1309695 玖、發明說明： 【發明所屬之技術領域】 ^ ΐ Γ02^7"30 a" ^ ^ ^ 邛分接續申請案。 本發明關於吊扇，特別是電動吊扇及其效率。 【先前技術】 夕年來由電動馬達所驅動之吊扁p，笛田 勒之币扇已運用於空氣循環，其 通常具有一位於罩框内且安裝 干之馬達，使風扇葉片 才干之軸線旋轉。傳統之風扇葉片為扁平狀，且以一傾 ，蝴俯仰角⑽ch)定位，以對葉片旋轉處的空氣 團（air mass)提供空氣一攻角（ n 又 MangIe of attack)，使空氣向 卜流勤。 當自其旋轉軸徑向伸展之 凤屬萊片轉動時，葉片尖端之 移動路徑在任何時間皆係遠大 疋八％根邛端之移動路徑，因此 葉片尖端移動之速度遠快於根部端。為平衡沿著葉片及宜 移動所產生氣流之風阻負載，風扃 '、 月戰1風扇葉片係設計具有一朝向 尖知縮小之攻角，此設計特徵常 1竹伋*見於其他旋轉葉片之設計 中，例如船隻螺旋槳葉及飛機螺旋槳葉。1309695 玖, invention description: [Technical field to which the invention belongs] ^ ΐ Γ02^7"30 a" ^ ^ ^ Sub-continuation application. The invention relates to ceiling fans, and in particular to electric ceiling fans and their efficiency. [Prior Art] In the past year, the slinger p, which is driven by an electric motor, has been used for air circulation. It usually has a motor located inside the hood and mounted with a dry motor to rotate the axis of the fan blade. Conventional fan blades are flat and are positioned at a tilting and pitching angle (10) ch) to provide an air angle of attack (n and MangIe of attack) to the air mass at which the blades rotate, allowing air to flow. When the phoenix slab that rotates radially from its axis of rotation rotates, the path of the tip of the blade is far greater than the movement path of the octopus at any time, so that the tip of the blade moves much faster than the root end. In order to balance the wind resistance load along the blade and the airflow generated by the movement, the wind fan's and the moon warfare 1 fan blade system design has an angle of attack that is pointed toward the narrower and narrower. This design feature is often 1 bamboo raft* seen in the design of other rotating blades. Medium, such as ship propeller blades and aircraft propeller blades.
Florida Solar Energy Center在 1997生 * 拈" ^ ^ 97年中執仃一有關數個 市场了靖付吊扇之效率研究’此測試報告發 0，039,541號專利中，此專利權 、國弟 』催所有者發現風扇葉片之設 什可k升能夏效率，即每功率 午/自耗（watts)之調〉、奋番 (CFM)，該葉片在根部端漸次的 ” φ* , . . 芩曲而向下均勻的窄縮為 較小之彎曲或為尖端之攻角 门 例如2〇英吋長之葉片（含^ 8719l-980216.doc 1309695 縮之弦狀部）根部具有26.7。之彎曲，在尖端具有69。之彎 曲0 另一與吊扇有關且長期存在之問題是氣流之分佈。葉片 具有一攻角之方位’惟大部分吊扇之葉片係在一水平面中 轉動，此迫使空氣向下而在風扇下方提供㈣，因氣流並 非直接自風扇處流動’故周遭之氣流不足。由於風扇葉片 之、、’°構為上反角（dihedral)的，此可減輕該問題之影響， 惟其需考量風扇下方氣流之不足。 【發明内容】 已矣攻角（attack angle)或扭角（twist)以均勻之比率 (rate)縮小對吊扇而言並非最有效率的。二呎長之葉片或 螺旋槳葉尖端所移動一圈之圓周為2Π⑺，因此其—呎中 或長度半移動之距離為2 Π (1 )，此線性關係對飛機螺 旋槳葉係恰當的，因其移動之軌道路徑通常落在垂直於飛 =路徑之平面中。然而吊扇轉動之執道路徑平行且位於氣 机下方故葉片並非均勻的撞擊空氣，其與飛機不同，此 現象之原因為吊扇葉片尖端處”置換"（rePlaeement)空氣之 效应大於葉片尖端内側。旋轉軸線附近之空氣須自周遭環 i兄移動經過天花板面與風扇葉片之間的空間而到達其根部 端。 、 基於此一理缺， 钟要柃昇吊扇效率，可使吊扇的葉片形； ^肖自根部端非均勻地擴大至尖端。特別是，較靠a ' 端處的攻角或俯仰角（pitch)之改變比率應大於才 部處改變之比率。、丄机 平這點可明顯迫使天花板下方風扇葉片r 87191-980216.doc 1309695 内置換空氣，故葉片根部端附近之空氣較易置換。但無論 此理論是否正確，#已證明效率之提昇。因葉片尖端處攻 角之變化大於根部處之攻角變化，其表示風扇效率將明顯 的提昇。 氣流分佈亦可藉由具有向上曲線之吊扇葉片獲得改善， 該葉片形成連續變化$ 負燹化之上反角（contmU〇Usly graduated chhedral)，其係自根部端延續至尖端。此外，纟亦可配人 前述的攻角或扭角非均句之縮減加以完成。提供吊扇之: 果不僅是效率提昇，氣流分佈亦較佳。 田葉片中心邠位之厚度小於兩側部位之厚度時，下降氣 流之操作效率將提昇m之頂面及底面為凹面，效率 之提昇介於3%至4%’故葉片沿著中心線從根部至尖端之 厚度約小於沿著兩側邊厚度之25% 。 【實施方式】 風扇葉片技術揭示於美國第6,〇39,541號專利，其假洲 流入風扇葉片之空氣皆來自垂直於葉片旋轉平面之；向“ 此外，當運用於飛機螺旋紫葉理論時，其假設氣流以 速度自葉片根部流至尖端。藉由此假設，葉片 端具有固定之扭絞率（iwistrate)。 穴 葉片之扭轉欲使相對於葉片表面之氣流方向相對 佳化，此可確保葉片由根部至尖端在最佳之攻 攻角係變化以符合苹片*她銘叙夕〜丄 月卜钿作。 穴知移動之迷度大於葉片根部移動 之速度’該速度之提昇使葉> 上風的方向改變。 此假設對吊扇而言係無效的。吊扇為空氣循環裝置，其 87191-980216.doc 1309695 未如同飛機螺旋槳葉一般使空氣移動，空氣自葉片根部端 至尖端並未以相同之向量或速度移動。 