Abstract:
A light hardening apparatus for hardening light hardenable material includes a printed circuit having a carrier layer comprised of isolating material. The printed circuit is bendable and has conductor paths extending thereon or therethrough at spacings from one another. The apparatus includes a cooling body and a light source having a plurality of light emitting diode (LED) chips.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims foreign priority benefits under 35 U.S.C. §119(a)–(d) from German patent application ser. no. P 102 42 366.0 filed Sep. 12, 2002. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a light hardening apparatus for hardening a light hardenable material. 
   A light hardening apparatus of this type has long been conventionally known, whereby reference can be had, for example, to the light hardening apparatus disclosed in DE-PS 198 15 846. Such light hardening apparatus operate to harden light hardenable material such as, for example, material in the mouth of a patient, and are additionally deployed for hardening light polymerizable dental material. Printed circuits are available when a rapid and cost efficient configuration of a circuit needs to be realized. In the solution disclosed in DE-PS 198 15 846, a conductor plate extends vertically to the light exit device of the light source transversely through the handgrip of the light hardening apparatus. Electronic and electrical components are disposed on the printed circuit which, in part, also contribute to a power loss and, thus, operate as heat sources. 
   Light hardening apparatus are typically provided with heat emitting light sources. In this respect, halogen lamps or a multiple arrangement of LED chips are deployed. The heat given off by the light source is typically conducted away by a blower which is arranged in the rearward region of the extent of the pistol-shaped light hardening apparatus. 
   In order to be able to cool the components mounted on the handgrip of the light hardening apparatus, such as, for example, a longitudinal regulation transistor for the light source, it has been suggested to provide additional cooling air slots on the underside of the handgrip. A neighboring cooling air stream is to be flowed through such slots with the neighboring cooling air stream combining with the principal cooling stream from the blower. However, this solution has various disadvantages. 
   One disadvantage is that the principal cooling air stream and the neighboring cooling air stream extend substantially vertically adjacent one another. In the region in which the streams combine with one another, there occurs turbulence which significantly reduces the flow strength of the air stream. 
   Diversion ribs can, indeed, be deployed in order to achieve a less turbulent air stream. However, in a hand-held device, only a relatively small amount of space is available and additional air stream diversion measures would extend the configured length of the device, which is undesirable. If the longitudinal control transistor is simply mounted on the printed circuit board, the cooling effect of the neighboring air stream is significantly limited, in that the neighboring cooling air stream can only flow over the transistor with a reduced flow velocity. The possibility exists to mount a cooling device on the transistor so that the cooling efficiency is substantially improved. A cooling device of this type is comprised principally of metal and increases the weight of the light hardening apparatus, which is not desired. 
   The use of a solution of this type is, in any event, not possible if a light hardening apparatus having an accumulator disposed thereon, whose energy source is located in the handgrip, is to be used, as this necessitates that the entire electronic layout must be disposed in the transition region between the handgrip and the balance of the light hardening apparatus. 
   SUMMARY OF THE INVENTION 
   The present invention provides, in contrast to the prior art, a solution to the challenge of providing a light hardening apparatus which can be flexibly deployed, which provides an improved working efficiency but is, however, of only relatively small dimension. 
   Via the configuration of the printed circuit in the inventive bent or angled form, the entire power electronics can, surprisingly, also be disposed in the balance of the light hardening apparatus so that the principal cooling air stream flows over these components. In this regard, the neighboring cooling air stream can be completely omitted so that the above-noted problems can be avoided from the beginning. The cooling air stream can flow in a substantially non-diverted path along the balance of the light hardening apparatus from the front cooling air slot to the blower. In this regard, the cooling efficiency is improved so that a blower with comparatively reduced power can be deployed. This has the advantage that the dentist deploying the device is less disturbed by the exit of the heated air and the noise level of the blower is lowered. 
   In accordance with the present invention, it is particularly advantageous if the printed circuit with the electronics thereon extends adjacent the cooling body of the light source. By the extension in the axial direction of the blower air stream and, at the same time, of the light source, the required number of electronic components can be installed despite the relatively narrow place arrangement. Also, by the use of a bendable carrier layer for the printed circuit, the present invention is not limited to a single layer board. Instead, the conventionally known multi-layer technique can be deployed. In this connection, it is especially advantageous if the light source is configured with LED technology or a low voltage halogen technology. The operational voltage lies in the double-digit voltage region so that the imperviousness to leakage of the carrier layer comprised of isolating material is exceptionally reduced. This favors, on the other hand, the free design choice of the inventive printed circuit, as thin foil plates permit easier bending or kinking without leading to material degradation or, more significantly, breakage of material. 
