Abstract:
A duct fan unit, which is a simple structure that can be disassembled by an easy operation and the manufacture cost thereof can be decreased. The duct fan unit comprises a duct and a fan. The duct, allows air to pass through is constructed by engaging two duct constructing members together. The fan is installed inside the duct. A guide portion having a rib shape is set on only one of the duct constructing members such that the fan can be installed easily. A resilient protrusion is set on the other duct constructing member such that the fan can be resiliently pressed for securing the fan in position. Therefore, by simply latching the connecting plate of one duct constructing member with the connecting hole of the other duct constructing member the two duct constructing members are fixed to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Japanese application serial no. 2001-284160, filed on Sep. 18, 2001 and 2002-234545, filed on Aug. 12, 2002. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a duct fan unit which is used for ventilating as a cooling device in various machines wherein a case thereof receives heat generation members such as a motor, a coil and a heater etc. 
     2. Description of the Related Art 
     In order to prevent temperature buildup inside a case due to continuous heat generation from the heat generation members that are disposed inside the case, such as a motor, a coil, a heater and a heat generation circuit etc., in an image forming apparatus, a communication equipment, other electrical equipment or various mechanism, a fan is used. The fan ventilates the heat generation member by removing the air inside the case to the outside. Thus the heat generated around the heat generation members can be radiated to outside. 
     It is well known that a fan and a duct are assembled to form a duct fan unit to achieve the function described above. FIG. 2 is a perspective view showing disassembling of a conventional duct fan unit. The duct  1  is generally made of resin. The duct  1  is disposed at a predetermined location inside a case containing a heat generation unit. The duct  1  is designed into a shape suitable for influx and exhaust of air. A fan  5  is embedded and fixed onto the inner wall of an opening  1   a  at one end of the duct  1 . The other end  1   b  of the duct  1  is attached to a vent hole set on a case (not shown). The fan  5  comprises a motor (not shown) disposed inside the outer frame  6  and blades  7  driven by the motor to rotate. In this example, the fan  5  is fixed onto the duct  1  as described below. Screw receivers  2  are for example are set on four corners of the duct  1 , and through holes  6   a  corresponding to these screw receivers  2  are set on the outer frame  6  of the fan  5 . Long screws  8  are driven through the through holes  6   a  and into the screw receivers  2  in order to fix the fan  5  onto the duct  1 . 
     However, in the conventional duct fan unit, because the screws  8  are used to fix the fan  5  inside the duct  1 , not only the assembly operation but also the disassembling operation is complicated. Thus both assembly and disassembly operations becomes very inconvenient and therefore cannot be effective. 
     The Japanese Laid-Open publication no. 2000-22375 discloses a structure in which the fan unit can be easily replaced when the fan unit is out of order. The structure is shown as FIGS. 3A and 3B, a resilient plate  42  and an engaging plate  43  are used to fix the fan unit  41  onto the fixing portion  44 . The resilient plate  42  is in contact with one side of the fan unit  41  and the resilient plate  42  presses the fan unit  41  to one side. The engaging plate  43  disposed opposite to the resilient plate  42  is latched to the fan unit  41  and the engaging plate  43  fixes the fan unit  41  at a predetermined position. Structure members for limiting the positions of the resilient plate  42  or the engaging plate  43  and the fan unit  41 , such as limiting portions  45 ,  46  etc. are integrally formed with the duct frame  40  that receives a heat generation unit. Furthermore, the resilient plate  42  and the engaging plate  43  are perpendicular to the flow passage of the cooling air of the fan unit  41 . 
     In spite of the simplified assembly and disassembly operations facilitated by the structure disclosed in the Japanese Laid-Open publication no. 2000-22375, however, it can be understood from the drawings that the structure is very complicated. Therefore, the manufacture cost becomes high. 
     Another Japanese Laid-Open publication no. He7-92862 as shown in FIG. 4, discloses a structure comprising a duct which is assembled by a pair of duct constructing members  51 ,  52  for ventilating air and a fan  53  that is clamped and supported within the duct by the pair of duct constructing members  51 ,  52 . The plane of engagement of the pair of duct constructing members  51 ,  52  of the duct is substantially along the air flow direction. When assembling, the fan  53  is positioned and clamped by using guide ribs  56 ,  57  that are formed as an individual pair of ribs on the inner wall of the duct constructing members  51 ,  52 , so that a duct is formed, then the duct constructing members  51 ,  52  are secured by the fastening screws. A duct case  55  where an ozone filter  54  is inserted to an end of the duct is fixed by screws. Each guide rib  56 ,  57  is constructed by a pair of rib portions protruding perpendicular with respect to air flow direction. 
