US2873527A - High speed angle hand piece - Google Patents

Description

Feb. 17, 1959 v P. FLATLAND 2,873,527

HIGH SPEED ANGLE HAND PIECE Filed Oct. 1, 1956 5 Sheets-Sheet l 33 l INVENTOR.

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ATTRNEYS' United States Patent HIGH SPEED ANGLE HAND PIECE Lloyd P. Flatland, San Francisco, Calif.

Application October 1, 1956, Serial No. 613,223

Claims. (Cl. 32-2'7) The invention relates to dental instruments and more particularly to dental instruments of the kind known as angle hand pieces.

In the practice of their profession dentists have long used angle hand pieces, the usual hand piece being connected to and driven by the endless cord of the customary dental unit. Hand pieces as heretofore constructed have served in a moderately satisfactory fashion; but, with the advent of modern cutting and excavating instruments, such as burrs and mounted points using materials which are especially suitable for high speed rotation, the previously used types of angle hand pieces have been found to be unsatisfactory owing to their relatively slow speed.

Attempts have been made to increase the rotational velocity of the instruments in the hand pieces, for example, by effecting certain electrical and mechanical changes in the dental unit motors. However, even with the most advanced types of hand pieces and with the best of motors, it is seldom that a shaft speed can be reached which is in excess of 15,000 R. P. M. This velocity is far below the speed suitable for eicient operation of modern cutting and excavating instruments, which commence to realize their full potential only at speeds which are well in excess of 100,000 R. P. M.

Furthermore, the angle hand pieces heretofore used have offered so much frictional. resistance that even though a shaft speed of 15,000 R. P. M. could be obtained under unloaded condition, when a load is placed upon the unit as by deep cutting or excavating the speed is frequently reduced to 7,000 or 8,000 R. P. M., far below the efficient operating speeds even for older style instruments.

It is therefore an object of the invention to provide a high speed angle handpiece which operates with but a negligible amount of friction and which is therefore efficient and coolin operation.

It is another object of the invention to provide a high speed angle hand piece which does not significantly reduce the rotational velocity of the cutting instrument even when a load is applied.

It is a further object of the invention to provide a high speed angle hand piece which is relatively economical to manufacture and which therefore can be placed within the financial reach of all persons whose activities require the use of such a device.

It is still further an object of the invention to provide a high speed angle hand piece which is readily adaptable for use with existing dental units.

It is another object of the invention to provide a high speed angle hand piece which enables the cutting instrument to be rotated, if necessary, at speeds up to well in excess of 200,000 R. P. M.

It is a still further object of the invention to provide a high speed angle hand piece in which all of the working parts, except the cutting portion of the instrument itself, are shielded so as to give a maximum of safety.

It is yet a further object of the invention to provide a 2,873,527 Patented Feb. 17, 1959 ICC high speed angle hand piece which is light in weight and which provides an extremely satisfactory balance when held in the hand of the dentist, and when it is manipulated by the dentist to assume its various attitudes and positions when working on a patients teeth.

It is a still further object of the invention to provide an angle piece which is extremely quiet in operation.

It is yet another object of the invention to provide a high speed angle hand piece in which the cutting instru* ment is easily inserted yet rmly held in the rotating member, and which can, by a relatively simple manipulation, be extracted from the rotating member.

It is a still further objectof the invention to provide a high speed angle hand piece in which the 4rotating member can be replaced as a unit and which therefore reduces to a minimum any inoperative time heretofore made necessary owing to repairs.

lt is a further object of the invention to provide an angle hand piece which is attachable to the wrist joint of a dental unit and which is not only freely rotatable about its own axis and which can be eiortlessly oriented so as to assume any required attitude and location, but which also avoids any tangling of the endless cord of the dental unit.

It is a `still further object of the invention to provide a generally improved high speed angle hand piece.

Other objects together with the foregoing are attained in the embodiment described below and shown in the accompanying drawings in which:

Figure l is a side elevation of one form of the high speed angle hand piece installed ina typical environment on a dental unit wrist and elbow joint.

Figure 2 is an exploded view to an enlarged scale of the upper end of the angle hand piece, showing the manner of attachment to the dental unit.

A Figure 3 is a view of the limit stop mechanism, the view being taken along the plane indicated by the line 3-3 in Figure 2.

Figure 4 is a median section to an enlarged scale of the spindle unit showing the cutting instrument in clamped or secured position within the unit.

