Dental-surgeon handpiece with battery lighting

This equipment for dental surgeons comprises a hand-piece incorporating at least one bulb for illuminating the treatment area and an endpiece housing a battery. This endpiece comprises on its front end a pair of springloaded contact studs adapted to engage with corresponding concentric tracks formed on the rear face of the handpiece for energizing the bulb. The battery is rechargeable by means of a device comprising two concentric tracks of same diameter as the handpiece tracks and connected to a circuit adapted to switch automatically between a quick-charging condition and a slow-charging condition according to the voltage developed across the battery terminals.

FIELD OF INVENTION 
The present invention relates in general to dentists' equipment and 
specifically relates to an improved handpiece comprising at least one bulb 
for illuminating the treatment area and an endpiece containing a battery 
and adapted to be connected to the rear end of the handpiece, this 
endpiece being provided at its front end with a projection adapted to fit 
into the handpiece. 
THE PRIOR ART 
A known proposition aiming to facilitate the dental-surgeon's task 
consisted in incorporating lighting means in the handpiece for 
illuminating the treatment area in the patient's mouth. In the case of a 
contra-angle handpiece, the shaft for driving the tool or instrument 
clamped in the head of the contra-angle is driven by a pneumatic or 
electric micromotor housed in an endpiece adapted to be connected to the 
rear end or handle of the handpiece. The micromotor shaft extends 
forwardly from the endpiece so as to be drivingly coupled to the rear end 
of the handpiece driving shaft. The bulb housed in the contra-angle head 
is energized by means of a battery housed in the micromotor containing 
endpiece, this battery delivering for example a 6-Volt D.C. This 
arrangement is disclosed in a co-pending patent application filed on May 
20, 1985 by the same applicants. However, this battery has a relatively 
short effective life and provides a sufficiently bright lighting during 
only about two hours. Now this can be regarded as constituting a serious 
inconvenience for the dental surgeon confronted with frequent replacements 
of discharged batteries. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to avoid the 
above-described inconvenience by providing a handpiece for dental-surgeons 
which comprises a rechargeable battery and assembly means that are simple 
and easily handled by the dentist, so that detrimental losses of time are 
safely avoided. 
For this purpose, the dentist's equipment according to the present 
invention is characterized by the fact that the endpiece associated with 
the front hand-piece is provided at its front end with spring-loaded 
contact studs connected to the two poles or terminals of the battery, the 
contact means at the rear end of the front handpiece consisting of 
concentric annular tracks resiliently engaged by the spring-loaded contact 
studs when the two members are assembled or coupled with each other, that 
said battery is of the rechargeable type and that a battery charger is 
also provided, this battery charger comprising in its upper portion a 
cavity adapted to be engaged with the projection and surrounded by a pair 
of concentric annular tracks constituting the output contacts of same 
diameter as the annular tracks formed on the rear face of the front 
handpiece, said last-mentioning pair of concentric annular tracks being 
engaged with the spring-loaded contact studs when the endpiece is fitted 
to the front handpiece with its projection engaged in the cavity. 
Thus, the practioner has at his disposal an apparatus of relatively simple 
construction which can be used very easily. Since, as a rule, burring 
operations require relatively little time, the contra-angle is provided 
preferably with a switch, as described in the above-mentioned co-pending 
patent application, so that the dentist can switch on the light only when 
necessary. Since the actual working time in a half-day is usually less 
than two hours, the dental surgeon, at the end of each working period, for 
example at noon or in the evening, can load the endpiece on the charger 
for recharging the battery. This rechargeable battery, consisting of five 
cells, has a diameter of about 16 mm and a length of about 32 mm, and can 
be housed in a cavity provided for this purpose in the endpiece, 
preferably behind the micromotor. In the case of a turbine-type handpiece, 
without micromotor, the endpiece encloses only the battery and the 
compressed-air supply, the compressed air being fed directly to the 
handpiece head. In the case of an old-type handpiece driven in the 
conventional manner by means of an external electric motor via a pulley 
and belt transmission, the endpiece contains means for converting the 
motion and also the battery. 
The charger supplyied with electric current from the main source may be 
either disposed near the dental unit, or incorporated in support means 
provided for supporting the handpiece on the dental unit. 
