US2791835A

US2791835A - Contra angle attachments for dental hand pieces

Info

Publication number: US2791835A
Application number: US395764A
Authority: US
Inventors: Staunt Martin
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-12-02
Filing date: 1953-12-02
Publication date: 1957-05-14
Anticipated expiration: 1974-05-14

Description

M. STAU NT May 14, 1957 CONTRA ANGLE ATTACHMENTS FOR DENTAL HAND PIECES Filed Dec. 2, 1953 3 Sheets-Sheet l IINVENTOR. zasmfi y 1957 M. STAUNT 2,791,835

CONTRA ANGLE ATTACHMENTS FOR DENTAL HAND PIECES Filed Dec. 2, 1953 s Sheds-Sheet 2 IN V EN TOR.

v BY @7 z zzghwzi WM M. STAUNT May 14, 1957 CONTRA ANGLE ATTACHMENTS FOR DENTAL HAND PIECES Filed Dec. 2,-1953 5 Sheets-Sheet 3 Q INVENTOR. fix??? 5Zazaz2 United States Patent 2,791,835 CONTRA ANGLE ATTACHMENTS FOR DENTAL HAND PIECES Martin Staunt, Des Plaines, 11]. Application December 2, 1953, Serial No. 395,764 20 Claims. (Cl. 32-27) The present invention relates to contra angle attachments for dental hand pieces, and is particularly concerned with the provision of an improved contra angle attachment adapted to be used upon various types of dental hand pieces.

One of the objects of the invention is the provision of an improved contra angle attachment for holding and driving burs and other tools in which the driving force causes the bur to be gripped by the driven tube or shaft.

Another object of the invention is the provision of an improved dental tool of the class described which is adapted to be used with dental burs or tools of the types which are standard in construction and already sold to the trade.

Another object ofthe invention is the provision of an improved dental tool in which the bur cannot drop out after it has been inserted in a chuck, but in which the burs may be readily withdrawn by pulling with the fingers.

Another object of the invention is the provision of an improved dental tool having a chuck for positively gripping the bur shank, in which the gripping force is proportional to the pressure or resistance that is exerted on the bur, so that the bur is firmly locked while it is being used, but it is, nevertheless, capable of being withdrawn by means of the fingers when it is not being driven and is not locked.

Another object of the invention is the provision of an improved contra angle in which axial or radial play of the bur shank is eliminated and vibration is eliminated so that the bur runs more smoothly and the hammering action, which might be caused by vibration, is eliminated.

Another object of the invention is the provision of an improved contra angle in which the but is adapted to be driven more smoothly and at a higher speed substantially without vibration so that the grinding stones are preserved; and less trauma is experienced by the patient.

Another object of the invention is the provision of an improved contra angle which is particularly adapted to be used with carbide and diamond burs, which break very easily, but which are protected against breakage in the present contra angle by the steady rotation without vibration.

Another object of the invention is the provision of an improved contra angle in which the bearings are protected against the ingress of any foreign material, such as grit or abrasives.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings, of which there are three sheets,

Fig. l is a side elevational view of a dental hand piece of the type with which this contra angle is preferably used;

Fig. 2 is an enlarged sectional view taken on a plane parallel to the paper in Fig. 1, the plane passing through the axis of the driving and driven shafts, with certain parts in elevation;

ice

Fig. 3 is a similar view of a modification employing a different type of bearing;

Fig. 4 is an enlarged elevational view of the collet for gripping the bur shank;

Fig. 5 is an enlarged end elevational view of the collet taken on the plane of the line 5-5 of Fig. 4;

Fig. 6 is an enlarged elevational view taken on the plane of the line 6-6 of Fig. 4, looking in the direction of the arrows;

Fig. 7 is an enlarged sectional view similar to Fig. 2, but showing the bur shank retaining spring in elevation.

Fig. 8 is an enlarged view of the retaining spring;

Fig. 9 is an enlarged view taken on the plane of the line 9-9 of Fig. 2, showing the collet and the gripping cams.

Referring to Fig. l, the present contra angle is adapted to be used with a handpiece 10 having a main housing 11 adapted to be held in the hand, and provided with a chuck 12 for engagement with the drive shaft 13 of an attachment 14 having a second shaft 15 housed in a bearing housing 16, and adapted to be adjusted to various different angular positions.

