Push-button operated chucking device for a dental angle piece

A chucking device for holding a dental tool by a collet chuck with collet chuck sleeve, wherein the collet chuck can be released by a push button against the force of clamping spring. The collet chuck sleeve has at both ends thereof axial slots, so that it is constructed at both ends as a collet chuck. The casing of the collet chuck is undercut at both ends, wherein the undercut at the side of the tool is mounted in an axially fixed, but rotating conical seat and the undercut on the side of the push button is mounted in a conical seat of an actuating member. The actuating member is under the influence of the clamping spring and, for releasing the collet chuck, the actuating member is displaceable against the force of the clamping spring toward the axially fixed seat. Instead of the collet chuck, it is also possible to provide two axially spaced apart groups of radially displaceable clamping elements.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a push button-operated chucking device for 
a dental angle piece including clamping elements which press radially 
against the tool shaft for holding the tool shaft in a frictionally 
engaging manner. By axially moving an actuating member connected to the 
push button, and in interaction with a conical control surface, the 
clamping elements can be moved radially outwardly and inwardly for 
releasing and clamping the tool shaft. 
2. Description of the Related Art 
Chucking devices of the above-described type are known in various 
embodiments. 
For example, from DE-C-2 29 05 484 and AT-B 373 488, it is known in the art 
to support the tool by means of a collet chuck which can be preferably 
released against the force of a spring by means of a push button arranged 
at an axial distance from the tool. The chucking action is obtained by the 
spring in interaction with a conical control surface for the outer side of 
the collet chuck. 
In the device according to DE-C-2 29 05 484, the chucking area is located 
seen in axial direction near the tool end, i.e., on the side of the push 
button, while in the device known from AT-B 373 488 the chucking area is 
near the opening for inserting the tool. 
Other means for fixing angle pieces in a frictionally engaging manner are 
also known in the art. For example, in accordance with Austrian Patent 
Application A 3448/84, a holding element which is elastic in radial 
direction by means of a slotted sleeve whose internal radius is smaller 
than the shaft radius, enlarges its internal radius by the approach of two 
conical control surfaces, and, thus, releases the tool. 
A similar type of support has become known from EP-A1-0 098 754. However, 
in this case, the change of the radius is achieved only by means of a 
conical surface. 
A different type of fixing device with frictional engagement has become 
known from EP-A10 420 169. A helical spring mounted in a holder is wound 
around a clamping member which is slotted in axial direction and presses 
the clamping member against the tool shaft. When an axial pressure is 
exerted on the spring, the internal radius of the spring is enlarged and 
the shaft is released. 
All of the above-discussed collet chucks have the significant disadvantage 
that the axial area in which the shaft is actually clamped, i.e., the 
clamping area, is relatively short. In addition, in the relatively long 
axial area in which the collet chucks do not rest against the tool shaft, 
the tool shaft is guided in a bore of the chucking sleeve, i.e., the guide 
length, which must have at least a diameter which corresponds to the 
largest possible diameter of the tool shaft due to tolerances. Since the 
bore itself is also subject to a tolerance, there is in practically all 
types of applications a play which may be small, but which is still 
noticeable because of the high rates of rotation which occur. This play is 
harmful to the tool and to the handpiece and is unpleasant or even painful 
to the patient, because it causes wobbling of the tool in its support. 
The fixing device according to EP-A1-0 420 169 has the additional 
disadvantage that during clamping not only the desired decrease of the 
internal radius of the spring occurs, but also an undesirable increase of 
the outer diameter thereof, so that, although the tool does not wobble in 
the clamping sleeve, the spring including tool and clamping sleeve wobbles 
in the holder. As a result, in spite of the relatively great axial length 
of clamping between tool and clamping sleeve, fixing with respect to the 
angle piece again takes place only at one axial location. 
Accordingly, all chucking devices have the decisive disadvantage that there 
is a large difference between the clamping length, i.e., length of contact 
with the clamping elements, and the guiding length, i.e., insertion length 
minus clamping length, which facilitates wobbling. 
Fixing devices which eliminate this problem have already been proposed in 
dental hand pieces in which the tool axis coincides with the principal 
axis of the handpiece and, thus, the axial extension of the tool holder 
does not play a role. 
