Abstract:
An improved liquid motion lamp includes a second heat source to reduce warm-up time and a removable base cover to simplify changing a first heat source. The first heat source is preferably a light bulb residing in the base of the lamp, which light bulb provides both heat to cause motion of liquids within the lamp, and light to enhance a viewing effect. The sliding cover is preferably an open ended cylinder which slides upwards to provide access to the light bulb. The liquids comprises a first liquid which is a solid at room temperature and which is preferably paraffin based, and a second liquid which is preferably water. The first liquid may be empirically determined by mixing trial batches of paraffin and chlorinated paraffin to determine the correct ratio for a given lot of paraffins. The first liquid may be prepared, and shipped with the lamp in a solid phase. The second liquid may be added at the lamp&#39;s final destination.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to decorative lighting and in particular to a liquid motion lamp. 
   Liquid motion lamps, commonly called “lava lamps” have been know since the 1960s. Such lamp is described in U.S. Pat. No. 3,387,396 for “Display Devices.” The &#39;396 patent describes a lamp having globules of a first liquid suspended in a second liquid, wherein the first liquid has a thermal expansion coefficient providing sufficient expansion, and therefore reduction in density, such that the first liquid is heavier than the second liquid at a lower temperature, and lighter than the second liquid at a higher temperature. The temperatures may be, for example 45 degrees Centigrade and 50 degrees Centigrade. The first and second liquids are contained in a clear container having a heat source at the bottom, and as a result, the first liquid is heated, rises within the second liquid, cools, and drops back to the bottom of the container. At least one of the liquids is preferably colored, and provides an entertaining motion for an observer. Lamps such as described by the &#39;396 patent are typically small and are sold as a sealed unit. 
   Recently, liquid motion lamps have gained popularity, and there is a desire to use such lamps in various commercial settings, for example hotel lobbies, clubs, lounges, etc. Unfortunately, simply scaling up known liquid motion lamps results in a product very expensive to ship, and which require as much as an eight hour or more warm-up period before use. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention addresses the above and other needs by providing an improved liquid motion lamp including a second heat source to reduce warm-up time and a removable base cover to simplify changing a first heat source, and further, a method for manufacturing the lamp allows filling with liquid after shipment of the lamp. A first heat source is preferably at least one light bulb residing in the base of the lamp, which light bulb provides both heat to cause motion of liquids within the lamp, and light to enhance a viewing effect. The sliding cover is preferably an open ended cylinder which slides upwards to provide access to the light bulb. The liquids comprises a first liquid which is preferably paraffin based, and a second liquid which is preferably water. The ratio of ingredients of the first liquid may be empirically determined by mixing trial batches of paraffin and chlorinated paraffin to determine the correct ratio for a given lot of paraffins. The specific gravity of the resulting mixture may be measured and compared to a desired specific gravity, and the result of the comparison used to adjust the ratio of the ingredients in the mixture. After determining the ratio, the first liquid may be prepared, and shipped with or in the lamp. The second liquid may be added at the lamp&#39;s final destination. 
   In accordance with one aspect of the invention, there is provided a liquid motion lamp comprising a container, a first liquid suitable for residing in the container, a base portion substantially below the container, the base portion including a heat source within the base portion and a base cover. It is to be understood that the first liquid is a solid at room temperature and becomes a liquid after heating, as the lamp is in use. The first liquid is adapted to cooperate with a second liquid, which second liquid is a liquid at room temperature, and which first liquid has a greater density than the second liquid at room temperature, and a lower density than the second liquid at a second and higher temperature, and which second liquid is a liquid at the second temperature. The base cover may be moved to replace the heat source without disturbing the container, and the heat source provides sufficient heat to maintain liquid motion of the first liquid within the second liquid. The lamp may further include a second heat source for reducing the time required to bring the lamp to operating temperature. 
