Medical or dental handpiece

A medical or dental handpiece having a grip sleeve formed with an outer gripping surface structure which provides improved grippability. The outer gripping surface structure is formed with alternate grooves and corrugations extending circumferentially around the sleeve and which, in cross-section, are axially spaced from each other. The grooves and corrugations are rounded concavely and convexly, respectively.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a medical or dental handpiece having a grip sleeve 
which extends with a straight or angled shape and has at its forward end a 
tool holder having a mounting device for a treatment tool arranged 
transversely of or along the longitudinal axis of the handpiece, and at 
its rearward end is releasibly connectable with a supply part by means of 
a coupling device, the grip sleeve having in the grip region which is 
grasped by an operating hand a superficial surface structure on its 
external surface which improves the grippability. 
2. Description of the Related Art 
Several demands are made of a handpiece of the kind being considered. On 
the one hand, it should be of a configuration which is easy to handle, so 
that the person carrying out a treatment can grasp it easily without 
exercising great force and attention and can hold and control the 
handpiece during treatment. This demand is of great significance because 
the quality of the treatment is dependent thereupon, the standard of 
which--in the treatment of the human or animal body--can have lasting 
positive or negative consequences. Thereby, the handpiece should be light, 
so that the person carrying out the treatment is able to guide it without 
great effort in terms of force. For the same reason, it should be securely 
grippable, to which end several superficial surface structures have 
already been proposed, e.g. projections arranged in circular ring form (DE 
31 41 534 C2) trough-like flattenings adjacent one another (DE-GM 79 10 
126) and grains or granulations embedded in the surface of the handpiece 
(EP-0 054 653 A2). 
Practice has shown that the superficial surface structure should on the one 
hand be securely grippable but, on the other hand, should exert a 
non-taxing effect on the hand of the person carrying out a treatment so 
that even after an extended treatment time the skin of the hand effecting 
the treatment is not subjected to excessive demands or irritated, which 
could influence or impair the treatment and also the quality of the 
treatment. 
On the other hand, a handpiece of the kind being considered is a product 
the manufacturing costs of which should be small, so that the treatment 
costs can also be kept down. 
SUMMARY OF THE INVENTION 
The object of the invention is to so configure a medical or dental 
handpiece of the kind under consideration that handling is easier to carry 
out, whilst reliable guidance is ensured. 
According to one aspect of this invention, there is provided a superficial 
surface structure for the handpiece in its grip region which--avoiding 
edges--is of soft structure and thus exerts a non-taxing and pleasant 
effect on the hand of the person carrying out a treatment, good 
graspability being attained which ensures the sought after reliable and 
light handling during the treatment. 
According to a further aspect of the invention not only can the weight of 
the handpiece be reduced but also its manufacturing costs, because the 
grip sleeve as a molded part, in particular of plastics, can be 
manufactured more economically and quickly and thus more cost effectively. 
Furthermore, this configuration leads to an improved heat insulation of 
the grip sleeve, whereby handling is likewise facilitated. 
According to further features of the invention, which is described herein 
the handling of the handpiece is improved simple and cost effective 
manufacturable constructions of compact dimensions are allowed mounting 
and de-mounting are simplified and possibilities are opened up for 
providing a handpiece with different features, in particular tool speeds 
of rotation, by variations of the assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the present exemplary embodiment shown in FIG. 1, a handpiece 1 is an 
exchangeable part of a dental treatment instrument 2 which comprehends the 
handpiece 1 and a supply part 3 to which the handpiece 1--at its rear 
end--can be readily and quickly coupled by means of a plug-in/rotary 
coupling 4 and which can be connected to a supply system by means of a 
supply line 5 to the rear, which supply system delivers the drive energy 
and treatment media for the treatment instrument 2, which are supplied 
through supply lines running in the flexible supply line 5. 
A drive motor 6 for a treatment tool 8, in this case a drill, which can be 
mounted at the forward head end of the handpiece 1 in a mounting device 7, 
is arranged as an electric motor in the supply part 3 and is drivingly 
connected with a mounting sleeve 11 which receives the tool by means of a 
drive train 9 which extends axially in the handpiece 1 and is rotatably 
mounted therein. The tool 8 is mounted to be rotatable transversely of the 
longitudinal middle axis of the handpiece 1, in a handpiece head 10 having 
the mounting sleeve 11, and the tool thus faces towards the so-called tool 
side. 