According to a preferred form of embodiment of the present invention, the 
battery is housed in a cavity located behind the motor unit, the ground 
contact being obtained via a battery supporting socket through conducting 
elements of the motor unit. The other contact is obtained via a pair of 
resilient blades bearing the one against the positive terminal of the 
battery and the other against an insulated conducting rod slidably mounted 
in a recess extending along the motor unit, the opposite end of the rod 
urging the spring-loaded contact stud forwards. 
The battery charger comprises preferably circuit means for switching 
automatically from a quick-charge operation to a slow-charge position, 
according to the voltage existing across the battery terminals, the 
circuit comprising an operational amplifier adapted to compare the battery 
voltage with an adjustable threshold voltage, the amplifier having two 
operating conditions according to the battery voltage. In a first 
condition, a high-current charging circuit is formed, and in the other 
condition, a low-current charging circuit is obtained. 
The invention will now be described with reference to the accompanying 
drawings illustrating a typical form of embodiment thereof which comprises 
a contra-angle handpiece, an endpiece and the charging device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The contra-angle dental handpiece illustrated in the drawings comprises 
separate front and rear pieces. The front piece consists in the known 
fashion of a handle or rear section 15 and a front section 27 
incorporating the head 27a in which a tool (not shown) is adapted to be 
fitted in a tool holder 30. This tool holder 30 is driven as conventional 
by a rotary shaft 28 housed in the front section 27 and provided at its 
rear end with a pinion 31 adapted to mesh with a corresponding pinion 32 
fixed to the front end of another shaft 28a rotatably mounted in the 
handle 15. This shaft 28a, in the example illustrated, is adapted to be 
driven by a micromotor (not shown) secured to the rear end of handle 15. 
In this case, the nose of the micromotor protrudes into the handle and its 
output shaft is in driving engagement with the fork 33 formed at the rear 
end of shaft 28a. The front section 27 is forcibly fitted in the outer 
cover 15a of handle or rear section 15 and rigidly connected thereto by 
means of a circlip 25 and positioned circonferentially by a radial pin 26 
secured to the head 27a. 
A cavity 29 formed in the head 27a is adapted to receive an electrical 
midget bulb 1 cemented or crimped in a conducting holder 1a screwed in the 
head 27a. This holder 1a has two diametral slots 1c formed therein so that 
it can be screwed in or out by means of a suitable screwdriver. The angle 
of inclination of the recess 29 relative to the tool axis is such that the 
light rays emitted by the bulb 1 are directed towards the treatment area 
at the tool end. The ground terminal of bulb 1, that is, the outer socket 
of the bulb base, is held in close contact, for example by welding, with 
the bulb holder 1a which engages in turn the shank of the ground-forming 
front section 27 also made from a suitable conducting metal. The other 
terminal 1b of bulb 1, which is the central contact of the bulb base, 
engages with a metal ring 2 crimped on a support 3 of insulating material 
acting as a front bearing or support for a bearing in which the shaft 28 
is rotatably mounted. This ring 2 is supplied with electric current 
through an insulated wire 4 having one end welded to the ring 2 and the 
other end welded to another metal ring 5 crimped in turn to another 
insulating support 6 acting as a rear bearing or support for another 
bearing for the shaft 28. 
Since the front section 27 must be separated from the handle or rear 
section 15, the current is fed to this second ring 5 via a resilient 
contact 9 consisting of a spring blade having one end embedded in an inner 
conducting socket 11 forming an integral part of the handle 15. This 
resilient contact 9 extends axially and can be caused to engage with the 
ring 5 of front section 27 at will through a switch 7 of the push-knob 
type which is slidably fitted in a ring 8 embedded in turn in the outer 
cover 15a of handle 15. The push-knob head is mushroom-shaped to prevent 
the ingress of dust and foreign substances from entering into the 
contra-angle. When the push-knob 7 is depressed by one of the fingers of 
the user's hand holding the handpiece, the spring blade 9 is deflected and 
moved towards the ring 5, thereby closing the contact. Therefore, the 
dental surgeon can turn the light on only when necessary, without 
necessarily actuating the tool at the same time. The circuit is opened 
automatically when the contra-angle is released, because the push-knob 7 
returns automatically to its inoperative position by the spring blade 9 
acting as a return spring. Thus, the operator has the certainty that when 
the contra-angle is not in use the bulb will remain deenergized. 