     In spite of the disassembly operation of the fan  53  from the duct facilitated by the structure disclosed in the Japanese Laid-Open publication no. He7-92862, the problem resulting from using the pair of guide ribs  56 ,  57  to fix the fan  53  to a fixed position the fan  53  inside the duct occurs. When assembling, if the direction of the guide ribs  56 ,  57  are not perpendicular to the air flow direction, the fan  53  cannot be clamped under the desired condition. Further, the duct constructing members  51 ,  52  cannot be correctly assembled to construct the duct. Therefore, the formation of the duct constructing members  51 ,  52  which are generally made of resin is required to be constructed under a precision conditions and thus the cost thereof is high. Furthermore, when the position of the guide ribs  56 ,  57  gets slightly changed, attempts to assemble the fan  53  and the duct constructing members  51 ,  52  by force may break the duct constructing members  51 ,  52 . 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a duct fan unit wherein the fan is installed inside a duct without those inconveniences described above. The structure of the duct fan unit is simpler and the operation of detaching the fan is easy and the manufacture cost can be decreased. 
     For solving the problems described above, another object of the present invention is to provide a duct fan unit wherein the fan is installed inside a duct to solve the inconvenience of detaching the fan as experienced by fixing the fan to the conventional duct using screws. 
     In accordance with the above objects and other advantages of the present invention, a structure of a duct fan unit is provided. The duct fan unit comprises a duct, at least a fan, at least a guide portion and at least a protrusion portion. The duct is divided into a pair of duct constructing members to allow air to pass through. The fan is clamped by the pair of duct constructing members and supported inside the duct, wherein a division direction of the duct is substantially along an air flow direction created by the fan. The guide portion is disposed at an inner wall of one of the duct constructing members to limit an installation position of the fan inside the duct. The guide portion extends from the inner wall of the duct member in a shape of a rib perpendicular to the division direction. The protrusion portion is disposed at an inner wall of the other duct constructing member to make contact with an outer wall of the fan and to resiliently press the fan towards a side of the duct constructing member. The protrusion portion protrudes towards a direction perpendicular to the division direction. 
     According to an aspect of the present invention, at a side wall where the protrusion portion is formed, a portion surrounding the protrusion portion is notched to form at least a pair of openings facing to each other. 
     According to another aspect of the present invention, the pair of openings is a pair of slots. 
     According to another aspect of the present invention, the duct fan unit comprises a duct and a fan. The duct allows air to pass through and the duct is divided into two duct constructing members along an axial direction of the duct. The fan is embedded on an inner wall of the duct. The fan is clamped by the two duct constructing members and an outer wall of the fan is pressed inward and supported by the inner wall of the duct 
     According to another aspect of the present invention, the duct constructing members comprise a connecting portion respectively formed on the ends of the duct constructing members with the connection portion of one duct constructing member facing the connecting portion of the other duct constructing member, and the two duct constructing members are detachably latched to each other through the connecting portion. The connecting portion comprise a connecting claw set at one of the duct constructing member and a receiving portion set at the other duct constructing member for receiving the connecting claw. 
     According to another aspect of the present invention, at least one duct constructing member further comprises a resilient portion disposed at an inner wall of the duct constructing member and the resilient portion is in contact with an outer wall of the fan, and the fan is resiliently pressed inward by the resilient portion. 
     Additionally, the fan mentioned in the present invention is not restricted to only the fan itself but other things assembled with fan, for example like the filter etc. disclosed in the Japanese Laid-Open publication no. 7-92862 are also involved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which: 
     FIG. 1A is a perspective view showing the disassembly of the duct fan unit according to one embodiment of the present invention; 
     FIG. 1B is a cross-sectional view taken along the B—B of FIG. 1A; 
     FIG. 2 is a perspective view showing a disassembly of a conventional duct fan unit; 
     FIGS. 3A and 3B show a conventional duct fan unit as another example, wherein FIG. 3A is a front view and FIG. 3B is cross-sectional view; and 
     FIG. 4 is a perspective view showing a disassembly of another conventional duct fan unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiment of the duct fan unit according to the present invention is explained in conjunction with the drawings as follows. Though one fan is explained as an example, the present invention is not limited to one fan. Though the constructing members are generally made of resin, the present invention is not limited to so, the constructing members made of metal can also be used to practice the present invention. 
