Device for operating dental hand pieces

Abstract

A device which can be used for operating a dental hand piece with a motor drive and a dental hand piece with a pneumatic drive, such as a turbine drive, has an electric circuit and a potentiometer connected to the input of the circuit and varying the voltage at its output. An electric valve varies the flow volume of the compressed air supplied to the pneumatic drive. A switching device connects selectively the electric motor and the electric valve with the output of the circuit.

Parent Case Text

The present application is a continuation-in-part of our copending patent application Ser. No. 48,616, filed May 15, 1970, now U.S. Pat. No. 3,844,039.

Description

This invention relates to a device for operating dental hand pieces.

Dental hand pieces with movable instruments are used for the treatment of teeth. It is required to use for such a treatment instruments with many different speeds. Such requirements cannot be taken care of by a single one hand piece. Consequently dental units have been provided which have electrical drives as well as compressed air turbine drives. The dentist decides depending upon the required treatment whether to operate with the turbine with a very high number of revolutions or with the electric motor drive with a low number of revolutions.

In case of hand pieces with a drive by an electric motor it is known to vary the number of revolutions of the drive within predetermined limits by a circuit device. This operational possibility does not exist for hand pieces with a compressed air drive, since most foot operated devices for supplying pressure means to the compressed air drive are in known devices only black and white switching devices, so that in these devices a magnetic valve located in the compressed air conduit can be either completely opened or completely closed.

An object of the present invention is the provision of a device for operating dental hand pieces which will greatly simplify the construction and service of the handpieces. The device of the present invention should have the largest amount of similar parts and should be able to control the r.p.m. of hand pieces with an electric motor drive as well as those with compressed air drive within wide limits.

Other objects of the present invention will become apparent in the course of the following specification.

In the accomplishment of the objectives of the present invention it was found desirable to provide a device for operating a dental hand piece with a motor drive and a dental hand piece with a pneumatic drive, such as a turbine drive, comprising a current source, an electric circuit connected to the current source, a potentiometer connected to the input of the circuit and varying the voltage at its output, an electric valve varying the flow volume of compressed air supplied to the pneumatic drive and switching means connected to said output and connecting selectively the electric motor and the electric valve with the output of the circuit.

The advantages of this deviceof the present invention include a saving in structural elements since it is not necessary to provide each drive with its own supply. On the contrary, all drives are actuated by a single common controlling device. The switching means can be so arranged that they are actuated when an instrument with a hand piece is removed from the storing carrier. In case of a hand piece with compressed air drive the electrical adjusting member consists of an electrical valve operating compressed air supplied to the drive. The valve operating the number of revolutions of an air pressure drive can preferably contain a piston operating the cross-section of the passage of the valve, the piston being adjustable by the magnetic rotor of the raising magnet. The piston can be guided so that it will move axially and can be provided with an axially extending radial part which interconnects the inlet and outlet openings of the valve and changes depending on the position of the piston the free passage cross-section of the valve.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings showing by way of example only, preferred embodimens of the inventive idea .

IN THE DRAWINGS

FIG. 1 is a circuit diagram illustrating a device of the present invention for controlling a dental hand piece driven by an electric motor and a hand piece driven by compressed air.

FIG. 2 is a section through the regulating valve of FIG. 1.

The device shown in FIG. 1 is used for controlling the number of revolutions of an instrument hand piece 1 driven by an electric motor and the number of revolutions of an instrument hand piece 2 driven by air. The hand pieces 1 and 2 are placed in supports 3 and 4 in or upon a conveniently located storer not shown in the drawings. The supports 3 and 4 are so mounted that when a hand piece is removed the switch 5 or the switch 6 will be actuated. This is produced by the pulling force of two traction springs at the supports and the diminution of weight when a hand piece with the instrument is removed.

The switch 5 switches on the circuit for the electric motor 7 located in the hand piece 1 and the switch 6 switches on the circuit for the supply of compressed air to a turbine actuated by an electromagnetic valve 8 and located in the head of the hand piece 2. Compressed air is produced by an air compressing device 9 and is supplied to the hand piece 2 by a compressed air conduit 10. The conduit 10 also carries a pressure reducing valve 11. The valve 8 is connected with the switching contacts of the changeover switch 6. The electric motor 7 located in the hand piece 1 is connected with the switching contacts of the switch 5. The two switches 5 and 6 are so constructed and so interconnected that only the hand piece removed from its support can be operated. The circuit of the other hand piece is interrupted. This locking arrangement is most advantageous since the user of the instruments provided with the hand pieces does not have to decide which of the drives should be operated. The two feed lines 12 and 13 to the motor 7 and to the winding of the electrical valve 8 are connected with the outputs 14 and 15 of a circuit device 16. The circuit device 16 provides the means for controlling the number of revolutions of a dental borer driven by an electic motor, for example the switch arrangement for the driving motor 7. At the input of the circuit device 16 which is fed from a source 17 of alternating current are connecting lines axtending to a regulatable resistance or potentiometer 18. The potentiometer 18 can be built into an actuating device operated by foot or it can be constructed as a shifting potentiometer actuated by hand. Its switch 19 switches on and off the respective drive (for the motor 7) or the electrical adjusting device of the drive (the magnetic valve 8). The switch 19 is advantageously coupled with the variable part of the potentiometer 18.

The circuit device 16 must carry out several functions for electrical borer drives, namely it must provide a continuous adjustability for the r.p.m., it must keep the r.p.m. constant independent of the load, it must limit the current flow and it must provide a reversal of the direction of rotation of the drive.

