Patent Publication Number: US-6668818-B2

Title: Safety guard for patio heater

Description:
FIELD OF THE INVENTION 
     This invention relates to a safety guard for a heating apparatus. More specifically, it relates to a guard that covers both the emitter and dome lid, providing additional protection compared to guards that allow the dome lid or the top of the emitter to remain exposed. 
     BACKGROUND 
     High efficiency heating apparatuses are available for warming a preselected outdoor area. It has become fashionable to sit outdoors, on a patio, deck or other open space, using a patio heater to supply warmth when the evening becomes chilly. Generally the units comprise a propane tank, a standard that holds an emitter a sufficient distance from the ground, a burner to support the combustion or propane and a dome cover. The dome reflects much of the heat due to both convection and radiation downward toward the persons trying to keep warm. Details of preferred patio heaters are described in U.S. Pat. No. 6,102,031, U.S. Ser. No. 09/640,199, and U.S. Ser. No. 29/143,937 herein incorporated by reference. 
     Persons seated around a table, however, may not receive the full benefit of the heating apparatus because of their location. If the standard is tall enough to provide heat over the heads of standing persons, the heat may dissipate before it gets low enough to fully benefit those sitting down. Mini-heaters, that rest on a table top, have become popular for such situations. These smaller heaters use a shorter standard, keeping the warm air at a lower level. 
     One shortcoming of patio heaters is that the emitter and the dome become very hot due to contact with the hot gasses generated by combustion of the propane. Hot gasses from the emitter have a tendency to rise, and collect under the concave dome covers most commonly found on patio heaters. As the hot gasses are trapped by the dome and cannot rise to escape, heat transfers from the hot gasses to the dome. When there is no wind to carry the heat away, the dome can reach temperatures of several hundred degrees. If the hot surfaces are touched by accident or by curious children who are unaware of the danger, serious burns could result. 
     The prior art provides guards for an emitter of a portable heater. Design of emitter guards is specified in safety standards, such as Canadian Standards Association (“CSA”) Standard 5-90US for gas fired infrared patio heaters. With guards or other protective devices in place, any heater surface that is accessible by a conical probe 5½ inches in length and up to 2¾ inches in diameter shall not exceed 180° F. above ambient temperature. Surfaces are also required to be cool enough that clothing does not ignite when brought in contact with the heater. The standard currently excludes any surface that is located more than 6.5 feet above the ground, which excludes the dome of most full size heaters. Conventional patio heaters with high standards are tall enough to provide some protection from touching of the dome under normal circumstances. Both the dome and the emitter are out of the reach of children, and are generally over the head of most standing adults. 
     There are times, however, when it is possible to touch the dome of an outdoor heater. After use, for example, two users may tip the unit, with one of them grabbing the dome to move it to a different location. The dome of a mini-heater may be within the reach of a curious child climbing on a picnic table. When located on a table top, the dome of a mini-heater is at a height of approximately six feet, within the reach of most adults, and within the range of surfaces tested according to the CSA standard 5-90US. 
     These, as well as a number of other examples, demonstrate the need to protect consumers from touching the dome of a portable heater. There is currently no standard providing a guard for the dome of a patio heater, and none are known in the prior art. 
     It is therefore an object of this invention to provide an improved guard for a portable heater that limits access to the surface of the dome cover. 
     It is another object of this invention to provide an improved guard for a table top gas fired patio heater that meets the requirements of CSA standard 5-90US. 
     It is still another object of this invention to provide an improved guard for a portable heater that limits access to the surface of the entire emitter and dome cover. 
     It is yet another object of this invention to provide an improved guard for a portable heater that is economical to make and to ship so as to minimize the cost of the safety guard. 
     SUMMARY OF THE INVENTION 
     These and other objects are met or exceeded by the present invention which features a dome guard for a dome cover of a heating apparatus. Use of the dome guard, either alone, or together with an emitter guard, reduces the chance of bums resulting from contact of a user&#39;s skin with the hot dome cover. 