The spring blade 9 is supplied with current by means of an insulated 
conducting wire 23 housed in a groove formed in an inner sleeve 14 of 
conducting metal. The front end of wire 23 is welded to the spring blade 9 
and its rear end is in electrical contact with an annular conducting track 
21 surrounding concentrically the shaft 28a and constituting the rear end 
of the handle. 
The other electric line constituting the ground consists of an inner socket 
11 and the inner sleeve 14 of conducting metal which are fitted in the 
handle 15. The socket 11 is embedded in the inner sleeve 14 so as to be in 
sliding contact engagement therewith, and these component elements 11 and 
14 are assembled by means of a ring nut 16 locked against rotation or 
release by a pin 17. On the rear surface of handle 15, of the front piece 
the ground line terminates with an annular track 18 consisting of a metal 
ring surrounding concentrically the other annular track 21 and secured to 
the inner sleeve 14 so as to hold in position an insulating ring 20 
separating the ring track 18 from the track 21 (FIGS. 1b and 2). 
Mounted in the socket 11 are two bearings 12,13 in which the shaft 28a is 
rotatably mounted. In addition, an orifice is formed in socket 11 in case 
the circulation of a cooling fluide were contemplated. In the example 
illustrated, this orifice is closed by a metal plug 11a. Preferably, the 
outer cover 15a is made of light alloy. To ensure an efficient contact 
between the conducting body of the front section 27 and the socket 11 of 
handle 15, a resilient contact 24 is provided, for example, in the form of 
a rod embedded at its rear end in socket 11 and curved at the front end so 
as to constantly engage with a bevelled portion of the body of front 
section by deflecting the rod 24 to thereby provide a good electrical 
contact. Thus, a simpe yet efficient and reliable electrical connection is 
obtained between the two sections of the contra-angle while permitting the 
easy and quick assembly and disassembly thereof by firstly pulling the 
front section 27 out of the handle 15, this movement causing the circlip 
25 to yield inwards, and by subsequently extracting from the handle 15 the 
complete assembly enclosed in socket 14 by releasing the nut 16. Moreover, 
the same handle 15 can be used with different heads. 
The handpiece is driven by means of a suitable pneumatic or electric 
mircomotor housed in an endpiece or rear piece 35 (FIGS. 3 and 4) adapted 
to be connected to the rear end of handle 15 of the front piece during use 
of the dental handpiece and comprising two contactcs 19 and 22, 
respectively, consisting of spring-loaded pistons and adapted to engage 
with the separate annular tracks 18 and 21, respectively, formed in the 
rear end of handle 15. The electric current for energizing the bulb 1 is 
supplied by a rechargeable battery 38 housed in the endpiece 35. 
FIGS. 3 and 4 of the drawings illustrate a typical form of an embodiment of 
the endpiece or rear piece 35 housing the motor unit 36 disposed between 
lateral plates 34 and 56, and rearwardly from this motor unit, a cavity 37 
is provided to receive the battery 38. In this example, the battery 38 
housed in cavity 37 has a diameter of about 16 mm and a length of about 32 
mm. This 6-Volt battery is capable of supplying a sufficiently bright 
lighting during ca. 2 hours. 
The endpiece 35 consists of a front socket 39 having a screw- threaded rear 
end 39a adapted to be engaged by an internally-threaded rear socket 40 
provided with a ring 41 for coupling this rear socket 40 to a current 
supply pipe. In the embodiment illustrated, the motor 36 is a pneumatic 
motor of known type having its blades driven by compressed air supplied 
from an external compressor via the coupling device 41 and two-way pipes 
42 (FIG.4). 
The endpiece 35 is provided at its front end with a hollow projection 43 
secured by means of a nut 44. The output shaft (not shown) of the 
micromotor extends through this projection 43 constituting the nose of the 
micromotor. The projection 43 is adapted to be inserted into the rear end 
of the handle 15 and fastened thereto by means of a spring-ring 46 of the 
known type. The front face of endpiece 35 has an annular groove 47 formed 
therein, and the annular tracks 18,21 of handle 15 are adapted to fit in 
the groove 47. The piston-like spring-loaded contact studs or pins 19,22 
project at a certain distance from the bottom of the annular groove 47. 
