Abstract:
A convection cooled liquid crystal display panel projector having a low wattage light source. The projector consist of a housing with a plurality of louvered vents preventing light from escaping from the housing while allowing air to circulate there through. A primary lens configuration having a light source, and a liquid crystal display panel, a Fresnel lens and a projector mirror. An overhead lens configuration by said light source and a Fresnel lens and liquid crystal display panel with a mirror in spaced relation thereto.

Description:
This patent application is a continuation in part of Ser. No. 10/444,040, Filed May 21, 2003, now abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to convection-cooled projectors and more particularly to employing a low illuminance lamp as a light source used in conjunction with a screen with a high gain rating. 
   2. Description of Prior Art 
   Prior art projectors in general use LCD panel projectors comprises a fan cooled box-like housing which supports an illumination lamp, an LCD panel bearing an image to be projected and various configurations of lenses used to magnify the image on the LCD panel. The exhaust fan is incorporated in the housing or exhausting air inside the housing through the air outlet. An 800 Watt to 1000 Watt projection light source is also provided in the housing for illuminating LCD panel. A projection lens is provided for projecting a magnified image on the LCD panel onto a remote viewing surface such as a screen and includes a focusing lens and may include a reflecting mirror for focusing and directing the image from the LCD panel to the screen. The projector of the above-described type recently employs a high illuminance lamp, for example, a halogen lamp, as the light source so that the visibility of the enlarged image projected on the screen can be improved. In this case, however, LCD panel placed would be subjected to high energy heat rays produced by the high illuminance lamp such that the LCD panel goes above 45 degrees Centigrade at which point it ceases to function properly. The use of a low illuminance lamp in conjunction with a high gain screen eliminates the need for a cooling fan. Means need to be provided enhancing convection cooling to stop heat buildup in the projector housing. 
   In the conventional projectors of the transmissive LCD panel type, air heated by the heat rays from the light source is exhausted by the exhaust fan of the housing. Furthermore, a cold mirror which reflects light energy but few heat rays is employed as a spherical reflecting mirror mounted in the rear of or below the lamp. Moreover, a heat ray-reflecting filter is interposed between the lamp and the Fresnel lens. 
   Transmissive LCD panels are used with the above described overhead projectors, however, the LCD panels must not heat up to above 45C or they will cease to function. Some LCD projectors have built in fans to provide additional cooling in addition to the cooling fans built into the conventional projectors utilizing high luminance lamps. These LCD panels functionality is easily degraded by heat. Furthermore, dark colored portions of a projected area of the transmissive LCD panels absorb heat rays. Consequently, the above-described conventional means cannot provide sufficient prevention of temperatures above 45C if a secondary fan is not included in the transmissive LCD panel. Use of the low illuminance lamp allows the removal of the need for the secondary fan in the transmissive LCD panel. See for example U.S. Pat. Nos. 3,711,194, 4,880,303, 4,882,599, and 4,904,079. 
   U.S. Pat. No. 3,711,194 an overhead projection apparatus is disclosed having a housing with a lamp casing therein for projecting a light beam onto a reflective surface that directs a beam upwardly through a film onto a lens assembly for projection of an image onto a screen. 
   U.S. Pat. No. 4,880,303 is directed towards an overhead projector having a housing with a Fresnel lens, a lamp is positioned within the housing to provide illumination to a liquid crystal display framed in a hinge mounting on the side of the housing which can be positioned down an operative position overlying a Fresnel lens. A projection lens is positioned in spaced relation to the LCD panel and a reflective mirror surface is provided for the output of the projection lens. 
   U.S. Pat. No. 4,882,599 an overhead projector is illustrated having a housing configuration with an internal light source and lens plus an internal reflective mirror which reflects an image up through a liquid crystal display and then through a projection lens and an angular image mirror thereabove. 
   U.S. Pat. No. 4,904,709 a liquid crystal display device for overhead projector is illustrated and described in which a liquid crystal lens display is sandwiched between protective plates which are separated from the cell surface to form an air passage provided with a fan so that an airflow can be directed there through which will come in direct contact with the cell cooling same. 
   Finally, in U.S. Pat. No. 5,683,160 an overhead projector with light illumines lamp as a light source is disclosed in which a housing is illustrated having a light source and mirror within and a pair of air inlets and outlets formed in the respective sidewalls with an exhaust fan incorporated within the housing to provide a cooling flow of air over the projected lens surface. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the present invention is to provide a projector wherein quieter operation can be obtained by employment of a low illumines projection lamp and transmissive LCD panel can be prevented from achieving temperatures greater than 45 degrees Celsius with simple quiet convection cooling. 
