign material from the interior of the housing by reason of the fact that such air is constantly issuing from the annular nozzle 40 in a conical stream directed toward the bur 111 (FIG. 6).
The handpiece is also provided with water and air tubes 144, 145 (FIG. 3) which selectively discharge water from the tube 144 toward the bur; and the end of the housing is provided with a groove 149 by means of which the water is directed from the water tube into the conical air stream issuing from the annular nozzle 40 so that the water is mixed with the air and atomized and directed into the cavity around the bur.
Operation The operation of the turbine will be apparent from the foregoing description of the parts and function thereof, but is summarized as follows:
Air containing lubricant mist is brought from the con trol unit under pressure and directed through the tube 139 into the turbine inlet 138 (FIG. 2), where it passes into the air manifold 81 of the stator. From the air manifold the air passes through the stator slots 87, which direct it toward the rotor and in a circumferential direction so that the air acts on the rotor in the curved slots 108 in such a manner as to drive the rotor clockwise, looking at the rotor from the top in FIG. 6; and the air is reversed in direction and directed backwardly out of the rotor into the lower expansion chamber 109.
The expansion chamber 109 is larger in volume than the air manifold 81 and permits the air to expand, reducing back pressure. From the exhaust chamber 109 the air passes through the exhaust port 110 of the turbine into the tube 140, which leads to the interior of the handpiece handle 31; and the exhaust air is carried back to the control unit, away from the mouth of the patient and the vicinity of the patient and operator.
The drive air which is supplied carries a lubricant mist in the form of an edible lubricant, which passes through the upper bearing assembly 57 and out of the port 50 to lubricate the upper hearing. The air lubricant mist also passes through the lower bearing assembly 61 and out of the conical nozzle 40, thereby lubricating the lower bearing assembly also.
The speed of rotation of the turbine increases with the air pressure of the air supplied at the inlet 138, and may be varied by varying the air pressure at the control unit from zero to 20 pounds per square inch or 30 pounds per square inch; and the speed of rotation may vary from a low speed to 200,000 r.p.m. or more, at which speed the present turbine is adapted to operatewith adequate lubrication and without damage to the bearings.
The present turbine is adapted to be operated without a run-away speed occurring, even at no load, because the ball retainers place a slight drag on the rotating parts, eliminating run-away action.
By providing twice as many stator slots, acting as nozzles, as there are rotor slots, a constant rotative force and a smooth torque are developed, which produce a minimum chatter and a smooth cutting action without stalling.
The air path through the turbine is as short as possible, reducing turbulence, which reduces vibration and noise; and the noise level is substantially reduced as compared with the devices of the prior art.
The present turbine unit is adapted to be removed from the handpiece in its entirety; and a new unit may be substituted therefor, thereby facilitating the replacement of parts and repair of the handpiece.
It will thus be observed that I have invented an improved air driven turbine, which may be operated at extremely high speeds, and which provides a smooth and uniform torque and a minimum amount of vibration.
My turbine is adapted to be embodied in extremely small miniature construction and used in dental handpieces in which the present turbines may be used for continuous service for long periods of time as compared with the devices of the prior art.