The shaft 15 is provided with a gear 17 secured to it with a pin 18, which may be riveted in place. The gear 17 has its end teeth 19 arranged in a circle and shaped as shown for driving a pinion 20 having its axis at right angles to the axis of the gear 17.

The teeth 21 of pinion 20 are suitably shaped to cooperate with the teeth 19 on the gear 17 with a rolling contact and smooth transmission of power.

The present attachment is provided with a housing 22 having an integral laterally projecting tubular member 23, which is internally threaded at 24 to receive the threaded end 25 of the bearing housing 16. When the threaded attachment housing 22 has its end 26 threaded home on the threads 25 against the shoulder 27 on the housing 16, the parts are so proportioned that the gear 17 is in position for proper engagement with the pinion 20.

The housing 22 has a lateral tubular extension 28 at right angles to the axis of housing 22 and another extension 29 coaxial with the extension 28, extending from the opposite side of housing 22. Housing 22 is provided with a bore 30 of suflicient size to pass the gear 17 with a clearance; and housing 22 has a transverse bore 31, ajcounterbore 32, and a second counterbore 33 of suitable size to house the parts, yet to be described.

Counterbore 33 is closed at its outer end, being provided with an end wall 34; and counterbore 33 is adapted to receive a bearing sleeve 35, which is soldered in place in the counterbore 33, and which has a cylindrical bore 36, serving as a hearing.

The cylindrical bore 36 in the embodiment of Fig. 2 communicates with a frusto-conical bore 37, which communicates with a smaller bore 38. The forward extension 29 of the housing 22 is provided with internal threads 39 and with a plane end surface 40, and is adapted to receive a bearing member 41, comprising a cylindrical tube provided with external threads 42 engaging inside the threads 39.

The bearing

members

41 and 35 are preferably made of stainless steel. The forward bearing 41 is provided with a laterally projecting flange 43, having a plane annular thrust surface 44, which engages the end of housing extension 29 when the bearing is threaded home.

Bearing 41 preferably has its outer surface 45 of noncircular shape to be engaged by a suitable wrench; and it preferably has a concavely curved annular tapered surface 46 leading to its plane end 47. The bearing 41 has a cylindrical bore 48 to provide a bearing for the spindle 49, which has a complementary external cylindrical hearing surface 50.

The spindle 49 comprises an integral tubular metal member preferably made of stainless steel and coated with an extremely thin layer of hard chromium, which provides a very smooth and long lasting bearing when rotating against the

stainless steel bearings

41 or 35.

The spindle 49 is provided with an integral pinion 20 located to have its annular surface 51 engaging an annular thrust surface 52 on the inner end of the bearing 41 to limit the end play of the spindle in one direction. The spindle 49 has a cylindrical outer surface 53 extending from the pinion 20 to an annular shoulder 54. From the annular shoulder 54, spindle 49 is reduced in size and provided with a reduced cylindrical end portion 55, which has a rotating fit in the cylindrical bore 36 of bearing 35.

The stainless steel spindle 49 is coated with chromium over all, including the bearing surface 55, giving a hard chromium surface engaging the inside of the stainless steel bearing 35.

In the embodiment of Fig. 2 the reduced size extension 55 has a frusto-conical end portion 56 engaging the frustoconical bearing surface 37; and the spindle is closed at its inner end, being provided with an end wall 57 and a plane end surface 58.

The spindle 49 is provided with an internal bore 59, which is not cylindrical, but is shaped as shown in Fig. 9, where the bore 59 can be seen to be formed with three

cylindrical curves

60, 61, and 62 of greater radius than the over-all radius of the spindle, and formed on the centers 60a, 61a, and 62a.

These curves join at the

apices

63, 64, and 65, which are visible in Fig. 9, due to its enlargement; and the curved surfaces 5961 form cams which act on a collet 66, which is shown in Fig. 4.

The collet 66 comprises a cylindrical tubular body having three axially extending

slots

67, 68, and 69, which extend from the outer plane end 70 well into the reduced cylindrical bore 69a, and therefore has a thinner side wall 72.. The reduced portion 71 constitutes a relief groove between the cam portion 73 of the collet and the cylindrical portion 74 of the collet.