Figure 5 is a view comparable to Fimire 4 but show-` ing the location of the parts when the cutting instrument is in unclamped position.

Figure 6 is `a view comparable in mostrespects to Figure 4 but showing the spindle unit within its mount or housing at the outer extremity of the angle hand piece.

Figure 7 is a perspective of a modified formof the high speed angle hand piece of the invention.

Figure 8 is a perspective to an enlarged scale of the rear end ofthe form of device shown in Figure 7. i

Figure 9 is a fragmentary median longitudinal section, the plane of section being indicated by the line 9--9 of Figure 8.

Figure 10 is a median longitudinal section of the form of device shown in Figure 7.

Figure 1l is a median vertical section of the structure at the right hand end of the device shown in Figure 10, and to an enlarged scale.

Figure 12 is a view of the collet jaws and cutting instrument shank shown in Figure 11, but to an enlarged scale.

Figure 13 is a view comparable to that of Figure 1l, but with the collet in an open jaw position upon being depressed by the thumb of a user.

Figure 14 is a perspective of another modication of the high speed angle hand piece of the invention.

Figure 15 is a median longitudinal section of the form of device illustrated in Figure 14, a portion of the figure being broken away to reduce its extent.

Figure 16 is a median section, taken on the plane of the cords, of the rear end of the modified form of device shown in Figure 14, to an enlarged scale, and indicating a variant collar structure.

While the angle hand piece of the invention is susceptible of numerous physical embodiments, depending upon the particular uses and environmental situations to be faced, a considerable number of herein shown and described embodiments have been made and used in actual dental practice, as well as in experimentation, and have performed in an eminently satisfactory manner.

The form of the high speed angle hand piece shown in Figure 1, and generally designated by the numeral 21, comprises a substantially symmetrical elongated and convergingly tapered hollow sheath 22 provided with a plurality of knurled bands 23 to assist the dentist in securely holding the device in his hand. The sheath 22 1s rotatably mounted on the conventional shaft 24 projecting outwardly from the wrist joint 26 of a dental unit owing to the provision of an intermediate member termed a mounting bracket 27 having one end in engagement with the shaft and the other end secured to the sheath 22.

The bracket 27 includes not only a mounting strip 31 secured longitudinally on the outer wall of the sheath but also a sleeve portion 32 coaxially disposed with the longitudinal axis 33 of the sheath, the sleeve 32 and strip 31 being linked by an interposed transverse member 34. The sleeve 32 is hollow and is journalled on a stepped down portion 36 of the dental unit shaft 24, the stepped down portion 36 having a flattened side surface 37 formed thereon, and having provided on its free end a drilled and tapped aperture 38. ln assembling the various components, shown most clearly in exploded fashion in Figure 2, the sleeve 32 is slid over the stepped down portion 36 until the end 41 of the sleeve 32 abuts a shoulder 42 formed by the reduced dimension of the stepped down portion 36 of the shaft, The length of the stepped down shaft 36 slightly exceeds the length of the sleeve 32. Thus, after the sleeve is assembled on the stepped down shaft the shaft portion 36 projects slightly outwardly from the far end of the sleeve 32. A washer 45 having an opening 46 with a flattened portion 47 is thereupon inserted on the portion of the shaft which extends outwardly from the sleeve 32, the flattened portion 47 being in engagement with the face 37 on the shaft. The assembly is completed by insertion of a machine screw 4S into the tapped aperture 33 in the stepped down shaft, the shoulder 49 ofthe machine screw 4S abutting the adjacent face of the washer 45 and thus securely conining the sleeve 32 between the washer l5 and the shoulder 42 on the dental unit shaft 24. Confinement is not so tight however but what the sleeve 32 is free to rotate on the shaft 36 about the axis 33. Consequently the sheath 22 is itself free to rotate or swing about the axis 33, the olfset portion 34 of the bracket 27 being so proportioned that the axis 33 of the sheath 22 coincides with the common axis of the dental unit shaft 24, the shaft portion 36 and the sleeve 32.