Thus, AT-B 300 176 discloses a handpiece which includes a double collet 
chuck which clamps the tool shaft at two axially spaced apart locations. 
Of course, because of the coaxial arrangement of drive axis and tool axis, 
the actuation of this collet chuck is only possible by means of 
complicated rotating mechanisms. 
An even more complicated mechanism is disclosed by DD-PS 118 800 because 
releasing and clamping of the double collet chuck is effected by means of 
a tilting lever which also rotates in the interior of the handpiece, so 
that higher rates of rotation are not possible. 
Another double collet chuck is known from U.S. Pat. No. 3,631,597. However, 
in this double collet chuck, only one end is utilized for clamping the 
tool shaft, while the other end is used for axially fixing the collet 
chuck. 
The use of a true double collet chuck is known from EP-A1-0 421 907. It is 
a true double collet chuck because it chucks as a result of an axial 
compression spring and not because of its own elasticity, and because it 
releases the tool shaft when the spring force is exceeded. As a result, it 
is possible to clamp the tool shaft at two locations which are axially 
spaced apart from each other. This double collet chuck has the 
disadvantage that, although the use of simple conventional conical 
counterpieces is possible, a lever mechanism for reversing the movement 
must be provided for the push button because of the construction of the 
collet chuck as a cylindrical sleeve with two hollow truncated cones which 
are mounted on the cylindrical sleeve and narrow in axial direction. In 
addition, the naturally flexible collet chuck has the tendency to buckle 
under compressive load at high rates of rotation, so that the collet chuck 
must be guided as exactly as possible along its entire external area. 
SUMMARY OF THE INVENTION 
Therefore, it is the primary object of the present invention to eliminate 
the above-described shortcomings of the angle pieces having two axially 
spaced apart clamping locations and an actuation by means of a push 
button, and to provide a fixing device in which the above-described 
disadvantages do not occur. 
In accordance with the present invention, clamping elements are provided at 
two locations which have an axially fixed distance from each other, 
wherein the actuating member acts on both groups of clamping elements in 
such a way that it has the tendency to move them apart from each other in 
axial direction, and wherein a conical control surface is provided for 
each group of clamping elements, wherein at least one control surface is 
axially displaceable by means of the actuating member. 
The measures provided by the present invention have the result that the 
tool is clamped at two axially spaced apart locations, so that the seat of 
the tool is significantly improved and a simple actuating mechanism can be 
used and an improved dynamic behavior is achieved because of the tensile 
load acting between the two clamping locations. 
When a double collet chuck is used, the clamping elements are the resilient 
tongues of the double collet chuck. During operation, the double collet 
chuck is subjected to axial tension in a favorable manner. The push button 
can be constructed without a complicated reversing mechanism and can act 
directly on the end of the spring facing the push button. The two ends of 
the double collet chuck are each provided with a conical portion supported 
in an undercut ring, wherein the tips of the conical portions are directed 
toward each other. 
When two groups of axially spaced apart and radially movable clamping 
elements are used, these clamping elements are mounted, for example, in a 
common sleeve. The conical control surface of the group of clamping 
elements located on the side of the push button is pulled toward the push 
button by the spring and the tensile force is transmitted through the 
sleeve to the group of clamping elements on the side of the tool, wherein 
the clamping elements on the side of the tool rest against an axially 
fixed conical control surface. 
In accordance with a preferred embodiment, the clamping elements are 
tongues of a collet chuck which has axial slots at both ends thereof. As a 
result, the collet chuck is constructed as a collet chuck at both ends 
thereof. In addition, the outer casing of the collet chuck is undercut at 
both ends to form the conical surfaces, so that clamping occurs during 
tensile loads, wherein the undercut on the side of the tool is mounted in 
an axially fixed conical seat which rotates together with the tool and the 
undercut on the side of the push button is mounted in a conical seat of 
the actuating member which is under the influence of a clamping spring and 
is movable by the push button against the force of this clamping spring in 
the direction toward the axially fixed seat. 
Because of the flying arrangement of the collet chuck between the two 
conical seats, it is possible to almost double the holding force of the 
tool while the force and characteristic of the collet chuck spring remains 
the same. 