   In accordance with another aspect of the present invention, a method for preparing a liquid motion lamp for shipping is described, wherein the final filling of liquid into the lamp may be done after shipping. The method comprises adding a first amount of paraffin to a second amount of chlorinated paraffin to create a mixture. The Specific Gravity (SG) of the mixture is measured, preferably at the operating temperature of the lamp, and more preferably at approximately 135 degrees Fahrenheit. The SG is compared to a lower limit SG 1 . If SG is not greater than a lower limit SG 1 , the first amount is increased (or the second amount in decreased) and the method is restarted. Otherwise, the SG is compared to an upper limit SG 2 . If SG is not less than the upper limit SG 2 , the first amount is decreased (or the second amount is increased) and the method is restarted. If SG is greater than the lower limit SG 1  and less than the upper limit SG 2 , a quantity of a first liquid is prepared based on the first amount and the second amount. An appropriate amount of the first liquid is added to a container of, or provided with, a liquid motion lamp. If the first liquid is added to the container, it is added in a fluid state and allowed to cool and solidify for shipping. The lamp containing the solidified first liquid is shipped, and a second liquid is added after the lamp is at it&#39;s final destination. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
       FIG. 1  is liquid motion lamp according to the present invention. 
       FIG. 2  shows a perspective view of the liquid motion lamp. 
       FIG. 3A  shows the liquid motion lamp with a base cover raised to gain access to a first heating element. 
       FIG. 3B  shows the liquid motion lamp with a base cover raised and with the first heating element removed. 
       FIG. 4  shows a cross-sectional view of the liquid motion lamp taken along line  4 — 4  of  FIG. 1 , showing a second heating element. 
       FIG. 4A  is a detailed view of a bottom portion of the cross-sectional view of the liquid motion lamp taken along line  4 — 4  of  FIG. 1 , showing bottom sealing details and a second heat source residing on the exterior of the container. 
       FIG. 4B  is a detailed view of the bottom portion of the cross-sectional view of the liquid motion lamp taken along line  4 — 4  of  FIG. 1 , showing bottom sealing details and a second heat source comprising a circular heating element suitable for immersion in the second liquid. 
       FIG. 5  shows the liquid motion lamp with a first liquid in solid form residing in the bottom of a container portion. 
       FIG. 6  describes a method for preparing a liquid motion lamp for shipment. 
   

   Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
   Liquid motion lamps, or lava lamps, are well known as small home decorative lighting. U.S. Pat. No. 3,387,396 for “Display Devices,” U.S. Pat. No. 3,570,156 for “Display Devices,” and U.S. Pat. No. 5,778,576 for “Novelty Lamp,” describe such lamps. A detailed description of liquids used in such lamps is provided in U.S. Pat. No. 4,419,283 for “Liquid compositions for display devices.” The &#39;396, &#39;156, &#39;576, and &#39;283 patents are herein incorporated by reference. 
   Although basic home lava lamps have become commonplace, large versions for commercial use have not been entirely practical for various reasons. The liquid motion lamp  10  shown in  FIG. 1  overcomes these obstacles. The lamp  10  includes a top piece  12 , a container  14 , and a base portion  19  including a base cover  16  and a base flange  18 . The container  14  is preferably transparent and more preferably made from boro silicate glass or any clear stable plastic, for example, acrylic or poly carbonate. The top piece  12 , base cover  16 , and base flange  18  are preferably made from cast aluminum. The container  14  preferably extends into the base portion  19 , and preferably, at least a portion of the base portion  19  is below the bottom of the container  14 . 
   The container  14  diameter D 1  is preferably be between six inches and 36 inches, the base cover diameter D 2  is preferably between approximately one inch and approximately two inches greater than the container diameter D 1 , and the base flange diameter D 3  is preferably between approximately two inches and approximately twelve inches greater than the container diameter D 1 . The overall height H 1  of the lamp  10  is between approximately three feet and approximately nine feet, and the height H 2  of the visible portion of the container  14  is preferably between approximately two feet and approximately six feet While the primary advantages of the present invention are directed to a lamp  10  having the preferred dimensions, any lamp including the present invention described herein is intended to come within the scope of the present invention. A perspective view of the lamp  10  is shown in  FIG. 2 . 