圖1顯示傳統構造之吊扇，除了其葉片之輪廓外。風扇 利用向下直桿女裝在天花板下方，該直桿自天花板伸展 至電動馬達及開關盒外框，且風扇在底端處具有一套輕裝 置。電力供應至馬達導體驅動葉片，導體經由該向下直桿 伸展至一局部電源。 螺旋狀之風扇葉片優於平坦狀之風扇葉片，且具有連續 變化之上反角。到達及離開風扇葉片之氣流以多條箭頭線 顯不藉此可理解為何風扇葉片並非如飛機螺旋槳葉一般 衝擊工軋’且葉片上方限定之空間使進入風扇之氣流向量 改變，其與飛機螺旋槳葉相反。 如圖2所不’風扇葉片隨著其寬度及弦(chord)窄^ (tapered) ’其自底部或根部端至尖端窄縮，故尖端之尺寸 較小。此外’葉片皆具有圖1所示之上反角，惟其並非能 實施本發明之優點。上反角在風扇下方提供較大之空 氧分佈。 有2及3 ’雖然葉片為單—之構造，圖式顯示葉片 率、 白Μ圖1方式扭轉’惟自根部扭轉至尖端之 示二二肖或攻角自根部端縮小為尖端之10。，如圖 個8英叶同之比率進行。與根《相鄰之第 寸與尖端相鄰之第三個部位中扭轉之 87191 -980216.doc :變化為u。/英吋。當然’相鄰部位之間存有些 8:(ι。因:V::)1外側部位一端至另—端之攻 差異約、為3» +>’中間部位之差異約為6。，内侧部位之 民圖5至7詳示圖1風扇之葉片10 ’其根部端11安裝至風扇 =轉子較12,尖端13位於轂之末端。如圖W示較以 化板垂直向下直桿之軸線旋轉，最清楚的係以葉片中心 有顯不’葉片在根部仙具有〇。之上反角，在尖端13呈 曲，之上反角d、風扇葉片兩端之間呈連續的弧形或彎 -故其上反角在兩端之間係連續的變化。如 ^氣流分佈，空氣直接分佈在風扇下方以及其周遭2 曰中。相反的，先前技藝之風扇主要將空氣導至其下 3遭空間中之氣流非直接流動且較弱。雖然沿著長度以 2之上反角傾斜之風扇葉片可解決此問題，惟 風扇下方較弱之氣流。 而Y里 葉片上反角可在兩端之間持續的變化，惟靠近根部端及 或為固定的，其餘部位為弧形或曲線狀 上’參見鶴烏之設計’最有效率之設計為自根部端至尖端 2間處之上反角為0。，之後持續增加到達尖端為10。。 在較佳具體實施例中，葉片根部端具有0。之上反角，尖端 。之上反角’惟根部端之上反角可小於或大於0。， 細之上反角可小於或大於10。。風扇尺寸、功率、 及應用皆為選取特定上反角之考量因素。 门义 吊扇能夠以傳統方式反向操作’如圖8A所示，由下方 87191-980216.doc 1309695 觀視時葉片係順時針糙叙 . ★ 才矸轉動，在此方向中及其攻角，葉片以 箭頭所示方向使空菊仓μ Λ 文工礼向上，廷點為空調中常見之例子，其 向下抽離風扇上方之執办备 . 熟工亂。如圖8Β所示，葉片亦可逆 時針旋轉，其在較埶之援$ …之％ i兄下將空氣吹至人們使其冷卻。Florida Solar Energy Center in 1997, * 拈 " ^ ^ In 1997, a study on the efficiency of Jingfu ceiling fans in several markets. This test report issued 0,039,541 patents, this patent, the younger brother urged all It is found that the fan blade can be set to increase the summer efficiency, that is, the tuning of each power/watt (watts), and the FFM (CFM), the blade gradually "φ*, at the root end. Uniformly narrowed down to a smaller bend or a tipped angled door such as a 2 inch long blade (containing a ^7719l-980216.doc 1309695 constricted portion) with a root of 26.7. The bend has a tip at the tip 69. Bending 0 Another problem associated with ceiling fans and long-standing is the distribution of airflow. The blades have an angle of attack. 'But most of the blades of the ceiling fan rotate in a horizontal plane, which forces the air down and below the fan. Providing (4), because the airflow does not flow directly from the fan, so the surrounding airflow is insufficient. Since the fan blade and the '° structure are dihedral, this can alleviate the problem, but it needs to consider the airflow under the fan. Lack of SUMMARY OF THE INVENTION The reduction of the attack angle or twist at a uniform rate is not the most efficient for the ceiling fan. The second blade or the tip of the propeller blade moves a circle. The circumference is 2Π(7), so the distance between the 呎 or the length of the half movement is 2 Π (1). This linear relationship is appropriate for the aircraft propeller blade, because the orbital path of its movement usually falls in the plane perpendicular to the flight=path. However, the path of the ceiling fan rotation is parallel and located below the air machine, so the blade does not uniformly hit the air, which is different from the aircraft. The reason for this phenomenon is that the effect of the “replacement” (rePlaeement) air at the tip of the ceiling fan blade is greater than the inner side of the blade tip. . The air near the axis of rotation must