Quickly Assembled Fan TECHNICAL FIELD 5 The present invention relates to the technical field of a fan, and more particularly to a fan which can be quickly assembled. BACKGROUND OF THE INVENTION 10 In a conventional fan, the fan blades are usually mounted at the drive motor by screws. In general, the installation operation comprises the steps of having an operator to remove screws and spring washers from the motor, aligning screw holes formed on a fixing end of the blade with mounting screw holes formed on the motor, inserting the screws into the screw holes on the fixing end of the blade and the 15 mounting screw holes on the motor, and screwing the screws to have the fan blade installed. As the blade is relatively heavy, it might be difficult to keep the alignment between the screw holes on the fixing end of the blade and the mounting screw holes on the motor during the installation process. Further, the operator has to stand on a ladder or a supporting platform when installing a ceiling fan, such that the 20 range of movement of his or her legs is limited, and the operator is prone to feeling tired and could not stand stably after standing for a relatively long period, and danger might thus be caused. In addition, the screws is apt to come out from the screw holes to fall off usually due to improper handling or unstable operation during the process of fixing the screws; and then the screws must be picked up by the 25 operator himself or others to resume the fixing operation of the blade. In this way, the installation process of the conventional fan is relatively troublesome and inconvenient, and it may consume a relatively long period of time. Chinese Patent No. ZL99252710.4 provides a fixing mechanism for fan blades comprising fixing members for connecting the fan blades to the motor, the fixing member for each of the fan blades comprises two screws respectively preset in two mounting screw holes on the motor of the ceiling fan and extending through two holes of the fixing member whereby fixing the fan blade to the motor of the ceiling fan, each fixing member having two holes respectively corresponding to the two 5 mounting screw holes on the motor. When it is required to mount the fan blades to the motor, the preset screws are placed into the respective holes of the fixing member of each fan blade, and are moved with the fixing member and the fan blade to the right position where they are screwed together. The fixing mechanism for the fan blades of this patent can prevent the screws from falling off during installation 10 process, and also possesses the advantages of easy installation, quick operation and the like. Chinese Patent No. ZL201120303011.9 provides a fan comprising a motor and multiple fan blades, wherein a fixing member is fixedly mounted at one end of the blade, and at least one screw is rotatably preset in a corresponding screw hole on a 15 portion of the fixing member protruding beyond the blade, and corresponding screw holes are arranged on the motor, such that the blade is fixedly connected to the motor by merely mounting and tightening the screws in the screw holes for assembling the fan. However, in this fan, one or more of the screw holes on the fan blade for realizing the fixed connection with the fixing member are arranged on the 20 winged portion of the fan blade which is arranged at an angle with the body portion of the fan blade, with a result that the plurality of screw holes on the fan blade are not located in the same plane. This causes difficulty in mounting of the fixing member onto the fan blade with poor coupling therebetween and offset of the winged portion. 25 SUMMARY OF THE INVENTION The features and advantages of the present invention will be described herein below, or would become apparent from the following description, or would be well known 2 by realizing the present invention. In order to overcome the drawbacks of the prior art, the present invention provides a quickly assembled fan, which not only enables a quick assembling of the blade and the motor, but also enables a more easy and firm connection between the blade and 5 the motor. Further, the fan of the invention enhances air flow, reduces noise in use and solves the problem of uneven installation, with lightweight blade, stable rotation and reduced oscillation of the blade. The technical solution of the present invention for solving the foregoing technical problems is to provide a quickly assembled fan comprising a motor, at least one 10 blade, and a fixing member for connecting firmly the blade to the motor, wherein the blade comprises a body portion and a winged portion extending in a width direction of the blade from the body portion over a full length of the blade and arranged at angle with the body portion; wherein the fixing member is fixedly connected to a fixing end of the body portion of the blade in a manner that all 15 connecting positions for