Patent Publication Number: US-2006006820-A1

Title: Horticultural lighting system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      Patents  
     
         
          U.S. Pat. No. 6,554,450 Apr. 29, 2003 Fang et al. “ARTIFICIAL LIGHTING APPARATUS FOR YOUNG PLANTS USING LIGHT EMITTING DIODES AS A LIGHT SOURCE” 
          U.S. 20010047618A1 Dec. 6, 2001 Fang, Wei; et al.  
       
    
     OTHER REFERENCES  
     
         
          1. “Gardening Indoors” Van Patten; Van Patten Publishing; 2002.  
          2. “Botany, An Introduction to Plant Biology” 5 th  ed.; T. Elliot Weier; U C Davis; 1950-1974.  
          3. “Plant Lighting Systems” Dr. W. M. Knott, Dr. R. M. Wheeler; NASA; 1998-2001.  
          4. “Development of Plant Growth Apparatus Using Blue and Red LED as Artificial Light Source” K. Okamoto, T. Yanagi, M. Tanaka, T. Higuchi, Y. Ushida, H. Watanabe; Kagawa University, Ryusho Industrial Co., Mitsubishi Chemical Corp.; 1996  
          5. “WSCAR Will Grow Seed-To-Seed Wheat Plants Aboard Mir . . . ” The Board of Regents; University of Wisconsin System; 1998-2002. 
 
 Internet Sources 
 
          1. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LightReactions.html; “Photosynthesis: The Role of Light;” 
          2. http://photoscience.1a.asu.edu/photosynthesis/photointro.html; “An Introduction to Photosynthesis and its Applications” Wim Vermaas; Arizona State University; 1998.  
          3. http://spot.colorado.edu/˜basey/green.htm; “Rate of Photosynthesis of Green and Yellow Leaves Under Green Light;” Rebecca Marcelliano, T. Dean Nelson, Joshua Prok, Ryan Mills, Kassi Neff;  
          4. http://www.actahort.org/books/22/22 — 16.htm; “Light Sources for Promoting Photosynthesis” I. J. Cooke, A. N. Burdett, S. F. Morgan.  
          5. http://149.152.32.5/Plant_Physiology/photoperiodisml.html; “Photoperiodism” 
       
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable  
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      This invention relates to a lighting system, which is highly efficient, reliable and versatile, yet specifically developed as an artificial plant-growth light.  
      Current fluorescent and gas discharge lights operate at relatively low conversion efficiency usually below twenty percent, emit excess light spectra, and lack longevity leaving room for improvement.  
      Until recently, Light Emitting Diodes (LEDs) have been manufactured and sold as “super bright” and typically consume  20  to  50  miliamps. These second generation LEDs have now been superceded by third generation devices consuming over 200 miliamps, which require thermal management means. It is a common misconception that LEDs emit no heat; with third generation LEDs, the amount of heat LEDs do emit becomes obvious. Therefore, thermal management and efficiency are important factors in the high-power LED lamp design claimed herein.  
      With LEDs comes the possibility of strongly monochromatic light and chroma-specific lighting fixtures. Photosynthetic plants make use of specific wavelengths i.e. colors of light as their energy source and for various types of stimulation. The wavelength requirements of the plants are determined by the specific light receptors and physiological needs present in the plants.  
      Until the advent of high-output third generation LEDs, LED plant-growth systems were unusable and unaffordable for anything more than tiny seedlings, and were not practical due to the large number of second gen. LED units required. Usage of third gen. LEDs eliminates these problems.  
      Daily on-off cycling typical in growing applications causes undue stress and premature failure of the gas-discharge lights. Never before has it been possible to achieve the longevity of a lighting fixture as with LEDs.  
      Commercial horticultural lighting systems currently available almost exclusively utilize gas-discharge technology. Some such fixtures include the following: 
      1. Fluorescent is a specific type of gas-discharge lighting technology. Firstly, utilizing a combination of chemical elements as the phosphor (light-emitting substance), some fluorescent bulbs are designed to produce horticulturally-specific output, i.e. red and blue, but the phosphors used result in a great proportion of spectra of which the plant utilizes only a small amount resulting in marginal performance. Secondly, these bulbs also typically utilize a heated filament, which is under stress and is frequently a cause of failure. Thirdly, fluorescent bulbs utilize mercury as the exciter element, which is toxic and escapes when the bulb eventually breaks.     2. High Intensity Discharge (HID) varieties operate under plasmatic conditions and are therefore inherently short-lived. These bulbs emit relatively intense infrared radiation and are known to cause damage to plant and animal tissue if precautions are not taken. Examples of HID lighting technologies include the following: 
        High Pressure Sodium (HPS): The spectra emitted from this type of light contain a proportion of some of the red light required for plant growth, but lack especially in the blue spectra resulting in abnormally slow-growing plants. In the event that the outer glass envelope breaks, HPS lamps emit hazardous levels of ultraviolet (UV) light.     Halide and Mercury Vapor: These bulbs partially solve the problem of lack of blue light, but also emit high proportions of green and yellow light resulting in a very white-appearing light, much of which is wasted as it is only utilized in small amounts by the plant.     “Combination”: Some horticultural fixtures utilize a combination of sodium and halide bulbs in attempt to meet both the red and blue light needs. While this is a sound concept, precise spectrum matching and longevity are limited.     “Conversion”: A bulb with known spectral qualities, which may be used to replace a given HPS, halide or mercury bulb, is known as conversion bulb.    
       