move from the surrounding ring to the root end of the space between the ceiling and the fan blades. Based on this lack of reason, the clock should be lifted to increase the efficiency of the ceiling fan, and the blade shape of the ceiling fan can be made; ^The root end of the fan is non-uniformly expanded to the tip end. In particular, the ratio of the angle of attack or pitch at the end of a ' should be greater than the ratio of the change at the point. This point can obviously force the air in the fan blade r 87191-980216.doc 1309695 below the ceiling to replace the air, so the air near the root end of the blade is easier to replace. But no matter whether this theory is correct or not, # has proved the improvement of efficiency. Since the change in the angle of attack at the tip of the blade is greater than the change in the angle of attack at the root, it indicates a significant increase in fan efficiency. The airflow distribution can also be improved by a ceiling fan blade having an upward curve that forms a continuous change (contUUUsly graduated chhedral) that extends from the root end to the tip end. In addition, the 纟 can also be completed with the aforementioned angle of attack or the reduction of the twist angle. Providing a ceiling fan: Not only is efficiency increased, but the airflow is also better. When the thickness of the center of the blade is less than the thickness of the two sides, the operating efficiency of the descending airflow will increase the top surface and the bottom surface of the m to be concave, and the efficiency is improved by 3% to 4%'. Therefore, the blade is along the center line from the root. The thickness to the tip is less than about 25% of the thickness along the sides. [Embodiment] The technology of the fan blade is disclosed in U.S. Patent No. 6, 39,541, the air flowing into the fan blade from the false state is from the plane perpendicular to the rotation of the blade; "In addition, when applied to the theory of aircraft spiral purple leaf, It is assumed that the airflow flows from the root of the blade to the tip at a speed. It is assumed that the blade end has a fixed twist ratio. The torsion of the blade is intended to optimize the direction of the airflow relative to the blade surface, which ensures that the blade is The root to the tip changes in the best attack angle to conform to the piece of cloth * her inscriptions ~ 丄 钿 。 。 。 。 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴 穴The direction of the wind changes. This assumption is not valid for the ceiling fan. The ceiling fan is an air circulation device, and its 87191-980216.doc 1309695 does not move the air like the propeller blades of the aircraft. The air is not the same from the blade root to the tip. Vector or speed movement. Figure 1 shows a conventionally constructed ceiling fan, in addition to its blade profile. The fan uses a downward straight rod to be worn under the ceiling, the straight rod The ceiling extends to the electric motor and the outer frame of the switch box, and the fan has a light device at the bottom end. Power is supplied to the motor conductor to drive the blade, and the conductor extends through the downward straight