     More specifically, the present invention provides a dome guard for a dome cover having an inside surface, an outside surface and a rim. The dome guard includes a heat resistant grid, at least one standoff for holding the dome guard a first predetermined distance from the dome cover, and a clip for engaging the rim of the dome cover. Contact of human skin with the rim of the dome is limited by the clip, which holds the dome guard a second predetermined distance from the rim of the dome. 
     By enclosing the dome in a wire grid that is maintained a predetermined distance away from the dome surface, access to the surface of the dome is limited and heat has a chance to dissipate in the intervening space. Contact of the hot surfaces, either by a child or by accident, is minimized. Although the dome guard is likely to itself become very warm, the severity of any bums that might result will be greatly reduced compared to touching of the hot surface itself. Further, the temperature of the dome guard would be insufficient to cause clothing to ignite if the clothing came in contact with the dome guard surface. Table top heaters are likely to have the dome surface within the 6½ foot height restriction, below which all of the surfaces must comply with the limitations of the standard. Thus it is important that the design of the dome guard meet requirements of CSA standard 5-90US. 
     Installation of the dome guard on the dome is also easy using the present invention. When it is desirable to install the dome guard, the dome is removed from the heating apparatus. The dome guard is then oriented with the standoffs against the top outside surface of the dome. The dome guard is then flexed, pushing the rim of the dome guard downward until the clips engage with the rim of the dome, holding the guard in place. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a patio heater with the safety guard of the present invention; 
     FIG. 2 shows an alternate base with the hidden fuel source and gas line shown in dashed lines; 
     FIG. 3 shows a two-piece standard with a hidden portion of the standard and the gas line shown in dashed lines; 
     FIG. 4 shows a top view of the preferred dome guard; 
     FIG. 5 shows a side cross-section of the dome guard of FIG. 4; 
     FIG. 6 shows a safety guard utilizing a second embodiment of the emitter guard, showing the dome guard in cross section and having a portion of the dome cover cut away to show the inside; 
     FIG. 7 shows a safety guard utilizing a third embodiment of the emitter guard showing the dome guard in cross section; 
     FIG. 8 shows a safety guard utilizing a fourth embodiment of the emitter guard showing the dome guard in cross section; 
     FIG. 9 shows a detail of the preferred method of mounting the emitter guard to the standard; and 
     FIG. 10 shows a detail of an alternate method of mounting the emitter guard to the standard. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a heating apparatus or patio heater, generally designated  10 , has a base  12 , a fuel source  14  (FIG.  2 ), a standard  16 , an emitter  18  and a dome  20 . Preferably these elements are arranged along a longitudinal axis. References to direction used herein are to be interpreted when the heater  10  is oriented as shown in FIG.  1 . 
     The base  12  supports the heating apparatus  10 , and has suitable weight and contact area with the substrate to provide stability for the heater  10  from tipping over. Preferably, the base  12  is generally cylindrical. An optional shroud  24  is used to cover unsightly portions of the base  12 . Space between the shroud  24  and the base  12  is suitable for storage space of any kind, but is particularly convenient for storage of the fuel source  14  as shown in FIG.  2 . Optionally, the base  12  rests on a plurality of legs (not shown). 
     As shown in FIG. 2, the fuel source  14  is preferably a propane tank, however, use of the heater  10  by direct connection to a fuel line is also contemplated. A 20 lb. propane tank is the most preferred fuel source  14  for a full size heater  10  due to ready availablilty and because it contains sufficient fuel that it does not require frequent replacement. Table top mini-heaters  10  are more conveniently transported and lifted to a table top position when the fuel source  14  is a one pound gas cylinder. Storage of the propane tank  14  inside the base  12  removes the unsightly tank from view, and also adds weight to the base, adding to the stability of the heater  10 . This invention would also be useful with heaters  10  adapted to operate with alternate fuels, such as butane or white gas. 