     FIG. 1A is an exploded view of a duct fan unit according to one embodiment of the present invention FIG. 1B is a cross-sectional view taking along a line B—B in FIG.  1 A. The duct fan unit comprises a duct  11  and a fan  21 . The duct  11  is a shell through which air passes. The fan  21  is embedded inside one end of the duct  11 . A pair of duct constructing members  12 ,  13  surrounds and clamps the outer wall of the fan  21 . The outer wall of the fan  21  is pressed and supported by the inner wall of the duct. 
     The fan  21  comprises an outer frame  22  and blades  23 , wherein a motor (not shown) is disposed inside the outer frame  22 . The outer frame  22  is formed in a shape suitable to be embedded in the inner wall of the duct  11 . The blades  23  are driven by the motor to rotate. Various fans other than the fan shown in the drawing can also be used in the present invention. 
     The pair of duct constructing members  12 ,  13  that constructs the duct  11  are detachably engaged to form the duct  11 , wherein a plane of engagement of the duct constructing members  12 ,  13  is along an axial direction of the duct  11 , that is, along the direction of the air flow inside the duct  11  due to the fan  21 . A connecting plate  12   b  and a connecting hole  13   b  that receives the connecting plate  12   b  and serves as a receiving portion are respectively formed on each latching end (opposite end)  12   a ,  13   a  of the duct constructing members  12 ,  13 . Alternatively, the hole can be set on the duct constructing member  12  and the protrusion can be set on the duct constructing member  13 . 
     The duct constructing member  12  is detachably latched to the duct constructing member  13 . The latching portion comprises a connecting claw  12   b  which constitutes a connecting plate of the duct constructing member  12  and a connecting hole  13   b  which constitutes a receiving portion of the duct constructing member  13 . The receiving portion  13   b  can be a hole as shown in the drawing or a protrusion. By inserting the claw  12   b  of the connecting portion  12   a  of the duct constructing member  12  into the connecting hole  13   b  of the connecting portion  13   a  of the duct connecting member  13 , the duct constructing members can be detachably latched to each other. Latch structures other than the latch structure shown in the present invention, such as the latch structure latched with ribs by using the latching ends  12   a ,  13   a , can also be used. 
     In this way, because the duct fan unit comprises a snap fitting structure constructed by the connecting claw  12   b  and the receiving portion  13   b  which is detachably latched to the connecting claw  12   b , the assembly and disassembly operation thereof is relatively easier compared to the structure which is assembled and disassembled using screws. The fan after assembling can be sufficiently supported in the structure of the present invention. 
     A pair of ribs  25  is respectively set on opposite sides of the inner wall of only one of the duct constructing members  12 ,  13 , specifically the pair of ribs  25  is set on only the duct constructing member  12  which is disposed at a lower side when assembling and installing. These ribs  25  protrude in a so-called rib shape extending from an inner wall perpendicular to the division direction of the duct  11  along the height direction and the width direction (except along the thickness direction). The fan  21  is clamped and can slide in between the ribs  25 . Therefore, the installation of the fan into the duct can be well insured. Alternatively the ribs  25  can be set on the bottom inner wall  12   c  of the duct constructing member  12 . 
     On the other hand, in the side walls of the duct constructing member  13 , a resilient protrusion  30  is formed at the top surface  13   c  that is parallel to the plane of engagement of the duct constructing members  12 ,  13 . During the assembly operation, the duct constructing member  13  is positioned at the lower side. The outer top face of the outer frame  22  of the fan  21  is pressed and in contact with the resilient protrusion  30 . The resilient protrusion  30  resiliently presses against the fan  21  towards the bottom face  12   c  of the other duct constructing member  12 . The resilient protrusion  30  is set to correspond the installation position of the fan  21  on the duct constructing member  12  at a height corresponding to the height of the fan  21 . 