While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:
1. A high speed air driven turbine assembly comprising a cylindrical shell having a cylindrical bore, open at both ends, and having a lateral inlet port and a lateral outlet port spaced axially from each other, a cylindrical stator having an axial through bore and fitting in said shell bore, and comprising a pair of cylindrical annular flanges separated by a peripheral groove communicating with said inlet port and forming an air manifold, one of said flanges engaging one end of said shell and closing off air from one end of said shell, and the other of said flanges having a plurality of diagonal open slots cut in its periphery and forming air nozzles receiving air from said air manifold, said slots being closed at the periphery of the stator by said shell, a ball bearing assembly at each end of said turbine assembly, each ball bearing assembly comprising an outer race, one outer race engaging the stator and the other outer race engaging one end of the shell, a plurality of spaced balls located in an inner continuous groove in each outer race, and an inner race at each end of the assembly, and each inner race having an outer continuous groove engaging the spaced balls of its ball bearing assembly, a cylindrical turbine shaft having an annular shoulder at one end and a threaded portion at its other end, a turbine rotor having a through bore fitting on said shaft, and comprising a cylindrical body with a tubular spacer sleeve at each end, said spacer sleeves each engaging the end of one of said inner races and a threaded member carried by said threaded portion of said shaft and clamping said inner races against the tubular spacers and against the annular shoulder at the end of the shaft, forming a unitary assembly, said rotor having a clearance between its spacer sleeve and the stator bore and between one end of the stator cylindrical body and the adjacent end of the cylindrical rotor body, permitting leakage of air through said clearances and through the spaces between the balls of the ball hearing at that end of the shell, said rotor having a plurality of curved concentric walled slots in its periphery, forming curved vanes located in close proximity to but having a clearance with respect to the bore in said shell, said air nozzles directing air peripherally and axially into said rotor slots in the direction of rotation of the rotor, which discharges the air downwardly from the rotor into an exhaust chamber communicating with said outlet port and with the spaces between the balls of the adjacent ball bearing assembly, for cooling the ball bearings and producing air flow out of the end of the assembly to exclude dirt by outward flow.
2. A self-lubricating air driven turbine assembly according to claim 1, in which drive air under pressure containin g lubricant in the form of a mist passes in at the inlet, drives the rotor, and passes through clearances between rotor and stator and shell to the spaces between the races and between spaced balls of each ball bearing assembly, depositing lubricant as a liquid on the balls and races as the air passes out of each ball bearing assembly, to effect continuous lubrication while the turbine is driven.
3. A turbine assembly according to claim 1, in which the shell and stator are enclosed in an outer housing vented at each end, and having inlet and outlet conduits communicating with the inlet and outlet ports, respectively, said housing having a bore with an annular shoulder engaging one outer race and a threaded end closure engaging the other outer race.
4. A turbine assembly according to claim 3, in which there is an enlargement on the end of the shaft which is externally frusto-conical, rotating in an internally frustoconical bore in the end of the housing, with a clearance, which forms an annular air nozzle directing air in a converging conical stream toward a point spaced from the adjacent end of the shaft to cool a tool and work piece on all sides.
5. A turbine assembly according to claim 1, in which the balls of each bearing assembly are held in spaced relation to each other by a tubular ball retainer floating between and clearing both races in each case, and comprising a plastic tube having an aperture for receiving each ball, each such aperture communicating with One end of the retainer through a restricted parallel walled slot slightly narrower than the ball diameter, retaining the balls in the retainer and the retainer on the balls in centered position, preventing the balls from engaging each other and spreading lubricant over the ball surfaces.
6. A turbine assembly according to claim 1, in which the continuous race grooves are of circular shape in cross section formed on a radius larger than the radius of the balls so that each ball has a single point contact in each race to operate with minimum friction.
7. A fluid driven turbine assembly comprising a light, thin-walled cylindrical shell having a cylindrical bore extending therethrough, said wall having axially spaced lateral inlet and lateral outlet ports, a driven shaft having an enlargement extending from one end to an annular shoulder, and having a threaded portion at its other end, a threaded member engaging said threaded portion, a rotor having a cylindrical body portion and an axial bore receiving and fitting on said shaft, and having an integral spacer tube at each end of said cylindrical body portion, two anti-friction bearings mounted on the ends of said shaft, each such anti-friction bearing including an inner race, an outer race and rolling elements, one of said inner races being confined between said annular shoulder and the end of one spacer tube on said rotor, and the other inner race being confined between the end of the other spacer tube on said rotor and said threaded member, said inner and outer races having continuous partially circular grooves without filling openings, and said rolling elements comprising a lesser complement of balls than required to fill the grooves, and a plastic ball retainer of tubular shape having a radial bore for each ball, and spacing the balls from each other in the grooves, each ball bore having a restricted slot passing the balls, but retaining the balls, and the retainer having a clearance with respect to both races, a stator having a plurality of axially and peripherally directed stator slots cut in its periphery and forming fluid nozzles between the stator and the shell, and said rotor having in its periphery a plurality of transverse slots curved to receive fluid from said nozzles at one end of the rotor and to discharge it backwardly with respect to the direction of rotation of the rotor at the other end of the rotor, said stator and shell engaging the inner ends of outer races of said antifriction bearings and forming a unitary assembly.