Between the reduced cylindrical portion 71 and the cam portion 73 there is a tapered annular surface 75; and another tapered annular surface 76 is located between the relief 71 and the cylindrical end portion 74 of the collet. The external surface of the cam portion 73of the collet is formed with three partially cylindrical

curved camming surfaces

77, 78, and 79, which are so formed that their apices would be at 80, 81, and 82, midway between the walls of the slots 67-69; but the collet is cut away at those points by the slots.

The external curves 7779 of the collet are again formed on a larger radius, using center 60a for curve 77, 62a for curve 79, and center 61a for curve 78. Thus the external camming surface 73 of the collet is formed with three uniformly curved camming surfaces adapted to cooperate with three opposed uniformly curved camming surfaces in such manner that the relative rotation of the collet 66 in the spindle causes the walls of the spindle to force the walls of the collet together.

In eflect, the slots 67--69 provide the collet with three jaws, which have the internal cylindrical surface 69, but which jaws are adapted to bend toward each other at the thinner portion of the wall 72 at reduced relief section 67 for the gripping of a tool shank. The cam action is such that all of the jaws of the collet are uniformly pressed inward at the same time, when the collet begins to rotate relative to the spindle for gripping the tool shank.

The spindle is provided with a cylindrical bore 83 (Fig. 2) for rotatably receiving the cylindrical end portion 74 of the collet; and the spindle i provided with an annular thrust surface 85 for engaging the end surface 86 of the collet. The spindle also preferably has a shallow annular groove 87 located between the cylindrical bore 83 and the cam shaped bore which is formed by the inner curved surfaces 60-62.

The interior of the collet 66 is preferably so shaped and constructed that it will take the shanks of standard tools, such as the standard burs which are now on the market; and it will also take the shanks of special burs or other tools which are adapted to be used with this attachment, such as the bur 88, which has a cylindrical shank 89, a cutting end portion 90, and a tapered stem 91 between the shank and bur end.

The cylindrical shank 89 is a close lit in the bore 69 of the collet 66 so that the jaws of the collet need only move the slightest amount to grip the shank. At its inner end the bur shank 89 is provided with a flattened end portion 92 and with an end shoulder 93 of segmental shape; and the collet 66 also has its bore 69 complementary in shape, being provided with an inwardly extending segmental portion 94, having a plane side surface 95 for engaging the flattened end portion 96 on the tool shank.

There is a suitable clearance 97 between the

surfaces

96 and 95 so as to permit some rotation of the tool shank in the collet; but the rotation is definitely limited by the surfaces coming into contact; and the tool shank cannot rotate beyond that point in the collet. Also, this is the shape of standard tool shanks on the market which are adapted to be received in the present collet as well.

The spindle is also provided with an annular groove 98 adjacent its annular thrust surface 54, the groove being partially circular in cross section and formed in the external cylindrical surface 53 to extend sufficiently about the periphery of the spindle 49 to receive the circular portion of the spring 99 (Fig. 8), which begins at 100 and ends at a bend 101.

Thus the circular portion of the spring extends over more than 180 degrees so that the spring grips the spindle 49 in the groove 98 and tends to be retained in the groove. The spring 99 has a straight portion 102 (Fig. 8), which extends across the tool shank and is located in an open slot 103 in the spindle so that the straight portion 102 may spring in or out; and it is adapted to engage the end portion 104 of the tool shank on one side.

The tool shank may be provided with a flattened surface 105 on the end portion 104 on that side which engages the straight portion 162 of the spring 99; and this flattened portion may terminate at a rectangular transverse slot 106, which has no function in securing the present tool shank in the present chuck, but enables the present tools to be used in the standard chucks on the market.

For this purpose the tool shank 89 has a reduced cylindrical portion 107, which constitutes that part of the tool shank that protrudes from the upper side of the contra angles of the prior art, and which engages in a groove in a pivoted retainer on the contra angles of the prior art, such as exemplified at 34 in Staunt Patent No. 2,098,317.

The tool shank 89 rotates with its central reduced cylindrical portion 109 in the groove of the prior art retainer.