   For example, the carrier layer can have a thickness of merely 0.1 mm or even 0.05 mm so that it can be designed in the region of the thickness of the guide paths. 
   It is to be understood that the thickness and width of the guide paths can be accommodated in a conventional manner to the operational requirements. Preferably, the thicknesses of the guide paths over the entire printed circuit are uniform in each layer and typically the flow-conducting conductors are substantially wider than the signal conductors. 
   It is particularly advantageous, as well, that the cooling ribs of the inventive light hardening apparatus can be deployed for conducting heat away from the heat emitting components of the electronics of the light hardening apparatus as well. The inventive cooling body, in this connection, has a double function—namely, on one hand, the cooling of the LED arrangement (or, as the case may be, the halogen glow lamp) and, as well, on the other hand, also conducting away the energy heat loss of the longitudinal regulator transistor, the thyristors or the like and this can be accomplished without imposing a demand for additional space availability in the hand grip of the light hardening apparatus. 
   The handgrip of the light hardening apparatus can be configured in any suitable desired manner so that the light hardening apparatus is, in its core configuration, also suitable for accumulator operation. 
   Due to the mounting of the heat source of the electronics on the cooling body of the light source in accordance with the present invention, a particular advantageous effect can be achieved: 
   In connection with reduced light strength according to the selected light hardening apparatus program of the operator, the light source emits at reduced power so that its power loss is correspondingly less. A regulation transistor, on the other hand, has, in connection with a reduced operational voltage of the light source, a relatively larger power loss. If, in the contrary situation, the regulator transistor is fully connected through, its power loss reduces relative to the multiplication product of the forward voltage and the operational flow of the light source. In contrast, in this operational condition, the light source is at its maximum performance and is subjected, therefore, to its maximum power loss. The sum of the so-produced power losses are, in this connection, less than the sum or total of the maxima, so that it is surprisingly possible, in accordance with the configuration of the blower, to design an overall reduced total heat loss operation. 
   Due to the bendable configuration of the printed circuit, the printed circuit conforms in a contour following manner to the profile of the cooling body so that the production and mounting thereof is exceptionally simple. Preferably, an isolation layer is provided between electronic conducting components of the printed circuit and the cooling body, which prevent the occurrence of short circuits. The printed circuit can also be adhered to the cooling body in an effective manner and it is possible, as well, to use printed circuits having soldering lugs as well as SMD technology. 
   In accordance with the present invention, it is particularly advantageous that the printed circuit can, in connection with an LED matrix light source, be disposed exceptionally close to the LED chips of the light source. In this connection, the LED chips can be connected to the printed circuit via bond technology. This solution has the advantage, as well, that the plastic housing of the LED chips, in which they are frequently cast, can be omitted. Instead, a cover disc such as, for example, a cover disc comprised of quartz glass, can be provided so that the reduction in working efficiency which would otherwise occur due to the use of a sealing mass around the LED chips can be prevented. Nonetheless, an encapsulated and hermetically sealed configuration of the LED matrix is made available by this approach. 
   Further advantages, details, and features are set forth in the hereinafter following description of the embodiment of an invention in connection with the schematic drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a cooling body for an inventive light hardening apparatus in one embodiment thereof; 
       FIG. 2  is a perspective view of a printed circuit of the inventive light hardening apparatus shown in  FIG. 1 ; 
       FIG. 3  is an illustration of a substrate body for receipt thereon of a light source for the light hardening apparatus shown in  FIG. 1 ; 
       FIG. 4  is an illustration of the substrate body having the LED chips as shown in  FIG. 3 , whereby, additionally, a cover disc has been installed; 
       FIG. 5  is an illustration of the mounted unit comprising first and second cooling bodies, a printed circuit, and a light source for deployment in the selected embodiment of the inventive light hardening apparatus; and 
       FIG. 6  is a view, in partial section, of the light hardening apparatus, whereby the mounted unit is already installed therein. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As seen in  FIG. 1 , a first cooling body  10  is comprised as part of an inventive light hardening apparatus in one embodiment of the present invention. The cooling body  10  comprises a plurality of cooling ribs  12  which extend parallel to one another along the cooling body longitudinal axis  18 . A light source  16  is disposed on the forward end of the cooling body  10 , whose configuration can be best seen in  FIGS. 4 and 5 . The light source emits light emissions for light hardening of polymer masses along the direction, as well, of the axis  18 . 