The plug-in/rotary coupling 4 is formed by means of a cylindrical coupling 
pin 12 and a hollow cylindrical coupling recess 13 into the which the 
coupling pin 12 can be inserted and, in the inserted position, releasibly 
latched, whereby in the latched position the rotatability of the handpiece 
1 on the coupling pin 12 is ensured. The latching device 14, which can be 
overcome by the application of force, is formed by a latch element 
15--mounted in a recess of the coupling pin 12 or of the coupling recess 
13 and biassed by a spring or formed by a spring--for example a spring 
ring which is capable of latching into a corresponding ring-shaped latch 
groove 16 in a manner which can be overcome by the application of force. 
In the present configuration the coupling pin 12 is arranged on the supply 
part 3, from which it axially projects, whilst the coupling recess 13 is 
arranged in the handpiece 1 and is open rearwardly. The drive train 9 has 
at its rearward end a plug-in coupling part 17 that, upon axial plugging 
together of the handpiece 1 and the supply part 3, is self-actingly 
couplable with a corresponding complementary plug-in coupling part (not 
shown) on the supply part 3. The coupling pin 12 is formed by means of a 
forwardly open sleeve into which, upon plugging together, the rearward end 
region of the drive train 9 is introduced so that the coupling pin 12 
engages over the portion of the drive train 9 extending into the coupling 
recess 13. 
The main parts of the handpiece 1, formed in the shape of a so-called 
angled piece, are a grip sleeve 18 the forward end region of which is 
angled at an acute angle W of approximately 21.degree. to the side away 
from the tool 8, a rear reinforcing sleeve 19--in particular of 
metal--which can be placed into the grip sleeve 18 from the rear and can 
be fixed therein by means of a fixing device 21, a forward reinforcing 
sleeve 22--in particular of metal--which can be placed from the front into 
a cylindrical hole of the grip sleeve 18 and can be fixed therein by means 
of a fixing device 23, the handpiece head 10, which receives the tool 8 
and is rotatably mounted, and which can be placed from the front into the 
forward reinforcing sleeve 22 with a rearward cylindrical plug-in coupling 
pin 24 and is secured therein by means of the fixing device 23 against 
unintended pulling out to the front and against rotation, the drive train 
9 which comprises a rear drive train part 9a which extends to the angle 
point 26 of the grip sleeve 18 and a forward drive train part 9b, which 
extends from the angle point 26, in the plug-in coupling pin 24, into the 
handpiece head 10 in which it is drivingly connected with the mounting 
sleeve 11 for the tool 8 by means of an angled gear transmission 27, and a 
media line 28 for a treatment medium, preferably water, which extends 
outside of the grip sleeve 18 at the outer surface thereof in the form of 
a small flexible hose 29 from the rearward end of the handpiece 1 to the 
handpiece head 10 in the region of which it is directed towards the 
treatment site. The drive train parts 9a, 9b are drivingly connected with 
one another in the region of the angle point 26 by means of two bevelled 
gears 31a, 31b mounted thereon. In the rear drive train 9a there may be 
integrated a step-up or step-down transmission 32 which in the exemplary 
embodiment according to FIG. 1 is connected as a constructional unit with 
the rear reinforcing sleeve 19 and can thus be installed or removed with 
this sleeve. The forward drive train part 9b is received and mounted in an 
axial mounting bore of the plug-in coupling pin. 
For mounting the rear reinforcing sleeve 19, the grip sleeve 18 has a 
centering means and a shoulder surface 33a against which the rear 
reinforcing sleeve 19 can be biassed with a corresponding shoulder surface 
33b on the transmission 32. For this purpose there is provided a ring nut 
34 which, with an external thread 35a, can be screwed into an internal 
thread 35b arranged at the rear end of the grip sleeve 18 and which 
presses against a rearwardly facing shoulder surface 36b on the 
reinforcing sleeve 19 with a shoulder surface 36a. In the present 
configuration, the shoulder surface pair 36a, 36b are forwardly diverging 
conical surfaces which form a centering means for the reinforcing sleeve 
19 in the rear region of the grip sleeve 18. A second centering means for 
the forward region of the rear reinforcing sleeve 19 is provided in the 
middle region of the grip sleeve 18--in the configuration in accordance 
with FIG. 1 directly behind the angle point 26--and the centering means is 
formed by means of a coaxial cylindrical hole 37 in the region of an inner 
angular projection 38 with the rearwardly facing approximately radial 
shoulder surface 33a. In the configuration according to FIG. 1, the 
transmission 32 is arranged in an internal housing 41 as a unit which is 
screwed together with, preferably screwed onto, the forward end of the 
rear reinforcing sleeve 19 by means of a rear thread 42. The internal 
housing 41 has at its forward end a cylindrical projection 43 which sits 
in the hole 37, with tolerance, and is thus centered. 