     Again referring to FIGS. 1 and 3, the standard or vertical pole  16  for the apparatus can be provided as a single unit or in two or more pole sections  16   a  and  16   b  with a detachable connection therebetween. Further detachable connections similar to that between pole sections  16   a  and  16   b  can be provided at the top  30  of the standard  16  between it and the emitter  18 , and at a bottom  32  of the standard  16  where it is tightly received in a central recess  34  formed at the top of the base  12 . Support is provided from the base  12  to the standard  16  in the form of a removable connection. Although a solid standard  16  is suitable, preferably the standard is a hollow tube with a gas feed line  36  running up the inside of the tube. The bottom of the gas line  36  is connected to the fuel source  14 . When the preferred propane tank  14  is used, it is optionally fitted with a quick disconnect fitting (not shown) for ease in changing the fuel tank  14 . 
     Referring to FIGS. 6 and 7, at the top of the standard  16  are a burner (not shown) and the emitter  18 . Fuel from the gas feed line  36  is oxidized at the burner, and the hot combustion gasses exit through the emitter  18 . The emitter surface  18  includes apertures  46  for directing heat generated by the ignited fuel out away from the burner. The emitter surface  18  is optionally inclined relative to the longitudinal axis (FIG. 7) of the heater  10  so as to direct heat in a generally downward direction about the longitudinal axis for maximum efficiency in warming of a preselected area by the heat emitted from the emitter  18 . Angling of the emitter surface  18  so that it is inclined relative to the vertical longitudinal axis of the heating apparatus  10  substantially reduces the need for the large reflector dome as used with prior commercially available patio heaters as heat is directed out away from the burner in a generally downward direction for heating of the preselected outdoor area. Further, because the emitter surface  18  directs heat in the downward direction due to its inclination to the vertical, radiant heat directed straight out radially as with cylindrical apertured emitter surfaces is avoided, minimizing the amount of heat lost over the heads of the users. Cylindrical emitters  18  are also useful. Angling of the emitter surface  18  is less important when a mini-heater is used, as shown in FIG. 6, because the users are closer to the same height as the emitter  18 . 
     Over the top of the burner and emitter  18  is the dome cover  20  that is preferably concave in shape. The dome has an inside  50  and an outside  52  and a rim  54 . In a preferred form, the dome cover  20  extends radially beyond the emitter  18  to protect it from exposure to wind and weather. The dome  20  is spaced above the emitter surface  18  along the longitudinal axis to reflect stray radiant heat that rises above the emitter  18  back in the downward direction around the longitudinal axis. 
     Referring to FIG. 6, a dome guard  60  may be retrofit to a heater  10  with an existing emitter guard  62  or is preferably part of a safety guard, generally  64 , designed to fit a particular heater. Usually the safety guard  64  will be made up of a dome guard  60  and emitter guard  62 , each as a separate apparatus. However, the construction of the safety guard  64  as a one-piece unit is contemplated. Either the dome guard  60  or the safety guard  64  may comprise one or more pieces. Regardless of the number of pieces, the safety guard  64  is preferably made of a construction that allows for easy assembly and disassembly with minimal use of tools. 
     Referring now to FIGS. 4 and 5, the dome guard  60  is formed with a flexible, first heat resistant grid  66 . Use of the term “heat resistant” is meant to convey that the grid material is suitable to withstand temperatures where it comes in contact with the dome  20  without igniting or losing shape. Metal or wire is the most preferred grid  66  material because of its low cost, ready availability, heat resistance and flexibility. However, the use of any heat resistant, flexible substance is suitable such as high temperature plastics. 