implementing the fixed connection of the fixing member to the body portion are located on a same plane; wherein bore holes are arranged on a portion of the fixing member protruding beyond the blade, and at least one mounting screw is rotatably preset in the one of the bore holes, and corresponding bore holes are arranged on the motor, such that the blade is fixedly connected to the 20 motor by mounting the mounting screws in the corresponding bore holes arranged on the motor thereby to achieve assembly of the fan. In a preferred embodiment of the present invention, the fixing member comprises an A-shaped upper portion provided with two or more bore holes for implementing the fixed connection of the fixing member with the body portion of the blade, and a 25 lower portion protruding beyond the blade and provided with at least two bore holes; and the mounting screws are rotatably preset in the bore holes for connecting firmly the fixing member to the motor. 3 In another preferred embodiment of the present invention, the bore holes on the lower portion of the fixing member are preset with threads for pre-screwing the mounting screws. In a further preferred embodiment of the present invention, the fixing member has a 5 pad located on a position where the fixing member is connected to the motor and sandwiched between the fixing member and the motor. The pad and the mounting screw are both preset on the fixing member. In still another preferred embodiment of the present invention, the blade has a tapered width from the fixing end thereof to a free end thereof. 10 In yet still another preferred embodiment of the present invention, at least one positioning hole or positioning member is arranged adjacent to the bore hole formed on the portion of the fixing member protruding beyond the blade, and at least one positioning hole or positioning member is correspondingly arranged adjacent to the bore hole of the motor so as to facilitate alignment between the mounting screws of 15 the fixing member and the corresponding bore holes arranged on the motor to assemble the fan. In another preferred embodiment of the present invention, the mounting screw comprises a screw head, a screw shank and a threaded portion. The screw shank is located between the screw head and the threaded portion, and the screw shank has a 20 diameter slightly smaller than that of the bore hole of the fixing member. the screw shank is disposed inside the bore hole of the fixing member and the threaded portion is screwed into the bore hole of the motor after the blade of the fan is assembled in place. Preferably, an end portion of the mounting screw is in a bulging shape or semi-spherical shape so as to facilitate its insertion into the corresponding bore hole 25 of the motor while assembling the fan. In a further preferred embodiment of the present invention, the fan comprises 2, 3, 4 or 5 blades arranged in rotational symmetry around the motor, wherein each of the 4 blades is fixedly connected with a fixing member, and the fixing member is respectively preset with at least two mounting screws for connection with the motor. The fixing mechanism of the fan blades of the present invention enables the blade to be fixed on the motor of the fan in a simple, fast and secure manner. Further, the 5 connection of the blade to the fixing member is a plane connection which allows for a more secured connection, as all of the bore holes for implementing the fixed connection between the fixing member and the blade are located on the same plane, which may avoid the problems of deformation in the connection and the offset of the winged portion, which are found in the case where the connecting positions for 10 implementing the fixed connection are not located on the same plane. In addition, the winged portion of the invention can be widened in the width direction of the blade to produce an enlarged winged portion for boosting the air flow. The pad sandwiched between the fixing member and the motor could reduce noise when the fan is in use, and ensure a relatively tight connection between the fixing member 15 and the motor. The blade has a tapered width from the fixing end of the blade to the free end of the blade, with a result of lightweight blade, stable rotation and reduced oscillation of the blade. According to the present invention, the width of the fixing member could be relatively small because the fixing member is only secured on the body portion of the blade, thus the portion of the fixing member used for connection 20 with the motor does not require additional positioning holes or positioning members for enhancing and positioning the fixed connection between the fixing member and the motor and achieve the same effect of firm connection. By reading the description provided herein, the features and contents of the invention will be readily understood by a person skilled in the art. 25 BRIEF DESCRIPTION OF THE DRAWINGS The advantages and embodiments of the present invention will become more 5 apparent with reference to the accompanying drawings in conjunction with the following detailed description of embodiments given by way of example, while the contents as shown in the drawings are merely illustrative and shall not be understood to limit the present invention. 