The fixing device 23 for the handpiece head 10 is formed by means of an 
arresting screw 45 having an in particular conical arresting portion which 
is screwed, from the outside, into a cylindrical hole 48 which receives 
its screw head 47, with tolerance, and into a threaded hole 49 of the 
forward reinforcing sleeve 22 and which can be Screwed--with its in 
particular conical arresting portion --into a correspondingly formed 
indentation in the plug-in coupling pin 24. By means of the arrangement of 
a plurality of indentations 51, arranged distributed around the 
circumference, it is possible to retain the handpiece head 10 selectively 
in a plurality of rotational positions which are rotated with respect to 
the illustrated position. In order more easily to be able to find these 
positions there is provided between the handpiece head 10 and the grip 
sleeve 18 or the forward reinforcing sleeve 22 a latch engagement means 
having a recess and a latch projection 52a which fits therein and in the 
present configuration is arranged rearwardly on the handpiece head 10, 
there being provided in each respective desired rotational position 
respective opposing latch recesses 52b. A preferred rotational position, 
having a corresponding indentation 51 and latch recess 52b, is provided 
which is rotated by 180.degree. with respect to the illustration in FIG. 
1. 
The media line 28 penetrates through the plug-in/rotary coupling 4 radially 
in such a manner that through-flow is ensured in any rotational position. 
For this purpose, an initially axis-parallel and then radially extending 
media channel 53, 54 opens at the outer surface of the coupling pin 12, a 
radial media channel 55 leading further in the rear reinforcing sleeve 19 
in the same radial plane. The sealing of the gap between the coupling pin 
12 and the coupling recess 13 is effected by means of sealing rings 56 
arranged to the two sides of the exit or entrance openings, which rings 
can each sit in an external groove of the coupling pin 12 or in an 
internal groove of the coupling recess 13. In order to ensure through-flow 
in any rotational position there is arranged an annular groove 55a in the 
transverse plane of the channel opening in the external surface of the 
coupling pin 12 or in the internal surface of the coupling recess 13. The 
media channel section 55 extends to an outwardly opening round hole 58 in 
the reinforcing sleeve 19 in which an angled connection pipelet 57 is 
fixedly and sealingly emplaced, for example soldered in or glued in. The 
bent-away pipe section 57a is arranged approximately axis-parallel or 
slightly outwardly diverging and it projects through and projects over the 
grip sleeve 18 to the outside and to the front, in a through hole 61, The 
hose 29 is pushed onto the external pipe section 57a. The pipe section 57a 
penetrates the grip sleeve 18 in the region of a radially extending wall 
62 which may be formed by means of a step-like cross-sectional enlargement 
of the grip sleeve 18 or by means of an external recess 63 in the grip 
sleeve 18. The recess 63 is of a size such that the hose 29 can be pushed 
on. 
This configuration is of particular advantage because it requires no 
sealing between the connection pipelet 57 and the grip sleeve 18. Further, 
it requires no attachment of the connection pipelet 57 to the grip sleeve. 
The connection pipelet 57 is, upon assembling the rear reinforcing sleeve 
19 into place, automatically brought into its mounting position externally 
on the grip sleeve without need for subsequent sealing. This is made 
possible by means of the approximately axis-parallel extension of the pipe 
section 57a and of the hole 61. 
The forward end of the hose 29 is pushed on to a second connection pipelet 
64 (FIG. 2) which is attached, for example soldered or glued, in a side 
position on the handpiece head 10 and is so angled that its rear pipe 
section 64a is approximately axis-parallel directed and its forward pipe 
section 64b is directed towards the treatment site. For reasons of 
handling; the rear connection pipelet 57 is located in the middle position 
of the upper right or left (for a right-handed person) quadrant, when 
viewed from the rear (FIG. 2). 
The exemplary embodiment according to FIG. 3, in which the same or similar 
parts are provided with the same reference signs, differs from the 
above-described exemplary embodiment solely in a different formation and 
configuration of the mounting of the forward end of the rear drive train 
part 9a. In those cases in which a different--or even no--transmission 32 
is to be provided, as shown in FIG. 3, there is employed a transmission 
unit with an internal housing 41 of different size or no transmission is 
employed, merely mounting parts, according to FIG. 3 one or two roller 
bearings 65 with different cross-sectional dimensions. For such cases it 
is possible to provide a plurality of grip sleeves 18 which differ with 
regard to the wall thickness indicated by D in FIG. 3 and which have each 
a cylindrical mounting hole 66 matched to the diameter of the roller 
bearings 65. Since with such a configuration there is no separate internal 
housing 41 as of the first exemplary embodiment there is needed a 
centering means of the forward end of the rear reinforcing sleeve 19. This 
centering means may be formed by means of a cylindrical ring portion 67 in 
the grip sleeve 18, in which ring portion the forward end region of the 
reinforcing sleeve 19 sits with tolerance, possibly being screwed in 
(thread 42). For axial positioning of the reinforcing sleeve 19 there 
likewise serves the shoulder surface 33a, the reinforcing sleeve 19 being 
biassed or restricted against the shoulder surface 33a by means of one or 
two of the roller bearings 65 and a spacing sleeve 68. 