      The only patent known to us indicating the use of LEDs for plant growth is U.S. Pat. No. 6,554,450 issued to Fang. Fang indicates use of blue light of 450 nm and red light of 660 nm. We find that this particular strongly dichromatic spectrum promotes phototropism to such a degree that many plants over-extend themselves, we utilize wavelengths in addition to the suggested 450 nanometers and 660 nanometers. Through our experiments with LED grow lights of various colors, we find that no plants do as well as the plants supplemented with green light. Fang further utilizes second gen. LEDs assembled on circuit boards and small growth chamber which is limited for tiny seedlings.  
      Other patents have described using LEDs for general lighting purposes. See for example U.S. Pat. No. 6,603,271B2 indicating red, green, blue and white luminary elements.  
      LEDs are very sensitive to excessive current. Typical commercially-available LED lamps utilize resistors as the current-limiting devices, which are non-regulating resulting in inconsistent light output and premature failure, and are inherently wasteful resulting in excessive heat dissipation and power consumption.  
      High efficiency and longevity are generally sacrificed due to the high cost of impedance-matching supplies vs. the cost of a second gen. LED&#39;s.  
      Usage of second gen. LEDs is materially inefficient due to the light-output capability in comparison to the total mass of the device.  
      Other systems, as described in a NASA bulletin entitled “Plant Lighting Systems” are elaborate devices indicated for highly experimental use for culturing young seedlings in orbit, and are unavailable to the public. These lighting systems still encounter limited light volume capability, which prohibits growing anything bigger than tiny young plants.  
     BRIEF SUMMARY OF THE INVENTION  
      It is therefore a general objective of this invention to provide a versatile and adaptable lighting system utilizing high efficiency luminary elements mounted on a substrate providing heat and physical stress management. A universal impedance-matching power supply, time-variable and color-intensity-variable spectral adjustments and electrical connection means are used.  
      A further objective is durability and high lumen maintenance, which are native features of LEDs and are far superior to any of the glass-based luminary elements currently available.  
      A primary objective of the invention is photosynthesis resulting in plant growth, i.e. the conversion of light into usable energy. This particular objective is attained as a byproduct of some of the other types of stimulation due to the wavelengths involved and wavelength specificity required by such stimulation as compared to that required for photosynthesis.  
      It is widely accepted that the action spectrum for photosynthesis in most plants is strongly dichromatic light with major peaks close to blue 435 nm and red 670 nm. Note that photosynthesis does not necessarily equate to growth.  
      Another general objective of the present invention is to provide spectra that will optimize growth rate considering the competing functions of plant strength vs. size in addition to other factors.  
      An additional objective of the present invention is phototropic stimulation. Phototropism is the phenomenon of structural adjustment response in plants due to changing light conditions. We consider the spectral response peaks for phototropism to be blue 445 nm and red 645 nm.  
      Yet another objective of this invention is photoperiodistic control. Photoperiodism is a well-know phenomenon observed in nature and known to signal to plants the current season. According to “Gardening Indoors” a shift in natural light spectra stimulate specific hormones in plans. Spectral control further increases the effectiveness and versatility of the horticultural lighting system claimed herein.  
      An advanced objective of the present invention is phytochrome stimulation. Phytochrome is a physiologically active pigment that regulates growth, and absorbs deep red light near 670 nm to 680 nm in the “Pr” form and 720 nm to 730 nm in the “Pfr” form.  
      A specialized objective of this invention is cryptochrome stimulation. Cryptochrome is so named for its mysterious presence evading identification for many years, though it is indirectly apparent for plant growth. It is a pigment known to absorb large amounts of light in the 290 nm and 320 nm to 380 nm in color.  
      A preferred embodiment utilizes luminaries operating near the aforementioned wavelengths.  
      Usage of LEDs with relatively coherent output virtually eliminates burns due to minimized infrared emissions allowing operation closer to plants than in prior art, and therefore more effectiveness, resulting in high yield with relatively small energy expenditure.  
      This invention describes a light fixture in which luminary elements are chosen carefully in order to achieve the desired spectral distribution so the maximum possible energy transfer is attained. The growth stage, plant type, quality of growth required and other specific circumstances determine the exact configuration of the lighting system.  