     Any pattern is suitable for use in the grid  66  that meets CSA standard 5-90US for gas fired infrared patio heaters. Scrolls, flowers and other decorative elements are suitable, as well as a cross-batch pattern or a pattern of concentric rings. For example, if the grid  66  were so open so as to allow a child&#39;s hand to slip between the elements of the grid unrestrained it would not be suitable. The most preferable grid  66  is a series of rings  70 , made of wire or thin rods and spaced less than 2 inches apart, connected by a series of from about 4 to about 10 radial spokes  72 , best seen in FIG.  4 . Each of the rings  70  has a center that falls on an imaginary line that would be approximately perpendicular to the circle bounded by a first ring  74 . For discussion purposes, the first ring  74  has the smallest diameter and is generally closest to the center of the dome. A last ring  76  is that farthest from the center of the first ring, as measured along the length of the radial spokes  72 . The grid  66  of suitably extends at least to the plane parallel to the rim  54  of the dome  20 , and preferably extends below that plane to provide some protection from contact with the inside rim  54  of the dome. The spokes  72  are optionally curved or of any shape to form the grid  66  that is approximately parallel to the surface of the dome  20 . 
     At least three functions are performed by the safety dome guard  64 . First, it prevents direct contact between people and hot surfaces. Also, by keeping a person&#39;s skin predetermined distances from the hot surfaces, the heat has the opportunity to dissipate and be cooled by the environment as it travels over the distances. Finally, it is made of a conductive material, the safety guard  64  will conduct heat away from the hot surface, acting as a heat sink. In the following description, several predetermined distances L 1 , L 2 , and L 3  are discussed. Choice of the predetermined distances will depend on a balance of the three factors. Specifically, the temperature and location of the hot surface and the conductance of the grid material must be considered in choosing the predetermined distances between the hot surface and the safety guard heater  10 . The values of L 1 , L 2  and L 3  are selected so that the dome guard  64  conforms with CSA Standard 5-90U5. All three factors must be considered in choosing any of them. L 1 , L 2  and L 3  may be the same or different values from each other due to the temperatures and location of the hot surfaces under the safety guard  64 . 
     Referring now to FIGS. 4 and 5, the dome guard  60  has at least one standoff  80  for holding the dome guard at least a first predetermined distance L 1 , from the dome. Preferably, the standoff  80  is constructed to provide a first predetermined distance of less than about 5 inches. Number and exact placement of the standoffs  80  is entirely discretionary, as long as the purpose of preventing contact with the hot surface of the dome  20  is fulfilled. When the preferred grid  66  arrangement is used, the standoffs  80  are suitably formed by extensions of the radial spokes  72  at the first ring  74 . 
     A mechanism is optionally provided to hold the standoff  80  in place on the dome cover  20 . Where the standoff  80  is a metal rod, a depression in the dome slightly larger than the standoff prevents the end of the rod from sliding on the surface of the dome. Preferably, the standoff  80  has a flattened end, or a loop, to form a foot  82  that is at an angle, α, to the longitudinal axis of the standoff, increasing contact between the dome guard  60  and the dome  20 . Suitable ranges for the angle, α, will depend on the exact shape of the dome  20 . When a concave dome  20  is used, the preferred range for α is from about 80° to about 90°. 
     One or more clips  84  are designed to engage the inside rim  54  of the dome  20  and hold the lower portion of the dome guard  60  a second predetermined distance, L 2 , from the rim of the dome, as shown in FIG.  7 . Preferably, the clip  84  includes a shaft  86  and a hook  88 . The shaft  86  begins at a bottom  89  of the grid  66 , which is beyond the last ring  76  of the preferred grid pattern, and extends toward the rim  54  of the dome  20 . The hook  88  is the portion of the clip  84  that contacts the inside rim  54  of the dome  20 , and is optionally at an angle, β, with the shaft  86 . β varies with the exact shape of the dome  20  and the dome guard  60 . If the dome guard  60  extends only to the plane formed by the rim  54  of the dome  20 , then a suitable clip  84  would be formed by a shaft  86  and hook  88  entirely within that plane. However, when the preferred dome guard  80  extends below the rim plane, β will assume the angle necessary to form a hook  88  that is approximately parallel to the plane formed by the rim  54  when the dome guard  60  is installed on the dome  20 . The hook  88  should be configured so that the distance from the tip of the hook to the center of the dome  20  is less than the distance from the rim  54  at the point of contact with the hook  88  to the center of the dome  20 . 