5 Figure 1 is an exploded view of the structure of the motor and the blade of the fan of the present invention. Figure 2 is another exploded view of the structure of the motor and the blade of the fan of the present invention. Figure 3 is a sectional view of the blade and the mounting screw of the fan of the 10 present invention as shown in Figure 1. Figure 4 is a sectional view of the blade and the motor of the fan in unassembled state of the present invention as shown in Figure 1. Figure 5 is a sectional view of the blade and the motor in assembled state of the fan of the present invention as shown in Figure 1. 15 Figure 6 is a side view of a preferred embodiment of the mounting screw of the present invention. Figure 7 is an enlarged view of a mounting portion of the mounting screw of the present invention as shown in Figure 5, wherein the motor and the blade are jointed together by the mounting screw. 20 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 1 and 2 are exploded views of the structure of the motor and the blade of the fan of the present invention. The fan as shown is a ceiling fan which serves as an 25 example of the invention, but it should be noted that the present invention is also 6 applicable to other types of fans, and even applicable to screw connection structures of any devices. For simplicity, Figures 1 and 2 depict only those components of the fan in relation to the present invention, and the other components of the fan (not shown) are omitted and well known in the prior art. 5 As shown in Figure 1, the fan comprises a motor 1 and one of blades 4. It should be understood that the fan might generally comprise, for example, two, three or more blades arranged usually in rotational symmetry around the motor 1 though Figure 1 shows only one blade. A fixing member 5 is fixedly connected to one end of the body portion 41 of each of the blades 4 in a screwing manner, a riveting manner, or 10 the like, for example. In the present embodiment, the body portion 41 is formed substantially flat, such that all connecting positions of the fixing member 5 on the blade 4 are located on the same plane, which will be described below in more details. A mounting screw 6 could be preset or prearranged on a portion of the fixing member 5 protruding beyond the blade 4. For example, the mounting screw 6 could 15 be rotatably preset in corresponding bore holes 51 on the fixing member 5, and would not drop off from the fixing member. According to actual needs, the fixing member 5 can be provided with one, two or more mounting screws 6. When the fan is ready for shipping, the mounting screw 6 has already preset on the fixing member 5 of the blade. The term "preset" means that the mounting screw 6 20 has been already screwed on the fixing member 5 of the blade and will not easily fall off therefrom. Preferably, a washer (not shown) and the mounting screw 6 could be muff coupled to prevent the mounting screw 6 from falling off. The blade 4 is fixedly connected to the motor 1 via the fixing member 5 by just simply screwing the mounting screws 6 one by one into the corresponding bore holes 2 arranged on 25 the motor 1 for the assembly of the fan. The width of the fixing member 5 could be relatively small as the fixing member 5 is only secured on the body portion 41 of the blade, therefore the portion of the fixing member 5 used for connection with the motor do not require the provision of 7 additional positioning holes or positioning members for enhancing and positioning the fixed connection between the fixing member and the motor. Definitely, a positioning hole 31 could be arranged on the portion of the fixing member 5 for connection with the motor (adjacent to the position of the mounting 5 screw 6) and a positioning member 3 could be correspondingly arranged adjacent to the bore hole 2 of the motor 1 so as to further facilitate the alignment between the blade 4 or the fixing member 5 and the motor 1 during the assembly process. Alternatively, the positioning member 3 and the positioning hole 31 could be interchanged in positional relation, namely, the positioning member 3 could be 10 arranged on the fixing member 5 while the positioning hole could be correspondingly arranged on the motor 1. The positioning hole 31 may be provided as the type of smooth hole without threads. The mounting screw 6 may generally be made of a metal material or a plastic material. The fixing member 5 and the blade 4 may be generally made of a plastic 15 material or a metal material. The mounting screw and the fixing member can be made