   The cooling body  10  comprises a rearward, substantially cylindrical region  20  and a forward conical region  22 . The conical region is, in conventional manner, received along with the light source  16  in a correspondingly formed portion of a housing of the light hardening apparatus, whereby reference is had in this regard to German patent application 101 27 416, which is fully incorporated by reference herein. The cylindrical region is, in any event, received in a correspondingly formed portion of the housing. Four support elements  24  are uniformly circumferentially distributed about the circumference for fixedly supporting the cooling body  10  in the housing. 
   In accordance with the present invention, the cooling body  10  is provided with two opposed channels, of which a channel  26  can be seen in  FIG. 1 . The configuration of the opposed channel  28  is symmetrical to that of the channel  26 . Each channel  26 ,  28  extends not only over the conical region  22  but, as well, extends over the cylindrical region  20  parallel to the axis  18  and, thus, adjacent the cooling ribs  12 . While grooves  30  are configured between the cooling ribs, each of whose width is merely somewhat greater than the width of a cooling rib itself or, alternatively, corresponds to the width of a cooling rib, the channels  26  and  28  are substantially wider. 
   Each channel  26  and  28  is operable to receive the inventive printed circuit. In accordance with the present invention, the printed circuit can be flexible and, as well, can be comprised of multiple components, whereby it is nonetheless preferred that the printed circuit is configured as a single integral unit and has the configuration as shown in  FIG. 2 . 
   Each channel  26  and  28  includes a floor  32  and two side flanks  34  and  36 , whereby the side flanks  34  and  36  diverge slightly from one another outwardly. Due to this configuration, the printed circuit can be arranged with space saving components and the printed circuit can be disposed in a channel of this configuration in a straightforward manner. 
   The cooling body  10  comprises, at its rear end, a blind hole-type recess  42  extending around its axis. 
     FIG. 2  shows a printed circuit  50  in an exemplary inventive embodiment. In this embodiment, the printed circuit  50  is a single integral unit, whereby it is to be understood that, instead of this configuration, it is also possible to select a multiple-component configuration and to interconnect the individual pieces of the printed circuit to one another via solder joints or, as the case may be, via plug and socket connections. 
   In accordance with the present invention, the printed circuit  50  is configured as a three-dimensional (3-D) configuration. The production of the printed circuit itself and the mounting thereon of its components occurs in the conventional manner—that is, this occurs as the printed circuit  50  still extends in planar form. By the selection of suitable bending means, the configuration of the printed circuit shown in  FIG. 4  is produced. In this configuration, the printed circuit comprises two principal strips  52  and  54  which are connected to one another via a connector ring  56 . Two wings  58  and  60  extend from each respective principal strip  52 ,  54  at an angle which corresponds to the angle of the side flanks  34  and  36  relative to the floor  32  of the channel  26 . 
   An angled region  64 ,  66  is provided on the rear end of each principal strip  52 ,  54 , respectively, with each angled region  64 ,  66 , supporting a plug element  66 ,  68 , respectively. Stop elements  65  and  67  are provided between the angled regions  64 ,  66  and the plug elements  66 ,  68 , the stop elements operating to axially support the plug elements  66 ,  68 . The stop elements  65 ,  67  extend sideways into an encircling groove  69  of the cooling body which is arranged in the rearward region of the cooling ribs. The axial length of this groove  69  substantially corresponds to the thickness of the stop elements  65 ,  67 . In the illustrated embodiment, the printed circuit  50  is substantially configured in SMD technology, while, in the region of the plug elements  66  and  68 , soldering lugs are provided. 
   The printed circuit  50  comprises not-illustrated conductor paths and supports numerous electrical and electronic components  70 , as are schematically shown in  FIG. 2 . To the extent that the components are configured via SMD technology and are configured on the surfaces of the wings  58  and  60 , it is also possible to provide punch outs or breakthroughs in the printed circuit and to permit the entire printed components with their cooling surfaces  72  to be sealed off in a flush manner with the underside of the printed circuit  50 . This solution permits a direct cooling of the respective components via the disposition of their cooling surface  72  on the bordering cooling ribs of the cooling body  10  to be ensured. 
   The connector ring  56  having an axial cutout  74  interconnects the principal strips  52  and  54  with one another. 