While rotational freedom of motion is highly to be desired from the aspect of the dentist who is using the angle hand piece it has been found that in order to prevent entanglement of the two runs of the dental unit endless cord 56, a limit stop mechanism, generally designated by the numeral 57 and appearing most clearly in Figure 3, is provided. A limit stop pin 51 is mounted on the o'- set link 34 of the bracket 27, the pin 51 being abutted by a spur 52 on the washer t5 in two extreme positions of the washer 45 as the washer is rotated relative to the pin. The sheath 22 is thus free to swing through approximatelyv 350 of arc as indicated by the double-ended arrow 59, but it is unable to rotate through more than a complete circle in any one direction. Thus, inadvertent crossing or tangling of the endless cord 56 is prevented. Figure 3 illustrates four random possible positions of the spur 52 and indicates that when the spur 52 comes into abutment with the piu 51 in either direction of rotation 4 the sheath must be turned to its opposite extremity if continued rotation of the sheath is required. This device has served most eftectivelylin actual practice to accom plish the result intended, and it has also been found that no inconvenience results from the limitation on rotating the sheath for more than the approximate 350 range in any one direction at a time.

As is customary with angle hand pieces generally the outermost portion 72 of the sheath is inclined or tilted with respect to the axis 33 of the sheath and assumes frequently an angular inclination of 15. The outermost portion 72 is conveniently cylindrical in shape and is hollow so as to conduct the cord 56. The outer end 73 of the cylinder 72 merges smoothly into a mounting block portion 74 appropriately bored in a transverse direction to provide a cylindrical aperture 76 terminating at its upper end in a shoulder 77, as appears in Figure 6. Within the aperture 76 and abutting the shoulder '7,7 in tight engagement is a sleeve 78 externally provided, adjacent its lower end, as appears most clearly in Figure 6, by suitable threads 79.

A spindle unit, generally designated by the numeral 81, is customarily manufactured and sold as a unit and is freely interchangeable with others of the same size and style, and each can be inserted in the sleeve 78 as an integral unit in the event that wear has taken place to the point where replacement is necessary. Between the spindle unit 81 and the sleeve 78 is a tubular liner 82 of neoprene or comparable material serving to deaden the sound and vibration and enabling the unit to be taken in or out of the sleeve with a minimum of effort. Additional sound and vibration damping is provided by an upward extension of the neoprene liner 82 folded inwardly to form an upper shoulder 83 against which the upper end of the spindle unit abuts. In comparable fashion a lower extension of the neoprene liner 82 is folded inwardly to form a lower shoulder 84 against which bears an abutting flange 86 of a screw cap 87 interiorly threaded to engage with the threads 79 on the lower end of the sleeve 78 and serving to lock the spindle unit in place.

As appears most clearly in Figures 4 and 5 the spindle unit 31 itself comprises a generally cylindrically housing t 91 turned inwardly adjacent its lowermost end to form a shoulder 92. Disposed coaxialy in the housing 91 is a collet, generally designated by the numeral 93. Throughout its upper portion 9d the collet is of a generally tubular configuration with a uniform wall thickness. However, adjacent its lower portion 96 the thickness of the collet walls increases so that the outermost wall surface of the collet diverges outwardly. At the lower end of the collet the material is turned inwardly to form teeth 97, and in particular to engage the annular slot 99 at the lower end of substantially all such instruments.

The collet 93 is surmounted adjacent its upper end by a pulley 101 having the usual pair of cheeks 192 and 103 and a gullet 104 or throat, in which is reeved the endless cord 56 of the dental unit. Figure 6 illustrates a unique and important variation in pulley shape, the lower cheek 1% being extended laterally so as to cover substantially the circular aperture l167 defined by the walls of the shoulder 77. While the cheek 106 is large enough substantially to cover the aperture 107, it is small enough in diameter to pass through the aperture 107. The close fit of the pulley cheek 106 acts as a slinger disk which when rotating at high speed throws ysaliva or other liquid and particles from the excavation in an outward direction and thus assists in keeping area clear of unwanted matter. In the modified form of pulley shown in Figure 6 the upper cheek 108 is considerably smaller in diameter than the lower pulley cheek 106 andis rounded at its periphery so as to minimize any abrasion or wearing on the cord as might possibly result from use of the larger pulley cheeks 102 as are illustrated in Figures 4 and 5. Nevertheless even though the pulley cheek 138 is relatively small in size an adequate gullet 109 lis formed in the pulley which serves to hold the turn in the cord without any risk of having the cord slip of.

