The light-emitting device 1 has a translucent cover 10 having a cylindrical shape and a flat light-projecting surface 11 facing to the light-emitting part of an LED 20. The LED 20 is arranged in close proximity with the flat light-projecting surface 11 in the translucent cover 10 to achieve efficient introduction of light from the LED 20 into a light-receiving surface of optical fibers.

FIELD OF ART

The present invention relates to a light-emitting device which may be used as a light source in a lighting device mounted on a dental handpiece. In particular, the present invention relates to a light-emitting device utilizing a light-emitting diode (LED).

BACKGROUND ART

LEDs have recently been attracting attention and widely used as a light source in a lighting device mounted on a dental handpiece for their lower electric power consumption and longer service life compared to conventional halogen lamps. JP-10-137263-A discloses a light-emitting device which includes an LED enclosed in a translucent cover, and electrode terminals electrically connected to and linearly extending from the LED, and is in a compact size as a whole suitable for installation in a dental handpiece. The translucent cover enclosing the LED is in the form of a bullet, out of which the two linear terminals (anode and cathode terminals) connected to the LED extend. The light-emitting device is installed in a dental handpiece with the two linear terminals being connected to the connecting terminals of a lighting device arranged in a coupling connecting a handpiece body and a hose. In the installed state, the light-emitting device is arranged facing to the light-receiving surface of the optical fibers disposed in the handpiece body to introduce light emitted from the LED into the optical fibers.

However, in such a conventional light-emitting device, the LED is inevitably arranged apart from the light-projecting surface of the translucent cover facing to the LED, due to the bullet shape of the cover and the semispherical shape of the light-projecting surface. Accordingly, the distance from the light-emitting part of the LED to the semispherical light-projecting surface is added to the distance between the light-emitting part of the LED and the light-receiving surface of the optical fibers. The light emitted from the LED is scattered between the light-emitting part of the LED and the semispherical light-projecting surface, and is not efficiently introduced into the light-receiving surface of the optical fibers. This reduces the amount of light entering the optical fibers to lower the intensity of illumination (brightness) and causes color shading.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a light-emitting device in which the light-emitting part of an LED is arranged in as close proximity to the light-receiving surface of optical fibers as possible for efficient introduction of light from the LED into the light-receiving surface to increase the amount of light entering the optical fibers, to improve the brightness of the lighting device, to eliminate or minimize color shading, and to improve the quality of the lighting device.

According to the present invention, there is provided a light-emitting device comprising:

a translucent cover,

a light-emitting diode (LED) enclosed in said translucent cover, and

electrode means electrically connected to said LED,

wherein said light-emitting device is in such a compact size as to be disposed in a dental handpiece,

characterized in that said translucent cover has a generally cylindrical shape and a flat light-projecting surface facing to a light-emitting part of said LED.

The light-emitting device according to the present invention, having the structure mentioned above, allows arrangement of the light-emitting part of the LED in as close proximity to the light-receiving surface of optical fibers as possible when the light-emitting device is installed in a lighting device having optical fibers. Thus, the light from the LED is efficiently introduced into the light-receiving surface of the optical fibers to maximize the amount of light entering the optical fibers. The increased amount of light improves the brightness of the lighting device and eliminates or minimizes color shading, to thereby improve the quality of the lighting device.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will now be explained in detail with reference to an embodiment taken in conjunction with the attached drawings.

FIGS. 1 to 5show an embodiment of the light-emitting device according to the present invention. Referring toFIGS. 1 and 3, the light-emitting device1has translucent cover10, LED20enclosed in the cover10, and electrode means30enclosed in the cover10and electrically connected to and extending from the LED20. The light-emitting device1as a whole is of such a compact size as to be installed in a dental handpiece.

The translucent cover10is a generally cylindrical member made of a transparent synthetic resin in its entirety, and has end face11at one end, which is a closed, flat, circular surface, and end opening12at the other end, which is a circular opening, as shown inFIG. 4. As can be seen inFIG. 5, inside the cover10, an annular step13is formed along the inner circumference near the end face11, and rectangular dent14is formed in the inner surface on the inside of the end face11. The dent14is sized to receive the LED20(in particular, LED chip21as will be discussed later) therein, and the end face11to be faced to the light-emitting part of the LED20acts as a light-projecting surface. The dent14is arranged so that the cover10and the LED20received therein are positioned concentrically.

Referring toFIG. 3, the LED20includes LED chip (LED element)21and substrate22. The LED chip21is a rectangular member, and is sized to be arranged in the dent14in the cover10. A fluorescent material is laminated on the LED chip21. The substrate22is in the form of a generally circular disk having a diameter smaller than the inner diameter of the cover10so as to be arranged in the cover10, and is slightly larger than the LED chip21. Two arcuate notches23,23are formed on the periphery of the substrate22at diametrally opposite positions.

As shown inFIGS. 2 and 3, the cathode terminal31is a generally cylindrical member having opening311at one end and opening317at the other end. The cathode terminal31has larger diameter section316, which has an outer diameter approximately the same as or slightly smaller than the inner diameter of the cover10and has a corrugated outer surface, and smaller diameter section312, which is continuous to the larger diameter section316and has an outer diameter smaller than the outer diameter of the larger diameter section316. Annular flange313is formed at the free end of the smaller diameter section312, which projects radially inwardly for supporting the substrate22of the LED20thereon. The flange313has two protrusions314,314projecting axially from its end face and arranged at diametrically opposite positions. Each protrusion314has an arcuate contour and is capable of being fitted in the notch23of the substrate22of LED20. Two recesses315,315are formed also in the end face of the flange313at diametrically opposite positions and at 90° angular distance from the protrusions314,314.