The spring 99 engages the flat surface on the bur shank 89 lightly, but with sufiicient friction to hold the bur in the contra angle against dropping out, but the bur can be pushed in or pulled out with the fingers. When the bur is pushed in, its end cams against the curved surface of the spring 102 and presses the spring 102 outward in the slot 103 a very slight amount, represented by the clearance at 195.

In the embodiment of Fig. 3 the bearing 35 is provided with the cylindrical bore 36 from end to end, eliminating the frusto-conical portion 37; and the spindle likewise eliminates the outer fmsto-conical surface 56. In such case the clearance between 54 and the end 110 of bearing 35 should be reduced to smaller dimensions to prevent end play.

At its opposite end the spindle 49 isv provided with a reduced cylindrical portion 111 and an annular shoulder 112 for being received in a complementary bore 113 in a centrifugal slinger 114. The centrifugal slinger comprises a circular metal member of stainless steel, having a bore 115 for passing the tool shank 89; and the slinger overhangs the end '70 of the collet, confining the collet in the spindle.

The slinger has a plane end surface 116 surrounding the bur shank and is provided with a backwardly turned flange 117, locating its rim 118 outwardly and backwardly of the bearing bore 48. The rim 118 is located adjacent the annular concave surface 46 on the end of bearing 41; and any grit, liquid, or foreign matter which may get on the slinger 13.4 finds itself by centrifugal force to the rim 118, where it is thrown off, away from the bearing bore.

Thus the bearing 41 is protected against the ingress of moisture, grit, or grime, or other foreign matter; and the other end of the contra angle being closed at 34, both bearings are protected.

The operation of my contra angle attachment is as follows:

When the attachment is secured to a handpiece as described, the shaft 15 and gear 17 are adapted to rotate the pinion 20 and with it the entire spindle, collet, and bur. When at our is to be inserted in the bur chuck or collet, the end of the bur shank is placed in the bore 69; and the bur is rotated until the flat end portion 96 registers with the flat surface 97 in the collet.

Then the bur may be inserted further until it engages the straight portion 192 of spring 99, which straight portion is pushed outward, engaging the surface 105 on the tool shank, and retaining the bur in the chuck so that the bur cannot fall out. The fiat portion 96 on the tool shank positively prevents the bur from rotating except a slight amount in the collet.

As soon as the working end 90 of the bur is applied to a working surface, such as a tooth, the bur 88 and the collet 66 are retarded inside the spindle 49; and the cam surfaces 77-7 rotatively engage the inner cam surfaces 60-62 in the spindle, causing the collet to grip the tool shank and eliminate any axial or radial play, which I have found in all other such attachments.

The thin deposit of hard chrome on the outside of the spindle or gear tube is ground to precision, and adapts the gear tube to rotation at a very high speed when used in the bearings of stainless steel.

The slinger serves as a cover to prevent the chuck or collet from slipping out, and also protects the inside mechanism from tooth powder, grit, and foreign particles. The bottom bearing, having no opening from the outside, no abrasives can enter at this end.

The contra angle saves the time of the dentist because it requires no extra operation to lock the bur. Because the bur is clamped by concentric earns, the bur runs truer, smoother, and with less vibration, which preserves the grinding stones; and less trauma is caused by the bur. Vibration causes a our to act like a mallet; and eliminating the vibration adapts the contra angle to be used with burs having carbide or diamond cutting edges. Such burs break very easily unless the rotation is steady and smooth and without vibration.

It will thus be observed that I have invented an improved contra angle attachment for dental handpieces, in which the bur shank is automatically gripped when the spindle or gear tube rotates; and the gripping being by three cams located at the same radius, the bur shank and bur are accurately located in an axial position. The bur cannot drop out, although it may be inserted merely by pushing it into its place with the fingers; and it can likewise be removed by pulling it out with the fingers, thus eliminating unnecessary operations of locking and unlocking the bur as in the devices of the prior art.