      A preferred embodiment of the present invention allows optimization of the lighting system for photosynthesis, phototropism, and photoperiodism for a variety of plant types in addition to other more broad applications. Each emitted light wavelength is independently adjustable and programmable in brightness and time.  
      Yet another feature of a the preferred embodiment is true current regulation using a switching regulator featuring impedance matching and good thermal management using heat conductive means to maximize efficiency and life expectancy of the system.  
      Simplicity of design is maximized by electrical connection schemes that use one current regulator for a plurality of luminary devices.  
      New third gen. LEDs are relatively high energy devices compared with still-popular second gen. LEDs producing greater light and proportionally more heat output and therefore require special consideration of heat dissipation means.  
      Usage of higher output third gen. devices also means less material overhead and therefore better environmental responsibility and lower manufacturing cost.  
      Expandability of the lighting system is accomplished by mounting additional power connectors on the fixture or the master unit allowing fixtures to be added to an existing system without additional power supplies.  
      Trough extensive experimentation, we have determined the optimum luminary elements to achieve the highest possible efficacy with respect to light creation, light utilization, financial practicality, and material responsibility.  
      Further advantages will become apparent upon study of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      To better understand the proposed lighting system, several diagrams are included:  
       FIG. 1  is a perspective view of the entire invention showing the horticultural lighting system.  
       FIG. 2  is a perspective view of the master unit showing the power cord and user interface.  
       FIG. 3  is a perspective view of the fixture illustrating one possible arrangement of the luminary elements.  
       FIG. 4  is a side view of the preferred disconnectable connection.  
       FIG. 5  is a diagramatic view of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As will become evident by further study of the drawings, the present invention relates to a versatile lighting system especially for plant-growth illumination.  
      According to the preferred embodiment of the present invention,  FIG. 1  of the drawings shows the horticultural lighting system comprising a master unit  10  and fixture  20 . The master unit  10  includes a standardized plug  101  affixed to the end of a power cord  102  and attached to a chassis  105 .  
      The chassis  105  comprises a lid  1051 , a main housing  1052 , fastening screws  1053 , rubber feet  1054  and a power cord clamp or gland  1055 . The chassis  105  houses a power supply  103  which includes a fuse  1031 , a surge protector  1032 , a switch  1033 , a power indicator  1034  and an inductive unit  1035 . The chassis  105  also houses a control unit  104  which includes a light controller  1041 , a timer  1042  and a user interface  1043 . In a preferred embodiment, a backup power unit  106  interfaces with the power supply  103 . The backup power unit  106  may include a battery (not shown) which helps to insure continuous operation during times lacking main power source, and further conditions the power source.  
      As shown in  FIG. 4 , a disconnectable connection  30  includes a quick-connect receptacle or output receptacle  301  and a quick-connect plug or input plug  302 .  
      The Power cord  102  is made of insulated flexible electrical wire, which is impervious to water to ensure adequate protection while conducting power to the master unit  10 , and is equipped with a standardized plug  101  able to be plugged into a standardized outlet (not shown). As shown in  FIG. 2 , the gland  1055  is mounted in the wire point-of-entry on the main housing  1052  and provides adequate support and moisture protection where the electrical-supply power cord  102  enters the chassis  105 .  
      Referring to  FIG. 3 , the chassis  105 , being made of any number of materials including poly-vinyl-chloride (PVC), poly-styrene (PS), poly-carbonate (sold under the trade name ‘Lexan’), aluminum or other durable material, includes a cover  1051  and a silicone seal or gasket  1056  whereby, when securing the cover  1051  to the housing  1052  with threaded screws  1053 , the silicone seal  1056  is sandwiched between the cover  1051  and base  1052  providing a water-resistant barrier.  
      Upon entering the chassis  105  through the gland  1055 , the power cord  102  connects to the power supply  103 . The fault-current disconnect, fuse or circuit breaker  1031  provides protection in an event of a device failure, for example, if one of the diodes of a bridge rectifier “blows short” causing a diode to be forward biased with the power source and a high current to pass.  