Preferably, however, only one and the same grip sleeve 18 is employed for 
above-described different configurations, a radial spacing sleeve 69 being 
emplaced in the grip sleeve 18 for matching of the corresponding 
cross-sectional dimension or for mounting the roller bearings 65, the 
external cross-sectional dimension 71a of the radial spacing sleeve being 
matched with tolerance to the internal cross-sectional dimension 7lb of 
the grip sleeve 18 and bearing against the shoulder surface 33a and being 
axially securable by means of suitable means. For this purpose, the 
spacing sleeve 69 may be, for example, pressed in or glued in or, for 
exchangeable attachment, there may be arranged a corresponding internal 
thread on the internal surface of the grip sleeve 18 and a corresponding 
external thread on the external surface of the spacing sleeve 69, so that 
the letter can be screwed in. In this case it is advantageous to arrange 
engagement elements, for example recesses or projections, at the rear end 
of the spacing sleeve 69 which elements allow screwing-in or screwing-out 
by means of a suitable tool. It is thereby advantageous to arrange the 
ring portion 67 as a piece rearwardly on the spacing sleeve 69. For 
transmissions 32 or mounting elements (roller bearings) of differing sizes 
there may be provided a plurality of spacing sleeves 69 in each case 
having an internal cross-section adapted to the size. 
For a handpiece 1 the superficial surface form and structure in the grip 
region 72 of the grip sleeve 18 is of substantial importance, since the 
grippability is dependent therefrom. There is a requirement for such a 
superficial surface structure that the handpiece lays or can be held 
stably and securely on the hand of the user without the grasping surface 
of the operating hand or the fingers thereof being the subject of 
excessive demands. Thereby, it is to be taken into consideration that in 
operation of the handpiece slight vibrations can hardly be avoided which 
increase the pressure demands of the grip surfaces. 
With the present configuration preferably two measures serve for meeting 
these requirements, namely on the one hand a corrugated or rippled outer 
surface and on the other hand a slight roughness of the outer surface in 
the grip region 72. Thereby, the form of the grip sleeve 18 also has a 
significant influence in providing a comfortable and secure grasping and 
holding of the handpiece 1. 
Below, the basic form of the grip sleeve 18 in the grip region 72 will be 
described with reference to FIG. 4. The grip sleeve can be divided from 
the rear to the front, in sequence, into four shape sections 73, 74, 75, 
76. The first shape section 73 is, relative to the second cylindrical 
shape section 74, rearwardly divergingly thickened, whereby this 
thickening may be conical or initially slightly concave rearwardly and 
then slightly convexly rounded, as is shown in the Figures. The third 
shape section 75 is in the region of the angle point 26. In the region of 
this shape section 75 the grip sleeve 18 is curved and at the same time 
forwardly tapered in cross-section, whereby the ratio of the 
cross-sectional dimensions at the beginning and at the end of this shape 
section 75 is approximately 1.2 to 1. The fourth shape section 76 is 
concentrically conically tapered towards the forward end, whereby the 
taper ratio in the region of the third shape section 75 and of the fourth 
shape section 76 is approximately equal. Preferably, the beginning points 
p1 and p2 of the third and fourth shape sections 75, 76 on the convex side 
of the grip sleeve 18 are somewhat rearwardly displaced relative to the 
beginning points p3 and p4. The outer diameter d1 of the grip sleeve 18 in 
the region of the second shape section 74 is about 13 to 17 mm, in 
particular approximately 15.2 mm. From this cross-sectional dimension, the 
grip sleeve 18 tapers to an external diameter d2 of about 7 to 11 mm, in 
particular approximately 9 mm, at its forward end. The length of the first 
and second shape sections 73, 74 on the concave side of the grip sleeve 
18, see 1.sub.1, is about 35 to 65 mm, preferably approximately 47.4 mm, 
and on the convex side, see 1.sub.2, about 20 to 45 mm, preferably 
approximately 41.3 mm. The central length 1.sub.3 of the fourth shape 
section 76 is about 12 to 20 mm, in particular approximately 15 mm. The 
beginning and end points p3, p4 of the third shape section 75 on the 
concave side of the grip sleeve 18 have a spacing 1.sub.4 from one another 
which is somewhat less than the length 1.sub.3 namely about 7 to 13 mm, in 
particular approximately 10 mm. The spacings 1.sub.5, 1.sub.6 of the angle 
point 26 in the middle region of the third shape section 75 from the rear 
and forward ends are respectively about 40 to 70 mm, in particular 
approximately 50.5 mm, and about 20 to 30 mm, in particular approximately 
23.2 mm. 