Throughout the lower, thickened portion of the collet a plurality of longitudinally extending slots 111 is provided, the slots 111 defining a plurality of jaws 112. The jaws 112 are given a pre-set outwardly adjacent their lowermost portions so that the jaws 112 tend normally to Spring outwardly, as is shown most clearly in Figure 5, when under no external force. The jaws 112, furthermore, when in a free state, spring outwardly far enough so that the teeth 97 at the lower ends of the jaws do not engage with the shoulders of the annular slot 99 at the lower end of the burr.

In order to effect clamping of the teeth 97 within the slot 99, unique mechanism is provided. Encircling the lower portion 96 of the collet is a lower anti-friction bearing 121 whose outer periphery 122 is spaced slightly from the adjacent inner wall 123 of the housing 91. The antifriction bearing 121, therefore, is translatable upwardly and downwardly within the housing. A helical spring 126 bearing at its upper end against a thrust plate 127 urges the anti-friction bearing 121 downwardly. The spring constant of the helical spring 126 is appropriately selected so that the anti-friction bearing 121 is urged downwardly with sufficient force to close or clamp the jaws 112 radially inwardly and to force the teeth 97 into overhanging relation with the slot 99 at the lower end of the cutting instrument 98. In operating condition, therefore, the collet and the burr assume the engagement illustrated most clearly in Figures 4 and 6.

The upper portion 94 of the collet is supported for smooth rotation by a second or upper anti-friction bearing, designated by the numeral 131. The'anti-friction bearing 131 is abutted against a shoulder 132 formed in the upper end of the collet and is held securely to the housing wall owing to the provision of a pair of annular inturned rings 136 and 137 spun in the housing after assembly of the anti-friction bearing 131, the spinning tool leaving the corresponding annular grooves 138 and 139 in the outer periphery of the housing walls, as shown in Figures 4 and 6.

It can therefore be seen that the collet while being rotatably supported in the anti-friction bearings 121 and 131, has its jaw positions controlled by appropriate posi-v tioning of the lowermost anti-friction bearing 121. Positioning of the anti-friction bearing 121 is obtained by appropriate translation of a button 141 having an outturned annular shoulder 142, or fiange, the shoulder 142 serving not only to confine the button within the housing but also enabling the user by pressing upwardly on the bottom surface 113 thereof forcibly to urge upwardly the anti-friction bearing 121 against the downward urgency of the helical spring 126. As appears most clearly in Figure 5, when the button 141 is urged upwardly, with a corresponding upward movement of the anti-friction bearing 121, the natural or inherent resiliency of the collet jaws causes the collet jaws to spring outwardly so that the teeth 97 are placed clear of the annular slot 99 thus permitting unhindered withdrawal of the burr or insertion thereof.

It is especially to be noted that when the button 141 is in its lowermost position and the burr is clamped, owing to the inward deformationof the jaws by the anti-friction bearing 121, there is no possibility whatsoever of the burr being pulled out of its location with the spindle unit even though the burr should accidently stick or catch or other* wise be urged in an outward or dislodging direction. This feature makes the spindle unit especially safe in use since there is never a possibility that the burr will become dislodged from the angle hand piece during any work. 'On the other hand, merely by pressing upwardly on the button the jaws are permitted to spring open so as t0 release the burr which can thereupon be easily eX- tracted. When installing the burr in the spindle unit, it is only necessary that the button be pushed upwardly and the burr slid downwardly until the lower end of the burr abuts against the button. At this juncture the button can be released and the jaws will immediately clamp upon the burr in a secure fashion.

Furthermore, and as previously mentioned, it can be seen by especial reference to Figure 6 that in the event the spindle unit becomes worn it is merely necessary to unscrew the cap 87 and withdraw the spindle unit as a whole to bereplaced by a new spindle unit. When the new spindle unit is placed in proper position the cap is again screwed up and the dentist can proceed with his work. The entire process can be effected in but a matter of moments.

