Cartridge Type Brush Holder

Abstract

A brush unit for use in a micromotor used in a dental instrument which comprises a support disk and a pair of brushes mounted on said support disk so that said brushes are held in contact with the commutator. The support disk and the brushes form a cartridge which can be detachably attached to said micromotor.

Description

This invention relates to a micromotor for use in a dental handpiece and more particularly to a brush used in the micromotor.

A dental handpiece is provided at its outer end with a detachable tool for cutting or drilling, which is rotated at a high speed when used for dental treatment. The handpiece contains a micromotor therein for rotating the tool. This micromotor is a direct current motor so that it has a commutator and brushes. The brushes are likely to be worn with use and must be exchanged for new ones every now and then. The dentist who uses such dental handpieces is not always an expert in electrical instruments so that he finds it somewhat difficult to exchange brushes in the motor of his handpiece. As the brushes become worn, graphite which is the material constituting them is ground into power, which is accumulated in the handpiece to deteriorate the working efficiency of the instrument. Therefore, the motor must sometimes be decomposed for cleaning by removing the accumulated powder therefrom, after which the component parts must again be assembled into the motor. The work requires considerable skill and time.

Accordingly it is one object of the invention to simplify work for exchange of brushes in micromotors for use in medical instruments.

Another object of the invention is to make it easy to remove from inside the motor graphite powder worn off from the brushes.

The invention will be described in detail with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal cross-section of one embodiment of the invention; and

FIG. 2 is a perspective view, on an enlarged scale, of the principal portion of the device shown in FIG. 1.

Referring now in detail to the drawings, there is shown a micromotor generally designated by 1. The motor is enclosed inside a handpiece, not shown, and secured to a suitable place therein. The motor comprises a field pole 2 made of a permanent magnet, an armature 3, an armature winding 4 and a shaft 5 journaled in an axially spaced pair of radial bearings 6 and 7. The leads connected to the armature winding 4 are passed through bores in a guide sleeve 8 to be connected to a commutator 9. A tool (not shown) to be rotated is connected to the left-hand side, as viewd in FIG. 1, of the shaft 5.

A brush unit 10 comprises a support disk 11 on which a pair of brush holder pins 12 are fixed and spaced apart diametrically of the disk. Each of the pins 12 pierces loosely through a sleeve 13 which can freely rotate about the pin and to which a brush holder 14 has its one end secured. The holder 14 is provided at its outer end with a brush 15, and a coil spring 16 encircling the sleeve 13 urges the holder 14 to turn about the pin 12 in such a direction as to press the brush against the commutator 9. A cap 17 is detachably attached to the disk to cover the brushes and other component parts thereon. The pins 12 are connected to a source of electricity, not shown.

The disk 11 with the cap 17 attached thereto can be put into or taken out of the motor casing like a cartridge.

When the brushes are worn and must be replaced by new brushes, the disk 11 with the cap 17 thereon is simply taken out from inside the motor casing, and a new brush unit 10 enclosing new brushes 15 is put into the casing. This is a very simply manual work.

The graphite powder produced by wear of the brushes has flown off due to centrifugal force to be attached to the inner surface of the cap and seldom flies out of the cap into that part of the motor casing where the armature is enclosed. Therefore, when the brush unit is taken out, the powder attached to the cap is also taken out. Then, the cap may be taken off from the disk 11 to brush off the attached powder.

Since the dental handpiece is used in the mouth of a patient to cut or drill the teeth, reduction of the insulation resistance of the instrument would result in leakage of electric current to the dental nerves which would incur a great danger to the patient's life. The device of the invention can completely eliminate such a danger.

Thus, in accordance with the invention, a simple manual work suffices for replacement of worn brushes for new ones in a micromotor used in a dental handpiece, and simultaneously with the replacement the graphite powder produced by the wear of the brushes can be removed from inside the motor.

Claims

What I claim is:

1. A brush holder cartridge for use in a micromotor, wherein the micromotor includes a casing having inner and outer surfaces, the brush holder cartridge comprising:

a support member;

a pair of brush holders secured to said support member, said pair of brush holders operative to hold a pair of brushes positioned therein in contact with a commutator of said micromotor; and

a cartridge cap, which cartridge cap engages said support member such that said support member and said cartridge cap substantially enclose said brush holders and brushes about said commutator, said cartridge cap being held in engagement with said support member by frictional contact between said cartridge cap and the inner surface of the micromotor casing when said brush holder cartridge is operatively positioned in said micromotor.

2. An apparatus of claim 1, wherein said support member has defined therein a notch around the periphery thereof, said notch receiving a portion of said cartridge cap, said support member and said cartridge cap thereby engaging one another, and wherein said cartridge cap is concentric with the inner surface of the casing.

3. A brush holder cartridge for use in a micromotor, wherein the micromotor includes a casing having inner and outer surfaces, the brush holder cartridge comprising:

a support member;

a pair of brush holders secured to said support member, said pair of brush holders operative to hold a pair of brushes positioned therein in contact with a commutator of said micromotor; and

a cartridge cap, which cartridge cap engages said support member such that said support member and said cartridge cap substantially enclose said brush holders and said brushes about said commutator, said support member including a pair of spaced electrically conductive pins integral at one end thereof with said support member, said conductive pins extending from said micromotor such that electrical energy may be applied thereto when said support member is operatively positioned in said micromotor.

4. An apparatus of claim 3, including a pair of sleeves, each sleeve being positioned around an electrically conductive pin and being rotatable thereabout, each sleeve having a brush holder fixedly secured thereto.

5. An apparatus of claim 4, wherein each of said pair of brush holders has associated therewith a spring for maintaining said brushes in contact with the commutator, each spring having two opposing ends and being positioned over a sleeve, one end of each spring being rigidly connected to said support member, the other end thereof being rigidly connected to its associated brush holder.