of the same or different materials. Since the blade 4 is generally quite long in length, and the requirements for the material property of the blade 4 and the fixing member 5 are different, the blade 4 and the fixing member 5 are preferably made of different materials to reduce production costs and technical difficulties of 20 production. As shown in Figures 1 and 2, the blade 4 of the present invention comprises a substantially planar body portion 41, and a winged portion 42 extending in the width direction of the blade 4 from the body portion 41 over the full length of the blade and arranged at angle with the body portion 41. The fixing member 5 is fixedly 25 connected to the fixing end of the substantially planar body portion 41 of the blade 4. The winged portion 42 might be of linear or curved cross section. In the present embodiment, the fixing member 5 has an A-shaped upper portion provided with two or more bore holes 52, for example three bore holes 52 in triangular arrangement, 8 and the three holes 52 are positioned to correspond to the body portion 41 of the blade 4, such that all the connection positions to the blade are located on a substantially planar horizontal plane, unlike the prior art where one or more screw holes are arranged on the winged portion which is at a plane different from the body 5 portion of the blade 4. The fixing member could form a fixed connection with the blade by screwing the screws into the bore holes 52. The connection of the fixing member 5 to the blade 4 is a plane connection, allowing the convenient and firm connection of the fixing member 5 to the blade. The lower portion of the fixing member 5 is protruding beyond the blade and 10 provided with two bore holes 51, and corresponding bore holes 2 are arranged on the motor 1, such that the fixing member 5 is fixedly connected to the motor 1 by screwing the mounting screws 6 into the bore holes 51 and 2. According to the present invention, a pad 7 is arranged at a position where the fixing member 5 is connected to the motor 1 and sandwiched between the fixing member 5 and the 15 motor 1 via adhesive, for example. The pad could reduce noise generated during the operation of the fan and ensure a relatively tight connection between the fixing member 5 and the motor 1. In this regard, the pad 7 and the mounting screws 6 of the present invention could be preset together on the fixing member 5, so as to simplify the assembling procedures of the fan. 20 Preferably, the blade 4 has a tapered width from the fixing end to the free end of the blade 4, which may reduce the weight of the blade and enable a stable rotation with little oscillation of the blade, and the power of the motor used by the present invention could be accordingly decreased. As described above, when the fixing member 5 is only connected to the body 25 portion 41 of the blade 4, the winged portion 42 can be widened in the width direction of the blade 4 to enlarge the winged portion for the purpose of enhancing the air flow. 9 Figure 3 is a sectional view of the blade and the mounting screw of the fan of the present invention as shown in Figure 1. As illustrated, the fixing member 5 is fixedly connected to the body portion 41 of the blade 4, and the mounting screws 6 may be pre-mounted on the blade 4 by screwing into the bore holes 51 of the fixing 5 member 5. Threads matched with the mounting screw 6 are arranged in both the bore holes 51 of the fixing member 5 and the bore holes of the body portion 41 of the blade 4. In addition, the pad 7 is pre-mounted at the end of the fixing member 5 for connecting with the motor 1 via adhesive, and the pad is provided with through holes at the positions corresponding to the bore holes 51. The mounting screws 6 are 10 screwed into the through holes of the pad 7 via the bore holes 51, such that the mounting screws 6 and the pad 7 are both pre-mounted on the fixing member 5. Figure 4 is a sectional view of the motor and the blade in unassembled state of the fan of the present invention as shown in Figure 1. The motor 1 and the blade 4 are separately illustrated, but the mounting screw 6 has been screwed into the bore hole 15 51 of the fixing member 5 and the through hole of the pad 7, and the mount screw 6 is preset together with the pad 7 on the fixing member 5 of the blade 4. Figure 5 is a sectional view of the motor and the blade in assembled state of the fan of the present invention as shown in Figure 1. The mounting screw 6 has been screwed into the corresponding bore hole 2 of the motor 1 via the bore hole 51 and 20 the through hole of the pad 7, such that the motor 1 and the blade 4 are connected together by the fixing member 5. Figure 6 is a side view of the mounting screw constructed according to a preferred embodiment of the present invention. Preferably, the mounting screw 6 comprises a screw head 64, a screw shank 61 and a threaded portion 62, and the screw shank 61 25 is located between the screw head 64 and the threaded portion 62. The mounting screw 6 further comprises an end portion 63. The screw head 64 has a relatively large diameter for screwing purpose, and "-" shaped or "+" shaped groove formed on the outer surface of the screw head 64 for insertion of a screwdriver, for example. 