   To achieve the object, the present invention provides a projector comprising a housing including a transmissive LCD panel bearing an image to be projected and air vents provided in the sidewalls of the projector housing. A low wattage projection light source is provided in the housing for illuminating the transmissive LCD panel such that convection cooling method of the invention is sufficient to keep the temperature of the LCD panel below 45C. Either of two general types of lens configurations are used. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the lens configuration of the invention for a vertical TV projector application of the convection-cooling device; 
       FIG. 2  is a schematic cross-sectional view of the convection cooling projector of the invention; 
       FIG. 3  is a schematic cross-sectional view of an alternate form of the invention on a horizontal orientation; 
       FIG. 4  is a perspective view of the convection cooling projector of the invention with a projection mirror attached thereto shown in broken lines; 
       FIG. 5  is a perspective view of an alternate overhead projector of the invention having a convection-cooling configuration with a projection lens mirror assembly positioned in spaced relation to the projector&#39;s output for overhead projection onto a remote screen; 
       FIG. 6  is a side elevational view of a second alternate form of the invention; 
       FIG. 7  is a top plan view thereof; 
       FIG. 8  is a side elevational view of a third alternate form of the invention in expanded use configuration; 
       FIG. 9  is a side elevational view thereof in collapsed transportable and storage position; and 
       FIG. 10  is a partial enlarged perspective view of the cooling air inlets and outlet vents of the invention illustrated in  FIGS. 8 and 9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1  of the drawings, a graphic illustration shows the basic elements of a convection-cooling projector  10  of the invention. The projector  10  has a main support frame  11  defining a rectangular enclosure with a base  12  having a projector light source  13  thereon. A liquid crystal display (LCD) image panel  14  is positioned within a support frame  15  in the main frame  11  in vertical spaced relation to the base  12 . A projection lens  16  (of a Fresnel type) is positioned in spaced vertical alignment within the main frame  11  so as to receive and project the images produced by the (LCD) panel  14  as will be well known and understood by those skilled in the art. 
   Referring now to  FIG. 2  of the drawings, a detailed sectional illustration of an application of the convection cooling projector  10  is shown in the cross-sectional illustration wherein a projection enclosure  17  has a base support  18  with a projector bulb  19  and concave reflector  20  in spaced relation thereto supported thereby. Pairs of oppositely disposed upstanding sidewalls  21 A and  21 B extend from the base support  18  defining a multi-wall projection enclosure  22 . The oppositely disposed sidewall pairs  21 A have a plurality of spaced parallel venting slots VS therein in vertical spaced relation to one another. A number of thermal bulkheads  23 ,  24  and  25  extend between the respective wall pairs  21 A and  21 B. Each of the thermal bulkheads  23 – 25  has a central optical transparent insert  23 A,  24 A and  25 A therein. The bulkheads  23 – 25  define multiple compartments within the enclosure  17  with the projector bulb  19  and reflector  20  in a first compartment C 1  beginning at the base  18 . The remaining compartments C 2 –C 4  provide thermal isolation between the projector bulb  19  and an (LCD) panel  26 . 
   Each compartment C 1 –C 5  has two pairs of light baffles  27 ,  28 ,  29  and  30  respectively in spaced adjacent relation to the respective slotted walls  21 A. The light baffles  27 – 30  extend from opposing bulk heads  23 – 26  and base  18  in parallel spaced overlapping orientation to prevent non-direct light indicated by light arrows L from passing directly out through the corresponding vent slots VS in each of the compartments C 1  and C 5  as hereinbefore described. 
   It will be evident by referring to  FIGS. 2 and 4  of the drawings that the space inbetween the bulkheads  23  and  26  is varied with the (LCD) panel  26  defining a final bulkhead. A projection lens  31  extends across the top of the enclosure  17  defined by the largest of the compartments C 5  therein. 
   In operation, the low wattage bulb  19  of reduced heat output can be used within the assembly and heat generated thereby being dissipated by the convection air currents generated through the hereinbefore disclosed thermal isolation compartments C 1 –C 5  and the multiple venting slots VS. It is important to dissipate the heat within the enclosure  17  given that the (LCD) panel  26  is heat sensitive and by the use of a lower watt low heat output bulb  19  the convection cooling imparted by the enclosure  17  of the invention is sufficient for maintaining the proper operation temperature without the use of a conventional fan (not shown). It will be evident that projection enclosure  17  can be created in reverse direction and still be functional. 
   Referring now to  FIG. 3  of the drawings, an alternate form of the invention can be seen wherein a horizontally oriented enclosure  32  is illustrated having a top  33  and support bottom  34  with support feet  34 A. Oppositely disposed upstanding sidewall pairs  35  and  36  and a projection end wall  37  define the parameters of the enclosure. 