     The preferred clip  84  engages the rim  54  of the dome  20  when the dome guard  80  is downwardly flexed sufficiently to allow the hook  88  to snap around the rim  54  and engage it when the pressure used to flex the dome guard  60  is removed. The dome guard  60  is held in place by upward pressure on the hook  88  as the grid  66  tries to flex back to its unflexed state. The grid  66  pattern and the material of which the grid  66  and clips  84  are constructed are selected to provide enough flex for this installation process. Optionally, the clip  84  is removably secured to the dome guard  60  using a fastener (not shown). 
     Still referring to FIG. 7, the length of the shaft  86  holds the dome guard in the second preferred distance L 2 , from the rim  54  of the dome  20 . The second predetermined distance L 2 , is determined by considering the same factors as used to determine the first predetermined distance, as discussed above. Generally, the rim  54  will have a lower temperature than the center of the dome  20  because some of the heat will have dissipated to the environment before it is conducted out to the rim  54 . Thus, the second predetermined distance L 2 , will generally be less than or equal to the first predetermined distance L 1 . Most preferably, L 2  is greater than 0.75 inches but less than 5 inches. 
     The clips  84  may be attached to the last ring  76  in any suitable manner. Preferably, the clips  84  are formed from extensions of portions of the grid  66 , such as the spokes  72 . Most preferably, the standoff  80 , the spoke  72  and the clip  84  are of unitary construction, with a series of bends to form the various elements. For example, a metal rod  90  is looped to form the foot  82 , then bent to form the standoff  80 . The standoff  80  is of sufficient length to hold the dome cover  60  the first predetermined distance L 1  from the dome  20 . At the first ring  74 , the rod  90  is again bent to form one of the spokes  72  and continues down the length of the grid  66 . Another bend beyond the last ring  76  forms the shaft  86  of the clip  84  having a length, L 2 , and finally, the hook  88  is formed. Although this example demonstrates a simple and economical method of forming these elements, the foot  82 , standoff  80 , and clip  84  are suitably made of distinct parts, or even of different materials, and attached to the grid  66 , for example by spot welding. 
     Although the dome guard  60  is suitable for use alone, preferably it is a portion of a safety guard  64  that includes the emitter guard  62 . The emitter guard  62  includes a heat resistant grid  92  similar to that used in the dome guard  60 . Grid patterns and materials of manufacture suitable for the dome guard are also used for the emitter guard  62 . Preferably, the grid  92  pattern includes a series of rings  94  parallel to the emitter surface  18 . 
     One or more offset fasteners  96  connect the grid  92  of the emitter guard  62  to the heater  10 , shown in FIGS. 9 and 10. Preferably, the grid  92  is removably attached to the standard  16 , however it is optionally connected to other parts of the heater  10  or safety guard  64 , such as the emitter  18 , the dome  20  or the dome guard  60 . When attaching the fastener  96  to the standard  16 , the preferred fastener  96  (FIG. 9) is a screw that attaches a loop  98  on the emitter guard to a corresponding opening  102  in the standard. Use of the screw  96  is most preferred because, when tightened down, the screw holds the guard  62  firmly in place, reducing the possibility of detaching it from the guard if it is bumped or jostled. Another of the preferred fasteners  96  is a hook  100  that engages the opening  102  having a slotted shape, as seen in FIG.  10 . Preferably the fastener  96  is located near the top  30  of the standard  16 , just below the base of the emitter  18 . However, the exact location of attachment is not critical, and many other locations on the standard  16  or the emitter  18  are suitable. When the hook  100  engages the slot  102  on the standard  16 , the weight of the emitter guard  62  is sufficient to hold it in place. 