   A lamp  10  intended for use in a commercial setting, for example, hotel lobbies, clubs, lounges, etc., may be much larger and heavier than known lava lamps. As a result, it is not practical to lift or move the lamp  10  to replace a heat source which has failed. To address replacement of the heat source, the base cover  16  is vertically moveable along an arrow  20  as shown in  FIG. 3A . With the base cover  16  raised, a first heat source  22  is accessible. The heat source  22  is preferably also a light source, and is more preferably an incandescent light bulb. The heat source  22  is electrically and mechanically connected to a socket  24 . A view of the lamp  10  with the heat source  22  removed is shown in  FIG. 3B . The container  14  is supported by supports  26  residing between the base flange  18  and the container  14 . There are preferably three supports  26 , and a container base  15  proximal to the bottom of the container  14 . 
   A cross-sectional view of the lamp  10  taken along line  4 — 4  of  FIG. 1  is shown in  FIG. 4 . An edge view of the second heat source  28  is shown circling the container  14 . The second heat source  28  preferably resides in or on a portion of the container  14  normally covered by the base cover  16 . The second heat source  28  may be potted to the container  14 , and may be a heat blanket, and preferably an approximately 250 watt to approximately 500 watt heat blanket. The heat source  28  is further preferably a dual filament heat blanket with configurable wiring  30  allowing the second heat source to be wired for 2 voltage levels, and more preferably for approximately 120 volts and for approximately 240 volts. The top piece  12  comprises a round cover  12   a  for the container  14  and a short cylindrical portion  12   b  for positioning the top piece  12  on the container  14 . The top piece  12  is preferably fabricated from the same material as the base cover  16  and the base flange  18 , and preferably provides a moisture proof seal to the container  14 . 
   While a single first heat source  22  comprising a single light is shown in  FIG. 4 , the first heat source  22  may comprise one, two, three, or more lights, for example, a single 175 watt light, or three 150 watt lights. Further, the present invention may be practiced without a second heat source  28 , thereby impacting the start-up time, but not the operation of the lamp  10 . The first heat source  22  and the second heat source  28  or  28   a  preferably receive electrical power through a power cord  32 . 
   A detailed view of a bottom portion of the cross-sectional view of the liquid motion lamp taken along line  4 — 4  of  FIG. 1  is shown in  FIG. 4A  showing bottom sealing details. A container base  15  surrounds and supports the bottom of the container  14 . The container base  15  is somewhat L shaped and reached under a lower edge of the container  14  to provide vertical support. The base  15  cooperates with a base ring  15   a  to form a seal between a container bottom  14   a  and the container  14 . The container bottom  14   a  is preferable fabricated from a transparent material to pass light from the heat source  22  into the container  14 , and the container bottom  14   a  is more preferably made from the same material as the container  14 . 
   The container bottom  14   a  is sandwiched between the base  15  and the base ring  15   a , and O-rings  17  reside on the top and bottom of the container bottom  14   a  to form a seal between the container bottom  14   a  and the base  15 , and between the container bottom  14   a  and the base ring  15   a . The second heat source  28  preferably resides between the base  15  and the container  14 , and is preferably potted in place. The supports  26  (see  FIGS. 3A ,  3 B) are attached to the base  15  using support studs  26   a , passing through the base ring  15   a , thereby joining the base ring  15   a  to the base  15 , and compressing O-rings  17 . 
   A detailed view of the bottom portion of the cross-sectional view of the liquid motion lamp taken along line  4 — 4  of  FIG. 1 , showing bottom sealing details and another preferred second heat source comprising a circular heating element  28   a  suitable for immersion in the second liquid is shown in  FIG. 4B . The heating element  28   a  resides inside the container  14  and receives power through heating element wires  36 . The heating element  28   a  has an outside diameter slightly smaller than an inside diameter of the container  14 , and there is preferably an approximately 0.25 inch gap between the heating element  28   a  and the container  14  inside surface, and is positioned vertically to be concealed by the base cover  16  (see  FIG. 1 ) when the base cover  16  is lowered over the base portion  19 , and/or is positioned vertically to be concealed by the base ring  15 . The heating element  28   a  is preferably an approximately 750 watt to approximately 1500 watt heating element. 