The present specification will describe only the switch circuit required for the continuous adjustment of the number of revolutions since only this part of the circuit device is of importance for the subject matter of the present invention.

For the adjustment of the number of revolutions are necessary the potentiometer 18 as variable resistance, the resistance 20 for limiting the upper number of revolutions, the resistance 21 for providing a limit for the lower number of revolutions, the transistors 22, 23, 24 and 25, as well as resistances 26 to 32, diodes 33 and 34 as well as direct voltage supply 35. At the transistor 24 which is located in the motor rotor circuit as a variable resistance, there is the certain voltage U.sub.T24. The base of the transistor 23 is actuated by the collector potential of the transistor 22. At the base-emitter stretch of this transistor 22 lies the actuating voltage U.sub.BE = U.sub.1 -(U.sub.2 +I.times.R.sub.31). The pre-voltage U.sub.1 is taken from a voltage divider formed by resistances 18 and 20, its voltage being held constant by the zener diode 33 independent of the amount of direct voltage applied from the voltage source 35. The smaller becomes the voltage U.sub.1 by the potentiometer 18 which sets the r.p.m., the smaller will be the base-emitter voltage U.sub.BE at the transistor 22 which then locks more. Then its collector potential will become more positive. The result is that the transistors 23 and 24 will open more. This reduces the voltage at the collector-emitter stretch of the transistor 24, and this results in that the voltage at the motor 7 will correspondingly increase and thus its revolutions will increase. A load dependent resistance is indicated by the numeral 31 in FIG. 1. The revolutions of the motor 7 decrease with a greater set voltage U.sub.1 in a manner similar to the one described.

Thus with this circuit device a variable voltage can be produced depending upon the setting of the potentiometer 18 at the outputs 14 and 15 of the controlling device 16 and this voltage can be used to change selectively within predetermined limits the r.p.m. of the motor 7 or the regulating valve 8 as far as its flow passage is concerned. If the hand piece 1 is removed from its support 3, the outgoing voltage of the circuit device 16 is transmitted through the change-over switch 5 to the motor drive. At the same time the switches 5 and 6 make certain that the circuit of the hand piece 2 which is not used, remains interrupted and that the valve 8 cannot be switched on, so that these parts are locked.

As shown in FIG. 2, the valve 8 consists substantially of two main parts, namely, a stroke magnet 40 and a throttle valve 41. Inside the magnet 40 there is located a magnetic armature or plunger 42 which is moved axially in the direction of the arrow when the magnetic winding 43 is excited. A piston 44 located in the valve 41 and also movable axially is actuated by the magnetic armature 42. The piston 44 has a radial recess 45 extending in its axial direction for connecting air inlet 46 through the two openings 48 and 47 to the outlet 49. Thus compressed air can flow to the turbine located in the hand piece 2 and drive it. The greater the excitation of the magnet 40 the greater will be the free cross-section provided by the piston 44 between the openings 47 and 48. A spring 50 presses the piston 44 against the action of the magnet and is so dimensioned that a linear movement of the piston 44 is possible. The valve operates in a voltage range of 8 to 20 v. The voltage 20 v. corresponds then to the final number of rotations of the driving motor 8.

The advantage of this construction is that for a hand piece with an electric drive and a hand piece with a turbine drive only a single providing circuit and a single operating device are necessary. Another advantage of the construction is that it is necessary to have only a single switch and only one regulating device for said two hand pieces.

Claims

What is claimed is:

1. A device for operating a dental hand piece with a motor drive and a dental hand piece with a pneumatic drive, such as a turbine drive, said device comprising a current source, an electric circuit device connected to the current source and having an input and an output, a potentiometer connected with said input and varying the voltage at the output, an electric valve varying the flow volume of the compressed air supplied to the pneumatic drive, and switching means connected with said output and connecting selectively said electric motor and said electric valve with the output of that circuit device, wherein said electric circuit device including an operating resistance connected with said potentiometer and a transistor having a collector-emitter connection connected in parallel with said operating resistance, said potentiometer being connected in parallel to said collector-emitter connection and said motor drive and in series to said operating resistance and influencing the basic potential of said transistor.

2. A device for operating a dental hand piece with a motor drive and a dental hand piece with a pneumatic drive, such as a turbine drive, said device comprising a current source, an electric circuit device connected to the current source and having an input and an output, a potentiometer connected with said input and varying the voltage at the output, an electric valve varying the flow volume of the compressed air supplied to the pneumatic drive, said valve comprising a casing having a flow passage, a valve body and a magnetic armature for moving said valve body depending upon the voltage of the outlet of the electric circuit device for varying said flow passage, and switching means connected with said output and connecting selectively said electric motor and the magnetic armature of said electric valve with the output of the circuit device.

3. A device for operating a dental hand piece with a motor drive and a dental hand piece with a pneumatic drive, such as a turbine drive, said device comprising a current source, an electric circuit device connected to the current source and having an input and an output, a potentiometer connected with said input and varying the voltage at the output, an electric valve varying the flow volume of the compressed air supplied to the pneumatic drive, and switching means connected with said output and connecting selectively said electric motor and said electric valve with the output of the circuit device, wherein said electrical valve comprises a casing having a flow passage, a piston movable in said casing to adjust said passage, a stroke magnet and a magnetic armature carried by said stroke magnet and actuating said piston.

4. A device in accordance with claim 3, wherein said piston is axially movable in said casing and comprises an axially extending radial recess adapted to interconnect opposite ends of said passage and varying the extent of flow in said passage.