Figure 7 shows a modified form of the high speed angle hand piece of my invention, and, while in some ways resembling the above described form, it diders in a number of respects. The modified form includes a sheath 201 tapered as before and with the customary roughening bands 202 to prevent slipping of the hand. The sheath 201 at its outermost end is a substantially cylindrical member 203 which itself terminates in a mounting block 204 adapted to receive in a transversely bored chamber a spindle unit 206. A sleeve guard 207 encircles the cy-` lindrical portion 203 and is slidable with respect thereto, the sleeve 207 having a transverse notch 203 and a longitudinal notch 209 encompassed by material given an initial deformation so that a slight clamping effect is obtained and which permits the sleeve to be located by the user in any desired position without its slipping. The sleeve 207 serves most effectively as a safety guard and covers all but a very small exposed portion of the endless cord 211 reeved about a pulley 212 forming a part of the spindle unit 206. The larger upper end of the sheath 201 is fitted with and substantially enclosed by a plug 216 having on each side of a central opening 217 therein a pair of apertures 218 smoothly faired to guide, with a minimum of wear, the corresponding mns of the endless cord 211. In order to give free flexibility to the sheath a ball and socket joint, generally designated 221 is provided. A connecting rod 222 is secure at one end to the adjacent dental unit wrist joint member 223 and at the other end is provided with a ball 226 separated from the main portion of the rod 222 by a neck portion 227 of reduced crosssection. The ball 226 fits with but slight clearance in a corresponding spherical opening 231 in the plug 216 and is held in place by a snap-type fastening formed, for example, by a split ring 233 expandable outwardly into a disk `shaved cavity 234 encircling a neck opening 236 formed in the plug and adjacent the spherical aperture 231. The neck opening 236 is faired outwardly to form an arcuate ring 237 against which the neck portion 227 bears as the sheath reaches the limit of its angular movement with respect to the rod 222. A highly flexible and easily orientable sheath mounting is thereby provided.

With especial reference to Figures l1 through 13 the construction of the modified form of spindle unit 206 can easily be seen. A collet 251 is disposed coaxially within a housing 252, generally cylindrical in conguration, the housing having its outer surface 253 threaded for engagement with corresponding threads 254 in the mounting block 204. The housing 252 terminates at its lowermost end in a cap 256 having a hollow interior 257 permitting of some freedom of motion upwardly and downwardly of the collet 251 and the instrument 261 confined therein. At the upper end of the collect 251 there is formed a pulley 262 about which is reeved the endless cord 211 of the dental unit, and which thereby rotates the collect at a high rate of speed depending upon the dimension assigned to the pulley. For example, with a given rate of cord run translation, a smaller pulley diameter will result in a higher pulley and collet rotation. The upper portion of the collet is encircled and supported by a first or upper anti-friction bearing 266 abutting the burr.

ass/e527 against a shoulder 267 between the pulley and the upper collet wall. Theupper anti-friction bearing 266 has an outer diameter slightly less than the inner diameter of the housing 252 and is therefore free, within limits, to translate vertically upwardly and downwardly. The upper bearing 266 is normally urged in an upward direction by virtue of the force exerted by a helical spring 268' abutting at its lower end against the inner race of a second antifriction bearing 271 which is in an interference iit'with the adjacent wall of the housing 252 and which is therefore not free to move. The lower end of the collet normally flares outwardly owing to the pre-set given to a plurality of jaws 272 having inturned teeth 273 to tit within the annular slot 274 at the lower end of the burr 261.

As can be seen by especial reference to Figure 13 the burr 261 is most easily either inserted or withdrawn by urging downwardly on the pulley 262 by the thumb 291 of the user. As the pulley 262 is urged downwardly, pushing ahead of it the upper anti-friction bearing 266 and compressing the helical spring 268, the jaws 272 at the lower end of the collet are released from the confinement of the fixed lower bearing 271 and are thus free to spread apart under the pre-set jaw teeth thereupon spring radially outwardly or away from the lower end of the burr and permit either withdrawal or insertion of Conveniently, when it is desired to insert the burr, the pulley is depressed as shown and the burr inserted downwardly through the center of the collet until the bottom of the burr abuts the upper face of the button 256. The pulley is thereupon released and as the pulley and collet Withdraw under spring urgency the jaws are forced inwardly by the camming action of the anti-friction bearing 271 and the jaws 272 are correspondingly forced inwardly until they directly engage with the burr, the teeth 273 also jutting into the annular slot 274, as appears in Figure 12 most clearly, and thus positively confining the burr against translation.

Figures 14-16 illustrate still another variant form of the *high speed angle hand piece of the invention and, in many respects, is the preferable form thereof.

A slightly tapering hollow sheath 3M assumes adjacent its outermost end 302 the customary angular o`t`- set of about l and is given a hollow circular cylindrical configuration, or barrel 303, with a forwardly projecting overhanging portion 304. Clipped securely to the barrel 34%3 and residing in an annular groove 306 therein is a cover guard 307. While the forward portion 30S, or nose, of the guard 307 is a continuous hemisphere the rearwardly extending member 309 of the guard is interrupted as at 311 in Figure 14 to permit a slight springing apart of upper spaced portions of the rearwardly extending member 309 during assembly.