   When the lamp  10  is in use, the container  14  is substantially filled with two immiscible liquids. The lamp  10  is shown in cut-away in  FIG. 5  with the first liquid  34  residing in the bottom of the container  14 , which first liquid  34  is preferably a solid at room temperature and preferably reside behind the base cover  16  when solidified, and is preferable below the heating element  28   a  when solidified. The second liquid (not shown) is preferably liquid at room temperature and more preferably comprises water. The first liquid  34  has greater density than the second liquid at room temperature. When heated to operating temperature, the first liquid  34  becomes less dense than the second liquid and rises in the container  14 , thereby creating liquid motion. As the first liquid  34  rises in the container  14 , the first liquid  34  cools sufficiently to become more dense than the second liquid, and thus drops back to the bottom of the container  14  where the first liquid  34  is again heated. The lamp preferably operates at between approximately 130 degrees Fahrenheit and approximately 135 degrees Fahrenheit. 
   An exemplar first liquid  34  is a paraffin based thermally expansive material, and preferably a combination of chlorinated paraffin and paraffin. The paraffin is preferably a low melting temperature paraffin, and more preferably a low oil content paraffin, and most preferably a less than three percent oil content paraffin, also known as a scale wax. The paraffin is preferable a low melting temperature paraffin to allow a low operating temperature for the lamp. A surfactant is preferably added to the container to reduce surface tension of the liquids, and a binder is preferably added to prevent the paraffin and chlorinated paraffin from separating. The surfactant is preferably a high cloud point surfactant, and the binder is preferably Polyboost binder made by Hase Petroleum Wax Co. in Arlington Heights, Ill. 
   A method for preparing the lamp  10  for shipping is described in  FIG. 6 . Generally, the specific density of paraffins varies from lot to lot. As a result, a single formula for mixing the paraffin and chlorinated paraffin is not available, and the ratio of paraffin to chlorinated paraffin must be determined empirically for each lot of material received. A preferred method comprises adding a first amount of paraffin to a mixture at step  100  and adding a second amount of chlorinated paraffin to the mixture at step  102 . The Specific Gravity (SG) of the mixture is measured at step  104 . The SG is compared to a lower limit SG 1  at step  106 . If SG is not greater than a lower limit SG 1 , the second amount is decreased at step  108  and the method is restarted. The SG is compared to an upper limit SG 2  at step  110 . If SG is not less than the upper limit SG 2 , the second amount is increased at step  112  and the method is restarted. If SG is greater than the lower limit SG 1  and less than the upper limit SG 2 , a quantity of the first liquid  34  is prepared based on the first amount and the second amount at step  114 . An appropriate amount of the first liquid  34  may be added to the container  14  (see  FIG. 5 ) of, or provided with, a liquid motion lamp  10  at step  116 . The lamp  10  containing the first liquid  34  in a solid room temperature phase is shipped at step  118 . A preferred starting first amount and second amount are approximately 100 units and 200 units respectively. 
   Other methods for determining a ratio of paraffin to chlorinated paraffin may be used, for example, measuring the specific density or other characteristics of the paraffin and/or chlorinated paraffin, and computing a mixing ratio, or making a trial mixture and observing the behavior of the trial mixture in water. A first liquid  34  made by any method, and included with a lamp  10  for shipping without any second liquid, or with a reduced quantity of the second liquid, is intended to come within the scope of the present invention. 
   The method described in  FIG. 6  may further include adding a binder to the mixture to prevent separation of the paraffin from the chlorinated paraffin, and/or adding a surfactant to the mixture. The surfactant is preferably a high cloud level surfactant. The specific gravity of the mixture is preferably measured using a pycno meter at elevated temperature, and preferably at lamp operating temperature, and more preferably at approximately 135 degrees Fahrenheit, and the lower limit SG 1  is preferably approximately 0.995 and the upper limit SG 2  is preferably approximately 0.998, although a wider range of specific gravity may be used with a higher power heat source. 
   Shipment without the second liquid substantially reduce the weight of the lamp  10 , and makes shipping the lamp  10  much easier. The first liquid  34  may be colored during preparation, or coloring may be provided with the lamp  10  to be added after the lamp  10  is delivered to a customer. Preferably, a coloring provided to a customer is in a solid form, and preferably coloring of several different colors is provided. 
   While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.