While I have illustrated a preferred embodiment of .6 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:

l. A chuck for tools having a cylindrical shank, comprising a collet having a cylindrical bore, said bore extending from end to end except for a transversely extending segmental portion at the inner end for engaging a complementary tool shank, and a driving tube comprising a tubular member having a circular bore at one end for receiving the external inner circular end portion of said collet, the said collet and driving tube having outer and inner surfaces, respectively, which are formed on a larger radius than the radius of the bore of the driving tube, and forming camming surfaces acting on said collet, which is split longitudinally and adapted to grip the tool shank upon relative rotation of the collet and driving tube, the said driving tube being provided with a pcripheral groove extending over more than one hundred and eightly degrees, and having an oppositely located through slot for receiving a spring wire having a complementary portion located in said groove, and a straight portion traversing said slot for engaging a tool shank in the collet, and retaining it against removal, which may be accomplished by mere finger pull.

2. In a dental handpiece and tool assembly, the combination of a dental tool having a Working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at is split end to grip the tool shank, taking up all looseuess between the tool shank, collet, and driving tube concentrically.

3. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to. grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said tool shank being provided on its inner end with a transversely extending cut-away portion, forming an end shoulder and a fiat side shoulder, and the said collet having complementary surfaces with a clearance, permitting the tool shank to be pressed in with the fingers or removed with the fingers.

4. In a dental handpiece and tool assembly, the combination of a dental tool having a workingend and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said tool shank being provided on its inner end with a transversely extending cut-away portion, forming an end shoulder and a flat side shoulder, and the said collet having complementary surfaces with a clearance, permitting the tool shank to be pressed in with the fingers or removed with the fingers, the said driving tube having a fixed peripheral spring with a portion extending through a lateral slot and engaging the tool shank to prevent the tool from falling out.

5. In a dental handpiece and tool assembly, the combination of a dental tool having a Working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner here at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said tool shank being provided on its inner end with a transversely extending cut-away portion, forming an end shoulder and a flat side shoulder, and the said collet having complementary surfaces with a clearance, permitting the tool shank to be pressed in with the fingers or removed with the fingers, the said driving tube having a fixed peripheral spring with a portion extending through a lateral slot and engaging the tool shank to prevent the tool from falling out, the said spring being circular in cross section to be cammed outward by engagement with the end corner of the tool shank.

6. A dental handpiece attachment, comprising a tubular rousing closed at one end and open at the other end, and provided With'a lateral extension for receiving a drive shaft, and a pinion with end teeth, stainless steel bearings, having cylindrical bearing bores carried one at each end of said housing, a gear tube rotatably mounted in said bearings and provided with complementary external cylindrical surfaces engaging in the bearings, and with an integral spur gear having teeth for engagement with the end teeth on the drive pinion, the said gear tube being made of stainless steel and covered over-all with a layer of hard chromium plating, and being ground in to fit said bearings, and rotate at high speed with a minimum amount of vibration, adapted to be used with hard carbide and diamond burs with a minimum amount of breakage because of the elimination of vibration.

7. A dental handpiece attachment, comprising a tubular housing closed at one end and open at the other end, and provided with a lateral extension for receiving a drive shaft, and a pinion with end teeth, stainless steel bearings, having cylindrical bearing bores carried one at each end of said housing, a gear tube rotatably mounted in said bearings and provided with complementary external cylindrical surfaces engaging in the bearings, and with an integral spur gear having teeth for engagement with the end teeth on the drive pinion, the said gear tube eing made of stainless steel and covered over-all with a layer of hard chromium plating, and being ground in to fit said bearings, and rotate at high speed with a minimum amount of vibration, adapted to be used with hard carbide and diamond burs with a minimum amount of breakage because of the elimination of vibration, said gear tube having a thrust surface on one side of its spur gear, engaging a thrust surface engaging a complementary thrust surface on the other bearing, the said thrust surface on the other bearing and on the gear tube being substantially ,Crusto-conical in shape.