   The configuration of the connector ring  56  for the receipt of the light source is shown in more detail in  FIG. 3 . 
   The connector ring  56  supports, on its underside, a disc-shaped substrate body  76 . The substrate body  76  receives, on its upper side, a plurality of LED chips, of which three chips  80 ,  82 , and  84  are shown. Also, in spite of the fact that only three chips are illustrated, it is to be understood that, in reality, a plurality of chips over the surface of the substrate body  76  and a matrix-type arrangement are provided. 
   The substrate body  76  comprises an effective heat conducting metal and has an outer shape  88  which is larger than the inner configuration of the cutout  74 . The substrate body  76  is secured by adhesion to the underside of the connector ring  56  but can, however, also be secured in any other suitable manner such as, for example, by clamping. 
   It is to be understood that the LED chips are electronically isolated relative to the metallic substrate body  76  in conventional manner such as, for example, via a thin silicon oxide layer. 
   Preferably, bondable chips are used which are connected with the not-illustrated bond wires to corresponding connecting surfaces or bond pads on the printed circuit  50 . In this connection, the possibility to realize substantially short bond wire length is directly due to an oval shape which is selected for the cutouts and the substrate body  76 . 
   It is preferred to use a cover disc  90  for protecting the chips from dirt and debris, as is illustrated in  FIG. 5 , which can be comprised of, for example, a high transparency quartz glass. The cover disc  90  is preferably secured by adhesion on the substrate body  76  so that an enclosed unit is formed which can be, as needed, also completely changed out for an exchange unit. A not-illustrated distance ring  75  can be arranged between the forward side of the connector ring  56  and the cover disc  80  so that a spacing between the chips and the cover disc  90  can be achieved. 
   It is to be understood that the connection of the LED matrix, which forms the light source  92 , can be disposed on the printed circuit  50  in any suitable desired manner. For example, a direct welding or soldering is possible. Alternatively, a small sister plate can be used which is insertable on the printed circuit and comprises a portion of the light source. 
   In accordance with the present invention, it is advantageous as well that, via the insertion of the substrate body  76  in the cutout  74 , an automatically correct orientation of the light source is produced so that an after adjustment of the light source can be omitted. 
   A mounted unit  54  is shown in  FIG. 5 , which is comprised of the cooling body  10 , the light source  92 , and the printed circuit  50 . As can be seen, the unit provides an exceptionally compact unit  94 . Via the intensive through flow of the significantly deeply extending cooling ribs  12 , a good cooling effect is achieved. Preferably, the grooves  30  adjacent the conical region  22  are somewhat less deep and have their maximum depth at the rearward end of the cooling body  10 . In this manner, the flow velocity of the cooling air at the transition between the conical region  22  and the cylindrical region  20  is especially large and is, in the rearward region, reduced, so that there occurs a longer residence time of the cooling air on the cooling ribs  12 . 
   In  FIG. 6 , an embodiment of an inventive light hardening apparatus  96  with an installed and mounted unit  94  is illustrated. Cooling air slots  98  can be provided in conventional manner on the housing in surrounding relation to the conical region  22  which conduct the cooling air thereto. The cooling air flows along the axis  18  on the unit  94  and is exhausted outwardly by a blower  100 . 
   As can be seen in  FIG. 6 , the unit  94 , which has the described printed circuit which is not otherwise illustrated in  FIG. 6 , is connected to an additional printed circuit  102 . The connection is preferably effected via bushings which correspond to the plug elements  66  and  68 . The printed circuit  102  serves as the connector of the blower motor and the light source but can, however, operate as the energy source of the electronics on the printed circuit  50  and operate, as well, as the connection to a finger pressure switch  104 . The energy supply can be configured either via accumulators, which are disposed in conventional manner on the hand grip  106  of the light hardening apparatus  96 , or can be configured as a connector cable extending outwardly under the handgrip  106  to a base station of the light hardening apparatus  96 , which ensures the electrical voltage supply. 
   It is to be understood that the printed circuit  102  can be configured in any suitable desired manner. It can also extend transversely through the handgrip  106  to the lower end thereof and thereat form a support position for the connector cables. 
   Although the herein described embodiment comprises a cooling body  10 , which extends along the printed circuit  50 , it is to be understood that, as needed, it is also possible without further substantial effort to configure the cooling body as a multiple-component cooling body, whereby a partition line extends, for example, along the groove. 
   The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.