WO2001052764A1

WO2001052764A1 - Retention quill for a chucking system in a dental handpiece

Info

Publication number: WO2001052764A1
Application number: PCT/US2001/001443
Authority: WO
Inventors: Jason E. Orgain; Larry E. Mcculloch
Original assignee: Lares Research
Priority date: 2000-01-18
Filing date: 2001-01-16
Publication date: 2001-07-26
Also published as: AU2001229522A1

Abstract

A retention quill for holding a dental tool in a push-button chuck of a dental handpiece is disclosed. The retention quill is configured with various high hardness material inserts and tapered lead-ins which provide extended wear resistance and less dental tool slippage, while speeding the process of inserting a dental tool within the handpiece.

Description

RETENTION QUILL FOR A CHUCKING SYSTEM IN A DENTAL HANDPIECE

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention pertains generally to dental handpieces, and more particularly to an improved retention system for dental tools used with dental handpieces. 2. Description of the Background Art In existing dental handpieces the bur, or dental tool, is interchangeably retained within the handpiece by a retention system, often referred to as a bur chuck, or chuck. The spindie of the handpiece is subject to rotational speeds of up to 500,000 revolutions per minute which are applied at the dental tool, or bur, with varying levels of application force. Numerous variations of dental tool retention systems within dental handpieces have been developed. For example, U.S. Patent 4,611 ,990 issued September 16, 1986 to Lares et al., which is incorporated herein by reference, is representative of a dental handpiece with a push button chuck that has a hollow spindle and a chuck. Dental tool retention systems generally employ steel chucks whose interior surfaces provide an annular attachment surface to retain the cylindrical shaft of an inserted dental tool.

Numerous drawbacks exist with push button chucks found in present day dental handpieces, however. For example, it is often difficult to quickly interchange the dental tools held by these chucks, and changing tools is further complicated by the fact that dentists typically perform all their work with gloved hands. Additionally, the push button chucks are prone to deformation and wear on the components of the chuck which contact the shaft of the dental tool. This deformation and wear can significantly reduce the retention capacity of the system over its useful life. The loss of retention capacity is partially due to a loss in chuck geometries which increase the travel distance required of the interfacing surfaces. The retention capacity, both torsional and axial, is directly proportional to the working height and compression of the energizing spring element. Hence, the farther the chuck deviates from its original engagement point, by loss of material at the contact point, the lower the retention capacity.

Deformation and wear on the surfaces within the chuck which mate with the dental tool occur during both tool insertion and during operation of the dental handpiece. During insertion and removal of a dental tool, drag exists between the tool and fingers of the chuck, which wears the inner surfaces of the chuck. This drag can increase greatly if the push button chuck is not fully in the release position when a dental tool is removed or inserted. The drag between the tool and the chuck causes burnishing of the contact surfaces as material is lost, thus resulting in a consequent loss of retention capacity. Deformation and wear also often occur during operation of the dental handpiece when slippage occurs between the shank of a dental tool, such as a cutting bur, and the chuck contact areas. Material is removed from both the chuck contact surfaces and the bur shank by the initial galling between similar materials along with the subsequent spalling which occurs when micro-adhesion is broken. At the elevated rotational speeds involved, even small amounts of slippage can quickly result in deformation and wear to the chuck and a loss of retention capacity.

The wearing effects described above are exacerbated by the presence of highly abrasive residues such as human saliva mixed with pulverized enamel and dentin. These abrasive substances are often present on the shaft of the dental tool itself as it is inserted within the dental handpiece. As the hardness of tooth enamel is significantly above that of conventionally processed metals, wearing can occur readily.

Accordingly a need exists for the development of a dental handpiece with a push button chuck that provides additional wear resistance and simplifies the insertion and removal of dental tools. The dental handpiece pushbutton chuck in accordance with the present invention satisfies that need, as well as others, and overcomes deficiencies in previously known techniques.

BRIEF SUMMARY OF THE INVENTION The present invention is a retention quill for a dental handpiece employing a push button chuck mechanism. The retention quill according to the present invention provides extended wear resistance, is less prone to slippage, and simplifies the process of tool insertion. By way of example, and not of limitation, a retention quill according to the invention employs a tapered lead-in with a contact shape that improves tool retention, as well as hardened materials in selected sections of the retention quill which increase wear resistance.

An object of the invention is to provide a longer lasting push button chuck assembly for use within a dental handpiece. Another object of the invention is to reduce the time required for the changing of tools within the dental handpiece.