8. A contra angle attachment for dental handpieces, comprising a metal housing having a tubular threaded sleeve adapted to be engaged with the external threaded bearing extension driven by a handpiece, and carrying a driving shaft with a gear having endteeth, said housing having a transversely extending tubular portion provided with a closed end and an open end, a bearing mounted in said closed end, and having a bearing bore, a bearing sleeve carried by the open end of said transverse portion, and having external threads engaging internal threads in the housing, said latter bearing having a bearing bore and a plane inner thrust surface, and a gear tube rotatably mounted in said bearing bore, said gear tube being provided with an internal bore and with a spur gear having teeth adapted to cooperate with the end teeth on the handpiece driving shaft, said gear tube bore having a circular portion and a cam shaped portion, and a collet comprising a tubular member provided with a cylindrical portion at one end and with a cam shaped portion at the other split end on the outside of said collet, said collet being contracted upon rotation of said gear tube by its external cam formation and the internal formation on said gear tube, to grip fixedly a tool shank upon rotation of the gear tube and a retarding force on the collet.

9. A contra angle attachment for dental handpieces, comprising a metal housing having a tubular threaded sleeve adapted to be engaged with the external threaded bearing extension driven by a handpiece, and carrying a driving shaft with a gear having end teeth, said housing having a transversely extending tubular portion provided with a closed end and an open end, a bearing mounted in said closed end, and having a bearing bore, a bearing sleeve carried by the open end of said transverse portion, and having external threads engaging internal threads in the housing, said latter bearing having a bearing bore and a plane inner thrust surface, and a gear tube rotatably mounted in said bearing bore, said gear tube being provided with an internal bore and a spur gear having teeth adapted to cooperate with the end teeth on the handpiece driving shaft, said gear tube bore having a circular portion and a cam shaped portion, and a collet comprising a tubular member provided with a cylindrical portion at one end and with a cam shaped portion at the other split end on the outside of said collet, said collet being con tracted upon rotation of said gear tube by its external cam formation and the internal formation on said gear tube, to grip fixedly a tool shank upon rotation of the gear tube and a retarding force on the collet, said gear tube being provided with a periphral groove extending over more than half its diameter for receiving and retaining a tool-engaging spring, and a spring of complementary shape in said groove, and having a straight portion extending transversely to the bore of the gear tube and adapted to frictionally engage the tool shank.

10. A contra angle attachment for dental handpieces, comprising a metal housing having a tubular threaded sleeve adapted to be engaged with the external threaded bearing extension driven by a handpiece, and carrying a driving shaft with a gear having end teeth, said housing having a transversely extending tubular portion provided with a closed end and an ogien end, a bearing mounted in said closed end, and having a bearing bore, a bearing sleeve carried by the open end of said transverse portion, and having external threads engaging internal threads in the housing, said later bearing having a bearing bore and a plane inner thrust surface, and a gear tube rotatably mounted in said bearing bore, said gear tube being provided with an internal bore and with a spur gear having teeth adapted to cooperate with the end teeth on the handpiece driving shaft, said gear tube bore having a circular portion and a cam shaped portion, and a collet comprising a tubular member provided with a cylindrical portion at one end and with a cam shaped portion at the other split end on the outside of said collet, said collet being contracted upon rotation of said gear tube by its external cam formation and the internal formation on said gear tube, to grip fixedly a tool shank upon rotation of the gear tube and a retarding force on the collet, the said gear tube being provided on its open end with a metal plate recessed to receive the gear tube and apertured to pass the tool shank, said plate retaining said collet in said gear tube.

11. A contra an le attachment for dental handpieces, comprising a metal housing having a tubular threaded sleeve adapted to be engaged with the external threaded bearing extension driven by a handpiece, and carrying a driving shaft with a gear having end teeth, said housing having a transversely extending tubular portion provided with a closed end and an open end, a bearing mounted in said closed end, and having a bearing bore, a bearing sleeve carried by the open end of said transverse portion, and having external threads engaging internal threads in the housing, said latter bearing having a bearing bore and a plane inner thrust surface, and a gear tube rotatably mounted in said bearing bore, said gear tube being provided with an internal bore and with a spur gear having teeth adapted to cooperate with the end teeth on the handpiece driving shaft, said gear tube bore having a circular portion and a cam shaped portion, and a collet comprising a tubular member provided with a cylindrical portion at one end and with a cam shaped portion at the other split end on the outside of said collet, said collet being contracted upon rotation of said gear tube by its external cam formation and the internal formation on said gear tube, a grip fixedly a tool shank upon rotation of the gear tube and a retarding force on the collet, the said gear tube being provided on its open end with a metal plate recessed to receive the gear tube and apertured to pass the tool shank, said plate retaining said collet in said gear tube, the said plate being provided with a downwardly turned diagonal flange having a circular border and adapted to receive grit and moisture which is thrown off said circular edge by centrifugal force.

12. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, said driving and supporting tube being provided with cylindrical end portions having bearing surfaces, and a housing member having a bore closed at one end and open at the other end and provided with bearings at the closed end and at the open end for rotatably supporting said tube.

13. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, said driving and supporting tube being provided with cylindrical end portions having bearing surfaces, and a housing member having a bore closed at one end and open at the other end and provided with bearings at the closed end and at the open end for rotatably supporting said tube, the said bearings having internal bearing surfaces engaging the bearing surfaces on said tube, and one of the engaging bearing surfaces in each case having a stainless steel finished surface, and the other bearing surface in each case being coated with chromium for reducing the wear between the engaging bearing surfaces.

14. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, a tubular housing having bearings at its ends for rotatably supporting said drivin tube, one of said bearings comprising a threaded collar threaded into said tubular housing, and said driving tube being provided with integral outwardly projecting driving teeth having a plane thrust surface engaging a complementary surface on said threaded bearing.

15. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of theexterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, a tubular housing having bearings at its ends for rotatably supporting said driving tube, one of said bearings comprising a threaded collar threaded into said tubular housing, and said driving tube being provided with integral outwardly projecting driving teeth having a plane thrust surface engaging a complementary surface on said threaded bearing, said driving tube extending through said threaded bearing and being provided on its end with a reduced portion supporting a circular plate, said circular plate having a bore of suflicient size to pass the tool shank, but said plate overlying the end of said collet to retain the collet in the driving tube.

16. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, said collet being provided with an annular inwardly extending relief groove between its cylindrical end and the cams located on the other end of said collet.

17. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said driving and supporting tube being provided on its inside with an enlarged counterbore providing a relief between its cylindrical inner bore and the cams formed on the inside of said driving tube at its other end.

18. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as earns, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said tool shank having a segmental portion removed from its inner end and the said driving tube being formed at that end with a complementary transversely extending portion in its cylindrical bore for engaging the adjacent flat part of the tool shank with a clearance, and said tool shank having an adjacent partially annular groove about its end portion for use in securing the tool shank in hand pieces having a retainer pivoting into said groove.

19. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said driving tube being provided with bearings at each of its ends mounted in a tubular housing and having one closed end and one threaded end, the closed end bearing having an inner partially conical surface and the end of the driving tube having a complementary partially conical surface, the threaded bearing being arranged to take up end play at said conical surfaces.

20. In a dental handpiece and tool assembly, the combination of a dental tool having a working end and a concentric cylindrical tool shank, with a tubular collet which has a plurality of longitudinally extending slots extending into one end, dividing the collet into plural tool shank gripping portions, and a driving and supporting tube for said collet, said tube having a cylindrical inner bore for receiving the cylindrical end of said collet, the opposite end of said collet having its external surface formed of a plurality of cylindrical portions formed on a radius which is larger than the general radius of the exterior of the collet, the said cylindrical portions on the collet acting as cams, the driving tube having its inner bore at that end provided with a plurality of similar partially cylindrical formations acting as cams on the collet, the relative rotation of the collet with respect to the driving tube causing the collet to be contracted at its split end to grip the tool shank, taking up all looseness between the tool shank, collet, and driving tube concentrically, the said tool shank having a slightly flat side portion at its inner end, and the said driving tube having an adjacent slot provided with a spring wire projecting slightly into the cylindrical bore into engagement with the slightly flat part of said shank to hold the shank in the driving tube for insertion or removal by mere finger force.

References Cited in the file of this patent UNITED STATES PATENTS 151,239 Morgan May 26, 1874 1,638,175 Terry Aug. 9, 1927 2,005,849 Skinner June 25, 1935 2,098,317 Staunt Nov. 9, 1937 2,504,233 Staunt Apr. 18, 1950 2,679,101 Steuer et a1 May 25, i954 FOREIGN PATENTS 555,559 Great Britain Aug. 27, 1943