The convergent outer surface in the fourth shape section 76 encloses an 
angle w1 of about 3.degree. to 9.degree., in particular approximately 
6.2.degree., with the associated longitudinal middle axis. 
In the grip region 72 which begins in the middle region of the second shape 
section 74 and extends to the middle region of the fourth shape section 
76, the external surface 77 of the grip sleeve 18 is slightly corrugated 
by means of circumferentially running, preferably continuous, grooves 78a 
and corrugations 78b which, as shown in FIG. 6, are rounded concavely and 
convexly, respectively in cross-section and may have a sine wave shape. 
Preferably, the radius r of the grooves 78a is equal to the radius r of 
the corrugations 78b and is about 3 to 5 mm, in particular approximately 4 
mm. The axial spacing a between two neighbouring grooves or corrugations 
is about 2 to 4 mm, preferably approximately 3.1 mm. The middle angle w2 
of the flanks is about 10.degree. to 30.degree., in particular 
approximately 21.degree.. It has been determined from trials that a groove 
depth t of about 0,015 to 0.3 mm, in particular approximately 0.15 mm, is 
very suitable. 
The corrugations and grooves preferably run parallel to one another. To 
compensate for the curvature there may be provided a plurality, for 
example, four compensation grooves or corrugations 78a1, 78b1 which widen 
towards the convex side with a wedge shape. 
Further, at least the flanks of the corrugations 78b and preferably also 
the corrugation peaks, and most preferably the external surface 77 in the 
grip region 72 as a whole, including also the grooves 78a, have a slight 
roughness which in particular together with the corrugated form make 
possible a holding in the operating hand which is not taxing for the skin 
of the operating hand and still allows secure grasping in the operating 
hand. Preferably, the external surface 77 is correspondingly rough over 
the whole length region of the grip sleeve 18, whereby the grippability is 
improved also in the case of other manipulations of the handpiece 1 such 
as for example upon grasping and plugging onto the supply part 3. Trials 
have shown that a depth of roughening of the class K of about 1.5 to 4 
.mu.m, in particular approximately 2.24 .mu.m is advantageously suitable 
(see VDI 3400(VDI guide lines). 
The grip sleeve 18 may be of corrosion resistant metal, in particular 
stainless steel, ceramics or preferably plastics, in particular 
fiber-reinforced plastics. It has likewise been determined in the trials, 
that polyetheretherketone (PEEK), in particular reinforced with glass 
fibers or carbon fibres, is particularly well suited. By these means the 
requirements to be met are fulfilled, namely great strength (in particular 
resistance to bending strain and tensile strength), temperature 
resistance, resistance to chemicals and resistance to radiation, with low 
weight. A PEEK thermoplastics which is well suited is available under the 
designation Victrex. 
With those materials which can be produced by molding, for example metal, 
plastics and ceramics, a simple and economical provision of the roughness 
is afforded when this is formed in the production by means of a 
corresponding roughness of the relevant mold surfaces of the mold. This 
method of production is particularly suitable for fiber-reinforced 
materials, in particular plastics, since by means of this method the 
fibres remain embedded in the material. 
Within the scope of the invention it is, however, also possible and 
advantageous, in particular with metallic materials, to produced the 
roughness or erosion structure by means of erosive working of the external 
surface 77. This may be electro-erosion processing, spark erosion, arc 
erosion or an erosion by means of sequential point by point burning by 
means of light beams, in particular laser beams, or also by etching. 
The corrugation or roughness in accordance with the invention need only, 
within the scope of the invention, extend over the part surfaces of the 
grip region 72 which are contacted by the operating hand. 
The above-described features of the superficial surface structure in the 
grip region are suitable also for handpieces which are straight. 
The production of the grip sleeve from plastics makes it possible also to 
manufacture the sleeve coloured throughout, in several colours. By this 
means not only can particular wishes by the person carrying out the 
treatment--with regard to colour--be taken into consideration, but it is 
also possible to use the colours for indicating particular types of 
handpiece 1 or of instrument 2, for example particular drive types (speeds 
of rotation).