rod to a local power source. In the flat fan blade, and has a continuous change above the reverse angle. The airflow to and from the fan blade is not shown by a plurality of arrow lines. It can be understood why the fan blade is not impacted as the aircraft propeller blade is above and above the blade. The defined space changes the airflow vector entering the fan, which is opposite to the aircraft propeller blade. As shown in Figure 2, the fan blade is narrower with its width and chord (tapered) from its bottom or root end to its tip. The tip is smaller in size. In addition, the 'blades have the opposite angles shown in Figure 1, but they are not capable of implementing the advantages of the present invention. The upper dihedral provides a larger air oxygen distribution below the fan. 2 and 3 'Although the blade is a single-structure, the pattern shows the blade rate, and the white Μ Figure 1 mode is twisted', but the rotation from the root to the tip indicates that the second or second angle is reduced from the root end to the tip. 10, as shown in Figure 8 with the same ratio of the same as the root of the adjacent third inch adjacent to the tip of the twisted 87191 -980216.doc: change to u. / inch. Of course, there are some 8 between adjacent parts: (ι.:V::)1 The difference between the outer end of one side and the other end is about 3» +> The difference between the middle parts is about 6. Figures 5 to 7 detail the blade 10' of the fan of Fig. 1 with its root end 11 mounted to the fan = rotor 12 and the tip 13 at the end of the hub. Figure W shows the axis of the vertical straight bar Rotation, the clearest is the center of the blade. The blade has a 在 in the root. The upper corner is curved at the tip 13 and the opposite angle d, continuous curved or curved between the ends of the fan blade. - Therefore, the upper contralateral angle is continuously changed between the two ends. For example, the air distribution is distributed directly under the fan and in the area around it. Conversely, prior art fans primarily direct air to the airflow in their lower space and are indirect flow and weak. Although fan blades that are inclined at a reverse angle of 2 above the length can solve this problem, the weaker airflow under the fan. The reverse angle of the Y-leaf blade can be continuously changed between the two ends, but it is fixed near the root end, and the rest is curved or curved. See the design of Hewu. The most efficient design is The opposite angle between the root end and the tip 2 is zero. After that, continue to increase to reach the tip of 10. . In a preferred embodiment, the blade root end has zero. On the opposite corner, the tip. Above the opposite angle ‘only the reverse angle above the root end can be less than or greater than zero. , the fine upper angle may be less than or greater than 10. . Fan size, power, and application are all factors that are considered to be specific to the opposite angle. The door hinge fan can be reversed in the traditional way' as shown in Figure 8A. When viewed from below 87191-980216.doc 1309695, the blade system is clockwise and rough. ★ 矸 矸, in this direction and its angle of attack, the blade In the direction indicated by the arrow, the empty chrysanthemum μ Λ Λ Λ , , , , , , , , , , , , , , , 廷 廷 廷 廷 廷 廷 廷 廷 廷 廷 廷 廷 廷 廷As shown in Fig. 8A, the blade can also be rotated counterclockwise, which blows the air to the person to cool it under the help of %.