     As shown in FIG. 7, when the fastener is engaged with the standard, the fastener  96  is offset to hold the grid a third predetermined distance, L 3 , downward along the standard  16  from the emitter surface  18 . Because the emitter  18  is directly distributing the hot gasses, it is most likely to the hottest exposed surface of the heater. The third predetermined distance, L 3 , is therefore suitably greater than either the first or second predetermined distances in most cases, but is determined using the same factors as discussed above. 
     Referring now to FIG. 6, the emitter guard  62  is optionally formed of two or more racks  104  that overlap to form a continuous guard. Two-piece emitter guards  62  are advantageously used to minimize shipping costs where two small pieces can be packed into a smaller space with the heater  10  in the shipping carton. Preferably, each of the racks  104   a ,  104   b  attaches directly to the standard  16  or the emitter  18 . Where two or more racks  104   a  and  104   b  are used, the racks optionally connect to each other, either instead of or in addition to any direct connection to the heater  10 . A preferred method of removably connecting two racks  104   a ,  104   b  is using a simple hook  106  on one rack that attaches to an eye  108  or any suitable location on the corresponding rack. As shown in FIG. 6, if the eyes  108  are located on the lower rack  104   b , and the hooks  106  on the upper rack  104   a , then the weight of the upper rack  104   a  is sufficient to hold the upper rack in place. Where such an arrangement is used, the removable connection between the lower rack  104   b  and the standard  16  is configured to hold the weight of all racks  104   a ,  104   b . Referring to the alternate embodiment in FIGS. 7 and 8, hooks  110  at the top of the emitter guard  62  removably attach to the dome guard  60  where the clip  84  is attached to the spoke  74  at the bottom  89  of the grid  66 . 
     The overall shape of the emitter guard  62  varies to provide protection as desired. FIGS. 6,  7  and  8  show a several alternate shapes for the emitter guard  62 . Most preferably, the emitter guard  62  is shaped so as to provide continuous protection when used with the dome guard  60  as part of a safety guard  64 . Two such preferred safety guards are shown in FIGS. 7 and 8. In both cases, the emitter guard  62  approaches the diameter of the dome guard  60 , providing protection from contact with the inside surface  50  of the dome cover  20  because there is insufficient space between the dome guard  60  and the emitter guard  62  for contact to accidentally occur. 
     Features shown in various figures are freely interchangeable with each other. The emitter guard  62  shape shown in FIG. 8, for example, can be used in the two-piece form shown in FIG.  6 . None of the features shown in a particular figure is necessarily intended to be limited to the shape of the emitter or other features with which it is shown. 
     The safety guard  64  is easily installed by the consumer. With the dome cover  20  removed, the emitter guard  62  is oriented to align the offset fasteners  96  with the corresponding opening in the standard  16 . The emitter guard  62  is then dropped down over the emitter  18  and removably fastened to the standard  16 , preferably by engaging the fasteners  96  on the emitter guard with corresponding openings  102  on the standard  16 . If the emitter guard  62  has two or more racks  104   a ,  104   b , subsequent racks are properly oriented, then removably fastened to the heater  10  or one or more previously mounted racks  104 . 
     Installation of the described dome guard  60  is accomplished entirely by hand and without the need for tools. The dome guard  60  is installed on the dome  20  prior to placement of the dome  20  on the heater  10 . The dome guard  60  is oriented with the standoffs  80  placed between the dome  20  and the dome guard  60 . With the dome guard  60  generally aligned in the installed position, the dome guard  60  is flexed downward to engage the rim  54  of the dome  20 . After installation of the dome guard  60 , the dome  20  is replaced on the heater  10 . If the dome guard  60  and the emitter guard  62  are interconnected, as in FIGS. 7 and 8, the dome  20  is placed so that the hooks  110  of the emitter guard are placed between the spokes  72  of the dome guard  60 . The dome  20  and dome guard  60  are then rotated until the hooks  110  engage the spokes  110  or clips  84  of the dome guard  60 . 
     While a particular embodiment of the present invention has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.