The upper central portion of the barrel overhang 304 is pierced by a circular aperture 312 and a registering arcuate portion 313 is' provided in the cover guard 307. Disposed within the aperture 312 and the portion 313 is a cylindrical housing 316 appropriately secured to the sheath barrel 363, as by soldering 317. Mounted within the housing 316 is a spindle unit 321 of the kind shown, for example, in Figure 4, and there designated by the reference numeral 3l. A depressable button 322 at one end of the spindle unit permits, in a fashion previously described, withdrawal and insertion of dental instrument 323, such as a burr, from the jaws of a collet rotatable in unison with a pulley 324 rotated by an endless cord 326 of the dental unit (not shown).

An opening 327 in the bottom of the cover guard 363 coaxial with the axis of the spindle unit 321 permits the burr 323 to project exteriorly of the guard. An aperture 328 displaced rearwardly from the opening 327 allows water or air to be directed toward the tooth or other area being worked on, the tiuid emanating from a nozzle 331 of a pipe 333 within the sheath and terminating in a nipple attachable to a conventional fluid conducting line of small diameter. Preferably the pipe 333 is disposed within the sheath, the pipe passing through an opening 334 adjacent the rear end of the sheath so as not to interfere with the dentists grasp on the sheath.

Freedom of rotation of the sheath is further enhanced owing to the unique mounting or connection 341 between the sheath and the dental unit joint, generally designated by the numeral 342. Rotatably disposed in an annular groove 343 adjacent the after end of the sheath 361 is a sleeve 344 confined against forward translation by the shoulder 346 and against rearward translation by a collar 347 having a forwardly projecting inner flange 348 in tight or interfering relation with the adjacent portion 349 of the sheath. In order to mount the collar 347 on the sheath even more securely, an annular crimp 351- is sometimes spun into the collar, as appears in Figure 16, the crimp causing a corresponding annular deformation 352 in the adjacent sheath wall. The outermost margin of the collar 347 conveniently assumes the shape of a skirt 353 spaced slightly from the sleeve 344 to allow free sheath rotation with respect to the sleeve but providing maximum security against translational separation between the sheath and the sleeve.

Mounted on the sleeve 3de is a bracket 361 having a rearwardly extending and downturned arm 362. Rotatably secured to the arm 362 for rotation about an axis transverse to the longitudinal axis of the sheath is a pair of pulleys 366. The tops of the pulleys, as appears in Figure 14 are so disposed with respect to the longitudinal axis of the sheath that the two runs of the cord 326 substantially define a plane coplanar with a diameter of the sheath and substantially transverse to the axis of the cutting instrument 323. Actually the cords are disposed on the collect pulley 324i at a slight angle, as appears in Figure 15. it has been found, however, that not only does the slight angularity not increase friction or wear to any measurable degree, but it serves to hold the collet spindle even more securely in a iixed running position. In other words, even though some wear might take place within the spindle unit, thus allowing a slight translational movement of the collet, the longitudinally upward (as appears in Figure 15) component of the cord thrust against the upper cheek of the pulley 324 serves to hold the pulley and thus the burr 323 in lixed longitudinal location during cutting.

The rearrnost portion 371 of the arm 362 has rotatably mounted thereon a sleeve 372 to which a stud 373 is secured. Rotatably mounted on the stud is a first idler wheel having one run 375 of the cord 326 disposed thereon. Also mounted on and pivoted to the stud is a link 376 having rotatably mounted on the opposite end a second idler wheel 377 having -reeved thereon the other run 37S of the cord 326. A connecting member 379 isV pivoted to the end of the link 376 and serves as a junction between the angle hand piece with its attendant parts and the conventional dental unit structure. The offset idler wheel mechanism, while not constituting any part of the present invention, has been found to be highly compatible with the high speed angle hand piece of the invention since it provides a relatively constant cord tension regardless of the rotational angularity and the attitude of the sheath with respect to the dental unit structure.