8. A fluid driven turbine assembly according to claim 7, in which the rotor slots are concentric walled slots of uniform width formed on an axis transverse to the axis of the shaft.
9. A fluid driven turbine assembly according to claim 7, in which the stator has a through bore clearing one tubular spacer of the rotor and the stator has a cylindrical body fitting in said shell and provided with an annular peripheral groove, forming a fluid manifold, with one wall adjacent the rotor, said latter wall having said stator slots, which comprise parallel plane walled slots cut in the stator periphery and closed at the stator periphery by said shell.
10. A fluid driven turbine assembly according to claim 9, in which the stator has a cylindrical enlargement on one side of said annular groove registering with the outside of said shell and engaging the end of said shell, said cylindrical enlargement having a concentric end bore receiving an outer race of the adjacent bearing, and the other end of the shell having an annular end surface engaging the inner end of the other outer race, forming a unitary self-supporting assembly.
11. A fluid driven turbine assembly according to claim 10, in which the assembly is removably mounted in an outer housing having a cylindrical bore receiving said shell and a counterbore seating one of the races of said anti-friction bearing, and the outer housing is provided with inner threads at its opposite end and with a threaded plug engaging said threads and engaging the end of the adjacent outer race, securing the assembly in said outer housing.
12. An air driven turbine and tool cutting assembly, comprising a cylindrical housing having a cylindrical bore, an annular shoulder, and a frusto-conical bore, all concentric and open at the end of the conical bore, internal threads at the other end of said cylindrical bore, a threaded cover cap engaging said threads, a ball bearing outer race engaging said cap, a cylindrical stator, a thin metal cylindrical shell and a second outer race, confined between the threaded cap and said annular shoulder in said housing, a tubular shaft having a frusto-conical head and an annular shoulder at its lower end and a threaded screw plug in its upper end, an inner race, a rotor and a second inner race, clamped between said sha'ft, annular shoulder,
and said plug on said shaft, said inner races registering with the outer races and the races containing spaced walls, said tubular shaft having a cylindrical bore provided with a plastic sleeve, a grinding tool having a shank frictionally supported in said chuck sleeve below said head, said housing having an annular air opening extending about said head, forming an annular air nozzle directed toward said tool to converge on the tool on all sides, said housing having an inlet for drive air connected to stator slots acting as nozzles, and said rotor having slots receiving air from the stator nozzles to drive the rotor, and auxiliary conduits carrying exhaust air to said annular nozzle for cooling the tool after air expansion in the turbine.
13. An assembly according to claim 12, including also a source of drive air under pressure entraining lubricant mist, and said turbine having clearances between its rotor and stator passing drive air and oil mist to the balls and both ball bearing assemblies to the atmosphere, depositing oil on the :balls and races and lubricating them continuously while operating.
14. An assembly according to claim 12, which includes a plastic ball retainer in each bearing assembly, each retainer comprising a tube having a radial circular bore for each ball, and holding the balls spaced from each other, each retainer having a clearance with respect to its inner and outer races, and each retainer bore having an axial restricted slot passing the balls, but retaining them.
15. An assembly according to claim 12, in which the stator has an annular groove, serving as an air manifold, said stator having a cylindrical flange engaging in the housing and closing one side of the groove, and a second cylindrical flange engaging in the said shell, and having said stator slots extending diagonally and closed peripherally by said shell.
16. An assembly according to claim 12, in which the rotor slots are curved, with concentric walls formed in the cylindrical periphery on an axis at right angles to the axis of the rotor.
References Cited UNITED STATES PATENTS 2,608,807 9/1952 Nilsen et a1. 2533 2,703,904 3/1955 De Long 2533 2,180,993 11/1939 Monnier 32-26 2,799,934 7/1957 Kern 32-27 2,911,268 11/1959 Staunt 308--201 2,911,721 11/1959 Staunt 3227 2,923,060 2/ 1960 Staunt 1 3227 2,945,299 7/1960 Fritz 32-27 LOUIS G. MANCENE, Primary Examiner.
R. PESHOCK, Assistant Examiner.