吾人發現，藉由使葦g I女 A 茶片具有不均勻的厚度，可提昇效率， 此最佳如圖8C所示，葉片自側邊窄縮(taper)至側邊。葉片 之頁鈿如,、底知-般略微的凹陷’以形成處位於其根部 與尖端之間的淺谷社椹, 久分、、·〇攝（shallow vaneys)。可產生最佳效 率之葉片係沿著中心部位夕厘麻I ^i a 丨1立之厚度小於兩側邊部位厚度約 25/。且頂面及底面宜具有相同之輪廓。吾人尚不瞭解這 點優於-平坦表面、縮小攻角及上反角變化之原因。為便 於說明及澄清’圖8C僅顯示沿著平面8_8之風扇葉片。 當葉片以圖8B所示方式旋轉形成向下氣流時，葉片側 邊之間厚度的改變使效率提昇3%至4%，若以圖8A方向轉 動時’效率之變化不明_ ’吾人已完全瞭解其成因特別 是僅一表面凹陷時效率之提昇較少。 風扇在Hunter Fan Company之實驗室測試，其通過環保 機關之認證執行Energy Star c〇mpUance測試。除了空氣速 度偵測器仍安裝在葉片頂端上方及附近之外，風扇根據I have found that by making the 苇g I female A tea sheet have a non-uniform thickness, the efficiency can be improved, and as best shown in Fig. 8C, the blade is tapered from the side to the side. The pages of the leaves are, for example, slightly recessed to form a shallow valley, between the roots and the tip, shallow vaneys. The blade system that produces the best efficiency has a thickness of less than 25/ of the thickness of the sides of the blade along the central portion of the I.i. And the top surface and the bottom surface should have the same contour. We still don't understand why this is better than the flat surface, the narrowing of the angle of attack and the change of the upper angle. For ease of illustration and clarification 'Figure 8C shows only the fan blades along plane 8-8. When the blade is rotated in the manner shown in Fig. 8B to form a downward airflow, the change in thickness between the sides of the blade increases the efficiency by 3% to 4%. If the rotation is in the direction of Fig. 8A, the change in efficiency is unknown _ 'I have fully understood The cause of this is especially the increase in efficiency when there is only one surface depression. The fan was tested in the Hunter Fan Company's laboratory and was certified by the environmental agency to perform the Energy Star c〇mpUance test. Except that the air velocity detector is still installed above and near the tip of the blade, the fan is based on
Energy Star測試規定加以測試，這點可量測風扇葉片附近 之空氣速度。測試過程中測得葉片根部端至尖端不同位置 處之不同空氣速度，圖4顯示測試參數，實際之測試結果 揭示於表1。 87191-980216.doc •10- 1309695 表1 偵測器 平均速度 空氣速度 轉子速度 合成 合成 —.—-[ 角度/ _FPM FPS " -^—- FPS 速 角度 0 283 4.7 22.7 23.2 1 1 7 1 303 5.1 24.4 24.9 11 7 ------ 0.07 2 320 5.3 26.2 ·'~~—I-- 26.7 11 5 0.16 3 325 5.4 27.9 28.4 110 -—-- 0.54 4 320 5.3 29.7 30.1 10 2 0.79 5 313 5.2 31.4 31.8 9 4 一 0.76 6 308 5.1 33.1 33.5 8 8 0.63 7 305 5.1 34.9 35.3 〇 · 〇 R 2 ^---- 0.51 8 290 4.8 36.6 37.0 〇 · J 7 5 -- 0.77 9 275 4.6 丨 _ — 38.4 38.7 (S R 0.71 10 262 4.4 40.1 40.4 W · 〇 6 2 0.60 11 235 3.9 --— 41.9 42.0 5 3 0.87 12 174 2.9 43.6 43.7 飞8 1.54 13 132 2.2 45.4 45.5 2.8 J^〇3_ 比較性之測試結果顯示於表2，其中葉片〗具有前述之 10。固定上反角，葉片2為第6,〇39,541號專利所示設計之 Hampton Bay G〇SSomer Wind/Windward葉片，葉片 3為具 有I5。固定攻角之平垣葉片 效率之改良。 如前文所界定’表列為能源 87191-980216.doc 1309695 表2 葉片 ---- 馬達 含圓柱 體 優於 Hampton Bay之改 良 優於標 準之改 良 無圓 柱體 優於 Hampton Bay之改 良 外侧4英 呎之改 良 172χ 1 18 AM 12,878 21% 29% 37,327 24% 27% 2 --- 188x15 10,639 NA 6% 30,034 一 NA NA 172x 3 ------ 18 AM 10,018 -6% NA 28,000 -7% -7% 因此，所示吊扇強化氣流分佈使能源效率優於先前技 藝。