      After passing through the fault-current disconnect  1031 , power is then routed through a sealed, manually-operated on-off power switch  1033 , which features moisture protection and gates power to the surge protector  1032 . After passing through the surge protector  1032 , which virtually eliminates transients including radio frequency (RF) noise and spikes present on the power source, power is then routed to inductive unit  1035 . In an alternate embodiment, the inductive unit  1035  includes a solid-state switching regulator circuit, which affects an AC voltage to the inductive element (not shown) to achieve impedance matching and therefore power efficiency, especially in cases where only DC power is available.  
      The inductive unit  1035  utilizes an inductive element to exchange voltage for current or current for voltage, i.e. to conserve power, in effect acting to match the impedance of the power source with that of the luminaries  204 . A light controller or current regulator  1041  further regulates the power to a drive current suitable for LEDs.  
      Power is further routed to a control unit  104 , which adjusts the lighting output. Through a user interface  1043 , the user programs the control unit  104 , which then uses the entered information to illuminate an appropriate luminary group to an appropriate intensity. In one possible embodiment, the program may consist of a single switch, which is either on or off, affecting the same condition in a luminary group. In an alternate embodiment, brightness of several different groups may be linearly and independently adjusted through the setting of a tactile actuator  1043 . In yet another embodiment, the color-intensities at specified time may be programmed using the tactile actuator  1043  so that the color output of the fixture  20  corresponds to the programmed setting. The appropriate spectrum simulates the time of day or time of season; the appropriate photoperiod is likewise programmable.  
      The output receptacle  301  is fixably mounted to the chassis  105 , receives power from the control unit  104  and facilitates multiple inputs  302  from fixtures  20 . A fixture  20  includes an input plug  302  affixed to the end of the link cable  202 , which electrically couples to the master unit  10 .  FIG. 1  further shows the fixture  20  with the input plug  302 , the link cable  202 , the strain relief  203 , the luminary elements  204 , the main substrate  205  and second substrate  206 .  
      In the preferred embodiment, as shown in  FIG. 4 , each quick connect receptacle  301  includes a plurality of female pin receptacles  3011 , a threaded barrel  3012  and a threaded mounting nut  3013 . The link cable  202  is fitted with a screw-type quick-connect plug  302  including a plurality of electrical contact pins  3021 , a retainer nut  3022  and a strain-relief clamp  3023 .  
      The quick connects  301  and  302  provide an adequate watertight barrier as well as a secure mechanical and electrical connection. Each quick connect receptacle  301  can receives any one of the quick connect plugs  302  of a given light fixtures  20 . Thus, a plurality of fixtures  20  may be plugged into and operated using a single master unit  10 , avoiding the need for a dedicated master unit  10  for each lighting fixture  20 , as is typically required with conventional plant lighting systems, improving system versatility.  
      According to the preferred embodiment, the main substrate  205  comprises a section of heavy-gauge cast aluminum to provide maximum support, heat dissipation, light direction, and imperviousness to moisture. The lighting fixture  20  of the present invention includes a plurality of luminary elements  204  affixed to the main substrate  205  in a manner which provides maximum lighting effectiveness by spreading the illumination over a relatively wide area while dissipating heat to ensure the luminaries  204  operate at minimal operating temperature which extends system life and efficiency.  
      As shown in  FIG. 1 , a link cable  202  conducts power from the master unit  10  to the light fixture  20 . The link cable  202 , in the preferred embodiment, is thinner than the power cord  102  for ease of movement of the fixture and is less cumbersome so as not to damage plants. A wide verity of conventional cables could be used for the link cable  202  provided the conductors are finely stranded bundles and the outer jacket  2021  is a resilient water-tight insulation to ensure long life of the cable  202  as well as to ensure a safe means of electrical power transmission to the light fixture  20 . As depicted in  FIG. 1 , the link cable  202  is secured to the light fixture  20  through a strain relief  203 , which is attached to the main substrate  205 .  
      Hookup wires (not shown) provide an electrical path from the strain relief  203  through holes (not shown) in the main substrate  205  to the luminaries  204 .  
      The luminaries  204 , in the preferred embodiment, are electrically connected in groups in series to facilitate current regulation.