The ground contact pin 19 urged by a spring 49 projects from the radially 
outer side of annular groove 47 and engages with the annular track 18, and 
the other contact pin 22 projects from the radially inner side of annular 
groove 47 and engages with the other annular track 21 of handle 15 of the 
front piece when the front and rear pieces are coupled with each other 
such that the pair of pins 19, 22 electrically and physically contact with 
the pair of annular tracks 18, 21 with a positional allowance for relative 
circumferential displacement therebetween. 
The rear portion of contact 22 bears against a conducting rod 50 insulated 
by a sheath 50a. This rod 50 is slidably mounted in a passage formed 
through the lateral plate 34, the motor unit 36, the lateral plate 56, an 
insulating ring 53 and a rear bearing carrier 57 (shown only 
diagrammaticaly) supporting the rear bearing 58 of motor 36. The rear end 
of rod 50 bears against a resilient blade 51 of conducting metal housed in 
an annular groove 53a formed in the insulating ring 53. This resilient 
blade 51 is connected by a rivet 52 to another resilient blade 51b bearing 
resiliently against the positive terminal of battery 38, the rivet 52 
being clinched in the insulating ring 53. The resilient blade 51 exerts an 
axial resilient pressure against the sliding rod 50 pressed in turn 
against the contact 22, so that this contact 22 is constantly urged 
resiliently axially outwards. 
The other spring-loaded contact 19 constituting the ground or negative 
contact is fed with energizing current via the battery supporting socket 
54 which, when the sockets 39 and 40 are assembled with each other by 
means of their screw-threaded portions, engages with a contact 55 urged by 
another spring 55a. This contact 55 bears against the metal lateral plate 
56 engaging with in turn one conducting metal portion of motor 36 in order 
to establish an electric connection with the spring-loaded contact 19 
(FIG. 3). 
When the handpiece is not used, or when the battery 38 is discharged, the 
practitioner loads the endpiece 35 upon a battery charger shown 
diagrammatically in FIG. 5. This battery charging device comprises a base 
plate 60 having a cavity 61 opening at its top surfac. The depth of this 
cavity 61 conforms to the length of the above-mentioned projection 43 of 
endpiece 35, that is, in the example illustrated, to the length of the 
micromotor nose. Two conducting concentric annular tracks or rings 62,63 
separated by an insulating ring 64 surround the cavity 61. These tracks or 
rings have exactly the same dimensions as the conducting tracks 18,21 
provided at the rear end of the handle 15 so as to penetrate into the 
annular groove 47 of endpiece 35 and thus engage with the corresponding 
springloaded contact studs 19,22 irrespective of the angular position of 
the endpiece about its longitudinal axis. Under these conditions, the 
dental surgeon is not required to pay any particular attention to the way 
in which he puts the instrument on the battery charging device. The 
aforesaid concentric tracks 62,63 are connected via conductors 65,66 to 
the output terminals S2,S1, respectively, of an electronic circuit 67 
shown diagrammatically in FIG. 6 to which reference will now be made for a 
detailed description hereinafter. 
This electronic circuit 67 operates to switch automatically from quick 
charging operation to slow charging operation, and vice versa, according 
to the voltage across the terminals of battery 38. The circuit comprises 
two input terminals E1, E2 connected to a transformer T adapted to be 
supplied with 110-V or 220-V main power. The output current of this 
transformer T is fed to a bridge rectifier RP connected in turn to an 
integrated circuit having constant-current characteristics for two current 
values, this circuit comprising an operational amplifier A operating as a 
voltage comparator. This circuit comprises output terminals S1,S2 
connected to the concentric tracks 63,62 formed on the top surface of the 
base plate 60 of charging device adapted to receive the endpiece 35 of 
which the battery needs a new charge. 
A capacitor C1 is connected across the negative and positive terminals of 
bridge rectifier RP, the negative terminal being connected via a line f2 
to the negative output terminal S2 of the electronic circuit. 