Another object of the invention is to provide a retention quill for a push button chuck assembly that exhibits improved resistance to slippage of the retained dental tool. Another object of the invention is to provide a dental handpiece in which dental tools may be quickly replaced.

Another object of the invention is to provide a retention quill that can be easily removed from the chuck assembly in a dental handpiece and replaced. Another object of the invention is to provide a retention quill for a push button chuck that may be easily manufactured while retaining consistent operation from one unit to another.

Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:

FIG. 1 is a cutaway view of a dental handpiece showing a retention quill according to the present invention positioned within a push button chuck which retains a dental tool.

FIG. 2 is an end view of the retention quill shown in FIG. 1. FIG. 3 is a partial cross-section of the retention quill shown in FIG. 2 taken through line 3-3. FIG. 4 is an end view of an alternative embodiment of the retention quill shown in FIG. 1 through FIG. 3.

FIG. 5 is a partial cross-section of the retention quill shown in FIG. 4 taken through line 5-5. DETAILED DESCRIPTION OF THE INVENTION Referring more specifically to the drawings for illustrative purposes, the present invention is embodied in the apparatus generally shown in FIG. 1 through FIG. 5. It will be appreciated, however, that the apparatus may vary as to configuration and as to details of the parts without departing from the basic concepts as disclosed herein.

Referring first to FIG. 1 , a dental handpiece assembly 10 employing a push button chuck with a retention quill according to the invention is shown. In the exemplary dental handpiece shown, the handpiece comprises a housing 12 with an operating handle 14, and is used for providing rotation of a dental tool 16. Dental tool 16 is shown as a conventional bur having a shaft 18 that terminates in a globular end 20 with cutting teeth. Dental handpieces are used with a variety of rotatable dental tools which typically either cut or polish dental surfaces, and dental tool 16 is simply one of many such tools that is shown for context purposes. During typical operation, the dental tool is rotated at speeds up to 500,000 RPM by the dental handpiece to allow removal of a material 22.

To hold the dental tool in place, a tool chuck assembly is used. In the present invention, the tool chuck assembly comprises a hollow spindle 24 containing a retention quill 26 having longitudinal intervening fingers 28 retaining shaft 18 of dental tool 16. In FIG. 1 dental handpiece 10 is shown in cutaway to reveal a side view of retention quill 26 holding dental tool 16. The intervening fingers 28 of the retention quill can be slid down into an enlarged chamber 30 within the hollow spindle 24 by applying sufficient pressure on the cap flange 32, acted upon by the plunger top 34, to overcome the tension in the nest of bent springs 36. When the protruding portions of intervening fingers 28 enter chamber 30, the intervening fingers open to allow easy removal or insertion of the dental tool. Spindle 24 preferably rotates on an upper bearing 38 and a lower bearing 40 while a set of turbine blades 42 surrounding the spindle within the housing form a high speed turbine. As can be seen, therefore, the present invention comprises an improved retention quill 26 that can be used with various dental handpieces such as that described in U.S. Patent Number 4,61 1 ,990 to Lares et al., which is incorporated herein by reference. The remaining description focuses on the preferred embodiments of the improved retention quill 26 according to the invention.

Referring also to FIG. 2 and FIG. 3, a first embodiment of retention quill 26 is shown in detail. As can be seen, the retention quill comprises a body 50 fabricated from a first material, which is typically steel, into which axial slots 52 have been cut to form a set of annularly disposed intervening fingers 28. The annular exterior 54 of intervening fingers 28 protrudes radially above a relieved section 56. Threads 58 provide for threadable engagement with cap flange 32.

Opposite the threaded end of the retention quill is the receiving end of the quill into which a dental tool is inserted. A second material 60 is shown attached to the contact areas within the inner surface of the intervening fingers 28 near the receiving end of the retention quill 26. This second material is harder than the first material and provides superior wear resistance. A preferred second material is tungsten carbide which can be attached on the interior of the intervening fingers with copper brazing, or like processes. Thus, retention quill 26 employs a hardened material attached within the lead-in of each resilient retention finger so as to form a contact area that resists wear.