In some environments and uses and depending partly on the predelictions of the dentist, it has been found that the dental unit as presently known is entirely eliminated. instead, at the rear end of the sheath, for example the sheath appearing in Figure l, there is mounted a pulley (not shown) rotatable about an axis transverse to the longitudinal axis of the sheath with the endless cord reeved about the pulley. Driving the pulley is a unit such as a motor of very small size powered by suitable electrical leads. The angle hand piece would in this case be substantially self-contained and be capable of exrernes of Orientation as required by the user. It is to bc realized that as a substitute for the small high speed electric motor, an air or hydraulically driven turbine or other drive could be used. The very low frictional loss encountered in the hand piece and the very great cutting ability of high speed instruments enables such small self-centained units to be utilized without significant loss of speed as load is applied.

It can therefore be seen that I have provided a highly versatile, safe and etlicient angle hand piece capable ot' operating at ultra high speeds, and incorporating a spindle unit which permits of easy and quick insertion, positive holding, and rapid interchange of dental cutting and cxcavating instruments.

What is claimed is:

1. A high speed angle hand piece comprising a hollow convergingly tapered conical sheath, a substantially cylindrical body mounted on the smaller end of said sheath and angullarly inclined thereto, said body including a hollow cylindrical tube portion and an elongated block portion, a spindle unit mounted transversely on said block portion, said spindle unit including a hollow cylindrical housing open at both ends, a tirst anti-friction bearing mounted in said housing at one end thereof, a collet extending through said housing and mounted in said iirst anti-friction bearing, a second anti-friction bearing ad- I" jacent the other end of said housing and slidably disposed therein, said second anti-friction bearing encircling the adjacent end of said collet, a helical spring interposed between said bearings, a push-button mounted on said other end of said housing and movable toward and away i from said second bearing, a pulley mounted on the end of said collet away from said push-button, and an endless motor-driven cord disposed within said sheath and said body and reeved about said pulley for rotation of said collet.

2. A high speed angle hand piece comprising a sheath, a driving cord disposed in said sheath a spindle unit mounting body mounted on one end of said sheath and angularly inclined thereto, a spindle unit disposed in said mounting body, said unit including a housing, a collet journalled in said housing, and a pulley mounted on said collet adapted to receive said driving cord and a sheath mounting bracket secured to the other end ot said sheath and rotatably mounted on the shaft of a dental unit wrist joint.

3. A high speed angle hand piece comprising an elon" gated sheath, a driving cord disposed in said sheath a spindle unit mounting block on one end of said sheath and angularly inclined thereto, a spindle unit mounted on said block, said spindle including an instrument holding collet, and a pulley adapted to receive said driving cord, means for rotatably connecting the other end of said sheath to a dental unit wrist joint, and means for limiting the rotation of said connecting means to a predetermined range of arc.

4. A high speed angle hand piece comprising a hollow sheath adapted to receive a driving cord, a driving cord passing through said sheath, an elongated block mounted on one end of said sheath, and a spindle unit including a hollow cylindrical housing, a iirst anti-friction bearing secured to said housing adjacent one end thereof, a collet mounted in said rst bearing coaxially with said housing, a pulley mounted on one end of said collet exteriorly of said housing, said pulley being engageable with Said driving cord, the other end of said collet terminating in a plurality of resilient tapered jaws, each of said jaws having an inwardly projecting tooth adapted to move into engagement with the annular slot in a dental instrument, a second anti-friction bearing translatably disposed in and adjacent the other end of said housing, a helical spring interposed between said first and said second bearing, said second bearing being urged by said spring into jaw closing relation with said collet jaws, and a button slidably mounted on said other end of said housing, said button including an out-turned margin urgable against said second bearing to overcome the collet jaw closing force of said spring.

5. A high speed angle hand piece comprising a tapered sheath, a mounting block secured on one end of said sheath and angularly inclined thereto, a spindle unit mounted on said block, said unit including a pulley, and an instrument holding collet coaxially mounted on said pulley, a cylindrical plug mounted on the other end of said sheath, said plug having a pair of apertures on each side of its axis, and a socket formed centrally therein, a ball disposable in said socket and mounted on the end of a dental unit connecting rod, and endless cord attached to a dental unit said cord being run through said pair of apertures and reeved about said pulley for direct rotation of said collet, and a sleeve guard sl'idably mounted on said one end of said sheath and slidable over said block to a location adjacent said pulley.

References Cited in the tile of this patent UNITED STATES PATENTS 2,078,859 Lapharn n Apr. 27, 1937 2,824,370 Page Feb. 25, 1958 FOREIGN PATENTS 515,349 Great Britain Dec. 4, 1939

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