Because of the novel configuration of the collet chuck which fixes during 
tension and releases without pressure, it is possible to substantially 
reduce the wall thickness of the collet chuck sleeve. 
Another advantage of this configuration is the fact that the length of the 
bore of the tool receiving means which must be produced precisely is 
substantially reduced or can even be produced with a slightly excess 
dimension which advantageously influences the manufacturing costs. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of the disclosure. For a better understanding of the invention, its 
operating advantages, specific objects attained by its use, reference 
should be had to the drawing and descriptive manner in which there are 
illustrated and described preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As illustrated in the drawing, a dental tool holder with tool holder head 1 
is provided with a receiving means 2 for a tool 3 which is only 
illustrated in broken lines. The receiving means is mounted in ball 
bearings 4 and has a drive sleeve 5 whose teeth 6 can be placed in 
engagement with a drive, not shown, on the side 7 of the head 1 facing the 
handpiece. 
Mounted in the interior of the drive sleeve 5 on the end facing the tool is 
a support ring 8 which rotates together with the drive sleeve 5 and which, 
on the side facing the head 1, has a conical undercut 9. The collet chuck 
10 constructed according to the present invention engages in this undercut 
9 with its end facing the tool. 
A push button 11 of the known type is mounted on the upper side of the head 
1. The push button 11 is under the influence of the force of a button-type 
spring 12 and, thus, is spaced apart from an actuating member 13 which is 
under the influence of a collet chuck spring 14 and rotates together with 
the drive sleeve 5. The actuating member 13 is connected to a sleeve 15 or 
is integrally manufactured with the sleeve 15. As a result, the sleeve 15 
is forced toward the push button 11 under the influence of the collet 
chuck spring 14 and, by means of a conical undercut 16 which is similar to 
the undercut 9 but is directed in the opposite direction, engages the end 
of the collet chuck 10 on the side of the push button and also tends to 
move it toward the push button 11. 
The end of the collet chuck 10 on the side of the push button is 
constructed analogously to the end facing the tool. In other words, slots 
17 are provided which permit a resilient deformation of the collet chuck 
in such a way that the distances between radially oppositely located 
collet chuck ends becomes smaller. The slots 17 on the end facing the push 
button are offset, preferably symmetrically offset, relative to the slots 
17' of the end of the collet chuck facing the tool. As a result, the 
collet chuck in its totality is composed of axial parts 18 which are 
connected to each other alternatingly at the ends facing the push button 
and at the ends facing the tool, so that a closed zig-zag configuration is 
formed along a cylindrical casing. 
Since the force of the collet chuck spring 14 is transmitted through the 
sleeve 15 and the conical seat 16 to the collet chuck 10 and further 
through the conical seat 9 to the axially fixed ring 8, the clamping force 
after resting against the tool shaft has been effected and, thus, in the 
stationary state and in the state of operation is equal to the clamping 
force in known collet chucks which, instead of the conical seat 16, either 
have a single-piece transition to the sleeve 15 or are fixedly connected 
to the sleeve 15 by means of a collar or the like. 
The present invention is not limited to the embodiment illustrated in the 
drawing. For example, it is possible that the collet chuck has a longer or 
shorter length, wherein it is advantageous to provide such an axial 
distance between the two clamping ends of the collet chuck that even 
larger moments can be absorbed without the occurrence of large individual 
lateral forces. Also, within certain limits determined by the size and use 
of the collet chuck, the number of axial tongues or parts 18 of the collet 
chuck can be freely selected. It may even be possible to provide a collet 
chuck which is axially divided. However, this does not change the 
construction according to the present invention which provides two 
clamping collet chuck ends which are arranged coaxially but directed 
against each other, wherein the two collet chuck ends are arranged at an 
invariable distance from each other and which are acted upon by the force 
of a single spring. 
It is also possible to further extend the collet chuck and to arrange the 
clamping spring between the rings with the conical control surfaces which 
engage the collet chuck ends and radially outwardly of the collet chuck 
sleeve. In this case, the actuating mechanism acts directly on one of the 
rings and compresses the clamping spring by means of this ring. 
The invention is not limited by the embodiments described above which are 
presented as examples only but can be modified in various ways within the 
scope of protection defined by the appended patent claims.