While it may appear simpler to fabricate body 50 from the same hard material used for contact areas 60, the hard second material is not appropriate for body 50 because it lacks the flexibility required within relieved sections 56 and threaded end 58 of the body, and is furthermore difficult and expensive to form or finish into small complex shapes. Furthermore, conventional treatments to harden the receiving end of retention quill 26 as a single unit would not provide sufficient toughness to the inner contact surface 64 while, at the same time, leave the exterior regions 54, 56, 58 sufficiently unaffected to provide proper flexibility and wear prevention within the hollow spindle 24. Also, the coatings in conventional hardening treatments would not be of sufficient depth to completely support the contact stresses imparted to the contact area by the dental tool, thereby causing permanent plastic deformation of the geometry of retention quill 26. Furthermore, using hard material on the exterior 54 of the retention quill 26 would cause wear within the hollow spindle 24 that can require replacement of the high speed turbine within the dental handpiece. In contrast, a worn retention quill 26 can simply be replaced. Note that the hard contact area 60 at the receiving end of each intervening finger 28 is shaped within this embodiment with a generally triangular cross- section. A lead-in taper 62 is provided to guide dental tools into the center of retention quill 26. The lead-in taper 62 shown is provided by an arcuate surface canted away from the center of retention quill 26, so as to provide a conical shaped guide surface for inserting the shaft of the dental tool. As can be seen, the lead-in taper 62 terminates at a point of contact 64 which contacts the shaft of the dental tool to hold it from slipping during operation of the dental handpiece. The hard contact area 60 has excellent wear resistance against the near as hard or softer material that comprises the shaft of the dental tool.

It will be appreciated that the teachings of the invention can be implemented in a variety of ways. For example, FIG. 4 and FIG. 5 show another embodiment of a retention quill according to the invention. In this embodiment, retention quill 70 is similarly formed with a body 72 having axial slots 74 which define intervening fingers 76. Each intervening finger 76 has an exterior protruding region 78 near the receiving end and a relieved section 80. A hard contact area 84 has a lead-in taper 86 for speeding insertion of the dental tool and reducing wear. The hard contact area 84 within this embodiment is configured, however, with a splined point of contact 88, which provides a more consistent contact profile as it wears as well as a larger area for the lead-in taper 86.

Accordingly, it will be seen that this invention of a dental handpiece push button chuck provides added wear resistance and ease of use. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of this invention should be determined by the appended claims and their legal equivalents.

Claims

CLAIMS What is claimed is:

1. A retention quill for a chucking system in a dental handpiece, comprising: (a) an annular body, said annular body including a opening configured to receive a dental tool;

(b) a plurality of spaced-apart resilient fingers radially disposed on said annular body and defining said opening, each of said resilient fingers having an inner surface; and (c) a contact material attached to said inside surface of each said resilient finger, said contact material having a hardness exceeding that of the resilient finger.

2. A retention quill as recited in claim 1 , said retention quill is configured for removal and insertion in said chucking system.

3. A retention quill as recited in claim 2, wherein said contact material forms a guide surface slanting outward conically.

4. A retention quill as recited in claim 1 , wherein said contact material forms a guide surface slanting outward conically.

5. A retention quill for a chucking system in a dental handpiece, comprising: (a) an annular body, said annular body including an opening configured to receive a dental tool;

(b) a plurality of spaced-apart resilient fingers radially disposed on said annular body and defining said opening, each of said resilient fingers having an inner surface; and (c) a contact material attached to said inner surface of each said resilient finger, said contact material having a hardness exceeding that of the resilient finger, said contact material forming a guide surface slanting outward conically.

6. A retention quill as recited in claim 5, said retention quill configured for removal and insertion in said chucking system.

7. A retention quill for a chucking system in a dental handpiece, comprising:

(a) an annular body, said annular body including a opening configured to receive a dental tool;

(b) a plurality of spaced-apart resilient fingers radially disposed on said annular body and defining said opening, each of said resilient fingers having an inner surface; and

(c) a contact material attached to said inside surface of each said resilient finger, said contact material having a hardness exceeding that of the resilient finger; (d) said retention quill configured for removal and insertion in said chucking system.

8. A retention quill as recited in claim 7, wherein said contact material forms a guide surface slanting outward conically.

9. A retention quill for a chucking system in a dental handpiece, comprising:

(a) an annular body, said annular body including a opening configured to receive a dental tool; (b) a plurality of spaced-apart resilient fingers radially disposed on said annular body and defining said opening, each of said resilient fingers having an inner surface; and

(c) a contact material attached to said inside surface of each said resilient finger, said contact material having a hardness exceeding that of the resilient finger, said contact material forming a guide surface slanting outward conically;

(d) said retention quill configured for removal and insertion in said chucking system.