     In this example, the resilient protrusion  30  is a protrusion comprising a half-ball shape and is set at the top surface  13   c  of the duct constructing member  13  with round shape protruding from the inner wall of the duct  11 . Punch holes  31  with slot shapes are set in the air flow direction both in front and behind of the resilient protrusion  30 . The portion where the resilient protrusion  30  is set is rendered with high resilience and flexibility due to the punch holes  31  such that the portion can easily elastically deform towards inside or outside of the duct  11 . The punch holes  31  are not limited to straight slot shapes as shown in the drawing. Alternatively, the punch holes  31  can have curved shapes surrounding the resilient protrusion  30 . 
     In the assembly of the duct  11  as shown in FIG. 1A, the duct constructing member  12  is arranged in a way that the bottom face  12   c  is disposed at the lower side to make the duct  11  open on the upper side. The fan  21  is slid clamped in between the ribs  25  to rest on the lower side. The duct constructing member  13  is hung from the upper side and the duct constructing member  12  is aligned with the duct constructing member  13  such that the latching ends  12   a ,  13   a  of the two duct constructing members  12 ,  13  fit with each other. The connecting plates  12   b  of the duct constructing member  12  is latched into the connecting holes  13   b  of the duct constructing member  13  in a way called snap fitting. 
     In doing so, the resilient protrusion  30  of the duct constructing member  13  comes in contact with the outer top surface of the outer frame  22  of the fan  21 . The fan  21  resiliently presses against the bottom surface  12   c  of the duct constructing member  12 . Thus the assembly can be easily completed. Under this condition, because the resilient protrusion  30  is disposed inside the frame of the image forming apparatus, the outer frame  22  of the fan  21  can be resiliently restricted to a certain position, thus the vibration noise of the fan  21  during operation can be absorbed and mitigated. 
     It is understood from the above description that in the present invention the duct constructing members  12 ,  13  can be latched with each other through only the connecting plates  12   b  and the connecting holes  13   b  independent of misalignment fitting etc. The position and height of the resilient protrusion  30  are favorably set in a way that the resilient protrusion  30  can be in contact with the outer face of the fan  21  when assembling to firmly fix the fan in position. The position and height of the resilient protrusion  30  are not necessary to be set and formed with high precision. Further, when forming the duct constructing members  12 ,  13  using resin, the mold shape and size does not require a high precision. The formation of the duct constructing members  12 ,  13  does not require high precision. No matter how much the formation inaccuracy of the assembly parts is, the assembly parts are usable. It is the same case with the duct constructing members  12 ,  13  constructed from a metal. 
     On the other hand, when disassembling the duct  11 , a hand tool such as a screw driver etc. may be used to detach the connecting plate  12   b  of the duct constructing member  12  out of the connecting hole  13   b  of the duct constructing member  13 . Then the duct constructing member  13  is lifted and taken off. Then the fan  21  is lifted by sliding it out between the ribs  25  and taken off. Thus the disassembly is easily completed. 
     The duct fan unit of the present invention is suitably used in machine, mechanism using a duct fan to cool or to ventilate. 
     With the structure of the present invention described above, with regard to the duct fan unit, the fan is installed inside the duct, and the duct is divided into two duct constructing members dividing the duct along a axial direction of the duct. Each duct constructing member is detachably engaged to each other by the connecting portion. Because the fan is clamped between the duct constructing members in a way that the outer wall of the fan is supported, therefore the inconvenience of disassembly due to fixing of the fan onto the duct using screws can be resolved. 
     Furthermore, because the claw is used as the connecting plate, therefore the unit can be assembled and disassembled easily. 
     The duct fan unit according to the present invention is according to the structure described above. The guide unit with a rib shape is used for securing the fan onto one of the duct constructing members. Therefore, the fan can be clamped inside the duct and the fan can be pressed within the duct by only hanging one of the duct constructing member and pressing the other duct constructing member against the duct constructing member for clamping the fan and the protrusion resiliently pressing against the fan. Thus the duct fan unit can be assembled and disassembled easily. 
     Furthermore, because the protrusion which is in contact with the outer wall of the fan and maintains pressure, therefore the outer wall of the fan is secured within the inner walls of the duct, thus the fan can firmly fixed inside the duct and the noise due to vibration can be substantially reduced. 
     Additionally, the opening is formed to further improve the resilient pressing effects of the protrusion. 
     While the present invention has been described with a preferred embodiment, this description is not intended to limit our invention. Various modifications of the embodiment will be apparent to those skilled in the art. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.