當然，風扇亦可應用於例如桌頂之其他場所。雖然本 文以較佳具體實施例加以揭示，惟其他變更、改良或刪除 事項皆在本發明申請專利範圍之精神及範嘴中。 【圖式簡單說明】 囷1為吊扇之側視圖，其為本發明一較佳具體實施例。 圖2為圖1風扇葉片之輪廓，其以假設之平面以利說明。 圖3為圖2葉片之輪廓，其顯示葉片沿著長度在不同位置 的螺旋。 圖4為氣流測試參數之圖形。 圖5為圖1風扇一葉片之側視圖。 圖6為圖1風扇一葉片之上視圖。 圖7為圖1風扇一葉片之端視圖。 圖8A及8B為圖1風扇一 国旧葉片之其他侧視圖，其以剖面顯 87191-980216.doc 1309695 示，圖8C為葉片沿著平面8-8之剖視圖。 【圖式代表符號說明】 10 葉片 11 根部端 12 單又 13 尖端 15 中心線 87191-980216.doc 13-The Energy Star test specifies testing to measure the air velocity near the fan blades. During the test, different air velocities at different positions from the root end to the tip were measured. Figure 4 shows the test parameters. The actual test results are shown in Table 1. 87191-980216.doc •10- 1309695 Table 1 Detector Average Speed Air Velocity Rotor Speed Synthesis Synthesis—.--[Angle / _FPM FPS " -^—- FPS Speed Angle 0 283 4.7 22.7 23.2 1 1 7 1 303 5.1 24.4 24.9 11 7 ------ 0.07 2 320 5.3 26.2 ·'~~—I-- 26.7 11 5 0.16 3 325 5.4 27.9 28.4 110 -—-- 0.54 4 320 5.3 29.7 30.1 10 2 0.79 5 313 5.2 31.4 31.8 9 4 -0.76 6 308 5.1 33.1 33.5 8 8 0.63 7 305 5.1 34.9 35.3 〇· 〇R 2 ^---- 0.51 8 290 4.8 36.6 37.0 〇· J 7 5 -- 0.77 9 275 4.6 丨 _ — 38.4 38.7 (SR 0.71 10 262 4.4 40.1 40.4 W · 〇6 2 0.60 11 235 3.9 --- 41.9 42.0 5 3 0.87 12 174 2.9 43.6 43.7 Fly 8 1.54 13 132 2.2 45.4 45.5 2.8 J^〇3_ Comparative test results display In Table 2, wherein the blade has the aforementioned ten. The upper angle is fixed, and the blade 2 is the Hampton Bay G〇SSomer Wind/Windward blade of the design shown in the sixth, 〇39,541 patent, the blade 3 has I5. Fixed angle of attack Improvement of the efficiency of the flat blade. As defined above, the table is listed as energy 87191-980216.doc 1309695 2 Blades---- Motor-containing cylinders are superior to Hampton Bay. Improvements are better than standard. No cylinders are better than Hampton Bay's improved outer 4 inches. Improvements 172χ 1 18 AM 12,878 21% 29% 37,327 24% 27% 2 --- 188x15 10,639 NA 6% 30,034 a NA NA 172x 3 ------ 18 AM 10,018 -6% NA 28,000 -7% -7% Therefore, the illustrated ceiling fan enhances airflow distribution to make energy efficiency superior to previous techniques . Of course, the fan can also be applied to other places such as the top of the table. Although the present invention is disclosed in the preferred embodiments, other changes, modifications, or deletions are in the spirit and scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS 囷 1 is a side view of a ceiling fan, which is a preferred embodiment of the present invention. Figure 2 is a profile of the fan blade of Figure 1, which is illustrated in a hypothetical plane. Figure 3 is a profile of the blade of Figure 2 showing the spiral of the blade at different locations along the length. Figure 4 is a graph of airflow test parameters. Figure 5 is a side elevational view of the fan-blade of Figure 1. Figure 6 is a top view of the fan-blade of Figure 1. Figure 7 is an end view of the fan-blade of Figure 1. Figures 8A and 8B are other side views of the old blade of the fan of Figure 1, shown in section 87191-980216.doc 1309695, and Figure 8C is a cross-sectional view of the blade along plane 8-8. [Graphic representation symbol] 10 blade 11 root end 12 single 13 tip 15 center line 87191-980216.doc 13-