The anode terminal32is generally in the form of a pin having a length approximately the same as the axial length of the cathode terminal31, and has a flange321projecting radially outwardly at one end and a tapered portion322at the other end.

The terminal support33is made of an electrically insulating material, and has a generally cylindrical form. The support33has an outer contour to fit inside the smaller diameter section312of the cathode terminal31, and a stepped recess330in one end face, in which the flange321of the anode terminal32is fitted.

Assembly of the electrode means30is explained with reference toFIG. 5. First, the anode terminal32is inserted into the terminal support33, and supported therein with the flange321being fitted in the stepped recess330and the tapered end322extending out of the free end of the support33. The support33, with the anode32supported therein, is then inserted into the cathode terminal31, and fit in the smaller diameter section312. The anode terminal32, the terminal support33, and the cathode terminal31are positioned concentrically, and the flange321of the anode terminal32is arranged in the opening311of the cathode terminal31via the support33without contacting the inner surface of the cathode terminal31.

Next, the assembly of the light-emitting device1is explained with reference toFIGS. 3 and 5.

The LED chip21is placed in the rectangular dent14formed inside the cover10so as to be positioned concentrically with the cover10and to face the light-emitting part of the LED20to the end face11of the cover10. To the electrode means30as assembled above, the substrate22of the LED20is attached on the flange313of the cathode terminal31, with the two protrusions314,314of the flange313being fitted in the two notches23,23of the substrate22. In this state, the flange313of the cathode terminal31is connected to the substrate22of the LED20, and the flange321of the anode terminal32is connected to the substrate22of the LED20. The electrode means30with the substrate22attached thereto is then inserted into the cover10. In this way, the LED20, the cathode terminal31, and the anode terminal32are all positioned concentrically in the cover10. In this assembly, the LED20is positioned close to the light-projecting surface11of the cover10, and the cathode and anode terminals31and32are connected to the LED20.

The light-emitting device1according to the present invention may be installed in a dental handpiece as a part of a lighting device. The connecting terminals on the side of the handpiece are in the form of a socket, which projects outwardly from the circuit board arranged in the coupling of the handpiece. The connecting terminals of the socket are configured as two concentric cylinders which are arranged via an electrically insulating material therebetween. The inner terminal has a smaller diameter so that the anode terminal32of the light-emitting device1is inserted and fitted therein. The outer terminal has a larger diameter so that the inner surface of the cathode terminal31of the light-emitting device1fits over the outer surface of the outer terminal. The connecting end of the outer terminal is divided into a plurality of flaps, which are flexed radially inwardly by means of an external force and elastically return to the initial position by removal of the external force.

The light-emitting device1may be connected to the circuit board in the handpiece simply by inserting the electrode means30of the light-emitting device1into the socket having the connecting terminals. That is, when the electrode means30of the light-emitting device1is inserted into the socket, the anode terminal32of the light-emitting device1is inserted into and brought into contact with the inner cylindrical terminal of the socket, whereas the cathode terminal31of the device1fits over the outer cylindrical terminal of the socket to bring the inner surface of the larger diameter portion316into press contact with the outer surface of the outer terminal, which elastic engagement holds the light-emitting device1in place in the socket. The difference in shape of the cathode terminal31and the anode terminal32clearly distinguishes the polarity of the electrode means30, so that the light-emitting device1will not fail to be connected to the socket on the side of the circuit board in correct polarity. The light-emitting device1thus installed on the handpiece is powered through the circuit board and emits light, which is introduced into the light-receiving surface of the optical fibers.

Since the light-emitting device1according to the present invention has the flat light-projecting surface11, and the LED20is positioned in close proximity to this surface11, the distance between the light-emitting part of the LED chip21and the light-receiving surface of the optical fibers is minimized to achieve efficient introduction of light from the LED20into the light-receiving surface of the optical fibers. Thus the amount of light entering the optical fibers is remarkably increased compared to the conventional light-emitting device, and the brightness of the lighting device is improved and color shading is eliminated or substantially reduced.

In the electrode means30, the cathode terminal31is in the form of a cylinder, while the anode terminal32is in the form of a pin, so that the two terminals have different shapes. This facilitates determination of the polarity of the electrode30to securely prevent connection of the light-emitting device1to the connecting terminals on the side of the circuit board in wrong polarity.

In the electrode means30, the cathode terminal31is formed in a cylindrical form, and the anode terminal32is formed in a pin form and enclosed in the cylindrical cathode terminal31. This arrangement makes the electrode means30compact compared to the conventional two linear terminals.

Since the cathode terminal31of the light-emitting device1is in the form of a cylinder, the surface area of the cathode terminal31is increased, which results in effective release of heat generated in the electrode means30through the cathode terminal31.

Further, by assembling the cover10, LED20, and electrode means30concentrically, the processing of each part of the light-emitting device1and the assembly thereof are facilitated.

Incidentally, according to the embodiment of the present invention described above, the electrode means30is integrally assembled in the translucent cover10together with the LED20. However, the flat light-projecting surface of the translucent cover may also be applied to a light-emitting device having two linear terminals extending from the translucent cover.

Although the present invention has been described with reference to the preferred embodiment, it should be understood that various modifications and variations can be easily made by those skilled in the art without departing from the spirit of the invention. Accordingly, the foregoing disclosure should be interpreted as illustrative only and is not to be interpreted in a limiting sense. The present invention is limited only by the scope of the following claims.

DESCRIPTION OF REFERENCE NUMERALS