The positive terminal of bridge rectifier RP is followed by a pnp-type 
transistor T2 having a resistor Rx inserted in its emitter circuit, this 
transistor T2 being cascade-connected to another transistor T3 of the npn 
type; the emitter of transistor T2 is connected via a conductor f1 
comprising a diode D5 to the positive output terminal S1. This diode D5 
protects the circuit against any undesired inversion of the battery 
polarity. A resistor RL is connected in parallel with resistor Rx and 
transistor T2. The base circuit of transistor T2 comprises two 
series-connected diodes D1,D2 and a resistor R2 for biasing said 
transistor T2, followed by another resistor R3 connected to the collector 
circuit of an npn transistor T1. The base of this transistor T1 is 
connected via a resistor R4 to a voltage divider consisting of resistors 
R5 and R6 connected in turn to the output S of the amplifier A. 
The operating voltage of amplifier A is obtained by means of a resistor R1 
connected to the positive terminal of bridge rectifier RP and to a 
conductor f3; a Zener diode Z1 is connected between conductor f3 and line 
f2 giving a constant operating voltage. 
The supply terminals of amplifier A are connected to conductors f3 and f2. 
The amplifier output S is connected to a voltage divider consisting of the 
series-connected circuit comprising, between conductors f3 and f2, a first 
electroluminescent diode (LED) LV acting as a pilot light, a resistor R7, 
another resistor R8, a pair of diodes D3 and D4 providing a constant 
voltage drop, and a second electroluminescent diode (LED) LR, acting as a 
pilot light, the output S being connected to the common terminal of 
resistors R7 and R8. 
The operational amplifier A has two inputs e1 and e2, that is: 
input e1 is connected via a resistor R11 to a voltage divider across the 
output terminals S1 and S2, the voltage divider comprising a resistor R13, 
a potentiometer R14 having its sliding contact connected via resistor R11 
to input e1, and another resistor R15. 
A capacitor C2 is mounted between input e1 and conductor f2: 
input e2 is connected via a resistor R10 to a voltage divider disposed 
between conductors f3 and f2, this voltage divider consisting of a 
resistor R12 and a Zener diode Z2 providing a constant voltage drop and 
consequently a fixed voltage at input e2. 
The operational amplifier A operates to compare the voltage value of the 
battery 38 connected across terminals S1 and S2 with a threshold value 
defined by the voltage divider and adjustable by means of the 
potentiometer R14. 
The above-described device operates as follows: 
When the battery voltage is low, therefore when the current flowing across 
outputs S1 and S2 through resistors R13 and R15 and potentiometer R14 is 
low, the voltage measured at potentiometer R14 and delivered to the input 
e1 of amplifier A is more negative than the reference potential at the 
other input e2. The output S of amplifier A is positive and the current 
flows through diode LR, producing, for example, a red light for indicating 
that the charge current is relatively high, the other diode L, giving, for 
example, a green light, remaining deenergized. The current flows through 
resistors R5 and R6, thereby biasing transistor T1 to its conductive 
state, and the other transistors T2 and T3 are acocrdingly switched to 
their conductive state; under these conditions, the charging current flows 
through resistor Rx, thus defining a relatively high charging current, for 
example, of the order of 12 mA, passing through transistor T3 and causing 
the battery 38 to be rapidly charged through its terminals S1,S2. 
If, on the contrary, the battery voltage is high, the voltage at R14 and at 
input e1 is more positive than the voltage at input e2, the output S of 
amplifier A is negative and a current is generated via the other circuit 
section through the now energized diode LV and resistor R7. The bias 
voltage at the base of transistor T1 is zero, this transistor being thus 
locked together with transistors T2 and T3. A relatively low charging 
current, for example, of the order of 6 mA, flows through the resistor RL 
and diode D5 to output S1, thus charging the battery 38 at a slow rate. 
This condition is indicated by the green light of diode LV. 
Of course, the present invention should not be construed as being a 
strictly limited by the specific form of embodiment shown and described 
herein, from the dual point of view of the endpiece and circuit 
structures, as well as of the type of handpiece. If the handpiece is 
designed for being driven in a conventional manner not by a micromotor but 
by an external motor via a pulley and belt transmission, in this case the 
element carrying the electric contact means is a coupling endpiece 
incorporating the movement converter and the battery. In the case of a 
turbine handpiece, the endpiece comprises conduit means for supplying 
compressed air and the battery.