   The top wall  33  and bottom  34  have a plurality of spaced parallel venting slots VS therein which are in communication with a number of thermal isolation compartments  38 A– 38 D. The compartments are defined within the enclosure  17  by thermal dividing walls  39 A– 39 C each of which has optically transparent center inserts therein  40 A– 40 C. 
   A projection light and reflector assembly  41  is positioned within the first compartment  38 A as will be well understood by those skilled in the art. 
   Pairs of oppositely disposed light baffles  42 ,  43 ,  44  and  44 A are arranged within the respective compartments  38 A– 38 D in spaced parallel overlapping relation to the respective venting slots VS in the top and bottom walls  33  and  34  respectively. 
   An LCD panel  45  is mounted within the compartment  38 D with a projection lens  46  in spaced adjacent relation thereto with the ventilation area there between so as to define in combination an effective end wall of the enclosure  32 . 
   In operation for both the primary form  10  and the alternate form of the invention, an image is electronically reproduced on the respective LCD panels  26  and  45  as is well known within the art and light from the projector bulbs  19  and light assembly  41  respectively pass there through projecting an image through the respective projection lenses  31  and  36  which in this example, as noted, are Fresnel lenses. 
   It will be evident from the above description that during use a cooling convection air current is established through the enclosures  17  and  33  bringing in cool air through the respective side and bottom vents VS and exiting hot air through the opposite side and top vents  33  vents VS as illustrated by the air arrows AA. 
   In the primary form of the invention  10  a convection air current is set up and will allow air to be drawn in through the respective vents VS and the sidewalls  21 A providing cross circulation to the respective thermal compartments as previously described. 
   Referring now to  FIG. 5  of the drawings, a second alternate form of the invention  46  can be seen having a secondary lens  47  and hinged mirror assembly  48  positioned in spaced aligned position with a projector P. An enclosure  49  has the same multiple thermal cooling chambers as the primary form of the invention with oppositely disposed slotted sidewalls  50  for creating a convection cooling current there through. Secondary lens  51  will allow a projected image I to be modified and reflected at angular inclination to the projector outlet surface at  52 . 
   Referring now to  FIGS. 6 and 7  of the drawings, a third alternate form of the invention can be seen wherein a hanging projector  54  can be seen having a light source and platform  55  supported by a plurality of support linkages  56  with an LCD panel  57  held in spaced relation thereto. The support linkage  56  is comprised of a plurality of cordage or other linkage construction such as metal chains which are secured to a plurality of opposing spaced parallel eyelets  59  extending from respective corners of the light source platform  56  and an LCD platform frame  61  in which the LCD panel  57  is positioned. An imaging and directional transfer assembly  62  is held in spaced vertical relation to the LCD frame  61  by the linkages  56  the imaging and directional transfer assembly  62  has a pair of square interengaged pivotal frames  62 A and  62 B with an optical quality mirror  64  secured within the frame  62 B as best seen in  FIG. 6  of the drawings. The projection principle is the same as that of the hereinbefore described primary and secondary forms of the invention in which the light source and platform  56  have a projector bulb  65  connected to a source of power with the image inducing LCD panel  57  within the LCD frame  61  to create an image which is then projected down to the angularly positioned optical quality mirror  64  and correspondingly projected onto a screen surface for viewing (not shown). 
   Referring to  FIGS. 8 ,  9  and  10  of the drawings, a fourth alternate form of the invention can be seen in which a suspended projector  70  is illustrated having a pair of conical pleated fabric baffles  71  and  72  extending from a central LCD supporting platform frame  73 . The baffle  71  has a light source and support frame platform  74  within at its free end. The baffle  72  has a pivoted mirror  75  and a support frame at its free end that will transfer the light image from the LCD panel  57  as hereinbefore described to a viewing surface (not shown). The respective baffles  71  and  72  may have a plurality of elongated slots and flap assemblies  76  within in both vertical and horizontally spaced relation to one another for cooling of a projection light source  77  and the LCD panel  57  as best seen in  FIGS. 8 and 10  of the drawings. The slot and flap assemblies  76  have internal slots S each with a light baffle flap F formed there from so as to eliminate ancillary light impingement beyond the confines of the respective baffle and closure  71  and  72  as best seen in  FIG. 10  of the drawings given the suspended projectors  70  baffled enclosures the slot and flap assemblies will provide for convection cooling thereof. 
   It will be apparent to those skilled in the art that such an alternate lens and mirror assemblies can also be used with the primary form of the projector  10 , also a variety of other mirror and lens elements may be used to further process the projected image once it passes through the primary projector lenses. 
   It will be evident to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.