10 The screw head 64 may be provided in other forms of screw, such as the form of a hexagon screw, or the like. The screw shank 61 is disposed inside the bore hole 51 of the fixing member 5 when the blade of the fan is assembled in place, and the screw shank 61 has a diameter slightly smaller than that of the bore hole 51. The 5 threaded portion 62 is screwed into the bore hole 2 of the motor 1. Preferably, the length of the screw body 61 is approximately 1-2 mm greater than the overall depth of the bore hole 51 of the fixing member 5 and the pad 7, such that the threaded portion 62 may be disengaged from the fixing member (or the blade 4) and the fixing member 5 could tightly abut against the motor 1 during the assembly 10 of the fan. Preferably, the end portion 63 of the mounting screw 6 is made in a bulging shape, for instance in form of a semi-spherical protrusion or a conical protrusion, rather than in form of a flat head screw, so as to facilitate insertion of the mounting screw 6 into the bore hole 2 of the motor 1 when assembling the fan. Similarly, a positioning 15 protrusion 3 arranged on the motor 1 may be made in a hemispherical shape, cylindrical shape, prismatic shape or tapered shape, for example, so as to facilitate its insertion into the positioning hole 31 on the blade 4 or the fixing member 5 while assembling the fan. Figure 7 is an enlarged view of the mounting screw of the present invention 20 mounted in the fan. The motor of the fan and the blade are jointed together by the mounting screw. As shown in Figure 7, the mounting screw 6 is mounted into the bore holes of the fixing member 5 and the motor 1, and the blade 4 is fixedly connected to the motor 1 of the fan via the fixing member 5. The length of the screw body 61 of the mounting screw 6 is slightly greater than the overall depth of the 25 bore hole 51 of the fixing member 5 and the pad 7, and the threaded portion 62 is merely disposed in the bore hole 2 of the motor 1, such that the fixing member 5 could be more tightly affixed to the motor 1. If the housing of the motor 1 is too thin to provide a sufficient number of threads in the bore hole 2 for the screwing of the 11 mounting screw 6, then the bore hole 2 might be projected inwardly a certain distance from the housing of the motor 1, as shown in Figure 7, to allow the depth of the bore hole 2 being sufficient for the screwing of the mounting screw 6. Compared with the prior art fan structures, the fan of the present invention has the 5 advantages of rapid installation, i.e. the mounting screw 6 can be preset on the fixing member 5 or the body portion 41 of the blade 4 when the fan is shipped, which could omit the anti-thrust device used in prior art, while the fan of the invention may eliminate the problem of the screws falling off or getting lost during the assembly of the fan, achieving a quick and easy assembly of the fan to the motor. 10 The fan of the present invention has further advantages that all bore holes for the fixed connection of the fixing member 5 to the blade are devised to be substantially located on the same plane, so as to realize a plane connection between the blade and the fixing member, which enables a more secured connection between the blade and the fixing member, and also avoids the problems of deformation in the connection 15 and the offset of the winged portion, which are usually found in the prior art where the connecting positions for the fixing member and the blade are not located on the same plane. In summary, the present invention not only is simple in structure, convenient to install, and easy to operate, but also enables a more stable fixing structure, and can 20 enhance air flow, reduce noise in use and solve the problem of uneven installation, with lightweight blade, stable rotation and reduced oscillation of the blade. While the embodiments of the present invention have been described above with reference to the drawings, it should be understood that those skilled in the art could realize the present invention with a variety of variants without departing from the 25 scope and spirit thereof. For example, a feature illustrated or described as a part of one embodiment can be employed in another embodiment to attain a further embodiment. The foregoing are merely some preferred embodiments of the present invention and in no way limiting the claimed scope of the present invention, while 12 various equivalent modifications and/or alterations made based on the contents of the foregoing description and the drawings shall all fall into the scope of the present invention. 13